On the no-gravity limit of gravity
J. Kowalski-Glikman; M. Szczachor
2012-12-21
We argue that Relative Locality may arise in the no gravity $G\\rightarrow0$ limit of gravity. In this limit gravity becomes a topological field theory of the BF type that, after coupling to particles, may effectively deform its dynamics. We briefly discuss another no gravity limit with a self dual ground state as well as the topological ultra strong $G\\rightarrow\\infty$ one.
Massive gravity as a limit of bimetric gravity
Martin-Moruno, Prado; Visser, Matt
2013-01-01
Massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure can lead to an interesting interplay between the "background" and "foreground" metrics in a cosmological context. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true.
Parameterized post-Newtonian limit of Horndeski's gravity theory
Manuel Hohmann
2015-08-20
We present a recent result on the parameterized post-Newtonian (PPN) limit of Horndeski's gravity theory and its consistency with solar system observations.
The Weak-Coupling Limit of Simplicial Quantum Gravity
G. Thorleifsson; P. Bialas; B. Petersson
1998-12-23
In the weak-coupling limit, kappa_0 going to infinity, the partition function of simplicial quantum gravity is dominated by an ensemble of triangulations with the ratio N_0/N_D close to the upper kinematic limit. For a combinatorial triangulation of the D--sphere this limit is 1/D. Defining an ensemble of maximal triangulations, i.e. triangulations that have the maximal possible number of vertices for a given volume, we investigate the properties of this ensemble in three dimensions using both Monte Carlo simulations and a strong-coupling expansion of the partition function, both for pure simplicial gravity and a with a suitable modified measure. For the latter we observe a continuous phase transition to a crinkled phase and we investigate the fractal properties of this phase.
Post-Minkowskian Limit and Gravitational Waves solutions of Fourth Order Gravity: a complete study
A. Stabile; S. Capozziello
2015-04-26
The post-Minkowskian limit and gravitational wave solutions for general fourth-order gravity theories are discussed. Specifically, we consider a Lagrangian with a generic function of curvature invariants $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta}, R_{\\alpha\\beta\\gamma\\delta}R^{\\alpha\\beta\\gamma\\delta})$. It is well known that when dealing with General Relativity such an approach provides massless spin-two waves as propagating degree of freedom of the gravitational field while this theory implies other additional propagating modes in the gravity spectra. We show that, in general, fourth order gravity, besides the standard massless graviton is characterized by two further massive modes with a finite-distance interaction. We find out the most general gravitational wave solutions in terms of Green functions in vacuum and in presence of matter sources. If an electromagnetic source is chosen, only the modes induced by $R_{\\alpha\\beta}R^{\\alpha\\beta}$ are present, otherwise, for any $f(R)$ gravity model, we have the complete analogy with tensor modes of General Relativity. Polarizations and helicity states are classified in the hypothesis of plane wave.
Post-Minkowskian Limit and Gravitational Waves solutions of Fourth Order Gravity: a complete study
Stabile, A
2015-01-01
The post-Minkowskian limit and gravitational wave solutions for general fourth-order gravity theories are discussed. Specifically, we consider a Lagrangian with a generic function of curvature invariants $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta}, R_{\\alpha\\beta\\gamma\\delta}R^{\\alpha\\beta\\gamma\\delta})$. It is well known that when dealing with General Relativity such an approach provides massless spin-two waves as propagating degree of freedom of the gravitational field while this theory implies other additional propagating modes in the gravity spectra. We show that, in general, fourth order gravity, besides the standard massless graviton is characterized by two further massive modes with a finite-distance interaction. We find out the most general gravitational wave solutions in terms of Green functions in vacuum and in presence of matter sources. If an electromagnetic source is chosen, only the modes induced by $R_{\\alpha\\beta}R^{\\alpha\\beta}$ are present, otherwise, for any $f(R)$ gravity model, we have the compl...
Oji, L. N.
2015-10-01
August 2015, scale solids from the 16H Evaporator Gravity Drain Line (GDL) to the Tank 38H were delivered to SRNL for analysis. The desired analytical goal was to identify and confirm the crystalline structure of the scale material and determine if the form of the aluminosilicate mineral was consistent with previous analysis of the scale material from the GDL.
Copyright 2013 IEEE. Reprinted, with permission from: Line Limit Preserving Power System Equivalent
system. Line limits are a fundamental part of the formulation for Power Flow problems, Optimal Power Flow (OPF) problems and Security-Constrained Optimal Power Flow (SCOPF) problems for electric power systems generation or loads
Liouville gravity from Einstein gravity
D. Grumiller; R. Jackiw
2007-12-28
We show that Liouville gravity arises as the limit of pure Einstein gravity in 2+epsilon dimensions as epsilon goes to zero, provided Newton's constant scales with epsilon. Our procedure - spherical reduction, dualization, limit, dualizing back - passes several consistency tests: geometric properties, interactions with matter and the Bekenstein-Hawking entropy are as expected from Einstein gravity.
Massive gravity from bimetric gravity
Baccetti, Valentina; Visser, Matt
2012-01-01
We discuss the subtle relationship between so-called massive gravity (that is, gravity incorporating a non-zero graviton mass) and bimetric gravity, focussing particularly on the manner in which massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure is more delicate than currently appreciated, and in particular, in a cosmological context can lead to an interesting interplay between the "background" and "foreground" metrics. The fact that in bimetric theories one always has two sets of metric equations of motion, one for each metric, continues to have an effect even in the massive gravity limit. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true.
Black Holes and Naked Singularities in Low Energy Limit of String Gravity with Modulus Field
S. Alexeyev; S. Mignemi
2001-03-16
We show that the black hole solutions of the effective string theory action, where one-loop effects that couple the moduli to gravity via a Gauss-Bonnet term are taken into account, admit primary scalar hair. The requirement of absence of naked singularities imposes an upper bound on the scalar charges.
Is nonrelativistic gravity possible?
Kocharyan, A. A.
2009-07-15
We study nonrelativistic gravity using the Hamiltonian formalism. For the dynamics of general relativity (relativistic gravity) the formalism is well known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the lapse function is constrained correctly, then nonrelativistic gravity is described by a consistent Hamiltonian system. Surprisingly, nonrelativistic gravity can have solutions identical to relativistic gravity ones. In particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of Horava gravity are locally identical.
Neronov, A
2015-01-01
We show that observation of the time-dependent effect of microlensing of relativistically broadened emission lines (such as e.g. the Fe Kalpha line in X-rays) in strongly lensed quasars could provide data on celestial mechanics of circular orbits in the direct vicinity of the horizon of supermassive black holes. This information can be extracted from the observation of evolution of red / blue edge of the magnified line just before and just after the period of crossing of the innermost stable circular orbit by the microlensing caustic. The functional form of this evolution is insensitive to numerous astrophysical parameters of the accreting black hole and of the microlensing caustics network system (as opposed to the evolution the full line spectrum). Measurement of the temporal evolution of the red / blue edge could provide a precision measurement of the radial dependence of the gravitational redshift and of velocity of the circular orbits, down to the innermost stable circular orbit. These measurements could...
Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.
1984-10-19
A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.
Cohen, Samuel A. (Hopewell, NJ); Hosea, Joel C. (Princeton, NJ); Timberlake, John R. (Allentown, NJ)
1986-01-01
A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.
Arkady L. Kholodenko
2015-08-18
Attempts to merge Einsteinian gravity with Newtonian run into inconsistencies because in Newton's gravity time is absolute and the speed of gravity is infinite. Such an assumption was in a focus of attention of scientists in 19th century interested in finding out if the speed of gravity is infinite. By analogy with electrodynamics, some retarded potentials replacing Newtonian were utilized. By using one of such potentials Gerber correctly calculated the perihelion shift for Mercury in 1902. Subsequent attempts at calculation of bending of light using Gerber-style calculations were not successful. Recently Gin\\'e (Chaos, Solitons and Fractals 42, 1893 (2009)) reobtained both the perihelion shift and the bending of light using retarded potential. His equations however are not those obtained by Einstein and his results coincide with those by Einstein only at the level of leading order terms of infinite series expansions. The obtained differential equations of motion are of delay-type. When applied to two-body dynamics, such equations lead to orbital quantization. In this work the Einsteinian approach is used to reproduce this quantization. Numerous arguments justifying the superiority of Einsteinian approach, including uses of the Bertrand spacetimes for description of motion of stars around galactic centers are provided. The developed formalism is tested by calculating the number of allowed stable orbits for planets and those for regular satellites of heavy planets resulting in reasonable agreement with observational data. The paper also discusses possible quantum mechanical nature of rings of heavy planets as well as of rotation curves of stars in spiral galaxies.
Oz, E.; Myers, C. E.; Yamada, M.; Ji, H.; Kulsrud, R. M.; Xie, J.
2011-07-19
The stability properties of partial toroidal flux ropes are studied in detail in the laboratory, motivated by ubiquitous arched magnetic structures found on the solar surface. The flux ropes studied here are magnetized arc discharges formed between two electrodes in the Magnetic Reconnection Experiment (MRX) [Yamada et al., Phys. Plasmas, 4, 1936 (1997)]. The three dimensional evolution of these flux ropes is monitored by a fast visible light framing camera, while their magnetic structure is measured by a variety of internal magnetic probes. The flux ropes are consistently observed to undergo large-scale oscillations as a result of an external kink instability. Using detailed scans of the plasma current, the guide field strength, and the length of the flux rope, we show that the threshold for kink stability is governed by the Kruskal-Shafranov limit for a flux rope that is held fixed at both ends (i.e., qa = 1).
Limits on Variations in Fundamental Constants from 21-cm and Ultraviolet Quasar Absorption Lines
Tzanavaris, P.; Webb, J.K.; Flambaum, V.V.; Curran, S.J.; Murphy, M.T.
2005-07-22
Quasar absorption spectra at 21-cm and UV rest wavelengths are used to estimate the time variation of x{identical_to}{alpha}{sup 2}g{sub p}{mu}, where {alpha} is the fine structure constant, g{sub p} the proton g factor, and m{sub e}/m{sub p}{identical_to}{mu} the electron/proton mass ratio. Over a redshift range 0.24 < or approx. z{sub abs} < or approx. 2.04, <{delta}x/x>{sub total}{sup weighted}=(1.17{+-}1.01)x10{sup -5}. A linear fit gives x/x=(-1.43{+-}1.27)x10{sup -15} yr{sup -1}. Two previous results on varying {alpha} yield the strong limits {delta}{mu}/{mu}=(2.31{+-}1.03)x10{sup -5} and {delta}{mu}/{mu}=(1.29{+-}1.01)x10{sup -5}. Our sample, 8x larger than any previous, provides the first direct estimate of the intrinsic 21-cm and UV velocity differences {approx}6 km s{sup -1}.
LIMITS ON THE NUMBER OF GALACTIC YOUNG SUPERNOVA REMNANTS EMITTING IN THE DECAY LINES OF {sup 44}Ti
Dufour, François; Kaspi, Victoria M., E-mail: dufourf@physics.mcgill.ca [Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8 (Canada)
2013-09-20
We revise the assumptions of the parameters involved in predicting the number of supernova remnants detectable in the nuclear lines of the decay chain of {sup 44}Ti. Specifically, we consider the distribution of the supernova progenitors, the supernova rate in the Galaxy, the ratios of supernova types, the Galactic production of {sup 44}Ti, and the {sup 44}Ti yield from supernovae of different types to derive credible bounds on the expected number of detectable remnants. We find that, within 1? uncertainty, the Galaxy should contain an average of 5.1{sup +2.4}{sub -2.0} remnants detectable to a survey with a {sup 44}Ti decay line flux limit of 10{sup –5} photons cm{sup –2} s{sup –1}, with a probability of detecting a single remnant of 2.7{sup +10.0}{sub -2.4}%, and an expected number of detections between two and nine remnants, making the single detection of Cas A unlikely but consistent with our models. Our results show that the probability of detecting the brightest {sup 44}Ti flux source at the high absolute Galactic longitude of Cas A or above is ?10%. Using the detected flux of Cas A, we attempt to constrain the Galactic supernova rate and Galactic production of {sup 44}Ti, but find the detection to be only weakly informative. We conclude that even future surveys having 200 times more sensitivity than state-of-the-art surveys can be guaranteed to detect only a few new remnants, with an expected number of detections between 8 and 21 at a limiting {sup 44}Ti decay flux of 10{sup –7} photons cm{sup –2} s{sup –1}.
Izmailov, Ramil; Filippov, Alexander I; Ghosh, Mithun; Nandi, Kamal K
2015-01-01
We investigate the stability of circular material orbits in the analytic galactic metric recently derived by Harko \\textit{et al.} (2014). It turnsout that stability depends more strongly on the dark matter central density $%\\rho_{0}$ than on other parameters of the solution. This property then yields an upper limit on $\\rho _{0}$ for each individual galaxy, which we call here $\\rho _{0}^{\\text{upper}}$, such that stable circular orbits are possible \\textit{only} when the constraint $\\rho _{0}\\leq \\rho _{0}^{\\text{upper}}$ is satisfied. This is our new result. To approximately quantify the upper limit, we consider as a familiar example our Milky Way galaxy that has a projected dark matter radius $R_{\\text{DM}}\\sim 180$ kpc and find that $\\rho _{0}^{\\text{upper}}\\sim 2.37\\times 10^{11}$ $M_{\\odot }$kpc$^{-3}$. This limit turns out to be about four orders of magnitude larger than the latest data on central density $\\rho _{0}$ arising from the fit to the Navarro-Frenk-White (NFW) and Burkert density profiles. Su...
Ramil Izmailov; Alexander A. Potapov; Alexander I. Filippov; Mithun Ghosh; Kamal K. Nandi
2015-06-11
We investigate the stability of circular material orbits in the analytic galactic metric recently derived by Harko \\textit{et al.} (2014). It turnsout that stability depends more strongly on the dark matter central density $%\\rho_{0}$ than on other parameters of the solution. This property then yields an upper limit on $\\rho _{0}$ for each individual galaxy, which we call here $\\rho _{0}^{\\text{upper}}$, such that stable circular orbits are possible \\textit{only} when the constraint $\\rho _{0}\\leq \\rho _{0}^{\\text{upper}}$ is satisfied. This is our new result. To approximately quantify the upper limit, we consider as a familiar example our Milky Way galaxy that has a projected dark matter radius $R_{\\text{DM}}\\sim 180$ kpc and find that $\\rho _{0}^{\\text{upper}}\\sim 2.37\\times 10^{11}$ $M_{\\odot }$kpc$^{-3}$. This limit turns out to be about four orders of magnitude larger than the latest data on central density $\\rho _{0}$ arising from the fit to the Navarro-Frenk-White (NFW) and Burkert density profiles. Such consistency indicates that the EiBI solution could qualify as yet another viable alternative model for dark matter.
B. L. Hu
1999-02-22
We give a summary of the status of current research in stochastic semiclassical gravity and suggest directions for further investigations. This theory generalizes the semiclassical Einstein equation to an Einstein-Langevin equation with a stochastic source term arising from the fluctuations of the energy-momentum tensor of quantum fields. We mention recent efforts in applying this theory to the study of black hole fluctuations and backreaction problems, linear response of hot flat space, and structure formation in inflationary cosmology. To explore the physical meaning and implications of this stochastic regime in relation to both classical and quantum gravity, we find it useful to take the view that semiclassical gravity is mesoscopic physics and that general relativity is the hydrodynamic limit of certain spacetime quantum substructures. Three basic issues - stochasticity, collectivity, correlations- and three processes - dissipation, fluctuations, decoherence- underscore the transformation from quantum micro structure and interaction to the emergence of classical macro structure and dynamics. We discuss ways to probe into the high energy activity from below and make two suggestions: via effective field theory and the correlation hierarchy. We discuss how stochastic behavior at low energy in an effective theory and how correlation noise associated with coarse-grained higher correlation functions in an interacting quantum field could carry nontrivial information about the high energy sector. Finally we describe processes deemed important at the Planck scale, including tunneling and pair creation, wave scattering in random geometry, growth of fluctuations and forms, Planck scale resonance states, and spacetime foams.
Zygmunt Lalak; Stefan Pokorski; Krzysztof Turzynski
2008-08-18
We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for mu and Bmu generation. Gravity sector can include stabilized moduli.
Entropic Gravity in Rindler Space
Edi Halyo
2011-04-13
We show that Rindler horizons are entropic screens and gravity is an entropic force in Rindler space by deriving the Verlinde entropy formula from the focusing of light due to a mass close to the horizon. Consequently, gravity is also entropic in the near horizon regions of Schwarzschild and de Sitter space-times. In different limits, the entropic nature of gravity in Rindler space leads to the Bekenstein entropy bound and the uncertainty principle.
COMPTEL limits on 26Al 1.809 MeV line emission from gamma^2 Velorum
U. Oberlack; U. Wessolowski; R. Diehl; K. Bennett; H. Bloemen; W. Hermsen; J. Knödlseder; D. Morris; V. Schönfelder; P. von Ballmoos
1999-10-29
The Wolf-Rayet binary system gamma^2 Vel (WR 11} is the closest known Wolf-Rayet (WR) star. Recently, its distance has been redetermined by parallax measurements with the HIPPARCOS astrometric satellite yielding 258^{+41}_{-31} pc, significantly lower than previous estimates (300 -- 450 pc). Wolf-Rayet stars have been proposed as a major source of the Galactic 26Al observed at 1.809 MeV. The gamma-ray telescope COMPTEL has previously reported 1.8 MeV emission from the Vela region, yet located closer to the Galactic plane than the position of gamma^2 Vel. We derive an upper 1.8 MeV flux limit of 1.1 10^{-5} ph cm^{-2} s^{-1} (2 \\sigma) for the WR star. With the new distance estimate, COMPTEL measurements place a limit of (6.3^{+2.1}_{-1.4}) 10^{-5} M_\\odot the 26Al yield of gamma^2 Vel, thus constrains theories of nucleosynthesis in Wolf-Rayet stars. We discuss the implications in the context of the binary nature of gamma^2 Vel and present a new interpretation of the IRAS Vela shell.
Farrell, Brian F.
Gravity Waves in a Horizontal Shear Flow. Part II: Interaction between Gravity Waves and Potential perturbations and propagating internal gravity waves in a horizon- tally sheared zonal flow is investigated. In the strong stratification limit, an initial vorticity perturbation weakly excites two propagating gravity
Einstein Gravity from Conformal Gravity
Juan Maldacena
2011-06-09
We show that that four dimensional conformal gravity plus a simple Neumann boundary condition can be used to get the semiclassical (or tree level) wavefunction of the universe of four dimensional asymptotically de-Sitter or Euclidean anti-de Sitter spacetimes. This simple Neumann boundary condition selects the Einstein solution out of the more numerous solutions of conformal gravity. It thus removes the ghosts of conformal gravity from this computation. In the case of a five dimensional pure gravity theory with a positive cosmological constant we show that the late time superhorizon tree level probability measure, $|\\Psi [ g ]|^2$, for its four dimensional spatial slices is given by the action of Euclidean four dimensional conformal gravity.
Lujan, Richard E. (Santa Fe, NM)
2001-01-01
A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.
The JPL lunar gravity field to spherical harmonic degree 660 from the GRAIL Primary Mission
Konopliv, Alex S.
The lunar gravity field and topography provide a way to probe the interior structure of the Moon. Prior to the Gravity Recovery and Interior Laboratory (GRAIL) mission, knowledge of the lunar gravity was limited mostly to ...
J. Brian Pitts
2015-09-09
Klein-Gordon gravity, 1920s-30s particle physics, and 1890s Neumann-Seeliger modified gravity suggest a "graviton mass term" *algebraic* in the potential. Unlike Nordstr\\"om's "massless" theory, massive scalar gravity is invariant under the Poincar\\'e group but not the 15-parameter conformal group. It thus exhibits the whole Minkowski space-time structure, indirectly for volumes. Massive scalar gravity is plausible as a field theory, but violates Einstein's principles of general covariance, general relativity, equivalence, and Mach. Geometry is a poor guide: matter sees a conformally flat metric due to universal coupling, but gravity sees the rest of the flat metric (on long distances) in the mass term. What is the `true' geometry, in line with Poincar\\'e's modal conventionality argument? Infinitely many theories exhibit this bimetric `geometry,' all with the total stress-energy's trace as source; geometry does not explain the field equations. The irrelevance of the Ehlers-Pirani-Schild construction to conventionalism is evident given multi-geometry theories. As Seeliger envisaged, the smooth massless limit yields underdetermination between massless and massive scalar gravities---an unconceived alternative. One version easily could have been developed before GR; it would have motivated thinking of Einstein's equations along the lines of his newly reappreciated "physical strategy" and suggested a rivalry from massive spin 2 for GR (massless spin 2, Pauli-Fierz 1939). The Putnam-Gr\\"unbaum debate on conventionality is revisited given a broad modal scope. Massive scalar gravity licenses a historically plausible rational reconstruction of much of space-time philosophy in light of particle physics. An appendix reconsiders the Malament-Weatherall-Manchak conformal restriction of conventionality and constructs the `universal force' in the null cones.
Horava-Lifshitz gravity with detailed balance
Daniele Vernieri; Thomas P. Sotiriou
2012-12-18
Horava-Lifshitz gravity with "detailed balance" but without the projectability assumption is discussed. It is shown that detailed balance is quite efficient in limiting the proliferation of couplings in Horava-Lifshitz gravity, and that its implementation without the projectability assumption leads to a theory with sensible dynamics. However, the (bare) cosmological constant is restricted to be large and negative.
Gravity Data for west-central Colorado
Zehner, Richard
2012-04-06
Modeled Bouger Gravity data was extracted from the Pan American Center for Earth and Environmental Studies Gravity Database of the U.S. at http://irpsrvgis08.utep.edu/viewers/Flex/GravityMagnetic/GravityMagnetic_CyberShare/ on 2/29/2012. The downloaded text file was opened in an Excel spreadsheet. This spreadsheet data was then converted into an ESRI point shapefile in UTM Zone 13 NAD27 projection, showing location and gravity (in milligals). This data was then converted to grid and then contoured using ESRI Spatial Analyst. This dataset contains the original spreadsheet data, a point shapefile showing gravity station locations and Bouger gravity, and a line shapefile showing 1 milligal contours. Projection: UTM Zone 13 NAD27 Gravity Contour Shapefile Extent: West -108.366690 East -105.478730 North 40.932318 South 36.961606 Gravity Point Shapefile Extent: West -108.366692 East -105.478847 North 40.932361 South 36.961606 Data from From University of Texas: Pan American Center for Earth and Environmental Studies
Hanson, Andrew J.
2011-01-01
more restrictive context of Einstein's theory of gravity.6782 TORSION AND QUANTUM GRAVITY Andrevr J, Him son Lawrencetorsion in conventional gravity cou~d in fact be dynamicaL A
Hang, Alice Thanh
2009-01-01
The front speed of intrusive gravity currents. J. FluidP.F. Linden. Intrusive gravity currents. J. Fluid Mechanics,of mesoscale variability of gravity waves. Part II: Frontal,
Overlap Fermion in External Gravity
Hiroto So; Masashi Hayakawa; Hiroshi Suzuki
2006-12-12
On a lattice, we construct an overlap Dirac operator which describes the propagation of a Dirac fermion in external gravity. The local Lorentz symmetry is manifestly realized as a lattice gauge symmetry, while the general coordinate invariance is expected to be restored only in the continuum limit. The lattice index density in the presence of a gravitational field is calculated.
Liouville quantum gravity and KPZ
Duplantier, Bertrand
Consider a bounded planar domain D, an instance h of the Gaussian free field on D, with Dirichlet energy ... and a constant 0[less than or equal to]?<2. The Liouville quantum gravity measure on D is the weak limit as ...
K. H. Mariwalla
2002-05-28
Basis and limitations of singularity theorems for Gravity are examined. As singularity is a critical situation in course of time, study of time paths, in full generality of Equivalence principle, provides two mechanisms to prevent singularity. Resolution of singular Time translation generators into space of its orbits, and essential higher dimensions for Relativistic particle interactions has facets to resolve any real singularity problem. Conceptually, these varied viewpoints have a common denominator: arbitrariness in the definition of `energy' intrinsic to the space of operation in each case, so as to render absence of singularity a tautology for self-consistency of the systems.
Consistent Modified Gravity Analysis of Anisotropic Galaxy Clustering Using BOSS DR11
Song, Yong-Seon; Linder, Eric; Koyama, Kazuya; Sabiu, Cristiano G; Zhao, Gong-Bo; Bernardeau, Francis; Nishimichi, Takahiro; Okumura, Teppei
2015-01-01
We analyse the clustering of cosmic large scale structure using a consistent modified gravity perturbation theory, accounting for anisotropic effects along and transverse to the line of sight. The growth factor has a particular scale dependence in f(R) gravity and we fit for the shape parameter f_{R0} simultaneously with the distance and the large scale (general relativity) limit of the growth function. Using more than 690,000 galaxies in the Baryon Oscillation Spectroscopy Survey Data Release 11, we find no evidence for extra scale dependence, with the 95\\% confidence upper limit |f_{R0}| <8 \\times 10^{-4}. Future clustering data, such as from the Dark Energy Spectroscopic Instrument, can use this consistent methodology to impose tighter constraints.
Chiral Gravity, Log Gravity and Extremal CFT
Alexander Maloney; Wei Song; Andrew Strominger
2009-03-26
We show that the linearization of all exact solutions of classical chiral gravity around the AdS3 vacuum have positive energy. Non-chiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity-- the theory with logarithmically relaxed boundary conditions --has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic CFT. Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We normally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.
Xavier Calmet; Priscila de Aquino
2009-10-08
It has recently been shown that if there is a large hidden sector in Nature, the scale of quantum gravity could be much lower than traditionally expected. We study the production of massless gravitons at the LHC and compare our results to those obtained in extra dimensional models. The signature in both cases is missing energy plus jets. In case of non observation, the LHC could be used to put the tightest limit to date on the value of the Planck mass.
Towards noncommutative gravity
D. V. Vassilevich
2009-02-17
In this short article accessible for non-experts I discuss possible ways of constructing a non-commutative gravity paying special attention to possibilities of realizing the full diffeomorphism symmetry and to relations with 2D gravities.
Rong-Jia Yang
2014-09-11
If we assume that the source of thermodynamic system, $\\rho$ and $p$, are also the source of gravity, thermal quantities, such as entropy, temperature, and chemical potential, can induce effects of gravity, or gravity can induce thermal effects. We find only for systems with constant temperature and zero chemical potential, gravity can be seen as an entropic force. The case for Newtonian approximation is discussed.
Karim Noui
2010-03-31
We tackle the question of motion in Quantum Gravity: what does motion mean at the Planck scale? Although we are still far from a complete answer we consider here a toy model in which the problem can be formulated and resolved precisely. The setting of the toy model is three dimensional Euclidean gravity. Before studying the model in detail, we argue that Loop Quantum Gravity may provide a very useful approach when discussing the question of motion in Quantum Gravity.
Terrestrial Gravity Fluctuations
Jan Harms
2015-07-21
The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.
Stephen Hawking Quantum Gravity
Visser, Matt
Stephen Hawking and Quantum Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 4 Nov 2000 #12; Stephen Hawking and Quantum Gravity Abstract: Through research, Stephen Hawking has captured a place in the popular imagina- tion. Quantum gravity in its various
Quantum Physics Einstein's Gravity
Visser, Matt
Quantum Physics confronts Einstein's Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 13 October 2001 #12; Quantum Physics confronts Einstein's Gravity and with Einstein's theory of gravity (the general relativity) is still the single biggest theoretical problem
Solar System experiments do not yet veto modified gravity models
Valerio Faraoni
2006-07-05
The dynamical equivalence between modified and scalar-tensor gravity theories is revisited and it is concluded that it breaks down in the limit to general relativity. A gauge-independent analysis of cosmological perturbations in both classes of theories lends independent support to this conclusion. As a consequence, the PPN formalism of scalar-tensor gravity and Solar System experiments do not veto modified gravity, as previously thought.
Quantization of Emergent Gravity
Hyun Seok Yang
2014-12-24
Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC spacetime, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing spacetime itself, leading to a dynamical NC spacetime. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.
Holographic superconductors from the massive gravity
Hua Bi Zeng; Jian-Pin Wu
2014-09-24
A holographic superconductor is constructed in the background of a massive gravity theory. In the normal state without condensation, the conductivity exhibits a Drude peak that approaches a delta function in the massless gravity limit as studied by David Vegh. In the superconducting state, besides the infinite DC conductivity, the AC conductivity has Drude behavior at low frequency followed by a power law-fall. These results are in agreement with that found earlier by Horowitz and Santos, who studied a holographic superconductor with an implicit periodic potential beyond the probe limit. The results also agree with measurements on some cuprates.
Nanodiamond interferometry meets quantum gravity
Albrecht, Andreas; Plenio, Martin B
2014-01-01
Interferometry with massive particles may have the potential to explore the limitations of standard quantum mechanics in particular where it concerns its boundary with general relativity and the yet to be developed theory of quantum gravity. This development is hindered considerably by the lack of experimental evidence and testable predictions. Analyzing effects that appear to be common to many of such theories, such as a modification of the energy dispersion and of the canonical commutation relation within the standard framework of quantum mechanics, has been proposed as a possible way forward. Here we analyze in some detail the impact of a modified energy-momentum dispersion in a Ramsey-Bord\\'e setup and provide achievable bounds of these correcting terms when operating such an interferometer with nanodiamonds. Thus, taking thermal and gravitational disturbances into account will show that without specific prerequisites, quantum gravity modifications may in general be suppressed requiring a revision of prev...
Konstantin G. Zloshchastiev
2009-11-30
Recently the Fermi GBM and LAT Collaborations reported their new observational data disfavoring quite a number of the quantum gravity theories, including the one suggesting the nonlinear (logarithmic) modification of a quantum wave equation. We show that the latter is still far from being ruled out: it is not only able to explain the new data but also its phenomenological implications turn out to be more vast (and more interesting) than one expected before.
Neutron stars: compact objects with relativistic gravity
Ek?i, K Yavuz
2015-01-01
General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role of opposing self-gravity. In general relativity all sources of energy and momentum contribute to the gravity. As a result the pressure not only opposes gravity but also enhances it. The later role of pressure becomes more pronounced with increasing compactness, $M/R$ where $M$ and $R$ are the mass and radius of the star, and sets a critical mass beyond which collapse is inevitable. This critical mass has no Newtonian analogue; it is conceptually different than the Stoner-Landau-Chandrasekhar limit in Newtonian gravity which is attained asymptotically for ultra-relativistic fermions. For white dwarfs the general relativistic critical mass is very close to the Stoner-Landau-Chandrasekhar limit. For neutron stars the maximum mass---so called Oppenheimer-Volkoff limit---is sig...
F. Henry-Couannier; A. Tilquin; C. Tao; A. Ealet
2007-10-24
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
Felix M. Lev
2010-05-16
We consider a possibility that gravity is not an interaction but a manifestation of a symmetry based on a Galois field.
Next steps in understanding the asymptotics of $3d$ quantum gravity
Maria Simonetta Bernabei; Horst Thaler
2014-12-10
Based on a combinatorial approach and random matrix theory, we show a central limit theorem that gives important insight into causally triangulated $3d$ quantum gravity.
Emergent gravity requires kinematic nonlocality
Marolf, D
2015-01-01
Saueressig, Quantum Einstein Gravity, New J.Phys. 14 (2012)T. Matsuki, and H. Terazawa, Gravity and Electromagnetism asat a lattice formulation of gravity, . http://cds.cern.ch/
Quantum gravity on the lattice
Hamber, Herbert W.
2009-01-01
the Conference Quantum Gravity: Challenges and Perspectives.divergences in quantum gravity. In: Hawking, S.W. , Israel,f ) V n?1 ( f ) = Quantum gravity on the lattice Similarly,
Topology in 4D simplicial quantum gravity
S. Bilke; Z. Burda; B. Petersson
1996-11-22
We simulate 4d simplicial gravity for three topologis S4, S3xS1, (S1)^4 and show that the free energy for these three fixed topology ensembles is the same in the thermodynamic limit. We show, that the next-to-leading order corrections, at least away from the critical point, can be described by kinematic sources.
Massive gravity on de Sitter and unique candidate for partially massless gravity
Rham, Claudia de; Renaux-Petel, Sébastien E-mail: srenaux@lpthe.jussieu.fr
2013-01-01
We derive the decoupling limit of Massive Gravity on de Sitter in an arbitrary number of space-time dimensions d. By embedding d-dimensional de Sitter into d+1-dimensional Minkowski, we extract the physical helicity-1 and helicity-0 polarizations of the graviton. The resulting decoupling theory is similar to that obtained around Minkowski. We take great care at exploring the partially massless limit and define the unique fully non-linear candidate theory that is free of the helicity-0 mode in the decoupling limit, and which therefore propagates only four degrees of freedom in four dimensions. In the latter situation, we show that a new Vainshtein mechanism is at work in the limit m{sup 2} ? 2H{sup 2} which decouples the helicity-0 mode when the parameters are different from that of partially massless gravity. As a result, there is no discontinuity between massive gravity and its partially massless limit, just in the same way as there is no discontinuity in the massless limit of massive gravity. The usual bounds on the graviton mass could therefore equivalently well be interpreted as bounds on m{sup 2}?2H{sup 2}. When dealing with the exact partially massless parameters, on the other hand, the symmetry at m{sup 2} = 2H{sup 2} imposes a specific constraint on matter. As a result the helicity-0 mode decouples without even the need of any Vainshtein mechanism.
Effects of 'Limited Product Line Audits'
Van Ormer, H.
2006-01-01
Wh Third-party Incentives Obtained: Audit Cost 5 of 12 Project Cost 8 of 12 RESULTS SUMMARY: Audit Costs (12 x 20,000) $240,000 Audit Rebates received $86,000 Net Audit Costs... $154,000 Project Cost $3,500,000 Project Rebates $1,200,000 Net Project Costs $2,300,000 Total Annual Electrical Energy Savings $3,663,000/yr Simple Payback 7 Months 2...
Topics in Nonsupersymmetric Scattering Amplitudes in Gauge and Gravity Theories
Nohle, Joshua David
2015-01-01
Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ultraviolet Properties of Gravity . . . . . . .Kinematics Duality and Gravity as a Double Copy of Yang-
Nonlocal Gravity in the Solar System
Chicone, C
2015-01-01
The implications of the recent classical nonlocal generalization of Einstein's theory of gravitation for gravitational physics in the Solar System are investigated. In this theory, the nonlocal character of gravity simulates dark matter. Nonlocal gravity in the Newtonian regime involves a reciprocal kernel with three spatial parameters, of which two have already been determined from the rotation curves of spiral galaxies and the internal dynamics of clusters of galaxies. However, the short-range parameter a_0 remains to be determined. In this connection, the nonlocal contribution to the perihelion precession of a planetary orbit is estimated and a preliminary lower limit on a_0 is determined.
Spacetime, Spin and Gravity Probe B
James M. Overduin
2015-04-22
It is more important than ever to push experimental tests of gravitational theory to the limits of existing technology in both range and sensitivity. This brief review focuses on spin-based tests of General Relativity and their implications for alternative, mostly non-metric theories of gravity motivated by the challenge of unification with the Standard Model of particle physics. The successful detection of geodetic precession and frame-dragging by Gravity Probe B places new constraints on a number of these theories, and increases our confidence in the theoretical mechanisms underpinning current ideas in astrophysics and cosmology.
Probability around the Quantum Gravity. Part 1: Planar Pure Gravity
Probability around the Quantum Gravity. Part 1: Planar Pure Gravity V.A.Malyshev \\Lambda September 17, 1998 Abstract In this paper we study stochastic dynamics which leaves quantum gravity equilibrium science and biology. At the same time the paper can serve an intro duction to quantum gravity
T. Jenke; G. Cronenberg; P. Geltenbort; A. N. Ivanov; T. Lauer; T. Lins; U. Schmidt; H. Saul; H. Abele
2012-08-19
The evidence for the observation of the Higgs spin-0-boson as a manifestation of a scalar field provides the missing corner stone for the standard model of particles (SM). However, the SM fails to explain the non-visible but gravitationally active part of the universe. Its nature is unknown but the confirmation of a scalar Higgs is giving a boost to scalar-field-theories. So far gravity experiments and observations performed at different distances find no deviation from Newton's gravity law. Therefore dark energy must possess a screening mechanism which suppresses the scalar-mediated fifth force. Our line of attack is a novel gravity experiment with neutrons based on a quantum interference technique. The spectroscopic measurement of quantum states on resonances with an external coupling makes this a powerful search for dark matter and dark energy contributions in the universe. Quantum states in the gravity potential are intimately related to other scalar field or spin-0-bosons if they exist. If the reason is that some undiscovered particle interact with a neutron, this results in a measurable energy shift of quantum states in the gravity potential, because for neutrons the screening effect is absent. We use Gravity Resonance Spectroscopy to measure the energy splitting at the highest level of precision, providing a constraint on any possible new interaction. We obtain a sensitivity of 10^-14 eV. We set an experimental limit on any fifth force, in particular on parameter \\beta<2x10^9 at n=3 for the scalar chameleon field, which is improved by a factor of 100 compared to our previous experiment and five orders of magnitude better than from precision tests of atomic spectra. The pseudoscalar axion coupling is constrained to gsgp/\\hbar c<3x10^-16 at 20\\mu m, which is an improvement by a factor of 30. These results indicate that gravity is understood at this improved level of precision.
Fermion Doubling in Loop Quantum Gravity
Jacob Barnett; Lee Smolin
2015-07-05
In this paper, we show that the Hamiltonian approach to loop quantum gravity has a fermion doubling problem. To obtain this result, we couple loop quantum gravity to a free massless scalar and a chiral fermion field, gauge fixing the many fingered time gauge invariance by interpreting the scalar field as a physical clock. We expand around a quantum gravity state based on a regular lattice and consider the limit where the bare cosmological constant is large but the fermonic excitations have energies low in Planck units. We then make the case for identifying the energy spectrum in this approximation with that of a model of lattice fermion theory which is known to double.
Quantum gravity effects in the Kerr spacetime
Reuter, M.; Tuiran, E.
2011-02-15
We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the 'dressing' of the black hole's mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.
Shan Gao
2011-07-16
It is argued that the existence of a minimum size of spacetime may imply the fundamental existence of gravity as a geometric property of spacetime described by general relativity.
Francis J. M. Farley
2015-08-14
In the muon storage rings the muons are subject to a very large radial acceleration. The equivalence principle implies a large gravity force. It has no effect on the muon lifetime.
Exercise in artificial gravity
Edmonds, Jessica Leigh
2005-01-01
Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility ...
Non-trivial 2+1-Dimensional Gravity
D. R. Grigore; G. Scharf
2010-08-07
We analyze 2+1-dimensional gravity in the framework of quantum gauge theory. We find that Einstein gravity has a trivial physical subspace which reflects the fact that the classical solution in empty space is flat. Therefore we study massive gravity which is not trivial. In the limit of vanishing graviton mass we obtain a non-trivial massless theory different from Einstein gravity. We derive the interaction from descent equations and obtain the cosmological topologically massive gravity. However, in addition to Einstein and Chern-Simons coupling we need coupling to fermionic ghost and anti-ghost fields and to a vector-graviton field with the same mass as the graviton.
Bulalo field, Philippines: Reservoir modeling for prediction of limits to sustainable generation
Strobel, Calvin J.
1993-01-28
The Bulalo geothermal field, located in Laguna province, Philippines, supplies 12% of the electricity on the island of Luzon. The first 110 MWe power plant was on line May 1979; current 330 MWe (gross) installed capacity was reached in 1984. Since then, the field has operated at an average plant factor of 76%. The National Power Corporation plans to add 40 MWe base load and 40 MWe standby in 1995. A numerical simulation model for the Bulalo field has been created that matches historic pressure changes, enthalpy and steam flash trends and cumulative steam production. Gravity modeling provided independent verification of mass balances and time rate of change of liquid desaturation in the rock matrix. Gravity modeling, in conjunction with reservoir simulation provides a means of predicting matrix dry out and the time to limiting conditions for sustainable levelized steam deliverability and power generation.
Gravity-driven intrusions in stratified fluids
Maurer, Benjamin Dudley
2011-01-01
5.5.1 Five interleaving interfacial gravity currents 5.5.2Ten interleaving interfacial gravity currents . 5.6partial- depth intrusive gravity currents,” Atmosphere -
Gravity Effects on Antimatter in the Standard-Model Extension
Jay D. Tasson
2015-01-30
The gravitational Standard-Model Extension (SME) is the general field-theory based framework for the analysis of CPT and Lorentz violation. In this work we summarize the implications of Lorentz and CPT violation for antimatter gravity in the context of the SME. Implications of various attempts to place indirect limits on anomalous antimatter gravity are considered in the context of SME-based models.
On the Hamiltonian form of 3D massive gravity
Olaf Hohm; Alasdair Routh; Paul K. Townsend; Baocheng Zhang
2012-09-14
We present a "Chern-Simons-like" action for the "general massive gravity" model propagating two spin-2 modes with independent masses in three spacetime dimensions (3D), and we use it to find a simple Hamiltonian form of this model. The number of local degrees of freedom, determined by the dimension of the physical phase space, agrees with a linearized analysis except in some limits, in particular that yielding "new topologically massive gravity", which therefore suffers from a linearization instability.
Gravity duals of N=(0,2) SCFTs from M5-branes
Bah, Ibrahima
2015-01-01
We describe the general BPS system that governs the gravity duals of N=(0,2) two-dimensional superconformal field theories in the low-energy limit of M5-branes on a four-manifold, M4. In order to preserve supersymmetry, we restrict to cases where the four-manifold is embedded in a Calabi-Yau fourfold that is a sum of two line bundles over M4. We further reduce the N=(0,2) system to describe the gravity duals of SCFTs with N=(0,4) and N=(2,2) supersymmetry. In the first case, the solutions fit in the larger class of AdS3xS2xCY3 solutions of M-theory dual to N=(0,4) SCFTs. In the case of the N=(2,2) theories, the near-horizon limit of M4 is necessarily a product of two constant curvature Riemann surfaces whose metrics are governed by a pair of Liouville equations.
Extra force in Kaluza-Klein gravity theory
W. B. Belayev
2007-06-18
In induced matter Kaluza-Klein gravity theory the solution of the dynamics equations for the test particle on null path leads to additional force in four-dimensional space-time. We find such force from five-dimensional geodesic line equations and apply this approach to analysis of the asymmetrically warped space-time.
Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity
Unnikrishnan, C S
2015-01-01
Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitati...
Polchinski, Joseph [Kavli Institute for Theoretical Physics
2010-09-01
Gauge theories, which describe the particle interactions, are well understood, while quantum gravity leads to many puzzles. Remarkably, in recent years we have learned that these are actually dual, the same system written in different variables. On the one hand, this provides our most precise description of quantum gravity, resolves some long-standing paradoxes, and points to new principles. On the other, it gives a new perspective on strong interactions, with surprising connections to other areas of physics. I describe these ideas, and discuss current and future directions.
Introduction Basics of gravity theory
Visser, Matt
Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion;Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion and Conclusions Victoria U of Wellington - Feb 2nd 2009 #12;Introduction Basics of gravity theory Actions and Field
Loop quantum gravity and observations
A. Barrau; J. Grain
2015-10-28
Quantum gravity has long been thought to be completely decoupled from experiments or observations. Although it is true that smoking guns are still missing, there are now serious hopes that quantum gravity phenomena might be tested. We review here some possible ways to observe loop quantum gravity effects either in the framework of cosmology or in astroparticle physics.
Even-dimensional topological gravity from Chern-Simons gravity
Nelson Merino; Alfredo Perez; Patricio Salgado
2009-10-08
It is shown that the topological action for gravity in 2n-dimensions can be obtained from the 2n+1-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a 2n+1-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field $\\phi^{a}$, which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).
From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity
Kristina Giesel; Hanno Sahlmann
2013-01-02
We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity.
Quantum Gravity and Turbulence
Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze
2010-05-18
We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.
Christian Wiesendanger
2009-07-25
Isometrodynamics (ID), the gauge theory of the group of volume-preserving diffeomorphisms of an "inner" D-dimensional flat space, is tentatively interpreted as a fundamental theory of gravity. Dimensional analysis shows that the Planck length l_P - and through it \\hbar and \\Gamma - enters the gauge field action linking ID and gravity in a natural way. Noting that the ID gauge field couples solely through derivatives acting on "inner" space variables all ID fields are Taylor-expanded in "inner" space. Integrating out the "inner" space variables yields an effective field theory for the coefficient fields with l_P^2 emerging as the expansion parameter. For \\hbar goint to zero only the leading order field does not vanish. This classical field couples to the matter Noether currents and charges related to the translation invariance in "inner" space. A model coupling this leading order field to a matter point source is established and solved. Interpreting the matter Noether charge in terms of gravitational mass Newton's inverse square law is finally derived for a static gauge field source and a slowly moving test particle. Gravity emerges as potentially related to field variations over "inner" space and might microscopically be described by the ID gauge field or equivalently by an infinite string of coefficient fields only the leading term of which is related to the macroscopical effects of gravity.
Cosmology in general massive gravity theories
Comelli, D.; Nesti, F.; Pilo, L. E-mail: fabrizio.nesti@aquila.infn.it
2014-05-01
We study the cosmological FRW flat solutions generated in general massive gravity theories. Such a model are obtained adding to the Einstein General Relativity action a peculiar non derivative potentials, function of the metric components, that induce the propagation of five gravitational degrees of freedom. This large class of theories includes both the case with a residual Lorentz invariance as well as the case with rotational invariance only. It turns out that the Lorentz-breaking case is selected as the only possibility. Moreover it turns out that that perturbations around strict Minkowski or dS space are strongly coupled. The upshot is that even though dark energy can be simply accounted by massive gravity modifications, its equation of state w{sub eff} has to deviate from -1. Indeed, there is an explicit relation between the strong coupling scale of perturbations and the deviation of w{sub eff} from -1. Taking into account current limits on w{sub eff} and submillimiter tests of the Newton's law as a limit on the possible strong coupling scale, we find that it is still possible to have a weakly coupled theory in a quasi dS background. Future experimental improvements on short distance tests of the Newton's law may be used to tighten the deviation of w{sub eff} form -1 in a weakly coupled massive gravity theory.
Three-dimensional gravity and deformations of relativistic symmetries
Trzesniewski, T
2015-01-01
It is possible that relativistic symmetries become deformed in the semiclassical regime of quantum gravity. Mathematically, such deformations lead to the noncommutativity of spacetime geometry and non-vanishing curvature of momentum space. The best studied example is given by the $\\kappa$-Poincar\\'e Hopf algebra, associated with $\\kappa$-Minkowski space. On the other hand, the curved momentum space is a well-known feature of particles coupled to three-dimensional gravity. The purpose of this thesis was to explore some properties and mutual relations of the above two models. In particular, I study extensively the spectral dimension of $\\kappa$-Minkowski space. I also present an alternative limit of the Chern-Simons theory describing three-dimensional gravity with particles. Then I discuss the spaces of momenta corresponding to conical defects in higher dimensional spacetimes. Finally, I consider the Fock space construction for the quantum theory of particles in three-dimensional gravity.
Consistent Evolution with Different Time-Slicings in Quantum Gravity
R. Cosgrove
1996-02-20
Rovelli's `` quantum mechanics without time'' motivates an intrinsically time-slicing independent picture of reduced phase space quantum gravity, which may be described as ``quantization after evolution''. Sufficient criteria for carrying out quantization after evolution are developed in terms of a general concept of the classical limit of quantum mechanics. If these criteria are satisfied then it is possible to have consistent unitary evolution of operators, with respect to an infinite parameter family of time-slicings (and probably all time-slicings), with the correct classical limit. The criteria are particularly amenable to study in (2+1)-dimensional gravity, where the reduced phase space is finite dimensional.
Transmission line capital costs
Hughes, K.R.; Brown, D.R.
1995-05-01
The displacement or deferral of conventional AC transmission line installation is a key benefit associated with several technologies being developed with the support of the U.S. Department of Energy`s Office of Energy Management (OEM). Previous benefits assessments conducted within OEM have been based on significantly different assumptions for the average cost per mile of AC transmission line. In response to this uncertainty, an investigation of transmission line capital cost data was initiated. The objective of this study was to develop a database for preparing preliminary estimates of transmission line costs. An extensive search of potential data sources identified databases maintained by the Bonneville Power Administration (BPA) and the Western Area Power Administration (WAPA) as superior sources of transmission line cost data. The BPA and WAPA data were adjusted to a common basis and combined together. The composite database covers voltage levels from 13.8 to 765 W, with cost estimates for a given voltage level varying depending on conductor size, tower material type, tower frame type, and number of circuits. Reported transmission line costs vary significantly, even for a given voltage level. This can usually be explained by variation in the design factors noted above and variation in environmental and land (right-of-way) costs, which are extremely site-specific. Cost estimates prepared from the composite database were compared to cost data collected by the Federal Energy Regulatory Commission (FERC) for investor-owned utilities from across the United States. The comparison was hampered because the only design specifications included with the FERC data were voltage level and line length. Working within this limitation, the FERC data were not found to differ significantly from the composite database. Therefore, the composite database was judged to be a reasonable proxy for estimating national average costs.
R. Bluhm
2013-07-22
Gravitational theories with Lorentz violation must account for a number of possible features in order to be consistent theoretically and phenomenologically. A brief summary of these features is given here. They include evasion of a no-go theorem, connections between spontaneous Lorentz breaking and diffeomorphism breaking, the appearance of massless Nambu-Goldstone modes and massive Higgs modes, and the possibility of a Higgs mechanism in gravity.
Gravity, Dimension, Equilibrium, & Thermodynamics
Jerome Perez
2006-03-30
Is it actually possible to interpret gravitation as space's property in a pure classical way. Then, we note that extended self-gravitating system equilibrium depends directly on the number of dimension of the space in which it evolves. Given those precisions, we review the principal thermodynamical knowledge in the context of classical gravity with arbitrary dimension of space. Stability analyses for bounded 3D systems, namely the Antonov instability paradigm, are then rapproched to some amazing properties of globular clusters and galaxies.
U.S. Energy Information Administration (EIA) Indexed Site
Finished motor gaso- line formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regu- Energy...
U.S. Energy Information Administration (EIA) Indexed Site
Finished motor gaso- line formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations...
Perturbations of nested branes with induced gravity
Sbisà, Fulvio; Koyama, Kazuya E-mail: kazuya.koyama@port.ac.uk
2014-06-01
We study the behaviour of weak gravitational fields in models where a 4D brane is embedded inside a 5D brane equipped with induced gravity, which in turn is embedded in a 6D spacetime. We consider a specific regularization of the branes internal structures where the 5D brane can be considered thin with respect to the 4D one. We find exact solutions corresponding to pure tension source configurations on the thick 4D brane, and study perturbations at first order around these background solutions. To perform the perturbative analysis, we adopt a bulk-based approach and we express the equations in terms of gauge invariant and master variables using a 4D scalar-vector-tensor decomposition. We then propose an ansatz on the behaviour of the perturbation fields when the thickness of the 4D brane goes to zero, which corresponds to configurations where gravity remains finite everywhere in the thin limit of the 4D brane. We study the equations of motion using this ansatz, and show that they give rise to a consistent set of differential equations in the thin limit, from which the details of the internal structure of the 4D brane disappear. We conclude that the thin limit of the ''ribbon'' 4D brane inside the (already thin) 5D brane is well defined (at least when considering first order perturbations around pure tension configurations), and that the gravitational field on the 4D brane remains finite in the thin limit. We comment on the crucial role of the induced gravity term on the 5D brane.
Massive Gravity from Higher Derivative Gravity with Boundary Conditions
Minjoon Park; Lorenzo Sorbo
2012-10-29
With an appropriate choice of parameters, a higher derivative theory of gravity can describe a normal massive sector and a ghost massless sector. We show that, when defined on an asymptotically de Sitter spacetime with Dirichlet boundary conditions, such a higher derivative gravity can provide a framework for a unitary theory of massive gravity in four spacetime dimensions. The resulting theory is free not only of higher derivative ghosts but also of the Boulware-Deser mode.
Marcus S. Cohen
2002-08-02
Quantum gravity has been so elusive because we have tried to approach it by two paths which can never meet: quantum mechanics and general relativity. These contradict each other not only in superdense regimes, but also in the vacuum. We explore a straight road to quantum gravity here--the one mandated by Clifford-algebra covariance. This bridges the gap from microscales--where the massive Dirac propagator is a sum over null zig-zags--to macroscales--where we see the energy-momentum current, *T and the resulting Einstein curvature, *G. For massive particles, *T flows in the "cosmic time" direction, y^0--centrifugally in an expanding universe. Neighboring centrifugal currents of *T present opposite spacetime vorticities *G to the boundaries of each others' worldtubes, so they advect--i.e. attract, as we show here by integrating a Spin^c-4 Lagrangian by parts in the spinfluid regime. This boundary integral not only explains why stress-energy *T is the source for gravitational curvature *G, but also gives a value for the gravitational constant, kappa(x^0) that depends on the current scale factor of our expanding Friedmann 3-brane. On the microscopic scale, quantum gravity appears naturally as the statistical mechanics of null zig-zags of massive particles in "imaginary time," y^0.
Dr. Z's Math251 Handout #14.2 [Limits and Continuity] By Doron Zeilberger
Zeilberger, Doron
that there are "differ- enet limits for different lines" and hence the limit itself definitely does not exist. Alas
Geometric scalar theory of gravity
Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D.; Moschella, U. E-mail: eduhsb@cbpf.br E-mail: egoulart@cbpf.br E-mail: toniato@cbpf.br
2013-06-01
We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor — which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models — does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.
Shan Gao
2011-07-16
The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde's example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde's argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.
Peter West
2014-11-04
We consider the equation of motion in the gravity sector that arises from the non-linear realisation of the semi-direct product of E11 and its first fundamental representation, denoted by l1, in four dimensions. This equation is first order in derivatives and at low levels relates the usual field of gravity to a dual gravity field. When the generalised space-time is restricted to be the usual four dimensional space-time we show that this equation does correctly describe Einstein's theory at the linearised level. We also comment on previous discussions of dual gravity.
An Underlying Theory for Gravity
Yuan K. Ha
2012-08-14
A new direction to understand gravity has recently been explored by considering classical gravity to be a derived interaction from an underlying theory. This underlying theory would involve new degrees of freedom at a deeper level and it would be structurally different from classical gravitation. It may conceivably be a quantum theory or a non-quantum theory. The relation between this underlying theory and Einstein's gravity is similar to the connection between statistical mechanics and thermodynamics. We discuss the apparent lack of evidence of any quantum nature of gravity in this context.
Lifshitz Gravity for Lifshitz Holography
Tom Griffin; Petr Horava; Charles M. Melby-Thompson
2012-11-20
We argue that Horava-Lifshitz (HL) gravity provides the minimal holographic dual for Lifshitz-type field theories with anisotropic scaling and dynamical exponent z. First we show that Lifshitz spacetimes are vacuum solutions of HL gravity, without need for additional matter. Then we perform holographic renormalization of HL gravity, and show how it reproduces the full structure of the z=2 anisotropic Weyl anomaly in dual field theories in 2+1 dimensions, while its minimal relativistic gravity counterpart yields only one of two independent central charges in the anomaly.
Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity
C. S. Unnikrishnan; George T. Gillies
2015-08-03
Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity.
DETECTING GRAVITY MODES IN THE SOLAR {sup 8} B NEUTRINO FLUX
Lopes, Ilídio; Turck-Chièze, Sylvaine E-mail: ilopes@uevora.pt
2014-09-10
The detection of gravity modes produced in the solar radiative zone has been a challenge in modern astrophysics for more than 30 yr and their amplitude in the core is not yet determined. In this Letter, we develop a new strategy to look for standing gravity modes through solar neutrino fluxes. We note that due to a resonance effect, the gravity modes of low degree and low order have the largest impact on the {sup 8} B neutrino flux. The strongest effect is expected to occur for the dipole mode with radial order 2, corresponding to periods of about 1.5 hr. These standing gravity waves produce temperature fluctuations that are amplified by a factor of 170 in the boron neutrino flux for the corresponding period, in consonance with the gravity modes. From current neutrino observations, we determine that the maximum temperature variation due to the gravity modes in the Sun's core is smaller than 5.8 × 10{sup –4}. This study clearly shows that due to their high sensitivity to the temperature, the {sup 8} B neutrino flux time series is an excellent tool to determine the properties of gravity modes in the solar core. Moreover, if gravity mode footprints are discovered in the {sup 8} B neutrino flux, this opens a new line of research to probe the physics of the solar core as non-standing gravity waves of higher periods cannot be directly detected by helioseismology but could leave their signature on boron neutrino or on other neutrino fluxes.
Cosmological stability bound in massive gravity and bigravity
Fasiello, Matteo; Tolley, Andrew J. E-mail: andrew.j.tolley@case.edu
2013-12-01
We give a simple derivation of a cosmological bound on the graviton mass for spatially flat FRW solutions in massive gravity with an FRW reference metric and for bigravity theories. This bound comes from the requirement that the kinetic term of the helicity zero mode of the graviton is positive definite. The bound is dependent only on the parameters in the massive gravity potential and the Hubble expansion rate for the two metrics. We derive the decoupling limit of bigravity and FRW massive gravity, and use this to give an independent derivation of the cosmological bound. We recover our previous results that the tension between satisfying the Friedmann equation and the cosmological bound is sufficient to rule out all observationally relevant FRW solutions for massive gravity with an FRW reference metric. In contrast, in bigravity this tension is resolved due to different nature of the Vainshtein mechanism. We find that in bigravity theories there exists an FRW solution with late-time self-acceleration for which the kinetic terms for the helicity-2, helicity-1 and helicity-0 are generically nonzero and positive making this a compelling candidate for a model of cosmic acceleration. We confirm that the generalized bound is saturated for the candidate partially massless (bi)gravity theories but the existence of helicity-1/helicity-0 interactions implies the absence of the conjectured partially massless symmetry for both massive gravity and bigravity.
The role of information in gravity
M. Spaans
2009-07-24
It is argued that particle-specific information on energy-momentum adjusts the strength of gravity. This form of gravity has no free parameters, preserves Einstein gravity locally and predicts 6 times stronger accelerations on galaxy scales.
Gravity-Driven Intrusions in Stratified Fluids
Maurer, Benjamin D.
2011-01-01
5.5.1 Five interleaving interfacial gravity currents 5.5.2Ten interleaving interfacial gravity currents . 5.6in Iceland showing multiple gravity-driven intrusions c ´
Emergent gravity and ether-drift experiments
M. Consoli; L. Pappalardo
2010-05-04
According to several authors, gravity might be a long-wavelength phenomenon emerging in some 'hydrodynamic limit' from the same physical, flat-space vacuum viewed as a form of superfluid medium. In this framework, light might propagate in an effective acoustic geometry and exhibit a tiny anisotropy that could be measurable in the present ether-drift experiments. By accepting this view of the vacuum, one should also consider the possibility of sizeable random fluctuations of the signal that reflect the stochastic nature of the underlying `quantum ether' and could be erroneously interpreted as instrumental noise. To test the present interpretation, we have extracted the mean amplitude of the signal from various experiments with different systematics, operating both at room temperature and in the cryogenic regime. They all give the same consistent value = O (10^{-15}) which is precisely the magnitude expected in an emergent-gravity approach, for an apparatus placed on the Earth's surface. Since physical implications could be substantial, it would be important to obtain more direct checks from the instantaneous raw data and, possibly, with new experimental set-ups operating in gravity-free environments.
Abelian-Higgs strings in Rastall gravity
Eugenio R. Bezerra de Mello; Julio C. Fabris; Betti Hartmann
2015-04-02
In this paper we analyze Abelian-Higgs strings in a phenomenological model that takes quantum effects in curved space-time into account. This model, first introduced by Rastall, cannot be derived from an action principle. We formulate phenomenological equations of motion under the guiding principle of minimal possible deformation of the standard equations. We construct string solutions that asymptote to a flat space-time with a deficit angle by solving the set of coupled non-linear ordinary differential equations numerically. Decreasing the Rastall parameter from its Einstein gravity value we find that the deficit angle of the space-time increases and becomes equal to $2\\pi$ at some critical value of this parameter that depends on the remaining couplings in the model. For smaller values the resulting solutions are supermassive string solutions possessing a singularity at a finite distance from the string core. Assuming the Higgs boson mass to be on the order of the gauge boson mass we find that also in Rastall gravity this happens only when the symmetry breaking scale is on the order of the Planck mass. We also observe that for specific values of the parameters in the model the energy per unit length becomes proportional to the winding number, i.e. the degree of the map $S^1 \\rightarrow S^1$. Unlike in the BPS limit in Einstein gravity, this is, however, not connect to an underlying mathematical structure, but rather constitutes a would-be-BPS bound.
Durmus A. Demir
2011-12-11
It is shown that, under a conformal transformation with reference to the Higgs field, the Higgs boson can be completely decoupled from electroweak interactions with no apparent change in known properties of leptons, quarks and vector bosons. Higgs boson becomes part of a scalar-tensor gravity which can be relevant for Dark Energy. It interacts with matter sector via higher-dimensional terms (e.g. neutrino Majorana mass), and via the fields (of new physics) whose masses are not generated by the Higgs mechanism. Dark Matter and two-Higgs-doublet model are the simplest examples.
Lubricated viscous gravity currents
Kowal, Katarzyna N.; Worster, M. Grae
2015-02-10
) at their base. The presence of subglacial meltwater can be attributed to geothermal heating, frictional heating from glacier sliding, and ice melting under pressure from the weight of the ice † Email address for correspondence: K.Kowal@damtp.cam.ac.uk 2 K. N... -fed and a constant head was maintained in the reservoir. To minimize the amount Lubricated viscous gravity currents 15 mirror syringe pump reservoir glass sheet perspex sheet screen Golden Syrup Salt Solution 1 m Figure 6: Schematic of our experimental...
A new quasidilaton theory of massive gravity
Mukohyama, Shinji
2014-12-01
We present a new quasidilaton theory of Poincare invariant massive gravity, based on the recently proposed framework of matter coupling that makes it possible for the kinetic energy of the quasidilaton scalar to couple to both physical and fiducial metrics simultaneously. We find a scaling-type exact solution that expresses a self-accelerating de Sitter universe, and then analyze linear perturbations around it. It is shown that in a range of parameters all physical degrees of freedom have non-vanishing quadratic kinetic terms and are stable in the subhorizon limit, while the effective Newton's constant for the background is kept positive.
A high frequency resonance gravity gradiometer
Bagaev, S. N.; Kvashnin, N. L.; Skvortsov, M. N.; Bezrukov, L. B.; Krysanov, V. A.; Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Samoilenko, A. A.; Yudin, I. S.; Rudenko, V. N.
2014-06-15
A new setup OGRAN—the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events—gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.
Bimetric gravity and dark matter
Laura Bernard; Luc Blanchet; Lavinia Heisenberg
2015-07-10
We review some recent proposals for relativistic models of dark matter in the context of bimetric gravity. The aim is to solve the problems of cold dark matter (CDM) at galactic scales, and to reproduce the phenomenology of the modified Newtonian dynamics (MOND), while still being in agreement with the standard cosmological model $\\Lambda$-CDM at large scales. In this context a promising alternative is dipolar dark matter (DDM) in which two different species of dark matter particles are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. The phenomenology of MOND then results from a mechanism of gravitational polarization. Probably the best formulation of the model is within the framework of recently developed massive bigravity theories. Then the gravitational sector of the model is safe by construction, but a ghostly degree of freedom in the decoupling limit is still present in the dark matter sector. Future work should analyse the cosmological solutions of the model and check the post-Newtonian parameters in the solar system.
Reduced models for quantum gravity
T. Thiemann
1999-10-04
The preceding talks given at this conference have dealt mainly with general ideas for, main problems of and techniques for the task of quantizing gravity canonically. Since one of the major motivations to arrange for this meeting was that it should serve as a beginner's introduction to canonical quantum gravity, we regard it as important to demonstrate the usefulness of the formalism by means of applying it to simplified models of quantum gravity, here formulated in terms of Ashtekar's new variables. From the various, completely solvable, models that have been discussed in the literature we choose those that we consider as most suitable for our pedagogical reasons, namely 2+1 gravity and the spherically symmetric model. The former model arises from a dimensional, the latter from a Killing reduction of full 3+1 gravity. While 2+1 gravity is usually treated in terms of closed topologies without boundary of the initial data hypersurface, the toplogy for the spherically symmetric system is chosen to be asymptotically flat. Finally, 2+1 gravity is more suitably quantized using the loop representation while spherically symmetric gravity is easier to quantize via the self-dual representation. Accordingly, both types of reductions, both types of topologies and both types of representations that are mainly employed in the literature in the context of the new variables come into practice. What makes the discussion especially clear is the fact that for both models the reduced phase space turns out to be finitely dimensional.
Irrotational-fluid cosmologies in fourth-order gravity
Amare Abebe; Maye Elmardi
2015-04-25
In this paper, we explore classes of irrotational-fluid cosmological models in the context of f(R)-gravity in an attempt to put some theoretical and mathematical restrictions on the form of the f(R) gravitational Lagrangian. In particular, we investigate the consistency of linearised dust models for shear-free cases as well as in the limiting cases when either the gravito-magnetic or gravito-elecric components of the Weyl tensor vanish. We also discuss the existence and consistency of classes of non-expanding irrotational spacetimes in f(R)-gravity.
A short note on gravity with tensor auxiliary fields
Máximo Bañados; Diego Cohen
2013-09-24
We consider gravity coupled to a second metric in the strong coupling limit, where the second kinetic term is absent. This system belongs to the recently discussed class of models of "gravity with auxiliary fields" by Pani et al. We prove that, in vacuum, these theories are always equivalent to GR with a cosmological constant, even in the case where the auxiliary field equations contain identities leaving undetermined functions. In the situation where some functions are undetermined, the actual value of the cosmological constant is dictated by an initial condition, and not by the parameters in the action.
CP violation and gravity as the weakest force
Archil Kobakhidze
2008-07-03
We argue that CP violation has rather dramatic impact on the "gravity as the weakest force" conjecture. Namely we find that new ultraviolet scale must be $\\Lambda \\lesssim \\theta g^3 M_P$, where $\\theta$ is an effective parameter describing CP violation and $g$ is the gauge coupling constant. The bound implies that CP-conserving limit is discontinuous, and possibly indicates that the class of effective theories with strict CP conservation is inconsistent with a fundamental theory incorporating quantum gravity. At the same time, the mass hierarchy problem can be explained due to the smallness of the CP violation, $\\theta \\sim 10^{-15}$ or so.
WILSON-BAPPU EFFECT: EXTENDED TO SURFACE GRAVITY
Park, Sunkyung; Kang, Wonseok; Lee, Jeong-Eun; Lee, Sang-Gak E-mail: wskang@khu.ac.kr E-mail: sanggak@snu.ac.kr
2013-10-01
In 1957, Wilson and Bappu found a tight correlation between the stellar absolute visual magnitude (M{sub V} ) and the width of the Ca II K emission line for late-type stars. Here, we revisit the Wilson-Bappu relationship (WBR) to claim that the WBR can be an excellent indicator of stellar surface gravity of late-type stars as well as a distance indicator. We have measured the width (W) of the Ca II K emission line in high-resolution spectra of 125 late-type stars obtained with the Bohyunsan Optical Echelle Spectrograph and adopted from the Ultraviolet and Visual Echelle Spectrograph archive. Based on our measurement of the emission line width (W), we have obtained a WBR of M{sub V} = 33.76 - 18.08 log W. In order to extend the WBR to being a surface gravity indicator, stellar atmospheric parameters such as effective temperature (T{sub eff}), surface gravity (log g), metallicity ([Fe/H]), and micro-turbulence ({xi}{sub tur}) have been derived from self-consistent detailed analysis using the Kurucz stellar atmospheric model and the abundance analysis code, MOOG. Using these stellar parameters and log W, we found that log g = -5.85 log W+9.97 log T{sub eff} - 23.48 for late-type stars.
Parameterized post-Newtonian formalism for multimetric gravity
Manuel Hohmann
2014-06-14
We discuss the post-Newtonian limit of multimetric gravity theories with $N \\geq 2$ metric tensors and a corresponding number of standard model copies, and construct an extension of the parameterized post-Newtonian (PPN) formalism. This extended formalism allows a characterization of multimetric gravity theories by a set of constant parameters. The multimetric PPN parameters we derive are a superset of the standard PPN parameters, which have been measured using high-precision experiments in the solar system. We apply our formalism to a class of theories which we previously discussed in the context of cosmology and gravitational waves, and which feature an accelerating expansion of the universe. A comparison between our results and the measured PPN parameters shows that multimetric gravity is fully compatible with solar system observations.
Spin-gravity coupling and gravity-induced quantum phases
Giorgio Papini
2007-09-06
External gravitational fields induce phase factors in the wave functions of particles. The phases are exact to first order in the background gravitational field, are manifestly covariant and gauge invariant and provide a useful tool for the study of spin-gravity coupling and of the optics of particles in gravitational or inertial fields. We discuss the role that spin-gravity coupling plays in particular problems.
Gravity's Rainbow: a bridge towards Horava-Lifshitz gravity
Remo Garattini; Emmanuel N. Saridakis
2014-11-25
We investigate the connection between Gravity's Rainbow and Horava-Lifshitz gravity, since both theories incorporate a modification in the UltraViolet regime which improves their quantum behavior at the cost of the Lorentz invariance loss. In particular, extracting the Wheeler-De Witt equations of the two theories in the case of Friedmann-Lemaitre-Robertson-Walker and spherically symmetric geometries, we establish a correspondence that bridges them.
Unscreening modified gravity in the matter power spectrum
Lucas Lombriser; Fergus Simpson; Alexander Mead
2015-01-20
Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k Solar System tests or distance indicators in unscreened dwarf galaxies.
Unscreening Modified Gravity in the Matter Power Spectrum
Lucas Lombriser; Fergus Simpson; Alexander Mead
2015-09-21
Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism.
Classifying Linearly Shielded Modified Gravity Models in Effective Field Theory
Lucas Lombriser; Andy Taylor
2015-01-31
We study the model space generated by the time-dependent operator coefficients in the effective field theory of the cosmological background evolution and perturbations of modified gravity and dark energy models. We identify three classes of modified gravity models that reduce to Newtonian gravity on the small scales of linear theory. These general classes contain enough freedom to simultaneously admit a matching of the concordance model background expansion history. In particular, there exists a large model space that mimics the concordance model on all linear quasistatic subhorizon scales as well as in the background evolution. Such models also exist when restricting the theory space to operators introduced in Horndeski scalar-tensor gravity. We emphasize that whereas the partially shielded scenarios might be of interest to study in connection with tensions between large and small scale data, with conventional cosmological probes, the ability to distinguish the fully shielded scenarios from the concordance model on near-horizon scales will remain limited by cosmic variance. Novel tests of the large-scale structure remedying this deficiency and accounting for the full covariant nature of the alternative gravitational theories, however, might yield further insights on gravity in this regime.
Cosmological perturbations in unimodular gravity
Gao, Caixia; Brandenberger, Robert H.; Cai, Yifu; Chen, Pisin E-mail: rhb@hep.physics.mcgill.ca E-mail: chen@slac.stanford.edu
2014-09-01
We study cosmological perturbation theory within the framework of unimodular gravity. We show that the Lagrangian constraint on the determinant of the metric required by unimodular gravity leads to an extra constraint on the gauge freedom of the metric perturbations. Although the main equation of motion for the gravitational potential remains the same, the shift variable, which is gauge artifact in General Relativity, cannot be set to zero in unimodular gravity. This non-vanishing shift variable affects the propagation of photons throughout the cosmological evolution and therefore modifies the Sachs-Wolfe relation between the relativistic gravitational potential and the microwave temperature anisotropies. However, for adiabatic fluctuations the difference between the result in General Relativity and unimodular gravity is suppressed on large angular scales. Thus, no strong constraints on the theory can be derived.
Gravity Currents in Aquatic Canopies
Tanino, Yukie
A lock exchange experiment is used to investigate the propagation of gravity currents through a random array of rigid, emergent cylinders which represents a canopy of aquatic plants. As canopy drag increases, the propagating ...
Gravity as an Entropic Phenomenon
Abhiram Chivukula
2010-11-19
The unification of gravity with the three other forces has been an important goal of physics for some time now, because a quantum theory of gravity is necessary to explain the universe at its earliest moments. Its pursuit has largely assumed gravity's independent existence, but E. Verlinde proposed that gravity is not a fundamental force but a macroscopic phenomenon that emerges as a result of thermodynamic principles applied to the information of mass distributions. Under this framework we consider the roles played by quantum microstates, entanglement, information theory, the AdS/CFT Correspondence, and String Theory in general. We also ask whether Verlinde's proposal suggests that action principles should be thermodynamic in nature.
Gravity as an Entropic Phenomenon
Chivukula, Abhiram
2010-01-01
The unification of gravity with the three other forces has been an important goal of physics for some time now, because a quantum theory of gravity is necessary to explain the universe at its earliest moments. Its pursuit has largely assumed gravity's independent existence, but E. Verlinde proposed that gravity is not a fundamental force but a macroscopic phenomenon that emerges as a result of thermodynamic principles applied to the information of mass distributions. Under this framework we consider the roles played by quantum microstates, entanglement, information theory, the AdS/CFT Correspondence, and String Theory in general. We also ask whether Verlinde's proposal suggests that action principles should be thermodynamic in nature.
Testing Gravity Theories Using Stars
Jeremy Sakstein; Bhuvnesh Jain; Vinu Vikram
2014-09-12
Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.
Zeilberger, Doron
that there are "differ- enet limits for different lines" and hence the limit itself definitely does not exist. Alas
Line-of-Sight Networks Alan Frieze
Kleinberg, Jon
-of-sight restrictions. Here we propose a random-graph model incorporating both range limitations and line-of-sight con- 0329064, CNS-0403340, and BCS-0537606; work done in part while on sabbatical leave at Carnegie Mellon
Dualities and Emergent Gravity: Gauge/Gravity Duality
Sebastian de Haro
2015-09-09
In this paper I develop a framework for relating dualities and emergence: two notions that are close to each other but also exclude one another. I adopt the conception of duality as 'isomorphism', cashing it out in terms of three conditions. These three conditions prompt two conceptually different ways in which a duality can be modified to make room for emergence; and I argue that this exhausts the possibilities for combining dualities and emergence (via coarse-graining). I apply this framework to gauge/gravity dualities, considering in detail three examples: AdS/CFT, Verlinde's scheme, and black holes. My main point about gauge/gravity dualities is that the theories involved, qua theories of gravity, must be background-independent. I distinguish two senses of background-independence: (i) minimalistic and (ii) extended. The former is sufficiently strong to allow for a consistent theory of quantum gravity; and AdS/CFT is background-independent on this account; while Verlinde's scheme best fits the extended sense. I argue that this extended sense should be applied with some caution: on pain of throwing the baby (general relativity) out with the bath-water (extended background-independence). Nevertheless, it is an interesting and potentially fruitful heuristic principle for quantum gravity theory construction. The interpretation of dualities is articulated in terms of: (i) epistemic and metaphysical commitments; (ii) parts vs. wholes. I then analyse the emergence of gravity in gauge/gravity dualities in terms of the two available conceptualisations of emergence; and I show how emergence in AdS/CFT and in Verlinde's scenario differ from each other. Finally, I give a novel derivation of the Bekenstein-Hawking black hole entropy formula based on Verlinde's scheme; the derivation sheds light on several aspects of Verlinde's scheme and how it compares to Bekenstein's original calculation.
E. Gaztanaga; R. Juszkiewicz
2001-08-21
We present a new constraint on the biased galaxy formation picture. Gravitational instability theory predicts that the two-point mass density correlation function, \\xi(r), has an inflection point at the separation r=r_0, corresponding to the boundary between the linear and nonlinear regime of clustering, \\xi = 1. We show how this feature can be used to constrain the square of the biasing parameter, b^2 = \\xi_g / \\xi on scales r = r_0, where \\xi_g is the galaxy-galaxy correlation function, allowed to differ from \\xi. We apply our method to real data: the \\xi_g(r), estimated from the APM galaxy survey. Our results suggest that the APM galaxies trace the mass at separations r > 5 Mpc/h, where h is the Hubble constant in units of 100 km/s Mpc. The present results agree with earlier studies, based on comparing higher order correlations in the APM with weakly non-linear perturbation theory. Both approaches constrain the "b" factor to be within 20% of unity. If the existence of the feature we identified in the APM \\xi_g(r) -- the inflection point near \\xi_g = 1 -- is confirmed by more accurate surveys, we may have discovered gravity's smoking gun: the long awaited ``shoulder'' in \\xi, predicted by Gott and Rees 25 years ago.
D. Fargion
2005-11-23
The present gravitational wave detectors are reaching lowest metric deviation fields able to detect galactic and extra-galactic gravitational waves, related to Supernova explosions up to Virgo cluster. The same gravitational wave detector are nevertheless almost able to reveal, in principle, near field Newtonian gravitational perturbations due to fast huge mass displacements as the ones occurring during largest Earth-Quake or Tsunami as the last on 26nd December 2004 in Asiatic area. Virgo and Ligo detector are unfortunately recording on high frequencies (above tens Hz) while the signal of the Tsunami lay at much lower range (below 0.1 Hz). Nevertheless prompt gravitational near field deformation by the Tsunami might reach the future LISA threshold sensitivity and frequency windows if such an array is located nearby (3000-10000) km distances. Unfortunately the present LISA system should be located at Lagrange point too far (1.5 million km. far away). We note however that the later continental mass rearrangement and their gravitational field assessment on Earth must induce, for Richter Magnitude 9-like Tsunami, a different terrestrial inertia momentum and a different principal rotation axis. In conclusion we remind that gravitational geodetic deviation on new precise satellites (GOCE 2006), assisted by GPS network, might nevertheless reach in the near future the needed threshold and accuracy to reveal Tsunami by their prompt tidal gravity field deviations . An array of such geoid detector maybe correlated with LISA-like satellite on Earth orbits may offer the fastest alarm system.
Critical gravity as van Dam-Veltman-Zakharov discontinuity in anti de Sitter space
Yun Soo Myung
2011-07-20
We consider critical gravity as van Dam-Vletman-Zakharov (vDVZ) discontinuity in anti de Sitter space. For this purpose, we introduce the higher curvature gravity. This discontinuity can be confirmed by calculating the residues of relevant poles explicitly. For the non-critical gravity of $0
GRAVITY: The adaptive optics assisted, two object beam combiner for the VLTI
S. Gillessen; G. Perrin; W. Brandner; C. Straubmeier; F. Eisenhauer; S. Rabien; A. Eckart; P. Lena; R. Genzel; T. Paumard; S. Hippler
2006-07-17
We present the adaptive optics assisted, near-infrared VLTI instrument - GRAVITY - for precision narrow-angle astrometry and interferometric phase referenced imaging of faint objects. Precision astrometry and phase-referenced interferometric imaging will realize the most advanced vision of optical/infrared interferometry with the VLT. Our most ambitious science goal is to study motions within a few times the event horizon size of the Galactic Center massive black hole and to test General Relativity in its strong field limit. We define the science reference cases for GRAVITY and derive the top level requirements for GRAVITY. The installation of the instrument at the VLTI is planned for 2012.
New ground state for quantum gravity
Joao Magueijo; Laura Bethke
2012-07-03
In this paper we conjecture the existence of a new "ground" state in quantum gravity, supplying a wave function for the inflationary Universe. We present its explicit perturbative expression in the connection representation, exhibiting the associated inner product. The state is chiral, dependent on the Immirzi parameter, and is the vacuum of a second quantized theory of graviton particles. We identify the physical and unphysical Hilbert sub-spaces. We then contrast this state with the perturbed Kodama state and explain why the latter can never describe gravitons in a de Sitter background. Instead, it describes self-dual excitations, which are composites of the positive frequencies of the right-handed graviton and the negative frequencies of the left-handed graviton. These excitations are shown to be unphysical under the inner product we have identified. Our rejection of the Kodama state has a moral tale to it: the semi-classical limit of quantum gravity can be the wrong path for making contact with reality (which may sometimes be perturbative but nonetheless fully quantum). Our results point towards a non-perturbative extension, and we present some conjectures on the nature of this hypothetical state.
Hemodynamic Monitoring TRANSTHORACIC LINES
Kay, Mark A.
and with position changes. 5. All lines should have either heparinized saline or D5W infusing. 6. Avoid infusing the line. 9. Never use LA for infusions or bolus medications. 10. Vigilant observation for AIR. B. Line
Conformal weldings of random surfaces: SLE and the quantum gravity zipper
Sheffield, Scott
2010-01-01
We construct a conformal welding of two Liouville quantum gravity random surfaces and show that the interface between them is a random fractal curve called the Schramm-Loewner evolution (SLE), thereby resolving a variant of a conjecture of Peter Jones. We also demonstrate some surprising symmetries of this construction, which are consistent with the belief that (path decorated) random planar maps have (SLE-decorated) Liouville quantum gravity as a scaling limit. We present several precise conjectures and open questions.
Conformal weldings of random surfaces: SLE and the quantum gravity zipper
Scott Sheffield
2015-09-23
We construct a conformal welding of two Liouville quantum gravity random surfaces and show that the interface between them is a random fractal curve called the Schramm-Loewner evolution (SLE), thereby resolving a variant of a conjecture of Peter Jones. We also demonstrate some surprising symmetries of this construction, which are consistent with the belief that (path decorated) random planar maps have (SLE-decorated) Liouville quantum gravity as a scaling limit. We present several precise conjectures and open questions.
Conformal Lifshitz Gravity from Holography
Tom Griffin; Petr Horava; Charles M. Melby-Thompson
2012-04-03
We show that holographic renormalization of relativistic gravity in asymptotically Lifshitz spacetimes naturally reproduces the structure of gravity with anisotropic scaling: The holographic counterterms induced near anisotropic infinity take the form of the action for gravity at a Lifshitz point, with the appropriate value of the dynamical critical exponent $z$. In the particular case of 3+1 bulk dimensions and $z=2$ asymptotic scaling near infinity, we find a logarithmic counterterm, related to anisotropic Weyl anomaly of the dual CFT, and show that this counterterm reproduces precisely the action of conformal gravity at a $z=2$ Lifshitz point in 2+1 dimensions, which enjoys anisotropic local Weyl invariance and satisfies the detailed balance condition. We explain how the detailed balance is a consequence of relations among holographic counterterms, and point out that a similar relation holds in the relativistic case of holography in $AdS_5$. Upon analytic continuation, analogous to the relativistic case studied recently by Maldacena, the action of conformal gravity at the $z=2$ Lifshitz point features in the ground-state wavefunction of a gravitational system with an interesting type of spatial anisotropy.
Nonsingular cosmology from evolutionary quantum gravity
Francesco Cianfrani; Giovanni Montani; Fabrizio Pittorino
2014-10-30
We provide a cosmological implementation of the evolutionary quantum gravity, describing an isotropic Universe, in the presence of a negative cosmological constant and a massive (preinflationary) scalar field. We demonstrate that the considered Universe has a nonsingular quantum behavior, associated to a primordial bounce, whose ground state has a high occupation number. Furthermore, in such a vacuum state, the super-Hamiltonian eigenvalue is negative, corresponding to a positive emerging dust energy density. The regularization of the model is performed via a polymer quantum approach to the Universe scale factor and the proper classical limit is then recovered, in agreement with a preinflationary state of the Universe. Since the dust energy density is redshifted by the Universe deSitter phase and the cosmological constant does not enter the ground state eigenvalue, we get a late-time cosmology, compatible with the present observations, endowed with a turning point in the far future.
Phenomenologically viable Lorentz-violating quantum gravity
Sotiriou, Thomas; Weinfurtner, Silke
2009-01-01
Horava's "Lifschitz point gravity" has many desirable features, but in its original incarnation one is forced to accept a non-zero cosmological constant of the wrong sign to be compatible with observation. We develop an extension of Horava's model that abandons "detailed balance", and in 3+1 dimensions exhibit all five marginal (renormalizable) and four relevant (super-renormalizable) operators, as determined by power counting. We also consider the classical limit of this theory, evaluate the Hamiltonian and super-momentum constraints, and extract the classical equations of motion in a form similar to the ADM formulation of general relativity. This puts the model in a framework amenable to developing detailed precision tests.
New Models of f(R) Theories of Gravity
J. Kluson
2009-11-04
We introduce new models of f(R) theories of gravity that are generalization of Horava-Lifshitz gravity.
Plains and Eastern Clean Line Transmission Line: Comment from...
Plains and Eastern Clean Line Transmission Line: Comment from Marshall Hughes Plains and Eastern Clean Line Transmission Line: Comment from Marshall Hughes Comment submitted on...
Plains and Eastern Clean Line Transmission Line: Comment from...
Office of Environmental Management (EM)
from Block Plains and Eastern Clean Line: Arkansas and Oklahoma Plains and Eastern Clean Line Transmission Line: Comment from Block Plains and Eastern Clean Line: Arkansas and...
The Gravity Field of the Earth and Coriolis Effects.... The gravity field
Riser, Stephen C.
The Gravity Field of the Earth and Coriolis Effects.... The gravity field Stationary particles #12;Gravity.... Newton's Universal Law of Gravitation: The force between any two particles having.673 ×10-11 newton-meter2/kilogram2) #12;Gravity.... In vector form, or, 21 è force on 2 due to 1 12 è
Fargion, D
2004-01-01
The present gravitational wave detectors are reaching lowest metric deviation fields able to detect galactic and extra-galactic gravitational waves, related to Supernova explosions up to Virgo cluster. The same gravitational wave detector are nevertheless almost able to reveal near field gravitational perturbations due to fast huge mass displacements as the ones occurring during largest Earth-Quake or Tsunami as the last on 26th December 2004 in Asiatic area. The prompt gravitational near field deformation by the Tsunami may reach the LIGO threshold sensitivity within 3000-10000 km distances. Their eventual discover (in LIGO data or in future on-line detector arrays) may offer the most rapid warning alarm system on earth. Nevertheless the later continental mass rearrangement and their gravitational field assessment on Earth must induce, for Richter Magnitude 9 Tsunami, a different terrestrial inertia momentum and a different rotation axis, as well as a detectable shrinking of the Earth radius of nearly R =1.7...
Modified Entropic Gravity and Cosmology
Miguel Zumalacarregui
2012-02-06
It has been recently proposed that gravity might be an entropic force. Although a well defined fundamental description for such a mechanism is still lacking, it is still possible to address the viability of phenomenological models of entropic-inspired modified gravities. I will summarize some recent work directed to using cosmology as a tool to constraint scenarios in which the modifications are aimed to explain the physics behind dark energy and inflation. A phenomenological modification is able to explain cosmic acceleration at the background level and fit observations, but simple inflation models with higher curvature corrections are in conflict with late time matter domination.
Starobinsky Model in Rainbow Gravity
Chatrabhuti, Auttakit; Channuie, Phongpichit
2015-01-01
In this work, we study Starobinsky model of inflation in the context of gravity's rainbow theory. We propose that gravity rainbow functions can be written in the power-law form of the Hubble parameter. We present a detailed derivation of the spectral index of curvature perturbation and the tensor-to-scalar ratio and compare the predictions of our models with Planck 2015 data. We discover, by taking $N_{k}=70$ e-folds and requiring our predictions to agree with the Planck data at the one sigma confidence level, the rainbow parameter would satisfy $\\lambda\\lesssim 1.0$.
de Sitter gravity/Euclidean conformal gravity correspondence
Chatterjee, Atreya
2015-01-01
The holographic dual of a gravitational theory around the de Sitter background is argued to be a Euclidean conformal gravity theory in one fewer dimensions. The measure for the holographic theory naturally includes a sum over topologies as well as conformal structures.
679.24 Gear Limitations 50 CFR 679b24.docx 679.24 Gear Limitations Page 1 of 5
§ 679.24 Gear Limitations 50 CFR 679b24.docx § 679.24 Gear Limitations Page 1 of 5 Updated May 5, 2014 § 679.24 Gear limitations. Regulations pertaining to vessel and gear markings are set forth to § 300.62 of chapter III of this title. (a) Marking of hook-and-line, longline pot, and pot-and-line gear
Gravity Transform for Input Conditioning in
Paiva, António R. C.
Gravity Transform for Input Conditioning in Brain Machine Interfaces António R. C. Paiva, José C. Motivation 2. Methods i. Gravity Transform ii. Modeling and output sensitivity analysis 3. Data Analysis #12;3 Outline 1. Motivation 2. Methods i. Gravity Transform ii. Modeling and output sensitivity analysis 3. Data
Emergent 4D Gravity from Matrix Models
Harold Steinacker
2007-12-19
Recent progress in the understanding of gravity on noncommutative spaces is discussed. A gravity theory naturally emerges from matrix models of noncommutative gauge theory. The effective metric depends on the dynamical Poisson structure, absorbing the degrees of freedom of the would-be U(1) gauge field. The gravity action is induced upon quantization.
Further stable neutron star models from f(R) gravity
Astashenok, Artyom V.; Capozziello, Salvatore; Odintsov, Sergei D. E-mail: capozziello@na.infn.it
2013-12-01
Neutron star models in perturbative f(R) gravity are considered with realistic equations of state. In particular, we consider the FPS, SLy and other equations of state and a case of piecewise equation of state for stars with quark cores. The mass-radius relations for f(R) = R+R(e{sup ?R/R{sub 0}}?1) model and for R{sup 2} models with logarithmic and cubic corrections are obtained. In the case of R{sup 2} gravity with cubic corrections, we obtain that at high central densities (? > 10?{sub ns}, where ?{sub ns} = 2.7 × 10{sup 14} g/cm{sup 3} is the nuclear saturation density), stable star configurations exist. The minimal radius of such stars is close to 9 km with maximal mass ? 1.9M{sub ?} (SLy equation). A similar situation takes place for AP4 and BSK20 EoS. Such an effect can give rise to more compact stars than in General Relativity. If observationally identified, such objects could constitute a formidable signature for modified gravity at astrophysical level. Another interesting result can be achieved in modified gravity with only a cubic correction. For some EoS, the upper limit of neutron star mass increases and therefore these EoS can describe realistic star configurations (although, in General Relativity, these EoS are excluded by observational constraints)
Wilson Line Integrals in the Unparticle Action
A. Lewis Licht
2008-05-25
We consider the unparticle action that is made gauge invariant by inclusion of an open Wilson line factor. In deriving vertexes from such an action it has been customary to use a form of differentiating the Wilson line originally proposed by Mandelstam. Using a simple example, we show that the Mandelstam derivative is mathematically inconsistent. We show that there are two ways to define differentiation of the Wilson line. The mathematically consistent method is to differentiate the explicit dependence of the line on the endpoint. The other method is a functional derivative and corresponds in a limiting case to the Mandelstam derivative. We also show that the only path that can be used in the Wilson line integral that leaves the unparticle action both Poincare and scale invariant is the straight line.
Thomas Rauch
2006-07-11
NLTE spectral analyses of high-gravity central stars by means of state-of-the-art model atmosphere techniques provide information about the precursor AGB stars. The hydrogen-deficient post-AGB stars allow investigations on the intershell matter which is apparently exhibited at the stellar surface. We summarize recent results from imaging, spectroscopy, and spectropolarimetry.
Kenneth Dalton
2010-06-11
It is shown that gravity generates mass for the fermion. It does so by coupling directly with the spinor field. The coupling term is invariant with respect to the electroweak gauge group $ U(1) \\otimes SU(2)_L. $ It replaces the fermion mass term $ m\\bar{\\psi} \\psi $.
Cosmological Hints of Modified Gravity ?
Eleonora Di Valentino; Alessandro Melchiorri; Joseph Silk
2015-09-24
The recent measurements of Cosmic Microwave Background temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the $\\Lambda$CDM cosmological model. However interesting hints of slight deviations from $\\Lambda$CDM have been found, including a $95 \\%$ c.l. preference for a "modified gravity" structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called $A_{lens}$ anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to $\\sigma_8=0.815_{-0.048}^{+0.032}$, in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of $\\tau=0.059\\pm0.020$ (to be compared with the value of $\\tau= 0.079 \\pm 0.017$ obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneracies with other parameters, including the neutrino effective number, the running of the spectral index and the amount of primordial helium. The indication for modified gravity is still present at about $95\\%$ c.l., and could become more significant if lower values of $\\tau$ were to be further confirmed by future cosmological and astrophysical data.
Astrophysical tests of modified gravity
Sakstein, Jeremy Aaron
2014-10-07
galaxies from our own. This means that the inferred distance to an unscreened galaxy using a stellar effect that depends on the law gravity will not agree with a measurement using a different method that is insensitive gravitational physics. We exploit...
Imprint of modified Einstein's gravity on white dwarfs: Unifying type Ia supernovae
Das, Upasana
2015-01-01
We establish the importance of modified Einstein's gravity (MG) in white dwarfs (WDs) for the first time in the literature. We show that MG leads to significantly sub- and super-Chandrasekhar limiting mass WDs, depending on a single model parameter. However, conventional WDs on approaching Chandrasekhar's limit are expected to trigger type Ia supernovae (SNeIa), a key to unravel the evolutionary history of the universe. Nevertheless, observations of several peculiar, under- and over-luminous SNeIa argue for the limiting mass widely different from Chandrasekhar's limit. Explosions of MG induced sub- and super-Chandrasekhar limiting mass WDs explain under- and over-luminous SNeIa respectively, thus unifying these two apparently disjoint sub-classes. Our discovery questions both the global validity of Einstein's gravity and the uniqueness of Chandrasekhar's limit.
Saturated nucleate pool boiling of oxygen under magnetically-enhanced effective gravity
T. A. Corcovilos; M. E. Turk; D. M. Strayer; N. N. Asplund; N. -C. Yeh
2007-02-01
We investigate the effect of enhancing gravity on saturated nucleate pool boiling of oxygen for effective gravities of 1g, 6.0g, and 16g (g=9.8 m/s^2) at a saturation pressure of 760 torr and for heat fluxes of 10 ~ 3000 W/m^2. The effective gravity on the oxygen is increased by applying a magnetic body force generated by a superconducting solenoid. We measure the heater temperature (expressed as a reduced superheat) as a function of heat flux and fit this data to a piecewise power-law/linear boiling curve. At low heat flux (<400 W/m^2) the superheat is proportional to the cube root of the heat flux. At higher heat fluxes, the superheat is a linear function of the heat flux. To within statistical uncertainties, which are limited by variations among experimental runs, we find no variation of the boiling curve over our applied gravity range.
The Dark Gravity model predictions for Gravity Probe B
Frederic Henry-Couannier
2007-10-23
The previous version of this article gave erroneous predictions. The correct uptodate predictions can be found in the section devoted to gravitomagnetism in the living review of the Dark Gravity theory: gr-qc/0610079 The most natural prediction is zero frame dragging and the same geodetic effect as predicted by GR. However, a straightforward extension of the theory could lead to the same frame-dragging as in GR.
Gravity monitoring of CO2 movement during sequestration: Model studies
Gasperikova, E.; Hoversten, G.M.
2008-07-15
We examine the relative merits of gravity measurements as a monitoring tool for geological CO{sub 2} sequestration in three different modeling scenarios. The first is a combined CO{sub 2} enhanced oil recovery (EOR) and sequestration in a producing oil field, the second is sequestration in a brine formation, and the third is for a coalbed methane formation. EOR/sequestration petroleum reservoirs have relatively thin injection intervals with multiple fluid components (oil, hydrocarbon gas, brine, and CO{sub 2}), whereas brine formations usually have much thicker injection intervals and only two components (brine and CO{sub 2}). Coal formations undergoing methane extraction tend to be thin (3-10 m), but shallow compared to either EOR or brine formations. The injection of CO{sub 2} into the oil reservoir produced a bulk density decrease in the reservoir. The spatial pattern of the change in the vertical component of gravity (G{sub z}) is directly correlated with the net change in reservoir density. Furthermore, time-lapse changes in the borehole G{sub z} clearly identified the vertical section of the reservoir where fluid saturations are changing. The CO{sub 2}-brine front, on the order of 1 km within a 20 m thick brine formation at 1900 m depth, with 30% CO{sub 2} and 70% brine saturations, respectively, produced a -10 Gal surface gravity anomaly. Such anomaly would be detectable in the field. The amount of CO{sub 2} in a coalbed methane test scenario did not produce a large enough surface gravity response; however, we would expect that for an industrial size injection, the surface gravity response would be measurable. Gravity inversions in all three scenarios illustrated that the general position of density changes caused by CO{sub 2} can be recovered, but not the absolute value of the change. Analysis of the spatial resolution and detectability limits shows that gravity measurements could, under certain circumstances, be used as a lower-cost alternative to seismic measurements.
Clouds of strings in third-order Lovelock gravity
Sushant G. Ghosh; Uma Papnoi; Sunil D. Maharaj
2014-08-20
Lovelock theory is a natural extension of the Einstein theory of general relativity to higher dimensions in which the first and second orders correspond, respectively, to general relativity and Einstein-Gauss-Bonnet gravity. We present exact black hole solutions of $D\\geq 4$-dimensional spacetime for first-, second-, and third-order Lovelock gravities in a string cloud background. Further, we compute the mass, temperature, and entropy of black hole solutions for the higher-dimensional general relativity and Einstein-Gauss-Bonnet theories and also perform thermodynamic stability of black holes. It turns out that the presence of the Gauss-Bonnet term and/or background string cloud completely changes the black hole thermodynamics. Interestingly, the entropy of a black hole is unaffected due to a background string cloud. We rediscover several known spherically symmetric black hole solutions in the appropriate limits.
MOND-like acceleration in integrable Weyl geometric gravity
Erhard Scholz
2015-10-15
In this paper a Weyl geometric scalar tensor theory of gravity with scalar field $\\Phi$ and scale invariant cubic ("aquadratic") kinetic Lagrangian is introduced. Einstein gauge (comparable to Einstein frame in Jordan-Brans-Dicke theory) is most natural for studying trajectories. In it, the Weylian scale connection induces an additional acceleration which in the weak field, static, low velocity limit acquires the deep MOND form of Milgrom/Bekenstein's gravity. The energy momentum of $\\Phi$ leads to another add on to Newton acceleration. Both additional accelerations together imply a MOND-ian phenomenology of the model. It has unusual transition functions. They imply higher phantom energy density than in the case of the more common MOND models with transition functions $\\mu_1(x), \\, \\mu_2(x)$. A considerable part of it is due to the scalar field's energy density which, in our model, gives a scale and generally covariant expression for the self-energy of the gravitational field.
Xiong, Ying, S.M. Massachusetts Institute of Technology
2010-01-01
Although most racers are good at controlling their cars, world champions are always talented at choosing the right racing line while others mostly fail to do that. Optimal racing line selection is a critical problem in car ...
New Branches of Massive Gravity
Comelli, Denis; Koyama, Kazuya; Pilo, Luigi; Tasinato, Gianmassimo
2015-01-01
The basic building block for Lorentz invariant and ghost free massive gravity is the square root of the combination $g^{-1}\\eta\\,$, where $g^{-1}$ is the inverse of the physical metric and $\\eta$ is a reference metric. Since the square root of a matrix is not uniquely defined, it is possible to have physically inequivalent potentials corresponding to different branches. We show that around Minkowski background the only perturbatively well defined branch is the potential proposed by de Rham, Gabadadze and Tolley. On the other hand, if Lorentz symmetry is broken spontaneously, other potentials exist with a standard perturbative expansion. We show this explicitly building new Lorentz invariant, ghost-free massive gravity potentials for theories that in the background preserve rotational invariance, but break Lorentz boosts.
Hybrid metric-Palatini gravity
Capozziello, Salvatore; Koivisto, Tomi S; Lobo, Francisco S N; Olmo, Gonzalo J
2015-01-01
Recently, the phenomenology of f(R) gravity has been scrutinized motivated by the possibility to account for the self-accelerated cosmic expansion without invoking dark energy sources. Besides, this kind of modified gravity is capable of addressing the dynamics of several self-gravitating systems alternatively to the presence of dark matter. It has been established that both metric and Palatini versions of these theories have interesting features but also manifest severe and different downsides. A hybrid combination of theories, containing elements from both these two formalisms, turns out to be also very successful accounting for the observed phenomenology and is able to avoid some drawbacks of the original approaches. This article reviews the formulation of this hybrid metric-Palatini approach and its main achievements in passing the local tests and in applications to astrophysical and cosmological scenarios, where it provides a unified approach to the problems of dark energy and dark matter.
Quantum gravity without Lorentz invariance
Sotiriou, Thomas P; Weinfurtner, Silke
2009-01-01
There has been a significant surge of interest in Horava's model for 3+1 dimensional quantum gravity, this model being based on anisotropic scaling at a z=3 Lifshitz point. Horava's model, and its variants, show dramatically improved ultra-violet behaviour at the cost of exhibiting violation of Lorentz invariance at ultra-high momenta. Following up on our earlier note, [arXiv:0904.4464 [hep-th
Solid Holography and Massive Gravity
Alberte, Lasma; Khmelnitsky, Andrei; Pujolas, Oriol
2015-01-01
Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric...
Emergent Horava gravity in graphene
Volovik, G.E.; L. D. Landau Institute for Theoretical Physics, Kosygina 2, 119334 Moscow ; Zubkov, M.A.
2014-01-15
First of all, we reconsider the tight-binding model of monolayer graphene, in which the variations of the hopping parameters are allowed. We demonstrate that the emergent 2D Weitzenbock geometry as well as the emergent U(1) gauge field appear. The emergent gauge field is equal to the linear combination of the components of the zweibein. Therefore, we actually deal with the gauge fixed version of the emergent 2+1 D teleparallel gravity. In particular, we work out the case, when the variations of the hopping parameters are due to the elastic deformations, and relate the elastic deformations with the emergent zweibein. Next, we investigate the tight-binding model with the varying intralayer hopping parameters for the multilayer graphene with the ABC stacking. In this case the emergent 2D Weitzenbock geometry and the emergent U(1) gauge field appear as well, and the emergent low energy effective field theory has the anisotropic scaling. -- Highlights: •The tight-binding model for graphene with varying hopping parameters is considered. •The emergent gravity and emergent gauge fields are derived. •For the case of the multilayer graphene we obtain the analogue of Horava gravity with anisotropic scaling.
Dynamical 3-Space: Emergent Gravity
Reginald T Cahill
2011-02-16
The laws of gravitation devised by Newton, and by Hilbert and Einstein, have failed many experimental and observational tests, namely the bore hole g anomaly, flat rotation curves for spiral galaxies, supermassive black hole mass spectrum, uniformly expanding universe, cosmic filaments, laboratory G measurements, galactic EM bending, precocious galaxy formation,.. The response has been the introduction of the new epicycles: ``dark matter", ``dark energy", and others. To understand gravity we must restart with the experimental discoveries by Galileo, and following a heuristic argument we are led to a uniquely determined theory of a dynamical 3-space. That 3-space exists has been missed from the beginning of physics, although it was 1st directly detected by Michelson and Morley in 1887. Uniquely generalising the quantum theory to include this dynamical 3-space we deduce the response of quantum matter and show that it results in a new account of gravity, and explains the above anomalies and others. The dynamical theory for this 3-space involves G, which determines the dissipation rate of space by matter, and alpha, which experiments and observation reveal to be the fine structure constant. For the 1st time we have a comprehensive account of space and matter and their interaction - gravity.
Cosmological Hints of Modified Gravity ?
Di Valentino, Eleonora; Silk, Joseph
2015-01-01
The recent measurements of Cosmic Microwave Background temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the $\\Lambda$CDM cosmological model. However interesting hints of slight deviations from $\\Lambda$CDM have been found, including a $95 \\%$ c.l. preference for a "modified gravity" structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called $A_{lens}$ anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to $\\sigma_8=0.815_{-0.048}^{+0.032}$, in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of $\\tau=0.059\\pm0.020$ (to be compared with the value of $\\tau= 0.079 \\pm 0.017$ obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneraci...
Entropic Motion in Loop Quantum Gravity
J. Manuel Garcia-Islas
2015-02-19
Entropic forces result from an increase of the entropy of a thermodynamical physical system. It has been proposed that gravity is such a phenomenon and many articles have appeared on the literature concerning this problem. Loop quantum gravity has also considered such possibility. We propose a new method in loop quantum gravity which reproduces an entropic force. By considering the interaction between a fixed gravity state space and a particle state in loop quantum gravity, we show that it leads to a mathematical description of a random walk of such particle. The random walk in special situations, can be seen as an entropic motion in such a way that the particle will move towards a location where entropy increases. This may prove that such theory can reproduce gravity as it is expected.
Simultaneous measurement of gravity acceleration and gravity gradient with an atom interferometer
Sorrentino, F.; Lien, Y.-H.; Rosi, G.; Tino, G. M.; Bertoldi, A.; Bodart, Q.; Cacciapuoti, L.; Angelis, M. de; Prevedelli, M.
2012-09-10
We demonstrate a method to measure the gravitational acceleration with a dual cloud atom interferometer; the use of simultaneous atom interferometers reduces the effect of seismic noise on the gravity measurement. At the same time, the apparatus is capable of accurate measurements of the vertical gravity gradient. The ability to determine the gravity acceleration and gravity gradient simultaneously and with the same instrument opens interesting perspectives in geophysical applications.
Gravity from the extension of spatial diffeomorphisms
Szilard Farkas; Emil J. Martinec
2010-02-24
The possibility of the extension of spatial diffeomorphisms to a larger family of symmetries in a class of classical field theories is studied. The generator of the additional local symmetry contains a quadratic kinetic term and a potential term which can be a general (not necessarily local) functional of the metric. From the perspective of the foundation of Einstein's gravity our results are positive: The extended constraint algebra is either that of Einstein's gravity, or ultralocal gravity. If our goal is a simple modification of Einstein's gravity that for example makes it perturbatively renormalizable, as has recently been suggested, then our results show that there is no such theory within this class.
Growth histories in bimetric massive gravity
Berg, Marcus; Buchberger, Igor; Enander, Jonas; Mörtsell, Edvard; Sjörs, Stefan E-mail: igor.buchberger@kau.se E-mail: edvard@fysik.su.se
2012-12-01
We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity for general homogeneous and isotropic backgrounds. In the de Sitter approximation, we obtain decoupled sets of massless and massive scalar gravitational fluctuations. Matter perturbations then evolve like in Einstein gravity. We perturb the future de Sitter regime by the ratio of matter to dark energy, producing quasi-de Sitter space. In this more general setting the massive and massless fluctuations mix. We argue that in the quasi-de Sitter regime, the growth of structure in bimetric gravity differs from that of Einstein gravity.
Spherically symmetric solution of $f(R,\\mathcal{G})$ gravity at low energy
Wu, Bofeng
2015-01-01
The weak-field and slow-motion limit of $f(R,\\mathcal{G})$ gravity is developed up to $(v/c)^{4}$ order in a spherically symmetric background. Considering the Taylor expansion of a general function $f$ around vanishing values of $R$ and $\\mathcal{G}$, we present general vacuum solutions up to $(v/c)^{4}$ order for the gravitational field generated by a ball-like source. The spatial behaviors at $(v/c)^{2}$ order are the same for $f(R,\\mathcal{G})$ gravity and $f(R)$ gravity, and their corresponding real valued static behaviors are presented and compared with the one in general relativity. The static Yukawa-like behavior is proved to be compatible with the previous result of the most general fourth-order theory. At $(v/c)^{4}$ order, the static corrections to the Yukawa-like behavior for $f(R,\\mathcal{G})$ gravity, $f(R)$ gravity, and the Starobinsky gravity are presented and compared with the one in general relativity.
Spherically symmetric solution of $f(R,\\mathcal{G})$ gravity at low energy
Bofeng Wu; Bo-Qiang Ma
2015-10-29
The weak-field and slow-motion limit of $f(R,\\mathcal{G})$ gravity is developed up to $(v/c)^{4}$ order in a spherically symmetric background. Considering the Taylor expansion of a general function $f$ around vanishing values of $R$ and $\\mathcal{G}$, we present general vacuum solutions up to $(v/c)^{4}$ order for the gravitational field generated by a ball-like source. The spatial behaviors at $(v/c)^{2}$ order are the same for $f(R,\\mathcal{G})$ gravity and $f(R)$ gravity, and their corresponding real valued static behaviors are presented and compared with the one in general relativity. The static Yukawa-like behavior is proved to be compatible with the previous result of the most general fourth-order theory. At $(v/c)^{4}$ order, the static corrections to the Yukawa-like behavior for $f(R,\\mathcal{G})$ gravity, $f(R)$ gravity, and the Starobinsky gravity are presented and compared with the one in general relativity.
Constraints on modified Gauss-Bonnet gravity during big bang nucleosynthesis
Motohiko Kusakabe; Seoktae Koh; K. S. Kim; Myung-Ki Cheoun
2015-07-20
The modified gravity is considered to be one of possible explanations of the accelerated expansions of the present and the early universe. We study effects of the modified gravity on big bang nucleosynthesis (BBN). If effects of the modified gravity are significant during the BBN epoch, they should be observed as changes of primordial light element abundances. We assume a $f(G)$ term with the Gauss-Bonnet term $G$, during the BBN epoch. A power-law relation of $df/dG \\propto t^p$ where $t$ is the cosmic time was assumed for the function $f(G)$ as an example case. We solve time evolutions of physical variables during BBN in the $f(G)$ gravity model numerically, and analyzed calculated results. It is found that a proper solution for the cosmic expansion rate can be lost in some parameter region. In addition, we show that calculated results of primordial light element abundances can be significantly different from observational data. Especially, observational limits on primordial D abundance leads to the strongest constraint on the $f(G)$ gravity. We then derive constraints on parameters of the $f(G)$ gravity taking into account the existence of the solution of expansion rate and final light element abundances.
On the stability of gravity with Dirichlet walls
Andrade, T; Kelly, WR; Marolf, D; Santos, JE
2015-01-01
Dirichlet problem : Fluid/Gravity on cut-off surfaces, JHEPWilsonian Approach to Fluid/Gravity Duality, JHEP 1103 (and other theories of gravity, Phys.Rev. D61 (2000) 084027 [
Gravity monitoring of CO2 movement during sequestration: Model studies
Gasperikova, E.
2008-01-01
right. Figure 14: Surface gravity response (?Gal) for theAbsolute and relative gravity integration for high precision2003, Seafloor Micro-gravity Survey of the Sleipner CO 2
Unification of Gravity and Electromagnetism I: Mach's Principle and Cosmology
Partha Ghose
2015-02-12
The phenomenological consequences of unification of Einstein gravity and electromagnetism in an early phase of a Machian universe with a very small and uniform electrical charge density $\\rho_q$ are explored. A form of the Strong Equivalence Principle for unified electrogravity is first formulated, and it immediately leads to (i) the empirical Schuster-Blackett law relating the magnetic moments and angular momenta of neutral astronomical bodies, (ii) an analogous relation between the linear acceleration of neutral massive bodies and associated electric fields, (iii) gravitational lensing in excess of Einstein gravity, and, with the additional assumption of scaling, to (iv) the Wesson relation between the angular momentum and the square of the mass of astronomical bodies. Incorporation of Sciama's version of Mach's principle leads to a new post-Newtonian dynamics (in the weak field limit of gravity alone without electromagnetism) that predicts flat rotation curves of galaxies without the need of dark matter haloes. Finally, it is shown that the unified theory with a broken symmetry predicts a flat expanding universe with a cosmological term intimately related to electrogravity unification, and can explain WMAP data with a single free parameter. WMAP data require $\\rho_q =6.1\\times 10^{-43}$ C/cc which is too small to be detected at
Disformal theories of gravity: from the solar system to cosmology
Sakstein, Jeremy
2014-12-01
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 M ?> O(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.
Wide binaries as a critical test for Gravity theories
X. Hernandez; M. A. Jimenez; C. Allen
2012-05-25
Assuming Newton's gravity and GR to be valid at all scales leads to the dark matter hypothesis as a requirement demanded by the observed dynamics and measured baryonic content at galactic and extragalactic scales. Alternatively, modified gravity scenarios where a change of regime appears at acceleration scales $a
Aspects of Neutrino Oscillation in Alternative Gravity Theories
Sumanta Chakraborty
2015-10-15
Neutrino spin and flavour oscillation in curved spacetime have been studied for the most general static spherically symmetric configuration. Using the symmetry properties we have derived spin oscillation frequency for neutrino moving along a geodesic or in a circular orbit. Starting from the expression of neutrino spin oscillation frequency we have shown that even in this general context, in high energy limit the spin oscillation frequency for neutrino moving along circular orbit vanishes. This finally lends itself to non-zero probability of neutrino helicity flip. While for neutrino flavour oscillation we have derived general results for oscillation phase, which subsequently have been applied to different gravity theories. These include dilaton field coupled to Maxwell field tensor, generalization of Schwarzschild solution by introduction of quadratic curvature terms of all possible form to the Einstein-Hilbert action and finally regular black hole solutions. In all these cases using the solar neutrino oscillation data we can put bounds on the parameters of these gravity theories. While for spin oscillation probability, we have considered two cases, Gauss-Bonnet term added to the Einstein-Hilbert action and the f(R) gravity theory. In both these cases we could impose bounds on the parameters which are consistent with previous considerations. Implications are also discussed.
Dust gravitational drift wave in complex plasma under gravity
Salahshoor, M. Niknam, A. R.
2014-12-15
The dispersion relation of electrostatic waves in a complex plasma under gravity is presented. It is assumed that the waves propagate parallel to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of microparticles. The numerical results show that, in the low pressure complex plasma under gravity, a low frequency drift wave can be developed in the long wavelength limit. The stability state of this wave is switched at a certain critical wavenumber in such a way that the damped mode is transformed into a growing one. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the wave instability is essentially due to the electrostatic streaming of plasma particles. It is also found that by increasing the electric field strength, the stability switching occurs at smaller wavenumbers.
Series Transmission Line Transformer
Buckles, Robert A. (Livermore, CA); Booth, Rex (Livermore, CA); Yen, Boris T. (El Cerrito, CA)
2004-06-29
A series transmission line transformer is set forth which includes two or more of impedance matched sets of at least two transmissions lines such as shielded cables, connected in parallel at one end ans series at the other in a cascading fashion. The cables are wound about a magnetic core. The series transmission line transformer (STLT) which can provide for higher impedance ratios and bandwidths, which is scalable, and which is of simpler design and construction.
Counterterms in Massive Gravity Theory
Cao, Li-Ming
2015-01-01
We derived local boundary counterterms in massive gravity theory with a negative cosmological constant in four dimensions. With these counterterms at hand we analyzed the properties of the boundary field theory in the context of AdS/CFT duality by calculating the boundary stress energy tensor. The calculation shows that the boundary stress energy tensor is conserved, and momentum dissipation might occur on the level of linear response only. We also calculated the thermodynamic quantities and the boundary stress energy tensor for a specific type of solutions. The thermodynamic potentials agree with the results of literature up to some constants which can be removed by adding finite counterterms.
Astrophysical tests of modified gravity: the morphology and kinematics of dwarf galaxies
Vikram, Vinu; Cabré, Anna; Jain, Bhuvnesh; VanderPlas, J.T. E-mail: annanusca@gmail.com E-mail: jakevdp@cs.washington.edu
2013-08-01
This paper is the third in a series on tests of gravity using observations of stars and nearby dwarf galaxies. We carry out four distinct tests using published data on the kinematics and morphology of dwarf galaxies, motivated by the theoretical work of Hui et al. (2009) and Jain and Vanderplas (2011). In a wide class of gravity theories a scalar field couples to matter and provides an attractive fifth force. Due to their different self-gravity, stars and gas may respond differently to the scalar force leading to several observable deviations from standard gravity. HI gas, red giant stars and main sequence stars can be displaced relative to each other, and the stellar disk can display warps or asymmetric rotation curves aligned with external potential gradients. To distinguish the effects of modified gravity from standard astrophysical phenomena, we use a control sample of galaxies that are expected to be screened from the fifth force. In all cases we find no significant deviation from the null hypothesis of general relativity. The limits obtained from dwarf galaxies are not yet competitive with the limits from cepheids obtained in our first paper, but can be improved to probe regions of parameter space that are inaccessible using other tests. We discuss how our methodology can be applied to new radio and optical observations of nearby galaxies.
A new quasidilaton theory of massive gravity (Journal Article...
Office of Scientific and Technical Information (OSTI)
A new quasidilaton theory of massive gravity Citation Details In-Document Search Title: A new quasidilaton theory of massive gravity We present a new quasidilaton theory of...
Ground Gravity Survey At Dixie Valley Geothermal Area (Allis...
Ground Gravity Survey At Dixie Valley Geothermal Area (Allis, Et Al., 2000) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity Survey...
Ground Gravity Survey At Roosevelt Hot Springs Geothermal Area...
Ground Gravity Survey At Roosevelt Hot Springs Geothermal Area (Faulder, 1991) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Hamiltonian analysis of self-dual gauge gravity
Steven Kerr
2015-04-15
The Hamiltonian analysis of the self-dual gauge gravity theory is carried out. The resulting canonical structure is equivalent to that of self-dual gravity.
Ground Gravity Survey At Neal Hot Springs Geothermal Area (Colwell...
Ground Gravity Survey At Neal Hot Springs Geothermal Area (Colwell, Et Al., 2012) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Ground Gravity Survey At Lake City Hot Springs Area (Warpinski...
Ground Gravity Survey At Lake City Hot Springs Area (Warpinski, Et Al., 2004) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Ground Gravity Survey At Under Steamboat Springs Area (Warpinski...
Ground Gravity Survey At Under Steamboat Springs Area (Warpinski, Et Al., 2004) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (FURUMOTO...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (FURUMOTO, 1976) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity Survey...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (Leslie...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (Leslie, Et Al., 2004) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (Broyles...
Ground Gravity Survey At Kilauea East Rift Geothermal Area (Broyles, Et Al., 1979) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Gravity...
Integration of Full Tensor Gravity and ZTEM Passive Low Frequency...
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Full Tensor Gravity and ZTEM Passive Low Frequency EM Instruments for Simultaneous Data Acquisition Integration of Full Tensor Gravity and ZTEM Passive Low Frequency EM Instruments...
Gravity in Complex Hermitian Space-Time
Ali H. Chamseddine
2006-10-09
A generalized theory unifying gravity with electromagnetism was proposed by Einstein in 1945. He considered a Hermitian metric on a real space-time. In this work we review Einstein's idea and generalize it further to consider gravity in a complex Hermitian space-time.
Gravity Capillary Standing Water Waves Pietro Baldi
Thomann, Laurent
Gravity Capillary Standing Water Waves Pietro Baldi Universit`a di Napoli Federico II Joint work with Thomas Alazard (ENS Paris) Pienza, 29 October 2014 Pietro Baldi Gravity Capillary Standing Water Waves construct small amplitude, standing solutions of Sobolev reg. (standing := periodic in time and space
Naked singularities and quantum gravity
Harada, Tomohiro; Iguchi, Hideo; Nakao, Ken-ichi; Singh, T. P.; Tanaka, Takahiro; Vaz, Cenalo
2001-08-15
There are known models of spherical gravitational collapse in which the collapse ends in a naked shell-focusing singularity for some initial data. If a massless scalar field is quantized on the classical background provided by such a star, it is found that the outgoing quantum flux of the scalar field diverges in the approach to the Cauchy horizon. We argue that the semiclassical approximation (i.e., quantum field theory on a classical curved background) used in these analyses ceases to be valid about one Planck time before the epoch of naked singularity formation, because by then the curvature in the central region of the star reaches the Planck scale. It is shown that during the epoch in which the semiclassical approximation is valid, the total emitted energy is about one Planck unit, and is not divergent. We also argue that back reaction in this model does not become important so long as gravity can be treated classically. It follows that the further evolution of the star will be determined by quantum gravitational effects, and without invoking quantum gravity it is not possible to say whether the star radiates away on a short time scale or settles down into a black hole state.
Transmission Line Security Monitor
None
2013-05-28
The Transmission Line Security Monitor is a multi-sensor monitor that mounts directly on high-voltage transmission lines to detect, characterize and communicate terrorist activity, human tampering and threatening conditions around support towers. For more information about INL's critical infrastructure protection research, visit http://www.facebook.com/idahonationallaboratory.
Transmission Line Security Monitor
2011-01-01
The Transmission Line Security Monitor is a multi-sensor monitor that mounts directly on high-voltage transmission lines to detect, characterize and communicate terrorist activity, human tampering and threatening conditions around support towers. For more information about INL's critical infrastructure protection research, visit http://www.facebook.com/idahonationallaboratory.
Solar System constraints to nonminimally coupled gravity
Orfeu Bertolami; Riccardo March; Jorge Páramos
2013-06-05
We extend the analysis of Chiba, Smith and Erickcek \\cite{CSE} of Solar System constraints on $f(R)$ gravity to a class of nonminimally coupled (NMC) theories of gravity. These generalize $f(R)$ theories by replacing the action functional of General Relativity (GR) with a more general form involving two functions $f^1(R)$ and $f^2(R)$ of the Ricci scalar curvature $R$. While the function $f^1(R)$ is a nonlinear term in the action, analogous to $f(R)$ gravity, the function $f^2(R)$ yields a NMC between the matter Lagrangian density $\\LL_m$ and the scalar curvature. The developed method allows for obtaining constraints on the admissible classes of functions $f^1(R)$ and $f^2(R)$, by requiring that predictions of NMC gravity are compatible with Solar System tests of gravity. We apply this method to a NMC model which accounts for the observed accelerated expansion of the Universe.
Classical and Quantum Gravity in 1+1 Dimensions, Part I: A Unifying Approach
T. Kloesch; T. Strobl
1997-08-11
We provide a concise approach to generalized dilaton theories with and without torsion and coupling to Yang-Mills fields. Transformations on the space of fields are used to trivialize the field equations locally. In this way their solution becomes accessible within a few lines of calculation only. In this first of a series of papers we set the stage for a thorough global investigation of classical and quantum aspects of more or less all available 2D gravity-Yang-Mills models.
Review of short-range gravity experiments in the LHC era
Jiro Murata; Saki Tanaka
2014-08-19
This document briefly reviews recent short-range gravity experiments that were performed at below laboratory scales to test the Newtonian inverse square law of gravity. To compare sensitivities of these measurements, estimates using the conventional Yukawa parametrization are introduced. Since these experiments were triggered by the prediction of the large extra-dimension model, experiments performed at different length scales are compared with this prediction. In this paper, a direct comparison between laboratory-scale experiments and the LHC results is presented for the first time. A laboratory experiment is shown to determine the best limit at $M_D > 4.6 \\;\\rm{TeV}$ and $\\lambdagravitational microlaboratories.
Inflation in Kaluza-Klein cosmology. 1; Transformation to fourth-order gravity
Schmidt, H.J. )
1990-12-20
This paper reports on the higher- dimensional Einstein equation with {Gamma}-term shown to be comformally equivalent to the four-dimensional field equation of scale-invariant fourth-order gravity. This holds for a general warped product between space-time and internal space of arbitrary dimension m which turns out to be an Einstein space. (The limit m {yields} {infinity} makes sense ) Thus, the results concerning the attractor property of the power- law inflationary solution derived for fourth-order gravity hold for the Kaluza-Klein model, too.
Coherent soliton communication lines
Yushko, O. V. Redyuk, A. A.; Fedoruk, M. P.; Turitsyn, S. K.
2014-11-15
The data transmission in coherent fiber-optical communication lines using solitons with a variable phase is studied. It is shown that nonlinear coherent structures (solitons) can be applied for effective signal transmission over a long distance using amplitude and optical-phase keying of information. The optimum ratio of the pulse width to the bit slot at which the spectral efficiency (transmitted bits per second and hertz) is maximal is determined. It is shown that soliton fiber-optical communication lines can ensure data transmission at a higher spectral efficiency as compared to traditional communication lines and at a high signal-to-noise ratio.
Modified Gravity N-body Code Comparison Project
Hans A. Winther; Fabian Schmidt; Alexandre Barreira; Christian Arnold; Sownak Bose; Claudio Llinares; Marco Baldi; Bridget Falck; Wojciech A. Hellwing; Kazuya Koyama; Baojiu Li; David F. Mota; Ewald Puchwein; Robert Smith; Gong-Bo Zhao
2015-06-21
Self-consistent ${\\it N}$-body simulations of modified gravity models are a key ingredient to obtain rigorous constraints on deviations from General Relativity using large-scale structure observations. This paper provides the first detailed comparison of the results of different ${\\it N}$-body codes for the $f(R)$, DGP, and Symmetron models, starting from the same initial conditions. We find that the fractional deviation of the matter power spectrum from $\\Lambda$CDM agrees to better than $1\\%$ up to $k \\sim 5-10~h/{\\rm Mpc}$ between the different codes. These codes are thus able to meet the stringent accuracy requirements of upcoming observational surveys. All codes are also in good agreement in their results for the velocity divergence power spectrum, halo abundances and halo profiles. We also test the quasi-static limit, which is employed in most modified gravity ${\\it N}$-body codes, for the Symmetron model for which the most significant non-static effects among the models considered are expected. We conclude that this limit is a very good approximation for all of the observables considered here.
Modified Gravity N-body Code Comparison Project
Hans A. Winther; Fabian Schmidt; Alexandre Barreira; Christian Arnold; Sownak Bose; Claudio Llinares; Marco Baldi; Bridget Falck; Wojciech A. Hellwing; Kazuya Koyama; Baojiu Li; David F. Mota; Ewald Puchwein; Robert E. Smith; Gong-Bo Zhao
2015-09-29
Self-consistent ${\\it N}$-body simulations of modified gravity models are a key ingredient to obtain rigorous constraints on deviations from General Relativity using large-scale structure observations. This paper provides the first detailed comparison of the results of different ${\\it N}$-body codes for the $f(R)$, DGP, and Symmetron models, starting from the same initial conditions. We find that the fractional deviation of the matter power spectrum from $\\Lambda$CDM agrees to better than $1\\%$ up to $k \\sim 5-10~h/{\\rm Mpc}$ between the different codes. These codes are thus able to meet the stringent accuracy requirements of upcoming observational surveys. All codes are also in good agreement in their results for the velocity divergence power spectrum, halo abundances and halo profiles. We also test the quasi-static limit, which is employed in most modified gravity ${\\it N}$-body codes, for the Symmetron model for which the most significant non-static effects among the models considered are expected. We conclude that this limit is a very good approximation for all of the observables considered here.
The Necessity of Quantizing Gravity
Adelman, Jeremy
2015-01-01
The Eppley Hannah thought experiment is often cited as justification for attempts by theorists to develop a complete, consistent theory of quantum gravity. A modification of the earlier "Heisenberg microscope" argument for the necessity of quantized light, the Eppley-Hannah thought experiment purports to show that purely classical gravitational waves would either not conserve energy or else allow for violations of the uncertainty principle. However, several subsequent papers have cast doubt as to the validity of the Eppley-Hannah argument. In this paper, we attempt to resurrect the Eppley-Hannah thought experiment by modifying the original argument in such a manner as to render it immune to the present criticisms levied against it.
A parametrix for quantum gravity?
Esposito, Giampiero
2015-01-01
In the sixties, DeWitt discovered that the advanced and retarded Green functions of the wave operator on metric perturbations in the de Donder gauge make it possible to define classical Poisson brackets on the space of functionals that are invariant under the action of the full diffeomorphism group of spacetime. He therefore tried to exploit this property to define invariant commutators for the quantized gravitational field, but the operator counterpart of such classical Poisson brackets turned out to be a hard task. On the other hand, the mathematical literature studies often an approximate inverse, the parametrix, which is, strictly, a distribution. We here suggest that such a construction might be exploited in canonical quantum gravity. We begin with the simplest case, i.e. fundamental solution and parametrix for the linear, scalar wave operator; the next step are tensor wave equations, again for linear theory, e.g. Maxwell theory in curved spacetime. Last, the nonlinear Einstein equations are studied, rel...
Dimensional Reduction in Quantum Gravity
G. 't Hooft
2009-03-20
The requirement that physical phenomena associated with gravitational collapse should be duly reconciled with the postulates of quantum mechanics implies that at a Planckian scale our world is not 3+1 dimensional. Rather, the observable degrees of freedom can best be described as if they were Boolean variables defined on a two-dimensional lattice, evolving with time. This observation, deduced from not much more than unitarity, entropy and counting arguments, implies severe restrictions on possible models of quantum gravity. Using cellular automata as an example it is argued that this dimensional reduction implies more constraints than the freedom we have in constructing models. This is the main reason why so-far no completely consistent mathematical models of quantum black holes have been found. Essay dedicated to Abdus Salam.
Testing Gravity Using Dwarf Stars
Sakstein, Jeremy
2015-01-01
Generic scalar-tensor theories of gravity predict deviations from Newtonian physics inside astrophysical bodies. In this paper, we point out that low mass stellar objects, red and brown dwarf stars, are excellent probes of these theories. We calculate two important and potentially observable quantities: the radius of brown dwarfs and the minimum mass for hydrogen burning in red dwarfs. The brown dwarf radius can differ significantly from the GR prediction and upcoming surveys that probe the mass-radius relation for stars with masses $hydrogen burning can be larger than several presently observed Red Dwarf stars. This places a new and extremely stringent constraint on the parameters that appear in the effective field theory of dark energy and rules out several well-studied dark energy models.
Testing Gravity Using Dwarf Stars
Jeremy Sakstein
2015-11-05
Generic scalar-tensor theories of gravity predict deviations from Newtonian physics inside astrophysical bodies. In this paper, we point out that low mass stellar objects, red and brown dwarf stars, are excellent probes of these theories. We calculate two important and potentially observable quantities: the radius of brown dwarfs and the minimum mass for hydrogen burning in red dwarfs. The brown dwarf radius can differ significantly from the GR prediction and upcoming surveys that probe the mass-radius relation for stars with masses $hydrogen burning can be larger than several presently observed Red Dwarf stars. This places a new and extremely stringent constraint on the parameters that appear in the effective field theory of dark energy and rules out several well-studied dark energy models.
Tom Fleming; Mark Gross; Ray Renken
1994-01-04
We define a simplified version of Regge quantum gravity where the link lengths can take on only two possible values, both always compatible with the triangle inequalities. This is therefore equivalent to a model of Ising spins living on the links of a regular lattice with somewhat complicated, yet local interactions. The measure corresponds to the natural sum over all 2^links configurations, and numerical simulations can be efficiently implemented by means of look-up tables. In three dimensions we find a peak in the ``curvature susceptibility'' which grows with increasing system size. However, the value of the corresponding critical exponent as well as the behavior of the curvature at the transition differ from that found by Hamber and Williams for the Regge theory with continuously varying link lengths.
Emergent Horava gravity in graphene
G. E. Volovik; M. A. Zubkov
2013-07-07
First of all, we reconsider the tight - binding model of monolayer graphene, in which the variations of the hopping parameters are allowed. We demonstrate that the emergent 2D Weitzenbock geometry as well as the emergent U(1) gauge field appear. The emergent gauge field is equal to the linear combination of the components of the zweibein. Therefore, we actually deal with the gauge fixed version of the emergent 2+1 D teleparallel gravity. In particular, we work out the case, when the variations of the hopping parameters are due to the elastic deformations, and relate the elastic deformations with the emergent zweibein. Next, we investigate the tight - binding model with the varying intralayer hopping parameters for the multilayer graphene with the ABC stacking. In this case the emergent 2D Weitzenbock geometry and the emergent U(1) gauge field appear as well, the emergent low energy effective field theory has the anisotropic scaling.
A STUDY OF ION LINE BROADENING IN THE TORMAC DISCHARGE.
Shaw, Robert Stephen
2010-01-01
of the main confinement magnetic field is not maintained fordrag. Magnetic probes indicate that the confinement fieldmagnetic field line configurations, such as the magnetic mirror, do not have this B limitation. However, particle confinement
Latorre, V.R.; Watwood, D.B.
1994-09-27
A short-range, radio frequency (RF) transmitting-receiving system that provides both visual and audio warnings to the pilot of a helicopter or light aircraft of an up-coming power transmission line complex. Small, milliwatt-level narrowband transmitters, powered by the transmission line itself, are installed on top of selected transmission line support towers or within existing warning balls, and provide a continuous RF signal to approaching aircraft. The on-board receiver can be either a separate unit or a portion of the existing avionics, and can also share an existing antenna with another airborne system. Upon receipt of a warning signal, the receiver will trigger a visual and an audio alarm to alert the pilot to the potential power line hazard. 4 figs.
On Non-Equilibrium Thermodynamics of Space-Time and Quantum Gravity
Joakim Munkhammar
2015-07-02
Based on recent results from general relativistic statistical mechanics and black hole information transfer limits a space-time entropy-action equivalence is proposed as a generalization of the holographic principle. With this conjecture, the action principle can be replaced by the second law of thermodynamics, and for the Einstein-Hilbert action the Einstein field equations are conceptually the result of thermodynamic equilibrium. For non-equilibrium situations Jaynes' information-theoretic approach to maximum entropy production is adopted instead of the second law of thermodynamics. As it turns out, for appropriate choices of constants quantum gravity is obtained. For the special case of a free particle the Bekenstein-Verlinde entropy-to-displacement relation of holographic gravity, and thus the traditional holographic principle, emerges. Although Jacobson's original thermodynamic equilibrium approach proposed that gravity might not necessarily be quantized, this particular non-equilibrium treatment might require it.
Gravity as BF theory plus potential
Kirill Krasnov
2009-07-23
Spin foam models of quantum gravity are based on Plebanski's formulation of general relativity as a constrained BF theory. We give an alternative formulation of gravity as BF theory plus a certain potential term for the B-field. When the potential is taken to be infinitely steep one recovers general relativity. For a generic potential the theory still describes gravity in that it propagates just two graviton polarizations. The arising class of theories is of the type amenable to spin foam quantization methods, and, we argue, may allow one to come to terms with renormalization in the spin foam context.
Ning Wu
2012-07-11
When we discuss problems on gravity, we can not avoid some fundamental physical problems, such as space-time, inertia, and inertial reference frame. The goal of this paper is to discuss the logic system of gravity theory and the problems of space-time, inertia, and inertial reference frame. The goal of this paper is to set up the theory on space-time in gauge theory of gravity. Based on this theory, it is possible for human kind to manipulate physical space-time on earth, and produce a machine which can physically prolong human's lifetime.
Surface gravities for non-Killing horizons
Cropp, Bethan; Visser, Matt
2013-01-01
There are many logically and computationally distinct characterizations of the surface gravity of a horizon, just as there are many logically rather distinct notions of horizon. Fortunately, in standard general relativity, for stationary horizons, most of these characterizations are degenerate. However, in modified gravity, or in analogue spacetimes, horizons may be non-Killing or even non-null, and hence these degeneracies can be lifted. We present a brief overview of the key issues, specifically focusing on horizons in analogue spacetimes and universal horizons in modified gravity.
Status of Horava gravity: A personal perspective
Visser, Matt
2011-01-01
Horava gravity is a relatively recent (Jan 2009) idea in theoretical physics for trying to develop a quantum field theory of gravity. It is not a string theory, nor loop quantum gravity, but is instead a traditional quantum field theory that breaks Lorentz invariance at ultra-high (presumably trans-Planckian) energies, while retaining approximate Lorentz invariance at low and medium (sub-Planckian) energies. The challenge is to keep the Lorentz symmetry breaking controlled and small - small enough to be compatible with experiment. I will give a very general overview of what is going on in this field, paying particular attention to the disturbing role of the scalar graviton.
Universality of the acceleration due to gravity on the surface of a rapidly rotating neutron star
AlGendy, Mohammad; Morsink, Sharon M.
2014-08-20
On the surface of a rapidly rotating neutron star, the effective centrifugal force decreases the effective acceleration due to gravity (as measured in the rotating frame) at the equator while increasing the acceleration at the poles due to the centrifugal flattening of the star into an oblate spheroid. We compute the effective gravitational acceleration for relativistic rapidly rotating neutron stars and show that for a star with mass M, equatorial radius R{sub e} , and angular velocity ?, the deviations of the effective acceleration due to gravity from the nonrotating case take on a universal form that depends only on the compactness ratio M/R{sub e} , the dimensionless square of the angular velocity ?{sup 2}R{sub e}{sup 3}/GM, and the latitude on the star's surface. This dependence is universal, in that it has very little dependence on the neutron star's equation of state. The effective gravity is expanded in the slow-rotation limit to show the dependence on the effective centrifugal force, oblate shape of the star, and the quadrupole moment of the gravitational field. In addition, an empirical fit and simple formula for the effective gravity is found. We find that the increase in the acceleration due to gravity at the poles is of the same order of magnitude as the decrease in the effective acceleration due to gravity at the equator for all realistic value of mass, radius, and spin. For neutron stars that spin with frequencies near 600 Hz, the difference between the effective gravity at the poles and the equator is about 20%.
Antimatter-Gravity Couplings, and Lorentz Symmetry
Jay D. Tasson
2015-01-27
Implications of possible CPT and Lorentz violation for antimatter-gravity experiments as well as other antimatter tests are considered in the context of the general field-theory-based framework of the Standard-Model Extension (SME).
Asymptotic safety of gravity-matter systems
Meibohm, Jan; Reichert, Manuel
2015-01-01
We study the ultraviolet stability of gravity-matter systems for general numbers of minimally coupled scalars and fermions. This is done within the functional renormalisation group setup put forward in \\cite{Christiansen:2015rva} for pure gravity. It includes full dynamical propagators and a genuine dynamical Newton's coupling, which is extracted from the graviton three-point function. We find ultraviolet stability of general gravity-fermion systems. Gravity-scalar systems are also found to be ultraviolet stable within validity bounds for the chosen generic class of regulators, based on the size of the anomalous dimension. Remarkably, the ultraviolet fixed points for the dynamical couplings are found to be significantly different from those of their associated background counterparts, once matter fields are included. In summary, the asymptotic safety scenario does not put constraints on the matter content of the theory within the validity bounds for the chosen generic class of regulators.
Quantum gravity and renormalization: The tensor track
Rivasseau, Vincent
2012-06-27
We propose a new program to quantize and renormalize gravity based on recent progress on the analysis of large random tensors. We compare it briefly with other existing approaches.
Energy conditions in f(R)-gravity
J. Santos; J. S. Alcaniz; M. J. Reboucas; F. C. Carvalho
2007-09-06
In order to shed some light on the current discussion about f(R)-gravity theories we derive and discuss the bounds imposed by the energy conditions on a general f(R) functional form. The null and strong energy conditions in this framework are derived from the Raychaudhuri's equation along with the requirement that gravity is attractive, whereas the weak and dominant energy conditions are stated from a comparison with the energy conditions that can be obtained in a direct approach via an effective energy-momentum tensor for f(R)-gravity. As a concrete application of the energy conditions to locally homogeneous and isotropic f(R)-cosmology, the recent estimated values of the deceleration and jerk parameters are used to examine the bounds from the weak energy condition on the parameters of two families of f(R)-gravity theories.
Test particle motion in modified gravity theories
Mahmood Roshan
2013-02-05
We derive the equations of motion of an electrically neutral test particle for modified gravity theories in which the covariant divergence of the ordinary matter energy-momentum tensor dose not vanish (i.e. $\
A new vacuum for Loop Quantum Gravity
Bianca Dittrich; Marc Geiller
2015-05-05
We construct a new vacuum for loop quantum gravity, which is dual to the Ashtekar-Lewandowski vacuum. Because it is based on BF theory, this new vacuum is physical for $(2+1)$-dimensional gravity, and much closer to the spirit of spin foam quantization in general. To construct this new vacuum and the associated representation of quantum observables, we introduce a modified holonomy-flux algebra which is cylindrically consistent with respect to the notion of refinement by time evolution suggested in [1]. This supports the proposal for a construction of a physical vacuum made in [1,2], also for $(3+1)$-dimensional gravity. We expect that the vacuum introduced here will facilitate the extraction of large scale physics and cosmological predictions from loop quantum gravity.
Gravity waves from vortex dipoles and jets
Wang, Shuguang
2009-05-15
The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here...
Primordial Density Fluctuations in Phase Coupling Gravity
C. E. M. Batista; M. Schiffer
1996-01-10
In this paper we study the evolution of density perturbations in the framework of Phase Coupling Gravity theory at the very early universe. We show that these perturbation display an exponential-like behaviour.
Oblique reflections of internal gravity wave beams
Karimi, Hussain H. (Hussain Habibullah)
2012-01-01
We study nonlinear effects in reflections of internal gravity wave beams in a continuously stratified liquid which are incident upon a uniform slope at an oblique angle. Wave motion in a stratified fluid medium is unique ...
Emergence in Holographic Scenarios for Gravity
Dennis Dieks; Jeroen van Dongen; Sebastian de Haro
2015-09-10
'Holographic' relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by Gerard 't Hooft on the basis of his studies of evaporating black holes. Soon afterwards the holographic 'AdS/CFT' duality was introduced, which since has been intensively studied in the string theory community and beyond. Recently, Erik Verlinde has proposed that even Newton's law of gravitation can be related holographically to the `thermodynamics of information' on screens. We discuss these scenarios, with special attention to the status of the holographic relation in them and to the question of whether they make gravity and spacetime emergent. We conclude that only Verlinde's scheme straightfowardly instantiates emergence. However, assuming a non-standard interpretation of AdS/CFT may create room for the emergence of spacetime and gravity there as well.
Brane worlds in gravity with auxiliary fields
Bin Guo; Yu-Xiao Liu; Ke Yang
2015-03-11
Recently, Pani, Sotiriou, and Vernieri explored a new theory of gravity by adding nondynamical fields, i.e., gravity with auxiliary fields [Phys. Rev. D 88, 121502(R) (2013)]. In this gravity theory, higher-order derivatives of matter fields generically appear in the field equations. In this paper we extend this theory to any dimensions and discuss the thick braneworld model in five dimensions. Domain wall solutions are obtained numerically. The stability of the brane system under the tensor perturbation is analyzed. We find that the system is stable under the tensor perturbation and the gravity zero mode is localized on the brane. Therefore, the four-dimensional Newtonian potential can be realized on the brane.
Gravity waves from cosmic bubble collisions
Salem, Michael P.; Saraswat, Prashant; Shaghoulian, Edgar E-mail: ps88@stanford.edu
2013-02-01
Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.
Green's Functions in Perturbative Quantum Gravity
Sudhaker Upadhyay; Bhabani Prasad Mandal
2015-04-03
We show that the Green's functions in non-linear gauge in the theory of perturbative quantum gravity is expressed as a series in terms of those in linear gauges. This formulation is also holds for operator Green's functions. We further derive the explicit relation between the Green's functions in the theory of perturbative quantum gravity in a pair of arbitary gauges. This process involves some sort of modified FFBRST transformations which is derivable from infinitesimal field-dependent BRST transformations.
Anisotropic induced gravity and inflationary universe
W. F. Kao
2006-12-09
Existence and stability analysis of the Kantowski-Sachs type universe in a higher derivative induced gravity theory is studied in details. Existence of one stable mode and one unstable mode is shown to be in favor of the inflationary universe. As a result, the de Sitter background can be made to be stable against anisotropic perturbations with proper constraints imposed on the coupling constants of the induced gravity model.
Polymer Quantum Mechanics and its Continuum Limit
Alejandro Corichi; Tatjana Vukasinac; Jose A. Zapata
2007-08-22
A rather non-standard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle and a simple cosmological model.
Analogue gravity in hyperbolic metamaterials
Igor I. Smolyaninov
2013-09-09
Sub-wavelength confinement of light in nonlinear hyperbolic metamaterials due to formation of spatial solitons has attracted much recent attention because of its seemingly counter-intuitive behavior. In order to achieve self-focusing in a hyperbolic wire medium, a nonlinear self-defocusing Kerr medium must be used as a dielectric host. Here we demonstrate that this behavior finds natural explanation in terms of analogue gravity. Wave equation describing propagation of extraordinary light inside hyperbolic metamaterials exhibits 2+1 dimensional Lorentz symmetry. The role of time in the corresponding effective 3D Minkowski spacetime is played by the spatial coordinate aligned with the optical axis of the metamaterial. Nonlinear optical Kerr effect bends this spacetime resulting in effective gravitational force between extraordinary photons. In order for the effective gravitational constant to be positive, negative self-defocusing Kerr medium must be used as a host. If gravitational self-interaction is strong enough, spatial soliton may collapse into a black hole analogue.
Measuring antimatter gravity with muonium
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kaplan, Daniel M.; Kirch, Klaus; Mancini, Derrick; Phillips, James D.; Phillips, Thomas J.; Roberts, Thomas J.; Terry, Jeff; Bravina, L.; Foka, Y.; Kabana, S.
2015-05-29
The gravitational acceleration of antimatter, ¯g, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Only two avenues for such a measurement appear to be feasible: antihydrogen and muonium. The muonium measurement requires a novel, monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating interferometer can be produced in silicon nitride or ultrananocrystalline diamond using state-of-the-art nanofabrication. The required precision alignment and calibration at the picometer level also appear to be feasible. With 100 nmmore »grating pitch, a 10% measurement of ¯g can be made using some months of surface-muon beam time, and a 1% or better measurement with a correspondingly larger exposure. This could constitute the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.« less
Measuring antimatter gravity with muonium
Kaplan, Daniel M.; Kirch, Klaus; Mancini, Derrick; Phillips, James D.; Phillips, Thomas J.; Roberts, Thomas J.; Terry, Jeff; Bravina, L.; Foka, Y.; Kabana, S.
2015-05-29
The gravitational acceleration of antimatter, ¯g, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Only two avenues for such a measurement appear to be feasible: antihydrogen and muonium. The muonium measurement requires a novel, monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating interferometer can be produced in silicon nitride or ultrananocrystalline diamond using state-of-the-art nanofabrication. The required precision alignment and calibration at the picometer level also appear to be feasible. With 100 nm grating pitch, a 10% measurement of ¯g can be made using some months of surface-muon beam time, and a 1% or better measurement with a correspondingly larger exposure. This could constitute the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.
Nonderivative modified gravity: a classification
Comelli, D.; Nesti, F.; Pilo, L. E-mail: fabrizio.nesti@irb.hr
2014-11-01
We analyze the theories of gravity modified by a generic nonderivative potential built from the metric, under the minimal requirement of unbroken spatial rotations. Using the canonical analysis, we classify the potentials V according to the number of degrees of freedom (DoF) that propagate at the nonperturbative level. We then compare the nonperturbative results with the perturbative DoF propagating around Minkowski and FRW backgrounds. A generic V implies 6 propagating DoF at the non-perturbative level, with a ghost on Minkowski background. There exist potentials which propagate 5 DoF, as already studied in previous works. Here, no V with unbroken rotational invariance admitting 4 DoF is found. Theories with 3 DoF turn out to be strongly coupled on Minkowski background. Finally, potentials with only the 2 DoF of a massive graviton exist. Their effect on cosmology is simply equivalent to a cosmological constant. Potentials with 2 or 5 DoF and explicit time dependence appear to be a further viable possibility.
Conditions for stimulated emission in anomalous gravity-superconductors interactions
G. Modanese; T. Junker
2009-08-19
Several authors have studied the generation of gravitational fields by condensed-matter systems in non-extreme density conditions. General Relativity and lowest-order perturbative Quantum Gravity predict in this case an extremely small emission rate, so these phenomena can become relevant only if some strong quantum effect occurs. Quantum aspects of gravity are still poorly understood. It is believed that they could play a role in systems which exhibit macroscopic quantum coherence, like superconductors and superfluids, leading to an "anomalous" coupling between matter and field. We mention here recent work in this field by Woods, Chiao, Becker, Agop et al., Ummarino, Kiefer and Weber. New results are presented concerning anomalous stimulated gravitational emission in a layered superconductor like YBCO. We model the superconductor as an array of intrinsic Josephson junctions. The superconducting parameters are defined by our preliminary measurements with melt-textured samples. We write explicitly and solve numerically the Josephson equations which give the normal and super components of the total current in the superconductor, and derive from this the total available power P=IV. Then, assuming that the coefficients A and B for spontaneous and stimulated gravitational emission are known, we apply to this case the Frantz-Nodvik equation for a laser amplifier. The equation is suitably modified in order to allow for a "continuous pumping" given by an oscillating transport current. The conclusions are relevant for the evaluation of gravitational emission from superconductors. We find that even if the A and B coefficients are anomalously large (possibly because of the Quantum Gravity effects mentioned above), the conditions for stimulated emission are quite strict and the emission rate strongly limited by the IV value.
Dynamic Line Rating: Research and Policy Evaluation
Jake P. Gentle; Kurt S. Myers; Michael R. West
2014-07-01
Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of electrical conductors to be increased based on local weather conditions. Overhead lines are conventionally given a conservative rating based on worst case scenarios. We demonstrate that observing the conditions in real time leads to additional capacity and safer operation. This paper provides a report of a pioneering scheme in the United States of America in which DLR has been applied. Thereby, we demonstrate that observing the local weather conditions in real time leads to additional capacity and safer operation. Secondly, we discuss limitations involved. In doing so, we arrive at novel insights which will inform and improve future DLR projects. Third, we provide a policy background and discussion to clarify the technology’s potential and identifies barriers to the imminent adoption of dynamic line rating systems. We provide suggestions for regulatory bodies about possible improvements in policy to encourage adoption of this beneficial technology.
A Kinetic Theory Approach to Quantum Gravity
B. L. Hu
2002-04-22
We describe a kinetic theory approach to quantum gravity -- by which we mean a theory of the microscopic structure of spacetime, not a theory obtained by quantizing general relativity. A figurative conception of this program is like building a ladder with two knotted poles: quantum matter field on the right and spacetime on the left. Each rung connecting the corresponding knots represent a distinct level of structure. The lowest rung is hydrodynamics and general relativity; the next rung is semiclassical gravity, with the expectation value of quantum fields acting as source in the semiclassical Einstein equation. We recall how ideas from the statistical mechanics of interacting quantum fields helped us identify the existence of noise in the matter field and its effect on metric fluctuations, leading to the establishment of the third rung: stochastic gravity, described by the Einstein-Langevin equation. Our pathway from stochastic to quantum gravity is via the correlation hierarchy of noise and induced metric fluctuations. Three essential tasks beckon: 1) Deduce the correlations of metric fluctuations from correlation noise in the matter field; 2) Reconstituting quantum coherence -- this is the reverse of decoherence -- from these correlation functions 3) Use the Boltzmann-Langevin equations to identify distinct collective variables depicting recognizable metastable structures in the kinetic and hydrodynamic regimes of quantum matter fields and how they demand of their corresponding spacetime counterparts. This will give us a hierarchy of generalized stochastic equations -- call them the Boltzmann-Einstein hierarchy of quantum gravity -- for each level of spacetime structure, from the macroscopic (general relativity) through the mesoscopic (stochastic gravity) to the microscopic (quantum gravity).
Lorentzian wormholes in Eddington-inspired Born-Infeld gravity
Rajibul Shaikh
2015-07-09
We show that it is possible to construct a wide class of Lorentzian wormholes in Eddington-inspired Born-Infeld gravity with a stress energy which does not violate the weak or null energy condition. The wormholes exist in a certain region of the parameter space. In fact, it is shown that there is a critical value of a parameter defined in our work, below which we have wormholes. Above the critical value, we have a regular black hole spacetime. We put a restriction on the equation of state parameter $\\alpha$ ($p_{\\theta}=\\alpha \\rho$) to have wormholes. We also put a lower limit on both the theory parameter $|\\kappa|$ and the throat radius, to restrict the tidal acceleration (at the throat) below one Earth gravity. As a special case of our general solution, we retrieve the wormhole supported by an electric field for a charge-to-mass ratio greater than the critical value $\\left(\\frac{Q}{M}\\right)_c\\approx 1.144$.
Lorentzian wormholes in Eddington-inspired Born-Infeld gravity
Shaikh, Rajibul
2015-01-01
We show, following the work of Olmo, Rubiera-Garcia and Sanchis-Alepuz (Eur. Phys. J. C {\\bf 74}, 2804 (2014)), that it is possible to construct a wide class of Lorentzian wormholes in Eddington-inspired Born-Infeld gravity with a stress energy which does not violate the Weak or Null Energy Condition. The wormholes exist for a negative value of $\\kappa$ (a parameter in the theory). In fact, it is shown that there is a critical value of $x$ (a parameter related to $\\kappa$) below which we have wormholes. Above the critical $x$, we have a regular black hole spacetime. We put a restriction on the equation of state parameter $\\alpha$ ($p_{\\theta}=\\alpha \\rho$) to have wormholes. We also put a lower limit on both $|\\kappa|$ and the throat radius, to restrict the tidal acceleration (at the throat) below one Earth gravity. As a special case of our general solution, we retrieve the wormhole supported by an electric field for a charge-to-mass ratio greater than the critical value $\\left(\\frac{Q}{M}\\right)_c\\approx 1.1...
Cosmological evolution in vector-tensor theories of gravity
Jose Beltran Jimenez; Antonio L. Maroto
2009-09-06
We present a detailed study of the cosmological evolution in general vector-tensor theories of gravity without potential terms. We consider the evolution of the vector field throughout the expansion history of the universe and carry out a classification of models according to the behavior of the vector field in each cosmological epoch. We also analyze the case in which the universe is dominated by the vector field, performing a complete analysis of the system phase map and identifying those attracting solutions which give rise to accelerated expansion. Moreover, we consider the evolution in a universe filled with a pressureless fluid in addition to the vector field and study the existence of attractors in which we can have a transition from matter-domination to vector-domination with accelerated expansion so that the vector field may play the role of dark energy. We find that the existence of solutions with late-time accelerated expansion is a generic prediction of vector-tensor theories and that such solutions typically lead to the presence of future singularities. Finally, limits from local gravity tests are used to get constraints on the value of the vector field at small (Solar System) scales.
Emission Line Properties of the Large Bright Quasar Survey
Karl Forster; Paul J. Green; Thomas L. Aldcroft; Marianne Vestergaard; Craig B. Foltz; Paul C. Hewett
2000-11-20
We present measurements of the optical/UV emission lines for a large homogeneous sample of 993 quasars from the Large Bright Quasar Survey. Our largely automated technique accounts for continuum breaks and galactic reddening, and we perform multicomponent fits to emission line profiles, including the effects of blended iron emission, and of absorption lines both galactic and intrinsic. Here we describe the fitting algorithm and present the results of line fits to the LBQS sample, including upper limits to line equivalent widths when warranted. The distribution of measured line parameters, principally equivalent width and FWHM, are detailed for a variety of lines, including upper limits. We thus initiate a large-scale investigation of correlations between the high energy continuum and emission lines in quasars, to be extended to complementary samples using similar techniques. High quality, reproducible measurements of emission lines for uniformly selected samples will advance our understanding of active galaxies, especially in a new era of large surveys selected by a variety of complementary methods.
Printed circuit dispersive transmission line
Ikezi, H.; Lin-Liu, Y.R.; DeGrassie, J.S.
1991-08-27
A printed circuit dispersive transmission line structure is disclosed comprising an insulator, a ground plane formed on one surface of the insulator, a first transmission line formed on a second surface of the insulator, and a second transmission line also formed on the second surface of the insulator and of longer length than the first transmission line and periodically intersecting the first transmission line. In a preferred embodiment, the transmission line structure exhibits highly dispersive characteristics by designing the length of one of the transmission line between two adjacent periodic intersections to be longer than the other. 5 figures.
Printed circuit dispersive transmission line
Ikezi, Hiroyuki (Rancho Santa Fe, CA); Lin-Liu, Yuh-Ren (San Diego, CA); DeGrassie, John S. (Encinitas, CA)
1991-01-01
A printed circuit dispersive transmission line structure is disclosed comprising an insulator, a ground plane formed on one surface of the insulator, a first transmission line formed on a second surface of the insulator, and a second transmission line also formed on the second surface of the insulator and of longer length than the first transmission line and periodically intersecting the first transmission line. In a preferred embodiment, the transmission line structure exhibits highly dispersive characteristics by designing the length of one of the transmission line between two adjacent periodic intersections to be longer than the other.
Newton-Cartan Gravity in Noninertial Reference Frames
Leo Rodriguez; James St. Germaine-Fuller; Sujeev Wickramasekara
2014-12-26
We study properties of Newton-Cartan gravity under transformations into all noninertial, nonrelativistic reference frames. The set of these transformations has the structure of an infinite dimensional Lie group, called the Galilean line group, which contains as a subgroup the Galilei group. We show that the fictitious forces of noninertial reference frames are naturally encoded in the Cartan connection transformed under the Galilean line group. These noninertial forces, which are coordinate effects, do not contribute to the Ricci tensor which describes the curvature of Newtonian spacetime. We show that only the $00$-component of the Ricci tensor is non-zero and equal to ($4\\pi$ times) the matter density in any inertial or noninetial reference frame and that it leads to what may be called Newtonian ADM mass. While the Ricci field equation and Gauss law are both fulfilled by the same physical matter density in inertial and linearly accelerating reference frames, there appears a discrepancy between the two in rotating reference frames in that Gauss law holds for an effective mass density that differs from the physical matter density. This effective density has its origin in the simulated magnetic field that appears in rotating frames, highlighting a rather striking difference between linearly and rotationally accelerating reference frames. We further show that the dynamical equations that govern the simulated gravitational and magnetic fields have the same form as Maxwell's equations, a surprising conclusion given that these equations are well-known to obey special relativity (and $U(1)$-gauge symmetry), rather than Galilean symmetry.
Review on the quantization of gravity
Benjamin Schulz
2014-09-29
This is a review article on quantum gravity. In section 1, the Penrose singularity theorem is proven. In section 2, the covariant quantization approach of gravity is reviewed. In section 3, an article by Hawking is reviewed that shows the gravitational path integral at one loop level to be dominated by contributions from some kind of virtual gravitational instantons. In section 4, the canonical, non-perturbative quantization approach is reviewed. In section 5, arguments from Hawking are mentioned which show the gravitational path integral to be an approximate solution of the Wheeler deWitt equation. In section 6, the black hole entropy is derived in various ways. Section 6.1 uses the gravitational path integral for this calculation. Section 6.2 shows how the black hole entropy can be derived from canonical quantum gravity. In section 7.1, arguments from Dvali and Gomez who claim that gravity can be quantized in a way which would be in some sense self-complete are critically assessed. In section 7.2 a model from Dvali and Gomez for the description of quantum mechanical black holes is critically assessed and compared with the standard quantization methods of gravity.
Massive gravity wrapped in the cosmic web
Shim, Junsup; Lee, Jounghun; Li, Baojiu E-mail: jounghun@astro.snu.ac.kr
2014-03-20
We study how the filamentary pattern of the cosmic web changes if the true gravity deviates from general relativity (GR) on a large scale. The f(R) gravity, whose strength is controlled to satisfy the current observational constraints on the cluster scale, is adopted as our fiducial model and a large, high-resolution N-body simulation is utilized for this study. By applying the minimal spanning tree algorithm to the halo catalogs from the simulation at various epochs, we identify the main stems of the rich superclusters located in the most prominent filamentary section of the cosmic web and determine their spatial extents per member cluster to be the degree of their straightness. It is found that the f(R) gravity has the effect of significantly bending the superclusters and that the effect becomes stronger as the universe evolves. Even in the case where the deviation from GR is too small to be detectable by any other observables, the degree of the supercluster straightness exhibits a conspicuous difference between the f(R) and the GR models. Our results also imply that the supercluster straightness could be a useful discriminator of f(R) gravity from the coupled dark energy since it is shown to evolve differently between the two models. As a final conclusion, the degree of the straightness of the rich superclusters should provide a powerful cosmological test of large scale gravity.
Constraints on Covariant Horava-Lifshitz Gravity from frame-dragging experiment
Radicella, Ninfa; Lambiase, Gaetano; Parisi, Luca; Vilasi, Gaetano E-mail: lambiase@sa.infn.it E-mail: vilasi@sa.infn.it
2014-12-01
The effects of Horava-Lifshitz corrections to the gravito-magnetic field are analyzed. Solutions in the weak field, slow motion limit, referring to the motion of a satellite around the Earth are considered. The post-newtonian paradigm is used to evaluate constraints on the Horava-Lifshitz parameter space from current satellite and terrestrial experiments data. In particular, we focus on GRAVITY PROBE B, LAGEOS and the more recent LARES mission, as well as a forthcoming terrestrial project, GINGER.
Static spherically symmetric perfect fluid solutions in $f(R)$ theories of gravity
T. Multamaki; I. Vilja
2006-12-29
Static spherically symmetric perfect fluid solutions are studied in metric $f(R)$ theories of gravity. We show that pressure and density do not uniquely determine $f(R)$ ie. given a matter distribution and an equation state, one cannot determine the functional form of $f(R)$. However, we also show that matching the outside Schwarzschild-de Sitter-metric to the metric inside the mass distribution leads to additional constraints that severely limit the allowed fluid configurations.
Drill string transmission line
Hall, David R. (Provo, UT); Hall, Jr., H. Tracy (Provo, UT); Pixton, David S. (Lehi, UT); Bradford, Kline (Orem, UT); Fox, Joe (Spanish Fork, UT)
2006-03-28
A transmission line assembly for transmitting information along a downhole tool comprising a pin end, a box end, and a central bore traveling between the pin end and the box end, is disclosed in one embodiment of the invention as including a protective conduit. A transmission line is routed through the protective conduit. The protective conduit is routed through the central bore and the ends of the protective conduit are routed through channels formed in the pin end and box end of the downhole tool. The protective conduit is elastically forced into a spiral or other non-linear path along the interior surface of the central bore by compressing the protective conduit to a length within the downhole tool shorter than the protective conduit.
Thermoelectric DC conductivities with momentum dissipation from higher derivative gravity
Long Cheng; Xian-Hui Ge; Zu-Yao Sun
2015-04-28
We present a mechanism of momentum relaxation in higher derivative gravity by adding linear scalar fields to the Gauss-Bonnet theory. We analytically computed all of the DC thermoelectric conductivities in this theory by adopting the method given by Donos and Gauntlett in [arXiv:1406.4742]. The results show that the DC electric conductivity is not a monotonic function of the effective impurity parameter $\\beta$: in the small $\\beta$ limit, the DC conductivity is dominated by the coherent phase, while for larger $\\beta$, pair creation contribution to the conductivity becomes dominant, signaling an incoherent phase. In addition, the DC heat conductivity is found independent of the Gauss-Bonnet coupling constant.
Astrophysical black holes in screened modified gravity
Davis, Anne-Christine; Jha, Rahul; Muir, Jessica; Gregory, Ruth E-mail: r.a.w.gregory@durham.ac.uk E-mail: jlmuir@umich.edu
2014-08-01
Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect.
Charged black holes in generalized teleparallel gravity
Rodrigues, M.E.; Houndjo, M.J.S.; Tossa, J.; Momeni, D.; Myrzakulov, R. E-mail: sthoundjo@yahoo.fr E-mail: d.momeni@yahoo.com
2013-11-01
In this paper we investigate charged static black holes in 4D for generalized teleparallel models of gravity, based on torsion as the geometric object for describing gravity according to the equivalence principle. As a motivated idea, we introduce a set of non-diagonal tetrads and derive the full system of non linear differential equations. We prove that the common Schwarzschild gauge is applicable only when we study linear f(T) case. We reobtain the Reissner-Nordstrom-de Sitter (or RN-AdS) solution for the linear case of f(T) and perform a parametric cosmological reconstruction for two nonlinear models. We also study in detail a type of the no-go theorem in the framework of this modified teleparallel gravity.
Solar System Constraints on Disformal Gravity Theories
Hiu Yan Ip; Jeremy Sakstein; Fabian Schmidt
2015-10-15
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating solutions. We derive the solution for a static isolated mass in generic disformal gravity theories and transform it into the parameterised post-Newtonian form. This allows us to investigate constraints placed on such theories by local tests of gravity. The tightest constraints come from preferred-frame effects due to the motion of the Solar System with respect to the evolving cosmological background field. The constraints we obtain improve upon the previous solar system constraints by two orders of magnitude, and constrain the scale of the disformal coupling for generic models to $\\mathcal{M} \\gtrsim 100$ eV. These constraints render all disformal effects irrelevant for cosmology.
Detailed balance in Horava-Lifshitz gravity
Gianluca Calcagni
2010-02-04
We study Horava-Lifshitz gravity in the presence of a scalar field. When the detailed balance condition is implemented, a new term in the gravitational sector is added in order to maintain ultraviolet stability. The four-dimensional theory is of a scalar-tensor type with a positive cosmological constant and gravity is nonminimally coupled with the scalar and its gradient terms. The scalar field has a double-well potential and, if required to play the role of the inflation, can produce a scale-invariant spectrum. The total action is rather complicated and there is no analog of the Einstein frame where Lorentz invariance is recovered in the infrared. For these reasons it may be necessary to abandon detailed balance. We comment on open problems and future directions in anisotropic critical models of gravity.
Solar System Constraints on Disformal Gravity Theories
Ip, Hiu Yan; Schmidt, Fabian
2015-01-01
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating solutions. We derive the solution for a static isolated mass in generic disformal gravity theories and transform it into the parameterised post-Newtonian form. This allows us to investigate constraints placed on such theories by local tests of gravity. The tightest constraints come from preferred-frame effects due to the motion of the Solar System with respect to the evolving cosmological background field. The constraints we obtain improve upon the previous solar system constraints by two orders of magnitude, and constrain the scale of the disformal coupling for generic models to $\\mathcal{M} \\gtrsim 100$ eV. These constraints render all disformal effects irrelevant for cosmology.
Gravity tests and the Pioneer anomaly
Marc-Thierry Jaekel; Serge Reynaud
2005-11-04
Experimental tests of gravity performed in the solar system show a good agreement with general relativity. The latter is however challenged by the Pioneer anomaly which might be pointing at some modification of gravity law at ranges of the order of the size of the solar system. We introduce a metric extension of general relativity which, while preserving the equivalence principle, modifies the coupling between curvature and stress tensors and, therefore, the metric solution in the solar system. The ``post-Einsteinian extension'' replaces Newton gravitation constant by two running coupling constants, which depend on the scale and differ in the sectors of traceless and traced tensors, so that the metric solution is characterized by two gravitation potentials. The extended theory has the capability to preserve compatibility with gravity tests while accounting for the Pioneer anomaly. It can also be tested by new experiments or, maybe, by having a new look at data of already performed experiments.
Solar System Constraints on Disformal Gravity Theories
Hiu Yan Ip; Jeremy Sakstein; Fabian Schmidt
2015-07-02
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating solutions. We derive the solution for a static isolated mass in generic disformal gravity theories and transform it into the parameterised post-Newtonian form. This allows us to investigate constraints placed on such theories by local tests of gravity. The tightest constraints come from preferred-frame effects due to the motion of the Solar System with respect to the evolving cosmological background field. The constraints we obtain improve upon the previous solar system constraints by two orders of magnitude, and constrain the scale of the disformal coupling for generic models to $\\mathcal{M} \\gtrsim 100$ eV. These constraints render all disformal effects irrelevant for cosmology.
The inverse-square law and quantum gravity
Nieto, M.M.; Goldman, T.; Hughes, R.J.
1988-01-01
This paper briefly discusses a modification to central potential of gravity when antimatter is involved and the possible existence of quantum gravity and a fifth force of nature. 1 ref. (LSP)
Correlation Between Precision Gravity and Subsidence Measurements at Cerro Prieto
Zelwer, R.
2010-01-01
PRECISION GRAVITY AND SUBSIDENCE MEASUREMENTS AT CERROPRECISION GRAVITY AND SUBSIDENCE MEASUREMENTS AT CERROn d i c a t e s t h a t subsidence took place. Uost of t h e
Theoretical and experimental study of nonlinear internal gravity wave beams
Tabaei Befrouei, Ali, 1974-
2005-01-01
Continuously stratified fluids, like the atmosphere and the oceans, support internal gravity waves due to the effect of buoyancy. This type of wave motion is anisotropic since gravity provides a preferred direction. As a ...
Stratospheric gravity wave simulation over Greenland during 24 January 2005
Limpasuvan, Varavut
gravity waves because of imbalance of the jet stream. Where the horizontal jet is rapidly changing speed anticyclonic jet stream over the North Atlantic. Likewise, inertia gravity waves can result from synoptic
Gravity modeling of Cenozoic extensional basins, offshore Vietnam
Mauri, Steven Joseph
1993-01-01
Integrating Bouguer gravity and satellite-derived free-air gravity data with published geological and geophysical data allows modeling crustal structure and estimating crustal extension for the hydrocarbon bearing Mekong and Song Hong - Yinggehai...
Ground Gravity Survey At Baltazor Hot Springs Area (Isherwood...
(Fig. 2) shows a gravity low within the valley area that presumably is related to low-density Cenozoic sediments. The steep gravity gradient along the east side of the valley...
A Finite Quantum Gravity Field Theory Model
Jorge Alfaro; Pablo González; Ricardo Avila
2011-09-22
We discuss the quantization of Delta gravity, a two symmetric tensors model of gravity. This model, in Cosmology, shows accelerated expansion without a cosmological constant. We present the $\\tilde{\\delta}$ transformation which defines the geometry of the model. Then we show that all delta type models live at one loop only. We apply this to General Relativity and we calculate the one loop divergent part of the Effective Action showing its null contribution in vacuum, implying a finite model. Then we proceed to study the existence of ghosts in the model. Finally, we study the form of the finite quantum corrections to the classical action of the model.
Differential geometry, Palatini gravity and reduction
Capriotti, S.
2014-01-15
The present article deals with a formulation of the so called (vacuum) Palatini gravity as a general variational principle. In order to accomplish this goal, some geometrical tools related to the geometry of the bundle of connections of the frame bundle LM are used. A generalization of Lagrange-Poincaré reduction scheme to these types of variational problems allows us to relate it with the Einstein-Hilbert variational problem. Relations with some other variational problems for gravity found in the literature are discussed.
Cosmological Evidence for Modified Gravity (MOG)
Moffat, J W
2015-01-01
Deviations from the standard $\\Lambda$CDM model motivate an interpretation of early universe cosmology using the Scalar-Tensor-Vector-Gravity (STVG) theory. A constraint analysis carried out by Valentino, Melchiorri and Silk, revealed deviations from the growth of structure predicted by General Relativity, and a lensing anomaly in the angular CMB power spectrum data with a $95\\%$ c.l. The modified gravity (MOG) theory resolves the lensing deviation from the standard model and provides an explanation of the CMB and structure growth data.
Violation of Energy Bounds in Designer Gravity
Thomas Hertog
2006-07-31
We continue our study of the stability of designer gravity theories, where one considers anti-de Sitter gravity coupled to certain tachyonic scalars with boundary conditions defined by a smooth function W. It has recently been argued there is a lower bound on the conserved energy in terms of the global minimum of W, if the scalar potential arises from a superpotential P and the scalar reaches an extremum of P at infinity. We show, however, there are superpotentials for which these bounds do not hold.
Prima Facie Questions in Quantum Gravity
C. J. Isham
1993-10-22
The long history of the study of quantum gravity has thrown up a complex web of ideas and approaches. The aim of this article is to unravel this web a little by analysing some of the {\\em prima facie\\/} questions that can be asked of almost any approach to quantum gravity and whose answers assist in classifying the different schemes. Particular emphasis is placed on (i) the role of background conceptual and technical structure; (ii) the role of spacetime diffeomorphisms; and (iii) the problem of time.
Linear Stability Analysis of Dynamical Quadratic Gravity
Dimitry Ayzenberg; Kent Yagi; Nicolas Yunes
2014-03-18
We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.
Energy Distribution in f(R) Gravity
M. Sharif; M. Farasat Shamir
2009-12-18
The well-known energy problem is discussed in f(R) theory of gravity. We use the generalized Landau-Lifshitz energy-momentum complex in the framework of metric f(R) gravity to evaluate the energy density of plane symmetric solutions for some general f(R) models. In particular, this quantity is found for some popular choices of f(R) models. The constant scalar curvature condition and the stability condition for these models are also discussed. Further, we investigate the energy distribution of cosmic string spacetime.
Hogg, Charlie A. R.; Dalziel, Stuart B.; Huppert, Herbert E.; Imberger, Jörg
2015-01-01
by noise in the conductivity measurements which was minimised by the median 10 Gravity currents filling basins: influence of Reynolds number on entrainment Source x z Outflow ? D zf A = D/(sin ? cos ?) FIG. 6: Schematic of the basin. The gravity current... in these experiments, the horizontal length at the top of the basin is A = D/(sin ? cos ?) . The virtual origin is the origin for a source of buoyancy alone that would give rise to the volume and buoyancy flux that occurs at the physical origin. 12 Gravity currents...
Violation of the Holographic Principle in the Loop Quantum Gravity
Ozan Sarg?n; Mir Faizal
2015-09-01
In this paper, we analyze the holographic principle using loop quantum gravity (LQG). This will be done by analysing a simple quantum mechanical system using polymeric quantization. As the polymeric quantization is the characteristic feature of loop quantum gravity, we will argue that this calculation will indicate the effect on the holographic principle from the loop quantum gravity. Thus, we will be able to explicitly demonstrate the violation of the holographic principle in the loop quantum gravity.
Quantum reduced loop gravity: extension to scalar field
Jakub Bilski; Emanuele Alesci; Francesco Cianfrani
2015-07-02
The quantization of the Hamiltonian for a scalar field is performed in the framework of Quantum Reduced Loop Gravity. We outline how the regularization can be performed by using the analogous tools adopted in full Loop Quantum Gravity and the matrix elements of the resulting operator between basis states are analytic coefficients. These achievements open the way for a consistent analysis of the Quantum Gravity corrections to the classical dynamics of gravity in the presence of a scalar field in a cosmological setting.
Notes on several phenomenological laws of quantum gravity
Jean-Philippe Bruneton
2013-08-19
Phenomenological approaches to quantum gravity try to infer model-independent laws by analyzing thought experiments and combining both quantum, relativistic, and gravitational ingredients. We first review these ingredients -three basic inequalities- and discuss their relationships with the nature of fundamental constants. In particular, we argue for a covariant mass bound conjecture: in a spacetime free of horizon, the mass inside a surface $A$ cannot exceed $16 \\pi G^2 m^2inequalities and find/review the following: (1) Any system must have a size greater than the Planck length, in the sense that there exists a minimal area (2) We comment on the Minimal Length Scenarios and the fate of Lorentz symmetry near the Planck scale (3) Quanta with transplanckian frequencies are allowed in a large enough boxes (4) There exists a mass-dependent maximal acceleration given by $m c^3/\\hbar$ if $mm_p$ (5) There exists a mass dependent maximal force and power (6) There exists a maximal energy density and pressure (7) Physical systems must obey the Holographic Principle (8) Holographic bounds can only be saturated by systems with $m>m_p$; systems lying on the ``Compton line'' $l \\sim 1/m$ are fundamental objects without substructures (9) We speculate on a new bound from above for the action. In passing, we note that the maximal acceleration is of the order of Milgrom's acceleration $a_0$ for ultra-light particles ($m\\sim H_0)$ that could be associated to the Dark Energy fluid. This suggests designing toy-models in which modified gravity in galaxies is driven by the DE field, via the maximal acceleration principle.
Gravity currents in two-layer stratified media
Flynn, Morris R.
Gravity currents in two-layer stratified media Morris R. Flynn & Alan W.Tan Dept. of Mechanical Engineering, U.Alberta Funding: NSERC #12;· Gravity currents appear over a broad range of time/length scales. (1999), Flynn & Linden (2006),White & Helfrich (2008), Ungarish (2009) Introduction current gravity
Gravity Surface Wave Bifurcation in a Highly Turbulent Swirling Flow
Witten, Thomas A.
Gravity Surface Wave Bifurcation in a Highly Turbulent Swirling Flow Michael Baumer University Gravity Wave 2 3 Measurements 3 4 Mechanical Hardware: Problems and Solutions 5 5 Results 7 6 Conclusions investigated a free-surface gravity wave bifurcation in the large-separation regime, that is, where
Gravity Wave Lensing Ryan Elandt, Mostafa Shakeri & Reza Alam
Alam, Mohammad-Reza
Gravity Wave Lensing Ryan Elandt, Mostafa Shakeri & Reza Alam Department of Mechanical Engineering waves caused by small seabed features (the so called Bragg resonance) can be utilized to create equivalent of lenses and curved mirrors for surface gravity waves. Such gravity wave lenses, which are merely
Spherical collapse in Galileon gravity: fifth force solutions, halo mass function and halo bias
Barreira, Alexandre; Li, Baojiu; Baugh, Carlton M.; Pascoli, Silvia E-mail: liqb@mail.ihep.ac.cn E-mail: silvia.pascoli@durham.ac.uk
2013-11-01
We study spherical collapse in the Quartic and Quintic Covariant Galileon gravity models within the framework of the excursion set formalism. We derive the nonlinear spherically symmetric equations in the quasi-static and weak-field limits, focusing on model parameters that fit current CMB, SNIa and BAO data. We demonstrate that the equations of the Quintic model do not admit physical solutions of the fifth force in high density regions, which prevents the study of structure formation in this model. For the Quartic model, we show that the effective gravitational strength deviates from the standard value at late times (z?<1), becoming larger if the density is low, but smaller if the density is high. This shows that the Vainshtein mechanism at high densities is not enough to screen all of the modifications of gravity. This makes halos that collapse at z?<1 feel an overall weaker gravity, which suppresses halo formation. However, the matter density in the Quartic model is higher than in standard ?CDM, which boosts structure formation and dominates over the effect of the weaker gravity. In the Quartic model there is a significant overabundance of high-mass halos relative to ?CDM. Dark matter halos are also less biased than in ?CDM, with the difference increasing appreciably with halo mass. However, our results suggest that the bias may not be small enough to fully reconcile the predicted matter power spectrum with LRG clustering data.
Quasi-Local Conserved Charges of Spin-3 Topologically Massive Gravity
Setare, M R
2016-01-01
In this paper we obtain conserved charges of spin-3 topologically massive gravity by using a quasi-local formalism. We find a general formula to calculate conserved charge of the spin-3 topologically massive gravity corresponds to a Killing vector field $\\xi$. We show that this general formula reduces to the previous one for the ordinary spin-3 gravity presented in \\cite{31} when we take into account only transformation under diffeomorphism, without considering generalized Lorentz gauge transformation (i.e. $\\lambda _{\\xi} =0$), and by taking $\\frac{1}{\\mu}\\rightarrow 0$. Then we obtain a general formula for the entropy of black hole solutions of the spin-3 topologically massive gravity. Finally we apply our formalism to calculate energy, angular momentum and entropy of a special black hole solution and we find that obtained results are consistent with previous results in the limiting cases. Moreover our result for energy, angular momentum and entropy are consistent with the first law of black hole mechanics.
Constraints on modified Gauss-Bonnet gravity during big bang nucleosynthesis
Kusakabe, Motohiko; Kim, K S; Cheoun, Myung-Ki
2015-01-01
The modified gravity is considered to be one of possible explanations of the accelerated expansions of the present and the early universe. We study effects of the modified gravity on big bang nucleosynthesis (BBN). If effects of the modified gravity are significant during the BBN epoch, they should be observed as changes of primordial light element abundances. We assume a $f(G)$ term with the Gauss-Bonnet term $G$, during the BBN epoch. A power-law relation of $df/dG \\propto t^p$ where $t$ is the cosmic time was assumed for the function $f(G)$ as an example case. We solve time evolutions of physical variables during BBN in the $f(G)$ gravity model numerically, and analyzed calculated results. It is found that a proper solution for the cosmic expansion rate can be lost in some parameter region. In addition, we show that calculated results of primordial light element abundances can be significantly different from observational data. Especially, observational limits on primordial D abundance leads to the stronge...
Fontana, Peter R.; Srivastava, Rajendra P.
1973-06-01
at E = 0 is 2le I' Ib/(t)I = @~ R~R~~»nh'(IRlyt)e"'" (13)a ylal 0 5 '7 FIG. 3. Probabilities of photon emission as a function of time. The frequency corresponds to the energy differ- ence between the unperturbed degenerate excited states and the ground... states 6 is 0. 5 ey. For V= 0 the emission line is Lorentzian, but for V0 a "hole" appears at the frequency equal to the frequency difference between the excited nondecay- ing state and the ground state. The position of the "hole" is independent...
Black Holes with Scalar Hairs in Einstein-Gauss-Bonnet Gravity
Y. Brihaye; L. Ducobu
2015-11-21
The Einstein-Gauss-Bonnet gravity in five dimensions is extended by scalar fields and the corresponding equations are reduced to a system of non-linear differential equations. A large family of regular solutions of these equations is shown to exist. Generically, these solutions are spinning black holes with scalar hairs. They can be characterized (but not uniquely) by an horizon and an angular velocity on this horizon. Taking particular limits the black holes approach boson star or become extremal, in any case the limiting configurations remain hairy.
Black Holes with Scalar Hairs in Einstein-Gauss-Bonnet Gravity
Brihaye, Y
2015-01-01
The Einstein-Gauss-Bonnet gravity in five dimensions is extended by scalar fields and the corresponding equations are reduced to a system of non-linear differential equations. A large family of regular solutions of these equations is shown to exist. Generically, these solutions are spinning black holes with scalar hairs. They can be characterized (but not uniquely) by an horizon and an angular velocity on this horizon. Taking particular limits the black holes approach boson star or become extremal, in any case the limiting configurations remain hairy.
Infrared lessons for ultraviolet gravity: the case of massive gravity and Born-Infeld
Jiménez, Jose Beltrán; Heisenberg, Lavinia; Olmo, Gonzalo J. E-mail: Lavinia.Heisenberg@unige.ch
2014-11-01
We generalize the ultraviolet sector of gravitation via a Born-Infeld action using lessons from massive gravity. The theory contains all of the elementary symmetric polynomials and is treated in the Palatini formalism. We show how the connection can be solved algebraically to be the Levi-Civita connection of an effective metric. The non-linearity of the algebraic equations yields several branches, one of which always reduces to General Relativity at low curvatures. We explore in detail a minimal version of the theory, for which we study solutions in the presence of a perfect fluid with special attention to the cosmological evolution. In vacuum we recover Ricci-flat solutions, but also an additional physical solution corresponding to an Einstein space. The existence of two physical branches remains for non-vacuum solutions and, in addition, the branch that connects to the Einstein space in vacuum is not very sensitive to the specific value of the energy density. For the branch that connects to the General Relativity limit we generically find three behaviours for the Hubble function depending on the equation of state of the fluid, namely: either there is a maximum value for the energy density that connects continuously with vacuum, or the energy density can be arbitrarily large but the Hubble function saturates and remains constant at high energy densities, or the energy density is unbounded and the Hubble function grows faster than in General Relativity. The second case is particularly interesting because it could offer an interesting inflationary epoch even in the presence of a dust component. Finally, we discuss the possibility of avoiding certain types of singularities within the minimal model.
The Mars Gravity Biosatellite as an innovative partial gravity research platform
Fulford-Jones, Thaddeus R. F
2008-01-01
The Mars Gravity Biosatellite is an unprecedented independent spaceflight platform for gravitational biology research. With a projected first launch after 2010, the low Earth orbit satellite will support a cohort of fifteen ...
Griffith, Arnold K.
1971-01-01
A line verifier is presented which, given the co-ordinates of the end points of the hypothesized line, returns a (possibly) more accurate version of the end points, together with an estimate of the probability that there ...
The diffeomorphism algebra approach to quantum gravity
T. A. Larsson
1999-09-13
The representation theory of non-centrally extended Lie algebras of Noether symmetries, including spacetime diffeomorphisms and reparametrizations of the observer's trajectory, has recently been developped. It naturally solves some long-standing problems in quantum gravity, e.g. the role of diffeomorphisms and the causal structure, but some new questions also arise.
Topological Black Holes in Quantum Gravity
J. Kowalski-Glikman; D. Nowak-Szczepaniak
2000-07-31
We derive the black hole solutions with horizons of non-trivial topology and investigate their properties in the framework of an approach to quantum gravity being an extension of Bohm's formulation of quantum mechanics. The solutions we found tend asymptotically (for large $r$) to topological black holes. We also analyze the thermodynamics of these space-times.
Energy definition for quadratic curvature gravities
Ahmet Baykal
2012-12-03
A conserved current for generic quadratic curvature gravitational models is defined, and it is shown that, at the linearized level, it corresponds to the Deser-Tekin charges. An explicit expression for the charge for new massive gravity in three dimensions is given. Some implications of the linearized equations are discussed.
p-wave superconductors in dilaton gravity
ZhongYing Fan
2013-10-08
In this paper, we study peculiar properties of p-wave superconductors in dilaton gravity. The scale invariance of the bulk geometry is effectively broken due to the existence of dilaton. By coupling the dilaton to the non-Abelian gauge field, i.e., $-\\frac14 e^{-\\beta \\Phi} F^a_{\\mu\
Ultrasonic hydrometer. [Specific gravity of electrolyte
Swoboda, C.A.
1982-03-09
The disclosed ultrasonic hydrometer determines the specific gravity (density) of the electrolyte of a wet battery, such as a lead-acid battery. The hydrometer utilizes a transducer that when excited emits an ultrasonic impulse that traverses through the electrolyte back and forth between spaced sonic surfaces. The transducer detects the returning impulse, and means measures the time t between the initial and returning impulses. Considering the distance d between the spaced sonic surfaces and the measured time t, the sonic velocity V is calculated with the equation V = 2d/t. The hydrometer also utilizes a thermocouple to measure the electrolyte temperature. A hydrometer database correlates three variable parameters including sonic velocity in and temperature and specific gravity of the electrolyte, for temperature values between 0 and 40/sup 0/C and for specific gravity values between 1.05 and 1.30. Upon knowing two parameters (the calculated sonic velocity and the measured temperature), the third parameter (specific gravity) can be uniquely found in the database. The hydrometer utilizes a microprocessor for data storage and manipulation.
Transmission Line Circuit Alexander Glasser
Anlage, Steven
Chaos in a Transmission Line Circuit Alexander Glasser Marshal Miller With... Prof. Edward Ott Prof times become shorter, circuit connections behave more and more like transmission lines. Theoretical(t) - Transmission Line (Zo, T) #12;5 Cf/Cr 1000 Vf Capacitance Voltage Cf Cr Model for Nonlinear Capacitor
On the z=4 Horava-Lifshitz Gravity
Rong-Gen Cai; Yan Liu; Ya-Wen Sun
2009-06-04
We consider z=4 Horava-Lifshitz gravity in both 3+1 and 4+1 dimensions. We find black hole solutions in the IR region for a kind of z=4 Horava-Lifshitz gravity which is inherited from the new massive gravity in three dimensions and an analog of the new massive gravity in four dimensions through the quantum inheritance principle. We analyze thermodynamic properties for the black hole solutions for z=4 Horava-Lifshitz gravity. We also write out the Friedmann equation in 3+1 dimensions for cosmological solutions.
Measuring the Earth's gravity field with cold atom interferometers
Olivier Carraz; Christian Siemes; Luca Massotti; Roger Haagmans; Pierluigi Silvestrin
2015-06-12
The scope of the paper is to propose different concepts for future space gravity missions using Cold Atom Interferometers (CAI) for measuring the diagonal elements of the gravity gradient tensor, the spacecraft angular velocity and the spacecraft acceleration. The aim is to achieve better performance than previous space gravity missions due to a very low white noise spectral behaviour of the CAI instrument and a very high common mode rejection, with the ultimate goals of determining the fine structures of the gravity field with higher accuracy than GOCE and detecting time-variable signals in the gravity field.
ExoMol line lists VIII: A variationally computed line list for hot formaldehyde
Al-Refaie, Ahmed F; Tennyson, Jonathan; Yurchenko, Sergei N
2015-01-01
A computed line list for formaldehyde, H$_2{}^{12}$C$^{16}$O, applicable to temperatures up to $T=1500$~K is presented. An empirical potential energy and {\\it ab initio} dipole moment surfaces are used as the input to nuclear motion program TROVE. The resulting line list, referred to as \\textit{AYTY}, contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies. Each transition includes associated Einstein-$A$ coefficients and absolute transition intensities, for wavenumbers below 10~000 cm\\(^{-1}\\) and rotational excitations up to \\(J=70\\). Room-temperature spectra are compared with laboratory measurements and data currently available in the HITRAN database. These spectra show excellent agreement with experimental spectra and highlight the gaps and limitations of the HITRAN data. The full line list is available from the CDS database as well as at \\url{www.exomol.com}.
Alexander Oshmyansky
2007-03-08
An alternative quantum field theory for gravity is proposed for low energies based on an attractive effect between contaminants in a Bose-Einstein Condensate rather than on particle exchange. In the ``contaminant in condensate effect," contaminants cause a potential in an otherwise uniform condensate, forcing the condensate between two contaminants to a higher energy state. The energy of the system decreases as the contaminants come closer together, causing an attractive force between contaminants. It is proposed that mass-energy may have a similar effect on Einstein's space-time field, and gravity is quantized by the same method by which the contaminant in condensate effect is quantized. The resulting theory is finite and, if a physical condensate is assumed to underly the system, predictive. However, the proposed theory has several flaws at high energies and is thus limited to low energies. Falsifiable predictions are given for the case that the Higgs condensate is assumed to be the condensate underlying gravity.
Geodesic Deviation Equation in $f(T)$ gravity
F. Darabi; M. Mousavi; K. Atazadeh
2015-04-14
In this work, we show that it is possible to study the notion of geodesic deviation equation in $f(T)$ gravity, in spite of the fact that in teleparallel gravity there is no notion of geodesics, and the torsion is responsible for the appearance of gravitational interaction. In this regard, we obtain the GR equivalent equations for $f(T)$ gravity which are in the modified gravity form such as $f(R)$ gravity. Then, we obtain the GDE within the context of this modified gravity. In this way, the obtained geodesic deviation equation will correspond to the $f(T)$ gravity. Eventually, we extend the calculations to obtain the modification of Matting relation.
On Effective Spacetime Dimension in the Ho\\v{r}ava-Lifshitz Gravity
Alencar, G; Cunha, M S; Muniz, C R
2015-01-01
In this manuscript we explicitly compute the effective dimension of spacetime in some backgrounds of Ho\\v{r}ava-Lifshitz (H-L) gravity. For all the cases considered, the results are compatible with a dimensional reduction of the spacetime to $d+1=2$, at high energies (ultraviolet limit), which is confirmed by other quantum gravity approaches, as well as to $d+1=4$, at low energies (infrared limit). This is obtained by computing the free energy of massless scalar and gauge fields. We find that the only effect of the background is to change the proportionality constant between the internal energy and temperature. Firstly, we consider both the non-perturbative and perturbative models involving the matter action, without gravitational sources but with manifest time and space symmetry breaking, in order to calculate modifications in the Stephan-Boltzmann law. When gravity is taken into account, we assume a scenario in which there is a spherical source with mass $M$ and radius $R$ in thermal equilibrium with radiat...
Analytic continuation of real Loop Quantum Gravity : Lessons from black hole thermodynamics
Jibril Ben Achour; Karim Noui
2015-01-22
This contribution is devoted to summarize the recent results obtained in the construction of an "analytic continuation" of Loop Quantum Gravity (LQG). By this, we mean that we construct analytic continuation of physical quantities in LQG from real values of the Barbero-Immirzi parameter $\\gamma$ to the purely imaginary value $\\gamma = \\pm i$. This should allow us to define a quantization of gravity with self-dual Ashtekar variables. We first realized in [1] that this procedure, when applied to compute the entropy of a spherical black hole in LQG for $\\gamma=\\pm i$, allows to reproduce exactly the Bekenstein-Hawking area law at the semi-classical limit. The rigorous construction of the analytic continuation of spherical black hole entropy has been done in [2]. Here, we start with a review of the main steps of this construction: we recall that our prescription turns out to be unique (under natural assumptions) and leads to the right semi-classical limit with its logarithmic quantum corrections. Furthermore, the discrete and $\\gamma$-dependent area spectrum of the black hole horizon becomes continuous and obviously $\\gamma$-independent. Then, we review how this analytic continuation could be interpreted in terms of an analytic continuation from the compact gauge group $SU(2)$ to the non-compact gauge group $SU(1,1)$ relying on an analysis of three dimensional quantum gravity.
Powerful evidences for supporting the claim that gamma-ray burst redshifts are gravity-generated
Fu-Gao Song
2012-06-24
At present, it is widely believed that the phenomenon of the gamma-ray burst redshift is cosmological origin. From a theoretical point of view, this redshift has either a cosmological or a cause that is related to gravity. However, the question of whether the gamma-ray burst redshift has a cosmological origin or not should be answerable in no uncertain terms because both the spectrum characteristics and the count distribution law arising from the two distinct settings are completely different. If the redshift of GRB is generated by gravity, then the afterglow spectrum will certainly contain both the gravitational redshits (containing emission and absorption feature) and Doppler absorption redshift, and hold a definite relation between the two redshifts. In this paper, we present nine direct and decisive evidences to show that the gamma-ray burst redshift is indeed generated by gravity of neutron stars in their merging process; in which, 114 GRBs' redshifts showed that the statistical count distribution law for the two kinds redshift is the same (with errors less than 1.5%), and 74 spectral line redshifts of two GRBs showed that the relation between the two kinds redshift is completely correct (with errors less than 0.0061%).
Projected Constraints on Lorentz-Violating Gravity with Gravitational Waves
Devin Hansen; Nicolas Yunes; Kent Yagi
2014-12-12
Gravitational waves are excellent tools to probe the foundations of General Relativity in the strongly dynamical and non-linear regime. One such foundation is Lorentz symmetry, which can be broken in the gravitational sector by the existence of a preferred time direction, and thus, a preferred frame at each spacetime point. This leads to a modification in the orbital decay rate of binary systems, and also in the generation and chirping of their associated gravitational waves. We here study whether waves emitted in the late, quasi-circular inspiral of non-spinning, neutron star binaries can place competitive constraints on two proxies of gravitational Lorentz-violation: Einstein-\\AE{}ther theory and khronometric gravity. We model the waves in the small-coupling (or decoupling) limit and in the post-Newtonian approximation, by perturbatively solving the field equations in small deformations from General Relativity and in the small-velocity/weak-gravity approximation. We assume a gravitational wave consistent with General Relativity has been detected with second- and third-generation, ground-based detectors, and with the proposed space-based mission, DECIGO, with and without coincident electromagnetic counterparts. Without a counterpart, a detection consistent with General Relativity of neutron star binaries can only place competitive constraints on gravitational Lorentz violation when using future, third-generation or space-based instruments. On the other hand, a single counterpart is enough to place constraints that are 10 orders of magnitude more stringent than current binary pulsar bounds, even when using second-generation detectors. This is because Lorentz violation forces the group velocity of gravitational waves to be different from that of light, and this difference can be very accurately constrained with coincident observations.
Analogue quantum gravity phenomenology from a two-component Bose-Einstein condensate
Stefano Liberati; Matt Visser; Silke Weinfurtner
2006-03-16
We present an analogue spacetime model that reproduces the salient features of the most common ansatz for quantum gravity phenomenology. We do this by investigating a system of two coupled Bose-Einstein condensates. This system can be tuned to have two "phonon" modes (one massive, one massless) which share the same limiting speed in the hydrodynamic approximation [Phys. Rev. D72 (2005) 044020, gr-qc/0506029; cond-mat/0409639]. The system nevertheless possesses (possibly non-universal) Lorentz violating terms at very high energies where "quantum pressure" becomes important. We investigate the physical interpretation of the relevant fine-tuning conditions, and discuss the possible lessons and hints that this analogue spacetime could provide for the phenomenology of real physical quantum gravity. In particular we show that the effective field theory of quasi-particles in such an emergent spacetime does not exhibit the so called "naturalness problem".
Plains and Eastern Clean Line Transmission Line: Federal Register...
Clean Line project. The project would include an overhead 600-kilovolt (kv) high voltage, direct current electric transmission system and associated facilities with the capacity to...
Proposed Project: Plains & Eastern Clean Line Transmission Line...
& Eastern Clean Line project (the proposed project) would include an overhead +- 600 kV direct current electric transmission system and associated facilities with the capacity to...
On Effective Spacetime Dimension in the Ho?ava-Lifshitz Gravity
G. Alencar; V. B. Bezerra; M. S. Cunha; C. R. Muniz
2015-05-22
In this manuscript we explicitly compute the effective dimension of spacetime in some backgrounds of Ho\\v{r}ava-Lifshitz (H-L) gravity. For all the cases considered, the results are compatible with a dimensional reduction of the spacetime to $d+1=2$, at high energies (ultraviolet limit), which is confirmed by other quantum gravity approaches, as well as to $d+1=4$, at low energies (infrared limit). This is obtained by computing the free energy of massless scalar and gauge fields. We find that the only effect of the background is to change the proportionality constant between the internal energy and temperature. Firstly, we consider both the non-perturbative and perturbative models involving the matter action, without gravitational sources but with manifest time and space symmetry breaking, in order to calculate modifications in the Stephan-Boltzmann law. When gravity is taken into account, we assume a scenario in which there is a spherical source with mass $M$ and radius $R$ in thermal equilibrium with radiation, and consider the static and spherically symmetric solution of the H-L theory found by Kehagias-Sfetsos (K-S), in the weak and strong field approximations. As byproducts, for the weak field regime, we used the current uncertainty of the solar radiance measurements to establish a constraint on the $\\omega$ free parameter of the K-S solution. We also calculate the corrections, due to gravity, to the recently predicted attractive force that black bodies exert on nearby neutral atoms and molecules.
Decoupling of gravity on non-susy D$p$ branes
Kuntal Nayek; Shibaji Roy
2015-06-29
We study the graviton scattering in the background of non-susy D$p$ branes of type II string theories consisting of a metric, a dilaton and a $(p+1)$ form gauge field. We show numerically that in these backgrounds graviton experiences a scattering potential which takes the form of an infinite barrier in the low energy (near brane) limit for $p\\leq 5$ and therefore is never able to reach the branes. This shows, contrary to what is known in the literature, that gravity indeed decouples from the non-susy D$p$ brane for $p \\leq 5$. For non-susy D6 brane, gravity couples as there is no such barrier for the potential. To give further credence to our claim we solve the scattering equation in certain situation analytically and calculate the graviton absorption cross-section on the non-susy branes and show that it vanishes for $p \\leq 4$ and diverges for $p=6$ in the low energy limit. This shows, as in the case of BPS branes, that gravity does decouple for non-susy D$p$ brane for $p\\leq 4$ but it does not decouple for D6 brane as the potential here is always attractive. We argue for the non-susy D5 brane that depending on one of the parameters of the solution gravity either always decouples (unlike the BPS D5 brane) or it decouples when the energy of the graviton is below certain critical value, otherwise it couples, very similar to BPS D5 brane.
Junction conditions in extended Teleparallel gravities
De la Cruz-Dombriz, Álvaro; Dunsby, Peter K.S.; Sáez-Gómez, Diego E-mail: peter.dunsby@uct.ac.za
2014-12-01
In the context of extended Teleparallel gravity theories, we address the issue of junction conditions required to guarantee the correct matching of different regions of spacetime. In the absence of shells/branes, these conditions turn out to be more restrictive than their counterparts in General Relativity as in other extended theories of gravity. In fact, the general junction conditions on the matching hypersurfaces depend on the underlying theory and a new condition on the induced tetrads in order to avoid delta-like distributions in the field equations. This result imposes strict consequences on the viability of standard solutions such as the Einstein-Straus-like construction. We find that the continuity of the scalar torsion is required in order to recover the usual General Relativity results.
Hydrogen atom in Palatini theories of gravity
Gonzalo J. Olmo
2008-06-03
We study the effects that the gravitational interaction of $f(R)$ theories of gravity in Palatini formalism has on the stationary states of the Hydrogen atom. We show that the role of gravity in this system is very important for lagrangians $f(R)$ with terms that grow at low curvatures, which have been proposed to explain the accelerated expansion rate of the universe. We find that new gravitationally induced terms in the atomic Hamiltonian generate a strong backreaction that is incompatible with the very existence of bound states. In fact, in the 1/R model, Hydrogen disintegrates in less than two hours. The universe that we observe is, therefore, incompatible with that kind of gravitational interaction. Lagrangians with high curvature corrections do not lead to such instabilities.
Infrared modification of gravity from conformal symmetry
Gegenberg, Jack; Seahra, Sanjeev S
2015-01-01
We reconsider a gauge theory of gravity in which the gauge group is the conformal group SO(4,2) and the action is of the Yang-Mills form, quadratic in the curvature. The resulting gravitational theory exhibits local conformal symmetry and reduces to Weyl-squared gravity under certain conditions. When the theory is linearized about flat spacetime, we find that matter which couples to the generators of special conformal transformations reproduces Newton's inverse square law. Conversely, matter which couples to generators of translations induces a constant and possibly repulsive force far from the source, which may be relevant for explaining the late time acceleration of the universe. The coupling constant of theory is dimensionless, which means that it is potentially renormalizable.
Conceptual Aspects of Gauge/Gravity Duality
de Haro, Sebastian; Butterfield, Jeremy
2015-01-01
We give an introductory review of gauge/gravity duality, and associated ideas of holography, emphasising the conceptual aspects. The opening Sections gather the ingredients, viz. anti-de Sitter spacetime, conformal field theory and string theory, that we need for presenting, in Section 5, the central and original example: Maldacena's AdS/CFT correspondence. Sections 6 and 7 develop the ideas of this example, also in applications to condensed matter systems, QCD, and hydrodynamics. Sections 8 and 9 discuss the possible extensions of holographic ideas to de Sitter spacetime and to black holes. Section 10 discusses the bearing of gauge/gravity duality on two philosophical topics: the equivalence of physical theories, and the idea that spacetime, or some features of it, are emergent.
Can $f(T)$ gravity theories mimic $?$CDM cosmic history
M. R. Setare; N. Mohammadipour
2013-01-12
Recently the teleparallel Lagrangian density described by the torsion scalar T has been extended to a function of T. The $f(T)$ modified teleparallel gravity has been proposed as the natural gravitational alternative for dark energy to explain the late time acceleration of the universe. In order to reconstruct the function $f(T)$ by demanding a background $\\Lambda$CDM cosmology we assume that, (i) the background cosmic history provided by the flat $\\Lambda$CDM (the radiation ere with $\\omega_{eff}=1/3$, matter and de Sitter eras with $\\omega_{eff}=0$ and $\\omega_{eff}=-1$, respectively) (ii) the radiation dominate in the radiation era with $\\Omega_{0r}=1$ and the matter dominate during the matter phases when $\\Omega_{0m}=1$. We find the cosmological dynamical system which can obey the $\\Lambda$CDM cosmic history. In each era, we find a critical lines that, the radiation dominated and the matter dominated are one points of them in the radiation and matter phases, respectively. Also, we drive the cosmologically viability condition for these models. We investigate the stability condition with respect to the homogeneous scalar perturbations in each era and we obtain the stability conditions for the fixed points in each eras. Finally, we reconstruct the function $f(T)$ which mimics cosmic expansion history.
Notes on several phenomenological laws of quantum gravity
Bruneton, Jean-Philippe
2013-01-01
Phenomenological approaches to quantum gravity try to infer model-independent laws by analyzing thought experiments and combining both quantum, relativistic, and gravitational ingredients. We first review these ingredients -three basic inequalities- and discuss their relationships with the nature of fundamental constants. In particular, we argue for a covariant mass bound conjecture: in a spacetime free of horizon, the mass inside a surface $A$ cannot exceed $16 \\pi G^2 m^2m_p$ (5) There exists a mass dependent maximal force and power (6) There exists a maximal energy density and pressure (7) Physical systems must obey the Holographic Principle (8) Holographic bounds can only be saturated by systems with $m>m_p$; systems lying on the ``Compton line'' $l \\sim 1/m$ are fundamental objects without substructures (9) We speculate on a new bound from above for the action. In passing, we note that the maximal acceleration is of the order of Milgrom's acceleration $a_0$ for ultra-light particles ($m\\sim H_0)$ that co...
Gravity controlled anti-reverse rotation device
Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wetherill, Todd M. (Lower Burrell, PA)
1983-01-01
A gravity assisted anti-reverse rotation device for preventing reverse rotation of pumps and the like. A horizontally mounted pawl is disposed to mesh with a fixed ratchet preventing reverse rotation when the pawl is advanced into intercourse with the ratchet by a vertically mounted lever having a lumped mass. Gravitation action on the lumped mass urges the pawl into mesh with the ratchet, while centrifugal force on the lumped mass during forward, allowed rotation retracts the pawl away from the ratchet.
Regulation of flexible arms under gravity
De Luca, A.; Siciliano, B.
1993-08-01
A simple controller is presented for the regulation problem of robot arms with flexible links under gravity. It consists of a joint PD feedback plus a constant feedforward. Global asymptotic stability of the reference equilibrium state is shown under a structural assumption about link elasticity and a mild condition on the proportional gain. The result holds also in the absence of internal damping of the flexible arm. A numerical case study is presented.
Charged Cylindrical Black Holes in Conformal Gravity
Jackson Levi Said; Joseph Sultana; Kristian Zarb Adami
2013-01-04
Considering cylindrical topology we present the static solution for a charged black hole in conformal gravity. We show that unlike the general relativistic case there are two different solutions, both including a factor that when set to zero recovers the familiar static charged black string solution in Einstein's theory. This factor gives rise to a linear term in the potential that also features in the neutral case and may have significant ramifications for particle trajectories.
Holographic Superconductivity with Gauss-Bonnet gravity
Ruth Gregory
2010-12-07
I review recent work on holographic superconductivity with Einstein-Gauss-Bonnet gravity, and show how the critical temperature of the superconductor depends on both gravitational backreaction and the Gauss-Bonnet parameter, using both analytic and numerical arguments. I also review computations of the conductivity, finding the energy gap, and demonstrating that there is no universal gap ratio, $\\omega_g/T_c$, for these superconductors.
Exact Gravity Dual of a Gapless Superconductor
George Koutsoumbas; Eleftherios Papantonopoulos; George Siopsis
2009-06-17
A model of an exact gravity dual of a gapless superconductor is presented in which the condensate is provided by a charged scalar field coupled to a bulk black hole of hyperbolic horizon in asymptotically AdS spacetime. Below a critical temperature, the black hole acquires its hair through a phase transition while an electromagnetic perturbation of the background Maxwell field determines the conductivity of the boundary theory.
Disformal Gravity Theories: A Jordan Frame Analysis
Sakstein, Jeremy
2015-01-01
The late-time cosmology of disformal gravity theories is studied in the Jordan frame using both dynamical systems methods, and by finding approximate solutions. We find that, either the disformal effects are irrelevant, or the universe evolves towards a phantom phase where the equation of state of dark energy is $-3$, in strong tension with observations. There is a marginal case where the asymptotic state of the universe depends on the model parameters and de-Sitter solutions can be obtained.
Critical regimes of internal gravity wave generation
Vitaly V. Bulatov; Yuriy V. Vladimirov; Vasily A. Vakorin
2005-11-27
The problem of constructing an asymptotic representation of the solution of the internal gravity wave field exited by a source moving at a velocity close to the maximum group velocity of the individual wave mode is considered. For the critical regimes of individual mode generation the asymptotic representation of the solution obtained is expressed in terms of a zero-order Macdonald function. The results of numerical calculations based on the exact and asymptotic formulas are given.
Rhodes, Mark A. (Pleasanton, CA)
2008-10-21
A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.
EC Transmission Line Materials
Bigelow, Tim S
2012-05-01
The purpose of this document is to identify materials acceptable for use in the US ITER Project Office (USIPO)-supplied components for the ITER Electron cyclotron Heating and Current Drive (ECH&CD) transmission lines (TL), PBS-52. The source of material property information for design analysis shall be either the applicable structural code or the ITER Material Properties Handbook. In the case of conflict, the ITER Material Properties Handbook shall take precedence. Materials selection, and use, shall follow the guidelines established in the Materials Assessment Report (MAR). Materials exposed to vacuum shall conform to the ITER Vacuum Handbook. [Ref. 2] Commercial materials shall conform to the applicable standard (e.g., ASTM, JIS, DIN) for the definition of their grade, physical, chemical and electrical properties and related testing. All materials for which a suitable certification from the supplier is not available shall be tested to determine the relevant properties, as part of the procurement. A complete traceability of all the materials including welding materials shall be provided. Halogenated materials (example: insulating materials) shall be forbidden in areas served by the detritiation systems. Exceptions must be approved by the Tritium System and Safety Section Responsible Officers.
Neutron stars as laboratories for gravity physics
Deliduman, Cemsinan
2014-01-01
We study the structure of neutron stars in R+?R² gravity model with perturbative method. We obtain mass-radius relations for four representative equations of state (EoS). We find that, for |?|~10? cm², the results differ substantially from the results of general relativity. The effects of modified gravity are seen as mimicking a stiff or soft EoS for neutron stars depending upon whether ? is negative or positive, respectively. Some of the soft EoS that are excluded within the framework of general relativity can be reconciled for certain values of ? of this order with the 2 solar mass neutron star recently observed. Indeed, if the EoS is ever established to be soft, modified gravity of the sort studied here may be required to explain neutron star masses as large as 2 M{sub ?}. The associated length scale ?(?)~10? cm is of the order of the the typical radius of neutron stars implying that this is the smallest value we could find by using neutron stars as a probe. We thus conclude that the true value of ? is most likely much smaller than 10? cm².
Cosmology with Coupled Gravity and Dark Energy
Ti-Pei Li
2015-01-13
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.
Thomas M. Stace
2010-06-08
The precision of typical thermometers consisting of $N$ particles is shot noise limited, improving as $\\sim1/\\sqrt{N}$. For high precision thermometry and thermometric standards this presents an important theoretical noise floor. Here it is demonstrated that thermometry may be mapped onto the problem of phase estimation, and using techniques from optimal phase estimation, it follows that the scaling of the precision of a thermometer may in principle be improved to $\\sim1/N$, representing a Heisenberg limit to thermometry.
Emergency pipe line repair connects subsea pipe lines
Lerique, M.P.; Thiberge, P. ); Wright, N. )
1990-11-01
Emergency repair of any subsea line pipe must form a high-integrity, metal-to-metal seal. This paper presents a remote, diverless repair system that utilizes master flanges, a connector and a spool piece to repair line pipe in deep offshore waters.
Fossati, L; Lanza, A F
2015-01-01
The chromospheric activity index logR'HK of stars hosting transiting hot Jupiters appears to be correlated with the planets' surface gravity. One of the possible explanations is based on the presence of condensations of planetary evaporated material located in a circumstellar cloud that absorbs the CaII H&K and MgII h&k resonance line emission flux, used to measure chromospheric activity. A larger column density in the condensations, or equivalently a stronger absorption in the chromospheric lines, is obtained when the evaporation rate of the planet is larger, which occurs for a lower gravity of the planet. We analyze here a sample of stars hosting transiting hot Jupiters tuned in order to minimize systematic effects (e.g., interstellar medium absorption). Using a mixture model, we find that the data are best fit by a two-linear-regression model. We interpret this result in terms of the Vaughan-Preston gap. We use a Monte Carlo approach to best take into account the uncertainties, finding that the two...
Kristofer Davis, M. Andy Kass, and Yaoguo Li, Center for Gravity, Electrical and Magnetic Studies, Colorado
Black Holes in Gauss-Bonnet Gravity's Rainbow
Seyed Hossein Hendi; Mir Faizal
2015-08-08
In this paper, we will generalize the Gauss-Bonnet gravity to an energy dependent Gauss-Bonnet theory of gravity, which we shall call as the Gauss-Bonnet gravity's rainbow. We will also couple this theory to a Maxwell's theory. We will analyze black hole solutions in this energy dependent Gauss-Bonnet gravity's rainbow. We will calculate the modifications to the thermodynamics of black holes in the Gauss-Bonnet's gravity's rainbow. We will demonstrate that even though the thermodynamics of the black holes get modified in the Gauss-Bonnet gravity's rainbow, the first law of thermodynamics still holds for this modified thermodynamics. We will also comment on the thermal stability of the black hole solutions in this theory.
Testing alternative theories of gravity using the Sun
Jordi Casanellas; Paolo Pani; Ilídio Lopes; Vitor Cardoso
2011-10-20
We propose a new approach to test possible corrections to Newtonian gravity using solar physics. The high accuracy of current solar models and new precise observations allow one to constrain corrections to standard gravity at unprecedented levels. Our case study is Eddington-inspired gravity, an attractive modified theory of gravity which results in non-singular cosmology and collapse. The theory is equivalent to standard gravity in vacuum, but it sensibly differs from it within matter, for instance it affects the evolution and the equilibrium structure of the Sun, giving different core temperature profiles, deviations in the observed acoustic modes and in solar neutrino fluxes. Comparing the predictions from a modified solar model with observations, we constrain the coupling parameter of the theory, |kappa_g| < 3x10^5 m^5 s^2 / kg. Our results show that the Sun can be used to efficiently constraint alternative theories of gravity.
Fab 5: noncanonical kinetic gravity, self tuning, and cosmic acceleration
Appleby, Stephen A.; Linder, Eric V. [Institute for the Early Universe WCU, Ewha Womans University, Seoul (Korea, Republic of); Felice, Antonio De, E-mail: stephen.appleby@ewha.ac.kr, E-mail: adefelic@gmail.com, E-mail: evlinder@lbl.gov [ThEP's CRL, NEP, The Institute for Fundamental Study, Naresuan University, Phitsanulok 65000 (Thailand)
2012-10-01
We investigate circumstances under which one can generalize Horndeski's most general scalar-tensor theory of gravity. Specifically we demonstrate that a nonlinear combination of purely kinetic gravity terms can give rise to an accelerating universe without the addition of extra propagating degrees of freedom on cosmological backgrounds, and exhibit self tuning to bring a large cosmological constant under control. This nonlinear approach leads to new properties that may be instructive for exploring the behaviors of gravity.
Action in the Entropic Revolution of Newtonian Gravity
Joakim Munkhammar
2010-05-17
The theory of gravity has undergone somewhat of a revolution lately. Gravity is no longer a fundamental force it seems, but rather an effect of holographic entropy. Building on the works by Jacobsson, Padmanabhan and Verlinde we review the concept of Newtonian gravity as an entropic force and discuss a possible general action approach to Verlinde's theory. We also discuss some open problems and future prospects of Verlinde's approach.
Covariant Symplectic Structure and Conserved Charges of Topologically Massive Gravity
Caner Nazaroglu; Yavuz Nutku; Bayram Tekin
2011-06-07
We present the covariant symplectic structure of the Topologically Massive Gravity and find a compact expression for the conserved charges of generic spacetimes with Killing symmetries.
Lorentz Invariant phenomenological model of quantum gravity: A minimalistic presentation
Bonder, Yuri
2012-08-24
The purpose of this paper is to give a minimalistic and self-contained presentation of a Lorentz Invariant phenomenological model of Quantum Gravity.
Gravity Survey of the Carson Sink - Data and Maps
Faulds, James E.
2013-12-31
A detailed gravity survey was carried out for the entire Carson Sink in western Nevada (Figure 1) through a subcontract to Zonge Engineering, Inc. The Carson Sink is a large composite basin containing three known, blind high?temperature geothermal systems (Fallon Airbase, Stillwater, and Soda Lake). This area was chosen for a detailed gravity survey in order to characterize the gravity signature of the known geothermal systems and to identify other potential blind systems based on the structural setting indicated by the gravity data. Data: Data were acquired at approximately 400, 800, and 1600 meter intervals for a total of 1,243 stations. The project location and station location points are presented in Figure 14. The station distribution for this survey was designed to complete regional gravity coverage in the Carson Sink area without duplication of available public and private gravity coverage. Gravity data were acquired using a Scintrex CG?5 gravimeter and a LaCoste and Romberg (L&R) Model?G gravimeter. The CG?5 gravity meter has a reading resolution of 0.001 milligals and a typical repeatability of less than 0.005 milligals. The L&R gravity meter has a reading resolution of 0.01 milligals and a typical repeatability of 0.02 milligals. The basic processing of gravimeter readings to calculate through to the Complete Bouguer Anomaly was made using the Gravity and Terrain Correction software version 7.1 for Oasis Montaj by Geosoft LTD. Results: The gravity survey of the Carson Sink yielded the following products. Project location and station location map (Figure 14). Complete Bouguer Anomaly @ 2.67 gm/cc reduction density. Gravity Complete Bouguer Anomaly at 2.50 g/cc Contour Map (Figure 15). Gravity Horizontal Gradient Magnitude Shaded Color Contour Map. Gravity 1st Vertical Derivative Color Contour Map. Interpreted Depth to Mesozoic Basement (Figure 16), incorporating drill?hole intercept values. Preliminary Interpretation of Results: The Carson Sink is a complex composite basin with several major depocenters (Figures 15 and 16). Major depocenters are present in the south?central, east?central, and northeastern parts of the basin. The distribution of gravity anomalies suggests a complex pattern of faulting in the subsurface of the basin, with many fault terminations, step?overs, and accommodation zones. The pattern of faulting implies that other, previously undiscovered blind geothermal systems are likely in the Carson Sink. The gravity survey was completed near the end of this project. Thus, more thorough analysis of the data and potential locations of blind geothermal systems is planned for future work.
Cosmological singularities in Born-Infeld determinantal gravity...
Office of Scientific and Technical Information (OSTI)
Cosmological singularities in Born-Infeld determinantal gravity Citation Details In-Document Search This content will become publicly available on December 16, 2015 Title:...
Dynamical stability of Minkowski space in higher order gravity
Petr V. Tretyakov
2015-05-19
We discuss the Minkowski stability problem in modified gravity by using dynamical system approach. The method to investigate dynamical stability of Minkowski space was proposed. This method was applied for some modified gravity theories, such as $f(R)$ gravity, $f(R)+\\alpha R\\Box R$ gravity and scalar-tensor gravity models with non-minimal kinetic coupling. It was shown that in the case of $f(R)$ gravity Minkowski solution asymptotically stable in ghost-free ($f'>0$) and tachyon-free ($f">0$) theories in expanding Universe with respect to isotropic and basic anisotropic perturbations. In the case of higher order gravity with $\\alpha R\\Box R$ correction conditions of Minkowski stability with respect to isotropic perturbations significantly different: $f'(0)0$. And in the case of scalar-tensor gravity with non-minimal kinetic coupling Minkowski solution asymptotically stable in expanding Universe with respect to isotropic perturbations of metric. Moreover the developed method may be used for finding additional restrictions on parameters of different modified gravity theories.
Ground Gravity Survey At Neal Hot Springs Geothermal Area (U...
Ground Gravity Survey At Neal Hot Springs Geothermal Area (U.S. Geothermal Inc., 2007) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground...
Geologic interpretation of gravity and magnetic data in the Salida...
Geologic interpretation of gravity and magnetic data in the Salida region, Colorado Jump to: navigation, search OpenEI Reference LibraryAdd to library Report: Geologic...
Unification of Gravity and Electromagnetism II A Geometric Theory
Partha Ghose
2015-02-11
It is shown that unification of gravity and electromagnetism can be achieved using an affine non-symmetric connection $\\Gamma^\\lambda_{\\mu\
Summary of Session A6: Alternative Theories of Gravity
R. B. Mann
1998-03-13
This is a summary of the workshop A.6 on Alternative Theories of Gravity, prepared for the proceedings for the GR15 conference.
Quantized gauge-affine gravity in the superfiber bundle approach
A. Meziane; M. Tahiri
2005-11-10
The quantization of gauge-affine gravity within the superfiber bundle formalism is proposed. By introducing an even pseudotensorial 1-superform over a principal superfibre bundle with superconnection, we obtain the geometrical Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST transformations of the fields occurring in such a theory. Reducing the four-dimensional general affine group double-covering to the Poincare group double-covering we also find the BRST and anti-BRST transformations of the fields present in Einstein's gravity. Furthermore, we give a prescription leading to the construction of both BRST-invariant gauge-fixing action for gauge-affine gravity and Einstein's gravity.
Exercise protocols during short-radius centrifugation for artificial gravity
Edmonds, Jessica Leigh
2008-01-01
Long-duration spaceflight results in severe physiological deconditioning, threatening the success of interplanetary travel. Exercise combined with artificial gravity provided by centrifugation may be the comprehensive ...
Bouguer gravity anomalies, depth to bedrock, and shallow temperature...
Bouguer gravity anomalies, depth to bedrock, and shallow temperature in the Humboldt House geothermal area, Pershing County, Nevada Jump to: navigation, search OpenEI Reference...
Ground Gravity Survey At Blue Mountain Geothermal Area (Fairbank...
Ground Gravity Survey At Blue Mountain Geothermal Area (Fairbank Engineering Ltd, 2003) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground...
Probing hybrid modified gravity by stellar motion around Galactic Centre
D. Borka; S. Capozziello; P. Jovanovi?; V. Borka Jovanovi?
2015-04-29
We consider possible signatures for the so called {\\it hybrid gravity} within the Galactic Central Parsec. This modified theory of gravity consists of a superposition of the metric Einstein-Hilbert Lagrangian with an $f(R)$ term constructed {\\it \\`{a} la Palatini } and can be easily reduced to an equivalent scalar-tensor theory. The present analysis is based on the S2 star orbital precession around the massive compact dark object at the Galactic Centre where the simulated orbits in hybrid modified gravity are compared with astronomical observations. These simulations result with strong constraints on the range of hybrid gravity interaction parameter $\\phi_0$ and show that its most probable value, in the case of S2 star, is around -0.0009 to -0.0002. At the same time, we are also able to obtain reliable constrains on the effective mass parameter $m_{\\phi}$ of hybrid modified gravity. Its most probable value, in the case of S2 star, is around -0.0034 to -0.0025. Furthermore, the hybrid gravity potential induces precession of S2 star orbit in the same direction as General Relativity. In previous papers, we considered other types of extended gravities, like metric power law $f(R)\\propto R^n$ gravity, inducing Yukawa and Sanders-like gravitational potentials, but it seems that hybrid gravity is the best among these models to explain different gravitational phenomena at different astronomical scales.
Hydrogen Burning in Low Mass Stars Constrains Alternative Gravity Theories
Jeremy Sakstein
2015-10-30
The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity, and find that it is always significantly larger than the general relativity prediction. The observation of several low mass Red Dwarf stars therefore rules out a large class of scalar-tensor gravity theories, and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.
Hydrogen Burning in Low Mass Stars Constrains Alternative Gravity Theories
Jeremy Sakstein
2015-10-20
The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity, and find that it is always significantly larger than the general relativity prediction. The observation of several low mass Red Dwarf stars therefore rules out a large class of scalar-tensor gravity theories, and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.
Review of Lattice Supersymmetry and Gauge-Gravity Duality
Joseph, Anosh
2015-01-01
We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that non-perturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.
Review of Lattice Supersymmetry and Gauge-Gravity Duality
Anosh Joseph
2015-09-04
We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that non-perturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.
Ground Gravity Survey At San Francisco Volcanic Field Area (Warpinski...
geologically mapped the target area, obtained rock samples for age dating and mineral chemistry, performed gravity and magnetic surveys, and integrated these results to identify...
Hydrogen Burning in Low Mass Stars Constrains Alternative Gravity Theories
Sakstein, Jeremy
2015-01-01
The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity, and find that it is always significantly larger than the general relativity prediction. The observation of several low mass Red Dwarf stars therefore rules out a large class of scalar-tensor gravity theories, and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.
Interfacial gravity currents. I. Mixing and entrainment B. R. Sutherland
Sutherland, Bruce
Interfacial gravity currents. I. Mixing and entrainment B. R. Sutherland Department of Mathematical energy are compared with theories that neglect mixing and entrainment processes. As the middle layer
McBranch, D.W.; Mattes, B.R.; Koskelo, A.C.; Heeger, A.J.; Robinson, J.M.; Smilowitz, L.B.; Klimov, V.I.; Cha, M.; Sariciftci, N.S.; Hummelen, J.C.
1998-04-21
Methanofullerenes, fulleroids and/or other fullerenes chemically altered for enhanced solubility, in liquid solution, and in solid blends with transparent glass (SiO{sub 2}) gels or polymers, or semiconducting (conjugated) polymers, are shown to be useful as optical limiters (optical surge protectors). The nonlinear absorption is tunable such that the energy transmitted through such blends saturates at high input energy per pulse over a wide range of wavelengths from 400--1,100 nm by selecting the host material for its absorption wavelength and ability to transfer the absorbed energy into the optical limiting composition dissolved therein. This phenomenon should be generalizable to other compositions than substituted fullerenes. 5 figs.
Primordial massive gravitational waves from Einstein-Chern-Simons-Weyl gravity
Myung, Yun Soo; Moon, Taeyoon E-mail: tymoon@inje.ac.kr
2014-08-01
We investigate the evolution of cosmological perturbations during de Sitter inflation in the Einstein-Chern-Simons-Weyl gravity. Primordial massive gravitational waves are composed of one scalar, two vector and four tensor circularly polarized modes. We show that the vector power spectrum decays quickly like a transversely massive vector in the superhorizon limit z ? 0. In this limit, the power spectrum coming from massive tensor modes decays quickly, leading to the conventional tensor power spectrum. Also, we find that in the limit of m{sup 2} ? 0 (keeping the Weyl-squared term only), the vector and tensor power spectra disappear. It implies that their power spectra are not gravitationally produced because they (vector and tensor) are decoupled from the expanding de Sitter background, as a result of conformal invariance.
and Yaoguo Li, Center for Gravity, Electrical and Magnetic Studies, Department of Geophysics, Colorado School
Effective Levi-Civita Dilaton theory from Metric Affine Dilaton Gravity
R. Scipioni
1999-05-25
We show how a Metric Affine theory of Dilaton gravity can be reduced to an effective Riemannian Dilaton gravity model. A simple generalization of the Obukhov-Tucker-Wang theorem to Dilaton gravity is then presented.
Horava Gravity in the Effective Field Theory formalism: from cosmology to observational constraints
Frusciante, Noemi; Vernieri, Daniele; Hu, Bin; Silvestri, Alessandra
2015-01-01
We consider Horava gravity within the framework of the EFT of dark energy and modified gravity. We work out a complete mapping of the theory into the EFT language for an action including all the operators which are relevant for linear perturbations with up to sixth order spatial derivatives. We then employ an updated version of the EFTCAMB/EFTCosmoMC package to study the cosmology of the low-energy limit of Horava gravity and place constraints on its parameters using several cosmological data sets. In particular we consider two cases: the first in which the three parameters of the low-energy theory are all varied and a second case that is tuned to evade PPN constraints, reducing the number of free parameters to two. We employ data sets which include the CMB TT and lensing power spectra by Planck 2013, WMAP low-l polarization spectra, the WiggleZ galaxy power spectrum, the local Hubble measurements, Supernovae data from SNLS, SDSS and HST and the BAO measurements from BOSS, SDSS and 6dFGS. For both cases we es...
Testing chameleon gravity with the Coma cluster
Terukina, Ayumu; Yamamoto, Kazuhiro; Lombriser, Lucas; Bacon, David; Koyama, Kazuya; Nichol, Robert C. E-mail: lucas.lombriser@port.ac.uk E-mail: david.bacon@port.ac.uk E-mail: bob.nichol@port.ac.uk
2014-04-01
We propose a novel method to test the gravitational interactions in the outskirts of galaxy clusters. When gravity is modified, this is typically accompanied by the introduction of an additional scalar degree of freedom, which mediates an attractive fifth force. The presence of an extra gravitational coupling, however, is tightly constrained by local measurements. In chameleon modifications of gravity, local tests can be evaded by employing a screening mechanism that suppresses the fifth force in dense environments. While the chameleon field may be screened in the interior of the cluster, its outer region can still be affected by the extra force, introducing a deviation between the hydrostatic and lensing mass of the cluster. Thus, the chameleon modification can be tested by combining the gas and lensing measurements of the cluster. We demonstrate the operability of our method with the Coma cluster, for which both a lensing measurement and gas observations from the X-ray surface brightness, the X-ray temperature, and the Sunyaev-Zel'dovich effect are available. Using the joint observational data set, we perform a Markov chain Monte Carlo analysis of the parameter space describing the different profiles in both the Newtonian and chameleon scenarios. We report competitive constraints on the chameleon field amplitude and its coupling strength to matter. In the case of f(R) gravity, corresponding to a specific choice of the coupling, we find an upper bound on the background field amplitude of |f{sub R0}| < 6 × 10{sup ?5}, which is currently the tightest constraint on cosmological scales.
Gravity duals for non-relativistic CFTs
Koushik Balasubramanian; John McGreevy
2008-08-01
We attempt to generalize the AdS/CFT correspondence to non-relativistic conformal field theories which are invariant under Galilean transformations. Such systems govern ultracold atoms at unitarity, nucleon scattering in some channels, and more generally, a family of universality classes of quantum critical behavior. We construct a family of metrics which realize these symmetries as isometries. They are solutions of gravity with negative cosmological constant coupled to pressureless dust. We discuss realizations of the dust, which include a bulk superconductor. We develop the holographic dictionary and compute some two-point correlators. A strange aspect of the correspondence is that the bulk geometry has two extra noncompact dimensions.
Loop Quantum Gravity: An Inside View
Thomas Thiemann
2006-08-29
This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The present text can be viewed in part as a response to an article by Nicolai, Peeters and Zamaklar [hep-th/0501114]. We also explain why certain no go conclusions drawn from a mathematically correct calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect.
Confronting Dilaton-exchange gravity with experiments
H. V. Klapdor-Kleingrothaus; H. Päs; U. Sarkar
2000-08-16
We study the experimental constraints on theories, where the equivalence principle is violated by dilaton-exchange contributions to the usual graviton-exchange gravity. We point out that in this case it is not possible to have any CPT violation and hence there is no constraint from the CPT violating measurements in the $K-$system. The most stringent bound is obtained from the $K_L - K_S$ mass difference. In contrast, neither neutrino oscillation experiments nor neutrinoless double beta decay imply significant constraints.
Static wormholes in vacuum for conformal gravity
Julio Oliva; David Tempo; Ricardo Troncoso
2009-07-07
A static spherically symmetric wormhole solution for conformal gravity in vacuum is found. The solution possesses a single integration constant which determines the size of the neck connecting two static homogeneous universes of constant spatial curvature. Time runs at different rates on each side of the neck, and depending on the value of the parameter, the wormhole can develop a cosmological horizon only at one side. It is shown that the wormholes correspond to the matching of different Einstein spacetimes by means of improper conformal transformations.
Gamma Ray Burst Neutrinos Probing Quantum Gravity
M. C. Gonzalez-Garcia; F. Halzen
2006-11-28
Very high energy, short wavelength, neutrinos may interact with the space-time foam predicted by theories of quantum gravity. They would propagate like light through a crystal lattice and be delayed, with the delay depending on the energy. This will appear to the observer as a violation of Lorenz invariance. Back of the envelope calculations imply that observations of neutrinos produced by gamma ray bursts may reach Planck-scale sensitivity. We revisit the problem considering two essential complications: the imprecise timing of the neutrinos associated with their poorly understood production mechanism in the source and the indirect nature of their energy measurement made by high energy neutrino telescopes.
Linearization of Moffat's Symmetric Complex Metric Gravity
Joakim Munkhammar
2009-09-19
In this paper we investigate a complex symmetric generalization of general relativity and in particular we investigate its linearized field equations. We begin by reviewing some basic definitions and structures in Moffat's symmetric complex metric field theory of gravity. We then move on to derive the linearized retarded complex field equations. In addition to this we also derive a linearization of Moffat's field equations based on the more rigorous Fermi coordinate approach. In conclusion it is shown that the linearized symmetric complex field equations leads to a complex form of gravitomagnetism. We also briefly review the gravitational wave equation from the source less linearized symmetric complex field equations and discuss some open problems.
Gravity can be neither classical nor quantized
Sabine Hossenfelder
2012-12-03
I argue that it is possible for a theory to be neither quantized nor classical. We should therefore give up the assumption that the fundamental theory which describes gravity at shortest distances must either be quantized, or quantization must emerge from a fundamentally classical theory. To illustrate my point I will discuss an example for a theory that is neither classical nor quantized, and argue that it has the potential to resolve the tensions between the quantum field theories of the standard model and general relativity.
Null Energy Condition violations in bimetric gravity
Baccetti, Valentina; Visser, Matt
2012-01-01
We consider the effective stress-energy tensors for the foreground and background sectors in ghost-free bimetric gravity. By considering the symmetries of the theory, we show that the foreground and background null energy conditions (NECs) are strongly anti-correlated. In particular, the NECs can only be simultaneously fulfilled when they saturate, corresponding to foreground and background cosmological constants. In all other situations, either the foreground or the background is subject to a NEC-violating contribution to the total stress-energy.
T. Thiemann
1993-11-11
We introduce a reduced model for a real sector of complexified Ashtekar gravity that does not correspond to a subset of Einstein's gravity but for which the programme of canonical quantization can be carried out completely, both, via the reduced phase space approach or along the lines of the algebraic quantization programme.\\\\ This model stands in a certain correspondence to the frequently treated cylindrically symmetric waves.\\\\ In contrast to other models that have been looked at up to now in terms of the new variables the reduced phase space is infinite dimensional while the scalar constraint is genuinely bilinear in the momenta.\\\\ The infinite number of Dirac observables can be expressed in compact and explicit form in terms of the original phase space variables.\\\\ They turn out, as expected, to be non-local and form naturally a set of countable cardinality.
Low-energy quantum gravity: new challenges for an experiment and observation
Michael A. Ivanov
2009-01-05
Some new challenges for an experiment and observation, which are consequences of the model of low-energy quantum gravity by the author, are considered here. In particular, the property of asymptotic freedom of this model leads to the unexpected consequence: if a black hole arises due to a collapse of a matter with some characteristic mass of particles, its full mass should be restricted from the bottom. For usual baryonic matter, this limit of mass is of the order $10^{7}M_{\\odot}$.
Gravitational Waves from Quasi-Circular Black Hole Binaries in Dynamical Chern-Simons Gravity
Kent Yagi; Nicolas Yunes; Takahiro Tanaka
2013-02-07
Dynamical Chern-Simons gravity cannot be strongly constrained with current experiments because it reduces to General Relativity in the weak-field limit. This theory, however, introduces modifications in the non-linear, dynamical regime, and thus, it could be greatly constrained with gravitational waves from the late inspiral of black hole binaries. We complete the first self-consistent calculation of such gravitational waves in this theory. For favorable spin-orientations, advanced ground-based detectors may improve existing solar-system constraints by 6 orders of magnitude.
Pulse shaping with transmission lines
Wilcox, Russell B. (Oakland, CA)
1987-01-01
A method and apparatus for forming shaped voltage pulses uses passive reflection from a transmission line with nonuniform impedance. The impedance of the reflecting line varies with length in accordance with the desired pulse shape. A high voltage input pulse is transmitted to the reflecting line. A reflected pulse is produced having the desired shape and is transmitted by pulse removal means to a load. Light activated photoconductive switches made of silicon can be utilized. The pulse shaper can be used to drive a Pockels cell to produce shaped optical pulses.
Electrical transmission line diametrical retainer
Hall, David R. (Provo, UT); Hall, Jr., H. Tracy (Provo, UT); Pixton, David (Lehi, UT); Dahlgren, Scott (Provo, UT); Sneddon, Cameron (Provo, UT); Briscoe, Michael (Lehi, UT); Fox, Joe (Spanish Fork, UT)
2004-12-14
The invention is a mechanism for retaining an electrical transmission line. In one embodiment of the invention it is a system for retaining an electrical transmission line within down hole components. In accordance with one aspect of the invention, the system includes a plurality of downhole components, such as sections of pipe in a drill string. The system also includes a coaxial cable running between the first and second end of a drill pipe, the coaxial cable having a conductive tube and a conductive core within it. The invention allows the electrical transmission line to with stand the tension and compression of drill pipe during routine drilling cycles.
Mass gap for gravity localized on Weyl thick branes
Barbosa-Cendejas, N.; Santos, M. A. Reyes; Herrera-Aguilar, A.; Schubert, C.
2008-06-15
We consider thick brane configurations in a pure geometric Weyl integrable 5D space-time, a non-Riemannian generalization of Kaluza-Klein (KK) theory involving a geometric scalar field. Thus, the 5D theory describes gravity coupled to a self-interacting scalar field which gives rise to the structure of the thick branes. We continue the study of the properties of a previously found family of solutions which is smooth at the position of the brane but involves naked singularities in the fifth dimension. Analyzing their graviton spectrum, we find that a particularly interesting situation arises for a special case in which the 4D graviton is separated from the KK gravitons by a mass gap. The corresponding effective Schroedinger equation has a modified Poeschl-Teller potential and can be solved exactly. Apart from the massless 4D graviton, it contains one massive KK bound state, and the continuum spectrum of delocalized KK modes. We also discuss the mass hierarchy problem, and explicitly compute the corrections to Newton's law in the thin brane limit.
Asymptotically flat radiating solutions in third order Lovelock gravity
Dehghani, M. H.; Farhangkhah, N.
2008-09-15
In this paper, we present an exact spherically symmetric solution of third order Lovelock gravity in n dimensions which describes the gravitational collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter or flat depending on the choice of the cosmological constant. Using the asymptotically flat solution for n{>=}7 with a power-law form of the mass as a function of the null coordinate, we present a model for a gravitational collapse in which a null dust fluid radially injects into an initially flat and empty region. It is found that a naked singularity is inevitably formed whose strength is different for the n=7 and n{>=}8 cases. In the n=7 case, the limiting focusing condition for the strength of curvature singularity is satisfied. But for n{>=}8, the strength of curvature singularity depends on the rate of increase of mass of the spacetime. These considerations show that the third order Lovelock term weakens the strength of the curvature singularity.
Bertotti-Robinson type solutions to Dilaton-Axion Gravity
Gerard Clement; Dmitri Gal'tsov
2001-02-06
We present a new solution to dilaton-axion gravity which looks like a rotating Bertotti-Robinson (BR) Universe. It is supported by an homogeneous Maxwell field and a linear axion and can be obtained as a near-horizon limit of extremal rotating dilaton-axion black holes. It has the isometry $SL(2,R)\\times U(1)$ where U(1) is the remnant of the SO(3) symmetry of BR broken by rotation, while $SL(2,R)$ corresponds to the $AdS_2$ sector which no longer factors out of the full spacetime. Alternatively our solution can be obtained from the D=5 vacuum counterpart to the dyonic BR with equal electric and magnetic field strengths. The derivation amounts to smearing it in D=6 and then reducing to D=4 with dualization of one Kaluza-Klein two-form in D=5 to produce an axion. Using a similar dualization procedure, the rotating BR solution is uplifted to D=11 supergravity. We show that it breaks all supersymmetries of N=4 supergravity in D=4, and that its higher dimensional embeddings are not supersymmetric either. But, hopefully it may provide a new arena for corformal mechanics and holography. Applying a complex coordinate transformation we also derive a BR solution endowed with a NUT parameter.
Bertotti-Robinson type solutions to Dilaton-Axion Gravity
Clément, G; Clement, Gerard; Gal'tsov, Dmitri
2001-01-01
We present a new solution to dilaton-axion gravity which looks like a rotating Bertotti-Robinson (BR) Universe. It is supported by an homogeneous Maxwell field and a linear axion and can be obtained as a near-horizon limit of extremal rotating dilaton-axion black holes. It has the isometry $SL(2,R)\\times U(1)$ where U(1) is the remnant of the SO(3) symmetry of BR broken by rotation, while $SL(2,R)$ corresponds to the $AdS_2$ sector which no longer factors out of the full spacetime. Alternatively our solution can be obtained from the D=5 vacuum counterpart to the dyonic BR with equal electric and magnetic field strengths. The derivation amounts to smearing it in D=6 and then reducing to D=4 with dualization of one Kaluza-Klein two-form in D=5 to produce an axion. Using a similar dualization procedure, the rotating BR solution is uplifted to D=11 supergravity. We show that it breaks all supersymmetries of N=4 supergravity in D=4, and that its higher dimensional embeddings are not supersymmetric either. But, hop...
Deep-water gravity waves: nonlinear theory of wave groups
Mindlin, I M
2014-01-01
Nonlinear initial-boundary value problem on deep-water gravity waves of finite amplitude is solved approximately (up to small terms of higher order) assuming that the waves are generated by an initial disturbance to the water and the horizontal dimensions of the initially disturbed body of the water are much larger than the magnitude of the free surface displacement. A numerable set of specific free surface waves is obtained in closed form and it is shown that free surface waves produced by an arbitrary initial disturbance to the water is a combination (not superposition: the waves are nonlinear) of the specific waves. A set of dispersive wave packets is found with one-to-one correspondence between the packets and positive integers, say, packet numbers, such that any initial free surface displacement gradually disintegrates into a number (limited or unlimited, depending on initial conditions) of the wave packets. The greater the packet number, the shorter the wavelength of the packet's carrier wave component,...
The Phoenix Project: Master Constraint Programme for Loop Quantum Gravity
Thomas Thiemann
2003-05-21
The Hamiltonian constraint remains the major unsolved problem in Loop Quantum Gravity (LQG). Seven years ago a mathematically consistent candidate Hamiltonian constraint has been proposed but there are still several unsettled questions which concern the algebra of commutators among smeared Hamiltonian constraints which must be faced in order to make progress. In this paper we propose a solution to this set of problems based on the so-called {\\bf Master Constraint} which combines the smeared Hamiltonian constraints for all smearing functions into a single constraint. If certain mathematical conditions, which still have to be proved, hold, then not only the problems with the commutator algebra could disappear, also chances are good that one can control the solution space and the (quantum) Dirac observables of LQG. Even a decision on whether the theory has the correct classical limit and a connection with the path integral (or spin foam) formulation could be in reach. While these are exciting possibilities, we should warn the reader from the outset that, since the proposal is, to the best of our knowledge, completely new and has been barely tested in solvable models, there might be caveats which we are presently unaware of and render the whole {\\bf Master Constraint Programme} obsolete. Thus, this paper should really be viewed as a proposal only, rather than a presentation of hard results, which however we intend to supply in future submissions.
Three Chinese Students’ Experiences of Taking On-line Courses in One American University
Yang, Xinyuan
2012-10-19
needs and expectations towards this new learning experience becomes critical. Chinese students are the second largest group of international students in the U.S., yet, studies on their learning needs and challenges in on-line learning are limited...
On coupling NEC-violating matter to gravity
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chatterjee, Saugata; Parikh, Maulik; van der Schaar, Jan Pieter
2015-05-01
We show that effective theories of matter that classically violate the null energy condition cannot be minimally coupled to Einstein gravity without being inconsistent with both string theory and black hole thermodynamics. We argue however that they could still be either non-minimally coupled or coupled to higher-curvature theories of gravity.
Stochastic cosmology, theories of perturbations and Lifshitz gravity
Khalatnikov, I M
2015-01-01
We review some works of E M Lifshitz connected with gravity and cosmology and also some later works, connected with his ideas. The main topics of this review are the stochastic cosmology of an anisotropic universe and of an isotropic universe with the scalar field, the quasi-isotropic (gradient) expansion in cosmology and Horava-Lifshitz gravity and cosmology.
Gravity Dual for Cyclic Renormalization Group Flow without Conformal Invariance
Yu Nakayama
2011-07-21
We construct a gravity dual for scale invariant but non-conformal field theories with a cyclic renormalization group flow. A slight modification of our construction gives a gravity dual of discretely scale invariant field theories. The underlying gravitational theory breaks the null energy condition.
Disformal transformations, veiled General Relativity and Mimetic Gravity
Deruelle, Nathalie; Rua, Josephine E-mail: rua@cbpf.br
2014-09-01
In this Note we show that Einstein's equations for gravity are generically invariant under ''disformations''. We also show that the particular subclass when this is not true yields the equations of motion of ''Mimetic Gravity''. Finally we give the ''mimetic'' generalization of the Schwarzschild solution.
Bimetric gravity doubly coupled to matter: theory and cosmological implications
Akrami, Yashar; Koivisto, Tomi S.; Mota, David F.; Sandstad, Marit E-mail: t.s.koivisto@astro.uio.no E-mail: marit.sandstad@astro.uio.no
2013-10-01
A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to explain the cosmic acceleration without resorting to dark energy.
Ph.D.Thesis Binary inversion of gravity
Ph.D.Thesis Binary inversion of gravity data for salt imaging Richard A. Krahenbuhl Center of Mines Golden, CO 80401 http://www.geophysics.mines.edu/cgem CGEM #12;#12;Ph.D.Thesis Binary inversion) #12;#12;BINARY INVERSION OF GRAVITY DATA FOR SALT IMAGING by Richard A. Krahenbuhl #12;#12;ii A thesis
Simulation of Gravity Flow of Granular Materials in Silos
and handle vast quantities of raw materials in granular form. The material is usually retrieved throughSimulation of Gravity Flow of Granular Materials in Silos Pierre A. Gremaud1 and John V. Matthews1 materials in silos under the action of gravity is considered. In the case of a Mohr-Coulomb material
Synoptic Responses to Mountain Gravity Waves Encountering Directional Critical Levels
Lott, Francois
Synoptic Responses to Mountain Gravity Waves Encountering Directional Critical Levels ARMEL MARTIN the synoptic response to mountain gravity waves (GWs) absorbed at directional critical levels. The model in the midtroposphere. First, the authors consider the case of an idealized mountain range such that the orographic
Gravity waves excited by jets: Propagation versus generation R. Plougonven
Plougonven, Riwal
Gravity waves excited by jets: Propagation versus generation R. Plougonven School of Mathematics imposed by the generation mechanism. In proceeding so, effects due to the propagation of the waves through in consequence that the gravity waves are generated in the jet-exit region. [4] To date, such arguments have
18 Maple Syrup Digest HIGH VACUUM IN GRAVITY TUBING
Hayden, Nancy J.
where elec- tricity is not available, time needed for maintenance of a pump and extractor gravity tubing, or tubing without the use of a pump, to be a poor substitute for a modern system with a pump, extractor, and the latest tubing arrangement. Sap yields from gravity systems are often half
The Gravity of Annual Freight and Logistics Symposium
Minnesota, University of
The Gravity of Logistics 17th Annual Freight and Logistics Symposium A Summary Report | December 6 to those who want them --the "gravity" of logistics--depends on infrastructure that can support and sustainth Annual State of Logistics Report--IsThis the New Normal? Rosalyn Wilson, Senior Business Analyst
Multimodal standing gravity waves: a completely resonant system.
Iooss, Gérard
Multimodal standing gravity waves: a completely resonant system. G´erard Iooss , Pavel Plotnikov@hydro.nsc.ru Abstract The standing gravity wave problem on an infinitely deep fluid layer is considered under the form be expanded in powers of amplitude is then given up to order 2 . Key words: nonlinear water waves, standing
Adjustable direct current and pulsed circuit fault current limiter
Boenig, Heinrich J.; Schillig, Josef B.
2003-09-23
A fault current limiting system for direct current circuits and for pulsed power circuit. In the circuits, a current source biases a diode that is in series with the circuits' transmission line. If fault current in a circuit exceeds current from the current source biasing the diode open, the diode will cease conducting and route the fault current through the current source and an inductor. This limits the rate of rise and the peak value of the fault current.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
User Experiment Time-Line Event Target Call for proposal 2 months before proposals are due PAC Proposals Due 7 weeks before PAC meeting TAC Report for PAC Proposals (includes...
Kim, Sue-Mie
1993-01-01
A line, the simplest way to express an artist's feelings or interpretation of an object, has its own emotions that an artist can employ for her purpose. Laser light, the most self-concentrated, self-sustained and directed, ...
A probabilistic approach to calculating AC induction levels on power line collocated pipelines
Dabkowski, J. [Electro Sciences, Inc., Crystal Lake, IL (United States)
1995-12-01
For calculating induced voltage levels on pipelines paralleling overhead power lines available computational methods assume that the line circuit currents are balanced, i.e., equal. In this paper probabilistic computational methods are used to calculate induction levels for the more realistic assumption that the line currents carry a small randomly fluctuating component, and therefore, are unbalanced. Results show that limiting consideration to the balanced currents case can result in substantially underestimated induced voltage levels on the pipeline.
Harko, Tiberiu; Lobo, Francisco S.N.; Otalora, G.; Saridakis, Emmanuel N. E-mail: flobo@cii.fc.ul.pt
2014-12-01
We present an extension of f(T) gravity, allowing for a general coupling of the torsion scalar T with the trace of the matter energy-momentum tensor T. The resulting f(T,T) theory is a new modified gravity, since it is different from all the existing torsion or curvature based constructions. Applied to a cosmological framework, it leads to interesting phenomenology. In particular, one can obtain a unified description of the initial inflationary phase, the subsequent non-accelerating, matter-dominated expansion, and then the transition to a late-time accelerating phase. Additionally, the effective dark energy sector can be quintessence or phantom-like, or exhibit the phantom-divide crossing during the evolution. Moreover, in the far future the universe results either to a de Sitter exponential expansion, or to eternal power-law accelerated expansions. Finally, a detailed study of the scalar perturbations at the linear level reveals that f(T,T) cosmology can be free of ghosts and instabilities for a wide class of ansatzes and model parameters.
Vacuum energy: quantum hydrodynamics vs quantum gravity
G. E. Volovik
2005-09-09
We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.
Quantum Foam, Gravity and Gravitational Waves
Cahill, R T
2003-01-01
The new information-theoretic Process Physics has shown that space is a quantum foam system with gravity being, in effect, an inhomogeneous in-flow of the quantum foam into matter. The theory predicts that absolute motion with respect to this system should be observable, and it is shown here that absolute motion has been detected in at least seven experiments. As well this experimental data also reveals the existence of a gravitational wave phenomena associated with the in-flow. It is shown that Galilean Relativity and Special Relativity are in fact compatible, contrary to current beliefs: absolute motion actually causes the special relativity effects. The new theory of gravity passes all the tests of the previous Newtonian and General Relativity theories, but in addition resolves the numerous gravitational anomalies such as the spiral galaxy `dark matter' effect, the absence of `dark matter' in elliptical galaxies, the inconsistencies in measuring G, the borehole g anomaly, and others. It is shown that Newto...
Motion in alternative theories of gravity
Gilles Esposito-Farese
2009-05-15
Although general relativity (GR) passes all present experimental tests with flying colors, it remains important to study alternative theories of gravity for several theoretical and phenomenological reasons that we recall in these lecture notes. The various possible ways of modifying GR are presented, and we notably show that the motion of massive bodies may be changed even if one assumes that matter is minimally coupled to the metric as in GR. This is illustrated with the particular case of scalar-tensor theories of gravity, whose Fokker action is discussed, and we also mention the consequences of the no-hair theorem on the motion of black holes. The finite size of the bodies modifies their motion with respect to pointlike particles, and we give a simple argument showing that the corresponding effects are generically much larger in alternative theories than in GR. We also discuss possible modifications of Newtonian dynamics (MOND) at large distances, which have been proposed to avoid the dark matter hypothesis. We underline that all the previous classes of alternatives to GR may a priori be used to predict such a phenomenology, but that they generically involve several theoretical and experimental difficulties.
Scattering amplitudes in super-renormalizable gravity
Pietro Donà; Stefano Giaccari; Leonardo Modesto; Leslaw Rachwal; Yiwei Zhu
2015-06-15
We explicitly compute the tree-level on-shell four-graviton amplitudes in four, five and six dimensions for local and weakly nonlocal gravitational theories that are quadratic in both, the Ricci and scalar curvature with form factors of the d'Alembertian operator inserted between. More specifically we are interested in renormalizable, super-renormalizable or finite theories. The scattering amplitudes for these theories turn out to be the same as the ones of Einstein gravity regardless of the explicit form of the form factors. As a special case the four-graviton scattering amplitudes in Weyl conformal gravity are identically zero. Using a field redefinition, we prove that the outcome is correct for any number of external gravitons (on-shell $n-$point functions) and in any dimension for a large class of theories. However, when an operator quadratic in the Riemann tensor is added in any dimension (with the exception of the Gauss-Bonnet term in four dimensions) the result is completely altered, and the scattering amplitudes depend on all the form factors introduced in the action.
Scattering amplitudes in super-renormalizable gravity
Donà, Pietro; Modesto, Leonardo; Rachwal, Leslaw; Zhu, Yiwei
2015-01-01
We explicitly compute the tree-level on-shell four-graviton amplitudes in four, five and six dimensions for local and weakly nonlocal gravitational theories that are quadratic in both, the Ricci and scalar curvature with form factors of the d'Alembertian operator inserted between. More specifically we are interested in renormalizable, super-renormalizable or finite theories. The scattering amplitudes for these theories turn out to be the same as the ones of Einstein gravity regardless of the explicit form of the form factors. As a special case the four-graviton scattering amplitudes in Weyl conformal gravity are identically zero. Using a field redefinition, we prove that the outcome is correct for any number of external gravitons (on-shell $n-$point functions) and in any dimension for a large class of theories. However, when an operator quadratic in the Riemann tensor is added in any dimension (with the exception of the Gauss-Bonnet term in four dimensions) the result is completely altered, and the scattering...
Capozziello, S; Salzano, V
2008-01-01
It is nowadays accepted that the universe is undergoing a phase of accelerated expansion as tested by the Hubble diagram of Type Ia Supernovae (SNeIa) and several LSS observations. Future SNeIa surveys and other probes will make it possible to better characterize the dynamical state of the universe renewing the interest in cosmography which allows a model independent analysis of the distance - redshift relation. On the other hand, fourth order theories of gravity, also referred to as $f(R)$ gravity, have attracted a lot of interest since they could be able to explain the accelerated expansion without any dark energy. We show here how it is possible to relate the cosmographic parameters (namely the deceleration $q_0$, the jerk $j_0$, the snap $s_0$ and the lerk $l_0$ parameters) to the present day values of $f(R)$ and its derivatives $f^{(n)}(R) = d^nf/dR^n$ (with $n = 1, 2, 3$) thus offering a new tool to constrain such higher order models. Our analysis thus offers the possibility to relate the model independ...
S. Capozziello; V. F. Cardone; V. Salzano
2008-07-08
It is nowadays accepted that the universe is undergoing a phase of accelerated expansion as tested by the Hubble diagram of Type Ia Supernovae (SNeIa) and several LSS observations. Future SNeIa surveys and other probes will make it possible to better characterize the dynamical state of the universe renewing the interest in cosmography which allows a model independent analysis of the distance - redshift relation. On the other hand, fourth order theories of gravity, also referred to as $f(R)$ gravity, have attracted a lot of interest since they could be able to explain the accelerated expansion without any dark energy. We show here how it is possible to relate the cosmographic parameters (namely the deceleration $q_0$, the jerk $j_0$, the snap $s_0$ and the lerk $l_0$ parameters) to the present day values of $f(R)$ and its derivatives $f^{(n)}(R) = d^nf/dR^n$ (with $n = 1, 2, 3$) thus offering a new tool to constrain such higher order models. Our analysis thus offers the possibility to relate the model independent results coming from cosmography to the theoretically motivated assumptions of $f(R)$ cosmology.
Reindel, John (San Diego, CA)
1990-01-01
A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.
Massive gravitational waves in Chern-Simons modified gravity
Myung, Yun Soo; Moon, Taeyoon E-mail: tymoon@inje.ac.kr
2014-10-01
We consider the nondynamical Chern-Simons (nCS) modified gravity, which is regarded as a parity-odd theory of massive gravity in four dimensions. We first find polarization modes of gravitational waves for ?=x/? in nCS modified gravity by using the Newman-Penrose formalism where the null complex tetrad is necessary to specify gravitational waves. We show that in the Newman–Penrose formalism, the number of polarization modes is one in addition to an unspecified ?{sub 4}, implying three degrees of freedom for ?=x/?. This compares with two for a canonical embedding of ?=t/?. Also, if one introduces the Ricci tensor formalism to describe a massive graviton arising from the nCS modified gravity, one finds one massive mode after making second-order wave equations, which is compared to five found from the parity-even Einstein–Weyl gravity.
Scalars, Vectors and Tensors from Metric-Affine Gravity
Karahan, Canan N; Demir, Durmus A
2011-01-01
The metric-affine gravity provides a useful framework for analyzing gravitational dynamics since it treats metric tensor and affine connection as fundamentally independent variables. In this work, we show that, a metric-affine gravity theory composed of the invariants formed from non-metricity, torsion and curvature tensors decomposes exhaustively into a theory of scalar, vector and tensor fields. These fields are natural candidates for the ones needed by various cosmological phenomena. Indeed, we show that the model accommodates TeVeS gravity (relativistic modified gravity theory), vector inflation, and aether-like models. Detailed analyses of these and other phenomena can lead to a standard metric-affine gravity model encoding scalars, vectors and tensors necessitated by cosmology.
Scalars, Vectors and Tensors from Metric-Affine Gravity
Canan N. Karahan; Asli Altas; Durmus A. Demir
2013-02-02
The metric-affine gravity provides a useful framework for analyzing gravitational dynamics since it treats metric tensor and affine connection as fundamentally independent variables. In this work, we show that, a metric-affine gravity theory composed of the invariants formed from non-metricity, torsion and curvature tensors can be decomposed into a theory of scalar, vector and tensor fields. These fields are natural candidates for the ones needed by various cosmological and other phenomena. Indeed, we show that the model accommodates TeVeS gravity (relativistic modified gravity theory), vector inflation, and aether-like models. Detailed analyses of these and other phenomena can lead to a standard metric-affine gravity model encoding scalars, vectors and tensors.
The Limit of Mental Structures
Mandler, George
2013-01-01
of constructing such structures. References A cautionaryTHE LIMIT OF MENTAL STRUCTURES Asch, S. E. , & Ebenholtz, S.100. THE LIMIT OF MENTAL STRUCTURES Halford, G. S. , Cowan,
Darmann, Francis Anthony
2013-10-08
A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.
Multiple gamma lines from semi-annihilation
D'Eramo, Francesco
Hints in the Fermi data for a 130 GeV gamma line from the galactic center have ignited interest in potential gamma line signatures of dark matter. Explanations of this line based on dark matter annihilation face a parametric ...
The Pulse Line Ion Accelerator Concept
Briggs, Richard J.
2006-01-01
field model of the pulse- line accelerator; relationship to3, 2006 LBNL-59492 The pulse line ion accelerator conceptCalifornia, 94507 The Pulse Line Ion Accelerator concept was
Qiang, Li-E
2015-01-01
High precision Superconductivity Gravity Gradiometers (SGG) are powerful tools for relativistic experiments. In this paper, we work out the tidal signals in non-dynamical Chern-Simons modified gravity, which could be measured by orbiting SGGs around Earth. We find that, with proper orientations of multi-axes SGGs, the tidal signals from the Chern-Simons modification can be isolated in the combined data of different axes. Furthermore, for three-axes SGGs, such combined data is the trace of the total tidal matrix, which is invariant under the rotations of SGG axes and thus free from axis pointing errors. Following nearly circular orbits, the tests of the parity-violating Chern-Simons modification and the measurements of the gravitomagnetic sector in parity-conserving metric theories can be carried out independently in the same time. A first step analysis on noise sources is also included.
Li-E Qiang; Peng Xu
2015-02-16
High precision Superconductivity Gravity Gradiometers (SGG) are powerful tools for relativistic experiments. In this paper, we work out the tidal signals in non-dynamical Chern-Simons modified gravity, which could be measured by orbiting SGGs around Earth. We find that, with proper orientations of multi-axes SGGs, the tidal signals from the Chern-Simons modification can be isolated in the combined data of different axes. Furthermore, for three-axes SGGs, such combined data is the trace of the total tidal matrix, which is invariant under the rotations of SGG axes and thus free from axis pointing errors. Following nearly circular orbits, the tests of the parity-violating Chern-Simons modification and the measurements of the gravitomagnetic sector in parity-conserving metric theories can be carried out independently in the same time. A first step analysis on noise sources is also included.
DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS
NA
2004-11-22
The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) important to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are in the form of tabulated functions with pH and log (line integral) CO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. The output data from this report are fundamental inputs for Total System Performance Assessment for the License Application (TSPA-LA) to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for all of the actinides. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or otherwise addressed.
The limits of the nuclear landscape
Nazarewicz, Witold; Erler, J.; Birge, N.; Kortelainen, E. M.; Olsen, E.; Perhac, A.; Stoitsov, M.
2012-01-01
In 2011, 100 new nuclides were discovered1. They joined the approximately 3,000 stable and radioactive nuclides that either occur naturally on Earth or are synthesized in the laboratory2,3. Every atomic nucleus, characterized by a specific number of protons and neutrons, occupies a spot on the chart of nuclides, which is bounded by drip lines indicating the values of neutron and proton number at which nuclear binding ends. The placement of the neutron drip line for the heavier elements is based on theoretical predictions using extreme extrapolations, and so is uncertain. However, it is not known how uncertain it is or how many protons and neutrons can be bound in a nucleus. Here we estimate these limits of the nuclear landscape and provide statistical and systematic uncertainties for our predictions. We use nuclear density functional theory, several Skyrme interactions and high-performance computing, and find that the number of bound nuclides with between 2 and 120 protons is around 7,000. We find that extrapolations for drip-line positions and selected nuclear properties, including neutron separation energies relevant to astrophysical processes, are very consistent between the models used.
(Limiting the greenhouse effect)
Rayner, S.
1991-01-07
Traveler attended the Dahlem Research Conference organized by the Freien Universitat, Berlin. The subject of the conference was Limiting the Greenhouse Effect: Options for Controlling Atmospheric CO{sub 2} Accumulation. Like all Dahlem workshops, this was a meeting of scientific experts, although the disciplines represented were broader than usual, ranging across anthropology, economics, international relations, forestry, engineering, and atmospheric chemistry. Participation by scientists from developing countries was limited. The conference was divided into four multidisciplinary working groups. Traveler acted as moderator for Group 3 which examined the question What knowledge is required to tackle the principal social and institutional barriers to reducing CO{sub 2} emissions'' The working rapporteur was Jesse Ausubel of Rockefeller University. Other working groups examined the economic costs, benefits, and technical feasibility of options to reduce emissions per unit of energy service; the options for reducing energy use per unit of GNP; and the significant of linkage between strategies to reduce CO{sub 2} emissions and other goals. Draft reports of the working groups are appended. Overall, the conference identified a number of important research needs in all four areas. It may prove particularly important in bringing the social and institutional research needs relevant to climate change closer to the forefront of the scientific and policy communities than hitherto.
The COMPTEL instrumental line background
G. Weidenspointner; M. Varendorff; U. Oberlack; D. Morris; S. Plueschke; R. Diehl; S. C. Kappadath; M. McConnell; J. Ryan; V. Schoenfelder; H. Steinle
2000-12-14
The instrumental line background of the Compton telescope COMPTEL onboard the Compton Gamma-Ray Observatory is due to the activation and/or decay of many isotopes. The major components of this background can be attributed to eight individual isotopes, namely 2D, 22Na, 24Na, 28Al, 40K, 52Mn, 57Ni, and 208Tl. The identification of instrumental lines with specific isotopes is based on the line energies as well as on the variation of the event rate with time, cosmic-ray intensity, and deposited radiation dose during passages through the South-Atlantic Anomaly. The characteristic variation of the event rate due to a specific isotope depends on its life-time, orbital parameters such as the altitude of the satellite above Earth, and the solar cycle. A detailed understanding of the background contributions from instrumental lines is crucial at MeV energies for measuring the cosmic diffuse gamma-ray background and for observing gamma-ray line emission in the interstellar medium or from supernovae and their remnants. Procedures to determine the event rate from each background isotope are described, and their average activity in spacecraft materials over the first seven years of the mission is estimated.
Analytic continuation of real Loop Quantum Gravity : Lessons from black hole thermodynamics
Achour, Jibril Ben
2015-01-01
This contribution is devoted to summarize the recent results obtained in the construction of an "analytic continuation" of Loop Quantum Gravity (LQG). By this, we mean that we construct analytic continuation of physical quantities in LQG from real values of the Barbero-Immirzi parameter $\\gamma$ to the purely imaginary value $\\gamma = \\pm i$. This should allow us to define a quantization of gravity with self-dual Ashtekar variables. We first realized in [1] that this procedure, when applied to compute the entropy of a spherical black hole in LQG for $\\gamma=\\pm i$, allows to reproduce exactly the Bekenstein-Hawking area law at the semi-classical limit. The rigorous construction of the analytic continuation of spherical black hole entropy has been done in [2]. Here, we start with a review of the main steps of this construction: we recall that our prescription turns out to be unique (under natural assumptions) and leads to the right semi-classical limit with its logarithmic quantum corrections. Furthermore, the...
A length operator for canonical quantum gravity
T. Thiemann
1996-06-29
We construct an operator that measures the length of a curve in four-dimensional Lorentzian vacuum quantum gravity. We work in a representation in which a $SU(2)$ connection is diagonal and it is therefore surprising that the operator obtained after regularization is densely defined, does not suffer from factor ordering singularities and does not require any renormalization. We show that the length operator admits self-adjoint extensions and compute part of its spectrum which like its companions, the volume and area operators already constructed in the literature, is purely discrete and roughly is quantized in units of the Planck length. The length operator contains full and direct information about all the components of the metric tensor which faciliates the construction of a new type of weave states which approximate a given classical 3-geometry.
Bi-metric Gravity and "Dark Matter"
I. T. Drummond
2000-08-18
We present a bi-metric theory of gravity containing a length scale of galactic size. For distances less than this scale the theory satisfies the standard tests of General Relativity. For distances greater than this scale the theory yields an effective gravitational constant much larger than the locally observed value of Newton's constant. The transition from one regime to the other through the galactic scale can explain the observed rotation curves of galaxies and hence the effects normally attributed to the presence of dark matter. Phenomena on an extragalactic scale such as galactic clusters and the expansion of the universe are controlled by the enhanced gravitational coupling. This provides an explanation of the missing matter normally invoked to account for the observed value of Hubble's constant in relation to observed matter.
Mixing lengths scaling in a gravity flow
Ecke, Robert E [Los Alamos National Laboratory; Rivera, Micheal [Los Alamos National Laboratory; Chen, Jun [Los Alamos National Laboratory; Ecke, Robert E [Los Alamos National Laboratory
2009-01-01
We present an experimental study of the mixing processes in a gravity current. The turbulent transport of momentum and buoyancy can be described in a very direct and compact form by a Prandtl mixing length model [1]: the turbulent vertical fluxes of momentum and buoyancy are found to scale quadraticatly with the vertical mean gradients of velocity and density. The scaling coefficient is the square of the mixing length, approximately constant over the mixing zone of the stratified shear layer. We show in this paper how, in different flow configurations, this length can be related to the shear length of the flow {radical}({var_epsilon}/{partial_derivative}{sub z}u{sup 3}).
Revisiting perturbations in extended quasidilaton massive gravity
Lavinia Heisenberg
2015-04-16
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Revisiting perturbations in extended quasidilaton massive gravity
Heisenberg, Lavinia
2015-01-01
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Black Hole Thermodynamics in Modified Gravity
Jonas R. Mureika; John W. Moffat; Mir Faizal
2015-03-03
We analyze the thermodynamics of a non-rotating and rotating black hole in a modified theory of gravity that includes scalar and vector modifications to general relativity, which results in a modified gravitational constant $G = G_N(1+\\alpha)$ and a new gravitational charge $Q = \\sqrt{\\alpha G_N}M$. The influence of the parameter $\\alpha$ alters the non-rotating black hole's lifetime, temperature and entropy profiles from the standard Schwarzschild case. The thermodynamics of a rotating black hole is analyzed and it is shown to possess stable, cold remnants. The thermodynamic properties of a vacuum solution regular at $r=0$ are investigated and the solution without a horizon called a "gray hole" is not expected to possess an information loss problem.
What is Dynamics in Quantum Gravity?
Malkiewicz, Przemyslaw
2015-01-01
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
What is Dynamics in Quantum Gravity?
Przemyslaw Malkiewicz
2015-05-18
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
Solar system tests of Ho?ava-Lifshitz gravity
Tiberiu Harko; Zoltan Kovács; Francisco S. N. Lobo
2010-10-28
Recently, a renormalizable gravity theory with higher spatial derivatives in four dimensions was proposed by Ho\\v{r}ava. The theory reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but it has improved UV behaviors. The spherically symmetric black hole solutions for an arbitrary cosmological constant, which represent the generalization of the standard Schwarzschild-(A)dS solution, has also been obtained for the Ho\\v{r}ava-Lifshitz theory. The exact asymptotically flat Schwarzschild type solution of the gravitational field equations in Ho\\v{r}ava gravity contains a quadratic increasing term, as well as the square root of a fourth order polynomial in the radial coordinate, and it depends on one arbitrary integration constant. The IR modified Ho\\v{r}ava gravity seems to be consistent with the current observational data, but in order to test its viability more observational constraints are necessary. In the present paper we consider the possibility of observationally testing Ho\\v{r}ava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the spherically symmetric black hole solution of Ho\\v{r}ava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of the gravity. Moreover, the study of the classical general relativistic tests also constrain the free parameter of the solution.
Grand Coulee Transmission Line Replacement Project
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& Reliability Projects Expand Projects Skip navigation links Line Projects Big Eddy-Knight Central Ferry Lower Monumental Grand Coulee Transmission Line Replacement...
Transmission Line MTF: Magnetized Target Fusion
Transmission Line MTF: Magnetized Target Fusion Initial target: preheated & magnetized Subsequent for the FRC. Abstract Block Diagram theta coil transmission line Bias cap. bank maincapacitor inductor PI cap
What can emission lines tell us?
G. Stasinska
2007-04-03
1 Generalities 2 Empirical diagnostics based on emission lines 3 Photoionization modelling 4 Pending questions 5 Appendix: Lists of useful lines and how to deal with them
PHYSICS OF FLUIDS 25, 086604 (2013) Gravity currents shoaling on a slope
Sutherland, Bruce
2013-01-01
water rivers into the saline ocean form surface gravity currents. The study of gravity currents is also spills in the ocean.6 Gravity currents in a channel have been well studied through lockPHYSICS OF FLUIDS 25, 086604 (2013) Gravity currents shoaling on a slope Bruce R. Sutherland,1,2,a
Gravity observations and 3D structure of the Earth , F. Chambat
1 Gravity observations and 3D structure of the Earth Y. Ricard1 , F. Chambat Laboratoire des, Michigan-Ann Harbor University, USA. Short title: GRAVITY OBSERVATIONS AND 3D STRUCTURE OF THE EARTH 1. The determination of Earth's gravity field has benefited from various gravity missions that have been launched
Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li
Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li Gravity contrast that gives rise to zero gravity response on the surface. As a result, part of the salt structure structure using gravity data can be divided into two general categories. The first are interface inversions
GRAVITY PERTURBED CRAPPER WAVES BENJAMIN F. AKERS, DAVID M. AMBROSE & J. DOUGLAS WRIGHT
Wright, J. Douglas
GRAVITY PERTURBED CRAPPER WAVES BENJAMIN F. AKERS, DAVID M. AMBROSE & J. DOUGLAS WRIGHT Abstract for but gravity is neglected. For certain parameter values, Crapper waves are known to have multi-valued height by the effect of gravity, yielding the existence of gravity-capillary waves nearby to the Crapper waves
Emergent gravity/Non-linear U(1) gauge theory correspondence
Supriya Kar; K. Priyabrat Pandey; Abhishek K. Singh; Sunita Singh
2010-02-21
Kaluza-Klein gravity is revisted, with renewed interest, in a type IIB string theory on $S^1\\times K3$. The irreducible curvature tensors are worked out in the, T-dual, emergent gravity in 4D to yield a non-linear U(1) gauge theory. Interestingly, the T-duality may be seen to describe an open/closed string duality at a self-dual string coupling. The obtained deformation in $AdS_5$ black hole is analyzed to introduce the notion of temperature in the emergent gravity underlying the recent idea of entropic force.
Particles on a Circle in Canonical Lineal Gravity
R. B. Mann
2001-05-02
A description of the canonical formulation of lineal gravity minimally coupled to N point particles in a circular topology is given. The Hamiltonian is found to be equal to the time-rate of change of the extrinsic curvature multiplied by the proper circumference of the circle. Exact solutions for pure gravity and for gravity coupled to a single particle are obtained. The presence of a single particle significantly modifies the spacetime evolution by either slowing down or reversing the cosmological expansion of the circle, depending upon the choice of parameters.
Flat space (higher spin) gravity with chemical potentials
Michael Gary; Daniel Grumiller; Max Riegler; Jan Rosseel
2014-11-24
We introduce flat space spin-3 gravity in the presence of chemical potentials and discuss some applications to flat space cosmology solutions, their entropy, free energy and flat space orbifold singularity resolution. Our results include flat space Einstein gravity with chemical potentials as special case. We discover novel types of phase transitions between flat space cosmologies with spin-3 hair and show that the branch that continuously connects to spin-2 gravity becomes thermodynamically unstable for sufficiently large temperature or spin-3 chemical potential.
Lassoing Line Outages in the Smart Power Grid
Zhu, Hao
2011-01-01
Fast and accurate unveiling of power line outages is of paramount importance not only for preventing faults that may lead to blackouts, but also for routine monitoring and control tasks of the smart grid, including state estimation and optimal power flow. Existing approaches are either challenged by the \\emph{combinatorial complexity} issues involved, and are thus limited to identifying single- and double-line outages; or, they invoke less pragmatic assumptions such as \\emph{conditionally independent} phasor angle measurements available across the grid. Using only a subset of voltage phasor angle data, the present paper develops a near real-time algorithm for identifying multiple line outages at the affordable complexity of solving a quadratic program via block coordinate descent iterations. The novel approach relies on reformulating the DC linear power flow model as a \\emph{sparse} overcomplete expansion, and leveraging contemporary advances in compressive sampling and variable selection using the least-abso...
Electric and magnetic field reduction by alternative transmission line options
Stewart, J.R. (Power Technologies, Inc., Schenectady, NY (United States)); Dale, S.J. (Oak Ridge National Lab., TN (United States)); Klein, K.W. (Energetics, Inc., Columbia, MD (United States))
1991-01-01
Ground level electric, and more recently magnetic, fields from overhead power transmission lines are increasingly important considerations in right of way specification, with states setting or planning to set edge of right of way limits. Research has been conducted in high phase order power transmission wherein six of twelve phases are used to transmit power in less physical space and with reduced electrical environmental effects than conventional designs. The first magnetic field testing, as reported in this paper, has verified predictive methods for determination of magnetic fields from high phase order lines. Based on these analytical methods, field profiles have been determined for lines of different phase order of comparable power capacity. Potential advantages of high phase order as a means of field mitigation are discussed. 10 refs., 12 figs., 3 tabs.
Tsujimoto, K.; Fujii, K.; Kubokawa, H.; Okomura, T.; Simojima, K.; Yoshioka, V.
1982-11-01
In Japan it has recently become necessary to shorten the interphase spacing in overhead transmission lines because of land limitations and economical considerations. In this connection, the authors have attempted to analyze, in-depth, the possibilities of shortened interphase spacing via conductor swinging caused by wind effects: one of the important factors in the design of more compact overhead lines. This paper describes not only the investigative results of conductor swinging that were obtained both through computer simulation and in 3 years of full scale field line testing, but also design methodology for compact overhead lines based on these results.
Coiled transmission line pulse generators
McDonald, Kenneth Fox (Columbia, MO)
2010-11-09
Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.
Oshmyansky, A
2007-01-01
An alternative quantum field theory for gravity is proposed for low energies based on an attractive effect between contaminants in a Bose-Einstein Condensate rather than on particle exchange. In the ``contaminant in condensate effect," contaminants cause a potential in an otherwise uniform condensate, forcing the condensate between two contaminants to a higher energy state. The energy of the system decreases as the contaminants come closer together, causing an attractive force between contaminants. It is proposed that mass-energy may have a similar effect on Einstein's space-time field, and gravity is quantized by the same method by which the contaminant in condensate effect is quantized. The resulting theory is finite and, if a physical condensate is assumed to underly the system, predictive. However, the proposed theory has several flaws at high energies and is thus limited to low energies. Falsifiable predictions are given for the case that the Higgs condensate is assumed to be the condensate underlying gr...
A Novel Two-Step Laser Ranging Technique for a Precision Test of the Theory of Gravity
Penanen, K; Penanen, Konstantin; Chui, Talso
2004-01-01
All powered spacecraft experience residual systematic acceleration due to anisotropy of the thermal radiation pressure and fuel leakage. The residual acceleration limits the accuracy of any test of gravity that relies on the precise determination of the spacecraft trajectory. We describe a novel two-step laser ranging technique, which largely eliminates the effects of non-gravity acceleration sources and enables celestial mechanics checks with unprecedented precision. A passive proof mass is released from the mother spacecraft on a solar system exploration mission. Retro-reflectors attached to the proof mass allow its relative position to the spacecraft to be determined using optical ranging techniques. Meanwhile, the position of the spacecraft relative to the Earth is determined by ranging with a laser transponder. The vector sum of the two is the position, relative to the Earth, of the proof mass, the measurement of which is not affected by the residual accelerations of the mother spacecraft. We also descri...
Asymptotically anti-de Sitter spacetimes in topologically massive gravity
Marc Henneaux; Cristian Martinez; Ricardo Troncoso
2009-03-31
We consider asymptotically anti-de Sitter spacetimes in three-dimensional topologically massive gravity with a negative cosmological constant, for all values of the mass parameter $\\mu$ ($\\mu\
TOPOLOGICAL GRAVITY IN GENUS 2 WITH TWO PRIMARY FIELDS
TOPOLOGICAL GRAVITY IN GENUS 2 WITH TWO PRIMARY FIELDS TOHRU EGUCHI, EZRA GETZLER AND CHUAN TOHRU EGUCHI, EZRA GETZLER AND CHUAN-SHENG XIONG 1.2. The topological recursion relation in genus 0
Application Of Gravity And Deep Dipole Geoelectrics In The Volcanic...
Application Of Gravity And Deep Dipole Geoelectrics In The Volcanic Area Of Mt Etna (Sicily) Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article:...
Gravity wave turbulence revealed by horizontal vibrations of the container
Bruno Issenmann; Eric Falcon
2012-12-20
We experimentally study the role of the forcing on gravity-capillary wave turbulence. Previous laboratory experiments using spatially localized forcing (vibrating blades) have shown that the frequency power-law exponent of the gravity wave spectrum depends on the forcing parameters. By horizontally vibrating the whole container, we observe a spectrum exponent that does not depend on the forcing parameters for both gravity and capillary regimes. This spatially extended forcing leads to a gravity spectrum exponent in better agreement with the theory than by using a spatially localized forcing. The role of the vessel shape has been also studied. Finally, the wave spectrum is found to scale linearly with the injected power for both regimes whatever the forcing type used.
Mixed convection and heat management in the Mars gravity biosatellite
Marsh, Jesse B. (Jesse Benjamin)
2007-01-01
The Mars Gravity Biosatellite will house fifteen mice in a low Earth orbit satellite spinning about its longitudinal axis. The satellite's payload thermal control system will reject heat through the base of the payload ...
Regional Gravity Survey of the Northern Great Salt Lake Desert...
Regional Gravity Survey of the Northern Great Salt Lake Desert and Adjacent Areas in Utah, Nevada, and Idaho Jump to: navigation, search OpenEI Reference LibraryAdd to library...
The Basics of Water Waves Theory for Analogue Gravity
Germain Rousseaux
2012-03-14
This chapter gives an introduction to the connection between the physics of water waves and analogue gravity. Only a basic knowledge of fluid mechanics is assumed as a prerequisite.
Light deflection in Weyl gravity: critical distances for photon paths
S. Pireaux
2004-03-16
The Weyl gravity appears to be a very peculiar theory. The contribution of the Weyl linear parameter to the effective geodesic potential is opposite for massive and nonmassive geodesics. However, photon geodesics do not depend on the unknown conformal factor, unlike massive geodesics. Hence light deflection offers an interesting test of the Weyl theory. In order to investigate light deflection in the setting of Weyl gravity, we first distinguish between a weak field and a strong field approximation. Indeed, the Weyl gravity does not turn off asymptotically and becomes even stronger at larger distances. We then take full advantage of the conformal invariance of the photon effective potential to provide the key radial distances in Weyl gravity. According to those, we analyze the weak and strong field regime for light deflection. We further show some amazing features of the Weyl theory in the strong regime.
Acoustic-Gravity Waves Interacting with a Rectangular Trench
Kadri, Usama
2015-01-01
A mathematical solution of the two-dimensional linear problem of an acoustic-gravity wave interacting with a rectangular trench, in a compressible ocean, is presented. Expressions for the flow field on both sides of the ...
Ionospheric acoustic and gravity waves associated with midlatitude thunderstorms
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lay, Erin H.; Shao, Xuan -Min; Kendrick, Alexander K.; Carrano, Charles S.
2015-07-30
Acoustic waves with periods of 2–4 min and gravity waves with periods of 6–16 min have been detected at ionospheric heights (25–350 km) using GPS total electron content measurements. The area disturbed by these waves and the wave amplitudes have been associated with underlying thunderstorm activity. A statistical study comparing Next Generation Weather Radar thunderstorm measurements with ionospheric acoustic and gravity waves in the midlatitude U.S. Great Plains region was performed for the time period of May–July 2005. An increase of ionospheric acoustic wave disturbed area and amplitude is primarily associated with large thunderstorms (mesoscale convective systems). Ionospheric gravity wavemore »disturbed area and amplitude scale with thunderstorm activity, with even small storms (i.e., individual storm cells) producing an increase of gravity waves.« less
Ground Gravity Survey At Dixie Valley Geothermal Area (Iovenitti...
project area. These data were used in conjunction with past gravity data reported in by Smith et al (2001) and Blackwell et al (2005). The analysis of these data had not been...
Sudarshan Ananth; Mahendra Mali
2015-04-11
We derive a closed form expression for the light-cone Lagrangian describing pure gravity on a four-dimensional de Sitter background. We provide a perturbative expansion, of this Lagrangian, to cubic order in the fields.
An alternative derivation of the Minimal massive 3D gravity
Ahmet Baykal
2014-12-23
By using the algebra of exterior forms and the first order formalism with constraints, an alternative derivation of the field equations for the Minimal massive 3D gravity model is presented.
Ground Gravity Survey At Mt Princeton Hot Springs Geothermal...
lithologic distrubtions Notes Gravity low associated with Mt. Princeton Batholith; density contrast of -0.5 gcm3 of valley-fill sediments relative to batholith References J.E....
Keeton, Charles R.; Petters, A.O.
2005-11-15
We are developing a general, unified, and rigorous analytical framework for using gravitational lensing by compact objects to test different theories of gravity beyond the weak-deflection limit. In this paper we present the formalism for computing corrections to lensing observables for static, spherically symmetric gravity theories in which the corrections to the weak-deflection limit can be expanded as a Taylor series in one parameter, namely, the gravitational radius of the lens object. We take care to derive coordinate-independent expressions and compute quantities that are directly observable. We compute series expansions for the observables that are accurate to second order in the ratio {epsilon}={theta} /{theta}{sub E} of the angle subtended by the lens's gravitational radius to the weak-deflection Einstein radius, which scales with mass as {epsilon}{proportional_to}M {sup 1/2}. The positions, magnifications, and time delays of the individual images have corrections at both first and second order in {epsilon}, as does the differential time delay between the two images. Interestingly, we find that the first-order corrections to the total magnification and centroid position vanish in all gravity theories that agree with general relativity in the weak-deflection limit, but they can remain nonzero in modified theories that disagree with general relativity in the weak-deflection limit. For the Reissner-Nordstroem metric and a related metric from heterotic string theory, our formalism reveals an intriguing connection between lensing observables and the condition for having a naked singularity, which could provide an observational method for testing the existence of such objects. We apply our formalism to the galactic black hole and predict that the corrections to the image positions are at the level of 10 {mu}arc s (microarcseconds), while the correction to the time delay is a few hundredths of a second. These corrections would be measurable today if a pulsar were found to be lensed by the galactic black hole, and they should be readily detectable with planned missions like MAXIM.
Extended disformal approach in the scenario of Rainbow Gravity
Carvalho, Gabriel G; Bittencourt, Eduardo
2015-01-01
We investigate all feasible mathematical representations of disformal transformations on a space-time metric according to the action of a linear operator upon the manifold's tangent and cotangent bundles. The geometric, algebraic and group structures of this operator and their interfaces are analyzed in detail. Then, we scrutinize a possible physical application, providing a new covariant formalism for a phenomenological approach to quantum gravity known as Rainbow Gravity.
Gravity-free hydraulic jumps and metal femtocups
Rama Govindarajan; Manikandan Mathur; Ratul DasGupta; N. R. Selvi; Neena Susan John; G. U. Kulkarni
2006-10-03
Hydraulic jumps created by gravity are seen every day in the kitchen sink. We show that at small scales a circular hydraulic jump can be created in the absence of gravity, by surface tension. The theory is motivated by our experimental finding of a height discontinuity in spreading submicron molten metal droplets created by pulsed-laser ablation. By careful control of initial conditions, we show that this leads to solid femtolitre cups of gold, silver, copper, niobium and tin.
Probing strongly coupled anisotropic plasmas from higher curvature gravity
Viktor Jahnke; Anderson Seigo Misobuchi
2015-10-23
We consider five-dimensional AdS-axion-dilaton gravity with a Gauss-Bonnet term and use a black brane solution displaying spatial anisotropy as the gravity dual of a strongly coupled anisotropic plasma. We compute several observables relevant to the study of the plasma, namely, the drag force, the jet quenching parameter, the quarkonium potential and the thermal photon production. The effects of higher derivative corrections and of the anisotropy are discussed and compared with previous results.
Entropy and Area of Black Holes in Loop Quantum Gravity
I. B. Khriplovich
2002-03-31
Simple arguments related to the entropy of black holes strongly constrain the spectrum of the area operator for a Schwarzschild black hole in loop quantum gravity. In particular, this spectrum is fixed completely by the assumption that the black hole entropy is maximum. Within the approach discussed, one arrives in loop quantum gravity at a quantization rule with integer quantum numbers $n$ for the entropy and area of a black hole.
Gravity interpretation of the northern Overthrust Belt, Idaho and Wyoming
Silver, Wendy Ilene
1979-01-01
GRAVITY INTERPRETATION OF THE NORTHERN OVERTHRUST BELT, IDAHO AND 'vlYOMING A Thesis by IJENDY ILENE SILVER Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirements for the deoree of MASTER... OF SCIFNCE December 1979 Major Subject: Geology GRAVITY INTERPRETATION OF THE NORTHERN OVERTHRUST lIELT, . IDAHO AND NYOMING A Thesis by NENDY ILEI'lE 5!, LVER Approved as to style and content by: (Chairman of Committee (Hea o epartment (i~1embe...
A Hopf Algebra Structure in Self-dual Gravity
Hugo Garcia-Compean; Laura E. Morales; Jerzy F. Plebanski
1996-01-20
The two-dimensional non-linear sigma model approach to Self-dual Yang-Mills theory and to Self-dual gravity given by Q-Han Park is an example of the deep interplay between two and four dimensional physics. In particular, Husain's two-dimensional chiral model approach to Self-dual gravity is studied. We show that the infinite hierarchy of conservation laws associated to the Husain model carries implicitly a hidden infinite Hopf algebra structure.
Perihelion precession for modified Newtonian gravity
Schmidt, Hans-Juergen
2008-07-15
We calculate the perihelion precession {delta} for nearly circular orbits in a central potential V(r). Differently from other approaches to this problem, we do not assume that the potential is close to the Newtonian one. The main idea in the deduction is to apply the underlying symmetries of the system to show that {delta} must be a function of r{center_dot}V{sup ''}(r)/V{sup '}(r) and to use the transformation behavior of {delta} in a rotating system of reference. This is equivalent to say that the effective potential can be written in a one-parameter set of possibilities as the sum of centrifugal potential and potential of the central force. We get the following universal formula valid for V{sup '}(r)>0 reading {delta}(r)=2{pi}{center_dot}[(1/{radical}(3+r{center_dot}V{sup ''}(r)/V{sup '}(r)))-1]. It has to be read as follows: a circular orbit at this value r exists and is stable if and only if this {delta} is well-defined as real; and if this is the case, then the angular difference from one perihelion to the next one for nearly circular orbits at this r is exactly 2{pi}+{delta}(r). Then we apply this result to examples of recent interest like modified Newtonian gravity and linearized fourth-order gravity. In the second part of the paper, we generalize this universal formula to static spherically symmetric space-times ds{sup 2}=-e{sup 2{lambda}}{sup (r)}dt{sup 2}+e{sup 2{mu}}{sup (r)}dr{sup 2}+r{sup 2}d{omega}{sup 2}; for orbits near r it reads {delta}=2{pi}{center_dot}[(e{sup {mu}}{sup (r)}/{radical}(3-2r{center_dot}{lambda}{sup '}(r)+r{center_dot}{lambda}{sup ''}(r)/{lambda}{sup '}(r)))-1] and can be applied to a large class of theories. For the Schwarzschild black hole with mass parameter m>0 it leads to {delta}=2{pi}{center_dot}[(1/{radical}(1-(6m/r)))-1], a surprisingly unknown formula. It represents a strict result and is applicable for all values r>6m and is in good agreement with the fact that stable circular orbits exist for r>6m only. For r>>m, one can develop in powers of m and get the well-known approximation {delta}{approx_equal}(6{pi}m/r)
Finite field-dependent symmetries in perturbative quantum gravity
Upadhyay, Sudhaker
2014-01-15
In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear Curci–Ferrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using Batalin–Vilkovisky (BV) formulation. -- Highlights: •The perturbative quantum gravity is treated as gauge theory. •BRST and anti-BRST transformations are developed in linear and non-linear gauges. •BRST transformation is generalized by making it finite and field dependent. •Connection between linear and non-linear gauges is established. •Using BV formulation the results are established at quantum level also.
The covariant formulation of $f(T)$ gravity
Krššák, Martin
2015-01-01
We show that the well-known problem of frame dependence and violation of local Lorentz invariance in the usual formulation of $f(T)$ gravity is a consequence of neglecting the role of spin connection. We re-formulate $f(T)$ gravity starting, instead of the "pure-tetrad" teleparallel gravity, from the covariant teleparallel gravity, using both the tetrad and the spin connection as dynamical variables, resulting in the fully covariant, consistent, and frame-independent, version of $f(T)$ gravity, which does not suffer from the notorious problems of the usual, pure-tetrad, $f(T)$ theory. We present the method to extract solutions for the most physically important cases, such as the Minkowski, the FRW and the spherically-symmetric ones. We show that in the covariant $f(T)$ gravity we are allowed to use an arbitrary tetrad in an arbitrary coordinate system along with the corresponding spin connection, resulting always to the same physically relevant field equations.
TESTING ALTERNATIVE THEORIES OF GRAVITY USING THE SUN
Casanellas, Jordi; Pani, Paolo; Lopes, Ilidio; Cardoso, Vitor E-mail: paolo.pani@ist.utl.pt E-mail: vitor.cardoso@ist.utl.pt
2012-01-20
We propose a new approach to test possible corrections to Newtonian gravity using solar physics. The high accuracy of current solar models and new precise observations allow us to constrain corrections to standard gravity at unprecedented levels. Our case study is Eddington-inspired gravity, an attractive modified theory of gravity which results in non-singular cosmology and collapse. The theory is equivalent to standard gravity in vacuum, but it sensibly differs from it within matter. For instance, it affects the evolution and the equilibrium structure of the Sun, giving different core temperature profiles, and deviations in the observed acoustic modes and in solar neutrino fluxes. Comparing the predictions from a modified solar model with observations, we constrain the coupling parameter of the theory, |{kappa}{sub g}| {approx}< 3 Multiplication-Sign 10{sup 5} m{sup 5} s{sup -2} kg{sup -1}. Our results show that the Sun can be used to efficiently constrain alternative theories of gravity.
Means for limiting and ameliorating electrode shorting
Van Konynenburg, Richard A. (Livermore, CA); Farmer, Joseph C. (Tracy, CA)
1999-01-01
A fuse and filter arrangement for limiting and ameliorating electrode shorting in capacitive deionization water purification systems utilizing carbon aerogel, for example. This arrangement limits and ameliorates the effects of conducting particles or debonded carbon aerogel in shorting the electrodes of a system such as a capacitive deionization water purification system. This is important because of the small interelectrode spacing and the finite possibility of debonding or fragmentation of carbon aerogel in a large system. The fuse and filter arrangement electrically protect the entire system from shutting down if a single pair of electrodes is shorted and mechanically prevents a conducting particle from migrating through the electrode stack, shorting a series of electrode pairs in sequence. It also limits the amount of energy released in a shorting event. The arrangement consists of a set of circuit breakers or fuses with one fuse or breaker in the power line connected to one electrode of each electrode pair and a set of screens of filters in the water flow channels between each set of electrode pairs.
Means for limiting and ameliorating electrode shorting
Konynenburg, R.A. van; Farmer, J.C.
1999-11-09
A fuse and filter arrangement is described for limiting and ameliorating electrode shorting in capacitive deionization water purification systems utilizing carbon aerogel, for example. This arrangement limits and ameliorates the effects of conducting particles or debonded carbon aerogel in shorting the electrodes of a system such as a capacitive deionization water purification system. This is important because of the small interelectrode spacing and the finite possibility of debonding or fragmentation of carbon aerogel in a large system. The fuse and filter arrangement electrically protect the entire system from shutting down if a single pair of electrodes is shorted and mechanically prevents a conducting particle from migrating through the electrode stack, shorting a series of electrode pairs in sequence. It also limits the amount of energy released in a shorting event. The arrangement consists of a set of circuit breakers or fuses with one fuse or breaker in the power line connected to one electrode of each electrode pair and a set of screens of filters in the water flow channels between each set of electrode pairs.
COMMENTARY:Limits to adaptation
Preston, Benjamin L
2013-01-01
An actor-centered, risk-based approach to defining limits to social adaptation provides a useful analytic framing for identifying and anticipating these limits and informing debates over society s responses to climate change.
AN EXTREME GRAVITATIONALLY REDSHIFTED IRON LINE AT 4.8 KeV IN Mrk 876
Bottacini, Eugenio; Orlando, Elena; Moskalenko, Igor [W. W. Hansen Experimental Physics Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University (United States); Greiner, Jochen [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Ajello, Marco [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States); Persic, Massimo, E-mail: eugenio.bottacini@stanford.edu [INAF-Trieste, via G.B.Tiepolo 11, I-34143 Trieste (Italy)
2015-01-01
X-ray spectral lines at unforeseen energies are important because they can shed light on the extreme physical conditions of the environment around the supermassive black holes of active galactic nuclei (AGNs). Mrk 876 displays such a line at 4.80{sub ?0.04}{sup +0.05} rest-frame energy. A possible interpretation of its origin can be found in the hotspot scenario. In this scenario, the primary radiation from a flare in the hot corona of an AGN illuminates a limited portion of the accretion disk that emits by fluorescence. In this context, the line can represent an extreme gravitationally redshifted Fe line originating on the accretion disk below six gravitational radii from a rotating supermassive black hole. The correct estimate of the line significance requires a dedicated approach. Based on an existing rigorous approach, we have performed extensive Monte Carlo simulations. We determine that the line is a real feature at a ?99% confidence level.
The list of tantalum lines for wavelengths calibration of the Hamilton echelle-spectrograph
Pakhomov, Yu V
2015-01-01
We present solution of the problem of wavelength calibration for Hamilton Echelle spectrograph using hollow cathode lamp, which was operated at Lick Observatory Shane telescope before June 9, 2011. The spectrum of the lamp claimed to be thorium-argon, contains, in addition to the lines of thorium and argon, a number of the unrecognized lines identified by us with tantalum. Using atomic data for measured lines of tantalum and thorium, we estimated the temperature of the gas in the lamp as T=3120+/-60 K. From the atomic line database VALD3 we selected all lines of TaI and TaII which can be seen in the spectrum of the lamp and compiled a list for the use in the processing of spectral observations. We note a limitation of the accuracy of calibration due to the influence of the hyperfine line splitting.
The local potential approximation in quantum gravity
Dario Benedetti; Francesco Caravelli
2012-10-09
Within the context of the functional renormalization group flow of gravity, we suggest that a generic f(R) ansatz (i.e. not truncated to any specific form, polynomial or not) for the effective action plays a role analogous to the local potential approximation (LPA) in scalar field theory. In the same spirit of the LPA, we derive and study an ordinary differential equation for f(R) to be satisfied by a fixed point of the renormalization group flow. As a first step in trying to assess the existence of global solutions (i.e. true fixed point) for such equation, we investigate here the properties of its solutions by a comparison of various series expansions and numerical integrations. In particular, we study the analyticity conditions required because of the presence of fixed singularities in the equation, and we develop an expansion of the solutions for large R up to order N=29. Studying the convergence of the fixed points of the truncated solutions with respect to N, we find a characteristic pattern for the location of the fixed points in the complex plane, with one point stemming out for its stability. Finally, we establish that if a non-Gaussian fixed point exists within the full f(R) approximation, it corresponds to an R^2 theory.
Wave Equations for Discrete Quantum Gravity
Gudder, Stan
2015-01-01
This article is based on the covariant causal set ($c$-causet) approach to discrete quantum gravity. A $c$-causet $x$ is a finite partially ordered set that has a unique labeling of its vertices. A rate of change on $x$ is described by a covariant difference operator and this operator acting on a wave function forms the left side of the wave equation. The right side is given by an energy term acting on the wave function. Solutions to the wave equation corresponding to certain pairs of paths in $x$ are added and normalized to form a unique state. The modulus squared of the state gives probabilities that a pair of interacting particles is at various locations given by pairs of vertices in $x$. We illustrate this model for a few of the simplest nontrivial examples of $c$-causets. Three forces are considered, the attractive and repulsive electric forces and the strong nuclear force. Large models get much more complicated and will probably require a computer to analyze.
Wave Equations for Discrete Quantum Gravity
Stan Gudder
2015-08-29
This article is based on the covariant causal set ($c$-causet) approach to discrete quantum gravity. A $c$-causet $x$ is a finite partially ordered set that has a unique labeling of its vertices. A rate of change on $x$ is described by a covariant difference operator and this operator acting on a wave function forms the left side of the wave equation. The right side is given by an energy term acting on the wave function. Solutions to the wave equation corresponding to certain pairs of paths in $x$ are added and normalized to form a unique state. The modulus squared of the state gives probabilities that a pair of interacting particles is at various locations given by pairs of vertices in $x$. We illustrate this model for a few of the simplest nontrivial examples of $c$-causets. Three forces are considered, the attractive and repulsive electric forces and the strong nuclear force. Large models get much more complicated and will probably require a computer to analyze.
Peralta, J.; López-Valverde, M. A.; Imamura, T.; Read, P. L.; Luz, D.; Piccialli, A.
2014-07-01
This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied—acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes.
Post-Newtonian, Quasi-Circular Binary Inspirals in Quadratic Modified Gravity
Kent Yagi; Leo C. Stein; Nicolas Yunes; Takahiro Tanaka
2012-04-16
We consider a general class of quantum gravity-inspired, modified gravity theories, where the Einstein-Hilbert action is extended through the addition of all terms quadratic in the curvature tensor coupled to scalar fields with standard kinetic energy. This class of theories includes Einstein-Dilaton-Gauss-Bonnet and Chern-Simons modified gravity as special cases. We analytically derive and solve the coupled field equations in the post-Newtonian approximation, assuming a comparable-mass, spinning black hole binary source in a quasi-circular, weak-field/slow-motion orbit. We find that a naive subtraction of divergent piece associated with the point-particle approximation is ill-suited to represent compact objects in these theories. Instead, we model them by appropriate effective sources built so that known strong-field solutions are reproduced in the far-field limit. In doing so, we prove that black holes in Einstein-Dilaton-Gauss-Bonnet and Chern-Simons theory can have hair, while neutron stars have no scalar monopole charge, in diametrical opposition to results in scalar-tensor theories. We then employ techniques similar to the direct integration of the relaxed Einstein equations to obtain analytic expressions for the scalar field, metric perturbation, and the associated gravitational wave luminosity measured at infinity. We find that scalar field emission mainly dominates the energy flux budget, sourcing electric-type (even-parity) dipole scalar radiation and magnetic-type (odd-parity) quadrupole scalar radiation, correcting the General Relativistic prediction at relative -1PN and 2PN orders. Such modifications lead to corrections in the emitted gravitational waves that can be mapped to the parameterized post-Einsteinian framework. Such modifications could be strongly constrained with gravitational wave observations.
Pento, Robert (Algonquin, IL); Marks, James E. (Glenville, NY); Staffanson, Clifford D. (S. Glens Falls, NY)
2000-01-01
A thermoelectric module with a plurality of electricity generating units each having a first end and a second end, the units being arranged first end to second end along an in-line axis. Each unit includes first and second elements each made of a thermoelectric material, an electrically conductive hot member arranged to heat one side of the first element, and an electrically conductive cold member arranged to cool another side of the first element and to cool one side of the second element. The hot member, the first element, the cold member and the second element are supported in a fixture, are electrically connected respectively to provide an electricity generating unit, and are arranged respectively in positions along the in-line axis. The individual components of each generating unit and the respective generating units are clamped in their in-line positions by a loading bolt at one end of the fixture and a stop wall at the other end of the fixture. The hot members may have a T-shape and the cold members an hourglass shape to facilitate heat transfer. The direction of heat transfer through the hot members may be perpendicular to the direction of heat transfer through the cold members, and both of these heat transfer directions may be perpendicular to the direction of current flow through the module.
ROHATGI,U.S.; JO,J.; CHUNG,B.D.; TAKAHASHI,H.
2002-06-09
Safety analyses of a proliferation resistant, economically competitive, high conversion, boiling water reactor (HCBWR) fueled with fissile plutonium and fertile thorium oxide fuel elements, and with passive safety systems are presented here. The HCBWR developed here is characterized by a very tight lattice with a relatively small water volume fraction in the core which therefore operates with a fast reactor neutron spectrum, and a considerably improved neutron economy compared to the current generation of Light Water Reactors. The tight lattice core has a very narrow flow channels with a hydraulic diameter less than half of the regular BWR core and, thus, presents a special challenge to core cooling, because of reduced water inventory and high friction in the core. The primary safety concern when reducing the moderator to fuel ratio and when using a tightly packed lattice arrangement is to maintain adequate cooling of the core during both normal operation and accident scenarios. In the preliminary HCBWR design, the core has been placed in a vessel with a large chimney section, and the vessel is connected with Isolation Condenser System (ICs). The vessel is placed in containment with Gravity Driven Cooling System (GDCS) and Passive Containment Cooling System (PCCS) in a configuration similar to General Electric's Simplified Boiling Water Reactor (SBWR). The safety systems are similar to SBWR; ICs and PCCS are scaled with power. An internal recirculation pump was placed in the downcomer to augment the buoyancy head provided by the chimney, since the buoyancy provided by the chimney alone could not generate sufficient recirculation in the vessel as the tight lattice configuration resulted in much larger friction in the core than the SBWR. The constitutive relationships for RELAP5 were assessed for narrow channels, and as a result the heat transfer package was modified. The modified RELAP5 was used to simulate and analyze two of the most limiting events for a tight pitch lattice core: the Station Blackout and the Main Steam Line Break events. The results of the analyses indicate that the HCBWR system will be safely brought to the shutdown condition for these transients.
Upendra Rohatgi; Jae Jo; Bub Dong Chung; Hiroshi Takahashi [Brookhaven National Laboratory, Energy Sciences and Technology Department, Upton, New York 11973 (United States); Downar, T.J. [Purdue University, School of Nuclear Engineering, West Lafayette, IN 47906-1290 (United States)
2002-07-01
Safety analyses of a proliferation resistant, economically competitive, high conversion, boiling water reactor (HCBWR) fueled with fissile plutonium and fertile thorium oxide fuel elements, and with passive safety systems are presented here. The HCBWR developed here is characterized by a very tight lattice with a relatively small water volume fraction in the core which therefore operates with a fast reactor neutron spectrum, and a considerably improved neutron economy compared to the current generation of Light Water Reactors. A tight lattice BWR core has very narrow flow channels with a hydraulic diameter less than half of the regular BWR core. The tight lattice core presented a special challenge to core cooling, because of reduced water inventory and high friction in the core. The primary safety concern when reducing the moderator to fuel ratio and when using a tightly packed lattice arrangement is to maintain adequate cooling of the core during both normal operation and accident scenarios. In the preliminary HCBWR design, the core has been placed in a vessel with a large chimney section, and the vessel is connected with an Isolation Cooling System (ICS). The vessel is placed in a containment with a Gravity Driven Cooling System (GDCS) and a Passive Containment Cooling System (PCCS) in a configuration similar to General Electric's (GE) Simplified Boiling Water Reactor (SBWR). The safety systems are similar to the SBWR; the ICS and PCCS are scaled with power. An internal recirculation pump was placed in the downcomer to augment the buoyancy head provided by the chimney. The buoyancy provided by the chimney alone could not generate sufficient recirculation in the vessel since the tight lattice configuration resulted in much larger friction in the core than the SBWR. A modified RELAP5 Code was used to simulate and analyze two of the most limiting events for a tight pitch lattice core: the Station Blackout and the Main Steam Line Break events. The constitutive relationships for RELAP5 were compared with the correlations and the data available for narrow channels, and the heat transfer package was modified for narrow channel application. The results of the analyses indicate that the HCBWR system will be safely shutdown for these transients. (authors)
2013 Macmillan Publishers Limited. All rights reserved. Weyl points and line nodes in gyroid
unidirectional 1D edge states are pro- tected against disorder912 . Similarly, it is expected that if a material dispersions robust against any per- turbation. In three dimensions, Weyl point dispersions are governed
Constraining models of f(R) gravity with Planck and WiggleZ power spectrum data
Dossett, Jason; Parkinson, David; Hu, Bin E-mail: hu@lorentz.leidenuniv.nl
2014-03-01
In order to explain cosmic acceleration without invoking ''dark'' physics, we consider f(R) modified gravity models, which replace the standard Einstein-Hilbert action in General Relativity with a higher derivative theory. We use data from the WiggleZ Dark Energy survey to probe the formation of structure on large scales which can place tight constraints on these models. We combine the large-scale structure data with measurements of the cosmic microwave background from the Planck surveyor. After parameterizing the modification of the action using the Compton wavelength parameter B{sub 0}, we constrain this parameter using ISiTGR, assuming an initial non-informative log prior probability distribution of this cross-over scale. We find that the addition of the WiggleZ power spectrum provides the tightest constraints to date on B{sub 0} by an order of magnitude, giving log{sub 10}(B{sub 0}) < ?4.07 at 95% confidence limit. Finally, we test whether the effect of adding the lensing amplitude A{sub Lens} and the sum of the neutrino mass ?m{sub ?} is able to reconcile current tensions present in these parameters, but find f(R) gravity an inadequate explanation.
A NUMERICAL ANALYSIS OF THE SINGLE-WELL STEAM ASSISTED GRAVITY DRAINAGE (SW-SAGD) PROCESS
K.T. Elliot; A.R. Kovscek
2001-06-01
Steam assisted gravity drainage (SAGD) is an effective method to produce heavy oil and bitumen which are important energy resources. In a typical SAGD approach, steam is injected into a horizontal well located directly above a horizontal producer helping to displace heated oil. Single-well (SW) SAGD attempts to create a similar process using only one horizontal well. To improve early-time response of SW-SAGD, it is necessary to heat the near-wellbore area to reduce oil viscosity and allow gravity drainage to begin. Ideally heating should occur with minimal circulation or bypassing of steam. We have investigated early-time processes to improve reservoir heating. A numerical simulation study was performed to gauge combinations of cyclic steam injection and steam circulation prior to SAGD in an effort to better understand and improve early-time performance. Results from this study, include cumulative recoveries, temperature distributions, and production rates. It is found that cyclic steaming of the reservoir offers the most favorable option for heating the near-wellbore area to create conditions that improve initial SAGD response. More favorable reservoir conditions such as low viscosity, thick oil zones, and solution gas, improved reservoir response. Under unfavorable conditions, response was limited.
Steven Abel; Chong-Sun Chu; Mark Goodsell
2006-09-27
We explore how the IR pathologies of noncommutative field theory are resolved when the theory is realized as open strings in background B-fields: essentially, since the IR singularities are induced by UV/IR mixing, string theory brings them under control in much the same way as it does the UV singularities. We show that at intermediate scales (where the Seiberg-Witten limit is a good approximation) the theory reproduces the noncommutative field theory with all the (un)usual features such as UV/IR mixing, but that outside this regime, in the deep infra-red, the theory flows continuously to the commutative theory and normal Wilsonian behaviour is restored. The resulting low energy physics resembles normal commutative physics, but with additional suppressed Lorentz violating operators. We also show that the phenomenon of UV/IR mixing occurs for the graviton as well, with the result that, in configurations where Planck's constant receives a significant one-loop correction (for example brane-induced gravity), the distance scale below which gravity becomes non-Newtonian can be much greater than any compact dimensions.
Testing quantum gravity by nanodiamond interferometry with nitrogen-vacancy centers
Andreas Albrecht; Alex Retzker; Martin B. Plenio
2014-10-08
Interferometry with massive particles may have the potential to explore the limitations of standard quantum mechanics in particular where it concerns its boundary with general relativity and the yet to be developed theory of quantum gravity. This development is hindered considerably by the lack of experimental evidence and testable predictions. Analyzing effects that appear to be common to many of such theories, such as a modification of the energy dispersion and of the canonical commutation relation within the standard framework of quantum mechanics, has been proposed as a possible way forward. Here we analyze in some detail the impact of a modified energy-momentum dispersion in a Ramsey-Bord\\'e setup and provide achievable bounds of these correcting terms when operating such an interferometer with nanodiamonds. Thus, taking thermal and gravitational disturbances into account will show that without specific prerequisites, quantum gravity modifications may in general be suppressed requiring a revision of previously estimated bounds. As a possible solution we propose a stable setup that is rather insensitive to these effects. Finally, we address the problems of decoherence and pulse errors in such setups and discuss the scalings and advantages with increasing particle mass.