Weak gravitational lensing with the Square Kilometre Array
Brown, M L; Camera, S; Harrison, I; Joachimi, B; Metcalf, R B; Pourtsidou, A; Takahashi, K; Zuntz, J A; Abdalla, F B; Bridle, S; Jarvis, M; Kitching, T D; Miller, L; Patel, P
2015-01-01T23:59:59.000Z
We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.
Atomic Inference from Weak Gravitational Lensing Data
Marshall, Phil; /KIPAC, Menlo Park
2005-12-14T23:59:59.000Z
We present a novel approach to reconstructing the projected mass distribution from the sparse and noisy weak gravitational lensing shear data. The reconstructions are regularized via the knowledge gained from numerical simulations of clusters, with trial mass distributions constructed from n NFW profile ellipsoidal components. The parameters of these ''atoms'' are distributed a priori as in the simulated clusters. Sampling the mass distributions from the atom parameter probability density function allows estimates of the properties of the mass distribution to be generated, with error bars. The appropriate number of atoms is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reecting the quality of the data. Ensemble average mass maps are found to be robust to the details of the noise realization, and succeed in recovering the demonstration input mass distribution (from a realistic simulated cluster) over a wide range of scales. As an application of such a reliable mapping algorithm, we comment on the residuals of the reconstruction and the implications for predicting convergence and shear at specific points on the sky.
Physical component analysis of galaxy cluster weak gravitational lensing data
Phil Marshall
2007-10-30T23:59:59.000Z
We present a novel approach for reconstructing the projected mass distribution of clusters of galaxies from sparse and noisy weak gravitational lensing shear data. The reconstructions are regularised using knowledge gained from numerical simulations of clusters: trial mass distributions are constructed from N physically-motivated components, each of which has the universal density profile and characteristic geometry observed in simulated clusters. The parameters of these components are assumed to be distributed \\emph{a priori} in the same way as they are in the simulated clusters. Sampling mass distributions from the components' parameters' posterior probability density function allows estimates of the mass distribution to be generated, with error bars. The appropriate number of components is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reflecting the quality of the simulated data used in this work. Ensemble average mass maps are found to be robust to the details of the noise realisation, and succeed in recovering the input mass distribution (from a realistic simulated cluster) over a wide range of scales. We comment on the residuals of the reconstruction and their implications, and discuss the extension of the method to include strong lensing information.
Imaging the 3-D cosmological mass distribution with weak gravitational lensing
A. N. Taylor
2001-11-30T23:59:59.000Z
I show how weak gravitational lensing can be used to image the 3-D mass distribution in the Universe. An inverse relation to the lensing equation, relating the lensing potential evaluated at each source to the full 3-D Newtonian potential, is derived. I consider the normal modes of the lensing problem and clarify the equations using a small-angle approximation. Finally I consider the prospects of using this method to estimate the 3-D matter distribution from a realistic galaxy lensing survey.
Statistical properties of the convergence due to weak gravitational lensing by non-linear structures
P. Valageas
2000-05-12T23:59:59.000Z
Density fluctuations in the matter distribution lead to distortions of the images of distant galaxies through weak gravitational lensing effects. This provides an efficient probe of the cosmological parameters and of the density field. In this article, we investigate the statistical properties of the convergence due to weak gravitational lensing by non-linear structures (i.e. we consider small angular windows $\\theta \\la 1'$). Previous studies have shown how to relate the second and third order moments of the convergence to those of the density contrast while models based on the Press-Schechter prescription provide an estimate of the tail of $P(\\kappa)$. Here we present a method to obtain an estimate of the full p.d.f. of the convergence $P(\\kappa)$. It is based on a realistic description of the density field which applies to overdense as well as underdense regions. We show that our predictions agree very well with the results of N-body simulations for the convergence. This could allow one to derive the cosmological parameters $(\\Omega_m,\\Omega_{\\Lambda})$ as well as the full p.d.f. $P(\\delta_R)$ of the density contrast itself in the non-linear regime from observations. Hence this gives a very powerfull tool to constrain scenarios of structure formation.
Andrew J. Barber; A. N. Taylor
2003-06-06T23:59:59.000Z
We present new results on the gravitational lensing shear and magnification power spectra obtained from numerical simulations of a flat cosmology with a cosmological constant. These results are of considerable interest since both the shear and the magnification are observables. We find that the power spectrum in the convergence behaves as expected, but the magnification develops a shot-noise spectrum due to the effects of discrete, massive clusters and symptomatic of moderate lensing beyond the weak-lensing regime. We find that this behaviour can be suppressed by "clipping" of the largest projected clusters. Our results are compared with predictions from a Halo Model-inspired functional fit for the non-linear evolution of the matter field and show excellent agreement. We also study the higher-order moments of the convergence field and find a new scaling relationship with redshift. In particular, the statistic $S_3$ is found to vary as $z_s^{-2.00\\pm 0.08}$ (where $z_s$ is the source redshift) for the cosmology studied, which makes corrections for different median redshifts in different observational surveys particularly simple to apply.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
Gyulchev, G. N. [Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, St. Kliment Ohridski, University of Sofia, 1 Kozyak str., 1407 Sofia (Bulgaria); Yazadjiev, S. S. [Department of Theoretical Physics, Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)
2010-11-25T23:59:59.000Z
We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r{sub {alpha}}/b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}}= Q{sup 2}/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.
Mischa Schirmer; Thomas Erben; Peter Schneider; Christian Wolf; Klaus Meisenheimer
2004-01-12T23:59:59.000Z
We report the first confirmation of colour-selected galaxy cluster candidates by means of weak gravitational lensing. Significant lensing signals were identified in the course of the shear-selection programme of dark matter haloes in the Garching-Bonn Deep Survey, which currently covers 20 square degrees of deep, high-quality imaging data on the southern sky. The detection was made in a field that was previously covered by the ESO Imaging Survey (EIS) in 1997. A highly significant shear-selected mass-concentration perfectly coincides with the richest EIS cluster candidate at z~0.2, thus confirming its cluster nature. Several other shear patterns in the field can also be identified with cluster candidates, one of which could possibly be part of a filament at z~0.45.
Aberration in gravitational lensing
Sereno, M. [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)
2008-10-15T23:59:59.000Z
It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild space-time of the lens, and, then, light-ray detection in the moving observer's frame. Because of the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective rescaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still pointlike. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z{sub d}) with respect to the static case, z{sub d} being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the {mu}arcsec in lensing towards the supermassive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of a cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too challenging.
What is Gravitational Lensing?
Alexie Leauthaud and Reiko Nakajima
2010-01-08T23:59:59.000Z
July 28, 2009 Berkeley Lab summer lecture: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
N. Padmanabhan; U. Seljak; U. L. Pen
2002-10-21T23:59:59.000Z
We present a survey of the cosmological applications of the next generation of weak lensing surveys, paying special attention to the computational challenges presented by the number of galaxies, $N_{gal} ~$ 10$^{5}$. We focus on optimal methods with no pixelization and derive a multigrid $P^3M$ algorithm that performs the relevant computations in $O(N_{gal} \\log N_{gal})$ time. We test the algorithm by studying three applications of weak lensing surveys - convergence map reconstruction, cluster detection and $E$ and $B$ power spectrum estimation using realistic 1 deg^{2} simulations derived from N-body simulations. The map reconstruction is able to reconstruct large scale features without artifacts. Detecting clusters using only weak lensing is difficult because of line of sight contamination and noise, with low completeness if one desires low contamination of the sample. A power spectrum analysis of the convergence field is more promising and we are able to reconstruct the convergence spectrum with no loss of information down to the smallest scales. The numerical methods used here can be applied to other data sets with same $O(N\\log N)$ scaling and can be generalised to a sphere.
On aberration in gravitational lensing
M. Sereno
2008-09-23T23:59:59.000Z
It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light-rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild spacetime of the lens, and, then, light-ray detection in the moving observer's frame. Due to the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective re-scaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still point-like. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z_d) with respect to the static case, z_d being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the microarcsec in lensing towards the super-massive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too much challenging.
Gravitational Lensing in Modified Gravity and the Lensing of Merging Clusters without Dark Matter
J. W. Moffat
2006-08-30T23:59:59.000Z
Gravitational lensing in a modified gravity (MOG) is derived and shown to describe lensing without postulating dark matter. The recent data for merging clusters identified with the interacting cluster 1E0657-56 is shown to be consistent with a weak lensing construction based on MOG without exotic dark matter.
Weak Lensing Detection in CMB Maps
F. Bernardeau
1997-03-05T23:59:59.000Z
The weak lensing effects are known to change only weakly the shape of the power spectrum of the Cosmic Microwave Background (CMB) temperature fluctuations. I show here that they nonetheless induce specific non-Gaussian effects that can be detectable with the four-point correlation function of the CMB anisotropies. The magnitude and geometrical dependences of this correlation function are investigated in detail. It is thus found to scale as the square of the derivative of the two-point correlation function and as the angular correlation function of the gravitational displacement field. It also contains specific dependences on the shape of the quadrangle formed by the four directions. When averaged at a given scale, the four-point function, that identifies with the connected part of the fourth moment of the probability distribution function of the local filtered temperature, scales as the square of logarithmic slope of its second moment, and as the variance of the gravitational magnification at the same angular scale. All these effects have been computed for specific cosmological models. It is worth noting that, as the amplitude of the gravitational lens effects has a specific dependence on the cosmological parameters, the detection of the four-point correlation function could provide precious complementary constraints to those brought by the temperature power spectrum.
Lossy compression of weak lensing data
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Vanderveld, R Ali [Chicago U., EFI; Caltech /Caltech, JPL; Bernstein, Gary M [Pennsylvania U.; Stoughton, Chris [Fermilab; Rhodes, Jason [Caltech; Caltech, JPL; Massey, Richard [Royal Observ., Edinburgh; Dobke, Benjamin M [Caltech; Caltech, JPL
2011-06-01T23:59:59.000Z
Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. (2010) for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is by construction less than the Poisson error from photon shot noise. For simulated space-based images (without cosmic rays) digitized to the typical 16 bits per pixel, application of the lossy compression followed by image-wise lossless compression yields images with only 2.4 bits per pixel, a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m {approx} -4 x 10{sup -4}. This bias is small when compared to the many other issues that precision weak lensing surveys must confront, and furthermore we expect it to be reduced further with better calibration of ellipticity measurement methods.
Lossy compression of weak lensing data
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Vanderveld, R Ali; Bernstein, Gary M; Stoughton, Chris; Rhodes, Jason; Massey, Richard; Dobke, Benjamin M
2011-06-01T23:59:59.000Z
Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. (2010) for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is by construction less than the Poisson error from photon shot noise. For simulated space-based images (without cosmicmore »rays) digitized to the typical 16 bits per pixel, application of the lossy compression followed by image-wise lossless compression yields images with only 2.4 bits per pixel, a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m {approx} -4 x 10{sup -4}. This bias is small when compared to the many other issues that precision weak lensing surveys must confront, and furthermore we expect it to be reduced further with better calibration of ellipticity measurement methods.« less
Natural wormholes as gravitational lenses
Cramer, J.G.; Forward, R.L.; Morris, M.S.; Visser, M.; Benford, G.; Landis, G.A. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States) Forward Unlimited, P.O. Box 2783, Malibu, California 90265 (United States) Department of Physics and Astronomy, Butler University, Indianapolis, Indiana 46208 (United States) Physics Department, Washington University, St. Louis, Missouri 63130-4899 (United States) Physics Department, University of California at Irvine, Irvine, California 92717-4575 (United States) NASA Lewis Research Center, Mail Code 302-1, Cleveland, Ohio 44135-3191 (United States))
1995-03-15T23:59:59.000Z
Once quantum mechanical effects are included, the hypotheses underlying the positive mass theorem of classical general relativity fail. As an example of the peculiarities attendant upon this observation, a wormhole mouth embedded in a region of high mass density might accrete mass, giving the other mouth a net [ital negative] mass of unusual gravitational properties. The lensing of such a gravitationally negative anomalous compact halo object (GNACHO) will enhance background stars with a time profile that is observable and qualitatively different from that recently observed for massive compact halo objects (MACHO's) of positive mass. While the analysis is discussed in terms of wormholes, the observational test proposed is more generally a search for compact negative mass objects of any origin. We recommend that MACHO search data be analyzed for GNACHO's.
A Computer Program to Visualize Gravitational Lenses
Francisco Frutos-Alfaro
2014-06-12T23:59:59.000Z
Gravitational lenses are presently playing an important role in astrophysics. By means of these lenses the parameters of the deflector such as its mass, ellipticity, etc. and Hubble's constant can be determined. Using C, Xforms, Mesa and Imlib a computer program to visualize this lens effect has been developed. This program has been applied to generate sequences of images of a source object and its corresponding images. It has also been used to visually test different models of gravitational lenses.
Magnified Weak Lensing Cross Correlation Tomography
Ulmer, Melville P., Clowe, Douglas I.
2010-11-30T23:59:59.000Z
This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60 nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is using the tomography data along with simulations in a thesis expected to be completed in Jun
Weak Lensing: Dark Matter, Dark Energy
Jain, Bhuvnesh (University of Pennsylvania) [University of Pennsylvania
2006-02-27T23:59:59.000Z
The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted. Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.
The Environments of SLACS Gravitational Lenses
M. W. Auger
2007-10-09T23:59:59.000Z
We report on an investigation of the environments of the SLACS sample of gravitational lenses. The local and global environments of the lenses are characterized using SDSS photometry and, when available, spectroscopy. We find that the lens systems that are best modelled with steeper than isothermal density profiles are more likely to have close companions than lenses with shallower than isothermal profiles. This suggests that the profile steepening may be caused by interactions with a companion galaxy as indicated by N-body simulations of group galaxies. The global environments of the SLACS lenses are typical of non-lensing SDSS galaxies with comparable properties to the lenses, and the richnesses of the lens groups are not as strongly correlated with the lens density profiles as the local environments. Furthermore, we investigate the possibility of line-of-sight contamination affecting the lens models but do not find a significant over-density of sources compared to lines of sight without lenses.
Oguri, Masamune; Hennawi, Joseph F.; Gladders, Michael D.; Dahle, Haakon; Natarajan, Priyamvada; Dalal, Neal; Koester, Benjamin P.; Sharon, Keren; Bayliss, Matthew
2009-01-29T23:59:59.000Z
We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed strong lens modeling with weak lensing shear measured from deep Subaru Suprime-cam images. Weak lensing signals are detected at high significance for all four clusters, whose redshifts range from z = 0.28 to 0.64. We demonstrate that adding strong lensing information with known arc redshifts significantly improves constraints on the mass density profile, compared to those obtained from weak lensing alone. While the mass profiles are well fitted by the universal form predicted in N-body simulations of the {Lambda}-dominated cold dark matter model, all four clusters appear to be slightly more centrally concentrated (the concentration parameters c{sub vir} {approx} 8) than theoretical predictions, even after accounting for the bias toward higher concentrations inherent in lensing selected samples. Our results are consistent with previous studies which similarly detected a concentration excess, and increases the total number of clusters studied with the combined strong and weak lensing technique to ten. Combining our sample with previous work, we find that clusters with larger Einstein radii are more anomalously concentrated. We also present a detailed model of the lensing cluster Abell 1703 with constraints from multiple image families, and find the dark matter inner density profile to be cuspy with the slope consistent with -1, in agreement with expectations.
Cosmological test using strong gravitational lensing systems
Yuan, C C
2015-01-01T23:59:59.000Z
As one of the probes of universe, strong gravitational lensing systems allow us to compare different cosmological models and constrain vital cosmological parameters. This purpose can be reached from the dynamic and geometry properties of strong gravitational lensing systems, for instance, time-delay $\\Delta\\tau$ of images, the velocity dispersion $\\sigma$ of the lensing galaxies and the combination of these two effects, $\\Delta\\tau/\\sigma^2$. In this paper, in order to carry out one-on-one comparisons between $\\Lambda$CDM universe and $R_h=ct$ universe, we use a sample containing 36 strong lensing systems with the measurement of velocity dispersion from the SLACS and LSD survey. Concerning the time-delay effect, 12 two-image lensing systems with $\\Delta\\tau$ are also used. In addition, Monte Carlo (MC) simulations are used to compare the efficiency of the three methods as mentioned above. From simulations, we estimate the number of lenses required to rule out one model at the $99.7\\%$ confidence level. Compar...
Perturbative analysis in planetary gravitational lensing
V. Bozza
1999-04-22T23:59:59.000Z
The traditional perturbative method is applied to the case of gravitational lensing of planetary systems. A complete and detailed description of the structure of caustics for a system with an arbitrary number of planets can be obtained. I have also found precise analytical expressions for microlensing light curves perturbed by the presence of planets.
A toolbox for general elliptical gravitational lenses
T. Schramm
1993-11-09T23:59:59.000Z
We introduce a formalism to describe 2D-Potentials for 2D-matter (or charge) distributions with arbitrary elliptical symmetry including varying eccentricity and twisting of the iso-density curves. We use this approach to describe elliptical matter distributions such as elliptical galaxies or clusters as gravitational lenses. Figures are available upon request: tschramm@hs.uni-hamburg.de
A Method for Weak Lensing Observations
Nick Kaiser; Gordon Squires; Tom Broadhurst
1994-11-01T23:59:59.000Z
We develop and test a method for measuring the gravitational lensing induced distortion of faint background galaxies. We first describe how we locate the galaxies and measure a 2-component `polarisation' or ellipticity statistic $e_\\alpha$ whose expectation value should be proportional to the gravitational shear $\\gamma_\\alpha$. We then show that an anisotropic instrumental psf perturbs the polarisation by $\\delta e_\\alpha = P^s_{\\alpha\\beta} p_\\beta$, where $p_\\alpha$ is a measure of the psf anisotropy and $P^s_{\\alpha\\beta}$ is the `linearised smear polarisability tensor'. By estimating $P^s_{\\alpha\\beta}$ for each object we can determine $p_\\alpha$ from the foreground stars and apply a correction $-P^s_{\\alpha\\beta}p_\\beta$ to the galaxies. We test this procedure using deep high-resolution images from HST which are smeared with an anisotropic psf and then have noise added to simulate ground-based observations. We find that the procedure works very well. A similar analysis yields a linear shear polarisability tensor $P^\\gamma_{\\alpha\\beta}$ which describes the response to a gravitational shear. This calibrates the polarisation-shear relation, but only for galaxies which are well resolved. To empirically calibrate the effect of seeing on the smaller galaxies we artificially stretch HST images to simulate lensing and then degrade them as before. These experiments provide a rigorous and exacting test of the method under realistic conditions. They show that it is possible to remove the effect of instrumental psf anisotropy, and that the method provides an efficient and quantitative measurement of the gravitational shear.
Strong gravitational lensing of gravitational waves in Einstein Telescope
Piórkowska, Aleksandra; Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Zhu, Zong-Hong, E-mail: aleksandra.piorkowska@us.edu.pl, E-mail: marek.biesiada@us.edu.pl, E-mail: zhuzh@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
2013-10-01T23:59:59.000Z
Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.
Spurious Shear in Weak Lensing with LSST
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
2012-09-19T23:59:59.000Z
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Wave optics and image formation in gravitational lensing
Yasusada Nambu
2012-07-30T23:59:59.000Z
We discuss image formation in gravitational lensing systems using wave optics. Applying the Fresnel-Kirchhoff diffraction formula to waves scattered by a gravitational potential of a lens object, we demonstrate how images of source objects are obtained directly from wave functions without using a lens equation for gravitational lensing.
Multipole Formulae for Gravitational Lensing Shear and Flexion
Gary M. Bernstein; Reiko Nakajima
2008-07-11T23:59:59.000Z
The gravitational lensing equations for convergence, potential, shear, and flexion are simple in polar coordinates and separate under a multipole expansion once the shear and flexion spinors are rotated into a ``tangential'' basis. We use this to investigate whether the useful monopole aperture-mass shear formulae generalize to all multipoles and to flexions. We re-derive the result of Schneider and Bartelmann that the shear multipole m at radius R is completely determined by the mass multipole at R, plus specific moments Q^m_in and Q^m_out of the mass multipoles internal and external, respectively, to R. The m>=0 multipoles are independent of Q_out. But in contrast to the monopole, the mmultipoles are independent of Q_in. These internal and external mass moments can be determined by shear (and/or flexion) data on the complementary portion of the plane, which has practical implications for lens modelling. We find that the ease of E/B separation in the monopole aperture moments does {\\em not} generalize to m!=0: the internal monopole moment is the {\\em only} non-local E/B discriminant available from lensing observations. We have also not found practical local E/B discriminants beyond the monopole, though they could exist. We show also that the use of weak-lensing data to constrain a constant shear term near a strong-lensing system is impractical without strong prior constraints on the neighboring mass distribution.
Constraints on warm dark matter from weak lensing in anomalous quadruple lenses
Kaiki Taro Inoue; Ryuichi Takahashi; Tomo Takahashi; Tomoaki Ishiyama
2015-02-12T23:59:59.000Z
We investigate the weak lensing effect by line-of-sight structures with a surface mass density of solar mass/arcsec^2 in QSO-galaxy quadruple lens systems. Using high-resolution N-body simulations in warm dark matter (WDM) models and observed four quadruple lenses that show anomalies in the flux ratios, we obtain constraints on the mass of thermal WDM, m_WDM>= 1.3keV(95%CL) assuming that the density of the primary lens is described by a singular isothermal ellipsoid (SIE). The obtained constraint is consistent with those from Lyman-$\\alpha$ forests and the number counts of high-redshift galaxies at z>4. Our results show that WDM with a free-streaming comoving wavenumber k_{fs} <= 27 h/Mpc is disfavored as the major component of cosmological density at redshifts 0.5 <~ z <~ 4 provided that the SIE models describe the gravitational potentials of the primary lenses correctly.
Three gravitationally lensed supernovae behind clash galaxy clusters
Patel, Brandon; McCully, Curtis; Jha, Saurabh W.; Holoien, Thomas W.-S. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Rodney, Steven A.; Jones, David O.; Graur, Or; Riess, Adam G. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States); Merten, Julian [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, Pasadena, CA 91109 (United States); Zitrin, Adi [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Matheson, Thomas [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Sako, Masao [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); Postman, Marc; Coe, Dan; Bradley, Larry [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Bartelmann, Matthias [Institut für Theoretische Astrophysik, Universität Heidelberg, Zentrum für Astronomie, Philosophenweg 12, D-69120 Heidelberg (Germany); Balestra, Italo [INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste (Italy); Benítez, Narciso [Instituto de Astrofísica de Andalucía (CSIC), Camino Bajo de Huétor 24, E-18008 Granada (Spain); Bouwens, Rychard [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Broadhurst, Tom, E-mail: bpatel02@physics.rutgers.edu [Department of Theoretical Physics, University of the Basque Country, P.O. Box 644, E-48080 Bilbao (Spain); and others
2014-05-01T23:59:59.000Z
We report observations of three gravitationally lensed supernovae (SNe) in the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z = 0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters, MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and A383 (z = 0.187), respectively. Each SN was detected in Hubble Space Telescope optical and infrared images. Based on photometric classification, we find that SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while the classification of SN CLA11Tib is inconclusive. Using multi-color light-curve fits to determine a standardized SN Ia luminosity distance, we infer that SN CLO12Car was ?1.0 ± 0.2 mag brighter than field SNe Ia at a similar redshift and ascribe this to gravitational lens magnification. Similarly, SN CLN12Did is ?0.2 ± 0.2 mag brighter than field SNe Ia. We derive independent estimates of the predicted magnification from CLASH strong+weak-lensing maps of the clusters (in magnitude units, 2.5 log{sub 10}?): 0.83 ± 0.16 mag for SN CLO12Car, 0.28 ± 0.08 mag for SN CLN12Did, and 0.43 ± 0.11 mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens model predictions: we find that the magnifications based on the SN Ia brightness and those predicted by the lens maps are consistent. Our results herald the promise of future observations of samples of cluster-lensed SNe Ia (from the ground or space) to help illuminate the dark-matter distribution in clusters of galaxies, through the direct determination of absolute magnifications.
Gravitational lensing in a non-uniform plasma
G. S. Bisnovatyi-Kogan; O. Yu. Tsupko
2010-06-11T23:59:59.000Z
We develop a model of gravitational lensing in a non-uniform plasma. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and of a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. We take into account both effects, and derive the expression for the lensing angle in the case of a strongly nonuniform plasma in presence of the gravitation. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for very long radiowaves. We discuss the observational appearances of this effect for the gravitational lens with a Schwarzschild metric, surrounded by a uniform plasma. We obtain formulae for the lensing angle and the magnification factors in this case and discuss a possibility of observation of this effect by the planned VLBI space project Radioastron. We also consider models with a nonuniform plasma distribution. For different gravitational lens models we compare the corrections to the vacuum lensing due to the gravitational effect in plasma, and due to the plasma inhomogeneity. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.
Disentangling dark sector models using weak lensing statistics
Giocoli, Carlo; Baldi, Marco; Meneghetti, Massimo; Moscardini, Lauro; Petkova, Margarita; -,; Astronomia, Dipartimento di Fisica e; di Bologna, Alma Mater Studiorum Università; di Bologna, INAF - Osservatorio Astronomico; di Bologna, INFN - Sezione; Université, Aix Marseille; CNRS,; LAM,; France,; Laboratory, Jet Propulsion; Physics, Department of; Ludwig-Maximilians-Universitaet),
2015-01-01T23:59:59.000Z
We perform multi-plane ray-tracing using the GLAMER gravitational lensing code within high-resolution light-cones extracted from the CoDECS simulations: a suite of cosmological runs featuring a coupling between Dark Energy and Cold Dark Matter. We show that the presence of the coupling is evident not only in the redshift evolution of the normalisation of the convergence power spectrum, but also in differences in non-linear structure formation with respect to {\\Lambda}CDM. Using a tomographic approach under the assumption of a {\\Lambda}CDM cosmology, we demonstrate that weak lensing measurements would result in a {\\sigma}8 value that changes with the source redshift if the true underlying cosmology is a coupled Dark Energy one. This provides a generic null test for these types of models. We also find that different models of coupled Dark Energy can show either an enhanced or a suppressed correlation between convergence maps with differing source redshifts as compared to {\\Lambda}CDM. This would provide a direc...
Gravitational lensing in eclipsing binary stars
T. R. Marsh
2000-12-18T23:59:59.000Z
I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focussing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If not accounted for, this may lead to under-estimation of the radius of the white dwarf compared to that of its companion. I show that the effect is significant for plausible binary parameters, and that it leads to ~25% reduction in the transit depth in the system KPD 1930+2752. The reduction of eclipse depth is degenerate with the stellar radius ratio, and therefore cannot be used to establish the existence of lensing. A second order effect of the light bending is to steepen the ingress and egress features of the secondary eclipse relative to the primary eclipse, although it will be difficult to see this in practice. I consider also binaries containing neutron stars and black-holes. I conclude that, although relatively large effects are possible in such systems, a combination of rarity, faintness and intrinsic variability make it unlikely that lensing will be detectable in them.
Potential sources of contamination to weak lensing measurements: constraints from N-body simulations
Catherine Heymans; Martin White; Alan Heavens; Chris Vale; Ludovic Van Waerbeke
2006-06-16T23:59:59.000Z
We investigate the expected correlation between the weak gravitational shear of distant galaxies and the orientation of foreground galaxies, through the use of numerical simulations. This shear-ellipticity correlation can mimic a cosmological weak lensing signal, and is potentially the limiting physical systematic effect for cosmology with future high-precision weak lensing surveys. We find that, if uncorrected, the shear-ellipticity correlation could contribute up to 10% of the weak lensing signal on scales up to 20 arcminutes, for lensing surveys with a median depth z=1. The most massive foreground galaxies are expected to cause the largest correlations, a result also seen in the Sloan Digital Sky Survey. We find that the redshift dependence of the effect is proportional to the lensing efficiency of the foreground, and this offers prospects for removal to high precision, although with some model dependence. The contamination is characterised by a weakly negative B-mode, which can be used as a diagnostic of systematic errors. We also provide more accurate predictions for a second potential source of error, the intrinsic alignment of nearby galaxies. This source of contamination is less important, however, as it can be easily removed with distance information.
What is Gravitational Lensing? (LBNL Summer Lecture Series)
Leauthaud, Alexie; Nakajima, Reiko [Berkeley Center for Cosmological Physics
2011-04-28T23:59:59.000Z
Summer Lecture Series 2009: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
Planck 2015 results. XV. Gravitational lensing
Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Bartolo, N; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Désert, F -X; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dunkley, J; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Lewis, A; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rowan-Robinson, M; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; White, M; Yvon, D; Zacchei, A; Zonca, A
2015-01-01T23:59:59.000Z
We present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40 sigma), using temperature and polarization data from the Planck 2015 full-mission release. Using a polarization-only estimator we detect lensing at a significance of 5 sigma. We cross-check the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40
The effect of weak lensing on distance estimates from supernovae
Smith, Mathew; Maartens, Roy [Department of Physics, University of the Western Cape, Cape Town 7535 (South Africa); Bacon, David J.; Nichol, Robert C.; Campbell, Heather; D'Andrea, Chris B. [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Clarkson, Chris [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa); Bassett, Bruce A. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa); Cinabro, David [Wayne State University, Department of Physics and Astronomy, Detroit, MI 48202 (United States); Finley, David A.; Frieman, Joshua A. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Galbany, Lluis [CENTRA Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon (Portugal); Garnavich, Peter M. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Olmstead, Matthew D. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Shapiro, Charles [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, La Canada Flintridge, CA 91109 (United States); Sollerman, Jesper, E-mail: matsmith2@gmail.com [The Oskar Klein Centre, Department of Astronomy, AlbaNova, SE-106 91 Stockholm (Sweden)
2014-01-01T23:59:59.000Z
Using a sample of 608 Type Ia supernovae from the SDSS-II and BOSS surveys, combined with a sample of foreground galaxies from SDSS-II, we estimate the weak lensing convergence for each supernova line of sight. We find that the correlation between this measurement and the Hubble residuals is consistent with the prediction from lensing (at a significance of 1.7?). Strong correlations are also found between the residuals and supernova nuisance parameters after a linear correction is applied. When these other correlations are taken into account, the lensing signal is detected at 1.4?. We show, for the first time, that distance estimates from supernovae can be improved when lensing is incorporated, by including a new parameter in the SALT2 methodology for determining distance moduli. The recovered value of the new parameter is consistent with the lensing prediction. Using cosmic microwave background data from WMAP7, H {sub 0} data from Hubble Space Telescope and Sloan Digital Sky Survey (SDSS) Baryon acoustic oscillations measurements, we find the best-fit value of the new lensing parameter and show that the central values and uncertainties on ? {sub m} and w are unaffected. The lensing of supernovae, while only seen at marginal significance in this low-redshift sample, will be of vital importance for the next generation of surveys, such as DES and LSST, which will be systematics-dominated.
Decaying $?$ cosmologies and statistical properties of gravitational lenses
L. F. Bloomfield Torres; I. Waga
1995-05-01T23:59:59.000Z
In this paper we investigate the statistical properties of gravitational lenses for models in which a cosmological term decreases with time as $\\Lambda \\propto a^{-m}$, where $a$ is the scale factor and $m$ is a parameter ($0 \\leq m }{\\sim}2$ have high likelihood to reproduce the observed lens statistics in the HST snapshot survey.
A New Weak Lensing Analysis of MS1224.7+2007
Philippe Fischer
1999-01-29T23:59:59.000Z
Galaxy cluster mass distributions are useful probes of Omega_0 and the nature of the dark matter. Large clusters will distort the observed shapes of background galaxies through gravitational lensing allowing the measurement of the cluster mass distributions. For most cases, the agreement between weak lensing and radial velocity mass measurements of clusters is reasonably good. There is, however, one significant exception, the z=0.32 cluster MS1224.7+2007, which has a lensing mass substantially larger than the virial mass and also a very high mass-to-light ratio. Since this controversial object might be an unusually dark mass a follow-up study is definitely warranted. In this paper we study the mass and light distributions of MS1224+2007 out to a projected radius of 800/h kpc by measuring the gravitationally-induced distortions of background galaxies. We detect a shear signal in the background galaxies in the radial range 27.5 arcsec < r < 275 arcsec at the 5.5 sigma level. The resultant mass map exhibits a peak centered on the dominant cluster galaxy and strong evidence for substructure which is even more strongly seen in the galaxy distribution. Assuming all the detected shear is due to mass at z=0.32 we find cluster mass-to-light ratio of M/L_R = 640 +/- 150. The mass profile is quite flat compared to other clusters, disagreeing with a pseudo-singular isothermal sphere at the 95% confidence level. Our mass and M/L estimates are consistent with the previous weak lensing result. The discrepancy between the lensing and virial mass remains although it might be partially explained by subclustering and infall perpendicular to the line-of-site. This cluster remains a candidate dark object deficient in baryons and as such severely tests cosmological models.
Strong gravitational lensing in a noncommutative black-hole spacetime
Ding Chikun; Kang Shuai; Chen Changyong; Chen Songbai; Jing Jiliang [Department of Physics and Information Engineering, Hunan Institute of Humanities Science and Technology, Loudi, Hunan 417000 (China); Institute of Physics and Department of Physics, Hunan Normal University, Changsha, Hunan 410081 (China) and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University), Ministry of Education (China)
2011-04-15T23:59:59.000Z
Noncommutative geometry may be a starting point to a quantum gravity. We study the influence of the spacetime noncommutative parameter on the strong field gravitational lensing in the noncommutative Schwarzschild black-hole spacetime and obtain the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy can be described by this metric, we estimate the numerical values of the coefficients and observables for strong gravitational lensing. In comparison to the Reissner-Norstroem black hole, we find that the influences of the spacetime noncommutative parameter is similar to those of the charge, but these influences are much smaller. This may offer a way to distinguish a noncommutative black hole from a Reissner-Norstroem black hole, and may permit us to probe the spacetime noncommutative constant {theta} by the astronomical instruments in the future.
Testing gravity with halo density profiles observed through gravitational lensing
Narikawa, Tatsuya; Yamamoto, Kazuhiro, E-mail: narikawa@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp [Department of Physical Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan)
2012-05-01T23:59:59.000Z
We present a new test of the modified gravity endowed with the Vainshtein mechanism with the density profile of a galaxy cluster halo observed through gravitational lensing. A scalar degree of freedom in the galileon modified gravity is screened by the Vainshtein mechanism to recover Newtonian gravity in high-density regions, however it might not be completely hidden on the outer side of a cluster of galaxies. Then the modified gravity might yield an observational signature in a surface mass density of a cluster of galaxies measured through gravitational lensing, since the scalar field could contribute to the lensing potential. We investigate how the transition in the Vainshtein mechanism affects the surface mass density observed through gravitational lensing, assuming that the density profile of a cluster of galaxies follows the original Navarro-Frenk-White (NFW) profile, the generalized NFW profile and the Einasto profile. We compare the theoretical predictions with observational results of the surface mass density reported recently by other researchers. We obtain constraints on the amplitude and the typical scale of the transition in the Vainshtein mechanism in a subclass of the generalized galileon model.
Cross-correlation of Planck CMB Lensing and CFHTLenS Galaxy Weak Lensing Maps
Liu, Jia
2015-01-01T23:59:59.000Z
We cross-correlate cosmic microwave background (CMB) lensing and galaxy weak lensing maps using the Planck 2013 and 2015 data and the 154 deg^2 Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). This measurement probes large-scale structure at intermediate redshifts ~0.9, between the high- and low-redshift peaks of the CMB and CFHTLenS lensing kernels, respectively. Using the noise properties of these data sets and standard Planck 2015 LCDM cosmological parameters, we forecast a signal-to-noise ratio ~4.6 for the cross-correlation. We find that the noise level of our actual measurement agrees well with this estimate, but the amplitude of the signal lies well below the theoretical prediction. The best-fit amplitudes of our measured cross-correlations are $A_{2013}=0.48\\pm0.26$ and $A_{2015}=0.44\\pm0.22$ using the 2013 and 2015 Planck CMB lensing maps, respectively, where $A=1$ corresponds to the fiducial Planck 2015 LCDM prediction. Due to the low measured amplitude, the detection significance is modera...
Gravitational Lensing Characteristics of the Transparent Sun
Bijunath Patla; Robert J. Nemiroff
2011-12-12T23:59:59.000Z
The transparent Sun is modeled as a spherically symmetric and centrally condensed gravitational lens using recent Standard Solar Model (SSM) data. The Sun's minimum focal length is computed to a refined accuracy of 23.5 +/- 0.1 AU, just beyond the orbit of Uranus. The Sun creates a single image of a distant point source visible to observers inside this minimum focal length and to observers sufficiently removed from the line connecting the source through the Sun's center. Regions of space are mapped where three images of a distant point source are created, along with their associated magnifications. Solar caustics, critical curves, and Einstein rings are computed and discussed. Extremely high gravitational lens magnifications exist for observers situated so that an angularly small, unlensed source appears near a three-image caustic. Types of radiations that might undergo significant solar lens magnifications as they can traverse the core of the Sun, including neutrinos and gravitational radiation, are discussed.
Corless, Virginia Leigh
2005-01-01T23:59:59.000Z
In this thesis, I design and construct a Monte-Carlo gravitational lensing simulation that statistically studies the strong lensing of extended galactic sources by dark matter distributions in galaxy clusters, using recent ...
WEAK LENSING MEASUREMENT OF GALAXY CLUSTERS IN THE CFHTLS-WIDE SURVEY
Shan Huanyuan; Tao Charling [Department of Physics and Tsinghua Center for Astrophysics, Tsinghua University, Beijing, 100084 (China); Kneib, Jean-Paul; Jauzac, Mathilde; Limousin, Marceau [Laboratoire d'Astrophysique de Marseille, CNRS-Universite de Provence, 38 rue Frederic Joliot-Curie, F-13388 Marseille Cedex 13 (France); Fan Zuhui [Department of Astronomy, Peking University, Beijing, 100871 (China); Massey, Richard [Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Thanjavur, Karun [Canada France Hawaii Telescope, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States); McCracken, Henry J., E-mail: shanhuany@gmail.com [Institude d'Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France)
2012-03-20T23:59:59.000Z
We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We study the 64 deg{sup 2} W1 field, the largest of the CFHTLS-Wide survey fields, and present the largest contiguous weak lensing convergence 'mass map' yet made. 2.66 million galaxy shapes are measured, using the Kaiser Squires and Broadhurst Method (KSB) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS. Our i'-band measurements are also consistent with an analysis of independent r'-band imaging. The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio {nu} > 3.5, consistent with predictions of a {Lambda}CDM model. Of these peaks, 126 lie within 3.'0 of a brightest central galaxy identified from multicolor optical imaging in an independent, red sequence survey. We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 deg{sup 2} XMM-LSS survey. With photometric redshift estimates for the source galaxies, we use a tomographic lensing method to fit the redshift and mass of each convergence peak. Matching these to the optical observations, we confirm 85 groups/clusters with {chi}{sup 2}{sub reduced} < 3.0, at a mean redshift (z{sub c} ) = 0.36 and velocity dispersion ({sigma}{sub c}) = 658.8 km s{sup -1}. Future surveys, such as DES, LSST, KDUST, and EUCLID, will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models.
Broad Iron Emission from Gravitationally Lensed Quasars Observed by Chandra
Walton, D J; Miller, J M; Reis, R C; Stern, D; Harrison, F A
2015-01-01T23:59:59.000Z
Recent work has demonstrated the potential of gravitationally lensed quasars to extend measurements of black hole spin out to high-redshift with the current generation of X-ray observatories. Here we present an analysis of a large sample of 27 lensed quasars in the redshift range 1.0permit the detection of iron emission from the inner accretion disk in individual cases in our sample, we find significant structure in the stacked residuals. In addition to the narrow core, seen almost ubiquitously in local AGN, we find evidence for an additional underlying broad component from the inner accretion disk, with a clear red wing to the emission profile. Based on simulations, we find the detection of this broader component to be significant at greater than the 3-sigma level. This implies that iron emission...
An attempt to measure the time delays of three gravitational lenses
Chistol, Gheorghe
2007-01-01T23:59:59.000Z
I present the results of reduction and analysis of two seasons of gravitational lens monitoring using the Very Large Array (VLA) at 8.5 GHz. The campaign monitored five gravitational lenses, GL1608, GL1830, GL1632, GL1838, ...
Gravitational lens equation for embedded lenses; magnification and ellipticity
Chen, B. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks, Norman, Oklahoma 73019 (United States); Mathematics Department, University of Oklahoma, 601 Elm Avenue, Norman, Oklahoma 73019 (United States); Kantowski, R.; Dai, X. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks, Norman, Oklahoma 73019 (United States)
2011-10-15T23:59:59.000Z
We give the lens equation for light deflections caused by point mass condensations in an otherwise spatially homogeneous and flat universe. We assume the signal from a distant source is deflected by a single condensation before it reaches the observer. We call this deflector an embedded lens because the deflecting mass is part of the mean density. The embedded lens equation differs from the conventional lens equation because the deflector mass is not simply an addition to the cosmic mean. We prescribe an iteration scheme to solve this new lens equation and use it to compare our results with standard linear lensing theory. We also compute analytic expressions for the lowest order corrections to image amplifications and distortions caused by incorporating the lensing mass into the mean. We use these results to estimate the effect of embedding on strong lensing magnifications and ellipticities and find only small effects, <1%, contrary to what we have found for time delays and for weak lensing, {approx}5%.
Marusa Bradac; Douglas Clowe; Anthony H. Gonzalez; Phil Marshall; William Forman; Christine Jones; Maxim Markevitch; Scott Randall; Tim Schrabback; Dennis Zaritsky
2006-08-18T23:59:59.000Z
The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of "weakly" lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004,2006a).
Gravitational lensing and the angular-diameter distance relation
Fedja Hadrovic; James Binney
1997-08-13T23:59:59.000Z
We show that the usual relation between redshift and angular-diameter distance can be obtained by considering light from a source to be gravitationally lensed by material that lies in the telescope beam as it passes from source to observer through an otherwise empty universe. This derivation yields an equation for the dependence of angular diameter on redshift in an inhomogeneous universe. We use this equation to model the distribution of angular-diameter distance for redshift z=3 in a realistically clustered cosmology. The distribution is such that attempts to determine q_0 from angular-diameter distances will systematically underestimate q_0 by ~0.15, and large samples would be required to beat down the intrinsic dispersion in measured values of q_0.
Choi, J -Y; Park, S -Y; Han, C; Gould, A; Sumi, T; Udalski, A; Beaulieu, J -P; Street, R; Dominik, M; Allen, W; Bos, M; Christie, G W; Depoy, D L; Dong, S; Drummond, J; Gal-Yam, A; Gaudi, B S; Henderson, C B; Hung, L -W; Janczak, J; Lee, C -U; Mallia, F; Maury, A; McCormick, J; McGregor, D; Monard, L A G; Moorhouse, D; Muñoz, J A; Natusch, T; Nelson, C; Park, B -G; Pogge, R W; Tan, T -G "TG"; Thornley, G; Yee, J C; Abe, F; Barnard, E; Baudry, J; Bennett, D P; Bond, I A; Botzler, C S; Freeman, M; Fukui, A; Furusawa, K; Hayashi, F; Hearnshaw, J B; Hosaka, S; Itow, Y; Kamiya, K; Kilmartin, P M; Kobara, S; Korpela, A; Lin, W; Ling, C H; Makita, S; Masuda, K; Matsubara, Y; Miyake, N; Muraki, Y; Nagaya, M; Nishimoto, K; Ohnishi, K; Okumura, T; Omori, K; Perrott, Y C; Rattenbury, N; Saito, To; Skuljan, L; Sullivan, D J; Suzuki, D; Suzuki, K; Sweatman, W L; Takino, S; Tristram, P J; Wada, K; Yock, P C M; Szyma?ski, M K; Kubiak, M; Pietrzy?ski, G; Soszy?ski, I; Poleski, R; Ulaczyk, K; Wyrzykowski, ?; Koz?owski, S; Pietrukowicz, P; Albrow, M D; Bachelett, E; Batista, V; Bennett, C; Bowens-Rubin, R; Brillant, S; Cassan, A; Cole, A; Corrales, E; Coutures, Ch; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Greenhill, J; Kane, S R; Menzies, J; Sahu, K C; Wambsganss, J; Williams, A; Zub, M; Allan, A; Bramich, D M; Browne, P; Clay, N; Fraser, S; Horne, K; Kains, N; Mottram, C; Snodgrass, C; Steele, I; Tsapras, Y; Alsubai, K A; Bozza, V; Burgdorf, M J; Novati, S Calchi; Dodds, P; Dreizler, S; Finet, F; Gerner, T; Glitrup, M; Grundahl, F; Hardis, S; Harpsøe, K; Hinse, T C; Hundertmark, M; Jørgensen, U G; Kerins, E; Liebig, C; Maier, G; Mancini, L; Mathiasen, M; Penny, M T; Proft, S; Rahvar, S; Ricci, D; Scarpetta, G; Schäfer, S; Schönebeck, F; Skottfelt, J; Surdej, J; Southworth, J; Zimmer, F
2011-01-01T23:59:59.000Z
We present the analysis of the light curves of 9 high-magnification gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For 8 events, we measure the Einstein radii and the lens-source relative proper motions. Among them, 6 events (OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2011-BLG-093, MOA-2011-BLG-274, and OGLE-2011-BLG-0990/MOA-2011-BLG-300) are found to have Einstein radii less than 0.2 mas, making the lenses candidates of very low-mass stars or brown dwarfs. For MOA-2011-BLG-274, especially, the small Einstein ...
Numerical wave optics and the lensing of gravitational waves by globular clusters
Andrew J. Moylan; David E. McClelland; Susan M. Scott; Antony C. Searle; G. V. Bicknell
2007-10-16T23:59:59.000Z
We consider the possible effects of gravitational lensing by globular clusters on gravitational waves from asymmetric neutron stars in our galaxy. In the lensing of gravitational waves, the long wavelength, compared with the usual case of optical lensing, can lead to the geometrical optics approximation being invalid, in which case a wave optical solution is necessary. In general, wave optical solutions can only be obtained numerically. We describe a computational method that is particularly well suited to numerical wave optics. This method enables us to compare the properties of several lens models for globular clusters without ever calling upon the geometrical optics approximation, though that approximation would sometimes have been valid. Finally, we estimate the probability that lensing by a globular cluster will significantly affect the detection, by ground-based laser interferometer detectors such as LIGO, of gravitational waves from an asymmetric neutron star in our galaxy, finding that the probability is insignificantly small.
Strong and weak gravitational field in $R+?^4/R$ gravity
Kh. Saaidi; A. Vajdi; S. W. Rabiei; A. Aghamohammadi; H. Sheikhahmadi
2012-01-18T23:59:59.000Z
We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\\mu\\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric.
Rozo, Eduardo; /U. Chicago /Chicago U., KICP; Wu, Hao-Yi; /KIPAC, Menlo Park; Schmidt, Fabian; /Caltech
2011-11-04T23:59:59.000Z
When extracting the weak lensing shear signal, one may employ either locally normalized or globally normalized shear estimators. The former is the standard approach when estimating cluster masses, while the latter is the more common method among peak finding efforts. While both approaches have identical signal-to-noise in the weak lensing limit, it is possible that higher order corrections or systematic considerations make one estimator preferable over the other. In this paper, we consider the efficacy of both estimators within the context of stacked weak lensing mass estimation in the Dark Energy Survey (DES). We find that the two estimators have nearly identical statistical precision, even after including higher order corrections, but that these corrections must be incorporated into the analysis to avoid observationally relevant biases in the recovered masses. We also demonstrate that finite bin-width effects may be significant if not properly accounted for, and that the two estimators exhibit different systematics, particularly with respect to contamination of the source catalog by foreground galaxies. Thus, the two estimators may be employed as a systematic cross-check of each other. Stacked weak lensing in the DES should allow for the mean mass of galaxy clusters to be calibrated to {approx}2% precision (statistical only), which can improve the figure of merit of the DES cluster abundance experiment by a factor of {approx}3 relative to the self-calibration expectation. A companion paper investigates how the two types of estimators considered here impact weak lensing peak finding efforts.
Effects of Gravitational Lensing in the Double Pulsar System J0737-3039
Dong Lai; Roman R. Rafikov
2005-01-26T23:59:59.000Z
We investigate the effects of gravitational lensing in the binary pulsar system J0737-3039. Current measurement of the orbital inclination allows the millisecond pulsar (A) to pass very close (at R_{min}=4000 km) in projection to the companion pulsar (B), with R_{min} comparable to the Einstein radius (2600 km). For this separation at the conjunction, lensing causes small (about 10%) magnification of the pulsar A signal on a timescale of several seconds, and displaces the pulsar image on the sky plane by about 1200 km. More importantly, lensing introduces a correction (of several microsec) to the conventional Shapiro delay formula used in pulsar timing analysis, and gives rise to a geometric time delay together with the delays associated with the pulsar spin period. These lensing effects can influence the determination of the system parameters by both timing and scintillation studies. Given the current uncertainty in the orbital inclination, more extreme manifestations of lensing (e.g. magnification by a factor of several) are possible. We compare our predictions with the existing observations and discuss the possibility of detecting gravitational lensing signatures in the system. The anomalously high point in A's lightcurve close to superior conjunction might be caused by gravitational lensing.
The Effect of the Cosmic Web on Cluster Weak Lensing Mass Estimates
Christopher A. Metzler; Martin White; Chris Loken
2001-03-08T23:59:59.000Z
In modern hierarchical theories of structure formation, rich clusters of galaxies form at the vertices of a weblike distribution of matter, with filaments emanating from them to large distances and with smaller objects forming and draining in along these filaments. The amount of mass contained in structure near the cluster can be comparable to the collapsed mass of the cluster itself. As the lensing kernel is quite broad along the line of sight around cluster lenses with typical redshifts near z=0.5, structures many Mpc away from the cluster are essentially at the same location as the cluster itself, when considering their effect on the cluster's weak lensing signal. We use large-scale numerical simulations of structure formation in a Lambda-dominated cold dark matter model to quantify the effect that large-scale structure near clusters has upon the cluster masses deduced from weak lensing analysis. A correction for the scatter in possible observed lensing masses should be included when interpreting mass functions from weak lensing surveys.
Gravitational lensing of quasars by edge-on spiral galaxies
Wang, Emily P
2007-01-01T23:59:59.000Z
In this thesis, I studied the lensed quasar CX2201-3201, which is lensed by an edge-on spiral galaxy. The unusually high tilt of the spiral galaxy provides us with a rare opportunity for mass modeling. In addition, the ...
Self-Calibration for 3-point Intrinsic Alignment Auto-Correlations in Weak Lensing Surveys
M. A. Troxel; Mustapha Ishak
2012-03-09T23:59:59.000Z
The weak lensing signal (cosmic shear) has been shown to be strongly contaminated by the various types of galaxy intrinsic alignment (IA) correlations, which poses a barrier to precision weak lensing measurements. The redshift dependence of the IA signal has been used at the 2-point level to reduce this contamination by only measuring cross-correlations between large redshift bins, which significantly reduces the galaxy intrinsic ellipticity - intrinsic ellipticity (II) correlation. A self-calibration technique based on the redshift dependences of the IA correlations has also been proposed as a means to remove the 2-point IA contamination from the lensing signal. We explore here the redshift dependences of the IA and lensing bispectra in order to propose a self-calibration of the IA auto-correlations at the 3-point level (i.e. GGI, GII, and III), which can be well understood without the assumption of any particular IA model. We find that future weak lensing surveys will be able to measure the distinctive IA redshift dependence over ranges of $|\\Delta z^P|\\le 0.2$. Using conservative estimates of photo-z accuracy, we describe the 3-point self-calibration technique for the total IA signal, which can be accomplished through lensing tomography of photo-z bin size $\\sim 0.01$. We find that the 3-point self-calibration can function at the accuracy of the 2-point technique with modest constraints in redshift separation. This allows the 3-point IA auto-correlation self-calibration technique proposed here to significantly reduce the contamination of the IA contamination to the weak lensing bispectrum.
Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky,; /KIPAC, Menlo Park /Bonn, Inst. Astrophys. /Arizona U., Astron. Dept. - Steward Observ. /Florida U. /Harvard-Smithsonian Ctr. Astrophys.
2006-09-27T23:59:59.000Z
The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of ''weakly'' lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004, 2006a) that the total mass does not trace the baryonic mass.
Distortion of the luminosity function of high-redshift galaxies by gravitational lensing
Fialkov, Anastasia
2015-01-01T23:59:59.000Z
The observed properties of high redshift galaxies depend on the underlying foreground distribution of large scale structure, which distorts their intrinsic properties via gravitational lensing. We focus on the regime where the dominant contribution originates from a single lens and examine the statistics of gravitational lensing by a population of virialized and non-virialized structures using sub-mm galaxies at z ~ 2.6 and Lyman-break galaxies at redshifts z ~ 6-15 as the background sources. We quantify the effect of lensing on the luminosity function of the high redshift sources, focusing on the intermediate and small magnifications (mu < 3) which affect the majority of the background galaxies. We show that depending on the intrinsic properties of the background galaxies, gravitational lensing can significantly affect the observed luminosity function even when no obvious strong lenses are present. Finally, we find that in the case of the Lyman-break galaxies it is important to account for the surface bri...
Testing gravity on kiloparsec scales with strong gravitational lenses
Tristan L. Smith
2010-04-12T23:59:59.000Z
Modifications to GR generically predict time and scale-dependent effects which may be probed by observations of strong lensing by galaxies. Measurements of the stellar velocity dispersion determine the dynamical mass whereas measurements of the Einstein radius determine the lensing mass. In GR these two masses are equal; in alternative gravity theories they may not be. Using measurements of the stellar velocity dispersion and strong lensing around galaxies from the Sloan Lens ACS (SLACS) survey we place constraints on lensing in modified gravity theories and extend previous studies by applying this data to explore its dependence on various properties of the lens such as the lens redshift or mass and thereby constrain scalar-tensor, f(R) gravity theories, and generic parameterizations of deviations from GR. Besides applying the observations to these specific gravity theories, the data places a constraint on a generic dependence of modifications to GR on the lens mass and redshift. At the 68% confidence level we find that the ratio between the lensing and dynamical masses can only vary by less then 50% over a mass range for the lens galaxies of 1E12 < M/Msun < 1E14 and less than 40% over the redshift range 0.06 < z < 0.36.
Gravitational Lensing Limits on Cold Dark Matter and Its Variants
Christopher S. Kochanek
1994-11-19T23:59:59.000Z
Standard $\\Omega_0=1$ cold dark matter (CDM) needs $0.27 < \\sigma_8 < 0.63$ ($2\\sigma$) to fit the observed number of large separation lenses, and the constraint is nearly independent of $H_0=100h^{-1}\\kms$ Mpc$^{-1}$. This range is strongly inconsistent with the COBE estimate of $\\sigma_8=(2.8\\pm0.2)h$. Tilting the primordial spectrum $\\propto k^n$ from $n=1$ to $0.3 \\ltorder n \\ltorder 0.7$, using an effective Hubble constant of $0.15 \\ltorder \\Gamma=h \\ltorder 0.30$, or reducing the matter density to $0.15 \\ltorder \\Omega_0 h \\ltorder 0.3$ either with no cosmological constant ($\\lambda_0=0$) or in a flat universe with a cosmological constant ($\\Omega_0+\\lambda_0=1$) can bring the lensing estimate of $\\sigma_8$ into agreement with the COBE estimates. The models and values for $\\sigma_8$ consistent with both lensing and COBE match the estimates from the local number density of clusters and correlation functions. The conclusions are insensitive to systematic errors except for the assumption that cluster core radii are singular. If clusters with $\\rho\\propto(r^2+s^2)^{-1}$ have core radii exceeding $s = 15h^{-1}\\sigma_3^2$ kpc for a cluster with velocity dispersion $\\sigma=10^3\\sigma_3 \\kms$ then the estimates are invalid. There is, however, a fine tuning problem in making the cluster core radii large enough to invalidate the estimates of $\\sigma_8$ while producing several lenses that do not have central or ``odd images.'' The estimated completeness of the current samples of lenses larger than $5\\parcs0$ is 20\\%, because neither quasar surveys nor lens surveys are optimized to this class of lenses.
Resolving the High Energy Universe with Strong Gravitational Lensing: The Case of PKS 1830-211
Barnacka, Anna; Dell'Antonio, Ian P; Benbow, Wystan
2015-01-01T23:59:59.000Z
Gravitational lensing is a potentially powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission from distance sources and produce time delays between mirage images. Gravitationally-induced time delays depend on the position of the emitting regions in the source plane. The Fermi/LAT satellite continuously monitors the entire sky and detects gamma-ray flares, including those from gravitationally-lensed blazars. Therefore, temporal resolution at gamma-ray energies can be used to measure these time delays, which, in turn, can be used to resolve the origin of the gamma-ray flares spatially. We provide a guide to the application and Monte Carlo simulation of three techniques for analyzing these unresolved light curves: the Autocorrelation Function, the Double Power Spectrum, and the Maximum Peak Method. We apply these methods to derive time delays from the gamma-ray light curve of the gravitationally-lensed blazar PKS 1830-211. The result of temporal an...
Gravitational Lensing by Power-Law Mass Distributions: A Fast and Exact Series Approach
Kyu-Hyun Chae; Valery K. Khersonsky; David A. Turnshek
1998-08-31T23:59:59.000Z
We present an analytical formulation of gravitational lensing using familiar triaxial power-law mass distributions, where the 3-dimensional mass density is given by $\\rho(X,Y,Z) = \\rho_0 [1 + (\\frac{X}{a})^2 + (\\frac{Y}{b})^2 + (\\frac{Z}{c})^2]^{-\
High-Resolution Radio Imaging of Gravitational Lensing Candidates in the 1 Jansky BL Lac Sample
T. A. Rector; J. T. Stocke
2003-02-19T23:59:59.000Z
While BL Lacertae objects are widely believed to be highly beamed, low-luminosity radio galaxies, many radio-selected BL Lacs have extended radio power levels and optical emission lines that are too luminous to be low-luminosity radio galaxies. Also, Stocke & Rector discovered an excess of MgII absorption systems along BL Lac sightlines compared to quasars, suggesting that gravitational lensing may be another means of creating the BL Lac phenomenon in some cases. We present a search for gravitationally-lensed BL Lacs with deep, high-resolution, two-frequency VLA radio maps of seven lensing candidates from the 1 Jansky BL Lac sample. We find that none of these objects are resolved into an Einstein ring like B 0218+357, nor do any show multiple images of the core. All of the lensing candidates that were resolved show a flat-spectrum core and very unusual, steep-spectrum extended morphology that is incompatible with a multiply lensed system. Thus, while these observations do not rule out microlensing, no macrolensing is observed.
Obinna Umeh; Chris Clarkson; Roy Maartens
2014-09-22T23:59:59.000Z
The next generation of telescopes will usher in an era of precision cosmology, capable of determining the cosmological model to beyond the percent level. For this to be effective, the theoretical model must be understood to at least the same level of precision. A range of subtle relativistic effects remain to be explored theoretically, and offer the potential for probing general relativity in this new regime. We present the distance-redshift relation to second order in cosmological perturbation theory for a general dark energy model. This relation determines the magnification of sources at high precision, as well as redshift space distortions in the mildly non-linear regime. We identify a range of new lensing effects, including: double-integrated and nonlinear integrated Sach-Wolfe contributions, transverse Doppler effects, lensing from the induced vector mode and gravitational wave backgrounds, in addition to lensing from the second-order potential. Modifications to Doppler lensing from redshift-space distortions are identified. Finally, we find a new double-coupling between the density fluctuations integrated along the line of sight, and gradients in the density fluctuations coupled to transverse velocities along the line of sight. These can be large and thus offer important new probes of gravitational lensing and general relativity. This paper accompanies arXiv:1402.1933, where a comprehensive derivation is given.
Sources of contamination to weak lensing three-point statistics: constraints from N-body simulations
Elisabetta Semboloni; Catherine Heymans; Ludovic van Waerbeke; Peter Schneider
2008-02-27T23:59:59.000Z
We investigate the impact of the observed correlation between a galaxies shape and its surrounding density field on the measurement of third order weak lensing shear statistics. Using numerical simulations, we estimate the systematic error contribution to a measurement of the third order moment of the aperture mass statistic (GGG) from three-point intrinsic ellipticity correlations (III), and the three-point coupling between the weak lensing shear experienced by distant galaxies and the shape of foreground galaxies (GGI and GII). We find that third-order weak lensing statistics are typically more strongly contaminated by these physical systematics compared to second-order shear measurements, contaminating the measured three-point signal for moderately deep surveys with a median redshift z_m ~ 0.7 by ~ 15%. It has been shown that accurate photometric redshifts will be crucial to correct for this effect, once a model and the redshift dependence of the effect can be accurately constrained. To this end we provide redshift-dependent fitting functions to our results and propose a new tool for the observational study of intrinsic galaxy alignments. For a shallow survey with z_m ~ 0.4 we find III to be an order of magnitude larger than the expected cosmological GGG shear signal. Compared to the two-point intrinsic ellipticity correlation which is similar in amplitude to the two-point shear signal at these survey depths, third order statistics therefore offer a promising new way to constrain models of intrinsic galaxy alignments. Early shallow data from the next generation of very wide weak lensing surveys will be optimal for this type of study.
Graham P. Smith
2002-01-15T23:59:59.000Z
We are conducting a systematic lensing survey of X-ray luminous galaxy clusters at z~0.2 using the Hubble Space Telescope and large ground-based telescopes. We summarize initial results from our survey, including a measurement of the inner slope of the mass profile of A383, and a search for gravitationally lensed Extremely Red Objects.
Effects of Gravitational Lensing in the Double Pulsar System J0737-3039
Lai, D; Lai, Dong; Rafikov, Roman R.
2004-01-01T23:59:59.000Z
We investigate the effects of gravitational lensing in the binary pulsar system J0737-3039. Current measurement of the orbital inclination (i=90.26\\pm 0.13) allows the millisecond pulsar (A) to pass very close (at R_{min}=4000 km) in projection to the companion pulsar (B), with R_{min} comparable to the Einstein radius (2600 km). For this separation at the conjunction, lensing causes small (about 10%) magnification of the pulsar A signal on a timescale of several seconds, and displaces the pulsar image on the sky plane by about 1200 km. More importantly, lensing introduces a correction (of several microsec) to the conventional Shapiro delay formula used in pulsar timing analysis, and gives rise to a geometric time delay together with the delays associated with the pulsar spin period. These lensing effects can influence the determination of the system parameters by both timing and scintillation studies. Given the current uncertainty in the orbital inclination, more extreme manifestations of lensing (e.g. magni...
The Optical Gravitational Lensing Experiment. the Early Warning System
A. Udalski; M. Szymanski; J. Kaluzny; M. Kubiak; M. Mateo; W. Krzeminski; B. Paczynski
1994-08-08T23:59:59.000Z
The discoveries of 17 microlensing event candidates have been reported over the last year by three teams conducting unprecedented mass photometric searches in the direction of the Galactic bulge and the Magellanic Clouds. These include 10 events found by the OGLE collaboration, 5 by the MACHO team and 2 by the EROS team. All searches have the main goal to detect dark matter in our Galaxy. The detection of 17 event candidates proves that the microlensing is a powerful tool in the search for dark matter, and it may be used for reliable mass determination when the geometry of the event is known. Here we present the first microlensing event, OGLE~\\#11, discovered in real time, using the newly implemented "Early Warning System". We describe our system which makes it possible to monitor and study in great details any very rare phenomena, not only lensing events, with a broad array of instruments almost immediately after they have changed their brightness.
Spatial and Temporal Variations of Light Curves in Gravitationally Lensed Sources
A. A. Minakov; V. G. Vakulik
2004-01-06T23:59:59.000Z
Effects of macro-and microlensing on the spatial and temporal characteristics of images of remote sources, observed through the inner regions of lensing galaxies are discussed. A particular attention was given to the case, when microlenses, - stars, star-like or planetary bodies, - are situated near the critical curves of macrolenses, - galaxies, stellar clusters, etc. The investigation is of interest for the gravitational lens (GL) systems, where the lensed images are observed close to the critical curve of a macrolens. Annular, arched or confluent images should be regarded as an indication to such a proximity. Numerical simulation allowed to determine the structure of critical curves and caustics, formed by macro and microlenses, and to evaluate possible distortions, caused by microlenses for various locations with respect to the critical curve of a regular lens. The difference of our results from those obtained earlier with the standard (linearized) approach to describe the regular gravitational lens was shown to be the larger the closer to the critical curve the microlenses are situated. In addition to spatial redistributions in the visible images, complicated deformation of their light curves occurs in gravitational lensing of variable in time and extended sources. The magnitude of the temporal variations depend not only on the GL parameters (e.g., mass distribution), but on the parameters of the source as well, such as linear dimension of the emitting region, its location with respect to the critical curve, and the impulse duration. The analysis shows, that in this case GL acts as a filter, which passes slow temporal variations without degradations, and smoothes the rapid ones.
Space Warps: I. Crowd-sourcing the Discovery of Gravitational Lenses
Marshall, Phil; More, Anupreeta; Davis, Chris; More, Surhud; Kapadia, Amit; Parrish, Michael; Snyder, Chris; Wilcox, Julianne; Baeten, Elisabeth; Macmillan, Christine; Cornen, Claude; Baumer, Michael; Simpson, Edwin; Lintott, Chris; Miller, David; Paget, Edward; Simpson, Robert; Smith, Arfon; Kueng, Rafael; Saha, Prasenjit; Collett, Tom; Tecza, Matthias
2015-01-01T23:59:59.000Z
We describe Space Warps, a novel gravitational lens discovery service that yields samples of high purity and completeness through crowd-sourced visual inspection. Carefully produced colour composite images are displayed to volunteers via a classi- fication interface which records their estimates of the positions of candidate lensed features. Simulated lenses, and expert-classified images which lack lenses, are inserted into the image stream at random intervals; this training set is used to give the vol- unteers feedback on their performance, as well as to calibrate it in order to allow dynamical updates to the probability of any image they classify to contain a lens. Low probability systems are retired from the site periodically, concentrating the sample towards a set of candidates. Having divided 160 square degrees of Canada-France- Hawaii Telescope Legacy Survey (CFHTLS) imaging into some 430,000 overlapping 84 by 84 arcsecond tiles and displaying them on the site, we were joined by around 37,000 volunteers...
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Petri, Andrea [Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States); May, Morgan [Brookhaven National Laboratory (BNL), Upton, NY (United States); Haiman, Zoltan [Columbia Univ., New York, NY (United States); Kratochvil, Jan M. [Univ. of KwaZulu-Natal, Durban (South Africa)
2014-12-01T23:59:59.000Z
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?m,w,?8) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from the PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?sys2?10-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg2, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
Petri, Andrea [Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States); May, Morgan [Brookhaven National Laboratory (BNL), Upton, NY (United States); Haiman, Zoltan [Columbia Univ., New York, NY (United States); Kratochvil, Jan M. [Univ. of KwaZulu-Natal, Durban (South Africa)
2014-12-01T23:59:59.000Z
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?_{m},w,?_{8}) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from the PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?_{sys}^{2}?10^{-7}, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg^{2}, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Petri, Andrea; May, Morgan; Haiman, Zoltan; Kratochvil, Jan M.
2014-12-01T23:59:59.000Z
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?m,w,?8) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from themore »PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?sys2?10-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg2, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.« less
Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey
Canameras, R; Guery, D; McKenzie, T; Koenig, S; Petitpas, G; Dole, H; Frye, B; Flores-Cacho, I; Montier, L; Negrello, M; Beelen, A; Boone, F; Dicken, D; Lagache, G; Floch, E Le; Altieri, B; Bethermin, M; Chary, R; De Zotti, G; Giard, M; Kneissl, R; Krips, M; Malhotra, S; Martinache, C; Omont, A; Pointecouteau, E; Puget, J -L; Scott, D; Soucail, G; Valtchanov, I; Welikala, N; Yan, L
2015-01-01T23:59:59.000Z
We present an analysis of 11 bright far-IR/submm sources discovered through a combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each source has a redshift z=2.2-3.6 obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA, and optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um and 2 mm, respectively. All objects are bright, isolated point sources in the 18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking either near the 350 um or the 500 um bands of SPIRE, and with apparent far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes, CO line widths and luminosities, dust temperatures, and far-infrared luminosities provide additional empirical evidence that these are strongly gravitationally lensed high-redshift gala...
Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Liu, Jia [Department of Astronomy and Astrophysics, Columbia University, New York, NY, (United States); May, Morgan [Physics Department, Brookhaven National Laboratory, Upton, NY, (United States); Petri, Andrea [Department of Physics, Columbia University, New York, NY, (United States); Haiman, Zoltan [Department of Astronomy and Astrophysics, Columbia University, New York, NY, (United States); Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP), Columbia University, New York, (United States); Hui, Lam [Department of Physics, Columbia University, New York, NY, (United States); Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP), Columbia University, New York, (United States); Kratochvil, Jan M. [Astrophysics and Cosmology Research Unit, University of KwaZulu-Natal, Westville, Durban, (South Africa)
2015-03-01T23:59:59.000Z
Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters ?m, ?8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of ? 5%, and compute the likelihood in the three-dimensional parameter space (?m, ?8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (?m, ?8) plane reduces by a factor of ? two, compared to using the power spectrum alone. For a flat ? cold dark matter model, combining both statistics, we obtain the constraint ?8(?m/0.27)0.63 = 0.85+0.03-0.03.
Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Liu, Jia; May, Morgan; Petri, Andrea; Haiman, Zoltan; Hui, Lam; Kratochvil, Jan M.
2015-03-01T23:59:59.000Z
Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters ?m, ?8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator thatmore »interpolates the power spectrum and the peak counts to an accuracy of ? 5%, and compute the likelihood in the three-dimensional parameter space (?m, ?8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (?m, ?8) plane reduces by a factor of ? two, compared to using the power spectrum alone. For a flat ? cold dark matter model, combining both statistics, we obtain the constraint ?8(?m/0.27)0.63 = 0.85+0.03-0.03.« less
Antonio C. C. Guimarães; Laerte Sodré Jr.
2007-06-21T23:59:59.000Z
We readdress the calculation of the mass of early-type galaxies using strong gravitational lensing and stellar dynamics. Our sample comprises 27 galaxies in the Sloan Lens ACS (SLACS) Survey. Comparing the mass estimates from these two independent methods in a Bayesian framework, we find evidence of significant line-of-sight mass contamination. Assuming a power-law mass distribution, the best fit density profile is given by $\\rho \\propto r^{-1.69\\pm0.05}$. We show that neglecting the line-of-sight mass contamination produces an overestimate of the mass attributed to the lens-galaxy by the lensing method, which introduces a bias in favor of a SIS profile when using the joint lensing and dynamic analysis to determine the slope of the density profile. We suggest that the line-of-sight contamination could also be important for other astrophysical and cosmological uses of joint lensing and dynamical measurements.
A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Redshift Catalog
Momcheva, Ivelina; Cool, Richard J; Keeton, Charles R; Zabludoff, Ann I
2015-01-01T23:59:59.000Z
We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multi-object spectrographs. We determine that no biases are introduced by combining datasets obtained with different instrument/spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large scale structure on lens statistics and lens-derived parameters.
Degeneracies and scaling relations in general power-law models for gravitational lenses
Olaf Wucknitz
2002-02-20T23:59:59.000Z
The time delay in gravitational lenses can be used to derive the Hubble constant in a relatively simple way. The results of this method are less dependent on astrophysical assumptions than in many other methods. The most important uncertainty is related to the mass model used. We discuss a family of models with a separable radial power-law and an arbitrary angular dependence for the potential psi = r^beta * F(theta). Isothermal potentials are a special case of these models with beta=1. An additional external shear is used to take into account perturbations from other galaxies. Using a simple linear formalism for quadruple lenses, we can derive H0 as a function of the observables and the shear. If the latter is fixed, the result depends on the assumed power-law exponent according to H0 proportional to (2-beta)/beta. The effect of external shear is quantified by introducing a `critical shear' gamma_c as a measure for the amount of shear that changes the result significantly. The analysis shows, that in the general case H0 and gamma_c do not depend on the position of the lens galaxy. We discuss these results and compare with numerical models for a number of real lens systems.
Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar
Oliver James; Eugenie von Tunzelmann; Paul Franklin; Kip S. Thorne
2015-02-16T23:59:59.000Z
Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie \\emph{Interstellar}, were generated with DNGR. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting.
Systematic Errors in Future Weak Lensing Surveys: Requirements and Prospects for Self-Calibration
Dragan Huterer; Masahiro Takada; Gary Bernstein; Bhuvnesh Jain
2005-06-02T23:59:59.000Z
We study the impact of systematic errors on planned weak lensing surveys and compute the requirements on their contributions so that they are not a dominant source of the cosmological parameter error budget. The generic types of error we consider are multiplicative and additive errors in measurements of shear, as well as photometric redshift errors. In general, more powerful surveys have stronger systematic requirements. For example, for a SNAP-type survey the multiplicative error in shear needs to be smaller than 1%(fsky/0.025)^{-1/2} of the mean shear in any given redshift bin, while the centroids of photometric redshift bins need to be known to better than 0.003(fsky/0.025)^{-1/2}. With about a factor of two degradation in cosmological parameter errors, future surveys can enter a self-calibration regime, where the mean systematic biases are self-consistently determined from the survey and only higher-order moments of the systematics contribute. Interestingly, once the power spectrum measurements are combined with the bispectrum, the self-calibration regime in the variation of the equation of state of dark energy w_a is attained with only a 20-30% error degradation.
Rapoport, Sharon; Onken, Christopher A.; Schmidt, Brian P.; Tucker, Brad E. [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Wyithe, J. Stuart B. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)
2012-08-01T23:59:59.000Z
Sixty percent of gamma-ray bursts (GRBs) reveal strong Mg II absorbing systems, which is a factor of {approx}2 times the rate seen along lines of sight to quasars. Previous studies argue that the discrepancy in the strong Mg II covering factor is most likely to be the result of either quasars being obscured due to dust or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of quasars that show strong foreground Mg II absorption. We find that GRB lines of sight pass closer to bright galaxies than would be expected for random lines of sight within the impact parameter expected for strong Mg II absorption. While this cannot be explained by obscuration in the GRB sample, it is a natural consequence of gravitational lensing. Upon examining the particular configurations of galaxies near a sample of GRBs with strong Mg II absorption, we find several intriguing lensing candidates. Our results suggest that lensing provides a viable contribution to the observed enhancement of strong Mg II absorption along lines of sight to GRBs, and we outline the future observations required to test this hypothesis conclusively.
Testing a phenomenologically extended DGP model with upcoming weak lensing surveys
Camera, Stefano; Diaferio, Antonaldo [Dipartimento di Fisica Generale ''A. Avogadro'', Università di Torino, via P. Giuria 1, 10125 Torino (Italy); Cardone, Vincenzo F., E-mail: camera@ph.unito.it, E-mail: diaferio@ph.unito.it, E-mail: winnyenodrac@gmail.com [Dipartimento di Scienze e Tecnologie per l'Ambiente e il Territorio, Università degli Studi del Molise, Contrada Fonte Lappone, 86090 Pesche (Italy)
2011-01-01T23:59:59.000Z
A phenomenological extension of the well-known brane-world cosmology of Dvali, Gabadadze and Porrati (eDGP) has recently been proposed. In this model, a cosmological-constant-like term is explicitly present as a non-vanishing tension ? on the brane, and an extra parameter ? tunes the cross-over scale r{sub c}, the scale at which higher dimensional gravity effects become non negligible. Since the Hubble parameter in this cosmology reproduces the same ?CDM expansion history, we study how upcoming weak lensing surveys, such as Euclid and DES (Dark Energy Survey), can confirm or rule out this class of models. We perform Monte Carlo Markov Chain simulations to determine the parameters of the model, using Type Ia Supernovæ, H(z) data, Gamma Ray Bursts and Baryon Acoustic Oscillations. We also fit the power spectrum of the temperature anisotropies of the Cosmic Microwave Background to obtain the correct normalisation for the density perturbation power spectrum. Then, we compute the matter and the cosmic shear power spectra, both in the linear and non-linear régimes. The latter is calculated with the two different approaches of Hu and Sawicki (2007) (HS) and Khoury and Wyman (2009) (KW). With the eDGP parameters coming from the Markov Chains, KW reproduces the ?CDM matter power spectrum at both linear and non-linear scales and the ?CDM and eDGP shear signals are degenerate. This result does not hold with the HS prescription. Indeed, Euclid can distinguish the eDGP model from ?CDM because their expected power spectra roughly differ by the 3? uncertainty in the angular scale range 700?
Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data
Chang, C.; Marshall, P.J.; Jernigan, J.G.; Peterson, J.R.; Kahn, S.M.; Gull, S.F.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Meert, A.
2012-09-19T23:59:59.000Z
A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time ({approx_equal}15 seconds) proposed, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multi-scale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, psfent, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a 5th-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, psfent predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than {approx} 13, compared to polynomial fitting. We estimate that with psfent and for stellar densities greater than {approx_equal}1/arcmin{sup 2}, the spurious shear correlation from PSF interpolation, after combining a complete 10-year dataset from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.
Neronov, A
2015-01-01T23:59:59.000Z
We show that observation of the time-dependent effect of microlensing of relativistically broadened emission lines (such as e.g. the Fe Kalpha line in X-rays) in strongly lensed quasars could provide data on celestial mechanics of circular orbits in the direct vicinity of the horizon of supermassive black holes. This information can be extracted from the observation of evolution of red / blue edge of the magnified line just before and just after the period of crossing of the innermost stable circular orbit by the microlensing caustic. The functional form of this evolution is insensitive to numerous astrophysical parameters of the accreting black hole and of the microlensing caustics network system (as opposed to the evolution the full line spectrum). Measurement of the temporal evolution of the red / blue edge could provide a precision measurement of the radial dependence of the gravitational redshift and of velocity of the circular orbits, down to the innermost stable circular orbit. These measurements could...
OGLE-IV: Fourth Phase of the Optical Gravitational Lensing Experiment
Udalski, A; Szyma?ski, G
2015-01-01T23:59:59.000Z
We present both the technical overview and main science drivers of the fourth phase of the Optical Gravitational Lensing Experiment (hereafter OGLE-IV). OGLE-IV is currently one of the largest sky variability surveys worldwide, targeting the densest stellar regions of the sky. The survey covers over 3000 square degrees in the sky and monitors regularly over a billion sources. The main targets include the inner Galactic Bulge and the Magellanic System. Their photometry spans the range of $12
On the Bias of the Distance-Redshift Relation from Gravitational Lensing
Kaiser, Nick
2015-01-01T23:59:59.000Z
A long standing question in cosmology is whether gravitational lensing changes the distance-redshift relation $D(z)$ or the mean flux density of sources. Interest in this has been rekindled by recent studies in non-linear relativistic perturbation theory that find biases in both the area of a surface of constant redshift and in the mean distance to this surface, with a fractional bias in both cases on the order of the mean squared convergence $\\langle \\kappa^2 \\rangle$. Any such area bias could alter CMB cosmology, and the corresponding bias in mean flux density could affect supernova cosmology. Here we show that, in an ensemble averaged sense, the perturbation to the area of a surface of constant redshift is in reality much smaller, being on the order of the cumulative bending angle squared, or roughly a part-in-a-million effect. This validates the arguments of Weinberg (1976) that the mean magnification $\\mu$ of sources is unity and of Kibble \\& Lieu (2005) that the mean direction-averaged inverse magni...
Simet, Melanie; Dodelson, Scott [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Kubo, Jeffrey M.; Annis, James T.; Hao Jiangang; Johnston, David; Lin, Huan; Soares-Santos, Marcelle [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Reis, Ribamar R. R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil); Seo, Hee-Jong [Berkeley Center for Cosmological Physics and Berkeley Lab, University of California, Berkeley, CA 94720 (United States)
2012-04-01T23:59:59.000Z
The shapes of distant galaxies are sheared by intervening galaxy clusters. We examine this effect in Stripe 82, a 275 deg{sup 2} region observed multiple times in the Sloan Digital Sky Survey (SDSS) and co-added to achieve greater depth. We obtain a mass-richness calibration that is similar to other SDSS analyses, demonstrating that the co-addition process did not adversely affect the lensing signal. We also propose a new parameterization of the effect of tomography on the cluster lensing signal which does not require binning in redshift, and we show that using this parameterization we can detect tomography for stacked clusters at varying redshifts. Finally, due to the sensitivity of the tomographic detection to accurately marginalize over the effect of the cluster mass, we show that tomography at low redshift (where dependence on exact cosmological models is weak) can be used to constrain mass profiles in clusters.
Weak Gravitational Field in Finsler-Randers Space and Raychaudhuri Equation
P. Stavrinos
2012-09-13T23:59:59.000Z
The linearized form of the metric of a Finsler - Randers space is studied in relation to the equations of motion, the deviation of geodesics and the generalized Raychaudhuri equation are given for a weak gravitational field. This equation is also derived in the framework of a tangent bundle. By using Cartan or Berwald-like connections we get some types "gravito - electromagnetic" curvature. In addition we investigate the conditions under which a definite Lagrangian in a Randers space leads to Einstein field equations under the presence of electromagnetic field. Finally, some applications of the weak field in a generalized Finsler spacetime for gravitational waves are given.
Constraining primordial non-Gaussianity with cosmological weak lensing: shear and flexion
Fedeli, C. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Bartelmann, M. [Zentrum für Astronomie, Universität Heidelberg, Albert-Überle-Straße 2, 69120 Heidelberg (Germany); Moscardini, L., E-mail: cosimo.fedeli@astro.ufl.edu, E-mail: bartelmann@uni-heidelberg.de, E-mail: lauro.moscardini@unibo.it [Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, 40127 Bologna (Italy)
2012-10-01T23:59:59.000Z
We examine the cosmological constraining power of future large-scale weak lensing surveys on the model of the ESA planned mission Euclid, with particular reference to primordial non-Gaussianity. Our analysis considers several different estimators of the projected matter power spectrum, based on both shear and flexion. We review the covariance and Fisher matrix for cosmic shear and evaluate those for cosmic flexion and for the cross-correlation between the two. The bounds provided by cosmic shear alone are looser than previously estimated, mainly due to the reduced sky coverage and background number density of sources for the latest Euclid specifications. New constraints for the local bispectrum shape, marginalized over ?{sub 8}, are at the level of ?f{sub NL} ? 100, with the precise value depending on the exact multipole range that is considered in the analysis. We consider three additional bispectrum shapes, for which the cosmic shear constraints range from ?f{sub NL} ? 340 (equilateral shape) up to ?f{sub NL} ? 500 (orthogonal shape). Also, constraints on the level of non-Gaussianity and on the amplitude of the matter power spectrum ?{sub 8} are almost perfectly anti-correlated, except for the orthogonal bispectrum shape for which they are correlated. The competitiveness of cosmic flexion constraints against cosmic shear ones depends by and large on the galaxy intrinsic flexion noise, that is still virtually unconstrained. Adopting the very high value that has been occasionally used in the literature results in the flexion contribution being basically negligible with respect to the shear one, and for realistic configurations the former does not improve significantly the constraining power of the latter. Since the shear shot noise is white, while the flexion one decreases with decreasing scale, by considering high enough multipoles the two contributions have to become comparable. Extending the analysis up to l{sub max} = 20,000 cosmic flexion, while being still subdominant, improves the shear constraints by ? 10% when added. However on such small scales the highly non-linear clustering of matter, the impact of baryonic physics, and the non-Gaussian part of the covariance matrix make any error estimation uncertain. By considering lower, and possibly more realistic, values of the flexion intrinsic shape noise results in flexion constraining power being a factor of ? 2 better than that of shear, and the bounds on ?{sub 8} and f{sub NL} being improved by a factor of ? 3 upon their combination.
Multipole Models of Four-Image Gravitational Lenses with Anomalous Flux Ratios
Arthur B. Congdon; Charles R. Keeton
2005-10-07T23:59:59.000Z
Anomalous radio flux ratios in four-image gravitational lens systems can be explained by adding a clumpy cold dark matter (CDM) component to the potential of the lens galaxy. Evans & Witt (2003) recently suggested that smooth multipole perturbations can provide a reasonable alternative to CDM substructure in some but not all cases. We generalize their method in two ways so as to determine whether multipole models can explain highly anomalous systems. We carry the multipole expansion to higher order, and also include external tidal shear as a free parameter. Fitting for the shear proves crucial to finding a physical (positive-definite density) model. For B1422+231, working to order k = 5 (and including shear) yields a model that is physical but implausible. Going to higher order (k >~ 9) reduces global departures from ellipticity at the cost of introducing small scale wiggles near the bright images. These localized undulations are more pronounced in B2045+265, where k ~ 17 multipoles are required to smooth out large scale deviations from elliptical symmetry. Such modes surely cannot be taken at face value; they must indicate that the models are trying to reproduce some other sort of structure. Our formalism naturally finds models that fit the data exactly, but we use B0712+472 to show that measurement uncertainties have little effect on our results. Finally, we consider the system B1933+503, where two sources are lensed by the same foreground galaxy. The additional constraints provided by the images of the second source render the multipole model unphysical. We conclude that external shear must be taken into account to obtain plausible models, and that a purely smooth angular structure for the lens galaxy does not provide a viable alternative to the prevailing CDM clump hypothesis.
New Dimensions in Cosmic Lensing
Andy Taylor
2003-06-13T23:59:59.000Z
I review the current status of combing weak gravitational lensing with depth information from redshifts as a direct probe of dark matter and dark energy in the Universe. In particular I highlight: (1) The first maximum likelihood measurement of the cosmic shear power spectrum, with the COMBO17 dataset (Brown et al 2003); (2) A new method for mapping the 3-D dark matter distribution from weak shear, and its first application to the COMBO17 dataset (Taylor et al 2003); (3) A new method for measuring the Dark Energy of the Universe using purely the geometry of gravitational lensing, based on cross-correlation tomography (Jain & Taylor 2003). I show that this method can constrain the equation of state of the universe and its evolution to a few percent accuracy.
Gravitational ultrarelativistic spin-orbit interaction and the weak equivalence principle
Roman Plyatsko
2005-07-07T23:59:59.000Z
It is shown that the gravitational ultrarelativistic spin-orbit interaction violates the weak equivalence principle in the traditional sense. This fact is a direct consequence of the Mathisson-Papapetrou equations in the frame of reference comoving with a spinning test particle. The widely held assumption that the deviation of a spinning test body from a geodesic trajectory is caused by tidal forces is not correct
Clowe, Douglas [Department of Physics and Astronomy, Ohio University, 251B Clippinger Labs, Athens, OH 45701 (United States); Markevitch, Maxim [NASA Goddard Space Flight Center, Code 662, 8800 Greenbelt Road, Greenbelt, MD 20706 (United States); Bradac, Marusa [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, Anthony H.; Chung, Sun Mi [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Massey, Richard [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Zaritsky, Dennis, E-mail: clowe@ohio.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
2012-10-20T23:59:59.000Z
Merging clusters of galaxies are unique in their power to directly probe and place limits on the self-interaction cross-section of dark matter. Detailed observations of several merging clusters have shown the intracluster gas to be displaced from the centroids of dark matter and galaxy density by ram pressure, while the latter components are spatially coincident, consistent with collisionless dark matter. This has been used to place upper limits on the dark matter particle self-interaction cross-section of order 1 cm{sup 2} g{sup -1}. The cluster A520 has been seen as a possible exception. We revisit A520 presenting new Hubble Space Telescope Advanced Camera for Surveys mosaic images and a Magellan image set. We perform a detailed weak-lensing analysis and show that the weak-lensing mass measurements and morphologies of the core galaxy-filled structures are mostly in good agreement with previous works. There is, however, one significant difference: We do not detect the previously claimed 'dark core' that contains excess mass with no significant galaxy overdensity at the location of the X-ray plasma. This peak has been suggested to be indicative of a large self-interaction cross-section for dark matter (at least {approx}5{sigma} larger than the upper limit of 0.7 cm{sup 2} g{sup -1} determined by observations of the Bullet Cluster). We find no such indication and instead find that the mass distribution of A520, after subtraction of the X-ray plasma mass, is in good agreement with the luminosity distribution of the cluster galaxies. We conclude that A520 shows no evidence to contradict the collisionless dark matter scenario.
Cooke, Ryan; Steidel, Charles C; King, Lindsay J; Rudie, Gwen C; Rakic, Olivera
2010-01-01T23:59:59.000Z
The sightline to the brighter member of the gravitationally lensed quasar pair UM 673A,B intersects a damped Lyman-alpha system (DLA) at z = 1.62650 which, because of its low redshift, has not been recognised before. Our high quality echelle spectra of the pair, obtained with HIRES on the Keck I telescope, show a drop in neutral hydrogen column density N(H I) by a factor of at least 400 between UM 673A and B, indicating that the DLA's extent in this direction is much less than the 2.7 kpc separation between the two sightlines at z = 1.62650. By reassessing this new case together with published data on other QSO pairs, we conclude that the typical size (radius) of DLAs at these redshifts is R ~ (5 +/- 3) kpc, smaller than previously realised. Highly ionized gas associated with the DLA is more extended, as we find only small differences in the C IV absorption profiles between the two sightlines. Coincident with UM 673B, we detect a weak and narrow Ly-alpha emission line which we attribute to star formation acti...
Maria Alice Gasparini; Phil Marshall; Tommaso Treu; Eric Morganson; Florian Dubath
2007-12-21T23:59:59.000Z
We use current theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of angular resolution and survey area. We show that angular resolution is the most important factor, and that interesting limits on the dimensionless string tension Gmu/c^2 can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope (0.14"), it is sufficient to survey of order a few square degrees -- well within reach of the current HST archive -- to probe the regime Gmu/c^2 ~ 10^{-7}. If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by a factor of two over that available from the cosmic microwave background. Future high resolution imaging surveys, covering a few hundred square degrees or more, either from space in the optical or from large-format radio telescopes on the ground, would be able to further lower this limit to Gmu/c^2 < 10^{-8}.
Gasparini, Maria Alice; Marshall, Phil; Treu, Tommaso; /UC, Santa Barbara; Morganson, Eric; /KIPAC, Menlo Park; Dubath, Florian; /Santa Barbara, KITP
2007-11-14T23:59:59.000Z
We use current theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of angular resolution and survey area. We show that angular resolution is the single most important factor, and that interesting limits on the dimensionless string tension G{mu}/c{sup 2} can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope (0'.14), it is sufficient to survey of order a square degree -- well within reach of the current HST archive -- to probe the regime G{mu}/c{sup 2} {approx} 10{sup -8}. If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by an order of magnitude on that available from the cosmic microwave background. At the resolution (0'.028) attainable with the next generation of large ground based instruments, both in the radio and the infra-red with adaptive optics, surveying a sky area of order ten square degrees will allow us to probe the G{mu}/c{sup 2} {approx} 10{sup -9} regime. These limits will not be improved significantly by increasing the solid angle of the survey.
Geach, J E; Verma, A; Marshall, P J; Jackson, N; Belles, P -E; Beswick, R; Baeten, E; Chavez, M; Cornen, C; Cox, B E; Erben, T; Erickson, N J; Garrington, S; Harrison, P A; Harrington, K; Hughes, D H; Ivison, R J; Jordan, C; Lin, Y -T; Leauthaud, A; Lintott, C; Lynn, S; Kapadia, A; Kneib, J -P; Macmillan, C; Makler, M; Miller, G; Montana, A; Mujica, R; Muxlow, T; Narayanan, G; Briain, D O; O'Brien, T; Oguri, M; Paget, E; Parrish, M; Ross, N P; Rozo, E; Rusu, E; Rykoff, E S; Sanchez-Arguelles, D; Simpson, R; Snyder, C; Schloerb, F P; Tecza, M; Van Waerbeke, L; Wilcox, J; Viero, M; Wilson, G W; Yun, M S; Zeballos, M
2015-01-01T23:59:59.000Z
We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (L_IR~10^13 L_sun) with strong radio emission (L_1.4GHz~10^25 W/Hz) at z=2.553. The source was identified in the citizen science project SpaceWarps through the visual inspection of tens of thousands of iJKs colour composite images of Luminous Red Galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (r_e~3") around an LRG at z=0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3-2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [OIII] and H-alpha line detections in the near-infrared from Subaru/IRCS. We have resolved the radio emission with high resolution (300-400 mas) eMERLIN L-band and JVLA C-band imaging. These observations are used in combination with the near-...
Hard Thermal Loops, Weak Gravitational Fields and The Quark Gluon Energy Momentum Tensor
E. A. Gaffney
1994-09-13T23:59:59.000Z
We use an auxiliary field construction to discuss the hard thermal loop effective action associated with massless thermal SU(N) QCD interacting with a weak gravitational field. It is demonstrated that the previous attempt to derive this effective action has only been partially successful and that it is presently only known to first order in the graviton coupling constant. This is still sufficient to enable a calculation of a symmetric traceless quark gluon plasma energy momentum tensor. Finally, we comment on the conserved currents and charges of the derived energy momentum tensor.
Geometrical approach to strong gravitational lensing in f(R) gravity
Nzioki, Anne Marie; Goswami, Rituparno [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 (South Africa); Dunsby, Peter K. S. [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 (South Africa); South African Astronomical Observatory, Observatory, Cape Town (South Africa); Carloni, Sante [Institut d'Estudis Espacials de Catalunya (IEEC), Campus UAB, Facultat Ciencies, Torre C5-Par-2a pl, E-08193 Bellaterra (Barcelona) (Spain)
2011-01-15T23:59:59.000Z
We present a framework for the study of lensing in spherically symmetric spacetimes within the context of f(R) gravity. Equations for the propagation of null geodesics, together with an expression for the bending angle, are derived for any f(R) theory and then applied to an exact spherically symmetric solution of R{sup n} gravity. We find that for this case more bending is expected for R{sup n} gravity theories in comparison to general relativity and is dependent on the value of n and the value of the distance of closest approach of the incident null geodesic.
M. Szymanski; A. Udalski; M. Kubiak; J. Kaluzny; M. Mateo; W. Krzeminski
1996-04-16T23:59:59.000Z
This paper presents the first part of the Optical Gravitational Lensing Experiment (OGLE) General Catalog of Stars in the Galactic bulge. The Catalog is based on observations collected during the OGLE microlensing search. This part contains 33196 stars brighter than I=18mag identified in the Baade's Window BWC field. Stars from remaining 20 OGLE fields will be presented in similar form in the next parts of the Catalog. The Catalog is available to the astronomical community over the Internet network.
Johnston, David E.; Sheldon, Erin S.; Wechsler, Risa H.; Rozo, Eduardo; Koester, Benjamin P.; Frieman, Joshua A.; McKay, Timothy A.; Evrard, August E.; Becker, Matthew; Annis, James
2007-09-28T23:59:59.000Z
We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. (2007). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of {approx} 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.
Dye, S; Swinbank, A M; Vlahakis, C; Nightingale, J W; Dunne, L; Eales, S A; Smail, Ian; Oteo-Gomez, I; Hunter, T; Negrello, M; Dannerbauer, H; Ivison, R J; Gavazzi, R; Cooray, A; van der Werf, P
2015-01-01T23:59:59.000Z
We have modelled Atacama Large Millimeter/sub-millimeter Array (ALMA) long baseline imaging of the strong gravitational lens system H-ATLAS J090311.6+003906 (SDP.81). We have reconstructed the distribution of continuum emission in the z=3.042 source and we have determined its kinematic properties by reconstructing CO line emission. The continuum imaging reveals a highly non-uniform distribution of dust with clumps on scales of ~200pc. In contrast, the CO line emission shows a relatively smooth velocity field which resembles disk-like dynamics. Modelling the velocity field as a rotating disk indicates an inclination angle of (40 +/- 5) degrees, implying an intrinsic asymptotic rotation velocity of 320km/s and a dynamical mass of 3.5x10^{10} M_sol within 1.5kpc. We obtain similar estimates of the total molecular gas mass of 2.7x10^{10} M_sol and 1.4x10^{10} M_sol from the dust continuum emission and CO emission respectively. Our new reconstruction of the lensed HST near-infrared emission shows two objects that ...
Andrei Lebed
2012-05-14T23:59:59.000Z
It is shown that weight operator of a composite quantum body in a weak external gravitational field in the post-Newtonian approximation of the General Relativity does not commute with its energy operator, taken in the absence of the field. Nevertheless, the weak equivalence between the expectations values of weight and energy is shown to survive at a macroscopic level for stationary quantum states for the simplest composite quantum body - a hydrogen atom. Breakdown of the weak equivalence between weight and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported and moved in the Earth gravitational field with constant velocity, using spacecraft or satellite. For superpositions of stationary quantum states, a breakdown of the above mentioned equivalence at a macroscopic level leads to time dependent oscillations of the expectation values of weight, where the equivalence restores after averaging over time procedure.
Buckley-Geer, E J; Lin, H; Drabek, E R; Allam, S S; Tucker, D L; Armstrong, R; Barkhouse, W A; Bertin, E; Brodwin, M; Desai, S; Frieman, J A
2011-11-03T23:59:59.000Z
We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in October 2006 during a BCS observing run. Follow-up spectroscopic observations with the GMOS instrument on the Gemini South 8m telescope confirmed the lensing nature of this system. Using weak plus strong lensing, velocity dispersion, cluster richness N_{200}, and fitting to an NFW cluster mass density profile, we have made three independent estimates of the mass M_{200} which are all very consistent with each other. The combination of the results from the three methods gives M_{200} = (5.1 x 1.3) x 10^{14} _{circle_dot}, which is fully consistent with the individual measurements. The final NFW concentration c_{200} from the combined fit is c_{200} = 5.4_{-1.1}^{+1.4}. We have compared our measurements of M_{200} and c_{200} with predictions for (a) clusters from ?CDM simulations, (b) lensing selected clusters from simulations, and (c) a real sample of cluster lenses. We find that we are most compatible with the predictions for ?CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to ?CDM. Finally, using the flux measured from the [OII]3727 line we have determined the star formation rate (SFR) of the source galaxy and find it to be rather modest given the assumed lens magnification.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Buckley-Geer, E J; Lin, H; Drabek, E R; Allam, S S; Tucker, D L; Armstrong, R; Barkhouse, W A; Bertin, E; Brodwin, M; Desai, S; et al
2011-11-03T23:59:59.000Z
We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in October 2006 during a BCS observing run. Follow-up spectroscopic observations with the GMOS instrument on the Gemini South 8m telescope confirmed the lensing nature of this system. Using weak plus strong lensing, velocity dispersion, cluster richness N200, and fitting to an NFW cluster mass density profile, we havemore »made three independent estimates of the mass M200 which are all very consistent with each other. The combination of the results from the three methods gives M200 = (5.1 x 1.3) x 1014 circle_dot, which is fully consistent with the individual measurements. The final NFW concentration c200 from the combined fit is c200 = 5.4-1.1+1.4. We have compared our measurements of M200 and c200 with predictions for (a) clusters from ?CDM simulations, (b) lensing selected clusters from simulations, and (c) a real sample of cluster lenses. We find that we are most compatible with the predictions for ?CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to ?CDM. Finally, using the flux measured from the [OII]3727 line we have determined the star formation rate (SFR) of the source galaxy and find it to be rather modest given the assumed lens magnification.« less
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Buckley-Geer, E J; Lin, H; Drabek, E R; Allam, S S; Tucker, D L; Armstrong, R; Barkhouse, W A; Bertin, E; Brodwin, M; Desai, S; Frieman, J A
2011-11-03T23:59:59.000Z
We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in October 2006 during a BCS observing run. Follow-up spectroscopic observations with the GMOS instrument on the Gemini South 8m telescope confirmed the lensing nature of this system. Using weak plus strong lensing, velocity dispersion, cluster richness N200, and fitting to an NFW cluster mass density profile, we have made three independent estimates of the mass M200 which are all very consistent with each other. The combination of the results from the three methods gives M200 = (5.1 x 1.3) x 1014 circle_dot, which is fully consistent with the individual measurements. The final NFW concentration c200 from the combined fit is c200 = 5.4-1.1+1.4. We have compared our measurements of M200 and c200 with predictions for (a) clusters from ?CDM simulations, (b) lensing selected clusters from simulations, and (c) a real sample of cluster lenses. We find that we are most compatible with the predictions for ?CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to ?CDM. Finally, using the flux measured from the [OII]3727 line we have determined the star formation rate (SFR) of the source galaxy and find it to be rather modest given the assumed lens magnification.
Marcin Sawicki
2001-02-12T23:59:59.000Z
A 2-hour service-mode SCUBA observation of the gravitationally-lensed Lyman break galaxy MS1512-cB58 resulted in a 3 sigma upper limit of 3.9 mJy at 850um. A comparison of this upper limit with values expected from rest-UV/optical measurements of extiction suggests that dust temperature (T_d) and/or emissivity index (beta) in cB58 may be substantially higher than is seen in local galaxies, or that the attenuation curve in cB58 may be even gentler than the already quite mild SMC dust law. If dust temperature T_d and emissivity index beta in cB58 are similar to those seen in local IRAS-seleceted galaxies, then cB58's dust mass is M_d <~ 10^7.7 Msun and its star formation rate is SFR <~ 10 Msun/yr (for q_0=0.1, H_0=75 km/s/Mpc). This SFR upper limit is lower than the star formation rate measured from Halpha, thus giving further support to the notion that (T_d, beta) values in cB58 are higher than those seen in local galaxies. It thus appears that our understanding of dust in this extensively studied Lyman break galaxy is poor, and observations at other wavelentghs are needed to better understand dust at high redshift. Such observations can be provided by the upcoming SIRTF mission for which cB58's expected flux densities are calculated.
Mahdavi, Andisheh [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94131 (United States); Hoekstra, Henk [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Babul, Arif; Bildfell, Chris [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Jeltema, Tesla [Santa Cruz Institute for Particle Physics, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Henry, J. Patrick [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
2013-04-20T23:59:59.000Z
We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15% {+-} 6% intrinsic scatter at r{sub 500}{sup WL} (the pseudo-pressure Y{sub X} yields a consistent scatter of 22% {+-} 5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small brightest cluster galaxy (BCG) to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller (<10%) deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure Y{sub X} does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r{sub 500}{sup WL}; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15%-20% bias between r{sub 2500}{sup WL} and r{sub 500}{sup WL}, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.
Hamano, Satoshi; Kondo, Sohei; Tsujimoto, Takuji; Okoshi, Katsuya; Shigeyama, Toshikazu
2012-01-01T23:59:59.000Z
Using the Subaru 8.2m Telescope with an IRCS Echelle spectrograph, we obtained high-resolution (R=10,000) near-infrared (1.01-1.38 \\mu m) spectra of images A and B of the gravitationally lensed QSO B1422+231 (z=3.628) consisting of four known lensed images. We detected MgII absorption lines at z=3.54, which show a large variance of column densities (~ 0.3 dex) and velocities (~ 10 km/s) between the sightlines A and B with a projected separation of only 8.4h_{70}^{-1} pc at the redshift. This is the smallest spatial structure of the high-z gas clouds ever detected after Rauch et al. found a 20-pc scale structure for the same z=3.54 absorption system using optical spectra of images A and C. The observed systematic variances imply that the system is an expanding shell as originally suggested by Rauch et al. By combining the data for three sightlines, we managed to constrain the radius and expansion velocity of the shell (~ 50-100 pc, 130 km/s), concluding that the shell is truly a supernova remnant (SNR) rather ...
Kyu-Hyun Chae
2001-12-10T23:59:59.000Z
Fourier series solutions to the deflection and magnification by a family of three-dimensional cusped two power-law ellipsoidal mass distributions are presented. The cusped two power-law ellipsoidal mass distributions are characterized by inner and outer power-law radial indices and a break (or, transition) radius. The model family includes mass models mimicking Jaffe, Hernquist, and $\\eta$ models and dark matter halo profiles from numerical simulations. The Fourier series solutions for the cusped two power-law mass distributions are relatively simple, and allow a very fast calculation even for a chosen small fractional calculational error (e.g. $10^{-5}$). These results will be particularly useful for studying lensed systems which provide a number of accurate lensing constraints and for systematic analyses of large numbers of lenses. Subroutines employing these results for the two power-law model and the results by Chae, Khersonsky, & Turnshek for the generalized single power-law mass model are made publicly available.
Hamano, Satoshi; Kobayashi, Naoto [Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Kondo, Sohei [Koyama Astronomical Observatory, Kyoto-Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555 (Japan); Tsujimoto, Takuji [National Astronomical Observatory of Japan and Department of Astronomical Science, Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Okoshi, Katsuya [Faculty of Industrial Science and Technology, Tokyo University of Science, 102-1 Tomino, Oshamanbe, Hokkaido 049-3514 (Japan); Shigeyama, Toshikazu, E-mail: hamano@ioa.s.u-tokyo.ac.jp [Research Center for the Early Universe, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)
2012-08-01T23:59:59.000Z
Using the Subaru 8.2 m Telescope with the IRCS Echelle spectrograph, we obtained high-resolution (R = 10,000) near-infrared (1.01-1.38 {mu}m) spectra of images A and B of the gravitationally lensed QSO B1422+231 (z = 3.628) consisting of four known lensed images. We detected Mg II absorption lines at z = 3.54, which show a large variance of column densities ({approx}0.3 dex) and velocities ({approx}10 km s{sup -1}) between sightlines A and B with a projected separation of only 8.4h{sup -1}{sub 70} pc at that redshift. This is the smallest spatial structure of the high-z gas clouds ever detected after Rauch et al. found a 20 pc scale structure for the same z = 3.54 absorption system using optical spectra of images A and C. The observed systematic variances imply that the system is an expanding shell as originally suggested by Rauch et al. By combining the data for three sightlines, we managed to constrain the radius and expansion velocity of the shell ({approx}50-100 pc, 130 km s{sup -1}), concluding that the shell is truly a supernova remnant (SNR) rather than other types of shell objects, such as a giant H II region. We also detected strong Fe II absorption lines for this system, but with much broader Doppler width than that of {alpha}-element lines. We suggest that this Fe II absorption line originates in a localized Fe II-rich gas cloud that is not completely mixed with plowed ambient interstellar gas clouds showing other {alpha}-element low-ion absorption lines. Along with the Fe richness, we conclude that the SNR is produced by an SN Ia explosion.
Mapping the 3-D Dark Matter potential with weak shear
D. J. Bacon; A. N. Taylor
2002-12-11T23:59:59.000Z
We investigate the practical implementation of Taylor's (2002) 3-dimensional gravitational potential reconstruction method using weak gravitational lensing, together with the requisite reconstruction of the lensing potential. This methodology calculates the 3-D gravitational potential given a knowledge of shear estimates and redshifts for a set of galaxies. We analytically estimate the noise expected in the reconstructed gravitational field, taking into account the uncertainties associated with a finite survey, photometric redshift uncertainty, redshift-space distortions, and multiple scattering events. In order to implement this approach for future data analysis, we simulate the lensing distortion fields due to various mass distributions. We create catalogues of galaxies sampling this distortion in three dimensions, with realistic spatial distribution and intrinsic ellipticity for both ground-based and space-based surveys. Using the resulting catalogues of galaxy position and shear, we demonstrate that it is possible to reconstruct the lensing and gravitational potentials with our method. For example, we demonstrate that a typical ground-based shear survey with redshift limit z=1 and photometric redshifts with error Delta z=0.05 is directly able to measure the 3-D gravitational potential for mass concentrations >10^14 M_\\odot between 0.1
Quider, Anna M; Pettini, Max; Steidel, Charles C; Stark, Daniel P
2009-01-01T23:59:59.000Z
We report the results of a study of the rest-frame UV spectrum of the Cosmic Eye, a luminous Lyman break galaxy at z=3.07331 gravitationally lensed by a factor of 25. The spectrum, recorded with the ESI spectrograph on the Keck II telescope, is rich in absorption features from the gas and massive stars in this galaxy. The interstellar absorption lines are resolved into two components of approximately equal strength and each spanning several hundred km/s in velocity. One component has a net blueshift of -70 km/s relative to the stars and H II regions and presumably arises in a galaxy-scale outflow similar to those seen in most star-forming galaxies at z = 2-3. The other is more unusual in showing a mean redshift of +350 km/s relative to the systemic redshift; possible interpretations include a merging clump, or material ejected by a previous star formation episode and now falling back onto the galaxy, or more simply a chance alignment with a foreground galaxy. In the metal absorption lines, both components onl...
Quider, Anna M; Shapley, Alice E; Steidel, Charles C
2009-01-01T23:59:59.000Z
Taking advantage of strong gravitational lensing, we have recorded the rest-frame UV spectrum of the z = 2.38115 galaxy `The Cosmic Horseshoe' (J1148+1930) at higher resolution and S/N than is currently feasible for unlensed galaxies at z = 2 -3. From the analysis of stellar spectral features, we conclude that a continuous mode of star formation with a Salpeter slope gives a good representation of the UV spectrum, ruling out significant departures from a `standard' IMF. Generally, we find good agreement between the values of metallicity deduced from stellar and nebular tracers. Interstellar absorption is present over a velocity range of 1000 km/s, from -800$ to +250 km/s relative to the stars and their H II regions, and there is evidence that the outflowing interstellar gas may be patchy, covering only 60% of the UV stellar continuum. The Lya line shares many of the characteristics of the so-called Lya emitters. Its double-peaked profile can be reproduced by models of Lya photons resonantly scattered by an ex...
Aravind Natarajan; Andrew R. Zentner; Nicholas Battaglia; Hy Trac
2014-09-04T23:59:59.000Z
We examine the importance of baryonic feedback effects on the matter power spectrum on small scales, and the implications for the precise measurement of neutrino masses through gravitational weak lensing. Planned large galaxy surveys such as the Large Synoptic Sky Telescope (LSST) and Euclid are expected to measure the sum of neutrino masses to extremely high precision, sufficient to detect non-zero neutrino masses even in the minimal mass normal hierarchy. We show that weak lensing of galaxies while being a very good probe of neutrino masses, is extremely sensitive to baryonic feedback processes. We use publicly available results from the Overwhelmingly Large Simulations (OWLS) project to investigate the effects of active galactic nuclei feedback, the nature of the stellar initial mass function, and gas cooling rates, on the measured weak lensing shear power spectrum. Using the Fisher matrix formalism and priors from CMB+BAO data, we show that when one does not account for feedback, the measured neutrino mass may be substantially larger or smaller than the true mass, depending on the dominant feedback mechanism, with the mass error |\\Delta m_nu| often exceeding the mass m_nu itself. We also consider gravitational lensing of the cosmic microwave background (CMB) and show that it is not sensitive to baryonic feedback on scales l < 2000, although CMB experiments that aim for sensitivities sigma(m_nu) < 0.02 eV will need to include baryonic effects in modeling the CMB lensing potential. A combination of CMB lensing and galaxy lensing can help break the degeneracy between neutrino masses and baryonic feedback processes. We conclude that future large galaxy lensing surveys such as LSST and Euclid can only measure neutrino masses accurately if the matter power spectrum can be measured to similar accuracy.
Analytical formulas for gravitational lensing
Paolo Amore; Santiago Arceo Diaz
2006-03-21T23:59:59.000Z
In this paper we discuss a new method which can be used to obtain arbitrarily accurate analytical expressions for the deflection angle of light propagating in a given metric. Our method works by mapping the integral into a rapidly convergent series and provides extremely accurate approximations already to first order. We have derived a general first order formula for a generic spherically symmetric static metric tensor and we have tested it in four different cases.
P. Chowdhury; D. Home; A. S. Majumdar; S. V. Mousavi; M. R. Mozaffari; S. Sinha
2011-12-27T23:59:59.000Z
The weak equivalence principle of gravity is examined at the quantum level in two ways. First, the position detection probabilities of particles described by a non-Gaussian wave-packet projected upwards against gravity around the classical turning point and also around the point of initial projection are calculated. These probabilities exhibit mass-dependence at both these points, thereby reflecting the quantum violation of the weak equivalence principle. Secondly, the mean arrival time of freely falling particles is calculated using the quantum probability current, which also turns out to be mass dependent. Such a mass-dependence is shown to be enhanced by increasing the non-Gaussianity parameter of the wave packet, thus signifying a stronger violation of the weak equivalence principle through a greater departure from Gaussianity of the initial wave packet. The mass-dependence of both the position detection probabilities and the mean arrival time vanish in the limit of large mass. Thus, compatibility between the weak equivalence principle and quantum mechanics is recovered in the macroscopic limit of the latter. A selection of Bohm trajectories is exhibited to illustrate these features in the free fall case.
Jacek Jezierski
1998-01-20T23:59:59.000Z
It is shown that the axial and polar perturbations of the spherically symmetric black hole can be described in a gauge-invariant way. The reduced phase space describing gravitational waves outside of the horizon is described by the gauge-invariant quantities. Both degrees of freedom fulfill generalized scalar wave equation. For the axial degree of freedom the radial part of the equation corresponds to the Regge-Wheeler result (Phys. Rev. 108, 1063-1069 (1957)) and for the polar one we get Zerilli result (Phys. Rev. D2, 2141-2160 (1970)), see also Chandrasekhar (The Mathematical Theory of Black Holes,(Clarendon Press Oxford, 1983)), Moncrief (Annals of Physics 88, 323-342 (1974)) for both. An important ingredient of the analysis is the concept of quasilocality which does duty for the separation of the angular variables in the usual approach. Moreover, there is no need to represent perturbations by normal modes (with time dependence $\\exp(-ikt)$), we have fields in spacetime and the Cauchy problem for them is well defined outside of the horizon. The reduced symplectic structure explains the origin of the axial and polar invariants. It allows to introduce an energy and angular momentum for the gravitational waves which is invariant with respect to the gauge transformations. Both generators represent quadratic approximation of the ADM nonlinear formulae in terms of the perturbations of the Schwarzschild metric. We also discuss the boundary-initial value problem for the linearized Einstein equations on a Schwarzschild background outside of the horizon.
Beach, R.J.; Benett, W.J.
1994-04-26T23:59:59.000Z
A lensing duct to condense (intensify) light using a combination of front surface lensing and reflective waveguiding is described. The duct tapers down from a wide input side to a narrow output side, with the input side being lens-shaped and coated with an antireflective coating for more efficient transmission into the duct. The four side surfaces are uncoated, preventing light from escaping by total internal reflection as it travels along the duct (reflective waveguiding). The duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials, and can be fabricated from inexpensive glass and plastic. 3 figures.
Gerold Doyen; Deiana Drakova
2014-08-12T23:59:59.000Z
We construct a world model consisting of a matter field living in 4 dimensional spacetime and a gravitational field living in 11 dimensional spacetime. The seven hidden dimensions are compactified within a radius estimated by reproducing the particle - wave characteristic of diffraction experiments. In the presence of matter fields the gravitational field develops localized modes with elementary excitations called gravonons which are induced by the sources (massive particles). The final world model treated here contains only gravonons and a scalar matter field. The solution of the Schroedinger equation for the world model yields matter fields which are localized in the 4 dimensional subspace. The localization has the following properties: (i) There is a chooser mechanism for the selection of the localization site. (ii) The chooser selects one site on the basis of minor energy differences and differences in the gravonon structure between the sites, which appear statistical. (iii) The changes from one localization site to a neighbouring one take place in a telegraph-signal like manner. (iv) The times at which telegraph like jumps occur dependent on subtleties of the gravonon structure which appear statistical. (v) The fact that the dynamical law acts in the configuration space of fields living in 11 dimensional spacetime lets the events observed in 4 dimensional spacetime appear non-local. In this way the phenomenology of Copenhagen quantum mechanics is obtained without the need of introducing the process of collapse and a probabilistic interpretation of the wave function. Operators defining observables need not be introduced. All experimental findings are explained in a deterministic way as a consequence of the time development of the wave function in configuration space according to Schroedinger's equation.
A TWO-YEAR TIME DELAY FOR THE LENSED QUASAR SDSS J1029+2623
Fohlmeister, Janine; Wambsganss, Joachim [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)] [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Kochanek, Christopher S. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)] [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Falco, Emilio E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Oguri, Masamune [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)] [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Dai, Xinyu [Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States)] [Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States)
2013-02-20T23:59:59.000Z
We present 279 epochs of optical monitoring data spanning 5.4 years from 2007 January to 2012 June for the largest image separation (22.''6) gravitationally lensed quasar, SDSS J1029+2623. We find that image A leads the images B and C by {Delta} t {sub AB} = (744 {+-} 10) days (90% confidence); the uncertainty includes both statistical uncertainties and systematic differences due to the choice of models. With only a {approx}1% fractional error, the interpretation of the delay is limited primarily by cosmic variance due to fluctuations in the mean line-of-sight density. We cannot separate the fainter image C from image B, but since image C trails image B by only 2-3 days in all models, the estimate of the time delay between images A and B is little affected by combining the fluxes of images B and C. There is weak evidence for a low level of microlensing, perhaps created by the small galaxy responsible for the flux ratio anomaly in this system. Interpreting the delay depends on better constraining the shape of the gravitational potential using the lensed host galaxy, other lensed arcs, and the structure of the X-ray emission.
Wide-Field Lensing Mass Maps from DES Science Verification Data
Vikram, V; Jain, B; Bacon, D; Amara, A; Becker, M; Bernstein, G; Bonnett, C; Bridle, S; Brout, D; Busha, M; Frieman, J; Gaztanaga, E; Hartley, W; Jarvis, M; Kacprzak, T; Lahav, O; Leistedt, B; Lin, H; Melchior, P; Peiris, H; Rozo, E; Rykoff, E; Sanchez, C; Sheldon, E; Troxel, M; Wechsler, R; Zuntz, J; Abbott, T; Abdalla, F B; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Levy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Castander, F J; Crocce, M; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Gerdes, D; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kent, S; Kuehn, K; Kuropatkin, N; Li, T S; Maia, M A G; Makler, M; March, M; Marshall, J; Martini, Paul; Merritt, K W; Miller, C J; Miquel, R; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Romer, A K; Roodman, A; Sanchez, E; Scarpine, V; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Weller, J
2015-01-01T23:59:59.000Z
Weak gravitational lensing allows one to reconstruct the spatial distribution of the projected mass density across the sky. These "mass maps" provide a powerful tool for studying cosmology as they probe both luminous and dark matter. In this paper, we present a weak lensing mass map reconstructed from shear measurements in a 139 deg^2 area from the Dark Energy Survey (DES) Science Verification (SV) data overlapping with the South Pole Telescope survey. We compare the distribution of mass with that of the foreground distribution of galaxies and clusters. The overdensities in the reconstructed map correlate well with the distribution of optically detected clusters. Cross-correlating the mass map with the foreground galaxies from the same DES SV data gives results consistent with mock catalogs that include the primary sources of statistical uncertainties in the galaxy, lensing, and photo-z catalogs. The statistical significance of the cross-correlation is at the 6.8 sigma level with 20 arcminute smoothing. A maj...
Diagnosing multiplicative error by lensing magnification of type Ia supernovae
Zhang, Pengjie
2015-01-01T23:59:59.000Z
Weak lensing causes spatially coherent fluctuations in flux of type Ia supernovae (SNe Ia). This lensing magnification allows for weak lensing measurement independent of cosmic shear. It is free of shape measurement errors associated with cosmic shear and can therefore be used to diagnose and calibrate multiplicative error. Although this lensing magnification is difficult to measure accurately in auto correlation, its cross correlation with cosmic shear and galaxy distribution in overlapping area can be measured to significantly higher accuracy. Therefore these cross correlations can put useful constraint on multiplicative error, and the obtained constraint is free of cosmic variance in weak lensing field. We present two methods implementing this idea and estimate their performances. We find that, with $\\sim 1$ million SNe Ia that can be achieved by the proposed D2k survey with the LSST telescope (Zhan et al. 2008), multiplicative error of $\\sim 0.5\\%$ for source galaxies at $z_s\\sim 1$ can be detected and la...
Caustics in special multiple lenses
V. Bozza
2000-01-13T23:59:59.000Z
Despite its mathematical complexity, the multiple gravitational lens can be studied in detail in every situation where a perturbative approach is possible. In this paper, we examine the caustics of a system with a lens very far from the others with respect to their Einstein radii, and a system where mutual distances between lenses are small compared to the Einstein radius of the total mass. Finally we review the case of a planetary system adding some new information (area of caustics, duality and higher order terms).
analysis identifies weak: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
parameter estimation via weak lensing, with an emphasis on the equation of state of dark energy. P. G. Castro; A. F. Heavens; T. D. Kitching 2005-07-20 5 Composite Weak...
Gravitational Correction in Neutrino Oscillations
Yasufumi Kojima
1996-12-17T23:59:59.000Z
We investigate the quantum mechanical oscillations of neutrinos propagating in weak gravitational field. The correction to the result in the flat space-time is derived.
P. E. Boynton; R. M. Bonicalzi; A. M. Kalet; A. M. Kleczewski; J. K. Lingwood; K. J. McKenney; M. W. Moore; J. H. Steffen; E. C. Berg; W. D. Cross; R. D. Newman; R. E. Gephart
2006-09-21T23:59:59.000Z
We report progress on a program of gravitational physics experiments using cryogenic torsion pendula undergoing large-amplitude torsion oscillation. This program includes tests of the gravitational inverse square law and of the weak equivalence principle. Here we describe our ongoing search for inverse-square-law violation at a strength down to $10^{-5}$ of standard gravity. The low-vibration environment provided by the Battelle Gravitation Physics Laboratory (BGPL) is uniquely suited to this study.
Optical Continuum Sources in Gravitationally Lensed Quasars
L. J. Goicoechea; D. Alcalde; V. N. Shalyapin
2002-10-30T23:59:59.000Z
We review some techniques to study the nature and size of the optical continuum sources in multiple QSOs. We focus on the source originating the events with several months timescale (the rapid variability source) as well as the source that is responsible for the non-variable background component (the background source). The techniques are used to study both the rapid variability source in Q0957+561 and the main (compact) background source in Q2237+0305.
Multipole Expansion Model in Gravitational Lensing
T. Fukuyama; Y. Kakigi; T. Okamura
1997-01-31T23:59:59.000Z
Non-transparent models of multipole expansion model and two point-mass model are analyzed from the catastrophe theory. Singularity behaviours of $2^n$-pole moments are discussed. We apply these models to triple quasar PG1115+080 and compare with the typical transparent model, softened power law spheroids. Multipole expansion model gives the best fit among them.
Lensing Basics: I. Introduction
. (2007) #12;6 Giant Lenses in the Sky Galaxy Cluster Abell 1689 [Image credit: NASA, Benitez et al.] #12;7 Giant Lenses in the Sky Galaxy Cluster Abell 1689 Multiple images of background source form giant arcs! [Michalitsianosetal.1997] VLA VLBI #12;15 Discovery of giant luminous arcs Lynds & Petrosian (1986) and Soucail et al
Mass Distributions of Clusters Using Gravitational Magnification
Tom Broadhurst
1995-05-03T23:59:59.000Z
Lensing in the context of rich clusters is normally quantified from small image distortions, yielding a relative mass distribution in the limit of weak lensing. Here we show the magnification effect of lensing can also be mapped over a cluster, resulting in absolute mass determinations for the weak limit. Furthermore, given both magnification and distortion measurements, the mass distribution may be constrained in the strong regime. Methods for obtaining the magnification using spectroscopic and/or photometric information are discussed, for object detection within a fixed isophote or to a given flux limit. A map of the magnification around A1689 is constructed from the observed depletion of background red galaxy counts.
SPATIALLY RESOLVED HST GRISM SPECTROSCOPY OF A LENSED EMISSION LINE GALAXY AT z {approx} 1
Frye, Brenda L. [Steward Observatory, Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Hurley, Mairead [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland); Bowen, David V. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08540 (United States); Meurer, Gerhardt [International Centre for Radio Astronomy Research, The University of Western Australia M468, 35 Stirling Highway, Crawley, WA 6009 (Australia); Sharon, Keren [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); Straughn, Amber [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Coe, Dan [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Broadhurst, Tom [Ikerbasque, Basque Foundation for Science, E-48011 Bilbao (Spain); Guhathakurta, Puragra, E-mail: bfrye@as.arizona.edu [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
2012-07-20T23:59:59.000Z
We take advantage of gravitational lensing amplification by A1689 (z 0.187) to undertake the first space-based census of emission line galaxies (ELGs) in the field of a massive lensing cluster. Forty-three ELGs are identified to a flux of i{sub 775} = 27.3 via slitless grism spectroscopy. One ELG (at z = 0.7895) is very bright owing to lensing magnification by a factor of Almost-Equal-To 4.5. Several Balmer emission lines (ELs) detected from ground-based follow-up spectroscopy signal the onset of a major starburst for this low-mass galaxy (M{sub *} Almost-Equal-To 2 Multiplication-Sign 10{sup 9} M{sub Sun }) with a high specific star formation rate ( Almost-Equal-To 20 Gyr{sup -1}). From the blue ELs we measure a gas-phase oxygen abundance consistent with solar (12+log(O/H) = 8.8 {+-} 0.2). We break the continuous line-emitting region of this giant arc into seven {approx}1 kpc bins (intrinsic size) and measure a variety of metallicity-dependent line ratios. A weak trend of increasing metal fraction is seen toward the dynamical center of the galaxy. Interestingly, the metal line ratios in a region offset from the center by {approx}1 kpc have a placement on the blue H II region excitation diagram with f ([O III])/f (H{beta}) and f ([Ne III])/f (H{beta}) that can be fitted by an active galactic nucleus (AGN). This asymmetrical AGN-like behavior is interpreted as a product of shocks in the direction of the galaxy's extended tail, possibly instigated by a recent galaxy interaction.
Gravitational LensingGravitational Lensing Physics 343, Lecture 11Physics 343, Lecture 11
Baker, Andrew J.
emission free from differential extinction concerns Biggs et al., 1999 #12;Time DelaysTime Delays Biggs et
Neutrino optics and oscillations in gravitational fields
G. Lambiase; G. Papini; R. Punzi; G. Scarpetta
2005-03-07T23:59:59.000Z
We study the propagation of neutrinos in gravitational fields using wave functions that are exact to first order in the metric deviation. For illustrative purposes, the geometrical background is represented by the Lense-Thirring metric. We derive explicit expressions for neutrino deflection, helicity transitions, flavor oscillations and oscillation Hamiltonian.
Lense-Thirring Field and the Solar Limb Effect
M. I. Wanas; A. B. Morcos; S. I. El Gammal
2010-08-05T23:59:59.000Z
Solar-Limb Effect is an observational phenomena connected to the solar gravitational red-shift. It shows a variation of the magnitude of the gravitational red-shift from the center to the limb of the solar disc. In the present work an attempt, for interpreting this phenomena using a general relativistic red-shift formula, is given . This formula takes into account the effect of the the Sun's gravitational field, the effect of the solar rotation, the effect of inclination of the line of sight and the motion of the observer. In this study the gravitational field of the Sun is assumed to be given by Lense-Thirring field instead of the Schwarzschild one. The Earth is assumed to move along an elliptic orbit. Comparison with a previous relativistic study and with observation is given.
Cosmological applications of weak gravitational flexion
Rowe, Barnaby Thomas Peter
Modern cosmology has reached an important juncture, at which the ability to make measurements of unprecedented accuracy has led to conclusions that are a fundamental challenge to natural science. The discovery that, in ...
Weak Interaction and Cosmology
P. R. Silva
2008-04-16T23:59:59.000Z
In this paper we examine the connection among the themes: the cosmological constant, the weak interaction and the neutrino mass. Our main propose is to review and modify the ideas first proposed by Hayakawa [ Prog. Theor. Phys.Suppl.,532(1965).], in the light of the new-fashioned features of contemporary physics. Assuming the pressure of a Fermi gas of neutrinos should be balanced by its gravitational attraction, we evaluate the mass of the background neutrino and its number.The neutrino mass here evaluated is compatible with the known value for the cosmological constant (or dark energy).Taking in account the role played by the weak forces experimented by the neutrinos, we also determined a value for the electroweak mixing angle. For sake of comparison, an alternative evaluation of the neutrino mass is also done.
CMB ISW-lensing bispectrum from cosmic strings
Daisuke Yamauchi; Yuuiti Sendouda; Keitaro Takahashi
2014-10-21T23:59:59.000Z
We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause weak lensing as well as an integrated Sachs-Wolfe (ISW) effect, the so-called Gott-Kaiser-Stebbins (GKS) effect, to the CMB temperature fluctuation, which are thus naturally cross-correlated. We point out that, in the presence of such a correlation, yet another kind of the post-recombination CMB temperature bispectra, the ISW-lensing bispectra, will arise in the form of products of the auto- and cross-power spectra. We first present an analytic method to calculate the autocorrelation of the temperature fluctuations induced by the strings, and the cross-correlation between the temperature fluctuation and the lensing potential both due to the string network. In our formulation, the evolution of the string network is assumed to be characterized by the simple analytic model, the velocity-dependent one scale model, and the intercommutation probability is properly incorporated in orderto characterize the possible superstringy nature. Furthermore, the obtained power spectra are dominated by the Poisson-distributed string segments, whose correlations are assumed to satisfy the simple relations. We then estimate the signal-to-noise ratios of the string-induced ISW-lensing bispectra and discuss the detectability of such CMB signals from the cosmic string network. It is found that in the case of the smaller string tension, $G\\mu\\ll 10^{-7}$\\,, the ISW-lensing bispectrum induced by a cosmic string network can constrain the string-model parameters even more tightly than the purely GKS-induced bispectrum in the ongoing and future CMB observations on small scales.
Bernard F Schutz
2000-03-16T23:59:59.000Z
Gravity is one of the fundamental forces of Nature, and it is the dominant force in most astronomical systems. In common with all other phenomena, gravity must obey the principles of special relativity. In particular, gravitational forces must not be transmitted or communicated faster than light. This means that when the gravitational field of an object changes, the changes ripple outwards through space and take a finite time to reach other objects. These ripples are called gravitational radiation or gravitational waves. This article gives a brief introduction to the physics of gravitational radiation, including technical material suitable for non-specialist scientists.
Combining time delays and image positions for quadruple lenses: a moment approach
Witt, Hans
2015-01-01T23:59:59.000Z
Time delays in gravitational lenses can be used to determine the Hubble constant and the lens potential. In future surveys, many gravitational lenses can be discovered, and their time delays and image positions can in principle be measured. Using an elliptical power-law potential, we show that combinations of image positions and time delays for quadruple lenses yield simple analytical expressions that are connected with observable quantities. These relations can be used to obtain the approximate axis ratio q, the Einstein radius and the slope. We apply this method to RX J1131-1231, and show that our analytical results match the full numerical determinations approximately. Our approach can quickly determine rough values of lens parameters, which can then be used as initial guesses for further refinement through numerical modelling and may be useful for automated lens search in large surveys.
Lorenzo Iorio; David M. Lucchesi
2003-05-20T23:59:59.000Z
In this paper we analyze quantitatively the concept of LAGEOS--type satellites in critical supplementary orbit configuration (CSOC) which has proven capable of yielding various observables for many tests of General Relativity in the terrestrial gravitational field, with particular emphasis on the measurement of the Lense--Thirring effect.
Iorio, L; Iorio, Lorenzo; Lucchesi, David M.
2003-01-01T23:59:59.000Z
In this paper we analyze quantitatively the concept of LAGEOS--type satellites in critical supplementary orbit configuration (CSOC) which has proven capable of yielding various observables for many tests of General Relativity in the terrestrial gravitational field, with particular emphasis on the measurement of the Lense--Thirring effect.
Impact of Atmospheric Chromatic Effects on Weak Lensing Measurements
Meyers, Joshua E
2014-01-01T23:59:59.000Z
Current and future imaging surveys will measure cosmic shear with statistical precision that demands a deeper understanding of potential systematic biases in galaxy shape measurements than has been achieved to date. We use analytic and computational techniques to study the impact on shape measurements of two atmospheric chromatic effects for ground-based surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST): (i) atmospheric differential chromatic refraction (DCR) and (ii) wavelength dependence of seeing. We investigate the effects of using the point spread function (PSF) measured with stars to determine the shape of a galaxy that has a different spectral energy distribution (SED) than the stars. For (i), we extend a study by Plazas & Bernstein based on analytic calculations that show that DCR leads to significant biases in galaxy shape measurements for future surveys, if not corrected. For (ii), we find that the wavelength dependence of seeing leads to significant bia...
Weak lensing flexion as a probe of galaxy cluster substructure
Cain, Benjamin Martin
2011-01-01T23:59:59.000Z
Measuring galaxy cluster total masses and the amount of dark matter substructure within galaxy cluster haloes is a fundamental probe of the ACDM model of structure formation, as well as the interactions between baryonic ...
Gravitational `Convergence' and Cluster Masses
Tom Broadhurst
1995-12-01T23:59:59.000Z
Two colour photometry of the cluster A1689 reveals a `relative magnification-bias' between lensed blue and red background galaxies, arising from a dependence of the faint galaxy count-slope on colour. The colour distribution is skewed blueward of the far field, allowing us to measure the cluster magnification and to understand the notorious blueness of large arcs. We show that the magnification information can be combined with the usual image distortion measurements to isolate the local `convergence' component of lensing and hence derive the projected mass. This is achieved through a simple local relation between the convergence and the observables, which can be applied generally over the surface a cluster. In the weak lensing limit, the convergence reduces to a dependence on the magnification alone, so that in the outskirts of clusters the surface-density of matter is obtained directly from the surface-density of background galaxies. Hence, useful lensing work requires colour information but not necessarily good seeing. Interestingly, convergence varies slowly at high redshift, saturating at a level depending on the Horizon distance, allowing a useful model-independent measurement of the Global Geometry.
Galaxy Galaxy Lensing as a Probe of Galaxy Dark Matter Halos
M. Limousin; J-P. Kneib; P. Natarajan
2006-06-19T23:59:59.000Z
Gravitational lensing has now become a popular tool to measure the mass distribution of structures in the Universe on various scales. Here we focus on the study of galaxy's scale dark matter halos with galaxy-galaxy lensing techniques: observing the shapes of distant background galaxies which have been lensed by foreground galaxies allows us to map the mass distribution of the foreground galaxies. The lensing effect is small compared to the intrinsic ellipticity distribution of galaxies, thus a statistical approach is needed to derive some constraints on an average lens population. An advantage of this method is that it provides a probe of the gravitational potential of the halos of galaxies out to very large radii, where few classical methods are viable, since dynamical and hydrodynamical tracers of the potential cannot be found at this radii. We will begin by reviewing the detections of galaxy-galaxy lensing obtained so far. Next we will present a maximum likelihood analysis of simulated data we performed to evaluate the accuracy and robustness of constraints that can be obtained on galaxy halo properties. Then we will apply this method to study the properties of galaxies which stand in massive cluster lenses at z~0.2. The main result of this work is to find dark matter halos of cluster galaxies to be significantly more compact compared to dark matter halos around field galaxies of equivalent luminosity, in agreement with early galaxy-galaxy lensing studies and with theoretical expectations, in particular with the tidal stripping scenario. We thus provide a strong confirmation of tidal truncation from a homogeneous sample of galaxy clusters. Moreover, it is the first time that cluster galaxies are probed successfully using galaxy-galaxy lensing techniques from ground based data.
Boyce, Edward R
2006-01-01T23:59:59.000Z
This thesis describes the Extragalactic Lens VLBI Imaging Survey (ELVIS), a search for central images in gravitational lenses. We present the first four ELVIS targets, for which we have radio VLBI observations with resolutions ...
Fast-light for astrophysics: super-sensitive gyroscopes and gravitational wave detectors
Shahriar, Selim
Fast-light for astrophysics: super-sensitive gyroscopes and gravitational wave detectors M. SALIT the sensitivity- bandwidth product of gravitational wave detection and terrestrial measurement of Lense, or even significantly greater, without contradicting any laws of physics. The dispersion profile
Acceleration of low energy charged particles by gravitational waves
G. Voyatzis; L. Vlahos; S. Ichtiaroglou; D. Papadopoulos
2005-12-07T23:59:59.000Z
The acceleration of charged particles in the presence of a magnetic field and gravitational waves is under consideration. It is shown that the weak gravitational waves can cause the acceleration of low energy particles under appropriate conditions. Such conditions may be satisfied close to the source of the gravitational waves if the magnetized plasma is in a turbulent state.
Class B0631+519: Last of the Class Lenses
York, Tom; Jackson, N.; Browne, I.W.A.; Koopmans, L.V.E.; McKean, J.P.; Norbury, M.A.; Biggs, A.D.; Blandford, R.D.; de Bruyn, A.G.; Fassnacht, C.D.; Myers, S.T.; Pearson, T.J.; Phillips, P.M.; Readhead, A.C.S.; Rusin, D.; Wilkinson, P.N.; /Jodrell Bank /Kapteyn Astron. Inst., Groningen /UC, Davis /JIVE, Dwingeloo /KIPAC, Menlo Park /NFRA,
2005-05-31T23:59:59.000Z
We report the discovery of the new gravitational lens system CLASS B0631+519. Imaging with the VLA, MERLIN and the VLBA reveals a doubly-imaged flat-spectrum radio core, a doubly-imaged steep-spectrum radio lobe and possible quadruply-imaged emission from a second lobe. The maximum separation between the lensed images is 1.16 arcsec. High resolution mapping with the VLBA at 5 GHz resolves the most magnified image of the radio core into a number of sub-components spread across approximately 20 mas. No emission from the lensing galaxy or an odd image is detected down to 0.31 mJy (5{sigma}) at 8.4 GHz. Optical and near-infrared imaging with the ACS and NICMOS cameras on the HST show that there are two galaxies along the line of sight to the lensed source, as previously discovered by optical spectroscopy. We find that the foreground galaxy at z=0.0896 is a small irregular, and that the other, at z=0.6196 is a massive elliptical which appears to contribute the majority of the lensing effect. The host galaxy of the lensed source is detected in the HST near-infrared imaging as a set of arcs, which form a nearly complete Einstein ring. Mass modeling using non-parametric techniques can reproduce the near-infrared observations and indicates that the small irregular galaxy has a (localized) effect on the flux density distribution in the Einstein ring at the 5-10% level.
Joseph Katz
2005-10-20T23:59:59.000Z
Observers at rest in a stationary spacetime flat at infinity can measure small amounts of rest-mass+internal energies+kinetic energies+pressure energy in a small volume of fluid attached to a local inertial frame. The sum of these small amounts is the total "matter energy" for those observers. The total mass-energy minus the matter energy is the binding gravitational energy. Misner, Thorne and Wheeler evaluated the gravitational energy of a spherically symmetric static spacetime. Here we show how to calculate gravitational energy in any static and stationary spacetime for isolated sources with a set of observers at rest. The result of MTW is recovered and we find that electromagnetic and gravitational 3-covariant energy densities in conformastatic spacetimes are of opposite signs. Various examples suggest that gravitational energy is negative in spacetimes with special symmetries or when the energy-momentum tensor satisfies usual energy conditions.
Fresnel phase plates as reconfigurable microfluidic lenses
Tsikata, Sedina, 1981-
2004-01-01T23:59:59.000Z
In this study, Fresnel phase plates were tested as reconfigurable lenses. The lenses were constructed from a Fresnel pattern which was transferred to a silicon substrate via photolithography. A layer of PDMS was spin-coated ...
Analytic models of plausible gravitational lens potentials
Edward A. Baltz; Phil Marshall; Masamune Oguri
2008-12-11T23:59:59.000Z
Gravitational lenses on galaxy scales are plausibly modelled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasising that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential. We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modelled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.
Analytic models of plausible gravitational lens potentials
Baltz, Edward A.; Marshall, Phil; Oguri, Masamune, E-mail: eabaltz@slac.stanford.edu, E-mail: pjm@physics.ucsb.edu, E-mail: oguri@slac.stanford.edu [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, PO Box 20450, MS29, Stanford, CA 94309 (United States)] [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, PO Box 20450, MS29, Stanford, CA 94309 (United States)
2009-01-15T23:59:59.000Z
Gravitational lenses on galaxy scales are plausibly modelled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasising that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential. We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modelled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.
Analytic Models of Plausible Gravitational Lens Potentials
Baltz, Edward A.; Marshall, Phil; Oguri, Masamune
2007-05-04T23:59:59.000Z
Gravitational lenses on galaxy scales are plausibly modeled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasizing that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential.We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modeled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.
Galaxy density profiles and shapes -- I. simulation pipeline for lensing by realistic galaxy models
Glenn van de Ven; Rachel Mandelbaum; Charles R. Keeton
2009-06-18T23:59:59.000Z
Studies of strong gravitational lensing in current and upcoming wide and deep photometric surveys, and of stellar kinematics from (integral-field) spectroscopy at increasing redshifts, promise to provide valuable constraints on galaxy density profiles and shapes. However, both methods are affected by various selection and modelling biases, whch we aim to investigate in a consistent way. In this first paper in a series we develop a flexible but efficient pipeline to simulate lensing by realistic galaxy models. These galaxy models have separate stellar and dark matter components, each with a range of density profiles and shapes representative of early-type, central galaxies without significant contributions from other nearby galaxies. We use Fourier methods to calculate the lensing properties of galaxies with arbitrary surface density distributions, and Monte Carlo methods to compute lensing statistics such as point-source lensing cross-sections. Incorporating a variety of magnification bias modes lets us examine different survey limitations in image resolution and flux. We rigorously test the numerical methods for systematic errors and sensitivity to basic assumptions. We also determine the minimum number of viewing angles that must be sampled in order to recover accurate orientation-averaged lensing quantities. We find that for a range of non-isothermal stellar and dark matter density profiles typical of elliptical galaxies, the combined density profile and corresponding lensing properties are surprisingly close to isothermal around the Einstein radius. The converse implication is that constraints from strong lensing and/or stellar kinematics, which are indeed consistent with isothermal models near the Einstein radius, cannot trivially be extrapolated to smaller and larger radii.
Monitoring lensed starlight emitted close to the Galactic Center
Adi Nusser; Tom Broadhurst
2004-07-12T23:59:59.000Z
We describe the feasibility of detecting the gravitational deflection of light emitted by stars moving under the influence of the massive object at the Galactic center. Light emitted by a star orbiting behind the central mass has a smaller impact parameter than the star itself, and suffers the effect of gravitational lensing, providing a closer probe of the central mass distribution and hence a stricter test of the black hole hypothesis. A mass of $4.3\\times 10^{6} M_{\\odot}$ causes a $0.1-2\\rm mas$ deviation in the apparent position of orbiting stars projected within $10^{\\circ}$ of the line of sight to the galactic center. In addtion, we may uniquely constrain the distance to the center of the galaxy because lensing deflections constrain the ratio $\\rg/R_{0}$ of the Schwarzschild radius to the distance to the black hole, $R_{o}$, whereas the ratio $\\rg/R_{o}^{3}$ is obtained by fitting the orbit.
Handbook for the GREAT08 Challenge: An image analysis competition for cosmological lensing
Bridle, Sarah; Amara, Adam; Applegate, Douglas; Balan, Sreekumar T; Bernstein, Gary; Berge, Joel; Dahle, Hakon; Erben, Thomas; Gill, Mandeep; Heavens, Alan; Heymans, Catherine; High, Will; Hoekstra, Henk; Jarvis, Mike; Kitching, Thomas; Kneib, Jean-Paul; Kuijken, Konrad; Lagattuta, David; Mandelbaum, Rachel; Massey, Richard; Mellier, Yannick; Moghaddam, Baback; Moudden, Yassir; Nakajima, Reiko; Paulin-Henriksson, Stephane; Pires, Sandrine; Rassat, Anais; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Semboloni, Elisabetta; Shmakova, Marina; van Waerbeke, Ludovic; Voigt, Lisa; Wittman, David
2008-01-01T23:59:59.000Z
The GRavitational lEnsing Accuracy Testing 2008 (GREAT08) Challenge focuses on a problem that is of crucial importance for future observations in cosmology. The shapes of distant galaxies can be used to determine the properties of dark energy and the nature of gravity, because light from those galaxies is bent by gravity from the intervening dark matter. The observed galaxy images appear distorted, although only slightly, and their shapes must be precisely disentangled from the effects of pixelisation, convolution and noise. The worldwide gravitational lensing community has made significant progress in techniques to measure these distortions via the Shear TEsting Program (STEP). Via STEP, we have run challenges within our own community, and come to recognise that this particular image analysis problem is ideally matched to experts in statistical inference, inverse problems and computational learning. Thus, in order to continue the progress seen in recent years, we are seeking an infusion of new ideas from the...
Hubble constant from lensing in plasma-redshift cosmology, and intrinsic redshift of quasars
Ari Brynjolfsson
2004-12-02T23:59:59.000Z
In a series of articles, we have shown that the newly discovered plasma-redshift cosmology gives a simpler, more accurate and consistent explanation of many cosmological phenomena than the big-bang cosmology. The SNe Ia observations are in better agreement with the magnitude-redshift relation predicted by the plasma redshift than that predicted by the multi-parameter big-bang cosmology. No deceleration or expansion parameters are needed. The plasma-redshift cosmology is flat and quasi-static on a large scale. The Hubble constant is no longer an expansion parameter, but is instead a measure of the average electron density along the line of sight towards an object. Perusal of the SNe Ia data and quasar data has shown that there is no time dilation. The conventional estimates of the Hubble constant from gravitational lensing observations use the big-bang cosmology for interpreting the observations. This has lead to a large spread and discordant estimates of the Hubble constant. The purpose of the present article is to show that the gravitational lensing observations are in agreement with the plasma-redshift cosmology, and to show how to evaluate the lensing observations based on the new plasma-redshift cosmology. The lensing observations also indicate that the quasars have large intrinsic redshifts.
TANGENTIAL VELOCITY OF THE DARK MATTER IN THE BULLET CLUSTER FROM PRECISE LENSED IMAGE REDSHIFTS
Molnar, Sandor M. [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan (China); Broadhurst, Tom [Fisika Teorikoa, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea UPV/EHU, 644 Posta Kutxatila, E-48080 Bilbao (Spain); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Zitrin, Adi [Universitaet Heidelberg, Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Philosophenweg 12, D-69120 Heidelberg (Germany); Rephaeli, Yoel; Shimon, Meir, E-mail: sandor@phys.ntu.edu.tw [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)
2013-09-01T23:59:59.000Z
We show that the fast-moving component of the ''Bullet Cluster'' (1E0657-56) can induce potentially resolvable redshift differences between multiply lensed images of background galaxies. This moving cluster effect, due to the tangential peculiar velocity of the lens, can be expressed as the scalar product of the lensing deflection angle with the tangential velocity of the mass components; the effect is maximal for clusters colliding in the plane of the sky with velocities boosted by their mutual gravity. The Bullet Cluster is likely to be the best candidate for the first measurement of this effect due to the large collision velocity and because the lensing deflection and the cluster fields can be calculated in advance. We derive the deflection field using multiply lensed background galaxies detected with the Hubble Space Telescope. The velocity field is modeled using self-consistent N-body/hydrodynamical simulations constrained by the observed X-ray and gravitational lensing features of this system. We predict that the triply lensed images of systems ''G'' and ''H'' straddling the critical curve of the bullet component will show the largest frequency shifts up to {approx}0.5 km s{sup -1}. These shifts are within the range of the Atacama Large Millimeter/Submillimeter Array for molecular emission, and are near the resolution limit of the new generation high-throughput optical-IR spectrographs. The detection of this effect measures the tangential motion of the subclusters directly, thereby clarifying the tension with {Lambda}CDM, which is inferred from the gas motion less directly. This method may be extended to smaller redshift differences using the Ly{alpha} forest toward QSOs lensed by more typical clusters of galaxies. More generally, the tangential component of the peculiar velocities of clusters derived by our method complements the radial component determined by the kinematic Sunyaev-Zel'dovich effect, providing a full three-dimensional description of velocities.
Gravitational microlensing results from MACHO
Alcock, C.; MACHO Collaboration
1996-09-01T23:59:59.000Z
The MACHO project is searching for dark qter inthe form of massive compact haio objects (Machos), by monitoring the brightness of millions of stars in the Magellanic Clouds to search for gravitational microlensing events. Analysis of our 1st 2.3 years of data for 8.5 million stars in the LMC yields 8 candidate microlensing events, well in excess of the {approx} 1 event expected from lensing by known low-mass stars. The event timescales range from 34 to 145 days, and the estimated optical depth is N 2x10{sup -7}, about half of that expected from a `standard` halo. Likelihood analysis indicates the typical lens mass is 0.5{sup +0.3}{sub -0.2}M{sub {circle_dot}}, suggesting they may be old white dwarfs.
Gravitational Radiation from Oscillating Gravitational Dipole
Fran De Aquino
2002-10-05T23:59:59.000Z
The concept of Gravitational Dipole is introduced starting from the recent discovery of negative gravitational mass (gr-qc/0005107 and physics/0205089). A simple experiment, a gravitational wave transmitter, to test this new concept of gravitational radiation source is presented.
Modified Entropic Gravitation in Superconductors
Clovis Jacinto de Matos
2011-08-19T23:59:59.000Z
Verlinde recently developed a theoretical account of gravitation in terms of an entropic force. The central element in Verlinde's derivation is information and its relation with entropy through the holographic principle. The application of this approach to the case of superconductors requires to take into account that information associated with superconductor's quantum vacuum energy is not stored on Planck size surface elements, but in four volume cells with Planck-Einstein size. This has profound consequences on the type of gravitational force generated by the quantum vacuum condensate in superconductors, which is closely related with the cosmological repulsive acceleration responsible for the accelerated expansion of the Universe. Remarkably this new gravitational type force depends on the level of breaking of the weak equivalence principle for cooper pairs in a given superconducting material, which was previously derived by the author starting from similar principles. It is also shown that this new gravitational force can be interpreted as a surface force. The experimental detection of this new repulsive gravitational-type force appears to be challenging.
Plasma waves driven by gravitational waves in an expanding universe
D. B. Papadopoulos
2002-05-22T23:59:59.000Z
In a Friedmann-Robertson-Walker (FRW) cosmological model with zero spatial curvature, we consider the interaction of the gravitational waves with the plasma in the presence of a weak magnetic field. Using the relativistic hydromagnetic equations it is verified that large amplitude magnetosonic waves are excited, assuming that both, the gravitational field and the weak magnetic field do not break the homogeneity and isotropy of the considered FRW spacetime.
Gravitational Lens Modeling with Genetic Algorithms and Particle Swarm Optimizers
Rogers, Adam
2011-01-01T23:59:59.000Z
Strong gravitational lensing of an extended object is described by a mapping from source to image coordinates that is nonlinear and cannot generally be inverted analytically. Determining the structure of the source intensity distribution also requires a description of the blurring effect due to a point spread function. This initial study uses an iterative gravitational lens modeling scheme based on the semilinear method to determine the linear parameters (source intensity profile) of a strongly lensed system. Our 'matrix-free' approach avoids construction of the lens and blurring operators while retaining the least squares formulation of the problem. The parameters of an analytical lens model are found through nonlinear optimization by an advanced genetic algorithm (GA) and particle swarm optimizer (PSO). These global optimization routines are designed to explore the parameter space thoroughly, mapping model degeneracies in detail. We develop a novel method that determines the L-curve for each solution automa...
MODEL-FREE MULTI-PROBE LENSING RECONSTRUCTION OF CLUSTER MASS PROFILES
Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
2013-05-20T23:59:59.000Z
Lens magnification by galaxy clusters induces characteristic spatial variations in the number counts of background sources, amplifying their observed fluxes and expanding the area of sky, the net effect of which, known as magnification bias, depends on the intrinsic faint-end slope of the source luminosity function. The bias is strongly negative for red galaxies, dominated by the geometric area distortion, whereas it is mildly positive for blue galaxies, enhancing the blue counts toward the cluster center. We generalize the Bayesian approach of Umetsu et al. for reconstructing projected cluster mass profiles, by incorporating multiple populations of background sources for magnification-bias measurements and combining them with complementary lens-distortion measurements, effectively breaking the mass-sheet degeneracy and improving the statistical precision of cluster mass measurements. The approach can be further extended to include strong-lensing projected mass estimates, thus allowing for non-parametric absolute mass determinations in both the weak and strong regimes. We apply this method to our recent CLASH lensing measurements of MACS J1206.2-0847, and demonstrate how combining multi-probe lensing constraints can improve the reconstruction of cluster mass profiles. This method will also be useful for a stacked lensing analysis, combining all lensing-related effects in the cluster regime, for a definitive determination of the averaged mass profile.
Medezinski, Elinor; Lemze, Doron; Ford, Holland [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Nonino, Mario [INAF/Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Merten, Julian; Mroczkowski, Tony [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, Pasadena, CA 91109 (United States); Zitrin, Adi [Institut für Theoretische Astrophysik, Universität Heidelberg, Zentrum für Astronomie, Philosophenweg 12, D-69120 Heidelberg (Germany); Broadhurst, Tom [Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, P.O. Box 644, E-48080 Bilbao (Spain); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Sayers, Jack; Czakon, Nicole [Division of Physics, Math, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Waizmann, Jean-Claude; Meneghetti, Massimo [Dipartimento di Astronomia, Universit'a di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Koekemoer, Anton; Coe, Dan; Postman, Marc [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Molino, Alberto [Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada (Spain); Melchior, Peter [Center for Cosmology and Astro-Particle Physics and Department of Physics, The Ohio State University, Columbus, OH 43210 (United States); Grillo, Claudio, E-mail: elinor@pha.jhu.edu [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark); and others
2013-11-01T23:59:59.000Z
The galaxy cluster MACS J0717.5+3745 (z = 0.55) is the largest known cosmic lens, with complex internal structures seen in deep X-ray, Sunyaev-Zel'dovich effect, and dynamical observations. We perform a combined weak- and strong-lensing analysis with wide-field BVR{sub c} i'z' Subaru/Suprime-Cam observations and 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble. We find consistent weak distortion and magnification measurements of background galaxies and combine these signals to construct an optimally estimated radial mass profile of the cluster and its surrounding large-scale structure out to 5 Mpc h {sup –1}. We find consistency between strong-lensing and weak-lensing in the region where these independent data overlap, <500 kpc h {sup –1}. The two-dimensional weak-lensing map reveals a clear filamentary structure traced by distinct mass halos. We model the lensing shear field with nine halos, including the main cluster, corresponding to mass peaks detected above 2.5?{sub ?}. The total mass of the cluster as determined by the different methods is M{sub vir} ? (2.8 ± 0.4) × 10{sup 15} M{sub ?}. Although this is the most massive cluster known at z > 0.5, in terms of extreme value statistics, we conclude that the mass of MACS J0717.5+3745 by itself is not in serious tension with ?CDM, representing only a ?2? departure above the maximum simulated halo mass at this redshift.
Lower Limit to the Scale of an Effective Theory of Gravitation
R. R. Caldwell; Daniel Grin
2008-02-26T23:59:59.000Z
We consider a linearized, effective quantum theory of gravitation in which gravity weakens at energies higher than ~10^-3 eV in order to accommodate the apparent smallness of the cosmological constant. Such a theory predicts departures from the static Newtonian inverse-square force law on distances below ~0.05 mm. However, we show that such a modification also leads to changes in the long-range behavior of gravity and is inconsistent with observed gravitational lenses.
T. Anguita; C. Faure; A. Yonehara; J. Wambsganss; J. -P. Kneib; G. Covone; D. Alloin
2008-02-04T23:59:59.000Z
CONTEXT: Gravitationally lensed quasars constitute an independent tool to derive H0 through time-delays; they offer as well the opportunity to study the mass distribution and interstellar medium of their lensing galaxies and, through microlensing they also allow one to study details of the emitting source. AIMS: For such studies, one needs to have an excellent knowledge of the close environment of the lensed images in order to model the lensing potential: this means observational data over a large field-of-view and spectroscopy at high spatial resolution. METHODS: We present VIMOS integral field observations around four lensed quasars: HE 0230-2130, RX J0911.4+0551, H 1413+117 and B 1359+154. Using the low, medium and high resolution modes, we study the quasar images and the quasar environments, as well as provide a detailed report of the data reduction. RESULTS: Comparison between the quasar spectra of the different images reveals differences for HE 0230-2130, RX J0911.4+0551 and H 1413+117: flux ratios between the images of the same quasar are different when measured in the emission lines and in the continuum. We have also measured the redshifts of galaxies in the neighborhood of HE 0230-2130 and RX J0911.4+0551 which possibly contribute to the total lensing potential. CONCLUSIONS: A careful analysis reveals that microlensing is the most natural explanation for the (de)magnification of the continuum emitting region of the background sources. In HE 0230-2130, image D is likely to be affected by microlensing magnification; in RX J0911.4+0551, images A1 and A3 are likely to be modified by microlensing de-magnification and in H 1413+117, at least image D is affected by microlensing.
Quantal Definition of the Weak Equivalence Principle
Abel Camacho; Arturo Camacho-Guardian
2008-11-03T23:59:59.000Z
The present work analyzes the meaning of the Weak Equivalence Principle in the context of quantum mechanics. A quantal definition for this principle is introduced. This definition does not require the concept of trajectory and relies upon the phase shift induced by a gravitational field in the context of a quantum interference experiment of two coherent beams of particles. In other words, it resorts to wave properties of the system and not to classical concepts as the idea of trajectory.
Deane, R P; Heywood, I
2015-01-01T23:59:59.000Z
Strong gravitational lensing provides some of the deepest views of the Universe, enabling studies of high-redshift galaxies only possible with next-generation facilities without the lensing phenomenon. To date, 21 cm radio emission from neutral hydrogen has only been detected directly out to z~0.2, limited by the sensitivity and instantaneous bandwidth of current radio telescopes. We discuss how current and future radio interferometers such as the Square Kilometre Array (SKA) will detect lensed HI emission in individual galaxies at high redshift. Our calculations rely on a semi-analytic galaxy simulation with realistic HI disks (by size, density profile and rotation), in a cosmological context, combined with general relativistic ray tracing. Wide-field, blind HI surveys with the SKA are predicted to be efficient at discovering lensed HI systems, increasingly so at z > 2. This will be enabled by the combination of the magnification boosts, the steepness of the HI luminosity function at the high-mass end, and t...
Cosmography with cluster strong lensing
James Gilmore; Priyamvada Natarajan
2009-05-29T23:59:59.000Z
By stacking an ensemble of strong lensing clusters, we demonstrate the feasibility of placing constraints on the dark energy equation of state. This is achieved by using multiple images of sources at two or more distinct redshift planes. The sample of smooth clusters in our simulations is based on observations of massive clusters and the distribution of background galaxies is constructed using the Hubble Deep Field. Our source distribution reproduces the observed redshift distribution of multiply imaged sources in Abell 1689. The cosmology recovery depends on the number of image families with known spectroscopic redshifts and the number of stacked clusters. Our simulations suggest that constraints comparable to those derived from other competing established techniques on a constant dark energy equation of state can be obtained using 10 to 40 clusters with 5 or more families of multiple images. We have also studied the observational errors in the image redshifts and positions. We find that spectroscopic redshifts and high resolution {\\it Hubble Space Telescope} images are required to eliminate confidence contour relaxation relative to the ideal case in our simulations. This suggests that the dark energy equation of state, and other cosmological parameters, can be constrained with existing {\\it Hubble Space Telescope} images of lensing clusters coupled with dedicated ground-based arc spectroscopy.
Tevatron Electron Lenses: Design and Operation
Shiltsev, Vladimir; /Fermilab; Bishofberger, Kip; /Los Alamos; Kamerdzhiev, Vsevolod; /Fermilab; Kozub, Sergei; /Serpukhov, IHEP; Kufer, Matthew; Kuznetsov, Gennady; Martinez, Alexander; Olson, Marvin; Pfeffer, Howard; Saewert, Greg; Scarpine, Vic; /Fermilab /SLAC /Fermilab /Serpukhov, IHEP /Novosibirsk, IYF /Serpukhov, IHEP /Fermilab
2008-08-01T23:59:59.000Z
The beam-beam effects have been the dominating sources of beam loss and lifetime limitations in the Tevatron proton-antiproton collider [1]. Electron lenses were originally proposed for compensation of electromagnetic long-range and head-on beam-beam interactions of proton and antiproton beams [2]. Results of successful employment of two electron lenses built and installed in the Tevatron are reported in [3,4,5]. In this paper we present design features of the Tevatron electron lenses (TELs), discuss the generation of electron beams, describe different modes of operation and outline the technical parameters of various subsystems.
Weakly sufficient quantum statistics
Katarzyna Lubnauer; Andrzej ?uczak; Hanna Pods?dkowska
2009-11-23T23:59:59.000Z
Some aspects of weak sufficiency of quantum statistics are investigated. In particular, we give necessary and sufficient conditions for the existence of a weakly sufficient statistic for a given family of vector states, investigate the problem of its minimality, and find the relation between weak sufficiency and other notions of sufficiency employed so far.
Tailoring Strong Lensing Cosmographic Observations
Linder, Eric V
2015-01-01T23:59:59.000Z
Strong lensing time delay cosmography has excellent complementarity with other dark energy probes, and will soon have abundant systems detected. We investigate two issues in the imaging and spectroscopic followup required to obtain the time delay distance. The first is optimization of spectroscopic resources. We develop a code to optimize the cosmological leverage under the constraint of constant spectroscopic time, and find that sculpting the lens system redshift distribution can deliver a 40% improvement in dark energy figure of merit. The second is the role of systematics, correlated between different quantities of a given system or model errors common to all systems. We show how the levels of different systematics affect the cosmological parameter estimation, and derive guidance for the fraction of double image vs quad image systems to follow as a function of differing systematics between them.
Christian Corda
2007-01-25T23:59:59.000Z
A derivation of the optical axis lenght fluctations due by tilts of the mirrors of the Fabry-Perot cavity of long-baseline interferometers for the detection of gravitational waves in presence of the gravitational field of the earth is discussed. By comparing with the typical tilt-induced noises it is shown that this potential signal, which is considered a weak source of noise, is negligible for the first generation of gravitational waves interferometers, but, in principle, this effect could be used for high precision measures of the gravitational acceleration if advanced projects will achieve an high sensitivity. In that case the precision of the misure could be higher than the gravimeter realized by the Istituto di Metrologia ``Gustavo Colonnetti''.
Gravitational lens modelling in a citizen science context
Küng, Rafael; More, Anupreeta; Baeten, Elisabeth; Coles, Jonathan; Cornen, Claude; Macmillan, Christine; Marshall, Phil; More, Surhud; Odermatt, Jonas; Verma, Aprajita; Wilcox, Julianne K
2015-01-01T23:59:59.000Z
We develop a method to enable collaborative modelling of gravitational lenses and lens candidates, that could be used by non-professional lens enthusiasts. It uses an existing free-form modelling program (glass), but enables the input to this code to be provided in a novel way, via a user-generated diagram that is essentially a sketch of an arrival-time surface. We report on an implementation of this method, SpaghettiLens, which has been tested in a modelling challenge using 29 simulated lenses drawn from a larger set created for the Space Warps citizen science strong lens search. We find that volunteers from this online community asserted the image parities and time ordering consistently in some lenses, but made errors in other lenses depending on the image morphology. While errors in image parity and time ordering lead to large errors in the mass distribution, the enclosed mass was found to be more robust: the model-derived Einstein radii found by the volunteers were consistent with those produced by one of...
Quantum-mechanical description of Lense-Thirring effect for relativistic scalar particles
Alexander J. Silenko
2014-08-10T23:59:59.000Z
Exact expression for the Foldy-Wouthuysen Hamiltonian of scalar particles is used for a quantum-mechanical description of the relativistic Lense-Thirring effect. The exact evolution of the angular momentum operator in the Kerr field approximated by a spatially isotropic metric is found. The quantum-mechanical description of the full Lense-Thirring effect based on the Laplace-Runge-Lenz vector is given in the nonrelativistic and weak-field approximation. Relativistic quantum-mechanical equations for the velocity and acceleration operators are obtained. The equation for the acceleration defines the Coriolis-like and centrifugal-like accelerations and presents the quantum-mechanical description of the frame-dragging effect.
On calculation of microlensing light curve by gravitational lens caustic
M. B. Bogdanov
2001-02-02T23:59:59.000Z
For an analysis of microlensing observational data in case of binary gravitational lenses as well as for an interpretation of observations of high magnification events in multiple images of a lensed quasar it is necessary to calculate for a given source the microlensing light curve by a fold caustic. This problem comes to the numerical calculation of a singular integral. We formulated the sufficient condition of a convergence of the integral sum for this singular integral. The strictly approach to the problem of a comparison of model results with the unequally sampled observational data consists in calculation of the model light curve in equidistant points of the canonical dissection of the integration segment and a following interpolation of its values at the moments of observations.
NEARBY PLANETARY SYSTEMS AS LENSES DURING PREDICTED CLOSE PASSAGES TO BACKGROUND STARS
Di Stefano, Rosanne; Matthews, James [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lepine, Sebastien [Department of Astrophysics, Division of Physical Sciences, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States)
2013-07-10T23:59:59.000Z
The Einstein rings and proper motions of nearby stars tend to be large. Thus, every year some foreground stars within a few hundred parsecs of Earth induce gravitational lensing events in background stars. In some of these cases, the events may exhibit evidence of planets orbiting the nearby star. In fact, planets can even be discovered during relatively distant passages. Here, we study the lensing signatures associated with planets orbiting nearby high-proper-motion stars. We find the following. (1) Wide-orbit planets can be detected for all distances of closest approach between the foreground and background stars, potentially producing independent events long before and/or after the closest approach. (2) Close-orbit planets can be detected for intermediate distances of closest approach, producing quasiperiodic signatures that may occur days or weeks before and after the stellar-lens event. (3) Planets in the so-called zone for resonant lensing can significantly increase the magnification when the distance of closest approach is small, making the stellar-lens event easier to detect, while simultaneously providing evidence for planets. Because approaches close enough to allow planets to be detected can be predicted, we can plan observing strategies to take advantage of the theoretical framework built in this paper, which describes the sequence of expected effects in terms of a sequence of detection regimes.
Determining the Lensing Fraction of SDSS Quasars Methods and Results from the EDR
Pindor, B; Lupton, R H; Brinkmann, J; Pindor, Bart; Turner, Edwin L.; Lupton, Robert H.
2003-01-01T23:59:59.000Z
We present an algorithm for selecting gravitational lens candidates from amongst Sloan Digital Sky Survey (SDSS) quasars. In median Early Data Release (EDR) conditions, the algorithm allows for the recovery of pairs of equal flux point sources down to separations of $\\sim 0{\\farcs}7$ or with flux ratios up to $\\sim$ 10:1 at a separation of $1\\farcs5$. The algorithm also recovers a wide variety of plausible quad geometries. We also present a method for determining the selection function of this algorithm through the use of simulated SDSS images and introduce a method for calibrating our simulated images through truth-testing with real SDSS data. Finally, we apply our algorithm and selection function to SDSS quasars from the EDR to get an upper bound on the lensing fraction. We find 13 candidates among 5120 z $>$ 0.6 SDSS quasars, implying an observed lensing fraction of not more than 4 $\\times 10^{-3}$. There is one likely lens system in our final sample, implying an observed lensing fraction of not less than ...
Determining the Lensing Fraction of SDSS Quasars: Methods and Results from the EDR
Bart Pindor; Edwin L. Turner; Robert H. Lupton; J. Brinkmann
2003-01-23T23:59:59.000Z
We present an algorithm for selecting gravitational lens candidates from amongst Sloan Digital Sky Survey (SDSS) quasars. In median Early Data Release (EDR) conditions, the algorithm allows for the recovery of pairs of equal flux point sources down to separations of $\\sim 0{\\farcs}7$ or with flux ratios up to $\\sim$ 10:1 at a separation of $1\\farcs5$. The algorithm also recovers a wide variety of plausible quad geometries. We also present a method for determining the selection function of this algorithm through the use of simulated SDSS images and introduce a method for calibrating our simulated images through truth-testing with real SDSS data. Finally, we apply our algorithm and selection function to SDSS quasars from the EDR to get an upper bound on the lensing fraction. We find 13 candidates among 5120 z $>$ 0.6 SDSS quasars, implying an observed lensing fraction of not more than 4 $\\times 10^{-3}$. There is one likely lens system in our final sample, implying an observed lensing fraction of not less than $3 \\times 10^{-5}$ (95% confidence levels).
Inverse Square Law of Gravitation in (2+1)-Dimensional Space-Time as a Consequence of Casimir Energy
H. H. Soleng
1993-10-04T23:59:59.000Z
The gravitational effect of vacuum polarization in space exterior to a particle in (2+1)-dimensional Einstein theory is investigated. In the weak field limit this gravitational field corresponds to an inverse square law of gravitational attraction, even though the gravitational mass of the quantum vacuum is negative. The paradox is resolved by considering a particle of finite extension and taking into account the vacuum polarization in its interior.
Fabrication of wedged multilayer Laue lenses
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Prasciolu, M.; Leontowich, A. F. G.; Krzywinski, J.; Andrejczuk, A.; Chapman, H. N.; Bajt, S.
2015-01-01T23:59:59.000Z
We present a new method to fabricate wedged multilayer Laue lenses, in which the angle of diffracting layers smoothly varies in the lens to achieve optimum diffracting efficiency across the entire pupil of the lens. This was achieved by depositing a multilayer onto a flat substrate placed in the penumbra of a straight-edge mask. The distance between the mask and the substrate was calibrated and the multilayer Laue lens was cut in a position where the varying layer thickness and the varying layer tilt simultaneously satisfy the Fresnel zone plate condition and Bragg’s law for all layers in the stack.more »This method can be used to extend the achievable numerical aperture of multilayer Laue lenses to reach considerably smaller focal spot sizes than achievable with lenses composed of parallel layers.« less
Galaxy Dynamics Predictions in the Nonsymmetric Gravitational Theory
J. W. Moffat
1994-12-28T23:59:59.000Z
In the weak field approximation, the nonsymmetric gravitational theory has, in addition to the Newtonian gravitational potential, a Yukawa potential produced by the exchange of a spin $1^+$ boson between fermions. If the range $r_0$ is of order $30$ kpc, then the potential due to the interaction of known neutrinos in the halos of galaxies can explain the flat rotation curves of galaxies. The results are based on a physical linear approximation to the NGT field equations and they are consistent with equivalence principle observations, other solar system gravitational experiments and the binary pulsar data.
Handbook for the GREAT08 Challenge: An image analysis competition for cosmological lensing
Sarah Bridle; John Shawe-Taylor; Adam Amara; Douglas Applegate; Sreekumar T. Balan; Joel Berge; Gary Bernstein; Hakon Dahle; Thomas Erben; Mandeep Gill; Alan Heavens; Catherine Heymans; F. William High; Henk Hoekstra; Mike Jarvis; Donnacha Kirk; Thomas Kitching; Jean-Paul Kneib; Konrad Kuijken; David Lagatutta; Rachel Mandelbaum; Richard Massey; Yannick Mellier; Baback Moghaddam; Yassir Moudden; Reiko Nakajima; Stephane Paulin-Henriksson; Sandrine Pires; Anais Rassat; Alexandre Refregier; Jason Rhodes; Tim Schrabback; Elisabetta Semboloni; Marina Shmakova; Ludovic van Waerbeke; Dugan Witherick; Lisa Voigt; David Wittman
2009-06-15T23:59:59.000Z
The GRavitational lEnsing Accuracy Testing 2008 (GREAT08) Challenge focuses on a problem that is of crucial importance for future observations in cosmology. The shapes of distant galaxies can be used to determine the properties of dark energy and the nature of gravity, because light from those galaxies is bent by gravity from the intervening dark matter. The observed galaxy images appear distorted, although only slightly, and their shapes must be precisely disentangled from the effects of pixelisation, convolution and noise. The worldwide gravitational lensing community has made significant progress in techniques to measure these distortions via the Shear TEsting Program (STEP). Via STEP, we have run challenges within our own community, and come to recognise that this particular image analysis problem is ideally matched to experts in statistical inference, inverse problems and computational learning. Thus, in order to continue the progress seen in recent years, we are seeking an infusion of new ideas from these communities. This document details the GREAT08 Challenge for potential participants. Please visit http://www.great08challenge.info for the latest information.
Regimbau, T.
Increasing the sensitivity of a gravitational-wave (GW) detector improves our ability to measure the characteristics of detected sources. It also increases the number of weak signals that contribute to the data. Because ...
A Gravitational Lens Solution for IRAS F10214+4724
Tom Broadhurst; Joseph Lehar
1995-05-03T23:59:59.000Z
We show that the high redshift IRAS source F10214 is highly magnified by the gravitational field of an intervening elliptical galaxy, accounting for its many anomalous properties. Detailed radio and near-IR images identify the IRAS source with a symmetric arc, centered on a red object, or lensing galaxy. To explain the observed structures, the center of the source must much more highly magnified than its outer regions. Lensing predicts a small counterimage to the arc, which we find adjacent to the lensing galaxy. A red component in the observed spectrum suggests a lens redshift of unity, and the lens model yields a mass estimate of $M(r<3kpc)\\approx10^{11}{M_solar}$, consistent with an ordinary elliptical galaxy. We present new high-resolution optical images which show a thin arc of emission, implying an intrinsically small source ($<0.5kpc$) which is highly magnified ($\\sim20\\times$). Since the optical is strongly polarized with a Seyfert~II spectrum, we propose that the optical arc is magnified image of the inner region of an obscured AGN. The obscuring ``torus'' will be similarly magnified, naturally accounting for the large IR flux. We show that finding objects like F10214+4724 in redshift surveys is probable, given the level of magnification bias expected for compact luminous IRAS sources. Such cases represent the obscured AGN counterparts to the lensed QSO population and, because of their extended sizes, are useful in determining the mass distribution in the lensing galaxies.
Scalar and Vector Field Constraints, Deflection of Light and Lensing in Modified Gravity (MOG)
J. W. Moffat
2014-10-06T23:59:59.000Z
A conformal coupling of the metric in the Jordan frame to the energy-momentum tensor, screens the scalar field gravitational coupling strength $G$ in modified gravity (MOG). The scalar field acquires a mass which depends on the local matter density: the scalar field particle is massive for the Sun and earth, where the density is high compared to low density environments in cosmology and astrophysics. Together with the screening of the vector field $\\phi_\\mu$, this guarantees that solar system tests of gravity are satisfied. The conformal metric is coupled to the electromagnetic matter field and energy-momentum tensor, screening $G$ for the Sun and the deflection of light by the Sun and the Shapiro time delay in MOG are in agreement with general relativity. For galaxies and galactic clusters the enhanced gravitational coupling constant $G$ leads to agreement with gravitational lensing without dark matter. For compact binary pulsars the screening of $G$ removes the monopole and dipole gravitational radiation modes in agreement with the binary pulsar timing data.
Compensation for thermal effects in mirrors of Gravitational Wave Interferometers
P. Hello
2001-04-18T23:59:59.000Z
In this paper we study several means of compensating for thermal lensing which, otherwise, should be a source of concern for future upgrades of interferometric detectors of gravitational waves. The methods we develop are based on the principle of heating the cold parts of the mirrors. We find that thermal compensation can help a lot but can not do miracles. It seems finally that the best strategy for future upgrades (``advanced configurations'') is maybe to use thermal compensation together with another substrate materials than Silica, for example Sapphire.
Gamma Ray Fresnel lenses - why not?
G. K. Skinner
2006-02-03T23:59:59.000Z
Fresnel lenses offer the possibility of concentrating the flux of X-rays or gamma-rays flux falling on a geometric area of many square metres onto a focal point which need only be a millimetre or so in diameter (and which may even be very much smaller). They can do so with an efficiency that can approach 100%, and yet they are easily fabricated and have no special alignment requirements. Fresnel lenses can offer diffraction-limited angular resolution, even in a domain where that limit corresponds to less than a micro second of arc. Given all these highly desirable attributes, it is natural to ask why Fresnel gamma ray lenses are not already being used, or at least why there is not yet any mission that plans to use the technology. Possible reasons (apart from the obvious one that nobody thought of doing so) include the narrow bandwidth of simple Fresnel lenses, their very long focal length, and the problems of target finding. It is argued that none of these is a "show stopper" and that this technique should be seriously considered for nuclear astrophysics.
Constraints on small-scale cosmological fluctuations from SNe lensing dispersion
Ben-Dayan, Ido
2015-01-01T23:59:59.000Z
We provide predictions on small-scale cosmological density power spectrum from supernova lensing dispersion. Parameterizing the primordial power spectrum with running $\\alpha$ and running of running $\\beta$ of the spectral index, we exclude large positive $\\alpha$ and $\\beta$ parameters which induce too large lensing dispersions over current observational upper bound. We ran cosmological N-body simulations of collisionless dark matter particles to investigate non-linear evolution of the primordial power spectrum with positive running parameters. The initial small-scale enhancement of the power spectrum is largely erased when entering into the non-linear regime. For example, even if the linear power spectrum at $k>10h {\\rm Mpc}^{-1}$ is enhanced by $1-2$ orders of magnitude, the enhancement much decreases to a factor of $2-3$ at late time ($z \\leq 1.5$). Therefore, the lensing dispersion induced by the dark matter fluctuations weakly constrains the running parameters. When including baryon-cooling effects (whi...
Sanyal, Devashish [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700032 (India)]. E-mail: tpds@mahendra.iacs.res.in; Sen, Siddhartha [School of Mathematics, Trinity College, Dublin 2 (Ireland)]. E-mail: sen@maths.tcd.ie
2006-06-15T23:59:59.000Z
The present manuscript dealing with large occupation of states of a quantum system, extends the study to the case of quantum weak turbulence. The quasiparticle spectrum, calculated for such a system, using a Green's function approach, establishes the dissipative and inertial regimes, hence a Kolmogorov type of picture.
Interferometric Plasmonic Lensing with Nanohole Arrays
Gong, Yu; Joly, Alan G.; El-Khoury, Patrick Z.; Hess, Wayne P.
2014-12-18T23:59:59.000Z
Nonlinear photoemission electron microscopy (PEEM) of nanohole arrays in gold films maps propagating surface plasmons (PSPs) launched from lithographically patterned structures. Strong near field photoemission patterns are observed in the PEEM images, recorded following low angle of incidence irradiation of nanohole arrays with sub-15 fs laser pulses centered at 780 nm. The recorded photoemission patterns are attributed to constructive and destructive interferences between PSPs launched from the individual nanoholes which comprise the array. By exploiting the wave nature of PSPs, we demonstrate how varying the array geometry (hole diameter, pitch, and number of rows/columns) ultimately yields intense localized photoemission. Through a combination of PEEM and finite-difference time-domain simulations, we identify the optimal array geometry for efficient light coupling and interferometric plasmonic lensing. We show a preliminary application of inteferometric plasmonic lensing by enhancing the photoemission from the vertex of a gold triangle using nanohole array.
Lorenzo Iorio
2009-11-30T23:59:59.000Z
According to general relativity, a spinning body of mass M and angular momentum S, like a star or a planet, generates a gravitomagnetic field which induces, among other phenomena, also the Lense-Thirring effect, i.e. secular precessions of the path of a test particle orbiting it. Direct and indisputable tests of such a relativistic prediction are still missing. We discuss some performed attempts to measure it in the gravitational fields of several bodies in the Solar System with natural and artificial objects. The focus is on the realistic evaluation of the impact of some competing classical forces regarded as sources of systematic uncertainties degrading the total accuracy obtainable.
Torsion-balance tests of the weak equivalence principle
T. A. Wagner; S. Schlamminger; J. H. Gundlach; E. G. Adelberger
2012-07-10T23:59:59.000Z
We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium-aluminum and beryllium-titanium test body pairs with precisions at the part in $10^{13}$ level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects for further improvements in experimental sensitivity.
Automation Enhancement of Multilayer Laue Lenses
Lauer K. R.; Conley R.
2010-12-01T23:59:59.000Z
X-ray optics fabrication at Brookhaven National Laboratory has been facilitated by a new, state of the art magnetron sputtering physical deposition system. With its nine magnetron sputtering cathodes and substrate carrier that moves on a linear rail via a UHV brushless linear servo motor, the system is capable of accurately depositing the many thousands of layers necessary for multilayer Laue lenses. I have engineered a versatile and automated control program from scratch for the base system and many subsystems. Its main features include a custom scripting language, a fully customizable graphical user interface, wireless and remote control, and a terminal-based interface. This control system has already been successfully used in the creation of many types of x-ray optics, including several thousand layer multilayer Laue lenses.Before reaching the point at which a deposition can be run, stencil-like masks for the sputtering cathodes must be created to ensure the proper distribution of sputtered atoms. Quality of multilayer Laue lenses can also be difficult to measure, given the size of the thin film layers. I employ my knowledge of software and algorithms to further ease these previously painstaking processes with custom programs. Additionally, I will give an overview of an x-ray optic simulator package I helped develop during the summer of 2010. In the interest of keeping my software free and open, I have worked mostly with the multiplatform Python and the PyQt application framework, utilizing C and C++ where necessary.
Propagation of gravitational waves in a universe with slowly-changing equation of state
Edmund Schluessel
2014-06-17T23:59:59.000Z
An exact solution for the expansion of a flat universe with dark energy evolving according to a simple model is explored. The equation for weak primordial gravitational waves propagating in this universe is solved and explored; gravitational waves in a flat cosmology possessing both a "big bang" singularity and a "big rip" singularity can be described with confluent Heun functions. We develop approximation methods for confluent Heun equations in regimes of interest to gravitational wave astronomers and predict the diminution in gravitational wave amplitude in a universe with both a Big Bang and a Big Rip.
accommodating intraocular lenses: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
vision (more) Ale Magar, Jit Bahadur 2010-01-01 2 Phakic Intraocular Lenses, ICL & PRL : silmnsisiset piilolinssit ja niiden tuottamat tulokset. Open Access Theses and...
aspheric intraocular lenses: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
lens (IOL). IOL optical designs Dainty, Chris 3 Phakic Intraocular Lenses, ICL & PRL : silmnsisiset piilolinssit ja niiden tuottamat tulokset. Open Access Theses and...
Mass profiles of clusters of galaxies : a comparison of X-ray and weak lensing observations
Peng, En-Hsin
2011-01-01T23:59:59.000Z
Clusters of galaxies are useful probes of cosmology because they are the most massive bound systems and fair representatives of the matter composition of the universe. For clusters to be used as tracers of cosmic evolution, ...
The Gravitational Cherenkov Radiation
A. M. Ignatov
2001-10-26T23:59:59.000Z
An example of discontinuity of the energy-momentum tensor moving at superluminal velocity is discussed. It is shown that the gravitational Mach cone is formed. The power spectrum of the corresponding Cherenkov radiation is evaluated.
Nonsymmetric Gravitational Theory
J. W. Moffat
1994-11-10T23:59:59.000Z
A new version of nonsymmetric gravitational theory is presented. The field equations are expanded about the Minkowski metric, giving in lowest order the linear Einstein field equations and massive Proca field equations for the antisymmetric field $g_{[\\mu\
Dust emission from the lensed Lyman break galaxy cB58
Baker, A J; Genzel, R; Tacconi, L J; Lehnert, M D
2001-01-01T23:59:59.000Z
We detect 1.2mm continuum emission from dust in the gravitationally lensed Lyman break galaxy MS 1512+36-cB58. Our detected flux is surprisingly low: relative to local starburst galaxies, cB58 appears to produce somewhat less far-IR emission than its UV reddening predicts. After comparing several different estimates of the source's dust content, we conclude that the apparent discrepancy is most likely related to uncertainty in its UV spectral slope. Alternate scenarios to account for a far-IR "deficit" which rely on a high dust temperature or differential magnification are less satisfactory. Our result underscores one of the risks inherent in characterizing the cosmic star formation history from rest-UV data alone.
Newman, Andrew B; Treu, Tommaso
2015-01-01T23:59:59.000Z
Observations of strong gravitational lensing, stellar kinematics, and mass tracers on larger scales enable accurate measures of the distribution of dark matter and baryons in massive early-type galaxies (ETGs). While such techniques have previously been applied to galaxy-scale and cluster-scale lenses, the paucity of intermediate-mass systems with high-quality data has precluded a uniform analysis of mass-dependent trends. With the aim of bridging this gap, we present new observations and analyses of 10 group-scale lenses at =0.36 characterized by Einstein radii 2.5"-5.1" and a mean halo mass of M_200 = 10^14.0 Msol. For these groups, we find a mean halo concentration c_200 = 5.0 +- 0.8 consistent with unmodified cold dark matter halos and recent simulations of galaxy formation. By combining our data with other lens samples in the literature, we analyze the mass structure of ETGs in halos spanning the mass range 10^13-10^15 Msol using homogeneous methods and data. We show that the slope of the total density p...
R. A. Daishev; Z. G. Murzakhanov; A. F. Skochilov
2008-01-04T23:59:59.000Z
A scheme of an optical detector is proposed for checking Einsteins equivalence principle (EEP) in a null gravitational redshift experiment and for testing methods for calculating the length of a resonator in a weak variable gravitational field by recording the variations of the difference frequency of resonators caused by lunisolar variations of the geopotential in a double or a two-resonator laser system.
Modeling a nonperturbative spinor vacuum interacting with a strong gravitational wave
Vladimir Dzhunushaliev; Vladimir Folomeev
2015-03-15T23:59:59.000Z
We consider the propagation of strong gravitational waves interacting with a nonperturbative vacuum of spinor fields. To described the latter, we suggest an approximate model. The corresponding Einstein equation has the form of the Schr\\"odinger equation. Its gravitational-wave solution is analogous to the solution of the Schr\\"odinger equation for an electron moving in a periodic potential. The general solution for the periodic gravitational waves is found. The analog of the Kronig-Penney model for gravitational waves is considered. It is shown that the suggested gravitational-wave model permits the existence of weak electric charge and current densities concomitant with the gravitational wave. Based on this observation, a possible experimental verification of the model is suggested.
Modeling a nonperturbative spinor vacuum interacting with a strong gravitational wave
Dzhunushaliev, Vladimir
2015-01-01T23:59:59.000Z
We consider the propagation of strong gravitational waves interacting with a nonperturbative vacuum of spinor fields. To described the latter, we suggest an approximate model. The corresponding Einstein equation has the form of the Schr\\"odinger equation. Its gravitational-wave solution is analogous to the solution of the Schr\\"odinger equation for an electron moving in a periodic potential. The general solution for the periodic gravitational waves is found. The analog of the Kronig-Penney model for gravitational waves is considered. It is shown that the suggested gravitational-wave model permits the existence of weak electric charge and current densities concomitant with the gravitational wave. Based on this observation, a possible experimental verification of the model is suggested.
Weak Interaction | Jefferson Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What'sis Taking Over OurThe Iron SpinPrincetonUsing Maps1DOETHE FUTURE LOOKSofthe Geeks: CelebratingWeak
Construction progress of the RHIC electron lenses
Fischer W.; Altinbas, Z.; Anerella, M.; Beebe, E.; et al
2012-05-20T23:59:59.000Z
In polarized proton operation the RHIC performance is limited by the head-on beam-beam effect. To overcome this limitation two electron lenses are under construction. We give an overview of the construction progress. Guns, collectors and the warm electron beam transport solenoids with their power supplies have been constructed. The superconducting solenoids that guide the electron beam during the interaction with the proton beam are near completion. A test stand has been set up to verify the performance of the gun, collector and some of the instrumentation. The infrastructure is being prepared for installation, and simulations continue to optimize the performance.
Bernstein, Gary
: Optimal Measurements for Weak Lensing G. M. Bernstein & M. Jarvis Dept. of Astronomy, University became available (Valdes, Tyson, & Jarvis 1983; Tyson et al. 1984). Furthermore, optical and atmospheric not occur until CCD images of suÃ?cient depth and #12;eld were available (Tyson, Valdes, & Wenk 1990
Analytic Expression of the Genus in Weakly Non-Gaussian Field Induced by Gravity
T. Matsubara
1994-05-16T23:59:59.000Z
The gravitational evolution of the genus of the density field in large-scale structure is analytically studied in a weakly nonlinear regime using second-order perturbation theory. Weakly nonlinear evolution produces asymmetry in the symmetric genus curve for Gaussian initial density field. The effect of smoothing the density field in perturbation theory on the genus curve is also evaluated and gives the dependence of the asymmetry of the genus curve on spectra of initial fluctuations.
Jackson, N. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom)
2011-09-20T23:59:59.000Z
We present new radio observations of the large-separation gravitationally lensed quasar SDSS J1004+4112, taken in a total of 6 hr of observations with the Expanded Very Large Array. The maps reach a thermal noise level of approximately 4 {mu}Jy. We detect four of the five lensed images at the 15-35 {mu}Jy level, representing a source of intrinsic flux density, after allowing for lensing magnification, of about 1 {mu}Jy, intrinsically probably the faintest radio source yet detected. This reinforces the utility of gravitational lensing in potentially allowing us to study nJy-level sources before the advent of the Square Kilometre Array. In an optical observation taken three months after the radio observation, image C is the brightest image, whereas the radio map shows flux density ratios consistent with previous optical observations. Future observations separated by a time delay will give the intrinsic flux ratios of the images in this source.
Compound Refractive Lenses for Thermal Neutron Applications
Gary, Charles K.
2013-11-12T23:59:59.000Z
This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 ?m which is better than has been previously shown. We have also determined designs for Fresnel CRLs that will greatly improve performance.
Cosmology of gravitational vacuum
V. Burdyuzha; G. Vereshkov; J. Pacheco
2007-12-29T23:59:59.000Z
Production of gravitational vacuum defects and their contribution to the energy density of our Universe are discussed. These topological microstructures (defects) could be produced in the result of creation of the Universe from "nothing" when a gravitational vacuum condensate has appeared. They must be isotropically distributed over the isotropic expanding Universe. After Universe inflation these microdefects are smoothed, stretched and broken up. A part of them could survive and now they are perceived as the structures of Lambda-term and an unclustered dark matter. It is shown that the parametrization noninvariance of the Wheeler-De Witt equation can be used to describe phenomenologically vacuum topological defects of different dimensions (worm-holes, micromembranes, microstrings and monopoles). The mathematical illustration of these processes may be the spontaneous breaking of the local Lorentz-invariance of the quasi-classical equations of gravity. Probably the gravitational vacuum condensate has fixed time in our Universe. Besides, 3-dimensional topological defects renormalize Lambda-term.
Klaus Wilhelm; Bhola N. Dwivedi
2014-04-16T23:59:59.000Z
The study of the gravitational redshift\\,---\\,a relative wavelength increase of $\\approx 2 \\times 10^{-6}$ was predicted for solar radiation by Einstein in 1908\\,---\\,is still an important subject in modern physics. In a dispute whether or not atom interferometry experiments can be employed for gravitational redshift measurements, two research teams have recently disagreed on the physical cause of the shift. Regardless of any discussion on the interferometer aspect\\,---\\,we find that both groups of authors miss the important point that the ratio of gravitational to the electrostatic forces is generally very small. For instance, the gravitational force acting on an electron in a hydrogen atom situated in the Sun's photosphere to the electrostatic force between the proton and the electron is approximately $3 \\times 10^{-21}$. A comparison of this ratio with the predicted and observed solar redshift indicates a discrepancy of many orders of magnitude. Here we show, with Einstein's early assumption of the frequency of spectral lines depending only on the generating ion itself as starting point, that a solution can be formulated based on a two-step process in analogy with Fermi's treatment of the Doppler effect. It provides a sequence of physical processes in line with the conservation of energy and momentum resulting in the observed shift and does not employ a geometric description. The gravitational field affects the release of the photon and not the atomic transition. The control parameter is the speed of light. The atomic emission is then contrasted with the gravitational redshift of matter-antimatter annihilation events.
Supersymmetry and gravitational duality
Argurio, Riccardo; Dehouck, Francois; Houart, Laurent [Physique Theorique et Mathematique and International Solvay Institutes, Universite Libre de Bruxelles, C.P. 231, 1050 Bruxelles (Belgium)
2009-06-15T23:59:59.000Z
We study how the supersymmetry algebra copes with gravitational duality. As a playground, we consider a charged Taub-Newman-Unti-Tamburino(NUT) solution of D=4, N=2 supergravity. We find explicitly its Killing spinors, and the projection they obey provides evidence that the dual magnetic momenta necessarily have to appear in the supersymmetry algebra. The existence of such a modification is further supported using an approach based on the Nester form. In the process, we find new expressions for the dual magnetic momenta, including the NUT charge. The same expressions are then rederived using gravitational duality.
Affine Defects and Gravitation
R. J. Petti
2014-12-12T23:59:59.000Z
We argue that the structure general relativity (GR) as a theory of affine defects is deeper than the standard interpretation as a metric theory of gravitation. Einstein-Cartan theory (EC), with its inhomogenous affine symmetry, should be the standard-bearer for GR-like theories. A discrete affine interpretation of EC (and gauge theory) yields topological definitions of momentum and spin (and Yang Mills current), and their conservation laws become discrete topological identities. Considerations from quantum theory provide evidence that discrete affine defects are the physical foundation for gravitation.
Spiral galaxy lensing: a model with twist
2014-05-27T23:59:59.000Z
May 27, 2014. Abstract. We propose a model for gravitational ..... h(s);k(s); c2 z2. ) , where B is the Beta function, h(s) = 1. 2. (. 1 + s2+is. 1+s2. ) , k(s)=1+ h(s).
X-ray Lenses Fabricated by LIGA Technology
Nazmov, Vladimir; Last, Arndt; Saile, Volker [Institut fuer Microstrukturtechnik, Forschungszentrum Karlsruhe GmbH, 76021 Karlsruhe (Germany); Karlsruhe University, 76131 Karlsruhe (Germany); Reznikova, Elena; Mohr, Jurgen [Institut fuer Microstrukturtechnik, Forschungszentrum Karlsruhe GmbH, 76021 Karlsruhe (Germany); Simon, Rolf [Institut fuer Synchrotronstrahlung, Forschungszentrum Karlsruhe GmbH, 76021 Karlsruhe (Germany); DiMichiel, Marco [European Synchrotron Radiation Facility, BP220, 38043, Grenoble (France)
2007-01-19T23:59:59.000Z
X-ray refractive optical lens systems have been successfully elaborated, designed, fabricated at the Institute for Microstructure Technology at the Forschungszentrum Karlsruhe (Germany) using LIGA technology in recent years. The lenses are structured in a SU-8 polymer. The capability of the LIGA technique to create an arbitrary profile of the focusing microstructures allow the fabrication of lenses with different curvature radius of parabolic geometry, minimized absorption and a large depth of focus. Also a set of planar lens systems on one substrate can be realized with 17 lenses providing identical focal distances for different X-ray energies from 2 to over 100 keV. Nickel lenses fabricated by electroforming using polymer templates can be applied for energies larger than 80 keV. The parabolic crossed lenses are used for 2D nano focusing of monochromatic beams. The quasi-parabolic crossed lenses with a submicron focus and a focus depth of the centimetre range can be used as an achromatic system. Mosaic truncated parabolic lenses with a focusing aperture up to 1 mm are made to increase the X-ray intensity in the focused spot.
Gravitational red-shift and deflection of slow light
J. Dressel; S. G. Rajeev; J. C. Howell; A. N. Jordan
2008-10-27T23:59:59.000Z
We explore the nature of the classical propagation of light through media with strong frequency-dependent dispersion in the presence of a gravitational field. In the weak field limit, gravity causes a redshift of the optical frequency, which the slow-light medium converts into a spatially-varying index of refraction. This results in the bending of a light ray in the medium. We further propose experimental techniques to amplify and detect the phenomenon using weak value measurements. Independent heuristic and rigorous derivations of this effect are given.
Alternatives to Schwarzschild in the weak field limit of General Relativity
V. Bozza; A. Postiglione
2015-04-28T23:59:59.000Z
The metric outside an isolated object made up of ordinary matter is bound to be the classical Schwarzschild vacuum solution of General Relativity. Nevertheless, some solutions are known (e.g. Morris-Thorne wormholes) that do not match Schwarzschild asymptotically. On a phenomenological point of view, gravitational lensing in metrics falling as $1/r^q$ has recently attracted great interest. In this work, we explore the conditions on the source matter for constructing static spherically symmetric metrics exhibiting an arbitrary power-law as Newtonian limit. For such space-times we also derive the expressions of gravitational redshift and force on probe masses, which, together with light deflection, can be used in astrophysical searches of non-Schwarzschild objects made up of exotic matter. Interestingly, we prove that even a minimally coupled scalar field with a power-law potential can support non-Schwarzschild metrics with arbitrary asymptotic behaviour.
Gravitational waves in the spectral action of noncommutative geometry
Nelson, William; Ochoa, Joseph; Sakellariadou, Mairi [Institute of Gravitation and the Cosmos, Penn State University, State College, Pennsylvania 16801 (United States); Department of Physics, King's College, University of London, Strand WC2R 2LS, London (United Kingdom)
2010-10-15T23:59:59.000Z
The spectral triple approach to noncommutative geometry allows one to develop the entire standard model (and supersymmetric extensions) of particle physics from a purely geometry standpoint and thus treats both gravity and particle physics on the same footing. The bosonic sector of the theory contains a modification to Einstein-Hilbert gravity, involving a nonconformal coupling of curvature to the Higgs field and conformal Weyl term (in addition to a nondynamical topological term). In this paper we derive the weak-field limit of this gravitational theory and show that the production and dynamics of gravitational waves are significantly altered. In particular, we show that the graviton contains a massive mode that alters the energy lost to gravitational radiation, in systems with evolving quadrupole moment. We explicitly calculate the general solution and apply it to systems with periodically varying quadrupole moments, focusing, in particular, on the well-known energy loss formula for circular binaries.
Design and demonstration of broadband thin planar diffractive acoustic lenses
Wang, Wenqi; Xie, Yangbo; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A., E-mail: cummer@ee.duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)
2014-09-08T23:59:59.000Z
We present here two diffractive acoustic lenses with subwavelength thickness, planar profile, and broad operation bandwidth. Tapered labyrinthine unit cells with their inherently broadband effective material properties are exploited in our design. Both the measured and the simulated results are showcased to demonstrate the lensing effect over more than 40% of the central frequency. The focusing of a propagating Gaussian modulated sinusoidal pulse is also demonstrated. This work paves the way for designing diffractive acoustic lenses and more generalized phase engineering diffractive elements with labyrinthine acoustic metamaterials.
The use of gravitational lenses in the study of distant galaxy mergers
Kats, A V
2013-01-01T23:59:59.000Z
Gravlenses are efficiently explored for detecting the most distant galaxies (up to z=10 redshifts). As an example of the role played by gravlenses we refer to the observation of the galaxy merger at z=3 (Borys, et al; Berciano Alba, et al). We derived solutions for the Smoluchowski kinetic equation for the mass function of galaxies, which describes mergers in differential approximation (minor mergers). It is shown that the evolution of the slope of luminosity function observed in the Ultra Deep Hubble Field (Bouwence et al) can be described as a result of explosive evolution driven by galaxy mergers.
clusters derived from gravitational lensing and x-ray data sometimes differ by up to a
mating swarms that their predators--principally birds--can consume no more than 15% of the peak numbers (2000). 8. G. G. Raffelt, Annu. Rev. Nucl. Part. Sci. 49, 163 (1999). 9. CERN Axion Solar Telescope
Time Delays in the Gravitationally Lensed Quasar H1413+117 (Cloverleaf)
Goicoechea, Luis J
2009-01-01T23:59:59.000Z
The quadruple quasar H1413+117 (z_s = 2.56) has been monitored with the 2.0 m Liverpool Telescope in the r Sloan band from 2008 February to July. This optical follow-up leads to accurate light curves of the four quasar images (A-D), which are defined by 33 epochs of observation and an average photometric error of \\sim 15 mmag. We then use the observed (intrinsic) variations of \\sim 50-100 mmag to measure the three time delays for the lens system for the first time (1\\sigma confidence intervals): \\Delta \\tau_{AB} = -17 +/- 3, \\Delta \\tau_{AC} = -20 +/- 4, and \\Delta \\tau_{AD} = 23 +/- 4 days (\\Delta \\tau_{ij} = \\tau_j - \\tau_i; B and C are leading, while D is trailing). Although time delays for lens systems are often used to obtain the Hubble constant (H_0), the unavailability of the spectroscopic lens redshift (z_l) in the system H1413+117 prevents a determination of H_0 from the measured delays. In this paper, the new time delay constraints and a concordance expansion rate (H_0 = 70 km s^{-1} Mpc^{-1}) allow...
Harmonic generation of gravitational wave induced Alfven waves
Mats Forsberg; Gert Brodin
2007-11-26T23:59:59.000Z
Here we consider the nonlinear evolution of Alfven waves that have been excited by gravitational waves from merging binary pulsars. We derive a wave equation for strongly nonlinear and dispersive Alfven waves. Due to the weak dispersion of the Alfven waves, significant wave steepening can occur, which in turn implies strong harmonic generation. We find that the harmonic generation is saturated due to dispersive effects, and use this to estimate the resulting spectrum. Finally we discuss the possibility of observing the above process.
Ultrahigh precision cosmology from gravitational waves
Cutler, Curt [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Holz, Daniel E. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2009-11-15T23:59:59.000Z
We show that the Big Bang Observer (BBO), a proposed space-based gravitational-wave (GW) detector, would provide ultraprecise measurements of cosmological parameters. By detecting {approx}3x10{sup 5} compact-star binaries, and utilizing them as standard sirens, BBO would determine the Hubble constant to {approx}0.1%, and the dark-energy parameters w{sub 0} and w{sub a} to {approx}0.01 and {approx}0.1, respectively. BBO's dark-energy figure-of-merit would be approximately an order of magnitude better than all other proposed, dedicated dark-energy missions. To date, BBO has been designed with the primary goal of searching for gravitational waves from inflation, down to the level {omega}{sub GW}{approx}10{sup -17}; this requirement determines BBO's frequency band (deci-Hz) and its sensitivity requirement (strain measured to {approx}10{sup -24}). To observe an inflationary GW background, BBO would first have to detect and subtract out {approx}3x10{sup 5} merging compact-star binaries, out to a redshift z{approx}5. It is precisely this carefully measured foreground which would enable high-precision cosmology. BBO would determine the luminosity distance to each binary to {approx} percent accuracy. In addition, BBO's angular resolution would be sufficient to uniquely identify the host galaxy for the majority of binaries; a coordinated optical/infrared observing campaign could obtain the redshifts. Combining the GW-derived distances and the electromagnetically-derived redshifts for such a large sample of objects, out to such high redshift, naturally leads to extraordinarily tight constraints on cosmological parameters. We emphasize that such 'standard siren' measurements of cosmology avoid many of the systematic errors associated with other techniques: GWs offer a physics-based, absolute measurement of distance. In addition, we show that BBO would also serve as an exceptionally powerful gravitational-lensing mission, and we briefly discuss other astronomical uses of BBO, including providing an early warning system for all short/hard gamma-ray bursts.
acrylic intraocular lenses: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a...
Possibility of Control of the Gravitational Mass by means of Extra-Low Frequencies Radiation
Fran De Aquino
2000-05-24T23:59:59.000Z
According to the weak form of Einstein's general relativity equivalence principle, the gravitational and inertial masses are equivalent. However recent calculations (gr-qc/9910036) have revealed that they are correlated by an adimensional factor, which is equal to one in absence of radiation only. We have built an experimental system to check this unexpected theoretical result. It verifies the effects of the extra-low frequency (ELF) radiation on the gravitational mass of a body. We show that there is a direct correlation between the radiation absorbed by the body and its gravitational mass, independently of the inertial mass. This has fundamental consequences to Unified Field Theory and Quantum Cosmology.
Packard, Richard E.
from the response of the cell to a step in the chemical potential difference across the array. When present a "Chemical potential battery" for superfluid 4He weak link cells, whereby a constant heater power in this dissertation represent a breakthrough in super- fluid 4He weak link research, and provide a big step
Weak Measurements via Quantum Erasure
Aharon Brodutch; Eliahu Cohen
2014-09-04T23:59:59.000Z
Weak measurement is increasingly acknowledged as an important theoretical and experimental tool. Until now however, it was not known how to perform an efficient weak non-local measurement of a general operator. We propose a novel scheme for performing non-local weak measurement which is based on the principle of quantum erasure. This method is then demonstrated within a few gedanken experiments, and also applied to the case of measuring sequential weak values. Comparison with other protocols for extracting non-local weak values offers several advantages of the suggested algorithm. In addition to the practical merits, this scheme sheds new light on fundamental topics such as causality, non-locality, measurement and uncertainty.
Gravitational Tunneling Radiation
Mario Rabinowitz
2002-12-11T23:59:59.000Z
The isolated black hole radiation of both Hawking and Zel'dovich are idealized abstractions as there is always another body to distort the potential. This is considered with respect to both gravitational tunneling, and black hole "no-hair" theorems. The effects of a second body are to lower the gravitational barrier of a black hole and to give the barrier a finite rather than infinite width so tha a particle can escape by tunneling (as in field emission) or over the top of the lowered barrier (as in Schottky emission). Thus radiation may be emitted from black holes in a process differing from that of Hawking radiation, P SH, which has been undetected for over 24 years. The radiated power from a black hole derived here is PR e ^2__ PSH, where e ^2__ is he ransmission probability for radiation through the barrier. This is similar to electric field emission of electrons from a metal in that the emission can in principle be modulated and beamed. The temperature and entropy of black holes are reexamined. Miniscule black holes herein may help explain the missing mass of the universe, accelerated expansion of the universe, and anomalous rotation of spiral galaxies. A gravitational interference effect for black hole radiation similar to the Aharonov-Bohm effect is also examined.
Thermodynamics and gravitational collapse
Daniele Malafarina; Pankaj S. Joshi
2011-06-19T23:59:59.000Z
It is known now that a typical gravitational collapse in general relativity, evolving from regular initial data and under physically reasonable conditions would end in either a black hole or a naked singularity final state. An important question that needs to be answered in this connection is, whether the analogues of the laws of thermodynamics, as formulated for relativistic horizons are respected by the dynamical spacetimes for collapse that end in the formation of a naked singularity. We investigate here the thermodynamical behaviour of the dynamical horizons that form in spherically symmetric gravitational collapse and we show that the first and second laws of black hole thermodynamics, as extended to dynamical spacetimes in a suitable manner, are not violated whether the collapse ends in a black hole or a naked singularity. We then make a distinction between the naked singularities that result from gravitational collapse, and those that exist in solutions of Einstein equations in vacuum axially symmetric and stationary spacetimes, and discuss their connection with thermodynamics in view of the cosmic censorship conjecture and the validity of the third law of black hole mechanics.
Adhesive Gravitational Clustering
Thomas Buchert; Alvaro Dominguez
2005-06-21T23:59:59.000Z
The notion of `adhesion' has been advanced for the phenomenon of stabilization of large-scale structure emerging from gravitational instability of a cold medium. Recently, the physical origin of adhesion has been identified: a systematic derivation of the equations of motion for the density and the velocity fields leads naturally to the key equation of the `adhesion approximation' - however, under a set of strongly simplifying assumptions. In this work, we provide an evaluation of the current status of adhesive gravitational clustering and a clear explanation of the assumptions involved. Furthermore, we propose systematic generalizations with the aim to relax some of the simplifying assumptions. We start from the general Newtonian evolution equations for self-gravitating particles on an expanding Friedmann background and recover the popular `dust model' (pressureless fluid), which breaks down after the formation of density singularities; then we investigate, in a unified framework, two other models which, under the restrictions referred to above, lead to the `adhesion approximation'. We apply the Eulerian and Lagrangian perturbative expansions to these new models and, finally, we discuss some non-perturbative results that may serve as starting points for workable approximations of non-linear structure formation in the multi-stream regime. In particular, we propose a new approximation that includes, in limiting cases, the standard `adhesion model' and the Eulerian as well as Lagrangian first-order approximations.
Weak Gravity Strongly Constrains Large-Field Axion Inflation
Ben Heidenreich; Matthew Reece; Tom Rudelius
2015-06-10T23:59:59.000Z
Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.
Constraints on Axion Inflation from the Weak Gravity Conjecture
Rudelius, Tom
2015-01-01T23:59:59.000Z
We derive constraints facing models of axion inflation based on decay constant alignment from a string-theoretic and quantum gravitational perspective. In particular, we investigate the prospects for alignment and `anti-alignment' of $C_4$ axion decay constants in type IIB string theory, deriving a strict no-go result in the latter case. We discuss the relationship of axion decay constants to the weak gravity conjecture and demonstrate agreement between our string-theoretic constraints and those coming from the `generalized' weak gravity conjecture. Finally, we consider a particular model of decay constant alignment in which the potential of $C_4$ axions in type IIB compactifications on a Calabi-Yau three-fold is dominated by contributions from $D7$-branes, pointing out that this model evades some of the challenges derived earlier in our paper but is highly constrained by other geometric considerations.
Weak Gravity Strongly Constrains Large-Field Axion Inflation
Heidenreich, Ben; Rudelius, Tom
2015-01-01T23:59:59.000Z
Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.
Projected Constraints on Lorentz-Violating Gravity with Gravitational Waves
Devin Hansen; Nicolas Yunes; Kent Yagi
2014-12-12T23:59:59.000Z
Gravitational waves are excellent tools to probe the foundations of General Relativity in the strongly dynamical and non-linear regime. One such foundation is Lorentz symmetry, which can be broken in the gravitational sector by the existence of a preferred time direction, and thus, a preferred frame at each spacetime point. This leads to a modification in the orbital decay rate of binary systems, and also in the generation and chirping of their associated gravitational waves. We here study whether waves emitted in the late, quasi-circular inspiral of non-spinning, neutron star binaries can place competitive constraints on two proxies of gravitational Lorentz-violation: Einstein-\\AE{}ther theory and khronometric gravity. We model the waves in the small-coupling (or decoupling) limit and in the post-Newtonian approximation, by perturbatively solving the field equations in small deformations from General Relativity and in the small-velocity/weak-gravity approximation. We assume a gravitational wave consistent with General Relativity has been detected with second- and third-generation, ground-based detectors, and with the proposed space-based mission, DECIGO, with and without coincident electromagnetic counterparts. Without a counterpart, a detection consistent with General Relativity of neutron star binaries can only place competitive constraints on gravitational Lorentz violation when using future, third-generation or space-based instruments. On the other hand, a single counterpart is enough to place constraints that are 10 orders of magnitude more stringent than current binary pulsar bounds, even when using second-generation detectors. This is because Lorentz violation forces the group velocity of gravitational waves to be different from that of light, and this difference can be very accurately constrained with coincident observations.
Equation of Motion of a Spinning Test Particle in Gravitational Field
Ning Wu
2006-08-08T23:59:59.000Z
Based on the coupling between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives out the same results as those of Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.
Geometry of Weak Stability Boundaries
Edward Belbruno; Marian Gidea; Francesco Topputo
2012-04-06T23:59:59.000Z
The notion of a weak stability boundary has been successfully used to design low energy trajectories from the Earth to the Moon. The structure of this boundary has been investigated in a number of studies, where partial results have been obtained. We propose a generalization of the weak stability boundary. We prove analytically that, in the context of the planar circular restricted three-body problem, under certain conditions on the mass ratio of the primaries and on the energy, the weak stability boundary about the heavier primary coincides with a branch of the global stable manifold of the Lyapunov orbit about one of the Lagrange points.
Spectrometer for new gravitational experiment with UCN
Kulin, G V; Goryunov, S V; Kustov, D V; Geltenbort, P; Jentschel, M; Strepetov, A N; Bushuev, V A
2015-01-01T23:59:59.000Z
We describe an experimental installation for a new test of the weak equivalence principle for neutron. The device is a sensitive gravitational spectrometer for ultra-cold neutrons allowing to precisely compare the gain in kinetic energy of free falling neutrons to quanta of energy ${\\hbar}{\\Omega}$ transferred to the neutron via a non stationary device, i.e. a quantum modulator. The results of first test experiments indicate a collection rate allowing measurements of the factor of equivalence $ { \\gamma}$ with a statistical uncertainty in the order of $5{\\times}10^{-3}$ per day. A number of systematic effects were found, which partially can be easily corrected. For the elimination of others more detailed investigations and analysis are needed. Some possibilities to improve the device are also discussed.
Constraining the Braneworld with Gravitational Wave Observations
McWilliams, Sean T. [Gravitational Astrophysics Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt Maryland 20771 (United States)
2010-04-09T23:59:59.000Z
Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, l, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes. We utilize this possibility to derive two novel methods for constraining l via gravitational wave measurements. We show that the EMRI event rate detected by LISA can constrain l at the {approx}1 {mu}m level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of l{<=}5 {mu}m.
On the Energy of Rotating Gravitational Waves
Bahram Mashhoon; James C. McClune; Enrique Chavez; Hernando Quevedo
1996-09-06T23:59:59.000Z
A class of solutions of the gravitational field equations describing vacuum spacetimes outside rotating cylindrical sources is presented. A subclass of these solutions corresponds to the exterior gravitational fields of rotating cylindrical systems that emit gravitational radiation. The properties of these rotating gravitational wave spacetimes are investigated. In particular, we discuss the energy density of these waves using the gravitational stress-energy tensor.
Searching for Novel Gravitational Effects
Christopher Stubb
2010-09-01T23:59:59.000Z
Stubbs, Chair of the Physics Department at Harvard University, discusses experiments that search for novel gravitational effect and scientific observations about it.
Metrization in weakly sequential spaces
Emerson, Dominique Margaret
1975-01-01T23:59:59.000Z
METRIZATION IN WEAXLY SEQUENTIAL SPACES A Thesis by DOMINIQUE MARGARET EMERSON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1975 Ma)or Sub...]ect: Mathematics METRIZATION IN WEAKLY SEQUENTIAL SPACES A Thesis by DOMINIQUE MARGARET EMERSON Approved as to style and content by: (Chairman of Committee) c-0 (Head of Department) ember) (Member) May 1975 ABSTRACT Metrization in Weakly Sequential...
Weak Deeply Virtual Compton Scattering
A. Psaker; W. Melnitchouk; A. V. Radyushkin
2006-12-21T23:59:59.000Z
We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.
Weak Deeply Virtual Compton Scattering
Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin
2007-03-01T23:59:59.000Z
We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.
Graham M Shore
2003-04-15T23:59:59.000Z
In quantum theory, the curved spacetime of Einstein's general theory of relativity acts as a dispersive optical medium for the propagation of light. Gravitational rainbows and birefringence replace the classical picture of light rays mapping out the null geodesics of curved spacetime. Even more remarkably, {\\it superluminal} propagation becomes a real possibility, raising the question of whether it is possible to send signals into the past. In this article, we review recent developments in the quantum theory of light propagation in general relativity and discuss whether superluminal light is compatible with causality.
Electromagnetic Induced Gravitational Perturbations
T. M. Adamo; E. T. Newman
2008-07-23T23:59:59.000Z
We study the physical consequences of two diffferent but closely related perturbation schemes applied to the Einstein-Maxwell equations. In one case the starting space-time is flat while in the other case it is Schwarzschild. In both cases the perturbation is due to a combined electric and magnetic dipole field. We can see, within the Einstein-Maxwell equations a variety of physical consequences. They range from induced gravitational energy-momentum loss, to a well defined spin angular momentum with its loss and a center-of-mass with its equations of motion.
Wang, X; Huang, K; Treu, T; Bradac, M; Schmidt, K B; Brammer, G B; Vulcani, B; Jones, T A; Ryan, R; Amorin, R; Castellano, M; Fontana, A; Merlin, E; Trenti, M
2015-01-01T23:59:59.000Z
We present a strong and weak lensing reconstruction of the massive cluster Abell 2744, the first cluster for which deep \\emph{Hubble Frontier Field} (HFF) images and spectroscopy from the \\emph{Grism Lens-Amplified Survey from Space} (GLASS) are available. By performing a targeted search for emission lines in multiply imaged sources using GLASS spectra, we obtain 5 secure spectroscopic redshifts and 2 tentative ones. We confirm 1 strongly lensed system by detecting the same emission lines in all 3 multiple images. We also search for additional line emitters blindly and use the full GLASS spectroscopic catalog to test reliability of photometric redshifts for faint line emitters. We see a reasonable agreement between our photometric and spectroscopic redshift measurements, when including nebular emission in photo-z estimations. We introduce a stringent procedure to identify only secure multiple image sets based on colors, morphology, and spectroscopy. By combining 7 multiple image systems with secure spectrosco...
A Lorentz-Poincaré type interpretation of the Weak Equivalence Principle
Jan; Broekaert
2007-03-22T23:59:59.000Z
The validity of the Weak Equivalence Principle relative to a local inertial frame is detailed in a scalar-vector gravitation model with Lorentz-Poincar\\'e type interpretation. Given the previously established first Post-Newtonian concordance of dynamics with General Relativity, the principle is to this order compatible with GRT. The gravitationally modified Lorentz transformations, on which the observations in physical coordinates depend, are shown to provide a physical interpretation of \\emph{parallel transport}. A development of ``geodesic'' deviation in terms of the present model is given as well.
Degradation of Iris Recognition Performance Due to Non-Cosmetic Prescription Contact Lenses
Bowyer, Kevin W.
stated as: "Subjects can generally be recognized through eyeglasses or contact lenses. Colored contact with the recognition technology" [5] and "Successful identification can be made through eyeglasses and contact lenses
USING THE BULLET CLUSTER AS A GRAVITATIONAL TELESCOPE TO STUDY z {approx}> 7 LYMAN BREAK GALAXIES
Hall, Nicholas; Bradac, Marusa [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Treu, Tommaso [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Clowe, Douglas [Department of Physics and Astronomy, Ohio University, Clippinger Labs 251B, Athens, OH 45701 (United States); Jones, Christine [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Stiavelli, Massimo [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Cuby, Jean-Gabriel; Clement, Benjamin, E-mail: nrhall@ucdavis.edu [Laboratoire d'Astrophysique de Marseille, OAMP, Universite Aix-Marseille and CNRS, 38 rue Frederic Joliot Curie, F-13388 Marseille cedex 13 (France)
2012-02-01T23:59:59.000Z
We use imaging obtained with the Hubble Space Telescope Wide Field Camera 3 to search for z{sub 850} dropouts at z {approx} 7 and J{sub 110} dropouts at z {approx} 9 lensed by the Bullet Cluster. In total we find 10 z{sub 850} dropouts in our 8.27 arcmin{sup 2} field. Using magnification maps from a combined weak- and strong-lensing mass reconstruction of the Bullet Cluster and correcting for estimated completeness levels, we calculate the surface density and luminosity function of our z{sub 850} dropouts as a function of intrinsic (accounting for magnification) magnitude. We find results consistent with published blank field surveys, despite using much shallower data, and demonstrate the effectiveness of cluster surveys in the search for z {approx} 7 galaxies.
Accurate and fast simulation of Fresnel zone plates and multi-level diffractive lenses
Jahns, Jürgen
Accurate and fast simulation of Fresnel zone plates and multi-level diffractive lenses Qing Cao, such as various Fresnel zone plates [1, 2] and muti-level diffractive lenses [3], can be used for focusing and fast simulation of various Fresnel zone plates and multi-level diffractive lenses. As two tests, we
State tomography via weak measurements
Shengjun Wu
2013-02-01T23:59:59.000Z
Recent work has revealed that the wave function of a pure state can be measured directly and that complementary knowledge of a quantum system can be obtained simultaneously by weak measurements. However, the original scheme applies only to pure states, and it is not efficient because most of the data are discarded by post-selection. Here, we propose tomography schemes for pure states and for mixed states via weak measurements, and our schemes are more efficient because we do not discard any data. Furthermore, we demonstrate that any matrix element of a general state can be directly read from an appropriate weak measurement. The density matrix (with all of its elements) represents all that is directly accessible from a general measurement.
CLUSTER LENSING PROFILES DERIVED FROM A REDSHIFT ENHANCEMENT OF MAGNIFIED BOSS-SURVEY GALAXIES
Coupon, Jean; Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Broadhurst, Tom, E-mail: coupon@asiaa.sinica.edu.tw [Department of Theoretical Physics, University of Basque Country UPV/EHU, P.O. Box 644, E-48080 Bilbao (Spain)
2013-07-20T23:59:59.000Z
We report the first detection of a redshift-depth enhancement of background galaxies magnified by foreground clusters. Using 300,000 BOSS survey galaxies with accurate spectroscopic redshifts, we measure their mean redshift depth behind four large samples of optically selected clusters from the Sloan Digital Sky Survey (SDSS) surveys, totaling 5000-15,000 clusters. A clear trend of increasing mean redshift toward the cluster centers is found, averaged over each of the four cluster samples. In addition, we find similar but noisier behavior for an independent X-ray sample of 158 clusters lying in the foreground of the current BOSS sky area. By adopting the mass-richness relationships appropriate for each survey, we compare our results with theoretical predictions for each of the four SDSS cluster catalogs. The radial form of this redshift enhancement is well fitted by a richness-to-mass weighted composite Navarro-Frenk-White profile with an effective mass ranging between M{sub 200} {approx} 1.4-1.8 Multiplication-Sign 10{sup 14} M{sub Sun} for the optically detected cluster samples, and M{sub 200} {approx} 5.0 Multiplication-Sign 10{sup 14} M{sub Sun} for the X-ray sample. This lensing detection helps to establish the credibility of these SDSS cluster surveys, and provides a normalization for their respective mass-richness relations. In the context of the upcoming bigBOSS, Subaru Prime Focus Spectrograph, and EUCLID-NISP spectroscopic surveys, this method represents an independent means of deriving the masses of cluster samples for examining the cosmological evolution, and provides a relatively clean consistency check of weak-lensing measurements, free from the systematic limitations of shear calibration.
Cosmology and the weak interaction
Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))
1989-12-01T23:59:59.000Z
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs.
Weak-Chaos Ratchet Accelerator
Itzhack Dana; Vladislav B. Roitberg
2012-05-28T23:59:59.000Z
Classical Hamiltonian systems with a mixed phase space and some asymmetry may exhibit chaotic ratchet effects. The most significant such effect is a directed momentum current or acceleration. In known model systems, this effect may arise only for sufficiently strong chaos. In this paper, a Hamiltonian ratchet accelerator is introduced, featuring a momentum current for arbitrarily weak chaos. The system is a realistic, generalized kicked rotor and is exactly solvable to some extent, leading to analytical expressions for the momentum current. While this current arises also for relatively strong chaos, the maximal current is shown to occur, at least in one case, precisely in a limit of arbitrarily weak chaos.
Sudden gravitational transition
Caldwell, Robert R. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, New Hampshire 03755 (United States); Komp, William [Physics Department, University of Louisville, 102 Natural Sciences, Louisville, Kentucky 40292 (United States); Parker, Leonard [Physics Department, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States); Vanzella, Daniel A. T. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (IFSC-USP), Av. Trabalhador Sao-carlense, 400 Cx. Postal 369 - CEP 13560-970, Sao Carlos, Sao Paulo (Brazil)
2006-01-15T23:59:59.000Z
We investigate the properties of a cosmological scenario which undergoes a gravitational phase transition at late times. In this scenario, the Universe evolves according to general relativity in the standard, hot big bang picture until a redshift z < or approx. 1. Nonperturbative phenomena associated with a minimally-coupled scalar field catalyzes a transition, whereby an order parameter consisting of curvature quantities such as R{sup 2}, R{sub ab}R{sup ab}, R{sub abcd}R{sup abcd} acquires a constant expectation value. The ensuing cosmic acceleration appears driven by a dark-energy component with an equation-of-state w<-1. We evaluate the constraints from type 1a supernovae, the cosmic microwave background, and other cosmological observations. We find that a range of models making a sharp transition to cosmic acceleration are consistent with observations.
Breakdown of the equivalence between gravitational mass and energy for a composite quantum body
Andrei G. Lebed
2014-04-14T23:59:59.000Z
The simplest quantum composite body, a hydrogen atom, is considered in the presence of a weak external gravitational field. We define an operator for the passive gravitational mass of the atom in the post-Newtonian approximation of the general relativity and show that it does not commute with its energy operator. Nevertheless, the equivalence between the expectation values of the mass and energy is shown to survive at a macroscopic level for stationary quantum states. Breakdown of the equivalence between passive gravitational mass and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported by and moving in the Earth's gravitational field with constant velocity, using spacecraft or satellite
Photon rockets and gravitational radiation
T. Damour
1994-12-21T23:59:59.000Z
The absence of gravitational radiation in Kinnersley's ``photon rocket'' solution of Einstein's equations is clarified by studying the mathematically well-defined problem of point-like photon rockets in Minkowski space (i.e. massive particles emitting null fluid anisotro\\-pically and accelerating because of the recoil). We explicitly compute the (uniquely defined) {\\it linearized} retarded gravitational waves emitted by such objects, which are the coherent superposition of the gravitational waves generated by the motion of the massive point-like rocket and of those generated by the energy-momentum distribution of the photon fluid. In the special case (corresponding to Kinnersley's solution) where the anisotropy of the photon emission is purely dipolar we find that the gravitational wave amplitude generated by the energy-momentum of the photons exactly cancels the usual $1/r$ gravitational wave amplitude generated by the accelerated motion of the rocket. More general photon anisotropies would, however, generate genuine gravitational radiation at infinity. Our explicit calculations show the compatibility between the non-radiative character of Kinnersley's solution and the currently used gravitational wave generation formalisms based on post-Minkowskian perturbation theory.
The gravitational energy-momentum tensor and the gravitational pressure
J. W. Maluf
2005-07-28T23:59:59.000Z
In the framework of the teleparallel equivalent of general relativity it is possible to establish the energy-momentum tensor of the gravitational field. This tensor has the following essential features: (1) it is identified directly in Einstein's field equations; (2) it is conserved and traceless; (3) it yields expressions for the energy and momentum of the gravitational field; (4)it is free of second (and highest) derivatives of the field variables; (5) the gravitational and matter energy-momentum tensors take place in the field equations on the same footing; (6) it is unique. However, it is not symmetric. We show that the spatial components of this tensor yield a consistent definition of the gravitational pressure.
The Cosmic Lens All-Sky Survey:II. Gravitational lens candidate selection and follow-up
I. W. A. Browne; P. N. Wilkinson; N. J. F. Jackson; S. T. Myers; C. D. Fassnacht; L. V. E. Koopmans; D. R. Marlow; M. Norbury; D. Rusin; C. M. Sykes; A. D. Biggs; R. D. Blandford; A. G. de Bruyn; K-H. Chae; P. Helbig; L. J. King; J. P. McKean; T. J. Pearson; P. M. Phillips; A. C. S. Readhead; E. Xanthopoulos; T. York
2002-11-11T23:59:59.000Z
We report the final results of the search for gravitationally lensed flat-spectrum radio sources found in the combination of CLASS (Cosmic Lens All Sky Survey) and JVAS (Jodrell-Bank VLA Astrometric Survey). VLA observations of 16,503 sources have been made, resulting in the largest sample of arcsec-scale lens systems available. Contained within the 16,503 sources is a complete sample of 11,685 sources having two-point spectral indices between 1.4 and 5 GHz flatter than -0.5 and 5 GHz flux densities $\\geq$30 mJy. A subset of 8,958 sources form a well-defined statistical sample suitable for analysis of the lens statistics. We describe the systematic process by which 149 candidate lensed sources were picked from the statistical sample on the basis of possessing multiple compact components in the 0.2 arcsec-resolution VLA maps. Candidates were followed up with 0.05 arcsec resolution MERLIN and 0.003 arcsec VLBA observations at 5 GHz and rejected as lens systems if they failed well-defined surface brightness and/or morphological tests. Maps for all the candidates can be found on the World Wide Web at http://www.jb.man.ac.uk/research/gravlens/index.html We summarize the properties of each of the 22 gravitational lens systems in JVAS/CLASS. Twelve are double-image systems, nine are four-image systems and one is a six-image system. Thirteen constitute a statistically well-defined sample giving a point-source lensing rate of 1:690$\\pm$190. The interpretation of the results in terms of the properties of the lensing galaxy population and cosmological parameters will be published elsewhere. (Abridged)
Weak Values and Relational Generalisations
Thomas Marlow
2006-04-20T23:59:59.000Z
We justify generalisations of weak values from a tentatively relational perspective by deriving them from a generalisation of Bayes' rule. We also argue that these generalisations have implications of quantum nonlocality and may form a novel approach to quantum gravity and cosmology.
Turbulent Angular Momentum Transport in Weakly-Ionized Accretion Disks
Bryan Mark Johnson
2005-09-13T23:59:59.000Z
Understanding the mechanism that drives accretion has been the primary challenge in accretion disk theory. Turbulence provides a natural means of dissipation and the removal of angular momentum, but firmly establishing its presence in disks proved for many years to be difficult. The realization in the 1990s that a weak magnetic field will destabilize a disk and result in a vigorous turbulent transport of angular momentum has revolutionized the field. Much of accretion disk research now focuses on understanding the implications of this mechanism for astrophysical observations. At the same time, the success of this mechanism depends upon a sufficient ionization level in the disk for the flow to be well-coupled to the magnetic field. Many disks, such as disks around young stars and disks in binary systems that are in quiescence, are too cold to be sufficiently ionized, and so efforts to establish the presence of turbulence in these disks continues. This dissertation focuses on several possible mechanisms for the turbulent transport of angular momentum in weakly-ionized accretion disks: gravitational instability, radial convection and vortices driving compressive motions. It appears that none of these mechanisms are very robust in driving accretion. A discussion is given, based on these results, as to the most promising directions to take in the search for a turbulent transport mechanism that does not require magnetic fields. Also discussed are the implications of assuming that no turbulent transport mechanism exists for weakly-ionized disks.
Week 13: Chapter 13 Universal Gravitation
1 Week 13: Chapter 13 Universal Gravitation Newton's Law of Universal Gravitation Every particle placed near the small ones The angle of rotation was measured Law of Gravitation, cont's Third Law action-reaction pair Gravitation is a field force that always exists between two particles
Testing the fracture of spectacle lenses Stephen K. Lucas1
Lucas, Stephen
Testing the fracture of spectacle lenses Stephen K. Lucas1 and James M. Hill2 Abstract SOLA. Ideally, SOLA International seeks a mathematical model which inputs lens geometry and material properties of these issues is outlined below. 1 Introduction 1.1 The Company SOLA International SOLA began in 1956, with nine
Dissipation of Modified Entropic Gravitational Energy Through Gravitational Waves
Clovis Jacinto de Matos
2011-11-04T23:59:59.000Z
The phenomenological nature of a new gravitational type interaction between two different bodies derived from Verlinde's entropic approach to gravitation in combination with Sorkin's definition of Universe's quantum information content, is investigated. Assuming that the energy stored in this entropic gravitational field is dissipated under the form of gravitational waves and that the Heisenberg principle holds for this system, one calculates a possible value for an absolute minimum time scale in nature $\\tau=15/16 \\frac{\\Lambda^{1/2}\\hbar G}{c^4}\\sim9.27\\times10^{-105}$ seconds, which is much smaller than the Planck time $t_{P}=(\\hbar G/c^5)^{1/2}\\sim 5.38\\times10^{-44}$ seconds. This appears together with an absolute possible maximum value for Newtonian gravitational forces generated by matter $F_g=32/30\\frac{c^7}{\\Lambda \\hbar G^2}\\sim 3.84\\times 10^{165}$ Newtons, which is much higher than the gravitational field between two Planck masses separated by the Planck length $F_{gP}=c^4/G\\sim1.21\\times10^{44}$ Newtons.
Linked and Knotted Gravitational Radiation
Amy Thompson; Joe Swearngin; Dirk Bouwmeester
2014-08-15T23:59:59.000Z
We show that the torus knot topology is inherent in electromagnetic and gravitational radiation by constructing spin-$N$ fields based on this topology from the elementary states of twistor theory. The twistor functions corresponding to the elementary states admit a parameterization in terms of the poloidal and toroidal winding numbers of the torus knots, allowing one to choose the degree of linking or knotting of the associated field configuration. Using the gravito-electromagnetic formalism, we show that the torus knot structure is exhibited in the tendex and vortex lines for the analogous linearized gravitational solutions. We describe the topology of the gravitational fields and its physical interpretation in terms of the tidal and frame drag forces of the gravitational field.
A Bayesian approach to strong lensing modelling of galaxy clusters
Eric Jullo; Jean-Paul Kneib; Marceau Limousin; Árdis Elíasdóttir; Phil Marshall; Tomas Verdugo
2007-12-26T23:59:59.000Z
In this paper, we describe a procedure for modelling strong lensing galaxy clusters with parametric methods, and to rank models quantitatively using the Bayesian evidence. We use a publicly available Markov chain Monte-Carlo (MCMC) sampler ('Bayesys'), allowing us to avoid local minima in the likelihood functions. To illustrate the power of the MCMC technique, we simulate three clusters of galaxies, each composed of a cluster-scale halo and a set of perturbing galaxy-scale subhalos. We ray-trace three light beams through each model to produce a catalogue of multiple images, and then use the MCMC sampler to recover the model parameters in the three different lensing configurations. We find that, for typical Hubble Space Telescope (HST)-quality imaging data, the total mass in the Einstein radius is recovered with ~1-5% error according to the considered lensing configuration. However, we find that the mass of the galaxies is strongly degenerated with the cluster mass when no multiple images appear in the cluster centre. The mass of the galaxies is generally recovered with a 20% error, largely due to the poorly constrained cut-off radius. Finally, we describe how to rank models quantitatively using the Bayesian evidence. We confirm the ability of strong lensing to constrain the mass profile in the central region of galaxy clusters in this way. Ultimately, such a method applied to strong lensing clusters with a very large number of multiple images may provide unique geometrical constraints on cosmology. The implementation of the MCMC sampler used in this paper has been done within the framework of the Lenstool software package, which is publicly available.
THE SLOAN BRIGHT ARCS SURVEY: DISCOVERY OF SEVEN NEW STRONGLY LENSED GALAXIES FROM z = 0.66-2.94
Kubo, Jeffrey M.; Allam, Sahar S.; Drabek, Emily; Lin, Huan; Tucker, Douglas; Buckley-Geer, Elizabeth J.; Diehl, H. Thomas; Soares-Santos, Marcelle; Hao Jiangang; Kubik, Donna; Annis, James; Frieman, Joshua A. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Wiesner, Matthew [Department of Physics, Northern Illinois University, DeKalb, IL 60115 (United States); West, Anderson [The Illinois Math and Science Academy, Aurora, IL 60506 (United States)
2010-12-01T23:59:59.000Z
We report the discovery of seven new, very bright gravitational lens systems from our ongoing gravitational lens search, the Sloan Bright Arcs Survey (SBAS). Two of the systems are confirmed to have high source redshifts z = 2.19 and z = 2.94. Three other systems lie at intermediate redshift with z = 1.33, 1.82, 1.93 and two systems are at low redshift z = 0.66, 0.86. The lensed source galaxies in all of these systems are bright, with i-band magnitudes ranging from 19.73 to 22.06. We present the spectrum of each of the source galaxies in these systems along with estimates of the Einstein radius for each system. The foreground lens in most systems is identified by a red sequence based cluster finder as a galaxy group; one system is identified as a moderately rich cluster. In total, SBAS has now discovered 19 strong lens systems in the SDSS imaging data, 8 of which are among the highest surface brightness z {approx_equal} 2-3 galaxies known.
Weak values and weak coupling maximizing the output of weak measurements
Di Lorenzo, Antonio, E-mail: dilorenzo.antonio@gmail.com
2014-06-15T23:59:59.000Z
In a weak measurement, the average output ?o? of a probe that measures an observable A{sup -hat} of a quantum system undergoing both a preparation in a state ?{sub i} and a postselection in a state E{sub f} is, to a good approximation, a function of the weak value A{sub w}=Tr[E{sub f}A{sup -hat} ?{sub i}]/Tr[E{sub f}?{sub i}], a complex number. For a fixed coupling ?, when the overlap Tr[E{sub f}?{sub i}] is very small, A{sub w} diverges, but ?o? stays finite, often tending to zero for symmetry reasons. This paper answers the questions: what is the weak value that maximizes the output for a fixed coupling? What is the coupling that maximizes the output for a fixed weak value? We derive equations for the optimal values of A{sub w} and ?, and provide the solutions. The results are independent of the dimensionality of the system, and they apply to a probe having a Hilbert space of arbitrary dimension. Using the Schrödinger–Robertson uncertainty relation, we demonstrate that, in an important case, the amplification ?o? cannot exceed the initial uncertainty ?{sub o} in the observable o{sup -hat}, we provide an upper limit for the more general case, and a strategy to obtain ?o???{sub o}. - Highlights: •We have provided a general framework to find the extremal values of a weak measurement. •We have derived the location of the extremal values in terms of preparation and postselection. •We have devised a maximization strategy going beyond the limit of the Schrödinger–Robertson relation.
Global Superdiffusion of Weak Chaos
Itzhack Dana
2003-10-20T23:59:59.000Z
A class of kicked rotors is introduced, exhibiting accelerator-mode islands (AIs) and {\\em global} superdiffusion for {\\em arbitrarily weak} chaos. The corresponding standard maps are shown to be exactly related to generalized web maps taken modulo an ``oblique cylinder''. Then, in a case that the web-map orbit structure is periodic in the phase plane, the AIs are essentially {\\em normal} web islands folded back into the cylinder. As a consequence, chaotic orbits sticking around the AI boundary are accelerated {\\em only} when they traverse tiny {\\em ``acceleration spots''}. This leads to chaotic flights having a quasiregular {\\em steplike} structure. The global weak-chaos superdiffusion is thus basically different in nature from the strong-chaos one in the usual standard and web maps.
Carl H. Gibson
2003-05-19T23:59:59.000Z
The first structures were proto-voids formed in the primordial plasma. Viscous and weak turbulence forces balanced gravitational forces when the scale of causal connection at time 30,000 years matched the viscous and turbulent Schwarz scales of hydro-gravitational theory (Gibson 1996). The photon viscosity allows only weak turbulence from the Reynolds number Re = 200, with fragmentation to give proto-supercluster voids, buoyancy forces, fossil vorticity turbulence, and strong sonic damping. The expanding, cooling, plasma continued fragmentation to proto-galaxy-mass with the density and rate-of-strain preserved as fossils of the weak turbulence and first structure. Turbulence fossilization by self-gravitational buoyancy explains the cosmic microwave background temperature fluctuations, not sonic oscillations in cold-dark-matter fragments. After plasma to gas transition at 300,000 years, gas fragmentation occurred within the proto-galaxies to form proto-globular-star-cluster (PGCs) clouds of small-planetary-mass primordial-fog-particles (PFPs). Dark PGC clumps of frozen PFPs persist as the inner-galaxy-halo dark matter, supporting Schild's 1996 quasar-microlensing interpretation. Non-baryonic dark matter diffused into the plasma proto-cluster-voids and later fragmented as outer-galaxy-halos at diffusive Schwarz scales, indicating light, weakly-collisional fluid particles (possibly neutrinos). Observations support the theory (Gibson and Schild 2003).
R. C. Gupta; Anirudh Pradhan; Sushant Gupta
2010-04-09T23:59:59.000Z
Many of the general-relativity-tests such as bending of light near a star and gravitational red/blue shift are explained without general-relativity & without Newtonian-approach. The authors first cast doubts on both, the Newtonian and the relativistic approach; and proposes a novel alternative-explanation. The new alternative explanation is based on refraction-phenomenon of optics. Estimation of results, with new approach, are in agreement with known values. Though physics is different, but it is argued that general-relativity based gravitational-bending and refraction-based bending have more in common than is generally realized. Also discussed are black-hole and gravitational-lensing in the new perspective of refraction. The new refraction-based theory makes a few new predictions and also suggests a few tests..
Metrization in weakly sequential spaces
Emerson, Dominique Margaret
1975-01-01T23:59:59.000Z
* dt f th ~ A t N h tf 1 ~Sit. of weakly sequential spaces along with that of cs-hereditarily closure-preserving families, the author has characterized metri- zability in spaces where sequences suffice. Chapter II contains the definitions of locally... Dugund]i [5]. One deviation from this convention is the use of the symbol "clX(A)" to denote the closure in the space X of a set A. The subscript "X" will be deleted when no confusion will arise. The letters Z and N will denote the set of integers...
Gravitational wave background from Standard Model physics: Qualitative features
Ghiglieri, J
2015-01-01T23:59:59.000Z
Because of physical processes ranging from microscopic particle collisions to macroscopic hydrodynamic fluctuations, any plasma in thermal equilibrium emits gravitational waves. For the largest wavelengths the emission rate is proportional to the shear viscosity of the plasma. In the Standard Model at T > 160 GeV, the shear viscosity is dominated by the most weakly interacting particles, right-handed leptons, and is relatively large. We estimate the order of magnitude of the corresponding spectrum of gravitational waves. Even though at small frequencies (corresponding to the sub-Hz range relevant for planned observatories such as eLISA) this background is tiny compared with that from non-equilibrium sources, the total energy carried by the high-frequency part of the spectrum is non-negligible if the production continues for a long time. We suggest that this may constrain (weakly) the highest temperature of the radiation epoch. Observing the high-frequency part directly sets a very ambitious goal for future ge...
Microscopic Lensing by a Dense, Cold Atomic Sample
Stetson Roof; Kasie Kemp; Mark Havey; I. M. Sokolov; D. V. Kupriyanov
2014-12-01T23:59:59.000Z
We demonstrate that a cold, dense sample of 87Rb atoms can exhibit a micron-scale lensing effect, much like that associated with a macroscopically-sized lens. The experiment is carried out in the fashion of traditional z-scan measurements but in much weaker fields and where close attention is paid to the detuning dependence of the transmitted light. The results are interpreted using numerical simulations and by modeling the sample as a thin lens with a spherical focal length.
Allam, Sahar S.; /Fermilab /Wyoming U.; Tucker, Douglas L.; Lin, Huan; Diehl, H.Thomas; Annis, James; Buckley-Geer, Elizabeth J.; /Fermilab; Frieman, Joshua A.; /Fermilab
2006-11-01T23:59:59.000Z
We report on the serendipitous discovery of the brightest Lyman Break Galaxy (LBG) currently known, a galaxy at z = 2.73 that is being strongly lensed by the z = 0.38 Luminous Red Galaxy (LRG) SDSS J002240.91+143110.4. The arc of this gravitational lens system, which we have dubbed the ''8 o'clock arc'' due to its time of discovery, was initially identified in the imaging data of the Sloan Digital Sky Survey Data Release 4 (SDSS DR4); followup observations on the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system and led to the identification of the arc's spectrum as that of an LBG. The arc has a spectrum and a redshift remarkably similar to those of the previous record-holder for brightest LBG (MS 1512-cB58, a.k.a ''cB58''), but, with an estimated total magnitude of (g,r,i) = (20.0,19.2,19.0) and surface brightness of ({mu}{sub g}, {mu}{sub r}, {mu}{sub i}) = (23.3, 22.5, 22.3) mag arcsec{sup -2}, the 8 o'clock arc is thrice as bright. The 8 o'clock arc, which consists of three lensed images of the LBG, is 162{sup o}(9.6'') long and has a length-to-width ratio of 6:1. A fourth image of the LBG--a counter-image--can also be identified in the ARC 3.5m g-band images. A simple lens model for the system assuming a singular isothermal ellipsoid potential yields an Einstein radius of {theta}{sub Ein} = 2.91'' {+-} 0.14'', a total mass for the lensing LRG (within the 10.6 {+-} 0.5 h{sup -1} kpc enclosed by the lensed images) of 1.04 x 10{sup 12} h{sup -1} M{sub {circle_dot}}, and a magnification factor for the LBG of 12.3{sub -3.6}{sup +15}. The LBG itself is intrinsically quite luminous ({approx} 6 x L{sub *}) and shows indications of massive recent star formation, perhaps as high as 160 h{sup -1} M{sub {circle_dot}} yr{sup -1}.
Gravitational Radiation From Cosmological Turbulence
Arthur Kosowsky; Andrew Mack; Tinatin Kahniashvili
2002-06-27T23:59:59.000Z
An injection of energy into the early Universe on a given characteristic length scale will result in turbulent motions of the primordial plasma. We calculate the stochastic background of gravitational radiation arising from a period of cosmological turbulence, using a simple model of isotropic Kolmogoroff turbulence produced in a cosmological phase transition. We also derive the gravitational radiation generated by magnetic fields arising from a dynamo operating during the period of turbulence. The resulting gravitational radiation background has a maximum amplitude comparable to the radiation background from the collision of bubbles in a first-order phase transition, but at a lower frequency, while the radiation from the induced magnetic fields is always subdominant to that from the turbulence itself. We briefly discuss the detectability of such a signal.
Optical Approach to Gravitational Redshift
Y. G. Yi
2012-04-12T23:59:59.000Z
An optical approach begins by interpreting the gravitational redshift resulting to a change in the relative velocity of light due to the medium of propagation in the gravitational field. The discussion continues by pointing out an agreement in structure between the equation for rays in geometrical optics and the geodesic equation of general relativity. From their comparison we learn that the path of rays should be given by the relation $ds^2=n^2(r)dr^2+r^2d\\theta^2$, not by $ds^2=dr^2+r^2d\\theta^2$, in a medium with spherical symmetry of refractive index $n(r)$. The development of an optical analogy suggests introducing $n^2(r)$ in place of $g_{rr}$ as an optical version of the Schwarzschild metric. In form and content, $n^2(r)$ is different from $g_{rr}$. The optical point of view replaces the general-relativity explanations in terms of time and gravitation.
Gravitational waves versus black holes
Trevor W. Marshall
2007-07-02T23:59:59.000Z
It is argued that, in order for the gravitational field to be propagated as a wave, it is necessary for it to satisfy a further set of field equations, in addition to those of Einstein and Hilbert, and these equations mean there is a preferred coordinate frame, called the Global Inertial Frame, giving rise to a unique metric . The implication is that a true gravitational field is not compatible with Einstein's Principle of Equivalence, which is in contradiction with his other fundamental concept of locality. The additional field equations ensure that gravitational collapse does not go below the Schwarzschild radius, thereby excluding the possibility of singular solutions (black holes) of the Einstein-Hilbert equations. Such solutions would also violate Einstein's locality principle.
Gravitational waves from merging compact binaries
Hughes, Scott A.
Largely motivated by the development of highly sensitive gravitational-wave detectors, our understanding of merging compact binaries and the gravitational waves they generate has improved dramatically in recent years. ...
Solid explosive plane-wave lenses pressed-to-shape with dies
Olinger, B.
2007-11-01T23:59:59.000Z
Solid-explosive plane-wave lenses 1", 2" and 4¼" in diameter have been mass-produced from components pressed-to-shape with aluminum dies. The method used to calculate the contour between the solid plane-wave lens components pressed-to-shape with the dies is explained. The steps taken to press, machine, and assemble the lenses are described. The method of testing the lenses, the results of those tests, and the corrections to the dies are reviewed. The work on the ½", 8", and 12" diameter lenses is also discussed.
Durability of Poly (Methyl Methacrylate) Lenses Used in Concentrating Photovoltaics (Presentation)
Miller, D.; Gedvilas, L.; To, B.; Kennedy, C.; Kurtz, S.
2010-10-21T23:59:59.000Z
This presentation reports the findings of NREL's screen test to characterize the durability of poly (methyl methacrylate) lenses used in concentrated photovoltaics.
Non-representative quantum mechanical weak values
B. E. Y. Svensson
2015-03-06T23:59:59.000Z
The operational definition of a weak value for a quantum mechanical system involves the limit of the weak measurement strength tending to zero. I study how this limit compares to the situation for the undisturbed (no weak measurement) system. Under certain conditions, which I investigate, this limit is discontinuous in the sense that it does not merge smoothly to the Hilbert space description of the undisturbed system. Hence, in these discontinuous cases, the weak value does not represent the undisturbed system. As a result, conclusions drawn from such weak values regarding the properties of the studied system cannot be upheld. Examples are given.
Lorentz Symmetry, the SME, and Gravitational Experiments
Jay D. Tasson
2012-12-10T23:59:59.000Z
This proceedings contribution summarizes the implications of recent SME-based investigations of Lorentz violation for gravitational experiments.
Lorentz Symmetry, the SME, and Gravitational Experiments
Tasson, Jay D
2012-01-01T23:59:59.000Z
This proceedings contribution summarizes the implications of recent SME-based investigations of Lorentz violation for gravitational experiments.
The Gravitational Instability of the Vacuum: Insight into the Cosmological Constant Problem
Alexander, S
2004-07-06T23:59:59.000Z
A mechanism for suppressing the cosmological constant is developed, based on an analogy with a superconducting phaseshift in which free fermions coupled perturbatively to a weak gravitational field are in an unstable false vacuum state. The coupling of the fermions to the gravitational field generates fermion condensates with zero momentum and a phase transition induces a nonperturbative transition to a true vacuum state by producing a positive energy gap {Delta} in the vacuum energy, identified with {radical}{Lambda}, where {Lambda} is the cosmological constant. In the strong coupling limit a large cosmological constant induces a period of inflation in the early universe, followed by a weak coupling limit in which {radical}{Lambda} vanishes exponentially fast as the universe expands due to the dependence of the energy gap on the density of Fermi surface fermions, D({epsilon}), predicting a small cosmological constant in the present universe.
Gravitation and Special Relativity D. H. Sattinger
Zakharov, Vladimir
of Maxwell's equations for gravitation, based on a mathematical proof of Faraday's Law, is presentedGravitation and Special Relativity D. H. Sattinger Department of Mathematics University of Arizona of the perturbation theory of Ein- stein's equations, puts the gravitational and electromagnetic fields on an equal
Electrostatic self-force in a static weak gravitational field with cylindrical symmetry
B. Boisseau; C. Charmousis; B. Linet
1996-03-04T23:59:59.000Z
We determine the electrostatic self-force at rest in an arbitrary static metric with cylindrical symmetry in the linear approximation in the Newtonian constant. In linearised Einstein theory, we express it in terms of the components of the energy-momentum tensor.
Gravitational Radiation in Noncommutative Gravity
A. Jahan; N. Sadeghnezhad
2014-11-24T23:59:59.000Z
The gravitational radiation power of a binary system in a noncommutative space is derived and it's rate of the period decrease is calculated to first order in noncommutativity parameter. By comparing the theoretical results with the observational data of the binary pulsar PSR 1913+16, we find a bound on the noncommutativity parameter.
Einstein, Black Holes Gravitational Waves
Cook, Greg
1 #12;Einstein, Black Holes and Gravitational Waves Gregory B. Cook Wake Forest University 2 #12;Einstein's Miraculous Year: 1905 · Einstein, A. "¨Uber einen die Erzeugung und Verwandlung des Lichtes Concerning the Production and Transformation of Light. · Einstein, A. "¨Uber die von der molekularkinetischen
Smith, Graham P. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Ebeling, Harald; Ma, Cheng-Jiun [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Limousin, Marceau; Kneib, Jean-Paul; Jauzac, Mathilde [Laboratoire d'Astrophysique de Marseille, CNRS-Universite Aix-Marseille, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France); Swinbank, A. M.; Richard, Johan; Edge, Alastair C.; Smail, Ian [Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, MS 169-506, Pasadena, CA 91125 (United States); Sand, David J., E-mail: gps@star.sr.bham.ac.u [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2009-12-20T23:59:59.000Z
We present Advanced Camera for Surveys observations of MACS J1149.5+2223, an X-ray luminous galaxy cluster at z = 0.544 discovered by the Massive Cluster Survey. The data reveal at least seven multiply imaged galaxies, three of which we have confirmed spectroscopically. One of these is a spectacular face-on spiral galaxy at z = 1.491, the four images of which are gravitationally magnified by 8 approx< mu approx< 23. We identify this as an L* (M{sub B} approx = -20.7), disk-dominated (B/T approx< 0.5) galaxy, forming stars at approx6 M{sub sun} yr{sup -1}. We use a robust sample of multiply imaged galaxies to constrain a parameterized model of the cluster mass distribution. In addition to the main cluster dark matter halo and the bright cluster galaxies, our best model includes three galaxy-group-sized halos. The relative probability of this model is P(N{sub halo} = 4)/P(N{sub halo} < 4) >= 10{sup 12} where N{sub halo} is the number of cluster/group-scale halos. In terms of sheer number of merging cluster/group-scale components, this is the most complex strong-lensing cluster core studied to date. The total cluster mass and fraction of that mass associated with substructures within R <= 500 kpc, are measured to be M{sub tot} = (6.7 +- 0.4) x 10{sup 14} M{sub sun} and f{sub sub} = 0.25 +- 0.12, respectively. Our model also rules out recent claims of a flat density profile at approx>7sigma confidence, thus highlighting the critical importance of spectroscopic redshifts of multiply imaged galaxies when modeling strong-lensing clusters. Overall our results attest to the efficiency of X-ray selection in finding the most powerful cluster lenses, including complicated merging systems.
Self-gravitating accretion discs
G. Lodato
2008-01-25T23:59:59.000Z
I review recent progresses in the dynamics and the evolution of self-gravitating accretion discs. Accretion discs are a fundamental component of several astrophysical systems on very diverse scales, and can be found around supermassive black holes in Active Galactic Nuclei (AGN), and also in our Galaxy around stellar mass compact objects and around young stars. Notwithstanding the specific differences arising from such diversity in physical extent, all these systems share a common feature where a central object is fed from the accretion disc, due to the effect of turbulence and disc instabilities, which are able to remove the angular momentum from the gas and allow its accretion. In recent years, it has become increasingly apparent that the gravitational field produced by the disc itself (the disc's self-gravity) is an important ingredient in the models, especially in the context of protostellar discs and of AGN discs. Indeed, it appears that in many cases (and especially in the colder outer parts of the disc) the development of gravitational instabilities can be one of the main agents in the redistribution of angular momentum. In some cases, the instability can be strong enough to lead to the formation of gravitationally bound clumps within the disc, and thus to determine the disc fragmentation. As a result, progress in our understanding of the dynamics of self-gravitating discs is essential to understand the processes that lead to the feeding of both young stars and of supermassive black holes in AGN. At the same time, understanding the fragmentation conditions is important to determine under which conditions AGN discs would fragment and form stars and whether protostellar discs might form giant gaseous planets through disc fragmentation.
Weak Boson Emission in Hadron Collider Processes
U. Baur
2006-11-17T23:59:59.000Z
The O(alpha) virtual weak radiative corrections to many hadron collider processes are known to become large and negative at high energies, due to the appearance of Sudakov-like logarithms. At the same order in perturbation theory, weak boson emission diagrams contribute. Since the W and Z bosons are massive, the O(alpha) virtual weak radiative corrections and the contributions from weak boson emission are separately finite. Thus, unlike in QED or QCD calculations, there is no technical reason for including gauge boson emission diagrams in calculations of electroweak radiative corrections. In most calculations of the O(alpha) electroweak radiative corrections, weak boson emission diagrams are therefore not taken into account. Another reason for not including these diagrams is that they lead to final states which differ from that of the original process. However, in experiment, one usually considers partially inclusive final states. Weak boson emission diagrams thus should be included in calculations of electroweak radiative corrections. In this paper, I examine the role of weak boson emission in those processes at the Fermilab Tevatron and the CERN LHC for which the one-loop electroweak radiative corrections are known to become large at high energies (inclusive jet, isolated photon, Z+1 jet, Drell-Yan, di-boson, t-bar t, and single top production). In general, I find that the cross section for weak boson emission is substantial at high energies and that weak boson emission and the O(alpha) virtual weak radiative corrections partially cancel.
Thermal Gravitational Waves from Primordial Black Holes
C. Sivaram; Kenath Arun
2010-05-19T23:59:59.000Z
Thermal gravitational waves can be generated in various sources such as, in the cores of stars, white dwarfs and neutron stars due to the fermion collisions in the dense degenerate Fermi gas. Such high frequency thermal gravitational waves can also be produced during the collisions in a gamma ray burst or during the final stages of the evaporation of primordial black holes. Here we estimate the thermal gravitational waves from primordial black holes and estimate the integrated energy of the gravitational wave emission over the entire volume of the universe and over Hubble time. We also estimate the gravitational wave flux from gamma ray bursts and jets.
Gravitational cooling of self-gravitating Bose-Condensates
F. Siddhartha Guzman; L. Arturo Urena-Lopez
2006-03-22T23:59:59.000Z
Equilibrium configurations for a self-gravitating scalar field with self-interaction are constructed. The corresponding Schr\\"odinger-Poisson (SP) system is solved using finite differences assuming spherical symmetry. It is shown that equilibrium configurations of the SP system are late-time attractor solutions for initially quite arbitrary density profiles, which relax and virialize through the emission of scalar field bursts; a process dubbed gravitational cooling. Among other potential applications, these results indicate that scalar field dark matter models (in its different flavors) tolerate the introduction of a self-interaction term in the SP equations. This study can be useful in exploring models in which dark matter in galaxies is not point-like.
Gravitational wave radiometry: Mapping a stochastic gravitational wave background
Mitra, Sanjit [Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007 (India); Observatoire de la Cote d'Azur, BP 4229, 06304 Nice Cedex 4 (France); Dhurandhar, Sanjeev; Souradeep, Tarun [Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007 (India); Lazzarini, Albert; Mandic, Vuk; Ballmer, Stefan [LIGO Laboratory, California Institute of Technology, MS 18-34, Pasadena, California 91125 (United States); Bose, Sukanta [Department of Physics, Washington State University, Pullman, Washington 99164-2814 (United States)
2008-02-15T23:59:59.000Z
The problem of the detection and mapping of a stochastic gravitational wave background (SGWB), either cosmological or astrophysical, bears a strong semblance to the analysis of the cosmic microwave background (CMB) anisotropy and polarization, which too is a stochastic field, statistically described in terms of its correlation properties. An astrophysical gravitational wave background (AGWB) will likely arise from an incoherent superposition of unmodelled and/or unresolved sources and cosmological gravitational wave backgrounds (CGWB) are also predicted in certain scenarios. The basic statistic we use is the cross correlation between the data from a pair of detectors. In order to ''point'' the pair of detectors at different locations one must suitably delay the signal by the amount it takes for the gravitational waves (GW) to travel to both detectors corresponding to a source direction. Then the raw (observed) sky map of the SGWB is the signal convolved with a beam response function that varies with location in the sky. We first present a thorough analytic understanding of the structure of the beam response function using an analytic approach employing the stationary phase approximation. The true sky map is obtained by numerically deconvolving the beam function in the integral (convolution) equation. We adopt the maximum likelihood framework to estimate the true sky map using the conjugate gradient method that has been successfully used in the broadly similar, well-studied CMB map-making problem. We numerically implement and demonstrate the method on signal generated by simulated (unpolarized) SGWB for the GW radiometer consisting of the LIGO pair of detectors at Hanford and Livingston. We include 'realistic' additive Gaussian noise in each data stream based on the LIGO-I noise power spectral density. The extension of the method to multiple baselines and polarized GWB is outlined. In the near future the network of GW detectors, including the Advanced LIGO and Virgo detectors that will be sensitive to sources within a thousand times larger spatial volume, could provide promising data sets for GW radiometry.
Quake, Stephen R.
Microfabricated rubber microscope using soft solid immersion lenses Yann Gambin, Olivier Legrand a technique of soft lithography to microfabricate efficient solid immersion lenses SIL out of rubber into a handheld rubber microscope for microfluidic flow cytometry and imaged single E. Coli cells by fluorescence
Weak measurement and control of entanglement generation
Charles D. Hill; J. F. Ralph
2008-01-28T23:59:59.000Z
In this paper we show how weak joint measurement and local feedback can be used to control entanglement generation between two qubits. To do this, we make use of a decoherence free subspace (DFS). Weak measurement and feedback can be used to drive the system into this subspace rapidly. Once within the subspace, feedback can generate entanglement rapidly, or turn off entanglement generation dynamically. We also consider, in the context of weak measurement, some of differences between purification and generating entanglement.
Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Anderson, S. B.; Araya, M.; Aso, Y. [LIGO-California Institute of Technology, Pasadena, CA 91125 (United States); Accadia, T. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-le-Vieux (France); Acernese, F. [INFN, Sezione di Napoli, Complesso Universitario di Monte Sant Angelo, I-80126 Napoli (Italy); Allen, B. [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-30167 Hannover (Germany); Allen, G. [Stanford University, Stanford, CA 94305 (United States); Ceron, E. Amador; Anderson, W. G. [University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States); Amin, R. S. [Louisiana State University, Baton Rouge, LA 70803 (United States); Antonucci, F. [INFN, Sezione di Roma, I-00185 Roma (Italy); Aoudia, S. [Universite Nice-Sophia-Antipolis, CNRS, Observatoire de la Cote d'Azur, F-06304 Nice (France); Arain, M. A. [University of Florida, Gainesville, FL 32611 (United States); Arun, K. G. [LAL, Universite Paris-Sud, IN2P3/CNRS, F-91898 Orsay (France); Aston, S. [University of Birmingham, Birmingham, B15 2TT (United Kingdom)
2010-06-01T23:59:59.000Z
Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. We present a search for these known gravitational-wave signatures in temporal and directional coincidence with 22 GRBs that had sufficient gravitational-wave data available in multiple instruments during LIGO's fifth science run, S5, and Virgo's first science run, VSR1. We find no statistically significant gravitational-wave candidates within a [ - 5, + 1) s window around the trigger time of any GRB. Using the Wilcoxon-Mann-Whitney U-test, we find no evidence for an excess of weak gravitational-wave signals in our sample of GRBs. We exclude neutron star-black hole progenitors to a median 90% confidence exclusion distance of 6.7 Mpc.
Optical loss due to diffraction by concentrator Fresnel lenses
Hornung, Thorsten, E-mail: thorsten.hornung@ise.fraunhofer.de; Nitz, Peter, E-mail: thorsten.hornung@ise.fraunhofer.de [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany)
2014-09-26T23:59:59.000Z
Fresnel lenses are widely used in concentrating photovoltaic (CPV) systems as a primary optical element. They focus sunlight on small solar cells or on the entrance apertures of secondary optical elements. A Fresnel lens consists of several prism rings and diffraction by these prism rings is unavoidable. Some of the light that would reach a designated target area according to geometric optics will miss it due to diffraction. This diffraction loss may be of relevant magnitude for CPV applications. The results of published analytical calculations are evaluated, discussed, and compared to computer simulations and measurements.
Gravitational waves from perturbed stars
Valeria Ferrari
2011-05-09T23:59:59.000Z
Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.
Gravitational energy of conical defects
J. W. Maluf; A. Kneip
1996-08-22T23:59:59.000Z
The energy density of asymptotically flat gravitational fields can be calculated from a simple expression involving the trace of the torsion tensor. Integration of this energy density over the whole space yields the ADM energy. Such expression can be justified within the framework of the teleparallel equivalent of general relativity, which is an alternative geometrical formulation of Einstein's general relativity. In this paper we apply this energy density to the evaluation of the energy per unit length of a class of conical defects of topological nature, which include disclinations and dislocations (in the terminology of crystallography). Disclinations correspond to cosmic strings, and for a spacetime endowed with only such a defect we obtain precisely the well known expression of energy per unit length. However for a pure spacetime dislocation the total gravitational energy is zero.
Equivalence Principle and Gravitational Redshift
Hohensee, Michael A.; Chu, Steven; Mueller, Holger [Department of Physics, University of California, Berkeley, California 94720 (United States); Peters, Achim [Institut fuer Physik, Humboldt-Universitaet zu Berlin, Newtonstrasse 15, 12489 Berlin (Germany)
2011-04-15T23:59:59.000Z
We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter-wave, microwave, optical, and Moessbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the 10{sup -6} level.
Superconductors as quantum transducers and antennas for gravitational and electromagnetic radiation
Raymond Y. Chiao
2002-07-29T23:59:59.000Z
Superconductors will be considered as macroscopic quantum gravitational antennas and transducers, which can directly convert upon reflection a beam of quadrupolar electromagnetic radiation into gravitational radiation, and vice versa, and thus serve as practical laboratory sources and receivers of microwave and other radio-frequency gravitational waves. An estimate of the transducer conversion efficiency on the order of unity comes out of the Ginzburg-Landau theory for an extreme type II, dissipationless superconductor with minimal coupling to weak gravitational and electromagnetic radiation fields, whose frequency is smaller than the BCS gap frequency, thus satisfying the quantum adiabatic theorem. The concept of ``the impedance of free space for gravitational plane waves'' is introduced, and leads to a natural impedance-matching process, in which the two kinds of radiation fields are impedance-matched to each other around a hundred coherence lengths beneath the surface of the superconductor. A simple, Hertz-like experiment has been performed to test these ideas, and preliminary results will be reported. (PACS nos.: 03.65.Ud, 04.30.Db, 04.30.Nk, 04.80.Nn, 74.60-w, 74.72.Bk)
Chasing 5-sigma: Prospects for searches for long-duration gravitational-waves without time slides
Michael Coughlin; Patrick Meyers; Shivaraj Kandhasamy; Eric Thrane; Nelson Christensen
2015-05-01T23:59:59.000Z
The detection of unmodeled gravitational-wave bursts by ground-based interferometric gravitational-wave detectors is a major goal for the advanced detector era. These searches are commonly cast as pattern recognition problems, where the goal is to identify statistically significant clusters in spectrograms of strain power when the precise signal morphology is unknown. In previous work, we have introduced a clustering algorithm referred to as "seedless clustering," and shown that it is a powerful tool for detecting weak long-lived (10-1000s) signals in background. However, as the algorithm is currently conceived, in order to carry out an all-sky search on a $\\approx$ year of data, significant computational resources may be required in order to carry out background estimation. Alternatively, some of the sensitivity of the search must be sacrificed to control computational costs. The sensitivity of the algorithm is limited by the amount of computing resources due to the requirement of performing background studies to assign significance in gravitational-wave searches. In this paper, we present an analytic method for estimating the background generated by the seedless clustering algorithm and compare the performance to both Monte Carlo Gaussian noise and time-shifted gravitational-wave data from a week of LIGO's 5th Science Run. We demonstrate qualitative agreement between the model and measured distributions and argue that the approximation will be useful to supplement conventional background estimation techniques for advanced detector searches for long-duration gravitational-wave transients.
Energy Conservation at the Gravitational Collapse
V. Majernik
2006-09-12T23:59:59.000Z
We apply the principle of energy conservation to the motion of the test particle in gravitational field by requiring that its energy, gained by gravitation, has to be balanced by decrease of its rest mass. Due to the change of mass in gravitational field Newton's force law between gravitating bodies is modified, too. With this modified force law we build up the the classical field theory of gravitation in which all relevant field quantities are in the definition domain $r\\in [0,\\infty)$ finite and positive. We show that under such circumstances, the energy release at any gravitational collapse is finite. On the other side, the energy conservation leads to an equation which relates the mass change of the test particle due to gravitation and the metric of the corresponding gravitational field. The mass change in Newton's gravitational field lead to a remarkable simple metric which shifts, in contrast to the Schwarzschild metric, the horizon of events to the gravity center of the gravitational collapse.
Self-consistent Gravitational Lens Reconstruction
S. Dye; A. Taylor
1998-08-13T23:59:59.000Z
We present a new method for directly determining accurate, self-consistent cluster lens mass and shear maps in the strong lensing regime from the magnification bias of background galaxies. The method relies upon pixellisation of the surface mass density distribution which allows us to write down a simple, solvable set of equations. We also show how pixellisation can be applied to methods of mass determination from measurements of shear and present a simplified method of application. The method is demonstrated with cluster models and applied to magnification data from the lensing cluster Abell 1689.
Gravitational Radiation from Gamma-Ray Bursts
Tsvi Piran
2001-02-19T23:59:59.000Z
Gamma Ray Bursts (GRBs) are the most relativistic objects known so far, involving, on one hand an ultra-relativistic motion with a Lorentz factor $\\Gamma > 100$ and on the other hand an accreting newborn black hole. The two main routes leading to this scenario: binary neutron star mergers and Collapsar - the collapse of a rotating star to a black hole, are classical sources for gravitational radiation. Additionally one expect a specific a gravitational radiation pulse associated with the acceleration of the relativistic ejecta. I consider here the implication of the observed rates of GRBs to the possibility of detection of a gravitational radiation signal associated with a GRB. Unfortunately I find that, with currently planned detectors it is impossible to detect the direct gravitational radiation associated with the GRB. It is also quite unlikely to detect gravitational radiation associated with Collapsars. However, the detection of gravitational radiation from a neutron star merger associated with a GRB is likely.
Gravitational wave energy spectrum of a parabolic encounter
Christopher P. L. Berry; Jonathan R. Gair
2010-11-18T23:59:59.000Z
We derive an analytic expression for the energy spectrum of gravitational waves from a parabolic Keplerian binary by taking the limit of the Peters and Matthews spectrum for eccentric orbits. This demonstrates that the location of the peak of the energy spectrum depends primarily on the orbital periapse rather than the eccentricity. We compare this weak-field result to strong-field calculations and find it is reasonably accurate (~10%) provided that the azimuthal and radial orbital frequencies do not differ by more than ~10%. For equatorial orbits in the Kerr spacetime, this corresponds to periapse radii of rp > 20M. These results can be used to model radiation bursts from compact objects on highly eccentric orbits about massive black holes in the local Universe, which could be detected by LISA.
Search for Gravitational Waves from Intermediate Mass Binary Black Holes
the LIGO Scientific Collaboration; the Virgo Collaboration; J. Abadie; B. P. Abbott; R. Abbott; T. D. Abbott; M. Abernathy; T. Accadia; F. Acernese; C. Adams; R. Adhikari; C. Affeldt; M. Agathos; K. Agatsuma; P. Ajith; B. Allen; E. Amador Ceron; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. A. Arain; M. C. Araya; S. M. Aston; P. Astone; D. Atkinson; P. Aufmuth; C. Aulbert; B. E. Aylott; S. Babak; P. Baker; G. Ballardin; S. Ballmer; J. C. B. Barayoga; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; D. Beck; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; A. Belletoile; I. Belopolski; M. Benacquista; J. M. Berliner; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; I. A. Bilenko; G. Billingsley; J. Birch; R. Biswas; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; O. Bock; T. P. Bodiya; C. Bogan; R. Bondarescu; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; B. Bouhou; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet-Castell; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; E. Calloni; J. B. Camp; P. Campsie; J. Cannizzo; K. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; S. Caudill; M. Cavaglia; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; O. Chaibi; T. Chalermsongsak; P. Charlton; E. Chassande-Mottin; S. Chelkowski; W. Chen; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. Cho; J. Chow; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; S. Chung; G. Ciani; F. Clara; D. E. Clark; J. Clark; J. H. Clayton; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; J. Colas; A. Colla; M. Colombini; A. Conte; R. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. Coughlin; J. -P. Coulon; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; A. Cumming; L. Cunningham; E. Cuoco; R. M. Cutler; K. Dahl; S. L. Danilishin; R. Dannenberg; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; G. Debreczeni; W. Del Pozzo; M. del Prete; T. Dent; V. Dergachev; R. DeRosa; R. DeSalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; M. Di Paolo Emilio; A. Di Virgilio; M. Diaz; A. Dietz; F. Donovan; K. L. Dooley; M. Drago; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; S. Dwyer; T. Eberle; M. Edgar; M. Edwards; A. Effler; P. Ehrens; G. Endroczi; R. Engel; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; Y. Fan; B. F. Farr; D. Fazi; H. Fehrmann; D. Feldbaum; F. Feroz; I. Ferrante; F. Fidecaro; L. S. Finn; I. Fiori; R. P. Fisher; R. Flaminio; M. Flanigan; S. Foley; E. Forsi; L. A. Forte; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Frasca; F. Frasconi; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. J. Fulda; M. Fyffe; J. Gair; M. Galimberti; L. Gammaitoni; J. Garcia; F. Garufi; M. E. Gaspar; G. Gemme; R. Geng; E. Genin; A. Gennai; L. A. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil; C. Gill; J. Gleason; E. Goetz; L. M. Goggin; G. Gonzalez; M. L. Gorodetsky; S. Gossler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; S. Gras; C. Gray; N. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Greverie; R. Grosso; H. Grote; S. Grunewald; G. M. Guidi; C. Guido; R. Gupta; E. K. Gustafson; R. Gustafson; T. Ha; J. M. Hallam; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. -F. Hayau; J. Heefner; A. Heidmann; M. C. Heintze; H. Heitmann; P. Hello; M. A. Hendry; I. S. Heng; A. W. Heptonstall; V. Herrera; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; D. J. Hosken; J. Hough; E. J. Howell; B. Hughey; S. Husa; S. H. Huttner; T. Huynh-Dinh; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; K. Izumi; M. Jacobson; E. James; Y. J. Jang; P. Jaranowski; E. Jesse; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kawabe; S. Kawamura; F. Kawazoe; D. Kelley; W. Kells; D. G. Keppel; Z. Keresztes; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov; B. Kim; C. Kim; H. Kim; K. Kim; N. Kim; Y. -M. Kim; P. J. King; D. L. Kinzel; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; S. Koranda; W. Z. Korth; I. Kowalska
2012-04-25T23:59:59.000Z
We present the results of a weakly modeled burst search for gravitational waves from mergers of non-spinning intermediate mass black holes (IMBH) in the total mass range 100--450 solar masses and with the component mass ratios between 1:1 and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the IMBH mergers as a function of the component masses. In the most efficiently detected bin centered on 88+88 solar masses, for non-spinning sources, the rate density upper limit is 0.13 per Mpc^3 per Myr at the 90% confidence level.
Evolution of simple configurations of gravitating gas
G. P. Pronko
2011-04-23T23:59:59.000Z
We considered the dynamics of gravitating gas - a continuous media with peculiar properties. The exact solutions of its Euler equations for simple initial conditions is obtained.
Expanding the Area of Gravitational Entropy
R. B. Mann
2002-11-12T23:59:59.000Z
I describe how gravitational entropy is intimately connected with the concept of gravitational heat, expressed as the difference between the total and free energies of a given gravitational system. From this perspective one can compute these thermodyanmic quantities in settings that go considerably beyond Bekenstein's original insight that the area of a black hole event horizon can be identified with thermodynamic entropy. The settings include the outsides of cosmological horizons and spacetimes with NUT charge. However the interpretation of gravitational entropy in these broader contexts remains to be understood.
Precision Measurement of the Newtonian Gravitational Constant Using Cold Atoms
G. Rosi; F. Sorrentino; L. Cacciapuoti; M. Prevedelli; G. M. Tino
2014-12-26T23:59:59.000Z
About 300 experiments have tried to determine the value of the Newtonian gravitational constant, G, so far, but large discrepancies in the results have made it impossible to know its value precisely. The weakness of the gravitational interaction and the impossibility of shielding the effects of gravity make it very difficult to measure G while keeping systematic effects under control. Most previous experiments performed were based on the torsion pendulum or torsion balance scheme as in the experiment by Cavendish in 1798, and in all cases macroscopic masses were used. Here we report the precise determination of G using laser-cooled atoms and quantum interferometry. We obtain the value G=6.67191(99) x 10^(-11) m^3 kg^(-1) s^(-2) with a relative uncertainty of 150 parts per million (the combined standard uncertainty is given in parentheses). Our value differs by 1.5 combined standard deviations from the current recommended value of the Committee on Data for Science and Technology. A conceptually different experiment such as ours helps to identify the systematic errors that have proved elusive in previous experiments, thus improving the confidence in the value of G. There is no definitive relationship between G and the other fundamental constants, and there is no theoretical prediction for its value, against which to test experimental results. Improving the precision with which we know G has not only a pure metrological interest, but is also important because of the key role that G has in theories of gravitation, cosmology, particle physics and astrophysics and in geophysical models.
Gravitational and non-gravitational energy: the need for background structures
Wüthrich, Christian
Gravitational and non-gravitational energy: the need for background structures Vincent Lam- tional energy within the general theory of relativity. Some aspects of the difficulties to ascribe the usual features of localization and conservation to gravitational energy are reviewed and considered
Kubo, Jeffrey M.; Allam, Sahar S.; Annis, James; Buckley-Geer, Elizabeth J.; Diehl, H.Thomas; Drabek, Emily; Frieman, Joshua A.; Hao, Jiangang; Kubik, Donna; Lin, Huan; Soares-Santos, Marcelle
2010-10-01T23:59:59.000Z
We report the discovery of seven new, very bright gravitational lens systems from our ongoing gravitational lens search, the Sloan Bright Arcs Survey (SBAS). Two of the systems are confirmed to have high source redshifts z = 2.19 and z = 2.94. Three other systems lie at intermediate redshift with z = 1.33, 1.82, 1.93 and two systems are at low redshift z = 0.66, 0.86. The lensed source galaxies in all of these systems are bright, with i-band magnitudes ranging from 19.73-22.06. We present the spectrum of each of the source galaxies in these systems along with estimates of the Einstein radius for each system. The foreground lens in most systems is identified by a red sequence based cluster finder as a galaxy group; one system is identified as a moderately rich cluster. In total the SBAS has now discovered nineteen strong lens systems in the SDSS imaging data, eight of which are among the highest surface brightness z {approx_equal} 2-3 galaxies known.
Hatsukade, Bunyo; Iono, Daisuke; Matsuda, Yuichi; Hayashi, Masao; Oguri, Masamune
2015-01-01T23:59:59.000Z
We present spatially-resolved properties of molecular gas and dust in a gravitationally-lensed submillimeter galaxy H-ATLAS J090311.6+003906 (SDP.81) at $z=3.042$ revealed by the Atacama Large Millimeter/submillimeter Array (ALMA). We identified 14 molecular clumps in the CO(5-4) line data, all with a spatial scale of $\\sim$50-300 pc in the source plane. The surface density of molecular gas ($\\Sigma_{\\rm H_2}$) and star-formation rate ($\\Sigma_{\\rm SFR}$) of the clumps are more than three orders of magnitude higher than those found in local spiral galaxies. The clumps are placed in the `burst' sequence in the $\\Sigma_{\\rm H_2}$-$\\Sigma_{\\rm SFR}$ plane, suggesting that $z \\sim 3$ molecular clumps follow the star-formation law derived for local starburst galaxies. With our gravitational lens model, the positions in the source plane are derived for the molecular clumps, dust clumps, and stellar components identified in the {\\sl Hubble Space Telescope} image. The molecular and dust clumps coexist in a similar re...
The Loudest Gravitational Wave Events
Hsin-Yu Chen; Daniel E. Holz
2014-09-04T23:59:59.000Z
As first emphasized by Bernard Schutz, there exists a universal distribution of signal-to-noise ratios for gravitational wave detection. Because gravitational waves (GWs) are almost impossible to obscure via dust absorption or other astrophysical processes, the strength of the detected signal is dictated solely by the emission strength and the distance to the source. Assuming that the space density of an arbitrary population of GW sources does not evolve, we show explicitly that the distribution of detected signal-to-noise (SNR) values depends solely on the detection threshold; it is independent of the detector network (interferometer or pulsar timing array), the individual detector noise curves (initial or Advanced LIGO), the nature of the GW sources (compact binary coalescence, supernova, or some other discrete source), and the distributions of source variables (only non-spinning neutron stars of mass exactly $1.4\\,M_\\odot$ or a complicated distribution of masses and spins). We derive the SNR distribution for each individual detector within a network as a function of the relative detector orientations and sensitivities. While most detections will have SNR near the detection threshold, there will be a tail of events to higher SNR. We derive the SNR distribution of the loudest (highest SNR) events in any given sample of detections. We find that the median SNR of the loudest out of the first four events should have an $\\mbox{SNR}=22$ (for a threshold of 12, appropriate for the Advanced LIGO/Virgo network), increasing to a median value for the loudest SNR of 47 for 40 detections. We expect these loudest events to provide particularly powerful constraints on their source parameters, and they will play an important role in extracting astrophysics from gravitational wave sources. These distributions also offer an important internal calibration of the response of the GW detector networks.
Gravitational waveforms with controlled accuracy
Roberto Gomez
2001-06-07T23:59:59.000Z
A partially first-order form of the characteristic formulation is introduced to control the accuracy in the computation of gravitational waveforms produced by highly distorted single black hole spacetimes. Our approach is to reduce the system of equations to first-order differential form on the angular derivatives, while retaining the proven radial and time integration schemes of the standard characteristic formulation. This results in significantly improved accuracy over the standard mixed-order approach in the extremely nonlinear post-merger regime of binary black hole collisions.
Gravitational duality and rotating solutions
Argurio, Riccardo; Dehouck, Francois [Physique Theorique et Mathematique and International Solvay Institutes, Universite Libre de Bruxelles, C.P. 231, 1050 Bruxelles (Belgium)
2010-03-15T23:59:59.000Z
We study how gravitational duality acts on rotating solutions, using the Kerr-NUT black hole as an example. After properly reconsidering how to take into account both electric (i.e. masslike) and magnetic (i.e. NUT-like) sources in the equations of general relativity, we propose a set of definitions for the dual Lorentz charges. We then show that the Kerr-NUT solution has nontrivial such charges. Further, we clarify in which respect Kerr's source can be seen as a mass M with a dipole of NUT charges.
Towards an Alternative Gravitational Theory
J. A. Nieto; L. A. Beltrán
2014-05-14T23:59:59.000Z
In 1680 Cassini proposed oval curves as alternative trajectories for the visible planets around the sun. The Cassini ovals were of course overshadow by the Kepler's first law (1609), namely the planets move around the sun describing conic orbits. Here we describe the possibility that the Cassini's idea works at larger or smaller scales. Indeed, we consider the Spiric curves (which are a generalization of the Cassini oval) and present the first steps towards a Spiric gravitational theory. We show that from our formalism an ellipse associated with a planet can be obtained as a particular case.
Observational determination of the time delays in gravitational lens system Q2237+030
V. Vakulik; R. Schild; V. Dudinov; S. Nuritdinov; V. Tsvetkova; O. Burkhonov; T. Akhunov
2005-09-19T23:59:59.000Z
We present new brightness monitoring observations of the 4 components of gravitationally lensed system Q2237+0305, which show detection of an intrinsic quasar brightness fluctuation at a time of subdued microlensing activity, between June 27 and October 12, 2003. These data were used to determine the time delays between the arrivals of the four images. The measured delays are -6, 35, and 2 hours for images B, C and D relative to A, respectively, so they confirm that the long history of brightness monitoring has produced significant detection of microlensing. However the error bars associated with the delays, of order 2 days, are too large to discriminate between competing macro-imaging models. Moreover, our simulations show that for the amplitude of this intrinsic fluctuation and for photometric errors intrinsic to optical monitoring from our 1.5-m telescope or from the OGLE monitoring, a daily sampled brightness record cannot produce reliable lags for model discrimination. We use our simulations to devise a strategy for future delay determination with optical data. Nevertheless, we regard these first estimates to be significant, since they are the first direct measurements of time delays made for this system from ground-based observations in the visual wavelengths. Our results provide the most convincing confirmation of the gravitational-lens nature of Q2237+0305, and give observational justification to the extensive literature which attributes the quasar's previously observed brightness fluctuations to microlensing.
Development of Ground-testable Phase Fresnel Lenses in Silicon
John Krizmanic; Brian Morgan; Robert Streitmatter; Neil Gehrels; Keith Gendreau; Zaven Arzoumanian; Reza Ghodssi; Gerry Skinner
2006-01-03T23:59:59.000Z
Diffractive/refractive optics, such as Phase Fresnel Lenses (PFL's), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a small detector area. In order to verify experimentally the imaging performance, we have fabricated PFL's in silicon using gray-scale lithography to produce the required Fresnel profile. These devices are to be evaluated in the recently constructed 600-meter x-ray interferometry testbed at NASA/GSFC. Profile measurements of the Fresnel structures in fabricated PFL's have been performed and have been used to obtain initial characterization of the expected PFL imaging efficiencies.
Gravitational Energy in Spherical Symmetry
Sean A. Hayward
2002-02-17T23:59:59.000Z
Various properties of the Misner-Sharp spherically symmetric gravitational energy E are established or reviewed. In the Newtonian limit of a perfect fluid, E yields the Newtonian mass to leading order and the Newtonian kinetic and potential energy to the next order. For test particles, the corresponding Hajicek energy is conserved and has the behaviour appropriate to energy in the Newtonian and special-relativistic limits. In the small-sphere limit, the leading term in E is the product of volume and the energy density of the matter. In vacuo, E reduces to the Schwarzschild energy. At null and spatial infinity, E reduces to the Bondi-Sachs and Arnowitt-Deser-Misner energies respectively. The conserved Kodama current has charge E. A sphere is trapped if E>r/2, marginal if E=r/2 and untrapped if E0, and temporal and untrapped if Eenergy condition. It follows that E>=0 on an untrapped spatial hypersurface with regular centre, and E>=r_0/2 on an untrapped spatial hypersurface bounded at the inward end by a marginal sphere of radius r_0. All these inequalities extend to the asymptotic energies, recovering the Bondi-Sachs energy loss and the positivity of the asymptotic energies, as well as proving the conjectured Penrose inequality for black or white holes. Implications for the cosmic censorship hypothesis and for general definitions of gravitational energy are discussed.
Can the trace formula describe weak localisation?
Robert S. Whitney; Igor V. Lerner; Robert A. Smith
1999-02-24T23:59:59.000Z
We attempt to systematically derive perturbative quantum corrections to the Berry diagonal approximation of the two-level correlation function (TLCF) for chaotic systems. To this end, we develop a ``weak diagonal approximation'' based on a recent description of the first weak localisation correction to conductance in terms of the Gutzwiller trace formula. This semiclassical method is tested by using it to derive the weak localisation corrections to the TLCF for a semiclassically disordered system. Unfortunately the method is unable to correctly reproduce the ``Hikami boxes'' (the relatively small regions where classical paths are glued together by quantum processes). This results in the method failing to reproduce the well known weak localisation expansion. It so happens that for the first order correction it merely produces the wrong prefactor. However for the second order correction, it is unable to reproduce certain contributions, and leads to a result which is of a different form to the standard one.
Quantum Gravity effect on neutrino oscillations in a strong gravitational field
Jonathan Miller; Roman Pasechnik
2014-11-14T23:59:59.000Z
In the framework of quantum field theory, a graviton interacts locally with a quantum state having definite mass, i.e. the gravitational mass eigenstate, while a weak boson interacts with a state having definite flavor, i.e. the flavor eigenstate. An interaction of a neutrino with an energetic graviton may trigger the collapse of the neutrino to a definite mass eigenstate with probability expressed in terms of PMNS mixing matrix elements. Thus, gravitons would induce quantum decoherence of a coherent neutrino flavor state similarly to how weak bosons induce quantum decoherence of a neutrino in a definite mass state. We demonstrate that such an essentially quantum gravity effect may have strong consequences for neutrino oscillation phenomena in astrophysics due to relatively large scattering cross sections of relativistic neutrinos undergoing large-angle radiation of energetic gravitons in gravitational field of a classical massive source (i.e. the quasi-classical case of gravitational Bethe-Heitler scattering). This graviton-induced {\\em decoherence} is compared to {\\em decoherence} due to propagation in the presence of the Earth matter effect. Based on this study, we propose a new technique for the indirect detection of energetic gravitons by measuring the flavor composition of astrophysical neutrinos.
The wave function of a gravitating shell
V. I. Dokuchaev; S. V. Chernov
2010-10-01T23:59:59.000Z
We have calculated a discrete spectrum and found an exact analytical solution in the form of Meixner polynomials for the wave function of a thin gravitating shell in the Reissner-Nordstrom geometry. We show that there is no extreme state in the quantum spectrum of the gravitating shell, as in the case of extreme black hole.
Gravitational force between two electrons in superconductors
Clovis Jacinto de Matos
2007-11-19T23:59:59.000Z
The attractive gravitational force between two electrons in superconductors is deduced from the Eddington-Dirac large number relation, together with Beck and Mackey electromagnetic model of vacuum energy in superconductors. This force is estimated to be weaker than the gravitational attraction between two electrons in the vacuum.
Large photon productions in a gravitational collapsing
She-Sheng Xue
2003-12-16T23:59:59.000Z
We study a possible gravitational vacuum-effect, in which vacuum-energy variation is due to variation of gravitational field, vacuum state gains gravitational energy and releases it by spontaneous photon emissions. Based on the path-integral representation, we present a general formulation of vacuum transition matrix and energy-momentum tensor of a quantum scalar field theory in curved spacetime. Using analytical continuation of dimensionality of the phase space, we calculate the difference of vacuum-energy densities in the presence and absence of gravitational field. Using the dynamical equation of gravitational collapse, we compute the rate of vacuum state gaining gravitational energy. Computing the transition amplitude from initial vacuum state to final vacuum state in gravitational collapsing process, we show the rate and spectrum of spontaneous photon emissions for releasing gravitational energy. The possible connection of our study to the genuine origin of gamma ray bursts is discussed. We compare our idea with the Schwinger idea for Sonoluminiescence and contrast our scenario with the Hawking effect.
A radiometer for stochastic gravitational waves
Stefan W. Ballmer
2005-10-20T23:59:59.000Z
The LIGO Scientific Collaboration recently reported a new upper limit on an isotropic stochastic background of gravitational waves obtained based on the data from the 3rd LIGO science Run (S3). Now I present a new method for obtaining directional upper limits that the LIGO Scientific Collaboration intends to use for future LIGO science runs and that essentially implements a gravitational wave radiometer.
Centrifugal deformations of the gravitational kink
Paolo Maraner; Jiannis K. Pachos
2008-11-29T23:59:59.000Z
The Kaluza-Klein reduction of 4d conformally flat spacetimes is reconsidered. The corresponding 3d equations are shown to be equivalent to 2d gravitational kink equations augmented by a centrifugal term. For space-like gauge fields and non-trivial values of the centrifugal term the gravitational kink solutions describe a spacetime that is divided in two disconnected regions.
Gravitational Field of Fractal Distribution of Particles
Vasily E. Tarasov
2006-04-24T23:59:59.000Z
In this paper we consider the gravitational field of fractal distribution of particles. To describe fractal distribution, we use the fractional integrals. The fractional integrals are considered as approximations of integrals on fractals. Using the fractional generalization of the Gauss's law, we consider the simple examples of the fields of homogeneous fractal distribution. The examples of gravitational moments for fractal distribution are considered.
On multitemporal generalization of Newton's gravitational law
V. D. Ivashchuk
2009-05-15T23:59:59.000Z
A n-time generalization of Newton's law (of universal gravitation) formula in N =n + d + 1-dimensional space-time is conjectured. This formula implies a relation for effective N-dimensional gravitational constant G_{eff} = G cos^2 \\theta, where \\theta is the angle between the direction of motion of two particles in n-dimensional time manifold R^n.
Newtonian Constant of Gravitation International Consortium
Newtonian Constant of Gravitation International Consortium I. BACKGROUND Recent measurements of the Newtonian constant of gravitation G are in disagreement, with discrepancies that are roughly ten times forces on a laboratory scale. It also raises the question of whether the Newtonian force law
Neutrino oscillations in the general spherically symmetric gravitational field
Godunov, S. I., E-mail: sgodunov@itep.ru; Pastukhov, G. S., E-mail: grigoriypas@gmail.com [Institute for Theoretical and Experimental Physics (Russian Federation)
2012-09-15T23:59:59.000Z
The results for neutrino oscillations in the gravitational field described by the Schwarzschild metric are generalized to the general spherically symmetric gravitational field.
Krill-eye : Superposition Compound Eye for Wide-Angle Imaging via GRIN Lenses
Hiura, Shinsaku
We propose a novel wide angle imaging system inspired by compound eyes of animals. Instead of using a single lens, well compensated for aberration, we used a number of simple lenses to form a compound eye which produces ...
Regularity Theorems in the Nonsymmetric Gravitational Theory
J. W. Moffat
1995-04-17T23:59:59.000Z
Regularity theorems are presented for cosmology and gravitational collapse in non-Riemannian gravitational theories. These theorems establish conditions necessary to allow the existence of timelike and null path complete spacetimes for matter that satisfies the positive energy condition. Non-Riemannian theories of gravity can have solutions that have a non-singular beginning of the universe, and the gravitational collapse of a star does not lead to a black hole event horizon and a singularity as a final stage of collapse. A perturbatively consistent version of nonsymmetric gravitational theory is studied that, in the long-range approximation, has a nonsingular static spherically symmetric solution which is path complete, does not have black hole event horizons and has finite curvature invariants. The theory satisfies the regularity theorems for cosmology and gravitational collapse. The elimination of black holes resolves the information loss puzzle.
Mead, Carver
2015-01-01T23:59:59.000Z
Gravitational coupling of the propagation four-vectors of matter wave functions is formulated in flat space-time. Coupling at the momentum level rather than at the "force-law" level greatly simplifies many calculations. This locally Lorentz-invariant approach (G4v) treats electromagnetic and gravitational coupling on an equal footing. Classical mechanics emerges from the incoherent aggregation of matter wave functions. The theory reproduces, to first order beyond Newton, the standard GR results for Gravity-Probe B, deflection of light by massive bodies, precession of orbits, gravitational red shift, and total gravitational-wave energy radiated by a circular binary system. Its predictions of total radiated energy from highly eccentric Kepler systems are slightly larger than those of similar GR treatments. G4v predictions differ markedly from those of GR for the gravitational-wave radiation patterns from rotating massive systems, and for the LIGO antenna pattern. The predicted antenna patterns have been shown t...
Miller, D. C.; Carloni, J. D.; Pankow, J. W.; Gjersing, E. L.; To, B.; Packard, C. E.; Kennedy, C. E.; Kurtz, S. R.
2012-01-01T23:59:59.000Z
Concentrating photovoltaic (CPV) technology recently gained interest based on its expected low levelized cost of electricity, high efficiency, and scalability. Many CPV systems employ Fresnel lenses composed of poly(methyl methacrylate) (PMMA) to obtain a high optical flux density on the cell. The optical and mechanical durability of these lenses, however, is not well established relative to the desired surface life of 30 years. Our research aims to quantify the expected lifetime of PMMA in key market locations (FL, AZ, and CO).
Gravitational energy as Noether charge
Sean A. Hayward
2000-04-13T23:59:59.000Z
A definition of gravitational energy is proposed for any theory described by a diffeomorphism-invariant Lagrangian. The mathematical structure is a Noether- current construction of Wald involving the boundary term in the action, but here it is argued that the physical interpretation of current conservation is conservation of energy. This leads to a quasi-local energy defined for compact spatial surfaces. The energy also depends on a vector generating a flow of time. Angular momentum may be similarly defined, depending on a choice of axial vector. For Einstein gravity: for the usual vector generating asymptotic time translations, the energy is the Bondi energy; for a stationary Killing vector, the energy is the Komar energy; in spherical symmetry, for the Kodama vector, the energy is the Misner-Sharp energy. In general, the lack of a preferred time indicates the lack of a preferred energy, reminiscent of the energy-time duality of quantum theory.
T-705: Linux Kernel Weakness in Sequence Number Generation Facilitates...
Broader source: Energy.gov (indexed) [DOE]
5: Linux Kernel Weakness in Sequence Number Generation Facilitates Packet Injection Attacks T-705: Linux Kernel Weakness in Sequence Number Generation Facilitates Packet Injection...
T-728: Apache Tomcat HTTP DIGEST Authentication Weaknesses Let...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
8: Apache Tomcat HTTP DIGEST Authentication Weaknesses Let Remote Users Conduct Bypass Attacks T-728: Apache Tomcat HTTP DIGEST Authentication Weaknesses Let Remote Users Conduct...
Contribution of muscular weakness to osteoporosis: Computational and animal models
Gefen, Amit
Contribution of muscular weakness to osteoporosis: Computational and animal models M. Be obtained herein indicate that muscular weakness may be an important factor contributing to osteoporosis. Ó
Theory and Modeling of Weakly Bound/Physisorbed Materials for...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Theory and Modeling of Weakly BoundPhysisorbed Materials for Hydrogen Storage Theory and Modeling of Weakly BoundPhysisorbed Materials for Hydrogen Storage Presentation on the...
Chasing 5-sigma: Prospects for searches for long-duration gravitational-waves without time slides
Coughlin, Michael; Kandhasamy, Shivaraj; Thrane, Eric; Christensen, Nelson
2015-01-01T23:59:59.000Z
The detection of unmodeled gravitational-wave bursts by ground-based interferometric gravitational-wave detectors is a major goal for the advanced detector era. These searches are commonly cast as pattern recognition problems, where the goal is to identify statistically significant clusters in spectrograms of strain power when the precise signal morphology is unknown. In previous work, we have introduced a clustering algorithm referred to as "seedless clustering," and shown that it is a powerful tool for detecting weak long-lived (10-1000s) signals in background. However, as the algorithm is currently conceived, in order to carry out an all-sky search on a $\\approx$ year of data, significant computational resources may be required in order to carry out background estimation. Alternatively, some of the sensitivity of the search must be sacrificed to control computational costs. The sensitivity of the algorithm is limited by the amount of computing resources due to the requirement of performing background studi...
Gravitationally Induced Neutrino-Oscillation Phases
D. V. Ahluwalia; C. Burgard
2004-01-22T23:59:59.000Z
In this essay, we introduce a new effect of gravitationally induced quantum mechanical phases in neutrino oscillations. These phases arise from an hitherto unexplored interplay of gravitation and the principle of the linear superposition of quantum mechanics. In the neighborhood of a 1.4 solar-mass neutron star, gravitationally induced quantum mechanical phases are roughly 20% of their kinematical counterparts. When this information is coupled with the mass square differences implied by the existing neutrino-oscillation data we find that the new effect may have profound consequences for type-II supernova evolution.
Interaction of gravitational waves with matter
A. Cetoli; C. J. Pethick
2011-10-03T23:59:59.000Z
We develop a unified formalism for describing the interaction of gravitational waves with matter that clearly separates the effects of general relativity from those due to interactions in the matter. Using it, we derive a general expression for the dispersion of gravitational waves in matter in terms of correlation functions for the matter in flat spacetime. The self energy of a gravitational wave is shown to have contributions analogous to the paramagnetic and diamagnetic contributions to the self energy of an electromagnetic wave. We apply the formalism to some simple systems - free particles, an interacting scalar field, and a fermionic superfluid.
Strong effects in weak nonleptonic decays
Wise, M.B.
1980-04-01T23:59:59.000Z
In this report the weak nonleptonic decays of kaons and hyperons are examined with the hope of gaining insight into a recently proposed mechanism for the ..delta..I = 1/2 rule. The effective Hamiltonian for ..delta..S = 1 weak nonleptonic decays and that for K/sup 0/-anti K/sup 0/ mixing are calculated in the six-quark model using the leading logarithmic approximation. These are used to examine the CP violation parameters of the kaon system. It is found that if Penguin-type diagrams make important contributions to K ..-->.. ..pi pi.. decay amplitudes then upcoming experiments may be able to distinguish the six-quark model for CP violation from the superweak model. The weak radiative decays of hyperons are discussed with an emphasis on what they can teach us about hyperon nonleptonic decays and the ..delta..I = 1/2 rule.
No-Hair Theorem for Weak Pulsar
Gruzinov, Andrei
2015-01-01T23:59:59.000Z
It is proposed that there exists a class of pulsars, called weak pulsars, for which the large-scale magnetosphere, and hence the gamma-ray emission, are independent of the detailed pattern of plasma production. The weak pulsar magnetosphere and its gamma-ray emission are uniquely determined by just three parameters: spin, dipole, and the spin-dipole angle. We calculate this supposedly unique pulsar magnetosphere in the axisymmetric case. The magnetosphere is found to be very close to (although interestingly not fully identical with) the magnetosphere we have previously calculated, explaining the phenomenological success of the old calculation. We offer only a highly tentative proof of this "Pulsar No-Hair Theorem". Our analytics, while convincing in its non-triviality, is incomplete, and counts only as a plausibility argument. Our numerics, while complete, is dubious. The plasma flow in the weak pulsar magnetosphere turns out to be even more intricate than what we have previously proposed: some particles, aft...
Wang, Wei Hua
;Topological insulators (TI) are a new class of quantum materials with insulating bulk enclosedCrossover between weak localization and weak antilocalization in magnetically doped topological insulator Minhao Liu1,* , Jinsong Zhang1,* , Cui-Zu Chang1,2,* , Zuocheng Zhang1 , Xiao Feng2 , Kang Li2
Hall Magnetohydrodynamics of weakly-ionized plasma
B. P. Pandey; Mark Wardle
2006-08-02T23:59:59.000Z
We show that the Hall scale in a weakly ionized plasma depends on the fractional ionization of the medium and, Hall MHD description becomes important whenever the ion-neutral collision frequency is comparable to the ion-gyration frequency, or, the ion-neutral collisional mean free path is smaller than the ion gyro-radius. Wave properties of a weakly-ionized plasma also depends on the fractional ionization and plasma Hall parameters, and whistler mode is the most dominant mode in such a medium. Thus Hall MHD description will be important in astrophysical disks, dark molecular clouds, neutron star crusts, and, solar and planetary atmosphere.
Weak Gravity Conjecture for Noncommutative Field Theory
Qing-Guo Huang; Jian-Huang She
2006-11-20T23:59:59.000Z
We investigate the weak gravity bounds on the U(1) gauge theory and scalar field theories in various dimensional noncommutative space. Many results are obtained, such as the upper bound on the noncommutative scale $g_{YM}M_p$ for four dimensional noncommutative U(1) gauge theory. We also discuss the weak gravity bounds on their commutative counterparts. For example, our result on 4 dimensional noncommutative U(1) gauge theory reduces in certain limit to its commutative counterpart suggested by Arkani-Hamed et.al at least at tree-level.
Gravitational radiation from dynamical black holes
Sean A. Hayward
2005-12-26T23:59:59.000Z
An effective energy tensor for gravitational radiation is identified for uniformly expanding flows of the Hawking mass-energy. It appears in an energy conservation law expressing the change in mass due to the energy densities of matter and gravitational radiation, with respect to a Killing-like vector encoding a preferred flow of time outside a black hole. In a spin-coefficient formulation, the components of the effective energy tensor can be understood as the energy densities of ingoing and outgoing, transverse and longitudinal gravitational radiation. By anchoring the flow to the trapping horizon of a black hole in a given sequence of spatial hypersurfaces, there is a locally unique flow and a measure of gravitational radiation in the strong-field regime.
Propagation of gravitational waves in multimetric gravity
Manuel Hohmann
2012-04-22T23:59:59.000Z
We discuss the propagation of gravitational waves in a recently discussed class of theories containing N >= 2 metric tensors and a corresponding number of standard model copies. Using the formalism of gauge-invariant linear perturbation theory we show that all gravitational waves propagate at the speed of light. We then employ the Newman-Penrose formalism to show that two to six polarizations of gravitational waves may exist, depending on the parameters entering the equations of motion. This corresponds to E(2) representations N_2, N_3, III_5 and II_6. We finally apply our general discussion to a recently presented concrete multimetric gravity model and show that it is of class N_2, i.e., it allows only two tensor polarizations, as it is the case for general relativity. Our results provide the theoretical background for tests of multimetric gravity theories using the upcoming gravitational wave experiments.
Planet migration in self-gravitating disks
Meru, Farzana; Baruteau, Clement
2010-01-01T23:59:59.000Z
and migration of the planet at the same time so that theG. W. 1978, Moon and Planets, 18, 5 Fukagawa, M. , Hayashi,Planet migration in self-gravitating protoplanetary discs
Gravitational clustering in Static and Expanding Backgrounds
T. Padmanabhan
2003-08-28T23:59:59.000Z
A brief summary of several topics in the study of gravitational many body problem is given. The discussion covers both static backgrounds (applicable to astrophysical systems) as well as clustering in an expanding background (relevant for cosmology)
Gravitational Anomalies in Noncommutative Field Theory
Sendic Estrada-Jimenez; Hugo Garcia-Compean; Carlos Soto-Campos
2004-04-14T23:59:59.000Z
Gravitational axial and chiral anomalies in a noncommutative space are examined through the explicit perturbative computation of one-loop diagrams in various dimensions. The analysis depend on how gravity is coupled to noncommutative matter fields. Delbourgo-Salam computation of the gravitational axial anomaly contribution to the pion decay into two photons, is studied in detail in this context. In the process we show that the two-dimensional chiral pure gravitational anomaly does not receive noncommutative corrections. Pure gravitational chiral anomaly in 4k+2 dimensions with matter fields being chiral fermions of spin-1/2 and spin-3/2, is discussed and a noncommutative correction is found in both cases. Mixed anomalies are finally considered in both cases.
Atom Interferometers and the Gravitational Redshift
Supurna Sinha; Joseph Samuel
2011-05-16T23:59:59.000Z
From the principle of equivalence, Einstein predicted that clocks slow down in a gravitational field. Since the general theory of relativity is based on the principle of equivalence, it is essential to test this prediction accurately. Muller, Peters and Chu claim that a reinterpretation of decade old experiments with atom interferometers leads to a sensitive test of this gravitational redshift effect at the Compton frequency. Wolf et al dispute this claim and adduce arguments against it. In this article, we distill these arguments to a single fundamental objection: an atom is NOT a clock ticking at the Compton frequency. We conclude that atom interferometry experiments conducted to date do not yield such sensitive tests of the gravitational redshift. Finally, we suggest a new interferometric experiment to measure the gravitational redshift, which realises a quantum version of the classical clock "paradox".
Planet formation in self-gravitating discs
Gibbons, Peter George
2013-11-28T23:59:59.000Z
The work performed here studies particle dynamics in local two-dimensional simulations of self-gravitating accretion discs with a simple cooling law. It is well known that the structure which arises in the gaseous component ...
Power recycling for an interferometric gravitational wave
Ejiri, Shinji
THESIS Power recycling for an interferometric gravitational wave detector Masaki Ando Department . . . . . . . . . . . . . . 48 3.3 Power recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.3.1 Principle of power recycling . . . . . . . . . . . . . . . . . 50 3.3.2 Recycling cavity
Rhodium Mossbauer Superradiance of Observable Gravitational Effect
Yao Cheng; Bing Xia
2007-11-18T23:59:59.000Z
We summarize the experimental observations of three case studies on the long-lived rhodium Mossbauer Effect. Extraordinary observations reported in this work manifest the open-up of photonic band gap in analogy to the superconducting gap. Observable gravitational effect is manifested by the superradiance of different sample orientations corresponding to the earth gravity. These observations are of potential importance for detecting gravitational waves and development of the two-photon gamma laser.
Spin-2 particles in gravitational fields
G. Papini
2007-02-01T23:59:59.000Z
We give a solution of the wave equation for massless, or massive spin-2 particles propagating in a gravitational background. The solution is covariant, gauge-invariant and exact to first order in the background gravitational field. The background contribution is confined to a phase factor from which geometrical and physical optics can be derived. The phase also describes Mashhoon's spin-rotation coupling and, in general, the spin-gravity interaction.
Gravitational Radiation Detection with Laser Interferometry
Rana X Adhikari
2014-03-13T23:59:59.000Z
Gravitational-wave detection has been pursued relentlessly for over 40 years. With the imminent operation of a new generation of laser interferometers, it is expected that detections will become a common occurrence. The research into more ambitious detectors promises to allow the field to move beyond detection and into the realm of precision science using gravitational radiation. In this article, I review the state of the art for the detectors and describe an outlook for the coming decades.
Gravitational Radiation Detection with Laser Interferometry
Adhikari, Rana X
2013-01-01T23:59:59.000Z
Gravitational-wave detection has been pursued relentlessly for over 40 years. With the imminent operation of a new generation of laser interferometers, it is expected that detections will become a common occurrence. The research into more ambitious detectors promises to allow the field to move beyond detection and into the realm of precision science using gravitational radiation. In this article, I review the state of the art for the detectors and describe an outlook for the coming decades.
Chiral Self-Gravitating Cosmic Vortices
Rybakov, Yu.P. [Department of Theoretical Physics, Russian University of Peoples' Friendship, ul. Miklukho-Maklaya 6, Moscow, 117198 (Russian Federation)
2005-06-01T23:59:59.000Z
In the framework of general relativity, an exact axisymmetric (vortex) solution of the equations of motion is obtained for the SU(2) symmetric sigma model. This solution is characterized by the topological charge (winding number) and angular deficit. In the linearized approximation, the Lyapunov stability of vortices is proved and the deflection angle of a light ray in the gravitational field of the vortex (gravitational lens effect) is calculated.
Alexander Dietz
2010-06-17T23:59:59.000Z
Mergers of two compact objects, like two neutron stars or a neutron star and a black hole, are the probable progenitor of short gamma-ray bursts. These events are also promising sources of gravitational waves, that are currently motivating related searches by an international network of gravitational wave detectors. Here we describe a search for gravitational waves from the in-spiral phase of two coalescing compact objects, in coincidence with short GRBs occurred during during LIGO's fifth science run and Virgo's first science run. The search includes 22 GRBs for which data from more than one of the detectors in the LIGO/Virgo network were available. No statistically significant gravitational-wave candidate has been found, and a parametric test shows no excess of weak gravitational-wave signals in our sample of GRBs. The 90\\%~C.L. median exclusion distance for GRBs in our sample is of 6.7 Mpc, under the hypothesis of a neutron star - black hole progenitor model.
Products, weak topologies, quotients and strong topologies.
Ferri, Stefano
Products, weak topologies, quotients and strong topologies. Stefano Ferri Abstract Again something from finite products of metric spaces, which are well known from the course Analysis I. Given two metric spaces (X, d) and (Y, ) we define the product space X Ã? Y in the following way. As a set we have
Carver Mead
2015-03-16T23:59:59.000Z
Gravitational coupling of the propagation four-vectors of matter wave functions is formulated in flat space-time. Coupling at the momentum level rather than at the "force-law" level greatly simplifies many calculations. This locally Lorentz-invariant approach (G4v) treats electromagnetic and gravitational coupling on an equal footing. Classical mechanics emerges from the incoherent aggregation of matter wave functions. The theory reproduces, to first order beyond Newton, the standard GR results for Gravity-Probe B, deflection of light by massive bodies, precession of orbits, gravitational red shift, and total gravitational-wave energy radiated by a circular binary system. Its predictions of total radiated energy from highly eccentric Kepler systems are slightly larger than those of similar GR treatments. G4v predictions differ markedly from those of GR for the gravitational-wave radiation patterns from rotating massive systems, and for the LIGO antenna pattern. The predicted antenna patterns have been shown to be highly distinguishable in the case of continuous gravitational-wave sources, and should therefore be testable as data from Advanced LIGO becomes available over the next few years.
Absolute Motion and Gravitational Effects
Cahill, R T
2003-01-01T23:59:59.000Z
The new Process Physics provides a new explanation of space as a quantum foam system in which gravity is an inhomogeneous flow of the quantum foam into matter. An analysis of various experiments demonstrates that absolute motion relative to space has been observed experimentally by Michelson and Morley, Miller, Illingworth, Torr and Kolen, and by DeWitte. The Dayton Miller and Roland DeWitte data also reveal the in-flow of space into matter which manifests as gravity. The in-flow also manifests turbulence and the experimental data confirms this as well, which amounts to the observation of a gravitational wave phenomena. The Einstein assumptions leading to the Special and General Theory of Relativity are shown to be falsified by the extensive experimental data. Contrary to the Einstein assumptions absolute motion is consistent with relativistic effects, which are caused by actual dynamical effects of absolute motion through the quantum foam, so that it is Lorentzian relativity that is seen to be essentially co...
Absolute Motion and Gravitational Effects
Reginald T Cahill
2003-06-29T23:59:59.000Z
The new Process Physics provides a new explanation of space as a quantum foam system in which gravity is an inhomogeneous flow of the quantum foam into matter. An analysis of various experiments demonstrates that absolute motion relative to space has been observed experimentally by Michelson and Morley, Miller, Illingworth, Torr and Kolen, and by DeWitte. The Dayton Miller and Roland DeWitte data also reveal the in-flow of space into matter which manifests as gravity. The in-flow also manifests turbulence and the experimental data confirms this as well, which amounts to the observation of a gravitational wave phenomena. The Einstein assumptions leading to the Special and General Theory of Relativity are shown to be falsified by the extensive experimental data. Contrary to the Einstein assumptions absolute motion is consistent with relativistic effects, which are caused by actual dynamical effects of absolute motion through the quantum foam, so that it is Lorentzian relativity that is seen to be essentially correct.
Gravitating discs around black holes
V. Karas; J. -M. Hure; O. Semerak
2004-01-16T23:59:59.000Z
Fluid discs and tori around black holes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a black hole--disc system by analytical solutions of stationary, axially symmetric Einstein's equations. Then, more detailed considerations are focused to middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring, however, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging and completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the environment around. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star--disc interactions, which can be recognised in observational properties, such as the relation between the central mass and stellar velocity dispersion.
Hydro-Gravitational-Dynamics of Planets and Dark Energy
Carl H. Gibson; Rudolph E. Schild
2008-08-24T23:59:59.000Z
Self-gravitational fluid mechanical methods termed hydro-gravitational-dynamics (HGD) predict plasma fragmentation 0.03 Myr after the turbulent big bang to form protosuperclustervoids, turbulent protosuperclusters, and protogalaxies at the 0.3 Myr transition from plasma to gas. Linear protogalaxyclusters fragment at 0.003 Mpc viscous-inertial scales along turbulent vortex lines or in spirals, as observed. The plasma protogalaxies fragment on transition into white-hot planet-mass gas clouds (PFPs) in million-solar-mass clumps (PGCs) that become globular-star-clusters (GCs) from tidal forces or dark matter (PGCs) by freezing and diffusion into 0.3 Mpc halos with 97% of the galaxy mass. The weakly collisional non-baryonic dark matter diffuses to > Mpc scales and frag-ments to form galaxy cluster halos. Stars and larger planets form by binary mergers of the trillion PFPs per PGC on 0.03 Mpc galaxy accretion disks. Star deaths depend on rates of planet accretion and internal star mixing. Moderate accretion rates produce white dwarfs that evaporate surrounding gas planets by spin-radiation to form planetary nebulae before Supernova Ia events, dimming some events to give systematic distance errors misinterpreted as the dark energy hypothesis and overestimates of the universe age. Failures of standard LCDM cosmological models reflect not only obsolete Jeans 1902 fluid mechanical assumptions, but also failures of standard turbulence models that claim the cascade of turbulent kinetic energy is from large scales to small. Because turbulence is always driven at all scales by inertial-vortex forces the turbulence cascade is always from small scales to large.
Nicolas Yunes; Richard O'Shaughnessy; Benjamin J. Owen; Stephon Alexander
2010-05-18T23:59:59.000Z
Gravitational parity violation is a possibility motivated by particle physics, string theory and loop quantum gravity. One effect of it is amplitude birefringence of gravitational waves, whereby left and right circularly-polarized waves propagate at the same speed but with different amplitude evolution. Here we propose a test of this effect through coincident observations of gravitational waves and short gamma-ray bursts from binary mergers involving neutron stars. Such gravitational waves are highly left or right circularly-polarized due to the geometry of the merger. Using localization information from the gamma-ray burst, ground-based gravitational wave detectors can measure the distance to the source with reasonable accuracy. An electromagnetic determination of the redshift from an afterglow or host galaxy yields an independent measure of this distance. Gravitational parity violation would manifest itself as a discrepancy between these two distance measurements. We exemplify such a test by considering one specific effective theory that leads to such gravitational parity-violation, Chern-Simons gravity. We show that the advanced LIGO-Virgo network and all-sky gamma-ray telescopes can be sensitive to the propagating sector of Chern-Simons gravitational parity violation to a level roughly two orders of magnitude better than current stationary constraints from the LAGEOS satellites.
From weak discontinuities to nondissipative shock waves
Garifullin, R. N., E-mail: rustem@matem.anrb.ru; Suleimanov, B. I., E-mail: bisul@mail.r [Ufa Scientific Center, Russian Academy of Sciences, Institute of Mathematics with Computing Center (Russian Federation)
2010-01-15T23:59:59.000Z
An analysis is presented of the effect of weak dispersion on transitions from weak to strong discontinuities in inviscid fluid dynamics. In the neighborhoods of transition points, this effect is described by simultaneous solutions to the Korteweg-de Vries equation u{sub t}'+ uu{sub x}' + u{sub xxx}' = 0 and fifth-order nonautonomous ordinary differential equations. As x{sup 2} + t{sup 2} {yields}{infinity}, the asymptotic behavior of these simultaneous solutions in the zone of undamped oscillations is given by quasi-simple wave solutions to Whitham equations of the form r{sub i}(t, x) = tl{sub i} x/t{sup 2}.
The strict-weak lattice polymer
Ivan Corwin; Timo Seppäläinen; Hao Shen
2015-07-06T23:59:59.000Z
We introduce the strict-weak polymer model, and show the KPZ universality of the free energy fluctuation of this model for a certain range of parameters. Our proof relies on the observation that the discrete time geometric q-TASEP model, studied earlier by A. Borodin and I. Corwin, scales to this polymer model in the limit q->1. This allows us to exploit the exact results for geometric q-TASEP to derive a Fredholm determinant formula for the strict-weak polymer, and in turn perform rigorous asymptotic analysis to show KPZ scaling and GUE Tracy-Widom limit for the free energy fluctuations. We also derive moments formulae for the polymer partition function directly by Bethe ansatz, and identify the limit of the free energy using a stationary version of the polymer model.
The strict-weak lattice polymer
Ivan Corwin; Timo Seppäläinen; Hao Shen
2014-09-05T23:59:59.000Z
We introduce the strict-weak polymer model, and show the KPZ universality of the free energy fluctuation of this model for a certain range of parameters. Our proof relies on the observation that the discrete time geometric q-TASEP model, studied earlier by A. Borodin and I. Corwin, scales to this polymer model in the limit q->1. This allows us to exploit the exact results for geometric q-TASEP to derive a Fredholm determinant formula for the strict-weak polymer, and in turn perform rigorous asymptotic analysis to show KPZ scaling and GUE Tracy-Widom limit for the free energy fluctuations. We also derive moments formulae for the polymer partition function directly by Bethe ansatz, and identify the limit of the free energy using a stationary version of the polymer model.
Spectral statistics for weakly correlated random potentials
Frédéric Klopp
2012-10-29T23:59:59.000Z
We study localization and derive stochastic estimates (in particular, Wegner and Minami estimates) for the eigenvalues of weakly correlated random discrete Schr\\"odinger operators in the localized phase. We apply these results to obtain spectral statistics for general discrete alloy type models where the single site perturbation is neither of finite rank nor of fixed sign. In particular, for the models under study, the random potential exhibits correlations at any range.
The performance of the corrector lenses for the Auger fluorescence detector
Sato, Ricardo; Escobar, Carlos O.; /Campinas State U.
2005-07-01T23:59:59.000Z
We present an analysis of the effect that the corrector lenses (Schmidt Optics) have on the overall performance of the Auger Fluorescence Detector. The analysis uses real data from the telescopes. Figures of merit for the corrector lenses performance include shower trigger rate and the distribution of the distance of closest approach to the shower axis. As a result of this analysis we may say that the effective light collection area of a telescope nearly doubles with the use of a corrector lens at its aperture.
Heating Cooling Flows with Weak Shock Waves
W. G. Mathews; A. Faltenbacher; F. Brighenti
2005-11-05T23:59:59.000Z
The discovery of extended, approximately spherical weak shock waves in the hot intercluster gas in Perseus and Virgo has precipitated the notion that these waves may be the primary heating process that explains why so little gas cools to low temperatures. This type of heating has received additional support from recent gasdynamical models. We show here that outward propagating, dissipating waves deposit most of their energy near the center of the cluster atmosphere. Consequently, if the gas is heated by (intermittent) weak shocks for several Gyrs, the gas within 30-50 kpc is heated to temperatures that far exceed observed values. This heating can be avoided if dissipating shocks are sufficiently infrequent or weak so as not to be the primary source of global heating. Local PV and viscous heating associated with newly formed X-ray cavities are likely to be small, which is consistent with the low gas temperatures generally observed near the centers of groups and clusters where the cavities are located.
$D^+ \\to K^- ?^+ ?^+$ - the weak vector current
P. C. Magalhães; M. R. Robilotta
2015-04-23T23:59:59.000Z
Studies of D and B mesons decays into hadrons have been used to test the standard model in the last fifteen years. A heavy meson decay involves the combined effects of a primary weak vertex and subsequent hadronic final state interactions, which determine the shapes of Dalitz plots. The fact that final products involve light mesons indicates that the QCD vacuum is an active part of the problem. This makes the description of these processes rather involved and, in spite of its importance, phenomenological analyses tend to rely on crude models. Our group produced, some time ago, a schematic calculation of the decay $D^+ \\to K^- \\pi^+ \\pi^+$, which provided a reasonable description of data. Its main assumption was the dominance of the weak vector-current, which yields a non-factorizable interaction. Here we refine that calculation by including the correct momentum dependence of the weak vertex and extending the energy ranges of $\\pi\\pi$ and $K\\pi$ subamplitudes present into the problem. These new features make the present treatment more realistic and bring theory closer to data.
Energy Contents of Gravitational Waves in Teleparallel Gravity
M. Sharif; Sumaira Taj
2009-10-02T23:59:59.000Z
The conserved quantities, that are, gravitational energy-momentum and its relevant quantities are investigated for cylindrical and spherical gravitational waves in the framework of teleparallel equivalent of General Relativity using the Hamiltonian approach. For both cylindrical and spherical gravitational waves, we obtain definite energy and constant momentum. The constant momentum shows consistency with the results available in General Relativity and teleparallel gravity. The angular momentum for cylindrical and spherical gravitational waves also turn out to be constant. Further, we evaluate their gravitational energy-momentum fluxes and gravitational pressure.
Thomas Peters; Dominik R. G. Schleicher; Ralf S. Klessen; Robi Banerjee; Christoph Federrath; Rowan J. Smith; Sharanya Sur
2012-09-26T23:59:59.000Z
Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k rho^Gamma, with both sub-isothermal exponents Gamma 1. We find significant differences between these two cases. For Gamma > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For Gamma < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.
Eisaku Sakane; Toshiharu Kawai
2002-09-30T23:59:59.000Z
In an extended, new form of general relativity, which is a teleparallel theory of gravity, we examine the energy-momentum and angular momentum carried by gravitational wave radiated from Newtonian point masses in a weak-field approximation. The resulting wave form is identical to the corresponding wave form in general relativity, which is consistent with previous results in teleparallel theory. The expression for the dynamical energy-momentum density is identical to that for the canonical energy-momentum density in general relativity up to leading order terms on the boundary of a large sphere including the gravitational source, and the loss of dynamical energy-momentum, which is the generator of \\emph{internal} translations, is the same as that of the canonical energy-momentum in general relativity. Under certain asymptotic conditions for a non-dynamical Higgs-type field $\\psi^{k}$, the loss of ``spin'' angular momentum, which is the generator of \\emph{internal} $SL(2,C)$ transformations, is the same as that of angular momentum in general relativity, and the losses of canonical energy-momentum and orbital angular momentum, which constitute the generator of Poincar\\'{e} \\emph{coordinate} transformations, are vanishing. The results indicate that our definitions of the dynamical energy-momentum and angular momentum densities in this extended new general relativity work well for gravitational wave radiations, and the extended new general relativity accounts for the Hulse-Taylor measurement of the pulsar PSR1913+16.
T. Dereli; J. Gratus; R. W. Tucker
2006-11-09T23:59:59.000Z
Electromagnetic properties of a simple polarisable medium may be parameterised in terms of a constitutive tensor whose properties can in principle be determined by experiments in non-inertial (accelerating) frames and in the presence of weak but variable gravitational fields. After establishing some geometric notation, discussion is given to basic concepts of stress, energy and momentum in the vacuum where the useful notion of a drive form is introduced in order to associate the conservation of currents involving the flux of energy, momentum and angular momentum with spacetime isometries. The definition of the stress-energy-momentum tensor is discussed with particular reference to its symmetry based on its role as a source of relativistic gravitation. General constitutive properties of material continua are formulated in terms of spacetime tensors including those that describe magneto-electric phenomena in moving media. This leads to a formulation of a self-adjoint constitutive tensor describing, in general, inhomogeneous, anisotropic, magneto-electric bulk matter in arbitrary motion. The question of an invariant characterisation of intrinsically magneto-electric media is explored. An action principle is established to generate the phenomenological Maxwell system and the use of variational derivatives to calculate stress-energy-momentum tensors is discussed in some detail. The relation of this result to tensors proposed by Abraham and others is discussed in the concluding section where the relevance of the whole approach to experiments on matter in non-inertial environments with variable gravitational and electromagnetic fields is stressed.
Gravitational Mass, Its Mechanics - What It Is; How It Operates
Roger Ellman
2006-03-06T23:59:59.000Z
The earlier paper, Inertial Mass, Its Mechanics - What It Is; How It Operates, developed the mechanics of inertial mass. The present paper is for the purpose of equivalently developing gravitation. The behavior of gravitation is well known, as described by Newton's Law of Gravitation. But just what gravitational mass is, how gravitational behavior comes about, what in material reality produces the effects of gravitational mass, has been little understood. The only extant hypotheses involve the unsuccessful efforts to develop "quantum gravitation" and to tie it into the rest of quantum mechanics, and the equally failed attempts to detect "gravitons" and "gravitational waves" in spite of very substantial efforts. From a starting point of only the limitation on the speed of light, the necessity of conservation, and the impossibility of an infinity in material reality, the present paper presents a new and comprehensive analysis of the phenomenon gravitational mass: - how it appears in particles, - how the Newtonian gravitational behavior arises from that, and - how the values of inertial mass and gravitational mass are identical, or, in other words, the mechanics of gravitational mass and gravitation.
Gravitational waves and gamma-ray bursts
Alessandra Corsi; for the LIGO Scientific Collaboration; for the Virgo Collaboration
2012-05-11T23:59:59.000Z
Gamma-Ray Bursts are likely associated with a catastrophic energy release in stellar mass objects. Electromagnetic observations provide important, but indirect information on the progenitor. On the other hand, gravitational waves emitted from the central source, carry direct information on its nature. In this context, I give an overview of the multi-messenger study of gamma-ray bursts that can be carried out by using electromagnetic and gravitational wave observations. I also underline the importance of joint electromagnetic and gravitational wave searches, in the absence of a gamma-ray trigger. Finally, I discuss how multi-messenger observations may probe alternative gamma-ray burst progenitor models, such as the magnetar scenario.
Self-gravitating system made of axions
Barranco, J.; Bernal, A. [Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Am Muehlenberg 1, D-14476 Golm (Germany); Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Am Muehlenberg 1, D-14476 Golm (Germany)
2011-02-15T23:59:59.000Z
We show that the inclusion of an axionlike effective potential in the construction of a self-gravitating system of scalar fields decreases its compactness when the value of the self-interaction coupling constant is increased. By including the current values for the axion mass m and decay constant f{sub a}, we have computed the mass and the radius for self-gravitating systems made of axion particles. It is found that such objects will have asteroid size masses and radii of a few meters, thus a self-gravitating system made of axions could play the role of scalar mini-MACHOs and mimic a cold dark matter model for the galactic halo.
Statistical mechanics of gravitating systems: An Overview
T. Padmanabhan
2009-02-16T23:59:59.000Z
I review several issues related to statistical description of gravitating systems in both static and expanding backgrounds. After briefly reviewing the results for the static background, I concentrate on gravitational clustering of collisionless particles in an expanding universe. In particular, I describe (a) how the non linear mode-mode coupling transfers power from one scale to another in the Fourier space if the initial power spectrum is sharply peaked at a given scale and (b) the asymptotic characteristics of gravitational clustering which are independent of the initial conditions. Numerical simulations as well as analytic work shows that power transfer leads to a universal power spectrum at late times, somewhat reminiscent of the existence of Kolmogorov spectrum in fluid turbulence.
On the Bel radiative gravitational fields
Joan Josep Ferrando; Juan Antonio Sáez
2012-04-18T23:59:59.000Z
We analyze the concept of intrinsic radiative gravitational fields defined by Bel and we show that the three radiative types, N, III and II, correspond with the three following different physical situations: {\\it pure radiation}, {\\it asymptotic pure radiation} and {\\it generic} (non pure, non asymptotic pure) {\\it radiation}. We introduce the concept of {\\em observer at rest} with respect to the gravitational field and that of {\\em proper super-energy} of the gravitational field and we show that, for non radiative fields, the minimum value of the relative super-energy density is the proper super-energy density, which is acquired by the observers at rest with respect to the field. Several {\\it super-energy inequalities} are also examined.
The gravitational wave symphony of the Universe
B. S. Sathyaprakash
2002-07-10T23:59:59.000Z
The new millennium will see the upcoming of several ground-based interferometric gravitational wave antennas. Within the next decade a space-based antenna may also begin to observe the distant Universe. These gravitational wave detectors will together operate as a network taking data continuously for several years, watching the transient and continuous phenomena occurring in the deep cores of astronomical objects and dense environs of the early Universe where gravity was extremely strong and highly non-linear. The network will listen to the waves from rapidly spinning non-axisymmetric neutron stars, normal modes of black holes, binary black hole inspiral and merger, phase transitions in the early Universe, quantum fluctuations resulting in a characteristic background in the early Universe. The gravitational wave antennas will open a new window to observe the dark Universe unreachable via other channels of astronomical observations.
A "Lorentz-Poincare"-Type Interpretation of Relativistic Gravitation
Jan; Broekaert
2005-10-05T23:59:59.000Z
The nature of 'time', 'space' and 'reality' are to large extent dependent on our interpretation of Special (SRT) and General Relativity Theory (GRT). In SRT essentially two distinct interpretations exist; the "geometrical" interpretation by Einstein based on the Principle of Relativity and the Invariance of the velocity of light and, the "physical" Lorentz-Poincar\\'e interpretation with underpinning by rod contractions, clock slowing and light synchronization, see e.g. (Bohm 1965, Bell 1987). It can be questioned whether the "Lorentz-Poincar\\'e"-interpretation of SRT can be continued into GRT. We have shown that till first Post-Newtonian order this is indeed possible (Broekaert 2004). This requires the introduction of gravitationally modified Lorentz transformations, with an intrinsical spatially-variable speed of light $c(r)$, a scalar scaling field $\\Phi$ and induced velocity field $w$. Still the invariance of the locally observed velocity of light is maintained (Broekaert 2005). The Hamiltonian description of particles and photons recovers the 1-PN approximation of GRT. At present we show the model does obey the Weak Equivalence Principle from a fixed perspective, and that the implied acceleration transformations are equivalent with those of GRT.
Environmental Effects for Gravitational-wave Astrophysics
Enrico Barausse; Vitor Cardoso; Paolo Pani
2015-01-07T23:59:59.000Z
The upcoming detection of gravitational waves by terrestrial interferometers will usher in the era of gravitational-wave astronomy. This will be particularly true when space-based detectors will come of age and measure the mass and spin of massive black holes with exquisite precision and up to very high redshifts, thus allowing for better understanding of the symbiotic evolution of black holes with galaxies, and for high-precision tests of General Relativity in strong-field, highly dynamical regimes. Such ambitious goals require that astrophysical environmental pollution of gravitational-wave signals be constrained to negligible levels, so that neither detection nor estimation of the source parameters are significantly affected. Here, we consider the main sources for space-based detectors -- the inspiral, merger and ringdown of massive black-hole binaries and extreme mass-ratio inspirals -- and account for various effects on their gravitational waveforms, including electromagnetic fields, cosmological evolution, accretion disks, dark matter, "firewalls" and possible deviations from General Relativity. We discover that the black-hole quasinormal modes are sharply different in the presence of matter, but the ringdown signal observed by interferometers is typically unaffected. The effect of accretion disks and dark matter depends critically on their geometry and density profile, but is negligible for most sources, except for few special extreme mass-ratio inspirals. Electromagnetic fields and cosmological effects are always negligible. We finally explore the implications of our findings for proposed tests of General Relativity with gravitational waves, and conclude that environmental effects will not prevent the development of precision gravitational-wave astronomy.
On chaotic behavior of gravitating stellar shells
M. V. Barkov; G. S. Bisnovatyi-Kogan; A. I. Neishtadt; V. A. Belinski
2004-12-10T23:59:59.000Z
Motion of two gravitating spherical stellar shells around a massive central body is considered. Each shell consists of point particles with the same specific angular momenta and energies. In the case when one can neglect the influence of gravitation of one ("light") shell onto another ("heavy") shell ("restricted problem") the structure of the phase space is described. The scaling laws for the measure of the domain of chaotic motion and for the minimal energy of the light shell sufficient for its escape to infinity are obtained.
Rhodium Mossbauer Superradiance of Observable Gravitational Effect
Cheng, Yao
2007-01-01T23:59:59.000Z
We report the direct observations of the entangled superradiance from rhodium nuclei oriented along the long edge of the polycrystalline sample. The long-lived rhodium Mossbauer effect is sensitive to the earth gravity, which opens up novel approaches of detecting the gravitational waves. Superradiance and exciton diffusion are enhanced by liquid-nitrogen cooling. Gravitational effect attributed to multipolar nuclear transition of the atto-eV natural linewidth is manifested by emissions from different sample orientations corresponding to the earth gravity. The long-range gamma coupling across grain boundaries despite the temperature variation inside sample is manifested by the observed dependence on macroscopic sample size.
Forces in electromagnetic field and gravitational field
Zihua Weng
2011-03-31T23:59:59.000Z
The force can be defined from the linear momentum in the gravitational field and electromagnetic field. But this definition can not cover the gradient of energy. In the paper, the force will be defined from the energy and torque in a new way, which involves the gravitational force, electromagnetic force, inertial force, gradient of energy, and some other new force terms etc. One of these new force terms can be used to explain why the solar wind varies velocity along the magnetic force line in the interplanetary space between the sun and the earth.
ngravs: Distinct gravitational interactions in GADGET-2
Croker, K A S
2015-01-01T23:59:59.000Z
We discuss an extension of the massively parallel cosmological simulation code GADGET-2, which enables investigation of distinct gravitational force laws between particle species. In addition to simplifying investigations of a universally modified force law, the ngravs extension allows state-of-the-art collisionless cosmological simulations of quite exotic gravitational scenarios. We briefly review the algorithms used by GADGET-2, and present our extension to multiple gravities, highlighting additional features that facilitate consideration of exotic force laws. We discuss the accuracy and performance of the ngravs extension, both internally and with an unaltered GADGET-2, under all relevant operational modes. The ngravs extension is publicly released to the research community.
The Gravitational Energy of a Point Mass is Finite
L. V. Verozub
1996-06-10T23:59:59.000Z
We argue that our equation of gravitation ( Phys.Lett. A 156 (1991) 404 ) lead in pseudo-Euclidean space-time to the finite energy of the gravitational field of a point mass.
Accelerated planetesimal growth in self-gravitating protoplanetary discs
Rice, William K; Lodato, G; Pringle, J E; Armitage, P J; Bonnell, I A
2004-01-01T23:59:59.000Z
self-gravitating protoplanetary discs W. K. M. Rice, 1 † G.in marginally stable, self-gravitating protoplanetary discs.The drag force between the disc gas and the em- bedded
Shoring up Infrastructure Weaknesses with Hybrid Cloud Storage
Chaudhuri, Surajit
Shoring up Infrastructure Weaknesses with Hybrid Cloud Storage #12;2StorSimple White Pages: Shoring Up Infrastructure Weaknesses with Hybrid Cloud Storage Table of Contents The Hybrid Cloud Context for IT Managers ............................................................. 3 The Bottleneck of Managing Storage
Wave turbulent statistics in non-weak wave turbulence
Naoto Yokoyama
2011-05-08T23:59:59.000Z
In wave turbulence, it has been believed that statistical properties are well described by the weak turbulence theory, in which nonlinear interactions among wavenumbers are assumed to be small. In the weak turbulence theory, separation of linear and nonlinear time scales derived from the weak nonlinearity is also assumed. However, the separation of the time scales is often violated even in weak turbulent systems where the nonlinear interactions are actually weak. To get rid of this inconsistency, closed equations are derived without assuming the separation of the time scales in accordance with Direct-Interaction Approximation (DIA), which has been successfully applied to Navier--Stokes turbulence. The kinetic equation of the weak turbulence theory is recovered from the DIA equations if the weak nonlinearity is assumed as an additional assumption. It suggests that the DIA equations is a natural extension of the conventional kinetic equation to not-necessarily-weak wave turbulence.
Gravitational lens modeling with basis sets
Birrer, Simon; Refregier, Alexandre
2015-01-01T23:59:59.000Z
We present a strong lensing modeling technique based on versatile basis sets for the lens and source planes. Our method uses high performance Monte Carlo algorithms, allows for an adaptive build up of complexity and bridges the gap between parametric and pixel based reconstruction methods. We apply our method to a HST image of the strong lens system RXJ1131-1231 and show that our method finds a reliable solution and is able to detect substructure in the lens and source planes simultaneously. Using mock data we show that our method is sensitive to sub-clumps with masses four orders of magnitude smaller than the main lens, which corresponds to about $10^8 M_{\\odot}$, without prior knowledge on the position and mass of the sub-clump. The modelling approach is flexible and maximises automation to facilitate the analysis of the large number of strong lensing systems expected in upcoming wide field surveys. The resulting search for dark sub-clumps in these systems, without mass-to-light priors, offers promise for p...
Magnification Ratio of the Fluctuating Light in Gravitational Lens 0957+561
William H. Press; George B. Rybicki
1998-03-17T23:59:59.000Z
Radio observations establish the B/A magnification ratio of gravitational lens 0957+561 at about 0.75. Yet, for more than 15 years, the optical magnfication ratio has been between 0.9 and 1.12. The accepted explanation is microlensing of the optical source. However, this explanation is mildly discordant with (i) the relative constancy of the optical ratio, and (ii) recent data indicating possible non-achromaticity in the ratio. To study these issues, we develop a statistical formalism for separately measuring, in a unified manner, the magnification ratio of the fluctuating and constant parts of the light curve. Applying the formalism to the published data of Kundi\\'c et al. (1997), we find that the magnification ratios of fluctuating parts in both the g and r colors agrees with the magnification ratio of the constant part in g-band, and tends to disagree with the r-band value. One explanation could be about 0.1 mag of consistently unsubtracted r light from the lensing galaxy G1, which seems unlikely. Another could be that 0957+561 is approaching a caustic in the microlensing pattern.
Stresses, energy flow and energy density of gravitational nature
A. Loinger
2001-05-03T23:59:59.000Z
Two arguments which show the validity of the concept of gravitational energy put forward by Lorentz and Levi-Civita.
Formation of ice lenses and frost heave A. W. Rempel1
Rempel, Alan W.
are promoted by the influence of mineral surfaces on the phase behavior of ice. A large body of experimental, but nevertheless ad hoc parameterizations for the ice particle interactions, the choice of functional form beingFormation of ice lenses and frost heave A. W. Rempel1 Received 13 April 2006; revised 26 January
Optical limiting and thermal lensing studies in C60 S. S. Harilal,a)
Harilal, S. S.
Optical limiting and thermal lensing studies in C60 S. S. Harilal,a) C. V. Bindhu, V. P. N 1999 Optical limiting and thermo-optic properties of C60 in toluene are studied using 532 nm, 9 ns pulses from a frequency-doubled Nd:YAG laser. Optical limiting studies in these fullerene molecules lead
Gradient-Index (GRIN) lenses by Slurry-based Three-Dimensional Printing (S-3DP)
Wang, Hong-Ren, 1973-
2005-01-01T23:59:59.000Z
GRIN lenses with vertical index variation and radial index variation have been successfully fabricated using S-3DPTM. Two silica-based material systems, A1203-SiO? and BaO-SiO?, have been studied and used for the fabrication ...
Quantum logic with weakly coupled qubits
Michael R. Geller; Emily J. Pritchett; Andrei Galiautdinov; John M. Martinis
2009-06-29T23:59:59.000Z
There are well-known protocols for performing CNOT quantum logic with qubits coupled by particular high-symmetry (Ising or Heisenberg) interactions. However, many architectures being considered for quantum computation involve qubits or qubits and resonators coupled by more complicated and less symmetric interactions. Here we consider a widely applicable model of weakly but otherwise arbitrarily coupled two-level systems, and use quantum gate design techniques to derive a simple and intuitive CNOT construction. Useful variations and extensions of the solution are given for common special cases.
Quantum logic with weakly coupled qubits
Geller, Michael R; Galiautdinov, Andrei; Martinis, John M
2009-01-01T23:59:59.000Z
There are well-known protocols for performing CNOT quantum logic with qubits coupled by particular high-symmetry (Ising or Heisenberg) interactions. However, many architectures being considered for quantum computation involve qubits or qubits and resonators coupled by more complicated and less symmetric interactions. Here we consider a widely applicable model of weakly but otherwise arbitrarily coupled two-level systems, and use quantum gate design techniques to derive a simple and intuitive CNOT construction. Useful variations and extensions of the solution are given for common special cases.
Supersymmetric Higgs Bosons in Weak Boson Fusion
W. Hollik; T. Plehn; M. Rauch; H. Rzehak
2008-04-17T23:59:59.000Z
We compute the complete supersymmetric next-to-leading order corrections to the production of a light Higgs boson in weak boson fusion. The size of the electroweak corrections is of similar order as the next-to-leading order corrections in the Standard Model. The supersymmetric QCD corrections turn out to be significantly smaller than their electroweak counterparts. These higher--order corrections are an important ingredient to a precision analysis of the (supersymmetric) Higgs sector at the LHC, either as a known correction factor or as a contribution to the theory error.
Weak Interaction Studies with 6He
A. Knecht; Z. T. Alexander; Y. Bagdasarova; T. M. Cope; B. G. Delbridge; X. Flechard; A. Garcia; R. Hong; E. Lienard; P. Mueller; O. Naviliat-Cuncic; A. S. C. Palmer; R. G. H. Robertson; D. W. Storm; H. E. Swanson; S. Utsuno; F. Wauters; W. Williams; C. Wrede; D. W. Zumwalt
2012-10-19T23:59:59.000Z
The 6He nucleus is an ideal candidate to study the weak interaction. To this end we have built a high-intensity source of 6He delivering ~10^10 atoms/s to experiments. Taking full advantage of that available intensity we have performed a high-precision measurement of the 6He half-life that directly probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a measurement of the beta-neutrino angular correlation in 6He beta decay that will allow to search for new physics beyond the Standard Model in the form of tensor currents.
Probing the Proton's Weak Side | Jefferson Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's Possible forPortsmouth/Paducah47,193.70 Hg Mercury 35 Br BromineProbing the Proton's Weak Side
Certification of Superconducting Solenoid-Based Focusing Lenses
DiMarco, E.Joseph; Hemmati, Ali M.; Orris, Darryl F.; Page, Thomas M.; Rabehl, Roger H.; Tartaglia, Michael A.; Terechkine, Iouri; Tompkins, John C.
2010-07-29T23:59:59.000Z
The first production focusing lens for the HINS beam line at Fermilab has been assembled into a cryostat and tested. A total of 5 devices will be tested before they are installed in the low energy section of the HINS beam line, which uses copper Crossbar-H (CH) style RF cavities. One of the tested CH-section lens assemblies includes a pair of weak orthogonal steering dipoles nested within a strong focusing solenoid, and has six vapor cooled power leads. The other device has only the strong focusing solenoid, and utilizes a single pair of HTS power leads. The production test program is designed to measure the thermal performance of the cryostat, minimum cooling requirements for the HTS leads, quench performance of all superconducting components, and precise determination of the magnetic axis and field angles. Results and future plans for the first production device tests are presented.
Yakunin, Konstantin N; Marronetti, Pedro; Yoshida, Shin'ichirou; Bruenn, Stephen W; Hix, W Raphael; Lentz, Eric J; Messer, O E Bronson; Harris, J Austin; Endeve, Eirik; Blondin, John M; Lingerfelt, Eric J
2015-01-01T23:59:59.000Z
We present the gravitational waveforms computed in ab initio two-dimensional core collapse supernova models evolved with the Chimera code for progenitor masses between 12 and 25 solar masses. All models employ multi-frequency neutrino transport in the ray-by-ray approximation, state-of-the-art weak interaction physics, relativistic transport corrections such as the gravitational redshift of neutrinos, two-dimensional hydrodynamics with the commensurate relativistic corrections, Newtonian self-gravity with a general relativistic monopole correction, and the Lattimer-Swesty equation of state with 220 MeV compressibility, and begin with the most recent Woosley-Heger nonrotating progenitors in this mass range. All of our models exhibit robust explosions. Therefore, our waveforms capture all stages of supernova development: 1) a relatively short and weak prompt signal, 2) a quiescent stage, 3) a strong signal due to convection and SASI activity, 4) termination of active accretion onto the proto-neutron star, and 5...
INVERSE-SQUARE LAW TESTS 1 TESTS OF THE GRAVITATIONAL
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
INVERSE-SQUARE LAW TESTS 1 TESTS OF THE GRAVITATIONAL INVERSE-SQUARE LAW E.G.Adelberger, B-1560 KEYWORDS: gravitation, experimental tests of inverse-square law, quantum gravity, extra dimensions ABSTRACT: We review recent experimental tests of the gravitational inverse-square law, and the wide variety
Relic gravitational waves and the generalized second law
German Izquierdo; Diego Pavon
2005-01-12T23:59:59.000Z
The generalized second law of gravitational thermodynamics is applied to the present era of accelerated expansion of the Universe. In spite of the fact that the entropy of matter and relic gravitational waves inside the event horizon diminish, the mentioned law is fulfilled provided that the expression for the entropy density of the gravitational waves satisfies a certain condition.
Gravitational Bending of Light with Frequency Shifts
P. D. Morley
1993-11-15T23:59:59.000Z
Non-static gravitational fields generally introduce frequency shifts when bending light. In this paper, I discuss the frequency shifts induced in the bending of light by moving masses. As examples, I treat the recently discovered high-velocity pulsar PSR 2224+65 and a typical Einstein ring.
Interaction of Gravitational Waves with Charged Particles
Thulsi Wickramasinghe; Will Rhodes; Mitchell Revalski
2015-02-03T23:59:59.000Z
It is shown here that a cloud of charged particles could in principle absorb energy from gravitational waves (GWs) incident upon it, resulting in wave attenuation. This could in turn have implications for the interpretation of future data from early universe GWs.
Geometrical vs wave optics under gravitational waves
Raymond Angélil; Prasenjit Saha
2015-05-20T23:59:59.000Z
We present some new derivations of the effect of a plane gravitational wave on a light ray. A simple interpretation of the results is that a gravitational wave causes a phase modulation of electromagnetic waves. We arrive at this picture from two contrasting directions, namely null geodesics and Maxwell's equations, or, geometric and wave optics. Under geometric optics, we express the geodesic equations in Hamiltonian form and solve perturbatively for the effect of gravitational waves. We find that the well-known time-delay formula for light generalizes trivially to massive particles. We also recover, by way of a Hamilton-Jacobi equation, the phase modulation obtained under wave optics. Turning then to wave optics - rather than solving Maxwell's equations directly for the fields, as in most previous approaches - we derive a perturbed wave equation (perturbed by the gravitational wave) for the electromagnetic four-potential. From this wave equation it follows that the four-potential and the electric and magnetic fields all experience the same phase modulation. Applying such a phase modulation to a superposition of plane waves corresponding to a Gaussian wave packet leads to time delays.
Cosmology constrains gravitational four-fermion interaction
Khriplovich, I.B.; Rudenko, A.S., E-mail: khriplovich@inp.nsk.su, E-mail: a.s.rudenko@inp.nsk.su [Budker Institute of Nuclear Physics, Novosibirsk State University, 630090 Novosibirsk (Russian Federation)
2012-11-01T23:59:59.000Z
If torsion exists, it generates gravitational four-fermion interaction (GFFI). This interaction gets dominating on the Planck scale. If one confines to the regular, axial-axial part of this interaction, the results do not comply with the Friedmann-Robertson-Walker (FRW) cosmology for the spatial flat or closed Universe. In principle, the anomalous, vector-vector interaction could restore the agreement.
Laser interferometer as a gravitational wave detector
Rudenko, V.N.; Sazhin, M.V.
1980-11-01T23:59:59.000Z
An analysis is made of the effect of a gravitational wave on coherently pumped Michelson and Fabry--Perot optical interferometers. Allowance is made for the complex structure of the response associated with the triplet character of the photon frequency perturbation in the interferometer. As a result, the response of the interferometer depends strongly on the angle of incidence of the gravitational wave not only in respect of intensity but also in terms of its profile. In the long-wavelength limit, these characteristics are only reflected in the angular structure of the phase of the response. For gravitational wave bursts shorter than the photon round trip time between the mirrors, the temporal and angular structure of the response is extremely specific so that the signal can be isolated from nongravitational perturbations. An analysis is made of the case of a Michelson interferometer with multiple reflections and the case of a gravitational optical resonance for a Fabry--Perot interferometer is also studied. Estimates are given of the sensitivity of such an interferometer ''antenna'' subject to the condition that the main noise is due to quantum fluctuations of the optical pumping.
Cosmology constrains gravitational four-fermion interaction
I. B. Khriplovich; A. S. Rudenko
2012-10-27T23:59:59.000Z
If torsion exists, it generates gravitational four-fermion interaction (GFFI). This interaction gets dominating on the Planck scale. If one confines to the regular, axial-axial part of this interaction, the results do not comply with the Friedmann-Robertson-Walker (FRW) cosmology for the spatial flat or closed Universe. In principle, the anomalous, vector-vector interaction could restore the agreement.
Gravitational repulsion in the Schwarzschild field
McGruder, C.H. III
1982-06-15T23:59:59.000Z
To the distant observer, who uses measuring instruments not affected by gravity, gravitational repulsion can occur anywhere in the Schwarzschild field. It depends on the relationship between the transverse and radial Schwarzschild velocities. On the other hand, local observers, whose measuring instruments are affected by gravity, can not detect a positive value for the acceleration of gravity.
On the Vacuum Propagation of Gravitational Waves
Xiao Liu
2007-06-05T23:59:59.000Z
We show that, for any local, causal quantum field theory which couples covariantly to gravity, and which admits Minkowski spacetime vacuum(a) invariant under the inhomogeneous proper orthochronous Lorentz group, plane gravitational waves propagating in such Minkowski vacuum(a) do not dissipate energy or momentum via quantum field theoretic effects.
Gravitational Correction to Running of Gauge Couplings
Sean P. Robinson; Frank Wilczek
2006-06-09T23:59:59.000Z
We calculate the contribution of graviton exchange to the running of gauge couplings at lowest non-trivial order in perturbation theory. Including this contribution in a theory that features coupling constant unification does not upset this unification, but rather shifts the unification scale. When extrapolated formally, the gravitational correction renders all gauge couplings asymptotically free.
Towards a noncommutative version of Gravitation
Franco, Nicolas [Groupe d'Applications Mathematiques aux Sciences du Cosmos, University of Namur FUNDP-Departement de Mathematiques, Rempart de la Vierge, 8 B-5000 Namur (Belgium)
2010-06-23T23:59:59.000Z
Alain Connes' noncommutative theory led to an interesting model including both Standard Model of particle physics and Euclidean Gravity. Nevertheless, an hyperbolic version of the gravitational part would be necessary to make physical predictions, but it is still under research. We shall present the difficulties to generalize the model from Riemannian to Lorentzian Geometry and discuss key ideas and current attempts.
Why does gravitational radiation produce vorticity?
L. Herrera; W. Barreto; J. Carot; A. Di Prisco
2007-03-26T23:59:59.000Z
We calculate the vorticity of world--lines of observers at rest in a Bondi--Sachs frame, produced by gravitational radiation, in a general Sachs metric. We claim that such an effect is related to the super--Poynting vector, in a similar way as the existence of the electromagnetic Poynting vector is related to the vorticity in stationary electrovacum spacetimes.
Carl H. Gibson; Rudy Schild
2003-07-01T23:59:59.000Z
Observations are compared to conflicting predictions about self-gravitational structure formation by the hydro-gravitational theory (HGT) of Gibson 1996-2003 versus cold-dark-matter hierarchical-clustering-cosmology (CDMHCC) and the Jeans 1902 criterion. According to HGT, gravitational structures form immediately after mass-energy equality by plasma fragmentation at 30,000 years when viscous and weak turbulence forces first balance gravitational forces within the horizon L_H = ct < L_J = c/[3\\rho G]^1/2, contrary to the Jeans 1902 criterion. Buoyancy forces fossilize the 10^-12 s^-1 rate-of-strain and the 10^-17 kg m^-3 baryonic density. The non-baryonic dark matter (NBDM) diffuses into the voids rather than forming cold-dark-matter (CDM) halos required by CDMHCC. From HGT, supercluster-mass to galaxy-mass fragments exist at the plasma to gas transition, and these fragment further to form proto-globular-star clusters (PGCs) and planetary-mass primordial-fog-particles (PFPs): the baryonic dark matter of the interstellar-medium and inner-galaxy-dark-matter-halos, from which all planets and stars are formed by accretion (Gibson 1996, Schild 1996). From HGT and a rich cluster mass profile (Tyson and Fischer 1995), D_NBDM = 6 x10^28 m^2 s^-1, m_NBDM <= 10^-33 kg, and the NBDM forms outer-galaxy halos after 300,000 years.
Quantum weak chaos in a degenerate system
V. Ya. Demikhovskii; D. I. Kamenev; G. A. Luna-Acosta
1998-09-27T23:59:59.000Z
Quantum weak chaos is studied in a perturbed degenerate system --- a charged particle interacting with a monochromatic wave in a transverse magnetic field. The evolution operator for an arbitrary number of periods of the external field is built and its structure is explored in terms of the QE (quasienergy eigenstates) under resonance condition (wave frequency $=$ cyclotron frequency) in the regime of weak classical chaos. The new phenomenon of diffusion via the quantum separatrices and the influence of chaos on diffusion are investigated and, in the quasi classical limit, compared with its classical dynamics. We determine the crossover from purely quantum diffusion to a diffusion which is the quantum manifestation of classical diffusion along the stochastic web. This crossover results from the non-monotonic dependence of the characteristic localization length of the QE states on the wave amplitude. The width of the quantum separatrices was computed and compared with the width of the classical stochastic web. We give the physical parameters which can be realized experimentally to show the manifestation of quantum chaos in nonlinear acoustic resonance.
Weak Scale From the Maximum Entropy Principle
Yuta Hamada; Hikaru Kawai; Kiyoharu Kawana
2014-09-23T23:59:59.000Z
The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\
Weak Scale From the Maximum Entropy Principle
Hamada, Yuta; Kawana, Kiyoharu
2014-01-01T23:59:59.000Z
The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\
V. M. Mostepanenko; M. Novello
2000-08-03T23:59:59.000Z
The recent ideas that the gravitational and gauge interactions become united at the weak scale lead to Yukawa-type corrections to the Newtonian gravitational law at small distances. We briefly summarize the best constraints on these corrections obtained recently from the experiments on the measurement of the Casimir force. The new constraints on the Yukawa-type interaction are derived from the latest Casimir force measurement between a large gold coated sphere and flat disk using an atomic force microscope. The obtained constraints are stronger up to 19 times comparing the previous experiment with aluminum surfaces and up to 4500 times comparing the Casimir force measurements between dielectrics. The application range of constraints obtained by means of an atomic force microscope is extended.
Bernstein, Gary
Survey M. Jarvis 1;2 , G. M. Bernstein 1;2 , P. Fischer 1;3 , D. Smith 1;4 Department of Astronomy to have #27; 8( m =0:3) 0:57 = 0:71 +0:12 0:16 (95% CL, #3;CDM, = 0:21), where the systematic error of matter uctuations in the Universe (Valdes, Tyson, & Jarvis 1983; Miralda-Escud#19;e 1991; Kaiser 1992
Connecting Numerical Relativity and Data Analysis of Gravitational Wave Detectors
Shoemaker, Deirdre; London, Lionel; Pekowsky, Larne
2015-01-01T23:59:59.000Z
Gravitational waves deliver information in exquisite detail about astrophysical phenomena, among them the collision of two black holes, a system completely invisible to the eyes of electromagnetic telescopes. Models that predict gravitational wave signals from likely sources are crucial for the success of this endeavor. Modeling binary black hole sources of gravitational radiation requires solving the Eintein equations of General Relativity using powerful computer hardware and sophisticated numerical algorithms. This proceeding presents where we are in understanding ground-based gravitational waves resulting from the merger of black holes and the implications of these sources for the advent of gravitational-wave astronomy.
Polarizable vacuum analysis of the gravitational metric tensor
Xing-Hao Ye
2009-03-21T23:59:59.000Z
The gravitational metric tensor implies a variable dielectric tensor of vacuum around gravitational matter. The curved spacetime in general relativity is then associated with a polarizable vacuum. It is found that the number density of the virtual dipoles in vacuum decreases with the distance from the gravitational centre. This result offers a polarizable vacuum interpretation of the gravitational force. Also, the anisotropy of vacuum polarization is briefly discussed, which appeals for observational proof of anisotropic light propagation in a vacuum altered by gravitational or electromagnetic field.
Weakly nonassociative algebras, Riccati and KP hierarchies
Aristophanes Dimakis; Folkert Muller-Hoissen
2008-01-16T23:59:59.000Z
It has recently been observed that certain nonassociative algebras (called "weakly nonassociative", WNA) determine, via a universal hierarchy of ordinary differential equations, solutions of the KP hierarchy with dependent variable in an associative subalgebra (the middle nucleus). We recall central results and consider a class of WNA algebras for which the hierarchy of ODEs reduces to a matrix Riccati hierarchy, which can be easily solved. The resulting solutions of a matrix KP hierarchy then determine (under a rank 1 condition) solutions of the scalar KP hierarchy. We extend these results to the discrete KP hierarchy. Moreover, we build a bridge from the WNA framework to the Gelfand-Dickey formulation of the KP hierarchy.
Is Fusion Inhibited for Weakly Bound Nuclei?
Takahashi, J.; Munhoz, M.; Szanto, E.M.; Carlin, N.; Added, N.; Suaide, A.A.; de Moura, M.M.; Liguori Neto, R.; Szanto de Toledo, A. [Universidade de Sao Paulo, Institute de Fisica, Departamento de Fisica Nuclear, Caixa Postal 66318, 05389-970 Sao Paulo, Sao Paulo, (Brasil)] [Universidade de Sao Paulo, Institute de Fisica, Departamento de Fisica Nuclear, Caixa Postal 66318, 05389-970 Sao Paulo, Sao Paulo, (Brasil); Canto, L.F. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21945-970 Rio de Janeiro, RJ, (Brasil)] [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21945-970 Rio de Janeiro, RJ, (Brasil)
1997-01-01T23:59:59.000Z
Complete fusion of light radioactive nuclei is predicted to be hindered at near-barrier energies. This feature is investigated in the case of the least bound stable nuclei. Evaporation residues resulting from the {sup 6,7}Li+{sup 9}Be and {sup 6,7}Li+{sup 12}C fusion reactions have been measured in order to study common features in reactions involving light weakly bound nuclei. The experimental excitation functions revealed that the fusion cross section is significantly smaller than the total reaction cross section and also smaller than the fusion cross section expected from the available systematics. A clear correlation between the fusion probability and nucleon (cluster) separation energy has been established.The results suggest that the breakup process has a strong influence on the hindrance of the fusion cross section. {copyright} {ital 1996} {ital The American Physical Society}
Thermal machines beyond the weak coupling regime
R. Gallego; A. Riera; J. Eisert
2014-11-13T23:59:59.000Z
How much work can be extracted from a heat bath using a thermal machine? The study of this question has a very long tradition in statistical physics in the weak-coupling limit, applied to macroscopic systems. However, the assumption that thermal heat baths remain uncorrelated with physical systems at hand is less reasonable on the nano-scale and in the quantum setting. In this work, we establish a framework of work extraction in the presence of quantum correlations. We show in a mathematically rigorous and quantitative fashion that quantum correlations and entanglement emerge as a limitation to work extraction compared to what would be allowed by the second law of thermodynamics. At the heart of the approach are operations that capture naturally non-equilibrium dynamics encountered when putting physical systems into contact with each other. We discuss various limits that relate to known results and put our work into context of approaches to finite-time quantum thermodynamics.
The Q_weak Experimental Apparatus
Qweak Collaboration; T. Allison; M. Anderson; D. Androic; D. S. Armstrong; A. Asaturyan; T. D. Averett; R. Averill; J. Balewski; J. Beaufait; R. S. Beminiwattha; J. Benesch; F. Benmokhtar; J. Bessuille; J. Birchall; E. Bonnell; J. Bowman; P. Brindza; D. B. Brown; R. D. Carlini; G. D. Cates; B. Cavness; G. Clark; J. C. Cornejo; S. Covrig Dusa; M. M. Dalton; C. A. Davis; D. C. Dean; W. Deconinck; J. Diefenbach; K. Dow; J. F. Dowd; J. A. Dunne; D. Dutta; W. S. Duvall; J. R. Echols; M. Elaasar; W. R. Falk; K. D. Finelli; J. M. Finn; D. Gaskell; M. T. W. Gericke; J. Grames; V. M. Gray; K. Grimm; F. Guo; J. Hansknecht; D. J. Harrison; E. Henderson; J. R. Hoskins; E. Ihloff; K. Johnston; D. Jones; M. Jones; R. Jones; M. Kargiantoulakis; J. Kelsey; N. Khan; P. M. King; E. Korkmaz; S. Kowalski; A. Kubera; J. Leacock; J. P. Leckey; A. R. Lee; J. H. Lee; L. Lee; Y. Liang; S. MacEwan; D. Mack; J. A. Magee; R. Mahurin; J. Mammei; J. W. Martin; A. McCreary; M. H. McDonald; M. J. McHugh; P. Medeiros; D. Meekins; J. Mei; R. Michaels; A. Micherdzinska; A. Mkrtchyan; H. Mkrtchyan; N. Morgan; J. Musson; K. E. Mesick; A. Narayan; L. Z. Ndukum; V. Nelyubin; Nuruzzaman; W. T. H. van Oers; A. K. Opper; S. A. Page; J. Pan; K. D. Paschke; S. K. Phillips; M. L. Pitt; M. Poelker; J. F. Rajotte; W. D. Ramsay; W. R. Roberts; J. Roche; P. W. Rose; B. Sawatzky; T. Seva; M. H. Shabestari; R. Silwal; N. Simicevic; G. R. Smith; S. Sobczynski; P. Solvignon; D. T. Spayde; B. Stokes; D. W. Storey; A. Subedi; R. Subedi; R. Suleiman; V. Tadevosyan; W. A. Tobias; V. Tvaskis; E. Urban; B. Waidyawansa; P. Wang; S. P. Wells; S. A. Wood; S. Yang; S. Zhamkochyan; R. B. Zielinski
2015-01-06T23:59:59.000Z
The Jefferson Lab Q_weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ${\\vec{e}}$p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 microA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicity-correlated beam properties that can induce false asymmetries. Moller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8 degrees and 11.6 degrees were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silica Cerenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q^2 = 0.025 GeV^2 was determined using dedicated low-current (~100 pA) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.
A. B. Balakin; Z. G. Murzakhanov; G. V. Kisun'ko
2005-11-10T23:59:59.000Z
We discuss a gravitationally induced nonlinearity in hierarchic systems. We consider the generation of extremely low-frequency radio waves with a frequency of the periodic gravitational radiation; the generation is due to an induced nonlinear self-action of electromagnetic radiation in the vicinity of the gravitational-radiation source. These radio waves are a fundamentally new type of response of an electrodynamic system to gravitational radiation. That is why we here use an unconventional term: radio-wave messengers of periodic gravitational radiation.
Blanchard, Peter K.
The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the ...
Gravitational radiation from preheating with many fields
Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Road, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier, E-mail: giblinj@kenyon.edu, E-mail: larry@gravity.phys.uwm.edu, E-mail: siemens@gravity.phys.uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin — Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)
2010-08-01T23:59:59.000Z
Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lemaître-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production — an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.
Gravitational Wave Sources from New Physics
Craig J. Hogan
2006-08-25T23:59:59.000Z
Forthcoming advances in direct gravitational wave detection from kilohertz to nanohertz frequencies have unique capabilities to detect signatures from or set meaningful constraints on a wide range of new cosmological phenomena and new fundamental physics. A brief survey is presented of the post-inflationary gravitational radiation backgrounds predicted in cosmologies that include intense new classical sources such as first-order phase transitions, late-ending inflation, and dynamically active mesoscopic extra dimensions. LISA will provide the most sensitive direct probes of such phenomena near TeV energies or Terascale. LISA will also deeply probe the broadband background, and possibly bursts, from loops of cosmic superstrings predicted to form in current models of brane inflation.
Prolate spheroidal harmonic expansion of gravitational field
Fukushima, Toshio, E-mail: Toshio.Fukushima@nao.ac.jp [National Astronomical Observatory, Ohsawa, Mitaka, Tokyo 181-8588 (Japan)
2014-06-01T23:59:59.000Z
As a modification of the oblate spheroidal case, a recursive method is developed to compute the point value and a few low-order derivatives of the prolate spheroidal harmonics of the second kind, Q{sub nm} (y), namely the unnormalized associated Legendre function (ALF) of the second kind with its argument in the domain, 1 < y < ?. They are required in evaluating the prolate spheroidal harmonic expansion of the gravitational field in addition to the point value and the low-order derivatives of P-bar {sub nm}(t), the 4? fully normalized ALF of the first kind with its argument in the domain, |t| ? 1. The new method will be useful in the gravitational field computation of elongated celestial objects.
Gravitational energy of rotating black holes
J. W. Maluf; E. F. Martins; A. Kneip
1996-08-21T23:59:59.000Z
In the teleparallel equivalent of general relativity the energy density of asymptotically flat gravitational fields can be naturaly defined as a scalar density restricted to a three-dimensional spacelike hypersurface $\\Sigma$. Integration over the whole $\\Sigma$ yields the standard ADM energy. After establishing the reference space with zero gravitational energy we obtain the expression of the localized energy for a Kerr black hole. The expression of the energy inside a surface of constant radius can be explicitly calculated in the limit of small $a$, the specific angular momentum. Such expression turns out to be exactly the same as the one obtained by means of the method preposed recently by Brown and York. We also calculate the energy contained within the outer horizon of the black hole for {\\it any} value of $a$. The result is practically indistinguishable from $E=2M_{ir}$, where $M_{ir}$ is the irreducible mass of the black hole.
A Pseudospectral Method for Gravitational Wave Collapse
Hilditch, David; Bruegmann, Bernd
2015-01-01T23:59:59.000Z
We present a new pseudospectral code, bamps, for numerical relativity written with the evolution of collapsing gravitational waves in mind. We employ the first order generalized harmonic gauge formulation. The relevant theory is reviewed and the numerical method is critically examined and specialized for the task at hand. In particular we investigate formulation parameters, gauge and constraint preserving boundary conditions well-suited to non-vanishing gauge source functions. Different types of axisymmetric twist-free moment of time symmetry gravitational wave initial data are discussed. A treatment of the axisymmetric apparent horizon condition is presented with careful attention to regularity on axis. Our apparent horizon finder is then evaluated in a number of test cases. Moving on to evolutions, we investigate modifications to the generalized harmonic gauge constraint damping scheme to improve conservation in the strong field regime. We demonstrate strong-scaling of our pseudospectral penalty code. We em...
Energy-momentum Density of Gravitational Waves
Amir M. Abbassi; Saeed Mirshekari
2014-11-29T23:59:59.000Z
In this paper, we elaborate the problem of energy-momentum in general relativity by energy-momentum prescriptions theory. Our aim is to calculate energy and momentum densities for the general form of gravitational waves. In this connection, we have extended the previous works by using the prescriptions of Bergmann and Tolman. It is shown that they are finite and reasonable. In addition, using Tolman prescription, exactly, leads to same results that have been obtained by Einstein and Papapetrou prescriptions.
Consistency of the Nonsymmetric Gravitational Theory
J. W. Moffat
1994-12-22T23:59:59.000Z
A nonsymmetric gravitational theory (NGT) is presented which is free of ghost poles, tachyons and higher-order poles and there are no problems with asymptotic boundary conditions. An extended Birkhoff theorem is shown to hold for the spherically symmetric solution of the field equations. A static spherically symmetric solution in the short-range approximation, $\\mu^{-1} > 2m$, is everywhere regular and does not contain a black hole event horizon.
On Principle of Universality of Gravitational Interactions
I. B. Pestov
2001-12-19T23:59:59.000Z
In this work, the experiment is discussed on the verification of the principle of universality of gravitational interactions and some related problems of gravity theory and physics of elementary particles. The meaning of this proposal lies in the fact that the self-consistency of General Relativity, as it turns out, presuppose the existence of the nongravitating form of energy. Theory predicts that electrons are particles that transfer the nongravitating form of energy.
Gravitational dynamics in Bose Einstein condensates
Florian Girelli; Stefano Liberati; Lorenzo Sindoni
2008-12-03T23:59:59.000Z
Analogue models for gravity intend to provide a framework where matter and gravity, as well as their intertwined dynamics, emerge from degrees of freedom that have a priori nothing to do with what we call gravity or matter. Bose Einstein condensates (BEC) are a natural example of analogue model since one can identify matter propagating on a (pseudo-Riemannian) metric with collective excitations above the condensate of atoms. However, until now, a description of the "analogue gravitational dynamics" for such model was missing. We show here that in a BEC system with massive quasi-particles, the gravitational dynamics can be encoded in a modified (semi-classical) Poisson equation. In particular, gravity is of extreme short range (characterized by the healing length) and the cosmological constant appears from the non-condensed fraction of atoms in the quasi-particle vacuum. While some of these features make the analogue gravitational dynamics of our BEC system quite different from standard Newtonian gravity, we nonetheless show that it can be used to draw some interesting lessons about "emergent gravity" scenarios.
LIGO and the Search for Gravitational Waves
Robertson, Norna A.
2006-10-16T23:59:59.000Z
Gravitational waves, predicted to exist by Einstein's General Theory of Relativity but as yet undetected, are expected to be emitted during violent astrophysical events such as supernovae, black hole interactions and the coalescence of compact binary systems. Their detection and study should lead to a new branch of astronomy. However the experimental challenge is formidable: ground-based detection relies on sensing displacements of order 10{sup -18} m over a frequency range of tens of hertz to a few kHz. There is currently a large international effort to commission and operate long baseline interferometric detectors including those that comprise LIGO - the Laser Interferometer Gravitational-Wave Observatory - in the USA. In this talk I will give an introduction to the topic of gravitational wave detection and in particular review the status of the LIGO project which is currently taking data at its design sensitivity. I will also look to the future to consider planned improvements in sensitivity for such detectors, focusing on Advanced LIGO, the proposed upgrade to the LIGO project.
Non-equilibrium thermodynamics of gravitational screens
Laurent Freidel; Yuki Yokokura
2014-05-19T23:59:59.000Z
We study the Einstein gravity equations projected on a timelike surface, which represents the time evolution of what we call a gravitational screen. We show that such a screen possesses a surface tension and an internal energy, and that the Einstein equations reduce to the thermodynamic equations of a viscous bubble. We also provide a complete dictionary between gravitational and thermodynamical variables. In the non-viscous cases there are three thermodynamic equations which characterise a bubble dynamics: These are the first law, the Marangoni flow equation and the Young-Laplace equation. In all three equations the surface tension plays a central role: In the first law it appears as a work term per unit area, in the Marangoni flow its gradient drives a force, and in the Young-Laplace equation it contributes to a pressure proportional to the surface curvature. The gravity equations appear as a natural generalization of these bubble equations when the bubble itself is viscous and dynamical. In particular, it shows that the mechanism of entropy production for the viscous bubble is mapped onto the production of gravitational waves. We also review the relationship between surface tension and temperature, and discuss the usual black-hole thermodynamics from this point of view.
Gillespie, G.H., Brown, T.A.
1998-05-01T23:59:59.000Z
A set of optical models for a variety of electrostatic lenses and accelerator columns has been developed for the computer code TRACE 3-D. TRACE 3-D is an envelope (matrix) code including space charge that is often used to model bunched beams in magnetic transport systems and radiofrequency (RF) accelerators when the effects of beam current may be important. Several new matrix models have been developed that allow the code to be used for modeling beam lines and accelerators with electrostatic components. The new models include a number of options for: (1) einzel lenses, (2) accelerator columns, (3) electrostatic deflectors (prisms), and (4) an electrostatic quadrupole. A prescription for setting up the initial beam appropriate to modeling 2-D (continuous) beams has also been developed. The new models for (2) are described in this paper, selected comparisons with other calculations are presented, and a beamline application is summarized.
Characterising the Gravitational Instability in Cooling Accretion Discs
Peter Cossins; Giuseppe Lodato; Cathie Clarke
2008-11-21T23:59:59.000Z
We perform numerical analyses of the structure induced by gravitational instabilities in cooling gaseous accretion discs. For low enough cooling rates a quasi-steady configuration is reached, with the instability saturating at a finite amplitude in a marginally stable disc. We find that the saturation amplitude scales with the inverse square root of the cooling parameter beta = t_cool / t_dyn, which indicates that the heating rate induced by the instability is proportional to the energy density of the induced density waves. We find that at saturation the energy dissipated per dynamical time by weak shocks due is of the order of 20 per cent of the wave energy. From Fourier analysis of the disc structure we find that while the azimuthal wavenumber is roughly constant with radius, the mean radial wavenumber increases with radius, with the dominant mode corresponding to the locally most unstable wavelength. We demonstrate that the density waves excited in relatively low mass discs are always close to co-rotation, deviating from it by approximately 10 per cent. This can be understood in terms of the flow Doppler-shifted phase Mach number -- the pattern speed self-adjusts so that the flow into spiral arms is always sonic. This has profound effects on the degree to which transport through self-gravity can be modelled as a viscous process. Our results thus provide (a) a detailed description of how the self-regulation mechanism is established for low cooling rates, (b) a clarification of the conditions required for describing the transport induced by self-gravity through an effective viscosity, (c) an estimate of the maximum amplitude of the density perturbation before fragmentation occurs, and (d) a simple recipe to estimate the density perturbation in different thermal regimes.
A Monitor of the Focusing Strength of Plasma Lenses Using MeV Synchrotron Radiation
Clive Field; Gholam Mazaheri; Johnny S. T. Ng
2002-01-17T23:59:59.000Z
The focusing strength of plasma lenses used with high energy electron or positron beams can give rise to synchrotron radiation with critical energies in the MeV range. A method is described for measuring the characteristic energy of this radiation as a way of monitoring the strength of the focus. The principle has been implemented in a plasma lens experiment with a 28.5 GeV positron beam.
Semianalytic model of electron pulse propagation: Magnetic lenses and rf pulse compression cavities
Berger, Joel A.; Schroeder, W. Andreas [Department of Physics, University of Illinois at Chicago, 845 W. Taylor (M/C 273), Chicago, Illinois 60607 (United States)
2010-12-15T23:59:59.000Z
The analytical Gaussian electron pulse propagation model of Michalik and Sipe [J. Appl. Phys. 99, 054908 (2006)] is extended to include the action of external forces on the pulse. The resultant ability to simulate efficiently the effect of electron optical elements (e.g., magnetic lenses and radio-frequency cavities) allows for the rapid assessment of electron pulse delivery systems in time-resolved ultrafast electron diffraction and microscopy experiments.
Weak nuclear forces cause the strong nuclear force
E. L. Koschmieder
2007-12-11T23:59:59.000Z
We determine the strength of the weak nuclear force which holds the lattices of the elementary particles together. We also determine the strength of the strong nuclear force which emanates from the sides of the nuclear lattices. The strong force is the sum of the unsaturated weak forces at the surface of the nuclear lattices. The strong force is then about ten to the power of 6 times stronger than the weak force between two lattice points.
Search for periodic gravitational radiation with the ALLEGRO gravitational wave detector
E. Mauceli; M. P. McHugh; W. O. Hamilton; W. W. Johnson; A. Morse
2000-07-11T23:59:59.000Z
We describe the search for a continuous signal of gravitational radiation from a rotating neutron star in the data taken by the ALLEGRO gravitational wave detector in early 1994. Since ALLEGRO is sensitive at frequencies near 1 kHz, only neutron stars with spin periods near 2 ms are potential sources. There are no known sources of this typ e for ALLEGRO, so we directed the search towards both the galactic center and the globular clus ter 47 Tucanae. The analysis puts a constraint of roughly $8 \\times 10^{-24}$ at frequencies near 1 kHz on the gravitational strain emitted from pulsar spin-down in either 47 Tucanae or the galactic center.
Search for periodic gravitational radiation with the ALLEGRO gravitational wave detector
Mauceli, E; Hamilton, W O; Johnson, W W; Morse, A
2002-01-01T23:59:59.000Z
We describe the search for a continuous signal of gravitational radiation from a rotating neutron star in the data taken by the ALLEGRO gravitational wave detector in early 1994. Since ALLEGRO is sensitive at frequencies near 1 kHz, only neutron stars with spin periods near 2 ms are potential sources. There are no known sources of this typ e for ALLEGRO, so we directed the search towards both the galactic center and the globular clus ter 47 Tucanae. The analysis puts a constraint of roughly $8 \\times 10^{-24}$ at frequencies near 1 kHz on the gravitational strain emitted from pulsar spin-down in either 47 Tucanae or the galactic center.
Comparisons between isothermal and NFW mass profiles for strong-lensing galaxy clusters
Shu, Chenggang; Bartelmann, Matthias; Comerford, Julia M; Huang, J -S; Mellier, Yannick
2008-01-01T23:59:59.000Z
While both isothermal and NFW-based mass models for galaxy clusters are widely adopted in strong-lensing studies, they cannot easily be distinguished based solely on observed positions of arcs and arclets. We compare the magnifications predicted for giant arcs obtained from isothermal and NFW profiles, taking axially-symmetric and asymmetric mass distributions into account. We find that arc magnifications can differ strongly between the two types of density profiles even if the image morphology is well reproduced. Magnifications by lenses with NFW density profiles are usually larger than those for lenses with singular or nearly singular isothermal density profiles, unless the latter have large cores. Asymmetries play an important role. We illustrate our results with the two well-studied clusters MS 2137 and A~370. We confirm earlier results showing that both isothermal and NFW mass models can very well reproduce the observed arcs, radial arcs and other arclets. While the mass model for MS 2137 is not very wel...
Mean and covariance matrix adaptive estimation for a weakly ...
2011-01-25T23:59:59.000Z
AMS 2000 subject classification: Primary: 62G05, 62M10; Secondary: 90C15. Key words and phrases: Adaptive estimation, weakly stationary process, stochastic ...
Study atom-vacuum interaction by the weak measurement technique
M. Zhang; S. Y. Zhu
2014-10-27T23:59:59.000Z
Quantum weak measurement attracts much interests recently [Rev. Mod. Phys. 86, 307 (2014)], as it could amplify some weak signals and provide a technique to observe the nonclassical phenomenons. Here, we apply this technique to study the interaction between the free atoms and the vacuum in a cavity. Due to the gradient field in the vacuum cavity, the external orbital motions and the internal electronic states of the atoms can be weakly coupled via the atom-field electric-dipole interaction. We show an interesting phenomenon that, within the properly post-selected internal states, the weak atom-vacuum interaction could generate a large change to the external motions of atoms.
Reversing the Weak Quantum Measurement for a Photonic Qubit
Yong-Su Kim; Young-Wook Cho; Young-Sik Ra; Yoon-Ho Kim
2009-03-18T23:59:59.000Z
We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.
Strengths and Weaknesses of Quantum Fingerprinting
Dmitry Gavinsky; Julia Kempe; Ronald de Wolf
2006-03-20T23:59:59.000Z
We study the power of quantum fingerprints in the simultaneous message passing (SMP) setting of communication complexity. Yao recently showed how to simulate, with exponential overhead, classical shared-randomness SMP protocols by means of quantum SMP protocols without shared randomness ($Q^\\parallel$-protocols). Our first result is to extend Yao's simulation to the strongest possible model: every many-round quantum protocol with unlimited shared entanglement can be simulated, with exponential overhead, by $Q^\\parallel$-protocols. We apply our technique to obtain an efficient $Q^\\parallel$-protocol for a function which cannot be efficiently solved through more restricted simulations. Second, we tightly characterize the power of the quantum fingerprinting technique by making a connection to arrangements of homogeneous halfspaces with maximal margin. These arrangements have been well studied in computational learning theory, and we use some strong results obtained in this area to exhibit weaknesses of quantum fingerprinting. In particular, this implies that for almost all functions, quantum fingerprinting protocols are exponentially worse than classical deterministic SMP protocols.
Graphene transparency in weak magnetic fields
David Valenzuela; Saúl Hernández-Ortiz; Marcelo Loewe; Alfredo Raya
2014-10-20T23:59:59.000Z
We carry out an explicit calculation of the vacuum polarization tensor for an effective low-energy model of monolayer graphene in the presence of a weak magnetic field of intensity $B$ perpendicularly aligned to the membrane. By expanding the quasiparticle propagator in the Schwinger proper time representation up to order $(eB)^2$, where $e$ is the unit charge, we find an explicitly transverse tensor, consistent with gauge invariance. Furthermore, assuming that graphene is radiated with monochromatic light of frequency $\\omega$ along the external field direction, from the modified Maxwell's equations we derive the intensity of transmitted light and the angle of polarization rotation in terms of the longitudinal ($\\sigma_{xx}$) and transverse ($\\sigma_{xy}$) conductivities. Corrections to these quantities, both calculated and measured, are of order $(eB)^2/\\omega^4$. Our findings generalize and complement previously known results reported in literature regarding the light absorption problem in graphene from the experimental and theoretical points of view, with and without external magnetic fields.
G. G. Nyambuya
2010-10-18T23:59:59.000Z
This paper is part of a series on the Azimuthally Symmetric Theory of Gravitation (ASTG) which is built on Laplace-Poisson's well known equation. We show herein that the emergent equations from the ASTG, under some critical conditions determined by the spin, do possess repulsive gravitational fields in the polar regions of the gravitating body in question. This places the ASTG on an interesting pedestal to infer the origins of outflows as a repulsive gravitational phenomenon. Outflows are a ubiquitous phenomenon found in star forming systems and their true origin is a question yet to be settled. Given the current thinking on their origin, the direction that the present paper takes is nothing short of an asymptotic break from conventional wisdom; at the very least, it is a complete paradigm shift because gravitation is not at all associated with this process, but rather it is thought to be an all-attractive force that only tries to squash matter together onto a single point. Additionally, we show that the emergent Azimuthally Symmetric Gravitational Field from the ASTG strongly suggests a solution to the supposed Radiation Problem that is thought to be faced by massive stars in their process of formation. That is, at about 8-10Msun radiation from the nascent star is expected to halt the accretion of matter. We show that in-falling material will fall onto the equatorial disk and from there, this material will be channeled onto the forming star via the equatorial plane, thus accretion of mass continues well past the value of about 8-10Msun, albeit via the disk. Along the equatorial plane, the net force (with the radiation force included) on any material there-on right up to the surface of the star is directed toward the forming star, hence accretion of mass by the nascent star is un-hampered.
Dynamics of a self-gravitating thin string in scalar-tensor theories of gravitation
B. Boisseau; B. Linet
1997-06-09T23:59:59.000Z
We examine the dynamics of a self-gravitating string in the scalar-tensor theories of gravitation by considering a thin tube of matter to describe it. For a class of solutions, we obtain in the generic case that the extrinsic curvature of the world sheet of the central line is null in the limit where the radius of the string tends to zero. However, if we impose a specific constraint on the behaviour of the solution then we find that only the mean curvature of the world sheet of the central line vanishes which is just the Nambu-Goto dynamics. This analysis can include the massless dilatonic theories of gravity.
Gravitational waves from a curvaton model with blue spectrum
Kawasaki, Masahiro; Kitajima, Naoya; Yokoyama, Shuichiro, E-mail: kawasaki@icrr.u-tokyo.ac.jp, E-mail: nk610@icrr.u-tokyo.ac.jp, E-mail: shu@icrr.u-tokyo.ac.jp [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)
2013-08-01T23:59:59.000Z
We investigate the gravitational wave background induced by the first order scalar perturbations in the curvaton models. We consider the quadratic and axion-like curvaton potential which can generate the blue-tilted power spectrum of curvature perturbations on small scales and derive the maximal amount of gravitational wave background today. We find the power spectrum of the induced gravitational wave background has a characteristic peak at the frequency corresponding to the scale reentering the horizon at the curvaton decay, in the case where the curvaton does not dominate the energy density of the Universe. We also find the enhancement of the amount of the gravitational waves in the case where the curvaton dominates the energy density of the Universe. Such induced gravitational waves would be detectable by the future space-based gravitational wave detectors or pulsar timing observations.
Constraints on Light Pseudoscalars Implied by Tests of the Gravitational Inverse-Square Law
Ephraim Fischbach; Dennis E. Krause
1999-06-03T23:59:59.000Z
The exchange of light pseudoscalars between fermions leads to a spin-independent potential in order g^4, where g is the Yukawa pseudoscalar-fermion coupling constant. This potential gives rise to detectable violations of both the weak equivalence principle (WEP) and the gravitational inverse-square law (ISL), even if g is quite small. We show that when previously derived WEP constraints are combined with those arisingfrom ISL tests, a direct experimental limit on the Yukawa coupling of light pseudoscalars to neutrons can be inferred for the first time (g_n^2/4pi < 1.6 \\times 10^-7), along with a new (and significantly improved) limit on the coupling of light pseudoscalars to protons.
Universal Gravitational Constant EX-9908 Page 1 of 13 Re-Written by Geoffrey R. Clarion
Dai, Pengcheng
Newton was able to deduce his law of universal gravitation. Newton's law of universal gravitation: 2 21 rUniversal Gravitational Constant EX-9908 Page 1 of 13 Re-Written by Geoffrey R. Clarion Universal Gravitational Constant EQUIPMENT 1 Gravitational Torsion Balance AP-8215 1 X-Y Adjustable Diode Laser OS-8526A 1
Influence of Gravitation on Mass-Energy Equivalence Relation
R. V. R. Pandya
2005-07-01T23:59:59.000Z
We study influence of gravitational field on the mass-energy equivalence relation by incorporating gravitation in the physical situation considered by Einstein (Ann. Physik, 17, 1905, English translation in ref. [1]) for his first derivation of mass-energy equivalence. In doing so, we also refine Einstein's expression (Ann. Physik, 35, 1911, English translation in ref. [3]) for increase in gravitational mass of the body when it absorbs E amount of radiation energy.
Gravitating Fermionic Lumps with a False Vacuum Core
Ramin G. Daghigh; Yutaka Hosotani
2004-02-03T23:59:59.000Z
We investigate gravitating lumps with a false vacuum core surrounded by the true vacuum in a scalar field potential. Such configurations become possible in the Einstein gravity in the presence of fermions at the core. Gravitational interactions as well as Yukawa interactions are essential for such lumps to exist. The mass and size of gravitating lumps sensitively depend on the scale characterizing the scalar field potential and the density of fermions. These objects can exist in the universe at various scales.
Mapping the nano-Hertz gravitational wave sky
Neil J. Cornish; Rutger van Haasteren
2014-06-19T23:59:59.000Z
We describe a new method for extracting gravitational wave signals from pulsar timing data. We show that any gravitational wave signal can be decomposed into an orthogonal set of sky maps, with the number of maps equal to the number of pulsars in the timing array. These maps may be used as a basis to construct gravitational wave templates for any type of source, including collections of point sources. A variant of the standard Hellings-Downs correlation analysis is recovered for statistically isotropic signals. The template based approach allows us to probe potential anisotropies in the signal and produce maps of the gravitational wave sky.
advanced gravitational-wave interferometric: Topics by E-print...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
detector General Relativity & Quantum Cosmology (arXiv) Summary: Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves, with the aim...
airborne gravitational noise: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
laser interferometry. This is possible due to two reasons: first, gravitational waves and displacement disturbances contribute to light propagation times in different...
Data Quality Studies of Enhanced Interferometric Gravitational Wave Detectors
Jessica McIver; for the LIGO Scientific Collaboration; for the Virgo Collaboration
2012-04-11T23:59:59.000Z
Data quality assessment plays an essential role in the quest to detect gravitational wave signals in data from the LIGO and Virgo interferometric gravitational wave detectors. Interferometer data contains a high rate of noise transients from the environment, the detector hardware, and the detector control systems. These transients severely limit the statistical significance of gravitational wave candidates of short duration and/or poorly modeled waveforms. This paper describes the data quality studies that have been performed in recent LIGO and Virgo observing runs to mitigate the impact of transient detector artifacts on the gravitational wave searches.
Galilean symmetry in a noncommutative gravitational quantum well
Saha, Anirban [Department of Physics and Astrophysics, West Bengal State University, Barasat, West Bengal (India)
2010-06-15T23:59:59.000Z
A thorough analysis of Galilean symmetries for the gravitational well problem on a noncommutative plane is presented. A complete closure of the one-parameter centrally extended Galilean algebra is realized for the model. This implies that the field theoretic model constructed to describe noncommutative gravitational quantum well in [A. Saha, Eur. Phys. J. C 51, 199 (2007).] is indeed independent of the coordinate choice. Hence the energy spectrum predicted by the model can be associated with the experimental results to establish the upper bound on a time-space noncommutative parameter. Interestingly, noncommutativity is shown to increase the gravitational pull on the neutron trapped in the gravitational well.
Aleksandr Fridrikson; Marina Kasatochkina
2009-04-08T23:59:59.000Z
The direct problem of the detection of the Earth's absolute gravitation potential maximum value (MGP) was solved. The inverse problem finding of the Earth maximum gravitation (where there is a maximum of gravitation field intensity and a potential function has a 'bending point') with the help of MGP was solved as well. The obtained results show that the revealed Earth maximum gravitation coincides quite strictly with the cseismic D" layer on the border of the inner and outer (liquid) core. The validity of the method of an absolute gravitation potential detection by the equal- potential velocity was proved as 'gravitation potential measurement' or 'Vs-gravity method'. The prospects of this method for detecting of low-power or distant geological objects with abnormal density and the possible earthquakes with low density was shown.
Ohanian, Hans C
2010-01-01T23:59:59.000Z
We establish a general relation between the canonical energy-momentum tensor and the tensor that acts as the source of the gravitational field in Einstein's equations. In General Relativity, we use this relation to give a general proof of the exact equality of the gravitational and inertial masses for any arbitrary system of matter and gravitational fields, regardless of the presence of nonminimal couplings. In the Brans-Dicke scalar field theory, we establish that the nonminimal coupling of the scalar field leads to an inequality between the gravitational and inertial masses, and we derive an exact formula for this inequality and confirm that it is approximately proportional to the gravitational self-energy (the Nordvedt effect), but with a constant of proportionality different from what is claimed in the published literature in calculations based on the PPN scheme. Similar inequalities of gravitational and inertial masses are expected to occur in other scalar and vector theories.
FROM DUST TO PLANETESIMALS: CRITERIA FOR GRAVITATIONAL INSTABILITY OF SMALL PARTICLES IN GAS
Shi, Ji-Ming; Chiang, Eugene, E-mail: jmshi@berkeley.edu [Department of Astronomy, UC Berkeley, Hearst Field Annex B-20, Berkeley, CA 94720-3411 (United States)] [Department of Astronomy, UC Berkeley, Hearst Field Annex B-20, Berkeley, CA 94720-3411 (United States)
2013-02-10T23:59:59.000Z
Dust particles sediment toward the midplanes of protoplanetary disks, forming dust-rich sublayers encased in gas. What densities must the particle sublayer attain before it can fragment by self-gravity? We describe various candidate threshold densities. One of these is the Roche density, which is that required for a strengthless satellite to resist tidal disruption by its primary. Another is the Toomre density, which is that required for de-stabilizing self-gravity to defeat the stabilizing influences of pressure and rotation. We show that for sublayers containing aerodynamically well-coupled dust, the Toomre density exceeds the Roche density by many (up to about four) orders of magnitude. We present three-dimensional shearing box simulations of self-gravitating, stratified, dust-gas mixtures to test which of the candidate thresholds is relevant for collapse. All of our simulations indicate that the larger Toomre density is required for collapse. This result is sensible because sublayers are readily stabilized by pressure. Sound-crossing times for thin layers are easily shorter than free-fall times, and the effective sound speed in dust-gas suspensions decreases only weakly with the dust-to-gas ratio (as the inverse square root). Our findings assume that particles are small enough that their stopping times in gas are shorter than all other timescales. Relaxing this assumption may lower the threshold for gravitational collapse back down to the Roche criterion. In particular, if the particle stopping time becomes longer than the sound-crossing time, then sublayers may lose pressure support and become gravitationally unstable.
On the Unreasonable Effectiveness of post-Newtonian Theory in Gravitational-Wave Physics
Clifford M. Will
2010-01-08T23:59:59.000Z
The first indirect detection of gravitational waves involved a binary system of neutron stars. In the future, the first direct detection may also involve binary systems -- inspiralling and merging binary neutron stars or black holes. This means that it is essential to understand in full detail the two-body system in general relativity, a notoriously difficult problem with a long history. Post-Newtonian approximation methods are thought to work only under slow motion and weak field conditions, while numerical solutions of Einstein's equations are thought to be limited to the final merger phase. Recent results have shown that post-Newtonian approximations seem to remain unreasonably valid well into the relativistic regime, while advances in numerical relativity now permit solutions for numerous orbits before merger. It is now possible to envision linking post-Newtonian theory and numerical relativity to obtain a complete ``solution'' of the general relativistic two-body problem. These solutions will play a central role in detecting and understanding gravitational wave signals received by interferometric observatories on Earth and in space.
Free-fall in a uniform gravitational field in non-commutative quantum mechanics
K. H. C. Castello-Branco; A. G. Martins
2011-05-23T23:59:59.000Z
We study the free-fall of a quantum particle in the context of noncommutative quantum mechanics (NCQM). Assuming noncommutativity of the canonical type between the coordinates of a two-dimensional configuration space, we consider a neutral particle trapped in a gravitational well and exactly solve the energy eigenvalue problem. By resorting to experimental data from the GRANIT experiment, in which the first energy levels of freely falling quantum ultracold neutrons were determined, we impose an upper-bound on the noncommutativity parameter. We also investigate the time of flight of a quantum particle moving in a uniform gravitational field in NCQM. This is related to the weak equivalence principle. As we consider stationary, energy eigenstates, i.e., delocalized states, the time of flight must be measured by a quantum clock, suitably coupled to the particle. By considering the clock as a small perturbation, we solve the (stationary) scattering problem associated and show that the time of flight is equal to the classical result, when the measurement is made far from the turning point. This result is interpreted as an extension of the equivalence principle to the realm of NCQM.
Free-fall in a uniform gravitational field in noncommutative quantum mechanics
Castello-Branco, K. H. C. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao-Carlense, 400, Sao Carlos, Sao Paulo 13560-970 (Brazil); Martins, A. G. [Departamento de Ciencias Naturais, Universidade do Estado do Para, Av. Djalma Dutra, s/n, Belem, Para 66113-200 (Brazil)
2010-10-15T23:59:59.000Z
We study the free-fall of a quantum particle in the context of noncommutative quantum mechanics (NCQM). Assuming noncommutativity of the canonical type between the coordinates of a two-dimensional configuration space, we consider a neutral particle trapped in a gravitational well and exactly solve the energy eigenvalue problem. By resorting to experimental data from the GRANIT experiment, in which the first energy levels of freely falling quantum ultracold neutrons were determined, we impose an upper-bound on the noncommutativity parameter. We also investigate the time of flight of a quantum particle moving in a uniform gravitational field in NCQM. This is related to the weak equivalence principle. As we consider stationary, energy eigenstates, i.e., delocalized states, the time of flight must be measured by a quantum clock, suitably coupled to the particle. By considering the clock as a small perturbation, we solve the (stationary) scattering problem associated and show that the time of flight is equal to the classical result, when the measurement is made far from the turning point. This result is interpreted as an extension of the equivalence principle to the realm of NCQM.
Higgs Production via Gluon-Induced Weak Boson Fusion
Jens Vollinga
2008-09-22T23:59:59.000Z
We present a calculation that allows for an estimation of the NNLO contributions to the Higgs production in the weak boson fusion channel. A possible deterioration of this important channel for the Higgs discoveries at the LHC can be ruled out by this calculation due to the small remaining cross section after the weak boson cuts.
Weakly Terminal Objects in Quasicategories of SET Endofunctors
Barto, Libor
Weakly Terminal Objects in Quasicategories of SET Endofunctors Libor Barto # Mathematical Institute and mappings) and all natural transformations has a terminal object -- the constant functor C1 . We construct here the terminal (or at least the smallest weakly terminal object, which is rigid) in some important
Weakly Terminal Objects in Quasicategories of SET Endofunctors
Barto, Libor
Weakly Terminal Objects in Quasicategories of SET Endofunctors Libor Barto Mathematical Institute and mappings) and all natural transformations has a terminal object the constant functor C1. We construct here the terminal (or at least the smallest weakly terminal object, which is rigid) in some important
Modeling active electrolocation in weakly electric fish Habib Ammari
Garnier, Josselin
Modeling active electrolocation in weakly electric fish Habib Ammari Thomas Boulier Josselin in weakly electric fishes. We first investigate the forward complex conductivity problem and derive the approx- imate boundary conditions on the skin of the fish. Then we provide a dipole approximation
PLM OPPORTUNITIES AND WEAKNESSES TO SUPPORT COLLABORATIVE ENGINEERING
Paris-Sud XI, Université de
PLM OPPORTUNITIES AND WEAKNESSES TO SUPPORT COLLABORATIVE ENGINEERING VALERY MERMINOD CERAM is to discuss the opportunities and the weaknesses of Product Lifecycle Management (PLM) technology to support is based on a 3 years analysis of a PLM system project in a large French company, int the sector of small
Phil Marshall; Roger Blandford; Masao Sako
2005-01-17T23:59:59.000Z
Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ``piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.
Gravitational leptogenesis, C, CP and strong equivalence
J. I. McDonald; Graham M. Shore
2014-11-13T23:59:59.000Z
The origin of matter-antimatter asymmetry is one of the most important outstanding problems at the interface of particle physics and cosmology. Gravitational leptogenesis (baryogenesis) provides a possible mechanism through explicit couplings of spacetime curvature to appropriate lepton (or baryon) currents. In this paper, the idea that these strong equivalence principle violating interactions could be generated automatically through quantum loop effects in curved spacetime is explored, focusing on the realisation of the discrete symmetries C, CP and CPT which must be broken to induce matter-antimatter asymmetry. The related issue of quantum corrections to the dispersion relation for neutrino propagation in curved spacetime is considered within a fully covariant framework.
Grand Unification and Enhanced Quantum Gravitational Effects
Calmet, Xavier [Catholic University of Louvain, Center for Particle Physics and Phenomenology, 2, Chemin du Cyclotron, B-1348 Louvain-la-Neuve (Belgium); Hsu, Stephen D. H.; Reeb, David [Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403 (United States)
2008-10-24T23:59:59.000Z
In grand unified theories with large numbers of fields, renormalization effects significantly modify the scale at which quantum gravity becomes strong. This in turn can modify the boundary conditions for coupling constant unification, if higher dimensional operators induced by gravity are taken into consideration. We show that the generic size of, and the uncertainty in, these effects from gravity can be larger than the two-loop corrections typically considered in renormalization group analyses of unification. In some cases, gravitational effects of modest size can render unification impossible.
Alternative Gravitational Theories in Four Dimensions
Friedrich W. Hehl
1997-12-26T23:59:59.000Z
We argue that from the point of view of gauge theory and of an appropriate interpretation of the interferometer experiments with matter waves in a gravitational field, the Einstein-Cartan theory is the best theory of gravity available. Alternative viable theories are general relativity and a certain teleparallelism model. Objections of Ohanian and Ruffini against the Einstein-Cartan theory are discussed. Subsequently we list the papers which were read at the `Alternative 4D Session' and try to order them, at least partially, in the light of the structures discussed.