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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2203.04477 | Wei-Liang Qian | Wei-Liang Qian and Kai Lin and Cai-Ying Shao and Bin Wang and Rui-Hong
Yue | On the late-time tails of massive perturbations in spherically symmetric
black holes | 18 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was first pointed out by Koyama and Tomimatsu that, under reasonable
assumptions, the asymptotic late-time tails of massive scalar perturbations in
the far zone of spherically symmetric black hole spacetimes decays universally
as $t^{-5/6}$. The late-time tail is furnished by the contribution from the
branch cut of the frequency-domain Green's function, which is constructed in
terms of two appropriate solutions of the corresponding homogeneous equation.
The present study is focused on some particular forms of the in-going wave that
were not explicitly considered in the original derivations but nonetheless have
been taken into account in the literature by other authors. In this regard, we
reassess the authors' arguments and provide a detailed complimentary analysis
that covers a few specific aspects. For some particular cases, the tail is
found to possess the form $t^{-1}$. We also discuss the possible implications
of the present findings.
| [
{
"created": "Wed, 9 Mar 2022 01:37:21 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Oct 2022 21:35:15 GMT",
"version": "v2"
}
] | 2022-10-18 | [
[
"Qian",
"Wei-Liang",
""
],
[
"Lin",
"Kai",
""
],
[
"Shao",
"Cai-Ying",
""
],
[
"Wang",
"Bin",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | It was first pointed out by Koyama and Tomimatsu that, under reasonable assumptions, the asymptotic late-time tails of massive scalar perturbations in the far zone of spherically symmetric black hole spacetimes decays universally as $t^{-5/6}$. The late-time tail is furnished by the contribution from the branch cut of the frequency-domain Green's function, which is constructed in terms of two appropriate solutions of the corresponding homogeneous equation. The present study is focused on some particular forms of the in-going wave that were not explicitly considered in the original derivations but nonetheless have been taken into account in the literature by other authors. In this regard, we reassess the authors' arguments and provide a detailed complimentary analysis that covers a few specific aspects. For some particular cases, the tail is found to possess the form $t^{-1}$. We also discuss the possible implications of the present findings. |
gr-qc/0106081 | Oscar J. C. Dias | Oscar J. C. Dias | Pair creation of particles and black holes in external fields | LaTeX file (World Scientific macros), no figures, 9 pages, talk given
at Xth Portuguese Meeting on Astronomy and Astrophysics, (Lisbon, Portugal,
27-28 July 2000), to be published in Proc. Xth A & A meeting, edited by J. P.
S. Lemos, A. Mourao, L. Teodoro, R. Ugoccioni, (World Scientific, 2001) | null | 10.1142/9789812811110_0013 | null | gr-qc | null | It is well known that massive black holes may form through the gravitational
collapse of a massive astrophysical body. Less known is the fact that a black
hole can be produced by the quantum process of pair creation in external
fields. These black holes may have a mass much lower than their astrophysical
counterparts. This mass can be of the order of Planck mass so that quantum
effects may be important. This pair creation process can be investigated
semiclassically using non-perturbative instanton methods, thus it may be used
as a theoretical laboratory to obtain clues for a quantum gravity theory. In
this work, we review briefly the history of pair creation of particles and
black holes in external fields. In order to present some features of the
euclidean instanton method which is used to calculate pair creation rates, we
study a simple model of a scalar field and propose an effective one-loop action
for a two-dimensional soliton pair creation problem. This action is built from
the soliton field itself and the soliton charge is no longer treated as a
topological charge but as a Noether charge. The results are also valid
straightforwardly to the problem of pair creation rate of domain walls in
dimensions greater than 2.
| [
{
"created": "Tue, 26 Jun 2001 11:46:12 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Dias",
"Oscar J. C.",
""
]
] | It is well known that massive black holes may form through the gravitational collapse of a massive astrophysical body. Less known is the fact that a black hole can be produced by the quantum process of pair creation in external fields. These black holes may have a mass much lower than their astrophysical counterparts. This mass can be of the order of Planck mass so that quantum effects may be important. This pair creation process can be investigated semiclassically using non-perturbative instanton methods, thus it may be used as a theoretical laboratory to obtain clues for a quantum gravity theory. In this work, we review briefly the history of pair creation of particles and black holes in external fields. In order to present some features of the euclidean instanton method which is used to calculate pair creation rates, we study a simple model of a scalar field and propose an effective one-loop action for a two-dimensional soliton pair creation problem. This action is built from the soliton field itself and the soliton charge is no longer treated as a topological charge but as a Noether charge. The results are also valid straightforwardly to the problem of pair creation rate of domain walls in dimensions greater than 2. |
gr-qc/0605125 | Feng Luo | Feng Luo, Hongya Liu | Exploring Extra Dimensions in Spectroscopy Experiments | 8 pages, 2 figures | Chin.Phys.Lett. 23 (2006) 2903 | 10.1088/0256-307X/23/11/006 | null | gr-qc | null | We propose an idea in spectroscopy to search for extra spatial dimensions as
well as to detect the possible deviation from Newton's inverse-square law at
small scale, and we take high-Z hydrogenic systems and muonic atoms as
illustrations. The relevant experiments might help to explore more than two
extra dimensions scenario in ADD's brane world model and to set constraints for
fundamental parameters such as the size of extra dimensions.
| [
{
"created": "Wed, 24 May 2006 15:09:02 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Luo",
"Feng",
""
],
[
"Liu",
"Hongya",
""
]
] | We propose an idea in spectroscopy to search for extra spatial dimensions as well as to detect the possible deviation from Newton's inverse-square law at small scale, and we take high-Z hydrogenic systems and muonic atoms as illustrations. The relevant experiments might help to explore more than two extra dimensions scenario in ADD's brane world model and to set constraints for fundamental parameters such as the size of extra dimensions. |
2305.09544 | Camilo Posada PhD | Philip Beltracchi and Camilo Posada | Slowly rotating ultracompact Schwarzschild star in the gravastar limit | Matches the published version in CQG | Class. Quantum Grav. 41 (2024) 045001 | 10.1088/1361-6382/ad1a52 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider the problem of a slowly rotating homogeneous star, or
Schwarzschild star, when its compactness goes beyond the Buchdahl bound and
approaches the gravastar limit $R\to 2M$. We compute surface and integral
properties of such configuration by integrating the Hartle-Thorne structure
equations for slowly rotating relativistic masses, at second order in angular
velocity. In the gravastar limit, we show that the metric of a slowly rotating
Schwarzschild star agrees with the Kerr metric, thus, within this
approximation, it is not possible to tell a gravastar from a Kerr black hole by
any observations from the spacetime exterior to the horizon.
| [
{
"created": "Tue, 16 May 2023 15:39:38 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Dec 2023 01:21:46 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Jan 2024 19:39:33 GMT",
"version": "v3"
}
] | 2024-01-23 | [
[
"Beltracchi",
"Philip",
""
],
[
"Posada",
"Camilo",
""
]
] | We reconsider the problem of a slowly rotating homogeneous star, or Schwarzschild star, when its compactness goes beyond the Buchdahl bound and approaches the gravastar limit $R\to 2M$. We compute surface and integral properties of such configuration by integrating the Hartle-Thorne structure equations for slowly rotating relativistic masses, at second order in angular velocity. In the gravastar limit, we show that the metric of a slowly rotating Schwarzschild star agrees with the Kerr metric, thus, within this approximation, it is not possible to tell a gravastar from a Kerr black hole by any observations from the spacetime exterior to the horizon. |
1301.4920 | Jose Manuel Velhinho | Jeronimo Cortez, Daniel Martin-de Blas, Guillermo A. Mena Marugan,
Jose M. Velhinho | Massless scalar field in de Sitter spacetime: unitary quantum time
evolution | 23 pages. Typos corrected, matches published version | Class. Quantum Grav. 30 (2013) 075015 | 10.1088/0264-9381/30/7/075015 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that, under the standard conformal scaling, a massless field in de
Sitter spacetime admits an O(4)-invariant Fock quantization such that time
evolution is unitarily implemented. This result disproves previous claims in
the literature. We discuss the relationship between this quantization with
unitary dynamics and the family of O(4)-invariant Hadamard states given by
Allen and Folacci, as well as with the Bunch-Davies vacuum.
| [
{
"created": "Mon, 21 Jan 2013 16:45:39 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Mar 2013 18:17:19 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Cortez",
"Jeronimo",
""
],
[
"Blas",
"Daniel Martin-de",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Velhinho",
"Jose M.",
""
]
] | We prove that, under the standard conformal scaling, a massless field in de Sitter spacetime admits an O(4)-invariant Fock quantization such that time evolution is unitarily implemented. This result disproves previous claims in the literature. We discuss the relationship between this quantization with unitary dynamics and the family of O(4)-invariant Hadamard states given by Allen and Folacci, as well as with the Bunch-Davies vacuum. |
1412.5420 | Muhammad Jamil Amir | M. Jamil Amir and Tahir Nazir | Teleparallel Energy-Momentum Distribution of Locally Rotationally
Symmetric Spacetimes | Accepted in Journal of Korean Physical Society. arXiv admin note:
substantial text overlap with arXiv:0704.2099 | null | 10.3938/jkps.65.1336 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we explore the energy-momentum distribution of locally
rotationally symmetric (LRS) spacetimes in the context of the teleparallel
theory of gravity by considering the three metrics, I, II and III, representing
the whole class of LRS sapcetimes. In this regard, we use the teleparallel
versions of the Einstein, Landau-Lifshitz, Bergmann-Thomson, and
M$\ddot{o}$ller prescriptions. The results show that the momentum density
components for the Einstein, Bergmann-Thomson, and M$\ddot{o}$ller
prescriptions turn out to be same in all cases of the metrics I, II and III,
but are different from those of the Landau- Lifshitz prescription, while the
energy components remain the same for these three prescriptions only in all
possible cases of the metrics I and II. We mention here that the
M$\ddot{o}$ller energy-momentum distribution is independent of the coupling
constant $\lambda$; that is, these results are valid for any teleparallel
models.
| [
{
"created": "Thu, 11 Dec 2014 12:06:05 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Amir",
"M. Jamil",
""
],
[
"Nazir",
"Tahir",
""
]
] | In this paper, we explore the energy-momentum distribution of locally rotationally symmetric (LRS) spacetimes in the context of the teleparallel theory of gravity by considering the three metrics, I, II and III, representing the whole class of LRS sapcetimes. In this regard, we use the teleparallel versions of the Einstein, Landau-Lifshitz, Bergmann-Thomson, and M$\ddot{o}$ller prescriptions. The results show that the momentum density components for the Einstein, Bergmann-Thomson, and M$\ddot{o}$ller prescriptions turn out to be same in all cases of the metrics I, II and III, but are different from those of the Landau- Lifshitz prescription, while the energy components remain the same for these three prescriptions only in all possible cases of the metrics I and II. We mention here that the M$\ddot{o}$ller energy-momentum distribution is independent of the coupling constant $\lambda$; that is, these results are valid for any teleparallel models. |
gr-qc/9401022 | Henri Waelbroeck | H. Waelbroeck | Canonical Quantization of (2+1)-Dimensional Gravity | 22 pages, Mexico preprint ICN-UNAM-93-14 | Phys.Rev. D50 (1994) 4982-4992 | 10.1103/PhysRevD.50.4982 | null | gr-qc | null | We consider the quantum dynamics of both open and closed two- dimensional
universes with ``wormholes'' and particles. The wave function is given as a sum
of freely propagating amplitudes, emitted from a network of mapping class
images of the initial state. Interference between these amplitudes gives
non-trivial scattering effects, formally analogous to the optical diffraction
by a multidimensional grating; the ``bright lines'' correspond to the most
probable geometries.
| [
{
"created": "Thu, 20 Jan 1994 02:09:58 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Waelbroeck",
"H.",
""
]
] | We consider the quantum dynamics of both open and closed two- dimensional universes with ``wormholes'' and particles. The wave function is given as a sum of freely propagating amplitudes, emitted from a network of mapping class images of the initial state. Interference between these amplitudes gives non-trivial scattering effects, formally analogous to the optical diffraction by a multidimensional grating; the ``bright lines'' correspond to the most probable geometries. |
gr-qc/0308013 | Pavel Krtous | Jiri Bicak, Petr Hajicek | Canonical theory of spherically symmetric spacetimes with
cross-streaming null dusts | 15 pages, 3 figures, submitted to Phys. Rev. D | Phys.Rev. D68 (2003) 104016 | 10.1103/PhysRevD.68.104016 | null | gr-qc hep-th | null | The Hamiltonian dynamics of two-component spherically symmetric null dust is
studied with regard to the quantum theory of gravitational collapse. The
components--the ingoing and outgoing dusts--are assumed to interact only
through gravitation. Different kinds of singularities, naked or "clothed", that
can form during collapse processes are described. The general canonical
formulation of the one-component null-dust dynamics by Bicak and Kuchar is
restricted to the spherically symmetric case and used to construct an action
for the two components. The transformation from a metric variable to the
quasilocal mass is shown to simplify the mathematics. The action is reduced by
a choice of gauge and the corresponding true Hamiltonian is written down.
Asymptotic coordinates and energy densities of dust shells are shown to form a
complete set of Dirac observables. The action of the asymptotic time
translation on the observables is defined but it has been calculated explicitly
only in the case of one-component dust (Vaidya metric).
| [
{
"created": "Wed, 6 Aug 2003 10:30:53 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bicak",
"Jiri",
""
],
[
"Hajicek",
"Petr",
""
]
] | The Hamiltonian dynamics of two-component spherically symmetric null dust is studied with regard to the quantum theory of gravitational collapse. The components--the ingoing and outgoing dusts--are assumed to interact only through gravitation. Different kinds of singularities, naked or "clothed", that can form during collapse processes are described. The general canonical formulation of the one-component null-dust dynamics by Bicak and Kuchar is restricted to the spherically symmetric case and used to construct an action for the two components. The transformation from a metric variable to the quasilocal mass is shown to simplify the mathematics. The action is reduced by a choice of gauge and the corresponding true Hamiltonian is written down. Asymptotic coordinates and energy densities of dust shells are shown to form a complete set of Dirac observables. The action of the asymptotic time translation on the observables is defined but it has been calculated explicitly only in the case of one-component dust (Vaidya metric). |
1504.07580 | Tomas Andrade | Tomas Andrade, William R. Kelly, Donald Marolf, Jorge E. Santos | On the stability of gravity with Dirichlet walls | 35 pages, 20 figures | null | 10.1088/0264-9381/32/23/235006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dirichlet walls -- timelike boundaries at finite distance from the bulk on
which the induced metric is held fixed -- have been used to model AdS
spacetimes with a finite cutoff. In the context of gauge/gravity duality, such
models are often described as dual to some novel UV-cufoff version of a
corresponding CFT that maintains local Lorentz invariance. We study linearized
gravity in the presence of such a wall and find it to differ significantly from
the seemingly-analogous case of Dirichlet boundary conditions for fields of
spins zero and one. In particular, using the Kodama-Ishibashi formalism, the
boundary condition that must be imposed on scalar-sector master field with
harmonic time dependence depends explicitly on their frequency. That this
feature first arises for spin-2 appears to be related to the second-order
nature of the equations of motion. It gives rise to a number of novel
instabilities, though both global and planar Anti-de Sitter remain (linearly)
stable in the presence of large-radius Dirichlet cutoffs. The instabilities
arise on the outside of spherical Dirichlet walls, and also inside sufficiently
large such spherical walls in de Sitter space. We analyze both inside and
outside of flat and spherical walls in Minkowski, de Sitter, and anti-de Sitter
space, as well as in certain black hole spacetimes and find stability for cases
not mentioned above. In particular, we find no linear instabilities in the
presence of flat walls. We also find evidence supporting the conjecture that
neutral black holes are repelled by Dirichlet walls.
| [
{
"created": "Tue, 28 Apr 2015 17:34:48 GMT",
"version": "v1"
}
] | 2015-11-18 | [
[
"Andrade",
"Tomas",
""
],
[
"Kelly",
"William R.",
""
],
[
"Marolf",
"Donald",
""
],
[
"Santos",
"Jorge E.",
""
]
] | Dirichlet walls -- timelike boundaries at finite distance from the bulk on which the induced metric is held fixed -- have been used to model AdS spacetimes with a finite cutoff. In the context of gauge/gravity duality, such models are often described as dual to some novel UV-cufoff version of a corresponding CFT that maintains local Lorentz invariance. We study linearized gravity in the presence of such a wall and find it to differ significantly from the seemingly-analogous case of Dirichlet boundary conditions for fields of spins zero and one. In particular, using the Kodama-Ishibashi formalism, the boundary condition that must be imposed on scalar-sector master field with harmonic time dependence depends explicitly on their frequency. That this feature first arises for spin-2 appears to be related to the second-order nature of the equations of motion. It gives rise to a number of novel instabilities, though both global and planar Anti-de Sitter remain (linearly) stable in the presence of large-radius Dirichlet cutoffs. The instabilities arise on the outside of spherical Dirichlet walls, and also inside sufficiently large such spherical walls in de Sitter space. We analyze both inside and outside of flat and spherical walls in Minkowski, de Sitter, and anti-de Sitter space, as well as in certain black hole spacetimes and find stability for cases not mentioned above. In particular, we find no linear instabilities in the presence of flat walls. We also find evidence supporting the conjecture that neutral black holes are repelled by Dirichlet walls. |
2310.08022 | Mustapha Azreg-A\"inou | Mustapha Azreg-A\"inou, Kauntey Acharya, and Pankaj S. Joshi | Joshi--Malafarina--Narayan singularity in weak magnetic field | 12 pages, 3 compound figures, sections added | Eur. Phys. J. C (2024) 84:535 | 10.1140/epjc/s10052-024-12905-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The importance and significance of magnetic fields in the astrophysical
scenario is well known. Many domains of astrophysical black hole physics such
as polarized shadow image, high energy emitting processes and jet formation are
dependent on the behavior of the magnetic fields in the vicinity of the compact
objects. In light of this, we determine the master equation and master
differential equation that determine the spatial behavior of the magnetic field
inside a matter distribution or vacuum region, of general spherically symmetric
metric, which is immersed in a test magnetic field. We also investigate here
the case of JMN-1 singularity immersed in a uniform weak magnetic field and
determine the behavior of magnetic fields by defining electromagnetic four
potential vector. We find that the tangential component of the magnetic field
is discontinuous at the matching surface of the JMN-1 singularity with the
external Schwarzschild metric, resulting in surface currents. We define the
covariant expression of surface current density in this scenario. We also
analyze the behavior of center-of-mass energy of two oppositely charged
particles in the geometry of the magnetized JMN-1 singularity. We briefly
discuss the possible scenarios which would possess a discontinuous magnetic
field and implications of the same and future possibilities in the realm of
astrophysics are indicated.
| [
{
"created": "Thu, 12 Oct 2023 03:43:27 GMT",
"version": "v1"
},
{
"created": "Tue, 21 May 2024 06:50:36 GMT",
"version": "v2"
}
] | 2024-05-30 | [
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Acharya",
"Kauntey",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | The importance and significance of magnetic fields in the astrophysical scenario is well known. Many domains of astrophysical black hole physics such as polarized shadow image, high energy emitting processes and jet formation are dependent on the behavior of the magnetic fields in the vicinity of the compact objects. In light of this, we determine the master equation and master differential equation that determine the spatial behavior of the magnetic field inside a matter distribution or vacuum region, of general spherically symmetric metric, which is immersed in a test magnetic field. We also investigate here the case of JMN-1 singularity immersed in a uniform weak magnetic field and determine the behavior of magnetic fields by defining electromagnetic four potential vector. We find that the tangential component of the magnetic field is discontinuous at the matching surface of the JMN-1 singularity with the external Schwarzschild metric, resulting in surface currents. We define the covariant expression of surface current density in this scenario. We also analyze the behavior of center-of-mass energy of two oppositely charged particles in the geometry of the magnetized JMN-1 singularity. We briefly discuss the possible scenarios which would possess a discontinuous magnetic field and implications of the same and future possibilities in the realm of astrophysics are indicated. |
gr-qc/0505035 | Mehmet Cem Calik | M.Arik M.C.Calik | Can Brans-Dicke scalar field account for dark energy and dark matter? | revised for typo addition and for one reference change | Mod.Phys.Lett.A21:1241-1248,2006 | 10.1142/S021773230602055X | null | gr-qc | null | By using a linearized non-vacuum late time solution in Brans-Dicke cosmology
we account for the seventy five percent dark energy contribution but not for
approximately twenty-three percent dark matter contribution to the present day
energy density of the universe.
| [
{
"created": "Mon, 9 May 2005 08:39:45 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2005 11:39:10 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Apr 2006 08:17:56 GMT",
"version": "v3"
}
] | 2010-11-11 | [
[
"Calik",
"M. Arik M. C.",
""
]
] | By using a linearized non-vacuum late time solution in Brans-Dicke cosmology we account for the seventy five percent dark energy contribution but not for approximately twenty-three percent dark matter contribution to the present day energy density of the universe. |
1603.00853 | Cassius de Melo | R. Casana, C. A. M. de Melo and B. M. Pimentel | Electromagnetic Field in Lyra Manifold: A First Order Approach | Matches version published ten years ago celebrating 100 years of
Relativity. arXiv admin note: substantial text overlap with
arXiv:gr-qc/0509117 | Braz. J. of Phys. v. 35, n.4B, p. 1151-1154, 2005 | 10.1590/S0103-97332005000700040 | null | gr-qc astro-ph.CO hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the coupling of the electromagnetic field with a curved and
torsioned Lyra manifold using the Duffin-Kemmer-Petiau theory. We will show how
to obtain the equations of motion and energy-momentum and spin density tensors
by means of the Schwinger Variational Principle.
| [
{
"created": "Wed, 2 Mar 2016 20:27:51 GMT",
"version": "v1"
}
] | 2016-03-09 | [
[
"Casana",
"R.",
""
],
[
"de Melo",
"C. A. M.",
""
],
[
"Pimentel",
"B. M.",
""
]
] | We discuss the coupling of the electromagnetic field with a curved and torsioned Lyra manifold using the Duffin-Kemmer-Petiau theory. We will show how to obtain the equations of motion and energy-momentum and spin density tensors by means of the Schwinger Variational Principle. |
gr-qc/0512083 | Yi Ling | Yi Ling, Bo Hu and Xiang Li | Modified dispersion relations and black hole physics | 4 pages, Revtex. Final version to appear in PRD | Phys.Rev. D73 (2006) 087702 | 10.1103/PhysRevD.73.087702 | null | gr-qc hep-th | null | A modified formulation of energy-momentum relation is proposed in the context
of doubly special relativity. We investigate its impact on black hole physics.
It turns out that such modification will give corrections to both the
temperature and the entropy of black holes. In particular this modified
dispersion relation also changes the picture of Hawking radiation greatly when
the size of black holes approaching the Planck scale. It can prevent black
holes from total evaporation, as a result providing a plausible mechanism to
treat the remnant of black holes as a candidate for dark matter.
| [
{
"created": "Wed, 14 Dec 2005 13:09:32 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Apr 2006 02:17:05 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Ling",
"Yi",
""
],
[
"Hu",
"Bo",
""
],
[
"Li",
"Xiang",
""
]
] | A modified formulation of energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such modification will give corrections to both the temperature and the entropy of black holes. In particular this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaching the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter. |
gr-qc/9709057 | Radu Ionicioiu | Radu Ionicioiu (DAMTP, University of Cambridge, UK) | Topology change from Kaluza-Klein dimensions | 5 pages, LaTeX, no figures, uses epsf | null | null | DAMTP-97-105 | gr-qc hep-th | null | In this letter we show that in a Kaluza-Klein framework we can have arbitrary
topology change between the macroscopic (i.e. noncompactified) spacelike
3-hypersurfaces. This is achieved by using the compactified dimensions as a
catalyser for topology change. In the case of odd-dimensional spacetimes (such
as the 11-dimensional M-theory) this is always possible. In the
even-dimensional case, a sufficient condition is the existence of a closed,
odd-dimensional manifold as a factor (such as S^1, S^3) in the Kaluza-Klein
sector. Since one of the most common manifolds used for compactification is the
torus T^k = S^1 \times ... \times S^1, in this case we can again induce an
arbitrary topology change on the 3-hypersurfaces.
| [
{
"created": "Mon, 22 Sep 1997 17:03:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ionicioiu",
"Radu",
"",
"DAMTP, University of Cambridge, UK"
]
] | In this letter we show that in a Kaluza-Klein framework we can have arbitrary topology change between the macroscopic (i.e. noncompactified) spacelike 3-hypersurfaces. This is achieved by using the compactified dimensions as a catalyser for topology change. In the case of odd-dimensional spacetimes (such as the 11-dimensional M-theory) this is always possible. In the even-dimensional case, a sufficient condition is the existence of a closed, odd-dimensional manifold as a factor (such as S^1, S^3) in the Kaluza-Klein sector. Since one of the most common manifolds used for compactification is the torus T^k = S^1 \times ... \times S^1, in this case we can again induce an arbitrary topology change on the 3-hypersurfaces. |
2310.01487 | Manuel Hohmann | Manuel Hohmann | Kinetic gases in static spherically symmetric modified dispersion
relations | 15 pages, 4 color figures; journal version | Class.Quant.Grav. 41 no. 1 (2023) 015025 | 10.1088/1361-6382/ad0fba | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of a collisionless kinetic gas in the most general
static, spherically symmetric dispersion relation. For a static, spherically
symmetric kinetic gas, we derive the most general solution to these dynamics,
and find that any solution is given by a one-particle distribution function
which depends on three variables. For two particular solutions, describing a
shell of monoenergetic orbiting particles and a purely radial inflow, we
calculate the particle density as a function of the radial coordinate. As a
particular example, we study a $\kappa$-Poincar\'e modification of the
Schwarzschild metric dispersion relation and derive its influence on the
particle density. Our results provide a possible route towards quantum gravity
phenomenology via the observation of matter dynamics in the vicinity of massive
compact objects.
| [
{
"created": "Mon, 2 Oct 2023 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Dec 2023 20:48:58 GMT",
"version": "v2"
}
] | 2023-12-22 | [
[
"Hohmann",
"Manuel",
""
]
] | We study the dynamics of a collisionless kinetic gas in the most general static, spherically symmetric dispersion relation. For a static, spherically symmetric kinetic gas, we derive the most general solution to these dynamics, and find that any solution is given by a one-particle distribution function which depends on three variables. For two particular solutions, describing a shell of monoenergetic orbiting particles and a purely radial inflow, we calculate the particle density as a function of the radial coordinate. As a particular example, we study a $\kappa$-Poincar\'e modification of the Schwarzschild metric dispersion relation and derive its influence on the particle density. Our results provide a possible route towards quantum gravity phenomenology via the observation of matter dynamics in the vicinity of massive compact objects. |
gr-qc/0604026 | Parthasarathi Majumdar | Parthasarathi Majumdar | Thermal stability of radiant black holes | Latex2e, 13 pages, 2 eps figures. Contribution to the volume to be
published by the Indian Association for the Cultivation of Science, Kolkata,
India in revered memory of Prof. A. K. Raychaudhuri | null | null | null | gr-qc | null | Beginning with a brief sketch of the derivation of Hawking's theorem of
horizon area increase, based on the Raychaudhuri equation, we go on to discuss
the issue as to whether generic black holes, undergoing Hawking radiation, can
ever remain in stable thermal equilibrium with that radiation. We derive a
universal criterion for such a stability, which relates the black hole mass and
microcanonical entropy, both of which are well-defined within the context of
the Isolated Horizon, and in principle calculable within Loop Quantum Gravity.
The criterion is argued to hold even when thermal fluctuations of electric
charge are considered, within a {\it grand} canonical ensemble.
| [
{
"created": "Thu, 6 Apr 2006 11:12:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Majumdar",
"Parthasarathi",
""
]
] | Beginning with a brief sketch of the derivation of Hawking's theorem of horizon area increase, based on the Raychaudhuri equation, we go on to discuss the issue as to whether generic black holes, undergoing Hawking radiation, can ever remain in stable thermal equilibrium with that radiation. We derive a universal criterion for such a stability, which relates the black hole mass and microcanonical entropy, both of which are well-defined within the context of the Isolated Horizon, and in principle calculable within Loop Quantum Gravity. The criterion is argued to hold even when thermal fluctuations of electric charge are considered, within a {\it grand} canonical ensemble. |
1103.3826 | Seiju Ohashi | Seiju Ohashi, Tetsuya Shiromizu, Sanjay Jhingan | Spherical collapse of inhomogeneous dust cloud in the Lovelock theory | 11 pages, 2 figures, typos corrected, reference added, appendix
added, accepted for publication in PRD | Phys.Rev.D84:024021,2011 | 10.1103/PhysRevD.84.024021 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational collapse of a spherically symmetric inhomogeneous dust
cloud in the Lovelock theory without cosmological constant. We show that the
final fate of gravitational collapse in this theory depends on the spacetime
dimensions. In odd dimensions the naked singularities formed are found to be
massive. In the even dimensions,on the other hand, the naked singularities are
found to be massless. We also show that the curvature strength of naked
singularity is independent of the spacetime dimensions in odd dimensions.
However, it depends on the spacetime dimensions in even dimension.
| [
{
"created": "Sun, 20 Mar 2011 02:23:23 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2011 02:37:15 GMT",
"version": "v2"
}
] | 2011-08-08 | [
[
"Ohashi",
"Seiju",
""
],
[
"Shiromizu",
"Tetsuya",
""
],
[
"Jhingan",
"Sanjay",
""
]
] | We study gravitational collapse of a spherically symmetric inhomogeneous dust cloud in the Lovelock theory without cosmological constant. We show that the final fate of gravitational collapse in this theory depends on the spacetime dimensions. In odd dimensions the naked singularities formed are found to be massive. In the even dimensions,on the other hand, the naked singularities are found to be massless. We also show that the curvature strength of naked singularity is independent of the spacetime dimensions in odd dimensions. However, it depends on the spacetime dimensions in even dimension. |
gr-qc/0102083 | Christian Klein | Christian Klein | Exact relativistic treatment of stationary counter-rotating dust disks
I: Boundary value problems and solutions | 32 pages, 1 figure, to appear in Phys. Rev. D | Phys.Rev. D63 (2001) 064033 | 10.1103/PhysRevD.63.064033 | null | gr-qc | null | This is the first in a series of papers on the construction of explicit
solutions to the stationary axisymmetric Einstein equations which describe
counter-rotating disks of dust. These disks can serve as models for certain
galaxies and accretion disks in astrophysics. We review the Newtonian theory
for disks using Riemann-Hilbert methods which can be extended to some extent to
the relativistic case where they lead to modular functions on Riemann surfaces.
In the case of compact surfaces these are Korotkin's finite gap solutions which
we will discuss in this paper. On the axis we establish for general genus
relations between the metric functions and hence the multipoles which are
enforced by the underlying hyperelliptic Riemann surface. Generalizing these
results to the whole spacetime we are able in principle to study the classes of
boundary value problems which can be solved on a given Riemann surface. We
investigate the cases of genus 1 and 2 of the Riemann surface in detail and
construct the explicit solution for a family of disks with constant angular
velocity and constant relative energy density which was announced in a previous
Physical Review Letter.
| [
{
"created": "Mon, 19 Feb 2001 15:17:51 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Klein",
"Christian",
""
]
] | This is the first in a series of papers on the construction of explicit solutions to the stationary axisymmetric Einstein equations which describe counter-rotating disks of dust. These disks can serve as models for certain galaxies and accretion disks in astrophysics. We review the Newtonian theory for disks using Riemann-Hilbert methods which can be extended to some extent to the relativistic case where they lead to modular functions on Riemann surfaces. In the case of compact surfaces these are Korotkin's finite gap solutions which we will discuss in this paper. On the axis we establish for general genus relations between the metric functions and hence the multipoles which are enforced by the underlying hyperelliptic Riemann surface. Generalizing these results to the whole spacetime we are able in principle to study the classes of boundary value problems which can be solved on a given Riemann surface. We investigate the cases of genus 1 and 2 of the Riemann surface in detail and construct the explicit solution for a family of disks with constant angular velocity and constant relative energy density which was announced in a previous Physical Review Letter. |
1605.03893 | Jonathan Luk | Jonathan Luk, Sung-Jin Oh, Shiwu Yang | Solutions to the Einstein-scalar-field system in spherical symmetry with
large bounded variation norms | null | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that small, regular, spherically symmetric characteristic
initial data to the Einstein-scalar-field system which are decaying towards
(future null) infinity give rise to solutions which are foward-in-time global
(in the sense of future causal geodesic completeness). We construct a class of
spherically symmetric solutions which are global but the initial norms are
consistent with initial data not decaying towards infinity. This gives the
following consequences: (1) We prove that there exist foward-in-time global
solutions with arbitrarily large (and in fact infinite) initial bounded
variation (BV) norms and initial Bondi masses. (2) While general solutions with
non-decaying data do not approach Minkowski spacetime, we show using the
results of Luk--Oh that if a sufficiently strong asymptotic flatness condition
is imposed on the initial data, then the solutions we construct (with large BV
norms) approach Minkowski spacetime with a sharp inverse polynomial rate. (3)
Our construction can be easily extended so that data are posed at past null
infinity and we obtain solutions with large BV norms which are causally
geodesically complete both to the past and to the future. Finally, we discuss
applications of our method to construct global solutions for other nonlinear
wave equations with infinite critical norms.
| [
{
"created": "Thu, 12 May 2016 16:57:52 GMT",
"version": "v1"
}
] | 2016-05-13 | [
[
"Luk",
"Jonathan",
""
],
[
"Oh",
"Sung-Jin",
""
],
[
"Yang",
"Shiwu",
""
]
] | It is well-known that small, regular, spherically symmetric characteristic initial data to the Einstein-scalar-field system which are decaying towards (future null) infinity give rise to solutions which are foward-in-time global (in the sense of future causal geodesic completeness). We construct a class of spherically symmetric solutions which are global but the initial norms are consistent with initial data not decaying towards infinity. This gives the following consequences: (1) We prove that there exist foward-in-time global solutions with arbitrarily large (and in fact infinite) initial bounded variation (BV) norms and initial Bondi masses. (2) While general solutions with non-decaying data do not approach Minkowski spacetime, we show using the results of Luk--Oh that if a sufficiently strong asymptotic flatness condition is imposed on the initial data, then the solutions we construct (with large BV norms) approach Minkowski spacetime with a sharp inverse polynomial rate. (3) Our construction can be easily extended so that data are posed at past null infinity and we obtain solutions with large BV norms which are causally geodesically complete both to the past and to the future. Finally, we discuss applications of our method to construct global solutions for other nonlinear wave equations with infinite critical norms. |
1008.2810 | Sascha Vongehr | Sascha Vongehr | Metric Expansion from Microscopic Dynamics in an Inhomogeneous Universe | 23 pages, no figures | Communications in Theoretical Physics 54 (3) pp. 477-483 (2010) | 10.1088/0253-6102/54/3/20 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories with ingredients like the Higgs mechanism, gravitons, and inflaton
fields rejuvenate the idea that relativistic kinematics is dynamically
emergent. Eternal inflation treats the Hubble constant H as depending on
location. Microscopic dynamics implies that H is over much smaller lengths than
pocket universes to be understood as a local space reproduction rate. We
illustrate this via discussing that even exponential inflation in TeV-gravity
is slow on the relevant time scale. In our on small scales inhomogeneous
cosmos, a reproduction rate H depends on position. We therefore discuss
Einstein-Straus vacuoles and a Lindquist-Wheeler like lattice to connect the
local rate properly with the scaling of an expanding cosmos. Consistency allows
H to locally depend on Weyl curvature similar to vacuum polarization. We derive
a proportionality constant known from Kepler's third law and discuss the
implications for the finiteness of the cosmological constant.
| [
{
"created": "Tue, 17 Aug 2010 03:52:12 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Vongehr",
"Sascha",
""
]
] | Theories with ingredients like the Higgs mechanism, gravitons, and inflaton fields rejuvenate the idea that relativistic kinematics is dynamically emergent. Eternal inflation treats the Hubble constant H as depending on location. Microscopic dynamics implies that H is over much smaller lengths than pocket universes to be understood as a local space reproduction rate. We illustrate this via discussing that even exponential inflation in TeV-gravity is slow on the relevant time scale. In our on small scales inhomogeneous cosmos, a reproduction rate H depends on position. We therefore discuss Einstein-Straus vacuoles and a Lindquist-Wheeler like lattice to connect the local rate properly with the scaling of an expanding cosmos. Consistency allows H to locally depend on Weyl curvature similar to vacuum polarization. We derive a proportionality constant known from Kepler's third law and discuss the implications for the finiteness of the cosmological constant. |
1602.00608 | Julien Larena | Jean-Philippe Bruneton and Julien Larena | Quantum theory of the Generalised Uncertainty Principle | 21 pages, no figures. Results unchanged. Unnecessary Appendix B
removed. Replaced to match final version published in General Relativity and
Gravitation. Title shortened at the request of the referee | Gen Relativ Gravit (2017) 49: 56 | 10.1007/s10714-017-2220-0 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend significantly previous works on the Hilbert space representations
of the Generalized Uncertainty Principle (GUP) in 3+1 dimensions of the form
$[X_i,P_j] = i F_{ij}$ where $ F_{ij} = f(P^2) \delta_{ij} + g(P^2) P_i P_j $
for any functions $f$. However, we restrict our study to the case of commuting
$X$'s. We focus in particular on the symmetries of the theory, and the minimal
length that emerge in some cases. We first show that, at the algebraic level,
there exists an unambiguous mapping between the GUP with a deformed quantum
algebra and a quadratic Hamiltonian into a standard, Heisenberg algebra of
operators and an aquadratic Hamiltonian, provided the boost sector of the
symmetries is modified accordingly. The theory can also be mapped to a
completely standard Quantum Mechanics with standard symmetries, but with
momentum dependent position operators. Next, we investigate the Hilbert space
representations of these algebraically equivalent models, and focus,
specifically on whether they exhibit a minimal length. We carry the functional
analysis of the various operators involved, and show that the appearance of a
minimal length critically depends on the relationship between the generators of
translations and the physical momenta. In particular, because this relationship
is preserved by the algebraic mapping presented in this paper, when a minimal
length is present in the standard GUP, it is also present in the corresponding
Aquadratic Hamiltonian formulation, despite the perfectly standard algebra of
this model. In general, a minimal length requires bounded generators of
translations, i.e. a specific kind of quantization of space, and this depends
on the precise shape of the function $f$ defined previously. This result
provides an elegant and unambiguous classification of which universal quantum
gravity corrections lead to the emergence of a minimal length.
| [
{
"created": "Mon, 1 Feb 2016 17:38:48 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Mar 2017 08:18:45 GMT",
"version": "v2"
}
] | 2017-03-22 | [
[
"Bruneton",
"Jean-Philippe",
""
],
[
"Larena",
"Julien",
""
]
] | We extend significantly previous works on the Hilbert space representations of the Generalized Uncertainty Principle (GUP) in 3+1 dimensions of the form $[X_i,P_j] = i F_{ij}$ where $ F_{ij} = f(P^2) \delta_{ij} + g(P^2) P_i P_j $ for any functions $f$. However, we restrict our study to the case of commuting $X$'s. We focus in particular on the symmetries of the theory, and the minimal length that emerge in some cases. We first show that, at the algebraic level, there exists an unambiguous mapping between the GUP with a deformed quantum algebra and a quadratic Hamiltonian into a standard, Heisenberg algebra of operators and an aquadratic Hamiltonian, provided the boost sector of the symmetries is modified accordingly. The theory can also be mapped to a completely standard Quantum Mechanics with standard symmetries, but with momentum dependent position operators. Next, we investigate the Hilbert space representations of these algebraically equivalent models, and focus, specifically on whether they exhibit a minimal length. We carry the functional analysis of the various operators involved, and show that the appearance of a minimal length critically depends on the relationship between the generators of translations and the physical momenta. In particular, because this relationship is preserved by the algebraic mapping presented in this paper, when a minimal length is present in the standard GUP, it is also present in the corresponding Aquadratic Hamiltonian formulation, despite the perfectly standard algebra of this model. In general, a minimal length requires bounded generators of translations, i.e. a specific kind of quantization of space, and this depends on the precise shape of the function $f$ defined previously. This result provides an elegant and unambiguous classification of which universal quantum gravity corrections lead to the emergence of a minimal length. |
2301.05268 | Chris Stevens | J\"org Frauendiener, Alex Goodenbour, Chris Stevens | The non-linear perturbation of a black hole by gravitational waves. III.
Newman-Penrose constants | 17 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we continue our study of the non-linear response of a
Schwarzschild black hole to an ingoing gravitational wave by computing the
Newman-Penrose (NP) constants. The NP constants are five complex,
supertranslation-invariant quantities defined on null infinity $\mathscr{I}^+$
and although put forward in the 60's, they have never been computed in a
non-stationary setting. We accomplish this through a numerical implementation
of Friedrich's generalized conformal field equations whose semi-global
evolution yields direct access to $\mathscr{I}+$. Generalizations of the NP
constants' integral expressions are made to allow their computation in a more
general gauge that better suits the output of a numerical evolution. Canonical
methods of fixing inherent degrees of freedom in their definitions are
discussed. The NP constants are then computed for a variety of different
ingoing wave profiles in axisymmetry, and then with no symmetry assumptions in
3+1 for which all five are non-zero.
| [
{
"created": "Thu, 12 Jan 2023 19:32:28 GMT",
"version": "v1"
}
] | 2023-01-16 | [
[
"Frauendiener",
"Jörg",
""
],
[
"Goodenbour",
"Alex",
""
],
[
"Stevens",
"Chris",
""
]
] | In this paper we continue our study of the non-linear response of a Schwarzschild black hole to an ingoing gravitational wave by computing the Newman-Penrose (NP) constants. The NP constants are five complex, supertranslation-invariant quantities defined on null infinity $\mathscr{I}^+$ and although put forward in the 60's, they have never been computed in a non-stationary setting. We accomplish this through a numerical implementation of Friedrich's generalized conformal field equations whose semi-global evolution yields direct access to $\mathscr{I}+$. Generalizations of the NP constants' integral expressions are made to allow their computation in a more general gauge that better suits the output of a numerical evolution. Canonical methods of fixing inherent degrees of freedom in their definitions are discussed. The NP constants are then computed for a variety of different ingoing wave profiles in axisymmetry, and then with no symmetry assumptions in 3+1 for which all five are non-zero. |
2201.01946 | Hideki Asada | Ryuya Kudo, Hideki Asada | Nondivergent deflection of light around a photon sphere of a compact
object | 10 pages, 4 figures, OSPS corrected to SOPS, potential added, figure
2 replaced, accepted for PRD | Phys. Rev. D 105, 084014 (2022) | 10.1103/PhysRevD.105.084014 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We demonstrate that the location of a stable photon sphere (PS) in a compact
object is not always an edge such as the inner boundary of a black hole shadow,
whereas the location of an unstable PS is known to be the shadow edge notably
in the Schwarzschild black hole. If a static spherically symmetric (SSS)
spacetime has the stable outermost PS, the spacetime cannot be asymptotically
flat. A nondivergent deflection is caused for a photon traveling around a
stable PS, though a logarithmic divergent behavior is known to appear in most
of SSS compact objects with an unstable photon sphere. The reason for the
nondivergence is that the closest approach of a photon is prohibited in the
immediate vicinity of the stable PS when the photon is emitted from a source
(or reaches a receiver) distant from a lens object. The finite gap size depends
on the receiver and source distances from the lens as well as the lens
parameters. The mild deflection angle of light can be approximated by an
arcsine function. A class of SSS solutions in Weyl gravity exemplify the
nondivergent deflection near the stable outer PS.
| [
{
"created": "Thu, 6 Jan 2022 07:27:08 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Mar 2022 23:57:13 GMT",
"version": "v2"
}
] | 2022-06-08 | [
[
"Kudo",
"Ryuya",
""
],
[
"Asada",
"Hideki",
""
]
] | We demonstrate that the location of a stable photon sphere (PS) in a compact object is not always an edge such as the inner boundary of a black hole shadow, whereas the location of an unstable PS is known to be the shadow edge notably in the Schwarzschild black hole. If a static spherically symmetric (SSS) spacetime has the stable outermost PS, the spacetime cannot be asymptotically flat. A nondivergent deflection is caused for a photon traveling around a stable PS, though a logarithmic divergent behavior is known to appear in most of SSS compact objects with an unstable photon sphere. The reason for the nondivergence is that the closest approach of a photon is prohibited in the immediate vicinity of the stable PS when the photon is emitted from a source (or reaches a receiver) distant from a lens object. The finite gap size depends on the receiver and source distances from the lens as well as the lens parameters. The mild deflection angle of light can be approximated by an arcsine function. A class of SSS solutions in Weyl gravity exemplify the nondivergent deflection near the stable outer PS. |
gr-qc/9308022 | Salman Habib | Salman Habib | Multiplicative Noise: Applications in Cosmology and Field Theory | 21 pages, LaTex, LA-UR-93-2105 | null | 10.1111/j.1749-6632.1993.tb24685.x | null | gr-qc hep-th | null | Physical situations involving multiplicative noise arise generically in
cosmology and field theory. In this paper, the focus is first on exact
nonlinear Langevin equations, appropriate in a cosmologica setting, for a
system with one degree of freedom. The Langevin equations are derived using an
appropriate time-dependent generalization of a model due to Zwanzig. These
models are then extended to field theories and the generation of multiplicative
noise in such a context is discussed. Important issues in both the cosmological
and field theoretic cases are the fluctuation-dissipation relations and the
relaxation time scale. Of some importance in cosmology is the fact that
multiplicative noise can substantially reduce the relaxation time. In the field
theoretic context such a noise can lead to a significant enhancement in the
nucleation rate of topological defects.
| [
{
"created": "Sat, 21 Aug 1993 03:46:45 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Habib",
"Salman",
""
]
] | Physical situations involving multiplicative noise arise generically in cosmology and field theory. In this paper, the focus is first on exact nonlinear Langevin equations, appropriate in a cosmologica setting, for a system with one degree of freedom. The Langevin equations are derived using an appropriate time-dependent generalization of a model due to Zwanzig. These models are then extended to field theories and the generation of multiplicative noise in such a context is discussed. Important issues in both the cosmological and field theoretic cases are the fluctuation-dissipation relations and the relaxation time scale. Of some importance in cosmology is the fact that multiplicative noise can substantially reduce the relaxation time. In the field theoretic context such a noise can lead to a significant enhancement in the nucleation rate of topological defects. |
0704.0332 | Timothy Sumner | M.B. Gerrard and T.J. Sumner | The effect of a fifth large-scale space-time dimension on the
conservation of energy in a four dimensional Universe | 9 pages, 2 figures version update to correct figure placement Final
update to include corrected typos and two additional equations | null | null | null | gr-qc | null | The effect of introducing a fifth large-scale space-time dimension to the
equations of orbital dynamics was analysed in an earlier paper by the authors.
The results showed good agreement with the observed flat rotation curves of
galaxies and the Pioneer Anomaly. This analysis did not require the
modification of Newtonian dynamics, but rather only their restatement in a five
dimensional framework. The same analysis derived a acceleration parameter ar,
which plays an important role in the restated equations of orbital dynamics,
and suggested a value for ar. In this companion paper, the principle of
conservation of energy is restated within the same five-dimensional framework.
The resulting analysis provides an alternative route to estimating the value of
ar, without reference to the equations of orbital dynamics, and based solely on
key cosmological constants and parameters, including the gravitational
constant, G. The same analysis suggests that: (i) the inverse square law of
gravity may itself be due to the conservation of energy at the boundary between
a four-dimensional universe and a fifth large-scale space-time dimension; and
(ii) there is a limiting case for the Tulley-Fisher relationship linking the
speed of light to the mass of the Universe.
| [
{
"created": "Tue, 3 Apr 2007 17:58:45 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Apr 2007 22:27:57 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Apr 2007 12:45:49 GMT",
"version": "v3"
},
{
"created": "Wed, 10 Oct 2007 13:10:38 GMT",
"version": "v4"
}
] | 2007-10-10 | [
[
"Gerrard",
"M. B.",
""
],
[
"Sumner",
"T. J.",
""
]
] | The effect of introducing a fifth large-scale space-time dimension to the equations of orbital dynamics was analysed in an earlier paper by the authors. The results showed good agreement with the observed flat rotation curves of galaxies and the Pioneer Anomaly. This analysis did not require the modification of Newtonian dynamics, but rather only their restatement in a five dimensional framework. The same analysis derived a acceleration parameter ar, which plays an important role in the restated equations of orbital dynamics, and suggested a value for ar. In this companion paper, the principle of conservation of energy is restated within the same five-dimensional framework. The resulting analysis provides an alternative route to estimating the value of ar, without reference to the equations of orbital dynamics, and based solely on key cosmological constants and parameters, including the gravitational constant, G. The same analysis suggests that: (i) the inverse square law of gravity may itself be due to the conservation of energy at the boundary between a four-dimensional universe and a fifth large-scale space-time dimension; and (ii) there is a limiting case for the Tulley-Fisher relationship linking the speed of light to the mass of the Universe. |
2007.05967 | Sergey Paston | A.D. Kapustin, S.A. Paston | Explicit isometric embeddings of black holes geometry with non-singular
matter distribution | LaTeX, 8 pages | Journal of Physics: Conference Series 1697 (2020) 012082 | 10.1088/1742-6596/1697/1/012082 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The work is devoted to the construction of explicit embeddings for the
metrics of the black holes, formed by nonsingular matter distribution. One of
the possible examples of such type of solutions is regular black hole. Using
the existing classification of minimal symmetric embeddings of the
Schwarzschild metric as a base, we construct embeddings for regular black holes
with de Sitter interior. Another simple example is black hole, formed by
collapsing homogeneous spherically symmetric cloud of dustlike matter. We
discuss embeddings for two variants of such black holes - the one with the
eternally existing horizon, when dust ball never leaves the interior of the
horizon, and another variant with the dynamically forming horizon.
| [
{
"created": "Sun, 12 Jul 2020 11:53:40 GMT",
"version": "v1"
}
] | 2021-06-08 | [
[
"Kapustin",
"A. D.",
""
],
[
"Paston",
"S. A.",
""
]
] | The work is devoted to the construction of explicit embeddings for the metrics of the black holes, formed by nonsingular matter distribution. One of the possible examples of such type of solutions is regular black hole. Using the existing classification of minimal symmetric embeddings of the Schwarzschild metric as a base, we construct embeddings for regular black holes with de Sitter interior. Another simple example is black hole, formed by collapsing homogeneous spherically symmetric cloud of dustlike matter. We discuss embeddings for two variants of such black holes - the one with the eternally existing horizon, when dust ball never leaves the interior of the horizon, and another variant with the dynamically forming horizon. |
gr-qc/0510077 | Sergei Kopeikin | Sergei M. Kopeikin (University of Missouri-Columbia, USA) and Edward
B. Fomalont (National Radio Astronomy Observatory, USA) | Gravimagnetism, Causality, and Aberration of Gravity in the
Gravitational Light-Ray Deflection Experiments | 44 pages including references, 7 figures, 1 table; accepted for
publication in General Relativity and Gravitation | Gen.Rel.Grav.39:1583-1624,2007 | 10.1007/s10714-007-0483-6 | null | gr-qc astro-ph | null | Experimental verification of the existence of gravimagnetic fields generated
by currents of matter is important for a complete understanding and formulation
of gravitational physics. Although the rotational `intrinsic' gravimagnetic
field has been extensively studied and is now being measured by the Gravity
Probe B, the `extrinsic' gravimagnetic field generated by the translational
current of matter is less well studied. The present paper uses the
post-Newtonian parametrized Einstein and light geodesics equations to show that
the `extrinsic' gravimagnetic field generated by the translational current of
matter can be measured by observing the relativistic time delay and/or light
deflection caused by the moving mass. We prove that the `extrinsic'
gravimagnetic field is generated by the relativistic effect of the aberration
of the gravity force caused by the Lorentz transformation of the metric tensor
and the Levi-Civita connection. We show that the Lorentz transformation of the
gravity field variables is equivalent to the technique of the retarded
Lienard-Wiechert gravitational potentials predicting that a light particle is
deflected by gravitational field of a moving body from its retarded position so
that both general-relativistic phenomena -- the aberration and the retardation
of gravity -- are tightly connected and observing the aberration of gravity
proves that gravity has a causal nature. We explain in this framework the 2002
deflection experiment of a quasar by Jupiter where the aberration of gravity
from its orbital motion was measured with accuracy 20%. We describe a theory of
VLBI experiment to measure the gravitational deflection of radio waves from a
quasar by the Sun, as viewed by a moving observer from the geocentric frame, to
improve the measurement accuracy of the aberration of gravity to a few percent.
| [
{
"created": "Sun, 16 Oct 2005 20:54:46 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Oct 2006 15:47:33 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Jan 2007 20:33:06 GMT",
"version": "v3"
},
{
"created": "Tue, 29 May 2007 22:17:32 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Kopeikin",
"Sergei M.",
"",
"University of Missouri-Columbia, USA"
],
[
"Fomalont",
"Edward B.",
"",
"National Radio Astronomy Observatory, USA"
]
] | Experimental verification of the existence of gravimagnetic fields generated by currents of matter is important for a complete understanding and formulation of gravitational physics. Although the rotational `intrinsic' gravimagnetic field has been extensively studied and is now being measured by the Gravity Probe B, the `extrinsic' gravimagnetic field generated by the translational current of matter is less well studied. The present paper uses the post-Newtonian parametrized Einstein and light geodesics equations to show that the `extrinsic' gravimagnetic field generated by the translational current of matter can be measured by observing the relativistic time delay and/or light deflection caused by the moving mass. We prove that the `extrinsic' gravimagnetic field is generated by the relativistic effect of the aberration of the gravity force caused by the Lorentz transformation of the metric tensor and the Levi-Civita connection. We show that the Lorentz transformation of the gravity field variables is equivalent to the technique of the retarded Lienard-Wiechert gravitational potentials predicting that a light particle is deflected by gravitational field of a moving body from its retarded position so that both general-relativistic phenomena -- the aberration and the retardation of gravity -- are tightly connected and observing the aberration of gravity proves that gravity has a causal nature. We explain in this framework the 2002 deflection experiment of a quasar by Jupiter where the aberration of gravity from its orbital motion was measured with accuracy 20%. We describe a theory of VLBI experiment to measure the gravitational deflection of radio waves from a quasar by the Sun, as viewed by a moving observer from the geocentric frame, to improve the measurement accuracy of the aberration of gravity to a few percent. |
gr-qc/0408063 | Volodymyr Pelykh | V. Pelykh | Sen-Witten orthonormal three-frame and gravitational energy
quasilocalization | 9 pages | Class.Quant.Grav. 20 (2003) 1115-1123 | 10.1088/0264-9381/20/6/306 | null | gr-qc | null | Expression for the Witten-Nester 4-spinor 3-form of the Hamiltonian density
of gravitational field in the asymptotically flat space-time in terms of the
Sommers-Sen spinors, direct with a certain orthonormal three-frame connect, is
obtained. A direct connection between the one and the ADM Hamiltonian density
in the Sen-Witten frame is established on this basis.
| [
{
"created": "Wed, 18 Aug 2004 13:49:28 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Pelykh",
"V.",
""
]
] | Expression for the Witten-Nester 4-spinor 3-form of the Hamiltonian density of gravitational field in the asymptotically flat space-time in terms of the Sommers-Sen spinors, direct with a certain orthonormal three-frame connect, is obtained. A direct connection between the one and the ADM Hamiltonian density in the Sen-Witten frame is established on this basis. |
2210.11351 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Generalized $R^p$-attractor Cosmology in the Jordan and Einstein Frames:
New Type of Attractors and Revisiting Standard Jordan Frame $R^p$ Inflation | IJMPD Accepted | null | 10.1142/S0218271822501358 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we shall study a new class of attractor models which we shall
call generalized $R^p$-attractor models. This class of models is based on a
generalization of the Einstein frame potential of $R^p$ $f(R)$ gravity models
in the Jordan frame. We present the attractor properties of the corresponding
non-minimally coupled Jordan frame theory, and we calculate the observational
indices of inflation in the Einstein frame. As we show, there is a large class
of non-minimally coupled scalar theories, with an arbitrary non-minimal
coupling which satisfies certain conditions, that yield the same Einstein frame
potential, this is why these models are characterized attractors. As we
demonstrate, the generalized $R^p$-attractor models are viable and well fitted
within the Planck constraints. This includes the subclass of the generalized
$R^p$-attractor models, namely the Einstein frame potential of $R^p$ inflation
in the Jordan frame, a feature also known in the literature. We also highlight
an important issue related to the $R^p$ inflation in the Jordan frame, which is
known to be non-viable. By conformal invariance, the $R^p$ inflation model
should also be viable in the Jordan frame, which is not. We pinpoint the source
of the problem using two different approaches in the $f(R)$ gravity Jordan
frame, and as we demonstrate, the problem arises in the literature due to some
standard simplifications made for the sake of analyticity. We demonstrate the
correct way to analyze $R^p$ inflation in the Jordan frame, using solely the
slow-roll conditions.
| [
{
"created": "Thu, 20 Oct 2022 15:38:33 GMT",
"version": "v1"
}
] | 2023-02-08 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | In this work we shall study a new class of attractor models which we shall call generalized $R^p$-attractor models. This class of models is based on a generalization of the Einstein frame potential of $R^p$ $f(R)$ gravity models in the Jordan frame. We present the attractor properties of the corresponding non-minimally coupled Jordan frame theory, and we calculate the observational indices of inflation in the Einstein frame. As we show, there is a large class of non-minimally coupled scalar theories, with an arbitrary non-minimal coupling which satisfies certain conditions, that yield the same Einstein frame potential, this is why these models are characterized attractors. As we demonstrate, the generalized $R^p$-attractor models are viable and well fitted within the Planck constraints. This includes the subclass of the generalized $R^p$-attractor models, namely the Einstein frame potential of $R^p$ inflation in the Jordan frame, a feature also known in the literature. We also highlight an important issue related to the $R^p$ inflation in the Jordan frame, which is known to be non-viable. By conformal invariance, the $R^p$ inflation model should also be viable in the Jordan frame, which is not. We pinpoint the source of the problem using two different approaches in the $f(R)$ gravity Jordan frame, and as we demonstrate, the problem arises in the literature due to some standard simplifications made for the sake of analyticity. We demonstrate the correct way to analyze $R^p$ inflation in the Jordan frame, using solely the slow-roll conditions. |
1708.00603 | Sunny Vagnozzi | Sunny Vagnozzi | Recovering a MOND-like acceleration law in mimetic gravity | 11 pages, accepted for publication in Class. Quant. Grav | Class. Quant. Grav. 34 (2017) 185006 | 10.1088/1361-6382/aa838b | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider the recently proposed mimetic gravity, focusing in particular
on whether the theory is able to reproduce the inferred flat rotation curves of
galaxies. We extend the theory by adding a non-minimal coupling between matter
and mimetic field. Such coupling leads to the appearance of an extra force
which renders the motion of test particles non-geodesic. By studying the weak
field limit of the resulting equations of motion, we demonstrate that in the
Newtonian limit the acceleration law induced by the non-minimal coupling
reduces to a Modified Newtonian Dynamics (MOND)-like one. In this way, it is
possible to reproduce the successes of MOND, namely the explanation for the
flat galactic rotation curves and the Tully-Fisher relation, within the
framework of mimetic gravity, without the need for particle dark matter. The
scale-dependence of the recovered acceleration scale opens up the possibility
of addressing the missing mass problem not only on galactic but also on cluster
scales: we defer a full study of this issue, together with a complete analysis
of fits to spiral galaxy rotation curves, to an upcoming companion paper.
| [
{
"created": "Wed, 2 Aug 2017 05:02:07 GMT",
"version": "v1"
}
] | 2018-12-13 | [
[
"Vagnozzi",
"Sunny",
""
]
] | We reconsider the recently proposed mimetic gravity, focusing in particular on whether the theory is able to reproduce the inferred flat rotation curves of galaxies. We extend the theory by adding a non-minimal coupling between matter and mimetic field. Such coupling leads to the appearance of an extra force which renders the motion of test particles non-geodesic. By studying the weak field limit of the resulting equations of motion, we demonstrate that in the Newtonian limit the acceleration law induced by the non-minimal coupling reduces to a Modified Newtonian Dynamics (MOND)-like one. In this way, it is possible to reproduce the successes of MOND, namely the explanation for the flat galactic rotation curves and the Tully-Fisher relation, within the framework of mimetic gravity, without the need for particle dark matter. The scale-dependence of the recovered acceleration scale opens up the possibility of addressing the missing mass problem not only on galactic but also on cluster scales: we defer a full study of this issue, together with a complete analysis of fits to spiral galaxy rotation curves, to an upcoming companion paper. |
1910.13259 | Changqing Liu Lcqliu | Changqing Liu Chikun Ding, Jiliang Jing | Thin accretion disk around a rotating Kerr-like black hole in
Einstein-bumblebee gravity model | 14 figures. arXiv admin note: substantial text overlap with
arXiv:1110.3462, arXiv:1106.5183; text overlap with arXiv:0909.1267 by other
authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the accretion process in the thin disk around a rotating Kerr-like
black hole in Einstein-bumblebee gravity model where Lorentz symmetry is
spontaneously broken once a vector field acquires a vacuum expectation value.
In the present paper we obtain the energy flux, the emission spectrum and
accretion efficiency from the accretion disks around the rotating Kerr-like
black hole, and we compare them to the general Kerr case. These significant
features in the mass accretion process may provide a possibility to test
whether the Lorentz symmetry is spontaneously broken or not in the
Einstein-bumblebee gravity model by future astronomical observations.
| [
{
"created": "Sat, 26 Oct 2019 11:52:18 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Nov 2019 02:47:34 GMT",
"version": "v2"
}
] | 2019-11-07 | [
[
"Ding",
"Changqing Liu Chikun",
""
],
[
"Jing",
"Jiliang",
""
]
] | We study the accretion process in the thin disk around a rotating Kerr-like black hole in Einstein-bumblebee gravity model where Lorentz symmetry is spontaneously broken once a vector field acquires a vacuum expectation value. In the present paper we obtain the energy flux, the emission spectrum and accretion efficiency from the accretion disks around the rotating Kerr-like black hole, and we compare them to the general Kerr case. These significant features in the mass accretion process may provide a possibility to test whether the Lorentz symmetry is spontaneously broken or not in the Einstein-bumblebee gravity model by future astronomical observations. |
1505.01518 | Juan D Reyes | Alejandro Corichi and Juan D. Reyes | The gravitational Hamiltonian, first order action, Poincar\'e charges
and surface terms | 56 pages, 4 figures. Minor typos corrected and references added. File
matches published version | Class. Quantum Grav. 32 (2015) 195024 | 10.1088/0264-9381/32/19/195024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the issue of attaining a consistent Hamiltonian formulation,
after a 3+1 splitting, of a well defined action principle for asymptotically
flat gravity. More precisely, our starting point is the gravitational first
order Holst action with surface terms and fall-off conditions that make the
variational principle and the covariant phase space formulation well defined
for asymptotically flat spacetimes. Keeping all surface terms and paying due
attention to subtleties that arise from the different cut-offs at infinity, we
give a derivation of the gravitational Hamiltonian starting from this action.
The 3+1 decomposition and time gauge fixing results in a well defined
Hamiltonian action and a well defined Hamiltonian formulation for the standard
-and more general- asymptotic ADM conditions. Unlike the case of the
Einstein-Hilbert action with Gibbons-Hawking-York or Hawking-Horowitz terms,
here we {\it {do}} recover the ADM energy-momentum from the covariant surface
term also when more general variations respecting asymptotic flatness are
allowed. Additionally, our strategy yields a derivation of the parity
conditions for connection variables independent of the conditions given by
Regge and Teitelboim for ADM variables. Finally, we exhibit the other
Poincar\'e generators in terms of real Ashtekar-Barbero variables. We
complement previous constructions in self-dual variables by pointing out
several subtleties and refining the argument showing that -on shell- they
coincide with the ADM charges. Our results represent the first consistent
treatment of the Hamiltonian formulation for the connection-tetrad
gravitational degrees of freedom, starting from a well posed action, in the
case of asymptotically flat boundary conditions.
| [
{
"created": "Wed, 6 May 2015 21:04:49 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2015 22:44:01 GMT",
"version": "v2"
}
] | 2015-11-09 | [
[
"Corichi",
"Alejandro",
""
],
[
"Reyes",
"Juan D.",
""
]
] | We consider the issue of attaining a consistent Hamiltonian formulation, after a 3+1 splitting, of a well defined action principle for asymptotically flat gravity. More precisely, our starting point is the gravitational first order Holst action with surface terms and fall-off conditions that make the variational principle and the covariant phase space formulation well defined for asymptotically flat spacetimes. Keeping all surface terms and paying due attention to subtleties that arise from the different cut-offs at infinity, we give a derivation of the gravitational Hamiltonian starting from this action. The 3+1 decomposition and time gauge fixing results in a well defined Hamiltonian action and a well defined Hamiltonian formulation for the standard -and more general- asymptotic ADM conditions. Unlike the case of the Einstein-Hilbert action with Gibbons-Hawking-York or Hawking-Horowitz terms, here we {\it {do}} recover the ADM energy-momentum from the covariant surface term also when more general variations respecting asymptotic flatness are allowed. Additionally, our strategy yields a derivation of the parity conditions for connection variables independent of the conditions given by Regge and Teitelboim for ADM variables. Finally, we exhibit the other Poincar\'e generators in terms of real Ashtekar-Barbero variables. We complement previous constructions in self-dual variables by pointing out several subtleties and refining the argument showing that -on shell- they coincide with the ADM charges. Our results represent the first consistent treatment of the Hamiltonian formulation for the connection-tetrad gravitational degrees of freedom, starting from a well posed action, in the case of asymptotically flat boundary conditions. |
1602.04738 | Alexander Zhidenko | Roman Konoplya and Alexander Zhidenko | Detection of gravitational waves from black holes: Is there a window for
alternative theories? | 5 pages, 1 figure | Phys.Lett.B756:350-353,2016 | 10.1016/j.physletb.2016.03.044 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently LIGO and VIRGO collaborations reported about observation of
gravitational-wave signal corresponding to the inspiral and merger of two black
holes, resulting into formation of the final black hole. It was shown that the
observations are consistent with the Einstein theory of gravity with high
accuracy limited mainly by the statistical error. Angular momentum and mass of
the final black hole were determined with rather large allowance of tens of
percents. Here we shall show that this indeterminacy in the range of the
black-hole parameters allows for some not negligible deformations of the Kerr
spacetime leading to the same frequencies of black-hole ringing. This means
that at the current precision of the experiment there remain some possibilities
for alternative theories of gravity.
| [
{
"created": "Mon, 15 Feb 2016 17:08:33 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2016 10:32:19 GMT",
"version": "v2"
},
{
"created": "Sat, 19 Mar 2016 18:07:37 GMT",
"version": "v3"
}
] | 2016-03-28 | [
[
"Konoplya",
"Roman",
""
],
[
"Zhidenko",
"Alexander",
""
]
] | Recently LIGO and VIRGO collaborations reported about observation of gravitational-wave signal corresponding to the inspiral and merger of two black holes, resulting into formation of the final black hole. It was shown that the observations are consistent with the Einstein theory of gravity with high accuracy limited mainly by the statistical error. Angular momentum and mass of the final black hole were determined with rather large allowance of tens of percents. Here we shall show that this indeterminacy in the range of the black-hole parameters allows for some not negligible deformations of the Kerr spacetime leading to the same frequencies of black-hole ringing. This means that at the current precision of the experiment there remain some possibilities for alternative theories of gravity. |
gr-qc/9912115 | Chunho Choi | Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh, and Jae Hyung
Yee | Gravitational Collapse and Calogero Model | null | null | 10.1103/PhysRevD.62.047504 | SNUTP 99-056 | gr-qc | null | We study the analytic structure of the S-matrix which is obtained from the
reduced Wheeler-DeWitt wave function describing spherically symmetric
gravitational collapse of massless scalar fields. The simple poles in the
S-matrix occur in the Euclidean spacetime, and the Euclidean Wheeler-DeWitt
equation is a variant of the Calogero models, which is discussed in connection
with conformal mechanics and a quantum instanton.
| [
{
"created": "Wed, 29 Dec 1999 09:03:03 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Bak",
"Dongsu",
""
],
[
"Kim",
"Sang Pyo",
""
],
[
"Kim",
"Sung Ku",
""
],
[
"Soh",
"Kwang-Sup",
""
],
[
"Yee",
"Jae Hyung",
""
]
] | We study the analytic structure of the S-matrix which is obtained from the reduced Wheeler-DeWitt wave function describing spherically symmetric gravitational collapse of massless scalar fields. The simple poles in the S-matrix occur in the Euclidean spacetime, and the Euclidean Wheeler-DeWitt equation is a variant of the Calogero models, which is discussed in connection with conformal mechanics and a quantum instanton. |
2102.08944 | Fay\c{c}al Hammad | F. Hammad, A. Landry, D. Dijamco | Influence of the dispersion relation on the Unruh effect according to
the relativistic Doppler shift method | 13 pages, no figures. To appear in PRD | Phys. Rev. D 103, 085010 (2021) | 10.1103/PhysRevD.103.085010 | null | gr-qc hep-th physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the influence of the dispersion relation on the Unruh effect by
Lorentz boosting the phase of Minkowski vacuum fluctuations endowed with an
arbitrary dispersion relation. We find that, unlike what happens with a linear
dispersion relation exhibited by massless fields, thermality is lost for
general dispersion relations. We show that thermality emerges with a varying
"apparent" Davies-Unruh temperature depending on the acceleration of the
observer and on the degree of departure from linearity of the dispersion
relation. The approach has the advantage of being intuitive and able to
pinpoint why such a loss of thermality occurs and when such a deviation from
thermality becomes significant. We discuss the link of our results with the
well-known fundamental difference between the thermalization theorem and the
concept of Rindler noise. We examine the possible experimental validation of
our results based on a successful setup for testing the classical analogue of
the Unruh effect recently described in the literature.
| [
{
"created": "Wed, 17 Feb 2021 18:56:57 GMT",
"version": "v1"
}
] | 2021-04-28 | [
[
"Hammad",
"F.",
""
],
[
"Landry",
"A.",
""
],
[
"Dijamco",
"D.",
""
]
] | We examine the influence of the dispersion relation on the Unruh effect by Lorentz boosting the phase of Minkowski vacuum fluctuations endowed with an arbitrary dispersion relation. We find that, unlike what happens with a linear dispersion relation exhibited by massless fields, thermality is lost for general dispersion relations. We show that thermality emerges with a varying "apparent" Davies-Unruh temperature depending on the acceleration of the observer and on the degree of departure from linearity of the dispersion relation. The approach has the advantage of being intuitive and able to pinpoint why such a loss of thermality occurs and when such a deviation from thermality becomes significant. We discuss the link of our results with the well-known fundamental difference between the thermalization theorem and the concept of Rindler noise. We examine the possible experimental validation of our results based on a successful setup for testing the classical analogue of the Unruh effect recently described in the literature. |
1010.1269 | Andrew J. S. Hamilton | Andrew J. S. Hamilton and Gavin Polhemus (JILA) | The interior structure of rotating black holes 1. Concise derivation | Version 1: 8 pages, 3 figures. Version 2: Extensively revised to
emphasize the derivation of the solution rather than the solution itself. 11
pages, 4 figures. Version 3: Minor changes to match published version.
Mathematica notebook available at
http://jila.colorado.edu/~ajsh/rotatinginflationary/rotatinginflationary.nb | Phys. Rev. D 84, 124055 (2011) | 10.1103/PhysRevD.84.124055 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents a concise derivation of a new set of solutions for the
interior structure of accreting, rotating black holes. The solutions are
conformally stationary, axisymmetric, and conformally separable.
Hyper-relativistic counter-streaming between freely-falling collisionless
ingoing and outgoing streams leads to mass inflation at the inner horizon,
followed by collapse. The solutions fail at an exponentially tiny radius, where
the rotational motion of the streams becomes comparable to their radial motion.
The papers provide a fully nonlinear, dynamical solution for the interior
structure of a rotating black hole from just above the inner horizon inward,
down to a tiny scale.
| [
{
"created": "Sun, 3 Oct 2010 17:51:59 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jan 2011 00:27:32 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Jan 2012 00:54:10 GMT",
"version": "v3"
}
] | 2015-03-17 | [
[
"Hamilton",
"Andrew J. S.",
"",
"JILA"
],
[
"Polhemus",
"Gavin",
"",
"JILA"
]
] | This paper presents a concise derivation of a new set of solutions for the interior structure of accreting, rotating black holes. The solutions are conformally stationary, axisymmetric, and conformally separable. Hyper-relativistic counter-streaming between freely-falling collisionless ingoing and outgoing streams leads to mass inflation at the inner horizon, followed by collapse. The solutions fail at an exponentially tiny radius, where the rotational motion of the streams becomes comparable to their radial motion. The papers provide a fully nonlinear, dynamical solution for the interior structure of a rotating black hole from just above the inner horizon inward, down to a tiny scale. |
1704.04386 | Luis Herrera | L. Herrera | The theory of gravitation: A tale of many questions and few answers | 22 pages latex. Partially based on a talk delivered at "70&70
Gravitation Fest", Cartagena, Colombia, September 2016. arXiv admin note:
text overlap with arXiv:1703.03958 | IOP Conf. Series: Journal of Physics: Conf. Series 831 (2017)
012001 | 10.1088/1742-6596/831/1/012001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss on different issues pertaining the theory of gravity, which pose
some unresolved fundamental questions. First we tackle the problem of observers
in general relativity, with particular emphasis in tilted observers. We explain
why these observers may detect dissipative processes in systems which appear
isentropic to comoving observers. Next we analyze the strange relationship
between vorticity and radiation, and underline the potential observational
consequences of such a link. Finally we summarize all the results that have
been obtained so far on the physical properties of the sources of gravitational
radiation. We conclude with a list of open questions which we believe deserve
further attention.
| [
{
"created": "Fri, 14 Apr 2017 10:22:06 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Herrera",
"L.",
""
]
] | We discuss on different issues pertaining the theory of gravity, which pose some unresolved fundamental questions. First we tackle the problem of observers in general relativity, with particular emphasis in tilted observers. We explain why these observers may detect dissipative processes in systems which appear isentropic to comoving observers. Next we analyze the strange relationship between vorticity and radiation, and underline the potential observational consequences of such a link. Finally we summarize all the results that have been obtained so far on the physical properties of the sources of gravitational radiation. We conclude with a list of open questions which we believe deserve further attention. |
gr-qc/0703018 | P. Marecki | P. Marecki | On the wave equation in spacetimes of Goedel type | Significantly updated version, also including discussion of the
Som-Raychaudhuri (flat) case; Chapter in "G\"odel-type spacetimes: history
and new developments", Annals of the Kurt G\"odel Society, ed. M. Scherfner
and M. Plaue (2010) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the d'Alembert equation in the Goedel-type spacetimes with
spherical and Lobachevsky sections (with sufficiently rapid rotation). By
separating the $t$ and $x_3$ dependence we reduce the problem to a
group-theoretical one. In the spherical case solutions have discrete
frequencies, and involve spin-weighted spherical harmonics. In the Lobachevsky
case we give simple formulas for obtaining all the solutions belonging to the
$D^\pm_\la$ sectors of the irreducible unitary representations of the reduced
Lorentz group. The wave equation enforces restrictions on $\la$ and the allowed
(here: continuous) spectrum of frequencies.
| [
{
"created": "Fri, 2 Mar 2007 17:06:44 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2012 10:51:07 GMT",
"version": "v2"
}
] | 2012-01-25 | [
[
"Marecki",
"P.",
""
]
] | We analyze the d'Alembert equation in the Goedel-type spacetimes with spherical and Lobachevsky sections (with sufficiently rapid rotation). By separating the $t$ and $x_3$ dependence we reduce the problem to a group-theoretical one. In the spherical case solutions have discrete frequencies, and involve spin-weighted spherical harmonics. In the Lobachevsky case we give simple formulas for obtaining all the solutions belonging to the $D^\pm_\la$ sectors of the irreducible unitary representations of the reduced Lorentz group. The wave equation enforces restrictions on $\la$ and the allowed (here: continuous) spectrum of frequencies. |
gr-qc/0509002 | Mauricio Bellini | Mariano Anabitarte, Mauricio Bellini (Mar del Plata University &
CONICET) | Space Time Matter inflation | accepted in JMP | J.Math.Phys. 47 (2006) 042502 | 10.1063/1.2186926 | null | gr-qc astro-ph hep-ph hep-th | null | We study a model of power-law inflationary inflation using the
Space-Time-Matter (STM) theory of gravity for a five dimensional (5D) canonical
metric that describes an apparent vacuum. In this approach the expansion is
governed by a single scalar (neutral) quantum field. In particular, we study
the case where the power of expansion of the universe is $p \gg 1$. This kind
of model is more successful than others in accounting for galaxy formation.
| [
{
"created": "Wed, 31 Aug 2005 22:17:01 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2006 15:48:58 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Anabitarte",
"Mariano",
"",
"Mar del Plata University &\n CONICET"
],
[
"Bellini",
"Mauricio",
"",
"Mar del Plata University &\n CONICET"
]
] | We study a model of power-law inflationary inflation using the Space-Time-Matter (STM) theory of gravity for a five dimensional (5D) canonical metric that describes an apparent vacuum. In this approach the expansion is governed by a single scalar (neutral) quantum field. In particular, we study the case where the power of expansion of the universe is $p \gg 1$. This kind of model is more successful than others in accounting for galaxy formation. |
2302.06666 | Flavio Rossetti | Flavio Rossetti, Alex Va\~n\'o-Vi\~nuales | Decay of solutions of the wave equation in cosmological spacetimes -- a
numerical analysis | null | Class. Quantum Grav. 40 (2023) 175004 | 10.1088/1361-6382/ace7a6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically evolve spherically symmetric solutions to the linear wave
equation on some expanding Friedmann-Lema\^itre-Robertson-Walker (FLRW)
spacetimes and study the respective asymptotics for large times. We find a
quantitative relation between the expansion rate of the underlying background
universe and the decay rate of linear waves, also in the context of
spatially-hyperbolic spacetimes, for which rigorous proofs of decay rates are
not generally known. A prominent role in the decay mechanism is shown to be
played by tails, i.e. scattered waves propagating in the interior of the
lightcone.
| [
{
"created": "Mon, 13 Feb 2023 19:58:28 GMT",
"version": "v1"
}
] | 2023-09-26 | [
[
"Rossetti",
"Flavio",
""
],
[
"Vañó-Viñuales",
"Alex",
""
]
] | We numerically evolve spherically symmetric solutions to the linear wave equation on some expanding Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetimes and study the respective asymptotics for large times. We find a quantitative relation between the expansion rate of the underlying background universe and the decay rate of linear waves, also in the context of spatially-hyperbolic spacetimes, for which rigorous proofs of decay rates are not generally known. A prominent role in the decay mechanism is shown to be played by tails, i.e. scattered waves propagating in the interior of the lightcone. |
2110.05510 | Yusuke Manita | Katsuki Aoki, Yusuke Manita and Shinji Mukohyama | Shift-symmetric $SO(N)$ multi-Galileon | 18 pages. v2: matches published version | JCAP12(2021)045 | 10.1088/1475-7516/2021/12/045 | KUNS-2894, YITP21-115, IPMU21-0063 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | A Poincar\`{e} invariant, local scalar field theory in which the Lagrangian
and the equation of motion contain only up to second-order derivatives of the
fields is called generalized Galileon. The covariant version of it in four
dimensions is called Horndeski theory, and has been vigorously studied in
applications to inflation and dark energy. In this paper, we study a class of
multi-field extensions of the generalized Galileon theory. By imposing shift
and $SO(N)$ symmetries on all the currently known multi-Galileon terms in
general dimensions, we find that the structure of the Lagrangian is uniquely
determined and parameterized by a series of coupling constants. We also study
tensor perturbation in the shift-symmetric $SO(3)$ multi-Galileon theory in
four dimensions. The tensor perturbations can obtain a mass term stemming from
the same symmetry breaking pattern as the solid inflation. We also find that
the shift-symmetric $SO(3)$ multi-Galileon theory gives rise to new cubic
interactions of the tensor modes, suggesting the existence of a new type of
tensor primordial non-Gaussianity.
| [
{
"created": "Mon, 11 Oct 2021 18:00:07 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Dec 2021 15:03:39 GMT",
"version": "v2"
}
] | 2021-12-23 | [
[
"Aoki",
"Katsuki",
""
],
[
"Manita",
"Yusuke",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | A Poincar\`{e} invariant, local scalar field theory in which the Lagrangian and the equation of motion contain only up to second-order derivatives of the fields is called generalized Galileon. The covariant version of it in four dimensions is called Horndeski theory, and has been vigorously studied in applications to inflation and dark energy. In this paper, we study a class of multi-field extensions of the generalized Galileon theory. By imposing shift and $SO(N)$ symmetries on all the currently known multi-Galileon terms in general dimensions, we find that the structure of the Lagrangian is uniquely determined and parameterized by a series of coupling constants. We also study tensor perturbation in the shift-symmetric $SO(3)$ multi-Galileon theory in four dimensions. The tensor perturbations can obtain a mass term stemming from the same symmetry breaking pattern as the solid inflation. We also find that the shift-symmetric $SO(3)$ multi-Galileon theory gives rise to new cubic interactions of the tensor modes, suggesting the existence of a new type of tensor primordial non-Gaussianity. |
gr-qc/9412003 | Melnikov Vitaly Nikolaevich | A.A.Kirillov | Quantum creation of an inhomogeneous unflationary universe | 6 pages, latex, no figures | Grav.Cosmol. 2 (1996) 35-37 | null | RGA-CSVR-015/94 | gr-qc | null | The process of quantum creation of a qusihomogeneous inflationary universe
near a cosmological singularity is considered. It is shown that during the
evolution quantum fluctuations of spatial topologies increase and the universe
acquires homogeneous and isotropic character on arbitrary large distances.
| [
{
"created": "Thu, 1 Dec 1994 15:44:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kirillov",
"A. A.",
""
]
] | The process of quantum creation of a qusihomogeneous inflationary universe near a cosmological singularity is considered. It is shown that during the evolution quantum fluctuations of spatial topologies increase and the universe acquires homogeneous and isotropic character on arbitrary large distances. |
gr-qc/0605105 | Smaragda Kessari | Smaragda Kessari | Affine Histories in Quantum Gravity: Introduction and the Representation
for a Cosmological Model | 31 pages, LaTeX, no figures | Class.Quant.Grav.24:1303-1330,2007 | 10.1088/0264-9381/24/5/014 | null | gr-qc | null | It is shown how consistent histories quantum cosmology can be realised
through Isham's Histories Projection Operator consistent histories scheme. This
is done by using an affine algebra instead of a canonical one and also by using
cocycle representations. A regularisation scheme allows us to find a history
Hamiltonian which exists as a proper self-adjoint operator. The role of a
cocycle choice is also discussed.
| [
{
"created": "Thu, 18 May 2006 17:19:16 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jun 2006 19:34:27 GMT",
"version": "v2"
},
{
"created": "Fri, 23 Jun 2006 12:33:11 GMT",
"version": "v3"
},
{
"created": "Mon, 26 Jun 2006 12:15:07 GMT",
"version": "v4"
},
{
"created": "Sun, 30 Jul 2006 15:30:41 GMT",
"version": "v5"
},
{
"created": "Tue, 27 Feb 2007 13:48:02 GMT",
"version": "v6"
},
{
"created": "Thu, 26 Apr 2007 15:36:22 GMT",
"version": "v7"
}
] | 2008-11-26 | [
[
"Kessari",
"Smaragda",
""
]
] | It is shown how consistent histories quantum cosmology can be realised through Isham's Histories Projection Operator consistent histories scheme. This is done by using an affine algebra instead of a canonical one and also by using cocycle representations. A regularisation scheme allows us to find a history Hamiltonian which exists as a proper self-adjoint operator. The role of a cocycle choice is also discussed. |
1501.06025 | Benrong Mu | Benrong Mu, Peng Wang and Haitang Yang | Minimal Length Effects on Tunnelling from Spherically Symmetric Black
Holes | 18 pages | Adv.High Energy Phys. 2015 (2015) 898916 | 10.1155/2015/898916 | CTP-SCU/2015003 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate effects of the minimal length on quantum
tunnelling from spherically symmetric black holes using the Hamilton-Jacobi
method incorporating the minimal length. We first derive the deformed
Hamilton-Jacobi equations for scalars and fermions, both of which have the same
expressions. The minimal length correction to the Hawking temperature is found
to depend on the black hole's mass and the mass and angular momentum of emitted
particles. Finally, we calculate a Schwarzschild black hole's luminosity and
find the black hole evaporates to zero mass in infinite time.
| [
{
"created": "Sat, 24 Jan 2015 10:49:40 GMT",
"version": "v1"
}
] | 2015-01-27 | [
[
"Mu",
"Benrong",
""
],
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
]
] | In this paper, we investigate effects of the minimal length on quantum tunnelling from spherically symmetric black holes using the Hamilton-Jacobi method incorporating the minimal length. We first derive the deformed Hamilton-Jacobi equations for scalars and fermions, both of which have the same expressions. The minimal length correction to the Hawking temperature is found to depend on the black hole's mass and the mass and angular momentum of emitted particles. Finally, we calculate a Schwarzschild black hole's luminosity and find the black hole evaporates to zero mass in infinite time. |
0908.0329 | Sam Dolan Dr | Sam R. Dolan and Adrian C. Ottewill | On an Expansion Method for Black Hole Quasinormal Modes and Regge Poles | 23 pages, 6 figures. Corrected typos in version 1, Eq. (21), (22),
(35) & (36). Matches published version | Class.Quant.Grav.26:225003,2009 | 10.1088/0264-9381/26/22/225003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new method for determining the frequencies and wavefunctions of
black hole quasinormal modes (QNMs) and Regge poles. The key idea is a novel
ansatz for the wavefunction, which relates the high-$l$ wavefunctions to null
geodesics which start at infinity and end in perpetual orbit on the photon
sphere. Our ansatz leads naturally to the expansion of QNMs in inverse powers
of angular momentum $L = l + 1/2$ (in 4D), and to the expansion of Regge poles
in inverse powers of frequency. The expansions can be taken to high orders. We
begin by applying the method to the Schwarzschild spacetime, and validate our
results against existing numerical and WKB methods. Next, we generalise the
method to treat static spherically-symmetric spacetimes of arbitrary spatial
dimension. We confirm that, at lowest order, the real and imaginary components
of the QNM frequency are related to the orbital frequency and the Lyapunov
exponent for geodesics at the unstable orbit. We apply the method to five
spacetimes of current interest, and conclude with a discussion of the
advantages and limitations of the new approach, and its practical applications.
| [
{
"created": "Tue, 4 Aug 2009 15:18:53 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Oct 2009 08:30:17 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Dolan",
"Sam R.",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We present a new method for determining the frequencies and wavefunctions of black hole quasinormal modes (QNMs) and Regge poles. The key idea is a novel ansatz for the wavefunction, which relates the high-$l$ wavefunctions to null geodesics which start at infinity and end in perpetual orbit on the photon sphere. Our ansatz leads naturally to the expansion of QNMs in inverse powers of angular momentum $L = l + 1/2$ (in 4D), and to the expansion of Regge poles in inverse powers of frequency. The expansions can be taken to high orders. We begin by applying the method to the Schwarzschild spacetime, and validate our results against existing numerical and WKB methods. Next, we generalise the method to treat static spherically-symmetric spacetimes of arbitrary spatial dimension. We confirm that, at lowest order, the real and imaginary components of the QNM frequency are related to the orbital frequency and the Lyapunov exponent for geodesics at the unstable orbit. We apply the method to five spacetimes of current interest, and conclude with a discussion of the advantages and limitations of the new approach, and its practical applications. |
1412.5851 | Marc Geiller | Olivier Asin, Jibril Ben Achour, Marc Geiller, Karim Noui, Alejandro
Perez | Black holes as gases of punctures with a chemical potential:
Bose-Einstein condensation and logarithmic corrections to the entropy | 22 pages | Phys. Rev. D 91, 084005 (2015) | 10.1103/PhysRevD.91.084005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamical properties of black holes when described as
gases of indistinguishable punctures with a chemical potential. In this
picture, which arises from loop quantum gravity, the black hole microstates are
defined by finite families of half-integers spins coloring the punctures, and
the near-horizon energy measured by quasi-local stationary observers defines
the various thermodynamical ensembles. The punctures carry excitations of
quantum geometry in the form of quanta of area, and the total horizon area
$a_\text{H}$ is given by the sum of these microscopic contributions. We assume
here that the system satisfies the Bose-Einstein statistics, and that each
microstate is degenerate with a holographic degeneracy given by
$\exp\big(\lambda a_\text{H}/\ell_\text{Pl}^2\big)$ and $\lambda>0$. We analyze
in detail the thermodynamical properties resulting from these inputs, and in
particular compute the grand canonical entropy. We explain why the requirements
that the temperature be fixed to the Unruh temperature and that the chemical
potential vanishes do not specify completely the semi-classical regime of large
horizon area, and classify in turn what the various regimes can be. When the
degeneracy saturates the holographic bound ($\lambda=1/4$), there exists a
semi-classical regime in which the subleading corrections to the entropy are
logarithmic. Furthermore, this regime corresponds to a Bose-Einstein
condensation, in the sense that it is dominated by punctures carrying the
minimal (or ground state) spin value $1/2$.
| [
{
"created": "Thu, 18 Dec 2014 13:29:35 GMT",
"version": "v1"
}
] | 2015-04-08 | [
[
"Asin",
"Olivier",
""
],
[
"Achour",
"Jibril Ben",
""
],
[
"Geiller",
"Marc",
""
],
[
"Noui",
"Karim",
""
],
[
"Perez",
"Alejandro",
""
]
] | We study the thermodynamical properties of black holes when described as gases of indistinguishable punctures with a chemical potential. In this picture, which arises from loop quantum gravity, the black hole microstates are defined by finite families of half-integers spins coloring the punctures, and the near-horizon energy measured by quasi-local stationary observers defines the various thermodynamical ensembles. The punctures carry excitations of quantum geometry in the form of quanta of area, and the total horizon area $a_\text{H}$ is given by the sum of these microscopic contributions. We assume here that the system satisfies the Bose-Einstein statistics, and that each microstate is degenerate with a holographic degeneracy given by $\exp\big(\lambda a_\text{H}/\ell_\text{Pl}^2\big)$ and $\lambda>0$. We analyze in detail the thermodynamical properties resulting from these inputs, and in particular compute the grand canonical entropy. We explain why the requirements that the temperature be fixed to the Unruh temperature and that the chemical potential vanishes do not specify completely the semi-classical regime of large horizon area, and classify in turn what the various regimes can be. When the degeneracy saturates the holographic bound ($\lambda=1/4$), there exists a semi-classical regime in which the subleading corrections to the entropy are logarithmic. Furthermore, this regime corresponds to a Bose-Einstein condensation, in the sense that it is dominated by punctures carrying the minimal (or ground state) spin value $1/2$. |
gr-qc/0312053 | M. Panahi | Mehrdad Panahi | Hidden connection between general relativity and Finsler geometry | LaTEX2e, 7 pages, no figures or tables | Nuovo Cim.B118:345-351,2003 | 10.1393/ncb/i2002-10007-0 | null | gr-qc | null | Modern formulation of Finsler geometry of a manifold M utilizes the
equivalence between this geometry and the Riemannian geometry of VTM, the
vertical bundle over the tangent bundle of M, treating TM as the base space. We
argue that this approach is unsatisfactory when there is an indefinite metric
on M because the corresponding Finsler fundamental function would not be
differentiable over TM (even without its zero section) and therefore TM cannot
serve as the base space. We then make the simple observation that for any
differentiable Lorentzian metric on a smooth space-time, the corresponding
Finsler fundamental function is differentiable exactly on a proper subbundle of
TM. This subbundle is then used, in place of TM, to provide a satisfactory
basis for modern Finsler geometry of manifolds with Lorentzian metrics.
Interestingly, this Finslerian property of Lorentzian metrics does not seem to
exist for general indefinite Finsler metrics and thus, Lorentzian metrics
appear to be of special relevance to Finsler geometry. We note that, in
contrast to the traditional formulation of Finsler geometry, having a
Lorentzian metric in the modern setting does not imply reduction to pseudo-
Riemannian geometry because metric and connection are entirely disentangled in
the modern formulation and there is a new indispensable non-linear connection,
necessary for construction of Finsler tensor bundles. It is concluded that
general relativity--without any modification--has a close bearing on Finsler
geometry and a modern Finsler formulation of the theory is an appealing idea...
| [
{
"created": "Tue, 9 Dec 2003 15:38:11 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Panahi",
"Mehrdad",
""
]
] | Modern formulation of Finsler geometry of a manifold M utilizes the equivalence between this geometry and the Riemannian geometry of VTM, the vertical bundle over the tangent bundle of M, treating TM as the base space. We argue that this approach is unsatisfactory when there is an indefinite metric on M because the corresponding Finsler fundamental function would not be differentiable over TM (even without its zero section) and therefore TM cannot serve as the base space. We then make the simple observation that for any differentiable Lorentzian metric on a smooth space-time, the corresponding Finsler fundamental function is differentiable exactly on a proper subbundle of TM. This subbundle is then used, in place of TM, to provide a satisfactory basis for modern Finsler geometry of manifolds with Lorentzian metrics. Interestingly, this Finslerian property of Lorentzian metrics does not seem to exist for general indefinite Finsler metrics and thus, Lorentzian metrics appear to be of special relevance to Finsler geometry. We note that, in contrast to the traditional formulation of Finsler geometry, having a Lorentzian metric in the modern setting does not imply reduction to pseudo- Riemannian geometry because metric and connection are entirely disentangled in the modern formulation and there is a new indispensable non-linear connection, necessary for construction of Finsler tensor bundles. It is concluded that general relativity--without any modification--has a close bearing on Finsler geometry and a modern Finsler formulation of the theory is an appealing idea... |
gr-qc/0510089 | Romualdo Tresguerres | A. Tiemblo and R. Tresguerres | Gauge theories of gravity: the nonlinear framework | Review article published in Recent Research Developments in Physics 5
(2004) 1255, Transworld Research Network | Recent Res.Devel.Phys. 5 (2004) 1255 | null | null | gr-qc | null | Nonlinear realizations of spacetime groups are presented as a versatile
mathematical tool providing a common foundation for quite different
formulations of gauge theories of gravity. We apply nonlinear realizations in
particular to both the Poincar\'e and the affine group in order to develop
Poincar\'e gauge theory (PGT) and metric-affine gravity (MAG) respectively.
Regarding PGT, two alternative nonlinear treatments of the Poincar\'e group are
developed, one of them being suitable to deal with the Lagrangian and the other
one with the Hamiltonian version of the same gauge theory. We argue that our
Hamiltonian approach to PGT is closely related to Ashtekar's approach to
gravity. On the other hand, a brief survey on MAG clarifies the role played by
the metric--affine metric tensor as a Goldsone field. All gravitational
quantities in fact --the metric as much as the coframes and connections-- are
shown to acquire a simple gauge--theoretical interpretation in the nonlinear
framework.
| [
{
"created": "Wed, 19 Oct 2005 18:50:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tiemblo",
"A.",
""
],
[
"Tresguerres",
"R.",
""
]
] | Nonlinear realizations of spacetime groups are presented as a versatile mathematical tool providing a common foundation for quite different formulations of gauge theories of gravity. We apply nonlinear realizations in particular to both the Poincar\'e and the affine group in order to develop Poincar\'e gauge theory (PGT) and metric-affine gravity (MAG) respectively. Regarding PGT, two alternative nonlinear treatments of the Poincar\'e group are developed, one of them being suitable to deal with the Lagrangian and the other one with the Hamiltonian version of the same gauge theory. We argue that our Hamiltonian approach to PGT is closely related to Ashtekar's approach to gravity. On the other hand, a brief survey on MAG clarifies the role played by the metric--affine metric tensor as a Goldsone field. All gravitational quantities in fact --the metric as much as the coframes and connections-- are shown to acquire a simple gauge--theoretical interpretation in the nonlinear framework. |
gr-qc/0202016 | Luc Blanchet | Luc Blanchet | Gravitational Radiation from Post-Newtonian Sources and Inspiralling
Compact Binaries | 109 pages, 1 figure; this version is an update of the Living Review
article originally published in 2002; available on-line at
http://www.livingreviews.org/ | LivingRev.Rel.5:3,2002 | 10.12942/lrr-2002-3 | null | gr-qc | null | The article reviews the current status of a theoretical approach to the
problem of the emission of gravitational waves by isolated systems in the
context of general relativity. Part A of the article deals with general
post-Newtonian sources. The exterior field of the source is investigated by
means of a combination of analytic post-Minkowskian and multipolar
approximations. The physical observables in the far-zone of the source are
described by a specific set of radiative multipole moments. By matching the
exterior solution to the metric of the post-Newtonian source in the near-zone
we obtain the explicit expressions of the source multipole moments. The
relationships between the radiative and source moments involve many non-linear
multipole interactions, among them those associated with the tails (and
tails-of-tails) of gravitational waves. Part B of the article is devoted to the
application to compact binary systems. We present the equations of binary
motion, and the associated Lagrangian and Hamiltonian, at the third
post-Newtonian (3PN) order beyond the Newtonian acceleration. The
gravitational-wave energy flux, taking consistently into account the
relativistic corrections in the binary moments as well as the various tail
effects, is derived through 3.5PN order with respect to the quadrupole
formalism. The binary's orbital phase, whose prior knowledge is crucial for
searching and analyzing the signals from inspiralling compact binaries, is
deduced from an energy balance argument.
| [
{
"created": "Wed, 6 Feb 2002 15:25:06 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2002 17:16:06 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Jun 2005 16:58:19 GMT",
"version": "v3"
},
{
"created": "Tue, 6 Jun 2006 17:48:54 GMT",
"version": "v4"
}
] | 2016-11-23 | [
[
"Blanchet",
"Luc",
""
]
] | The article reviews the current status of a theoretical approach to the problem of the emission of gravitational waves by isolated systems in the context of general relativity. Part A of the article deals with general post-Newtonian sources. The exterior field of the source is investigated by means of a combination of analytic post-Minkowskian and multipolar approximations. The physical observables in the far-zone of the source are described by a specific set of radiative multipole moments. By matching the exterior solution to the metric of the post-Newtonian source in the near-zone we obtain the explicit expressions of the source multipole moments. The relationships between the radiative and source moments involve many non-linear multipole interactions, among them those associated with the tails (and tails-of-tails) of gravitational waves. Part B of the article is devoted to the application to compact binary systems. We present the equations of binary motion, and the associated Lagrangian and Hamiltonian, at the third post-Newtonian (3PN) order beyond the Newtonian acceleration. The gravitational-wave energy flux, taking consistently into account the relativistic corrections in the binary moments as well as the various tail effects, is derived through 3.5PN order with respect to the quadrupole formalism. The binary's orbital phase, whose prior knowledge is crucial for searching and analyzing the signals from inspiralling compact binaries, is deduced from an energy balance argument. |
0811.1548 | Laszlo Arpad Gergely | L\'aszl\'o \'Arp\'ad Gergely, Narit Pidokrajt, Sergei Winitzki | Geometro-thermodynamics of tidal charged black holes | v3: 23 pages, 8 figures, 1 table, published version | Eur.Phys.J.C71:1569,2011 | 10.1140/epjc/s10052-011-1569-6 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tidal charged spherically symmetric vacuum brane black holes are
characterized by their mass m and tidal charge q, an imprint of the
5-dimensional Weyl curvature. For q>0 they are formally identical to the
Reissner-Nordstr\"om black hole of general relativity. We study the
thermodynamics and thermodynamic geometries of tidal charged black holes and
discuss similarities and differences as compared to the Reissner-Nordstr\"om
black hole. As a similarity, we show that (for q>0) the heat capacity of the
tidal charged black hole diverges on a set of measure zero of the parameter
space, nevertheless both the regularity of the Ruppeiner metric and a
Poincar\'e stability analysis shows no phase transition at those points. The
thermodynamic state spaces being different indicates that the underlying
statistical models could be different. We find that the q<0 parameter range,
which enhances the localization of gravity on the brane, is thermodynamically
preferred. Finally we constrain for the first time the possible range of the
tidal charge from the thermodynamic limit on gravitational radiation efficiency
at black hole mergers.
| [
{
"created": "Mon, 10 Nov 2008 19:32:14 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Oct 2009 21:41:03 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Mar 2011 08:24:01 GMT",
"version": "v3"
}
] | 2011-05-10 | [
[
"Gergely",
"László Árpád",
""
],
[
"Pidokrajt",
"Narit",
""
],
[
"Winitzki",
"Sergei",
""
]
] | Tidal charged spherically symmetric vacuum brane black holes are characterized by their mass m and tidal charge q, an imprint of the 5-dimensional Weyl curvature. For q>0 they are formally identical to the Reissner-Nordstr\"om black hole of general relativity. We study the thermodynamics and thermodynamic geometries of tidal charged black holes and discuss similarities and differences as compared to the Reissner-Nordstr\"om black hole. As a similarity, we show that (for q>0) the heat capacity of the tidal charged black hole diverges on a set of measure zero of the parameter space, nevertheless both the regularity of the Ruppeiner metric and a Poincar\'e stability analysis shows no phase transition at those points. The thermodynamic state spaces being different indicates that the underlying statistical models could be different. We find that the q<0 parameter range, which enhances the localization of gravity on the brane, is thermodynamically preferred. Finally we constrain for the first time the possible range of the tidal charge from the thermodynamic limit on gravitational radiation efficiency at black hole mergers. |
1509.01378 | Yosuke Misonoh | Yosuke Misonoh and Kei-ichi Maeda | Black Holes and Thunderbolt Singularities with Lifshitz Scaling Terms | 24 pages, 17 figures, 6 tables; v2 : typos corrected, minor changes,
version accepted for publication in PRD | Phys. Rev. D 92, 084049 (2015) | 10.1103/PhysRevD.92.084049 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a static, spherically symmetric and asymptotic flat spacetime,
assuming the hypersurface orthogonal Einstein-aether theory with an ultraviolet
modification motivated by the Horava-Lifshitz theory, which is composed of the
$z=2$ Lifshitz scaling terms such as scalar combinations of a three-Ricci
curvature and the acceleration of the aether field. For the case with the
quartic term of the acceleration of the aether field, we obtain a two-parameter
family of black hole solutions, which possess a regular universal horizon.
While, if three-Ricci curvature squared term is joined in ultraviolet
modification, we find a solution with a thunderbolt singularity such that the
universal horizon turns to be a spacelike singularity.
| [
{
"created": "Fri, 4 Sep 2015 09:23:52 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2015 03:45:58 GMT",
"version": "v2"
}
] | 2015-10-28 | [
[
"Misonoh",
"Yosuke",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We study a static, spherically symmetric and asymptotic flat spacetime, assuming the hypersurface orthogonal Einstein-aether theory with an ultraviolet modification motivated by the Horava-Lifshitz theory, which is composed of the $z=2$ Lifshitz scaling terms such as scalar combinations of a three-Ricci curvature and the acceleration of the aether field. For the case with the quartic term of the acceleration of the aether field, we obtain a two-parameter family of black hole solutions, which possess a regular universal horizon. While, if three-Ricci curvature squared term is joined in ultraviolet modification, we find a solution with a thunderbolt singularity such that the universal horizon turns to be a spacelike singularity. |
0804.3863 | Olivier Minazzoli | Olivier Minazzoli and Bertrand Chauvineau | A 2 PN/RM metric of General Relativity | 4 pages, conference (2008) at the graduate school of fundamental and
applied Sciences at the University of Nice Sophia-Antipolis, France. The
acronym "PN/RM" is defined in the text | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a derivation of 2PN/RM metric field equations from the Einstein
field equation in General Relativity. We use the exponential parametrization
and the $c^{-3}$ isotropic spatial coordinates such as in IAU2000
recommendations.
| [
{
"created": "Thu, 24 Apr 2008 13:12:22 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2010 14:16:23 GMT",
"version": "v2"
}
] | 2010-02-19 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Chauvineau",
"Bertrand",
""
]
] | We present a derivation of 2PN/RM metric field equations from the Einstein field equation in General Relativity. We use the exponential parametrization and the $c^{-3}$ isotropic spatial coordinates such as in IAU2000 recommendations. |
gr-qc/9401014 | null | Edward Malec and Niall \'O Murchadha | Trapped surfaces and the Penrose inequality in spherically symmetric
geometries | plain tex | Phys.Rev. D49 (1994) 6931-6934 | 10.1103/PhysRevD.49.6931 | null | gr-qc | null | We demonstrate that the Penrose inequality is valid for spherically symmetric
geometries even when the horizon is immersed in matter. The matter field need
not be at rest. The only restriction is that the source satisfies the weak
energy condition outside the horizon. No restrictions are placed on the matter
inside the horizon. The proof of the Penrose inequality gives a new necessary
condition for the formation of trapped surfaces. This formulation can also be
adapted to give a sufficient condition. We show that a modification of the
Penrose inequality proposed by Gibbons for charged black holes can be broken in
early stages of gravitational collapse. This investigation is based exclusively
on the initial data formulation of General Relativity.
| [
{
"created": "Mon, 17 Jan 1994 10:39:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Malec",
"Edward",
""
],
[
"Murchadha",
"Niall Ó",
""
]
] | We demonstrate that the Penrose inequality is valid for spherically symmetric geometries even when the horizon is immersed in matter. The matter field need not be at rest. The only restriction is that the source satisfies the weak energy condition outside the horizon. No restrictions are placed on the matter inside the horizon. The proof of the Penrose inequality gives a new necessary condition for the formation of trapped surfaces. This formulation can also be adapted to give a sufficient condition. We show that a modification of the Penrose inequality proposed by Gibbons for charged black holes can be broken in early stages of gravitational collapse. This investigation is based exclusively on the initial data formulation of General Relativity. |
2008.02062 | Bijan Saha Dr. | Bijan Saha | Spinors in cylindrically symmetric space-time | 10 pages, 4 figures | Universe V. 6, 152 (2020) | 10.3390/universe6090152 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We studied the behavior of nonlinear spinor field within the scope of a
static cylindrically symmetric space-time. It is found that the energy-momentum
tensor (EMT) of the spinor field in this case possesses nontrivial non-diagonal
components. The presence of non-diagonal components of the EMT imposes
three-way restrictions wither on the space-time geometry or on the components
of the spinor field or on both. It should be noted that analogical situation
occurs in cosmology when nonlinear spinor field is exploited as a source of
gravitational field given by Bianchi type-I cosmological model.
| [
{
"created": "Wed, 5 Aug 2020 12:07:28 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Sep 2020 12:28:01 GMT",
"version": "v2"
}
] | 2020-09-21 | [
[
"Saha",
"Bijan",
""
]
] | We studied the behavior of nonlinear spinor field within the scope of a static cylindrically symmetric space-time. It is found that the energy-momentum tensor (EMT) of the spinor field in this case possesses nontrivial non-diagonal components. The presence of non-diagonal components of the EMT imposes three-way restrictions wither on the space-time geometry or on the components of the spinor field or on both. It should be noted that analogical situation occurs in cosmology when nonlinear spinor field is exploited as a source of gravitational field given by Bianchi type-I cosmological model. |
gr-qc/0605039 | Brihaye Yves | Y. Brihaye, T. Delsate | Inflating Brane inside hyper-spherically symmetric defects | 23 pages, 9 figures, results extended, references added | Class.Quant.Grav.24:1279-1292,2007 | 10.1088/0264-9381/24/5/012 | null | gr-qc hep-th | null | Static and inflating brane world models are considered in $4+n$-dimensions
with a non zero bulk cosmological constant and with a hyper-spherically
symmetric topological defect residing in the $n$ extra dimensions. Several
vacuum solutions can be constructed explicitely when the bulk and inflating
constants are non zero. We study how these solutions are deformed by the
presence of a global monopole for generic values of $n$ and a local monopole
for $n=3$. New types of solutions, regular and periodic in the radial variable
relative to the extra dimensions, are constructed.
| [
{
"created": "Sun, 7 May 2006 14:21:19 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2006 14:44:11 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Oct 2006 13:38:49 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Brihaye",
"Y.",
""
],
[
"Delsate",
"T.",
""
]
] | Static and inflating brane world models are considered in $4+n$-dimensions with a non zero bulk cosmological constant and with a hyper-spherically symmetric topological defect residing in the $n$ extra dimensions. Several vacuum solutions can be constructed explicitely when the bulk and inflating constants are non zero. We study how these solutions are deformed by the presence of a global monopole for generic values of $n$ and a local monopole for $n=3$. New types of solutions, regular and periodic in the radial variable relative to the extra dimensions, are constructed. |
1106.3179 | J. Fernando Barbero G. | J. Fernando Barbero G., Eduardo J. S. Villase\~nor | The thermodynamic limit and black hole entropy in the area ensemble | 23 pages, 3 figures | Class.Quant.Grav.28:215014,2011 | 10.1088/0264-9381/28/21/215014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the thermodynamic limit in the canonical area ensemble used in
loop quantum gravity to model quantum black holes. The computation of the
thermodynamic limit is the rigorous way to obtain a smooth entropy from the
counting entropy given by a direct determination of the number of microstates
compatible with macroscopic quantities (the energy in standard statistical
mechanics or the area in the framework presented here). As we will show in
specific examples the leading behavior of the smoothed entropy for large
horizon areas is the same as the counting entropy but the subleading
contributions differ. This is important because these corrections determine the
concavity or convexity of the entropy as a function of the area.
| [
{
"created": "Thu, 16 Jun 2011 09:20:30 GMT",
"version": "v1"
}
] | 2011-09-27 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We discuss the thermodynamic limit in the canonical area ensemble used in loop quantum gravity to model quantum black holes. The computation of the thermodynamic limit is the rigorous way to obtain a smooth entropy from the counting entropy given by a direct determination of the number of microstates compatible with macroscopic quantities (the energy in standard statistical mechanics or the area in the framework presented here). As we will show in specific examples the leading behavior of the smoothed entropy for large horizon areas is the same as the counting entropy but the subleading contributions differ. This is important because these corrections determine the concavity or convexity of the entropy as a function of the area. |
gr-qc/9901060 | Valeria Ferrari | V. Ferrari, L. Gualtieri, A. Borrelli | Stellar Pulsations excited by a scattered mass | 23 pages, 6 figures, RevTeX | Phys.Rev. D59 (1999) 124020 | 10.1103/PhysRevD.59.124020 | null | gr-qc | null | We compute the energy spectra of the gravitational signals emitted when a
mass m is scattered by the gravitational field of a star of mass M >> m. We
show that, unlike black holes in similar processes, the quasi-normal modes of
the star are excited, and that the amount of energy emitted in these modes
depends on how close the exciting mass can get to the star.
| [
{
"created": "Fri, 22 Jan 1999 15:29:47 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ferrari",
"V.",
""
],
[
"Gualtieri",
"L.",
""
],
[
"Borrelli",
"A.",
""
]
] | We compute the energy spectra of the gravitational signals emitted when a mass m is scattered by the gravitational field of a star of mass M >> m. We show that, unlike black holes in similar processes, the quasi-normal modes of the star are excited, and that the amount of energy emitted in these modes depends on how close the exciting mass can get to the star. |
1306.3241 | Marc Geiller | Jibril Ben Achour, Marc Geiller, Karim Noui, Chao Yu | Testing the role of the Barbero-Immirzi parameter and the choice of
connection in Loop Quantum Gravity | 36 pages | Phys. Rev. D 91, 104016 (2015) | 10.1103/PhysRevD.91.104016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the role of the Barbero-Immirzi parameter $\gamma$ and the choice of
connection in the construction of (a symmetry-reduced version of) loop quantum
gravity. We start with the four-dimensional Lorentzian Holst action that we
reduce to three dimensions in a way that preserves the presence of $\gamma$. In
the time gauge, the phase space of the resulting three-dimensional theory
mimics exactly that of the four-dimensional one. Its quantization can be
performed, and on the kinematical Hilbert space spanned by SU(2) spin network
states the spectra of geometric operators are discrete and $\gamma$-dependent.
However, because of the three-dimensional nature of the theory, its SU(2)
Ashtekar-Barbero Hamiltonian constraint can be traded for the flatness
constraint of an sl(2,C) connection, and we show that this latter has to
satisfy a linear simplicity-like condition analogous to the one used in the
construction of spin foam models. The physically relevant solution to this
constraint singles out the non-compact subgroup SU(1,1), which in turn leads to
the disappearance of the Barbero-Immirzi parameter and to a continuous length
spectrum, in agreement with what is expected from Lorentzian three-dimensional
gravity.
| [
{
"created": "Thu, 13 Jun 2013 20:06:53 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Achour",
"Jibril Ben",
""
],
[
"Geiller",
"Marc",
""
],
[
"Noui",
"Karim",
""
],
[
"Yu",
"Chao",
""
]
] | We study the role of the Barbero-Immirzi parameter $\gamma$ and the choice of connection in the construction of (a symmetry-reduced version of) loop quantum gravity. We start with the four-dimensional Lorentzian Holst action that we reduce to three dimensions in a way that preserves the presence of $\gamma$. In the time gauge, the phase space of the resulting three-dimensional theory mimics exactly that of the four-dimensional one. Its quantization can be performed, and on the kinematical Hilbert space spanned by SU(2) spin network states the spectra of geometric operators are discrete and $\gamma$-dependent. However, because of the three-dimensional nature of the theory, its SU(2) Ashtekar-Barbero Hamiltonian constraint can be traded for the flatness constraint of an sl(2,C) connection, and we show that this latter has to satisfy a linear simplicity-like condition analogous to the one used in the construction of spin foam models. The physically relevant solution to this constraint singles out the non-compact subgroup SU(1,1), which in turn leads to the disappearance of the Barbero-Immirzi parameter and to a continuous length spectrum, in agreement with what is expected from Lorentzian three-dimensional gravity. |
1110.0094 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Halilsoy and T. Tahamtan | Colliding plane wave solution in F(R)=R^{N} gravity | 9 pages, 2 figures | Eur. Phys. J. Plus 131, 350 (2016) | 10.1140/epjp/i2016-16350-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We identify a region of F(R)=R^{N} gravity without external sources which is
isometric to the spacetime of colliding plane waves (CPW). From the derived
curvature sources, N (N>1) measures the strength (i.e. the charge) of the
source. The analogy renders construction and collision of plane waves in
F(R)=R^{N} gravity possible, as in the Einstein-Maxwell (EM) theory, simply
because R=0. A plane wave in this type of gravity is equivalent to a Weyl
curvature plus an electromagnetic energy-momentum-like term (i.e. 'source
without source'). For N=1 we recover naturally the plane waves (and their
collision) in Einstein's theory. Our aim is to find the effect of an expanding
universe by virtue of F(R)=R^{N} on the colliding gravitational plane waves of
Einstein.
| [
{
"created": "Sat, 1 Oct 2011 12:00:32 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jan 2012 17:04:37 GMT",
"version": "v2"
}
] | 2016-09-29 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Tahamtan",
"T.",
""
]
] | We identify a region of F(R)=R^{N} gravity without external sources which is isometric to the spacetime of colliding plane waves (CPW). From the derived curvature sources, N (N>1) measures the strength (i.e. the charge) of the source. The analogy renders construction and collision of plane waves in F(R)=R^{N} gravity possible, as in the Einstein-Maxwell (EM) theory, simply because R=0. A plane wave in this type of gravity is equivalent to a Weyl curvature plus an electromagnetic energy-momentum-like term (i.e. 'source without source'). For N=1 we recover naturally the plane waves (and their collision) in Einstein's theory. Our aim is to find the effect of an expanding universe by virtue of F(R)=R^{N} on the colliding gravitational plane waves of Einstein. |
gr-qc/9907013 | Sungwon | S.-W. Kim and H. Lee | Wormhole as the end state of two-dimensional black hole evaporation | 13 pages, 1 figure, latex. to appear in Phys. Lett. B (1999) | Phys.Lett. B458 (1999) 245-251 | 10.1016/S0370-2693(99)00581-X | null | gr-qc hep-th | null | We present a specific two-dimensional dilaton gravity model in which a black
hole evaporates leaving a wormhole at the end state. As the black hole formed
by infalling matter in a initially static spacetime evaporates by emitting
Hawking radiation, the black hole singularity that is initially hidden behind a
timelike apparent horizon meets the shrinking horizon. At this intersection
point, we imposed boundary conditions which require disappearance of the black
hole singularity and generation of the exotic matter which is the source of the
wormhole as the end state of the black hole. These, of course, preserve energy
conservation and continuity of the metric.
| [
{
"created": "Mon, 5 Jul 1999 08:10:28 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kim",
"S. -W.",
""
],
[
"Lee",
"H.",
""
]
] | We present a specific two-dimensional dilaton gravity model in which a black hole evaporates leaving a wormhole at the end state. As the black hole formed by infalling matter in a initially static spacetime evaporates by emitting Hawking radiation, the black hole singularity that is initially hidden behind a timelike apparent horizon meets the shrinking horizon. At this intersection point, we imposed boundary conditions which require disappearance of the black hole singularity and generation of the exotic matter which is the source of the wormhole as the end state of the black hole. These, of course, preserve energy conservation and continuity of the metric. |
gr-qc/0007067 | Vitaly Melnikov | Vitaly N. Melnikov | Gravity as a Key Problem of the Millenium | 19 pages, LaTeX, no figures | null | null | null | gr-qc | null | Gravitation as a fundamental interaction that governs all phenomena at large
and very small scales, but still not well understood at a quantum level, is a
missing cardinal link to unification of all physical interactions. Problems of
the absolute G measurements and its possible time and range variations are
reflections of the unification problem. Integrable multidimensional models of
gravitation and cosmology make up one of the proper approaches to study basic
issues and strong field objects, the Early Universe and black hole physics in
particular. The choice, nature, classification and precision of determination
of fundamental physical constants are described. The problem of their temporal
variations is also discussed, temporal and range variations of G in particular.
A need for further absolute measurements of G, its possible range and time
variations is pointed out. The novel multipurpose space project SEE, aimed for
measuring G and its stability in space and time 3-4 orders better than at
present, may answer many important questions posed by gravitation, cosmology
and unified theories.
| [
{
"created": "Tue, 25 Jul 2000 07:27:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Melnikov",
"Vitaly N.",
""
]
] | Gravitation as a fundamental interaction that governs all phenomena at large and very small scales, but still not well understood at a quantum level, is a missing cardinal link to unification of all physical interactions. Problems of the absolute G measurements and its possible time and range variations are reflections of the unification problem. Integrable multidimensional models of gravitation and cosmology make up one of the proper approaches to study basic issues and strong field objects, the Early Universe and black hole physics in particular. The choice, nature, classification and precision of determination of fundamental physical constants are described. The problem of their temporal variations is also discussed, temporal and range variations of G in particular. A need for further absolute measurements of G, its possible range and time variations is pointed out. The novel multipurpose space project SEE, aimed for measuring G and its stability in space and time 3-4 orders better than at present, may answer many important questions posed by gravitation, cosmology and unified theories. |
gr-qc/0210048 | Graham Shore | G.M. Shore | Constructing Time Machines | 36 pages, 14 figures, TeX with harvmac; Review article prepared for
Int. J. Mod. Phys. A | Int.J.Mod.Phys. A18 (2003) 4169-4200 | 10.1142/S0217751X03015118 | SWAT 02/348 | gr-qc hep-th | null | The existence of time machines, understood as spacetime constructions
exhibiting physically realised closed timelike curves (CTCs), would raise
fundamental problems with causality and challenge our current understanding of
classical and quantum theories of gravity. In this paper, we investigate three
proposals for time machines which share some common features: cosmic strings in
relative motion, where the conical spacetime appears to allow CTCs; colliding
gravitational shock waves, which in Aichelburg-Sexl coordinates imply
discontinuous geodesics; and the superluminal propagation of light in
gravitational radiation metrics in a modified electrodynamics featuring
violations of the strong equivalence principle. While we show that ultimately
none of these constructions creates a working time machine, their study
illustrates the subtle levels at which causal self-consistency imposes itself,
and we consider what intuition can be drawn from these examples for future
theories.
| [
{
"created": "Tue, 15 Oct 2002 14:18:48 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Shore",
"G. M.",
""
]
] | The existence of time machines, understood as spacetime constructions exhibiting physically realised closed timelike curves (CTCs), would raise fundamental problems with causality and challenge our current understanding of classical and quantum theories of gravity. In this paper, we investigate three proposals for time machines which share some common features: cosmic strings in relative motion, where the conical spacetime appears to allow CTCs; colliding gravitational shock waves, which in Aichelburg-Sexl coordinates imply discontinuous geodesics; and the superluminal propagation of light in gravitational radiation metrics in a modified electrodynamics featuring violations of the strong equivalence principle. While we show that ultimately none of these constructions creates a working time machine, their study illustrates the subtle levels at which causal self-consistency imposes itself, and we consider what intuition can be drawn from these examples for future theories. |
2105.03079 | Matt Visser | Jessica Santiago (Victoria University of Wellington), Sebastian
Schuster (Charles University of Prague), and Matt Visser (Victoria University
of Wellington) | Generic warp drives violate the null energy condition | V1: 37 pages, zero figures, 100 references. V2: 46 pages, one figure,
107 references. (This version closely resembles the final version accepted
and in press at PRD.) Arguments clarified and made more precise; no
significant change in physics conclusions. Several appendices added | null | 10.1103/PhysRevD.105.064038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Three very recent articles have claimed that it is possible to, at least in
theory, either set up positive energy warp drives satisfying the weak energy
condition (WEC), or at the very least, to minimize the WEC violations. These
claims are at best incomplete, since the arguments presented only demonstrate
the existence of one set of timelike observers, the co-moving Eulerian
observers, who see "nice" physics. While these observers might see a positive
energy density, the WEC requires all timelike observers to see positive energy
density. Therefore, one should revisit this issue. A more careful analysis
shows that the situation is actually much grimmer than advertised -- all
physically reasonable warp drives will violate the null energy condition, and
so also automatically violate the WEC, and both the strong and dominant energy
conditions. While warp drives are certainly interesting examples of speculative
physics, the violation of the energy conditions, at least within the framework
of standard general relativity, is unavoidable. Even in modified gravity,
physically reasonable warp drives will still violate the purely geometrical
null convergence condition and the timelike convergence condition which, in
turn, will place very strong constraints on any modified-gravity warp drive.
| [
{
"created": "Fri, 7 May 2021 06:25:26 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Feb 2022 23:32:51 GMT",
"version": "v2"
}
] | 2022-04-06 | [
[
"Santiago",
"Jessica",
"",
"Victoria University of Wellington"
],
[
"Schuster",
"Sebastian",
"",
"Charles University of Prague"
],
[
"Visser",
"Matt",
"",
"Victoria University\n of Wellington"
]
] | Three very recent articles have claimed that it is possible to, at least in theory, either set up positive energy warp drives satisfying the weak energy condition (WEC), or at the very least, to minimize the WEC violations. These claims are at best incomplete, since the arguments presented only demonstrate the existence of one set of timelike observers, the co-moving Eulerian observers, who see "nice" physics. While these observers might see a positive energy density, the WEC requires all timelike observers to see positive energy density. Therefore, one should revisit this issue. A more careful analysis shows that the situation is actually much grimmer than advertised -- all physically reasonable warp drives will violate the null energy condition, and so also automatically violate the WEC, and both the strong and dominant energy conditions. While warp drives are certainly interesting examples of speculative physics, the violation of the energy conditions, at least within the framework of standard general relativity, is unavoidable. Even in modified gravity, physically reasonable warp drives will still violate the purely geometrical null convergence condition and the timelike convergence condition which, in turn, will place very strong constraints on any modified-gravity warp drive. |
gr-qc/9610002 | Ladygin V. P. | V.P. Ladygin, N.B. Ladygina (LHE-JINR, Dubna, Moscow Region, Russia) | Full determination of the $dp$ backward elastic scattering matrix
element | 15 pages, LaTeX | J.Phys.G23:847-856,1997 | 10.1088/0954-3899/23/7/009 | E1-96-322 | gr-qc | null | The model independent analysis of the $dp$ elastic scattering in the
collinear geometry has been performed. It is shown that the measurements of 10
polarization observables of the first and second order realize the complete
experimental program on the determination of the amplitudes of the $dp$
backward elastic scattering reaction.
| [
{
"created": "Tue, 1 Oct 1996 14:48:03 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Ladygin",
"V. P.",
"",
"LHE-JINR, Dubna, Moscow Region, Russia"
],
[
"Ladygina",
"N. B.",
"",
"LHE-JINR, Dubna, Moscow Region, Russia"
]
] | The model independent analysis of the $dp$ elastic scattering in the collinear geometry has been performed. It is shown that the measurements of 10 polarization observables of the first and second order realize the complete experimental program on the determination of the amplitudes of the $dp$ backward elastic scattering reaction. |
1810.06602 | Damianos Iosifidis | Damianos Iosifidis, Anastasios C. Petkou, Christos G. Tsagas | Torsion/non-metricity duality in f(R) gravity | 11 pages, no figures | null | 10.1007/s10714-019-2539-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Torsion and nonmetricity are inherent ingredients in modifications of
Eintein's gravity that are based on affine spacetime geometries. In the context
of pure f(R) gravity we discuss here, in some detail, the relatively unnoticed
duality between torsion and nonmetricity. In particular we show that for R2
gravity torsion and nonmetricity are related by projective transformations.
Since the latter correspond simply to redefining the affine parameters of
autoparallels, we conclude that torsion and nonmetricity are physically
equivalent properties of spacetime. As a simple example we show that both
torsion and nonmetricity can act as geometric sources of accelerated expansion
in a spatially homogenous cosmological model within R2 gravity and we brie y
discuss possible implications of our results.
| [
{
"created": "Mon, 15 Oct 2018 18:28:06 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Petkou",
"Anastasios C.",
""
],
[
"Tsagas",
"Christos G.",
""
]
] | Torsion and nonmetricity are inherent ingredients in modifications of Eintein's gravity that are based on affine spacetime geometries. In the context of pure f(R) gravity we discuss here, in some detail, the relatively unnoticed duality between torsion and nonmetricity. In particular we show that for R2 gravity torsion and nonmetricity are related by projective transformations. Since the latter correspond simply to redefining the affine parameters of autoparallels, we conclude that torsion and nonmetricity are physically equivalent properties of spacetime. As a simple example we show that both torsion and nonmetricity can act as geometric sources of accelerated expansion in a spatially homogenous cosmological model within R2 gravity and we brie y discuss possible implications of our results. |
gr-qc/0404013 | Daniel Mayerhofer | D. Grumiller, D. Mayerhofer | On static solutions in 2D dilaton gravity with scalar matter | 33 pages, 2 eps-figures | Class.Quant.Grav. 21 (2004) 5893-5914 | 10.1088/0264-9381/21/24/012 | TUW-03-22 | gr-qc hep-th | null | Within the first order formalism static solutions of generic dilaton gravity
in 2D with self-interacting (scalar) matter can be discussed with ease. The
question of (non)existence of Killing horizons is addressed and the interplay
with asymptotic conditions is investigated. Naturally, such an analysis has to
be a global one. A central element in the discussion is the rank of the Jacobi
matrix of the underlying dynamical system. With some (pathological) exceptions
Killing horizons exist only if it equals to 3. For certain self-interactions
asymptotically flat black holes with scalar hair do exist. An example relevant
to general relativity is provided. Finally, generalizations are addressed
including 2D type 0A string theory as a particular example. Additionally, in a
pedagogical appendix the mass definition in dilaton gravity is briefly reviewed
and a unique prescription to fix scaling and shift ambiguity is presented.
| [
{
"created": "Fri, 2 Apr 2004 13:57:54 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jul 2004 10:56:42 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Oct 2004 14:10:19 GMT",
"version": "v3"
},
{
"created": "Fri, 26 Nov 2004 14:53:17 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Grumiller",
"D.",
""
],
[
"Mayerhofer",
"D.",
""
]
] | Within the first order formalism static solutions of generic dilaton gravity in 2D with self-interacting (scalar) matter can be discussed with ease. The question of (non)existence of Killing horizons is addressed and the interplay with asymptotic conditions is investigated. Naturally, such an analysis has to be a global one. A central element in the discussion is the rank of the Jacobi matrix of the underlying dynamical system. With some (pathological) exceptions Killing horizons exist only if it equals to 3. For certain self-interactions asymptotically flat black holes with scalar hair do exist. An example relevant to general relativity is provided. Finally, generalizations are addressed including 2D type 0A string theory as a particular example. Additionally, in a pedagogical appendix the mass definition in dilaton gravity is briefly reviewed and a unique prescription to fix scaling and shift ambiguity is presented. |
1509.02685 | Roberto Chan | O. Goldoni, M.F.A. da Silva and R. Chan | Shear-free Dust Solution in General Covariant Ho\v{r}ava-Lifshitz
Gravity | 12 pages and 1 figure. arXiv admin note: substantial text overlap
with arXiv:1412.5045. Accepted for publication in Gen. Rel. Grav | General Relativity and Gravitation 48, 20 (2016) | 10.1007/s10714-015-2013-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have studied non stationary dust spherically symmetric
spacetime, in general covariant theory ($U(1)$ extension) of the
Ho\v{r}ava-Lifshitz gravity with the minimally coupling and non-minimum
coupling with matter, in the post-newtonian approximation (PPN) in the infrared
limit. The Newtonian prepotential $\varphi$ was assumed null. The aim of this
work is to know if we can have the same spacetime, as we know in the General
Relativity Theory (GRT), in Ho\v{r}ava-Lifshitz Theory (HLT) in this limit. We
have shown that there is not an analogy of the dust solution in HLT with the
minimally coupling, as in GRT.
Using non-minimum coupling with matter, we have shown that the solution
admits a process of gravitational collapse, leaving a singularity at the end.
This solution has, qualitatively, the same temporal behaviour as the dust
collapse in GRT. However, we have also found a second possible solution,
representing a bounce behavior that is not found in GRT.
| [
{
"created": "Wed, 9 Sep 2015 09:08:22 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2015 17:30:17 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Dec 2015 19:14:00 GMT",
"version": "v3"
}
] | 2016-02-09 | [
[
"Goldoni",
"O.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Chan",
"R.",
""
]
] | In this paper, we have studied non stationary dust spherically symmetric spacetime, in general covariant theory ($U(1)$ extension) of the Ho\v{r}ava-Lifshitz gravity with the minimally coupling and non-minimum coupling with matter, in the post-newtonian approximation (PPN) in the infrared limit. The Newtonian prepotential $\varphi$ was assumed null. The aim of this work is to know if we can have the same spacetime, as we know in the General Relativity Theory (GRT), in Ho\v{r}ava-Lifshitz Theory (HLT) in this limit. We have shown that there is not an analogy of the dust solution in HLT with the minimally coupling, as in GRT. Using non-minimum coupling with matter, we have shown that the solution admits a process of gravitational collapse, leaving a singularity at the end. This solution has, qualitatively, the same temporal behaviour as the dust collapse in GRT. However, we have also found a second possible solution, representing a bounce behavior that is not found in GRT. |
gr-qc/0506134 | J. Mark Heinzle | J. Mark Heinzle, Alan D. Rendall | Power-law Inflation in Spacetimes without Symmetry | 16 pages | Commun.Math.Phys. 269 (2007) 1-15 | 10.1007/s00220-006-0133-y | null | gr-qc | null | We consider models of accelerated cosmological expansion described by the
Einstein equations coupled to a nonlinear scalar field with a suitable
exponential potential. We show that homogeneous and isotropic solutions are
stable under small nonlinear perturbations without any symmetry assumptions.
Our proof is based on results on the nonlinear stability of de Sitter spacetime
and Kaluza-Klein reduction techniques.
| [
{
"created": "Wed, 29 Jun 2005 13:25:32 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Heinzle",
"J. Mark",
""
],
[
"Rendall",
"Alan D.",
""
]
] | We consider models of accelerated cosmological expansion described by the Einstein equations coupled to a nonlinear scalar field with a suitable exponential potential. We show that homogeneous and isotropic solutions are stable under small nonlinear perturbations without any symmetry assumptions. Our proof is based on results on the nonlinear stability of de Sitter spacetime and Kaluza-Klein reduction techniques. |
1607.05715 | Artur Alho | Artur Alho, Sante Carloni, Claes Uggla | On dynamical systems approaches and methods in $f(R)$ cosmology | 36 pages, 7 figures. v2: references added, matches published version | null | 10.1088/1475-7516/2016/08/064 | null | gr-qc astro-ph.CO math-ph math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss dynamical systems approaches and methods applied to flat
Robertson-Walker models in $f(R)$-gravity. We argue that a complete description
of the solution space of a model requires a global state space analysis that
motivates globally covering state space adapted variables. This is shown
explicitly by an illustrative example, $f(R) = R + \alpha R^2$, $\alpha > 0$,
for which we introduce new regular dynamical systems on global compactly
extended state spaces for the Jordan and Einstein frames. This example also
allows us to illustrate several local and global dynamical systems techniques
involving, e.g., blow ups of nilpotent fixed points, center manifold analysis,
averaging, and use of monotone functions. As a result of applying dynamical
systems methods to globally state space adapted dynamical systems formulations,
we obtain pictures of the entire solution spaces in both the Jordan and the
Einstein frames. This shows, e.g., that due to the domain of the conformal
transformation between the Jordan and Einstein frames, not all the solutions in
the Jordan frame are completely contained in the Einstein frame. We also make
comparisons with previous dynamical systems approaches to $f(R)$ cosmology and
discuss their advantages and disadvantages.
| [
{
"created": "Tue, 19 Jul 2016 19:57:36 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Aug 2016 21:05:57 GMT",
"version": "v2"
}
] | 2016-09-07 | [
[
"Alho",
"Artur",
""
],
[
"Carloni",
"Sante",
""
],
[
"Uggla",
"Claes",
""
]
] | We discuss dynamical systems approaches and methods applied to flat Robertson-Walker models in $f(R)$-gravity. We argue that a complete description of the solution space of a model requires a global state space analysis that motivates globally covering state space adapted variables. This is shown explicitly by an illustrative example, $f(R) = R + \alpha R^2$, $\alpha > 0$, for which we introduce new regular dynamical systems on global compactly extended state spaces for the Jordan and Einstein frames. This example also allows us to illustrate several local and global dynamical systems techniques involving, e.g., blow ups of nilpotent fixed points, center manifold analysis, averaging, and use of monotone functions. As a result of applying dynamical systems methods to globally state space adapted dynamical systems formulations, we obtain pictures of the entire solution spaces in both the Jordan and the Einstein frames. This shows, e.g., that due to the domain of the conformal transformation between the Jordan and Einstein frames, not all the solutions in the Jordan frame are completely contained in the Einstein frame. We also make comparisons with previous dynamical systems approaches to $f(R)$ cosmology and discuss their advantages and disadvantages. |
2012.03962 | Shahar Hod | Shahar Hod | Lower bound on the radii of black-hole photonspheres | 8 pages | Physical Review D 101, 084033 (2020) | 10.1103/PhysRevD.101.084033 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The existence of closed null circular geodesics around black holes is one of
the most intriguing predictions of general relativity. It has recently been
conjectured that the radii of black-hole photonspheres are bounded from below
by the simple relation $r_{\text{ph}}\geq {3\over2}r_{\text{H}}$, where
$r_{\text{H}}$ is the radius of the outer black-hole horizon. We here prove the
validity of this conjecture for spherically symmetric hairy black-hole
configurations whose radial pressure function $P\equiv |r^3p|$ decreases
monotonically.
| [
{
"created": "Mon, 7 Dec 2020 19:00:02 GMT",
"version": "v1"
}
] | 2020-12-16 | [
[
"Hod",
"Shahar",
""
]
] | The existence of closed null circular geodesics around black holes is one of the most intriguing predictions of general relativity. It has recently been conjectured that the radii of black-hole photonspheres are bounded from below by the simple relation $r_{\text{ph}}\geq {3\over2}r_{\text{H}}$, where $r_{\text{H}}$ is the radius of the outer black-hole horizon. We here prove the validity of this conjecture for spherically symmetric hairy black-hole configurations whose radial pressure function $P\equiv |r^3p|$ decreases monotonically. |
2111.04388 | Georgios Karagiannis | Athanasios Chatzistavrakidis, Georgios Karagiannis, George Manolakos,
Peter Schupp | Axion gravitodynamics, Lense-Thirring effect, and gravitational waves | Minor changes; now matches the published version | Phys. Rev. D 105, 104029 (2022) | 10.1103/PhysRevD.105.104029 | RBI-ThPhys-2021-38 | gr-qc cond-mat.str-el hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate physical implications of a gravitational analog of axion
electrodynamics with a parity-violating gravitoelectromagnetic theta term. This
is related to the Nieh-Yan topological invariant in gravity with torsion, in
contrast to the well-studied gravitational Chern-Simons term quadratic in
curvature, coupled via a dynamical axionlike scalar field. Axion
gravitodynamics is the corresponding linearized theory. We find that
potentially observable effects are over 80 orders of magnitude stronger than
for its Chern-Simons counterpart and could be in reach for detection by
experiments in the near future. For a near-Earth scenario, we derive
corrections to the Lense-Thirring effect and compare them to data from
satellite-based experiments (Gravity Probe B). For gravitational waves, we find
modified dispersion relations, derive the corresponding polarization-dependent
modified group and phase velocities, and compare them to data from neutron star
mergers (GW170817) to derive even stronger bounds.
| [
{
"created": "Mon, 8 Nov 2021 11:19:33 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2022 10:36:25 GMT",
"version": "v2"
}
] | 2022-05-18 | [
[
"Chatzistavrakidis",
"Athanasios",
""
],
[
"Karagiannis",
"Georgios",
""
],
[
"Manolakos",
"George",
""
],
[
"Schupp",
"Peter",
""
]
] | We investigate physical implications of a gravitational analog of axion electrodynamics with a parity-violating gravitoelectromagnetic theta term. This is related to the Nieh-Yan topological invariant in gravity with torsion, in contrast to the well-studied gravitational Chern-Simons term quadratic in curvature, coupled via a dynamical axionlike scalar field. Axion gravitodynamics is the corresponding linearized theory. We find that potentially observable effects are over 80 orders of magnitude stronger than for its Chern-Simons counterpart and could be in reach for detection by experiments in the near future. For a near-Earth scenario, we derive corrections to the Lense-Thirring effect and compare them to data from satellite-based experiments (Gravity Probe B). For gravitational waves, we find modified dispersion relations, derive the corresponding polarization-dependent modified group and phase velocities, and compare them to data from neutron star mergers (GW170817) to derive even stronger bounds. |
1910.04800 | Pratik Wagle | Pratik Wagle, Alexander Saffer and Nicolas Yunes | Polarization modes of gravitational waves in Quadratic Gravity | 14 pages, 1 figure, Submitted to PRD | Phys. Rev. D 100, 124007 (2019) | 10.1103/PhysRevD.100.124007 | Phys. Rev. D 100, 124007 | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of the inspiral and merger of compact binaries by the
LIGO-Virgo collaboration has allowed for new tests of Einstein's theory in the
extreme gravity regime, where gravitational interactions are simultaneously
strong, non-linear, and dynamical. Theories beyond Einstein's can also be
constrained by detecting the polarization modes of gravitational waves. In this
paper, we show that dynamical Chern-Simons and Einstein-dilaton-Gauss-Bonnet
gravity cannot be differentiated from general relativity based on the detection
of polarization modes alone. To prove this result, we use the Newman-Penrose
method and an irreducible decomposition method to find that only the tensorial
modes can be detected in both these theories.
| [
{
"created": "Thu, 10 Oct 2019 18:29:05 GMT",
"version": "v1"
}
] | 2019-12-11 | [
[
"Wagle",
"Pratik",
""
],
[
"Saffer",
"Alexander",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The observation of the inspiral and merger of compact binaries by the LIGO-Virgo collaboration has allowed for new tests of Einstein's theory in the extreme gravity regime, where gravitational interactions are simultaneously strong, non-linear, and dynamical. Theories beyond Einstein's can also be constrained by detecting the polarization modes of gravitational waves. In this paper, we show that dynamical Chern-Simons and Einstein-dilaton-Gauss-Bonnet gravity cannot be differentiated from general relativity based on the detection of polarization modes alone. To prove this result, we use the Newman-Penrose method and an irreducible decomposition method to find that only the tensorial modes can be detected in both these theories. |
0808.2272 | L. C. Garcia de Andrade | Garcia de Andrade | Effective black holes from non-Riemannian vortex acoustics in ABC flows | Dept Fisica Teorica-IF-UERJ-Brasil | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since Alfven, dynamo and sound waves and the existence of general
relativistic black holes are well stablished in plasma physics, this provides
enough motivation to investigate the presence of acoustic black-hole effective
metric of analogue Einstein's gravity in dynamo flows. From nonlinear dynamo
equations, one obtains a non-homogeneous wave equation where it is shown that
the non-homogeneous factor is proportional to time evolution of the
compressibility factor. In the Navier-Stokes case for a finite Reynolds number
the acoustic black-holes also exists on the stretching plasma flows. In the
magnetostatic case the dynamo is marginal. Analog models are usually applied to
a superfluid analog spacetime, instead of the plasma setting used here. A
coupled nonlinear plasma flow solution is found for the dynamo equation where
the effective black hole solution of the scalar effective equation yields an
imaginary part of the growth of magnetic field. Therefore though the real part
of the growth rate of the magnetic field is negative or null, since there is a
temporal oscillation in magnetic field, the solution represents a slow dynamo.
Thus acoustic black holes are shown to definitely contribute to dynamo action
of the effective plasma spacetime. It is suggested that a fast dynamo effective
spacetime may also contain an acoustic black hole. I the case of planar waves
the effective metric can be cast in Kerr-Schild spacetime form. The Killing
symmetries are explicitly given in this metric and the growth of dynamo waves.
| [
{
"created": "Sat, 16 Aug 2008 20:47:26 GMT",
"version": "v1"
}
] | 2008-08-19 | [
[
"de Andrade",
"Garcia",
""
]
] | Since Alfven, dynamo and sound waves and the existence of general relativistic black holes are well stablished in plasma physics, this provides enough motivation to investigate the presence of acoustic black-hole effective metric of analogue Einstein's gravity in dynamo flows. From nonlinear dynamo equations, one obtains a non-homogeneous wave equation where it is shown that the non-homogeneous factor is proportional to time evolution of the compressibility factor. In the Navier-Stokes case for a finite Reynolds number the acoustic black-holes also exists on the stretching plasma flows. In the magnetostatic case the dynamo is marginal. Analog models are usually applied to a superfluid analog spacetime, instead of the plasma setting used here. A coupled nonlinear plasma flow solution is found for the dynamo equation where the effective black hole solution of the scalar effective equation yields an imaginary part of the growth of magnetic field. Therefore though the real part of the growth rate of the magnetic field is negative or null, since there is a temporal oscillation in magnetic field, the solution represents a slow dynamo. Thus acoustic black holes are shown to definitely contribute to dynamo action of the effective plasma spacetime. It is suggested that a fast dynamo effective spacetime may also contain an acoustic black hole. I the case of planar waves the effective metric can be cast in Kerr-Schild spacetime form. The Killing symmetries are explicitly given in this metric and the growth of dynamo waves. |
gr-qc/9811053 | Fotini Markopoulou | Fotini Markopoulou | The internal description of a causal set: What the universe looks like
from the inside | Version to appear in Comm.Math.Phys. (minor modifications). 37 pages,
several eps figures | Commun.Math.Phys.211:559-583,2000 | 10.1007/s002200050826 | null | gr-qc hep-th | null | We describe an algebraic way to code the causal information of a discrete
spacetime. The causal set C is transformed to a description in terms of the
causal pasts of the events in C. This is done by an evolving set, a functor
which to each event of C assigns its causal past. Evolving sets obey a Heyting
algebra which is characterised by a non-standard notion of complement.
Conclusions about the causal structure of the causal set can be drawn by
calculating the complement of the evolving set. A causal quantum theory can be
based on the quantum version of evolving sets, which we briefly discuss.
| [
{
"created": "Tue, 17 Nov 1998 19:28:10 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Nov 1999 17:32:41 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Markopoulou",
"Fotini",
""
]
] | We describe an algebraic way to code the causal information of a discrete spacetime. The causal set C is transformed to a description in terms of the causal pasts of the events in C. This is done by an evolving set, a functor which to each event of C assigns its causal past. Evolving sets obey a Heyting algebra which is characterised by a non-standard notion of complement. Conclusions about the causal structure of the causal set can be drawn by calculating the complement of the evolving set. A causal quantum theory can be based on the quantum version of evolving sets, which we briefly discuss. |
gr-qc/9803060 | Saulo Carneiro | F. Bunchaft and S. Carneiro | The static spacetime relative acceleration for the general free fall and
its possible experimental test | To appear in Classical and Quantum Gravity, 15 pages, Latex | Class.Quant.Grav.15:1557,1998 | 10.1088/0264-9381/15/6/012 | null | gr-qc | null | Mishra has recently established, using a generic static metric, the relative
local proper-time 3-acceleration of a test-particle in one-dimensional free
fall relative to a static reference frame in any static spacetime. In this
paper, on the grounds of gravitoelectromagnetism we establish, in a covariant
spacetime form, the relative 4-acceleration for the general free fall,
indicating its canonical representation with its 3-space cinematical content.
Then we obtain the relation between this representation and the very known
expression for the relative free fall acceleration in Fermi coordinates. Taking
this into account, it is shown that an experiment with relativistic beams in a
circular accelerator, modelled by Fermi coordinates, recently proposed by
Moliner et al, can test the here established covariant result and, therefore,
can also verify Mishra's formula. This possibility of experimental
verification, besides its intrinsic importance, can answer a recent inquire by
Vigier, related to his recent proposal of derivation of inertial forces.
| [
{
"created": "Tue, 17 Mar 1998 14:03:03 GMT",
"version": "v1"
}
] | 2010-03-19 | [
[
"Bunchaft",
"F.",
""
],
[
"Carneiro",
"S.",
""
]
] | Mishra has recently established, using a generic static metric, the relative local proper-time 3-acceleration of a test-particle in one-dimensional free fall relative to a static reference frame in any static spacetime. In this paper, on the grounds of gravitoelectromagnetism we establish, in a covariant spacetime form, the relative 4-acceleration for the general free fall, indicating its canonical representation with its 3-space cinematical content. Then we obtain the relation between this representation and the very known expression for the relative free fall acceleration in Fermi coordinates. Taking this into account, it is shown that an experiment with relativistic beams in a circular accelerator, modelled by Fermi coordinates, recently proposed by Moliner et al, can test the here established covariant result and, therefore, can also verify Mishra's formula. This possibility of experimental verification, besides its intrinsic importance, can answer a recent inquire by Vigier, related to his recent proposal of derivation of inertial forces. |
1110.4773 | Kazuyuki Sugimura | Kazuyuki Sugimura, Daisuke Yamauchi and Misao Sasaki | Multi-field open inflation model and multi-field dynamics in tunneling | 13 pages, 4 figures | null | 10.1088/1475-7516/2012/01/027 | YITP-11-88; ICRR-Report-596-2011-13 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a multi-field open inflation model, in which one of the fields
dominates quantum tunneling from a false vacuum while the other field governs
slow-roll inflation within the bubble nucleated from false vacuum decay. We
call the former the tunneling field and the latter the inflaton field. In the
limit of a negligible interaction between the two fields, the false vacuum
decay is described by a Coleman-De Luccia instanton. Here we take into account
the coupling between the two fields and construct explicitly a multi-field
instanton for a simple quartic potential model. We also solve the evolution of
the scalar fields within the bubble. We find our model realizes open inflation
successfully. This is the first concrete, viable model of open inflation
realized with a simple potential. We then study the effect of the multi-field
dynamics on the false vacuum decay, specifically on the tunneling rate. We find
the tunneling rate increases in general in comparison with the single field
case, though the increase is small unless the inflaton affects the instanton
solution substantially.
| [
{
"created": "Fri, 21 Oct 2011 12:23:33 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Nov 2011 02:13:37 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Sugimura",
"Kazuyuki",
""
],
[
"Yamauchi",
"Daisuke",
""
],
[
"Sasaki",
"Misao",
""
]
] | We consider a multi-field open inflation model, in which one of the fields dominates quantum tunneling from a false vacuum while the other field governs slow-roll inflation within the bubble nucleated from false vacuum decay. We call the former the tunneling field and the latter the inflaton field. In the limit of a negligible interaction between the two fields, the false vacuum decay is described by a Coleman-De Luccia instanton. Here we take into account the coupling between the two fields and construct explicitly a multi-field instanton for a simple quartic potential model. We also solve the evolution of the scalar fields within the bubble. We find our model realizes open inflation successfully. This is the first concrete, viable model of open inflation realized with a simple potential. We then study the effect of the multi-field dynamics on the false vacuum decay, specifically on the tunneling rate. We find the tunneling rate increases in general in comparison with the single field case, though the increase is small unless the inflaton affects the instanton solution substantially. |
1508.07261 | Tom Chang | Tom T.S. Chang | Complexity Induced Sporadic Localized Multifractal Antiscreening in
Gravitational Evolution at Large Scales | 16 pages | null | null | null | gr-qc astro-ph.CO cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been suggested that antiscreening effects due to the running of the
gravitational constant G might provide a partial solution to the dark matter
mystery. It has also been hypothesized that renormalization group scaling
transformations at large scales might supply the theoretical explanation. In
this letter, we demonstrate that multifractal coarse-graining scaling effects
due to classical fluctuations in the IR with consecutive symmetry breakings in
gravitational evolution and induced running of the gravitational constant with
fractal structures at larger scales may provide the plausible explanation of
the observed results of weak lensing observations and beyond. The sporadic and
localized antiscreening due to the running of the gravitational constant can
also provide the backbone for the cosmic evolution and large scale structure
formation. Our interpretation of this interesting finding is that such effects
are the result of the complexity phenomenon involving the evolution of
large-scale multifractal structures and accompanying fluctuations, not the
conventional arguments suggesting quantum gravity being the primary cause. We
also suggest that the running of the cosmological constant due to such
stochastic complexity evolution may provide a key to the understanding of the
observed cosmic acceleration.
| [
{
"created": "Thu, 27 Aug 2015 02:45:13 GMT",
"version": "v1"
}
] | 2015-08-31 | [
[
"Chang",
"Tom T. S.",
""
]
] | It has been suggested that antiscreening effects due to the running of the gravitational constant G might provide a partial solution to the dark matter mystery. It has also been hypothesized that renormalization group scaling transformations at large scales might supply the theoretical explanation. In this letter, we demonstrate that multifractal coarse-graining scaling effects due to classical fluctuations in the IR with consecutive symmetry breakings in gravitational evolution and induced running of the gravitational constant with fractal structures at larger scales may provide the plausible explanation of the observed results of weak lensing observations and beyond. The sporadic and localized antiscreening due to the running of the gravitational constant can also provide the backbone for the cosmic evolution and large scale structure formation. Our interpretation of this interesting finding is that such effects are the result of the complexity phenomenon involving the evolution of large-scale multifractal structures and accompanying fluctuations, not the conventional arguments suggesting quantum gravity being the primary cause. We also suggest that the running of the cosmological constant due to such stochastic complexity evolution may provide a key to the understanding of the observed cosmic acceleration. |
1504.02993 | Francisco Diego Mazzitelli | Mauro El\'ias and Francisco D. Mazzitelli | Ultraviolet cutoffs for quantum fields in cosmological spacetimes | 19 pages. Minor changes. References added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze critically the renormalization of quantum fields in cosmological
spacetimes, using non covariant ultraviolet cutoffs. We compute explicitly the
counterterms necessary to renormalize the semiclassical Einstein equations,
using comoving and physical ultraviolet cutoffs. In the first case, the
divergences renormalize bare conserved fluids, while in the second case it is
necessary to break the covariance of the bare theory. We point out that, in
general, the renormalized equations differ from those obtained with covariant
methods, even after absorbing the infinities and choosing the renormalized
parameters to force the consistency of the renormalized theory. We repeat the
analysis for the evolution equation for the mean value of an interacting scalar
field
| [
{
"created": "Sun, 12 Apr 2015 17:24:51 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Apr 2015 09:31:47 GMT",
"version": "v2"
}
] | 2015-04-28 | [
[
"Elías",
"Mauro",
""
],
[
"Mazzitelli",
"Francisco D.",
""
]
] | We analyze critically the renormalization of quantum fields in cosmological spacetimes, using non covariant ultraviolet cutoffs. We compute explicitly the counterterms necessary to renormalize the semiclassical Einstein equations, using comoving and physical ultraviolet cutoffs. In the first case, the divergences renormalize bare conserved fluids, while in the second case it is necessary to break the covariance of the bare theory. We point out that, in general, the renormalized equations differ from those obtained with covariant methods, even after absorbing the infinities and choosing the renormalized parameters to force the consistency of the renormalized theory. We repeat the analysis for the evolution equation for the mean value of an interacting scalar field |
2201.02581 | Lang Liu | Lang Liu and Sang Pyo Kim | Merger rate of charged black holes from the two-body dynamical capture | 17 pages, 2 figures | JCAP03(2022)059 | 10.1088/1475-7516/2022/03/059 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the two-body dynamical capture of black holes carrying U(1)
charge which can not only correspond to electric or magnetic charge but also
have other physical interpretations such as dark or hidden charge. In the
low-velocity and weak-field regime, we study gravitational and electromagnetic
radiations from point masses with U(1) charges in a hyperbolic orbit, and we
develop a formalism to derive the merger rate of charged black holes from the
two-body dynamical capture. We apply the formalism to find the effects of the
charge-to-mass ratio on the merger rate for possible different cases and
discover that the effects depend on the models.
| [
{
"created": "Thu, 6 Jan 2022 16:44:21 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Mar 2022 14:16:57 GMT",
"version": "v2"
},
{
"created": "Sun, 17 Apr 2022 13:31:39 GMT",
"version": "v3"
}
] | 2022-04-19 | [
[
"Liu",
"Lang",
""
],
[
"Kim",
"Sang Pyo",
""
]
] | We consider the two-body dynamical capture of black holes carrying U(1) charge which can not only correspond to electric or magnetic charge but also have other physical interpretations such as dark or hidden charge. In the low-velocity and weak-field regime, we study gravitational and electromagnetic radiations from point masses with U(1) charges in a hyperbolic orbit, and we develop a formalism to derive the merger rate of charged black holes from the two-body dynamical capture. We apply the formalism to find the effects of the charge-to-mass ratio on the merger rate for possible different cases and discover that the effects depend on the models. |
2203.03983 | Amin Salehi | M. Yarahmadi, S. Fathi, A. Salehi | Can Chameleon fields be the source of both the dark energy dipole and
the CMB dipole? | 17 pages , 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent research shows that the local group is moving toward (l,b)=(276,30)
relative to the cosmic background radiation at a speed of about $600 kms^{-1}$
which is known as the cosmic background radiation dipole. The exact cause of
this movement is still unknown. Areas with high mass densities such as galactic
superclusters seem to be one of the causes of this flow. There are several
methods for simulating the motion of local clusters, one of which is the bulk
flow. The bulk current can be seen as a mass movement of a large part of the
universe. This anisotropy at the local scale seems to have the same origin as
the anisotropy at the larger scale. In this paper, anisotropies on both small
and large scales were investigated using chameleon fields. The data used are
Type Ia supernovae (Pantheon catalog for a total of 1,048 supernovae in
redshift (0.15<z<2.3)). The results showed that on a smaller scale (less than
150 MPa) the direction of motion of the local group galaxies is the same as the
direction of the bulk, and on larger scales, the direction of the bulk current
is the same as the direction of the current of dark energy dipole.
| [
{
"created": "Tue, 8 Mar 2022 10:17:46 GMT",
"version": "v1"
}
] | 2022-03-09 | [
[
"Yarahmadi",
"M.",
""
],
[
"Fathi",
"S.",
""
],
[
"Salehi",
"A.",
""
]
] | Recent research shows that the local group is moving toward (l,b)=(276,30) relative to the cosmic background radiation at a speed of about $600 kms^{-1}$ which is known as the cosmic background radiation dipole. The exact cause of this movement is still unknown. Areas with high mass densities such as galactic superclusters seem to be one of the causes of this flow. There are several methods for simulating the motion of local clusters, one of which is the bulk flow. The bulk current can be seen as a mass movement of a large part of the universe. This anisotropy at the local scale seems to have the same origin as the anisotropy at the larger scale. In this paper, anisotropies on both small and large scales were investigated using chameleon fields. The data used are Type Ia supernovae (Pantheon catalog for a total of 1,048 supernovae in redshift (0.15<z<2.3)). The results showed that on a smaller scale (less than 150 MPa) the direction of motion of the local group galaxies is the same as the direction of the bulk, and on larger scales, the direction of the bulk current is the same as the direction of the current of dark energy dipole. |
gr-qc/9801111 | Alpan Raval | Leonard Parker and Alpan Raval | Relation Between Einstein And Quantum Field Equations | Latex, 24 pages. Minor changes in text from original version | Phys.Rev. D57 (1998) 7327-7339 | 10.1103/PhysRevD.57.7327 | WISC-MILW-TH-98-10 | gr-qc | null | We show that there exists a choice of scalar field modes, such that the
evolution of the quantum field in the zero-mass and large-mass limits is
consistent with the Einstein equations for the background geometry. This choice
of modes is also consistent with zero production of these particles and thus
corresponds to a preferred vacuum state preserved by the evolution. In the
zero-mass limit, we find that the quantum field equation implies the Einstein
equation for the scale factor of a radiation-dominated universe; in the
large-mass case, it implies the corresponding Einstein equation for a
matter-dominated universe. Conversely, if the classical radiation-dominated or
matter-dominated Einstein equations hold, there is no production of scalar
particles in the zero and large mass limits, respectively. The suppression of
particle production in the large mass limit is over and above the expected
suppression at large mass. Our results hold for a certain class of conformally
ultrastatic background geometries and therefore generalize previous results by
one of us for spatially flat Robertson-Walker background geometries. In these
geometries, we find that the temporal part of the graviton equations reduces to
the temporal equation for a massless minimally coupled scalar field, and
therefore the results for massless particle production hold also for gravitons.
Within the class of modes we study, we also find that the requirement of zero
production of massless scalar particles is not consistent with a non-zero
cosmological constant. Possible implications are discussed.
| [
{
"created": "Fri, 30 Jan 1998 22:04:05 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Feb 1998 17:26:10 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Parker",
"Leonard",
""
],
[
"Raval",
"Alpan",
""
]
] | We show that there exists a choice of scalar field modes, such that the evolution of the quantum field in the zero-mass and large-mass limits is consistent with the Einstein equations for the background geometry. This choice of modes is also consistent with zero production of these particles and thus corresponds to a preferred vacuum state preserved by the evolution. In the zero-mass limit, we find that the quantum field equation implies the Einstein equation for the scale factor of a radiation-dominated universe; in the large-mass case, it implies the corresponding Einstein equation for a matter-dominated universe. Conversely, if the classical radiation-dominated or matter-dominated Einstein equations hold, there is no production of scalar particles in the zero and large mass limits, respectively. The suppression of particle production in the large mass limit is over and above the expected suppression at large mass. Our results hold for a certain class of conformally ultrastatic background geometries and therefore generalize previous results by one of us for spatially flat Robertson-Walker background geometries. In these geometries, we find that the temporal part of the graviton equations reduces to the temporal equation for a massless minimally coupled scalar field, and therefore the results for massless particle production hold also for gravitons. Within the class of modes we study, we also find that the requirement of zero production of massless scalar particles is not consistent with a non-zero cosmological constant. Possible implications are discussed. |
1108.3121 | Marc Favata | Marc Favata | The gravitational-wave memory from eccentric binaries | 25 pages, 8 figures. v2: minor changes to match published version | Phys.Rev.D84:124013,2011 | 10.1103/PhysRevD.84.124013 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonlinear gravitational-wave memory causes a time-varying but
nonoscillatory correction to the gravitational-wave polarizations. It arises
from gravitational waves that are sourced by gravitational waves. Previous
considerations of the nonlinear memory effect have focused on quasicircular
binaries. Here, I consider the nonlinear memory from Newtonian orbits with
arbitrary eccentricity. Expressions for the waveform polarizations and
spin-weighted spherical-harmonic modes are derived for elliptic, hyperbolic,
parabolic, and radial orbits. In the hyperbolic, parabolic, and radial cases
the nonlinear memory provides a 2.5 post-Newtonian (PN) correction to the
leading-order waveforms. This is in contrast to the elliptical and
quasicircular cases, where the nonlinear memory corrects the waveform at
leading (0PN) order. This difference in PN order arises from the fact that the
memory builds up over a short "scattering" time scale in the hyperbolic case,
as opposed to a much longer radiation-reaction time scale in the elliptical
case. The nonlinear memory corrections presented here complete our knowledge of
the leading-order (Peters-Mathews) waveforms for elliptical orbits. These
calculations are also relevant for binaries with quasicircular orbits in the
present epoch which had, in the past, large eccentricities. Because the
nonlinear memory depends sensitively on the past evolution of a binary, I
discuss the effect of this early-time eccentricity on the value of the
late-time memory in nearly circularized binaries. I also discuss the
observability of large "memory jumps" in a binary's past that could arise from
its formation in a capture process. Lastly, I provide estimates of the
signal-to-noise ratio of the linear and nonlinear memories from hyperbolic and
parabolic binaries.
| [
{
"created": "Mon, 15 Aug 2011 23:55:11 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jan 2012 04:18:11 GMT",
"version": "v2"
}
] | 2012-01-06 | [
[
"Favata",
"Marc",
""
]
] | The nonlinear gravitational-wave memory causes a time-varying but nonoscillatory correction to the gravitational-wave polarizations. It arises from gravitational waves that are sourced by gravitational waves. Previous considerations of the nonlinear memory effect have focused on quasicircular binaries. Here, I consider the nonlinear memory from Newtonian orbits with arbitrary eccentricity. Expressions for the waveform polarizations and spin-weighted spherical-harmonic modes are derived for elliptic, hyperbolic, parabolic, and radial orbits. In the hyperbolic, parabolic, and radial cases the nonlinear memory provides a 2.5 post-Newtonian (PN) correction to the leading-order waveforms. This is in contrast to the elliptical and quasicircular cases, where the nonlinear memory corrects the waveform at leading (0PN) order. This difference in PN order arises from the fact that the memory builds up over a short "scattering" time scale in the hyperbolic case, as opposed to a much longer radiation-reaction time scale in the elliptical case. The nonlinear memory corrections presented here complete our knowledge of the leading-order (Peters-Mathews) waveforms for elliptical orbits. These calculations are also relevant for binaries with quasicircular orbits in the present epoch which had, in the past, large eccentricities. Because the nonlinear memory depends sensitively on the past evolution of a binary, I discuss the effect of this early-time eccentricity on the value of the late-time memory in nearly circularized binaries. I also discuss the observability of large "memory jumps" in a binary's past that could arise from its formation in a capture process. Lastly, I provide estimates of the signal-to-noise ratio of the linear and nonlinear memories from hyperbolic and parabolic binaries. |
1912.05154 | Rahul Kumar | Rahul Kumar, Sushant G. Ghosh, Anzhong Wang | Shadow cast and deflection of light by charged rotating regular black
holes | 32 Pages, 14 figures and 4 tables | Phys. Rev. D 100, 124024 (2019) | 10.1103/PhysRevD.100.124024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the horizon properties, shadow cast, and the weak gravitational
lensing of charged rotating regular black holes, which in addition to mass
($M$) and rotation parameter ($a$) have an electric charge ($Q$) and magnetic
charge ($g$). The considered regular black holes are the generalization of the
Kerr ($Q=g=0$) and Kerr-Newman ($g=0$) black holes. Interestingly, for a given
parameter set, the apparent size of the shadow monotonically decreases and the
shadow gets more distorted with increasing charge parameter $Q$. We put
constraints on the black hole parameters with the aid of recent M87* shadow
observation. The conserved quantities associated with the rotating regular
black holes are calculated and also a brief description of the weak
gravitational lensing using the Gauss-Bonnet theorem is presented.
Interestingly, the deflection angle decreases with the charge of the black
hole. Our results \textit{vis-\`{a}-vis} go over to the Kerr and Kerr-Newman
black holes in the appropriate limits.
| [
{
"created": "Wed, 11 Dec 2019 07:54:16 GMT",
"version": "v1"
}
] | 2019-12-12 | [
[
"Kumar",
"Rahul",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Wang",
"Anzhong",
""
]
] | We discuss the horizon properties, shadow cast, and the weak gravitational lensing of charged rotating regular black holes, which in addition to mass ($M$) and rotation parameter ($a$) have an electric charge ($Q$) and magnetic charge ($g$). The considered regular black holes are the generalization of the Kerr ($Q=g=0$) and Kerr-Newman ($g=0$) black holes. Interestingly, for a given parameter set, the apparent size of the shadow monotonically decreases and the shadow gets more distorted with increasing charge parameter $Q$. We put constraints on the black hole parameters with the aid of recent M87* shadow observation. The conserved quantities associated with the rotating regular black holes are calculated and also a brief description of the weak gravitational lensing using the Gauss-Bonnet theorem is presented. Interestingly, the deflection angle decreases with the charge of the black hole. Our results \textit{vis-\`{a}-vis} go over to the Kerr and Kerr-Newman black holes in the appropriate limits. |
1208.0106 | Hongsheng Zhang | Hongsheng Zhang, Xin-Zhou Li | Critical behaviors of gravity under quantum perturbations | 6 pages, two figures,match the published version | Journal of Shanghai Normal University( Natural
Sciences)V43,1,P44(2014) | 10.3969/J.ISSN.1000-5137.2014.01.006 | null | gr-qc cond-mat.stat-mech hep-th | http://creativecommons.org/licenses/by/3.0/ | Phase transition and critical phenomenon is a very interesting topic in
thermodynamics and statistical mechanics. Gravity is believed to has deep and
inherent relation to thermodynamics. Near the critical point, the perturbation
becomes significant. Thus for ordinary matter (govern by interactions besides
gravity) the critical behavior will become very different if we ignore the
perturbations around the critical point, such as mean field theory. We find
that the critical exponents for RN-AdS spacetime keeps the same values even we
consider the full quantum perturbations. This indicates a key difference
between gravity and ordinary thermodynamic system.
| [
{
"created": "Wed, 1 Aug 2012 05:32:25 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Dec 2014 13:02:56 GMT",
"version": "v2"
}
] | 2014-12-22 | [
[
"Zhang",
"Hongsheng",
""
],
[
"Li",
"Xin-Zhou",
""
]
] | Phase transition and critical phenomenon is a very interesting topic in thermodynamics and statistical mechanics. Gravity is believed to has deep and inherent relation to thermodynamics. Near the critical point, the perturbation becomes significant. Thus for ordinary matter (govern by interactions besides gravity) the critical behavior will become very different if we ignore the perturbations around the critical point, such as mean field theory. We find that the critical exponents for RN-AdS spacetime keeps the same values even we consider the full quantum perturbations. This indicates a key difference between gravity and ordinary thermodynamic system. |
1808.06692 | Carlos A. R. Herdeiro | Pedro V. P. Cunha, Carlos A. R. Herdeiro, Eugen Radu | Isolated black holes without $\mathbb{Z}_2$ isometry | 6 pages, 5 figures; v2. Matches the version to be published in Phys.
Rev. D | Phys. Rev. D 98, 104060 (2018) | 10.1103/PhysRevD.98.104060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A mechanism to construct asymptotically flat, isolated, stationary black hole
(BH) spacetimes with no $\mathbb{Z}_2$ (No$\mathbb{Z}$) isometry is described.
In particular, the horizon geometry of such No$\mathbb{Z}$ BHs does not have
the usual north-south (reflection) symmetry. We discuss two explicit families
of models wherein No$\mathbb{Z}$ BHs arise. In one of these families, we
exhibit the intrinsic horizon geometry of an illustrative example by
isometrically embedding it in Euclidean 3-space, resulting in an "egg-like"
shaped horizon. This asymmetry leaves an imprint in the No$\mathbb{Z}$ BH
phenomenology, for instance in its lensing of light; but it needs not be
manifest in the BH shadow, which in some cases can be analytically shown to
retain a $\mathbb{Z}_2$ symmetry. Light absorption and scattering due to an
isotropic source surrounding a No$\mathbb{Z}$ BH endows it with a non-zero
momentum, producing an asymmetry triggered BH rocket effect.
| [
{
"created": "Mon, 20 Aug 2018 21:03:35 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Nov 2018 13:54:43 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Cunha",
"Pedro V. P.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | A mechanism to construct asymptotically flat, isolated, stationary black hole (BH) spacetimes with no $\mathbb{Z}_2$ (No$\mathbb{Z}$) isometry is described. In particular, the horizon geometry of such No$\mathbb{Z}$ BHs does not have the usual north-south (reflection) symmetry. We discuss two explicit families of models wherein No$\mathbb{Z}$ BHs arise. In one of these families, we exhibit the intrinsic horizon geometry of an illustrative example by isometrically embedding it in Euclidean 3-space, resulting in an "egg-like" shaped horizon. This asymmetry leaves an imprint in the No$\mathbb{Z}$ BH phenomenology, for instance in its lensing of light; but it needs not be manifest in the BH shadow, which in some cases can be analytically shown to retain a $\mathbb{Z}_2$ symmetry. Light absorption and scattering due to an isotropic source surrounding a No$\mathbb{Z}$ BH endows it with a non-zero momentum, producing an asymmetry triggered BH rocket effect. |
1504.07637 | Piero Nicolini | Bernard J. Carr and Jonas Mureika and Piero Nicolini | Sub-Planckian black holes and the Generalized Uncertainty Principle | 12 pages, 9 figures, version published in J. High En. Phys | JHEP 1507 (2015) 052 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Black Hole Uncertainty Principle correspondence suggests that there could
exist black holes with mass beneath the Planck scale but radius of order the
Compton scale rather than Schwarzschild scale. We present a modified, self-dual
Schwarzschild-like metric that reproduces desirable aspects of a variety of
disparate models in the sub-Planckian limit, while remaining Schwarzschild in
the large mass limit. The self-dual nature of this solution under $M
\leftrightarrow M^{-1}$ naturally implies a Generalized Uncertainty Principle
with the linear form $\Delta x \sim \frac{1}{\Delta p} + \Delta p$. We also
demonstrate a natural dimensional reduction feature, in that the gravitational
radius and thermodynamics of sub-Planckian objects resemble that of $(1+1)$-D
gravity. The temperature of sub-Planckian black holes scales as $M$ rather than
$M^{-1}$ but the evaporation of those smaller than $10^{-36}$g is suppressed by
the cosmic background radiation. This suggests that relics of this mass could
provide the dark matter.
| [
{
"created": "Tue, 28 Apr 2015 20:00:49 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jul 2015 16:34:56 GMT",
"version": "v2"
}
] | 2015-07-20 | [
[
"Carr",
"Bernard J.",
""
],
[
"Mureika",
"Jonas",
""
],
[
"Nicolini",
"Piero",
""
]
] | The Black Hole Uncertainty Principle correspondence suggests that there could exist black holes with mass beneath the Planck scale but radius of order the Compton scale rather than Schwarzschild scale. We present a modified, self-dual Schwarzschild-like metric that reproduces desirable aspects of a variety of disparate models in the sub-Planckian limit, while remaining Schwarzschild in the large mass limit. The self-dual nature of this solution under $M \leftrightarrow M^{-1}$ naturally implies a Generalized Uncertainty Principle with the linear form $\Delta x \sim \frac{1}{\Delta p} + \Delta p$. We also demonstrate a natural dimensional reduction feature, in that the gravitational radius and thermodynamics of sub-Planckian objects resemble that of $(1+1)$-D gravity. The temperature of sub-Planckian black holes scales as $M$ rather than $M^{-1}$ but the evaporation of those smaller than $10^{-36}$g is suppressed by the cosmic background radiation. This suggests that relics of this mass could provide the dark matter. |
1106.5072 | Giancarlo Cella | F. Bosi, G. Cella, A. Di Virgilio, A.Ortolan, A. Porzio, S. Solimeno,
M. Cerdonio, J. P. Zendri, M. Allegrini, J. Belfi, N. Beverini, B. Bouhadef,
l G. Carelli, I. Ferrante, E. Maccioni, R. Passaquieti, F. Stefani, M. L.
Ruggiero, A. Tartaglia, K. U. Schreiber, A. Gebauer, and J-P. R. Wells | Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope | 24 pages, 26 Postscript figures | Phys. Rev. D 84, 122002 (2011) | 10.1103/PhysRevD.84.122002 | null | gr-qc physics.geo-ph physics.ins-det physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an under-ground experiment to detect the general relativistic
effects due to the curvature of space-time around the Earth (de Sitter effect)
and to rotation of the planet (dragging of the inertial frames or
Lense-Thirring effect). It is based on the comparison between the IERS value of
the Earth rotation vector and corresponding measurements obtained by a
tri-axial laser detector of rotation. The proposed detector consists of six
large ring-lasers arranged along three orthogonal axes.
In about two years of data taking, the 1% sensitivity required for the
measurement of the Lense-Thirring drag can be reached with square rings of 6
$m$ side, assuming a shot noise limited sensitivity ($ 20 prad/s/\sqrt{Hz}$).
The multi-gyros system, composed of rings whose planes are perpendicular to one
or the other of three orthogonal axes, can be built in several ways. Here, we
consider cubic and octahedron structures. The symmetries of the proposed
configurations provide mathematical relations that can be used to study the
stability of the scale factors, the relative orientations or the ring-laser
planes, very important to get rid of systematics in long-term measurements,
which are required in order to determine the relativistic effects.
| [
{
"created": "Fri, 24 Jun 2011 22:02:45 GMT",
"version": "v1"
}
] | 2011-12-20 | [
[
"Bosi",
"F.",
""
],
[
"Cella",
"G.",
""
],
[
"Di Virgilio",
"A.",
""
],
[
"Ortolan",
"A.",
""
],
[
"Porzio",
"A.",
""
],
[
"Solimeno",
"S.",
""
],
[
"Cerdonio",
"M.",
""
],
[
"Zendri",
"J. P.",
""
],
[
"Allegrini",
"M.",
""
],
[
"Belfi",
"J.",
""
],
[
"Beverini",
"N.",
""
],
[
"Bouhadef",
"B.",
""
],
[
"Carelli",
"l G.",
""
],
[
"Ferrante",
"I.",
""
],
[
"Maccioni",
"E.",
""
],
[
"Passaquieti",
"R.",
""
],
[
"Stefani",
"F.",
""
],
[
"Ruggiero",
"M. L.",
""
],
[
"Tartaglia",
"A.",
""
],
[
"Schreiber",
"K. U.",
""
],
[
"Gebauer",
"A.",
""
],
[
"Wells",
"J-P. R.",
""
]
] | We propose an under-ground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a tri-axial laser detector of rotation. The proposed detector consists of six large ring-lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 $m$ side, assuming a shot noise limited sensitivity ($ 20 prad/s/\sqrt{Hz}$). The multi-gyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedron structures. The symmetries of the proposed configurations provide mathematical relations that can be used to study the stability of the scale factors, the relative orientations or the ring-laser planes, very important to get rid of systematics in long-term measurements, which are required in order to determine the relativistic effects. |
0807.0207 | Maciej Dunajski | Maciej Dunajski and Gary Gibbons | Cosmic Jerk, Snap and Beyond | 10 pages. Minor revisions, added summary. Final version to appear in
CQG | Class.Quant.Grav.25:235012,2008 | 10.1088/0264-9381/25/23/235012 | DAMTP-2008-58 | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We clarify the procedure for expressing the Friedmann equation in terms of
directly measurable cosmological scalars constructed out of higher derivatives
of the scale factor. We carry out this procedure for pure dust, Chaplygin gas
and generalised Chaplygin gas energy-momentum tensors. In each case it leads to
a constraint on the scalars thus giving rise to a test of General Relativity.
We also discuss a formulation of the Friedmann equation as unparametrised
geodesic motion and its connection with the Lagrangian treatment of perfect
fluids coupled to gravity.
| [
{
"created": "Tue, 1 Jul 2008 17:22:02 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 2008 12:52:50 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Dunajski",
"Maciej",
""
],
[
"Gibbons",
"Gary",
""
]
] | We clarify the procedure for expressing the Friedmann equation in terms of directly measurable cosmological scalars constructed out of higher derivatives of the scale factor. We carry out this procedure for pure dust, Chaplygin gas and generalised Chaplygin gas energy-momentum tensors. In each case it leads to a constraint on the scalars thus giving rise to a test of General Relativity. We also discuss a formulation of the Friedmann equation as unparametrised geodesic motion and its connection with the Lagrangian treatment of perfect fluids coupled to gravity. |
0805.4505 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado G\'omez-Lobo and Juan A. Valiente Kroon | Kerr Initial data | 23 pages, 1 figure. Minor typos corrected and remark 2 added. To
appear in Classical and Quantum Gravity | Class.Quant.Grav.25:205018,2008 | 10.1088/0264-9381/25/20/205018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exploiting a 3+1 analysis of the Mars-Simon tensor, conditions on a vacuum
initial data set ensuring that its development is isometric to a subset of the
Kerr spacetime are found. These conditions are expressed in terms of the
vanishing of a positive scalar function defined on the initial data
hypersurface. Applications of this result are discussed.
| [
{
"created": "Thu, 29 May 2008 10:15:08 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Aug 2008 15:58:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | Exploiting a 3+1 analysis of the Mars-Simon tensor, conditions on a vacuum initial data set ensuring that its development is isometric to a subset of the Kerr spacetime are found. These conditions are expressed in terms of the vanishing of a positive scalar function defined on the initial data hypersurface. Applications of this result are discussed. |
2208.06754 | Simran Arora | Tee-How Loo, Avik De, Simran Arora, P.K. Sahoo | Impact of curvature based geometric constraints on $F(R)$ theory | EPJC accepted version | European Physical Journal C 82 (2022) 705 | 10.1140/epjc/s10052-022-10672-8 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Theories of gravity are fundamentally a relation between matter and the
geometric structure of the underlying spacetime. So once we put some additional
restrictions on the spacetime geometry, the theory of gravity is bound to get
the impact, irrespective of whether it is general relativity or the modified
theories of gravity. In the present article, we consider two curvature-based
constraints, namely the almost pseudo-Ricci symmetric and weakly Ricci
symmetric condition. As a novel result, such spacetimes with non-null
associated vectors are entirely classified, and then applying the obtained
results, we investigate these spacetimes as solutions of the $F(R)$-gravity
theory. The modified Friedmann equations are derived and analysed in a
model-independent way first. Finally, two $F(R)$ gravity models are examined
for recent observational constrained values of the deceleration, jerk, and
Hubble parameters. We further discuss the behavior of energy conditions.
| [
{
"created": "Sun, 14 Aug 2022 01:14:52 GMT",
"version": "v1"
}
] | 2022-08-16 | [
[
"Loo",
"Tee-How",
""
],
[
"De",
"Avik",
""
],
[
"Arora",
"Simran",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Theories of gravity are fundamentally a relation between matter and the geometric structure of the underlying spacetime. So once we put some additional restrictions on the spacetime geometry, the theory of gravity is bound to get the impact, irrespective of whether it is general relativity or the modified theories of gravity. In the present article, we consider two curvature-based constraints, namely the almost pseudo-Ricci symmetric and weakly Ricci symmetric condition. As a novel result, such spacetimes with non-null associated vectors are entirely classified, and then applying the obtained results, we investigate these spacetimes as solutions of the $F(R)$-gravity theory. The modified Friedmann equations are derived and analysed in a model-independent way first. Finally, two $F(R)$ gravity models are examined for recent observational constrained values of the deceleration, jerk, and Hubble parameters. We further discuss the behavior of energy conditions. |
1204.2411 | Chul-Moon Yoo | Chul-Moon Yoo, Hiroyuki Abe, Yohsuke Takamori and Ken-ichi Nakao | Black Hole Universe: Construction and Analysis of Initial Data | 24 pages, 12 figures, analyses have been improved in the 2nd version | null | 10.1103/PhysRevD.86.044027 | YITP-12-29; OCU-PHYS-365; AP-GR-97 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically construct an one-parameter family of initial data of an
expanding inhomogeneous universe model which is composed of regularly aligned
black holes with an identical mass. They are initial data for vacuum solutions
of the Einstein equations. We call this universe model the "black hole
universe" and analyze the structure of these initial data. We study the
relation between the mean expansion rate of the 3-space, which corresponds to
the Hubble parameter, and the mass density of black holes. The result implies
that the same relation as that of the Einstein-de Sitter universe is realized
in the limit of the large separation between neighboring black holes. The
applicability of the cosmological Newtonian $N$-body simulation to the dark
matter composed of black holes is also discussed. The deviation of the spatial
metric of the cosmological Newtonian $N$-body system from that of the black
hole universe is found to be smaller than about 1% in a region distant from the
particles, if the separation length between neighboring particles is 20 times
larger than their gravitational radius. By contrast, the deviation of the
square of the Hubble parameter of the cosmological Newtonian $N$-body system
from that of the black hole universe is about 20% for the same separation
length.
| [
{
"created": "Wed, 11 Apr 2012 10:57:37 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jun 2012 03:04:47 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Yoo",
"Chul-Moon",
""
],
[
"Abe",
"Hiroyuki",
""
],
[
"Takamori",
"Yohsuke",
""
],
[
"Nakao",
"Ken-ichi",
""
]
] | We numerically construct an one-parameter family of initial data of an expanding inhomogeneous universe model which is composed of regularly aligned black holes with an identical mass. They are initial data for vacuum solutions of the Einstein equations. We call this universe model the "black hole universe" and analyze the structure of these initial data. We study the relation between the mean expansion rate of the 3-space, which corresponds to the Hubble parameter, and the mass density of black holes. The result implies that the same relation as that of the Einstein-de Sitter universe is realized in the limit of the large separation between neighboring black holes. The applicability of the cosmological Newtonian $N$-body simulation to the dark matter composed of black holes is also discussed. The deviation of the spatial metric of the cosmological Newtonian $N$-body system from that of the black hole universe is found to be smaller than about 1% in a region distant from the particles, if the separation length between neighboring particles is 20 times larger than their gravitational radius. By contrast, the deviation of the square of the Hubble parameter of the cosmological Newtonian $N$-body system from that of the black hole universe is about 20% for the same separation length. |
1910.03100 | Mar\'ia Jos\'e Guzm\'an | Mar\'ia Jos\'e Guzm\'an, Rafael Ferraro | Degrees of freedom and Hamiltonian formalism for $f(T)$ gravity | 4 pages, no figures, to appear in the conference proceedings of the
10th Alexander Friedmann International Seminar on Gravitation and Cosmology,
International Journal of Modern Physics A, World Scientific Publishing
Company | Int. J. Mod. Phys. A 35, No. 02n03, 2040022 (2020) | 10.1142/S0217751X20400229 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The existence of an extra degree of freedom (d.o.f.) in $f(T)$ gravity has
been recently proved by means of the Dirac formalism for constrained
Hamiltonian systems. We will show a toy model displaying the essential feature
of $f(T)$ gravity, which is the pseudoinvariance of T under a local symmetry,
to understand the nature of the extra d.o.f.
| [
{
"created": "Mon, 7 Oct 2019 21:42:03 GMT",
"version": "v1"
}
] | 2020-04-09 | [
[
"Guzmán",
"María José",
""
],
[
"Ferraro",
"Rafael",
""
]
] | The existence of an extra degree of freedom (d.o.f.) in $f(T)$ gravity has been recently proved by means of the Dirac formalism for constrained Hamiltonian systems. We will show a toy model displaying the essential feature of $f(T)$ gravity, which is the pseudoinvariance of T under a local symmetry, to understand the nature of the extra d.o.f. |
2211.16189 | Vitalii Vertogradov | Vitalii Vertogradov | On the particle collisions during gravitational collapse of Vaidya
spacetimes | 11 pages, corrected version | Physics of Complex Systems. - 2023. - Volume 4, N 1. - P. 17-23 | 10.33910/2687-153X-2022-4-1-17-23 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The center-of-mass energy can be arbitrarily high in Schwarzschild spacetime
if one considers the front collision of two particles, one of which moves along
so-called white hole geodesics and another one along a black hole geodesic.
This process can take place if one considers the gravitational collapse model.
In this paper, we consider the well-known naked singularity formation in Vaidya
spacetime and investigate the question about two particle collision near the
boundary of the collapsing cloud. The center-of-mass energy of the front
collision is considered. One particle moves away from the naked singularity and
another one falls onto a collapsing cloud. We show that the center-of-mass
energy grows unboundly if the collision takes place in the vicinity of the
conformal Killing horizon.
| [
{
"created": "Tue, 29 Nov 2022 13:33:11 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Nov 2023 12:38:41 GMT",
"version": "v2"
}
] | 2023-11-21 | [
[
"Vertogradov",
"Vitalii",
""
]
] | The center-of-mass energy can be arbitrarily high in Schwarzschild spacetime if one considers the front collision of two particles, one of which moves along so-called white hole geodesics and another one along a black hole geodesic. This process can take place if one considers the gravitational collapse model. In this paper, we consider the well-known naked singularity formation in Vaidya spacetime and investigate the question about two particle collision near the boundary of the collapsing cloud. The center-of-mass energy of the front collision is considered. One particle moves away from the naked singularity and another one falls onto a collapsing cloud. We show that the center-of-mass energy grows unboundly if the collision takes place in the vicinity of the conformal Killing horizon. |
2203.04257 | Vyacheslav Dokuchaev | V. A. Berezin and V. I. Dokuchaev | Weyl cosmology | 10 pages | IJMPA Vol. 37, No. 20n21, 2243005 (2022) | 10.1142/S0217751X22430059 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The homogeneous and isotropic cosmological model in the Weyl conformal
geometry is considered. We showed that, despite the conformal invariance, the
dust matter is allowed in such a universe. It is shown that the number of dust
particles is not conserved, i. e., they are continuously produced. The general
form of the law for their creation is found.
| [
{
"created": "Tue, 8 Mar 2022 18:19:17 GMT",
"version": "v1"
}
] | 2022-10-14 | [
[
"Berezin",
"V. A.",
""
],
[
"Dokuchaev",
"V. I.",
""
]
] | The homogeneous and isotropic cosmological model in the Weyl conformal geometry is considered. We showed that, despite the conformal invariance, the dust matter is allowed in such a universe. It is shown that the number of dust particles is not conserved, i. e., they are continuously produced. The general form of the law for their creation is found. |
2010.01857 | Juan Calderon Bustillo | Juan Calder\'on Bustillo, Paul D. Lasky and Eric Thrane | Black-hole spectroscopy, the no-hair theorem and GW150914: Kerr vs.
Occam | 12 pages, 4 figures, Version Accepted for publication in Phys.Rev.D | Phys. Rev. D 103, 024041 (2021) | 10.1103/PhysRevD.103.024041 | LIGO P-2000372 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The "no-hair" theorem states that astrophysical black holes are fully
characterised by just two numbers: their mass and spin. The gravitational-wave
emission from a perturbed black-hole consists of a superposition of damped
sinusoids, known as \textit{quasi-normal modes}. Quasi-normal modes are
specified by three integers $(\ell,m,n)$: the $(\ell, m)$ integers describe the
angular properties and $(n)$ specifies the (over)tone. If the no-hair theorem
holds, the frequencies and damping times of quasi-normal modes are determined
uniquely by the mass and spin of the black hole, while phases and amplitudes
depend on the particular perturbation. Current tests of the no-hair theorem,
attempt to identify these modes in a semi-agnostic way, without imposing priors
on the source of the perturbation. This is usually known as \textit{black-hole
spectroscopy}. Applying this framework to GW150914, the measurement of the
first overtone led to the confirmation of the theorem to $20\%$ level. We show,
however, that such semi-agnostic tests cannot provide strong evidence in favour
of the no-hair theorem, even for extremely loud signals, given the increasing
number of overtones (and free parameters) needed to fit the data. This can be
solved by imposing prior assumptions on the origin of the perturbed black hole
that can further constrain the explored parameters: in particular, our
knowledge that the ringdown is sourced by a binary black hole merger. Applying
this strategy to GW150914 we find a natural log Bayes factor of $\sim 6.5$ in
favour of the Kerr nature of its remnant, indicating that the hairy object
hypothesis is disfavoured with $<1:600$ with respect to the Kerr black-hole
one.
| [
{
"created": "Mon, 5 Oct 2020 08:43:43 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jan 2021 23:51:08 GMT",
"version": "v2"
}
] | 2021-02-03 | [
[
"Bustillo",
"Juan Calderón",
""
],
[
"Lasky",
"Paul D.",
""
],
[
"Thrane",
"Eric",
""
]
] | The "no-hair" theorem states that astrophysical black holes are fully characterised by just two numbers: their mass and spin. The gravitational-wave emission from a perturbed black-hole consists of a superposition of damped sinusoids, known as \textit{quasi-normal modes}. Quasi-normal modes are specified by three integers $(\ell,m,n)$: the $(\ell, m)$ integers describe the angular properties and $(n)$ specifies the (over)tone. If the no-hair theorem holds, the frequencies and damping times of quasi-normal modes are determined uniquely by the mass and spin of the black hole, while phases and amplitudes depend on the particular perturbation. Current tests of the no-hair theorem, attempt to identify these modes in a semi-agnostic way, without imposing priors on the source of the perturbation. This is usually known as \textit{black-hole spectroscopy}. Applying this framework to GW150914, the measurement of the first overtone led to the confirmation of the theorem to $20\%$ level. We show, however, that such semi-agnostic tests cannot provide strong evidence in favour of the no-hair theorem, even for extremely loud signals, given the increasing number of overtones (and free parameters) needed to fit the data. This can be solved by imposing prior assumptions on the origin of the perturbed black hole that can further constrain the explored parameters: in particular, our knowledge that the ringdown is sourced by a binary black hole merger. Applying this strategy to GW150914 we find a natural log Bayes factor of $\sim 6.5$ in favour of the Kerr nature of its remnant, indicating that the hairy object hypothesis is disfavoured with $<1:600$ with respect to the Kerr black-hole one. |
1001.2621 | Kouji Nakamura | Kouji Nakamura | Second-order Gauge-invariant Cosmological Perturbation Theory: Current
Status | 26 pages, 2 figures, Summary report on the current status of the
second-order gauge-invariant cosmological perturbation theory, Published as
an invited review in the Special Issue "Testing the Gaussianity and
Statistical Isotropy of the Universe" in Advances in Astronomy | Advances in Astronomy vol. 2010 (2010), 576273 | 10.1155/2010/576273 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current status of the recent developments of the second-order
gauge-invariant cosmological perturbation theory is reviewed. To show the
essence of this perturbation theory, we concentrate only on the universe filled
with a single scalar field. Through this review, we point out the problems
which should be clarified for the further theoretical sophistication of this
perturbation theory. We also expect that this theoretical sophistication will
be also useful to discuss the theoretical predictions of Non-Gaussianity in CMB
and comparison with observations.
| [
{
"created": "Fri, 15 Jan 2010 06:43:23 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Dec 2010 06:14:28 GMT",
"version": "v2"
}
] | 2016-08-24 | [
[
"Nakamura",
"Kouji",
""
]
] | The current status of the recent developments of the second-order gauge-invariant cosmological perturbation theory is reviewed. To show the essence of this perturbation theory, we concentrate only on the universe filled with a single scalar field. Through this review, we point out the problems which should be clarified for the further theoretical sophistication of this perturbation theory. We also expect that this theoretical sophistication will be also useful to discuss the theoretical predictions of Non-Gaussianity in CMB and comparison with observations. |
1301.6353 | Soon-Tae Hong | Soon-Tae Hong | Geometrical and hydrodynamic aspects of five-dimensional Schwarzschild
black hole | 8 pages | null | 10.3938/jkps.64.1928 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exploiting the five-dimensional Schwarzschild black hole, we study the
geometrical natures of the higher dimensional black hole to yield the (6+1)
dimensional global embedding Minkowski space structure. We next obtain the
Hawking temperature on this five-dimensional manifold, whose result is
different from the four-dimensional one. On the contrary, the radial component
of the Einstein equation for the massive particles or photons on the
five-dimensional spacetime is shown to have the same form as the
four-dimensional black hole one. Moreover, we construct the effective potential
on equatorial plane of the restricted three-brane to investigate the behavior
of the particles or photons on this restricted brane.
| [
{
"created": "Sun, 27 Jan 2013 14:08:28 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Hong",
"Soon-Tae",
""
]
] | Exploiting the five-dimensional Schwarzschild black hole, we study the geometrical natures of the higher dimensional black hole to yield the (6+1) dimensional global embedding Minkowski space structure. We next obtain the Hawking temperature on this five-dimensional manifold, whose result is different from the four-dimensional one. On the contrary, the radial component of the Einstein equation for the massive particles or photons on the five-dimensional spacetime is shown to have the same form as the four-dimensional black hole one. Moreover, we construct the effective potential on equatorial plane of the restricted three-brane to investigate the behavior of the particles or photons on this restricted brane. |
1510.07561 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado G\'omez-Lobo | A local non-negative initial data scalar characterisation of the Kerr
solution | 18 pages, no figures. Typos corrected and dropped artificial
restriction on the vacuum initial data set used to define the positive
scalar. To appear in Physical Review D | Phys. Rev. D 92, 124053 (2015) | 10.1103/PhysRevD.92.124053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For any vacuum initial data set, we define a local, non-negative scalar
quantity which vanishes at every point of the data hypersurface if and only if
the data are {\em Kerr initial} data. Our scalar quantity only depends on the
quantities used to construct the vacuum initial data set which are the
Riemannian metric defined on the initial data hypersurface and a symmetric
tensor which plays the role of the second fundamental form of the embedded
initial data hypersurface. The dependency is {\em algorithmic} in the sense
that given the initial data one can compute the scalar quantity by algebraic
and differential manipulations, being thus suitable for an implementation in a
numerical code. The scalar could also be useful in studies of the non-linear
stability of the Kerr solution because it serves to measure the deviation of a
vacuum initial data set from the Kerr initial data in a local and algorithmic
way.
| [
{
"created": "Mon, 26 Oct 2015 17:39:47 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Nov 2015 13:27:25 GMT",
"version": "v2"
}
] | 2015-12-30 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
]
] | For any vacuum initial data set, we define a local, non-negative scalar quantity which vanishes at every point of the data hypersurface if and only if the data are {\em Kerr initial} data. Our scalar quantity only depends on the quantities used to construct the vacuum initial data set which are the Riemannian metric defined on the initial data hypersurface and a symmetric tensor which plays the role of the second fundamental form of the embedded initial data hypersurface. The dependency is {\em algorithmic} in the sense that given the initial data one can compute the scalar quantity by algebraic and differential manipulations, being thus suitable for an implementation in a numerical code. The scalar could also be useful in studies of the non-linear stability of the Kerr solution because it serves to measure the deviation of a vacuum initial data set from the Kerr initial data in a local and algorithmic way. |
2010.02161 | Sebasti\'an Bahamonde Dr | Sebastian Bahamonde, Christian Pfeifer | General Teleparallel Modifications of Schwarzschild Geometry | 17 pages; v2 has some new additions matching the published version | Int. J. Geom. Methods Mod. Phys. 18 (2021) | 10.1142/S0219887821400016 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Teleparallel theories of gravity are described in terms of the tetrad of a
metric and a flat connection with torsion. In this paper, we study spherical
symmetry in a modified teleparallel theory of gravity which is based on an
arbitrary function of the five possible scalars constructed from the
irreducible parts of torsion. This theory is a generalisation of the so-called
New General Relativity theory. We find that only two scalars are different to
zero in spherical symmetry and we solve the corresponding field equations
analytically for conformal Teleparallel gravity, and then perturbatively around
Schwarzschild geometry for the general perturbative theory around GR. Finally,
we compute phenomenological effects from the perturbed solutions such as the
photon sphere, perihelion shift, Shapiro delay, and the light deflection. We
find their correspondent correction to the standard GR contribution and their
dependence on the three model parameters.
| [
{
"created": "Mon, 5 Oct 2020 17:08:49 GMT",
"version": "v1"
},
{
"created": "Wed, 5 May 2021 00:18:53 GMT",
"version": "v2"
}
] | 2021-05-06 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Pfeifer",
"Christian",
""
]
] | Teleparallel theories of gravity are described in terms of the tetrad of a metric and a flat connection with torsion. In this paper, we study spherical symmetry in a modified teleparallel theory of gravity which is based on an arbitrary function of the five possible scalars constructed from the irreducible parts of torsion. This theory is a generalisation of the so-called New General Relativity theory. We find that only two scalars are different to zero in spherical symmetry and we solve the corresponding field equations analytically for conformal Teleparallel gravity, and then perturbatively around Schwarzschild geometry for the general perturbative theory around GR. Finally, we compute phenomenological effects from the perturbed solutions such as the photon sphere, perihelion shift, Shapiro delay, and the light deflection. We find their correspondent correction to the standard GR contribution and their dependence on the three model parameters. |
1503.06109 | W. G. Unruh | M. Hotta, R. Sch\"utzhold, W. G. Unruh | On the partner particles for moving mirror radiation and black hole
evaporation | 12 pages, 3 figures-- v3-- corrected typos and a few notation
inconsistencies | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The partner mode with respect to a vacuum state for a given mode (like that
corresponding to one of the thermal particles emitted by a black hole) is
defined and calculated. The partner modes are explicitly calculated for a
number of cases, in particular for the modes corresponding to a particle
detector being excited by turn-on/turn-off transients, or with the thermal
particles emitted by the accelerated mirror model for black hole evaporation.
One of the key results is that the partner mode in general is just a vacuum
fluctuation, and one can have the partner mode be located in a region where the
state cannot be distinguished from the vacuum state by any series of local
measurements, including the energy density. I.e., "information" (the
correlations with the thermal emissions) need not be associated with any energy
transport. The idea that black holes emit huge amounts of energy in their last
stages because of all the information which must be emitted under the
assumption of black-hole unitarity is found not necessarily to be the case.
| [
{
"created": "Fri, 20 Mar 2015 15:29:05 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Apr 2015 19:48:55 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Apr 2015 19:31:13 GMT",
"version": "v3"
}
] | 2015-04-22 | [
[
"Hotta",
"M.",
""
],
[
"Schützhold",
"R.",
""
],
[
"Unruh",
"W. G.",
""
]
] | The partner mode with respect to a vacuum state for a given mode (like that corresponding to one of the thermal particles emitted by a black hole) is defined and calculated. The partner modes are explicitly calculated for a number of cases, in particular for the modes corresponding to a particle detector being excited by turn-on/turn-off transients, or with the thermal particles emitted by the accelerated mirror model for black hole evaporation. One of the key results is that the partner mode in general is just a vacuum fluctuation, and one can have the partner mode be located in a region where the state cannot be distinguished from the vacuum state by any series of local measurements, including the energy density. I.e., "information" (the correlations with the thermal emissions) need not be associated with any energy transport. The idea that black holes emit huge amounts of energy in their last stages because of all the information which must be emitted under the assumption of black-hole unitarity is found not necessarily to be the case. |
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