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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2002.08559 | Zack Carson | Zack Carson and Kent Yagi | Probing string-inspired gravity with the inspiral-merger-ringdown
consistency tests of gravitational waves | 13 pages, 3 figures; updated to published version. Carson et al 2020
Class. Quantum Grav | null | 10.1088/1361-6382/aba221 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The extreme-gravity collisions between black holes allow us to probe the
underlying theory of gravity. We apply the theory-agnostic
inspiral-merger-ringdown consistency test to an example theory beyond general
relativity for the first time. Here we focus on the string-inspired
Einstein-dilaton Gauss-Bonnet gravity and modify the inspiral, ringdown, and
remnant black hole properties of the gravitational waveform. We found that
future multiband observations allow us to constrain the theory stronger than
current observations by an order of magnitude. The formalism developed here can
easily be applied to other theories.
| [
{
"created": "Thu, 20 Feb 2020 04:12:29 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jul 2020 15:08:09 GMT",
"version": "v2"
}
] | 2020-07-06 | [
[
"Carson",
"Zack",
""
],
[
"Yagi",
"Kent",
""
]
] | The extreme-gravity collisions between black holes allow us to probe the underlying theory of gravity. We apply the theory-agnostic inspiral-merger-ringdown consistency test to an example theory beyond general relativity for the first time. Here we focus on the string-inspired Einstein-dilaton Gauss-Bonnet gravity and modify the inspiral, ringdown, and remnant black hole properties of the gravitational waveform. We found that future multiband observations allow us to constrain the theory stronger than current observations by an order of magnitude. The formalism developed here can easily be applied to other theories. |
2404.09049 | Shankar Dayal Pathak | Gaurav Bhandari, S. D. Pathak, Manabendra Sharma, Anzhong Wang | Quantum deformed phantom dynamics in light of the generalized
uncertainty principle | null | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Quantum gravity has been baffling the theoretical physicist for decades now:
both for its mathematical obscurity and phenomenological testing. Nevertheless,
the new era of precision cosmology presents a promising avenue to test the
effects of quantum gravity. In this study, we consider a bottom-up approach.
Without resorting to any candidate quantum gravity, we invoke a generalized
uncertainty principle (GUP) directly into the cosmological Hamiltonian for a
universe sourced by a phantom scalar field with potential to study the early
epoch of the evolution. This is followed by a systematic analysis of the
dynamics, both qualitatively and quantitatively. Our qualitative analysis shows
that the introduction of GUP significantly alters the existence of fixed points
for the potential considered in this contribution. In addition, we confirm the
existence of an inflationary epoch and analyze the behavior of relevant
cosmological parameters with respect to the strength of GUP distortion.
| [
{
"created": "Sat, 13 Apr 2024 17:27:47 GMT",
"version": "v1"
}
] | 2024-04-16 | [
[
"Bhandari",
"Gaurav",
""
],
[
"Pathak",
"S. D.",
""
],
[
"Sharma",
"Manabendra",
""
],
[
"Wang",
"Anzhong",
""
]
] | Quantum gravity has been baffling the theoretical physicist for decades now: both for its mathematical obscurity and phenomenological testing. Nevertheless, the new era of precision cosmology presents a promising avenue to test the effects of quantum gravity. In this study, we consider a bottom-up approach. Without resorting to any candidate quantum gravity, we invoke a generalized uncertainty principle (GUP) directly into the cosmological Hamiltonian for a universe sourced by a phantom scalar field with potential to study the early epoch of the evolution. This is followed by a systematic analysis of the dynamics, both qualitatively and quantitatively. Our qualitative analysis shows that the introduction of GUP significantly alters the existence of fixed points for the potential considered in this contribution. In addition, we confirm the existence of an inflationary epoch and analyze the behavior of relevant cosmological parameters with respect to the strength of GUP distortion. |
2108.07766 | Ali \"Ovg\"un Dr. | Mert Okyay, Ali \"Ovg\"un | Nonlinear electrodynamics effects on the black hole shadow, deflection
angle, quasinormal modes and greybody factors | 36 pages. Accepted for publication in Journal of Cosmology and
Astroparticle Physics (JCAP) | JCAP01(2022)009 | 10.1088/1475-7516/2022/01/009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we discuss the effects of nonlinear electrodynamics (NED) on
non-rotating black holes, parametrized by the field coupling parameter $\beta$
and magnetic charge parameter $P$ in detail. Particularly, we survey physical
properties of the magnetically charged black hole, thermodynamic properties,
observational appearance, quasinormal modes and absorption cross sections. We
then show that the black hole gets colder with increasing charge. Investigating
the heat capacity, we see that the black hole is thermally stable, which is
amplified by introduction of a generalized uncertainty principle (GUP) with a
quantum gravity parameter $\lambda$. Then we compute the deflection angle at
the weak field limit, by the Gauss-Bonnet theorem and the geodesic equation,
showing that the magnetic charge has a contribution at the first order. By
ray-tracing we simulate the observational appearance of a NED black hole with
thin disk and spherical accretion. We find that the parameter $P$ has a very
strong effect on the shadow radius. We consider quasinormal modes under
massless scalar perturbations of the black hole and the greybody factor. We
find that the charge introduces a slight difference in the fundamental
frequency and that the greybody factor of the NED black hole is strongly
steepened by the introduction of increasing charge. To present observational
constrains, we show that the magnetic charge of the M87* black hole is between
$0\leq P\leq0.024$ in units of M, in agreement with the idea that real
astrophysical black holes are mostly neutral. We also find that LIGO/VIRGO and
LISA could detect NED black hole perturbations from BHs with masses between
$5M_\odot$ and $8.0\cdot 10^8\,M_\odot$. We finally show that for black holes
with masses detected with LIGO so far, charged NED black holes would deviate
from Schwarzschild by $5\sim 10$ Hz in their fundamental frequencies.
| [
{
"created": "Tue, 17 Aug 2021 17:17:19 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Aug 2021 17:38:41 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Jan 2022 20:57:09 GMT",
"version": "v3"
}
] | 2022-01-06 | [
[
"Okyay",
"Mert",
""
],
[
"Övgün",
"Ali",
""
]
] | In this paper, we discuss the effects of nonlinear electrodynamics (NED) on non-rotating black holes, parametrized by the field coupling parameter $\beta$ and magnetic charge parameter $P$ in detail. Particularly, we survey physical properties of the magnetically charged black hole, thermodynamic properties, observational appearance, quasinormal modes and absorption cross sections. We then show that the black hole gets colder with increasing charge. Investigating the heat capacity, we see that the black hole is thermally stable, which is amplified by introduction of a generalized uncertainty principle (GUP) with a quantum gravity parameter $\lambda$. Then we compute the deflection angle at the weak field limit, by the Gauss-Bonnet theorem and the geodesic equation, showing that the magnetic charge has a contribution at the first order. By ray-tracing we simulate the observational appearance of a NED black hole with thin disk and spherical accretion. We find that the parameter $P$ has a very strong effect on the shadow radius. We consider quasinormal modes under massless scalar perturbations of the black hole and the greybody factor. We find that the charge introduces a slight difference in the fundamental frequency and that the greybody factor of the NED black hole is strongly steepened by the introduction of increasing charge. To present observational constrains, we show that the magnetic charge of the M87* black hole is between $0\leq P\leq0.024$ in units of M, in agreement with the idea that real astrophysical black holes are mostly neutral. We also find that LIGO/VIRGO and LISA could detect NED black hole perturbations from BHs with masses between $5M_\odot$ and $8.0\cdot 10^8\,M_\odot$. We finally show that for black holes with masses detected with LIGO so far, charged NED black holes would deviate from Schwarzschild by $5\sim 10$ Hz in their fundamental frequencies. |
2401.12040 | Sergey Yu. Vernov | Ekaterina O. Pozdeeva and Sergey Yu. Vernov | Construction of Chiral Cosmological Models Unifying Inflation and
Primordial Black Hole Formation | 6 pages | SPACE, TIME AND FUNDAMENTAL INTERACTIONS, 2024, V. 1 (46), P. 90 | 10.17238/issn2226-8812.2024.1.90-94 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose the method for construction of $F(R,\xi)$ gravity model, unifying
inflation and primordial black hole formation. The proposed models are based on
the Starobinsky $R+R^2$ inflationary model, so, the function $F(R,\xi)$ is a
quadratic polynomial of the Ricci scalar $R$. We show that the potential of the
corresponding two-field chiral cosmological model in the Einstein frame can be
always found in terms of the elementary functions. The special choice of the
function $F(R,\xi)$ allows us to get such a generalization of the hybrid
inflation that can describe both inflation, and the primordial black hole
formation.
| [
{
"created": "Mon, 22 Jan 2024 15:27:36 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Pozdeeva",
"Ekaterina O.",
""
],
[
"Vernov",
"Sergey Yu.",
""
]
] | We propose the method for construction of $F(R,\xi)$ gravity model, unifying inflation and primordial black hole formation. The proposed models are based on the Starobinsky $R+R^2$ inflationary model, so, the function $F(R,\xi)$ is a quadratic polynomial of the Ricci scalar $R$. We show that the potential of the corresponding two-field chiral cosmological model in the Einstein frame can be always found in terms of the elementary functions. The special choice of the function $F(R,\xi)$ allows us to get such a generalization of the hybrid inflation that can describe both inflation, and the primordial black hole formation. |
1201.4429 | Alexandre Baranov | A.M.Baranov | Interior Static Stellar Model with Electric Charge as an Oscillator | 2 pages, Talk presented at the 5th Int. Conf. on Grav. and Astrophys.
of Acian-Pacific Countries (ICGA-5), Moscow, 2001 | Gravitation and Cosmology, Vol.8 (2002), Supplement II, pp.10-11 | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model approach to the description of static stars filled with a charged
Pascal perfect fluid within the framework of general relativity is
investigated. The metric is written in Bondi's radiation coordinates. The
gravitational equations are reduced to a nonlinear oscillator equation after
transfomation to a new variable as a function of the radial coordinate. It is
shown that in this case exact solutions of the Einstein-Maxwell equations for a
concrete energy density distribution law of the charged fluid may be obtained
as solution of the harmonic oscillator equation.
| [
{
"created": "Sat, 21 Jan 2012 03:54:40 GMT",
"version": "v1"
}
] | 2012-01-24 | [
[
"Baranov",
"A. M.",
""
]
] | A model approach to the description of static stars filled with a charged Pascal perfect fluid within the framework of general relativity is investigated. The metric is written in Bondi's radiation coordinates. The gravitational equations are reduced to a nonlinear oscillator equation after transfomation to a new variable as a function of the radial coordinate. It is shown that in this case exact solutions of the Einstein-Maxwell equations for a concrete energy density distribution law of the charged fluid may be obtained as solution of the harmonic oscillator equation. |
1107.3749 | Daniele Malafarina | Pankaj S. Joshi, Daniele Malafarina, Ravindra V. Saraykar | Genericity aspects in gravitational collapse to black holes and naked
singularities | 24 pages, 6 figures, some changes in text and figures to match the
version accepted for publication by IJMPD | null | 10.1142/S0218271812500666 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate here the genericity and stability aspects for naked
singularities and black holes that arise as the final states for a complete
gravitational collapse of a spherical massive matter cloud. The form of the
matter considered is a general Type I matter field, which includes most of the
physically reasonable matter fields such as dust, perfect fluids and such other
physically interesting forms of matter widely used in gravitation theory. We
first study here in some detail the effects of small pressure perturbations in
an otherwise pressure-free collapse scenario, and examine how a collapse
evolution that was going to the black hole endstate would be modified and go to
a naked singularity, once small pressures are introduced in the initial data.
This allows us to understand the distribution of black holes and naked
singularities in the initial data space. Collapse is examined in terms of the
evolutions allowed by Einstein equations, under suitable physical conditions
and as evolving from a regular initial data. We then show that both black holes
and naked singularities are generic outcomes of a complete collapse, when
genericity is defined in a suitable sense in an appropriate space.
| [
{
"created": "Tue, 19 Jul 2011 15:41:58 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jul 2012 13:36:06 GMT",
"version": "v2"
}
] | 2012-11-15 | [
[
"Joshi",
"Pankaj S.",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Saraykar",
"Ravindra V.",
""
]
] | We investigate here the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the matter considered is a general Type I matter field, which includes most of the physically reasonable matter fields such as dust, perfect fluids and such other physically interesting forms of matter widely used in gravitation theory. We first study here in some detail the effects of small pressure perturbations in an otherwise pressure-free collapse scenario, and examine how a collapse evolution that was going to the black hole endstate would be modified and go to a naked singularity, once small pressures are introduced in the initial data. This allows us to understand the distribution of black holes and naked singularities in the initial data space. Collapse is examined in terms of the evolutions allowed by Einstein equations, under suitable physical conditions and as evolving from a regular initial data. We then show that both black holes and naked singularities are generic outcomes of a complete collapse, when genericity is defined in a suitable sense in an appropriate space. |
2305.10776 | Viola De Renzis | Viola De Renzis | Up-down binaries are unstable and we want to know | Contribution to the 2023 Gravitation session of the 57th Rencontres
de Moriond | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relativistic spin-precession equations for black-hole binaries have four
different equilibrium solutions that correspond to systems where the two
individual black hole spins are either aligned or anti-aligned with the orbital
angular momentum. Surprisingly, it was demonstrated that only three of these
equilibrium solutions are stable. Binary systems in the up-down configuration,
where the spin of the heavier (lighter) black hole is co- (counter-) aligned
with the orbital angular momentum, might be unstable to small perturbations of
the spin directions. After the onset of the up-down instability, that occurs
after a specific critical orbital separation $r_\mathrm{UD+}$, the binary
becomes unstable to spin precession leading to large misalignment of the spins.
In this work, we present a Bayesian procedure based on the Savage-Dickey
density ratio to test the up-down origin of gravitational-wave events. We apply
this procedure to look for promising candidates among the events detected so
far during the first three observing runs performed by LIGO/Virgo.
| [
{
"created": "Thu, 18 May 2023 07:35:05 GMT",
"version": "v1"
}
] | 2023-05-19 | [
[
"De Renzis",
"Viola",
""
]
] | The relativistic spin-precession equations for black-hole binaries have four different equilibrium solutions that correspond to systems where the two individual black hole spins are either aligned or anti-aligned with the orbital angular momentum. Surprisingly, it was demonstrated that only three of these equilibrium solutions are stable. Binary systems in the up-down configuration, where the spin of the heavier (lighter) black hole is co- (counter-) aligned with the orbital angular momentum, might be unstable to small perturbations of the spin directions. After the onset of the up-down instability, that occurs after a specific critical orbital separation $r_\mathrm{UD+}$, the binary becomes unstable to spin precession leading to large misalignment of the spins. In this work, we present a Bayesian procedure based on the Savage-Dickey density ratio to test the up-down origin of gravitational-wave events. We apply this procedure to look for promising candidates among the events detected so far during the first three observing runs performed by LIGO/Virgo. |
2111.06441 | Angelo E. S. Hartmann | Mario Novello, Angelo E. S. Hartmann, E. Bittencourt | Galaxy rotation curves in the light of the Spinor Theory of Gravity | 5 pages | Mod. Phys. Lett. A 36 (2021) 2150248 | 10.1142/S0217732321502485 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We analyze the recently obtained static and spherically symmetric solution of
the Spinor Theory of Gravity (STG) which, in the weak field limit, presents an
effective Newtonian potential that contains an extra logarithmic behavior. We
apply this solution to the description of the galaxy rotation curves finding an
interesting analogy with the dark matter halo profile proposed by Navarro,
Frenk and White.
| [
{
"created": "Thu, 11 Nov 2021 19:45:52 GMT",
"version": "v1"
}
] | 2021-12-20 | [
[
"Novello",
"Mario",
""
],
[
"Hartmann",
"Angelo E. S.",
""
],
[
"Bittencourt",
"E.",
""
]
] | We analyze the recently obtained static and spherically symmetric solution of the Spinor Theory of Gravity (STG) which, in the weak field limit, presents an effective Newtonian potential that contains an extra logarithmic behavior. We apply this solution to the description of the galaxy rotation curves finding an interesting analogy with the dark matter halo profile proposed by Navarro, Frenk and White. |
1410.5785 | Dario Nunez Dr. | Juan Carlos Degollado, Victor Gualajara, Claudia Moreno, and Dar\'io
N\'u\~nez | Electromagnetic partner of the gravitational signal during accretion
onto black holes | 12 pages, six figures | null | 10.1007/s10714-014-1819-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the generation of electromagnetic and gravitational radiation
in the vicinity of a perturbed Schwarzschild black hole. The gravitational
perturbations and the electromagnetic field are studied by solving the
Teukolsky master equation with sources, which we take to be locally charged,
radially infalling, matter. Our results show that, in addition to the
gravitational wave generated as the matter falls into the black hole, there is
also a burst of electromagnetic radiation. This electromagnetic field has a
characteristic set of quasinormal frequencies, and the gravitational radiation
has the quasinormal frequencies of a Schwarzschild black hole. This scenario
allows us to compare the gravitational and electromagnetic signals that are
generated by a common source.
| [
{
"created": "Tue, 21 Oct 2014 18:55:23 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Degollado",
"Juan Carlos",
""
],
[
"Gualajara",
"Victor",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Núñez",
"Darío",
""
]
] | We investigate the generation of electromagnetic and gravitational radiation in the vicinity of a perturbed Schwarzschild black hole. The gravitational perturbations and the electromagnetic field are studied by solving the Teukolsky master equation with sources, which we take to be locally charged, radially infalling, matter. Our results show that, in addition to the gravitational wave generated as the matter falls into the black hole, there is also a burst of electromagnetic radiation. This electromagnetic field has a characteristic set of quasinormal frequencies, and the gravitational radiation has the quasinormal frequencies of a Schwarzschild black hole. This scenario allows us to compare the gravitational and electromagnetic signals that are generated by a common source. |
gr-qc/9710039 | Jerzy Kowalski-Glikman | A. B{\l}aut and J. Kowalski-Glikman | Constraints and Solutions of Quantum Gravity in Metric Representation | 17 pages, plain LaTeX | null | null | null | gr-qc | null | We construct the regularised Wheeler-De Witt operator demanding that the
algebra of constraints of quantum gravity is anomaly free. We find that for a
subset of all wavefunctions being integrals of scalar densities this condition
can be satisfied. We proceed to finding exact solutions of quantum gravity
being of the form of functionals of volume and average curvature of compact
three-manifold.
| [
{
"created": "Tue, 7 Oct 1997 15:42:05 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Błaut",
"A.",
""
],
[
"Kowalski-Glikman",
"J.",
""
]
] | We construct the regularised Wheeler-De Witt operator demanding that the algebra of constraints of quantum gravity is anomaly free. We find that for a subset of all wavefunctions being integrals of scalar densities this condition can be satisfied. We proceed to finding exact solutions of quantum gravity being of the form of functionals of volume and average curvature of compact three-manifold. |
2403.07250 | Haoxuan Sun | Zirui Hu, Haoxuan Sun | Integrating Gauss-Bonnet Corrections in Quantum Field Theory:
Implications for Torsion, Gauge Bosons, and the Hubble Constant | null | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We explore matter fields containing Gauss-Bonnet correction terms within the
framework of renormalizable quantum field theory. By revising the gauge model
with a charged scalar multiplier and two sets of fermion families within a flat
universe model using torsion, we introduce Gauss-Bonnet corrections into the
action to investigate field equations within the context of supersymmetric
mixed inflationary models. After analytically computing the modified gauge
boson field equations through the incorporation of Gauss-Bonnet theory into the
fundamental field equations, we derive the torsion characteristics and
energy-momentum tensor properties of a flat universe. Our analysis can extend
to more specific Gauss-Bonnet correction models, enabling the derivation of
gravitational characteristic equations with practical applications. This
streamlines Gauss-Bonnet models, assesses the model's sensitivity to correction
parameters, and explores high-sensitivity models with observational
significance. Furthermore, in this derivation process, we identify that
Gauss-Bonnet correction terms can directly impact the Hubble constant through
Einstein's equations, indicating the potential for verifying Gauss-Bonnet
theory through astronomical observations.
| [
{
"created": "Tue, 12 Mar 2024 02:18:54 GMT",
"version": "v1"
}
] | 2024-03-13 | [
[
"Hu",
"Zirui",
""
],
[
"Sun",
"Haoxuan",
""
]
] | We explore matter fields containing Gauss-Bonnet correction terms within the framework of renormalizable quantum field theory. By revising the gauge model with a charged scalar multiplier and two sets of fermion families within a flat universe model using torsion, we introduce Gauss-Bonnet corrections into the action to investigate field equations within the context of supersymmetric mixed inflationary models. After analytically computing the modified gauge boson field equations through the incorporation of Gauss-Bonnet theory into the fundamental field equations, we derive the torsion characteristics and energy-momentum tensor properties of a flat universe. Our analysis can extend to more specific Gauss-Bonnet correction models, enabling the derivation of gravitational characteristic equations with practical applications. This streamlines Gauss-Bonnet models, assesses the model's sensitivity to correction parameters, and explores high-sensitivity models with observational significance. Furthermore, in this derivation process, we identify that Gauss-Bonnet correction terms can directly impact the Hubble constant through Einstein's equations, indicating the potential for verifying Gauss-Bonnet theory through astronomical observations. |
1609.04812 | J. Brian Pitts | J. Brian Pitts | Equivalent Theories Redefine Hamiltonian Observables to Exhibit Change
in General Relativity | Published in Classical and Quantum Gravity. A related CQG+ article is
on the way | Classical and Quantum Gravity 34 (2017) 055008 | 10.1088/1361-6382/aa5ce8 | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Change and local spatial variation are missing in canonical General
Relativity's observables as usually defined, part of the problem of time.
Definitions can be tested using equivalent formulations, non-gauge and gauge,
because they must have equivalent observables and everything is observable in
the non-gauge formulation. Taking an observable from the non-gauge formulation
and finding the equivalent in the gauge formulation, one requires that the
equivalent be an observable, constraining definitions. For massive photons, the
de Broglie-Proca non-gauge formulation observable A_{\mu} is equivalent to the
Stueckelberg-Utiyama gauge formulation quantity A_{\mu}+\partial_{\mu} \phi.
Thus observables must have 0 Poisson bracket not with each first-class
constraint, but with the Rosenfeld-Anderson-Bergmann-Castellani gauge generator
G, a tuned sum of first-class constraints, in accord with the
Pons-Salisbury-Sundermeyer definition of observables.
The definition for external gauge symmetries can be tested using massive
gravity, where one can install gauge freedom by parametrization with clock
fields X^A. The non-gauge observable g^{\mu\nu} has the gauge equivalent
X^A,_{\mu} g^{\mu\nu} X^B,_{\nu}. The Poisson bracket of X^A,_{\mu} g^{\mu\nu}
X^B,_{\nu} with G turns out to be not 0 but a Lie derivative. This non-zero
Poisson bracket refines and systematizes Kuchar's proposal to relax the 0
Poisson bracket condition with the Hamiltonian constraint. Thus observables
need covariance, not invariance, in relation to external gauge symmetries.
The Lagrangian and Hamiltonian for massive gravity are those of General
Relativity + Lambda + 4 scalars, so the same definition of observables applies
to General Relativity. Local fields such as g_{\mu\nu} are observables. Thus
observables change. Requiring equivalent observables for equivalent theories
also recovers Hamiltonian-Lagrangian equivalence.
| [
{
"created": "Thu, 15 Sep 2016 18:38:12 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2017 13:27:55 GMT",
"version": "v2"
}
] | 2017-03-06 | [
[
"Pitts",
"J. Brian",
""
]
] | Change and local spatial variation are missing in canonical General Relativity's observables as usually defined, part of the problem of time. Definitions can be tested using equivalent formulations, non-gauge and gauge, because they must have equivalent observables and everything is observable in the non-gauge formulation. Taking an observable from the non-gauge formulation and finding the equivalent in the gauge formulation, one requires that the equivalent be an observable, constraining definitions. For massive photons, the de Broglie-Proca non-gauge formulation observable A_{\mu} is equivalent to the Stueckelberg-Utiyama gauge formulation quantity A_{\mu}+\partial_{\mu} \phi. Thus observables must have 0 Poisson bracket not with each first-class constraint, but with the Rosenfeld-Anderson-Bergmann-Castellani gauge generator G, a tuned sum of first-class constraints, in accord with the Pons-Salisbury-Sundermeyer definition of observables. The definition for external gauge symmetries can be tested using massive gravity, where one can install gauge freedom by parametrization with clock fields X^A. The non-gauge observable g^{\mu\nu} has the gauge equivalent X^A,_{\mu} g^{\mu\nu} X^B,_{\nu}. The Poisson bracket of X^A,_{\mu} g^{\mu\nu} X^B,_{\nu} with G turns out to be not 0 but a Lie derivative. This non-zero Poisson bracket refines and systematizes Kuchar's proposal to relax the 0 Poisson bracket condition with the Hamiltonian constraint. Thus observables need covariance, not invariance, in relation to external gauge symmetries. The Lagrangian and Hamiltonian for massive gravity are those of General Relativity + Lambda + 4 scalars, so the same definition of observables applies to General Relativity. Local fields such as g_{\mu\nu} are observables. Thus observables change. Requiring equivalent observables for equivalent theories also recovers Hamiltonian-Lagrangian equivalence. |
2111.10052 | Li Tang | Li Tang, Hai-Nan Lin, Xin Li and Liang Liu | Reconstructing the Hubble diagram of gamma-ray bursts using deep
learning | 10 pages, 6 figures, 3 tables | Monthly Notices of the Royal Astronomical Society, 509, 1194-1200
(2022) | 10.1093/mnras/stab2932 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calibrate the distance and reconstruct the Hubble diagram of gamma-ray
bursts (GRBs) using deep learning. We construct an artificial neural network,
which combines the recurrent neural network and Bayesian neural network, and
train the network using the Pantheon compilation of type-Ia supernovae. The
trained network is used to calibrate the distance of 174 GRBs based on the
Combo-relation. We verify that there is no evident redshift evolution of
Combo-relation, and obtain the slope and intercept parameters,
$\gamma=0.856^{+0.083}_{-0.078}$ and $\log A=49.661^{+0.199}_{-0.217}$, with an
intrinsic scatter $\sigma_{\rm int}=0.228^{+0.041}_{-0.040}$. Our calibrating
method is independent of cosmological model, thus the calibrated GRBs can be
directly used to constrain cosmological parameters. It is shown that GRBs alone
can tightly constrain the $\Lambda$CDM model, with $\Omega_{\rm
M}=0.280^{+0.049}_{-0.057}$. However, the constraint on the $\omega$CDM model
is relatively looser, with $\Omega_{\rm M}=0.345^{+0.059}_{-0.060}$ and
$\omega<-1.414$. The combination of GRBs and Pantheon can tightly constrain the
$\omega$CDM model, with $\Omega_{\rm M}=0.336^{+0.055}_{-0.050}$ and
$\omega=-1.141^{+0.156}_{-0.135}$.
| [
{
"created": "Fri, 19 Nov 2021 05:31:34 GMT",
"version": "v1"
}
] | 2021-11-22 | [
[
"Tang",
"Li",
""
],
[
"Lin",
"Hai-Nan",
""
],
[
"Li",
"Xin",
""
],
[
"Liu",
"Liang",
""
]
] | We calibrate the distance and reconstruct the Hubble diagram of gamma-ray bursts (GRBs) using deep learning. We construct an artificial neural network, which combines the recurrent neural network and Bayesian neural network, and train the network using the Pantheon compilation of type-Ia supernovae. The trained network is used to calibrate the distance of 174 GRBs based on the Combo-relation. We verify that there is no evident redshift evolution of Combo-relation, and obtain the slope and intercept parameters, $\gamma=0.856^{+0.083}_{-0.078}$ and $\log A=49.661^{+0.199}_{-0.217}$, with an intrinsic scatter $\sigma_{\rm int}=0.228^{+0.041}_{-0.040}$. Our calibrating method is independent of cosmological model, thus the calibrated GRBs can be directly used to constrain cosmological parameters. It is shown that GRBs alone can tightly constrain the $\Lambda$CDM model, with $\Omega_{\rm M}=0.280^{+0.049}_{-0.057}$. However, the constraint on the $\omega$CDM model is relatively looser, with $\Omega_{\rm M}=0.345^{+0.059}_{-0.060}$ and $\omega<-1.414$. The combination of GRBs and Pantheon can tightly constrain the $\omega$CDM model, with $\Omega_{\rm M}=0.336^{+0.055}_{-0.050}$ and $\omega=-1.141^{+0.156}_{-0.135}$. |
1908.06759 | Pardyumn Kumar Sahoo | Snehasish Bhattacharjee, P.K. Sahoo | Constraining f(R,T) Gravity From The Dark Energy Density Parameter
$\Omega_{\Lambda}$ | To appear in Gravitation and Cosmology | Gravitation and Cosmology, 26(3) (2020) 281-284 | 10.1134/S0202289320030032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | $f(R,T)$ gravity is a widely used extended theory of gravity introduced in
\cite{9} which is a straightforward generalization of $f(R)$ gravity. The
action in this extended theory of gravity incorporates well motivated
functional forms of the Ricci scalar $R$ and trace of energy momentum tensor
$T$. The present manuscript aims at constraining the most widely used $f(R,T)$
gravity model of the form $f(R+2\lambda T)$ to understand its coherency and
applicability in cosmology. We communicate here a novel method to find an lower
bound on the model parameter $\lambda \gtrsim -1.9 \times 10^{-8}$ through the
equation relating the cosmological constant ($\Lambda$) and the critical
density of the universe ($\rho_{cr}$).
| [
{
"created": "Fri, 16 Aug 2019 01:33:57 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Sep 2019 03:45:50 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Nov 2019 09:05:10 GMT",
"version": "v3"
},
{
"created": "Thu, 4 Jun 2020 06:42:45 GMT",
"version": "v4"
}
] | 2020-07-09 | [
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | $f(R,T)$ gravity is a widely used extended theory of gravity introduced in \cite{9} which is a straightforward generalization of $f(R)$ gravity. The action in this extended theory of gravity incorporates well motivated functional forms of the Ricci scalar $R$ and trace of energy momentum tensor $T$. The present manuscript aims at constraining the most widely used $f(R,T)$ gravity model of the form $f(R+2\lambda T)$ to understand its coherency and applicability in cosmology. We communicate here a novel method to find an lower bound on the model parameter $\lambda \gtrsim -1.9 \times 10^{-8}$ through the equation relating the cosmological constant ($\Lambda$) and the critical density of the universe ($\rho_{cr}$). |
1507.03127 | J Erik Baxter | J. Erik Baxter | Stable topological hairy black holes in $\mathfrak{su}(N)$ EYM theory
with $\Lambda<0$ | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the linear stability of topological black hole solutions to
four-dimensional SU(N) Einstein-Yang-Mills theory with a negative cosmological
constant. We here extend recent results in the field which prove the existence
of hairy black hole solutions to such equations, and the stability of their
spherically symmetric analogues. We find the analysis carries over very
similarly, with some important differences in the final stages. Nevertheless,
we establish the existence of non-trivial solutions stable under linear
perturbations, in a sufficiently small neighbourhood of some existing trivial
solutions; in fact, stable topological solutions turn out to be likely more
abundant in the parameter space than their spherically symmetric analogues.
| [
{
"created": "Sat, 11 Jul 2015 17:03:12 GMT",
"version": "v1"
}
] | 2015-07-14 | [
[
"Baxter",
"J. Erik",
""
]
] | We investigate the linear stability of topological black hole solutions to four-dimensional SU(N) Einstein-Yang-Mills theory with a negative cosmological constant. We here extend recent results in the field which prove the existence of hairy black hole solutions to such equations, and the stability of their spherically symmetric analogues. We find the analysis carries over very similarly, with some important differences in the final stages. Nevertheless, we establish the existence of non-trivial solutions stable under linear perturbations, in a sufficiently small neighbourhood of some existing trivial solutions; in fact, stable topological solutions turn out to be likely more abundant in the parameter space than their spherically symmetric analogues. |
1205.4530 | Steven Hergt | Steven Hergt, Jan Steinhoff and Gerhard Schaefer | On the comparison of results regarding the post-Newtonian approximate
treatment of the dynamics of extended spinning compact binaries | Conference proceedings for the 7th International Conference on
Gravitation and Cosmology (ICGC2011), 4 pages | null | 10.1088/1742-6596/484/1/012018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief review is given of all the Hamiltonians and effective potentials
calculated hitherto covering the post-Newtonian (pN) dynamics of a two body
system. A method is presented to compare (conservative) reduced Hamiltonians
with nonreduced potentials directly at least up to the next-to-leading-pN
order.
| [
{
"created": "Mon, 21 May 2012 09:13:51 GMT",
"version": "v1"
}
] | 2016-06-15 | [
[
"Hergt",
"Steven",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Schaefer",
"Gerhard",
""
]
] | A brief review is given of all the Hamiltonians and effective potentials calculated hitherto covering the post-Newtonian (pN) dynamics of a two body system. A method is presented to compare (conservative) reduced Hamiltonians with nonreduced potentials directly at least up to the next-to-leading-pN order. |
gr-qc/9711056 | Steven Weinstein | Steven Weinstein (Dept. of Philosophy, Northwestern University) | Time, Gauge, and the Superposition Principle in Quantum Gravity | 3 pages, LaTeX. Requires mprocl.sty, available at
ftp://shemesh.fiz.huji.ac.il/pub/mprocl.sty . To be published in the
proceedings of the Eighth Marcel Grossmann Meeting on General Relativity.
(Jerusalem, June, 1997) | null | null | null | gr-qc quant-ph | null | The quantization of time-reparametrization invariant systems such as general
relativity is plagued by an ambiguity relating to the role of time in the
theory. If one parametrizes observables by the (unobservable) time, and then
relies on the existence of an approximate "clock" degree of freedom to give
physical meaning to the observables, one finds multiple quantum states that
yield the same predictions yet interfere with each other.
| [
{
"created": "Tue, 18 Nov 1997 16:28:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Weinstein",
"Steven",
"",
"Dept. of Philosophy, Northwestern University"
]
] | The quantization of time-reparametrization invariant systems such as general relativity is plagued by an ambiguity relating to the role of time in the theory. If one parametrizes observables by the (unobservable) time, and then relies on the existence of an approximate "clock" degree of freedom to give physical meaning to the observables, one finds multiple quantum states that yield the same predictions yet interfere with each other. |
1002.1472 | Lan-Hsuan Huang | Lan-Hsuan Huang | Solutions of special asymptotics to the Einstein constraint equations | 13 pages; the error in Lemma 3.5 fixed and typos corrected; to appear
in Class. Quantum Grav | null | 10.1088/0264-9381/27/24/245002 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct solutions with prescribed asymptotics to the Einstein constraint
equations using a cut-off technique. Moreover, we give various examples of
vacuum asymptotically flat manifolds whose center of mass and angular momentum
are ill-defined.
| [
{
"created": "Sun, 7 Feb 2010 18:10:59 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Oct 2010 13:53:49 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Huang",
"Lan-Hsuan",
""
]
] | We construct solutions with prescribed asymptotics to the Einstein constraint equations using a cut-off technique. Moreover, we give various examples of vacuum asymptotically flat manifolds whose center of mass and angular momentum are ill-defined. |
1705.03495 | Tomas Ortin | Tomas Ortin | Higher order gravities and the Strong Equivalence Principle | Additional resulting the gauge transformation of the gravitational
energy-momentum tensor and references added. 18 pages, no figures | null | 10.1007/JHEP09(2017)152 | IFT-UAM/CSIC-17-032 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that, in all metric theories of gravity with a general covariant
action, gravity couples to the gravitational energy-momentum tensor in the same
way it couples to the matter energy-momentum tensor order by order in the weak
field approximation around flat spacetime. We discuss the relation of this
property to the Strong Equivalence Principle. We also study the gauge
transformation properties of the gravitational energy-momentum tensor.
| [
{
"created": "Tue, 9 May 2017 19:15:27 GMT",
"version": "v1"
},
{
"created": "Thu, 18 May 2017 16:04:16 GMT",
"version": "v2"
}
] | 2017-10-25 | [
[
"Ortin",
"Tomas",
""
]
] | We show that, in all metric theories of gravity with a general covariant action, gravity couples to the gravitational energy-momentum tensor in the same way it couples to the matter energy-momentum tensor order by order in the weak field approximation around flat spacetime. We discuss the relation of this property to the Strong Equivalence Principle. We also study the gauge transformation properties of the gravitational energy-momentum tensor. |
2205.08160 | Aneta Wojnar | Aneta Wojnar | Stellar and substellar objects in modified gravity | 20 pages, 1 figure, Invited contribution to the forthcoming book
"Modified and Quantum Gravity - From theory to experimental searches on all
scales", Springer Nature, Eds C. L\"ammerzahl and C. Pfeifer | null | 10.1007/978-3-031-31520-6 | null | gr-qc astro-ph.EP astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The last findings on stellar and substellar objects in modified gravity are
presented, allowing a reader to quickly jump into this topic. Early stellar
evolution of low-mass stars, cooling models of brown dwarfs and giant gaseous
exoplanets as well as internal structure of terrestrial planets are discussed.
Moreover, possible test of models of gravity with the use of the discussed
objects are proposed.
| [
{
"created": "Tue, 17 May 2022 07:51:57 GMT",
"version": "v1"
}
] | 2023-11-27 | [
[
"Wojnar",
"Aneta",
""
]
] | The last findings on stellar and substellar objects in modified gravity are presented, allowing a reader to quickly jump into this topic. Early stellar evolution of low-mass stars, cooling models of brown dwarfs and giant gaseous exoplanets as well as internal structure of terrestrial planets are discussed. Moreover, possible test of models of gravity with the use of the discussed objects are proposed. |
gr-qc/0108086 | Luc Blanchet | Luc Blanchet | On the two-body problem in general relativity | 10 pages, to appear in a special issue of Comptes Rendus de
l'Academie des Sciences, Paris, on the subject "Missions Spatiales en
Physique Fondamentale" | null | 10.1016/S1296-2147(01)01267-7 | null | gr-qc | null | We consider the two-body problem in post-Newtonian approximations of general
relativity. We report the recent results concerning the equations of motion,
and the associated Lagrangian formulation, of compact binary systems, at the
third post-Newtonian order (1/c^6 beyond the Newtonian acceleration). These
equations are necessary when constructing the theoretical templates for
searching and analyzing the gravitational-wave signals from inspiralling
compact binaries in VIRGO-type experiments.
| [
{
"created": "Fri, 31 Aug 2001 11:56:29 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Blanchet",
"Luc",
""
]
] | We consider the two-body problem in post-Newtonian approximations of general relativity. We report the recent results concerning the equations of motion, and the associated Lagrangian formulation, of compact binary systems, at the third post-Newtonian order (1/c^6 beyond the Newtonian acceleration). These equations are necessary when constructing the theoretical templates for searching and analyzing the gravitational-wave signals from inspiralling compact binaries in VIRGO-type experiments. |
gr-qc/0310017 | Massimo Tinto | Massimo Tinto, Frank B. Estabrook, adn J.W. Armstrong | Time Delay Interferometry with Moving Spacecraft Arrays | Modified version, which is scheduled to appear on the PRD April 15,
2004 issue | Phys.Rev. D69 (2004) 082001 | 10.1103/PhysRevD.69.082001 | null | gr-qc | null | Space-borne interferometric gravitational wave detectors, sensitive in the
low-frequency (millihertz) band, will fly in the next decade. In these
detectors the spacecraft-to-spacecraft light-travel-times will necessarily be
unequal, time-varying, and (due to aberration) have different time delays on
up- and down-links. Reduction of data from moving interferometric laser arrays
in solar orbit will in fact encounter non-symmetric up- and downlink light time
differences that are about 100 times larger than has previously been
recognized. The time-delay interferometry (TDI) technique uses knowledge of
these delays to cancel the otherwise dominant laser phase noise and yields a
variety of data combinations sensitive to gravitational waves. Under the
assumption that the (different) up- and downlink time delays are constant, we
derive the TDI expressions for those combinations that rely only on four
inter-spacecraft phase measurements. We then turn to the general problem that
encompasses time-dependence of the light-travel times along the laser links. By
introducing a set of non-commuting time-delay operators, we show that there
exists a quite general procedure for deriving generalized TDI combinations that
account for the effects of time-dependence of the arms. By applying our
approach we are able to re-derive the ``flex-free'' expression for the
unequal-arm Michelson combinations $X_1$, first presented in \cite{STEA}, and
obtain the generalized expressions for the TDI combinations called Relay,
Beacon, Monitor, and Symmetric Sagnac.
| [
{
"created": "Fri, 3 Oct 2003 07:15:55 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Mar 2004 23:18:06 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Tinto",
"Massimo",
""
],
[
"Estabrook",
"Frank B.",
""
],
[
"Armstrong",
"adn J. W.",
""
]
] | Space-borne interferometric gravitational wave detectors, sensitive in the low-frequency (millihertz) band, will fly in the next decade. In these detectors the spacecraft-to-spacecraft light-travel-times will necessarily be unequal, time-varying, and (due to aberration) have different time delays on up- and down-links. Reduction of data from moving interferometric laser arrays in solar orbit will in fact encounter non-symmetric up- and downlink light time differences that are about 100 times larger than has previously been recognized. The time-delay interferometry (TDI) technique uses knowledge of these delays to cancel the otherwise dominant laser phase noise and yields a variety of data combinations sensitive to gravitational waves. Under the assumption that the (different) up- and downlink time delays are constant, we derive the TDI expressions for those combinations that rely only on four inter-spacecraft phase measurements. We then turn to the general problem that encompasses time-dependence of the light-travel times along the laser links. By introducing a set of non-commuting time-delay operators, we show that there exists a quite general procedure for deriving generalized TDI combinations that account for the effects of time-dependence of the arms. By applying our approach we are able to re-derive the ``flex-free'' expression for the unequal-arm Michelson combinations $X_1$, first presented in \cite{STEA}, and obtain the generalized expressions for the TDI combinations called Relay, Beacon, Monitor, and Symmetric Sagnac. |
1907.12890 | Filiz \c{C}a\u{g}atay U\c{c}gun | Filiz \c{C}a\u{g}atay U\c{c}gun, O\u{g}ul Esen and Hasan G\"umral | Reductions of Topologically Massive Gravity II: First Order Realizations
of Second Order Lagrangians | 35 pages | null | 10.1063/1.5123020 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Second order degenerate Cl\`ement and Sar{\i}o\u{g}lu-Tekin Lagrangians are
casted into forms of various first order Lagrangians. Hamiltonian analysis of
these equivalent formalisms are performed by means of Dirac-Bergmann constraint
algorithm.
| [
{
"created": "Wed, 24 Jul 2019 06:45:12 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Uçgun",
"Filiz Çağatay",
""
],
[
"Esen",
"Oğul",
""
],
[
"Gümral",
"Hasan",
""
]
] | Second order degenerate Cl\`ement and Sar{\i}o\u{g}lu-Tekin Lagrangians are casted into forms of various first order Lagrangians. Hamiltonian analysis of these equivalent formalisms are performed by means of Dirac-Bergmann constraint algorithm. |
2007.09481 | Lorenzo Gavassino | Lorenzo Gavassino, Marco Antonelli and Brynmor Haskell | Multifluid Modelling of Relativistic Radiation Hydrodynamics | 19 pages, 0 figures, published on Symmetry | null | 10.3390/sym12091543 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formulation of a universal theory for bulk viscosity and heat conduction
represents a theoretical challenge for our understanding of relativistic fluid
dynamics. Recently, it has been shown that the multifluid variational approach
championed by Carter and collaborators has the potential to be a general and
natural framework to derive (hyperbolic) hydrodynamic equations for
relativistic dissipative systems. Furthermore, it also allows to keep direct
contact with non-equilibrium thermodynamics, providing a clear microscopic
interpretation of the elements of the theory. To provide an example of its
universal applicability, in this paper we derive the fundamental equations of
the radiation hydrodynamics directly in the context of Carter's multifluid
theory. This operation unveils a novel set of thermodynamic constraints that
must be respected by any microscopic model. Then, we prove that the radiation
hydrodynamics becomes a multifluid model for bulk viscosity or heat conduction
in some appropriate physical limits.
| [
{
"created": "Sat, 18 Jul 2020 17:20:37 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 18:59:32 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Oct 2020 13:29:52 GMT",
"version": "v3"
}
] | 2020-10-15 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Haskell",
"Brynmor",
""
]
] | The formulation of a universal theory for bulk viscosity and heat conduction represents a theoretical challenge for our understanding of relativistic fluid dynamics. Recently, it has been shown that the multifluid variational approach championed by Carter and collaborators has the potential to be a general and natural framework to derive (hyperbolic) hydrodynamic equations for relativistic dissipative systems. Furthermore, it also allows to keep direct contact with non-equilibrium thermodynamics, providing a clear microscopic interpretation of the elements of the theory. To provide an example of its universal applicability, in this paper we derive the fundamental equations of the radiation hydrodynamics directly in the context of Carter's multifluid theory. This operation unveils a novel set of thermodynamic constraints that must be respected by any microscopic model. Then, we prove that the radiation hydrodynamics becomes a multifluid model for bulk viscosity or heat conduction in some appropriate physical limits. |
2404.16943 | Alexander Florian Jercher | Alexander F. Jercher, Jos\'e Diogo Sim\~ao, Sebastian Steinhaus | Partial absence of cosine problem in 3d Lorentzian spin foams | 5 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the semi-classical limit of the recently proposed coherent spin foam
model for (2+1) Lorentzian quantum gravity. Specifically, we analyze the gluing
equations derived from the stationary phase approximation of the vertex
amplitude. Typically these exhibit two solutions yielding a cosine of the Regge
action. However, by inspection of the algebraic equations as well as their
geometrical realization, we show in this note that the behavior is more
nuanced: when all triangles are either spacelike or timelike, two solutions
exist. In any other case, only a single solution is obtained, thus yielding a
single Regge exponential.
| [
{
"created": "Thu, 25 Apr 2024 18:00:19 GMT",
"version": "v1"
}
] | 2024-04-29 | [
[
"Jercher",
"Alexander F.",
""
],
[
"Simão",
"José Diogo",
""
],
[
"Steinhaus",
"Sebastian",
""
]
] | We study the semi-classical limit of the recently proposed coherent spin foam model for (2+1) Lorentzian quantum gravity. Specifically, we analyze the gluing equations derived from the stationary phase approximation of the vertex amplitude. Typically these exhibit two solutions yielding a cosine of the Regge action. However, by inspection of the algebraic equations as well as their geometrical realization, we show in this note that the behavior is more nuanced: when all triangles are either spacelike or timelike, two solutions exist. In any other case, only a single solution is obtained, thus yielding a single Regge exponential. |
1601.02895 | Salako Ines Godonou SIG | M. G. Ganiou (Benin, IMSP), Ines G. Salako (Benin, IMSP & Ketou U.),
M. J. S. Houndjo (Benin, IMSP & Natitingou U.), J. Tossa (Benin, IMSP) | Geodesic Deviation Equation in $\Lambda$CDM $f(T,\mathcal{T})$ gravity | 20 pages, 2 figures | Int J Theor Phys, Vol. 55, No. 5 (2016) 2303 - 2696 | 10.1007/s10773-016-3025-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geodesic deviation equation has been investigated in the framework of
$f(T,\mathcal{T})$ gravity, where $T$ denotes the torsion and $\mathcal{T}$ is
the trace of the energy-momentum tensor, respectively. The FRW metric is
assumed and the geodesic deviation equation has been established following the
General Relativity approach in the first hand and secondly, by a direct method
using the modified Friedmann equations. Via fundamental observers and null
vector fields with FRW background, we have generalized the Raychaudhuri
equation and the Mattig relation in $f(T,\mathcal{T})$ gravity. Furthermore, we
have numerically solved the geodesic deviation equation for null vector fields
by considering a particular form of $f(T,\mathcal{T})$ which induces
interesting results susceptible to be tested with observational data.
| [
{
"created": "Thu, 31 Dec 2015 11:50:44 GMT",
"version": "v1"
}
] | 2016-05-06 | [
[
"Ganiou",
"M. G.",
"",
"Benin, IMSP"
],
[
"Salako",
"Ines G.",
"",
"Benin, IMSP & Ketou U."
],
[
"Houndjo",
"M. J. S.",
"",
"Benin, IMSP & Natitingou U."
],
[
"Tossa",
"J.",
"",
"Benin, IMSP"
]
] | The geodesic deviation equation has been investigated in the framework of $f(T,\mathcal{T})$ gravity, where $T$ denotes the torsion and $\mathcal{T}$ is the trace of the energy-momentum tensor, respectively. The FRW metric is assumed and the geodesic deviation equation has been established following the General Relativity approach in the first hand and secondly, by a direct method using the modified Friedmann equations. Via fundamental observers and null vector fields with FRW background, we have generalized the Raychaudhuri equation and the Mattig relation in $f(T,\mathcal{T})$ gravity. Furthermore, we have numerically solved the geodesic deviation equation for null vector fields by considering a particular form of $f(T,\mathcal{T})$ which induces interesting results susceptible to be tested with observational data. |
1403.6937 | Gamal G.L. Nashed | G. G. L. Nashed | Regularization of $f(T)$ gravity theories and local Lorentz
transformation | 12 pages | Advances in High Energy Physics, Volume 2015 (2015), Article ID
680457, 8 pages | 10.1155/2015/680457 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We regularized the field equations of $f(T)$ gravity theories such that the
effect of Local Lorentz Transformation (LLT), in the case of spherical
symmetry, is removed. A "general tetrad field", with an arbitrary function of
radial coordinate preserving spherical symmetry is provided. We split that
tetrad field into two matrices; the first represents a LLT, which contains an
arbitrary function, the second matrix represents a proper tetrad field which is
a solution to the field equations of $f(T)$ gravitational theory, (which are
not invariant under LLT). This "general tetrad field" is then applied to the
regularized field equations of $f(T)$. We show that the effect of the arbitrary
function which is involved in the LLT invariably disappears.
| [
{
"created": "Thu, 27 Mar 2014 07:45:20 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jan 2015 07:53:02 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Jul 2015 14:09:33 GMT",
"version": "v3"
}
] | 2015-07-21 | [
[
"Nashed",
"G. G. L.",
""
]
] | We regularized the field equations of $f(T)$ gravity theories such that the effect of Local Lorentz Transformation (LLT), in the case of spherical symmetry, is removed. A "general tetrad field", with an arbitrary function of radial coordinate preserving spherical symmetry is provided. We split that tetrad field into two matrices; the first represents a LLT, which contains an arbitrary function, the second matrix represents a proper tetrad field which is a solution to the field equations of $f(T)$ gravitational theory, (which are not invariant under LLT). This "general tetrad field" is then applied to the regularized field equations of $f(T)$. We show that the effect of the arbitrary function which is involved in the LLT invariably disappears. |
0910.0102 | Balakin Alexander | A.B. Balakin and H. Dehnen | Accelerated expansion of the Universe driven by dynamic self-interaction | 9 pages, no figures, accepted for publication in Phys.Letters B | Phys.Lett.B681:113-117,2009 | 10.1016/j.physletb.2009.10.004 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish a new model, which takes into account a dynamic (inertial)
self-interaction of gravitating systems. The model is formulated by
introduction of a new function depending on the square of the covariant
derivative of the velocity four-vector of the system as a whole into the
Lagrangian. This term is meant for description of both self-action of the
system irregularly moving in the gravitational field, and back-reaction of the
motion irregularities on the gravity field. We discuss one example of exact
solution to the extended master equations in the framework of cosmological
model of the FLRW type with vanishing cosmological constant. It is shown that
accelerated expansion of the Universe can be driven by traditional matter with
positive pressure (e.g., dust, ultrarelativistic fluid) due to the
back-reaction of the gravity field induced by irregular motion of the system as
a whole; this back-reaction is shown to be characterized by the negative
effective pressure.
| [
{
"created": "Thu, 1 Oct 2009 07:55:16 GMT",
"version": "v1"
}
] | 2009-12-17 | [
[
"Balakin",
"A. B.",
""
],
[
"Dehnen",
"H.",
""
]
] | We establish a new model, which takes into account a dynamic (inertial) self-interaction of gravitating systems. The model is formulated by introduction of a new function depending on the square of the covariant derivative of the velocity four-vector of the system as a whole into the Lagrangian. This term is meant for description of both self-action of the system irregularly moving in the gravitational field, and back-reaction of the motion irregularities on the gravity field. We discuss one example of exact solution to the extended master equations in the framework of cosmological model of the FLRW type with vanishing cosmological constant. It is shown that accelerated expansion of the Universe can be driven by traditional matter with positive pressure (e.g., dust, ultrarelativistic fluid) due to the back-reaction of the gravity field induced by irregular motion of the system as a whole; this back-reaction is shown to be characterized by the negative effective pressure. |
1710.10763 | Yu-Hsiang Lin | Yu-Hsiang Lin | Initial Condition of the Inflationary Universe and Its Imprint on the
Cosmic Microwave Background | 129 pages, 32 figures, Ph.D. thesis at National Taiwan University,
June 2017 | null | 10.6342/NTU201701823 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is an apparent power deficit relative to the Lambda-CDM prediction of
the CMB spectrum at large scales, which, though not yet statistically
significant, persists from WMAP to Planck data. We first present a simple toy
model corresponding to a network of frustrated topological defects of domain
walls or cosmic strings that exist previous to the standard slow-roll
inflationary era of the universe. Those features are phenomenologically modeled
by a Chaplygin gas that can interpolate between a network of frustrated
topological defects and a de Sitter-like or a power-law inflationary era. We
show that these scenarios can alleviate the quadrupole anomaly of the CMB
spectrum, based on the approximate initial conditions for the long-wavelength
perturbations. We then go further to show that the large-scale spectrum at the
end of inflation reflects the super-horizon spectrum of the initial state of
the inflaton field. By studying the curvature perturbations of a scalar field
in the FLRW universe parameterized by the equation of state parameter w, we
find that the large-scale spectrum is suppressed if the universe begins with
the adiabatic vacuum in a superinflation (w < -1) or positive-pressure (w > 0)
era. In the latter case, there is however no causal mechanism to establish the
initial adiabatic vacuum. To search for a more realistic initial condition of
the inflationary universe, we consider the Hartle-Hawking no-boundary wave
function, which is a solution to the Wheeler-DeWitt equation, as the initial
condition of the universe. We find that the power suppression can be the
consequence of a massive inflaton, whose initial vacuum is the Euclidean
instanton in a compact manifold. We calculate the primordial power spectrum of
the perturbations and show that, as long as the scalar field is moderately
massive, the power spectrum is suppressed at the long-wavelength scales.
| [
{
"created": "Mon, 30 Oct 2017 03:55:17 GMT",
"version": "v1"
}
] | 2017-10-31 | [
[
"Lin",
"Yu-Hsiang",
""
]
] | There is an apparent power deficit relative to the Lambda-CDM prediction of the CMB spectrum at large scales, which, though not yet statistically significant, persists from WMAP to Planck data. We first present a simple toy model corresponding to a network of frustrated topological defects of domain walls or cosmic strings that exist previous to the standard slow-roll inflationary era of the universe. Those features are phenomenologically modeled by a Chaplygin gas that can interpolate between a network of frustrated topological defects and a de Sitter-like or a power-law inflationary era. We show that these scenarios can alleviate the quadrupole anomaly of the CMB spectrum, based on the approximate initial conditions for the long-wavelength perturbations. We then go further to show that the large-scale spectrum at the end of inflation reflects the super-horizon spectrum of the initial state of the inflaton field. By studying the curvature perturbations of a scalar field in the FLRW universe parameterized by the equation of state parameter w, we find that the large-scale spectrum is suppressed if the universe begins with the adiabatic vacuum in a superinflation (w < -1) or positive-pressure (w > 0) era. In the latter case, there is however no causal mechanism to establish the initial adiabatic vacuum. To search for a more realistic initial condition of the inflationary universe, we consider the Hartle-Hawking no-boundary wave function, which is a solution to the Wheeler-DeWitt equation, as the initial condition of the universe. We find that the power suppression can be the consequence of a massive inflaton, whose initial vacuum is the Euclidean instanton in a compact manifold. We calculate the primordial power spectrum of the perturbations and show that, as long as the scalar field is moderately massive, the power spectrum is suppressed at the long-wavelength scales. |
gr-qc/9604006 | Julio Cesar Fabris | Julio C. Fabris and Joel Tossa | Scalar Perturbations and Conformal Transformation | Latex, 14 pages | Grav.Cosmol. 3 (1997) 165-171 | null | IC/95/379 | gr-qc | null | The non-minimal coupling of gravity to a scalar field can be transformed into
a minimal coupling through a conformal transformation. We show how to connect
the results of a perturbation calculation, performed around a
Friedmann-Robertson-Walker background solution, before and after the conformal
transformation. We work in the synchronous gauge, but we discuss the
implications of employing other formalisms.
| [
{
"created": "Tue, 2 Apr 1996 17:03:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fabris",
"Julio C.",
""
],
[
"Tossa",
"Joel",
""
]
] | The non-minimal coupling of gravity to a scalar field can be transformed into a minimal coupling through a conformal transformation. We show how to connect the results of a perturbation calculation, performed around a Friedmann-Robertson-Walker background solution, before and after the conformal transformation. We work in the synchronous gauge, but we discuss the implications of employing other formalisms. |
2009.04572 | Mario Neves Junior | M. J. Neves, Everton M. C. Abreu, Jorge B. de Oliveira and Marcelo
Kesseles Gon\c{c}alves | Thermostatistical analysis for short-range interaction Potentials | 25 pages, 14 figures | International Journal of Geometric Methods in Modern Physics, vol
17, 2020 | 10.1142/S0219887820501935 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the thermodynamics of short-range central potentials,
namely, the Lee-Wick potential, and the Plasma potential. In the first part of
the paper we obtain the numerical solution for the orbits equation for these
potentials. Posteriorly, we introduce the thermodynamics through the
microcanonical and canonical ensembles formalism defined on the phase space of
the system. We calculate the density of states associated with the Lee-Wick and
the Plasma potentials. From density of states, we obtain the thermodynamical
physical quantities like entropy and temperature as functions of the energy. We
also use the Boltzmann-Gibbs formalism to obtain the partition functions, the
mean energy and the thermal capacity for these short-range potentials.
| [
{
"created": "Wed, 9 Sep 2020 21:03:53 GMT",
"version": "v1"
}
] | 2020-09-11 | [
[
"Neves",
"M. J.",
""
],
[
"Abreu",
"Everton M. C.",
""
],
[
"de Oliveira",
"Jorge B.",
""
],
[
"Gonçalves",
"Marcelo Kesseles",
""
]
] | In this paper, we study the thermodynamics of short-range central potentials, namely, the Lee-Wick potential, and the Plasma potential. In the first part of the paper we obtain the numerical solution for the orbits equation for these potentials. Posteriorly, we introduce the thermodynamics through the microcanonical and canonical ensembles formalism defined on the phase space of the system. We calculate the density of states associated with the Lee-Wick and the Plasma potentials. From density of states, we obtain the thermodynamical physical quantities like entropy and temperature as functions of the energy. We also use the Boltzmann-Gibbs formalism to obtain the partition functions, the mean energy and the thermal capacity for these short-range potentials. |
1309.4553 | Timoshkin Alexandr V | V.V. Obukhov, A.V. Timoshkin and E.V Savushkin | Rip Cosmology via Inhomogeneous Fluid | 107-113 | null | 10.3390/galaxies1020107 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The conditions for the appearance of the Little Rip, Pseudo Rip and Quasi Rip
universes in the terms of the parameters in the equation of state of some dark
fluid are investigated. Several examples of the Rip cosmologies are
investigated.
| [
{
"created": "Wed, 18 Sep 2013 07:14:32 GMT",
"version": "v1"
}
] | 2013-09-19 | [
[
"Obukhov",
"V. V.",
""
],
[
"Timoshkin",
"A. V.",
""
],
[
"Savushkin",
"E. V",
""
]
] | The conditions for the appearance of the Little Rip, Pseudo Rip and Quasi Rip universes in the terms of the parameters in the equation of state of some dark fluid are investigated. Several examples of the Rip cosmologies are investigated. |
2105.07728 | Abhik Kumar Sanyal Dr. | Marcelo Byrro Ribeiro and Abhik Kumar Sanyal | Bianchi VI0 viscous fluid cosmology with magnetic field | 7 pages, 0 figures | Journal of Mathematical Physics 28, 657 (1987) | 10.1063/1.527599 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A spatially homogeneous Bianchi type VI0 model containing a viscous fluid in
the presence of an axial magnetic field has been studied. A barotropic equation
of state together with a pair of linear relations among the square root of
matter density, shear scalar, and expansion scalar have been assumed. Solutions
are obtained in the presence of a magnetic field, only in two special cases,
which are comparatively simpler. The complete solutions for this model in the
absence of a magnetic field are also obtained. The presence of a magnetic field
in the former case however, does not in effect cause any major modification in
the fundamental nature of the initial singularity of the expanding model.
| [
{
"created": "Mon, 17 May 2021 10:54:48 GMT",
"version": "v1"
}
] | 2021-05-18 | [
[
"Ribeiro",
"Marcelo Byrro",
""
],
[
"Sanyal",
"Abhik Kumar",
""
]
] | A spatially homogeneous Bianchi type VI0 model containing a viscous fluid in the presence of an axial magnetic field has been studied. A barotropic equation of state together with a pair of linear relations among the square root of matter density, shear scalar, and expansion scalar have been assumed. Solutions are obtained in the presence of a magnetic field, only in two special cases, which are comparatively simpler. The complete solutions for this model in the absence of a magnetic field are also obtained. The presence of a magnetic field in the former case however, does not in effect cause any major modification in the fundamental nature of the initial singularity of the expanding model. |
gr-qc/0512011 | Valentin Gladush | Valentin D. Gladush | A vacuum-like configuration in General Relativity as a manifestation of
a Lorentz-invariant mode of five-dimensional gravity | 24 pages, revtex | Int.J.Mod.Phys.D16:711-736,2007 | 10.1142/S0218271807009851 | null | gr-qc | null | A Lorentz-invariant cosmological model is constructed within the framework of
five-dimensional gravity. The five-dimensional theorem which is analogical to
the generalized Birkhoff theorem is proved, that corresponds to the Kaluza's
``cylinder condition''. The five-dimensional vacuum Einstein equations have an
integral of motion corresponding to this symmetry, the integral of motion is
similar to the mass function in general relativity (GR). Space closure with
respect to the extra dimensionality follows from the requirement of the absence
of a conical singularity. Thus, the Kaluza-Klein (KK) model is realized
dynamically as a Lorentz-invariant mode of five-dimensional general relativity.
After the dimensional reduction and conformal mapping the model is reduced to
the GR configuration. It contains a scalar field with a vanishing conformally
invariant energy-momentum tensor on the flat space-time background. This zero
mode can be interpreted as a vacuum configuration in GR. As a result the
vacuum-like configuration in GR can be considered as a manifestation of the
Lorentz-invariant empty five-dimensional space.
| [
{
"created": "Thu, 1 Dec 2005 12:41:52 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Gladush",
"Valentin D.",
""
]
] | A Lorentz-invariant cosmological model is constructed within the framework of five-dimensional gravity. The five-dimensional theorem which is analogical to the generalized Birkhoff theorem is proved, that corresponds to the Kaluza's ``cylinder condition''. The five-dimensional vacuum Einstein equations have an integral of motion corresponding to this symmetry, the integral of motion is similar to the mass function in general relativity (GR). Space closure with respect to the extra dimensionality follows from the requirement of the absence of a conical singularity. Thus, the Kaluza-Klein (KK) model is realized dynamically as a Lorentz-invariant mode of five-dimensional general relativity. After the dimensional reduction and conformal mapping the model is reduced to the GR configuration. It contains a scalar field with a vanishing conformally invariant energy-momentum tensor on the flat space-time background. This zero mode can be interpreted as a vacuum configuration in GR. As a result the vacuum-like configuration in GR can be considered as a manifestation of the Lorentz-invariant empty five-dimensional space. |
1711.10475 | Kazuharu Bamba | Kazuharu Bamba, Davood Momeni and Mudhahir Al Ajmi | Phase Space description of Nonlocal Teleparallel Gravity | 14 pages, 3 figures, title changed, version accepted for publication
in European Physical Journal C | Eur.Phys.J. C78 (2018) no.9, 771 | 10.1140/epjc/s10052-018-6240-z | FU-PCG-23 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological solutions in nonlocal teleparallel gravity or $f(T)$
theory, where $T$ is the torsion scalar in teleparallel gravity. This is a
natural extenstion of the usual teleparallel gravity with nonlocal terms. In
this work the phase space portrait proposed to describe the dynamics of an
arbitrary flat, homogeneous cosmological background with a number of matter
contents, both in early and late time epochs. The aim was to convert the system
of the equations of the motion to a first order autonomous dynamical system and
to find fixed points and attractors using numerical codes. For this purpose,
firstly we derive effective forms of cosmological field equations describing
the whole cosmic evolution history in a homogeneous and isotropic cosmological
background and construct the autonomous system of the first order dynamical
equations. In addition, we investigate the local stability in the dynamical
systems called "the stable/unstable manifold" by introducing a specific form of
the interaction between matter, dark energy, radiation and a scalar field.
Furthermore, we explore the exact solutions of the cosmological equations in
the case of de Sitter spacetime. In particular, we examine the role of an
auxiliary function called "gauge" $\eta$ in the formation of such cosmological
solutions and show whether the de Sitter solutions can exist or not. Moreover,
we study the stability issue of the de Sitter solutions both in vacuum and
non-vacuum spacetimes. It is demonstrated that for nonlocal $f(T)$ gravity, the
stable de Sitter solutions can be produced even in vacuum spacetime.
| [
{
"created": "Mon, 27 Nov 2017 13:27:43 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Sep 2018 06:45:30 GMT",
"version": "v2"
}
] | 2018-10-09 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Momeni",
"Davood",
""
],
[
"Ajmi",
"Mudhahir Al",
""
]
] | We study cosmological solutions in nonlocal teleparallel gravity or $f(T)$ theory, where $T$ is the torsion scalar in teleparallel gravity. This is a natural extenstion of the usual teleparallel gravity with nonlocal terms. In this work the phase space portrait proposed to describe the dynamics of an arbitrary flat, homogeneous cosmological background with a number of matter contents, both in early and late time epochs. The aim was to convert the system of the equations of the motion to a first order autonomous dynamical system and to find fixed points and attractors using numerical codes. For this purpose, firstly we derive effective forms of cosmological field equations describing the whole cosmic evolution history in a homogeneous and isotropic cosmological background and construct the autonomous system of the first order dynamical equations. In addition, we investigate the local stability in the dynamical systems called "the stable/unstable manifold" by introducing a specific form of the interaction between matter, dark energy, radiation and a scalar field. Furthermore, we explore the exact solutions of the cosmological equations in the case of de Sitter spacetime. In particular, we examine the role of an auxiliary function called "gauge" $\eta$ in the formation of such cosmological solutions and show whether the de Sitter solutions can exist or not. Moreover, we study the stability issue of the de Sitter solutions both in vacuum and non-vacuum spacetimes. It is demonstrated that for nonlocal $f(T)$ gravity, the stable de Sitter solutions can be produced even in vacuum spacetime. |
gr-qc/0502016 | Claus Kiefer | Claus Kiefer | Quantum Cosmology and the Arrow of Time | 10 pages, contribution to the Proceedings of the conference DICE2004,
Piombino, Italy, September 2004 | Braz.J.Phys. 35 (2005) 296-299 | null | null | gr-qc | null | Although most fundamental laws are invariant under time reversal, experience
exhibits the presence of irreversible phenomena -- the arrows of time. Their
origin lies in cosmology, and I argue that only quantum cosmology can provide
the appropriate formal framework. After briefly reviewing the formalism, I
discuss how a simple and natural boundary condition can lead to the observed
arrows of time. This yields at the same time interesting consequences for black
holes.
| [
{
"created": "Thu, 3 Feb 2005 16:37:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kiefer",
"Claus",
""
]
] | Although most fundamental laws are invariant under time reversal, experience exhibits the presence of irreversible phenomena -- the arrows of time. Their origin lies in cosmology, and I argue that only quantum cosmology can provide the appropriate formal framework. After briefly reviewing the formalism, I discuss how a simple and natural boundary condition can lead to the observed arrows of time. This yields at the same time interesting consequences for black holes. |
1612.04823 | Shahar Hod | Shahar Hod | No-scalar-hair theorem for spherically symmetric reflecting stars | 6 pages | Physical Review D 94, 104073 (2016) | 10.1103/PhysRevD.94.104073 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is proved that spherically symmetric compact reflecting objects cannot
support static bound-state configurations made of scalar fields whose
self-interaction potential $V(\psi^2)$ is a monotonically increasing function
of its argument. Our theorem rules out, in particular, the existence of massive
scalar hair outside the surface of a spherically symmetric compact reflecting
star.
| [
{
"created": "Wed, 14 Dec 2016 21:00:03 GMT",
"version": "v1"
}
] | 2017-04-27 | [
[
"Hod",
"Shahar",
""
]
] | It is proved that spherically symmetric compact reflecting objects cannot support static bound-state configurations made of scalar fields whose self-interaction potential $V(\psi^2)$ is a monotonically increasing function of its argument. Our theorem rules out, in particular, the existence of massive scalar hair outside the surface of a spherically symmetric compact reflecting star. |
1506.06478 | Nami Uchikata | Nami Uchikata and Shijun Yoshida | Slowly rotating regular black holes with a charged thin shell | 21 pages, 20 figures | Physical Review D 90, 064042 (2014) | 10.1103/PhysRevD.90.064042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain rotating solutions of regular black holes which are constructed of
de Sitter spacetime with the axisymmetric stationary perturbation within the
timelike charged thin shell and the Kerr-Newman geometry with sufficiently
small rotation outside the shell. To treat the slowly rotating thin shell, we
employ the method developed by de la Cruz and Israel. The thin shell is assumed
to be composed of a dust in the zero-rotation limit and located inside the
inner horizon of the black hole solution. We expand the perturbation in powers
of the rotation parameter of the Kerr-Newman metric up to the second order. It
is found that with the present treatment, the stress tensor of the thin shell
in general has anisotropic pressure, i.e., the thin shell cannot be composed of
a dust if the rotational effects are taken into account. However, the thin
shell can be composed of a perfect fluid with isotropic pressure if the degrees
of freedom appearing in the physically acceptable matching of the two distinct
spacetimes are suitably used. We numerically investigate the rotational effects
on the spherically symmetric charged regular black hole obtained by Uchikata,
Yoshida and Futamase in detail.
| [
{
"created": "Mon, 22 Jun 2015 06:13:56 GMT",
"version": "v1"
}
] | 2015-07-01 | [
[
"Uchikata",
"Nami",
""
],
[
"Yoshida",
"Shijun",
""
]
] | We obtain rotating solutions of regular black holes which are constructed of de Sitter spacetime with the axisymmetric stationary perturbation within the timelike charged thin shell and the Kerr-Newman geometry with sufficiently small rotation outside the shell. To treat the slowly rotating thin shell, we employ the method developed by de la Cruz and Israel. The thin shell is assumed to be composed of a dust in the zero-rotation limit and located inside the inner horizon of the black hole solution. We expand the perturbation in powers of the rotation parameter of the Kerr-Newman metric up to the second order. It is found that with the present treatment, the stress tensor of the thin shell in general has anisotropic pressure, i.e., the thin shell cannot be composed of a dust if the rotational effects are taken into account. However, the thin shell can be composed of a perfect fluid with isotropic pressure if the degrees of freedom appearing in the physically acceptable matching of the two distinct spacetimes are suitably used. We numerically investigate the rotational effects on the spherically symmetric charged regular black hole obtained by Uchikata, Yoshida and Futamase in detail. |
1004.0513 | Gregory J. Galloway | Piotr T. Chru\'sciel, Gregory J. Galloway | Uniqueness of static black-holes without analyticity | 6 pages, 1 figure | Class.Quant.Grav.27:152001,2010 | 10.1088/0264-9381/27/15/152001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the hypothesis of analyticity in the uniqueness theory of
vacuum, or electrovacuum, static black holes is not needed. More generally, we
show that prehorizons covering a closed set cannot occur in well-behaved
domains of outer communications.
| [
{
"created": "Sun, 4 Apr 2010 15:27:46 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Galloway",
"Gregory J.",
""
]
] | We show that the hypothesis of analyticity in the uniqueness theory of vacuum, or electrovacuum, static black holes is not needed. More generally, we show that prehorizons covering a closed set cannot occur in well-behaved domains of outer communications. |
1703.00543 | Qingdi Wang | Qingdi Wang, Zhen Zhu, William G. Unruh | How the huge energy of quantum vacuum gravitates to drive the slow
accelerating expansion of the Universe | 35 pages, 8 figures, PRD Editors' Suggestion | Phys. Rev. D 95, 103504 (2017) | 10.1103/PhysRevD.95.103504 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gravitational property of the quantum vacuum by treating
its large energy density predicted by quantum field theory seriously and
assuming that it does gravitate to obey the equivalence principle of general
relativity. We find that the quantum vacuum would gravitate differently from
what people previously thought. The consequence of this difference is an
accelerating universe with a small Hubble expansion rate $H\propto \Lambda
e^{-\beta\sqrt{G}\Lambda}\to 0$ instead of the previous prediction
$H=\sqrt{8\pi G\rho^{vac}/3}\propto\sqrt{G}\Lambda^2\to\infty$ which was
unbounded, as the high energy cutoff $\Lambda$ is taken to infinity. In this
sense, at least the "old" cosmological constant problem would be resolved.
Moreover, it gives the observed slow rate of the accelerating expansion as
$\Lambda$ is taken to be some large value of the order of Planck energy or
higher. This result suggests that there is no necessity to introduce the
cosmological constant, which is required to be fine tuned to an accuracy of
$10^{-120}$, or other forms of dark energy, which are required to have peculiar
negative pressure, to explain the observed accelerating expansion of the
Universe.
| [
{
"created": "Wed, 1 Mar 2017 23:09:20 GMT",
"version": "v1"
},
{
"created": "Thu, 11 May 2017 21:12:33 GMT",
"version": "v2"
}
] | 2019-04-22 | [
[
"Wang",
"Qingdi",
""
],
[
"Zhu",
"Zhen",
""
],
[
"Unruh",
"William G.",
""
]
] | We investigate the gravitational property of the quantum vacuum by treating its large energy density predicted by quantum field theory seriously and assuming that it does gravitate to obey the equivalence principle of general relativity. We find that the quantum vacuum would gravitate differently from what people previously thought. The consequence of this difference is an accelerating universe with a small Hubble expansion rate $H\propto \Lambda e^{-\beta\sqrt{G}\Lambda}\to 0$ instead of the previous prediction $H=\sqrt{8\pi G\rho^{vac}/3}\propto\sqrt{G}\Lambda^2\to\infty$ which was unbounded, as the high energy cutoff $\Lambda$ is taken to infinity. In this sense, at least the "old" cosmological constant problem would be resolved. Moreover, it gives the observed slow rate of the accelerating expansion as $\Lambda$ is taken to be some large value of the order of Planck energy or higher. This result suggests that there is no necessity to introduce the cosmological constant, which is required to be fine tuned to an accuracy of $10^{-120}$, or other forms of dark energy, which are required to have peculiar negative pressure, to explain the observed accelerating expansion of the Universe. |
gr-qc/0604111 | Amr Sid-Ahmed M. | Nabil L. Youssef and Amr M. Sid-Ahmed | Linear Connections and Curvature Tensors in the Geometry of
Parallelizable Manifolds | 16 pages LaTeX file, Changed title, Changed content, Added
references, Physical features stressed | Rept.Math.Phys.60:39-53,2007 | 10.1016/S0034-4877(07)00020-1 | null | gr-qc math.DG | null | In this paper we discuss curvature tensors in the context of Absolute
Parallelism geometry. Different curvature tensors are expressed in a compact
form in terms of the torsion tensor of the canonical connection. Using the
Bianchi identities some other identities are derived from the expressions
obtained. These identities, in turn, are used to reveal some of the properties
satisfied by an intriguing fourth order tensor which we refer to as Wanas
tensor. A further condition on the canonical connection is imposed, assuming it
is semi-symmetric. The formulae thus obtained, together with other formulae
(Ricci tensors and scalar curvatures of the different connections admitted by
the space) are calculated under this additional assumption. Considering a
specific form of the semi-symmetric connection causes all nonvanishing
curvature tensors to coincide, up to a constant, with the Wanas tensor.
Physical aspects of some of the geometric objects considered are mentioned.
| [
{
"created": "Wed, 26 Apr 2006 12:44:02 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2007 18:23:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Youssef",
"Nabil L.",
""
],
[
"Sid-Ahmed",
"Amr M.",
""
]
] | In this paper we discuss curvature tensors in the context of Absolute Parallelism geometry. Different curvature tensors are expressed in a compact form in terms of the torsion tensor of the canonical connection. Using the Bianchi identities some other identities are derived from the expressions obtained. These identities, in turn, are used to reveal some of the properties satisfied by an intriguing fourth order tensor which we refer to as Wanas tensor. A further condition on the canonical connection is imposed, assuming it is semi-symmetric. The formulae thus obtained, together with other formulae (Ricci tensors and scalar curvatures of the different connections admitted by the space) are calculated under this additional assumption. Considering a specific form of the semi-symmetric connection causes all nonvanishing curvature tensors to coincide, up to a constant, with the Wanas tensor. Physical aspects of some of the geometric objects considered are mentioned. |
gr-qc/0403040 | Sigbjorn Hervik | Sigbjorn Hervik | The Asymptotic Behaviour of Tilted Bianchi type VI$_0$ Universes | 22 pages, 4 figures, to appear in CQG | Class.Quant.Grav. 21 (2004) 2301-2317 | 10.1088/0264-9381/21/9/007 | DAMTP-2004-28 | gr-qc astro-ph | null | We study the asymptotic behaviour of the Bianchi type VI$_0$ universes with a
tilted $\gamma$-law perfect fluid. The late-time attractors are found for the
full 7-dimensional state space and for several interesting invariant subspaces.
In particular, it is found that for the particular value of the equation of
state parameter, $\gamma=6/5$, there exists a bifurcation line which signals a
transition of stability between a non-tilted equilibrium point to an extremely
tilted equilibrium point. The initial singular regime is also discussed and we
argue that the initial behaviour is chaotic for $\gamma<2$.
| [
{
"created": "Tue, 9 Mar 2004 18:53:49 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Hervik",
"Sigbjorn",
""
]
] | We study the asymptotic behaviour of the Bianchi type VI$_0$ universes with a tilted $\gamma$-law perfect fluid. The late-time attractors are found for the full 7-dimensional state space and for several interesting invariant subspaces. In particular, it is found that for the particular value of the equation of state parameter, $\gamma=6/5$, there exists a bifurcation line which signals a transition of stability between a non-tilted equilibrium point to an extremely tilted equilibrium point. The initial singular regime is also discussed and we argue that the initial behaviour is chaotic for $\gamma<2$. |
1212.2197 | Mengjie Wang | Mengjie Wang, Marco O. P. Sampaio, Carlos Herdeiro | Hawking radiation for a Proca field in D dimensions II: charged field in
a brane charged black hole | 11 pages, 4 figures, matched to published version | Phys. Rev. D 87, 044011 (2013) | 10.1103/PhysRevD.87.044011 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalise our first analysis of the wave equation for a massive vector
boson in the background of a D-dimensional Schwarzschild black hole, by adding
charge both to the field and the black hole, on the 3+1 dimensional Standard
Model brane. A detailed numerical study is performed to obtain the transmission
factor for the coupled (as well as decoupled) system of equations describing
the Proca field modes, varying the angular momentum number, mass, charge and
space-time dimensions. A qualitatively new feature arising from the
introduction of charge is the appearance of superradiant modes, which we
investigate. We then compute the Hawking fluxes, and analyse the effect of the
charge. In particular we observe an inverted charge splitting effect for small
energies and for two or more extra dimensions. For neutral fields, we compare
the emission of massive particles with spins up to one and also compare the
Proca bulk-to-brane ratio of energy emission, showing that, as for a scalar
field, most of the energy is emitted on the brane.
| [
{
"created": "Mon, 10 Dec 2012 20:48:34 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Feb 2013 20:33:50 GMT",
"version": "v2"
}
] | 2013-02-27 | [
[
"Wang",
"Mengjie",
""
],
[
"Sampaio",
"Marco O. P.",
""
],
[
"Herdeiro",
"Carlos",
""
]
] | We generalise our first analysis of the wave equation for a massive vector boson in the background of a D-dimensional Schwarzschild black hole, by adding charge both to the field and the black hole, on the 3+1 dimensional Standard Model brane. A detailed numerical study is performed to obtain the transmission factor for the coupled (as well as decoupled) system of equations describing the Proca field modes, varying the angular momentum number, mass, charge and space-time dimensions. A qualitatively new feature arising from the introduction of charge is the appearance of superradiant modes, which we investigate. We then compute the Hawking fluxes, and analyse the effect of the charge. In particular we observe an inverted charge splitting effect for small energies and for two or more extra dimensions. For neutral fields, we compare the emission of massive particles with spins up to one and also compare the Proca bulk-to-brane ratio of energy emission, showing that, as for a scalar field, most of the energy is emitted on the brane. |
1411.4716 | Jonathan Holland | Jonathan Holland and George Sparling | Cosmology: macro and micro | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new approach to cosmology and space-time is developed, which emphasizes the
description of the matter degrees of freedom of Einstein's theory of gravity by
a family of K\"ahler-Einstein Fano manifolds.
| [
{
"created": "Tue, 18 Nov 2014 01:59:07 GMT",
"version": "v1"
}
] | 2014-11-19 | [
[
"Holland",
"Jonathan",
""
],
[
"Sparling",
"George",
""
]
] | A new approach to cosmology and space-time is developed, which emphasizes the description of the matter degrees of freedom of Einstein's theory of gravity by a family of K\"ahler-Einstein Fano manifolds. |
gr-qc/0107011 | Tiberiu Harko | M. K. Mak, Peter N. Dobson Jr., T. Harko | Maximum Mass-Radius Ratios for Charged Compact General Relativistic
Objects | 6 pages, 2 figures, RevTex. To appear in Europhys. Lett | Europhys.Lett. 55 (2001) 310-316 | 10.1209/epl/i2001-00416-x | null | gr-qc | null | Upper limits for the mass-radius ratio and total charge are derived for
stable charged general relativistic matter distributions. For charged compact
objects the mass-radius ratio exceeds the value 4/9 corresponding to neutral
stars. General restrictions for the redshift and total energy (including the
gravitational contribution) are also obtained.
| [
{
"created": "Wed, 4 Jul 2001 03:07:55 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Mak",
"M. K.",
""
],
[
"Dobson",
"Peter N.",
"Jr."
],
[
"Harko",
"T.",
""
]
] | Upper limits for the mass-radius ratio and total charge are derived for stable charged general relativistic matter distributions. For charged compact objects the mass-radius ratio exceeds the value 4/9 corresponding to neutral stars. General restrictions for the redshift and total energy (including the gravitational contribution) are also obtained. |
0911.2622 | Luca Fabbri | Luca Fabbri | Causal propagation for ELKO fields | 7 pages | Mod.Phys.Lett.A25:151-157,2010; Erratum-ibid A25:1295,2010;
Mod.Phys.Lett.A25:1295,2010 | 10.1142/S0217732310032408 10.1142/S0217732310033463 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We shall consider the general problem of causal propagation for spinor
fields, focus attention in particular on the case constituted by ELKO fields
and will show that the problem of causal propagation for ELKO fields is always
solvable.
| [
{
"created": "Fri, 13 Nov 2009 14:44:45 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jan 2010 13:41:05 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Aug 2010 09:19:51 GMT",
"version": "v3"
},
{
"created": "Fri, 10 Sep 2010 07:25:18 GMT",
"version": "v4"
},
{
"created": "Wed, 15 Jun 2011 14:35:52 GMT",
"version": "v5"
}
] | 2011-06-16 | [
[
"Fabbri",
"Luca",
""
]
] | We shall consider the general problem of causal propagation for spinor fields, focus attention in particular on the case constituted by ELKO fields and will show that the problem of causal propagation for ELKO fields is always solvable. |
gr-qc/0511053 | Zufar Murzakhanov | A.B. Balakin, Z.G. Murzakhanov (Kazan State U.), G.V. Kisun'ko
(Moscow, Creative Problems Dept.) | Radio Wave 'Messengers' of Periodic Gravitational Radiation and the
Problem of Gravitationally Induced Nonlinearity in Electrodynamic Systems | 5 pages, no figures | Phys.Dokl. 41 (1996) 331-333; Dokl.Akad.Nauk Ser.Fiz. 349 (1996)
326-328 | null | null | gr-qc | null | We discuss a gravitationally induced nonlinearity in hierarchic systems. We
consider the generation of extremely low-frequency radio waves with a frequency
of the periodic gravitational radiation; the generation is due to an induced
nonlinear self-action of electromagnetic radiation in the vicinity of the
gravitational-radiation source. These radio waves are a fundamentally new type
of response of an electrodynamic system to gravitational radiation. That is why
we here use an unconventional term: radio-wave messengers of periodic
gravitational radiation.
| [
{
"created": "Thu, 10 Nov 2005 10:52:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Balakin",
"A. B.",
"",
"Kazan State U."
],
[
"Murzakhanov",
"Z. G.",
"",
"Kazan State U."
],
[
"Kisun'ko",
"G. V.",
"",
"Moscow, Creative Problems Dept."
]
] | We discuss a gravitationally induced nonlinearity in hierarchic systems. We consider the generation of extremely low-frequency radio waves with a frequency of the periodic gravitational radiation; the generation is due to an induced nonlinear self-action of electromagnetic radiation in the vicinity of the gravitational-radiation source. These radio waves are a fundamentally new type of response of an electrodynamic system to gravitational radiation. That is why we here use an unconventional term: radio-wave messengers of periodic gravitational radiation. |
1311.1030 | Otari Sakhelashvili | Otari Sakhelashvili | 6D Standing Wave Braneworld with Ghost Scalar Fields | null | International Journal of Theoretical Physics: Volume 53, Issue 6
(2014), Page 1940-1946 | 10.1007/s10773-014-1999-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 6D braneworld with the phantom-like bulk scalar field is considered. We
demonstrate pure gravitational localization of scalar field zero modes on the
brane.
| [
{
"created": "Tue, 5 Nov 2013 12:28:00 GMT",
"version": "v1"
}
] | 2014-05-13 | [
[
"Sakhelashvili",
"Otari",
""
]
] | The 6D braneworld with the phantom-like bulk scalar field is considered. We demonstrate pure gravitational localization of scalar field zero modes on the brane. |
1801.05920 | Jieci Wang | Tonghua Liu, Jieci Wang, Jiliang Jing, Heng Fan | The influence of Unruh effect on quantum steering for accelerated
two-level detectors with different measurements | 18 pages, 3 figures | Annals of Physics 390, 334-344 (2018) | 10.1016/j.aop.2018.01.019 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of steering between two correlated Unruh-Dewitt
detectors when one of them locally interacts with external scalar field via
different quantifiers. We find that the quantum steering, either measured by
the entropic steering inequality or the Cavalcanti-Jones-Wiseman-Reid
inequality, is fragile under the influence of Unruh thermal noise. The quantum
steering is found always asymmetric and the asymmetry is extremely sensitive to
the initial state parameter. In addition, the steering-type quantum
correlations experience "sudden death" for some accelerations, which are quite
different from the behaviors of other quantum correlations in the same system.
It is worth noting that the domination value of the tight quantum steering
exists a transformation point with increasing acceleration. We also find that
the robustness of quantum steerability under the Unruh thermal noise can be
realized by choosing the smallest energy gap in the detectors.
| [
{
"created": "Thu, 18 Jan 2018 03:08:21 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Liu",
"Tonghua",
""
],
[
"Wang",
"Jieci",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Fan",
"Heng",
""
]
] | We study the dynamics of steering between two correlated Unruh-Dewitt detectors when one of them locally interacts with external scalar field via different quantifiers. We find that the quantum steering, either measured by the entropic steering inequality or the Cavalcanti-Jones-Wiseman-Reid inequality, is fragile under the influence of Unruh thermal noise. The quantum steering is found always asymmetric and the asymmetry is extremely sensitive to the initial state parameter. In addition, the steering-type quantum correlations experience "sudden death" for some accelerations, which are quite different from the behaviors of other quantum correlations in the same system. It is worth noting that the domination value of the tight quantum steering exists a transformation point with increasing acceleration. We also find that the robustness of quantum steerability under the Unruh thermal noise can be realized by choosing the smallest energy gap in the detectors. |
1808.08638 | James Bardeen | James M. Bardeen | Interpreting the semi-classical stress-energy tensor in a Schwarzschild
background, implications for the information paradox | 27 pages, 5 figures. There is considerable overlap with
arXiv:1706.09204, but the analysis is based on more accurate data, and there
are substantial additions and deletions | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical results for the semi-classical stress-energy tensor outside the
horizon of a Schwarzschild black hole obtained in the 1980's and 1990's are re-
examined in order to better understand the origin of Hawking radiation and the
implications for the black hole information paradox. Polynomial fits to the
numerical results for the 4D transverse stress are obtained for
conformally-coupled spin 0 and spin 1 fields in the Hartle-Hawking and Unruh
states and. Analysis of the spin 0 Unruh state results clearly shows that the
origin of the Hawking radiation is not pair creation or tunneling very close to
the black hole horizon, but rather is a nonlocal process extending beyond r =
3M . Arguments are presented that the black hole information paradox cannot
plausibly be addressed by processes occurring on or very close to the horizon
of a large black hole whose geometry is close to Schwarzschild.
| [
{
"created": "Sun, 26 Aug 2018 22:55:38 GMT",
"version": "v1"
}
] | 2018-08-28 | [
[
"Bardeen",
"James M.",
""
]
] | Numerical results for the semi-classical stress-energy tensor outside the horizon of a Schwarzschild black hole obtained in the 1980's and 1990's are re- examined in order to better understand the origin of Hawking radiation and the implications for the black hole information paradox. Polynomial fits to the numerical results for the 4D transverse stress are obtained for conformally-coupled spin 0 and spin 1 fields in the Hartle-Hawking and Unruh states and. Analysis of the spin 0 Unruh state results clearly shows that the origin of the Hawking radiation is not pair creation or tunneling very close to the black hole horizon, but rather is a nonlocal process extending beyond r = 3M . Arguments are presented that the black hole information paradox cannot plausibly be addressed by processes occurring on or very close to the horizon of a large black hole whose geometry is close to Schwarzschild. |
1705.06621 | Siyuan Ma | Siyuan Ma | Uniform energy bound and Morawetz estimate for extreme components of
spin fields in the exterior of a slowly rotating Kerr black hole I: Maxwell
field | published version | Annales Henri Poincar\'e volume 21, 2020 | 10.1007/s00023-020-00884-7 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This first part of the series treats the Maxwell equations in the exterior of
a slowly rotating Kerr black hole. By performing a first-order differential
operator on each extreme Newman-Penrose (N-P) scalar in a Kinnersley tetrad,
the resulting equation and the Teukolsky master equation for the extreme N-P
component are both in the form of an inhomogeneous
\textquotedblleft{spin-weighted Fackerell-Ipser equation\textquotedblright}
(SWFIE) and constitute a weakly coupled system. We first prove energy estimate
and integrated local energy decay (Morawetz) estimate for this type of
inhomogeneous SWFIE following the method in (Dafermos and Rodnianski in Decay
for solutions of the wave equation on Kerr exterior spacetimes I-II: the cases
$|a|\ll M$ or axisymmetry, 2010, arXiv:1010.5132), and then utilize these
estimates to achieve both a uniform bound of a positive definite energy and a
Morawetz estimate for the coupled system of each extreme N-P component. The
same type of estimates for the regular extreme N-P components defined in the
regular Hawking-Hartle tetrad is also proved. The hierarchy here is generalized
in our second part (Ma in Uniform energy bound and Morawetz estimates for
extreme components of spin fields in the exterior of a slowly rotating Kerr
black hole II: linearized gravity, 2017, arXiv:1708.07385) of this series to
treat the extreme components of linearized gravity.
| [
{
"created": "Thu, 18 May 2017 14:38:49 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Aug 2017 12:53:21 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Jan 2018 20:14:02 GMT",
"version": "v3"
},
{
"created": "Thu, 27 Aug 2020 14:28:20 GMT",
"version": "v4"
}
] | 2020-08-28 | [
[
"Ma",
"Siyuan",
""
]
] | This first part of the series treats the Maxwell equations in the exterior of a slowly rotating Kerr black hole. By performing a first-order differential operator on each extreme Newman-Penrose (N-P) scalar in a Kinnersley tetrad, the resulting equation and the Teukolsky master equation for the extreme N-P component are both in the form of an inhomogeneous \textquotedblleft{spin-weighted Fackerell-Ipser equation\textquotedblright} (SWFIE) and constitute a weakly coupled system. We first prove energy estimate and integrated local energy decay (Morawetz) estimate for this type of inhomogeneous SWFIE following the method in (Dafermos and Rodnianski in Decay for solutions of the wave equation on Kerr exterior spacetimes I-II: the cases $|a|\ll M$ or axisymmetry, 2010, arXiv:1010.5132), and then utilize these estimates to achieve both a uniform bound of a positive definite energy and a Morawetz estimate for the coupled system of each extreme N-P component. The same type of estimates for the regular extreme N-P components defined in the regular Hawking-Hartle tetrad is also proved. The hierarchy here is generalized in our second part (Ma in Uniform energy bound and Morawetz estimates for extreme components of spin fields in the exterior of a slowly rotating Kerr black hole II: linearized gravity, 2017, arXiv:1708.07385) of this series to treat the extreme components of linearized gravity. |
gr-qc/0501102 | Ghanashyam Date | Kinjal Banerjee and Ghanashyam Date | Discreteness Corrections to the Effective Hamiltonian of Isotropic Loop
Quantum Cosmology | Revtex4, 24 pages, 3 figures. In version 2, one reference and a para
pertaining to it are added. In the version 3, some typos are corrected and
remark 4 in section III is revised. Final version to appear in Class. Quantum
Grav | Class.Quant.Grav. 22 (2005) 2017-2033 | 10.1088/0264-9381/22/11/007 | IMSc/2005/01/01 | gr-qc astro-ph hep-th | null | One of the qualitatively distinct and robust implication of Loop Quantum
Gravity (LQG) is the underlying discrete structure. In the cosmological context
elucidated by Loop Quantum Cosmology (LQC), this is manifested by the
Hamiltonian constraint equation being a (partial) difference equation. One
obtains an effective Hamiltonian framework by making the continuum
approximation followed by a WKB approximation. In the large volume regime,
these lead to the usual classical Einstein equation which is independent of
both the Barbero-Immirzi parameter $\gamma$ as well as $\hbar$. In this work we
present an alternative derivation of the effective Hamiltonian by-passing the
continuum approximation step. As a result, the effective Hamiltonian is
obtained as a close form expression in $\gamma$. These corrections to the
Einstein equation can be thought of as corrections due to the underlying
discrete (spatial) geometry with $\gamma$ controlling the size of these
corrections. These corrections imply a bound on the rate of change of the
volume of the isotropic universe. In most cases these are perturbative in
nature but for cosmological constant dominated isotropic universe, there are
significant deviations.
| [
{
"created": "Mon, 31 Jan 2005 13:44:00 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Feb 2005 12:42:30 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Mar 2005 07:21:42 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Banerjee",
"Kinjal",
""
],
[
"Date",
"Ghanashyam",
""
]
] | One of the qualitatively distinct and robust implication of Loop Quantum Gravity (LQG) is the underlying discrete structure. In the cosmological context elucidated by Loop Quantum Cosmology (LQC), this is manifested by the Hamiltonian constraint equation being a (partial) difference equation. One obtains an effective Hamiltonian framework by making the continuum approximation followed by a WKB approximation. In the large volume regime, these lead to the usual classical Einstein equation which is independent of both the Barbero-Immirzi parameter $\gamma$ as well as $\hbar$. In this work we present an alternative derivation of the effective Hamiltonian by-passing the continuum approximation step. As a result, the effective Hamiltonian is obtained as a close form expression in $\gamma$. These corrections to the Einstein equation can be thought of as corrections due to the underlying discrete (spatial) geometry with $\gamma$ controlling the size of these corrections. These corrections imply a bound on the rate of change of the volume of the isotropic universe. In most cases these are perturbative in nature but for cosmological constant dominated isotropic universe, there are significant deviations. |
gr-qc/9906030 | Leonardo Fernandez-Jambrina | Leonardo Fernandez-Jambrina | Geodesic Completeness of Orthogonally Transitive Cylindrical Spacetimes | 9 pages, to appear in Journal of Mathematical Physics | J.Math.Phys. 40 (1999) 4028-4034 | 10.1063/1.532940 | null | gr-qc | null | In this paper a theorem is derived in order to provide a wide sufficient
condition for an orthogonally transitive cylindrical spacetime to be
singularity-free. The applicability of the theorem is tested on examples
provided by the literature that are known to have regular curvature invariants.
| [
{
"created": "Tue, 8 Jun 1999 12:52:52 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Fernandez-Jambrina",
"Leonardo",
""
]
] | In this paper a theorem is derived in order to provide a wide sufficient condition for an orthogonally transitive cylindrical spacetime to be singularity-free. The applicability of the theorem is tested on examples provided by the literature that are known to have regular curvature invariants. |
gr-qc/0610011 | Ettore Minguzzi | E. Minguzzi | Classical aspects of lightlike dimensional reduction | Latex2e, 28 pages, 3 figures, uses psfrag | Class.Quant.Grav.23:7085-7110,2006 | 10.1088/0264-9381/23/23/029 | null | gr-qc | null | Some aspects of lightlike dimensional reduction in flat spacetime are studied
with emphasis to classical applications. Among them the Galilean transformation
of shadows induced by inertial frame changes is studied in detail by proving
that, (i) the shadow of an object has the same shape in every
orthogonal-to-light screen, (ii) if two shadows are simultaneous in an
orthogonal-to-light screen then they are simultaneous in any such screen. In
particular, the Galilean group in 2+1 dimensions is recognized as an exact
symmetry of Nature which acts on the shadows of the events instead that on the
events themselves. The group theoretical approach to lightlike dimensional
reduction is used to solve the reconstruction problem of a trajectory starting
from its acceleration history or from its projected (shadow) trajectory. The
possibility of obtaining a Galilean projected physics starting from a
Poincar\'e invariant physics is stressed through the example of relativistic
collisions. In particular, it is shown that the projection of a relativistic
collision between massless particles gives a non-relativistic collision in
which the kinetic energy is conserved.
| [
{
"created": "Tue, 3 Oct 2006 14:41:13 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Minguzzi",
"E.",
""
]
] | Some aspects of lightlike dimensional reduction in flat spacetime are studied with emphasis to classical applications. Among them the Galilean transformation of shadows induced by inertial frame changes is studied in detail by proving that, (i) the shadow of an object has the same shape in every orthogonal-to-light screen, (ii) if two shadows are simultaneous in an orthogonal-to-light screen then they are simultaneous in any such screen. In particular, the Galilean group in 2+1 dimensions is recognized as an exact symmetry of Nature which acts on the shadows of the events instead that on the events themselves. The group theoretical approach to lightlike dimensional reduction is used to solve the reconstruction problem of a trajectory starting from its acceleration history or from its projected (shadow) trajectory. The possibility of obtaining a Galilean projected physics starting from a Poincar\'e invariant physics is stressed through the example of relativistic collisions. In particular, it is shown that the projection of a relativistic collision between massless particles gives a non-relativistic collision in which the kinetic energy is conserved. |
2408.05091 | Yermek Aldabergenov | Andrea Addazi, Yermek Aldabergenov, Yifu Cai | Sound Speed Resonance of Gravitational Waves in Gauss-Bonnet-coupled
inflation | 8 pages, 4 figures | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate the occurrence of Sound Speed Resonances (SSR) in
Gauss-Bonnet-coupled inflation across a wide range of coupling functions and
parameters. After inflation, the damped oscillations of the inflaton around its
potential minimum induces damped oscillations of the sound speed of tensor
modes, leading to resonant amplification of the latter. Once the inflaton
stabilizes around the minimum, the tensor sound speed reduces to unity (speed
of light). In the context of multi-field inflation, the sound speed
oscillations can be followed by a second phase of inflation, resulting in a
distinctive stochastic background of Gravitational Waves (GWs). We show that
these GW signals can be probed by upcoming experiments such as $\textbf{SKA}$,
$\textbf{DECIGO}$, and $\textbf{BBO}$ depending on the duration of the second
inflationary phase.
| [
{
"created": "Fri, 9 Aug 2024 14:33:15 GMT",
"version": "v1"
}
] | 2024-08-12 | [
[
"Addazi",
"Andrea",
""
],
[
"Aldabergenov",
"Yermek",
""
],
[
"Cai",
"Yifu",
""
]
] | We demonstrate the occurrence of Sound Speed Resonances (SSR) in Gauss-Bonnet-coupled inflation across a wide range of coupling functions and parameters. After inflation, the damped oscillations of the inflaton around its potential minimum induces damped oscillations of the sound speed of tensor modes, leading to resonant amplification of the latter. Once the inflaton stabilizes around the minimum, the tensor sound speed reduces to unity (speed of light). In the context of multi-field inflation, the sound speed oscillations can be followed by a second phase of inflation, resulting in a distinctive stochastic background of Gravitational Waves (GWs). We show that these GW signals can be probed by upcoming experiments such as $\textbf{SKA}$, $\textbf{DECIGO}$, and $\textbf{BBO}$ depending on the duration of the second inflationary phase. |
gr-qc/0505024 | Tomas Liko | Tomas Liko, Paul S. Wesson | An exact solution of the five-dimensional Einstein equations with
four-dimensional de Sitter-like expansion | 6 pages; to appear in Journal of Mathematical Physics; v2: reference
3 corrected | J.Math.Phys. 46 (2005) 062504 | 10.1063/1.1926168 | null | gr-qc | null | We present an exact solution to the Einstein field equations which is Ricci
and Riemann flat in five dimensions, but in four dimensions is a good model for
the early vacuum-dominated universe.
| [
{
"created": "Wed, 4 May 2005 22:53:05 GMT",
"version": "v1"
},
{
"created": "Sun, 8 May 2005 23:52:19 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Liko",
"Tomas",
""
],
[
"Wesson",
"Paul S.",
""
]
] | We present an exact solution to the Einstein field equations which is Ricci and Riemann flat in five dimensions, but in four dimensions is a good model for the early vacuum-dominated universe. |
1912.10859 | Daniel Boyanovsky | Nathan Herring, Daniel Boyanovsky, Andrew R. Zentner | Non-adiabatic cosmological production of ultra-light Dark Matter | Discussion on isocurvature perturbations. To appear in PRD | Phys. Rev. D 101, 083516 (2020) | 10.1103/PhysRevD.101.083516 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the non-adiabatic cosmological production of ultra light dark matter
(ULDM) under a minimal set of assumptions: a free ultra light real scalar as a
spectator field in its Bunch-Davies vacuum state during inflation and
instantaneous reheating into a radiation dominated era. For (ULDM) fields
minimally coupled to gravity, non-adiabatic particle production yields a
\emph{distribution function} peaked at \emph{low} comoving momentum
$\mathcal{N}_k \propto 1/k^3$. The infrared behavior is a remnant of the
infrared enhancement of light minimally coupled fields during inflation. We
obtain the full energy momentum tensor, show explicity its equivalence with the
fluid-kinetic one in the adiabatic regime, and extract the abundance, equation
of state and free streaming length (cutoff in the matter power spectrum).
Taking the upper bound on the scale of inflation from Planck, the (UDLM)
saturates the dark matter abundance for $m \simeq 1.5\,\times
10^{-5}\mathrm{eV}$ with an equation of state parameter $w \simeq 10^{-14}$ and
a free streaming length $\lambda_{fs} \simeq 70\,\mathrm{pc}$. Thus this
cosmologically produced (ULDM) yields a \emph{cold} dark matter particle. We
argue that the abundance from non-adiabatic production yields a \emph{lower
bound} on generic (ULDM) and axion-like particles that must be included in any
assessment of (ULDM) as a dark matter candidate.
| [
{
"created": "Fri, 20 Dec 2019 14:56:52 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Mar 2020 22:07:32 GMT",
"version": "v2"
}
] | 2020-04-13 | [
[
"Herring",
"Nathan",
""
],
[
"Boyanovsky",
"Daniel",
""
],
[
"Zentner",
"Andrew R.",
""
]
] | We study the non-adiabatic cosmological production of ultra light dark matter (ULDM) under a minimal set of assumptions: a free ultra light real scalar as a spectator field in its Bunch-Davies vacuum state during inflation and instantaneous reheating into a radiation dominated era. For (ULDM) fields minimally coupled to gravity, non-adiabatic particle production yields a \emph{distribution function} peaked at \emph{low} comoving momentum $\mathcal{N}_k \propto 1/k^3$. The infrared behavior is a remnant of the infrared enhancement of light minimally coupled fields during inflation. We obtain the full energy momentum tensor, show explicity its equivalence with the fluid-kinetic one in the adiabatic regime, and extract the abundance, equation of state and free streaming length (cutoff in the matter power spectrum). Taking the upper bound on the scale of inflation from Planck, the (UDLM) saturates the dark matter abundance for $m \simeq 1.5\,\times 10^{-5}\mathrm{eV}$ with an equation of state parameter $w \simeq 10^{-14}$ and a free streaming length $\lambda_{fs} \simeq 70\,\mathrm{pc}$. Thus this cosmologically produced (ULDM) yields a \emph{cold} dark matter particle. We argue that the abundance from non-adiabatic production yields a \emph{lower bound} on generic (ULDM) and axion-like particles that must be included in any assessment of (ULDM) as a dark matter candidate. |
gr-qc/0609058 | Farid Ya. Khalili | F.Ya.Khalili | Quantum variational measurement in the next generation
gravitational-wave detectors | 12 pages, 4 figures; NSNS SNR estimates added; misprints corrected | Phys.Rev.D76:102002,2007 | 10.1103/PhysRevD.76.102002 | null | gr-qc | null | A relatively simple method of overcoming the Standard Quantum Limit in the
next-generation Advanced LIGO gravitational wave detector is considered. It is
based on the quantum variational measurement with a single short (a few tens of
meters) filter cavity. Estimates show that this method allows to reduce the
radiation pressure noise at low frequencies ($<100 \mathrm{Hz}$) to the level
comparable with or smaller than the low-frequency noises of non-quantum origin
(mirrors suspension noise, mirrors internal thermal noise, and gravity
gradients fluctuations).
| [
{
"created": "Fri, 15 Sep 2006 13:21:41 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 2007 10:56:14 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Khalili",
"F. Ya.",
""
]
] | A relatively simple method of overcoming the Standard Quantum Limit in the next-generation Advanced LIGO gravitational wave detector is considered. It is based on the quantum variational measurement with a single short (a few tens of meters) filter cavity. Estimates show that this method allows to reduce the radiation pressure noise at low frequencies ($<100 \mathrm{Hz}$) to the level comparable with or smaller than the low-frequency noises of non-quantum origin (mirrors suspension noise, mirrors internal thermal noise, and gravity gradients fluctuations). |
1312.1546 | Sunil Maharaj | M. Govender, K. P. Reddy, S. D. Maharaj | The role of shear in dissipative gravitational collapse | 15 pages, To appear in Int. J. Mod. Phys. D | null | 10.1142/S0218271814500138 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the physics of a radiating star undergoing
dissipative collapse in the form of a radial heat flux. Our treatment clearly
demonstrates how the presence of shear affects the collapse process; we are in
a position to contrast the physical features of the collapsing sphere in the
presence of shear with the shear-free case. By employing a causal heat
transport equation of the Maxwell-Cattaneo form we show that the shear leads to
an enhancement of the core temperature thus emphasizing that relaxational
effects cannot be ignored when the star leaves hydrostatic equilibrium.
| [
{
"created": "Thu, 5 Dec 2013 13:55:43 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Govender",
"M.",
""
],
[
"Reddy",
"K. P.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | In this paper we investigate the physics of a radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse process; we are in a position to contrast the physical features of the collapsing sphere in the presence of shear with the shear-free case. By employing a causal heat transport equation of the Maxwell-Cattaneo form we show that the shear leads to an enhancement of the core temperature thus emphasizing that relaxational effects cannot be ignored when the star leaves hydrostatic equilibrium. |
0906.2588 | Alberto Saa | Michele Ferraz Figueiro and Alberto Saa | Anisotropic singularities in modified gravity models | 6 pages, final version to appear in PRD | Phys.Rev.D80:063504,2009 | 10.1103/PhysRevD.80.063504 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the common singularities present in generic modified gravity
models governed by actions of the type $S=\int d^4x \sqrt{-g}f(R,\phi,X)$, with
$X= -{1/2}g^{ab}\partial_a\phi\partial_b\phi$, are essentially the same
anisotropic instabilities associated to the hypersurface $F(\phi)=0$ in the
case of a non-minimal coupling of the type $F(\phi)R$, enlightening the
physical origin of such singularities that typically arise in rather complex
and cumbersome inhomogeneous perturbation analyses. We show, moreover, that
such anisotropic instabilities typically give rise to dynamically unavoidable
singularities, precluding completely the possibility of having physically
viable models for which the hypersurface $\frac{\partial f}{\partial R}=0$
exists. Some examples are explicitly discussed.
| [
{
"created": "Mon, 15 Jun 2009 01:19:44 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Aug 2009 11:12:00 GMT",
"version": "v2"
}
] | 2009-09-24 | [
[
"Figueiro",
"Michele Ferraz",
""
],
[
"Saa",
"Alberto",
""
]
] | We show that the common singularities present in generic modified gravity models governed by actions of the type $S=\int d^4x \sqrt{-g}f(R,\phi,X)$, with $X= -{1/2}g^{ab}\partial_a\phi\partial_b\phi$, are essentially the same anisotropic instabilities associated to the hypersurface $F(\phi)=0$ in the case of a non-minimal coupling of the type $F(\phi)R$, enlightening the physical origin of such singularities that typically arise in rather complex and cumbersome inhomogeneous perturbation analyses. We show, moreover, that such anisotropic instabilities typically give rise to dynamically unavoidable singularities, precluding completely the possibility of having physically viable models for which the hypersurface $\frac{\partial f}{\partial R}=0$ exists. Some examples are explicitly discussed. |
gr-qc/0007009 | Janos Kannar | Janos Kannar | On Killing vectors in initial value problems for asymptotically flat
space-times | null | Class.Quant.Grav. 17 (2000) 4981-4990 | 10.1088/0264-9381/17/24/303 | null | gr-qc | null | The existence of symmetries in asymptotically flat space-times are studied
from the point of view of initial value problems. General necessary and
sufficient (implicit) conditions are given for the existence of Killing vector
fields in the asymptotic characteristic and in the hyperboloidal initial value
problem (both of them are formulated on the conformally compactified space-time
manifold).
| [
{
"created": "Fri, 7 Jul 2000 13:23:14 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kannar",
"Janos",
""
]
] | The existence of symmetries in asymptotically flat space-times are studied from the point of view of initial value problems. General necessary and sufficient (implicit) conditions are given for the existence of Killing vector fields in the asymptotic characteristic and in the hyperboloidal initial value problem (both of them are formulated on the conformally compactified space-time manifold). |
1104.0858 | Alfredo Sandoval-Villalbazo | D. Brun-Battistini, A. Sandoval-Villalbazo and A. L. Garcia-Perciante | Maxwell-Cattaneo's equation and the stability of fluctuations in the
relativistic fluid | 9 pages, no figures. Typos corrected | null | null | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extended theories are widely used in the literature to describe the
relativistic fluid. The motivation for this is mostly due to the causality
issues allegedly present in the first order theories. However, the decay of
fluctuations in the system is also at stake when first order theories
\emph{that couple heat with acceleration} are used. In this paper it is shown
how the generic instabilities in relativistic fluids are not present when a
Maxwell-Cattaneo type law is introduced in the system of hydrodynamic
equations. Emphasis is made on the fact that the stabilization is only due to
the difference in characteristic times for heat flux relaxation and
instabilities onset. This gives further evidence that Eckart's like
constitutive equations are responsible for the first order sytem exhibiting
unphysical behavior.
| [
{
"created": "Tue, 5 Apr 2011 14:34:40 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2011 18:47:51 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Apr 2011 14:50:04 GMT",
"version": "v3"
}
] | 2011-04-13 | [
[
"Brun-Battistini",
"D.",
""
],
[
"Sandoval-Villalbazo",
"A.",
""
],
[
"Garcia-Perciante",
"A. L.",
""
]
] | Extended theories are widely used in the literature to describe the relativistic fluid. The motivation for this is mostly due to the causality issues allegedly present in the first order theories. However, the decay of fluctuations in the system is also at stake when first order theories \emph{that couple heat with acceleration} are used. In this paper it is shown how the generic instabilities in relativistic fluids are not present when a Maxwell-Cattaneo type law is introduced in the system of hydrodynamic equations. Emphasis is made on the fact that the stabilization is only due to the difference in characteristic times for heat flux relaxation and instabilities onset. This gives further evidence that Eckart's like constitutive equations are responsible for the first order sytem exhibiting unphysical behavior. |
0908.0620 | Wolfgang Tichy | Wolfgang Tichy | A new numerical method to construct binary neutron star initial data | 18 pages, 8 figures, 1 table | Class.Quant.Grav.26:175018,2009 | 10.1088/0264-9381/26/17/175018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new numerical method for the generation of binary neutron star
initial data using a method along the lines of the the Wilson-Mathews or the
closely related conformal thin sandwich approach. Our method uses six different
computational domains, which include spatial infinity. Each domain has its own
coordinates which are chosen such that the star surfaces always coincide with
domain boundaries. These properties facilitate the imposition of boundary
conditions. Since all our fields are smooth inside each domain, we are able to
use an efficient pseudospectral method to solve the elliptic equations
associated with the conformal thin sandwich approach. Currently we have
implemented corotating configurations with arbitrary mass ratios, but an
extension to arbitrary spins is possible. The main purpose of this paper is to
introduce our new method and to test our code for several different
configurations.
| [
{
"created": "Wed, 5 Aug 2009 08:53:41 GMT",
"version": "v1"
}
] | 2010-12-02 | [
[
"Tichy",
"Wolfgang",
""
]
] | We present a new numerical method for the generation of binary neutron star initial data using a method along the lines of the the Wilson-Mathews or the closely related conformal thin sandwich approach. Our method uses six different computational domains, which include spatial infinity. Each domain has its own coordinates which are chosen such that the star surfaces always coincide with domain boundaries. These properties facilitate the imposition of boundary conditions. Since all our fields are smooth inside each domain, we are able to use an efficient pseudospectral method to solve the elliptic equations associated with the conformal thin sandwich approach. Currently we have implemented corotating configurations with arbitrary mass ratios, but an extension to arbitrary spins is possible. The main purpose of this paper is to introduce our new method and to test our code for several different configurations. |
1810.09560 | Eugen Radu | Yves Brihaye, Carlos Herdeiro and Eugen Radu | The scalarised Schwarzschild-NUT spacetime | 12 pages, 6 figures; v2: references added | null | 10.1016/j.physletb.2018.11.022 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been suggested that vacuum black holes of General Relativity
(GR) can become spontaneously scalarised when appropriate non-minimal couplings
to curvature invariants are considered. These models circumvent the standard
black hole no scalar hair theorems of GR, allowing both the standard GR
solutions and new scalarised ($a.k.a.$ hairy) solutions, which in some cases
are thermodynamically preferred. Up to now, however, only (static and
spherically symmetric) scalarised Schwarzschild solutions have been considered.
It would be desirable to take into account the effect of rotation; however, the
higher curvature invariants introduce a considerable challenge in obtaining the
corresponding scalarised rotating black holes. As a toy model for rotation, we
present here the scalarised generalisation of the Schwarzschild-NUT solution,
taking either the Gauss-Bonnet (GB) or the Chern-Simons (CS) curvature
invariant. The NUT charge $n$ endows spacetime with "rotation", but the angular
dependence of the corresponding scalarised solutions factorises, leading to a
considerable technical simplification. For GB, but not for CS, scalarisation
occurs for $n=0$. This basic difference leads to a distinct space of solutions
in the CS case, in particular exhibiting a double branch structure. In the GB
case, increasing the horizon area demands a stronger non-minimal coupling for
scalarisation; in the CS case, due to the double branch structure, both this
and the opposite trend are found. We briefly comment also on the scalarised
Reissner-Nordstr\"om-NUT solutions.
| [
{
"created": "Mon, 22 Oct 2018 21:15:09 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Oct 2018 17:13:03 GMT",
"version": "v2"
}
] | 2018-11-21 | [
[
"Brihaye",
"Yves",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
]
] | It has recently been suggested that vacuum black holes of General Relativity (GR) can become spontaneously scalarised when appropriate non-minimal couplings to curvature invariants are considered. These models circumvent the standard black hole no scalar hair theorems of GR, allowing both the standard GR solutions and new scalarised ($a.k.a.$ hairy) solutions, which in some cases are thermodynamically preferred. Up to now, however, only (static and spherically symmetric) scalarised Schwarzschild solutions have been considered. It would be desirable to take into account the effect of rotation; however, the higher curvature invariants introduce a considerable challenge in obtaining the corresponding scalarised rotating black holes. As a toy model for rotation, we present here the scalarised generalisation of the Schwarzschild-NUT solution, taking either the Gauss-Bonnet (GB) or the Chern-Simons (CS) curvature invariant. The NUT charge $n$ endows spacetime with "rotation", but the angular dependence of the corresponding scalarised solutions factorises, leading to a considerable technical simplification. For GB, but not for CS, scalarisation occurs for $n=0$. This basic difference leads to a distinct space of solutions in the CS case, in particular exhibiting a double branch structure. In the GB case, increasing the horizon area demands a stronger non-minimal coupling for scalarisation; in the CS case, due to the double branch structure, both this and the opposite trend are found. We briefly comment also on the scalarised Reissner-Nordstr\"om-NUT solutions. |
1403.2122 | BingKan Xue | BingKan Xue, Edward Belbruno | Regularization of the big bang singularity with a time varying equation
of state $w > 1$ | minor changes to published version | Class.Quant.Grav. 31 (2014) 165002 | 10.1088/0264-9381/31/16/165002 | null | gr-qc astro-ph.CO hep-th math-ph math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the classical dynamics of the universe undergoing a transition from
contraction to expansion through a big bang singularity. The dynamics is
described by a system of differential equations for a set of physical
quantities, such as the scale factor $a$, the Hubble parameter $H$, the
equation of state parameter $w$, and the density parameter $\Omega$. The
solutions of the dynamical system have a singularity at the big bang. We study
if the solutions can be regularized at the singularity in the sense of whether
they have unique branch extensions through the singularity. In particular, we
consider the model in which the contracting universe is dominated by a scalar
field with a time varying equation of state $w$, which approaches a constant
value $w_c$ near the singularity. We prove that, for $w_c > 1$, the solutions
are regularizable only for a discrete set of $w_c$ values that satisfy a
coprime number condition. Our result implies that the evolution of a bouncing
universe through the big bang singularity does not have a continuous classical
limit unless the equation of state is extremely fine-tuned.
| [
{
"created": "Mon, 10 Mar 2014 01:25:55 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Apr 2015 03:32:16 GMT",
"version": "v2"
}
] | 2015-04-14 | [
[
"Xue",
"BingKan",
""
],
[
"Belbruno",
"Edward",
""
]
] | We study the classical dynamics of the universe undergoing a transition from contraction to expansion through a big bang singularity. The dynamics is described by a system of differential equations for a set of physical quantities, such as the scale factor $a$, the Hubble parameter $H$, the equation of state parameter $w$, and the density parameter $\Omega$. The solutions of the dynamical system have a singularity at the big bang. We study if the solutions can be regularized at the singularity in the sense of whether they have unique branch extensions through the singularity. In particular, we consider the model in which the contracting universe is dominated by a scalar field with a time varying equation of state $w$, which approaches a constant value $w_c$ near the singularity. We prove that, for $w_c > 1$, the solutions are regularizable only for a discrete set of $w_c$ values that satisfy a coprime number condition. Our result implies that the evolution of a bouncing universe through the big bang singularity does not have a continuous classical limit unless the equation of state is extremely fine-tuned. |
2006.12300 | Alfred Y. Shaikh | A.Y.Shaikh, A.S.Shaikh, K.S.Wankhade | Panoroma behaviour of Domain walls cosmological models in teleparallel
gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The work is devoted to LRS Bianchi I domain walls cosmological models within
the framework of teleparallel gravity using volumetric expansions laws for the
depiction model. The physical and kinematical properties are discussed. The
statefinder parameters are also analysed along with the jerk parameter and
cosmological constraints.
| [
{
"created": "Fri, 19 Jun 2020 13:06:35 GMT",
"version": "v1"
}
] | 2020-06-23 | [
[
"Shaikh",
"A. Y.",
""
],
[
"Shaikh",
"A. S.",
""
],
[
"Wankhade",
"K. S.",
""
]
] | The work is devoted to LRS Bianchi I domain walls cosmological models within the framework of teleparallel gravity using volumetric expansions laws for the depiction model. The physical and kinematical properties are discussed. The statefinder parameters are also analysed along with the jerk parameter and cosmological constraints. |
1502.07005 | Vasilis Oikonomou | S. Nojiri, S.D. Odintsov, V.K. Oikonomou | A quantitative analysis of singular inflation with scalar-tensor and
modified gravity | Version accepted by PRD | null | 10.1103/PhysRevD.91.084059 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a detailed quantitative description of singular inflation. Its
close analogy with finite-time future singularity which is associated to dark
energy era is described. Calling and classifying the singularities of such
inflation as finite-time cosmological singularities we investigate their
occurrence, with special emphasis on the Type IV singularity. The study is
performed in the context of a general non-canonical scalar-tensor theory. In
addition, the impact of finite time singularities on the slow-roll parameters
is also investigated. Particularly, we study three cases, in which the
singularity occurs during the inflationary era, at the end, and also we study
the case that the singularity occurs much more later than inflation ends. Using
the obtained slow-roll parameters, for each case, we calculate explicitly the
spectral index of primordial curvature perturbations $n_s$, the associated
running of the spectral index $a_s$ and of the scalar-to-tensor ratio $r$ and
compare the resulting values to the Planck and BICEP2 data. As we demonstrate,
in some cases corresponding to the Type IV singularity, there might be the
possibility of agreement with the observational data, when the singularity
occurs at the end, or after inflation. However, absolute concordance of all
observational indices is not achieved. On the contrary, if the singularity
occurs during the inflationary era, this is catastrophic for the theory, since
the observational indices become divergent. We also show how a Type IV
singularity may be consistently accommodated in the Universe's late time
evolution.
| [
{
"created": "Tue, 24 Feb 2015 23:31:40 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Apr 2015 17:37:54 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We provide a detailed quantitative description of singular inflation. Its close analogy with finite-time future singularity which is associated to dark energy era is described. Calling and classifying the singularities of such inflation as finite-time cosmological singularities we investigate their occurrence, with special emphasis on the Type IV singularity. The study is performed in the context of a general non-canonical scalar-tensor theory. In addition, the impact of finite time singularities on the slow-roll parameters is also investigated. Particularly, we study three cases, in which the singularity occurs during the inflationary era, at the end, and also we study the case that the singularity occurs much more later than inflation ends. Using the obtained slow-roll parameters, for each case, we calculate explicitly the spectral index of primordial curvature perturbations $n_s$, the associated running of the spectral index $a_s$ and of the scalar-to-tensor ratio $r$ and compare the resulting values to the Planck and BICEP2 data. As we demonstrate, in some cases corresponding to the Type IV singularity, there might be the possibility of agreement with the observational data, when the singularity occurs at the end, or after inflation. However, absolute concordance of all observational indices is not achieved. On the contrary, if the singularity occurs during the inflationary era, this is catastrophic for the theory, since the observational indices become divergent. We also show how a Type IV singularity may be consistently accommodated in the Universe's late time evolution. |
2104.09797 | Oleg Evnin | Oleg Evnin | Resonant Hamiltonian systems and weakly nonlinear dynamics in AdS
spacetimes | topical review for Clas. Quant. Grav; v2: slightly expanded, accepted
for publication | Class. Quant. Grav. 38 (2021) 203001 | 10.1088/1361-6382/ac1b46 | null | gr-qc hep-th math-ph math.AP math.MP | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Weakly nonlinear dynamics in anti-de Sitter (AdS) spacetimes is reviewed,
keeping an eye on the AdS instability conjecture and focusing on the resonant
approximation that accurately captures in a simplified form the long-term
evolution of small initial data. Topics covered include turbulent and regular
motion, dynamical recurrences analogous to the Fermi-Pasta-Ulam phenomena in
oscillator chains, and relations between AdS dynamics and nonrelativistic
nonlinear Schrodinger equations in harmonic potentials. Special mention is
given to the way the classical dynamics of weakly nonlinear strongly resonant
systems is illuminated by perturbative considerations within the corresponding
quantum theories, in particular, in relation to quantum chaos theory.
| [
{
"created": "Tue, 20 Apr 2021 07:19:32 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Aug 2021 02:48:46 GMT",
"version": "v2"
}
] | 2021-09-24 | [
[
"Evnin",
"Oleg",
""
]
] | Weakly nonlinear dynamics in anti-de Sitter (AdS) spacetimes is reviewed, keeping an eye on the AdS instability conjecture and focusing on the resonant approximation that accurately captures in a simplified form the long-term evolution of small initial data. Topics covered include turbulent and regular motion, dynamical recurrences analogous to the Fermi-Pasta-Ulam phenomena in oscillator chains, and relations between AdS dynamics and nonrelativistic nonlinear Schrodinger equations in harmonic potentials. Special mention is given to the way the classical dynamics of weakly nonlinear strongly resonant systems is illuminated by perturbative considerations within the corresponding quantum theories, in particular, in relation to quantum chaos theory. |
1507.00973 | Aurel Bejancu | Aurel Bejancu | Kinematic Quantities and Raychaudhuri Equations in a $5D$ Universe | 27 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on some ideas emerged from the classical Kaluza-Klein theory, we
present a $5D$ universe as a product bundle over the $4D$ spacetime. This
enables us to introduce and study two categories of kinematic quantities
(expansions, shear, vorticity) in a $5D$ universe. One category is related to
the fourth dimension (time), and the other one comes from the assumption of the
existence of the fifth dimension. The Raychaudhuri type equations that we
obtain in the paper, lead us to results on the evolution of both the $4D$
expansion and $5D$ expansion in a $5D$ universe.
| [
{
"created": "Mon, 22 Jun 2015 07:48:12 GMT",
"version": "v1"
}
] | 2015-07-06 | [
[
"Bejancu",
"Aurel",
""
]
] | Based on some ideas emerged from the classical Kaluza-Klein theory, we present a $5D$ universe as a product bundle over the $4D$ spacetime. This enables us to introduce and study two categories of kinematic quantities (expansions, shear, vorticity) in a $5D$ universe. One category is related to the fourth dimension (time), and the other one comes from the assumption of the existence of the fifth dimension. The Raychaudhuri type equations that we obtain in the paper, lead us to results on the evolution of both the $4D$ expansion and $5D$ expansion in a $5D$ universe. |
2310.19705 | Takuya Katagiri | Takuya Katagiri, Tact Ikeda, Vitor Cardoso | Parametrized Love numbers of non-rotating black holes | 25 pages, 4 figures, v2: minor corrections, accepted for publication
in PRD | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | A set of tidal Love numbers quantifies tidal deformation of compact objects
and is a detectable imprint in gravitational waves from inspiralling binary
systems. The measurement of black hole Love numbers allows to test strong-field
gravity. In this paper, we present a parametrized formalism to compute the Love
numbers of static and spherically symmetric black hole backgrounds, connecting
the underlying equations of a given theory with detectable quantities in
gravitational-wave observations in a theory-agnostic way. With this formalism,
we compute the Love numbers in several systems. We further classify black hole
Love numbers according to whether they vanish, are nonzero, or are ``running''
(scale-dependent), in theories or backgrounds that deviate perturbatively from
the GR values. The construction relies on static linear perturbations and
scattering theory. Our analytic and numerical results are in excellent
agreement. As a side result, we show how to use Chandrasekhar's relations to
relate basis of even parity to odd parity.
| [
{
"created": "Mon, 30 Oct 2023 16:32:11 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2024 05:41:44 GMT",
"version": "v2"
}
] | 2024-02-15 | [
[
"Katagiri",
"Takuya",
""
],
[
"Ikeda",
"Tact",
""
],
[
"Cardoso",
"Vitor",
""
]
] | A set of tidal Love numbers quantifies tidal deformation of compact objects and is a detectable imprint in gravitational waves from inspiralling binary systems. The measurement of black hole Love numbers allows to test strong-field gravity. In this paper, we present a parametrized formalism to compute the Love numbers of static and spherically symmetric black hole backgrounds, connecting the underlying equations of a given theory with detectable quantities in gravitational-wave observations in a theory-agnostic way. With this formalism, we compute the Love numbers in several systems. We further classify black hole Love numbers according to whether they vanish, are nonzero, or are ``running'' (scale-dependent), in theories or backgrounds that deviate perturbatively from the GR values. The construction relies on static linear perturbations and scattering theory. Our analytic and numerical results are in excellent agreement. As a side result, we show how to use Chandrasekhar's relations to relate basis of even parity to odd parity. |
1805.05513 | Jose Wadih Maluf Dr. | J. W. Maluf, J. F. da Rocha-Neto, S. C. Ulhoa, F. L. Carneiro | Variations of the Energy of Free Particles in the pp-Wave Spacetimes | 20 pages, 18 figures, further arguments supporting the localizability
of the gravitational energy are presented, published in Universe | Universe 2018, 4(7), 74 | 10.3390/universe4070074 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the action of exact plane gravitational waves, or pp-waves, on
free particles. The analysis is carried out by investigating the variations of
the geodesic trajectories of the particles, before and after the passage of the
wave. The initial velocities of the particles are non-vanishing. We evaluate
numerically the Kinetic energy per unit mass of the free particles, and obtain
interesting, quasi-periodic behaviour of the variations of the Kinetic energy
with respect to the width $\lambda$ of the gaussian that represents the wave.
The variation of the energy of the free particle is expected to be exactly
minus the variation of the energy of the gravitational field, and therefore
provides an estimation of the local variation of the gravitational energy. The
investigation is carried out in the context of short bursts of gravitational
waves, and of waves described by normalised gaussians, that yield impulsive
waves in a certain limit.
| [
{
"created": "Tue, 15 May 2018 01:17:21 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jun 2018 13:10:32 GMT",
"version": "v2"
}
] | 2018-06-25 | [
[
"Maluf",
"J. W.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Carneiro",
"F. L.",
""
]
] | We consider the action of exact plane gravitational waves, or pp-waves, on free particles. The analysis is carried out by investigating the variations of the geodesic trajectories of the particles, before and after the passage of the wave. The initial velocities of the particles are non-vanishing. We evaluate numerically the Kinetic energy per unit mass of the free particles, and obtain interesting, quasi-periodic behaviour of the variations of the Kinetic energy with respect to the width $\lambda$ of the gaussian that represents the wave. The variation of the energy of the free particle is expected to be exactly minus the variation of the energy of the gravitational field, and therefore provides an estimation of the local variation of the gravitational energy. The investigation is carried out in the context of short bursts of gravitational waves, and of waves described by normalised gaussians, that yield impulsive waves in a certain limit. |
2001.07540 | Kamal Hajian | Kamal Hajian | Light speed memory as a local observable for soft hairs | 7 pages, published version | EPL, 136 (2021) 29001 | 10.1209/0295-5075/ac29f0 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Einstein observers in flat space-time are inertial observers which use light
to synchronize their clocks. For such observers, speed of light is a constant
by construction. However, one can use super-translations to change coordinates
from Einstein to BMS coordinates. From the point of view of BMS observers,
speed of light is not a constant all over the space-time and in all directions.
So in general, clocks which are synchronized for Einstein observers are not
synchronized for BMS observers, and vice versa. Based on this fact, we propose
a local observable for detecting the soft hairs, which is the variations in
speed of light for such observers. We also investigate the relation of this
observable to gravitational memory, which is a permanent change of position of
test particles at infinity, after a gravitational wave passes completely from
them. It is shown that the BMS time coordinate is the physical time after a
gravitational wave, and it is the legitimate time to be used to calculate the
light speed. Based on this argument, the analysis predicts a permanent change
in the speed of light rays which propagate in asymptotics after a gravitational
wave. Moreover, it is explained how this change is related to the gravitational
memory by comparing their significance in observations.
| [
{
"created": "Tue, 21 Jan 2020 14:43:54 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2020 10:34:16 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Jul 2021 08:33:34 GMT",
"version": "v3"
},
{
"created": "Thu, 3 Feb 2022 16:14:59 GMT",
"version": "v4"
}
] | 2022-02-04 | [
[
"Hajian",
"Kamal",
""
]
] | Einstein observers in flat space-time are inertial observers which use light to synchronize their clocks. For such observers, speed of light is a constant by construction. However, one can use super-translations to change coordinates from Einstein to BMS coordinates. From the point of view of BMS observers, speed of light is not a constant all over the space-time and in all directions. So in general, clocks which are synchronized for Einstein observers are not synchronized for BMS observers, and vice versa. Based on this fact, we propose a local observable for detecting the soft hairs, which is the variations in speed of light for such observers. We also investigate the relation of this observable to gravitational memory, which is a permanent change of position of test particles at infinity, after a gravitational wave passes completely from them. It is shown that the BMS time coordinate is the physical time after a gravitational wave, and it is the legitimate time to be used to calculate the light speed. Based on this argument, the analysis predicts a permanent change in the speed of light rays which propagate in asymptotics after a gravitational wave. Moreover, it is explained how this change is related to the gravitational memory by comparing their significance in observations. |
1409.1818 | Maurizio Gasperini | M. Gasperini | The twin paradox in the presence of gravity | 5 pages, 2 figures. Published in Mod. Phys. Lett. A 29, 1450149
(2014) | Mod. Phys. Lett. A 29, 1450149 (2014) | 10.1142/S0217732314501491 | BA-TH/668-13 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conventional wisdom, based on kinematic (flat-space) intuition, tell us that
a static twin is aging faster than his traveling twin brother. However, such a
situation could be exactly inverted if the two twins are embedded in an
external gravitational field, and if the (dynamical) distortion of the
space-time geometry, due to gravity, is strong enough to compensate the
kinematic effect of the relative twin motion.
| [
{
"created": "Fri, 5 Sep 2014 14:31:44 GMT",
"version": "v1"
}
] | 2014-09-08 | [
[
"Gasperini",
"M.",
""
]
] | Conventional wisdom, based on kinematic (flat-space) intuition, tell us that a static twin is aging faster than his traveling twin brother. However, such a situation could be exactly inverted if the two twins are embedded in an external gravitational field, and if the (dynamical) distortion of the space-time geometry, due to gravity, is strong enough to compensate the kinematic effect of the relative twin motion. |
0905.3657 | Bibekananda Nayak jr | Bibekananda Nayak, Lambodar Prasad Singh | Brans-Dicke Theory and primordial black holes in Early Matter-Dominated
Era | 9 pages | null | 10.1007/s10773-011-1014-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that primordial black holes can be formed in the matter-dominated era
with gravity described by the Brans-Dicke theory. Considering an early
matter-dominated era between inflation and reheating, we found that the
primordial black holes formed during that era evaporate at a quicker than those
of early radiation-dominated era. Thus, in comparison with latter case, less
number of primordial black holes could exist today. Again the constraints on
primordial black hole formation tend towards the larger value than their
radiation-dominated era counterparts indicating a significant enhancement in
the formation of primordial black holes during the matter-dominaed era.
| [
{
"created": "Fri, 22 May 2009 10:35:11 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jun 2009 10:05:11 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Sep 2010 14:45:46 GMT",
"version": "v3"
},
{
"created": "Mon, 27 Jun 2011 15:01:59 GMT",
"version": "v4"
}
] | 2012-01-20 | [
[
"Nayak",
"Bibekananda",
""
],
[
"Singh",
"Lambodar Prasad",
""
]
] | We show that primordial black holes can be formed in the matter-dominated era with gravity described by the Brans-Dicke theory. Considering an early matter-dominated era between inflation and reheating, we found that the primordial black holes formed during that era evaporate at a quicker than those of early radiation-dominated era. Thus, in comparison with latter case, less number of primordial black holes could exist today. Again the constraints on primordial black hole formation tend towards the larger value than their radiation-dominated era counterparts indicating a significant enhancement in the formation of primordial black holes during the matter-dominaed era. |
0803.2671 | Megan McClure | M. L. McClure, Kaem Anderson, Kirk Bardahl | Non-isolated dynamic black holes and white holes | To appear in Physical Review D | Phys.Rev.D77:104008,2008 | 10.1103/PhysRevD.77.104008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modifying the Kerr-Schild transformation used to generate black and white
hole spacetimes, new dynamic black and white holes are obtained using a
time-dependent Kerr-Schild scalar field. Physical solutions are found for black
holes that shrink with time and for white holes that expand with time. The
black hole spacetimes are physical only in the vicinity of the black hole, with
the physical region increasing in radius with time. The white hole spacetimes
are physical throughout. Unlike the standard Schwarzschild solution the
singularities are non-isolated, since the time-dependence introduces a
mass-energy distribution. The surfaces in the metrics where g_{tt}=g^{rr}=0 are
dynamic, moving inward with time for the black holes and outward for the white
holes, which leads to a question of whether these spacetimes truly have event
horizons--a problem shared with Vaidya's cosmological black hole spacetimes. By
finding a surface that shrinks or expands at the same rate as the null
geodesics move, and within which null geodesics move inward or outward faster
than the surfaces shrink or expand respectively, it is verified that these do
in fact behave like black and white holes.
| [
{
"created": "Tue, 18 Mar 2008 16:37:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"McClure",
"M. L.",
""
],
[
"Anderson",
"Kaem",
""
],
[
"Bardahl",
"Kirk",
""
]
] | Modifying the Kerr-Schild transformation used to generate black and white hole spacetimes, new dynamic black and white holes are obtained using a time-dependent Kerr-Schild scalar field. Physical solutions are found for black holes that shrink with time and for white holes that expand with time. The black hole spacetimes are physical only in the vicinity of the black hole, with the physical region increasing in radius with time. The white hole spacetimes are physical throughout. Unlike the standard Schwarzschild solution the singularities are non-isolated, since the time-dependence introduces a mass-energy distribution. The surfaces in the metrics where g_{tt}=g^{rr}=0 are dynamic, moving inward with time for the black holes and outward for the white holes, which leads to a question of whether these spacetimes truly have event horizons--a problem shared with Vaidya's cosmological black hole spacetimes. By finding a surface that shrinks or expands at the same rate as the null geodesics move, and within which null geodesics move inward or outward faster than the surfaces shrink or expand respectively, it is verified that these do in fact behave like black and white holes. |
2307.12210 | Guangzhou Guo | Guangzhou Guo, Peng Wang, Houwen Wu, Haitang Yang | Scalarized Kerr-Newman Black Holes | v1:22pages, 4 figures; v2: 22pages, 4 figures, references added | null | null | CTP-SCU/2023018 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct scalarized rotating black holes within the
framework of Einstein-Maxwell-scalar models. These models incorporate
non-minimal couplings that can induce tachyonic instabilities, leading to the
spontaneous scalarization of Kerr-Newman (KN) black holes. By exploring the
domain of existence, we observe that the presence of scalarized KN black holes
is suppressed by the black hole spin, with a maximum spin threshold beyond
which scalarized solutions cease to exist. Intriguingly, we find that in
specific parameter regimes, scalarized KN black holes can exhibit the presence
of two unstable and one stable light rings on the equatorial plane, manifesting
in both prograde and retrograde directions.
| [
{
"created": "Sun, 23 Jul 2023 02:52:50 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Aug 2023 03:05:51 GMT",
"version": "v2"
}
] | 2023-08-02 | [
[
"Guo",
"Guangzhou",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | In this paper, we construct scalarized rotating black holes within the framework of Einstein-Maxwell-scalar models. These models incorporate non-minimal couplings that can induce tachyonic instabilities, leading to the spontaneous scalarization of Kerr-Newman (KN) black holes. By exploring the domain of existence, we observe that the presence of scalarized KN black holes is suppressed by the black hole spin, with a maximum spin threshold beyond which scalarized solutions cease to exist. Intriguingly, we find that in specific parameter regimes, scalarized KN black holes can exhibit the presence of two unstable and one stable light rings on the equatorial plane, manifesting in both prograde and retrograde directions. |
2201.05210 | Anne Franzen | Jo\~ao L. Costa, Anne T. Franzen, and Jes\'us Oliver | Semilinear wave equations on accelerated expanding FLRW spacetimes | 15 pages, 4 figures | null | 10.1007/s00023-023-01319-9 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We identify a large class of systems of semilinear wave equations, on fixed
accelerated expanding FLRW spacetimes, with nearly at spatial slices, for which
we prove small data future global well-posedness. The family of systems we
consider is large in the sense that, among other examples, it includes general
wave maps, as well as natural generalizations of some of Fritz John's "blow up"
equations (whose future blow up disappears, in our setting, as a consequence of
the spacetime expansion). We also establish decay upper bounds, which are sharp
within the family of systems under analysis.
| [
{
"created": "Thu, 13 Jan 2022 21:00:03 GMT",
"version": "v1"
}
] | 2023-08-09 | [
[
"Costa",
"João L.",
""
],
[
"Franzen",
"Anne T.",
""
],
[
"Oliver",
"Jesús",
""
]
] | We identify a large class of systems of semilinear wave equations, on fixed accelerated expanding FLRW spacetimes, with nearly at spatial slices, for which we prove small data future global well-posedness. The family of systems we consider is large in the sense that, among other examples, it includes general wave maps, as well as natural generalizations of some of Fritz John's "blow up" equations (whose future blow up disappears, in our setting, as a consequence of the spacetime expansion). We also establish decay upper bounds, which are sharp within the family of systems under analysis. |
1812.06966 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s} and Mubasher Jamil | String analog of Reissner-Nordstr\"om black holes cannot be overcharged | Accepted to appear in MPLA | Modern Physics Letters A 34 (2019) 1950248 | 10.1142/S0217732319502481 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we attempt to overcharge extremal and nearly extremal charged
black holes in string theory, known as the Garfinkle-Horowitz-Strominger
solution. We first show that extremal black holes cannot be overcharged
analogous to the case of Reissner-Nordstr\"{o}m black holes. Contrary to their
analogues in general relativity, nearly extremal black holes can neither be
overcharged beyond extremality, nor can they be driven to extremality by the
interaction with test particles. Therefore the analysis in this work also imply
that the third law of black hole thermodynamics holds for the relevant charged
black holes in string theory perturbed by test particles. This can be
interpreted as a stronger version of the third law since one can drop out the
continuity proviso for the relevant process.
| [
{
"created": "Sat, 15 Dec 2018 18:12:55 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Jul 2019 13:53:13 GMT",
"version": "v2"
}
] | 2019-08-02 | [
[
"Düztaş",
"Koray",
""
],
[
"Jamil",
"Mubasher",
""
]
] | In this work we attempt to overcharge extremal and nearly extremal charged black holes in string theory, known as the Garfinkle-Horowitz-Strominger solution. We first show that extremal black holes cannot be overcharged analogous to the case of Reissner-Nordstr\"{o}m black holes. Contrary to their analogues in general relativity, nearly extremal black holes can neither be overcharged beyond extremality, nor can they be driven to extremality by the interaction with test particles. Therefore the analysis in this work also imply that the third law of black hole thermodynamics holds for the relevant charged black holes in string theory perturbed by test particles. This can be interpreted as a stronger version of the third law since one can drop out the continuity proviso for the relevant process. |
2312.05683 | Joel Saavedra | Joaquin Housset, Joel F. Saavedra and Francisco Tello-Ortiz | Cosmological FLRW phase transitions and micro-structure under Kaniadakis
statistics | 11 pages, 4 figures. Accepted version at Physics Letter B | null | 10.1016/j.physletb.2024.138686 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This article is devoted to the study of the thermodynamics phase transitions
and critical phenomena of an FLRW cosmological model under the so-called
Kaniadakis's statistics. The equation of state is derived from the corrected
Friedmann field equations and the thermodynamics unified first law. This
reveals the existence of non-trivial critical points where a first-order phase
transition takes place. The system behaves as an "inverted" van der Waals fluid
in this concern. Interestingly, the numerical values of the critical exponents
are the same as those of the van der Waals system. Besides, to obtain more
insights into the thermodynamics description, the so-called Ruppeiner's
geometry is studied through the normalized scalar curvature, disclosing this
invariant zone where the system undergoes repulsive/attractive interactions.
Near the critical point, this curvature provides again the same critical
exponent and universal constant value as for van der Waals fluid.
| [
{
"created": "Sat, 9 Dec 2023 21:15:20 GMT",
"version": "v1"
},
{
"created": "Wed, 8 May 2024 13:30:29 GMT",
"version": "v2"
}
] | 2024-05-09 | [
[
"Housset",
"Joaquin",
""
],
[
"Saavedra",
"Joel F.",
""
],
[
"Tello-Ortiz",
"Francisco",
""
]
] | This article is devoted to the study of the thermodynamics phase transitions and critical phenomena of an FLRW cosmological model under the so-called Kaniadakis's statistics. The equation of state is derived from the corrected Friedmann field equations and the thermodynamics unified first law. This reveals the existence of non-trivial critical points where a first-order phase transition takes place. The system behaves as an "inverted" van der Waals fluid in this concern. Interestingly, the numerical values of the critical exponents are the same as those of the van der Waals system. Besides, to obtain more insights into the thermodynamics description, the so-called Ruppeiner's geometry is studied through the normalized scalar curvature, disclosing this invariant zone where the system undergoes repulsive/attractive interactions. Near the critical point, this curvature provides again the same critical exponent and universal constant value as for van der Waals fluid. |
1512.02142 | Gray Reid | Gray D. Reid, Matthew W. Choptuik | Nonminimally coupled topological-defect boson stars: Static solutions | 17 pages, 24 figures | Phys. Rev. D 93, 044022 (2016) | 10.1103/PhysRevD.93.044022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spherically symmetric static composite structures consisting of a
boson star and a global monopole, minimally or non-minimally coupled to the
general relativistic gravitational field. In the non-minimally coupled case,
Marunovic and Murkovic have shown that these objects, so-called boson D-stars,
can be sufficiently gravitationally compact so as to potentially mimic black
holes. Here, we present the results of an extensive numerical parameter space
survey which reveals additional new and unexpected phenomenology in the model.
In particular, focusing on families of boson D-stars which are parameterized by
the central amplitude of the boson field, we find configurations for both the
minimally and non-minimally coupled cases that contain one or more shells of
bosonic matter located far from the origin. In parameter space, each shell
spontaneously appears as one tunes through some critical central amplitude of
the boson field. In some cases the shells apparently materialize at spatial
infinity: in these instances their areal radii are observed to obey a universal
scaling law in the vicinity of the critical amplitude. We derive this law from
the equations of motion and the asymptotic behavior of the fields.
| [
{
"created": "Mon, 7 Dec 2015 17:48:39 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Aug 2023 21:19:29 GMT",
"version": "v2"
}
] | 2023-08-09 | [
[
"Reid",
"Gray D.",
""
],
[
"Choptuik",
"Matthew W.",
""
]
] | We consider spherically symmetric static composite structures consisting of a boson star and a global monopole, minimally or non-minimally coupled to the general relativistic gravitational field. In the non-minimally coupled case, Marunovic and Murkovic have shown that these objects, so-called boson D-stars, can be sufficiently gravitationally compact so as to potentially mimic black holes. Here, we present the results of an extensive numerical parameter space survey which reveals additional new and unexpected phenomenology in the model. In particular, focusing on families of boson D-stars which are parameterized by the central amplitude of the boson field, we find configurations for both the minimally and non-minimally coupled cases that contain one or more shells of bosonic matter located far from the origin. In parameter space, each shell spontaneously appears as one tunes through some critical central amplitude of the boson field. In some cases the shells apparently materialize at spatial infinity: in these instances their areal radii are observed to obey a universal scaling law in the vicinity of the critical amplitude. We derive this law from the equations of motion and the asymptotic behavior of the fields. |
2103.14413 | Chen Lan | Chen Lan and Yan-Gang Miao | Gliner Vacuum, Self-consistent Theory of Ruppeiner Geometry for Regular
Black Holes | 23 pages, major revision, Published in EPJC | Eur. Phys. J. C (2022) 82:1152 | 10.1140/epjc/s10052-022-11123-0 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the view of the Gliner vacuum, we remove the deformations in the first law
of mechanics for regular black holes, where one part of deformations associated
with black hole mass will be absorbed into enthalpy or internal energy, and the
other part associated with parameters rather than mass will constitute a
natural $V$-$P$ term. The improved first law of mechanics redisplays its
resemblance to the first law of thermodynamic systems, which implies a restored
correspondence of the mechanic variables to the thermodynamic ones. In
particular, the linear relation between the entropy and horizon area remains
unchanged for regular black holes. Based on the modified first law of
thermodynamics, we establish a self-consistent theory of Ruppeiner geometry and
obtain a universal attractive property for the microstructure of regular black
holes. In addition, the repulsive and attractive interactions inside and
outside regular black holes are analyzed in detail.
| [
{
"created": "Fri, 26 Mar 2021 11:50:24 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 2021 07:55:23 GMT",
"version": "v2"
},
{
"created": "Tue, 25 May 2021 01:16:53 GMT",
"version": "v3"
},
{
"created": "Sat, 9 Oct 2021 05:48:05 GMT",
"version": "v4"
},
{
"created": "Wed, 21 Dec 2022 01:38:53 GMT",
"version": "v5"
}
] | 2022-12-22 | [
[
"Lan",
"Chen",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | In the view of the Gliner vacuum, we remove the deformations in the first law of mechanics for regular black holes, where one part of deformations associated with black hole mass will be absorbed into enthalpy or internal energy, and the other part associated with parameters rather than mass will constitute a natural $V$-$P$ term. The improved first law of mechanics redisplays its resemblance to the first law of thermodynamic systems, which implies a restored correspondence of the mechanic variables to the thermodynamic ones. In particular, the linear relation between the entropy and horizon area remains unchanged for regular black holes. Based on the modified first law of thermodynamics, we establish a self-consistent theory of Ruppeiner geometry and obtain a universal attractive property for the microstructure of regular black holes. In addition, the repulsive and attractive interactions inside and outside regular black holes are analyzed in detail. |
gr-qc/9402043 | Riccardo Capovilla | Riccardo Capovilla and Octavio Obregon | No Quantum Super-Minisuperspace with $\Lambda \ne 0$ | 9 pages, LaTeX, CIEA-94-02 | Phys.Rev. D49 (1994) 6562-6565 | 10.1103/PhysRevD.49.6562 | null | gr-qc | null | We show that the quantum super-minisuperspace of N=1 supergravity with
$\Lambda \ne 0 $ has no non-trivial physical states for class A Bianchi models.
Hence, in super quantum cosmology, the vanishing of $\Lambda$ is a condition
for the existence of the universe. We argue that this result implies that in
full supergravity with $\Lambda$ there are no non-trivial physical states with
a finite number of fermionic fields. We use the Jacobson canonical formulation.
| [
{
"created": "Thu, 24 Feb 1994 17:38:17 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Capovilla",
"Riccardo",
""
],
[
"Obregon",
"Octavio",
""
]
] | We show that the quantum super-minisuperspace of N=1 supergravity with $\Lambda \ne 0 $ has no non-trivial physical states for class A Bianchi models. Hence, in super quantum cosmology, the vanishing of $\Lambda$ is a condition for the existence of the universe. We argue that this result implies that in full supergravity with $\Lambda$ there are no non-trivial physical states with a finite number of fermionic fields. We use the Jacobson canonical formulation. |
1610.05965 | S. Sedigheh Hashemi | S. Sedigheh Hashemi and Nematollah Riazi | Vacuum $ f(R)$ thick brane solution with a Gaussian warp function | 14 pages, 6 figures | Annals of Physics 399 (2018) | 10.1016/j.aop.2018.10.010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work deals with $f(R)$ modified gravity in five dimensional space-time.
The Gaussian thick brane is shown to be an exact solution in the frame work of
$f(R)$ gravity in five dimensions with a bulk cosmological constant. Response
of the brane to gravitational fluctuations and concordance with the Starobinsky
model is addressed. It is shown that the matter which supports the Starobinsky
$f(R)$ solution with the background geometry being flat FLRW with a Gaussian
warp function, behaves like a radiation dominated era of universe, gradually
changing to a dark energy dominated era.
| [
{
"created": "Wed, 19 Oct 2016 11:39:33 GMT",
"version": "v1"
}
] | 2019-02-12 | [
[
"Hashemi",
"S. Sedigheh",
""
],
[
"Riazi",
"Nematollah",
""
]
] | This work deals with $f(R)$ modified gravity in five dimensional space-time. The Gaussian thick brane is shown to be an exact solution in the frame work of $f(R)$ gravity in five dimensions with a bulk cosmological constant. Response of the brane to gravitational fluctuations and concordance with the Starobinsky model is addressed. It is shown that the matter which supports the Starobinsky $f(R)$ solution with the background geometry being flat FLRW with a Gaussian warp function, behaves like a radiation dominated era of universe, gradually changing to a dark energy dominated era. |
1503.07755 | Romulus Breban | Romulus Breban | On spinless null propagation in five dimensional space-times with
approximate space-like Killing symmetry | 6 pages, Typos corrected | null | 10.1140/epjc/s10052-016-4337-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Five-dimensional (5D) space-time symmetry greatly facilitates how a 4D
observer perceives the propagation of a single spinless particle in a 5D
space-time. In particular, if the 5D geometry is independent of the fifth
coordinate then the 5D physics may be interpreted as 4D quantum mechanics. In
this work we address the case where symmetry is approximate, focusing on the
case where the 5D geometry depends weakly on the fifth coordinate. We show that
concepts developed for the case of exact symmetry approximately hold when other
concepts such as decaying quantum states, resonant quantum scattering and
Stokes drag are adopted, as well. We briefly comment on the optical model of
the nuclear interactions and Millikan's oil drop experiment.
| [
{
"created": "Wed, 25 Mar 2015 15:05:45 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Mar 2015 09:36:53 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jul 2016 15:22:09 GMT",
"version": "v3"
}
] | 2016-09-21 | [
[
"Breban",
"Romulus",
""
]
] | Five-dimensional (5D) space-time symmetry greatly facilitates how a 4D observer perceives the propagation of a single spinless particle in a 5D space-time. In particular, if the 5D geometry is independent of the fifth coordinate then the 5D physics may be interpreted as 4D quantum mechanics. In this work we address the case where symmetry is approximate, focusing on the case where the 5D geometry depends weakly on the fifth coordinate. We show that concepts developed for the case of exact symmetry approximately hold when other concepts such as decaying quantum states, resonant quantum scattering and Stokes drag are adopted, as well. We briefly comment on the optical model of the nuclear interactions and Millikan's oil drop experiment. |
1106.4626 | Ritabrata Biswas | Ritabrata Biswas, Nairwita Mazumder, Subenoy Chakraborty | Interacting Holographic Dark Energy Model as a Dynamical system and the
Coincidence Problem | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the evolution of a holographic cosmological model with future
event horizon as the infrared cut-off and dark matter and dark energy do not
evolve independently $-$ there is interaction between them. The basic evolution
equations are reduced to an autonomous system and corresponding phase space is
analyzed.
| [
{
"created": "Thu, 23 Jun 2011 05:01:59 GMT",
"version": "v1"
}
] | 2011-06-24 | [
[
"Biswas",
"Ritabrata",
""
],
[
"Mazumder",
"Nairwita",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | We examine the evolution of a holographic cosmological model with future event horizon as the infrared cut-off and dark matter and dark energy do not evolve independently $-$ there is interaction between them. The basic evolution equations are reduced to an autonomous system and corresponding phase space is analyzed. |
2211.02931 | P. A. Gonzalez | Ram\'on B\'ecar, P. A. Gonz\'alez, Yerko V\'asquez | Charged scalar field perturbations in Ernst black holes | 14 pages and 7 figures. arXiv admin note: text overlap with
arXiv:gr-qc/0211035 by other authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the propagation of a charged massive scalar field in the
background of a four-dimensional Ernst black hole and study its stability
analyzing the quasinormal modes (QNMs), which are calculated using the
semi-analytical Wentzel-Kramers-Brillouin method and numerically using the
continued fraction method. Mainly, we find that for a scalar field mass less
than a critical mass, the decay rate of the QNMs decreases when the harmonic
angular number $\ell$ increases; and for a scalar field mass greater than the
critical mass the behaviour is inverted, i.e, the longest-lived modes are
always the ones with the lowest angular number recovering the standard
behaviour. Also, we find a critical value of the external magnetic field, as
well as, a critical value of the scalar field charge that exhibit the same
behaviour with respect to the angular harmonic numbers. In addition, we show
that the spacetime allows stable quasibound states and we observe a splitting
of the spectrum due to the Zeeman effect. Finally, we show that the unstable
null geodesic in the equatorial plane is connected with the QNMs when the
azimuthal quantum number satisfy $m= \pm \ell$ in the eikonal limit.
| [
{
"created": "Sat, 5 Nov 2022 15:50:22 GMT",
"version": "v1"
}
] | 2022-11-08 | [
[
"Bécar",
"Ramón",
""
],
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We consider the propagation of a charged massive scalar field in the background of a four-dimensional Ernst black hole and study its stability analyzing the quasinormal modes (QNMs), which are calculated using the semi-analytical Wentzel-Kramers-Brillouin method and numerically using the continued fraction method. Mainly, we find that for a scalar field mass less than a critical mass, the decay rate of the QNMs decreases when the harmonic angular number $\ell$ increases; and for a scalar field mass greater than the critical mass the behaviour is inverted, i.e, the longest-lived modes are always the ones with the lowest angular number recovering the standard behaviour. Also, we find a critical value of the external magnetic field, as well as, a critical value of the scalar field charge that exhibit the same behaviour with respect to the angular harmonic numbers. In addition, we show that the spacetime allows stable quasibound states and we observe a splitting of the spectrum due to the Zeeman effect. Finally, we show that the unstable null geodesic in the equatorial plane is connected with the QNMs when the azimuthal quantum number satisfy $m= \pm \ell$ in the eikonal limit. |
gr-qc/0111048 | Serge Winitzki | Serge Winitzki | The eternal fractal in the universe | Conversion to RevTeX4; minor changes; version accepted by Phys. Rev.
D | Phys.Rev. D65 (2002) 083506 | 10.1103/PhysRevD.65.083506 | null | gr-qc astro-ph | null | Models of eternal inflation predict a stochastic self-similar geometry of the
universe at very large scales and allow existence of points that never
thermalize. I explore the fractal geometry of the resulting spacetime, using
coordinate-independent quantities. The formalism of stochastic inflation can be
used to obtain the fractal dimension of the set of eternally inflating points
(the ``eternal fractal''). I also derive a nonlinear branching diffusion
equation describing global properties of the eternal set and the probability to
realize eternal inflation. I show gauge invariance of the condition for
presence of eternal inflation. Finally, I consider the question of whether all
thermalized regions merge into one connected domain. Fractal dimension of the
eternal set provides a (weak) sufficient condition for merging.
| [
{
"created": "Thu, 15 Nov 2001 20:50:15 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jan 2002 18:07:09 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Winitzki",
"Serge",
""
]
] | Models of eternal inflation predict a stochastic self-similar geometry of the universe at very large scales and allow existence of points that never thermalize. I explore the fractal geometry of the resulting spacetime, using coordinate-independent quantities. The formalism of stochastic inflation can be used to obtain the fractal dimension of the set of eternally inflating points (the ``eternal fractal''). I also derive a nonlinear branching diffusion equation describing global properties of the eternal set and the probability to realize eternal inflation. I show gauge invariance of the condition for presence of eternal inflation. Finally, I consider the question of whether all thermalized regions merge into one connected domain. Fractal dimension of the eternal set provides a (weak) sufficient condition for merging. |
gr-qc/0101114 | Yousuke Itoh | Yousuke Itoh (1), Toshifumi Futamase (1), Hideki Asada (2) ((1) Tohoku
University, (2) Hirosaki University) | Equation of motion for relativistic compact binaries with the strong
field point particle limit : the second and half post-Newtonian order | 48 pages, revtex, accepted for publication in Phys. Rev. D | Phys.Rev.D63:064038,2001 | 10.1103/PhysRevD.63.064038 | null | gr-qc | null | We study the equation of motion appropriate to an inspiralling binary star
system whose constituent stars have strong internal gravity. We use the
post-Newtonian approximation with the strong field point particle limit by
which we can introduce into general relativity a notion of a point-like
particle with strong internal gravity without using Dirac delta distribution.
Besides this limit, to deal with strong internal gravity we express the
equation of motion in surface integral forms and calculate these integrals
explicitly. As a result we obtain the equation of motion for a binary of
compact bodies accurate through the second and half post-Newtonian (2.5 PN)
order. This equation is derived in the harmonic coordinate. Our resulting
equation perfectly agrees with Damour and Deruelle 2.5 PN equation of motion.
Hence it is found that the 2.5 PN equation of motion is applicable to a
relativistic compact binary.
| [
{
"created": "Tue, 30 Jan 2001 04:49:44 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Itoh",
"Yousuke",
""
],
[
"Futamase",
"Toshifumi",
""
],
[
"Asada",
"Hideki",
""
]
] | We study the equation of motion appropriate to an inspiralling binary star system whose constituent stars have strong internal gravity. We use the post-Newtonian approximation with the strong field point particle limit by which we can introduce into general relativity a notion of a point-like particle with strong internal gravity without using Dirac delta distribution. Besides this limit, to deal with strong internal gravity we express the equation of motion in surface integral forms and calculate these integrals explicitly. As a result we obtain the equation of motion for a binary of compact bodies accurate through the second and half post-Newtonian (2.5 PN) order. This equation is derived in the harmonic coordinate. Our resulting equation perfectly agrees with Damour and Deruelle 2.5 PN equation of motion. Hence it is found that the 2.5 PN equation of motion is applicable to a relativistic compact binary. |
0910.1321 | Michael Martin Nieto | Michael Martin Nieto and John D. Anderson | Earth Flyby Anomalies | 5 pagea 3 figures | Physics Today {\bf 62} (No. 10 Oct.), 76-77 (2009) | 10.1063/1.3248495 | LA-UR-09-04811 | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a reference frame fixed to the solar system's center of mass, a
satellite's energy will change as it is deflected by a planet. But a number of
satellites flying by Earth have also experienced energy changes in the
Earth-centered frame -- and that's a mystery.
| [
{
"created": "Wed, 7 Oct 2009 17:11:30 GMT",
"version": "v1"
}
] | 2015-05-14 | [
[
"Nieto",
"Michael Martin",
""
],
[
"Anderson",
"John D.",
""
]
] | In a reference frame fixed to the solar system's center of mass, a satellite's energy will change as it is deflected by a planet. But a number of satellites flying by Earth have also experienced energy changes in the Earth-centered frame -- and that's a mystery. |
1806.07639 | Roberto Casadio | R. Casadio, M. Lenzi, O. Micu | Bootstrapping Newton Gravity | 23 pages, 20 plots. New section and appendix about stability and the
pressure clarify comparison with GR. Conclusions rewritten to make
motivations clearer | Phys. Rev. D 98, 104016 (2018) | 10.1103/PhysRevD.98.104016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-linear equation obtained by adding gravitational self-interaction terms
to the Poisson equation for Newtonian gravity is here employed in order to
analyse a static spherically sym- metric homogeneous compact source of given
proper mass and radius and the outer vacuum. The main feature of this picture
is that, although the freedom of shifting the potential by an ar- bitrary
constant is of course lost, the solutions remain qualitatively very close to
the Newtonian behaviour. We also notice that the negative gravitational
potential energy is smaller than the proper mass for sources with small
compactness, but for sources that should form black holes according to General
Relativity, the gravitational potential energy becomes of the same order of
magnitude of the proper mass, or even larger. Moreover, the pressure overcomes
the energy density for large values of the compactness, but it remains finite
for finite compactness, hence there exists no Buchdahl limit. This classical
description is meant to serve as the starting point for investigating quantum
features of (near) black hole configurations within the corpuscular picture of
gravity in future developments.
| [
{
"created": "Wed, 20 Jun 2018 09:46:07 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Oct 2018 15:26:40 GMT",
"version": "v2"
}
] | 2018-11-21 | [
[
"Casadio",
"R.",
""
],
[
"Lenzi",
"M.",
""
],
[
"Micu",
"O.",
""
]
] | A non-linear equation obtained by adding gravitational self-interaction terms to the Poisson equation for Newtonian gravity is here employed in order to analyse a static spherically sym- metric homogeneous compact source of given proper mass and radius and the outer vacuum. The main feature of this picture is that, although the freedom of shifting the potential by an ar- bitrary constant is of course lost, the solutions remain qualitatively very close to the Newtonian behaviour. We also notice that the negative gravitational potential energy is smaller than the proper mass for sources with small compactness, but for sources that should form black holes according to General Relativity, the gravitational potential energy becomes of the same order of magnitude of the proper mass, or even larger. Moreover, the pressure overcomes the energy density for large values of the compactness, but it remains finite for finite compactness, hence there exists no Buchdahl limit. This classical description is meant to serve as the starting point for investigating quantum features of (near) black hole configurations within the corpuscular picture of gravity in future developments. |
gr-qc/0201073 | Pio J. Arias | Victor Varela (Universidad Central de Venezuela) | Construction of Sources for Majumdar-Papapetrou Spacetimes | 15 pages, LaTeX | Gen.Rel.Grav. 35 (2003) 1815-1831 | 10.1023/A:1026014114308 | null | gr-qc | null | We study Majumdar-Papapetrou solutions for the 3+1 Einstein-Maxwell
equations, with charged dust acting as the external source for the fields. The
spherically symmetric solution of G\"{u}rses is considered in detail. We
introduce new parameters that simplify the construction of class $C^1$,
singularity-free geometries. The arising sources are bounded or unbounded, and
the redshift of light signals allows an observer at spatial infinity to
distinguish these cases. We find out an interesting affinity between the
conformastatic metric and some homothetic, matter and Ricci collineations. The
associated non-Noetherian symmetries provide us with distinctive solutions that
can be used to construct non-singular sources for Majumdar-Papapetrou
spacetimes.}
| [
{
"created": "Tue, 22 Jan 2002 06:25:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Varela",
"Victor",
"",
"Universidad Central de Venezuela"
]
] | We study Majumdar-Papapetrou solutions for the 3+1 Einstein-Maxwell equations, with charged dust acting as the external source for the fields. The spherically symmetric solution of G\"{u}rses is considered in detail. We introduce new parameters that simplify the construction of class $C^1$, singularity-free geometries. The arising sources are bounded or unbounded, and the redshift of light signals allows an observer at spatial infinity to distinguish these cases. We find out an interesting affinity between the conformastatic metric and some homothetic, matter and Ricci collineations. The associated non-Noetherian symmetries provide us with distinctive solutions that can be used to construct non-singular sources for Majumdar-Papapetrou spacetimes.} |
2108.02462 | Davide Gerosa | Christopher J. Moore and Davide Gerosa | Population-informed priors in gravitational-wave astronomy | 11 pages, 5 figures + supplementary material | Phys. Rev. D 104, 083008 (2021) | 10.1103/PhysRevD.104.083008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a Bayesian formalism for analyzing individual gravitational-wave
events in light of the rest of an observed population. This analysis reveals
how the idea of a "population-informed prior" arises naturally from a suitable
marginalization of an underlying hierarchical Bayesian model which consistently
accounts for selection effects. Our formalism naturally leads to the presence
of "leave-one-out" distributions which include subsets of events. This differs
from other approximations, also known as empirical Bayes methods, which
effectively double count one or more events. We design a double-reweighting
post-processing strategy that uses only existing data products to reconstruct
the resulting population-informed posterior distributions. Although the
correction we highlight is an important conceptual point, we find it has a
limited impact on the current catalog of gravitational-wave events. Our
approach further allows us to study, for the first time in the
gravitational-wave literature, correlations between the parameters of
individual events and those of the population.
| [
{
"created": "Thu, 5 Aug 2021 09:04:21 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Nov 2021 09:48:44 GMT",
"version": "v2"
}
] | 2021-11-11 | [
[
"Moore",
"Christopher J.",
""
],
[
"Gerosa",
"Davide",
""
]
] | We describe a Bayesian formalism for analyzing individual gravitational-wave events in light of the rest of an observed population. This analysis reveals how the idea of a "population-informed prior" arises naturally from a suitable marginalization of an underlying hierarchical Bayesian model which consistently accounts for selection effects. Our formalism naturally leads to the presence of "leave-one-out" distributions which include subsets of events. This differs from other approximations, also known as empirical Bayes methods, which effectively double count one or more events. We design a double-reweighting post-processing strategy that uses only existing data products to reconstruct the resulting population-informed posterior distributions. Although the correction we highlight is an important conceptual point, we find it has a limited impact on the current catalog of gravitational-wave events. Our approach further allows us to study, for the first time in the gravitational-wave literature, correlations between the parameters of individual events and those of the population. |
gr-qc/0006079 | Ken-ichi Nakao | Ken-ichi Nakao, Tomohiro Harada, Masaru Shibata, Seiji Kawamura and
Takashi Nakamura | Response of Interferometric Detectors to Scalar Gravitational Waves | 20 pages, 7 figures | Phys.Rev.D63:082001,2001 | 10.1103/PhysRevD.63.082001 | OCU-PHYS-175, WU-AP/101/00 | gr-qc | null | We rigorously analyze the frequency response functions and antenna
sensitivity patterns of three types of interferometric detectors to scalar mode
of gravitational waves which is predicted to exist in the scalar-tensor theory
of gravity. By a straightforward treatment, we show that the antenna
sensitivity pattern of the simple Michelson interferometric detector depends
strongly on the wave length $\lambda_{\rm SGW}$ of the scalar mode of
gravitational waves if $\lambda_{\rm SGW}$ is comparable to the arm length of
the interferometric detector. For the Delay-Line and Fabry-Perot
interferometric detectors with arm length much shorter than $\lambda_{\rm
SGW}$, however, the antenna sensitivity patterns depend weakly on $\lambda_{\rm
SGW}$ even though $\lambda_{\rm SGW}$ is comparable to the effective path
length of those interferometers. This agrees with the result obtained by
Maggiore and Nicolis.
| [
{
"created": "Thu, 22 Jun 2000 02:44:56 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Nakao",
"Ken-ichi",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Nakamura",
"Takashi",
""
]
] | We rigorously analyze the frequency response functions and antenna sensitivity patterns of three types of interferometric detectors to scalar mode of gravitational waves which is predicted to exist in the scalar-tensor theory of gravity. By a straightforward treatment, we show that the antenna sensitivity pattern of the simple Michelson interferometric detector depends strongly on the wave length $\lambda_{\rm SGW}$ of the scalar mode of gravitational waves if $\lambda_{\rm SGW}$ is comparable to the arm length of the interferometric detector. For the Delay-Line and Fabry-Perot interferometric detectors with arm length much shorter than $\lambda_{\rm SGW}$, however, the antenna sensitivity patterns depend weakly on $\lambda_{\rm SGW}$ even though $\lambda_{\rm SGW}$ is comparable to the effective path length of those interferometers. This agrees with the result obtained by Maggiore and Nicolis. |
1707.08056 | Jessie Durk | Jessie Durk, Timothy Clifton | A Quasi-Static Approach to Structure Formation in Black Hole Universes | 33 pages, 10 figures, v2: matches published version, typos corrected | JCAP 10 (2017) 012 | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the existence of hierarchies of structure in the Universe, we
present four new families of exact initial data for inhomogeneous cosmological
models at their maximum of expansion. These data generalise existing black hole
lattice models to situations that contain clusters of masses, and hence allow
the consequences of cosmological structures to be considered in a well-defined
and non-perturbative fashion. The degree of clustering is controlled by a
parameter $\lambda$, in such a way that for $\lambda \sim 0$ or $1$ we have
very tightly clustered masses, whilst for $\lambda \sim 0.5$ all masses are
separated by cosmological distance scales. We study the consequences of
structure formation on the total net mass in each of our clusters, as well as
calculating the cosmological consequences of the interaction energies both
within and between clusters. The locations of the shared horizons that appear
around groups of black holes, when they are brought sufficiently close
together, are also identified and studied. We find that clustering can have
surprisingly large effects on the scale of the cosmology, with models that
contain thousands of black holes sometimes being as little as 30% of the size
of comparable Friedmann models with the same total proper mass. This deficit is
comparable to what might be expected to occur from neglecting gravitational
interaction energies in Friedmann cosmology, and suggests that these quantities
may have a significant influence on the properties of the large-scale
cosmology.
| [
{
"created": "Tue, 25 Jul 2017 15:52:27 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Oct 2017 17:13:52 GMT",
"version": "v2"
}
] | 2017-10-20 | [
[
"Durk",
"Jessie",
""
],
[
"Clifton",
"Timothy",
""
]
] | Motivated by the existence of hierarchies of structure in the Universe, we present four new families of exact initial data for inhomogeneous cosmological models at their maximum of expansion. These data generalise existing black hole lattice models to situations that contain clusters of masses, and hence allow the consequences of cosmological structures to be considered in a well-defined and non-perturbative fashion. The degree of clustering is controlled by a parameter $\lambda$, in such a way that for $\lambda \sim 0$ or $1$ we have very tightly clustered masses, whilst for $\lambda \sim 0.5$ all masses are separated by cosmological distance scales. We study the consequences of structure formation on the total net mass in each of our clusters, as well as calculating the cosmological consequences of the interaction energies both within and between clusters. The locations of the shared horizons that appear around groups of black holes, when they are brought sufficiently close together, are also identified and studied. We find that clustering can have surprisingly large effects on the scale of the cosmology, with models that contain thousands of black holes sometimes being as little as 30% of the size of comparable Friedmann models with the same total proper mass. This deficit is comparable to what might be expected to occur from neglecting gravitational interaction energies in Friedmann cosmology, and suggests that these quantities may have a significant influence on the properties of the large-scale cosmology. |
1306.5063 | Avirup Ghosh | Olaf Dreyer, Amit Ghosh, Avirup Ghosh | Entropy from near-horizon geometries of Killing horizons | 8 pages, no figures | Phys. Rev. D 89, 024035 (2014) | 10.1103/PhysRevD.89.024035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive black hole entropy based on the near-horizon symmetries of black
hole space-times. To derive these symmetries we make use of an $(R,T)$-plane
close to a Killing horizon. We identify a set of vector fields that preserves
this plane and forms a Witt algebra. The corresponding algebra of Hamiltonians
is shown to have a non-trivial central extension. Using the Cardy formula and
the central charge we obtain the Bekenstein-Hawking entropy.
| [
{
"created": "Fri, 21 Jun 2013 07:09:44 GMT",
"version": "v1"
}
] | 2014-02-04 | [
[
"Dreyer",
"Olaf",
""
],
[
"Ghosh",
"Amit",
""
],
[
"Ghosh",
"Avirup",
""
]
] | We derive black hole entropy based on the near-horizon symmetries of black hole space-times. To derive these symmetries we make use of an $(R,T)$-plane close to a Killing horizon. We identify a set of vector fields that preserves this plane and forms a Witt algebra. The corresponding algebra of Hamiltonians is shown to have a non-trivial central extension. Using the Cardy formula and the central charge we obtain the Bekenstein-Hawking entropy. |
2205.00297 | Tiberiu Harko | Tiberiu Harko, Eniko J. Madarassy | Bose-Einstein Condensate dark matter models in the presence of baryonic
matter and random confining potentials | 29 pages, 15 figures, accepted for publication in EPJC | null | 10.1140/epjc/s10052-022-10344-7 | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the effects of an uncorrelated random potential on the properties
of Bose-Einstein Condensate (BEC) dark matter halos, which acts as a source of
disorder, and which is added as a new term in the Gross-Pitaevskii equation,
describing the properties of the halo. By using the hydrodynamic representation
we derive the basic equation describing the density distribution of the
galactic dark matter halo, by also taking into account the effects of the
baryonic matter, and of the rotation. The density, mass and tangential velocity
profiles are obtained exactly in spherical symmetry by considering a simple
exponential density profile for the baryonic matter, and a Gaussian type
disorder potential. To test the theoretical model we compare its predictions
with a set of 39 galaxies from the Spitzer Photometry \& Accurate Rotation
Curves (SPARC) database. We obtain estimates of the relevant astrophysical
parameters of the dark matter dominated galaxies, including the baryonic matter
properties, and the parameters of the random potential. The BEC model in the
presence of baryonic matter and a random confining potential gives a good
statistical description of the SPARC data. The presence of the condensate dark
matter could also provide a solution for the core/cusp problem.
| [
{
"created": "Sat, 30 Apr 2022 15:48:59 GMT",
"version": "v1"
}
] | 2022-05-18 | [
[
"Harko",
"Tiberiu",
""
],
[
"Madarassy",
"Eniko J.",
""
]
] | We consider the effects of an uncorrelated random potential on the properties of Bose-Einstein Condensate (BEC) dark matter halos, which acts as a source of disorder, and which is added as a new term in the Gross-Pitaevskii equation, describing the properties of the halo. By using the hydrodynamic representation we derive the basic equation describing the density distribution of the galactic dark matter halo, by also taking into account the effects of the baryonic matter, and of the rotation. The density, mass and tangential velocity profiles are obtained exactly in spherical symmetry by considering a simple exponential density profile for the baryonic matter, and a Gaussian type disorder potential. To test the theoretical model we compare its predictions with a set of 39 galaxies from the Spitzer Photometry \& Accurate Rotation Curves (SPARC) database. We obtain estimates of the relevant astrophysical parameters of the dark matter dominated galaxies, including the baryonic matter properties, and the parameters of the random potential. The BEC model in the presence of baryonic matter and a random confining potential gives a good statistical description of the SPARC data. The presence of the condensate dark matter could also provide a solution for the core/cusp problem. |
1908.07171 | Dipanjan Dey | Parth Bambhaniya, Ashok B. Joshi, Dipanjan Dey, Pankaj S. Joshi | Timelike geodesics in Naked Singularity and Black Hole Spacetimes | 14 pages, 18 figures | Phys. Rev. D 100, 124020 (2019) | 10.1103/PhysRevD.100.124020 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we derive the solutions of orbit equations for a class of
naked singularity spacetimes, and compare these with timelike orbits, that is,
particle trajectories in the Schwarzschild black hole spacetime. The
Schwarzschild and naked singularity spacetimes considered here can be formed as
end state of a spherically symmetric gravitational collapse of a matter cloud.
We find and compare the perihelion precession of the particle orbits in the
naked singularity spacetime with that of the Schwarzschild black hole. We then
discuss different distinguishable physical properties of timelike orbits in the
black hole and naked singularity spacetimes and implications are discussed.
Several interesting differences follow from our results, including the
conclusion that in naked singularity spacetimes, particle bound orbits can
precess in the opposite direction of particle motion, which is not possible in
Schwarzschild spacetime.
| [
{
"created": "Tue, 20 Aug 2019 05:34:51 GMT",
"version": "v1"
}
] | 2019-12-11 | [
[
"Bambhaniya",
"Parth",
""
],
[
"Joshi",
"Ashok B.",
""
],
[
"Dey",
"Dipanjan",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | In this paper, we derive the solutions of orbit equations for a class of naked singularity spacetimes, and compare these with timelike orbits, that is, particle trajectories in the Schwarzschild black hole spacetime. The Schwarzschild and naked singularity spacetimes considered here can be formed as end state of a spherically symmetric gravitational collapse of a matter cloud. We find and compare the perihelion precession of the particle orbits in the naked singularity spacetime with that of the Schwarzschild black hole. We then discuss different distinguishable physical properties of timelike orbits in the black hole and naked singularity spacetimes and implications are discussed. Several interesting differences follow from our results, including the conclusion that in naked singularity spacetimes, particle bound orbits can precess in the opposite direction of particle motion, which is not possible in Schwarzschild spacetime. |
1707.07457 | Ana Alonso-Serrano | Ana Alonso-Serrano (Charles University of Prague) and Matt Visser
(Victoria University of Wellington) | Entropy budget for Hawking evaporation | Proceedings of the conference "VARCOSMOFUN'16" in Szczecin, Poland,
12-17 September, 2016. Accepted for publication in "Universe", belonging to
the Special Issue "Varying Constants and Fundamental Cosmology" | Universe 2017, 3(3), 58 | 10.1016/j.physletb.2017.11.020 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Blackbody radiation, emitted from a furnace and described by a Planck
spectrum, contains (on average) an entropy of $3.9\pm 2.5$ bits per photon.
Since normal physical burning is a unitary process, this amount of entropy is
compensated by the same amount of "hidden information" in correlations between
the photons. The importance of this result lies in the posterior extension of
this argument to the Hawking radiation from black holes, demonstrating that the
assumption of unitarity leads to a perfectly reasonable entropy/information
budget for the evaporation process. In order to carry out this calculation we
adopt a variant of the "average subsystem" approach, but consider a tripartite
pure system that includes the influence of the rest of the universe, and which
allows "young" black holes to still have a non-zero entropy; which we identify
with the standard Bekenstein entropy.
| [
{
"created": "Mon, 24 Jul 2017 09:50:52 GMT",
"version": "v1"
}
] | 2018-02-01 | [
[
"Alonso-Serrano",
"Ana",
"",
"Charles University of Prague"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Blackbody radiation, emitted from a furnace and described by a Planck spectrum, contains (on average) an entropy of $3.9\pm 2.5$ bits per photon. Since normal physical burning is a unitary process, this amount of entropy is compensated by the same amount of "hidden information" in correlations between the photons. The importance of this result lies in the posterior extension of this argument to the Hawking radiation from black holes, demonstrating that the assumption of unitarity leads to a perfectly reasonable entropy/information budget for the evaporation process. In order to carry out this calculation we adopt a variant of the "average subsystem" approach, but consider a tripartite pure system that includes the influence of the rest of the universe, and which allows "young" black holes to still have a non-zero entropy; which we identify with the standard Bekenstein entropy. |
2007.06333 | Xiao-Xiong Zeng | Xiao-Xiong Zeng, Hai-Qing Zhang | Influence of quintessence dark energy on the shadow of black hole | references added | null | 10.1140/epjc/s10052-020-08656-7 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate the effects of quintessence dark energy on the shadows of
black hole, surrounded by various profiles of accretions. For the thin disk
accretion, the images of the black hole comprises the dark region and bright
region, including direct emission, lensing rings and photon rings. Although
their details depend on the form of the emission, generically, the direct
emission plays a major role for the observed brightness of the black hole,
while the lensing ring makes a small contribution and photon ring makes a
negligible contribution. The existence of cosmological horizon also plays an
important role in the shadows, since the observer in the domain of outer
communications is nearby the cosmological horizon. For the spherically
symmetric accretion, the static and infalling matters are considered. We find
that the positions of photon spheres are the same for both static and infalling
accretions. However, the observed specific intensity of the image for the
infalling accretion is darker than the static accretion, due to the Doppler
effect of the infalling movement.
| [
{
"created": "Mon, 13 Jul 2020 12:06:05 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jul 2020 02:27:46 GMT",
"version": "v2"
}
] | 2020-12-02 | [
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Zhang",
"Hai-Qing",
""
]
] | We investigate the effects of quintessence dark energy on the shadows of black hole, surrounded by various profiles of accretions. For the thin disk accretion, the images of the black hole comprises the dark region and bright region, including direct emission, lensing rings and photon rings. Although their details depend on the form of the emission, generically, the direct emission plays a major role for the observed brightness of the black hole, while the lensing ring makes a small contribution and photon ring makes a negligible contribution. The existence of cosmological horizon also plays an important role in the shadows, since the observer in the domain of outer communications is nearby the cosmological horizon. For the spherically symmetric accretion, the static and infalling matters are considered. We find that the positions of photon spheres are the same for both static and infalling accretions. However, the observed specific intensity of the image for the infalling accretion is darker than the static accretion, due to the Doppler effect of the infalling movement. |
gr-qc/9812052 | O. B. Zaslavskii | O.B. Zaslavskii (Department of Physics, Kharkov Karazin's National
University) | Nonextreme black holes near the extreme state and acceleration horizons:
thermodynamics and quantum-corrected geometry | 27 pages, REVTeX 3.0. Expanded from previous version. Title somewhat
changed. Qualitative explanation of effects of strong quantum backreaction on
geometry suggested in terms of induced cosmological constant. Stressed that
if this constant is positive, solutions found can be considered as quantum
versions of charged Nariai one. Accepted for publication in Class. Quant.
Grav | Class.Quant.Grav. 17 (2000) 497-512 | 10.1088/0264-9381/17/2/315 | null | gr-qc hep-th | null | We consider the class of metrics that can be obtained from those of
nonextreme black holes by limiting transitions to the extreme state such that
the near-horizon geometry expands into a whole manifold. These metrics include,
in particular, the Rindler and Bertotti - Robinson spacetimes. The general
formula for the entropy of massless radiation valid either for black-hole or
for acceleration horizons is derived. It is argued that, as a black hole
horizon in the limit under consideration turns into an acceleration one, the
thermodynamic entropy $S_{q}$ of quantum radiation is due to the Unruh effect
entirely and $S_{q}=0$ exactly. The contribution to the quasilocal energy from
a given curved spacetime is equal to zero and the only nonvanishing term stems
from a reference metric. In the variation procedure necessary for the
derivation of the general first law, the metric on a horizon surface changes
along with the boundary one, and the account for gravitational and matter
stresses is an essential ingredient of the first law. This law confirms the
property $S_{q}=0$. The quantum-corrected geometry of the Bertotti - Robinson
spacetime is found and it is argued that backreaction of quantum fields mimics
the effect of the cosmological constant $\Lambda_{eff\text{}}$ and can
drastically change the character of spacetime depending on the sign of $\Lambda
_{eff}$ --- for instance, turn $AdS_{2}\times S_{2}$ into $dS_{2}\times S_{2}$
or $Rindler_{2}\times S_{2}$. Two latter solutions can be thought of as the
quantum versions of the cold and ultracold limits of the Reissner-Nordstrom-de
Sitter metric.
| [
{
"created": "Tue, 15 Dec 1998 23:09:18 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Feb 1999 18:18:42 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Jul 1999 08:29:15 GMT",
"version": "v3"
},
{
"created": "Wed, 24 Nov 1999 11:36:04 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Zaslavskii",
"O. B.",
"",
"Department of Physics, Kharkov Karazin's National\n University"
]
] | We consider the class of metrics that can be obtained from those of nonextreme black holes by limiting transitions to the extreme state such that the near-horizon geometry expands into a whole manifold. These metrics include, in particular, the Rindler and Bertotti - Robinson spacetimes. The general formula for the entropy of massless radiation valid either for black-hole or for acceleration horizons is derived. It is argued that, as a black hole horizon in the limit under consideration turns into an acceleration one, the thermodynamic entropy $S_{q}$ of quantum radiation is due to the Unruh effect entirely and $S_{q}=0$ exactly. The contribution to the quasilocal energy from a given curved spacetime is equal to zero and the only nonvanishing term stems from a reference metric. In the variation procedure necessary for the derivation of the general first law, the metric on a horizon surface changes along with the boundary one, and the account for gravitational and matter stresses is an essential ingredient of the first law. This law confirms the property $S_{q}=0$. The quantum-corrected geometry of the Bertotti - Robinson spacetime is found and it is argued that backreaction of quantum fields mimics the effect of the cosmological constant $\Lambda_{eff\text{}}$ and can drastically change the character of spacetime depending on the sign of $\Lambda _{eff}$ --- for instance, turn $AdS_{2}\times S_{2}$ into $dS_{2}\times S_{2}$ or $Rindler_{2}\times S_{2}$. Two latter solutions can be thought of as the quantum versions of the cold and ultracold limits of the Reissner-Nordstrom-de Sitter metric. |
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