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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1009.0589 | Olivier Sarbach | Oscar Reula and Olivier Sarbach | The Initial-Boundary Value Problem in General Relativity | 11 pages, 2 figures. Contribution to a special volume for Mario
Castagnino's seventy fifth birthday | Int.J.Mod.Phys.D20:767-783,2011 | 10.1142/S0218271811019116 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we summarize what is known about the initial-boundary value
problem for general relativity and discuss present problems related to it.
| [
{
"created": "Fri, 3 Sep 2010 05:25:46 GMT",
"version": "v1"
}
] | 2011-05-25 | [
[
"Reula",
"Oscar",
""
],
[
"Sarbach",
"Olivier",
""
]
] | In this article we summarize what is known about the initial-boundary value problem for general relativity and discuss present problems related to it. |
1208.2146 | Hyeong-Chan Kim | Inyong Cho, Hyeong-Chan Kim, and Taeyoon Moon | Universe Driven by Perfect Fluid in Eddington-inspired Born-Infeld
Gravity | 24 pages, 5 figures | PRD 86, 084018 (2002) | 10.1103/PhysRevD.86.084018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the evolution of the Universe filled with barotropic perfect
fluid in Eddington-inspired Born-Infeld gravity. We consider both the isotropic
and the anisotropic universe. At the early stage when the energy density is
high, the evolution is modified considerably compared with that in general
relativity. For the equation-of-state parameter $w>0$, the initial singularity
is not accompanied as it was discovered for radiation in earlier work. More
interestingly, for pressureless dust ($w=0$), the initial state approaches a de
Sitter state. This fact opens a new possibility of singularity-free nature of
the theory. The anisotropy is mild, and does not develop curvature
singularities in spacetime contrary to general relativity.
| [
{
"created": "Fri, 10 Aug 2012 11:27:46 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Cho",
"Inyong",
""
],
[
"Kim",
"Hyeong-Chan",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We investigate the evolution of the Universe filled with barotropic perfect fluid in Eddington-inspired Born-Infeld gravity. We consider both the isotropic and the anisotropic universe. At the early stage when the energy density is high, the evolution is modified considerably compared with that in general relativity. For the equation-of-state parameter $w>0$, the initial singularity is not accompanied as it was discovered for radiation in earlier work. More interestingly, for pressureless dust ($w=0$), the initial state approaches a de Sitter state. This fact opens a new possibility of singularity-free nature of the theory. The anisotropy is mild, and does not develop curvature singularities in spacetime contrary to general relativity. |
1308.2550 | Jozef Skakala | Jozef Skakala | Quantization of horizon entropy and the thermodynamics of spacetime | 24 pages, (invited) review of some of my previous published results
with some new arguments / results added | Braz.Jour.Phys. 44, 2-3, 2014, p. 291-304 | 10.1007/s13538-014-0177-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a review of my work published in the papers [1-4]. It offers a more
detailed discussion of the results than what was given in the published papers
and it links my results to some conclusions recently made by other people. It
also offers some new arguments for the conclusions previously made. The
fundamental idea of this work is that the semi-classical quantization of the
black hole entropy, as suggested by Bekenstein [5], holds (at least)
generically for the spacetime horizons. We support this conclusion by two
separate arguments: 1. we generalize Bekenstein's lower bound on the horizon
area transition to much larger class of horizons than only the black hole
horizon, 2. we obtain the same entropy spectra via the asymptotic quasi-normal
frequencies of some particular spherically symmetric multi-horizon spacetimes,
(in the way proposed by Maggiore [6]). The main result of this paper supports
the conclusions made by other people in [7,8], but uses different arguments.
| [
{
"created": "Mon, 12 Aug 2013 13:16:45 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Oct 2013 01:16:05 GMT",
"version": "v2"
}
] | 2014-06-03 | [
[
"Skakala",
"Jozef",
""
]
] | This is a review of my work published in the papers [1-4]. It offers a more detailed discussion of the results than what was given in the published papers and it links my results to some conclusions recently made by other people. It also offers some new arguments for the conclusions previously made. The fundamental idea of this work is that the semi-classical quantization of the black hole entropy, as suggested by Bekenstein [5], holds (at least) generically for the spacetime horizons. We support this conclusion by two separate arguments: 1. we generalize Bekenstein's lower bound on the horizon area transition to much larger class of horizons than only the black hole horizon, 2. we obtain the same entropy spectra via the asymptotic quasi-normal frequencies of some particular spherically symmetric multi-horizon spacetimes, (in the way proposed by Maggiore [6]). The main result of this paper supports the conclusions made by other people in [7,8], but uses different arguments. |
2002.03603 | Wen-Hong Ruan | Wen-Hong Ruan, Chang Liu, Zong-Kuan Guo, Yue-Liang Wu, Rong-Gen Cai | The LISA-Taiji network | 6 pages. 2 figures | Nature Astronomy 4 (2020) 108-109 | 10.1038/s41550-019-1008-4 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Both LISA and Taiji, planned space-based gravitational-wave detectors in
orbit around the Sun, are expected to launch in 2030-2035. Assuming a one-year
overlap, we explore a potential LISA-Taiji network to fast and accurately
localize the gravitational-wave sources.
| [
{
"created": "Mon, 10 Feb 2020 08:43:08 GMT",
"version": "v1"
}
] | 2020-02-11 | [
[
"Ruan",
"Wen-Hong",
""
],
[
"Liu",
"Chang",
""
],
[
"Guo",
"Zong-Kuan",
""
],
[
"Wu",
"Yue-Liang",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | Both LISA and Taiji, planned space-based gravitational-wave detectors in orbit around the Sun, are expected to launch in 2030-2035. Assuming a one-year overlap, we explore a potential LISA-Taiji network to fast and accurately localize the gravitational-wave sources. |
2005.05258 | Antonio Ferreiro | Antonio Ferreiro and Jose Navarro-Salas | Running gravitational couplings, decoupling, and curved spacetime
renormalization | Some points clarified, misprints corrected; to appear in Phys. Rev. D | Phys. Rev. D 102, 045021 (2020) | 10.1103/PhysRevD.102.045021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose to slightly generalize the DeWitt-Schwinger adiabatic
renormalization subtractions in curved space to include an arbitrary
renormalization mass scale $\mu$. The new predicted running for the
gravitational couplings are fully consistent with decoupling of heavy massive
fields. This is a somewhat improvement with respect to the more standard
treatment of minimal (DeWitt-Schwinger) subtractions via dimensional
regularization. We also show how the vacuum metamorphosis model emerges from
the running couplings.
| [
{
"created": "Mon, 11 May 2020 16:59:04 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Aug 2020 16:20:39 GMT",
"version": "v2"
}
] | 2020-09-02 | [
[
"Ferreiro",
"Antonio",
""
],
[
"Navarro-Salas",
"Jose",
""
]
] | We propose to slightly generalize the DeWitt-Schwinger adiabatic renormalization subtractions in curved space to include an arbitrary renormalization mass scale $\mu$. The new predicted running for the gravitational couplings are fully consistent with decoupling of heavy massive fields. This is a somewhat improvement with respect to the more standard treatment of minimal (DeWitt-Schwinger) subtractions via dimensional regularization. We also show how the vacuum metamorphosis model emerges from the running couplings. |
2205.00654 | Wei Sun | Wei Sun, Xian-Hui Ge | Holographic heat engine efficiency of hyperbolic charged black holes | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a four-dimensional charged hyperbolic black hole as working
matter to establish a black hole holographic heat engine, and use the
rectangular cycle to obtain the heat engine efficiency. We find that when the
increasing of entropy is zero, the heat engine efficiency of the hyperbolic
black hole becomes the well-known Carnot efficiency. We also find that less
charge corresponds to higher efficiency in the case of q > 0. Furthermore, we
study the efficiency of the flat case and spherical case and compare the
efficiency with that of the hyperbolic charged black holes. Finally, we use
numerical simulation to study the efficiency in benchmark scheme.
| [
{
"created": "Mon, 2 May 2022 04:59:03 GMT",
"version": "v1"
}
] | 2022-05-03 | [
[
"Sun",
"Wei",
""
],
[
"Ge",
"Xian-Hui",
""
]
] | We consider a four-dimensional charged hyperbolic black hole as working matter to establish a black hole holographic heat engine, and use the rectangular cycle to obtain the heat engine efficiency. We find that when the increasing of entropy is zero, the heat engine efficiency of the hyperbolic black hole becomes the well-known Carnot efficiency. We also find that less charge corresponds to higher efficiency in the case of q > 0. Furthermore, we study the efficiency of the flat case and spherical case and compare the efficiency with that of the hyperbolic charged black holes. Finally, we use numerical simulation to study the efficiency in benchmark scheme. |
gr-qc/0106042 | Naresh Dadhich | Z. Ya. Turakulov and N. Dadhich | A stationary vacuum solution dual to the Kerr solution | Latex, 4 pages, minor modifications in title and discussion. Accepted
in Mod. Phys. Lett. A | Mod.Phys.Lett. A16 (2001) 1959-1962 | 10.1142/S0217732301005084 | IUCAA-30/2001 | gr-qc | null | We present a stationary axially symmetric two parameter vacuum solution which
could be considered as ``dual'' to the Kerr solution. It is obtained by
removing the mass parameter from the function of the radial coordinate and
introducing a dimensionless parameter in the function of the angle coordinate
in the metric functions. It turns out that it is in fact the massless limit of
the Kerr - NUT solution.
| [
{
"created": "Wed, 13 Jun 2001 14:10:39 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Sep 2001 05:08:01 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Turakulov",
"Z. Ya.",
""
],
[
"Dadhich",
"N.",
""
]
] | We present a stationary axially symmetric two parameter vacuum solution which could be considered as ``dual'' to the Kerr solution. It is obtained by removing the mass parameter from the function of the radial coordinate and introducing a dimensionless parameter in the function of the angle coordinate in the metric functions. It turns out that it is in fact the massless limit of the Kerr - NUT solution. |
gr-qc/0702128 | Michael P. Ryan jr | L. Ort\'iz and M. P. Ryan Jr | The complete quantum collapse scenario of 2+1 dust shell: Preliminary
Calculations | 28 pages, 13 figures, to appear in the proceedings of NEB XII,
Nauplion, Greece | J.Phys.Conf.Ser.68:012047,2007 | 10.1088/1742-6596/68/1/012047 | null | gr-qc | null | If we consider the gravitational collapse of a material object to a black
hole, we would expect, for ranges of mass where a black hole would form, the
following scenario. A large enough object would collapse classically until an
event horizon forms, and to an external observer the object would be lost fom
view. However, once the horizon has formed the black hole will begin to emit
Hawking radiation and the hole will lose mass and the horizon will shrink. The
final state of this process could be either a zero-mass "black hole" with
consequent information loss, or some sort of "quantum remnant.
A complete investigation of this process would require: 1) A complete and
consistent theory of quantum gravity coupled to some kind of field that would
provide the Hawking radiation (which could be the gravitational field itself
--gravitons); 2) Some kind of definition of a "horizon" in this quantum
gravity, and; 3) The calculational tools to achieve a description of the
scenario. Lacking these, one may resort to toy models to try to give some sort
of preliminary answer.
In this paper we will consider the collapse of an infinitesimally thin dust
shell in 2+1 gravity, where an exact minisuperspace quantum solution exists,
and try to make rough estimates of the collapse-Hawking radiation-remnant
formation process.
| [
{
"created": "Sat, 24 Feb 2007 03:20:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ortíz",
"L.",
""
],
[
"Ryan",
"M. P.",
"Jr"
]
] | If we consider the gravitational collapse of a material object to a black hole, we would expect, for ranges of mass where a black hole would form, the following scenario. A large enough object would collapse classically until an event horizon forms, and to an external observer the object would be lost fom view. However, once the horizon has formed the black hole will begin to emit Hawking radiation and the hole will lose mass and the horizon will shrink. The final state of this process could be either a zero-mass "black hole" with consequent information loss, or some sort of "quantum remnant. A complete investigation of this process would require: 1) A complete and consistent theory of quantum gravity coupled to some kind of field that would provide the Hawking radiation (which could be the gravitational field itself --gravitons); 2) Some kind of definition of a "horizon" in this quantum gravity, and; 3) The calculational tools to achieve a description of the scenario. Lacking these, one may resort to toy models to try to give some sort of preliminary answer. In this paper we will consider the collapse of an infinitesimally thin dust shell in 2+1 gravity, where an exact minisuperspace quantum solution exists, and try to make rough estimates of the collapse-Hawking radiation-remnant formation process. |
gr-qc/9707033 | Daniel STAF Tilley | Roy Maartens and Daniel Tilley (Portsmouth University) | Exact Perturbations for inflation with smooth exit | Minor errors corrected | Gen.Rel.Grav. 30 (1998) 289-297; Erratum-ibid. 30 (1998) 519 | 10.1023/A:1018852929430 | null | gr-qc | null | Toy models for the Hubble rate or the scalar field potential have been used
to analyze the amplification of scalar perturbations through a smooth
transition from inflation to the radiation era. We use a Hubble rate that
arises consistently from a decaying vacuum cosmology, which evolves smoothly
from nearly de Sitter inflation to radiation domination. We find exact
solutions for super-horizon perturbations (scalar and tensor), and for
sub-horizon perturbations in the vacuum- and radiation-dominated eras. The
standard conserved quantity for super-horizon scalar perturbations is exactly
constant for growing modes, and zero for the decaying modes.
| [
{
"created": "Tue, 15 Jul 1997 12:25:39 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Apr 1998 11:28:25 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Maartens",
"Roy",
"",
"Portsmouth University"
],
[
"Tilley",
"Daniel",
"",
"Portsmouth University"
]
] | Toy models for the Hubble rate or the scalar field potential have been used to analyze the amplification of scalar perturbations through a smooth transition from inflation to the radiation era. We use a Hubble rate that arises consistently from a decaying vacuum cosmology, which evolves smoothly from nearly de Sitter inflation to radiation domination. We find exact solutions for super-horizon perturbations (scalar and tensor), and for sub-horizon perturbations in the vacuum- and radiation-dominated eras. The standard conserved quantity for super-horizon scalar perturbations is exactly constant for growing modes, and zero for the decaying modes. |
gr-qc/0010001 | Roh Suan Tung | Roh S. Tung (CIPA and Univ of Chicago), James M. Nester (National
Central Univ, Taiwan) | Gravitational Energy-Momentum in the Tetrad and Quadratic Spinor
Representations of General Relativity | 9 pages. Proceedings of the Vigier III Symposium (August 21-25, 2000,
U. C. Berkeley), Kluwer Academic, to be published | null | null | null | gr-qc hep-th | null | In the Tetrad Representation of General Relativity, the energy-momentum
expression, found by Moller in 1961, is a tensor wrt coordinate transformations
but is not a tensor wrt local Lorentz frame rotations. This local Lorentz
freedom is shown to be the same as the six parameter normalized spinor degrees
of freedom in the Quadratic Spinor Representation of General Relativity. From
the viewpoint of a gravitational field theory in flat space-time, these extra
spinor degrees of freedom allow us to obtain a local energy-momentum density
which is a true tensor over both coordinate and local Lorentz frame rotations.
| [
{
"created": "Sun, 1 Oct 2000 05:31:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tung",
"Roh S.",
"",
"CIPA and Univ of Chicago"
],
[
"Nester",
"James M.",
"",
"National\n Central Univ, Taiwan"
]
] | In the Tetrad Representation of General Relativity, the energy-momentum expression, found by Moller in 1961, is a tensor wrt coordinate transformations but is not a tensor wrt local Lorentz frame rotations. This local Lorentz freedom is shown to be the same as the six parameter normalized spinor degrees of freedom in the Quadratic Spinor Representation of General Relativity. From the viewpoint of a gravitational field theory in flat space-time, these extra spinor degrees of freedom allow us to obtain a local energy-momentum density which is a true tensor over both coordinate and local Lorentz frame rotations. |
1104.1383 | Steinar Johannesen | Oyvind Gron and Steinar Johannesen | A solution of the Einstein-Maxwell equations describing conformally flat
spacetime outside a charged domain wall | 11 pages, 0 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive and discuss the physical interpretation of a conformally flat,
static solution of the Einstein-Maxwell equations. It is argued that it
describes a conformally flat, static spacetime outside a charged spherically
symmetric domain wall. The acceleration of gravity is directed away from the
wall in spite of the positive gravitational mass of the electric field outside
the wall, as given by the Tolman-Whittaker expression. The reason for the
repulsive gravitation is the strain of the wall which is calculated using the
Israel formalism for singular surfaces.
| [
{
"created": "Thu, 7 Apr 2011 17:08:14 GMT",
"version": "v1"
}
] | 2011-04-08 | [
[
"Gron",
"Oyvind",
""
],
[
"Johannesen",
"Steinar",
""
]
] | We derive and discuss the physical interpretation of a conformally flat, static solution of the Einstein-Maxwell equations. It is argued that it describes a conformally flat, static spacetime outside a charged spherically symmetric domain wall. The acceleration of gravity is directed away from the wall in spite of the positive gravitational mass of the electric field outside the wall, as given by the Tolman-Whittaker expression. The reason for the repulsive gravitation is the strain of the wall which is calculated using the Israel formalism for singular surfaces. |
1008.1803 | Lee Lindblom | Lee Lindblom, John G. Baker, and Benjamin J. Owen | Improved Time-Domain Accuracy Standards for Model Gravitational
Waveforms | 10 pages, 5 figures | Phys.Rev.D82:084020,2010 | 10.1103/PhysRevD.82.084020 | LIGO Document Number LIGO-P1000078-v2 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Model gravitational waveforms must be accurate enough to be useful for
detection of signals and measurement of their parameters, so appropriate
accuracy standards are needed. Yet these standards should not be unnecessarily
restrictive, making them impractical for the numerical and analytical modelers
to meet. The work of Lindblom, Owen, and Brown [Phys. Rev. D 78, 124020 (2008)]
is extended by deriving new waveform accuracy standards which are significantly
less restrictive while still ensuring the quality needed for gravitational-wave
data analysis. These new standards are formulated as bounds on certain norms of
the time-domain waveform errors, which makes it possible to enforce them in
situations where frequency-domain errors may be difficult or impossible to
estimate reliably. These standards are less restrictive by about a factor of 20
than the previously published time-domain standards for detection, and up to a
factor of 60 for measurement. These new standards should therefore be much
easier to use effectively.
| [
{
"created": "Tue, 10 Aug 2010 20:43:17 GMT",
"version": "v1"
}
] | 2011-05-04 | [
[
"Lindblom",
"Lee",
""
],
[
"Baker",
"John G.",
""
],
[
"Owen",
"Benjamin J.",
""
]
] | Model gravitational waveforms must be accurate enough to be useful for detection of signals and measurement of their parameters, so appropriate accuracy standards are needed. Yet these standards should not be unnecessarily restrictive, making them impractical for the numerical and analytical modelers to meet. The work of Lindblom, Owen, and Brown [Phys. Rev. D 78, 124020 (2008)] is extended by deriving new waveform accuracy standards which are significantly less restrictive while still ensuring the quality needed for gravitational-wave data analysis. These new standards are formulated as bounds on certain norms of the time-domain waveform errors, which makes it possible to enforce them in situations where frequency-domain errors may be difficult or impossible to estimate reliably. These standards are less restrictive by about a factor of 20 than the previously published time-domain standards for detection, and up to a factor of 60 for measurement. These new standards should therefore be much easier to use effectively. |
gr-qc/9911107 | Julio Cesar Fabris | M. Azreg-Ainou, G. Clement, C.P. Constantinidis and J.C. Fabris | Electrostatic solutions in Kaluza-Klein theory: geometry and stability | Latex file, 21 pages | Grav.Cosmol.6:207-218,2000 | null | null | gr-qc hep-th | null | We investigate the family of electrostatic spherically symmetric solutions of
the five-dimensional Kaluza-Klein theory. Both charged and neutral cases are
considered. The analysis of the solutions, through their geometrical
properties, reveals the existence of black holes, wormholes and naked
singularities. A new class of regular solutions is identified. A monopole
perturbation study of all these solutions is carried out, enabling us to prove
analytically the stability of large classes of solutions. In particular, the
black hole solutions are stable, while for the regular solutions the stability
analysis leads to an eigenvalue problem.
| [
{
"created": "Fri, 26 Nov 1999 14:45:37 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Azreg-Ainou",
"M.",
""
],
[
"Clement",
"G.",
""
],
[
"Constantinidis",
"C. P.",
""
],
[
"Fabris",
"J. C.",
""
]
] | We investigate the family of electrostatic spherically symmetric solutions of the five-dimensional Kaluza-Klein theory. Both charged and neutral cases are considered. The analysis of the solutions, through their geometrical properties, reveals the existence of black holes, wormholes and naked singularities. A new class of regular solutions is identified. A monopole perturbation study of all these solutions is carried out, enabling us to prove analytically the stability of large classes of solutions. In particular, the black hole solutions are stable, while for the regular solutions the stability analysis leads to an eigenvalue problem. |
1005.0294 | D. Petroff | Stefan Horatschek and David Petroff | Uniformly Rotating Homogeneous Rings in post-Newtonian Gravity | 12 pages, 7 figures, v1: 2 tables added, agrees with published
version | Mon. Not. R. Astron. Soc., vol. 408, p. 1749 (2010) | 10.1111/j.1365-2966.2010.17241.x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper uniformly rotating relativistic rings are investigated
analytically utilizing two different approximations simultaneously: (1) an
expansion about the thin ring limit (the cross-section is small compared with
the size of the whole ring) (2) post-Newtonian expansions. The analytic results
for rings are compared with numerical solutions.
| [
{
"created": "Mon, 3 May 2010 13:50:09 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Dec 2010 19:15:03 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Horatschek",
"Stefan",
""
],
[
"Petroff",
"David",
""
]
] | In this paper uniformly rotating relativistic rings are investigated analytically utilizing two different approximations simultaneously: (1) an expansion about the thin ring limit (the cross-section is small compared with the size of the whole ring) (2) post-Newtonian expansions. The analytic results for rings are compared with numerical solutions. |
gr-qc/9509021 | null | Dmitri V. Vasilevich | Gauge-invariance in one-loop quantum cosmology | LATeX, 8 pages | null | null | Talk at VI Semin. on Quantum Gravity | gr-qc | null | We study the problem of gauge-invariance and gauge-dependence in one-loop
quantum cosmology. We formulate some requirements which should be satisfied by
boundary conditions in order to give gauge-independent path integral. The case
of QED is studied in some detail. We outline difficulties in gauge-invariant
quantization of gravitational field in a bounded region.
| [
{
"created": "Sat, 9 Sep 1995 20:57:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vasilevich",
"Dmitri V.",
""
]
] | We study the problem of gauge-invariance and gauge-dependence in one-loop quantum cosmology. We formulate some requirements which should be satisfied by boundary conditions in order to give gauge-independent path integral. The case of QED is studied in some detail. We outline difficulties in gauge-invariant quantization of gravitational field in a bounded region. |
gr-qc/0601089 | Christian Boehmer | Christian G. Boehmer, Piotr Bronowski | The homogeneous and isotropic Weyssenhoff fluid | 9 pages, invited submission by UJP; revised acknowledgements | Ukr.J.Phys. 55 (2010) 607-612 | null | ASGBG/CIU Preprint: 22.01.2006B | gr-qc | null | We consider a Weyssenhoff fluid assuming that the spacetime is homogeneous
and isotropic, therefore being relevant for cosmological considerations of
gravity theories with torsion. In this paper, it is explicitely shown that the
Weyssenhoff fluids obeying the Frenkel condition or the Papapetrou-Corinaldesi
condition are incompatible with the cosmological principle, which restricts the
torsion tensor to have only a vector and an axial vector component. Moreover it
turns out that the Weyssenhoff fluid obeying the Tulczyjew condition is also
incompatible with the cosmological principle. Based on this result we propose
to reconsider a number of previous works that analysed cosmological solutions
of Einstein-Cartan theory, since their spin fluids usually did not obey the
cosmological principle.
| [
{
"created": "Mon, 23 Jan 2006 05:52:29 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jan 2006 04:58:52 GMT",
"version": "v2"
}
] | 2010-05-21 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Bronowski",
"Piotr",
""
]
] | We consider a Weyssenhoff fluid assuming that the spacetime is homogeneous and isotropic, therefore being relevant for cosmological considerations of gravity theories with torsion. In this paper, it is explicitely shown that the Weyssenhoff fluids obeying the Frenkel condition or the Papapetrou-Corinaldesi condition are incompatible with the cosmological principle, which restricts the torsion tensor to have only a vector and an axial vector component. Moreover it turns out that the Weyssenhoff fluid obeying the Tulczyjew condition is also incompatible with the cosmological principle. Based on this result we propose to reconsider a number of previous works that analysed cosmological solutions of Einstein-Cartan theory, since their spin fluids usually did not obey the cosmological principle. |
0805.1908 | Cenalo Vaz | Cenalo Vaz and K. R. Koehler | A Rotating, Inhomogeneous Dust Interior for the BTZ Black Hole | 16 pages, no figures | Phys.Rev.D78:024038,2008 | 10.1103/PhysRevD.78.024038 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present exact solutions describing rotating, inhomogeneous dust with
generic initial data in 2+1 dimensional AdS spacetime and show how they are
smoothly matched to the Banados-Teitelboim-Zanelli (BTZ) solution in the
exterior. The metrics, which are the rotational analogues of the 2+1
dimensional LeMaitre-Tolman-Bondi (LTB) family, are described by their angular
momentum and one additional constant which, together with the angular momentum,
determines the energy density of the dust cloud. The weak energy condition
gives a constraint on the angular momentum profile inside the cloud. Solutions
can be stationary or time dependent, but only the time dependent solutions can
be matched consistently to a BTZ exterior. No singularity is formed in either
the stationary or the time dependent cases.
| [
{
"created": "Tue, 13 May 2008 19:08:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Vaz",
"Cenalo",
""
],
[
"Koehler",
"K. R.",
""
]
] | We present exact solutions describing rotating, inhomogeneous dust with generic initial data in 2+1 dimensional AdS spacetime and show how they are smoothly matched to the Banados-Teitelboim-Zanelli (BTZ) solution in the exterior. The metrics, which are the rotational analogues of the 2+1 dimensional LeMaitre-Tolman-Bondi (LTB) family, are described by their angular momentum and one additional constant which, together with the angular momentum, determines the energy density of the dust cloud. The weak energy condition gives a constraint on the angular momentum profile inside the cloud. Solutions can be stationary or time dependent, but only the time dependent solutions can be matched consistently to a BTZ exterior. No singularity is formed in either the stationary or the time dependent cases. |
0912.1433 | \"Ozg\"ur Acik | \"Umit Ertem, \"Ozg\"ur A\c{c}{\i}k | Generalized Chern-Simons Modified Gravity in First-Order Formalism | 8 pages, an author added, new paragraphs, comments and references
added, published in Gen. Relativ. Gravit | Gen. Relativ. Gravit. 45, 477 (2013) | 10.1007/s10714-012-1483-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a generalization of Chern-Simons (CS) modified gravity in
first-order formalism. CS modified gravity action has a term that comes from
the chiral anomaly which is Pontryagin invariant. First-order CS modified
gravity is a torsional theory and in a space-time with torsion the chiral
anomaly includes a torsional topological term called Nieh-Yan invariant. We
generalize the CS modified gravity by adding the Nieh-Yan term to the action
and find the effective theory. We compare the generalized theory with the
first-order CS modified gravity and comment on the similarities and
differences.
| [
{
"created": "Tue, 8 Dec 2009 08:47:40 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Nov 2012 06:03:33 GMT",
"version": "v2"
}
] | 2016-08-14 | [
[
"Ertem",
"Ümit",
""
],
[
"Açık",
"Özgür",
""
]
] | We propose a generalization of Chern-Simons (CS) modified gravity in first-order formalism. CS modified gravity action has a term that comes from the chiral anomaly which is Pontryagin invariant. First-order CS modified gravity is a torsional theory and in a space-time with torsion the chiral anomaly includes a torsional topological term called Nieh-Yan invariant. We generalize the CS modified gravity by adding the Nieh-Yan term to the action and find the effective theory. We compare the generalized theory with the first-order CS modified gravity and comment on the similarities and differences. |
1309.1252 | Patryk Mach | Patryk Mach, Edward Malec, Janusz Karkowski | Spherical steady accretion flows -- dependence on the cosmological
constant, exact isothermal solutions and applications to cosmology | 19 pages, 10 figures | Phys. Rev. D 88, 084056 (2013) | 10.1103/PhysRevD.88.084056 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate spherical, isothermal and polytropic steady accretion models
in the presence of the cosmological constant. Exact solutions are found for
three classes of isothermal fluids, assuming the test gas approximation. The
cosmological constant damps the mass accretion rate and - above certain limit -
completely stops the steady accretion onto black holes. A "homoclinic-type"
accretion flow of polytropic gas has been discovered in AdS spacetimes in the
test-gas limit. These results can have cosmological connotation, through the
Einstein--Straus vacuole model of embedding local structures into
Friedman-Lemaitre-Robertson-Walker spacetimes. In particular one infers that
steady accretion would not exist in the late phases of the Penrose's scenario
of the evolution of the Universe, known as the Weyl curvature hypothesis.
| [
{
"created": "Thu, 5 Sep 2013 07:51:19 GMT",
"version": "v1"
}
] | 2013-11-13 | [
[
"Mach",
"Patryk",
""
],
[
"Malec",
"Edward",
""
],
[
"Karkowski",
"Janusz",
""
]
] | We investigate spherical, isothermal and polytropic steady accretion models in the presence of the cosmological constant. Exact solutions are found for three classes of isothermal fluids, assuming the test gas approximation. The cosmological constant damps the mass accretion rate and - above certain limit - completely stops the steady accretion onto black holes. A "homoclinic-type" accretion flow of polytropic gas has been discovered in AdS spacetimes in the test-gas limit. These results can have cosmological connotation, through the Einstein--Straus vacuole model of embedding local structures into Friedman-Lemaitre-Robertson-Walker spacetimes. In particular one infers that steady accretion would not exist in the late phases of the Penrose's scenario of the evolution of the Universe, known as the Weyl curvature hypothesis. |
1406.6884 | Hor\'acio Vieira | H. S. Vieira, V. B. Bezerra | Acoustic black holes: massless scalar field analytic solutions and
analogue Hawking radiation | 26 pages, with erratum. arXiv admin note: text overlap with
arXiv:1405.7846 | Gen Relativ Gravit (2016) 48:88, Gen Relativ Gravit (2019) 51:51 | 10.1007/s10714-016-2082-x, 10.1007/s10714-019-2529-y | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the analytic solutions of the radial part of the massless
Klein-Gordon equation in the spacetime of both three dimensional rotating and
four dimensional canonical acoustic black holes, which are given in terms of
the confluent Heun functions. From these solutions, we obtain the scalar waves
near the acoustic horizon. We discuss the analogue Hawking radiation of
massless scalar particles and the features of the spectrum associated with the
radiation emitted by these acoustic black holes.
| [
{
"created": "Thu, 26 Jun 2014 13:38:36 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2015 13:20:25 GMT",
"version": "v2"
},
{
"created": "Sun, 12 Jun 2016 13:26:55 GMT",
"version": "v3"
},
{
"created": "Sat, 6 Apr 2019 20:51:56 GMT",
"version": "v4"
}
] | 2019-04-10 | [
[
"Vieira",
"H. S.",
""
],
[
"Bezerra",
"V. B.",
""
]
] | We obtain the analytic solutions of the radial part of the massless Klein-Gordon equation in the spacetime of both three dimensional rotating and four dimensional canonical acoustic black holes, which are given in terms of the confluent Heun functions. From these solutions, we obtain the scalar waves near the acoustic horizon. We discuss the analogue Hawking radiation of massless scalar particles and the features of the spectrum associated with the radiation emitted by these acoustic black holes. |
1905.00451 | Manuel Hohmann | Manuel Hohmann | Disformal Transformations in Scalar-Torsion Gravity | LaTeX, 11 pages. Contribution to the proceedings of the conference
"Teleparallel Universes" in Salamanca 26-28 November 2018; published version | Universe 5 (2019) 167 | 10.3390/universe5070167 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study disformal transformations in the context of scalar extensions to
teleparallel gravity, in which the gravitational interaction is mediated by the
torsion of a flat, metric compatible connection. We find a generic class of
scalar-torsion actions which is invariant under disformal transformations, and
which possesses different invariant subclasses. For the most simple of these
subclasses we explicitly derive all terms that may appear in the action. We
propose to study actions from this class as possible teleparallel analogues of
healthy beyond Horndeski theories.
| [
{
"created": "Wed, 1 May 2019 19:02:48 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jul 2019 16:10:24 GMT",
"version": "v2"
}
] | 2019-10-02 | [
[
"Hohmann",
"Manuel",
""
]
] | We study disformal transformations in the context of scalar extensions to teleparallel gravity, in which the gravitational interaction is mediated by the torsion of a flat, metric compatible connection. We find a generic class of scalar-torsion actions which is invariant under disformal transformations, and which possesses different invariant subclasses. For the most simple of these subclasses we explicitly derive all terms that may appear in the action. We propose to study actions from this class as possible teleparallel analogues of healthy beyond Horndeski theories. |
gr-qc/0211109 | Roche Philippe | Karim Noui, Philippe Roche | Cosmological Deformation of Lorentzian Spin Foam Models | 37 pages, 7 figures included | Class.Quant.Grav.20:3175-3214,2003 | 10.1088/0264-9381/20/14/318 | null | gr-qc hep-th | null | We study the quantum deformation of the Barrett-Crane Lorentzian spin foam
model which is conjectured to be the discretization of Lorentzian Plebanski
model with positive cosmological constant and includes therefore as a
particular sector quantum gravity in de-Sitter space. This spin foam model is
constructed using harmonic analysis on the quantum Lorentz group. The
evaluation of simple spin networks are shown to be non commutative integrals
over the quantum hyperboloid defined as a pile of fuzzy spheres. We show that
the introduction of the cosmological constant removes all the infrared
divergences: for any fixed triangulation, the integration over the area
variables is finite for a large class of normalization of the amplitude of the
edges and of the faces.
| [
{
"created": "Fri, 29 Nov 2002 17:25:07 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Noui",
"Karim",
""
],
[
"Roche",
"Philippe",
""
]
] | We study the quantum deformation of the Barrett-Crane Lorentzian spin foam model which is conjectured to be the discretization of Lorentzian Plebanski model with positive cosmological constant and includes therefore as a particular sector quantum gravity in de-Sitter space. This spin foam model is constructed using harmonic analysis on the quantum Lorentz group. The evaluation of simple spin networks are shown to be non commutative integrals over the quantum hyperboloid defined as a pile of fuzzy spheres. We show that the introduction of the cosmological constant removes all the infrared divergences: for any fixed triangulation, the integration over the area variables is finite for a large class of normalization of the amplitude of the edges and of the faces. |
0710.5155 | Gilberto Medeiros Kremer | M. O. Ribas, F. P. Devecchi and G. M. Kremer | Cosmological model with non-minimally coupled fermionic field | Accepted for publication in Europhysics Letters | Europhys.Lett.81:19001,2008 | 10.1209/0295-5075/81/19001 | null | gr-qc | null | A model for the Universe is proposed whose constituents are: (a) a dark
energy field modeled by a fermionic field non-minimally coupled with the
gravitational field, (b) a matter field which consists of pressureless baryonic
and dark matter fields and (c) a field which represents the radiation and the
neutrinos. The coupled system of Dirac's equations and Einstein field equations
is solved numerically by considering a spatially flat homogeneous and isotropic
Universe. It is shown that the proposed model can reproduce the expected
red-shift behaviors of the deceleration parameter, of the density parameters of
each constituent and of the luminosity distance. Furthermore, for small values
of the red-shift the constant which couples the fermionic and gravitational
fields has a remarkable influence on the density and deceleration parameters.
| [
{
"created": "Fri, 26 Oct 2007 17:55:37 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ribas",
"M. O.",
""
],
[
"Devecchi",
"F. P.",
""
],
[
"Kremer",
"G. M.",
""
]
] | A model for the Universe is proposed whose constituents are: (a) a dark energy field modeled by a fermionic field non-minimally coupled with the gravitational field, (b) a matter field which consists of pressureless baryonic and dark matter fields and (c) a field which represents the radiation and the neutrinos. The coupled system of Dirac's equations and Einstein field equations is solved numerically by considering a spatially flat homogeneous and isotropic Universe. It is shown that the proposed model can reproduce the expected red-shift behaviors of the deceleration parameter, of the density parameters of each constituent and of the luminosity distance. Furthermore, for small values of the red-shift the constant which couples the fermionic and gravitational fields has a remarkable influence on the density and deceleration parameters. |
gr-qc/9709064 | Jemal Guven | Jemal Guven and Niall O Murchadha | Geometric Bounds in Spherically Symmetric General Relativity | 16 pages, revtex, submitted to Phys. Rev. D | Phys.Rev. D56 (1997) 7650-7657 | 10.1103/PhysRevD.56.7650 | null | gr-qc | null | We exploit an arbitrary extrinsic time foliation of spacetime to solve the
constraints in spherically symmetric general relativity. Among such foliations
there is a one parameter family, linear and homogeneous in the extrinsic
curvature, which permit the momentum constraint to be solved exactly. This
family includes, as special cases, the extrinsic time gauges that have been
exploited in the past. These foliations have the property that the extrinsic
curvature is spacelike with respect to the the spherically symmetric superspace
metric. What is remarkable is that the linearity can be relaxed at no essential
extra cost which permits us to isolate a large non - pathological dense subset
of all extrinsic time foliations. We identify properties of solutions which are
independent of the particular foliation within this subset. When the geometry
is regular, we can place spatially invariant numerical bounds on the values of
both the spatial and the temporal gradients of the scalar areal radius, $R$.
These bounds are entirely independent of the particular gauge and of the
magnitude of the sources. When singularities occur, we demonstrate that the
geometry behaves in a universal way in the neighborhood of the singularity.
| [
{
"created": "Wed, 24 Sep 1997 22:13:13 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Guven",
"Jemal",
""
],
[
"Murchadha",
"Niall O",
""
]
] | We exploit an arbitrary extrinsic time foliation of spacetime to solve the constraints in spherically symmetric general relativity. Among such foliations there is a one parameter family, linear and homogeneous in the extrinsic curvature, which permit the momentum constraint to be solved exactly. This family includes, as special cases, the extrinsic time gauges that have been exploited in the past. These foliations have the property that the extrinsic curvature is spacelike with respect to the the spherically symmetric superspace metric. What is remarkable is that the linearity can be relaxed at no essential extra cost which permits us to isolate a large non - pathological dense subset of all extrinsic time foliations. We identify properties of solutions which are independent of the particular foliation within this subset. When the geometry is regular, we can place spatially invariant numerical bounds on the values of both the spatial and the temporal gradients of the scalar areal radius, $R$. These bounds are entirely independent of the particular gauge and of the magnitude of the sources. When singularities occur, we demonstrate that the geometry behaves in a universal way in the neighborhood of the singularity. |
gr-qc/9701029 | Kevin Chan | Kevin C.K. Chan (University of Waterloo) | Is mass conformally invariant? | 8 pages, Latex | null | null | WATPHY-TH-96/14 | gr-qc | null | By using the Garfinkle, Horowitz and Strominger black hole solutions as
examples, we illustrate that, with respect to the reference action functional
proposed by Hawking and Horowitz, the asymptotic mass parameter is not
invariant between two conformally related static spherically symmetric metrics.
| [
{
"created": "Tue, 14 Jan 1997 04:41:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chan",
"Kevin C. K.",
"",
"University of Waterloo"
]
] | By using the Garfinkle, Horowitz and Strominger black hole solutions as examples, we illustrate that, with respect to the reference action functional proposed by Hawking and Horowitz, the asymptotic mass parameter is not invariant between two conformally related static spherically symmetric metrics. |
2105.08930 | Deepali Agarwal | Deepali Agarwal, Jishnu Suresh, Sanjit Mitra, Anirban Ain | Upper limits on persistent gravitational waves using folded data and the
full covariance matrix from Advanced LIGO$'$s first two observing runs | 18 pages, 7 figures, published version with a revised figure and
clarified main text, results unchanged, typos and grammatical corrections | Phys. Rev. D 104, 123018 (2021) | 10.1103/PhysRevD.104.123018 | LIGO-P2000499 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stochastic gravitational-wave background (SGWB) created by astrophysical
sources in the nearby Universe is likely to be anisotropic. Upper limits on
SGWB anisotropy have been produced for all major data-taking runs by the
ground-based laser interferometric detectors. However, due to the challenges
involved in numerically inverting the pixel-to-pixel noise covariance matrix,
which is necessary for setting upper limits, the searches accounted for angular
correlations in the map by using the spherical harmonic basis, where
regularization was relatively easier. This approach is better suited though for
extended sources. Moreover, the upper-limit maps produced in the two different
bases are seemingly different. While the upper limits may be consistent within
statistical errors, it was important to check whether the results would remain
consistent if the full noise covariance matrix was used in the pixel basis.
Here, we use the full pixel- to-pixel Fisher information matrix to create
upper-limit maps of SGWB anisotropy. We first perform an unmodeled search for
persistent, directional gravitational-wave sources using folded data from the
first (O1) and second (O2) observing runs of Advanced LIGO and show that the
results are consistent with the upper limits published by the LIGO-Virgo
Collaboration (LVC). We then explore various ways to account for the
pixel-to-pixel Fisher information matrix using singular-value decomposition and
Bayesian regularization schemes. We do not find evidence for any SGWB signal in
the data and the upper limits are consistent with the LVC results within
statistical errors. Through an injection study, we show that they are all valid
95\% upper limits, that is, the upper limit in a pixel is less than the
injected signal strength in less than 5\% of the pixels.
| [
{
"created": "Wed, 19 May 2021 05:24:47 GMT",
"version": "v1"
},
{
"created": "Sat, 13 May 2023 12:19:51 GMT",
"version": "v2"
}
] | 2023-07-18 | [
[
"Agarwal",
"Deepali",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Mitra",
"Sanjit",
""
],
[
"Ain",
"Anirban",
""
]
] | The stochastic gravitational-wave background (SGWB) created by astrophysical sources in the nearby Universe is likely to be anisotropic. Upper limits on SGWB anisotropy have been produced for all major data-taking runs by the ground-based laser interferometric detectors. However, due to the challenges involved in numerically inverting the pixel-to-pixel noise covariance matrix, which is necessary for setting upper limits, the searches accounted for angular correlations in the map by using the spherical harmonic basis, where regularization was relatively easier. This approach is better suited though for extended sources. Moreover, the upper-limit maps produced in the two different bases are seemingly different. While the upper limits may be consistent within statistical errors, it was important to check whether the results would remain consistent if the full noise covariance matrix was used in the pixel basis. Here, we use the full pixel- to-pixel Fisher information matrix to create upper-limit maps of SGWB anisotropy. We first perform an unmodeled search for persistent, directional gravitational-wave sources using folded data from the first (O1) and second (O2) observing runs of Advanced LIGO and show that the results are consistent with the upper limits published by the LIGO-Virgo Collaboration (LVC). We then explore various ways to account for the pixel-to-pixel Fisher information matrix using singular-value decomposition and Bayesian regularization schemes. We do not find evidence for any SGWB signal in the data and the upper limits are consistent with the LVC results within statistical errors. Through an injection study, we show that they are all valid 95\% upper limits, that is, the upper limit in a pixel is less than the injected signal strength in less than 5\% of the pixels. |
2212.00312 | Ali Pourmand | Nakul Aggarwal, Ali Pourmand, Fatimah Shojai, Harish Parthasarathy | Constraining Generalized Chaplygin Gas in Non-Minimally Coupled $f(Q)$
Cosmology using Quasars and $H(z)$ Data | 17 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the current framework of Einstein's equations in general relativity (GR),
gravity is described by the spacetime curvature. However, there are other
descriptions where the origin of gravity can be understood through torsion and
non-metricity $Q$. In this work, we discuss a modified theory of gravity namely
$f(Q)$ gravity, which considers a non-linear extension of $Q$. In particular,
we study the case where it is non-minimally coupled to matter. Motivated by the
recent success of Chaplygin gas models in the explanation of dark energy, we
assume a pressureless baryonic matter and a generalized Chaplygin gas as the
background fluid. We constrain the proposed model using two different datasets:
one for Hubble measurements and the other for quasars (which we calibrated)
with Markov-Chain Monte Carlo (MCMC) methods. We employ kinematic tools such as
deceleration and jerk parameters to determine deviations of the proposed model
from $\Lambda$CDM. We establish that the transition redshift $z_T$ in the
deceleration parameter $q$ is $0.607$ and $0.204$ with the two datasets
respectively, therefore describing the universe's acceleration.
| [
{
"created": "Thu, 1 Dec 2022 07:03:19 GMT",
"version": "v1"
}
] | 2022-12-02 | [
[
"Aggarwal",
"Nakul",
""
],
[
"Pourmand",
"Ali",
""
],
[
"Shojai",
"Fatimah",
""
],
[
"Parthasarathy",
"Harish",
""
]
] | In the current framework of Einstein's equations in general relativity (GR), gravity is described by the spacetime curvature. However, there are other descriptions where the origin of gravity can be understood through torsion and non-metricity $Q$. In this work, we discuss a modified theory of gravity namely $f(Q)$ gravity, which considers a non-linear extension of $Q$. In particular, we study the case where it is non-minimally coupled to matter. Motivated by the recent success of Chaplygin gas models in the explanation of dark energy, we assume a pressureless baryonic matter and a generalized Chaplygin gas as the background fluid. We constrain the proposed model using two different datasets: one for Hubble measurements and the other for quasars (which we calibrated) with Markov-Chain Monte Carlo (MCMC) methods. We employ kinematic tools such as deceleration and jerk parameters to determine deviations of the proposed model from $\Lambda$CDM. We establish that the transition redshift $z_T$ in the deceleration parameter $q$ is $0.607$ and $0.204$ with the two datasets respectively, therefore describing the universe's acceleration. |
gr-qc/0211072 | L. C. Garcia de Andrade | L.C. Garcia de Andrade (Departamento de Fisica Teorica-IF-UERJ) | Spin polarised magnetized cylinder in torsioned spacetime | Latex file | Gen.Rel.Grav. 35 (2003) 1279-1283 | 10.1023/A:1024406009917 | null | gr-qc | null | A Spin-polarised cylindrically symmetric exact class of solutions endowed
with magnetic fields in Einstein-Cartan-Maxwell gravity is obtained.
Application of matching conditions to this interior solution having an exterior
as Einstein's vacuum solution shows that for this class of metrics the
Riemann-Cartan (RC) rotation vanishes which makes the solution static.
Therefore we end up with a magnetized static spin polarised cylinder where the
pressure along the symmetry axis is negative.
| [
{
"created": "Fri, 22 Nov 2002 07:21:43 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"de Andrade",
"L. C. Garcia",
"",
"Departamento de Fisica Teorica-IF-UERJ"
]
] | A Spin-polarised cylindrically symmetric exact class of solutions endowed with magnetic fields in Einstein-Cartan-Maxwell gravity is obtained. Application of matching conditions to this interior solution having an exterior as Einstein's vacuum solution shows that for this class of metrics the Riemann-Cartan (RC) rotation vanishes which makes the solution static. Therefore we end up with a magnetized static spin polarised cylinder where the pressure along the symmetry axis is negative. |
2103.16595 | Leonardo Gualtieri | Gon\c{c}alo Castro, Leonardo Gualtieri, Paolo Pani | Hidden symmetry between rotational tidal Love numbers of spinning
neutron stars | 13 pages, 2 figures; minor changes | Phys. Rev. D 104, 044052 (2021) | 10.1103/PhysRevD.104.044052 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The coupling between the angular momentum of a compact object and an external
tidal field gives rise to the "rotational" tidal Love numbers, which affect the
tidal deformability of a spinning self-gravitating body and enter the
gravitational waveform of a binary inspiral at high post-Newtonian order. We
provide numerical evidence for a surprising "hidden" symmetry among the
rotational tidal Love numbers with opposite parities, which are associated to
perturbations belonging to separate sectors. This symmetry, whose existence had
been suggested on the basis of a Lagrangian description of the tidal
interaction in a binary system, holds independently of the equation of state of
the star.
| [
{
"created": "Tue, 30 Mar 2021 18:07:02 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Apr 2021 18:20:31 GMT",
"version": "v2"
}
] | 2021-08-25 | [
[
"Castro",
"Gonçalo",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Pani",
"Paolo",
""
]
] | The coupling between the angular momentum of a compact object and an external tidal field gives rise to the "rotational" tidal Love numbers, which affect the tidal deformability of a spinning self-gravitating body and enter the gravitational waveform of a binary inspiral at high post-Newtonian order. We provide numerical evidence for a surprising "hidden" symmetry among the rotational tidal Love numbers with opposite parities, which are associated to perturbations belonging to separate sectors. This symmetry, whose existence had been suggested on the basis of a Lagrangian description of the tidal interaction in a binary system, holds independently of the equation of state of the star. |
1210.7561 | P.A. Gonzalez | Ramon Becar, P. A. Gonzalez and Yerko Vasquez | Quasinormal modes and stability analysis for z=4 Topological black hole
in 4+1 dimensional Horava-Lifshitz gravity | 7 pages | null | 10.1142/S0218271813500077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study z=4 Topological black hole in 4+1 dimensional Horava-Lifshitz
gravity and we calculate analytically the quasinormal modes of scalar
perturbations and from these quasinormal modes we show that z=4 Topological
black hole in 4+1 dimensional Horava-Lifshitz gravity is stable.
| [
{
"created": "Mon, 29 Oct 2012 05:08:21 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Becar",
"Ramon",
""
],
[
"Gonzalez",
"P. A.",
""
],
[
"Vasquez",
"Yerko",
""
]
] | We study z=4 Topological black hole in 4+1 dimensional Horava-Lifshitz gravity and we calculate analytically the quasinormal modes of scalar perturbations and from these quasinormal modes we show that z=4 Topological black hole in 4+1 dimensional Horava-Lifshitz gravity is stable. |
1909.02890 | Noshad Khosravi Largani | Noshad Khosravi Largani, Mohammad Taghi Mirtorabi | Chameleon Mechanism in Inhomogeneous Astrophysical Objects | 5 pages, 3 figures, Proceedings of The XXIII International Scientific
Conference of Young Scientists and Specialists (AYSS-2019), Dubna, April
15-19, 2019 | AIP Conference Proceedings , Volume 2163, 090008 (2019) | 10.1063/1.5130130 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observational evidence implying the accelerated expansion of the universe has
been the motivation to develop various classes of modified gravity theories.
One of them uses the so-called "screening mechanism", which is successful in
reproducing the observed gravitational behavior in large scales as well as
being in agreement with tests of general relativity in the solar system. In
this work, we investigate an example of scalar-tensor theories with screening
mechanism, namely the profile of a Chameleon field around inhomogeneous
astrophysical objects. According to [Khoury and Weltman(2004)], one can define
two kinds of approaches applicable to the thin shell and thick shell regimes,
that allow for a solution to the Chameleon equation of motion. For sufficiently
large objects, the scalar field can be assumed to propagate from a thin shell
of the object instead of the whole body, which simplifies the problem. On the
other hand, this solution is not practical in small objects. We find that in
inhomogeneous objects this is not trivial and at least one more factor, which
turns out to be the density, can change the way of approaching this problem.
| [
{
"created": "Fri, 6 Sep 2019 13:24:10 GMT",
"version": "v1"
}
] | 2019-11-18 | [
[
"Largani",
"Noshad Khosravi",
""
],
[
"Mirtorabi",
"Mohammad Taghi",
""
]
] | Observational evidence implying the accelerated expansion of the universe has been the motivation to develop various classes of modified gravity theories. One of them uses the so-called "screening mechanism", which is successful in reproducing the observed gravitational behavior in large scales as well as being in agreement with tests of general relativity in the solar system. In this work, we investigate an example of scalar-tensor theories with screening mechanism, namely the profile of a Chameleon field around inhomogeneous astrophysical objects. According to [Khoury and Weltman(2004)], one can define two kinds of approaches applicable to the thin shell and thick shell regimes, that allow for a solution to the Chameleon equation of motion. For sufficiently large objects, the scalar field can be assumed to propagate from a thin shell of the object instead of the whole body, which simplifies the problem. On the other hand, this solution is not practical in small objects. We find that in inhomogeneous objects this is not trivial and at least one more factor, which turns out to be the density, can change the way of approaching this problem. |
2112.12309 | Mehdi Shokri | Mehdi Shokri, Jafar Sadeghi, Ram\'on Herrera, Saeed Noori Gashti | Warm inflation with bulk viscous pressure for different solutions of an
anisotropic universe | 26 pages, 21 figures | null | null | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/publicdomain/zero/1.0/ | We study a warm inflationary model for different expansions assuming an
anisotropic universe described by Bianchi I metric. The universe is filled with
a scalar field or inflaton, radiation, and bulk viscous pressure. We carry out
the inflationary analysis for different solutions of such universe in two
different cases of the bulk viscosity coefficient $\xi$ and the dissipation
coefficient $\Gamma$ as constant and variable parameters, respectively. We
compare the obtained results with the recent observations, in order to find the
observational constraints on the parameters space of the models. Moreover, we
attempt to present a better judgment among the considered models by calculation
of the non-linear parameter $f_{NL}$ describing the non-Gaussianity property of
the models. Additionally, we investigate the warm inflationary models with
viscous pressure from the Weak Gravity Conjecture approach, considering the
swampland criteria.
| [
{
"created": "Thu, 23 Dec 2021 02:06:49 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Feb 2022 13:08:44 GMT",
"version": "v2"
}
] | 2022-02-07 | [
[
"Shokri",
"Mehdi",
""
],
[
"Sadeghi",
"Jafar",
""
],
[
"Herrera",
"Ramón",
""
],
[
"Gashti",
"Saeed Noori",
""
]
] | We study a warm inflationary model for different expansions assuming an anisotropic universe described by Bianchi I metric. The universe is filled with a scalar field or inflaton, radiation, and bulk viscous pressure. We carry out the inflationary analysis for different solutions of such universe in two different cases of the bulk viscosity coefficient $\xi$ and the dissipation coefficient $\Gamma$ as constant and variable parameters, respectively. We compare the obtained results with the recent observations, in order to find the observational constraints on the parameters space of the models. Moreover, we attempt to present a better judgment among the considered models by calculation of the non-linear parameter $f_{NL}$ describing the non-Gaussianity property of the models. Additionally, we investigate the warm inflationary models with viscous pressure from the Weak Gravity Conjecture approach, considering the swampland criteria. |
gr-qc/0307109 | Piotr Chrusciel | P.T. Chrusciel, J. Jezierski, S. Leski | The Trautman-Bondi mass of initial data sets | latex2e, 51 pages in A4, minor typos corrected | Adv.Theor.Math.Phys. 8 (2004) 83-139 | null | null | gr-qc | null | We give a definition of mass for conformally compactifiable initial data
sets. The asymptotic conditions are compatible with existence of gravitational
radiation, and the compactifications are allowed to be polyhomogeneous. We show
that the resulting mass is a geometric invariant, and we prove positivity
thereof in the case of a spherical conformal infinity. When R(g) - or,
equivalently, the trace of the extrinsic curvature tensor - tends to a negative
constant to order one at infinity, the definition is expressed purely in terms
of three-dimensional or two-dimensional objects.
| [
{
"created": "Fri, 25 Jul 2003 15:45:42 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2004 16:43:12 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Chrusciel",
"P. T.",
""
],
[
"Jezierski",
"J.",
""
],
[
"Leski",
"S.",
""
]
] | We give a definition of mass for conformally compactifiable initial data sets. The asymptotic conditions are compatible with existence of gravitational radiation, and the compactifications are allowed to be polyhomogeneous. We show that the resulting mass is a geometric invariant, and we prove positivity thereof in the case of a spherical conformal infinity. When R(g) - or, equivalently, the trace of the extrinsic curvature tensor - tends to a negative constant to order one at infinity, the definition is expressed purely in terms of three-dimensional or two-dimensional objects. |
1906.00337 | Carlos A. S. Almeida | J. E. G. Silva, L. J. S. Sousa, W. T. Cruz, C. A. S. Almeida | Torsion braneworlds in a tensor-vector gravity | 19 pages, 12 figures. Modified text to match the accepted version in
International Journal of Modern Physics D | null | 10.1142/S0218271822500304 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the properties of gravity and bulk fields living in a torsion warped
braneworld. The torsion is driven by a background vector whose norm provides a
source for the bulk cosmological constant. For a vector as the derivative of a
scalar field, we find new isotropic and anisotropic thick brane geometries. We
analyse the features of bosonic and fermionic fields in this isotropic and in
standing wave scenarios. The background vector provides nonminimal coupling
between the field and the geometry leading to modifications in the Kaluza-Klein
states. The spinor connection is modified by the torsion and a derivative
Yukawa-like coupling is proposed. The effects of these new couplings are
investigated.
| [
{
"created": "Sun, 2 Jun 2019 04:03:36 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2022 14:24:28 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Mar 2022 02:41:51 GMT",
"version": "v3"
}
] | 2022-03-14 | [
[
"Silva",
"J. E. G.",
""
],
[
"Sousa",
"L. J. S.",
""
],
[
"Cruz",
"W. T.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] | We study the properties of gravity and bulk fields living in a torsion warped braneworld. The torsion is driven by a background vector whose norm provides a source for the bulk cosmological constant. For a vector as the derivative of a scalar field, we find new isotropic and anisotropic thick brane geometries. We analyse the features of bosonic and fermionic fields in this isotropic and in standing wave scenarios. The background vector provides nonminimal coupling between the field and the geometry leading to modifications in the Kaluza-Klein states. The spinor connection is modified by the torsion and a derivative Yukawa-like coupling is proposed. The effects of these new couplings are investigated. |
1607.03928 | Emre Dil Dr. | Emre Dil | Interacting dark matter and q-deformed dark energy non-minimally coupled
to gravity | null | Advances in High Energy Physics vol. 2016, Article ID 7380372, 17
pages, 2016 | 10.1155/2016/7380372 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we propose a new approach to study the dark sector of the
universe by considering the dark energy as emerging a q-deformed bosonic scalar
field which is not only interacting with the dark matter, but also
non-minimally coupled to gravity, in the framework of standard Einsteinian
gravity. In order to analyze the dynamic of the system, we first give the
quantum field theoretical description of the q-deformed scalar field dark
energy, then construct the action and the dynamical structure of these
interacting and non-minimally coupled dark sector. As a second issue, we
perform the phase space analysis of the model to check the reliability of our
proposal by searching the stable attractor solutions implying the late-time
accelerating expansion phase of the universe.
| [
{
"created": "Thu, 30 Jun 2016 13:17:32 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Oct 2016 17:19:04 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Nov 2016 10:28:36 GMT",
"version": "v3"
}
] | 2016-12-23 | [
[
"Dil",
"Emre",
""
]
] | In this paper, we propose a new approach to study the dark sector of the universe by considering the dark energy as emerging a q-deformed bosonic scalar field which is not only interacting with the dark matter, but also non-minimally coupled to gravity, in the framework of standard Einsteinian gravity. In order to analyze the dynamic of the system, we first give the quantum field theoretical description of the q-deformed scalar field dark energy, then construct the action and the dynamical structure of these interacting and non-minimally coupled dark sector. As a second issue, we perform the phase space analysis of the model to check the reliability of our proposal by searching the stable attractor solutions implying the late-time accelerating expansion phase of the universe. |
0801.4387 | Luis Lehner | Matthew Anderson, Eric W. Hirschmann, Luis Lehner, Steven L. Liebling,
Patrick M. Motl, David Neilsen, Carlos Palenzuela, Joel E. Tohline | Magnetized Neutron Star Mergers and Gravitational Wave Signals | Replaced with accepted PRL version. (Figures have been reduced in
quality) | Phys.Rev.Lett.100:191101,2008 | 10.1103/PhysRevLett.100.191101 | null | gr-qc astro-ph physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the influence of magnetic fields upon the dynamics of and
resulting gravitational waves from a binary neutron star merger in full general
relativity coupled to ideal magnetohydrodynamics (MHD). We consider two merger
scenarios, one where the stars begin with initially aligned poloidal magnetic
fields and one with no magnetic field. Both mergers result in a strongly
differentially rotating object. In comparison to the non-magnetized scenario,
the aligned magnetic fields delay the final merger of the two stars. During and
after merger we observe phenomena driven by the magnetic field, including
Kelvin-Helmholtz instabilities in shear layers, winding of the field lines, and
transition from poloidal to toroidal fields. These effects not only produce
electromagnetic radiation, but also can have a strong influence on the
gravitational waves. Thus, there are promising prospects for studying such
systems with both types of waves.
| [
{
"created": "Mon, 28 Jan 2008 22:14:51 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jun 2008 23:24:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Anderson",
"Matthew",
""
],
[
"Hirschmann",
"Eric W.",
""
],
[
"Lehner",
"Luis",
""
],
[
"Liebling",
"Steven L.",
""
],
[
"Motl",
"Patrick M.",
""
],
[
"Neilsen",
"David",
""
],
[
"Palenzuela",
"Carlos",
""
],
[
"Tohline",
"Joel E.",
""
]
] | We investigate the influence of magnetic fields upon the dynamics of and resulting gravitational waves from a binary neutron star merger in full general relativity coupled to ideal magnetohydrodynamics (MHD). We consider two merger scenarios, one where the stars begin with initially aligned poloidal magnetic fields and one with no magnetic field. Both mergers result in a strongly differentially rotating object. In comparison to the non-magnetized scenario, the aligned magnetic fields delay the final merger of the two stars. During and after merger we observe phenomena driven by the magnetic field, including Kelvin-Helmholtz instabilities in shear layers, winding of the field lines, and transition from poloidal to toroidal fields. These effects not only produce electromagnetic radiation, but also can have a strong influence on the gravitational waves. Thus, there are promising prospects for studying such systems with both types of waves. |
gr-qc/0503078 | Alejandro Corichi | Alejandro Corichi and Daniel Sudarsky | Towards a new approach to quantum gravity phenomenology | 13 pages, no figures. Discussion added, same conclusions | Int.J.Mod.Phys.D14:1685-1698,2005 | 10.1142/S0218271805007541 | ICN-UNAM-05/01 | gr-qc | null | The idea that quantum gravity manifestations would be associated with a
violation of Lorentz invariance is very strongly bounded and faces serious
theoretical challenges. This leads us to consider an alternative line of
thought for such phenomenological search. We discuss the underlying viewpoint
and briefly mention its possible connections with current theoretical ideas. We
also outline the challenges that the experimental search of the effects would
seem to entail.
| [
{
"created": "Thu, 17 Mar 2005 20:33:07 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2005 19:55:43 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | The idea that quantum gravity manifestations would be associated with a violation of Lorentz invariance is very strongly bounded and faces serious theoretical challenges. This leads us to consider an alternative line of thought for such phenomenological search. We discuss the underlying viewpoint and briefly mention its possible connections with current theoretical ideas. We also outline the challenges that the experimental search of the effects would seem to entail. |
1202.6676 | Javier E. Cuch\'i MSc | Javier E. Cuch\'i, Alfred Molina and Eduardo Ruiz | Comparison of metrics obtained with analytic perturbation theory and a
numerical code | 4 pages, 2 figures and 1 table. To appear in the proceedings of the
2011 Spanish Relativity Meeting ERE2011 | null | 10.1063/1.4734437 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare metrics obtained through analytic perturbation theory with their
numerical counterparts. The analytic solutions are computed with the CMMR
post-Minkowskian and slow rotation approximation due to Cabezas et al. (2007)
for an asymptotically flat stationary spacetime containing a rotating perfect
fluid compact source. The same spacetime is studied with the AKM numerical
multi-domain spectral code (Ansorg et al., 2002,2003). We then study their
differences inside the source, near the infinity and in the matching surface,
or equivalently, the global character of the analytic perturbation scheme.
| [
{
"created": "Wed, 29 Feb 2012 20:36:37 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Cuchí",
"Javier E.",
""
],
[
"Molina",
"Alfred",
""
],
[
"Ruiz",
"Eduardo",
""
]
] | We compare metrics obtained through analytic perturbation theory with their numerical counterparts. The analytic solutions are computed with the CMMR post-Minkowskian and slow rotation approximation due to Cabezas et al. (2007) for an asymptotically flat stationary spacetime containing a rotating perfect fluid compact source. The same spacetime is studied with the AKM numerical multi-domain spectral code (Ansorg et al., 2002,2003). We then study their differences inside the source, near the infinity and in the matching surface, or equivalently, the global character of the analytic perturbation scheme. |
gr-qc/0507124 | Filimonova Irina V | V.O.Soloviev | Black Hole Statistical Physics: Entropy | Plenary talk presented at Workshop on High Energy Physics&Field
Theory (Protvino, Russia, 2004) | null | null | HEPFT/2004/5 | gr-qc | null | We discuss the most interesting approaches to derivation of the
Bekenstein-Hawking entropy formula from a statistical theory.
| [
{
"created": "Fri, 29 Jul 2005 06:46:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Soloviev",
"V. O.",
""
]
] | We discuss the most interesting approaches to derivation of the Bekenstein-Hawking entropy formula from a statistical theory. |
0905.3695 | Marco Valerio Battisti | Marco Valerio Battisti, Riccardo Belvedere, Giovanni Montani | Semiclassical suppression of weak anisotropies of a generic Universe | 6 pages, to appear in Europhys.Lett | Europhys.Lett.86:69001,2009 | 10.1209/0295-5075/86/69001 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | A semiclassical mechanism which suppresses the weak anisotropies of an
inhomogeneous cosmological model is developed. In particular, a wave function
of this Universe having a meaningful probabilistic interpretation is obtained
that is in agreement with the Copenhagen School. It describes the evolution of
the anisotropies with respect to the isotropic scale factor which is regarded
as a semiclassical variable playing an observer-like role. Near the
cosmological singularity the solution spreads over all values of the
anisotropies while, when the Universe expands sufficiently, the closed
Friedmann-Robertson-Walker model appears to be the favorite state.
| [
{
"created": "Fri, 22 May 2009 14:47:40 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jun 2009 13:37:17 GMT",
"version": "v2"
}
] | 2009-08-03 | [
[
"Battisti",
"Marco Valerio",
""
],
[
"Belvedere",
"Riccardo",
""
],
[
"Montani",
"Giovanni",
""
]
] | A semiclassical mechanism which suppresses the weak anisotropies of an inhomogeneous cosmological model is developed. In particular, a wave function of this Universe having a meaningful probabilistic interpretation is obtained that is in agreement with the Copenhagen School. It describes the evolution of the anisotropies with respect to the isotropic scale factor which is regarded as a semiclassical variable playing an observer-like role. Near the cosmological singularity the solution spreads over all values of the anisotropies while, when the Universe expands sufficiently, the closed Friedmann-Robertson-Walker model appears to be the favorite state. |
0810.2198 | Yousef Sobouti | Yousef Sobouti | Dark companion of baryonic matter | 4 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Whenever and wherever one talks of dark matter, one does so when and where
there is a luminous matter and a dynamical issue to be settled. We promote this
observation to the status of an axiom and assume that there is a dark companion
to every luminous matter and there are orders to this companionship. To pursue
the proposition in a formal and quantitative manner, we consider the anomalous
rotation curves of spiral galaxies. From the available observations, we infer
the gravitational potential prevailing in the outer parts of the galaxy and,
thereof, construct the tt- component of the metric of the embedding spacetime.
Next we examine a perfect fluid candidate as the dark companion and solve the
relevant GR equations. We are able to determine the strength and the
distribution of the dark fluid that accompanies a point baryonic mass. Finally,
we argue that the whole paradigm can be explained just as well in terms of an
alternative theory.
Keywords: Dark matter; Alternative GR; Spiral galaxies, rotation curves of
| [
{
"created": "Mon, 13 Oct 2008 10:12:03 GMT",
"version": "v1"
}
] | 2008-10-14 | [
[
"Sobouti",
"Yousef",
""
]
] | Whenever and wherever one talks of dark matter, one does so when and where there is a luminous matter and a dynamical issue to be settled. We promote this observation to the status of an axiom and assume that there is a dark companion to every luminous matter and there are orders to this companionship. To pursue the proposition in a formal and quantitative manner, we consider the anomalous rotation curves of spiral galaxies. From the available observations, we infer the gravitational potential prevailing in the outer parts of the galaxy and, thereof, construct the tt- component of the metric of the embedding spacetime. Next we examine a perfect fluid candidate as the dark companion and solve the relevant GR equations. We are able to determine the strength and the distribution of the dark fluid that accompanies a point baryonic mass. Finally, we argue that the whole paradigm can be explained just as well in terms of an alternative theory. Keywords: Dark matter; Alternative GR; Spiral galaxies, rotation curves of |
1409.5333 | Maximilian Thaller | H{\aa}kan Andr\'easson, David Fajman, Maximilian Thaller | Static solutions to the Einstein-Vlasov system with non-vanishing
cosmological constant | 31 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct spherically symmetric, static solutions to the Einstein-Vlasov
system with non-vanishing cosmological constant $\Lambda$. The results are
divided as follows. For small $\Lambda>0$ we show existence of globally regular
solutions which coincide with the Schwarzschild-deSitter solution in the
exterior of the matter sources. For $\Lambda<0$ we show via an energy estimate
the existence of globally regular solutions which coincide with the
Schwarzschild-Anti-deSitter solution in the exterior vacuum region. We also
construct solutions with a Schwarzschild singularity at the center regardless
of the sign of $\Lambda$. For all solutions considered, the energy density and
the pressure components have bounded support. Finally, we point out a
straightforward method to obtain a large class of globally non-vacuum
spacetimes with topologies $\mathbb R\times S^3$ and $\mathbb R\times S^2\times
\mathbb R$ which arise from our solutions using the periodicity of the
Schwarzschild-deSitter solution. A subclass of these solutions contains black
holes of different masses.
| [
{
"created": "Thu, 18 Sep 2014 15:12:59 GMT",
"version": "v1"
}
] | 2014-09-19 | [
[
"Andréasson",
"Håkan",
""
],
[
"Fajman",
"David",
""
],
[
"Thaller",
"Maximilian",
""
]
] | We construct spherically symmetric, static solutions to the Einstein-Vlasov system with non-vanishing cosmological constant $\Lambda$. The results are divided as follows. For small $\Lambda>0$ we show existence of globally regular solutions which coincide with the Schwarzschild-deSitter solution in the exterior of the matter sources. For $\Lambda<0$ we show via an energy estimate the existence of globally regular solutions which coincide with the Schwarzschild-Anti-deSitter solution in the exterior vacuum region. We also construct solutions with a Schwarzschild singularity at the center regardless of the sign of $\Lambda$. For all solutions considered, the energy density and the pressure components have bounded support. Finally, we point out a straightforward method to obtain a large class of globally non-vacuum spacetimes with topologies $\mathbb R\times S^3$ and $\mathbb R\times S^2\times \mathbb R$ which arise from our solutions using the periodicity of the Schwarzschild-deSitter solution. A subclass of these solutions contains black holes of different masses. |
2202.04919 | Hans Ringstr\"om | Hans Ringstr\"om | Initial data on big bang singularities | 54 pages, 1 figure. Second version: minor improvements, updated
references | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The goal of this article is to parametrise solutions to Einstein's equations
with big bang singularities and quiescent asymptotics. To this end, we
introduce a notion of initial data on big bang singularities and conjecture
that it can be used to parametrise quiescent solutions. A mathematical
statement of the conjecture presupposes a precise definition of the class of
quiescent solutions as well as a proof of existence and uniqueness of
developments corresponding to initial data on a big bang singularity. We
provide one definition of quiescence here. We also appeal to existing results
in order to illustrate that, in certain cases, there are unique developments
corresponding to initial data on the singularity. However, our perspective
leads to a large class of open problems corresponding to the general
conjecture. An additional benefit of the notion of initial data developed here
is that it can be used to give a unified perspective on the existing results
concerning quiescent singularities. In fact, we provide several examples of how
existing results can be considered to be special cases of the framework
developed here. A second, potential, application is to oscillatory and
spatially inhomogeneous big bang singularities. Considering the existing
arguments in the spatially homogeneous setting, a crucial first step in the
study of oscillatory behaviour is to understand how solutions approach the
Kasner circle along a stable manifold, and then depart via an unstable
manifold. In order to carry out a similar analysis in the spatially
inhomogeneous setting, it is of central importance to first identify the stable
manifold. Building on the work of Fournodavlos and Luk, we here propose such an
identification.
| [
{
"created": "Thu, 10 Feb 2022 09:19:38 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2022 07:21:36 GMT",
"version": "v2"
}
] | 2022-06-22 | [
[
"Ringström",
"Hans",
""
]
] | The goal of this article is to parametrise solutions to Einstein's equations with big bang singularities and quiescent asymptotics. To this end, we introduce a notion of initial data on big bang singularities and conjecture that it can be used to parametrise quiescent solutions. A mathematical statement of the conjecture presupposes a precise definition of the class of quiescent solutions as well as a proof of existence and uniqueness of developments corresponding to initial data on a big bang singularity. We provide one definition of quiescence here. We also appeal to existing results in order to illustrate that, in certain cases, there are unique developments corresponding to initial data on the singularity. However, our perspective leads to a large class of open problems corresponding to the general conjecture. An additional benefit of the notion of initial data developed here is that it can be used to give a unified perspective on the existing results concerning quiescent singularities. In fact, we provide several examples of how existing results can be considered to be special cases of the framework developed here. A second, potential, application is to oscillatory and spatially inhomogeneous big bang singularities. Considering the existing arguments in the spatially homogeneous setting, a crucial first step in the study of oscillatory behaviour is to understand how solutions approach the Kasner circle along a stable manifold, and then depart via an unstable manifold. In order to carry out a similar analysis in the spatially inhomogeneous setting, it is of central importance to first identify the stable manifold. Building on the work of Fournodavlos and Luk, we here propose such an identification. |
1006.2210 | Jibitesh Dutta | Jibitesh Dutta and Subenoy Chakraborty | Generalised second law of thermodynamics for interacting dark energy in
the DGP brane world | null | Int.J.Theor.Phys. 50 (2011) 2383-2390 | 10.1007/s10773-011-0721-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the validity of the generalized second law of
thermodynamics (GSLT) in the DGP brane world when universe is filled with
interacting two fluid system: one in the form of cold dark matter and other is
holographic dark energy. The boundary of the universe is assumed to be enclosed
by the dynamical apparent horizon or the event horizon. The universe is chosen
to be homogeneous and isotropic FRW model and the validity of the first law has
been assumed here.
| [
{
"created": "Fri, 11 Jun 2010 06:50:09 GMT",
"version": "v1"
}
] | 2015-05-11 | [
[
"Dutta",
"Jibitesh",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this paper, we investigate the validity of the generalized second law of thermodynamics (GSLT) in the DGP brane world when universe is filled with interacting two fluid system: one in the form of cold dark matter and other is holographic dark energy. The boundary of the universe is assumed to be enclosed by the dynamical apparent horizon or the event horizon. The universe is chosen to be homogeneous and isotropic FRW model and the validity of the first law has been assumed here. |
gr-qc/9302037 | null | M.Ferraris, M.Francaviglia and I.Volovich | A Model of Topological Affine Gravity in Two Dimensions | 11 pages, TO-JLL-P2/92 | Int.J.Mod.Phys. A12 (1997) 5067-5080 | 10.1142/S0217751X9700270X | null | gr-qc hep-th | null | A model of two--dimensional gravity with an action depending only on a linear
connection is considered. This model is a topological one, in the sense that
the classical action does not contain a metric or zweibein at all. A metric and
an additional vector field are instead introduced in the process of solving
equations of motion for the connection. They satisfy the constant curvature
equation. It is shown that the general solution of these equations of motion
can be described by using the space of orbits under the action of the Weyl
group in the functional space containing all pairs formed by a metric and a
vectorfield. It is shown also that this model admits an equivalent description
by using a family of actions depending on the metric and the connection as
independent variables.
| [
{
"created": "Fri, 26 Feb 1993 21:43:00 GMT",
"version": "v1"
}
] | 2019-08-17 | [
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Volovich",
"I.",
""
]
] | A model of two--dimensional gravity with an action depending only on a linear connection is considered. This model is a topological one, in the sense that the classical action does not contain a metric or zweibein at all. A metric and an additional vector field are instead introduced in the process of solving equations of motion for the connection. They satisfy the constant curvature equation. It is shown that the general solution of these equations of motion can be described by using the space of orbits under the action of the Weyl group in the functional space containing all pairs formed by a metric and a vectorfield. It is shown also that this model admits an equivalent description by using a family of actions depending on the metric and the connection as independent variables. |
gr-qc/0702109 | Adellane Sousa | A. A. Sousa, J. S. Moura and R. B. Pereira | Energy in an Expanding Universe in the Teleparallel Geometry | 19 pages, no figures. Revised in view of Referee's comments. Version
to appear in the Brazilian Journal of Physics | Braz.J.Phys.40:1,2010 | 10.1590/S0103-97332010000100001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main purpose of this paper is to explicitly verify the consistency of the
energy-momentum and angular momentum tensor of the gravitational field
established in the Hamiltonian structure of the Teleparallel Equivalent of
General Relativity (TEGR). In order to reach these objectives, we obtained the
total energy and angular momentum (matter plus gravitational field) of the
closed universe of the Friedmann-Lemaitre-Robertson-Walker (FLRW). The result
is compared with those obtained from the pseudotensors of Einstein and
Landau-Lifshitz. We also applied the field equations (TEGR) in an expanding
FLRW universe. Considering the stress energy-momentum tensor for a perfect
fluid, we found a teleparallel equivalent of Friedmann equations of General
Relativity (GR).
| [
{
"created": "Tue, 20 Feb 2007 14:28:01 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Mar 2008 23:11:41 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Dec 2009 18:47:51 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Sousa",
"A. A.",
""
],
[
"Moura",
"J. S.",
""
],
[
"Pereira",
"R. B.",
""
]
] | The main purpose of this paper is to explicitly verify the consistency of the energy-momentum and angular momentum tensor of the gravitational field established in the Hamiltonian structure of the Teleparallel Equivalent of General Relativity (TEGR). In order to reach these objectives, we obtained the total energy and angular momentum (matter plus gravitational field) of the closed universe of the Friedmann-Lemaitre-Robertson-Walker (FLRW). The result is compared with those obtained from the pseudotensors of Einstein and Landau-Lifshitz. We also applied the field equations (TEGR) in an expanding FLRW universe. Considering the stress energy-momentum tensor for a perfect fluid, we found a teleparallel equivalent of Friedmann equations of General Relativity (GR). |
2003.13127 | Elena P. Savelova Dr. | A.A. Kirillov, E.P. Savelova, and O.M. Lecian | Scattering of GWs on wormholes: foreshadow and afterglow/echoes from
binary merges | revised version, 15 pages, 3 fig | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study specific features of the scattering of gravitational waves on
wormholes and normal matter objects. We derive and solve the GW energy
transport equation and show that the scattered signal lies in the same
frequency spectrum bands as the basic signal. The scattering forms specific
long living tails which always accompany the basic signal and have a universal
form. The scattering on normal matter objects forms tails which have always the
retarding character, while wormholes lead to advanced tails as well. In
addition, wormholes may produce considerably stronger effect, when the total
energy in tails exceeds the energy of the incident wave by the factor up to
$10^{3}$ . In both cases the retarding tails have a long living character when
the mean amplitude behaves with time as $h\sim 1/\sqrt{t+R/c}$. For a single GW
event the echo tails give only a tiny contribution to the mean amplitude.
However such tails accumulate with events and may be observed by their
contribution to the noise produced by the stochastic GW background.
| [
{
"created": "Sun, 29 Mar 2020 20:12:36 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2020 09:04:32 GMT",
"version": "v2"
}
] | 2020-09-29 | [
[
"Kirillov",
"A. A.",
""
],
[
"Savelova",
"E. P.",
""
],
[
"Lecian",
"O. M.",
""
]
] | We study specific features of the scattering of gravitational waves on wormholes and normal matter objects. We derive and solve the GW energy transport equation and show that the scattered signal lies in the same frequency spectrum bands as the basic signal. The scattering forms specific long living tails which always accompany the basic signal and have a universal form. The scattering on normal matter objects forms tails which have always the retarding character, while wormholes lead to advanced tails as well. In addition, wormholes may produce considerably stronger effect, when the total energy in tails exceeds the energy of the incident wave by the factor up to $10^{3}$ . In both cases the retarding tails have a long living character when the mean amplitude behaves with time as $h\sim 1/\sqrt{t+R/c}$. For a single GW event the echo tails give only a tiny contribution to the mean amplitude. However such tails accumulate with events and may be observed by their contribution to the noise produced by the stochastic GW background. |
2111.12576 | Stephen Adler | Stephen L. Adler | Is "Dark Energy" a Quantum Vacuum Energy? | 26 pages; invited mini-review for Modern Physics Letters A, to be
submitted 12/15. In v2, references added in footnote on p3. Comments welcome | Modern Phys. Letters A 36, 2130027 (2021) | 10.1142/S0217732321300275 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the origins, motivations, and implications for cosmology and black
holes, of our proposal that "dark energy" is not a quantum vacuum energy, but
rather arises from a Weyl scaling invariant nonderivative component of the
gravitational action.
| [
{
"created": "Wed, 24 Nov 2021 15:57:49 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Dec 2021 21:16:18 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Adler",
"Stephen L.",
""
]
] | We review the origins, motivations, and implications for cosmology and black holes, of our proposal that "dark energy" is not a quantum vacuum energy, but rather arises from a Weyl scaling invariant nonderivative component of the gravitational action. |
2110.07620 | Rodrigo Vicente | Rodrigo Vicente | The Gravity of Classical Fields: And Its Effect on the Dynamics of
Gravitational Systems | PhD thesis in Physics. arXiv admin note: text overlap with
arXiv:2009.00012 | null | null | null | gr-qc astro-ph.GA astro-ph.HE hep-ph | http://creativecommons.org/licenses/by/4.0/ | Classical fields are ubiquitous in theoretical physics. They find
applications in almost all areas of physics, from condensed matter and particle
physics to cosmology and astrophysics. Scalar fields, in particular, can give
rise to confined structures, such as boson stars, oscillatons or Q-balls. These
objects are interesting hypothetical new "dark matter stars", but also good
descriptions of dark matter cores when the fields are ultralight. In this
thesis, we study the dynamical response of such confined bosonic structures
when excited by external matter (stars, planets or black holes) in their
vicinities. Such perturbers can either be piercing through the bosonic
configuration or undergoing periodic motion at its center (e.g., binaries). Our
setup can also efficiently describe the interaction between a moving massive
black hole and the surrounding environment. It also depicts dark matter
depletion as a reaction to an inspiralling binary within a dark matter core.
Our results provide a complete picture of the interaction between black holes
or stars and the ultralight dark matter core environment where they may live
in. This thesis also deals with several classical field environmental effects
on the motion (or, ultimately, the survival) of compact objects, like black
holes.
| [
{
"created": "Thu, 14 Oct 2021 18:00:04 GMT",
"version": "v1"
}
] | 2021-10-18 | [
[
"Vicente",
"Rodrigo",
""
]
] | Classical fields are ubiquitous in theoretical physics. They find applications in almost all areas of physics, from condensed matter and particle physics to cosmology and astrophysics. Scalar fields, in particular, can give rise to confined structures, such as boson stars, oscillatons or Q-balls. These objects are interesting hypothetical new "dark matter stars", but also good descriptions of dark matter cores when the fields are ultralight. In this thesis, we study the dynamical response of such confined bosonic structures when excited by external matter (stars, planets or black holes) in their vicinities. Such perturbers can either be piercing through the bosonic configuration or undergoing periodic motion at its center (e.g., binaries). Our setup can also efficiently describe the interaction between a moving massive black hole and the surrounding environment. It also depicts dark matter depletion as a reaction to an inspiralling binary within a dark matter core. Our results provide a complete picture of the interaction between black holes or stars and the ultralight dark matter core environment where they may live in. This thesis also deals with several classical field environmental effects on the motion (or, ultimately, the survival) of compact objects, like black holes. |
gr-qc/0312122 | Sergio M. C. V. Goncalves | Sergio M. C. V. Goncalves | No-horizon theorem for spacetimes with spacelike G1 isometry groups | 8 pages, LaTeX, uses IOP package; published in Class. Quantum Grav | Class.Quant.Grav. 20 (2003) 5399-5405 | 10.1088/0264-9381/20/24/012 | null | gr-qc | null | We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the
Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike
$G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local
analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on
${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent
horizons. Given any (3+1) spacetime with spacelike translational isometry, the
no-horizon condition can be readily tested without the need for dimensional
reduction. This provides thus a useful and encompassing apparent horizon test
for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence
towards the validity of the hoop conjecture, and signals possible violations of
strong cosmic censorship.
| [
{
"created": "Tue, 30 Dec 2003 19:51:17 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Goncalves",
"Sergio M. C. V.",
""
]
] | We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike $G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on ${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent horizons. Given any (3+1) spacetime with spacelike translational isometry, the no-horizon condition can be readily tested without the need for dimensional reduction. This provides thus a useful and encompassing apparent horizon test for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence towards the validity of the hoop conjecture, and signals possible violations of strong cosmic censorship. |
2012.12037 | Geraint F. Lewis Prof | Geraint F. Lewis and Luke A. Barnes | The One-Way Speed of Light and the Milne Universe | 7 pages, 5 figures, to appear in PASA | Publ. Astron. Soc. Aust. 38 (2021) e007 | 10.1017/pasa.2021.2 | GFL-001 | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In Einstein's Special Theory of Relativity, all observers measure the speed
of light, $c$, to be the same. However, this refers to the round trip speed,
where a clock at the origin times the outward and return trip of light
reflecting off a distant mirror. Measuring the one-way speed of light is
fraught with issues of clock synchronisation, and, as long as the average speed
of light remains $c$, the speeds on the outward and return legs could be
different. One objection to this anisotropic speed of light is that views of
the distant universe would be different in different directions, especially
with regards to the ages of observed objects and the smoothness of the Cosmic
Microwave Background. In this paper, we explore this in the Milne universe, the
limiting case of a Friedmann-Robertson-Walker universe containing no matter,
radiation or dark energy. Given that this universe is empty, it can be mapped
onto flat Minkowski space-time, and so can be explored in terms of the one-way
speed of light. The conclusion is that the presence of an anisotropic speed of
light leads to anisotropic time dilation effects, and hence observers in the
Milne universe would be presented with an isotropic view of the distant cosmos.
| [
{
"created": "Fri, 18 Dec 2020 02:34:20 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Lewis",
"Geraint F.",
""
],
[
"Barnes",
"Luke A.",
""
]
] | In Einstein's Special Theory of Relativity, all observers measure the speed of light, $c$, to be the same. However, this refers to the round trip speed, where a clock at the origin times the outward and return trip of light reflecting off a distant mirror. Measuring the one-way speed of light is fraught with issues of clock synchronisation, and, as long as the average speed of light remains $c$, the speeds on the outward and return legs could be different. One objection to this anisotropic speed of light is that views of the distant universe would be different in different directions, especially with regards to the ages of observed objects and the smoothness of the Cosmic Microwave Background. In this paper, we explore this in the Milne universe, the limiting case of a Friedmann-Robertson-Walker universe containing no matter, radiation or dark energy. Given that this universe is empty, it can be mapped onto flat Minkowski space-time, and so can be explored in terms of the one-way speed of light. The conclusion is that the presence of an anisotropic speed of light leads to anisotropic time dilation effects, and hence observers in the Milne universe would be presented with an isotropic view of the distant cosmos. |
2107.12546 | Genly Le\'on | Andronikos Paliathanasis (DUT, Durban and Chile Austral U., Valdivia),
Genly Leon (Catolica del Norte U.) | Einstein-{\ae}ther Scalar-tensor Cosmology | 22 pages, 1 compound figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an Einstein-{\ae}ther scalar-tensor cosmological model. In
particular in the scalar-tensor Action Integral we introduce the {\ae}ther
field with {\ae}ther coefficients to be functions of the scalar field. This
cosmological model extends previous studies on Lorentz-violating theories. For
a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker background space
we write the field equations which are of second-order with dynamical variables
the scale factor and the scalar field. The physical evolution of the field
equations depends upon three unknown functions which are related to the
scalar-tensor coupling function, the scalar field potential and the {\ae}ther
coefficient functions. We investigate the existence of analytic solutions for
the field equations and the integrability properties according to the existence
of linear in the momentum conservation laws. We define a new set of variables
in which the dynamical evolution depends only upon the scalar field potential.
Furthermore, the asymptotic behaviour and the cosmological history is
investigated where we find that the theory provides inflationary eras similar
with that of scalar-tensor theory but with Lorentz-violating terms provided by
the {\ae}ther field. Finally, in the new variables we found that the field
equations are integrable due to the existence of nonlocal conservation laws for
arbitrary functional forms of the three free functions.
| [
{
"created": "Tue, 27 Jul 2021 01:41:27 GMT",
"version": "v1"
}
] | 2021-07-28 | [
[
"Paliathanasis",
"Andronikos",
"",
"DUT, Durban and Chile Austral U., Valdivia"
],
[
"Leon",
"Genly",
"",
"Catolica del Norte U."
]
] | We propose an Einstein-{\ae}ther scalar-tensor cosmological model. In particular in the scalar-tensor Action Integral we introduce the {\ae}ther field with {\ae}ther coefficients to be functions of the scalar field. This cosmological model extends previous studies on Lorentz-violating theories. For a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker background space we write the field equations which are of second-order with dynamical variables the scale factor and the scalar field. The physical evolution of the field equations depends upon three unknown functions which are related to the scalar-tensor coupling function, the scalar field potential and the {\ae}ther coefficient functions. We investigate the existence of analytic solutions for the field equations and the integrability properties according to the existence of linear in the momentum conservation laws. We define a new set of variables in which the dynamical evolution depends only upon the scalar field potential. Furthermore, the asymptotic behaviour and the cosmological history is investigated where we find that the theory provides inflationary eras similar with that of scalar-tensor theory but with Lorentz-violating terms provided by the {\ae}ther field. Finally, in the new variables we found that the field equations are integrable due to the existence of nonlocal conservation laws for arbitrary functional forms of the three free functions. |
0803.1401 | Thomas Buchert | Thomas Buchert, Mauro Carfora | On the curvature of the present-day Universe | 43 pages, 19 figures included, matches published version in C.Q.G. | Class.Quant.Grav.25:195001,2008 | 10.1088/0264-9381/25/19/195001 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the effect of curvature and matter inhomogeneities on the averaged
scalar curvature of the present-day Universe. Motivated by studies of averaged
inhomogeneous cosmologies, we contemplate on the question whether it is
sensible to assume that curvature averages out on some scale of homogeneity, as
implied by the standard concordance model of cosmology, or whether the averaged
scalar curvature can be largely negative today, as required for an explanation
of Dark Energy from inhomogeneities. We confront both conjectures with a
detailed analysis of the kinematical backreaction term and estimate its
strength for a multi-scale inhomogeneous matter and curvature distribution. Our
main result is a formula for the spatially averaged scalar curvature involving
quantities that are all measurable on regional (i.e. up to 100 Mpc) scales. We
propose strategies to quantitatively evaluate the formula, and pinpoint the
assumptions implied by the conjecture of a small or zero averaged curvature. We
reach the conclusion that the standard concordance model needs fine-tuning in
the sense of an assumed equipartition law for curvature in order to reconcile
it with the estimated properties of the averaged physical space, whereas a
negative averaged curvature is favoured, independent of the prior on the value
of the cosmological constant.
| [
{
"created": "Mon, 10 Mar 2008 12:51:41 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jul 2008 18:42:51 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Buchert",
"Thomas",
""
],
[
"Carfora",
"Mauro",
""
]
] | We discuss the effect of curvature and matter inhomogeneities on the averaged scalar curvature of the present-day Universe. Motivated by studies of averaged inhomogeneous cosmologies, we contemplate on the question whether it is sensible to assume that curvature averages out on some scale of homogeneity, as implied by the standard concordance model of cosmology, or whether the averaged scalar curvature can be largely negative today, as required for an explanation of Dark Energy from inhomogeneities. We confront both conjectures with a detailed analysis of the kinematical backreaction term and estimate its strength for a multi-scale inhomogeneous matter and curvature distribution. Our main result is a formula for the spatially averaged scalar curvature involving quantities that are all measurable on regional (i.e. up to 100 Mpc) scales. We propose strategies to quantitatively evaluate the formula, and pinpoint the assumptions implied by the conjecture of a small or zero averaged curvature. We reach the conclusion that the standard concordance model needs fine-tuning in the sense of an assumed equipartition law for curvature in order to reconcile it with the estimated properties of the averaged physical space, whereas a negative averaged curvature is favoured, independent of the prior on the value of the cosmological constant. |
1706.08842 | Etienne Baffou | E. H. Baffou, M. J. S. Houndjo, M. Hamani-Daouda and F. G. Alvarenga | Late time cosmological approach in mimetic $f(R,T)$ gravity | 18 pages, 2 figures | null | 10.1140/epjc/s10052-017-5291-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the late-time cosmic acceleration in mimetic
$f(R,T)$ gravity with Lagrange multiplier and potential in a Universe
containing, besides radiation and dark energy, a self-interacting (collisional)
matter. We obtain through the modified Friedmann equations, the main equation
that can describe the cosmological evolution and with several models from
$Q(z)$ and the well known particular model $f(R, T)$, we perform an analysis of
the late-time evolution. We examine the behavior of the Hubble parameter, the
dark energy equation of state and the total effective equation of state and we
compare in each case the resulting picture with the non-collisional matter
(assumed as dust) and also with the collisional matter in mimetic $f(R, T)$
gravity. The results obtained are in good agreement with the observational data
and show that in presence of the collisional matter the dark energy
oscillations in mimetic f(R, T) gravity can be damped.
| [
{
"created": "Sat, 24 Jun 2017 10:50:05 GMT",
"version": "v1"
}
] | 2017-11-22 | [
[
"Baffou",
"E. H.",
""
],
[
"Houndjo",
"M. J. S.",
""
],
[
"Hamani-Daouda",
"M.",
""
],
[
"Alvarenga",
"F. G.",
""
]
] | In this paper, we investigate the late-time cosmic acceleration in mimetic $f(R,T)$ gravity with Lagrange multiplier and potential in a Universe containing, besides radiation and dark energy, a self-interacting (collisional) matter. We obtain through the modified Friedmann equations, the main equation that can describe the cosmological evolution and with several models from $Q(z)$ and the well known particular model $f(R, T)$, we perform an analysis of the late-time evolution. We examine the behavior of the Hubble parameter, the dark energy equation of state and the total effective equation of state and we compare in each case the resulting picture with the non-collisional matter (assumed as dust) and also with the collisional matter in mimetic $f(R, T)$ gravity. The results obtained are in good agreement with the observational data and show that in presence of the collisional matter the dark energy oscillations in mimetic f(R, T) gravity can be damped. |
1604.01258 | Herman Telkamp | Herman Telkamp | Machian derivation of the Friedmann equation | 5 pages, 1 fig | Phys. Rev. D 94, 043520 (2016) | 10.1103/PhysRevD.94.043520 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite all fundamental objections against Newtonian concepts in cosmology,
the Friedmann equation derives from these in an astoundingly simple way through
application of the shell theorem and conservation of Newtonian energy in an
infinite universe. However, Friedmann universes in general posses a finite
gravitational horizon, as a result of which the application of the shell
theorem fails and the Newtonian derivation collapses. We show that in the
presence of a gravitational horizon the Friedmann equation can be derived from
a Machian definition of kinetic energy, without invoking the shell theorem.
Whereas in the Newtonian case total energy translates to curvature energy
density, in the Machian case total energy takes on different identities,
depending on the evolution of the horizon; we show that in the de Sitter
universe Machian total energy density is constant, i.e. appears as cosmological
constant.
| [
{
"created": "Fri, 1 Apr 2016 16:47:37 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jun 2016 11:53:30 GMT",
"version": "v2"
}
] | 2017-04-05 | [
[
"Telkamp",
"Herman",
""
]
] | Despite all fundamental objections against Newtonian concepts in cosmology, the Friedmann equation derives from these in an astoundingly simple way through application of the shell theorem and conservation of Newtonian energy in an infinite universe. However, Friedmann universes in general posses a finite gravitational horizon, as a result of which the application of the shell theorem fails and the Newtonian derivation collapses. We show that in the presence of a gravitational horizon the Friedmann equation can be derived from a Machian definition of kinetic energy, without invoking the shell theorem. Whereas in the Newtonian case total energy translates to curvature energy density, in the Machian case total energy takes on different identities, depending on the evolution of the horizon; we show that in the de Sitter universe Machian total energy density is constant, i.e. appears as cosmological constant. |
gr-qc/0605025 | Michael Wernig-Pichler | Michael Wernig-Pichler | Relativistic elastodynamics | PHD-thesis, 140 pages, 2 figures | null | null | null | gr-qc | null | There are many different formulations of relativistic elasticity. Most of
them are only concerned with formal questions rather than questions regarding
the PDE point of view. The aim of this thesis is to obtain various local
existence results for dynamical scenarios involving elastic matter. Following
Beig and Schmidt we treat relativistic elasticity as a Lagrangian field theory.
The basic unknowns are mappings between spacetime and an abstract material
manifold. The equations of motion will be the Euler-Lagrange equations arising
from the action principle. Under certain (physically reasonable) restrictions
on the elastic properties of the material the resulting system is hyperbolic
and local existence results can be derived. This way we can show well-posedness
for the equations describing elastic matter on a fixed gravitational
background, self-gravitating elastic matter and a finite elastic body on a
fixed background. The thesis also contains some results on energy conservation
and on linearized elasticity.
| [
{
"created": "Thu, 4 May 2006 10:07:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wernig-Pichler",
"Michael",
""
]
] | There are many different formulations of relativistic elasticity. Most of them are only concerned with formal questions rather than questions regarding the PDE point of view. The aim of this thesis is to obtain various local existence results for dynamical scenarios involving elastic matter. Following Beig and Schmidt we treat relativistic elasticity as a Lagrangian field theory. The basic unknowns are mappings between spacetime and an abstract material manifold. The equations of motion will be the Euler-Lagrange equations arising from the action principle. Under certain (physically reasonable) restrictions on the elastic properties of the material the resulting system is hyperbolic and local existence results can be derived. This way we can show well-posedness for the equations describing elastic matter on a fixed gravitational background, self-gravitating elastic matter and a finite elastic body on a fixed background. The thesis also contains some results on energy conservation and on linearized elasticity. |
2005.03044 | Christopher Munna | Christopher Munna, Charles R. Evans, Seth Hopper, Erik Forseth | Determination of new coefficients in the angular momentum and energy
fluxes at infinity to 9PN for eccentric Schwarzschild extreme-mass-ratio
inspirals using mode-by-mode fitting | 36 pages, 1 figure | Phys. Rev. D 102, 024047 (2020) | 10.1103/PhysRevD.102.024047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an extension of work in an earlier paper showing high precision
comparisons between black hole perturbation theory and post-Newtonian (PN)
theory in their region of overlapping validity for bound, eccentric-orbit,
Schwarzschild extreme-mass-ratio inspirals. As before we apply a numerical
fitting scheme to extract eccentricity coefficients in the PN expansion of the
gravitational wave fluxes, which are then converted to exact analytic form
using an integer-relation algorithm. In this work, however, we fit to
individual $lmn$ modes to exploit simplifying factorizations that lie therein.
Since the previous paper focused solely on the energy flux, here we concentrate
initially on analyzing the angular momentum flux to infinity. A first step
involves finding convenient forms for hereditary contributions to the flux at
low-PN order, analogous to similar terms worked out previously for the energy
flux. We then apply the upgraded techniques to find new PN terms through 9PN
order and (at many PN orders) to $e^{30}$ in the power series in eccentricity.
With the new approach applied to angular momentum fluxes, we return to the
energy fluxes at infinity to extend those previous results. Like before, the
underlying method uses a \textsc{Mathematica} code based on use of the
Mano-Suzuki-Takasugi (MST) function expansion formalism to represent
gravitational perturbations and spectral source integration (SSI) to find
numerical results at arbitrarily high precision.
| [
{
"created": "Wed, 6 May 2020 18:00:13 GMT",
"version": "v1"
}
] | 2020-07-22 | [
[
"Munna",
"Christopher",
""
],
[
"Evans",
"Charles R.",
""
],
[
"Hopper",
"Seth",
""
],
[
"Forseth",
"Erik",
""
]
] | We present an extension of work in an earlier paper showing high precision comparisons between black hole perturbation theory and post-Newtonian (PN) theory in their region of overlapping validity for bound, eccentric-orbit, Schwarzschild extreme-mass-ratio inspirals. As before we apply a numerical fitting scheme to extract eccentricity coefficients in the PN expansion of the gravitational wave fluxes, which are then converted to exact analytic form using an integer-relation algorithm. In this work, however, we fit to individual $lmn$ modes to exploit simplifying factorizations that lie therein. Since the previous paper focused solely on the energy flux, here we concentrate initially on analyzing the angular momentum flux to infinity. A first step involves finding convenient forms for hereditary contributions to the flux at low-PN order, analogous to similar terms worked out previously for the energy flux. We then apply the upgraded techniques to find new PN terms through 9PN order and (at many PN orders) to $e^{30}$ in the power series in eccentricity. With the new approach applied to angular momentum fluxes, we return to the energy fluxes at infinity to extend those previous results. Like before, the underlying method uses a \textsc{Mathematica} code based on use of the Mano-Suzuki-Takasugi (MST) function expansion formalism to represent gravitational perturbations and spectral source integration (SSI) to find numerical results at arbitrarily high precision. |
gr-qc/9704011 | Steven G. Harris | Steven G. Harris | Universality of the Future Chronological Boundary | 25 pages, AMS-TeX; 2 figures, PostScript (separate); captions
(separate); submitted to Class. Quantum Grav, slight revision: bottom lines
legible, figures added, expanded discussion and examples | null | 10.1063/1.532582 | null | gr-qc | null | The purpose of this note is to establish, in a categorical manner, the
universality of the Geroch-Kronheimer-Penrose causal boundary when considering
the types of causal structures that may profitably be put on any sort of
boundary for a spacetime. Actually, this can only be done for the future causal
boundary (or the past causal boundary) separately; furthermore, only the
chronology relation, not the causality relation, is considered, and the GKP
topology is eschewed. The final result is that there is a unique map, with the
proper causal properties, from the future causal boundary of a spacetime onto
any ``reasonable" boundary which supports some sort of chronological structure
and which purports to consist of a future completion of the spacetime.
Furthermore, the future causal boundary construction is categorically unique in
this regard.
| [
{
"created": "Fri, 4 Apr 1997 21:28:02 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Sep 1997 23:41:29 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Harris",
"Steven G.",
""
]
] | The purpose of this note is to establish, in a categorical manner, the universality of the Geroch-Kronheimer-Penrose causal boundary when considering the types of causal structures that may profitably be put on any sort of boundary for a spacetime. Actually, this can only be done for the future causal boundary (or the past causal boundary) separately; furthermore, only the chronology relation, not the causality relation, is considered, and the GKP topology is eschewed. The final result is that there is a unique map, with the proper causal properties, from the future causal boundary of a spacetime onto any ``reasonable" boundary which supports some sort of chronological structure and which purports to consist of a future completion of the spacetime. Furthermore, the future causal boundary construction is categorically unique in this regard. |
gr-qc/0411017 | Hideaki Kudoh | Hideaki Kudoh, Atsushi Taruya | Probing anisotropies of gravitational-wave backgrounds with a
space-based interferometer: geometric properties of antenna patterns and
their angular power | RevTex4, 22 pages, 6 figures (low resolution), typos corrected | Phys.Rev. D71 (2005) 024025 | 10.1103/PhysRevD.71.024025 | UTAP-504, RESCEU-35/04 | gr-qc astro-ph | null | We discuss the sensitivity to anisotropies of stochastic gravitational-wave
backgrounds (GWBs) observed via space-based interferometer. In addition to the
unresolved galactic binaries as the most promising GWB source of the planned
Laser Interferometer Space Antenna (LISA), the extragalactic sources for GWBs
might be detected in the future space missions. The anisotropies of the GWBs
thus play a crucial role to discriminate various components of the GWBs. We
study general features of antenna pattern sensitivity to the anisotropies of
GWBs beyond the low-frequency approximation. We show that the sensitivity of
space-based interferometer to GWBs is severely restricted by the data
combinations and the symmetries of the detector configuration. The spherical
harmonic analysis of the antenna pattern functions reveals that the angular
power of the detector response increases with frequency and the detectable
multipole moments with effective sensitivity h_{eff} \sim 10^{-20} Hz^{-1/2}
may reach $\ell \sim$ 8-10 at $f \sim f_*=10$ mHz in the case of the single
LISA detector. However, the cross correlation of optimal interferometric
variables is blind to the monopole (\ell=0) intensity anisotropy, and also to
the dipole (\ell=1) in some case, irrespective of the frequency band. Besides,
all the self-correlated signals are shown to be blind to the odd multipole
moments (\ell=odd), independently of the frequency band.
| [
{
"created": "Wed, 3 Nov 2004 10:54:23 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Feb 2005 15:23:43 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Kudoh",
"Hideaki",
""
],
[
"Taruya",
"Atsushi",
""
]
] | We discuss the sensitivity to anisotropies of stochastic gravitational-wave backgrounds (GWBs) observed via space-based interferometer. In addition to the unresolved galactic binaries as the most promising GWB source of the planned Laser Interferometer Space Antenna (LISA), the extragalactic sources for GWBs might be detected in the future space missions. The anisotropies of the GWBs thus play a crucial role to discriminate various components of the GWBs. We study general features of antenna pattern sensitivity to the anisotropies of GWBs beyond the low-frequency approximation. We show that the sensitivity of space-based interferometer to GWBs is severely restricted by the data combinations and the symmetries of the detector configuration. The spherical harmonic analysis of the antenna pattern functions reveals that the angular power of the detector response increases with frequency and the detectable multipole moments with effective sensitivity h_{eff} \sim 10^{-20} Hz^{-1/2} may reach $\ell \sim$ 8-10 at $f \sim f_*=10$ mHz in the case of the single LISA detector. However, the cross correlation of optimal interferometric variables is blind to the monopole (\ell=0) intensity anisotropy, and also to the dipole (\ell=1) in some case, irrespective of the frequency band. Besides, all the self-correlated signals are shown to be blind to the odd multipole moments (\ell=odd), independently of the frequency band. |
gr-qc/0603045 | Heinrich P\"as | Heinrich P\"as, Sandip Pakvasa, James Dent, Thomas J. Weiler | Closed timelike curves in asymmetrically warped brane universes | 24 pages, 2 figures; major corrections: CTC metric generalized from
5D to 6D, the new 6D metric satisfies the conclusions attributed
(incorrectly) to the 5D metric in v1 | Phys.Rev.D80:044008,2009 | 10.1103/PhysRevD.80.044008 | null | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In asymmetrically warped spacetimes different warp factors are assigned to
space and to time. We discuss causality properties of these warped brane
universes and argue that scenarios with two extra dimensions may allow for
timelike curves which can be closed via paths in the extra-dimensional bulk. In
particular, necessary and sufficient conditions on the metric for the existence
of closed timelike curves are presented. We find a six-dimensional warped
metric which satisfies the CTC conditions, and where the null, weak and
dominant energy conditions are satisfied on the brane (although only the former
remains satisfied in the bulk). Such scenarios are interesting, since they open
the possibility of experimentally testing the chronology protection conjecture
by manipulating on our brane initial conditions of gravitons or hypothetical
gauge-singlet fermions (sterile neutrinos) which then propagate in the extra
dimensions.
| [
{
"created": "Mon, 13 Mar 2006 02:36:01 GMT",
"version": "v1"
},
{
"created": "Mon, 18 May 2009 14:20:50 GMT",
"version": "v2"
}
] | 2009-09-02 | [
[
"Päs",
"Heinrich",
""
],
[
"Pakvasa",
"Sandip",
""
],
[
"Dent",
"James",
""
],
[
"Weiler",
"Thomas J.",
""
]
] | In asymmetrically warped spacetimes different warp factors are assigned to space and to time. We discuss causality properties of these warped brane universes and argue that scenarios with two extra dimensions may allow for timelike curves which can be closed via paths in the extra-dimensional bulk. In particular, necessary and sufficient conditions on the metric for the existence of closed timelike curves are presented. We find a six-dimensional warped metric which satisfies the CTC conditions, and where the null, weak and dominant energy conditions are satisfied on the brane (although only the former remains satisfied in the bulk). Such scenarios are interesting, since they open the possibility of experimentally testing the chronology protection conjecture by manipulating on our brane initial conditions of gravitons or hypothetical gauge-singlet fermions (sterile neutrinos) which then propagate in the extra dimensions. |
2403.16532 | Leo C.Y. Ng | Leo C. Y. Ng, Justin Janquart, Hemantakumar Phurailatpam, Harsh
Narola, Jason S. C. Poon, Chris Van Den Broeck, Otto A. Hannuksela | Uncovering faint lensed gravitational-wave signals and reprioritizing
their follow-up analysis using galaxy lensing forecasts with detected
counterparts | 15 pages, 28 figures, 1 table | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Like light, gravitational waves can be gravitationally lensed by massive
astrophysical objects. For galaxy and galaxy-cluster lenses, one expects to see
strong lensing -- forecasted to become observable in the coming years -- where
the original wave is split into multiple copies with the same frequency
evolution but different overall arrival times, phases, amplitudes, and signal
strengths. Some of these images can be below the detection threshold and
require targeted search methods, based on tailor-made template banks. These
searches can be made more sensitive by using our knowledge of the typical
distribution and morphology of lenses to predict the time delay, magnification,
and image-type ordering of the lensed images. Here, we show that when a subset
of the images is super-threshold, they can be used to construct a more
constrained prediction of the arrival time of the remaining signals, enhancing
our ability to identify lensing candidate signals. Our suggested method
effectively reduces the list of triggers requiring follow-up and generally
re-ranks the genuine counterpart higher in the lensing candidate list.
Therefore, in the future, if one observes two or three lensed images, the
information they provide can be used to identify their sub-threshold
counterparts, thus allowing identification of additional lensed images. Finding
such images would also strengthen our evidence for the event being lensed.
| [
{
"created": "Mon, 25 Mar 2024 08:19:07 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Apr 2024 08:32:20 GMT",
"version": "v2"
}
] | 2024-04-08 | [
[
"Ng",
"Leo C. Y.",
""
],
[
"Janquart",
"Justin",
""
],
[
"Phurailatpam",
"Hemantakumar",
""
],
[
"Narola",
"Harsh",
""
],
[
"Poon",
"Jason S. C.",
""
],
[
"Broeck",
"Chris Van Den",
""
],
[
"Hannuksela",
"Otto A.",
""
]
] | Like light, gravitational waves can be gravitationally lensed by massive astrophysical objects. For galaxy and galaxy-cluster lenses, one expects to see strong lensing -- forecasted to become observable in the coming years -- where the original wave is split into multiple copies with the same frequency evolution but different overall arrival times, phases, amplitudes, and signal strengths. Some of these images can be below the detection threshold and require targeted search methods, based on tailor-made template banks. These searches can be made more sensitive by using our knowledge of the typical distribution and morphology of lenses to predict the time delay, magnification, and image-type ordering of the lensed images. Here, we show that when a subset of the images is super-threshold, they can be used to construct a more constrained prediction of the arrival time of the remaining signals, enhancing our ability to identify lensing candidate signals. Our suggested method effectively reduces the list of triggers requiring follow-up and generally re-ranks the genuine counterpart higher in the lensing candidate list. Therefore, in the future, if one observes two or three lensed images, the information they provide can be used to identify their sub-threshold counterparts, thus allowing identification of additional lensed images. Finding such images would also strengthen our evidence for the event being lensed. |
1909.10890 | Kevin Ludwick | Kevin J. Ludwick, Holston Sebaugh | Deriving the Dark Matter-Dark Energy Interaction Term in the Continuity
Equation from the Boltzmann Equation | 10+3 pages, 1 figure; accepted to Modern Physics Letters A | Modern Physics Letters A, Vol. 36, No. 18, 2150122 (2021) | 10.1142/S0217-7323(21)50122-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Dark energy and dark matter are two of the biggest mysteries of modern
cosmology, and our understanding of their fundamental nature is incomplete.
Many parameterizations of couplings between the two in the continuity equation
have been studied in the literature, and observational data from the growth of
perturbations can constrain these parameterizations. Assuming standard general
relativity with a simple Yukawa-type coupling between dark energy and dark
matter fields in the Lagrangian, we use the Boltzmann equation to analytically
express and calculate the interaction kernel $Q$ in the continuity equation and
compare it to that of a typical parametrization. We arrive at a comparably very
small result, as expected. Since the interaction is a function of the dark
matter mass, other observational data sets can be used to constrain the mass.
This calculation can be modified to account for other couplings of the dark
energy and dark matter fields. This calculation required obtaining a
distribution function for dark energy that leads to an equation of state
parameter that is negative, which neither Bose-Einstein nor Fermi-Dirac
statistics can supply, and this is the main result of this paper. Treating dark
energy as a quantum scalar field, we use adiabatic subtraction to obtain a
finite analytic approximation for its distribution function that assumes the
FLRW metric and nothing more.
| [
{
"created": "Sat, 21 Sep 2019 17:07:52 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Mar 2021 14:38:49 GMT",
"version": "v2"
}
] | 2021-06-25 | [
[
"Ludwick",
"Kevin J.",
""
],
[
"Sebaugh",
"Holston",
""
]
] | Dark energy and dark matter are two of the biggest mysteries of modern cosmology, and our understanding of their fundamental nature is incomplete. Many parameterizations of couplings between the two in the continuity equation have been studied in the literature, and observational data from the growth of perturbations can constrain these parameterizations. Assuming standard general relativity with a simple Yukawa-type coupling between dark energy and dark matter fields in the Lagrangian, we use the Boltzmann equation to analytically express and calculate the interaction kernel $Q$ in the continuity equation and compare it to that of a typical parametrization. We arrive at a comparably very small result, as expected. Since the interaction is a function of the dark matter mass, other observational data sets can be used to constrain the mass. This calculation can be modified to account for other couplings of the dark energy and dark matter fields. This calculation required obtaining a distribution function for dark energy that leads to an equation of state parameter that is negative, which neither Bose-Einstein nor Fermi-Dirac statistics can supply, and this is the main result of this paper. Treating dark energy as a quantum scalar field, we use adiabatic subtraction to obtain a finite analytic approximation for its distribution function that assumes the FLRW metric and nothing more. |
1810.03059 | H\'ector Hern\'andez | J. Ospino, J.L. Hern\'andez-Pastora, H. Hern\'andez and L.A. N\'u\~nez | Are there any models with homogeneous energy density? | 17 pages | null | 10.1007/s10714-018-2467-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By applying a recent method --based on a tetrad formalism in General
Relativity and the orthogonal splitting of the Riemann tensor-- to the simple
spherical static case, we found that the only static solution with homogeneous
energy density is the Schwarzschild solution and that there are no spherically
symmetric dynamic solutions consistent with the homogeneous energy density
assumption. Finally, a circular equivalence is shown among the most frequent
conditions considered in the spherical symmetric case: homogeneous density,
isotropy in pressures, conformally flatness and shear-free conditions. We
demonstrate that, due to the regularity conditions at the center of the matter
distribution, the imposition of two conditions necessarily leads to the static
case.
| [
{
"created": "Sat, 6 Oct 2018 22:17:15 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Oct 2018 15:32:16 GMT",
"version": "v2"
}
] | 2018-10-24 | [
[
"Ospino",
"J.",
""
],
[
"Hernández-Pastora",
"J. L.",
""
],
[
"Hernández",
"H.",
""
],
[
"Núñez",
"L. A.",
""
]
] | By applying a recent method --based on a tetrad formalism in General Relativity and the orthogonal splitting of the Riemann tensor-- to the simple spherical static case, we found that the only static solution with homogeneous energy density is the Schwarzschild solution and that there are no spherically symmetric dynamic solutions consistent with the homogeneous energy density assumption. Finally, a circular equivalence is shown among the most frequent conditions considered in the spherical symmetric case: homogeneous density, isotropy in pressures, conformally flatness and shear-free conditions. We demonstrate that, due to the regularity conditions at the center of the matter distribution, the imposition of two conditions necessarily leads to the static case. |
1601.07477 | Martin Bojowald | M. M. Amaral and Martin Bojowald | A path-integral approach to the problem of time | 19 pages, v2: additional remarks on topological turning points | Annals of Physics 388C (2018) 241-266 | 10.1016/j.aop.2017.11.027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum transition amplitudes are formulated for a model system with local
internal time, using path integrals. The amplitudes are shown to be more
regular near a turning point of internal time than could be expected based on
existing canonical treatments. In particular, a successful transition through a
turning point is provided in the model system, together with a new definition
of such a transition in general terms. Some of the results rely on a fruitful
relation between the problem of time and general Gribov problems.
| [
{
"created": "Wed, 27 Jan 2016 18:10:34 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Feb 2016 15:39:00 GMT",
"version": "v2"
}
] | 2017-12-19 | [
[
"Amaral",
"M. M.",
""
],
[
"Bojowald",
"Martin",
""
]
] | Quantum transition amplitudes are formulated for a model system with local internal time, using path integrals. The amplitudes are shown to be more regular near a turning point of internal time than could be expected based on existing canonical treatments. In particular, a successful transition through a turning point is provided in the model system, together with a new definition of such a transition in general terms. Some of the results rely on a fruitful relation between the problem of time and general Gribov problems. |
gr-qc/0501088 | Carlos O. Lousto | Carlos O. Lousto | Reconstruction of Black Hole Metric Perturbations from Weyl Curvature
II: The Regge-Wheeler gauge | 22 pages, no figures | Class.Quant.Grav. 22 (2005) S569-S588 | 10.1088/0264-9381/22/15/002 | null | gr-qc | null | Perturbation theory of rotating black holes is described in terms of the Weyl
scalars $\psi_4$ and $\psi_0$; each satisfying the Teukolsky's complex master
wave equation with spin $s=\mp2$, and respectively representing outgoing and
ingoing radiation. We explicitly construct the metric perturbations out of
these Weyl scalars in the Regge-Wheeler gauge in the nonrotating limit. We
propose a generalization of the Regge-Wheeler gauge for Kerr background in the
Newman-Penrose language, and discuss the approach for building up the perturbed
spacetime of a rotating black hole. We also provide both-way relationships
between waveforms defined in the metric and curvature approaches in the time
domain, also known as the (inverse-) Chandrasekhar transformations, generalized
to include matter.
| [
{
"created": "Thu, 27 Jan 2005 20:20:44 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Aug 2005 19:36:06 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Lousto",
"Carlos O.",
""
]
] | Perturbation theory of rotating black holes is described in terms of the Weyl scalars $\psi_4$ and $\psi_0$; each satisfying the Teukolsky's complex master wave equation with spin $s=\mp2$, and respectively representing outgoing and ingoing radiation. We explicitly construct the metric perturbations out of these Weyl scalars in the Regge-Wheeler gauge in the nonrotating limit. We propose a generalization of the Regge-Wheeler gauge for Kerr background in the Newman-Penrose language, and discuss the approach for building up the perturbed spacetime of a rotating black hole. We also provide both-way relationships between waveforms defined in the metric and curvature approaches in the time domain, also known as the (inverse-) Chandrasekhar transformations, generalized to include matter. |
2112.12293 | Jiri Podolsky | David Matejov, Jiri Podolsky | Extremal isolated horizons with $\Lambda$ and the related unique type D
black holes | 28 pages, 1 figure | Phys. Rev. D 105, 064016 (2022) | 10.1103/PhysRevD.105.064016 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We extend our previous work in which we derived the most general form of an
induced metric describing the geometry of an axially symmetric extremal
isolated horizon (EIH) in asymptotically flat spacetime. Here we generalize it
to EIHs in asymptotically (anti-)de Sitter spacetime. The resulting metric
conveniently forms a 6-parameter family which, in addition to a cosmological
constant $\Lambda$, depends on the area of the horizon, total electric and
magnetic charges, and two deficit angles representing conical singularities at
poles. Such a metric is consistent with results obtained in the context of
near-horizon geometries. Moreover, we study extremal horizons of all black
holes within the class of Plebanski-Demianski exact (electro)vacuum spacetimes
of the algebraic type D. In an important special case of non-accelerating black
holes, that is the famous Kerr-Newman-NUT-(A)dS metric, we were able to
identify the corresponding extremal horizons, including their position and
geometry, and find explicit relations between the physical parameters of the
metric and the geometrical parameters of the EIHs.
| [
{
"created": "Thu, 23 Dec 2021 00:59:20 GMT",
"version": "v1"
}
] | 2022-08-23 | [
[
"Matejov",
"David",
""
],
[
"Podolsky",
"Jiri",
""
]
] | We extend our previous work in which we derived the most general form of an induced metric describing the geometry of an axially symmetric extremal isolated horizon (EIH) in asymptotically flat spacetime. Here we generalize it to EIHs in asymptotically (anti-)de Sitter spacetime. The resulting metric conveniently forms a 6-parameter family which, in addition to a cosmological constant $\Lambda$, depends on the area of the horizon, total electric and magnetic charges, and two deficit angles representing conical singularities at poles. Such a metric is consistent with results obtained in the context of near-horizon geometries. Moreover, we study extremal horizons of all black holes within the class of Plebanski-Demianski exact (electro)vacuum spacetimes of the algebraic type D. In an important special case of non-accelerating black holes, that is the famous Kerr-Newman-NUT-(A)dS metric, we were able to identify the corresponding extremal horizons, including their position and geometry, and find explicit relations between the physical parameters of the metric and the geometrical parameters of the EIHs. |
2010.14526 | Merced Montesinos | Mariano Celada, Ricardo Escobedo, Merced Montesinos | Canonical analysis of $BF$ gravity in $n$ dimensions | null | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we perform in a manifestly $SO(n-1,1)$ [or, alternatively
$SO(n)$] covariant fashion, the canonical analysis of general relativity in $n$
dimensions written as a constrained $BF$ theory. Since the Lagrangian action of
the theory can be written in two classically equivalent ways, we analyze each
case separately. We show that for either action the canonical analysis can be
accomplished without introducing second-class constraints during the whole
process. Furthermore, in each case the resulting Hamiltonian formulation is the
same as the canonical formulation with only first-class constraints recently
obtained in M. Montesinos, R. Escobedo, J. Romero, and M. Celada, Phys. Rev. D
101, 024042 (2020) from the $n$-dimensional Palatini action.
| [
{
"created": "Tue, 27 Oct 2020 18:00:43 GMT",
"version": "v1"
}
] | 2020-10-29 | [
[
"Celada",
"Mariano",
""
],
[
"Escobedo",
"Ricardo",
""
],
[
"Montesinos",
"Merced",
""
]
] | In this paper we perform in a manifestly $SO(n-1,1)$ [or, alternatively $SO(n)$] covariant fashion, the canonical analysis of general relativity in $n$ dimensions written as a constrained $BF$ theory. Since the Lagrangian action of the theory can be written in two classically equivalent ways, we analyze each case separately. We show that for either action the canonical analysis can be accomplished without introducing second-class constraints during the whole process. Furthermore, in each case the resulting Hamiltonian formulation is the same as the canonical formulation with only first-class constraints recently obtained in M. Montesinos, R. Escobedo, J. Romero, and M. Celada, Phys. Rev. D 101, 024042 (2020) from the $n$-dimensional Palatini action. |
2203.09209 | Flavio Bombacigno | Flavio Bombacigno | Quasinormal modes of Schwarzschild black holes in metric affine
Chern-Simons theory | Contribution to the 2022 Gravitation session of the 56th Rencontres
de Moriond | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We reformulate the Chern-Simons modified gravity in the metric-affine
formalism, by enlarging the Pontryagin density with homothetic curvature terms
which restore projective invariance without spoiling topologicity. The latter
is then violated by promoting the coupling of the Chern-Simons term to a
(pseudo)-scalar field. We derive the perturbative solutions for torsion and
nonmetricity from the background fields, and we describe the dynamics for the
resulting linearized metric and the scalar fields in a Schwarzschild black hole
background. Then, by adopting numerical techniques we compute the quasinormal
mode spectrum and the late-time tails for scalar and metric perturbations.
| [
{
"created": "Thu, 17 Mar 2022 10:00:29 GMT",
"version": "v1"
}
] | 2022-03-18 | [
[
"Bombacigno",
"Flavio",
""
]
] | We reformulate the Chern-Simons modified gravity in the metric-affine formalism, by enlarging the Pontryagin density with homothetic curvature terms which restore projective invariance without spoiling topologicity. The latter is then violated by promoting the coupling of the Chern-Simons term to a (pseudo)-scalar field. We derive the perturbative solutions for torsion and nonmetricity from the background fields, and we describe the dynamics for the resulting linearized metric and the scalar fields in a Schwarzschild black hole background. Then, by adopting numerical techniques we compute the quasinormal mode spectrum and the late-time tails for scalar and metric perturbations. |
1706.04441 | Dao-Jun Liu | Yang Huang, Dao-Jun Liu, Xiang-Hua Zhai and Xin-Zhou Li | Scalar clouds around Kerr-Sen black holes | 15 pages, 7 figures, accepted for publication in Class. Quantum Grav | null | 10.1088/1361-6382/aa7964 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the behaviour of a charged massive scalar test field in the
background of a Kerr-Sen black hole is investigated. A kind of stationary
solutions, dubbed scalar clouds, are obtained numerically and expressed by the
existence lines in the parameter space. We show that for fixed background and a
given set of harmonic indices, the mass and charge of the scalar clouds are
limited in a finite region in the parameter space of the scalar field.
Particularly, the maximum values of the mass and charge of the clouds around
extremal Kerr-Sen black holes are independent of the angular velocity of the
black hole, whereas those in the extremal Kerr-Newman background depend on the
angular velocity. In addition, it is demonstrated that, as the static limit of
Kerr-Sen black hole, Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole can
not support scalar cloud.
| [
{
"created": "Wed, 14 Jun 2017 12:31:29 GMT",
"version": "v1"
}
] | 2017-07-26 | [
[
"Huang",
"Yang",
""
],
[
"Liu",
"Dao-Jun",
""
],
[
"Zhai",
"Xiang-Hua",
""
],
[
"Li",
"Xin-Zhou",
""
]
] | In this paper, the behaviour of a charged massive scalar test field in the background of a Kerr-Sen black hole is investigated. A kind of stationary solutions, dubbed scalar clouds, are obtained numerically and expressed by the existence lines in the parameter space. We show that for fixed background and a given set of harmonic indices, the mass and charge of the scalar clouds are limited in a finite region in the parameter space of the scalar field. Particularly, the maximum values of the mass and charge of the clouds around extremal Kerr-Sen black holes are independent of the angular velocity of the black hole, whereas those in the extremal Kerr-Newman background depend on the angular velocity. In addition, it is demonstrated that, as the static limit of Kerr-Sen black hole, Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole can not support scalar cloud. |
gr-qc/0404074 | Stefan Hollands | Stefan Hollands and Robert M. Wald | Conservation of the stress tensor in perturbative interacting quantum
field theory in curved spacetimes | 88 pages, latex, no figures, v2: changes in the proof of proposition
3.1 | Rev.Math.Phys. 17 (2005) 227-312 | 10.1142/S0129055X05002340 | null | gr-qc hep-th math-ph math.MP | null | We propose additional conditions (beyond those considered in our previous
papers) that should be imposed on Wick products and time-ordered products of a
free quantum scalar field in curved spacetime. These conditions arise from a
simple ``Principle of Perturbative Agreement'': For interaction Lagrangians
$L_1$ that are such that the interacting field theory can be constructed
exactly--as occurs when $L_1$ is a ``pure divergence'' or when $L_1$ is at most
quadratic in the field and contains no more than two derivatives--then
time-ordered products must be defined so that the perturbative solution for
interacting fields obtained from the Bogoliubov formula agrees with the exact
solution. The conditions derived from this principle include a version of the
Leibniz rule (or ``action Ward identity'') and a condition on time-ordered
products that contain a factor of the free field $\phi$ or the free
stress-energy tensor $T_{ab}$. The main results of our paper are (1) a proof
that in spacetime dimensions greater than 2, our new conditions can be
consistently imposed in addition to our previously considered conditions and
(2) a proof that, if they are imposed, then for {\em any} polynomial
interaction Lagrangian $L_1$ (with no restriction on the number of derivatives
appearing in $L_1$), the stress-energy tensor $\Theta_{ab}$ of the interacting
theory will be conserved. Our work thereby establishes (in the context of
perturbation theory) the conservation of stress-energy for an arbitrary
interacting scalar field in curved spacetimes of dimension greater than 2. Our
approach requires us to view time-ordered products as maps taking classical
field expressions into the quantum field algebra rather than as maps taking
Wick polynomials of the quantum field into the quantum field algebra.
| [
{
"created": "Fri, 16 Apr 2004 18:40:09 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jan 2005 13:22:08 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Hollands",
"Stefan",
""
],
[
"Wald",
"Robert M.",
""
]
] | We propose additional conditions (beyond those considered in our previous papers) that should be imposed on Wick products and time-ordered products of a free quantum scalar field in curved spacetime. These conditions arise from a simple ``Principle of Perturbative Agreement'': For interaction Lagrangians $L_1$ that are such that the interacting field theory can be constructed exactly--as occurs when $L_1$ is a ``pure divergence'' or when $L_1$ is at most quadratic in the field and contains no more than two derivatives--then time-ordered products must be defined so that the perturbative solution for interacting fields obtained from the Bogoliubov formula agrees with the exact solution. The conditions derived from this principle include a version of the Leibniz rule (or ``action Ward identity'') and a condition on time-ordered products that contain a factor of the free field $\phi$ or the free stress-energy tensor $T_{ab}$. The main results of our paper are (1) a proof that in spacetime dimensions greater than 2, our new conditions can be consistently imposed in addition to our previously considered conditions and (2) a proof that, if they are imposed, then for {\em any} polynomial interaction Lagrangian $L_1$ (with no restriction on the number of derivatives appearing in $L_1$), the stress-energy tensor $\Theta_{ab}$ of the interacting theory will be conserved. Our work thereby establishes (in the context of perturbation theory) the conservation of stress-energy for an arbitrary interacting scalar field in curved spacetimes of dimension greater than 2. Our approach requires us to view time-ordered products as maps taking classical field expressions into the quantum field algebra rather than as maps taking Wick polynomials of the quantum field into the quantum field algebra. |
gr-qc/9411068 | Ysfujii | Yasunori Fujii | Induced Violation of Weak Equivalence Principle in the Brans-Dicke
Theory | 7 pages, LaTex | Mod.Phys.Lett. A9 (1994) 3685-3690 | 10.1142/S021773239400352X | null | gr-qc | null | A quantum correction to the Brans-Dicke theory due to interactions among
matter fields is calculated, resulting in violation of WEP, hence giving a
constraint on the parameter $\omega$ far more stringent than accepted so far.
The tentative estimate gives the lower bounds $\gsim 10^{6}$ and $\gsim 10^{8}$
for the assumed force-range $\gsim 1$m and $\gsim 1$AU, respectively.
| [
{
"created": "Tue, 29 Nov 1994 04:16:13 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Fujii",
"Yasunori",
""
]
] | A quantum correction to the Brans-Dicke theory due to interactions among matter fields is calculated, resulting in violation of WEP, hence giving a constraint on the parameter $\omega$ far more stringent than accepted so far. The tentative estimate gives the lower bounds $\gsim 10^{6}$ and $\gsim 10^{8}$ for the assumed force-range $\gsim 1$m and $\gsim 1$AU, respectively. |
0912.4054 | Eugenio Bianchi | Eugenio Bianchi, Elena Magliaro, Claudio Perini | Coherent spin-networks | 15 pages | Phys.Rev.D82:024012,2010 | 10.1103/PhysRevD.82.024012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss a proposal of coherent states for Loop Quantum
Gravity. These states are labeled by a point in the phase space of General
Relativity as captured by a spin-network graph. They are defined as the gauge
invariant projection of a product over links of Hall's heat-kernels for the
cotangent bundle of SU(2). The labels of the state are written in terms of two
unit-vectors, a spin and an angle for each link of the graph. The heat-kernel
time is chosen to be a function of the spin. These labels are the ones used in
the Spin Foam setting and admit a clear geometric interpretation. Moreover, the
set of labels per link can be written as an element of SL(2,C). Therefore,
these states coincide with Thiemann's coherent states with the area operator as
complexifier. We study the properties of semiclassicality of these states and
show that, for large spins, they reproduce a superposition over spins of
spin-networks with nodes labeled by Livine-Speziale coherent intertwiners.
Moreover, the weight associated to spins on links turns out to be given by a
Gaussian times a phase as originally proposed by Rovelli.
| [
{
"created": "Sun, 20 Dec 2009 21:11:09 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Feb 2010 20:34:10 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Feb 2010 22:31:52 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Sep 2010 18:28:26 GMT",
"version": "v4"
}
] | 2010-09-20 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Magliaro",
"Elena",
""
],
[
"Perini",
"Claudio",
""
]
] | In this paper we discuss a proposal of coherent states for Loop Quantum Gravity. These states are labeled by a point in the phase space of General Relativity as captured by a spin-network graph. They are defined as the gauge invariant projection of a product over links of Hall's heat-kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit-vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the Spin Foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). Therefore, these states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli. |
1101.2425 | Jose Wadih Maluf Dr. | J. F. da Rocha-Neto, J. W. Maluf and S. C. Ulhoa | Hamiltonian formulation of unimodular gravity in the teleparallel
geometry | 21 pages, no figures | Phys.Rev.D82:124035,2010 | 10.1103/PhysRevD.82.124035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of the teleparallel equivalent of general relativity we
establish the Hamiltonian formulation of the unimodular theory of gravity. Here
we do not carry out the usual $3+1$ decomposition of the field quantities in
terms of the lapse and shift functions, as in the ADM formalism. The
corresponding Lagrange multiplier is the timelike component of the tetrad
field. The dynamics is determined by the Hamiltonian constraint ${\cal H}'_0$
and a set of primary constraints. The constraints are first class and satisfy
an algebra that is similar to the algebra of the Poincar\'e group.
| [
{
"created": "Wed, 12 Jan 2011 19:00:12 GMT",
"version": "v1"
}
] | 2011-01-17 | [
[
"da Rocha-Neto",
"J. F.",
""
],
[
"Maluf",
"J. W.",
""
],
[
"Ulhoa",
"S. C.",
""
]
] | In the context of the teleparallel equivalent of general relativity we establish the Hamiltonian formulation of the unimodular theory of gravity. Here we do not carry out the usual $3+1$ decomposition of the field quantities in terms of the lapse and shift functions, as in the ADM formalism. The corresponding Lagrange multiplier is the timelike component of the tetrad field. The dynamics is determined by the Hamiltonian constraint ${\cal H}'_0$ and a set of primary constraints. The constraints are first class and satisfy an algebra that is similar to the algebra of the Poincar\'e group. |
gr-qc/9903033 | Wai-Mo Suen | K.S. Cheng, Y.Li and W.-M. Suen | The Thermal Response of a Pulsar Glitch : The Non-spherical Symmetric
Case | Published in Ap. J. Lett | null | null | null | gr-qc astro-ph | null | We study the thermal evolution of a pulsar after a glitch in which the energy
is released from a relative compact region. A set of relativistic thermal
transport and energy balance equations is used to study the thermal evolution,
without making the assumption of spherical symmetry. We use an exact cooling
model to solve this set of differential equtions. Our results differ
significantly from those obtained under the assumption of spherical symmetry.
Even for young pulsars with a hot core like the Vela pulsar, we find that a
detectable hot spot can be observed after a glitch. The results suggest that
the intensity variation and the relative phases of hard X-ray emissions in
different epoches can provide important information on the equation of state.
| [
{
"created": "Mon, 8 Mar 1999 23:38:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cheng",
"K. S.",
""
],
[
"Li",
"Y.",
""
],
[
"Suen",
"W. -M.",
""
]
] | We study the thermal evolution of a pulsar after a glitch in which the energy is released from a relative compact region. A set of relativistic thermal transport and energy balance equations is used to study the thermal evolution, without making the assumption of spherical symmetry. We use an exact cooling model to solve this set of differential equtions. Our results differ significantly from those obtained under the assumption of spherical symmetry. Even for young pulsars with a hot core like the Vela pulsar, we find that a detectable hot spot can be observed after a glitch. The results suggest that the intensity variation and the relative phases of hard X-ray emissions in different epoches can provide important information on the equation of state. |
gr-qc/9710049 | Jerry Griffiths | J Podolsky and J B Griffiths | Impulsive waves in de Sitter and anti-de Sitter space-times generated by
null particles with an arbitrary multipole structure | 12 pages, LaTeX, one eps figure included using graphicx, To appear in
Classical and Quantum Gravity | Class.Quant.Grav. 15 (1998) 453-463 | 10.1088/0264-9381/15/2/018 | null | gr-qc | null | We describe a class of impulsive gravitational waves which propagate either
in a de Sitter or an anti-de Sitter background. They are conformal to impulsive
waves of Kundt's class. In a background with positive cosmological constant
they are spherical (but non-expanding) waves generated by pairs of particles
with arbitrary multipole structure propagating in opposite directions. When the
cosmological constant is negative, they are hyperboloidal waves generated by a
null particle of the same type. In this case, they are included in the
impulsive limit of a class of solutions described by Siklos that are conformal
to pp-waves.
| [
{
"created": "Wed, 8 Oct 1997 12:50:01 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Podolsky",
"J",
""
],
[
"Griffiths",
"J B",
""
]
] | We describe a class of impulsive gravitational waves which propagate either in a de Sitter or an anti-de Sitter background. They are conformal to impulsive waves of Kundt's class. In a background with positive cosmological constant they are spherical (but non-expanding) waves generated by pairs of particles with arbitrary multipole structure propagating in opposite directions. When the cosmological constant is negative, they are hyperboloidal waves generated by a null particle of the same type. In this case, they are included in the impulsive limit of a class of solutions described by Siklos that are conformal to pp-waves. |
2408.02596 | Volker Schlue | Grigorios Fournodavlos and Volker Schlue | Stability of the expanding region of Kerr de Sitter spacetimes | 45 pages, 3 figures | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the nonlinear stability of the cosmological region of Kerr de Sitter
spacetimes. More precisely, we show that solutions to the Einstein vacuum
equations with positive cosmological constant arising from data on a cylinder
that is uniformly close to the Kerr de Sitter geometry (with possibly different
mass and angular momentum parameters at either end) are future geodesically
complete and display asymptotically de Sitter-like degrees of freedom. The
proof uses an ADM formulation of the Einstein equations in parabolic gauge.
Together with a well-known theorem of Hintz-Vasy [Acta Math. 220 (2018)], our
result yields a global stability result for Kerr de Sitter from Cauchy data on
a spacelike hypersurface bridging two black hole exteriors.
| [
{
"created": "Mon, 5 Aug 2024 16:12:39 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Fournodavlos",
"Grigorios",
""
],
[
"Schlue",
"Volker",
""
]
] | We prove the nonlinear stability of the cosmological region of Kerr de Sitter spacetimes. More precisely, we show that solutions to the Einstein vacuum equations with positive cosmological constant arising from data on a cylinder that is uniformly close to the Kerr de Sitter geometry (with possibly different mass and angular momentum parameters at either end) are future geodesically complete and display asymptotically de Sitter-like degrees of freedom. The proof uses an ADM formulation of the Einstein equations in parabolic gauge. Together with a well-known theorem of Hintz-Vasy [Acta Math. 220 (2018)], our result yields a global stability result for Kerr de Sitter from Cauchy data on a spacelike hypersurface bridging two black hole exteriors. |
gr-qc/0611023 | Davi Giugno | E. Abdalla, D. Giugno | An Extensive Search for Overtones in Schwarzschild Black Holes | 2 figures, revtex4 used | Braz.J.Phys.37:450-456,2007 | 10.1590/S0103-97332007000300018 | null | gr-qc | null | In this paper we show that with standard methods it is possible to obtain
highly precise results for QNMs. In particular, secondary modes are obtained by
numerical integration. We compare several results making a detailed analysis.
| [
{
"created": "Fri, 3 Nov 2006 19:10:14 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Abdalla",
"E.",
""
],
[
"Giugno",
"D.",
""
]
] | In this paper we show that with standard methods it is possible to obtain highly precise results for QNMs. In particular, secondary modes are obtained by numerical integration. We compare several results making a detailed analysis. |
gr-qc/9909026 | Saul A. Teukolsky | Saul A. Teukolsky | On the Stability of the Iterated Crank-Nicholson Method in Numerical
Relativity | 2 pages | Phys.Rev. D61 (2000) 087501 | 10.1103/PhysRevD.61.087501 | null | gr-qc | null | The iterated Crank-Nicholson method has become a popular algorithm in
numerical relativity. We show that one should carry out exactly two iterations
and no more. While the limit of an infinite number of iterations is the
standard Crank-Nicholson method, it can in fact be worse to do more than two
iterations, and it never helps. We explain how this paradoxical result arises.
| [
{
"created": "Tue, 7 Sep 1999 14:35:30 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Teukolsky",
"Saul A.",
""
]
] | The iterated Crank-Nicholson method has become a popular algorithm in numerical relativity. We show that one should carry out exactly two iterations and no more. While the limit of an infinite number of iterations is the standard Crank-Nicholson method, it can in fact be worse to do more than two iterations, and it never helps. We explain how this paradoxical result arises. |
2212.06671 | Pierre Teyssandier | P. Teyssandier | Time transfer functions without enhanced terms in stationary spacetime
-- Application to an isolated, axisymmetric spinning body | 17 pages, 1 figure | null | null | null | gr-qc astro-ph.EP | http://creativecommons.org/licenses/by/4.0/ | We develop a new perturbation method for determining a class of time transfer
functions in a stationary spacetime when its metric is a small deformation of a
background metric for which the time transfer functions are known in a closed
form. The perturbation terms are expressed as line integrals along the null
geodesic paths of the background metric. Unlike what happens with the other
procedures proposed until now, the time transfer functions obtained in this way
are completely free of unbounded terms and do not generate any enhancement in
the light travel time. Our procedure proves to be very efficient when the
background metric is a linearized Schwarzschild-like metric. Its application to
an isolated body slowly rotating about an axis of symmetry leads to integrals
which can be calculated with any symbolic computer program. Explicit
expressions are obtained for the mass dipole and quadrupole moments and for the
leading gravitomagnetic term induced by the spin of the body. A brief numerical
discussion is given for the 2002 Cassini experiment.
| [
{
"created": "Tue, 13 Dec 2022 15:48:26 GMT",
"version": "v1"
}
] | 2022-12-14 | [
[
"Teyssandier",
"P.",
""
]
] | We develop a new perturbation method for determining a class of time transfer functions in a stationary spacetime when its metric is a small deformation of a background metric for which the time transfer functions are known in a closed form. The perturbation terms are expressed as line integrals along the null geodesic paths of the background metric. Unlike what happens with the other procedures proposed until now, the time transfer functions obtained in this way are completely free of unbounded terms and do not generate any enhancement in the light travel time. Our procedure proves to be very efficient when the background metric is a linearized Schwarzschild-like metric. Its application to an isolated body slowly rotating about an axis of symmetry leads to integrals which can be calculated with any symbolic computer program. Explicit expressions are obtained for the mass dipole and quadrupole moments and for the leading gravitomagnetic term induced by the spin of the body. A brief numerical discussion is given for the 2002 Cassini experiment. |
0912.3875 | Hai Siong Tan | H. S. Tan | A Proof for a Theorem of Wald in Arbitrary Dimensions | Part of author's B.Sc. Honors Thesis (NUS, 2003) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Static, axisymmetric solutions form a large class of important black holes in
classical GR. In four dimensions, the existence of their most general metric
ansatz relies on the fact that two-dimensional subspaces of the tangent space
at each point spanned by vectors orthogonal to the time-translation and
rotation Killing fields are integrable. This was first proved by Wald via an
application of Frobenius theorem. In this note, we furnish an elementary proof
for this theorem by Wald in arbitrary dimensions which yields the metric ansatz
for the most general solution of the D-dimensional vacuum Einstein equations
that admits D-2 orthogonal and commuting Killing vector fields.
| [
{
"created": "Sat, 19 Dec 2009 09:12:16 GMT",
"version": "v1"
}
] | 2009-12-22 | [
[
"Tan",
"H. S.",
""
]
] | Static, axisymmetric solutions form a large class of important black holes in classical GR. In four dimensions, the existence of their most general metric ansatz relies on the fact that two-dimensional subspaces of the tangent space at each point spanned by vectors orthogonal to the time-translation and rotation Killing fields are integrable. This was first proved by Wald via an application of Frobenius theorem. In this note, we furnish an elementary proof for this theorem by Wald in arbitrary dimensions which yields the metric ansatz for the most general solution of the D-dimensional vacuum Einstein equations that admits D-2 orthogonal and commuting Killing vector fields. |
2009.12777 | Salvatore Capozziello | Salvatore Capozziello, Maurizio Capriolo, and Shin'ichi Nojiri | Considerations on gravitational waves in higher-order local and
non-local gravity | 15 pages, to appear in Physics. Lett. B | null | 10.1016/j.physletb.2020.135821 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of gravitational wave modes and polarizations could constitute
an extremely important signature to discriminate among different theories of
gravity. According to this statement, it is possible to prove that higher-order
non-local gravity has formally the same gravitational spectrum of higher-order
local gravity. In particular, we consider the cases of $f \left( R, \Box R,
\Box^2 R, \cdots, \Box^n R \right) = R + \sum_{i=1}^n \alpha_i R \Box^i R$
gravity, linear with respect to both $R$ and $\Box^i R$ and $ f \left( R, \Box
R \right) = R + \alpha \left(\Box R\right)^2 $ gravity, quadratic with respect
to $\Box R$, where it is demonstrated the graviton amplitude changes if
compared with General Relativity. We also obtain the gravitational spectrum of
higher-order non-local gravity $ f \left( R, \Box^{-1} R, \Box^{-2} R, \cdots,
\Box^{-n} R \right) = R + \sum_{i=1}^n \alpha_i R \Box^{-i} R$. In this case,
we have three state of polarization and $n+3$ oscillation modes. More in
detail, it is possible to derive two transverse tensor $(+)$ and $(\times)$
standard polarization modes of frequency $\omega_{1}$, massless and with
2-helicity; $n+1$ further scalar modes of frequency
$\omega_{2},\dots,\omega_{n+2}$, massive and with 0-helicity, each of which has
the same mixed polarization, partly longitudinal and partly transverse.
| [
{
"created": "Sun, 27 Sep 2020 07:42:56 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Capriolo",
"Maurizio",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | The detection of gravitational wave modes and polarizations could constitute an extremely important signature to discriminate among different theories of gravity. According to this statement, it is possible to prove that higher-order non-local gravity has formally the same gravitational spectrum of higher-order local gravity. In particular, we consider the cases of $f \left( R, \Box R, \Box^2 R, \cdots, \Box^n R \right) = R + \sum_{i=1}^n \alpha_i R \Box^i R$ gravity, linear with respect to both $R$ and $\Box^i R$ and $ f \left( R, \Box R \right) = R + \alpha \left(\Box R\right)^2 $ gravity, quadratic with respect to $\Box R$, where it is demonstrated the graviton amplitude changes if compared with General Relativity. We also obtain the gravitational spectrum of higher-order non-local gravity $ f \left( R, \Box^{-1} R, \Box^{-2} R, \cdots, \Box^{-n} R \right) = R + \sum_{i=1}^n \alpha_i R \Box^{-i} R$. In this case, we have three state of polarization and $n+3$ oscillation modes. More in detail, it is possible to derive two transverse tensor $(+)$ and $(\times)$ standard polarization modes of frequency $\omega_{1}$, massless and with 2-helicity; $n+1$ further scalar modes of frequency $\omega_{2},\dots,\omega_{n+2}$, massive and with 0-helicity, each of which has the same mixed polarization, partly longitudinal and partly transverse. |
0712.0713 | Luis Herrera | L. Herrera, J. Ospino and A. Di Prisco | All static spherically symmetric anisotropic solutions of Einstein's
equations | 8 pages Latex. To appear in Phys. Rev. D. New reference added. Some
references corrected | Phys.Rev.D77:027502,2008 | 10.1103/PhysRevD.77.027502 | null | gr-qc astro-ph | null | An algorithm recently presented by Lake to obtain all static spherically
symmetric perfect fluid solutions, is extended to the case of locally
anisotropic fluids (principal stresses unequal). As expected, the new formalism
requires the knowledge of two functions (instead of one) to generate all
possible solutions. To illustrate the method some known cases are recovered.
| [
{
"created": "Wed, 5 Dec 2007 13:17:29 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Dec 2007 22:11:04 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Jan 2008 14:57:32 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Herrera",
"L.",
""
],
[
"Ospino",
"J.",
""
],
[
"Di Prisco",
"A.",
""
]
] | An algorithm recently presented by Lake to obtain all static spherically symmetric perfect fluid solutions, is extended to the case of locally anisotropic fluids (principal stresses unequal). As expected, the new formalism requires the knowledge of two functions (instead of one) to generate all possible solutions. To illustrate the method some known cases are recovered. |
1911.08257 | Jo\~ao Lu\'is Rosa | Jo\~ao Lu\'is Rosa | Cosmological and astrophysical applications of modified theories of
gravity | PhD Thesis | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study cosmological and astrophysical applications of the
recently proposed generalized hybrid metric-Palatini gravity theory, which
combines features of both the metric and the Palatini approaches to the
variational method in $f\left(R\right)$ gravity. This theory arises as a
natural generalization of the hybrid metric-Palatini gravity which has been
proven to be the first theory to unify the cosmic acceleration with the solar
system constraints, without resource to the chameleon mechanism.
In the cosmological point of view, we show using reconstruction methods that
the usual power-law and exponential scale factor behaviors in FLRW universes
exist for various different distributions of matter, along with solutions for
collapsing universes. Using the dynamical system approach, we also show that no
global attractors can exist in the cosmological phase space and that stable
universes can either be described by scale factors that diverge in finite time
or asymptotically approach constant values. Furthermore, we also study the
cosmological phase space of theories of gravity with terms of order six and
eight in the derivatives of the metric and we conclude that the higher-order
terms are not neglectable.
In the area of astrophysics, we show that using the junction conditions of
the theory it is possible to obtain solutions for compact objects supported by
thin-shells, such as self-gravitating shells with and without perfect fluids on
their exteriors, and also traversable wormhole solutions which satisfy the null
energy condition for the whole spacetime, thus not needing the support of
exotic matter. Furthermore, we show that there exist specific forms of the
action for which the massive scalar degree of freedom of the theory is stable
in the scope of rotating black-holes described by the Kerr metric.
| [
{
"created": "Tue, 19 Nov 2019 13:35:46 GMT",
"version": "v1"
}
] | 2019-11-20 | [
[
"Rosa",
"João Luís",
""
]
] | In this work, we study cosmological and astrophysical applications of the recently proposed generalized hybrid metric-Palatini gravity theory, which combines features of both the metric and the Palatini approaches to the variational method in $f\left(R\right)$ gravity. This theory arises as a natural generalization of the hybrid metric-Palatini gravity which has been proven to be the first theory to unify the cosmic acceleration with the solar system constraints, without resource to the chameleon mechanism. In the cosmological point of view, we show using reconstruction methods that the usual power-law and exponential scale factor behaviors in FLRW universes exist for various different distributions of matter, along with solutions for collapsing universes. Using the dynamical system approach, we also show that no global attractors can exist in the cosmological phase space and that stable universes can either be described by scale factors that diverge in finite time or asymptotically approach constant values. Furthermore, we also study the cosmological phase space of theories of gravity with terms of order six and eight in the derivatives of the metric and we conclude that the higher-order terms are not neglectable. In the area of astrophysics, we show that using the junction conditions of the theory it is possible to obtain solutions for compact objects supported by thin-shells, such as self-gravitating shells with and without perfect fluids on their exteriors, and also traversable wormhole solutions which satisfy the null energy condition for the whole spacetime, thus not needing the support of exotic matter. Furthermore, we show that there exist specific forms of the action for which the massive scalar degree of freedom of the theory is stable in the scope of rotating black-holes described by the Kerr metric. |
gr-qc/0009043 | Michael A. Ivanov | Michael A. Ivanov | Non-dopplerian cosmological redshift parameters in a model of
graviton-dusty universe | 5 pages. It was presented: at SIGRAV'2000 Congress, Italy (this
version); in Proc. of the Int. Symp. "FFP 4" (9-13 Dec 2000, Hyderabad,
India), Sidharth& Altaisky, Eds., Kluwer Academic/Plenum, 2001;in Proc. of
the 4th Edoardo Amaldi Conference on GW (Perth, W. Australia, 8-13 July 2001) | Class.Quant.Grav. 19 (2002) 1351-1354 | 10.1088/0264-9381/19/7/317 | null | gr-qc | null | Possible effects are considered which would be caused by a hypothetical
superstrong interaction of photons or massive bodies with single gravitons of
the graviton background. If full cosmological redshift magnitudes are caused by
the interaction, then the luminosity distance in a flat non-expanding universe
as a function of redshift is very similar to the specific function which fits
supernova cosmology data by Riess et al. From another side, in this case every
massive body, slowly moving relatively to the background, would experience a
constant acceleration, proportional to the Hubble constant, of the same order
as a small additional acceleration of Pioneer 10, 11.
| [
{
"created": "Wed, 13 Sep 2000 06:31:25 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Dec 2004 12:02:56 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Ivanov",
"Michael A.",
""
]
] | Possible effects are considered which would be caused by a hypothetical superstrong interaction of photons or massive bodies with single gravitons of the graviton background. If full cosmological redshift magnitudes are caused by the interaction, then the luminosity distance in a flat non-expanding universe as a function of redshift is very similar to the specific function which fits supernova cosmology data by Riess et al. From another side, in this case every massive body, slowly moving relatively to the background, would experience a constant acceleration, proportional to the Hubble constant, of the same order as a small additional acceleration of Pioneer 10, 11. |
gr-qc/0304099 | Brian Edgar | S.Brian Edgar, Ola Wingbrant | Old and new results for superenergy tensors from dimensionally dependent
tensor identities | 18 pages; TeX file | J.Math.Phys. 44 (2003) 6140-6159 | 10.1063/1.1624094 | null | gr-qc | null | It is known that some results for spinors, and in particular for superenergy
spinors, are much less transparent and require a lot more effort to establish,
when considered from the tensor viewpoint. In this paper we demonstrate how the
use of dimensionally dependent tensor identities enables us to derive a number
of 4-dimensional identities by straightforward tensor methods in a signature
independent manner. In particular, we consider the quadratic identity for the
Bel-Robinson tensor ${\cal T}_{abcx}{\cal T}^{abcy} = \delta_x^y {\cal
T}_{abcd}{\cal T}^{abcd}/4$ and also the new conservation laws for the
Chevreton tensor, both of which have been obtained by spinor means; both of
these results are rederived by {\it tensor} means for 4-dimensional spaces of
any signature, using dimensionally dependent identities, and also we are able
to conclude that there are no {\it direct} higher dimensional analogues. In
addition we demonstrate a simple way to show non-existense of such identities
via counter examples; in particular we show that there is no non-trivial Bel
tensor analogue of this simple Bel-Robinson tensor quadratic identity. On the
other hand, as a sample of the power of generalising dimensionally dependent
tensor identities from four to higher dimensions, we show that the symmetry
structure, trace-free and divergence-free nature of the four dimensional
Bel-Robinson tensor does have an analogue for a class of tensors in higher
dimensions.
| [
{
"created": "Mon, 28 Apr 2003 15:23:30 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Edgar",
"S. Brian",
""
],
[
"Wingbrant",
"Ola",
""
]
] | It is known that some results for spinors, and in particular for superenergy spinors, are much less transparent and require a lot more effort to establish, when considered from the tensor viewpoint. In this paper we demonstrate how the use of dimensionally dependent tensor identities enables us to derive a number of 4-dimensional identities by straightforward tensor methods in a signature independent manner. In particular, we consider the quadratic identity for the Bel-Robinson tensor ${\cal T}_{abcx}{\cal T}^{abcy} = \delta_x^y {\cal T}_{abcd}{\cal T}^{abcd}/4$ and also the new conservation laws for the Chevreton tensor, both of which have been obtained by spinor means; both of these results are rederived by {\it tensor} means for 4-dimensional spaces of any signature, using dimensionally dependent identities, and also we are able to conclude that there are no {\it direct} higher dimensional analogues. In addition we demonstrate a simple way to show non-existense of such identities via counter examples; in particular we show that there is no non-trivial Bel tensor analogue of this simple Bel-Robinson tensor quadratic identity. On the other hand, as a sample of the power of generalising dimensionally dependent tensor identities from four to higher dimensions, we show that the symmetry structure, trace-free and divergence-free nature of the four dimensional Bel-Robinson tensor does have an analogue for a class of tensors in higher dimensions. |
1804.09224 | Jezreel Castillo | Jezreel Castillo, Ian Vega and Barry Wardell | Self-force on a scalar charge in a circular orbit about a
Reissner-Nordstr\"{o}m black hole | 8 pages, 5 figures, accepted for publication in PRD | Phys. Rev. D 98, 024024 (2018) | 10.1103/PhysRevD.98.024024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by applications to the study of self-force effects in scalar-tensor
theories of gravity, we calculate the self-force exerted on a scalar charge in
a circular orbit about a Reissner-Nordstr\"{o}m black hole. We obtain the
self-force via a mode-sum calculation, and find that our results differ from
recent post-Newtonian calculations even in the slow-motion regime. We compute
the radiative fluxes towards infinity and down the black hole, and verify that
they are balanced by energy dissipated through the local self-force - in
contrast to the reported post-Newtonian results. The self-force and radiative
fluxes depend solely on the black hole's charge-to-mass ratio, the controlling
parameter of the Reissner-Nordstr\"{o}m geometry. They both monotonically
decrease as the black hole reaches extremality. With respect to an extremality
parameter $\epsilon$, the energy flux through the event horizon is found to
scale as $\sim \epsilon^{5/4}$ as $\epsilon \rightarrow 0$.
| [
{
"created": "Tue, 24 Apr 2018 19:29:00 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Apr 2018 00:13:09 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Jun 2018 08:07:47 GMT",
"version": "v3"
}
] | 2018-07-18 | [
[
"Castillo",
"Jezreel",
""
],
[
"Vega",
"Ian",
""
],
[
"Wardell",
"Barry",
""
]
] | Motivated by applications to the study of self-force effects in scalar-tensor theories of gravity, we calculate the self-force exerted on a scalar charge in a circular orbit about a Reissner-Nordstr\"{o}m black hole. We obtain the self-force via a mode-sum calculation, and find that our results differ from recent post-Newtonian calculations even in the slow-motion regime. We compute the radiative fluxes towards infinity and down the black hole, and verify that they are balanced by energy dissipated through the local self-force - in contrast to the reported post-Newtonian results. The self-force and radiative fluxes depend solely on the black hole's charge-to-mass ratio, the controlling parameter of the Reissner-Nordstr\"{o}m geometry. They both monotonically decrease as the black hole reaches extremality. With respect to an extremality parameter $\epsilon$, the energy flux through the event horizon is found to scale as $\sim \epsilon^{5/4}$ as $\epsilon \rightarrow 0$. |
1901.11522 | Lucas Gardai Collodel | Lucas G. Collodel, Burkhard Kleihaus, Jutta Kunz | On the Structure of Rotating Charged Boson Stars | null | Phys. Rev. D 99, 104076 (2019) | 10.1103/PhysRevD.99.104076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present full sets of solutions for rotating charged boson
stars with different coupling values. By adopting local comoving coordinates,
we are able to find expressions for the effective hydrodynamic quantities of
the fluids as seen by this class of observers. We show that not only is the
energy density non zero at the center, for the uncharged case it has a local
maximum at the core from which it decreases until the point of local minimum
where its variation is discontinuous. For the first time, it is reported how
rotating boson stars, charged and uncharged, are completely anisotropic fluids
featuring three different pressures. Furthermore, the character of the
electromagnetic fields is analyzed.
| [
{
"created": "Thu, 31 Jan 2019 18:43:02 GMT",
"version": "v1"
}
] | 2019-06-05 | [
[
"Collodel",
"Lucas G.",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | In this work we present full sets of solutions for rotating charged boson stars with different coupling values. By adopting local comoving coordinates, we are able to find expressions for the effective hydrodynamic quantities of the fluids as seen by this class of observers. We show that not only is the energy density non zero at the center, for the uncharged case it has a local maximum at the core from which it decreases until the point of local minimum where its variation is discontinuous. For the first time, it is reported how rotating boson stars, charged and uncharged, are completely anisotropic fluids featuring three different pressures. Furthermore, the character of the electromagnetic fields is analyzed. |
2201.01484 | Sanjit Das | Gowtham Sidharth M and Sanjit Das | Shadow of Non-singular Rotating Magnetic Monopole in Perfect Fluid Dark
matter | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Bardeen proposed a gravitationally collapsing magnetic monopole black hole
solution which is free of singularity. In this article, we have studied the
size and shape of the rotating Bardeen blackhole shadow in presence of perfect
fluid dark matter. we have discussed how the parameters such a spin, magnetic
monopole charge and influence of dark matter affects the shadow of our
blackhole. The apparent shape of the blackhole was studied by using two
observables, the radius Rs and the distortion parameter R_s. Further the
blackhole emission rate is also studied, we found out that for rotating Bardeen
in PFDM ,For a constant monopole charge, the emission rate increases with
increase in dark matter parameter, the emission rate decreases with increase in
magnetic charge and spin.
| [
{
"created": "Wed, 5 Jan 2022 07:06:21 GMT",
"version": "v1"
}
] | 2022-01-06 | [
[
"M",
"Gowtham Sidharth",
""
],
[
"Das",
"Sanjit",
""
]
] | Bardeen proposed a gravitationally collapsing magnetic monopole black hole solution which is free of singularity. In this article, we have studied the size and shape of the rotating Bardeen blackhole shadow in presence of perfect fluid dark matter. we have discussed how the parameters such a spin, magnetic monopole charge and influence of dark matter affects the shadow of our blackhole. The apparent shape of the blackhole was studied by using two observables, the radius Rs and the distortion parameter R_s. Further the blackhole emission rate is also studied, we found out that for rotating Bardeen in PFDM ,For a constant monopole charge, the emission rate increases with increase in dark matter parameter, the emission rate decreases with increase in magnetic charge and spin. |
2009.02367 | Ramin G. Daghigh | Ramin G. Daghigh, Michael D. Green, Jodin C. Morey, Gabor Kunstatter | Scalar Perturbations of a Single-Horizon Regular Black Hole | 17 pages, 14 figures, accepted for publication in PRD | Phys. Rev. D 102, 104040 (2020) | 10.1103/PhysRevD.102.104040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the massless scalar field perturbations, including the
quasinormal mode spectrum and the ringdown waveform, of a regular black hole
spacetime that was derived via the Loop Quantum Gravity inspired polymer
quantization of spherical $4$D black holes. In contrast to most, if not all, of
the other regular black holes considered in the literature, the resulting
nonsingular spacetime has a single bifurcative horizon and hence no mass
inflation. In the interior, the areal radius decreases to a minimum given by
the Polymerization constant, $k$, and then re-expands into a Kantowski-Sachs
universe. We find indications that this black hole model is stable against
small scalar perturbations. We also show that an increase in the magnitude of
$k$ will decrease the height of the QNM potential and gives oscillations with
lower frequency and less damping.
| [
{
"created": "Fri, 4 Sep 2020 19:20:50 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Nov 2020 22:27:15 GMT",
"version": "v2"
}
] | 2020-11-25 | [
[
"Daghigh",
"Ramin G.",
""
],
[
"Green",
"Michael D.",
""
],
[
"Morey",
"Jodin C.",
""
],
[
"Kunstatter",
"Gabor",
""
]
] | We investigate the massless scalar field perturbations, including the quasinormal mode spectrum and the ringdown waveform, of a regular black hole spacetime that was derived via the Loop Quantum Gravity inspired polymer quantization of spherical $4$D black holes. In contrast to most, if not all, of the other regular black holes considered in the literature, the resulting nonsingular spacetime has a single bifurcative horizon and hence no mass inflation. In the interior, the areal radius decreases to a minimum given by the Polymerization constant, $k$, and then re-expands into a Kantowski-Sachs universe. We find indications that this black hole model is stable against small scalar perturbations. We also show that an increase in the magnitude of $k$ will decrease the height of the QNM potential and gives oscillations with lower frequency and less damping. |
gr-qc/0005083 | Badri Krishnan | Abhay Ashtekar, Stephen Fairhurst and Badri Krishnan | Isolated Horizons: Hamiltonian Evolution and the First Law | 56 pages, 1 figure, Revtex; Final Version, to appear in PRD | Phys.Rev. D62 (2000) 104025 | 10.1103/PhysRevD.62.104025 | null | gr-qc hep-th | null | A framework was recently introduced to generalize black hole mechanics by
replacing stationary event horizons with isolated horizons. That framework is
significantly extended. The extension is non-trivial in that not only do the
boundary conditions now allow the horizon to be distorted and rotating, but
also the subsequent analysis is based on several new ingredients. Specifically,
although the overall strategy is closely related to that in the previous work,
the dynamical variables, the action principle and the Hamiltonian framework are
all quite different. More importantly, in the non-rotating case, the first law
is shown to arise as a necessary and sufficient condition for the existence of
a consistent Hamiltonian evolution. Somewhat surprisingly, this consistency
condition in turn leads to new predictions even for static black holes. To
complement the previous work, the entire discussion is presented in terms of
tetrads and associated (real) Lorentz connections.
| [
{
"created": "Thu, 18 May 2000 21:30:03 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2000 17:30:14 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Aug 2000 19:11:40 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Fairhurst",
"Stephen",
""
],
[
"Krishnan",
"Badri",
""
]
] | A framework was recently introduced to generalize black hole mechanics by replacing stationary event horizons with isolated horizons. That framework is significantly extended. The extension is non-trivial in that not only do the boundary conditions now allow the horizon to be distorted and rotating, but also the subsequent analysis is based on several new ingredients. Specifically, although the overall strategy is closely related to that in the previous work, the dynamical variables, the action principle and the Hamiltonian framework are all quite different. More importantly, in the non-rotating case, the first law is shown to arise as a necessary and sufficient condition for the existence of a consistent Hamiltonian evolution. Somewhat surprisingly, this consistency condition in turn leads to new predictions even for static black holes. To complement the previous work, the entire discussion is presented in terms of tetrads and associated (real) Lorentz connections. |
2204.12510 | Gon\c{c}alo Castro | Gon\c{c}alo Castro, Leonardo Gualtieri, Andrea Maselli, Paolo Pani | Impact and detectability of spin-tidal couplings in neutron star
inspirals | 11 pages, 4 figures | null | 10.1103/PhysRevD.106.024011 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational wave signal from a binary neutron star merger carries the
imprint of the deformability properties of the coalescing bodies, and then of
the equation of state of neutron stars. In current models of the waveforms
emitted in these events, the contribution of tidal deformation is encoded in a
set of parameters, the tidal Love numbers. More refined models include
tidal-rotation couplings, described by an additional set of parameters, the
rotational tidal Love numbers, which appear in the waveform at $6.5$
post-Newtonian order. For neutron stars with spins as large as $\sim0.1$, we
show that neglecting tidal-rotation couplings may lead to a significant error
in the parameter estimation by third-generation gravitational wave detectors.
By performing a Fisher matrix analysis we assess the measurability of
rotational tidal Love numbers, showing that their contribution in the waveform
could be measured by third-generation detectors. Our results suggest that
current models of tidal deformation in late inspiral should be improved in
order to avoid waveform systematics and extract reliable information from
gravitational wave signals observed by next generation detectors.
| [
{
"created": "Tue, 26 Apr 2022 18:00:03 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Castro",
"Gonçalo",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
]
] | The gravitational wave signal from a binary neutron star merger carries the imprint of the deformability properties of the coalescing bodies, and then of the equation of state of neutron stars. In current models of the waveforms emitted in these events, the contribution of tidal deformation is encoded in a set of parameters, the tidal Love numbers. More refined models include tidal-rotation couplings, described by an additional set of parameters, the rotational tidal Love numbers, which appear in the waveform at $6.5$ post-Newtonian order. For neutron stars with spins as large as $\sim0.1$, we show that neglecting tidal-rotation couplings may lead to a significant error in the parameter estimation by third-generation gravitational wave detectors. By performing a Fisher matrix analysis we assess the measurability of rotational tidal Love numbers, showing that their contribution in the waveform could be measured by third-generation detectors. Our results suggest that current models of tidal deformation in late inspiral should be improved in order to avoid waveform systematics and extract reliable information from gravitational wave signals observed by next generation detectors. |
1905.03943 | Shankaranarayanan S | S. Shankaranarayanan (IIT Bombay) | Strong gravity signatures in the polarization of gravitational waves | Received Honourable mention in Gravity Research Foundation essay
competition-2019 | Int. J. Mod. Phys. D, 19440206 (2019) | 10.1142/S0218271819440206 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity is a hugely successful description of gravitation.
However, both theory and observations suggest that General Relativity might
have significant classical and quantum corrections in the Strong Gravity
regime. Testing the strong field limit of gravity is one of the main objectives
of the future gravitational wave detectors. One way to detect strong gravity is
through the polarization of gravitational waves. For quasi-normal modes of
black-holes in General Relativity, the two polarisation states of gravitational
waves have the same amplitude and frequency spectrum. Using the principle of
energy conservation, we show that, the polarisations differ for modified
gravity theories. We obtain a diagnostic parameter for polarization mismatch
that provides a unique way to distinguish General Relativity and modified
gravity theories in gravitational wave detectors.
| [
{
"created": "Fri, 10 May 2019 05:13:18 GMT",
"version": "v1"
}
] | 2019-09-27 | [
[
"Shankaranarayanan",
"S.",
"",
"IIT Bombay"
]
] | General Relativity is a hugely successful description of gravitation. However, both theory and observations suggest that General Relativity might have significant classical and quantum corrections in the Strong Gravity regime. Testing the strong field limit of gravity is one of the main objectives of the future gravitational wave detectors. One way to detect strong gravity is through the polarization of gravitational waves. For quasi-normal modes of black-holes in General Relativity, the two polarisation states of gravitational waves have the same amplitude and frequency spectrum. Using the principle of energy conservation, we show that, the polarisations differ for modified gravity theories. We obtain a diagnostic parameter for polarization mismatch that provides a unique way to distinguish General Relativity and modified gravity theories in gravitational wave detectors. |
1201.1778 | Luc Blanchet | Peter Wolf, Luc Blanchet, Christian J. Bord\'e, Serge Reynaud,
Christophe Salomon, Claude Cohen-Tannoudji | Reply to the comment on: "Does an atom interferometer test the
gravitational redshift at the Compton frequency?" | To appear in Classical and Quantum Gravity | Classical and Quantum Gravity 29 (2012) 048002 | 10.1088/0264-9381/29/4/048002 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hohensee, Chu, Peters and M\"uller have submitted a comment (arXiv:1112.6039
[gr-qc]) on our paper "Does an atom interferometer test the gravitational
redshift at the Compton frequency?", Classical and Quantum Gravity 28, 145017
(2011), arXiv:1009.2485 [gr-qc]. Here we reply to this comment and show that
the main result of our paper, namely that atom interferometric gravimeters do
not test the gravitational redshift at the Compton frequency, remains valid.
| [
{
"created": "Mon, 9 Jan 2012 14:26:41 GMT",
"version": "v1"
}
] | 2014-09-16 | [
[
"Wolf",
"Peter",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Bordé",
"Christian J.",
""
],
[
"Reynaud",
"Serge",
""
],
[
"Salomon",
"Christophe",
""
],
[
"Cohen-Tannoudji",
"Claude",
""
]
] | Hohensee, Chu, Peters and M\"uller have submitted a comment (arXiv:1112.6039 [gr-qc]) on our paper "Does an atom interferometer test the gravitational redshift at the Compton frequency?", Classical and Quantum Gravity 28, 145017 (2011), arXiv:1009.2485 [gr-qc]. Here we reply to this comment and show that the main result of our paper, namely that atom interferometric gravimeters do not test the gravitational redshift at the Compton frequency, remains valid. |
0909.0341 | Azam Izadi | Azam Izadi and Ali Shojai | Speed of light in the extended gravity theories | 19 pages. to appear in Classical Quantum Gravity | Class.Quant.Grav.26:195006,2009 | 10.1088/0264-9381/26/19/195006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We shall investigate the possibility of formulation of varying speed of light
(VSL) in the framework of Palatini non-linear Ricci scalar and Ricci squared
theories. Different speeds of light including the causal structure constant,
electromagnetic, and gravitational wave speeds are discussed. We shall see that
two local frames are distinguishable and discuss about the velocity of light in
these two frames. We shall investigate which one of these local frames is
inertial.
| [
{
"created": "Wed, 2 Sep 2009 08:08:00 GMT",
"version": "v1"
}
] | 2009-11-19 | [
[
"Izadi",
"Azam",
""
],
[
"Shojai",
"Ali",
""
]
] | We shall investigate the possibility of formulation of varying speed of light (VSL) in the framework of Palatini non-linear Ricci scalar and Ricci squared theories. Different speeds of light including the causal structure constant, electromagnetic, and gravitational wave speeds are discussed. We shall see that two local frames are distinguishable and discuss about the velocity of light in these two frames. We shall investigate which one of these local frames is inertial. |
1507.05560 | Matthew Wright | Matthew Wright | Buchdahl's inequality in five dimensional Gauss-Bonnet gravity | Matches published version | General Relativity and Gravitation, 48(7), 1-15 (2016) | 10.1007/s10714-016-2091-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Buchdahl limit for static spherically symmetric isotropic stars is
generalised to the case of five dimensional Gauss-Bonnet gravity. Our result
depends on the sign of the Gauss-Bonnet coupling constant $\alpha$. When
$\alpha>0$, we find, unlike in general relativity, that the bound is dependent
on the stellar structure, in particular the central energy density. We find
that stable stellar structures can exist arbitrarily close to the event
horizon. Thus stable stars can exist with extra mass in this theory compared to
five dimensional general relativity. For $\alpha<0$ it is found that the
Buchdahl bound is more restrictive than the general relativistic case.
| [
{
"created": "Mon, 20 Jul 2015 16:46:44 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jun 2016 09:29:40 GMT",
"version": "v2"
}
] | 2016-06-21 | [
[
"Wright",
"Matthew",
""
]
] | The Buchdahl limit for static spherically symmetric isotropic stars is generalised to the case of five dimensional Gauss-Bonnet gravity. Our result depends on the sign of the Gauss-Bonnet coupling constant $\alpha$. When $\alpha>0$, we find, unlike in general relativity, that the bound is dependent on the stellar structure, in particular the central energy density. We find that stable stellar structures can exist arbitrarily close to the event horizon. Thus stable stars can exist with extra mass in this theory compared to five dimensional general relativity. For $\alpha<0$ it is found that the Buchdahl bound is more restrictive than the general relativistic case. |
gr-qc/9302002 | Pohle | G.W. Gibbons and H.J. Pohle | Complex Numbers, Quantum Mechanics and the Beginning of Time | 27 pages LATEX, UCSBTH-93-03 | Nucl.Phys.B410:117-142,1993 | 10.1016/0550-3213(93)90575-A | null | gr-qc | null | A basic problem in quantizing a field in curved space is the decomposition of
the classical modes in positive and negative frequency. The decomposition is
equivalent to a choice of a complex structure in the space of classical
solutions. In our construction the real tunneling geometries provide the link
between the this complex structure and analytic properties of the classical
solutions in a Riemannian section of space. This is related to the Osterwalder-
Schrader approach to Euclidean field theory.
| [
{
"created": "Tue, 2 Feb 1993 22:58:27 GMT",
"version": "v1"
}
] | 2009-10-07 | [
[
"Gibbons",
"G. W.",
""
],
[
"Pohle",
"H. J.",
""
]
] | A basic problem in quantizing a field in curved space is the decomposition of the classical modes in positive and negative frequency. The decomposition is equivalent to a choice of a complex structure in the space of classical solutions. In our construction the real tunneling geometries provide the link between the this complex structure and analytic properties of the classical solutions in a Riemannian section of space. This is related to the Osterwalder- Schrader approach to Euclidean field theory. |
2308.00012 | Faizuddin Ahmed | Faizuddin Ahmed | A topologically charged four-dimensional wormhole and the energy
conditions | 19 pages; 6 figures, versionv2, published in JCAP
(https://doi.org/10.1088/1475-7516/2023/11/082) | JCAP 11 (2023) 082 | 10.1088/1475-7516/2023/11/082 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this research work, our primary focus revolves around the examination of a
specific category of traversable wormholes known as topologically charged
generalized Schwarzschild-Simpson-Visser-type wormhole,
$ds^2=-\Big(1-\frac{2\,M}{\sqrt{x^2+b^2}}\Big)\,dt^2+\Big(1-\frac{2\,M}{\sqrt{x^2+b^2}}\Big)^{-1}\,\Big(\frac{dx^2}{\alpha^2}\Big)+(x^2+a^2)\,(d\theta^2+\sin^2
\theta\,d\phi^2)$. This wormhole is uniquely defined by a pair of key
parameters (length scales $a$ and $b$), together with the global monopole
charge $\alpha$. A noteworthy outcome of our investigation is the observation
that the energy-momentum tensor associated with this wormhole complies with
both the weak energy condition (WEC) and the null energy condition (NEC).
Furthermore, incorporation of global monopole charge introduces a substantial
influence on the curvature properties of wormhole space-time and various
associated physical quantities derived from this geometry.
| [
{
"created": "Sun, 30 Jul 2023 04:23:06 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2023 02:55:40 GMT",
"version": "v2"
}
] | 2023-11-29 | [
[
"Ahmed",
"Faizuddin",
""
]
] | In this research work, our primary focus revolves around the examination of a specific category of traversable wormholes known as topologically charged generalized Schwarzschild-Simpson-Visser-type wormhole, $ds^2=-\Big(1-\frac{2\,M}{\sqrt{x^2+b^2}}\Big)\,dt^2+\Big(1-\frac{2\,M}{\sqrt{x^2+b^2}}\Big)^{-1}\,\Big(\frac{dx^2}{\alpha^2}\Big)+(x^2+a^2)\,(d\theta^2+\sin^2 \theta\,d\phi^2)$. This wormhole is uniquely defined by a pair of key parameters (length scales $a$ and $b$), together with the global monopole charge $\alpha$. A noteworthy outcome of our investigation is the observation that the energy-momentum tensor associated with this wormhole complies with both the weak energy condition (WEC) and the null energy condition (NEC). Furthermore, incorporation of global monopole charge introduces a substantial influence on the curvature properties of wormhole space-time and various associated physical quantities derived from this geometry. |
2001.11357 | Gamal G.L. Nashed | E. Elizalde, G.G.L. Nashed, S. Nojiri and S.D. Odintsov | Spherically symmetric black holes with electric and magnetic charge in
extended gravity: Physical properties, causal structure, and stability
analysis in Einstein's and Jordan's frames | 27 pages, 18 figures, will appear in EPJC | Eur. Phys. J. C (2020) 80:109 | 10.1140/epjc/s10052-020-7686-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Novel static black hole solutions with electric and magnetic charges are
derived for the class of modified gravities: $f({\cal R})={\cal
R}+2\beta\sqrt{{\cal R}}$, with or without a cosmological constant. The new
black holes behave asymptotically as flat or (A)dS space-times with a dynamical
value of the Ricci scalar given by $R=\frac{1}{r^2}$ and
$R=\frac{8r^2\Lambda+1}{r^2}$, respectively. They are characterized by three
parameters, namely their mass and electric and magnetic charges, and constitute
black hole solutions different from those in Einstein's general relativity.
Their singularities are studied by obtaining the Kretschmann scalar and Ricci
tensor, which shows a dependence on the parameter $\beta$ that is not permitted
to be zero. A conformal transformation is used to display the black holes in
Einstein's frame and check if its physical behavior is changed w.r.t. the
Jordan one. The thermal stability of the solutions is discussed by using
thermodynamical quantities, in particular the entropy, the Hawking temperature,
the quasi-local energy, and the Gibbs free energy. Also, the casual structure
of the new black holes is studied, and a stability analysis is performed in
both frames using the odd perturbations technique and the study of the geodesic
deviation. It is concluded that, generically, there is coincidence of the
physical properties of the novel black holes in both frames, although this
turns not to be the case for the Hawking temperature.
| [
{
"created": "Wed, 29 Jan 2020 08:38:49 GMT",
"version": "v1"
}
] | 2020-02-14 | [
[
"Elizalde",
"E.",
""
],
[
"Nashed",
"G. G. L.",
""
],
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | Novel static black hole solutions with electric and magnetic charges are derived for the class of modified gravities: $f({\cal R})={\cal R}+2\beta\sqrt{{\cal R}}$, with or without a cosmological constant. The new black holes behave asymptotically as flat or (A)dS space-times with a dynamical value of the Ricci scalar given by $R=\frac{1}{r^2}$ and $R=\frac{8r^2\Lambda+1}{r^2}$, respectively. They are characterized by three parameters, namely their mass and electric and magnetic charges, and constitute black hole solutions different from those in Einstein's general relativity. Their singularities are studied by obtaining the Kretschmann scalar and Ricci tensor, which shows a dependence on the parameter $\beta$ that is not permitted to be zero. A conformal transformation is used to display the black holes in Einstein's frame and check if its physical behavior is changed w.r.t. the Jordan one. The thermal stability of the solutions is discussed by using thermodynamical quantities, in particular the entropy, the Hawking temperature, the quasi-local energy, and the Gibbs free energy. Also, the casual structure of the new black holes is studied, and a stability analysis is performed in both frames using the odd perturbations technique and the study of the geodesic deviation. It is concluded that, generically, there is coincidence of the physical properties of the novel black holes in both frames, although this turns not to be the case for the Hawking temperature. |
gr-qc/9303036 | null | R. Laflamme and A. Matacz | Decoherence Functional and Inhomogeneities in the Early Universe | 15 pages in plain tex | Int. J. Mod. Phys. D2 (1993) 171-182 | 10.1142/S0218271893000155 | null | gr-qc | null | We investigate the quantum to classical transition of small inhomogeneous
fluctuations in the early Universe using the decoherence functional of
Gell-Mann and Hartle. We study two types of coarse graining; one due to coarse
graining the value of the scalar field and the other due to summing over an
environment. We compare the results with a previous study using an environment
and the off-diagonal rule proposed by Zurek. We show that the two methods give
different results.
| [
{
"created": "Tue, 30 Mar 1993 15:08:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Laflamme",
"R.",
""
],
[
"Matacz",
"A.",
""
]
] | We investigate the quantum to classical transition of small inhomogeneous fluctuations in the early Universe using the decoherence functional of Gell-Mann and Hartle. We study two types of coarse graining; one due to coarse graining the value of the scalar field and the other due to summing over an environment. We compare the results with a previous study using an environment and the off-diagonal rule proposed by Zurek. We show that the two methods give different results. |
gr-qc/0107055 | Moninder Singh Modgil | Moninder Singh Modgil and Deshdeep Sahdev | Recurrence metrics and the physics of closed time-like curves | null | null | null | null | gr-qc | null | We investigate vacuum solutions of Einstein's equation for a universe with an
S^1 topology of time. Such a universe behaves like a time-machine and has
geodesics which coincide with closed time-like curves (CTCs). A system evolving
along a CTC experiences the Loschmidt velocity reversion and undergoes a
recurrence commensurate with the universal period. We indicate why this
universe is free of the causality paradoxes, usually associated with CTCs.
| [
{
"created": "Mon, 16 Jul 2001 11:21:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Modgil",
"Moninder Singh",
""
],
[
"Sahdev",
"Deshdeep",
""
]
] | We investigate vacuum solutions of Einstein's equation for a universe with an S^1 topology of time. Such a universe behaves like a time-machine and has geodesics which coincide with closed time-like curves (CTCs). A system evolving along a CTC experiences the Loschmidt velocity reversion and undergoes a recurrence commensurate with the universal period. We indicate why this universe is free of the causality paradoxes, usually associated with CTCs. |
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