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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1505.05550 | Anamar\'ia Navarro | Guillermo A. Gonz\'alez, Anamar\'ia Navarro and Luis A. N\'u\~nez | Cracking in charged relativistic spheres | 14 pages, 6 eps figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the concept of cracking, we have explored the influence of density
fluctuations on isotropic and anisotropic charged matter configurations in
General Relativity with "barotropic" equations of state, $P = P(\rho)$ and
$P_{\perp}= P_{\perp}(\rho)$ and a mass-charge relation $Q=Q(\rho)$. We have
refined the idea that density fluctuations affect physical variables and their
gradients, i.e. the radial pressure and charge density gradients. It is found
that not only anisotropic charged models could present cracking (or
overturning), but also isotropic charged matter configurations could be
affected by density fluctuations.
| [
{
"created": "Wed, 20 May 2015 23:08:16 GMT",
"version": "v1"
}
] | 2015-05-22 | [
[
"González",
"Guillermo A.",
""
],
[
"Navarro",
"Anamaría",
""
],
[
"Núñez",
"Luis A.",
""
]
] | Using the concept of cracking, we have explored the influence of density fluctuations on isotropic and anisotropic charged matter configurations in General Relativity with "barotropic" equations of state, $P = P(\rho)$ and $P_{\perp}= P_{\perp}(\rho)$ and a mass-charge relation $Q=Q(\rho)$. We have refined the idea that density fluctuations affect physical variables and their gradients, i.e. the radial pressure and charge density gradients. It is found that not only anisotropic charged models could present cracking (or overturning), but also isotropic charged matter configurations could be affected by density fluctuations. |
1508.07874 | Tomislav Prokopec | Tomislav Prokopec (Utrecht) | Late time solution for interacting scalar in accelerating spaces | 13 pages | null | 10.1088/1475-7516/2015/11/016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider stochastic inflation in an interacting scalar field in spatially
homogeneous accelerating space-times with a constant principal slow roll
parameter $\epsilon$. We show that, if the scalar potential is scale invariant
(which is the case when scalar contains quartic self-interaction and couples
non-minimally to gravity), the late-time solution on accelerating FLRW spaces
can be described by a probability distribution function (PDF) $\rho$ which is a
function of $\varphi/H$ only, where $\varphi=\varphi(\vec x)$ is the scalar
field and $H=H(t)$ denotes the Hubble parameter. We give explicit late-time
solutions for $\rho\rightarrow \rho_\infty(\varphi/H)$, and thereby find the
order $\epsilon$ corrections to the Starobinsky-Yokoyama result. This PDF can
then be used to calculate e.g. various $n-$point functions of the
(self-interacting) scalar field, which are valid at late times in arbitrary
accelerating space-times with $\epsilon=$ constant.
| [
{
"created": "Mon, 31 Aug 2015 15:40:03 GMT",
"version": "v1"
}
] | 2015-11-18 | [
[
"Prokopec",
"Tomislav",
"",
"Utrecht"
]
] | We consider stochastic inflation in an interacting scalar field in spatially homogeneous accelerating space-times with a constant principal slow roll parameter $\epsilon$. We show that, if the scalar potential is scale invariant (which is the case when scalar contains quartic self-interaction and couples non-minimally to gravity), the late-time solution on accelerating FLRW spaces can be described by a probability distribution function (PDF) $\rho$ which is a function of $\varphi/H$ only, where $\varphi=\varphi(\vec x)$ is the scalar field and $H=H(t)$ denotes the Hubble parameter. We give explicit late-time solutions for $\rho\rightarrow \rho_\infty(\varphi/H)$, and thereby find the order $\epsilon$ corrections to the Starobinsky-Yokoyama result. This PDF can then be used to calculate e.g. various $n-$point functions of the (self-interacting) scalar field, which are valid at late times in arbitrary accelerating space-times with $\epsilon=$ constant. |
1601.04519 | Iver Brevik | Ben David Normann and Iver Brevik | General Bulk-Viscous Solutions and Estimates of Bulk Viscosity in the
Cosmic Fluid | 15 pages, one figure. Major revision of the manuscript; new title.
Version to appear in Entropy | Entropy, Vol. 18, article 215 (2016) | 10.3390/e18060215 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a general formalism for bulk viscous solutions of the
energy-conservation-equation for $\rho(a,\zeta)$, both for a single-component
and a multicomponent fluid in the Friedmann universe. For our purposes these
general solutions become valuable in estimating order of magnitude of the
phenomenological viscosity in the cosmic fluid at present. $H(z)$ observations
are found to put an upper limit on the magnitude of the modulus of the present
day bulk viscosity. It is found to be $\zeta_0\sim 10^6~$Pa s, in agreement
with previous works. We point out that this magnitude is acceptable from a
hydrodynamic point of view. Finally, we bring new insight by using our
estimates of $\zeta$ to analyse the fate of the future universe. Of special
interest is the case $\zeta \propto \sqrt{\rho}$ for which the fluid,
originally situated in the quintessence region, may slide through the phantom
barrier and inevitably be driven into a big rip. Typical rip times are found to
be a few hundred Gy.
| [
{
"created": "Mon, 18 Jan 2016 14:01:27 GMT",
"version": "v1"
},
{
"created": "Fri, 27 May 2016 08:05:00 GMT",
"version": "v2"
}
] | 2016-06-03 | [
[
"Normann",
"Ben David",
""
],
[
"Brevik",
"Iver",
""
]
] | We derive a general formalism for bulk viscous solutions of the energy-conservation-equation for $\rho(a,\zeta)$, both for a single-component and a multicomponent fluid in the Friedmann universe. For our purposes these general solutions become valuable in estimating order of magnitude of the phenomenological viscosity in the cosmic fluid at present. $H(z)$ observations are found to put an upper limit on the magnitude of the modulus of the present day bulk viscosity. It is found to be $\zeta_0\sim 10^6~$Pa s, in agreement with previous works. We point out that this magnitude is acceptable from a hydrodynamic point of view. Finally, we bring new insight by using our estimates of $\zeta$ to analyse the fate of the future universe. Of special interest is the case $\zeta \propto \sqrt{\rho}$ for which the fluid, originally situated in the quintessence region, may slide through the phantom barrier and inevitably be driven into a big rip. Typical rip times are found to be a few hundred Gy. |
1808.09749 | Reetika Dudi | Reetika Dudi, Francesco Pannarale, Tim Dietrich, Mark Hannam,
Sebastiano Bernuzzi, Frank Ohme, Bernd Bruegmann | Relevance of tidal effects and post-merger dynamics for binary neutron
star parameter estimation | null | Phys. Rev. D 98, 084061 (2018) | 10.1103/PhysRevD.98.084061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Measurements of the properties of binary neutron star systems from
gravitational-wave observations require accurate theoretical models for such
signals. However, current models are incomplete, as they do not take into
account all of the physics of these systems: some neglect possible tidal
effects, others neglect spin-induced orbital precession, and no existing model
includes the post-merger regime consistently. In this work, we explore the
importance of two physical ingredients: tidal interactions during the inspiral
and the imprint of the post-merger stage. We use complete
inspiral--merger--post-merger waveforms constructed from a tidal
effective-one-body approach and numerical-relativity simulations as signals
against which we perform parameter estimates with waveform models of standard
LIGO-Virgo analyses. We show that neglecting tidal effects does not lead to
appreciable measurement biases in masses and spin for typical observations
(small tidal deformability and signal-to-noise ratio $\sim$ 25). However, with
increasing signal-to-noise ratio or tidal deformability there are biases in the
estimates of the binary parameters. The post-merger regime, instead, has no
impact on gravitational-wave measurements with current detectors for the
signal-to-noise ratios we consider.
| [
{
"created": "Wed, 29 Aug 2018 12:13:53 GMT",
"version": "v1"
}
] | 2018-11-07 | [
[
"Dudi",
"Reetika",
""
],
[
"Pannarale",
"Francesco",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Hannam",
"Mark",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Ohme",
"Frank",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | Measurements of the properties of binary neutron star systems from gravitational-wave observations require accurate theoretical models for such signals. However, current models are incomplete, as they do not take into account all of the physics of these systems: some neglect possible tidal effects, others neglect spin-induced orbital precession, and no existing model includes the post-merger regime consistently. In this work, we explore the importance of two physical ingredients: tidal interactions during the inspiral and the imprint of the post-merger stage. We use complete inspiral--merger--post-merger waveforms constructed from a tidal effective-one-body approach and numerical-relativity simulations as signals against which we perform parameter estimates with waveform models of standard LIGO-Virgo analyses. We show that neglecting tidal effects does not lead to appreciable measurement biases in masses and spin for typical observations (small tidal deformability and signal-to-noise ratio $\sim$ 25). However, with increasing signal-to-noise ratio or tidal deformability there are biases in the estimates of the binary parameters. The post-merger regime, instead, has no impact on gravitational-wave measurements with current detectors for the signal-to-noise ratios we consider. |
2309.01794 | Kirill Bronnikov | Kirill A. Bronnikov, Sergei V. Bolokhov, Milena V. Skvortsova, Kodir
Badalov, Rustam Ibadov | On the stability of spherically symmetric space-times in scalar-tensor
gravity | 16 pages, 4 figures, each of 2 parts. Minor corrections, matching to
the journal version | Grav. Cosmol. 29 (4), 374-386 (2023) | 10.1134/S0202289323040059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the linear stability of vacuum static, spherically symmetric
solutions to the gravitational field equations of the
Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories (STT) of gravity,
restricting ourselves to nonphantom theories, massless scalar fields and
configurations with positive Schwarzschild mass. We consider only small radial
(monopole) perturbations as the ones most likely to cause an instability. The
problem reduces to the same Schroedinger-like master equation as is known for
perturbations of Fisher's solution of general relativity (GR), but the
corresponding boundary conditions that affect the final result of the study
depend on the choice of the STT and a particular solution within it. The
stability or instability conclusions are obtained for the Brans-Dicke, Barker
and Schwinger STT as well as for GR nonminimally coupled to a scalar field with
an arbitrary parameter $\xi$.
| [
{
"created": "Mon, 4 Sep 2023 20:10:58 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Nov 2023 11:06:12 GMT",
"version": "v2"
}
] | 2023-11-14 | [
[
"Bronnikov",
"Kirill A.",
""
],
[
"Bolokhov",
"Sergei V.",
""
],
[
"Skvortsova",
"Milena V.",
""
],
[
"Badalov",
"Kodir",
""
],
[
"Ibadov",
"Rustam",
""
]
] | We study the linear stability of vacuum static, spherically symmetric solutions to the gravitational field equations of the Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories (STT) of gravity, restricting ourselves to nonphantom theories, massless scalar fields and configurations with positive Schwarzschild mass. We consider only small radial (monopole) perturbations as the ones most likely to cause an instability. The problem reduces to the same Schroedinger-like master equation as is known for perturbations of Fisher's solution of general relativity (GR), but the corresponding boundary conditions that affect the final result of the study depend on the choice of the STT and a particular solution within it. The stability or instability conclusions are obtained for the Brans-Dicke, Barker and Schwinger STT as well as for GR nonminimally coupled to a scalar field with an arbitrary parameter $\xi$. |
gr-qc/9911074 | caroline dos santos | Caroline Santos | Dilatonic String through black holes | Poster. 5 pages in Portuguese. Published in Actas VIII National
Meeting in Astronomy and Astrophysics, IST - Porto, 1998 | null | null | null | gr-qc | null | We study the gravi-dilaton field of a Schwarzschild black hole pierced by a
thin cosmic string in both massless and massive dilatonic gravity. We conclude
that in the thin vortex approximation the string's spacetime is asymptotically
flat with a conical deficit angle and that the inertial mass of the black hole
is different from the gravitational one. We generalize our results to charged
black holes.
| [
{
"created": "Fri, 19 Nov 1999 17:14:04 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Santos",
"Caroline",
""
]
] | We study the gravi-dilaton field of a Schwarzschild black hole pierced by a thin cosmic string in both massless and massive dilatonic gravity. We conclude that in the thin vortex approximation the string's spacetime is asymptotically flat with a conical deficit angle and that the inertial mass of the black hole is different from the gravitational one. We generalize our results to charged black holes. |
gr-qc/9903064 | B. Linet | B. Linet | Entropy bound for a charged object from the Kerr-Newman black hole | latex, 4 pages, no figures. In this version, the desired bound is
well obtained by varying correctly the entropy of the black hole | Gen.Rel.Grav. 31 (1999) 1609-1613 | 10.1023/A:1026790606235 | null | gr-qc | null | We derive again the upper entropy bound for a charged object by employing
thermodynamics of the Kerr-Newman black hole linearised with respect to its
electric charge
| [
{
"created": "Wed, 17 Mar 1999 15:18:38 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Mar 1999 13:47:55 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Mar 1999 13:31:44 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Linet",
"B.",
""
]
] | We derive again the upper entropy bound for a charged object by employing thermodynamics of the Kerr-Newman black hole linearised with respect to its electric charge |
1804.03067 | Giovanni Manfredi | Giovanni Manfredi, Jean-Louis Rouet, Bruce Miller, Gabriel Chardin | Cosmological structure formation with negative mass | Equation 14 has been corrected (NB: typo in the published PRD
version) | Phys. Rev. D 98, 023514 (2018) | 10.1103/PhysRevD.98.023514 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a family of models with negative gravitational mass in the
context of Newtonian gravity. We focus in particular on a model that reproduces
the features of the so-called Dirac-Milne universe, a matter-antimatter
symmetric universe that was recently proposed as an alternative cosmological
scenario [A. Benoit-Levy and G. Chardin, A&A 537, A78 (2012)]. We perform
one-dimensional N-body simulations of these negative-mass models for an
expanding universe and study the associated formation of gravitational
structures. The similarities and differences with the standard cosmological
model are highlighted and discussed.
| [
{
"created": "Mon, 9 Apr 2018 15:56:32 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jun 2018 15:28:49 GMT",
"version": "v2"
},
{
"created": "Mon, 10 Dec 2018 11:51:07 GMT",
"version": "v3"
}
] | 2018-12-11 | [
[
"Manfredi",
"Giovanni",
""
],
[
"Rouet",
"Jean-Louis",
""
],
[
"Miller",
"Bruce",
""
],
[
"Chardin",
"Gabriel",
""
]
] | We construct a family of models with negative gravitational mass in the context of Newtonian gravity. We focus in particular on a model that reproduces the features of the so-called Dirac-Milne universe, a matter-antimatter symmetric universe that was recently proposed as an alternative cosmological scenario [A. Benoit-Levy and G. Chardin, A&A 537, A78 (2012)]. We perform one-dimensional N-body simulations of these negative-mass models for an expanding universe and study the associated formation of gravitational structures. The similarities and differences with the standard cosmological model are highlighted and discussed. |
0704.2736 | Jacques L. Rubin | T. Grandou, J.L. Rubin | Twin Paradox and Causality | 17 pages, no figures, submitted to Am. J. Phys | ECONFC0706044:15,2007 | null | INLN 2006#06 | gr-qc | null | After pointing out the historical avatar at the origin of a would be twin or
clock paradox, we argue that, at least on a local scale, the (re-qualified)
paradox is but a necessary consequence of the sole principle of causality.
| [
{
"created": "Fri, 20 Apr 2007 15:50:12 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Grandou",
"T.",
""
],
[
"Rubin",
"J. L.",
""
]
] | After pointing out the historical avatar at the origin of a would be twin or clock paradox, we argue that, at least on a local scale, the (re-qualified) paradox is but a necessary consequence of the sole principle of causality. |
gr-qc/0410031 | Ujjal Debnath | Ujjal Debnath, Subenoy Chakraborty, Naresh Dadhich | A dynamical symmetry of the spherical dust collapse | 4 pages, no figure, Revtex | null | 10.1142/S021827180500736X | null | gr-qc | null | By linearly scaling the initial data set (mass and kinetic energy functions)
together with the initial area radius of a collapsing dust sphere, we find a
symmetry of the collapse dynamics. That is, the linear transformation defines
an equivalence class of data sets which lead to the same end result as well as
its evolution all through. In particular, the density and shear remain
invariant initially as well as during the collapse. What the transformation is
exhibiting is an interesting scaling relationship between mass, kinetic energy
and the size of the collapsing dust sphere.
| [
{
"created": "Thu, 7 Oct 2004 10:23:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Subenoy",
""
],
[
"Dadhich",
"Naresh",
""
]
] | By linearly scaling the initial data set (mass and kinetic energy functions) together with the initial area radius of a collapsing dust sphere, we find a symmetry of the collapse dynamics. That is, the linear transformation defines an equivalence class of data sets which lead to the same end result as well as its evolution all through. In particular, the density and shear remain invariant initially as well as during the collapse. What the transformation is exhibiting is an interesting scaling relationship between mass, kinetic energy and the size of the collapsing dust sphere. |
0810.3172 | Wlodzimierz Piechocki | Piotr Dzierzak, Jacek Jezierski, Przemyslaw Malkiewicz and Wlodzimierz
Piechocki | The minimum length problem of loop quantum cosmology | 9 pages, no figures, revtex4; version published by Acta Physica
Polonica | Acta Phys. Polon. B41:717-726,2010 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The appearance of the big bounce (BB) in the evolution of the universe is
analyzed in the setting of loop quantum cosmology (LQC). Making use of an idea
of a minimum length turns classical Big Bang into BB. We argue why the spectrum
of the kinematical area operator of loop quantum gravity cannot be used for the
determination of this length. We find that the fundamental length, at the
present stage of development of LQC, is a free parameter of this model.
| [
{
"created": "Fri, 17 Oct 2008 14:48:51 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Jan 2009 15:07:55 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Mar 2010 16:16:10 GMT",
"version": "v3"
}
] | 2015-03-13 | [
[
"Dzierzak",
"Piotr",
""
],
[
"Jezierski",
"Jacek",
""
],
[
"Malkiewicz",
"Przemyslaw",
""
],
[
"Piechocki",
"Wlodzimierz",
""
]
] | The appearance of the big bounce (BB) in the evolution of the universe is analyzed in the setting of loop quantum cosmology (LQC). Making use of an idea of a minimum length turns classical Big Bang into BB. We argue why the spectrum of the kinematical area operator of loop quantum gravity cannot be used for the determination of this length. We find that the fundamental length, at the present stage of development of LQC, is a free parameter of this model. |
0909.0895 | Salvatore Capozziello | S. Capozziello, M. De Laurentis, L. Forte, F. Garufi, L. Milano | Gravitomagnetic corrections on gravitational waves | 14 pages, 7 figures | null | 10.1088/0031-8949/81/03/035008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waveforms and production could be considerably affected by
gravitomagnetic corrections considered in relativistic theory of orbits. Beside
the standard periastron effect of General Relativity, new nutation effects come
out when c^{-3} corrections are taken into account. Such corrections emerge as
soon as matter-current densities and vector gravitational potentials cannot be
discarded into dynamics. We study the gravitational waves emitted through the
capture, in the gravitational field of massive binary systems (e.g. a very
massive black hole on which a stellar object is inspiralling) via the
quadrupole approximation, considering precession and nutation effects. We
present a numerical study to obtain the gravitational wave luminosity, the
total energy output and the gravitational radiation amplitude. From a crude
estimate of the expected number of events towards peculiar targets (e.g.
globular clusters) and in particular, the rate of events per year for dense
stellar clusters at the Galactic Center (SgrA*), we conclude that this type of
capture could give signatures to be revealed by interferometric GW antennas, in
particular by the forthcoming laser interferometer space antenna LISA.
| [
{
"created": "Fri, 4 Sep 2009 12:07:17 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Capozziello",
"S.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Forte",
"L.",
""
],
[
"Garufi",
"F.",
""
],
[
"Milano",
"L.",
""
]
] | Gravitational waveforms and production could be considerably affected by gravitomagnetic corrections considered in relativistic theory of orbits. Beside the standard periastron effect of General Relativity, new nutation effects come out when c^{-3} corrections are taken into account. Such corrections emerge as soon as matter-current densities and vector gravitational potentials cannot be discarded into dynamics. We study the gravitational waves emitted through the capture, in the gravitational field of massive binary systems (e.g. a very massive black hole on which a stellar object is inspiralling) via the quadrupole approximation, considering precession and nutation effects. We present a numerical study to obtain the gravitational wave luminosity, the total energy output and the gravitational radiation amplitude. From a crude estimate of the expected number of events towards peculiar targets (e.g. globular clusters) and in particular, the rate of events per year for dense stellar clusters at the Galactic Center (SgrA*), we conclude that this type of capture could give signatures to be revealed by interferometric GW antennas, in particular by the forthcoming laser interferometer space antenna LISA. |
1909.10010 | Chinmay Kalaghatgi Mr. | Chinmay Kalaghatgi, Mark Hannam, Vivien Raymond | Parameter Estimation with a spinning multi-mode waveform model:
IMRPhenomHM | 14 pages, 7 figures | Phys. Rev. D 101, 103004 (2020) | 10.1103/PhysRevD.101.103004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from compact binary coalescence sources can be decomposed
into spherical-harmonic multipoles, the dominant being the quadrupole ($\ell=2,
m=\pm2$) modes. The contribution of sub-dominant modes towards total signal
power increases with increasing binary mass ratio and source inclination to the
detector. It is well-known that in these cases neglecting higher modes could
lead to measurement biases, but these have not yet been quantified with a
higher-mode model that includes spin effects. In this study, we use the
multi-mode aligned-spin phenomenological waveform model IMRPhenomHM to
investigate the effects of including multi-mode content in estimating source
parameters and contrast the results with using a quadrupole-only model
(IMRPhenomD). We use as sources IMRPhenomHM and hybrid EOB-NR waveforms over a
range of mass-ratio and inclination combinations, and recover the parameters
with IMRPhenomHM and IMRPhenomD. These allow us to quantify the accuracy of
parameter measurements using a multi-mode model, the biases incurred when using
a quadrupole-only model to recover full (multi-mode) signals, and the
systematic errors in the IMRPhenomHM model. We see that the parameters
recovered by multi-mode templates are more precise for all non-zero
inclinations as compared to quadrupole templates. For multi-mode injections,
IMRPhenomD recovers biased parameters for non-zero inclinations with lower
likelihood while IMRPhenomHM recovered parameters are accurate for most cases,
and if a bias exists, it can be explained as a combined effect of observational
priors and (in the case of hybrid-NR signals) waveform inaccuracies. For cases
where IMRPhenomHM recovers biased parameters, the bias is always smaller than
the corresponding IMRPhenomD recovery, and we conclude that IMRPhenomHM will be
sufficiently accurate to allow unbiased measurements for most GW observations.
| [
{
"created": "Sun, 22 Sep 2019 14:03:54 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Oct 2019 12:10:48 GMT",
"version": "v2"
}
] | 2020-05-06 | [
[
"Kalaghatgi",
"Chinmay",
""
],
[
"Hannam",
"Mark",
""
],
[
"Raymond",
"Vivien",
""
]
] | Gravitational waves from compact binary coalescence sources can be decomposed into spherical-harmonic multipoles, the dominant being the quadrupole ($\ell=2, m=\pm2$) modes. The contribution of sub-dominant modes towards total signal power increases with increasing binary mass ratio and source inclination to the detector. It is well-known that in these cases neglecting higher modes could lead to measurement biases, but these have not yet been quantified with a higher-mode model that includes spin effects. In this study, we use the multi-mode aligned-spin phenomenological waveform model IMRPhenomHM to investigate the effects of including multi-mode content in estimating source parameters and contrast the results with using a quadrupole-only model (IMRPhenomD). We use as sources IMRPhenomHM and hybrid EOB-NR waveforms over a range of mass-ratio and inclination combinations, and recover the parameters with IMRPhenomHM and IMRPhenomD. These allow us to quantify the accuracy of parameter measurements using a multi-mode model, the biases incurred when using a quadrupole-only model to recover full (multi-mode) signals, and the systematic errors in the IMRPhenomHM model. We see that the parameters recovered by multi-mode templates are more precise for all non-zero inclinations as compared to quadrupole templates. For multi-mode injections, IMRPhenomD recovers biased parameters for non-zero inclinations with lower likelihood while IMRPhenomHM recovered parameters are accurate for most cases, and if a bias exists, it can be explained as a combined effect of observational priors and (in the case of hybrid-NR signals) waveform inaccuracies. For cases where IMRPhenomHM recovers biased parameters, the bias is always smaller than the corresponding IMRPhenomD recovery, and we conclude that IMRPhenomHM will be sufficiently accurate to allow unbiased measurements for most GW observations. |
gr-qc/0005024 | Riazuelo | Alain Riazuelo and Nathalie Deruelle | Cosmic microwave background anisotropies seeded by incoherent sources | 11 pages, 1 figure | Annalen Phys. 9 (2000) 288-298 | 10.1002/(SICI)1521-3889(200005)9:3/5<288::AID-ANDP288>3.0.CO;2-M | null | gr-qc | null | The cosmic microwave background anisotropies produced by active seeds, such
as topological defects, have been computed recently for a variety of models by
a number of authors. In this paper we show how the generic features of the
anisotropies caused by active, incoherent, seeds (that is the absence of
acoustic peaks at small scales) can be obtained semi-analytically, without
entering into the model dependent details of their formation, structure and
evolution.
| [
{
"created": "Tue, 9 May 2000 08:40:15 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Riazuelo",
"Alain",
""
],
[
"Deruelle",
"Nathalie",
""
]
] | The cosmic microwave background anisotropies produced by active seeds, such as topological defects, have been computed recently for a variety of models by a number of authors. In this paper we show how the generic features of the anisotropies caused by active, incoherent, seeds (that is the absence of acoustic peaks at small scales) can be obtained semi-analytically, without entering into the model dependent details of their formation, structure and evolution. |
1101.2141 | Alfredo Sandoval-Villalbazo | J. H. Mondragon Suarez, A. Sandoval-Villalbazo | Jeans instability analysis in the presence of heat in Eckart's frame | 9 pages, no figures | Gen. Relativ. Gravit. (2012) 44:139-145 | 10.1007/s10714-011-1267-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the coupling of heat with acceleration first proposed by
Eckart would have an overwhelming effect in the growth of density mass
fluctuations, even in non-relativistic fluids in the presence of a
gravitational field. Gravitational effects would be negligible if the
heat-acceleration relation is assumed to be valid for the hydrodynamic
equations. A direct implication of this result is that recent alternative first
order in the gradients theories must be taken into account while describing a
special relativistic fluid.
| [
{
"created": "Tue, 11 Jan 2011 15:08:35 GMT",
"version": "v1"
}
] | 2012-01-30 | [
[
"Suarez",
"J. H. Mondragon",
""
],
[
"Sandoval-Villalbazo",
"A.",
""
]
] | It is shown that the coupling of heat with acceleration first proposed by Eckart would have an overwhelming effect in the growth of density mass fluctuations, even in non-relativistic fluids in the presence of a gravitational field. Gravitational effects would be negligible if the heat-acceleration relation is assumed to be valid for the hydrodynamic equations. A direct implication of this result is that recent alternative first order in the gradients theories must be taken into account while describing a special relativistic fluid. |
gr-qc/0412104 | Kirill Krasnov | Kirill Krasnov | Holography for the Lorentz Group Racah Coefficients | 12 pages, 2 figures; v2: minor changes; v3: "extended" tetrahedron
interpretation added | Class.Quant.Grav. 22 (2005) 1933-1944 | 10.1088/0264-9381/22/11/003 | null | gr-qc hep-th | null | A known realization of the Lorentz group Racah coefficients is given by an
integral of a product of 6 ``propagators'' over 4 copies of the hyperbolic
space. These are ``bulk-to-bulk'' propagators in that they are functions of two
points in the hyperbolic space. It is known that the bulk-to-bulk propagator
can be constructed out of two bulk-to-boundary ones. We point out that there is
another way to obtain the same object. Namely, one can use two bulk-to-boundary
and one boundary-to-boundary propagator. Starting from this construction and
carrying out the bulk integrals we obtain a realization of the Racah
coefficients that is ``holographic'' in the sense that it only involves
boundary objects. This holographic realization admits a geometric
interpretation in terms of an ``extended'' tetrahedron.
| [
{
"created": "Tue, 21 Dec 2004 15:28:30 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Feb 2005 11:58:07 GMT",
"version": "v2"
},
{
"created": "Sun, 3 Apr 2005 16:27:42 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Krasnov",
"Kirill",
""
]
] | A known realization of the Lorentz group Racah coefficients is given by an integral of a product of 6 ``propagators'' over 4 copies of the hyperbolic space. These are ``bulk-to-bulk'' propagators in that they are functions of two points in the hyperbolic space. It is known that the bulk-to-bulk propagator can be constructed out of two bulk-to-boundary ones. We point out that there is another way to obtain the same object. Namely, one can use two bulk-to-boundary and one boundary-to-boundary propagator. Starting from this construction and carrying out the bulk integrals we obtain a realization of the Racah coefficients that is ``holographic'' in the sense that it only involves boundary objects. This holographic realization admits a geometric interpretation in terms of an ``extended'' tetrahedron. |
1410.6202 | Stefano Ansoldi | Stefano Ansoldi and Takahiro Tanaka | Tunnelling with wormhole creation | 13 pages; 4 figures | null | 10.1134/S1063776115030139 | KUNS-2524; YITP-14-82 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The description of quantum tunnelling in the presence of gravity shows
subtleties in some cases. Here we discuss wormhole production in the context of
the spherically symmetric thin-shell approximation. By presenting a fully
consistent treatment based on canonical quantization, we solve a controversy
present in literature.
| [
{
"created": "Wed, 22 Oct 2014 21:55:00 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Ansoldi",
"Stefano",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | The description of quantum tunnelling in the presence of gravity shows subtleties in some cases. Here we discuss wormhole production in the context of the spherically symmetric thin-shell approximation. By presenting a fully consistent treatment based on canonical quantization, we solve a controversy present in literature. |
1102.0589 | Glenn Barnich | Glenn Barnich and Pierre-Henry Lambert | A note on the Newman-Unti group and the BMS charge algebra in terms of
Newman-Penrose coefficients | v2: 16 pages Latex file, considerably expanded version containing
transformations of fields and surface charge algebra; v3: cosmetic changes,
agrees with published version | Advances in Mathematical Physics, vol. 2012, Article ID 197385,
2012 | 10.1155/2012/197385 | ULB-TH/11-01 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The symmetry algebra of asymptotically flat spacetimes at null infinity in
four dimensions in the sense of Newman and Unti is revisited. As in the
Bondi-Metzner-Sachs gauge, it is shown to be isomorphic to the direct sum of
the abelian algebra of infinitesimal conformal rescalings with bms4. The latter
algebra is the semi-direct sum of infinitesimal supertranslations with the
conformal Killing vectors of the Riemann sphere. Infinitesimal local conformal
transformations can then consistently be included. We work out the local
conformal properties of the relevant Newman-Penrose coefficients, construct the
surface charges and derive their algebra.
| [
{
"created": "Wed, 2 Feb 2011 23:59:07 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2011 17:27:26 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Jan 2013 15:28:21 GMT",
"version": "v3"
}
] | 2013-01-24 | [
[
"Barnich",
"Glenn",
""
],
[
"Lambert",
"Pierre-Henry",
""
]
] | The symmetry algebra of asymptotically flat spacetimes at null infinity in four dimensions in the sense of Newman and Unti is revisited. As in the Bondi-Metzner-Sachs gauge, it is shown to be isomorphic to the direct sum of the abelian algebra of infinitesimal conformal rescalings with bms4. The latter algebra is the semi-direct sum of infinitesimal supertranslations with the conformal Killing vectors of the Riemann sphere. Infinitesimal local conformal transformations can then consistently be included. We work out the local conformal properties of the relevant Newman-Penrose coefficients, construct the surface charges and derive their algebra. |
0809.3444 | Martin Reiris | Martin Reiris | The ground state and the long-time evolution in the CMC Einstein flow | 40 pages. This article is an improved version of the second part of
the First Version of arXiv:0705.3070 | Annales Henri Poincare 10:1559-1604,2010 | 10.1007/s00023-010-0027-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Let (g,K)(k) be a CMC (vacuum) Einstein flow over a compact three-manifold M
with non-positive Yamabe invariant (Y(M)). As noted by Fischer and Moncrief,
the reduced volume V(k)=(-k/3)^{3}Vol_{g(k)}(M) is monotonically decreasing in
the expanding direction and bounded below by V_{\inf}=(-1/6)Y(M))^{3/2}.
Inspired by this fact we define the ground state of the manifold M as "the
limit" of any sequence of CMC states {(g_{i},K_{i})} satisfying: i. k_{i}=-3,
ii. V_{i} --> V_{inf}, iii. Q_{0}((g_{i},K_{i}))< L where Q_{0} is the
Bel-Robinson energy and L is any arbitrary positive constant. We prove that (as
a geometric state) the ground state is equivalent to the Thurston
geometrization of M. Ground states classify naturally into three types. We
provide examples for each class, including a new ground state (the Double Cusp)
that we analyze in detail. Finally consider a long time and cosmologically
normalized flow (\g,\K)(s)=((-k/3)^{2}g,(-k/3))K) where s=-ln(-k) is in
[a,\infty). We prove that if E_{1}=E_{1}((\g,\K))< L (where E_{1}=Q_{0}+Q_{1},
is the sum of the zero and first order Bel-Robinson energies) the flow
(\g,\K)(s) persistently geometrizes the three-manifold M and the geometrization
is the ground state if V --> V_{inf}.
| [
{
"created": "Fri, 19 Sep 2008 19:30:23 GMT",
"version": "v1"
}
] | 2010-05-07 | [
[
"Reiris",
"Martin",
""
]
] | Let (g,K)(k) be a CMC (vacuum) Einstein flow over a compact three-manifold M with non-positive Yamabe invariant (Y(M)). As noted by Fischer and Moncrief, the reduced volume V(k)=(-k/3)^{3}Vol_{g(k)}(M) is monotonically decreasing in the expanding direction and bounded below by V_{\inf}=(-1/6)Y(M))^{3/2}. Inspired by this fact we define the ground state of the manifold M as "the limit" of any sequence of CMC states {(g_{i},K_{i})} satisfying: i. k_{i}=-3, ii. V_{i} --> V_{inf}, iii. Q_{0}((g_{i},K_{i}))< L where Q_{0} is the Bel-Robinson energy and L is any arbitrary positive constant. We prove that (as a geometric state) the ground state is equivalent to the Thurston geometrization of M. Ground states classify naturally into three types. We provide examples for each class, including a new ground state (the Double Cusp) that we analyze in detail. Finally consider a long time and cosmologically normalized flow (\g,\K)(s)=((-k/3)^{2}g,(-k/3))K) where s=-ln(-k) is in [a,\infty). We prove that if E_{1}=E_{1}((\g,\K))< L (where E_{1}=Q_{0}+Q_{1}, is the sum of the zero and first order Bel-Robinson energies) the flow (\g,\K)(s) persistently geometrizes the three-manifold M and the geometrization is the ground state if V --> V_{inf}. |
2311.18247 | Konstantin Osetrin | Vladimir Y. Epp and Konstantin E. Osetrin | Induced electromagnetic radiation from a charged cloud in a plane
gravitational wave | 9 pages | Astrophysics, 2024, v.67, N1, p.121-128 | 10.54503/0002-3051-2024.77.1-121 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | For the perturbative model of a plane gravitational wave on a flat background
of Minkowski space-time, electromagnetic radiation from a charged cloud in the
field of a gravitational wave, detected by a remote observer, was found. It is
shown that the charge density in the cloud does not change, and the radiation
is generated by currents induced by the gravitational wave. The angular
distribution of the radiation is obtained. If the refractive index of the cloud
medium is greater than unity, Cherenkov-type radiation is generated.
| [
{
"created": "Thu, 30 Nov 2023 04:42:28 GMT",
"version": "v1"
}
] | 2024-04-12 | [
[
"Epp",
"Vladimir Y.",
""
],
[
"Osetrin",
"Konstantin E.",
""
]
] | For the perturbative model of a plane gravitational wave on a flat background of Minkowski space-time, electromagnetic radiation from a charged cloud in the field of a gravitational wave, detected by a remote observer, was found. It is shown that the charge density in the cloud does not change, and the radiation is generated by currents induced by the gravitational wave. The angular distribution of the radiation is obtained. If the refractive index of the cloud medium is greater than unity, Cherenkov-type radiation is generated. |
1603.05726 | David Radice | David Radice and Sebastiano Bernuzzi and Christian D. Ott | The One-Armed Spiral Instability in Neutron Star Mergers and its
Detectability in Gravitational Waves | 7 pages, 3 figures. Comments are welcome | null | 10.1103/PhysRevD.94.064011 | LIGO-P1600075-v1 and YITP-16-21 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the development and saturation of the $m=1$ one-armed spiral
instability in remnants of binary neutron star mergers by means of
high-resolution long-term numerical relativity simulations. Our results suggest
that this instability is a generic outcome of neutron stars mergers in
astrophysically relevant configurations; including both "stiff" and "soft"
nuclear equations of state. We find that, once seeded at merger, the $m=1$ mode
saturates within $\sim 10\ \mathrm{ms}$ and persists over secular timescales.
Gravitational waves emitted by the $m=1$ instability have a peak frequency
around $1-2\ \mathrm{kHz}$ and, if detected, could be used to constrain the
equation of state of neutron stars. We construct hybrid waveforms spanning the
entire Advanced LIGO band by combining our high-resolution numerical data with
state-of-the-art effective-one-body waveforms including tidal effects. We use
the complete hybrid waveforms to study the detectability of the one-armed
spiral instability for both Advanced LIGO and the Einstein Telescope. We
conclude that the one-armed spiral instability is not an efficient
gravitational wave emitter. Its observation by current generation detectors is
unlikely and will require third-generation interferometers.
| [
{
"created": "Thu, 17 Mar 2016 23:30:44 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Sep 2016 19:46:31 GMT",
"version": "v2"
}
] | 2016-09-23 | [
[
"Radice",
"David",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Ott",
"Christian D.",
""
]
] | We study the development and saturation of the $m=1$ one-armed spiral instability in remnants of binary neutron star mergers by means of high-resolution long-term numerical relativity simulations. Our results suggest that this instability is a generic outcome of neutron stars mergers in astrophysically relevant configurations; including both "stiff" and "soft" nuclear equations of state. We find that, once seeded at merger, the $m=1$ mode saturates within $\sim 10\ \mathrm{ms}$ and persists over secular timescales. Gravitational waves emitted by the $m=1$ instability have a peak frequency around $1-2\ \mathrm{kHz}$ and, if detected, could be used to constrain the equation of state of neutron stars. We construct hybrid waveforms spanning the entire Advanced LIGO band by combining our high-resolution numerical data with state-of-the-art effective-one-body waveforms including tidal effects. We use the complete hybrid waveforms to study the detectability of the one-armed spiral instability for both Advanced LIGO and the Einstein Telescope. We conclude that the one-armed spiral instability is not an efficient gravitational wave emitter. Its observation by current generation detectors is unlikely and will require third-generation interferometers. |
2206.13532 | Carlos O. Lousto | Alessandro Ciarfella, James Healy, Carlos O. Lousto, and Hiroyuki
Nakano | Eccentricity estimation from initial data for Numerical Relativity
Simulations | 7 pages, 7 figures, 1 Table | null | 10.1103/PhysRevD.106.104035 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe and study an instantaneous definition of eccentricity to be
applied at the initial moment of full numerical simulations of binary black
holes. The method consists of evaluating the eccentricity at the moment of
maximum separation of the binary. We estimate it using up to third
post-Newtonian (3PN) order, and compare these results with those of evolving
(conservative) 3PN equations of motion for a full orbit and compute the
eccentricity $e_r$ from the radial turning points, finding excellent agreement.
We next include terms with spins up to 3.5PN, and then compare this method with
the corresponding estimates of the eccentricity $e_r^{NR}$ during full
numerical evolutions of spinning binary black holes, characterized invariantly
by a fractional factor $0\leq f\leq1$ of the initial tangential momenta. It is
found that our initial instantaneous definition is a very useful tool to
predict and characterize even highly eccentric full numerical simulations.
| [
{
"created": "Mon, 27 Jun 2022 18:00:02 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Ciarfella",
"Alessandro",
""
],
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Nakano",
"Hiroyuki",
""
]
] | We describe and study an instantaneous definition of eccentricity to be applied at the initial moment of full numerical simulations of binary black holes. The method consists of evaluating the eccentricity at the moment of maximum separation of the binary. We estimate it using up to third post-Newtonian (3PN) order, and compare these results with those of evolving (conservative) 3PN equations of motion for a full orbit and compute the eccentricity $e_r$ from the radial turning points, finding excellent agreement. We next include terms with spins up to 3.5PN, and then compare this method with the corresponding estimates of the eccentricity $e_r^{NR}$ during full numerical evolutions of spinning binary black holes, characterized invariantly by a fractional factor $0\leq f\leq1$ of the initial tangential momenta. It is found that our initial instantaneous definition is a very useful tool to predict and characterize even highly eccentric full numerical simulations. |
1602.03066 | Behrouz Mirza | Seyed Ali Hosseini Mansoori, Behrouz Mirza, Elham Sharifian | Extrinsic and intrinsic curvatures in thermodynamic geometry | 10 pages, 4 figures | Physics Letters B 759 (2016) 298-305 | 10.1016/j.physletb.2016.05.096 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the intrinsic and extrinsic curvatures of certain
hypersurfaces in the thermodynamic geometry of a physical system and show that
they contain useful thermodynamic information. For an
anti-Reissner-Nordstr\"{o}m-(A)de Sitter black hole (Phantom), the extrinsic
curvature of a constant $Q$ hypersurface has the same sign as the heat capacity
around the phase transition points. For a Kerr-Newmann-AdS (KN-AdS) black hole,
the extrinsic curvature of $Q \to 0$ hypersurface (Kerr black hole) or $J \to
0$ hypersurface (RN black black hole) has the same sign as the heat capacity
around the phase transition points. The extrinsic curvature also diverges at
the phase transition points. The intrinsic curvature of the hypersurfaces
diverges at the critical points but has no information about the sign of the
heat capacity. Our study explains the consistent relationship holding between
the thermodynamic geometry of the KN-AdS black holes and those of the RN and
Kerr ones \cite{ref1}. This approach can be easily generalized to an arbitrary
thermodynamic system.
| [
{
"created": "Mon, 8 Feb 2016 15:37:27 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Jun 2016 08:30:11 GMT",
"version": "v2"
}
] | 2016-06-14 | [
[
"Mansoori",
"Seyed Ali Hosseini",
""
],
[
"Mirza",
"Behrouz",
""
],
[
"Sharifian",
"Elham",
""
]
] | We investigate the intrinsic and extrinsic curvatures of certain hypersurfaces in the thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner-Nordstr\"{o}m-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant $Q$ hypersurface has the same sign as the heat capacity around the phase transition points. For a Kerr-Newmann-AdS (KN-AdS) black hole, the extrinsic curvature of $Q \to 0$ hypersurface (Kerr black hole) or $J \to 0$ hypersurface (RN black black hole) has the same sign as the heat capacity around the phase transition points. The extrinsic curvature also diverges at the phase transition points. The intrinsic curvature of the hypersurfaces diverges at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN and Kerr ones \cite{ref1}. This approach can be easily generalized to an arbitrary thermodynamic system. |
gr-qc/0510048 | Sergei Kopeikin | Sergei M. Kopeikin (University of Missouri-Columbia) | Comment on 'Model-dependence of Shapiro time delay and the "speed of
gravity/speed of light" controversy' | 8 pages, no figures, accepted to Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) 5181-5186 | 10.1088/0264-9381/22/23/N01 | null | gr-qc | null | In a recent paper published in Classical and Quantum Gravity, 2004, vol. 21,
p. 3803 Carlip used a vector-tensor theory of gravity to calculate the Shapiro
time delay by a moving gravitational lens. He claimed that the relativistic
correction of the order of v/c beyond the static part of the Shapiro delay
depends on the speed of light c and, hence, the Fomalont-Kopeikin experiment is
not sensitive to the speed of gravity c_g. In this letter we analyze Carlip's
calculation and demonstrate that it implies a gravitodynamic (non-metric)
system of units based on the principle of the constancy of the speed of gravity
but it is disconnected from the practical method of measurement of astronomical
distances based on the principle of the constancy of the speed of light and the
SI metric (electrodynamic) system of units. Re-adjustment of
theoretically-admissible but practically unmeasurable Carlip's coordinates to
the SI metric system of units used in JPL ephemeris, reveals that the
velocity-dependent correction to the static part of the Shapiro time delay does
depend on the speed of gravity c_g as shown by Kopeikin in Classical and
Quantum Gravity, 2004, vol. 21, p. 1. This analysis elucidates the importance
of employing the metric system of units for physically meaningful
interpretation of gravitational experiments.
| [
{
"created": "Mon, 10 Oct 2005 15:08:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kopeikin",
"Sergei M.",
"",
"University of Missouri-Columbia"
]
] | In a recent paper published in Classical and Quantum Gravity, 2004, vol. 21, p. 3803 Carlip used a vector-tensor theory of gravity to calculate the Shapiro time delay by a moving gravitational lens. He claimed that the relativistic correction of the order of v/c beyond the static part of the Shapiro delay depends on the speed of light c and, hence, the Fomalont-Kopeikin experiment is not sensitive to the speed of gravity c_g. In this letter we analyze Carlip's calculation and demonstrate that it implies a gravitodynamic (non-metric) system of units based on the principle of the constancy of the speed of gravity but it is disconnected from the practical method of measurement of astronomical distances based on the principle of the constancy of the speed of light and the SI metric (electrodynamic) system of units. Re-adjustment of theoretically-admissible but practically unmeasurable Carlip's coordinates to the SI metric system of units used in JPL ephemeris, reveals that the velocity-dependent correction to the static part of the Shapiro time delay does depend on the speed of gravity c_g as shown by Kopeikin in Classical and Quantum Gravity, 2004, vol. 21, p. 1. This analysis elucidates the importance of employing the metric system of units for physically meaningful interpretation of gravitational experiments. |
gr-qc/9707041 | Novak | J. Novak (DARC, CNRS, Observatoire de Paris) | Spherical neutron star collapse toward a black hole in tensor-scalar
theory of gravity | 23 pages, LaTeX, 21 PostScript figures, uses RevTeX, accepted for
publication in Physical Review D Numerical appendix added, sec.III rewritten,
figures changed | Phys.Rev. D57 (1998) 4789-4801 | 10.1103/PhysRevD.57.4789 | null | gr-qc astro-ph | null | Complete tensor-scalar and hydrodynamic equations are presented and
integrated, for a self-gravitating perfect fluid. The initial conditions
describe unstable-equilibrium neutron star configuration, with a polytropic
equation of state. They are necessary in order to follow the gravitational
collapse (including full hydrodynamics) of this star toward a black hole and to
study the resulting scalar gravitational wave. The amplitude of this wave, as
well as the radiated energy dramatically increase above some critical value of
the parameter of the coupling function, due to the spontaneous scalarization,
an effect not present in Brans-Dicke theory. In most cases, the pressure of the
collapsing fluid does not have a significant impact on the resulting signal.
These kind of sources are not likely to be observed by future laser
interferometric detectors (such as VIRGO or LIGO) of gravitational waves, if
they are located at more than a few 100 kpc. However, spontaneous scalarization
could be constrained if such a gravitational collapse is detected by its
quadrupolar gravitational signal, since this latter is quite lower than the
monopolar one.
| [
{
"created": "Fri, 18 Jul 1997 15:15:59 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jan 1998 14:01:28 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Novak",
"J.",
"",
"DARC, CNRS, Observatoire de Paris"
]
] | Complete tensor-scalar and hydrodynamic equations are presented and integrated, for a self-gravitating perfect fluid. The initial conditions describe unstable-equilibrium neutron star configuration, with a polytropic equation of state. They are necessary in order to follow the gravitational collapse (including full hydrodynamics) of this star toward a black hole and to study the resulting scalar gravitational wave. The amplitude of this wave, as well as the radiated energy dramatically increase above some critical value of the parameter of the coupling function, due to the spontaneous scalarization, an effect not present in Brans-Dicke theory. In most cases, the pressure of the collapsing fluid does not have a significant impact on the resulting signal. These kind of sources are not likely to be observed by future laser interferometric detectors (such as VIRGO or LIGO) of gravitational waves, if they are located at more than a few 100 kpc. However, spontaneous scalarization could be constrained if such a gravitational collapse is detected by its quadrupolar gravitational signal, since this latter is quite lower than the monopolar one. |
gr-qc/0307087 | Ivan S. N. Booth | Ivan Booth, Stephen Fairhurst | The first law for slowly evolving horizons | 4 pages, typos fixed, minor changes in wording for clarity, to appear
in PRL | Phys.Rev.Lett. 92 (2004) 011102 | 10.1103/PhysRevLett.92.011102 | null | gr-qc | null | We study the mechanics of Hayward's trapping horizons, taking isolated
horizons as equilibrium states. Zeroth and second laws of dynamic horizon
mechanics come from the isolated and trapping horizon formalisms respectively.
We derive a dynamical first law by introducing a new perturbative formulation
for dynamic horizons in which "slowly evolving" trapping horizons may be viewed
as perturbatively non-isolated.
| [
{
"created": "Fri, 18 Jul 2003 19:15:14 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Jan 2004 16:30:19 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Booth",
"Ivan",
""
],
[
"Fairhurst",
"Stephen",
""
]
] | We study the mechanics of Hayward's trapping horizons, taking isolated horizons as equilibrium states. Zeroth and second laws of dynamic horizon mechanics come from the isolated and trapping horizon formalisms respectively. We derive a dynamical first law by introducing a new perturbative formulation for dynamic horizons in which "slowly evolving" trapping horizons may be viewed as perturbatively non-isolated. |
2401.10097 | Yusuke Mikura | Yusuke Mikura, Roberto Percacci | Some simple theories of gravity with propagating nonmetricity | 20 pages | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate symmetric Metric-Affine Theories of Gravity with a Lagrangian
containing all operators of dimension up to four that are relevant to free
propagation in flat space. Complementing recent work in the antisymmetric case,
we derive the conditions for the existence of a single massive particle with
good properties, in addition to the graviton.
| [
{
"created": "Thu, 18 Jan 2024 16:06:32 GMT",
"version": "v1"
}
] | 2024-01-19 | [
[
"Mikura",
"Yusuke",
""
],
[
"Percacci",
"Roberto",
""
]
] | We investigate symmetric Metric-Affine Theories of Gravity with a Lagrangian containing all operators of dimension up to four that are relevant to free propagation in flat space. Complementing recent work in the antisymmetric case, we derive the conditions for the existence of a single massive particle with good properties, in addition to the graviton. |
1806.10488 | Bruno Barros | Bruno J. Barros, Francisco S. N. Lobo | Wormhole geometries supported by three-form fields | 8 pages, 5 figures. V2: Matches published version | Phys. Rev. D 98, 044012 (2018) | 10.1103/PhysRevD.98.044012 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we find novel static and spherically symmetric wormhole
geometries using a three-form field. By solving the gravitational field
equations, we find a variety of analytical and numerical solutions and show
that it is possible for the matter fields threading the wormhole to satisfy the
null and weak energy conditions throughout the spacetime, when the three-form
field is present. In these cases, the form field is responsible for supporting
the wormhole and all the exoticity is confined to it. Thus, the three-form
curvature terms, which may be interpreted as a gravitational fluid, sustain
these non-standard wormhole geometries, fundamentally different from their
counterparts in General Relativity. We also show that in the case of a
vanishing redshift function the field can display a cosmological constant
behavior.
| [
{
"created": "Wed, 27 Jun 2018 13:52:42 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2018 11:41:20 GMT",
"version": "v2"
}
] | 2018-08-10 | [
[
"Barros",
"Bruno J.",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this work, we find novel static and spherically symmetric wormhole geometries using a three-form field. By solving the gravitational field equations, we find a variety of analytical and numerical solutions and show that it is possible for the matter fields threading the wormhole to satisfy the null and weak energy conditions throughout the spacetime, when the three-form field is present. In these cases, the form field is responsible for supporting the wormhole and all the exoticity is confined to it. Thus, the three-form curvature terms, which may be interpreted as a gravitational fluid, sustain these non-standard wormhole geometries, fundamentally different from their counterparts in General Relativity. We also show that in the case of a vanishing redshift function the field can display a cosmological constant behavior. |
2003.02299 | Christian Pfeifer | Manuel Hohmann, Christian Pfeifer, Nicoleta Voicu | Cosmological Finsler Spacetimes | 14 pages, contribution to the Special Issue "Finsler Modification of
Classical General Relativity" in the Journal Universe | Universe 2020, 6(5), 65 | 10.3390/universe6050065 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Applying the cosmological principle to Finsler spacetimes, we identify the
Lie Algebra of symmetry generators of spatially homogeneous and isotropic
Finsler geometries, thus generalising Friedmann-Lema\^{i}tre-Robertson-Walker
geometry. In particular, we find the most general spatially homogeneous and
isotropic Berwald spacetimes, which are Finsler spacetimes that can be regarded
as closest to pseudo-Riemannian geometry. They are defined by a Finsler
Lagrangian built from a zero-homogeneous function on the tangent bundle, which
encodes the velocity dependence of the Finsler Lagrangian in a very specific
way. The obtained cosmological Berwald geometries are candidates for the
description of the geometry of the universe, when they are obtained as
solutions from a Finsler gravity equation.
| [
{
"created": "Wed, 4 Mar 2020 19:28:54 GMT",
"version": "v1"
},
{
"created": "Tue, 5 May 2020 14:37:13 GMT",
"version": "v2"
}
] | 2020-05-06 | [
[
"Hohmann",
"Manuel",
""
],
[
"Pfeifer",
"Christian",
""
],
[
"Voicu",
"Nicoleta",
""
]
] | Applying the cosmological principle to Finsler spacetimes, we identify the Lie Algebra of symmetry generators of spatially homogeneous and isotropic Finsler geometries, thus generalising Friedmann-Lema\^{i}tre-Robertson-Walker geometry. In particular, we find the most general spatially homogeneous and isotropic Berwald spacetimes, which are Finsler spacetimes that can be regarded as closest to pseudo-Riemannian geometry. They are defined by a Finsler Lagrangian built from a zero-homogeneous function on the tangent bundle, which encodes the velocity dependence of the Finsler Lagrangian in a very specific way. The obtained cosmological Berwald geometries are candidates for the description of the geometry of the universe, when they are obtained as solutions from a Finsler gravity equation. |
0908.0355 | Reiner Hedrich | Reiner Hedrich | Quantum Gravity: Motivations and Alternatives | 32 pages | Phys. Phil.2010:016,2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mutual conceptual incompatibility between GR and QM/QFT is generally seen
as the most essential motivation for the development of a theory of Quantum
Gravity (QG). It leads to the insight that, if gravity is a fundamental
interaction and QM is universally valid, the gravitational field will have to
be quantized, not at least because of the inconsistency of semi-classical
theories of gravity. If this means to quantize GR, its identification of the
gravitational field with the spacetime metric has to be taken into account. And
the resulting quantum theory has to be background-independent. This can not be
achieved by means of quantum field theoretical procedures. More sophisticated
strategies have to be applied. One of the basic requirements for such a
quantization strategy is that the resulting quantum theory has GR as a
classical limit. - However, should gravity not be a fundamental, but an
residual, emergent interaction, it could very well be an intrinsically
classical phenomenon. Should QM be nonetheless universally valid, we had to
assume a quantum substrate from which gravity would result as an emergent
classical phenomenon. And there would be no conflict with the arguments against
semi-classical theories, because there would be no gravity at all on the
substrate level. The gravitational field would not have any quantum properties,
and a quantization of GR would not lead to any fundamental theory. The
objective of a theory of 'QG' would instead be the identification of the
quantum substrate from which gravity results. - The paper tries to give an
overview over the main options for theory construction in the field of QG.
Because of the still unclear status of gravity and spacetime, it pleads for the
necessity of a plurality of conceptually different approaches to QG.
| [
{
"created": "Mon, 3 Aug 2009 22:07:48 GMT",
"version": "v1"
}
] | 2011-03-04 | [
[
"Hedrich",
"Reiner",
""
]
] | The mutual conceptual incompatibility between GR and QM/QFT is generally seen as the most essential motivation for the development of a theory of Quantum Gravity (QG). It leads to the insight that, if gravity is a fundamental interaction and QM is universally valid, the gravitational field will have to be quantized, not at least because of the inconsistency of semi-classical theories of gravity. If this means to quantize GR, its identification of the gravitational field with the spacetime metric has to be taken into account. And the resulting quantum theory has to be background-independent. This can not be achieved by means of quantum field theoretical procedures. More sophisticated strategies have to be applied. One of the basic requirements for such a quantization strategy is that the resulting quantum theory has GR as a classical limit. - However, should gravity not be a fundamental, but an residual, emergent interaction, it could very well be an intrinsically classical phenomenon. Should QM be nonetheless universally valid, we had to assume a quantum substrate from which gravity would result as an emergent classical phenomenon. And there would be no conflict with the arguments against semi-classical theories, because there would be no gravity at all on the substrate level. The gravitational field would not have any quantum properties, and a quantization of GR would not lead to any fundamental theory. The objective of a theory of 'QG' would instead be the identification of the quantum substrate from which gravity results. - The paper tries to give an overview over the main options for theory construction in the field of QG. Because of the still unclear status of gravity and spacetime, it pleads for the necessity of a plurality of conceptually different approaches to QG. |
1112.5269 | Paingalil Kunjan Suresh | Rizwan Ul Haq Ansari and P. K. Suresh | Evolution of the density parameter in the anisotropic DGP cosmology | To apper in Int.J.Mod.Phys.D, 14 pages, 6 figures | null | 10.1142/S0218271811020512 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Evolution of the density parameter in the anisotropic DGP braneworld model is
studied. The role of shear and cross-over scale in the evolution of
$\Omega_\rho$ is examined for both the branches of solution in the DGP model.
The evolution is modified significantly compared to the FRW model and further
it does not depend on the value of $\gamma$ alone. Behaviour of the
cosmological density parameter $\Omega_\rho$ is unaltered in the late universe.
The study of decceleration parameter shows that the entry of the universe into
self accelerating phase is determined by the value of shear. We also obtain an
estimate of the shear parameter $\frac{\Sigma}{H_0} \sim 1.68 \times 10^{-10}$,
which is in agreement with the constraints obtained in the literature using
data.
| [
{
"created": "Thu, 22 Dec 2011 10:45:34 GMT",
"version": "v1"
}
] | 2011-12-23 | [
[
"Ansari",
"Rizwan Ul Haq",
""
],
[
"Suresh",
"P. K.",
""
]
] | Evolution of the density parameter in the anisotropic DGP braneworld model is studied. The role of shear and cross-over scale in the evolution of $\Omega_\rho$ is examined for both the branches of solution in the DGP model. The evolution is modified significantly compared to the FRW model and further it does not depend on the value of $\gamma$ alone. Behaviour of the cosmological density parameter $\Omega_\rho$ is unaltered in the late universe. The study of decceleration parameter shows that the entry of the universe into self accelerating phase is determined by the value of shear. We also obtain an estimate of the shear parameter $\frac{\Sigma}{H_0} \sim 1.68 \times 10^{-10}$, which is in agreement with the constraints obtained in the literature using data. |
2107.12400 | Maciej Dunajski | Maciej Dunajski, Paul Tod | The Kijowski--Liu--Yau quasi-local mass of the Kerr black hole horizon | 9 pages. Dedicated to Gary Gibbons on the occasion of his 75th
birthday. Numerical methods used in the paper clarified. Final version, to
appear in Classical and Quantum Gravity | null | 10.1088/1361-6382/ac2cb6 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the isometric embedding of the spatial horizon of fast rotating Kerr
black hole in a hyperbolic space to compute the quasi-local mass of the horizon
for any value of the spin parameter $j=J/m^2$. The mass is monotonically
decreasing from twice the ADM mass at $j=0$ to $1.76569m$ at $j=\sqrt{3}/2$. It
then monotonicaly increases to a maximum around $j=0.99907$, and finally
decreases to $2.01966m$ for $j=1$ which corresponds to the extreme Kerr black
hole.
| [
{
"created": "Mon, 26 Jul 2021 18:00:13 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2021 20:56:42 GMT",
"version": "v2"
}
] | 2021-11-17 | [
[
"Dunajski",
"Maciej",
""
],
[
"Tod",
"Paul",
""
]
] | We use the isometric embedding of the spatial horizon of fast rotating Kerr black hole in a hyperbolic space to compute the quasi-local mass of the horizon for any value of the spin parameter $j=J/m^2$. The mass is monotonically decreasing from twice the ADM mass at $j=0$ to $1.76569m$ at $j=\sqrt{3}/2$. It then monotonicaly increases to a maximum around $j=0.99907$, and finally decreases to $2.01966m$ for $j=1$ which corresponds to the extreme Kerr black hole. |
2402.04813 | Gaurav Gadbail | Gaurav N. Gadbail, Simran Arora, P.K. Sahoo, and Kazuharu Bamba | Reconstruction of the singularity-free $f(\mathcal{R})$ gravity via
Raychaudhuri equations | EPJC published version | Eur. Phys. J. C 84(7), (2024) 752 | 10.1140/epjc/s10052-024-13107-8 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the bounce cosmology to construct a singularity-free
$f(\mathcal{R})$ model using the reconstruction technique. The formulation of
the $f(\mathcal{R})$ model is based on the Raychaudhari equation, a key element
employed in reconstructed models to eliminate singularities. We explore the
feasibility of obtaining stable gravitational Lagrangians, adhering to the
conditions $f_{\mathcal{R}}>0$ and $f_{\mathcal{R}\mathcal{R}}>0$.
Consequently, both models demonstrate stability, effectively avoiding the
Dolgov-Kawasaki instability. Our assessment extends to testing the
reconstructed model using energy conditions and the effective equation-of-state
(EoS). Our findings indicate that the reconstructed super-bounce model
facilitates the examination of a singularity-free accelerating universe for
both phantom and non-phantom phases. However, in the case of the reconstructed
oscillatory bounce model, two scenarios are considered with $\omega=-1/3$ and
$\omega=-2/3$. While the model proves suitable for studying a singular-free
accelerating universe in the $\omega=-1/3$ case, it fails to demonstrate such
behavior under energy conditions for the $\omega=-2/3$ scenario. The
reconstructed models accommodate early-time bouncing behavior and late-
| [
{
"created": "Wed, 7 Feb 2024 13:04:25 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Feb 2024 17:01:23 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Jul 2024 17:02:23 GMT",
"version": "v3"
}
] | 2024-07-30 | [
[
"Gadbail",
"Gaurav N.",
""
],
[
"Arora",
"Simran",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | We study the bounce cosmology to construct a singularity-free $f(\mathcal{R})$ model using the reconstruction technique. The formulation of the $f(\mathcal{R})$ model is based on the Raychaudhari equation, a key element employed in reconstructed models to eliminate singularities. We explore the feasibility of obtaining stable gravitational Lagrangians, adhering to the conditions $f_{\mathcal{R}}>0$ and $f_{\mathcal{R}\mathcal{R}}>0$. Consequently, both models demonstrate stability, effectively avoiding the Dolgov-Kawasaki instability. Our assessment extends to testing the reconstructed model using energy conditions and the effective equation-of-state (EoS). Our findings indicate that the reconstructed super-bounce model facilitates the examination of a singularity-free accelerating universe for both phantom and non-phantom phases. However, in the case of the reconstructed oscillatory bounce model, two scenarios are considered with $\omega=-1/3$ and $\omega=-2/3$. While the model proves suitable for studying a singular-free accelerating universe in the $\omega=-1/3$ case, it fails to demonstrate such behavior under energy conditions for the $\omega=-2/3$ scenario. The reconstructed models accommodate early-time bouncing behavior and late- |
gr-qc/9911036 | Stanislav Alexeyev | S.O. Alexeyev, M.V. Sazhin and M.V. Pomazanov (Moscow State
University) | Black Holes of a Minimal Size in String Gravity | 6 LaTeX pages, 1 PostScript figure (epsfig.sty), minor changes in the
text and references, submitted to Int.J.Mod.Phys | Int.J.Mod.Phys. D10 (2001) 225-230 | 10.1142/S0218271801000780 | null | gr-qc | null | A lower limit for a neutral black hole size is obtained in the frames of the
string gravity model with the second order curvature correction. It is shown
that this effect remains when the third order curvature correction is also
taken into account and argued that such restriction does exist in all
perturbative orders of curvature expansions.
| [
{
"created": "Wed, 10 Nov 1999 07:35:15 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Nov 1999 06:46:45 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Alexeyev",
"S. O.",
"",
"Moscow State\n University"
],
[
"Sazhin",
"M. V.",
"",
"Moscow State\n University"
],
[
"Pomazanov",
"M. V.",
"",
"Moscow State\n University"
]
] | A lower limit for a neutral black hole size is obtained in the frames of the string gravity model with the second order curvature correction. It is shown that this effect remains when the third order curvature correction is also taken into account and argued that such restriction does exist in all perturbative orders of curvature expansions. |
1412.3249 | Oleg Evnin | Ben Craps, Oleg Evnin and Joris Vanhoof | Renormalization, averaging, conservation laws and AdS (in)stability | v3: 28 pages, minor improvements, JHEP version | JHEP 01 (2015) 108 | 10.1007/JHEP01(2015)108 | null | gr-qc hep-th nlin.CD | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We continue our analytic investigations of non-linear spherically symmetric
perturbations around the anti-de Sitter background in gravity-scalar field
systems, and focus on conservation laws restricting the (perturbatively) slow
drift of energy between the different normal modes due to non-linearities. We
discover two conservation laws in addition to the energy conservation
previously discussed in relation to AdS instability. A similar set of three
conservation laws was previously noted for a self-interacting scalar field in a
non-dynamical AdS background, and we highlight the similarities of this system
to the fully dynamical case of gravitational instability. The nature of these
conservation laws is best understood through an appeal to averaging methods
which allow one to derive an effective Lagrangian or Hamiltonian description of
the slow energy transfer between the normal modes. The conservation laws in
question then follow from explicit symmetries of this averaged effective
theory.
| [
{
"created": "Wed, 10 Dec 2014 10:36:16 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Dec 2014 17:21:00 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Jan 2015 22:47:33 GMT",
"version": "v3"
}
] | 2015-01-22 | [
[
"Craps",
"Ben",
""
],
[
"Evnin",
"Oleg",
""
],
[
"Vanhoof",
"Joris",
""
]
] | We continue our analytic investigations of non-linear spherically symmetric perturbations around the anti-de Sitter background in gravity-scalar field systems, and focus on conservation laws restricting the (perturbatively) slow drift of energy between the different normal modes due to non-linearities. We discover two conservation laws in addition to the energy conservation previously discussed in relation to AdS instability. A similar set of three conservation laws was previously noted for a self-interacting scalar field in a non-dynamical AdS background, and we highlight the similarities of this system to the fully dynamical case of gravitational instability. The nature of these conservation laws is best understood through an appeal to averaging methods which allow one to derive an effective Lagrangian or Hamiltonian description of the slow energy transfer between the normal modes. The conservation laws in question then follow from explicit symmetries of this averaged effective theory. |
2012.07639 | Saeed Ullah Khan | Saeed Ullah Khan and Jingli Ren | Geodesics and optical properties of rotating black hole in
Randall-Sundrum brane with a cosmological constant | 15 Pages, 11 Figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of tidal charge and a cosmological constant has considerable
consequences on the spacetime geometry and its study is much important from the
observational point of view. Henceforth, we investigate their effects on
particle dynamics and the shadow cast by a Randall-Sundrum braneworld black
hole with a cosmological constant. On studying the circular geodesics of
timelike particles, we have acquired the expressions of energy, angular
momentum and effective potential. We noted that the negative values of tidal
charge and cosmological constant decreases the energy of particles. In
addition, the negative value of cosmological constant leads us to the stable
circular orbits, whereas its positive value destabilizes the circular orbits.
Our exploration shows that the cosmological constant diminishes the radius of
the black hole shadow. In response to the dragging effect, black hole rotation
elongates its shadow toward the rotational axis. Besides, black hole spin and
positive charge distort shadow and its distortion become maximum as far as the
black hole rotates faster. We also discussed the energy emission rate by
considering different cases and compared our result with the standard Kerr
black hole.
| [
{
"created": "Fri, 11 Dec 2020 07:48:50 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Jan 2021 18:04:04 GMT",
"version": "v2"
}
] | 2021-01-12 | [
[
"Khan",
"Saeed Ullah",
""
],
[
"Ren",
"Jingli",
""
]
] | The presence of tidal charge and a cosmological constant has considerable consequences on the spacetime geometry and its study is much important from the observational point of view. Henceforth, we investigate their effects on particle dynamics and the shadow cast by a Randall-Sundrum braneworld black hole with a cosmological constant. On studying the circular geodesics of timelike particles, we have acquired the expressions of energy, angular momentum and effective potential. We noted that the negative values of tidal charge and cosmological constant decreases the energy of particles. In addition, the negative value of cosmological constant leads us to the stable circular orbits, whereas its positive value destabilizes the circular orbits. Our exploration shows that the cosmological constant diminishes the radius of the black hole shadow. In response to the dragging effect, black hole rotation elongates its shadow toward the rotational axis. Besides, black hole spin and positive charge distort shadow and its distortion become maximum as far as the black hole rotates faster. We also discussed the energy emission rate by considering different cases and compared our result with the standard Kerr black hole. |
gr-qc/0003032 | Kip S. Thorne | Amos Ori (1), Kip S. Thorne (2) ((1) Department of Physics, Technion -
Israel Institute of Technology, (2) Theoretical Astophysics, California
Institute of Technology) | The Transition from Inspiral to Plunge for a Compact Body in a Circular
Equatorial Orbit Around a Massive, Spinning Black Hole | 8 Pages and 3 Figures; RevTeX; submitted to Physical Review D | Phys.Rev. D62 (2000) 124022 | 10.1103/PhysRevD.62.124022 | null | gr-qc | null | There are three regimes of gravitational-radiation-reaction-induced inspiral
for a compact body with mass mu, in a circular, equatorial orbit around a Kerr
black hole with mass M>>mu: (i) The "adiabatic inspiral regime", in which the
body gradually descends through a sequence of circular, geodesic orbits. (ii) A
"transition regime", near the innermost stable circular orbit (isco). (iii) The
"plunge regime", in which the body travels on a geodesic from slightly below
the isco into the hole's horizon. This paper gives an analytic treatment of the
transition regime and shows that, with some luck, gravitational waves from the
transition might be measurable by the space-based LISA mission.
| [
{
"created": "Wed, 8 Mar 2000 18:55:53 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ori",
"Amos",
""
],
[
"Thorne",
"Kip S.",
""
]
] | There are three regimes of gravitational-radiation-reaction-induced inspiral for a compact body with mass mu, in a circular, equatorial orbit around a Kerr black hole with mass M>>mu: (i) The "adiabatic inspiral regime", in which the body gradually descends through a sequence of circular, geodesic orbits. (ii) A "transition regime", near the innermost stable circular orbit (isco). (iii) The "plunge regime", in which the body travels on a geodesic from slightly below the isco into the hole's horizon. This paper gives an analytic treatment of the transition regime and shows that, with some luck, gravitational waves from the transition might be measurable by the space-based LISA mission. |
1410.7715 | Hao Wei | Zu-Cheng Chen, You Wu, Hao Wei | Post-Newtonian Approximation of Teleparallel Gravity Coupled with a
Scalar Field | 15 pages, revtex4; v2: discussions added, Nucl. Phys. B in press; v3:
published version | Nucl.Phys.B894:422-438,2015 | 10.1016/j.nuclphysb.2015.03.012 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the parameterized post-Newtonian (PPN) formalism to explore the weak
field approximation of teleparallel gravity non-minimally coupling to a scalar
field $\phi$, with arbitrary coupling function $\omega(\phi)$ and potential
$V(\phi)$. We find that all the PPN parameters are identical to general
relativity (GR), which makes this class of theories compatible with the Solar
System experiments. This feature also makes the theories quite different from
the scalar-tensor theories, which might be subject to stringent constraints on
the parameter space, or need some screening mechanisms to pass the Solar System
experimental constraints.
| [
{
"created": "Tue, 28 Oct 2014 18:00:00 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Mar 2015 04:19:00 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Mar 2015 04:59:00 GMT",
"version": "v3"
}
] | 2015-03-25 | [
[
"Chen",
"Zu-Cheng",
""
],
[
"Wu",
"You",
""
],
[
"Wei",
"Hao",
""
]
] | We use the parameterized post-Newtonian (PPN) formalism to explore the weak field approximation of teleparallel gravity non-minimally coupling to a scalar field $\phi$, with arbitrary coupling function $\omega(\phi)$ and potential $V(\phi)$. We find that all the PPN parameters are identical to general relativity (GR), which makes this class of theories compatible with the Solar System experiments. This feature also makes the theories quite different from the scalar-tensor theories, which might be subject to stringent constraints on the parameter space, or need some screening mechanisms to pass the Solar System experimental constraints. |
2205.07412 | Grigoris Panotopoulos | Grigoris Panotopoulos, \'Angel Rinc\'on, Il\'idio Lopes | Binary X-ray sources in massive Brans-Dicke gravity | 11 pages, 4 figures, accepted for publication in Universe. arXiv
admin note: text overlap with arXiv:2108.12984 | Universe 2022, 8(5), 285 | 10.3390/universe8050285 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study focuses on the X-ray emission of low-mass black hole binaries in
massive Brans-Dicke gravity. First, we compute the accretion disk adopting the
well-known Shakura-Sunyaev model for an optically thick, cool, and
geometrically thin disk. Moreover, we assume that the gravitational field
generated by the stellar-mass black hole is an analogue of the Schwarzschild
space-time of Einstein's theory in massive Brans-Dicke gravity. We compute the
most relevant quantities of interest, i.e., i) the radial velocity, ii) the
energy and surface density, and iii) the pressure as a function entirely of the
radial coordinate. We also compute the soft spectral component of the X-ray
emission produced by the disk. Furthermore, we investigate in detail how the
mass of the scalar field modifies the properties of the binary as described by
the more standard Schwarzschild solution.
| [
{
"created": "Mon, 16 May 2022 01:11:10 GMT",
"version": "v1"
}
] | 2022-06-07 | [
[
"Panotopoulos",
"Grigoris",
""
],
[
"Rincón",
"Ángel",
""
],
[
"Lopes",
"Ilídio",
""
]
] | This study focuses on the X-ray emission of low-mass black hole binaries in massive Brans-Dicke gravity. First, we compute the accretion disk adopting the well-known Shakura-Sunyaev model for an optically thick, cool, and geometrically thin disk. Moreover, we assume that the gravitational field generated by the stellar-mass black hole is an analogue of the Schwarzschild space-time of Einstein's theory in massive Brans-Dicke gravity. We compute the most relevant quantities of interest, i.e., i) the radial velocity, ii) the energy and surface density, and iii) the pressure as a function entirely of the radial coordinate. We also compute the soft spectral component of the X-ray emission produced by the disk. Furthermore, we investigate in detail how the mass of the scalar field modifies the properties of the binary as described by the more standard Schwarzschild solution. |
1812.10670 | Sergey Paston | R.V. Ilin, S.A. Paston | Noether and Belinfante stress-energy tensors for theories with arbitrary
Lagrangians of tensor fields | LaTeX, 6 pages, based on a talk given at the International Conference
PhysicA.SPb/2018, Saint Petersburg, Russia, 23-25 October 2018 | Journal of Physics: Conference Series 1135 (2018) 012007 | 10.1088/1742-6596/1135/1/012007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the connection between stress-energy tensor (SET) arising from
Noether's theorem and Belinfante SET which can be obtained as a right-hand side
of the Einstein's equation in the flat metric limit. This question is studied
in the wide class of Poincar\`e-invariant field theories with actions which
depend on the tensor fields of arbitrary rank and their derivatives of
arbitrary order. For this class we derive the relation between these SET and
present the exact expression for the difference between them. We also show that
the difference between corresponding integrals of motion can be expressed as a
surface integral over 2-dimensinal infinitely remote surface.
| [
{
"created": "Thu, 27 Dec 2018 09:29:49 GMT",
"version": "v1"
}
] | 2018-12-31 | [
[
"Ilin",
"R. V.",
""
],
[
"Paston",
"S. A.",
""
]
] | We investigate the connection between stress-energy tensor (SET) arising from Noether's theorem and Belinfante SET which can be obtained as a right-hand side of the Einstein's equation in the flat metric limit. This question is studied in the wide class of Poincar\`e-invariant field theories with actions which depend on the tensor fields of arbitrary rank and their derivatives of arbitrary order. For this class we derive the relation between these SET and present the exact expression for the difference between them. We also show that the difference between corresponding integrals of motion can be expressed as a surface integral over 2-dimensinal infinitely remote surface. |
0811.1727 | Robert Beig | Robert Beig and Richard M. Schoen | On Static n-body Configurations in Relativity | 10 pages; result generalized to allow for more than one
asymptotically flat end | Class.Quant.Grav.26:075014,2009 | 10.1088/0264-9381/26/7/075014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The static n-body problem of General Relativity states that there are, under
a reasonable energy condition, no static $n$-body configurations for $n > 1$,
provided the configuration of the bodies satisfies a suitable separation
condition. In this paper we solve this problem in the case that there exists a
closed, noncompact, totally geodesic surface disjoint from the bodies. This
covers the situation where the configuration has a reflection symmetry across a
noncompact surface disjoint from the bodies.
| [
{
"created": "Tue, 11 Nov 2008 16:10:26 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Mar 2009 15:18:15 GMT",
"version": "v2"
}
] | 2009-03-24 | [
[
"Beig",
"Robert",
""
],
[
"Schoen",
"Richard M.",
""
]
] | The static n-body problem of General Relativity states that there are, under a reasonable energy condition, no static $n$-body configurations for $n > 1$, provided the configuration of the bodies satisfies a suitable separation condition. In this paper we solve this problem in the case that there exists a closed, noncompact, totally geodesic surface disjoint from the bodies. This covers the situation where the configuration has a reflection symmetry across a noncompact surface disjoint from the bodies. |
gr-qc/0305085 | Josep Llosa | J. Llosa and D. Soler | Reference frames and rigid motions in relativity | 30 pages | Class.Quant.Grav.21:3067-3094,2004 | 10.1088/0264-9381/21/13/001 | null | gr-qc | null | A reference frame consists of: a reference space, a time scale and a spatial
metric. The geometric structure induced by these objects in spacetime is
developed. The existence of a class of spatial metrics that are rigid, have
free mobility and can be derived as a slight deformation of the radar metric,
is shown.
| [
{
"created": "Thu, 22 May 2003 11:47:31 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Llosa",
"J.",
""
],
[
"Soler",
"D.",
""
]
] | A reference frame consists of: a reference space, a time scale and a spatial metric. The geometric structure induced by these objects in spacetime is developed. The existence of a class of spatial metrics that are rigid, have free mobility and can be derived as a slight deformation of the radar metric, is shown. |
2105.06997 | Faizuddin Ahmed | Faizuddin Ahmed | Comment on "An axially symmetric spacetime with causality violation
[Phys. Scr. 96 (07), 075208 (2021)], arXiv:2004.13769[gr-qc]" | 4 pages, comment on arXiv:2004.13769 [gr-qc] | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, an axially symmetric spacetime with causality violation is appeared
in Ref. [1]. There, author presented a type III metric with vanishing
expansion, shear and twist. The matter-energy represents a pure radial field
with a negative cosmological constant. The spacetime is asymptotically anti-de
Sitter space in the radial direction. Actually, this work with different for
the metric was already published in Ref. [4]. Therefore, the current paper Ref.
[1] is a duplicate one of the previous work.
| [
{
"created": "Fri, 14 May 2021 13:59:25 GMT",
"version": "v1"
}
] | 2021-05-18 | [
[
"Ahmed",
"Faizuddin",
""
]
] | Recently, an axially symmetric spacetime with causality violation is appeared in Ref. [1]. There, author presented a type III metric with vanishing expansion, shear and twist. The matter-energy represents a pure radial field with a negative cosmological constant. The spacetime is asymptotically anti-de Sitter space in the radial direction. Actually, this work with different for the metric was already published in Ref. [4]. Therefore, the current paper Ref. [1] is a duplicate one of the previous work. |
gr-qc/0401044 | Dinesh Singh | Dinesh Singh | Neutrino Helicity and Chirality Transitions in Schwarzschild Space-Time | REVTeX 4.0 file; 15 pages, no figures | Phys. Rev. D71 (2005) 105003 | 10.1103/PhysRevD.71.105003 | null | gr-qc astro-ph hep-ph | null | We study the helicity and chirality transitions of a high-energy neutrino
propagating in a Schwarzschild space-time background. Using both traditional
Schwarzschild and isotropic spherical co-ordinates, we derive an
ultrarelativistic approximation of the Dirac Hamiltonian to first-order in the
neutrino's rest mass, via a generalization of the Cini-Touschek transformation
that incorporates non-inertial frame effects due to the noncommutative nature
of the momentum states in curvilinear co-ordinates. Under general conditions,
we show that neutrino's helicity is not a constant of the motion in the
massless limit due to space-time curvature, while the chirality transition rate
still retains an overall dependence on mass. We show that the chirality
transition rate generally depends on the zeroth-order component of the
neutrino's helicity transition rate under the Cini-Touschek transformation. It
is also shown that the chiral current for high-energy neutrinos is altered by
corrections due to curvature and frame-dependent effects, but should have no
significant bearing on the chiral anomaly in curved space-time. We determine
the upper bound for helicity and chirality transitions near the event horizon
of a black hole. The special case of a weak-field approximation is also
considered, which includes the gravitational analogue of Berry's phase first
proposed by Cai and Papini. Finally, we propose a method for estimating the
absolute neutrino mass and the number of right-handed chiral states from the
expectation values of the helicity and chirality transition rates in the
weak-field limit.
| [
{
"created": "Sun, 11 Jan 2004 18:39:18 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jan 2004 20:17:29 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Mar 2005 23:42:22 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Singh",
"Dinesh",
""
]
] | We study the helicity and chirality transitions of a high-energy neutrino propagating in a Schwarzschild space-time background. Using both traditional Schwarzschild and isotropic spherical co-ordinates, we derive an ultrarelativistic approximation of the Dirac Hamiltonian to first-order in the neutrino's rest mass, via a generalization of the Cini-Touschek transformation that incorporates non-inertial frame effects due to the noncommutative nature of the momentum states in curvilinear co-ordinates. Under general conditions, we show that neutrino's helicity is not a constant of the motion in the massless limit due to space-time curvature, while the chirality transition rate still retains an overall dependence on mass. We show that the chirality transition rate generally depends on the zeroth-order component of the neutrino's helicity transition rate under the Cini-Touschek transformation. It is also shown that the chiral current for high-energy neutrinos is altered by corrections due to curvature and frame-dependent effects, but should have no significant bearing on the chiral anomaly in curved space-time. We determine the upper bound for helicity and chirality transitions near the event horizon of a black hole. The special case of a weak-field approximation is also considered, which includes the gravitational analogue of Berry's phase first proposed by Cai and Papini. Finally, we propose a method for estimating the absolute neutrino mass and the number of right-handed chiral states from the expectation values of the helicity and chirality transition rates in the weak-field limit. |
1509.01664 | Marcelo Salgado | Pedro Ca\~nate, Luisa G. Jaime, Marcelo Salgado | Spherically symmetric black holes in $f(R)$ gravity: Is geometric scalar
hair supported ? | 32 pages, 11 figures | null | 10.1088/0264-9381/33/15/155005 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss with a rather critical eye the current situation of black hole
(BH) solutions in $f(R)$ gravity and shed light about its geometrical and
physical significance. We also argue about the meaning, existence or lack
thereof of a Birkhoff's theorem in this kind of modified gravity. We focus then
on the analysis and quest of $non-trivial$ (i.e. hairy)
$asymptotically\,\,flat$ (AF) BH solutions in static and spherically symmetric
(SSS) spacetimes in vacuum having the property that the Ricci scalar does $not$
vanish identically in the domain of outer communication. To do so, we provide
and enforce the $regularity\,\,conditions$ at the horizon in order to prevent
the presence of singular solutions there. Specifically, we consider several
classes of $f(R)$ models like those proposed recently for explaining the
accelerated expansion in the universe and which have been thoroughly tested in
several physical scenarios. Finally, we report analytical and numerical
evidence about the $absence$ of $geometric\,\,hair$ in AFSSSBH solutions in
those $f(R)$ models. First, we submit the models to the available no-hair
theorems, and in the cases where the theorems apply, the absence of hair is
demonstrated analytically. In the cases where the theorems do not apply, we
resort to a numerical analysis due to the complexity of the non-linear
differential equations. Within that aim, a code to solve the equations
numerically was built and tested using well know exact solutions. In a future
investigation we plan to analyze the problem of hair in De Sitter and Anti-De
Sitter backgrounds.
| [
{
"created": "Sat, 5 Sep 2015 05:31:41 GMT",
"version": "v1"
}
] | 2016-07-20 | [
[
"Cañate",
"Pedro",
""
],
[
"Jaime",
"Luisa G.",
""
],
[
"Salgado",
"Marcelo",
""
]
] | We discuss with a rather critical eye the current situation of black hole (BH) solutions in $f(R)$ gravity and shed light about its geometrical and physical significance. We also argue about the meaning, existence or lack thereof of a Birkhoff's theorem in this kind of modified gravity. We focus then on the analysis and quest of $non-trivial$ (i.e. hairy) $asymptotically\,\,flat$ (AF) BH solutions in static and spherically symmetric (SSS) spacetimes in vacuum having the property that the Ricci scalar does $not$ vanish identically in the domain of outer communication. To do so, we provide and enforce the $regularity\,\,conditions$ at the horizon in order to prevent the presence of singular solutions there. Specifically, we consider several classes of $f(R)$ models like those proposed recently for explaining the accelerated expansion in the universe and which have been thoroughly tested in several physical scenarios. Finally, we report analytical and numerical evidence about the $absence$ of $geometric\,\,hair$ in AFSSSBH solutions in those $f(R)$ models. First, we submit the models to the available no-hair theorems, and in the cases where the theorems apply, the absence of hair is demonstrated analytically. In the cases where the theorems do not apply, we resort to a numerical analysis due to the complexity of the non-linear differential equations. Within that aim, a code to solve the equations numerically was built and tested using well know exact solutions. In a future investigation we plan to analyze the problem of hair in De Sitter and Anti-De Sitter backgrounds. |
gr-qc/0611077 | Muzaffer Adak | M. Adak (Pamukkale U.) | The Symmetric Teleparallel Gravity | Paper presented at The 5th Workshop on Quantization, Dualities and
Integrable Systems, Pamukkale University, 23-28 January 2006, Denizli, Turkey | Turk.J.Phys. 30 (2006) 379-390 | null | null | gr-qc | null | We study symmetric teleparallel (STP) gravity model, in which only spacetime
non-metricity is nonzero. First we obtain STP equivalent Einstein-Hilbert
Lagrangian and give an approach for a generic solution in terms of only metric
tensor. Then we obtain a spherically symmetric static solution to the
Einstein's equation in STP space-time and discuss the singularities. Finally,
we study a model given by a Lagrangian 4-form quadratic in non-metricity. Thus,
we seek Schwarzschild-type solutions because of its observational success and
obtain some sets of solutions. Finally, we discuss physical relevance of the
solutions.
| [
{
"created": "Tue, 14 Nov 2006 15:50:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Adak",
"M.",
"",
"Pamukkale U."
]
] | We study symmetric teleparallel (STP) gravity model, in which only spacetime non-metricity is nonzero. First we obtain STP equivalent Einstein-Hilbert Lagrangian and give an approach for a generic solution in terms of only metric tensor. Then we obtain a spherically symmetric static solution to the Einstein's equation in STP space-time and discuss the singularities. Finally, we study a model given by a Lagrangian 4-form quadratic in non-metricity. Thus, we seek Schwarzschild-type solutions because of its observational success and obtain some sets of solutions. Finally, we discuss physical relevance of the solutions. |
1612.04239 | Abhik Kumar Sanyal Dr. | Behzad Tajahmad and Abhik Kumar Sanyal | Unified cosmology with Non-minimally coupled scalar-tensor theory of
gravity | 9 pages, 7 figures | null | 10.1140/epjc/s10052-017-4785-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unlike Noether symmetry, a metric independent general conserved current exits
for non-minimally coupled scalar-tensor theory of gravity, if the trace of the
energy momentum tensor vanishes. Thus, in the context of cosmology, a symmetry
exists both in the early vacuum and radiation dominated era. For slow roll,
symmetry is sacrificed, but at the end of early inflation, such a symmetry
leads to a Friedmann-like radiation era. Late time cosmic acceleration in the
matter dominated era is realized in the absence of symmetry, in view of the
same decayed and red-shifted scalar field. Thus, unification of early inflation
with late time cosmic acceleration with a single scalar field, may be realized.
| [
{
"created": "Fri, 9 Dec 2016 03:35:34 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Tajahmad",
"Behzad",
""
],
[
"Sanyal",
"Abhik Kumar",
""
]
] | Unlike Noether symmetry, a metric independent general conserved current exits for non-minimally coupled scalar-tensor theory of gravity, if the trace of the energy momentum tensor vanishes. Thus, in the context of cosmology, a symmetry exists both in the early vacuum and radiation dominated era. For slow roll, symmetry is sacrificed, but at the end of early inflation, such a symmetry leads to a Friedmann-like radiation era. Late time cosmic acceleration in the matter dominated era is realized in the absence of symmetry, in view of the same decayed and red-shifted scalar field. Thus, unification of early inflation with late time cosmic acceleration with a single scalar field, may be realized. |
2201.05866 | Shaoqi Hou | Shou-shan Bao, Shaoqi Hou, Hong Zhang | Searching for wormholes with gravitational wave scattering | 10 pages, 8 figures. Match the published version | Eur. Phys. J. C (2023) 83:127 | 10.1140/epjc/s10052-023-11281-9 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormholes bridging distant places of the universe are well-known solutions of
general relativity. In particular, traversable wormholes which allow
interstellar traveling are also popular in science fiction. However, no hint of
their existence has been found yet. In this work, we propose using the
gravitational wave (GW) scattering off spherical wormholes to search for their
existence. We carefully calculate the reflected and transmitted waveforms with
time-independent scattering theory. Our results quantitatively show the echo
signatures in the two universes on both sides of the wormhole. In a certain
wormhole mass range, the transmitted wave has a unique isolated chirp without
an inspiral waveform, and the reflected wave has the anti-chirp behavior, i.e.,
the missing of the chirping signal. We also calculate the searching range of
the current and projected GW telescopes. Our method can be adapted to
efficiently calculate the templates to search for wormholes.
| [
{
"created": "Sat, 15 Jan 2022 14:52:34 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Feb 2023 03:27:32 GMT",
"version": "v2"
}
] | 2023-02-28 | [
[
"Bao",
"Shou-shan",
""
],
[
"Hou",
"Shaoqi",
""
],
[
"Zhang",
"Hong",
""
]
] | Wormholes bridging distant places of the universe are well-known solutions of general relativity. In particular, traversable wormholes which allow interstellar traveling are also popular in science fiction. However, no hint of their existence has been found yet. In this work, we propose using the gravitational wave (GW) scattering off spherical wormholes to search for their existence. We carefully calculate the reflected and transmitted waveforms with time-independent scattering theory. Our results quantitatively show the echo signatures in the two universes on both sides of the wormhole. In a certain wormhole mass range, the transmitted wave has a unique isolated chirp without an inspiral waveform, and the reflected wave has the anti-chirp behavior, i.e., the missing of the chirping signal. We also calculate the searching range of the current and projected GW telescopes. Our method can be adapted to efficiently calculate the templates to search for wormholes. |
1105.1340 | Martin Bojowald | Martin Bojowald, George M. Paily, Juan D. Reyes, Rakesh Tibrewala | Black-hole horizons in modified space-time structures arising from
canonical quantum gravity | 43 pages, 3 figures | Class. Quantum Grav. 28 (2011) 185006 | 10.1088/0264-9381/28/18/185006 | IGC-11/5-1 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several properties of canonical quantum gravity modify space-time structures,
sometimes to the degree that no effective line elements exist to describe the
geometry. An analysis of solutions, for instance in the context of black holes,
then requires new insights. In this article, standard definitions of horizons
in spherical symmetry are first reformulated canonically, and then evaluated
for solutions of equations and constraints modified by inverse-triad
corrections of loop quantum gravity. When possible, a space-time analysis is
performed which reveals a mass threshold for black holes and small changes to
Hawking radiation. For more general conclusions, canonical perturbation theory
is developed to second order to include back-reaction from matter. The results
shed light on the questions of whether renormalization of Newton's constant or
other modifications of horizon conditions should be taken into account in
computations of black-hole entropy in loop quantum gravity.
| [
{
"created": "Fri, 6 May 2011 17:47:40 GMT",
"version": "v1"
}
] | 2011-11-04 | [
[
"Bojowald",
"Martin",
""
],
[
"Paily",
"George M.",
""
],
[
"Reyes",
"Juan D.",
""
],
[
"Tibrewala",
"Rakesh",
""
]
] | Several properties of canonical quantum gravity modify space-time structures, sometimes to the degree that no effective line elements exist to describe the geometry. An analysis of solutions, for instance in the context of black holes, then requires new insights. In this article, standard definitions of horizons in spherical symmetry are first reformulated canonically, and then evaluated for solutions of equations and constraints modified by inverse-triad corrections of loop quantum gravity. When possible, a space-time analysis is performed which reveals a mass threshold for black holes and small changes to Hawking radiation. For more general conclusions, canonical perturbation theory is developed to second order to include back-reaction from matter. The results shed light on the questions of whether renormalization of Newton's constant or other modifications of horizon conditions should be taken into account in computations of black-hole entropy in loop quantum gravity. |
gr-qc/0312063 | Hrvoje Nikolic | H. Nikolic | Time in quantum gravity by weakening the Hamiltonian constraint | 4 pages | null | null | null | gr-qc hep-th quant-ph | null | We replace the usual Hamiltonian constraint of quantum gravity H|psi>=0 by a
weaker one <psi|H|psi>=0. This allows |psi> to satisfy the time-dependent
functional Schrodinger equation. In general, only the phase of the wave
function appears to be time independent. The resulting quantum theory has the
correct classical limit and thus provides a viable theory of quantum gravity
that solves the problem of time without introducing additional nongravitational
degrees of freedom.
| [
{
"created": "Thu, 11 Dec 2003 15:16:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nikolic",
"H.",
""
]
] | We replace the usual Hamiltonian constraint of quantum gravity H|psi>=0 by a weaker one <psi|H|psi>=0. This allows |psi> to satisfy the time-dependent functional Schrodinger equation. In general, only the phase of the wave function appears to be time independent. The resulting quantum theory has the correct classical limit and thus provides a viable theory of quantum gravity that solves the problem of time without introducing additional nongravitational degrees of freedom. |
0909.4227 | Alexander Kamenshchik | Alexander Yu. Kamenshchik, Chiara M.F. Mingarelli | A generalized Heckmann-Schucking cosmological solution in the presence
of a negative cosmological constant | 10 pages | Phys.Lett.B693:213-217,2010 | 10.1016/j.physletb.2010.08.065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An exact solution of the Einstein equations for a Bianchi-I universe in the
presence of dust, stiff matter and a negative cosmological constant,
generalising the well-known Heckmann-Schucking solution is presented. This
solution describes a universe existing during a finite period of cosmic time,
where the beginning and the end of its evolution are characterized by the
presence of Kasner type cosmological singularities.
| [
{
"created": "Wed, 23 Sep 2009 15:24:23 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Mingarelli",
"Chiara M. F.",
""
]
] | An exact solution of the Einstein equations for a Bianchi-I universe in the presence of dust, stiff matter and a negative cosmological constant, generalising the well-known Heckmann-Schucking solution is presented. This solution describes a universe existing during a finite period of cosmic time, where the beginning and the end of its evolution are characterized by the presence of Kasner type cosmological singularities. |
1307.4360 | Shih-Yuin Lin | Jason Doukas, Shih-Yuin Lin, B. L. Hu, Robert B. Mann | Unruh Effect under Non-equilibrium conditions: Oscillatory motion of an
Unruh-DeWitt detector | 23 pages, 11 figures. Minor revision, new references added | JHEP 11 (2013) 119 | 10.1007/JHEP11(2013)119 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Unruh effect refers to the thermal fluctuations a detector experiences
while undergoing linear motion with uniform acceleration in a Minkowski vacuum.
This thermality can be demonstrated by tracing the vacuum state of the field
over the modes beyond the accelerated detector's event horizon. However, the
event horizon is well-defined only if the detector moves with eternal uniform
linear acceleration. This idealized condition cannot be fulfilled in realistic
situations when the motion unavoidably involves periods of non-uniform
acceleration. Many experimental proposals to test the Unruh effect are of this
nature. Often circular or oscillatory motion, which lacks an obvious geometric
description, is considered in such proposals. The proper perspective for
theoretically going beyond, or experimentally testing, the Unruh-Hawking effect
in these more general conditions has to be offered by concepts and techniques
in non-equilibrium quantum field theory. In this paper we provide a detailed
analysis of how an Unruh-DeWitt detector undergoing oscillatory motion responds
to the fluctuations of a quantum field. Numerical results for the late-time
temperatures of the oscillating detector are presented. We comment on the
digressions of these results from what one would obtain from a naive
application of Unruh's result.
| [
{
"created": "Tue, 16 Jul 2013 17:56:53 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Dec 2013 08:00:12 GMT",
"version": "v2"
}
] | 2013-12-10 | [
[
"Doukas",
"Jason",
""
],
[
"Lin",
"Shih-Yuin",
""
],
[
"Hu",
"B. L.",
""
],
[
"Mann",
"Robert B.",
""
]
] | The Unruh effect refers to the thermal fluctuations a detector experiences while undergoing linear motion with uniform acceleration in a Minkowski vacuum. This thermality can be demonstrated by tracing the vacuum state of the field over the modes beyond the accelerated detector's event horizon. However, the event horizon is well-defined only if the detector moves with eternal uniform linear acceleration. This idealized condition cannot be fulfilled in realistic situations when the motion unavoidably involves periods of non-uniform acceleration. Many experimental proposals to test the Unruh effect are of this nature. Often circular or oscillatory motion, which lacks an obvious geometric description, is considered in such proposals. The proper perspective for theoretically going beyond, or experimentally testing, the Unruh-Hawking effect in these more general conditions has to be offered by concepts and techniques in non-equilibrium quantum field theory. In this paper we provide a detailed analysis of how an Unruh-DeWitt detector undergoing oscillatory motion responds to the fluctuations of a quantum field. Numerical results for the late-time temperatures of the oscillating detector are presented. We comment on the digressions of these results from what one would obtain from a naive application of Unruh's result. |
gr-qc/9404049 | Gregory A. Burnett | Gregory A. Burnett | Closed spherically symmetric massless scalar field spacetimes have
finite lifetimes | 8 pages (uuencoded postscript file), NCSU-MP-9401 | Phys.Rev.D50:6158-6164,1994 | 10.1103/PhysRevD.50.6158 | null | gr-qc | null | The closed-universe recollapse conjecture is studied for a class of closed
spherically symmetric spacetimes which includes those having as a matter
source: (1) a massless scalar field; (2) a perfect fluid obeying the equation
of state $\rho = P$; and (3) null dust. It is proven that all timelike curves
in any such spacetime must have length less than $6 \max_\Sigma(2m)$, where $m$
is the mass associated with the spheres of symmetry and $\Sigma$ is any Cauchy
surface for the spacetime. The simplicity of this result leads us to conjecture
that a similar bound can be established for the more general spherically
symmetric spacetimes.
| [
{
"created": "Tue, 26 Apr 1994 17:10:01 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Burnett",
"Gregory A.",
""
]
] | The closed-universe recollapse conjecture is studied for a class of closed spherically symmetric spacetimes which includes those having as a matter source: (1) a massless scalar field; (2) a perfect fluid obeying the equation of state $\rho = P$; and (3) null dust. It is proven that all timelike curves in any such spacetime must have length less than $6 \max_\Sigma(2m)$, where $m$ is the mass associated with the spheres of symmetry and $\Sigma$ is any Cauchy surface for the spacetime. The simplicity of this result leads us to conjecture that a similar bound can be established for the more general spherically symmetric spacetimes. |
2402.16922 | Mubasher Jamil | Tao Zhu, Hoang Ky Nguyen, Mustapha Azreg-A\"inou, Mubasher Jamil | Observational tests of asymptotically flat ${\cal R}^{2}$ spacetimes | 13 pages, no figure, to appear in EPJC | Eur. Phys. J. C (2024) 84:330 | 10.1140/epjc/s10052-024-12610-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A novel class of Buchdahl-inspired metrics with closed-form expressions was
recently obtained based on Buchdahl's seminal work on searching for static,
spherically symmetric metrics in ${\cal R}^{2}$ gravity in vacuo.
Buchdahl-inspired spacetimes provide an interesting framework for testing
predictions of ${\cal R}^{2}$ gravity models against observations. To test
these Buchdahl-inspired spacetimes, we consider observational constraints
imposed on the deviation parameter, which characterizes the deviation of the
asymptotically flat Buchdahl-inspired metric from the Schwarzschild spacetime.
We utilize several recent solar system experiments and observations of the S2
star in the Galactic center and the black hole shadow. By calculating the
effects of Buchdahl-inspired spacetimes on astronomical observations both
within and outside of the solar system, including the deflection angle of light
by the Sun, gravitational time delay, perihelion advance, shadow, and geodetic
precession, we determine observational constraints on the corresponding
deviation parameters by comparing theoretical predictions with the most recent
observations. Among these constraints, we find that the tightest one comes from
the Cassini mission's measurement of gravitational time delay.
| [
{
"created": "Mon, 26 Feb 2024 09:56:02 GMT",
"version": "v1"
}
] | 2024-04-01 | [
[
"Zhu",
"Tao",
""
],
[
"Nguyen",
"Hoang Ky",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jamil",
"Mubasher",
""
]
] | A novel class of Buchdahl-inspired metrics with closed-form expressions was recently obtained based on Buchdahl's seminal work on searching for static, spherically symmetric metrics in ${\cal R}^{2}$ gravity in vacuo. Buchdahl-inspired spacetimes provide an interesting framework for testing predictions of ${\cal R}^{2}$ gravity models against observations. To test these Buchdahl-inspired spacetimes, we consider observational constraints imposed on the deviation parameter, which characterizes the deviation of the asymptotically flat Buchdahl-inspired metric from the Schwarzschild spacetime. We utilize several recent solar system experiments and observations of the S2 star in the Galactic center and the black hole shadow. By calculating the effects of Buchdahl-inspired spacetimes on astronomical observations both within and outside of the solar system, including the deflection angle of light by the Sun, gravitational time delay, perihelion advance, shadow, and geodetic precession, we determine observational constraints on the corresponding deviation parameters by comparing theoretical predictions with the most recent observations. Among these constraints, we find that the tightest one comes from the Cassini mission's measurement of gravitational time delay. |
gr-qc/0505036 | Thomas Waters | Brien C. Nolan, Thomas J. Waters | Even perturbations of self-similar Vaidya space-time | Accepted for publication in Physical Review D, 27 pages | Phys.Rev. D71 (2005) 104030 | 10.1103/PhysRevD.71.104030 | null | gr-qc | null | We study even parity metric and matter perturbations of all angular modes in
self-similar Vaidya space-time. We focus on the case where the background
contains a naked singularity. Initial conditions are imposed describing a
finite perturbation emerging from the portion of flat space-time preceding the
matter-filled region of space-time. The most general perturbation satisfying
the initial conditions is allowed impinge upon the Cauchy horizon (CH), whereat
the perturbation remains finite: there is no ``blue-sheet'' instability.
However when the perturbation evolves through the CH and onto the second future
similarity horizon of the naked singularity, divergence necessarily occurs:
this surface is found to be unstable. The analysis is based on the study of
individual modes following a Mellin transform of the perturbation. We present
an argument that the full perturbation remains finite after resummation of the
(possibly infinite number of) modes.
| [
{
"created": "Mon, 9 May 2005 14:37:02 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Nolan",
"Brien C.",
""
],
[
"Waters",
"Thomas J.",
""
]
] | We study even parity metric and matter perturbations of all angular modes in self-similar Vaidya space-time. We focus on the case where the background contains a naked singularity. Initial conditions are imposed describing a finite perturbation emerging from the portion of flat space-time preceding the matter-filled region of space-time. The most general perturbation satisfying the initial conditions is allowed impinge upon the Cauchy horizon (CH), whereat the perturbation remains finite: there is no ``blue-sheet'' instability. However when the perturbation evolves through the CH and onto the second future similarity horizon of the naked singularity, divergence necessarily occurs: this surface is found to be unstable. The analysis is based on the study of individual modes following a Mellin transform of the perturbation. We present an argument that the full perturbation remains finite after resummation of the (possibly infinite number of) modes. |
0809.4744 | Kourosh Nozari | Kourosh Nozari and S. Davood Sadatian | Late-time acceleration and Phantom Divide Line Crossing with Non-minimal
Coupling and Lorentz Invariance Violation | 25 pages, 8 figures | Eur.Phys.J.C58:499-510,2008 | 10.1140/epjc/s10052-008-0767-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider two alternative dark energy models: a Lorentz invariance
preserving model with a nonminimally coupled scalar field and a Lorentz
invariance violating model with a minimally coupled scalar field. We study
accelerated expansion and dynamics of equation of state parameter in these
scenarios. While a minimally coupled scalar field has not the capability to be
a successful dark energy candidate with cosmological constant line crossing, a
nonminimally coupled scalar field in the presence of Lorentz invariance or a
minimally coupled scalar field with Lorentz invariance violation have this
capability. In the later case, accelerated expansion and phantom divide line
crossing are the results of interactive nature of this Lorentz violating
scenario.
| [
{
"created": "Sat, 27 Sep 2008 06:46:13 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Nozari",
"Kourosh",
""
],
[
"Sadatian",
"S. Davood",
""
]
] | We consider two alternative dark energy models: a Lorentz invariance preserving model with a nonminimally coupled scalar field and a Lorentz invariance violating model with a minimally coupled scalar field. We study accelerated expansion and dynamics of equation of state parameter in these scenarios. While a minimally coupled scalar field has not the capability to be a successful dark energy candidate with cosmological constant line crossing, a nonminimally coupled scalar field in the presence of Lorentz invariance or a minimally coupled scalar field with Lorentz invariance violation have this capability. In the later case, accelerated expansion and phantom divide line crossing are the results of interactive nature of this Lorentz violating scenario. |
gr-qc/0402025 | Cenalo Vaz | Cenalo Vaz | Quantizing Gravitational Collapse | 7 pages, LaTeX. Contribution to the proceedings of QTS3, held the
University of Cincinnati, September 10-14, 2003 | null | 10.1142/9789812702340_0021 | null | gr-qc | null | I summarize some results obtained from a canonical quantization of
gravitational collapse. The quantization is carried out in Kuchar variables on
the LeMaitre-Tolman-Bondi family of spacetimes. I show how mass quantization,
the black hole entropy and Hawking radiation may be understood in these models.
Hawking radiation is obtained in the WKB approximation but the first order
quantum gravity correction makes the near-horizon spectrum non-thermal,
suggesting that unitarity is preserved. The quantization may be used to study
quantum gravity effects in collapse leading to the formation of both covered
and naked singularities.
| [
{
"created": "Wed, 4 Feb 2004 20:37:20 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Vaz",
"Cenalo",
""
]
] | I summarize some results obtained from a canonical quantization of gravitational collapse. The quantization is carried out in Kuchar variables on the LeMaitre-Tolman-Bondi family of spacetimes. I show how mass quantization, the black hole entropy and Hawking radiation may be understood in these models. Hawking radiation is obtained in the WKB approximation but the first order quantum gravity correction makes the near-horizon spectrum non-thermal, suggesting that unitarity is preserved. The quantization may be used to study quantum gravity effects in collapse leading to the formation of both covered and naked singularities. |
0809.1284 | Tiberiu Harko | C. S. J. Pun, Z. Kovacs, T. Harko | Thin accretion disks onto brane world black holes | 37 pages, 14 figures, accepted for publication in PRD | Phys.Rev.D78:084015,2008 | 10.1103/PhysRevD.78.084015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The braneworld description of our universe entails a large extra dimension
and a fundamental scale of gravity that might be lower by several orders of
magnitude as compared to the Planck scale. An interesting consequence of the
braneworld scenario is in the nature of the vacuum solutions of the brane
gravitational field equations, with properties quite distinct as compared to
the standard black hole solutions of general relativity. One possibility of
observationally discriminating between different types of black holes is the
study of the emission properties of the accretion disks. In the present paper
we obtain the energy flux, the emission spectrum and accretion efficiency from
the accretion disks around several classes of static and rotating brane world
black holes, and we compare them to the general relativistic case. Particular
signatures can appear in the electromagnetic spectrum, thus leading to the
possibility of directly testing extra-dimensional physical models by using
astrophysical observations of the emission spectra from accretion disks.
| [
{
"created": "Mon, 8 Sep 2008 07:22:21 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Sep 2008 07:34:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pun",
"C. S. J.",
""
],
[
"Kovacs",
"Z.",
""
],
[
"Harko",
"T.",
""
]
] | The braneworld description of our universe entails a large extra dimension and a fundamental scale of gravity that might be lower by several orders of magnitude as compared to the Planck scale. An interesting consequence of the braneworld scenario is in the nature of the vacuum solutions of the brane gravitational field equations, with properties quite distinct as compared to the standard black hole solutions of general relativity. One possibility of observationally discriminating between different types of black holes is the study of the emission properties of the accretion disks. In the present paper we obtain the energy flux, the emission spectrum and accretion efficiency from the accretion disks around several classes of static and rotating brane world black holes, and we compare them to the general relativistic case. Particular signatures can appear in the electromagnetic spectrum, thus leading to the possibility of directly testing extra-dimensional physical models by using astrophysical observations of the emission spectra from accretion disks. |
gr-qc/9411015 | J. L. Rosales | J.L. Rosales | Cosmological solution for the problem of rotation velocities in galaxies | 7 pages, file 'curve.eps' is available from the author by e-mail | null | null | FTUAM 94-25 | gr-qc | null | A solution for the problem of understanding observed rotation curves in
galaxies without the introduction of dark matter halos is presented. This
solution has been obtained upon considering the distribution of masses in the
expanding universe, then, having a cosmological character. A formal limiting
radius for galaxies depending on cosmological parameters is given. The
empirical conclusions derived from the theory of M. Milgrom and J. Bekenstein
arise as direct consequences of the present approach without any need of
drastically modifying newtonian dynamics.
| [
{
"created": "Mon, 7 Nov 1994 19:25:38 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Rosales",
"J. L.",
""
]
] | A solution for the problem of understanding observed rotation curves in galaxies without the introduction of dark matter halos is presented. This solution has been obtained upon considering the distribution of masses in the expanding universe, then, having a cosmological character. A formal limiting radius for galaxies depending on cosmological parameters is given. The empirical conclusions derived from the theory of M. Milgrom and J. Bekenstein arise as direct consequences of the present approach without any need of drastically modifying newtonian dynamics. |
2401.05658 | Zeus Sales Moreira | Zeus S. Moreira, Carlos A. R. Herdeiro, Lu\'is C. B. Crispino | Twisting shadows: light rings, lensing and shadows of black holes in
swirling universes | 21 pages, 14 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Using the Ernst formalism, a novel solution of vacuum General Relativity was
recently obtained [1], describing a Schwarzschild black hole (BH) immersed in a
non-asymptotically flat rotating background, dubbed swirling universe, with the
peculiar property that north and south hemispheres spin in opposite directions.
We investigate the null geodesic flow and, in particular, the existence of
light rings in this vacuum geometry. By evaluating the total topological charge
$w$, we show that there exists one unstable light ring ($w=-1$) for each
rotation sense of the background. We observe that the swirling background
drives the Schwarzschild BH light rings outside the equatorial plane,
displaying counter-rotating motion with respect to each other, while (both)
co-rotating with respect to the swirling universe. Using backwards ray-tracing,
we obtain the shadow and gravitational lensing effects, revealing a novel
feature for observers on the equatorial plane: the BH shadow displays an odd
$\mathbb{Z}_2$ (north-south) symmetry, inherited from the same type of symmetry
of the spacetime itself: a twisted shadow.
| [
{
"created": "Thu, 11 Jan 2024 04:42:44 GMT",
"version": "v1"
}
] | 2024-01-12 | [
[
"Moreira",
"Zeus S.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | Using the Ernst formalism, a novel solution of vacuum General Relativity was recently obtained [1], describing a Schwarzschild black hole (BH) immersed in a non-asymptotically flat rotating background, dubbed swirling universe, with the peculiar property that north and south hemispheres spin in opposite directions. We investigate the null geodesic flow and, in particular, the existence of light rings in this vacuum geometry. By evaluating the total topological charge $w$, we show that there exists one unstable light ring ($w=-1$) for each rotation sense of the background. We observe that the swirling background drives the Schwarzschild BH light rings outside the equatorial plane, displaying counter-rotating motion with respect to each other, while (both) co-rotating with respect to the swirling universe. Using backwards ray-tracing, we obtain the shadow and gravitational lensing effects, revealing a novel feature for observers on the equatorial plane: the BH shadow displays an odd $\mathbb{Z}_2$ (north-south) symmetry, inherited from the same type of symmetry of the spacetime itself: a twisted shadow. |
1210.4397 | Jiang Qing-Quan | Qing-Quan Jiang | On black hole spectroscopy via quantum tunneling | 10 pages, submitted | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent work [\emph{Quantum tunneling and black hole spectroscopy, Phys.
Lett.} B686 (2010) 279, arXiv:0907.4271, by Banerjee et al.], it has been
shown, in the tunneling mechanism, the area spacing parameter of a black hole
horizon is given by $\gamma=4$. In this paper, by carefully analyzing the
tunneling process of the black hole radiation, we interestingly find that the
most qualified candidate for a universal area gap in the tunneling mechanism is
$\gamma=8\pi$. First, we develop the Banerjee's treatment and the Kunstatter's
conjecture to revisit the black hole spectroscopy via quantum tunneling, and
find for a real tunneling process, the area spacing parameter is given by the
possible value $\gamma\geq 4$. That is, the previous model-dependent area
spacing parameters, i.e. $\gamma=8\pi, 4\ln 3, 4$, are all possible in the
tunneling mechanism. Finally, some discussions are followed to find, in the
tunneling mechanism, $\gamma=8\pi$ is the most qualified candidate for a
universal area spacing parameter.
| [
{
"created": "Tue, 16 Oct 2012 13:24:32 GMT",
"version": "v1"
}
] | 2012-10-17 | [
[
"Jiang",
"Qing-Quan",
""
]
] | In recent work [\emph{Quantum tunneling and black hole spectroscopy, Phys. Lett.} B686 (2010) 279, arXiv:0907.4271, by Banerjee et al.], it has been shown, in the tunneling mechanism, the area spacing parameter of a black hole horizon is given by $\gamma=4$. In this paper, by carefully analyzing the tunneling process of the black hole radiation, we interestingly find that the most qualified candidate for a universal area gap in the tunneling mechanism is $\gamma=8\pi$. First, we develop the Banerjee's treatment and the Kunstatter's conjecture to revisit the black hole spectroscopy via quantum tunneling, and find for a real tunneling process, the area spacing parameter is given by the possible value $\gamma\geq 4$. That is, the previous model-dependent area spacing parameters, i.e. $\gamma=8\pi, 4\ln 3, 4$, are all possible in the tunneling mechanism. Finally, some discussions are followed to find, in the tunneling mechanism, $\gamma=8\pi$ is the most qualified candidate for a universal area spacing parameter. |
1406.5446 | Gines Perez Teruel | Gin\'es R.P\'erez Teruel | Implications of nonsymmetric metric theories for particle physics. New
interpretation of the Pauli coupling | null | Mod. Phys. Lett. A, 29, 1450098 (2014) | 10.1142/S0217732314500989 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we provide a possible geometrical interpretation of the spin of
elementary particles. In particular, it is investigated how the wave equations
of matter are altered by the addition of an antisymmetric contribution to the
metric tensor. In this scenario the explicit form of the matter wave equations
is investigated in a general curved space-time, and then the equations are
particularized to the flat case. Unlike traditional approaches of NGT, in which
the gravitational field is responsible for breaking the symmetry of the flat
Minkowski metric, we find more natural to consider that, in general, the metric
of the space-time could be nonsymmetric even in the flat case. The physical
consequences of this assumption are explored in detail. Interestingly enough,
it is found that the metric tensor splits into a bosonic and a fermionic; the
antisymmetric part of the metric is very sensitive to the spin and turns out to
be undetectable for spinless scalar particles. However, fermions couple to it
in a non-trivial way (only when there are interactions). In addition, the Pauli
coupling is derived automatically as a consequence of the nonsymmetric nature
of the metric
| [
{
"created": "Fri, 20 Jun 2014 16:13:45 GMT",
"version": "v1"
}
] | 2014-06-23 | [
[
"Teruel",
"Ginés R. Pérez",
""
]
] | In this work we provide a possible geometrical interpretation of the spin of elementary particles. In particular, it is investigated how the wave equations of matter are altered by the addition of an antisymmetric contribution to the metric tensor. In this scenario the explicit form of the matter wave equations is investigated in a general curved space-time, and then the equations are particularized to the flat case. Unlike traditional approaches of NGT, in which the gravitational field is responsible for breaking the symmetry of the flat Minkowski metric, we find more natural to consider that, in general, the metric of the space-time could be nonsymmetric even in the flat case. The physical consequences of this assumption are explored in detail. Interestingly enough, it is found that the metric tensor splits into a bosonic and a fermionic; the antisymmetric part of the metric is very sensitive to the spin and turns out to be undetectable for spinless scalar particles. However, fermions couple to it in a non-trivial way (only when there are interactions). In addition, the Pauli coupling is derived automatically as a consequence of the nonsymmetric nature of the metric |
1611.09660 | Cristina Blaga | Cristina Blaga | Circular orbits, Lyapunov stability and Manev-type forces | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study the stability in the sense of Lyapunov of the
circular orbits in the generalized Manev two bodies problem. First, we explore
the existence of the circular orbits and determine their radius. Then, using
the first integrals of motion we build a positive definite function, known as a
Lyapunov function. It's existence proves that the circular orbit is stable in
the sense of Lyapunov. In the end, we consider several real systems of two
bodies and compare the characteristics of the circular orbits in Newtonian and
modified Manev gravitational field, arguing about our possibilities to observe
the differences between the motion in these two fields.
| [
{
"created": "Sun, 27 Nov 2016 14:04:24 GMT",
"version": "v1"
}
] | 2016-11-30 | [
[
"Blaga",
"Cristina",
""
]
] | In this article we study the stability in the sense of Lyapunov of the circular orbits in the generalized Manev two bodies problem. First, we explore the existence of the circular orbits and determine their radius. Then, using the first integrals of motion we build a positive definite function, known as a Lyapunov function. It's existence proves that the circular orbit is stable in the sense of Lyapunov. In the end, we consider several real systems of two bodies and compare the characteristics of the circular orbits in Newtonian and modified Manev gravitational field, arguing about our possibilities to observe the differences between the motion in these two fields. |
1005.1614 | Robert Geroch | Robert Geroch | Faster Than Light? | 13 pages; submitted to J. Lorentz Geometry | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is argued that special relativity remains a viable physical theory even
when there is permitted signals traveling faster than light.
| [
{
"created": "Mon, 10 May 2010 17:42:11 GMT",
"version": "v1"
}
] | 2010-05-11 | [
[
"Geroch",
"Robert",
""
]
] | It is argued that special relativity remains a viable physical theory even when there is permitted signals traveling faster than light. |
gr-qc/9809067 | Michael Reisenberger | Michael P. Reisenberger | On relativistic spin network vertices | 15 pages, one postscript figure (uses psfig) | J.Math.Phys. 40 (1999) 2046-2054 | 10.1063/1.532850 | null | gr-qc | null | Barrett and Crane have proposed a model of simplicial Euclidean quantum
gravity in which a central role is played by a class of Spin(4) spin networks
called "relativistic spin networks" which satisfy a series of physically
motivated constraints. Here a proof is presented that demonstrates that the
intertwiner of a vertex of such a spin network is uniquely determined, up to
normalization, by the representations on the incident edges and the
constraints. Moreover, the constraints, which were formulated for four valent
spin networks only, are extended to networks of arbitrary valence, and the
generalized relativistic spin networks proposed by Yetter are shown to form the
entire solution set (mod normalization) of the extended constraints. Finally,
using the extended constraints, the Barrett-Crane model is generalized to
arbitrary polyhedral complexes (instead of just simplicial complexes)
representing spacetime. It is explained how this model, like the Barret-Crane
model can be derived from BF theory by restricting the sum over histories to
ones in which the left handed and right handed areas of any 2-surface are
equal. It is known that the solutions of classical Euclidean GR form a branch
of the stationary points of the BF action with respect to variations preserving
this condition.
| [
{
"created": "Wed, 23 Sep 1998 19:37:36 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Reisenberger",
"Michael P.",
""
]
] | Barrett and Crane have proposed a model of simplicial Euclidean quantum gravity in which a central role is played by a class of Spin(4) spin networks called "relativistic spin networks" which satisfy a series of physically motivated constraints. Here a proof is presented that demonstrates that the intertwiner of a vertex of such a spin network is uniquely determined, up to normalization, by the representations on the incident edges and the constraints. Moreover, the constraints, which were formulated for four valent spin networks only, are extended to networks of arbitrary valence, and the generalized relativistic spin networks proposed by Yetter are shown to form the entire solution set (mod normalization) of the extended constraints. Finally, using the extended constraints, the Barrett-Crane model is generalized to arbitrary polyhedral complexes (instead of just simplicial complexes) representing spacetime. It is explained how this model, like the Barret-Crane model can be derived from BF theory by restricting the sum over histories to ones in which the left handed and right handed areas of any 2-surface are equal. It is known that the solutions of classical Euclidean GR form a branch of the stationary points of the BF action with respect to variations preserving this condition. |
gr-qc/0405047 | Michele Maggiore | Eugenio Coccia, Florian Dubath and Michele Maggiore | On the possible sources of gravitational wave bursts detectable today | 24 pages, 20 figures | Phys.Rev.D70:084010,2004 | 10.1103/PhysRevD.70.084010 | null | gr-qc astro-ph | null | We discuss the possibility that galactic gravitational wave sources might
give burst signals at a rate of several events per year, detectable by
state-of-the-art detectors. We are stimulated by the results of the data
collected by the EXPLORER and NAUTILUS bar detectors in the 2001 run, which
suggest an excess of coincidences between the two detectors, when the resonant
bars are orthogonal to the galactic plane. Signals due to the coalescence of
galactic compact binaries fulfill the energy requirements but are problematic
for lack of known candidates with the necessary merging rate. We examine the
limits imposed by galactic dynamics on the mass loss of the Galaxy due to GW
emission, and we use them to put constraints also on the GW radiation from
exotic objects, like binaries made of primordial black holes. We discuss the
possibility that the events are due to GW bursts coming repeatedly from a
single or a few compact sources. We examine different possible realizations of
this idea, such as accreting neutron stars, strange quark stars, and the highly
magnetized neutron stars (``magnetars'') introduced to explain Soft Gamma
Repeaters. Various possibilities are excluded or appear very unlikely, while
others at present cannot be excluded.
| [
{
"created": "Sun, 9 May 2004 10:06:45 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2004 09:17:07 GMT",
"version": "v2"
}
] | 2011-08-17 | [
[
"Coccia",
"Eugenio",
""
],
[
"Dubath",
"Florian",
""
],
[
"Maggiore",
"Michele",
""
]
] | We discuss the possibility that galactic gravitational wave sources might give burst signals at a rate of several events per year, detectable by state-of-the-art detectors. We are stimulated by the results of the data collected by the EXPLORER and NAUTILUS bar detectors in the 2001 run, which suggest an excess of coincidences between the two detectors, when the resonant bars are orthogonal to the galactic plane. Signals due to the coalescence of galactic compact binaries fulfill the energy requirements but are problematic for lack of known candidates with the necessary merging rate. We examine the limits imposed by galactic dynamics on the mass loss of the Galaxy due to GW emission, and we use them to put constraints also on the GW radiation from exotic objects, like binaries made of primordial black holes. We discuss the possibility that the events are due to GW bursts coming repeatedly from a single or a few compact sources. We examine different possible realizations of this idea, such as accreting neutron stars, strange quark stars, and the highly magnetized neutron stars (``magnetars'') introduced to explain Soft Gamma Repeaters. Various possibilities are excluded or appear very unlikely, while others at present cannot be excluded. |
1504.04290 | J. W. van Holten | J.W. van Holten | Spinning bodies in General Relativity | 8 pages including references. New version: text rewritten and
background material added. Results and conclusions unaltered. Version
presented at the meeting "Variational Principles and Conservation Laws in
General Relativity" (Torino, June 25 2015) | Int. J. of Geom. Methods in Mod. Physics 13 (2016), 1640002 | 10.1142/S0219887816400028 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant hamiltonian formalism for the dynamics of compact spinning bodies
in curved space-time in the test-particle limit is described. The construction
allows a large class of hamiltonians accounting for specific properties and
interactions of spinning bodies. The dynamics for a minimal and a specific
non-minimal hamiltonian is discussed. An independent derivation of the
equations of motion from an appropriate energy-momentum tensor is provided. It
is shown how to derive constants of motion, both background-independent and
background-dependent ones.
| [
{
"created": "Thu, 16 Apr 2015 16:23:22 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2015 09:40:26 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"van Holten",
"J. W.",
""
]
] | A covariant hamiltonian formalism for the dynamics of compact spinning bodies in curved space-time in the test-particle limit is described. The construction allows a large class of hamiltonians accounting for specific properties and interactions of spinning bodies. The dynamics for a minimal and a specific non-minimal hamiltonian is discussed. An independent derivation of the equations of motion from an appropriate energy-momentum tensor is provided. It is shown how to derive constants of motion, both background-independent and background-dependent ones. |
2404.00643 | Zeeshan Gul | M. Zeeshan Gul, M. Sharif and Adeeba Arooj | Study of Viable Compact Stellar Structures in Non-Riemannian Geometry | 39 pages, 9 figures | Phys. Scr. 99(2024)045006 | 10.1088/1402-4896/ad2c49 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main objective of this article is to study the viable compact stellar
structures in non-Riemannian geometry, i.e., $f(\mathbb{Q},T)$ theory, where
$\mathbb{Q}$ defines the non-metricity and $T$ represents trace of the
stress-energy tensor. In this perspective, we consider a static spherical
metric with anisotropic matter configuration to examine the geometry of
considered compact stars. A specific model of this theory is used to derive the
explicit expressions of energy density and pressure components that govern the
relationship between matter and geometry. The unknown parameters are evaluated
by using the continuity of inner and outer spacetimes to examine the
configuration of spherical stellar structures. Physical parameters such as
fluid characteristics, energy constraints and equation of state parameters are
analyzed to examine the viability of the considered stellar objects. Further,
we use Tolman-Oppenheimer-Volkoff equation, sound speed and adiabatic index
methods to analyze the equilibrium state and stability of the proposed stellar
objects. The rigorous analysis and satisfaction of necessary conditions lead to
the conclusion that the stellar objects studied in this framework are viable
and stable.
| [
{
"created": "Sun, 31 Mar 2024 11:00:08 GMT",
"version": "v1"
}
] | 2024-04-02 | [
[
"Gul",
"M. Zeeshan",
""
],
[
"Sharif",
"M.",
""
],
[
"Arooj",
"Adeeba",
""
]
] | The main objective of this article is to study the viable compact stellar structures in non-Riemannian geometry, i.e., $f(\mathbb{Q},T)$ theory, where $\mathbb{Q}$ defines the non-metricity and $T$ represents trace of the stress-energy tensor. In this perspective, we consider a static spherical metric with anisotropic matter configuration to examine the geometry of considered compact stars. A specific model of this theory is used to derive the explicit expressions of energy density and pressure components that govern the relationship between matter and geometry. The unknown parameters are evaluated by using the continuity of inner and outer spacetimes to examine the configuration of spherical stellar structures. Physical parameters such as fluid characteristics, energy constraints and equation of state parameters are analyzed to examine the viability of the considered stellar objects. Further, we use Tolman-Oppenheimer-Volkoff equation, sound speed and adiabatic index methods to analyze the equilibrium state and stability of the proposed stellar objects. The rigorous analysis and satisfaction of necessary conditions lead to the conclusion that the stellar objects studied in this framework are viable and stable. |
gr-qc/9507035 | null | E.S.C. Ching, P.T. Leung, W.M. Suen and K. Young | Wave Propagation in Gravitational Systems: Late Time Behavior | null | Phys.Rev. D52 (1995) 2118-2132 | 10.1103/PhysRevD.52.2118 | WUGRAV-94-8 | gr-qc | null | It is well-known that the dominant late time behavior of waves propagating on
a Schwarzschild spacetime is a power-law tail; tails for other spacetimes have
also been studied. This paper presents a systematic treatment of the tail
phenomenon for a broad class of models via a Green's function formalism and
establishes the following. (i) The tail is governed by a cut of the frequency
Green's function $\tilde G(\omega)$ along the $-$~Im~$\omega$ axis,
generalizing the Schwarzschild result. (ii) The $\omega$ dependence of the cut
is determined by the asymptotic but not the local structure of space. In
particular it is independent of the presence of a horizon, and has the same
form for the case of a star as well. (iii) Depending on the spatial
asymptotics, the late time decay is not necessarily a power law in time. The
Schwarzschild case with a power-law tail is exceptional among the class of the
potentials having a logarithmic spatial dependence. (iv) Both the amplitude and
the time dependence of the tail for a broad class of models are obtained
analytically. (v) The analytical results are in perfect agreement with
numerical calculations.
| [
{
"created": "Fri, 14 Jul 1995 19:25:49 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Ching",
"E. S. C.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Suen",
"W. M.",
""
],
[
"Young",
"K.",
""
]
] | It is well-known that the dominant late time behavior of waves propagating on a Schwarzschild spacetime is a power-law tail; tails for other spacetimes have also been studied. This paper presents a systematic treatment of the tail phenomenon for a broad class of models via a Green's function formalism and establishes the following. (i) The tail is governed by a cut of the frequency Green's function $\tilde G(\omega)$ along the $-$~Im~$\omega$ axis, generalizing the Schwarzschild result. (ii) The $\omega$ dependence of the cut is determined by the asymptotic but not the local structure of space. In particular it is independent of the presence of a horizon, and has the same form for the case of a star as well. (iii) Depending on the spatial asymptotics, the late time decay is not necessarily a power law in time. The Schwarzschild case with a power-law tail is exceptional among the class of the potentials having a logarithmic spatial dependence. (iv) Both the amplitude and the time dependence of the tail for a broad class of models are obtained analytically. (v) The analytical results are in perfect agreement with numerical calculations. |
1108.6207 | Soichiro Isoyama Mr | Soichiro Isoyama, Norichika Sago and Takahiro Tanaka | Cosmic censorship in overcharging a Reissner-Nordstr\"{o}m black hole
via charged particle absorption | 18 pages, revtex4, minor revision and reference added, version to
appear in PRD | Phys.Rev.D84:124024,2011 | 10.1103/PhysRevD.84.124024 | YITP-11-77 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a claim that a static charged black hole (Reissner-Nordstr\"{o}m
black hole) can be overcharged by absorbing a charged test particle. If it is
true, it might give a counter example to the weak cosmic censorship conjecture,
which states that spacetime singularities are never observed by a distant
observer. However, so far the proposed process has only been analyzed within a
test particle approximation. Here we claim that the back reaction effects of a
charged particle cannot be neglected when judging whether the suggested process
is really a counter example to the cosmic censorship conjecture or not.
Furthermore, we argue that all the back reaction effects can be properly taken
into account when we consider the trajectory of a particle on the border
between the plunge and bounce orbits. In such marginal cases we find that the
Reissner-Nordstr\"{o}m black hole can never be overcharged via the absorption
of a charged particle. Since all the plunge orbits are expected to have a
higher energy than the marginal orbit, we conclude that there is no supporting
evidence that indicates the violation of the cosmic censorship in the proposed
overcharging process.
| [
{
"created": "Wed, 31 Aug 2011 12:32:40 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Oct 2011 08:58:54 GMT",
"version": "v2"
}
] | 2011-12-20 | [
[
"Isoyama",
"Soichiro",
""
],
[
"Sago",
"Norichika",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | There is a claim that a static charged black hole (Reissner-Nordstr\"{o}m black hole) can be overcharged by absorbing a charged test particle. If it is true, it might give a counter example to the weak cosmic censorship conjecture, which states that spacetime singularities are never observed by a distant observer. However, so far the proposed process has only been analyzed within a test particle approximation. Here we claim that the back reaction effects of a charged particle cannot be neglected when judging whether the suggested process is really a counter example to the cosmic censorship conjecture or not. Furthermore, we argue that all the back reaction effects can be properly taken into account when we consider the trajectory of a particle on the border between the plunge and bounce orbits. In such marginal cases we find that the Reissner-Nordstr\"{o}m black hole can never be overcharged via the absorption of a charged particle. Since all the plunge orbits are expected to have a higher energy than the marginal orbit, we conclude that there is no supporting evidence that indicates the violation of the cosmic censorship in the proposed overcharging process. |
gr-qc/0606003 | Paul Lasky | Paul Lasky, Anthony Lun and Raymond Burston (Monash University) | Initial value formalism for dust collapse | Accepted for publication in the ANZIAM journal | null | null | null | gr-qc | null | Formulating a dust filled spherically symmetric metric utilizing the 3+1
formalism for general relativity, we show that the metric coefficients are
completely determined by the matter distribution throughout the spacetime.
Furthermore, the metric describes both inhomogeneous dust regions and also
vacuum regions in a single coordinate patch, thus alleviating the need for
complicated matching schemes at the interfaces. In this way, the system is
established as an initial-boundary value problem, which has many benefits for
its numerical evolution. We show the dust part of the metric is equivalent to
the class of Lemaitre-Tolman-Bondi (LTB) metrics under a coordinate
transformation. In this coordinate system, shell crossing singularities (SCS)
are exhibited as fluid shock waves, and we therefore discuss possibilities for
the dynamical extension of shell crossings through the initial point of
formation by borrowing methods from classical fluid dynamics. This paper fills
a void in the present literature associated with these collapse models by fully
developing the formalism in great detail. Furthermore, the applications provide
examples of the benefits of the present model.
| [
{
"created": "Thu, 1 Jun 2006 01:32:36 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Aug 2007 02:29:21 GMT",
"version": "v2"
}
] | 2011-11-09 | [
[
"Lasky",
"Paul",
"",
"Monash University"
],
[
"Lun",
"Anthony",
"",
"Monash University"
],
[
"Burston",
"Raymond",
"",
"Monash University"
]
] | Formulating a dust filled spherically symmetric metric utilizing the 3+1 formalism for general relativity, we show that the metric coefficients are completely determined by the matter distribution throughout the spacetime. Furthermore, the metric describes both inhomogeneous dust regions and also vacuum regions in a single coordinate patch, thus alleviating the need for complicated matching schemes at the interfaces. In this way, the system is established as an initial-boundary value problem, which has many benefits for its numerical evolution. We show the dust part of the metric is equivalent to the class of Lemaitre-Tolman-Bondi (LTB) metrics under a coordinate transformation. In this coordinate system, shell crossing singularities (SCS) are exhibited as fluid shock waves, and we therefore discuss possibilities for the dynamical extension of shell crossings through the initial point of formation by borrowing methods from classical fluid dynamics. This paper fills a void in the present literature associated with these collapse models by fully developing the formalism in great detail. Furthermore, the applications provide examples of the benefits of the present model. |
gr-qc/9305001 | Geza Ful{\o}p | G\'eza F\"ul\"op | About a Super-Ashtekar-Renteln Ansatz | 15 pages, G\"oteborg, ITP 93-7 | Class.Quant.Grav.11:1-10,1994 | 10.1088/0264-9381/11/1/005 | null | gr-qc hep-th | null | The Ashtekar-Renteln Ansatz gives the self-dual solutions to the Einstein
equation. A direct generalization of the Ashtekar-Renteln An\-satz to N=1
supergravity is given both in the canonical and in the covariant formulation
and a geometrical property of the solutions is pointed out. (Changes: the
covariant formulation and some comments about a wave function has been added)
| [
{
"created": "Mon, 3 May 1993 08:18:27 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Sep 1993 10:40:19 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Fülöp",
"Géza",
""
]
] | The Ashtekar-Renteln Ansatz gives the self-dual solutions to the Einstein equation. A direct generalization of the Ashtekar-Renteln An\-satz to N=1 supergravity is given both in the canonical and in the covariant formulation and a geometrical property of the solutions is pointed out. (Changes: the covariant formulation and some comments about a wave function has been added) |
2112.02099 | M Blagojevi\'c | Milutin Blagojevi\'c and Branislav Cvetkovi\'c | Entropy of Reissner-Nordstr\"om-like black holes | LaTex, 10 pages; v2: math symbols in abstract corrected | Phys. Lett. B 824 (2022), 136815 | 10.1016/j.physletb.2021.136815 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Poincar\'e gauge theory, black hole entropy is defined canonically by the
variation of a boundary term $\Gamma_H$, located at horizon. For a class of
static and spherically symmetric black holes in vacuum, the explicit formula
reads $\delta\Gamma_H=T\delta S$, where $T$ is black hole temperature and $S$
entropy. Here, we analyze a new member of the same class, the
Reissner-Nordstr\"om-like black hole with torsion [1], where the electric
charge of matter is replaced by a gravitational parameter, induced by the
existence of torsion. This parameter affects $\delta\Gamma_H$ in a way that
ensures the validity of the first law.
| [
{
"created": "Thu, 2 Dec 2021 22:16:49 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Feb 2022 14:25:58 GMT",
"version": "v2"
}
] | 2022-02-21 | [
[
"Blagojević",
"Milutin",
""
],
[
"Cvetković",
"Branislav",
""
]
] | In Poincar\'e gauge theory, black hole entropy is defined canonically by the variation of a boundary term $\Gamma_H$, located at horizon. For a class of static and spherically symmetric black holes in vacuum, the explicit formula reads $\delta\Gamma_H=T\delta S$, where $T$ is black hole temperature and $S$ entropy. Here, we analyze a new member of the same class, the Reissner-Nordstr\"om-like black hole with torsion [1], where the electric charge of matter is replaced by a gravitational parameter, induced by the existence of torsion. This parameter affects $\delta\Gamma_H$ in a way that ensures the validity of the first law. |
2304.00842 | Sen Guo | Guan-Ru Li, Guo-Ping Li, Sen Guo | Phase transition grade and microstructure of AdS black holes in massive
gravity | 17 pages, 3 figures | Class.Quant.Grav. 39 (2022) 19, 195011 | 10.1088/1361-6382/ac8c7c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering that under the framework of the massive gravity theory, the
interaction between the mass gravitons and Schwarzschild black hole (BH) could
make it carry a scalar charge, the phase transition process caused by this
scalar charge is investigated in this analysis. The phase transition grade and
microstructure of those BHs are investigated from both macroscopic and
microscopic points of view. From the macroscopic point of view, it is found
that Ehrenfest equations are satisfied at the phase transition critical point,
which implies that the phase transition grade of those BHs is second-order.
Based on the BH molecules model and Landau continuous phase transition theory,
the phase transition of those BHs from the microcosmic point of view is
analyzed. The critical exponents obtained from the two perspectives are
consistent. By investigating the Ruppeiner geometry, the microstructure feature
of those BHs is revealed. These results suggest that the phase transition of BH
in massive gravity is a standard second-order phase transition at the critical
point, and the microscopic details of those BHs are different from the RN-AdS
BH in standard Einstein gravity.
| [
{
"created": "Mon, 3 Apr 2023 09:37:45 GMT",
"version": "v1"
}
] | 2023-04-04 | [
[
"Li",
"Guan-Ru",
""
],
[
"Li",
"Guo-Ping",
""
],
[
"Guo",
"Sen",
""
]
] | Considering that under the framework of the massive gravity theory, the interaction between the mass gravitons and Schwarzschild black hole (BH) could make it carry a scalar charge, the phase transition process caused by this scalar charge is investigated in this analysis. The phase transition grade and microstructure of those BHs are investigated from both macroscopic and microscopic points of view. From the macroscopic point of view, it is found that Ehrenfest equations are satisfied at the phase transition critical point, which implies that the phase transition grade of those BHs is second-order. Based on the BH molecules model and Landau continuous phase transition theory, the phase transition of those BHs from the microcosmic point of view is analyzed. The critical exponents obtained from the two perspectives are consistent. By investigating the Ruppeiner geometry, the microstructure feature of those BHs is revealed. These results suggest that the phase transition of BH in massive gravity is a standard second-order phase transition at the critical point, and the microscopic details of those BHs are different from the RN-AdS BH in standard Einstein gravity. |
0910.5406 | Rakhi R | R. Rakhi, K. Indulekha | Dark Energy and Tracker Solution- A Review | 24 Pages, 1 Figure, 7 Tables | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, basics and some theoretical models of dark energy are
reviewed. Theoretical models include cosmological constant, vacuum fluctuations
of quantum fields, scalar field models, chaplygin gas, vector field models and
Brane world models. Besides this, some alternate models of dark energy are also
included. Finally, some elementary ideas on tracker models are also discussed.
| [
{
"created": "Wed, 28 Oct 2009 15:37:09 GMT",
"version": "v1"
}
] | 2009-10-29 | [
[
"Rakhi",
"R.",
""
],
[
"Indulekha",
"K.",
""
]
] | In this paper, basics and some theoretical models of dark energy are reviewed. Theoretical models include cosmological constant, vacuum fluctuations of quantum fields, scalar field models, chaplygin gas, vector field models and Brane world models. Besides this, some alternate models of dark energy are also included. Finally, some elementary ideas on tracker models are also discussed. |
0901.3011 | Lorenzo Iorio | Lorenzo Iorio | MOND orbits in the Oort cloud | LaTex, 28 pages, no tables, 22 figures, 36 references. To appear in
The Open Astronomy Journal (TOAJ) | Open Astron.J.3:156-166,2010 | 10.2174/1874381101003010156 | null | gr-qc astro-ph.EP astro-ph.GA hep-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigate the features of typical orbits occurring in the
Oort cloud (r\approx 50-150 kAU) in the low-acceleration regime of the MOdified
Newtonian Dynamics (MOND). We take into account the so-called External Field
Effect (EFE) because the solar system is embedded in the Milky Way. In the
framework of MOND this does matter since the gravitational acceleration of
Galactic origin felt by the solar system is of the same order of magnitude of
the characteristic MOND acceleration scale A_0\approx 10^-10 m s^-2. We use
three different forms of the MOND interpolating function \mu(x) and two
different values for the Galactic field at the Sun's location. We find that
MOND produces highly distorted trajectories with respect to the Newtonian case,
especially for very eccentric orbits. It turns out that the shape of the MOND
orbits strongly depend on the initial conditions. For particular initial state
vectors, the MOND paths in the ecliptic plane get shrunk extending over much
smaller spatial regions than in the Newtonian case, and experience high
frequency variations over one Keplerian orbital period. Ecliptic orbits with
different initial conditions and nearly polar orbits are quite different
getting distorted as well, but they occupy more extended spatial regions. This
facts may have consequences on the composition and the dynamical history of the
Oort cloud which are difficult to predict.
| [
{
"created": "Tue, 20 Jan 2009 10:17:45 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jan 2009 10:16:11 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Feb 2009 17:26:38 GMT",
"version": "v3"
},
{
"created": "Wed, 4 Mar 2009 16:39:45 GMT",
"version": "v4"
},
{
"created": "Wed, 1 Apr 2009 17:08:57 GMT",
"version": "v5"
},
{
"created": "Fri, 31 Jul 2009 07:35:07 GMT",
"version": "v6"
},
{
"created": "Mon, 15 Feb 2010 19:53:12 GMT",
"version": "v7"
},
{
"created": "Fri, 27 Aug 2010 09:02:40 GMT",
"version": "v8"
}
] | 2011-04-07 | [
[
"Iorio",
"Lorenzo",
""
]
] | We numerically investigate the features of typical orbits occurring in the Oort cloud (r\approx 50-150 kAU) in the low-acceleration regime of the MOdified Newtonian Dynamics (MOND). We take into account the so-called External Field Effect (EFE) because the solar system is embedded in the Milky Way. In the framework of MOND this does matter since the gravitational acceleration of Galactic origin felt by the solar system is of the same order of magnitude of the characteristic MOND acceleration scale A_0\approx 10^-10 m s^-2. We use three different forms of the MOND interpolating function \mu(x) and two different values for the Galactic field at the Sun's location. We find that MOND produces highly distorted trajectories with respect to the Newtonian case, especially for very eccentric orbits. It turns out that the shape of the MOND orbits strongly depend on the initial conditions. For particular initial state vectors, the MOND paths in the ecliptic plane get shrunk extending over much smaller spatial regions than in the Newtonian case, and experience high frequency variations over one Keplerian orbital period. Ecliptic orbits with different initial conditions and nearly polar orbits are quite different getting distorted as well, but they occupy more extended spatial regions. This facts may have consequences on the composition and the dynamical history of the Oort cloud which are difficult to predict. |
1302.6966 | Jean-Marc Schlenker | Francesco Bonsante, Catherine Meusburger, Jean-Marc Schlenker | Recovering the geometry of a flat spacetime from background radiation | 42 pages, several figures | Annales Henri Poincar\'e (2013) 1-67 | 10.1007/s00023-013-0300-6 | null | gr-qc math.DG math.GT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider globally hyperbolic flat spacetimes in 2+1 and 3+1 dimensions, in
which a uniform light signal is emitted on the $r$-level surface of the
cosmological time for $r\to 0$. We show that the frequency of this signal, as
perceived by a fixed observer, is a well-defined, bounded function which is
generally not continuous. This defines a model with anisotropic background
radiation that contains information about initial singularity of the spacetime.
In dimension 2+1, we show that this observed frequency function is stable under
suitable perturbations of the spacetime, and that, under certain conditions, it
contains sufficient information to recover its geometry and topology. We
compute an approximation of this frequency function for a few simple examples.
| [
{
"created": "Wed, 27 Feb 2013 19:26:48 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jun 2013 08:24:19 GMT",
"version": "v2"
}
] | 2018-03-28 | [
[
"Bonsante",
"Francesco",
""
],
[
"Meusburger",
"Catherine",
""
],
[
"Schlenker",
"Jean-Marc",
""
]
] | We consider globally hyperbolic flat spacetimes in 2+1 and 3+1 dimensions, in which a uniform light signal is emitted on the $r$-level surface of the cosmological time for $r\to 0$. We show that the frequency of this signal, as perceived by a fixed observer, is a well-defined, bounded function which is generally not continuous. This defines a model with anisotropic background radiation that contains information about initial singularity of the spacetime. In dimension 2+1, we show that this observed frequency function is stable under suitable perturbations of the spacetime, and that, under certain conditions, it contains sufficient information to recover its geometry and topology. We compute an approximation of this frequency function for a few simple examples. |
2307.07585 | Massimo Tinto | Massimo Tinto, Sanjeev Dhurandhar | Higher-order Time-Delay Interferometry | 9 pages, 1 figure. arXiv admin note: text overlap with
arXiv:2212.05967 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time-Delay Interferometry (TDI) is the data processing technique that cancels
the large laser phase fluctuations affecting the one-way Doppler measurements
made by unequal-arm space-based gravitational wave interferometers. In a
previous publication we derived TDI combinations that exactly cancel the laser
phase fluctuations up to first order in the inter-spacecraft velocities. This
was done by interfering two digitally-synthesized optical beams propagating a
number of times clock- and counter-clock-wise around the array. Here we extend
that approach by showing that the number of loops made by each beam before
interfering corresponds to a specific higher-order TDI space. In it the
cancellation of laser noise terms that depend on the acceleration and
higher-order time derivatives of the inter-spacecraft light-travel-times is
achieved exactly. Similarly to what we proved for the second-generation TDI
space, elements of a specific higher-order TDI space can be obtained by first
``lifting'' the basis ($\a, \b, \g, X$) of the $1^{\rm st}$-generation TDI
space to the higher-order space of interest and then taking linear combinations
of them with coefficients that are polynomials of the six delays operators.
Higher-Order TDI might be required by future interplanetary gravitational wave
missions whose inter-spacecraft distances vary appreciably with time, in
particular, relative velocities are much larger than those of currently planned
arrays.
| [
{
"created": "Fri, 14 Jul 2023 19:24:19 GMT",
"version": "v1"
}
] | 2023-07-18 | [
[
"Tinto",
"Massimo",
""
],
[
"Dhurandhar",
"Sanjeev",
""
]
] | Time-Delay Interferometry (TDI) is the data processing technique that cancels the large laser phase fluctuations affecting the one-way Doppler measurements made by unequal-arm space-based gravitational wave interferometers. In a previous publication we derived TDI combinations that exactly cancel the laser phase fluctuations up to first order in the inter-spacecraft velocities. This was done by interfering two digitally-synthesized optical beams propagating a number of times clock- and counter-clock-wise around the array. Here we extend that approach by showing that the number of loops made by each beam before interfering corresponds to a specific higher-order TDI space. In it the cancellation of laser noise terms that depend on the acceleration and higher-order time derivatives of the inter-spacecraft light-travel-times is achieved exactly. Similarly to what we proved for the second-generation TDI space, elements of a specific higher-order TDI space can be obtained by first ``lifting'' the basis ($\a, \b, \g, X$) of the $1^{\rm st}$-generation TDI space to the higher-order space of interest and then taking linear combinations of them with coefficients that are polynomials of the six delays operators. Higher-Order TDI might be required by future interplanetary gravitational wave missions whose inter-spacecraft distances vary appreciably with time, in particular, relative velocities are much larger than those of currently planned arrays. |
gr-qc/0702015 | Gregory Adkins | Gregory S. Adkins and Jordan McDonnell | Orbital precession due to central-force perturbations | 10 pages, 1 figure | Phys.Rev.D75:082001,2007 | 10.1103/PhysRevD.75.082001 | null | gr-qc | null | We calculate the precession of Keplerian orbits under the influence of
arbitrary central-force perturbations. Our result is in the form of a
one-dimensional integral that is straightforward to evaluate numerically. We
demonstrate the effectiveness of our formula for the case of the Yukawa
potential. We obtain analytic results for potentials of the form V(r) = \alpha
r^n and V(r) = \alpha \ln(r/\lambda) in terms of the hypergeometric function
{_2F_1} (1/2-n/2,1-n/2; 2; e^2), where e is the eccentricity. Our results
reproduce the known general relativistic (n=-3), constant force (n=1), and
cosmological constant (n=2) precession formulas. Planetary precessions are
often used to constrain the sizes of hypothetical new weak forces--our results
allow for more precise, and often stronger, constraints on such proposed new
forces.
| [
{
"created": "Fri, 2 Feb 2007 18:45:37 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Adkins",
"Gregory S.",
""
],
[
"McDonnell",
"Jordan",
""
]
] | We calculate the precession of Keplerian orbits under the influence of arbitrary central-force perturbations. Our result is in the form of a one-dimensional integral that is straightforward to evaluate numerically. We demonstrate the effectiveness of our formula for the case of the Yukawa potential. We obtain analytic results for potentials of the form V(r) = \alpha r^n and V(r) = \alpha \ln(r/\lambda) in terms of the hypergeometric function {_2F_1} (1/2-n/2,1-n/2; 2; e^2), where e is the eccentricity. Our results reproduce the known general relativistic (n=-3), constant force (n=1), and cosmological constant (n=2) precession formulas. Planetary precessions are often used to constrain the sizes of hypothetical new weak forces--our results allow for more precise, and often stronger, constraints on such proposed new forces. |
gr-qc/0208019 | Nathaniel Obadia | N. Obadia and R. Parentani | Uniformly Accelerated Mirrors. Part 1: Mean Fluxes | 23 pages, 7 postscript figures | Phys.Rev. D67 (2003) 024021 | 10.1103/PhysRevD.67.024021 | null | gr-qc | null | The Davies-Fulling model describes the scattering of a massless field by a
moving mirror in 1+1 dimensions. When the mirror travels under uniform
acceleration, one encounters severe problems which are due to the infinite blue
shift effects associated with the horizons. On one hand, the Bogoliubov
coefficients are ill-defined and the total energy emitted diverges. On the
other hand, the instantaneous mean flux vanishes. To obtained well-defined
expressions we introduce an alternative model based on an action principle. The
usefulness of this model is to allow to switch on and off the interaction at
asymptotically large times. By an appropriate choice of the switching function,
we obtain analytical expressions for the scattering amplitudes and the fluxes
emitted by the mirror. When the coupling is constant, we recover the vanishing
flux. However it is now followed by transients which inevitably become singular
when the switching off is performed at late time. Our analysis reveals that the
scattering amplitudes (and the Bogoliubov coefficients) should be seen as
distributions and not as mere functions. Moreover, our regularized amplitudes
can be put in a one to one correspondence with the transition amplitudes of an
accelerated detector, thereby unifying the physics of uniformly accelerated
systems. In a forthcoming article, we shall use our scattering amplitudes to
analyze the quantum correlations amongst emitted particles which are also
ill-defined in the Davies-Fulling model in the presence of horizons.
| [
{
"created": "Wed, 7 Aug 2002 14:13:40 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Obadia",
"N.",
""
],
[
"Parentani",
"R.",
""
]
] | The Davies-Fulling model describes the scattering of a massless field by a moving mirror in 1+1 dimensions. When the mirror travels under uniform acceleration, one encounters severe problems which are due to the infinite blue shift effects associated with the horizons. On one hand, the Bogoliubov coefficients are ill-defined and the total energy emitted diverges. On the other hand, the instantaneous mean flux vanishes. To obtained well-defined expressions we introduce an alternative model based on an action principle. The usefulness of this model is to allow to switch on and off the interaction at asymptotically large times. By an appropriate choice of the switching function, we obtain analytical expressions for the scattering amplitudes and the fluxes emitted by the mirror. When the coupling is constant, we recover the vanishing flux. However it is now followed by transients which inevitably become singular when the switching off is performed at late time. Our analysis reveals that the scattering amplitudes (and the Bogoliubov coefficients) should be seen as distributions and not as mere functions. Moreover, our regularized amplitudes can be put in a one to one correspondence with the transition amplitudes of an accelerated detector, thereby unifying the physics of uniformly accelerated systems. In a forthcoming article, we shall use our scattering amplitudes to analyze the quantum correlations amongst emitted particles which are also ill-defined in the Davies-Fulling model in the presence of horizons. |
gr-qc/0502025 | Antonio J. Segui | M. A. Per and A. Segui | Holographic Cosmology and Uncertainty Relation | 6 pages, 4 figures. To appear in the proceedings of 27th Spanish
Relativity Meeting: Beyond General Relativity (ERES 2004), Madrid, Spain,
23-25 Sep 2004 | null | null | null | gr-qc astro-ph hep-th | null | It is believed that a primary principle of the theory of quantum gravity is
the Holographic Principle according to which a physical system can be described
only by degrees of freedom living on its boundary. The generalized covariant
formulation of the principle considers the entropy content on truncated
light-sheets: light-like hypersurfaces of non-positive expansion orthogonally
generated from a boundary. When we construct the truncated light-sheets for
cosmological observers we find a general expression for the minimum cosmic time
interval from the apparent horizon to verify the holographic prescription; this
minimum time is related to quantum effects involved in the entropy computation.
Finally, we arrive to the uncertainty relation from the Holographic Principle,
which suggests a deep connection between general covariance, entropy bounds and
quantum mechanics.
| [
{
"created": "Mon, 7 Feb 2005 19:03:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Per",
"M. A.",
""
],
[
"Segui",
"A.",
""
]
] | It is believed that a primary principle of the theory of quantum gravity is the Holographic Principle according to which a physical system can be described only by degrees of freedom living on its boundary. The generalized covariant formulation of the principle considers the entropy content on truncated light-sheets: light-like hypersurfaces of non-positive expansion orthogonally generated from a boundary. When we construct the truncated light-sheets for cosmological observers we find a general expression for the minimum cosmic time interval from the apparent horizon to verify the holographic prescription; this minimum time is related to quantum effects involved in the entropy computation. Finally, we arrive to the uncertainty relation from the Holographic Principle, which suggests a deep connection between general covariance, entropy bounds and quantum mechanics. |
gr-qc/9811051 | Alan D. Rendall | A. D. Rendall, K. P. Tod | Dynamics of spatially homogeneous solutions of the Einstein-Vlasov
equations which are locally rotationally symmetric | 27 pages, 3 figures, LaTeX | Class.Quant.Grav. 16 (1999) 1705-1726 | 10.1088/0264-9381/16/6/305 | null | gr-qc | null | The dynamics of a class of cosmological models with collisionless matter and
four Killing vectors is studied in detail and compared with that of
corresponding perfect fluid models. In many cases it is possible to identify
asymptotic states of the spacetimes near the singularity or in a phase of
unlimited expansion. Bianchi type II models show oscillatory behaviour near the
initial singularity which is, however, simpler than that of the mixmaster
model.
| [
{
"created": "Mon, 16 Nov 1998 15:59:46 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Rendall",
"A. D.",
""
],
[
"Tod",
"K. P.",
""
]
] | The dynamics of a class of cosmological models with collisionless matter and four Killing vectors is studied in detail and compared with that of corresponding perfect fluid models. In many cases it is possible to identify asymptotic states of the spacetimes near the singularity or in a phase of unlimited expansion. Bianchi type II models show oscillatory behaviour near the initial singularity which is, however, simpler than that of the mixmaster model. |
1403.7279 | Ran Li | Ran Li, Junkun Zhao | Superradiant instability of the charged scalar field in stringy black
hole mirror system | 5 pages, no figure, published version | Eur. Phys. J. C (2014) 74:3051 | 10.1140/epjc/s10052-014-3051-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that the mass of the scalar field in the charged stringy
black hole is never able to generate a potential well outside the event horizon
to trap the superradiant modes. This is to say that the charged stringy black
hole is stable against the massive charged scalar perturbation. In this paper
we will study the superradiant instability of the massless scalar field in the
background of charged stringy black hole due to a mirror-like boundary
condition. The analytical expression of the unstable superradiant modes is
derived by using the asymptotic matching method. It is also pointed out that
the black hole mirror system becomes extremely unstable for a large charge $q$
of scalar field and the small mirror radius $r_m$.
| [
{
"created": "Fri, 28 Mar 2014 04:24:24 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Dec 2014 01:07:33 GMT",
"version": "v2"
}
] | 2014-12-05 | [
[
"Li",
"Ran",
""
],
[
"Zhao",
"Junkun",
""
]
] | It has been shown that the mass of the scalar field in the charged stringy black hole is never able to generate a potential well outside the event horizon to trap the superradiant modes. This is to say that the charged stringy black hole is stable against the massive charged scalar perturbation. In this paper we will study the superradiant instability of the massless scalar field in the background of charged stringy black hole due to a mirror-like boundary condition. The analytical expression of the unstable superradiant modes is derived by using the asymptotic matching method. It is also pointed out that the black hole mirror system becomes extremely unstable for a large charge $q$ of scalar field and the small mirror radius $r_m$. |
2211.06653 | Shafqat Ul Islam | Shafqat Ul Islam, Jitendra Kumar, Rahul Kumar Walia, Sushant G. Ghosh | Investigating Loop Quantum Gravity with EHT Observational Effects of
Rotating Black holes | 16 Pages, 10 Figures, 2 Tables, Text matched with published version
in 'The Astrophysical Journal' | ApJ 943, 22 (2023) | 10.3847/1538-4357/aca411 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A mathematically consistent rotating black hole model in loop quantum gravity
(LQG) is yet lacking. The scarcity of rotating black hole solutions in LQG
substantially hampers the development of testing LQG from observations, e.g.,
from the Event Horizon Telescope (EHT) observations. The EHT observation
revealed event horizon-scale images of the supermassive black holes Sgr A* and
M87*. The EHT results are consistent with the shadow of a Kerr black hole of
general relativity. We present LQG-motivated rotating black hole (LMRBH)
spacetimes, which are regular everywhere and asymptotically encompass the Kerr
black hole as a particular case. The LMRBH metric describes a multi-horizon
black hole in the sense that it can admit up to three horizons, such that an
extremal LMRBH, unlike the Kerr black hole, refers to a black hole with angular
momentum $a>M$. The metric, depending on the parameters, describes (1) black
holes with only one horizon (BH-I), (2) black holes with an event horizon and a
Cauchy horizons (BH-II), (3) black holes with three horizons (BH-III) or (4)
no-horizon (NH) spacetime, which, we show, is almost ruled out by the EHT
observations. We constrain the LQG parameter with the aid of the EHT shadow
observational results of M87* and Sgr A*,respectively, for an inclination angle
of $17^0$ and $50^0$. In particular, the VLTI bound for the Sgr A*, $\delta\in
(-0.17,0.01)$, constrains the parameters ($a,l$) such that for $0< l\leq
0.347851M\; (l\leq 2\times 10^6$ km), the allowed range of $a$ is
$(0,1.0307M)$. Together with the EHT bounds of Sgr A$^*$ and M87$^*$
observables, our analysis concludes that a substantial part of BH-I and BH-II
parameter space agrees with the EHT results of M87* and Sgr A*. While the EHT
M87* results totally rule out the BH-III, but not that by Sgr A*.
| [
{
"created": "Sat, 12 Nov 2022 12:43:34 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jan 2023 20:52:36 GMT",
"version": "v2"
}
] | 2023-01-25 | [
[
"Islam",
"Shafqat Ul",
""
],
[
"Kumar",
"Jitendra",
""
],
[
"Walia",
"Rahul Kumar",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | A mathematically consistent rotating black hole model in loop quantum gravity (LQG) is yet lacking. The scarcity of rotating black hole solutions in LQG substantially hampers the development of testing LQG from observations, e.g., from the Event Horizon Telescope (EHT) observations. The EHT observation revealed event horizon-scale images of the supermassive black holes Sgr A* and M87*. The EHT results are consistent with the shadow of a Kerr black hole of general relativity. We present LQG-motivated rotating black hole (LMRBH) spacetimes, which are regular everywhere and asymptotically encompass the Kerr black hole as a particular case. The LMRBH metric describes a multi-horizon black hole in the sense that it can admit up to three horizons, such that an extremal LMRBH, unlike the Kerr black hole, refers to a black hole with angular momentum $a>M$. The metric, depending on the parameters, describes (1) black holes with only one horizon (BH-I), (2) black holes with an event horizon and a Cauchy horizons (BH-II), (3) black holes with three horizons (BH-III) or (4) no-horizon (NH) spacetime, which, we show, is almost ruled out by the EHT observations. We constrain the LQG parameter with the aid of the EHT shadow observational results of M87* and Sgr A*,respectively, for an inclination angle of $17^0$ and $50^0$. In particular, the VLTI bound for the Sgr A*, $\delta\in (-0.17,0.01)$, constrains the parameters ($a,l$) such that for $0< l\leq 0.347851M\; (l\leq 2\times 10^6$ km), the allowed range of $a$ is $(0,1.0307M)$. Together with the EHT bounds of Sgr A$^*$ and M87$^*$ observables, our analysis concludes that a substantial part of BH-I and BH-II parameter space agrees with the EHT results of M87* and Sgr A*. While the EHT M87* results totally rule out the BH-III, but not that by Sgr A*. |
2210.00324 | Pedro Pessoa | Pedro Pessoa, Bruno Arderucio Costa, Steve Press\'e | Revisiting Claims in "Black Hole Entropy: A Closer Look" | null | null | null | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we explain how C. Tsallis' reply (Entropy 2021, 23(5), 630) fails to
respond to points raised in (Entropy 2020, 22(10), 1110) and introduces further
inconsistencies on the origin of black hole entropy. In his reply, Tsallis
argues that the extensivity of thermodynamical entropy with respect to chosen
variables needs to be preserved. Consequently the entropy functional is
inadequate for black holes. Here we explain the undesirable consequences of
this reasoning on black hole thermodynamics.
| [
{
"created": "Sat, 1 Oct 2022 17:12:18 GMT",
"version": "v1"
}
] | 2022-10-04 | [
[
"Pessoa",
"Pedro",
""
],
[
"Costa",
"Bruno Arderucio",
""
],
[
"Pressé",
"Steve",
""
]
] | Here we explain how C. Tsallis' reply (Entropy 2021, 23(5), 630) fails to respond to points raised in (Entropy 2020, 22(10), 1110) and introduces further inconsistencies on the origin of black hole entropy. In his reply, Tsallis argues that the extensivity of thermodynamical entropy with respect to chosen variables needs to be preserved. Consequently the entropy functional is inadequate for black holes. Here we explain the undesirable consequences of this reasoning on black hole thermodynamics. |
2304.13581 | Zihan Zhang | Zi-han Zhang, Bin Liu, Sheng-hua Yu, and Jie Yang | The Gravitational Wave Forms of Galactic Compact Binaries with
Mass-Transfer Correction | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we focus on the effect of mass-transfer between compact
binaries like neutron-star-neutron-star (NS-NS) systems and
neutron-star-white-dwarf (NS-WD) systems on gravitational waves (GWs). We adopt
the mass quadrupole formula with 2.5 order Post-Newtonian (2.5 PN)
approximation to calculate the GW radiation and the orbital evolution. After a
reasonable discussion of astrophysical processes concerning our scenario, two
kinds of mass-transfer models are applied here. One is the mass overflow of the
atmosphere, where the companion star orbits into the primary's Roche limit and
its atmosphere overflows into the common envelope. The other one is the tidal
disruption of the core, which is viewed as incompressible fluid towards the
primary star, and in the near region branches into an accretion disc (AD) and
direct accretion flow. Viewing this envelope and as a background, the GW of its
spin can be calculated as a rotating non-spherically symmetric star. We
eventually obtained the corrected gravitational waveform (GWF) templates for
different initial states in the inspiral phase.
| [
{
"created": "Wed, 26 Apr 2023 14:18:38 GMT",
"version": "v1"
},
{
"created": "Sun, 14 May 2023 09:20:48 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Jun 2023 06:20:25 GMT",
"version": "v3"
},
{
"created": "Mon, 12 Jun 2023 14:59:23 GMT",
"version": "v4"
},
{
"created": "Tue, 28 Nov 2023 16:58:08 GMT",
"version": "v5"
},
{
"created": "Tue, 5 Dec 2023 05:26:12 GMT",
"version": "v6"
},
{
"created": "Wed, 13 Mar 2024 11:31:35 GMT",
"version": "v7"
}
] | 2024-03-14 | [
[
"Zhang",
"Zi-han",
""
],
[
"Liu",
"Bin",
""
],
[
"Yu",
"Sheng-hua",
""
],
[
"Yang",
"Jie",
""
]
] | In this paper, we focus on the effect of mass-transfer between compact binaries like neutron-star-neutron-star (NS-NS) systems and neutron-star-white-dwarf (NS-WD) systems on gravitational waves (GWs). We adopt the mass quadrupole formula with 2.5 order Post-Newtonian (2.5 PN) approximation to calculate the GW radiation and the orbital evolution. After a reasonable discussion of astrophysical processes concerning our scenario, two kinds of mass-transfer models are applied here. One is the mass overflow of the atmosphere, where the companion star orbits into the primary's Roche limit and its atmosphere overflows into the common envelope. The other one is the tidal disruption of the core, which is viewed as incompressible fluid towards the primary star, and in the near region branches into an accretion disc (AD) and direct accretion flow. Viewing this envelope and as a background, the GW of its spin can be calculated as a rotating non-spherically symmetric star. We eventually obtained the corrected gravitational waveform (GWF) templates for different initial states in the inspiral phase. |
1805.12362 | Dong-Han Yeom | Anna Nakonieczna, {\L}ukasz Nakonieczny, Dong-han Yeom | Black hole factory: a review of double-null formalism | 28 pages, 17 figures; Invited review for Int.J.Mod.Phys. D | Int.J.Mod.Phys. D28, 1930006 (2019) | 10.1142/S0218271819300064 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review paper, we comprehensively summarize numerical applications of
double-null formalism for studying dynamics within the theory of gravity. By
using the double-null coordinates, we can investigate dynamical black holes and
gravitational phenomena within spherical symmetry, including gravitational
collapse, formation of horizons and singularities, as well as evaporations.
This formalism can be extended to generic situations, where we can change
dimensions, topologies, the gravity sector, as well as the matter sector. We
also discuss its possible implications for black hole physics and particle
astrophysics. This strong numerical tool will have lots of future applications
for various research areas including general relativity, string theory, and
various approaches to quantum gravity.
| [
{
"created": "Thu, 31 May 2018 07:48:15 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2019 04:04:52 GMT",
"version": "v2"
}
] | 2019-02-13 | [
[
"Nakonieczna",
"Anna",
""
],
[
"Nakonieczny",
"Łukasz",
""
],
[
"Yeom",
"Dong-han",
""
]
] | In this review paper, we comprehensively summarize numerical applications of double-null formalism for studying dynamics within the theory of gravity. By using the double-null coordinates, we can investigate dynamical black holes and gravitational phenomena within spherical symmetry, including gravitational collapse, formation of horizons and singularities, as well as evaporations. This formalism can be extended to generic situations, where we can change dimensions, topologies, the gravity sector, as well as the matter sector. We also discuss its possible implications for black hole physics and particle astrophysics. This strong numerical tool will have lots of future applications for various research areas including general relativity, string theory, and various approaches to quantum gravity. |
1911.08602 | Brien C. Nolan | Brien C. Nolan | Causality violation without time-travel: closed lightlike paths in
G\"{o}del's universe | 38 pages (incl. 7 of appendices), 7 figures | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the issue of causality violations in G\"{o}del's universe,
restricting to geodesic motions. It is well-known that while there are closed
timelike curves in this spacetime, there are no closed causal geodesics. We
show further that no observer can communicate directly (i.e.\ using a single
causal geodesic) with their own past. However, we show that this type of
causality violation can be achieved by a system of relays: we prove that from
any event $P$ in G\"{o}del's universe, there is a future-directed lightlike
path - a sequence of future-directed null geodesic segments, laid end to end -
which has $P$ as its past and future endpoints. By analysing the envelope of
the family of future directed null geodesics emanating from a point of the
spacetime, we show that this lightlike path must contain a minimum of eight
geodesic segments, and show further that this bound is attained. We prove a
related general result, that events of a time orientable spacetime are
connected by a (closed) timelike curve if and only if they are connected by a
(closed) lightlike path. This suggests a means of violating causality in
G\"{o}del's universe without the need for unfeasibly large accelerations, using
instead a sequence of light signals reflected by a suitably located system of
mirrors.
| [
{
"created": "Tue, 19 Nov 2019 21:42:53 GMT",
"version": "v1"
}
] | 2019-11-21 | [
[
"Nolan",
"Brien C.",
""
]
] | We revisit the issue of causality violations in G\"{o}del's universe, restricting to geodesic motions. It is well-known that while there are closed timelike curves in this spacetime, there are no closed causal geodesics. We show further that no observer can communicate directly (i.e.\ using a single causal geodesic) with their own past. However, we show that this type of causality violation can be achieved by a system of relays: we prove that from any event $P$ in G\"{o}del's universe, there is a future-directed lightlike path - a sequence of future-directed null geodesic segments, laid end to end - which has $P$ as its past and future endpoints. By analysing the envelope of the family of future directed null geodesics emanating from a point of the spacetime, we show that this lightlike path must contain a minimum of eight geodesic segments, and show further that this bound is attained. We prove a related general result, that events of a time orientable spacetime are connected by a (closed) timelike curve if and only if they are connected by a (closed) lightlike path. This suggests a means of violating causality in G\"{o}del's universe without the need for unfeasibly large accelerations, using instead a sequence of light signals reflected by a suitably located system of mirrors. |
gr-qc/0111065 | Deruelle | Nathalie Deruelle | Stars on branes: the view from the brane | null | null | null | null | gr-qc astro-ph hep-th | null | We consider spherically symmetric matter configurations on a four dimensional
"brane" embedded in a five dimensional $Z_2$-symmetric "bulk". We write the
junction conditions between the interior and exterior of these "stars", treat a
couple of static examples in order to point out the differences with ordinary
four dimensional Einstein gravity, consider briefly a collapse situation and
conclude with the importance of a global view including asymptotic and
regularity conditions in the bulk.
| [
{
"created": "Tue, 20 Nov 2001 13:55:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Deruelle",
"Nathalie",
""
]
] | We consider spherically symmetric matter configurations on a four dimensional "brane" embedded in a five dimensional $Z_2$-symmetric "bulk". We write the junction conditions between the interior and exterior of these "stars", treat a couple of static examples in order to point out the differences with ordinary four dimensional Einstein gravity, consider briefly a collapse situation and conclude with the importance of a global view including asymptotic and regularity conditions in the bulk. |
2211.12041 | Mohit Sharma | Mayukh R. Gangopadhyay, Shibesh K. Jas Pacif, M. Sami, and Mohit K.
Sharma | Generic modification of gravity, late time acceleration and Hubble
tension | null | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We consider a scenario of large-scale modification of gravity that does not
invoke extra degrees of freedom but includes coupling between baryonic matter
and dark matter in the Einstein frame. The total matter energy density follows
the standard conservation, and evolution has the character of deceleration in
this frame. The model exhibits interesting features in the Jordan frame
realized by virtue of a disformal transformation where individual matter
components adhere to standard conservation but gravity is modified. A generic
parametrization of disformal transformation leaves thermal history intact. It
gives rise to late time acceleration in the Jordan frame, which necessarily
includes phantom crossing, which, in the standard framework, can be realized
using at least two scalar fields. This scenario is embodied by two
distinguishing features, namely, acceleration in the Jordan frame and
deceleration in the Einstein frame, and the possibility of resolution of the
Hubble tension thanks to the emergence of the phantom phase at late times.
| [
{
"created": "Tue, 22 Nov 2022 06:24:13 GMT",
"version": "v1"
}
] | 2022-11-23 | [
[
"Gangopadhyay",
"Mayukh R.",
""
],
[
"Pacif",
"Shibesh K. Jas",
""
],
[
"Sami",
"M.",
""
],
[
"Sharma",
"Mohit K.",
""
]
] | We consider a scenario of large-scale modification of gravity that does not invoke extra degrees of freedom but includes coupling between baryonic matter and dark matter in the Einstein frame. The total matter energy density follows the standard conservation, and evolution has the character of deceleration in this frame. The model exhibits interesting features in the Jordan frame realized by virtue of a disformal transformation where individual matter components adhere to standard conservation but gravity is modified. A generic parametrization of disformal transformation leaves thermal history intact. It gives rise to late time acceleration in the Jordan frame, which necessarily includes phantom crossing, which, in the standard framework, can be realized using at least two scalar fields. This scenario is embodied by two distinguishing features, namely, acceleration in the Jordan frame and deceleration in the Einstein frame, and the possibility of resolution of the Hubble tension thanks to the emergence of the phantom phase at late times. |
1203.2807 | Ali Kaya | Ali Kaya | Comments on the Canonical Measure in Cosmology | 9 pages, 4 figures, revtex4-1, v2: minor typos corrected | Phys.Lett. B713 (2012) 1-5 | 10.1016/j.physletb.2012.05.035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the mini-superspace approximation to cosmology, the canonical measure can
be used to compute probabilities when a cutoff is introduced in the phase space
to regularize the divergent measure. However, the region initially constrained
by a simple cutoff evolves non-trivially under the Hamiltonian flow. We
determine the deformation of the regularized phase space along the orbits when
a cutoff is introduced for the scale factor of the universe or for the Hubble
parameter. In the former case, we find that the cutoff for the scale factor
varies in the phase space and effectively decreases as one evolves backwards in
time. In the later case, we calculate the probability of slow-roll inflation in
a chaotic model with a massive scalar, which turns out to be cutoff dependent
but not exponentially suppressed. We also investigate the measure problem for
non-abelian gauge fields giving rise to inflation.
| [
{
"created": "Tue, 13 Mar 2012 13:46:00 GMT",
"version": "v1"
},
{
"created": "Mon, 14 May 2012 07:07:34 GMT",
"version": "v2"
}
] | 2013-06-04 | [
[
"Kaya",
"Ali",
""
]
] | In the mini-superspace approximation to cosmology, the canonical measure can be used to compute probabilities when a cutoff is introduced in the phase space to regularize the divergent measure. However, the region initially constrained by a simple cutoff evolves non-trivially under the Hamiltonian flow. We determine the deformation of the regularized phase space along the orbits when a cutoff is introduced for the scale factor of the universe or for the Hubble parameter. In the former case, we find that the cutoff for the scale factor varies in the phase space and effectively decreases as one evolves backwards in time. In the later case, we calculate the probability of slow-roll inflation in a chaotic model with a massive scalar, which turns out to be cutoff dependent but not exponentially suppressed. We also investigate the measure problem for non-abelian gauge fields giving rise to inflation. |
gr-qc/0304094 | Sijie Gao | Sijie Gao | First law of black hole mechanics in Einstein-Maxwell and
Einstein-Yang-Mills theories | Modified version, major changes made in the introduction. 14 pages,
no figure | Phys.Rev. D68 (2003) 044016 | 10.1103/PhysRevD.68.044016 | null | gr-qc | null | The first law of black hole mechanics is derived from the Einstein-Maxwell
(EM) Lagrangian by comparing two infinitesimally nearby stationary black holes.
With similar arguments, the first law of black hole mechanics in
Einstein-Yang-Mills (EYM) theory is also derived.
| [
{
"created": "Thu, 24 Apr 2003 09:53:46 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Aug 2003 09:10:36 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Gao",
"Sijie",
""
]
] | The first law of black hole mechanics is derived from the Einstein-Maxwell (EM) Lagrangian by comparing two infinitesimally nearby stationary black holes. With similar arguments, the first law of black hole mechanics in Einstein-Yang-Mills (EYM) theory is also derived. |
1511.03508 | Meng-Sen Ma | Meng-Sen Ma, Ren Zhao | Stability of black holes based on horizon thermodynamics | 6 pages, 7 figures | Physics Letters B 751(2015)278 | 10.1016/j.physletb.2015.10.061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of horizon thermodynamics we study the thermodynamic stability
of black holes constructed in general relativity and Gauss-Bonnet gravity. In
the framework of horizon thermodynamics there are only five thermodynamic
variables $E,P,V,T,S$. It is not necessary to consider concrete matter fields,
which may contribute to the pressure of black hole thermodynamic system. In
non-vacuum cases, we can derive the equation of state, $P=P(V,T)$. According to
the requirements of stable equilibrium in conventional thermodynamics, we start
from these thermodynamic variables to calculate the heat capacity at constant
pressure and Gibbs free energy and analyze the local and global thermodynamic
stability of black holes. It is shown that $P>0$ is the necessary condition for
black holes in general relativity to be thermodynamically stable, however this
condition cannot be satisfied by many black holes in general relativity. For
black hole in Gauss-Bonnet gravity negative pressure can be feasible, but only
local stable black hole exists in this case.
| [
{
"created": "Wed, 11 Nov 2015 14:07:49 GMT",
"version": "v1"
}
] | 2015-11-12 | [
[
"Ma",
"Meng-Sen",
""
],
[
"Zhao",
"Ren",
""
]
] | On the basis of horizon thermodynamics we study the thermodynamic stability of black holes constructed in general relativity and Gauss-Bonnet gravity. In the framework of horizon thermodynamics there are only five thermodynamic variables $E,P,V,T,S$. It is not necessary to consider concrete matter fields, which may contribute to the pressure of black hole thermodynamic system. In non-vacuum cases, we can derive the equation of state, $P=P(V,T)$. According to the requirements of stable equilibrium in conventional thermodynamics, we start from these thermodynamic variables to calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of black holes. It is shown that $P>0$ is the necessary condition for black holes in general relativity to be thermodynamically stable, however this condition cannot be satisfied by many black holes in general relativity. For black hole in Gauss-Bonnet gravity negative pressure can be feasible, but only local stable black hole exists in this case. |
gr-qc/0508125 | Eugene J. Surowitz | Alex Harvey, Engelbert L. Schucking, Eugene J. Surowitz | Redshifts and Killing Vectors | 16 Latex pages, 6 postscript figures, submitted to Am. J. Phys | Am.J.Phys.74:1017-1024,2006 | 10.1119/1.2338544 | null | gr-qc | null | Courses in introductory special and general relativity have increasingly
become part of the curriculum for upper-level undergraduate physics majors and
master's degree candidates. One of the topics rarely discussed is symmetry,
particularly in the theory of general relativity. The principal tool for its
study is the Killing vector. We provide an elementary introduction to the
concept of a Killing vector field, its properties, and as an example of its
utility apply these ideas to the rigorous determination of gravitational and
cosmological redshifts.
| [
{
"created": "Wed, 31 Aug 2005 01:39:37 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Harvey",
"Alex",
""
],
[
"Schucking",
"Engelbert L.",
""
],
[
"Surowitz",
"Eugene J.",
""
]
] | Courses in introductory special and general relativity have increasingly become part of the curriculum for upper-level undergraduate physics majors and master's degree candidates. One of the topics rarely discussed is symmetry, particularly in the theory of general relativity. The principal tool for its study is the Killing vector. We provide an elementary introduction to the concept of a Killing vector field, its properties, and as an example of its utility apply these ideas to the rigorous determination of gravitational and cosmological redshifts. |
2407.13487 | Umananda Dev Goswami | Pranjal Sarmah and Umananda Dev Goswami | Anisotropic cosmology in Bumblebee gravity theory | 20 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Bumblebee vector model of spontaneous Lorentz symmetry breaking (LSB) in
Bianchi type I (BI) Universe to observe its effect on cosmological evolution is
an interesting aspect of study in anisotropic cosmology. In this study, we have
considered a Bumblebee field under vacuum expectation value condition (VEV)
with BI metric and studied the cosmological parameters along with observational
data. Further, we have studied the effect of anisotropy and the Bumblebee field
in cosmic evolution. We have also studied the effect of both anisotropy and
Bumblebee field while considering the Universe as a dynamical system. We have
found that there are some prominent roles of both anisotropy and the Bumblebee
field in cosmic evolutions. We have also observed an elongated matter-dominated
phase as compared to standard cosmology. Moreover, while studying the dynamical
system analysis, we have also observed the shift of critical points from
standard $\Lambda$CDM results showing the anisotropy and the Bumblebee field
effect.
| [
{
"created": "Thu, 18 Jul 2024 13:07:55 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Sarmah",
"Pranjal",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | The Bumblebee vector model of spontaneous Lorentz symmetry breaking (LSB) in Bianchi type I (BI) Universe to observe its effect on cosmological evolution is an interesting aspect of study in anisotropic cosmology. In this study, we have considered a Bumblebee field under vacuum expectation value condition (VEV) with BI metric and studied the cosmological parameters along with observational data. Further, we have studied the effect of anisotropy and the Bumblebee field in cosmic evolution. We have also studied the effect of both anisotropy and Bumblebee field while considering the Universe as a dynamical system. We have found that there are some prominent roles of both anisotropy and the Bumblebee field in cosmic evolutions. We have also observed an elongated matter-dominated phase as compared to standard cosmology. Moreover, while studying the dynamical system analysis, we have also observed the shift of critical points from standard $\Lambda$CDM results showing the anisotropy and the Bumblebee field effect. |
0809.2945 | Marek Nowakowski | M. Nowakowski, I. Arraut | The fate of a gravitational wave in de Sitter spacetime | 17 pages, LaTex | Acta Phys.Polon.B41:911-925,2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If we want to explain the recently discovered accelerated stage of the
universe, one of the option we have is to modify the Einstein tensor. The
simplest such modification, in agreement with all observations, is the positive
cosmological constant $\Lambda$. Such a modification will also have its impact
on local observables and on the propagation of weak gravitational waves. We
show here that the inclusion of a cosmological constant impedes the detection
of a gravitational wave if the latter is produced at a distance larger than
${\cal L}_{\rm crit}=(6\sqrt{2}\pi f \hat{h}/\sqrt{5})r_{\Lambda}^2$ where
$r_{\Lambda}=1/\sqrt{\Lambda}$ and $f$ and $\hat{h}$ are the frequency and the
strain of the wave, respectively. ${\cal L}_{\rm crit}$ is of astrophysical
order of magnitude. We interpret the result in the sense that the gravitational
wave interpretation is only possible if the characteristic wave properties are
smaller than the non-oscillatory solution due to $\Lambda$.
| [
{
"created": "Wed, 17 Sep 2008 15:04:18 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Nowakowski",
"M.",
""
],
[
"Arraut",
"I.",
""
]
] | If we want to explain the recently discovered accelerated stage of the universe, one of the option we have is to modify the Einstein tensor. The simplest such modification, in agreement with all observations, is the positive cosmological constant $\Lambda$. Such a modification will also have its impact on local observables and on the propagation of weak gravitational waves. We show here that the inclusion of a cosmological constant impedes the detection of a gravitational wave if the latter is produced at a distance larger than ${\cal L}_{\rm crit}=(6\sqrt{2}\pi f \hat{h}/\sqrt{5})r_{\Lambda}^2$ where $r_{\Lambda}=1/\sqrt{\Lambda}$ and $f$ and $\hat{h}$ are the frequency and the strain of the wave, respectively. ${\cal L}_{\rm crit}$ is of astrophysical order of magnitude. We interpret the result in the sense that the gravitational wave interpretation is only possible if the characteristic wave properties are smaller than the non-oscillatory solution due to $\Lambda$. |
2305.11708 | Jefferson Toledo | F. F. Nascimento, V. B. Bezerra, J. M. Toledo | Some remarks on Hayward black hole with a cloud of strings | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We obtain the metric corresponding to the Hayward black hole spacetime
surrounded by a cloud of strings and investigate the role played by this cloud
on the horizons, geodesics, effective potential and thermodynamics. We compare
the obtained results with the ones of the literature, corresponding to the
Hayward black hole, when the cloud of strings is absent. Also, the question
related to its nature, with respect to regularity, in this scenario, is
examined.
| [
{
"created": "Fri, 19 May 2023 14:42:14 GMT",
"version": "v1"
}
] | 2023-05-22 | [
[
"Nascimento",
"F. F.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Toledo",
"J. M.",
""
]
] | We obtain the metric corresponding to the Hayward black hole spacetime surrounded by a cloud of strings and investigate the role played by this cloud on the horizons, geodesics, effective potential and thermodynamics. We compare the obtained results with the ones of the literature, corresponding to the Hayward black hole, when the cloud of strings is absent. Also, the question related to its nature, with respect to regularity, in this scenario, is examined. |
2303.14594 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou, F.P. Fronimos | Inflationary Dynamics and Swampland Criteria for Modified Gauss-Bonnet
Gravity Compatible with GW170817 | PRD Accepted, abstract reduced due to arXiv limitations | Phys.Rev.D 107 (2023) 08, 084007 | 10.1103/PhysRevD.107.084007 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we present an alternative formalism for the inflationary
phenomenology of rescaled Einstein-Gauss-Bonnet models which are in agreement
with the GW170817 event. By constraining the propagation velocity of primordial
tensor perturbations, an approximate form for the time derivative of the scalar
field coupled to the Gauss-Bonnet density is extracted. In turn, the overall
degrees of freedom decrease and similar to the case of the canonical scalar
field, only one scalar function needs to be designated, while the other is
extracted from the continuity equation of the scalar field. We showcase
explicitly that the slow-roll indices can be written in a closed form as
functions of three dimensionless parameters, namely
$x=\frac{1}{2\alpha}\bigg(\frac{\kappa\xi'}{\xi''}\bigg)^2$, $\beta=8H^2\xi''$
and $\gamma=\frac{\xi'\xi'''}{\xi''^2}$ and in turn, we prove that the
Einstein-Gauss-Bonnet model can in fact produce a blue-tilted tensor spectral
index if the condition $\beta\geq1$ is satisfied, which is possible only for
Einstein-Gauss-Bonnet models with $\xi''(\phi_k)>0$. Afterwards, a brief
comment on the running of the spectral indices is made where it is shown that
$a_{\mathcal{S}}(k_*)$ and $a_{\mathcal{T}}(k_*)$ in the constrained case are
approximately of the order $\mathcal{O}(10^{-3})$, if not smaller. Last but not
least, we examine the conditions under which the Swampland criteria are
satisfied. We connect the tracking condition related to scalar field theories
with the present models, and we highlight the important feature of the models
we propose that the tracking condition can be satisfied only if the Swampland
criteria are simultaneously satisfied, however the cases with $\xi\sim1/V$ and
$\xi\sim V$ are excluded, as they cannot describe the inflationary era
properly.
| [
{
"created": "Sun, 26 Mar 2023 00:30:11 GMT",
"version": "v1"
}
] | 2023-08-01 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Fronimos",
"F. P.",
""
]
] | In this article we present an alternative formalism for the inflationary phenomenology of rescaled Einstein-Gauss-Bonnet models which are in agreement with the GW170817 event. By constraining the propagation velocity of primordial tensor perturbations, an approximate form for the time derivative of the scalar field coupled to the Gauss-Bonnet density is extracted. In turn, the overall degrees of freedom decrease and similar to the case of the canonical scalar field, only one scalar function needs to be designated, while the other is extracted from the continuity equation of the scalar field. We showcase explicitly that the slow-roll indices can be written in a closed form as functions of three dimensionless parameters, namely $x=\frac{1}{2\alpha}\bigg(\frac{\kappa\xi'}{\xi''}\bigg)^2$, $\beta=8H^2\xi''$ and $\gamma=\frac{\xi'\xi'''}{\xi''^2}$ and in turn, we prove that the Einstein-Gauss-Bonnet model can in fact produce a blue-tilted tensor spectral index if the condition $\beta\geq1$ is satisfied, which is possible only for Einstein-Gauss-Bonnet models with $\xi''(\phi_k)>0$. Afterwards, a brief comment on the running of the spectral indices is made where it is shown that $a_{\mathcal{S}}(k_*)$ and $a_{\mathcal{T}}(k_*)$ in the constrained case are approximately of the order $\mathcal{O}(10^{-3})$, if not smaller. Last but not least, we examine the conditions under which the Swampland criteria are satisfied. We connect the tracking condition related to scalar field theories with the present models, and we highlight the important feature of the models we propose that the tracking condition can be satisfied only if the Swampland criteria are simultaneously satisfied, however the cases with $\xi\sim1/V$ and $\xi\sim V$ are excluded, as they cannot describe the inflationary era properly. |
gr-qc/9311033 | Henri Waelbroeck | Henri Waelbroeck | B^F Theory and Flat Spacetimes | 21 pp., Mexico Preprint ICN-UNAM-93-12 | Commun.Math.Phys. 170 (1995) 63-78 | 10.1007/BF02099439 | null | gr-qc | null | We propose a reduced constrained Hamiltonian formalism for the exactly
soluble $B \wedge F$ theory of flat connections and closed two-forms over
manifolds with topology $\Sigma^3 \times (0,1)$. The reduced phase space
variables are the holonomies of a flat connection for loops which form a basis
of the first homotopy group $\pi_1(\Sigma^3)$, and elements of the second
cohomology group of $\Sigma^3$ with value in the Lie algebra $L(G)$. When
$G=SO(3,1)$, and if the two-form can be expressed as $B= e\wedge e$, for some
vierbein field $e$, then the variables represent a flat spacetime. This is not
always possible: We show that the solutions of the theory generally represent
spacetimes with ``global torsion''. We describe the dynamical evolution of
spacetimes with and without global torsion, and classify the flat spacetimes
which admit a locally homogeneous foliation, following Thurston's
classification of geometric structures.
| [
{
"created": "Fri, 26 Nov 1993 15:31:39 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Waelbroeck",
"Henri",
""
]
] | We propose a reduced constrained Hamiltonian formalism for the exactly soluble $B \wedge F$ theory of flat connections and closed two-forms over manifolds with topology $\Sigma^3 \times (0,1)$. The reduced phase space variables are the holonomies of a flat connection for loops which form a basis of the first homotopy group $\pi_1(\Sigma^3)$, and elements of the second cohomology group of $\Sigma^3$ with value in the Lie algebra $L(G)$. When $G=SO(3,1)$, and if the two-form can be expressed as $B= e\wedge e$, for some vierbein field $e$, then the variables represent a flat spacetime. This is not always possible: We show that the solutions of the theory generally represent spacetimes with ``global torsion''. We describe the dynamical evolution of spacetimes with and without global torsion, and classify the flat spacetimes which admit a locally homogeneous foliation, following Thurston's classification of geometric structures. |
gr-qc/9411052 | null | I.B. Khriplovich | Superluminal Velocity of Photons in a Gravitational Background | 5 pages, LaTeX | Phys.Lett. B346 (1995) 251-254 | 10.1016/0370-2693(94)01679-7 | BINP 94-88 | gr-qc | null | The influence of radiative corrections on the photon propagation in a
gravitational background is investigated without the low-frequency
approximation $\omega \ll m$. The conclusion is made in this way that the
velocity of light can exceed unity.
| [
{
"created": "Sun, 20 Nov 1994 09:27:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Khriplovich",
"I. B.",
""
]
] | The influence of radiative corrections on the photon propagation in a gravitational background is investigated without the low-frequency approximation $\omega \ll m$. The conclusion is made in this way that the velocity of light can exceed unity. |
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