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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9711026 | Marcelo Jose Reboucas | M.J. Reboucas, R.K. Tavakol, A.F.F. Teixeira | Topology and Fragility in Cosmology | 12 pages, LaTex file, to appear in Gen. Rel. Grav. (1998) | Gen.Rel.Grav. 30 (1998) 535-543 | 10.1023/A:1018809922606 | CBPF-NF-036/96 | gr-qc astro-ph hep-ph hep-th | null | We introduce the notion of topological fragility and briefly discuss some
examples from the literature. An important example of this type of fragility is
the way globally anisotropic Bianchi V generalisations of the FLRW $k=-1$ model
result in a radical restriction on the allowed topology of spatial sections,
thereby excluding compact cosmological models with negatively curved
three-sections with anisotropy. An outcome of this is to exclude chaotic mixing
in such models, which may be relevant, given the many recent attempts at
employing compact FLRW $k=-1$ models to produce chaotic mixing in the cosmic
microwave background radiation, if the Universe turns out to be globally
anisotropic.
| [
{
"created": "Thu, 6 Nov 1997 23:34:23 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Reboucas",
"M. J.",
""
],
[
"Tavakol",
"R. K.",
""
],
[
"Teixeira",
"A. F. F.",
""
]
] | We introduce the notion of topological fragility and briefly discuss some examples from the literature. An important example of this type of fragility is the way globally anisotropic Bianchi V generalisations of the FLRW $k=-1$ model result in a radical restriction on the allowed topology of spatial sections, thereby excluding compact cosmological models with negatively curved three-sections with anisotropy. An outcome of this is to exclude chaotic mixing in such models, which may be relevant, given the many recent attempts at employing compact FLRW $k=-1$ models to produce chaotic mixing in the cosmic microwave background radiation, if the Universe turns out to be globally anisotropic. |
1905.05007 | \"Ozg\"ur \"Okc\"u | \"Ozg\"ur \"Okc\"u, Ekrem Aydiner | GUP-Corrected van der Waals Black Holes | 16 pages, 7 figures, 1 appendix. References added. Accepted version | null | 10.1007/s10773-020-04544-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the generalized uncertainty principle (GUP) effects
for the van der Waals (vdW) black holes. In order to obtain the GUP-corrected
solution, we consider GUP-corrected black hole temperature. We also study the
thermodynamics and phase transition of GUP-corrected vdW black holes. We
compare the differences between thermodynamic properties of both modified and
orginal solutions. We show that P-V criticality is physically acceptable in the
presence of GUP-correction.
| [
{
"created": "Fri, 10 May 2019 00:48:38 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Dec 2019 16:49:23 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Jul 2020 11:33:32 GMT",
"version": "v3"
}
] | 2020-07-27 | [
[
"Ökcü",
"Özgür",
""
],
[
"Aydiner",
"Ekrem",
""
]
] | In this paper, we study the generalized uncertainty principle (GUP) effects for the van der Waals (vdW) black holes. In order to obtain the GUP-corrected solution, we consider GUP-corrected black hole temperature. We also study the thermodynamics and phase transition of GUP-corrected vdW black holes. We compare the differences between thermodynamic properties of both modified and orginal solutions. We show that P-V criticality is physically acceptable in the presence of GUP-correction. |
gr-qc/9509040 | Arkadiusz Blaut | Arkadiusz Blaut and Jerzy Kowalski-Glikman | Quantum Potential Approach to Class of Cosmological Models | The corrected version of gr-qc/9506081, 18 pages LaTeX, to appear in
Classical and Quantum Gravity | Class.Quant.Grav. 13 (1996) 39-50 | 10.1088/0264-9381/13/1/005 | null | gr-qc | null | In this paper we discuss the quantum potential approach of Bohm in the
context of quantum cosmological model. This approach makes it possible to
convert the wavefunction of the universe to a set of equations describing the
time evolution of the universe. Following Ashtekar et.\ al., we make use of
quantum canonical transformation to cast a class of quantum cosmological models
to a simple form in which they can be solved explicitly, and then we use the
solutions do recover the time evolution.
| [
{
"created": "Fri, 22 Sep 1995 13:12:04 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Blaut",
"Arkadiusz",
""
],
[
"Kowalski-Glikman",
"Jerzy",
""
]
] | In this paper we discuss the quantum potential approach of Bohm in the context of quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe to a set of equations describing the time evolution of the universe. Following Ashtekar et.\ al., we make use of quantum canonical transformation to cast a class of quantum cosmological models to a simple form in which they can be solved explicitly, and then we use the solutions do recover the time evolution. |
gr-qc/0005011 | Ugo Moschella | A. Yu. Kamenshchik, U. Moschella, V. Pasquier | Chaplygin-like gas and branes in black hole bulks | 11 pages, 1 figure | Phys.Lett. B487 (2000) 7-13 | 10.1016/S0370-2693(00)00805-4 | null | gr-qc hep-th | null | We explore the possibility to locate a brane in black hole bulks. We study
explicitly the cases of BHTZ and Schwarzschild-anti de Sitter (AdS) black
holes. Our result is that in these cases branes cannot be supported by brane
tension alone and it is necessary to introduce other forms of matter on the
brane. We find classes of perfect fluid solutions obeying to peculiar state
equations. For the case of BHTZ bulk geometry the state equation takes exactly
the form of a ``Chaplygin gas'', which is relevant in the brane context. In the
Schwarzschild-AdS case we find new state equations which reduce to the
Chaplygin form when the brane is located near the horizon.
| [
{
"created": "Wed, 3 May 2000 15:34:39 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kamenshchik",
"A. Yu.",
""
],
[
"Moschella",
"U.",
""
],
[
"Pasquier",
"V.",
""
]
] | We explore the possibility to locate a brane in black hole bulks. We study explicitly the cases of BHTZ and Schwarzschild-anti de Sitter (AdS) black holes. Our result is that in these cases branes cannot be supported by brane tension alone and it is necessary to introduce other forms of matter on the brane. We find classes of perfect fluid solutions obeying to peculiar state equations. For the case of BHTZ bulk geometry the state equation takes exactly the form of a ``Chaplygin gas'', which is relevant in the brane context. In the Schwarzschild-AdS case we find new state equations which reduce to the Chaplygin form when the brane is located near the horizon. |
1506.08652 | Binaya Bishi Kumar | G.P.Singh, Binaya K. Bishi | Bianchi type-I Universe with Cosmological constant and quadratic
equation of state in f(R,T) modified gravity | 10 pages,5 figure ,regular article | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article deals with the study of Bianchi type-I universe in the context
of f(R,T) gravity. Einstein's field equations in f(R,T) gravity has been solved
in presence of cosmological constant ? and quadratic equation of state. Here we
have discussed two classes of f(R,T) gravity i.e. f(R,T) = R + 2f(T) and f(R,T)
= f_1(R) + f_2(T). A set of models has been taken into consideration based on
the plausible relation. Also we have studied the some physical and kinematical
properties of the models.
| [
{
"created": "Wed, 17 Jun 2015 04:37:11 GMT",
"version": "v1"
}
] | 2016-10-31 | [
[
"Singh",
"G. P.",
""
],
[
"Bishi",
"Binaya K.",
""
]
] | This article deals with the study of Bianchi type-I universe in the context of f(R,T) gravity. Einstein's field equations in f(R,T) gravity has been solved in presence of cosmological constant ? and quadratic equation of state. Here we have discussed two classes of f(R,T) gravity i.e. f(R,T) = R + 2f(T) and f(R,T) = f_1(R) + f_2(T). A set of models has been taken into consideration based on the plausible relation. Also we have studied the some physical and kinematical properties of the models. |
1112.5779 | Piotr T. Chru\'sciel | Piotr T. Chru\'sciel | On maximal globally hyperbolic vacuum space-times | various improvements | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove existence and uniqueness of maximal global hyperbolic developments
of vacuum general relativistic initial data sets with initial data (g,K) in
Sobolev spaces $H^s\oplus H^{s-1}$ with integer s > n/2 +1.
| [
{
"created": "Sun, 25 Dec 2011 13:35:16 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Oct 2013 05:23:28 GMT",
"version": "v2"
}
] | 2013-10-11 | [
[
"Chruściel",
"Piotr T.",
""
]
] | We prove existence and uniqueness of maximal global hyperbolic developments of vacuum general relativistic initial data sets with initial data (g,K) in Sobolev spaces $H^s\oplus H^{s-1}$ with integer s > n/2 +1. |
2206.14920 | Pedro Moraes | H. Shabani and P.H.R.S. Moraes | The galaxy rotation curves in the $f(R,T)$ modified gravity formalism | 9 pages, 4 figures | null | 10.1088/1402-4896/acd36d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astronomical data have shown that the galaxy rotation curves are mostly flat
in the far distance of the galactic cores, which reveals the insufficiency of
our knowledges about how gravity works in these regimes. In this paper we
introduce a resolution of this issue from the $f(R,T)$ modified gravity
formalism perspective. By investigating two classes of models with separable
(minimal coupling model) and inseparable (non-minimal coupling model) parts of
the Ricci scalar $R$ and trace of the energy-momentum tensor $T$, we find that
only in the latter models it is possible to attain flat galaxy rotation curves.
| [
{
"created": "Wed, 29 Jun 2022 21:26:24 GMT",
"version": "v1"
}
] | 2023-05-31 | [
[
"Shabani",
"H.",
""
],
[
"Moraes",
"P. H. R. S.",
""
]
] | Astronomical data have shown that the galaxy rotation curves are mostly flat in the far distance of the galactic cores, which reveals the insufficiency of our knowledges about how gravity works in these regimes. In this paper we introduce a resolution of this issue from the $f(R,T)$ modified gravity formalism perspective. By investigating two classes of models with separable (minimal coupling model) and inseparable (non-minimal coupling model) parts of the Ricci scalar $R$ and trace of the energy-momentum tensor $T$, we find that only in the latter models it is possible to attain flat galaxy rotation curves. |
2007.12938 | Stephen D. H. Hsu | Stephen D.H. Hsu | Discrete Hilbert Space, the Born Rule, and Quantum Gravity | 10 pages, 1 figure | null | 10.1142/S0217732321500139 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravitational effects suggest a minimal length, or spacetime
interval, of order the Planck length. This in turn suggests that Hilbert space
itself may be discrete rather than continuous. One implication is that quantum
states with norm below some very small threshold do not exist. The exclusion of
what Everett referred to as maverick branches is necessary for the emergence of
the Born Rule in no collapse quantum mechanics. We discuss this in the context
of quantum gravity, showing that discrete models (such as simplicial or lattice
quantum gravity) indeed suggest a discrete Hilbert space with minimum norm.
These considerations are related to the ultimate level of fine-graining found
in decoherent histories (of spacetime geometry plus matter fields) produced by
quantum gravity.
| [
{
"created": "Sat, 25 Jul 2020 14:13:04 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Hsu",
"Stephen D. H.",
""
]
] | Quantum gravitational effects suggest a minimal length, or spacetime interval, of order the Planck length. This in turn suggests that Hilbert space itself may be discrete rather than continuous. One implication is that quantum states with norm below some very small threshold do not exist. The exclusion of what Everett referred to as maverick branches is necessary for the emergence of the Born Rule in no collapse quantum mechanics. We discuss this in the context of quantum gravity, showing that discrete models (such as simplicial or lattice quantum gravity) indeed suggest a discrete Hilbert space with minimum norm. These considerations are related to the ultimate level of fine-graining found in decoherent histories (of spacetime geometry plus matter fields) produced by quantum gravity. |
2102.13573 | George Pappas Dr | Kostas Glampedakis and George Pappas | Can supermassive black hole shadows test the Kerr metric? | 5 pages, 1 figure, accepted for publication as a Letter in Physical
Review D | Phys. Rev. D 104, L081503 (2021) | 10.1103/PhysRevD.104.L081503 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The unprecedented image of the M87* supermassive black hole has sparked some
controversy over its usefulness as a test of the general relativistic Kerr
metric. The criticism is mainly related to the black hole's quasi-circular
shadow and advocates that its radius depends not only on the black hole's true
spacetime properties but also on the poorly known physics of the illuminating
accretion flow. In this paper we take a sober view of the problem and argue
that our ability to probe gravity with a black hole shadow is only partially
impaired by the matter degrees of freedom and the number of non-Kerr parameters
used in the model. As we show here, a more intriguing situation arises from the
mass scaling of the dimensional coupling constants that typically appear in
non-GR theories of gravity. Existing limits from gravitational wave
observations imply that supermassive systems like the M87* black hole would
suffer a suppression of all non-GR deviation parameters in their metric, making
the spacetime and the produced shadow virtually Kerr. Therefore, a supermassive
black hole shadow is likely to probe only those extensions of General
Relativity which are endowed with dimensionless coupling constants or other
special cases with a screening mechanism for black holes or certain types of
spontaneous scalarisation.
| [
{
"created": "Fri, 26 Feb 2021 16:31:32 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Oct 2021 14:34:43 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Oct 2021 10:28:48 GMT",
"version": "v3"
}
] | 2021-10-22 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Pappas",
"George",
""
]
] | The unprecedented image of the M87* supermassive black hole has sparked some controversy over its usefulness as a test of the general relativistic Kerr metric. The criticism is mainly related to the black hole's quasi-circular shadow and advocates that its radius depends not only on the black hole's true spacetime properties but also on the poorly known physics of the illuminating accretion flow. In this paper we take a sober view of the problem and argue that our ability to probe gravity with a black hole shadow is only partially impaired by the matter degrees of freedom and the number of non-Kerr parameters used in the model. As we show here, a more intriguing situation arises from the mass scaling of the dimensional coupling constants that typically appear in non-GR theories of gravity. Existing limits from gravitational wave observations imply that supermassive systems like the M87* black hole would suffer a suppression of all non-GR deviation parameters in their metric, making the spacetime and the produced shadow virtually Kerr. Therefore, a supermassive black hole shadow is likely to probe only those extensions of General Relativity which are endowed with dimensionless coupling constants or other special cases with a screening mechanism for black holes or certain types of spontaneous scalarisation. |
1008.2678 | Muhammad Sharif | M. Sharif and H. Rizwana Kausar | Effects of f(R) Dark Energy on Dissipative Anisotropic Collapsing Fluid | 16 pages, accepted for publication in Mod. Phys. Lett. A | Mod.Phys.Lett.A25:3299-3311,2010 | 10.1142/S0217732310034195 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to study the effects of dark energy on dynamics
of the collapsing fluid within the framework of metric f(R) gravity. The fluid
distribution is assumed to be locally anisotropic and undergoing dissipation in
the form of heat flow, null radiations and shear viscosity. For this purpose,
we take general spherical symmetric spacetime. Dynamical equations are obtained
and also some special solutions are found by considering shearing expansionfree
evolution of the fluid. It is found that dark energy affects the mass of the
collapsing matter and rate of collapse but does not affect the hydrostatic
equilibrium.
| [
{
"created": "Fri, 13 Aug 2010 04:26:55 GMT",
"version": "v1"
}
] | 2011-03-28 | [
[
"Sharif",
"M.",
""
],
[
"Kausar",
"H. Rizwana",
""
]
] | The purpose of this paper is to study the effects of dark energy on dynamics of the collapsing fluid within the framework of metric f(R) gravity. The fluid distribution is assumed to be locally anisotropic and undergoing dissipation in the form of heat flow, null radiations and shear viscosity. For this purpose, we take general spherical symmetric spacetime. Dynamical equations are obtained and also some special solutions are found by considering shearing expansionfree evolution of the fluid. It is found that dark energy affects the mass of the collapsing matter and rate of collapse but does not affect the hydrostatic equilibrium. |
1411.2812 | Jakub Mielczarek Ph.D. | Jakub Mielczarek, Wlodzimierz Piechocki | Level spacing distribution for the prototype of the Bianchi IX model | Presented at the conference Random Matrix Theory: Foundations and
Applications, 1-6 July 2014, Cracow | null | 10.5506/APhysPolB.46.1729 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our results concern quantum chaos of the vacuum Bianchi IX model. We apply
the equilateral triangle potential well approximation to the potential of the
Bianchi IX model to solve the eigenvalue problem for the physical Hamiltonian.
Such approximation is well satisfied in vicinity of the cosmic singularity.
Level spacing distribution of the eigenvalues is studied with and without
applying the unfolding procedure. In both cases, the obtained distributions are
qualitatively described by Brody's distribution with the parameter
$\beta\approx0.3$, revealing some sort of the level repulsion. The observed
repulsion may reflect chaotic nature of the classical dynamics of the Bianchi
IX universe. However, full understanding of this effects will require
examination of the Bianchi IX model with the exact potential.
| [
{
"created": "Tue, 11 Nov 2014 14:05:28 GMT",
"version": "v1"
}
] | 2015-10-28 | [
[
"Mielczarek",
"Jakub",
""
],
[
"Piechocki",
"Wlodzimierz",
""
]
] | Our results concern quantum chaos of the vacuum Bianchi IX model. We apply the equilateral triangle potential well approximation to the potential of the Bianchi IX model to solve the eigenvalue problem for the physical Hamiltonian. Such approximation is well satisfied in vicinity of the cosmic singularity. Level spacing distribution of the eigenvalues is studied with and without applying the unfolding procedure. In both cases, the obtained distributions are qualitatively described by Brody's distribution with the parameter $\beta\approx0.3$, revealing some sort of the level repulsion. The observed repulsion may reflect chaotic nature of the classical dynamics of the Bianchi IX universe. However, full understanding of this effects will require examination of the Bianchi IX model with the exact potential. |
1607.06726 | Jaume Haro | Jaume de Haro, Jaume Amor\'os and Supriya Pan | Simple inflationary quintessential model II: Power law potentials | Version accepted for publication in PRD | Phys. Rev. D 94, 064060 (2016) | 10.1103/PhysRevD.94.064060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work is a sequel of our previous work Phys.Rev.D { 93}, 084018
(2016) [arXiv:1601.08175 [gr-qc]] cite{hap} which depicted a simple version of
an inflationary quintessential model whose inflationary stage was described by
a Higgs type potential and the quintessential phase was responsible due to an
exponential potential. Additionally, the model predicted a nonsingular universe
in past which was geodesically past incomplete. Further, it was also found that
the model is in agreement with the Planck 2013 data when running is allowed.
But, this model was found to be unsuccessful with Planck 2015 data with or
without running. However, in this sequel we propose a family of models runs by
a single parameter $alpha in [0, 1]$ which proposes another "inflationary
quintessential model" where the inflation and the quintessence regimes are
respectively described by a power law potential and a cosmological constant.
The model is also nonsingular although geodesically past incomplete as in the
cited model. However, the present one is found to be more simple in compared to
the previous model and it is in excellent agreement with the observational
data. We note that unlike the previous model which matched only with Planck
2013 data in presence of running, a large number of the models of this family
with $alpha in [0,1/2)$ matches with both Planck 2013 and Planck 2015 data
whether the running is allowed or not. Thus, the properties in the current
family of models in compared to its past companion justify its need for a
better cosmological model with the successive improvement of the observational
data.1
| [
{
"created": "Fri, 22 Jul 2016 16:18:44 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2016 18:55:11 GMT",
"version": "v2"
}
] | 2016-09-28 | [
[
"de Haro",
"Jaume",
""
],
[
"Amorós",
"Jaume",
""
],
[
"Pan",
"Supriya",
""
]
] | The present work is a sequel of our previous work Phys.Rev.D { 93}, 084018 (2016) [arXiv:1601.08175 [gr-qc]] cite{hap} which depicted a simple version of an inflationary quintessential model whose inflationary stage was described by a Higgs type potential and the quintessential phase was responsible due to an exponential potential. Additionally, the model predicted a nonsingular universe in past which was geodesically past incomplete. Further, it was also found that the model is in agreement with the Planck 2013 data when running is allowed. But, this model was found to be unsuccessful with Planck 2015 data with or without running. However, in this sequel we propose a family of models runs by a single parameter $alpha in [0, 1]$ which proposes another "inflationary quintessential model" where the inflation and the quintessence regimes are respectively described by a power law potential and a cosmological constant. The model is also nonsingular although geodesically past incomplete as in the cited model. However, the present one is found to be more simple in compared to the previous model and it is in excellent agreement with the observational data. We note that unlike the previous model which matched only with Planck 2013 data in presence of running, a large number of the models of this family with $alpha in [0,1/2)$ matches with both Planck 2013 and Planck 2015 data whether the running is allowed or not. Thus, the properties in the current family of models in compared to its past companion justify its need for a better cosmological model with the successive improvement of the observational data.1 |
1508.00532 | Michael Feldman | John D. Anderson, Gerald Schubert, Virginia Trimble and Michael R.
Feldman | Reply to comment by M. Pitkin on "Measurements of Newton's gravitational
constant and the length of day" | 2 pages, 3 figures, accepted for publication in EPL | EPL 111 (2015) 30003 | 10.1209/0295-5075/111/30003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We offer a response to recent claims that a constant $G$ measurement model
with an additional Gaussian noise term fits the experimental data better than a
model containing periodic terms.
| [
{
"created": "Thu, 30 Jul 2015 16:02:38 GMT",
"version": "v1"
}
] | 2015-08-19 | [
[
"Anderson",
"John D.",
""
],
[
"Schubert",
"Gerald",
""
],
[
"Trimble",
"Virginia",
""
],
[
"Feldman",
"Michael R.",
""
]
] | We offer a response to recent claims that a constant $G$ measurement model with an additional Gaussian noise term fits the experimental data better than a model containing periodic terms. |
gr-qc/0606109 | Shuang Wang | Shuang Wang | Thermodynamics of high dimensional Schwarzschild de Sitter spacetimes:
variable cosmological constant | 6 pages, revtex4 | null | null | null | gr-qc | null | We study the thermodynamic properties of high dimensional Schwarzschild de
Sitter spacetimes with the consideration of quantum effects. It is shown that
by considering the cosmological constant as a variable state parameter and
adding an extra term which denotes the vacuum energy, both the differential and
integral mass formulas of the first law of Schwarzschild de Sitter spacetimes
can be directly derived from the general Schwarzschild de Sitter metrics in a
simple and natural way. Furthermore, after taking quantum effects into account,
we can see that the cosmological constant must decrease and the spontaneous
decay of the vacuum energy never makes the entropy of Schwarzschild de Sitter
spacetimes decrease. In addition, though the laws of thermodynamics are very
powerful, at least the third law can not be applied to the Schwarzschild de
Sitter spacetimes. It should be emphasized that these conclusions come into
existence in any dimension.
| [
{
"created": "Mon, 26 Jun 2006 03:35:22 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2006 06:12:14 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Jul 2006 14:00:29 GMT",
"version": "v3"
},
{
"created": "Sun, 18 Mar 2007 15:42:27 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Wang",
"Shuang",
""
]
] | We study the thermodynamic properties of high dimensional Schwarzschild de Sitter spacetimes with the consideration of quantum effects. It is shown that by considering the cosmological constant as a variable state parameter and adding an extra term which denotes the vacuum energy, both the differential and integral mass formulas of the first law of Schwarzschild de Sitter spacetimes can be directly derived from the general Schwarzschild de Sitter metrics in a simple and natural way. Furthermore, after taking quantum effects into account, we can see that the cosmological constant must decrease and the spontaneous decay of the vacuum energy never makes the entropy of Schwarzschild de Sitter spacetimes decrease. In addition, though the laws of thermodynamics are very powerful, at least the third law can not be applied to the Schwarzschild de Sitter spacetimes. It should be emphasized that these conclusions come into existence in any dimension. |
2312.02563 | Leo Brewin | Leo Brewin | A power series expansion of Teukolsky linearised gravitational waves | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A power series, suitable for use in a numerical relativity code, will be
presented for the time symmetric Teukolsky linearised gravitational waves.
| [
{
"created": "Tue, 5 Dec 2023 08:15:49 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Brewin",
"Leo",
""
]
] | A power series, suitable for use in a numerical relativity code, will be presented for the time symmetric Teukolsky linearised gravitational waves. |
1407.2428 | Parampreet Singh | Anton Joe, Parampreet Singh | Kantowski-Sachs spacetime in loop quantum cosmology: bounds on expansion
and shear scalars and the viability of quantization | Revised to match the published version in CQG. Discussion expanded
and references added | Class. Quant. Grav. 32 (2015) 015009 | 10.1088/0264-9381/32/1/015009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using effective dynamics, we investigate the behavior of expansion and shear
scalars in different proposed quantizations of the Kantowski-Sachs spacetime
with matter in loop quantum cosmology. We find that out of the various proposed
choices, there is only one known prescription which leads to the generic
bounded behavior of these scalars. The bounds turn out to be universal and are
determined by the underlying quantum geometry. This quantization is analogous
to the so called 'improved dynamics' in the isotropic loop quantum cosmology,
which is also the only one to respect the freedom of the rescaling of the
fiducial cell at the level of effective spacetime description. Other proposed
quantization prescriptions yield expansion and shear scalars which may not be
bounded for certain initial conditions within the validity of effective
spacetime description. These prescriptions also have a limitation that the
"quantum geometric effects" can occur at an arbitrary scale. We show that the
`improved dynamics' of Kantowski-Sachs spacetime turns out to be a unique
choice in a general class of possible quantization prescriptions, in the sense
of leading to generic bounds on expansion and shear scalars and the associated
physics being free from fiducial cell dependence. The behavior of the energy
density in the `improved dynamics' reveals some interesting features. Even
without considering any details of the dynamical evolution, it is possible to
rule out pancake singularities in this spacetime. The energy density is found
to be dynamically bounded. These results show that the Planck scale physics of
the loop quantized Kantowski-Sachs spacetime has key features common with the
loop quantization of isotropic and Bianchi-I spacetimes.
| [
{
"created": "Wed, 9 Jul 2014 10:41:55 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jan 2015 15:47:23 GMT",
"version": "v2"
}
] | 2015-01-08 | [
[
"Joe",
"Anton",
""
],
[
"Singh",
"Parampreet",
""
]
] | Using effective dynamics, we investigate the behavior of expansion and shear scalars in different proposed quantizations of the Kantowski-Sachs spacetime with matter in loop quantum cosmology. We find that out of the various proposed choices, there is only one known prescription which leads to the generic bounded behavior of these scalars. The bounds turn out to be universal and are determined by the underlying quantum geometry. This quantization is analogous to the so called 'improved dynamics' in the isotropic loop quantum cosmology, which is also the only one to respect the freedom of the rescaling of the fiducial cell at the level of effective spacetime description. Other proposed quantization prescriptions yield expansion and shear scalars which may not be bounded for certain initial conditions within the validity of effective spacetime description. These prescriptions also have a limitation that the "quantum geometric effects" can occur at an arbitrary scale. We show that the `improved dynamics' of Kantowski-Sachs spacetime turns out to be a unique choice in a general class of possible quantization prescriptions, in the sense of leading to generic bounds on expansion and shear scalars and the associated physics being free from fiducial cell dependence. The behavior of the energy density in the `improved dynamics' reveals some interesting features. Even without considering any details of the dynamical evolution, it is possible to rule out pancake singularities in this spacetime. The energy density is found to be dynamically bounded. These results show that the Planck scale physics of the loop quantized Kantowski-Sachs spacetime has key features common with the loop quantization of isotropic and Bianchi-I spacetimes. |
gr-qc/0609032 | Hanno Sahlmann | Hanno Sahlmann | Exploring the diffeomorphism invariant Hilbert space of a scalar field | 20 pages, no figures; v3: corrected typos, added reference, some
clarifications added; version as published in CQG | Class.Quant.Grav.24:4601-4616,2007 | 10.1088/0264-9381/24/18/003 | ITP-UU-06/35, SPIN-06/31 | gr-qc hep-th math-ph math.MP | null | As a toy model for the implementation of the diffeomorphism constraint, the
interpretation of the resulting states, and the treatment of ordering
ambiguities in loop quantum gravity, we consider the Hilbert space of spatially
diffeomorphism invariant states for a scalar field. We give a very explicit
formula for the scalar product on this space, and discuss its structure.
Then we turn to the quantization of a certain class of diffeomorphism
invariant quantities on that space, and discuss in detail the ordering issues
involved. On a technical level these issues bear some similarity to those
encountered in full loop quantum gravity.
| [
{
"created": "Fri, 8 Sep 2006 10:17:35 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Apr 2007 18:25:07 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Aug 2007 07:52:00 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Sahlmann",
"Hanno",
""
]
] | As a toy model for the implementation of the diffeomorphism constraint, the interpretation of the resulting states, and the treatment of ordering ambiguities in loop quantum gravity, we consider the Hilbert space of spatially diffeomorphism invariant states for a scalar field. We give a very explicit formula for the scalar product on this space, and discuss its structure. Then we turn to the quantization of a certain class of diffeomorphism invariant quantities on that space, and discuss in detail the ordering issues involved. On a technical level these issues bear some similarity to those encountered in full loop quantum gravity. |
gr-qc/9709076 | Andrea Barbieri | A. Barbieri | Space of the vertices of relativistic spin networks | 3 pages, LaTeX, previous results clarified, new statements made | null | null | IFUP-TH/47-97 | gr-qc | null | The general solutin to the constraints that define relativistic spin networks
vertices is given and their relations with 3-dimensional quantum tetrahedra is
dicussed. An alternative way to handle the constraints is also presented.
| [
{
"created": "Tue, 30 Sep 1997 00:49:07 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Oct 1997 12:20:12 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Oct 1997 11:53:07 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Barbieri",
"A.",
""
]
] | The general solutin to the constraints that define relativistic spin networks vertices is given and their relations with 3-dimensional quantum tetrahedra is dicussed. An alternative way to handle the constraints is also presented. |
2012.06114 | Hong Wang | Hong Wang and Jin Wang | Quantum geometrical current and coherence of the open gravitation
system: loop quantum gravity coupled with a thermal scalar field | 55 pages,6 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Open quantum systems interacting with the environments often show interesting
behaviors, such as decoherence, non-unitary evolution, dissipation, etc. It is
interesting but still challenging to study the open quantum gravitation system
interacting with the environments. In this work, we develop a general
parameterized theoretical framework for the open quantum gravitation system.
Under the Born-Markov approximation, we derived the quantum master equation
with a new method which determines the evolution for certain types of open
quantum gravitation system. Finally, we studied a specific model where the real
scalar field plays the role of the environment and the spacetime is assumed to
be homogeneous and isotropic. We quantize the spacetime through the loop
quantum gravity. We show that the scalar field can induce the quantum geometry
in the equilibrium state when the scalar field is under the thermal
equilibrium. For the non-steady state, the quantum geometry flux emerges. We
point out that the quantum geometry flux and the coherence can drive the
evolution of the spacetime geometry. This provides us a new view on the
evolution of the spacetime geometry. Our results shown that the coherence of
the spacetime monotonically decreases as the temperature of the bath decreases.
This indicates that a classical cold universe can emerge from an initial hot
quantum universe. We found in this model that the entanglement entropy of the
gravitation system is related to the average volume of the space. We take the
continuous limit for studying the loop quantum cosmology and approximately
obtain a tunneling probability of the spacetime from the zero volume state to
the finite volume state.
| [
{
"created": "Fri, 11 Dec 2020 04:15:04 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Jul 2021 00:58:01 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Apr 2022 02:57:31 GMT",
"version": "v3"
},
{
"created": "Wed, 1 Feb 2023 01:21:13 GMT",
"version": "v4"
}
] | 2023-02-02 | [
[
"Wang",
"Hong",
""
],
[
"Wang",
"Jin",
""
]
] | Open quantum systems interacting with the environments often show interesting behaviors, such as decoherence, non-unitary evolution, dissipation, etc. It is interesting but still challenging to study the open quantum gravitation system interacting with the environments. In this work, we develop a general parameterized theoretical framework for the open quantum gravitation system. Under the Born-Markov approximation, we derived the quantum master equation with a new method which determines the evolution for certain types of open quantum gravitation system. Finally, we studied a specific model where the real scalar field plays the role of the environment and the spacetime is assumed to be homogeneous and isotropic. We quantize the spacetime through the loop quantum gravity. We show that the scalar field can induce the quantum geometry in the equilibrium state when the scalar field is under the thermal equilibrium. For the non-steady state, the quantum geometry flux emerges. We point out that the quantum geometry flux and the coherence can drive the evolution of the spacetime geometry. This provides us a new view on the evolution of the spacetime geometry. Our results shown that the coherence of the spacetime monotonically decreases as the temperature of the bath decreases. This indicates that a classical cold universe can emerge from an initial hot quantum universe. We found in this model that the entanglement entropy of the gravitation system is related to the average volume of the space. We take the continuous limit for studying the loop quantum cosmology and approximately obtain a tunneling probability of the spacetime from the zero volume state to the finite volume state. |
gr-qc/9906077 | Andrei Kirilyuk | Andrei P. Kirilyuk | Universal gravitation as a complex-dynamical process, renormalised
Planckian units, and the spectrum of elementary particles | 71 pages; 15 pages of the necessary minimum (1-8,48-56); PostScript
3.0; a part of the author's book "Universal Concept of Complexity by the
Dynamic Redundance Paradigm: Causal Randomness, Complete Wave Mechanics, and
the Ultimate Unification of Knowledge" (Kiev, Naukova Dumka, 1997; 550 p., in
English), see physics/9806002 | null | null | null | gr-qc hep-ph | null | The new, complex-dynamical mechanism of the universal gravitation naturally
incorporating dynamical quantization, wave-particle duality, and relativity of
physically emerging space and time (quant-ph/9902015,16) provides the realistic
meaning and fundamentally substantiated modification of the Planckian units of
mass, length, and time approaching them closely to the extreme values observed
for already discovered elementary particles. This result suggests the important
change of research strategy in high-energy/particle physics, displacing it
towards the already attained energy scales and permitting one to exclude the
existence of elementary objects in the inexplicably large interval of
parameters separating the known, practically more than sufficient set of
elementary species and the conventional, mechanistically exaggerated values of
the Planckian units. This conclusion is supported by the causally complete
(physically and mathematically consistent) picture of the fundamental levels of
reality derived, without artificial introduction of any structure or
'principle', from the unreduced analysis of the (generic) interaction process
between two primal, physically real, but a priori structureless entities, the
electromagnetic and gravitational protofields. The naturally emerging
phenomenon of universal dynamic redundance (multivaluedness) of interaction
process gives rise to the intrinsically unified hierarchy of unreduced dynamic
complexity of the world, starting from the lowest levels of elementary objects,
and explains the irreducible limitations of the basically single-valued
approach of the canonical science leading to the well-known 'mysteries',
separations, and loss of certainty.
| [
{
"created": "Thu, 17 Jun 1999 15:50:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kirilyuk",
"Andrei P.",
""
]
] | The new, complex-dynamical mechanism of the universal gravitation naturally incorporating dynamical quantization, wave-particle duality, and relativity of physically emerging space and time (quant-ph/9902015,16) provides the realistic meaning and fundamentally substantiated modification of the Planckian units of mass, length, and time approaching them closely to the extreme values observed for already discovered elementary particles. This result suggests the important change of research strategy in high-energy/particle physics, displacing it towards the already attained energy scales and permitting one to exclude the existence of elementary objects in the inexplicably large interval of parameters separating the known, practically more than sufficient set of elementary species and the conventional, mechanistically exaggerated values of the Planckian units. This conclusion is supported by the causally complete (physically and mathematically consistent) picture of the fundamental levels of reality derived, without artificial introduction of any structure or 'principle', from the unreduced analysis of the (generic) interaction process between two primal, physically real, but a priori structureless entities, the electromagnetic and gravitational protofields. The naturally emerging phenomenon of universal dynamic redundance (multivaluedness) of interaction process gives rise to the intrinsically unified hierarchy of unreduced dynamic complexity of the world, starting from the lowest levels of elementary objects, and explains the irreducible limitations of the basically single-valued approach of the canonical science leading to the well-known 'mysteries', separations, and loss of certainty. |
1311.3946 | Rafael Ferraro | Rafael Ferraro | Untangling the Newman-Janis algorithm | 11 pages. Minor changes. Published version | Gen. Relativ. Gravit. 46(2014), 1705 (1-15) | 10.1007/s10714-014-1705-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Newman-Janis algorithm for Kerr-Newman geometry is reanalyzed in the light of
Cartan calculus.
| [
{
"created": "Fri, 15 Nov 2013 18:44:13 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Apr 2014 19:46:03 GMT",
"version": "v2"
}
] | 2014-04-09 | [
[
"Ferraro",
"Rafael",
""
]
] | Newman-Janis algorithm for Kerr-Newman geometry is reanalyzed in the light of Cartan calculus. |
gr-qc/0205027 | Osvaldo M. Moreschi | Osvaldo Moreschi, Alejandro Perez and Luis Lehner | Energy and angular momentum radiated for non head-on binary black hole
collisions | 9 pages, 2 figures | Phys.Rev. D66 (2002) 104017 | 10.1103/PhysRevD.66.104017 | null | gr-qc | null | We investigate the possible total radiated energy produced by a binary black
hole system containing non-vanishing total angular momentum. For the scenearios
considered we find that the total radiated energy does not exceed 1%.
Additionally we explore the gravitational radiation field and the variation of
angular momentum in the process.
| [
{
"created": "Tue, 7 May 2002 18:06:16 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2002 18:14:20 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Moreschi",
"Osvaldo",
""
],
[
"Perez",
"Alejandro",
""
],
[
"Lehner",
"Luis",
""
]
] | We investigate the possible total radiated energy produced by a binary black hole system containing non-vanishing total angular momentum. For the scenearios considered we find that the total radiated energy does not exceed 1%. Additionally we explore the gravitational radiation field and the variation of angular momentum in the process. |
1607.03384 | Antonio Pasqua Dr. | Antonio Pasqua, Surajit Chattopadhyay and Aroonkumar Beesham | A look into the cosmological consequences of a dark energy model with
higher derivatives of $H$ in the framework of Chameleon Brans-Dicke Cosmology | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study some relevant cosmological features of a Dark Energy
(DE) model with Granda-Oliveiros cut-off, which is just a specific case of
Nojiri-Odintsov holographic DE unifying phantom inflation with late-time
acceleration, in the framework of Chameleon Brans-Dicke (BD) Cosmology.
Choosing a particular ansatz for some of the quantities involved, we derive the
expressions of some important cosmological quantities, like the Equation of
State (EoS) parameter of DE $w_D$, the effective EoS parameter $w_{eff}$, the
pressure of DE $p_D$ and the deceleration parameter $q$. Moreover, we study the
behavior of statefinder parameters $r$ and $s$, of the cosmographic parameters
$j$, $s_{cosmo}$, $l$ and $m$ and of the squared speed of the sound $v_s^2$ for
both case corresponding to non interacting and interacting Dark Sectors. We
also plot the quantities we have derived and we calculate their values for
$t\rightarrow 0$ (i.e. for the beginning of the Universe history), for
$t\rightarrow \infty$ (i.e. for far future) and for the present time, indicated
with $t_0$. The EoS parameters have been tested against various observational
values available in the literature.
| [
{
"created": "Mon, 11 Jul 2016 07:45:31 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Jan 2019 21:01:46 GMT",
"version": "v2"
}
] | 2019-01-23 | [
[
"Pasqua",
"Antonio",
""
],
[
"Chattopadhyay",
"Surajit",
""
],
[
"Beesham",
"Aroonkumar",
""
]
] | In this paper, we study some relevant cosmological features of a Dark Energy (DE) model with Granda-Oliveiros cut-off, which is just a specific case of Nojiri-Odintsov holographic DE unifying phantom inflation with late-time acceleration, in the framework of Chameleon Brans-Dicke (BD) Cosmology. Choosing a particular ansatz for some of the quantities involved, we derive the expressions of some important cosmological quantities, like the Equation of State (EoS) parameter of DE $w_D$, the effective EoS parameter $w_{eff}$, the pressure of DE $p_D$ and the deceleration parameter $q$. Moreover, we study the behavior of statefinder parameters $r$ and $s$, of the cosmographic parameters $j$, $s_{cosmo}$, $l$ and $m$ and of the squared speed of the sound $v_s^2$ for both case corresponding to non interacting and interacting Dark Sectors. We also plot the quantities we have derived and we calculate their values for $t\rightarrow 0$ (i.e. for the beginning of the Universe history), for $t\rightarrow \infty$ (i.e. for far future) and for the present time, indicated with $t_0$. The EoS parameters have been tested against various observational values available in the literature. |
2304.07736 | Betti Hartmann | Yves Brihaye (Universite de Mons, Belgium) and Betti Hartmann
(University College London, UK) | Charged and rotating boson stars in 5-dimensional
Einstein-Maxwell(-Chern-Simons) theory | 11 pages including 8 figures | null | 10.1103/PhysRevD.107.124060 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study charged and rotating boson stars in 5-dimensional
Einstein-Maxwell(-Chern-Simons) theory assuming the two angular momenta
associated to the two orthogonal planes of rotation to be equal. Next to the
angular momenta, the boson stars carry electric charge and magnetic moment.
Interestingly, we find new branches of Einstein-Maxwell-Chern-Simons solutions
for which the spatial part of the gauge potential possesses nodes.
Consequently, the magnetic moment and the gyromagnetic ratio have opposite sign
as compared to the solutions on the main branch. For sufficiently large energy
density we find that the solutions possess ergoregions.
| [
{
"created": "Sun, 16 Apr 2023 09:39:20 GMT",
"version": "v1"
}
] | 2023-07-12 | [
[
"Brihaye",
"Yves",
"",
"Universite de Mons, Belgium"
],
[
"Hartmann",
"Betti",
"",
"University College London, UK"
]
] | We study charged and rotating boson stars in 5-dimensional Einstein-Maxwell(-Chern-Simons) theory assuming the two angular momenta associated to the two orthogonal planes of rotation to be equal. Next to the angular momenta, the boson stars carry electric charge and magnetic moment. Interestingly, we find new branches of Einstein-Maxwell-Chern-Simons solutions for which the spatial part of the gauge potential possesses nodes. Consequently, the magnetic moment and the gyromagnetic ratio have opposite sign as compared to the solutions on the main branch. For sufficiently large energy density we find that the solutions possess ergoregions. |
1309.6384 | Muhammad Sharif | M. Sharif and Wajiha Javed | Fermions Tunneling from Plebanski-Demianski Black Holes | 22 pages, 6 figures | Gen. Relativ. Gravit 45(2013)1051-1068 | 10.1007/s10714-013-1512-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation spectrum via fermions tunneling is investigated through
horizon radii of Pleba$\acute{\textmd{n}}$ski-Demia$\acute{\textmd{n}}$ski
family of black holes. To this end, we determine the tunneling probabilities
for outgoing and incoming charged fermion particles and obtain their
corresponding Hawking temperatures. The graphical behavior of Hawking
temperatures and horizon radii (cosmological and event horizons) is also
studied. We find consistent results with those already available in literature.
| [
{
"created": "Wed, 25 Sep 2013 02:40:28 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Sharif",
"M.",
""
],
[
"Javed",
"Wajiha",
""
]
] | Hawking radiation spectrum via fermions tunneling is investigated through horizon radii of Pleba$\acute{\textmd{n}}$ski-Demia$\acute{\textmd{n}}$ski family of black holes. To this end, we determine the tunneling probabilities for outgoing and incoming charged fermion particles and obtain their corresponding Hawking temperatures. The graphical behavior of Hawking temperatures and horizon radii (cosmological and event horizons) is also studied. We find consistent results with those already available in literature. |
1206.0028 | Robert Reasenberg | Robert D. Reasenberg, Biju R. Patla, James D. Phillips, and Rajesh
Thapa | Design and characteristics of a WEP test in a sounding-rocket payload | 20 pages, 5 figures (color) | null | 10.1088/0264-9381/29/18/184013 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/publicdomain/ | We describe SR-POEM, a Galilean test of the weak equivalence principle that
is to be conducted during the free fall portion of the flight of a sounding
rocket payload. This test of a single pair of substances will have a
measurement uncertainty of {\sigma}({\eta}) < 2 10^17 after averaging the
results of eight separate drops, each of 120 s duration. The entire payload is
inverted between successive drops to cancel potential sources of systematic
error. The weak equivalence principle measurement is made with a set of four of
the SAO laser gauges, which have achieved an Allan deviation of 0.04 pm for an
averaging time of 30 s. We discuss aspects of the current design with an
emphasis on those that bear on the accuracy of the determination of {\eta}. The
discovery of a violation ({\eta} \neq 0) would have profound implications for
physics, astrophysics and cosmology.
| [
{
"created": "Thu, 31 May 2012 20:37:34 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Reasenberg",
"Robert D.",
""
],
[
"Patla",
"Biju R.",
""
],
[
"Phillips",
"James D.",
""
],
[
"Thapa",
"Rajesh",
""
]
] | We describe SR-POEM, a Galilean test of the weak equivalence principle that is to be conducted during the free fall portion of the flight of a sounding rocket payload. This test of a single pair of substances will have a measurement uncertainty of {\sigma}({\eta}) < 2 10^17 after averaging the results of eight separate drops, each of 120 s duration. The entire payload is inverted between successive drops to cancel potential sources of systematic error. The weak equivalence principle measurement is made with a set of four of the SAO laser gauges, which have achieved an Allan deviation of 0.04 pm for an averaging time of 30 s. We discuss aspects of the current design with an emphasis on those that bear on the accuracy of the determination of {\eta}. The discovery of a violation ({\eta} \neq 0) would have profound implications for physics, astrophysics and cosmology. |
2312.16849 | Vyacheslav Dokuchaev | Vyacheslav Ivanovich Dokuchaev | Quantum correction to black hole accretion | 5 pages, 3 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe quantum correction to the accreting hot plasma onto black holes.
This quantum correction is related with the Hawking radiation, which heats the
accreting plasma. The hot accreting gas is heated additionally by the quantum
Hawking radiation. It is demonstrated that Hawking radiation prevails over the
Compton scattering of hot electrons in the accreting flow onto the small enough
evaporating black holes with masses $M<M_q\simeq 4.61\cdot10^{29}$ grams. In
result, the evaporating black holes with masses $M<M_q$ reverse the inflowing
plasma into outflowing one and stop the black hole accretion at all. The black
holes with masses $M<M_q$ made contribute to the enigmatic dark matter at the
galactic disks, galactic halos and even in the intergalactic space, if these
black holes are primordial in origin.
| [
{
"created": "Thu, 28 Dec 2023 06:35:24 GMT",
"version": "v1"
}
] | 2024-01-01 | [
[
"Dokuchaev",
"Vyacheslav Ivanovich",
""
]
] | We describe quantum correction to the accreting hot plasma onto black holes. This quantum correction is related with the Hawking radiation, which heats the accreting plasma. The hot accreting gas is heated additionally by the quantum Hawking radiation. It is demonstrated that Hawking radiation prevails over the Compton scattering of hot electrons in the accreting flow onto the small enough evaporating black holes with masses $M<M_q\simeq 4.61\cdot10^{29}$ grams. In result, the evaporating black holes with masses $M<M_q$ reverse the inflowing plasma into outflowing one and stop the black hole accretion at all. The black holes with masses $M<M_q$ made contribute to the enigmatic dark matter at the galactic disks, galactic halos and even in the intergalactic space, if these black holes are primordial in origin. |
1306.1883 | Mohammad Nouri-Zonoz | M. Nouri-Zonoz and A. Parvizi | Gaussian Curvature and Global effects : gravitational Aharonov-Bohm
effect revisited | 14 pages,2 figures, RevTex | Phys. Rev. D. 88, 023004 (2013) | 10.1103/PhysRevD.88.023004 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Gauss-Bonnet formula, integral of the Gaussian curvature over a
2-surface enclosed by a curve in the asymptotically flat region of a static
spacetime was found to be a measure of a gravitational analogue of
Aharonov-Bohm effect by Ford and Vilenkin in the linearized regime. Employing
the 1+3 formulation of spacetime decomposition we study the same effect in the
context of full Einstein field equations for stationary spacetimes. Applying
our approach to static tube-like and cylindrical distributions of dust not only
we recover their result but also obtain an extra term which is interpreted to
be representing the classical version of the Colella-Overhauser-Werner effect
(the COW experiment).
| [
{
"created": "Sat, 8 Jun 2013 05:14:12 GMT",
"version": "v1"
}
] | 2013-07-26 | [
[
"Nouri-Zonoz",
"M.",
""
],
[
"Parvizi",
"A.",
""
]
] | Using the Gauss-Bonnet formula, integral of the Gaussian curvature over a 2-surface enclosed by a curve in the asymptotically flat region of a static spacetime was found to be a measure of a gravitational analogue of Aharonov-Bohm effect by Ford and Vilenkin in the linearized regime. Employing the 1+3 formulation of spacetime decomposition we study the same effect in the context of full Einstein field equations for stationary spacetimes. Applying our approach to static tube-like and cylindrical distributions of dust not only we recover their result but also obtain an extra term which is interpreted to be representing the classical version of the Colella-Overhauser-Werner effect (the COW experiment). |
gr-qc/0609011 | Stefan Nobbenhuis | Stefan Nobbenhuis | The Cosmological Constant Problem, an Inspiration for New Physics | Ph.D. Thesis | null | null | ITP-UU-06/36, SPIN-06/30 | gr-qc | null | We have critically compared different approaches to the cosmological constant
problem, which is at the edge of elementary particle physics and cosmology.
This problem is deeply connected with the difficulties formulating a theory of
quantum gravity. After the 1998 discovery that our universe's expansion is
accelerating, the cosmological constant problem has obtained a new dimension.
We are mainly interested in the question why the cosmological constant is so
small. We have identified four different classes of solutions: a symmetry, a
back-reaction mechanism, a violation of (some of) the building blocks of
general relativity, and statistical approaches. In this thesis we carefully
study all known potential candidates for a solution, but conclude that so far
none of the approaches gives a satisfactory solution. A symmetry would be the
most elegant solution and we study a new symmetry under transformation to
imaginary spacetime.
| [
{
"created": "Mon, 4 Sep 2006 17:30:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nobbenhuis",
"Stefan",
""
]
] | We have critically compared different approaches to the cosmological constant problem, which is at the edge of elementary particle physics and cosmology. This problem is deeply connected with the difficulties formulating a theory of quantum gravity. After the 1998 discovery that our universe's expansion is accelerating, the cosmological constant problem has obtained a new dimension. We are mainly interested in the question why the cosmological constant is so small. We have identified four different classes of solutions: a symmetry, a back-reaction mechanism, a violation of (some of) the building blocks of general relativity, and statistical approaches. In this thesis we carefully study all known potential candidates for a solution, but conclude that so far none of the approaches gives a satisfactory solution. A symmetry would be the most elegant solution and we study a new symmetry under transformation to imaginary spacetime. |
gr-qc/9812069 | Ruth Lazkoz | Ruth Lazkoz | G1 Cosmologies with Gravitational and Scalar Waves | 24 pages, 2 figures | Phys. Rev. D 60, 104008 (1999) | 10.1103/PhysRevD.60.104008 | null | gr-qc | null | I present here a new algorithm to generate families of inhomogeneous massless
scalar field cosmologies. New spacetimes, having a single isometry, are
generated by breaking the homogeneity of massless scalar field $G_2$ models
along one direction. As an illustration of the technique I construct
cosmological models which in their late time limit represent perturbations in
the form of gravitational and scalar waves propagating on a non-static
inhomogeneous background. Several features of the obtained metrics are
discussed, such as their early and late time limits, structure of singularities
and physical interpretation.
| [
{
"created": "Fri, 18 Dec 1998 15:56:20 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Lazkoz",
"Ruth",
""
]
] | I present here a new algorithm to generate families of inhomogeneous massless scalar field cosmologies. New spacetimes, having a single isometry, are generated by breaking the homogeneity of massless scalar field $G_2$ models along one direction. As an illustration of the technique I construct cosmological models which in their late time limit represent perturbations in the form of gravitational and scalar waves propagating on a non-static inhomogeneous background. Several features of the obtained metrics are discussed, such as their early and late time limits, structure of singularities and physical interpretation. |
gr-qc/0412095 | Christian Schubert | Fiorenzo Bastianelli (Bologna University) and Christian Schubert
(UTPA) | One loop photon-graviton mixing in an electromagnetic field: Part 1 | 27 pages, final published version (minor corrections) | JHEP 0502 (2005) 069 | 10.1088/1126-6708/2005/02/069 | AEI-2004-047 | gr-qc hep-th | null | Photon-graviton mixing in an electromagnetic field is a process of potential
interest for cosmology and astrophysics. At the tree level it has been studied
by many authors. We consider the one-loop contribution to this amplitude
involving a charged spin 0 or spin 1/2 particle in the loop and an arbitrary
constant field. In the first part of this article, the worldline formalism is
used to obtain a compact two-parameter integral representation for this
amplitude, valid for arbitrary photon energies and background field strengths.
The calculation is manifestly covariant througout.
| [
{
"created": "Mon, 20 Dec 2004 08:50:47 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Mar 2005 22:39:41 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Bastianelli",
"Fiorenzo",
"",
"Bologna University"
],
[
"Schubert",
"Christian",
"",
"UTPA"
]
] | Photon-graviton mixing in an electromagnetic field is a process of potential interest for cosmology and astrophysics. At the tree level it has been studied by many authors. We consider the one-loop contribution to this amplitude involving a charged spin 0 or spin 1/2 particle in the loop and an arbitrary constant field. In the first part of this article, the worldline formalism is used to obtain a compact two-parameter integral representation for this amplitude, valid for arbitrary photon energies and background field strengths. The calculation is manifestly covariant througout. |
1503.01011 | Behzad Eslam Panah | S. H. Hendi, G. H. Bordbar, B. Eslam Panah and M. Najafi | Dilatonic Equation of Hydrostatic Equilibrium and Neutron Star Structure | 10 pages with 4 figures, Numerical analysis added | Astrophys Space Sci. 358, 30 (2015) | 10.1007/s10509-015-2429-x | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present a new hydrostatic equilibrium equation related to
dilaton gravity. We consider a spherical symmetric metric to obtain the
hydrostatic equilibrium equation of stars in $4$-dimensions, and generalize TOV
equation to the case of regarding a dilaton field. Then, we calculate the
structure properties of neutron star using our obtained hydrostatic equilibrium
equation employing the modern equations of state of neutron star matter derived
from microscopic calculations. We show that the maximum mass of neutron star
depends on the parameters of dilaton field and cosmological constant. In other
words, by setting the parameters of new hydrostatic equilibrium equation, we
calculate the maximum mass of neutron star.
| [
{
"created": "Tue, 3 Mar 2015 16:58:57 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2015 08:12:52 GMT",
"version": "v2"
}
] | 2015-07-27 | [
[
"Hendi",
"S. H.",
""
],
[
"Bordbar",
"G. H.",
""
],
[
"Panah",
"B. Eslam",
""
],
[
"Najafi",
"M.",
""
]
] | In this paper, we present a new hydrostatic equilibrium equation related to dilaton gravity. We consider a spherical symmetric metric to obtain the hydrostatic equilibrium equation of stars in $4$-dimensions, and generalize TOV equation to the case of regarding a dilaton field. Then, we calculate the structure properties of neutron star using our obtained hydrostatic equilibrium equation employing the modern equations of state of neutron star matter derived from microscopic calculations. We show that the maximum mass of neutron star depends on the parameters of dilaton field and cosmological constant. In other words, by setting the parameters of new hydrostatic equilibrium equation, we calculate the maximum mass of neutron star. |
gr-qc/0310127 | Lars Andersson | Lars Andersson (University of Miami), Henk van Elst (Queen Mary,
University of London), Claes Uggla (University of Karlstad) | Gowdy phenomenology in scale-invariant variables | 33 pages, 17 figures. To appear in A Spacetime Safari: Papers in
Honour of Vincent Moncrief | Class.Quant.Grav. 21 (2004) S29-S57 | 10.1088/0264-9381/21/3/003 | null | gr-qc | null | The dynamics of Gowdy vacuum spacetimes is considered in terms of
Hubble-normalized scale-invariant variables, using the timelike area temporal
gauge. The resulting state space formulation provides for a simple mechanism
for the formation of ``false'' and ``true spikes'' in the approach to the
singularity, and a geometrical formulation for the local attractor.
| [
{
"created": "Thu, 30 Oct 2003 16:06:48 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Andersson",
"Lars",
"",
"University of Miami"
],
[
"van Elst",
"Henk",
"",
"Queen Mary,\n University of London"
],
[
"Uggla",
"Claes",
"",
"University of Karlstad"
]
] | The dynamics of Gowdy vacuum spacetimes is considered in terms of Hubble-normalized scale-invariant variables, using the timelike area temporal gauge. The resulting state space formulation provides for a simple mechanism for the formation of ``false'' and ``true spikes'' in the approach to the singularity, and a geometrical formulation for the local attractor. |
2202.02122 | Cosimo Bambi | Temurbek Mirzaev, Askar B. Abdikamalov, Ahmadjon A. Abdujabbarov,
Dimitry Ayzenberg, Bobomurat Ahmedov, Cosimo Bambi | Observational appearance of Kaluza-Klein black holes | 13 pages, 9 figures. v2: refereed version | Eur. Phys. J. C (2023) 83:800 | 10.1140/epjc/s10052-023-11985-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The optical properties of rotating black holes in Kaluza-Klein theory
described by the total mass, spin, and electric and magnetic charges are
investigated in detail. Using a developed general relativistic ray-tracing code
to calculate the motion of photons, the numerous shadows of Kaluza-Klein black
holes are generated. The properties of the black hole shadow and the light
deflection angle around these black holes are also studied in order to put
constraints on the parameters of Kaluza-Klein black holes using M87* shadow
observations. The possibility of imposing constraints on Kaluza-Klein black
holes using shadow observations is investigated. Moreover, we find that small
charges (electric and magnetic) of the black hole can meet these constraints.
We conclude that with the current precision of the M87* black hole shadow image
observation by the EHT collaboration, the shadow observations of Kaluza-Klein
black holes are indistinguishable from that of the Kerr black hole. Much better
observational accuracy than the current capabilities of the EHT collaboration
are required in order to place verified constraints on the parameters of
modified theories of gravity in the strong field regime.
| [
{
"created": "Fri, 4 Feb 2022 13:18:49 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Sep 2023 14:19:13 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Mirzaev",
"Temurbek",
""
],
[
"Abdikamalov",
"Askar B.",
""
],
[
"Abdujabbarov",
"Ahmadjon A.",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Bambi",
"Cosimo",
""
]
] | The optical properties of rotating black holes in Kaluza-Klein theory described by the total mass, spin, and electric and magnetic charges are investigated in detail. Using a developed general relativistic ray-tracing code to calculate the motion of photons, the numerous shadows of Kaluza-Klein black holes are generated. The properties of the black hole shadow and the light deflection angle around these black holes are also studied in order to put constraints on the parameters of Kaluza-Klein black holes using M87* shadow observations. The possibility of imposing constraints on Kaluza-Klein black holes using shadow observations is investigated. Moreover, we find that small charges (electric and magnetic) of the black hole can meet these constraints. We conclude that with the current precision of the M87* black hole shadow image observation by the EHT collaboration, the shadow observations of Kaluza-Klein black holes are indistinguishable from that of the Kerr black hole. Much better observational accuracy than the current capabilities of the EHT collaboration are required in order to place verified constraints on the parameters of modified theories of gravity in the strong field regime. |
gr-qc/9305020 | Steven Carlip | S. Carlip | Six ways to quantize (2+1)-dimensional gravity | 21 pages, U.C. Davis preprint UCD-93-15 and Santa Barbara ITP
preprint NSF-ITP-93-63 | null | null | null | gr-qc hep-th | null | We do not yet know how to quantize gravity in 3+1 dimensions, but in lower
dimensions we face the opposite problem: many of the approaches originally
developed for (3+1)-dimensional gravity can be successfully implemented in 2+1
dimensions, but the resulting quantum theories are not all equivalent. In this
talk, I discuss six such approaches --- reduced phase space ADM quantization,
the Chern-Simons/connection representation, covariant canonical quantization,
the loop representation, the Wheeler-DeWitt equation, and lattice methods ---
for the simple case of a spacetime whose spatial topology is that of a torus. A
comparison of the resulting quantum theories can provide some useful insights
into the conceptual issues that underlie quantum gravity in any number of
dimensions. (Talk given at the Fifth Canadian Conference on General Relativity
and Relativistic Astrophysics, Waterloo, Ontario, May 1993)
| [
{
"created": "Mon, 24 May 1993 20:07:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carlip",
"S.",
""
]
] | We do not yet know how to quantize gravity in 3+1 dimensions, but in lower dimensions we face the opposite problem: many of the approaches originally developed for (3+1)-dimensional gravity can be successfully implemented in 2+1 dimensions, but the resulting quantum theories are not all equivalent. In this talk, I discuss six such approaches --- reduced phase space ADM quantization, the Chern-Simons/connection representation, covariant canonical quantization, the loop representation, the Wheeler-DeWitt equation, and lattice methods --- for the simple case of a spacetime whose spatial topology is that of a torus. A comparison of the resulting quantum theories can provide some useful insights into the conceptual issues that underlie quantum gravity in any number of dimensions. (Talk given at the Fifth Canadian Conference on General Relativity and Relativistic Astrophysics, Waterloo, Ontario, May 1993) |
1906.11063 | Mohsen Dehghani | M. Dehghani and M.R. Setare | Dilaton black holes with power law electrodynamics | 21 pages with 9 captioned figures | Phys. Rev. D 100, 044022 (2019) | 10.1103/PhysRevD.100.044022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, the new black hole solutions to the
Einstein-power-Maxwell-dilaton gravity theory have been investigated in a
four-dimensional space-time. The coupled scalar, electromagnetic and
gravitational field equations have been solved in a static and spherically
symmetric geometry. It has been shown that dilatonic potential, as the solution
to the scalar field equation, can be written in the form of a generalized
Liouville potential. Also, three classes of novel charged dilaton black hole
solutions, in the presence of power law nonlinear electrodynamics, have been
constructed out which are asymptotically non-flat and non-AdS. The conserved
and thermodynamic quantities have been calculated from geometrical and
thermodynamical approaches, separately. Since the results of these two
alternative approaches are identical one can argue that the first law of black
hole thermodynamics is valid for all of the new black hole solutions. The
thermodynamic stability or phase transition of the black holes have been
studied, making use of the canonical ensemble method. The points of type-1 and
type-2 phase transitions as well as the ranges at which the black holes are
stable have been indicated by considering the heat capacity of the new black
hole solutions. The global stability of the black holes have been studied
through the grand canonical ensemble method. Regarding the Gibbs free energy of
the black holes, the points of Hawking-Page phase transition and ranges of the
horizon radii at which the black holes are globally stable have been
determined.
| [
{
"created": "Mon, 24 Jun 2019 18:56:11 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jun 2019 06:00:55 GMT",
"version": "v2"
}
] | 2019-08-13 | [
[
"Dehghani",
"M.",
""
],
[
"Setare",
"M. R.",
""
]
] | In this article, the new black hole solutions to the Einstein-power-Maxwell-dilaton gravity theory have been investigated in a four-dimensional space-time. The coupled scalar, electromagnetic and gravitational field equations have been solved in a static and spherically symmetric geometry. It has been shown that dilatonic potential, as the solution to the scalar field equation, can be written in the form of a generalized Liouville potential. Also, three classes of novel charged dilaton black hole solutions, in the presence of power law nonlinear electrodynamics, have been constructed out which are asymptotically non-flat and non-AdS. The conserved and thermodynamic quantities have been calculated from geometrical and thermodynamical approaches, separately. Since the results of these two alternative approaches are identical one can argue that the first law of black hole thermodynamics is valid for all of the new black hole solutions. The thermodynamic stability or phase transition of the black holes have been studied, making use of the canonical ensemble method. The points of type-1 and type-2 phase transitions as well as the ranges at which the black holes are stable have been indicated by considering the heat capacity of the new black hole solutions. The global stability of the black holes have been studied through the grand canonical ensemble method. Regarding the Gibbs free energy of the black holes, the points of Hawking-Page phase transition and ranges of the horizon radii at which the black holes are globally stable have been determined. |
gr-qc/0305087 | Tirthabir Biswas | Tirthabir Biswas | Quintessential Transition of the Internal Manifold | addition of a reference, minor editorial changes | null | null | YITP-SB-03-18 | gr-qc hep-th | null | In this paper, I study the dynamics of the Kaluza-Klein internal manifold
using its ``shape'' and the ``size'' as collective coordinates. The essential
motivation is to be able to explain symmetry breaking in gauge theories through
a transition of the internal manifold from a symmetrical metric space to a less
symmetric one. We find that this may be possible depending on the values of
certain group theoretical parameters. Further, this transition resembles a
``quintessential inflation'' scenario, the feasibility of which however, needs
to be further studied in details.
| [
{
"created": "Thu, 22 May 2003 16:03:38 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jun 2003 21:05:10 GMT",
"version": "v2"
}
] | 2018-01-23 | [
[
"Biswas",
"Tirthabir",
""
]
] | In this paper, I study the dynamics of the Kaluza-Klein internal manifold using its ``shape'' and the ``size'' as collective coordinates. The essential motivation is to be able to explain symmetry breaking in gauge theories through a transition of the internal manifold from a symmetrical metric space to a less symmetric one. We find that this may be possible depending on the values of certain group theoretical parameters. Further, this transition resembles a ``quintessential inflation'' scenario, the feasibility of which however, needs to be further studied in details. |
gr-qc/0303036 | G. Bergqvist | G. Bergqvist, I. Eriksson and J. M. M. Senovilla | New electromagnetic conservation laws | 6 pages | Class.Quant.Grav. 20 (2003) 2663-2668 | 10.1088/0264-9381/20/13/313 | null | gr-qc | null | The Chevreton superenergy tensor was introduced in 1964 as a counterpart, for
electromagnetic fields, of the well-known Bel-Robinson tensor of the
gravitational field. We here prove the unnoticed facts that, in the absence of
electromagnetic currents, Chevreton's tensor (i) is completely symmetric, and
(ii) has a trace-free divergence if Einstein-Maxwell equations hold. It follows
that the trace of the Chevreton tensor is a rank-2, symmetric, trace-free, {\em
conserved} tensor, which is different from the energy-momentum tensor, and
nonetheless can be constructed for any test Maxwell field, or any
Einstein-Maxwell spacetime.
| [
{
"created": "Mon, 10 Mar 2003 09:37:51 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bergqvist",
"G.",
""
],
[
"Eriksson",
"I.",
""
],
[
"Senovilla",
"J. M. M.",
""
]
] | The Chevreton superenergy tensor was introduced in 1964 as a counterpart, for electromagnetic fields, of the well-known Bel-Robinson tensor of the gravitational field. We here prove the unnoticed facts that, in the absence of electromagnetic currents, Chevreton's tensor (i) is completely symmetric, and (ii) has a trace-free divergence if Einstein-Maxwell equations hold. It follows that the trace of the Chevreton tensor is a rank-2, symmetric, trace-free, {\em conserved} tensor, which is different from the energy-momentum tensor, and nonetheless can be constructed for any test Maxwell field, or any Einstein-Maxwell spacetime. |
2010.07202 | Che-Yu Chen | Che-Yu Chen, Yu-Hsien Kung, Pisin Chen | Black Hole Perturbations and Quasinormal Modes in Hybrid Metric-Palatini
Gravity | 11 pages, 2 figures. Updated to match the published version | Phys. Rev. D 102, 124033 (2020) | 10.1103/PhysRevD.102.124033 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The rapid advancement of gravitational wave astronomy in recent years has
paved the way for the burgeoning development of black hole spectroscopy, which
enhances the possibility of testing black holes by their quasinormal modes
(QNMs). In this paper, the axial gravitational perturbations and the QNM
frequencies of black holes in the hybrid metric-Palatini gravity (HMPG) are
investigated. The HMPG theory is characterized by a dynamical scalar degree of
freedom and is able to explain the late-time accelerating expansion of the
universe without introducing any \textit{ad hoc} screening mechanism to
preserve the dynamics at the Solar System scale. We obtain the master equation
governing the axial gravitational perturbations of the HMPG black holes and
calculate the QNM frequencies. Moreover, in the scrutiny of the black holes and
their QNMs, we take into account the constraints on the model parameters based
on the post-Newtonian analysis, and show how the QNM frequencies of the HMPG
black holes would be altered in the observationally consistent range of
parameter space.
| [
{
"created": "Wed, 14 Oct 2020 16:14:24 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Dec 2020 05:32:22 GMT",
"version": "v2"
}
] | 2020-12-16 | [
[
"Chen",
"Che-Yu",
""
],
[
"Kung",
"Yu-Hsien",
""
],
[
"Chen",
"Pisin",
""
]
] | The rapid advancement of gravitational wave astronomy in recent years has paved the way for the burgeoning development of black hole spectroscopy, which enhances the possibility of testing black holes by their quasinormal modes (QNMs). In this paper, the axial gravitational perturbations and the QNM frequencies of black holes in the hybrid metric-Palatini gravity (HMPG) are investigated. The HMPG theory is characterized by a dynamical scalar degree of freedom and is able to explain the late-time accelerating expansion of the universe without introducing any \textit{ad hoc} screening mechanism to preserve the dynamics at the Solar System scale. We obtain the master equation governing the axial gravitational perturbations of the HMPG black holes and calculate the QNM frequencies. Moreover, in the scrutiny of the black holes and their QNMs, we take into account the constraints on the model parameters based on the post-Newtonian analysis, and show how the QNM frequencies of the HMPG black holes would be altered in the observationally consistent range of parameter space. |
1602.06903 | Nicola Tamanini | Nicola Tamanini and Matthew Wright | Cosmological dynamics of extended chameleons | JCAP style, 31 pages, 6 figures, 8 tables; v2: acknowledgements added | null | 10.1088/1475-7516/2016/04/032 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological dynamics of the recently proposed extended
chameleon models at both background and linear perturbation levels. Dynamical
systems techniques are employed to fully characterize the evolution of the
universe at the largest distances, while structure formation is analysed at
sub-horizon scales within the quasi-static approximation. The late time
dynamical transition from dark matter to dark energy domination can be well
described by almost all extended chameleon models considered, with no
deviations from $\Lambda$CDM results at both background and perturbation
levels. The results obtained in this work confirm the cosmological viability of
extended chameleons as alternative dark energy models.
| [
{
"created": "Mon, 22 Feb 2016 19:40:23 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Mar 2017 15:09:17 GMT",
"version": "v2"
}
] | 2017-03-09 | [
[
"Tamanini",
"Nicola",
""
],
[
"Wright",
"Matthew",
""
]
] | We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from $\Lambda$CDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models. |
0801.1119 | Alejandro Corichi | Alejandro Corichi | On the geometry of quantum constrained systems | 14 pages, no figures. Discussion expanded. Version published in CQG | Class.Quant.Grav.25:135013,2008 | 10.1088/0264-9381/25/13/135013 | IGPG-08/1-1 | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The use of geometric methods has proved useful in the hamiltonian description
of classical constrained systems. In this note we provide the first steps
toward the description of the geometry of quantum constrained systems. We make
use of the geometric formulation of quantum theory in which unitary
transformations (including time evolution) can be seen, just as in the
classical case, as finite canonical transformations on the quantum state space.
We compare from this perspective the classical and quantum formalisms and argue
that there is an important difference between them, that suggests that the
condition on observables to become physical is through the double commutator
with the square of the constraint operator. This provides a bridge between the
standard Dirac procedure --through its geometric implementation-- and the
Master Constraint program.
| [
{
"created": "Tue, 8 Jan 2008 16:44:38 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jun 2008 17:48:17 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
]
] | The use of geometric methods has proved useful in the hamiltonian description of classical constrained systems. In this note we provide the first steps toward the description of the geometry of quantum constrained systems. We make use of the geometric formulation of quantum theory in which unitary transformations (including time evolution) can be seen, just as in the classical case, as finite canonical transformations on the quantum state space. We compare from this perspective the classical and quantum formalisms and argue that there is an important difference between them, that suggests that the condition on observables to become physical is through the double commutator with the square of the constraint operator. This provides a bridge between the standard Dirac procedure --through its geometric implementation-- and the Master Constraint program. |
2011.07763 | Wei-Hsiang Shao | Wei-Hsiang Shao, Che-Yu Chen, and Pisin Chen | Generating Rotating Spacetime in Ricci-Based Gravity: Naked Singularity
as a Black Hole Mimicker | 33 pages, 4 figures; reference added, updated to match the published
version | JCAP 03 (2021) 041 | 10.1088/1475-7516/2021/03/041 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the lack of rotating solutions sourced by matter in General
Relativity as well as in modified gravity theories, we extend a recently
discovered exact rotating solution of the minimal Einstein-scalar theory to its
counterpart in Eddington-inspired Born-Infeld gravity coupled to a Born-Infeld
scalar field. This is accomplished with the implementation of a well-developed
mapping between solutions of Ricci-Based Palatini theories of gravity and
General Relativity. The new solution is parametrized by the scalar charge and
the Born-Infeld coupling constant apart from the mass and spin of the compact
object. Compared to the spacetime prior to the mapping, we find that the
high-energy modifications at the Born-Infeld scale are able to suppress but not
remove the curvature divergence of the original naked null singularity.
Depending on the sign of the Born-Infeld coupling constant, these modifications
may even give rise to an additional timelike singularity exterior to the null
one. In spite of that, both of the naked singularities before and after the
mapping are capable of casting shadows, and as a consequence of the mapping
relation, their shadows turn out to be identical as seen by a distant observer
on the equatorial plane. Even though the scalar field induces a certain
oblateness to the appearance of the shadow with its left and right endpoints
held fixed, the closedness condition for the shadow contour sets a small upper
bound on the absolute value of the scalar charge, which leads to observational
features of the shadow closely resembling those of a Kerr black hole.
| [
{
"created": "Mon, 16 Nov 2020 07:49:13 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Mar 2021 07:52:19 GMT",
"version": "v2"
}
] | 2021-03-17 | [
[
"Shao",
"Wei-Hsiang",
""
],
[
"Chen",
"Che-Yu",
""
],
[
"Chen",
"Pisin",
""
]
] | Motivated by the lack of rotating solutions sourced by matter in General Relativity as well as in modified gravity theories, we extend a recently discovered exact rotating solution of the minimal Einstein-scalar theory to its counterpart in Eddington-inspired Born-Infeld gravity coupled to a Born-Infeld scalar field. This is accomplished with the implementation of a well-developed mapping between solutions of Ricci-Based Palatini theories of gravity and General Relativity. The new solution is parametrized by the scalar charge and the Born-Infeld coupling constant apart from the mass and spin of the compact object. Compared to the spacetime prior to the mapping, we find that the high-energy modifications at the Born-Infeld scale are able to suppress but not remove the curvature divergence of the original naked null singularity. Depending on the sign of the Born-Infeld coupling constant, these modifications may even give rise to an additional timelike singularity exterior to the null one. In spite of that, both of the naked singularities before and after the mapping are capable of casting shadows, and as a consequence of the mapping relation, their shadows turn out to be identical as seen by a distant observer on the equatorial plane. Even though the scalar field induces a certain oblateness to the appearance of the shadow with its left and right endpoints held fixed, the closedness condition for the shadow contour sets a small upper bound on the absolute value of the scalar charge, which leads to observational features of the shadow closely resembling those of a Kerr black hole. |
2302.06362 | Baocheng Zhang | Feifan He and Baocheng Zhang | Generation of entanglement between two laser pulses through
gravitational interaction | null | Eur. Phys. J. Plus (2023) 138:141 | 10.1140/epjp/s13360-023-03766-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate entanglement generation between two pulses through the
gravitational interaction in the framework of linearized quantum gravity.
Different from the earlier suggestions that two massive particles can be
entangled through the gravitational field produced by the particles themselves,
we use the massless particles (a laser pulse) to generate the gravitational
field. In our proposal, the propagating retarded effect of the gravitational
perturbation generated by the laser pulses can be incorporated into the
interaction, which is significant for supporting the assumption of local
interaction. It is found that the locally linearized quantum gravitational
interaction can indeed lead to the generation of entanglement between two
pulses, and the result is dependent on the propagating time of the
gravitational perturbation. We also provide a measurement suggestion using a
Holometer-like interferometers structure to present this result of
gravitation-induced entanglement, which could show that the gravitational
mediator is quantum in future experiments.
| [
{
"created": "Mon, 13 Feb 2023 13:48:54 GMT",
"version": "v1"
}
] | 2023-02-14 | [
[
"He",
"Feifan",
""
],
[
"Zhang",
"Baocheng",
""
]
] | We investigate entanglement generation between two pulses through the gravitational interaction in the framework of linearized quantum gravity. Different from the earlier suggestions that two massive particles can be entangled through the gravitational field produced by the particles themselves, we use the massless particles (a laser pulse) to generate the gravitational field. In our proposal, the propagating retarded effect of the gravitational perturbation generated by the laser pulses can be incorporated into the interaction, which is significant for supporting the assumption of local interaction. It is found that the locally linearized quantum gravitational interaction can indeed lead to the generation of entanglement between two pulses, and the result is dependent on the propagating time of the gravitational perturbation. We also provide a measurement suggestion using a Holometer-like interferometers structure to present this result of gravitation-induced entanglement, which could show that the gravitational mediator is quantum in future experiments. |
1503.01507 | Edward Anderson | Edward Anderson | Configuration Spaces in Fundamental Physics | 35 pages including 16 Figures. Several new figures and Appendices
added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I consider configuration spaces for $N$-body problems, gauge theories and for
GR in both geometrodynamical and Ashtekar variables forms, including
minisuperspace and inhomogeneous perturbations thereabout in the former case.
These examples include many interesting spaces of shapes (with and without
whichever of local or global notions of scale). In considering reduced
configuration spaces, stratified manifolds arise. Three strategies to deal with
these are `excise', `unfold' and `accept'. I show that spaces of triangles
arising from various interpretations of 3-body problems already serve as model
arena for all three. I furthermore argue in favour of the `accept' strategy on
relational grounds. This approach requires sheaf methods (which go beyond fibre
bundles and general bundles, which I contrast with sheaves and presheaves in
some appendices). Sheaf methods are also required for the stratifold construct
that pairs some well-behaved stratified manifolds with sheaves. I apply arguing
against `excise' and `unfold' to GR's superspace and thin sandwich, and to the
removal of collinear configurations in mechanics. Non-redundant configurations
are also useful in providing more accurate names for various spaces and
theories.
| [
{
"created": "Thu, 5 Mar 2015 01:24:51 GMT",
"version": "v1"
},
{
"created": "Wed, 13 May 2015 21:17:03 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Apr 2016 19:00:58 GMT",
"version": "v3"
}
] | 2016-04-20 | [
[
"Anderson",
"Edward",
""
]
] | I consider configuration spaces for $N$-body problems, gauge theories and for GR in both geometrodynamical and Ashtekar variables forms, including minisuperspace and inhomogeneous perturbations thereabout in the former case. These examples include many interesting spaces of shapes (with and without whichever of local or global notions of scale). In considering reduced configuration spaces, stratified manifolds arise. Three strategies to deal with these are `excise', `unfold' and `accept'. I show that spaces of triangles arising from various interpretations of 3-body problems already serve as model arena for all three. I furthermore argue in favour of the `accept' strategy on relational grounds. This approach requires sheaf methods (which go beyond fibre bundles and general bundles, which I contrast with sheaves and presheaves in some appendices). Sheaf methods are also required for the stratifold construct that pairs some well-behaved stratified manifolds with sheaves. I apply arguing against `excise' and `unfold' to GR's superspace and thin sandwich, and to the removal of collinear configurations in mechanics. Non-redundant configurations are also useful in providing more accurate names for various spaces and theories. |
1408.1798 | Andronikos Paliathanasis | Andronikos Paliathanasis and Michael Tsamparlis | Two scalar field cosmology: Conservation laws and exact solutions | 17 pages, to be published in Phys. Rev. D | Phys. Rev. D 90, 043529 (2014) | 10.1103/PhysRevD.90.043529 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the two scalar field cosmology in a FRW spatially flat spacetime
where the scalar fields interact both in the kinetic part and the potential. We
apply the Noether point symmetries in order to define the interaction of the
scalar fields. We use the point symmetries in order to write the field
equations in the normal coordinates and we find that the Lagrangian of the
field equations which admits at least three Noether point symmetries describes
linear Newtonian systems. Furthermore, by using the corresponding conservation
laws we find exact solutions of the field equations. Finally, we generalize our
results to the case of N scalar fields interacting both in their potential and
their kinematic part in a flat FRW background.
| [
{
"created": "Fri, 8 Aug 2014 09:43:15 GMT",
"version": "v1"
}
] | 2014-09-09 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Tsamparlis",
"Michael",
""
]
] | We consider the two scalar field cosmology in a FRW spatially flat spacetime where the scalar fields interact both in the kinetic part and the potential. We apply the Noether point symmetries in order to define the interaction of the scalar fields. We use the point symmetries in order to write the field equations in the normal coordinates and we find that the Lagrangian of the field equations which admits at least three Noether point symmetries describes linear Newtonian systems. Furthermore, by using the corresponding conservation laws we find exact solutions of the field equations. Finally, we generalize our results to the case of N scalar fields interacting both in their potential and their kinematic part in a flat FRW background. |
1410.3023 | Massimo Tinto | Massimo Tinto, Jose C. N. de Araujo, Helio K. Kuga, Marcio E. S.
Alves, Odylio D. Aguiar | Orbit analysis of a geostationary gravitational wave interferometer
detector array | In This article we analyze the trajectories of three geostationary
satellites forming a gravitational wave interferometer. The article is 16
pages long and contains 5 figures | null | 10.1088/0264-9381/32/18/185017 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the trajectories of three geostationary satellites forming the
GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\cite{tinto}, a
space-based laser interferometer mission aiming to detect and study
gravitational radiation in the ($10^{-4} - 10$) Hz band.
The combined effects of the gravity fields of the Earth, the Sun and the Moon
make the three satellites deviate from their nominally stationary, equatorial
and equilateral configuration. Since changes in the satellites relative
distances and orientations could negatively affect the precision of the laser
heterodyne measurements, we have derived the time-dependence of the
inter-satellite distances and velocities, the variations of the polar angles
made by the constellation's three arms with respect to a chosen reference
frame, and the time changes of the triangle's enclosed angles. We find that,
during the time between two consecutive station-keeping maneuvers (about two
weeks), the relative variations of the inter-satellite distances do not exceed
a value of $0.05$ percent, while the relative velocities between pairs of
satellites remain smaller than about $0.7 \ {\rm m/s}$. In addition, we find
the angles made by the arms of the triangle with the equatorial plane to be
periodic functions of time whose amplitudes grow linearly with time; the
maximum variations experienced by these angles as well as by those within the
triangle remain smaller than $3$ arc-minutes, while the East-West angular
variations of the three arms remain smaller than about $15$ arc-minutes during
the two-weeks period. The relatively small variations of these orbit parameters
result into a set of system functional and performance requirements that are
less stringent than those characterizing an interplanetary mission.
| [
{
"created": "Sat, 11 Oct 2014 19:32:27 GMT",
"version": "v1"
}
] | 2015-09-23 | [
[
"Tinto",
"Massimo",
""
],
[
"de Araujo",
"Jose C. N.",
""
],
[
"Kuga",
"Helio K.",
""
],
[
"Alves",
"Marcio E. S.",
""
],
[
"Aguiar",
"Odylio D.",
""
]
] | We analyze the trajectories of three geostationary satellites forming the GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\cite{tinto}, a space-based laser interferometer mission aiming to detect and study gravitational radiation in the ($10^{-4} - 10$) Hz band. The combined effects of the gravity fields of the Earth, the Sun and the Moon make the three satellites deviate from their nominally stationary, equatorial and equilateral configuration. Since changes in the satellites relative distances and orientations could negatively affect the precision of the laser heterodyne measurements, we have derived the time-dependence of the inter-satellite distances and velocities, the variations of the polar angles made by the constellation's three arms with respect to a chosen reference frame, and the time changes of the triangle's enclosed angles. We find that, during the time between two consecutive station-keeping maneuvers (about two weeks), the relative variations of the inter-satellite distances do not exceed a value of $0.05$ percent, while the relative velocities between pairs of satellites remain smaller than about $0.7 \ {\rm m/s}$. In addition, we find the angles made by the arms of the triangle with the equatorial plane to be periodic functions of time whose amplitudes grow linearly with time; the maximum variations experienced by these angles as well as by those within the triangle remain smaller than $3$ arc-minutes, while the East-West angular variations of the three arms remain smaller than about $15$ arc-minutes during the two-weeks period. The relatively small variations of these orbit parameters result into a set of system functional and performance requirements that are less stringent than those characterizing an interplanetary mission. |
1911.04949 | Plamen Fiziev | Plamen P. Fiziev | The Era of Gravitational Astronomy and Gravitational Field of
Non-Rotating Single Point Particle in General Relativity | 35 pages, 1 figure, corrections with respect to journal publication
in some formulas in Section IV are made. arXiv admin note: substantial text
overlap with arXiv:gr-qc/0306088 | Physycs or Particles and Nuclei, Vol. 50 (6), pp. 944-972 (2019) | null | SU-2019 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Utilizing various gauges of the radial coordinate, we give a General
Relativistic (GR) description of static spherically symmetric spacetimes with a
massive point source and vacuum outside this singularity. We show that in GR
there exists a two-parameter family of such solutions to the Einstein equations
which are physically distinguishable and describe the gravitational field of a
single massive point particle with positive proper mass $M_0$ and positive
Keplerian mass $M<M_0$. In particular, we show that the widespread Hilbert form
of the Schwarzschild solution, which depends only on the Keplerian mass $M$ and
describes Black Holes (BH), does not solve the Einstein equations with a
massive point particle stress-energy tensor. Novel normal coordinates for the
gravitational field and a new physical class of gauges are proposed, thus
achieving a correct description of a point mass source in GR. We also introduce
a gravitational mass defect of a point particle and determine the dependence of
the solutions on this mass defect. The result can be described as a change of
the Newton potential $\varphi_{\!{}_N}=-G_{\!{}_N}M/r$ to a modified one
$\varphi_{\!{}_G}=-G_{\!{}_N}M/ \left(r+G_{\!{}_N} M/c^2\ln{{M_0}\over
M}\right)$ and the corresponding modification of the four-interval. We show
that the proper 3D flat space, where these two potentials can be compared, is
the tangent space above the position of the massive point source. In addition,
we present invariant characteristics of the physically and geometrically
different classes of spherically symmetric static spacetimes created by a point
mass. Our findings are important for description of Extremely Compact Objects
(ECOs) studied in relation with possible echoes in Gravitational Waves (GW)
recently discovered by the LIGO/VIRGO collaboration. %
| [
{
"created": "Mon, 11 Nov 2019 07:59:40 GMT",
"version": "v1"
}
] | 2019-11-13 | [
[
"Fiziev",
"Plamen P.",
""
]
] | Utilizing various gauges of the radial coordinate, we give a General Relativistic (GR) description of static spherically symmetric spacetimes with a massive point source and vacuum outside this singularity. We show that in GR there exists a two-parameter family of such solutions to the Einstein equations which are physically distinguishable and describe the gravitational field of a single massive point particle with positive proper mass $M_0$ and positive Keplerian mass $M<M_0$. In particular, we show that the widespread Hilbert form of the Schwarzschild solution, which depends only on the Keplerian mass $M$ and describes Black Holes (BH), does not solve the Einstein equations with a massive point particle stress-energy tensor. Novel normal coordinates for the gravitational field and a new physical class of gauges are proposed, thus achieving a correct description of a point mass source in GR. We also introduce a gravitational mass defect of a point particle and determine the dependence of the solutions on this mass defect. The result can be described as a change of the Newton potential $\varphi_{\!{}_N}=-G_{\!{}_N}M/r$ to a modified one $\varphi_{\!{}_G}=-G_{\!{}_N}M/ \left(r+G_{\!{}_N} M/c^2\ln{{M_0}\over M}\right)$ and the corresponding modification of the four-interval. We show that the proper 3D flat space, where these two potentials can be compared, is the tangent space above the position of the massive point source. In addition, we present invariant characteristics of the physically and geometrically different classes of spherically symmetric static spacetimes created by a point mass. Our findings are important for description of Extremely Compact Objects (ECOs) studied in relation with possible echoes in Gravitational Waves (GW) recently discovered by the LIGO/VIRGO collaboration. % |
2111.07835 | Claus Kiefer | Claus Kiefer and Tatevik Vardanyan | Power spectrum for perturbations in an inflationary model for a closed
universe | 20 pages, 1 figure, Invited contribution to a Topical Collection in
memory of Prof. T. Padmanabhan, final version | General Relativity and Gravitation 54, article number: 30 (2022) | 10.1007/s10714-022-02918-3 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the power spectrum of primordial quantum fluctuations in an
inflationary universe for curvature parameter ${\mathcal K}=1$. This is
achieved through a Born--Oppenheimer type of approximation scheme from the
Wheeler--DeWitt equation of canonical quantum gravity using gauge-invariant
variables. Compared to the flat model, the closed model exhibits a deficit of
power at large scales.
| [
{
"created": "Mon, 15 Nov 2021 15:22:58 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Apr 2022 07:33:02 GMT",
"version": "v2"
}
] | 2022-04-05 | [
[
"Kiefer",
"Claus",
""
],
[
"Vardanyan",
"Tatevik",
""
]
] | We derive the power spectrum of primordial quantum fluctuations in an inflationary universe for curvature parameter ${\mathcal K}=1$. This is achieved through a Born--Oppenheimer type of approximation scheme from the Wheeler--DeWitt equation of canonical quantum gravity using gauge-invariant variables. Compared to the flat model, the closed model exhibits a deficit of power at large scales. |
1909.04995 | Wei-Tou Ni | Wei-Tou Ni, Gang Wang and An-Ming Wu | Astrodynamical middle-frequency interferometric gravitational wave
observatory AMIGO: Mission concept and orbit design | 29 pages, 21 figures, 6 tables. arXiv admin note: text overlap with
arXiv:1709.05659 | International Journal of Modern Physics D 29 (2020) 1940007 (32
pages) | 10.1142/S0218271819400078 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | AMIGO is a first-generation Astrodynamical Middle-frequency Interferometric
GW Observatory. The scientific goals of AMIGO are: to bridge the spectra gap
between first-generation high-frequency and low-frequency GW sensitivities; to
detect intermediate mass BH coalescence; to detect inspiral phase and predict
time of binary black hole coalescence together with neutron star coalescence
for ground interferometers; to detect compact binary inspirals for studying
stellar evolution and galactic population. The mission concept is to use time
delay interferometry for a nearly triangular formation of 3 drag-free
spacecraft with nominal arm length 10,000 km, emitting laser power 2-10 W and
telescope diameter 300-500 mm. The design GW sensitivity in the middle
frequency band is 3 x 10^(-21) Hz^(-1/2). Both heliocentric and geocentric
orbits are under study. All options have LISA-like formations, that is the
triangular formation is 60 deg inclined to the orbit plane. For AMIGO, the
first-generation time delay interferometry is good enough for the laser
frequency noise suppression. We also investigate for each options of orbits
under study, whether constant equal-arm implementation is feasible. For the
solar-orbit option, the acceleration to maintain the formation can be designed
to be less than 15 nm/s2 with the thruster requirement in the 15 {\mu}N range.
AMIGO would be a good place to implement the constant equal-arm option. Fuel
requirement, thruster noise requirement and test mass acceleration actuation
requirement are briefly considered. From the orbit study, the solar orbit
option is the first mission orbit choice. We study the deployment for this
orbit option. A last-stage launch from 300 km LEO (Low Earth Orbit) to an
appropriate 2-degree-behind-the-Earth AMIGO formation in 95 days requires only
a {\delta}v of 75 m/s.
| [
{
"created": "Wed, 11 Sep 2019 12:12:57 GMT",
"version": "v1"
}
] | 2020-07-14 | [
[
"Ni",
"Wei-Tou",
""
],
[
"Wang",
"Gang",
""
],
[
"Wu",
"An-Ming",
""
]
] | AMIGO is a first-generation Astrodynamical Middle-frequency Interferometric GW Observatory. The scientific goals of AMIGO are: to bridge the spectra gap between first-generation high-frequency and low-frequency GW sensitivities; to detect intermediate mass BH coalescence; to detect inspiral phase and predict time of binary black hole coalescence together with neutron star coalescence for ground interferometers; to detect compact binary inspirals for studying stellar evolution and galactic population. The mission concept is to use time delay interferometry for a nearly triangular formation of 3 drag-free spacecraft with nominal arm length 10,000 km, emitting laser power 2-10 W and telescope diameter 300-500 mm. The design GW sensitivity in the middle frequency band is 3 x 10^(-21) Hz^(-1/2). Both heliocentric and geocentric orbits are under study. All options have LISA-like formations, that is the triangular formation is 60 deg inclined to the orbit plane. For AMIGO, the first-generation time delay interferometry is good enough for the laser frequency noise suppression. We also investigate for each options of orbits under study, whether constant equal-arm implementation is feasible. For the solar-orbit option, the acceleration to maintain the formation can be designed to be less than 15 nm/s2 with the thruster requirement in the 15 {\mu}N range. AMIGO would be a good place to implement the constant equal-arm option. Fuel requirement, thruster noise requirement and test mass acceleration actuation requirement are briefly considered. From the orbit study, the solar orbit option is the first mission orbit choice. We study the deployment for this orbit option. A last-stage launch from 300 km LEO (Low Earth Orbit) to an appropriate 2-degree-behind-the-Earth AMIGO formation in 95 days requires only a {\delta}v of 75 m/s. |
0712.2359 | Katarzyna Ostasiewicz | A. Radosz, A. T. Augousti, K. Ostasiewicz | Decoupling of kinematical time dilation and gravitational time dilation
in particular geometries | 4 pages | ActaPhys.Polon.B39:1357-1362,2008 | null | null | gr-qc | null | Two different forms of time dilation, namely, the kinematical time dilation
of special relativity and gravitational red shift are coupled during
observations of systems moving through a gravitational field. In the particular
situation of free fall in a Schwarzschild geometry these two effects are
decoupled and in consequence the time dilation, as observed by a distant
observer, factorises. Such a factorization is not a universal feature. We
define here a necessary and sufficient criterion for time dilation and
gravitational red-shift decoupling. This property is manifested in a particular
form of the Doppler shift in Schwarzschild geometry.
| [
{
"created": "Fri, 14 Dec 2007 14:27:49 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Radosz",
"A.",
""
],
[
"Augousti",
"A. T.",
""
],
[
"Ostasiewicz",
"K.",
""
]
] | Two different forms of time dilation, namely, the kinematical time dilation of special relativity and gravitational red shift are coupled during observations of systems moving through a gravitational field. In the particular situation of free fall in a Schwarzschild geometry these two effects are decoupled and in consequence the time dilation, as observed by a distant observer, factorises. Such a factorization is not a universal feature. We define here a necessary and sufficient criterion for time dilation and gravitational red-shift decoupling. This property is manifested in a particular form of the Doppler shift in Schwarzschild geometry. |
2011.11838 | Andrea Giusti | Bardia H. Fahim, Valerio Faraoni, and Andrea Giusti | Brans-Dicke analogue of the Roberts geometry | 6 pages, no figures. Title changed. Updated to match the published
version | Phys. Rev. D 103, 084004 (2021) | 10.1103/PhysRevD.103.084004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report a new one-parameter family of spherically symmetric, inhomogeneous,
and time-dependent solutions of the vacuum Brans-Dicke field equations which
are conformal to the Roberts scalar field geometries of Einstein gravity. The
new solution is spherical and time-dependent and contains a naked central
singularity. We use it as a seed to generate another two-parameter family of
solutions using a known symmetry of vacuum Brans-Dicke gravity.
| [
{
"created": "Tue, 24 Nov 2020 02:13:35 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Apr 2021 11:11:17 GMT",
"version": "v2"
}
] | 2021-04-12 | [
[
"Fahim",
"Bardia H.",
""
],
[
"Faraoni",
"Valerio",
""
],
[
"Giusti",
"Andrea",
""
]
] | We report a new one-parameter family of spherically symmetric, inhomogeneous, and time-dependent solutions of the vacuum Brans-Dicke field equations which are conformal to the Roberts scalar field geometries of Einstein gravity. The new solution is spherical and time-dependent and contains a naked central singularity. We use it as a seed to generate another two-parameter family of solutions using a known symmetry of vacuum Brans-Dicke gravity. |
2107.00741 | Rohit Subbarayan Chandramouli | Rohit S. Chandramouli, Nicol\'as Yunes | Ready-to-use analytic model for gravitational waves from a hierarchical
triple with Kozai-Lidov oscillations | 30 pages, 13 figures | null | 10.1103/PhysRevD.105.064009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves emitted by inner binaries in hierarchical triple systems
are interesting astrophysical candidates for space-based detectors like the
Laser Interferometer Space Antenna, LISA. In the presence of a third body, such
as a supermassive black hole, an inner binary consisting of intermediate mass
black holes can undergo oscillations in eccentricity and inclination angle due
to the Kozai-Lidov mechanism. In this work, we construct analytic gravitational
waveforms in the Fourier domain, taking into account the Kozai-Lidov effect at
Newtonian (leading) order. Using multiple-scale analysis, we make use of the
separability of timescales to combine the effects of both Kozai-Lidov
oscillations and radiation-reaction. We assume small eccentricity and present
analytic solutions to the evolution of the other orbital elements. Our analytic
calculation can be systematically extended to higher orders in eccentricity,
and can be used to construct inspiral-merger-ringdown models. The imprint on
the waveform, due to this combined evolution, is computed under the
stationary-phase approximation. We find that the oscillations leave a clear
signature on the Fourier amplitude of the waveform while leaving a measurable
imprint on the gravitational wave phase, and that our analytic results are
consistent with numerics. Further, with our study of the astrophysical
parameters of the hierarchical triple, we outline potential source candidates,
along with potential implications for gravitational wave data analysis.
| [
{
"created": "Thu, 1 Jul 2021 20:46:48 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Aug 2021 15:22:20 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Dec 2021 20:58:20 GMT",
"version": "v3"
},
{
"created": "Wed, 9 Mar 2022 02:11:23 GMT",
"version": "v4"
}
] | 2022-03-10 | [
[
"Chandramouli",
"Rohit S.",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Gravitational waves emitted by inner binaries in hierarchical triple systems are interesting astrophysical candidates for space-based detectors like the Laser Interferometer Space Antenna, LISA. In the presence of a third body, such as a supermassive black hole, an inner binary consisting of intermediate mass black holes can undergo oscillations in eccentricity and inclination angle due to the Kozai-Lidov mechanism. In this work, we construct analytic gravitational waveforms in the Fourier domain, taking into account the Kozai-Lidov effect at Newtonian (leading) order. Using multiple-scale analysis, we make use of the separability of timescales to combine the effects of both Kozai-Lidov oscillations and radiation-reaction. We assume small eccentricity and present analytic solutions to the evolution of the other orbital elements. Our analytic calculation can be systematically extended to higher orders in eccentricity, and can be used to construct inspiral-merger-ringdown models. The imprint on the waveform, due to this combined evolution, is computed under the stationary-phase approximation. We find that the oscillations leave a clear signature on the Fourier amplitude of the waveform while leaving a measurable imprint on the gravitational wave phase, and that our analytic results are consistent with numerics. Further, with our study of the astrophysical parameters of the hierarchical triple, we outline potential source candidates, along with potential implications for gravitational wave data analysis. |
1207.0115 | Norman Metzner | Norman Metzner | Twistor Theory of Higher-Dimensional Black Holes | DPhil Thesis (University of Oxford, submitted February 2012), 119
pages, 15 figures | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The correspondence of stationary, axisymmetric, asymptotically flat
space-times and bundles over a reduced twistor space has been established in
four dimensions. The main impediment for an application of this correspondence
to examples in higher dimensions is the lack of a higher-dimensional equivalent
of the Ernst potential. This thesis will propose such a generalized Ernst
potential, point out where the rod structure of the space-time can be found in
the twistor picture and thereby provide a procedure for generating solutions to
the Einstein field equations in higher dimensions from the rod structure, other
asymptotic data, and the requirement of a regular axis. Examples in five
dimensions are studied and necessary tools are developed, in particular rules
for the transition between different adaptations of the patching matrix and
rules for the elimination of conical singularities.
| [
{
"created": "Sat, 30 Jun 2012 16:32:02 GMT",
"version": "v1"
}
] | 2012-07-03 | [
[
"Metzner",
"Norman",
""
]
] | The correspondence of stationary, axisymmetric, asymptotically flat space-times and bundles over a reduced twistor space has been established in four dimensions. The main impediment for an application of this correspondence to examples in higher dimensions is the lack of a higher-dimensional equivalent of the Ernst potential. This thesis will propose such a generalized Ernst potential, point out where the rod structure of the space-time can be found in the twistor picture and thereby provide a procedure for generating solutions to the Einstein field equations in higher dimensions from the rod structure, other asymptotic data, and the requirement of a regular axis. Examples in five dimensions are studied and necessary tools are developed, in particular rules for the transition between different adaptations of the patching matrix and rules for the elimination of conical singularities. |
1406.5112 | Thomas Linz | Thomas M. Linz, John L. Friedman, Alan G. Wiseman | Combined gravitational and electromagnetic self-force on charged
particles in electrovac spacetimes | Submitted to Phys Rev. D | Phys. Rev. D 90, 084031 (2014) | 10.1103/PhysRevD.90.084031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the self-force on a charged particle moving in a curved spacetime
with a background electromagnetic field, extending previous studies to
situations in which gravitational and electromagnetic perturbations are
comparable. The formal expression $f^{ret}_\alpha$ for the self-force on a
particle, written in terms of the retarded perturbed fields, is divergent, and
a renormalization is needed to find the particle's acceleration at linear order
in its mass $m$ and charge $e$. We assume that, as in previous work in a Lorenz
gauge, the renormalization for accelerated motion comprises an angle average
and mass renormalization. Using the short distance expansion of the perturbed
electromagnetic and gravitational fields, we show that the renormalization is
equivalent to that obtained from a mode sum regularization in which one
subtracts from the expression for the self-force in terms of the retarded
fields a singular part field comprising only the leading and subleading terms
in the mode sum. The most striking part of our result, arising from a
remarkable cancellation, is that the renormalization involves no mixing of
electromagnetic and gravitational fields. In particular, the renormalized mass
is obtained by subtracting (1) the purely electromagnetic contribution from a
point charge moving along an accelerated trajectory and (2) the purely
gravitational contribution from a point mass moving along the same trajectory.
In a mode-sum regularization, the same cancellation implies that the required
regularization parameters are sums of their purely electromagnetic and
gravitational values.
| [
{
"created": "Thu, 19 Jun 2014 17:00:12 GMT",
"version": "v1"
}
] | 2014-10-22 | [
[
"Linz",
"Thomas M.",
""
],
[
"Friedman",
"John L.",
""
],
[
"Wiseman",
"Alan G.",
""
]
] | We consider the self-force on a charged particle moving in a curved spacetime with a background electromagnetic field, extending previous studies to situations in which gravitational and electromagnetic perturbations are comparable. The formal expression $f^{ret}_\alpha$ for the self-force on a particle, written in terms of the retarded perturbed fields, is divergent, and a renormalization is needed to find the particle's acceleration at linear order in its mass $m$ and charge $e$. We assume that, as in previous work in a Lorenz gauge, the renormalization for accelerated motion comprises an angle average and mass renormalization. Using the short distance expansion of the perturbed electromagnetic and gravitational fields, we show that the renormalization is equivalent to that obtained from a mode sum regularization in which one subtracts from the expression for the self-force in terms of the retarded fields a singular part field comprising only the leading and subleading terms in the mode sum. The most striking part of our result, arising from a remarkable cancellation, is that the renormalization involves no mixing of electromagnetic and gravitational fields. In particular, the renormalized mass is obtained by subtracting (1) the purely electromagnetic contribution from a point charge moving along an accelerated trajectory and (2) the purely gravitational contribution from a point mass moving along the same trajectory. In a mode-sum regularization, the same cancellation implies that the required regularization parameters are sums of their purely electromagnetic and gravitational values. |
1508.03247 | Wenliang Li | Wenliang Li | A unifying framework for ghost-free Lorentz-invariant Lagrangian field
theories | 8 pages, two columns, final version | null | 10.1016/j.physletb.2017.06.073 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a framework for Lorentz-invariant Lagrangian field theories where
Ostrogradsky's scalar ghosts could be absent. A key ingredient is the
generalized Kronecker delta. The general Lagrangians are reformulated in the
language of differential forms. The absence of higher order equations of motion
for the scalar modes stems from the basic fact that every exact form is closed.
The well-established Lagrangian theories for spin-0, spin-1, p-form, spin-2
fields have natural formulations in this framework. We also propose novel
building blocks for Lagrangian field theories. Some of them are novel nonlinear
derivative terms for spin-2 fields. It is nontrivial that Ostrogradsky's scalar
ghosts are absent in these fully nonlinear theories.
| [
{
"created": "Thu, 13 Aug 2015 15:22:40 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2015 15:47:39 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Feb 2018 08:06:21 GMT",
"version": "v3"
}
] | 2018-02-27 | [
[
"Li",
"Wenliang",
""
]
] | We propose a framework for Lorentz-invariant Lagrangian field theories where Ostrogradsky's scalar ghosts could be absent. A key ingredient is the generalized Kronecker delta. The general Lagrangians are reformulated in the language of differential forms. The absence of higher order equations of motion for the scalar modes stems from the basic fact that every exact form is closed. The well-established Lagrangian theories for spin-0, spin-1, p-form, spin-2 fields have natural formulations in this framework. We also propose novel building blocks for Lagrangian field theories. Some of them are novel nonlinear derivative terms for spin-2 fields. It is nontrivial that Ostrogradsky's scalar ghosts are absent in these fully nonlinear theories. |
gr-qc/9210014 | Robert Brandenberger | Robert H. Brandenberger | A Nonsingular Universe | 11 pages, 2 figures (available from the author), uses phyzzx | null | null | Brown University, BROWN-HET-876 | gr-qc astro-ph hep-th | null | We construct an effective action for gravity in which all homogeneous
solutions are nonsingular. In particular, there is neither a big bang nor a big
crunch. The action is a higher derivative modification of Einstein's theory
constructed in analogy to how the action for point particle motion in special
relativity is obtained from Newtonian mechanics.
| [
{
"created": "Sat, 24 Oct 1992 19:41:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brandenberger",
"Robert H.",
""
]
] | We construct an effective action for gravity in which all homogeneous solutions are nonsingular. In particular, there is neither a big bang nor a big crunch. The action is a higher derivative modification of Einstein's theory constructed in analogy to how the action for point particle motion in special relativity is obtained from Newtonian mechanics. |
2404.14742 | Seoktae Koh | Peter K. S. Dunsby, Seoktae Koh, Abbas M. Sherif | Causal dynamics of null horizons under linear perturbations | 18 pages, no figures, all comments are welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the causal dynamics of an embedded null horizon foliated by
marginally outer trapped surfaces (MOTS) for a locally rotationally symmetric
background spacetime subjected to linear perturbations. We introduce a simple
procedure which characterizes the transition of the causal character of the
null horizon. We apply our characterization scheme to non-dissipative
perturbations of the Schwarzschild and spatially homogeneous backgrounds. For
the latter, a linear equation of state was imposed. Assuming a harmonic
decomposition of the linearized field equations, we clarify the variables of a
formal solution to the linearized system that determine how the null horizon
evolves. For both classes of backgrounds, the shear and vorticity 2-vectors are
essential to the characterization, and their roles are made precise. Finally,
we discuss aspects of the relationship between the characterizing conditions.
Various properties related to the self-adjointness of the MOTS stability
operator are extensively discussed.
| [
{
"created": "Tue, 23 Apr 2024 04:50:53 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Dunsby",
"Peter K. S.",
""
],
[
"Koh",
"Seoktae",
""
],
[
"Sherif",
"Abbas M.",
""
]
] | We study the causal dynamics of an embedded null horizon foliated by marginally outer trapped surfaces (MOTS) for a locally rotationally symmetric background spacetime subjected to linear perturbations. We introduce a simple procedure which characterizes the transition of the causal character of the null horizon. We apply our characterization scheme to non-dissipative perturbations of the Schwarzschild and spatially homogeneous backgrounds. For the latter, a linear equation of state was imposed. Assuming a harmonic decomposition of the linearized field equations, we clarify the variables of a formal solution to the linearized system that determine how the null horizon evolves. For both classes of backgrounds, the shear and vorticity 2-vectors are essential to the characterization, and their roles are made precise. Finally, we discuss aspects of the relationship between the characterizing conditions. Various properties related to the self-adjointness of the MOTS stability operator are extensively discussed. |
1004.5337 | Sergei Maydanyuk | Sergei P. Maydanyuk | Quantum method of determination of penetrability in FRW model with
radiation | 6 pages, Talk in the Humboldt-Kolleg "Humboldt Cosmos: Science and
Society", HCS2-Kiev2009 (Kiev, Ukraine, 19-22 of November, 2009) | Bullettin Univ. Kyiv. Ser.: Phys. Math. 3 (2010), 6p | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In paper the closed Friedmann-Robertson-Walker model with quantization in
presence of the positive cosmological constant, radiation and Chaplygin gas is
studied. For analysis of tunneling probability for birth of an asymptotically
deSitter, inflationary Universe as a function of the radiation energy a new
definition of a "free" wave propagating inside strong fields is introduced.
Vilenkin's tunneling boundary condition is corrected, penetrability and
reflection are calculated in fully quantum stationary approach.
| [
{
"created": "Thu, 29 Apr 2010 16:38:19 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jul 2014 09:18:19 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Maydanyuk",
"Sergei P.",
""
]
] | In paper the closed Friedmann-Robertson-Walker model with quantization in presence of the positive cosmological constant, radiation and Chaplygin gas is studied. For analysis of tunneling probability for birth of an asymptotically deSitter, inflationary Universe as a function of the radiation energy a new definition of a "free" wave propagating inside strong fields is introduced. Vilenkin's tunneling boundary condition is corrected, penetrability and reflection are calculated in fully quantum stationary approach. |
1509.01833 | Martin Bojowald | Martin Bojowald | (Loop) quantum gravity and the inflationary scenario | 10 pages, 1 figure, invited contribution to a special issue published
by the French Academy of Sciences | Comptes Rendus - Physique 16 (2015) 1012-1017 | 10.1016/j.crhy.2015.08.007 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity, as a fundamental theory of space-time, is expected to reveal
how the universe may have started, perhaps during or before an inflationary
epoch. It may then leave a potentially observable (but probably minuscule)
trace in cosmic large-scale structures that seem to match well with predictions
of inflation models. A systematic quest to derive such tiny effects using one
approach, loop quantum gravity, has, however, led to unexpected obstacles. Such
models remain incomplete, and it is not clear whether loop quantum gravity can
be consistent as a full theory. But some surprising effects appear to be
generic and would drastically alter our understanding of space-time at large
density. These new high-curvature phenomena are a consequence of a widening gap
between quantum gravity and ordinary quantum-field theory on a background.
| [
{
"created": "Sun, 6 Sep 2015 17:11:59 GMT",
"version": "v1"
}
] | 2015-12-17 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum gravity, as a fundamental theory of space-time, is expected to reveal how the universe may have started, perhaps during or before an inflationary epoch. It may then leave a potentially observable (but probably minuscule) trace in cosmic large-scale structures that seem to match well with predictions of inflation models. A systematic quest to derive such tiny effects using one approach, loop quantum gravity, has, however, led to unexpected obstacles. Such models remain incomplete, and it is not clear whether loop quantum gravity can be consistent as a full theory. But some surprising effects appear to be generic and would drastically alter our understanding of space-time at large density. These new high-curvature phenomena are a consequence of a widening gap between quantum gravity and ordinary quantum-field theory on a background. |
gr-qc/0503021 | Slava G. Turyshev | Slava G. Turyshev, Michael Martin Nieto, and John D. Anderson | A Route to Understanding of the Pioneer Anomaly | 9 pages, 5 figures. Invited talk given at ``The XXII Texas Symposium
on Relativistic Astrophysics,'' Stanford University, December 13-17, 2004 | `The XXII Texas Symposium on Relativistic Astrophysics,'' Stanford
U, December 13-17, 2004, edited by P. Chen, E. Bloom, G. Madejski, and V.
Petrosian. SLAC-R-752, Stanford e-Conf #C041213, paper #0310 | null | LA-UR-05-1570 | gr-qc | null | The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep
space to date. However, while at heliocentric distance of $\sim$ 20--70 AU, the
accuracies of their orbit reconstructions were limited by a small, anomalous,
Doppler frequency drift. This drift can be interpreted as a sunward constant
acceleration of $a_P = (8.74 \pm 1.33)\times 10^{-8}$ cm/s$^2$ which is now
commonly known as the Pioneer anomaly. Here we discuss the Pioneer anomaly and
present the next steps towards understanding of its origin. They are: 1)
Analysis of the entire set of existing Pioneer 10 and 11 data, obtained from
launch to the last telemetry received from Pioneer 10, on 27 April 2002, when
it was at a heliocentric distance of 80 AU. This data could yield critical new
information about the anomaly. If the anomaly is confirmed, 2) Development of
an instrumental package to be operated on a deep space mission to provide an
independent confirmation on the anomaly. If further confirmed, 3) Development
of a deep-space experiment to explore the Pioneer anomaly in a dedicated
mission with an accuracy for acceleration resolution at the level of $10^{-10}$
cm/s$^2$ in the extremely low frequency range. In Appendices we give a summary
of the Pioneer anomaly's characteristics, outline in more detail the steps
needed to perform an analysis of the entire Pioneer data set, and also discuss
the possibility of extracting some useful information from the Cassini mission
cruise data.
| [
{
"created": "Fri, 4 Mar 2005 21:28:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Nieto",
"Michael Martin",
""
],
[
"Anderson",
"John D.",
""
]
] | The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep space to date. However, while at heliocentric distance of $\sim$ 20--70 AU, the accuracies of their orbit reconstructions were limited by a small, anomalous, Doppler frequency drift. This drift can be interpreted as a sunward constant acceleration of $a_P = (8.74 \pm 1.33)\times 10^{-8}$ cm/s$^2$ which is now commonly known as the Pioneer anomaly. Here we discuss the Pioneer anomaly and present the next steps towards understanding of its origin. They are: 1) Analysis of the entire set of existing Pioneer 10 and 11 data, obtained from launch to the last telemetry received from Pioneer 10, on 27 April 2002, when it was at a heliocentric distance of 80 AU. This data could yield critical new information about the anomaly. If the anomaly is confirmed, 2) Development of an instrumental package to be operated on a deep space mission to provide an independent confirmation on the anomaly. If further confirmed, 3) Development of a deep-space experiment to explore the Pioneer anomaly in a dedicated mission with an accuracy for acceleration resolution at the level of $10^{-10}$ cm/s$^2$ in the extremely low frequency range. In Appendices we give a summary of the Pioneer anomaly's characteristics, outline in more detail the steps needed to perform an analysis of the entire Pioneer data set, and also discuss the possibility of extracting some useful information from the Cassini mission cruise data. |
1806.05728 | Ceren Bayraktar | Ceren H. Bayraktar | Thermodynamics of regular black holes with cosmic strings | Accepted for publication in EPJ Plus, 6 pages | Eur. Phys. J. Plus (2018) 133: 377 | 10.1140/epjp/i2018-12216-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, the thermodynamics of regular black holes with a cosmic
string passing through it is studied. We will observe that the string has no
effect on the temperature as well as the relation between entropy S and horizon
area A.
| [
{
"created": "Thu, 14 Jun 2018 20:23:25 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jun 2018 15:45:12 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Aug 2018 19:11:14 GMT",
"version": "v3"
}
] | 2018-09-20 | [
[
"Bayraktar",
"Ceren H.",
""
]
] | In this article, the thermodynamics of regular black holes with a cosmic string passing through it is studied. We will observe that the string has no effect on the temperature as well as the relation between entropy S and horizon area A. |
2304.12601 | Celia Escamilla-Rivera | Jos\'e Antonio N\'ajera, Carlos Ar\'aoz Alvarado and Celia
Escamilla-Rivera | Constraints on $f(Q)$ logarithmic model using gravitational wave
standard sirens | 17 pages, 3 figures. Version accepted in MNRAS | Monthly Notices of the Royal Astronomical Society, Volume 524,
Issue 4, October 2023, Pages 5280-5290 | 10.1093/mnras/stad2180 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the constraints on the $f(Q)=Q/(8\pi G) - \alpha
\ln(Q/Q_0)$, symmetric teleparallel model using local measurements and
gravitational wave mock standard sirens. Using observational local SNIa and BAO
data and energy conditions, the logarithmic $f(Q)$ model is capable of
explaining the cosmic late-time acceleration by geometrical means. This result
suggests that the logarithmic symmetric teleparallel model could be a candidate
to solve the cosmological constant problem. In the case of the simulated
standard siren data, by using the performance of the future ET and LISA
detectors, we expect to be able to measure the current Hubble constant $H_0$,
and the matter content $\Omega_m$, with a precision better than 1\% and 6\%,
respectively. Furthermore, we explore the predicted $f(Q)$ logarithmic model
deviation from the standard GR using ET and LISA mock standard sirens. The
ratio $d_L^{\text{gw}}(z)/d_L^{\text{em}}(z)$, which quantifies the deviation
from GR gives us a significant deviation higher than 13\% at $z=1$, and it
continues growing to reach a deviation higher than 18\% in its median value.
Future standard siren data will be able to quantify the strength of the
deviation from GR and hence whether a cosmology like the one implied by this
$f(Q)$ model is feasible.
| [
{
"created": "Tue, 25 Apr 2023 06:18:52 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jul 2023 03:29:53 GMT",
"version": "v2"
}
] | 2023-08-14 | [
[
"Nájera",
"José Antonio",
""
],
[
"Alvarado",
"Carlos Aráoz",
""
],
[
"Escamilla-Rivera",
"Celia",
""
]
] | In this paper, we study the constraints on the $f(Q)=Q/(8\pi G) - \alpha \ln(Q/Q_0)$, symmetric teleparallel model using local measurements and gravitational wave mock standard sirens. Using observational local SNIa and BAO data and energy conditions, the logarithmic $f(Q)$ model is capable of explaining the cosmic late-time acceleration by geometrical means. This result suggests that the logarithmic symmetric teleparallel model could be a candidate to solve the cosmological constant problem. In the case of the simulated standard siren data, by using the performance of the future ET and LISA detectors, we expect to be able to measure the current Hubble constant $H_0$, and the matter content $\Omega_m$, with a precision better than 1\% and 6\%, respectively. Furthermore, we explore the predicted $f(Q)$ logarithmic model deviation from the standard GR using ET and LISA mock standard sirens. The ratio $d_L^{\text{gw}}(z)/d_L^{\text{em}}(z)$, which quantifies the deviation from GR gives us a significant deviation higher than 13\% at $z=1$, and it continues growing to reach a deviation higher than 18\% in its median value. Future standard siren data will be able to quantify the strength of the deviation from GR and hence whether a cosmology like the one implied by this $f(Q)$ model is feasible. |
1810.05645 | Zhongwen Feng | Zhong-Wen Feng, Qun-Chao Ding, Shu-Zheng Yang | Fermions tunneling from higher-dimensional charged AdS black hole in
dRGT massive gravity within modified dispersion relation | 7 pages, corrected typos | European Physical Journal C, 2019, 79:445 | 10.1140/epjc/s10052-019-6959-1 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The tunneling behavior of fermions with half-integral spin from a higher
dimensional charged anti-de Sitter (AdS) black hole in de Rham, Gabadadze and
Tolley (dRGT) massive gravity is investigated via a modified Hamilton-Jacobi
equation. The results demonstrate that the modified thermodynamic quantities
not only are related to the properties of the higher dimensional charged AdS
black hole in dRGT massive gravity but also depend on the parameter $\beta$,
the coupling constant $\sigma$ and the mass of emitted particles $m$. In
addition, the modified Hawking temperature is higher than the original
temperature; hence, the effect of MDR can significantly enhance the evolution
of the black hole. Besides, our results can be verified using the modified
Stefan-Boltzmann law.
| [
{
"created": "Sun, 14 Oct 2018 09:05:04 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Nov 2018 02:34:34 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Apr 2019 08:14:55 GMT",
"version": "v3"
},
{
"created": "Mon, 27 May 2019 02:33:07 GMT",
"version": "v4"
}
] | 2019-05-28 | [
[
"Feng",
"Zhong-Wen",
""
],
[
"Ding",
"Qun-Chao",
""
],
[
"Yang",
"Shu-Zheng",
""
]
] | The tunneling behavior of fermions with half-integral spin from a higher dimensional charged anti-de Sitter (AdS) black hole in de Rham, Gabadadze and Tolley (dRGT) massive gravity is investigated via a modified Hamilton-Jacobi equation. The results demonstrate that the modified thermodynamic quantities not only are related to the properties of the higher dimensional charged AdS black hole in dRGT massive gravity but also depend on the parameter $\beta$, the coupling constant $\sigma$ and the mass of emitted particles $m$. In addition, the modified Hawking temperature is higher than the original temperature; hence, the effect of MDR can significantly enhance the evolution of the black hole. Besides, our results can be verified using the modified Stefan-Boltzmann law. |
gr-qc/9807006 | Tom Martin | Tom Martin | On the Motion of Free Material Test Particles in Arbitrary Spatial Flows | 9 pages, URL included | null | null | GRI-980630 | gr-qc | null | We show how the motion of free material test particles in arbitrary spatial
flows is easily determined within the context of ordinary vector calculus. This
may be useful for everyone, including engineers and other non-specialists, when
thinking about gravitational problems. It already has valid application to
simple problems such as the problems of motion in rotating and accelerating
frames and to the gravitational problem of the single spherically symmetric
attractor. When applied to the two body gravitational problem, it may help us
determine the actual direction of the flow.
| [
{
"created": "Thu, 2 Jul 1998 19:36:20 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Jul 1998 21:45:02 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jun 1999 17:49:35 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Martin",
"Tom",
""
]
] | We show how the motion of free material test particles in arbitrary spatial flows is easily determined within the context of ordinary vector calculus. This may be useful for everyone, including engineers and other non-specialists, when thinking about gravitational problems. It already has valid application to simple problems such as the problems of motion in rotating and accelerating frames and to the gravitational problem of the single spherically symmetric attractor. When applied to the two body gravitational problem, it may help us determine the actual direction of the flow. |
1404.1944 | Ulrich Jentschura | U. D. Jentschura | Fine-Structure Constant for Gravitational and Scalar Interactions | 6 pages; RevTeX | Phys.Rev.A 90 (2014) 022112 | 10.1103/PhysRevA.90.022112 | null | gr-qc hep-ph hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the coupling of a relativistic quantum particle to the curved
Schwarzschild space-time, we show that the Dirac--Schwarzschild problem has
bound states and calculate their energies including relativistic corrections.
Relativistic effects are shown to be suppressed by the gravitational
fine-structure constant alpha_G = G m_1 m_2/(hbar c), where G is Newton's
gravitational constant, c is the speed of light and m_1 and m_2 >> m_1 are the
masses of the two particles. The kinetic corrections due to space-time
curvature are shown to lift the familiar (n,j) degeneracy of the energy levels
of the hydrogen atom. We supplement the discussion by a consideration of an
attractive scalar potential, which, in the fully relativistic Dirac formalism,
modifies the mass of the particle according to the replacement m -> m (1 -
\lambda/r), where r is the radial coordinate. We conclude with a few comments
regarding the (n,j) degeneracy of the energy levels, where n is the principal
quantum number, and j is the total angular momentum, and illustrate the
calculations by way of a numerical example.
| [
{
"created": "Thu, 3 Apr 2014 19:32:40 GMT",
"version": "v1"
}
] | 2014-08-21 | [
[
"Jentschura",
"U. D.",
""
]
] | Starting from the coupling of a relativistic quantum particle to the curved Schwarzschild space-time, we show that the Dirac--Schwarzschild problem has bound states and calculate their energies including relativistic corrections. Relativistic effects are shown to be suppressed by the gravitational fine-structure constant alpha_G = G m_1 m_2/(hbar c), where G is Newton's gravitational constant, c is the speed of light and m_1 and m_2 >> m_1 are the masses of the two particles. The kinetic corrections due to space-time curvature are shown to lift the familiar (n,j) degeneracy of the energy levels of the hydrogen atom. We supplement the discussion by a consideration of an attractive scalar potential, which, in the fully relativistic Dirac formalism, modifies the mass of the particle according to the replacement m -> m (1 - \lambda/r), where r is the radial coordinate. We conclude with a few comments regarding the (n,j) degeneracy of the energy levels, where n is the principal quantum number, and j is the total angular momentum, and illustrate the calculations by way of a numerical example. |
gr-qc/0110120 | Maharana | Jnanadeva Maharana | From Big Crunch to Big Bang: A Quantum String Cosmology Perspective | 5 pages, Revtex, references added, discussions elaborated. To appear
in Physical Review D | Phys.Rev.D65:103504,2002 | 10.1103/PhysRevD.65.103504 | null | gr-qc astro-ph hep-th | null | The scenario that the Universe contracts towards a big crunch and then
undergoes a transition to expanding Universe in envisaged in the quantum string
cosmology approach. The Wheeler-De Witt equation is solved exactly for an
exponential dilaton potential. S-duality invariant cosmological effective
action, for type IIB theory, is considered to derive classical solutions and
solve WDW equations.
| [
{
"created": "Mon, 29 Oct 2001 12:34:20 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Mar 2002 06:08:33 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Maharana",
"Jnanadeva",
""
]
] | The scenario that the Universe contracts towards a big crunch and then undergoes a transition to expanding Universe in envisaged in the quantum string cosmology approach. The Wheeler-De Witt equation is solved exactly for an exponential dilaton potential. S-duality invariant cosmological effective action, for type IIB theory, is considered to derive classical solutions and solve WDW equations. |
1504.07397 | Nicola Tamanini | Nicola Tamanini | On phenomenological models of dark energy interacting with dark matter | v2: matching published version | Phys. Rev. D 92, 043524 (2015) | 10.1103/PhysRevD.92.043524 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An interaction between dark matter and dark energy is usually introduced by a
phenomenological modification of the matter conservation equations, while the
Einstein equations are left unchanged. Starting from some general and
fundamental considerations, in this work it is shown that a coupling in the
dark sector is likely to introduce new terms also in the gravitational
dynamics. Specifically in the cosmological background equations a bulk
dissipative pressure, characterizing viscous effects and able to suppress
structure formation at small scales, should appear from the dark coupling. At
the level of the perturbations the analysis presented in this work reveals
instead the difficulties in properly defining the dark sector interaction from
a phenomenological perspective.
| [
{
"created": "Tue, 28 Apr 2015 09:51:17 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2015 10:04:55 GMT",
"version": "v2"
}
] | 2015-09-16 | [
[
"Tamanini",
"Nicola",
""
]
] | An interaction between dark matter and dark energy is usually introduced by a phenomenological modification of the matter conservation equations, while the Einstein equations are left unchanged. Starting from some general and fundamental considerations, in this work it is shown that a coupling in the dark sector is likely to introduce new terms also in the gravitational dynamics. Specifically in the cosmological background equations a bulk dissipative pressure, characterizing viscous effects and able to suppress structure formation at small scales, should appear from the dark coupling. At the level of the perturbations the analysis presented in this work reveals instead the difficulties in properly defining the dark sector interaction from a phenomenological perspective. |
1409.6044 | Jose M. M. Senovilla | Jos\'e M. M. Senovilla and Ram\'on Torres | Particle production from marginally trapped surfaces of general
spacetimes | 24 pages, 2 figures. Section 4.2, concerning the analysis of the
Kerr-Vaidya solution, has been rewritten, correcting mistakes in previous
versions. The corrected calculations do support our claims. A corrigendum has
also been sent to CQG. New references added. Some of the mistakes in previous
versions are actually common and spread in the literature on the Kerr-Vaidya
solution | null | 10.1088/0264-9381/32/8/085004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a general formalism that allows to analyze the phenomenon of
tunneling in arbitrary spacetimes. We show that a flux of particles produced by
tunneling through general marginally trapped surfaces may be perceived by some
privileged observers. We discuss how this particle perception can be related to
Hawking/Unruh radiation in specific cases. Our approach naturally leads to an
expression for the effective surface gravity of marginally trapped surfaces.
The procedure is applicable to general astrophysical and cosmological dynamical
situations. Some practical examples for known and new cases are provided.
| [
{
"created": "Sun, 21 Sep 2014 21:44:10 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Dec 2014 22:10:39 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Feb 2015 18:07:26 GMT",
"version": "v3"
},
{
"created": "Sat, 27 Jun 2015 17:29:19 GMT",
"version": "v4"
}
] | 2015-06-30 | [
[
"Senovilla",
"José M. M.",
""
],
[
"Torres",
"Ramón",
""
]
] | We provide a general formalism that allows to analyze the phenomenon of tunneling in arbitrary spacetimes. We show that a flux of particles produced by tunneling through general marginally trapped surfaces may be perceived by some privileged observers. We discuss how this particle perception can be related to Hawking/Unruh radiation in specific cases. Our approach naturally leads to an expression for the effective surface gravity of marginally trapped surfaces. The procedure is applicable to general astrophysical and cosmological dynamical situations. Some practical examples for known and new cases are provided. |
1007.3571 | Rong-Jia Yang | Rong-Jia Yang | New types of $f(T)$ gravity | 6 pages, 9 figures, some changes are made | Eur. Phys. J. C 71, 1797 (2011) | 10.1140/epjc/s10052-011-1797-9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently $f(T)$ theories based on modifications of teleparallel gravity where
torsion is the geometric object describing gravity instead of curvature have
been proposed to explain the present cosmic accelerating expansion. The field
equations are always second order, remarkably simpler than $f(R)$ theories. In
analogy to the $f(R)$ theory, we consider here three types of $f(T)$ gravity,
and find that all of them can give rise to cosmic acceleration with interesting
features, respectively.
| [
{
"created": "Wed, 21 Jul 2010 07:26:08 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 2010 09:09:15 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Nov 2011 14:07:17 GMT",
"version": "v3"
}
] | 2011-11-10 | [
[
"Yang",
"Rong-Jia",
""
]
] | Recently $f(T)$ theories based on modifications of teleparallel gravity where torsion is the geometric object describing gravity instead of curvature have been proposed to explain the present cosmic accelerating expansion. The field equations are always second order, remarkably simpler than $f(R)$ theories. In analogy to the $f(R)$ theory, we consider here three types of $f(T)$ gravity, and find that all of them can give rise to cosmic acceleration with interesting features, respectively. |
gr-qc/0002026 | Sandro S. e Costa | Sandro S. e Costa | Some integrals ocurring in a topology change problem | RevTeX article, 4 pages, 1 figure | Phys.Rev. D62 (2000) 047303 | 10.1103/PhysRevD.62.047303 | null | gr-qc | null | In a paper presented a few years ago, De Lorenci et al. showed, in the
context of canonical quantum cosmology, a model which allowed space topology
changes (Phys. Rev. D 56, 3329 (1997)). The purpose of this present work is to
go a step further in that model, by performing some calculations only estimated
there for several compact manifolds of constant negative curvature, such as the
Weeks and Thurston spaces and the icosahedral hyperbolic space (Best space).
| [
{
"created": "Mon, 7 Feb 2000 13:28:11 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Costa",
"Sandro S. e",
""
]
] | In a paper presented a few years ago, De Lorenci et al. showed, in the context of canonical quantum cosmology, a model which allowed space topology changes (Phys. Rev. D 56, 3329 (1997)). The purpose of this present work is to go a step further in that model, by performing some calculations only estimated there for several compact manifolds of constant negative curvature, such as the Weeks and Thurston spaces and the icosahedral hyperbolic space (Best space). |
gr-qc/0407100 | Gregory J. Galloway | Gregory J. Galloway | Cosmological Spacetimes with $\Lambda > 0$ | 14 pages, 4 figures; based on a talk given at the Beemfest in May,
2003; to appear in Contemporary Mathematics | null | null | null | gr-qc | null | We discuss some global properties of cosmological spacetimes of de Sitter
type, based on results with Lars Andersson obtained in hep-th/0202161. We
relate the geometry and topology of conformal infinity to the occurrence of
singularities in such spacetimes, thereby extending to a much broader context
certain properties of some well-known cosmological models.
| [
{
"created": "Tue, 27 Jul 2004 14:56:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Galloway",
"Gregory J.",
""
]
] | We discuss some global properties of cosmological spacetimes of de Sitter type, based on results with Lars Andersson obtained in hep-th/0202161. We relate the geometry and topology of conformal infinity to the occurrence of singularities in such spacetimes, thereby extending to a much broader context certain properties of some well-known cosmological models. |
1810.06073 | Yen Chin Ong | Shi-Qian Hu, Xiao-Mei Kuang, Yen Chin Ong | A Note on Smarr Relation and Coupling Constants | published version | Gen Relativ Gravit 51 (2019) 55 | 10.1007/s10714-019-2540-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Smarr relation plays an important role in black hole thermodynamics. It
is often claimed that the Smarr relation can be written down simply by
observing the scaling behavior of the various thermodynamical quantities. We
point out that this is not necessarily so in the presence of dimensionful
coupling constants, and discuss the issues involving the identification of
thermodynamical variables.
| [
{
"created": "Sun, 14 Oct 2018 17:59:24 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2019 07:37:08 GMT",
"version": "v2"
}
] | 2019-05-14 | [
[
"Hu",
"Shi-Qian",
""
],
[
"Kuang",
"Xiao-Mei",
""
],
[
"Ong",
"Yen Chin",
""
]
] | The Smarr relation plays an important role in black hole thermodynamics. It is often claimed that the Smarr relation can be written down simply by observing the scaling behavior of the various thermodynamical quantities. We point out that this is not necessarily so in the presence of dimensionful coupling constants, and discuss the issues involving the identification of thermodynamical variables. |
1503.02618 | Abhay Shah | Abhay G. Shah, Bernard F. Whiting | Raising and Lowering operators of spin-weighted spheroidal harmonics | null | General Relativity and Gravitation 2016, 48:78 | 10.1007/s10714-016-2064-z | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we generalize the spin-raising and lowering operators of
spin-weighted spherical harmonics to linear-in-$\gamma$ spin-weighted
spheroidal harmonics where $\gamma$ is an additional parameter present in the
second order ordinary differential equation governing these harmonics. One can
then generalize these operators to higher powers in $\gamma$. Constructing
these operators required calculating the $\ell$-, $s$- and $m$-raising and
lowering operators (and various combinations of them) of spin-weighted
spherical harmonics which have been calculated and shown explicitly in this
paper.
| [
{
"created": "Mon, 9 Mar 2015 18:58:38 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2016 14:52:33 GMT",
"version": "v2"
}
] | 2016-06-06 | [
[
"Shah",
"Abhay G.",
""
],
[
"Whiting",
"Bernard F.",
""
]
] | In this paper we generalize the spin-raising and lowering operators of spin-weighted spherical harmonics to linear-in-$\gamma$ spin-weighted spheroidal harmonics where $\gamma$ is an additional parameter present in the second order ordinary differential equation governing these harmonics. One can then generalize these operators to higher powers in $\gamma$. Constructing these operators required calculating the $\ell$-, $s$- and $m$-raising and lowering operators (and various combinations of them) of spin-weighted spherical harmonics which have been calculated and shown explicitly in this paper. |
2001.06644 | M. Farasat Shamir | M. Farasat Shamir, Tayyaba Naz | Stellar Structures in $f(\mathcal{G})$ Gravity with Tolman-Kuchowicz
Spacetime | 16 pages, accepted for publication in Physics of the Dark Universe | Phys. Dark Universe 27, 100472 (2020) | 10.1016/j.dark.2020.100472 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to explore some relativistic configurations of stellar
objects for static spherically symmetric structures in the context of modified
$f(\mathcal{G})$ gravity, by exploiting the Tolman-Kuchowicz spacetime [1,2].
We develop the equations of motion for spherically symmetric spacetime in the
presence of anisotropic matter distribution by considering the physically valid
expressions of the metric potentials, $\nu=Br^2+2lnC$ and $\lambda=ln(1 +
ar^2+br^4)$. To attain the values of the unknown constants we consider the
observational data of $Cen~ X-3$, $EXO ~1785-248$ and $LMC~ X-4$ star models.
Further, by using evaluated form of the solutions we provide many aspects which
are described by the physical status like effective energy density, components
of radial and transverse pressure, energy conditions, stability against
equilibrium of the forces, speed of sound, mass-radius relation, surface
redshift, compactness parameter, adiabatic index and anisotropic measurement.
It is observed that all these features follow physically accepted patterns and
the resulting outcome is in the experimental range which depicts the viability
of our presented $f(\mathcal{G})$ gravity models.
| [
{
"created": "Sat, 18 Jan 2020 10:26:40 GMT",
"version": "v1"
}
] | 2020-01-23 | [
[
"Shamir",
"M. Farasat",
""
],
[
"Naz",
"Tayyaba",
""
]
] | This paper is devoted to explore some relativistic configurations of stellar objects for static spherically symmetric structures in the context of modified $f(\mathcal{G})$ gravity, by exploiting the Tolman-Kuchowicz spacetime [1,2]. We develop the equations of motion for spherically symmetric spacetime in the presence of anisotropic matter distribution by considering the physically valid expressions of the metric potentials, $\nu=Br^2+2lnC$ and $\lambda=ln(1 + ar^2+br^4)$. To attain the values of the unknown constants we consider the observational data of $Cen~ X-3$, $EXO ~1785-248$ and $LMC~ X-4$ star models. Further, by using evaluated form of the solutions we provide many aspects which are described by the physical status like effective energy density, components of radial and transverse pressure, energy conditions, stability against equilibrium of the forces, speed of sound, mass-radius relation, surface redshift, compactness parameter, adiabatic index and anisotropic measurement. It is observed that all these features follow physically accepted patterns and the resulting outcome is in the experimental range which depicts the viability of our presented $f(\mathcal{G})$ gravity models. |
gr-qc/0207071 | Enrico Calzavarini | Enrico Calzavarini, Laura Sartori, Fabio Schifano, Raffaele
Tripiccione, Andrea Vicere' | Matched filters for coalescing binaries detection on massively parallel
computers | 19 pages, 6 figures | Comput.Phys.Commun.152:295-306,2003 | 10.1016/S0010-4655(02)00848-2 | null | gr-qc | null | We discuss some computational problems associated to matched filtering of
experimental signals from gravitational wave interferometric detectors in a
parallel-processing environment. We then specialize our discussion to the use
of the APEmille and apeNEXT processors for this task. Finally, we accurately
estimate the performance of an APEmille system on a computational load
appropriate for the LIGO and VIRGO experiments, and extrapolate our results to
apeNEXT.
| [
{
"created": "Thu, 18 Jul 2002 14:19:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Calzavarini",
"Enrico",
""
],
[
"Sartori",
"Laura",
""
],
[
"Schifano",
"Fabio",
""
],
[
"Tripiccione",
"Raffaele",
""
],
[
"Vicere'",
"Andrea",
""
]
] | We discuss some computational problems associated to matched filtering of experimental signals from gravitational wave interferometric detectors in a parallel-processing environment. We then specialize our discussion to the use of the APEmille and apeNEXT processors for this task. Finally, we accurately estimate the performance of an APEmille system on a computational load appropriate for the LIGO and VIRGO experiments, and extrapolate our results to apeNEXT. |
gr-qc/0508030 | Ru-Keng Su | Cheng-Gang Shao, Jianyong Shen, Bin Wang, Ru-Keng Su | Dirac Cosmology and the Acceleration of the Contemporary Universe | 13 pages, 8 figures | Class.Quant.Grav. 23 (2006) 3707-3720 | 10.1088/0264-9381/23/11/003 | null | gr-qc | null | A model is suggested to unify the Einstein GR and Dirac Cosmology. There is
one adjusted parameter $b_2$ in our model. After adjusting the parameter $b_2$
in the model by using the supernova data, we have calculated the gravitational
constant $\bar G$ and the physical quantities of $a(t)$, $q(t)$ and $\rho_r(t)/
\rho_b(t)$ by using the present day quantities as the initial conditions and
found that the equation of state parameter $w_{\theta}$ equals to -0.83, the
ratio of the density of the addition creation $\Omega_{\Lambda}=0.8$ and the
ratio of the density of the matter including multiplication creation, radiation
and normal matter $\Omega_m =0.2$ at present. The results are self-consistent
and in good agreement with present knowledge in cosmology. These results
suggest that the addition creation and multiplication creation in Dirac
cosmology play the role of the dark energy and dark matter.
| [
{
"created": "Tue, 9 Aug 2005 06:28:38 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Shao",
"Cheng-Gang",
""
],
[
"Shen",
"Jianyong",
""
],
[
"Wang",
"Bin",
""
],
[
"Su",
"Ru-Keng",
""
]
] | A model is suggested to unify the Einstein GR and Dirac Cosmology. There is one adjusted parameter $b_2$ in our model. After adjusting the parameter $b_2$ in the model by using the supernova data, we have calculated the gravitational constant $\bar G$ and the physical quantities of $a(t)$, $q(t)$ and $\rho_r(t)/ \rho_b(t)$ by using the present day quantities as the initial conditions and found that the equation of state parameter $w_{\theta}$ equals to -0.83, the ratio of the density of the addition creation $\Omega_{\Lambda}=0.8$ and the ratio of the density of the matter including multiplication creation, radiation and normal matter $\Omega_m =0.2$ at present. The results are self-consistent and in good agreement with present knowledge in cosmology. These results suggest that the addition creation and multiplication creation in Dirac cosmology play the role of the dark energy and dark matter. |
gr-qc/0012027 | C. M. zhang | C.M. Zhang | Mass neutrino flavor evolution in spacetime with torsion | 8 papes, no fiure | Nuovo Cim.B115:437-444,2000 | null | null | gr-qc | null | In the framework of the spacetime with torsion, we obtain the flavor
evolution equation of the mass neutrino oscillation in vacuum. A comparison
with the result of general relativity case, it shows that the flavor
evolutionary equations in Riemann spacetime and Weitzenb\"ock spacetimes are
equivalent in the spherical symmetric Schwarzschild spacetime, but turns out to
be different in the case of the axial symmetry.
| [
{
"created": "Wed, 6 Dec 2000 15:14:55 GMT",
"version": "v1"
}
] | 2011-09-13 | [
[
"Zhang",
"C. M.",
""
]
] | In the framework of the spacetime with torsion, we obtain the flavor evolution equation of the mass neutrino oscillation in vacuum. A comparison with the result of general relativity case, it shows that the flavor evolutionary equations in Riemann spacetime and Weitzenb\"ock spacetimes are equivalent in the spherical symmetric Schwarzschild spacetime, but turns out to be different in the case of the axial symmetry. |
gr-qc/9903037 | Marcelo J. Reboucas | G.I. Gomero, M.J. Reboucas, A.F.F. Teixeira, A. Bernui | Topological Reverberations in Flat Space-times | 16 pages, 4 figures, REVTEX; Added five references and inserted
clarifying details. Version to appear in Int. J. Mod. Phys. A (2000) | Int.J.Mod.Phys. A15 (2000) 4141-4162 | 10.1142/S0217751X00002081 | CBPF-NF-051/98 | gr-qc astro-ph hep-th math-ph math.MP | null | We study the role played by multiply-connectedness in the time evolution of
the energy E(t) of a radiating system that lies in static flat space-time
manifolds M_4 whose t=const spacelike sections M_3 are compact in at least one
spatial direction. The radiation reaction equation of the radiating source is
derived for the case where M_3 has any non-trivial flat topology, and an exact
solution is obtained. We also show that when the spacelike sections are
multiply-connected flat 3-manifolds the energy E(t) exhibits a reverberation
pattern with discontinuities in the derivative of E(t) and a set of relative
minima and maxima, followed by a growth of E(t). It emerges from this result
that the compactness in at least one spatial direction of Minkowski space-time
is sufficient to induce this type of topological reverberation, making clear
that our radiating system is topologically fragile. An explicit solution of the
radiation reaction equation for the case where M_3 = R^2 x S^1 is discussed,
and graphs which reveal how the energy varies with the time are presented and
analyzed.
| [
{
"created": "Tue, 9 Mar 1999 22:36:46 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Sep 2000 00:35:26 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Gomero",
"G. I.",
""
],
[
"Reboucas",
"M. J.",
""
],
[
"Teixeira",
"A. F. F.",
""
],
[
"Bernui",
"A.",
""
]
] | We study the role played by multiply-connectedness in the time evolution of the energy E(t) of a radiating system that lies in static flat space-time manifolds M_4 whose t=const spacelike sections M_3 are compact in at least one spatial direction. The radiation reaction equation of the radiating source is derived for the case where M_3 has any non-trivial flat topology, and an exact solution is obtained. We also show that when the spacelike sections are multiply-connected flat 3-manifolds the energy E(t) exhibits a reverberation pattern with discontinuities in the derivative of E(t) and a set of relative minima and maxima, followed by a growth of E(t). It emerges from this result that the compactness in at least one spatial direction of Minkowski space-time is sufficient to induce this type of topological reverberation, making clear that our radiating system is topologically fragile. An explicit solution of the radiation reaction equation for the case where M_3 = R^2 x S^1 is discussed, and graphs which reveal how the energy varies with the time are presented and analyzed. |
gr-qc/9706033 | Doug Eardley | Shawn J. Kolitch (Physics, UCSB) and Douglas M. Eardley (ITP, UCSB) | Quantum Decay of Domain Walls in Cosmology II: Hamiltonian Approach | 27 pages LaTeX, using revtex and psfig. 3 figures | Phys. Rev. D 56, 4663 (1997) | 10.1103/PhysRevD.56.4663 | NSF-ITP-97-051 | gr-qc hep-th | null | This paper studies the decay of a large, closed domain wall in a closed
universe. Such walls can form in the presence of a broken, discrete symmetry.
We study a novel process of quantum decay for such a wall, in which the vacuum
fluctuates from one discrete state to another throughout one half of the
universe, so that the wall decays into pure field energy. Equivalently, the
fluctuation can be thought of as the nucleation of a second closed domain wall
of zero size, followed by its growth by quantum tunnelling and its collision
with the first wall, annihilating both. We therefore study the 2-wall system
coupled to a spherically symmetric gravitational field. We derive a simple form
of the 2-wall action, use Dirac quantization, obtain the 2-wall wave function
for annihilation, find from it the barrier factor for this quantum tunneling,
and thereby get the decay probability. This is the second paper of a series.
| [
{
"created": "Thu, 12 Jun 1997 17:32:06 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Kolitch",
"Shawn J.",
"",
"Physics, UCSB"
],
[
"Eardley",
"Douglas M.",
"",
"ITP, UCSB"
]
] | This paper studies the decay of a large, closed domain wall in a closed universe. Such walls can form in the presence of a broken, discrete symmetry. We study a novel process of quantum decay for such a wall, in which the vacuum fluctuates from one discrete state to another throughout one half of the universe, so that the wall decays into pure field energy. Equivalently, the fluctuation can be thought of as the nucleation of a second closed domain wall of zero size, followed by its growth by quantum tunnelling and its collision with the first wall, annihilating both. We therefore study the 2-wall system coupled to a spherically symmetric gravitational field. We derive a simple form of the 2-wall action, use Dirac quantization, obtain the 2-wall wave function for annihilation, find from it the barrier factor for this quantum tunneling, and thereby get the decay probability. This is the second paper of a series. |
1906.08166 | Susanne Schander | S. Schander, T. Thiemann | Quantum Cosmological Backreactions I: Cosmological Space Adiabatic
Perturbation Theory | 35 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The search for quantum gravity fingerprints in currently available
cosmological data that have their origin from the Planck era is of growing
interest due to major recent progress both in the theoretical modelling as well
as the observational precision. Unsurprisingly, the theoretical predictions are
very sensitive to the quantum effects that occur close to the classical big
bang singularity. It is therefore of substantial interest to describe these
effects as precisely as possible. This is the first in a series of papers that
aim at improving on the treatment of quantum effects that arise due to
backreactions between matter and geometry. The technique we employ is space
adiabatic perturbation theory (SAPT) in the form developed in seminal papers by
Panati, Spohn and Teufel. SAPT is a generalisation of the more familiar Born
Oppenheimer Approximation (BOA) that applies well in systems that allow a split
of the degrees of freedom into two sets that propagate on rather different time
scales such as the homogeneous and inhomogeneous field modes in cosmology. We
will show that this leads to presently neglected correction terms in the
quantum Friedman equations.
In the present paper we adapt and generalise SAPT to the hybrid approach to
quantum cosmology developed by Mena Marugan et al. that allows for a systematic
quantum separation of the (in)homogeneous modes. Since SAPT was developed for
quantum mechanics rather than quantum field theory, several challenges have to
be met.
| [
{
"created": "Wed, 19 Jun 2019 15:44:25 GMT",
"version": "v1"
}
] | 2019-06-20 | [
[
"Schander",
"S.",
""
],
[
"Thiemann",
"T.",
""
]
] | The search for quantum gravity fingerprints in currently available cosmological data that have their origin from the Planck era is of growing interest due to major recent progress both in the theoretical modelling as well as the observational precision. Unsurprisingly, the theoretical predictions are very sensitive to the quantum effects that occur close to the classical big bang singularity. It is therefore of substantial interest to describe these effects as precisely as possible. This is the first in a series of papers that aim at improving on the treatment of quantum effects that arise due to backreactions between matter and geometry. The technique we employ is space adiabatic perturbation theory (SAPT) in the form developed in seminal papers by Panati, Spohn and Teufel. SAPT is a generalisation of the more familiar Born Oppenheimer Approximation (BOA) that applies well in systems that allow a split of the degrees of freedom into two sets that propagate on rather different time scales such as the homogeneous and inhomogeneous field modes in cosmology. We will show that this leads to presently neglected correction terms in the quantum Friedman equations. In the present paper we adapt and generalise SAPT to the hybrid approach to quantum cosmology developed by Mena Marugan et al. that allows for a systematic quantum separation of the (in)homogeneous modes. Since SAPT was developed for quantum mechanics rather than quantum field theory, several challenges have to be met. |
2202.09453 | Allen Stern | S. Fabi, A. Stern and Chuang Xu | Cosmic acceleration in Regge-Teitelboim gravity | 11 pages, 3 figures | null | 10.1088/1361-6382/ac813f | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The Regge-Teitelboim formulation of gravity, which utilizes dynamical
embeddings in a background space, effectively introduces source terms in the
standard Einstein equations that are not attributable to the energy-momentum
tensor. We show that for a simple class of embeddings of the Robertson-Walker
metric, these source terms naturally generate cosmic acceleration.
| [
{
"created": "Fri, 18 Feb 2022 22:19:35 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Fabi",
"S.",
""
],
[
"Stern",
"A.",
""
],
[
"Xu",
"Chuang",
""
]
] | The Regge-Teitelboim formulation of gravity, which utilizes dynamical embeddings in a background space, effectively introduces source terms in the standard Einstein equations that are not attributable to the energy-momentum tensor. We show that for a simple class of embeddings of the Robertson-Walker metric, these source terms naturally generate cosmic acceleration. |
2212.02829 | Mario Martinez Dr. | M. Andres-Carcasona, A. Menendez-Vazquez, M. Martinez, Ll. M. Mir | Searches for Mass-Asymmetric Compact Binary Coalescence Events using
Neural Networks in the LIGO/Virgo Third Observation Period | 8 pages, 12 figures, 4 tables, to be submitted to PRD. arXiv admin
note: text overlap with arXiv:2012.10702 | null | 10.1103/PhysRevD.107.082003 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present the results on the search for the coalescence of compact binary
mergers with very asymmetric mass configurations using convolutional neural
networks and the LIGO/Virgo data for the O3 observation period. Two-dimensional
images in time and frequency are used as input. Masses in the range between
0.01 Msun and 20 Msun are considered. We explore neural networks trained with
input information from a single interferometer, pairs of interferometers, or
all three interferometers together, indicating that the use of the maximum
information available leads to an improved performance. A scan over the O3 data
set using the convolutional neural networks for detection results into no
significant excess from an only-noise hypothesis. The results are translated
into 90% confidence level upper limits on the merger rate as a function of the
mass parameters of the binary system.
| [
{
"created": "Tue, 6 Dec 2022 08:57:24 GMT",
"version": "v1"
}
] | 2023-04-26 | [
[
"Andres-Carcasona",
"M.",
""
],
[
"Menendez-Vazquez",
"A.",
""
],
[
"Martinez",
"M.",
""
],
[
"Mir",
"Ll. M.",
""
]
] | We present the results on the search for the coalescence of compact binary mergers with very asymmetric mass configurations using convolutional neural networks and the LIGO/Virgo data for the O3 observation period. Two-dimensional images in time and frequency are used as input. Masses in the range between 0.01 Msun and 20 Msun are considered. We explore neural networks trained with input information from a single interferometer, pairs of interferometers, or all three interferometers together, indicating that the use of the maximum information available leads to an improved performance. A scan over the O3 data set using the convolutional neural networks for detection results into no significant excess from an only-noise hypothesis. The results are translated into 90% confidence level upper limits on the merger rate as a function of the mass parameters of the binary system. |
gr-qc/0201042 | R. S. Ward | R. S. Ward | Stability of Sigma-Model Strings and Textures | 9 pages, to be published in Classical and Quantum Gravity | Class.Quant.Grav.19:L17,2002 | 10.1088/0264-9381/19/4/101 | DCPT-02/05 | gr-qc | null | In flat space-time, sigma-model strings and textures are both unstable to
collapse and subsequent decay. With sufficient cosmological expansion, however,
they are stable in a generalized sense: a small perturbation will cause them to
change their shape, but they do not decay. The current rate of expansion is
sufficient to stabilize strings, but not textures.
| [
{
"created": "Mon, 14 Jan 2002 13:13:36 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Ward",
"R. S.",
""
]
] | In flat space-time, sigma-model strings and textures are both unstable to collapse and subsequent decay. With sufficient cosmological expansion, however, they are stable in a generalized sense: a small perturbation will cause them to change their shape, but they do not decay. The current rate of expansion is sufficient to stabilize strings, but not textures. |
0912.3641 | Nakia Carlevaro | Nakia Carlevaro, Giovanni Montani | Gravitational Instability in Presence of Bulk Viscosity: the Jeans Mass
and the Quasi-Isotropic Solution | 3 pages, Proceedings of The XII Marcel Grossmann Meeting | null | 10.1142/9789814374552_0212 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper focuses on the analysis of the gravitational instability in
presence of bulk viscosity both in Newtonian regime and in the
fully-relativistic approach. The standard Jeans Mechanism and the
Quasi-Isotropic Solution are treated expressing the bulk-viscosity coefficient
$\zeta$ as a power-law of the fluid energy density $\rho$, i.e.,
$\zeta=\zo\rho^{s}$. In the Newtonian regime, the perturbation evolution is
founded to be damped by viscosity and the top-down mechanism of structure
fragmentation is suppressed. The value of the Jeans Mass remains unchanged also
in presence of viscosity. In the relativistic approach, we get a power-law
solution existing only in correspondence to a restricted domain of $\zo$.
| [
{
"created": "Fri, 18 Dec 2009 10:55:36 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Carlevaro",
"Nakia",
""
],
[
"Montani",
"Giovanni",
""
]
] | This paper focuses on the analysis of the gravitational instability in presence of bulk viscosity both in Newtonian regime and in the fully-relativistic approach. The standard Jeans Mechanism and the Quasi-Isotropic Solution are treated expressing the bulk-viscosity coefficient $\zeta$ as a power-law of the fluid energy density $\rho$, i.e., $\zeta=\zo\rho^{s}$. In the Newtonian regime, the perturbation evolution is founded to be damped by viscosity and the top-down mechanism of structure fragmentation is suppressed. The value of the Jeans Mass remains unchanged also in presence of viscosity. In the relativistic approach, we get a power-law solution existing only in correspondence to a restricted domain of $\zo$. |
2301.02398 | Soumya Mohanty | Soumya D. Mohanty, Mohammad A. T. Chowdhury | Glitch subtraction from gravitational wave data using adaptive spline
fitting | 17 pages, 7 figures, revised version (new figure added) | null | 10.1088/1361-6382/acd0fe | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Transient signals of instrumental and environmental origins ("glitches") in
gravitational wave data elevate the false alarm rate of searches for
astrophysical signals and reduce their sensitivity. Glitches that directly
overlap astrophysical signals hinder their detection and worsen parameter
estimation errors. As the fraction of data occupied by detectable astrophysical
signals will be higher in next generation detectors, such problematic overlaps
could become more frequent. These adverse effects of glitches can be mitigated
by estimating and subtracting them out from the data, but their unpredictable
waveforms and large morphological diversity pose a challenge. Subtraction of
glitches using data from auxiliary sensors as predictors works but not for the
majority of cases. Thus, there is a need for nonparametric glitch mitigation
methods that do not require auxiliary data, work for a large variety of
glitches, and have minimal effect on astrophysical signals in the case of
overlaps. In order to cope with the high rate of glitches, it is also desirable
that such methods be computationally fast. We show that adaptive spline
fitting, in which the placement of free knots is optimized to estimate both
smooth and non-smooth curves in noisy data, offers a promising approach to
satisfying these requirements for broadband short-duration glitches, the type
that appear quite frequently. The method is demonstrated on glitches drawn from
three distinct classes in the Gravity Spy database as well as on the glitch
that overlapped the binary neutron star signal GW170817. The impact of glitch
subtraction on the GW170817 signal, or those like it injected into the data, is
seen to be negligible.
| [
{
"created": "Fri, 6 Jan 2023 06:32:59 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Feb 2023 06:18:53 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Mar 2023 21:42:33 GMT",
"version": "v3"
}
] | 2023-05-24 | [
[
"Mohanty",
"Soumya D.",
""
],
[
"Chowdhury",
"Mohammad A. T.",
""
]
] | Transient signals of instrumental and environmental origins ("glitches") in gravitational wave data elevate the false alarm rate of searches for astrophysical signals and reduce their sensitivity. Glitches that directly overlap astrophysical signals hinder their detection and worsen parameter estimation errors. As the fraction of data occupied by detectable astrophysical signals will be higher in next generation detectors, such problematic overlaps could become more frequent. These adverse effects of glitches can be mitigated by estimating and subtracting them out from the data, but their unpredictable waveforms and large morphological diversity pose a challenge. Subtraction of glitches using data from auxiliary sensors as predictors works but not for the majority of cases. Thus, there is a need for nonparametric glitch mitigation methods that do not require auxiliary data, work for a large variety of glitches, and have minimal effect on astrophysical signals in the case of overlaps. In order to cope with the high rate of glitches, it is also desirable that such methods be computationally fast. We show that adaptive spline fitting, in which the placement of free knots is optimized to estimate both smooth and non-smooth curves in noisy data, offers a promising approach to satisfying these requirements for broadband short-duration glitches, the type that appear quite frequently. The method is demonstrated on glitches drawn from three distinct classes in the Gravity Spy database as well as on the glitch that overlapped the binary neutron star signal GW170817. The impact of glitch subtraction on the GW170817 signal, or those like it injected into the data, is seen to be negligible. |
gr-qc/0410097 | Yasunori Fujii | Yasunori Fujii | Some aspects of the scalar-tensor theory | 12 pages 4 figures. Based on the talks delivered at Second Advanced
Research Workshop, Gravity, Astrophysics, and Strings, Kiten, Bulgaria, June
10-16, 2004 | null | null | null | gr-qc | null | The scalar-tensor theory of gravitation has been and still is one of the most
widely discussed "alternative theories" to General Relativity (GR). Despite
nearly half a century of its age, it continues to attract renewed interests of
not only theorists but also experimentalists when we now face such issues like
the accelerating universe and possible time-variability of the fine-structure
constant, both viewed as something beyond the standard GR. It appears that the
theory provides realistic results sometimes even beyond what is expected from
the quintessence approach aimed primarily to be more phenomenological. It seems
nevertheless as if some of the unique aspects of this theory are not fully
understood, even leading to occasional confusions. I try in my lectures, partly
using the contents of our book (Y.F. and K. Maeda, Scalar-tensor theory of
gravitation, Cambridge University Press, 2003), to discuss some of the most
crucial concepts starting from elementary introduction to the theory.
Particular emphases will be placed on the unique features of the nonminimal
coupling term, the roles of the conformal transformations together with the
choice of a physical conformal frame and the value of the coupling strength to
the matter. Readers are advised to refer to the references for more details.
| [
{
"created": "Wed, 20 Oct 2004 07:33:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fujii",
"Yasunori",
""
]
] | The scalar-tensor theory of gravitation has been and still is one of the most widely discussed "alternative theories" to General Relativity (GR). Despite nearly half a century of its age, it continues to attract renewed interests of not only theorists but also experimentalists when we now face such issues like the accelerating universe and possible time-variability of the fine-structure constant, both viewed as something beyond the standard GR. It appears that the theory provides realistic results sometimes even beyond what is expected from the quintessence approach aimed primarily to be more phenomenological. It seems nevertheless as if some of the unique aspects of this theory are not fully understood, even leading to occasional confusions. I try in my lectures, partly using the contents of our book (Y.F. and K. Maeda, Scalar-tensor theory of gravitation, Cambridge University Press, 2003), to discuss some of the most crucial concepts starting from elementary introduction to the theory. Particular emphases will be placed on the unique features of the nonminimal coupling term, the roles of the conformal transformations together with the choice of a physical conformal frame and the value of the coupling strength to the matter. Readers are advised to refer to the references for more details. |
1406.7135 | Katerina Chatziioannou | Katerina Chatziioannou, Kent Yagi, and Nicolas Yunes | Toward Realistic and Practical No-Hair Relations for Neutron Stars in
the Non-Relativistic Limit | 10 pages, 5 figures, published version | null | 10.1103/PhysRevD.90.064030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational properties of astrophysical objects depend sensitively on
their internal structure. In Newtonian theory, the gravitational potential of a
rotating star can be fully described by an infinite number of multipole moments
of its mass distribution. Recently, this infinite number of moments for
uniformly-rotating stars were shown semi-analytically to be expressible in
terms of just the first three: the mass, the spin, and the quadrupole moment of
the star. The relations between the various lower multipole moments were
additionally shown to depend weakly on the equation of state, when considering
neutron stars and assuming single polytropic equations of state. Here we extend
this result in two ways. First, we show that the universality also holds for
realistic equations of state, thus relaxing the need to use single polytropes.
Second, we derive purely analytical universal relations by perturbing the
equations of structure about an $n=0$ polytrope that reproduce semi-analytic
results to $\mathcal{O}(1\%)$. We also find that the linear-order perturbation
vanishes in some cases, which provides further evidence and a deeper
understanding of the universality.
| [
{
"created": "Fri, 27 Jun 2014 10:02:34 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Sep 2014 04:23:53 GMT",
"version": "v2"
}
] | 2014-10-01 | [
[
"Chatziioannou",
"Katerina",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The gravitational properties of astrophysical objects depend sensitively on their internal structure. In Newtonian theory, the gravitational potential of a rotating star can be fully described by an infinite number of multipole moments of its mass distribution. Recently, this infinite number of moments for uniformly-rotating stars were shown semi-analytically to be expressible in terms of just the first three: the mass, the spin, and the quadrupole moment of the star. The relations between the various lower multipole moments were additionally shown to depend weakly on the equation of state, when considering neutron stars and assuming single polytropic equations of state. Here we extend this result in two ways. First, we show that the universality also holds for realistic equations of state, thus relaxing the need to use single polytropes. Second, we derive purely analytical universal relations by perturbing the equations of structure about an $n=0$ polytrope that reproduce semi-analytic results to $\mathcal{O}(1\%)$. We also find that the linear-order perturbation vanishes in some cases, which provides further evidence and a deeper understanding of the universality. |
1201.5470 | I\~naki Garay | Enrique F. Borja, Jacobo D\'iaz-Polo, Laurent Freidel, I\~naki Garay,
Etera R. Livine | New tools for Loop Quantum Gravity with applications to a simple model | 4 pages, to appear in Proceedings of Spanish Relativity Meeting 2011
(ERE 2011) held in Madrid, Spain | null | 10.1063/1.4734429 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Quantum Gravity is now a well established approach to quantum gravity.
One of the main challenges still faced by the theory is constructing a
consistent dynamics which would lead back to the standard dynamics of the
gravitational field at large scales. Here we will review the recent U(N)
framework for Loop Quantum Gravity and the new spinor representation (that
provides a classical setting for the U(N) framework). Then, we will apply these
techniques to a simple model in order to propose a dynamics for a symmetry
reduced sector of the theory. Furthermore, we will explore certain analogies of
this model with Loop Quantum Cosmology.
| [
{
"created": "Thu, 26 Jan 2012 10:13:33 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Borja",
"Enrique F.",
""
],
[
"Díaz-Polo",
"Jacobo",
""
],
[
"Freidel",
"Laurent",
""
],
[
"Garay",
"Iñaki",
""
],
[
"Livine",
"Etera R.",
""
]
] | Loop Quantum Gravity is now a well established approach to quantum gravity. One of the main challenges still faced by the theory is constructing a consistent dynamics which would lead back to the standard dynamics of the gravitational field at large scales. Here we will review the recent U(N) framework for Loop Quantum Gravity and the new spinor representation (that provides a classical setting for the U(N) framework). Then, we will apply these techniques to a simple model in order to propose a dynamics for a symmetry reduced sector of the theory. Furthermore, we will explore certain analogies of this model with Loop Quantum Cosmology. |
gr-qc/0509010 | Muzaffer Adak | Muzaffer Adak, (Pamukkale Univ., Turkey) | Nonmetricity and torsion induced by dilaton gravity in two dimension | Added references, Accepted for publication in GRG | Gen.Rel.Grav. 38 (2006) 971-980 | 10.1007/s10714-006-0298-x | null | gr-qc | null | We develop a theory in which there are couplings amongst Dirac spinor,
dilaton and non-Riemannian gravity and explore the nature of connection-induced
dilaton couplings to gravity and Dirac spinor when the theory is reformulated
in terms of the Levi-Civita connection. After presenting some exact solutions
without spinors, we investigate the minimal spinor couplings to the model and
in conclusion we can not find any nontrivial dilaton couplings to spinor.
| [
{
"created": "Fri, 2 Sep 2005 09:50:18 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Nov 2005 08:16:42 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Feb 2006 09:44:15 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Adak",
"Muzaffer",
""
]
] | We develop a theory in which there are couplings amongst Dirac spinor, dilaton and non-Riemannian gravity and explore the nature of connection-induced dilaton couplings to gravity and Dirac spinor when the theory is reformulated in terms of the Levi-Civita connection. After presenting some exact solutions without spinors, we investigate the minimal spinor couplings to the model and in conclusion we can not find any nontrivial dilaton couplings to spinor. |
gr-qc/0612189 | Robert Beig | Robert Beig, Bernd G. Schmidt | Celestial mechanics of elastic bodies | 16 pages, 2 figures, several typos removed, erratum appeared in
MathZ.263:233,2009 | Math.Z.258:381-394,2008 | 10.1007/s00209-007-0177-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct time independent configurations of two gravitating elastic
bodies. These configurations either correspond to the two bodies moving in a
circular orbit around their center of mass or strictly static configurations.
| [
{
"created": "Fri, 29 Dec 2006 14:43:11 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jul 2009 14:37:20 GMT",
"version": "v2"
}
] | 2009-07-27 | [
[
"Beig",
"Robert",
""
],
[
"Schmidt",
"Bernd G.",
""
]
] | We construct time independent configurations of two gravitating elastic bodies. These configurations either correspond to the two bodies moving in a circular orbit around their center of mass or strictly static configurations. |
1805.00588 | Kiyoshi Shiraishi | Katsuhiko Yoshida, Satoru Hirenzaki, Kiyoshi Shiraishi | Euclidean wormhole solutions of Einstein-Yang-Mills theory in diverse
dimensions | 16 pages, 10 figures | Physical Review D42, No. 6, pp.1973-1981, 15 September 1990 | 10.1103/PhysRevD.42.1973 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the Euclidean Einstein equations with non-Abelian gauge fields of
sufficiently large symmetry in various dimensions. In higher-dimensional
spaces, we find the solutions which are similar to so-called scalar wormholes.
In four-dimensional space-time, we find singular wormhole solutions with
infinite Euclidean action. Wormhole solutions in the three-dimensional
Einstein-Yang-Mills theory with a Chern-Simons term are also constructed.
| [
{
"created": "Wed, 2 May 2018 00:44:21 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Yoshida",
"Katsuhiko",
""
],
[
"Hirenzaki",
"Satoru",
""
],
[
"Shiraishi",
"Kiyoshi",
""
]
] | We solve the Euclidean Einstein equations with non-Abelian gauge fields of sufficiently large symmetry in various dimensions. In higher-dimensional spaces, we find the solutions which are similar to so-called scalar wormholes. In four-dimensional space-time, we find singular wormhole solutions with infinite Euclidean action. Wormhole solutions in the three-dimensional Einstein-Yang-Mills theory with a Chern-Simons term are also constructed. |
gr-qc/0204026 | Luca Fabbri | Luca Fabbri | Taking Kaluza seriously leads to a non-gauge-invariant electromagnetic
theory in a curved space-time | 6 pages, corrected typos | Annales Fond.Broglie 29:641-649,2004 | null | null | gr-qc | null | Kaluza's mertic with the cylinder condition is considered without the weak
gravitational field approximation. It is shown that these hypoteses lead to a
non-gauge-invariant electromagnetic theory in a curved space-time. The problem
of electro-gravitational unification is considered from this point of view.
| [
{
"created": "Fri, 5 Apr 2002 14:56:24 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jul 2004 15:43:36 GMT",
"version": "v2"
}
] | 2009-05-18 | [
[
"Fabbri",
"Luca",
""
]
] | Kaluza's mertic with the cylinder condition is considered without the weak gravitational field approximation. It is shown that these hypoteses lead to a non-gauge-invariant electromagnetic theory in a curved space-time. The problem of electro-gravitational unification is considered from this point of view. |
2008.10026 | Cl\'audio Gomes | Cl\'audio Gomes | Jeans Instability in Non-Minimal Matter-Curvature Coupling Gravity | 8 pages, 1 figure | Eur.Phys.J.C 80 (2020) 7, 633 | 10.1140/epjc/s10052-020-8189-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The weak field limit of the nonminimally coupled Boltzmann equation is
studied, and relations between the invariant Bardeen scalar potentials are
derived. The Jean's criterion for instabilities is found through the modified
dispersion relation. Special cases are scrutinised and considerations on the
model parameters are discussed for Bok globules.
| [
{
"created": "Sun, 23 Aug 2020 12:18:55 GMT",
"version": "v1"
}
] | 2020-08-25 | [
[
"Gomes",
"Cláudio",
""
]
] | The weak field limit of the nonminimally coupled Boltzmann equation is studied, and relations between the invariant Bardeen scalar potentials are derived. The Jean's criterion for instabilities is found through the modified dispersion relation. Special cases are scrutinised and considerations on the model parameters are discussed for Bok globules. |
gr-qc/0301044 | Campo David | David Campo and Renaud Parentani | Space-time correlations within pairs produced during inflation, a
wave-packet analysis | discussion clarified, acknowledgements and references added, version
accepted in PRD | Phys.Rev. D67 (2003) 103522 | 10.1103/PhysRevD.67.103522 | null | gr-qc astro-ph hep-th | null | In homogeneous universes the propagation of quantum fields gives rise to pair
creation of quanta with opposite momenta. When computing expectation values of
operators, the correlations between these quanta are averaged out and no
space-time structure is obtained. In this article, by an appropriate use of
wave packets, we reveal the space-time structure of these correlations. We show
that every pair emerges from vacuum configurations which are torn apart so as
to give rise to two semi-classical currents: that carried by the particle and
that of its `partner'. The partner's current lives behind the Hubble horizon
centered around the particle. Hence any measurement performed within a Hubble
patch would correspond to an uncorrelated density matrix, as for Hawking
radiation. However, when inflation stops, the Hubble radius grows and
eventually encompasses the partner. When this is realized the coherence is
recovered within a patch. Our analysis applies to rare pair creation events as
well as to cases leading to arbitrary high occupation numbers. Hence it might
be applied to primordial gravitational waves which evolve into highly squeezed
states.
| [
{
"created": "Mon, 13 Jan 2003 17:05:06 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Apr 2003 11:15:03 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Campo",
"David",
""
],
[
"Parentani",
"Renaud",
""
]
] | In homogeneous universes the propagation of quantum fields gives rise to pair creation of quanta with opposite momenta. When computing expectation values of operators, the correlations between these quanta are averaged out and no space-time structure is obtained. In this article, by an appropriate use of wave packets, we reveal the space-time structure of these correlations. We show that every pair emerges from vacuum configurations which are torn apart so as to give rise to two semi-classical currents: that carried by the particle and that of its `partner'. The partner's current lives behind the Hubble horizon centered around the particle. Hence any measurement performed within a Hubble patch would correspond to an uncorrelated density matrix, as for Hawking radiation. However, when inflation stops, the Hubble radius grows and eventually encompasses the partner. When this is realized the coherence is recovered within a patch. Our analysis applies to rare pair creation events as well as to cases leading to arbitrary high occupation numbers. Hence it might be applied to primordial gravitational waves which evolve into highly squeezed states. |
1503.00359 | Leonard Parker | Leonard Parker | Creation of quantized particles, gravitons and scalar perturbations by
the expanding universe | Plenary Lecture given September 2, 2014 at the ERE2014 Conference in
Valencia, Spain To appear in the Proceedings of the ERE2014 Conference | null | 10.1088/1742-6596/600/1/012001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum creation processes during the very rapid early expansion of the
universe are believed to give rise to temperature anisotropies and polarization
patterns in the CMB radiation. These have been observed by satellites such as
COBE, WMAP, and PLANCK, and by bolometric instruments placed near the South
Pole by the BICEP collaborations. The expected temperature anisotropies are
well-confirmed. The B-mode polarization patterns in the CMB are currently under
measurement jointly by the PLANCK and BICEP groups to determine the extent to
which the B-modes can be attributed to gravitational waves from the creation of
gravitons in the earliest universe. It was during 1962 that I proved that
quanta of the minimally-coupled scalar field were created by the general
expanding FLRW universe. This was relevant also to the creation of quantized
perturbations of the gravitational field, since these perturbations satisfied
linear field equations that could be quantized in the same way as the
minimally-coupled scalar field equation. In fact, in 1946, E.M. Lifshitz had
considered the classical Einstein gravitational field in FLRW expanding
universes and had shown that the classical linearized Einstein field equations
reduced, in what is now known as the Lifshitz gauge, to two separate classical
minimally-coupled massless scalar field equations. These field equations of
Lifshitz, when quantized, correspond to the field equations for massless
gravitons, one equation for each of the two independent polarization components
of the spin-2 massless graviton. I will discuss this further in this article.1
1 Plenary Lecture given September 2, 2014 at the ERE2014 Conference in
Valencia, Spain
| [
{
"created": "Sun, 1 Mar 2015 21:47:37 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Parker",
"Leonard",
""
]
] | Quantum creation processes during the very rapid early expansion of the universe are believed to give rise to temperature anisotropies and polarization patterns in the CMB radiation. These have been observed by satellites such as COBE, WMAP, and PLANCK, and by bolometric instruments placed near the South Pole by the BICEP collaborations. The expected temperature anisotropies are well-confirmed. The B-mode polarization patterns in the CMB are currently under measurement jointly by the PLANCK and BICEP groups to determine the extent to which the B-modes can be attributed to gravitational waves from the creation of gravitons in the earliest universe. It was during 1962 that I proved that quanta of the minimally-coupled scalar field were created by the general expanding FLRW universe. This was relevant also to the creation of quantized perturbations of the gravitational field, since these perturbations satisfied linear field equations that could be quantized in the same way as the minimally-coupled scalar field equation. In fact, in 1946, E.M. Lifshitz had considered the classical Einstein gravitational field in FLRW expanding universes and had shown that the classical linearized Einstein field equations reduced, in what is now known as the Lifshitz gauge, to two separate classical minimally-coupled massless scalar field equations. These field equations of Lifshitz, when quantized, correspond to the field equations for massless gravitons, one equation for each of the two independent polarization components of the spin-2 massless graviton. I will discuss this further in this article.1 1 Plenary Lecture given September 2, 2014 at the ERE2014 Conference in Valencia, Spain |
1603.00151 | Yi-Zen Chu | Yi-Zen Chu | Gravitational Wave Memory In dS$_{4+2n}$ and 4D Cosmology | 30 pages, 1 figure | null | 10.1088/1361-6382/34/3/035009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that massless gravitons in all even dimensional de Sitter (dS)
spacetimes higher than two admit a linear memory effect arising from their
propagation inside the null cone. Assume that gravitational waves (GWs) are
being generated by an isolated source, and over only a finite period of time.
Outside of this time interval, suppose the shear-stress of the GW source
becomes negligible relative to its energy-momentum and its mass quadrupole
moments settle to static values. We then demonstrate, the transverse-traceless
(TT) GW contribution to the perturbation of any dS$_{4+2n}$ written in a
conformally flat form -- after the source has ceased and the primary GW train
has passed -- amounts to a spacetime constant shift in the flat metric
proportional to the difference between the TT parts of the source's final and
initial mass quadrupole moments. As a byproduct, we present solutions to
Einstein's equations linearized about de Sitter backgrounds of all dimensions
greater than three. We then point out there is a similar but approximate tail
induced linear GW memory effect in 4D matter dominated universes. Our work here
serves to improve upon and extend the 4D cosmological results of
arXiv:1504.06337, which in turn preceded complementary work by Bieri, Garfinkle
and Yau (arXiv:1509.01296) and by Kehagias and Riotto (arXiv:1602.02653).
| [
{
"created": "Tue, 1 Mar 2016 05:40:40 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Mar 2016 08:34:53 GMT",
"version": "v2"
}
] | 2017-01-18 | [
[
"Chu",
"Yi-Zen",
""
]
] | We argue that massless gravitons in all even dimensional de Sitter (dS) spacetimes higher than two admit a linear memory effect arising from their propagation inside the null cone. Assume that gravitational waves (GWs) are being generated by an isolated source, and over only a finite period of time. Outside of this time interval, suppose the shear-stress of the GW source becomes negligible relative to its energy-momentum and its mass quadrupole moments settle to static values. We then demonstrate, the transverse-traceless (TT) GW contribution to the perturbation of any dS$_{4+2n}$ written in a conformally flat form -- after the source has ceased and the primary GW train has passed -- amounts to a spacetime constant shift in the flat metric proportional to the difference between the TT parts of the source's final and initial mass quadrupole moments. As a byproduct, we present solutions to Einstein's equations linearized about de Sitter backgrounds of all dimensions greater than three. We then point out there is a similar but approximate tail induced linear GW memory effect in 4D matter dominated universes. Our work here serves to improve upon and extend the 4D cosmological results of arXiv:1504.06337, which in turn preceded complementary work by Bieri, Garfinkle and Yau (arXiv:1509.01296) and by Kehagias and Riotto (arXiv:1602.02653). |
1605.02781 | Kimet Jusufi | Kimet Jusufi | Light Deflection with Torsion Effects Caused by a Spinning Cosmic String | 7 pages, accepted for publication in European Physical Journal C | Eur. Phys. J. C (2016) 76:332 | 10.1140/epjc/s10052-016-4185-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a new geometrical method introduced by Werner, we find the deflection
angle in the weak limit approximation by a spinning cosmic string in the
context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the
String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the
optical geometry and derive the leading terms of the deflection angle in the
equatorial plane. Calculations shows that light deflection is affected by the
intrinsic spin of the cosmic string and torsion.
| [
{
"created": "Mon, 9 May 2016 21:02:06 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2016 11:13:58 GMT",
"version": "v2"
}
] | 2016-06-17 | [
[
"Jusufi",
"Kimet",
""
]
] | Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculations shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion. |
1711.04254 | Dr. Sudhaker Upadhyay | Sudhaker Upadhyay and Behnam Pourhassan | Logarithmic corrected Van der Waals black holes in higher dimensional
AdS space | 18 pages, 18 captioned figures, to appear in PTEP | Prog. Theor. Exp. Phys. 2019, 013B03 | 10.1093/ptep/pty145 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider AdS black hole in $d$-dimensional space-time and
calculate the logarithmic corrected thermodynamics quantities. We study the
effects of thermal fluctuations on the thermodynamics of higher dimensional AdS
black hole. We exploit such logarithmic corrected quantities to construct Van
der Walls black holes solution and study the effects of logarithmic correction
on the Van der Waals black holes. We also investigate the effect of thermal
fluctuations on the equation of state. We find that the Van der Waals black
hole is completely stable in the presence of the logarithmic correction.
| [
{
"created": "Sun, 12 Nov 2017 09:06:19 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jul 2018 08:05:17 GMT",
"version": "v2"
},
{
"created": "Sat, 8 Dec 2018 14:23:14 GMT",
"version": "v3"
}
] | 2019-08-21 | [
[
"Upadhyay",
"Sudhaker",
""
],
[
"Pourhassan",
"Behnam",
""
]
] | In this paper, we consider AdS black hole in $d$-dimensional space-time and calculate the logarithmic corrected thermodynamics quantities. We study the effects of thermal fluctuations on the thermodynamics of higher dimensional AdS black hole. We exploit such logarithmic corrected quantities to construct Van der Walls black holes solution and study the effects of logarithmic correction on the Van der Waals black holes. We also investigate the effect of thermal fluctuations on the equation of state. We find that the Van der Waals black hole is completely stable in the presence of the logarithmic correction. |
2009.04335 | Andrea Giusti | Andrea Giusti, Roberto Garrappa, Genevi\`eve Vachon | On the Kuzmin model in fractional Newtonian gravity | 13 pages, 8 figures, published in EPJ Plus | Eur. Phys. J. Plus 135 (2020) 798 | 10.1140/epjp/s13360-020-00831-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fractional Newtonian gravity, based on the fractional generalization of
Poisson's equation for Newtonian gravity, is a novel approach to Galactic
dynamics aimed at providing an alternative to the dark matter paradigm through
a non-local modification of Newton's theory. We provide an in-depth discussion
of the gravitational potential for the Kuzmin disk within this new approach.
Specifically, we derive an integral and a series representation for the
potential, we verify its asymptotic behavior at large scales, and we provide
illuminating plots of the resulting equipotential surfaces.
| [
{
"created": "Wed, 9 Sep 2020 14:47:23 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Oct 2020 12:23:20 GMT",
"version": "v2"
}
] | 2020-10-12 | [
[
"Giusti",
"Andrea",
""
],
[
"Garrappa",
"Roberto",
""
],
[
"Vachon",
"Geneviève",
""
]
] | Fractional Newtonian gravity, based on the fractional generalization of Poisson's equation for Newtonian gravity, is a novel approach to Galactic dynamics aimed at providing an alternative to the dark matter paradigm through a non-local modification of Newton's theory. We provide an in-depth discussion of the gravitational potential for the Kuzmin disk within this new approach. Specifically, we derive an integral and a series representation for the potential, we verify its asymptotic behavior at large scales, and we provide illuminating plots of the resulting equipotential surfaces. |
0801.3740 | Massimo Bassan | A.V.Gusev, V.N.Rudenko, S.A.Cheprasov, M.Bassan | Reception frequency bandwidth of a gravitational resonant detector with
optical readout | 16 pages + 3 figures. Accepted for publicationi in Class. Quantum
Grav | null | 10.1088/0264-9381/25/5/055006 | null | gr-qc | null | A gravitational resonant bar detector with a large scale Fabry-Perot cavity
as an optical read out and a mechanical displacement transformer is considered.
We calculate, in a fully analytical way, the final receiver bandwidth in which
the potential sensitivity, limited only by the bar thermal noise, is maintained
despite the additional thermal noise of the transformer and the additive noise
of the optical readout. We discuss also an application to the OGRAN project,
where the bar is instrumented with a 2m long FP cavity.
| [
{
"created": "Thu, 24 Jan 2008 12:29:55 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Feb 2008 17:54:13 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Gusev",
"A. V.",
""
],
[
"Rudenko",
"V. N.",
""
],
[
"Cheprasov",
"S. A.",
""
],
[
"Bassan",
"M.",
""
]
] | A gravitational resonant bar detector with a large scale Fabry-Perot cavity as an optical read out and a mechanical displacement transformer is considered. We calculate, in a fully analytical way, the final receiver bandwidth in which the potential sensitivity, limited only by the bar thermal noise, is maintained despite the additional thermal noise of the transformer and the additive noise of the optical readout. We discuss also an application to the OGRAN project, where the bar is instrumented with a 2m long FP cavity. |
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