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1

The Atacama Cosmology Telescope Project: A Progress Report  

E-Print Network [OSTI]

The Atacama Cosmology Telescope is a project to map the microwave background radiation at arcminute angular resolution and high sensitivity in three frequency bands over substantial sky areas. Cosmological signals driving such an experiment are reviewed, and current progress in hardware construction is summarized. Complementary astronomical observations in other wavebands are also discussed.

Arthur Kosowsky; for the ACT Collaboration

2006-08-25T23:59:59.000Z

2

THE ATACAMA COSMOLOGY TELESCOPE: DATA CHARACTERIZATION AND MAPMAKING  

SciTech Connect (OSTI)

We present a description of the data reduction and mapmaking pipeline used for the 2008 observing season of the Atacama Cosmology Telescope (ACT). The data presented here at 148 GHz represent 12% of the 90 TB collected by ACT from 2007 to 2010. In 2008 we observed for 136 days, producing a total of 1423 hr of data (11 TB for the 148 GHz band only), with a daily average of 10.5 hr of observation. From these, 1085 hr were devoted to an 850 deg{sup 2} stripe (11.2 hr by 9. Degree-Sign 1) centered on a declination of -52. Degree-Sign 7, while 175 hr were devoted to a 280 deg{sup 2} stripe (4.5 hr by 4. Degree-Sign 8) centered at the celestial equator. The remaining 163 hr correspond to calibration runs. We discuss sources of statistical and systematic noise, calibration, telescope pointing, and data selection. For the 148 GHz band, out of 1260 survey hours and 1024 detectors in the array, 816 hr and 593 effective detectors remain after data selection, yielding a 38% survey efficiency. The total sensitivity in 2008, determined from the noise level between 5 Hz and 20 Hz in the time-ordered data stream (TOD), is 32 {mu}K{radical}s in cosmic microwave background units. Atmospheric brightness fluctuations constitute the main contaminant in the data and dominate the detector noise covariance at low frequencies in the TOD. The maps were made by solving the least-squares problem using the Preconditioned Conjugate Gradient method, incorporating the details of the detector and noise correlations. Simulations, as well as cross-correlations with Wilkinson Microwave Anisotropy Probe sky maps on large angular scales, reveal that our maps are unbiased at multipoles l > 300. This paper accompanies the public release of the 148 GHz southern stripe maps from 2008. The techniques described here will be applied to future maps and data releases.

Duenner, Rolando; Aguirre, Paula; Barrientos, L. Felipe [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)] [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Hasselfield, Matthew; Amiri, Mandana; Battistelli, Elia S.; Burger, Bryce [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada)] [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Marriage, Tobias A.; Acquaviva, Viviana; Das, Sudeep [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)] [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Sievers, Jon; Appel, John William [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States)] [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Addison, Graeme E.; Calabrese, Erminia [Department of Astrophysics, Oxford University, Oxford OX1 3RH (United Kingdom)] [Department of Astrophysics, Oxford University, Oxford OX1 3RH (United Kingdom); Ade, Peter A. R. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom)] [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom); Bond, J. Richard [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada)] [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Brown, Ben [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States)] [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Chervenak, Jay [Code 553/665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)] [Code 553/665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Devlin, Mark J.; Dicker, Simon R. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)] [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); and others

2013-01-01T23:59:59.000Z

3

E-Print Network 3.0 - atacama cosmology telescope Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

achievements: The CSO has carried out... distant, cosmological events, and further exploration of the multiscale star formation process with high... of unique radio...

4

HIGH-FREQUENCY RADIO SPECTRAL ENERGY DISTRIBUTIONS AND POLARIZATION FRACTIONS OF SOURCES IN AN ATACAMA COSMOLOGY TELESCOPE SURVEY FIELD  

SciTech Connect (OSTI)

We present flux densities and polarization percentages of 159 radio galaxies based on nearly simultaneous Very Large Array observations at four frequencies, 4.86, 8.46, 22.46, and 43.34 GHz. This sample is selected from the high-frequency Australia Telescope 20 GHz (AT20G) survey and consists of all sources with flux density S{sub 20GHz} > 40 mJy in an equatorial field of the Atacama Cosmology Telescope (ACT) survey. For a subset of 25 of these sources, we used the Green Bank Telescope (GBT) to obtain 90 GHz data. The goals of this program are: (1) a characterization of the spectra, polarization, and variability of high-frequency-selected radio sources, (2) extrapolating from the few GHz regime to the {approx}150 GHz regime of the ACT survey, allowing for more accurate removal of the radio source signal in our particular field, and (3) providing a data set that will allow more accurate modeling of the high-frequency radio source contamination in current and future Sunyaev-Zeldovich and cosmic microwave background experiments. We find that, as expected, this sample consists of flatter spectrum and more compact or point-like sources than low-frequency-selected samples. In the K band, variability is typically {approx}<20%, although there are exceptions. The higher frequency data are well suited to the detection of extreme gigahertz peak spectrum sources. The inclusion of the 43 GHz data causes the relative fraction of inverted spectrum sources to go down and of peaked spectrum sources to go up when compared with the AT20G survey results. The trend largely continues with the inclusion of the 90 GHz data, although {approx}10% of the sources with GBT data show a spectral upturn from 43 GHz to 90 GHz. The measured polarization fractions are typically <5%, although in some cases they are measured to be up to {approx}20%. For sources with detected polarized flux in all four bands, about 40% of the sample, the polarization fractions typically increase with frequency. This trend is stronger for steeper spectrum sources as well as for the lower flux density sources.

Sajina, Anna [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Partridge, Bruce; Evans, Tyler; Vechik, Nicholas [Department of Physics and Astronomy, Haverford College, Haverford, PA 19041 (United States); Stefl, Shannon [Kent State University, Kent, OH 44242 (United States); Myers, Steve [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Dicker, Simon; Korngut, Phillip [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2011-05-01T23:59:59.000Z

5

E-Print Network 3.0 - atacama telescope ccat Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

applicability of Electric Vehicles (EVs) is the scarce capacity of Summary: a main solar panel on the roof and a secondary, telescopic panel under the main panel. When...

6

EFFECT OF MEASUREMENT ERRORS ON PREDICTED COSMOLOGICAL CONSTRAINTS FROM SHEAR PEAK STATISTICS WITH LARGE SYNOPTIC SURVEY TELESCOPE  

SciTech Connect (OSTI)

We study the effect of galaxy shape measurement errors on predicted cosmological constraints from the statistics of shear peak counts with the Large Synoptic Survey Telescope (LSST). We use the LSST Image Simulator in combination with cosmological N-body simulations to model realistic shear maps for different cosmological models. We include both galaxy shape noise and, for the first time, measurement errors on galaxy shapes. We find that the measurement errors considered have relatively little impact on the constraining power of shear peak counts for LSST.

Bard, D.; Chang, C.; Kahn, S. M.; Gilmore, K.; Marshall, S. [KIPAC, Stanford University, 452 Lomita Mall, Stanford, CA 94309 (United States); Kratochvil, J. M.; Huffenberger, K. M. [Department of Physics, University of Miami, Coral Gables, FL 33124 (United States); May, M. [Physics Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); AlSayyad, Y.; Connolly, A.; Gibson, R. R.; Jones, L.; Krughoff, S. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Ahmad, Z.; Bankert, J.; Grace, E.; Hannel, M.; Lorenz, S. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Haiman, Z.; Jernigan, J. G., E-mail: djbard@slac.stanford.edu [Department of Astronomy and Astrophysics, Columbia University, New York, NY 10027 (United States); and others

2013-09-01T23:59:59.000Z

7

COSMOLOGICAL CONSTRAINTS FROM SUNYAEV-ZEL'DOVICH-SELECTED CLUSTERS WITH X-RAY OBSERVATIONS IN THE FIRST 178 deg[superscript 2] OF THE SOUTH POLE TELESCOPE SURVEY  

E-Print Network [OSTI]

We use measurements from the South Pole Telescope (SPT) Sunyaev-Zel'dovich (SZ) cluster survey in combination with X-ray measurements to constrain cosmological parameters. We present a statistical method that fits for the ...

Andersson, Karl

8

Cosmological data and indications for new physics  

SciTech Connect (OSTI)

Data from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), combined with the nine-year data release from the WMAP satellite, provide very precise measurements of the cosmic microwave background (CMB) angular anisotropies down to very small angular scales. Augmented with measurements from Baryonic Acoustic Oscillations surveys and determinations of the Hubble constant, we investigate whether there are indications for new physics beyond a Harrison-Zel'dovich model for primordial perturbations and the standard number of relativistic degrees of freedom at primordial recombination. All combinations of datasets point to physics beyond the minimal Harrison-Zel'dovich model in the form of either a scalar spectral index different from unity or additional relativistic degrees of freedom at recombination (e.g., additional light neutrinos). Beyond that, the extended datasets including either ACT or SPT provide very different indications: while the extended-ACT (eACT) dataset is perfectly consistent with the predictions of standard slow-roll inflation, the extended-SPT (eSPT) dataset prefers a non-power-law scalar spectral index with a very large variation with scale of the spectral index. Both eACT and eSPT favor additional light degrees of freedom on top of the Harrison-Zel'dovich model. eACT is consistent with zero neutrino masses, while eSPT favors nonzero neutrino masses at more than 95% confidence.

Benetti, Micol [Physics Department and ICRA, Università di Roma ''La Sapienza'', Ple. Aldo Moro 2, 00185, Rome (Italy); Gerbino, Martina; Melchiorri, Alessandro; Pagano, Luca [Physics Department and INFN, Università di Roma ''La Sapienza'', Ple Aldo Moro 2, 00185, Rome (Italy); Kinney, William H. [Department of Physics, University at Buffalo, the State University of New York, Buffalo, NY 14260-1500 (United States); Kolb, Edward W. [Department of Astronomy and Astrophysics, Enrico Fermi Institute, and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637-1433 (United States); Lattanzi, Massimiliano [Dipartimento di Fisica e Science della Terra, Università di Ferrara and INFN, sezione di Ferrara, Polo Scientifico e Tecnologico - Edificio C Via Saragat, 1, I-44122 Ferrara Italy (Italy); Riotto, Antonio, E-mail: micol.benetti@roma1.infn.it, E-mail: martina.gerbino@roma1.infn.it, E-mail: whkinney@buffalo.edu, E-mail: Rocky.Kolb@uchicago.edu, E-mail: lattanzi@fe.infn.it, E-mail: alessandro.melchiorri@roma1.infn.it, E-mail: luca.pagano@roma1.infn.it, E-mail: antonio.riotto@unige.ch [Department of Theoretical Physics and Center for Astroparticle Physics (CAP) 24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)

2013-10-01T23:59:59.000Z

9

The Cherenkov Telescope Array Large Size Telescope  

E-Print Network [OSTI]

The two arrays of the Very High Energy gamma-ray observatory Cherenkov Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA to achieve a low-energy threshold of 20 GeV, which is critical for important studies in astrophysics, astroparticle physics and cosmology. This work presents the key specifications and performance of the current LST design in the light of the CTA scientific objectives.

Ambrosi, G; Baba, H; Bamba, A; Barceló, M; de Almeida, U Barres; Barrio, J A; Bigas, O Blanch; Boix, J; Brunetti, L; Carmona, E; Chabanne, E; Chikawa, M; Colin, P; Conteras, J L; Cortina, J; Dazzi, F; Deangelis, A; Deleglise, G; Delgado, C; Díaz, C; Dubois, F; Fiasson, A; Fink, D; Fouque, N; Freixas, L; Fruck, C; Gadola, A; García, R; Gascon, D; Geffroy, N; Giglietto, N; Giordano, F; Grañena, F; Gunji, S; Hagiwara, R; Hamer, N; Hanabata, Y; Hassan, T; Hatanaka, K; Haubold, T; Hayashida, M; Hermel, R; Herranz, D; Hirotani, K; Inoue, S; Inoue, Y; Ioka, K; Jablonski, C; Kagaya, M; Katagiri, H; Kishimoto, T; Kodani, K; Kohri, K; Konno, Y; Koyama, S; Kubo, H; Kushida, J; Lamanna, G; Flour, T Le; López-Moya, M; López, R; Lorenz, E; Majumdar, P; Manalaysay, A; Mariotti, M; Martínez, G; Martínez, M; Mazin, D; Miranda, J M; Mirzoyan, R; Monteiro, I; Moralejo, A; Murase, K; Nagataki, S; Nakajima, D; Nakamori, T; Nishijima, K; Noda, K; Nozato, A; Ohira, Y; Ohishi, M; Ohoka, H; Okumura, A; Orito, R; Panazol, J L; Paneque, D; Paoletti, R; Paredes, J M; Pauletta, G; Podkladkin, S; Prast, J; Rando, R; Reimann, O; Ribó, M; Rosier-Lees, S; Saito, K; Saito, T; Saito, Y; Sakaki, N; Sakonaka, R; Sanuy, A; Sasaki, H; Sawada, M; Scalzotto, V; Schultz, S; Schweizer, T; Shibata, T; Shu, S; Sieiro, J; Stamatescu, V; Steiner, S; Straumann, U; Sugawara, R; Tajima, H; Takami, H; Tanaka, S; Tanaka, M; Tejedor, L A; Terada, Y; Teshima, M; Totani, T; Ueno, H; Umehara, K; Vollhardt, A; Wagner, R; Wetteskind, H; Yamamoto, T; Yamazaki, R; Yoshida, A; Yoshida, T; Yoshikoshi, T

2013-01-01T23:59:59.000Z

10

VST telescope dynamic analisys and position control algorithms  

E-Print Network [OSTI]

The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope to be installed on Cerro Paranal in the Atacama desert, Northern Chile, in the European Southern Observatory (ESO) site. The VST is a wide-field imaging facility planned to supply databases for the ESO Very Large Telescope (VLT) science and carry out stand-alone observations in the UV to I spectral range. So far no telescope has been dedicated entirely to surveys; the VST will be the first survey telescope to start the operation, as a powerful survey facility for the VLT observatory. This paper will focus on the axes motion control system. The dynamic model of the telescope will be analyzed, as well as the effect of the wind disturbance on the telescope performance. Some algorithms for the telescope position control will be briefly discussed.

P. Schipani; D. Mancini

2001-12-05T23:59:59.000Z

11

Solar Simulations for the Atacama Large Millimeter Observatory Network  

E-Print Network [OSTI]

The Atacama Large Millimeter/submillimeter Array (ALMA) will be a valuable tool for observing the chromosphere of our Sun at (sub-)millimeter wavelengths at high spatial, temporal and spectral resolution and as such has great potential to address long-standing scientific questions in solar physics. In order to make the best use of this scientific opportunity, the Solar Simulations for the Atacama Large Millimeter Observatory Network has been initiated. A key goal of this international collaboration is to support the preparation and interpretation of future observations of the Sun with ALMA.

Wedemeyer, Sven; Brajsa, Roman; Barta, Miroslav; Shimojo, Masumi

2015-01-01T23:59:59.000Z

12

HEAVY DUST OBSCURATION OF z = 7 GALAXIES IN A COSMOLOGICAL HYDRODYNAMIC SIMULATION  

SciTech Connect (OSTI)

Hubble Space Telescope observations with the Wide Field Camera 3/Infrared reveal that galaxies at z ? 7 have very blue ultraviolet (UV) colors, consistent with these systems being dominated by young stellar populations with moderate or little attenuation by dust. We investigate UV and optical properties of the high-z galaxies in the standard cold dark matter model using a high-resolution adaptive mesh refinement cosmological hydrodynamic simulation. For this purpose, we perform panchromatic three-dimensional dust radiative transfer calculations on 198 galaxies of stellar mass 5 × 10{sup 8}-3 × 10{sup 10} M{sub ?} with three parameters: the dust-to-metal ratio, the extinction curve, and the fraction of directly escaped light from stars (f{sub esc}). Our stellar mass function is found to be in broad agreement with Gonzalez et al., independent of these parameters. We find that our heavily dust-attenuated galaxies (A{sub V} ? 1.8) can also reasonably match modest UV-optical colors, blue UV slopes, as well as UV luminosity functions, provided that a significant fraction (?10%) of light directly escapes from them. The observed UV slope and scatter are better explained with a Small-Magellanic-Cloud-type extinction curve, whereas a Milky-Way-type curve also predicts blue UV colors due to the 2175 Å bump. We expect that upcoming observations by the Atacama Large Millimeter/submillimeter Array will be able to test this heavily obscured model.

Kimm, Taysun; Cen, Renyue [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States)

2013-10-10T23:59:59.000Z

13

E-Print Network 3.0 - allen telescope array Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

5 FISICA: The Florida Image Slicer for Infrared Cosmology & Astrophysics Summary: - to 10-meter telescopes); multi-element mirror arrays (requiring painstaking alignment and...

14

Iron control of past productivity in the coastal upwelling system off the Atacama Desert, Chile  

E-Print Network [OSTI]

Iron control of past productivity in the coastal upwelling system off the Atacama Desert, Chile in the productivity of the upwelling system off presently arid northern Chile during the last 100,000 years. Changes in productivity are found to be in phase with the precessional cycle ($20,000 years) and with inputs of iron from

Demouchy, Sylvie

15

Laser Cosmology  

E-Print Network [OSTI]

Recent years have seen tremendous progress in our understanding of the cosmos, which in turn points to even deeper questions to be further addressed. Concurrently the laser technology has undergone dramatic revolutions, providing exciting opportunity for science applications. History has shown that the symbiosis between direct observations and laboratory investigation is instrumental in the progress of astrophysics. We believe that this remains true in cosmology. Current frontier phenomena related to particle astrophysics and cosmology typically involve one or more of the following conditions: (1) extremely high energy events; (2) very high density, high temperature processes; (3) super strong field environments. Laboratory experiments using high intensity lasers can calibrate astrophysical observations, investigate underlying dynamics of astrophysical phenomena, and probe fundamental physics in extreme limits. In this article we give an overview of the exciting prospect of laser cosmology. In particular, we showcase its unique capability of investigating frontier cosmology issues such as cosmic accelerator and quantum gravity.

Pisin Chen

2014-02-24T23:59:59.000Z

16

SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network  

E-Print Network [OSTI]

The Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) was initiated in 2014 in connection with two ALMA development studies. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new tool, which can also observe the Sun at high spatial, temporal, and spectral resolution. The international SSALMONetwork aims at coordinating the further development of solar observing modes for ALMA and at promoting scientific opportunities for solar physics with particular focus on numerical simulations, which can provide important constraints for the observing modes and can aid the interpretation of future observations. The radiation detected by ALMA originates mostly in the solar chromosphere - a complex and dynamic layer between the photosphere and corona, which plays an important role in the transport of energy and matter and the heating of the outer layers of the solar atmosphere. Potential targets include active regions, prominences, quiet Sun regions, flares. Here, we give a...

Wedemeyera, S; Brajsa, R; Barta, M; Hudson, H; Fleishman, G; Loukitcheva, M; Fleck, B; Kontar, E; De Pontieu, B; Tiwari, S; Kato, Y; Soler, R; Yagoubov, P; Black, J H; Antolin, P; Gunar, S; Labrosse, N; Benz, A O; Nindos, A; Steffen, M; Scullion, E; Doyle, J G; Zaqarashvili, T; Hanslmeier, A; Nakariakov, V M; Heinzel, P; Ayres, T; Karlicky, M

2015-01-01T23:59:59.000Z

17

On an Alternative Cosmology  

E-Print Network [OSTI]

The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key words: standard cosmological model, alternative cosmology, barionic symmetry, typical universe, quasars, cosmic rays.

A. Vankov

1998-11-10T23:59:59.000Z

18

The supernova cosmology cookbook: Bayesian numerical recipes  

E-Print Network [OSTI]

Theoretical and observational cosmology have enjoyed a number of significant successes over the last two decades. Cosmic microwave background measurements from the Wilkinson Microwave Anisotropy Probe and Planck, together with large-scale structure and supernova (SN) searches, have put very tight constraints on cosmological parameters. Type Ia supernovae (SNIa) played a central role in the discovery of the accelerated expansion of the Universe, recognised by the Nobel Prize in Physics in 2011. The last decade has seen an enormous increase in the amount of high quality SN observations, with SN catalogues now containing hundreds of objects. This number is expected to increase to thousands in the next few years, as data from next-generation missions, such as the Dark Energy Survey and Large Synoptic Survey Telescope become available. In order to exploit the vast amount of forthcoming high quality data, it is extremely important to develop robust and efficient statistical analysis methods to answer cosmological q...

Karpenka, N V

2015-01-01T23:59:59.000Z

19

SYSTEMATICS AND EVOLUTION IN THE TRIBE SCHIZOPETALAE (BRASSICACEAE): A MOLECULAR, MORPHOLOGICAL, AND ECOLOGICAL ANALYSIS OF THE DIVERSIFICATION OF AN ENDEMIC LINEAGE FROM THE ATACAMA DESERT (CHILE)  

E-Print Network [OSTI]

As aridity has been identified as an active promoter of diversification in deserts, attempts to test organismal differentiation in the Atacama Desert have resulted particularly challenging. Most limitations are related to ...

Toro Nunez, Oscar Fernando

2013-12-31T23:59:59.000Z

20

Alignment telescope for Antares  

SciTech Connect (OSTI)

The Antares Automatic Alignment System employs a specially designed telescope for alignment of its laser beamlines. There are two telescopes in the system, and since each telescope is a primary alignment reference, stringent boresight accuracy and stability over the focus range were required. Optical and mechanical designs, which meet this requirement as well as that of image quality over a wide wavelength band, are described. Special test techniques for initial assembly and alignment of the telescope are also presented. The telescope, which has a 180-mm aperture FK51-KZF2 type glass doublet objective, requires a boresight accuracy of 2.8 ..mu..rad at two focal lengths, and object distances between 11 meters and infinity. Travel of a smaller secondary doublet provides focus from 11 m to infinity with approximately 7.8 m effective focal length. By flipping in a third doublet, the effective focal length is reduced to 2.5 m. Telescope alignment was accomplished by using a rotary air bearing to establish an axis in front of the system and placing the focus of a Laser Unequal Path Interferometer (LUPI) at the image plane.

Appert, Q.D.; Swann, T.A.; Ward, J.H.; Hardesty, C.; Wright, L.

1983-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

LXCDM cosmologies: solving the cosmological coincidence problem?  

E-Print Network [OSTI]

We explore the possibility of having a composite (self-conserved) dark energy (DE) whose dynamics is controlled by the quantum running of the cosmological parameters. We find that within this scenario it is feasible to find an explanation for the cosmological coincidence problem and at the same time a good qualitative description of the present data.

Javier Grande; Joan Sola; Hrvoje Stefancic

2006-09-25T23:59:59.000Z

22

Cosmology with Supernovae  

E-Print Network [OSTI]

This review gives an update of the cosmological use of SNe Ia and the progress made in testing their properties from the local universe to high-z. The cosmological road from high-z supernovae down to Galactic SNe Ia is followed in search of the answer to standing questions on their nature and their validity as cosmological indicators.

P. Ruiz-Lapuente

2003-04-07T23:59:59.000Z

23

PLANETARY TRANSITS WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY RADIO INTERFEROMETER  

SciTech Connect (OSTI)

Planetary transits are commonly observed at visible wavelengths. Here we investigate the shape of a planetary transit observed at radio wavelengths. Solar maps at 17 GHz are used as a proxy for the stellar eclipse by several sizes of planets from super-Earths to hot Jupiters. The relative depth at mid-transit is the same as observed at visible wavelengths, but the limb brightening of the stellar disk at 17 GHz is clearly seen in the shape of the transit light curve. Moreover, when the planet occults an active region the depth of the transit decreases even further, depending on the brightness of the active region relative to the surrounding disk. For intense active region, with 50 times the brightness temperature of the surrounding disk, the decrease can supercede the unperturbed transit depth depending on the size of the eclipsing planet. For a super-Earth (R{sub p} = 0.02 R{sub s} ) crossing, the decrease in intensity is 0.04%, increasing to 0.86% in the case when a strong active region is present. On the other hand, for a hot Jupiter with R{sub p} = 0.17R{sub s} , the unperturbed transit depth is 3% increasing to 4.7% when covering this strong active region. This kind of behavior can be verified with observation of planetary transits with the Atacama Large Millimeter/submillimeter Array radio interferometer.

Selhorst, C. L.; Barbosa, C. L. [IP and D, Universidade do Vale do Paraíba (UNIVAP), São José dos Campos, SP (Brazil)] [IP and D, Universidade do Vale do Paraíba (UNIVAP), São José dos Campos, SP (Brazil); Válio, Adriana, E-mail: caius@univap.br [CRAAM, Universidade Presbiteriana Mackenzie, São Paulo, SP (Brazil)] [CRAAM, Universidade Presbiteriana Mackenzie, São Paulo, SP (Brazil)

2013-11-10T23:59:59.000Z

24

Averaging Hypotheses in Newtonian Cosmology  

E-Print Network [OSTI]

Average properties of general inhomogeneous cosmological models are discussed in the Newtonian framework. It is shown under which circumstances the average flow reduces to a member of the standard Friedmann--Lema\\^\\i tre cosmologies. Possible choices of global boundary conditions of inhomogeneous cosmologies as well as consequences for the interpretation of cosmological parameters are put into perspective.

T. Buchert

1995-12-20T23:59:59.000Z

25

Neutrino conversions in cosmological gamma-ray burst fireballs  

E-Print Network [OSTI]

We study neutrino conversions in a recently envisaged source of high-energy neutrinos (E \\geq 10^6 GeV), that is, in the vicinity of cosmological Gamma-Ray Burst fireballs (GRB). We consider the effects of flavor and spin-flavor conversions and point out that in both situations, a some what higher than estimated high energy tau neutrino flux from GRBs is expected in new km^2 surface area under water/ice neutrino telescopes.

H. Athar

2000-04-20T23:59:59.000Z

26

Cosmology and New Physics  

E-Print Network [OSTI]

A comparison of the standard models in particle physics and in cosmology demonstrates that they are not compatible, though both are well established. Basics of modern cosmology are briefly reviewed. It is argued that the measurements of the main cosmological parameters are achieved through many independent physical phenomena and this minimizes possible interpretation errors. It is shown that astronomy demands new physics beyond the frameworks of the (minimal) standard model in particle physics. More revolutionary modifications of the basic principles of the theory are also discussed.

A. D. Dolgov

2006-06-21T23:59:59.000Z

27

Grid Integration of Robotic Telescopes  

E-Print Network [OSTI]

Robotic telescopes and grid technology have made significant progress in recent years. Both innovations offer important advantages over conventional technologies, particularly in combination with one another. Here, we introduce robotic telescopes used by the Astrophysical Institute Potsdam as ideal instruments for building a robotic telescope network. We also discuss the grid architecture and protocols facilitating the network integration that is being developed by the German AstroGrid-D project. Finally, we present three user interfaces employed for this purpose.

F. Breitling; T. Granzer; H. Enke

2009-03-23T23:59:59.000Z

28

Cosmological Ontology and Epistemology  

E-Print Network [OSTI]

In cosmology, we would like to explain our observations and predict future observations from theories of the entire universe. Such cosmological theories make ontological assumptions of what entities exist and what their properties and relationships are. One must also make epistemological assumptions or metatheories of how one can test cosmological theories. Here I shall propose a Bayesian analysis in which the likelihood of a complete theory is given by the normalized measure it assigns to the observation used to test the theory. In this context, a discussion is given of the trade-off between prior probabilities and likelihoods, of the measure problem of cosmology, of the death of Born's rule, of the Boltzmann brain problem, of whether there is a better principle for prior probabilities than mathematical simplicity, and of an Optimal Argument for the Existence of God.

Don N. Page

2014-12-23T23:59:59.000Z

29

Massive neutrinos and cosmology  

E-Print Network [OSTI]

The present experimental results on neutrino flavour oscillations provide evidence for non-zero neutrino masses, but give no hint on their absolute mass scale, which is the target of beta decay and neutrinoless double-beta decay experiments. Crucial complementary information on neutrino masses can be obtained from the analysis of data on cosmological observables, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure. In this review we describe in detail how free-streaming massive neutrinos affect the evolution of cosmological perturbations. We summarize the current bounds on the sum of neutrino masses that can be derived from various combinations of cosmological data, including the most recent analysis by the WMAP team. We also discuss how future cosmological experiments are expected to be sensitive to neutrino masses well into the sub-eV range.

Julien Lesgourgues; Sergio Pastor

2006-05-29T23:59:59.000Z

30

Dark gravity and cosmology  

E-Print Network [OSTI]

The previous version of this article was a first attempt to confront the Dark Gravity theory to cosmological data. However, more recent developments lead to the conclusion that the cosmological principle is probably not valid in Dark Gravity so that this kind of analysis is at best very premature. A more recent and living review of the Dark Gravity theory can be found in gr-qc/0610079

F. Henry-Couannier; A. Tilquin; C. Tao; A. Ealet

2007-10-24T23:59:59.000Z

31

High Energy Neutrino Telescopes  

E-Print Network [OSTI]

This paper presents a review of the history, motivation and current status of high energy neutrino telescopes. Many years after these detectors were first conceived, the operation of kilometer-cubed scale detectors is finally on the horizon at both the South Pole and in the Mediterranean Sea. These new detectors will perhaps provide us the first view of high energy astrophysical objects with a new messenger particle and provide us with our first real glimpse of the distant universe at energies above those accessible by gamma-ray instruments. Some of the topics that can be addressed by these new instruments include the origin of cosmic rays, the nature of dark matter, and the mechanisms at work in high energy astrophysical objects such as gamma-ray bursts, active galactic nuclei, pulsar wind nebula and supernova remnants.

K. D. Hoffman

2008-12-18T23:59:59.000Z

32

Space Telescope Programs Hubble Observatory  

E-Print Network [OSTI]

Assurance/Configuration Management Mr. Christopher Scholz EAG QA Manager #12;Space Telescope Programs Hubble · COS-UCB-002 QA Implementation Plan Released December 1, 1999 · COS-UCB-003 CM Plan released DecemberSpace Telescope Programs Hubble Observatory HST-COS FUV PER 11/8/00 FUV Detector System Quality

Colorado at Boulder, University of

33

Cosmology and the Bispectrum  

SciTech Connect (OSTI)

The present spatial distribution of galaxies in the Universe is non-Gaussian, with 40% skewness in 50 h{sup -1} Mpc spheres, and remarkably little is known about the information encoded in it about cosmological parameters beyond the power spectrum. In this work they present an attempt to bridge this gap by studying the bispectrum, paying particular attention to a joint analysis with the power spectrum and their combination with CMB data. They address the covariance properties of the power spectrum and bispectrum including the effects of beat coupling that lead to interesting cross-correlations, and discuss how baryon acoustic oscillations break degeneracies. They show that the bispectrum has significant information on cosmological parameters well beyond its power in constraining galaxy bias, and when combined with the power spectrum is more complementary than combining power spectra of different samples of galaxies, since non-Gaussianity provides a somewhat different direction in parameter space. In the framework of flat cosmological models they show that most of the improvement of adding bispectrum information corresponds to parameters related to the amplitude and effective spectral index of perturbations, which can be improved by almost a factor of two. Moreover, they demonstrate that the expected statistical uncertainties in {sigma}s of a few percent are robust to relaxing the dark energy beyond a cosmological constant.

Sefusatti, Emiliano; /Fermilab /CCPP, New York; Crocce, Martin; Pueblas, Sebastian; Scoccimarro, Roman; /CCPP, New York

2006-04-01T23:59:59.000Z

34

Nuclear physics and cosmology  

SciTech Connect (OSTI)

There are important aspects of Cosmology, the scientific study of the large scale properties of the universe as a whole, for which nuclear physics can provide insights. Here, we will focus on Standard Big-Bang Nucleosynthesis and we refer to the previous edition of the School [1] for the aspects concerning the variations of constants in nuclear cosmo-physics.

Coc, Alain [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), CNRS/IN2P3, Université Paris Sud 11, UMR 8609, Bâtiment 104, F-91405 Orsay Campus (France)

2014-05-09T23:59:59.000Z

35

Relativistic Fractal Cosmologies  

E-Print Network [OSTI]

This article reviews an approach for constructing a simple relativistic fractal cosmology whose main aim is to model the observed inhomogeneities of the distribution of galaxies by means of the Lemaitre-Tolman solution of Einstein's field equations for spherically symmetric dust in comoving coordinates. This model is based on earlier works developed by L. Pietronero and J.R. Wertz on Newtonian cosmology, whose main points are discussed. Observational relations in this spacetime are presented, together with a strategy for finding numerical solutions which approximate an averaged and smoothed out single fractal structure in the past light cone. Such fractal solutions are shown, with one of them being in agreement with some basic observational constraints, including the decay of the average density with the distance as a power law (the de Vaucouleurs' density power law) and the fractal dimension in the range 1 fractal model we find that all Friedmann models look inhomogeneous along the backward null cone, with a departure from the observable homogeneous region at relatively close ranges. It is also shown that with these same observational relations the Einstein-de Sitter model can have an interpretation where it has zero global density, a result consistent with the "zero global density postulate" advanced by Wertz for hierarchical cosmologies and conjectured by Pietronero for fractal cosmological models. The article ends with a brief discussion on the possible link between this model and nonlinear and chaotic dynamics.

Marcelo B. Ribeiro

2009-10-26T23:59:59.000Z

36

Supersymmetric quantum cosmological billiards  

SciTech Connect (OSTI)

D=11 supergravity near a spacelike singularity admits a cosmological billiard description based on the hyperbolic Kac-Moody group E{sub 10}. The quantization of this system via the supersymmetry constraint is shown to lead to wave functions involving automorphic (Maass wave) forms under the modular group W{sup +}(E{sub 10}) congruent with PSL{sub 2}(O) with Dirichlet boundary conditions on the billiard domain. A general inequality for the Laplace eigenvalues of these automorphic forms implies that the wave function of the Universe is generically complex and always tends to zero when approaching the initial singularity. We discuss possible implications of this result for the question of singularity resolution in quantum cosmology and comment on the differences with other approaches.

Kleinschmidt, Axel; Koehn, Michael; Nicolai, Hermann [Physique Theorique et Mathematique and International Solvay Institutes, Universite Libre de Bruxelles, Boulevard du Triomphe, ULB-CP231, BE-1050 Bruxelles (Belgium); Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, DE-14476 Golm (Germany)

2009-09-15T23:59:59.000Z

37

Cosmological Insights from Supernovae  

E-Print Network [OSTI]

While low-z Type Ia supernovae are used to measure the present rate of expansion of the Universe, high-z Type Ia measure its variation due to the cosmic matter-energy content. Results from those determinations imply a low matter density Universe with a non-zero cosmological constant (vacuum-energy component). The expansion rate of the Universe accelerates, according to these determinations. The validity of the Type Ia supernova approach for this cosmological research is addressed. An account is given of additional prospects to further investigate through supernovae what the Universe is made of. Those attempts range from constraining the large scale dark matter distribution to further test and interpret the presence of a vacuum energy component.

P. Ruiz-Lapuente

1998-10-26T23:59:59.000Z

38

Quantum cosmology: a review  

E-Print Network [OSTI]

In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity: De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting "microscopic" degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.

Bojowald, Martin

2015-01-01T23:59:59.000Z

39

Holography from quantum cosmology  

E-Print Network [OSTI]

The Weyl-Wigner-Groenewold-Moyal formalism of deformation quantization is applied to the closed Friedmann-Lema\\^itre-Robertson-Walker (FLRW) cosmological model. We show that the phase space average for the surface of the apparent horizon is quantized in units of the Planck's surface, and that the total entropy of the universe is also quantized. Taking into account these two concepts, it is shown that 't Hooft conjecture on the cosmological holographic principle (CHP) in radiation and dust dominated quantum universes is satisfied as a manifestation of quantization. This suggests that the entire universe (not only inside the apparent horizon) can be seen as a two-dimensional information structure encoded on the apparent horizon.

M. Rashki; S. Jalalzadeh

2014-12-12T23:59:59.000Z

40

Quantum cosmology: a review  

E-Print Network [OSTI]

In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity: De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting "microscopic" degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.

Martin Bojowald

2015-01-20T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Cosmology with running parameters  

E-Print Network [OSTI]

The experimental evidence that the equation of state (EOS) of the dark energy (DE) could be evolving with time/redshift (including the possibility that it might behave phantom-like near our time) suggests that there might be dynamical DE fields that could explain this behavior. We propose, instead, that a variable cosmological term (including perhaps a variable Newton's gravitational coupling too) may account in a natural way for all these features.

Joan Sola

2005-12-05T23:59:59.000Z

42

Standard cosmology delayed  

SciTech Connect (OSTI)

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Choudhury, Debajyoti [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Ghoshal, Debashis [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Sen, Anjan Ananda, E-mail: debajyoti.choudhury@gmail.com, E-mail: dghoshal@mail.jnu.ac.in, E-mail: anjan.ctp@jmi.ac.in [Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi 110025 (India)

2012-02-01T23:59:59.000Z

43

Standard Cosmology Delayed  

E-Print Network [OSTI]

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Debajyoti Choudhury; Debashis Ghoshal; Anjan Ananda Sen

2012-02-06T23:59:59.000Z

44

Standard Cosmology Delayed  

E-Print Network [OSTI]

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Choudhury, Debajyoti; Sen, Anjan Ananda

2011-01-01T23:59:59.000Z

45

Cosmological shock waves  

E-Print Network [OSTI]

Large-scale structure formation, accretion and merging processes, AGN activity produce cosmological gas shocks. The shocks convert a fraction of the energy of gravitationally accelerated flows to internal energy of the gas. Being the main gas-heating agent, cosmological shocks could amplify magnetic fields and accelerate energetic particles via the multi-fluid plasma relaxation processes. We first discuss the basic properties of standard single-fluid shocks. Cosmological plasma shocks are expected to be collisionless. We then review the plasma processes responsible for the microscopic structure of collisionless shocks. A tiny fraction of the particles crossing the shock is injected into the non-thermal energetic component that could get a substantial part of the ram pressure power dissipated at the shock. The energetic particles penetrate deep into the shock upstream producing an extended shock precursor. Scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are discussed. We show that the multi-fluid nature of collisionless shocks results in excessive gas compression, energetic particle acceleration, precursor gas heating, magnetic field amplification and non-thermal emission. Multi-fluid shocks provide a reduced gas entropy production and could also modify the observable thermodynamic scaling relations for clusters of galaxies.

A. M. Bykov; K. Dolag; F. Durret

2008-01-07T23:59:59.000Z

46

Particle Physics and Cosmology  

E-Print Network [OSTI]

Today, both particle physics and cosmology are described by few parameter Standard Models, i.e. it is possible to deduce consequence of particle physics in cosmology and vice verse. The former is examined in this lecture, in light of the recent systematic exploration of the electroweak scale by the LHC experiments. The two main results of the first phase of the LHC, the discovery of a Higgs-like particle and the absence so far of new particles predicted by "natural" theories beyond the Standard Model (supersymmetry, extra-dimension and composite Higgs) are put in a historical context to enlighten their importance and then presented extensively. To be complete, a short review from the neutrino physics, which can not be probed at LHC, is also given. The ability of all these results to resolve the 3 fundamental questions of cosmology about the nature of dark energy and dark matter as well as the origin of matter-antimatter asymmetry is discussed in each case.

P. Pralavorio

2014-12-04T23:59:59.000Z

47

Wide field of view telescope  

DOE Patents [OSTI]

A wide field of view telescope having two concave and two convex reflective surfaces, each with an aspheric surface contour, has a flat focal plane array. Each of the primary, secondary, tertiary, and quaternary reflective surfaces are rotationally symmetric about the optical axis. The combination of the reflective surfaces results in a wide field of view in the range of approximately 3.8.degree. to approximately 6.5.degree.. The length of the telescope along the optical axis is approximately equal to or less than the diameter of the largest of the reflective surfaces.

Ackermann, Mark R. (Albuquerque, NM); McGraw, John T. (Placitas, NM); Zimmer, Peter C. (Albuquerque, NM)

2008-01-15T23:59:59.000Z

48

Cosmology for high energy physicists  

SciTech Connect (OSTI)

The standard big bang model of cosmology is presented. Although not perfect, its many successes make it a good starting point for most discussions of cosmology. Places are indicated where well understood laboratory physics is incorporated into the big bang, leading to successful predictions. Much less established aspects of high energy physics and some of the new ideas they have introduced into the field of cosmology are discussed, such as string theory, inflation and monopoles. 49 refs., 5 figs.

Albrecht, A.

1987-11-01T23:59:59.000Z

49

Neutrino telescopes in the World  

SciTech Connect (OSTI)

Neutrino astronomy has rapidly developed these last years, being the only way to get specific and reliable information about astrophysical objects still poorly understood.Currently two neutrino telescopes are operational in the World: BAIKAL, in the lake of the same name in Siberia, and AMANDA, in the ices of the South Pole. Two telescopes of the same type are under construction in the Mediterranean Sea: ANTARES and NESTOR. All these telescopes belong to a first generation, with an instrumented volume smaller or equal to 0.02 km3. Also in the Mediterranean Sea, the NEMO project is just in its stag phase, within the framework of a cubic kilometer size neutrino telescope study. Lastly, the ICECUBE detector, with a volume reaching about 1 km3, is under construction on the site of AMANDA experiment, while an extension of the BAIKAL detector toward km3 is under study. We will present here the characteristics of these experiments, as well as the results of their observations.

Ernenwein, J.-P. [GRPHE, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse cedex (France)

2007-01-12T23:59:59.000Z

50

FISICA: The Florida Image Slicer for Infrared Cosmology & Astrophysics  

E-Print Network [OSTI]

We report on the design, fabrication, and on-sky performance of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA)- a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R \\sim 1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. Finally, we present performance results from observations with FISICA at the KPNO 4-m telescope and comparisons of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.

Stephen Eikenberry; S. Nicholas Raines; Nicolas Gruel; Richard Elston; Rafael Guzman; Jeff Julian; Glenn Boreman; Paul Glenn; Greg Hull-Allen; Jeff Hoffmann; Michael Rodgers; Kevin Thompson; Scott Flint; Lovell Comstock; Bruce Myrick

2006-04-27T23:59:59.000Z

51

Cosmological models with isotropic singularities  

E-Print Network [OSTI]

In 1985 Goode and Wainwright devised the concept of an isotropic singularity. Since that time, numerous authors have explored the interesting consequences, in mathematical cosmology, of assuming the existence of this type of singularity. In this paper, we collate all examples of cosmological models which are known to admit an isotropic singularity, and make a number of observations regarding their general characteristics.

Susan M. Scott; Geoffery Ericksson

1998-12-07T23:59:59.000Z

52

The Standard Cosmological Model  

E-Print Network [OSTI]

The Standard Model of Particle Physics (SMPP) is an enormously successful description of high energy physics, driving ever more precise measurements to find "physics beyond the standard model", as well as providing motivation for developing more fundamental ideas that might explain the values of its parameters. Simultaneously, a description of the entire 3-dimensional structure of the present-day Universe is being built up painstakingly. Most of the structure is stochastic in nature, being merely the result of the particular realisation of the "initial conditions" within our observable Universe patch. However, governing this structure is the Standard Model of Cosmology (SMC), which appears to require only about a dozen parameters. Cosmologists are now determining the values of these quantities with increasing precision in order to search for "physics beyond the standard model", as well as trying to develop an understanding of the more fundamental ideas which might explain the values of its parameters. Although it is natural to see analogies between the two Standard Models, some intrinsic differences also exist, which are discussed here. Nevertheless, a truly fundamental theory will have to explain both the SMPP and SMC, and this must include an appreciation of which elements are deterministic and which are accidental. Considering different levels of stochasticity within cosmology may make it easier to accept that physical parameters in general might have a non-deterministic aspect.

Douglas Scott

2005-10-26T23:59:59.000Z

53

Cosmology with decaying particles  

SciTech Connect (OSTI)

We consider a cosmological model in which an unstable massive relic particle species (denoted by X) has an initial mass density relative to baryons ..beta../sup -1/ identically equal rho/sub X//rho/sub B/ >> 1, and then decays recently (redshift z less than or equal to 1000) into particles which are still relativistic today (denoted by R). We write down and solve the coupled equations for the cosmic scale factor a(t), the energy density in the various components (rho/sub X/, rho/sub R/, rho/sub B/), and the growth of linear density perturbations (delta rho/rho). The solutions form a one parameter (..beta..) family of solutions; physically ..beta../sup -1/ approx. = (..cap omega../sub R//..cap omega../sub NR/) x (1 + z/sub D/) = (ratio today of energy density of relativistic to nonrelativistic particles) x (1 + redshift of (decay)). We discuss the observational implications of such a cosmological model and compare our results to earlier results computed in the simultaneous decay approximation. In an appendix we briefly consider the case where one of the decay products of the X is massive and becomes nonrelativistic by the present epoch. 21 references.

Turner, M.S.

1984-09-01T23:59:59.000Z

54

THE OPTIMAL GRAVITATIONAL LENS TELESCOPE  

SciTech Connect (OSTI)

Given an observed gravitational lens mirage produced by a foreground deflector (cf. galaxy, quasar, cluster, ...), it is possible via numerical lens inversion to retrieve the real source image, taking full advantage of the magnifying power of the cosmic lens. This has been achieved in the past for several remarkable gravitational lens systems. Instead, we propose here to invert an observed multiply imaged source directly at the telescope using an ad hoc optical instrument which is described in the present paper. Compared to the previous method, this should allow one to detect fainter source features as well as to use such an optimal gravitational lens telescope to explore even fainter objects located behind and near the lens. Laboratory and numerical experiments illustrate this new approach.

Surdej, J.; Hanot, C.; Sadibekova, T. [Department of Astrophysics, Geophysics and Oceanography (AGO), AEOS Group, Liege University, Allee du 6 Aout 17, 4000 Liege (Belgium); Delacroix, C.; Habraken, S. [Department of Physics (DEPHY), Hololab Group, Liege University, Allee du 6 Aout 17, 4000 Liege (Belgium); Coleman, P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Dominik, M. [SUPA, University of St Andrews, School of Physics and Astronomy, North Haugh, St Andrews, KY16 9SS (United Kingdom); Le Coroller, H. [Observatoire de Haute Provence, F-04870 Saint Michel l'Observatoire (France); Mawet, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Quintana, H. [Departmento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, CL 22 Santiago (Chile); Sluse, D., E-mail: surdej@astro.ulg.ac.b [Astronomisches Rechen-Institut am Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstrasse 12-14, 69120 Heidelberg (Germany)

2010-05-15T23:59:59.000Z

55

Large Synoptic Survey Telescope: Dark Energy Science Collaboration  

E-Print Network [OSTI]

This white paper describes the LSST Dark Energy Science Collaboration (DESC), whose goal is the study of dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST). It provides an overview of dark energy science and describes the current and anticipated state of the field. It makes the case for the DESC by laying out a robust analytical framework for dark energy science that has been defined by its members and the comprehensive three-year work plan they have developed for implementing that framework. The analysis working groups cover five key probes of dark energy: weak lensing, large scale structure, galaxy clusters, Type Ia supernovae, and strong lensing. The computing working groups span cosmological simulations, galaxy catalogs, photon simulations and a systematic software and computational framework for LSST dark energy data analysis. The technical working groups make the connection between dark energy science and the LSST system. The working groups have close linkages, especially through the use of the photon simulations to study the impact of instrument design and survey strategy on analysis methodology and cosmological parameter estimation. The white paper describes several high priority tasks identified by each of the 16 working groups. Over the next three years these tasks will help prepare for LSST analysis, make synergistic connections with ongoing cosmological surveys and provide the dark energy community with state of the art analysis tools. Members of the community are invited to join the LSST DESC, according to the membership policies described in the white paper. Applications to sign up for associate membership may be made by submitting the Web form at http://www.slac.stanford.edu/exp/lsst/desc/signup.html with a short statement of the work they wish to pursue that is relevant to the LSST DESC.

LSST Dark Energy Science Collaboration

2012-11-01T23:59:59.000Z

56

Nuclear & Particle Physics, Astrophysics, Cosmology  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

production, nuclear weapons, and nuclear threat reduction Proton radiography, muon tomography, proton active interrogation, wide-angle, fast-response optical telescopes, and...

57

Testing cosmology with cosmic sound waves  

SciTech Connect (OSTI)

Wilkinson Microwave Anisotropy Probe (WMAP) observations have accurately determined the position of the first two peaks and dips in the cosmic microwave background (CMB) temperature power spectrum. These encode information on the ratio of the distance to the last scattering surface to the sound horizon at decoupling. However prerecombination processes can contaminate this distance information. In order to assess the amplitude of these effects, we use the WMAP data and evaluate the relative differences of the CMB peak and dip multipoles. We find that the position of the first peak is largely displaced with respect to the expected position of the sound horizon scale at decoupling. In contrast, the relative spacings of the higher extrema are statistically consistent with those expected from perfect harmonic oscillations. This provides evidence for a scale dependent phase shift of the CMB oscillations which is caused by gravitational driving forces affecting the propagation of sound waves before recombination. By accounting for these effects we have performed a Markov Chain Monte Carlo likelihood analysis of the location of WMAP extrema to constrain, in combination with recent BAO data, a constant dark energy equation of state parameter w. For a flat universe we find a strong 2{sigma} upper limit w<-1.10, and including the Hubble Space Telescope prior, we obtain w<-1.14, which is only marginally consistent with limits derived from the Supernova Legacy Survey sample. On the other hand, we infer larger limits for nonflat cosmologies. From the full CMB likelihood analysis, we also estimate the values of the shift parameter R and the multipole l{sub a} of the acoustic horizon at decoupling for several cosmologies, to test their dependence on model assumptions. Although the analysis of the full CMB spectra should always be preferred, using the position of the CMB peaks and dips provides a simple and consistent method for combining CMB constraints with other data sets.

Corasaniti, Pier Stefano [LUTH, Observatoire de Paris, CNRS UMR 8102, Universite Paris Diderot, 5 Place Jules Janssen, 92195 Meudon Cedex (France); Melchiorri, Alessandro [Dipartimento di Fisica e Sezione INFN, Universita degli Studi di Roma 'La Sapienza', Ple Aldo Moro 5, 00185, Rome (Italy); CERN, Theory Division, CH-1211 Geneva 23 (Switzerland)

2008-05-15T23:59:59.000Z

58

Cosmological perturbations on local systems  

E-Print Network [OSTI]

We study the effect of cosmological expansion on orbits--galactic, planetary, or atomic--subject to an inverse-square force law. We obtain the laws of motion for gravitational or electrical interactions from general relativity--in particular, we find the gravitational field of a mass distribution in an expanding universe by applying perturbation theory to the Robertson-Walker metric. Cosmological expansion induces an ($\\ddot a/a) \\vec r$ force where $a(t)$ is the cosmological scale factor. In a locally Newtonian framework, we show that the $(\\ddot a/a) \\vec r$ term represents the effect of a continuous distribution of cosmological material in Hubble flow, and that the total force on an object, due to the cosmological material plus the matter perturbation, can be represented as the negative gradient of a gravitational potential whose source is the material actually present. We also consider the effect on local dynamics of the cosmological constant. We calculate the perihelion precession of elliptical orbits due to the cosmological constant induced force, and work out a generalized virial relation applicable to gravitationally bound clusters.

Gregory S. Adkins; Jordan McDonnell; Richard N. Fell

2006-12-22T23:59:59.000Z

59

Protein folding and cosmology  

E-Print Network [OSTI]

Protein denaturing induced by supercooling is interpreted as a process where some or all internal symmetries of the native protein are spontaneously broken. Hence, the free-energy potential corresponding to a folding-funnel landscape becomes temperature-dependent and describes a phase transition. The idea that deformed vortices could be produced in the transition induced by temperature quenching, from native proteins to unfolded conformations is discussed in terms of the Zurek mechanism that implements the analogy between vortices, created in the laboratory at low energy, and the cosmic strings which are thought to have been left after symmetry breaking phase transitions in the early universe. An experiment is proposed to test the above idea which generalizes the cosmological analogy to also encompass biological systems and push a step ahead the view that protein folding is a biological equivalent of the big bang.

González-Diáz, P F

1997-01-01T23:59:59.000Z

60

Cosmological Collider Physics  

E-Print Network [OSTI]

We study the imprint of new particles on the primordial cosmological fluctuations. New particles with masses comparable to the Hubble scale produce a distinctive signature on the non-gaussianities. This feature arises in the squeezed limit of the correlation functions of primordial fluctuations. It consists of particular power law, or oscillatory, behavior that contains information about the masses of new particles. There is an angular dependence that gives information about the spin. We also have a relative phase that crucially depends on the quantum mechanical nature of the fluctuations and can be viewed as arising from the interference between two processes. While some of these features were noted before in the context of specific inflationary scenarios, here we give a general description emphasizing the role of symmetries in determining the final result.

Arkani-Hamed, Nima

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Protein folding and cosmology  

E-Print Network [OSTI]

Protein denaturing induced by supercooling is interpreted as a process where some or all internal symmetries of the native protein are spontaneously broken. Hence, the free-energy potential corresponding to a folding-funnel landscape becomes temperature-dependent and describes a phase transition. The idea that deformed vortices could be produced in the transition induced by temperature quenching, from native proteins to unfolded conformations is discussed in terms of the Zurek mechanism that implements the analogy between vortices, created in the laboratory at low energy, and the cosmic strings which are thought to have been left after symmetry breaking phase transitions in the early universe. An experiment is proposed to test the above idea which generalizes the cosmological analogy to also encompass biological systems and push a step ahead the view that protein folding is a biological equivalent of the big bang.

P. F. Gonzalez-Diaz; C. L. Siguenza

1997-06-04T23:59:59.000Z

62

Cosmology and the weak interaction  

SciTech Connect (OSTI)

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.

Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))

1989-12-01T23:59:59.000Z

63

Cosmological and supernova neutrinos  

SciTech Connect (OSTI)

The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial {sup 7}Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and {sup 7}Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like {sup 7}Li, {sup 11}B, {sup 92}Nb, {sup 138}La and {sup 180}Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect. Combining the recent experimental constraints on ?{sub 13} with predicted and observed supernova-produced abundance ratio {sup 11}B/{sup 7}Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.

Kajino, T. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Aoki, W. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Balantekin, A. B. [Department of Physics, University of Wisconsin - Madison, Wisconsin 53706 (United States); Cheoun, M.-K. [Department of Physics, Soongsil University, Seoul 156-743 (Korea, Republic of); Hayakawa, T. [Japan Atomic Energy Agency, Shirakara-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Hidaka, J. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Hirai, Y.; Shibagaki, S. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan and Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Kusakabe, M. [School of Liberal Arts and Science, Korea Aerospace University, Goyang 412-791 (Korea, Republic of); Mathews, G. J. [Department of Physics, University of Notre Dame, IN 46556 (United States); Nakamura, K. [Waseda University, Ohkubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Pehlivan, Y. [Mimar Sinan GSÜ, Department of Physics, ?i?li, ?stanbul 34380 (Turkey); Suzuki, T. [Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550 (Japan)

2014-06-24T23:59:59.000Z

64

Thermodynamics in Loop Quantum Cosmology  

E-Print Network [OSTI]

Loop quantum cosmology (LQC) is very powerful to deal with the behavior of early universe. And the effective loop quantum cosmology gives a successful description of the universe in the semiclassical region. We consider the apparent horizon of the Friedmann-Robertson-Walker universe as a thermodynamical system and investigate the thermodynamics of LQC in the semiclassical region. The effective density and effective pressure in the modified Friedmann equation from LQC not only determine the evolution of the universe in LQC scenario but are actually also found to be the thermodynamic quantities. This result comes from the energy definition in cosmology (the Misner-Sharp gravitational energy) and is consistent with thermodynamic laws. We prove that within the framework of loop quantum cosmology, the elementary equation of equilibrium thermodynamics is still valid.

Li-Fang Li; Jian-Yang Zhu

2008-12-18T23:59:59.000Z

65

Cosmology with the SKA -- overview  

E-Print Network [OSTI]

The new frontier of cosmology will be led by three-dimensional surveys of the large-scale structure of the Universe. Based on its all-sky surveys and redshift depth, the SKA is destined to revolutionize cosmology, in combination with future optical/ infrared surveys such as Euclid and LSST. Furthermore, we will not have to wait for the full deployment of the SKA in order to see transformational science. In the first phase of deployment (SKA1), all-sky HI intensity mapping surveys and all-sky continuum surveys are forecast to be at the forefront on the major questions of cosmology. We give a broad overview of the major contributions predicted for the SKA. The SKA will not only deliver precision cosmology -- it will also probe the foundations of the standard model and open the door to new discoveries on large-scale features of the Universe.

Maartens, Roy; Jarvis, Matt; Santos, Mario G

2015-01-01T23:59:59.000Z

66

Inflationary Cosmology: Theory and Phenomenology  

E-Print Network [OSTI]

This article gives a brief overview of some of the theory behind the inflationary cosmology, and discusses prospects for constraining inflation using observations. Particular care is given to the question of falsifiability of inflation or of subsets of inflationary models.

Andrew R Liddle

2001-10-18T23:59:59.000Z

67

Precision Cosmology and the Landscape  

E-Print Network [OSTI]

After reviewing the cosmological constant problem - why is Lambda not huge? - I outline the two basic approaches that had emerged by the late 1980s, and note that each made a clear prediction. Precision cosmological experiments now indicate that the cosmological constant is nonzero. This result strongly favors the environmental approach, in which vacuum energy can vary discretely among widely separated regions in the universe. The need to explain this variation from first principles constitutes an observational constraint on fundamental theory. I review arguments that string theory satisfies this constraint, as it contains a dense discretuum of metastable vacua. The enormous landscape of vacua calls for novel, statistical methods of deriving predictions, and it prompts us to reexamine our description of spacetime on the largest scales. I discuss the effects of cosmological dynamics, and I speculate that weighting vacua by their entropy production may allow for prior-free predictions that do not resort to explicitly anthropic arguments.

Raphael Bousso

2006-11-03T23:59:59.000Z

68

Bimetric gravity is cosmologically viable  

E-Print Network [OSTI]

Bimetric theory describes gravitational interactions in the presence of an extra spin-2 field. Previous work has suggested that its cosmological solutions are generically plagued by instabilities. We show that by taking the Planck mass for the second metric, $M_f$, to be small, these instabilities can be pushed back to unobservably early times. In this limit, the theory approaches general relativity with an effective cosmological constant which is, remarkably, determined by the spin-2 interaction scale. This provides a late-time expansion history which is extremely close to $\\Lambda$CDM, but with a technically-natural value for the cosmological constant. We find $M_f$ should be no larger than the electroweak scale in order for cosmological perturbations to be stable by big-bang nucleosynthesis.

Akrami, Yashar; Könnig, Frank; Schmidt-May, Angnis; Solomon, Adam R

2015-01-01T23:59:59.000Z

69

An inhomogeneous fractal cosmological model  

E-Print Network [OSTI]

We present a cosmological model in which the metric allows for an inhomogeneous Universe with no intrinsic symmetries (Stephani models), providing the ideal features to describe a fractal distribution of matter. Constraints on the metric functions are derived using the expansion and redshift relations and allowing for scaling number counts, as expected in a fractal set. The main characteristics of such a cosmological model are discussed.

Fulvio Pompilio; Marco Montuori

2001-11-28T23:59:59.000Z

70

?CDM cosmology from matter only  

E-Print Network [OSTI]

I discuss a matter-only interpretation of {\\Lambda}CDM cosmology, based on conservation of energy and assuming a Machian definition of inertia. {\\Lambda}CDM cosmology can be linked to a Newtonian cosmic potential, subject to a propagating gravitational horizon. In a matter-only universe where total energy is conserved, Machian inertia related to the evolving potential may cause both deceleration and acceleration of recession.

Herman Telkamp

2015-04-08T23:59:59.000Z

71

Large aperture diffractive space telescope  

DOE Patents [OSTI]

A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

Hyde, Roderick A. (Livermore, CA)

2001-01-01T23:59:59.000Z

72

Varying constants quantum cosmology  

E-Print Network [OSTI]

We discuss minisuperspace models within the framework of varying physical constants theories including $\\Lambda$-term. In particular, we consider the varying speed of light (VSL) theory and varying gravitational constant theory (VG) using the specific ans\\"atze for the variability of constants: $c(a) = c_0 a^n$ and $G(a)=G_0 a^q$. We find that most of the varying $c$ and $G$ minisuperspace potentials are of the tunneling type which allows to use WKB approximation of quantum mechanics. Using this method we show that the probability of tunneling of the universe "from nothing" ($a=0)$ to a Friedmann geometry with the scale factor $a_t$ is large for growing $c$ models and is strongly suppressed for diminishing $c$ models. As for $G$ varying, the probability of tunneling is large for $G$ diminishing, while it is small for $G$ increasing. In general, both varying $c$ and $G$ change the probability of tunneling in comparison to the standard matter content (cosmological term, dust, radiation) universe models.

Katarzyna Leszczynska; Adam Balcerzak; Mariusz P. Dabrowski

2015-01-26T23:59:59.000Z

73

Lectures on Quantum Cosmology  

E-Print Network [OSTI]

The problems encountered in trying to quantize the various cosmological models, are brought forward by means of a concrete example. The Automorphism groups are revealed as the key element through which G.C.T.'s can be used for a general treatment of these problems. At the classical level, the time dependent automorphisms lead to significant simplifications of the line element for the generic spatially homogeneous geometry, without loss of generality. At the quantum level, the ''frozen'' automorphisms entail an important reduction of the configuration space --spanned by the 6 components of the scale factor matrix-- on which the Wheeler-DeWitt equation, is to be based. In this spirit the canonical quantization of the most general minisuperspace actions --i.e. with all six scale factor as well as the lapse function and the shift vector present-- describing the vacuum type II, I geometries, is considered. The reduction to the corresponding physical degrees of freedom is achieved through the usage of the linear constraints as well as the quantum version of the entire set of all classical integrals of motion.

T. Christodoulakis

2001-09-18T23:59:59.000Z

74

Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array  

E-Print Network [OSTI]

We provide an overview of the science benefits of combining information from the Square Kilometre Array (SKA) and the Large Synoptic Survey Telescope (LSST). We first summarise the capabilities and timeline of the LSST and overview its science goals. We then discuss the science questions in common between the two projects, and how they can be best addressed by combining the data from both telescopes. We describe how weak gravitational lensing and galaxy clustering studies with LSST and SKA can provide improved constraints on the causes of the cosmological acceleration. We summarise the benefits to galaxy evolution studies of combining deep optical multi-band imaging with radio observations. Finally, we discuss the excellent match between one of the most unique features of the LSST, its temporal cadence in the optical waveband, and the time resolution of the SKA.

Bacon, David; Abdalla, Filipe B; Brown, Michael; Bull, Philip; Camera, Stefano; Fender, Rob; Grainge, Keith; Ivezic, Zeljko; Jarvis, Matt; Jackson, Neal; Kirk, Donnacha; Mann, Bob; McEwen, Jason; McKean, John; Newman, Jeffrey A; Raccanelli, Alvise; Sahlen, Martin; Santos, Mario; Tyson, Anthony; Zhao, Gong-Bo

2015-01-01T23:59:59.000Z

75

SLAC Cosmic Ray Telescope Facility  

SciTech Connect (OSTI)

SLAC does not have a test beam for the HEP detector development at present. We have therefore created a cosmic ray telescope (CRT) facility, which is presently being used to test the FDIRC prototype. We have used it in the past to debug this prototype with the original SLAC electronics before going to the ESA test beam. Presently, it is used to test a new waveform digitizing electronics developed by the University of Hawaii, and we are also planning to incorporate the new Orsay TDC/ADC electronics. As a next step, we plan to put in a full size DIRC bar box with a new focusing optics, and test it together with a final SuberB electronics. The CRT is located in building 121 at SLAC. We anticipate more users to join in the future. This purpose of this note is to provide an introductory manual for newcomers.

Va'vra, J.

2010-02-15T23:59:59.000Z

76

Adaptive Optics for Large Telescopes  

SciTech Connect (OSTI)

The use of adaptive optics was originally conceived by astronomers seeking to correct the blurring of images made with large telescopes due to the effects of atmospheric turbulence. The basic idea is to use a device, a wave front corrector, to adjust the phase of light passing through an optical system, based on some measurement of the spatial variation of the phase transverse to the light propagation direction, using a wave front sensor. Although the original concept was intended for application to astronomical imaging, the technique can be more generally applied. For instance, adaptive optics systems have been used for several decades to correct for aberrations in high-power laser systems. At Lawrence Livermore National Laboratory (LLNL), the world's largest laser system, the National Ignition Facility, uses adaptive optics to correct for aberrations in each of the 192 beams, all of which must be precisely focused on a millimeter scale target in order to perform nuclear physics experiments.

Olivier, S

2008-06-27T23:59:59.000Z

77

Recent Results from Telescope Array  

E-Print Network [OSTI]

The Telescope Array (TA) is an experiment to observe Ultra-High Energy Cosmic Rays (UHECRs). TA's recent results, the energy spectrum and anisotropy based on the 6-year surface array data, and the primary composition obtained from the shower maximum Xmax are reported. The spectrum demonstrates a clear dip and cutoff. The shape of the spectrum is well described by the energy loss of extra-galactic protons interacting with the cosmic microwave background (CMB). Above the cutoff, a medium-scale (20 degrees radius) flux enhancement was observed near the Ursa-Major. A chance probability of creating this hotspot from the isotropic flux is 4.0 sigma. The measured Xmax is consistent with the primary being proton or light nuclei for energies 10^18.2 eV - 10^19.2 eV.

Fukushima, M

2015-01-01T23:59:59.000Z

78

Galaxy Cosmological Mass Function  

E-Print Network [OSTI]

We study the galaxy cosmological mass function (GCMF) in a semi-empirical relativistic approach using observational data provided by galaxy redshift surveys. Starting from the theory of Ribeiro & Stoeger (2003, arXiv:astro-ph/0304094) between the mass-to-light ratio, the selection function obtained from the luminosity function (LF) data and the luminosity density, the average luminosity $L$ and the average galactic mass $\\mathcal{M}_g$ are computed in terms of the redshift. $\\mathcal{M}_g$ is also alternatively estimated by a method that uses the galaxy stellar mass function (GSMF). Comparison of these two forms of deriving the average galactic mass allows us to infer a possible bias introduced by the selection criteria of the survey. We used the FORS Deep Field galaxy survey sample of 5558 galaxies in the redshift range $0.5 light ratio and its GSMF data. Assuming ${\\mathcal{M}_{g_0}} \\approx 10^{11} \\mathcal{M}_\\odot$ as the local value of the average galactic mass, the LF approach results in $L_{B} \\propto (1+z)^{(2.40 \\pm 0.03)}$ and $\\mathcal{M}_g \\propto (1+z)^{(1.1\\pm0.2)}$. However, using the GSMF results produces $\\mathcal{M}_g \\propto (1+z)^{(-0.58 \\pm 0.22)}$. We chose the latter result as it is less biased. We then obtained the theoretical quantities of interest, such as the differential number counts, to calculate the GCMF, which can be fitted by a Schechter function. The derived GCMF follows theoretical predictions in which the less massive objects form first, being followed later by more massive ones. In the range $0.5 < z < 2.0$ the GCMF has a strong variation that can be interpreted as a higher rate of galaxy mergers or as a strong evolution in the star formation history of these galaxies.

Amanda R. Lopes; Alvaro Iribarrem; Marcelo B. Ribeiro; William R. Stoeger

2014-12-03T23:59:59.000Z

79

Optical aperture synthesis with electronically connected telescopes  

E-Print Network [OSTI]

Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances, and at successively shorter wavelengths. Here, we present the first diffraction-limited images in visual light, produced by an array of independent optical telescopes, connected electronically only, with no optical links between them. With an array of small telescopes, second-order optical coherence of the sources is measured through intensity interferometry over 180 baselines between pairs of telescopes, and two-dimensional images reconstructed. The technique aims at diffraction-limited optical aperture synthesis over kilometre-long baselines to reach resolutions showing details on stellar surfaces and perhaps even the silhouettes of transiting exoplanets. Intensity interferometry circumvents problems of atmospheric turbulence that constrain ordinary interferometry. Since the electronic signal can be copied, many baselines can be built up between dispersed telescopes, and over long...

Dravins, Dainis; Nuñez, Paul D

2015-01-01T23:59:59.000Z

80

Null geodesics and observational cosmology  

E-Print Network [OSTI]

The Universe is not isotropic or spatially homogeneous on local scales. The averaging of local inhomogeneities in general relativity can lead to significant dynamical effects on the evolution of the Universe, and even if the effects are at the 1% level they must be taken into account in a proper interpretation of cosmological observations. We discuss the effects that averaging (and inhomogeneities in general) can have on the dynamical evolution of the Universe and the interpretation of cosmological data. All deductions about cosmology are based on the paths of photons. We discuss some qualitative aspects of the motion of photons in an averaged geometry, particularly within the context of the luminosity distance-redshift relation in the simple case of spherical symmetry.

A. A. Coley

2008-12-24T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Cosmological dark energy effects from entanglement  

E-Print Network [OSTI]

The thorny issue of relating information theory to cosmology is here addressed by assuming a possible connection between quantum entanglement measures and observable universe. In particular, we propose a cosmological toy model, where the equation of state of the cosmological fluid, which drives the today observed cosmic acceleration, can be inferred from quantum entanglement between different cosmological epochs. In such a way the dynamical dark energy results as byproduct of quantum entanglement.

S. Capozziello; O. Luongo; S. Mancini

2013-02-24T23:59:59.000Z

82

Cosmological science enabled by Planck  

E-Print Network [OSTI]

Planck will be the first mission to map the entire cosmic microwave background (CMB) sky with mJy sensitivity and resolution better than 10'. The science enabled by such a mission spans many areas of astrophysics and cosmology. In particular it will lead to a revolution in our understanding of primary and secondary CMB anisotropies, the constraints on many key cosmological parameters will be improved by almost an order of magnitude (to sub-percent levels) and the shape and amplitude of the mass power spectrum at high redshift will be tightly constrained.

Martin White

2006-06-27T23:59:59.000Z

83

Quasar Structure and Cosmological Feedback  

E-Print Network [OSTI]

Feedback from quasars and AGNs is being invoked frequently in several cosmological settings. Currently, order of magnitude, or more, uncertainties in the structure of both the wind and the 'obscuring torus' make predictions highly uncertain. To make testable models of this 'cosmological feedback' it is essential to understand the detailed structure of AGNs sufficiently well to predict their properties for the whole quasar population, at all redshifts. Progress in both areas is rapid, and I describe the near-term prospects for reducing these uncertainties for 'slow' (non-relativistic) AGN winds and the obscuring torus.

Martin Elvis

2006-06-05T23:59:59.000Z

84

Stringy Model of Cosmological Dark Energy  

E-Print Network [OSTI]

A string field theory(SFT) nonlocal model of the cosmological dark energy providing w<-1 is briefly surveyed. We summarize recent developments and open problems, as well as point out some theoretical issues related with others applications of the SFT nonlocal models in cosmology, in particular, in inflation and cosmological singularity.

Irina Ya. Aref'eva

2007-10-16T23:59:59.000Z

85

The Space Infrared Telescope for Cosmology and Astrophysics: SPICA A joint mission between JAXA and ESA  

E-Print Network [OSTI]

Vandenbussche (KUL), Christoffel Waelkens (KUL), Peter Davis (BSS), James Di Francesco (HIA/NRC), Mark Halpern. (CESR), Ravera, L. (CESR), Ristorcelli, I. (CESR), Rodriguez, L. (SAP), Vives, S. (OAMP), Zavagno, A Ramon Pardo (CSIC), Francisca Gomez (CSIC), Nieves Castro Rodriguez (CSIC), Peter Ade (CU), Mike Barlow

Naylor, David A.

86

Asymmetric cyclic evolution in polymerised cosmology  

SciTech Connect (OSTI)

The dynamical systems methods are used to study evolution of the polymerised scalar field cosmologies with the cosmological constant. We have found all evolutional paths admissible for all initial conditions on the two-dimensional phase space. We have shown that the cyclic solutions are generic. The exact solution for polymerised cosmology is also obtained. Two basic cases are investigated, the polymerised scalar field and the polymerised gravitational and scalar field part. In the former the division on the cyclic and non-cyclic behaviour is established following the sign of the cosmological constant. The value of the cosmological constant is upper bounded purely from the dynamical setting.

Hrycyna, Orest [Department of Theoretical Physics, Faculty of Philosophy, The John Paul II Catholic University of Lublin, Al. Rac?awickie 14, 20-950 Lublin (Poland); Mielczarek, Jakub; Szyd?owski, Marek, E-mail: hrycyna@kul.lublin.pl, E-mail: jakub.mielczarek@uj.edu.pl, E-mail: uoszydlo@cyf-kr.edu.pl [Astronomical Observatory, Jagiellonian University, Orla 171, 30-244 Kraków (Poland)

2009-12-01T23:59:59.000Z

87

Electric Time in Quantum Cosmology  

E-Print Network [OSTI]

Effective quantum cosmology is formulated with a realistic global internal time given by the electric vector potential. New possibilities for the quantum behavior of space-time are found, and the high-density regime is shown to be very sensitive to the specific form of state realized.

Stephon Alexander; Martin Bojowald; Antonino Marciano; David Simpson

2012-12-10T23:59:59.000Z

88

Numerical Simulations in Cosmology I  

E-Print Network [OSTI]

The purpose of these lectures is to give a short introduction into a very vast field of numerical simulations for cosmological applications. I focus on major features of the simulations: the equations, main numerical techniques, effects of resolution, and methods of halo identification.

A. Klypin

1996-05-30T23:59:59.000Z

89

James Webb Space Telescope: PM Lessons Applied - Eric Smith,...  

Energy Savers [EERE]

James Webb Space Telescope: PM Lessons Applied - Eric Smith, Deputy Program Director, NASA James Webb Space Telescope: PM Lessons Applied - Eric Smith, Deputy Program Director,...

90

A Comparison of Cosmological Models Using Time Delay Lenses  

E-Print Network [OSTI]

The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of $\\Lambda$CDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between {\\it competing} models. The currently available sample indicates a likelihood of $\\sim 70-80%$ that the $R_{\\rm h}=ct$ Universe is the correct cosmology versus $\\sim 20-30%$ for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic sa...

Wei, Jun-Jie; Melia, Fulvio

2014-01-01T23:59:59.000Z

91

Digital Frequency Domain Multiplexer for mm-Wavelength Telescopes  

SciTech Connect (OSTI)

An FPGA based digital signal processing (DSP) system for biasing and reading out multiplexed bolometric detectors for mm-wavelength telescopes is presented. This readout system is being deployed for balloon-borne and ground based cosmology experiments with the primary goal of measuring the signature of inflation with the Cosmic Microwave Background Radiation. The system consists of analog superconducting electronics running at 250 mK and 4 K, coupled to digital room temperature backend electronics described here. The digital electronics perform the real time functionality with DSP algorithms implemented in firmware. A soft embedded processor provides all of the slow housekeeping control and communications. Each board in the system synthesizes multi-frequency combs of 8 to 32 carriers in the MHz band to bias the detectors. After the carriers have been modulated with the sky-signal by the detectors, the same boards digitize the comb directly. The carriers are mixed down to base-band and low pass filtered. The signal bandwidth of 0.050Hz-100 Hz places extreme requirements on stability and requires powerful filtering techniques to recover the sky-signal from the MHz carriers.

Spieler, Helmuth G; Dobbs, Matt; Bissonnette, Eric; Spieler, Helmuth G.

2007-07-23T23:59:59.000Z

92

Cosmological Analysis of Pilgrim Dark Energy in Loop Quantum Cosmology  

E-Print Network [OSTI]

The proposal of pilgrim dark energy is based on speculation that phantom-like dark energy (with strong enough resistive force) can prevent black hole formation in the universe. We explore this phenomenon in loop quantum cosmology framework by taking Hubble horizon as an infra-red cutoff in pilgrim dark energy. We evaluate the cosmological parameters such as Hubble, equation of state parameter, squared speed of sound and also cosmological planes like $\\omega_{\\vartheta}-\\omega'_{\\vartheta}$ and $r-s$ on the basis of pilgrim dark energy parameter ($u$) and interacting parameter ($d^2$). It is found that values of Hubble parameter lies in the range $74^{+0.005}_{-0.005}$. It is mentioned here that equation state parameter lies within the ranges $-1\\mp0.00005$ for $u=2, 1$ and $(-1.12,-1), (-5,-1)$ for $u=-1,-2$, respectively. Also, $\\omega_{\\vartheta}-\\omega'_{\\vartheta}$ planes provide $\\Lambda$CDM limit, freezing and thawing regions for all cases of $u$. It is also interesting to mention here that $\\omega_{\\va...

Jawad, Abdul

2015-01-01T23:59:59.000Z

93

The Schwarzschild Static Cosmological Model  

E-Print Network [OSTI]

The present work describes an immersion in 5D of the interior Schwarzschild solution of the general relativity equations. The model theory is defined in the context of a flat 5D space time matter Minkowski model, using a Tolman like technique, which shows via Lorentz transformations that the solution is compatible with homogeneity and isotropy,thus obeying the cosmological principle. These properties permit one to consider the solution in terms of a cosmological model. In this model, the Universe may be treated as an idealized star with constant density and variable pressure, where each observer can be the center of the same. The observed redshift appears as a static gravitational effect which obeys the sufficiently verified and generally accepted square distance law. The Buchdahl stability theorem establishes a limit of distance observation with density dependence.

P. H. Pereyra

2009-04-16T23:59:59.000Z

94

Cosmology: a bird's eye view  

E-Print Network [OSTI]

In this essay we discuss the difference in views of the Universe as seen by two different observers. While one of the observers follows a geodesic congruence defined by the geometry of the cosmological model, the other observer follows the fluid flow lines of a perfect fluid with a linear equation of state. We point out that the information these observers collect regarding the state of the Universe can be radically different; while one observes a non-inflating ever-expanding ever-lasting universe, the other observer can experience a dynamical behaviour reminiscent to that of quintessence or even that of a phantom cosmology leading to a 'big rip' singularity within finite time (but without the need for exotic forms of matter).

Alan A. Coley; Sigbjorn Hervik; Woei Chet Lim

2006-05-15T23:59:59.000Z

95

Cosmology, Thermodynamics and Matter Creation  

E-Print Network [OSTI]

Several approaches to the matter creation problem in the context of cosmological models are summarily reviewed. A covariant formulation of the general relativistic imperfect simple fluid endowed with a process of matter creation is presented. By considering the standard big bang model, it is shown how the recent results of Prigogine et alii \\cite{1} can be recovered and, at the same time their limits of validity are explicited.

J. A. S. Lima; M. O. Calvao; I. Waga

2007-08-24T23:59:59.000Z

96

Disformal transformation of cosmological perturbations  

E-Print Network [OSTI]

We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar-tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar-tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (non)conservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame.

Masato Minamitsuji

2014-09-04T23:59:59.000Z

97

Emergent cosmological constant from colliding electromagnetic waves  

E-Print Network [OSTI]

In this study we advocate the view that the cosmological constant is of electromagnetic (em) origin, which can be generated from the collision of em shock waves coupled with gravitational shock waves. The wave profiles that participate in the collision have different amplitudes. It is shown that, circular polarization with equal amplitude waves does not generate cosmological constant. We also prove that the generation of the cosmological constant is related to the linear polarization. The addition of cross polarization generates no cosmological constant. Depending on the value of the wave amplitudes, the generated cosmological constant can be positive or negative. We show additionally that, the collision of nonlinear em waves in a particular class of Born-Infeld theory also yields a cosmological constant.

M. Halilsoy; S. Habib Mazharimousavi; O. Gurtug

2014-10-15T23:59:59.000Z

98

String Gas Cosmology and Non-Gaussianities  

E-Print Network [OSTI]

Recently it has been shown that string gas cosmology, an alternative model of the very early universe which does not involve a period of cosmological inflation, can give rise to an almost scale invariant spectrum of metric perturbations. Here we calculate the non-Gaussianities of the spectrum of cosmological fluctuations in string gas cosmology, and find that these non-Gaussianities depend linearly on the wave number and that their amplitude depends sensitively on the string scale. If the string scale is at the TeV scale, string gas cosmology could lead to observable non-Gaussianities, if it is close to the Planck scale, then the non-Gaussianities on current cosmological scales are negligible.

Bin Chen; Yi Wang; Wei Xue; Robert Brandenberger

2008-03-05T23:59:59.000Z

99

Collecting Light with Telescopes How do telescopes help us learn about the universe?  

E-Print Network [OSTI]

. Light Pollution #12;Star viewed with ground-based telescope 2. Turbulence causes twinkling blurs images pollution and turbulence. · Nothing short of going to space can solve problem of atmospheric absorption telescope. Very Large Array (VLA), New Mexico #12;Very Large Array (VLA), New Mexico #12;Very Long Baseline

Shirley, Yancy

100

The Telescope Control System of the New Solar Telescope at Big Bear Solar Observatory  

E-Print Network [OSTI]

mirror (M1) and its alignment with the secondary mirror (M2) will be actively controlled. HighThe Telescope Control System of the New Solar Telescope at Big Bear Solar Observatory G. Yang*a, J of Technology, 323 Martin Luther King Blvd., Newark, NJ 07104; bBig Bear Solar Observatory, 40386 North Shore

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

The Berry phase in inflationary cosmology  

E-Print Network [OSTI]

We derive an analogue of the Berry phase associated with inflationary cosmological perturbations of quantum mechanical origin by obtaining the corresponding wavefunction. We have further shown that cosmological Berry phase can be completely envisioned through the observable parameters, viz. spectral indices. Finally, physical significance of this phase is discussed from the point of view of theoretical and observational aspects with some possible consequences of this quantity in inflationary cosmology.

Barun Kumar Pal; Supratik Pal; B. Basu

2013-04-25T23:59:59.000Z

102

First trillion particle cosmological simulation completed  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

trillion particle cosmological simulation completed A team of astrophysicists and computer scientists has created high-resolution cyber images of our cosmos. December 3, 2014...

103

Landscape Predictions from Cosmological Vacuum Selection  

E-Print Network [OSTI]

In BP models with hundreds of fluxes, we compute the effects of cosmological dynamics on the probability distribution of landscape vacua. Starting from generic initial conditions, we find that most fluxes are dynamically driven into a different and much narrower range of values than expected from landscape statistics alone. Hence, cosmological evolution will access only a tiny fraction of the vacua with small cosmological constant. This leads to a host of sharp predictions. Unlike other approaches to eternal inflation, the holographic measure employed here does not lead to "staggering", an excessive spread of probabilities that would doom the string landscape as a solution to the cosmological constant problem.

Raphael Bousso; I-Sheng Yang

2007-05-09T23:59:59.000Z

104

Variable cosmological term - geometry and physics  

E-Print Network [OSTI]

We describe the dynamics of a cosmological term in the spherically symmetric case by an r-dependent second rank symmetric tensor \\Lambda_{\\mu\

Irina Dymnikova

2000-10-04T23:59:59.000Z

105

Telescopic nanotube device for hot nanolithography  

DOE Patents [OSTI]

A device for maintaining a constant tip-surface distance for producing nanolithography patterns on a surface using a telescopic nanotube for hot nanolithography. An outer nanotube is attached to an AFM cantilever opposite a support end. An inner nanotube is telescopically disposed within the outer nanotube. The tip of the inner nanotube is heated to a sufficiently high temperature and brought in the vicinity of the surface. Heat is transmitted to the surface for thermal imprinting. Because the inner tube moves telescopically along the outer nanotube axis, a tip-surface distance is maintained constant due to the vdW force interaction, which in turn eliminates the need of an active feedback loop.

Popescu, Adrian; Woods, Lilia M

2014-12-30T23:59:59.000Z

106

Mirror Development for the Cherenkov Telescope Array  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) is a planned observatory for very-high energy gamma-ray astronomy. It will consist of several tens of telescopes of different sizes, with a total mirror area of up to 10,000 square meters. Most mirrors of current installations are either polished glass mirrors or diamond-turned aluminium mirrors, both labour intensive technologies. For CTA, several new technologies for a fast and cost-efficient production of light-weight and reliable mirror substrates have been developed and industrial pre-production has started for most of them. In addition, new or improved aluminium-based and dielectric surface coatings have been developed to increase the reflectance over the lifetime of the mirrors compared to those of current Cherenkov telescope instruments.

Förster, A; Baba, H; Bähr, J; Bonardi, A; Bonnoli, G; Brun, P; Canestrari, R; Chadwick, P; Chikawa, M; Carton, P -H; De Souza, V; Dipold, J; Doro, M; Durand, D; Dyrda, M; Giro, E; Glicenstein, J -F; Hanabata, Y; Hayashida, M; Hrabovski, M; Jeanney, C; Kagaya, M; Katagiri, H; Lessio, L; MANDAT, D; Mariotti, M; Medina, C; Micha?owski, J; Micolon, P; Nakajima, D; Niemiec, J; Nozato, A; Palatka, M; Pareschi, G; Pech, M; Peyaud, B; Pühlhofer, G; Rataj, M; Rodeghiero, G; Rojas, G; Rousselle, J; Sakonaka, R; Schovanek, P; Seweryn, K; Schultz, C; Shu, S; Stinzing, F; Stodulski, M; Teshima, M; Travniczek, P; Van Eldik, C; Vassiliev, V; Wi?niewski, ?; Wörnlein, A; Yoshida, T

2013-01-01T23:59:59.000Z

107

Multimessenger astronomy with the Einstein Telescope  

E-Print Network [OSTI]

Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.

Eric Chassande-Mottin; Martin Hendry; Patrick J. Sutton; Szabolcs Márka

2010-04-12T23:59:59.000Z

108

Telescope Spectrophotometric and Absolute Flux Calibration, and National Security Applications, Using a Tunable Laser on a Satellite  

E-Print Network [OSTI]

We propose a tunable laser-based satellite-mounted spectrophotometric and absolute flux calibration system, to be utilized by ground- and space-based telescopes. As uncertainties on the photometry, due to imperfect knowledge of both telescope optics and the atmosphere, will in the near future begin to dominate the uncertainties on fundamental cosmological parameters such as Omega_Lambda and w in measurements from SNIa, weak gravitational lensing, and baryon oscillations, a method for reducing such uncertainties is needed. We propose to improve spectrophotometric calibration, currently obtained using standard stars, by placing a tunable laser and a wide-angle light source on a satellite by early next decade (perhaps included in the upgrade to the GPS satellite network) to improve absolute flux calibration to 0.1% and relative spectrophotometric calibration to better than 0.001% across the visible and near-infrared spectrum. As well as fundamental astrophysical applications, the system proposed here potentially...

Albert, J; Rhodes, J; Albert, Justin; Burgett, William; Rhodes, Jason

2006-01-01T23:59:59.000Z

109

Supersymmetric quantum solution for FRW cosmological model with matter  

E-Print Network [OSTI]

Using technique of supersymmetric quantum mechanics we present new cosmological quantum solution, in the regime for FRW cosmological model using a barotropic perfect fluid as matter field.

J. Socorro

2001-08-09T23:59:59.000Z

110

4 m Davies-Cotton telescope for the Cherenkov Telescope Array  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) is the next generation very high energy gamma-ray observatory. It will consist of three classes of telescopes, of large, medium and small sizes. The small telescopes, of 4 m diameter, will be dedicated to the observations of the highest energy gamma-rays, above several TeV. We present the technical characteristics of a single mirror, 4 m diameter, Davies-Cotton telescope for the CTA and the performance of the sub-array consisting of the telescopes of this type. The telescope will be equipped with a fully digital camera based on custom made, hexagonal Geiger-mode avalanche photodiodes. The development of cameras based on such devices is an RnD since traditionally photomultipliers are used. The photodiodes are now being characterized at various institutions of the CTA Consortium. Glass mirrors will be used, although an alternative is being considered: composite mirrors that could be adopted if they meet the project requirements. We present a design of the telescope structure,...

Moderski, R; Barnacka, A; Basili, A; Boccone, V; Bogacz, L; Cadoux, F; Christov, A; Della Volpe, M; Dyrda, M; Frankowski, A; Grudzi?ska, M; Janiak, M; Karczewski, M; Kasperek, J; Kocha?ski, W; Korohoda, P; Kozio?, J; Lubi?ski, P; Ludwin, J; Lyard, E; Marsza?ek, A; Micha?owski, J; Montaruli, T; Nicolau-Kukli?ski, J; Niemiec, J; Ostrowski, M; P?atos, ?; Rajda, P J; Rameez, M; Romaszkan, W; Rupi?ski, M; Seweryn, K; Stodulska, M; Stodulski, M; Walter, R; Winiarski, K; Wi?niewski, ?; Zagda?ski, A; Zietara, K; Zió?kowski, P; ?ychowski, P

2013-01-01T23:59:59.000Z

111

Quasilocal Energy in FRW Cosmology  

E-Print Network [OSTI]

This paper presents a calculation of the quasilocal energy of a generic FRW model of the universe. The results have the correct behavior in the small-sphere limit and vanish for the empty Milne universe. Higher order corrections are found when comparing these results to classical calculations of cosmological energy. This case is different from others in the literature chiefly in that it involves a non-stationary spacetime. This fact can be used to differentiate between the various formulations of quasilocal energy. In particular, the formulation due to Brown and York is compared to that of Epp. Only one of these is seen to have the correct classical limit.

M. M. Afshar

2009-10-03T23:59:59.000Z

112

Surface brightness in plasma-redshift cosmology  

E-Print Network [OSTI]

In 2001 Lori M. Lubin and Allan Sandage, using big-bang cosmology for interpreting the data, found the surface brightness of galaxies to be inversely proportional to about the third power of (1+z), while the contemporary big-bang cosmology predicts that the surface brightness is inversely proportional to the fourth power of (1+z). In contrast, these surface brightness observations are in agreement with the predictions of the plasma-redshift cosmology. Lubin and Sandage (2001) and Barden et al. (2005), who surmised the big-bang expansion, interpreted the observations to indicate that the diameters of galaxies are inversely proportional to (1+z). In contrast, when assuming plasma-redshift cosmology, the diameters of galaxies are observed to be constant independent of redshift and any expansion. Lubin and Sandage (2001) and Barden et al. (2005), when using big-bang cosmology, observed the average absolute magnitude of galaxies to decrease with redshift; while in plasma redshift cosmology it is a constant. Lubin and Sandage and Barden et al. suggested that a coherent evolution could explain the discrepancy between the observed relations and those predicted in the big-bang cosmology. We have failed to find support for this explanation. We consider the observed relations between the redshift and the surface-brightness, the galaxy diameter, and the absolute magnitude to be robust confirmations of plasma-redshift cosmology.

Ari Brynjolfsson

2006-05-31T23:59:59.000Z

113

A Time-dependent Cosmological Constant Phenomenology  

E-Print Network [OSTI]

We construct a cosmological toy model in which a step-function ``cosmological constant'' is taken into consideration beside ordinary matter. We assume that $\\Lambda$ takes two values depending on the epoch, and matter goes from a radiation dominated era to a dust dominated era. The model is exactly solvable and it can be compared with recent observations.

Salvatore Capozziello; Ruggiero de Ritis; Alma Angela Marino

1996-05-29T23:59:59.000Z

114

Planck Scale Cosmology in Resummed Quantum Gravity  

E-Print Network [OSTI]

We show that, by using resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

B. F. L. Ward

2008-08-23T23:59:59.000Z

115

Planck Scale Cosmology and Resummed Quantum Gravity  

E-Print Network [OSTI]

We show that, by using amplitude-based resummation techniques for Feynman's formulation of Einstein's theory, we get quantum field theoretic 'first principles' predictions for the UV fixed-point values of the dimensionless gravitational and cosmological constants. Connections to the phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter are discussed.

B. F. L. Ward

2009-10-13T23:59:59.000Z

116

Optical Technology Needs for Future Space Telescopes  

E-Print Network [OSTI]

instruments & sensors. Future Space Telescopes will operate over broad spectrum: Gamma Rays, X-Rays, XUV and Sensors Direct Sensing of Particles, Fields and Waves See Scientific Instruments and Sensors (SIS Structure #12;NASA's Science Missions Directorate Themes: Earth Science Sun-Solar System Connection Solar

Van Stryland, Eric

117

The High Energy Telescope on EXIST  

E-Print Network [OSTI]

The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed next generation multi-wavelength survey mission. The primary instrument is a High Energy telescope (HET) that conducts the deepest survey for Gamma-ray Bursts (GRBs), obscured-accreting and dormant Supermassive Black Holes and Transients of all varieties for immediate followup studies by the two secondary instruments: a Soft X-ray Imager (SXI) and an Optical/Infrared Telescope (IRT). EXIST will explore the early Universe using high redshift GRBs as cosmic probes and survey black holes on all scales. The HET is a coded aperture telescope employing a large array of imaging CZT detectors (4.5 m^2, 0.6 mm pixel) and a hybrid Tungsten mask. We review the current HET concept which follows an intensive design revision by the HET imaging working group and the recent engineering studies in the Instrument and Mission Design Lab at the Goddard Space Flight Center. The HET will locate GRBs and transients quickly (<10-30 sec) and accurately (< 20") f...

Hong, J; Allen, B; Barthelmy, S D; Skinner, G K; Gehrels, N

2009-01-01T23:59:59.000Z

118

Vacuum energy and cosmological evolution  

E-Print Network [OSTI]

An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature $R$ as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect $\\delta\\Lambda\\sim R\\sim H^2$. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological data, and conveniently extended can account for the complete cosmic evolution from the inflationary epoch till the present days. These models are very close to the $\\Lambda$CDM model for the late universe, but very different from it at the early times. Traces of the inherent vacuum dynamics could be detectable in our recent past.

Joan Sola

2014-03-03T23:59:59.000Z

119

Relaxing a large cosmological constant  

E-Print Network [OSTI]

The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter is presently so close to the CC density. However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of the CC at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could solve the big CC problem and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the LCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments.

Florian Bauer; Joan Sola; Hrvoje Stefancic

2009-07-23T23:59:59.000Z

120

Statistical Mechanics and Quantum Cosmology  

E-Print Network [OSTI]

Statistical mechanical concepts and processes such as decoherence, correlation, and dissipation can prove to be of basic importance to understanding some fundamental issues of quantum cosmology and theoretical physics such as the choice of initial states, quantum to classical transition and the emergence of time. Here we summarize our effort in 1) constructing a unified theoretical framework using techniques in interacting quantum field theory such as influence functional and coarse-grained effective action to discuss the interplay of noise, fluctuation, dissipation and decoherence; and 2) illustrating how these concepts when applied to quantum cosmology can alter the conventional views on some basic issues. Two questions we address are 1) the validity of minisuperspace truncation, which is usually assumed without proof in most discussions, and 2) the relevance of specific initial conditions, which is the prevailing view of the past decade. We also mention how some current ideas in chaotic dynamics, dissipative collective dynamics and complexity can alter our view of the quantum nature of the universe.

B. L. Hu

1995-11-29T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Analogue models for FRW cosmologies  

E-Print Network [OSTI]

It is by now well known that various condensed matter systems may be used to mimic many of the kinematic aspects of general relativity, and in particular of curved-spacetime quantum field theory. In this essay we will take a look at what would be needed to mimic a cosmological spacetime -- to be precise a spatially flat FRW cosmology -- in one of these analogue models. In order to do this one needs to build and control suitable time dependent systems. We discuss here two quite different ways to achieve this goal. One might rely on an explosion, physically mimicking the big bang by an outflow of whatever medium is being used to carry the excitations of the analogue model, but this idea appears to encounter dynamical problems in practice. More subtly, one can avoid the need for any actual physical motion (and avoid the dynamical problems) by instead adjusting the propagation speed of the excitations of the analogue model. We shall focus on this more promising route and discuss its practicality.

Carlos Barcelo; Stefano Liberati; Matt Visser

2003-05-16T23:59:59.000Z

122

E-Print Network 3.0 - apex telescope large Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Telescopes Reference Reading Summary: telescopes are good for small telescopes (<1 meter) because it's very difficult to manufacture large lenses... fast system bright...

123

THE NEED FOR A PARADIGM SHIFT IN OPTICAL ASTRONOMY: A SOLUTION GIVEN BY LIQUID MIRRORS AND EXAMPLES OF THEIR APPLICATIONS TO COSMOLOGY  

E-Print Network [OSTI]

I argue that there is a crisis in optical Astronomy due to a paucity of telescopes and thus the need for a paradigm shift in telescope technology. Large increases in collecting areas and observing time/astronomer are only possible if we forgo the fully steerable multipurpose telescope with a glass primary mirror that has dominated astronomical research. Only by adopting entirely novel technologies that allow one to build large and inexpensive telescopes can we achieve truly large improvements. This may come at the expense of versatility and may entail changes in the observing strategies astronomers are now accustomed to. I build my case around a new technology, liquid mirrors, that although in its infancy has achieved credibility. I argue that forthcoming technological improvements will make Liquid Mirror Telescopes (LMTs) nearly as versatile as conventional telescopes. I address the issue of the fields accessible to LMTs equipped with novel optical correctors. Optical design work and exploratory laboratory work indicate that a single LMT should be able to access, with excellent images, subregions anywhere inside fields as large as 45 degrees. As a practical example of what an LMT can do with the present technology, I examine the expected performance of a 5-m liquid mirror telescope, presently under construction, dedicated to a cosmological survey. It is rather impressive, due to the fact that the instrument works full-time on a four-year survey: Spectrophotometry reaches B=24 with a signal to noise ratio of 10 within a 200\\AA bandpass for all objects within 300 square degrees and wide-band photometry reaches about B=27. I give three examples of cosmological projects that can be done with the data.

E. F. Borra

1995-03-03T23:59:59.000Z

124

Large fully retractable telescope enclosures still closable in strong wind  

E-Print Network [OSTI]

built for the high-resolution solar telescopes DOT (Dutch Open Telescope) and GREGOR, both located be closed and opened with wind speeds of 20 m/s without any problems or restrictions. The DOT successfully of the air changes with the temperature. Objects near the telescope have the tendency to produce air bubbles

Rutten, Rob

125

Telescoping MATLAB for DSP Applications PhD Thesis Defense  

E-Print Network [OSTI]

Telescoping MATLAB for DSP Applications PhD Thesis Defense Arun Chauhan Computer Science, Rice University PhD Thesis Defense July 10, 2003 #12;Two True Stories PhD Thesis Defense: Telescoping MATLABD Thesis Defense: Telescoping MATLAB for DSP Applications July 10, 2003 #12;Two True Stories · the world

Chauhan, Arun

126

AUTOMATIC GUIDING OF THE PRIMARY IMAGE OF SOLAR GREGORY TELESCOPES  

E-Print Network [OSTI]

and declination angles of the Sun. Gregory-type telescopes have an elliptical secondary mirror behind the primeAUTOMATIC GUIDING OF THE PRIMARY IMAGE OF SOLAR GREGORY TELESCOPES G. KÃ?VELER1, E. WIEHR2, D of solar Gregory telescopes is used for automatic guiding. This new system avoids temporal varying

127

Accelerated expansion from cosmological holography  

E-Print Network [OSTI]

It is shown that holographic cosmology implies an evolving Hubble radius $c^{-1}\\dot{R}_H = -1 + 3\\Omega_m$ in the presence of a dimensionless matter density $\\Omega_m$ scaled to the closure density $3H^2/8\\pi G$, where $c$ denotes the velocity of light and $H$ and $G$ denote the Hubble parameter and Newton's constant. It reveals a dynamical dark energy and a sixfold increase in gravitational attraction to matter on the scale of the Hubble acceleration. It reproduces the transition redshift $z_t\\simeq 0.4$ to the present epoch of accelerated expansion and is consistent with $(q_0,(dq/dz)_0)$ of the deceleration parameter $q(z)=q_0+(dq/dz)_0z$ observed in Type Ia supernovae.

van Putten, Maurice H P M

2015-01-01T23:59:59.000Z

128

Gravitational wave astronomy and cosmology  

E-Print Network [OSTI]

The first direct observation of gravitational waves' action upon matter has recently been reported by the BICEP2 experiment. Advanced ground-based gravitational-wave detectors are being installed. They will soon be commissioned, and then begin searches for high-frequency gravitational waves at a sensitivity level that is widely expected to reach events involving compact objects like stellar mass black holes and neutron stars. Pulsar timing arrays continue to improve the bounds on gravitational waves at nanohertz frequencies, and may detect a signal on roughly the same timescale as ground-based detectors. The science case for space-based interferometers targeting millihertz sources is very strong. The decade of gravitational-wave discovery is poised to begin. In this writeup of a talk given at the 2013 TAUP conference, we will briefly review the physics of gravitational waves and gravitational-wave detectors, and then discuss the promise of these measurements for making cosmological measurements in the near future.

Scott A. Hughes

2014-05-02T23:59:59.000Z

129

Island Cosmology in the Landscape  

E-Print Network [OSTI]

In the eternally inflationary background driven by the metastable vacua of the landscape, it is possible that some local quantum fluctuations with the null energy condition violation can be large enough to stride over the barriers among different vacua, so that create some islands full of radiation in new vacua, and then these emergently thermalized islands will enter into the evolution of standard big bang cosmology. In this paper, we calculate the spectrum of curvature perturbation generated during the emergence of island. We find that generally the spectrum obtained is nearly scale invariant, which can be well related to that of slow roll inflation by a simple duality. This in some sense suggests a degeneracy between their scalar spectra. In addition, we also simply estimate the non-Gaussianity of perturbation, which is naturally large, yet, can lie well in the observational bound. The results shown here indicate that the island emergently thermalized in the landscape can be consistent with our observable universe.

Yun-Song Piao

2008-06-11T23:59:59.000Z

130

Introductory Lectures on Quantum Cosmology (1990)  

E-Print Network [OSTI]

We describe the modern approach to quantum cosmology, as initiated by Hartle and Hawking, Linde, Vilenkin and others. The primary aim is to explain how one determines the consequences for the late universe of a given quantum theory of cosmological initial or boundary conditions. An extensive list of references is included, together with a guide to the literature. It also includes a detailed treatment of the WKB interpretation, which is relevant to a forthcoming article by the author on the decoherent histories approach to quantum cosmology.

J. J. Halliwell

2009-09-14T23:59:59.000Z

131

Cosmological Solutions of Emergent Noncommutative Gravity  

SciTech Connect (OSTI)

Matrix models of the Yang-Mills type lead to an emergent gravity theory, which does not require fine-tuning of a cosmological constant. We find cosmological solutions of the Friedmann-Robertson-Walker type. They generically have a big bounce, and an early inflationlike phase with graceful exit. The mechanism is purely geometrical; no ad hoc scalar fields are introduced. The solutions are stabilized through vacuum fluctuations and are thus compatible with quantum mechanics. This leads to a Milne-like universe after inflation, which appears to be in remarkably good agreement with observation and may provide an alternative to standard cosmology.

Klammer, Daniela; Steinacker, Harold [Fakultaet fuer Physik, Universitaet Wien, A-1090 Wien (Austria)

2009-06-05T23:59:59.000Z

132

Isotropic cosmological singularities: other matter models  

E-Print Network [OSTI]

Isotropic cosmological singularities are singularities which can be removed by rescaling the metric. In some cases already studied (gr-qc/9903008, gr-qc/9903009, gr-qc/9903018) existence and uniqueness of cosmological models with data at the singularity has been established. These were cosmologies with, as source, either perfect fluids with linear equations of state or massless, collisionless particles. In this article we consider how to extend these results to a variety of other matter models. These are scalar fields, massive collisionless matter, the Yang-Mills plasma of Choquet-Bruhat, or matter satisfying the Einstein-Boltzmann equation.

K. P. Tod

2002-09-20T23:59:59.000Z

133

Very Large Aperture Diffractive Space Telescope  

SciTech Connect (OSTI)

A very large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass ''aiming'' at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The magnifying glass includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the magnifying glass, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets.

Hyde, Roderick Allen

1998-04-20T23:59:59.000Z

134

The Automated Palomar 60-Inch Telescope  

E-Print Network [OSTI]

We have converted the Palomar 60-inch telescope (P60) from a classical night assistant-operated telescope to a fully robotic facility. The automated system, which has been operational since September 2004, is designed for moderately fast (t <~ 3 minutes) and sustained (R <~ 23 mag) observations of gamma-ray burst afterglows and other transient events. Routine queue-scheduled observations can be interrupted in response to electronic notification of transient events. An automated pipeline reduces data in real-time, which is then stored on a searchable web-based archive for ease of distribution. We describe here the design requirements, hardware and software upgrades, and lessons learned from roboticization. We present an overview of the current system performance as well as plans for future upgrades.

Cenko, S B; Moon, D S; Harrison, F A; Kulkarni, S R; Henning, J R; Guzman, C D; Bonati, M; Smith, R M; Thicksten, R P; Doyle, M W; Petrie, H L; Gal-Yam, A; Soderberg, A M; Anagnostou, N L; Laity, A C; Fox, Derek B.; Moon, Dae-Sik; Harrison, Fiona A.; Henning, John R.; Bonati, Marco; Smith, Roger M.; Thicksten, Robert P.; Doyle, Michael W.; Petrie, Hal L.; Gal-Yam, Avishay; Soderberg, Alicia M.; Anagnostou, Nathaniel L.; Laity, Anastasia C.

2006-01-01T23:59:59.000Z

135

The Automated Palomar 60-Inch Telescope  

E-Print Network [OSTI]

We have converted the Palomar 60-inch telescope (P60) from a classical night assistant-operated telescope to a fully robotic facility. The automated system, which has been operational since September 2004, is designed for moderately fast (t <~ 3 minutes) and sustained (R <~ 23 mag) observations of gamma-ray burst afterglows and other transient events. Routine queue-scheduled observations can be interrupted in response to electronic notification of transient events. An automated pipeline reduces data in real-time, which is then stored on a searchable web-based archive for ease of distribution. We describe here the design requirements, hardware and software upgrades, and lessons learned from roboticization. We present an overview of the current system performance as well as plans for future upgrades.

S. Bradley Cenko; Derek B. Fox; Dae-Sik Moon; Fiona A. Harrison; S. R. Kulkarni; John R. Henning; C. Dani Guzman; Marco Bonati; Roger M. Smith; Robert P. Thicksten; Michael W. Doyle; Hal L. Petrie; Avishay Gal-Yam; Alicia M. Soderberg; Nathaniel L. Anagnostou; Anastasia C. Laity

2006-08-15T23:59:59.000Z

136

Telescoping magnetic ball bar test gage  

DOE Patents [OSTI]

A telescoping magnetic ball bar test gage for determining the accuracy of machine tools, including robots, and those measuring machines having non-disengagable servo drives which cannot be clutched out. Two gage balls are held and separated from one another by a telescoping fixture which allows them relative radial motional freedom but not relative lateral motional freedom. The telescoping fixture comprises a parallel reed flexure unit and a rigid member. One gage ball is secured by a magnetic socket knuckle assembly which fixes its center with respect to the machine being tested. The other gage ball is secured by another magnetic socket knuckle assembly which is engaged or held by the machine in such manner that the center of that ball is directed to execute a prescribed trajectory, all points of which are equidistant from the center of the fixed gage ball. As the moving ball executes its trajectory, changes in the radial distance between the centers of the two balls caused by inaccuracies in the machine are determined or measured by a linear variable differential transformer (LVDT) assembly actuated by the parallel reed flexure unit. Measurements can be quickly and easily taken for multiple trajectories about several different fixed ball locations, thereby determining the accuracy of the machine.

Bryan, J.B.

1982-03-15T23:59:59.000Z

137

Telescoping magnetic ball bar test gage  

DOE Patents [OSTI]

A telescoping magnetic ball bar test gage for determining the accuracy of machine tools, including robots, and those measuring machines having non-disengageable servo drives which cannot be clutched out. Two gage balls (10, 12) are held and separated from one another by a telescoping fixture which allows them relative radial motional freedom but not relative lateral motional freedom. The telescoping fixture comprises a parallel reed flexure unit (14) and a rigid member (16, 18, 20, 22, 24). One gage ball (10) is secured by a magnetic socket knuckle assembly (34) which fixes its center with respect to the machine being tested. The other gage ball (12) is secured by another magnetic socket knuckle assembly (38) which is engaged or held by the machine in such manner that the center of that ball (12) is directed to execute a prescribed trajectory, all points of which are equidistant from the center of the fixed gage ball (10). As the moving ball (12) executes its trajectory, changes in the radial distance between the centers of the two balls (10, 12) caused by inaccuracies in the machine are determined or measured by a linear variable differential transformer (LVDT) assembly (50, 52, 54, 56, 58, 60) actuated by the parallel reed flexure unit (14). Measurements can be quickly and easily taken for multiple trajectories about several different fixed ball (10) locations, thereby determining the accuracy of the machine.

Bryan, James B. (Pleasanton, CA)

1984-01-01T23:59:59.000Z

138

Development of a mid-sized Schwarzschild-Couder Telescope for the Cherenkov Telescope Array  

SciTech Connect (OSTI)

The Cherenkov Telescope Array (CTA) is a ground-based observatory for very high-energy (10 GeV to 100 TeV) gamma rays, planned for operation starting in 2018. It will be an array of dozens of optical telescopes, known as Atmospheric Cherenkov Telescopes (ACTs), of 8 m to 24 m diameter, deployed over an area of more than 1 square km, to detect flashes of Cherenkov light from showers initiated in the Earth's atmosphere by gamma rays. CTA will have improved angular resolution, a wider energy range, larger fields of view and an order of magnitude improvement in sensitivity over current ACT arrays such as H.E.S.S., MAGIC and VERITAS. Several institutions have proposed a research and development program to eventually contribute 36 medium-sized telescopes (9 m to 12 m diameter) to CTA to enhance and optimize its science performance. The program aims to construct a prototype of an innovative, Schwarzschild-Couder telescope (SCT) design that will allow much smaller and less expensive cameras and much larger fields of view than conventional Davies-Cotton designs, and will also include design and testing of camera electronics for the necessary advances in performance, reliability and cost. We report on the progress of the mid-sized SCT development program.

Cameron, Robert A.

2012-06-28T23:59:59.000Z

139

Conformally Friedmann-Lemaitre-Robertson-Walker cosmologies  

E-Print Network [OSTI]

In a universe where, according to the standard cosmological models, some 97% of the total mass-energy is still "missing in action" it behooves us to spend at least a little effort critically assessing and exploring radical alternatives. Among possible, (dare we say plausible), nonstandard but superficially viable models, those spacetimes conformal to the standard Friedmann-Lemaitre-Robertson-Walker class of cosmological models play a very special role --- these models have the unique and important property of permitting large non-perturbative geometric deviations from Friedmann-Lemaitre-Robertson-Walker cosmology without unacceptably distorting the cosmic microwave background. Performing a "cosmographic" analysis, (that is, temporarily setting aside the Einstein equations, since the question of whether or not the Einstein equations are valid on galactic and cosmological scales is essentially the same question as whether or not dark matter/dark energy actually exist), and using both supernova data and informat...

Visser, Matt

2015-01-01T23:59:59.000Z

140

Cosmology on the Beach - George Smoot  

SciTech Connect (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

George Smoot

2009-05-06T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Cosmology at the Beach Lecture: Anne Green  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.  

Ann Green

2010-01-08T23:59:59.000Z

142

Cosmology at the Beach Lecture: David Hughes  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

David Hughes

2010-01-08T23:59:59.000Z

143

Cosmology at the Beach Lecture: Simon White  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Simon White

2010-01-08T23:59:59.000Z

144

Cosmology on the Beach: Kendrick Smith  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

George Smoot

2010-01-08T23:59:59.000Z

145

Cosmology on the Beach - George Smoot  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

George Smoot

2010-01-08T23:59:59.000Z

146

An Inertial Reaction to Cosmological Accelerations  

E-Print Network [OSTI]

Mach's "fixed stars" are actually not fixed at all. The distant clusters of galaxies are not only receding from each observer but they are also accelerating since the rate of cosmological expansion is not constant. If the distant cosmic masses in someway constitute the frame of inertial reference then an additional force should be generated among local bodies in reaction to the apparent cosmological accelerations of the distant galaxies.

Scott Funkhouser

2005-05-17T23:59:59.000Z

147

Mass Spectrum, Actons and Cosmological Landscape  

E-Print Network [OSTI]

It is suggested that the properties of the mass spectrum of elementary particles could be related with cosmology. Solutions of the Klein-Gordon equation on the Friedmann type manifold with the finite action are constructed. These solutions (actons) have a discrete mass spectrum. We suggest that such solutions could select a universe from cosmological landscape. In particular the solutions with the finite action on de Sitter space are investigated.

V. V. Kozlov; I. V. Volovich

2006-12-13T23:59:59.000Z

148

{\\Lambda}CDM cosmology from matter only  

E-Print Network [OSTI]

I discuss a matter-only interpretation of {\\Lambda}CDM cosmology, based on conservation of energy and assuming a Machian definition of inertia. {\\Lambda}CDM cosmology can be linked to a Newtonian cosmic potential, subject to a propagating gravitational horizon. In a matter-only universe where total energy is conserved, Machian inertia related to the evolving potential may cause both deceleration and acceleration of recession.

Telkamp, Herman

2015-01-01T23:59:59.000Z

149

Towards a Cosmological Hubble Diagram for Type II-PSupernovae  

SciTech Connect (OSTI)

We present the first high-redshift Hubble diagram for Type II-P supernovae (SNe II-P) based upon five events at redshift upto z {approx}0.3. This diagram was constructed using photometry from the Canada-France-Hawaii Telescope Supernova Legacy Survey and absorption line spectroscopy from the Keck observatory. The method used to measure distances to these supernovae is based on recent work by Hamuy&Pinto (2002) and exploits a correlation between the absolute brightness of SNeII-P and the expansion velocities derived from the minimum of the Fe II 516.9 nm P-Cygni feature observed during the plateau phases. We present three refinements to this method which significantly improve the practicality of measuring the distances of SNe II-P at cosmologically interesting redshifts. These are an extinction correction measurement based on the V-I colors at day 50, across-correlation measurement for the expansion velocity and the ability to extrapolate such velocities accurately over almost the entire plateau phase. We apply this revised method to our dataset of high-redshift SNe II-P and find that the resulting Hubble diagram has a scatter of only 0.26 magnitudes, thus demonstrating the feasibility of measuring the expansion history, with present facilities, using a method independent of that based upon supernovae of Type Ia.

Nugent, Peter; Sullivan, Mark; Ellis, Richard; Gal-Yam, Avishay; Leonard, Douglas C.; Howell, D. Andrew; Astier, Pierre; Carlberg, RaymondG.; Conley, Alex; Fabbro, Sebastien; Fouchez, Dominique; Neill, James D.; Pain, Reynald; Perrett, Kathy; Pritchet, Chris J; Regnault, Nicolas

2006-03-20T23:59:59.000Z

150

Cosmological Acceleration: Dark Energy or Modified Gravity?  

E-Print Network [OSTI]

We review the evidence for recently accelerating cosmological expansion or "dark energy", either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any Dark Energy constituent. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of "dark energy" cannot be derived from the homogeneous expansion alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, with nearly static Dark Energy, or with gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish static "dark energy" from dynamic "dark energy" with equation of state $w(z)$ either changing rapidly or tracking the background matter. But to cosmologically distinguish $\\Lambda$CDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati modifications of Einstein gravity may also be detected in refined bservations in the solar system or at the intermediate Vainstein scale. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence ("Why now?") without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity.

Sidney Bludman

2006-06-12T23:59:59.000Z

151

Quantum Coherence Arguments for Cosmological Scale  

SciTech Connect (OSTI)

Homogeneity and correlations in the observed CMB are indicative of some form of cosmological coherence in early times. Quantum coherence in the early universe would be expected to give space-like phase coherence to any effects sourced to those times. If dark energy de-coherence is assumed to occur when the rate of expansion of the relevant cosmological scale parameter in the Friedmann-Lemaitre equations is no longer supra-luminal, a critical energy density is immediately defined. It is shown that the general class of dynamical models so defined necessarily requires a spatially flat cosmology in order to be consistent with observed structure formation. The basic assumption is that the dark energy density which is fixed during de-coherence is to be identified with the cosmological constant. It is shown for the entire class of models that the expected amplitude of fluctuations driven by the dark energy de-coherence process is of the order needed to evolve into the fluctuations observed in cosmic microwave background radiation and galactic clustering. The densities involved during de-coherence which correspond to the measured dark energy density turn out to be of the electroweak symmetry restoration scale. In an inflationary cosmology, this choice of the scale parameter in the FL equations directly relates the scale of dark energy decoherence to the De Sitter scales (associated with the positive cosmological constants) at both early and late times.

Lindesay, James; /SLAC

2005-05-27T23:59:59.000Z

152

Quantum Vacuum Structure and Cosmology  

SciTech Connect (OSTI)

Contemporary physics faces three great riddles that lie at the intersection of quantum theory, particle physics and cosmology. They are: (1) The expansion of the universe is accelerating - an extra factor of two appears in the size; (2) Zero-point fluctuations do not gravitate - a matter of 120 orders of magnitude; and (3) The 'True' quantum vacuum state does not gravitate. The latter two are explicitly problems related to the interpretation and the physical role and relation of the quantum vacuum with and in general relativity. Their resolution may require a major advance in our formulation and understanding of a common unified approach to quantum physics and gravity. To achieve this goal we must develop an experimental basis and much of the discussion we present is devoted to this task. In the following, we examine the observations and the theory contributing to the current framework comprising these riddles. We consider an interpretation of the first riddle within the context of the universe's quantum vacuum state, and propose an experimental concept to probe the vacuum state of the universe.

Rafelski, Johann; Labun, Lance; Hadad, Yaron; /Arizona U. /Munich U.; Chen, Pisin; /Taiwan, Natl. Taiwan U. /KIPAC, Menlo Park /SLAC

2011-12-05T23:59:59.000Z

153

Cosmological perturbations for imperfect fluids  

E-Print Network [OSTI]

Interacting fluids, endowed with bulk viscous stresses, are discussed in a unified perspective with the aim of generalizing the treatment of cosmological perturbation theory to the case where both fluctuating decay rates and fluctuating bulk viscosity coefficients are simultaneously present in the relativistic plasma. A gauge-invariant treatment of the qualitatively new phenomena arising in this context is provided. In a complementary approach, faithful gauge-fixed descriptions of the gravitational and hydrodynamical fluctuations are developed and exploited. To deepen the interplay between bulk viscous stresses and fluctuating decay rates, illustrative examples are proposed and discussed both analytically and numerically. Particular attention is paid to the coupled evolution of curvature and entropy fluctuations when, in the relativistic plasma, at least one of the interacting fluids possesses a fluctuating bulk viscosity coefficient. It is argued that this class of models may be usefully employed as an effective description of the decay of the inflaton as well as of other phenomena involving imperfect relativistic fluids.

Massimo Giovannini

2005-11-11T23:59:59.000Z

154

Friction forces in cosmological models  

E-Print Network [OSTI]

We investigate the dynamics of test particles undergoing friction forces in a Friedmann-Robertson-Walker (FRW) spacetime. The interaction with the background fluid is modeled by introducing a Poynting-Robertson-like friction force in the equations of motion, leading to measurable (at least in principle) deviations of the particle trajectories from geodesic motion. The effect on the peculiar velocities of the particles is investigated for various equations of state of the background fluid and different standard cosmological models. The friction force is found to have major effects on particle motion in closed FRW universes, where it turns the time-asymptotic value (approaching the recollapse) of the peculiar particle velocity from ultra-relativistic (close to light speed) to a co-moving one, i.e., zero peculiar speed. On the other hand, for open or flat universes the effect of the friction is not so significant, because the time-asymptotic peculiar particle speed is largely non-relativistic also in the geodesic case.

Donato Bini; Andrea Geralico; Daniele Gregoris; Sauro Succi

2014-08-23T23:59:59.000Z

155

Gamma-ray Burst Cosmology  

E-Print Network [OSTI]

Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

Wang, F Y; Liang, E W

2015-01-01T23:59:59.000Z

156

Review of the Solar Array Telescopes  

E-Print Network [OSTI]

For several years the only experiments sensitive to astrophysical gamma rays with energies beyond the reach of EGRET but below that of the Cherenkov imaging telescopes have been the "solar tower" detectors. They use >2000 m2 mirror areas to sample the Cherenkov wavefront generated by <100 GeV gamma rays, obtaining Crab sensitivities of more than 6$\\sigma$ in one ON-source hour. I will review the history of the solar tower Cherenkov experiments from 1992 to the present and their key design features. I will describe some successful analysis strategies, then summarize the principal results obtained.

David A. Smith

2006-08-11T23:59:59.000Z

157

ANTARES deep sea neutrino telescope results  

SciTech Connect (OSTI)

The ANTARES experiment is currently the largest underwater neutrino telescope in the Northern Hemisphere. It is taking high quality data since 2007. Its main scientific goal is to search for high energy neutrinos that are expected from the acceleration of cosmic rays from astrophysical sources. This contribution reviews the status of the detector and presents several analyses carried out on atmospheric muons and neutrinos. For example it shows the results from the measurement of atmospheric muon neutrino spectrum and of atmospheric neutrino oscillation parameters as well as searches for neutrinos from steady cosmic point-like sources, for neutrinos from gamma ray bursts and for relativistic magnetic monopoles.

Mangano, Salvatore [IFIC - Instituto de Física Corpuscular, Edificio Institutos de Investigatión, 46071 Valencia (Spain); Collaboration: ANTARES Collaboration

2014-06-24T23:59:59.000Z

158

A 16-m Telescope for the Advanced Technology Large Aperture Telescope (ATLAST) Mission  

E-Print Network [OSTI]

for the telescope and its instruments. Solar array panels, an antenna and a solar sail are also folded up against compartment which is attached to a spacecraft bus which provides power, attitude control and communications and is separated from the launch vehicle, its solar arrays and high gain antenna will be deployed

Sirianni, Marco

159

Fermi Large Area Telescope Third Source Catalog  

E-Print Network [OSTI]

We present the third Fermi Large Area Telescope source catalog (3FGL) of sources in the 100~MeV--300~GeV range. Based on the first four years of science data from the Fermi Gamma-ray Space Telescope mission, it is the deepest yet in this energy range. Relative to the 2FGL catalog, the 3FGL catalog incorporates twice as much data as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for Galactic diffuse gamma-ray emission, a refined procedure for source detection, and improved methods for associating LAT sources with potential counterparts at other wavelengths. The 3FGL catalog includes 3033 sources above 4 sigma significance, with source location regions, spectral properties, and monthly light curves for each. Of these, 78 are flagged as potentially being due to imperfections in the model for Galactic diffuse emission. Twenty-five sources are modeled explicitly as spatially extended, and overall 232 sources are considered as identifie...

,

2015-01-01T23:59:59.000Z

160

The X-ray Telescope of CAST  

E-Print Network [OSTI]

The Cern Axion Solar Telescope (CAST) is in operation and taking data since 2003. The main objective of the CAST experiment is to search for a hypothetical pseudoscalar boson, the axion, which might be produced in the core of the sun. The basic physics process CAST is based on is the time inverted Primakoff effect, by which an axion can be converted into a detectable photon in an external electromagnetic field. The resulting X-ray photons are expected to be thermally distributed between 1 and 7 keV. The most sensitive detector system of CAST is a pn-CCD detector combined with a Wolter I type X-ray mirror system. With the X-ray telescope of CAST a background reduction of more than 2 orders off magnitude is achieved, such that for the first time the axion photon coupling constant g_agg can be probed beyond the best astrophysical constraints g_agg < 1 x 10^-10 GeV^-1.

M. Kuster; H. Bräuninger; S. Cébrian; M. Davenport; C. Elefteriadis; J. Englhauser; H. Fischer; J. Franz; P. Friedrich; R. Hartmann; F. H. Heinsius; D. H. H. Hoffmann; G. Hoffmeister; J. N. Joux; D. Kang; K. Königsmann; R. Kotthaus; T. Papaevangelou; C. Lasseur; A. Lippitsch; G. Lutz; J. Morales; A. Rodríguez; L. Strüder; J. Vogel; K. Zioutas

2007-05-10T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Dissipative or Conservative cosmology with dark energy ?  

E-Print Network [OSTI]

All evolutional paths for all admissible initial conditions of FRW cosmological models with dissipative dust fluid (described by dark matter, baryonic matter and dark energy) are analyzed using dynamical system approach. With that approach, one is able to see how generic the class of solutions leading to the desired property -- acceleration -- is. The theory of dynamical systems also offers a possibility of investigating all possible solutions and their stability with tools of Newtonian mechanics of a particle moving in a 1-dimensional potential which is parameterized by the cosmological scale factor. We demonstrate that flat cosmology with bulk viscosity can be treated as a conservative system with a potential function of the Chaplygin gas type. We also confront viscous models with SNIa observations. The best fitted models are obtained by minimizing the $\\chi^{2}$ function which is illustrated by residuals and $\\chi^{2}$ levels in the space of model independent parameters. The general conclusion is that SNIa data supports the viscous model without the cosmological constant. The obtained values of $\\chi^{2}$ statistic are comparable for both the viscous model and LCDM model. The Bayesian information criteria are used to compare the models with different power law parameterization of viscous effects. Our result of this analysis shows that SNIa data supports viscous cosmology more than the LCDM model if the coefficient in viscosity parameterization is fixed. The Bayes factor is also used to obtain the posterior probability of the model.

Marek Szydlowski; Orest Hrycyna

2007-11-24T23:59:59.000Z

162

Status of the second phase of the MAGIC telescope  

E-Print Network [OSTI]

The MAGIC 17m diameter Cherenkov telescope will be upgraded with a second telescope with advanced photon detectors and ultra fast readout within the year 2007. The sensitivity of MAGIC-II, the two telescope system, will be improved by a factor of 2. In addition the energy threshold will be reduced and the energy and angular resolution will be improved. The design, status and expected performance of MAGIC-II is presented here.

Florian Goebel; for the MAGIC collaboration

2007-09-17T23:59:59.000Z

163

Beyond the Cosmological Standard Model  

E-Print Network [OSTI]

After a decade and a half of research motivated by the accelerating universe, theory and experiment have a reached a certain level of maturity. The development of theoretical models beyond \\Lambda, or smooth dark energy, often called modified gravity, has led to broader insights into a path forward, and a host of observational and experimental tests have been developed. In this review we present the current state of the field and describe a framework for anticipating developments in the next decade. We identify the guiding principles for rigorous and consistent modifications of the standard model, and discuss the prospects for empirical tests. We begin by reviewing attempts to consistently modify Einstein gravity in the infrared, focusing on the notion that additional degrees of freedom introduced by the modification must screen themselves from local tests of gravity. We categorize screening mechanisms into three broad classes: mechanisms which become active in regions of high Newtonian potential, those in which first derivatives become important, and those for which second derivatives are important. Examples of the first class, such as f(R) gravity, employ the familiar chameleon or symmetron mechanisms, whereas examples of the last class are galileon and massive gravity theories, employing the Vainshtein mechanism. In each case, we describe the theories as effective theories. We describe experimental tests, summarizing laboratory and solar system tests and describing in some detail astrophysical and cosmological tests. We discuss future tests which will be sensitive to different signatures of new physics in the gravitational sector. Parts that are more relevant to theorists vs. observers/experimentalists are clearly indicated, in the hope that this will serve as a useful reference for both audiences, as well as helping those interested in bridging the gap between them.

Austin Joyce; Bhuvnesh Jain; Justin Khoury; Mark Trodden

2014-12-15T23:59:59.000Z

164

The Robotic Super-LOTIS Telescope: Results & Future Plans  

E-Print Network [OSTI]

We provide an overview of the robotic Super-LOTIS (Livermore Optical Transient Imaging System) telescope and present results from gamma-ray burst (GRB) afterglow observations using Super-LOTIS and other Steward Observatory telescopes. The 0.6-m Super-LOTIS telescope is a fully robotic system dedicated to the measurement of prompt and early time optical emission from GRBs. The system began routine operations from its Steward Observatory site atop Kitt Peak in April 2000 and currently operates every clear night. The telescope is instrumented with an optical CCD camera and a four position filter wheel. It is capable of observing Swift Burst Alert Telescope (BAT) error boxes as early or earlier than the Swift UV/Optical Telescope (UVOT). Super-LOTIS complements the UVOT observations by providing early R- and I-band imaging. We also use the suite of Steward Observatory telescopes including the 1.6-m Kuiper, the 2.3-m Bok, the 6.5-m MMT, and the 8.4-m Large Binocular Telescope to perform follow-up optical and near infrared observations of GRB afterglows. These follow-up observations have traditionally required human intervention but we are currently working to automate the 1.6-m Kuiper telescope to minimize its response time.

G. G. Williams; P. A. Milne; H. S. Park; S. D. Barthelmy; D. H. Hartmann; A. Updike; K. Hurley

2008-02-29T23:59:59.000Z

165

amanda neutrino telescope: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

neutrino flux, permanent and transient point source analyses, and indirect dark matter searches. A brief outlook on the IceCube neutrino telescope currently under...

166

amanda neutrino telescopes: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

neutrino flux, permanent and transient point source analyses, and indirect dark matter searches. A brief outlook on the IceCube neutrino telescope currently under...

167

Light right-handed neutrinos: + an incursion in cosmology  

E-Print Network [OSTI]

Light right-handed neutrinos: why not? + an incursion in cosmology R. Barbieri "Neutrinos in Venice? " The typical lifetime of a new trend in high energy physics and cosmology nowadays is about 5 to 10 years

Abbondandolo, Alberto

168

Scrutinizing Exotic Cosmological Models Using ESSENCE Supernova Data Combined With Other Cosmological Probes  

SciTech Connect (OSTI)

The first cosmological results from the ESSENCE supernova survey (Wood-Vasey et al. 2007) are extended to a wider range of cosmological models including dynamical dark energy and non-standard cosmological models. We fold in a greater number of external data sets such as the recent Higher-z release of high-redshift supernovae (Riess et al. 2007) as well as several complementary cosmological probes. Model comparison statistics such as the Bayesian and Akaike information criteria are applied to gauge the worth of models. These statistics favor models that give a good fit with fewer parameters. Based on this analysis, the preferred cosmological model is the flat cosmological constant model, where the expansion history of the universe can be adequately described with only one free parameter describing the energy content of the universe. Amongst the more exotic models that provide good fits to the data, we note a preference for models whose best-fit parameters reduce them to the cosmological constant model.

Davis, Tamara M.; Mortsell, E.; Sollerman, J.; Becker, A.C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Filippenko, A.V.; Foley, R.J.; Garnavich, P.M.; Jha, S.; Krisciunas, K.; Kirshner, R.P.; Leibundgut, B.; Li, W.; Matheson, T.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A.G.; Schmidt, B.P.; /Bohr Inst. /Stockholm U. /Washington U.,

2007-01-25T23:59:59.000Z

169

Cosmological 3-point correlators from holography  

SciTech Connect (OSTI)

We investigate the non-Gaussianity of primordial cosmological perturbations using holographic methods. In particular, we derive holographic formulae that relate all cosmological 3-point correlation functions, including both scalar and tensor perturbations, to stress-energy correlation functions of a holographically dual three-dimensional quantum field theory. These results apply to general single scalar inflationary universes that at late times approach either de Sitter spacetime or accelerating power-law cosmologies. We further show that in Einstein gravity all 3-point functions involving tensors may be obtained from correlators containing only positive helicity gravitons, with the ratios of these to the correlators involving one negative helicity graviton being given by universal functions of momenta, irrespectively of the potential of the scalar field. As a by-product of this investigation, we obtain holographic formulae for the full 3-point function of the stress-energy tensor along general holographic RG flows. These results should have applications in a wider holographic context.

McFadden, Paul; Skenderis, Kostas, E-mail: P.L.McFadden@uva.nl, E-mail: K.Skenderis@uva.nl [Institute for Theoretical Physics, Science Park 904, 1090 GL Amsterdam (Netherlands)

2011-06-01T23:59:59.000Z

170

Accelerating Cosmologies with Extended Product Spaces  

E-Print Network [OSTI]

Accelerating cosmologies in extra dimensional spaces have been studied. These extra dimensional spaces are products of many spaces. The physical behaviors of accelerating cosmologies are investigated from Einstein's field equation in higher dimensional Friedmann-Robertson-Walker (FRW) universe and superstring/M theory points of view. It is found that if some assumptions of flatness are made for sector of the FRW universe, the remaining sector needs to be hyperbolic. These properties are in parallel with those found in the model of superstring/M theory. The extended product made for the superstring model did not show any more new features other than those already found. A similar accelerating phase of this product space cosmology was found with difference in numerical values of the accelerating period.

Han Siong Ch'ng

2008-10-15T23:59:59.000Z

171

Quantum Exclusion of Positive Cosmological Constant?  

E-Print Network [OSTI]

We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state because of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources.

Gia Dvali; Cesar Gomez

2014-12-27T23:59:59.000Z

172

Brane f(R) gravity cosmologies  

SciTech Connect (OSTI)

By the application of the generalized Israel junction conditions we derive cosmological equations for the fourth-order f(R) brane gravity and study their cosmological solutions. We show that there exists a nonstatic solution which describes a four-dimensional de Sitter (dS{sub 4}) brane embedded in a five-dimensional anti-de Sitter (AdS{sub 5}) bulk for a vanishing Weyl tensor contribution. On the other hand, for the case of a nonvanishing Weyl tensor contribution, there exists a static brane solution only. We claim that in order to get some more general nonstatic f(R) brane configurations, one needs to admit a dynamical matter energy-momentum tensor in the bulk rather than just a bulk cosmological constant.

Balcerzak, Adam; DaPbrowski, Mariusz P. [Institute of Physics, University of Szczecin, Wielkopolska 15, 70-451 Szczecin (Poland)

2010-06-15T23:59:59.000Z

173

Cosmological perturbations in mimetic matter model  

E-Print Network [OSTI]

We investigate the cosmological evolution of mimetic matter model with arbitrary scalar potential. The cosmological reconstruction is explicitly done for different choices of potential. The cases that mimetic matter model shows the evolution as Cold Dark Matter(CDM), wCDM model, dark matter and dark energy with dynamical $Om(z)$ or phantom dark energy with phantom-non-phantom crossing are presented in detail. The cosmological perturbations for such evolution are studied in mimetic matter model. For instance, the evolution behavior of the matter density contrast which is different from usual one, i.e. $\\ddot \\delta + 2 H \\dot \\delta - \\kappa ^2 \\rho \\delta /2 = 0$ is investigated. The possibility of peculiar evolution of $\\delta$ in the model under consideration is shown. Special attention is paid to the behavior of matter density contrast near to future singularity where decay of perturbations may occur much earlier the singularity.

Matsumoto, Jiro; Sushkov, Sergey V

2015-01-01T23:59:59.000Z

174

Cosmological and Astrophysical Probes of Vacuum Energy  

E-Print Network [OSTI]

Vacuum energy changes during cosmological phase transitions and becomes relatively important at epochs just before phase transitions. For a viable cosmology the vacuum energy just after a phase transition must be set by the critical temperature of the next phase transition, which exposes the cosmological constant problem from a different angle. Here we propose to experimentally test the properties of vacuum energy under circumstances different from our current vacuum. One promising avenue is to consider the effect of high density phases of QCD in neutron stars. Such phases have different vacuum expectation values and a different vacuum energy from the normal phase, which can contribute an order one fraction to the mass of neutron stars. Precise observations of the mass of neutron stars can potentially yield information about the gravitational properties of vacuum energy, which can significantly affect their mass-radius relation. A more direct test of cosmic evolution of vacuum energy could be inferred from a ...

Bellazzini, Brando; Hubisz, Jay; Serra, Javi; Terning, John

2015-01-01T23:59:59.000Z

175

Analysis of inflationary cosmological models in gauge theories of gravitation  

E-Print Network [OSTI]

Inflationary homogeneous isotropic cosmological models filled by scalar fields and ultrarelativistic matter are examined in the framework of gauge theories of gravitation. By using quadratic scalar field potential numerical analysis of flat, open and closed models is curried out. Properties of cosmological models are investigated in dependence on indefinite parameter of cosmological equations and initial conditions at a bounce. Fulfilled analysis demonstrates regular character of all cosmological models.

A. V. Minkevich; A. S. Garkun

2005-12-22T23:59:59.000Z

176

Future Singularities and Completeness in Cosmology  

E-Print Network [OSTI]

We review recent work on the existence and nature of cosmological singularities that can be formed during the evolution of generic as well as specific cosmological spacetimes in general relativity. We first discuss necessary and sufficient conditions for the existence of geodesically incomplete spacetimes based on a tensorial analysis of the geodesic equations. We then classify the possible singularities of isotropic globally hyperbolic universes using the Bel-Robinson slice energy that closely monitors the asymptotic properties of fields near the singularity. This classification includes all known forms of spacetime singularities in isotropic universes and also predicts new types.

Spiros Cotsakis

2006-06-04T23:59:59.000Z

177

Thermodynamics of Ideal Gas in Cosmology  

E-Print Network [OSTI]

The equation of state and the state functions for the gravitational source are necessary conditions for solving cosmological model and stellar structure. The usual treatments are directly based on the laws of thermodynamics, and the physical meanings of some concepts are obscure. This letter show that, we can actually derive all explicit fundamental state functions for the ideal gas in the context of cosmology via rigorous dynamical and statistical calculation. These relations have clear physical meanings, and are valid in both non-relativistic and ultra-relativistic cases. Some features of the equation of state are important for a stable structure of a star with huge mass.

Ying-Qiu Gu

2009-10-04T23:59:59.000Z

178

Non-standard loop quantum cosmology  

E-Print Network [OSTI]

We present results concerning the nature of the cosmological big bounce(BB) transition within the loop geometry underlying loop quantum cosmology (LQC). Our canonical quantization method is an alternative to the standard LQC. An evolution parameter we use has clear interpretation both at classical and quantum levels. The physical volume operator has discrete spectrum which is bounded from below. The minimum gap in the spectrum defines a quantum of the volume. The spectra of operators are parametrized by a free parameter to be determined.

Wlodzimierz Piechocki

2010-01-19T23:59:59.000Z

179

Radiation-dominated area metric cosmology  

E-Print Network [OSTI]

We provide further crucial support for a refined, area metric structure of spacetime. Based on the solution of conceptual issues, such as the consistent coupling of fermions and the covariant identification of radiation fields on area metric backgrounds, we show that the radiation-dominated epoch of area metric cosmology is equivalent to that epoch in standard Einstein cosmology. This ensures, in particular, successful nucleosynthesis. This surprising result complements the previously derived prediction of a small late-time acceleration of an area metric universe.

Frederic P. Schuller; Mattias N. R. Wohlfarth

2007-06-12T23:59:59.000Z

180

Asymptotic safety and the cosmological constant  

E-Print Network [OSTI]

We study the non-perturbative renormalisation of quantum gravity in four dimensions. Taking care to disentangle physical degrees of freedom, we observe the topological nature of conformal fluctuations arising from the functional measure. The resulting beta functions possess an asymptotically safe fixed point with a global phase structure leading to classical general relativity for positive, negative or vanishing cosmological constant. If only the conformal fluctuations are quantised we find an asymptotically safe fixed point predicting a vanishing cosmological constant on all scales. At this fixed point we reproduce the critical exponent, $\

Kevin Falls

2014-08-01T23:59:59.000Z

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While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Cosmology as Science?: From Inflation to Eternity  

ScienceCinema (OSTI)

The last decade or two have represented the golden age of observational cosmology, producing a revolution in our picture of the Universe on its largest scales, and perhaps also its smallest ones. I will argue that these recent development bring to the forefront some vexing questions about whether various fundamental assumptions about the universe are in fact falsifiable. I will focus on 3 issues: (1) "Proving" Inflation, (2) Dark Energy and Anthropic Arguments, and (3) Cosmology of the far future.Interview with Lawrence M. Krauss

None

2011-10-06T23:59:59.000Z

182

THE CHERENKOV TELESCOPE ARRAY for the CTA Consortium  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) is a next-generation observatory proposed for very high-energy gamma rays imaging air Cherenkov telescopes (IACTs), cover an energy range of about four decades (from a few tens of GeV to above 100 TeV), and to enhance angular and energy resolutions. CTA will have a large discovery

Boyer, Edmond

183

VERITAS The Very Energetic Radiation Imaging Telescope Array System  

E-Print Network [OSTI]

A next generation atmospheric Cherenkov observatory is described based on the Whipple Observatory $\\gamma$-ray telescope. A total of nine such imaging telescopes will be deployed in an array that will permit the maximum versatility and give high sensitivity in the 50 GeV - 50 TeV band (with maximum sensitivity from 100 GeV to 10 TeV).

Weekes, T C; Biller, S D; Breslin, A C; Buckley, J H; Carter-Lewis, D A; Catanese, M; Cawley, M F; Dingus, B L; Fazio, G G; Fegan, D J; Finley, J; Fishman, G; Gaidos, J A; Gillanders, G H; Gorham, P W; Grindlay, J E; Hillas, A M; Huchra, J P; Kaaret, P E; Kertzman, M P; Kieda, D B; Krennrich, F; Lamb, R C; Lang, M J; Marscher, A P; Matz, S; McKay, T; Müller, D; Ong, R; Purcell, W; Rose, J; Sembroski, G H; Seward, F D; Slane, P O; Swordy, S P; Tümer, T O; Ulmer, M P; Urban, M; Wilkes, B J

1997-01-01T23:59:59.000Z

184

VERITAS: Very LArge Energetic Radiation Imaging Telescope Array System  

E-Print Network [OSTI]

A next generation atmospheric Cherenkov observatory is described based on the Whipple Observatory $\\gamma$-ray telescope. A total of nine such imaging telescopes will be deployed in an array that will permit the maximum versatility and give high sensitivity in the 50 GeV - 50 TeV band (with maximum sensitivity from 100 GeV to 10 TeV).

T. C. Weekes; C. Akerlof; S. Biller; A. C. Breslin; J. H. Buckley; D. A. Carter-Lewis; M. Catanese; M. F. Cawley; B. Dingus; G. G. Fazio; D. J. Fegan; J. Finley; G. Fishman; J. Gaidos; G. H. Gillanders; P. Gorham; J. E. Grindlay; A. M. Hillas; J. Huchra; P. Kaaret; M. Kertzman; D. Kieda; F. Krennrich; R. C. Lamb; M. J. Lang; A. P. Marscher; S. Matz; T. McKay; D. Muller; R. Ong; W. Purcell; J. Rose; G. Sembroski; F. D. Seward; P. Slane; S. Swordy; T. Tumer; M. Ulmer; M. Urban; B. J. Wilkes

1997-06-15T23:59:59.000Z

185

SST-GATE: A dual mirror telescope for the Cherenkov Telescope Array  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) will be the world's first open observatory for very high energy gamma-rays. Around a hundred telescopes of different sizes will be used to detect the Cherenkov light that results from gamma-ray induced air showers in the atmosphere. Amongst them, a large number of Small Size Telescopes (SST), with a diameter of about 4 m, will assure an unprecedented coverage of the high energy end of the electromagnetic spectrum (above ~1TeV to beyond 100 TeV) and will open up a new window on the non-thermal sky. Several concepts for the SST design are currently being investigated with the aim of combining a large field of view (~9 degrees) with a good resolution of the shower images, as well as minimizing costs. These include a Davies-Cotton configuration with a Geiger-mode avalanche photodiode (GAPD) based camera, as pioneered by FACT, and a novel and as yet untested design based on the Schwarzschild-Couder configuration, which uses a secondary mirror to reduce the plate-scale and to all...

Zech, A; Blake, S; Boisson, C; Costille, C; De-Frondat, F; Dournaux, J -L; Dumas, D; Fasola, G; Greenshaw, T; Hervet, O; Huet, J -M; Laporte, P; Rulten, C; Savoie, D; Sayede, F; Schmoll, J

2013-01-01T23:59:59.000Z

186

Surface Tension and the Cosmological Constant  

E-Print Network [OSTI]

The astronomically observed value of the cosmological constant is small but non-zero. This raises two questions together known as the cosmological constant problem a) why is lambda so nearly zero? b) why is lambda not EXACTLY zero? Sorkin has proposed that b) can be naturally explained as a one by square root N fluctuation by invoking discreteness of spacetime at the Planck scale due to quantum gravity. In this paper we shed light on these questions by developing an analogy between the cosmological constant and the surface tension of membranes. The ``cosmological constant problem'' has a natural analogue in the membrane context: the vanishingly small surface tension of fluid membranes provides an example where question a) above arises and is answered. We go on to find a direct analogue of Sorkin's proposal for answering question b) in the membrane context, where the discreteness of spacetime translates into the molecular structure of matter. We propose analogue experiments to probe a small and fluctuating surface tension in fluid membranes. A counterpart of dimensional reduction a la Kaluza-Klein and large extra dimensions also appears in the physics of fluid membranes.

Joseph Samuel; Supurna Sinha

2006-04-18T23:59:59.000Z

187

ccsd00000531 Early Cosmology and Fundamental Physics  

E-Print Network [OSTI]

, open problems and future perspectives in connection with dark energy and string theory are overviewed. Contents I. The history of the universe 1 II. Fundamental Physics 2 III. Essentials of Cosmology 3 IV and Outlook 13 References 14 I. THE HISTORY OF THE UNIVERSE The history of the universe is a history

188

Warm inflationary model in loop quantum cosmology  

SciTech Connect (OSTI)

A warm inflationary universe model in loop quantum cosmology is studied. In general we discuss the condition of inflation in this framework. By using a chaotic potential, V({phi}){proportional_to}{phi}{sup 2}, we develop a model where the dissipation coefficient {Gamma}={Gamma}{sub 0}=constant. We use recent astronomical observations for constraining the parameters appearing in our model.

Herrera, Ramon [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Avenida Brasil 2950, Casilla 4059, Valparaiso (Chile)

2010-06-15T23:59:59.000Z

189

Observed Cosmological Redshifts Support Contracting Accelerating Universe  

E-Print Network [OSTI]

The main argument that Universe is currently expanding is observed redshift increase by distance. However, this conclusion may not be correct, because cosmological redshift depends only on the scaling factors, the change in the size of the universe during the time of light propagation and is not related to the speed of observer or speed of the object emitting the light. An observer in expanding universe will measure the same redshift as observer in contracting universe with the same scaling. This was not taken into account in analysing the SN Ia data related to the universe acceleration. Possibility that universe may contract, but that the observed light is cosmologically redshifted allows for completely different set of cosmological parameters $\\Omega_M, \\Omega_{\\Lambda}$, including the solution $\\Omega_M=1, \\Omega_{\\Lambda}=0$. The contracting and in the same time accelerating universe explains observed deceleration and acceleration in SN Ia data, but also gives significantly larger value for the age of the universe, $t_0 = 24$ Gyr. This allows to reconsider classical cosmological models with $\\Lambda =0$. The contracting stage also may explain the observed association of high redshifted quasars to low redshifted galaxies.

Branislav Vlahovic

2012-07-02T23:59:59.000Z

190

Cosmology at the Beach Lecture: Wayne Hu  

ScienceCinema (OSTI)

Wayne Hu lectures on Secondary Anisotropy in the CMB. The lecture is the first in a series of 3 he delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Wayne Hu

2010-01-08T23:59:59.000Z

191

Cosmology with SKA Radio Continuum Surveys  

E-Print Network [OSTI]

Radio continuum surveys have, in the past, been of restricted use in cosmology. Most studies have concentrated on cross-correlations with the cosmic microwave background to detect the integrated Sachs-Wolfe effect, due to the large sky areas that can be surveyed. As we move into the SKA era, radio continuum surveys will have sufficient source density and sky area to play a major role in cosmology on the largest scales. In this chapter we summarise the experiments that can be carried out with the SKA as it is built up through the coming decade. We show that the SKA can play a unique role in constraining the non-Gaussianity parameter to \\sigma(f_NL) ~ 1, and provide a unique handle on the systematics that inhibit weak lensing surveys. The SKA will also provide the necessary data to test the isotropy of the Universe at redshifts of order unity and thus evaluate the robustness of the cosmological principle.Thus, SKA continuum surveys will turn radio observations into a central probe of cosmological research in th...

Jarvis, Matt J; Blake, Chris; Brown, Michael L; Lindsay, Sam N; Raccanelli, Alvise; Santos, Mario; Schwarz, Dominik

2015-01-01T23:59:59.000Z

192

COSMOLOGICAL LITHIUM PROBLEM: A DIFFERENT APPROACH  

E-Print Network [OSTI]

LITHIUM 7Li sources BBN cosmic-ray interactions (ingredients: shock waves, magnetic field, chargedCOSMOLOGICAL LITHIUM PROBLEM: A DIFFERENT APPROACH Tijana Prodanovi, University of Novi Sad Tamara Observations - boxes 4He ­ OK D ­ right on! 7Li ­ problem! Factor of 3-4 discrepancy! LITHIUM PROBLEM

?umer, Slobodan

193

Cosmology with Coupled Gravity and Dark Energy  

E-Print Network [OSTI]

Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way that dark energy and gravity are introduced into the cosmological field equation in parallel with each other from the beginning. The DEMC universe possesses a composite symmetry from global Galileo invariance and local Lorentz invariance. The observed evolution of the universe expansion rate at redshift z>1 is in tension with the standard LCDM model, but can be well predicted by the DEMC model from measurements of only nearby epochs. The so far most precise measured expansion rate at high z is quite a bit slower than the expectations from LCDM, but remarkably consistent with that from DEMC. It is hoped that the DEMC scenario can also help to solve other existing challenges to cosmology: large scale anomalies in CMB maps and large structures up to about 10^3 Mpc of a quasar group. The DEMC universe is a well defined mechanical system. From measurements we can quantitatively evaluate its total rest energy, present absolute radius and expanding speed.

Ti-Pei Li

2015-01-13T23:59:59.000Z

194

Cosmologies with a time dependent vacuum  

E-Print Network [OSTI]

The idea that the cosmological term, Lambda, should be a time dependent quantity in cosmology is a most natural one. It is difficult to conceive an expanding universe with a strictly constant vacuum energy density, namely one that has remained immutable since the origin of time. A smoothly evolving vacuum energy density that inherits its time-dependence from cosmological functions, such as the Hubble rate or the scale factor, is not only a qualitatively more plausible and intuitive idea, but is also suggested by fundamental physics, in particular by quantum field theory (QFT) in curved space-time. To implement this notion, is not strictly necessary to resort to ad hoc scalar fields, as usually done in the literature (e.g. in quintessence formulations and the like). A "running" Lambda term can be expected on very similar grounds as one expects (and observes) the running of couplings and masses with a physical energy scale in QFT. Furthermore, the experimental evidence that the equation of state of the dark energy could be evolving with time/redshift (including the possibility that it might currently behave phantom-like) suggests that a time-variable Lambda term (possibly accompanied by a variable Newton's gravitational coupling G=G(t)) could account in a natural way for all these features. Remarkably enough, a class of these models (the "new cosmon") could even be the clue for solving the old cosmological constant problem, including the coincidence problem.

Joan Sola

2011-02-09T23:59:59.000Z

195

Density Perturbations for Running Cosmological Constant  

E-Print Network [OSTI]

The dynamics of density and metric perturbations is investigated for the previously developed model where the decay of the vacuum energy into matter (or vice versa) is due to the renormalization group (RG) running of the cosmological constant (CC) term. The evolution of the CC depends on the single parameter \

Julio C. Fabris; Ilya L. Shapiro; Joan Sola

2007-01-26T23:59:59.000Z

196

Fluctuation, Dissipation and Irreversibility in Cosmology  

E-Print Network [OSTI]

We discuss the appearance of time-asymmetric behavior in physical processes in cosmology and in the dynamics of the Universe itself. We begin with an analysis of the nature and origin of irreversibility in well-known physical processes such as dispersion, diffusion, dissipation and mixing, and make the distinction between processes whose irreversibility arises from the stipulation of special initial conditions, and those arising from the system's interaction with a coarse-grained environment. We then study the irreversibility associated with quantum fluctuations in cosmological processes like particle creation and the `birth of the Universe'. We suggest that the backreaction effect of such quantum processes can be understood as the manifestation of a fluctuation-dissipation relation relating fluctuations of quantum fields to dissipations in the dynamics of spacetime. For the same reason it is shown that dissipation is bound to appear in the dynamics of minisuperspace cosmologies. This provides a natural course for the emergence of a cosmological and thermodynamic arrow of time and suggests a meaningful definition of gravitational entropy. We conclude with a discussion on the criteria for the choice of coarse-grainings and the stability of persistent physical structures. Invited Talk given at the Conference on The Physical Origin of Time-Asymmetry Huelva, Spain, Oct. 1991, Proceedings eds. J. J. Halliwell, J. Perez-Mercader and W. H. Zurek, Cambridge University Press, 1993

B. L. Hu

1993-02-18T23:59:59.000Z

197

Cosmological model with movement in fifth dimension  

E-Print Network [OSTI]

Presented cosmological model is 3D brane world sheet moved in extra dimension with variable scale factor. Analysis of the geodesic motion of the test particle gives settle explanation of the Pioneer effect. It is found that for considered metric the solution of the semi-classical Einstein equations with various parameters conforms to isotropic expanded and anisotropic stationary universe.

W. B. Belayev

2001-10-24T23:59:59.000Z

198

A Critical Review of Classical Bouncing Cosmologies  

E-Print Network [OSTI]

Given the proliferation of bouncing models in recent years, we gather and critically assess these proposals in a comprehensive review. The Planck data shows an unmistakably red, quasi scale-invariant, purely adiabatic primordial power spectrum and no primary non-Gaussianities. While these observations are consistent with inflationary predictions, bouncing cosmologies aspire to provide an alternative framework to explain them. Such models face many problems, both of the purely theoretical kind, such as the necessity of violating the NEC and instabilities, and at the cosmological application level, as exemplified by the possible presence of shear. We provide a pedagogical introduction to these problems and also assess the fitness of different proposals with respect to the data. For example, many models predict a slightly blue spectrum and must be fine-tuned to generate a red spectral index; as a side effect, large non-Gaussianities often result. We highlight several promising attempts to violate the NEC without introducing dangerous instabilities at the classical and/or quantum level. If primordial gravitational waves are observed, certain bouncing cosmologies, such as the cyclic scenario, are in trouble, while others remain valid. We conclude that, while most bouncing cosmologies are far from providing an alternative to the inflationary paradigm, a handful of interesting proposals have surfaced, which warrant further research. The constraints and lessons learned as laid out in this review might guide future research.

Diana Battefeld; Patrick Peter

2014-12-02T23:59:59.000Z

199

The Cosmological Constant and the String Landscape  

E-Print Network [OSTI]

Theories of the cosmological constant fall into two classes, those in which the vacuum energy is fixed by the fundamental theory and those in which it is adjustable in some way. For each class we discuss key challenges. The string theory landscape is an example of an adjustment mechanism. We discuss the status of this idea, and future directions.

Joseph Polchinski

2006-04-21T23:59:59.000Z

200

Design of a telescope pointing and tracking subsystem for the Big Bear Solar Observatory New Solar Telescope  

E-Print Network [OSTI]

, California, U.S.A.; bNew Jersey Institute of Technology, Newark, New Jersey, U.S.A. ABSTRACT The New SolarDesign of a telescope pointing and tracking subsystem for the Big Bear Solar Observatory New Solar Telescope J. R. Varsika and G.Yangb aBig Bear Solar Observatory, 40386 North Shore Lane, Big Bear City

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Cosmology with a stiff matter era  

E-Print Network [OSTI]

We provide a simple analytical solution of the Friedmann equations for a universe made of stiff matter, dust matter, and dark energy. A stiff matter era is present in the cosmological model of Zel'dovich (1972) where the primordial universe is assumed to be made of a cold gas of baryons. It also occurs in certain cosmological models where dark matter is made of relativistic self-gravitating Bose-Einstein condensates (BECs). When the energy density of the stiff matter is positive, the primordial universe is singular. It starts from a state with a vanishing scale factor and an infinite density. We consider the possibility that the energy density of the stiff matter is negative (anti-stiff matter). This happens, for example, when the BECs have an attractive self-interaction. In that case, the primordial universe is non-singular. It starts from a state in which the scale factor is finite and the energy density is equal to zero. For the sake of generality, we consider a cosmological constant of arbitrary sign. When the cosmological constant is positive, the universe asymptotically reaches a de Sitter phase where the scale factor increases exponentially rapidly. This can account for the accelerating expansion of the universe that we observe at present. When the cosmological constant is negative (anti-de Sitter), the evolution of the universe is cyclic. Therefore, depending on the sign of the energy density of the stiff matter and of the dark energy, we obtain singular and non-singular expanding or cyclic universes.

Pierre-Henri Chavanis

2014-11-27T23:59:59.000Z

202

The Liverpool Telescope: Rapid follow-up observation of Targets of opportunity with a 2 m robotic telescope  

E-Print Network [OSTI]

The Liverpool Telescope, situated at Roque de los Muchachos Observatory, La Palma, Canaries, is the first 2-m, fully instrumented robotic telescope. It recently began observations. Among Liverpool Telescope's primary scientific goals is to monitor variable objects on all timescales from seconds to years. An additional benefit of its robotic operation is rapid reaction to unpredictable phenomena and their systematic follow up, simultaneous or coordinated with other facilities. The Target of Opportunity Programme of the Liverpool Telescope includes the prompt search for and observation of GRB and XRF counterparts. A special over-ride mode implemented for GRB/XRF follow-up enables observations commencing less than a minute after the alert, including optical and near infrared imaging and spectroscopy. In particular, the moderate aperture and rapid automated response make the Liverpool Telescope excellently suited to help solving the mystery of optically dark GRBs and for the investigation of currently unstudied short bursts and XRFs.

A. Gomboc; M. F. Bode; D. Carter; C. G. Mundell; A. M. Newsam; R. J. Smith; I. A. Steele

2003-11-04T23:59:59.000Z

203

Finite Future Cosmological Singularity Times and Maximum Predictability Times in a Nonlinear FRW-KG Scalar Cosmology  

E-Print Network [OSTI]

We investigate the relative time scales associated with finite future cosmological singularities, especially those classified as Big Rip cosmologies, and the maximum predictability time of a coupled FRW-KG scalar cosmology with chaotic regimes. Our approach is to show that by starting with a FRW-KG scalar cosmology with a potential that admits an analytical solution resulting in a finite time future singularity there exists a Lyapunov time scale that is earlier than the formation of the singularity. For this singularity both the cosmological scale parameter a(t) and the Hubble parameter H(t) become infinite at a finite future time, the Big Rip time. We compare this time scale to the predictability time scale for a chaotic FRW-KG scalar cosmology. We find that there are cases where the chaotic time scale is earlier than the Big Rip singularity calling for special care in interpreting and predicting the formation of the future cosmological singularity.

John Max Wilson; Keith Andrew

2012-07-27T23:59:59.000Z

204

Real-time condition assessment of RAPTOR telescope systems  

SciTech Connect (OSTI)

The RAPid Telescopes for Optical Response (RAPTOR) observatory network consists of several robotic astronomical telescopes primarily designed to search for astrophysical transients called a gamma-ray bursts (GRBs). Although intrinsically bright, GRBs are difficult to detect because of their short duration. Typically, they are first observed by satellites that then relay the coordinates of the GRB to a ground station which, in turn, distributes the coordinates over the internet so that ground based observers can perform follow-up observations. Typically the ground based observations begin after the GRB has ended and only residual emiSSion (the 'afterglow') is left. However, if the satellite relays the GRB coordinates quickly enough, a 'fast' robotic telescope on the ground may be able to catch the GRB in progress. The RAPTOR telescope system is one of only a few in the world to have accomplished this feat. In order to achieve these results, the RAPTOR telescopes must operate autonomously at a high duty-cycle and in peak operating condition. Currently the telescopes are maintained in an ad hoc manner, often in a run-to-failure mode. The RAPTOR project could benefit greatly from a structural health monitoring (SHM) system, especially as more complex units are added to the suite of telescopes. This paper will summarize preliminary results from an SHM study performed on one of the RAPTOR telescopes. Damage scenarios that are of concern and that have been previously observed are first summarized. Then a specific study of damage to the telescope drive mechanism is presented where the data acquisition system is first described. Next, damage detection algorithms are developed with LANL's new publically available software SHMTools and the results of this process are discussed in detail. The paper will conclude with a summary of future planned refinemenls of the RAPTOR SHM system.

Stull, Chris [Los Alamos National Laboratory; Taylor, Stuart [Los Alamos National Laboratory; Wren, James [Los Alamos National Laboratory; Farrar, Charles [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

2010-11-30T23:59:59.000Z

205

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission  

SciTech Connect (OSTI)

The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy {gamma}-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy {gamma}-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic {gamma}-ray background up to TeV energies, and (7) explore the discovery space for dark matter.

Atwood, W.B.; /UC, Santa Cruz; Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Anderson, B. /UC, Santa Cruz; Axelsson, M.; /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bartelt, J.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bederede, D.; /DAPNIA, Saclay; Bellardi, F.; /INFN, Pisa; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bignami, G.F.; /Pavia U.; Bisello, D.; /INFN, Padua /Padua U.; Bissaldi, E.; /Garching, Max Planck Inst., MPE; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Pisa /INFN, Pisa /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /INFN, Padua /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /Kalmar U. /Royal Inst. Tech., Stockholm /DAPNIA, Saclay /ASI, Rome /INFN, Pisa /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /DAPNIA, Saclay /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors.; ,

2009-05-15T23:59:59.000Z

206

SciTech Connect: The Nuclear Spectroscopic Telescope Array (NuSTAR...  

Office of Scientific and Technical Information (OSTI)

The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Citation Details In-Document Search Title: The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Authors: Harrison,...

207

E-Print Network 3.0 - area space telescope Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

in space than ground? It's difficult to build telescopes in space. 12;Telescope Optics: Seeing... ", there is no seeing at the space, seeing is also wavelength dependent...

208

E-Print Network 3.0 - advanced compton telescope Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Detector Subsystem Summary: COMPTEL Compton Telescope on CGRO COS-B European Gamma-ray Astronomy Satellite DAPNIA Departement d... Telescope AGILE Astro-rivelatore Gamma a...

209

E-Print Network 3.0 - area telescope measurements Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

focused telescope: Requirement of on-off- measurements With exception of: gamma-ray bursts & solar flares short time... Compton telescopes would measure: ... Source:...

210

Testing the Bimodal/Schizophrenic Neutrino Hypothesis in Neutrinoless Double Beta Decay and Neutrino Telescopes  

E-Print Network [OSTI]

The standard assumption is that all three neutrino mass states are either Dirac or Majorana. However, it was recently suggested by Allaverdi, Dutta and one of the authors (R.N.M.) that mixed, or bimodal, flavor neutrino scenarios are conceivable and are consistent with all known observations (these were called "schizophrenic" in the ADM paper). In that case each individual mass eigenstate can be either Dirac or Majorana, so that the flavor eigenstates are "large" admixtures of both. An example of this "bimodal" situation is to consider one mass state as a Dirac particle (with a sterile partner), while the other two are of Majorana type. Since only Majorana particles contribute to neutrinoless double beta decay, the usual dependence of this observable on the neutrino mass is modified within this scenario. We study this in detail and, in particular, generalize the idea for all possible bimodal combinations. Inevitably, radiative corrections will induce a pseudo-Dirac nature to the Dirac states at the one-loop level, and the effects of the pseudo-Dirac mass splitting will show up in the flavor ratios of neutrinos from distant cosmological sources. Comparison of the effective mass in neutrinoless double beta decay as well as flavor ratios at neutrino telescopes, for different pseudo-Dirac cases and with their usual phenomenology, can distinguish the different bimodal possibilities.

James Barry; Rabindra N. Mohapatra; Werner Rodejohann

2011-06-27T23:59:59.000Z

211

A Cosmology Forecast Toolkit -- CosmoLib  

E-Print Network [OSTI]

The package CosmoLib is a combination of a cosmological Boltzmann code and a simulation toolkit to forecast the constraints on cosmological parameters from future observations. In this paper we describe the released linear-order part of the package. We discuss the stability and performance of the Boltzmann code. This is written in Newtonian gauge and including dark energy perturbations. In CosmoLib the integrator that computes the CMB angular power spectrum is optimized for a $\\ell$-by-$\\ell$ brute-force integration, which is useful for studying inflationary models predicting sharp features in the primordial power spectrum of metric fluctuations. The numerical code and its documentation are available at http://www.cita.utoronto.ca/~zqhuang/CosmoLib.

Zhiqi Huang

2012-06-11T23:59:59.000Z

212

EUNHA: a new cosmological hydro simulation code  

E-Print Network [OSTI]

We have developed a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order linear perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature uctuations at the initial particle position are determined by the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We have tested the code in several standard cases such as one-dimensional Riemann prob...

Shina, Jihye; Kim, Sungsoo S; Park, Changbom

2014-01-01T23:59:59.000Z

213

Cosmology of a Lorentz violating Galileon theory  

E-Print Network [OSTI]

We modify the scalar Einstein-aether theory by breaking the Lorentz invariance of a gravitational theory coupled to a Galileon type scalar field. This is done by introducing a Lagrange multiplier term into the action, thus ensuring that the gradient of the scalar field is time-like, with unit norm. The resulting theory is then generally invariant at the level of action, breaking the Lorentz invariance at the level of equations of motion. The theory can also be considered as an extension to the mimetic dark matter theory, by adding some derivative self interactions to the action, which keeps the equations of motion at most second order in time derivatives. The cosmological implications of the model are discussed in detail. In particular, we show that a matter dominated (dust) universe experiences a late time acceleration. The cosmological implications of a special coupling between the scalar field and the trace of the energy-momentum tensor are also explored.

Haghani, Zahra; Sepangi, Hamid Reza; Shahidi, Shahab

2015-01-01T23:59:59.000Z

214

Nonsingular Decaying Vacuum Cosmology and Entropy Production  

E-Print Network [OSTI]

The thermodynamic behavior of a decaying vacuum cosmology describing the entire cosmological history evolving between two extreme (early and late time) de Sitter eras is investigated. The thermal evolution from the early de Sitter to the radiation phase is discussed in detail. The temperature evolution law and the increasing entropy function are analytically determined. The entropy of the effectively massless particles is initially zero but evolves continuously to the present day maximum value within the current Hubble radius, $S_0 \\sim 10^{88}$ in natural units. By using the Gibbons-Hawking temperature relation for the de Sitter spacetime, it is found that the ratio between the primeval and the late time vacuum energy densities is $\\rho_{vI}/\\rho_{v0} \\sim 10^{123}$, as required by some naive estimates from quantum field theory.

J. A. S. Lima; S. Basilakos; Joan Solà

2015-03-08T23:59:59.000Z

215

A versatile digital camera trigger for telescopes in the Cherenkov Telescope Array  

E-Print Network [OSTI]

This paper describes the concept of an FPGA-based digital camera trigger for imaging atmospheric Cherenkov telescopes, developed for the future Cherenkov Telescope Array (CTA). The proposed camera trigger is designed to select images initiated by the Cherenkov emission of extended air showers from very-high energy (VHE, E>20 GeV) photons and charged particles while suppressing signatures from background light. The trigger comprises three stages. A first stage employs programmable discriminators to digitize the signals arriving from the camera channels (pixels). At the second stage, a grid of low-cost FPGAs is used to process the digitized signals for camera regions with 37 pixels. At the third stage, trigger conditions found independently in any of the overlapping 37-pixel regions are combined into a global camera trigger by few central FPGAs. Trigger prototype boards based on Xilinx FPGAs have been designed, built and tested and were shown to function properly. Using these components a full camera trigger wi...

Schwanke, U; Sulanke, K -H; Vorobiov, S; Wischnewski, R

2015-01-01T23:59:59.000Z

216

Cosmological Perturbations with Multiple Scalar Fields  

E-Print Network [OSTI]

In this brief note we present a set of equations describing the evolution of perturbed scalar fields in a cosmological spacetime with multiple scalar fields. We take into account of the simultaneously excited full metric perturbations in the context of the uniform-curvature gauge which is known to be the best choice. The equations presented in a compact form will be useful for handling the structure formation processes under the multiple episodes of inflation.

J. Hwang

1996-08-08T23:59:59.000Z

217

Cosmological Constant Problems and Renormalization Group  

E-Print Network [OSTI]

The Cosmological Constant Problem emerges when Quantum Field Theory is applied to the gravitational theory, due to the enormous magnitude of the induced energy of the vacuum. The unique known solution of this problem involves an extremely precise fine-tuning of the vacuum counterpart. We review a few of the existing approaches to this problem based on the account of the quantum (loop) effects and pay special attention to the ones involving the renormalization group.

Ilya L. Shapiro; Joan Sola

2007-01-05T23:59:59.000Z

218

Physical space and cosmology. I: Model  

E-Print Network [OSTI]

The nature of the physical space seems the most important subject in physics. A present paper proceeds from the assumption of physical reality of space contrary to the standard view of the space as a purely relational nonexistence - void. The space and its evolution are the primary sources of phenomena in Mega- and micro-worlds. Thus cosmology and particle physics have the same active agent - physical space.

Valeriy P. Polulyakh

2011-02-01T23:59:59.000Z

219

The Construction of Sudden Cosmological Singularities  

E-Print Network [OSTI]

Solutions of the Friedmann-Lemaitre cosmological equations of general relativity have been found with finite-time singularities that are everywhere regular, have regular Hubble expansion rate, and obey the strong-energy conditions but possess pressure and acceleration singularities at finite time that are not associated with geodesic incompleteness. We show how these solutions with sudden singularities can be constructed using fractional series methods and find the limiting form of the equation of state on approach to the singularity.

John D. Barrow; S. Cotsakis; A. Tsokaros

2010-03-04T23:59:59.000Z

220

Simple Cosmological Model with Relativistic Gas  

E-Print Network [OSTI]

We construct simple and useful approximation for the relativistic gas of massive particles. The equation of state is given by an elementary function and admits analytic solution of the Friedmann equation, including more complex cases when the relativistic gas of massive particles is considered together with radiation or with dominating cosmological constant. The model of relativistic gas may be interesting for the description of primordial Universe, especially as a candidate for the role of a Dark Matter.

Guilherme de Berredo-Peixoto; Ilya L. Shapiro; Flavia Sobreira

2005-06-16T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

area telescope catalog: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Catalog CERN Preprints Summary: We present the second catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on...

222

area telescope view: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

of the Core of the Radio Galaxy Centaurus A CERN Preprints Summary: We present gamma-ray observations with the LAT on board the Fermi Gamma-Ray Telescope of the nearby radio...

223

Cross section dependence of event rates at neutrino telescopes  

E-Print Network [OSTI]

We examine the dependence of event rates at neutrino telescopes on the neutrino-nucleon cross section for neutrinos with energy above 1 PeV, and contrast the results with those for cosmic ray experiments. Scaling of the ...

Marfatia, Danny; Seckel, D.; McKay, D. W.; Hussain, S.

2006-10-20T23:59:59.000Z

224

atmospheric fluorescence telescopes: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

become a powerful tool for accurate measurements of the energy and mass of ultra-high energy cosmic ray particles. Employing large area imaging telescopes with mirror areas of...

225

Minimizing High Spatial Frequency Residual in Active Space Telescope Mirrors  

E-Print Network [OSTI]

. Miller June 2008 SSL # 4-08 #12;#12;Minimizing High Spatial Frequency Residual in Active Space Telescope Mirrors Thomas Gray, David W. Miller June 2008 SSL # 4-08 This work is based on the unaltered text

226

Robust model comparison disfavors power law cosmology  

E-Print Network [OSTI]

Late-time power law expansion has been proposed as an alternative to the standard cosmological model and shown to be consistent with some low-redshift data. We test power law expansion against the standard flat $\\Lambda$CDM cosmology using goodness-of-fit and model comparison criteria. We consider Type Ia supernova (SN Ia) data from two current compilations (Union2.1 and JLA) along with a current set of baryon acoustic oscillation (BAO) measurements that includes the high-redshift Lyman-$\\alpha$ forest measurements from BOSS quasars. We find that neither power law expansion nor $\\Lambda$CDM is strongly preferred over the other when the SN Ia and BAO data are analyzed separately but that power law expansion is strongly disfavored by the combination. We treat the $R_\\text{h} = ct$ cosmology (a constant rate of expansion) separately and find that it is conclusively disfavored by all combinations of data that include SN Ia observations and a poor overall fit when systematic errors in the SN Ia measurements are ig...

Shafer, Daniel L

2015-01-01T23:59:59.000Z

227

Cosmological parameter estimation: impact of CMB aberration  

SciTech Connect (OSTI)

The peculiar motion of an observer with respect to the CMB rest frame induces an apparent deflection of the observed CMB photons, i.e. aberration, and a shift in their frequency, i.e. Doppler effect. Both effects distort the temperature multipoles a{sub lm}'s via a mixing matrix at any l. The common lore when performing a CMB based cosmological parameter estimation is to consider that Doppler affects only the l = 1 multipole, and neglect any other corrections. In this paper we reconsider the validity of this assumption, showing that it is actually not robust when sky cuts are included to model CMB foreground contaminations. Assuming a simple fiducial cosmological model with five parameters, we simulated CMB temperature maps of the sky in a WMAP-like and in a Planck-like experiment and added aberration and Doppler effects to the maps. We then analyzed with a MCMC in a Bayesian framework the maps with and without aberration and Doppler effects in order to assess the ability of reconstructing the parameters of the fiducial model. We find that, depending on the specific realization of the simulated data, the parameters can be biased up to one standard deviation for WMAP and almost two standard deviations for Planck. Therefore we conclude that in general it is not a solid assumption to neglect aberration in a CMB based cosmological parameter estimation.

Catena, Riccardo [Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Notari, Alessio, E-mail: riccardo.catena@theorie.physik.uni-goettingen.de, E-mail: notari@ffn.ub.es [Departament de Física Fondamental i Institut de Ciéncies del Cosmos, Universitat de Barcelona, Martí i Franqués 1, 08028 Barcelona (Spain)

2013-04-01T23:59:59.000Z

228

Is Cosmological Constant Needed in Higgs Inflation?  

E-Print Network [OSTI]

The detection of B-mode shows a very powerful constraint to theoretical inflation models through the measurement of the tensor-to-scalar ratio $r$. Higgs boson is the most likely candidate of the inflaton field. But usually, Higgs inflation models predict a small value of $r$, which is not quite consistent with the recent results from BICEP2. In this paper, we explored whether a cosmological constant energy component is needed to improve the situation. And we found the answer is yes. For the so-called Higgs chaotic inflation model with a quadratic potential, it predicts $r\\approx 0.2$, $n_s\\approx0.96$ with e-folds number $N\\approx 56$, which is large enough to overcome the problems such as the horizon problem in the Big Bang cosmology. The required energy scale of the cosmological constant is roughly $\\Lambda \\sim (10^{14} \\text{GeV})^2 $, which means a mechanism is still needed to solve the fine-tuning problem in the later time evolution of the universe, e.g. by introducing some dark energy component.

Feng, Chao-Jun

2014-01-01T23:59:59.000Z

229

Is Cosmological Constant Needed in Higgs Inflation?  

E-Print Network [OSTI]

The detection of B-mode shows a very powerful constraint to theoretical inflation models through the measurement of the tensor-to-scalar ratio $r$. Higgs boson is the most likely candidate of the inflaton field. But usually, Higgs inflation models predict a small value of $r$, which is not quite consistent with the recent results from BICEP2. In this paper, we explored whether a cosmological constant energy component is needed to improve the situation. And we found the answer is yes. For the so-called Higgs chaotic inflation model with a quadratic potential, it predicts $r\\approx 0.2$, $n_s\\approx0.96$ with e-folds number $N\\approx 56$, which is large enough to overcome the problems such as the horizon problem in the Big Bang cosmology. The required energy scale of the cosmological constant is roughly $\\Lambda \\sim (10^{14} \\text{GeV})^2 $, which means a mechanism is still needed to solve the fine-tuning problem in the later time evolution of the universe, e.g. by introducing some dark energy component.

Chao-Jun Feng; Xin-Zhou Li

2014-04-15T23:59:59.000Z

230

3D acoustic imaging applied to the Baikal Neutrino Telescope  

E-Print Network [OSTI]

A hydro-acoustic imaging system was tested in a pilot study on distant localization of elements of the Baikal underwater neutrino telescope. For this innovative approach, based on broad band acoustic echo signals and strictly avoiding any active acoustic elements on the telescope, the imaging system was temporarily installed just below the ice surface, while the telescope stayed in its standard position at 1100 m depth. The system comprised an antenna with four acoustic projectors positioned at the corners of a 50 meter square; acoustic pulses were "linear sweep-spread signals" - multiple-modulated wide-band signals (10-22 kHz) of 51.2 s duration. Three large objects (two string buoys and the central electronics module) were localized by the 3D acoustic imaging, with a accuracy of ~0.2 m (along the beam) and ~1.0 m (transverse). We discuss signal forms and parameters necessary for improved 3D acoustic imaging of the telescope, and suggest a layout of a possible stationary bottom based 3D imaging setup. The presented technique may be of interest for neutrino telescopes of km3-scale and beyond, as a flexible temporary or as a stationary tool to localize basic telescope elements, while these are completely passive.

K. G. Kebkal; R. Bannasch; O. G. Kebkal; A. I. Panfilov; R. Wischnewski

2008-11-07T23:59:59.000Z

231

Isotropic singularities in shear-free perfect fluid cosmologies  

E-Print Network [OSTI]

We investigate barotropic perfect fluid cosmologies which admit an isotropic singularity. From the General Vorticity Result of Scott, it is known that these cosmologies must be irrotational. In this paper we prove, using two different methods, that if we make the additional assumption that the perfect fluid is shear-free, then the fluid flow must be geodesic. This then implies that the only shear-free, barotropic, perfect fluid cosmologies which admit an isotropic singularity are the FRW models.

Geoffery Ericksson; Susan M. Scott

2001-08-02T23:59:59.000Z

232

A Cosmology Calculator for the World Wide Web  

E-Print Network [OSTI]

A cosmology calculator that computes times and distances as a function of redshift for user-defined cosmological parameters is available on the World Wide Web. This note gives the formulae used by the cosmology calculator and discusses some of its implementation. A version of the calculator that allows one to specify the equation of state parameter w and w' and neutrino masses, and a version for converting the light travel times usually given in the popular press into redshifts are also available.

Edward L. Wright

2006-10-10T23:59:59.000Z

233

Cosmological Evolution of Fundamental Constants: From Theory to Experiment  

E-Print Network [OSTI]

In this paper we discuss a possible cosmological time evolution of fundamental constants from the theoretical and experimental point of views. On the theoretical side, we explain that such a cosmological time evolution is actually something very natural which can be described by mechanisms similar to those used to explain cosmic inflation. We then discuss implications for grand unified theories, showing that the unification condition of the gauge coupling could evolve with cosmological time. Measurements of the electron-to-proton mass ratio can test grand unified theories using low energy data. Following the theoretical discussion, we review the current status of precision measurements of fundamental constants and their potential cosmological time dependence.

Xavier Calmet; Matthias Keller

2014-12-05T23:59:59.000Z

234

A new multidimensional AMR Hydro+Gravity Cosmological code  

E-Print Network [OSTI]

A new cosmological multidimensional hydrodynamic and N-body code based on an Adaptive Mesh Refinement scheme is described and tested. The hydro part is based on modern high-resolution shock-capturing techniques, whereas N-body approach is based on the Particle Mesh method. The code has been specifically designed for cosmological applications. Tests including shocks, strong gradients, and gravity have been considered. A cosmological test based on Santa Barbara cluster is also presented. The usefulness of the code is discussed. In particular, this powerful tool is expected to be appropriate to describe the evolution of the hot gas component located inside asymmetric cosmological structures.

Vicent Quilis

2004-05-20T23:59:59.000Z

235

accelerating frw cosmology: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

parametres. Taymaz Ghaneh; Farhad Darabi; Hossein Motavalli 2012-12-05 14 Dark energy FRW cosmology - dynamical system reconstruction CERN Preprints Summary: We...

236

Constraining gravitational and cosmological parameters with astrophysical data  

E-Print Network [OSTI]

We use astrophysical data to shed light on fundamental physics by constraining parametrized theoretical cosmological and gravitational models. Gravitational parameters are those constants that parametrize possible departures ...

Mao, Yi, Ph. D. Massachusetts Institute of Technology

2008-01-01T23:59:59.000Z

237

Phenomenology and cosmology of weakly coupled string theory  

E-Print Network [OSTI]

ph/9805320 May 1998 Phenomenology and cosmology of weaklyThe important point for phenomenology is the decomposition2]. Implications for phenomenology and open questions The

Gaillard, Mary K.

1998-01-01T23:59:59.000Z

238

Energy Conservation in Flat FRW Cosmology  

E-Print Network [OSTI]

The consequence of energy conservation in the flat Friedmannn-Robertson-Walker (FRW) cosmology is a strictly positive accelerating expansion. A mechanism is proposed for this expansion due to the effect of the attractive (negative) gravitational potential of matter as it is being included within the expanding horizon, and the offsetting work of metric expansion, which takes place at sub-luminal speed. In our semi-classical treatment, we deal with a quintic as the equation for the scale parameter. Implications for modeling the earliest parts of the primordial expansion are discussed.

Steven Maxson

2009-01-07T23:59:59.000Z

239

Cosmological Evolution of Pilgrim Dark Energy  

E-Print Network [OSTI]

We study pilgrim dark energy model by taking IR cut-offs as particle and event horizons as well as conformal age of the universe. We derive evolution equations for fractional energy density and equation of state parameters for pilgrim dark energy. The phantom cosmic evolution is established in these scenarios which is well supported by the cosmological parameters such as deceleration parameter, statefinder parameters and phase space of $\\omega_\\vartheta$ and $\\omega'_\\vartheta$. We conclude that the consistent value of parameter $\\mu$ is $\\mu<0$ in accordance with the current Planck and WMAP$9$ results.

Sharif, M

2015-01-01T23:59:59.000Z

240

Scalar field collapse with negative cosmological constant  

E-Print Network [OSTI]

The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter, which determines the equation of state and decides the fate of the spacetime. Without fine tuning the value of this parameter the collapse ends in a generic formation of a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

R. Baier; Hiromichi Nishimura; S. A. Stricker

2014-10-13T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Scalar field collapse with negative cosmological constant  

E-Print Network [OSTI]

The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter which determines the equation of state and decides the fate of the spacetime. Depending on the value of this parameter the collapse ends in a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

Baier, R; Stricker, S A

2014-01-01T23:59:59.000Z

242

Cosmological bounds on oscillating dark energy models  

E-Print Network [OSTI]

We study some cosmological constraints on the two phenomenological models of oscillating dark energy. In these scenarios, the equation of state of dark energy varies periodically and may provide a way to unify the early acceleration (inflation) and the late time acceleration of the universe. These models give also an effective way to tackle the so-called cosmic coincidence problem. We examine observational constraints on this class of models from the latest observational data including the \\emph{gold} sample of 182 type Ia supernovae, the CMB shift parameter $R$ and the BAO measurements from the Sloan Digital Sky Survey.

Deepak Jain; Abha Dev; J. S. Alcaniz

2007-09-26T23:59:59.000Z

243

Cosmological Evolution of Pilgrim Dark Energy  

E-Print Network [OSTI]

We study pilgrim dark energy model by taking IR cut-offs as particle and event horizons as well as conformal age of the universe. We derive evolution equations for fractional energy density and equation of state parameters for pilgrim dark energy. The phantom cosmic evolution is established in these scenarios which is well supported by the cosmological parameters such as deceleration parameter, statefinder parameters and phase space of $\\omega_\\vartheta$ and $\\omega'_\\vartheta$. We conclude that the consistent value of parameter $\\mu$ is $\\mu<0$ in accordance with the current Planck and WMAP$9$ results.

M. Sharif; M. Zubair

2014-09-26T23:59:59.000Z

244

Tunneling decay rate in quantum cosmology  

E-Print Network [OSTI]

In canonical quantum cosmology, the wave function of the universe lacks explicit time dependence. However, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. In this paper, we apply this approach to an oscillating universe model recently introduced by Graham et al. By extending the model to include a massless, minimally coupled scalar field $\\phi$ which has little effect on the dynamics but can play the role of a "clock", we determine the decay rate of the oscillating universe.

Mithani, Audrey T

2015-01-01T23:59:59.000Z

245

Tunneling decay rate in quantum cosmology  

E-Print Network [OSTI]

In canonical quantum cosmology, the wave function of the universe lacks explicit time dependence. However, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. In this paper, we apply this approach to an oscillating universe model recently introduced by Graham et al. By extending the model to include a massless, minimally coupled scalar field $\\phi$ which has little effect on the dynamics but can play the role of a "clock", we determine the decay rate of the oscillating universe.

Audrey T. Mithani; Alexander Vilenkin

2015-03-02T23:59:59.000Z

246

SKA SA test telescope reveals binary star system South Africa's test telescope reveals secrets of a binary star system and proves the country is able to  

E-Print Network [OSTI]

SKA SA test telescope reveals binary star system South Africa's test telescope reveals secrets, has created huge research and job opportunities. South Africa's Karoo Array Telescope (KAT-7) has at the SKA South Africa. The 64-dish MeerKAT ­ which SKA South Africa director Bernie Fanaroff once described

Jarrett, Thomas H.

247

Effective Matter Cosmologies of Massive Gravity: Physical Fluids  

E-Print Network [OSTI]

We derive new cosmological solutions of the ghost-free massive gravity with a general background metric in which the contribution of the mass sector to the metric one is modeled by an effective cosmological constant and an ideal fluid which obeys the first law of thermodynamics; thus it satisfies the ordinary energy-momentum conservation or continuity equation.

Nejat Tevfik Yilmaz

2014-12-16T23:59:59.000Z

248

Inflationary Cosmology: Is Our Universe Part of a Multiverse?  

SciTech Connect (OSTI)

In this talk, Guth explains the inflationary theory and reviews the features that make it scientifically plausible. In addition, he discusses the biggest mystery in cosmology: Why is the value of the cosmological constant, sometimes called the "anti-gravity" effect, so remarkably small compared to theoretical expectations?

Alan Guth

2008-11-06T23:59:59.000Z

249

ON PROVING FUTURE STABILITY OF COSMOLOGICAL SOLUTIONS WITH ACCELERATED EXPANSION  

E-Print Network [OSTI]

ON PROVING FUTURE STABILITY OF COSMOLOGICAL SOLUTIONS WITH ACCELERATED EXPANSION HANS RINGSTR at an accelerated rate. As a consequence, it is of interest to prove that cosmological solutions to Ein- stein's equations with accelerated expansion are future stable. That is the topic of the present contribution

Ringström, Hans

250

Cosmology as Science: From Inflation to the Future  

ScienceCinema (OSTI)

Recent developments in cosmology bring to the forefront fundamental questions about our ability to falsify various fundamental assumptions about the universe.  I will discuss three issues that reflect different aspects of these questions:  (1) "Proving" Inflation (2) Anthropic "Explanations" (3) Cosmology of the far future.

Lawrence Krauss

2010-01-08T23:59:59.000Z

251

BUILDING COSMOLOGICAL MODELS VIA NONCOMMUTATIVE GEOMETRY MATILDE MARCOLLI  

E-Print Network [OSTI]

of theoretical high energy physics models that are capable of producing a range of predictions, bothBUILDING COSMOLOGICAL MODELS VIA NONCOMMUTATIVE GEOMETRY MATILDE MARCOLLI and cosmology to formulate testable predictions that can be confronted with the data. While model building

Marcolli, Matilde

252

Evolution of density perturbations in decaying vacuum cosmology  

SciTech Connect (OSTI)

We study cosmological perturbations in the context of an interacting dark energy model, in which the cosmological term decays linearly with the Hubble parameter, with concomitant matter production. A previous joint analysis of the redshift-distance relation for type Ia supernovas, barionic acoustic oscillations, and the position of the first peak in the anisotropy spectrum of the cosmic microwave background has led to acceptable values for the cosmological parameters. Here we present our analysis of small perturbations, under the assumption that the cosmological term, and therefore the matter production, are strictly homogeneous. Such a homogeneous production tends to dilute the matter contrast, leading to a late-time suppression in the power spectrum. Nevertheless, an excellent agreement with the observational data can be achieved by using a higher matter density as compared to the concordance value previously obtained. This may indicate that our hypothesis of homogeneous matter production must be relaxed by allowing perturbations in the interacting cosmological term.

Borges, H. A.; Pigozzo, C. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Carneiro, S. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); International Centre for Theoretical Physics, Trieste (Italy); Fabris, J. C. [Institut d'Astrophysique de Paris, Paris (France)

2008-02-15T23:59:59.000Z

253

The Very Energetic Radiation Imaging Telescope Array System (VERITAS)  

E-Print Network [OSTI]

We give an overview of the current status and scientific goals of VERITAS, a proposed hexagonal array of seven 10 m aperture imaging Cherenkov telescopes. The selected site is Montosa Canyon (1390 m a.s.l.) at the Whipple Observatory, Arizona. Each telescope, of 12 m focal length, will initially be equipped with a 499 element photomultiplier camera covering a 3.5 degree field of view. A central station will initiate the readout of 500 MHz FADCs upon receipt of multiple telescope triggers. The minimum detectable flux sensitivity will be 0.5% of the Crab Nebula flux at 200 GeV. Detailed simulations of the array's performance are presented elsewhere at this meeting. VERITAS will operate primarily as a gamma-ray observatory in the 50 GeV to 50 TeV range for the study of active galaxies, supernova remnants, pulsars and gamma-ray bursts.

Bradbury, S M; Breslin, A C; Buckley, J H; Carter-Lewis, D A; Catanese, M; Criswell, S; Dingus, B L; Fegan, D J; Finley, J P; Gaidos, J A; Grindlay, J; Hillas, A M; Harris, K; Hermann, G; Kaaret, P E; Kieda, D B; Knapp, J; Krennrich, F; Le Bohec, S; Lessard, R W; Lloyd-Evans, J; McKernan, B; Müller, D; Ong, R; Quenby, J J; Quinn, J; Rochester, G D; Rose, H J; Salamon, M B; Sembroski, G H; Sumner, T J; Swordy, S P; Vasilev, V; Weekes, T C

1999-01-01T23:59:59.000Z

254

Indirect Dark Matter search with large neutrino telescopes  

E-Print Network [OSTI]

Dark matter is one of the main goals of neutrino astronomy. At present, there are two big neutrino telescopes based on the Cherenkov technique in ice and water: IceCube at the South Pole and ANTARES in the northern hemisphere. Both telescopes are performing an indirect search for Dark Matter by looking for a statistical excess of neutrinos coming from astrophysical massive objects. This excess could be an evidence of the possible annihilation of dark matter particles in the centre of these objects. In one of the most popular scenarios the Dark Matter is composed of WIMP particles. The analysis and results of the ANTARES neutrino telescope for the indirect detection of Dark Matter fluxes from the Sun are here presented, as well as the latest IceCube published sensitivity results, for different Dark Matter models.

Fermani, Paolo

2013-01-01T23:59:59.000Z

255

The Very Energetic Radiation Imaging Telescope Array System (VERITAS)  

E-Print Network [OSTI]

We give an overview of the current status and scientific goals of VERITAS, a proposed hexagonal array of seven 10 m aperture imaging Cherenkov telescopes. The selected site is Montosa Canyon (1390 m a.s.l.) at the Whipple Observatory, Arizona. Each telescope, of 12 m focal length, will initially be equipped with a 499 element photomultiplier camera covering a 3.5 degree field of view. A central station will initiate the readout of 500 MHz FADCs upon receipt of multiple telescope triggers. The minimum detectable flux sensitivity will be 0.5% of the Crab Nebula flux at 200 GeV. Detailed simulations of the array's performance are presented elsewhere at this meeting. VERITAS will operate primarily as a gamma-ray observatory in the 50 GeV to 50 TeV range for the study of active galaxies, supernova remnants, pulsars and gamma-ray bursts.

S. M. Bradbury; I. H. Bond; A. C. Breslin; J. H. Buckley; D. A. Carter-Lewis; M. Catanese; S. Criswell; B. L. Dingus; D. J. Fegan; J. P. Finley; J. Gaidos; J. Grindlay; A. M. Hillas; K. Harris; G. Hermann; P. Kaaret; D. Kieda; J. Knapp; F. Krennrich; S. LeBohec; R. W. Lessard; J. Lloyd-Evans; B. McKernan; D. Mueller; R. Ong; J. J. Quenby; J. Quinn; G. Rochester; H. J. Rose; M. Salamon; G. H. Sembroski; T. Sumner; S. Swordy; V. V. Vassiliev; T. C. Weekes

1999-07-19T23:59:59.000Z

256

The Atmospheric Monitoring Strategy for the Cherenkov Telescope Array  

E-Print Network [OSTI]

The Imaging Atmospheric Cherenkov Technique (IACT) is unusual in astronomy as the atmosphere actually forms an intrinsic part of the detector system, with telescopes indirectly detecting very high energy particles by the generation and transport of Cherenkov photons deep within the atmosphere. This means that accurate measurement, characterisation and monitoring of the atmosphere is at the very heart of successfully operating an IACT system. The Cherenkov Telescope Array (CTA) will be the next generation IACT observatory with an ambitious aim to improve the sensitivity of an order of magnitude over current facilities, along with corresponding improvements in angular and energy resolution and extended energy coverage, through an array of Large (23m), Medium (12m) and Small (4m) sized telescopes spread over an area of order ~km$^2$. Whole sky coverage will be achieved by operating at two sites: one in the northern hemisphere and one in the southern hemisphere. This proceedings will cover the characterisation of...

Daniel, M K

2015-01-01T23:59:59.000Z

257

MACHO Mass Determination Based on Space Telescope Observation  

E-Print Network [OSTI]

We investigate the possibility of lens mass determination for a caustic crossing microlensing event based on a space telescope observation. We demonstrate that the parallax due to the orbital motion of a space telescope causes a periodic fluctuation of the light curve, from which the lens distance can be derived. Since the proper motion of the lens relative to the source is also measurable for a caustic crossing event, one can find a full solution for microlensing properties of the event, including the lens mass. To determine the lens mass with sufficient accuracy, the light curve near the caustic crossing should be observed within uncertainty of $\\sim$ 1%. We argue that the Hubble Space Telescope observation of the caustic crossing supplied with ground-based observations of the full light curve will enable us to determine the mass of MACHOs, which is crucial for understanding the nature of MACHOs.

Mareki Honma

1999-03-24T23:59:59.000Z

258

Probing Cosmological Isotropy With Type IA Supernovae  

E-Print Network [OSTI]

We investigate the validity of the Cosmological Principle by mapping the cosmological parameters $H_0$ and $q_0$ through the celestial sphere. In our analysis, performed in a low-redshift regime to follow a model-independent approach, we use two compilations of type Ia Supernovae (SNe Ia), namely the Union2.1 and the JLA datasets. Firstly, we show that the angular distributions for both SNe Ia datasets are statistically anisotropic at high confidence level ($p$-value $<$ 0.0001), in particular the JLA sample. Then we find that the cosmic expansion and acceleration are mainly of dipolar type, with maximal anisotropic expansion [acceleration] pointing towards $(l,b) \\simeq (326^{\\circ},12^{\\circ})$ [$(l,b) \\simeq (174^{\\circ},27^{\\circ})$], and $(l,b) \\simeq (58^{\\circ},-60^{\\circ})$ [$(l,b) \\simeq (225^{\\circ},51^{\\circ})$] for the Union2.1 and JLA data, respectively. Secondly, we use a geometrical method to test the hypothesis that the non-uniformly distributed SNe Ia events could introduce anisotropic imp...

Bengaly, C A P; Alcaniz, J S

2015-01-01T23:59:59.000Z

259

The Problem of the Cosmological Constant  

E-Print Network [OSTI]

ElectroMagnetic Quantum Gravity (EMQG) is applied to the problem of the Cosmological Constant. EMQG is a quantum gravity theory (ref. 1) in which the virtual particles of the quantum vacuum play a very important role in all gravitational interactions, and also in accelerated motion. According to EMQG theory (and quantum field theory in general), empty space is populated by vast numbers of virtual particles, consisting of virtual fermion and virtual anti-fermion particles, which posses mass, and also virtual boson particles of all the various force particle species. Therefore the problem of the cosmological constant is essentially equivalent to a determination of the mass contributed by all the virtual particles of the vacuum to the overall curvature and dynamics of the entire universe. Our original analysis was based on the assumption of perfect symmetry in the creation and destruction of virtual fermion and virtual anti-fermion particle pairs in the quantum vacuum, which is in accordance with the existing la...

Ostoma, T; Ostoma, Tom; Trushyk, Mike

1999-01-01T23:59:59.000Z

260

Planck 2015 results. XIII. Cosmological parameters  

E-Print Network [OSTI]

We present results based on full-mission Planck observations of temperature and polarization anisotropies of the CMB. These data are consistent with the six-parameter inflationary LCDM cosmology. From the Planck temperature and lensing data, for this cosmology we find a Hubble constant, H0= (67.8 +/- 0.9) km/s/Mpc, a matter density parameter Omega_m = 0.308 +/- 0.012 and a scalar spectral index with n_s = 0.968 +/- 0.006. (We quote 68% errors on measured parameters and 95% limits on other parameters.) Combined with Planck temperature and lensing data, Planck LFI polarization measurements lead to a reionization optical depth of tau = 0.066 +/- 0.016. Combining Planck with other astrophysical data we find N_ eff = 3.15 +/- 0.23 for the effective number of relativistic degrees of freedom and the sum of neutrino masses is constrained to Spatial curvature is found to be |Omega_K| < 0.005. For LCDM we find a limit on the tensor-to-scalar ratio of r <0.11 consistent with the B-mode constraints fr...

,

2015-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Holographic Dark Energy with Cosmological Constant  

E-Print Network [OSTI]

Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the $\\Lambda$HDE model. By studying the $\\Lambda$HDE model theoretically, we find that the parameters $c$ and $\\Omega_{hde}$ are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the $\\Lambda$HDE model by using the recent observational data. We find the model yields $\\chi^2_{\\rm min}=426.27$ when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant $\\Lambda$CDM model (431.35). At 68.3\\% CL, we obtain $-0.07<\\Omega_{\\Lambda0}<0.68$ and correspondingly $0.04<\\Omega_{hde0}<0.79$, implying at present there is considerable degeneracy bet...

Hu, Yazhou; Li, Nan; Zhang, Zhenhui

2015-01-01T23:59:59.000Z

262

Dynamical dark energy or variable cosmological parameters?  

E-Print Network [OSTI]

One of the main aims in the next generation of precision cosmology experiments will be an accurate determination of the equation of state (EOS) for the dark energy (DE). If the latter is dynamical, the resulting barotropic index \\omega should exhibit a non-trivial evolution with the redshift. Usually this is interpreted as a sign that the mechanism responsible for the DE is related to some dynamical scalar field, and in some cases this field may behave non-canonically (phantom field). Present observations seem to favor an evolving DE with a potential phantom phase near our time. In the literature there is a plethora of dynamical models trying to describe this behavior. Here we show that the simplest option, namely a model with a variable cosmological term, \\Lambda=\\Lambda(t), leads in general to a non-trivial effective EOS, with index \\omega_e, which may naturally account for these data features. We prove that in this case there is always a ``crossing'' of the \\omega_e=-1 barrier near our time. We also show how this effect is modulated (or even completely controled) by a variable Newton's constant G=G(t).

Joan Sola; Hrvoje Stefancic

2005-12-21T23:59:59.000Z

263

Cosmology calculations almost without general relativity  

E-Print Network [OSTI]

The Friedmann equation is derived for a Newtonian universe. Changing mass density to energy density gives exactly the Friedmann equation of general relativity. Accounting for work done by pressure then yields the two Einstein equations that govern the expansion of the universe. Descriptions and explanations of radiation pressure and vacuum pressure are added to complete a basic kit of cosmology tools. It provides a basis for teaching cosmology to undergraduates in a way that quickly equips them to do basic calculations. This is demonstrated with calculations involving: characteristics of the expansion for densities dominated by radiation, matter, or vacuum; the closeness of the density to the critical density; how much vacuum energy compared to matter energy is needed to make the expansion accelerate; and how little is needed to make it stop. Travel time and luninosity distance are calculated in terms of the redshift and the densities of matter and vacuum energy, using a scaled Friedmann equation with the constant in the curvature term determined by matching with the present values of the Hubble parameter and energy density. General relativity is needed only for the luminosity distance, to describe how the curvature of space, determined by the energy density, can change the intensity of light by changing the area of the sphere to which the light has spread. Thirty-one problems are included.

Thomas F. Jordan

2004-12-08T23:59:59.000Z

264

Conserved Currents in Supersymmetric Quantum Cosmology?  

E-Print Network [OSTI]

In this paper we investigate whether conserved currents can be sensibly defined in supersymmetric minisuperspaces. Our analysis deals with k=1 FRW and Bianchi class--A models. Supermatter in the form of scalar supermultiplets is included in the former. Moreover, we restrict ourselves to the first-order differential equations derived from the Lorentz and supersymmetry constraints. The ``square-root'' structure of N=1 supergravity was our motivation to contemplate this interesting research. We show that conserved currents cannot be adequately established except for some very simple scenarios. Otherwise, conservation equations may only be obtained from Wheeler-DeWitt--like equations, which are derived from the supersymmetric algebra of constraints. Two appendices are included. In appendix A we describe some interesting features of quantum FRW cosmologies with complex scalar fields when supersymmetry is present. In particular, we explain how the Hartle-Hawking state can now be satisfactorily identified. In appendix B we initiate a discussion about the retrieval of classical properties from supersymmetric quantum cosmologies.

P. V. Moniz

1997-10-20T23:59:59.000Z

265

The Standard Cosmological Model and CMB Anisotropies  

E-Print Network [OSTI]

This is a course on cosmic microwave background (CMB) anisotropies in the standard cosmological model, designed for beginning graduate students and advanced undergraduates. ``Standard cosmological model'' in this context means a Universe dominated by some form of cold dark matter (CDM) with adiabatic perturbations generated at some initial epoch, e.g., Inflation, and left to evolve under gravity alone (which distinguishes it from defect models). The course is primarily theoretical and concerned with the physics of CMB anisotropies in this context and their relation to structure formation. Brief presentations of the uniform Big Bang model and of the observed large--scale structure of the Universe are given. The bulk of the course then focuses on the evolution of small perturbations to the uniform model and on the generation of temperature anisotropies in the CMB. The theoretical development is performed in the (pseudo--)Newtonian gauge because it aids intuitive understanding by providing a quick reference to classical (Newtonian) concepts. The fundamental goal of the course is not to arrive at a highly exact nor exhaustive calculation of the anisotropies, but rather to a good understanding of the basic physics that goes into such calculations.

James G. Bartlett

1999-03-17T23:59:59.000Z

266

Verifying the Cosmological Utility of Type Ia Supernovae: Implications of a Dispersion in the Ultraviolet Spectra  

SciTech Connect (OSTI)

We analyze the mean rest-frame ultraviolet (UV) spectrum of Type Ia Supernovae (SNe) and its dispersion using high signal-to-noise ratio Keck-I/LRIS-B spectroscopy for a sample of 36 events at intermediate redshift (z=0.5) discovered by the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We introduce a new method for removing host galaxy contamination in our spectra, exploiting the comprehensive photometric coverage of the SNLS SNe and their host galaxies, thereby providing the first quantitative view of the UV spectral properties of a large sample of distant SNe Ia. Although the mean SN Ia spectrum has not evolved significantly over the past 40percent of cosmic history, precise evolutionary constraints are limited by the absence of a comparable sample of high-quality local spectra. The mean UV spectrum of our z~;;=0.5 SNe Ia and its dispersion is tabulated for use in future applications. Within the high-redshift sample, we discover significant UV spectral variations and exclude dust extinction as the primary cause by examining trends with the optical SN color. Although progenitor metallicity may drive some of these trends, the variations we see are much larger than predicted in recent models and do not follow expected patterns. An interesting new result is a variation seen in the wavelength of selected UV features with phase. We also demonstrate systematic differences in the SN Ia spectral features with SN light curve width in both the UV and the optical. We show that these intrinsic variations could represent a statistical limitation in the future use of high-redshift SNe Ia for precision cosmology. We conclude that further detailed studies are needed, both locally and at moderate redshift where the rest-frame UV can be studied precisely, in order that future missions can confidently be planned to fully exploit SNe Ia as cosmological probes.

Nugent, Peter E; Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam, A.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R.; Conley, A.; Fouchez, D.; Guy, J.; Hardin, D.; Hook, I.; Pain, R.; Perrett, K.; Pritchet, C.J.; Regnault, N.

2008-02-28T23:59:59.000Z

267

Cosmological model-independent Gamma-ray bursts calibration and its cosmological constraint to dark energy  

SciTech Connect (OSTI)

As so far, the redshift of Gamma-ray bursts (GRBs) can extend to z ? 8 which makes it as a complementary probe of dark energy to supernova Ia (SN Ia). However, the calibration of GRBs is still a big challenge when they are used to constrain cosmological models. Though, the absolute magnitude of GRBs is still unknown, the slopes of GRBs correlations can be used as a useful constraint to dark energy in a completely cosmological model independent way. In this paper, we follow Wang's model-independent distance measurement method and calculate their values by using 109 GRBs events via the so-called Amati relation. Then, we use the obtained model-independent distances to constrain ?CDM model as an example.

Xu, Lixin, E-mail: lxxu@dlut.edu.cn [Institute of Theoretical Physics, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian, 116024 (China)

2012-04-01T23:59:59.000Z

268

High-Energy Cosmology: gamma rays and neutrinos from beyond the galaxy  

E-Print Network [OSTI]

Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new discoveries from Swift and HESS, results from MAGIC and VERITAS starting to be reported, the upcoming launches of the gamma-ray space telescopes GLAST and AGILE, and anticipated data releases from IceCube and Auger. A formalism for calculating statistical properties of cosmological gamma-ray sources is presented. Application is made to model calculations of the statistical distributions of gamma-ray and neutrino emission from (i) beamed sources, specifically, long-duration GRBs, blazars, and extagalactic microquasars, and (ii) unbeamed sources, including normal galaxies, starburst galaxies and clusters. Expressions for the integrated intensities of faint beamed and unbeamed high-energy radiation sources are also derived. A toy model for the background intensity of radiation from dark-matter annihilation taking place in the early universe is constructed. Estimates for the gamma-ray fluxes of local group galaxies, starburst, and infrared luminous galaxies are briefly reviewed. Because the brightest extragalactic gamma-ray sources are flaring sources, and these are the best targets for sources of PeV -- EeV neutrinos and ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC and an all-sky gamma-ray observatory beyond Milagro will be crucial for optimal science return in the multi-messenger age.

Charles D. Dermer

2006-11-06T23:59:59.000Z

269

Dynamics of interacting dark energy model in Einstein and Loop Quantum Cosmology  

E-Print Network [OSTI]

We investigate the background dynamics when dark energy is coupled to dark matter in the universe described by Einstein cosmology and Loop Quantum Cosmology. We introduce a new general form of dark sector coupling, which presents us a more complicated dynamical phase space. Differences in the phase space in obtaining the accelerated scaling attractor in Einstein cosmology and Loop Quantum Cosmology are disclosed.

Songbai Chen; Bin Wang; Jiliang Jing

2008-11-10T23:59:59.000Z

270

Cosmological Landscape From Nothing: Some Like It Hot  

E-Print Network [OSTI]

We suggest a novel picture of the quantum Universe -- its creation is described by the {\\em density matrix} defined by the Euclidean path integral. This yields an ensemble of universes -- a cosmological landscape -- in a mixed state which is shown to be dynamically more preferable than the pure quantum state of the Hartle-Hawking type. The latter is dynamically suppressed by the infinitely large positive action of its instanton, generated by the conformal anomaly of quantum fields within the cosmological bootstrap (the self-consistent back reaction of hot matter). This bootstrap suggests a solution to the problem of boundedness of the on-shell cosmological action and eliminates the infrared catastrophe of small cosmological constant in Euclidean quantum gravity. The cosmological landscape turns out to be limited to a bounded range of the cosmological constant $\\Lambda_{\\rm min}\\leq \\Lambda \\leq \\Lambda_{\\rm max}$. The domain $\\Lambdalandscape. The dependence of the cosmological constant range on particle phenomenology suggests a possible dynamical selection mechanism for the landscape of string vacua.

A. O. Barvinsky; A. Yu. Kamenshchik

2006-09-13T23:59:59.000Z

271

New Astronomy Reviews 42 (1998) 485488 The Dutch Open Telescope  

E-Print Network [OSTI]

obstructions around it. The Dutch Open Telescope (DOT) is a 15-m high For protection against the sometimes very. No warm air bubbles are forced upwards floor will be made for protection against moisture against Muchachos Observatory (ORM) The primary mirror of the DOT was tested inter- is an excellent site for testing

Rutten, Rob

272

Origami Sunshield Concepts for Space Telescopes and Sergio Pellegrino  

E-Print Network [OSTI]

booms. This whole structure needs to be shrouded in a sunshield to maintain thermal stability high envelope when it is folded. The envelope available for the packaged sunshield is defined envelope, limited by 5 m diameter fairing on the outside and by the telescope on the inside. This paper

Pellegrino, Sergio

273

Results of a Si/CdTe Compton Telescope  

E-Print Network [OSTI]

We have been developing a semiconductor Compton telescope to explore the universe in the energy band from several tens of keV to a few MeV. We use a Si strip and CdTe pixel detector for the Compton telescope to cover an energy range from 60 keV. For energies above several hundred keV, the higher efficiency of CdTe semiconductor in comparison with Si is expected to play an important role as an absorber and a scatterer. In order to demonstrate the spectral and imaging capability of a CdTe-based Compton Telescope, we have developed a Compton telescope consisting of a stack of CdTe pixel detectors as a small scale prototype. With this prototype, we succeeded in reconstructing images and spectra by solving the Compton equation from 122 keV to 662 keV. The energy resolution (FWHM) of reconstructed spectra is 7.3 keV at 511 keV and 3.1 keV at 122 keV, respectively. The angular resolution obtained at 511 keV is measured to be 12.2 degree (FWHM).

Kousuke Oonuki; Takaaki Tanaka; Shin Watanabe; Shin'ichiro Takeda; Kazuhiro Nakazawa; Takefumi Mitani; Tadayuki Takahashi; Hiroyasu Tajima; Yasushi Fukazawa; Masaharu Nomachi

2005-09-21T23:59:59.000Z

274

Review of the Solar Array Telescopes David A. Smith  

E-Print Network [OSTI]

to believe that at lower energy, wavefront sampling could have advantages [34]. After the 1973 oil crisisReview of the Solar Array Telescopes David A. Smith Centre d'Etudes Nucl´eaires de Bordeaux sensitive to astrophysical gamma rays with energies beyond the reach of EGRET but below

Paris-Sud XI, Université de

275

SCIENCE: JAMES WEBB SPACE TELESCOPE (JWST) Budget Authority Actual Estimate  

E-Print Network [OSTI]

) Prior FY 2011 FY 2012 FY 2013 FY 2014 FY 2015 FY 2016 FY 2017 BTC Total FY 2013 President's Budget TELESCOPE (JWST) Formulation Development Operations JWST-2 FY 2013 BUDGET Budget Authority Actual Estimate (in $ millions) Prior FY 2011 FY 2012 2013 FY 2014 FY 2015 FY 2016 FY 2017 BTC Total FY 2013 President

276

Collecting Light with Telescopes Two Fundamentally Different Spectral Mechanisms  

E-Print Network [OSTI]

;Observing problems due to Earth's atmosphere 1. Light Pollution #12;Star viewed with ground-based telescope. · Location/technology can help overcome light pollution and turbulence. · Nothing short of going to space can Mexico #12;Very Large Array (VLA), New Mexico #12;Very Long Baseline Array (VLBA) #12;Large Binocular

Shirley, Yancy

277

Recent results from the ANTARES neutrino telescope Veronique Van Elewycka  

E-Print Network [OSTI]

, and microquasars. Further topics of investigation, covering e.g. the search for neutrinos from dark matter Cit´e, France Abstract The ANTARES neutrino telescope is currently the largest operating water nor absorbed by ambient matter and radiation. High-energy (>TeV) neutri- nos are expected

Boyer, Edmond

278

Indirect Search for Dark Matter with the ANTARES Neutrino Telescope  

E-Print Network [OSTI]

significant high energy neutrino fluxes. Indirect search for Dark Matter looking at such neutrino fluxes for the Cherenkov light induced by high energy muons during their travel in the sea water throughout the detectorIndirect Search for Dark Matter with the ANTARES Neutrino Telescope V. Bertin1 on behalf

Paris-Sud XI, Université de

279

Gamma-ray Sky Observed with Fermi Large Area Telescope  

E-Print Network [OSTI]

detection reported Flare activity reported via ATel Gamma Ray Bursts reported via GCN Giant MC imageGamma-ray Sky Observed with Fermi Large Area Telescope RESCEU Symposium on Astroparticle Physics) Measure the photon direction Identification of the gamma-ray shower 36 planes of Si strip detectors (228 m

Yamamoto, Hirosuke

280

VISUALIZATION AND ANALYTICS Galileo Galilei's improvements to early telescope  

E-Print Network [OSTI]

-sized machines and generate vast amounts of output data. Managing and under- standing such data is widely the Copernican heliocentric model of the solar system: that it is the Sun, rather than the Earth, which is the center of the solar sys- tem. Thus, the telescope became the first device to make the unseeable seeable

Knowles, David William

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Integrating Seeing Measurements into the Operations of Solar Telescopes  

E-Print Network [OSTI]

conditions for solar observations: Big Bear Solar Observatory in California, Haleakala on Maui, HawaiiIntegrating Seeing Measurements into the Operations of Solar Telescopes C. Denker and A. P. Verdoni New Jersey Institute of Technology, Center for Solar-Terrestrial Research 323 Martin Luther King Blvd

282

Field Fractal Cosmological Model As an Example of Practical Cosmology Approach  

E-Print Network [OSTI]

The idea of the global gravitational effect as the source of cosmological redshift was considered by de Sitter (1916, 1917), Eddington (1923), Tolman (1929) and Bondi (1947), also Hubble (1929) called the discovered distance-redshift relation as "De Sitter effect". For homogeneous matter distribution cosmological gravitational redshift is proportional to square of distance: z_grav ~ r^2. However for a fractal matter distribution having the fractal dimension D=2 the global gravitational redshift is the linear function of distance: z_grav ~ r, which gives possibility for interpretation of the Hubble law without the space expansion. Here the field gravity fractal cosmological model (FGF) is presented, which based on two initial principles. The first assumption is that the field gravity theory describes the gravitational interaction within the conceptual unity of all fundamental physical interactions. The second hypothesis is that the spatial distribution of matter is a fractal at all scales up to the Hubble radius. The fractal dimension of matter distribution is assumed to be D = 2, which implies that the global gravitational redshift is the explanation of the observed linear Hubble law. In the frame of the FGF all three phenomena - the cosmic background radiation, the fractal large scale structure, and the Hubble law, -could be consequences of a unique evolution process of the initially homogeneous cold gas. Within field gravity fractal framework a new qualitative picture of the structure and evolution of the Universe has emerged, with some quantitative results that may be tested by current and forthcoming observations.

Yu. V. Baryshev

2008-10-01T23:59:59.000Z

283

Five-Dimensional Cosmological Scaling Solution  

E-Print Network [OSTI]

A five-dimensional Ricci-flat cosmological solution is studied by assuming that the induced 4D matter contains two components: the usual fluid for dark matter as well as baryons and a scalar field with an exponential potential for dark energy. With use of the phase-plane analysis it is shown that there exist two late-time attractors one of which corresponds to a universe dominated by the scalar field alone and the other is a scaling solution in which the energy density of the scalar field remains proportional to that of the dark matter. It is furthermore shown that for this 5D scaling solution the universe expands with the same rate as in the 4D FRW models and not relies on which 4D hypersurface the universe is located in the 5D manifold.

Baorong Chang; Hongya Liu; Huanying Liu; Lixin Xu

2005-05-08T23:59:59.000Z

284

Some Cosmological Consequences of Weyl Invariance  

E-Print Network [OSTI]

Some Weyl invariant cosmological models are examined in the framework of dilaton gravity. It will be shown that When the FRW ansatz for the spacetime metric is assumed, the Ward identity for conformal invariance guarantees that the gravitational equations hold whenever the matter EM do so. It follows that any scale factor can solve the theory provided a non-trivial profile for a dilaton field. In particular, accelerated expansion is a natural solution to the full set of equations. When two or more scalar fields are coupled to gravity in a Weyl invariant way there is an antigravity phase in which the effective Newton constant is negative. This phase is separated from the atractive gravity phase by a strong coupling barrier. Nevertheles, and perhaps contradicting na\\"ive beliefs, the antigravity phase does not imply accelerated expansion, although it is compatible with it.

Álvarez, Enrique; Herrero-Valea, Mario

2015-01-01T23:59:59.000Z

285

Replication regulates volume weighting in quantum cosmology  

SciTech Connect (OSTI)

Probabilities for observations in cosmology are conditioned both on the Universe's quantum state and on local data specifying the observational situation. We show the quantum state defines a measure for prediction through such conditional probabilities that is well-behaved for spatially large or infinite universes when the probabilities that our data are replicated are taken into account. In histories where our data are rare volume weighting connects top-down probabilities conditioned on both the data and the quantum state to the bottom-up probabilities conditioned on the quantum state alone. We apply these principles to a calculation of the number of inflationary e-folds in a homogeneous, isotropic minisuperspace model with a single scalar field moving in a quadratic potential. We find that volume weighting is justified and the top-down probabilities favor a large number of e-folds, hereby predicting the curvature of our Universe at the present time to be approximately zero.

Hartle, James [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Hertog, Thomas [APC, UMR 7164 (CNRS, Universite Paris 7), 10 rue A.Domon et L.Duquet, 75205 Paris (France) and Intl Solvay Institutes, Boulevard du Triomphe, ULB-C.P. 231, 1050 Brussels (Belgium)

2009-09-15T23:59:59.000Z

286

Gravitational Instability of Yang-Mills Cosmologies  

E-Print Network [OSTI]

The gravitational instability of Yang-Mills cosmologies is numerically studied with the hamiltonian formulation of the spherically symmetric Einstein-Yang-Mills equations with SU(2) gauge group. On the short term, the expansion dilutes the energy densities of the Yang-Mills fluctuations due to their conformal invariance. In this early regime, the gauge potentials appear oscillating quietly in an interaction potential quite similar to the one of the homogeneous case. However, on the long term, the expansion finally becomes significantly inhomogeneous and no more mimics a conformal transformation of the metric. Thereafter, the Yang-Mills fluctuations enter a complex non-linear regime, accompanied by diffusion, while their associated energy contrasts grow.

A. Fuzfa

2003-10-06T23:59:59.000Z

287

On the energy of homogeneous cosmologies  

E-Print Network [OSTI]

An energy for the homogeneous cosmological models is presented. More specifically, using an appropriate natural prescription, we find the energy within any region with any gravitational source for a large class of gravity theories--namely those with a tetrad description--for all 9 Bianchi types. Our energy is given by the value of the Hamiltonian with homogeneous boundary conditions; this value vanishes for all regions in all Bianchi class A models, and it does not vanish for any class B model. This is so not only for Einstein's general relativity but, moreover, for the whole 3-parameter class of tetrad-teleparallel theories. For the physically favored one parameter subclass, which includes the teleparallel equivalent of Einstein's theory as an important special case, the energy for all class B models is, contrary to expectation, negative.

James M. Nester; Lau Loi So; T. Vargas

2008-03-23T23:59:59.000Z

288

Eternal Higgs inflation and cosmological constant problem  

E-Print Network [OSTI]

We investigate the Higgs potential beyond the Planck scale in the superstring theory, under the assumption that the supersymmetry is broken at the string scale. We identify the Higgs field as a massless state of the string, which is indicated by the fact that the bare Higgs mass can be zero around the string scale. We find that, in the large field region, the Higgs potential is connected to a runaway vacuum with vanishing energy, which corresponds to opening up an extra dimension. We verify that such universal behavior indeed follows from the toroidal compactification of the non-supersymmetric $SO(16)\\times SO(16)$ heterotic string theory. We show that this behavior fits in the picture that the Higgs field is the source of the eternal inflation. The observed small value of the cosmological constant of our universe may be understood as the degeneracy with this runaway vacuum, which has vanishing energy, as is suggested by the multiple point criticality principle.

Hamada, Yuta; Oda, Kin-ya

2015-01-01T23:59:59.000Z

289

On the geometry of cosmological model building  

E-Print Network [OSTI]

This article analyzes the present anomalies of cosmology from the point of view of integrable Weyl geometry. It uses P.A.M. Dirac's proposal for a weak extension of general relativity, with some small adaptations. Simple models with interesting geometrical and physical properties, not belonging to the Friedmann-Lema\\^{\\i}tre class, are studied in this frame. Those with positive spatial curvature (Einstein-Weyl universes) go well together with observed mass density $\\Omega_m$, CMB, supernovae Ia data, and quasar frequencies. They suggest a physical role for an equilibrium state of the Maxwell field proposed by I.E. Segal in the 1980s (Segal background) and for a time invariant balancing condition of vacuum energy density. The latter leads to a surprising agreement with the BF-theoretical calculation proposed by C. Castro (2002).

Erhard Scholz

2005-11-21T23:59:59.000Z

290

Cosmological origin of anomalous radio background  

SciTech Connect (OSTI)

The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate several potential mechanisms and show that injection of relativistic electrons through late decays of a metastable particle can give rise to the observed excess radio spectrum through synchrotron emission. However, constraints from the cosmic microwave background (CMB) anisotropy, on injection of charged particles and on the primordial magnetic field, present a challenge. The simplest scenario is with a ?>9 GeV particle decaying into e{sup +}e{sup ?} at a redshift of z ? 5, in a magnetic field of ? 5?G, which exceeds the CMB B-field constraints, unless the field was generated after decoupling. Decays into exotic millicharged particles can alleviate this tension, if they emit synchroton radiation in conjunction with a sufficiently large background magnetic field of a dark U(1)' gauge field.

Cline, James M. [Department of Physics, McGill University, 3600 Rue University, Montréal, Québec, H3A 2T8 Canada (Canada); Vincent, Aaron C., E-mail: jcline@physics.mcgill.ca, E-mail: vincent@ific.uv.es [Instituto de Física Corpuscular, Universitat de València - CSIC, 46071, Valencia (Spain)

2013-02-01T23:59:59.000Z

291

Non minimally coupled condensate cosmologies: a phase space analysis  

E-Print Network [OSTI]

We present an analysis of the phase space of cosmological models based on a non minimal coupling between the geometry and a fermionic condensate. We obtain that the strong constraint coming from the Dirac equations allows a detailed design of the cosmology of these models and at the same time guarantees an evolution towards a state indistinguishable from General Relativistic cosmological models. In this light, we show how the use of some specific potentials is able to reproduce naturally two de Sitter phases separated by a power law expansion which could be an interesting model for the unification of an inflationary phase and a dark energy era.

Sante Carloni; Stefano Vignolo; Roberto Cianci

2014-03-11T23:59:59.000Z

292

Testing Cosmology with Cosmic Sound Waves  

E-Print Network [OSTI]

WMAP observations have accurately determined the position of the first two peaks and dips in the CMB temperature power spectrum. These encode information on the ratio of the distance to the last scattering surface to the sound horizon at decoupling. However pre-recombination processes can contaminate this distance information. In order to assess the amplitude of these effects we use the WMAP data and evaluate the relative differences of the CMB peaks and dips multipoles. We find that the position of the first peak is largely displaced with the respect to the expected position of the sound horizon scale at decoupling. In contrast the relative spacings of the higher extrema are statistically consistent with those expected from perfect harmonic oscillations. This provides evidence for a scale dependent phase shift of the CMB oscillations which is caused by gravitational driving forces affecting the propagation of sound waves before recombination. By accounting for these effects we have performed a MCMC likelihood analysis to constrain in combination with recent BAO data a constant dark energy equation w. For a flat universe we find at 95% upper limit w<-1.10, and including the HST prior w<-1.14, which are only marginally consistent with limits derived from the supernova SNLS sample. Larger limits are obtained for non-flat cosmologies. From the full CMB likelihood analysis we also estimate the values of the shift parameter R and the multipole l_a of the acoustic horizon at decoupling for several cosmologies to test their dependence on model assumptions. Although the analysis of the full CMB spectra should be always preferred, using the position of the CMB peaks and dips provide a simple and consistent method for combining CMB constraints with other datasets.

Pier Stefano Corasaniti; Alessandro Melchiorri

2008-03-25T23:59:59.000Z

293

Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report  

E-Print Network [OSTI]

This report describes the 2014 study by the Science Definition Team (SDT) of the Wide-Field Infrared Survey Telescope (WFIRST) mission. It is a space observatory that will addresses the most compelling scientific problems in dark energy, exoplanets and general astrophysics using a 2.4m telescope with a wide-field infrared instrument and an optical coronagraph. The Astro2010 Decadal Survey recommended a Wide Field Infrared Survey Telescope as its top priority for a new large space mission. As conceived by the decadal survey, WFIRST would carry out a dark energy science program, a microlensing program to determine the demographics of exoplanets, and a general observing program utilizing its ultra wide field. In October 2012, NASA chartered a Science Definition Team (SDT) to produce, in collaboration with the WFIRST Study Office at GSFC and the Program Office at JPL, a Design Reference Mission (DRM) for an implementation of WFIRST using one of the 2.4-m, Hubble-quality telescope assemblies recently made availabl...

Spergel, D; Baltay, C; Bennett, D; Breckinridge, J; Donahue, M; Dressler, A; Gaudi, B S; Greene, T; Guyon, O; Hirata, C; Kalirai, J; Kasdin, N J; Macintosh, B; Moos, W; Perlmutter, S; Postman, M; Rauscher, B; Rhodes, J; Wang, Y; Weinberg, D; Benford, D; Hudson, M; Jeong, W -S; Mellier, Y; Traub, W; Yamada, T; Capak, P; Colbert, J; Masters, D; Penny, M; Savransky, D; Sterns, D; Zimmerman, N; Barry, R; Bartusek, L; Carpenter, K; Cheng, E; Content, D; Dekens, F; Demers, R; Grady, K; Jackson, C; Kuan, G; Kruk, J; Melton, M; Nemati, B; Parvin, B; Poberezhskiy, I; Peddie, C; Ruffa, J; Wallace, J K; Whipple, A; Wollack, E; Zhao, F

2015-01-01T23:59:59.000Z

294

The Photodetector Plane of the 4m Davies Cotton Small Size Telescope for the Cherenkov Telescope Array  

E-Print Network [OSTI]

Photomultipliers (PMTs) are currently adopted for the photodetector plane of Imaging Atmospheric Cherenkov Telescopes (IACTs). Even though PMT quantum efficiency has improved impressively in the recent years, one of the main limitation for their application in the gamma-astronomy field - the impossibility to operate with moon light - still remains. As a matter of fact, the light excess would lead to significant and faster camera ageing. Solid state detectors, in particular Geiger-mode avalanche photo-diodes (G-APDs) represent a valuable alternative solution to overcome this limitation as demonstrated in the field by the FACT experiment (The First G- APD Cherenkov Telescope). They can be regarded as a more promising long term approach, which can be easily adopted for the new generation of cameras and for the Cherenkov Telescope Array (CTA). We describe here the Photo-Detector Plane (PDP) of the camera for the 4 m Davies Cotton CTA Small Size Telescopes, for which large area G-APD coupled to non-imaging light c...

Boccone, V; Basili, A; Christov, A; della Volpe, M; Montaruli, T

2013-01-01T23:59:59.000Z

295

Design Concepts for the Cherenkov Telescope Array CTA: An Advanced Facility for Ground-Based High-Energy Gamma-Ray Astronomy  

SciTech Connect (OSTI)

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.

Actis, M

2012-04-17T23:59:59.000Z

296

Joel R. Primack Distinguished Professor of Physics, University of California, Santa Cruz  

E-Print Network [OSTI]

Proposal 2001; Chair, NASA Cosmology panel on LTSA and ADP 2001; Cosmology Panel, Hubble Space Telescope

California at Santa Cruz, University of

297

E-Print Network 3.0 - axion solar telescope Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

solar telescope Search Powered by Explorit Topic List Advanced Search Sample search results for: axion solar telescope Page: << < 1 2 3 4 5 > >> 1 In Search Of Axions: The CAST...

298

Ion implantation for figure correction of high-resolution x-ray telescope mirrors  

E-Print Network [OSTI]

Fabricating mirrors for future high-resolution, large-aperture x-ray telescopes continues to challenge the x-ray astronomy instrumentation community. Building a large-aperture telescope requires thin, lightweight mirrors; ...

Chalifoux, Brandon D

2014-01-01T23:59:59.000Z

299

Tradespace Investigation of a Telescope Architecture for Next-generation Space Astronomy and Exploration  

E-Print Network [OSTI]

Humanity’s endeavor to further its scientific understanding of the celestial heavens has led to the creation and evolution of increasingly powerful and complex space telescopes. Space telescopes provide a view of the solar ...

Cataldo, Giuseppe

2014-12-19T23:59:59.000Z

300

Evolving Lorentzian wormholes supported by phantom matter and cosmological constant  

SciTech Connect (OSTI)

In this paper we study the possibility of sustaining an evolving wormhole via exotic matter made of phantom energy in the presence of a cosmological constant. We derive analytical evolving wormhole geometries by supposing that the radial tension of the phantom matter, which is negative to the radial pressure, and the pressure measured in the tangential directions have barotropic equations of state with constant state parameters. In this case the presence of a cosmological constant ensures accelerated expansion of the wormhole configurations. More specifically, for positive cosmological constant we have wormholes which expand forever and, for negative cosmological constant we have wormholes which expand to a maximum value and then recollapse. At spatial infinity the energy density and the pressures of the anisotropic phantom matter threading the wormholes vanish; thus these evolving wormholes are asymptotically vacuum {lambda}-Friedmann models with either open or closed or flat topologies.

Cataldo, Mauricio; Campo, Sergio del; Minning, Paul; Salgado, Patricio [Departamento de Fisica, Facultad de Ciencias, Universidad del Bio-Bio, Avenida Collao 1202, Casilla 5-C, Concepcion (Chile); Instituto de Fisica, Facultad de Ciencias, Pontificia Universidad Catolica de Valparaiso, Avenida Brasil 2950, Valparaiso (Chile); Departamento de Fisica, Facultad de Ciencias Fisicas y Matematicas, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

2009-01-15T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Cosmology at the Beach Lecture: Chung-Pei Ma  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Chung-Pei Ma

2010-01-08T23:59:59.000Z

302

Observational constraints on late-time {lambda}(t) cosmology  

SciTech Connect (OSTI)

The cosmological constant {lambda}, i.e., the energy density stored in the true vacuum state of all existing fields in the Universe, is the simplest and the most natural possibility to describe the current cosmic acceleration. However, despite its observational successes, such a possibility exacerbates the well-known {lambda} problem, requiring a natural explanation for its small, but nonzero, value. In this paper we study cosmological consequences of a scenario driven by a varying cosmological term, in which the vacuum energy density decays linearly with the Hubble parameter, {lambda}{proportional_to}H. We test the viability of this scenario and study a possible way to distinguish it from the current standard cosmological model by using recent observations of type Ia supernova (Supernova Legacy Survey Collaboration), measurements of the baryonic acoustic oscillation from the Sloan Digital Sky Survey, and the position of the first peak of the cosmic microwave background angular spectrum from the three-year Wilkinson Microwave Anisotropy Probe.

Carneiro, S.; Pigozzo, C. [Instituto de Fisica, Universidade Federal da Bahia, Salvador-BA, 40210-340 (Brazil); Dantas, M. A. [Departamento de Astronomia, Observatorio Nacional, Rio de Janeiro-RJ, 20921-400 (Brazil); Alcaniz, J. S. [Departamento de Astronomia, Observatorio Nacional, Rio de Janeiro-RJ, 20921-400 (Brazil); Instituto Nacional de Pesquisas Espaciais/CRN, 59076-740, Natal-RN (Brazil)

2008-04-15T23:59:59.000Z

303

A new type of second order cosmological lagrangians  

E-Print Network [OSTI]

We investigate a possible connection between Galileon gravity and teleparallel gravity. We also propose a new type of second order cosmological lagrangian and study a some of its properties.

P. Tretyakov

2013-03-19T23:59:59.000Z

304

On Relation between String Theory and Multidimensional Cosmology  

E-Print Network [OSTI]

It is shown that a transition from a multidimensional cosmological model with one internal space of the dimension d_1 to the effective tree-level bosonic string corresponds to an infinite number of the internal dimensions: d_1 -> infinity.

A. Zhuk

1996-11-05T23:59:59.000Z

305

Dark energy in some integrable and nonintegrable FRW cosmological models  

E-Print Network [OSTI]

One of the greatest challenges in cosmology today is to determine the nature of dark energy, the sourse of the observed present acceleration of the Universe. Besides the vacuum energy, various dark energy models have been suggested. The Friedmann - Robertson - Walker (FRW) spacetime plays an important role in modern cosmology. In particular, the most popular models of dark energy work in the FRW spacetime. In this work, a new class of integrable FRW cosmological models is presented. These models induced by the well-known Painlev$\\acute{e}$ equations. Some nonintegrable FRW models are also considered. These last models are constructed with the help of Pinney, Schr$\\ddot{o}$dinger and hypergeometric equations. Scalar field description and two-dimensional generalizations of some cosmological models are presented. Finally some integrable and nonintegrable $F(R)$ and $F(G)$ gravity models are constructed.

Kuralay Esmakhanova; Nurgissa Myrzakulov; Gulgasyl Nugmanova; Yerlan Myrzakulov; Leonid Chechin; Ratbay Myrzakulov

2011-09-14T23:59:59.000Z

306

accelerated cosmological lattice: Topics by E-print Network  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

theory that predicts a late-time accelerated attractor with a constant dark matter to dark energy ratio can be said to solve the Coincidence Problem. Such cosmologies are...

307

Cosmological Parameters From Supernovae Associated With Gamma-ray Bursts  

E-Print Network [OSTI]

We report estimates of the cosmological parameters $\\Omega_m$ and $\\Omega_{\\Lambda}$ obtained using supernovae (SNe) associated with gamma-ray bursts (GRBs) at redshifts up to 0.606. Eight high-fidelity GRB-SNe with well-sampled light curves across the peak are used. We correct their peak magnitudes for a luminosity-decline rate relation to turn them into accurate standard candles with dispersion $\\sigma = 0.18$ mag. We also estimate the peculiar velocity of the host galaxy of SN 1998bw, using constrained cosmological simulations. In a flat universe, the resulting Hubble diagram leads to best-fit cosmological parameters of $(\\Omega_m, \\Omega_{\\Lambda}) = (0.52^{+0.34}_{-0.31},0.48^{+0.31}_{-0.34})$. This exploratory study suggests that GRB-SNe can potentially be used as standardizable candles to high redshifts to measure distances in the universe and constrain cosmological parameters.

Li, Xue; Wojtak, Rados?aw

2014-01-01T23:59:59.000Z

308

Cosmology on the Beach - Carlos Frenk, Lecture 3  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Carlos Frenk

2010-01-08T23:59:59.000Z

309

Cosmology on the Beach - Carlos Frenk, Lecture 2  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Carlos Frenk

2010-01-08T23:59:59.000Z

310

Cosmology on the Beach - Eric Linder, Lecture 2  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.  

Eric Linder

2010-01-08T23:59:59.000Z

311

Cosmology on the Beach: Eric Linder, lecture 3  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Eric Linder

2010-01-08T23:59:59.000Z

312

Cosmology on the Beach - Chung-Pei Ma, Lecture 3  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Chung-Pei Ma

2010-01-08T23:59:59.000Z

313

Cosmology on the Beach - Simon White, Lecture 3  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Simon White

2010-01-08T23:59:59.000Z

314

Cosmology on the Beach - Chung-Pei Ma: Lecture 2  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009

Chung-Pei Ma

2010-01-08T23:59:59.000Z

315

Cosmology on the Beach - Eric Linder: Lecture 1  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Eric Linder

2010-01-08T23:59:59.000Z

316

Cosmology on the Beach - Wayne Hu: Lecture 2  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Wayne Hu

2010-01-08T23:59:59.000Z

317

Cosmology on the Beach - Carlos Frenk: Lecture 1  

ScienceCinema (OSTI)

The lecture was delivered as part of the "Cosmology at the Beach" winter school organized by Berkeley Lab's George Smoot in Los Cabos, Mexico from Jan. 12-16, 2009.

Carlos Frenk

2010-01-08T23:59:59.000Z

318

Visualization of Cosmological Particle-Based Datasets  

E-Print Network [OSTI]

We describe our visualization process for a particle-based simulation of the formation of the first stars and their impact on cosmic history. The dataset consists of several hundred time-steps of point simulation data, with each time-step containing approximately two million point particles. For each time-step, we interpolate the point data onto a regular grid using a method taken from the radiance estimate of photon mapping. We import the resulting regular grid representation into ParaView, with which we extract isosurfaces across multiple variables. Our images provide insights into the evolution of the early universe, tracing the cosmic transition from an initially homogeneous state to one of increasing complexity. Specifically, our visualizations capture the build-up of regions of ionized gas around the first stars, their evolution, and their complex interactions with the surrounding matter. These observations will guide the upcoming James Webb Space Telescope, the key astronomy mission of the next decade.

Paul Arthur Navrátil; Jarrett L. Johnson; Volker Bromm

2007-08-07T23:59:59.000Z

319

Anisotropic Bianchi types VIII and IX locally rotationally symmetric cosmologies  

SciTech Connect (OSTI)

We present a class of exact cosmological solutions of Einstein-Maxwell equations, which are anisotropic and spatially homogeneous of Bianchi types VIII and IX, and class IIIb in the Stewart-Ellis classification of locally rotationally symmetric models. If we take the electromagnetic field equal to zero, a class of Bianchi types VIII/IX spatially homogeneous anisotropic cosmological solutions with perfect fluid is obtained.

Assad, M.J.D.; Soares, I.D.

1983-10-15T23:59:59.000Z

320

The Interpretation of Quantum Cosmology and the Problem of Time  

E-Print Network [OSTI]

The development of quantum cosmology, in which Stephen Hawking played a crucial role, has frequently encountered substantial conceptual and technical difficulties related to the problem of time in quantum gravity and to general issues concerning the foundations of quantum theory. In this contribution to Stephen's 60th Birthday Conference, I describe some recent work in which the decoherent histories approach to quantum theory is used to quantize simple cosmological models and perhaps shed some light on some of these difficulties.

J. J. Halliwell

2002-08-08T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

A Newtonian approach to the cosmological dark fluids  

E-Print Network [OSTI]

We review the hydrodynamics of the dark sector components in Cosmology. For this purpose we use the approach of Newtonian gravitational instability, and thereafter we add corrections to arrive to a full relativistic description. In Cosmology and Astrophysics, it is usual to decompose the dark sector into two species, dark matter and dark energy. We will use instead a unified approach by describing a single unified dark fluid with very simple assumptions, namely the dark fluid is barotropic and its sound speed vanishes.

Aviles, Alejandro; Klapp, Jaime; Luongo, Orlando; Quevedo, Hernando

2015-01-01T23:59:59.000Z

322

A Cosmological Modification to Energy from Mach-Hamilton Consistency  

E-Print Network [OSTI]

If Mach's Principle explains the Newtonian inertial reaction to acceleration then the role of the 'fixed stars' should also be manifest through Hamilton's formulation of mechanics. This consistency may be achieved if the expression for relativistic energy contains a cosmological coefficient that is (currently) equal to one. The presence of the required cosmological term exactly identifies the rest energy of a body as its gravitational potential energy due to the mass of the Universe.

Scott Funkhouser

2004-03-24T23:59:59.000Z

323

Yang-Mills coupling and cosmological duality of extended objects  

E-Print Network [OSTI]

YANG ? MILLS COUPLING AND COSMOLOGICAL DUALITY OF EXTENDED OB JECTS A Thesis by JAN CHRISTOPH PLEFKA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1992 Major Subject: Physics YANG ? MILLS COUPLING AND COSMOLOGICAL DUALITY OF EXTENDED OBJECTS A Thesis by JAN CHRISTOPH PLEFKA Approved as to style and content by: Micha, el J. D (Chair of Committee) tephen A. Fulling (Member...

Plefka, Jan Christoph

1992-01-01T23:59:59.000Z

324

Power Spectra to 1% Accuracy between Dynamical Dark Energy Cosmologies  

E-Print Network [OSTI]

For dynamical dark energy cosmologies we carry out a series of N-body gravitational simulations, achieving percent level accuracy in the relative mass power spectra at any redshift. Such accuracy in the power spectrum is necessary for next generation cosmological mass probes. Our matching procedure reproduces the CMB distance to last scattering and delivers subpercent level power spectra at z=0 and z~3. We discuss the physical implications for probing dark energy with surveys of large scale structure.

Matthew J. Francis; Geraint F. Lewis; Eric V. Linder

2007-04-03T23:59:59.000Z

325

Iso-spectral potential and inflationary quantum cosmology  

E-Print Network [OSTI]

Using the factorization approach of quantum mechanics, we obtain a family of isospectral scalar potentials for power law inflationary cosmology. The construction is based on a scattering Wheeler-DeWitt solution. These iso-spectrals have new features, they give a mechanism to end inflation, as well as the possibility to have new inflationary epochs. The procedure can be extended to other cosmological models.

A. Garcia; W. Guzman; M. Sabido; J. Socorro

2006-06-29T23:59:59.000Z

326

Large open telescope: size-upscaling from DOT to LOT Robert H. Hammerschlaga  

E-Print Network [OSTI]

Large open telescope: size-upscaling from DOT to LOT Robert H. Hammerschlaga , Aswin P. L. Jägersb, telescope drives 1. INTRODUCTION The Dutch Open Telescope (DOT) on the Canary island La Palma consists temperature homogeneous. No warm air bubbles are forced upwards against the closed wall of a tower and no heat

Rutten, Rob

327

Management of the Gemini 8M Telescopes Project R. Kurz, M. Mountain  

E-Print Network [OSTI]

of the project. The Gemini Science Committee (GSC) is responsible for scientific oversight and advice. The GSCManagement of the Gemini 8­M Telescopes Project R. Kurz, M. Mountain Gemini Telescopes Project, 950 Project Richard Kurz and Matt Mountain Gemini 8­M Telescopes Project 950 N. Cherry Avenue, Tucson, AZ

328

Future singularities and teleparallelism in loop quantum cosmology  

SciTech Connect (OSTI)

We demonstrate how holonomy corrections in loop quantum cosmology (LQC) prevent the Big Rip singularity by introducing a quadratic modification in terms of the energy density ? in the Friedmann equation in the Friedmann-Lemaître-Robertson-Walker (FLRW) space-time in a consistent and useful way. In addition, we investigate whether other kind of singularities like Type II,III and IV singularities survive or are avoided in LQC when the universe is filled by a barotropic fluid with the state equation P = ???f(?), where P is the pressure and f(?) a function of ?. It is shown that the Little Rip cosmology does not happen in LQC. Nevertheless, the occurrence of the Pseudo-Rip cosmology, in which the phantom universe approaches the de Sitter one asymptotically, is established, and the corresponding example is presented. It is interesting that the disintegration of bound structures in the Pseudo-Rip cosmology in LQC always takes more time than that in Einstein cosmology. Our investigation on future singularities is generalized to that in modified teleparallel gravity, where LQC and Brane Cosmology in the Randall-Sundrum scenario are the best examples. It is remarkable that F(T) gravity may lead to all the kinds of future singularities including Little Rip.

Bamba, Kazuharu [Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Haro, Jaume de [Departament de Matemàtica Aplicada I, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Odintsov, Sergei D., E-mail: bamba@kmi.nagoya-u.ac.jp, E-mail: jaime.haro@upc.edu, E-mail: odintsov@ieec.uab.es [Dept. Gen. and Theor. Phys. and Eurasian International Center for Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan)

2013-02-01T23:59:59.000Z

329

Planned Dark Matter searches with the MAGIC Telescope  

E-Print Network [OSTI]

The MAGIC 17m-diameter Imaging Air Cherenkov Telescope (IACT) has been commissioned beginning of 2005. The telescope has been designed to achieve the lower detection energy threshold ever obtained with an IACT, about 50 GeV. A new window in gamma-ray astronomy is being opened with great impact for exciting new physics and new discoveries. Among the targets of MAGIC is the indirect detection of Dark Matter (DM). We have considered different DM halo models of high DM density objects like the center of the Milky Way, its closest satellites and nearby galaxies (M31,M87). For each object, detection limits are computed for different DM halo models in a mSUGRA scenario for supersymmetric neutralino annihilation $\\gamma$-ray production. Advantages and drawbacks of these objects and plans for future observations are discussed.

J. Flix

2005-05-15T23:59:59.000Z

330

Gamma-Ray Imaging with the Coded Mask IBIS Telescope  

E-Print Network [OSTI]

The IBIS telescope onboard INTEGRAL, the ESA gamma-ray space mission to be launched in 2002, is a soft gamma-ray (20 keV - 10 MeV) device based on a coded aperture imaging system. We describe here basic concepts of coded masks, the imaging system of the IBIS telescope, and the standard data analysis procedures to reconstruct sky images. This analysis includes, for both the low-energy detector layer (ISGRI) and the high energy layer (PICSIT), iterative procedures which decode recorded shadowgrams, search for and locate sources, clean for secondary lobes, and then rotate and compose sky images. These procedures will be implemented in the Quick Look and Standard Analysis of the INTEGRAL Science Data Center (ISDC) as IBIS Instrument Specific Software.

Goldwurm, A; Gros, A; Stephen, J; Foschini, L; Gianotti, F; Natalucci, L; De Cesare, G; Santo, M D

2000-01-01T23:59:59.000Z

331

Thermal characteristics of a classical solar telescope primary mirror  

E-Print Network [OSTI]

We present a detailed thermal and structural analysis of a 2m class solar telescope mirror which is subjected to a varying heat load at an observatory site. A 3-dimensional heat transfer model of the mirror takes into account the heating caused by a smooth and gradual increase of the solar flux during the day-time observations and cooling resulting from the exponentially decaying ambient temperature at night. The thermal and structural response of two competing materials for optical telescopes, namely Silicon Carbide -best known for excellent heat conductivity and Zerodur -preferred for its extremely low coefficient of thermal expansion, is investigated in detail. The insight gained from these simulations will provide a valuable input for devising an efficient and stable thermal control system for the primary mirror.

Banyal, Ravinder K

2011-01-01T23:59:59.000Z

332

SLAC All Access: Fermi Gamma-ray Space Telescope  

ScienceCinema (OSTI)

Three hundred and fifty miles overhead, the Fermi Gamma-ray Space Telescope silently glides through space. From this serene vantage point, the satellite's instruments watch the fiercest processes in the universe unfold. Pulsars spin up to 700 times a second, sweeping powerful beams of gamma-ray light through the cosmos. The hyperactive cores of distant galaxies spew bright jets of plasma. Far beyond, something mysterious explodes with unfathomable power, sending energy waves crashing through the universe. Stanford professor and KIPAC member Roger W. Romani talks about this orbiting telescope, the most advanced ever to view the sky in gamma rays, a form of light at the highest end of the energy spectrum that's created in the hottest regions of the universe.

Romani, Roger

2014-06-24T23:59:59.000Z

333

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF GRB 110625A  

SciTech Connect (OSTI)

Gamma-ray bursts (GRBs) that emit photons at GeV energies form a small but significant population of GRBs. However, the number of GRBs whose GeV-emitting period is simultaneously observed in X-rays remains small. We report {gamma}-ray observations of GRB 110625A using Fermi's Large Area Telescope in the energy range 100 MeV-20 GeV. Gamma-ray emission at these energies was clearly detected using data taken between 180 s and 580 s after the burst, an epoch after the prompt emission phase. The GeV light curve differs from a simple power-law decay, and probably consists of two emission periods. Simultaneous Swift X-Ray Telescope observations did not show flaring behaviors as in the case of GRB 100728A. We discuss the possibility that the GeV emission is the synchrotron self-Compton radiation of underlying ultraviolet flares.

Tam, P. H. T.; Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Fan Yizhong, E-mail: phtam@phys.nthu.edu.tw [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-08-01T23:59:59.000Z

334

The data acquisition system for the ANTARES neutrino telescope  

E-Print Network [OSTI]

The ANTARES neutrino telescope is being constructed in the Mediterranean Sea. It consists of a large three-dimensional array of photo-multiplier tubes. The data acquisition system of the detector takes care of the digitisation of the photo-multiplier tube signals, data transport, data filtering, and data storage. The detector is operated using a control program interfaced with all elements. The design and the implementation of the data acquisition system are described.

Aguilar, J A; Ameli, F; Anghinolfi, M; Anton, G; Anvar, S; Aslanides, E; Aubert, Jean-Jacques; Barbarito, E; Basa, S; Battaglieri, M; Becherini, Y; Bellotti, R; Beltramelli, J; Bertin, V; Bigi, A; Billault, M; Blaes, R; De Botton, N R; Bouwhuis, M C; Bradbury, S M; Bruijn, R; Brunner, J; Burgio, G F; Busto, J; Cafagna, F; Caillat, L; Calzas, A; Capone, A; Caponetto, L; Carmona, E; Carr, J; Cartwright, S L; Castel, D; Castorina, E; Cavasinni, V; Cecchini, S; Ceres, A; Charvis, P; Chauchot, P; Chiarusi, T; Circella, M; Colnard, C; Compere, C; Coniglione, R; Cottini, N; Coyle, P; Cuneo, S; Cussatlegras, A S; Damy, G; Van Dantzig, R; De Marzo, C; Dekeyser, I; Delagnes, E; Denans, D; Deschamps, A; Dessages-Ardellier, F; Destelle, J J; Dinkespieler, B; Distefano, C; Donzaud, C; Drogou, J F; Druillole, F; Durand, D; Ernenwein, J P; Escoffier, S; Falchini, E; Favard, S; Feinstein, F; Ferry, S; Festy, D; Fiorello, C; Flaminio, V; Galeotti, S; Gallone, J M; Giacomelli, G; Girard, N; Gojak, C; Goret, P; Graf, K; Hallewell, G D; Harakeh, M N; Hartmann, B; Heijboer, A; Heine, E; Hello, Y; Hernández-Rey, J J; Hossl, J; Hoffman, C; Hogenbirk, J; Hubbard, John R; Jaquet, M; Jaspers, M; De Jong, M; Jouvenot, F; Kalantar-Nayestanaki, N; Kappes, A; Karg, T; Karkar, S; Katz, U; Keller, P; Kok, H; Kooijman, P; Kopper, C; Korolkova, E V; Kouchner, A; Kretschmer, W; Kruijer, A; Kuch, S; Kudryavtsev, V A; Lachartre, D; Lafoux, H; Lagier, P; Lahmann, R; Lamanna, G; Lamare, P; Languillat, J C; Laschinsky, H; Le Guen, Y; Le Provost, H; Le Van-Suu, A; Legou, T; Lim, G; Lo Nigro, L; Lo Presti, D; Löhner, H; Loucatos, Sotirios S; Louis, F; Lucarelli, F; Lyashuk, V; Marcelin, M; Margiotta, A; Masullo, R; Mazéas, F; Mazure, A; McMillan, J E; Megna, R; Melissas, M; Migneco, E; Milovanovic, A; Mongelli, M; Montaruli, T; Morganti, M; Moscoso, L; Musumeci, M; Naumann, C; Naumann-Godo, M; Niess, V; Olivetto, C; Ostasch, R; Palanque-Delabrouille, Nathalie; Payre, P; Peek, H; Petta, C; Piattelli, P; Pineau, J P; Poinsignon, J; Popa, V; Pradier, T; Racca, C; Randazzo, N; Van Randwijk, J; Real, D; Van Rens, B; Rethore, F; Rewiersma, P A M; Riccobene, G; Rigaud, V; Ripani, M; Roca, V; Roda, C; Rolin, J F; Romita, M; Rose, H J; Rostovtsev, A; Roux, J; Ruppi, M; Russo, G V; Salesa, F; Salomon, K; Sapienza, P; Schmitt, F; Schuller, J P; Shanidze, R; Sokalski, I A; Spona, T; Spurio, M; van der Steenhoven, G; Stolarczyk, T; Streeb, K; Stubert, D; Sulak, L; Taiuti, M; Tamburini, C; Tao, C; Terreni, G; Thompson, L F; Valdy, P; Valente, V; Vallage, B; Venekamp, G; Verlaat, B; Vernin, P; De Vita, R; De Vries, G; Van Wijk, R F; De Witt-Huberts, P K A; Wobbe, G; De Wolf, E; Yao, A F; Zaborov, D; Zaccone, Henri; De Dios-Zornoza-Gomez, Juan; Zúñiga, J; al, et

2006-01-01T23:59:59.000Z

335

Minimal Stereoscopic Analysis for Imaging Atmospheric Cherenkov Telescope Arrays  

E-Print Network [OSTI]

The trajectory of a primary gamma-ray detected with an array of at least four atmospheric Cherenkov imaging telescopes can be reconstructed from the shower image centroid positions and geometrical considerations independent of the primary energy. Using only the image centroid positions some cosmic-ray discrimination is also possible. This minimal approach opens the possibility of pushing the analysis threshold to lower values, close to the hardware threshold.

S. LeBohec; C. Duke; P. Jordan

2006-08-15T23:59:59.000Z

336

Laser metrology for coherent multi-telescope arrays  

DOE Patents [OSTI]

In multi-telescope arrays that comprise multiple telescopes, a beam-combining module, and flat mirrors for directing light beams from the multiple telescopes to the beam combining module, a laser metrology system is used for monitoring various pathlengths along a beam path where deviations are likely. Some pathlengths are defined simply by a pair of retroreflectors or reflectors at both ends. Lengths between pairs of retroreflectors are measured and monitored by laser interferometers. One critical pathlength deviation is related to the displacement of the flat mirror. A reference frame is set up relative to the beam-combining module to form and define the coordinate system within which the positions of the flat mirrors are measured and monitored. In the preferred embodiment, a pair of retroreflectors along the optical axis of the beam-combining module defines a reference frame. A triangle is formed by the reference frame as the base and another retroreflector at the flat mirror as the vertex. The triangle is used to monitor the position of the flat mirror. A beam's pathlength is dynamically corrected in response to the monitored deviations.

Shao, M.; Massie, N.A.

1993-05-04T23:59:59.000Z

337

Observational tests for ?(t)CDM cosmology  

SciTech Connect (OSTI)

We investigate the observational viability of a class of cosmological models in which the vacuum energy density decays linearly with the Hubble parameter, resulting in a production of cold dark matter particles at late times. Similarly to the flat ?CDM case, there is only one free parameter to be adjusted by the data in this class of ?(t)CDM scenarios, namely, the matter density parameter. To perform our analysis we use three of the most recent SNe Ia compilation sets (Union2, SDSS and Constitution) along with the current measurements of distance to the BAO peaks at z = 0.2 and z = 0.35 and the position of the first acoustic peak of the CMB power spectrum. We show that in terms of ?{sup 2} statistics both models provide good fits to the data and similar results. A quantitative analysis discussing the differences in parameter estimation due to SNe light-curve fitting methods (SALT2 and MLCS2k2) is studied using the current SDSS and Constitution SNe Ia compilations. A matter power spectrum analysis using the 2dFGRS is also performed, providing a very good concordance with the constraints from the SDSS and Constitution MLCS2k2 data.

Pigozzo, C.; Carneiro, S. [Instituto de Física, Universidade Federal da Bahia, 40210-340 Salvador, BA (Brazil); Dantas, M.A.; Alcaniz, J.S., E-mail: cpigozzo@ufba.br, E-mail: aldinez@on.br, E-mail: saulo.carneiro@pq.cnpq.br, E-mail: alcaniz@on.br [Observatório Nacional, 20921-400 Rio de Janeiro, RJ (Brazil)

2011-08-01T23:59:59.000Z

338

Is Cosmology Compatible with Sterile Neutrinos?  

SciTech Connect (OSTI)

By combining data from cosmic microwave background experiments (including the recent WMAP third year results), large scale structure, and Lyman-{alpha} forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless+1 massive neutrino case, we bound the mass of the sterile neutrino to m{sub s}<0.26 eV (0.44 eV) at 95% (99.9%) C.L., which excludes at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We generalize the analysis to account for active neutrino masses and the possibility that the sterile abundance is not thermal. In the latter case, the contraints in the (mass,density) plane are nontrivial. For a mass of >1 or <0.05 eV, the cosmological energy density in sterile neutrinos is always constrained to be {omega}{sub {nu}}<0.003 at 95% C.L., but for a mass of {approx}0.25 eV, {omega}{sub {nu}} can be as large as 0.01.

Dodelson, Scott; Melchiorri, Alessandro; Slosar, Anze [Particle Astrophysics Center, FERMILAB, Batavia, Illinois 60510-0500 (United States); Physics Department and Sezione INFN, University of Rome 'La Sapienza', Ple Aldo Moro 2, 00185 Rome (Italy); Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana (Slovenia)

2006-07-28T23:59:59.000Z

339

ALFALFA: HI Cosmology in the Local Universe  

E-Print Network [OSTI]

For the last 25 years, the 21 cm line has been used productively to investigate the large-scale structure of the Universe, its peculiar velocity field and the measurement of cosmic parameters. In February 2005 a blind HI survey that will cover 7074 square degrees of the high latitude sky was started at Arecibo, using the 7-beam feed L-band feed array (ALFA). Known as the Arecibo Legacy Fast ALFA (ALFALFA) Survey, the program is producing a census of HI-bearing objects over a cosmologically significant volume of the local Universe. With respect to previous blind HI surveys, ALFALFA offers an improvement of about one order of magnitude in sensitivity, 4 times the angular resolution, 3 times the spectral resolution, and 1.6 times the total bandwidth of HIPASS. ALFALFA can detect 7 X 10**4 D**2 solar masses of HI, where D is the source distance in Mpc. As of mid 2007, 44% of the survey observations and 15% of the source extraction are completed. We discuss the status of the survey and present a few preliminary re...

Giovanelli, Riccardo

2007-01-01T23:59:59.000Z

340

ALFALFA: HI Cosmology in the Local Universe  

E-Print Network [OSTI]

For the last 25 years, the 21 cm line has been used productively to investigate the large-scale structure of the Universe, its peculiar velocity field and the measurement of cosmic parameters. In February 2005 a blind HI survey that will cover 7074 square degrees of the high latitude sky was started at Arecibo, using the 7-beam feed L-band feed array (ALFA). Known as the Arecibo Legacy Fast ALFA (ALFALFA) Survey, the program is producing a census of HI-bearing objects over a cosmologically significant volume of the local Universe. With respect to previous blind HI surveys, ALFALFA offers an improvement of about one order of magnitude in sensitivity, 4 times the angular resolution, 3 times the spectral resolution, and 1.6 times the total bandwidth of HIPASS. ALFALFA can detect 7 X 10**4 D**2 solar masses of HI, where D is the source distance in Mpc. As of mid 2007, 44% of the survey observations and 15% of the source extraction are completed. We discuss the status of the survey and present a few preliminary results, in particular with reference to the proposed "dark galaxy" VirgoHI21.

Riccardo Giovanelli

2007-07-22T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

K-mouflage Cosmology: the Background Evolution  

E-Print Network [OSTI]

We study the cosmology of K-mouflage theories at the background level. We show that the effects of the scalar field are suppressed at high matter density in the early Universe and only play a role in the late time Universe where the deviations of the Hubble rate from its $\\Lambda$-CDM counterpart can be of the order five percent for redshifts $1 \\lesssim z \\lesssim 5$. Similarly, we find that the equation of state can cross the phantom divide in the recent past and even diverge when the effective scalar energy density goes negative and subdominant compared to matter, preserving the positivity of the squared Hubble rate. These features are present in models for which Big Bang Nucleosynthesis is not affected. We analyze the fate of K-mouflage when the nonlinear kinetic terms give rise to ghosts, particle excitations with negative energy. In this case, we find that the K-mouflage theories can only be considered as an effective description of the Universe at low energy below $1$ keV. In the safe ghost-free models, we find that the equation of state always diverges in the past and changes significantly by a few percent since $z\\lesssim 1$.

Philippe Brax; Patrick Valageas

2014-11-30T23:59:59.000Z

342

E-Print Network 3.0 - annihilation radiation telescope Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Collection: Physics 3 MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Summary: Gamma ray bursts Cosmology Diffuse extragalactic radiation fields via cutoff in AGN spectra and...

343

High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center  

DOE Patents [OSTI]

A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes. 15 figs.

Norbert, M.A.; Yale, O.

1992-04-28T23:59:59.000Z

344

Cosmological reconstruction of $f(T,\\mathcal{T})$ Gravity  

E-Print Network [OSTI]

Motivated by the newly proposal for gravity as the effect of the torsion scalar $T$ and trace of the energy momentum tensor $\\mathcal{T}$,we investigate the cosmological reconstruction of different models of the Universe. Our aim here is to show that how this modified gravity model, $f(T,\\mathcal{T})$ is able to reproduce different epoches of the cosmological history. We explicitly show that $f(T,\\mathcal{T})$ can be reconstructed for $\\Lambda $CDM as the most popular and consistent model. Also we study the mathematical reconstruction of $f(T,\\mathcal{T})$ for a flat cosmological background filled by two fluids mixture. Such model describes phantom-non-phantom era as well as the purely phantom cosmology. We extend our investigation to more cosmological models like perfect fluid,Chaplygin gas and massless scalar field. In each case we obtain some specific forms of $f(T,\\mathcal{T})$. These families of $f(T,\\mathcal{T})$ contain arbitrary function of torsion and trace of the energy momentum.

Davood Momeni; Ratbay Myrzakulov

2014-05-29T23:59:59.000Z

345

On a New 4-Vector Cosmological Field Theory  

E-Print Network [OSTI]

The original Dirac Equation is modified in the simplest imaginable and most trivial manner to include a universal 4-Vector Cosmological Field term in the space and time dimensions. This cosmological field leads to a modified Dirac Equation capable of explaining why the Universe appears to be made up chiefly of matter. It is seen that this 4-Vector Cosmological Field is actually a particle field and this particle field can possibly be identified with the darkmatter and darkenergy field. Further, this 4-Vector Cosmological Field is seen to give spacetime the desired quantum mechanical properties of randomness. Furthermore, it is seen that in the emergent Universe, the position coordinates of a particle in space -- contrary to the widely accepted belief that the position of a particle in space has no physical significance, we see that that opposite is true - namely that the position of a particle has physical significance. We further note that the 4-Vector Cosmological Field modification to the Dirac Equation leads us to a vacuum model redolent but different from that of Quantum Electrodynamics (QED). This new vacuum model is without virtual particles but darkparticles. We dare to make the suggestion that these darkparticles may possibly explain the current mystery of what really is darkmatter and darkenergy.

G. G. Nyambuya

2009-05-05T23:59:59.000Z

346

Anisotropic Homogeneous Cosmologies in the Post-Newtonian Approximation  

E-Print Network [OSTI]

In this paper we explore how far the post-Newtonian theory goes in overcoming the difficulties associated with anisotropic homogeneous cosmologies in the Newtonian approximation. It will be shown that, unlike in the Newtonian case, the cosmological equations of the post-Newtonian approximation are much more in the spirit of general relativity with regard to the nine Bianchi types and issues of singularities. The situations of vanishing rotation and vanishing shear are treated separately. The homogeneous Bianchi I model is considered as an example of a rotation-free cosmology with anisotropy. It is found in the Newtonian approximation that there are arbitrary functions that need to be given for all time if the initial value problem is to be well-posed, while in the post-Newtonian case there is no such need. For the general case of a perfect fluid only the post-Newtonian theory can satisfactorily describe the effects of pressure. This is in accordance with findings in an earlier paper where the post-Newtonian approximation was applied to homogeneous cosmologies. For a shear-free anisotropic homogeneous cosmology the Newtonian theory of Heckmann and Sch\\"ucking is explored. Comparisons with its relativistic and post-Newtonian counterparts are made. In the Newtonian theory solutions exist to which there are no analogues in general relativity. The post-Newtonian approximation may provide a way out.

Tamath Rainsford

2000-07-23T23:59:59.000Z

347

Freshman Seminar on New Cosmology MAE 87 8-10 am in EBUII 479  

E-Print Network [OSTI]

the standard NASA-and (dark energy) CDM (cold dark matter) HC (hierarchical clustering) cosmological model-gravitational-dynamics HGD emerges. According to HGD cosmology, life begins soon after the big bang in hot water oceans

Wang, Deli

348

From theoretical promise to observational reality : calibration, foreground subtraction, and signal extraction in hydrogen cosmology  

E-Print Network [OSTI]

By using the hyperfine 21 cm transition to map out the distribution of neutral hydrogen at high redshifts, hydrogen cosmology has the potential to place exquisite constraints on fundamental cosmological parameters, as well ...

Liu, Adrian Chi-Yan

2012-01-01T23:59:59.000Z

349

Exponential cosmological redshift in a linearly expanding universe  

E-Print Network [OSTI]

The first principles analysis of the radiation by an arbitrary source in a flat Friedmann-Robertson-Walker space-time is presented. The obtained analytical solution explicitly shows that the cosmological redshift is not of kinematic origin and that the source and the observer may be regarded as being at rest with respect to eachother at all times. At the same time the effect of the time-variation of the metric on the propagation of light appears to be underestimated in the standard cosmology. The cosmological redshift caused by the linear time-variation of the metric turns out to be an exponential rather than linear function of the well-defined spatial distance and the apparent brightness of the source contains an even stronger exponential decay factor.

Neil V. Budko

2009-07-03T23:59:59.000Z

350

Thermodynamics of de Sitter Black Holes: Thermal Cosmological Constant  

E-Print Network [OSTI]

We study the thermodynamic properties associated with the black hole event horizon and the cosmological horizon for black hole solutions in asymptotically de Sitter spacetimes. We examine thermodynamics of these horizons on the basis of the conserved charges according to Teitelboim's method. In particular, we have succeeded in deriving the generalized Smarr formula among thermodynamical quantities in a simple and natural way. We then show that cosmological constant must decrease when one takes into account the quantum effect. These observations have been obtained if and only if cosmological constant plays the role of a thermodynamical state variable. We also touch upon the relation between inflation of our universe and a phase transition of black holes.

Yuichi Sekiwa

2006-04-10T23:59:59.000Z

351

Perturbative stability of SFT-based cosmological models  

SciTech Connect (OSTI)

We review the appearance of multiple scalar fields in linearized SFT based cosmological models with a single non-local scalar field. Some of these local fields are canonical real scalar fields and some are complex fields with unusual coupling. These systems only admit numerical or approximate analysis. We introduce a modified potential for multiple scalar fields that makes the system exactly solvable in the cosmological context of Friedmann equations and at the same time preserves the asymptotic behavior expected from SFT. The main part of the paper consists of the analysis of inhomogeneous cosmological perturbations in this system. We show numerically that perturbations corresponding to the new type of complex fields always vanish. As an example of application of this model we consider an explicit construction of the phantom divide crossing and prove the perturbative stability of this process at the linear order. The issue of ghosts and ways to resolve it are briefly discussed.

Galli, Federico; Koshelev, Alexey S., E-mail: fgalli@tena4.vub.ac.be, E-mail: alexey.koshelev@vub.ac.be [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium)

2011-05-01T23:59:59.000Z

352

Dark Energy Dipole in f(R T) Cosmological Model  

E-Print Network [OSTI]

Recent astronomical observations show that the universe may be anisotropic on large scales. The Union2 SnIa data hint that the universe has a preferred direction. If such a cosmological privileged axis indeed exists, one has to consider an anisotropic expanding Universe, instead of the isotropic cosmological model. In this paper, we present a detailed analysis of the cosmic dipoles in f(R; T) Cosmological Model. the maximum anisotropic deviation direction is (l, b) = (137,23) or equivalently (l, b) = (317,-23). Our numerical results show that, using Union2 data, the anisotropic f(R, T) model provides a significantly better fit than the isotropic f(R, T), CPL, and {\\Lambda}CDM models.

Salehi, Amin

2015-01-01T23:59:59.000Z

353

On higher derivative gravity, c-theorems and cosmology  

E-Print Network [OSTI]

We consider higher derivative gravity lagrangians in 3 and 4 dimensions, which admit simple c-theorems, including upto six derivative curvature invariants. Following a suggestion by Myers, these lagrangians are restricted such that the fluctuations around (anti) de Sitter spaces have second order linearized equations of motion. We study c-theorems both in the context of AdS/CFT and cosmology. In the context of cosmology, the monotonic function is the entropy defined on the apparent horizon through Wald's formula. Exact black hole solutions which are asymptotically (anti) de Sitter are presented. An interesting lower bound for entropy is found in de Sitter space. Some aspects of cosmology in both D=3 and D=4 are discussed.

Aninda Sinha

2010-10-01T23:59:59.000Z

354

Structure of Cosmological CP Violation via Neutrino Seesaw  

E-Print Network [OSTI]

The cosmological matter-antimatter asymmetry can originate from CP-violating interactions of seesaw Majorana neutrinos via leptogenesis in the thermal phase of the early universe. Having the cosmological CP-phase for leptogenesis requires at least two right-handed Majorana neutrinos. Using only the low energy neutrino observables we quantitatively reconstruct a minimal neutrino seesaw. We establish a general criterion for minimal seesaw schemes in which the cosmological CP-phase is {\\it completely} reconstructed from the low energy CP-phases measured by neutrino oscillation and neutrinoless double-beta decay experiments. We reveal and analyze two distinct classes of such minimal schemes that are shown to be highly predictive. Extension of our reconstruction formalism to a three-heavy-neutrino seesaw is discussed.

V. Barger; Duane A. Dicus; Hong-Jian He; Tianjun Li

2003-12-16T23:59:59.000Z

355

Planck Scale Cosmology and Asymptotic Safety in Resummed Quantum Gravity  

E-Print Network [OSTI]

In Weinberg's asymptotic safety approach, a finite dimensional critical surface for a UV stable fixed point generates a theory of quantum gravity with a finite number of physical parameters. We argue that, in an extension of Feynman's original formulation of the theory, we recover this fixed-point UV behavior from an exact re-arrangement of the respective perturbative series. Our results are consistent with the exact field space Wilsonian renormalization group results of Reuter {\\it et al.} and with recent Hopf- algebraic Dyson-Schwinger renormalization theory results of Kreimer. We obtain the first "first principles" predictions of the dimensionless gravitational and cosmological constants and our results support the Planck scale cosmology of Bonanno and Reuter. We conclude with an estimate for the currently observed value of the cosmological constant.

B. F. L. Ward

2010-12-13T23:59:59.000Z

356

A Nested Sampling Algorithm for Cosmological Model Selection  

E-Print Network [OSTI]

The abundance of new cosmological data becoming available means that a wider range of cosmological models are testable than ever before. However, an important distinction must be made between parameter fitting and model selection. While parameter fitting simply determines how well a model fits the data, model selection statistics, such as the Bayesian Evidence, are now necessary to choose between these different models, and in particular to assess the need for new parameters. We implement a new evidence algorithm known as nested sampling, which combines accuracy, generality of application and computational feasibility, and apply it to some cosmological datasets and models. We find that a five-parameter model with Harrison-Zel'dovich initial spectrum is currently preferred.

Pia Mukherjee; David Parkinson; Andrew R. Liddle

2006-01-11T23:59:59.000Z

357

Type IIP supernovae as cosmological probes: A SEAM distance to SN 1999em  

E-Print Network [OSTI]

Type IIP Supernovae as Cosmological Probes: A SEAM Distanceintrinsic brightness, supernovae make excellent cosmologicalstars: atmospheres — supernovae: 1999em Distances from

Baron, E.; Nugent, Peter E.; Branch, David; Hauschildt, Peter H.

2004-01-01T23:59:59.000Z

358

Reconstruction of $5D$ Cosmological Models From Equation of State of Dark Energy  

E-Print Network [OSTI]

We consider a class of five-dimensional cosmological solutions which contains two arbitrary function $\\mu(t)$ and $\

Lixin Xu; Hongya Liu; Chengwu Zhang

2005-10-24T23:59:59.000Z

359

Theoretical Research in Cosmology, High-Energy Physics and String Theory  

SciTech Connect (OSTI)

The research was in the area of Theoretical Physics: Cosmology, High-Energy Physics and String Theory

Ng, Y Jack; Dolan, Louise; Mersini-Houghton, Laura; Frampton, Paul

2013-07-29T23:59:59.000Z

360

Nonlocal String Tachyon as a Model for Cosmological Dark Energy  

SciTech Connect (OSTI)

There are many different phenomenological models describing the cosmological dark energy and accelerating Universe by choosing adjustable functions. In this paper we consider a specific model of scalar tachyon field which is derived from the NSR string field theory and study its cosmological applications. We find that in the effective field theory approximation the equation of state parameter w < -1, i.e. one has a phantom Universe. It is shown that due to nonlocal effects there is no quantum instability that the usual phantom models suffer from. Moreover due to a flip effect of the potential the Universe does not enter to a future singularity.

Aref'eva, Irina Ya. [Steklov Mathematical Institute, Russian Academy of Sciences, Gubkin st. 8, Moscow, 119991 (Russian Federation)

2006-03-29T23:59:59.000Z

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361

Primordial black hole evolution in tensor-scalar cosmology  

E-Print Network [OSTI]

A perturbative analysis shows that black holes do not remember the value of the scalar field $\\phi$ at the time they formed if $\\phi$ changes in tensor-scalar cosmology. Moreover, even when the black hole mass in the Einstein frame is approximately unaffected by the changing of $\\phi$, in the Jordan-Fierz frame the mass increases. This mass increase requires a reanalysis of the evaporation of primordial black holes in tensor-scalar cosmology. It also implies that there could have been a significant magnification of the (Jordan-Fierz frame) mass of primordial black holes.

Ted Jacobson

1999-09-06T23:59:59.000Z

362

General properties of cosmological models with an Isotropic Singularity  

E-Print Network [OSTI]

Much of the published work regarding the Isotropic Singularity is performed under the assumption that the matter source for the cosmological model is a barotropic perfect fluid, or even a perfect fluid with a $\\gamma$-law equation of state. There are, however, some general properties of cosmological models which admit an Isotropic Singularity, irrespective of the matter source. In particular, we show that the Isotropic Singularity is a point-like singularity and that vacuum space-times cannot admit an Isotropic Singularity. The relationships between the Isotropic Singularity, and the energy conditions, and the Hubble parameter is explored. A review of work by the authors, regarding the Isotropic Singularity, is presented.

Geoffery Ericksson; Susan M. Scott

2003-02-25T23:59:59.000Z

363

Implementing the DC Mode in Cosmological Simulations with Supercomoving Variables  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

As emphasized by previous studies, proper treatment of the density fluctuation on the fundamental scale of a cosmological simulation volume - the 'DC mode' - is critical for accurate modeling of spatial correlations on scales ~> 10% of simulation box size. We provide further illustration of the effects of the DC mode on the abundance of halos in small boxes and show that it is straightforward to incorporate this mode in cosmological codes that use the 'supercomoving' variables. The equations governing evolution of dark matter and baryons recast with these variables are particularly simple and include the expansion factor, and hence the effect of the DC mode, explicitly only in the Poisson equation.

Gnedin, Nickolay Y.; Kravtsov, Andrey V.; Rudd, Douglas H.

2011-06-02T23:59:59.000Z

364

The Quantum Vacuum and the Cosmological Constant Problem  

E-Print Network [OSTI]

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physical real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined.

Svend Erik Rugh; Henrik Zinkernagel

2000-12-28T23:59:59.000Z

365

The Quantum Vacuum and the Cosmological Constant Problem  

E-Print Network [OSTI]

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physical real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined.

Rugh, S E; Rugh, Svend Erik; Zinkernagel, Henrik

2000-01-01T23:59:59.000Z

366

Coincidence of Universe age in $?$CDM and Milne cosmologies  

E-Print Network [OSTI]

The age of the Universe in the $\\Lambda$CDM cosmology with $\\Omega_{matter}=0.26$ and $\\Omega_{\\Lambda}=0.74$ is the same as in the Milne cosmology which correspods to an almost empty universe. In both cases it is a reciprocal Hubble constant, $1/H_0$, that for now preferred value $H_0=71 km/s/Mpc$ is 13.7 billion years. The most curious coincidence is that at the present time, in the $\\Lambda$CDM model the decelerated expansion is exactly compensated by the accelerated expansion, as if the Universe coast for 13.7 billion years.

M. Kutschera; M. Dyrda

2006-11-09T23:59:59.000Z

367

Mathematical problems in higher order gravity and cosmology  

E-Print Network [OSTI]

We discuss the issue of motivating the analysis of higher order gravity theories and their cosmologies and introduce a rule which states that these theories may be considered as a vehicle for testing whether certain properties may be of relevance to quantum theory. We discuss the physicality issue arising as a consequence of the conformal transformation theorem, the question of formulating a consistent first order formalism of such theories and also the isotropization problem for a class of generalized cosmologies. We point out that this field may have an important role to play in clarifying issues arising also in general relativity.

S. Cotsakis

1997-12-10T23:59:59.000Z

368

Strong gravitational lensing of gravitational waves in Einstein Telescope  

SciTech Connect (OSTI)

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.

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

369

4MOST - 4-metre Multi-Object Spectroscopic Telescope  

E-Print Network [OSTI]

The 4MOST consortium is currently halfway through a Conceptual Design study for ESO with the aim to develop a wide-field (>3 square degree, goal >5 square degree), high-multiplex (>1500 fibres, goal 3000 fibres) spectroscopic survey facility for an ESO 4m-class telescope (VISTA). 4MOST will run permanently on the telescope to perform a 5 year public survey yielding more than 20 million spectra at resolution R~5000 ({\\lambda}=390-1000 nm) and more than 2 million spectra at R~20,000 (395-456.5 nm & 587-673 nm). The 4MOST design is especially intended to complement three key all-sky, space-based observatories of prime European interest: Gaia, eROSITA and Euclid. Initial design and performance estimates for the wide-field corrector concepts are presented. We consider two fibre positioner concepts, a well-known Phi-Theta system and a new R-Theta concept with a large patrol area. The spectrographs are fixed configuration two-arm spectrographs, with dedicated spectrographs for the high- and low-resolution. A ful...

de Jong, Roelof S; Chiappini, Cristina; Depagne, Éric; Haynes, Roger; Johl, Diane; Schnurr, Olivier; Schwope, Axel; Walcher, Jakob; Dionies, Frank; Haynes, Dionne; Kelz, Andreas; Kitaura, Francisco S; Lamer, Georg; Minchev, Ivan; Müller, Volker; Nuza, Sebastián E; Olaya, Jean-Christophe; Piffl, Tilmann; Popow, Emil; Steinmetz, Matthias; Ural, U?ur; Williams, Mary; Winkler, Roland; Wisotzki, Lutz; Ansorgb, Wolfgang R; Banerji, Manda; Solares, Eduardo Gonzalez; Irwin, Mike; Kennicutt, Robert C; King, David; McMahon, Richard; Koposov, Sergey; Parry, Ian R; Walton, Nicholas A; Finger, Gert; Iwert, Olaf; Krumpe, Mirko; Lizon, Jean-Louis; Vincenzo, Mainieri; Amans, Jean-Philippe; Bonifacio, Piercarlo; Cohen, Mathieu; Francois, Patrick; Jagourel, Pascal; Mignot, Shan B; Royer, Frédéric; Sartoretti, Paola; Bender, Ralf; Grupp, Frank; Hess, Hans-Joachim; Lang-Bardl, Florian; Muschielok, Bernard; Böhringer, Hans; Boller, Thomas; Bongiorno, Angela; Brusa, Marcella; Dwelly, Tom; Merloni, Andrea; Nandra, Kirpal; Salvato, Mara; Pragt, Johannes H; Navarro, Ramón; Gerlofsma, Gerrit; Roelfsema, Ronald; Dalton, Gavin B; Middleton, Kevin F; Tosh, Ian A; Boeche, Corrado; Caffau, Elisabetta; Christlieb, Norbert; Grebel, Eva K; Hansen, Camilla; Koch, Andreas; Ludwig, Hans-G; Quirrenbach, Andreas; Sbordone, Luca; Seifert, Walter; Thimm, Guido; Trifonov, Trifon; Helmi, Amina; Trager, Scott C; Feltzing, Sofia; Korn, Andreas; Boland, Wilfried

2012-01-01T23:59:59.000Z

370

Sites in Argentina for the Cherenkov Telescope Array Project  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) Project will consist of two arrays of atmospheric Cherenkov telescopes to study high-energy gamma radiation in the range of a few tens of GeV to beyond 100 TeV. To achieve full-sky coverage, the construction of one array in each terrestrial hemisphere is considered. Suitable candidate sites are being explored and characterized. The candidate sites in the Southern Hemisphere include two locations in Argentina, one in San Antonio de los Cobres (Salta Province, Lat. 24:02:42 S, Long. 66:14:06 W, at 3600 m.a.s.l) and another one in El Leoncito (San Juan Province, Lat. 31:41:49 S, Long. 69:16:21 W, at 2600 m.a.s.l). Here we describe the two sites and the instrumentation that has been deployed to characterize them. We summarize the geographic, atmospheric and climatic data that have been collected for both of them.

Allekotte, Ingo; Etchegoyen, Alberto; García, Beatriz; Mancilla, Alexis; Maya, Javier; Ravignani, Diego; Rovero, Adrián

2013-01-01T23:59:59.000Z

371

The Trigger Algorithm for the Burst Alert Telescope on Swift  

E-Print Network [OSTI]

The Swift Burst Alert Telescope (BAT) is a huge (5200 cm2) coded aperture imager that will detect gamma-ray bursts in real time and provide a location that the Swift satellite will use to slew the optical and x-ray telescopes. The huge size of BAT is a challenge for the on-board triggering: a change as small as 1% is equivalent to a 1 sigma statistical variation in 1 second. There will be three types of triggers, two based on rates and one based on images. The first type of trigger is for short time scales (4 msec to 64 msec). These will be traditional triggers (single background) and we check about 25,000 combinations of time-energy-focal plane subregions per second. The second type of trigger will be similar to what is used on HETE: fits to multiple background regions to remove trends for time scales between 64 msec and 64 seconds. About 500 triggers will be checked per second. For these rate triggers, false triggers and variable non-GRB sources will be rejected by requiring a new source to be present in an...

Fenimore, E; Galassi, M; Gehrels, N; Palmer, D; Parsons, A; Tavenner, T; Tüller, J

2004-01-01T23:59:59.000Z

372

Design constraints on Cherenkov telescopes with Davies-Cotton reflectors  

E-Print Network [OSTI]

This paper discusses the construction of high-performance ground-based gamma-ray Cherenkov telescopes with a Davies-Cotton reflector. For the design of such telescopes, usually physics constrains the field-of-view, while the photo-sensor size is defined by limited options. Including the effect of light-concentrators in front of the photo sensor, it is demonstrated that these constraints are enough to mutually constrain all other design parameters. The dependability of the various design parameters naturally arises once a relationship between the value of the point-spread functions at the edge of the field-of-view and the pixel field-of-view is introduced. To be able to include this constraint into a system of equations, an analytical description for the point-spread function of a tessellated Davies-Cotton reflector is derived from Taylor developments and ray-tracing simulations. Including higher order terms renders the result precise on the percent level. Design curves are provided within the typical phase sp...

Bretz, Thomas

2013-01-01T23:59:59.000Z

373

Evolution of density perturbations in decaying vacuum cosmology: The case of nonzero perturbations in the cosmological term  

SciTech Connect (OSTI)

We extend the results of a previous paper where a model of interacting dark energy, with a cosmological term decaying linearly with the Hubble parameter, is tested against the observed mass power spectrum. In spite of the agreement with observations of type Ia supernovas, baryonic acoustic oscillations, and the cosmic microwave background, we had shown previously that no good concordance is achieved if we include the mass power spectrum. However, our analysis was based on the ad hoc assumption that the interacting cosmological term is strictly homogeneous. Now we perform a more complete analysis, by perturbing such a term. Although our conclusions are still based on a particular, scale-invariant choice of the primordial spectrum of dark energy perturbations, we show that a cosmological term decaying linearly with the Hubble parameter is indeed disfavored as compared to the standard model.

Borges, H. A. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Centro de Formacao de Professores, Universidade Federal do Reconcavo da Bahia, Amargosa, BA (Brazil); Carneiro, S. [Instituto de Fisica, Universidade Federal da Bahia, Salvador, BA (Brazil); Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, London (United Kingdom); Fabris, J. C. [Departamento de Fisica, Universidade Federal do Espirito Santo, Vitoria, ES (Brazil); Institut d'Astrophysique de Paris, Paris (France)

2008-12-15T23:59:59.000Z

374

Status of the technologies for the production of the Cherenkov Telescope Array (CTA) mirrors  

E-Print Network [OSTI]

The Cherenkov Telescope Array (CTA) is the next generation very high-energy gamma-ray observatory, with at least 10 times higher sensitivity than current instruments. CTA will comprise several tens of Imaging Atmospheric Cherenkov Telescopes (IACTs) operated in array-mode and divided into three size classes: large, medium and small telescopes. The total reflective surface could be up to 10,000 m2 requiring unprecedented technological efforts. The properties of the reflector directly influence the telescope performance and thus constitute a fundamental ingredient to improve and maintain the sensitivity. The R&D status of lightweight, reliable and cost-effective mirror facets for the CTA telescope reflectors for the different classes of telescopes is reviewed in this paper.

Pareschi, G; Baba, H; Bähr, J; Bonardi, A; Bonnoli, G; Brun, P; Canestrari, R; Chadwick, P; Chikawa, M; Carton, P -H; de Souza, V; Dipold, J; Doro, M; Durand, D; Dyrda, M; Förster, A; Garczarczyk, M; Giro, E; Glicenstein, J -F; Hanabata, Y; Hayashida, M; Hrabovski, M; Jeanney, C; Kagaya, M; Katagiri, H; Lessio, L; Mandat, D; Mariotti, M; Medina, C; Micha?owski, J; Micolon, P; Nakajima, D; Niemiec, J; Nozato, A; Palatka, M; Pech, M; Peyaud, B; Pühlhofer, G; Rataj, M; Rodeghiero, G; Rojas, G; Rousselle, J; Sakonaka, R; Schovanek, P; Seweryn, K; Schultz, C; Shu, S; Stinzing, F; Stodulski, M; Teshima, M; Travniczek, P; van Eldik, C; Vassiliev, V; Wi?niewski, ?; Wörnlein, A; Yoshida, T

2013-01-01T23:59:59.000Z

375

Pseudo-Dirac Neutrinos, a Challenge for Neutrino Telescopes  

E-Print Network [OSTI]

Neutrinos may be pseudo-Dirac states, such that each generation is actually composed of two maximally-mixed Majorana neutrinos separated by a tiny mass difference. The usual active neutrino oscillation phenomenology would be unaltered if the pseudo-Dirac splittings are $\\delta m^2 \\alt 10^{-12}$ eV$^2$; in addition, neutrinoless double beta decay would be highly suppressed. However, it may be possible to distinguish pseudo-Dirac from Dirac neutrinos using high-energy astrophysical neutrinos. By measuring flavor ratios as a function of $L/E$, mass-squared differences down to $\\delta m^2 \\sim 10^{-18}$ eV$^2$ can be reached. We comment on the possibility of probing cosmological parameters with neutrinos.

John F. Beacom; Nicole F. Bell; Dan Hooper; John G. Learned; Sandip Pakvasa; Thomas J. Weiler

2004-01-05T23:59:59.000Z

376

Verifying the Cosmological Utility of Type Ia Supernovae:Implications of a Dispersion in the Ultraviolet Spectra  

SciTech Connect (OSTI)

We analyze the mean rest-frame ultraviolet (UV) spectrum ofType Ia Supernovae(SNe) and its dispersion using high signal-to-noiseKeck-I/LRIS-B spectroscopyfor a sample of 36 events at intermediateredshift (z=0.5) discoveredby the Canada-France-Hawaii TelescopeSupernova Legacy Survey (SNLS). Weintroduce a new method for removinghost galaxy contamination in our spectra,exploiting the comprehensivephotometric coverage of the SNLS SNe and theirhost galaxies, therebyproviding the first quantitative view of the UV spectralproperties of alarge sample of distant SNe Ia. Although the mean SN Ia spectrumhas notevolved significantly over the past 40 percent of cosmic history,preciseevolutionary constraints are limited by the absence of acomparable sample ofhigh quality local spectra. The mean UV spectrum ofour z 0.5 SNe Ia and itsdispersion is tabulated for use in futureapplications. Within the high-redshiftsample, we discover significant UVspectral variations and exclude dust extinctionas the primary cause byexamining trends with the optical SN color. Although progenitormetallicity may drive some of these trends, the variations we see aremuchlarger than predicted in recent models and do not follow expectedpatterns.An interesting new result is a variation seen in the wavelengthof selected UVfeatures with phase. We also demonstrate systematicdifferences in the SN Iaspectral features with SN lightcurve width inboth the UV and the optical. Weshow that these intrinsic variations couldrepresent a statistical limitation in thefuture use of high-redshift SNeIa for precision cosmology. We conclude thatfurther detailed studies areneeded, both locally and at moderate redshift wherethe rest-frame UV canbe studied precisely, in order that future missions canconfidently beplanned to fully exploit SNe Ia as cosmological probes.

Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam,A.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R.G.; Conley,A.; Fouchez, D.; Guy, J.; Hardin, D.; Hook, I.; Pain, R.; Perrett, K.; Pritchet, C.J.; Regnault, N.

2007-11-02T23:59:59.000Z

377

E-Print Network 3.0 - aperture submillimeter telescope Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

telescopes have arrived in Chile, ranging from small... to make way for the 10-meter South Pole ... Source: Ashley, Michael C. B. - School of Physics, University of New...

378

First Fruits of the Spitzer Space Telescope: Galactic and Solar System Studies  

E-Print Network [OSTI]

This article provides a brief overview of the Spitzer Space Telescope and discusses its initial scientific results on galactic and solar system science.

M. Werner; G. Fazio; G. Rieke; T. Roellig; D. Watson

2006-06-22T23:59:59.000Z

379

Testing Cosmological Models with Type Ic Super Luminous Supernovae  

E-Print Network [OSTI]

The use of type Ic Super Luminous Supernovae (SLSN Ic) to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 11 SLSNe Ic, which have thus far been used solely in tests involving $\\Lambda$CDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between the $R_{\\rm h}=ct$ and $\\Lambda$CDM cosmologies. We individually optimize the parameters in each cosmological model by minimizing the $\\chi^{2}$ statistic. We also carry out Monte Carlo simulations based on these current SLSN Ic measurements to estimate how large the sample would have to be in order to rule out either model at a $\\sim 99.7\\%$ confidence level. The currently available sample indicates a likelihood of $\\sim$$70-80\\%$ that the $R_{\\rm h}=ct$ Universe is the correct cosmology versus $\\sim$$20-30\\%$ for the standard model. These results are suggest...

Wei, Jun-Jie; Melia, Fulvio

2015-01-01T23:59:59.000Z

380

Disformal Theories of Gravity: From the Solar System to Cosmology  

E-Print Network [OSTI]

This paper is concerned with theories of gravity that contain a scalar coupled both conformally and disformally to matter through the metric. By systematically deriving the non-relativistic limit, it is shown that no new non-linear screening mechanisms are present beyond the Vainshtein mechanism and chameleon-like screening. If one includes the cosmological expansion of the universe, disformal effects that are usually taken to be absent can be present in the solar system. When the conformal factor is absent, fifth-forces can be screened on all scales when the cosmological field is slowly-rolling. We investigate the cosmology of these models and use local tests of gravity to place new constraints on the disformal coupling and find $\\mathcal{M}>\\mathcal{O}(\\textrm{eV})$, which is not competitive with laboratory tests. Finally, we discuss the future prospects for testing these theories and the implications for other theories of modified gravity. In particular, the Vainshtein radius of solar system objects can be altered from the static prediction when cosmological time-derivatives are non-negligible.

Jeremy Sakstein

2014-10-20T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Cosmological Constraints from the SDSS maxBCG Cluster Catalog  

SciTech Connect (OSTI)

We use the abundance and weak lensing mass measurements of the SDSS maxBCG cluster catalog to simultaneously constrain cosmology and the richness-mass relation of the clusters. Assuming a flat {Lambda}CDM cosmology, we find {sigma}{sub 8}({Omega}{sub m}/0.25){sup 0.41} = 0.832 {+-} 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, the primary two being the absolute mass scale of the weak lensing masses of the maxBCG clusters, and uncertainty in the scatter of the richness-mass relation. Our constraints are fully consistent with the WMAP five-year data, and in a joint analysis we find {sigma}{sub 8} = 0.807 {+-} 0.020 and {Omega}{sub m} = 0.265 {+-} 0.016, an improvement of nearly a factor of two relative to WMAP5 alone. Our results are also in excellent agreement with and comparable in precision to the latest cosmological constraints from X-ray cluster abundances. The remarkable consistency among these results demonstrates that cluster abundance constraints are not only tight but also robust, and highlight the power of optically-selected cluster samples to produce precision constraints on cosmological parameters.

Rozo, Eduardo; /CCAPP; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Rykoff, Eli S.; /UC, Santa Barbara; Annis, James T.; /Fermilab; Becker, Matthew R.; /Chicago U. /KICP, Chicago; Evrard, August E.; /Michigan U. /Michigan U., MCTP; Frieman, Joshua A.; /Fermilab /KICP, Chicago /Chicago U.; Hansen, Sarah M.; /UC, Santa Cruz; Hao, Jia; /Michigan U.; Johnston, David E.; /Northwestern U.; Koester, Benjamin P.; /KICP, Chicago /Chicago U.; McKay, Timothy A.; /Michigan U. /Michigan U., MCTP; Sheldon, Erin S.; /Brookhaven; Weinberg, David H.; /CCAPP /Ohio State U.

2009-08-03T23:59:59.000Z

382

Decaying $?$ cosmologies and statistical properties of gravitational lenses  

E-Print Network [OSTI]

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.

L. F. Bloomfield Torres; I. Waga

1995-05-01T23:59:59.000Z

383

Dark energy and dark matter from cosmological observations  

E-Print Network [OSTI]

The present status of our knowledge about the dark matter and dark energy is reviewed. Bounds on the content of cold and hot dark matter from cosmological observations are discussed in some detail. I also review current bounds on the physical properties of dark energy, mainly its equation of state and effective speed of sound.

Steen Hannestad

2005-09-14T23:59:59.000Z

384

CAPUT DARK ENERGY TOPICS, 2013 1. The Cosmological Constant  

E-Print Network [OSTI]

CAPUT DARK ENERGY TOPICS, 2013 1 #12;1. The Cosmological Constant - The acceleration as curvature term in the Einstein field equation and not a form of dark energy. Provide a critical discussion., Rovelli C., 2010 Is dark energy really a mystery ? Nature, 466, 321 (July 2010) - Padmanabhan T., 2003

Weijgaert, Rien van de

385

Kaluza-Klein Cosmology With Modified Holographic Dark Energy  

E-Print Network [OSTI]

We investigate the compact Kaluza-Klein cosmology in which modified holographic dark energy is interacting with dark matter. Using this scenario, we evaluate equation of state parameter as well as equation of evolution of the modified holographic dark energy. Further, it is shown that the generalized second law of thermodynamics holds without any constraint.

M. Sharif; Farida Khanum

2011-06-13T23:59:59.000Z

386

Dark Energy: The Cosmological Challenge of the T. Padmanabhan  

E-Print Network [OSTI]

Dark Energy: The Cosmological Challenge of the Millennium T. Padmanabhan IUCAA, Pune Observational. It is made of a very exotic species called dark energy which exerts negative pressure. This is more esoteric per cent dark 1 #12;energy. The key direct evidence, however, came in late ninetees from the analysis

Udgaonkar, Jayant B.

387

No Open or Flat Bouncing Cosmologies in Einstein Gravity  

E-Print Network [OSTI]

We show that bouncing open or flat Friedmann-Robertson-Walker cosmologies are inconsistent with worldsheet string theory to first approximation. Specifically, the Virasoro constraint translates to the null energy condition in spacetime at leading order in the alpha-prime expansion. Thus one must go beyond minimally-coupled Einstein gravity in order to find bounce solutions.

Parikh, Maulik K

2015-01-01T23:59:59.000Z

388

Cosmological-Parameter Determination with Microwave Background Maps  

E-Print Network [OSTI]

The angular power spectrum of the cosmic microwave background (CMB) contains information on virtually all cosmological parameters of interest, including the geometry of the Universe ($\\Omega$), the baryon density, the Hubble constant ($h$), the cosmological constant ($\\Lambda$), the number of light neutrinos, the ionization history, and the amplitudes and spectral indices of the primordial scalar and tensor perturbation spectra. We review the imprint of each parameter on the CMB. Assuming only that the primordial perturbations were adiabatic, we use a covariance-matrix approach to estimate the precision with which these parameters can be determined by a CMB temperature map as a function of the fraction of sky mapped, the level of pixel noise, and the angular resolution. For example, with no prior information about any of the cosmological parameters, a full-sky CMB map with $0.5^\\circ$ angular resolution and a noise level of 15 $\\mu$K per pixel can determine $\\Omega$, $h$, and $\\Lambda$ with standard errors of $\\pm0.1$ or better, and provide determinations of other parameters which are inaccessible with traditional observations. Smaller beam sizes or prior information on some of the other parameters from other observations improves the sensitivity. The dependence on the the underlying cosmological model is discussed.

Gerard Jungman; Marc Kamionkowski; Arthur Kosowsky; David N. Spergel

1996-05-23T23:59:59.000Z

389

Measurement of the cosmological constant P. Antilogus a  

E-Print Network [OSTI]

. The usage of SN Ia to probe the vacuum energy and more generally to study the dark energy seems quite, let us expect a break through in the understanding of the dark energy, energy at the source of the observed acceleration of the universe expansion. 2. From the cosmological constant to the dark energy

Paris-Sud XI, Université de

390

The Age-Redshift Relation for Standard Cosmology  

E-Print Network [OSTI]

We present compact, analytic expressions for the age-redshift relation $\\tau(z)$ for standard Friedmann-Lema\\^ \\itre-Robertson-Walker (FLRW) cosmology. The new expressions are given in terms of incomplete Legendre elliptic integrals and evaluate much faster than by direct numerical integration.

R. C. Thomas; R. Kantowski

2000-08-10T23:59:59.000Z

391

The impact of spurious shear on cosmological parameter estimates from weak lensing observables  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

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.

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

392

PROSPECTS FOR GRB SCIENCE WITH THE FERMI LARGE AREA TELESCOPE  

SciTech Connect (OSTI)

The Large Area Telescope (LAT) instrument on the Fermi mission will reveal the rich spectral and temporal gamma-ray burst (GRB) phenomena in the >100 MeV band. The synergy with Fermi's Gamma-ray Burst Monitor detectors will link these observations to those in the well explored 10-1000 keV range; the addition of the >100 MeV band observations will resolve theoretical uncertainties about burst emission in both the prompt and afterglow phases. Trigger algorithms will be applied to the LAT data both onboard the spacecraft and on the ground. The sensitivity of these triggers will differ because of the available computing resources onboard and on the ground. Here we present the LAT's burst detection methodologies and the instrument's GRB capabilities.

Band, D. L. [Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Axelsson, M. [Stockholm Observatory, Albanova, SE-106 91 Stockholm (Sweden); Baldini, L.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Battelino, M. [Department of Physics, Royal Institute of Technology (KTH), AlbaNova, SE-106 91 Stockholm (Sweden); Bissaldi, E. [Max-Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Bogaert, G. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Bonnell, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Chiang, J.; Do Couto e Silva, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94305 (United States); Cohen-Tanugi, J. [Laboratoire de Physique Theorique et Astroparticules, Universite Montpellier 2, CNRS/IN2P3, Montpellier (France); Connaughton, V. [University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Cutini, S. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati (Roma) (Italy); De Palma, F. [Dipt. di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Dingus, B. L. [Los Alamos National Lab., Los Alamos, NM 87545 (United States); Fishman, G. [NASA Marshall Space Flight Center, Huntsville, AL 35805 (United States)], E-mail: nicola.omodei@pi.infn.it (and others)

2009-08-20T23:59:59.000Z

393

The Balloon-borne Large Aperture Sub-millimetre Telescope  

E-Print Network [OSTI]

The Balloon-borne Large-Aperture Sub-millimetre Telescope (BLAST) will operate on a Long Duration Balloon platform with large format bolometer arrays at 250, 350 and 500 microns, initially using a 2m mirror, with plans to increase to 2.5m. BLAST is a collaboration between scientists in the USA, Canada, UK, Italy and Mexico. Funding has been approved and it is now in its building phase. The test flight is scheduled for 2002, with the first long duration flight the following year. The scientific goals are to learn about the nature of distant extragalactic star forming galaxies and cold pre-stellar sources by making deep maps both at high and low galactic latitudes. BLAST will be useful for planning Herschel key projects which use SPIRE.

Douglas Scott; the BLAST Team

2001-04-03T23:59:59.000Z

394

High precision astrometry with a diffractive pupil telescope  

E-Print Network [OSTI]

Astrometric detection and mass determination of Earth-mass exoplanets requires sub-microarcsec accuracy, which is theoretically possible with an imaging space telescope using field stars as an astrometric reference. The measurement must however overcome astrometric distortions which are much larger than the photon noise limit. To address this issue, we propose to generate faint stellar diffraction spikes using a two-dimensional grid of regularly spaced small dark spots added to the surface of the primary mirror (PM). Accurate astrometric motion of the host star is obtained by comparing the position of the spikes to the background field stars. The spikes do not contribute to scattered light in the central part of the field and therefore allow unperturbed coronagraphic observation of the star's immediate surrounding. Because the diffraction spikes are created on the PM and imaged on the same focal plane detector as the background stars, astrometric distortions affect equally the diffraction spikes and the backg...

Guyon, Olivier; Milster, Thomas D; Eisner, Josh A; Angel, Roger; Woolf, Neville J; Ammons, Stephen M; Shao, Michael; Shaklan, Stuart; Levine, Marie; Nemati, Bijan; Pitman, Joe; Woodruff, Robert A; Belikov, Ruslan; 10.1088/0067-0049/200/2/11

2013-01-01T23:59:59.000Z

395

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope  

E-Print Network [OSTI]

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

G. G. Fazio; the IRAC team

2004-05-31T23:59:59.000Z

396

Methods for point source analysis in high energy neutrino telescopes  

E-Print Network [OSTI]

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.

Jim Braun; Jon Dumm; Francesco De Palma; Chad Finley; Albrecht Karle; Teresa Montaruli

2008-01-10T23:59:59.000Z

397

LXCDM: a cosmon model solution to the cosmological coincidence problem?  

E-Print Network [OSTI]

We consider the possibility that the total dark energy (DE) of the Universe is made out of two dynamical components of different nature: a variable cosmological term, Lambda, and a dynamical ``cosmon'', X, possibly interacting with Lambda but not with matter -- which remains conserved. We call this scenario the LXCDM model. One possibility for X would be a scalar field, but it is not the only one. The overall equation of state (EOS) of the LXCDM model can effectively appear as quintessence or phantom energy depending on the mixture of the two components. Both the dynamics of Lambda and of X could be linked to high energy effects near the Planck scale. In the case of Lambda it may be related to the running of this parameter under quantum effects, whereas X might be identified with some fundamental field (say, a dilaton) left over as a low-energy ``relic'' by e.g. string theory. We find that the dynamics of the LXCDM model can trigger a future stopping of the Universe expansion and can keep the ratio rho_D/rho_m (DE density to matter-radiation density) bounded and of order 1. Therefore, the model could explain the so-called ``cosmological coincidence problem''. This is in part related to the possibility that the present value of the cosmological term can be Lambda0 because of the peculiar behavior of X as ``Phantom Matter''. We describe various cosmological scenarios made possible by the composite and dynamical nature of LXCDM, and discuss in detail their impact on the cosmological coincidence problem.

Javier Grande; Joan Sola; Hrvoje Stefancic

2006-08-06T23:59:59.000Z

398

Origin of Matter from Vacuum in Conformal Cosmology  

E-Print Network [OSTI]

We introduce the hypothesis that the matter content of the universe can be a product of the decay of primordial vector bosons. The effect of the intensive cosmological creation of these primordial vector $W, ~Z $ bosons from the vacuum is studied in the framework of General Relativity and the Standard Model where the relative standard of measurement identifying conformal quantities with the measurable ones is accepted. The relative standard leads to the conformal cosmology with the z-history of masses with the constant temperature, instead of the conventional z-history of the temperature with constant masses in inflationary cosmology. In conformal cosmology both the latest supernova data and primordial nucleosynthesis are compatible with a stiff equation of state associated with one of the possible states of the infrared gravitation field. The distribution function of the created bosons in the lowest order of perturbation theory exposes a cosmological singularity as a consequence of the theorem about the absence of the massless limit of massive vector fields in quantum theory. This singularity can be removed by taking into account the collision processes leading to a thermalization of the created particles. The cosmic microwave background (CMB) temperature T=(M_W^2H_0)^{1/3} ~ 2.7 K occurs as an integral of motion for the universe in the stiff state. We show that this temperature can be attained by the CMB radiation being the final product of the decay of primordial bosons. The effect of anomalous nonconservation of baryon number due to the polarization of the Dirac sea vacuum by these primordial bosons is considered.

D. Blaschke; V. Pervushin; D. Proskurin; S. Vinitsky; A. Gusev

2002-06-30T23:59:59.000Z

399

HIGH-PRECISION ASTROMETRY WITH A DIFFRACTIVE PUPIL TELESCOPE  

SciTech Connect (OSTI)

Astrometric detection and mass determination of Earth-mass exoplanets require sub-{mu}as accuracy, which is theoretically possible with an imaging space telescope using field stars as an astrometric reference. The measurement must, however, overcome astrometric distortions, which are much larger than the photon noise limit. To address this issue, we propose to generate faint stellar diffraction spikes using a two-dimensional grid of regularly spaced small dark spots added to the surface of the primary mirror (PM). Accurate astrometric motion of the host star is obtained by comparing the position of the spikes to the background field stars. The spikes do not contribute to scattered light in the central part of the field and therefore allow unperturbed coronagraphic observation of the star's immediate surroundings. Because the diffraction spikes are created on the PM and imaged on the same focal plane detector as the background stars, astrometric distortions affect equally the diffraction spikes and the background stars and are therefore calibrated. We describe the technique, detail how the data collected by the wide-field camera are used to derive astrometric motion, and identify the main sources of astrometric error using numerical simulations and analytical derivations. We find that the 1.4 m diameter telescope, 0.3 deg{sup 2} field we adopt as a baseline design achieves 0.2 {mu}as single measurement astrometric accuracy. The diffractive pupil concept thus enables sub-{mu}as astrometry without relying on the accurate pointing, external metrology, or high-stability hardware required with previously proposed high-precision astrometry concepts.

Guyon, Olivier; Eisner, Josh A.; Angel, Roger; Woolf, Neville J. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Bendek, Eduardo A.; Milster, Thomas D. [College of Optical Sciences, University of Arizona, Tucson, AZ 85721 (United States); Mark Ammons, S. [Lawrence Livermore National Laboratory, Physics Division L-210, 7000 East Ave., Livermore, CA 94550 (United States); Shao, Michael; Shaklan, Stuart; Levine, Marie; Nemati, Bijan [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Pitman, Joe [Exploration Sciences, P.O. Box 24, Pine, CO 80470 (United States); Woodruff, Robert A. [2081 Evergreen Avenue, Boulder, CO 80304 (United States); Belikov, Ruslan, E-mail: guyon@naoj.org [NASA Ames Research Center, Moffett Field, CA 94035 (United States)

2012-06-01T23:59:59.000Z

400

Design study of 8 meter monolithic mirror UV/optical space telescope H. Philip Stahl  

E-Print Network [OSTI]

Design study of 8 meter monolithic mirror UV/optical space telescope H. Philip Stahl NASA Marshall Space Flight Center, Huntsville, AL 35812 ABSTRACT The planned Ares V launch vehicle with its 10 meter to 8 meter class monolithic primary mirror telescope to Sun-Earth L2 using an Ares V. Specific

Sirianni, Marco

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Point-spread function stability of the SNAP telescope M.J. Sholl1  

E-Print Network [OSTI]

the SNAP telescope and detector images, and identified the effects of secondary mirror misalignment, the effects of seasonal variations in solar flux, transients introduced when pointing the body-fixed Ka, with predicted daily changes well within WL limts. Keywords: three-mirror telescopes, space astronomy, dark

California at Berkeley, University of

402

THE PREFLIGHT PHOTOMETRIC CALIBRATION OF THE EXTREME-ULTRAVIOLET IMAGING TELESCOPE EIT  

E-Print Network [OSTI]

Abstract. This paper presents the preflight photometric calibration of the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). The EIT consists of a Ritchey–Chrétien telescope with multilayer coatings applied to four quadrants of the primary and secondary mirrors, several filters and a backside-thinned CCD detector. The quadrants of the EIT

K. P. Dere; J. D. Moses; J. -p. Delaboudinière; J. Brunaud; C. Carabetian; J. -f. Hochedez; X. Y. Song; R. C. Catura; F. Clette

1999-01-01T23:59:59.000Z

403

Active Optics Performance Study of the Primary Mirror of the Gemini Telescopes Project  

E-Print Network [OSTI]

Active Optics Performance Study of the Primary Mirror of the Gemini Telescopes Project Myung K. Cho Optical Sciences Center in the University of Arizona Tucson, AZ 85721 and Gemini Telescopes Project P. O. Box 26732 Tucson, AZ 85726­6732 Gemini Preprint #9 #12; Active optics performance study of the primary

404

The Universe Viewed in Gamma-Rays 1 High-Resolution Cherenkov Telescopes for the Observation  

E-Print Network [OSTI]

The Universe Viewed in Gamma-Rays 1 High-Resolution Cherenkov Telescopes for the Observation of High-Energy Gamma Rays F.Kajino, T.Wasio, I.Tada, T.Oda, E.Choi, S.Hayashi, M.Sakata, Y optics and camera used for recent Cherenkov telescopes is usually limited to be only about 0.1 degree

Enomoto, Ryoji

405

March 18, 2010 James Webb Space Telescope Studies of Dark Energy  

E-Print Network [OSTI]

March 18, 2010 James Webb Space Telescope Studies of Dark Energy Jonathan P. Gardner (NASA. Introduction The Hubble Space Telescope (HST) has contributed significantly to studies of dark energy) was due to dark energy rather than observational or astrophysical effects such as systematic errors

Sirianni, Marco

406

Cornelis Zwaan, open principle, and the future of high-resolution solar telescopes  

E-Print Network [OSTI]

Cornelis Zwaan, open principle, and the future of high-resolution solar telescopes Robert H erected up till 30 m height with sensors at several heights for the measurement of temperature; (iii) the design consequences for the new generation of high-resolution solar telescopes. Keywords

Rutten, Rob

407

In-orbit performance of the XMM-Newton X-ray telescopes: images and spectra  

E-Print Network [OSTI]

The performance of the three X-ray telescopes on-board of XMM-Newton is evaluated addressing imaging characteristics and effective collecting area. The agreement with ground calibration data is excellent. The analysis of images and spectra of cosmic X-ray sources, emphazising supernova and supernova remnants, prooves that the telescopes are even better than originally required.

B. Aschenbach

2001-09-21T23:59:59.000Z

408

The Universe Viewed in Gamma-Rays 1 The Control System of the MAGIC telescope  

E-Print Network [OSTI]

will be commissioned during this year. The control system of the telescope is distributed over a number of functional on the Central Control and Camera Control systems. 1. Introduction MAGIC[1] is a new generation Imaging Air Cherenkov Telescope (IACT) allocated at the IAC site in the Canary island of La Palma. The aim of the tele

Enomoto, Ryoji

409

Development of a correlation tracker system for the New Solar Telescope  

E-Print Network [OSTI]

Development of a correlation tracker system for the New Solar Telescope Seonghwan Choi on the NST. Keywords: correlation tracker, solar telescope, parallel programming 1. INTRODUCTION The New, Newark, New Jersey 07102, USA d Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA

410

Electronic Noise Calibrator for the Small Radio Telescope RODOLFO MONTEZ JR.  

E-Print Network [OSTI]

Electronic Noise Calibrator for the Small Radio Telescope RODOLFO MONTEZ JR. University of Texas at Austin, Department of Astronomy, Austin, TX 78712; rudy@astro.as.utexas.edu ABSTRACT An electronic noise calibrator for MIT Haystack Observatory's Small Radio Telescope (SRT) is described. The electronic noise

Seager, Sara

411

Hubble Space Telescope FOS Optical and Ultraviolet Spectroscopy of the Bow Shock HH 47A 1  

E-Print Network [OSTI]

Hubble Space Telescope FOS Optical and Ultraviolet Spectroscopy of the Bow Shock HH 47A 1 Patrick Telescope of the HH 47A bow shock and Mach disk that cover the entire spectral range between 2220 Å¡ that the Fe II line broadening must exceed that expected from thermal motions. Excitation of ultraviolet Fe II

Hartigan, Patrick

412

The MAGIC Telescope Project for Gamma Astronomy above 10 GeV  

E-Print Network [OSTI]

A project to construct a 17 m diameter imaging air Cherenkov telescope, called the MAGIC Telescope, is described. The aim of the project is to close the observation gap in the gamma-ray sky extending from 10 GeV as the highest energy measurable by space-borne experiments to 300 GeV, the lowest energy measurable by the current generation of ground-based Cherenkov telescopes. The MAGIC Telescope will incorporate several new features in order to reach the very low energy threshold. At the same time the new technology will yield an improvement in sensitivity in the energy region where current Cherenkov telescopes are measuring by about an order of magnitude.

N. Magnussen

1998-05-14T23:59:59.000Z

413

First cosmological constraints on the Superfluid Chaplygin gas model  

E-Print Network [OSTI]

In this work we set observational constraints of the Superfluid Chaplygin gas model, which gives a unified description of the dark sector of the Universe as a Bose-Einstein condensate (BEC) that behaves as dark energy (DE) while it is in the ground state and as dark matter (DM) when it is in the excited state. We first show and perform the various steps leading to a form of the equations suitable for the observational tests to be carried out. Then, by using a Markov Chain Monte Carlo (MCMC) code, we constrain the model with a sample of cosmology-independent long gamma-ray bursts (LGRBs) calibrated using their Type I Fundamental Plane, as well as the Union2.1 set and observational Hubble parameter data. In this analysis, using our cosmological constraints, we sketch the effective equation of state parameter and deceleration parameter, and we also obtain the redshift of the transition from deceleration to acceleration: $z_t$.

Lazkoz, Ruth; Salzano, Vincenzo

2012-01-01T23:59:59.000Z

414

First cosmological constraints on the Superfluid Chaplygin gas model  

E-Print Network [OSTI]

In this work we set observational constraints of the Superfluid Chaplygin gas model, which gives a unified description of the dark sector of the Universe as a Bose-Einstein condensate (BEC) that behaves as dark energy (DE) while it is in the ground state and as dark matter (DM) when it is in the excited state. We first show and perform the various steps leading to a form of the equations suitable for the observational tests to be carried out. Then, by using a Markov Chain Monte Carlo (MCMC) code, we constrain the model with a sample of cosmology-independent long gamma-ray bursts (LGRBs) calibrated using their Type I Fundamental Plane, as well as the Union2.1 set and observational Hubble parameter data. In this analysis, using our cosmological constraints, we sketch the effective equation of state parameter and deceleration parameter, and we also obtain the redshift of the transition from deceleration to acceleration: $z_t$.

Ruth Lazkoz; Ariadna Montiel; Vincenzo Salzano

2012-11-15T23:59:59.000Z

415

Nuclear and particle physics, astrophysics and cosmology (NPAC) capability review  

SciTech Connect (OSTI)

The present document represents a summary self-assessment of the status of the Nuclear and Particle Physics, Astrophysics and Cosmology (NPAC) capability across Los Alamos National Laboratory (LANL). For the purpose of this review, we have divided the capability into four theme areas: Nuclear Physics, Particle Physics, Astrophysics and Cosmology, and Applied Physics. For each theme area we have given a general but brief description of the activities under the area, a list of the Laboratory divisions involved in the work, connections to the goals and mission of the Laboratory, a brief description of progress over the last three years, our opinion of the overall status of the theme area, and challenges and issues.

Redondo, Antonio [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

416

Cosmological viability conditions for f(T) dark energy models  

SciTech Connect (OSTI)

Recently f(T) modified teleparallel gravity where T is the torsion scalar has been proposed as the natural gravitational alternative for dark energy. We perform a detailed dynamical analysis of these models and find conditions for the cosmological viability of f(T) dark energy models as geometrical constraints on the derivatives of these models. We show that in the phase space exists two cosmologically viable trajectory which (i) The universe would start from an unstable radiation point, then pass a saddle standard matter point which is followed by accelerated expansion de sitter point. (ii) The universe starts from a saddle radiation epoch, then falls onto the stable matter era and the system can not evolve to the dark energy dominated epoch. Finally, for a number of f(T) dark energy models were proposed in the more literature, the viability conditions are investigated.

Setare, M.R.; Mohammadipour, N., E-mail: rezakord@ipm.ir, E-mail: N.Mohammadipour@uok.ac.ir [Department of Science, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

2012-11-01T23:59:59.000Z

417

Cosmology from HI galaxy surveys with the SKA  

E-Print Network [OSTI]

The Square Kilometer Array (SKA) has the potential to produce galaxy redshift surveys which will be competitive with other state of the art cosmological experiments in the next decade. In this chapter we summarise what capabilities the first and the second phases of the SKA will be able to achieve in its current state of design. We summarise the different cosmological experiments which are outlined in further detail in other chapters of this Science Book. The SKA will be able to produce competitive Baryonic Oscillation (BAOs) measurements in both its phases. The first phase of the SKA will provide similar measurements as optical and IR experiments with completely different systematic effects whereas the second phase being transformational in terms of its statistical power. The SKA will produce very accurate Redshift Space Distortions (RSD) measurements, being superior to other experiments at lower redshifts, due to the large number of galaxies. Cross correlations of the galaxy redshift data from the SKA with ...

Abdalla, Filipe B; Camera, Stefano; Benoit-Lévy, Aurélien; Joachimi, Benjamin; Kirk, Donnacha; Klöckner, Hans-Rainer; Maartens, Roy; Raccanelli, Alvise; Santos, Mario G; Zhao, Gong-Bo

2015-01-01T23:59:59.000Z

418

Transition redshift in $f(T)$ cosmology and observational constraints  

E-Print Network [OSTI]

We extract constraints on the transition redshift $z_{tr}$, determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of $f(T)$ gravity. In particular, employing cosmography we obtain bounds on the viable $f(T)$ forms and their derivatives. Since this procedure is model independent, as long as the scalar curvature is fixed, we are able to determine intervals for $z_{tr}$. In this way we guarantee that the Solar-System constraints are preserved and moreover we extract bounds on the transition time and the free parameters of the scenario. We find that the transition redshifts predicted by $f(T)$ cosmology, although compatible with the standard $\\Lambda$CDM predictions, are slightly smaller. Finally, in order to obtain observational constraints on $f(T)$ cosmology, we perform a Monte Carlo fitting using supernova data, involving the most recent union 2.1 data set.

Capozziello, Salvatore; Saridakis, Emmanuel N

2015-01-01T23:59:59.000Z

419

Dark radiation from particle decay: cosmological constraints and opportunities  

SciTech Connect (OSTI)

We study particle decay as the origin of dark radiation. After elaborating general properties and useful parametrisations we provide model-independent and easy-to-use constraints from nucleosynthesis, the cosmic microwave background and structure formation. Bounds on branching ratios and mass hierarchies depend in a unique way on the time of decay. We demonstrate their power to exclude well-motivated scenarios taking the example of the lightest ordinary sparticle decaying into the gravitino. We point out signatures and opportunities in cosmological observations and structure formation. For example, if there are two dark decay modes, dark radiation and the observed dark matter with adjustable free-streaming can originate from the same decaying particle, solving small-scale problems of structure formation. Hot dark matter mimicking a neutrino mass scale as deduced from cosmological observations can arise and possibly be distinguished after a discovery. Our results can be used as a guideline for model building.

Hasenkamp, Jasper; Kersten, Jörn, E-mail: Jasper.Hasenkamp@desy.de, E-mail: Joern.Kersten@desy.de [II. Institute for Theoretical Physics, University of Hamburg, 22761 Hamburg (Germany)

2013-08-01T23:59:59.000Z

420

Dark radiation from particle decay: cosmological constraints and opportunities  

E-Print Network [OSTI]

We study particle decay as the origin of dark radiation. After elaborating general properties and useful parametrisations we provide model-independent and easy-to-use constraints from nucleosynthesis, the cosmic microwave background and structure formation. Bounds on branching ratios and mass hierarchies depend in a unique way on the time of decay. We demonstrate their power to exclude well-motivated scenarios taking the example of the lightest ordinary sparticle decaying into the gravitino. We point out signatures and opportunities in cosmological observations and structure formation. For example, if there are two dark decay modes, dark radiation and the observed dark matter with adjustable free-streaming can originate from the same decaying particle, solving small-scale problems of structure formation. Hot dark matter mimicking a neutrino mass scale as deduced from cosmological observations can arise and possibly be distinguished after a discovery. Our results can be used as a guideline for model building.

Jasper Hasenkamp; Jörn Kersten

2014-02-13T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

D-branes in Standard Model building, Gravity and Cosmology  

E-Print Network [OSTI]

D-branes are by now an integral part of our toolbox towards understanding nature. In this review we will describe recent progress in their use to realize fundamental interactions. The realization of the Standard Model and relevant physics and problems will be detailed. New ideas on realizing 4-dimensional gravity use the brane idea in an important way. Such approaches will be reviewed and compared to the standard paradigm of compactification. Branes can play a pivotal role both in early- and late-universe cosmology mainly via the brane-universe paradigm. Brane realizations of various cosmological ideas (early inflation, sources for dark matter and dark energy, massive gravity etc) will be also reviewed.

Elias Kiritsis

2004-05-14T23:59:59.000Z

422

Consistent metric combinations in cosmology of massive bigravity  

E-Print Network [OSTI]

Massive bigravity models are interesting alternatives to standard cosmology. In most cases however these models have been studied for a simplified scenario in which both metrics take homogeneous and isotropic forms (Friedmann-Lema\\^{i}tre-Robertson-Walker; FLRW) with the same spatial curvatures. The interest to consider more general geometries arises in particular in view of the difficulty so far encountered in building stable cosmological solutions with homogeneous and isotropic metrics. Here we consider a number of cases in which the two metrics take more general forms, namely FLRW with different spatial curvatures, Lema\\^{i}tre, Lema\\^{i}tre-Tolman-Bondi (LTB), and Bianchi I, as well as cases where only one metric is linearly perturbed. We discuss possible consistent combinations and find that only some special cases of FLRW-Lema\\^{i}tre, LTB-LTB and FLRW-Bianchi I combinations give consistent, non-trivial solutions.

Henrik Nersisyan; Yashar Akrami; Luca Amendola

2015-02-13T23:59:59.000Z

423

Quintessence and (anti-)Chaplygin gas in loop quantum cosmology  

SciTech Connect (OSTI)

The concordance model of cosmology contains several unknown components such as dark matter and dark energy. Many proposals have been made to describe them by choosing an appropriate potential for a scalar field. We study four models in the realm of loop quantum cosmology: the Chaplygin gas, an inflationary and radiationlike potential, quintessence and an anti-Chaplygin gas. For the latter we show that all trajectories start and end with a type II singularity and, depending on the initial value, may go through a bounce. On the other hand the evolution under the influence of the first three scalar fields behaves classically at times far away from the big bang singularity and bounces as the energy density approaches the critical density.

Lamon, Raphael; Woehr, Andreas J. [Institut fuer Theoretische Physik, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany)

2010-01-15T23:59:59.000Z

424

Colliding Impulsive Gravitational Waves and a Cosmological Constant  

E-Print Network [OSTI]

We present a space--time model of the collision of two homogeneous, plane impulsive gravitational waves (each having a delta function profile) propagating in a vacuum before collision and for which the post collision space--time has constant curvature. The profiles of the incoming waves are $k\\,\\delta(u)$ and $l\\,\\delta(v)$ where $k, l$ are real constants and $u=0, v=0$ are intersecting null hypersurfaces. The cosmological constant $\\Lambda$ in the post collision region of the space--time is given by $\\Lambda=-6\\,k\\,l$. In this sense this model collision provides a mechanism for generating a cosmological constant and therefore may be relevant to the theoretical description of dark energy.

Barrabès, C

2015-01-01T23:59:59.000Z

425

Dark Energy Coupled with Dark Matter in Viscous Fluid Cosmology  

E-Print Network [OSTI]

We investigate cosmological models with two interacting fluids: dark energy and dark matter in flat Friedmann-Robertson-Walker universe. The interaction between dark energy and dark matter is described in terms of the parameters present in the inhomogeneous equation of state when allowance is made for bulk viscosity, for the Little Rip, the Pseudo Rip, and the bounce universes. We obtain analytic representation for characteristic properties in these cosmological models, in particular the bulk viscosity $\\zeta=\\zeta(H,t)$ as function of Hubble parameter and time. We discuss the corrections of thermodynamical parameters in the equations of state due coupling between the viscous fluid and dark matter. Some common properties of these corrections are elucidated.

I. Brevik; V. V. Obukhov; A. V. Timoshkin

2014-10-10T23:59:59.000Z

426

Interacting Dark Energy in Ho?ava-Lifshitz Cosmology  

E-Print Network [OSTI]

In the usual Ho\\v{r}ava-Lifshitz cosmological models, the scalar field is responsible for dark matter. Using an additional scalar field, Saridakis \\cite{sari} has formulated Ho\\v{r}ava-Lifshitz cosmology with an effective dark energy sector. In the paper \\cite{sari} the scalar fields do not interact with each other, here we extend this work to the interacting case, where matter scalar field $\\phi$ interact with dark energy scalar field $\\sigma$. We will show that in contrast with \\cite{sari}, where $\\sigma$-filed is absent, we can obtain $w_d ^{\\rm eff}dark energy presenting phantom behaviour. This behaviour is pure effect of the interaction.

M R Setare

2009-12-02T23:59:59.000Z

427

On a super-selection rule in quantum cosmology  

E-Print Network [OSTI]

The discarding of negative frequency solutions in a quantum field theory brings about the absence of antiparticles which, after all, means the violation of 4-inversion symmetry $(x \\rightarrow -x, t \\rightarrow-t)$ which is a (improper) Lorentz transformation. Suppose you have a theory of quantum gravity which lacks the negative frequency solutions (like usually people have in quantum cosmology, invoking a super-selection rule). Taking some limit in this theory in order to obtain the weak (or null) gravitational regime, the result is a theory that does not respect that symmetry and does not have place for antiparticles. That is, a theory of fields is not obtained, as it should be. For the case of a quantum cosmology model we show that if we ignore the negative frequency solutions, the rich processes of creation/annihilation of universes at the Planck scale, are lost.

E. Sergio Santini

2014-12-26T23:59:59.000Z

428

Cosmology on the Largest Scales with the SKA  

E-Print Network [OSTI]

The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, amongst next-generation cosmological experiments, for scrutinising the Universe's properties on the largest cosmic scales. Probing cosmic structures on extremely large scales will have many advantages. For instance, the growth of perturbations is well understood for those modes, since it falls fully within the linear regime. Also, such scales are unaffected by the poorly understood feedback of baryonic physics. On ultra-large cosmic scales, two key effects become significant: primordial non-Gaussianity and relativistic corrections to cosmological observables. Moreover, if late-time acceleration is driven not by dark energy but by modifications to general relativity, then such modifications should become apparent near and above the horizon scale. As a result, the SKA is forecast to deliver transf...

Camera, S; Bull, P; Bertacca, D; Chen, X; Ferreira, P G; Kunz, M; Maartens, R; Mao, Y; Santos, M G; Shapiro, P R; Viel, M; Xu, Y

2015-01-01T23:59:59.000Z

429

Cosmological viability conditions for $f(T)$ dark energy models  

E-Print Network [OSTI]

Recently $f(T)$ modified teleparallel gravity where T is the torsion scalar has been proposed as the natural gravitational alternative for dark energy. We perform a detailed dynamical analysis of these models and find conditions for the cosmological viability of $f(T)$ dark energy models as geometrical constraints on the derivatives of these models. We show that in the phase space exists two cosmologically viable trajectory which (i) The universe would start from an unstable radiation point, then pass a saddle standard matter point which is followed by accelerated expansion de sitter point. (ii) The universe starts from a saddle radiation epoch, then falls onto the stable matter era and the system can not evolve to the dark energy dominated epoch. Finally, for a number of $f(T)$ dark energy models were proposed in the more literature, the viability conditions are investigated.

M. R. Setare; N. Mohammadipour

2012-11-06T23:59:59.000Z

430

Reconstructing Dark Energy : A Comparison of Cosmological Parameters  

E-Print Network [OSTI]

A large number of cosmological parameters have been suggested for obtaining information on the nature of dark energy. In this work, we study the efficacy of these different parameters in discriminating theoretical models of dark energy, using both currently available supernova (SNe) data, and simulations of future observations. We find that the current data does not put strong constraints on the nature of dark energy, irrespective of the cosmological parameter used. For future data, we find that the although deceleration parameter can accurately reconstruct some dark energy models, it is unable to discriminate between different models of dark energy, therefore limiting its usefulness. Physical parameters such as the equation of state of dark energy, or the dark energy density do a good job of both reconstruction and discrimination if the matter density is known to high accuracy. However, uncertainty in matter density reduces the efficacy of these parameters. A recently proposed parameter, Om(z), constructed f...

Pan, Alexander V

2010-01-01T23:59:59.000Z

431

Revisiting Noether gauge symmetry approach in quintom cosmology  

E-Print Network [OSTI]

The Noether gauge symmetry approach is revisited to study various quintom scenarios (those that arise by the presence of two dynamical scalar fields) to comprehend the role of dark energy in our universe. For such models, we obtain smooth parameterizations of the equation of state of dark energy across the boundary of cosmological constant $w_{\\Lambda}=-1$. This study gives rise to two new cases of the potential $V(\\phi, \\sigma)$, due to a quintom field in which nonlinear coupling of the scalar fields arise. Besides we report that a few cases of Noether gauge symmetries and their invariants in [Adnan Aslam, et. al., Astrophys Space Sci (2013), 348:533-540] are incorrect. Consequently, the given cosmological model in their paper is not a feasible quintom model.

Ali, Sajid

2015-01-01T23:59:59.000Z

432

Cosmic expansion and structure formation in running vacuum cosmologies  

E-Print Network [OSTI]

We investigate the dynamics of the FLRW flat cosmological models in which the vacuum energy varies with redshift. A particularly well motivated model of this type is the so-called quantum field vacuum, in which both kind of terms $H^{2}$ and constant appear in the effective dark energy density affecting the evolution of the main cosmological functions at the background and perturbation levels. Specifically, it turns out that the functional form of the quantum vacuum endows the vacuum energy of a mild dynamical evolution which could be observed nowadays and appears as dynamical dark energy. Interestingly, the low-energy behaviour is very close to the usual $\\Lambda$CDM model, but it is by no means identical. Finally, within the framework of the quantum field vacuum we generalize the large scale structure properties, namely growth of matter perturbations, cluster number counts and spherical collapse model.

Basilakos, Spyros

2015-01-01T23:59:59.000Z

433

Cosmological and astrophysical constraints on superconducting cosmic strings  

SciTech Connect (OSTI)

We investigate the cosmological and astrophysical constraints on superconducting cosmic strings (SCSs). SCS loops emit strong bursts of electromagnetic waves, which might affect various cosmological and astrophysical observations. We take into account the effect on the CMB anisotropy, CMB blackbody spectrum, BBN, observational implications on radio wave burst and X-ray or ?-ray events, and stochastic gravitational wave background measured by pulsar timing experiments. We then derive constraints on the parameters of SCS from current observations and estimate prospects for detecting SCS signatures in on-going observations. As a result, we find that these constraints exclude broad parameter regions, and also that on-going radio wave observations can probe large parameter space.

Miyamoto, Koichi [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan); Nakayama, Kazunori, E-mail: miyamone@icrr.u-tokyo.ac.jp, E-mail: kazunori@hep-th.phys.s.u-tokyo.ac.jp [Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-07-01T23:59:59.000Z

434

Asymptotically Flat Wormhole Solutions in a Generic Cosmological Constant Background  

E-Print Network [OSTI]

There are a number of reasons to study wormholes with generic cosmological constant $\\Lambda$. Recent observations indicate that present accelerating expansion of the universe demands $\\Lambda>0$. On the other hand, some extended theories of gravitation such as supergravity and superstring theories posses vacuum states with $\\Lambdaenergy density and pressure profiles which support such a geometry are obtained. It is shown that for having such a geometry, the wormhole throat $r_0$, the cosmological constant $\\Lambda$ and the equation of state parameter $\\omega$ should satisfy two specific conditions. The possibility of setting different values for the parameters of the model helps us to find exact solutions for the metric functions, mass functions and energy-momentum profiles. At last, the volume integral quantifier, which provides useful information about the total amount of energy condition violating matter is discussed briefly.

Y. Heydarzade; N. Riazi; H. Moradpour

2015-01-09T23:59:59.000Z

435

Exponential cosmological redshift in a linearly expanding universe  

E-Print Network [OSTI]

Analytical solution of the Maxwell equations in a flat expanding Friedmann-Robertson-Walker space-time is presented. The solution is valid for arbitrary sources and for expansion rates described by positive functions of time. The near-, intermediate-, and far-field terms are explicitly identified. It is shown that the cosmological redshift introduced by a linearly expanding space-time is an exponential function of the distance factor.

Budko, Neil V

2009-01-01T23:59:59.000Z

436

The Dynamics of Brane-World Cosmological Models  

E-Print Network [OSTI]

Brane-world cosmology is motivated by recent developments in string/M-theory and offers a new perspective on the hierarchy problem. In the brane-world scenario, our Universe is a four-dimensional subspace or {\\em brane} embedded in a higher-dimensional {\\em bulk} spacetime. Ordinary matter fields are confined to the brane while the gravitational field can also propagate in the bulk, leading to modifications of Einstein's theory of general relativity at high energies. In particular, the Randall-Sundrum-type models are self-consistent and simple and allow for an investigation of the essential non-linear gravitational dynamics. The governing field equations induced on the brane differ from the general relativistic equations in that there are nonlocal effects from the free gravitational field in the bulk, transmitted via the projection of the bulk Weyl tensor, and the local quadratic energy-momentum corrections, which are significant in the high-energy regime close to the initial singularity. In this review we discuss the asymptotic dynamical evolution of spatially homogeneous brane-world cosmological models containing both a perfect fluid and a scalar field close to the initial singularity. Using dynamical systems techniques it is found that, for models with a physically relevant equation of state, an isotropic singularity is a past-attractor in all orthogonal spatially homogeneous models (including Bianchi type IX models). In addition, we describe the dynamics in a class of inhomogeneous brane-world models, and show that these models also have an isotropic initial singularity. These results provide support for the conjecture that typically the initial cosmological singularity is isotropic in brane-world cosmology.

A. A. Coley

2005-04-09T23:59:59.000Z

437

Graceful exit via polymerization of pre-big bang cosmology  

E-Print Network [OSTI]

We consider a phenomenological modification of the Pre Big Bang scenario using ideas from the resolution of curvature singularities in Loop Quantum Cosmology. We show that non-perturbative Loop modifications to the dynamics, arising from the underlying polymer representation, can resolve the graceful exit problem. The curvature and the dilaton energy stay finite at all times, in both the string and Einstein frames. In the string frame, the dilaton tends to a constant value at late times after the bounce.

Giuseppe De Risi; Roy Maartens; Parampreet Singh

2007-09-25T23:59:59.000Z

438

A Comparison of Cosmological Models Using Strong Gravitational Lensing Galaxies  

E-Print Network [OSTI]

Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems, and carry out a one-on-one comparison between the standard model, LCDM, and the R_h=ct Universe. We find that both models account for the lens observations quite well, though the precision of these measurements does not appear to be good enough to favor one model over the other. Part of the reason is the so-called bulge-halo conspiracy that, on average, results in a baryonic velocity dispersion within a fraction of the optical effective radius virtually identical to that expected for the whole luminous-dark matter distribution. Given the limitations of doing precision cosmological testing using the current sample, we also carry out Monte Carlo simulations based on the current lens measurements to estimate how large the source catalog would have to be in order to rule out either model at a ~99.7% confidence level. We find that if the real cosmology is LCDM, a sample of ~200 strong gravitational lenses would be sufficient to rule out R_h=ct at this level of accuracy, while ~300 strong gravitational lenses would be required to rule out LCDM if the real Universe were instead R_h=ct. The difference in required sample size reflects the greater number of free parameters available to fit the data with LCDM. We point out that, should the R_h=ct Universe eventually emerge as the correct cosmology, its lack of any free parameters for this kind of work will provide a remarkably powerful probe of the mass structure in lensing galaxies, and a means of better understanding the origin of the bulge-halo conspiracy.

Fulvio Melia; Jun-Jie Wei; Xue-Feng Wu

2014-10-03T23:59:59.000Z

439

Neutron beta-decay, Standard Model and cosmology  

E-Print Network [OSTI]

The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. The neutron lifetime recently obtained, 878.5 +/- 0.7stat +/- 0.3sys s, is the most accurate one to date. The new result for the neutron lifetime differs from the world average value by 6.5 standard deviations. The impact of the new result on testing of Standard Model and on data analysis for the primordial nucleosynthesis model is scrutinized.

A. P. Serebrov

2006-11-22T23:59:59.000Z

440

Cosmology using the Parkes Multibeam Southern-Sky HI Survey  

E-Print Network [OSTI]

I discuss the implications of the Parkes HI Multibeam Southern Sky Survey for cosmology. It will determine the local mass function of HI clouds, detecting several hundred per decade of mass. Each of these will come with a redshift and, for the more massive clouds, an estimate of the velocity width. This will provide an ideal database for peculiar motion studies and for measurements of biasing of galaxies relative to the underlying matter distribution.

P. A. Thomas

1996-07-02T23:59:59.000Z

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

HI Cosmology in the Local Universe with ALFALFA  

E-Print Network [OSTI]

The Arecibo Legacy Fast ALFA (ALFALFA) survey is an on-going second generation blind extragalactic HI survey exploiting Arecibo's superior sensitivity, angular resolution and digital technology to conduct a census of the local HI universe over a cosmologically significant volume. As of mid-2007, ~4500 good quality extragalactic HI line sources have been extracted in ~15% of the final survey area. ALFALFA is detecting HI masses as low as 10**6 Msun and as high as 10**10.8 Msun with positional accuracies typically better than 20 arcsec, allowing immediate identification of the most probable optical counterparts. Only 3% of all extragalactic HI sources and fewer than 1% of detections with M(HI) > 10**9.5 Msun cannot be identified with a stellar component. First ALFALFA results already suggest, in agreement with previous studies, that there does not appear to be a cosmologically significant population of optically dark but HI rich galaxies. ALFALFA promises a wealthy dataset for the exploration of many issues in near-field cosmology and galaxy evolution studies, setting the stage for their extension to higher redshifts with the Square Kilometer Array (SKA).

Martha P. Haynes

2007-08-19T23:59:59.000Z

442

Fluid Mechanics Explains Cosmology, Dark Matter, Dark Energy, and Life  

E-Print Network [OSTI]

Observations of the interstellar medium by the Herschel, Planck etc. infrared satellites throw doubt on standard {\\Lambda}CDMHC cosmological processes to form gravitational structures. According to the Hydro-Gravitational-Dynamics (HGD) cosmology of Gibson (1996), and the quasar microlensing observations of Schild (1996), the dark matter of galaxies consists of Proto-Globular-star-Cluster (PGC) clumps of Earth-mass primordial gas planets in metastable equilibrium since PGCs began star production at 0.3 Myr by planet mergers. Dark energy and the accelerating expansion of the universe inferred from SuperNovae Ia are systematic dimming errors produced as frozen gas dark matter planets evaporate to form stars. Collisionless cold dark matter that clumps and hierarchically clusters does not exist. Clumps of PGCs began diffusion from the Milky Way Proto-Galaxy upon freezing at 14 Myr to give the Magellanic Clouds and the faint dwarf galaxies of the 10^22 m diameter baryonic dark matter Galaxy halo. The first stars persist as old globular star clusters (OGCs). Water oceans and the biological big bang occurred at 2-8 Myr. Life inevitably formed and evolved in the cosmological primordial organic soup provided by 10^80 big bang planets and their hot oceans as they gently merged to form larger binary planets and small binary stars.

Carl H. Gibson

2012-11-02T23:59:59.000Z

443

The Hubble constant and dark energy from cosmological distance measures  

E-Print Network [OSTI]

We study how the determination of the Hubble constant from cosmological distance measures is affected by models of dark energy and vice versa. For this purpose, constraints on the Hubble constant and dark energy are investigated using the cosmological observations of cosmic microwave background, baryon acoustic oscillations and type Ia suprenovae. When one investigates dark energy, the Hubble constant is often a nuisance parameter, thus it is usually marginalized over. On the other hand, when one focuses on the Hubble constant, simple dark energy models such as a cosmological constant and a constant equation of state are usually assumed. Since we do not know the nature of dark energy yet, it is interesting to investigate the Hubble constant assuming some types of dark energy and see to what extent the constraint on the Hubble constant is affected by the assumption concerning dark energy. We show that the constraint on the Hubble constant is not affected much by the assumption for dark energy. We furthermore show that this holds true even if we remove the assumption that the universe is flat. We also discuss how the prior on the Hubble constant affects the constraints on dark energy and/or the curvature of the universe.

Kazuhide Ichikawa; Tomo Takahashi

2008-05-03T23:59:59.000Z

444

On the possible running of the cosmological "constant"  

E-Print Network [OSTI]

Despite the many outstanding cosmological observations leading to a strong evidence for a nonvanishing cosmological constant (CC) term in the gravitational field equations, the theoretical status of this quantity seems to be lagging well behind the observational successes. It thus seems timely to revisit some fundamental aspects of the CC term in Quantum Field Theory (QFT). We emphasize that, in curved space-time, nothing a priori prevents this term from potentially having a mild running behavior associated to quantum effects. Remarkably, this could be the very origin of the dynamical nature of the Dark Energy, in contrast to many other popular options considered in the literature. In discussing this possibility, we also address some recent criticisms concerning the possibility of such running. Our conclusion is that, while there is no comprehensive proof of the CC running, there is no proof of the non-running either. The problem can be solved only through a deeper understanding of the vacuum contributions of massive quantum fields on a curved spacetime background. We suggest that such investigations are at the heart of one of the most important endeavors of fundamental theoretical cosmology in the years to come.

Ilya L. Shapiro; Joan Sola

2009-10-26T23:59:59.000Z

445

Bouncing scalar field cosmology in the polymeric minisuperspace picture  

E-Print Network [OSTI]

We study a cosmological setup consisting of a FRW metric as the background geometry with a massless scalar field in the framework of classical polymerization of a given dynamical system. To do this, we first introduce the polymeric representation of the quantum operators. We then extend the corresponding process to reach a transformation which maps any classical variable to its polymeric counterpart. It is shown that such a formalism has also an analogue in terms of the symplectic structure, i.e., instead of applying polymerization to the classical Hamiltonian to arrive its polymeric form, one can use a new set of variables in terms of which Hamiltonian retains its form but now the corresponding symplectic structure gets a new deformed functional form. We show that these two methods are equivalent and by applying of them to the scalar field FRW cosmology see that the resulting scale factor exhibits a bouncing behavior from a contraction phase to an expanding era. Since the replacing of the big bang singularity by a bouncing behavior is one of the most important predictions of the quantum cosmological theories, we may claim that our polymerized classical model brings with itself some signals from quantum theory.

B. Vakili; K. Nozari; V. Hosseinzadeh; M. A. Gorji

2014-08-20T23:59:59.000Z

446

Active optics and coronography with the Hubble Space Telescope  

E-Print Network [OSTI]

In the field of planet and proto-planetary disk detection, achieving high angular resolution and high dynamic range is a necessity. Coronography coupled with adaptive optics on Hubble Space Telescope is a way to get both good spatial resolution and high dynamic range. However, because of the residual figure errors on the primary and on the secondary, HST has a scattered light level that prevents it from detecting extra-solar planets. Our simulations show that by using an active mirror (400-1000 actuators) in the optical path of HST with adaptive optics, we can correct the mirror errors and decrease the scattering level by a factor 10.sup(2) (from 10.sup(-4) to 10.sup(-6) fainter than the star). Furthermore, by controlling the spatial frequencies of the active mirror with a {\\em dark hole\\/} algorithm we can decrease the scattering level in image zones where planet detection is likely. Using this technique, we have succeeded in decreasing the scattering level to 3 x 10.sup(-8) of the star intensity within 1 ar...

Malbet, F; Yu, J; Fabien Malbet; Michael Shao; Jeffrey Yu

1994-01-01T23:59:59.000Z

447

Active Optics and Coronography with the Hubble Space Telescope  

E-Print Network [OSTI]

In the field of planet and proto-planetary disk detection, achieving high angular resolution and high dynamic range is a necessity. Coronography coupled with adaptive optics on Hubble Space Telescope is a way to get both good spatial resolution and high dynamic range. However, because of the residual figure errors on the primary and on the secondary, HST has a scattered light level that prevents it from detecting extra-solar planets. Our simulations show that by using an active mirror (400-1000 actuators) in the optical path of HST with adaptive optics, we can correct the mirror errors and decrease the scattering level by a factor $10^{2}$ (from $10^{-4}$ to $10^{-6}$ fainter than the star). Furthermore, by controlling the spatial frequencies of the active mirror with a {\\em dark hole\\/} algorithm we can decrease the scattering level in image zones where planet detection is likely. Using this technique, we have succeeded in decreasing the scattering level to $3\\times 10^{-8}$ of the star intensity within 1 arcsec from the central star. This will allow the detection of a Jupiter-like planet $10^{-9}$ times dimmer than the central star located 10 pc away in 1 hour of integration time with a signal-to-noise ratio of 5. This paper describes the method used to determine the actuator strokes applied to a deformable mirror to achieve planet detection and the design of a coronograph which implements this novel technique.

Fabien Malbet; Michael Shao; Jeffrey Yu

1994-04-12T23:59:59.000Z

448

Hubble Space Telescope Observations of Novae in M49  

E-Print Network [OSTI]

A search for novae in M49 (NGC 4472) has been undertaken with the Hubble Space Telescope. A 55-day observing campaign in F555W (19 epochs) and F814W (five epochs) has led to the discovery of nine novae. We find that M49 may be under-abundant in slow, faint novae relative to the Milky Way and M31. Instead, the decline rates of the M49 novae are remarkably similar to those of novae in the LMC. This fact argues against a simple classification of novae in "bulge" and "disk" sub-classes. We examine the Maximum-Magnitude versus Rate of Decline (MMRD) relation for novae in M49, finding only marginal agreement with the Galactic and M31 MMRD relations. A recalibration of the Buscombe-de Vaucouleurs relation gives an absolute magnitude 15 days past maximum of M_{V,15} = -6.36+/-0.19, which is substantially brighter than previous calibrations based on Galactic novae. Monte Carlo simulations yield a global nova rate for M49 of 100{+35}{-30} per year, and a luminosity-specific nova rate in the range \

Laura Ferrarese; Patrick Cote; Andres Jordan

2003-09-30T23:59:59.000Z

449

Paradoxes of cosmological physics in the beginning of the 21-st century  

E-Print Network [OSTI]

In the history of cosmology physical paradoxes played important role for development of contemporary world models. Within the modern standard cosmological model there are both observational and conceptual cosmological paradoxes which stimulate to search their solution. Confrontation of theoretical predictions of the standard cosmological model with the latest astrophysical observational data is considered. A review of conceptual problems of the Friedmann space expending models, which are in the bases of modern cosmological model, is discussed. The main paradoxes, which are discussed in modern literature, are the Newtonian character of the exact Friedmann equation, the violation of the energy conservation within any comoving local volume, violation of the limiting recession velocity of galaxies for the observed high redshift objects. Possible observational tests of the nature of the cosmological redshift are discussed

Yurij Baryshev

2015-01-04T23:59:59.000Z

450

Paradoxes of cosmological physics in the beginning of the 21-st century  

E-Print Network [OSTI]

In the history of cosmology physical paradoxes played important role for development of contemporary world models. Within the modern standard cosmological model there are both observational and conceptual cosmological paradoxes which stimulate to search their solution. Confrontation of theoretical predictions of the standard cosmological model with the latest astrophysical observational data is considered. A review of conceptual problems of the Friedmann space expending models, which are in the bases of modern cosmological model, is discussed. The main paradoxes, which are discussed in modern literature, are the Newtonian character of the exact Friedmann equation, the violation of the energy conservation within any comoving local volume, violation of the limiting recession velocity of galaxies for the observed high redshift objects. Possible observational tests of the nature of the cosmological redshift are discussed

Baryshev, Yurij

2015-01-01T23:59:59.000Z

451

Wide-eld CCD imager for the 6.5m MMT telescope Brian McLeod  

E-Print Network [OSTI]

from six 1.8-m mirrors to a single f 1.25 6.5-m mirror. The new telescope will have several secondary of the Multiple Mirror Telescope fromsix 1.8mmirrors to a single 6.5mmirror willsigni cantly increase its and searches for objects in the outer solar system. Keywords: CCDs, imaging, astronomy, telescopes, cameras 1

452

Testing foundations of modern cosmology with SKA all-sky surveys  

E-Print Network [OSTI]

Continuum and HI surveys with the Square Kilometre Array (SKA) will allow us to probe some of the most fundamental assumptions of modern cosmology, including the Cosmological Principle. SKA all-sky surveys will map an enormous slice of space-time and reveal cosmology at superhorizon scales and redshifts of order unity. We illustrate the potential of these surveys and discuss the prospects to measure the cosmic radio dipole at high fidelity. We outline several potentially transformational tests of cosmology to be carried out by means of SKA all-sky surveys.

Schwarz, Dominik J; Chen, Song; Clarkson, Chris; Huterer, Dragan; Kunz, Martin; Maartens, Roy; Raccanelli, Alvise; Rubart, Matthias; Starck, Jean-Luc

2015-01-01T23:59:59.000Z

453

E-Print Network 3.0 - axion cosmology revisited Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Loeb Lecture April 23, 2009 Peering Beyond the Horizon with Axions Summary: Axion phenomenology Axion dark matter Inflationary cosmology Thursday, April 23, 2009 12;David B... ,...

454

E-Print Network 3.0 - anisotropic cosmological models Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

by a class of cosmological models that rely... (Sahni, 2002; Padmanabhan, 2003). In this model the role of dark energy is ... Source: Gibson, Carl H. - Scripps Institution of...

455

Kasner Solution in Brans-Dicke Theory and its Corresponding Reduced Cosmology  

E-Print Network [OSTI]

We present a brief review of the modified Brans-Dicke theory (MBDT) in arbitrary dimensions, whereby the ($N+1$)-dimensional field equations reduce to the $N$-dimensional $(ND)$ configuration with sources and an effective induced scalar potential. We then investigate a generalized Bianchi type~I anisotropic cosmology in $5D$ BD theory that leads to an extended Kasner solution. By employing the original equations of MBDT, we probe the reduced Kasner cosmology on the hypersuface with proceeding the investigations for a few cosmological quantities, explaining their properties for some cosmological models.}

S. M. M. Rasouli

2014-05-26T23:59:59.000Z

456

Green Bank Telescope Studies of Giant Pulses from Millisecond Pulsars  

E-Print Network [OSTI]

We have conducted a search for giant pulses from four millisecond pulsars using the 100m Green Bank Telescope. Coherently dedispersed time-series from PSR J0218+4232 were found to contain giant pulses of very short intrinsic duration whose energies follow power-law statistics. The giant pulses are in phase with the two minima of the radio integrated pulse profile but are phase aligned with the peaks of the X-ray profile. Historically, individual pulses more than 10-20 times the mean pulse energy have been deemed to be ``giant pulses''. As only 4 of the 155 pulses had energies greater than 10 times the mean pulse-energy, we argue the emission mechanism responsible for giant pulses should instead be defined through: (a) intrinsic timescales of microsecond or nanosecond duration; (b) power-law energy statistics; and (c) emission occurring in narrow phase-windows coincident with the phase windows of non-thermal X-ray emission. Four short-duration pulses with giant-pulse characteristics were also observed from PSR B1957+20. As the inferred magnetic fields at the light cylinders of the millisecond pulsars that emit giant pulses are all very high, this parameter has previously been considered to be an indicator of giant pulse emissivity. However, the frequency of giant pulse emission from PSR~B1957+20 is significantly lower than for other millisecond pulsars that have similar magnetic fields at their light cylinders. This suggests that the inferred magnetic field at the light cylinder is a poor indicator of the rate of emission of giant pulses.

H. S. Knight; M. Bailes; R. N. Manchester; S. M. Ord; B. A. Jacoby

2005-12-13T23:59:59.000Z

457

DEEP HUBBLE SPACE TELESCOPE IMAGING IN NGC 6397: STELLAR DYNAMICS  

SciTech Connect (OSTI)

Multi-epoch observations with the Advanced Camera for Surveys on the Hubble Space Telescope provide a unique and comprehensive probe of stellar dynamics within NGC 6397. We are able to confront analytic models of the globular cluster with the observed stellar proper motions. The measured proper motions probe well along the main sequence from 0.8 to below 0.1 M{sub Sun} as well as white dwarfs younger than 1 Gyr. The observed field lies just beyond the half-light radius where standard models of globular cluster dynamics (e.g., based on a lowered Maxwellian phase-space distribution) make very robust predictions for the stellar proper motions as a function of mass. The observed proper motions show no evidence for anisotropy in the velocity distribution; furthermore, the observations agree in detail with a straightforward model of the stellar distribution function. We do not find any evidence that the young white dwarfs have received a natal kick in contradiction with earlier results. Using the observed proper motions of the main-sequence stars, we obtain a kinematic estimate of the distance to NGC 6397 of 2.2{sup +0.5}{sub -0.7} kpc and a mass of the cluster of 1.1 {+-} 0.1 Multiplication-Sign 10{sup 5} M{sub Sun} at the photometric distance of 2.53 kpc. One of the main-sequence stars appears to travel on a trajectory that will escape the cluster, yielding an estimate of the evaporation timescale, over which the number of stars in the cluster decreases by a factor of e, of about 3 Gyr. The proper motions of the youngest white dwarfs appear to resemble those of the most massive main-sequence stars, providing the first direct constraint on the relaxation time of the stars in a globular cluster of greater than or about 0.7 Gyr.

Heyl, J. S.; Richer, H.; Woodley, K. A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Anderson, J.; Dotter, A.; Kalirai, J. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Fahlman, G.; Stetson, P. [Herzberg Institute for Astrophysics, National Research Council, Victoria, BC (Canada); Hurley, J. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia); Rich, R. M. [Division of Astronomy, University of California, Los Angeles, CA 90095-1562 (United States); Shara, M.; Zurek, D. [American Museum of Natural History, New York, NY 10024-5192 (United States)

2012-12-10T23:59:59.000Z

458

EVIDENCE FOR TYPE Ia SUPERNOVA DIVERSITY FROM ULTRAVIOLET OBSERVATIONS WITH THE HUBBLE SPACE TELESCOPE  

E-Print Network [OSTI]

We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This ...

Lewin, Walter H. G.

459

Thin optic surface analysis for high resolution X-ray telescopes  

E-Print Network [OSTI]

The art of glass developed throughout the years has covered artifacts ranging from crude ornaments to high precision optics used in flat panel displays, hard disk drives, and x-ray telescopes. Methods for manufacturing ...

Akilian, Mireille

2004-01-01T23:59:59.000Z

460

Design and Optimization of Lightweight Space Telescope Andrzej M. Stewart and David W. Miller  

E-Print Network [OSTI]

. Miller May 2007 SSL # 9-07 #12;#12;Design and Optimization of Lightweight Space Telescope Structures, for seeing enough promise in me to bring me into the SSL, for always ensuring that I had a source of funding

Note: This page contains sample records for the topic "atacama cosmology telescope" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Minimizing Actuator-Induced Residual Error in Active Space Telescope Primary Mirrors  

E-Print Network [OSTI]

. Smith, David W. Miller September 2010 SSL #12-10 #12;#12;Minimizing Actuator-Induced Residual Error in Active Space Telescope Primary Mirrors Matthew W. Smith, David W. Miller September 2010 SSL #12

462

E-Print Network 3.0 - australia telescope facilities Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Large Area... -NonCommercial-ShareAlike Licence. http:pos.sissa.it 12;PoS(PRA2009)028 ATLAS ... Source: Norris, Ray - Australia Telescope National Facility, CSIRO Collection:...

463

E-Print Network 3.0 - african large telescope Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

The Anglo-Australian Telescope 12;15 12;16 The 2dF 6 element... Midi Observatory (French Pyrenees) 12;42 The Overwhelmingly Large ... Source: Parker, Quentin A. -...

464

E-Print Network 3.0 - australia telescope low-brightness Sample...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Blue Bump BL Lac: BL Lacert26; object CASPIR: Cryogenic Array... SpectrometerImager near-infrared detector on the Australian National University's 2.3m telescope EGRET... :...

465

E-Print Network 3.0 - australia telescope compact Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Blue Bump BL Lac: BL Lacert26; object CASPIR: Cryogenic Array... SpectrometerImager near-infrared detector on the Australian National University's 2.3m telescope EGRET... :...

466

The Gemini 8m Telescopes C.M. Mountain, F.C. Gillett, J. Oschmann  

E-Print Network [OSTI]

ranging in ranging in distance from within our own Solar System to within 10% of the observable horizon and its instrumentation can be encapsulated in the formula: S a Telescope Diameter . h 1/2 1. N Delivered

467

Digital signal processing hardware for a fast fourier transform radio telescope  

E-Print Network [OSTI]

21-cm tomography is a devoloping technique for measuring the Epoch of Reionization in the universe's history. The nature of the signal measured in 21-cm tomography is such that a new kind of radio telescope is needed: one ...

Losh, Jonathan L

2012-01-01T23:59:59.000Z

468

Watching an uniformly moving source of light using a telescope and a frequency-meter  

E-Print Network [OSTI]

We propose a scenario that involves a stationary observer who detects a point like source of light moving with constant velocity at a constant altitude, using a telescope and a frequency-meter. We derive a formula for the angular velocity at which we should rotate the axis of the telescope and a formula that relates the proper period at which the source emits successive wave crests and the proper period at which the stationary observer receives them

Bernhard Rothenstein; Ioan Damian

2005-04-04T23:59:59.000Z

469

Cosmological implications of baryon acoustic oscillation (BAO) measurements  

E-Print Network [OSTI]

We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) and Type Ia supernova (SN) data. We take advantage of high-precision BAO measurements from galaxy clustering and the Ly-alpha forest (LyaF) in the BOSS survey of SDSS-III. BAO data alone yield a high confidence detection of dark energy, and in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Combining BAO and SN data into an "inverse distance ladder" yields a 1.7% measurement of $H_0=67.3 \\pm1.1$ km/s/Mpc. This measurement assumes standard pre-recombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat LCDM cosmology is an important corroboration of this minimal cosmological model. For open LCDM, our BAO+SN+CMB combination yields $\\Omega_m=0.301 \\pm 0.008$ and curvature $\\Omega_k=-0.003 \\pm 0.003$. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints remain consistent with flat LCDM. While the overall $\\chi^2$ of model fits is satisfactory, the LyaF BAO measurements are in moderate (2-2.5 sigma) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshifts remain consistent with our constraints, but models where dark matter decays into radiation are sharply limited. Expansion history alone yields an upper limit of 0.56 eV on the summed mass of neutrino species, improving to 0.26 eV if we include Planck CMB lensing. Standard dark energy models constrained by our data predict a level of matter clustering that is high compared to most, but not all, observational estimates. (Abridged)

Éric Aubourg; Stephen Bailey; Julian E. Bautista; Florian Beutler; Vaishali Bhardwaj; Dmitry Bizyaev; Michael Blanton; Michael Blomqvist; Adam S. Bolton; Jo Bovy; Howard Brewington; J. Brinkmann; Joel R. Brownstein; Angela Burden; Nicolás G. Busca; William Carithers; Chia-Hsun Chuang; Johan Comparat; Antonio J. Cuesta; Kyle S. Dawson; Timothée Delubac; Daniel J. Eisenstein; Andreu Font-Ribera; Jian Ge; J. -M. Le Goff; Satya Gontcho A Gontcho; J. Richard Gott III; James E. Gunn; Hong Guo; Julien Guy; Jean-Christophe Hamilton; Shirley Ho; Klaus Honscheid; Cullan Howlett; David Kirkby; Francisco S. Kitaura; Jean-Paul Kneib; Khee-Gan Lee; Dan Long; Robert H. Lupton; Mariana Vargas Magaña; Viktor Malanushenko; Elena Malanushenko; Marc Manera; Claudia Maraston; Daniel Margala; Cameron K. McBride; Jordi Miralda-Escudé; Adam D. Myers; Robert C. Nichol; Pasquier Noterdaeme; Sebastián E. Nuza; Matthew D. Olmstead; Daniel Oravetz; Isabelle Pâris; Nikhil Padmanabhan; Nathalie Palanque-Delabrouille; Kaike Pan; Marcos Pellejero-Ibanez; Will J. Percival; Patrick Petitjean; Matthew M. Pieri; Francisco Prada; Beth Reid; Natalie A. Roe; Ashley J. Ross; Nicholas P. Ross; Graziano Rossi; Jose Alberto Rubiño-Martín; Ariel G. Sánchez; Lado Samushia; Ricardo Tanausú Génova Santos; Claudia G. Scóccola; David J. Schlegel; Donald P. Schneider; Hee-Jong Seo; Erin Sheldon; Audrey Simmons; Ramin A. Skibba; Anže Slosar; Michael A. Strauss; Daniel Thomas; Jeremy L. Tinker; Rita Tojeiro; Jose Alberto Vazquez; Matteo Viel; David A. Wake; Benjamin A. Weaver; David H. Weinberg; W. M. Wood-Vasey; Christophe Yèche; Idit Zehavi; Gong-Bo Zhao

2014-11-18T23:59:59.000Z

470

Large Synoptic Survey Telescope: From Science Drivers to Reference Design  

SciTech Connect (OSTI)

In the history of astronomy, major advances in our understanding of the Universe have come from dramatic improvements in our ability to accurately measure astronomical quantities. Aided by rapid progress in information technology, current sky surveys are changing the way we view and study the Universe. Next-generation surveys will maintain this revolutionary progress. We focus here on the most ambitious survey currently planned in the visible band, the Large Synoptic Survey Telescope (LSST). LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: constraining dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. It will be a large, wide-field ground-based system designed to obtain multiple images covering the sky that is visible from Cerro Pachon in Northern Chile. The current baseline design, with an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg{sup 2} field of view, and a 3,200 Megapixel camera, will allow about 10,000 square degrees of sky to be covered using pairs of 15-second exposures in two photometric bands every three nights on average. The system is designed to yield high image quality, as well as superb astrometric and photometric accuracy. The survey area will include 30,000 deg{sup 2} with {delta} < +34.5{sup o}, and will be imaged multiple times in six bands, ugrizy, covering the wavelength range 320-1050 nm. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will observe a 20,000 deg{sup 2} region about 1000 times in the six bands during the anticipated 10 years of operation. These data will result in databases including 10 billion galaxies and a similar number of stars, and will serve the majority of science programs. The remaining 10% of the observing time will be allocated to special programs such as Very Deep and Very Fast time domain surveys. We describe how the LSST science drivers led to these choices of system parameters.

Ivezic, Z.; Axelrod, T.; Brandt, W.N.; Burke, D.L.; Claver, C.F.; Connolly, A.; Cook, K.H.; Gee, P.; Gilmore, D.K.; Jacoby, S.H.; Jones, R.L.; Kahn, S.M.; Kantor, J.P.; Krabbendam, V.; Lupton, R.H.; Monet, D.G.; Pinto, P.A.; Saha, A.; Schalk, T.L.; Schneider, D.P.; Strauss, Michael A.; /Washington U., Seattle, Astron. Dept. /LSST Corp. /Penn State U., Astron. Astrophys. /KIPAC, Menlo Park /NOAO, Tucson /LLNL, Livermore /UC, Davis /Princeton U., Astrophys. Sci. Dept. /Naval Observ., Flagstaff /Arizona U., Astron. Dept. - Steward Observ. /UC, Santa Cruz /Harvard U. /Johns Hopkins U. /Illinois U., Urbana

2011-10-14T23:59:59.000Z

471

Can mirror matter solve the the cosmological lithium problem?  

SciTech Connect (OSTI)

The abundance of lithium-7 confronts cosmology with a long lasting inconsistency between the predictions of standard Big Bang Nucleosynthesis with the baryonic density determined from the Cosmic Microwave Background observations on the one hand, and the spectroscopic determination of the lithium-7 abundance on the other hand. We investigated the influence of the existence of a mirror world, focusing on models in which mirror neutrons can oscillate into ordinary neutrons. Such a mechanism allows for an effective late time neutron injection, which induces an increase of the destruction of beryllium-7and thus a lower final lithium-7 abundance.

Coc, Alain [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), CNRS/IN2P3, Université Paris Sud 11, UMR 8609, Bâtiment 104, 91405 Orsay Campus (France); Uzan, Jean-Philippe; Vangioni, Elisabeth [Institut d'Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, 98 bis bd Arago, 75014 Paris, France and Sorbonne Universités, Institut Lagrange de Paris, 98 bis bd Arago, 75014 Paris (France)

2014-05-02T23:59:59.000Z

472

Loop Quantum Gravity and Cosmology: A dynamical introduction  

E-Print Network [OSTI]

Loop quantum gravity and cosmology are reviewed with an emphasis on evaluating the dynamics, rather than constructing it. The three crucial parts of such an analysis are (i) deriving effective equations, (ii) controlling the theory's microscopic degrees of freedom that lead to its spatial discreteness and refinement, and (iii) ensuring consistency and anomaly-freedom. All three issues are crucial for making the theory testable by conceptual and observational means, and they remain challenging. Throughout this review, the Hamiltonian nature of the theory will play a large role for properties of space-time structure within the framework discussed.

Bojowald, Martin

2011-01-01T23:59:59.000Z

473

New Hamiltonian analysis of Regge Teitelboim minisuperspace cosmology  

E-Print Network [OSTI]

A new Hamiltonian formulation of the minisuperspace cosmology following from the geodetic brane gravity model introduced by Regge and Teitelboim is presented. The model is considered in the framework of higher derivative theories which facilitates Hamiltonian formulation. The analysis is done using the equivalent first order approach. The constraint algebra is shown to realize a truncated Virasoro algebra. The gauge generator containing the exact number of gauge parameters is constructed. Equivalence between the gauge and reparametrization symmetries has been demonstrated. Complete gauge fixed computations have been provided and formal quantization is indicated.

Rabin Banerjee; Pradip Mukherjee; Biswajit Paul

2014-01-09T23:59:59.000Z

474

Statefinder hierarchy of bimetric and galileon models for concordance cosmology  

SciTech Connect (OSTI)

In this paper, we use Statefinder hierarchy method to distinguish between bimetric theory of massive gravity, galileon modified gravity and DGP models applied to late time expansion of the universe. We also carry out comparison between bimetric and DGP models using Statefinder pairs (r,s) and (r,q). We show that statefinder diagnostic can differentiate between ?CDM and above mentioned cosmological models of dark energy, and finally show that Statefinder S{sub 2} is an excellent discriminant of ?CDM and modified gravity models.

Myrzakulov, R. [Department of General and Theoretical Physics, Eurasian National University, Astana (Kazakhstan); Shahalam, M., E-mail: rmyrzakulov@gmail.com, E-mail: mdshahalam@ctp-jamia.res.in [Center For Theoretical Physics, Jamia Millia Islamia, New Delhi-110025 (India)

2013-10-01T23:59:59.000Z

475

Effective Fluid FLRW Cosmologies of Minimal Massive Gravity  

E-Print Network [OSTI]

By using a solution ansatz we partially decouple the metric and the Stuckelberg sectors of the minimal massive gravity (MMGR). In this scheme for a diagonal physical metric we find the general solutions for the scalars of the theory and the particular fiducial (background) metric which leads to these solutions. Then we adopt this general formalism to construct the derivation of new FLRW cosmologies of the theory in the presence of a so-called effective ideal fluid which arises from our solution ansatz as a modifying, non-physical source for the Einstein and the corresponding Friedmann equations.

Nejat Tevfik Yilmaz

2014-09-23T23:59:59.000Z

476

Dynamics of the Cosmological Apparent Horizon: Surface Gravity & Temperature  

E-Print Network [OSTI]

In the context of thermodynamics applied to our cosmological apparent horizon, we explicit in greater details our previous work which established the Friedmann Equations from projection of Hayward's Unified First Law. In particular, we show that the dynamical Hayward-Kodama surface gravity is perfectly well-defined and is suitable for this derivation. We then relate this surface gravity to a physical notion of temperature, and show this has constant, positive sign for any kind of past-inner trapping horizons. Hopefully this will clarify the choice of temperature in a dynamical Friedmann-Lema\\^itre-Roberston-Walker spacetime.

Helou, Alexis

2015-01-01T23:59:59.000Z

477

Discrete canonical analysis of three dimensional gravity with cosmological constant  

E-Print Network [OSTI]

We discuss the interplay between standard canonical analysis and canonical discretization in three-dimensional gravity with cosmological constant. By using the Hamiltonian analysis, we find that the continuum local symmetries of the theory are given by the on-shell space-time diffeomorphisms, which at the action level, corresponds to the Kalb-Ramond transformations. At the time of discretization, although this symmetry is explicitly broken, we prove that the theory still preserves certain gauge freedom generated by a constant curvature relation in terms of holonomies and the Gauss's law in the lattice approach.

J. Berra-Montiel; J. E. Rosales-Quintero

2014-06-03T23:59:59.000Z

478

Testing the consistency between cosmological measurements of distance and age  

E-Print Network [OSTI]

We present a model independent method to test the consistency between cosmological measurements of distance and age, assuming the distance duality relation. We use type Ia supernovae, baryon acoustic oscillations, and observational Hubble data, to reconstruct the luminosity distance D_L(z), the angle averaged distance D_V(z) and the Hubble rate H(z), using Gaussian processes regression technique. We obtain estimate of the distance duality relation in the redshift range 0.1

Nair, Remya; Jain, Deepak

2015-01-01T23:59:59.000Z

479

The spherical collapse model in time varying vacuum cosmologies  

E-Print Network [OSTI]

We investigate the virialization of cosmic structures in the framework of flat FLRW cosmological models, in which the vacuum energy density evolves with time. In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, "turn around" and finally collapse. We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, $\\Lambda=\\Lambda(H)$. A particularly well motivated model of this type is the so-called quantum field vacuum, in which $\\Lambda(H)$ is a quadratic function, $\\Lambda(H)=n_0+n_2\\,H^2$, with $n_0\

S. Basilakos; M. Plionis; J. Sola

2010-09-22T23:59:59.000Z

480

On the time arrows, and randomness in cosmological signals  

E-Print Network [OSTI]

Arrows of time - thermodynamical, cosmological, electromagnetic, quantum mechanical, psychological - are basic properties of Nature. For a quantum system-bath closed system the de-correlated initial conditions and no-memory (Markovian) dynamics are outlined as necessary conditions for the appearance of the thermodynamical arrow. The emergence of the arrow for the system evolving according to non-unitary dynamics due to the presence of the bath, then, is a result of limited observability, and we conjecture the arrow in the observable Universe as determined by the dark sector acting as a bath. The voids in the large scale matter distribution induce hyperbolicity of the null geodesics, with possible observational consequences.

V. G. Gurzadyan; S. Sargsyan; G. Yegorian

2013-02-21T23:59:59.000Z

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481

Gamma ray burst distances and the timescape cosmology  

E-Print Network [OSTI]

Gamma ray bursts can potentially be used as distance indicators, providing the possibility of extending the Hubble diagram to redshifts ~7. Here we follow the analysis of Schaefer (2007), with the aim of distinguishing the timescape cosmological model from the \\LambdaCDM model by means of the additional leverage provided by GRBs in the range 2 < z < 7. We find that the timescape model fits the GRB sample slightly better than the \\LambdaCDM model, but that the systematic uncertainties are still too little understood to distinguish the models.

Peter R. Smale

2011-08-22T23:59:59.000Z

482

Cosmological Parameters and the case for Cold Dark Matter  

E-Print Network [OSTI]

Determinations of the main cosmological parameters are reviewed and the implications for cold dark matter discussed. There is no longer an age problem for an $\\Omega_o = 1, \\Lambda = 0$ model and, if anything, there is now an age problem for low $\\Omega_o, \\Lambda > 0$ models. Large scale structure and CMB fluctuation data are best fitted by a mixed dark matter $\\Omega_o$ = 1 universe. Difficulties for this model with cluster evolution, the baryon content of clusters, high z Lyman $\\alpha$ galaxies, and the evidence from Type Ia supernovae favouring low $\\Omega_o, \\Lambda > 0$ models, are discussed critically.

M. Rowan-Robinson

1999-06-16T23:59:59.000Z

483

Production and detection of relic dilatons in string cosmology  

E-Print Network [OSTI]

This paper summarizes the contribution presented at the {\\sl IX Marcel Grossmann Meeting} (Rome, July 2000). It is stressed, in particular, that a non-relativistic background of ultra-light dilatons, produced in the context of string cosmology, could represent today a significant fraction of cold dark matter. If the dilaton mass lies within the resonant band of present gravitational antennas, a stochastic dilaton background with a nearly critical density could be visible, in principle, already at the level of sensitivity of the detectors in operation and presently under construction.

M. Gasperini

2000-09-28T23:59:59.000Z

484

Stochastic background of gravitational waves from cosmological sources  

E-Print Network [OSTI]

Gravitational waves (GW) can constitute a unique probe of the primordial universe. In many cases, the characteristic frequency of the emitted GW is directly related to the energy scale at which the GW source is operating in the early universe. Consequently, different GW detectors can probe different energy scales in the evolution of the universe. After a general introduction on the properties of a GW stochastic background of primordial origin, some examples of cosmological sources are presented, which may lead to observable GW signals.

Caprini, Chiara

2015-01-01T23:59:59.000Z

485

Design of a 7m Davies-Cotton Cherenkov telescope mount for the high energy section of the Cherenkov Telescope Array  

E-Print Network [OSTI]

The Cherenkov Telescope Array is the next generation ground-based observatory for the study of very-high-energy gamma-rays. It will provide an order of magnitude more sensitivity and greater angular resolution than present systems as well as an increased energy range (20 GeV to 300 TeV). For the high energy portion of this range, a relatively large area has to be covered by the array. For this, the construction of ~7 m diameter Cherenkov telescopes is an option under study. We have proposed an innovative design of a Davies-Cotton mount for such a telescope, within Cherenkov Telescope Array specifications, and evaluated its mechanical and optical performance. The mount is a reticulated-type structure with steel tubes and tensioned wires, designed in three main parts to be assembled on site. In this work we show the structural characteristics of the mount and the optical aberrations at the focal plane for three options of mirror facet size caused by mount deformations due to wind and gravity.

Rovero, A C; Vallejo, G; Supanitsky, A D; Actis, M; Botani, A; Ochoa, I; Hughes, G

2013-01-01T23:59:59.000Z

486

SFT non-locality in cosmology: solutions, perturbations and observational evidences  

SciTech Connect (OSTI)

In this note cosmological models coming out of the String Field Theory (SFT) in application to the Dark Energy are reviewed. A way of solution construction in case of linear models is outlined, cosmological perturbations and observational evidences of such models are explored.

Koshelev, Alexey S. [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium)

2010-06-23T23:59:59.000Z

487

Generalized de Sitter solution in multidimensional cosmology with static internal spaces  

E-Print Network [OSTI]

A multidimensional cosmological model with space-time consisting of n (n>1) Einstein spaces M_i is investigated in the presence of a cosmological constant Lambda and a homogeneous minimally coupled free scalar field. Generalized de Sitter solution was found for Lambda > 0 and Ricci-flat external space for the case of static internal spaces with fine tuning of parameters.

A. Zhuk

2002-05-28T23:59:59.000Z

488

Hubble constant from lensing in plasma-redshift cosmology, and intrinsic redshift of quasars  

E-Print Network [OSTI]

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.

Ari Brynjolfsson

2004-12-02T23:59:59.000Z

489

Composite dark energy: cosmon models with running cosmological term and gravitational coupling  

E-Print Network [OSTI]

In the recent literature on dark energy (DE) model building we have learnt that cosmologies with variable cosmological parameters can mimic more traditional DE pictures exclusively based on scalar fields (e.g. quintessence and phantom). In a previous work we have illustrated this situation within the context of a renormalization group running cosmological term, Lambda. Here we analyze the possibility that both the cosmological term and the gravitational coupling, G, are running parameters within a more general framework (a variant of the so-called ``LXCDM models'') in which the DE fluid can be a mixture of a running Lambda and another dynamical entity X (the ``cosmon'') which may behave quintessence-like or phantom-like. We compute the effective EOS parameter, w, of this composite fluid and show that the LXCDM can mimic to a large extent the standard LCDM model while retaining features hinting at its potential composite nature (such as the smooth crossing of the cosmological constant boundary w=-1). We further argue that the LXCDM models can cure the cosmological coincidence problem. All in all we suggest that future experimental studies on precision cosmology should take seriously the possibility that the DE fluid can be a composite medium whose dynamical features are partially caused and renormalized by the quantum running of the cosmological parameters.

Javier Grande; Joan Sola; Hrvoje Stefancic