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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2109.02816 | Cosimo Bambi | Bakhtiyor Narzilloev, Sanjar Shaymatov, Ibrar Hussain, Ahmadjon
Abdujabbarov, Bobomurat Ahmedov, Cosimo Bambi | Motion of Particles and Gravitational Lensing Around (2+1)-dimensional
BTZ black holes in Gauss-Bonnet Gravity | 11 pages, 6 figures. Accepted for publication in EPJC | Eur. Phys. J. C (2021) 81:849 | 10.1140/epjc/s10052-021-09617-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study motion of test particles and photons in the vicinity of (2+1)
dimensional Gauss-Bonnet (GB) BTZ black hole. We find that the presence of the
coupling constant serves as an attractive gravitational charge, shifting the
innermost stable circular orbits outward with respect to the one for this
theory in 4 dimensions. Further we consider the gravitational lensing, to test
the GB gravity in (2+1) dimensions and show that the presence of GB parameter
causes the bending angle to grow up first with the increase of the inverse of
closest approach distance, $u_0$, then have its maximum value for specific
$u_0^*$, and then reduce until zero. We also show that increase in the value of
the GB parameter makes the bending angle smaller and the increase in the
absolute value of the negative cosmological constant produces opposite effect
on this angle.
| [
{
"created": "Tue, 7 Sep 2021 02:02:38 GMT",
"version": "v1"
}
] | 2021-09-29 | [
[
"Narzilloev",
"Bakhtiyor",
""
],
[
"Shaymatov",
"Sanjar",
""
],
[
"Hussain",
"Ibrar",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Bambi",
"Cosimo",
""
]
] | We study motion of test particles and photons in the vicinity of (2+1) dimensional Gauss-Bonnet (GB) BTZ black hole. We find that the presence of the coupling constant serves as an attractive gravitational charge, shifting the innermost stable circular orbits outward with respect to the one for this theory in 4 dimensions. Further we consider the gravitational lensing, to test the GB gravity in (2+1) dimensions and show that the presence of GB parameter causes the bending angle to grow up first with the increase of the inverse of closest approach distance, $u_0$, then have its maximum value for specific $u_0^*$, and then reduce until zero. We also show that increase in the value of the GB parameter makes the bending angle smaller and the increase in the absolute value of the negative cosmological constant produces opposite effect on this angle. |
gr-qc/9711015 | Steve Brandt | S. R. Brandt, and B. Bruegmann | BH Punctures as Initial Data for General Relativity | 3 pages, 2 postscript figures, LaTeX, uses mprocl.sty (available at
http://shemesh.fiz.huji.ac.il/MG8/submission.html) To appear in the
proceedings of the Marcel Grossmann 8 (Jerusalem, 1997) | null | null | EFI-94-11 | gr-qc | null | We construct initial data for several black holes with arbitrary momenta and
spins by a new method that is based on a compactification of Brill-Lindquist
wormholes. When treated numerically, the method leads to a significant
simplification over the conventional approach which is based on throats and an
isometry condition.
| [
{
"created": "Wed, 5 Nov 1997 17:11:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brandt",
"S. R.",
""
],
[
"Bruegmann",
"B.",
""
]
] | We construct initial data for several black holes with arbitrary momenta and spins by a new method that is based on a compactification of Brill-Lindquist wormholes. When treated numerically, the method leads to a significant simplification over the conventional approach which is based on throats and an isometry condition. |
1601.06436 | Torsten Asselmeyer-Maluga | Torsten Asselmeyer-Maluga | Smooth quantum gravity: Exotic smoothness and Quantum gravity | 52 pages, 11 figure, on the occasion of the 80-th birthday of Carl H.
Brans To appear in "At the Frontiers of Spacetime: Scalar-Tensor Theory,
Bell's Inequality, Mach's Principle, Exotic Smoothness" Springer 2016, in
honor of Carl Brans's 80th birthday. arXiv admin note: text overlap with
arXiv:q-alg/9710003, arXiv:1007.4094, arXiv:gr-qc/0312060 by other authors | null | null | null | gr-qc hep-th math-ph math.GT math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Over the last two decades, many unexpected relations between exotic
smoothness, e.g. exotic $\mathbb{R}^{4}$, and quantum field theory were found.
Some of these relations are rooted in a relation to superstring theory and
quantum gravity. Therefore one would expect that exotic smoothness is directly
related to the quantization of general relativity. In this article we will
support this conjecture and develop a new approach to quantum gravity called
\emph{smooth quantum gravity} by using smooth 4-manifolds with an exotic
smoothness structure. In particular we discuss the appearance of a wildly
embedded 3-manifold which we identify with a quantum state. Furthermore, we
analyze this quantum state by using foliation theory and relate it to an
element in an operator algebra. Then we describe a set of geometric,
non-commutative operators, the skein algebra, which can be used to determine
the geometry of a 3-manifold. This operator algebra can be understood as a
deformation quantization of the classical Poisson algebra of observables given
by holonomies. The structure of this operator algebra induces an action by
using the quantized calculus of Connes. The scaling behavior of this action is
analyzed to obtain the classical theory of General Relativity (GRT) for large
scales. This approach has some obvious properties: there are non-linear
gravitons, a connection to lattice gauge field theory and a dimensional
reduction from 4D to 2D. Some cosmological consequences like the appearance of
an inflationary phase are also discussed. At the end we will get the simple
picture that the change from the standard $\mathbb{R}^{4}$ to the exotic
$R^{4}$ is a quantization of geometry.
| [
{
"created": "Sun, 24 Jan 2016 22:27:05 GMT",
"version": "v1"
}
] | 2016-01-27 | [
[
"Asselmeyer-Maluga",
"Torsten",
""
]
] | Over the last two decades, many unexpected relations between exotic smoothness, e.g. exotic $\mathbb{R}^{4}$, and quantum field theory were found. Some of these relations are rooted in a relation to superstring theory and quantum gravity. Therefore one would expect that exotic smoothness is directly related to the quantization of general relativity. In this article we will support this conjecture and develop a new approach to quantum gravity called \emph{smooth quantum gravity} by using smooth 4-manifolds with an exotic smoothness structure. In particular we discuss the appearance of a wildly embedded 3-manifold which we identify with a quantum state. Furthermore, we analyze this quantum state by using foliation theory and relate it to an element in an operator algebra. Then we describe a set of geometric, non-commutative operators, the skein algebra, which can be used to determine the geometry of a 3-manifold. This operator algebra can be understood as a deformation quantization of the classical Poisson algebra of observables given by holonomies. The structure of this operator algebra induces an action by using the quantized calculus of Connes. The scaling behavior of this action is analyzed to obtain the classical theory of General Relativity (GRT) for large scales. This approach has some obvious properties: there are non-linear gravitons, a connection to lattice gauge field theory and a dimensional reduction from 4D to 2D. Some cosmological consequences like the appearance of an inflationary phase are also discussed. At the end we will get the simple picture that the change from the standard $\mathbb{R}^{4}$ to the exotic $R^{4}$ is a quantization of geometry. |
2110.00799 | Recai Erdem | Recai Erdem, Bet\"ul Demirkaya, and Kemal G\"ultekin | Curved space and particle physics effects on the formation of
Bose-Einstein condensation around a Reissner-Nordstr\"om black hole | The submitted version of the paper. The revised form of the paper is
published in European Physical Journal Plus 136 (2021) 972 | null | null | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by-sa/4.0/ | We consider two scalar fields interacting through a $\chi^*\chi\phi^*\phi$
term in the presence of a Reissner-Nordstrom black hole. Initially, only $\chi$
particles are present. We find that the produced $\phi$ particles are localized
in a region around the black hole and have a tendency towards condensation
provided that $\phi$ particles are much heavier than the $\chi$ particles. We
also find that such a configuration is phenomenologically viable only if the
scalars and the black hole have dark electric charges.
| [
{
"created": "Sat, 2 Oct 2021 13:26:20 GMT",
"version": "v1"
}
] | 2021-10-05 | [
[
"Erdem",
"Recai",
""
],
[
"Demirkaya",
"Betül",
""
],
[
"Gültekin",
"Kemal",
""
]
] | We consider two scalar fields interacting through a $\chi^*\chi\phi^*\phi$ term in the presence of a Reissner-Nordstrom black hole. Initially, only $\chi$ particles are present. We find that the produced $\phi$ particles are localized in a region around the black hole and have a tendency towards condensation provided that $\phi$ particles are much heavier than the $\chi$ particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges. |
gr-qc/0409076 | Emilio Elizalde | Emilio Elizalde | Cosmology: Techniques and Observations | 64 pages, 12 figures, lectures | null | null | null | gr-qc astro-ph hep-th | null | These lectures were addressed to nonspecialists willing to learn some basic
facts, approaches, tools and observational evidence which conform modern
cosmology. The aim is also to try to complement the many excellent treatises
that exists on the subject (an exhaustive treatment being in any case
impossible for lack of time, in the lectures, and of space here), instead of
trying to cover everything in a telegraphic way. We start by recalling in the
introduction a couple of philosophical questions that have always upset
inquiring minds. We then present some original mathematical approaches to
investigate a number of basic questions, as the comparison of two point
distributions (each point corresponding to a galaxy or galaxy cluster), the use
of non-standard statistics in the analysis of possible non-Gaussianities, and
the use of zeta regularization in the study of the contributions of vacuum
energy effects at the cosmological scale. And we also summarize a number of
important issues which are both undoubtedly beautiful (from the physical
viewpoint) and useful in present-day observational cosmology. To finish, the
reader should be warned that, for the reasons already given and lack of space,
some fundamental issues, as inflation, quantum gravity and string theoretical
fundamental approaches to cosmology will not be dealt with here. A minimal
treatment of any of them would consume more pages than the ones at disposal
and, again, a number of excellent treatments of these subjects are available.
| [
{
"created": "Mon, 20 Sep 2004 16:27:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Elizalde",
"Emilio",
""
]
] | These lectures were addressed to nonspecialists willing to learn some basic facts, approaches, tools and observational evidence which conform modern cosmology. The aim is also to try to complement the many excellent treatises that exists on the subject (an exhaustive treatment being in any case impossible for lack of time, in the lectures, and of space here), instead of trying to cover everything in a telegraphic way. We start by recalling in the introduction a couple of philosophical questions that have always upset inquiring minds. We then present some original mathematical approaches to investigate a number of basic questions, as the comparison of two point distributions (each point corresponding to a galaxy or galaxy cluster), the use of non-standard statistics in the analysis of possible non-Gaussianities, and the use of zeta regularization in the study of the contributions of vacuum energy effects at the cosmological scale. And we also summarize a number of important issues which are both undoubtedly beautiful (from the physical viewpoint) and useful in present-day observational cosmology. To finish, the reader should be warned that, for the reasons already given and lack of space, some fundamental issues, as inflation, quantum gravity and string theoretical fundamental approaches to cosmology will not be dealt with here. A minimal treatment of any of them would consume more pages than the ones at disposal and, again, a number of excellent treatments of these subjects are available. |
2209.12865 | Marco Antonelli | Lorenzo Gavassino, Marco Antonelli | Relativistic Liquids: GENERIC or EIT? | 16 pages, no figures. Published in CQG,
https://doi.org/10.1088/1361-6382/acc165 | Class. Quantum Grav. 40 (2023) 075012 (22pp) | 10.1088/1361-6382/acc165 | null | gr-qc astro-ph.HE physics.flu-dyn | http://creativecommons.org/licenses/by/4.0/ | We study the GENERIC hydrodynamic theory for relativistic liquids formulated
by Ottinger and collaborators. We use the maximum entropy principle to derive
its conditions for linear stability (in an arbitrary reference frame) and for
relativistic causality. In addition, we show that, in the linear regime, its
field equations can be recast into a symmetric-hyperbolic form. Once rewritten
in this way, the linearised field equations turn out to be a particular
realization of the Israel-Stewart theory, where some of the Israel-Stewart free
parameters are constrained. This also allows us to reinterpret the GENERIC
framework in view of the principles of Extended Irreversible Thermodynamics
(EIT) and to discuss its physical relevance to model (possibly viscoelastic)
fluids.
| [
{
"created": "Mon, 26 Sep 2022 17:31:56 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Mar 2023 13:46:40 GMT",
"version": "v2"
}
] | 2023-03-16 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
]
] | We study the GENERIC hydrodynamic theory for relativistic liquids formulated by Ottinger and collaborators. We use the maximum entropy principle to derive its conditions for linear stability (in an arbitrary reference frame) and for relativistic causality. In addition, we show that, in the linear regime, its field equations can be recast into a symmetric-hyperbolic form. Once rewritten in this way, the linearised field equations turn out to be a particular realization of the Israel-Stewart theory, where some of the Israel-Stewart free parameters are constrained. This also allows us to reinterpret the GENERIC framework in view of the principles of Extended Irreversible Thermodynamics (EIT) and to discuss its physical relevance to model (possibly viscoelastic) fluids. |
2203.00901 | Sobhan Kazempour | Amin Rezaei Akbarieh, Sobhan Kazempour, and Lijing Shao | Cosmology and perturbations in tachyonic massive gravity | null | Phys. Rev. D 105, 023501 (2022) | 10.1103/PhysRevD.105.023501 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | As massive gravity and its extensions offer physically well-defined
gravitational theories with a nonzero graviton mass, we present a new extension
of the de Rham-Gabadadze-Tolley (dRGT)massive gravity, which is tachyonic
massive gravity theory. We firstly introduce the new extension of the dRGT
massive gravity, constructed by adding a tachyonic term. We then find the
cosmological background equations, and present the analysis of
self-accelerating solutions. We examine the tensor perturbations to calculate
the dispersion relation of gravitational waves (GWs). In a special case, we
consider a constant tachyon potential for the tachyon field, and calculate the
equations of motion and self-accelerating solutions. Finally, we investigate
the background perturbations, which include tensor, vector, and scalar
perturbations in this case. We calculate the dispersion relation of GWs in the
FLRW cosmology in a tachyonic massive gravity theory. These analyses provide
potential inputs to future applications in cosmology and GWs propagation.
| [
{
"created": "Wed, 2 Mar 2022 07:14:37 GMT",
"version": "v1"
}
] | 2022-03-03 | [
[
"Akbarieh",
"Amin Rezaei",
""
],
[
"Kazempour",
"Sobhan",
""
],
[
"Shao",
"Lijing",
""
]
] | As massive gravity and its extensions offer physically well-defined gravitational theories with a nonzero graviton mass, we present a new extension of the de Rham-Gabadadze-Tolley (dRGT)massive gravity, which is tachyonic massive gravity theory. We firstly introduce the new extension of the dRGT massive gravity, constructed by adding a tachyonic term. We then find the cosmological background equations, and present the analysis of self-accelerating solutions. We examine the tensor perturbations to calculate the dispersion relation of gravitational waves (GWs). In a special case, we consider a constant tachyon potential for the tachyon field, and calculate the equations of motion and self-accelerating solutions. Finally, we investigate the background perturbations, which include tensor, vector, and scalar perturbations in this case. We calculate the dispersion relation of GWs in the FLRW cosmology in a tachyonic massive gravity theory. These analyses provide potential inputs to future applications in cosmology and GWs propagation. |
2103.11416 | Ming Zhang | Ming Zhang and Jie Jiang | NUT charges and black hole shadows | 7 pages | null | 10.1016/j.physletb.2021.136213 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the nontrivial effects of the NUT charges on the shadows of the
Kerr-Taub-NUT black holes seen by zero-angular-momentum-observers. Inclination
angles with which the observers gain maximal, locally extreme or minimal shadow
sizes and distortions are investigated for the black holes with different NUT
charges and distributions of string singularities. Typically, we discover that
when the observer approaches the string singularity, the shadow size can be
relatively very small while the shadow distortion being relatively quite large.
And exceptionally, we find that when the string singularity locates only at the
south pole axis of the black hole with large enough NUT charge, the shadow size
is maximal for a north pole observer.
| [
{
"created": "Sun, 21 Mar 2021 15:03:15 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Zhang",
"Ming",
""
],
[
"Jiang",
"Jie",
""
]
] | We study the nontrivial effects of the NUT charges on the shadows of the Kerr-Taub-NUT black holes seen by zero-angular-momentum-observers. Inclination angles with which the observers gain maximal, locally extreme or minimal shadow sizes and distortions are investigated for the black holes with different NUT charges and distributions of string singularities. Typically, we discover that when the observer approaches the string singularity, the shadow size can be relatively very small while the shadow distortion being relatively quite large. And exceptionally, we find that when the string singularity locates only at the south pole axis of the black hole with large enough NUT charge, the shadow size is maximal for a north pole observer. |
1007.1861 | Angelo Tartaglia | A. Di Virgilio, K. U. Schreiber, A. Gebauer, J-P. R. Wells, A.
Tartaglia, J. Belfi, N. Beverini, A.Ortolan | A laser gyroscope system to detect the Gravito-Magnetic effect on Earth | 9 pages, 6 figures. 2010 Honourable mention of the Gravity Research
Foundation; to be published on J. Mod. Phys. D | Int.J.Mod.Phys.D19:2331-2343,2010 | 10.1142/S0218271810018360 | null | gr-qc physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Large scale square ring laser gyros with a length of four meters on each side
are approaching a sensitivity of 1x10^-11 rad/s/sqrt(Hz). This is about the
regime required to measure the gravitomagnetic effect (Lense Thirring) of the
Earth. For an ensemble of linearly independent gyros each measurement signal
depends upon the orientation of each single axis gyro with respect to the
rotational axis of the Earth. Therefore at least 3 gyros are necessary to
reconstruct the complete angular orientation of the apparatus. In general, the
setup consists of several laser gyroscopes (we would prefer more than 3 for
sufficient redundancy), rigidly referenced to each other. Adding more gyros for
one plane of observation provides a cross-check against intra-system biases and
furthermore has the advantage of improving the signal to noise ratio by the
square root of the number of gyros. In this paper we analyze a system of two
pairs of identical gyros (twins) with a slightly different orientation with
respect to the Earth axis. The twin gyro configuration has several interesting
properties. The relative angle can be controlled and provides a useful null
measurement. A quadruple twin system could reach a 1% sensitivity after 3:2
years of data, provided each square ring has 6 m length on a side, the system
is shot noise limited and there is no source for 1/f- noise.
| [
{
"created": "Mon, 12 Jul 2010 10:36:15 GMT",
"version": "v1"
}
] | 2011-01-17 | [
[
"Di Virgilio",
"A.",
""
],
[
"Schreiber",
"K. U.",
""
],
[
"Gebauer",
"A.",
""
],
[
"Wells",
"J-P. R.",
""
],
[
"Tartaglia",
"A.",
""
],
[
"Belfi",
"J.",
""
],
[
"Beverini",
"N.",
""
],
[
"Ortolan",... | Large scale square ring laser gyros with a length of four meters on each side are approaching a sensitivity of 1x10^-11 rad/s/sqrt(Hz). This is about the regime required to measure the gravitomagnetic effect (Lense Thirring) of the Earth. For an ensemble of linearly independent gyros each measurement signal depends upon the orientation of each single axis gyro with respect to the rotational axis of the Earth. Therefore at least 3 gyros are necessary to reconstruct the complete angular orientation of the apparatus. In general, the setup consists of several laser gyroscopes (we would prefer more than 3 for sufficient redundancy), rigidly referenced to each other. Adding more gyros for one plane of observation provides a cross-check against intra-system biases and furthermore has the advantage of improving the signal to noise ratio by the square root of the number of gyros. In this paper we analyze a system of two pairs of identical gyros (twins) with a slightly different orientation with respect to the Earth axis. The twin gyro configuration has several interesting properties. The relative angle can be controlled and provides a useful null measurement. A quadruple twin system could reach a 1% sensitivity after 3:2 years of data, provided each square ring has 6 m length on a side, the system is shot noise limited and there is no source for 1/f- noise. |
1109.5602 | Sergio Dain | Sergio Dain and Jos\'e Luis Jaramillo and Mart\'in Reiris | Area-charge inequality for black holes | 21 pages, 2 figures | null | 10.1088/0264-9381/29/3/035013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inequality between area and charge $A\geq 4\pi Q^2$ for dynamical black
holes is proved. No symmetry assumption is made and charged matter fields are
included. Extensions of this inequality are also proved for regions in the
spacetime which are not necessarily black hole boundaries.
| [
{
"created": "Mon, 26 Sep 2011 15:30:26 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Dain",
"Sergio",
""
],
[
"Jaramillo",
"José Luis",
""
],
[
"Reiris",
"Martín",
""
]
] | The inequality between area and charge $A\geq 4\pi Q^2$ for dynamical black holes is proved. No symmetry assumption is made and charged matter fields are included. Extensions of this inequality are also proved for regions in the spacetime which are not necessarily black hole boundaries. |
1408.1235 | Sergey Sushkov | R.V. Korolev and Sergey V. Sushkov | Exact wormhole solutions with nonminimal kinetic coupling | 7 pages, 3 figures, to be submitted to PRD | null | 10.1103/PhysRevD.90.124025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider static spherically symmetric solutions in the scalar-tensor
theory of gravity with a scalar field possessing the nonminimal kinetic
coupling to the curvature. The lagrangian of the theory contains the term
$(\varepsilon g^{\mu\nu}+\eta G^{\mu \nu})\phi_{,\mu}\phi_{,\nu}$ and
represents a particular case of the general Horndeski lagrangian, which leads
to second-order equations of motion. We use the Rinaldi approach to construct
analytical solutions describing wormholes with nonminimal kinetic coupling. It
is shown that wormholes exist only if $\varepsilon=-1$ (phantom case) and
$\eta>0$. The wormhole throat connects two anti-de Sitter spacetimes. The
wormhole metric has a coordinate singularity at the throat. However, since all
curvature invariants are regular, there is no curvature singularity there.
| [
{
"created": "Wed, 6 Aug 2014 10:20:04 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Korolev",
"R. V.",
""
],
[
"Sushkov",
"Sergey V.",
""
]
] | We consider static spherically symmetric solutions in the scalar-tensor theory of gravity with a scalar field possessing the nonminimal kinetic coupling to the curvature. The lagrangian of the theory contains the term $(\varepsilon g^{\mu\nu}+\eta G^{\mu \nu})\phi_{,\mu}\phi_{,\nu}$ and represents a particular case of the general Horndeski lagrangian, which leads to second-order equations of motion. We use the Rinaldi approach to construct analytical solutions describing wormholes with nonminimal kinetic coupling. It is shown that wormholes exist only if $\varepsilon=-1$ (phantom case) and $\eta>0$. The wormhole throat connects two anti-de Sitter spacetimes. The wormhole metric has a coordinate singularity at the throat. However, since all curvature invariants are regular, there is no curvature singularity there. |
2302.06627 | Nils Siemonsen | Nils Siemonsen, William E. East | Binary boson stars: Merger dynamics and formation of rotating remnant
stars | 29 pages, 20 figures; updated to match PRD version | Phys. Rev. D 107, 124018 (2023) | 10.1103/PhysRevD.107.124018 | null | gr-qc astro-ph.HE hep-ph | http://creativecommons.org/licenses/by/4.0/ | Scalar boson stars have attracted attention as simple models for exploring
the nonlinear dynamics of a large class of ultra compact and black hole
mimicking objects. Here, we study the impact of interactions in the scalar
matter making up these stars. In particular, we show the pivotal role the
scalar phase and vortex structure play during the late inspiral, merger, and
post-merger oscillations of a binary boson star, as well as their impact on the
properties of the merger remnant. To that end, we construct constraint
satisfying binary boson star initial data and numerically evolve the nonlinear
set of Einstein-Klein-Gordon equations. We demonstrate that the scalar
interactions can significantly affect the inspiral gravitational wave amplitude
and phase, and the length of a potential hypermassive phase shortly after
merger. If a black hole is formed after merger, we find its spin angular
momentum to be consistent with similar binary black hole and binary neutron
star merger remnants. Furthermore, we formulate a mapping that approximately
predicts the remnant properties of any given binary boson star merger. Guided
by this mapping, we use numerical evolutions to explicitly demonstrate, for the
first time, that rotating boson stars can form as remnants from the merger of
two non-spinning boson stars. We characterize this new formation mechanism and
discuss its robustness. Finally, we comment on the implications for rotating
Proca stars.
| [
{
"created": "Mon, 13 Feb 2023 19:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2023 14:37:54 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Siemonsen",
"Nils",
""
],
[
"East",
"William E.",
""
]
] | Scalar boson stars have attracted attention as simple models for exploring the nonlinear dynamics of a large class of ultra compact and black hole mimicking objects. Here, we study the impact of interactions in the scalar matter making up these stars. In particular, we show the pivotal role the scalar phase and vortex structure play during the late inspiral, merger, and post-merger oscillations of a binary boson star, as well as their impact on the properties of the merger remnant. To that end, we construct constraint satisfying binary boson star initial data and numerically evolve the nonlinear set of Einstein-Klein-Gordon equations. We demonstrate that the scalar interactions can significantly affect the inspiral gravitational wave amplitude and phase, and the length of a potential hypermassive phase shortly after merger. If a black hole is formed after merger, we find its spin angular momentum to be consistent with similar binary black hole and binary neutron star merger remnants. Furthermore, we formulate a mapping that approximately predicts the remnant properties of any given binary boson star merger. Guided by this mapping, we use numerical evolutions to explicitly demonstrate, for the first time, that rotating boson stars can form as remnants from the merger of two non-spinning boson stars. We characterize this new formation mechanism and discuss its robustness. Finally, we comment on the implications for rotating Proca stars. |
0711.0117 | Kristina Giesel | K. Giesel, S. Hofmann, T. Thiemann, O. Winkler | Manifestly Gauge-Invariant General Relativistic Perturbation Theory: II.
FRW Background and First Order | 51 pages, no figures | Class.Quant.Grav.27:055006,2010 | 10.1088/0264-9381/27/5/055006 | AEI-2007-151 | gr-qc astro-ph hep-th | null | In our companion paper we identified a complete set of manifestly
gauge-invariant observables for general relativity. This was possible by
coupling the system of gravity and matter to pressureless dust which plays the
role of a dynamically coupled observer. The evolution of those observables is
governed by a physical Hamiltonian and we derived the corresponding equations
of motion. Linear perturbation theory of those equations of motion around a
general exact solution in terms of manifestly gauge invariant perturbations was
then developed. In this paper we specialise our previous results to an FRW
background which is also a solution of our modified equations of motion. We
then compare the resulting equations with those derived in standard
cosmological perturbation theory (SCPT). We exhibit the precise relation
between our manifestly gauge-invariant perturbations and the linearly
gauge-invariant variables in SCPT. We find that our equations of motion can be
cast into SCPT form plus corrections. These corrections are the trace that the
dust leaves on the system in terms of a conserved energy momentum current
density. It turns out that these corrections decay, in fact, in the late
universe they are negligible whatever the value of the conserved current. We
conclude that the addition of dust which serves as a test observer medium,
while implying modifications of Einstein's equations without dust, leads to
acceptable agreement with known results, while having the advantage that one
now talks about manifestly gauge-invariant, that is measurable, quantities,
which can be used even in perturbation theory at higher orders.
| [
{
"created": "Thu, 1 Nov 2007 18:05:49 GMT",
"version": "v1"
}
] | 2010-02-17 | [
[
"Giesel",
"K.",
""
],
[
"Hofmann",
"S.",
""
],
[
"Thiemann",
"T.",
""
],
[
"Winkler",
"O.",
""
]
] | In our companion paper we identified a complete set of manifestly gauge-invariant observables for general relativity. This was possible by coupling the system of gravity and matter to pressureless dust which plays the role of a dynamically coupled observer. The evolution of those observables is governed by a physical Hamiltonian and we derived the corresponding equations of motion. Linear perturbation theory of those equations of motion around a general exact solution in terms of manifestly gauge invariant perturbations was then developed. In this paper we specialise our previous results to an FRW background which is also a solution of our modified equations of motion. We then compare the resulting equations with those derived in standard cosmological perturbation theory (SCPT). We exhibit the precise relation between our manifestly gauge-invariant perturbations and the linearly gauge-invariant variables in SCPT. We find that our equations of motion can be cast into SCPT form plus corrections. These corrections are the trace that the dust leaves on the system in terms of a conserved energy momentum current density. It turns out that these corrections decay, in fact, in the late universe they are negligible whatever the value of the conserved current. We conclude that the addition of dust which serves as a test observer medium, while implying modifications of Einstein's equations without dust, leads to acceptable agreement with known results, while having the advantage that one now talks about manifestly gauge-invariant, that is measurable, quantities, which can be used even in perturbation theory at higher orders. |
gr-qc/0003046 | Arthur G. Wasserman | Arthur G. Wasserman | Solutions of the spherically symmetric SU(2) Einstein-Yang-Mills
equations defined in the far field | 15 pages | J.Math.Phys.41:6930-6936,2000 | 10.1063/1.1288796 | null | gr-qc | null | It is shown analytically that every static, spherically symmetric solution to
the Einstein Yang Mills equations with SU(2) gauge group that is defined in the
far field has finite ADM mass. Moreover, there can be at most two horizons for
such solutions. The three types of solutions possible, Bartnik-McKinnon
particle-like solutions, Reissner-Nordstrom-like solutions, and black hole
solutions having only one horizon are distinguished by the behavior of the
metric coefficients at the origin.
| [
{
"created": "Mon, 13 Mar 2000 20:04:38 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Wasserman",
"Arthur G.",
""
]
] | It is shown analytically that every static, spherically symmetric solution to the Einstein Yang Mills equations with SU(2) gauge group that is defined in the far field has finite ADM mass. Moreover, there can be at most two horizons for such solutions. The three types of solutions possible, Bartnik-McKinnon particle-like solutions, Reissner-Nordstrom-like solutions, and black hole solutions having only one horizon are distinguished by the behavior of the metric coefficients at the origin. |
2007.07974 | Surjeet Rajendran | Yi Chen, Muamer Kadic, David E. Kaplan, Surjeet Rajendran, Alexander
O. Sushkov and Martin Wegener | High-Frequency Gravitational-Wave Detection Using a Chiral Resonant
Mechanical Element and a Short Unstable Optical Cavity | 6 pages, 6 figures | null | null | null | gr-qc hep-ph hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Present gravitational wave detectors are based on the measurement of linear
displacement in stable optical cavities. Here, we instead suggest the
measurement of the twist of a chiral mechanical element induced by a
gravitational wave. The induced twist rotates a flat optical mirror on top of
this chiral element, leading to the deflection of an incident laser beam. This
angle change is enhanced by multiple bounces of light between the rotating
mirror and an originally parallel nearby fixed flat mirror. Based on detailed
continuum-mechanics calculations, we present a feasible design for the chiral
mechanical element including the rotating mirror. Our approach is most useful
for signals in the frequency band 1 -- 100 kHz where we show that fundamental
metrological limits would allow for smaller shot noise in this setup in
comparison to the detection of linear displacement. We estimate a gravitational
wave strain sensitivity between 10^{-21}/\sqrt{Hz} and 10^{-23}/\sqrt{Hz} at
around 10 kHz frequency. When appropriately scaling the involved geometrical
parameters, the strain sensitivity is proportional to frequency.
| [
{
"created": "Wed, 15 Jul 2020 20:09:43 GMT",
"version": "v1"
}
] | 2020-07-17 | [
[
"Chen",
"Yi",
""
],
[
"Kadic",
"Muamer",
""
],
[
"Kaplan",
"David E.",
""
],
[
"Rajendran",
"Surjeet",
""
],
[
"Sushkov",
"Alexander O.",
""
],
[
"Wegener",
"Martin",
""
]
] | Present gravitational wave detectors are based on the measurement of linear displacement in stable optical cavities. Here, we instead suggest the measurement of the twist of a chiral mechanical element induced by a gravitational wave. The induced twist rotates a flat optical mirror on top of this chiral element, leading to the deflection of an incident laser beam. This angle change is enhanced by multiple bounces of light between the rotating mirror and an originally parallel nearby fixed flat mirror. Based on detailed continuum-mechanics calculations, we present a feasible design for the chiral mechanical element including the rotating mirror. Our approach is most useful for signals in the frequency band 1 -- 100 kHz where we show that fundamental metrological limits would allow for smaller shot noise in this setup in comparison to the detection of linear displacement. We estimate a gravitational wave strain sensitivity between 10^{-21}/\sqrt{Hz} and 10^{-23}/\sqrt{Hz} at around 10 kHz frequency. When appropriately scaling the involved geometrical parameters, the strain sensitivity is proportional to frequency. |
1703.09722 | Christopher Berry | Stanislav Babak, Jonathan Gair, Alberto Sesana, Enrico Barausse,
Carlos F. Sopuerta, Christopher P. L. Berry, Emanuele Berti, Pau
Amaro-Seoane, Antoine Petiteau, and Antoine Klein | Science with the space-based interferometer LISA. V: Extreme mass-ratio
inspirals | 13 figures, 22 pages; updated to match published version | Phys. Rev. D; 95(10):103012(21); 2017 | 10.1103/PhysRevD.95.103012 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space-based Laser Interferometer Space Antenna (LISA) will be able to
observe the gravitational-wave signals from systems comprised of a massive
black hole and a stellar-mass compact object. These systems are known as
extreme-mass-ratio inspirals (EMRIs) and are expected to complete $\sim
10^4$-$10^5$ cycles in band, thus allowing exquisite measurements of their
parameters. In this work, we attempt to quantify the astrophysical
uncertainties affecting the predictions for the number of EMRIs detectable by
LISA, and find that competing astrophysical assumptions produce a variance of
about three orders of magnitude in the expected intrinsic EMRI rate. However,
we find that irrespective of the astrophysical model, at least a few EMRIs per
year should be detectable by the LISA mission, with up to a few thousands per
year under the most optimistic astrophysical assumptions. We also investigate
the precision with which LISA will be able to extract the parameters of these
sources. We find that typical fractional statistical errors with which the
intrinsic parameters (redshifted masses, massive black hole spin and orbital
eccentricity) can be recovered are $\sim 10^{-6}$-$10^{-4}$. Luminosity
distance (which is required to infer true masses) is inferred to about $10\%$
precision and sky position is localized to a few square degrees, while tests of
the multipolar structure of the Kerr metric can be performed to percent-level
precision or better.
| [
{
"created": "Tue, 28 Mar 2017 18:00:17 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Apr 2018 11:52:26 GMT",
"version": "v2"
}
] | 2018-04-12 | [
[
"Babak",
"Stanislav",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Sesana",
"Alberto",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Sopuerta",
"Carlos F.",
""
],
[
"Berry",
"Christopher P. L.",
""
],
[
"Berti",
"Emanuele",
... | The space-based Laser Interferometer Space Antenna (LISA) will be able to observe the gravitational-wave signals from systems comprised of a massive black hole and a stellar-mass compact object. These systems are known as extreme-mass-ratio inspirals (EMRIs) and are expected to complete $\sim 10^4$-$10^5$ cycles in band, thus allowing exquisite measurements of their parameters. In this work, we attempt to quantify the astrophysical uncertainties affecting the predictions for the number of EMRIs detectable by LISA, and find that competing astrophysical assumptions produce a variance of about three orders of magnitude in the expected intrinsic EMRI rate. However, we find that irrespective of the astrophysical model, at least a few EMRIs per year should be detectable by the LISA mission, with up to a few thousands per year under the most optimistic astrophysical assumptions. We also investigate the precision with which LISA will be able to extract the parameters of these sources. We find that typical fractional statistical errors with which the intrinsic parameters (redshifted masses, massive black hole spin and orbital eccentricity) can be recovered are $\sim 10^{-6}$-$10^{-4}$. Luminosity distance (which is required to infer true masses) is inferred to about $10\%$ precision and sky position is localized to a few square degrees, while tests of the multipolar structure of the Kerr metric can be performed to percent-level precision or better. |
1602.06300 | Jaiyul Yoo | Jaiyul Yoo (Z\"urich), Jinn-Ouk Gong (APCTP, Pohang) | Exact Analytic Solution for Non-Linear Density Fluctuation in a LCDM
Universe | 20 pages, no figures, published in JCAP | JCAP 07 (2016) 017 | 10.1088/1475-7516/2016/07/017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the exact third-order analytic solution of the matter density
fluctuation in the proper-time hypersurface in a $\Lambda$CDM universe,
accounting for the explicit time-dependence and clarifying the relation to the
initial condition. Furthermore, we compare our analytic solution to the
previous calculation in the comoving gauge, and to the standard Newtonian
perturbation theory by providing Fourier kernels for the relativistic effects.
Our results provide an essential ingredient for a complete description of
galaxy bias in the relativistic context.
| [
{
"created": "Fri, 19 Feb 2016 21:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2016 14:27:09 GMT",
"version": "v2"
}
] | 2016-07-14 | [
[
"Yoo",
"Jaiyul",
"",
"Zürich"
],
[
"Gong",
"Jinn-Ouk",
"",
"APCTP, Pohang"
]
] | We derive the exact third-order analytic solution of the matter density fluctuation in the proper-time hypersurface in a $\Lambda$CDM universe, accounting for the explicit time-dependence and clarifying the relation to the initial condition. Furthermore, we compare our analytic solution to the previous calculation in the comoving gauge, and to the standard Newtonian perturbation theory by providing Fourier kernels for the relativistic effects. Our results provide an essential ingredient for a complete description of galaxy bias in the relativistic context. |
2104.00596 | Mehdi Shokri | Mehdi Shokri, Jafar Sadeghi, Mohammad Reza Setare and Salvatore
Capozziello | Nonminimal coupling inflation with constant slow roll | 15 pages, 6 figures, Accepted for publication in Int. J. Mod. Phys. D | null | 10.1142/S021827182150070X | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We study a single field inflationary model modified by a non-minimal coupling
term between the Ricci scalar $R$ and the scalar field $\varphi$ in the context
of constant-roll inflation. The first-order formalism is used to analyse the
constant-roll inflation instead of the standard methods used in the literature.
In principle, the formalism considers two functions of the scalar field,
$W=W(\varphi)$ and $Z=Z(\varphi)$, which lead to the reduction of the equations
of motion to first-order differential equations. The approach can be applied to
a wide range of cosmological situations since it directly relates the function
$W$ with Hubble parameter $H$. We perform the inflationary analysis for
power-law and exponential couplings, separately. Then, we investigate the
features of constant-roll potentials as inflationary potentials. Finally, we
compare the inflationary parameters of the models with the observations of CMB
anisotropies in view of realize a physically motivated model.
| [
{
"created": "Wed, 31 Mar 2021 13:07:31 GMT",
"version": "v1"
},
{
"created": "Thu, 6 May 2021 09:39:59 GMT",
"version": "v2"
},
{
"created": "Sun, 30 May 2021 14:25:48 GMT",
"version": "v3"
}
] | 2021-08-11 | [
[
"Shokri",
"Mehdi",
""
],
[
"Sadeghi",
"Jafar",
""
],
[
"Setare",
"Mohammad Reza",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | We study a single field inflationary model modified by a non-minimal coupling term between the Ricci scalar $R$ and the scalar field $\varphi$ in the context of constant-roll inflation. The first-order formalism is used to analyse the constant-roll inflation instead of the standard methods used in the literature. In principle, the formalism considers two functions of the scalar field, $W=W(\varphi)$ and $Z=Z(\varphi)$, which lead to the reduction of the equations of motion to first-order differential equations. The approach can be applied to a wide range of cosmological situations since it directly relates the function $W$ with Hubble parameter $H$. We perform the inflationary analysis for power-law and exponential couplings, separately. Then, we investigate the features of constant-roll potentials as inflationary potentials. Finally, we compare the inflationary parameters of the models with the observations of CMB anisotropies in view of realize a physically motivated model. |
1810.04667 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Embedding black holes and other inhomogeneities in the universe in
various theories of gravity: a short review | Invited paper to appear in "Theories of gravity: alternatives to the
cosmological and particle standard models", special issue of Universe, S.
Bellucci and O. Luongo eds. arXiv admin note: text overlap with
arXiv:1309.4915 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classic black hole mechanics and thermodynamics are formulated for
stationary black holes with event horizons. Alternative theories of gravity of
interest for cosmology contain a built-in time-dependent cosmological
"constant" and black holes are not stationary. Realistic black holes are anyway
dynamical because they interact with astrophysical environments or, at a more
fundamental level, because of backreaction by Hawking radiation. In these
situations the teleological concept of event horizon fails and apparent or
trapping horizons are used instead. Even as toy models, black holes embedded in
cosmological "backgrounds" and other inhomogeneous universes constitute an
interesting class of solutions of various theories of gravity. We discuss the
known phenomenology of apparent and trapping horizons in these geometries,
focusing on spherically symmetric inhomogeneous universes.
| [
{
"created": "Tue, 9 Oct 2018 21:07:33 GMT",
"version": "v1"
}
] | 2018-10-12 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | The classic black hole mechanics and thermodynamics are formulated for stationary black holes with event horizons. Alternative theories of gravity of interest for cosmology contain a built-in time-dependent cosmological "constant" and black holes are not stationary. Realistic black holes are anyway dynamical because they interact with astrophysical environments or, at a more fundamental level, because of backreaction by Hawking radiation. In these situations the teleological concept of event horizon fails and apparent or trapping horizons are used instead. Even as toy models, black holes embedded in cosmological "backgrounds" and other inhomogeneous universes constitute an interesting class of solutions of various theories of gravity. We discuss the known phenomenology of apparent and trapping horizons in these geometries, focusing on spherically symmetric inhomogeneous universes. |
gr-qc/9907027 | Leonid Grishchuk | S V Babak and L P Grishchuk | The Energy-Momentum Tensor for the Gravitational Field | 32 pages, revised version, additional references, to be published in
Phys. Rev. D | Phys.Rev. D61 (2000) 024038 | 10.1103/PhysRevD.61.024038 | null | gr-qc astro-ph hep-th | null | The search for the gravitational energy-momentum tensor is often qualified as
an attempt of looking for ``the right answer to the wrong question''. This
position does not seem convincing to us. We think that we have found the right
answer to the properly formulated question. We have further developed the field
theoretical formulation of the general relativity which treats gravity as a
non-linear tensor field in flat space-time. The Minkowski metric is a
reflection of experimental facts, not a possible choice of the artificial
``prior geometry''. In this approach, we have arrived at the gravitational
energy-momentum tensor which is: 1) derivable from the Lagrangian in a regular
prescribed way, 2) tensor under arbitrary coordinate transformations, 3)
symmetric in its components, 4) conserved due to the equations of motion
derived from the same Lagrangian, 5) free of the second (highest) derivatives
of the field variables, and 6) is unique up to trivial modifications not
containing the field variables. There is nothing else, in addition to these 6
conditions, that one could demand from an energy-momentum object, acceptable
both on physical and mathematical grounds. The derived gravitational
energy-momentum tensor should be useful in practical applications.
| [
{
"created": "Wed, 7 Jul 1999 11:37:16 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Oct 1999 23:06:30 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Babak",
"S V",
""
],
[
"Grishchuk",
"L P",
""
]
] | The search for the gravitational energy-momentum tensor is often qualified as an attempt of looking for ``the right answer to the wrong question''. This position does not seem convincing to us. We think that we have found the right answer to the properly formulated question. We have further developed the field theoretical formulation of the general relativity which treats gravity as a non-linear tensor field in flat space-time. The Minkowski metric is a reflection of experimental facts, not a possible choice of the artificial ``prior geometry''. In this approach, we have arrived at the gravitational energy-momentum tensor which is: 1) derivable from the Lagrangian in a regular prescribed way, 2) tensor under arbitrary coordinate transformations, 3) symmetric in its components, 4) conserved due to the equations of motion derived from the same Lagrangian, 5) free of the second (highest) derivatives of the field variables, and 6) is unique up to trivial modifications not containing the field variables. There is nothing else, in addition to these 6 conditions, that one could demand from an energy-momentum object, acceptable both on physical and mathematical grounds. The derived gravitational energy-momentum tensor should be useful in practical applications. |
1905.07633 | Yerko V\'asquez | P. A. Gonz\'alez, Samuel Reyes and Yerko V\'asquez | Teleparallel Equivalent of Lovelock Gravity, Generalizations and
Cosmological Applications | Version accepted for publication in JCAP | null | 10.1088/1475-7516/2019/07/040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the teleparallel equivalent of Lovelock gravity and its natural
extension, where the action is given by an arbitrary function $f(T_{_{L_1}},
T_{_{L_2}},\cdot \cdot \cdot , T_{_{L_n}})$ of the torsion invariants
$T_{_{L_i}}$, which contain higher order torsion terms, and derive its field
equations. Then, we consider the special case of $f(T_{_{L_1}}, T_{_{L_2}})$
gravity and study a cosmological scenario by selecting a particular
$f(T_{_{L_1}}, T_{_{L_2}})$, and derive the Friedmann equations. Also, we
perform a dynamical systems analysis to extract information on the evolution of
the cosmological model. Mainly, we find that the model has a very rich
phenomenology and can describe the acceleration of the universe at late times
| [
{
"created": "Sat, 18 May 2019 19:48:53 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Jun 2019 19:09:36 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Jul 2019 16:26:34 GMT",
"version": "v3"
}
] | 2019-07-31 | [
[
"González",
"P. A.",
""
],
[
"Reyes",
"Samuel",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We consider the teleparallel equivalent of Lovelock gravity and its natural extension, where the action is given by an arbitrary function $f(T_{_{L_1}}, T_{_{L_2}},\cdot \cdot \cdot , T_{_{L_n}})$ of the torsion invariants $T_{_{L_i}}$, which contain higher order torsion terms, and derive its field equations. Then, we consider the special case of $f(T_{_{L_1}}, T_{_{L_2}})$ gravity and study a cosmological scenario by selecting a particular $f(T_{_{L_1}}, T_{_{L_2}})$, and derive the Friedmann equations. Also, we perform a dynamical systems analysis to extract information on the evolution of the cosmological model. Mainly, we find that the model has a very rich phenomenology and can describe the acceleration of the universe at late times |
1208.5562 | Mohammad Vahid Takook | M. Enayati, S. Rouhani, M.V. Takook | Quantum Linear Gravity in de Sitter Universe On Gupta-Bleuler vacuum
state | 19 pages, typos corrected, reference addeded, further comments add | Int J Theor Phys 55(2016)5005 | 10.1007/s10773-016-3249-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Application of Krein space quantization to the linear gravity in de Sitter
space-time have constructed on Gupta-Bleuler vacuum state, resulting in removal
of infrared divergence and preserving de Sitter covariant. By pursuing this
path, the non uniqueness of vacuum expectation value of the product of field
operators in curved space-time disappears as well. Then the vacuum expectation
value of the product of field operators can be defined properly and uniquely.
| [
{
"created": "Tue, 28 Aug 2012 06:08:03 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Aug 2014 08:42:29 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Jun 2016 05:54:45 GMT",
"version": "v3"
}
] | 2019-07-02 | [
[
"Enayati",
"M.",
""
],
[
"Rouhani",
"S.",
""
],
[
"Takook",
"M. V.",
""
]
] | Application of Krein space quantization to the linear gravity in de Sitter space-time have constructed on Gupta-Bleuler vacuum state, resulting in removal of infrared divergence and preserving de Sitter covariant. By pursuing this path, the non uniqueness of vacuum expectation value of the product of field operators in curved space-time disappears as well. Then the vacuum expectation value of the product of field operators can be defined properly and uniquely. |
1705.06711 | Matti Raasakka | Matti Raasakka | Local Lorentz covariance in finite-dimensional Local Quantum Physics | 7 pages; v3: Minor typos fixed, matches the published version. v2:
The definition of local Hamiltonians is slightly changed from the previous
version in order to better justify the physical identification of SL(2,C)
transformations with Lorentz transformations. The rest of the paper has been
modified to accommodate this change | Phys. Rev. D 96, 086023 (2017) | 10.1103/PhysRevD.96.086023 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that local Lorentz covariance arises canonically as the group of
transformations between local thermal states in the framework of Local Quantum
Physics, given the following three postulates: (i) Local observable algebras
are finite-dimensional. (ii) Minimal local observable algebras are isomorphic
to $\mathbb{M}_2(\mathbb{C})$, the observable algebra of a single qubit. (iii)
The vacuum restricted to any minimal local observable algebra is a
non-maximally mixed thermal state. The derivation reveals a new and surprising
relation between spacetime structure and local quantum states. In particular,
we show how local restrictions of the vacuum can determine the connection
between different local inertial reference frames.
| [
{
"created": "Thu, 18 May 2017 17:28:48 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Sep 2017 10:02:31 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Dec 2017 13:39:10 GMT",
"version": "v3"
}
] | 2017-12-07 | [
[
"Raasakka",
"Matti",
""
]
] | We show that local Lorentz covariance arises canonically as the group of transformations between local thermal states in the framework of Local Quantum Physics, given the following three postulates: (i) Local observable algebras are finite-dimensional. (ii) Minimal local observable algebras are isomorphic to $\mathbb{M}_2(\mathbb{C})$, the observable algebra of a single qubit. (iii) The vacuum restricted to any minimal local observable algebra is a non-maximally mixed thermal state. The derivation reveals a new and surprising relation between spacetime structure and local quantum states. In particular, we show how local restrictions of the vacuum can determine the connection between different local inertial reference frames. |
1905.07352 | Ruben Cordero | R. Cordero (1), O. G. Miranda (2) and M. Serrano-Crivelli (1) ((1)
Mexico, ESFM, (2) CINVESTAV, IPN) | K-essence and kinetic gravity braiding models in two-field measure
theory | 21 pages, 1 figure | null | 10.1088/1475-7516/2019/07/027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that, in the context of the two-field measure theory, any k-essence
model leads to the existence of a fluid made of non-relativistic matter and
cosmological constant that would explain the dark matter and dark energy
problem at the same time. On the other hand, kinetic gravity braiding models
can lead to different behaviors, such as phantom dark energy, stiff matter, and
a cosmological constant. For stiff matter, there even exists the case where the
scalar field does not have any effect in the dynamics of the Universe.
| [
{
"created": "Fri, 17 May 2019 16:18:26 GMT",
"version": "v1"
}
] | 2019-07-24 | [
[
"Cordero",
"R.",
""
],
[
"Miranda",
"O. G.",
""
],
[
"Serrano-Crivelli",
"M.",
""
]
] | We show that, in the context of the two-field measure theory, any k-essence model leads to the existence of a fluid made of non-relativistic matter and cosmological constant that would explain the dark matter and dark energy problem at the same time. On the other hand, kinetic gravity braiding models can lead to different behaviors, such as phantom dark energy, stiff matter, and a cosmological constant. For stiff matter, there even exists the case where the scalar field does not have any effect in the dynamics of the Universe. |
0710.2158 | Vladimir S. Manko | Vladimir S. Manko | The double-Reissner-Nordstrom solution and the interaction force between
two spherically symmetric charged particles | 14 pages, 1 figure; submitted to Physical Review D | Phys.Rev.D76:124032,2007 | 10.1103/PhysRevD.76.124032 | null | gr-qc | null | The physical representation of the general double-Reissner-Nordstrom solution
is obtained by rewriting the N=2 Breton-Manko-Aguilar electrostatic solution in
the Varzugin-Chistyakov parametrization (M_i, Q_i, R). A concise analytical
formula is derived for the interaction force between two arbitrary
Reissner-Nordstrom constituents, and an example of the equilibrium
configuration involving two oppositely charged particles which confirms earlier
Bonnor's prediction of the existence of such configurations is given.
| [
{
"created": "Thu, 11 Oct 2007 03:33:15 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Manko",
"Vladimir S.",
""
]
] | The physical representation of the general double-Reissner-Nordstrom solution is obtained by rewriting the N=2 Breton-Manko-Aguilar electrostatic solution in the Varzugin-Chistyakov parametrization (M_i, Q_i, R). A concise analytical formula is derived for the interaction force between two arbitrary Reissner-Nordstrom constituents, and an example of the equilibrium configuration involving two oppositely charged particles which confirms earlier Bonnor's prediction of the existence of such configurations is given. |
2405.16986 | Tolga Birkandan | Emir Baysazan, Tolga Birkandan, Ismail Eyuphan Unver | Analysis of scalar fields with series convolution | 14 pages | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Wave equations for some curved spacetimes may involve functions that prevent
a solution in a closed form. In some cases, these functions can be eliminated
by transformations and the solutions can be found analytically. In the cases
where such transformations are not available, the infinite series expansions of
these functions can be convoluted with the power series solution ansatz. We
study such an example where the solution is based on a special function.
| [
{
"created": "Mon, 27 May 2024 09:31:25 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Baysazan",
"Emir",
""
],
[
"Birkandan",
"Tolga",
""
],
[
"Unver",
"Ismail Eyuphan",
""
]
] | Wave equations for some curved spacetimes may involve functions that prevent a solution in a closed form. In some cases, these functions can be eliminated by transformations and the solutions can be found analytically. In the cases where such transformations are not available, the infinite series expansions of these functions can be convoluted with the power series solution ansatz. We study such an example where the solution is based on a special function. |
0904.3779 | Federico Urban | Evan C. Thomas, Federico R. Urban, Ariel R. Zhitnitsky | The cosmological constant as a manifestation of the conformal anomaly? | 15 pages - v2 with extended introduction to match published version | JHEP 0908:043,2009 | 10.1088/1126-6708/2009/08/043 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that the solution to the cosmological vacuum energy puzzle may
come from the infrared sector of the effective theory of gravity, where the
impact of the trace anomaly is of upmost relevance. We proceed by introducing
two auxiliary fields, which are capable of describing a diversity of quantum
states via specification of their macroscopic (IR) boundary conditions, in
contrast to ultraviolet quantum effects. Our investigation aims at finding a
realistic cosmological solution which interprets the observed cosmological
constant as a well defined deficit in the zero point energy density of the
Universe. The energy density arises from a phase transition, which alters the
properties of the quantum ground state. We explicitly formulate low energy
gravity as an effective field theory with a precise definition of the "point of
normalization" as the point at which the "renormalized cosmological constant"
is set to zero in the Minkowski vacuum, in which the Einstein equations are
automatically satisfied as the Ricci tensor identically vanishes. With this
definition the effective QFT of gravity has a predictive power. In particular,
it must predict the evolution of the system in any nontrivial geometry,
including the vacuum energy behaviour as a function of infrared, rather than
ultraviolet, input parameters.
| [
{
"created": "Fri, 24 Apr 2009 02:05:41 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Aug 2009 17:12:46 GMT",
"version": "v2"
}
] | 2009-08-12 | [
[
"Thomas",
"Evan C.",
""
],
[
"Urban",
"Federico R.",
""
],
[
"Zhitnitsky",
"Ariel R.",
""
]
] | We propose that the solution to the cosmological vacuum energy puzzle may come from the infrared sector of the effective theory of gravity, where the impact of the trace anomaly is of upmost relevance. We proceed by introducing two auxiliary fields, which are capable of describing a diversity of quantum states via specification of their macroscopic (IR) boundary conditions, in contrast to ultraviolet quantum effects. Our investigation aims at finding a realistic cosmological solution which interprets the observed cosmological constant as a well defined deficit in the zero point energy density of the Universe. The energy density arises from a phase transition, which alters the properties of the quantum ground state. We explicitly formulate low energy gravity as an effective field theory with a precise definition of the "point of normalization" as the point at which the "renormalized cosmological constant" is set to zero in the Minkowski vacuum, in which the Einstein equations are automatically satisfied as the Ricci tensor identically vanishes. With this definition the effective QFT of gravity has a predictive power. In particular, it must predict the evolution of the system in any nontrivial geometry, including the vacuum energy behaviour as a function of infrared, rather than ultraviolet, input parameters. |
2309.11383 | Soumya Jana | Md. Golam Mafuz, Rishank Diwan, Soumya Jana, Sayan Kar | Shadows of a generic class of spherically symmetric, static spacetimes | 32 pages, 11 figures, references added. Matched with published
version | Eur. Phys. J. Plus, 139:219 (2024) | 10.1140/epjp/s13360-024-04993-8 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We explore the characteristics of shadows for a general class of spherically
symmetric, static spacetimes, which may arise in general relativity or in
modified theories of gravity. The chosen line element involves a sum (with
constant but different coefficients) of integer powers of $\frac{1}{\text{r}}$
in $\text{g}_\text{tt}$ and $\text{g}_\text{rr}$, in the Schwarzschild gauge.
We begin our discussion by motivating the line element through a study of the
energy conditions (null and weak) and the extent to which they are
satisfied/violated for diverse choices of the parameters appearing in the
metric functions. Subsequently, we construct the circular shadows and analyse
the dependence of the shadow radius on the metric parameters. We find that with
specific choices of the metric parameters (within the ranges allowed by the
energy conditions) one can, in principle, obtain values that conform with
recent observations on shadows, as available in the literature. We also mention
where such metrics may arise (i.e., in which theory of gravity and the physical
scenario therein), thereby proposing that the observed shadows may be
representative signatures of different theoretical contexts.
| [
{
"created": "Wed, 20 Sep 2023 15:10:02 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Sep 2023 17:07:09 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Mar 2024 17:41:10 GMT",
"version": "v3"
}
] | 2024-03-19 | [
[
"Mafuz",
"Md. Golam",
""
],
[
"Diwan",
"Rishank",
""
],
[
"Jana",
"Soumya",
""
],
[
"Kar",
"Sayan",
""
]
] | We explore the characteristics of shadows for a general class of spherically symmetric, static spacetimes, which may arise in general relativity or in modified theories of gravity. The chosen line element involves a sum (with constant but different coefficients) of integer powers of $\frac{1}{\text{r}}$ in $\text{g}_\text{tt}$ and $\text{g}_\text{rr}$, in the Schwarzschild gauge. We begin our discussion by motivating the line element through a study of the energy conditions (null and weak) and the extent to which they are satisfied/violated for diverse choices of the parameters appearing in the metric functions. Subsequently, we construct the circular shadows and analyse the dependence of the shadow radius on the metric parameters. We find that with specific choices of the metric parameters (within the ranges allowed by the energy conditions) one can, in principle, obtain values that conform with recent observations on shadows, as available in the literature. We also mention where such metrics may arise (i.e., in which theory of gravity and the physical scenario therein), thereby proposing that the observed shadows may be representative signatures of different theoretical contexts. |
gr-qc/0301072 | Luisa T. Buchman | L. T. Buchman and J. M. Bardeen | A hyperbolic tetrad formulation of the Einstein equations for numerical
relativity | Eqs. (59), (B3), (B4), and (B5) have been corrected (multiplied by
-1). Two typos have been fixed, and citations have been removed from the
abstract | Phys.Rev.D67:084017,2003; Erratum-ibid.D72:049903,2005 | 10.1103/PhysRevD.67.084017 10.1103/PhysRevD.72.049903 | null | gr-qc | null | The tetrad-based equations for vacuum gravity published by Estabrook,
Robinson, and Wahlquist are simplified and adapted for numerical relativity. We
show that the evolution equations as partial differential equations for the
Ricci rotation coefficients constitute a rather simple first-order
symmetrizable hyperbolic system, not only for the Nester gauge condition on the
acceleration and angular velocity of the tetrad frames considered by Estabrook
et al., but also for the Lorentz gauge condition of van Putten and Eardley, and
for a fixed gauge condition. We introduce a lapse function and a shift vector
to allow general coordinate evolution relative to the timelike congruence
defined by the tetrad vector field.
| [
{
"created": "Tue, 21 Jan 2003 03:56:15 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2005 20:57:52 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Buchman",
"L. T.",
""
],
[
"Bardeen",
"J. M.",
""
]
] | The tetrad-based equations for vacuum gravity published by Estabrook, Robinson, and Wahlquist are simplified and adapted for numerical relativity. We show that the evolution equations as partial differential equations for the Ricci rotation coefficients constitute a rather simple first-order symmetrizable hyperbolic system, not only for the Nester gauge condition on the acceleration and angular velocity of the tetrad frames considered by Estabrook et al., but also for the Lorentz gauge condition of van Putten and Eardley, and for a fixed gauge condition. We introduce a lapse function and a shift vector to allow general coordinate evolution relative to the timelike congruence defined by the tetrad vector field. |
1504.05178 | Maurice H. P. M. van Putten | Maurice H.P.M. van Putten | Accelerated expansion from cosmological holography | 5 pages, 2 figures | MNRAS 450 L48 (2015) | 10.1093/mnrasl/slv038 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that holographic cosmology implies an evolving Hubble radius
$c^{-1}\dot{R}_H = -1 + 3\Omega_m$ in the presence of a dimensionless matter
density $\Omega_m$ scaled to the closure density $3H^2/8\pi G$, where $c$
denotes the velocity of light and $H$ and $G$ denote the Hubble parameter and
Newton's constant. It reveals a dynamical dark energy and a sixfold increase in
gravitational attraction to matter on the scale of the Hubble acceleration. It
reproduces the transition redshift $z_t\simeq 0.4$ to the present epoch of
accelerated expansion and is consistent with $(q_0,(dq/dz)_0)$ of the
deceleration parameter $q(z)=q_0+(dq/dz)_0z$ observed in Type Ia supernovae.
| [
{
"created": "Mon, 20 Apr 2015 13:25:58 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"van Putten",
"Maurice H. P. M.",
""
]
] | It is shown that holographic cosmology implies an evolving Hubble radius $c^{-1}\dot{R}_H = -1 + 3\Omega_m$ in the presence of a dimensionless matter density $\Omega_m$ scaled to the closure density $3H^2/8\pi G$, where $c$ denotes the velocity of light and $H$ and $G$ denote the Hubble parameter and Newton's constant. It reveals a dynamical dark energy and a sixfold increase in gravitational attraction to matter on the scale of the Hubble acceleration. It reproduces the transition redshift $z_t\simeq 0.4$ to the present epoch of accelerated expansion and is consistent with $(q_0,(dq/dz)_0)$ of the deceleration parameter $q(z)=q_0+(dq/dz)_0z$ observed in Type Ia supernovae. |
gr-qc/0605017 | Frederic P. Schuller | Raffaele Punzi, Frederic P. Schuller, Mattias N. R. Wohlfarth | Geometric obstruction of black holes | 50 pages, 2 figures | Annals Phys.322:1335-1372,2007 | 10.1016/j.aop.2006.07.005 | null | gr-qc hep-th | null | We study the global structure of Lorentzian manifolds with partial sectional
curvature bounds. In particular, we prove completeness theorems for homogeneous
and isotropic cosmologies as well as static spherically symmetric spacetimes.
The latter result is used to rigorously prove the absence of static spherically
symmetric black holes in more than three dimensions. The proofs of these new
results are preceded by a detailed exposition of the local aspects of sectional
curvature bounds for Lorentzian manifolds, which extends and strengthens
previous constructions.
| [
{
"created": "Tue, 2 May 2006 16:16:56 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Punzi",
"Raffaele",
""
],
[
"Schuller",
"Frederic P.",
""
],
[
"Wohlfarth",
"Mattias N. R.",
""
]
] | We study the global structure of Lorentzian manifolds with partial sectional curvature bounds. In particular, we prove completeness theorems for homogeneous and isotropic cosmologies as well as static spherically symmetric spacetimes. The latter result is used to rigorously prove the absence of static spherically symmetric black holes in more than three dimensions. The proofs of these new results are preceded by a detailed exposition of the local aspects of sectional curvature bounds for Lorentzian manifolds, which extends and strengthens previous constructions. |
1703.08654 | Jie-Xiong Mo | Jie-Xiong Mo, Gu-Qiang Li, Xiao-Bao Xu | Universal ratios of critical physical quantities of charged AdS black
holes | null | null | 10.1088/1475-7516/2018/07/017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the ratios of critical physical quantities related to the
$T-S$ criticality of charged AdS black holes. It is shown that the ratio
$\frac{T_cS_c}{Q_c}$ is universal while $\frac{T_cr_c}{Q_c}$ is not. This
finding is quite interesting considering the former observation that both the
$T-S$ graph and $T-r_+$ graph exhibit reverse van der Waals behavior. It is
also worth noting that the value of $\frac{T_cS_c}{Q_c}$ differs from that of
$\frac{P_cv_c}{T_c}$ for $P-V$ criticality. Moreover, we discuss universal
ratios for the $P-V$ criticality and $Q-\Phi$ criticality. We successfully
interpret the former finding that the ratio $\frac{\Phi_cQ_c}{T_c}$ is not
universal and construct two universal ratios for the $Q-\Phi$ criticality
instead. To the best of our knowledge, we are the first to introduce the
dimensional analysis technique to study the ratios of critical physical
quantities. It is expected that this technique can be generalized to probe the
universal ratios for $Y-X$ criticality in future research.
| [
{
"created": "Sat, 25 Mar 2017 06:40:05 GMT",
"version": "v1"
}
] | 2018-07-25 | [
[
"Mo",
"Jie-Xiong",
""
],
[
"Li",
"Gu-Qiang",
""
],
[
"Xu",
"Xiao-Bao",
""
]
] | We investigate the ratios of critical physical quantities related to the $T-S$ criticality of charged AdS black holes. It is shown that the ratio $\frac{T_cS_c}{Q_c}$ is universal while $\frac{T_cr_c}{Q_c}$ is not. This finding is quite interesting considering the former observation that both the $T-S$ graph and $T-r_+$ graph exhibit reverse van der Waals behavior. It is also worth noting that the value of $\frac{T_cS_c}{Q_c}$ differs from that of $\frac{P_cv_c}{T_c}$ for $P-V$ criticality. Moreover, we discuss universal ratios for the $P-V$ criticality and $Q-\Phi$ criticality. We successfully interpret the former finding that the ratio $\frac{\Phi_cQ_c}{T_c}$ is not universal and construct two universal ratios for the $Q-\Phi$ criticality instead. To the best of our knowledge, we are the first to introduce the dimensional analysis technique to study the ratios of critical physical quantities. It is expected that this technique can be generalized to probe the universal ratios for $Y-X$ criticality in future research. |
gr-qc/0207041 | Hendryk Pfeiffer | Daniele Oriti and Hendryk Pfeiffer | A spin foam model for pure gauge theory coupled to quantum gravity | 18 pages, LaTeX, 1 figure, v2: details clarified, references added | Phys.Rev.D66:124010,2002 | 10.1103/PhysRevD.66.124010 | DAMTP-2002-72 | gr-qc hep-th | null | We propose a spin foam model for pure gauge fields coupled to Riemannian
quantum gravity in four dimensions. The model is formulated for the
triangulation of a four-manifold which is given merely combinatorially. The
Riemannian Barrett--Crane model provides the gravity sector of our model and
dynamically assigns geometric data to the given combinatorial triangulation.
The gauge theory sector is a lattice gauge theory living on the same
triangulation and obtains from the gravity sector the geometric information
which is required to calculate the Yang--Mills action. The model is designed so
that one obtains a continuum approximation of the gauge theory sector at an
effective level, similarly to the continuum limit of lattice gauge theory, when
the typical length scale of gravity is much smaller than the Yang--Mills scale.
| [
{
"created": "Tue, 9 Jul 2002 17:49:40 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Nov 2002 23:30:52 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Oriti",
"Daniele",
""
],
[
"Pfeiffer",
"Hendryk",
""
]
] | We propose a spin foam model for pure gauge fields coupled to Riemannian quantum gravity in four dimensions. The model is formulated for the triangulation of a four-manifold which is given merely combinatorially. The Riemannian Barrett--Crane model provides the gravity sector of our model and dynamically assigns geometric data to the given combinatorial triangulation. The gauge theory sector is a lattice gauge theory living on the same triangulation and obtains from the gravity sector the geometric information which is required to calculate the Yang--Mills action. The model is designed so that one obtains a continuum approximation of the gauge theory sector at an effective level, similarly to the continuum limit of lattice gauge theory, when the typical length scale of gravity is much smaller than the Yang--Mills scale. |
gr-qc/0110034 | Thomas Thiemann | Thomas Thiemann | Introduction to Modern Canonical Quantum General Relativity | 301 pages, Latex; based in part on the author's Habilitation Thesis
"Mathematische Formulierung der Quanten-Einstein-Gleichungen", University of
Potsdam, Potsdam, Germany, January 2000; submitted to the on-line journal
Living Reviews; subject to being updated on at least a bi-annual basis | null | null | AEI-2001-119 | gr-qc hep-th math-ph math.FA math.MP math.OA math.SG quant-ph | null | This is an introduction to the by now fifteen years old research field of
canonical quantum general relativity, sometimes called "loop quantum gravity".
The term "modern" in the title refers to the fact that the quantum theory is
based on formulating classical general relativity as a theory of connections
rather than metrics as compared to in original version due to Arnowitt, Deser
and Misner. Canonical quantum general relativity is an attempt to define a
mathematically rigorous, non-perturbative, background independent theory of
Lorentzian quantum gravity in four spacetime dimensions in the continuum. The
approach is minimal in that one simply analyzes the logical consequences of
combining the principles of general relativity with the principles of quantum
mechanics. The requirement to preserve background independence has lead to new,
fascinating mathematical structures which one does not see in perturbative
approaches, e.g. a fundamental discreteness of spacetime seems to be a
prediction of the theory providing a first substantial evidence for a theory in
which the gravitational field acts as a natural UV cut-off. An effort has been
made to provide a self-contained exposition of a restricted amount of material
at the appropriate level of rigour which at the same time is accessible to
graduate students with only basic knowledge of general relativity and quantum
field theory on Minkowski space.
| [
{
"created": "Fri, 5 Oct 2001 18:16:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Thiemann",
"Thomas",
""
]
] | This is an introduction to the by now fifteen years old research field of canonical quantum general relativity, sometimes called "loop quantum gravity". The term "modern" in the title refers to the fact that the quantum theory is based on formulating classical general relativity as a theory of connections rather than metrics as compared to in original version due to Arnowitt, Deser and Misner. Canonical quantum general relativity is an attempt to define a mathematically rigorous, non-perturbative, background independent theory of Lorentzian quantum gravity in four spacetime dimensions in the continuum. The approach is minimal in that one simply analyzes the logical consequences of combining the principles of general relativity with the principles of quantum mechanics. The requirement to preserve background independence has lead to new, fascinating mathematical structures which one does not see in perturbative approaches, e.g. a fundamental discreteness of spacetime seems to be a prediction of the theory providing a first substantial evidence for a theory in which the gravitational field acts as a natural UV cut-off. An effort has been made to provide a self-contained exposition of a restricted amount of material at the appropriate level of rigour which at the same time is accessible to graduate students with only basic knowledge of general relativity and quantum field theory on Minkowski space. |
0812.4055 | Aristide Baratin | Aristide Baratin, Cecilia Flori, Thomas Thiemann | The Holst Spin Foam Model via Cubulations | 25 pages, 1 figure; v3: published version. arXiv admin note:
substantial text overlap with arXiv:0911.2135 | New J. Phys. 14 (2012) 103054 | 10.1088/1367-2630/14/10/103054 | AEI-2008-093 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin foam models are an attempt for a covariant, or path integral formulation
of canonical loop quantum gravity. The construction of such models usually rely
on the Plebanski formulation of general relativity as a constrained BF theory
and is based on the discretization of the action on a simplicial triangulation,
which may be viewed as an ultraviolet regulator. The triangulation dependence
can be removed by means of group field theory techniques, which allows one to
sum over all triangulations. The main tasks for these models are the correct
quantum implementation of the Plebanski constraints, the existence of a
semiclassical sector implementing additional "Regge-like" constraints arising
from simplicial triangulations, and the definition of the physical inner
product of loop quantum gravity via group field theory. Here we propose a new
approach to tackle these issues stemming directly from the Holst action for
general relativity, which is also a proper starting point for canonical loop
quantum gravity. The discretization is performed by means of a "cubulation" of
the manifold rather than a triangulation. We give a direct interpretation of
the resulting spin foam model as a generating functional for the n-point
functions on the physical Hilbert space at finite regulator. This paper focuses
on ideas and tasks to be performed before the model can be taken seriously.
However, our analysis reveals some interesting features of this model: first,
the structure of its amplitudes differs from the standard spin foam models.
Second, the tetrad n-point functions admit a "Wick-like" structure. Third, the
restriction to simple representations does not automatically occur -- unless
one makes use of the time gauge, just as in the classical theory.
| [
{
"created": "Sun, 21 Dec 2008 19:52:38 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Dec 2008 09:42:51 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Nov 2012 11:39:03 GMT",
"version": "v3"
}
] | 2015-05-13 | [
[
"Baratin",
"Aristide",
""
],
[
"Flori",
"Cecilia",
""
],
[
"Thiemann",
"Thomas",
""
]
] | Spin foam models are an attempt for a covariant, or path integral formulation of canonical loop quantum gravity. The construction of such models usually rely on the Plebanski formulation of general relativity as a constrained BF theory and is based on the discretization of the action on a simplicial triangulation, which may be viewed as an ultraviolet regulator. The triangulation dependence can be removed by means of group field theory techniques, which allows one to sum over all triangulations. The main tasks for these models are the correct quantum implementation of the Plebanski constraints, the existence of a semiclassical sector implementing additional "Regge-like" constraints arising from simplicial triangulations, and the definition of the physical inner product of loop quantum gravity via group field theory. Here we propose a new approach to tackle these issues stemming directly from the Holst action for general relativity, which is also a proper starting point for canonical loop quantum gravity. The discretization is performed by means of a "cubulation" of the manifold rather than a triangulation. We give a direct interpretation of the resulting spin foam model as a generating functional for the n-point functions on the physical Hilbert space at finite regulator. This paper focuses on ideas and tasks to be performed before the model can be taken seriously. However, our analysis reveals some interesting features of this model: first, the structure of its amplitudes differs from the standard spin foam models. Second, the tetrad n-point functions admit a "Wick-like" structure. Third, the restriction to simple representations does not automatically occur -- unless one makes use of the time gauge, just as in the classical theory. |
1605.01544 | Francesco Cianfrani dr | Francesco Cianfrani | Physical states in Quantum Einstein-Cartan Gravity | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The definition of physical states is the main technical issue of canonical
approaches towards Quantum Gravity. In this work, we outline how those states
can be found in Einstein-Cartan theory via a continuum limit and they are given
by finite dimensional representations of the Lorentz group.
| [
{
"created": "Thu, 5 May 2016 10:25:23 GMT",
"version": "v1"
}
] | 2016-05-06 | [
[
"Cianfrani",
"Francesco",
""
]
] | The definition of physical states is the main technical issue of canonical approaches towards Quantum Gravity. In this work, we outline how those states can be found in Einstein-Cartan theory via a continuum limit and they are given by finite dimensional representations of the Lorentz group. |
1706.08220 | S. Kalyana Rama | S. Kalyana Rama | Variety of $(d + 1)$ dimensional Cosmological Evolutions with and
without bounce in a class of LQC -- inspired Models | Version 1. 41 pages. Version 2. 41 pages. Remark (3) rewritten -- a
minor change. To appear in General Relativity and Gravitation | General Relativity and Gravitation (2017) 49:113 | 10.1007/s10714-017-2277-9 | IMSc/2017/06/04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The bouncing evolution of an universe in Loop Quantum Cosmolgy can be
described very well by a set of effective equations, involving a function $sin
\; x$. Recently, we have generalised these effective equations to $(d + 1)$
dimensions and to any function $f(x) \;$. Depending on $f(x) \;$ in these
models inspired by Loop Quantum Cosmolgy, a variety of cosmological evolutions
are possible, singular as well as non singular. In this paper, we study them in
detail. Among other things, we find that the scale factor $a(t) \; \propto \;
t^{ \frac {2 q} {(2 q - 1) \; (1 + w) d}} \;$ for $f(x) = x^q \;$, and find
explicit Kasner--type solutions if $w = 2 q - 1 \;$ also. A result which we
find particularly fascinating is that, for $f(x) = \sqrt{x} \;$, the evolution
is non singular and the scale factor $a(t)$ grows exponentially at a rate set,
not by a constant density, but by a quantum parameter related to the area
quantum.
| [
{
"created": "Mon, 26 Jun 2017 04:02:51 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jul 2017 06:03:34 GMT",
"version": "v2"
}
] | 2017-08-02 | [
[
"Rama",
"S. Kalyana",
""
]
] | The bouncing evolution of an universe in Loop Quantum Cosmolgy can be described very well by a set of effective equations, involving a function $sin \; x$. Recently, we have generalised these effective equations to $(d + 1)$ dimensions and to any function $f(x) \;$. Depending on $f(x) \;$ in these models inspired by Loop Quantum Cosmolgy, a variety of cosmological evolutions are possible, singular as well as non singular. In this paper, we study them in detail. Among other things, we find that the scale factor $a(t) \; \propto \; t^{ \frac {2 q} {(2 q - 1) \; (1 + w) d}} \;$ for $f(x) = x^q \;$, and find explicit Kasner--type solutions if $w = 2 q - 1 \;$ also. A result which we find particularly fascinating is that, for $f(x) = \sqrt{x} \;$, the evolution is non singular and the scale factor $a(t)$ grows exponentially at a rate set, not by a constant density, but by a quantum parameter related to the area quantum. |
1301.4703 | Patrick Peter | Yi-Fu Cai, Robert Brandenberger and Patrick Peter | Anisotropy in a Nonsingular Bounce | 12 pages, 5 figures | Class. Quantum Grav. 30 (2013) 075019 | 10.1088/0264-9381/30/7/075019 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following recent claims relative to the question of large anisotropy
production in regular bouncing scenarios, we study the evolution of such
anisotropies in a model where an Ekpyrotic phase of contraction is followed by
domination of a Galileon-type Lagrangian which generates a non-singular bounce.
We show that the anisotropies decrease during the phase of Ekpyrotic
contraction (as expected) and that they can be constrained to remain small
during the non-singular bounce phase (a non-trivial result). Specifically, we
derive the e-folding number of the phase of Ekpyrotic contraction which leads
to a present-day anisotropy in agreement with current observational bounds.
| [
{
"created": "Sun, 20 Jan 2013 22:37:42 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Jan 2013 13:22:35 GMT",
"version": "v2"
}
] | 2013-03-15 | [
[
"Cai",
"Yi-Fu",
""
],
[
"Brandenberger",
"Robert",
""
],
[
"Peter",
"Patrick",
""
]
] | Following recent claims relative to the question of large anisotropy production in regular bouncing scenarios, we study the evolution of such anisotropies in a model where an Ekpyrotic phase of contraction is followed by domination of a Galileon-type Lagrangian which generates a non-singular bounce. We show that the anisotropies decrease during the phase of Ekpyrotic contraction (as expected) and that they can be constrained to remain small during the non-singular bounce phase (a non-trivial result). Specifically, we derive the e-folding number of the phase of Ekpyrotic contraction which leads to a present-day anisotropy in agreement with current observational bounds. |
gr-qc/9803036 | Detlev Buchholz | Hans-Juergen Borchers, Detlev Buchholz | Global Properties of Vacuum States in de Sitter Space | 15 pages, Latex, published version (some typos corrected) | Annales Poincare Phys.Theor. A70 (1999) 23-40 | null | null | gr-qc hep-th | null | Starting from the assumption that vacuum states in de Sitter space look for
any geodesic observer like equilibrium states with some a priori arbitrary
temperature, an analysis of their global properties is carried out in the
algebraic framework of local quantum physics. It is shown that these states
have the Reeh-Schlieder property and that any primary vacuum state is also pure
and weakly mixing. Moreover, the geodesic temperature of vacuum states has to
be equal to the Gibbons-Hawking temperature and this fact is closely related to
the existence of a discrete PCT-like symmetry. It is also shown that the global
algebras of observables in vacuum sectors have the same structure as their
counterparts in Minkowski space theories.
| [
{
"created": "Tue, 10 Mar 1998 16:53:55 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Mar 1999 13:23:14 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Borchers",
"Hans-Juergen",
""
],
[
"Buchholz",
"Detlev",
""
]
] | Starting from the assumption that vacuum states in de Sitter space look for any geodesic observer like equilibrium states with some a priori arbitrary temperature, an analysis of their global properties is carried out in the algebraic framework of local quantum physics. It is shown that these states have the Reeh-Schlieder property and that any primary vacuum state is also pure and weakly mixing. Moreover, the geodesic temperature of vacuum states has to be equal to the Gibbons-Hawking temperature and this fact is closely related to the existence of a discrete PCT-like symmetry. It is also shown that the global algebras of observables in vacuum sectors have the same structure as their counterparts in Minkowski space theories. |
1808.10526 | H\'ector Hern\'andez | H\'ector Hern\'andez, Luis A. N\'u\~nez and Adriana
V\'asquez-Ram\'irez | Convection and cracking stability of spheres in General Relativity | 16 pages, 5 figures | null | 10.1140/epjc/s10052-018-6365-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we consider convection and cracking instabilities as
well as their interplay. We develop a simple criterion to identify equations of
state unstable to convection, and explore the influence of buoyancy on cracking
(or overturning) for isotropic and anisotropic relativistic spheres. We show
that a density profile $\rho(r)$, monotonous, decreasing and concave , i.e.
$\rho' < 0$ and $\rho'' < 0$, will be stable against convection, if the radial
sound velocity monotonically decreases outward. We also studied the cracking
instability scenarios and found that isotropic models can be unstable, when the
reaction of the pressure gradient is neglected, i.e. $\delta \mathcal{R}_p =
0$; but if it is considered, the instabilities may vanish and this result is
valid, for both isotropic and anisotropic matter distributions.
| [
{
"created": "Thu, 30 Aug 2018 21:23:34 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2018 17:49:18 GMT",
"version": "v2"
}
] | 2018-11-14 | [
[
"Hernández",
"Héctor",
""
],
[
"Núñez",
"Luis A.",
""
],
[
"Vásquez-Ramírez",
"Adriana",
""
]
] | In the present paper we consider convection and cracking instabilities as well as their interplay. We develop a simple criterion to identify equations of state unstable to convection, and explore the influence of buoyancy on cracking (or overturning) for isotropic and anisotropic relativistic spheres. We show that a density profile $\rho(r)$, monotonous, decreasing and concave , i.e. $\rho' < 0$ and $\rho'' < 0$, will be stable against convection, if the radial sound velocity monotonically decreases outward. We also studied the cracking instability scenarios and found that isotropic models can be unstable, when the reaction of the pressure gradient is neglected, i.e. $\delta \mathcal{R}_p = 0$; but if it is considered, the instabilities may vanish and this result is valid, for both isotropic and anisotropic matter distributions. |
1203.6639 | Johannes Noller | Johannes Noller | Derivative Chameleons | 28 pages, 4 figures | JCAP07(2012)013 | 10.1088/1475-7516/2012/07/013 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider generalized chameleon models where the conformal coupling between
matter and gravitational geometries is not only a function of the chameleon
field \phi, but also of its derivatives via higher order co-ordinate
invariants. Specifically we consider the first such non-trivial conformal
factor A(\phi,X), where X is the canonical kinetic term for \phi. The
associated phenomenology is investigated and we show that such theories have a
new generic mass-altering mechanism, potentially assisting the generation of a
sufficiently large chameleon mass in dense environments. The most general
effective potential is derived for such derivative chameleon setups and
explicit examples are given. Interestingly this points us to the existence of a
purely derivative chameleon protected by a shift symmetry for \phi. We also
discuss potential ghost-like instabilities associated with mass-lifting
mechanisms and find another, mass-lowering and instability-free, branch of
solutions. This suggests that, barring fine-tuning, stable derivative models
are in fact typically anti-chameleons that suppress the field's mass in dense
environments. Furthermore we investigate modifications to the thin-shell regime
and prove a no-go theorem for chameleon effects in non-conformal geometries of
the disformal type.
| [
{
"created": "Thu, 29 Mar 2012 19:32:34 GMT",
"version": "v1"
}
] | 2012-07-10 | [
[
"Noller",
"Johannes",
""
]
] | We consider generalized chameleon models where the conformal coupling between matter and gravitational geometries is not only a function of the chameleon field \phi, but also of its derivatives via higher order co-ordinate invariants. Specifically we consider the first such non-trivial conformal factor A(\phi,X), where X is the canonical kinetic term for \phi. The associated phenomenology is investigated and we show that such theories have a new generic mass-altering mechanism, potentially assisting the generation of a sufficiently large chameleon mass in dense environments. The most general effective potential is derived for such derivative chameleon setups and explicit examples are given. Interestingly this points us to the existence of a purely derivative chameleon protected by a shift symmetry for \phi. We also discuss potential ghost-like instabilities associated with mass-lifting mechanisms and find another, mass-lowering and instability-free, branch of solutions. This suggests that, barring fine-tuning, stable derivative models are in fact typically anti-chameleons that suppress the field's mass in dense environments. Furthermore we investigate modifications to the thin-shell regime and prove a no-go theorem for chameleon effects in non-conformal geometries of the disformal type. |
2306.17394 | Carlos Albertho Benavides-Gallego | Carlos A. Benavides-Gallego, Jose Miguel Ladino and Eduard Larra\~naga | Comparing spin supplementary conditions for particle motion around
traversable wormholes | 19 pages, 8 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Mathisson-Papapetrou-Dixon (MPD) equations describe the motion of
spinning test particles. It is well-known that these equations, which couple
the Riemann curvature tensor with the antisymmetric spin tensor S, together
with the normalization condition for the four-velocity, is a system of eleven
equations relating fourteen unknowns. To ``close'' the system, it is necessary
to introduce a constraint of the form V_\mu S^{\mu \nu} = 0, usually known as
the spin supplementary condition (SSC), where V_\mu is a future-oriented
reference vector satisfying the normalization condition V_\alpha V^\alpha = -1.
There are several SSCs in the literature. In particular, the Tulzcyjew-Dixon,
Mathisson-Pirani, and Ohashi-Kyrian-Semer\'ak are the most used by the
community. From the physical point of view, choosing a different SSC (a
different reference vector $V^\mu$) is equivalent to fixing the centroid of the
test particle. In this manuscript, we compare different SSCs for spinning test
particles moving around a Morris-Thorne traversable wormhole. To do so, we
first obtain the orbital frequency and expand it up to third-order in the
particle's spin; as expected, the zero-order coincides with the Keplerian
frequency, the same in all SSCs; nevertheless, we found that differences appear
in the second order of the expansion, similar to the Schwarzschild and Kerr
black holes. We also compare the behavior of the innermost stable circular
orbit (ISCO). Since each SSC is associated with a different centroid of the
test particle, we analyze (separately) the radial and spin corrections for each
SSC. We found that the radial corrections improve the convergence, especially
between Tulzcyjew-Dixon and Mathisson-Pirani SSCs. In the case of
Ohashi-Kyrian-Semer\'ak, we found that the spin corrections remove the
divergence for the ISCO and extend its existence for higher values of the
particle's spin.
| [
{
"created": "Fri, 30 Jun 2023 04:17:54 GMT",
"version": "v1"
}
] | 2023-07-03 | [
[
"Benavides-Gallego",
"Carlos A.",
""
],
[
"Ladino",
"Jose Miguel",
""
],
[
"Larrañaga",
"Eduard",
""
]
] | The Mathisson-Papapetrou-Dixon (MPD) equations describe the motion of spinning test particles. It is well-known that these equations, which couple the Riemann curvature tensor with the antisymmetric spin tensor S, together with the normalization condition for the four-velocity, is a system of eleven equations relating fourteen unknowns. To ``close'' the system, it is necessary to introduce a constraint of the form V_\mu S^{\mu \nu} = 0, usually known as the spin supplementary condition (SSC), where V_\mu is a future-oriented reference vector satisfying the normalization condition V_\alpha V^\alpha = -1. There are several SSCs in the literature. In particular, the Tulzcyjew-Dixon, Mathisson-Pirani, and Ohashi-Kyrian-Semer\'ak are the most used by the community. From the physical point of view, choosing a different SSC (a different reference vector $V^\mu$) is equivalent to fixing the centroid of the test particle. In this manuscript, we compare different SSCs for spinning test particles moving around a Morris-Thorne traversable wormhole. To do so, we first obtain the orbital frequency and expand it up to third-order in the particle's spin; as expected, the zero-order coincides with the Keplerian frequency, the same in all SSCs; nevertheless, we found that differences appear in the second order of the expansion, similar to the Schwarzschild and Kerr black holes. We also compare the behavior of the innermost stable circular orbit (ISCO). Since each SSC is associated with a different centroid of the test particle, we analyze (separately) the radial and spin corrections for each SSC. We found that the radial corrections improve the convergence, especially between Tulzcyjew-Dixon and Mathisson-Pirani SSCs. In the case of Ohashi-Kyrian-Semer\'ak, we found that the spin corrections remove the divergence for the ISCO and extend its existence for higher values of the particle's spin. |
gr-qc/0506126 | Sean A. Hayward | Sean A. Hayward | Formation and evaporation of non-singular black holes | 4 revtex4 pages, 5 eps figures. Correction concerning surface layer,
revised discussion, title change | Phys.Rev.Lett. 96 (2006) 031103 | 10.1103/PhysRevLett.96.031103 | null | gr-qc hep-th | null | Regular (non-singular) space-times are given which describe the formation of
a (locally defined) black hole from an initial vacuum region, its quiescence as
a static region, and its subsequent evaporation to a vacuum region. The static
region is Bardeen-like, supported by finite density and pressures, vanishing
rapidly at large radius and behaving as a cosmological constant at small
radius. The dynamic regions are Vaidya-like, with ingoing radiation of positive
energy flux during collapse and negative energy flux during evaporation, the
latter balanced by outgoing radiation of positive energy flux and a surface
pressure at a pair creation surface. The black hole consists of a compact
space-time region of trapped surfaces, with inner and outer boundaries which
join circularly as a single smooth trapping horizon.
| [
{
"created": "Tue, 28 Jun 2005 10:23:55 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Dec 2005 21:08:24 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Hayward",
"Sean A.",
""
]
] | Regular (non-singular) space-times are given which describe the formation of a (locally defined) black hole from an initial vacuum region, its quiescence as a static region, and its subsequent evaporation to a vacuum region. The static region is Bardeen-like, supported by finite density and pressures, vanishing rapidly at large radius and behaving as a cosmological constant at small radius. The dynamic regions are Vaidya-like, with ingoing radiation of positive energy flux during collapse and negative energy flux during evaporation, the latter balanced by outgoing radiation of positive energy flux and a surface pressure at a pair creation surface. The black hole consists of a compact space-time region of trapped surfaces, with inner and outer boundaries which join circularly as a single smooth trapping horizon. |
gr-qc/9609056 | Bijan Saha | B. Saha and G. N. Shikin | Interacting Spinor and Scalar Fields in Bianchi type-I Universe filled
with Perfect Fluid: Exact Self-consistent Solutions | LaTex, 15 pages, Submitted to General Relativity and Gravitation | Gen.Rel.Grav. 29 (1997) 1099-1113 | 10.1023/A:1018887024268 | null | gr-qc | null | Self-consistent solutions to interacting spinor and scalar field equations in
General Relativity are studied for the case of Bianchi type-I space-time filled
with perfect fluid. The initial and the asymptotic behavior of the field
functions and the metric one has been thoroughly studied.
| [
{
"created": "Tue, 24 Sep 1996 14:07:16 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Sep 1996 17:52:55 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Saha",
"B.",
""
],
[
"Shikin",
"G. N.",
""
]
] | Self-consistent solutions to interacting spinor and scalar field equations in General Relativity are studied for the case of Bianchi type-I space-time filled with perfect fluid. The initial and the asymptotic behavior of the field functions and the metric one has been thoroughly studied. |
1702.06833 | Oyvind Gron | Matthew T. Aadne and Oivind G. Gron | Exact Solutions of the Field Equations for Empty Space in the Nash
Gravitational Theory | 7 pages | Universe 2017, 3, 10 | 10.3390/universe3010010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | John Nash has proposed a new theory of gravity. We define a Nash-tensor equal
to the curvature tensor appearing in the Nash field equations for empty space,
and calculate its components for two cases. 1. A static, spherically symmetric
space, and 2. The expanding, homogeneous and isotropic space of the
Friedmann-Lemaitre-Robertson-Walker (FLRW) universe models. We find the
general, exact solution of the Nash field equations for empty space in the
static case. The line element turns out to represent the Schwarzschild-de
Sitter spacetime. Also we find the simplest non-trivial solution of the field
equations in the cosmological case, which gives the scale factor corresponding
to the de Sitter spacetime. Hence empty space in the Nash theory corresponds to
a space with Lorentz Invariant Vacuum Energy (LIVE) in the Einstein theory.
This suggests that dark energy may be superfluous according to the Nash theory.
We also consider a radiation filled universe model in an effort to find out how
energy and matter may be incorporated into the Nash theory. A tentative
interpretation of the Nash theory as a unified theory of gravity and
electromagnetism leads to a very simple form of the field equations in the
presence of matter. It should be noted, however, that the Nash theory is still
unfinished. A satifying way of including energy-momentum into the theory has
yet to be found.
| [
{
"created": "Mon, 20 Feb 2017 11:17:48 GMT",
"version": "v1"
}
] | 2017-02-23 | [
[
"Aadne",
"Matthew T.",
""
],
[
"Gron",
"Oivind G.",
""
]
] | John Nash has proposed a new theory of gravity. We define a Nash-tensor equal to the curvature tensor appearing in the Nash field equations for empty space, and calculate its components for two cases. 1. A static, spherically symmetric space, and 2. The expanding, homogeneous and isotropic space of the Friedmann-Lemaitre-Robertson-Walker (FLRW) universe models. We find the general, exact solution of the Nash field equations for empty space in the static case. The line element turns out to represent the Schwarzschild-de Sitter spacetime. Also we find the simplest non-trivial solution of the field equations in the cosmological case, which gives the scale factor corresponding to the de Sitter spacetime. Hence empty space in the Nash theory corresponds to a space with Lorentz Invariant Vacuum Energy (LIVE) in the Einstein theory. This suggests that dark energy may be superfluous according to the Nash theory. We also consider a radiation filled universe model in an effort to find out how energy and matter may be incorporated into the Nash theory. A tentative interpretation of the Nash theory as a unified theory of gravity and electromagnetism leads to a very simple form of the field equations in the presence of matter. It should be noted, however, that the Nash theory is still unfinished. A satifying way of including energy-momentum into the theory has yet to be found. |
gr-qc/9505008 | Jose Wadih Maluf | J. W. Maluf and A. Kneip (Universidade de Brasilia) | Gravitational energy of conical defects | 16 pages, LaTex file, no figure, additional text included, to appear
in the J. Math. Phys | J.Math.Phys. 38 (1997) 458-465 | 10.1063/1.531827 | null | gr-qc | null | The energy density of asymptotically flat gravitational fields can be
calculated from a simple expression involving the trace of the torsion tensor.
Integration of this energy density over the whole space yields the ADM energy.
Such expression can be justified within the framework of the teleparallel
equivalent of general relativity, which is an alternative geometrical
formulation of Einstein's general relativity. In this paper we apply this
energy density to the evaluation of the energy per unit length of a class of
conical defects of topological nature, which include disclinations and
dislocations (in the terminology of crystallography). Disclinations correspond
to cosmic strings, and for a spacetime endowed with only such a defect we
obtain precisely the well known expression of energy per unit length. However
for a pure spacetime dislocation the total gravitational energy is zero.
| [
{
"created": "Sun, 7 May 1995 18:34:24 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Aug 1996 19:27:27 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Maluf",
"J. W.",
"",
"Universidade de Brasilia"
],
[
"Kneip",
"A.",
"",
"Universidade de Brasilia"
]
] | The energy density of asymptotically flat gravitational fields can be calculated from a simple expression involving the trace of the torsion tensor. Integration of this energy density over the whole space yields the ADM energy. Such expression can be justified within the framework of the teleparallel equivalent of general relativity, which is an alternative geometrical formulation of Einstein's general relativity. In this paper we apply this energy density to the evaluation of the energy per unit length of a class of conical defects of topological nature, which include disclinations and dislocations (in the terminology of crystallography). Disclinations correspond to cosmic strings, and for a spacetime endowed with only such a defect we obtain precisely the well known expression of energy per unit length. However for a pure spacetime dislocation the total gravitational energy is zero. |
2309.12604 | Qiyuan Pan | Lina Zhang, Songbai Chen, Qiyuan Pan, Jiliang Jing | Chaotic motion of scalar particle coupling to Chern-Simons invariant in
the stationary axisymmetric Einstein-Maxwell dilaton black hole spacetime | 17 pages, 10 figures | Eur. Phys. J. C 83, 828 (2023) | 10.1140/epjc/s10052-023-12008-6 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate the motion of a test scalar particle coupling to the
Chern-Simons (CS) invariant in the background of a stationary axisymmetric
black hole in the Einstein-Maxwell-Dilaton-Axion (EMDA) gravity. Comparing with
the case of a Kerr black hole, we observe that the presence of the dilation
parameter makes the CS invariant more complex, and changes the range of the
coupling parameter and the spin parameter where the chaotic motion appears for
the scalar particle. Moreover, we find that the coupling parameter together
with the spin parameter also affects the range of the dilation parameter where
the chaos occurs. We also probe the effects of the dilation parameter on the
chaotic strength of the chaotic orbits for the coupled particle. Our results
indicate that the coupling between the CS invariant and the scalar particle
yields the richer dynamical behavior of the particle in the rotating EMDA black
hole spacetime.
| [
{
"created": "Fri, 22 Sep 2023 03:38:20 GMT",
"version": "v1"
}
] | 2023-09-25 | [
[
"Zhang",
"Lina",
""
],
[
"Chen",
"Songbai",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
]
] | We investigate the motion of a test scalar particle coupling to the Chern-Simons (CS) invariant in the background of a stationary axisymmetric black hole in the Einstein-Maxwell-Dilaton-Axion (EMDA) gravity. Comparing with the case of a Kerr black hole, we observe that the presence of the dilation parameter makes the CS invariant more complex, and changes the range of the coupling parameter and the spin parameter where the chaotic motion appears for the scalar particle. Moreover, we find that the coupling parameter together with the spin parameter also affects the range of the dilation parameter where the chaos occurs. We also probe the effects of the dilation parameter on the chaotic strength of the chaotic orbits for the coupled particle. Our results indicate that the coupling between the CS invariant and the scalar particle yields the richer dynamical behavior of the particle in the rotating EMDA black hole spacetime. |
2211.16674 | Shio Sakon | Shio Sakon and Leo Tsukada and Heather Fong and Chad Hanna and James
Kennington and Wanting Niu and Shomik Adhicary and Pratyusava Baral and
Amanda Baylor and Kipp Cannon and Sarah Caudill and Bryce Cousins and Jolien
D. E. Creighton and Becca Ewing and Patrick Godwin and Reiko Harada and
Yun-Jing Huang and Rachael Huxford and Prathamesh Joshi and Soichiro Kuwahara
and Alvin K. Y. Li and Ryan Magee and Duncan Meacher and Cody Messick and
Soichiro Morisaki and Debnandini Mukherjee and Alex Pace and Cort Posnansky
and Surabhi Sachdev and Divya Singh and Ron Tapia and Takuya Tsutsui and Koh
Ueno and Aaron Viets and Leslie Wade and Madeline Wade and Jonathan Wang | Template bank for compact binary mergers in the fourth observing run of
Advanced LIGO, Advanced Virgo, and KAGRA | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Matched-filtering gravitational wave search pipelines identify gravitational
wave signals by computing correlations, i.e., signal-to-noise ratios, between
gravitational wave detector data and gravitational wave template waveforms.
Intrinsic parameters, the component masses and spins, of the gravitational wave
waveforms are often stored in "template banks", and the construction of a
densely populated template bank is essential for some gravitational wave search
pipelines. This paper presents a template bank that is currently being used by
the GstLAL-based compact binary search pipeline in the fourth observing run of
the LIGO, Virgo, and KAGRA collaboration, and was generated with a new binary
tree approach of placing templates, {\fontfamily{qcr}\selectfont manifold}. The
template bank contains $1.8 \times 10^6$ sets of template parameters covering
plausible neutron star and black hole systems up to a total mass of $400$
$M_\odot$ with component masses between $1$-$200$ $M_\odot$ and mass ratios
between $1$ and $20$ under the assumption that each component object's angular
momentum is aligned with the orbital angular momentum. We validate the template
bank generated with our new method, {\fontfamily{qcr}\selectfont manifold}, by
comparing it with a template bank generated with the previously used stochastic
template placement method. We show that both template banks have similar
effectualness. The {\fontfamily{qcr}\selectfont GstLAL} search pipeline
performs singular value decomposition (SVD) on the template banks to reduce the
number of filters used. We describe a new grouping of waveforms that improves
the computational efficiency of SVD by nearly $5$ times as compared to
previously reported SVD sorting schemes.
| [
{
"created": "Wed, 30 Nov 2022 01:36:20 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jan 2023 19:20:49 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Apr 2023 00:23:49 GMT",
"version": "v3"
},
{
"created": "Tue, 18 Apr 2023 21:06:17 GMT",
"version": "v4"
},
{
"c... | 2023-12-22 | [
[
"Sakon",
"Shio",
""
],
[
"Tsukada",
"Leo",
""
],
[
"Fong",
"Heather",
""
],
[
"Hanna",
"Chad",
""
],
[
"Kennington",
"James",
""
],
[
"Niu",
"Wanting",
""
],
[
"Adhicary",
"Shomik",
""
],
[
"Baral",... | Matched-filtering gravitational wave search pipelines identify gravitational wave signals by computing correlations, i.e., signal-to-noise ratios, between gravitational wave detector data and gravitational wave template waveforms. Intrinsic parameters, the component masses and spins, of the gravitational wave waveforms are often stored in "template banks", and the construction of a densely populated template bank is essential for some gravitational wave search pipelines. This paper presents a template bank that is currently being used by the GstLAL-based compact binary search pipeline in the fourth observing run of the LIGO, Virgo, and KAGRA collaboration, and was generated with a new binary tree approach of placing templates, {\fontfamily{qcr}\selectfont manifold}. The template bank contains $1.8 \times 10^6$ sets of template parameters covering plausible neutron star and black hole systems up to a total mass of $400$ $M_\odot$ with component masses between $1$-$200$ $M_\odot$ and mass ratios between $1$ and $20$ under the assumption that each component object's angular momentum is aligned with the orbital angular momentum. We validate the template bank generated with our new method, {\fontfamily{qcr}\selectfont manifold}, by comparing it with a template bank generated with the previously used stochastic template placement method. We show that both template banks have similar effectualness. The {\fontfamily{qcr}\selectfont GstLAL} search pipeline performs singular value decomposition (SVD) on the template banks to reduce the number of filters used. We describe a new grouping of waveforms that improves the computational efficiency of SVD by nearly $5$ times as compared to previously reported SVD sorting schemes. |
1511.04533 | Donato Bini | Donato Bini, Thibault Damour and Andrea Geralico | Confirming and improving post-Newtonian and effective-one-body results
from self-force computations along eccentric orbits around a Schwarzschild
black hole | 14 pages, 3 figures, revtex macros used | Phys. Rev. D 93, 064023 (2016) | 10.1103/PhysRevD.93.064023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically compute, through the six-and-a-half post-Newtonian order, the
second-order-in-eccentricity piece of the Detweiler-Barack-Sago gauge-invariant
redshift function for a small mass in eccentric orbit around a Schwarzschild
black hole. Using the first law of mechanics for eccentric orbits [A. Le Tiec,
Phys. Rev. D {\bf 92}, 084021 (2015)] we transcribe our result into a
correspondingly accurate knowledge of the second radial potential of the
effective-one-body formalism [A. Buonanno and T. Damour, Phys. Rev. D {\bf 59},
084006 (1999)]. We compare our newly acquired analytical information to several
different numerical self-force data and find good agreement, within estimated
error bars. We also obtain, for the first time, independent analytical checks
of the recently derived, comparable-mass fourth-post-Newtonian order dynamics
[T. Damour, P. Jaranowski and G. Shaefer, Phys. Rev. D {\bf 89}, 064058
(2014)].
| [
{
"created": "Sat, 14 Nov 2015 09:19:34 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
],
[
"Geralico",
"Andrea",
""
]
] | We analytically compute, through the six-and-a-half post-Newtonian order, the second-order-in-eccentricity piece of the Detweiler-Barack-Sago gauge-invariant redshift function for a small mass in eccentric orbit around a Schwarzschild black hole. Using the first law of mechanics for eccentric orbits [A. Le Tiec, Phys. Rev. D {\bf 92}, 084021 (2015)] we transcribe our result into a correspondingly accurate knowledge of the second radial potential of the effective-one-body formalism [A. Buonanno and T. Damour, Phys. Rev. D {\bf 59}, 084006 (1999)]. We compare our newly acquired analytical information to several different numerical self-force data and find good agreement, within estimated error bars. We also obtain, for the first time, independent analytical checks of the recently derived, comparable-mass fourth-post-Newtonian order dynamics [T. Damour, P. Jaranowski and G. Shaefer, Phys. Rev. D {\bf 89}, 064058 (2014)]. |
1605.02241 | Kofinas Georgios | Georgios Kofinas, Vasilios Zarikas | Asymptotically Safe gravity and non-singular inflationary Big Bang with
vacuum birth | 18 pages, no figures, version to app. in Phys. Rev. D | Phys. Rev. D 94, 103514 (2016) | 10.1103/PhysRevD.94.103514 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General non-singular accelerating cosmological solutions for an initial
cosmic period of pure vacuum birth era are derived. This vacuum era is
described by a varying cosmological "constant" suggested by the Renormalisation
Group flow of Asymptotic Safety scenario near the ultraviolet fixed point. In
this scenario, natural exit from inflation to the standard decelerating
cosmology occurs when the energy scale lowers and the cosmological "constant"
becomes insignificant. In the following period where matter is also present,
cosmological solutions with characteristics similar to the vacuum case are
generated. Remarkably the set of equations allow for particle production and
entropy generation. Alternatively, in the case of non-zero bulk viscosity,
entropy production and reheating is found. As for the equations of motion, they
modify Einstein equations by adding covariant kinetic terms of the cosmological
"constant" which respect the Bianchi identities. An advance of the proposed
framework is that it ensures a consistent description of both a quantum vacuum
birth of the universe and a subsequent cosmic era in the presence of matter.
| [
{
"created": "Sat, 7 May 2016 20:17:08 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 2016 20:34:54 GMT",
"version": "v2"
}
] | 2016-11-23 | [
[
"Kofinas",
"Georgios",
""
],
[
"Zarikas",
"Vasilios",
""
]
] | General non-singular accelerating cosmological solutions for an initial cosmic period of pure vacuum birth era are derived. This vacuum era is described by a varying cosmological "constant" suggested by the Renormalisation Group flow of Asymptotic Safety scenario near the ultraviolet fixed point. In this scenario, natural exit from inflation to the standard decelerating cosmology occurs when the energy scale lowers and the cosmological "constant" becomes insignificant. In the following period where matter is also present, cosmological solutions with characteristics similar to the vacuum case are generated. Remarkably the set of equations allow for particle production and entropy generation. Alternatively, in the case of non-zero bulk viscosity, entropy production and reheating is found. As for the equations of motion, they modify Einstein equations by adding covariant kinetic terms of the cosmological "constant" which respect the Bianchi identities. An advance of the proposed framework is that it ensures a consistent description of both a quantum vacuum birth of the universe and a subsequent cosmic era in the presence of matter. |
gr-qc/0507009 | Christiane Lechner | Christiane Lechner | Staticity, Self-Similarity and Critical Phenomena in a Self-Gravitating
Nonlinear Sigma Model | PhD thesis, University of Vienna, October 2001, 165 pages, many
figures | null | null | null | gr-qc | null | The main part of the thesis deals with continuously and discretely
self-similar solutions and type II critical phenomena in a family of
self-gravitating non-linear sigma-models. The phenomena strongly depend on the
dimensionless coupling constant. For small couplings we numerically construct
continuously self-similar (CSS) solutions and analyze their stability
properties. For large couplings we construct a discretely self-similar (DSS)
solution with one unstable mode. We argue that at some critical coupling the
DSS solution bifurcates from the first CSS excitation in a heteroclinic loop
bifurcation. We study critical phenomena between dispersal and singularity
formation (at very small couplings) respectively black hole formation (for
larger couplings). We give numerical evidence that for very small couplings the
generic end state of ``intermediately strong'' data is the stable CSS ground
state. For small couplings the critical solution is the first CSS excitation
whereas for strong couplings the threshold of black hole formation is governed
by the DSS solution. We describe the phenomena occurring at intermediate
couplings where the critical solution changes from CSS to DSS.
Content and references are at the state of October 2001.
| [
{
"created": "Sat, 2 Jul 2005 16:36:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lechner",
"Christiane",
""
]
] | The main part of the thesis deals with continuously and discretely self-similar solutions and type II critical phenomena in a family of self-gravitating non-linear sigma-models. The phenomena strongly depend on the dimensionless coupling constant. For small couplings we numerically construct continuously self-similar (CSS) solutions and analyze their stability properties. For large couplings we construct a discretely self-similar (DSS) solution with one unstable mode. We argue that at some critical coupling the DSS solution bifurcates from the first CSS excitation in a heteroclinic loop bifurcation. We study critical phenomena between dispersal and singularity formation (at very small couplings) respectively black hole formation (for larger couplings). We give numerical evidence that for very small couplings the generic end state of ``intermediately strong'' data is the stable CSS ground state. For small couplings the critical solution is the first CSS excitation whereas for strong couplings the threshold of black hole formation is governed by the DSS solution. We describe the phenomena occurring at intermediate couplings where the critical solution changes from CSS to DSS. Content and references are at the state of October 2001. |
1408.1641 | Stoytcho Yazadjiev | Daniela D. Doneva, Stoytcho S. Yazadjiev, Kalin V. Staykov, Kostas D.
Kokkotas | Universal I-Q relations for rapidly rotating neutron and strange stars
in scalar-tensor theories | 8 pages, 3 figures | null | 10.1103/PhysRevD.90.104021 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study how rapid rotation influences the relation between the normalized
moment of inertia $\bar{I}$ and quadrupole moment $\bar{Q}$ for scalarized
neutron stars. The questions one has to answer are whether the EOS universality
is preserved in this regime and what are the deviations from general
relativity. Our results show that the $\bar{I}-\bar{Q}$ relation is nearly EOS
independent for scalarized rapidly rotating stars, but the differences with
pure Einstein's theory increase compared to the slowly rotating case. In
general, smaller negative values of the scalar field coupling parameters
$\beta$ lead to larger deviations, but these deviations are below the expected
accuracy of the future astrophysical observations if one considers values of
$\beta$ in agreement with the current observational constraint. An important
remark is that although the normalized $\bar{I}-\bar{Q}$ relation is quite
similar for scalar-tensor theories and general relativity, the unnormalized
moment of inertia and quadrupole moment can be very different in the two
theories. This demonstrates that although the $\bar{I}-\bar{Q}$ relations are
potentially very useful for some purposes, they might not serve us well when
trying to distinguish between different theories of gravity.
| [
{
"created": "Thu, 7 Aug 2014 16:15:24 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Staykov",
"Kalin V.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | We study how rapid rotation influences the relation between the normalized moment of inertia $\bar{I}$ and quadrupole moment $\bar{Q}$ for scalarized neutron stars. The questions one has to answer are whether the EOS universality is preserved in this regime and what are the deviations from general relativity. Our results show that the $\bar{I}-\bar{Q}$ relation is nearly EOS independent for scalarized rapidly rotating stars, but the differences with pure Einstein's theory increase compared to the slowly rotating case. In general, smaller negative values of the scalar field coupling parameters $\beta$ lead to larger deviations, but these deviations are below the expected accuracy of the future astrophysical observations if one considers values of $\beta$ in agreement with the current observational constraint. An important remark is that although the normalized $\bar{I}-\bar{Q}$ relation is quite similar for scalar-tensor theories and general relativity, the unnormalized moment of inertia and quadrupole moment can be very different in the two theories. This demonstrates that although the $\bar{I}-\bar{Q}$ relations are potentially very useful for some purposes, they might not serve us well when trying to distinguish between different theories of gravity. |
1512.09019 | Slava G. Turyshev | Slava G. Turyshev, Nan Yu, and Viktor T. Toth | General relativistic observables for the ACES experiment | 24 pages, 2 figures, 2 tables, revtex4 | Phys. Rev. D 93, 045027 (2016) | 10.1103/PhysRevD.93.045027 | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a high-precision model for relativistic observables of the Atomic
Clock Ensemble in Space (ACES) experiment on the International Space Station
(ISS). We develop all relativistic coordinate transformations that are needed
to describe the motion of ACES in Earth orbit and to compute observable
quantities. We analyze the accuracy of the required model as it applies to the
proper-to-coordinate time transformations, light time equation, and spacecraft
equations of motion. We consider various sources of nongravitational noise and
their effects on ACES. We estimate the accuracy of orbit reconstruction that is
needed to satisfy the ACES science objectives. Based on our analysis, we derive
models for the relativistic observables of ACES, which also account for the
contribution of atmospheric drag on the clock rate. We include the Earth's
oblateness coefficient $J_2$ and the effects of major nongravitational forces
on the orbit of the ISS. We demonstrate that the ACES reference frame is
pseudo-inertial at the level of accuracy required by the experiment. We
construct a Doppler-canceled science observable representing the gravitational
redshift. We derive accuracy requirements for ISS navigation. The improved
model is accurate up to $<1$ ps and $\sim 4\times 10^{-17}$ for time and
frequency transfers, correspondingly. These limits are determined by the higher
order harmonics in Earth's gravitational potential.
| [
{
"created": "Wed, 30 Dec 2015 17:08:53 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Feb 2016 06:06:06 GMT",
"version": "v2"
}
] | 2016-02-25 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Yu",
"Nan",
""
],
[
"Toth",
"Viktor T.",
""
]
] | We develop a high-precision model for relativistic observables of the Atomic Clock Ensemble in Space (ACES) experiment on the International Space Station (ISS). We develop all relativistic coordinate transformations that are needed to describe the motion of ACES in Earth orbit and to compute observable quantities. We analyze the accuracy of the required model as it applies to the proper-to-coordinate time transformations, light time equation, and spacecraft equations of motion. We consider various sources of nongravitational noise and their effects on ACES. We estimate the accuracy of orbit reconstruction that is needed to satisfy the ACES science objectives. Based on our analysis, we derive models for the relativistic observables of ACES, which also account for the contribution of atmospheric drag on the clock rate. We include the Earth's oblateness coefficient $J_2$ and the effects of major nongravitational forces on the orbit of the ISS. We demonstrate that the ACES reference frame is pseudo-inertial at the level of accuracy required by the experiment. We construct a Doppler-canceled science observable representing the gravitational redshift. We derive accuracy requirements for ISS navigation. The improved model is accurate up to $<1$ ps and $\sim 4\times 10^{-17}$ for time and frequency transfers, correspondingly. These limits are determined by the higher order harmonics in Earth's gravitational potential. |
gr-qc/9802069 | Lee Ashton Wild | Philippos Papadopoulos, Edward Seidel, and Lee Wild | Adaptive computation of gravitational waves from black hole interactions | 16 Pages, RevTeX, 13 figures | Phys.Rev. D58 (1998) 084002 | 10.1103/PhysRevD.58.084002 | null | gr-qc | null | We construct a class of linear partial differential equations describing
general perturbations of non-rotating black holes in 3D Cartesian coordinates.
In contrast to the usual approach, a single equation treats all radiative $\ell
-m$ modes simultaneously, allowing the study of wave perturbations of black
holes with arbitrary 3D structure, as would be present when studying the full
set of nonlinear Einstein equations describing a perturbed black hole. This
class of equations forms an excellent testbed to explore the computational
issues of simulating black spacetimes using a three dimensional adaptive mesh
refinement code. Using this code, we present results from the first fully
resolved 3D solution of the equations describing perturbed black holes. We
discuss both fixed and adaptive mesh refinement, refinement criteria, and the
computational savings provided by adaptive techniques in 3D for such model
problems of distorted black holes.
| [
{
"created": "Fri, 27 Feb 1998 17:08:53 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Papadopoulos",
"Philippos",
""
],
[
"Seidel",
"Edward",
""
],
[
"Wild",
"Lee",
""
]
] | We construct a class of linear partial differential equations describing general perturbations of non-rotating black holes in 3D Cartesian coordinates. In contrast to the usual approach, a single equation treats all radiative $\ell -m$ modes simultaneously, allowing the study of wave perturbations of black holes with arbitrary 3D structure, as would be present when studying the full set of nonlinear Einstein equations describing a perturbed black hole. This class of equations forms an excellent testbed to explore the computational issues of simulating black spacetimes using a three dimensional adaptive mesh refinement code. Using this code, we present results from the first fully resolved 3D solution of the equations describing perturbed black holes. We discuss both fixed and adaptive mesh refinement, refinement criteria, and the computational savings provided by adaptive techniques in 3D for such model problems of distorted black holes. |
gr-qc/0212122 | Richard Gass | Andrew Royston and Richard Gass | An Optical Analog of a Black Holes | four pages, 1 figure | null | null | null | gr-qc | null | Using media with extremely low group velocities one can create an optical
analog of a curved space-time. Leonhardt and Piwnicki have proposed that a
vortex flow will act as an optical black hole. We show that although the
Leonhardt - Piwnicki flow has an orbit of no return and an infinite red-shift
surface, it is not a true black hole since it lacks a null hypersurface.
However a radial flow will produce a true optical black hole that has a Hawking
temperature and obeys the first law of black hole mechanics. By combining the
Leonhardt - Piwnicki flow with a radial flow we obtain the analog of the Kerr
black hole.
| [
{
"created": "Mon, 30 Dec 2002 14:16:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Royston",
"Andrew",
""
],
[
"Gass",
"Richard",
""
]
] | Using media with extremely low group velocities one can create an optical analog of a curved space-time. Leonhardt and Piwnicki have proposed that a vortex flow will act as an optical black hole. We show that although the Leonhardt - Piwnicki flow has an orbit of no return and an infinite red-shift surface, it is not a true black hole since it lacks a null hypersurface. However a radial flow will produce a true optical black hole that has a Hawking temperature and obeys the first law of black hole mechanics. By combining the Leonhardt - Piwnicki flow with a radial flow we obtain the analog of the Kerr black hole. |
2308.00765 | Silvia Pla Garc\'ia | Jean Alexandre, Katy Clough and Silvia Pla | Tunnelling-induced cosmic bounce in the presence of anisotropies | 9 pages, 5 figures, minor changes, version accepted for publication
in Physical Review D | Phys. Rev. D 108, 103515 (2023) | 10.1103/PhysRevD.108.103515 | KCL-PH-TH/2023-42 | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | If we imagine rewinding the universe to early times, the scale factor shrinks
and the existence of a finite spatial volume may play a role in quantum
tunnelling effects in a closed universe. It has recently been shown that such
finite volume effects dynamically generate an effective equation of state that
could support a cosmological bounce. In this work we extend the analysis to the
case in which a (homogeneous) anisotropy is present, and identify a criteria
for a successful bounce in terms of the size of the closed universe and the
properties of the quantum field.
| [
{
"created": "Tue, 1 Aug 2023 18:04:17 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Nov 2023 16:54:53 GMT",
"version": "v2"
}
] | 2023-11-15 | [
[
"Alexandre",
"Jean",
""
],
[
"Clough",
"Katy",
""
],
[
"Pla",
"Silvia",
""
]
] | If we imagine rewinding the universe to early times, the scale factor shrinks and the existence of a finite spatial volume may play a role in quantum tunnelling effects in a closed universe. It has recently been shown that such finite volume effects dynamically generate an effective equation of state that could support a cosmological bounce. In this work we extend the analysis to the case in which a (homogeneous) anisotropy is present, and identify a criteria for a successful bounce in terms of the size of the closed universe and the properties of the quantum field. |
1409.4400 | Artur Alho | Artur Alho, Simone Calogero, Maria P. Machado Ramos and Ana J. Soares | Dynamics of Robertson-Walker spacetimes with diffusion | 19 pages, 4 figures. Matches final version | null | 10.1016/j.aop.2015.01.010 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of spatially homogeneous and isotropic spacetimes
containing a fluid undergoing microscopic velocity diffusion in a cosmological
scalar field. After deriving a few exact solutions of the equations, we
continue by analyzing the qualitative behavior of general solutions. To this
purpose we recast the equations in the form of a two dimensional dynamical
system and perform a global analysis of the flow. Among the admissible
behaviors, we find solutions that are asymptotically de-Sitter both in the past
and future time direction and which undergo accelerated expansion at all times.
| [
{
"created": "Mon, 15 Sep 2014 19:56:22 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Feb 2015 16:28:42 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Alho",
"Artur",
""
],
[
"Calogero",
"Simone",
""
],
[
"Ramos",
"Maria P. Machado",
""
],
[
"Soares",
"Ana J.",
""
]
] | We study the dynamics of spatially homogeneous and isotropic spacetimes containing a fluid undergoing microscopic velocity diffusion in a cosmological scalar field. After deriving a few exact solutions of the equations, we continue by analyzing the qualitative behavior of general solutions. To this purpose we recast the equations in the form of a two dimensional dynamical system and perform a global analysis of the flow. Among the admissible behaviors, we find solutions that are asymptotically de-Sitter both in the past and future time direction and which undergo accelerated expansion at all times. |
0911.1565 | Gaurav Khanna | Gaurav Khanna | The CBE Hardware Accelerator for Numerical Relativity: A Simple Approach | 5 pages, 2 figures; Accepted for publication in the International
Journal of Modeling, Simulation, and Scientific Computing (IJMSSC) | Int.J.Model.Simul.Sci.Comput.1:147,2010 | 10.1142/S1793962310000043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hardware accelerators (such as the Cell Broadband Engine) have recently
received a significant amount of attention from the computational science
community because they can provide significant gains in the overall performance
of many numerical simulations at a low cost. However, such accelerators usually
employ a rather unfamiliar and specialized programming model that often
requires advanced knowledge of their hardware design. In this article, we
demonstrate an alternate and simpler approach towards managing the main
complexities in the programming of the Cell processor, called software caching.
We apply this technique to a numerical relativity application: a time-domain,
finite-difference Kerr black hole perturbation evolver, and present the
performance results. We obtain gains in the overall performance of generic
simulations that are close to the theoretical maximum that can be obtained
through our parallelization approach.
| [
{
"created": "Sun, 8 Nov 2009 22:15:49 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Khanna",
"Gaurav",
""
]
] | Hardware accelerators (such as the Cell Broadband Engine) have recently received a significant amount of attention from the computational science community because they can provide significant gains in the overall performance of many numerical simulations at a low cost. However, such accelerators usually employ a rather unfamiliar and specialized programming model that often requires advanced knowledge of their hardware design. In this article, we demonstrate an alternate and simpler approach towards managing the main complexities in the programming of the Cell processor, called software caching. We apply this technique to a numerical relativity application: a time-domain, finite-difference Kerr black hole perturbation evolver, and present the performance results. We obtain gains in the overall performance of generic simulations that are close to the theoretical maximum that can be obtained through our parallelization approach. |
0912.4067 | Eduardo Rodrigues | H. P. de Oliveira, E. L. Rodrigues and I. Dami\~ao Soares | The dynamics of apparent horizons in Robinson-Trautman spacetimes | 9 pages, 7 figures | null | 10.1007/s13538-011-0036-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an alternative scheme of finding apparent horizons based on
spectral methods applied to Robinson-Trautman spacetimes. We have considered
distinct initial data such as representing the spheroids of matter and the
head-on collision of two non-rotating black holes. The evolution of the
apparent horizon is presented. We have obtained in some cases a mass gap
between the final Bondi and apparent horizon masses, whose implications were
briefly commented in the light of the thermodynamics of black holes.
| [
{
"created": "Mon, 21 Dec 2009 02:00:16 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"de Oliveira",
"H. P.",
""
],
[
"Rodrigues",
"E. L.",
""
],
[
"Soares",
"I. Damião",
""
]
] | We present an alternative scheme of finding apparent horizons based on spectral methods applied to Robinson-Trautman spacetimes. We have considered distinct initial data such as representing the spheroids of matter and the head-on collision of two non-rotating black holes. The evolution of the apparent horizon is presented. We have obtained in some cases a mass gap between the final Bondi and apparent horizon masses, whose implications were briefly commented in the light of the thermodynamics of black holes. |
2301.00571 | Telem Ibungochouba Singh | Y. Onika Laxmi and T. Ibungochouba Singh | Modified Hawking temperature and entropy of Kerr-de Sitter black hole in
Lorentz violation theory | null | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we discuss the tunneling of scalar particles near the event
horizon of stationary and nonstationary Kerr-de Sitter black hole using Lorentz
violation theory in curved space time. The modified form of Hamilton-Jacobi
equation is derived from the Klein-Gordon equation by applying Lorentz
violation theory. The Hawking temperatures derived from stationary and
nonstationary Kerr-de Sitter black holes are modified due to Lorentz violation
theory. It is noted that the change in Bekenstein-Hawking entropy and modified
Hawking temperatures of stationary and nonstationary Kerr-de Sitter black hole
not only depend on the black hole parameters but also on ether like vectors
${\rm u^\alpha}$.
| [
{
"created": "Mon, 2 Jan 2023 09:18:57 GMT",
"version": "v1"
}
] | 2023-01-03 | [
[
"Laxmi",
"Y. Onika",
""
],
[
"Singh",
"T. Ibungochouba",
""
]
] | In this paper, we discuss the tunneling of scalar particles near the event horizon of stationary and nonstationary Kerr-de Sitter black hole using Lorentz violation theory in curved space time. The modified form of Hamilton-Jacobi equation is derived from the Klein-Gordon equation by applying Lorentz violation theory. The Hawking temperatures derived from stationary and nonstationary Kerr-de Sitter black holes are modified due to Lorentz violation theory. It is noted that the change in Bekenstein-Hawking entropy and modified Hawking temperatures of stationary and nonstationary Kerr-de Sitter black hole not only depend on the black hole parameters but also on ether like vectors ${\rm u^\alpha}$. |
1307.7782 | Harald P. Pfeiffer | Harald P. Pfeiffer and Andrew I. MacFadyen | Hyperbolicity of Force-Free Electrodynamics | 11 pages | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the equations of relativistic magnetized plasma dynamics in the
limiting case that electromagnetic stress-energy is dominant over pressure and
rest mass energy density. The naive formulation of these equations is shown to
be not hyperbolic. Modifying the equations by terms that vanish for all
physical solutions, we obtain a symmetric hyperbolic evolution system, which
should exhibit improved numerical behavior.
| [
{
"created": "Tue, 30 Jul 2013 01:57:58 GMT",
"version": "v1"
}
] | 2013-07-31 | [
[
"Pfeiffer",
"Harald P.",
""
],
[
"MacFadyen",
"Andrew I.",
""
]
] | We analyze the equations of relativistic magnetized plasma dynamics in the limiting case that electromagnetic stress-energy is dominant over pressure and rest mass energy density. The naive formulation of these equations is shown to be not hyperbolic. Modifying the equations by terms that vanish for all physical solutions, we obtain a symmetric hyperbolic evolution system, which should exhibit improved numerical behavior. |
2105.07075 | Ezequiel Boero | Ezequiel F. Boero and Osvaldo M. Moreschi | Strong gravitational lens image of the M87 black hole with a simple
accreting matter model | 18 pages,16 figures | null | 10.1093/mnras/stab2336 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study simulated images generated from an accretion disk surrounding the
supermassive black hole hosted in the nearby galaxy M87. We approach the
problem employing very simple accreting models inspired from
magnetohydrodynamical simulations and introducing a new recipe for dealing with
the combined integration of the geodesic and geodesic deviation equations in
Kerr spacetime, which allows for a convenient and efficient way to manage the
system of equations. The geometry of the basic emission model is given by a two
temperature thin disk in the equatorial plane of the black hole supplemented by
an asymmetric bar structure. We show that this configuration permits to
generate the most salient features appearing in the EHT Collaboration images of
M87 with impressive fidelity.
| [
{
"created": "Fri, 14 May 2021 21:35:29 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Aug 2021 13:49:38 GMT",
"version": "v2"
}
] | 2021-08-18 | [
[
"Boero",
"Ezequiel F.",
""
],
[
"Moreschi",
"Osvaldo M.",
""
]
] | We study simulated images generated from an accretion disk surrounding the supermassive black hole hosted in the nearby galaxy M87. We approach the problem employing very simple accreting models inspired from magnetohydrodynamical simulations and introducing a new recipe for dealing with the combined integration of the geodesic and geodesic deviation equations in Kerr spacetime, which allows for a convenient and efficient way to manage the system of equations. The geometry of the basic emission model is given by a two temperature thin disk in the equatorial plane of the black hole supplemented by an asymmetric bar structure. We show that this configuration permits to generate the most salient features appearing in the EHT Collaboration images of M87 with impressive fidelity. |
1207.0887 | Alejandro Corichi | Alejandro Corichi | Energy of test objects on black hole spacetimes: A brief review | 16 pages, no figures. Discussion expanded, de Sitter BH case
included. Matches published version | Int Jour Mod Phys D24, No. 14 (2015) 1550103 | 10.1142/S0218271815501035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we review the issue of defining energy for test particles on a
background stationary spacetime. We revisit the different notions of energy as
defined by different observers. As is well known, the existence of a time-like
isometry allows for the notion of total conserved energy to be well defined. We
use this well known quantity to show that a gravitational potential energy can
be consistently defined. As examples, we study the case of the exterior regions
of an asymptotically flat black hole and of the $\Lambda>0$ Schwarzschild de
Sitter case, where an asymptotic region is not available. We then consider the
situation in which the test particle is absorbed by the black hole, and analyze
the energetics in detail. In particular, we show that the notion of horizon
energy as defined by the isolated horizons formalism provides a satisfactory
notion of energy compatible with the particle's total conserved energy. With
these choices, there is a global conservation of energy. Finally, we comment on
a recent proposal to define energy of the black hole as seen by a nearby
observer at rest, for which this feature is lost.
| [
{
"created": "Wed, 4 Jul 2012 03:39:29 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jul 2012 18:09:32 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Sep 2015 19:16:23 GMT",
"version": "v3"
}
] | 2015-09-08 | [
[
"Corichi",
"Alejandro",
""
]
] | In this paper, we review the issue of defining energy for test particles on a background stationary spacetime. We revisit the different notions of energy as defined by different observers. As is well known, the existence of a time-like isometry allows for the notion of total conserved energy to be well defined. We use this well known quantity to show that a gravitational potential energy can be consistently defined. As examples, we study the case of the exterior regions of an asymptotically flat black hole and of the $\Lambda>0$ Schwarzschild de Sitter case, where an asymptotic region is not available. We then consider the situation in which the test particle is absorbed by the black hole, and analyze the energetics in detail. In particular, we show that the notion of horizon energy as defined by the isolated horizons formalism provides a satisfactory notion of energy compatible with the particle's total conserved energy. With these choices, there is a global conservation of energy. Finally, we comment on a recent proposal to define energy of the black hole as seen by a nearby observer at rest, for which this feature is lost. |
2203.06030 | Simon Riquelme | Cristi\'an Erices, Sim\'on Riquelme and Nicol\'as Zalaquett | EFT Approach to Black Hole Scalarization and its Compatibility with
Cosmic Evolution | 28 pages, 3 Figures | null | 10.1103/PhysRevD.106.044046 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the issue of black hole scalarization and its compatibility with
cosmic inflation and big bang cosmology from an effective field theory (EFT)
point of view. In practice, using a well-defined and healthy toy model which
(in part) has been broadly considered in the literature, we consider how
higher-order theories of gravity, up to cubic operators in Riemann curvature,
fit within this context. Interestingly enough, we find that already at this
minimal level, there is a non-trivial interplay between the Wilson coefficients
which are otherwise completely independent, constraining the parameter space
where scalarization may actually occur. Conclusively, we claim that the EFT
does exhibit black hole scalarization, remaining compatible with the
inflationary paradigm, and admitting General Relativity as a cosmological
attractor.
| [
{
"created": "Fri, 11 Mar 2022 15:54:18 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Erices",
"Cristián",
""
],
[
"Riquelme",
"Simón",
""
],
[
"Zalaquett",
"Nicolás",
""
]
] | We address the issue of black hole scalarization and its compatibility with cosmic inflation and big bang cosmology from an effective field theory (EFT) point of view. In practice, using a well-defined and healthy toy model which (in part) has been broadly considered in the literature, we consider how higher-order theories of gravity, up to cubic operators in Riemann curvature, fit within this context. Interestingly enough, we find that already at this minimal level, there is a non-trivial interplay between the Wilson coefficients which are otherwise completely independent, constraining the parameter space where scalarization may actually occur. Conclusively, we claim that the EFT does exhibit black hole scalarization, remaining compatible with the inflationary paradigm, and admitting General Relativity as a cosmological attractor. |
2205.14910 | Xisco Jim\'enez Forteza | Xisco Jim\'enez Forteza, Swetha Bhagwat, Sumit Kumar, Paolo Pani | A novel ringdown amplitude-phase consistency test | Matches the version to appear in PRL | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ringdown signal emitted during a binary black hole coalescence can be
modeled as a linear superposition of the characteristic damped modes of the
remnant black hole that get excited during the merger phase. While checking the
consistency of the measured frequencies and damping times against the Kerr BH
spectrum predicted by General Relativity (GR) is a cornerstone of strong-field
tests of gravity, the consistency of measured excitation amplitudes and phases
have been largely left unexplored. For a nonprecessing, quasi-circular binary
black hole merger, we find that GR predicts a narrow region in the space of
mode amplitude ratio and phase difference, independently of the spin of the
binary components. % Using this unexpected result, we develop a new null test
of strong-field gravity which demands that the measured amplitudes and phases
of different ringdown modes should lie within this narrow region predicted by
GR. We call this the \emph{amplitude-phase consistency test} and introduce a
procedure for performing it using information from the ringdown signal. Lastly,
we apply this test to the GW190521 event, using the multimodal ringdown
parameters inferred by Capano et al. (2021) \cite{Capano:2021etf}. While
ringdown measurements errors for this event are large, we show that GW190521 is
consistent with the amplitude-phase consistency test. Our test is particularly
well suited for accommodating multiple loud ringdown detections as those
expected in the near future, and can be used complementarily to standard
black-hole spectroscopy as a proxy for modified gravity, compact objects other
than black holes, binary precession and eccentricity.
| [
{
"created": "Mon, 30 May 2022 08:10:38 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Nov 2022 06:21:36 GMT",
"version": "v2"
}
] | 2022-11-17 | [
[
"Forteza",
"Xisco Jiménez",
""
],
[
"Bhagwat",
"Swetha",
""
],
[
"Kumar",
"Sumit",
""
],
[
"Pani",
"Paolo",
""
]
] | The ringdown signal emitted during a binary black hole coalescence can be modeled as a linear superposition of the characteristic damped modes of the remnant black hole that get excited during the merger phase. While checking the consistency of the measured frequencies and damping times against the Kerr BH spectrum predicted by General Relativity (GR) is a cornerstone of strong-field tests of gravity, the consistency of measured excitation amplitudes and phases have been largely left unexplored. For a nonprecessing, quasi-circular binary black hole merger, we find that GR predicts a narrow region in the space of mode amplitude ratio and phase difference, independently of the spin of the binary components. % Using this unexpected result, we develop a new null test of strong-field gravity which demands that the measured amplitudes and phases of different ringdown modes should lie within this narrow region predicted by GR. We call this the \emph{amplitude-phase consistency test} and introduce a procedure for performing it using information from the ringdown signal. Lastly, we apply this test to the GW190521 event, using the multimodal ringdown parameters inferred by Capano et al. (2021) \cite{Capano:2021etf}. While ringdown measurements errors for this event are large, we show that GW190521 is consistent with the amplitude-phase consistency test. Our test is particularly well suited for accommodating multiple loud ringdown detections as those expected in the near future, and can be used complementarily to standard black-hole spectroscopy as a proxy for modified gravity, compact objects other than black holes, binary precession and eccentricity. |
gr-qc/0602112 | Ujjal Debnath | Subenoy Chakraborty, Asit Banerjee, Ujjal Debnath | A New Result on the Dynamical Symmetry of Spherical Collapse | 6 Latex pages, No figure, ReVTeX style | null | null | null | gr-qc | null | A dynamical symmetry for spherical collapse has been studied using a linear
transformation of the initial data set (mass and kinetic energy function) and
the area radius. With proper choice of the initial area radius, the evolution
as well as the physical parameters namely energy density and shear remain
invariant both initially and at any time instant. Finally, it is found that the
final outcome of collapse depends on the initial choice of the area radius.
| [
{
"created": "Mon, 27 Feb 2006 13:18:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chakraborty",
"Subenoy",
""
],
[
"Banerjee",
"Asit",
""
],
[
"Debnath",
"Ujjal",
""
]
] | A dynamical symmetry for spherical collapse has been studied using a linear transformation of the initial data set (mass and kinetic energy function) and the area radius. With proper choice of the initial area radius, the evolution as well as the physical parameters namely energy density and shear remain invariant both initially and at any time instant. Finally, it is found that the final outcome of collapse depends on the initial choice of the area radius. |
gr-qc/0103063 | Emilio Elizalde | Emilio Elizalde and Sergi R. Hildebrandt | A family of regular quantum interiors for non-rotating black holes I:
The GRNSS spacetimes | latex, 38 pages | null | null | null | gr-qc astro-ph hep-th math-ph math.MP | null | A seemingly natural mechanism is proposed, that could stop the gravitational
collapse of a very massive body. Without needing to change the concept of the
collapsing process itself, that is, without invoking thin layers nor resorting
to asymptoticity (as has been usually done in the literature), it is proven
that a model can be built in which the quantum vacuum is able to produce a
negative stress that may stop the collapse of the black hole, reaching a final
state of the spacetime structure that is a static de Sitter model. The solution
is found by looking into a generic family of spacetimes: that of maximal
spherically symmetric ones expanded by a geodesic radial null one-form from
flat spacetime. They are called here GRNSS spaces, and are proven to constitute
a distinguished family of Kerr-Schild metrics. The models considered previously
in the literature are easily recovered in this approach, which yields,
moreover, an infinite set of possible candidates for the interior of the black
hole. First steps towards their semiclassical quantization are undertaken. It
is shown that the quantization protocol may be here more easily carried out
than within conformal field theory.
| [
{
"created": "Fri, 16 Mar 2001 16:49:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Elizalde",
"Emilio",
""
],
[
"Hildebrandt",
"Sergi R.",
""
]
] | A seemingly natural mechanism is proposed, that could stop the gravitational collapse of a very massive body. Without needing to change the concept of the collapsing process itself, that is, without invoking thin layers nor resorting to asymptoticity (as has been usually done in the literature), it is proven that a model can be built in which the quantum vacuum is able to produce a negative stress that may stop the collapse of the black hole, reaching a final state of the spacetime structure that is a static de Sitter model. The solution is found by looking into a generic family of spacetimes: that of maximal spherically symmetric ones expanded by a geodesic radial null one-form from flat spacetime. They are called here GRNSS spaces, and are proven to constitute a distinguished family of Kerr-Schild metrics. The models considered previously in the literature are easily recovered in this approach, which yields, moreover, an infinite set of possible candidates for the interior of the black hole. First steps towards their semiclassical quantization are undertaken. It is shown that the quantization protocol may be here more easily carried out than within conformal field theory. |
gr-qc/9603042 | Sergey Krasnikov | S.Krasnikov | Paradoxes of time travel | 9 LaTeX pages, 23k. bezier.sty is desirable, but its absence will
only damage two figures | null | null | null | gr-qc | null | Paradoxes that can supposedly occur if a time machine is created are
discussed. It is shown that the existence of trajectories of ``multiplicity
zero'' (i.e. trajectories that describe a ball hitting its younger self so that
the latter cannot fall into the time machine) is not paradoxical by itself.
This {\em apparent paradox} can be resolved (at least sometimes) without any
harm to local physics or to the time machine. Also a simple model is adduced
for which the absence of {\em true} paradoxes caused by self-interaction is
proved.
| [
{
"created": "Mon, 25 Mar 1996 10:12:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Krasnikov",
"S.",
""
]
] | Paradoxes that can supposedly occur if a time machine is created are discussed. It is shown that the existence of trajectories of ``multiplicity zero'' (i.e. trajectories that describe a ball hitting its younger self so that the latter cannot fall into the time machine) is not paradoxical by itself. This {\em apparent paradox} can be resolved (at least sometimes) without any harm to local physics or to the time machine. Also a simple model is adduced for which the absence of {\em true} paradoxes caused by self-interaction is proved. |
gr-qc/9302004 | null | S.D.Odintsov | Two-loop effective potential in quantum field theory in curved
space-time | 8pages | Phys.Lett.B306:233-236,1993 | 10.1016/0370-2693(93)90073-Q | null | gr-qc | null | The method of the calculation of effective potential (in linear curvature
approximation and at any loop) in massless gauge theory in curved space- time
by the direct solution of RG equation is given.The closed expression for
two-loop effective potential is obtained.Two-loop effective potential in scalar
self-interacting theory is written explicitly.Some comments about it as well as
about two-loop effective potential in standard model are presented.
| [
{
"created": "Fri, 5 Feb 1993 16:49:53 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Odintsov",
"S. D.",
""
]
] | The method of the calculation of effective potential (in linear curvature approximation and at any loop) in massless gauge theory in curved space- time by the direct solution of RG equation is given.The closed expression for two-loop effective potential is obtained.Two-loop effective potential in scalar self-interacting theory is written explicitly.Some comments about it as well as about two-loop effective potential in standard model are presented. |
0808.2347 | Seyed Hossein Hendi | S. H. Hendi | Rotating Black Branes in Brans-Dicke-Born-Infeld Theory | to be appear in JMP | J.Math.Phys.49:082501,2008 | 10.1063/1.2968342 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present a new class of charged rotating black brane
solutions in the higher dimensional Brans-Dicke-Born-Infeld theory and
investigate their properties. Solving the field equations directly is a
non-trivial task because they include the second derivatives of the scalar
field. We remove this difficulty through a conformal transformation. Also, we
find that the suitable Lagrangian of Einstein-Born-Infeld-dilaton gravity is
not the same as presented in \cite{DHSR}. We show that the given solutions can
present black brane, with inner and outer event horizons, an extreme black
brane or a naked singularity provided the parameters of the solutions are
chosen suitably. These black brane solutions are neither asymptotically flat
nor (anti)-de Sitter. Then we calculate finite Euclidean action, the conserved
and thermodynamic quantities through the use of counterterm method. Finally, we
argue that these quantities satisfy the first law of thermodynamics, and the
entropy does not follow the area law.
| [
{
"created": "Mon, 18 Aug 2008 07:26:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hendi",
"S. H.",
""
]
] | In this paper, we present a new class of charged rotating black brane solutions in the higher dimensional Brans-Dicke-Born-Infeld theory and investigate their properties. Solving the field equations directly is a non-trivial task because they include the second derivatives of the scalar field. We remove this difficulty through a conformal transformation. Also, we find that the suitable Lagrangian of Einstein-Born-Infeld-dilaton gravity is not the same as presented in \cite{DHSR}. We show that the given solutions can present black brane, with inner and outer event horizons, an extreme black brane or a naked singularity provided the parameters of the solutions are chosen suitably. These black brane solutions are neither asymptotically flat nor (anti)-de Sitter. Then we calculate finite Euclidean action, the conserved and thermodynamic quantities through the use of counterterm method. Finally, we argue that these quantities satisfy the first law of thermodynamics, and the entropy does not follow the area law. |
1111.6564 | Franklin Felber | Franklin Felber | Comment on "Reversed gravitational acceleration...", arXiv:1102.2870v2 | 1 page, 2 figures, typographical changes only | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hilbert's 1917 discovery of reversed gravitational acceleration is discussed,
and the connection to arXiv:1102.2870v2 [gr-qc] is explained.
| [
{
"created": "Mon, 28 Nov 2011 19:52:04 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Dec 2014 01:23:05 GMT",
"version": "v2"
}
] | 2014-12-11 | [
[
"Felber",
"Franklin",
""
]
] | Hilbert's 1917 discovery of reversed gravitational acceleration is discussed, and the connection to arXiv:1102.2870v2 [gr-qc] is explained. |
1704.07514 | Vee-Liem Saw | Vee-Liem Saw | Mass loss due to gravitational waves with $\Lambda>0$ | 5 pages. Proceedings from the Conference on Cosmology, Gravitational
Waves and Particles, 6th to 10th of February, 2017, held at the Institute of
Advanced Studies, Nanyang Technological University, Singapore, published as a
brief review in Modern Physics Letters A | Modern Physics Letters A, Vol. 32, No. 22, (2017) 1730020 | 10.1142/S0217732317300208 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theoretical basis for the energy carried away by gravitational waves that
an isolated gravitating system emits was first formulated by Hermann Bondi
during the 1960s. Recent findings from looking at distant supernovae revealed
that the rate of expansion of our universe is accelerating, which may be
well-explained by sticking in a positive cosmological constant into the
Einstein field equations for general relativity. By solving the Newman-Penrose
equations (which are equivalent to the Einstein field equations), we generalise
this notion of Bondi mass-energy and thereby provide a firm theoretical
description of how an isolated gravitating system loses energy as it radiates
gravitational waves, in a universe that expands at an accelerated rate. This is
in line with the observational front of LIGO's first announcement in February
2016 that gravitational waves from the merger of a binary black hole system
have been detected.
| [
{
"created": "Tue, 25 Apr 2017 02:05:06 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2017 11:21:24 GMT",
"version": "v2"
}
] | 2017-06-30 | [
[
"Saw",
"Vee-Liem",
""
]
] | The theoretical basis for the energy carried away by gravitational waves that an isolated gravitating system emits was first formulated by Hermann Bondi during the 1960s. Recent findings from looking at distant supernovae revealed that the rate of expansion of our universe is accelerating, which may be well-explained by sticking in a positive cosmological constant into the Einstein field equations for general relativity. By solving the Newman-Penrose equations (which are equivalent to the Einstein field equations), we generalise this notion of Bondi mass-energy and thereby provide a firm theoretical description of how an isolated gravitating system loses energy as it radiates gravitational waves, in a universe that expands at an accelerated rate. This is in line with the observational front of LIGO's first announcement in February 2016 that gravitational waves from the merger of a binary black hole system have been detected. |
1410.3909 | Maxim Eingorn | Maxim Brilenkov, Maxim Eingorn, Alexander Zhuk | Lattice Universe: examples and problems | 11 pages, 1 figure | The European Physical Journal C 75, 217 (2015) | 10.1140/epjc/s10052-015-3445-2 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider lattice Universes with spatial topologies $T\times T\times T$,
$\; T\times T\times R\; $ and $\; T\times R\times R$. In the Newtonian limit of
General Relativity, we solve the Poisson equation for the gravitational
potential in the enumerated models. In the case of point-like massive sources
in the $T\times T\times T$ model, we demonstrate that the gravitational
potential has no definite values on the straight lines joining identical masses
in neighboring cells, i.e. at points where masses are absent. Clearly, this is
a nonphysical result since the dynamics of cosmic bodies is not determined in
such a case. The only way to avoid this problem and get a regular solution at
any point of the cell is the smearing of these masses over some region.
Therefore, the smearing of gravitating bodies in $N$-body simulations is not
only a technical method but also a physically substantiated procedure. In the
cases of $\; T\times T\times R\; $ and $\; T\times R\times R$ topologies, there
is no way to get any physically reasonable and nontrivial solution. The only
solutions we can get here are the ones which reduce these topologies to the
$T\times T\times T$ one.
| [
{
"created": "Wed, 15 Oct 2014 02:37:13 GMT",
"version": "v1"
},
{
"created": "Sat, 23 May 2015 22:10:58 GMT",
"version": "v2"
}
] | 2015-05-26 | [
[
"Brilenkov",
"Maxim",
""
],
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We consider lattice Universes with spatial topologies $T\times T\times T$, $\; T\times T\times R\; $ and $\; T\times R\times R$. In the Newtonian limit of General Relativity, we solve the Poisson equation for the gravitational potential in the enumerated models. In the case of point-like massive sources in the $T\times T\times T$ model, we demonstrate that the gravitational potential has no definite values on the straight lines joining identical masses in neighboring cells, i.e. at points where masses are absent. Clearly, this is a nonphysical result since the dynamics of cosmic bodies is not determined in such a case. The only way to avoid this problem and get a regular solution at any point of the cell is the smearing of these masses over some region. Therefore, the smearing of gravitating bodies in $N$-body simulations is not only a technical method but also a physically substantiated procedure. In the cases of $\; T\times T\times R\; $ and $\; T\times R\times R$ topologies, there is no way to get any physically reasonable and nontrivial solution. The only solutions we can get here are the ones which reduce these topologies to the $T\times T\times T$ one. |
2008.12663 | Paolo Marcoccia | Paolo Marcoccia, Felicia Fredriksson, Alex B. Nielsen and Germano
Nardini | Pearson cross-correlation in the first four black hole binary mergers | 17 pages, 6 figures; matches published version | JCAP 11 (2020) 043 | 10.1088/1475-7516/2020/11/043 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We adopt the Pearson cross-correlation measure to analyze the LIGO Hanford
and LIGO Livingston detector data streams around the events GW150914,
GW151012,GW151226 and GW170104. We find that the Pearson cross-correlation
method is sensitive to these signals, with correlations peaking when the black
hole binaries reconstructed by the LIGO Scientific and Virgo Collaborations,
are merging. We compare the obtained cross-correlations with the statistical
correlation fluctuations arising in simulated Gaussian noise data and in LIGO
data at times when no event is claimed. Our results for the significance of the
observed cross-correlations are broadly consistent with those announced by the
LIGO Scientific and Virgo Collaborations based on matched-filter analysis. In
the same data, if we subtract the maximum likelihood waveforms corresponding to
the announced signals, no residual cross-correlations persists at a
statistically significant level.
| [
{
"created": "Fri, 28 Aug 2020 14:02:30 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2020 12:12:36 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Dec 2020 11:48:14 GMT",
"version": "v3"
}
] | 2020-12-03 | [
[
"Marcoccia",
"Paolo",
""
],
[
"Fredriksson",
"Felicia",
""
],
[
"Nielsen",
"Alex B.",
""
],
[
"Nardini",
"Germano",
""
]
] | We adopt the Pearson cross-correlation measure to analyze the LIGO Hanford and LIGO Livingston detector data streams around the events GW150914, GW151012,GW151226 and GW170104. We find that the Pearson cross-correlation method is sensitive to these signals, with correlations peaking when the black hole binaries reconstructed by the LIGO Scientific and Virgo Collaborations, are merging. We compare the obtained cross-correlations with the statistical correlation fluctuations arising in simulated Gaussian noise data and in LIGO data at times when no event is claimed. Our results for the significance of the observed cross-correlations are broadly consistent with those announced by the LIGO Scientific and Virgo Collaborations based on matched-filter analysis. In the same data, if we subtract the maximum likelihood waveforms corresponding to the announced signals, no residual cross-correlations persists at a statistically significant level. |
gr-qc/0308088 | Bijan Saha | Bijan Saha (LIT, JINR) | Nonlinear spinor field in cosmology | RevTex4, 19 pages, 4 figures | Phys.Rev. D69 (2004) 124006 | 10.1103/PhysRevD.69.124006 | null | gr-qc | null | Within the scope of Bianchi type VI (BVI) model the self-consistent system of
nonlinear spinor and gravitational fields is considered. Exact self-consistent
solutions to the spinor and gravitational field equations are obtained for some
special choice of spatial inhomogeneity and nonlinear spinor term. The role of
inhomogeneity in the evolution of spinor and gravitational field is studied.
Oscillatory mode of expansion of the BVI universe is obtained for some special
choice of spinor field nonlinearity.
| [
{
"created": "Thu, 28 Aug 2003 11:33:14 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
"",
"LIT, JINR"
]
] | Within the scope of Bianchi type VI (BVI) model the self-consistent system of nonlinear spinor and gravitational fields is considered. Exact self-consistent solutions to the spinor and gravitational field equations are obtained for some special choice of spatial inhomogeneity and nonlinear spinor term. The role of inhomogeneity in the evolution of spinor and gravitational field is studied. Oscillatory mode of expansion of the BVI universe is obtained for some special choice of spinor field nonlinearity. |
gr-qc/9706036 | Ruth Lazkoz Saez | A. Feinstein, J. Ib\'a\~nez, R. Lazkoz | Disks in Expanding FRW Universes | Revised version to appear in ApJ, Latex, 17 pages, 10 figures, uses
aaspp4 and epsf style files | Astrophys.J. 495 (1998) 131 | 10.1086/305276 | EHU-FT/9706 | gr-qc astro-ph | null | We construct exact solutions to Einstein equations which represent
relativistic disks immersed into an expanding FRW Universe. It is shown that
the expansion influences dynamical characteristics of the disks such as
rotational curves, surface mass density, etc. The effects of the expansion is
exemplified with non-static generalizations of Kuzmin-Curzon and generalized
Schwarzschild disks.
| [
{
"created": "Fri, 13 Jun 1997 14:22:15 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Oct 1997 13:58:48 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Feinstein",
"A.",
""
],
[
"Ibáñez",
"J.",
""
],
[
"Lazkoz",
"R.",
""
]
] | We construct exact solutions to Einstein equations which represent relativistic disks immersed into an expanding FRW Universe. It is shown that the expansion influences dynamical characteristics of the disks such as rotational curves, surface mass density, etc. The effects of the expansion is exemplified with non-static generalizations of Kuzmin-Curzon and generalized Schwarzschild disks. |
2304.09817 | Tobias Mistele | Tobias Mistele | Comment on "Observational Evidence for Cosmological Coupling of Black
Holes and its Implications for an Astrophysical Source of Dark Energy" | 5 pages | Res. Notes AAS 7 101, 2023 | 10.3847/2515-5172/acd767 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently claimed that black holes can explain the accelerated
expansion of the universe. Here I point out that this claim is based on a
confusion about the principle of least action, undermining the link between
black holes and dark energy.
| [
{
"created": "Wed, 19 Apr 2023 17:18:11 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2023 19:23:06 GMT",
"version": "v2"
}
] | 2023-05-26 | [
[
"Mistele",
"Tobias",
""
]
] | It was recently claimed that black holes can explain the accelerated expansion of the universe. Here I point out that this claim is based on a confusion about the principle of least action, undermining the link between black holes and dark energy. |
0902.2462 | H Mohseni Sadjadi | H. Mohseni Sadjadi | Crossing the phantom divide line in the Holographic dark energy model in
a closed universe | 10 pages, accepted for publication in Eur. Phys. J. C | Eur.Phys.J.C62:419-424,2009 | 10.1140/epjc/s10052-009-1045-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conditions needed to cross the phantom divide line in an interacting
holographic dark energy model in closed Friedmann- Robertson-Walker universe
are discussed. The probable relationship between this crossing and the
coincidence problem is studied.
| [
{
"created": "Sat, 14 Feb 2009 12:23:28 GMT",
"version": "v1"
},
{
"created": "Sun, 3 May 2009 11:30:50 GMT",
"version": "v2"
}
] | 2009-07-24 | [
[
"Sadjadi",
"H. Mohseni",
""
]
] | Conditions needed to cross the phantom divide line in an interacting holographic dark energy model in closed Friedmann- Robertson-Walker universe are discussed. The probable relationship between this crossing and the coincidence problem is studied. |
gr-qc/0106036 | Hans-Juergen Schmidt | H.-J. Schmidt | On Ellis' programme within fourth order gravity | 9 pages, LaTeX, no figure | Astron.Nachr. 309 (1988) 307 | null | Report UNIPO-MATH-01-Jun-05 | gr-qc | null | For the non-tachyonic curvature squared action we show that the expanding
Bianchi-type I models tend to the dust-filled Einstein-de Sitter model for t
tending to infinity if the metric is averaged over the typical oscillation
period. Applying a conformal equivalence between curvature squared action and a
minimally coupled scalar field (which holds for all dimensions > 2) the problem
is solved by discussing a massive scalar field in an anisotropic cosmological
model.
| [
{
"created": "Mon, 11 Jun 2001 14:28:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schmidt",
"H. -J.",
""
]
] | For the non-tachyonic curvature squared action we show that the expanding Bianchi-type I models tend to the dust-filled Einstein-de Sitter model for t tending to infinity if the metric is averaged over the typical oscillation period. Applying a conformal equivalence between curvature squared action and a minimally coupled scalar field (which holds for all dimensions > 2) the problem is solved by discussing a massive scalar field in an anisotropic cosmological model. |
1011.6401 | Aidan Keane | Aidan J Keane and Brian O J Tupper | Killing tensors in pp-wave spacetimes | 18 pages | Class. Quantum Grav. 27 (2010) 245011 | 10.1088/0264-9381/27/24/245011 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formal solution of the second order Killing tensor equations for the
general pp-wave spacetime is given. The Killing tensor equations are integrated
fully for some specific pp-wave spacetimes. In particular, the complete
solution is given for the conformally flat plane wave spacetimes and we find
that irreducible Killing tensors arise for specific classes. The maximum number
of independent irreducible Killing tensors admitted by a conformally flat plane
wave spacetime is shown to be six. It is shown that every pp-wave spacetime
that admits an homothety will admit a Killing tensor of Koutras type and, with
the exception of the singular scale-invariant plane wave spacetimes, this
Killing tensor is irreducible.
| [
{
"created": "Mon, 29 Nov 2010 22:03:48 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Keane",
"Aidan J",
""
],
[
"Tupper",
"Brian O J",
""
]
] | The formal solution of the second order Killing tensor equations for the general pp-wave spacetime is given. The Killing tensor equations are integrated fully for some specific pp-wave spacetimes. In particular, the complete solution is given for the conformally flat plane wave spacetimes and we find that irreducible Killing tensors arise for specific classes. The maximum number of independent irreducible Killing tensors admitted by a conformally flat plane wave spacetime is shown to be six. It is shown that every pp-wave spacetime that admits an homothety will admit a Killing tensor of Koutras type and, with the exception of the singular scale-invariant plane wave spacetimes, this Killing tensor is irreducible. |
2408.08094 | Bahtiyar \"Ozg\"ur Sar{\i}o\u{g}lu | Deniz Olgu Devecio\u{g}lu, Ulf Lindstr\"om, \"Ozg\"ur Sar{\i}o\u{g}lu | On the maximally symmetric vacua of generic Lovelock gravities | prepared as a contribution to the special issue of "Journal of
Physics A: Mathematical and Theoretical" dedicated to the memory of Stanley
Deser; 20 pages, no figures | null | null | Uppsala Theoretical Physics preprint UUITP-23/24 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We survey elementary features of Lovelock gravity and its maximally symmetric
vacuum solutions. The latter is solely determined by the real roots of a
dimension-dependent polynomial. We also recover the static spherically
symmetric (black hole) solutions of Lovelock gravity using Palais' symmetric
criticality principle. We show how to linearize the generic field equations of
Lovelock models about a given maximally symmetric vacuum, which turns out to
factorize into the product of yet another dimension-dependent polynomial and
the linearized Einstein tensor about the relevant background. We also describe
how to compute conserved charges using linearized field equations along with
the relevant background Killing isometries. We further describe and discuss the
special vacua which are defined by the simultaneous vanishing of the
aforementioned polynomials.
| [
{
"created": "Thu, 15 Aug 2024 11:36:20 GMT",
"version": "v1"
}
] | 2024-08-16 | [
[
"Devecioğlu",
"Deniz Olgu",
""
],
[
"Lindström",
"Ulf",
""
],
[
"Sarıoğlu",
"Özgür",
""
]
] | We survey elementary features of Lovelock gravity and its maximally symmetric vacuum solutions. The latter is solely determined by the real roots of a dimension-dependent polynomial. We also recover the static spherically symmetric (black hole) solutions of Lovelock gravity using Palais' symmetric criticality principle. We show how to linearize the generic field equations of Lovelock models about a given maximally symmetric vacuum, which turns out to factorize into the product of yet another dimension-dependent polynomial and the linearized Einstein tensor about the relevant background. We also describe how to compute conserved charges using linearized field equations along with the relevant background Killing isometries. We further describe and discuss the special vacua which are defined by the simultaneous vanishing of the aforementioned polynomials. |
gr-qc/9911101 | Gianluca Cruciani | Gianluca Cruciani | Deriving the Regge-Wheeler and Zerilli equations in the general static
spherically-symmetric case with Mathematica and MathTensor | 6 pages, 3 figures | Nuovo Cim. B115 (2000) 693-698 | null | null | gr-qc | null | An efficient approach to tensor perturbation calculations by proper use of
computer algebra methods is described, reaching the sufficient generality
required for a comprehensive analysis of the Schwarzschild and
Reissner-Nordstroem metric stability.
| [
{
"created": "Thu, 25 Nov 1999 22:28:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cruciani",
"Gianluca",
""
]
] | An efficient approach to tensor perturbation calculations by proper use of computer algebra methods is described, reaching the sufficient generality required for a comprehensive analysis of the Schwarzschild and Reissner-Nordstroem metric stability. |
2004.14738 | Hong Lu | Liang Ma and H. Lu | Vacua and Exact Solutions in Lower-$D$ Limits of EGB | Latex, 19 pages | null | 10.1140/epjc/s10052-020-08780-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the action principles that are the lower dimensional limits of
the Einstein-Gauss-Bonnet gravity {\it via} the Kaluza-Klein route. We study
the vacua and obtain some exact solutions. We find that the reality condition
of the theories may select one vacuum over the other from the two vacua that
typically arise in Einstein-Gauss-Bonnet gravity. We obtain exact black hole
and cosmological solutions carrying scalar hair, including scalar hairy BTZ
black holes with both mass and angular momentum turned on. We also discuss the
holographic central charges in the asymptotic AdS backgrounds.
| [
{
"created": "Thu, 30 Apr 2020 12:55:06 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Ma",
"Liang",
""
],
[
"Lu",
"H.",
""
]
] | We consider the action principles that are the lower dimensional limits of the Einstein-Gauss-Bonnet gravity {\it via} the Kaluza-Klein route. We study the vacua and obtain some exact solutions. We find that the reality condition of the theories may select one vacuum over the other from the two vacua that typically arise in Einstein-Gauss-Bonnet gravity. We obtain exact black hole and cosmological solutions carrying scalar hair, including scalar hairy BTZ black holes with both mass and angular momentum turned on. We also discuss the holographic central charges in the asymptotic AdS backgrounds. |
2005.13732 | David Kubiznak | Robie A. Hennigar, David Kubiznak, Robert B. Mann | Rotating Gauss-Bonnet BTZ Black Holes | 7 pages, 2 figures | null | 10.1088/1361-6382/abce48 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain rotating black hole solutions to the novel 3D Gauss-Bonnet theory
of gravity recently proposed. These solutions generalize the BTZ metric and are
not of constant curvature. They possess an ergoregion and outer horizon, but do
not have an inner horizon. We present their basic properties and show that they
break the universality of thermodynamics present for their static charged
counterparts, whose properties we also discuss. Extending our considerations to
higher dimensions, we also obtain novel 4D Gauss-Bonnet rotating black strings.
| [
{
"created": "Thu, 28 May 2020 01:51:48 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Hennigar",
"Robie A.",
""
],
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | We obtain rotating black hole solutions to the novel 3D Gauss-Bonnet theory of gravity recently proposed. These solutions generalize the BTZ metric and are not of constant curvature. They possess an ergoregion and outer horizon, but do not have an inner horizon. We present their basic properties and show that they break the universality of thermodynamics present for their static charged counterparts, whose properties we also discuss. Extending our considerations to higher dimensions, we also obtain novel 4D Gauss-Bonnet rotating black strings. |
2007.09135 | James Dent | James B. Dent, William E. Gabella, Kelly Holley-Bockelmann, Thomas W.
Kephart | The Sound of Clearing the Throat: Gravitational Waves from a Black Hole
Orbiting in a Wormhole Geometry | 6 pages, 4 figures | Phys. Rev. D 104, 044030 (2021) | 10.1103/PhysRevD.104.044030 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current ground-based gravitational wave detectors are tuned to capture the
collision of compact objects such as stellar origin black holes and neutron
stars; over 20 such events have been published to date. Theoretically, however,
more exotic compact objects may exist, collisions of which should also generate
copious gravitational waves. In this paper, we model the inspiral of a stellar
mass black hole into a stable, non-spinning, traversable wormhole, and find a
characteristic waveform -- an anti-chirp and/or burst -- as the black hole
emerges, i.e., outspirals, into our region of the Universe. This novel waveform
signature may be useful in searches for wormholes in future gravitational wave
data or used to constrain possible wormhole geometries in our Universe.
| [
{
"created": "Fri, 17 Jul 2020 17:51:04 GMT",
"version": "v1"
}
] | 2021-08-18 | [
[
"Dent",
"James B.",
""
],
[
"Gabella",
"William E.",
""
],
[
"Holley-Bockelmann",
"Kelly",
""
],
[
"Kephart",
"Thomas W.",
""
]
] | Current ground-based gravitational wave detectors are tuned to capture the collision of compact objects such as stellar origin black holes and neutron stars; over 20 such events have been published to date. Theoretically, however, more exotic compact objects may exist, collisions of which should also generate copious gravitational waves. In this paper, we model the inspiral of a stellar mass black hole into a stable, non-spinning, traversable wormhole, and find a characteristic waveform -- an anti-chirp and/or burst -- as the black hole emerges, i.e., outspirals, into our region of the Universe. This novel waveform signature may be useful in searches for wormholes in future gravitational wave data or used to constrain possible wormhole geometries in our Universe. |
gr-qc/0605031 | Sam Dolan Mr | Sam Dolan, Chris Doran and Anthony Lasenby | Fermion scattering by a Schwarzschild black hole | Minor changes, 1 figure added. Version to appear in Phys. Rev. D. 36
pages, 13 figures | Phys.Rev. D74 (2006) 064005 | 10.1103/PhysRevD.74.064005 | null | gr-qc astro-ph hep-th | null | We study the scattering of massive spin-half waves by a Schwarzschild black
hole using analytical and numerical methods. We begin by extending a recent
perturbation theory calculation to next order to obtain Born series for the
differential cross section and Mott polarization, valid at small couplings. We
continue by deriving an approximation for glory scattering of massive spinor
particles by considering classical timelike geodesics and spin precession.
Next, we formulate the Dirac equation on a black hole background, and outline a
simple numerical method for finding partial wave series solutions. Finally, we
present our numerical calculations of absorption and scattering cross sections
and polarization, and compare with theoretical expectations.
| [
{
"created": "Fri, 5 May 2006 17:19:41 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Sep 2006 19:34:46 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Dolan",
"Sam",
""
],
[
"Doran",
"Chris",
""
],
[
"Lasenby",
"Anthony",
""
]
] | We study the scattering of massive spin-half waves by a Schwarzschild black hole using analytical and numerical methods. We begin by extending a recent perturbation theory calculation to next order to obtain Born series for the differential cross section and Mott polarization, valid at small couplings. We continue by deriving an approximation for glory scattering of massive spinor particles by considering classical timelike geodesics and spin precession. Next, we formulate the Dirac equation on a black hole background, and outline a simple numerical method for finding partial wave series solutions. Finally, we present our numerical calculations of absorption and scattering cross sections and polarization, and compare with theoretical expectations. |
1006.3745 | Ninfa Radicella | Ninfa Radicella and Diego Pav\'on | The generalized second law in universes with quantum corrected entropy
relations | 11 pages, 5 figures, accepted for publication on PLB | Phys.Lett.B691:121-126,2010 | 10.1016/j.physletb.2010.06.019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the generalized second law of thermodynamics to discriminate among
quantum corrections (whether logarithmic or power-law) to the entropy of the
apparent horizon in spatially Friedmann-Robertson-Walker universes. We use the
corresponding modified Friedmann equations along with either Clausius relation
or the principle of equipartition of the energy to set limits on the value of a
characteristic parameter entering the said corrections.
| [
{
"created": "Fri, 18 Jun 2010 16:38:45 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Radicella",
"Ninfa",
""
],
[
"Pavón",
"Diego",
""
]
] | We apply the generalized second law of thermodynamics to discriminate among quantum corrections (whether logarithmic or power-law) to the entropy of the apparent horizon in spatially Friedmann-Robertson-Walker universes. We use the corresponding modified Friedmann equations along with either Clausius relation or the principle of equipartition of the energy to set limits on the value of a characteristic parameter entering the said corrections. |
gr-qc/0308070 | T. Padmanabhan | T. Padmanabhan | Entropy of Static Spacetimes and Microscopic Density of States | Extensively revised with more details and clarifications; 12 pages;
accepted for publication in Class.Quant.Grav | Class.Quant.Grav.21:4485-4494,2004 | 10.1088/0264-9381/21/18/013 | null | gr-qc hep-th | null | A general ansatz for gravitational entropy can be provided using the
criterion that, any patch of area which acts as a horizon for a suitably
defined accelerated observer, must have an entropy proportional to its area.
After providing a brief justification for this ansatz, several consequences are
derived: (i) In any static spacetime with a horizon and associated temperature
$\beta^{-1}$, this entropy satisfies the relation $S=(1/2)\beta E$ where $E$ is
the energy source for gravitational acceleration, obtained as an integral of
$(T_{ab}-(1/2)Tg_{ab})u^au^b$. (ii) With this ansatz of $S$, the minimization
of Einstein-Hilbert action is equivalent to minimizing the free energy $F$ with
$\beta F=\beta U-S$ where $U$ is the integral of $T_{ab}u^au^b$. We discuss the
conditions under which these results imply $S\propto E^2$ and/or $S\propto U^2$
thereby generalizing the results known for black holes. This approach links
with several other known results, especially the holographic views of
spacetime.
| [
{
"created": "Thu, 21 Aug 2003 14:05:59 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Aug 2004 10:19:27 GMT",
"version": "v2"
}
] | 2011-05-05 | [
[
"Padmanabhan",
"T.",
""
]
] | A general ansatz for gravitational entropy can be provided using the criterion that, any patch of area which acts as a horizon for a suitably defined accelerated observer, must have an entropy proportional to its area. After providing a brief justification for this ansatz, several consequences are derived: (i) In any static spacetime with a horizon and associated temperature $\beta^{-1}$, this entropy satisfies the relation $S=(1/2)\beta E$ where $E$ is the energy source for gravitational acceleration, obtained as an integral of $(T_{ab}-(1/2)Tg_{ab})u^au^b$. (ii) With this ansatz of $S$, the minimization of Einstein-Hilbert action is equivalent to minimizing the free energy $F$ with $\beta F=\beta U-S$ where $U$ is the integral of $T_{ab}u^au^b$. We discuss the conditions under which these results imply $S\propto E^2$ and/or $S\propto U^2$ thereby generalizing the results known for black holes. This approach links with several other known results, especially the holographic views of spacetime. |
gr-qc/9710112 | Lior M. Burko | Lior M. Burko | Structure of the black hole's Cauchy horizon singularity | 4 pages, RevTeX, 4 Encapsulated PostScript figures, submitted to
Phys. Rev. Lett | Phys.Rev.Lett. 79 (1997) 4958-4961 | 10.1103/PhysRevLett.79.4958 | null | gr-qc | null | We study the Cauchy horizon (CH) singularity of a spherical charged black
hole perturbed nonlinearly by a self-gravitating massless scalar field. We show
numerically that the singularity is weak both at the early and at the late
sections of the CH, where the focusing of the area coordinate $r$ is strong. In
the early section the metric is almost Reissner-Nordstr\"{o}m, and the fields
behave according to perturbation analysis. We find exact analytical expressions
for the gradients of $r$ and of the scalar field, which are valid at both
sections. We then verify these analytical results numerically.
| [
{
"created": "Sun, 26 Oct 1997 14:45:16 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Burko",
"Lior M.",
""
]
] | We study the Cauchy horizon (CH) singularity of a spherical charged black hole perturbed nonlinearly by a self-gravitating massless scalar field. We show numerically that the singularity is weak both at the early and at the late sections of the CH, where the focusing of the area coordinate $r$ is strong. In the early section the metric is almost Reissner-Nordstr\"{o}m, and the fields behave according to perturbation analysis. We find exact analytical expressions for the gradients of $r$ and of the scalar field, which are valid at both sections. We then verify these analytical results numerically. |
1504.05426 | Zi-Liang Wang | Zi-Liang Wang, Wen-Yuan Ai, Hua Chen, Jian-Bo Deng | A cosmological model from emergence of space | 15 pages, 0 figure, 1 table | Phys. Rev. D 92, 024051 (2015) | 10.1103/PhysRevD.92.024051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many studies have been carried out since T.Padmanabhan proposed that the
cosmic acceleration can be understood from the perspective that spacetime
dynamics is an emergent phenomenon. Motivated by such a new paradigm, we
firstly study the de Sitter universe from emergence of space. After that we
investigate the universes in general cases and then narrow down our discussions
into one of them with a detailed discussion of the possibility in describing
our real universe classically. Furthermore, a constraint on $Ht$ and a
estimated value of $\tilde\Omega _{\Lambda}$ (caused by $\rho _{vac}$) can be
derived from our model, the comparison with experiments is also presented. The
results show the validity of our model.
| [
{
"created": "Tue, 21 Apr 2015 13:27:47 GMT",
"version": "v1"
},
{
"created": "Mon, 18 May 2015 08:22:31 GMT",
"version": "v2"
}
] | 2015-08-05 | [
[
"Wang",
"Zi-Liang",
""
],
[
"Ai",
"Wen-Yuan",
""
],
[
"Chen",
"Hua",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | Many studies have been carried out since T.Padmanabhan proposed that the cosmic acceleration can be understood from the perspective that spacetime dynamics is an emergent phenomenon. Motivated by such a new paradigm, we firstly study the de Sitter universe from emergence of space. After that we investigate the universes in general cases and then narrow down our discussions into one of them with a detailed discussion of the possibility in describing our real universe classically. Furthermore, a constraint on $Ht$ and a estimated value of $\tilde\Omega _{\Lambda}$ (caused by $\rho _{vac}$) can be derived from our model, the comparison with experiments is also presented. The results show the validity of our model. |
gr-qc/0506025 | John T. Whelan | John T. Whelan, Sukanta Bose, Jonathan Hanson, Ik Siong Heng, Warren
W. Johnson, Martin P. McHugh, and Peter Zhang | A Data Analysis Technique for the LIGO-ALLEGRO Stochastic Background
Search | 10 pages, LaTeX with IOP style files; 2 encapsulated postscript
figures Submitted to Classical and Quantum Gravity for 2004 GWDAW proceedings | Class.Quant.Grav. 22 (2005) S1087-S1096 | 10.1088/0264-9381/22/18/S23 | null | gr-qc | null | We describe the cross-correlation measurements being carried out on data from
the LIGO Livingston Observatory and the ALLEGRO resonant bar detector. The LIGO
data are sampled at 16384 Hz while the ALLEGRO data are base-banded, i.e.,
heterodyned at 899 Hz and then sampled at 250 Hz. We handle these different
sampling parameters by working in the Fourier domain, and demonstrate the
approximate equivalence of this measurement to a hypothetical time-domain
method in which both data streams are upsampled.
| [
{
"created": "Sun, 5 Jun 2005 19:10:04 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Whelan",
"John T.",
""
],
[
"Bose",
"Sukanta",
""
],
[
"Hanson",
"Jonathan",
""
],
[
"Heng",
"Ik Siong",
""
],
[
"Johnson",
"Warren W.",
""
],
[
"McHugh",
"Martin P.",
""
],
[
"Zhang",
"Peter",
""
]
] | We describe the cross-correlation measurements being carried out on data from the LIGO Livingston Observatory and the ALLEGRO resonant bar detector. The LIGO data are sampled at 16384 Hz while the ALLEGRO data are base-banded, i.e., heterodyned at 899 Hz and then sampled at 250 Hz. We handle these different sampling parameters by working in the Fourier domain, and demonstrate the approximate equivalence of this measurement to a hypothetical time-domain method in which both data streams are upsampled. |
1705.01329 | Mohammad Sami | Chao-Qiang Geng, Chung-Chi Lee, M. Sami, Emmanuel N. Saridakis, Alexei
A. Starobinsky | Observational constraints on successful model of quintessential
Inflation | 14 pages,2 tables and six figures.Minor changes in reference section,
to appear in JCAP | JCAP 1706 (2017)011 | 10.1088/1475-7516/2017/06/011 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study quintessential inflation using a generalized exponential potential
$V(\phi)\propto exp(-\lambda \phi^n/Mpl^n), n>1$, the model admits slow-roll
inflation at early times and leads to close-to-scaling behaviour in the post
inflationary era with an exit to dark energy at late times. We present detailed
investigations of the inflationary stage in the light of the Planck 2015
results, study post-inflationary dynamics and analytically confirm the
existence of an approximately scaling solution. Additionally, assuming that
standard massive neutrinos are non-minimally coupled, makes the field $\phi$
dominant once again at late times giving rise to present accelerated expansion
of the Universe. We derive observational constraints on the field and
time-dependent neutrino masses. In particular, for $n=6 (8)$, the parameter
$\lambda$ is constrained to be,$\log \lambda > -7.29 (-11.7)$; the model
produces the spectral index of the power spectrum of primordial scalar (matter
density) perturbations as $ n_s = 0.959 \pm 0.001 (0.961 \pm 0.001)$ and tiny
tensor-to-scalar ratio, $r<1.72 \times 10^{-2} (2.32 \times 10^{-2})$
respectively. Consequently, the upper bound on possible values of the sum of
neutrino masses $\Sigma m_{\nu} \lesssim 2.5$ eV significantly enhances
compared to that in the standard $\Lambda$CDM model.
| [
{
"created": "Wed, 3 May 2017 09:39:10 GMT",
"version": "v1"
},
{
"created": "Mon, 29 May 2017 09:10:58 GMT",
"version": "v2"
}
] | 2017-06-21 | [
[
"Geng",
"Chao-Qiang",
""
],
[
"Lee",
"Chung-Chi",
""
],
[
"Sami",
"M.",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Starobinsky",
"Alexei A.",
""
]
] | We study quintessential inflation using a generalized exponential potential $V(\phi)\propto exp(-\lambda \phi^n/Mpl^n), n>1$, the model admits slow-roll inflation at early times and leads to close-to-scaling behaviour in the post inflationary era with an exit to dark energy at late times. We present detailed investigations of the inflationary stage in the light of the Planck 2015 results, study post-inflationary dynamics and analytically confirm the existence of an approximately scaling solution. Additionally, assuming that standard massive neutrinos are non-minimally coupled, makes the field $\phi$ dominant once again at late times giving rise to present accelerated expansion of the Universe. We derive observational constraints on the field and time-dependent neutrino masses. In particular, for $n=6 (8)$, the parameter $\lambda$ is constrained to be,$\log \lambda > -7.29 (-11.7)$; the model produces the spectral index of the power spectrum of primordial scalar (matter density) perturbations as $ n_s = 0.959 \pm 0.001 (0.961 \pm 0.001)$ and tiny tensor-to-scalar ratio, $r<1.72 \times 10^{-2} (2.32 \times 10^{-2})$ respectively. Consequently, the upper bound on possible values of the sum of neutrino masses $\Sigma m_{\nu} \lesssim 2.5$ eV significantly enhances compared to that in the standard $\Lambda$CDM model. |
gr-qc/0606001 | Paulo M. S\'a | Paulo M. S\'a and Brigitte Tom\'e | The influence of differential rotation on the detectability of
gravitational waves from the r-mode instability | 8 pages, 6 figures, revtex4 | Phys.Rev. D74 (2006) 044011 | 10.1103/PhysRevD.74.044011 | null | gr-qc | null | Recently, it was shown that differential rotation is an unavoidable feature
of nonlinear r-modes. We investigate the influence of this differential
rotation on the detectability of gravitational waves emitted by a newly born,
hot, rapidly-rotating neutron star, as it spins down due to the r-mode
instability. We conclude that gravitational radiation may be detected by the
advanced laser interferometer detector LIGO if the amount of differential
rotation at the time the r-mode instability becomes active is not very high.
| [
{
"created": "Wed, 31 May 2006 21:09:37 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sá",
"Paulo M.",
""
],
[
"Tomé",
"Brigitte",
""
]
] | Recently, it was shown that differential rotation is an unavoidable feature of nonlinear r-modes. We investigate the influence of this differential rotation on the detectability of gravitational waves emitted by a newly born, hot, rapidly-rotating neutron star, as it spins down due to the r-mode instability. We conclude that gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation at the time the r-mode instability becomes active is not very high. |
1204.2497 | Jessica McIver | Jessica McIver (for the LIGO Scientific Collaboration, and for the
Virgo Collaboration) | Data Quality Studies of Enhanced Interferometric Gravitational Wave
Detectors | 12 pages, 7 figures | null | 10.1088/0264-9381/29/12/124010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Data quality assessment plays an essential role in the quest to detect
gravitational wave signals in data from the LIGO and Virgo interferometric
gravitational wave detectors. Interferometer data contains a high rate of noise
transients from the environment, the detector hardware, and the detector
control systems. These transients severely limit the statistical significance
of gravitational wave candidates of short duration and/or poorly modeled
waveforms. This paper describes the data quality studies that have been
performed in recent LIGO and Virgo observing runs to mitigate the impact of
transient detector artifacts on the gravitational wave searches.
| [
{
"created": "Wed, 11 Apr 2012 16:57:14 GMT",
"version": "v1"
}
] | 2019-08-15 | [
[
"McIver",
"Jessica",
"",
"for the LIGO Scientific Collaboration, and for the\n Virgo Collaboration"
]
] | Data quality assessment plays an essential role in the quest to detect gravitational wave signals in data from the LIGO and Virgo interferometric gravitational wave detectors. Interferometer data contains a high rate of noise transients from the environment, the detector hardware, and the detector control systems. These transients severely limit the statistical significance of gravitational wave candidates of short duration and/or poorly modeled waveforms. This paper describes the data quality studies that have been performed in recent LIGO and Virgo observing runs to mitigate the impact of transient detector artifacts on the gravitational wave searches. |
2306.10593 | Juan Garcia-Bellido | Juan Garcia-Bellido | Cosmic GREA from SMBH growth | 4 pages | null | null | IFT-UAM/CSIC-23-72 | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | General Relativistic Entropic Acceleration (GREA) gives a general framework
in which to study multiple out-of-equilibrium phenomena in the context of
general relativity, like the late accelerated expansion of the universe or the
formation of galaxies and the large scale structure of the universe. Here we
study the consequences of mass accretion onto massive Black Holes. We find that
a population of Super Massive Black Holes (SMBH) whose mass grows significantly
due to accretion can act as a source of entropic acceleration and constitute a
significant part of the present acceleration of the Universe.
| [
{
"created": "Sun, 18 Jun 2023 16:35:44 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Garcia-Bellido",
"Juan",
""
]
] | General Relativistic Entropic Acceleration (GREA) gives a general framework in which to study multiple out-of-equilibrium phenomena in the context of general relativity, like the late accelerated expansion of the universe or the formation of galaxies and the large scale structure of the universe. Here we study the consequences of mass accretion onto massive Black Holes. We find that a population of Super Massive Black Holes (SMBH) whose mass grows significantly due to accretion can act as a source of entropic acceleration and constitute a significant part of the present acceleration of the Universe. |
gr-qc/0702064 | David Mulryne | Filipe C. Mena, David J. Mulryne, Reza Tavakol | Non-linear vector perturbations in a contracting universe | 16 pages, no figures | Class.Quant.Grav.24:2721-2734,2007 | 10.1088/0264-9381/24/10/015 | DAMTP-2007-12 | gr-qc astro-ph hep-th | null | A number of scalar field models proposed as alternatives to the standard
inflationary scenario involve contracting phases which precede the universe's
present phase of expansion. An important question concerning such models is
whether there are effects which could potentially distinguish them from purely
expanding cosmologies. Vector perturbations have recently been considered in
this context. At first order such perturbations are not supported by a scalar
field. In this paper, therefore, we consider second order vector perturbations.
We show that such perturbations are generated by first order scalar mode-mode
couplings, and give an explicit expression for them. We compare the magnitude
of vector perturbations produced in collapsing models with the corresponding
amplitudes produced during inflation, using a number of suitable power-law
solutions to model the inflationary and collapsing scenarios. We conclude that
the ratios of the magnitudes of these perturbations depend on the details of
the collapsing scenario as well as on how the hot big bang is recovered, but
for certain cases could be large, growing with the duration of the collapse.
| [
{
"created": "Mon, 12 Feb 2007 18:04:14 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mena",
"Filipe C.",
""
],
[
"Mulryne",
"David J.",
""
],
[
"Tavakol",
"Reza",
""
]
] | A number of scalar field models proposed as alternatives to the standard inflationary scenario involve contracting phases which precede the universe's present phase of expansion. An important question concerning such models is whether there are effects which could potentially distinguish them from purely expanding cosmologies. Vector perturbations have recently been considered in this context. At first order such perturbations are not supported by a scalar field. In this paper, therefore, we consider second order vector perturbations. We show that such perturbations are generated by first order scalar mode-mode couplings, and give an explicit expression for them. We compare the magnitude of vector perturbations produced in collapsing models with the corresponding amplitudes produced during inflation, using a number of suitable power-law solutions to model the inflationary and collapsing scenarios. We conclude that the ratios of the magnitudes of these perturbations depend on the details of the collapsing scenario as well as on how the hot big bang is recovered, but for certain cases could be large, growing with the duration of the collapse. |
gr-qc/0107049 | Jacob D. Bekenstein | Jacob D. Bekenstein | Quantum Information and Quantum Black Holes | Lectures delivered at NATO Advanced Study Institute as 17th course of
the International School of Cosmology and Gravitation, Erice, 30 April-10
May, 2001, 26 pages, LaTeX209 with crckab.sty (provided) | in Advances in the Interplay between Quantum and Gravity Physics,
ed. P. G. Bergmann and V. de Sabbata (Kluwer, Dordrecht 2002). pp. 1-26 | null | null | gr-qc astro-ph hep-th quant-ph | null | First, the relation between black holes and limitations on information of
other systems is developed. After reviewing the relation of entropy to
information, we derive the entropy bound, review its applications to cosmology
and its extensions to higher dimensions, and discuss why black holes behave as
1-D objects when emitting entropy. We also discuss fundamental limitations on
the information of pulses in curved space, and on the rate of disposal of
information into a black hole. We then move on to a discussion of quantum black
holes motivated by the adiabatic invariance of horizon area of classical holes.
We develop an algebraic formalism based on symmetry which gives information on
the area (or mass) spectrum of quantum black holes, and on the degeneracy of
the levels. This last turns out to be consistent with the horizon area-black
hole entropy proportionality while leaving room for corrections.
| [
{
"created": "Fri, 13 Jul 2001 04:47:13 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 2002 08:45:57 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Bekenstein",
"Jacob D.",
""
]
] | First, the relation between black holes and limitations on information of other systems is developed. After reviewing the relation of entropy to information, we derive the entropy bound, review its applications to cosmology and its extensions to higher dimensions, and discuss why black holes behave as 1-D objects when emitting entropy. We also discuss fundamental limitations on the information of pulses in curved space, and on the rate of disposal of information into a black hole. We then move on to a discussion of quantum black holes motivated by the adiabatic invariance of horizon area of classical holes. We develop an algebraic formalism based on symmetry which gives information on the area (or mass) spectrum of quantum black holes, and on the degeneracy of the levels. This last turns out to be consistent with the horizon area-black hole entropy proportionality while leaving room for corrections. |
2006.01390 | Sanjar Shaymatov | Sanjar Shaymatov, Bobomurat Ahmedov, Mubasher Jamil | Testing the weak cosmic censorship conjecture for a
Reissner-Nordstr\"{o}m-de Sitter black hole surrounded by perfect fluid dark
matter | 11 pages, one figure; Title changed and corrections made. Accepted
for publication in Eur. Phys. J. C | Eur. Phys. J. C (2021) 81:588 | 10.1140/epjc/s10052-021-09499-6 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we test the weak cosmic censorship conjecture (WCCC) for the
Reissner-Nordstr\"{o}m-de Sitter (RN-dS) black hole surrounded by perfect fluid
dark matter. We consider a spherically symmetric perturbation on deriving
linear and non-linear order perturbation inequalities by applying new version
of gedanken experiments well accepted from the work of Sorce and Wald. Contrary
to the well-known result that the Reissner-Nordstr\"{o}m (RN) black hole could
be overcharged under linear order particle accretion it is hereby shown that
the same black hole in perfect fluid dark matter with cosmological parameter
cannot be overcharged. Considering a realistic scenario in which black holes
can not be considered to be in vacuum we investigate the contribution of dark
matter and cosmological constant in the overcharging process of an electrically
charged black hole. We demonstrate that the black hole can be overcharged only
when two fields induced by dark matter and cosmological parameter are
completely balanced. Further we give a remarkable result that black hole cannot
be overcharged beyond a certain threshold limit for which the effect arising
from the cosmological constant dominates over the effect by the perfect fluid
dark matter. Thus even for linear accretion process, the black hole cannot
always be overcharged and hence obeys the WCCC in general. This result would
continues be fulfilled for non-linear order accretion.
| [
{
"created": "Tue, 2 Jun 2020 04:58:44 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jun 2021 19:35:15 GMT",
"version": "v2"
}
] | 2021-09-01 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Jamil",
"Mubasher",
""
]
] | In this paper, we test the weak cosmic censorship conjecture (WCCC) for the Reissner-Nordstr\"{o}m-de Sitter (RN-dS) black hole surrounded by perfect fluid dark matter. We consider a spherically symmetric perturbation on deriving linear and non-linear order perturbation inequalities by applying new version of gedanken experiments well accepted from the work of Sorce and Wald. Contrary to the well-known result that the Reissner-Nordstr\"{o}m (RN) black hole could be overcharged under linear order particle accretion it is hereby shown that the same black hole in perfect fluid dark matter with cosmological parameter cannot be overcharged. Considering a realistic scenario in which black holes can not be considered to be in vacuum we investigate the contribution of dark matter and cosmological constant in the overcharging process of an electrically charged black hole. We demonstrate that the black hole can be overcharged only when two fields induced by dark matter and cosmological parameter are completely balanced. Further we give a remarkable result that black hole cannot be overcharged beyond a certain threshold limit for which the effect arising from the cosmological constant dominates over the effect by the perfect fluid dark matter. Thus even for linear accretion process, the black hole cannot always be overcharged and hence obeys the WCCC in general. This result would continues be fulfilled for non-linear order accretion. |
1703.06850 | Tomasz Stachowiak | Tomasz Stachowiak | Tensor $f(R)$ theory of gravity | Version 1: 21 pages, 6 figures; Version 2: 24 pages, 7 figures,
published text | Phys. Rev. D 96, 044013 (2017) | 10.1103/PhysRevD.96.044013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I propose an alternative $f(R)$ theory of gravity constructed by applying the
function $f$ directly to the Ricci tensor instead of the Ricci scalar. The main
goal of this study is to derive the resulting modified Einstein equations for
the metric case with Levi-Civita connection, as well as for the general
nonmetric connection with torsion. The modification is then applied to the
Robertson-Walker metric so that the cosmological evolution corresponding to the
standard model can be studied. An appealing feature is that even in the vacuum
case, scenarios without initial singularity and exponential expansion can be
recovered. Finally, formulae for possible observational tests are given.
| [
{
"created": "Mon, 20 Mar 2017 17:09:04 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Aug 2017 09:48:16 GMT",
"version": "v2"
}
] | 2017-08-16 | [
[
"Stachowiak",
"Tomasz",
""
]
] | I propose an alternative $f(R)$ theory of gravity constructed by applying the function $f$ directly to the Ricci tensor instead of the Ricci scalar. The main goal of this study is to derive the resulting modified Einstein equations for the metric case with Levi-Civita connection, as well as for the general nonmetric connection with torsion. The modification is then applied to the Robertson-Walker metric so that the cosmological evolution corresponding to the standard model can be studied. An appealing feature is that even in the vacuum case, scenarios without initial singularity and exponential expansion can be recovered. Finally, formulae for possible observational tests are given. |
2210.12139 | Dina Traykova | Masaru Shibata, Dina Traykova | Properties of scalar wave emission in a scalar-tensor theory with
kinetic screening | 13 pages, 8 figures; Minor changes, version as accepted in PRD | null | 10.1103/PhysRevD.107.044068 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study numerically the scalar wave emission by a non-spherical oscillation
of neutron stars in a scalar-tensor theory of gravity with kinetic screening,
considering both the monopole and quadrupole mode emission. In agreement with
previous results in the literature, we find that the monopole is always
suppressed by the screening effect, regardless of the size of the screening
radius, $r_{\rm sc}$. For the quadrupole mode, however, our analysis shows that
the suppression only occurs for screening radius larger than the wavelength of
scalar waves, $\lambda_{\rm wave}$, but not for $r_{\rm sc} < \lambda_{\rm
wave}$. This demonstrates that to fully understand the nature of this theory,
it is necessary to study other more complex systems, such as neutron star
binaries, considering a wide range of $r_{\rm sc}$ values.
| [
{
"created": "Fri, 21 Oct 2022 17:50:20 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Feb 2023 12:00:27 GMT",
"version": "v2"
}
] | 2023-03-08 | [
[
"Shibata",
"Masaru",
""
],
[
"Traykova",
"Dina",
""
]
] | We study numerically the scalar wave emission by a non-spherical oscillation of neutron stars in a scalar-tensor theory of gravity with kinetic screening, considering both the monopole and quadrupole mode emission. In agreement with previous results in the literature, we find that the monopole is always suppressed by the screening effect, regardless of the size of the screening radius, $r_{\rm sc}$. For the quadrupole mode, however, our analysis shows that the suppression only occurs for screening radius larger than the wavelength of scalar waves, $\lambda_{\rm wave}$, but not for $r_{\rm sc} < \lambda_{\rm wave}$. This demonstrates that to fully understand the nature of this theory, it is necessary to study other more complex systems, such as neutron star binaries, considering a wide range of $r_{\rm sc}$ values. |
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