id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1212.0484 | Alexey Toporensky | D. M. Chirkov, A. V. Toporensky | On stability of power-law solution in multidimensional Gauss-Bonnet
cosmology | 23 pages with 6 figures | null | 10.1134/S020228931304004X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider dynamics of a flat anisotropic multidimensional cosmological
model in Gauss-Bonnet gravity in the presence of a homogeneous magnetic field.
In particular, we find conditions under which the known power-law vacuum
solution can be an attractor for the case with non-zero magnetic field. We also
describe a particular class of numerical solution in $(5+1)$-dimensional case
which does not approach the power-law regime.
| [
{
"created": "Mon, 3 Dec 2012 18:42:04 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Chirkov",
"D. M.",
""
],
[
"Toporensky",
"A. V.",
""
]
] | We consider dynamics of a flat anisotropic multidimensional cosmological model in Gauss-Bonnet gravity in the presence of a homogeneous magnetic field. In particular, we find conditions under which the known power-law vacuum solution can be an attractor for the case with non-zero magnetic field. We also describe a particular class of numerical solution in $(5+1)$-dimensional case which does not approach the power-law regime. |
gr-qc/9803004 | Tsvi Piran | Shahar Hod and Tsvi Piran | Mass-Inflation in Dynamical Gravitational Collapse of a Charged
Scalar-Field | Latex, 13 pages including 4 figures, Revtex.sty | Phys.Rev.Lett. 81 (1998) 1554-1557 | 10.1103/PhysRevLett.81.1554 | null | gr-qc | null | We study the inner-structure of a charged black-hole which is formed from the
gravitational collapse of a self-gravitating charged scalar-field. Starting
with a regular spacetime, we follow the evolution through the formation of an
apparent horizon, a Cauchy horizon and a final central singularity. We find a
null, weak, mass-inflation singularity along the Cauchy horizon, which is a
precursor of a strong, spacelike singularity along the $r=0$ hypersurface.
| [
{
"created": "Sun, 1 Mar 1998 16:45:10 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Hod",
"Shahar",
""
],
[
"Piran",
"Tsvi",
""
]
] | We study the inner-structure of a charged black-hole which is formed from the gravitational collapse of a self-gravitating charged scalar-field. Starting with a regular spacetime, we follow the evolution through the formation of an apparent horizon, a Cauchy horizon and a final central singularity. We find a null, weak, mass-inflation singularity along the Cauchy horizon, which is a precursor of a strong, spacelike singularity along the $r=0$ hypersurface. |
2407.12974 | David Keitel | David Keitel | False positives for gravitational lensing: the gravitational-wave
perspective | 14 pages, 2 figures, submitted to Philosophical Transactions of the
Royal Society special issue on Multi-Messenger Gravitational Lensing | null | null | LIGO-P2400196 | gr-qc astro-ph.HE physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the first detection of a novel astrophysical phenomenon, scientific
standards are particularly high. Especially in a multi-messenger context, there
are also opportunity costs to follow-up observations on any detection claims.
So in searching for the still elusive lensed gravitational waves, care needs to
be taken in controlling false positives. In particular, many methods for
identifying strong lensing rely on some form of parameter similarity or
waveform consistency, which under rapidly growing catalog sizes can expose them
to false positives from coincident but unlensed events if proper care is not
taken. And searches for waveform deformations in all lensing regimes are
subject to degeneracies we need to mitigate between lensing, intrinsic
parameters, insufficiently modelled effects such as orbital eccentricity, or
even deviations from general relativity. Robust lensing studies also require
understanding and mitigating glitches and non-stationarities in the detector
data. This article reviews sources of possible false positives (and their flip
side: false negatives) in gravitational-wave lensing searches and the main
approaches the community is pursuing to mitigate them.
| [
{
"created": "Wed, 17 Jul 2024 19:41:35 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Keitel",
"David",
""
]
] | For the first detection of a novel astrophysical phenomenon, scientific standards are particularly high. Especially in a multi-messenger context, there are also opportunity costs to follow-up observations on any detection claims. So in searching for the still elusive lensed gravitational waves, care needs to be taken in controlling false positives. In particular, many methods for identifying strong lensing rely on some form of parameter similarity or waveform consistency, which under rapidly growing catalog sizes can expose them to false positives from coincident but unlensed events if proper care is not taken. And searches for waveform deformations in all lensing regimes are subject to degeneracies we need to mitigate between lensing, intrinsic parameters, insufficiently modelled effects such as orbital eccentricity, or even deviations from general relativity. Robust lensing studies also require understanding and mitigating glitches and non-stationarities in the detector data. This article reviews sources of possible false positives (and their flip side: false negatives) in gravitational-wave lensing searches and the main approaches the community is pursuing to mitigate them. |
1510.02859 | Xin-Zhou Li | Ping Xi and Ping Li | Reexamining generalized Chaplygin gas with the sign-changeable
interaction | 6 pages, 7figures | Astrophys Space Sci 360 (2015) 3 | 10.1007/s10509-015-2512-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we reexamine the generalized Chaplygin gas (GCG) cosmology
with the sign-changeable interaction. The dynamical analysis show that there
exists de-Sitter attractors in this model, which means that the late-time
behaviors of the model is insensitive to the initial condition and thus
alleviates the coincidence problem. Furthermore, we find that this interaction
oscillates and tends to zero finally by numerical calculations of the nonlinear
equations. In some specific cases of initial conditions, the interaction is
positive (the energy transition from dark energy to dark matter) at high
redshift while it is negative (the energy transition from dark matter to dark
energy) at low redshift for suitable ranges of the parameters.
| [
{
"created": "Sat, 10 Oct 2015 00:42:16 GMT",
"version": "v1"
}
] | 2015-10-13 | [
[
"Xi",
"Ping",
""
],
[
"Li",
"Ping",
""
]
] | In this paper, we reexamine the generalized Chaplygin gas (GCG) cosmology with the sign-changeable interaction. The dynamical analysis show that there exists de-Sitter attractors in this model, which means that the late-time behaviors of the model is insensitive to the initial condition and thus alleviates the coincidence problem. Furthermore, we find that this interaction oscillates and tends to zero finally by numerical calculations of the nonlinear equations. In some specific cases of initial conditions, the interaction is positive (the energy transition from dark energy to dark matter) at high redshift while it is negative (the energy transition from dark matter to dark energy) at low redshift for suitable ranges of the parameters. |
0806.1277 | Terry Pilling | Richard T Hammond and Terry Pilling | Dark Entropy | 7 pages, 1 figure | null | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the consequences of a universe with a non-constant cosmological
term in Einstein's equations and find that the Bianchi identities reduce to the
first law of thermodynamics when cosmological term is identified as being
proportional to the entropy density of the universe. This means that
gravitating dark energy can be viewed as entropy, but more, the holographic
principle along with the known expansion of the universe indicates that the
entropy of the universe is growing with time and this leads to a cosmic
repulsion that also grows with time. Direct implications of this result are
calculated and shown to be in good accord with recent observational data.
| [
{
"created": "Sat, 7 Jun 2008 11:05:09 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Sep 2008 18:54:40 GMT",
"version": "v2"
}
] | 2008-09-04 | [
[
"Hammond",
"Richard T",
""
],
[
"Pilling",
"Terry",
""
]
] | We examine the consequences of a universe with a non-constant cosmological term in Einstein's equations and find that the Bianchi identities reduce to the first law of thermodynamics when cosmological term is identified as being proportional to the entropy density of the universe. This means that gravitating dark energy can be viewed as entropy, but more, the holographic principle along with the known expansion of the universe indicates that the entropy of the universe is growing with time and this leads to a cosmic repulsion that also grows with time. Direct implications of this result are calculated and shown to be in good accord with recent observational data. |
1909.08420 | Hirotaka Yoshino | Hirotaka Yoshino, Keisuke Izumi, Tetsuya Shiromizu, Yoshimune Tomikawa | Transversely trapping surfaces: Dynamical version | 34 pages, 10 figures, figures improved, minor corrections, published
version | Prog. Theor. Exp. Phys. (2020) 023E02 | 10.1093/ptep/ptz161 | OCU-PHYS-510, AP-GR-157 | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We propose new concepts, a dynamically transversely trapping surface (DTTS)
and a marginally DTTS, as indicators for a strong gravity region. A DTTS is
defined as a two-dimensional closed surface on a spacelike hypersurface such
that photons emitted from arbitrary points on it in transverse directions are
acceleratedly contracted in time, and a marginally DTTS is reduced to the
photon sphere in spherically symmetric cases. (Marginally) DTTSs have a close
analogy with (marginally) trapped surfaces in many aspects. After preparing the
method of solving for a marginally DTTS in the time-symmetric initial data and
the momentarily stationary axisymmetric initial data, some examples of
marginally DTTSs are numerically constructed for systems of two black holes in
the Brill-Lindquist initial data and in the Majumdar-Papapetrou spacetimes.
Furthermore, the area of a DTTS is proved to satisfy the Penrose-like
inequality, $A_0\le 4\pi (3GM)^2$, under some assumptions. Differences and
connections between a DTTS and the other two concepts proposed by us
previously, a loosely trapped surface [arXiv:1701.00564] and a
static/stationary transversely trapping surface [arXiv:1704.04637], are also
discussed. A (marginally) DTTS provides us with a theoretical tool to
significantly advance our understanding of strong gravity fields. Also, since
DTTSs are located outside the event horizon, they could possibly be related
with future observations of strong gravity regions in dynamical evolutions.
| [
{
"created": "Wed, 18 Sep 2019 12:57:42 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Feb 2020 09:05:43 GMT",
"version": "v2"
}
] | 2020-02-26 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Izumi",
"Keisuke",
""
],
[
"Shiromizu",
"Tetsuya",
""
],
[
"Tomikawa",
"Yoshimune",
""
]
] | We propose new concepts, a dynamically transversely trapping surface (DTTS) and a marginally DTTS, as indicators for a strong gravity region. A DTTS is defined as a two-dimensional closed surface on a spacelike hypersurface such that photons emitted from arbitrary points on it in transverse directions are acceleratedly contracted in time, and a marginally DTTS is reduced to the photon sphere in spherically symmetric cases. (Marginally) DTTSs have a close analogy with (marginally) trapped surfaces in many aspects. After preparing the method of solving for a marginally DTTS in the time-symmetric initial data and the momentarily stationary axisymmetric initial data, some examples of marginally DTTSs are numerically constructed for systems of two black holes in the Brill-Lindquist initial data and in the Majumdar-Papapetrou spacetimes. Furthermore, the area of a DTTS is proved to satisfy the Penrose-like inequality, $A_0\le 4\pi (3GM)^2$, under some assumptions. Differences and connections between a DTTS and the other two concepts proposed by us previously, a loosely trapped surface [arXiv:1701.00564] and a static/stationary transversely trapping surface [arXiv:1704.04637], are also discussed. A (marginally) DTTS provides us with a theoretical tool to significantly advance our understanding of strong gravity fields. Also, since DTTSs are located outside the event horizon, they could possibly be related with future observations of strong gravity regions in dynamical evolutions. |
1110.1310 | Plyatsko Roman | Roman Plyatsko, Oleksandr Stefanyshyn, Mykola Fenyk | Highly relativistic spinning particle starting near $r_{ph}^{(-)}$ in a
Kerr field | 10 pages, 12 figures | Phys. Rev. D 82, 044015 (2010) | 10.1103/PhysRevD.82.044015 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Mathisson-Papapetrou-Dixon (MPD) equations, we investigate the
trajectories of a spinning particle starting near $r_{ph}^{(-)}$ in a Kerr
field and moving with the velocity close to the velocity of light
($r_{ph}^{(-)}$ is the Boyer-Lindquist radial coordinate of the
counter-rotation circular photon orbits). First, as a partial case of these
trajectories, we consider the equatorial circular orbit with $r=r_{ph}^{(-)}$.
This orbit is described by the solution that is common for the rigorous MPD
equations and their linear spin approximation. Then different cases of the
nonequatorial motions are computed and illustrated by the typical figures. All
these orbits exhibit the effects of the significant gravitational repulsion
that are caused by the spin-gravity interaction. Possible applications in
astrophysics are discussed.
| [
{
"created": "Thu, 6 Oct 2011 16:14:01 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Plyatsko",
"Roman",
""
],
[
"Stefanyshyn",
"Oleksandr",
""
],
[
"Fenyk",
"Mykola",
""
]
] | Using the Mathisson-Papapetrou-Dixon (MPD) equations, we investigate the trajectories of a spinning particle starting near $r_{ph}^{(-)}$ in a Kerr field and moving with the velocity close to the velocity of light ($r_{ph}^{(-)}$ is the Boyer-Lindquist radial coordinate of the counter-rotation circular photon orbits). First, as a partial case of these trajectories, we consider the equatorial circular orbit with $r=r_{ph}^{(-)}$. This orbit is described by the solution that is common for the rigorous MPD equations and their linear spin approximation. Then different cases of the nonequatorial motions are computed and illustrated by the typical figures. All these orbits exhibit the effects of the significant gravitational repulsion that are caused by the spin-gravity interaction. Possible applications in astrophysics are discussed. |
0810.4914 | Laura Mersini-Houghton | L.Mersini-Houghton and F.Adams | Limitations of anthropic predictions for the cosmological constant
$\Lambda$: Cosmic Heat Death of Anthropic Observers | 7pgs, published | Class.Quant.Grav.25:165002,2008 | 10.1088/0264-9381/25/16/165002 | null | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates anthropic bounds on the vacuum energy $\Lambda$. We
first consider the possibility of cosmic observers existing at any random time
(including the future) for constant $\Lambda$, and take into account the
suppression of new structure formation as the universe approaches its eternal
DeSitter (DS) geometry. Structures that collapse prior to the era of
$\Lambda$-domination will lose causal contact with our Hubble volume within a
finite (short) conformal time $\tau_{\ast}$. Any remnants within our Hubble
volume then suffer a cosmological heat death after the universe becomes DS. The
probability for finding observers by random measurements in the volume bound by
the DeSitter horizon is $P \simeq 0$, and it is a simple consequence of the
information loss problem for eternal DS spaces resulting from the finite and
constant value of its temperature $T_{DS} \simeq \Lambda^{-1/2}$ and entropy $S
= 3/(G\Lambda)$. By contrast, for geometries with $\Lambda = 0$, structures can
condense and entropy production can continue without bounds at any epoch. The
probability of finding observers in $\Lambda = 0$ geometries is thus
overwhelming higher than in DS spaces. As a result, anthropic reasoning does
not explain the small but nonzero vacuum energy observed in our universe. We
also address the case where observers are considered only at a specially chosen
time -- like the present epoch -- but relax the allowed values of starting
density fluctuations and hence the redshift of galaxy formation. In this latter
case, the bounds on a $\Lambda$ can be millions of times larger than previous
estimates -- and the observed value. We thus conclude that anthropic reasoning
has limited predictive power.
| [
{
"created": "Mon, 27 Oct 2008 19:41:08 GMT",
"version": "v1"
}
] | 2009-01-22 | [
[
"Mersini-Houghton",
"L.",
""
],
[
"Adams",
"F.",
""
]
] | This paper investigates anthropic bounds on the vacuum energy $\Lambda$. We first consider the possibility of cosmic observers existing at any random time (including the future) for constant $\Lambda$, and take into account the suppression of new structure formation as the universe approaches its eternal DeSitter (DS) geometry. Structures that collapse prior to the era of $\Lambda$-domination will lose causal contact with our Hubble volume within a finite (short) conformal time $\tau_{\ast}$. Any remnants within our Hubble volume then suffer a cosmological heat death after the universe becomes DS. The probability for finding observers by random measurements in the volume bound by the DeSitter horizon is $P \simeq 0$, and it is a simple consequence of the information loss problem for eternal DS spaces resulting from the finite and constant value of its temperature $T_{DS} \simeq \Lambda^{-1/2}$ and entropy $S = 3/(G\Lambda)$. By contrast, for geometries with $\Lambda = 0$, structures can condense and entropy production can continue without bounds at any epoch. The probability of finding observers in $\Lambda = 0$ geometries is thus overwhelming higher than in DS spaces. As a result, anthropic reasoning does not explain the small but nonzero vacuum energy observed in our universe. We also address the case where observers are considered only at a specially chosen time -- like the present epoch -- but relax the allowed values of starting density fluctuations and hence the redshift of galaxy formation. In this latter case, the bounds on a $\Lambda$ can be millions of times larger than previous estimates -- and the observed value. We thus conclude that anthropic reasoning has limited predictive power. |
gr-qc/0507140 | Stephen R. Lau | Stephen R. Lau | Analytic structure of radiation boundary kernels for blackhole
perturbations | revtex4, 14 pages, 12 figures, 3 tables | J.Math.Phys. 46 (2005) 102503 | 10.1063/1.2073287 | null | gr-qc | null | Exact outer boundary conditions for gravitational perturbations of the
Schwarzschild metric feature integral convolution between a time-domain
boundary kernel and each radiative mode of the perturbation. For both axial
(Regge-Wheeler) and polar (Zerilli) perturbations, we study the Laplace
transform of such kernels as an analytic function of (dimensionless) Laplace
frequency. We present numerical evidence indicating that each such
frequency-domain boundary kernel admits a "sum-of-poles" representation. Our
work has been inspired by Alpert, Greengard, and Hagstrom's analysis of
nonreflecting boundary conditions for the ordinary scalar wave equation.
| [
{
"created": "Fri, 29 Jul 2005 17:35:36 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Lau",
"Stephen R.",
""
]
] | Exact outer boundary conditions for gravitational perturbations of the Schwarzschild metric feature integral convolution between a time-domain boundary kernel and each radiative mode of the perturbation. For both axial (Regge-Wheeler) and polar (Zerilli) perturbations, we study the Laplace transform of such kernels as an analytic function of (dimensionless) Laplace frequency. We present numerical evidence indicating that each such frequency-domain boundary kernel admits a "sum-of-poles" representation. Our work has been inspired by Alpert, Greengard, and Hagstrom's analysis of nonreflecting boundary conditions for the ordinary scalar wave equation. |
0710.0606 | Balakin Alexander | A. B. Balakin | Extended Einstein-Maxwell model | 27 pages | Grav.Cosmol.13:163-177,2007 | null | null | gr-qc astro-ph hep-th | null | A self-consistent extended Einstein-Maxwell model for relativistic
non-stationary polarizable-magnetizable anisotropic media is presented. Based
on the analogy with relativistic extended irreversible (transient)
thermodynamics, the extended constitutive equations for the electrodynamics of
continua are formulated phenomenologically, the convective derivatives of the
first, second, etc. orders being taken into account. The master equations for
the gravity field contain a modified effective (symmetric) stress-energy tensor
of the electromagnetic field in a material medium, the use of this tensor being
motivated both by historical analogies and direct variational procedure. By way
of example we consider the exact solution of the extended Einstein-Maxwell
model, describing the isotropic cosmological model with hidden non-vanishing
electromagnetic field, electric polarization and magnetization.
| [
{
"created": "Tue, 2 Oct 2007 19:24:25 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Balakin",
"A. B.",
""
]
] | A self-consistent extended Einstein-Maxwell model for relativistic non-stationary polarizable-magnetizable anisotropic media is presented. Based on the analogy with relativistic extended irreversible (transient) thermodynamics, the extended constitutive equations for the electrodynamics of continua are formulated phenomenologically, the convective derivatives of the first, second, etc. orders being taken into account. The master equations for the gravity field contain a modified effective (symmetric) stress-energy tensor of the electromagnetic field in a material medium, the use of this tensor being motivated both by historical analogies and direct variational procedure. By way of example we consider the exact solution of the extended Einstein-Maxwell model, describing the isotropic cosmological model with hidden non-vanishing electromagnetic field, electric polarization and magnetization. |
2107.01648 | Matthew Robbins | Matthew P. G. Robbins and Robert B. Mann | Anti-Hawking Phenomena around a Rotating BTZ Black Hole | 10 pages, 7 figures | null | 10.1103/PhysRevD.106.045018 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In both flat and curved spacetimes, there are weak and strong versions of the
anti-Unruh/anti-Hawking effects, in which the KMS field temperature is
anti-correlated with the response of a detector and its inferred temperature.
We investigate for the first time the effects on the weak and strong
anti-Hawking effects for an Unruh-DeWitt detector orbiting a BTZ black hole in
the co-rotating frame. We find that rotation can significantly amplify the
strength of the weak anti-Hawking effect, whereas it can either amplify or
reduce the strength of the strong anti-Hawking effect depending on boundary
conditions. For the strong anti-Hawking effect, we find a non-monotonic
relationship between the angular momentum and detector temperature for each
boundary condition. In addition, we note that the weak anti-Hawking effect is
independent of a changing AdS length, while a longer AdS length increases the
temperature range of the strong anti-Hawking effect.
| [
{
"created": "Sun, 4 Jul 2021 14:30:55 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Robbins",
"Matthew P. G.",
""
],
[
"Mann",
"Robert B.",
""
]
] | In both flat and curved spacetimes, there are weak and strong versions of the anti-Unruh/anti-Hawking effects, in which the KMS field temperature is anti-correlated with the response of a detector and its inferred temperature. We investigate for the first time the effects on the weak and strong anti-Hawking effects for an Unruh-DeWitt detector orbiting a BTZ black hole in the co-rotating frame. We find that rotation can significantly amplify the strength of the weak anti-Hawking effect, whereas it can either amplify or reduce the strength of the strong anti-Hawking effect depending on boundary conditions. For the strong anti-Hawking effect, we find a non-monotonic relationship between the angular momentum and detector temperature for each boundary condition. In addition, we note that the weak anti-Hawking effect is independent of a changing AdS length, while a longer AdS length increases the temperature range of the strong anti-Hawking effect. |
2202.11708 | Sara Kanzi | Sara Kanzi, \.Izzet Sakall{\i} | Reply to "Comment on 'Greybody radiation and quasinormal modes of
Kerr-like black hole in Bumblebee gravity model' " | null | EUROPEAN PHYSICAL JOURNAL C 82, 93 (2022) | 10.1140/epjc/s10052-022-10044-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our recent study Ref. [1]: Eur. Phys. J. C 81, 501 (2021) , the main goal
was to reveal the Lorentz symmetry breaking (LSB) effect in the rotating black
holes via the greybody factor and quasinormal mode analyzes. Ding et al. [2]
Kerr-like black hole solution of the bumblebee gravity model used in our paper
[1] has unquestionably proven by Maluf and Muniz [3] that it is wrong. We now
explain under which condition the greybody factor and quasinormal mode analyzes
performed in [1] become valid. We re-make the calculations according to the
condition in question and present the new results in this reply.
| [
{
"created": "Wed, 23 Feb 2022 12:27:56 GMT",
"version": "v1"
}
] | 2022-06-22 | [
[
"Kanzi",
"Sara",
""
],
[
"Sakallı",
"İzzet",
""
]
] | In our recent study Ref. [1]: Eur. Phys. J. C 81, 501 (2021) , the main goal was to reveal the Lorentz symmetry breaking (LSB) effect in the rotating black holes via the greybody factor and quasinormal mode analyzes. Ding et al. [2] Kerr-like black hole solution of the bumblebee gravity model used in our paper [1] has unquestionably proven by Maluf and Muniz [3] that it is wrong. We now explain under which condition the greybody factor and quasinormal mode analyzes performed in [1] become valid. We re-make the calculations according to the condition in question and present the new results in this reply. |
1808.07863 | Kartik Prabhu | Kartik Prabhu | Conservation of asymptotic charges from past to future null infinity:
Maxwell fields | v3: M=Misner in ADM; author thanks D for this correction! v2:
references updated, minor typos fixed, few explanatory comments added
(published in JHEP) v1: 33 pages, 2 figures | JHEP 2018 (2018) 113 | 10.1007/JHEP10(2018)113 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On any asymptotically-flat spacetime, we show that the asymptotic symmetries
and charges of Maxwell fields on past null infinity can be related to those on
future null infinity as recently proposed by Strominger. We extend the
covariant formalism of Ashtekar and Hansen by constructing a 3-manifold of both
null and spatial directions of approach to spatial infinity. This allows us to
systematically impose appropriate regularity conditions on the Maxwell fields
near spatial infinity along null directions. The Maxwell equations on this
3-manifold and the regularity conditions imply that the relevant field
quantities on past null infinity are antipodally matched to those on future
null infinity. Imposing the condition that in a scattering process the total
flux of charges through spatial infinity vanishes, we isolate the subalgebra of
totally fluxless symmetries near spatial infinity. This subalgebra provides a
natural isomorphism between the asymptotic symmetry algebras on past and future
null infinity, such that the corresponding charges are equal near spatial
infinity. This proves that the flux of charges is conserved from past to future
null infinity in a classical scattering process of Maxwell fields. We also
comment on possible extensions of our method to scattering in general
relativity.
| [
{
"created": "Thu, 23 Aug 2018 17:51:56 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Oct 2018 09:42:37 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Oct 2018 19:08:32 GMT",
"version": "v3"
}
] | 2018-10-22 | [
[
"Prabhu",
"Kartik",
""
]
] | On any asymptotically-flat spacetime, we show that the asymptotic symmetries and charges of Maxwell fields on past null infinity can be related to those on future null infinity as recently proposed by Strominger. We extend the covariant formalism of Ashtekar and Hansen by constructing a 3-manifold of both null and spatial directions of approach to spatial infinity. This allows us to systematically impose appropriate regularity conditions on the Maxwell fields near spatial infinity along null directions. The Maxwell equations on this 3-manifold and the regularity conditions imply that the relevant field quantities on past null infinity are antipodally matched to those on future null infinity. Imposing the condition that in a scattering process the total flux of charges through spatial infinity vanishes, we isolate the subalgebra of totally fluxless symmetries near spatial infinity. This subalgebra provides a natural isomorphism between the asymptotic symmetry algebras on past and future null infinity, such that the corresponding charges are equal near spatial infinity. This proves that the flux of charges is conserved from past to future null infinity in a classical scattering process of Maxwell fields. We also comment on possible extensions of our method to scattering in general relativity. |
1702.01603 | Andronikos Paliathanasis | N. Dimakis, Alex Giacomini, Sameerah Jamal, Genly Leon and Andronikos
Paliathanasis | Noether symmetries and stability of ideal gas solution in Galileon
Cosmology | 14 pages, 4 figures; discussion improved; to appear in Phys. Rev. D | Phys. Rev. D 95, 064031 (2017) | 10.1103/PhysRevD.95.064031 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of generalized Galileon cosmological models, which can be described
by a point-like Lagrangian, is considered in order to utilize Noether's Theorem
to determine conservation laws for the field equations. In the
Friedmann-Lema\^itre-Robertson-Walker universe, the existence of a nontrivial
conservation law indicates the integrability of the field equations. Due to the
complexity of the latter, we apply the differential invariants approach in
order to construct special power-law solutions and study their stability.
| [
{
"created": "Mon, 6 Feb 2017 13:11:32 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Mar 2017 19:05:17 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Mar 2017 15:21:50 GMT",
"version": "v3"
}
] | 2017-03-23 | [
[
"Dimakis",
"N.",
""
],
[
"Giacomini",
"Alex",
""
],
[
"Jamal",
"Sameerah",
""
],
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | A class of generalized Galileon cosmological models, which can be described by a point-like Lagrangian, is considered in order to utilize Noether's Theorem to determine conservation laws for the field equations. In the Friedmann-Lema\^itre-Robertson-Walker universe, the existence of a nontrivial conservation law indicates the integrability of the field equations. Due to the complexity of the latter, we apply the differential invariants approach in order to construct special power-law solutions and study their stability. |
1701.06892 | Muhammad Zubair | M. Zubair, Farzana Kousar, Saira Waheed | Reconstruction of Scalar Potentials in $f(R,R_{\alpha\beta}
R^{\alpha\beta},\phi)$ theory of gravity | 30 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we explore the nature of scalar field potential in $f(R,
R_{\alpha\beta} R^{\alpha\beta},\phi)$ gravity using a well-motivated
reconstruction scheme for flat FRW geometry. The beauty of this scheme lies in
the assumption that the Hubble parameter can be expressed in terms of scalar
field and vice versa. Firstly, we develop field equations in this gravity and
present some general explicit forms of scalar field potential via this
technique. In the first case, we take De Sitter universe model and construct
some field potentials by taking different cases for coupling function. In the
second case, we derive some field potentials using power law model in the
presence of different matter sources like barotropic fluid, cosmological
constant and Chaplygin gas for some coupling functions. From graphical
analysis, it is concluded that using some specific values of the involved
parameters, the reconstructed scalar field potentials are cosmologically viable
in both cases.
| [
{
"created": "Tue, 17 Jan 2017 09:07:29 GMT",
"version": "v1"
}
] | 2017-01-25 | [
[
"Zubair",
"M.",
""
],
[
"Kousar",
"Farzana",
""
],
[
"Waheed",
"Saira",
""
]
] | In this paper, we explore the nature of scalar field potential in $f(R, R_{\alpha\beta} R^{\alpha\beta},\phi)$ gravity using a well-motivated reconstruction scheme for flat FRW geometry. The beauty of this scheme lies in the assumption that the Hubble parameter can be expressed in terms of scalar field and vice versa. Firstly, we develop field equations in this gravity and present some general explicit forms of scalar field potential via this technique. In the first case, we take De Sitter universe model and construct some field potentials by taking different cases for coupling function. In the second case, we derive some field potentials using power law model in the presence of different matter sources like barotropic fluid, cosmological constant and Chaplygin gas for some coupling functions. From graphical analysis, it is concluded that using some specific values of the involved parameters, the reconstructed scalar field potentials are cosmologically viable in both cases. |
2405.19467 | Mohamed Ibrahim Nouh | Mohamed S. Aboueisha, Mohamed I. Nouh, Emad A-B. Abdel-Salam. Tarek M.
Kamel, Mohamed M. Beheary and Kamel A. K. Gadallah | Analysis of the Fractional Relativistic Polytropic Gas Sphere | null | Scientific Reports, 2023, 13, 14304 | null | null | gr-qc astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | Many stellar configurations, including white dwarfs, neutron stars, black
holes, supermassive stars, and star clusters, rely on relativistic effects. The
Tolman-Oppenheimer-Volkoff (TOV) equation of the polytropic gas sphere is
ultimately a hydrostatic equilibrium equation developed from the general
relativity framework. In the modified Rieman Liouville (mRL) frame, we
formulate the fractional TOV (FTOV) equations and introduce an analytical
solution. Using power series expansions to solve the fractional TOV equations
yields a limited physical range to the convergent power series solution.
Therefore, the two techniques of Euler-Abel transformation and Pade
approximation have been combined to improve the convergence of the obtained
series solutions. For all possible values of the relativistic parameters
(\sigma), we calculated twenty fractional gas models for the polytropic indexes
n=0, 0.5, 1, 1.5, 2. Investigating the impacts of fractional and relativistic
parameters on the models revealed fascinating phenomena; the two effects for
n=0.5 are that the sphere's volume and mass decrease with increasing \sigma and
the fractional parameter (\alpha). For n=1, the volume decreases when
\sigma=0.1 and then increases when \sigma=0.2 and 0.3. The volume of the sphere
reduces as both \sigma and \alpha increase for n=1.5 and n=2. We calculated the
maximum mass and the corresponding minimum radius of the white dwarfs modeled
with polytropic index n=3 and several fractional and relativistic parameter
values. We obtained a mass limit for the white dwarfs somewhat near the
Chandrasekhar limit for the integer models with small relativistic parameters
(\alpha=1, \sigma=0.001). The situation is altered by lowering the fractional
parameter; the mass limit increases to Mlimit=1.63348 M at \alpha=0.95 and
\sigma=0.001.
| [
{
"created": "Wed, 29 May 2024 19:24:54 GMT",
"version": "v1"
}
] | 2024-05-31 | [
[
"Aboueisha",
"Mohamed S.",
""
],
[
"Nouh",
"Mohamed I.",
""
],
[
"Kamel",
"Emad A-B. Abdel-Salam. Tarek M.",
""
],
[
"Beheary",
"Mohamed M.",
""
],
[
"Gadallah",
"Kamel A. K.",
""
]
] | Many stellar configurations, including white dwarfs, neutron stars, black holes, supermassive stars, and star clusters, rely on relativistic effects. The Tolman-Oppenheimer-Volkoff (TOV) equation of the polytropic gas sphere is ultimately a hydrostatic equilibrium equation developed from the general relativity framework. In the modified Rieman Liouville (mRL) frame, we formulate the fractional TOV (FTOV) equations and introduce an analytical solution. Using power series expansions to solve the fractional TOV equations yields a limited physical range to the convergent power series solution. Therefore, the two techniques of Euler-Abel transformation and Pade approximation have been combined to improve the convergence of the obtained series solutions. For all possible values of the relativistic parameters (\sigma), we calculated twenty fractional gas models for the polytropic indexes n=0, 0.5, 1, 1.5, 2. Investigating the impacts of fractional and relativistic parameters on the models revealed fascinating phenomena; the two effects for n=0.5 are that the sphere's volume and mass decrease with increasing \sigma and the fractional parameter (\alpha). For n=1, the volume decreases when \sigma=0.1 and then increases when \sigma=0.2 and 0.3. The volume of the sphere reduces as both \sigma and \alpha increase for n=1.5 and n=2. We calculated the maximum mass and the corresponding minimum radius of the white dwarfs modeled with polytropic index n=3 and several fractional and relativistic parameter values. We obtained a mass limit for the white dwarfs somewhat near the Chandrasekhar limit for the integer models with small relativistic parameters (\alpha=1, \sigma=0.001). The situation is altered by lowering the fractional parameter; the mass limit increases to Mlimit=1.63348 M at \alpha=0.95 and \sigma=0.001. |
1901.01202 | Sam Dolan Dr | Sam R. Dolan | Comment on "Geodesic dynamics on Chazy-Curzon spacetimes" | 7 pages, 1 figure. See also arXiv:1812.08663 | null | null | null | gr-qc nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent numerical results of Dubeibe et al. [arXiv:1812.08663] were
interpreted as hinting at the existence of a fourth constant of motion
(Carter's constant) for geodesics on Chazy-Curzon spacetimes. Here we show
that, to the contrary, the geodesic dynamics of the single-particle
Chazy-Curzon spacetime exhibit features of a non-integrable system: chaotic
orbits in the meridian plane, and Birkhoff chains in the surface of section.
Thus, one should not expect Liouville-integrability, nor a fourth constant, for
this system.
| [
{
"created": "Fri, 4 Jan 2019 16:43:38 GMT",
"version": "v1"
}
] | 2019-01-07 | [
[
"Dolan",
"Sam R.",
""
]
] | The recent numerical results of Dubeibe et al. [arXiv:1812.08663] were interpreted as hinting at the existence of a fourth constant of motion (Carter's constant) for geodesics on Chazy-Curzon spacetimes. Here we show that, to the contrary, the geodesic dynamics of the single-particle Chazy-Curzon spacetime exhibit features of a non-integrable system: chaotic orbits in the meridian plane, and Birkhoff chains in the surface of section. Thus, one should not expect Liouville-integrability, nor a fourth constant, for this system. |
2305.08554 | Jose Luis Jaramillo | Jos\'e Luis Jaramillo, Badri Krishnan, Carlos F. Sopuerta | Universality in Binary Black Hole Dynamics: An Integrability Conjecture | 17 pages, no figures. Essay awarded a honorable mention in the 2023
Gravity Research Foundation essay competition | null | null | null | gr-qc hep-th math-ph math.MP nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The waveform of a binary black hole coalescence appears to be both simple and
universal. In this essay we argue that the dynamics should admit a separation
into 'fast and slow' degrees of freedom, such that the latter are described by
an integrable system of equations, accounting for the simplicity and
universality of the waveform. Given that Painlev\'e transcendents are a smoking
gun of integrable structures, we propose the Painlev\'e-II transcendent as the
key structural element threading a hierarchy of asymptotic models aiming at
capturing different (effective) layers in the dynamics. Ward's conjecture
relating integrable and (anti)self-dual solutions can provide the avenue to
encode background binary black hole data in (non-local) twistor structures.
| [
{
"created": "Mon, 15 May 2023 11:33:21 GMT",
"version": "v1"
}
] | 2023-05-16 | [
[
"Jaramillo",
"José Luis",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Sopuerta",
"Carlos F.",
""
]
] | The waveform of a binary black hole coalescence appears to be both simple and universal. In this essay we argue that the dynamics should admit a separation into 'fast and slow' degrees of freedom, such that the latter are described by an integrable system of equations, accounting for the simplicity and universality of the waveform. Given that Painlev\'e transcendents are a smoking gun of integrable structures, we propose the Painlev\'e-II transcendent as the key structural element threading a hierarchy of asymptotic models aiming at capturing different (effective) layers in the dynamics. Ward's conjecture relating integrable and (anti)self-dual solutions can provide the avenue to encode background binary black hole data in (non-local) twistor structures. |
2203.13515 | Francesco Sannino | Emanuele Binetti, Manuel Del Piano, Stefan Hohenegger, Franco
Pezzella, Francesco Sannino | The Effective Theory of Quantum Black Holes | Revised version matching the published one | null | 10.1103/PhysRevD.106.046006 | CERN-TH-2022-048 | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We explore the quantum nature of black holes by introducing an effective
framework that takes into account deviations from the classical results. The
approach is based on introducing quantum corrections to the classical
Schwarzschild geometry in a way that is consistent with the physical scales of
the black hole and its classical symmetries. This is achieved by organizing the
quantum corrections in inverse powers of a physical distance. By solving the
system in a self-consistent way we show that the derived physical quantities,
such as event horizons, temperature and entropy can be expressed in a well
defined expansion in the inverse powers of the black hole mass. The approach
captures the general form of the quantum corrections to black hole physics
without requiring to commit to a specific model of quantum gravity.
| [
{
"created": "Fri, 25 Mar 2022 09:04:40 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 07:25:14 GMT",
"version": "v2"
},
{
"created": "Sat, 6 Aug 2022 15:04:11 GMT",
"version": "v3"
}
] | 2022-09-14 | [
[
"Binetti",
"Emanuele",
""
],
[
"Del Piano",
"Manuel",
""
],
[
"Hohenegger",
"Stefan",
""
],
[
"Pezzella",
"Franco",
""
],
[
"Sannino",
"Francesco",
""
]
] | We explore the quantum nature of black holes by introducing an effective framework that takes into account deviations from the classical results. The approach is based on introducing quantum corrections to the classical Schwarzschild geometry in a way that is consistent with the physical scales of the black hole and its classical symmetries. This is achieved by organizing the quantum corrections in inverse powers of a physical distance. By solving the system in a self-consistent way we show that the derived physical quantities, such as event horizons, temperature and entropy can be expressed in a well defined expansion in the inverse powers of the black hole mass. The approach captures the general form of the quantum corrections to black hole physics without requiring to commit to a specific model of quantum gravity. |
2005.03434 | Jo\~ao L. Costa | Jo\~ao L. Costa | The formation of trapped surfaces in the gravitational collapse of
spherically symmetric scalar fields with a positive cosmological constant | 18 pages | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given spherically symmetric characteristic initial data for the
Einstein-scalar field system with a positive cosmological constant, we provide
a criterion, in terms of the dimensionless size and dimensionless renormalized
mass content of an annular region of the data, for the formation of a future
trapped surface. This corresponds to an extension of Christodoulou's classical
criterion by the inclusion of the cosmological term.
| [
{
"created": "Thu, 7 May 2020 13:03:27 GMT",
"version": "v1"
}
] | 2020-05-08 | [
[
"Costa",
"João L.",
""
]
] | Given spherically symmetric characteristic initial data for the Einstein-scalar field system with a positive cosmological constant, we provide a criterion, in terms of the dimensionless size and dimensionless renormalized mass content of an annular region of the data, for the formation of a future trapped surface. This corresponds to an extension of Christodoulou's classical criterion by the inclusion of the cosmological term. |
1512.07279 | Artyom Astashenok V | A.V. Astashenok and S.D. Odintsov | From neutron stars to quark stars in mimetic gravity | 13 pages, 6 figures, 3 tables | Phys. Rev. D 94, 063008 (2016) | 10.1103/PhysRevD.94.063008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Realistic models of neutron and quark stars in the framework of mimetic
gravity with Lagrange multiplier constraint are presented. We discuss the
effect of mimetic scalar aiming to describe dark matter on mass-radius relation
and the moment of inertia for slowly rotating relativistic stars. The
mass-radius relation and moment of inertia depend on the value of mimetic
scalar in the center of star. This fact leads to the ambiguity in the
mass-radius relation for a given equation of state. {Such ambiguity allows to
explain some observational facts better than in standard General Relativity}.
The case of two mimetic potentials namely $V(\phi)\sim A\phi^{-2}$ and
$V(\phi)\sim Ae^{B\phi^{2}}$ is considered in detail. The relative deviation of
maximal moment of inertia is approximately twice larger than the relative
deviation of maximal stellar mass. We also briefly discuss the mimetic $f(R)$
gravity. In the case of $f(R)=R+aR^2$ mimetic gravity it is expected that
increase of maximal mass and maximal moment of inertia due to mimetic scalar
becomes much stronger with bigger parameter $a$. The contribution of scalar
field in mimetic gravity can lead to possible existence of extreme neutron
stars with large masses.
| [
{
"created": "Tue, 22 Dec 2015 22:06:34 GMT",
"version": "v1"
}
] | 2016-09-28 | [
[
"Astashenok",
"A. V.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | Realistic models of neutron and quark stars in the framework of mimetic gravity with Lagrange multiplier constraint are presented. We discuss the effect of mimetic scalar aiming to describe dark matter on mass-radius relation and the moment of inertia for slowly rotating relativistic stars. The mass-radius relation and moment of inertia depend on the value of mimetic scalar in the center of star. This fact leads to the ambiguity in the mass-radius relation for a given equation of state. {Such ambiguity allows to explain some observational facts better than in standard General Relativity}. The case of two mimetic potentials namely $V(\phi)\sim A\phi^{-2}$ and $V(\phi)\sim Ae^{B\phi^{2}}$ is considered in detail. The relative deviation of maximal moment of inertia is approximately twice larger than the relative deviation of maximal stellar mass. We also briefly discuss the mimetic $f(R)$ gravity. In the case of $f(R)=R+aR^2$ mimetic gravity it is expected that increase of maximal mass and maximal moment of inertia due to mimetic scalar becomes much stronger with bigger parameter $a$. The contribution of scalar field in mimetic gravity can lead to possible existence of extreme neutron stars with large masses. |
gr-qc/9904037 | Emulsion-Lab | S. Q. Wu and X. Cai | Exact Solutions to Sourceless Charged Massive Scalar Field Equation on
Kerr-Newman Background | 22 Pages, in LaTex, no figure, to appear in J. Math. Phys | J.Math.Phys. 40 (1999) 4538-4548 | 10.1063/1.532985 | null | gr-qc | null | The separated radial part of a sourceless massive complex scalar field
equation on the Kerr-Newman black hole background is shown to be a generalized
spin-weighted spheroidal wave equation of imaginary number order. While the
separated angular part is an ordinary spheroidal wave equation. General exact
solutions in integral forms and in power series expansion as well as several
special solutions with physical interest are given for the radial equation in
the non-extreme case. In the extreme case, power series solution to the radial
equation is briefly studied. Recurrence relations between coefficients in power
series expansion of general solutions and connection between the radial
equation are discussed in both cases.
| [
{
"created": "Thu, 15 Apr 1999 04:19:19 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Wu",
"S. Q.",
""
],
[
"Cai",
"X.",
""
]
] | The separated radial part of a sourceless massive complex scalar field equation on the Kerr-Newman black hole background is shown to be a generalized spin-weighted spheroidal wave equation of imaginary number order. While the separated angular part is an ordinary spheroidal wave equation. General exact solutions in integral forms and in power series expansion as well as several special solutions with physical interest are given for the radial equation in the non-extreme case. In the extreme case, power series solution to the radial equation is briefly studied. Recurrence relations between coefficients in power series expansion of general solutions and connection between the radial equation are discussed in both cases. |
2402.14171 | Marc Casals | Christiane Klein, Mojgan Soltani, Marc Casals and Stefan Hollands | Infinite quantum twisting at the Cauchy horizon of rotating black holes | 5 pages of main text plus 10 pages of Supplemental Material (merged
in one single file, in this version), 9 figures in total. Published in Phys.
Rev. Lett | Phys. Rev. Lett. 132, 121501 (2024) | 10.1103/PhysRevLett.132.121501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a numerical calculation of the expectation value of the quantum
angular-momentum current flux density for a scalar field in the Unruh state
near the inner horizon of a Kerr-de Sitter black hole. Our results indicate
that this flux diverges as $V_-^{-1}$ in a suitable Kruskal coordinate such
that $V_-=0$ at the inner horizon. Depending on the parameter values of the
scalar field and black hole that we consider, and depending on the polar angle
(latitude), this flux can have different signs. In the near extremal cases
considered, the angle average of the expectation value of the quantum angular
momentum current flux is of the opposite sign as the angular momentum of the
background itself, suggesting that, in the cases considered, quantum effects
tend to decrease the total angular momentum of the spheres away from the
extremal value. We also numerically calculate the energy flux component, which
provides the leading order divergence of the quantum stress energy tensor,
dominant over the classical stress energy tensor, at the inner horizon. Taking
our expectation value of the quantum stress tensor as the source in the
semiclassical Einstein equation, our analysis suggests that the spheres
approaching the inner horizon can undergo an infinite twisting due to quantum
effects along latitudes separating regions of infinite expansion and
contraction.
| [
{
"created": "Wed, 21 Feb 2024 23:20:07 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2024 23:05:46 GMT",
"version": "v2"
}
] | 2024-03-27 | [
[
"Klein",
"Christiane",
""
],
[
"Soltani",
"Mojgan",
""
],
[
"Casals",
"Marc",
""
],
[
"Hollands",
"Stefan",
""
]
] | We present a numerical calculation of the expectation value of the quantum angular-momentum current flux density for a scalar field in the Unruh state near the inner horizon of a Kerr-de Sitter black hole. Our results indicate that this flux diverges as $V_-^{-1}$ in a suitable Kruskal coordinate such that $V_-=0$ at the inner horizon. Depending on the parameter values of the scalar field and black hole that we consider, and depending on the polar angle (latitude), this flux can have different signs. In the near extremal cases considered, the angle average of the expectation value of the quantum angular momentum current flux is of the opposite sign as the angular momentum of the background itself, suggesting that, in the cases considered, quantum effects tend to decrease the total angular momentum of the spheres away from the extremal value. We also numerically calculate the energy flux component, which provides the leading order divergence of the quantum stress energy tensor, dominant over the classical stress energy tensor, at the inner horizon. Taking our expectation value of the quantum stress tensor as the source in the semiclassical Einstein equation, our analysis suggests that the spheres approaching the inner horizon can undergo an infinite twisting due to quantum effects along latitudes separating regions of infinite expansion and contraction. |
1510.05522 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Stable wormholes on a noncommutative-geometry background admitting a
one-parameter group of conformal motions | 12 pages, 1 figure | Indian J. Phys., 90(7), 837-842 (2016) | 10.1007/s12648-015-0812-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When Morris and Thorne first proposed the possible existence of traversable
wormholes, they adopted the following strategy: maintain complete control over
the geometry, thereby leaving open the determination of the stress-energy
tensor. In this paper we determine this tensor by starting with a
noncommutative-geometry background and assuming that the static and spherically
symmetric spacetime admits conformal motions. This had been established in a
previous collaboration with Rahaman et al. using a slightly different approach.
Accordingly, the main purpose of this paper is to show that the wormhole
obtained can be made stable to linearized radial perturbations.
| [
{
"created": "Mon, 19 Oct 2015 15:14:38 GMT",
"version": "v1"
},
{
"created": "Mon, 23 May 2016 18:33:56 GMT",
"version": "v2"
}
] | 2016-05-24 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | When Morris and Thorne first proposed the possible existence of traversable wormholes, they adopted the following strategy: maintain complete control over the geometry, thereby leaving open the determination of the stress-energy tensor. In this paper we determine this tensor by starting with a noncommutative-geometry background and assuming that the static and spherically symmetric spacetime admits conformal motions. This had been established in a previous collaboration with Rahaman et al. using a slightly different approach. Accordingly, the main purpose of this paper is to show that the wormhole obtained can be made stable to linearized radial perturbations. |
1712.01404 | Nelson Velandia | Nelson Velandia-Heredia and Juan Manuel Tejeiro-Sarmiento | Numerical solution of Mathisson-Papapetrou-Dixon equations for spinning
test particles in a Kerr metric | 17 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1609.03630 | Momento, N\'umero 57, p.60-85, 2018 | 10.15446/mo.n57.73391 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we calculate some estimations of the gravitomagnetic clock
effect, taking into consideration not only the rotating gravitational field of
the central mass, but also the spin of the test particle, obtaining values for
$\Delta t=t_{+}-t_{-}=2.5212079035\times10^{-8} \textrm{s}$. We use the
formulation of Mathisson-Papapetrou-Dixon equations for this problem in a Kerr
metric. In order to compare our numerical results with previous works, we
consider initially only the equatorial plane and also apply the
Mathisson-Pirani supplementary spin condition for the spinning test particle.
| [
{
"created": "Mon, 4 Dec 2017 23:00:19 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Apr 2018 22:31:43 GMT",
"version": "v2"
}
] | 2018-07-18 | [
[
"Velandia-Heredia",
"Nelson",
""
],
[
"Tejeiro-Sarmiento",
"Juan Manuel",
""
]
] | In this work we calculate some estimations of the gravitomagnetic clock effect, taking into consideration not only the rotating gravitational field of the central mass, but also the spin of the test particle, obtaining values for $\Delta t=t_{+}-t_{-}=2.5212079035\times10^{-8} \textrm{s}$. We use the formulation of Mathisson-Papapetrou-Dixon equations for this problem in a Kerr metric. In order to compare our numerical results with previous works, we consider initially only the equatorial plane and also apply the Mathisson-Pirani supplementary spin condition for the spinning test particle. |
1001.4173 | Salvatore Capozziello | S. Capozziello, M. De Laurentis, D. Vernieri | Neutrino oscillation phase dynamically induced by f(R)-gravity | 4 pages | null | 10.1142/S0217732310033025 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational phase shift of neutrino oscillation can be discussed in the
framework of f(R)-gravity. We show that the shift of quantum mechanical phase
can depend on the given f(R)-theory that we choose. This fact is general and
could constitute a fundamental test to discriminate among the various
alternative relativistic theories of gravity. Estimations of ratio between the
gravitational phase shift and the standard phase are carried out for the
electronic Solar neutrinos.
| [
{
"created": "Sat, 23 Jan 2010 17:11:58 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Capozziello",
"S.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Vernieri",
"D.",
""
]
] | The gravitational phase shift of neutrino oscillation can be discussed in the framework of f(R)-gravity. We show that the shift of quantum mechanical phase can depend on the given f(R)-theory that we choose. This fact is general and could constitute a fundamental test to discriminate among the various alternative relativistic theories of gravity. Estimations of ratio between the gravitational phase shift and the standard phase are carried out for the electronic Solar neutrinos. |
gr-qc/0104055 | null | S. Q. Wu and X. Cai | Hawking Radiation of Dirac Particles in a Variable-mass Kerr Space-time | 12 pages in 12pt Revtex, no figure, to appear in Gen. Rel. Grav.
Vol.33, No.7 (2001) | Gen.Rel.Grav. 33 (2001) 1181-1195; Erratum-ibid. 34 (2002)
2019-2019 | 10.1023/A:1012033317604 | null | gr-qc | null | Hawking effect of Dirac particles in a variable-mass Kerr space-time is
investigated by using a method called as the generalized tortoise coordinate
transformation. The location and the temperature of the event horizon of the
non-stationary Kerr black hole are derived. It is shown that the temperature
and the shape of the event horizon depend not only on the time but also on the
angle. However, the Fermi-Dirac spectrum displays a residual term which is
absent from that of Bose-Einstein distribution.
| [
{
"created": "Wed, 18 Apr 2001 02:29:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Wu",
"S. Q.",
""
],
[
"Cai",
"X.",
""
]
] | Hawking effect of Dirac particles in a variable-mass Kerr space-time is investigated by using a method called as the generalized tortoise coordinate transformation. The location and the temperature of the event horizon of the non-stationary Kerr black hole are derived. It is shown that the temperature and the shape of the event horizon depend not only on the time but also on the angle. However, the Fermi-Dirac spectrum displays a residual term which is absent from that of Bose-Einstein distribution. |
gr-qc/9902006 | Oscar Alejandro Reula | Oscar A. Reula | Exponential Decay for Small Non-Linear Perturbations of Expanding Flat
Homogeneous Cosmologies | null | Phys. Rev. D 60, 083507 (1999) | 10.1103/PhysRevD.60.083507 | FaMAF-GRG: 1/99 | gr-qc | null | It is shown that during expanding phases of flat homogeneous cosmologies all
small enough non-linear perturbations decay exponentially. This result holds
for a large class of perfect fluid equations of state, but notably not for very
``stiff'' fluids as the pure radiation case.
| [
{
"created": "Mon, 1 Feb 1999 17:25:00 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Reula",
"Oscar A.",
""
]
] | It is shown that during expanding phases of flat homogeneous cosmologies all small enough non-linear perturbations decay exponentially. This result holds for a large class of perfect fluid equations of state, but notably not for very ``stiff'' fluids as the pure radiation case. |
0704.1685 | Xin-Zhou Li | Xing-hua Jin, Xin-zhou Li and Dao-jun Liu | Gravitating Global k-monopole | 9 pages, 2 figures, references added, typos corrected, accepted by
Class. Quantum Grav | Class.Quant.Grav.24:2773-2780,2007 | 10.1088/0264-9381/24/11/001 | null | gr-qc | null | A gravitating global k-monopole produces a tiny gravitational field outside
the core in addition to a solid angular deficit in the k-field theory. As a new
feature, the gravitational field can be attractive or repulsive depending on
the non-canonical kinetic term.
| [
{
"created": "Fri, 13 Apr 2007 01:48:38 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Apr 2007 03:18:19 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Jin",
"Xing-hua",
""
],
[
"Li",
"Xin-zhou",
""
],
[
"Liu",
"Dao-jun",
""
]
] | A gravitating global k-monopole produces a tiny gravitational field outside the core in addition to a solid angular deficit in the k-field theory. As a new feature, the gravitational field can be attractive or repulsive depending on the non-canonical kinetic term. |
0902.3903 | Daniele Oriti | Daniele Oriti | Group field theory and simplicial quantum gravity | 14 pages, no figures; RevTex4; v2: definition of the model modified,
discussion extended and improved | Class.Quant.Grav.27:145017,2010 | 10.1088/0264-9381/27/14/145017 | ITP-UU-08/58, SPIN-08/45, AEI-2009-022 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new Group Field Theory for 4d quantum gravity. It incorporates
the constraints that give gravity from BF theory, and has quantum amplitudes
with the explicit form of simplicial path integrals for 1st order gravity. The
geometric interpretation of the variables and of the contributions to the
quantum amplitudes is manifest. This allows a direct link with other simplicial
gravity approaches, like quantum Regge calculus, in the form of the amplitudes
of the model, and dynamical triangulations, which we show to correspond to a
simple restriction of the same.
| [
{
"created": "Mon, 23 Feb 2009 13:14:08 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Sep 2009 14:50:09 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Oriti",
"Daniele",
""
]
] | We present a new Group Field Theory for 4d quantum gravity. It incorporates the constraints that give gravity from BF theory, and has quantum amplitudes with the explicit form of simplicial path integrals for 1st order gravity. The geometric interpretation of the variables and of the contributions to the quantum amplitudes is manifest. This allows a direct link with other simplicial gravity approaches, like quantum Regge calculus, in the form of the amplitudes of the model, and dynamical triangulations, which we show to correspond to a simple restriction of the same. |
0705.2388 | Carlo Rovelli | Jonathan Engle, Roberto Pereira, Carlo Rovelli | The loop-quantum-gravity vertex-amplitude | 6pages | Phys.Rev.Lett.99:161301,2007 | 10.1103/PhysRevLett.99.161301 | null | gr-qc | null | Spinfoam theories are hoped to provide the dynamics of non-perturbative loop
quantum gravity. But a number of their features remain elusive. The best
studied one -the euclidean Barrett-Crane model- does not have the boundary
state space needed for this, and there are recent indications that,
consequently, it may fail to yield the correct low-energy $n$-point functions.
These difficulties can be traced to the SO(4) -> SU(2) gauge fixing and the way
certain second class constraints are imposed, arguably incorrectly, strongly.
We present an alternative model, that can be derived as a bona fide
quantization of a Regge discretization of euclidean general relativity, and
where the constraints are imposed weakly. Its state space is a natural subspace
of the SO(4) spin-network space and matches the SO(3) hamiltonian spin network
space. The model provides a long sought SO(4)-covariant vertex amplitude for
loop quantum gravity.
| [
{
"created": "Wed, 16 May 2007 16:03:25 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Engle",
"Jonathan",
""
],
[
"Pereira",
"Roberto",
""
],
[
"Rovelli",
"Carlo",
""
]
] | Spinfoam theories are hoped to provide the dynamics of non-perturbative loop quantum gravity. But a number of their features remain elusive. The best studied one -the euclidean Barrett-Crane model- does not have the boundary state space needed for this, and there are recent indications that, consequently, it may fail to yield the correct low-energy $n$-point functions. These difficulties can be traced to the SO(4) -> SU(2) gauge fixing and the way certain second class constraints are imposed, arguably incorrectly, strongly. We present an alternative model, that can be derived as a bona fide quantization of a Regge discretization of euclidean general relativity, and where the constraints are imposed weakly. Its state space is a natural subspace of the SO(4) spin-network space and matches the SO(3) hamiltonian spin network space. The model provides a long sought SO(4)-covariant vertex amplitude for loop quantum gravity. |
2003.04236 | Francesco Belgiorno | F. Belgiorno, S.L. Cacciatori and A. Vigan\`o | Analogue Hawking Effect: a master equation | 26 pages, 2 figures. Published version. Title a bit changed in PRD | Phys. Rev. D 102, 105003 (2020) | 10.1103/PhysRevD.102.105003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider further on the problem of the analogue Hawking radiation. We
propose a fourth order ordinary differential equation, which allows to discuss
the problem of Hawking radiation in analogue gravity in a unified way,
encompassing fluids and dielectric media. In a suitable approximation,
involving weak dispersive effects, WKB solutions are obtained far from the
horizon (turning point), and furthermore an equation governing the behaviour
near the horizon is derived, and a complete set of analytical solutions is
obtained also near the horizon. The subluminal case of the original fluid model
introduced by Corley and Jacobson, the case of dielectric media are discussed.
We show that in this approximation scheme there is a mode which is not directly
involved in the pair-creation process. Thermality is verified and a framework
for calculating the grey-body factor is provided.
| [
{
"created": "Mon, 9 Mar 2020 16:20:58 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2020 11:43:09 GMT",
"version": "v2"
}
] | 2020-11-25 | [
[
"Belgiorno",
"F.",
""
],
[
"Cacciatori",
"S. L.",
""
],
[
"Viganò",
"A.",
""
]
] | We consider further on the problem of the analogue Hawking radiation. We propose a fourth order ordinary differential equation, which allows to discuss the problem of Hawking radiation in analogue gravity in a unified way, encompassing fluids and dielectric media. In a suitable approximation, involving weak dispersive effects, WKB solutions are obtained far from the horizon (turning point), and furthermore an equation governing the behaviour near the horizon is derived, and a complete set of analytical solutions is obtained also near the horizon. The subluminal case of the original fluid model introduced by Corley and Jacobson, the case of dielectric media are discussed. We show that in this approximation scheme there is a mode which is not directly involved in the pair-creation process. Thermality is verified and a framework for calculating the grey-body factor is provided. |
gr-qc/0411127 | Francois Limousin | Francois Limousin (LUTH), Dorota Gondek-Rosinska (LUTH, CAMK), Eric
Gourgoulhon (LUTH) | Last orbits of binary strange quark stars | 11 pages, 10 figures, improved conclusion and figures, references
added, accepted for publication in Phys. Rev. D | Phys.Rev.D71:064012,2005 | 10.1103/PhysRevD.71.064012 | null | gr-qc astro-ph | null | We present the first relativistic calculations of the final phase of inspiral
of a binary system consisting of two stars built predominantely of strange
quark matter (strange quark stars). We study the precoalescing stage within the
Isenberg-Wilson-Mathews approximation of general relativity using a multidomain
spectral method. A hydrodynamical treatment is performed under the assumption
that the flow is either rigidly rotating or irrotational, taking into account
the finite density at the stellar surface -- a distinctive feature with respect
to the neutron star case. The gravitational-radiation driven evolution of the
binary system is approximated by a sequence of quasi-equilibrium configurations
at fixed baryon number and decreasing separation. We find that the innermost
stable circular orbit (ISCO) is given by an orbital instability both for
synchronized and irrotational systems. This constrasts with neutron stars for
which the ISCO is given by the mass-shedding limit in the irrotational case.
The gravitational wave frequency at the ISCO, which marks the end of the
inspiral phase, is found to be 1400 Hz for two irrotational 1.35 Msol strange
stars and for the MIT bag model of strange matter with massless quarks and a
bag constant B=60 MeV/fm^3. Detailed comparisons with binary neutrons star
models, as well as with third order Post-Newtonian point-mass binaries are
given.
| [
{
"created": "Fri, 26 Nov 2004 20:15:22 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Mar 2005 10:15:26 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Limousin",
"Francois",
"",
"LUTH"
],
[
"Gondek-Rosinska",
"Dorota",
"",
"LUTH, CAMK"
],
[
"Gourgoulhon",
"Eric",
"",
"LUTH"
]
] | We present the first relativistic calculations of the final phase of inspiral of a binary system consisting of two stars built predominantely of strange quark matter (strange quark stars). We study the precoalescing stage within the Isenberg-Wilson-Mathews approximation of general relativity using a multidomain spectral method. A hydrodynamical treatment is performed under the assumption that the flow is either rigidly rotating or irrotational, taking into account the finite density at the stellar surface -- a distinctive feature with respect to the neutron star case. The gravitational-radiation driven evolution of the binary system is approximated by a sequence of quasi-equilibrium configurations at fixed baryon number and decreasing separation. We find that the innermost stable circular orbit (ISCO) is given by an orbital instability both for synchronized and irrotational systems. This constrasts with neutron stars for which the ISCO is given by the mass-shedding limit in the irrotational case. The gravitational wave frequency at the ISCO, which marks the end of the inspiral phase, is found to be 1400 Hz for two irrotational 1.35 Msol strange stars and for the MIT bag model of strange matter with massless quarks and a bag constant B=60 MeV/fm^3. Detailed comparisons with binary neutrons star models, as well as with third order Post-Newtonian point-mass binaries are given. |
0706.2891 | Steven Willison | F. Canfora, A. Giacomini, S. Willison | Some exact solutions with torsion in 5-D Einstein-Gauss-Bonnet gravity | 19 pages, LaTex, no figures. References added, notation clarified.
Accepted for publication on Physical Review D | Phys.Rev.D76:044021,2007 | 10.1103/PhysRevD.76.044021 | CECS-PHY-07/11 | gr-qc hep-th | null | Exact solutions with torsion in Einstein-Gauss-Bonnet gravity are derived.
These solutions have a cross product structure of two constant curvature
manifolds. The equations of motion give a relation for the coupling constants
of the theory in order to have solutions with nontrivial torsion. This relation
is not the Chern-Simons combination. One of the solutions has a $AdS_2\times
S^3$ structure and is so the purely gravitational analogue of the
Bertotti-Robinson space-time where the torsion can be seen as the dual of the
covariantly constant electromagnetic field.
| [
{
"created": "Tue, 19 Jun 2007 23:37:33 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jul 2007 16:06:57 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Canfora",
"F.",
""
],
[
"Giacomini",
"A.",
""
],
[
"Willison",
"S.",
""
]
] | Exact solutions with torsion in Einstein-Gauss-Bonnet gravity are derived. These solutions have a cross product structure of two constant curvature manifolds. The equations of motion give a relation for the coupling constants of the theory in order to have solutions with nontrivial torsion. This relation is not the Chern-Simons combination. One of the solutions has a $AdS_2\times S^3$ structure and is so the purely gravitational analogue of the Bertotti-Robinson space-time where the torsion can be seen as the dual of the covariantly constant electromagnetic field. |
gr-qc/0402048 | Branchina | Vincenzo Branchina, Alice Gasparini, Anna Rissone | Electronic contribution to the oscillations of a gravitational antenna | 25 pages, no figures | Phys.Rev. D70 (2004) 024004 | 10.1103/PhysRevD.70.024004 | null | gr-qc | null | We carefully analyse the contribution to the oscillations of a metallic
gravitational antenna due to the interaction between the electrons of the bar
and the incoming gravitational wave. To this end, we first derive the total
microscopic Hamiltonian of the wave-antenna system and then compute the
contribution to the attenuation factor due to the electron-graviton
interaction. As compared to the ordinary damping factor, which is due to the
electron viscosity, this term turns out to be totally negligible. This result
confirms that the only relevant mechanism for the interaction of a
gravitational wave with a metallic antenna is its direct coupling with the bar
normal modes.
| [
{
"created": "Wed, 11 Feb 2004 18:46:42 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Branchina",
"Vincenzo",
""
],
[
"Gasparini",
"Alice",
""
],
[
"Rissone",
"Anna",
""
]
] | We carefully analyse the contribution to the oscillations of a metallic gravitational antenna due to the interaction between the electrons of the bar and the incoming gravitational wave. To this end, we first derive the total microscopic Hamiltonian of the wave-antenna system and then compute the contribution to the attenuation factor due to the electron-graviton interaction. As compared to the ordinary damping factor, which is due to the electron viscosity, this term turns out to be totally negligible. This result confirms that the only relevant mechanism for the interaction of a gravitational wave with a metallic antenna is its direct coupling with the bar normal modes. |
2403.19942 | Jianbo Lu | Jianbo Lu, Shining Yang, Yuying Zhang, Liu Yang, Mou Xu | Research on high-frequency quasi-periodic oscillations in generalized
black-bounce spacetime | 20 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to solve problem of spacetime singularity in theoretical physics,
researchers proposed the regular black holes (BH). The generalized black-bounce
(GBB) spacetime, as a unified treatment of distinct kinds of geometries in the
framework of general relativity (e.g. regular BH and wormholes), has been
extensively studied. Firstly, we derive to give the explicit forms of
Lagrangian for a nonlinear electromagnetic field and potential for a
non-canonical phantom field in the action of gravitational system corresponding
to GBB solution. Secondly, this paper computes the radius of the innermost
stable circular orbit (ISCO) and the stable circular orbit region for different
types of celestial bodies in GBB spacetime. The research suggests that
traversable wormholes may have two ISCOs or one ISCO depending on the throat's
scale, whereas regular BH and extremal BH possess only one ISCO. Thirdly,
quasi-periodic oscillations (QPOs) have been found to be a reliable tool for
testing gravitational theories. Therefore, we compute the radial and azimuthal
epicyclic angular frequencies of particles oscillating on stable circular
orbits around various celestial bodies and compare them with the oscillation
frequency properties of schwarzschild BH. Moreover, due to the limited amount
of research on the high-frequency quasi-periodic oscillations (HFQPOs)
phenomenon and its generation mechanisms around particles near wormholes using
observational data, this paper aims to study theoretical models that can
simultaneously describe both BH and wormholes by fitting observational data.
Using resonance models and associated frequency ratios, we are able to locate
the resonances of different celestial bodies within the GBB spacetime.
| [
{
"created": "Fri, 29 Mar 2024 02:49:34 GMT",
"version": "v1"
}
] | 2024-04-01 | [
[
"Lu",
"Jianbo",
""
],
[
"Yang",
"Shining",
""
],
[
"Zhang",
"Yuying",
""
],
[
"Yang",
"Liu",
""
],
[
"Xu",
"Mou",
""
]
] | In order to solve problem of spacetime singularity in theoretical physics, researchers proposed the regular black holes (BH). The generalized black-bounce (GBB) spacetime, as a unified treatment of distinct kinds of geometries in the framework of general relativity (e.g. regular BH and wormholes), has been extensively studied. Firstly, we derive to give the explicit forms of Lagrangian for a nonlinear electromagnetic field and potential for a non-canonical phantom field in the action of gravitational system corresponding to GBB solution. Secondly, this paper computes the radius of the innermost stable circular orbit (ISCO) and the stable circular orbit region for different types of celestial bodies in GBB spacetime. The research suggests that traversable wormholes may have two ISCOs or one ISCO depending on the throat's scale, whereas regular BH and extremal BH possess only one ISCO. Thirdly, quasi-periodic oscillations (QPOs) have been found to be a reliable tool for testing gravitational theories. Therefore, we compute the radial and azimuthal epicyclic angular frequencies of particles oscillating on stable circular orbits around various celestial bodies and compare them with the oscillation frequency properties of schwarzschild BH. Moreover, due to the limited amount of research on the high-frequency quasi-periodic oscillations (HFQPOs) phenomenon and its generation mechanisms around particles near wormholes using observational data, this paper aims to study theoretical models that can simultaneously describe both BH and wormholes by fitting observational data. Using resonance models and associated frequency ratios, we are able to locate the resonances of different celestial bodies within the GBB spacetime. |
gr-qc/0504126 | Marcelo Salgado | Alejandro Corichi, Ulises Nucamendi, Marcelo Salgado | Scalar hairy black holes and scalarons in the isolated horizons
formalism | 17 pages, 10 figures; revtex style; figures added; text updated to
match the published paper | Phys.Rev.D73:084002,2006 | 10.1103/PhysRevD.73.084002 | null | gr-qc | null | The Isolated Horizons (IH) formalism, together with a simple phenomenological
model for colored black holes has been used to predict non-trivial formulae
that relate the ADM mass of the solitons and hairy Black Holes of
Gravity-Matter system on the one hand, and several horizon properties of the
black holes in the other. In this article, the IH formalism is tested
numerically for spherically symmetric solutions to an Einstein-Higgs system
where hairy black holes were recently found to exist. It is shown that the mass
formulae still hold and that, by appropriately extending the current model, one
can account for the behavior of the horizon properties of these new solutions.
An empirical formula that approximates the ADM mass of hairy solutions is put
forward, and some of its properties are analyzed.
| [
{
"created": "Tue, 26 Apr 2005 00:54:31 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Aug 2006 23:23:01 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Salgado",
"Marcelo",
""
]
] | The Isolated Horizons (IH) formalism, together with a simple phenomenological model for colored black holes has been used to predict non-trivial formulae that relate the ADM mass of the solitons and hairy Black Holes of Gravity-Matter system on the one hand, and several horizon properties of the black holes in the other. In this article, the IH formalism is tested numerically for spherically symmetric solutions to an Einstein-Higgs system where hairy black holes were recently found to exist. It is shown that the mass formulae still hold and that, by appropriately extending the current model, one can account for the behavior of the horizon properties of these new solutions. An empirical formula that approximates the ADM mass of hairy solutions is put forward, and some of its properties are analyzed. |
1702.01688 | Mehdi Assanioussi | Mehdi Assanioussi, Jerzy Lewandowski, Ilkka M\"akinen | Time evolution in deparametrized models of loop quantum gravity | 23 pages, 18 figures | Phys. Rev. D 96, 024043 (2017) | 10.1103/PhysRevD.96.024043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important aspect in understanding the dynamics in the context of
deparametrized models of LQG is to obtain a sufficient control on the quantum
evolution generated by a given Hamiltonian operator. More specifically, we need
to be able to compute the evolution of relevant physical states and observables
with a relatively good precision. In this article, we introduce an
approximation method to deal with the physical Hamiltonian operators in
deparametrized LQG models, and apply it to models in which a free Klein-Gordon
scalar field or a non-rotational dust field is taken as the physical time
variable. This method is based on using standard time-independent perturbation
theory of quantum mechanics to define a perturbative expansion of the
Hamiltonian operator, the small perturbation parameter being determined by the
Barbero-Immirzi parameter $\beta$. This method allows us to define an
approximate spectral decomposition of the Hamiltonian operators and hence to
compute the evolution over a certain time interval. As a specific example, we
analyze the evolution of expectation values of the volume and curvature
operators starting with certain physical initial states, using both the
perturbative method and a straightforward expansion of the expectation value in
powers of the time variable. This work represents a first step towards
achieving the goal of understanding and controlling the new dynamics developed
in [25, 26].
| [
{
"created": "Mon, 6 Feb 2017 16:26:53 GMT",
"version": "v1"
}
] | 2017-08-02 | [
[
"Assanioussi",
"Mehdi",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Mäkinen",
"Ilkka",
""
]
] | An important aspect in understanding the dynamics in the context of deparametrized models of LQG is to obtain a sufficient control on the quantum evolution generated by a given Hamiltonian operator. More specifically, we need to be able to compute the evolution of relevant physical states and observables with a relatively good precision. In this article, we introduce an approximation method to deal with the physical Hamiltonian operators in deparametrized LQG models, and apply it to models in which a free Klein-Gordon scalar field or a non-rotational dust field is taken as the physical time variable. This method is based on using standard time-independent perturbation theory of quantum mechanics to define a perturbative expansion of the Hamiltonian operator, the small perturbation parameter being determined by the Barbero-Immirzi parameter $\beta$. This method allows us to define an approximate spectral decomposition of the Hamiltonian operators and hence to compute the evolution over a certain time interval. As a specific example, we analyze the evolution of expectation values of the volume and curvature operators starting with certain physical initial states, using both the perturbative method and a straightforward expansion of the expectation value in powers of the time variable. This work represents a first step towards achieving the goal of understanding and controlling the new dynamics developed in [25, 26]. |
2109.01867 | Changqing Liu Lcqliu | Changqing Liu, Li Tang, Jiliang Jing | Image of the Schwarzschild black hole pierced by a cosmic string with a
thin accretion disk | null | International Journal of Modern Physics D (2022) 2250041 | 10.1142/S0218271822500419 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the optical appearance of a thin accretion disk around a
Schwarzschild black hole pierced by a cosmic string with a semi-analytic method
of Luminet [11]. Direct and secondary images with different parameters observed
by a distant observer is plotted. The cosmic string parameter s can modify the
shape and size of the thin disk image. We calculate and plot the distribution
of both redshift and observed flux as seen by distant observers at different
inclination angles. Those distributions are dependent on the inclination angel
of the observer and cosmic parameter s.
| [
{
"created": "Sat, 4 Sep 2021 13:47:31 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Sep 2021 12:48:07 GMT",
"version": "v2"
}
] | 2022-04-12 | [
[
"Liu",
"Changqing",
""
],
[
"Tang",
"Li",
""
],
[
"Jing",
"Jiliang",
""
]
] | We study the optical appearance of a thin accretion disk around a Schwarzschild black hole pierced by a cosmic string with a semi-analytic method of Luminet [11]. Direct and secondary images with different parameters observed by a distant observer is plotted. The cosmic string parameter s can modify the shape and size of the thin disk image. We calculate and plot the distribution of both redshift and observed flux as seen by distant observers at different inclination angles. Those distributions are dependent on the inclination angel of the observer and cosmic parameter s. |
0904.2950 | Chen Songbai | Songbai Chen, Jiliang Jing | Dark energy model with higher derivative of Hubble parameter | 11 pages, 6 figures, the correct version accepted for publication in
PLB | Phys. Lett. B 679 (2009) 144-150 | 10.1016/j.physletb.2009.07.018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we consider a dark energy model in which the energy density is
a function of the Hubble parameter $H$ and its derivative with respect to time
$\rho_{de}=3\alpha \ddot{H}H^{-1}+3\beta\dot{H}+3\gamma H^2$. The behavior of
the dark energy and the expansion history of the Universe depend heavily on the
parameters of the model $\alpha$, $\beta$ and $\gamma$. It is very interesting
that the age problem of the well-known three old objects can be alleviated in
this models.
| [
{
"created": "Mon, 20 Apr 2009 06:38:49 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 2009 01:25:53 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Jun 2009 09:02:00 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Jul 2009 03:54:44 GMT",
"version": "v4"
}
] | 2015-05-13 | [
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | In this letter we consider a dark energy model in which the energy density is a function of the Hubble parameter $H$ and its derivative with respect to time $\rho_{de}=3\alpha \ddot{H}H^{-1}+3\beta\dot{H}+3\gamma H^2$. The behavior of the dark energy and the expansion history of the Universe depend heavily on the parameters of the model $\alpha$, $\beta$ and $\gamma$. It is very interesting that the age problem of the well-known three old objects can be alleviated in this models. |
gr-qc/9711003 | Robert Mann | H. Burton, R.B. Mann | Palatini Variational Principle for an Extended Einstein-Hilbert Action | 14 pages, LaTeX | Phys.Rev. D57 (1998) 4754-4759 | 10.1103/PhysRevD.57.4754 | WATPHYS TH-97/17 | gr-qc | null | We consider a Palatini variation on a generalized Einstein-Hilbert action. We
find that the Hilbert constraint, that the connection equals the Christoffel
symbol, arises only as a special case of this general action, while for
particular values of the coefficients of this generalized action, the
connection is completely unconstrained. We discuss the relationship between
this situation and that usually encountered in the Palatini formulation.
| [
{
"created": "Mon, 3 Nov 1997 18:15:40 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Burton",
"H.",
""
],
[
"Mann",
"R. B.",
""
]
] | We consider a Palatini variation on a generalized Einstein-Hilbert action. We find that the Hilbert constraint, that the connection equals the Christoffel symbol, arises only as a special case of this general action, while for particular values of the coefficients of this generalized action, the connection is completely unconstrained. We discuss the relationship between this situation and that usually encountered in the Palatini formulation. |
gr-qc/9701001 | Motoyuki Saijo | Motoyuki Saijo, Hisa-aki Shinkai and Kei-ichi Maeda | Gravitational Waves in Brans-Dicke Theory : Analysis by Test Particles
around a Kerr Black Hole | 24 pages, revtex, 18 figures are attached with ps files | Phys.Rev. D56 (1997) 785-797 | 10.1103/PhysRevD.56.785 | WU-AP/64/96 (Waseda Univ. Astrophysics) | gr-qc | null | Analyzing test particles falling into a Kerr black hole, we study
gravitational waves in Brans-Dicke theory of gravity. First we consider a test
particle plunging with a constant azimuthal angle into a rotating black hole
and calculate the waveform and emitted energy of both scalar and tensor modes
of gravitational radiation. We find that the waveform as well as the energy of
the scalar gravitational waves weakly depends on the rotation parameter of
black hole $a$ and on the azimuthal angle.
Secondly, using a model of a non-spherical dust shell of test particles
falling into a Kerr black hole, we study when the scalar modes dominate. When a
black hole is rotating, the tensor modes do not vanish even for a ``spherically
symmetric" shell, instead a slightly oblate shell minimizes their energy but
with non-zero finite value, which depends on Kerr parameter $a$. As a result,
we find that the scalar modes dominate only for highly spherical collapse, but
they never exceed the tensor modes unless the Brans-Dicke parameter
$\omega_{BD} \lsim 750 $ for $a/M=0.99$ or unless $\omega_{BD} \lsim 20,000 $
for $a/M=0.5$, where $M$ is mass of black hole.
We conclude that the scalar gravitational waves with $\omega_{BD} \lsim$
several thousands do not dominate except for very limited situations
(observation from the face-on direction of a test particle falling into a
Schwarzschild black hole or highly spherical dust shell collapse into a Kerr
black hole). Therefore observation of polarization is also required when we
determine the theory of gravity by the observation of gravitational waves.
| [
{
"created": "Wed, 1 Jan 1997 03:07:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Saijo",
"Motoyuki",
""
],
[
"Shinkai",
"Hisa-aki",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | Analyzing test particles falling into a Kerr black hole, we study gravitational waves in Brans-Dicke theory of gravity. First we consider a test particle plunging with a constant azimuthal angle into a rotating black hole and calculate the waveform and emitted energy of both scalar and tensor modes of gravitational radiation. We find that the waveform as well as the energy of the scalar gravitational waves weakly depends on the rotation parameter of black hole $a$ and on the azimuthal angle. Secondly, using a model of a non-spherical dust shell of test particles falling into a Kerr black hole, we study when the scalar modes dominate. When a black hole is rotating, the tensor modes do not vanish even for a ``spherically symmetric" shell, instead a slightly oblate shell minimizes their energy but with non-zero finite value, which depends on Kerr parameter $a$. As a result, we find that the scalar modes dominate only for highly spherical collapse, but they never exceed the tensor modes unless the Brans-Dicke parameter $\omega_{BD} \lsim 750 $ for $a/M=0.99$ or unless $\omega_{BD} \lsim 20,000 $ for $a/M=0.5$, where $M$ is mass of black hole. We conclude that the scalar gravitational waves with $\omega_{BD} \lsim$ several thousands do not dominate except for very limited situations (observation from the face-on direction of a test particle falling into a Schwarzschild black hole or highly spherical dust shell collapse into a Kerr black hole). Therefore observation of polarization is also required when we determine the theory of gravity by the observation of gravitational waves. |
gr-qc/0307094 | Stephane Fay | Stephane Fay, Jean-Pierre Luminet | Isotropisation of flat homogeneous universes with scalar fields | 35 pages, 11 figures, higher-quality images are available on request
to steph.fay@wanadoo.fr, to be published in Class. Quant. Grav | Class.Quant.Grav. 21 (2004) 1849-1878 | 10.1088/0264-9381/21/7/009 | null | gr-qc astro-ph | null | Starting from an anisotropic flat cosmological model(Bianchi type $I$), we
show that conditions leading to isotropisation fall into 3 classes,
respectively 1, 2, 3. We look for necessary conditions such that a Bianchi type
$I$ model reaches a stable isotropic state due to the presence of several
massive scalar fields minimally coupled to the metric with a perfect fluid for
class 1 isotropisation. The conditions are written in terms of some functions
$\ell$ of the scalar fields. Two types of theories are studied. The first one
deals with scalar tensor theories resulting from extra-dimensions
compactification, where the Brans-Dicke coupling functions only depend on their
associated scalar fields. The second one is related to the presence of complex
scalar fields. We give the metric and potential asymptotical behaviours
originating from class 1 isotropisation. The results depend on the domination
of the scalar field potential compared to the perfect fluid energy density. We
give explicit examples showing that some hybrid inflation theories do not lead
to isotropy contrary to some high-order theories, whereas the most common forms
of complex scalar fields undergo a class 3 isotropisation, characterised by
strong oscillations of the $\ell$ functions.
| [
{
"created": "Mon, 21 Jul 2003 15:25:04 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Nov 2003 17:36:31 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Feb 2004 12:45:13 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Fay",
"Stephane",
""
],
[
"Luminet",
"Jean-Pierre",
""
]
] | Starting from an anisotropic flat cosmological model(Bianchi type $I$), we show that conditions leading to isotropisation fall into 3 classes, respectively 1, 2, 3. We look for necessary conditions such that a Bianchi type $I$ model reaches a stable isotropic state due to the presence of several massive scalar fields minimally coupled to the metric with a perfect fluid for class 1 isotropisation. The conditions are written in terms of some functions $\ell$ of the scalar fields. Two types of theories are studied. The first one deals with scalar tensor theories resulting from extra-dimensions compactification, where the Brans-Dicke coupling functions only depend on their associated scalar fields. The second one is related to the presence of complex scalar fields. We give the metric and potential asymptotical behaviours originating from class 1 isotropisation. The results depend on the domination of the scalar field potential compared to the perfect fluid energy density. We give explicit examples showing that some hybrid inflation theories do not lead to isotropy contrary to some high-order theories, whereas the most common forms of complex scalar fields undergo a class 3 isotropisation, characterised by strong oscillations of the $\ell$ functions. |
gr-qc/9807034 | null | Reinoud J. Slagter (University of Amsterdam) | Self-Gravitating Non-Abelian Cosmic String Solution | 12 pages in REVTEX with 7 figures in postscript. To appear in PRD
nov.'98 | Phys.Rev. D59 (1999) 025009 | 10.1103/PhysRevD.59.025009 | null | gr-qc | null | The coupled Einstein-Yang-Mills equations on a time dependent axially
symmetric spacetime are investigated, without a priori any conditions on the
gauge field. There is numerical evidence for the existence of a regular
solution with the desired asymptotic features. Just as in the supermassive
abelian counterpart model, the formation of a singularity at finite distance of
the core of the string depends critically on a parameter of the model, i.e.,
the constant value of one of the magnetic components of the YM potentials. The
multiple-scale method could supply decisive answers concerning the stability of
the solution.
| [
{
"created": "Wed, 15 Jul 1998 10:37:14 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 1998 20:44:27 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Slagter",
"Reinoud J.",
"",
"University of Amsterdam"
]
] | The coupled Einstein-Yang-Mills equations on a time dependent axially symmetric spacetime are investigated, without a priori any conditions on the gauge field. There is numerical evidence for the existence of a regular solution with the desired asymptotic features. Just as in the supermassive abelian counterpart model, the formation of a singularity at finite distance of the core of the string depends critically on a parameter of the model, i.e., the constant value of one of the magnetic components of the YM potentials. The multiple-scale method could supply decisive answers concerning the stability of the solution. |
1907.12083 | Eleonora Giovannetti | Eleonora Giovannetti and Giovanni Montani | Polymer representation of the Bianchi IX Cosmology in the Misner
variables | 14 pages, 6 figures | Phys. Rev. D 100, 104058 (2019) | 10.1103/PhysRevD.100.104058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the Bianchi IX Universe in the Polymer Quantum Mechanics framework
by facing both semiclassical and purely quantum effects near the cosmological
singularity. We adopt Misner variables to describe the model dynamics, applying
the polymer paradigm simultaneously to the isotropic one (linked to the
Universe volume) and to the two anisotropy ones (characterizing the physical
gravitational degrees of freedom). Setting two different cut-off scales for the
two different variable sets, i.e. the geometrical volume and the gravity tensor
modes, we demonstrate how the semiclassical properties of the Bianchi IX
dynamics are sensitive to the ratio of the cut-off parameters. In particular,
the semiclassical evolution turns out to be chaotic only if the parameter
associated to the volume discretization is greater or equal to that one of the
anisotropies. Concerning the chaotic case we perform a purely quantum polymer
analysis, demonstrating that the original Misner result about the existence of
quasi-classical states near the singularity (in the sense of high occupation
numbers) is still valid in the revised approach and able to account for cut-off
physics effects. The possibility for a comparison with the original study by
Misner is possible because the singularity is still present in the
semiclassical evolution of the cosmological model for all the parameter space.
We interpret this surprising feature as the consequence of a geometrical volume
discretization which does not prevent the volume from vanishing, i.e. restoring
in the Minisuperspace analysis its zero value.
| [
{
"created": "Sun, 28 Jul 2019 14:00:38 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Nov 2019 17:43:59 GMT",
"version": "v2"
}
] | 2019-12-03 | [
[
"Giovannetti",
"Eleonora",
""
],
[
"Montani",
"Giovanni",
""
]
] | We analyze the Bianchi IX Universe in the Polymer Quantum Mechanics framework by facing both semiclassical and purely quantum effects near the cosmological singularity. We adopt Misner variables to describe the model dynamics, applying the polymer paradigm simultaneously to the isotropic one (linked to the Universe volume) and to the two anisotropy ones (characterizing the physical gravitational degrees of freedom). Setting two different cut-off scales for the two different variable sets, i.e. the geometrical volume and the gravity tensor modes, we demonstrate how the semiclassical properties of the Bianchi IX dynamics are sensitive to the ratio of the cut-off parameters. In particular, the semiclassical evolution turns out to be chaotic only if the parameter associated to the volume discretization is greater or equal to that one of the anisotropies. Concerning the chaotic case we perform a purely quantum polymer analysis, demonstrating that the original Misner result about the existence of quasi-classical states near the singularity (in the sense of high occupation numbers) is still valid in the revised approach and able to account for cut-off physics effects. The possibility for a comparison with the original study by Misner is possible because the singularity is still present in the semiclassical evolution of the cosmological model for all the parameter space. We interpret this surprising feature as the consequence of a geometrical volume discretization which does not prevent the volume from vanishing, i.e. restoring in the Minisuperspace analysis its zero value. |
2111.03338 | Simon Boudet | Flavio Bombacigno, Simon Boudet, Gonzalo J. Olmo, Giovanni Montani | Big-Bounce in projectively invariant Nieh-Yan models: the Bianchi I case | To appear in the Proceedings of the 16th Marcel Grossmann meeting
(5-10 July, 2021) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We show that the Nieh-Yan topological invariant breaks projective symmetry
and loses its topological character in presence of non vanishing nonmetricity.
The notion of the Nieh-Yan topological invariant is then extended to the
generic metric-affine case, defining a generalized Nieh-Yan term, which allows
to recover topologicity and projective invariance, independently. As a concrete
example a class of modified theories of gravity is considered and its dynamical
properties are investigated in a cosmological setting. In particular, bouncing
cosmological solutions in Bianchi I models are derived. Finite time
singularities affecting these solutions are analysed, showing that the geodesic
completeness and the regular behavior of scalar perturbations in these
space-times are not spoiled.
| [
{
"created": "Fri, 5 Nov 2021 09:13:24 GMT",
"version": "v1"
}
] | 2021-11-08 | [
[
"Bombacigno",
"Flavio",
""
],
[
"Boudet",
"Simon",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Montani",
"Giovanni",
""
]
] | We show that the Nieh-Yan topological invariant breaks projective symmetry and loses its topological character in presence of non vanishing nonmetricity. The notion of the Nieh-Yan topological invariant is then extended to the generic metric-affine case, defining a generalized Nieh-Yan term, which allows to recover topologicity and projective invariance, independently. As a concrete example a class of modified theories of gravity is considered and its dynamical properties are investigated in a cosmological setting. In particular, bouncing cosmological solutions in Bianchi I models are derived. Finite time singularities affecting these solutions are analysed, showing that the geodesic completeness and the regular behavior of scalar perturbations in these space-times are not spoiled. |
1002.0138 | Viqar Husain | Viqar Husain, Andreas Kreienbuehl | Ultraviolet behavior in background independent quantum field theory | 8 pages, 5 figures | Phys. Rev. D 81 (2010) 084043 | 10.1103/PhysRevD.81.084043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a background independent quantization of the scalar field that
provides an explicit realization of Fock-like states and associated operators
in a polymer Hilbert space. The vacuum expectation values of the commutator and
anti-commutator of the creation and annihilation operators become energy
dependent, and exhibit a surprising transition to fermionic behavior at high
energy. Furthermore the approach yields a modified dispersion relation with a
leading correction proportional to the momentum cubed. These results suggests a
fundamental change in the ultraviolet properties of quantum fields.
| [
{
"created": "Sun, 31 Jan 2010 16:09:12 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Husain",
"Viqar",
""
],
[
"Kreienbuehl",
"Andreas",
""
]
] | We describe a background independent quantization of the scalar field that provides an explicit realization of Fock-like states and associated operators in a polymer Hilbert space. The vacuum expectation values of the commutator and anti-commutator of the creation and annihilation operators become energy dependent, and exhibit a surprising transition to fermionic behavior at high energy. Furthermore the approach yields a modified dispersion relation with a leading correction proportional to the momentum cubed. These results suggests a fundamental change in the ultraviolet properties of quantum fields. |
1004.0917 | Hideki Maeda | Hideki Maeda | Gauss-Bonnet black holes with non-constant curvature horizons | 15 pages, 1 figure; v2, discussion clarified and references added;
v3, published version; v4, Eqs.(4.22)-(4.24) corrected, which do not change
Eqs.(4.25)-(4.27) | Phys.Rev.D81:124007,2010 | 10.1103/PhysRevD.81.124007 | CECS-PHY-10/05 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate static and dynamical n(\ge 6)-dimensional black holes in
Einstein-Gauss-Bonnet gravity of which horizons have the isometries of an
(n-2)-dimensional Einstein space with a condition on its Weyl tensor originally
given by Dotti and Gleiser. Defining a generalized Misner-Sharp quasi-local
mass that satisfies the unified first law, we show that most of the properties
of the quasi-local mass and the trapping horizon are shared with the case with
horizons of constant curvature. It is shown that the Dotti-Gleiser solution is
the unique vacuum solution if the warp factor on the (n-2)-dimensional Einstein
space is non-constant. The quasi-local mass becomes constant for the
Dotti-Gleiser black hole and satisfies the first law of the black-hole
thermodynamics with its Wald entropy. In the non-negative curvature case with
positive Gauss-Bonnet constant and zero cosmological constant, it is shown that
the Dotti-Gleiser black hole is thermodynamically unstable. Even if it becomes
locally stable for the non-zero cosmological constant, it cannot be globally
stable for the positive cosmological constant.
| [
{
"created": "Tue, 6 Apr 2010 18:14:29 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2010 18:37:48 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jun 2010 00:17:05 GMT",
"version": "v3"
},
{
"created": "Thu, 23 Dec 2010 22:56:50 GMT",
"version": "v4"
}
] | 2010-12-27 | [
[
"Maeda",
"Hideki",
""
]
] | We investigate static and dynamical n(\ge 6)-dimensional black holes in Einstein-Gauss-Bonnet gravity of which horizons have the isometries of an (n-2)-dimensional Einstein space with a condition on its Weyl tensor originally given by Dotti and Gleiser. Defining a generalized Misner-Sharp quasi-local mass that satisfies the unified first law, we show that most of the properties of the quasi-local mass and the trapping horizon are shared with the case with horizons of constant curvature. It is shown that the Dotti-Gleiser solution is the unique vacuum solution if the warp factor on the (n-2)-dimensional Einstein space is non-constant. The quasi-local mass becomes constant for the Dotti-Gleiser black hole and satisfies the first law of the black-hole thermodynamics with its Wald entropy. In the non-negative curvature case with positive Gauss-Bonnet constant and zero cosmological constant, it is shown that the Dotti-Gleiser black hole is thermodynamically unstable. Even if it becomes locally stable for the non-zero cosmological constant, it cannot be globally stable for the positive cosmological constant. |
2311.03860 | Bill Atkins | Bill Atkins, Gianmassimo Tasinato | Hidden conformal symmetries for black holes in modified gravity | 22 pages, no figures | null | 10.1103/PhysRevD.108.104070 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We determine hidden conformal symmetries behind the evolution equations of
black hole perturbations in a vector-tensor theory of gravity. Such hidden
symmetries are valid everywhere in the exterior region of a spherically
symmetric, asymptotically flat black hole geometry. They allow us to factorize
second order operators controlling the black hole perturbations into a product
of two commuting first order operators. As a consequence, we are able to
analytically determine the most general time-dependent solutions for the black
hole perturbation equations. We focus on solutions belonging to a highest
weight representation of a conformal symmetry, showing that they correspond to
quasi-bound states with an ingoing behaviour into the black hole horizon, and
exponential decay at spatial infinity. Their time-dependence is characterized
by purely imaginary frequencies, with imaginary parts separated by integer
numbers, as the overtones of quasi-normal modes in General Relativity.
| [
{
"created": "Tue, 7 Nov 2023 10:21:49 GMT",
"version": "v1"
}
] | 2023-12-04 | [
[
"Atkins",
"Bill",
""
],
[
"Tasinato",
"Gianmassimo",
""
]
] | We determine hidden conformal symmetries behind the evolution equations of black hole perturbations in a vector-tensor theory of gravity. Such hidden symmetries are valid everywhere in the exterior region of a spherically symmetric, asymptotically flat black hole geometry. They allow us to factorize second order operators controlling the black hole perturbations into a product of two commuting first order operators. As a consequence, we are able to analytically determine the most general time-dependent solutions for the black hole perturbation equations. We focus on solutions belonging to a highest weight representation of a conformal symmetry, showing that they correspond to quasi-bound states with an ingoing behaviour into the black hole horizon, and exponential decay at spatial infinity. Their time-dependence is characterized by purely imaginary frequencies, with imaginary parts separated by integer numbers, as the overtones of quasi-normal modes in General Relativity. |
gr-qc/0211091 | Ettore Minguzzi | E. Minguzzi and A. Macdonald | Universal one-way light speed from a universal light speed over closed
paths | RevTex4, 6 pages, 2 figures, uses psfrag. New sections added,
discussion expanded | Found.Phys.Lett. 16 (2003) 593-604 | 10.1023/B:FOPL.0000012785.16203.52 | null | gr-qc physics.ed-ph | null | This paper gives two complete and elementary proofs that if the speed of
light over closed paths has a universal value $c$, then it is possible to
synchronize clocks in such a way that the one-way speed of light is c. The
first proof is an elementary version of a recent proof. The second provides
high precision experimental evidence that it is possible to synchronize clocks
in such a way that the one-way speed of light has a universal value. We also
discuss an old incomplete proof by Weyl which is important from an historical
perspective.
| [
{
"created": "Wed, 27 Nov 2002 10:03:11 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Dec 2002 14:21:18 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Oct 2003 11:38:27 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Minguzzi",
"E.",
""
],
[
"Macdonald",
"A.",
""
]
] | This paper gives two complete and elementary proofs that if the speed of light over closed paths has a universal value $c$, then it is possible to synchronize clocks in such a way that the one-way speed of light is c. The first proof is an elementary version of a recent proof. The second provides high precision experimental evidence that it is possible to synchronize clocks in such a way that the one-way speed of light has a universal value. We also discuss an old incomplete proof by Weyl which is important from an historical perspective. |
1504.04844 | Guillermo Andree Oliva-Mercado | Guillermo Andree Oliva-Mercado, Javier Bonatti-Gonz\'alez, Iv\'an
Cordero-Garc\'ia, Francisco Frutos-Alfaro | A Visualization of Null Geodesics for the Bonnor Massive Dipole | 9 pages, 5 figures, Presented at XIX Simposio Internacional de
M\'etodos Matem\'aticos Aplicados a las Ciencias (19th International
Symposium of Mathematical Methods Applied to Sciences, XIX-SIMMAC) | Revista de Matem\'atica: Teor\'ia y Aplicaciones 2015 22(2)
255-264 | 10.15517/rmta.v22i2.20723 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we simulate null geodesics for the Bonnor massive dipole metric
by implementing a symbolic-numerical algorithm in Sage and Python. This program
is also capable of visualizing in 3D, in principle, the geodesics for any given
metric. Geodesics are launched from a common point, collectively forming a cone
of light beams, simulating a solid-angle section of a point source in front of
a massive object with a magnetic field. Parallel light beams also were
considered, and their bending due to the curvature of the space-time was
simulated.
| [
{
"created": "Sun, 19 Apr 2015 16:11:21 GMT",
"version": "v1"
}
] | 2015-10-20 | [
[
"Oliva-Mercado",
"Guillermo Andree",
""
],
[
"Bonatti-González",
"Javier",
""
],
[
"Cordero-García",
"Iván",
""
],
[
"Frutos-Alfaro",
"Francisco",
""
]
] | In this work we simulate null geodesics for the Bonnor massive dipole metric by implementing a symbolic-numerical algorithm in Sage and Python. This program is also capable of visualizing in 3D, in principle, the geodesics for any given metric. Geodesics are launched from a common point, collectively forming a cone of light beams, simulating a solid-angle section of a point source in front of a massive object with a magnetic field. Parallel light beams also were considered, and their bending due to the curvature of the space-time was simulated. |
0905.2263 | Roman Sverdlov | Roman Sverdlov | Ph.D. Thesis: Quantum Field Theory and Gravity in Causal Sets | 211 pages, no figures | R. Sverdlov; Quantum Field Theory and Gravity in Causal Sets; PhD
Thesis (University of Michigan 2009) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is is a copy of dissertation that I have submitted in defense of my
ph.d. thesis, with some minor changes that I have made since then. The goal of
the project is to generalize matter fields and their Lagrangians from regular
space time to causal sets.
| [
{
"created": "Thu, 14 May 2009 07:09:42 GMT",
"version": "v1"
}
] | 2012-06-15 | [
[
"Sverdlov",
"Roman",
""
]
] | This is is a copy of dissertation that I have submitted in defense of my ph.d. thesis, with some minor changes that I have made since then. The goal of the project is to generalize matter fields and their Lagrangians from regular space time to causal sets. |
1812.01076 | Cemsinan Deliduman | Oguzhan Kasikci and Cemsinan Deliduman | Gravitational Lensing in Weyl Gravity | 14 pages; v2: published version | Phys. Rev. D 100, 024019 (2019) | 10.1103/PhysRevD.100.024019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the deflection angle of light from a distant source by a galaxy
cluster in Weyl's conformal gravity. The general method of calculation is first
applied to calculate the deflection angle in Schwarzschild-de Sitter (Kottler)
spacetime. The deflection angle calculated in Kottler spacetime includes the
contribution of the cosmological constant, which quantitatively agrees with one
work and disagrees with many works in the literature. We then calculate the
deflection angle in Mannheim-Kazanas spacetime in two conformally related
coordinate systems and find that the result includes contributions from both
the cosmological constant and the Mannheim-Kazanas parameter. There are
conflicting results on the deflection angle for light in Weyl gravity in the
literature. We point out a possible reason for the discrepancy between our work
and the others.
| [
{
"created": "Mon, 3 Dec 2018 20:44:46 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Oct 2019 15:25:52 GMT",
"version": "v2"
}
] | 2019-10-18 | [
[
"Kasikci",
"Oguzhan",
""
],
[
"Deliduman",
"Cemsinan",
""
]
] | We calculate the deflection angle of light from a distant source by a galaxy cluster in Weyl's conformal gravity. The general method of calculation is first applied to calculate the deflection angle in Schwarzschild-de Sitter (Kottler) spacetime. The deflection angle calculated in Kottler spacetime includes the contribution of the cosmological constant, which quantitatively agrees with one work and disagrees with many works in the literature. We then calculate the deflection angle in Mannheim-Kazanas spacetime in two conformally related coordinate systems and find that the result includes contributions from both the cosmological constant and the Mannheim-Kazanas parameter. There are conflicting results on the deflection angle for light in Weyl gravity in the literature. We point out a possible reason for the discrepancy between our work and the others. |
2403.13052 | Jorge Castelo Mourelle | Jorge Castelo Mourelle, Christoph Adam, Juan Calder\'on Bustillo,
Nicolas Sanchis-Gual | Rotating Fermion-Boson Stars | 19 pages, 8 figures. We have added the treatment of static solutions,
improved some discussions about the results, and corrected various typos | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Rotating fermion-boson stars are hypothetical celestial objects that consist
of both fermionic and bosonic matter interacting exclusively through gravity.
Bosonic fields are believed to arise in certain models of particle physics
describing dark matter and could accumulate within neutron stars, modifying
some of their properties and gravitational wave emission. Fermion-boson stars
have been extensively studied in the static non-rotating case, exploring their
combined stability and their gravitational radiation in binary mergers.
However, stationary rotating configurations were yet to be found and
investigated. The presence of a bosonic component could impact the development
of the bar-mode instability in differentially rotating neutron stars.
Therefore, the study of rotating fermion-boson stars has important implications
for astrophysics, as they could provide a new avenue for the detection of
gravitational waves. In addition, these objects may shed light on the behavior
of matter under extreme conditions, such as those found in the cores of neutron
stars, and explain any tension in the determination of the dense-matter
equation of state from multi-messenger observations. In this work we study a
new consistent method of constructing uniformly rotating fermion-boson stars
and we analyse some of their main properties. These objects might offer
alternative explanations for current observations populating the lower
black-hole mass gap, as the $2.6 M_\odot$ compact object involved in GW190814.
| [
{
"created": "Tue, 19 Mar 2024 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2024 10:43:16 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Apr 2024 13:14:22 GMT",
"version": "v3"
},
{
"created": "Tue, 18 Jun 2024 14:17:42 GMT",
"version": "v4"
}
] | 2024-06-19 | [
[
"Mourelle",
"Jorge Castelo",
""
],
[
"Adam",
"Christoph",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
]
] | Rotating fermion-boson stars are hypothetical celestial objects that consist of both fermionic and bosonic matter interacting exclusively through gravity. Bosonic fields are believed to arise in certain models of particle physics describing dark matter and could accumulate within neutron stars, modifying some of their properties and gravitational wave emission. Fermion-boson stars have been extensively studied in the static non-rotating case, exploring their combined stability and their gravitational radiation in binary mergers. However, stationary rotating configurations were yet to be found and investigated. The presence of a bosonic component could impact the development of the bar-mode instability in differentially rotating neutron stars. Therefore, the study of rotating fermion-boson stars has important implications for astrophysics, as they could provide a new avenue for the detection of gravitational waves. In addition, these objects may shed light on the behavior of matter under extreme conditions, such as those found in the cores of neutron stars, and explain any tension in the determination of the dense-matter equation of state from multi-messenger observations. In this work we study a new consistent method of constructing uniformly rotating fermion-boson stars and we analyse some of their main properties. These objects might offer alternative explanations for current observations populating the lower black-hole mass gap, as the $2.6 M_\odot$ compact object involved in GW190814. |
1306.1943 | Mehrdad Farhoudi Prof. | Amir F. Bahrehbakhsh, Mehrdad Farhoudi, Hajar Vakili | Dark Energy From Fifth Dimensional Brans-Dicke Theory | 16 pages, 5 figures, 3 tables | Inter. J. Mod. Phys. D Vol. 22, No. 12 (2013) 1350070 (18 pages) | 10.1142/S0218271813500703 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following the approach of the induced-matter theory, we investigate the
cosmological implications of a five-dimensional Brans-Dicke theory, and propose
to explain the acceleration of the universe. After inducing in a
four-dimensional hypersurface, we classify the energy-momentum tensor into two
parts in a way that, one part represents all kind of the matter (the baryonic
and dark) and the other one contains every extra terms emerging from the scale
factor of the fifth dimension and the scalar field, which we consider as the
energy-momentum tensor of dark energy. We also separate the energy-momentum
conservation equation into two conservation equations, one for matter and the
other for dark energy. We perform this procedure for different cases, without
interacting term and with two particular (suitable) interacting terms between
the two parts. By assuming the parameter of the state equation for dark energy
to be constant, the equations of the model admit the power-law solutions.
Though, the non-interacting case does not give any accelerated universe, but
the interacting cases give both decelerated and accelerated universes. For the
interacting cases, we figure out analytically the acceptable ranges of some
parameters of the model, and also investigate the data analysis to test the
model parameter values consistency with the observational data of the distance
modulus of 580 SNe Ia compiled in Union2.1. For one of these interacting cases,
the best fitted values suggest that the Brans-Dicke coupling constant
({\omega}) is -7.75, however, it also gives the state parameter of dark energy
(wX) equal to -0.67. In addition, the model gives the Hubble and deceleration
parameters at the present time to be H0 = 69.4 (km/s)/Mpc and q0 = -0.38
(within their confidence intervals), where the scale factor of the fifth
dimension shrinks with the time.
| [
{
"created": "Sat, 8 Jun 2013 16:58:32 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2013 14:04:54 GMT",
"version": "v2"
}
] | 2013-07-10 | [
[
"Bahrehbakhsh",
"Amir F.",
""
],
[
"Farhoudi",
"Mehrdad",
""
],
[
"Vakili",
"Hajar",
""
]
] | Following the approach of the induced-matter theory, we investigate the cosmological implications of a five-dimensional Brans-Dicke theory, and propose to explain the acceleration of the universe. After inducing in a four-dimensional hypersurface, we classify the energy-momentum tensor into two parts in a way that, one part represents all kind of the matter (the baryonic and dark) and the other one contains every extra terms emerging from the scale factor of the fifth dimension and the scalar field, which we consider as the energy-momentum tensor of dark energy. We also separate the energy-momentum conservation equation into two conservation equations, one for matter and the other for dark energy. We perform this procedure for different cases, without interacting term and with two particular (suitable) interacting terms between the two parts. By assuming the parameter of the state equation for dark energy to be constant, the equations of the model admit the power-law solutions. Though, the non-interacting case does not give any accelerated universe, but the interacting cases give both decelerated and accelerated universes. For the interacting cases, we figure out analytically the acceptable ranges of some parameters of the model, and also investigate the data analysis to test the model parameter values consistency with the observational data of the distance modulus of 580 SNe Ia compiled in Union2.1. For one of these interacting cases, the best fitted values suggest that the Brans-Dicke coupling constant ({\omega}) is -7.75, however, it also gives the state parameter of dark energy (wX) equal to -0.67. In addition, the model gives the Hubble and deceleration parameters at the present time to be H0 = 69.4 (km/s)/Mpc and q0 = -0.38 (within their confidence intervals), where the scale factor of the fifth dimension shrinks with the time. |
gr-qc/0506014 | Joel Franklin | S. Deser and J. Franklin | Birkhoff for Lovelock Redux | Submitted to CQG | Class.Quant.Grav.22:L103-L106,2005 | 10.1088/0264-9381/22/16/L03 | null | gr-qc hep-th | null | We show succinctly that all metric theories with second order field equations
obey Birkhoff's theorem: their spherically symmetric solutions are static.
| [
{
"created": "Thu, 2 Jun 2005 19:54:32 GMT",
"version": "v1"
}
] | 2010-11-05 | [
[
"Deser",
"S.",
""
],
[
"Franklin",
"J.",
""
]
] | We show succinctly that all metric theories with second order field equations obey Birkhoff's theorem: their spherically symmetric solutions are static. |
1302.1016 | Daniel Kennefick | Shasvath J. Kapadia, Daniel Kennefick and Kostas Glampedakis | Do floating orbits in extreme mass ratio binary black holes exist? | 11 pages, 7 Figures | null | 10.1103/PhysRevD.87.044050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper examines the possibility of floating or non-decaying orbits for
extreme mass ratio binary black holes. In the adiabatic approximation, valid in
the extreme mass ratio case, if the orbital flux lost due to gravitational
radiation reaction is compensated for by the orbital flux gained from the spins
of the black holes via superradiant scattering (or, equivalently, tidal
acceleration) the orbital decay would be stalled, causing the binary to
"float". We show that this flux balance is not, in practice, possible for
extreme mass ratio binary black holes with circular equatorial orbits;
furthermore, adding eccentricity and inclination to the orbits will not
significantly change this null result, thus ruling out the possibility of
floating orbits for extreme mass ratio binary black holes. We also argue that
binaries consisting of material bodies dense and massive enough to generate
gravitational waves detectable by any kind of gravitational wave detector are
also unlikely to float. Using a multipolar analysis, we show that a non-Kerr
spacetime which could produce a floating orbit (given the same amount of tidal
acceleration as in the case of a Kerr black hole) would need to be rapidly
rotating prolate spheroid, which would be an exotic object indeed.
| [
{
"created": "Tue, 5 Feb 2013 12:51:41 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Kapadia",
"Shasvath J.",
""
],
[
"Kennefick",
"Daniel",
""
],
[
"Glampedakis",
"Kostas",
""
]
] | This paper examines the possibility of floating or non-decaying orbits for extreme mass ratio binary black holes. In the adiabatic approximation, valid in the extreme mass ratio case, if the orbital flux lost due to gravitational radiation reaction is compensated for by the orbital flux gained from the spins of the black holes via superradiant scattering (or, equivalently, tidal acceleration) the orbital decay would be stalled, causing the binary to "float". We show that this flux balance is not, in practice, possible for extreme mass ratio binary black holes with circular equatorial orbits; furthermore, adding eccentricity and inclination to the orbits will not significantly change this null result, thus ruling out the possibility of floating orbits for extreme mass ratio binary black holes. We also argue that binaries consisting of material bodies dense and massive enough to generate gravitational waves detectable by any kind of gravitational wave detector are also unlikely to float. Using a multipolar analysis, we show that a non-Kerr spacetime which could produce a floating orbit (given the same amount of tidal acceleration as in the case of a Kerr black hole) would need to be rapidly rotating prolate spheroid, which would be an exotic object indeed. |
1910.09980 | Farhad Darabi | H. Hadi, Y. Heydarzade, F. Darabi and K. Atazadeh | D-bound and Bekenstein bound for McVittie solution surrounded by dark
energy cosmological fields | 13 pages, Minor revision | Eur. Phys. J. Plus, 135:584, (2020) | 10.1140/epjp/s13360-020-00601-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological candidate fields for dark energy as quintessence, phantom
and cosmological constant, are studied in terms of an entropic hypothesis
imposed on the McVittie solution surrounded by dark energy. We certify this
hypothesis as "$D$-bound-Bekenstein bound identification" for dilute systems
and use it as a criterion to determine which candidate of dark energy can
satisfy this criterion for a dilute McVittie solution. It turns out that only
the cosmological constant can pass this criterion successfully while the
quintessence and phantom fields fail, as non-viable dark energy fields for this
particular black hole solution. Moreover, assuming this black hole to possess
the saturated entropy, the entropy-area law and the holographic principle can
put two constraints on the radius $R$ of the cosmological horizon. The first
one shows that the Hubble radius is discrete such that for any arbitrary value
of the black hole mass $m_{0}$, the value of $R$ is determined up to an integer
number. The latter one shows that when a black hole is immersed in a
cosmological background, the radius of the cosmological horizon is constrained
as $R<\frac{1}{H}$.
| [
{
"created": "Mon, 21 Oct 2019 09:44:53 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Dec 2020 16:04:01 GMT",
"version": "v2"
}
] | 2020-12-16 | [
[
"Hadi",
"H.",
""
],
[
"Heydarzade",
"Y.",
""
],
[
"Darabi",
"F.",
""
],
[
"Atazadeh",
"K.",
""
]
] | The cosmological candidate fields for dark energy as quintessence, phantom and cosmological constant, are studied in terms of an entropic hypothesis imposed on the McVittie solution surrounded by dark energy. We certify this hypothesis as "$D$-bound-Bekenstein bound identification" for dilute systems and use it as a criterion to determine which candidate of dark energy can satisfy this criterion for a dilute McVittie solution. It turns out that only the cosmological constant can pass this criterion successfully while the quintessence and phantom fields fail, as non-viable dark energy fields for this particular black hole solution. Moreover, assuming this black hole to possess the saturated entropy, the entropy-area law and the holographic principle can put two constraints on the radius $R$ of the cosmological horizon. The first one shows that the Hubble radius is discrete such that for any arbitrary value of the black hole mass $m_{0}$, the value of $R$ is determined up to an integer number. The latter one shows that when a black hole is immersed in a cosmological background, the radius of the cosmological horizon is constrained as $R<\frac{1}{H}$. |
1409.4854 | Masashi Kuniyasu | Masashi Kuniyasu | New Solutions of the $2+1$ Dimensional Einstein Gravity Coupled to
Maxwell Power type Non Linear Electric field with Dilaton field | 6 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New solutions are derived in the $2+1$ gravity which is coupled to $|{\cal
F}|^k$ type non-linear electric field in Maxwell Power theory with dilaton
field. We obtain consistent solutions in general $k$ case. We also investigate
the behavior of the metric function with the space-time singularity. Then, we
found some black hole solutions when the space-time has a singular point at
$r=0$. Addition, we derive the Brown-York mass when the space-time represents
black hole.
| [
{
"created": "Wed, 17 Sep 2014 02:22:56 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Nov 2014 08:43:21 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Nov 2014 05:49:35 GMT",
"version": "v3"
},
{
"created": "Tue, 27 Jan 2015 07:12:17 GMT",
"version": "v4"
}
] | 2015-01-28 | [
[
"Kuniyasu",
"Masashi",
""
]
] | New solutions are derived in the $2+1$ gravity which is coupled to $|{\cal F}|^k$ type non-linear electric field in Maxwell Power theory with dilaton field. We obtain consistent solutions in general $k$ case. We also investigate the behavior of the metric function with the space-time singularity. Then, we found some black hole solutions when the space-time has a singular point at $r=0$. Addition, we derive the Brown-York mass when the space-time represents black hole. |
1511.00388 | Kartik Prabhu | Kartik Prabhu | The First Law of Black Hole Mechanics for Fields with Internal Gauge
Freedom | v4: 69 pages, shorter, less pedagogical version, updated references
(published in CQG). v3: minor typographic corrections (PhD thesis version).
v2: 80 pages, 1 figure, significant changes to presentation and text; added
Thm 1 and Thm2. v1: 64 pages, 1 figure | Class. Quantum Grav. 34 035011, 2017 | 10.1088/1361-6382/aa536b | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the first law of black hole mechanics for physical theories based
on a local, covariant and gauge-invariant Lagrangian where the dynamical fields
transform non-trivially under the action of internal gauge transformations. The
theories of interest include General Relativity formulated in terms of tetrads,
Einstein-Yang-Mills theory and Einstein-Dirac theory. Since the dynamical
fields of these theories have gauge freedom, we argue that there is no group
action of diffeomorphisms of spacetime on such dynamical fields. In general,
such fields cannot even be represented as smooth, globally well-defined tensor
fields on spacetime. Consequently the derivation of the first law by Iyer-Wald
cannot be used directly. We show how such theories can be formulated on a
principal bundle and that there is a natural action of automorphisms of the
bundle on the fields. These bundle automorphisms encode both spacetime
diffeomorphisms and gauge transformations. Using this reformulation we define
the Noether charge associated to an infinitesimal automorphism and the
corresponding notion of stationarity and axisymmetry of the dynamical fields.
We define certain potentials and charges at the horizon of a black hole so that
the potentials are constant on the bifurcate Killing horizon, giving a
generalised zeroth law for bifurcate Killing horizons. We identify the
gravitational potential and perturbed charge as the temperature and perturbed
entropy of the black hole which gives an explicit formula for the perturbed
entropy analogous to the Wald entropy formula. We obtain a general first law of
black hole mechanics for such theories. The first law relates the perturbed
Hamiltonians at spatial infinity and the horizon, and the horizon contributions
take the form of a potential times perturbed charge term. We also comment on
the ambiguities in defining a prescription for the total entropy for black
holes.
| [
{
"created": "Mon, 2 Nov 2015 05:50:42 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jun 2016 21:22:14 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Dec 2016 20:46:29 GMT",
"version": "v3"
},
{
"created": "Tue, 10 Jan 2017 20:47:21 GMT",
"version": "v4"
}
] | 2017-01-12 | [
[
"Prabhu",
"Kartik",
""
]
] | We derive the first law of black hole mechanics for physical theories based on a local, covariant and gauge-invariant Lagrangian where the dynamical fields transform non-trivially under the action of internal gauge transformations. The theories of interest include General Relativity formulated in terms of tetrads, Einstein-Yang-Mills theory and Einstein-Dirac theory. Since the dynamical fields of these theories have gauge freedom, we argue that there is no group action of diffeomorphisms of spacetime on such dynamical fields. In general, such fields cannot even be represented as smooth, globally well-defined tensor fields on spacetime. Consequently the derivation of the first law by Iyer-Wald cannot be used directly. We show how such theories can be formulated on a principal bundle and that there is a natural action of automorphisms of the bundle on the fields. These bundle automorphisms encode both spacetime diffeomorphisms and gauge transformations. Using this reformulation we define the Noether charge associated to an infinitesimal automorphism and the corresponding notion of stationarity and axisymmetry of the dynamical fields. We define certain potentials and charges at the horizon of a black hole so that the potentials are constant on the bifurcate Killing horizon, giving a generalised zeroth law for bifurcate Killing horizons. We identify the gravitational potential and perturbed charge as the temperature and perturbed entropy of the black hole which gives an explicit formula for the perturbed entropy analogous to the Wald entropy formula. We obtain a general first law of black hole mechanics for such theories. The first law relates the perturbed Hamiltonians at spatial infinity and the horizon, and the horizon contributions take the form of a potential times perturbed charge term. We also comment on the ambiguities in defining a prescription for the total entropy for black holes. |
gr-qc/0405054 | Yasuo Ezawa | Y.Ezawa, H.Iwasaki, Y.Ohkuwa, T.Uegaki, N.Yamada and T.Yano | Interpretation of the first order formalism of f(R)-type gravity and the
corresponding second order formalism | 7 pages, extended and revised version of gr-qc/0309010 | Nuovo Cim.B119:1141-1148,2004 | 10.1393/ncb/i2004-10127-5 | null | gr-qc | null | f(R)-type gravity in the first order formalism is interpreted as Einstein
gravity with non-minimal coupling arising from the use of unphysical frame.
Identification of the corresponding second order higher-curvature gravity in
the physical frame is proposed by requiring that the action is the same.
| [
{
"created": "Tue, 11 May 2004 11:53:34 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Ezawa",
"Y.",
""
],
[
"Iwasaki",
"H.",
""
],
[
"Ohkuwa",
"Y.",
""
],
[
"Uegaki",
"T.",
""
],
[
"Yamada",
"N.",
""
],
[
"Yano",
"T.",
""
]
] | f(R)-type gravity in the first order formalism is interpreted as Einstein gravity with non-minimal coupling arising from the use of unphysical frame. Identification of the corresponding second order higher-curvature gravity in the physical frame is proposed by requiring that the action is the same. |
1006.5118 | Vladimir S. Manko | F.J. Ernst, V.S. Manko and E. Ruiz | On interrelations between Sibgatullin's and Alekseev's approaches to the
construction of exact solutions of the Einstein-Maxwell equations | 7 pages, no figures, section II extended | J.Phys.Conf.Ser.229:012050,2010 | 10.1088/1742-6596/229/1/012050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The integral equations involved in Alekseev's "monodromy transform" technique
are shown to be simple combinations of Sibgatullin's integral equations and
normalizing conditions. An additional complex conjugation introduced by
Alekseev in the integrands makes his scheme mathematically inconsistent;
besides, in the electrovac case all Alekseev's principal value integrals
contain an intrinsic error which has never been identified before. We also
explain how operates a non-trivial double-step algorithm devised by Alekseev
for rewriting, by purely algebraic manipulations and in a different (more
complicated) parameter set, any particular specialization of the known
analytically extended N-soliton electrovac solution obtained in 1995 with the
aid of Sibgatullin's method.
| [
{
"created": "Sat, 26 Jun 2010 08:00:03 GMT",
"version": "v1"
}
] | 2010-12-17 | [
[
"Ernst",
"F. J.",
""
],
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
]
] | The integral equations involved in Alekseev's "monodromy transform" technique are shown to be simple combinations of Sibgatullin's integral equations and normalizing conditions. An additional complex conjugation introduced by Alekseev in the integrands makes his scheme mathematically inconsistent; besides, in the electrovac case all Alekseev's principal value integrals contain an intrinsic error which has never been identified before. We also explain how operates a non-trivial double-step algorithm devised by Alekseev for rewriting, by purely algebraic manipulations and in a different (more complicated) parameter set, any particular specialization of the known analytically extended N-soliton electrovac solution obtained in 1995 with the aid of Sibgatullin's method. |
gr-qc/0603087 | Domenico Giulini | Domenico Giulini | Some remarks on the notions of general covariance and background
independence | 26 pages, 3 figures. Contribution to ``An assessment of current
paradigms in the physics of fundamental interactions'', edited by I.O.
Stamatescu (Springer Verlag, to appear) | Lect.NotesPhys.721:105-120,2007 | 10.1007/978-3-540-71117-9_6 | Freiburg THEP-06/04 | gr-qc | null | In the first part of this paper I review some of the difficulties that seem
to obstruct generally valid definitions of "general covariance" and/or
"background independence" The second and more historical part deals with a
rather strange argument that Einstein put forward in his 1913 "Entwurf paper"
with M. Grossmann to discredit scalar theories of gravity in order to promote
general covariance.
| [
{
"created": "Wed, 22 Mar 2006 14:59:24 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Giulini",
"Domenico",
""
]
] | In the first part of this paper I review some of the difficulties that seem to obstruct generally valid definitions of "general covariance" and/or "background independence" The second and more historical part deals with a rather strange argument that Einstein put forward in his 1913 "Entwurf paper" with M. Grossmann to discredit scalar theories of gravity in order to promote general covariance. |
gr-qc/9505026 | Jorma Louko | Jorma Louko | Witten's 2+1 gravity on R x (Klein bottle) | 33 pages, REVTeX v3.0, 3 figures in a separate PostScript file | Class.Quant.Grav. 12 (1995) 2441-2468 | 10.1088/0264-9381/12/10/006 | WISC--MILW--95--TH--15 | gr-qc hep-th | null | Witten's formulation of 2+1 gravity is investigated on the nonorientable
three-manifold R x (Klein bottle). The gauge group is taken to consist of all
four components of the 2+1 Poincare group. We analyze in detail several
components of the classical solution space, and we show that from four of the
components one can recover nondegenerate spacetime metrics. In particular, from
one component we recover metrics for which the Klein bottles are spacelike. An
action principle is formulated for bundles satisfying a certain orientation
compatibility property, and the corresponding components of the classical
solution space are promoted into a phase space. Avenues towards quantization
are briefly discussed.
| [
{
"created": "Wed, 17 May 1995 00:09:02 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Louko",
"Jorma",
""
]
] | Witten's formulation of 2+1 gravity is investigated on the nonorientable three-manifold R x (Klein bottle). The gauge group is taken to consist of all four components of the 2+1 Poincare group. We analyze in detail several components of the classical solution space, and we show that from four of the components one can recover nondegenerate spacetime metrics. In particular, from one component we recover metrics for which the Klein bottles are spacelike. An action principle is formulated for bundles satisfying a certain orientation compatibility property, and the corresponding components of the classical solution space are promoted into a phase space. Avenues towards quantization are briefly discussed. |
2203.11215 | Olivier Minazzoli | Olivier Minazzoli | On the shortcomings of the Shapiro delay tests of the equivalence
principle | 2 pages. Contribution to the 2022 Gravitation session of the 56th
Rencontres de Moriond | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are several shortcomings in the "standard" Shapiro delay tests of the
equivalence principle on cosmological scales \cite{minazzoli:2019pr}. Although
many people in the community already acknowledged this in the literature, and
proposed alternative ways to compare potential Shapiro delays over cosmological
scales -- e.g. \cite{bartlett:2021pr,hashimoto:2021pr} and references therein
-- papers are still submitted to journals with the usual issues.
| [
{
"created": "Mon, 21 Mar 2022 16:54:40 GMT",
"version": "v1"
}
] | 2022-03-23 | [
[
"Minazzoli",
"Olivier",
""
]
] | There are several shortcomings in the "standard" Shapiro delay tests of the equivalence principle on cosmological scales \cite{minazzoli:2019pr}. Although many people in the community already acknowledged this in the literature, and proposed alternative ways to compare potential Shapiro delays over cosmological scales -- e.g. \cite{bartlett:2021pr,hashimoto:2021pr} and references therein -- papers are still submitted to journals with the usual issues. |
1602.02552 | Deng Wang | Guang Yang, Deng Wang, and Xinhe Meng | Diagnostics and future evolution analysis of the two parametric models | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we apply three diagnostics including $Om$, Statefinder
hierarchy and the growth rate of perturbations into discriminating the two
parametric models for the effective pressure with the $\Lambda$CDM model. By
using the $Om$ diagnostic, we find that both the model 1 and the model 2 can be
hardly distinguished from each other as well as the $\Lambda$CDM model in terms
of 68\% confidence level. As a supplement, by using the Statefinder hierarchy
diagnostics and the growth rate of perturbations, we discover that not only can
our two parametric models be well distinguished from $\Lambda$CDM model, but
also, by comparing with $Om$ diagnostic, the model 1 and the model 2 can be
distinguished better from each other. In addition, we also explore the fate of
universe evolution of our two models by means of the rip analysis.
| [
{
"created": "Mon, 8 Feb 2016 13:12:35 GMT",
"version": "v1"
}
] | 2016-02-09 | [
[
"Yang",
"Guang",
""
],
[
"Wang",
"Deng",
""
],
[
"Meng",
"Xinhe",
""
]
] | In this paper, we apply three diagnostics including $Om$, Statefinder hierarchy and the growth rate of perturbations into discriminating the two parametric models for the effective pressure with the $\Lambda$CDM model. By using the $Om$ diagnostic, we find that both the model 1 and the model 2 can be hardly distinguished from each other as well as the $\Lambda$CDM model in terms of 68\% confidence level. As a supplement, by using the Statefinder hierarchy diagnostics and the growth rate of perturbations, we discover that not only can our two parametric models be well distinguished from $\Lambda$CDM model, but also, by comparing with $Om$ diagnostic, the model 1 and the model 2 can be distinguished better from each other. In addition, we also explore the fate of universe evolution of our two models by means of the rip analysis. |
1607.06695 | Mahsa Sanati | Fatimah Shojai, Mahsa Sanati | Investigation of energy conditions in the vicinity of future
cosmological singularities | I withdraw this paper since my former supervisor require me to
withdraw this paper | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, considering the energy conditions we shall show that some of
the energy conditions are violated in the vicinity of future singularities with
the scale factor suggested by Dabrowski - Marosek.
| [
{
"created": "Thu, 21 Jul 2016 07:44:29 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jul 2016 18:27:29 GMT",
"version": "v2"
}
] | 2016-07-27 | [
[
"Shojai",
"Fatimah",
""
],
[
"Sanati",
"Mahsa",
""
]
] | In this paper, considering the energy conditions we shall show that some of the energy conditions are violated in the vicinity of future singularities with the scale factor suggested by Dabrowski - Marosek. |
2008.02137 | Viktor T. Toth | J. W. Moffat and V. T. Toth | Applying Modified Gravity (MOG) to the Lensing and Einstein Ring in
Abell 3827 | 4 pages, 1 figure. Minor corrections. arXiv admin note: substantial
text overlap with arXiv:2006.12550 | Phys. Rev. D 103, 044045 (2021) | 10.1103/PhysRevD.103.044045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The lensing and Einstein ring at the core of the galaxy cluster Abell 3827
are reproduced in the modified gravity theory MOG. The estimated effective
lensing mass $M_L=(1+\alpha)M_b=5.2\times 10^{12} M_\odot$ within $R=18.3$~kpc
for a baryon mass $M_b=1.0\times 10^{12} M_\odot$ within the same radius
produces the observed Einstein ring angular radius $\theta_E=10''$. A detailed
derivation of the total lensing mass is based on modeling of the cluster
configuration of galaxies, intracluster light and X-ray emission. The MOG can
fit the lensing and Einstein ring in Abell 3827 without dark matter as well as
General Relativity with dark matter.
| [
{
"created": "Tue, 4 Aug 2020 15:38:15 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Aug 2020 15:40:07 GMT",
"version": "v2"
}
] | 2021-02-24 | [
[
"Moffat",
"J. W.",
""
],
[
"Toth",
"V. T.",
""
]
] | The lensing and Einstein ring at the core of the galaxy cluster Abell 3827 are reproduced in the modified gravity theory MOG. The estimated effective lensing mass $M_L=(1+\alpha)M_b=5.2\times 10^{12} M_\odot$ within $R=18.3$~kpc for a baryon mass $M_b=1.0\times 10^{12} M_\odot$ within the same radius produces the observed Einstein ring angular radius $\theta_E=10''$. A detailed derivation of the total lensing mass is based on modeling of the cluster configuration of galaxies, intracluster light and X-ray emission. The MOG can fit the lensing and Einstein ring in Abell 3827 without dark matter as well as General Relativity with dark matter. |
0911.2450 | Anil Zenginoglu C | Anil Zenginoglu | Asymptotics of Schwarzschild black hole perturbations | 9 pages, 8 figures; changed title, updated references, matches the
published version | Class.Quant.Grav.27:045015,2010 | 10.1088/0264-9381/27/4/045015 | CSCAMM-09-21 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear gravitational perturbations of Schwarzschild spacetime by
solving numerically Regge-Wheeler-Zerilli equations in time domain using
hyperboloidal surfaces and a compactifying radial coordinate. We stress the
importance of including the asymptotic region in the computational domain in
studies of gravitational radiation. The hyperboloidal approach should be
helpful in a wide range of applications employing black hole perturbation
theory.
| [
{
"created": "Thu, 12 Nov 2009 19:16:45 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2010 03:09:47 GMT",
"version": "v2"
}
] | 2010-03-26 | [
[
"Zenginoglu",
"Anil",
""
]
] | We study linear gravitational perturbations of Schwarzschild spacetime by solving numerically Regge-Wheeler-Zerilli equations in time domain using hyperboloidal surfaces and a compactifying radial coordinate. We stress the importance of including the asymptotic region in the computational domain in studies of gravitational radiation. The hyperboloidal approach should be helpful in a wide range of applications employing black hole perturbation theory. |
gr-qc/0203025 | Guillermo A. Mena Marugan | Saulo Carneiro and Guillermo A. Mena Marugan | An anisotropic cosmological model with isotropic background radiation | 4 pages; contribution to the Proceedings of the 24th Spanish
Relativity Meeting (ERE2001) | Lect.Notes Phys. 617 (2003) 302 | 10.1007/3-540-36973-2_17 | null | gr-qc astro-ph | null | We present an exact solution of Einstein equations that describes a Bianchi
type III spacetime with conformal expansion. The matter content is given by an
anisotropic scalar field and two perfect fluids representing dust and isotropic
radiation. Based on this solution, we construct a cosmological model that
respects the evolution of the scale factor predicted in standard cosmology.
| [
{
"created": "Thu, 7 Mar 2002 17:51:00 GMT",
"version": "v1"
}
] | 2013-11-11 | [
[
"Carneiro",
"Saulo",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | We present an exact solution of Einstein equations that describes a Bianchi type III spacetime with conformal expansion. The matter content is given by an anisotropic scalar field and two perfect fluids representing dust and isotropic radiation. Based on this solution, we construct a cosmological model that respects the evolution of the scale factor predicted in standard cosmology. |
gr-qc/9508052 | Larry Shepley | J M Pons (Univ Barcelona) & L C Shepley (Univ Texas Austin) | Evolutionary Laws, Initial Conditions, and Gauge Fixing in Constrained
Systems | 23 pages; plain TeX. To appear: Classical & Quantum Gravity | Class.Quant.Grav.12:1771-1790,1995 | 10.1088/0264-9381/12/7/018 | null | gr-qc | null | We describe in detail how to eliminate nonphysical degrees of freedom in the
Lagrangian and Hamiltonian formulations of a constrained system. Two important
and distinct steps in our method are the fixing of ambiguities in the dynamics
and the determination of inequivalent initial data. The Lagrangian discussion
is novel, and a proof is given that the final number of degrees of freedom in
the two formulations agrees. We give applications to reparameterization
invariant theories, where we prove that one of the constraints must be
explicitly time dependent. We illustrate our procedure with the examples of
trajectories in spacetime and with spatially homogeneous cosmological models.
Finally, we comment briefly on Dirac's extended Hamiltonian technique.
| [
{
"created": "Fri, 25 Aug 1995 16:35:32 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Pons",
"J M",
"",
"Univ Barcelona"
],
[
"Shepley",
"L C",
"",
"Univ Texas Austin"
]
] | We describe in detail how to eliminate nonphysical degrees of freedom in the Lagrangian and Hamiltonian formulations of a constrained system. Two important and distinct steps in our method are the fixing of ambiguities in the dynamics and the determination of inequivalent initial data. The Lagrangian discussion is novel, and a proof is given that the final number of degrees of freedom in the two formulations agrees. We give applications to reparameterization invariant theories, where we prove that one of the constraints must be explicitly time dependent. We illustrate our procedure with the examples of trajectories in spacetime and with spatially homogeneous cosmological models. Finally, we comment briefly on Dirac's extended Hamiltonian technique. |
gr-qc/9312004 | null | G. L. Rcheulishvili | Conformal Killing Vectors in Five-Dimensional Space | 9 pages, LaTeX file, IHEP 93-121 | null | null | null | gr-qc | null | The solutions of generalized Killing equation have been obtained for line
element with initial $t^2 \oplus so(3)$ symmetry. The coefficients of the
metric $g$ corresponding to these vector fields are written down.
| [
{
"created": "Thu, 2 Dec 1993 13:26:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rcheulishvili",
"G. L.",
""
]
] | The solutions of generalized Killing equation have been obtained for line element with initial $t^2 \oplus so(3)$ symmetry. The coefficients of the metric $g$ corresponding to these vector fields are written down. |
gr-qc/0002060 | Jose Wadih Maluf | J. W. Maluf and A. A. Sousa | Hamiltonian formulation of teleparallel theories of gravity in the time
gauge | 22 pages, Latex file, no figures | null | null | null | gr-qc | null | We consider the most general class of teleparallel theories of gravity
quadratic in the torsion tensor, and carry out a detailed investigation of its
Hamiltonian formulation in the time gauge. Such general class is given by a
three-parameter family of theories. A consistent implementation of the Legendre
transform reduces the original theory to a one-parameter theory determined in
terms of first class constraints. The free parameter is fixed by requiring the
Newtonian limit. The resulting theory is the teleparallel equivalent of general
relativity.
| [
{
"created": "Wed, 16 Feb 2000 22:17:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Maluf",
"J. W.",
""
],
[
"Sousa",
"A. A.",
""
]
] | We consider the most general class of teleparallel theories of gravity quadratic in the torsion tensor, and carry out a detailed investigation of its Hamiltonian formulation in the time gauge. Such general class is given by a three-parameter family of theories. A consistent implementation of the Legendre transform reduces the original theory to a one-parameter theory determined in terms of first class constraints. The free parameter is fixed by requiring the Newtonian limit. The resulting theory is the teleparallel equivalent of general relativity. |
0706.2905 | Myungseok Yoon | Chang-Young Ee, Daeho Lee, and Myungseok Yoon | Entropy of Schwarzschild Black Holes on DGP Brane | 6 pages, 1 figure; to appear in J. Kor. Phys. Soc | J.Korean Phys.Soc. 51 (2007) 2091-2093 | null | null | gr-qc | null | We study the entropy of Schwarzschild black holes on DGP brane. The radius of
event horizon on DGP brane is obtained by a numerical method. It is smaller
than that of Einstein gravity in the conventional branch, and is larger in the
accelerated branch. However, the difference is very small. The entropy of the
black hole is calculated by using the improved brick-wall method.
| [
{
"created": "Wed, 20 Jun 2007 03:29:54 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Nov 2007 05:32:31 GMT",
"version": "v2"
}
] | 2008-10-21 | [
[
"Ee",
"Chang-Young",
""
],
[
"Lee",
"Daeho",
""
],
[
"Yoon",
"Myungseok",
""
]
] | We study the entropy of Schwarzschild black holes on DGP brane. The radius of event horizon on DGP brane is obtained by a numerical method. It is smaller than that of Einstein gravity in the conventional branch, and is larger in the accelerated branch. However, the difference is very small. The entropy of the black hole is calculated by using the improved brick-wall method. |
gr-qc/9904012 | Gravity Research Group | Alexander Burinskii and Giulio Magli | Kerr-Schild Approach to the Boosted Kerr Solution | 16 pages, LaTeX | Phys.Rev. D61 (2000) 044017 | 10.1103/PhysRevD.61.044017 | null | gr-qc hep-th | null | Using a complex representation of the Debney-Kerr-Schild (DKS) solutions and
the Kerr theorem we analyze the boosted Kerr geometries and give the exact and
explicit expressions for the metrics, the principal null congruences, the
coordinate systems and the location of the singularities for arbitrary value
and orientation of the boost with respect to the angular momentum. In the
limiting, ultrarelativistic case we obtain light-like solutions possessing
diverging and twisting principal null congruences and having, contrary to the
known pp-wave limiting solutions, a non-zero value of the total angular
momentum. The implications of the above results in various related fields are
discussed.
| [
{
"created": "Tue, 6 Apr 1999 13:33:26 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Burinskii",
"Alexander",
""
],
[
"Magli",
"Giulio",
""
]
] | Using a complex representation of the Debney-Kerr-Schild (DKS) solutions and the Kerr theorem we analyze the boosted Kerr geometries and give the exact and explicit expressions for the metrics, the principal null congruences, the coordinate systems and the location of the singularities for arbitrary value and orientation of the boost with respect to the angular momentum. In the limiting, ultrarelativistic case we obtain light-like solutions possessing diverging and twisting principal null congruences and having, contrary to the known pp-wave limiting solutions, a non-zero value of the total angular momentum. The implications of the above results in various related fields are discussed. |
1002.0524 | Panagiotis Kordas Dr | Panagiotis Kordas | Transition Matrix, Poisson Bracket for gravitational solitons in the
dressing formalism | 9 pages, Comments welcome, results explicitly expressed in
Introduction and abstract | null | null | null | gr-qc hep-th nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian methods of the theory of solitons are applied to
gravisolitons in the dressing formalism. The Poisson bracket for the
Lie-algebra valued one-form $A(\varsigma, \eta,
\gamma)=\Psi_{,\gamma}\Psi^{-1}$, for gravisolitons in the dressing formalism,
for a specific background solution, is defined and computed, agreeing with
results previously obtained. A transition matrix ${\cal T}=A(\varsigma, \eta,
\gamma) A^{-1}(\eta, \xi, -\gamma)$ for $A$ is defined relating $A$ at ingoing
and outgoing light cones. It is proved that it satisfies equations familiar
from integrable pde's with the role of time played by the null coordinate
$\eta$. This is a new result mathematically, since there has not been a
transition matrix for $A$ in the litterature, while physically it presents the
possibility of obtaining integrals of motion (for appropriate boundary
conditions), from the trace of the derivative with respect to the null
coordinate $\eta$, of ${\cal T}$, in terms of classical relativity connections,
since $A(\gamma = \pm 1)$ can be expressed in a simple way in terms of the
classical Christoffel symbols. This may prove of use upon quantization since
connections are fundamental variables of quantum gravity. The roles of $\eta$
and $\varsigma $ may be reversed to obtain integrals of motion for $\varsigma$,
thus $\varsigma$ playing the role of time. This ties well with the two-time
interpretation and approach already established before.
| [
{
"created": "Tue, 2 Feb 2010 16:24:42 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Dec 2010 11:09:20 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Jan 2011 18:15:01 GMT",
"version": "v3"
}
] | 2011-01-31 | [
[
"Kordas",
"Panagiotis",
""
]
] | The Hamiltonian methods of the theory of solitons are applied to gravisolitons in the dressing formalism. The Poisson bracket for the Lie-algebra valued one-form $A(\varsigma, \eta, \gamma)=\Psi_{,\gamma}\Psi^{-1}$, for gravisolitons in the dressing formalism, for a specific background solution, is defined and computed, agreeing with results previously obtained. A transition matrix ${\cal T}=A(\varsigma, \eta, \gamma) A^{-1}(\eta, \xi, -\gamma)$ for $A$ is defined relating $A$ at ingoing and outgoing light cones. It is proved that it satisfies equations familiar from integrable pde's with the role of time played by the null coordinate $\eta$. This is a new result mathematically, since there has not been a transition matrix for $A$ in the litterature, while physically it presents the possibility of obtaining integrals of motion (for appropriate boundary conditions), from the trace of the derivative with respect to the null coordinate $\eta$, of ${\cal T}$, in terms of classical relativity connections, since $A(\gamma = \pm 1)$ can be expressed in a simple way in terms of the classical Christoffel symbols. This may prove of use upon quantization since connections are fundamental variables of quantum gravity. The roles of $\eta$ and $\varsigma $ may be reversed to obtain integrals of motion for $\varsigma$, thus $\varsigma$ playing the role of time. This ties well with the two-time interpretation and approach already established before. |
1410.6065 | Andrew Scacco | Daniel Phillips, Andrew Scacco, and Andreas Albrecht | Holographic bounds and finite inflation | 14 pages, 10 figures | Phys. Rev. D 91, 043513 (2015) | 10.1103/PhysRevD.91.043513 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare two holographic arguments that impose especially strong bounds on
the amount of inflation. One comes from the de Sitter Equilibrium cosmology and
the other from the work of Banks and Fischler. We find that simple versions of
these two approaches yield the same bound on the number of e-foldings. A
careful examination reveals that while these pictures are similar in spirit,
they are not necessarily identical prescriptions. We apply the two pictures to
specific cosmologies which expose potentially important differences and which
also demonstrate ways these seemingly simple proposals can be tricky to
implement in practice.
| [
{
"created": "Mon, 13 Oct 2014 22:02:45 GMT",
"version": "v1"
}
] | 2015-03-05 | [
[
"Phillips",
"Daniel",
""
],
[
"Scacco",
"Andrew",
""
],
[
"Albrecht",
"Andreas",
""
]
] | We compare two holographic arguments that impose especially strong bounds on the amount of inflation. One comes from the de Sitter Equilibrium cosmology and the other from the work of Banks and Fischler. We find that simple versions of these two approaches yield the same bound on the number of e-foldings. A careful examination reveals that while these pictures are similar in spirit, they are not necessarily identical prescriptions. We apply the two pictures to specific cosmologies which expose potentially important differences and which also demonstrate ways these seemingly simple proposals can be tricky to implement in practice. |
1203.5709 | T.G Zlosnik | H. F. Westman and T. G. Zlosnik | Gravity, Cartan geometry, and idealized waywisers | Some typos corrected and presentation cleaned up in places. Much of
the content of this paper may also be found in the larger and more recent
paper arXiv:1411.1679 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The primary aim of this paper is to provide a simple and concrete
interpretation of Cartan geometry in terms of the mathematics of idealized
waywisers. Waywisers, also called hodometers, are instruments traditionally
used to measure distances. The mathematical representation of an idealized
waywiser consists of a choice of symmetric space called a {\em model space} and
represents the `wheel' of the idealized waywiser. The geometry of a manifold is
then completely characterized by a pair of variables $\{V^A(x),A^{AB}(x)\}$,
each of which admit simple interpretations: $V^A$ is the point of contact
between the waywiser's idealized wheel and the manifold whose geometry one
wishes to characterize, and $A^{AB}=A_\mu^{\phantom{\mu} AB}dx^\mu$ is a
connection one-form dictating how much the idealized wheel of the waywiser has
rotated when rolled along the manifold. The familiar objects from differential
geometry (e.g. metric $g_{\mu\nu}$, affine connection $\Gamma^\rho_{\mu\nu}$,
co-tetrad $e^I$, torsion $T^I$, spin-connection $\omega^{IJ}$, Riemannian
curvature $R^{IJ}$) can be seen as compound objects made out of the waywiser
variables $\{V^A,A^{AB}\}$. We then generalize this waywiser approach to
relativistic spacetimes and exhibit action principles for General Relativity in
terms of the waywiser variables for two choices of model spacetimes: De Sitter
and anti-De Sitter spacetimes.
| [
{
"created": "Mon, 26 Mar 2012 16:04:35 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Mar 2012 17:13:24 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Apr 2012 21:08:08 GMT",
"version": "v3"
},
{
"created": "Mon, 16 Feb 2015 14:57:35 GMT",
"version": "v4"
}
] | 2015-02-17 | [
[
"Westman",
"H. F.",
""
],
[
"Zlosnik",
"T. G.",
""
]
] | The primary aim of this paper is to provide a simple and concrete interpretation of Cartan geometry in terms of the mathematics of idealized waywisers. Waywisers, also called hodometers, are instruments traditionally used to measure distances. The mathematical representation of an idealized waywiser consists of a choice of symmetric space called a {\em model space} and represents the `wheel' of the idealized waywiser. The geometry of a manifold is then completely characterized by a pair of variables $\{V^A(x),A^{AB}(x)\}$, each of which admit simple interpretations: $V^A$ is the point of contact between the waywiser's idealized wheel and the manifold whose geometry one wishes to characterize, and $A^{AB}=A_\mu^{\phantom{\mu} AB}dx^\mu$ is a connection one-form dictating how much the idealized wheel of the waywiser has rotated when rolled along the manifold. The familiar objects from differential geometry (e.g. metric $g_{\mu\nu}$, affine connection $\Gamma^\rho_{\mu\nu}$, co-tetrad $e^I$, torsion $T^I$, spin-connection $\omega^{IJ}$, Riemannian curvature $R^{IJ}$) can be seen as compound objects made out of the waywiser variables $\{V^A,A^{AB}\}$. We then generalize this waywiser approach to relativistic spacetimes and exhibit action principles for General Relativity in terms of the waywiser variables for two choices of model spacetimes: De Sitter and anti-De Sitter spacetimes. |
gr-qc/0602076 | Stefan Nobbenhuis | Gerard 't Hooft and Stefan Nobbenhuis | Invariance under complex transformations, and its relevance to the
cosmological constant problem | Some clarifications and references added | Class.Quant.Grav.23:3819-3832,2006 | 10.1088/0264-9381/23/11/009 | ITP-UU-06/06, SPIN-06/04 | gr-qc hep-th | null | In this paper we study a new symmetry argument that results in a vacuum state
with strictly vanishing vacuum energy. This argument exploits the well-known
feature that de Sitter and Anti- de Sitter space are related by analytic
continuation. When we drop boundary and hermiticity conditions on quantum
fields, we get as many negative as positive energy states, which are related by
transformations to complex space. The paper does not directly solve the
cosmological constant problem, but explores a new direction that appears
worthwhile.
| [
{
"created": "Mon, 20 Feb 2006 16:15:48 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Apr 2006 13:34:07 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Hooft",
"Gerard 't",
""
],
[
"Nobbenhuis",
"Stefan",
""
]
] | In this paper we study a new symmetry argument that results in a vacuum state with strictly vanishing vacuum energy. This argument exploits the well-known feature that de Sitter and Anti- de Sitter space are related by analytic continuation. When we drop boundary and hermiticity conditions on quantum fields, we get as many negative as positive energy states, which are related by transformations to complex space. The paper does not directly solve the cosmological constant problem, but explores a new direction that appears worthwhile. |
gr-qc/9806109 | Kourosh Nozari | Reza Mansouri and Kourosh Nozari | Signature Change, Inflation, and the Cosmological Constant | 15 pages, Latex, no figures | null | null | IPM/P - 98/15 | gr-qc | null | Colombeau's generalized functions are used to adapt the distributional
approach to singular hypersurfaces in general relativity with signature change.
Equations governing the dynamics of singular hypersurface is obtained and it is
shown that matching leads to de Sitter space for the Lorentzian region. The
matching is possible for different sections of the de Sitter hyperboloid. A
relation between the radius of $S^4$, as the Euclidean manifold, and the
cosmological constant leading to inflation after signature change is obtained.
| [
{
"created": "Sat, 27 Jun 1998 06:57:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mansouri",
"Reza",
""
],
[
"Nozari",
"Kourosh",
""
]
] | Colombeau's generalized functions are used to adapt the distributional approach to singular hypersurfaces in general relativity with signature change. Equations governing the dynamics of singular hypersurface is obtained and it is shown that matching leads to de Sitter space for the Lorentzian region. The matching is possible for different sections of the de Sitter hyperboloid. A relation between the radius of $S^4$, as the Euclidean manifold, and the cosmological constant leading to inflation after signature change is obtained. |
2207.10202 | Tetsuya Shiromizu | Tetsuya Shiromizu, Keisuke Izumi, Kangjae Lee and Diego Soligon | Maximum size of black holes in our accelerating Universe | 8 pages, minor corrections, to apper in PRD | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In accordance with current models of the accelerating Universe as a spacetime
with a positive cosmological constant, new results about a cosmological upper
bound for the area of stable marginally outer trapped surfaces are found taking
into account angular momentum, gravitational waves and matter. Compared to
previous results which take into account only some of the aforementioned
variables, the bound is found to be tighter, giving a concrete limit to the
size of black holes especially relevant in the early Universe.
| [
{
"created": "Wed, 20 Jul 2022 21:41:43 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2022 06:20:42 GMT",
"version": "v2"
}
] | 2022-10-11 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Izumi",
"Keisuke",
""
],
[
"Lee",
"Kangjae",
""
],
[
"Soligon",
"Diego",
""
]
] | In accordance with current models of the accelerating Universe as a spacetime with a positive cosmological constant, new results about a cosmological upper bound for the area of stable marginally outer trapped surfaces are found taking into account angular momentum, gravitational waves and matter. Compared to previous results which take into account only some of the aforementioned variables, the bound is found to be tighter, giving a concrete limit to the size of black holes especially relevant in the early Universe. |
1504.05818 | A. N. Ivanov | A. N. Ivanov and M. Wellenzohn | Standard Electroweak Interactions in Gravitational Theory with Chameleon
Field and Torsion | 26 pages, 8 figures | Phys. Rev. D 91, 085025 (2015) | 10.1103/PhysRevD.91.085025 | null | gr-qc hep-ph nucl-ex | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a version of a gravitational theory with the torsion field,
induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141
(1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised
by extending the Einstein gravity to the Einstein-Cartan gravity with the
torsion field as a gradient of the chameleon field through a modification of
local gauge invariance of minimal coupling in the Weinberg-Salam electroweak
model. The contributions of the chameleon (torsion) field to the observables of
electromagnetic and weak processes are calculated. Since in our approach the
chameleon-photon coupling constant beta_(gamma) is equal to the
chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the
experimental constraints on beta, obtained in terrestrial laboratories by T.
Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al.
(Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical
sources of chameleons, proposed by C. Burrage et al. (Phys. Rev. D79, 044028
(2009)), A.-Ch. Davis et al. (Phys. Rev. D80, 064016 (2009), and in references
therein, where chameleons induce photons because of direct chameleon-photon
transitions in the magnetic fields.
| [
{
"created": "Wed, 22 Apr 2015 14:18:49 GMT",
"version": "v1"
}
] | 2015-04-23 | [
[
"Ivanov",
"A. N.",
""
],
[
"Wellenzohn",
"M.",
""
]
] | We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. (Phys. Rev. D79, 044028 (2009)), A.-Ch. Davis et al. (Phys. Rev. D80, 064016 (2009), and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields. |
1312.7684 | Farook Rahaman | Farook Rahaman, Ayan Banerjee, Mubasher Jamil, Anil Kumar Yadav,
Humaira Idris | Noncommutative Wormholes in $f(R)$ Gravity with Lorentzian Distribution | 9 apges 4 groups of plots. Accepted in Int.J.Theor.Phys | Int.J.Theor.Phys. (2014) 53:1910-1919 | 10.1007/s10773-013-1993-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we derive some new exact solutions of static wormholes in
$f(R)$ gravity supported by the matter possesses Lorentizian density
distribution of a particle-like gravitational source. We derive the wormhole's
solutions in two possible schemes for a given Lorentzian distribution: assuming
an astrophysically viable $F(R)$ function such as a power-law form and discuss
several solutions corresponding to different values of the exponent (here $F
=\frac{df}{dR}$). In the second scheme, we consider particular form of two
shape functions and have reconstructed f(R) in both cases. We have discussed
all the solutions with graphical point of view.
| [
{
"created": "Mon, 30 Dec 2013 11:38:12 GMT",
"version": "v1"
}
] | 2015-01-28 | [
[
"Rahaman",
"Farook",
""
],
[
"Banerjee",
"Ayan",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Yadav",
"Anil Kumar",
""
],
[
"Idris",
"Humaira",
""
]
] | In this paper, we derive some new exact solutions of static wormholes in $f(R)$ gravity supported by the matter possesses Lorentizian density distribution of a particle-like gravitational source. We derive the wormhole's solutions in two possible schemes for a given Lorentzian distribution: assuming an astrophysically viable $F(R)$ function such as a power-law form and discuss several solutions corresponding to different values of the exponent (here $F =\frac{df}{dR}$). In the second scheme, we consider particular form of two shape functions and have reconstructed f(R) in both cases. We have discussed all the solutions with graphical point of view. |
gr-qc/0607118 | Alvaro De La Cruz-Dombriz | A. de la Cruz-Dombriz and A. Dobado | A f(R) gravity without cosmological constant | 5 pages, no figures | Phys.Rev. D74 (2006) 087501 | 10.1103/PhysRevD.74.087501 | null | gr-qc | null | In this work we consider the possibility of describing the current evolution
of the universe, without the introduction of any cosmological constant or dark
energy (DE), by modifying the Einstein-Hilbert (EH) action. In the context of
the f(R) gravities within the metric formalism, we show that it is possible to
find an action without cosmological constant which exactly reproduces the
behavior of the EH action with cosmological constant. In addition the f(R)
action is analytical at the origin having Minkowski and Schwarzschild as vacuum
solutions. The found f(R) action is highly non-trivial and must be written in
terms of hypergeometric functions but, in spite of looking somewhat artificial,
it shows that the cosmological constant, or more generally the DE, is not a
logical necessity.
| [
{
"created": "Wed, 26 Jul 2006 12:19:06 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"de la Cruz-Dombriz",
"A.",
""
],
[
"Dobado",
"A.",
""
]
] | In this work we consider the possibility of describing the current evolution of the universe, without the introduction of any cosmological constant or dark energy (DE), by modifying the Einstein-Hilbert (EH) action. In the context of the f(R) gravities within the metric formalism, we show that it is possible to find an action without cosmological constant which exactly reproduces the behavior of the EH action with cosmological constant. In addition the f(R) action is analytical at the origin having Minkowski and Schwarzschild as vacuum solutions. The found f(R) action is highly non-trivial and must be written in terms of hypergeometric functions but, in spite of looking somewhat artificial, it shows that the cosmological constant, or more generally the DE, is not a logical necessity. |
2211.03092 | Yakov Itin | Yakov Itin | Hilbert's energy-momentum tensor extended | null | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | A variational derivative of a Lagrangian with regard to the metric tensor is
used in classical field models to define Hilbert's energy-momentum tensor for a
matter field. In solid-state physics, constitutive relationships between
fundamental field variables are a topic that is covered by a broad variety of
models. In this context, a constitutive tensor of higher order replaces the of
the second-order metric tensor. For the classical field models of gravity and
electrodynamics, a similar premetric description with a linear constitutive
relation has recently presented. In this paper, we analyze the extension of the
Hilbert definition of the energy-momentum tensor to models with general linear
constitutive law. Differential forms are required for the covariant treatment
of integrals on a differential manifold. The Lagrangian, electromagnetic
current, and energy-momentum current must all be represented as twisted
4-forms, 3-forms, and vector-valued 3-forms, respectively. For an arbitrary
linear map on forms, we derive a commutative variation identity that allows
direct variation procedures without having to deal with the individual
components. One can deal with Maxwell-type Lagrangians in any dimension by
restricting the linear map to the generalized Hodge dual map (constitutive
law). The Hilbert energy-momentum current, which is defined as a variation
derivative of the Lagrangian with regard to a coframe field, is derived in
differential form. It is demonstrated that the commutative variation identity
is closely connected to the explicit form of the energy-momentum current. This
construction is applied to a number of field models having a general linear
constitutive law.
| [
{
"created": "Sun, 6 Nov 2022 11:54:52 GMT",
"version": "v1"
}
] | 2022-11-08 | [
[
"Itin",
"Yakov",
""
]
] | A variational derivative of a Lagrangian with regard to the metric tensor is used in classical field models to define Hilbert's energy-momentum tensor for a matter field. In solid-state physics, constitutive relationships between fundamental field variables are a topic that is covered by a broad variety of models. In this context, a constitutive tensor of higher order replaces the of the second-order metric tensor. For the classical field models of gravity and electrodynamics, a similar premetric description with a linear constitutive relation has recently presented. In this paper, we analyze the extension of the Hilbert definition of the energy-momentum tensor to models with general linear constitutive law. Differential forms are required for the covariant treatment of integrals on a differential manifold. The Lagrangian, electromagnetic current, and energy-momentum current must all be represented as twisted 4-forms, 3-forms, and vector-valued 3-forms, respectively. For an arbitrary linear map on forms, we derive a commutative variation identity that allows direct variation procedures without having to deal with the individual components. One can deal with Maxwell-type Lagrangians in any dimension by restricting the linear map to the generalized Hodge dual map (constitutive law). The Hilbert energy-momentum current, which is defined as a variation derivative of the Lagrangian with regard to a coframe field, is derived in differential form. It is demonstrated that the commutative variation identity is closely connected to the explicit form of the energy-momentum current. This construction is applied to a number of field models having a general linear constitutive law. |
2107.12735 | Diego Cruces Mateo | Diego Cruces and Cristiano Germani | Stochastic inflation at all order in slow-roll parameters: foundations | 38 pages, 11 figures, typos corrected, ref added, results unchanged,
accepted in Physical Review D | null | 10.1103/PhysRevD.105.023533 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we develop the formalism for the stochastic approach to
inflation at all order in slow-roll parameters. This is done by including the
momentum and Hamiltonian constraints into the stochastic equations. We then
specialise to the widely used Starobinski approximation where interactions
between IR and UV modes are neglected. We show that, whenever this
approximation holds, no significant deviations are observed when comparing the
two-point correlation functions (power spectrum) calculated with stochastic
methods, to the ones calculated with the QFT approach to linear theory. As a
byproduct, we argue that: a) the approaches based on the Starobinski
approximation, generically, do not capture any loop effects of the quantum
scalar-gravity system; b) correlations functions can only be calculated in the
linear theory regimes, thus, no non-perturbative statistics can be extracted
within this approximation, as commonly claimed.
| [
{
"created": "Tue, 27 Jul 2021 11:29:25 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2022 20:12:10 GMT",
"version": "v2"
}
] | 2022-02-09 | [
[
"Cruces",
"Diego",
""
],
[
"Germani",
"Cristiano",
""
]
] | In this paper we develop the formalism for the stochastic approach to inflation at all order in slow-roll parameters. This is done by including the momentum and Hamiltonian constraints into the stochastic equations. We then specialise to the widely used Starobinski approximation where interactions between IR and UV modes are neglected. We show that, whenever this approximation holds, no significant deviations are observed when comparing the two-point correlation functions (power spectrum) calculated with stochastic methods, to the ones calculated with the QFT approach to linear theory. As a byproduct, we argue that: a) the approaches based on the Starobinski approximation, generically, do not capture any loop effects of the quantum scalar-gravity system; b) correlations functions can only be calculated in the linear theory regimes, thus, no non-perturbative statistics can be extracted within this approximation, as commonly claimed. |
1411.1077 | Steffen Gielen | Steffen Gielen | Perturbing a quantum gravity condensate | 10 pages, APS style, revtex; v2: more discussion and references
added, unchanged results, v3: minor changes to match journal version | Phys. Rev. D 91, 043526 (2015) | 10.1103/PhysRevD.91.043526 | Imperial/TP/2014/SG/1 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent proposal using the group field theory approach, a spatially
homogeneous (generally anisotropic) universe is described as a quantum gravity
condensate of "atoms of space," which allows the derivation of an effective
cosmological Friedmann equation from the microscopic quantum gravity dynamics.
Here we take a first step towards the study of cosmological perturbations over
the homogeneous background. We consider a state in which a single "atom" is
added to an otherwise homogeneous condensate. Backreaction of the perturbation
on the background is negligible and the background dynamics can be solved
separately. The dynamics for the perturbation takes the form of a quantum
cosmology Hamiltonian for a "wave function," depending on background and
perturbations, of the product form usually assumed in a Born-Oppenheimer
approximation. We show that the perturbation we consider corresponds to a
spatially homogeneous metric perturbation, and for this case derive the usual
procedures in quantum cosmology from fundamental quantum gravity.
| [
{
"created": "Tue, 4 Nov 2014 21:04:22 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jan 2015 19:34:19 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Feb 2015 19:40:25 GMT",
"version": "v3"
}
] | 2015-02-23 | [
[
"Gielen",
"Steffen",
""
]
] | In a recent proposal using the group field theory approach, a spatially homogeneous (generally anisotropic) universe is described as a quantum gravity condensate of "atoms of space," which allows the derivation of an effective cosmological Friedmann equation from the microscopic quantum gravity dynamics. Here we take a first step towards the study of cosmological perturbations over the homogeneous background. We consider a state in which a single "atom" is added to an otherwise homogeneous condensate. Backreaction of the perturbation on the background is negligible and the background dynamics can be solved separately. The dynamics for the perturbation takes the form of a quantum cosmology Hamiltonian for a "wave function," depending on background and perturbations, of the product form usually assumed in a Born-Oppenheimer approximation. We show that the perturbation we consider corresponds to a spatially homogeneous metric perturbation, and for this case derive the usual procedures in quantum cosmology from fundamental quantum gravity. |
1201.6672 | Abel Camacho Mr. | A. Camacho (Departamento de F\'isica, Universidad Aut\'onoma
Metropolitana--Iztapalapa, M\'exico) E. Castellanos (ZARM, Universit\"at
Bremen, Am Fallturm, Bremen, Germany) | Ultra--cold gases and the detection of the Earth's rotation: Bogoliubov
space and gravitomagnetism | 4 pages | null | 10.1142/S0217732312501982 | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work analyzes the consequences of the gravitomagnetic effect of
the Earth upon a bosonic gas in which the corresponding atoms have a
non--vanishing orbital angular momentum. Concerning the ground state of the
Bogoliubov space of this system we deduce the consequences, on the pressure and
on the speed of sound, of the gravitomagnetic effect. We prove that the effect
on a single atom is very small, but we also show that for some thermodynamical
properties the consequences scale as a non--trivial function of the number of
particles.
| [
{
"created": "Tue, 31 Jan 2012 20:23:05 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Camacho",
"A.",
"",
"Departamento de Física, Universidad Autónoma\n Metropolitana--Iztapalapa, México"
],
[
"Castellanos",
"E.",
"",
"ZARM, Universität\n Bremen, Am Fallturm, Bremen, Germany"
]
] | The present work analyzes the consequences of the gravitomagnetic effect of the Earth upon a bosonic gas in which the corresponding atoms have a non--vanishing orbital angular momentum. Concerning the ground state of the Bogoliubov space of this system we deduce the consequences, on the pressure and on the speed of sound, of the gravitomagnetic effect. We prove that the effect on a single atom is very small, but we also show that for some thermodynamical properties the consequences scale as a non--trivial function of the number of particles. |
2210.00837 | Athanasios Lahanas | A. B. Lahanas | Issues in Palatini ${\cal{R}}^2$ inflation: Bounds on the Reheating
Temperature | 35 pages, 18 figures, PDFLaTeX, text and references added, typos
corrected | null | 10.1103/PhysRevD.106.123530 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider ${\cal{R}}^2$-inflation in Palatini gravity, in the presence of
scalar fields coupled to gravity. These theories, in the Einstein frame, and
for one scalar field $h$, share common features with $K$ - inflation models. We
apply this formalism for the study of single-field inflationary models, whose
potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer.
We also study the Higgs model non-minimally coupled to gravity. With
${\cal{R}}^2$-terms coupled to gravity as $\sim \alpha {\cal{R}}^2 $, with
$\alpha$ constant, the instantaneous reheating temperature $T_{ins}$, is
bounded by $ T_{ins} \leq { 0.290 \, m_{Planck}} / {\, \alpha^{1/4}} $, with
the upper bound being saturated for large $\alpha$. For such large $\alpha$
need go beyond slow-roll to calculate reliably the cosmological parameters,
among these the end of inflation through which $T_{ins}$ is determined. In
fact, as inflaton rolls towards the end of inflation point, the quartic in the
velocity terms, unavoidable in Palatini gravity, play a significant role and
can not be ignored. The values of $\alpha$, and other parameters, are
constrained by cosmological data, setting bounds on the inflationary scale
$M_{s} \sim 1/\sqrt{\alpha}$ and the reheating temperature of the Universe.
| [
{
"created": "Mon, 3 Oct 2022 11:55:34 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Oct 2022 10:50:00 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Dec 2022 10:09:08 GMT",
"version": "v3"
}
] | 2023-01-11 | [
[
"Lahanas",
"A. B.",
""
]
] | We consider ${\cal{R}}^2$-inflation in Palatini gravity, in the presence of scalar fields coupled to gravity. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ - inflation models. We apply this formalism for the study of single-field inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. With ${\cal{R}}^2$-terms coupled to gravity as $\sim \alpha {\cal{R}}^2 $, with $\alpha$ constant, the instantaneous reheating temperature $T_{ins}$, is bounded by $ T_{ins} \leq { 0.290 \, m_{Planck}} / {\, \alpha^{1/4}} $, with the upper bound being saturated for large $\alpha$. For such large $\alpha$ need go beyond slow-roll to calculate reliably the cosmological parameters, among these the end of inflation through which $T_{ins}$ is determined. In fact, as inflaton rolls towards the end of inflation point, the quartic in the velocity terms, unavoidable in Palatini gravity, play a significant role and can not be ignored. The values of $\alpha$, and other parameters, are constrained by cosmological data, setting bounds on the inflationary scale $M_{s} \sim 1/\sqrt{\alpha}$ and the reheating temperature of the Universe. |
0904.2546 | Pablo Hernan Pereyra | P. H. Pereyra | The Schwarzschild Static Cosmological Model | 10 pages, 5 figures | Int.J.Mod.Phys.D16:553-562,2007 | 10.1142/S0218271807010390 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work describes an immersion in 5D of the interior Schwarzschild
solution of the general relativity equations. The model theory is defined in
the context of a flat 5D space time matter Minkowski model, using a Tolman like
technique, which shows via Lorentz transformations that the solution is
compatible with homogeneity and isotropy,thus obeying the cosmological
principle. These properties permit one to consider the solution in terms of a
cosmological model. In this model, the Universe may be treated as an idealized
star with constant density and variable pressure, where each observer can be
the center of the same. The observed redshift appears as a static gravitational
effect which obeys the sufficiently verified and generally accepted square
distance law. The Buchdahl stability theorem establishes a limit of distance
observation with density dependence.
| [
{
"created": "Thu, 16 Apr 2009 17:36:23 GMT",
"version": "v1"
}
] | 2009-04-21 | [
[
"Pereyra",
"P. H.",
""
]
] | The present work describes an immersion in 5D of the interior Schwarzschild solution of the general relativity equations. The model theory is defined in the context of a flat 5D space time matter Minkowski model, using a Tolman like technique, which shows via Lorentz transformations that the solution is compatible with homogeneity and isotropy,thus obeying the cosmological principle. These properties permit one to consider the solution in terms of a cosmological model. In this model, the Universe may be treated as an idealized star with constant density and variable pressure, where each observer can be the center of the same. The observed redshift appears as a static gravitational effect which obeys the sufficiently verified and generally accepted square distance law. The Buchdahl stability theorem establishes a limit of distance observation with density dependence. |
0706.0466 | Aleksandar Mikovic | A. Mikovic | Spin Network Wavefunction and the Graviton Propagator | 8 pages | null | 10.1002/prop.200710522 | null | gr-qc | null | We show that if the flat-spacetime wavefunction in the spin network basis of
Loop Quantum Gravity has a large-spin asymptotics given by Rovelli's ansatz
then the corresponding graviton propagator has the correct large-distance
asymptotics nonperturbatively and independently of the spin foam model used to
describe the evolution operator. We also argue that even in the Rovelli
approach the wavefunction should satisfy the Hamiltonian constraint and we give
an explanation for the spin parameter appearing in Rovelli's ansatz.
| [
{
"created": "Mon, 4 Jun 2007 16:05:06 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Mikovic",
"A.",
""
]
] | We show that if the flat-spacetime wavefunction in the spin network basis of Loop Quantum Gravity has a large-spin asymptotics given by Rovelli's ansatz then the corresponding graviton propagator has the correct large-distance asymptotics nonperturbatively and independently of the spin foam model used to describe the evolution operator. We also argue that even in the Rovelli approach the wavefunction should satisfy the Hamiltonian constraint and we give an explanation for the spin parameter appearing in Rovelli's ansatz. |
1412.8124 | Sunil Maharaj | P. Mafa Takisa, S. D. Maharaj, Subharthi Ray | Stellar objects in the quadratic regime | 8 pages, Submitted for publication | Astrophys. Space Sci. 354: 463-470 (2014) | 10.1007/s10509-014-2120-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We model a charged anisotropic relativistic star with a quadratic equation of
state. Physical features of an exact solution of the Einstein-Maxwell system
are studied by incorporating the effect of the nonlinear term from the equation
of state. It is possible to regain the masses, radii and central densities for
a linear equation of state in our analysis. We generate masses for stellar
compact objects and perform a detailed study of PSR J1614-2230 in particular.
We also show the influence of the nonlinear equation of state on physical
features of the matter distribution. We demonstrate that it is possible to
incorporate the effects of charge, anisotropy and a quadratic term in the
equation of state in modelling a compact relativistic body.
| [
{
"created": "Sun, 28 Dec 2014 07:29:05 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Takisa",
"P. Mafa",
""
],
[
"Maharaj",
"S. D.",
""
],
[
"Ray",
"Subharthi",
""
]
] | We model a charged anisotropic relativistic star with a quadratic equation of state. Physical features of an exact solution of the Einstein-Maxwell system are studied by incorporating the effect of the nonlinear term from the equation of state. It is possible to regain the masses, radii and central densities for a linear equation of state in our analysis. We generate masses for stellar compact objects and perform a detailed study of PSR J1614-2230 in particular. We also show the influence of the nonlinear equation of state on physical features of the matter distribution. We demonstrate that it is possible to incorporate the effects of charge, anisotropy and a quadratic term in the equation of state in modelling a compact relativistic body. |
1905.02622 | Haryanto Siahaan | Haryanto M. Siahaan | Kerr-Sen-Taub-NUT spacetime and circular geodesics | 20 pages, 7 figures;V3, minor revisions; V2, refs added | null | 10.1140/epjc/s10052-020-08561-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel solution obeying classical equation of motion in the low
energy limit of heterotic string theory. The solution represents a rotating
mass with electric charge and gravitomagnetic monopole moment. The
corresponding conserved charges are discussed. We also study the test body
circular equatorial motions in the spacetime.
| [
{
"created": "Tue, 7 May 2019 14:50:49 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jun 2019 19:25:47 GMT",
"version": "v2"
},
{
"created": "Tue, 5 May 2020 09:05:17 GMT",
"version": "v3"
},
{
"created": "Sat, 23 May 2020 08:45:53 GMT",
"version": "v4"
}
] | 2020-12-02 | [
[
"Siahaan",
"Haryanto M.",
""
]
] | We present a novel solution obeying classical equation of motion in the low energy limit of heterotic string theory. The solution represents a rotating mass with electric charge and gravitomagnetic monopole moment. The corresponding conserved charges are discussed. We also study the test body circular equatorial motions in the spacetime. |
1507.01281 | Stanley P. Gudder | Stan Gudder | Inflation and Dirac in the Causal Set Approach to Discrete Quantum
Gravity | 23 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this approach to discrete quantum gravity the basic structural element is
a covariant causal set ($c$-causet). The geometry of a $c$-causet is described
by a shell-sequence that determines the discrete gravity of a universe. In this
growth model, universes evolve in discrete time by adding new vertices to their
generating $c$-causet. We first describe an inflationary period that is common
to all universes. After this very brief cycle, the model enters a multiverse
period in which the system diverges in various ways forming paths of
$c$-causets. At the beginning of the multiverse period, the structure of a
four-dimensional discrete manifold emerges and quantum mechanics enters the
picture. A natural Hilbert space is defined and a discrete, free Dirac operator
is introduced. We determine the eigenvalues and eigenvectors of this operator.
Finally, we propose values for coupling constants that determine multiverse
probabilities. These probabilities predict the dominance of pulsating
universes.
| [
{
"created": "Sun, 5 Jul 2015 21:55:14 GMT",
"version": "v1"
}
] | 2015-07-07 | [
[
"Gudder",
"Stan",
""
]
] | In this approach to discrete quantum gravity the basic structural element is a covariant causal set ($c$-causet). The geometry of a $c$-causet is described by a shell-sequence that determines the discrete gravity of a universe. In this growth model, universes evolve in discrete time by adding new vertices to their generating $c$-causet. We first describe an inflationary period that is common to all universes. After this very brief cycle, the model enters a multiverse period in which the system diverges in various ways forming paths of $c$-causets. At the beginning of the multiverse period, the structure of a four-dimensional discrete manifold emerges and quantum mechanics enters the picture. A natural Hilbert space is defined and a discrete, free Dirac operator is introduced. We determine the eigenvalues and eigenvectors of this operator. Finally, we propose values for coupling constants that determine multiverse probabilities. These probabilities predict the dominance of pulsating universes. |
gr-qc/0003068 | Pawel Zieba | W. Rudnicki, P. Zieba | On the strength of the Kerr singularity and cosmic censorship | RevTeX, 6 pages, no figures, to appear in Phys. Lett. A | Phys.Lett. A268 (2000) 228-234 | 10.1016/S0375-9601(00)00185-7 | null | gr-qc | null | It has been suggested by Israel that the Kerr singularity cannot be strong in
the sense of Tipler, for it tends to cause repulsive effects. We show here
that, contrary to that suggestion, nearly all null geodesics reaching this
singularity do in fact terminate in Tipler's strong curvature singularity.
Implications of this result are discussed in the context of an earlier cosmic
censorship theorem which constraints the occurrence of Kerr-like naked
singularities in generic collapse situations.
| [
{
"created": "Thu, 16 Mar 2000 14:06:42 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Rudnicki",
"W.",
""
],
[
"Zieba",
"P.",
""
]
] | It has been suggested by Israel that the Kerr singularity cannot be strong in the sense of Tipler, for it tends to cause repulsive effects. We show here that, contrary to that suggestion, nearly all null geodesics reaching this singularity do in fact terminate in Tipler's strong curvature singularity. Implications of this result are discussed in the context of an earlier cosmic censorship theorem which constraints the occurrence of Kerr-like naked singularities in generic collapse situations. |
1812.07168 | Pujian Mao | Pujian Mao and Xiaoning Wu | More on gravitational memory | v3: presentation improved, discussion extended, typos corrected,
refs. added v4: typos corrected | JHEP 05 (2019) 058 | 10.1007/JHEP05(2019)058 | CJQS-2019-014 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two novel results for the gravitational memory effect are presented in this
paper. We first extend the formula for the memory effect to solutions with
arbitrary two surface boundary topology. The memory effect for the
Robinson-Trautman solution is obtained in its standard form. Then we propose a
new observational effect for the spin memory. It is a time delay of time-like
free falling observers.
| [
{
"created": "Tue, 18 Dec 2018 04:49:01 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jan 2019 05:47:36 GMT",
"version": "v2"
},
{
"created": "Fri, 10 May 2019 14:13:42 GMT",
"version": "v3"
},
{
"created": "Thu, 10 Oct 2019 05:59:02 GMT",
"version": "v4"
}
] | 2020-11-24 | [
[
"Mao",
"Pujian",
""
],
[
"Wu",
"Xiaoning",
""
]
] | Two novel results for the gravitational memory effect are presented in this paper. We first extend the formula for the memory effect to solutions with arbitrary two surface boundary topology. The memory effect for the Robinson-Trautman solution is obtained in its standard form. Then we propose a new observational effect for the spin memory. It is a time delay of time-like free falling observers. |
1011.3126 | Alexander Agathonov | Yurii Ignatyev and Alexander Agathonov | Exact Solutions of the Self-consistent System of Relativistic
Magnetohydrodynamics Equations for an Anisotropic Plasma on the Background of
Bondi-Pirani-Robinson's Metric | 20 pages | null | null | null | gr-qc physics.plasm-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exact solutions of the self-consistent relativistic magnetohydrodynamics
equations for an anisotropic magnetized plasma on the background of
Bondi-Pirani-Robinson's vacuum plane gravitational wave (PGW) metric with an
arbitrary polarization are obtained, which generalize the results obtained
earlier by one of the authors for the transverse polarization of a
gravitational wave. Based on the reformulated energobalance equation it is
shown that in the linear approximation by gravitational wave amplitude only the
transverse polarization of PGW interacts with magnetized plasma.
| [
{
"created": "Sat, 13 Nov 2010 11:28:32 GMT",
"version": "v1"
}
] | 2010-11-16 | [
[
"Ignatyev",
"Yurii",
""
],
[
"Agathonov",
"Alexander",
""
]
] | Exact solutions of the self-consistent relativistic magnetohydrodynamics equations for an anisotropic magnetized plasma on the background of Bondi-Pirani-Robinson's vacuum plane gravitational wave (PGW) metric with an arbitrary polarization are obtained, which generalize the results obtained earlier by one of the authors for the transverse polarization of a gravitational wave. Based on the reformulated energobalance equation it is shown that in the linear approximation by gravitational wave amplitude only the transverse polarization of PGW interacts with magnetized plasma. |
1712.00577 | Inyong Cho | Inyong Cho | Fluid Black Holes with Electric Field | 11 pages, 6 figures. Version to appear in EPJC | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gravitational field of static perfect-fluid in the
presence of electric field. We adopt the equation of state $p(r)=-\rho(r)/3$
for the fluid in order to consider the closed ($S_3$) or the open ($H_3$)
background spatial topology. Depending on the scales of the mass,
spatial-curvature and charge parameters ($K$, $R_0$, $Q$), there are several
types of solutions in $S_3$ and $H_3$ classes. Out of them, the most
interesting solution is the Reisner-Norstr\"om type of black hole. Due to the
electric field, there are two horizons in the geometry. There exists a
curvature singularity inside the inner horizon as usual. In addition, there
exists a naked singularity at the antipodal point in $S_3$ outside the outer
horizon due to the fluid. Both of the singularities can be accessed only by
radial null rays.
| [
{
"created": "Sat, 2 Dec 2017 09:23:39 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jan 2019 05:14:48 GMT",
"version": "v2"
}
] | 2019-01-21 | [
[
"Cho",
"Inyong",
""
]
] | We investigate the gravitational field of static perfect-fluid in the presence of electric field. We adopt the equation of state $p(r)=-\rho(r)/3$ for the fluid in order to consider the closed ($S_3$) or the open ($H_3$) background spatial topology. Depending on the scales of the mass, spatial-curvature and charge parameters ($K$, $R_0$, $Q$), there are several types of solutions in $S_3$ and $H_3$ classes. Out of them, the most interesting solution is the Reisner-Norstr\"om type of black hole. Due to the electric field, there are two horizons in the geometry. There exists a curvature singularity inside the inner horizon as usual. In addition, there exists a naked singularity at the antipodal point in $S_3$ outside the outer horizon due to the fluid. Both of the singularities can be accessed only by radial null rays. |
1308.2770 | Olivier Minazzoli | Olivier Minazzoli and Aur\'elien Hees | Intrinsic Solar System decoupling of a scalar-tensor theory with a
universal coupling between the scalar field and the matter Lagrangian | Accepted for publication in Phys. Rev. D. 6 pages | Phys. Rev. D 88, 041504 (2013) | 10.1103/PhysRevD.88.041504 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this communication, we present a class of Brans-Dicke-like theories with a
universal coupling between the scalar field and the matter Lagrangian. We show
this class of theories naturally exhibits a decoupling mechanism between the
scalar field and matter. As a consequence, this coupling leads to almost the
same phenomenology as general relativity in the Solar System: the trajectories
of massive bodies and the light propagation differ from general relativity only
at the second post-Newtonian order. Deviations from general relativity are
beyond present detection capabilities. However, this class of theories predicts
a deviation of the gravitational redshift at a level detectable by the future
ACES and STE/QUEST missions.
| [
{
"created": "Tue, 13 Aug 2013 07:10:42 GMT",
"version": "v1"
}
] | 2013-09-03 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Hees",
"Aurélien",
""
]
] | In this communication, we present a class of Brans-Dicke-like theories with a universal coupling between the scalar field and the matter Lagrangian. We show this class of theories naturally exhibits a decoupling mechanism between the scalar field and matter. As a consequence, this coupling leads to almost the same phenomenology as general relativity in the Solar System: the trajectories of massive bodies and the light propagation differ from general relativity only at the second post-Newtonian order. Deviations from general relativity are beyond present detection capabilities. However, this class of theories predicts a deviation of the gravitational redshift at a level detectable by the future ACES and STE/QUEST missions. |
gr-qc/0107054 | Sergio M. C. V. Goncalves | Sergio M. C. V. Goncalves (Caltech) and Sanjay Jhingan (YITP, Japan) | Singularities in gravitational collapse with radial pressure | to appear in GRG; LaTeX, 22 pages, 2 eps figures | Gen.Rel.Grav.33:2125-2149,2001 | 10.1023/A:1015285531320 | null | gr-qc | null | We analyze spherical dust collapse with non-vanishing radial pressure, $\Pi$,
and vanishing tangential stresses. Considering a barotropic equation of state,
$\Pi=\gamma\rho$, we obtain an analytical solution in closed form---which is
exact for $\gamma=-1,0$, and approximate otherwise---near the center of
symmetry (where the curvature singularity forms). We study the formation,
visibility, and curvature strength of singularities in the resulting spacetime.
We find that visible, Tipler strong singularities can develop from generic
initial data. Radial pressure alters the spectrum of possible endstates for
collapse, increasing the parameter space region that contains no visible
singularities, but cannot by itself prevent the formation of visible
singularities for sufficiently low values of the energy density. Known results
from pressureless dust are recovered in the $\gamma=0$ limit.
| [
{
"created": "Mon, 16 Jul 2001 10:51:41 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Goncalves",
"Sergio M. C. V.",
"",
"Caltech"
],
[
"Jhingan",
"Sanjay",
"",
"YITP, Japan"
]
] | We analyze spherical dust collapse with non-vanishing radial pressure, $\Pi$, and vanishing tangential stresses. Considering a barotropic equation of state, $\Pi=\gamma\rho$, we obtain an analytical solution in closed form---which is exact for $\gamma=-1,0$, and approximate otherwise---near the center of symmetry (where the curvature singularity forms). We study the formation, visibility, and curvature strength of singularities in the resulting spacetime. We find that visible, Tipler strong singularities can develop from generic initial data. Radial pressure alters the spectrum of possible endstates for collapse, increasing the parameter space region that contains no visible singularities, but cannot by itself prevent the formation of visible singularities for sufficiently low values of the energy density. Known results from pressureless dust are recovered in the $\gamma=0$ limit. |
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