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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2106.03672 | Joao Paulo Morais Graca | P. H. Morais, G. V. Silva, J. P. Morais Gra\c{c}a and V. B. Bezerra | Thermodynamics and remnants of Kiselev black holes in Rainbow gravity | null | null | 10.1007/s10714-021-02897-x | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We do a detailed study of the thermodynamics of black holes in Rainbow
gravity in the framework of the Kiselev metric, taking into account different
cosmic fluids which can mimic several kinds of dark energy scenarios. A
discussion related to the appearance of black hole remnants is presented and,
unlike other studies on the same topic, we found no evidence of the appearance
of remnants in Rainbow gravity, except in peculiar cases.
| [
{
"created": "Mon, 7 Jun 2021 14:52:51 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Morais",
"P. H.",
""
],
[
"Silva",
"G. V.",
""
],
[
"Graça",
"J. P. Morais",
""
],
[
"Bezerra",
"V. B.",
""
]
] | We do a detailed study of the thermodynamics of black holes in Rainbow gravity in the framework of the Kiselev metric, taking into account different cosmic fluids which can mimic several kinds of dark energy scenarios. A discussion related to the appearance of black hole remnants is presented and, unlike other studies on the same topic, we found no evidence of the appearance of remnants in Rainbow gravity, except in peculiar cases. |
2211.06340 | Donato Bini | Donato Bini, Thibault Damour | Radiation-reaction and angular momentum loss at the second
Post-Minkowskian order | 18 pages, 2 eps figures | null | 10.1103/PhysRevD.106.124049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the variation of the Fokker-Wheeler-Feynman total linear and
angular momentum of a gravitationally interacting binary system under the
second post-Minkowskian retarded dynamics. The resulting $O(G^2)$
equations-of-motion-based, total change in the system's angular momentum is
found to agree with existing computations that assumed balance with angular
momentum fluxes in the radiation zone.
| [
{
"created": "Fri, 11 Nov 2022 16:39:11 GMT",
"version": "v1"
}
] | 2023-01-11 | [
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
]
] | We compute the variation of the Fokker-Wheeler-Feynman total linear and angular momentum of a gravitationally interacting binary system under the second post-Minkowskian retarded dynamics. The resulting $O(G^2)$ equations-of-motion-based, total change in the system's angular momentum is found to agree with existing computations that assumed balance with angular momentum fluxes in the radiation zone. |
1106.0627 | Pieter Miedema | P.G.Miedema | Relativistic Cosmological Perturbation Theory and the Evolution of
Small-Scale Inhomogeneities | 37 pages including Maxima CAS files and R file. Textual improvements.
Section VI on the standard Newtonian perturbation equation rewritten.
Conclusions unchanged. Any comments, reviews, critiques, or objections are
invited and should be send to the author by e-mail | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that a first-order relativistic perturbation theory for the open,
flat or closed Friedmann-Lemaitre-Robertson-Walker universe admits one, and
only one, gauge-invariant quantity which describes the perturbation to the
energy density and which becomes equal to the usual Newtonian energy density in
the non-relativistic limit. The same holds true for the perturbation to the
particle number density. These facts exclude all definitions of gauge-invariant
quantities used to describe density perturbations in former theories. Using
these two new quantities, a manifestly covariant and gauge-invariant
cosmological perturbation theory, adapted to non-barotropic equations of state
for the pressure, has been developed. The new theory is valid for all scales
since metric gradients do not occur in the final evolution equations. The new
theory has an exact non-relativistic limit with a time-independent Newtonian
potential. The usual Newtonian perturbation theory is inadequate to study the
evolution of density perturbations. In the radiation-dominated era,
perturbations in the particle number density are gravitationally coupled to
perturbations in the total energy density, irrespective of the nature of the
particles. This implies that structure formation can commence only after
decoupling of matter and radiation. After decoupling of matter and radiation
density perturbations evolve diabatically, i.e., they exchange heat with their
environment. This heat loss of a perturbation may enhance the growth rate of
its mass sufficiently to explain stellar formation in the early universe, a
phenomenon not understood, as yet, without the additional assumption of the
existence of Cold Dark Matter. This theoretical observation is the main result
of this article.
| [
{
"created": "Fri, 3 Jun 2011 12:57:00 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jan 2012 16:02:41 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Jul 2012 06:36:27 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Jul 2013 14:21:00 GMT",
"version": "v4"
},
{
"created": "Mon, 24 Mar 2014 09:41:16 GMT",
"version": "v5"
}
] | 2014-03-25 | [
[
"Miedema",
"P. G.",
""
]
] | It is shown that a first-order relativistic perturbation theory for the open, flat or closed Friedmann-Lemaitre-Robertson-Walker universe admits one, and only one, gauge-invariant quantity which describes the perturbation to the energy density and which becomes equal to the usual Newtonian energy density in the non-relativistic limit. The same holds true for the perturbation to the particle number density. These facts exclude all definitions of gauge-invariant quantities used to describe density perturbations in former theories. Using these two new quantities, a manifestly covariant and gauge-invariant cosmological perturbation theory, adapted to non-barotropic equations of state for the pressure, has been developed. The new theory is valid for all scales since metric gradients do not occur in the final evolution equations. The new theory has an exact non-relativistic limit with a time-independent Newtonian potential. The usual Newtonian perturbation theory is inadequate to study the evolution of density perturbations. In the radiation-dominated era, perturbations in the particle number density are gravitationally coupled to perturbations in the total energy density, irrespective of the nature of the particles. This implies that structure formation can commence only after decoupling of matter and radiation. After decoupling of matter and radiation density perturbations evolve diabatically, i.e., they exchange heat with their environment. This heat loss of a perturbation may enhance the growth rate of its mass sufficiently to explain stellar formation in the early universe, a phenomenon not understood, as yet, without the additional assumption of the existence of Cold Dark Matter. This theoretical observation is the main result of this article. |
gr-qc/9801030 | Hagen Kleinert | H. Kleinert and A. Pelster | Novel Geometric Gauge Invariance of Autoparallels | Corrected typos. Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Paper also at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re262/preprint.html fuer
Theoretische Physik | Acta Phys.Polon.B29:1015,1998 | null | null | gr-qc | null | We draw attention to a novel type of geometric gauge invariance relating the
autoparallel equations of motion in different Riemann-Cartan spacetimes with
each other. The novelty lies in the fact that the equations of motion are
invariant even though the actions are not. As an application we use this gauge
transformation to map the action of a spinless point particle in a
Riemann-Cartan spacetime with a gradient torsion to a purely Riemann spacetime,
in which the initial torsion appears as a nongeometric external field. By
extremizing the transformed action in the usual way, we obtain the same
autoparallel equations of motion as those derived in the initial spacetime with
torsion via a recently-discovered variational principle.
| [
{
"created": "Sat, 10 Jan 1998 16:48:36 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Jan 1998 07:02:19 GMT",
"version": "v2"
}
] | 2011-03-17 | [
[
"Kleinert",
"H.",
""
],
[
"Pelster",
"A.",
""
]
] | We draw attention to a novel type of geometric gauge invariance relating the autoparallel equations of motion in different Riemann-Cartan spacetimes with each other. The novelty lies in the fact that the equations of motion are invariant even though the actions are not. As an application we use this gauge transformation to map the action of a spinless point particle in a Riemann-Cartan spacetime with a gradient torsion to a purely Riemann spacetime, in which the initial torsion appears as a nongeometric external field. By extremizing the transformed action in the usual way, we obtain the same autoparallel equations of motion as those derived in the initial spacetime with torsion via a recently-discovered variational principle. |
gr-qc/0502084 | Nail Khusnutdinov | S. V. Sushkov | Wormholes supported by a phantom energy | 4 figures, accepted in PRD | Phys.Rev. D71 (2005) 043520 | 10.1103/PhysRevD.71.043520 | null | gr-qc | null | We extend the notion of phantom energy--which is generally accepted for
homogeneously distributed matter with $w<-1$ in the universe--on inhomogeneous
spherically symmetric spacetime configurations. A spherically symmetric
distribution of phantom energy is shown to be able to support the existence of
static wormholes. We find an exact solution describing a static spherically
symmetric wormhole with phantom energy and show that a spatial distribution of
the phantom energy is mainly restricted by the vicinity of the wormhole's
throat. The maximal size of the spherical region, surrounding the throat and
containing the most part of the phantom energy, depends on the
equation-of-state parameter $w$ and cannot exceed some upper limit.
| [
{
"created": "Mon, 21 Feb 2005 13:11:39 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sushkov",
"S. V.",
""
]
] | We extend the notion of phantom energy--which is generally accepted for homogeneously distributed matter with $w<-1$ in the universe--on inhomogeneous spherically symmetric spacetime configurations. A spherically symmetric distribution of phantom energy is shown to be able to support the existence of static wormholes. We find an exact solution describing a static spherically symmetric wormhole with phantom energy and show that a spatial distribution of the phantom energy is mainly restricted by the vicinity of the wormhole's throat. The maximal size of the spherical region, surrounding the throat and containing the most part of the phantom energy, depends on the equation-of-state parameter $w$ and cannot exceed some upper limit. |
2305.07306 | Piotr T. Chru\'sciel | Piotr T. Chrusciel, Roger Tagne Wafo and Finnian Gray | The "neighborhood theorem" for the general relativistic characteristic
Cauchy problem in higher dimension | The same result has already been established in [13]. arXiv admin
note: text overlap with arXiv:1406.3009 | null | null | UWThPh-2023-15 | gr-qc math.DG | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We show that the maximal globally hyperbolic solution of the initial-value
problem for the higher-dimensional vacuum Einstein equations on two
transversally intersecting characteristic hypersurfaces contains a future
neighborhood of the hypersurfaces.
| [
{
"created": "Fri, 12 May 2023 08:25:16 GMT",
"version": "v1"
}
] | 2023-05-15 | [
[
"Chrusciel",
"Piotr T.",
""
],
[
"Wafo",
"Roger Tagne",
""
],
[
"Gray",
"Finnian",
""
]
] | We show that the maximal globally hyperbolic solution of the initial-value problem for the higher-dimensional vacuum Einstein equations on two transversally intersecting characteristic hypersurfaces contains a future neighborhood of the hypersurfaces. |
gr-qc/0402054 | D. F. Mota | Yves Gaspar | Time Asymmetry and Chaos in General Relativity | Latex, 14 pages, no figures. Submitted to Gen. Rel. Grav | Gen.Rel.Grav.36:2085-2094,2004 | 10.1023/B:GERG.0000038473.76575.b0 | null | gr-qc | null | In this work the late-time evolution of Bianchi type $VIII$ models is
discussed. These cosmological models exhibit a chaotic behaviour towards the
initial singularity and our investigations show that towards the future, far
from the initial singularity, these models have a non-chaotic evolution, even
in the case of vacuum and without inflation. These space-time solutions turn
out to exhibit a particular time asymmetry. On the other hand, investigations
of the late-time behaviour of type $VIII$ models by another author have the
result that chaos continues for ever in the far future and that these solutions
have a time symmetric behaviour: this result was obtained using the
approximation methods of Belinski, Khalatnikov and Lifshitz ($BKL$) and we try
to find out a possible reason explaining why the different approaches lead to
distinct outcomes. It will be shown that, at a heuristic level, the $BKL$
method gives a valid approximation of the late-time evolution of type $VIII$
models, agreeing with the result of our investigations.
| [
{
"created": "Thu, 12 Feb 2004 12:10:01 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Gaspar",
"Yves",
""
]
] | In this work the late-time evolution of Bianchi type $VIII$ models is discussed. These cosmological models exhibit a chaotic behaviour towards the initial singularity and our investigations show that towards the future, far from the initial singularity, these models have a non-chaotic evolution, even in the case of vacuum and without inflation. These space-time solutions turn out to exhibit a particular time asymmetry. On the other hand, investigations of the late-time behaviour of type $VIII$ models by another author have the result that chaos continues for ever in the far future and that these solutions have a time symmetric behaviour: this result was obtained using the approximation methods of Belinski, Khalatnikov and Lifshitz ($BKL$) and we try to find out a possible reason explaining why the different approaches lead to distinct outcomes. It will be shown that, at a heuristic level, the $BKL$ method gives a valid approximation of the late-time evolution of type $VIII$ models, agreeing with the result of our investigations. |
1705.04191 | Haizhao Zhi | Haizhao Zhi | Behavior of vacuum and naked singularity under smooth gauge function in
Lyra geometry | 24 pages, 1 figures | Canadian Journal of Physics, Published on the web 9 January 2018 | 10.1139/cjp-2017-0681 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lyra geometry is a conformal geometry originated from Weyl geometry. In this
article, we derive the exterior field equation under spherically symmetric
gauge function $x^0(r)$ and metric in Lyra geometry. When we impose a specific
form of the gauge function $x^0(r)$, the radial differential equation of the
metric component $g_{00}$ will possess an irregular singular point(ISP) at
$r=0$. Moreover, we apply the method of dominant balance and then get the
asymptotic behavior of the new spacetime solution. The significance of this
work is that we could use a series of smooth gauge functions $x^0(r)$ to
modulate the degree of divergence of the singularity at $r=0$ and the
singularity will become a naked singularity under certain conditions.
Furthermore, we investigate the physical meaning of this novel behavior of
spacetime in Lyra geometry and find out that no spaceship with finite
integrated acceleration could arrive at this singularity at $r=0$. The physical
meaning of gauge function and integrability is also discussed.
| [
{
"created": "Wed, 10 May 2017 15:37:13 GMT",
"version": "v1"
},
{
"created": "Sat, 13 May 2017 05:13:03 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Jul 2017 09:30:14 GMT",
"version": "v3"
},
{
"created": "Sun, 26 Nov 2017 12:56:40 GMT",
"version": "v4"
},
{
"created": "Thu, 14 Dec 2017 11:14:49 GMT",
"version": "v5"
}
] | 2018-01-12 | [
[
"Zhi",
"Haizhao",
""
]
] | Lyra geometry is a conformal geometry originated from Weyl geometry. In this article, we derive the exterior field equation under spherically symmetric gauge function $x^0(r)$ and metric in Lyra geometry. When we impose a specific form of the gauge function $x^0(r)$, the radial differential equation of the metric component $g_{00}$ will possess an irregular singular point(ISP) at $r=0$. Moreover, we apply the method of dominant balance and then get the asymptotic behavior of the new spacetime solution. The significance of this work is that we could use a series of smooth gauge functions $x^0(r)$ to modulate the degree of divergence of the singularity at $r=0$ and the singularity will become a naked singularity under certain conditions. Furthermore, we investigate the physical meaning of this novel behavior of spacetime in Lyra geometry and find out that no spaceship with finite integrated acceleration could arrive at this singularity at $r=0$. The physical meaning of gauge function and integrability is also discussed. |
0906.3602 | Clifford M. Will | Adamantios Stavridis (Washington U. St. Louis) and Clifford M. Will
(Washington U. St. Louis & Institut d'Astrophysique de Paris) | Bounding the mass of the graviton with gravitational waves: Effect of
spin precessions in massive black hole binaries | 10 pages, 5 figures; version accepted for publication | Phys.Rev.D80:044002,2009 | 10.1103/PhysRevD.80.044002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observations of gravitational waves from massive binary black hole systems at
cosmological distances can be used to search for a dependence of the speed of
propagation of the waves on wavelength, and thereby to bound the mass of a
hypothetical graviton. We study the effects of precessions of the spins of the
black holes and of the orbital angular momentum on the process of parameter
estimation using matched filtering of gravitational-wave signals vs.
theoretical template waveforms. For the proposed space interferometer LISA, we
show that precessions, and the accompanying modulations of the gravitational
waveforms, are effective in breaking degeneracies among the parameters being
estimated, and effectively restore the achievable graviton-mass bounds to
levels obtainable from binary inspirals without spin. For spinning, precessing
binary black hole systems of equal masses (10^6 solar masses) at 3 Gpc, the
bounds on the graviton Compton wavelength achievable are of the order of 5 X
10^{16} km.
| [
{
"created": "Fri, 19 Jun 2009 08:26:08 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Aug 2009 08:56:52 GMT",
"version": "v2"
}
] | 2009-09-02 | [
[
"Stavridis",
"Adamantios",
"",
"Washington U. St. Louis"
],
[
"Will",
"Clifford M.",
"",
"Washington U. St. Louis & Institut d'Astrophysique de Paris"
]
] | Observations of gravitational waves from massive binary black hole systems at cosmological distances can be used to search for a dependence of the speed of propagation of the waves on wavelength, and thereby to bound the mass of a hypothetical graviton. We study the effects of precessions of the spins of the black holes and of the orbital angular momentum on the process of parameter estimation using matched filtering of gravitational-wave signals vs. theoretical template waveforms. For the proposed space interferometer LISA, we show that precessions, and the accompanying modulations of the gravitational waveforms, are effective in breaking degeneracies among the parameters being estimated, and effectively restore the achievable graviton-mass bounds to levels obtainable from binary inspirals without spin. For spinning, precessing binary black hole systems of equal masses (10^6 solar masses) at 3 Gpc, the bounds on the graviton Compton wavelength achievable are of the order of 5 X 10^{16} km. |
1510.01351 | Irina Dymnikova | Irina Dymnikova and Maxim Khlopov | Regular black hole remnants and graviatoms with de Sitter interior as
heavy dark matter candidates probing inhomogeneity of early universe | 11 pages, 2 figures | International Journal of Modern Physics D Vol. 24, No. 11 (2015)
1545002 (special issue "Composite dark matter") | 10.1142/S0218271815450029 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the question of regular primordial black holes with de Sitter
interior, their remnants and gravitational vacuum solitons G-lumps as heavy
dark matter candidates providing signatures for inhomogeneity of early
universe, which is severely constrained by the condition that the contribution
of these objects in the modern density does not exceed the total density of
dark matter. Primordial black holes and their remnants seem to be most elusive
among dark matter candidates. However, we reveal a nontrivial property of
compact objects with de Sitter interior to induce proton decay or decay of
neutrons in neutron stars. The point is that they can form graviatoms, binding
electrically charged particles. Their observational signatures as dark matter
candidates provide also signatures for inhomogeneity of the early universe. In
graviatoms, the cross-section of the induced proton decay is strongly enhanced,
what provides the possibility of their experimental searches. We predict proton
decay paths induced by graviatoms in the matter as an observational signature
for heavy dark matter searches at the IceCUBE experiment.
| [
{
"created": "Fri, 2 Oct 2015 11:45:13 GMT",
"version": "v1"
}
] | 2015-10-07 | [
[
"Dymnikova",
"Irina",
""
],
[
"Khlopov",
"Maxim",
""
]
] | We address the question of regular primordial black holes with de Sitter interior, their remnants and gravitational vacuum solitons G-lumps as heavy dark matter candidates providing signatures for inhomogeneity of early universe, which is severely constrained by the condition that the contribution of these objects in the modern density does not exceed the total density of dark matter. Primordial black holes and their remnants seem to be most elusive among dark matter candidates. However, we reveal a nontrivial property of compact objects with de Sitter interior to induce proton decay or decay of neutrons in neutron stars. The point is that they can form graviatoms, binding electrically charged particles. Their observational signatures as dark matter candidates provide also signatures for inhomogeneity of the early universe. In graviatoms, the cross-section of the induced proton decay is strongly enhanced, what provides the possibility of their experimental searches. We predict proton decay paths induced by graviatoms in the matter as an observational signature for heavy dark matter searches at the IceCUBE experiment. |
0912.0128 | Istv\'an R\'acz | Istvan Racz | Gravitational radiation and isotropic change of the spatial geometry | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To simplify a number of considerations in the weak field approximation,
including the determination of the response of interferometric gravitational
wave detectors, the "transverse traceless" (TT) gauge is often used. While the
identification of the corresponding gauge invariant part of the metric
perturbations in the pure vacuum case is obvious, it is not widely known that
the determination and the use of the TT part is much more complicated and, in
turn, much less rewarding when sources are involved. It is shown here that
likewise the transverse part of the electric current in the Coulomb gauge
within Maxwell's theory the sources of the TT gauge part of the metric
perturbations become non-local. This, in practice, invokes the necessity of the
use of more adequate projection operators then the ones applied, e.g, in the
weak field limit, and in many post-Newtonian considerations. It is also pointed
out that, whenever nonlinear effects are taken into account, some of the
conclusions concerning the response of interferometric gravitational wave
detectors may be influenced. In particular, attention is called on the
possibility that gravitational radiation may produce an isotropic change of the
spatial geometry.
| [
{
"created": "Tue, 1 Dec 2009 12:02:36 GMT",
"version": "v1"
}
] | 2009-12-02 | [
[
"Racz",
"Istvan",
""
]
] | To simplify a number of considerations in the weak field approximation, including the determination of the response of interferometric gravitational wave detectors, the "transverse traceless" (TT) gauge is often used. While the identification of the corresponding gauge invariant part of the metric perturbations in the pure vacuum case is obvious, it is not widely known that the determination and the use of the TT part is much more complicated and, in turn, much less rewarding when sources are involved. It is shown here that likewise the transverse part of the electric current in the Coulomb gauge within Maxwell's theory the sources of the TT gauge part of the metric perturbations become non-local. This, in practice, invokes the necessity of the use of more adequate projection operators then the ones applied, e.g, in the weak field limit, and in many post-Newtonian considerations. It is also pointed out that, whenever nonlinear effects are taken into account, some of the conclusions concerning the response of interferometric gravitational wave detectors may be influenced. In particular, attention is called on the possibility that gravitational radiation may produce an isotropic change of the spatial geometry. |
2108.05012 | Shantanu Desai | Srinikitha Bhagvati, Shantanu Desai | Search for variability in Newton's constant using local gravitational
acceleration measurements | 8 pages, 4 figures | Class. Quantum Grav. 39, 017001 (2022) | 10.1088/1361-6382/ac3c8c | null | gr-qc astro-ph.CO astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | In a recent work, Dai (arXiv:2103.11157) searched for a variability in
Newton's constant $G$ using the IGETS based gravitational acceleration
measurements. However, this analysis, obtained from $\chi^2$ minimization, did
not incorporate the errors in the gravitational acceleration measurements. We
carry out a similar search with one major improvement, wherein we incorporate
these aforementioned errors. To model any possible variation in the
gravitational acceleration, we fit the data to four models: a constant value,
two sinusoidal models, and finally, a linear model for the variation of
gravitational acceleration. We find that none of the four models provides a
good fit to the data, showing that there is no evidence for a periodicity or a
linear temporal variation in the acceleration measurements. We then redid these
analyses after accounting for an unknown intrinsic scatter. After this, we find
that although a constant model is still favored over the sinusoidal models, the
linear variation for $G$ is marginally preferred over a constant value, using
information theory-based methods.
| [
{
"created": "Wed, 11 Aug 2021 03:47:42 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Nov 2021 14:21:13 GMT",
"version": "v2"
}
] | 2021-12-14 | [
[
"Bhagvati",
"Srinikitha",
""
],
[
"Desai",
"Shantanu",
""
]
] | In a recent work, Dai (arXiv:2103.11157) searched for a variability in Newton's constant $G$ using the IGETS based gravitational acceleration measurements. However, this analysis, obtained from $\chi^2$ minimization, did not incorporate the errors in the gravitational acceleration measurements. We carry out a similar search with one major improvement, wherein we incorporate these aforementioned errors. To model any possible variation in the gravitational acceleration, we fit the data to four models: a constant value, two sinusoidal models, and finally, a linear model for the variation of gravitational acceleration. We find that none of the four models provides a good fit to the data, showing that there is no evidence for a periodicity or a linear temporal variation in the acceleration measurements. We then redid these analyses after accounting for an unknown intrinsic scatter. After this, we find that although a constant model is still favored over the sinusoidal models, the linear variation for $G$ is marginally preferred over a constant value, using information theory-based methods. |
1403.2682 | Tim-Torben Paetz | Tim-Torben Paetz | Killing Initial Data on spacelike conformal boundaries | 27 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze Killing Initial Data on Cauchy surfaces in conformally rescaled
vacuum space-times satisfying Friedrich's conformal field equations. As an
application, we derive the KID equations on a spacelike $\mathcal{J}^-$.
| [
{
"created": "Tue, 11 Mar 2014 18:44:45 GMT",
"version": "v1"
}
] | 2014-03-12 | [
[
"Paetz",
"Tim-Torben",
""
]
] | We analyze Killing Initial Data on Cauchy surfaces in conformally rescaled vacuum space-times satisfying Friedrich's conformal field equations. As an application, we derive the KID equations on a spacelike $\mathcal{J}^-$. |
gr-qc/9610015 | Matthew S. Piper | W.B.Bonnor, M.S.Piper | Implosion of quadrupole gravitational waves | 7 pages LaTex | null | null | null | gr-qc | null | Einstein's vacuum equations are solved up to the second approximation for
imploding quadrupole gravitational waves. The implosion generates a black hole
singularity irrespective of the strength of the waves.
| [
{
"created": "Thu, 10 Oct 1996 10:21:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bonnor",
"W. B.",
""
],
[
"Piper",
"M. S.",
""
]
] | Einstein's vacuum equations are solved up to the second approximation for imploding quadrupole gravitational waves. The implosion generates a black hole singularity irrespective of the strength of the waves. |
gr-qc/0202033 | Jiri Podolsky | J. Podolsky | Accelerating black holes in anti-de Sitter universe | 8 pages, 2 figures | Czech.J.Phys. 52 (2002) 1-10 | 10.1023/A:1013961411430 | null | gr-qc | null | A physical interpretation of the C-metric with a negative cosmological
constant $\Lambda$ is suggested. Using a convenient coordinate system it is
demonstrated that this class of exact solutions of Einstein's equations
describes uniformly accelerating (possibly charged) black holes in anti-de
Sitter universe. Main differences from the analogous de Sitter case are
emphasised.
| [
{
"created": "Mon, 11 Feb 2002 14:44:02 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Podolsky",
"J.",
""
]
] | A physical interpretation of the C-metric with a negative cosmological constant $\Lambda$ is suggested. Using a convenient coordinate system it is demonstrated that this class of exact solutions of Einstein's equations describes uniformly accelerating (possibly charged) black holes in anti-de Sitter universe. Main differences from the analogous de Sitter case are emphasised. |
2003.00889 | Naveena Kumara A | A. Naveena Kumara, C.L. Ahmed Rizwan, Kartheek Hegde, Ajith K.M., Md
Sabir Ali | Microstructure and continuous phase transition of a regular Hayward
black hole in anti-de Sitter spacetime | 15 pages, 2 figures | PTEP 7 (2021) 073E01 | 10.1093/ptep/ptab065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the phase transition of a regular Hayward-AdS black hole by
introducing a new order parameter, the potential conjugate to the magnetic
charge due to the non-linearly coupled electromagnetic field. We use Landau
continuous phase transition theory to discuss the van der Waals like critical
phenomena of the black hole. The popular interpretation of the AdS black hole
phase transition as between a large and a small black hole is reinterpreted as
the transition between a high potential phase and a low potential phase. The
underlying microstructure for this phase transition is probed using the
Ruppeiner geometry. By investigating the behaviour of the Ruppeiner scalar
curvature, we find that the charged and uncharged (effective) molecules of the
black hole have distinct microstructures analogous to fermion and boson gas.
| [
{
"created": "Mon, 2 Mar 2020 13:19:42 GMT",
"version": "v1"
}
] | 2021-08-10 | [
[
"Kumara",
"A. Naveena",
""
],
[
"Rizwan",
"C. L. Ahmed",
""
],
[
"Hegde",
"Kartheek",
""
],
[
"M.",
"Ajith K.",
""
],
[
"Ali",
"Md Sabir",
""
]
] | We study the phase transition of a regular Hayward-AdS black hole by introducing a new order parameter, the potential conjugate to the magnetic charge due to the non-linearly coupled electromagnetic field. We use Landau continuous phase transition theory to discuss the van der Waals like critical phenomena of the black hole. The popular interpretation of the AdS black hole phase transition as between a large and a small black hole is reinterpreted as the transition between a high potential phase and a low potential phase. The underlying microstructure for this phase transition is probed using the Ruppeiner geometry. By investigating the behaviour of the Ruppeiner scalar curvature, we find that the charged and uncharged (effective) molecules of the black hole have distinct microstructures analogous to fermion and boson gas. |
1605.03297 | Peter Hayman | C.P. Burgess, Jared J.H. Enns, Peter Hayman and Subodh P. Patil | Goldilocks Models of Higher-Dimensional Inflation (including modulus
stabilization) | 29 pages, 11 figures | JCAP 1608 (2016) 045 | 10.1088/1475-7516/2016/08/045 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the mechanics of inflation in simplified extra-dimensional models
involving an inflaton interacting with the Einstein-Maxwell system in two extra
dimensions. The models are Goldilocks-like in that they are just complicated
enough to include a mechanism to stabilize the extra-dimensional size, yet
simple enough to solve the full 6D field equations using basic tools. The
solutions are not limited to the effective 4D regime with H << m_KK (the latter
referring to the mass splitting of the Kaluza-Klein excitations) because the
full 6D Einstein equations are solved. This allows an exploration of
inflationary physics in a controlled regime away from the usual 4D lamp-post.
The inclusion of modulus stabilization is important as experience with string
models teaches that this is usually what makes models fail: stabilization
energies dominate the shallow potentials required by slow roll and open up
directions to evolve that are steeper than those of the putative inflationary
direction. We explore three representative inflationary scenarios within this
simple setup. In one the radion is trapped in an inflaton-dependent local
minimum whose non-zero energy drives inflation. Inflation ends as this energy
relaxes to zero when the inflaton finds its minimum. The others involve
power-law solutions during inflation. One is an attractor whose features are
relatively insensitive to initial conditions but whose slow-roll parameters
cannot be arbitrarily small; the other is not an attractor but can roll much
more slowly, until eventually decaying to the attractor. These solutions can
satisfy H > m_KK, but when they do standard 4D fluctuation calculations need
not apply. When in a 4D regime the solutions predict eta ~ 0 hence r ~ 0.11
when n_s ~ 0.96 and so are ruled out if tensor modes remain unseen. Analysis of
general parameters is difficult without a full 6D fluctuation calculation.
| [
{
"created": "Wed, 11 May 2016 06:26:26 GMT",
"version": "v1"
},
{
"created": "Thu, 12 May 2016 05:00:32 GMT",
"version": "v2"
},
{
"created": "Tue, 24 May 2016 20:13:32 GMT",
"version": "v3"
}
] | 2016-08-31 | [
[
"Burgess",
"C. P.",
""
],
[
"Enns",
"Jared J. H.",
""
],
[
"Hayman",
"Peter",
""
],
[
"Patil",
"Subodh P.",
""
]
] | We explore the mechanics of inflation in simplified extra-dimensional models involving an inflaton interacting with the Einstein-Maxwell system in two extra dimensions. The models are Goldilocks-like in that they are just complicated enough to include a mechanism to stabilize the extra-dimensional size, yet simple enough to solve the full 6D field equations using basic tools. The solutions are not limited to the effective 4D regime with H << m_KK (the latter referring to the mass splitting of the Kaluza-Klein excitations) because the full 6D Einstein equations are solved. This allows an exploration of inflationary physics in a controlled regime away from the usual 4D lamp-post. The inclusion of modulus stabilization is important as experience with string models teaches that this is usually what makes models fail: stabilization energies dominate the shallow potentials required by slow roll and open up directions to evolve that are steeper than those of the putative inflationary direction. We explore three representative inflationary scenarios within this simple setup. In one the radion is trapped in an inflaton-dependent local minimum whose non-zero energy drives inflation. Inflation ends as this energy relaxes to zero when the inflaton finds its minimum. The others involve power-law solutions during inflation. One is an attractor whose features are relatively insensitive to initial conditions but whose slow-roll parameters cannot be arbitrarily small; the other is not an attractor but can roll much more slowly, until eventually decaying to the attractor. These solutions can satisfy H > m_KK, but when they do standard 4D fluctuation calculations need not apply. When in a 4D regime the solutions predict eta ~ 0 hence r ~ 0.11 when n_s ~ 0.96 and so are ruled out if tensor modes remain unseen. Analysis of general parameters is difficult without a full 6D fluctuation calculation. |
gr-qc/0111016 | Carlo Rovelli | Michael Reisenberger, Carlo Rovelli | Spacetime states and covariant quantum theory | 20 pages, no figures. Revision: minor corrections and references
added | Phys.Rev. D65 (2002) 125016 | 10.1103/PhysRevD.65.125016 | null | gr-qc | null | In it's usual presentation, classical mechanics appears to give time a very
special role. But it is well known that mechanics can be formulated so as to
treat the time variable on the same footing as the other variables in the
extended configuration space. Such covariant formulations are natural for
relativistic gravitational systems, where general covariance conflicts with the
notion of a preferred physical-time variable. The standard presentation of
quantum mechanics, in turns, gives again time a very special role, raising well
known difficulties for quantum gravity. Is there a covariant form of
(canonical) quantum mechanics? We observe that the preferred role of time in
quantum theory is the consequence of an idealization: that measurements are
instantaneous. Canonical quantum theory can be given a covariant form by
dropping this idealization. States prepared by non-instantaneous measurements
are described by "spacetime smeared states". The theory can be formulated in
terms of these states, without making any reference to a special time variable.
The quantum dynamics is expressed in terms of the propagator, an object
covariantly defined on the extended configuration space.
| [
{
"created": "Tue, 6 Nov 2001 18:16:53 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2002 11:09:01 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Reisenberger",
"Michael",
""
],
[
"Rovelli",
"Carlo",
""
]
] | In it's usual presentation, classical mechanics appears to give time a very special role. But it is well known that mechanics can be formulated so as to treat the time variable on the same footing as the other variables in the extended configuration space. Such covariant formulations are natural for relativistic gravitational systems, where general covariance conflicts with the notion of a preferred physical-time variable. The standard presentation of quantum mechanics, in turns, gives again time a very special role, raising well known difficulties for quantum gravity. Is there a covariant form of (canonical) quantum mechanics? We observe that the preferred role of time in quantum theory is the consequence of an idealization: that measurements are instantaneous. Canonical quantum theory can be given a covariant form by dropping this idealization. States prepared by non-instantaneous measurements are described by "spacetime smeared states". The theory can be formulated in terms of these states, without making any reference to a special time variable. The quantum dynamics is expressed in terms of the propagator, an object covariantly defined on the extended configuration space. |
1309.3213 | Alejandro Cabo | Alejandro Cabo Montes de Oca and Nana Geraldine Cabo-Bizet | Newton-like equations for a radiating particle | 18 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Second order Newton equations of motion for a radiating particle are
presented. It is argued that the trajectories obeying them also satisfy the
Abraham-Lorentz-Dirac (ALD) equations for general 3D motions in the
non-relativistic and relativistic limits. The case of forces only depending of
the proper time is here considered. For these properties to hold, it is
sufficient that the external force to be infinitely smooth and that a series
formed with its time derivatives converges. This series define in a special
local way the effective forces entering the Newton equations. When the external
force vanishes in an open vicinity of a given time, the effective one also
becomes null. Thus, the proper solutions of the effective equations can not
show runaway or pre-acceleration effects. The Newton equations are numerically
solved for a pulsed force given by an analytic function along the proper time
axis. The simultaneous satisfaction of the ALD equations is numerically
checked. Further, a set of modified ALD equations for almost everywhere
infinitely smooth forces, but including step like discontinuities in some
points is also presented for the case of collinear motions. The form of the
equations supports the statement argued in a previous work, about that the
causal Lienard-Wiechert field solution surrounding a radiating particle,
implies that the effective force on the particle should instantaneously vanish
when the external force is retired. The modified ALD equations proposed in the
previous work are here derived in a generalized way including the same effect
also when a the force is instantly connected.
| [
{
"created": "Thu, 12 Sep 2013 16:31:23 GMT",
"version": "v1"
}
] | 2013-09-13 | [
[
"de Oca",
"Alejandro Cabo Montes",
""
],
[
"Cabo-Bizet",
"Nana Geraldine",
""
]
] | Second order Newton equations of motion for a radiating particle are presented. It is argued that the trajectories obeying them also satisfy the Abraham-Lorentz-Dirac (ALD) equations for general 3D motions in the non-relativistic and relativistic limits. The case of forces only depending of the proper time is here considered. For these properties to hold, it is sufficient that the external force to be infinitely smooth and that a series formed with its time derivatives converges. This series define in a special local way the effective forces entering the Newton equations. When the external force vanishes in an open vicinity of a given time, the effective one also becomes null. Thus, the proper solutions of the effective equations can not show runaway or pre-acceleration effects. The Newton equations are numerically solved for a pulsed force given by an analytic function along the proper time axis. The simultaneous satisfaction of the ALD equations is numerically checked. Further, a set of modified ALD equations for almost everywhere infinitely smooth forces, but including step like discontinuities in some points is also presented for the case of collinear motions. The form of the equations supports the statement argued in a previous work, about that the causal Lienard-Wiechert field solution surrounding a radiating particle, implies that the effective force on the particle should instantaneously vanish when the external force is retired. The modified ALD equations proposed in the previous work are here derived in a generalized way including the same effect also when a the force is instantly connected. |
1812.02755 | Merced Montesinos | Merced Montesinos, Jorge Romero, Ricardo Escobedo, Mariano Celada | $SU(1,1)$ Barbero-like variables derived from Holst action | It matches published version | Phys. Rev. D 98, 124002 (2018) | 10.1103/PhysRevD.98.124002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We work on a spacetime manifold foliated by timelike leaves. In this setting,
we explore the solution of the second-class constraints arising during the
canonical analysis of the Holst action with a cosmological constant. The
solution is given in a manifestly Lorentz-covariant fashion, and the resulting
canonical formulation is expressed using several sets of real variables that
are related to one another by canonical transformations. By applying a gauge
fixing to this formulation, we obtain a description of gravity as an $SU(1,1)$
gauge theory that resembles the Ashtekar-Barbero formulation.
| [
{
"created": "Thu, 6 Dec 2018 19:01:04 GMT",
"version": "v1"
}
] | 2018-12-10 | [
[
"Montesinos",
"Merced",
""
],
[
"Romero",
"Jorge",
""
],
[
"Escobedo",
"Ricardo",
""
],
[
"Celada",
"Mariano",
""
]
] | We work on a spacetime manifold foliated by timelike leaves. In this setting, we explore the solution of the second-class constraints arising during the canonical analysis of the Holst action with a cosmological constant. The solution is given in a manifestly Lorentz-covariant fashion, and the resulting canonical formulation is expressed using several sets of real variables that are related to one another by canonical transformations. By applying a gauge fixing to this formulation, we obtain a description of gravity as an $SU(1,1)$ gauge theory that resembles the Ashtekar-Barbero formulation. |
1402.6904 | Tsuyoshi Houri | Kazuki Hinoue, Tsuyoshi Houri, Christina Rugina and Yukinori Yasui | General Wahlquist Metrics in All Dimensions | 14 pages, no figures, v2: references added, version to appear in
Phys. Rev. D | Phys. Rev. D 90, 024037 (2014) | 10.1103/PhysRevD.90.024037 | OCU-PHYS 398, RUP-14-3 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the Wahlquist metric, which is a stationary, axially
symmetric perfect fluid solution with $\rho+3p=\text{const.}$, admits a rank-2
generalized closed conformal Killing-Yano tensor with a skew-symmetric torsion.
Taking advantage of the presence of such a tensor, we obtain a
higher-dimensional generalization of the Wahlquist metric in arbitrary
dimensions, including a family of vacuum black hole solutions with spherical
horizon topology such as Schwarzschild-Tangherlini, Myers-Perry and
higher-dimensional Kerr-NUT-(A)dS metrics and a family of static, spherically
symmetric perfect fluid solutions in higher dimensions.
| [
{
"created": "Thu, 27 Feb 2014 13:46:42 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jul 2014 00:54:23 GMT",
"version": "v2"
}
] | 2014-10-07 | [
[
"Hinoue",
"Kazuki",
""
],
[
"Houri",
"Tsuyoshi",
""
],
[
"Rugina",
"Christina",
""
],
[
"Yasui",
"Yukinori",
""
]
] | It is shown that the Wahlquist metric, which is a stationary, axially symmetric perfect fluid solution with $\rho+3p=\text{const.}$, admits a rank-2 generalized closed conformal Killing-Yano tensor with a skew-symmetric torsion. Taking advantage of the presence of such a tensor, we obtain a higher-dimensional generalization of the Wahlquist metric in arbitrary dimensions, including a family of vacuum black hole solutions with spherical horizon topology such as Schwarzschild-Tangherlini, Myers-Perry and higher-dimensional Kerr-NUT-(A)dS metrics and a family of static, spherically symmetric perfect fluid solutions in higher dimensions. |
2102.02328 | Marcelo Oyarzo | Jos\'e Figueroa and Marcelo Oyarzo | Slowly rotating black holes modeled by Solv geometries | Proceeding SOCHIFI 2020 (Sociedad Chilena de F\'isica). 7 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We present a slowly rotating generalization of a black hole modeled by a Solv
horizon geometry, in five dimensional General Relativity. A separable ansatz
compatible with Einstein equations is proposed, which is integrated in terms of
hypergeometric and exponential functions. The solution highly simplifies after
requiring to maintain the same asymptotic behaviour as the non-rotating black
hole and to have finite, non-vanishing charges. We compute the charges of the
solution and also comment on its importance for studying the phase space of the
theory in this sector.
| [
{
"created": "Wed, 3 Feb 2021 23:09:07 GMT",
"version": "v1"
}
] | 2021-02-05 | [
[
"Figueroa",
"José",
""
],
[
"Oyarzo",
"Marcelo",
""
]
] | We present a slowly rotating generalization of a black hole modeled by a Solv horizon geometry, in five dimensional General Relativity. A separable ansatz compatible with Einstein equations is proposed, which is integrated in terms of hypergeometric and exponential functions. The solution highly simplifies after requiring to maintain the same asymptotic behaviour as the non-rotating black hole and to have finite, non-vanishing charges. We compute the charges of the solution and also comment on its importance for studying the phase space of the theory in this sector. |
0710.2171 | Charles Hellaby | Charles Hellaby, Andrzej Krasinski | Physical and Geometrical Interpretation of the epsilon <= 0 Szekeres
Models | REVTex, 21 pages, 10 figures | Phys.Rev.D77:023529,2008 | 10.1103/PhysRevD.77.023529 | uct-cosmology-2007-10-11-08-30 | gr-qc | null | We study the properties and behaviour of the quasi-pseudospherical and
quasi-planar Szekeres models, obtain the regularity conditions, and analyse
their consequences. The quantities associated with "radius" and "mass" in the
quasi-spherical case must be understood in a different way for these cases. The
models with pseudospherical foliation can have spatial maxima and minima, but
no origins. The "mass" and "radius" functions may be one increasing and one
decreasing without causing shell crossings. This case most naturally describes
a snake-like, variable density void in a more gently varying inhomogeneous
background, although regions that develop an overdensity are also possible. The
Szekeres models with plane foliation can have neither spatial extrema nor
origins, cannot be spatially flat, and they cannot have more inhomogeneity than
the corresponding Ellis model, but a planar surface can be the boundary between
regions of spherical and pseudospherical foliation.
| [
{
"created": "Thu, 11 Oct 2007 07:50:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hellaby",
"Charles",
""
],
[
"Krasinski",
"Andrzej",
""
]
] | We study the properties and behaviour of the quasi-pseudospherical and quasi-planar Szekeres models, obtain the regularity conditions, and analyse their consequences. The quantities associated with "radius" and "mass" in the quasi-spherical case must be understood in a different way for these cases. The models with pseudospherical foliation can have spatial maxima and minima, but no origins. The "mass" and "radius" functions may be one increasing and one decreasing without causing shell crossings. This case most naturally describes a snake-like, variable density void in a more gently varying inhomogeneous background, although regions that develop an overdensity are also possible. The Szekeres models with plane foliation can have neither spatial extrema nor origins, cannot be spatially flat, and they cannot have more inhomogeneity than the corresponding Ellis model, but a planar surface can be the boundary between regions of spherical and pseudospherical foliation. |
2303.04640 | Mouhssine Koussour | N. Myrzakulov, M. Koussour and Dhruba Jyoti Gogoi | A New $Om(z)$ Diagnostic of Dark Energy in General Relativity Theory | The European Physical Journal C accepted version | Eur. Phys. J. C 83, 594 (2023) | 10.1140/epjc/s10052-023-11794-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we propose a new parametrization of dark energy based on the
$Om(z)$ diagnostic tool behavior. For this purpose, we investigate a functional
form of the $Om(z)$ that predicts the popular dark energy dynamical models,
namely phantom and quintessence. We also found the famous cosmological constant
for specified values of the model's parameters. We employed the Markov Chain
Monte Carlo approach to constrain the cosmological model using Hubble, Pantheon
samples, and BAO datasets. Finally, we used observational constraints to
investigate the characteristics of dark energy evolution and compare our
findings to cosmological predictions.
| [
{
"created": "Wed, 8 Mar 2023 14:58:11 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Mar 2023 12:34:39 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Jul 2023 08:45:28 GMT",
"version": "v3"
}
] | 2023-07-13 | [
[
"Myrzakulov",
"N.",
""
],
[
"Koussour",
"M.",
""
],
[
"Gogoi",
"Dhruba Jyoti",
""
]
] | In this paper, we propose a new parametrization of dark energy based on the $Om(z)$ diagnostic tool behavior. For this purpose, we investigate a functional form of the $Om(z)$ that predicts the popular dark energy dynamical models, namely phantom and quintessence. We also found the famous cosmological constant for specified values of the model's parameters. We employed the Markov Chain Monte Carlo approach to constrain the cosmological model using Hubble, Pantheon samples, and BAO datasets. Finally, we used observational constraints to investigate the characteristics of dark energy evolution and compare our findings to cosmological predictions. |
1208.3335 | Deepak Vaid | Deepak Vaid | Quantum Hall Effect and Black Hole Entropy in Loop Quantum Gravity | 24 pages, 7 figures; comments welcome | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | In LQG, black hole horizons are described by 2+1 dimensional boundaries of a
bulk 3+1 dimensional spacetime. The horizon is endowed with area by lines of
gravitational flux which pierce the surface. As is well known, counting of the
possible states associated with a given set of punctures allows us to recover
the famous Bekenstein-Hawking area law according to which the entropy of a
black hole is proportional to the area of the associated horizon $ S_{BH}
\propto A_{Hor} $. It is also known that the dynamics of the horizon degrees of
freedom is described by the Chern-Simons action of a $\mathfrak{su(2)}$ (or
$\mathfrak{u(1)}$ after a certain gauge fixing) valued gauge field $A_{\mu}^i$.
Recent numerical work which performs the state-counting for punctures, from
first-principles, reveals a step-like structure in the entropy-area relation.
We argue that both the presence of the Chern-Simons action and the step-like
structure in the entropy-area curve are indicative of the fact that the
effective theory which describes the dynamics of punctures on the horizon is
that of the Quantum Hall Effect.
| [
{
"created": "Thu, 16 Aug 2012 10:30:10 GMT",
"version": "v1"
}
] | 2012-08-17 | [
[
"Vaid",
"Deepak",
""
]
] | In LQG, black hole horizons are described by 2+1 dimensional boundaries of a bulk 3+1 dimensional spacetime. The horizon is endowed with area by lines of gravitational flux which pierce the surface. As is well known, counting of the possible states associated with a given set of punctures allows us to recover the famous Bekenstein-Hawking area law according to which the entropy of a black hole is proportional to the area of the associated horizon $ S_{BH} \propto A_{Hor} $. It is also known that the dynamics of the horizon degrees of freedom is described by the Chern-Simons action of a $\mathfrak{su(2)}$ (or $\mathfrak{u(1)}$ after a certain gauge fixing) valued gauge field $A_{\mu}^i$. Recent numerical work which performs the state-counting for punctures, from first-principles, reveals a step-like structure in the entropy-area relation. We argue that both the presence of the Chern-Simons action and the step-like structure in the entropy-area curve are indicative of the fact that the effective theory which describes the dynamics of punctures on the horizon is that of the Quantum Hall Effect. |
2109.02170 | Valerio De Luca | Susanna Barsanti, Valerio De Luca, Andrea Maselli, Paolo Pani | Detecting Subsolar-Mass Primordial Black Holes in Extreme Mass-Ratio
Inspirals with LISA and Einstein Telescope | 7 pages, 2 figures. v2: matching version to appear in PRL | null | 10.1103/PhysRevLett.128.111104 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black holes possibly formed in the early universe could provide a
significant fraction of the dark matter and would be unique probes of
inflation. A smoking gun for their discovery would be the detection of a
subsolar mass compact object. We argue that extreme mass-ratio inspirals will
be ideal to search for subsolar-mass black holes not only with LISA but also
with third-generation ground-based detectors such as Cosmic Explorer and the
Einstein Telescope. These sources can provide unparalleled measurements of the
mass of the secondary object at subpercent level for primordial black holes as
light as ${\cal O}(0.01)M_\odot$ up to luminosity distances around hundred
megaparsec and few gigaparsec for LISA and Einstein Telescope, respectively, in
a complementary frequency range. This would allow claiming, with very high
statistical confidence, the detection of a subsolar-mass black hole, which
would also provide a novel (and currently undetectable) family of sources for
third-generation detectors.
| [
{
"created": "Sun, 5 Sep 2021 21:33:57 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2022 16:29:57 GMT",
"version": "v2"
}
] | 2022-04-06 | [
[
"Barsanti",
"Susanna",
""
],
[
"De Luca",
"Valerio",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
]
] | Primordial black holes possibly formed in the early universe could provide a significant fraction of the dark matter and would be unique probes of inflation. A smoking gun for their discovery would be the detection of a subsolar mass compact object. We argue that extreme mass-ratio inspirals will be ideal to search for subsolar-mass black holes not only with LISA but also with third-generation ground-based detectors such as Cosmic Explorer and the Einstein Telescope. These sources can provide unparalleled measurements of the mass of the secondary object at subpercent level for primordial black holes as light as ${\cal O}(0.01)M_\odot$ up to luminosity distances around hundred megaparsec and few gigaparsec for LISA and Einstein Telescope, respectively, in a complementary frequency range. This would allow claiming, with very high statistical confidence, the detection of a subsolar-mass black hole, which would also provide a novel (and currently undetectable) family of sources for third-generation detectors. |
gr-qc/9708044 | null | Pedro F. Gonzalez-Diaz | Observable effects from spacetime tunneling | 5 pages, RevTex, 2 figures (available upon request), to appear in
Phys. Rev. D | Phys.Rev. D56 (1997) 6293-6297 | 10.1103/PhysRevD.56.6293 | IMAFF-RCA-97-06 | gr-qc astro-ph | null | Assuming that spacetime tunnels -wormholes and ringholes- naturally exist in
the universe, we investigate the conditions making them embeddible in Friedmann
space, and the possible observable effects of these tunnels, including: lensing
and frequency-shifting of emitting sources, discontinuous change of background
temperature, broadening and intensity enhancement of spectral lines, so as a
dramatic increase of the luminosity of any object at the tunnel's throat.
| [
{
"created": "Tue, 19 Aug 1997 18:38:48 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Gonzalez-Diaz",
"Pedro F.",
""
]
] | Assuming that spacetime tunnels -wormholes and ringholes- naturally exist in the universe, we investigate the conditions making them embeddible in Friedmann space, and the possible observable effects of these tunnels, including: lensing and frequency-shifting of emitting sources, discontinuous change of background temperature, broadening and intensity enhancement of spectral lines, so as a dramatic increase of the luminosity of any object at the tunnel's throat. |
2305.06834 | Jens Boos | Jens Boos | Black hole entropy contributions from Euclidean cores | Essay written for the Gravity Research Foundation 2023 Awards for
Essays on Gravitation; awarded an Honorable Mention; 7 pages | Int. J. Mod. Phys. D 32, 2342011 (2023) | 10.1142/S0218271823420117 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entropy of a Schwarzschild black hole, as computed via the semiclassical
Euclidean path integral in a stationary phase approximation, is determined not
by the on-shell value of the action (which vanishes), but by the
Gibbons--Hawking--York boundary term evaluated on a suitable hypersurface,
which can be chosen arbitrarily far away from the horizon. For this reason, the
black hole singularity seemingly has no influence on the Bekenstein--Hawking
area law. In this Essay we estimate how a regular black hole core, deep inside
a Euclidean black hole of mass $M$ and generated via a UV regulator length
scale $\ell > 0$, affects the black hole entropy. The contributions are
suppressed by factors of $\ell/(2GM)$; demanding exact agreement with the area
law as well as a self-consistent first law of black hole thermodynamics at all
orders, however, demands that these contributions vanish identically via
uniformly bounded curvature. This links the limiting curvature hypothesis to
black hole thermodynamics.
| [
{
"created": "Thu, 11 May 2023 14:26:52 GMT",
"version": "v1"
}
] | 2023-12-19 | [
[
"Boos",
"Jens",
""
]
] | The entropy of a Schwarzschild black hole, as computed via the semiclassical Euclidean path integral in a stationary phase approximation, is determined not by the on-shell value of the action (which vanishes), but by the Gibbons--Hawking--York boundary term evaluated on a suitable hypersurface, which can be chosen arbitrarily far away from the horizon. For this reason, the black hole singularity seemingly has no influence on the Bekenstein--Hawking area law. In this Essay we estimate how a regular black hole core, deep inside a Euclidean black hole of mass $M$ and generated via a UV regulator length scale $\ell > 0$, affects the black hole entropy. The contributions are suppressed by factors of $\ell/(2GM)$; demanding exact agreement with the area law as well as a self-consistent first law of black hole thermodynamics at all orders, however, demands that these contributions vanish identically via uniformly bounded curvature. This links the limiting curvature hypothesis to black hole thermodynamics. |
1712.10175 | Kimet Jusufi | Kimet Jusufi, Nayan Sarkar, Farook Rahaman, Ayan Banerjee, Sudan
Hansraj | Deflection of light by black holes and massless wormholes in massive
gravity | 21 pages, 3 figures, accepted for publication in European Physical
Journal C | Eur. Phys. J. C (2018) 78: 349 | 10.1140/epjc/s10052-018-5823-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Weak gravitational lensing by black holes and wormholes in the context of
massive gravity (Bebronne and Tinyakov 2009) theory is studied. The particular
solution examined is characterized by two integration constants, the mass $M$
and an extra parameter $S$ namely `scalar charge'. These black hole reduce to
the standard Schwarzschild black hole solutions when the scalar charge is zero
and the mass is positive. In addition, a parameter $\lambda$ in the metric
characterizes so-called 'hair'. The geodesic equations are used to examine the
behavior of the deflection angle in four relevant cases of the parameter
$\lambda$. Then, by introducing a simple coordinate transformation
$r^\lambda=S+v^2$ into the black hole metric, we were able to find a massless
wormhole solution of Einstein-Rosen (ER) \cite{Einstein} type with scalar
charge $S$. The programme is then repeated in terms of the Gauss--Bonnet
theorem in the weak field limit after a method is established to deal with the
angle of deflection using different domains of integration depending on the
parameter $\lambda$. In particular, we have found new analytical results
corresponding to four special cases which generalize the well known deflection
angles reported in the literature. Finally, we have established the time delay
problem in the spacetime of black holes and wormholes, respectively.
| [
{
"created": "Fri, 29 Dec 2017 10:40:48 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Apr 2018 11:32:33 GMT",
"version": "v2"
}
] | 2018-05-01 | [
[
"Jusufi",
"Kimet",
""
],
[
"Sarkar",
"Nayan",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Banerjee",
"Ayan",
""
],
[
"Hansraj",
"Sudan",
""
]
] | Weak gravitational lensing by black holes and wormholes in the context of massive gravity (Bebronne and Tinyakov 2009) theory is studied. The particular solution examined is characterized by two integration constants, the mass $M$ and an extra parameter $S$ namely `scalar charge'. These black hole reduce to the standard Schwarzschild black hole solutions when the scalar charge is zero and the mass is positive. In addition, a parameter $\lambda$ in the metric characterizes so-called 'hair'. The geodesic equations are used to examine the behavior of the deflection angle in four relevant cases of the parameter $\lambda$. Then, by introducing a simple coordinate transformation $r^\lambda=S+v^2$ into the black hole metric, we were able to find a massless wormhole solution of Einstein-Rosen (ER) \cite{Einstein} type with scalar charge $S$. The programme is then repeated in terms of the Gauss--Bonnet theorem in the weak field limit after a method is established to deal with the angle of deflection using different domains of integration depending on the parameter $\lambda$. In particular, we have found new analytical results corresponding to four special cases which generalize the well known deflection angles reported in the literature. Finally, we have established the time delay problem in the spacetime of black holes and wormholes, respectively. |
0707.0585 | Sergei Maydanyuk | Sergei P. Maydanyuk | Wave function of the Universe in the early stage of its evolution | 19 pages, 21 files for 10 EPS figures, LaTeX svjour style. The Sec.2
(formalism of Wheeler-De Witt equation) is reduced. In Sec.3.1 definition of
the outgoing wave from barrier is defined more accurately. In Sec.4.1
semiclassical calculations of wavew function and penetrability are performed
and comparison with results in fully quantum approach is added | Eur.Phys.J.C57:769-784,2008 | 10.1140/epjc/s10052-008-0723-2 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In quantum cosmological models, constructed in the framework of
Friedmann-Robertson-Walker metrics, a nucleation of the Universe with its
further expansion is described as a tunneling transition through an effective
barrier between regions with small and large values of the scale factor $a$ at
non-zero (or zero) energy. The approach for describing this tunneling consists
of constructing a wave function satisfying an appropriate boundary condition.
There are various ways for defining the boundary condition that lead to
different estimates of the barrier penetrability and the tunneling time.
In order to describe the escape from the tunneling region as accurately as
possible and to construct the total wave function on the basis of its two
partial solutions unambiguously, we use the tunneling boundary condition that
the total wave function must represent only the outgoing wave at the point of
escape from the barrier, where the following definition for the wave is
introduced: the wave is represented by the wave function whose modulus changes
minimally under a variation of the scale factor $a$. We construct a new method
for a direct non-semiclassical calculation of the total stationary wave
function of the Universe, analyze the behavior of this wave function in the
tunneling region, near the escape point and in the asymptotic region, and
estimate the barrier penetrability. We observe oscillations of modulus of wave
function in the external region starting from the turning point which decrease
with increasing of $a$ and which are not shown in semiclassical calculations.
The period of such an oscillation decreases uniformly with increasing $a$ and
can be used as a fully quantum dynamical characteristic of the expansion of the
Universe.
| [
{
"created": "Wed, 4 Jul 2007 15:38:16 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2008 07:13:20 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Nov 2008 08:33:21 GMT",
"version": "v3"
}
] | 2008-12-18 | [
[
"Maydanyuk",
"Sergei P.",
""
]
] | In quantum cosmological models, constructed in the framework of Friedmann-Robertson-Walker metrics, a nucleation of the Universe with its further expansion is described as a tunneling transition through an effective barrier between regions with small and large values of the scale factor $a$ at non-zero (or zero) energy. The approach for describing this tunneling consists of constructing a wave function satisfying an appropriate boundary condition. There are various ways for defining the boundary condition that lead to different estimates of the barrier penetrability and the tunneling time. In order to describe the escape from the tunneling region as accurately as possible and to construct the total wave function on the basis of its two partial solutions unambiguously, we use the tunneling boundary condition that the total wave function must represent only the outgoing wave at the point of escape from the barrier, where the following definition for the wave is introduced: the wave is represented by the wave function whose modulus changes minimally under a variation of the scale factor $a$. We construct a new method for a direct non-semiclassical calculation of the total stationary wave function of the Universe, analyze the behavior of this wave function in the tunneling region, near the escape point and in the asymptotic region, and estimate the barrier penetrability. We observe oscillations of modulus of wave function in the external region starting from the turning point which decrease with increasing of $a$ and which are not shown in semiclassical calculations. The period of such an oscillation decreases uniformly with increasing $a$ and can be used as a fully quantum dynamical characteristic of the expansion of the Universe. |
1301.5218 | Alexander Zhuk | Alexey Chopovsky, Maxim Eingorn and Alexander Zhuk | Many-body problem in Kaluza-Klein models: theory and observational
consequences | Eqs. (16), (21), (23) and (24) corrected. Title, abstract,
introduction and conclusions changed. New section and references added. arXiv
admin note: substantial text overlap with arXiv:1302.0501 | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a system of gravitating bodies in Kaluza-Klein models with
toroidal compactification of extra dimensions. To simulate the astrophysical
objects (e.g., our Sun and pulsars) with the energy density much greater than
the pressure, we suppose that these bodies are pressureless in the external/our
space. At the same time, they may have nonzero parameters \omega_{(\bar\alpha
-3)} \, (\bar\alpha =4,...,D) of the equations of state in the extra
dimensions. We construct the Lagrange function of this many-body system for any
value of \Sigma =\sum_{\bar\alpha} \omega_{(\bar\alpha -3)}. Moreover, the
gravitational tests (PPN parameters, perihelion/periastron advance) require
negligible deviation from the latent soliton value \Sigma =-(D-3)/2. However,
the presence of pressure/tension in the internal space results necessarily in
the smearing of the gravitating masses over the internal space and in the
absence of the KK modes. This looks very unnatural from the point of quantum
physics.
| [
{
"created": "Tue, 22 Jan 2013 16:04:16 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jun 2013 18:26:28 GMT",
"version": "v2"
}
] | 2013-06-18 | [
[
"Chopovsky",
"Alexey",
""
],
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We consider a system of gravitating bodies in Kaluza-Klein models with toroidal compactification of extra dimensions. To simulate the astrophysical objects (e.g., our Sun and pulsars) with the energy density much greater than the pressure, we suppose that these bodies are pressureless in the external/our space. At the same time, they may have nonzero parameters \omega_{(\bar\alpha -3)} \, (\bar\alpha =4,...,D) of the equations of state in the extra dimensions. We construct the Lagrange function of this many-body system for any value of \Sigma =\sum_{\bar\alpha} \omega_{(\bar\alpha -3)}. Moreover, the gravitational tests (PPN parameters, perihelion/periastron advance) require negligible deviation from the latent soliton value \Sigma =-(D-3)/2. However, the presence of pressure/tension in the internal space results necessarily in the smearing of the gravitating masses over the internal space and in the absence of the KK modes. This looks very unnatural from the point of quantum physics. |
gr-qc/0210092 | Piotr Chrusciel | Piotr T. Chrusciel | On solutions of the vacuum Einstein equation in the radiation regime | to appear in the proceedings of the Elba Conference in memory of
A.Lichnerowicz, June 2002 | null | null | null | gr-qc | null | We review recent results by the author, in collaboration with Erwann Delay,
Olivier Lengard, and Rafe Mazzeo, on existence and properties of space-times
with controlled asymptotic behavior at null infinity.
| [
{
"created": "Sun, 27 Oct 2002 10:15:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chrusciel",
"Piotr T.",
""
]
] | We review recent results by the author, in collaboration with Erwann Delay, Olivier Lengard, and Rafe Mazzeo, on existence and properties of space-times with controlled asymptotic behavior at null infinity. |
0806.2180 | Sergio Dain | Sergio Dain and Mar\'ia E. Gabach Cl\'ement | Extreme Bowen-York initial data | 21 pages | Class.Quant.Grav.26:035020,2009 | 10.1088/0264-9381/26/3/035020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bowen-York family of spinning black hole initial data depends essentially
on one, positive, free parameter. The extreme limit corresponds to making this
parameter equal to zero. This choice represents a singular limit for the
constraint equations. We prove that in this limit a new solution of the
constraint equations is obtained. These initial data have similar properties to
the extreme Kerr and Reissner-Nordstrom black hole initial data. In particular,
in this limit one of the asymptotic ends changes from asymptotically flat to
cylindrical. The existence proof is constructive, we actually show that a
sequence of Bowen-York data converges to the extreme solution.
| [
{
"created": "Fri, 13 Jun 2008 15:10:27 GMT",
"version": "v1"
}
] | 2009-01-27 | [
[
"Dain",
"Sergio",
""
],
[
"Clément",
"María E. Gabach",
""
]
] | The Bowen-York family of spinning black hole initial data depends essentially on one, positive, free parameter. The extreme limit corresponds to making this parameter equal to zero. This choice represents a singular limit for the constraint equations. We prove that in this limit a new solution of the constraint equations is obtained. These initial data have similar properties to the extreme Kerr and Reissner-Nordstrom black hole initial data. In particular, in this limit one of the asymptotic ends changes from asymptotically flat to cylindrical. The existence proof is constructive, we actually show that a sequence of Bowen-York data converges to the extreme solution. |
1502.03000 | Rex Liu | Rex G. Liu and Ruth M. Williams | Regge calculus models of closed lattice universes | 34 pages, 9 figures. Expanded Introduction: elaborated on
cosmological context for work and referenced recent work on studying lattice
universes using a wide variety of approaches. Corrected an error in the LW
graphs in Fig 3 | Phys. Rev. D 93, 023502 (2016) | 10.1103/PhysRevD.93.023502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper examines the behaviour of closed `lattice universes' wherein
masses are distributed in a regular lattice on the Cauchy surfaces of closed
vacuum universes. Such universes are approximated using a form of Regge
calculus originally developed by Collins and Williams to model closed FLRW
universes. We consider two types of lattice universes, one where all masses are
identical to each other and another where one mass gets perturbed in magnitude.
In the unperturbed universe, we consider the possible arrangements of the
masses in the Regge Cauchy surfaces and demonstrate that the model will only be
stable if each mass lies within some spherical region of convergence. We also
briefly discuss the existence of Regge models that are dual to the ones we have
considered. We then model a perturbed lattice universe and demonstrate that the
model's evolution is well-behaved, with the expansion increasing in magnitude
as the perturbation is increased.
| [
{
"created": "Tue, 10 Feb 2015 17:23:47 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2015 15:59:53 GMT",
"version": "v2"
}
] | 2016-01-13 | [
[
"Liu",
"Rex G.",
""
],
[
"Williams",
"Ruth M.",
""
]
] | This paper examines the behaviour of closed `lattice universes' wherein masses are distributed in a regular lattice on the Cauchy surfaces of closed vacuum universes. Such universes are approximated using a form of Regge calculus originally developed by Collins and Williams to model closed FLRW universes. We consider two types of lattice universes, one where all masses are identical to each other and another where one mass gets perturbed in magnitude. In the unperturbed universe, we consider the possible arrangements of the masses in the Regge Cauchy surfaces and demonstrate that the model will only be stable if each mass lies within some spherical region of convergence. We also briefly discuss the existence of Regge models that are dual to the ones we have considered. We then model a perturbed lattice universe and demonstrate that the model's evolution is well-behaved, with the expansion increasing in magnitude as the perturbation is increased. |
0811.1132 | Haryanto Siahaan Mangaratua | Haryanto M. Siahaan and Triyanta | Hawking Radiation from a Vaidya Black Hole: A Semi-Classical Approach
and Beyond | Corrected version of presented talk at 2nd ICMNS (October 28, 2008),
Bandung, Indonesia. 13 pages, jhep style, v4: some minor corrections,
references added | null | null | null | gr-qc | http://creativecommons.org/licenses/publicdomain/ | We derive the Hawking radiation for Vaidya black hole in the tunneling
picture from the corresponding single particle action by the use of the radial
null geodesic and the Hamilton-Jacobi method (beyond semi-classical
approximation). Both results are then analyzed and compared.
| [
{
"created": "Fri, 7 Nov 2008 12:33:51 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Nov 2008 14:00:36 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Nov 2008 03:54:54 GMT",
"version": "v3"
},
{
"created": "Wed, 19 Nov 2008 11:17:52 GMT",
"version": "v4"
}
] | 2008-11-19 | [
[
"Siahaan",
"Haryanto M.",
""
],
[
"Triyanta",
"",
""
]
] | We derive the Hawking radiation for Vaidya black hole in the tunneling picture from the corresponding single particle action by the use of the radial null geodesic and the Hamilton-Jacobi method (beyond semi-classical approximation). Both results are then analyzed and compared. |
1907.10546 | Martin Pernot-Borr\`as | Martin Pernot-Borr\`as, Joel Berg\'e, Philippe Brax, Jean-Philippe
Uzan | A general study of chameleon fifth force in gravity space experiments | Submitted to Phys. Rev. D | Phys. Rev. D 100, 084006 (2019) | 10.1103/PhysRevD.100.084006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article investigates the profile of the scalar field of a scalar-tensor
theory subject to the chameleon mechanism in the context of gravity space
missions like the MICROSCOPE experiment. It analyses the experimental
situations for models with an inverse power law potential that can in principle
induce a fifth force inside the satellite, hence either be detected or
constrained. As the mass of the scalar field depends on the local matter
density, the screening of the scalar field depends crucially on both the
parameters of the theory (potential and non-minimal coupling to matter) and on
the geometry of the satellite. We calculate the profile of the scalar field in
1-, 2- and 3-dimensional satellite configurations without relying on the thick
or thin shell approximations for the scalar field. In particular we consider
the typical geometry with nested cylinders which is close to the MICROSCOPE
design. In this case we evaluate the corresponding fifth force on a test body
inside the satellite. This analysis clarifies previous claims on the
detectability of the chameleon force by space-borne experiments.
| [
{
"created": "Wed, 24 Jul 2019 16:29:41 GMT",
"version": "v1"
}
] | 2019-10-09 | [
[
"Pernot-Borràs",
"Martin",
""
],
[
"Bergé",
"Joel",
""
],
[
"Brax",
"Philippe",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | This article investigates the profile of the scalar field of a scalar-tensor theory subject to the chameleon mechanism in the context of gravity space missions like the MICROSCOPE experiment. It analyses the experimental situations for models with an inverse power law potential that can in principle induce a fifth force inside the satellite, hence either be detected or constrained. As the mass of the scalar field depends on the local matter density, the screening of the scalar field depends crucially on both the parameters of the theory (potential and non-minimal coupling to matter) and on the geometry of the satellite. We calculate the profile of the scalar field in 1-, 2- and 3-dimensional satellite configurations without relying on the thick or thin shell approximations for the scalar field. In particular we consider the typical geometry with nested cylinders which is close to the MICROSCOPE design. In this case we evaluate the corresponding fifth force on a test body inside the satellite. This analysis clarifies previous claims on the detectability of the chameleon force by space-borne experiments. |
1609.06383 | M. D. Maia | M.D. Maia, Ivan S. Ferreira, Claudio M. G. Sousa, Nadja S. Magalhaes
and Carlos Frajuca | Omnidirectional Gravitational Wave Detector with a Laser-Interferometric
Gravitational Compass | 6 pages 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the Szekeres-Pirani gravitational compass we suggest the addition of
a fourth, non-coplanar mass/mirror to the presently existing laser based
gravitational wave observatories, enabling them to operate omnidirectionally,
to filter out ambiguous interpretations and to point out the direction of the
gravitational wave source.
| [
{
"created": "Tue, 20 Sep 2016 23:27:36 GMT",
"version": "v1"
}
] | 2016-09-22 | [
[
"Maia",
"M. D.",
""
],
[
"Ferreira",
"Ivan S.",
""
],
[
"Sousa",
"Claudio M. G.",
""
],
[
"Magalhaes",
"Nadja S.",
""
],
[
"Frajuca",
"Carlos",
""
]
] | Based on the Szekeres-Pirani gravitational compass we suggest the addition of a fourth, non-coplanar mass/mirror to the presently existing laser based gravitational wave observatories, enabling them to operate omnidirectionally, to filter out ambiguous interpretations and to point out the direction of the gravitational wave source. |
1509.03827 | Hernando Quevedo | K. Boshkayev, E. Gasperin, A. C. Gutierrez-Pineres, H. Quevedo and S.
Toktarbay | Motion of test particles in the field of a naked singularity | Corrected typos | Phys. Rev. D 93, 024024 (2016) | 10.1103/PhysRevD.93.024024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the motion of test particles in the gravitational field of a
static naked singularity generated by a mass distribution with quadrupole
moment. We use the quadrupole-metric ($q-$metric) which is the simplest
generalization of the Schwarzschild metric with a quadrupole parameter. We
study the influence of the quadrupole on the motion of massive test particles
and photons and show that the behavior of the geodesics can drastically depend
on the values of the quadrupole parameter. In particular, we prove explicitly
that the perihelion distance depends on the value of the quadrupole. Moreover,
we show that an accretion disk on the equatorial plane of the quadrupole source
can be either continuous or discrete, depending on the value of the quadrupole.
The inner radius of the disk can be used in certain cases to determine the
value of the quadrupole parameter. The case of a discrete accretion is
interpreted as due to the presence of repulsive gravity generated by the naked
singularity. Radial geodesics are also investigated and compared with the
Schwarzschild counterparts.
| [
{
"created": "Sun, 13 Sep 2015 09:28:22 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Nov 2015 05:04:49 GMT",
"version": "v2"
}
] | 2016-01-20 | [
[
"Boshkayev",
"K.",
""
],
[
"Gasperin",
"E.",
""
],
[
"Gutierrez-Pineres",
"A. C.",
""
],
[
"Quevedo",
"H.",
""
],
[
"Toktarbay",
"S.",
""
]
] | We investigate the motion of test particles in the gravitational field of a static naked singularity generated by a mass distribution with quadrupole moment. We use the quadrupole-metric ($q-$metric) which is the simplest generalization of the Schwarzschild metric with a quadrupole parameter. We study the influence of the quadrupole on the motion of massive test particles and photons and show that the behavior of the geodesics can drastically depend on the values of the quadrupole parameter. In particular, we prove explicitly that the perihelion distance depends on the value of the quadrupole. Moreover, we show that an accretion disk on the equatorial plane of the quadrupole source can be either continuous or discrete, depending on the value of the quadrupole. The inner radius of the disk can be used in certain cases to determine the value of the quadrupole parameter. The case of a discrete accretion is interpreted as due to the presence of repulsive gravity generated by the naked singularity. Radial geodesics are also investigated and compared with the Schwarzschild counterparts. |
1809.02071 | Martin Lesourd Mr | Martin Lesourd | Cosmological singularities from high matter density without global
topological assumptions | null | null | 10.1007/s10714-019-2590-6 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological singularity theorems such as that of Hawking and Penrose assume
local curvature conditions as well as global ones like the existence of a
compact (achronal) slice. Here, we prove a new singularity theorem for
chronological spacetimes that satisfy what we call a `past null focusing'
condition. Such a condition forces all null geodesics with future endpoint to
develop a pair of conjugate points if past complete. By the Einstein field
equations, such a condition will be satisfied if the density of matter fields
remains sufficiently high towards the past of the spacetime, as may be expected
in certain cosmological scenarios. The theorem obtained doesn't make starting
assumptions about the spacetime's topology, such as the existence of a compact
achronal slice, and if in addition to a `past null focusing' condition we
assume the timelike convergence condition, then further consequences pertaining
to the existence of CMC foliations and the character of the singularity are
obtained. With the addition of the timelike convergence condition, we obtain
the conclusion that all timelike geodesics are past incomplete, which is much
stronger than the usual single incomplete non-spacelike geodesic.
| [
{
"created": "Wed, 5 Sep 2018 10:56:31 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Sep 2018 10:06:40 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Sep 2018 18:46:57 GMT",
"version": "v3"
},
{
"created": "Mon, 28 Jan 2019 11:00:23 GMT",
"version": "v4"
},
{
"created": "Thu, 20 Jun 2019 09:12:44 GMT",
"version": "v5"
},
{
"created": "Wed, 28 Aug 2019 13:17:33 GMT",
"version": "v6"
}
] | 2019-08-29 | [
[
"Lesourd",
"Martin",
""
]
] | Cosmological singularity theorems such as that of Hawking and Penrose assume local curvature conditions as well as global ones like the existence of a compact (achronal) slice. Here, we prove a new singularity theorem for chronological spacetimes that satisfy what we call a `past null focusing' condition. Such a condition forces all null geodesics with future endpoint to develop a pair of conjugate points if past complete. By the Einstein field equations, such a condition will be satisfied if the density of matter fields remains sufficiently high towards the past of the spacetime, as may be expected in certain cosmological scenarios. The theorem obtained doesn't make starting assumptions about the spacetime's topology, such as the existence of a compact achronal slice, and if in addition to a `past null focusing' condition we assume the timelike convergence condition, then further consequences pertaining to the existence of CMC foliations and the character of the singularity are obtained. With the addition of the timelike convergence condition, we obtain the conclusion that all timelike geodesics are past incomplete, which is much stronger than the usual single incomplete non-spacelike geodesic. |
1412.2249 | Luca Parisi Ph.D. | Luca Parisi, Ninfa Radicella, Gaetano Vilasi | Kantowski-Sachs Universes sourced by a Skyrme fluid | 9 pages, 7 figures, 3 tables; v2 Sec. II extended, typos corrected.
Matches the published version | Phys.Rev. D91 (2015) 6, 063533 | 10.1103/PhysRevD.91.063533 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kantowski-Sachs cosmological model sourced by a Skyrme field and a
cosmological constant is considered in the framework of General Relativity.
Assuming a constant radial profile function for the hedgehog ansatz, the Skyrme
contribution to Einstein equations is shown to be equivalent to an anisotropic
fluid. Using dynamical system techniques, a qualitative analysis of the
cosmological equations is presented. Physically interesting features of the
model such as isotropization, bounce and recollapse are discussed.
| [
{
"created": "Sat, 6 Dec 2014 16:01:38 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2015 10:13:12 GMT",
"version": "v2"
}
] | 2015-04-06 | [
[
"Parisi",
"Luca",
""
],
[
"Radicella",
"Ninfa",
""
],
[
"Vilasi",
"Gaetano",
""
]
] | The Kantowski-Sachs cosmological model sourced by a Skyrme field and a cosmological constant is considered in the framework of General Relativity. Assuming a constant radial profile function for the hedgehog ansatz, the Skyrme contribution to Einstein equations is shown to be equivalent to an anisotropic fluid. Using dynamical system techniques, a qualitative analysis of the cosmological equations is presented. Physically interesting features of the model such as isotropization, bounce and recollapse are discussed. |
1312.3641 | Mark Hannam | Mark Hannam | Modelling gravitational waves from precessing black-hole binaries:
Progress, challenges and prospects | Invited review for General Relativity and Gravitation | null | 10.1007/s10714-014-1767-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inspiral and merger of two orbiting black holes is among the most
promising sources for the first (hopefully imminent) direct detection of
gravitational waves (GWs), and measurements of these signals could provide a
wealth of information about astrophysics, fundamental physics and cosmology.
Detection and measurement require a theoretical description of the GW signals
from all possible black-hole-binary configurations, which can include
complicated precession effects due to the black-hole spins. Modelling the GW
signal from generic precessing binaries is therefore one of the most urgent
theoretical challenges facing GW astronomy. This article briefly reviews the
phenomenology of generic-binary dynamics and waveforms, and recent advances in
modelling them.
| [
{
"created": "Thu, 12 Dec 2013 21:00:06 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Hannam",
"Mark",
""
]
] | The inspiral and merger of two orbiting black holes is among the most promising sources for the first (hopefully imminent) direct detection of gravitational waves (GWs), and measurements of these signals could provide a wealth of information about astrophysics, fundamental physics and cosmology. Detection and measurement require a theoretical description of the GW signals from all possible black-hole-binary configurations, which can include complicated precession effects due to the black-hole spins. Modelling the GW signal from generic precessing binaries is therefore one of the most urgent theoretical challenges facing GW astronomy. This article briefly reviews the phenomenology of generic-binary dynamics and waveforms, and recent advances in modelling them. |
2407.07010 | Franco Fiorini | Franco Fiorini and Juan Manuel P\'aez | Regular out of the singular: exacts results on top of a curvature
singularity | 9 pages, 4 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By constructing a model of spacetime having a strong curvature singularity in
which causal geodesics are complete, but more generic causal curves are not, we
explicitly show that some electrostatic field configurations on that background
are regular everywhere, including \emph{there} where the spacetime ceases to be
described by a pseudo-Riemannian manifold. Our calculations are performed using
the analogue-gravity description provided by Plebanski and Tamm, according to
which the characterization of the electromagnetic field on a generic curved
background is equivalent to solving Maxwell's equations in flat space with a
matter content verifying certain non-trivial constitutive relations. The
regularity of the electric field in what could be considered the worst
conceivable physical condition, opens the door to further investigation into
the possibility of propagating signals capable of crossing a spacetime
singularity.
| [
{
"created": "Tue, 9 Jul 2024 16:26:39 GMT",
"version": "v1"
}
] | 2024-07-10 | [
[
"Fiorini",
"Franco",
""
],
[
"Páez",
"Juan Manuel",
""
]
] | By constructing a model of spacetime having a strong curvature singularity in which causal geodesics are complete, but more generic causal curves are not, we explicitly show that some electrostatic field configurations on that background are regular everywhere, including \emph{there} where the spacetime ceases to be described by a pseudo-Riemannian manifold. Our calculations are performed using the analogue-gravity description provided by Plebanski and Tamm, according to which the characterization of the electromagnetic field on a generic curved background is equivalent to solving Maxwell's equations in flat space with a matter content verifying certain non-trivial constitutive relations. The regularity of the electric field in what could be considered the worst conceivable physical condition, opens the door to further investigation into the possibility of propagating signals capable of crossing a spacetime singularity. |
gr-qc/0205077 | Dr. S. Biswas | S. Biswas, P. Misra and I. Chowdhury | The CWKB Method of Particle Production Near Chronology Horizon | 8 pages, latex, to appear in GRG vol 34 (2002) in May issue | Gen.Rel.Grav. 34 (2002) 697-705 | 10.1023/A:1015994313112 | null | gr-qc | null | In this paper we investigate the phenomenon of particle production of massles
scalar field, in a model of spacetime where the chronology horizon could be
formrd, using the method of complex time WKB approximation (CWKB). For the
purpose, we take two examples in a model of spacetime, one already discussed by
Sushkov, to show that the mode of particle production near chronology horizon
possesses the similar characteristic features as are found while discussing
particle production in time dependent curved background. We get identical
results as that obtained by Sushkov in this direction. We find, in both the
examples studied, that the total number of particles remain finite at the
moment of the formation of the chronology horizon.
| [
{
"created": "Fri, 17 May 2002 10:34:47 GMT",
"version": "v1"
}
] | 2021-10-20 | [
[
"Biswas",
"S.",
""
],
[
"Misra",
"P.",
""
],
[
"Chowdhury",
"I.",
""
]
] | In this paper we investigate the phenomenon of particle production of massles scalar field, in a model of spacetime where the chronology horizon could be formrd, using the method of complex time WKB approximation (CWKB). For the purpose, we take two examples in a model of spacetime, one already discussed by Sushkov, to show that the mode of particle production near chronology horizon possesses the similar characteristic features as are found while discussing particle production in time dependent curved background. We get identical results as that obtained by Sushkov in this direction. We find, in both the examples studied, that the total number of particles remain finite at the moment of the formation of the chronology horizon. |
2307.13761 | Yurii Ignat'ev | Yu.G. Ignat'ev | Similarity of cosmological models and its application to the analysis of
cosmological evolution | 13 pages, 14 figures, 13 references | Theor. Math. Phys. 219, 688 (2024) | 10.1134/S0040577924040123 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scale transformations of cosmological models based on a statistical system of
degenerate fermions with a scalar Higgs interaction are studied. The similarity
properties of cosmological models are revealed under the scale transformation
of their fundamental parameters. The laws of transformation of the coordinates
of singular points and eigenvalues of the characteristic matrix of the
dynamical system of the cosmological model under its scale transformations are
established. With the help of the previously studied dynamical system of
scalarly charged fermions is transformed to new variables and modified to a
dynamical system with a nondegenerate characteristic matrix and its
nondegenerate branch, the singular points and eigenvalues of the characteristic
matrix are found, which coincide with the corresponding values for the vacuum
field model. Examples of numerical simulation of such cosmological models are
given.
Keywords: scalarly charged plasma, cosmological model, Higgs scalar field,
similarity trans\-for\-mation, qualitative analysis.
| [
{
"created": "Tue, 25 Jul 2023 18:40:31 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | Scale transformations of cosmological models based on a statistical system of degenerate fermions with a scalar Higgs interaction are studied. The similarity properties of cosmological models are revealed under the scale transformation of their fundamental parameters. The laws of transformation of the coordinates of singular points and eigenvalues of the characteristic matrix of the dynamical system of the cosmological model under its scale transformations are established. With the help of the previously studied dynamical system of scalarly charged fermions is transformed to new variables and modified to a dynamical system with a nondegenerate characteristic matrix and its nondegenerate branch, the singular points and eigenvalues of the characteristic matrix are found, which coincide with the corresponding values for the vacuum field model. Examples of numerical simulation of such cosmological models are given. Keywords: scalarly charged plasma, cosmological model, Higgs scalar field, similarity trans\-for\-mation, qualitative analysis. |
1508.07488 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Viable Mimetic $F(R)$ Gravity Compatible with Planck Observations | Revised version to appear in AOP | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using Mukhanov-Chamseddine mimetic approach, we study $F(R)$ gravity with
scalar potential and Lagrange multiplier constraint. As we demonstrate, for a
given $F(R)$ gravity and for suitably chosen mimetic potential, it is possible
to realize inflationary cosmology consistent with Planck observations. We also
investigate the de Sitter solutions of the mimetic $F(R)$ theory and study the
stability of the solutions, when these exist, towards linear perturbations,
with the unstable solutions, which can provide a mechanism for graceful exit
from inflation. Finally, we describe a reconstruction method which can yield
the $F(R)$ gravity that can generate realistic inflationary cosmological
evolution, given the mimetic potential and the Hubble rate.
| [
{
"created": "Sat, 29 Aug 2015 18:39:51 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Nov 2015 19:56:01 GMT",
"version": "v2"
}
] | 2015-11-10 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | Using Mukhanov-Chamseddine mimetic approach, we study $F(R)$ gravity with scalar potential and Lagrange multiplier constraint. As we demonstrate, for a given $F(R)$ gravity and for suitably chosen mimetic potential, it is possible to realize inflationary cosmology consistent with Planck observations. We also investigate the de Sitter solutions of the mimetic $F(R)$ theory and study the stability of the solutions, when these exist, towards linear perturbations, with the unstable solutions, which can provide a mechanism for graceful exit from inflation. Finally, we describe a reconstruction method which can yield the $F(R)$ gravity that can generate realistic inflationary cosmological evolution, given the mimetic potential and the Hubble rate. |
gr-qc/9608021 | Galtsov Dmitzi | D.V. Gal'tsov | Square of General Relativity | A talk at the First Australasian Conference on General Relativity and
Gravitation, Adelaide, February 12--17, 1996, to be published in the
Proceedings | null | null | DTP-MSU/96-14 | gr-qc hep-th | null | We consider dilaton--axion gravity interacting with $p\;\, U(1)$ vectors
($p=6$ corresponding to $N=4$ supergravity) in four--dimensional spacetime
admitting a non--null Killing vector field. It is argued that this theory
exibits features of a ``square'' of vacuum General Relativity. In the
three--dimensional formulation it is equivalent to a gravity coupled
$\sigma$--model with the $(4+2p)$--dimensional target space
$SO(2,2+p)/(SO(2)\times SO(2+p))$. K\"ahler coordinates are introduced on the
target manifold generalising Ernst potentials of General Relativity. The
corresponding K\"ahler potential is found to be equal to the logarithm of the
product of the four--dimensional metric component $g_{00}$ in the Einstein
frame and the dilaton factor, independently on presence of vector fields. The
K\"ahler potential is invariant under exchange of the Ernst potential and the
complex axidilaton field, while it undergoes holomorphic/antiholomorphic
transformations under general target space isometries. The ``square'' property
is also manifest in the two--dimensional reduction of the theory as a matrix
generalization of the Kramer--Neugebauer map.
| [
{
"created": "Thu, 8 Aug 1996 20:46:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gal'tsov",
"D. V.",
""
]
] | We consider dilaton--axion gravity interacting with $p\;\, U(1)$ vectors ($p=6$ corresponding to $N=4$ supergravity) in four--dimensional spacetime admitting a non--null Killing vector field. It is argued that this theory exibits features of a ``square'' of vacuum General Relativity. In the three--dimensional formulation it is equivalent to a gravity coupled $\sigma$--model with the $(4+2p)$--dimensional target space $SO(2,2+p)/(SO(2)\times SO(2+p))$. K\"ahler coordinates are introduced on the target manifold generalising Ernst potentials of General Relativity. The corresponding K\"ahler potential is found to be equal to the logarithm of the product of the four--dimensional metric component $g_{00}$ in the Einstein frame and the dilaton factor, independently on presence of vector fields. The K\"ahler potential is invariant under exchange of the Ernst potential and the complex axidilaton field, while it undergoes holomorphic/antiholomorphic transformations under general target space isometries. The ``square'' property is also manifest in the two--dimensional reduction of the theory as a matrix generalization of the Kramer--Neugebauer map. |
0812.1294 | Sebastiano Sonego | Sebastiano Sonego, Massimo Pin | Foundations of anisotropic relativistic mechanics | 41 pages, 4 figures | J. Math. Phys. 50, 042902 (2009) | 10.1063/1.3104065 | null | gr-qc math-ph math.MP physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We lay down the foundations of particle dynamics in mechanical theories that
satisfy the relativity principle and whose kinematics can be formulated
employing reference frames of the type usually adopted in special relativity.
Such mechanics allow for the presence of anisotropy, both conventional (due to
non-standard synchronisation protocols) and real (leading to detectable
chronogeometrical effects, independent of the choice of synchronisation). We
give a general method for finding the fundamental dynamical quantities
(Lagrangian, energy and momentum), and write their explicit expression in all
the kinematics compatible with the basic requirements. We also write the
corresponding dispersion relations and outline a formulation of these theories
in terms of a pseudo-Finslerian spacetime geometry. Although the treatment is
restricted to the case of one spatial dimension, an extension to three
dimensions is almost straightforward.
| [
{
"created": "Sat, 6 Dec 2008 15:25:01 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2009 11:19:57 GMT",
"version": "v2"
}
] | 2009-06-30 | [
[
"Sonego",
"Sebastiano",
""
],
[
"Pin",
"Massimo",
""
]
] | We lay down the foundations of particle dynamics in mechanical theories that satisfy the relativity principle and whose kinematics can be formulated employing reference frames of the type usually adopted in special relativity. Such mechanics allow for the presence of anisotropy, both conventional (due to non-standard synchronisation protocols) and real (leading to detectable chronogeometrical effects, independent of the choice of synchronisation). We give a general method for finding the fundamental dynamical quantities (Lagrangian, energy and momentum), and write their explicit expression in all the kinematics compatible with the basic requirements. We also write the corresponding dispersion relations and outline a formulation of these theories in terms of a pseudo-Finslerian spacetime geometry. Although the treatment is restricted to the case of one spatial dimension, an extension to three dimensions is almost straightforward. |
1703.01481 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Accounting for some aspects of dark matter and dark energy via
noncommutative geometry | 8 pages, 1 figure, special issue on string theory | Journal of Modern Physics, vol. 8, pp. 323-329 (2017) | 10.4236/jmp.2017.83021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to seek a connection between noncommutative
geometry, an offshoot of string theory, and certain aspects of dark matter and
dark energy. The former case is based on a simple mathematical argument showing
that the main manifestation of dark matter in connection with flat rotation
curves in galaxies and clusters of galaxies is also a consequence of
noncommutative geometry. The latter case requires an examination of the local
effect of noncommutative geometry and the subsequent extension to the global
phenomenon of an accelerating Universe.
| [
{
"created": "Sat, 4 Mar 2017 15:41:26 GMT",
"version": "v1"
},
{
"created": "Mon, 15 May 2017 16:51:13 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Sep 2017 17:54:14 GMT",
"version": "v3"
},
{
"created": "Sun, 19 May 2019 20:12:06 GMT",
"version": "v4"
}
] | 2019-05-21 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | The purpose of this paper is to seek a connection between noncommutative geometry, an offshoot of string theory, and certain aspects of dark matter and dark energy. The former case is based on a simple mathematical argument showing that the main manifestation of dark matter in connection with flat rotation curves in galaxies and clusters of galaxies is also a consequence of noncommutative geometry. The latter case requires an examination of the local effect of noncommutative geometry and the subsequent extension to the global phenomenon of an accelerating Universe. |
2102.02004 | Nicolas Chamel | Lo\"ic Perot, Nicolas Chamel | Role of dense matter in tidal deformations of inspiralling neutron stars
and in gravitational waveform with unified equations of state | 35 pages, 25 figures, accepted for publication in Physical Review C | null | 10.1103/PhysRevC.103.025801 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The role of dense-matter properties in the tidal deformability of a cold
nonaccreted neutron star is further investigated. Using the set of
Brussels-Montreal unified equations of state, we have computed the
gravitoelectric Love numbers $k_\ell$ and the gravitomagnetic Love numbers
$j_\ell$ up to $\ell=5$. Their relative importance and their sensitivity to the
symmetry energy and the neutron-matter stiffness are numerically assessed.
Their impact on the phase of the gravitational-wave signal emitted by binary
neutron star inspirals is also discussed.
| [
{
"created": "Wed, 3 Feb 2021 11:07:08 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Perot",
"Loïc",
""
],
[
"Chamel",
"Nicolas",
""
]
] | The role of dense-matter properties in the tidal deformability of a cold nonaccreted neutron star is further investigated. Using the set of Brussels-Montreal unified equations of state, we have computed the gravitoelectric Love numbers $k_\ell$ and the gravitomagnetic Love numbers $j_\ell$ up to $\ell=5$. Their relative importance and their sensitivity to the symmetry energy and the neutron-matter stiffness are numerically assessed. Their impact on the phase of the gravitational-wave signal emitted by binary neutron star inspirals is also discussed. |
2202.04117 | Nicolas Yunes | Nicolas Yunes, M. Coleman Miller, Kent Yagi | Gravitational-Wave and X-ray Probes of the Neutron Star Equation of
State | Published in Nature Reviews Physics (2022) | null | 10.1038/s42254-022-00420-y | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutron stars are a remarkable marriage of Einstein's theory of general
relativity with nuclear physics. Their interiors harbor extreme matter that
cannot be probed in the laboratory. At such high densities and pressures, their
cores may consist predominantly of exotic matter such as free quarks or
hyperons. Gravitational wave observations from the Laser Interferometer
Gravitational-wave Observatory (LIGO) and from other interferometers, and X-ray
observations from the Neutron Star Interior Composition Explorer (NICER), are
beginning to pierce through the veil. These observations provide information
about neutron star cores, and therefore, about the physics that makes such
objects possible. In this review, we discuss what we have learned about the
physics of neutron stars from gravitational wave and X-ray observations. We
focus on what has been observed with certainty and what should be observable in
the near future, with an eye out for the physics that these new observations
will teach us.
| [
{
"created": "Tue, 8 Feb 2022 19:40:20 GMT",
"version": "v1"
}
] | 2022-02-10 | [
[
"Yunes",
"Nicolas",
""
],
[
"Miller",
"M. Coleman",
""
],
[
"Yagi",
"Kent",
""
]
] | Neutron stars are a remarkable marriage of Einstein's theory of general relativity with nuclear physics. Their interiors harbor extreme matter that cannot be probed in the laboratory. At such high densities and pressures, their cores may consist predominantly of exotic matter such as free quarks or hyperons. Gravitational wave observations from the Laser Interferometer Gravitational-wave Observatory (LIGO) and from other interferometers, and X-ray observations from the Neutron Star Interior Composition Explorer (NICER), are beginning to pierce through the veil. These observations provide information about neutron star cores, and therefore, about the physics that makes such objects possible. In this review, we discuss what we have learned about the physics of neutron stars from gravitational wave and X-ray observations. We focus on what has been observed with certainty and what should be observable in the near future, with an eye out for the physics that these new observations will teach us. |
2112.08400 | David Pere\~n\'iguez Mr | David Pere\~niguez and Vitor Cardoso | Love numbers and magnetic susceptibility of charged black holes | v1:12 pages, 4 figures. v2: few comments and references added, minor
typos fixed, matches version published in PRD | null | 10.1103/PhysRevD.105.044026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The response of black holes to companions is of fundamental importance in the
context of their dynamics and of gravitational-wave emission. Here, we explore
the effect of charge on the static response of black holes. With a view to
constraining broader setups, we consider charged geometries in an arbitrary
number of spacetime dimensions $D\geq4$. Tensor tidal Love numbers are shown to
follow a power law in the black hole temperature $\sim T_{H}^{2l+1}$, and thus
vanish at extremality. In contrast, the black hole charge $Q$ excites new modes
of polarisation in the vector sector that are otherwise not responsive in the
neutral limit. In four dimensions, Love numbers and magnetic susceptibilities
vanish for all values of the charge that respect the extremality bound. Using
the theory of Fuchsian equations we are able to obtain analytical results in
most cases, even beyond the hypergeometric instances.
| [
{
"created": "Wed, 15 Dec 2021 19:00:08 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2022 16:53:00 GMT",
"version": "v2"
}
] | 2022-03-01 | [
[
"Pereñiguez",
"David",
""
],
[
"Cardoso",
"Vitor",
""
]
] | The response of black holes to companions is of fundamental importance in the context of their dynamics and of gravitational-wave emission. Here, we explore the effect of charge on the static response of black holes. With a view to constraining broader setups, we consider charged geometries in an arbitrary number of spacetime dimensions $D\geq4$. Tensor tidal Love numbers are shown to follow a power law in the black hole temperature $\sim T_{H}^{2l+1}$, and thus vanish at extremality. In contrast, the black hole charge $Q$ excites new modes of polarisation in the vector sector that are otherwise not responsive in the neutral limit. In four dimensions, Love numbers and magnetic susceptibilities vanish for all values of the charge that respect the extremality bound. Using the theory of Fuchsian equations we are able to obtain analytical results in most cases, even beyond the hypergeometric instances. |
0705.4452 | Tony Rothman | Alessandro Giuliani and Tony Rothman | Absolute Stability Limit for Relativistic Charged Spheres | 25 pages, 1 figure 1 June 07: Replaced with added citations to prior
work along same lines | Gen.Rel.Grav.40:1427-1447,2008 | 10.1007/s10714-007-0539-7 | null | gr-qc | null | We find an exact solution for the stability limit of relativistic charged
spheres for the case of constant gravitational mass density and constant charge
density. We argue that this provides an absolute stability limit for any
relativistic charged sphere in which the gravitational mass density decreases
with radius and the charge density increases with radius. We then provide a
cruder absolute stability limit that applies to any charged sphere with a
spherically symmetric mass and charge distribution. We give numerical results
for all cases. In addition, we discuss the example of a neutral sphere
surrounded by a thin, charged shell.
| [
{
"created": "Wed, 30 May 2007 18:52:10 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Jun 2007 15:04:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Giuliani",
"Alessandro",
""
],
[
"Rothman",
"Tony",
""
]
] | We find an exact solution for the stability limit of relativistic charged spheres for the case of constant gravitational mass density and constant charge density. We argue that this provides an absolute stability limit for any relativistic charged sphere in which the gravitational mass density decreases with radius and the charge density increases with radius. We then provide a cruder absolute stability limit that applies to any charged sphere with a spherically symmetric mass and charge distribution. We give numerical results for all cases. In addition, we discuss the example of a neutral sphere surrounded by a thin, charged shell. |
gr-qc/0405082 | Stefan Hollands | Stefan Hollands and Robert M. Wald | Quantum Field Theory Is Not Merely Quantum Mechanics Applied to Low
Energy Effective Degrees of Freedom | Latex, 8 Pages, 5th Prize Essay, Gravity Research Foundation | Gen.Rel.Grav. 36 (2004) 2595-2603 | 10.1023/B:GERG.0000048980.00020.9a | null | gr-qc | null | It is commonly assumed that quantum field theory arises by applying ordinary
quantum mechanics to the low energy effective degrees of freedom of a more
fundamental theory defined at ultra-high-energy/short-wavelength scales. We
shall argue here that, even for free quantum fields, there are holistic aspects
of quantum field theory that cannot be properly understood in this manner.
Specifically, the ``subtractions'' needed to define nonlinear polynomial
functions of a free quantum field in curved spacetime are quite simple and
natural from the quantum field theoretic point of view, but are at best
extremely ad hoc and unnatural if viewed as independent renormalizations of
individual modes of the field. We illustrate this point by contrasting the
analysis of the Casimir effect, the renormalization of the stress-energy tensor
in time-dependent spacetimes, and anomalies from the point of quantum field
theory and from the point of view of quantum mechanics applied to the
independent low energy modes of the field. Some implications for the
cosmological constant problem are discussed.
| [
{
"created": "Sun, 16 May 2004 13:56:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Hollands",
"Stefan",
""
],
[
"Wald",
"Robert M.",
""
]
] | It is commonly assumed that quantum field theory arises by applying ordinary quantum mechanics to the low energy effective degrees of freedom of a more fundamental theory defined at ultra-high-energy/short-wavelength scales. We shall argue here that, even for free quantum fields, there are holistic aspects of quantum field theory that cannot be properly understood in this manner. Specifically, the ``subtractions'' needed to define nonlinear polynomial functions of a free quantum field in curved spacetime are quite simple and natural from the quantum field theoretic point of view, but are at best extremely ad hoc and unnatural if viewed as independent renormalizations of individual modes of the field. We illustrate this point by contrasting the analysis of the Casimir effect, the renormalization of the stress-energy tensor in time-dependent spacetimes, and anomalies from the point of quantum field theory and from the point of view of quantum mechanics applied to the independent low energy modes of the field. Some implications for the cosmological constant problem are discussed. |
1409.7652 | Daniela Pugliese Dr | D. Pugliese and H. Quevedo | The ergoregion in the Kerr spacetime: properties of the equatorial
circular motion | 19 pages, 9 figure multi-panels; 3 Tables. This and a slightly
modified version with the addition of new references and some new discussion.
To appear in EPJC | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate in detail the circular motion of test particles on the
equatorial plane of the ergoregion in the Kerr spacetime. We consider all the
regions where circular motion is allowed, and we analyze the stability
properties and the energy and angular momentum of the test particles. We show
that the structure of the stability regions has definite features that make it
possible to distinguish between black holes and naked singularities. The naked
singularity case presents a very structured non-connected set of regions of
orbital stability, where the presence of counterrotating particles and zero
angular momentum particles for a specific class of naked singularities is
interpreted as due to the presence of a repulsive field generated by the
central source of gravity. In particular, we analyze the effects of the
dynamical structure of the ergoregion (the union of the orbital regions for
different attractor spins) on the behavior of accretion disks around the
central source. The properties of the circular motion turn out to be so
distinctive that they allow the introduction of a complete classification of
Kerr spacetimes, each class of which is characterized by different physical
effects that could be of especial relevance in observational Astrophysics. We
also identify some special black hole spacetimes where these effects could be
relevant.
| [
{
"created": "Fri, 26 Sep 2014 17:56:09 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Mar 2015 22:02:40 GMT",
"version": "v2"
},
{
"created": "Tue, 12 May 2015 21:00:47 GMT",
"version": "v3"
}
] | 2015-05-14 | [
[
"Pugliese",
"D.",
""
],
[
"Quevedo",
"H.",
""
]
] | We investigate in detail the circular motion of test particles on the equatorial plane of the ergoregion in the Kerr spacetime. We consider all the regions where circular motion is allowed, and we analyze the stability properties and the energy and angular momentum of the test particles. We show that the structure of the stability regions has definite features that make it possible to distinguish between black holes and naked singularities. The naked singularity case presents a very structured non-connected set of regions of orbital stability, where the presence of counterrotating particles and zero angular momentum particles for a specific class of naked singularities is interpreted as due to the presence of a repulsive field generated by the central source of gravity. In particular, we analyze the effects of the dynamical structure of the ergoregion (the union of the orbital regions for different attractor spins) on the behavior of accretion disks around the central source. The properties of the circular motion turn out to be so distinctive that they allow the introduction of a complete classification of Kerr spacetimes, each class of which is characterized by different physical effects that could be of especial relevance in observational Astrophysics. We also identify some special black hole spacetimes where these effects could be relevant. |
gr-qc/9904061 | Ram Brustein | Ram Brustein | The Generalized Second Law of Thermodynamics in Cosmology | 12 pages, no figures | Phys.Rev.Lett. 84 (2000) 2072 | 10.1103/PhysRevLett.84.2072 | null | gr-qc hep-th | null | A classical and quantum mechanical generalized second law of thermodynamics
in cosmology implies constraints on the effective equation of state of the
universe in the form of energy conditions, obeyed by many known cosmological
solutions, and is compatible with entropy bounds which forbid certain
cosmological singularities. In string cosmology the second law provides new
information about the existence of non-singular solutions, and the nature of
the graceful exit transition from dilaton-driven inflation.
| [
{
"created": "Mon, 26 Apr 1999 15:51:13 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2000 14:56:33 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Brustein",
"Ram",
""
]
] | A classical and quantum mechanical generalized second law of thermodynamics in cosmology implies constraints on the effective equation of state of the universe in the form of energy conditions, obeyed by many known cosmological solutions, and is compatible with entropy bounds which forbid certain cosmological singularities. In string cosmology the second law provides new information about the existence of non-singular solutions, and the nature of the graceful exit transition from dilaton-driven inflation. |
1109.0803 | Guillermo Chac\'on-Acosta | Guillermo Chac\'on-Acosta, Elisa Manrique, Leonardo Dagdug, Hugo A.
Morales-T\'ecotl | Statistical Thermodynamics of Polymer Quantum Systems | null | SIGMA 7 (2011), 110, 23 pages | 10.3842/SIGMA.2011.110 | null | gr-qc cond-mat.stat-mech hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Polymer quantum systems are mechanical models quantized similarly as loop
quantum gravity. It is actually in quantizing gravity that the polymer term
holds proper as the quantum geometry excitations yield a reminiscent of a
polymer material. In such an approach both non-singular cosmological models and
a microscopic basis for the entropy of some black holes have arisen. Also
important physical questions for these systems involve thermodynamics. With
this motivation, in this work, we study the statistical thermodynamics of two
one dimensional {\em polymer} quantum systems: an ensemble of oscillators that
describe a solid and a bunch of non-interacting particles in a box, which thus
form an ideal gas. We first study the spectra of these polymer systems. It
turns out useful for the analysis to consider the length scale required by the
quantization and which we shall refer to as polymer length. The dynamics of the
polymer oscillator can be given the form of that for the standard quantum
pendulum. Depending on the dominance of the polymer length we can distinguish
two regimes: vibrational and rotational. The first occur for small polymer
length and here the standard oscillator in Schr\"odinger quantization is
recovered at leading order. The second one, for large polymer length, features
dominant polymer effects. In the case of the polymer particles in the box, a
bounded and oscillating spectrum that presents a band structure and a Brillouin
zone is found. The thermodynamical quantities calculated with these spectra
have corrections with respect to standard ones and they depend on the polymer
length. For generic polymer length, thermodynamics of both systems present an
anomalous peak in their heat capacity $C_V$.
| [
{
"created": "Mon, 5 Sep 2011 05:44:18 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2011 06:56:27 GMT",
"version": "v2"
}
] | 2011-12-05 | [
[
"Chacón-Acosta",
"Guillermo",
""
],
[
"Manrique",
"Elisa",
""
],
[
"Dagdug",
"Leonardo",
""
],
[
"Morales-Técotl",
"Hugo A.",
""
]
] | Polymer quantum systems are mechanical models quantized similarly as loop quantum gravity. It is actually in quantizing gravity that the polymer term holds proper as the quantum geometry excitations yield a reminiscent of a polymer material. In such an approach both non-singular cosmological models and a microscopic basis for the entropy of some black holes have arisen. Also important physical questions for these systems involve thermodynamics. With this motivation, in this work, we study the statistical thermodynamics of two one dimensional {\em polymer} quantum systems: an ensemble of oscillators that describe a solid and a bunch of non-interacting particles in a box, which thus form an ideal gas. We first study the spectra of these polymer systems. It turns out useful for the analysis to consider the length scale required by the quantization and which we shall refer to as polymer length. The dynamics of the polymer oscillator can be given the form of that for the standard quantum pendulum. Depending on the dominance of the polymer length we can distinguish two regimes: vibrational and rotational. The first occur for small polymer length and here the standard oscillator in Schr\"odinger quantization is recovered at leading order. The second one, for large polymer length, features dominant polymer effects. In the case of the polymer particles in the box, a bounded and oscillating spectrum that presents a band structure and a Brillouin zone is found. The thermodynamical quantities calculated with these spectra have corrections with respect to standard ones and they depend on the polymer length. For generic polymer length, thermodynamics of both systems present an anomalous peak in their heat capacity $C_V$. |
gr-qc/0608137 | Spiros Cotsakis | Spiros Cotsakis, John D. Barrow | The Dominant Balance at Cosmological Singularities | 13 pages, to appear in the Proceedings of the Greek Relativity
Meeting NEB12, June 29-July 2, 2006, Nauplia, Greece | J.Phys.Conf.Ser.68:012004,2007 | 10.1088/1742-6596/68/1/012004 | null | gr-qc | null | We define the notion of a finite-time singularity of a vector field and then
discuss a technique suitable for the asymptotic analysis of vector fields and
their integral curves in the neighborhood of such a singularity. Having in mind
the application of this method to cosmology, we also provide an analysis of the
time singularities of an isotropic universe filled with a perfect fluid in
general relativity.
| [
{
"created": "Thu, 31 Aug 2006 06:12:13 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cotsakis",
"Spiros",
""
],
[
"Barrow",
"John D.",
""
]
] | We define the notion of a finite-time singularity of a vector field and then discuss a technique suitable for the asymptotic analysis of vector fields and their integral curves in the neighborhood of such a singularity. Having in mind the application of this method to cosmology, we also provide an analysis of the time singularities of an isotropic universe filled with a perfect fluid in general relativity. |
1806.04666 | Marco de Cesare | Marco de Cesare, Mairi Sakellariadou and Patrizia Vitale | Noncommutative gravity with self-dual variables | 52 pages; v2: added references, corrected minor typos; matches
published version | Class. Quantum Grav. 35 (2018) 215009 | 10.1088/1361-6382/aae3f5 | KCL-PH-TH/2018-24 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We build a noncommutative extension of Palatini-Holst theory on a
twist-deformed spacetime, generalizing a model that has been previously
proposed by Aschieri and Castellani. The twist deformation entails an
enlargement of the gauge group, and leads to the introduction of new
gravitational degrees of freedom. In particular, the tetrad degrees of freedom
must be doubled, thus leading to a bitetrad theory of gravity. The model is
shown to exhibit new duality symmetries. The introduction of the Holst term
leads to a dramatic simplification of the dynamics, which is achieved when the
Barbero-Immirzi parameter takes the value $\beta=-i$, corresponding to a
self-dual action. We study in detail the commutative limit of the model,
focusing in particular on the role of torsion and non-metricity. The effects of
spacetime noncommutativity are taken into account perturbatively, and are
computed explicitly in a simple example. Connections with bimetric theories and
the role of local conformal invariance in the commutative limit are also
explored.
| [
{
"created": "Tue, 12 Jun 2018 17:58:32 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Oct 2018 16:17:46 GMT",
"version": "v2"
}
] | 2018-10-22 | [
[
"de Cesare",
"Marco",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Vitale",
"Patrizia",
""
]
] | We build a noncommutative extension of Palatini-Holst theory on a twist-deformed spacetime, generalizing a model that has been previously proposed by Aschieri and Castellani. The twist deformation entails an enlargement of the gauge group, and leads to the introduction of new gravitational degrees of freedom. In particular, the tetrad degrees of freedom must be doubled, thus leading to a bitetrad theory of gravity. The model is shown to exhibit new duality symmetries. The introduction of the Holst term leads to a dramatic simplification of the dynamics, which is achieved when the Barbero-Immirzi parameter takes the value $\beta=-i$, corresponding to a self-dual action. We study in detail the commutative limit of the model, focusing in particular on the role of torsion and non-metricity. The effects of spacetime noncommutativity are taken into account perturbatively, and are computed explicitly in a simple example. Connections with bimetric theories and the role of local conformal invariance in the commutative limit are also explored. |
1305.3755 | Jason Bates | Jason D. Bates | Non-Gaussian Stochastic Gravity | 11 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents a new, non-Gaussian formulation of stochastic gravity by
incorporating the higher moments of the fluctuations of the quantum stress
energy tensor for a free quantum scalar field in a consistent way. A scheme is
developed for obtaining realizations of these fluctuations in terms of the
Wightman function, and the behavior of the fluctuations is investigated. The
resulting probability distribution for fluctuations of the energy density in
Minkowski spacetime is found to be similar to a shifted Gamma distribution.
This distribution features a minimum energy density cutoff at a small negative
value, but a sharp peak in the vicinity of this cutoff such that the total
probability of observing a negative value is approximately 62%, balanced by
correspondingly larger but rarer positive values.
| [
{
"created": "Thu, 16 May 2013 10:45:59 GMT",
"version": "v1"
}
] | 2013-05-17 | [
[
"Bates",
"Jason D.",
""
]
] | This paper presents a new, non-Gaussian formulation of stochastic gravity by incorporating the higher moments of the fluctuations of the quantum stress energy tensor for a free quantum scalar field in a consistent way. A scheme is developed for obtaining realizations of these fluctuations in terms of the Wightman function, and the behavior of the fluctuations is investigated. The resulting probability distribution for fluctuations of the energy density in Minkowski spacetime is found to be similar to a shifted Gamma distribution. This distribution features a minimum energy density cutoff at a small negative value, but a sharp peak in the vicinity of this cutoff such that the total probability of observing a negative value is approximately 62%, balanced by correspondingly larger but rarer positive values. |
gr-qc/0604054 | Jun-Ichirou Koga | Jun-ichirou Koga | Universal properties from local geometric structure of Killing horizon | 14 pages, v2. minor corrections | Class.Quant.Grav.24:3067-3084,2007 | 10.1088/0264-9381/24/11/018 | WU-AP/244/06 | gr-qc hep-th | null | We consider universal properties that arise from a local geometric structure
of a Killing horizon. We first introduce a non-perturbative definition of such
a local geometric structure, which we call an asymptotic Killing horizon. It is
shown that infinitely many asymptotic Killing horizons reside on a common null
hypersurface, once there exists one asymptotic Killing horizon. The
acceleration of the orbits of the vector that generates an asymptotic Killing
horizon is then considered. We show that there exists the $\textit{diff}(S^1)$
or $\textit{diff}(R^1)$ sub-algebra on an asymptotic Killing horizon
universally, which is picked out naturally based on the behavior of the
acceleration. We also argue that the discrepancy between string theory and the
Euclidean approach in the entropy of an extreme black hole may be resolved, if
the microscopic states responsible for black hole thermodynamics are connected
with asymptotic Killing horizons.
| [
{
"created": "Tue, 11 Apr 2006 14:27:04 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Sep 2006 16:51:16 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Koga",
"Jun-ichirou",
""
]
] | We consider universal properties that arise from a local geometric structure of a Killing horizon. We first introduce a non-perturbative definition of such a local geometric structure, which we call an asymptotic Killing horizon. It is shown that infinitely many asymptotic Killing horizons reside on a common null hypersurface, once there exists one asymptotic Killing horizon. The acceleration of the orbits of the vector that generates an asymptotic Killing horizon is then considered. We show that there exists the $\textit{diff}(S^1)$ or $\textit{diff}(R^1)$ sub-algebra on an asymptotic Killing horizon universally, which is picked out naturally based on the behavior of the acceleration. We also argue that the discrepancy between string theory and the Euclidean approach in the entropy of an extreme black hole may be resolved, if the microscopic states responsible for black hole thermodynamics are connected with asymptotic Killing horizons. |
1107.0395 | Atsushi Higuchi | Mir Faizal and Atsushi Higuchi | Physical equivalence between the covariant and physical graviton
two-point functions in de Sitter spacetime | 33 pages (Revtex), no figures, misprints corrected, reference added | Phys. Rev. D85: 12402, 2012 | 10.1103/PhysRevD.85.124021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the covariant graviton two-point function in de Sitter
spacetime is infrared divergent for some choices of gauge parameters. On the
other hand it is also known that there are no infrared divergences requiring an
infrared cutoff for the physical graviton two-point function for this spacetime
in the transverse-traceless-synchronous gauge in the global coordinate system.
We show in this paper that the covariant graviton Wightman two-point function
with two gauge parameters is equivalent to the physical one in the global
coordinate system in the sense that they produce the same two-point function of
any local gauge-invariant tensor linear in the graviton field such as the
linearized Weyl tensor. This confirms the fact, pointed out decades ago, that
the infrared divergences of the graviton two-point function in the covariant
gauge for some choices of gauge parameters are gauge artifact in the sense that
they do not contribute to the Wightman two-point function of any local gauge
invariant tensor field in linearized theory.
| [
{
"created": "Sat, 2 Jul 2011 16:55:29 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Jul 2011 20:44:53 GMT",
"version": "v2"
},
{
"created": "Tue, 31 Jul 2012 13:26:42 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Faizal",
"Mir",
""
],
[
"Higuchi",
"Atsushi",
""
]
] | It is known that the covariant graviton two-point function in de Sitter spacetime is infrared divergent for some choices of gauge parameters. On the other hand it is also known that there are no infrared divergences requiring an infrared cutoff for the physical graviton two-point function for this spacetime in the transverse-traceless-synchronous gauge in the global coordinate system. We show in this paper that the covariant graviton Wightman two-point function with two gauge parameters is equivalent to the physical one in the global coordinate system in the sense that they produce the same two-point function of any local gauge-invariant tensor linear in the graviton field such as the linearized Weyl tensor. This confirms the fact, pointed out decades ago, that the infrared divergences of the graviton two-point function in the covariant gauge for some choices of gauge parameters are gauge artifact in the sense that they do not contribute to the Wightman two-point function of any local gauge invariant tensor field in linearized theory. |
gr-qc/0308016 | Maurice H. P. M. van Putten | Maurice H.P.M. van Putten, Amir Levinson, Hyun Kyu Lee, Tania
Regimbau, Michele Punturo, Gregory M. Harry | Gravitational radiation from gamma-ray bursts as observational
opportunities for LIGO and VIRGO | to appear in PRD, 49p | Phys.Rev.D69:044007,2004 | 10.1103/PhysRevD.69.044007 | LIGO-P030041-00-D | gr-qc astro-ph | null | Gamma-ray bursts are believed to originate in core-collapse of massive stars.
This produces an active nucleus containing a rapidly rotating Kerr black hole
surrounded by a uniformly magnetized torus represented by two counter-oriented
current rings. We quantify black hole spin-interactions with the torus and
charged particles along open magnetic flux-tubes subtended by the event
horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of
frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with
GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii)
aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich
et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al.
2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating
LIGO/Virgo detectors enables searches for nearby events and their spectral
closure density 6e-9 around 250Hz in the stochastic background radiation in
gravitational waves. At current sensitivity, LIGO-Hanford may place an upper
bound around 150MSolar in GRB030329. Detection of Egw thus provides a method
for identifying Kerr black holes by calorimetry.
| [
{
"created": "Wed, 6 Aug 2003 19:44:11 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Oct 2003 12:28:03 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"van Putten",
"Maurice H. P. M.",
""
],
[
"Levinson",
"Amir",
""
],
[
"Lee",
"Hyun Kyu",
""
],
[
"Regimbau",
"Tania",
""
],
[
"Punturo",
"Michele",
""
],
[
"Harry",
"Gregory M.",
""
]
] | Gamma-ray bursts are believed to originate in core-collapse of massive stars. This produces an active nucleus containing a rapidly rotating Kerr black hole surrounded by a uniformly magnetized torus represented by two counter-oriented current rings. We quantify black hole spin-interactions with the torus and charged particles along open magnetic flux-tubes subtended by the event horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii) aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al. 2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating LIGO/Virgo detectors enables searches for nearby events and their spectral closure density 6e-9 around 250Hz in the stochastic background radiation in gravitational waves. At current sensitivity, LIGO-Hanford may place an upper bound around 150MSolar in GRB030329. Detection of Egw thus provides a method for identifying Kerr black holes by calorimetry. |
2209.11357 | Sinya Aoki | Sinya Aoki | Colliding gravitational waves and singularities | 23 pages, 5 figures. More detailed explanations in Sec.3.1 and some
modifications in Sec. 3.3 have been added | null | null | YITP-22-102 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have investigated a model of colliding plain gravitational waves, proposed
by Szekeres, whose structure of singularities is determined. We have evaluated
a total energy of matter as a volume integral of the energy momentum tensor
(EMT), whose contributions arise only at these singularities. The total matter
energy is conserved before a collision of two plane gravitational waves but
decreases during the collision and becomes zero at the end of the collision. We
thus interpret that this model of colliding plane gravitational waves is a
spacetime describing a pair annihilation of plan gravitational waves. We have
also calculated a matter conserved charge proposed by the present author and
his collaborators. The matter charge is indeed conserved but is zero due to a
cancellation between two plain gravitational waves. This seems natural since
nothing remains after a pair annihilation, and give a hint on a physical
interpretation of the conserved charge, which we call the gravitational charge.
By modifying the space time for the pair annihilation, we newly construct two
types of a scattering plane gravitational wave and a pair creation of plane
gravitational waves, and combining all, a Minkowski vacuum bottle, a Minkowski
spacetime surrounded by two moving plane gravitational waves.
| [
{
"created": "Fri, 23 Sep 2022 00:59:25 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 2023 05:49:20 GMT",
"version": "v2"
}
] | 2023-06-07 | [
[
"Aoki",
"Sinya",
""
]
] | We have investigated a model of colliding plain gravitational waves, proposed by Szekeres, whose structure of singularities is determined. We have evaluated a total energy of matter as a volume integral of the energy momentum tensor (EMT), whose contributions arise only at these singularities. The total matter energy is conserved before a collision of two plane gravitational waves but decreases during the collision and becomes zero at the end of the collision. We thus interpret that this model of colliding plane gravitational waves is a spacetime describing a pair annihilation of plan gravitational waves. We have also calculated a matter conserved charge proposed by the present author and his collaborators. The matter charge is indeed conserved but is zero due to a cancellation between two plain gravitational waves. This seems natural since nothing remains after a pair annihilation, and give a hint on a physical interpretation of the conserved charge, which we call the gravitational charge. By modifying the space time for the pair annihilation, we newly construct two types of a scattering plane gravitational wave and a pair creation of plane gravitational waves, and combining all, a Minkowski vacuum bottle, a Minkowski spacetime surrounded by two moving plane gravitational waves. |
0809.1529 | Muhammad Sharif | M. Sharif and M. Jamil Amir | Energy-Momentum of the Friedmann Models in General Relativity and
Teleparallel Theory of Gravity | 14 pages, accepted for publication in Canadian J. Phys | Can.J.Phys.86:1297-1302,2008 | 10.1139/P08-073 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to the evaluation of the energy-momentum density
components for the Friedmann models. For this purpose, we have used
M${\o}$ller's pseudotensor prescription in General Relativity and a certain
energy-momentum density developed from his teleparallel formulation. It is
shown that the energy density of the closed Friedmann universe vanishes on the
spherical shell at the radius $\rho=2\sqrt{3}$. This coincides with the earlier
results available in the literature. We also discuss the energy of the flat and
open models. A comparison shows a partial consistency between the M${\o}$ller's
pseudotensor for General Relativity and teleparallel theory. Further, it is
shown that the results are independent of the free dimensionless coupling
constant of the teleparallel gravity.
| [
{
"created": "Tue, 9 Sep 2008 10:26:28 GMT",
"version": "v1"
}
] | 2011-01-27 | [
[
"Sharif",
"M.",
""
],
[
"Amir",
"M. Jamil",
""
]
] | This paper is devoted to the evaluation of the energy-momentum density components for the Friedmann models. For this purpose, we have used M${\o}$ller's pseudotensor prescription in General Relativity and a certain energy-momentum density developed from his teleparallel formulation. It is shown that the energy density of the closed Friedmann universe vanishes on the spherical shell at the radius $\rho=2\sqrt{3}$. This coincides with the earlier results available in the literature. We also discuss the energy of the flat and open models. A comparison shows a partial consistency between the M${\o}$ller's pseudotensor for General Relativity and teleparallel theory. Further, it is shown that the results are independent of the free dimensionless coupling constant of the teleparallel gravity. |
1911.11200 | Francesco Di Filippo | Ra\'ul Carballo-Rubio, Francesco Di Filippo, Stefano Liberati, Matt
Visser | Geodesically complete black holes | 22 pages, 16 figures | Phys. Rev. D 101, 084047 (2020) | 10.1103/PhysRevD.101.084047 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 1965 Penrose singularity theorem demonstrates the utterly inevitable and
unavoidable formation of spacetime singularities under physically reasonable
assumptions, and it remains one of the main results in our understanding of
black holes. It is standard lore that quantum gravitational effects will always
tame these singularities in black hole interiors. However, the Penrose's
theorem provides no clue as to the possible (non-singular) geometries that may
be realized in theories beyond general relativity as the result of singularity
regularization. In this paper we analyze this problem in spherically symmetric
situations, being completely general otherwise, in particular regarding the
dynamics of the gravitational and matter fields. Our main result is that,
contrary to what one might expect, the set of regular geometries that arises is
remarkably limited. We rederive geometries that have been analyzed before, but
also uncover some new possibilities. Moreover, the complete catalogue of
possibilities that we obtain allows us to draw the novel conclusion that there
is a clear tradeoff between internal and external consistency: One has to
choose between models that display internal inconsistencies, or models that
include significant deviations with respect to general relativity, which should
therefore be amenable to observational tests via multi-messenger astrophysics.
| [
{
"created": "Mon, 25 Nov 2019 20:06:31 GMT",
"version": "v1"
}
] | 2020-04-29 | [
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Di Filippo",
"Francesco",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Visser",
"Matt",
""
]
] | The 1965 Penrose singularity theorem demonstrates the utterly inevitable and unavoidable formation of spacetime singularities under physically reasonable assumptions, and it remains one of the main results in our understanding of black holes. It is standard lore that quantum gravitational effects will always tame these singularities in black hole interiors. However, the Penrose's theorem provides no clue as to the possible (non-singular) geometries that may be realized in theories beyond general relativity as the result of singularity regularization. In this paper we analyze this problem in spherically symmetric situations, being completely general otherwise, in particular regarding the dynamics of the gravitational and matter fields. Our main result is that, contrary to what one might expect, the set of regular geometries that arises is remarkably limited. We rederive geometries that have been analyzed before, but also uncover some new possibilities. Moreover, the complete catalogue of possibilities that we obtain allows us to draw the novel conclusion that there is a clear tradeoff between internal and external consistency: One has to choose between models that display internal inconsistencies, or models that include significant deviations with respect to general relativity, which should therefore be amenable to observational tests via multi-messenger astrophysics. |
0704.2647 | Muhammad Sharif | M. Sharif and Zahid Ahmad | High-Speed Cylindrical Collapse of Two Perfect Fluids | 11 pages, 1 figure, accepted for publication in Gen. Rel. Grav | Gen.Rel.Grav.39:1331-1344,2007 | 10.1007/s10714-007-0440-4 | null | gr-qc | null | In this paper, the study of the gravitational collapse of cylindrically
distributed two perfect fluid system has been carried out. It is assumed that
the collapsing speeds of the two fluids are very large. We explore this
condition by using the high-speed approximation scheme. There arise two cases,
i.e., bounded and vanishing of the ratios of the pressures with densities of
two fluids given by $c_s, d_s$. It is shown that the high-speed approximation
scheme breaks down by non-zero pressures $p_1, p_2$ when $c_s, d_s$ are bounded
below by some positive constants. The failure of the high-speed approximation
scheme at some particular time of the gravitational collapse suggests the
uncertainity on the evolution at and after this time. In the bounded case, the
naked singularity formation seems to be impossible for the cylindrical two
perfect fluids. For the vanishing case, if a linear equation of state is used,
the high-speed collapse does not break down by the effects of the pressures and
consequently a naked singularity forms. This work provides the generalisation
of the results already given by Nakao and Morisawa [1] for the perfect fluid.
| [
{
"created": "Fri, 20 Apr 2007 02:20:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
],
[
"Ahmad",
"Zahid",
""
]
] | In this paper, the study of the gravitational collapse of cylindrically distributed two perfect fluid system has been carried out. It is assumed that the collapsing speeds of the two fluids are very large. We explore this condition by using the high-speed approximation scheme. There arise two cases, i.e., bounded and vanishing of the ratios of the pressures with densities of two fluids given by $c_s, d_s$. It is shown that the high-speed approximation scheme breaks down by non-zero pressures $p_1, p_2$ when $c_s, d_s$ are bounded below by some positive constants. The failure of the high-speed approximation scheme at some particular time of the gravitational collapse suggests the uncertainity on the evolution at and after this time. In the bounded case, the naked singularity formation seems to be impossible for the cylindrical two perfect fluids. For the vanishing case, if a linear equation of state is used, the high-speed collapse does not break down by the effects of the pressures and consequently a naked singularity forms. This work provides the generalisation of the results already given by Nakao and Morisawa [1] for the perfect fluid. |
2301.06120 | Zhi Luo | Zhi Luo, Hao Yu, Shuo Cao, Jin Li | Shadow thermodynamics of the Hayward-AdS black hole | 14 pages, 6 figures | null | 10.1088/1674-1137/acc570 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the phase structure of the Hayward-AdS black hole (BH) is
studied using shadow formalism. It has been found that the shadow radius is a
monotonic function of the horizon radius and can therefore play an equivalent
role to the horizon radius in characterizing the thermodynamics of Hayward-AdS
BH. The thermodynamic phase transition (PT) of the Hayward-AdS BH is
investigated with the shadow radius. It is shown that as the magnetic charge
increases, the shadow radius becomes larger, while the coexistence temperature
becomes lower. The thermal profile of the Hayward-AdS BH is established by
combining the temperature diagram and the shadow cast diagram, which shows that
for a fixed magnetic charge, the temperature of the Hayward-AdS BH increases
with the pressure while the region of the thermal profile decreases with the
pressure. In particular, the temperature of the Hayward-AdS BH follows an
N-type change trend when it is smaller than the critical temperature. This
imply that the BH shadow may be used to investigate the thermodynamics of the
Hayward-AdS BH.
| [
{
"created": "Sun, 15 Jan 2023 15:31:57 GMT",
"version": "v1"
}
] | 2023-05-03 | [
[
"Luo",
"Zhi",
""
],
[
"Yu",
"Hao",
""
],
[
"Cao",
"Shuo",
""
],
[
"Li",
"Jin",
""
]
] | In this paper, the phase structure of the Hayward-AdS black hole (BH) is studied using shadow formalism. It has been found that the shadow radius is a monotonic function of the horizon radius and can therefore play an equivalent role to the horizon radius in characterizing the thermodynamics of Hayward-AdS BH. The thermodynamic phase transition (PT) of the Hayward-AdS BH is investigated with the shadow radius. It is shown that as the magnetic charge increases, the shadow radius becomes larger, while the coexistence temperature becomes lower. The thermal profile of the Hayward-AdS BH is established by combining the temperature diagram and the shadow cast diagram, which shows that for a fixed magnetic charge, the temperature of the Hayward-AdS BH increases with the pressure while the region of the thermal profile decreases with the pressure. In particular, the temperature of the Hayward-AdS BH follows an N-type change trend when it is smaller than the critical temperature. This imply that the BH shadow may be used to investigate the thermodynamics of the Hayward-AdS BH. |
2001.09889 | Harald Skarke | Harald Skarke | Redshift and gauge choice | 15 pages, clarifications and comparisons with other gauges added | Phys. Rev. D 102, 123520 (2020) | 10.1103/PhysRevD.102.123520 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a specific gauge choice comes extremely close to defining a
frame whose preferred observers see a dipole-free CMB. In this gauge the metric
is the product of a scale factor depending on all spacetime coordinates, and a
metric featuring an expansion-free geodesic timelike vector field. This setup
facilitates the computation of redshift and other distance measures and
explains why we can have a highly isotropic CMB despite large inhomogeneities.
| [
{
"created": "Mon, 27 Jan 2020 16:23:48 GMT",
"version": "v1"
},
{
"created": "Mon, 11 May 2020 13:20:16 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Skarke",
"Harald",
""
]
] | We show that a specific gauge choice comes extremely close to defining a frame whose preferred observers see a dipole-free CMB. In this gauge the metric is the product of a scale factor depending on all spacetime coordinates, and a metric featuring an expansion-free geodesic timelike vector field. This setup facilitates the computation of redshift and other distance measures and explains why we can have a highly isotropic CMB despite large inhomogeneities. |
1403.3467 | Friedrich W. Hehl | Peter Baekler (Duesseldorf), Alberto Favaro (Oldenburg), Yakov Itin
(Jerusalem), Friedrich W. Hehl (Cologne and Columbia, Missouri) | The Kummer tensor density in electrodynamics and in gravity | 54 pages, 6 figures, written in LaTex; improved version in accordance
with the referee report | Annals of Physics (NY) 349 (2014) 297--324 | 10.1016/j.aop.2014.06.007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Guided by results in the premetric electrodynamics of local and linear media,
we introduce on 4-dimensional spacetime the new abstract notion of a Kummer
tensor density of rank four, ${\cal K}^{ijkl}$. This tensor density is, by
definition, a cubic algebraic functional of a tensor density of rank four
${\cal T}^{ijkl}$, which is antisymmetric in its first two and its last two
indices: ${\cal T}^{ijkl} = - {\cal T}^{jikl} = - {\cal T}^{ijlk}$. Thus,
${\cal K}\sim {\cal T}^3$, see Eq.(46). (i) If $\cal T$ is identified with the
electromagnetic response tensor of local and linear media, the Kummer tensor
density encompasses the generalized {\it Fresnel wave surfaces} for propagating
light. In the reversible case, the wave surfaces turn out to be {\it Kummer
surfaces} as defined in algebraic geometry (Bateman 1910). (ii) If $\cal T$ is
identified with the {\it curvature} tensor $R^{ijkl}$ of a Riemann-Cartan
spacetime, then ${\cal K}\sim R^3$ and, in the special case of general
relativity, ${\cal K}$ reduces to the Kummer tensor of Zund (1969). This $\cal
K$ is related to the {\it principal null directions} of the curvature. We
discuss the properties of the general Kummer tensor density. In particular, we
decompose $\cal K$ irreducibly under the 4-dimensional linear group $GL(4,R)$
and, subsequently, under the Lorentz group $SO(1,3)$.
| [
{
"created": "Fri, 14 Mar 2014 00:33:07 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Sep 2014 20:50:29 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Baekler",
"Peter",
"",
"Duesseldorf"
],
[
"Favaro",
"Alberto",
"",
"Oldenburg"
],
[
"Itin",
"Yakov",
"",
"Jerusalem"
],
[
"Hehl",
"Friedrich W.",
"",
"Cologne and Columbia, Missouri"
]
] | Guided by results in the premetric electrodynamics of local and linear media, we introduce on 4-dimensional spacetime the new abstract notion of a Kummer tensor density of rank four, ${\cal K}^{ijkl}$. This tensor density is, by definition, a cubic algebraic functional of a tensor density of rank four ${\cal T}^{ijkl}$, which is antisymmetric in its first two and its last two indices: ${\cal T}^{ijkl} = - {\cal T}^{jikl} = - {\cal T}^{ijlk}$. Thus, ${\cal K}\sim {\cal T}^3$, see Eq.(46). (i) If $\cal T$ is identified with the electromagnetic response tensor of local and linear media, the Kummer tensor density encompasses the generalized {\it Fresnel wave surfaces} for propagating light. In the reversible case, the wave surfaces turn out to be {\it Kummer surfaces} as defined in algebraic geometry (Bateman 1910). (ii) If $\cal T$ is identified with the {\it curvature} tensor $R^{ijkl}$ of a Riemann-Cartan spacetime, then ${\cal K}\sim R^3$ and, in the special case of general relativity, ${\cal K}$ reduces to the Kummer tensor of Zund (1969). This $\cal K$ is related to the {\it principal null directions} of the curvature. We discuss the properties of the general Kummer tensor density. In particular, we decompose $\cal K$ irreducibly under the 4-dimensional linear group $GL(4,R)$ and, subsequently, under the Lorentz group $SO(1,3)$. |
1312.4891 | Kirill Bronnikov | K.A. Bronnikov, J.C. Fabris, R. Silveira, O.B. Zaslavskii | Dilaton gravity, (quasi-) black holes, and scalar charge | 22 pages, 2 figures. Published version | Gen. Rel. Grav. 46 (9), 1775 (2014) | 10.1007/s10714-014-1775-2 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider static electrically charged dust configurations in the framework
of Einstein-Maxwell-dilaton gravity with the interaction term P(\chi) F_{mn}
F^{mn} in the Lagrangian, where P(\chi) is an arbitrary function of the dilaton
field \chi, and the latter is allowed to be normal or phantom. It is shown
that, for any regular P(\chi), static configurations are possible with
arbitrary functions g_{00} = e^{2\gamma(x^i)} (i=1,2,3) and \chi =
\chi(\gamma), without any assumption of spatial symmetry. The corresponding
matter, electric charge and scalar charge densities are found from the field
equations. Meanwhile, configurations with nontrivial \chi(x^i) generically
require a nonzero scalar charge density distribution. The classical
Majumdar-Papapetrou (MP) system is obtained as a special case where \chi =
const; there is its scalar analogue in the case F_{mn} = 0, but only with a
phantom \chi field. Among possible solutions are black-hole (BH) and
quasi-black-hole (QBH) ones. Some general results on QBH properties obtained
previously for the MP system are here extended to systems with the dilaton.
Particular examples of asymptotically flat spherically symmetric BH and QBH
solutions are found, some of them being phantom-free, that is, exist with
positive energy densities of matter and both scalar and electromagnetic fields.
| [
{
"created": "Tue, 17 Dec 2013 18:42:09 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Dec 2013 18:45:37 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Aug 2014 03:29:08 GMT",
"version": "v3"
}
] | 2014-08-15 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Silveira",
"R.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider static electrically charged dust configurations in the framework of Einstein-Maxwell-dilaton gravity with the interaction term P(\chi) F_{mn} F^{mn} in the Lagrangian, where P(\chi) is an arbitrary function of the dilaton field \chi, and the latter is allowed to be normal or phantom. It is shown that, for any regular P(\chi), static configurations are possible with arbitrary functions g_{00} = e^{2\gamma(x^i)} (i=1,2,3) and \chi = \chi(\gamma), without any assumption of spatial symmetry. The corresponding matter, electric charge and scalar charge densities are found from the field equations. Meanwhile, configurations with nontrivial \chi(x^i) generically require a nonzero scalar charge density distribution. The classical Majumdar-Papapetrou (MP) system is obtained as a special case where \chi = const; there is its scalar analogue in the case F_{mn} = 0, but only with a phantom \chi field. Among possible solutions are black-hole (BH) and quasi-black-hole (QBH) ones. Some general results on QBH properties obtained previously for the MP system are here extended to systems with the dilaton. Particular examples of asymptotically flat spherically symmetric BH and QBH solutions are found, some of them being phantom-free, that is, exist with positive energy densities of matter and both scalar and electromagnetic fields. |
gr-qc/0303011 | Massimiliano Giammatteo | M. Giammatteo | Quasinormal modes of Kerr black holes: The determination of the
quasinormal frequencies with a new technique | 10 pages, 4 figures, Revtex4 style | null | null | null | gr-qc | null | We compute the quasinormal frequencies of rotating black holes using the
continued fraction method first proposed by Leaver. The main difference with
former works, is that our results are obtained by a new numerical technique
which avoids the use of two dimensional root-finding routines. The technique is
applied to evaluate the angular eigenvalues of Teukolsky's angular equation.
This method allow us to calculate both the slowly and the rapidly damped
quasinormal frequencies with excellent accuracy.
| [
{
"created": "Mon, 3 Mar 2003 18:29:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Giammatteo",
"M.",
""
]
] | We compute the quasinormal frequencies of rotating black holes using the continued fraction method first proposed by Leaver. The main difference with former works, is that our results are obtained by a new numerical technique which avoids the use of two dimensional root-finding routines. The technique is applied to evaluate the angular eigenvalues of Teukolsky's angular equation. This method allow us to calculate both the slowly and the rapidly damped quasinormal frequencies with excellent accuracy. |
1108.2102 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | A symmetry of the spatially flat Friedmann equations with barotropic
fluid | 10 pages, no figures, to appear in Phys. Lett. B | null | 10.1016/j.physletb.2011.08.018 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-sa/3.0/ | A string-inspired duality symmetry of the spatially flat Friedmann equations
of general-relativistic cosmology is discussed and generalized, providing a map
between exact solutions corresponding to different values of the barotropic
index.
| [
{
"created": "Wed, 10 Aug 2011 06:17:07 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | A string-inspired duality symmetry of the spatially flat Friedmann equations of general-relativistic cosmology is discussed and generalized, providing a map between exact solutions corresponding to different values of the barotropic index. |
2011.13264 | Alesandro Santos | J. S. Gon\c{c}alves and A. F. Santos | G\"{o}del and G\"{o}del-type solutions in the Palatini $f(R,T)$ gravity
theory | 15 pages, accepted for publication in IJMPD | null | 10.1142/S0218271821500140 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Palatini $f(R,T)$ gravity theory is considered. The standard
Einstein-Hilbert action is replaced by an arbitrary function of the Ricci
scalar $R$ and of the trace $T$ of the energy-momentum tensor. In the Palatini
approach, the Ricci scalar is a function of the metric and the connection.
These two quantities, metric and connection, are taken as independents
variables. Then, it is examined whether Palatini $f(R,T)$ gravity theory allows
solutions in which lead to violation of causality. The G\"{o}del and
G\"{o}del-type space-times are considered. In addition, a critical radius,
which permits to examine limits for violation of causality, is calculated. It
is shown that, for different matter contents, non-causal solutions can be
avoided in this Palatini gravitational theory.
| [
{
"created": "Thu, 26 Nov 2020 12:47:27 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Gonçalves",
"J. S.",
""
],
[
"Santos",
"A. F.",
""
]
] | The Palatini $f(R,T)$ gravity theory is considered. The standard Einstein-Hilbert action is replaced by an arbitrary function of the Ricci scalar $R$ and of the trace $T$ of the energy-momentum tensor. In the Palatini approach, the Ricci scalar is a function of the metric and the connection. These two quantities, metric and connection, are taken as independents variables. Then, it is examined whether Palatini $f(R,T)$ gravity theory allows solutions in which lead to violation of causality. The G\"{o}del and G\"{o}del-type space-times are considered. In addition, a critical radius, which permits to examine limits for violation of causality, is calculated. It is shown that, for different matter contents, non-causal solutions can be avoided in this Palatini gravitational theory. |
1408.5505 | Alexandre Le Tiec | Alexandre Le Tiec | The Overlap of Numerical Relativity, Perturbation Theory and
Post-Newtonian Theory in the Binary Black Hole Problem | 35 pages, 9 figures; invited review for IJMPD; v2: references added,
matches published version | Int.J.Mod.Phys.D.23:1430022,2014 | 10.1142/S0218271814300225 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspiralling and coalescing binary black holes are promising sources of
gravitational radiation. The orbital motion and gravitational-wave emission of
such system can be modelled using a variety of approximation schemes and
numerical methods in general relativity: the post-Newtonian formalism, black
hole perturbation theory, numerical relativity simulations, and the effective
one-body model. We review recent work at the multiple interfaces of these
analytical and numerical techniques, emphasizing the use of
coordinate-invariant relationships to perform meaningful comparisons. Such
comparisons provide independent checks of the validity of the various
calculations, they inform the development of a universal, semi-analytical model
of the binary dynamics and gravitational-wave emission, and they help to
delineate the respective domains of validity of each approximation method. For
instance, several recent comparisons suggest that perturbation theory may find
applications in a broader range of physical problems than previously thought,
including the radiative inspiral of intermediate mass-ratio and comparable-mass
black hole binaries.
| [
{
"created": "Sat, 23 Aug 2014 15:39:37 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Oct 2014 11:39:10 GMT",
"version": "v2"
}
] | 2014-10-06 | [
[
"Tiec",
"Alexandre Le",
""
]
] | Inspiralling and coalescing binary black holes are promising sources of gravitational radiation. The orbital motion and gravitational-wave emission of such system can be modelled using a variety of approximation schemes and numerical methods in general relativity: the post-Newtonian formalism, black hole perturbation theory, numerical relativity simulations, and the effective one-body model. We review recent work at the multiple interfaces of these analytical and numerical techniques, emphasizing the use of coordinate-invariant relationships to perform meaningful comparisons. Such comparisons provide independent checks of the validity of the various calculations, they inform the development of a universal, semi-analytical model of the binary dynamics and gravitational-wave emission, and they help to delineate the respective domains of validity of each approximation method. For instance, several recent comparisons suggest that perturbation theory may find applications in a broader range of physical problems than previously thought, including the radiative inspiral of intermediate mass-ratio and comparable-mass black hole binaries. |
1606.04529 | Prabir Rudra | Prabir Rudra, Mir Faizal, Ahmed Farag Ali | Vaidya Spacetime for Galileon Gravity's Rainbow | 13 pages, 10 figures (Accepted for publication in Nucl. Phys. B) | Nucl. Phys. B 909, 725 (2016) | 10.1016/j.nuclphysb.2016.06.002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analyze Vaidya spacetime with an energy dependent metric in
Galileon gravity's rainbow. This will be done using the rainbow functions which
are motivated from the results obtained in loop quantum gravity approach and
non-commutative geometry. We will investigate the Gravitational collapse in
this Galileon gravity's rainbow. We will discuss the behavior of singularities
formed from the gravitational collapse in this rainbow deformed Galileon
gravity.
| [
{
"created": "Tue, 7 Jun 2016 11:55:48 GMT",
"version": "v1"
}
] | 2016-06-28 | [
[
"Rudra",
"Prabir",
""
],
[
"Faizal",
"Mir",
""
],
[
"Ali",
"Ahmed Farag",
""
]
] | In this paper, we analyze Vaidya spacetime with an energy dependent metric in Galileon gravity's rainbow. This will be done using the rainbow functions which are motivated from the results obtained in loop quantum gravity approach and non-commutative geometry. We will investigate the Gravitational collapse in this Galileon gravity's rainbow. We will discuss the behavior of singularities formed from the gravitational collapse in this rainbow deformed Galileon gravity. |
gr-qc/0507121 | J. -F. Pascual-Sanchez | J.-F. Pascual-Sanchez | Introducing Relativity in Global Navigation Satellite Systems | 24 pages, RevTeX 4, based on a talk given in "International School:
Relativistic Coordinates, Reference and Positioning Systems", Salamanca
(Spain), January 21-25, 2005; final version with an extended section on the
SYPOR project, accepted in Annalen der Physik (Leipzig) | Annalen Phys.16:258-273,1997 | 10.1002/andp.200610229 | null | gr-qc physics.class-ph | null | Today, the Global Navigation Satellite Systems, used as global positioning
systems, are the GPS and the GLONASS. They are based on a Newtonian model and
hence they are only operative when several relativistic effects are taken into
account. The most important relativistic effects (to order 1/c^2) are: the
Einstein gravitational blue shift effect of the satellite clock frequency
(Equivalence Principle of General Relativity) and the Doppler red shift of
second order, due to the motion of the satellite (Special Relativity).
On the other hand, in a few years the Galileo system will be built, copying
the GPS system unless an alternative project is designed. In this work, it will
be also shown that the SYPOR project, using fully relativistic concepts, is an
alternative to a mere copy of the GPS system. According to this project, the
Galileo system would be exact and there would be no need for relativistic
corrections.
| [
{
"created": "Thu, 28 Jul 2005 19:11:27 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2005 20:48:07 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Dec 2006 18:07:25 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Pascual-Sanchez",
"J. -F.",
""
]
] | Today, the Global Navigation Satellite Systems, used as global positioning systems, are the GPS and the GLONASS. They are based on a Newtonian model and hence they are only operative when several relativistic effects are taken into account. The most important relativistic effects (to order 1/c^2) are: the Einstein gravitational blue shift effect of the satellite clock frequency (Equivalence Principle of General Relativity) and the Doppler red shift of second order, due to the motion of the satellite (Special Relativity). On the other hand, in a few years the Galileo system will be built, copying the GPS system unless an alternative project is designed. In this work, it will be also shown that the SYPOR project, using fully relativistic concepts, is an alternative to a mere copy of the GPS system. According to this project, the Galileo system would be exact and there would be no need for relativistic corrections. |
2204.08371 | Jorge Pullin | Rodolfo Gambini, Jorge Pullin | The solution to the problem of time in quantum gravity also solves the
time of arrival problem in quantum mechanics | 14 pages, LaTex, 5 figure, to appear in New Journal of Physics | New Journal of Physics 24 053011 (2022) | 10.1088/1367-2630/ac6768 | LSU-REL-041822 | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduced with coauthors some years ago a solution to the problem of time
in quantum gravity which consists in formulating the quantum theory in terms of
real clocks. It combines Page and Wootters' relational proposal with Rovelli's
evolving constants of the motion. Time is associated with an operator and not a
classical parameter. We show here that this construction provides a natural
solution to the time of arrival problem in quantum mechanics and leads to a
well defined time-energy uncertainty relation for the clocks.
| [
{
"created": "Mon, 18 Apr 2022 15:30:24 GMT",
"version": "v1"
}
] | 2022-05-03 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We introduced with coauthors some years ago a solution to the problem of time in quantum gravity which consists in formulating the quantum theory in terms of real clocks. It combines Page and Wootters' relational proposal with Rovelli's evolving constants of the motion. Time is associated with an operator and not a classical parameter. We show here that this construction provides a natural solution to the time of arrival problem in quantum mechanics and leads to a well defined time-energy uncertainty relation for the clocks. |
2210.09062 | Wen-Xiang Chen | Wen-Xiang Chen, Jun-Xian Li, Jing-Yi Zhang | Calculating the Hawking Temperatures of Conventional Black Holes in the
f(R) Gravity Models with the RVB Method | null | null | 10.1007/s10773-023-05335-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper attempted to apply the RVB method for calculating the Hawking
temperatures of black holes under f(R) gravity. In calculating the Hawking
temperature, we found a difference in the integration constant between the RVB
and general methods.
| [
{
"created": "Thu, 13 Oct 2022 23:52:13 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2022 02:31:08 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Chen",
"Wen-Xiang",
""
],
[
"Li",
"Jun-Xian",
""
],
[
"Zhang",
"Jing-Yi",
""
]
] | This paper attempted to apply the RVB method for calculating the Hawking temperatures of black holes under f(R) gravity. In calculating the Hawking temperature, we found a difference in the integration constant between the RVB and general methods. |
2105.10521 | Dipayan Mukherjee | Dipayan Mukherjee, H. K. Jassal and Kinjalk Lochan | $f(R)$ Dual Theories of Quintessence : Expansion-Collapse Duality | 29 pages, 5 figures, accepted for publication in JCAP | null | 10.1088/1475-7516/2021/12/016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerated expansion of the universe demands presence of an exotic
matter, namely the dark energy. Though the cosmological constant fits this role
very well, a scalar field minimally coupled to gravity, or quintessence, can
also be considered as a viable alternative for the cosmological constant. We
study $f(R)$ gravity models which can lead to an effective description of dark
energy implemented by quintessence fields in Einstein gravity, using the
Einstein frame-Jordan frame duality. For a family of viable quintessence
models, the reconstruction of the $f(R)$ function in the Jordan frame consists
of two parts. We first obtain a perturbative solution of $f(R)$ in the Jordan
frame, applicable near the present epoch. Second, we obtain an asymptotic
solution for $f(R)$, consistent with the late time limit of the Einstein frame
if the quintessence field drives the universe. We show that for certain class
of viable quintessence models, the Jordan frame universe grows to a maximum
finite size, after which it begins to collapse back. Thus, there is a
possibility that in the late time limit where the Einstein frame universe
continues to expand, the Jordan frame universe collapses. The condition for
this expansion-collapse duality is then generalized to time varying equations
of state models, taking into account the presence of non-relativistic matter or
any other component in the Einstein frame universe. This mapping between an
expanding geometry and a collapsing geometry at the field equation level may
have interesting potential implications on the growth of perturbations therein
at late times.
| [
{
"created": "Fri, 21 May 2021 18:07:48 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jun 2021 05:22:30 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Dec 2021 08:40:22 GMT",
"version": "v3"
}
] | 2021-12-09 | [
[
"Mukherjee",
"Dipayan",
""
],
[
"Jassal",
"H. K.",
""
],
[
"Lochan",
"Kinjalk",
""
]
] | The accelerated expansion of the universe demands presence of an exotic matter, namely the dark energy. Though the cosmological constant fits this role very well, a scalar field minimally coupled to gravity, or quintessence, can also be considered as a viable alternative for the cosmological constant. We study $f(R)$ gravity models which can lead to an effective description of dark energy implemented by quintessence fields in Einstein gravity, using the Einstein frame-Jordan frame duality. For a family of viable quintessence models, the reconstruction of the $f(R)$ function in the Jordan frame consists of two parts. We first obtain a perturbative solution of $f(R)$ in the Jordan frame, applicable near the present epoch. Second, we obtain an asymptotic solution for $f(R)$, consistent with the late time limit of the Einstein frame if the quintessence field drives the universe. We show that for certain class of viable quintessence models, the Jordan frame universe grows to a maximum finite size, after which it begins to collapse back. Thus, there is a possibility that in the late time limit where the Einstein frame universe continues to expand, the Jordan frame universe collapses. The condition for this expansion-collapse duality is then generalized to time varying equations of state models, taking into account the presence of non-relativistic matter or any other component in the Einstein frame universe. This mapping between an expanding geometry and a collapsing geometry at the field equation level may have interesting potential implications on the growth of perturbations therein at late times. |
1705.00398 | Viqar Husain | Syed Moeez Hassan, Viqar Husain | Semiclassical cosmology with polymer matter | 11 pages, 3 figures. (CQG Focus issue: Applications of loop quantum
gravity to cosmology) | Class. Quantum Grav. 34 084003 (2017) | 10.1088/1361-6382/aa6455 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In loop quantum cosmology, polymer quantization is applied to gravity and
Schrodinger quantization to matter. This approach misses interesting
cosmological dynamics coming from the polymer quantization of matter. We
demonstrate this in semiclassical cosmology with a scalar field and
pressureless dust: gravity is kept classical, dust is used to fix the time
gauge, and polymer quantization effects are isolated in the scalar field. The
resulting dynamics shows a period of inflation, both with and without a scalar
potential, and the emergence of a classical universe at late times. Since
gravity is not quantized, the cosmological singularity is not resolved, but our
results suggest that polymer quantization of both gravity and matter are
important for a complete picture.
| [
{
"created": "Mon, 1 May 2017 01:35:04 GMT",
"version": "v1"
}
] | 2017-05-10 | [
[
"Hassan",
"Syed Moeez",
""
],
[
"Husain",
"Viqar",
""
]
] | In loop quantum cosmology, polymer quantization is applied to gravity and Schrodinger quantization to matter. This approach misses interesting cosmological dynamics coming from the polymer quantization of matter. We demonstrate this in semiclassical cosmology with a scalar field and pressureless dust: gravity is kept classical, dust is used to fix the time gauge, and polymer quantization effects are isolated in the scalar field. The resulting dynamics shows a period of inflation, both with and without a scalar potential, and the emergence of a classical universe at late times. Since gravity is not quantized, the cosmological singularity is not resolved, but our results suggest that polymer quantization of both gravity and matter are important for a complete picture. |
1507.01617 | Pawel Gusin | Pawel Gusin, Bartosz Kusnierz, Andrzej Radosz | Observers in spacetimes with spherical and axial symmetries | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce in the explicit form the tetrads of arbitrary observers in
spacetimes with spherical and axial symmetries. The observers confined to the
equatorial plane are parametrized by the pair of functions. We apply this
description in the analysis of the null-geodesics in the observers' frames. The
observers with the constant acceleration are distinguished.
| [
{
"created": "Mon, 6 Jul 2015 20:50:18 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Aug 2015 07:48:44 GMT",
"version": "v2"
}
] | 2015-08-06 | [
[
"Gusin",
"Pawel",
""
],
[
"Kusnierz",
"Bartosz",
""
],
[
"Radosz",
"Andrzej",
""
]
] | We introduce in the explicit form the tetrads of arbitrary observers in spacetimes with spherical and axial symmetries. The observers confined to the equatorial plane are parametrized by the pair of functions. We apply this description in the analysis of the null-geodesics in the observers' frames. The observers with the constant acceleration are distinguished. |
2107.00543 | Soumya Chakrabarti | Soumya Chakrabarti (Saha Institute of Nuclear Physics, Kolkata) | Cosmic Variation of Proton to Electron Mass Ratio with an interacting
Higgs Scalar Field | 17 pages, 17 figures, accepted for publication in the Monthly Notices
of the Royal Astronomical Society | null | 10.1093/mnras/stab1910 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss that it is quite possible to realize the smooth transition of the
universe between a matter/radiation dominated deceleration and a dark energy
dominated acceleration, even with a variation of proton-to-electron mass ratio.
The variation is incorporated into the theory of gravity using a cosmological
Higgs scalar field with a non-trivial self-interaction potential, leading to a
varying Higgs vacuum expectation value (VEV). This matches well with the data
from molecular absorption spectra of a series of Quasars. In comparison with
late-time cosmology, an observational consistency is reached using a Markov
chain Monte Carlo simulation and JLA+OHD+BAO data sets. We find that the
pattern of variation is embedded within the evolving Equation of State (EOS) of
the scalar Dark Energy/Matter components, but leaves negligible trace on the
effective EOS of the system. We discuss three cases of scalar extended theory
of gravity, (a) a minimally coupled scalar, (b) a non-minimally coupled scalar
and (c) a generalized Brans-Dicke setup. We also give a toy model of a unified
cosmic history from inflation to the present era and discuss how the Higg VEV
might have changed as a function of look back time.
| [
{
"created": "Thu, 1 Jul 2021 15:34:24 GMT",
"version": "v1"
}
] | 2021-07-14 | [
[
"Chakrabarti",
"Soumya",
"",
"Saha Institute of Nuclear Physics, Kolkata"
]
] | We discuss that it is quite possible to realize the smooth transition of the universe between a matter/radiation dominated deceleration and a dark energy dominated acceleration, even with a variation of proton-to-electron mass ratio. The variation is incorporated into the theory of gravity using a cosmological Higgs scalar field with a non-trivial self-interaction potential, leading to a varying Higgs vacuum expectation value (VEV). This matches well with the data from molecular absorption spectra of a series of Quasars. In comparison with late-time cosmology, an observational consistency is reached using a Markov chain Monte Carlo simulation and JLA+OHD+BAO data sets. We find that the pattern of variation is embedded within the evolving Equation of State (EOS) of the scalar Dark Energy/Matter components, but leaves negligible trace on the effective EOS of the system. We discuss three cases of scalar extended theory of gravity, (a) a minimally coupled scalar, (b) a non-minimally coupled scalar and (c) a generalized Brans-Dicke setup. We also give a toy model of a unified cosmic history from inflation to the present era and discuss how the Higg VEV might have changed as a function of look back time. |
0706.0114 | Edward Porter | Edward K. Porter | A New Template Family For The Detection Of Gravitational Waves From
Comparable Mass Black Hole Binaries | Final published version. Accepted for publication in Phys. Rev. D | Phys.Rev.D76:104002,2007 | 10.1103/PhysRevD.76.104002 | null | gr-qc | null | In order to improve the phasing of the comparable-mass waveform as we
approach the last stable orbit for a system, various re-summation methods have
been used to improve the standard post-Newtonian waveforms. In this work we
present a new family of templates for the detection of gravitational waves from
the inspiral of two comparable-mass black hole binaries. These new adiabatic
templates are based on re-expressing the derivative of the binding energy and
the gravitational wave flux functions in terms of shifted Chebyshev
polynomials. The Chebyshev polynomials are a useful tool in numerical methods
as they display the fastest convergence of any of the orthogonal polynomials.
In this case they are also particularly useful as they eliminate one of the
features that plagues the post-Newtonian expansion. The Chebyshev binding
energy now has information at all post-Newtonian orders, compared to the
post-Newtonian templates which only have information at full integer orders. In
this work, we compare both the post-Newtonian and Chebyshev templates against a
fiducially exact waveform. This waveform is constructed from a hybrid method of
using the test-mass results combined with the mass dependent parts of the
post-Newtonian expansions for the binding energy and flux functions. Our
results show that the Chebyshev templates achieve extremely high fitting
factors at all PN orders and provide excellent parameter extraction. We also
show that this new template family has a faster Cauchy convergence, gives a
better prediction of the position of the Last Stable Orbit and in general
recovers higher Signal-to-Noise ratios than the post-Newtonian templates.
| [
{
"created": "Fri, 1 Jun 2007 10:15:34 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2007 12:26:25 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Nov 2007 11:16:12 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Porter",
"Edward K.",
""
]
] | In order to improve the phasing of the comparable-mass waveform as we approach the last stable orbit for a system, various re-summation methods have been used to improve the standard post-Newtonian waveforms. In this work we present a new family of templates for the detection of gravitational waves from the inspiral of two comparable-mass black hole binaries. These new adiabatic templates are based on re-expressing the derivative of the binding energy and the gravitational wave flux functions in terms of shifted Chebyshev polynomials. The Chebyshev polynomials are a useful tool in numerical methods as they display the fastest convergence of any of the orthogonal polynomials. In this case they are also particularly useful as they eliminate one of the features that plagues the post-Newtonian expansion. The Chebyshev binding energy now has information at all post-Newtonian orders, compared to the post-Newtonian templates which only have information at full integer orders. In this work, we compare both the post-Newtonian and Chebyshev templates against a fiducially exact waveform. This waveform is constructed from a hybrid method of using the test-mass results combined with the mass dependent parts of the post-Newtonian expansions for the binding energy and flux functions. Our results show that the Chebyshev templates achieve extremely high fitting factors at all PN orders and provide excellent parameter extraction. We also show that this new template family has a faster Cauchy convergence, gives a better prediction of the position of the Last Stable Orbit and in general recovers higher Signal-to-Noise ratios than the post-Newtonian templates. |
2008.10093 | Mourad Halla | Mourad Halla and Volker Perlick | Application of the Gauss-Bonnet theorem to lensing in the NUT metric | null | Gen. Rel. Grav. 52, 112 (2020) | 10.1007/s10714-020-02766-z | null | gr-qc astro-ph.GA math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show with the help of Fermat's principle that every lightlike geodesic in
the NUT metric projects to a geodesic of a two-dimensional Riemannian metric
which we call the optical metric. The optical metric is defined on a
(coordinate) cone whose opening angle is determined by the impact parameter of
the lightlike geodesic. We show that, surprisingly, the optical metrics on
cones with different opening angles are locally (but not globally) isometric.
With the help of the Gauss-Bonnet theorem we demonstrate that the deflection
angle of a lightlike geodesic is determined by an area integral over the
Gaussian curvature of the optical metric. A similar result is known to be true
for static and spherically symmetric spacetimes. The generalisation to the NUT
spacetime, which is neither static nor spherically symmetric (at least not in
the usual sense), is rather non-trivial.
| [
{
"created": "Sun, 23 Aug 2020 19:06:43 GMT",
"version": "v1"
}
] | 2021-03-25 | [
[
"Halla",
"Mourad",
""
],
[
"Perlick",
"Volker",
""
]
] | We show with the help of Fermat's principle that every lightlike geodesic in the NUT metric projects to a geodesic of a two-dimensional Riemannian metric which we call the optical metric. The optical metric is defined on a (coordinate) cone whose opening angle is determined by the impact parameter of the lightlike geodesic. We show that, surprisingly, the optical metrics on cones with different opening angles are locally (but not globally) isometric. With the help of the Gauss-Bonnet theorem we demonstrate that the deflection angle of a lightlike geodesic is determined by an area integral over the Gaussian curvature of the optical metric. A similar result is known to be true for static and spherically symmetric spacetimes. The generalisation to the NUT spacetime, which is neither static nor spherically symmetric (at least not in the usual sense), is rather non-trivial. |
1608.06940 | Lucien Hardy | Lucien Hardy | Operational General Relativity: Possibilistic, Probabilistic, and
Quantum | 235 pages. Many figures | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we develop an operational formulation of General Relativity
similar in spirit to existing operational formulations of Quantum Theory. To do
this we introduce an operational space (or op-space) built out of scalar
fields. A point in op-space corresponds to some nominated set of scalar fields
taking some given values in coincidence. We assert that op-space is the space
in which we observe the world. We introduce also a notion of agency (this
corresponds to the ability to set knob settings just like in Operational
Quantum Theory). The effects of agents' actions should only be felt to the
future so we introduce also a time direction field. Agency and time direction
can be understood as effective notions. We show how to formulate General
Relativity as a possibilistic theory and as a probabilistic theory. In the
possibilistic case we provide a compositional framework for calculating whether
some operationally described situation is possible or not. In the probabilistic
version we introduce probabilities and provide a compositional framework for
calculating the probability of some operationally described situation. Finally
we look at the quantum case. We review the operator tensor formulation of
Quantum Theory and use it to set up an approach to Quantum Field Theory that is
both operational and compositional. Then we consider strategies for solving the
problem of Quantum Gravity. By referring only to operational quantities we are
able to provide formulations for the possibilistic, probabilistic, and (the
nascent) quantum cases that are manifestly invariant under diffeomorphisms.
| [
{
"created": "Wed, 24 Aug 2016 20:00:05 GMT",
"version": "v1"
}
] | 2016-08-26 | [
[
"Hardy",
"Lucien",
""
]
] | In this paper we develop an operational formulation of General Relativity similar in spirit to existing operational formulations of Quantum Theory. To do this we introduce an operational space (or op-space) built out of scalar fields. A point in op-space corresponds to some nominated set of scalar fields taking some given values in coincidence. We assert that op-space is the space in which we observe the world. We introduce also a notion of agency (this corresponds to the ability to set knob settings just like in Operational Quantum Theory). The effects of agents' actions should only be felt to the future so we introduce also a time direction field. Agency and time direction can be understood as effective notions. We show how to formulate General Relativity as a possibilistic theory and as a probabilistic theory. In the possibilistic case we provide a compositional framework for calculating whether some operationally described situation is possible or not. In the probabilistic version we introduce probabilities and provide a compositional framework for calculating the probability of some operationally described situation. Finally we look at the quantum case. We review the operator tensor formulation of Quantum Theory and use it to set up an approach to Quantum Field Theory that is both operational and compositional. Then we consider strategies for solving the problem of Quantum Gravity. By referring only to operational quantities we are able to provide formulations for the possibilistic, probabilistic, and (the nascent) quantum cases that are manifestly invariant under diffeomorphisms. |
2201.00502 | Simran Arora | P.K. Sahoo, Sanjay Mandal, Simran Arora | Energy Conditions in Non-minimally Coupled $f(R,T)$ Gravity | Astronomische Nachrichten published version | Astronomische Nachrichten, 342 (2021) 89-95 | 10.1002/asna.202113886 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In today's scenario, going beyond Einstein's theory of gravity leads us to
some more complete and modified gravity theories. One of them is the $f(R,T)$
gravity in which $ R $ is the Ricci scalar, and $ T $ is the trace of the
energy-momentum tensor. Using a well-motivated linear $f(R,T)$ gravity model
with a single parameter, we studied the strong energy condition (SEC), the weak
energy condition (WEC), the null energy condition (NEC), and the dominant
energy condition (DEC) under the simplest non-minimal matter geometry coupling
with a perfect fluid distribution. The model parameter is constrained by energy
conditions and a single parameter proposed equation of state (EoS), resulting
in the compatibility of the $f(R,T)$ models with the accelerated expansion of
the universe. It is seen that the EoS parameter illustrate the quintessence
phase in a dominated accelerated phase, pinpoint to the cosmological constant
yields as a prediction the phantom era. Also, the present values of the
cosmological constant and the acceleration of the universe are used to check
the viability of our linear $f(R,T)$ model of gravity. It is observed that the
positive behavior of DEC and WEC indicates the validation of the model. In
contrast, SEC is violating the condition resulting in the accelerated expansion
of the universe.
| [
{
"created": "Mon, 3 Jan 2022 07:29:56 GMT",
"version": "v1"
}
] | 2022-01-04 | [
[
"Sahoo",
"P. K.",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Arora",
"Simran",
""
]
] | In today's scenario, going beyond Einstein's theory of gravity leads us to some more complete and modified gravity theories. One of them is the $f(R,T)$ gravity in which $ R $ is the Ricci scalar, and $ T $ is the trace of the energy-momentum tensor. Using a well-motivated linear $f(R,T)$ gravity model with a single parameter, we studied the strong energy condition (SEC), the weak energy condition (WEC), the null energy condition (NEC), and the dominant energy condition (DEC) under the simplest non-minimal matter geometry coupling with a perfect fluid distribution. The model parameter is constrained by energy conditions and a single parameter proposed equation of state (EoS), resulting in the compatibility of the $f(R,T)$ models with the accelerated expansion of the universe. It is seen that the EoS parameter illustrate the quintessence phase in a dominated accelerated phase, pinpoint to the cosmological constant yields as a prediction the phantom era. Also, the present values of the cosmological constant and the acceleration of the universe are used to check the viability of our linear $f(R,T)$ model of gravity. It is observed that the positive behavior of DEC and WEC indicates the validation of the model. In contrast, SEC is violating the condition resulting in the accelerated expansion of the universe. |
gr-qc/9905046 | Serguei N. Manida | S.N.Manida (Saint-Petersburg State University) | Fock-Lorentz transformations and time-varying speed of light | 24 pages, LaTeX | null | null | NIIF/99-033 | gr-qc astro-ph physics.ed-ph | null | The theory of relativity was built up on linear Lorentz transformation.
However, in his fundamental work "Theory of Space, Time and Gravitation"
V.A.Fock shows that the general form of the transformation between the
coordinates in the two inertial frames could be taken to be linear fractional.
The implicit form of this transformation contains two constants of different
space-time dimensions. They can be reduced to the constant "c" with the
dimension of speed ("speed of light"), and to the constant "R" with the
dimension of length (an invariant radius of the visible part of the Universe).
The geometry of the "light cones" shows that "R" is a fundamental constant, but
"c" depends on the time of transformation.
| [
{
"created": "Fri, 14 May 1999 14:28:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Manida",
"S. N.",
"",
"Saint-Petersburg State University"
]
] | The theory of relativity was built up on linear Lorentz transformation. However, in his fundamental work "Theory of Space, Time and Gravitation" V.A.Fock shows that the general form of the transformation between the coordinates in the two inertial frames could be taken to be linear fractional. The implicit form of this transformation contains two constants of different space-time dimensions. They can be reduced to the constant "c" with the dimension of speed ("speed of light"), and to the constant "R" with the dimension of length (an invariant radius of the visible part of the Universe). The geometry of the "light cones" shows that "R" is a fundamental constant, but "c" depends on the time of transformation. |
gr-qc/0405024 | Mauricio Bellini | Jose Edgar Madriz Aguilar (IFM, Michoacana University) and Mauricio
Bellini (Mar del Plata University & CONICET) | Noncompact Kaluza-Klein theory and inflationary cosmology: a complete
formalism | to be published in Phys. Lett. B | Phys.Lett. B596 (2004) 116-122 | 10.1016/j.physletb.2004.06.093 | null | gr-qc hep-ph | null | A formalization of the recently introduced formalism for inflation is
developed from noncompact Kaluza-Klein theory. In particular, the case for a
single scalar field inflationary model is studied. We obtain that the scalar
potential, which assume different representations in different frames, has a
geometrical origin.
| [
{
"created": "Wed, 5 May 2004 22:43:50 GMT",
"version": "v1"
},
{
"created": "Fri, 21 May 2004 15:40:28 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Jun 2004 18:40:54 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Jul 2004 13:41:00 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Aguilar",
"Jose Edgar Madriz",
"",
"IFM, Michoacana University"
],
[
"Bellini",
"Mauricio",
"",
"Mar del Plata University & CONICET"
]
] | A formalization of the recently introduced formalism for inflation is developed from noncompact Kaluza-Klein theory. In particular, the case for a single scalar field inflationary model is studied. We obtain that the scalar potential, which assume different representations in different frames, has a geometrical origin. |
1605.02726 | Lorenzo Sebastiani | Shynaray Myrzakul, Ratbay Myrzakulov, Lorenzo Sebastiani | K-essence in Horndeski models | final version, accepted in Astrophys.Space Sci., 14 pages | null | 10.1007/s10509-016-2846-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate a simple class of Horndeski models where the
scalar field plays the role of a k-essence fluid. We present several solutions
for early-time universe, namely inflation and cosmological bounce, by making
use of some reconstruction technique. Moreover, we furnish the formalism to
calculate perturbations in FRW space-time and we compute the spectral index and
the tensor-to-scalar ratio during inflation.
| [
{
"created": "Mon, 9 May 2016 11:02:18 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2016 15:59:02 GMT",
"version": "v2"
}
] | 2016-07-20 | [
[
"Myrzakul",
"Shynaray",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Sebastiani",
"Lorenzo",
""
]
] | In this paper, we investigate a simple class of Horndeski models where the scalar field plays the role of a k-essence fluid. We present several solutions for early-time universe, namely inflation and cosmological bounce, by making use of some reconstruction technique. Moreover, we furnish the formalism to calculate perturbations in FRW space-time and we compute the spectral index and the tensor-to-scalar ratio during inflation. |
gr-qc/9505034 | Stefan Mashkevich | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Indeterministic Quantum Gravity II: Refinements and Developments | null | null | null | IP 5/95 | gr-qc quant-ph | null | This paper is a continuation of the paper [V.S.Mashkevich, gr-qc/9409010].
Indeterministic quantum gravity is a theory that unifies general relativity and
quantum theory involving indeterministic conception, i.e., quantum jumps. By
the same token the theory claims to describe all the universe.
Spacetime is the direct product of cosmic time and space. The state of the
universe is given by metric, its derivative with respect to cosmic time, and
the number of an energy level. A quantum jump occurs at the tangency of two
levels. Equations of motion are the restricted Einstein equation (the cosmic
space part thereof) and a probability rule for the quantum jump.
Keywords: indeterminism, quantum jumps, state vector reduction, cosmology,
cosmic spacetime
| [
{
"created": "Fri, 19 May 1995 19:08:44 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] | This paper is a continuation of the paper [V.S.Mashkevich, gr-qc/9409010]. Indeterministic quantum gravity is a theory that unifies general relativity and quantum theory involving indeterministic conception, i.e., quantum jumps. By the same token the theory claims to describe all the universe. Spacetime is the direct product of cosmic time and space. The state of the universe is given by metric, its derivative with respect to cosmic time, and the number of an energy level. A quantum jump occurs at the tangency of two levels. Equations of motion are the restricted Einstein equation (the cosmic space part thereof) and a probability rule for the quantum jump. Keywords: indeterminism, quantum jumps, state vector reduction, cosmology, cosmic spacetime |
0811.4347 | Frans Klinkhamer | F.R. Klinkhamer, G.E. Volovik | Gluonic vacuum, q-theory, and the cosmological constant | 20 pages; v6: published version | Phys.Rev.D79:063527,2009 | 10.1103/PhysRevD.79.063527 | KA-TP-30-2008 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous work, q-theory was introduced to describe the gravitating
macroscopic behavior of a conserved microscopic variable q. In this article,
the gluon condensate of quantum chromodynamics is considered in terms of
q-theory. The remnant vacuum energy density (i.e., cosmological constant) of an
expanding universe is estimated as K_{QCD}^3 / E_{Planck}^2, with string
tension K_{QCD} \approx (10^2 MeV)^2 and gravitational scale E_{Planck} \approx
10^{19} GeV. The only input for this estimate is general relativity, quantum
chromodynamics, and the Hubble expansion of the present Universe.
| [
{
"created": "Wed, 26 Nov 2008 19:55:54 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Dec 2008 11:25:05 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Dec 2008 13:27:43 GMT",
"version": "v3"
},
{
"created": "Tue, 6 Jan 2009 16:04:12 GMT",
"version": "v4"
},
{
"created": "Wed, 25 Feb 2009 15:32:35 GMT",
"version": "v5"
},
{
"created": "Sat, 28 Mar 2009 10:22:58 GMT",
"version": "v6"
}
] | 2009-11-13 | [
[
"Klinkhamer",
"F. R.",
""
],
[
"Volovik",
"G. E.",
""
]
] | In previous work, q-theory was introduced to describe the gravitating macroscopic behavior of a conserved microscopic variable q. In this article, the gluon condensate of quantum chromodynamics is considered in terms of q-theory. The remnant vacuum energy density (i.e., cosmological constant) of an expanding universe is estimated as K_{QCD}^3 / E_{Planck}^2, with string tension K_{QCD} \approx (10^2 MeV)^2 and gravitational scale E_{Planck} \approx 10^{19} GeV. The only input for this estimate is general relativity, quantum chromodynamics, and the Hubble expansion of the present Universe. |
gr-qc/0007015 | Lorenzo Iorio | Erricos C. Pavlis and Lorenzo Iorio | The impact of tidal errors on the determination of the Lense-Thirring
effect from satellite laser ranging | 24 pages, 4 tables, 6 figures, submitted to Int. Journal of Mod.
Phys. D. Changes in auctorship, references and content | Int.J.Mod.Phys.D11:599-618,2002 | 10.1142/S0218271802001883 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | null | The general relativistic Lense-Thirring effect can be detected by means of a
suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS
II satellites. While this observable is not affected by the orbital
perturbation induced by the zonal Earth solid and ocean tides, it is sensitive
to those generated by the tesseral and sectorial tides. The assessment of their
influence on the measurement of the parameter mu, with which the
gravitomagnetic effect is accounted for, is the goal of this paper. After
simulating the combined residual curve by calculating accurately the
mismodeling of the more effective tidal perturbations, it has been found that,
while the solid tides affect the recovery of mu at a level always well below
1%, for the ocean tides and the other long-period signals Delta mu depends
strongly on the observational period and the noise level: Delta mu(tides)
amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and
SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years,
on the perigee of LAGEOS II yield to a maximum systematic uncertainty on
$\m_{LT}$ of less than 4% over different observational periods. The zonal
18.6-year tide does not affect the combined residuals.
| [
{
"created": "Mon, 10 Jul 2000 08:49:32 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jan 2001 16:32:10 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Jan 2001 17:58:03 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Pavlis",
"Erricos C.",
""
],
[
"Iorio",
"Lorenzo",
""
]
] | The general relativistic Lense-Thirring effect can be detected by means of a suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS II satellites. While this observable is not affected by the orbital perturbation induced by the zonal Earth solid and ocean tides, it is sensitive to those generated by the tesseral and sectorial tides. The assessment of their influence on the measurement of the parameter mu, with which the gravitomagnetic effect is accounted for, is the goal of this paper. After simulating the combined residual curve by calculating accurately the mismodeling of the more effective tidal perturbations, it has been found that, while the solid tides affect the recovery of mu at a level always well below 1%, for the ocean tides and the other long-period signals Delta mu depends strongly on the observational period and the noise level: Delta mu(tides) amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years, on the perigee of LAGEOS II yield to a maximum systematic uncertainty on $\m_{LT}$ of less than 4% over different observational periods. The zonal 18.6-year tide does not affect the combined residuals. |
1704.00353 | Jan Sbierski | Gregory J. Galloway, Eric Ling, Jan Sbierski | Timelike completeness as an obstruction to $C^0$-extensions | v2: pertinent citations added and minor changes, v3: small
refinements and improvements; theorem added, v4: added figure, minor changes,
version accepted for publication in CMP | null | 10.1007/s00220-017-3019-2 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of low regularity (in-)extendibility of Lorentzian manifolds is
motivated by the question whether a given solution to the Einstein equations
can be extended (or is maximal) as a weak solution. In this paper we show that
a timelike complete and globally hyperbolic Lorentzian manifold is
$C^0$-inextendible. For the proof we make use of the result, recently
established by S\"amann [17], that even for \emph{continuous} Lorentzian
manifolds that are globally hyperbolic, there exists a length-maximizing causal
curve between any two causally related points.
| [
{
"created": "Sun, 2 Apr 2017 19:24:57 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Apr 2017 13:50:58 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Apr 2017 15:39:10 GMT",
"version": "v3"
},
{
"created": "Thu, 2 Nov 2017 16:58:18 GMT",
"version": "v4"
}
] | 2017-12-06 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Ling",
"Eric",
""
],
[
"Sbierski",
"Jan",
""
]
] | The study of low regularity (in-)extendibility of Lorentzian manifolds is motivated by the question whether a given solution to the Einstein equations can be extended (or is maximal) as a weak solution. In this paper we show that a timelike complete and globally hyperbolic Lorentzian manifold is $C^0$-inextendible. For the proof we make use of the result, recently established by S\"amann [17], that even for \emph{continuous} Lorentzian manifolds that are globally hyperbolic, there exists a length-maximizing causal curve between any two causally related points. |
1311.5307 | Rong-Jia Yang | Rong-Jia Yang, Bohai Chen, Jun Li, Jingzhao Qi | The evolution of the power law k-essence cosmology | 9 pages, 4 figures, some comments are added | Astrophys. Space Sci. 356 (2015) 399-405 | 10.1007/s10509-014-2218-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the evolution of the power law k-essence field in FRWL
spacetime. The autonomous dynamical system and critical points are obtained.
The corresponding cosmological parameters, such as $\Omega _{\phi }$ and
$w_{\phi }$, are calculated at these critical points. We find it is possible to
achieve an equation of state crossing through $-1$ for k-essence field. The
results we obtained indicate that the power law k-essence dark energy model can
be compatible with observations.
| [
{
"created": "Thu, 21 Nov 2013 03:54:30 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jan 2014 10:01:36 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Mar 2015 14:16:49 GMT",
"version": "v3"
}
] | 2015-03-24 | [
[
"Yang",
"Rong-Jia",
""
],
[
"Chen",
"Bohai",
""
],
[
"Li",
"Jun",
""
],
[
"Qi",
"Jingzhao",
""
]
] | We investigate the evolution of the power law k-essence field in FRWL spacetime. The autonomous dynamical system and critical points are obtained. The corresponding cosmological parameters, such as $\Omega _{\phi }$ and $w_{\phi }$, are calculated at these critical points. We find it is possible to achieve an equation of state crossing through $-1$ for k-essence field. The results we obtained indicate that the power law k-essence dark energy model can be compatible with observations. |
1612.09308 | Charalampos Markakis | Charalampos Markakis, K\=oji Ury\=u, Eric Gourgoulhon, Jean-Philippe
Nicolas, Nils Andersson, Athina Pouri, Vojtech Witzany | Conservation laws and evolution schemes in geodesic, hydrodynamic and
magnetohydrodynamic flows | 23 pages | Phys. Rev. D 96, 064019 (2017) | 10.1103/PhysRevD.96.064019 | null | gr-qc astro-ph.HE math-ph math.MP physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Carter and Lichnerowicz have established that barotropic fluid flows are
conformally geodesic and obey Hamilton's principle. This variational approach
can accommodate neutral, or charged and poorly conducting, fluids. We show
that, unlike what has been previously thought, this approach can also
accommodate perfectly conducting magnetofluids, via the Bekenstein-Oron
description of ideal magnetohydrodynamics. When Noether symmetries associated
with Killing vectors or tensors are present in geodesic flows, they lead to
constants of motion polynomial in the momenta. We generalize these concepts to
hydrodynamic flows. Moreover, the Hamiltonian descriptions of ideal
magnetohydrodynamics allow one to cast the evolution equations into a
hyperbolic form useful for evolving rotating or binary compact objects with
magnetic fields in numerical general relativity. Conserved circulation laws,
such as those of Kelvin, Alfv\'en and Bekenstein-Oron, emerge simply as special
cases of the Poincar\'e-Cartan integral invariant of Hamiltonian systems. We
use this approach to obtain an extension of Kelvin's theorem to baroclinic
(non-isentropic) fluids, based on a temperature-dependent time parameter. We
further extend this result to perfectly or poorly conducting baroclinic
magnetoflows. Finally, in the barotropic case, such magnetoflows are shown to
also be geodesic, albeit in a Finsler (rather than Riemann) space.
| [
{
"created": "Thu, 29 Dec 2016 21:16:34 GMT",
"version": "v1"
}
] | 2017-09-20 | [
[
"Markakis",
"Charalampos",
""
],
[
"Uryū",
"Kōji",
""
],
[
"Gourgoulhon",
"Eric",
""
],
[
"Nicolas",
"Jean-Philippe",
""
],
[
"Andersson",
"Nils",
""
],
[
"Pouri",
"Athina",
""
],
[
"Witzany",
"Vojtech",
""
]
] | Carter and Lichnerowicz have established that barotropic fluid flows are conformally geodesic and obey Hamilton's principle. This variational approach can accommodate neutral, or charged and poorly conducting, fluids. We show that, unlike what has been previously thought, this approach can also accommodate perfectly conducting magnetofluids, via the Bekenstein-Oron description of ideal magnetohydrodynamics. When Noether symmetries associated with Killing vectors or tensors are present in geodesic flows, they lead to constants of motion polynomial in the momenta. We generalize these concepts to hydrodynamic flows. Moreover, the Hamiltonian descriptions of ideal magnetohydrodynamics allow one to cast the evolution equations into a hyperbolic form useful for evolving rotating or binary compact objects with magnetic fields in numerical general relativity. Conserved circulation laws, such as those of Kelvin, Alfv\'en and Bekenstein-Oron, emerge simply as special cases of the Poincar\'e-Cartan integral invariant of Hamiltonian systems. We use this approach to obtain an extension of Kelvin's theorem to baroclinic (non-isentropic) fluids, based on a temperature-dependent time parameter. We further extend this result to perfectly or poorly conducting baroclinic magnetoflows. Finally, in the barotropic case, such magnetoflows are shown to also be geodesic, albeit in a Finsler (rather than Riemann) space. |
1403.2424 | Shahram Jalalzadeh | S. Jalalzadeh and P. V. Moniz | Dirac observables and boundary proposals in quantum cosmology | 6 pages, no figures, to appear in Phys. Rev. D | Phys. Rev. D 89, (2014) 083504 | 10.1103/PhysRevD.89.083504 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the reduced phase space quantization of a closed Friedmann Universe,
where matter content is constituted by two (no-interacting) fluids, namely dust
(or cold dark matter) and radiation. It is shown that, for this particular
model, specific boundary conditions can be related to the algebra of Dirac
observables.
| [
{
"created": "Mon, 10 Mar 2014 21:57:28 GMT",
"version": "v1"
}
] | 2014-07-28 | [
[
"Jalalzadeh",
"S.",
""
],
[
"Moniz",
"P. V.",
""
]
] | We study the reduced phase space quantization of a closed Friedmann Universe, where matter content is constituted by two (no-interacting) fluids, namely dust (or cold dark matter) and radiation. It is shown that, for this particular model, specific boundary conditions can be related to the algebra of Dirac observables. |
gr-qc/9704018 | Alan Gray Wiseman | Alan G. Wiseman (Caltech) | The central density of neutron stars in close binaries | RevTex, submitted to PRL, 4 pages | Phys.Rev.Lett. 79 (1997) 1189-1192 | 10.1103/PhysRevLett.79.1189 | GRP-463 | gr-qc | null | Recent numerical simulations of coalescing binary neutron stars conducted by
Wilson, Mathews and Marronetti (WMM) show a rising central energy density of
the stars as the orbital separation shrinks, i.e. the stars are individually
crushed as they near coalescence. They claim this ``star-crushing'' effect is
partially due to a non-linear, first post-Newtonian order enhancement of the
self-gravity of each star caused by the presence of the other star. We present
a concrete calculation which shows, within general relativity, first
post-Newtonian order interactions with the other star leave the central energy
density unchanged as the orbital radius shrinks. The results presented here are
in sharp disagreement with the WMM claim. However, alternative gravitational
theories, such as Brans-Dicke theory, can exhibit a small crushing effect in
the binary constituents as they near coalescence. We show that the absence of
the star-crushing effect at first post-Newtonian order is related to adherence
to the strong equivalence principle.
| [
{
"created": "Tue, 8 Apr 1997 01:27:17 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Wiseman",
"Alan G.",
"",
"Caltech"
]
] | Recent numerical simulations of coalescing binary neutron stars conducted by Wilson, Mathews and Marronetti (WMM) show a rising central energy density of the stars as the orbital separation shrinks, i.e. the stars are individually crushed as they near coalescence. They claim this ``star-crushing'' effect is partially due to a non-linear, first post-Newtonian order enhancement of the self-gravity of each star caused by the presence of the other star. We present a concrete calculation which shows, within general relativity, first post-Newtonian order interactions with the other star leave the central energy density unchanged as the orbital radius shrinks. The results presented here are in sharp disagreement with the WMM claim. However, alternative gravitational theories, such as Brans-Dicke theory, can exhibit a small crushing effect in the binary constituents as they near coalescence. We show that the absence of the star-crushing effect at first post-Newtonian order is related to adherence to the strong equivalence principle. |
2401.01567 | Ran Chen | Ran Chen, Yi-Ying Wang, Lei Zu, and Yi-Zhong Fan | Prospects of constraining $f(T)$ gravity with the third-generation
gravitational-wave detectors | 12 pages, 6 figures, 3 tables | Phys. Rev. D 109, 024041 (2024) | 10.1103/PhysRevD.109.024041 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mergers of binary compact objects, accompanied with electromagnetic (EM)
counterparts, offer excellent opportunities to explore varied cosmological
models, since gravitational waves (GWs) and EM counterparts always carry the
information of luminosity distance and redshift, respectively. $f(T)$ gravity,
which alters the background evolution and provides a friction term in the
propagation of GWs, can be tested by comparing the modified GW luminosity
distance with the EM luminosity distance. Considering the third-generation
gravitational-wave detectors, Einstein Telescope and two cosmic explorers, we
simulate a series of GW events of binary neutron stars and
neutron-star-black-hole binaries with EM counterparts. These simulations can be
used to constrain $f(T)$ gravity [especially the power-law model
$f(T)=T+\alpha(-T)^\beta$ in this work] and other cosmological parameters, such
as $\beta$ and the Hubble constant. In addition, combining simulations with
current observations of type Ia supernovae and baryon acoustic oscillations, we
obtain tighter limitations for $f(T)$ gravity. We find that the estimated
precision significantly improved when all three datasets are combined ($\Delta
\beta \sim 0.03$), compared to analyzing the current observations alone
($\Delta \beta \sim 0.3$). Simultaneously, the uncertainty of the Hubble
constant can be reduced to approximately $1\%$.
| [
{
"created": "Wed, 3 Jan 2024 06:44:26 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jan 2024 06:50:44 GMT",
"version": "v2"
}
] | 2024-01-31 | [
[
"Chen",
"Ran",
""
],
[
"Wang",
"Yi-Ying",
""
],
[
"Zu",
"Lei",
""
],
[
"Fan",
"Yi-Zhong",
""
]
] | Mergers of binary compact objects, accompanied with electromagnetic (EM) counterparts, offer excellent opportunities to explore varied cosmological models, since gravitational waves (GWs) and EM counterparts always carry the information of luminosity distance and redshift, respectively. $f(T)$ gravity, which alters the background evolution and provides a friction term in the propagation of GWs, can be tested by comparing the modified GW luminosity distance with the EM luminosity distance. Considering the third-generation gravitational-wave detectors, Einstein Telescope and two cosmic explorers, we simulate a series of GW events of binary neutron stars and neutron-star-black-hole binaries with EM counterparts. These simulations can be used to constrain $f(T)$ gravity [especially the power-law model $f(T)=T+\alpha(-T)^\beta$ in this work] and other cosmological parameters, such as $\beta$ and the Hubble constant. In addition, combining simulations with current observations of type Ia supernovae and baryon acoustic oscillations, we obtain tighter limitations for $f(T)$ gravity. We find that the estimated precision significantly improved when all three datasets are combined ($\Delta \beta \sim 0.03$), compared to analyzing the current observations alone ($\Delta \beta \sim 0.3$). Simultaneously, the uncertainty of the Hubble constant can be reduced to approximately $1\%$. |
2101.08186 | Subhajit Barman | Subhajit Barman and Bibhas Ranjan Majhi | Radiative process of two entangled uniformly accelerated atoms in a
thermal bath: a possible case of anti-Unruh event | Minor modifications, to appear in JHEP | JHEP 03 (2021) 245 | 10.1007/JHEP03(2021)245 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the radiative process of two entangled two-level atoms uniformly
accelerated in a thermal bath, coupled to a massless scalar field. First, using
the positive frequency Wightman function from the Minkowski modes with a
Rindler transformation we provide the transition probabilities for the
transitions from maximally entangled symmetric and anti-symmetric Bell states
to the collective excited state in $(1+1)$ and $(1+3)$ dimensions. We observe a
possible case of \emph{anti-Unruh-like} event in these transition
probabilities, though the $(1+1)$ and $(1+3)$ dimensional results are not
completely equivalent. We infer that thermal bath plays a major role in the
occurrence of the anti-Unruh-like effect, as it is also present in the
transition probabilities corresponding to a single detector in this case.
Second, we have considered the Green's functions in terms of the Rindler modes
with the vacuum of Unruh modes for estimating the same. Here the anti-Unruh
effect appears only for the transition from the anti-symmetric state to the
collective excited state. It is noticed that here the $(1+1)$ and $(1+3)$
dimensional results are equivalent, and for a single detector, we do not
observe any anti-Unruh effect. This suggests that the entanglement between the
states of the atoms is the main cause for the observed anti-Unruh effect in
this case. In going through the investigation, we find that the transition
probability for a single detector case is symmetric under the interchange
between the thermal bath's temperature and the Unruh temperature for Rindler
mode analysis; whereas this is not the case for Minkowski mode. We further
comment on whether this observation may shed light on the analogy between an
accelerated observer and a real thermal bath. An elaborate investigation for
the classifications of our observed anti-Unruh effects is also thoroughly
demonstrated.
| [
{
"created": "Wed, 20 Jan 2021 15:31:13 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2021 10:00:19 GMT",
"version": "v2"
}
] | 2021-05-25 | [
[
"Barman",
"Subhajit",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | We study the radiative process of two entangled two-level atoms uniformly accelerated in a thermal bath, coupled to a massless scalar field. First, using the positive frequency Wightman function from the Minkowski modes with a Rindler transformation we provide the transition probabilities for the transitions from maximally entangled symmetric and anti-symmetric Bell states to the collective excited state in $(1+1)$ and $(1+3)$ dimensions. We observe a possible case of \emph{anti-Unruh-like} event in these transition probabilities, though the $(1+1)$ and $(1+3)$ dimensional results are not completely equivalent. We infer that thermal bath plays a major role in the occurrence of the anti-Unruh-like effect, as it is also present in the transition probabilities corresponding to a single detector in this case. Second, we have considered the Green's functions in terms of the Rindler modes with the vacuum of Unruh modes for estimating the same. Here the anti-Unruh effect appears only for the transition from the anti-symmetric state to the collective excited state. It is noticed that here the $(1+1)$ and $(1+3)$ dimensional results are equivalent, and for a single detector, we do not observe any anti-Unruh effect. This suggests that the entanglement between the states of the atoms is the main cause for the observed anti-Unruh effect in this case. In going through the investigation, we find that the transition probability for a single detector case is symmetric under the interchange between the thermal bath's temperature and the Unruh temperature for Rindler mode analysis; whereas this is not the case for Minkowski mode. We further comment on whether this observation may shed light on the analogy between an accelerated observer and a real thermal bath. An elaborate investigation for the classifications of our observed anti-Unruh effects is also thoroughly demonstrated. |
1902.01703 | Hooman Moradpour | H. Moradpour, C. Corda, A. H. Ziaie, S. Ghaffari | The extended uncertainty principle inspires the R\'{e}nyi entropy | null | EPL, (2019) | 10.1209/0295-5075/127/60006 | 127, 60006 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the extended uncertainty principle (EUP) in order to obtain the
R\'{e}nyi entropy for a black hole (BH). The result implies that the
non-extensivity parameter, appeared in the R\'{e}nyi entropy formalism, may be
evaluated from the considerations which lead to EUP. It is also shown that, for
excited BHs, the R\'{e}nyi entropy is a function of the BH principal quantum
number, i.e. the BH quantum excited state. Temperature and heat capacity of the
excited BHs are also investigated addressing two phases while only one of them
can be stable. At this situation, whereas entropy is vanished, temperature may
take a non-zero positive minimum value, depending on the value of the
non-extensivity parameter. The evaporation time of excited BH has also been
studied.
| [
{
"created": "Sun, 3 Feb 2019 05:12:57 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jun 2019 07:56:10 GMT",
"version": "v2"
}
] | 2019-11-12 | [
[
"Moradpour",
"H.",
""
],
[
"Corda",
"C.",
""
],
[
"Ziaie",
"A. H.",
""
],
[
"Ghaffari",
"S.",
""
]
] | We use the extended uncertainty principle (EUP) in order to obtain the R\'{e}nyi entropy for a black hole (BH). The result implies that the non-extensivity parameter, appeared in the R\'{e}nyi entropy formalism, may be evaluated from the considerations which lead to EUP. It is also shown that, for excited BHs, the R\'{e}nyi entropy is a function of the BH principal quantum number, i.e. the BH quantum excited state. Temperature and heat capacity of the excited BHs are also investigated addressing two phases while only one of them can be stable. At this situation, whereas entropy is vanished, temperature may take a non-zero positive minimum value, depending on the value of the non-extensivity parameter. The evaporation time of excited BH has also been studied. |
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