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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1611.04284 | Parthapratim Pradhan | Parthapratim Pradhan | Thermodynamic Volume Product in Spherically Symmetric and Axisymmetric
Spacetime | 19 pages, Invited Article, Accepted in Advances in High Energy
Physics, 2018 | null | 10.1155/2018/5816826 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Letter, we have examined the thermodynamic volume products for
spherically symmetric and axisymmetric spacetimes in the framework of
\emph{extended phase space}. Such volume products usually formulated in terms
of the outer horizon~(${\cal H}^{+}$) and the inner horizon~(${\cal H}^{-}$) of
black hole ~ (BH) spacetime. Besides volume product, the other thermodynamic
formulations like \emph{volume sum, volume minus and volume division} are
considered for a wide variety of spherically symmetric spacetime and
axisymmetric spacetimes. Like area~(or entropy) product of multihorizons, the
mass-independent~(universal) feature of volume products are sometimes also
\emph{fail}. In particular for a spherically symmetric AdS spacetimes the
simple thermodynamic volume product of ${\cal H}^{\pm}$ is not
mass-independent. In this case, more complicated combinations of outer and
inner horizon volume products are indeed mass-independent. For a particular
class of spherically symmetric cases i.e. Reissner Nordstr\"om BH of Einstein
gravity and Kehagias-Sfetsos BH of Ho\v{r}ava Lifshitz gravity, the
thermodynamic volume products of ${\cal H}^{\pm}$ is indeed \emph{universal}.
For axisymmetric class of BH spacetime in Einstein gravity all the combinations
are \emph{mass-dependent}. There has been no chance to formulate any
combinations of volume product relation is to be mass-independent.
Interestingly, \emph{only the rotating BTZ black hole} in 3D provides the
volume product formula is mass-independent i.e. \emph{universal} and hence it
is quantized.
| [
{
"created": "Mon, 14 Nov 2016 08:39:26 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Jun 2018 16:19:19 GMT",
"version": "v2"
}
] | 2018-06-19 | [
[
"Pradhan",
"Parthapratim",
""
]
] | In this Letter, we have examined the thermodynamic volume products for spherically symmetric and axisymmetric spacetimes in the framework of \emph{extended phase space}. Such volume products usually formulated in terms of the outer horizon~(${\cal H}^{+}$) and the inner horizon~(${\cal H}^{-}$) of black hole ~ (BH) spacetime. Besides volume product, the other thermodynamic formulations like \emph{volume sum, volume minus and volume division} are considered for a wide variety of spherically symmetric spacetime and axisymmetric spacetimes. Like area~(or entropy) product of multihorizons, the mass-independent~(universal) feature of volume products are sometimes also \emph{fail}. In particular for a spherically symmetric AdS spacetimes the simple thermodynamic volume product of ${\cal H}^{\pm}$ is not mass-independent. In this case, more complicated combinations of outer and inner horizon volume products are indeed mass-independent. For a particular class of spherically symmetric cases i.e. Reissner Nordstr\"om BH of Einstein gravity and Kehagias-Sfetsos BH of Ho\v{r}ava Lifshitz gravity, the thermodynamic volume products of ${\cal H}^{\pm}$ is indeed \emph{universal}. For axisymmetric class of BH spacetime in Einstein gravity all the combinations are \emph{mass-dependent}. There has been no chance to formulate any combinations of volume product relation is to be mass-independent. Interestingly, \emph{only the rotating BTZ black hole} in 3D provides the volume product formula is mass-independent i.e. \emph{universal} and hence it is quantized. |
2311.12362 | Shu-Min Wu | Shu-Min Wu, Xiao-Wei Teng, Jin-Xuan Li, Si-Han Li, Tong-Hua Liu,
Jie-Ci Wang | Genuinely accessible and inaccessible entanglement in Schwarzschild
black hole | 14 pages, 1 figure | Phys. Lett. B 848 (2024) 138334 | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | The genuine entanglement of Dirac fields for an N-partite system is
investigated in Schwarzschild spacetime and the analysis is carried out using
the single-mode approximation. Due to the Hawking effect, quantum entanglement
is divided into two parts physically accessible and inaccessible entanglement.
We obtain a general analytic expression of genuine N-partite entanglement that
includes all accessible and inaccessible entanglement in a Schwarzschild black
hole. Unlike bosonic entanglement, the accessible N-partite entanglement of
Dirac fields monotonically decreases to a nonzero value with the Hawking
temperature. Interestingly, the inaccessible N-partite entanglement is a
monotonic or non-monotonic function of the Hawking temperature, depending on
the ratio between accessible and inaccessible modes, in contrast to bipartite
or tripartite entanglement that is only a monotonic function of the Hawking
temperature. Finally, we obtain two restrictive relationships for the quantum
information of the black hole. This conclusion provides a new understanding of
Hawking effect of the black hole.
| [
{
"created": "Tue, 21 Nov 2023 05:47:24 GMT",
"version": "v1"
}
] | 2023-11-22 | [
[
"Wu",
"Shu-Min",
""
],
[
"Teng",
"Xiao-Wei",
""
],
[
"Li",
"Jin-Xuan",
""
],
[
"Li",
"Si-Han",
""
],
[
"Liu",
"Tong-Hua",
""
],
[
"Wang",
"Jie-Ci",
""
]
] | The genuine entanglement of Dirac fields for an N-partite system is investigated in Schwarzschild spacetime and the analysis is carried out using the single-mode approximation. Due to the Hawking effect, quantum entanglement is divided into two parts physically accessible and inaccessible entanglement. We obtain a general analytic expression of genuine N-partite entanglement that includes all accessible and inaccessible entanglement in a Schwarzschild black hole. Unlike bosonic entanglement, the accessible N-partite entanglement of Dirac fields monotonically decreases to a nonzero value with the Hawking temperature. Interestingly, the inaccessible N-partite entanglement is a monotonic or non-monotonic function of the Hawking temperature, depending on the ratio between accessible and inaccessible modes, in contrast to bipartite or tripartite entanglement that is only a monotonic function of the Hawking temperature. Finally, we obtain two restrictive relationships for the quantum information of the black hole. This conclusion provides a new understanding of Hawking effect of the black hole. |
1507.00612 | Yu Shi | Yue Dai, Zhejun Shen, Yu Shi | Killing quantum entanglement by acceleration or a black hole | 14 pages | JHEP 09 (2015) 071 | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider two entangled accelerating qubits coupled with real scalar
fields, each described by the Unruh-Wald model. It is demonstrated that because
of the Unruh effect, the bipartite entanglement of the two qubits suddenly dies
when the acceleration of one or more qubits are large enough. We also consider
three entangled accelerating qubits in GHZ state and in W state, with equal
acceleration-frequency ratio, and found that in either state, the tripartite
entanglement suddenly dies at a certain value of acceleration-frequency ratio.
The equivalence between the Rindler metric and the Schwarzchild metric in the
vicinity of the horizon of a black hole implies that for the two entangled
qubits outside a black hole, the entanglement suddenly dies when one or both of
the qubits are close enough to the horizon, while for the three entangled
qubits in GHZ or W state, the tripartite entanglement suddenly dies when these
qubits are close enough to the horizon.
| [
{
"created": "Thu, 2 Jul 2015 15:05:02 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Dec 2015 14:10:47 GMT",
"version": "v2"
}
] | 2015-12-15 | [
[
"Dai",
"Yue",
""
],
[
"Shen",
"Zhejun",
""
],
[
"Shi",
"Yu",
""
]
] | We consider two entangled accelerating qubits coupled with real scalar fields, each described by the Unruh-Wald model. It is demonstrated that because of the Unruh effect, the bipartite entanglement of the two qubits suddenly dies when the acceleration of one or more qubits are large enough. We also consider three entangled accelerating qubits in GHZ state and in W state, with equal acceleration-frequency ratio, and found that in either state, the tripartite entanglement suddenly dies at a certain value of acceleration-frequency ratio. The equivalence between the Rindler metric and the Schwarzchild metric in the vicinity of the horizon of a black hole implies that for the two entangled qubits outside a black hole, the entanglement suddenly dies when one or both of the qubits are close enough to the horizon, while for the three entangled qubits in GHZ or W state, the tripartite entanglement suddenly dies when these qubits are close enough to the horizon. |
2407.15968 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | Quantum two-level systems and gravitational waves | 14 pages, LaTeX | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the interaction between gravitational waves and a quantum two-level
system consisting of a spin 1/2 particle using the formalism of the proper
detector frame. This approach highlights the effects of gravitational waves on
both the particles and the observer, emphasizing that only relative
measurements can be made. Specifically, within this framework, the
gravitational field of the waves is described using the gravitoelectromagnetic
analogy. The interaction of the system is then determined by the
gravitomagnetic field of the wave, which induces a time-dependent perturbation.
We analyze this perturbation for both generic frequencies and resonance
conditions, and discuss its implications.
| [
{
"created": "Mon, 22 Jul 2024 18:28:53 GMT",
"version": "v1"
}
] | 2024-07-24 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | We study the interaction between gravitational waves and a quantum two-level system consisting of a spin 1/2 particle using the formalism of the proper detector frame. This approach highlights the effects of gravitational waves on both the particles and the observer, emphasizing that only relative measurements can be made. Specifically, within this framework, the gravitational field of the waves is described using the gravitoelectromagnetic analogy. The interaction of the system is then determined by the gravitomagnetic field of the wave, which induces a time-dependent perturbation. We analyze this perturbation for both generic frequencies and resonance conditions, and discuss its implications. |
gr-qc/9803084 | Plamen Fiziev | T. Boyadjiev, P. Fiziev, S. Yazadjiev | Neutron star in presence of torsion-dilaton field | 29 pages, latex, 24 figures, final version. Added: 1)comments on
different possible mass definitions; 2)new sections: a)the inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments;
b)stability analysis via catastrophe theory; 3)new figers added and some
figures replaced. 4)new references | Class.Quant.Grav.16:2359-2380,1999 | 10.1088/0264-9381/16/7/314 | SU-FzF: 2/98 | gr-qc astro-ph nucl-th | null | We develop the general theory of stars in Saa's model of gravity with
propagating torsion and study the basic stationary state of neutron star. Our
numerical results show that the torsion force decreases the role of the gravity
in the star configuration leading to significant changes in the neutron star
masses depending on the equation of state of star matter. The inconsistency of
the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments is
discussed.
| [
{
"created": "Thu, 26 Mar 1998 09:25:00 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jun 1998 06:27:42 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Jul 1999 08:24:08 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Boyadjiev",
"T.",
""
],
[
"Fiziev",
"P.",
""
],
[
"Yazadjiev",
"S.",
""
]
] | We develop the general theory of stars in Saa's model of gravity with propagating torsion and study the basic stationary state of neutron star. Our numerical results show that the torsion force decreases the role of the gravity in the star configuration leading to significant changes in the neutron star masses depending on the equation of state of star matter. The inconsistency of the Saa's model with Roll-Krotkov-Dicke and Braginsky-Panov experiments is discussed. |
2104.13115 | Umananda Dev Goswami | Dhruba Jyoti Gogoi, Umananda Dev Goswami | Quasinormal Modes of Black Holes with Non-Linear-Electrodynamic sources
in Rastall Gravity | 24 pages, 20 figures; Title is changed slightly; Added some
explanations; This is the accepted version in Physics of the Dark Universe | Physics of the Dark Universe 33, 100860 (2021) | 10.1016/j.dark.2021.100860 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | One of the notable modifications of General Relativity (GR) is the Rastall
gravity. We have studied the polarization modes of Gravitational Waves (GWs) in
this gravity. It is found that at a very far distance away from the source of
GWs, Rastall gravity behaves identically to GR. That is, we get only two
massless tensor polarization modes of GWs in the theory. Afterwards, we have
extended our study to quasinormal modes of black holes in Rastall gravity in
presence of non-linear electrodynamic sources. Here the impacts of cosmological
field, dust field, phantom field, quintessence field and radiation field on the
quasinormal modes in presence of electrodynamic sources have been investigated.
Apart from this, we have also checked the dependency of quasinormal modes with
the Rastall parameter $\lambda$, black hole structural constant $N_s$ and
charge of the black hole $Q$. The study shows that the quasinormal modes
corresponding to the black hole with non-linear electrodynamic sources show
significant deviations from a general charged black hole in Rastall gravity
under certain conditions. Further, the behaviour of black holes and hence the
quasinormal modes depend on the type of surrounding field considered.
| [
{
"created": "Tue, 27 Apr 2021 11:30:06 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jul 2021 13:03:26 GMT",
"version": "v2"
}
] | 2021-08-03 | [
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | One of the notable modifications of General Relativity (GR) is the Rastall gravity. We have studied the polarization modes of Gravitational Waves (GWs) in this gravity. It is found that at a very far distance away from the source of GWs, Rastall gravity behaves identically to GR. That is, we get only two massless tensor polarization modes of GWs in the theory. Afterwards, we have extended our study to quasinormal modes of black holes in Rastall gravity in presence of non-linear electrodynamic sources. Here the impacts of cosmological field, dust field, phantom field, quintessence field and radiation field on the quasinormal modes in presence of electrodynamic sources have been investigated. Apart from this, we have also checked the dependency of quasinormal modes with the Rastall parameter $\lambda$, black hole structural constant $N_s$ and charge of the black hole $Q$. The study shows that the quasinormal modes corresponding to the black hole with non-linear electrodynamic sources show significant deviations from a general charged black hole in Rastall gravity under certain conditions. Further, the behaviour of black holes and hence the quasinormal modes depend on the type of surrounding field considered. |
2304.08019 | Yongqiang Wang | Tian-Xiang Ma, Chen Liang, Jie Yang, Yong-Qiang Wang | Hybrid Proca-boson stars | 29 pages, 14 figures. arXiv admin note: text overlap with
arXiv:2207.11147 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct a hybrid boson star model that contains a complex
scalar field and a Proca field. The scalar field is in the ground state, while
the Proca field is in the first excited state. We numerically solve the model
and obtain solution families of different coexisting states by considering both
synchronized and nonsynchronized cases. By examining the relation between ADM
mass and synchronized frequency $\tilde{\omega}$ or nonsynchronized frequency
$\tilde{\omega}_P$, we identify several types of solution families for the
hybrid boson stars. In addition to solutions that intersect the scalar field
and the Proca field at each end, there are also several types of multi-branch
coexisting state solutions. The characteristics of various solutions are
analyzed and discussed in detail. We calculate the binding energy $E$ of the
hybrid Proca-boson stars and provide the relationship between $E$ and both
synchronized frequency $\tilde{\omega}$ and nonsynchronized frequency
$\tilde{\omega}_P$. Furthermore, we obtain the stability of the corresponding
hybrid star solution families from these analyses above.
| [
{
"created": "Mon, 17 Apr 2023 06:56:10 GMT",
"version": "v1"
}
] | 2023-04-18 | [
[
"Ma",
"Tian-Xiang",
""
],
[
"Liang",
"Chen",
""
],
[
"Yang",
"Jie",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we construct a hybrid boson star model that contains a complex scalar field and a Proca field. The scalar field is in the ground state, while the Proca field is in the first excited state. We numerically solve the model and obtain solution families of different coexisting states by considering both synchronized and nonsynchronized cases. By examining the relation between ADM mass and synchronized frequency $\tilde{\omega}$ or nonsynchronized frequency $\tilde{\omega}_P$, we identify several types of solution families for the hybrid boson stars. In addition to solutions that intersect the scalar field and the Proca field at each end, there are also several types of multi-branch coexisting state solutions. The characteristics of various solutions are analyzed and discussed in detail. We calculate the binding energy $E$ of the hybrid Proca-boson stars and provide the relationship between $E$ and both synchronized frequency $\tilde{\omega}$ and nonsynchronized frequency $\tilde{\omega}_P$. Furthermore, we obtain the stability of the corresponding hybrid star solution families from these analyses above. |
gr-qc/0207060 | Sawa Manoff | Sawa Manoff and Bogdan Dimitrov | Flows and particles with shear-free and expansion-free velocities in
(L^-_n,g)- and Weyl's spaces | 20 pages, LaTeX, to appear in Classical and Quantum Gravity. arXiv
admin note: substantial text overlap with arXiv:gr-qc/0011045 | Class.Quant.Grav. 19 (2002) 4377-4398 | 10.1088/0264-9381/19/16/311 | null | gr-qc | null | Conditions for the existence of flows with non-null shear-free and
expansion-free velocities in spaces with affine connections and metrics are
found. On their basis, generalized Weyl's spaces with shear-free and
expansion-free conformal Killing vectors as velocity's vectors of spinless test
particles moving in a Weyl's space are considered. The necessary and sufficient
conditions are found under which a free spinless test particle could move in
spaces with affine connections and metrics on a curve described by means of an
auto-parallel equation. In Weyl's spaces with Weyl's covector, constructed by
the use of a dilaton field, the dilaton field appears as a scaling factor for
the rest mass density of the test particle. PACS numbers: 02.40.Ky, 04.20.Cv,
04.50.+h, 04.90.+e
| [
{
"created": "Tue, 16 Jul 2002 10:52:22 GMT",
"version": "v1"
}
] | 2012-07-10 | [
[
"Manoff",
"Sawa",
""
],
[
"Dimitrov",
"Bogdan",
""
]
] | Conditions for the existence of flows with non-null shear-free and expansion-free velocities in spaces with affine connections and metrics are found. On their basis, generalized Weyl's spaces with shear-free and expansion-free conformal Killing vectors as velocity's vectors of spinless test particles moving in a Weyl's space are considered. The necessary and sufficient conditions are found under which a free spinless test particle could move in spaces with affine connections and metrics on a curve described by means of an auto-parallel equation. In Weyl's spaces with Weyl's covector, constructed by the use of a dilaton field, the dilaton field appears as a scaling factor for the rest mass density of the test particle. PACS numbers: 02.40.Ky, 04.20.Cv, 04.50.+h, 04.90.+e |
gr-qc/0104077 | Carl E. Dolby | Carl E. Dolby, Stephen F. Gull | On Radar Time and the Twin `Paradox' | 9 pages, 10 figures. Minor changes (includes minor corrections not in
published version) | Am.J.Phys. 69 (2001) 1257-1261 | 10.1119/1.1407254 | null | gr-qc hep-th | null | In this paper we apply the concept of radar time (popularised by Bondi in his
work on k-calculus) to the well-known relativistic twin `paradox'. Radar time
is used to define hypersurfaces of simultaneity for a class of travelling
twins, from the `Immediate Turn-around' case, through the `Gradual Turn-around'
case, to the `Uniformly Accelerating' case. We show that this definition of
simultaneity is independent of choice of coordinates, and assigns a unique time
to any event (with which the travelling twin can send and receive signals),
resolving some common misconceptions.
| [
{
"created": "Tue, 24 Apr 2001 15:25:21 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2002 13:33:50 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Dolby",
"Carl E.",
""
],
[
"Gull",
"Stephen F.",
""
]
] | In this paper we apply the concept of radar time (popularised by Bondi in his work on k-calculus) to the well-known relativistic twin `paradox'. Radar time is used to define hypersurfaces of simultaneity for a class of travelling twins, from the `Immediate Turn-around' case, through the `Gradual Turn-around' case, to the `Uniformly Accelerating' case. We show that this definition of simultaneity is independent of choice of coordinates, and assigns a unique time to any event (with which the travelling twin can send and receive signals), resolving some common misconceptions. |
1710.08198 | Boris Latosh | Andrej Arbuzov, Boris Latosh | Conformally Coupled General Relativity | 20 pages | Universe 2018, 4(2), 38 | 10.3390/universe4020038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity model developed in the series of papers
\cite{Arbuzov:2009zza,Arbuzov:2010fz,Pervushin:2011gz} is revisited. Model is
based on Ogievetsky theorem that specifies structure of general coordinate
transformation group. The theorem is implemented in the context of Noether
theorem with the use of nonlinear representation technique. Canonical
quantization is performed with the use of reparametrization-invariant time and
ADM foliation techniques. Basic quantum features of the models are discussed.
Mistakes occurred in the previous papers are corrected.
| [
{
"created": "Mon, 23 Oct 2017 10:59:05 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2018 09:31:43 GMT",
"version": "v2"
}
] | 2018-02-15 | [
[
"Arbuzov",
"Andrej",
""
],
[
"Latosh",
"Boris",
""
]
] | Gravity model developed in the series of papers \cite{Arbuzov:2009zza,Arbuzov:2010fz,Pervushin:2011gz} is revisited. Model is based on Ogievetsky theorem that specifies structure of general coordinate transformation group. The theorem is implemented in the context of Noether theorem with the use of nonlinear representation technique. Canonical quantization is performed with the use of reparametrization-invariant time and ADM foliation techniques. Basic quantum features of the models are discussed. Mistakes occurred in the previous papers are corrected. |
gr-qc/0605078 | Matteo Carrera | Matteo Carrera and Domenico Giulini | On Doppler tracking in cosmological spacetimes | 10 pages, 1 figure. Journal version | Class.Quant.Grav. 23 (2006) 7483-7492 | 10.1088/0264-9381/23/24/019 | Freiburg THEP-06/06 | gr-qc astro-ph physics.space-ph | null | We give a rigorous derivation of the general-relativistic formula for the
two-way Doppler tracking of a spacecraft in Friedmann-Lemaitre-Robertson-Walker
and in McVittie spacetimes. The leading order corrections of the so-determined
acceleration to the Newtonian acceleration are due to special-relativistic
effects and cosmological expansion. The latter, although linear in the Hubble
constant, is negligible in typical applications within the Solar System.
| [
{
"created": "Fri, 12 May 2006 19:45:38 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jul 2006 16:18:18 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Nov 2006 14:54:31 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Carrera",
"Matteo",
""
],
[
"Giulini",
"Domenico",
""
]
] | We give a rigorous derivation of the general-relativistic formula for the two-way Doppler tracking of a spacecraft in Friedmann-Lemaitre-Robertson-Walker and in McVittie spacetimes. The leading order corrections of the so-determined acceleration to the Newtonian acceleration are due to special-relativistic effects and cosmological expansion. The latter, although linear in the Hubble constant, is negligible in typical applications within the Solar System. |
1607.08610 | Juliano Neves | J. C. S. Neves | Bouncing cosmology inspired by regular black holes | 9 pages, 1 figure. Version 3 matches the published version in General
Relativity and Gravitation | Gen. Relativ. Gravit. 49, 124 (2017) | 10.1007/s10714-017-2288-6 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we present a bouncing cosmology inspired by a family of
regular black holes. This scale-dependent cosmology deviates from the
cosmological principle by means of a scale factor which depends on the time and
the radial coordinate as well. The model is isotropic but not perfectly
homogeneous. That is, this cosmology describes a universe almost homogeneous
only for large scales, such as our observable universe.
| [
{
"created": "Thu, 28 Jul 2016 18:45:05 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Aug 2016 15:19:29 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Aug 2017 13:58:56 GMT",
"version": "v3"
}
] | 2017-08-30 | [
[
"Neves",
"J. C. S.",
""
]
] | In this article, we present a bouncing cosmology inspired by a family of regular black holes. This scale-dependent cosmology deviates from the cosmological principle by means of a scale factor which depends on the time and the radial coordinate as well. The model is isotropic but not perfectly homogeneous. That is, this cosmology describes a universe almost homogeneous only for large scales, such as our observable universe. |
gr-qc/0301012 | Wai-Mo Suen | J. L. Lu and W.-M. Suen | Extrinsic Curvature Embedding Diagrams | 22 pages, 4 figures | Gen.Rel.Grav. 35 (2003) 1175-1189 | 10.1023/A:1024441623121 | Wugrav-03-03 | gr-qc | null | Embedding diagrams have been used extensively to visualize the properties of
curved space in Relativity. We introduce a new kind of embedding diagram based
on the {\it extrinsic} curvature (instead of the intrinsic curvature). Such an
extrinsic curvature embedding diagram, when used together with the usual kind
of intrinsic curvature embedding diagram, carries the information of how a
surface is {\it embedded} in the higher dimensional curved space. Simple
examples are given to illustrate the idea.
| [
{
"created": "Sun, 5 Jan 2003 15:22:28 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Lu",
"J. L.",
""
],
[
"Suen",
"W. -M.",
""
]
] | Embedding diagrams have been used extensively to visualize the properties of curved space in Relativity. We introduce a new kind of embedding diagram based on the {\it extrinsic} curvature (instead of the intrinsic curvature). Such an extrinsic curvature embedding diagram, when used together with the usual kind of intrinsic curvature embedding diagram, carries the information of how a surface is {\it embedded} in the higher dimensional curved space. Simple examples are given to illustrate the idea. |
2312.02115 | Roberto A. Sussman | Roberto A Sussman and Sebastian Najera | Exact solutions of Cotton Gravity in its Codazzi formulation | Important updates and corrections, new references added, discussion
on criticism of the theory. Typos and minors errors corrected. 11 pages, one
figure | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The "Codazzi formulation", based on a Codazzi tensor, provides a more robust
and straightforward theoretical framework for "Cotton Gravity" (CG) than its
original formulation in terms of the Cotton tensor. Using this formulation we
provide a self-consistent procedure to generate non-trivial exact solutions in
CG that generalize well known General Relativity (GR) solutions. We re-derive a
known CG solution that generalizes the Schwarzschild solution of GR, showing
that it is the unique vacuum solution of static spherical symmetry in CG,
extending this result to a CG generalization of the Reissner-Nordstrom solution
of GR, all of which places a strong case supporting the fulfillment of
Birkhoff's theorem. When applied to Friedman-Lema\^\i tre-Robertson-Walker
(FLRW) models CG naturally identifies the $\Lambda$CDM model as the unique FLRW
dust model with constant negative spatial curvature. We also obtain CG
generalizations of the Lema\^\i tre-Tolman-Bondi (LTB) and Szekeres dust
solutions of GR, allowing for time and space dependent changes from decelerated
to accelerated evolution, without necessarily assuming a dark energy source.
The CG generalization of static perfect fluid spheres allows in the weak field
regime to model the flattening of rotation velocities in spherical galactic
systems without assuming dark matter. We also generalize non-static spherically
symmetric perfect fluid solutions with a shear-free 4 velocity. Our results
suggest the need for further research using the Codazzi formulation to explore
the potential for applications of CG to current open problems in gravitational
systems.
| [
{
"created": "Mon, 4 Dec 2023 18:47:36 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2024 22:49:26 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Feb 2024 02:54:04 GMT",
"version": "v3"
}
] | 2024-02-05 | [
[
"Sussman",
"Roberto A",
""
],
[
"Najera",
"Sebastian",
""
]
] | The "Codazzi formulation", based on a Codazzi tensor, provides a more robust and straightforward theoretical framework for "Cotton Gravity" (CG) than its original formulation in terms of the Cotton tensor. Using this formulation we provide a self-consistent procedure to generate non-trivial exact solutions in CG that generalize well known General Relativity (GR) solutions. We re-derive a known CG solution that generalizes the Schwarzschild solution of GR, showing that it is the unique vacuum solution of static spherical symmetry in CG, extending this result to a CG generalization of the Reissner-Nordstrom solution of GR, all of which places a strong case supporting the fulfillment of Birkhoff's theorem. When applied to Friedman-Lema\^\i tre-Robertson-Walker (FLRW) models CG naturally identifies the $\Lambda$CDM model as the unique FLRW dust model with constant negative spatial curvature. We also obtain CG generalizations of the Lema\^\i tre-Tolman-Bondi (LTB) and Szekeres dust solutions of GR, allowing for time and space dependent changes from decelerated to accelerated evolution, without necessarily assuming a dark energy source. The CG generalization of static perfect fluid spheres allows in the weak field regime to model the flattening of rotation velocities in spherical galactic systems without assuming dark matter. We also generalize non-static spherically symmetric perfect fluid solutions with a shear-free 4 velocity. Our results suggest the need for further research using the Codazzi formulation to explore the potential for applications of CG to current open problems in gravitational systems. |
gr-qc/9507055 | I. Racz | Istvan Racz and Robert M. Wald | Global Extensions of Spacetimes Describing Asymptotic Final States of
Black Holes | 20 pages, plain tex | Class.Quant.Grav. 13 (1996) 539-553 | 10.1088/0264-9381/13/3/017 | null | gr-qc | null | We consider a globally hyperbolic, stationary spacetime containing a black
hole but no white hole. We assume, further, that the event horizon, $\tn$, of
the black hole is a Killing horizon with compact cross-sections. We prove that
if surface gravity is non-zero constant throughout the horizon one can {\it
globally} extend such a spacetime so that the image of $\cal N$ is a proper
subset of a regular bifurcate Killing horizon in the enlarged spacetime. The
necessary and sufficient conditions are given for the extendibility of matter
fields to the enlarged spacetime. These conditions are automatically satisfied
if the spacetime is static (and, hence ``$t$"-reflection symmetric) or
stationary-axisymmetric with ``$t-\phi$" reflection isometry and the matter
fields respect the reflection isometry. In addition, we prove that a necessary
and sufficient condition for the constancy of the surface gravity on a Killing
horizon is that the exterior derivative of the twist of the horizon Killing
field vanish on the horizon. As a corollary of this, we recover a result of
Carter that constancy of surface gravity holds for any black hole which is
static or stationary- axisymmetric with the ``$t-\phi$" reflection isometry. No
use of Einstein's equation is made in obtaining any of the above results. Taken
together, these results support the view that any spacetime representing the
asymptotic final state of a black hole formed by gravitational collapse may be
assumed to possess a bifurcate Killing horizon or a Killing horizon with
vanishing surface gravity.
| [
{
"created": "Fri, 28 Jul 1995 14:58:15 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Racz",
"Istvan",
""
],
[
"Wald",
"Robert M.",
""
]
] | We consider a globally hyperbolic, stationary spacetime containing a black hole but no white hole. We assume, further, that the event horizon, $\tn$, of the black hole is a Killing horizon with compact cross-sections. We prove that if surface gravity is non-zero constant throughout the horizon one can {\it globally} extend such a spacetime so that the image of $\cal N$ is a proper subset of a regular bifurcate Killing horizon in the enlarged spacetime. The necessary and sufficient conditions are given for the extendibility of matter fields to the enlarged spacetime. These conditions are automatically satisfied if the spacetime is static (and, hence ``$t$"-reflection symmetric) or stationary-axisymmetric with ``$t-\phi$" reflection isometry and the matter fields respect the reflection isometry. In addition, we prove that a necessary and sufficient condition for the constancy of the surface gravity on a Killing horizon is that the exterior derivative of the twist of the horizon Killing field vanish on the horizon. As a corollary of this, we recover a result of Carter that constancy of surface gravity holds for any black hole which is static or stationary- axisymmetric with the ``$t-\phi$" reflection isometry. No use of Einstein's equation is made in obtaining any of the above results. Taken together, these results support the view that any spacetime representing the asymptotic final state of a black hole formed by gravitational collapse may be assumed to possess a bifurcate Killing horizon or a Killing horizon with vanishing surface gravity. |
0904.0423 | Kirill Krasnov | Kirill Krasnov | Plebanski Formulation of General Relativity: A Practical Introduction | (v1) 13 pages, no figures (v2) 15 pages, published version | Gen.Rel.Grav.43:1-15,2011 | 10.1007/s10714-010-1061-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a pedagogical introduction into an old, but unfortunately not
commonly known formulation of GR in terms of self-dual two-forms due to in
particular Jerzy Plebanski. Our presentation is rather explicit in that we show
how the familiar textbook solutions: Schwarzschild, Volkoff-Oppenheimer, as
well as those describing the Newtonian limit, a gravitational wave and the
homogeneous isotropic Universe can be obtained within this formalism. Our
description shows how Plebanski formulation gives quite an economical
alternative to the usual metric and frame-based schemes for deriving Einstein
equations.
| [
{
"created": "Thu, 2 Apr 2009 16:36:19 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Sep 2010 12:21:34 GMT",
"version": "v2"
}
] | 2011-03-04 | [
[
"Krasnov",
"Kirill",
""
]
] | We give a pedagogical introduction into an old, but unfortunately not commonly known formulation of GR in terms of self-dual two-forms due to in particular Jerzy Plebanski. Our presentation is rather explicit in that we show how the familiar textbook solutions: Schwarzschild, Volkoff-Oppenheimer, as well as those describing the Newtonian limit, a gravitational wave and the homogeneous isotropic Universe can be obtained within this formalism. Our description shows how Plebanski formulation gives quite an economical alternative to the usual metric and frame-based schemes for deriving Einstein equations. |
gr-qc/0501045 | Robert Carroll | Robert Carroll | Fluctuations, gravity, and the quantum potential | 50 pages, Latex | null | null | null | gr-qc | null | We show how the quantum potential arises in various ways and trace its
connection to quantum fluctuations and Fisher information along with its
realization in terms of Weyl curvature. It is a quantization factor for certain
classical systems as well as an expression for quantum matter in gravity
theories of Weyl-Dirac type. We extract theories and examples from the
literature, providing connections and interpretations, and make a few new
observations.
| [
{
"created": "Thu, 13 Jan 2005 16:07:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carroll",
"Robert",
""
]
] | We show how the quantum potential arises in various ways and trace its connection to quantum fluctuations and Fisher information along with its realization in terms of Weyl curvature. It is a quantization factor for certain classical systems as well as an expression for quantum matter in gravity theories of Weyl-Dirac type. We extract theories and examples from the literature, providing connections and interpretations, and make a few new observations. |
1202.1204 | Sergey Paston | S. A. Paston, A. A. Sheykin | Embeddings for Schwarzschild metric: classification and new results | LaTeX, 19 pages | Class. Quantum Grav. 29 (2012) 095022 | 10.1088/0264-9381/29/9/095022 | SPbU-IP-12-01 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest a method to search the embeddings of Riemannian spaces with a high
enough symmetry in a flat ambient space. It is based on a procedure of
construction surfaces with a given symmetry. The method is used to classify the
embeddings of the Schwarzschild metric which have the symmetry of this
solution, and all such embeddings in a six-dimensional ambient space (i.e. a
space with a minimal possible dimension) are constructed. Four of the six
possible embeddings are already known, while the two others are new. One of the
new embeddings is asymptotically flat, while the other embeddings in a
six-dimensional ambient space do not have this property. The asymptotically
flat embedding can be of use in the analysis of the many-body problem, as well
as for the development of gravity description as a theory of a surface in a
flat ambient space.
| [
{
"created": "Mon, 6 Feb 2012 17:03:38 GMT",
"version": "v1"
}
] | 2012-04-23 | [
[
"Paston",
"S. A.",
""
],
[
"Sheykin",
"A. A.",
""
]
] | We suggest a method to search the embeddings of Riemannian spaces with a high enough symmetry in a flat ambient space. It is based on a procedure of construction surfaces with a given symmetry. The method is used to classify the embeddings of the Schwarzschild metric which have the symmetry of this solution, and all such embeddings in a six-dimensional ambient space (i.e. a space with a minimal possible dimension) are constructed. Four of the six possible embeddings are already known, while the two others are new. One of the new embeddings is asymptotically flat, while the other embeddings in a six-dimensional ambient space do not have this property. The asymptotically flat embedding can be of use in the analysis of the many-body problem, as well as for the development of gravity description as a theory of a surface in a flat ambient space. |
1310.1452 | Mohammad Reza Tanhayi | R. Vazirian, M. R. Tanhayi and Z. A. Motahar | Weyl-invariant extension of the Metric-Affine Gravity | 10 pages, no figure, references added, typos corrected and overall
improvement | Advances in High Energy Physics 2015, 902396, 7 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Metric-affine geometry provides a non-trivial extension of the general
relativity where the metric and connection are treated as the two independent
fundamental quantities in constructing the space-time (with non-vanishing
torsion and non-metricity). In this paper we study the generic form of action
in this formalism, and then construct the Weyl-invariant version of this
theory. It is shown that in Weitzenbock space, the obtained Weyl-invariant
action can cover the conformally invariant teleparallel action. Finally the
related field equations are obtained in the general case.
| [
{
"created": "Sat, 5 Oct 2013 07:31:39 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Dec 2013 07:46:01 GMT",
"version": "v2"
}
] | 2015-01-23 | [
[
"Vazirian",
"R.",
""
],
[
"Tanhayi",
"M. R.",
""
],
[
"Motahar",
"Z. A.",
""
]
] | Metric-affine geometry provides a non-trivial extension of the general relativity where the metric and connection are treated as the two independent fundamental quantities in constructing the space-time (with non-vanishing torsion and non-metricity). In this paper we study the generic form of action in this formalism, and then construct the Weyl-invariant version of this theory. It is shown that in Weitzenbock space, the obtained Weyl-invariant action can cover the conformally invariant teleparallel action. Finally the related field equations are obtained in the general case. |
2001.01363 | Xiang-Hua Zhai | Rui-Hui Lin, Rui Jiang, Yang Huang and Xiang-Hua Zhai | Probing the conformal invariance around the nonsingular static spherical
black holes with waves | 21 pages, 12 figures, title, abstract and some contents changed, an
appendix added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conformal invariance can ameliorate or eliminate the singularities residing
in the black holes, and may still exist in the strong gravity regimes close to
these black holes.
In this paper, we try to probe this conformal invariance by looking into the
wave absorption and scattering by the nonsingular static spherical black holes.
The partial and total absorption cross section, as well as the differential
scattering cross section, are presented for black holes with different choices
of conformal parameters.
Although the photon trajectories are unchanged from the Schwarzschild case
since the spacetimes are conformally related, the wave optics are affected by
the conformal parameters.
As a result, the absorption of waves generally increases with the conformal
parameters, while the shadow of the black holes remains the same as the
Schwarzschild case.
Moreover, the peaks in the oscillatory pattern of scattering shift towards
smaller observing angles as the conformal parameters grows, while the widths of
the glory peaks do not show sensitive dependence.
The unique signature of the wave absorption and scattering by the nonsingular
static spherical black holes in conformal gravity thus can serve to distinguish
themselves from the Schwarzschild in the low frequency regime, and from other
spherical black holes of alternative gravities in the high frequency limit and
glory peaks.
| [
{
"created": "Mon, 6 Jan 2020 02:23:26 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jan 2020 05:55:01 GMT",
"version": "v2"
},
{
"created": "Fri, 17 Jan 2020 12:58:06 GMT",
"version": "v3"
},
{
"created": "Sun, 7 Jun 2020 03:30:50 GMT",
"version": "v4"
}
] | 2020-06-09 | [
[
"Lin",
"Rui-Hui",
""
],
[
"Jiang",
"Rui",
""
],
[
"Huang",
"Yang",
""
],
[
"Zhai",
"Xiang-Hua",
""
]
] | Conformal invariance can ameliorate or eliminate the singularities residing in the black holes, and may still exist in the strong gravity regimes close to these black holes. In this paper, we try to probe this conformal invariance by looking into the wave absorption and scattering by the nonsingular static spherical black holes. The partial and total absorption cross section, as well as the differential scattering cross section, are presented for black holes with different choices of conformal parameters. Although the photon trajectories are unchanged from the Schwarzschild case since the spacetimes are conformally related, the wave optics are affected by the conformal parameters. As a result, the absorption of waves generally increases with the conformal parameters, while the shadow of the black holes remains the same as the Schwarzschild case. Moreover, the peaks in the oscillatory pattern of scattering shift towards smaller observing angles as the conformal parameters grows, while the widths of the glory peaks do not show sensitive dependence. The unique signature of the wave absorption and scattering by the nonsingular static spherical black holes in conformal gravity thus can serve to distinguish themselves from the Schwarzschild in the low frequency regime, and from other spherical black holes of alternative gravities in the high frequency limit and glory peaks. |
0906.3947 | Jan Ambjorn | Jan Ambjorn, Jerzy Jurkiewicz and Renate Loll | Quantum gravity as sum over spacetimes | references added, typos corrected. 67 pages, lectures given at the
summer school "New Paths Towards Quantum Gravity", May 12-16 2008. To appear
as part of a Springer Lecture Notes in Physics publication: "Quantum Gravity
- New Paths Towards Unification" | Lect.Notes Phys.807:59-124,2010 | 10.1007/978-3-642-11897-5_2 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A major unsolved problem in theoretical physics is to reconcile the classical
theory of general relativity with quantum mechanics. These lectures will deal
with an attempt to describe quantum gravity as a path integral over geometries
known as "Causal Dynamical Triangulations" (CDT).
| [
{
"created": "Mon, 22 Jun 2009 08:55:27 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2009 21:30:42 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Ambjorn",
"Jan",
""
],
[
"Jurkiewicz",
"Jerzy",
""
],
[
"Loll",
"Renate",
""
]
] | A major unsolved problem in theoretical physics is to reconcile the classical theory of general relativity with quantum mechanics. These lectures will deal with an attempt to describe quantum gravity as a path integral over geometries known as "Causal Dynamical Triangulations" (CDT). |
1006.1586 | Sergio Zerbini | Guido Cognola, Lorenzo Sebastiani and Sergio Zerbini | Stability in Generalized Modified Gravity | 4 pages, Latex file, Proceeding MG12, Paris, added one reference | null | null | UTN2010-6 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stability issue of generalized modified gravitational models is discussed
with particular emphasis to de Sitter solutions. Two approaches are briefly
presented.
| [
{
"created": "Tue, 8 Jun 2010 15:27:36 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2010 08:13:42 GMT",
"version": "v2"
}
] | 2010-06-10 | [
[
"Cognola",
"Guido",
""
],
[
"Sebastiani",
"Lorenzo",
""
],
[
"Zerbini",
"Sergio",
""
]
] | The stability issue of generalized modified gravitational models is discussed with particular emphasis to de Sitter solutions. Two approaches are briefly presented. |
1201.0080 | Hossein Farajollahi | Hossein Farajollahi, Amin Salehi, Mohammad Nasiri | Constraints on scalar-tensor theories from observations | 16 pages, 32 figures | Phys. Rev. D 84, 124045 (2011) | 10.1103/PhysRevD.84.124045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamical description of scalar-tensor gravity by performing the
best-fit analysis for two cases of exponential and power-law form of the
potential and scalar field function coupled to the curvature. The models are
then tested against observational data. The results show that in both scenarios
the Universe undergoes an acceleration expansion period and the geometrical
equivalent of dark energy is associated with a time-dependent equation of
state.
| [
{
"created": "Fri, 30 Dec 2011 08:46:06 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Farajollahi",
"Hossein",
""
],
[
"Salehi",
"Amin",
""
],
[
"Nasiri",
"Mohammad",
""
]
] | We study the dynamical description of scalar-tensor gravity by performing the best-fit analysis for two cases of exponential and power-law form of the potential and scalar field function coupled to the curvature. The models are then tested against observational data. The results show that in both scenarios the Universe undergoes an acceleration expansion period and the geometrical equivalent of dark energy is associated with a time-dependent equation of state. |
gr-qc/9707011 | Yoonbai Kim | Nakwoo Kim, Yoonbai Kim and Kyoungtae Kimm | Charged Black Cosmic String | ll pages, LaTeX | Class.Quant.Grav.15:1513-1520,1998 | 10.1088/0264-9381/15/6/007 | SNUTP-97-022 | gr-qc hep-th | null | Global U(1) strings with cylindrical symmetry are studied in anti-de Sitter
spacetime. According as the magnitude of negative cosmological constant, they
form regular global cosmic strings, extremal black cosmic strings and charged
black cosmic strings, but no curvature singularity is involved. The
relationship between the topological charge of a neutral global string and the
black hole charge is clarified by duality transformation. Physical relevance as
straight string is briefly discussed.
| [
{
"created": "Fri, 4 Jul 1997 06:58:30 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Kim",
"Nakwoo",
""
],
[
"Kim",
"Yoonbai",
""
],
[
"Kimm",
"Kyoungtae",
""
]
] | Global U(1) strings with cylindrical symmetry are studied in anti-de Sitter spacetime. According as the magnitude of negative cosmological constant, they form regular global cosmic strings, extremal black cosmic strings and charged black cosmic strings, but no curvature singularity is involved. The relationship between the topological charge of a neutral global string and the black hole charge is clarified by duality transformation. Physical relevance as straight string is briefly discussed. |
1610.00448 | Nils Andersson | N. Andersson, I. Hawke, K. Dionysopoulou and G.L. Comer | Beyond ideal magnetohydrodynamics: From fibration to 3+1 foliation | 35 pages, no figures | null | 10.1088/1361-6382/aa6b39 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a resistive multi-fluid framework from the 3+1 space-time
foliation point-of-view, paying particular attention to issues relating to the
use of multi-parameter equations of state and the associated inversion from
evolved to primitive variables. We highlight relevant numerical issues that
arise for general systems with relative flows. As an application of the new
formulation, we consider a three-component system relevant for hot neutron
stars. In this case we let the baryons (neutrons and protons) move together,
but allow heat and electrons to exhibit relative flow. This reduces the problem
to three momentum equations; overall energy-momentum conservation, a
generalised Ohm's law and a heat equation. Our results provide a hierarchy of
increasingly complex models and prepare the ground for new state-of-the-art
simulations of relevant scenarios in relativistic astrophysics.
| [
{
"created": "Mon, 3 Oct 2016 08:57:49 GMT",
"version": "v1"
}
] | 2017-05-31 | [
[
"Andersson",
"N.",
""
],
[
"Hawke",
"I.",
""
],
[
"Dionysopoulou",
"K.",
""
],
[
"Comer",
"G. L.",
""
]
] | We consider a resistive multi-fluid framework from the 3+1 space-time foliation point-of-view, paying particular attention to issues relating to the use of multi-parameter equations of state and the associated inversion from evolved to primitive variables. We highlight relevant numerical issues that arise for general systems with relative flows. As an application of the new formulation, we consider a three-component system relevant for hot neutron stars. In this case we let the baryons (neutrons and protons) move together, but allow heat and electrons to exhibit relative flow. This reduces the problem to three momentum equations; overall energy-momentum conservation, a generalised Ohm's law and a heat equation. Our results provide a hierarchy of increasingly complex models and prepare the ground for new state-of-the-art simulations of relevant scenarios in relativistic astrophysics. |
2211.03156 | Xiongjun Fang | Wentao Liu, Xiongjun Fang, Jiliang Jing, Jieci Wang | QNMs of slowly rotating Einstein-Bumblebee Black Hole | 16 pages, 6 figures | Eur. Phys. J. C 83:83 (2023) | 10.1140/epjc/s10052-023-11231-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied the quasinormal modes (QNMs) of a slowly rotating black hole
with Lorentz-violating parameter in Einstein-bumblebee gravity. We analyse the
slow rotation approximation of the rotating black hole in the
Einstein-bumblebee gravity, and obtain the master equations for scalar
perturbation, vector perturbation and axial gravitational perturbation,
respectively. Using the matrix method and the continuous fraction method, we
numerically calculate the QNM frequencies. In particular, for scalar field, it
shows that the QNMs up to the second order of rotation parameter have higher
accuracy. The numerical results show that, for both scalar and vector fields,
the Lorentz-violating parameter has a significant effect on the imaginary part
of the QNM frequencies, while having a relatively smaller impact on the real
part of the QNM frequencies. But for axial gravitational perturbation, the
effect of increasing the Lorentz-violating parameter $\ell$ is similar to that
of increasing the rotation parameter $\tilde{a}$.
| [
{
"created": "Sun, 6 Nov 2022 15:45:31 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jan 2023 07:29:45 GMT",
"version": "v2"
}
] | 2023-01-31 | [
[
"Liu",
"Wentao",
""
],
[
"Fang",
"Xiongjun",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Jieci",
""
]
] | We have studied the quasinormal modes (QNMs) of a slowly rotating black hole with Lorentz-violating parameter in Einstein-bumblebee gravity. We analyse the slow rotation approximation of the rotating black hole in the Einstein-bumblebee gravity, and obtain the master equations for scalar perturbation, vector perturbation and axial gravitational perturbation, respectively. Using the matrix method and the continuous fraction method, we numerically calculate the QNM frequencies. In particular, for scalar field, it shows that the QNMs up to the second order of rotation parameter have higher accuracy. The numerical results show that, for both scalar and vector fields, the Lorentz-violating parameter has a significant effect on the imaginary part of the QNM frequencies, while having a relatively smaller impact on the real part of the QNM frequencies. But for axial gravitational perturbation, the effect of increasing the Lorentz-violating parameter $\ell$ is similar to that of increasing the rotation parameter $\tilde{a}$. |
1709.09592 | Diego Rubiera-Garcia | C. Menchon, Gonzalo J. Olmo, D. Rubiera-Garcia | Nonsingular black holes, wormholes, and de Sitter cores from anisotropic
fluids | 15 double column pages; 7 figures | Phys. Rev. D 96, 104028 (2017) | 10.1103/PhysRevD.96.104028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Born-Infeld gravity coupled to an anisotropic fluid in a static,
spherically symmetric background. The free function characterizing the fluid is
selected on the following grounds: i) recovery of the Reissner-Nordstr\"om
solution of GR at large distances, ii) fulfillment of classical energy
conditions and iii) inclusion of models of nonlinear electrodynamics as
particular examples. Four branches of solutions are obtained, depending on the
signs of two parameters on the gravity and matter sectors. On each branch, we
discuss in detail the modifications on the innermost region of the
corresponding solutions, which provides a plethora of configurations, including
nonsingular black holes and naked objects, wormholes and de Sitter cores. The
regular character of these configurations is discussed according to the
completeness of geodesics and the behaviour of curvature scalars.
| [
{
"created": "Wed, 27 Sep 2017 15:51:24 GMT",
"version": "v1"
}
] | 2017-11-22 | [
[
"Menchon",
"C.",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"D.",
""
]
] | We study Born-Infeld gravity coupled to an anisotropic fluid in a static, spherically symmetric background. The free function characterizing the fluid is selected on the following grounds: i) recovery of the Reissner-Nordstr\"om solution of GR at large distances, ii) fulfillment of classical energy conditions and iii) inclusion of models of nonlinear electrodynamics as particular examples. Four branches of solutions are obtained, depending on the signs of two parameters on the gravity and matter sectors. On each branch, we discuss in detail the modifications on the innermost region of the corresponding solutions, which provides a plethora of configurations, including nonsingular black holes and naked objects, wormholes and de Sitter cores. The regular character of these configurations is discussed according to the completeness of geodesics and the behaviour of curvature scalars. |
gr-qc/9911065 | Dmitrij Fursaev | D.V. Fursaev | Black Hole Entropy in Induced Gravity and Information Loss | 4 pages, the talk given at 3d Meeting on Constrained Dynamics and
Quantum Gravity, Villasimius, Sardinia, Italy, 14-18 September, 1999 | Nucl.Phys.Proc.Suppl. 88 (2000) 277-280 | 10.1016/S0920-5632(00)00784-2 | null | gr-qc hep-th | null | The basic assumption of the induced gravity approach is that Einstein theory
is an effective, low energy-form of a quantum theory of constituents. In this
approach the Bekenstein-Hawking entropy S^{BH} of a black hole can be
interpreted as a measure of the loss of information about constituents inside
the black hole horizon. To be more exact, S^{BH} is determined by quantum
correlations between "observable" and "non-observable" states with positive and
negative energy $\cal E$, respectively. It is important that for non-minimally
coupled constituents $\cal E$ differs from the canonical Hamiltonian $\cal H$.
This explains why previous definitions of the entanglement entropy in terms of
$\cal H$ failed to reproduce S^{BH}.
| [
{
"created": "Thu, 18 Nov 1999 10:26:58 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Fursaev",
"D. V.",
""
]
] | The basic assumption of the induced gravity approach is that Einstein theory is an effective, low energy-form of a quantum theory of constituents. In this approach the Bekenstein-Hawking entropy S^{BH} of a black hole can be interpreted as a measure of the loss of information about constituents inside the black hole horizon. To be more exact, S^{BH} is determined by quantum correlations between "observable" and "non-observable" states with positive and negative energy $\cal E$, respectively. It is important that for non-minimally coupled constituents $\cal E$ differs from the canonical Hamiltonian $\cal H$. This explains why previous definitions of the entanglement entropy in terms of $\cal H$ failed to reproduce S^{BH}. |
1103.5190 | B. V. Ivanov | B.V.Ivanov | Self-gravitating spheres of anisotropic fluid in geodesic flow | 21 pages | Int.J.Mod.Phys.D 20 (2011) 319 | 10.1142/S0218271811018858 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fluid models mentioned in the title are classified. All characteristics
of the fluid are expressed through a master potential, satisfying an ordinary
second order differential equation. Different constraints are imposed on this
core of relations, finding new solutions and deriving the classical results for
perfect fluids and dust as particular cases. Many uncharged and charged
anisotropic solutions, all conformally flat and some uniform density solutions
are found. A number of solutions with linear equation among the two pressures
are derived, including the case of vanishing tangential pressure.
| [
{
"created": "Sun, 27 Mar 2011 06:49:59 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Ivanov",
"B. V.",
""
]
] | The fluid models mentioned in the title are classified. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids and dust as particular cases. Many uncharged and charged anisotropic solutions, all conformally flat and some uniform density solutions are found. A number of solutions with linear equation among the two pressures are derived, including the case of vanishing tangential pressure. |
1503.08709 | Dong-han Yeom | Pisin Chen, Taotao Qiu, Dong-han Yeom | Phantom of the Hartle-Hawking instanton: connecting inflation with dark
energy | 20 pages, 7 figures | Eur.Phys.J. C76 (2016) 91 | 10.1140/epjc/s10052-016-3932-0 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the Hartle-Hawking wave function is the correct boundary condition of our
universe, the history of our universe will be well approximated by an
instanton. Although this instanton should be classicalized at infinity, as long
as we are observing a process of each history, we may detect a
non-classicalized part of field combinations. When we apply it to a dark energy
model, this non-classicalized part of fields can be well embedded to a
quintessence and a phantom model, i.e., a quintom model. Because of the
property of complexified instantons, the phantomness will be naturally free
from a big rip singularity. This phantomness does not cause perturbative
instabilities, as it is an effect emergent from the entire wave function. Our
work may thus provide a theoretical basis for the quintom models, whose
equation of state (EoS) can cross the cosmological constant boundary (CCB)
phenomenologically.
| [
{
"created": "Mon, 30 Mar 2015 15:23:52 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Feb 2016 08:51:32 GMT",
"version": "v2"
}
] | 2016-02-23 | [
[
"Chen",
"Pisin",
""
],
[
"Qiu",
"Taotao",
""
],
[
"Yeom",
"Dong-han",
""
]
] | If the Hartle-Hawking wave function is the correct boundary condition of our universe, the history of our universe will be well approximated by an instanton. Although this instanton should be classicalized at infinity, as long as we are observing a process of each history, we may detect a non-classicalized part of field combinations. When we apply it to a dark energy model, this non-classicalized part of fields can be well embedded to a quintessence and a phantom model, i.e., a quintom model. Because of the property of complexified instantons, the phantomness will be naturally free from a big rip singularity. This phantomness does not cause perturbative instabilities, as it is an effect emergent from the entire wave function. Our work may thus provide a theoretical basis for the quintom models, whose equation of state (EoS) can cross the cosmological constant boundary (CCB) phenomenologically. |
gr-qc/9508046 | null | G. Sardanashvily | Fermions in Gravitation Theory | 10 pp LaTeX file. The report on the Workshop "New Frontiers of
Gravitation Theory" (Monteroduni, August 1995) | null | null | null | gr-qc | null | In gravitation theory, a fermion field must be regarded only in a pair with a
certain tetrad gravitational field. These pairs can be represented by sections
of the composite spinor bundle $S\to\Si\to X^4$ where values of gravitational
fields play the role of parameter coordinates, besides the familiar world
coordinates.
| [
{
"created": "Mon, 21 Aug 1995 09:26:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sardanashvily",
"G.",
""
]
] | In gravitation theory, a fermion field must be regarded only in a pair with a certain tetrad gravitational field. These pairs can be represented by sections of the composite spinor bundle $S\to\Si\to X^4$ where values of gravitational fields play the role of parameter coordinates, besides the familiar world coordinates. |
1705.00297 | Jia-An Lu | Jia-An Lu | On the difference between Poincar\'e and Lorentz gravity | 11 pages | Gen. Relativ. Gravit. 49, 138 (2017) | 10.1007/s10714-017-2296-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Poincar\'e invariance of GR is usually interpreted as Lorentz invariance
plus diffeomorphism invariance. In this paper, by introducing the local
inertial coordinates (LIC), it is shown that a theory with Lorentz and
diffeomorphism invariance is not necessarily Poincar\'e invariant. Actually,
the energy-momentum conservation is violated there. On the other hand, with the
help of the LIC, the Poincar\'e invariance is reinterpreted as an internal
symmetry. In this formalism, the conservation law is derived, which has not
been sufficiently explored before.
| [
{
"created": "Sun, 30 Apr 2017 11:05:48 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Oct 2017 01:51:41 GMT",
"version": "v2"
}
] | 2017-10-25 | [
[
"Lu",
"Jia-An",
""
]
] | The Poincar\'e invariance of GR is usually interpreted as Lorentz invariance plus diffeomorphism invariance. In this paper, by introducing the local inertial coordinates (LIC), it is shown that a theory with Lorentz and diffeomorphism invariance is not necessarily Poincar\'e invariant. Actually, the energy-momentum conservation is violated there. On the other hand, with the help of the LIC, the Poincar\'e invariance is reinterpreted as an internal symmetry. In this formalism, the conservation law is derived, which has not been sufficiently explored before. |
2012.05068 | Milko Estrada | Milko Estrada and Francisco Tello-Ortiz | A new model of regular black hole in $(2+1)$ dimensions | accepted for publication in EPL | EPL 135 (2021) 2, 20001 | 10.1209/0295-5075/ac0ed0 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We provide a new regular black hole solution in $(2+1)$ dimensions with
presence of matter fields in the energy momentum tensor, having its core a flat
or (A)dS structure. Since the first law of thermodynamics for regular black
holes is modified by the presence of the matter fields, we provide a new
version of the first law, where a local definition of the variation of energy
is defined, and, where the entropy and temperature are consistent with the
previously known in literature. It is shown that the signs of the variations of
the local definition of energy and of the total energy coincide. Furthermore,
at infinite, the usual first law $dM=TdS$ is recovered. It is showed that the
formalism used is effective to compute the total energy of regular black holes
in $(2+1)$ with presence of matter in the energy momentum tensor. This latter
suggests the potential applicability of this formalism to calculate the mass of
other models of regular black holes in $d \ge 4$ dimensions.
| [
{
"created": "Wed, 9 Dec 2020 14:20:17 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jun 2021 17:09:32 GMT",
"version": "v2"
}
] | 2021-11-09 | [
[
"Estrada",
"Milko",
""
],
[
"Tello-Ortiz",
"Francisco",
""
]
] | We provide a new regular black hole solution in $(2+1)$ dimensions with presence of matter fields in the energy momentum tensor, having its core a flat or (A)dS structure. Since the first law of thermodynamics for regular black holes is modified by the presence of the matter fields, we provide a new version of the first law, where a local definition of the variation of energy is defined, and, where the entropy and temperature are consistent with the previously known in literature. It is shown that the signs of the variations of the local definition of energy and of the total energy coincide. Furthermore, at infinite, the usual first law $dM=TdS$ is recovered. It is showed that the formalism used is effective to compute the total energy of regular black holes in $(2+1)$ with presence of matter in the energy momentum tensor. This latter suggests the potential applicability of this formalism to calculate the mass of other models of regular black holes in $d \ge 4$ dimensions. |
0911.2139 | Mariafelicia De Laurentis | Mariafelicia De Laurentis, Salvatore Capozziello, Shin'ichi Nojiri,
Sergei Odintsov | PPN limit and cosmological gravitational waves as tools to constrain
f(R)-gravity | 4 pages, Grassmann Meeting 2009, Annalen der Physik | Annalen Phys.19:347-350,2010 | 10.1002/andp.201010444 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the PPN Solar-System constraints and the GW stochastic background
considering some recently proposed $f(R)$ gravity models which satisfy both
cosmological and stability conditions. Using the definition of PPN-parameters
$\gamma$ and $\beta$ in terms of $f(R)$-models and the definition of scalar
GWs, we compare and discuss if it is possible to search for parameter ranges of
$f(R)$-models working at Solar System and GW stochastic background scale.
| [
{
"created": "Wed, 11 Nov 2009 14:08:27 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei",
""
]
] | We discuss the PPN Solar-System constraints and the GW stochastic background considering some recently proposed $f(R)$ gravity models which satisfy both cosmological and stability conditions. Using the definition of PPN-parameters $\gamma$ and $\beta$ in terms of $f(R)$-models and the definition of scalar GWs, we compare and discuss if it is possible to search for parameter ranges of $f(R)$-models working at Solar System and GW stochastic background scale. |
2401.13039 | Duarte Miguel Da Silva Feiteira | Duarte Feiteira, Jos\'e P. S. Lemos, Oleg B. Zaslavskii | Penrose process in Reissner-Nordstr\"om-AdS black hole spacetimes: Black
hole energy factories and black hole bombs | 20 pages, 1 figure | Phys. Rev. D 109, 064065 (2024) | 10.1103/PhysRevD.109.064065 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The Penrose process for the decay of electrically charged particles in a
Reissner-Nordstr\"om-anti-de Sitter black hole spacetime is studied. To extract
large quantities of energy one needs to mount a recursive Penrose process where
particles are confined and can bounce back to suffer ever again a decaying
process in the black hole electric ergoregion. In an asymptotically anti-de
Sitter (AdS) spacetime, two situations of confinement are possible. One
situation uses a reflecting mirror at some radius, which obliges the energetic
outgoing particles to return to the decaying point. The other situation uses
the natural AdS property that sends back at some intrinsic returning radius
those outgoing energetic particles. In addition, besides the conservation laws
the decaying process must obey, one has to set conditions at the decaying point
for the particles debris. These conditions restrain the possible scenarios, but
there are still a great number of available scenarios for the decays. Within
these, we choose two scenarios, scenario 1 and scenario 2, that pertain to the
masses and electric charges of the final particles. Thus, in the mirror
situation we find that scenario 1 leads to a black hole energy factory, and
scenario 2 ends in a black hole bomb. In the no mirror situation, i.e., pure
Reissner-Nordstr\"om-AdS, scenario 1 leads again to a black hole energy
factory, but scenario 2 yields no bomb. This happens because the volume in
which the particles are confined increases to infinity along the chain of
decays, leading to a zero value of the extracted energy per unit volume and the
bomb is demined. The whole treatment performed here involves no backreaction on
the black hole mass and electric charge, nevertheless we speculate that the end
state of the recursive process is a Reissner-Nordstr\"om-AdS black hole with
very short hair, i.e., with one particle at rest at some definite radius.
| [
{
"created": "Tue, 23 Jan 2024 19:00:06 GMT",
"version": "v1"
}
] | 2024-03-27 | [
[
"Feiteira",
"Duarte",
""
],
[
"Lemos",
"José P. S.",
""
],
[
"Zaslavskii",
"Oleg B.",
""
]
] | The Penrose process for the decay of electrically charged particles in a Reissner-Nordstr\"om-anti-de Sitter black hole spacetime is studied. To extract large quantities of energy one needs to mount a recursive Penrose process where particles are confined and can bounce back to suffer ever again a decaying process in the black hole electric ergoregion. In an asymptotically anti-de Sitter (AdS) spacetime, two situations of confinement are possible. One situation uses a reflecting mirror at some radius, which obliges the energetic outgoing particles to return to the decaying point. The other situation uses the natural AdS property that sends back at some intrinsic returning radius those outgoing energetic particles. In addition, besides the conservation laws the decaying process must obey, one has to set conditions at the decaying point for the particles debris. These conditions restrain the possible scenarios, but there are still a great number of available scenarios for the decays. Within these, we choose two scenarios, scenario 1 and scenario 2, that pertain to the masses and electric charges of the final particles. Thus, in the mirror situation we find that scenario 1 leads to a black hole energy factory, and scenario 2 ends in a black hole bomb. In the no mirror situation, i.e., pure Reissner-Nordstr\"om-AdS, scenario 1 leads again to a black hole energy factory, but scenario 2 yields no bomb. This happens because the volume in which the particles are confined increases to infinity along the chain of decays, leading to a zero value of the extracted energy per unit volume and the bomb is demined. The whole treatment performed here involves no backreaction on the black hole mass and electric charge, nevertheless we speculate that the end state of the recursive process is a Reissner-Nordstr\"om-AdS black hole with very short hair, i.e., with one particle at rest at some definite radius. |
1208.6489 | Louis Gallouin | Louis Gallouin, Hiroyuki Nakano, Nicolas Yunes and Manuela Campanelli | Asymptotically Matched Spacetime Metric for Non-Precessing, Spinning
Black Hole Binaries | null | null | 10.1088/0264-9381/29/23/235013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a closed-form, fully analytical 4-metric that approximately
represents the spacetime evolution of non-precessing, spinning black hole
binaries from infinite separations up to a few orbits prior to merger. We
employ the technique of asymptotic matching to join a perturbed Kerr metric in
the neighborhood of each spinning black hole to a near-zone, post-Newtonian
metric farther out. The latter is already naturally matched to a far-zone,
post-Minkowskian metric that accounts for full temporal retardation. The result
is a 4-metric that is approximately valid everywhere in space and in a small
bundle of spatial hypersurfaces. We here restrict our attention to quasi-
circular orbits, but the method is valid for any orbital motion or physical
scenario, provided an overlapping region of validity or buffer zone exists. A
simple extension of such a metric will allow for future studies of the
accretion disk and jet dynamics around spinning back hole binaries.
| [
{
"created": "Fri, 31 Aug 2012 13:20:04 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Gallouin",
"Louis",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Campanelli",
"Manuela",
""
]
] | We construct a closed-form, fully analytical 4-metric that approximately represents the spacetime evolution of non-precessing, spinning black hole binaries from infinite separations up to a few orbits prior to merger. We employ the technique of asymptotic matching to join a perturbed Kerr metric in the neighborhood of each spinning black hole to a near-zone, post-Newtonian metric farther out. The latter is already naturally matched to a far-zone, post-Minkowskian metric that accounts for full temporal retardation. The result is a 4-metric that is approximately valid everywhere in space and in a small bundle of spatial hypersurfaces. We here restrict our attention to quasi- circular orbits, but the method is valid for any orbital motion or physical scenario, provided an overlapping region of validity or buffer zone exists. A simple extension of such a metric will allow for future studies of the accretion disk and jet dynamics around spinning back hole binaries. |
0708.3729 | Alessandro Pesci | Alessandro Pesci | From Unruh temperature to generalized Bousso bound | 5 pages. v2: some changes to clarify the path to the obtained
results; two (final) paragraphs, the acknowledgments and a reference added | Class.Quant.Grav.24:6219-6226,2007 | 10.1088/0264-9381/24/24/005 | null | gr-qc | null | In a classical spacetime satisfying Einstein's equation and the null
convergence condition, the same quantum mechanical effects that cause black
holes to have a temperature are found to imply, if joined to the macroscopic
nature of entropy, the covariant entropy bound in its generalized form. This is
obtained from thermodynamics, as applied across the local Rindler causal
horizon through every point p of the null hypersurfaces L the covariant entropy
bound refers to, in the direction of the null geodesics generating L.
| [
{
"created": "Tue, 28 Aug 2007 09:45:37 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2007 11:20:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pesci",
"Alessandro",
""
]
] | In a classical spacetime satisfying Einstein's equation and the null convergence condition, the same quantum mechanical effects that cause black holes to have a temperature are found to imply, if joined to the macroscopic nature of entropy, the covariant entropy bound in its generalized form. This is obtained from thermodynamics, as applied across the local Rindler causal horizon through every point p of the null hypersurfaces L the covariant entropy bound refers to, in the direction of the null geodesics generating L. |
gr-qc/0701028 | Jiri Kovar | Jiri Kovar, Zdenek Stuchlik | Optical reference geometry and inertial forces in Kerr-de Sitter
spacetimes | 31 pages, 10 figures | Class.Quant.Grav.24:565-594,2007 | 10.1088/0264-9381/24/3/004 | null | gr-qc | null | Optical reference geometry and related concept of inertial forces are
investigated in Kerr-de Sitter spacetimes. Properties of the inertial forces
are summarized and their typical behaviour is illustrated. The intuitive
'Newtonian' application of the forces in the relativistic dynamics is
demonstrated in the case of the test particle circular motion, static
equilibrium positions and perfect fluid toroidal configurations. Features of
the optical geometry are illustrated by the embedding diagrams of its
equatorial plane. The embedding diagrams do not cover whole the stationary
regions of the spacetimes, therefore the limits of embeddability are
established. A shape of the embedding diagrams is related to the behaviour of
the centrifugal force and it is characterized by the number of turning points
of the diagrams. Discussion of the number of embeddable photon circular orbits
is also included and the typical embedding diagrams are constructed. The
Kerr-de Sitter spacetimes are classified according to the properties of the
inertial forces and embedding diagrams.
| [
{
"created": "Wed, 3 Jan 2007 16:58:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kovar",
"Jiri",
""
],
[
"Stuchlik",
"Zdenek",
""
]
] | Optical reference geometry and related concept of inertial forces are investigated in Kerr-de Sitter spacetimes. Properties of the inertial forces are summarized and their typical behaviour is illustrated. The intuitive 'Newtonian' application of the forces in the relativistic dynamics is demonstrated in the case of the test particle circular motion, static equilibrium positions and perfect fluid toroidal configurations. Features of the optical geometry are illustrated by the embedding diagrams of its equatorial plane. The embedding diagrams do not cover whole the stationary regions of the spacetimes, therefore the limits of embeddability are established. A shape of the embedding diagrams is related to the behaviour of the centrifugal force and it is characterized by the number of turning points of the diagrams. Discussion of the number of embeddable photon circular orbits is also included and the typical embedding diagrams are constructed. The Kerr-de Sitter spacetimes are classified according to the properties of the inertial forces and embedding diagrams. |
1602.03622 | Steven B. Giddings | Steven B. Giddings | Gravitational wave tests of quantum modifications to black hole
structure -- with post-GW150914 update | v2: Major revision: incorporating discussion of data from GW150914
and priorities for future work. v3: Added comments re. constraints from
current LIGO data, and directions for improving constraints. Version to
appear in Classical and Quantum Gravity | Classical and Quantum Gravity, 33 (2016) 235010 | 10.1088/0264-9381/33/23/235010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A preliminary discussion is given of the prospects that gravitational-wave
observations of binary inspiral of black holes could reveal or constrain
quantum modifications to black hole dynamics, such as are required to preserve
postulates of quantum mechanics. Different proposals for such modifications are
characterized by different scales, and the size of these scales relative to
those probed by observation of inspiral signals is important in determining the
feasibility of finding experimental signatures. Certain scenarios with strong
quantum modifications in a region extending well outside the horizon are
expected to modify classical evolution, and distort the near-peak gravitational
wave signal, suggesting a search for departures from waveforms predicted by
general relativity. The near agreement of the GW150914 signal with such
waveforms is discussed, and indicates constraints on some such scenarios.
Important strategies for more precise future tests are 1) to develop more
precise predictions from scenarios proposing quantum modifications, and 2)
searching for observed deviations from numerical relativity predictions via
analysis of gravity wave data, particularly focussing on the signal region
corresponding to plunge and merger.
| [
{
"created": "Thu, 11 Feb 2016 06:03:13 GMT",
"version": "v1"
},
{
"created": "Tue, 3 May 2016 21:24:36 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Nov 2016 23:46:35 GMT",
"version": "v3"
}
] | 2016-11-08 | [
[
"Giddings",
"Steven B.",
""
]
] | A preliminary discussion is given of the prospects that gravitational-wave observations of binary inspiral of black holes could reveal or constrain quantum modifications to black hole dynamics, such as are required to preserve postulates of quantum mechanics. Different proposals for such modifications are characterized by different scales, and the size of these scales relative to those probed by observation of inspiral signals is important in determining the feasibility of finding experimental signatures. Certain scenarios with strong quantum modifications in a region extending well outside the horizon are expected to modify classical evolution, and distort the near-peak gravitational wave signal, suggesting a search for departures from waveforms predicted by general relativity. The near agreement of the GW150914 signal with such waveforms is discussed, and indicates constraints on some such scenarios. Important strategies for more precise future tests are 1) to develop more precise predictions from scenarios proposing quantum modifications, and 2) searching for observed deviations from numerical relativity predictions via analysis of gravity wave data, particularly focussing on the signal region corresponding to plunge and merger. |
2403.18289 | Abolhassan Mohammadi | Abolhassan Mohammadi | Exploring the pre-inflationary dynamics in loop quantum cosmology with a
DBI scalar field | 11 pages, 7 figures, 1 table, submitted version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop quantum cosmology is a symmetry-reduced application of loop quantum
gravity. The theory predicts a bounce for the universe at the Planck scale and
resolves the singularity of standard cosmology. The dynamics is also governed
by an effective Hamiltonian, which predicts a modified Friedmann equation
containing the quadratic terms of the energy density. The term plays an
essential role in the high energy regime, but the equations return to the
standard form in the low energy regime. The evolution of the universe in the
pre-inflationary period is studied in the framework of loop quantum cosmology,
where the DBI scalar field is assumed to be the dominant component of the
universe. Using the numerical method, we provide the evolution of the DBI
field. The background evolution shows that there are three phases as: bouncing
phase, transition phase and slow-roll inflationary phase. There is also a short
period of super-inflation just at the beginning of the bounce phase. The field
first climbs the potential and then reaches the turning point where
$\dot{\phi}$ disappears and the potential energy becomes the dominant part of
the energy density. This is the time when the slow roll inflation begins and
the field slowly rolls down the potential. The results indicate that there are
a few e-fold expansions in the bounce phase, about $N = 3.5-4$, and the
universe experiences about $N = 59$ e-fold expansions in the slow-roll
inflation phase.
| [
{
"created": "Wed, 27 Mar 2024 06:27:25 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jun 2024 05:49:28 GMT",
"version": "v2"
}
] | 2024-06-27 | [
[
"Mohammadi",
"Abolhassan",
""
]
] | Loop quantum cosmology is a symmetry-reduced application of loop quantum gravity. The theory predicts a bounce for the universe at the Planck scale and resolves the singularity of standard cosmology. The dynamics is also governed by an effective Hamiltonian, which predicts a modified Friedmann equation containing the quadratic terms of the energy density. The term plays an essential role in the high energy regime, but the equations return to the standard form in the low energy regime. The evolution of the universe in the pre-inflationary period is studied in the framework of loop quantum cosmology, where the DBI scalar field is assumed to be the dominant component of the universe. Using the numerical method, we provide the evolution of the DBI field. The background evolution shows that there are three phases as: bouncing phase, transition phase and slow-roll inflationary phase. There is also a short period of super-inflation just at the beginning of the bounce phase. The field first climbs the potential and then reaches the turning point where $\dot{\phi}$ disappears and the potential energy becomes the dominant part of the energy density. This is the time when the slow roll inflation begins and the field slowly rolls down the potential. The results indicate that there are a few e-fold expansions in the bounce phase, about $N = 3.5-4$, and the universe experiences about $N = 59$ e-fold expansions in the slow-roll inflation phase. |
gr-qc/9903038 | S. R. Lau | S. R. Lau (UNC Chapel Hill) | Lightcone reference for total gravitational energy | latex, 7 pages, no figures. Uses an amstex symbol | Phys.Rev. D60 (1999) 104034 | 10.1103/PhysRevD.60.104034 | TAR-067-UNC | gr-qc | null | We give an explicit expression for gravitational energy, written solely in
terms of physical spacetime geometry, which in suitable limits agrees with the
total Arnowitt-Deser-Misner and Trautman-Bondi-Sachs energies for
asymptotically flat spacetimes and with the Abbot-Deser energy for
asymptotically anti-de Sitter spacetimes. Our expression is a boundary value of
the standard gravitational Hamiltonian. Moreover, although it stands alone as
such, we derive the expression by picking the zero-point of energy via a
``lightcone reference.''
| [
{
"created": "Wed, 10 Mar 1999 21:03:39 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lau",
"S. R.",
"",
"UNC Chapel Hill"
]
] | We give an explicit expression for gravitational energy, written solely in terms of physical spacetime geometry, which in suitable limits agrees with the total Arnowitt-Deser-Misner and Trautman-Bondi-Sachs energies for asymptotically flat spacetimes and with the Abbot-Deser energy for asymptotically anti-de Sitter spacetimes. Our expression is a boundary value of the standard gravitational Hamiltonian. Moreover, although it stands alone as such, we derive the expression by picking the zero-point of energy via a ``lightcone reference.'' |
1106.0102 | Hao Wei | Hao Wei, Xiao-Peng Ma, Hao-Yu Qi | $f(T)$ Theories and Varying Fine Structure Constant | 12 pages, 4 figures, 1 table, revtex4; v2: discussions added, Phys.
Lett. B in press; v3: published version | Phys.Lett.B703:74-80,2011 | 10.1016/j.physletb.2011.07.042 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In analogy to $f(R)$ theory, recently a new modified gravity theory, namely
the so-called $f(T)$ theory, has been proposed to drive the current accelerated
expansion without invoking dark energy. In the present work, by extending
Bisabr's idea, we try to constrain $f(T)$ theories with the varying fine
structure "constant", $\alpha\equiv e^2/\hbar c$. We find that the constraints
on $f(T)$ theories from the observational $\Delta\alpha/\alpha$ data are very
severe. In fact, they make $f(T)$ theories almost indistinguishable from
$\Lambda$CDM model.
| [
{
"created": "Wed, 1 Jun 2011 06:41:00 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jul 2011 06:41:00 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Aug 2011 09:00:00 GMT",
"version": "v3"
}
] | 2011-08-25 | [
[
"Wei",
"Hao",
""
],
[
"Ma",
"Xiao-Peng",
""
],
[
"Qi",
"Hao-Yu",
""
]
] | In analogy to $f(R)$ theory, recently a new modified gravity theory, namely the so-called $f(T)$ theory, has been proposed to drive the current accelerated expansion without invoking dark energy. In the present work, by extending Bisabr's idea, we try to constrain $f(T)$ theories with the varying fine structure "constant", $\alpha\equiv e^2/\hbar c$. We find that the constraints on $f(T)$ theories from the observational $\Delta\alpha/\alpha$ data are very severe. In fact, they make $f(T)$ theories almost indistinguishable from $\Lambda$CDM model. |
1805.10442 | Thomas W. Baumgarte | Juliana Celestino and Thomas W. Baumgarte | Critical collapse of ultra-relativistic fluids: damping or growth of
aspherical deformations | 11 pages, 8 figures; see also
http://www.bowdoin.edu/~tbaumgar/rad_fluid_movie.mp4 for an animation | Phys. Rev. D 98, 024053 (2018) | 10.1103/PhysRevD.98.024053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform fully nonlinear numerical simulations to study aspherical
deformations of the critical self-similar solution in the gravitational
collapse of ultra-relativistic fluids. Adopting a perturbative calculation,
Gundlach predicted that these perturbations behave like damped or growing
oscillations, with the frequency and damping (or growth) rates depending on the
equation of state. We consider a number of different equations of state and
degrees of asphericity and find very good agreement with the findings of
Gundlach for polar $\ell = 2$ modes. For sufficiently soft equations of state,
the modes are damped, meaning that, in the limit of perfect fine-tuning, the
spherically symmetric critical solution is recovered. We find that the degree
of asphericity has at most a small effect on the frequency and damping
parameter, or on the critical exponents in the power-law scalings. Our findings
also confirm, for the first time, Gundlach's prediction that the $\ell = 2$
modes become unstable for sufficiently stiff equations of state. In this regime
the spherically symmetric self-similar solution can no longer be recovered by
fine-tuning to the black-hole threshold, and one can no longer expect power-law
scaling to hold to arbitrarily small scales.
| [
{
"created": "Sat, 26 May 2018 07:57:41 GMT",
"version": "v1"
}
] | 2018-08-08 | [
[
"Celestino",
"Juliana",
""
],
[
"Baumgarte",
"Thomas W.",
""
]
] | We perform fully nonlinear numerical simulations to study aspherical deformations of the critical self-similar solution in the gravitational collapse of ultra-relativistic fluids. Adopting a perturbative calculation, Gundlach predicted that these perturbations behave like damped or growing oscillations, with the frequency and damping (or growth) rates depending on the equation of state. We consider a number of different equations of state and degrees of asphericity and find very good agreement with the findings of Gundlach for polar $\ell = 2$ modes. For sufficiently soft equations of state, the modes are damped, meaning that, in the limit of perfect fine-tuning, the spherically symmetric critical solution is recovered. We find that the degree of asphericity has at most a small effect on the frequency and damping parameter, or on the critical exponents in the power-law scalings. Our findings also confirm, for the first time, Gundlach's prediction that the $\ell = 2$ modes become unstable for sufficiently stiff equations of state. In this regime the spherically symmetric self-similar solution can no longer be recovered by fine-tuning to the black-hole threshold, and one can no longer expect power-law scaling to hold to arbitrarily small scales. |
1909.10003 | Abhik Kumar Sanyal Dr. | Manas Chakrabortty, Nayem Sk and Abhik Kumar Sanyal | Some aspects of modified theory of gravity in Palatini formalism
unveiled | 12 pages, 0 figures | null | 10.1142/S021773232050162X | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Under conformal transformation, f(R) theory of gravity in Palatini formalism
leads to a Brans-Dicke type of scalar-tensor equivalent theory with a wrong
sign in the effective kinetic energy term. This means, the effective scalar
acts as the dark energy and so late-time cosmic acceleration in
matter-dominated era is accountable. However, we unveil some aspects of
Palatini formalism, which clearly reveals the fact that the formalism is not
suitable to explain the cosmological evolution of the early universe with
$f(\mathfrak{R})$ gravity alone. Additionally, it is noticed that some authors,
in an attempt to explore Noether symmetry of the theory changed the sign of the
kinetic term and hence obtained the wrong answer. Here, we make the correction
and unmask a very interesting aspect of symmetry analysis.
| [
{
"created": "Sun, 22 Sep 2019 13:27:16 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Chakrabortty",
"Manas",
""
],
[
"Sk",
"Nayem",
""
],
[
"Sanyal",
"Abhik Kumar",
""
]
] | Under conformal transformation, f(R) theory of gravity in Palatini formalism leads to a Brans-Dicke type of scalar-tensor equivalent theory with a wrong sign in the effective kinetic energy term. This means, the effective scalar acts as the dark energy and so late-time cosmic acceleration in matter-dominated era is accountable. However, we unveil some aspects of Palatini formalism, which clearly reveals the fact that the formalism is not suitable to explain the cosmological evolution of the early universe with $f(\mathfrak{R})$ gravity alone. Additionally, it is noticed that some authors, in an attempt to explore Noether symmetry of the theory changed the sign of the kinetic term and hence obtained the wrong answer. Here, we make the correction and unmask a very interesting aspect of symmetry analysis. |
2109.11743 | Viktor T. Toth | Viktor T. Toth and Slava G. Turyshev | Efficient trace-free decomposition of symmetric tensors of arbitrary
rank | 14 pages, no figures | Int. J. Geom. Meth. Mod. Phys. 19 (13), 2250201 (2022) | 10.1142/S0219887822502012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Symmetric trace-free tensors are used in many areas of physics, including
electromagnetism, relativistic celestial mechanics and geodesy, as well as in
the study of gravitational radiation and gravitational lensing. Their use
allows integration of the relevant wave propagation equations to arbitrary
order. We present an improved iterative method for the trace-free decomposition
of symmetric tensors of arbitrary rank. The method can be used both in
coordinate-free symbolic derivations using a computer algebra system and in
numerical modeling. We obtain a closed-form representation of the trace-free
decomposition in arbitrary dimensions. To demonstrate the results, we compute
the coordinate combinations representing the symmetric trace-free (STF) mass
multipole moments for rank 5 through 8, not readily available in the
literature.
| [
{
"created": "Fri, 24 Sep 2021 04:29:41 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Oct 2022 23:03:29 GMT",
"version": "v2"
}
] | 2022-11-29 | [
[
"Toth",
"Viktor T.",
""
],
[
"Turyshev",
"Slava G.",
""
]
] | Symmetric trace-free tensors are used in many areas of physics, including electromagnetism, relativistic celestial mechanics and geodesy, as well as in the study of gravitational radiation and gravitational lensing. Their use allows integration of the relevant wave propagation equations to arbitrary order. We present an improved iterative method for the trace-free decomposition of symmetric tensors of arbitrary rank. The method can be used both in coordinate-free symbolic derivations using a computer algebra system and in numerical modeling. We obtain a closed-form representation of the trace-free decomposition in arbitrary dimensions. To demonstrate the results, we compute the coordinate combinations representing the symmetric trace-free (STF) mass multipole moments for rank 5 through 8, not readily available in the literature. |
1604.07742 | Hector O. Silva | Masato Minamitsuji, Hector O. Silva | Relativistic stars in scalar-tensor theories with disformal coupling | 23 pages, 7 figures. v2: Improved discussion in the Conclusions.
Matches version published in PRD | Phys. Rev. D 93, 124041 (2016) | 10.1103/PhysRevD.93.124041 | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general formulation to analyze the structure of slowly rotating
relativistic stars in a broad class of scalar-tensor theories with disformal
coupling to matter. Our approach includes theories with generalized kinetic
terms, generic scalar field potentials and contains theories with conformal
coupling as particular limits. In order to investigate how the disformal
coupling affects the structure of relativistic stars, we propose a minimal
model of a massless scalar-tensor theory and investigate in detail how the
disformal coupling affects the spontaneous scalarization of slowly rotating
neutron stars. We show that for negative values of the disformal coupling
parameter between the scalar field and matter, scalarization can be suppressed,
while for large positive values of the disformal coupling parameter stellar
models cannot be obtained. This allows us to put a mild upper bound on this
parameter. We also show that these properties can be qualitatively understood
by linearizing the scalar field equation of motion in the background of a
general-relativistic incompressible star. To address the intrinsic degeneracy
between uncertainties in the equation-of-state of neutron stars and
gravitational theory, we also show the existence of universal
equation-of-state-independent relations between the moment of inertia and
compactness of neutron stars in this theory. We show that in a certain range of
the theory's parameter space the universal relation largely deviates from that
of general relativity, allowing, in principle, to probe the existence of
spontaneous scalarization with future observations.
| [
{
"created": "Tue, 26 Apr 2016 16:25:49 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 2016 11:56:23 GMT",
"version": "v2"
}
] | 2016-06-22 | [
[
"Minamitsuji",
"Masato",
""
],
[
"Silva",
"Hector O.",
""
]
] | We present a general formulation to analyze the structure of slowly rotating relativistic stars in a broad class of scalar-tensor theories with disformal coupling to matter. Our approach includes theories with generalized kinetic terms, generic scalar field potentials and contains theories with conformal coupling as particular limits. In order to investigate how the disformal coupling affects the structure of relativistic stars, we propose a minimal model of a massless scalar-tensor theory and investigate in detail how the disformal coupling affects the spontaneous scalarization of slowly rotating neutron stars. We show that for negative values of the disformal coupling parameter between the scalar field and matter, scalarization can be suppressed, while for large positive values of the disformal coupling parameter stellar models cannot be obtained. This allows us to put a mild upper bound on this parameter. We also show that these properties can be qualitatively understood by linearizing the scalar field equation of motion in the background of a general-relativistic incompressible star. To address the intrinsic degeneracy between uncertainties in the equation-of-state of neutron stars and gravitational theory, we also show the existence of universal equation-of-state-independent relations between the moment of inertia and compactness of neutron stars in this theory. We show that in a certain range of the theory's parameter space the universal relation largely deviates from that of general relativity, allowing, in principle, to probe the existence of spontaneous scalarization with future observations. |
1907.09221 | Jibitesh Dutta | Wompherdeiki Khyllep and Jibitesh Dutta | Linear growth index of matter perturbations in Rastall gravity | 8 pages, 4 figures. Accepted in Physics Letters B. Comments Welcome | null | 10.1016/j.physletb.2019.134796 | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | Rastall gravity theory shows notable features consistent with physical
observations in comparison to the standard Einstein theory. Recently, there has
been a debate about the equivalence of Rastall gravity and general relativity.
Motivated by this open issue, in the present work, we attempt to shed some
light on this debate by analyzing the evolution of the Rastall based
cosmological model at the background as well as perturbation level. Employing
the dynamical system techniques, we found that at late times, the dynamics of
the model resembles the $\Lambda$CDM model at the background level irrespective
of the choice of Rastall's parameter. However, at the perturbation level, we
found that the evolution of the growth index heavily depends on the Rastall's
parameter and displays a significant deviation from the $\Lambda$CDM model.
| [
{
"created": "Mon, 22 Jul 2019 10:31:38 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Khyllep",
"Wompherdeiki",
""
],
[
"Dutta",
"Jibitesh",
""
]
] | Rastall gravity theory shows notable features consistent with physical observations in comparison to the standard Einstein theory. Recently, there has been a debate about the equivalence of Rastall gravity and general relativity. Motivated by this open issue, in the present work, we attempt to shed some light on this debate by analyzing the evolution of the Rastall based cosmological model at the background as well as perturbation level. Employing the dynamical system techniques, we found that at late times, the dynamics of the model resembles the $\Lambda$CDM model at the background level irrespective of the choice of Rastall's parameter. However, at the perturbation level, we found that the evolution of the growth index heavily depends on the Rastall's parameter and displays a significant deviation from the $\Lambda$CDM model. |
gr-qc/9805080 | Alberto Saa | Alberto Saa and Marcelo Schiffer | The gravitational Vavilov-Cherenkov effect | 9 pages, Honorable Mention from the Gravity Research Foundation, 1998 | Mod.Phys.Lett. A13 (1998) 1557 | 10.1142/S0217732398001637 | null | gr-qc | null | In this essay we show that an uncharged black-hole moving superluminally in a
transparent dielectric medium violates Hawking's area theorem. The violation is
overcome through the emission of radiation. Since modes cannot emerge from the
black hole itself, this radiation must originate from a collective effect in
the medium, in complete analogy with the Vavilov-Cherenkov effect. However,
because the black-hole is uncharged, the emission mechanism must be different.
We discuss the physical origin of the effect and obtain a Newtonian estimative.
Then we obtain the appropriate equations in the relativistic case and show that
the field which is radiated away is a combination of gravitational and
electromagnetic degrees of freedom. Possible astrophysical relevance for the
detection of primordial black-holes and binary systems is discussed.
| [
{
"created": "Wed, 20 May 1998 18:28:11 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Saa",
"Alberto",
""
],
[
"Schiffer",
"Marcelo",
""
]
] | In this essay we show that an uncharged black-hole moving superluminally in a transparent dielectric medium violates Hawking's area theorem. The violation is overcome through the emission of radiation. Since modes cannot emerge from the black hole itself, this radiation must originate from a collective effect in the medium, in complete analogy with the Vavilov-Cherenkov effect. However, because the black-hole is uncharged, the emission mechanism must be different. We discuss the physical origin of the effect and obtain a Newtonian estimative. Then we obtain the appropriate equations in the relativistic case and show that the field which is radiated away is a combination of gravitational and electromagnetic degrees of freedom. Possible astrophysical relevance for the detection of primordial black-holes and binary systems is discussed. |
1406.3536 | Marco Sampaio | Marco O. P. Sampaio, Carlos Herdeiro, Mengjie Wang | Marginal scalar and Proca clouds around Reissner-Nordstr\"om black holes | 12 pages, 5 figures, 2 tables | Phys. Rev. D 90, 064004 (2014) | 10.1103/PhysRevD.90.064004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive scalar test fields around Kerr black holes can form quasi-bound
states with complex frequencies. Some of these states decay in time, but some
others -- in the superradiant regime -- grow, causing a superradiant
instability. Precisely at the threshold between decaying and growing modes,
there exist bound states with real frequency, known as scalar clouds. Fully
non-linear counterparts of these clouds have been shown to yield Kerr black
holes with scalar hair. Here, we consider massive, (electrically) charged, test
scalar and Proca fields on the background of Reissner-Nordstr\"om black holes.
By computing the quasi-bound state frequencies, we establish that no such
states exist in the superradiant regime for the Proca field -- a similar
behavior to that known for scalar fields. But decaying quasi-bound states with
an arbitrarily small imaginary part of the frequency exist and thus which are
arbitrarily long lived. In the limit of vanishing imaginary part of the
frequency, the field does not trivialize and we dub the corresponding
configurations as marginal (charged) scalar or Proca clouds, since they are
only marginally bound. We comment on the possible existence of non-linear
counterparts to these marginal clouds.
| [
{
"created": "Fri, 13 Jun 2014 13:56:37 GMT",
"version": "v1"
}
] | 2014-09-10 | [
[
"Sampaio",
"Marco O. P.",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Wang",
"Mengjie",
""
]
] | Massive scalar test fields around Kerr black holes can form quasi-bound states with complex frequencies. Some of these states decay in time, but some others -- in the superradiant regime -- grow, causing a superradiant instability. Precisely at the threshold between decaying and growing modes, there exist bound states with real frequency, known as scalar clouds. Fully non-linear counterparts of these clouds have been shown to yield Kerr black holes with scalar hair. Here, we consider massive, (electrically) charged, test scalar and Proca fields on the background of Reissner-Nordstr\"om black holes. By computing the quasi-bound state frequencies, we establish that no such states exist in the superradiant regime for the Proca field -- a similar behavior to that known for scalar fields. But decaying quasi-bound states with an arbitrarily small imaginary part of the frequency exist and thus which are arbitrarily long lived. In the limit of vanishing imaginary part of the frequency, the field does not trivialize and we dub the corresponding configurations as marginal (charged) scalar or Proca clouds, since they are only marginally bound. We comment on the possible existence of non-linear counterparts to these marginal clouds. |
1806.03996 | Ahmad Sheykhi | Ahmad Sheykhi | Modified Friedmann Equations from Tsallis Entropy | 11 pages, two columns. A new section regarding the cosmological
consequences of this model was added. Also text was revised and new
references added | null | 10.1016/j.physletb.2018.08.036 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It was shown by Tsallis and Cirto that thermodynamical entropy of a
gravitational system such as black hole must be generalized to the non-additive
entropy, which is given by $S_h=\gamma A^{\beta}$, where $A$ is the horizon
area and $\beta$ is the nonextensive parameter \cite{Tsa}. In this paper, by
taking the entropy associated with the apparent horizon of the
Friedmann-Robertson-Walker (FRW) Universe in the form of Tsallis entropy, and
assuming the first law of thermodynamics, $dE=T_hdS_h+WdV$, holds on the
apparent horizon, we are able to derive the corresponding Friedmann equations
describing the dynamics of the universe with any spatial curvature. We also
examine the time evolution of the total entropy and show that the generalized
second law of thermodynamics is fulfilled in a region enclosed by the apparent
horizon. Then, modifying the emergence proposal of gravity proposed by
Padmanabhan and calculating the difference between the surface degrees of
freedom and the bulk degrees of freedom in a region of space, we again arrive
at the modified Friedmann equation of the FRW Universe with any spatial
curvature which is the same as one obtained from the first law of
thermodynamics. We also study the cosmological consequences of Tsallis
cosmology. Interestingly enough, we find that this model can explain
simultaneously the late time acceleration in the universe filled with
pressureless matter without invoking dark energy, as well as the early
deceleration. Besides, the age problem can be circumvented automatically for an
accelerated universe and is estimated larger than $3/2$ age of the universe in
standard cosmology. For $\beta=2/5$, we find $13.12$ Gyr $< t_0 < 16.32 $ Gyr,
which is consistent with recent observations. We also comment on the density
perturbation in the context of Tsallis cosmology.
| [
{
"created": "Thu, 7 Jun 2018 23:30:49 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jun 2018 17:25:00 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Aug 2018 07:29:52 GMT",
"version": "v3"
}
] | 2018-09-26 | [
[
"Sheykhi",
"Ahmad",
""
]
] | It was shown by Tsallis and Cirto that thermodynamical entropy of a gravitational system such as black hole must be generalized to the non-additive entropy, which is given by $S_h=\gamma A^{\beta}$, where $A$ is the horizon area and $\beta$ is the nonextensive parameter \cite{Tsa}. In this paper, by taking the entropy associated with the apparent horizon of the Friedmann-Robertson-Walker (FRW) Universe in the form of Tsallis entropy, and assuming the first law of thermodynamics, $dE=T_hdS_h+WdV$, holds on the apparent horizon, we are able to derive the corresponding Friedmann equations describing the dynamics of the universe with any spatial curvature. We also examine the time evolution of the total entropy and show that the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. Then, modifying the emergence proposal of gravity proposed by Padmanabhan and calculating the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space, we again arrive at the modified Friedmann equation of the FRW Universe with any spatial curvature which is the same as one obtained from the first law of thermodynamics. We also study the cosmological consequences of Tsallis cosmology. Interestingly enough, we find that this model can explain simultaneously the late time acceleration in the universe filled with pressureless matter without invoking dark energy, as well as the early deceleration. Besides, the age problem can be circumvented automatically for an accelerated universe and is estimated larger than $3/2$ age of the universe in standard cosmology. For $\beta=2/5$, we find $13.12$ Gyr $< t_0 < 16.32 $ Gyr, which is consistent with recent observations. We also comment on the density perturbation in the context of Tsallis cosmology. |
1603.05714 | Kento Osuga | Kento Osuga, Don N. Page | A New Way to Derive the Taub-NUT Metric with Positive Cosmological
Constant | null | null | 10.1063/1.4999998 | Alberta-Thy-02-16 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a biaxial Bianchi IX model with positive cosmological
constant, which is sometimes called the Lambda-Taub-NUT spacetime, whose exact
solution is well known. The minisuperspace of biaxial Bianchi IX models admits
two non-trivial Killing tensors that play an important role for deriving the
Taub-NUT metric. We also give a brief discussion about the asymptotic behaviour
of Bianchi IX models.
| [
{
"created": "Thu, 17 Mar 2016 22:27:35 GMT",
"version": "v1"
}
] | 2017-09-13 | [
[
"Osuga",
"Kento",
""
],
[
"Page",
"Don N.",
""
]
] | We investigate a biaxial Bianchi IX model with positive cosmological constant, which is sometimes called the Lambda-Taub-NUT spacetime, whose exact solution is well known. The minisuperspace of biaxial Bianchi IX models admits two non-trivial Killing tensors that play an important role for deriving the Taub-NUT metric. We also give a brief discussion about the asymptotic behaviour of Bianchi IX models. |
1509.03422 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi | Tolman temperature once again: A derivation from gravitational surface
action | 8 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The temperature distribution in presence of gravity, as measured by a local
observer, is given by the Tolman expression. Here I derive the same only from
the Gibbon's-Hawking-York surface term. In this process no explicit use of
Einstein's equations of motion is done. Therefore, the present one is an
off-shell analysis. Finally I discuss the importance and various implications
of the derivation.
| [
{
"created": "Fri, 11 Sep 2015 09:00:34 GMT",
"version": "v1"
}
] | 2015-09-14 | [
[
"Majhi",
"Bibhas Ranjan",
""
]
] | The temperature distribution in presence of gravity, as measured by a local observer, is given by the Tolman expression. Here I derive the same only from the Gibbon's-Hawking-York surface term. In this process no explicit use of Einstein's equations of motion is done. Therefore, the present one is an off-shell analysis. Finally I discuss the importance and various implications of the derivation. |
1011.2062 | Stanislav Babak | Stanislav Babak, Jonathan R. Gair, Antoine Petiteau, Alberto Sesana | Fundamental physics and cosmology with LISA | Based on the talk given at GR19. 10 pages, 2 figures. Revised
version, accepted in CQG | Class.Quant.Grav.28:114001,2011 | 10.1088/0264-9381/28/11/114001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we give a brief review of the fundamental physics that can be
done with the future space-based gravitational wave detector LISA. This
includes detection of gravitational wave bursts coming from cosmic strings,
measuring a stochastic gravitational wave background, mapping spacetime around
massive compact objects in galactic nuclei with extreme-mass-ratio inspirals
and testing the predictions of General Relativity for the strong dynamical
fields of inspiralling binaries. We give particular attention to new results
which show the capability of LISA to constrain cosmological parameters using
observations of coalescing massive Black Hole binaries.
| [
{
"created": "Tue, 9 Nov 2010 12:42:50 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2011 09:59:44 GMT",
"version": "v2"
}
] | 2011-05-25 | [
[
"Babak",
"Stanislav",
""
],
[
"Gair",
"Jonathan R.",
""
],
[
"Petiteau",
"Antoine",
""
],
[
"Sesana",
"Alberto",
""
]
] | In this article we give a brief review of the fundamental physics that can be done with the future space-based gravitational wave detector LISA. This includes detection of gravitational wave bursts coming from cosmic strings, measuring a stochastic gravitational wave background, mapping spacetime around massive compact objects in galactic nuclei with extreme-mass-ratio inspirals and testing the predictions of General Relativity for the strong dynamical fields of inspiralling binaries. We give particular attention to new results which show the capability of LISA to constrain cosmological parameters using observations of coalescing massive Black Hole binaries. |
1104.2938 | Curt Cutler | Curt Cutler | An improved, "phase-relaxed" F-statistic for gravitational-wave data
analysis | 8 pages, 4 figures, submitted to PRD | null | 10.1103/PhysRevD.86.063012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rapidly rotating, slightly non-axisymmetric neutron stars emit nearly
periodic gravitational waves (GWs), quite possibly at levels detectable by
ground-based GW interferometers. We refer to these sources as "GW pulsars". For
any given sky position and frequency evolution, the F-statistic is the optimal
(frequentist) statistic for the detection of GW pulsars. However, in "all-sky"
searches for previously unknown GW pulsars, it would be computationally
intractable to calculate the (fully coherent) F-statistic at every point of a
(suitably fine) grid covering the parameter space: the number of gridpoints is
many orders of magnitude too large for that. Here we introduce a
"phase-relaxed" F-statistic, which we denote F_pr, for incoherently combining
the results of fully coherent searches over short time intervals. We estimate
(very roughly) that for realistic searches, our F_pr is ~10-15% more sensitive
than the "semi-coherent" F-statistic that is currently used. Moreover, as a
byproduct of computing F_pr, one obtains a rough determination of the
time-evolving phase offset between one's template and the true signal imbedded
in the detector noise. Almost all the ingredients that go into calculating F_pr
are already implemented in LAL, so we expect that relatively little additional
effort would be required to develop a search code that uses F_pr.
| [
{
"created": "Thu, 14 Apr 2011 22:27:44 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Cutler",
"Curt",
""
]
] | Rapidly rotating, slightly non-axisymmetric neutron stars emit nearly periodic gravitational waves (GWs), quite possibly at levels detectable by ground-based GW interferometers. We refer to these sources as "GW pulsars". For any given sky position and frequency evolution, the F-statistic is the optimal (frequentist) statistic for the detection of GW pulsars. However, in "all-sky" searches for previously unknown GW pulsars, it would be computationally intractable to calculate the (fully coherent) F-statistic at every point of a (suitably fine) grid covering the parameter space: the number of gridpoints is many orders of magnitude too large for that. Here we introduce a "phase-relaxed" F-statistic, which we denote F_pr, for incoherently combining the results of fully coherent searches over short time intervals. We estimate (very roughly) that for realistic searches, our F_pr is ~10-15% more sensitive than the "semi-coherent" F-statistic that is currently used. Moreover, as a byproduct of computing F_pr, one obtains a rough determination of the time-evolving phase offset between one's template and the true signal imbedded in the detector noise. Almost all the ingredients that go into calculating F_pr are already implemented in LAL, so we expect that relatively little additional effort would be required to develop a search code that uses F_pr. |
1903.09204 | Daniel Williams | Daniel Williams, Ik Siong Heng, Jonathan Gair, James A Clark, Bhavesh
Khamesra | A Precessing Numerical Relativity Waveform Surrogate Model for Binary
Black Holes: A Gaussian Process Regression Approach | 13 pages, with 7 figures. Accepted by Physical Review D | Phys. Rev. D 101, 063011 (2020) | 10.1103/PhysRevD.101.063011 | null | gr-qc physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave astrophysics relies heavily on the use of matched
filtering both to detect signals in noisy data from detectors, and to perform
parameter estimation on those signals. Matched filtering relies upon prior
knowledge of the signals expected to be produced by a range of astrophysical
systems, such as binary black holes. These waveform signals can be computed
using numerical relativity techniques, where the Einstein field equations are
solved numerically, and the signal is extracted from the simulation. Numerical
relativity simulations are, however, computationally expensive, leading to the
need for a surrogate model which can predict waveform signals in regions of the
physical parameter space which have not been probed directly by simulation. We
present a method for producing such a surrogate using Gaussian process
regression which is trained directly on waveforms generated by numerical
relativity. This model returns not just a single interpolated value for the
waveform at a new point, but a full posterior probability distribution on the
predicted value. This model is therefore an ideal component in a Bayesian
analysis framework, through which the uncertainty in the interpolation can be
taken into account when performing parameter estimation of signals.
| [
{
"created": "Thu, 21 Mar 2019 19:08:13 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Sep 2019 14:44:31 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Feb 2020 16:01:16 GMT",
"version": "v3"
}
] | 2020-03-18 | [
[
"Williams",
"Daniel",
""
],
[
"Heng",
"Ik Siong",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Clark",
"James A",
""
],
[
"Khamesra",
"Bhavesh",
""
]
] | Gravitational wave astrophysics relies heavily on the use of matched filtering both to detect signals in noisy data from detectors, and to perform parameter estimation on those signals. Matched filtering relies upon prior knowledge of the signals expected to be produced by a range of astrophysical systems, such as binary black holes. These waveform signals can be computed using numerical relativity techniques, where the Einstein field equations are solved numerically, and the signal is extracted from the simulation. Numerical relativity simulations are, however, computationally expensive, leading to the need for a surrogate model which can predict waveform signals in regions of the physical parameter space which have not been probed directly by simulation. We present a method for producing such a surrogate using Gaussian process regression which is trained directly on waveforms generated by numerical relativity. This model returns not just a single interpolated value for the waveform at a new point, but a full posterior probability distribution on the predicted value. This model is therefore an ideal component in a Bayesian analysis framework, through which the uncertainty in the interpolation can be taken into account when performing parameter estimation of signals. |
1603.03429 | Omar Roldan | Omar Roldan, C.C. Barros Jr | Geometrical Aspects of non-gravitational interactions | 17 pages | null | null | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we look for a geometric description of non-gravitational forces.
The basic ideas are proposed studying the interaction between a punctual
particle and an electromagnetic external field. For this purpose, we introduce
the concept of proper space-time, that allow us to describe this interaction in
a way analogous to the one that the general relativity theory does for
gravitation. The field equations that define this geometry are similar to the
Einstein's equations, where in general, the energy-momentum tensor have
information of both, the particle and the external field. In this formalism we
consider the particle path as being a geodesic in a curved space-time, and so,
the electromagnetic force is understood in a purely geometric way.
| [
{
"created": "Thu, 10 Mar 2016 20:36:34 GMT",
"version": "v1"
}
] | 2016-03-14 | [
[
"Roldan",
"Omar",
""
],
[
"Barros",
"C. C.",
"Jr"
]
] | In this work we look for a geometric description of non-gravitational forces. The basic ideas are proposed studying the interaction between a punctual particle and an electromagnetic external field. For this purpose, we introduce the concept of proper space-time, that allow us to describe this interaction in a way analogous to the one that the general relativity theory does for gravitation. The field equations that define this geometry are similar to the Einstein's equations, where in general, the energy-momentum tensor have information of both, the particle and the external field. In this formalism we consider the particle path as being a geodesic in a curved space-time, and so, the electromagnetic force is understood in a purely geometric way. |
1208.0736 | Yi Xie | Yi Xie | Testing Lorentz violation with binary pulsars: constraints on standard
model extension | 4 pages, no figure, accepted for publication in RAA | Research in Astronomy and Astrophysics, Volume 13, Issue 1, pp.
1-4 (2013) | 10.1088/1674-4527/13/1/001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Under the standard model extension (SME) framework, Lorentz invariance is
tested in five binary pulsars: PSR J0737-3039, PSR B1534+12, PSR J1756-2251,
PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we
obtain the constraints on a dimensionless combination of SME parameters that is
sensitive to timing observations. The results imply no evidence for the break
of Lorentz invariance at $10^{-10}$ level, one order of magnitude larger than
previous estimation.
| [
{
"created": "Fri, 3 Aug 2012 13:21:53 GMT",
"version": "v1"
}
] | 2013-03-05 | [
[
"Xie",
"Yi",
""
]
] | Under the standard model extension (SME) framework, Lorentz invariance is tested in five binary pulsars: PSR J0737-3039, PSR B1534+12, PSR J1756-2251, PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we obtain the constraints on a dimensionless combination of SME parameters that is sensitive to timing observations. The results imply no evidence for the break of Lorentz invariance at $10^{-10}$ level, one order of magnitude larger than previous estimation. |
1606.04996 | Andrea Maselli | Andrea Maselli, Stefania Marassi, Valeria Ferrari, Kostas Kokkotas and
Raffaella Schneider | Constraining modified theories of gravity with gravitational wave
stochastic background | Results updated to match the version accepted on Phys. Rev. Lett | Phys. Rev. Lett. 117, 091102 (2016) | 10.1103/PhysRevLett.117.091102 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct discovery of gravitational waves has finally opened a new
observational window on our Universe, suggesting that the population of
coalescing binary black holes is larger than previously expected. These sources
produce an unresolved background of gravitational waves, potentially
observables by ground-based interferometers. In this paper we investigate how
modified theories of gravity, modeled using the ppE formalism, affect the
expected signal, and analyze the detectability of the resulting stochastic
background by current and future ground-based interferometers. We find the
constraints that AdLIGO would be able to set on modified theories, showing that
they may significantly improve the current bounds obtained from astrophysical
observations of binary pulsars.
| [
{
"created": "Wed, 15 Jun 2016 22:34:04 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Aug 2016 07:40:47 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Maselli",
"Andrea",
""
],
[
"Marassi",
"Stefania",
""
],
[
"Ferrari",
"Valeria",
""
],
[
"Kokkotas",
"Kostas",
""
],
[
"Schneider",
"Raffaella",
""
]
] | The direct discovery of gravitational waves has finally opened a new observational window on our Universe, suggesting that the population of coalescing binary black holes is larger than previously expected. These sources produce an unresolved background of gravitational waves, potentially observables by ground-based interferometers. In this paper we investigate how modified theories of gravity, modeled using the ppE formalism, affect the expected signal, and analyze the detectability of the resulting stochastic background by current and future ground-based interferometers. We find the constraints that AdLIGO would be able to set on modified theories, showing that they may significantly improve the current bounds obtained from astrophysical observations of binary pulsars. |
gr-qc/9712034 | Hans-Juergen Schmidt | H.-J. Schmidt | A two-dimensional representation of four-dimensional gravitational waves | 12 pages, LaTeX, no figures, Int. J. Mod. Phys. D in print | Int.J.Mod.Phys. D7 (1998) 215-224 | 10.1142/S0218271898000176 | Preprint UNIPO-MATH-97-December-5 | gr-qc | null | The Einstein equation in D dimensions, if restricted to the class of
space-times possessing n = D - 2 commuting hypersurface-orthogonal Killing
vectors, can be equivalently written as metric-dilaton gravity in 2 dimensions
with n scalar fields. For n = 2, this results reduces to the known reduction of
certain 4-dimensional metrics which include gravitational waves. Here, we give
such a representation which leads to a new proof of the Birkhoff theorem for
plane-symmetric space--times, and which leads to an explanation, in which sense
two (spin zero-) scalar fields in 2 dimensions may incorporate the (spin two-)
gravitational waves in 4 dimensions. (This result should not be mixed up with
well--known analogous statements where, however, the 4-dimensional space-time
is supposed to be spherically symmetric, and then, of course, the equivalent
2-dimensional picture cannot mimic any gravitational waves.) Finally, remarks
on hidden symmetries in 2 dimensions are made.
| [
{
"created": "Sat, 6 Dec 1997 12:35:26 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Schmidt",
"H. -J.",
""
]
] | The Einstein equation in D dimensions, if restricted to the class of space-times possessing n = D - 2 commuting hypersurface-orthogonal Killing vectors, can be equivalently written as metric-dilaton gravity in 2 dimensions with n scalar fields. For n = 2, this results reduces to the known reduction of certain 4-dimensional metrics which include gravitational waves. Here, we give such a representation which leads to a new proof of the Birkhoff theorem for plane-symmetric space--times, and which leads to an explanation, in which sense two (spin zero-) scalar fields in 2 dimensions may incorporate the (spin two-) gravitational waves in 4 dimensions. (This result should not be mixed up with well--known analogous statements where, however, the 4-dimensional space-time is supposed to be spherically symmetric, and then, of course, the equivalent 2-dimensional picture cannot mimic any gravitational waves.) Finally, remarks on hidden symmetries in 2 dimensions are made. |
1910.14035 | Vicharit Yingcharoenrat | Paolo Creminelli, Giovanni Tambalo, Filippo Vernizzi, and Vicharit
Yingcharoenrat | Dark-Energy Instabilities induced by Gravitational Waves | 26 pages, 4 figures. Matches JCAP version | null | 10.1088/1475-7516/2020/05/002 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that dark-energy perturbations may become unstable in the
presence of a gravitational wave of sufficiently large amplitude. We study this
effect for the cubic Horndeski operator (braiding), proportional to
$\alpha_{\rm B}$. The scalar that describes dark-energy fluctuations features
ghost and/or gradient instabilities for gravitational-wave amplitudes that are
produced by typical binary systems. Taking into account the populations of
binary systems, we conclude that the instability is triggered in the whole
Universe for $|\alpha_{\rm B} |\gtrsim 10^{-2}$, i.e. when the modification of
gravity is sizeable. The instability is triggered by massive black-hole
binaries down to frequencies corresponding to $10^{10}$ km: the instability is
thus robust, unless new physics enters on even longer wavelengths. The fate of
the instability and the subsequent time-evolution of the system depend on the
UV completion, so that the theory may end up in a state very different from the
original one. The same kind of instability is present in beyond-Horndeski
theories for $|\alpha_{\rm H}| \gtrsim 10^{-20}$. In conclusion, the only
dark-energy theories with sizeable cosmological effects that avoid these
problems are $k$-essence models, with a possible conformal coupling with
matter.
| [
{
"created": "Wed, 30 Oct 2019 17:55:21 GMT",
"version": "v1"
},
{
"created": "Mon, 4 May 2020 15:03:54 GMT",
"version": "v2"
}
] | 2020-05-05 | [
[
"Creminelli",
"Paolo",
""
],
[
"Tambalo",
"Giovanni",
""
],
[
"Vernizzi",
"Filippo",
""
],
[
"Yingcharoenrat",
"Vicharit",
""
]
] | We point out that dark-energy perturbations may become unstable in the presence of a gravitational wave of sufficiently large amplitude. We study this effect for the cubic Horndeski operator (braiding), proportional to $\alpha_{\rm B}$. The scalar that describes dark-energy fluctuations features ghost and/or gradient instabilities for gravitational-wave amplitudes that are produced by typical binary systems. Taking into account the populations of binary systems, we conclude that the instability is triggered in the whole Universe for $|\alpha_{\rm B} |\gtrsim 10^{-2}$, i.e. when the modification of gravity is sizeable. The instability is triggered by massive black-hole binaries down to frequencies corresponding to $10^{10}$ km: the instability is thus robust, unless new physics enters on even longer wavelengths. The fate of the instability and the subsequent time-evolution of the system depend on the UV completion, so that the theory may end up in a state very different from the original one. The same kind of instability is present in beyond-Horndeski theories for $|\alpha_{\rm H}| \gtrsim 10^{-20}$. In conclusion, the only dark-energy theories with sizeable cosmological effects that avoid these problems are $k$-essence models, with a possible conformal coupling with matter. |
gr-qc/0511005 | Donald Neville | Donald E. Neville (Temple University) | The volume operator for spin networks with planar or cylindrical
symmetry | 35 pages | Phys.Rev.D73:124004,2006; Erratum-ibid.D77:129901,2008 | 10.1103/PhysRevD.73.124004 10.1103/PhysRevD.77.129901 | null | gr-qc | null | This paper constructs a kinematic basis for spin networks with planar or
cylindrical symmetry, by exploiting the fact that the basis elements are
representations of an O(3) subgroup of O(4). The action of the volume operator
on this basis gives a difference equation for the eigenvalues and eigenvectors
of the volume operator. For basis elements of low spin, the difference equation
can be solved readily on a computer. For higher spins, I solve for the
eigenvalues using a WKBJ method. This paper considers only the case where the
gravitational wave can have both polarizations. The single polarization case is
considered in a spearate paper.
| [
{
"created": "Tue, 1 Nov 2005 20:09:20 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2006 15:41:18 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Neville",
"Donald E.",
"",
"Temple University"
]
] | This paper constructs a kinematic basis for spin networks with planar or cylindrical symmetry, by exploiting the fact that the basis elements are representations of an O(3) subgroup of O(4). The action of the volume operator on this basis gives a difference equation for the eigenvalues and eigenvectors of the volume operator. For basis elements of low spin, the difference equation can be solved readily on a computer. For higher spins, I solve for the eigenvalues using a WKBJ method. This paper considers only the case where the gravitational wave can have both polarizations. The single polarization case is considered in a spearate paper. |
gr-qc/0110126 | Marcello Ortaggio | Marcello Ortaggio (Universita' degli Studi di Trento and INFN) | Impulsive waves in the Nariai universe | 9 pages, 4 figures, REVTeX 4. v3: added Appendix B, revised
references, minor changes in the text. To appear in Phys. Rev. D | Phys.Rev. D65 (2002) 084046 | 10.1103/PhysRevD.65.084046 | null | gr-qc hep-th | null | A new class of exact solutions is presented which describes impulsive waves
propagating in the Nariai universe. It is constructed using a six-dimensional
embedding formalism adapted to the background. Due to the topology of the
latter, the wave front consists of two non-expanding spheres. Special
sub-classes representing pure gravitational waves (generated by null particles
with an arbitrary multipole structure) or shells of null dust are analyzed in
detail. Smooth isometries of the metrics are briefly discussed. Furthermore, it
is shown that the considered solutions are impulsive members of a more general
family of radiative Kundt spacetimes of type-II. A straightforward
generalization to impulsive waves in the anti-Nariai and Bertotti-Robinson
backgrounds is described. For a vanishing cosmological constant and
electromagnetic field, results for well known impulsive pp-waves are recovered.
| [
{
"created": "Wed, 31 Oct 2001 17:48:58 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Oct 2001 22:10:04 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Feb 2002 10:58:11 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Ortaggio",
"Marcello",
"",
"Universita' degli Studi di Trento and INFN"
]
] | A new class of exact solutions is presented which describes impulsive waves propagating in the Nariai universe. It is constructed using a six-dimensional embedding formalism adapted to the background. Due to the topology of the latter, the wave front consists of two non-expanding spheres. Special sub-classes representing pure gravitational waves (generated by null particles with an arbitrary multipole structure) or shells of null dust are analyzed in detail. Smooth isometries of the metrics are briefly discussed. Furthermore, it is shown that the considered solutions are impulsive members of a more general family of radiative Kundt spacetimes of type-II. A straightforward generalization to impulsive waves in the anti-Nariai and Bertotti-Robinson backgrounds is described. For a vanishing cosmological constant and electromagnetic field, results for well known impulsive pp-waves are recovered. |
1802.07660 | Sourav Bhattacharya | Sourav Bhattacharya, Stefanos R Kousvos, Stylianos Romanopoulos and
Theodore N Tomaras | Cosmological screening and the phantom braneworld model | v2, 14pp, 3 figs; mistake in the +- sign in the spatially homogeneous
eqn in v1 corrected; consequently, the conclusions of the current version
differ from those of v1 | Eur. Phys. J. C (2018) 78 : 637 | 10.1140/epjc/s10052-018-6119-z | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scalar and vector cosmological perturbations at all length scales of our
Universe are studied in the framework of the phantom braneworld model. The
model is characterized by the parameter $\Omega_M\equiv M^3/2m^2H_0$, with $M$
and $m$ the 5- and 4-dimensional Planck scales, respectively, and $H_0$ the
Hubble parameter today, while $\Omega_M\rightarrow 0$ recovers the $\Lambda\rm
CDM$ model. Ignoring the backreaction due to the peculiar velocities and also
the bulk cosmological constant, allows the explicit computation of the
gravitational potentials, $\Phi$ and $\Psi$. They exhibit exponentially
decreasing screening behaviour characterized by a screening length which is a
function of the quasidensity parameter $ \Omega_M$.
| [
{
"created": "Wed, 21 Feb 2018 16:47:26 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jun 2018 05:25:34 GMT",
"version": "v2"
}
] | 2018-08-14 | [
[
"Bhattacharya",
"Sourav",
""
],
[
"Kousvos",
"Stefanos R",
""
],
[
"Romanopoulos",
"Stylianos",
""
],
[
"Tomaras",
"Theodore N",
""
]
] | The scalar and vector cosmological perturbations at all length scales of our Universe are studied in the framework of the phantom braneworld model. The model is characterized by the parameter $\Omega_M\equiv M^3/2m^2H_0$, with $M$ and $m$ the 5- and 4-dimensional Planck scales, respectively, and $H_0$ the Hubble parameter today, while $\Omega_M\rightarrow 0$ recovers the $\Lambda\rm CDM$ model. Ignoring the backreaction due to the peculiar velocities and also the bulk cosmological constant, allows the explicit computation of the gravitational potentials, $\Phi$ and $\Psi$. They exhibit exponentially decreasing screening behaviour characterized by a screening length which is a function of the quasidensity parameter $ \Omega_M$. |
1410.4411 | Astrid Eichhorn | P. Don\`a, Astrid Eichhorn, Roberto Percacci | Consistency of matter models with asymptotically safe quantum gravity | prepared for the proceedings of Theory Canada 9; new results on the
gravitino, 8 pages, 1 figure, 1 table | null | 10.1139/cjp-2014-0574 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the compatibility of quantum gravity with dynamical matter degrees
of freedom. Specifically, we present bounds we obtained in [1] on the allowed
number and type of matter fields within asymptotically safe quantum gravity. As
a novel result, we show bounds on the allowed number of spin-3/2
(Rarita-Schwinger) fields, e.g., the gravitino. These bounds, obtained within
truncated Renormalization Group flows, indicate the compatibility of asymptotic
safety with the matter fields of the standard model. Further, they suggest that
extensions of the matter content of the standard model are severely restricted
in asymptotic safety. This means that searches for new particles at colliders
could provide experimental tests for this particular approach to quantum
gravity.
| [
{
"created": "Thu, 16 Oct 2014 13:21:14 GMT",
"version": "v1"
}
] | 2023-07-19 | [
[
"Donà",
"P.",
""
],
[
"Eichhorn",
"Astrid",
""
],
[
"Percacci",
"Roberto",
""
]
] | We discuss the compatibility of quantum gravity with dynamical matter degrees of freedom. Specifically, we present bounds we obtained in [1] on the allowed number and type of matter fields within asymptotically safe quantum gravity. As a novel result, we show bounds on the allowed number of spin-3/2 (Rarita-Schwinger) fields, e.g., the gravitino. These bounds, obtained within truncated Renormalization Group flows, indicate the compatibility of asymptotic safety with the matter fields of the standard model. Further, they suggest that extensions of the matter content of the standard model are severely restricted in asymptotic safety. This means that searches for new particles at colliders could provide experimental tests for this particular approach to quantum gravity. |
1412.3977 | Dijana Tolic | Neven Bilic, Dijana Tolic | Cosmological particle creation in a hadronic fluid | 13 pages, 4 figures, revised to match the version published in Phys.
Rev. D., section IIB rewritten, section IIIC expanded, discussion on
adiabaticity expanded and clarified, three references added, results
unchanged | Phys. Rev. D 91, 104025 (2015) | 10.1103/PhysRevD.91.104025 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Acoustic perturbations in an expanding hadronic fluid at temperatures below
the chiral transition point represent massless pions propagating in curved
spacetime geometry. In comoving coordinates the corresponding analog metric
tensor describes a hyperbolic FRW spacetime. We study the analog cosmological
particle creation of pions below the critical point of the chiral phase
transition. We compare the cosmological creation spectrum with the spectrum of
analog Hawking radiation at the analog trapping horizon.
| [
{
"created": "Fri, 12 Dec 2014 12:52:07 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jan 2015 16:46:16 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Jun 2015 07:32:35 GMT",
"version": "v3"
}
] | 2015-06-12 | [
[
"Bilic",
"Neven",
""
],
[
"Tolic",
"Dijana",
""
]
] | Acoustic perturbations in an expanding hadronic fluid at temperatures below the chiral transition point represent massless pions propagating in curved spacetime geometry. In comoving coordinates the corresponding analog metric tensor describes a hyperbolic FRW spacetime. We study the analog cosmological particle creation of pions below the critical point of the chiral phase transition. We compare the cosmological creation spectrum with the spectrum of analog Hawking radiation at the analog trapping horizon. |
1607.03702 | Jie-Xiong Mo | Jie-Xiong Mo | An alternative perspective to observe the critical phenomena of dilaton
AdS black holes | Comments welcome. 19 pages, 10 figures, 8 tables | null | 10.1140/epjc/s10052-017-5103-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The critical phenomena of dilaton AdS black holes are probed from a totally
different perspective other than the $P-v$ criticality and the $q-U$
criticality discussed in the former literature. We investigate not only the two
point correlation function but also the entanglement entropy of dilaton AdS
black holes. We achieve this goal by solving the equation of motion constrained
by the boundary condition numerically and we concentrate on $\delta L$ and
$\delta S$ which have been regularized by subtracting the terms in pure AdS
with the same boundary region. For both the two point correlation function and
the entanglement entropy, we consider $4\times2\times2=16$ cases due to
different choices of parameters. The van der Waals like behavior can be clearly
witnessed from all the $T-\delta L$ ($T-\delta S$) graphs for $q<q_c$.
Moreover, the effects of dilaton gravity and the spacetime dimensionality on
the phase structure of dilaton AdS black holes are disclosed. Furthermore, we
discuss the stability of dilaton AdS black holes by applying the analogous
specific heat definition and remove the unstable branch by introducing a bar
$T=T_*$. It is shown that the first order phase transition temperature $T_*$ is
affected by both $\alpha$ and $n$. The analogous equal area laws for both the
$T-\delta L$ graph and the $T-\delta S$ graph are examined numerically. The
relative errors for all the cases are small enough that we can safely conclude
that the analogous equal area laws hold for $T-\delta L$ ($T-\delta S$) graph
of dilaton AdS black holes.
| [
{
"created": "Wed, 13 Jul 2016 12:40:51 GMT",
"version": "v1"
}
] | 2017-09-13 | [
[
"Mo",
"Jie-Xiong",
""
]
] | The critical phenomena of dilaton AdS black holes are probed from a totally different perspective other than the $P-v$ criticality and the $q-U$ criticality discussed in the former literature. We investigate not only the two point correlation function but also the entanglement entropy of dilaton AdS black holes. We achieve this goal by solving the equation of motion constrained by the boundary condition numerically and we concentrate on $\delta L$ and $\delta S$ which have been regularized by subtracting the terms in pure AdS with the same boundary region. For both the two point correlation function and the entanglement entropy, we consider $4\times2\times2=16$ cases due to different choices of parameters. The van der Waals like behavior can be clearly witnessed from all the $T-\delta L$ ($T-\delta S$) graphs for $q<q_c$. Moreover, the effects of dilaton gravity and the spacetime dimensionality on the phase structure of dilaton AdS black holes are disclosed. Furthermore, we discuss the stability of dilaton AdS black holes by applying the analogous specific heat definition and remove the unstable branch by introducing a bar $T=T_*$. It is shown that the first order phase transition temperature $T_*$ is affected by both $\alpha$ and $n$. The analogous equal area laws for both the $T-\delta L$ graph and the $T-\delta S$ graph are examined numerically. The relative errors for all the cases are small enough that we can safely conclude that the analogous equal area laws hold for $T-\delta L$ ($T-\delta S$) graph of dilaton AdS black holes. |
2312.17277 | Jainendra Kumar Singh Dr. | Harshna Balhara, J. K. Singh and Emmanuel N. Saridakis | Observational constraints and cosmographic analysis of
$f({T},{T}_{{G}})$ gravity and cosmology | 12 pages, 11 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We perform observational confrontation and cosmographic analysis of
$f(T,T_G)$ gravity and cosmology. This higher-order torsional gravity is based
on both the torsion scalar, as well as on the teleparallel equivalent of the
Gauss-Bonnet combination, and gives rise to an effective dark-energy sector
which depends on the extra torsion contributions. We employ observational data
from the Hubble function and Supernova Type Ia Pantheon datasets, applying a
Markov Chain Monte Carlo sampling technique, and we provide the iso-likelihood
contours, as well as the best-fit values for the parameters of the power-law
model. Additionally, we reconstruct the effective dark-energy equation-of-state
parameter, which exhibits a quintessence-like behavior, while in the future the
Universe enters into the phantom regime, before it tends asymptotically to the
cosmological constant value. Furthermore, we perform a detailed cosmographic
analysis, examining the deceleration, jerk, snap and lerk parameters, showing
that the transition to acceleration occurs in the redshift range $ 0.52 \leq
z_{tr} \leq 0.89 $, as well as the preference of the scenario for
quintessence-like behavior. Finally, we apply the Om diagnostic analysis, as a
cross-verification of the obtained behavior.
| [
{
"created": "Wed, 27 Dec 2023 19:28:25 GMT",
"version": "v1"
}
] | 2024-01-01 | [
[
"Balhara",
"Harshna",
""
],
[
"Singh",
"J. K.",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We perform observational confrontation and cosmographic analysis of $f(T,T_G)$ gravity and cosmology. This higher-order torsional gravity is based on both the torsion scalar, as well as on the teleparallel equivalent of the Gauss-Bonnet combination, and gives rise to an effective dark-energy sector which depends on the extra torsion contributions. We employ observational data from the Hubble function and Supernova Type Ia Pantheon datasets, applying a Markov Chain Monte Carlo sampling technique, and we provide the iso-likelihood contours, as well as the best-fit values for the parameters of the power-law model. Additionally, we reconstruct the effective dark-energy equation-of-state parameter, which exhibits a quintessence-like behavior, while in the future the Universe enters into the phantom regime, before it tends asymptotically to the cosmological constant value. Furthermore, we perform a detailed cosmographic analysis, examining the deceleration, jerk, snap and lerk parameters, showing that the transition to acceleration occurs in the redshift range $ 0.52 \leq z_{tr} \leq 0.89 $, as well as the preference of the scenario for quintessence-like behavior. Finally, we apply the Om diagnostic analysis, as a cross-verification of the obtained behavior. |
1508.05474 | Oleg Evnin | Ben Craps, Oleg Evnin, Puttarak Jai-akson, Joris Vanhoof | Ultraviolet asymptotics for quasiperiodic AdS_4 perturbations | 18 pages; v3: minor improvements, published version | JHEP 1510 (2015) 080 | 10.1007/JHEP10(2015)080 | null | gr-qc hep-th nlin.CD | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Spherically symmetric perturbations in AdS-scalar field systems of small
amplitude epsilon approximately periodic on time scales of order 1/epsilon^2
(in the sense that no significant transfer of energy between the AdS normal
modes occurs) have played an important role in considerations of AdS stability.
They are seen as anchors of stability islands where collapse of small
perturbations to black holes does not occur. (This collapse, if it happens,
typically develops on time scales of the order 1/epsilon^2.) We construct an
analytic treatment of the frequency spectra of such quasiperiodic
perturbations, paying special attention to the large frequency asymptotics. For
the case of a self-interacting phi^4 scalar field in a non-dynamical AdS
background, we arrive at a fairly complete analytic picture involving
quasiperiodic spectra with an exponential suppression modulated by a power law
at large mode numbers. For the case of dynamical gravity, the structure of the
large frequency asymptotics is more complicated. We give analytic explanations
for the general qualitative features of quasiperiodic solutions localized
around a single mode, in close parallel to our discussion of the probe scalar
field, and find numerical evidence for logarithmic modulations in the
gravitational quasiperiodic spectra existing on top of the formulas previously
reported in the literature.
| [
{
"created": "Sat, 22 Aug 2015 07:23:10 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Sep 2015 04:54:35 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Oct 2015 05:53:11 GMT",
"version": "v3"
}
] | 2015-10-30 | [
[
"Craps",
"Ben",
""
],
[
"Evnin",
"Oleg",
""
],
[
"Jai-akson",
"Puttarak",
""
],
[
"Vanhoof",
"Joris",
""
]
] | Spherically symmetric perturbations in AdS-scalar field systems of small amplitude epsilon approximately periodic on time scales of order 1/epsilon^2 (in the sense that no significant transfer of energy between the AdS normal modes occurs) have played an important role in considerations of AdS stability. They are seen as anchors of stability islands where collapse of small perturbations to black holes does not occur. (This collapse, if it happens, typically develops on time scales of the order 1/epsilon^2.) We construct an analytic treatment of the frequency spectra of such quasiperiodic perturbations, paying special attention to the large frequency asymptotics. For the case of a self-interacting phi^4 scalar field in a non-dynamical AdS background, we arrive at a fairly complete analytic picture involving quasiperiodic spectra with an exponential suppression modulated by a power law at large mode numbers. For the case of dynamical gravity, the structure of the large frequency asymptotics is more complicated. We give analytic explanations for the general qualitative features of quasiperiodic solutions localized around a single mode, in close parallel to our discussion of the probe scalar field, and find numerical evidence for logarithmic modulations in the gravitational quasiperiodic spectra existing on top of the formulas previously reported in the literature. |
1802.04150 | Sumanta Chakraborty | Rabin Banerjee, Sumanta Chakraborty and Pradip Mukherjee | Late-time acceleration driven by shift-symmetric Galileon in the
presence of Torsion | Minor revision, Published version, 11 pages, 1 figure | Phys. Rev. D 98, 083506 (2018) | 10.1103/PhysRevD.98.083506 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A shift-symmetric Galileon model in presence of spacetime torsion has been
constructed for the first time. This has been realized by localizing (or,
gauging) the Galileon symmetry in flat spacetime in an appropriate manner. We
have applied the above model to study the evolution of the universe at a
cosmological scale. Interestingly, for a wide class of torsional structures we
have shown that the model leads to late time cosmic acceleration. Furthermore,
as torsion vanishes, our model reproduces the standard results.
| [
{
"created": "Fri, 9 Feb 2018 11:40:25 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Oct 2018 00:48:31 GMT",
"version": "v2"
}
] | 2018-10-09 | [
[
"Banerjee",
"Rabin",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"Mukherjee",
"Pradip",
""
]
] | A shift-symmetric Galileon model in presence of spacetime torsion has been constructed for the first time. This has been realized by localizing (or, gauging) the Galileon symmetry in flat spacetime in an appropriate manner. We have applied the above model to study the evolution of the universe at a cosmological scale. Interestingly, for a wide class of torsional structures we have shown that the model leads to late time cosmic acceleration. Furthermore, as torsion vanishes, our model reproduces the standard results. |
2106.13450 | Piyabut Burikham | Sitthichai Pinkanjanarod, Piyabut Burikham, Supakchai Ponglertsakul | Tidal Deformation and Radial Pulsations of Neutron Star with Holographic
Multiquark Core | 9 pages, 5 figures, to appear in EPJC | null | 10.1140/epjc/s10052-022-10106-5 | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | Tidal deformation of neutron star with multiquark core is calculated using
nuclear and multiquark equations of state. The equation of state of the
multiquark phase from the holographic Sakai-Sugimoto~(SS) model is relatively
stiff in the low density region and becomes softer at high densities. The
values of Love number and dimensionless deformation parameter, $k_{2}$ and
$\Lambda$, are found to be within the physically viable range under the present
constraints. Radial pulsation frequencies of the multiquark core for $n=0-5$
modes are calculated for the entire mass range. For $M_{\rm core}\simeq 2
M_{\odot}$, the fundamental-mode frequency is approximately $2.5$ kHz for the
energy density scale $\epsilon_{s}=23.2037$ GeV/fm$^{3}$ of the holographic SS
model, this frequency is proportional to $\sqrt{\epsilon_{s}}$.
| [
{
"created": "Fri, 25 Jun 2021 06:27:44 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Dec 2021 10:01:17 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Feb 2022 14:14:08 GMT",
"version": "v3"
}
] | 2022-03-02 | [
[
"Pinkanjanarod",
"Sitthichai",
""
],
[
"Burikham",
"Piyabut",
""
],
[
"Ponglertsakul",
"Supakchai",
""
]
] | Tidal deformation of neutron star with multiquark core is calculated using nuclear and multiquark equations of state. The equation of state of the multiquark phase from the holographic Sakai-Sugimoto~(SS) model is relatively stiff in the low density region and becomes softer at high densities. The values of Love number and dimensionless deformation parameter, $k_{2}$ and $\Lambda$, are found to be within the physically viable range under the present constraints. Radial pulsation frequencies of the multiquark core for $n=0-5$ modes are calculated for the entire mass range. For $M_{\rm core}\simeq 2 M_{\odot}$, the fundamental-mode frequency is approximately $2.5$ kHz for the energy density scale $\epsilon_{s}=23.2037$ GeV/fm$^{3}$ of the holographic SS model, this frequency is proportional to $\sqrt{\epsilon_{s}}$. |
2009.13433 | Patryk Mach | Patryk Mach, Andrzej Odrzywolek | Accretion of the relativistic Vlasov gas onto a moving Schwarzschild
black hole: Exact solutions | 22 pages, 8 figures | Phys. Rev. D 103, 024044 (2021) | 10.1103/PhysRevD.103.024044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an exact, axially symmetric solution representing stationary
accretion of the relativistic, collisionless Vlasov gas onto a moving
Schwarzschild black hole. The gas is assumed to be in thermal equilibrium at
infinity, where it obeys the Maxwell-J\"{u}ttner distribution. The Vlasov
equation is solved analytically in terms of suitable action-angle variables. We
provide explicit expressions for the particle current density and accretion
rates. In the limit of infinite asymptotic temperature of the gas, we recover
the qualitative picture known form the relativistic Bondi-Hoyle-Lyttleton
accretion of the perfect gas with the ultra-hard equation of state, in which
the mass accretion is proportional to the Lorentz factor associated with the
black-hole velocity. For a finite asymptotic temperature, the mass accretion
rate is not in general a monotonic function of the velocity of the black hole.
| [
{
"created": "Mon, 28 Sep 2020 16:01:39 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Dec 2020 20:19:50 GMT",
"version": "v2"
},
{
"created": "Sun, 17 Jan 2021 19:34:40 GMT",
"version": "v3"
}
] | 2021-01-27 | [
[
"Mach",
"Patryk",
""
],
[
"Odrzywolek",
"Andrzej",
""
]
] | We derive an exact, axially symmetric solution representing stationary accretion of the relativistic, collisionless Vlasov gas onto a moving Schwarzschild black hole. The gas is assumed to be in thermal equilibrium at infinity, where it obeys the Maxwell-J\"{u}ttner distribution. The Vlasov equation is solved analytically in terms of suitable action-angle variables. We provide explicit expressions for the particle current density and accretion rates. In the limit of infinite asymptotic temperature of the gas, we recover the qualitative picture known form the relativistic Bondi-Hoyle-Lyttleton accretion of the perfect gas with the ultra-hard equation of state, in which the mass accretion is proportional to the Lorentz factor associated with the black-hole velocity. For a finite asymptotic temperature, the mass accretion rate is not in general a monotonic function of the velocity of the black hole. |
1902.00265 | Supakchai Ponglertsakul | Sirachak Panpanich, Supakchai Ponglertsakul and Kei-ichi Maeda | Cosmological Dynamics and Double Screening of DBI Galileon Gravity | 16 pages, 10 figures, matched with the PRD version | Phys. Rev. D 100, 044038 (2019) | 10.1103/PhysRevD.100.044038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate cosmological dynamics and screening mechanism of the
Dirac-Born-Infeld (DBI) Galileon model. The model has been divided into two
regimes, one has positive signs in front of scalar field kinetic terms
so-called the DBI galileon, another one has negative signs and it is dubbed as
the DBIonic galileon. We find de Sitter solution and evolution of the Universe
starting from radiation dominated era to late-time accelerated expansion in the
DBI galileon model without the presence of potential term. In one of the
attractors, the ghost and Laplacian instabilities vanishes for the whole
evolution. We find mixing of screening mechanisms between the Vainshtein
mechanism and the DBIonic screening mechanism in the DBIonic galileon model, in
which a scale changing between these two mechanisms depends on a mass of a
source.
| [
{
"created": "Fri, 1 Feb 2019 10:24:01 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Aug 2019 01:45:00 GMT",
"version": "v2"
}
] | 2019-08-28 | [
[
"Panpanich",
"Sirachak",
""
],
[
"Ponglertsakul",
"Supakchai",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We investigate cosmological dynamics and screening mechanism of the Dirac-Born-Infeld (DBI) Galileon model. The model has been divided into two regimes, one has positive signs in front of scalar field kinetic terms so-called the DBI galileon, another one has negative signs and it is dubbed as the DBIonic galileon. We find de Sitter solution and evolution of the Universe starting from radiation dominated era to late-time accelerated expansion in the DBI galileon model without the presence of potential term. In one of the attractors, the ghost and Laplacian instabilities vanishes for the whole evolution. We find mixing of screening mechanisms between the Vainshtein mechanism and the DBIonic screening mechanism in the DBIonic galileon model, in which a scale changing between these two mechanisms depends on a mass of a source. |
gr-qc/9509053 | Jerome Martin | Jerome Martin | Cosmological perturbations and classical change of signature | 35 pages, latex, 2 figures available at jmartin@ccr.jussieu.fr, to
appear in Physical Review D | Phys.Rev. D52 (1995) 6708-6716 | 10.1103/PhysRevD.52.6708 | null | gr-qc | null | Cosmological perturbations on a manifold admitting signature change are
studied. The background solution consists in a Friedmann-Lemaitre-Robertson-
Walker (FLRW) Universe filled by a constant scalar field playing the role of a
cosmological constant. It is shown that no regular solution exist satisfying
the junction conditions at the surface of change. The comparison with similar
studies in quantum cosmology is made.
| [
{
"created": "Wed, 27 Sep 1995 13:48:26 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Martin",
"Jerome",
""
]
] | Cosmological perturbations on a manifold admitting signature change are studied. The background solution consists in a Friedmann-Lemaitre-Robertson- Walker (FLRW) Universe filled by a constant scalar field playing the role of a cosmological constant. It is shown that no regular solution exist satisfying the junction conditions at the surface of change. The comparison with similar studies in quantum cosmology is made. |
1709.01949 | Sebastian De Haro | Sebastian De Haro | The Invisibility of Diffeomorphisms | 28+7 pages, 1 figure. v2: published version, minor corrections | Foundations of Physics, 47 (11), 2017, pp. 1464-1497 | 10.1007/s10701-017-0117-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I examine the relationship between $(d+1)$-dimensional Poincar\'e metrics and
$d$-dimensional conformal manifolds, from both mathematical and physical
perspectives. The results have a bearing on several conceptual issues relating
to asymptotic symmetries, in general relativity and in gauge-gravity duality,
as follows:
(1: Ambient Construction) I draw from the remarkable work by Fefferman and
Graham (1985, 2012) on conformal geometry, in order to prove two propositions
and a theorem that characterise the classes of diffeomorphisms that qualify as
gravity-invisible. I define natural notions of gravity-invisibility (strong,
weak, and simpliciter) which apply to the diffeomorphisms of Poincar\'e metrics
in any dimension.
(2: Dualities) I apply the notions of invisibility to gauge-gravity
dualities: which, roughly, relate Poincar\'e metrics in $d+1$ dimensions to
QFTs in $d$ dimensions. I contrast QFT-visible vs. QFT-invisible
diffeomorphisms: those gravity diffeomorphisms that can, respectively cannot,
be seen from the QFT.
The QFT-invisible diffeomorphisms are the ones which are relevant to the hole
argument in Einstein spaces. The results on dualities are surprising, because
the class of QFT-visible diffeomorphisms is larger than expected, and the class
of QFT-invisible ones is smaller than expected, or usually believed, i.e.
larger than the PBH diffeomorphisms in Imbimbo et al. (2000). I also give a
general derivation of the asymptotic conformal Killing equation, which has not
appeared in the literature before.
| [
{
"created": "Wed, 6 Sep 2017 18:06:06 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jan 2018 11:42:25 GMT",
"version": "v2"
}
] | 2018-01-04 | [
[
"De Haro",
"Sebastian",
""
]
] | I examine the relationship between $(d+1)$-dimensional Poincar\'e metrics and $d$-dimensional conformal manifolds, from both mathematical and physical perspectives. The results have a bearing on several conceptual issues relating to asymptotic symmetries, in general relativity and in gauge-gravity duality, as follows: (1: Ambient Construction) I draw from the remarkable work by Fefferman and Graham (1985, 2012) on conformal geometry, in order to prove two propositions and a theorem that characterise the classes of diffeomorphisms that qualify as gravity-invisible. I define natural notions of gravity-invisibility (strong, weak, and simpliciter) which apply to the diffeomorphisms of Poincar\'e metrics in any dimension. (2: Dualities) I apply the notions of invisibility to gauge-gravity dualities: which, roughly, relate Poincar\'e metrics in $d+1$ dimensions to QFTs in $d$ dimensions. I contrast QFT-visible vs. QFT-invisible diffeomorphisms: those gravity diffeomorphisms that can, respectively cannot, be seen from the QFT. The QFT-invisible diffeomorphisms are the ones which are relevant to the hole argument in Einstein spaces. The results on dualities are surprising, because the class of QFT-visible diffeomorphisms is larger than expected, and the class of QFT-invisible ones is smaller than expected, or usually believed, i.e. larger than the PBH diffeomorphisms in Imbimbo et al. (2000). I also give a general derivation of the asymptotic conformal Killing equation, which has not appeared in the literature before. |
1808.10602 | Gizem \c{S}eng\"or | Gizem \c{S}eng\"or | Hidden regimes during preheating | Sections IV and V and figures have been improved | Phys. Rev. D 100, 043503 (2019) | 10.1103/PhysRevD.100.043503 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Effective Field Theory (EFT) of Preheating with scalar fields, implies
three types of derivative couplings between the inflaton and the reheating
field. Two of these couplings lead to scales below which only one of the two
species appear as the low energy modes. In this paper, the variety of low
energy regimes in terms of the species they accommodate are explored by
studying the scales introduced by the derivative couplings and the dispersion
relations they lead to. It is noted that the EFT of two scalar fields can give
rise to non-trivial sound speed for both the inflation and reheating sector
even at scales where modes of both species propagate freely, suggesting the
presence of additional heavy fields. The regimes where one of the species
affects the dispersion relation of the other while not appearing as an
effective mode itself, are named as "Hidden Regimes" during preheating.
| [
{
"created": "Fri, 31 Aug 2018 05:50:20 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Aug 2019 10:15:32 GMT",
"version": "v2"
}
] | 2019-08-21 | [
[
"Şengör",
"Gizem",
""
]
] | The Effective Field Theory (EFT) of Preheating with scalar fields, implies three types of derivative couplings between the inflaton and the reheating field. Two of these couplings lead to scales below which only one of the two species appear as the low energy modes. In this paper, the variety of low energy regimes in terms of the species they accommodate are explored by studying the scales introduced by the derivative couplings and the dispersion relations they lead to. It is noted that the EFT of two scalar fields can give rise to non-trivial sound speed for both the inflation and reheating sector even at scales where modes of both species propagate freely, suggesting the presence of additional heavy fields. The regimes where one of the species affects the dispersion relation of the other while not appearing as an effective mode itself, are named as "Hidden Regimes" during preheating. |
1703.08156 | Sebastian V\"olkel | Sebastian H. V\"olkel and Kostas D. Kokkotas | A Semi-analytic Study of Axial Perturbations of Ultra Compact Stars | Accepted for publication in CQG, 13 pages, 3 figures, 5 tables | null | 10.1088/1361-6382/aa68cc | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compact object perturbations, at linear order, often lead in solving one or
more coupled wave equations. The study of these equations was typically done by
numerical or semi-analytical methods. The WKB method and the associated
Bohr-Sommerfeld rule have been proved extremely useful tools in the study of
black-hole perturbations and the estimation of the related quasi-normal modes.
Here we present an extension of the aforementioned semi-analytic methods in the
study of perturbations of ultra-compact stars and gravastars.
| [
{
"created": "Thu, 23 Mar 2017 17:33:11 GMT",
"version": "v1"
}
] | 2017-03-24 | [
[
"Völkel",
"Sebastian H.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | Compact object perturbations, at linear order, often lead in solving one or more coupled wave equations. The study of these equations was typically done by numerical or semi-analytical methods. The WKB method and the associated Bohr-Sommerfeld rule have been proved extremely useful tools in the study of black-hole perturbations and the estimation of the related quasi-normal modes. Here we present an extension of the aforementioned semi-analytic methods in the study of perturbations of ultra-compact stars and gravastars. |
gr-qc/0503018 | Martin Zofka | Jiri Bicak and Joseph Katz | On the uniqueness of harmonic coordinates | 14 pages, no figures | Czech.J.Phys. 55 (2005) 105-118 | 10.1007/s10582-005-0024-z | null | gr-qc | null | Harmonic coordinate conditions in stationary asymptotically flat spacetimes
with matter sources have more than one solution. The solutions depend on the
degree of smoothness of the metric and its first derivatives, which we wish to
impose across the material boundary, and on the conditions at infinity and at a
suitable point inside the matter. This is illustrated in detail by simple fully
solvable examples of static spherically symmetric spacetimes in global harmonic
coordinates. Examples of stationary electrovacuum spacetimes described simply
in harmonic coordinates are also given. They can represent the exterior fields
of material discs.
The use of an appropriate background metric considerably simplifies the
calculations.
| [
{
"created": "Fri, 4 Mar 2005 15:03:15 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Bicak",
"Jiri",
""
],
[
"Katz",
"Joseph",
""
]
] | Harmonic coordinate conditions in stationary asymptotically flat spacetimes with matter sources have more than one solution. The solutions depend on the degree of smoothness of the metric and its first derivatives, which we wish to impose across the material boundary, and on the conditions at infinity and at a suitable point inside the matter. This is illustrated in detail by simple fully solvable examples of static spherically symmetric spacetimes in global harmonic coordinates. Examples of stationary electrovacuum spacetimes described simply in harmonic coordinates are also given. They can represent the exterior fields of material discs. The use of an appropriate background metric considerably simplifies the calculations. |
2105.13243 | Maria Caruana | Sebastian Bahamonde, Maria Caruana, Konstantinos F. Dialektopoulos,
Viktor Gakis, Manuel Hohmann, Jackson Levi Said, Emmanuel N. Saridakis,
Joseph Sultana | Gravitational Wave Propagation and Polarizations in the Teleparallel
analog of Horndeski Gravity | null | null | 10.1103/PhysRevD.104.084082 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves (GWs) have opened a new window on fundamental physics in
a number of important ways. The next generation of GW detectors may reveal more
information about the polarization structure of GWs. Additionally, there is
growing interest in theories of gravity beyond GR. One such theory which
remains viable within the context of recent measurements of the speed of
propagation of GWs is the teleparallel analogue of Horndeski gravity. In this
work, we explore the polarization structure of this newly proposed formulation
of Horndeski theory. In curvature-based gravity, Horndeski theory is almost
synonymous with extensions to GR since it spans a large portion of these
possible extensions. We perform this calculation by taking perturbations about
a Minkowski background and consider which mode propagates. The result is that
the polarization structure depends on the choice of model parameters in the
teleparallel Horndeski Lagrangian with a maximum of seven propagating degrees
of freedom. While the curvature-based Horndeski results follows as a particular
limit within this setup, we find a much richer structure of both massive and
massless cases which produce scalar--vector--tensor propagating degrees of
freedom. We also find that the GW polarization that emerges from the
teleparallel analogue of Horndeski gravity results in analogous massive and
massless modes which take on at most four polarizations in the massless sector
and two scalar ones in the massive sector. In none of the cases do we find
vector polarizations.
| [
{
"created": "Thu, 27 May 2021 15:40:56 GMT",
"version": "v1"
}
] | 2021-11-03 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Caruana",
"Maria",
""
],
[
"Dialektopoulos",
"Konstantinos F.",
""
],
[
"Gakis",
"Viktor",
""
],
[
"Hohmann",
"Manuel",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Sultana",
"Joseph",
""
]
] | Gravitational waves (GWs) have opened a new window on fundamental physics in a number of important ways. The next generation of GW detectors may reveal more information about the polarization structure of GWs. Additionally, there is growing interest in theories of gravity beyond GR. One such theory which remains viable within the context of recent measurements of the speed of propagation of GWs is the teleparallel analogue of Horndeski gravity. In this work, we explore the polarization structure of this newly proposed formulation of Horndeski theory. In curvature-based gravity, Horndeski theory is almost synonymous with extensions to GR since it spans a large portion of these possible extensions. We perform this calculation by taking perturbations about a Minkowski background and consider which mode propagates. The result is that the polarization structure depends on the choice of model parameters in the teleparallel Horndeski Lagrangian with a maximum of seven propagating degrees of freedom. While the curvature-based Horndeski results follows as a particular limit within this setup, we find a much richer structure of both massive and massless cases which produce scalar--vector--tensor propagating degrees of freedom. We also find that the GW polarization that emerges from the teleparallel analogue of Horndeski gravity results in analogous massive and massless modes which take on at most four polarizations in the massless sector and two scalar ones in the massive sector. In none of the cases do we find vector polarizations. |
gr-qc/0508113 | Yuxiao Liu | Yu-Xiao Liu, Yi-Shi Duan, Li-Jie Zhang | Angular Momentum Conservation Law for Randall-Sundrum Models | 10 pages, no figures, accepted by Mod. Phys. Lett. A | Mod.Phys.Lett.A22:2855-2864,2007 | 10.1142/S0217732307023365 | null | gr-qc | null | In Randall-Sundrum models, by the use of general Noether theorem, the
covariant angular momentum conservation law is obtained with the respect to the
local Lorentz transformations. The angular momentum current has also
superpotential and is therefore identically conserved. The space-like
components $J_{ij}$ of the angular momentum for Randall-Sundrum models are
zero. But the component $J_{04}$ is infinite.
| [
{
"created": "Sat, 27 Aug 2005 14:55:33 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2005 04:24:55 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Sep 2005 09:43:05 GMT",
"version": "v3"
},
{
"created": "Mon, 1 Jan 2007 10:32:18 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Liu",
"Yu-Xiao",
""
],
[
"Duan",
"Yi-Shi",
""
],
[
"Zhang",
"Li-Jie",
""
]
] | In Randall-Sundrum models, by the use of general Noether theorem, the covariant angular momentum conservation law is obtained with the respect to the local Lorentz transformations. The angular momentum current has also superpotential and is therefore identically conserved. The space-like components $J_{ij}$ of the angular momentum for Randall-Sundrum models are zero. But the component $J_{04}$ is infinite. |
2401.06844 | David Trestini | David Trestini | Quasi-Keplerian parametrization for eccentric compact binaries in
scalar-tensor theories at second post-Newtonian order and applications | 22 pages, 1 table, 3 figures. v2: some references were added. v3:
title changed, and other minor changes reflecting the referee report. v4:
minor modifications, matches the version published in PRD | Phys. Rev. D 109, 104003 (2024) | 10.1103/PhysRevD.109.104003 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The generalized post-Keplerian parametrization for compact binaries on
eccentric bound orbits is established at second post-Newtonian (2PN) order in a
class of massless scalar-tensor theories. This result is used to compute the
orbit-averaged flux of energy and angular momentum at Newtonian order, which
means relative 1PN order beyond the leading-order dipolar radiation of
scalar-tensor theories. The secular evolution of the orbital elements is then
computed at 1PN order. At leading order, the closed form "Peters and Mathews"
relation between the semi-major axis $a$ and the eccentricity $e$ is found to
be independent of any scalar-tensor parameter, and is given by $a \propto
e^{4/3}/(1-e^2)$. Finally, the waveform is obtained at Newtonian order in the
form of a spherical harmonic mode decomposition, extending to eccentric orbits
the results obtained in arXiv:2201.10924.
| [
{
"created": "Fri, 12 Jan 2024 19:00:01 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jan 2024 11:53:16 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Mar 2024 16:49:19 GMT",
"version": "v3"
},
{
"created": "Thu, 2 May 2024 14:31:26 GMT",
"version": "v4"
}
] | 2024-05-03 | [
[
"Trestini",
"David",
""
]
] | The generalized post-Keplerian parametrization for compact binaries on eccentric bound orbits is established at second post-Newtonian (2PN) order in a class of massless scalar-tensor theories. This result is used to compute the orbit-averaged flux of energy and angular momentum at Newtonian order, which means relative 1PN order beyond the leading-order dipolar radiation of scalar-tensor theories. The secular evolution of the orbital elements is then computed at 1PN order. At leading order, the closed form "Peters and Mathews" relation between the semi-major axis $a$ and the eccentricity $e$ is found to be independent of any scalar-tensor parameter, and is given by $a \propto e^{4/3}/(1-e^2)$. Finally, the waveform is obtained at Newtonian order in the form of a spherical harmonic mode decomposition, extending to eccentric orbits the results obtained in arXiv:2201.10924. |
gr-qc/9805035 | W. Robert Wood | A. Feoli, W.R. Wood, G. Papini | A dynamical symmetry breaking model in Weyl space | 18 pages, RevTex, to be published in J. Math. Phys | J.Math.Phys.39:3322-3331,1998 | 10.1063/1.532256 | REGINA - 98 - 1 | gr-qc | null | The dynamical process following the breaking of Weyl geometry to Riemannian
geometry is considered by studying the motion of de Sitter bubbles in a Weyl
vacuum. The bubbles are given in terms of an exact, spherically symmetric thin
shell solution to the Einstein equations in a Weyl-Dirac theory with a
time-dependent scalar field of the form beta = f(t)/r. The dynamical solutions
obtained lead to a number of possible applications. An important feature of the
thin shell model is the manner in which beta provides a connection between the
interior and exterior geometries since information about the exterior geometry
is contained in the boundary conditions for beta.
| [
{
"created": "Mon, 11 May 1998 15:52:48 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Feoli",
"A.",
""
],
[
"Wood",
"W. R.",
""
],
[
"Papini",
"G.",
""
]
] | The dynamical process following the breaking of Weyl geometry to Riemannian geometry is considered by studying the motion of de Sitter bubbles in a Weyl vacuum. The bubbles are given in terms of an exact, spherically symmetric thin shell solution to the Einstein equations in a Weyl-Dirac theory with a time-dependent scalar field of the form beta = f(t)/r. The dynamical solutions obtained lead to a number of possible applications. An important feature of the thin shell model is the manner in which beta provides a connection between the interior and exterior geometries since information about the exterior geometry is contained in the boundary conditions for beta. |
2306.11088 | Andrea Antonelli | Andrea Antonelli, Konstantinos Kritos, Ken K. Y. Ng, Roberto Cotesta,
Emanuele Berti | Classifying the generation and formation channels of individual
LIGO-Virgo-KAGRA observations from dynamically formed binaries | 9 pages, 2 figures. Public code at:
https://github.com/aantonelli94/TheBHClassifier | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address two important questions in gravitational-wave astronomy. What is
the astrophysical formation scenario leading to black-hole binary mergers? Did
some of the merging black holes form hierarchically through previous
generations of mergers? Leveraging fast-to-generate astrophysical simulations
from the rapster code and a random forest algorithm, we develop a pipeline to
accurately classify the most likely generation and formation scenario of
dynamically formed BHs on an event-by-event basis. We test our framework on
four merger events with features suggesting a dynamical origin: the large total
mass event GW190521, GW190412 (with large mass asymmetry), and two events with
effective spins antialigned with the orbital angular momentum (GW191109 and
GW200225). Within the models we consider, and assuming these events to be
formed dynamically, we find that one of the component black holes in GW190521
formed from a previous merger with high probability ($\gtrsim 85\%$). GW190521,
GW191109 and GW200225 are compatible with formation through three-body
interactions, while the most likely formation channel for GW190412 are two-body
captures. We also rule out that GW191109 contains only first-generation black
holes with a probability of 97$\%$. Our pipeline could be useful to identify
the evolutionary path of individual GW observations once it is trained on more
comprehensive sets of binary formation simulations.
| [
{
"created": "Mon, 19 Jun 2023 18:00:00 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Antonelli",
"Andrea",
""
],
[
"Kritos",
"Konstantinos",
""
],
[
"Ng",
"Ken K. Y.",
""
],
[
"Cotesta",
"Roberto",
""
],
[
"Berti",
"Emanuele",
""
]
] | We address two important questions in gravitational-wave astronomy. What is the astrophysical formation scenario leading to black-hole binary mergers? Did some of the merging black holes form hierarchically through previous generations of mergers? Leveraging fast-to-generate astrophysical simulations from the rapster code and a random forest algorithm, we develop a pipeline to accurately classify the most likely generation and formation scenario of dynamically formed BHs on an event-by-event basis. We test our framework on four merger events with features suggesting a dynamical origin: the large total mass event GW190521, GW190412 (with large mass asymmetry), and two events with effective spins antialigned with the orbital angular momentum (GW191109 and GW200225). Within the models we consider, and assuming these events to be formed dynamically, we find that one of the component black holes in GW190521 formed from a previous merger with high probability ($\gtrsim 85\%$). GW190521, GW191109 and GW200225 are compatible with formation through three-body interactions, while the most likely formation channel for GW190412 are two-body captures. We also rule out that GW191109 contains only first-generation black holes with a probability of 97$\%$. Our pipeline could be useful to identify the evolutionary path of individual GW observations once it is trained on more comprehensive sets of binary formation simulations. |
2209.03414 | Bivudutta Mishra Dr. | L.K. Duchaniya, S.A. Kadam, Jackson Levi Said, B. Mishra | Dynamical systems analysis in $f(T,\phi)$ gravity | 15 pages, 4 figures | Eur. Phys. J. C, 83, 27 (2023) | 10.1140/epjc/s10052-022-11155-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Teleparallel based cosmological models provide a description of gravity in
which torsion is the mediator of gravitation. Several extensions have been made
within the so-called Teleparallel equivalent of general relativity which is
equivalent to general relativity at the level of the equations of motion where
attempts are made to study the extensions of this form of gravity and to
describe more general functions of the torsion scalar $T$. One of these
extensions is $f(T,\phi)$ gravity; $T$ and $\phi$ respectively denote the
torsion scalar and scalar field. In this work, the dynamical system analysis
has been performed for this class of theories to obtain the cosmological
behaviour of a number of models. Two models are presented here with some
functional form of the torsion scalar and the critical points are obtained. For
each critical point, the stability behaviour and the corresponding cosmology
are shown. Through the graphical representation the equation of state parameter
and the density parameters for matter-dominated, radiation-dominated and dark
energy phase are also presented for both the models.
| [
{
"created": "Sat, 3 Sep 2022 04:47:42 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jan 2023 14:58:45 GMT",
"version": "v2"
}
] | 2023-01-18 | [
[
"Duchaniya",
"L. K.",
""
],
[
"Kadam",
"S. A.",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Mishra",
"B.",
""
]
] | Teleparallel based cosmological models provide a description of gravity in which torsion is the mediator of gravitation. Several extensions have been made within the so-called Teleparallel equivalent of general relativity which is equivalent to general relativity at the level of the equations of motion where attempts are made to study the extensions of this form of gravity and to describe more general functions of the torsion scalar $T$. One of these extensions is $f(T,\phi)$ gravity; $T$ and $\phi$ respectively denote the torsion scalar and scalar field. In this work, the dynamical system analysis has been performed for this class of theories to obtain the cosmological behaviour of a number of models. Two models are presented here with some functional form of the torsion scalar and the critical points are obtained. For each critical point, the stability behaviour and the corresponding cosmology are shown. Through the graphical representation the equation of state parameter and the density parameters for matter-dominated, radiation-dominated and dark energy phase are also presented for both the models. |
2201.03752 | Anna Ijjas | Anna Ijjas | Numerical Relativity as a New Tool for Fundamental Cosmology | 16 pages, 3 figures | Physics 4 (2022) 301-314 | 10.3390/physics4010021 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Advances in our understanding of the origin, evolution and structure of the
universe have long been driven by cosmological perturbation theory, model
building and effective field theory. In this review, we introduce numerical
relativity as a powerful new complementary tool for fundamental cosmology. To
illustrate its power, we discuss applications of numerical relativity to
studying the robustness of slow contraction and inflation in homogenizing,
isotropizing and flattening the universe beginning from generic unsmooth
initial conditions. In particular, we describe how recent numerical relativity
studies of slow contraction have revealed a novel, non-linear smoothing
mechanism based on ultralocality that challenges the conventional view on what
is required to explain the large-scale homogeneity and isotropy of the
observable universe.
| [
{
"created": "Tue, 11 Jan 2022 02:46:10 GMT",
"version": "v1"
}
] | 2022-03-08 | [
[
"Ijjas",
"Anna",
""
]
] | Advances in our understanding of the origin, evolution and structure of the universe have long been driven by cosmological perturbation theory, model building and effective field theory. In this review, we introduce numerical relativity as a powerful new complementary tool for fundamental cosmology. To illustrate its power, we discuss applications of numerical relativity to studying the robustness of slow contraction and inflation in homogenizing, isotropizing and flattening the universe beginning from generic unsmooth initial conditions. In particular, we describe how recent numerical relativity studies of slow contraction have revealed a novel, non-linear smoothing mechanism based on ultralocality that challenges the conventional view on what is required to explain the large-scale homogeneity and isotropy of the observable universe. |
gr-qc/9706034 | Adrian Gentle | Adrian P. Gentle and Warner A. Miller | A fully (3+1)-D Regge calculus model of the Kasner cosmology | 22 pages, 5 eps figures, LaTeX. Updated and expanded version | Class.Quant.Grav. 15 (1998) 389-405 | 10.1088/0264-9381/15/2/013 | Monash Mathematics Report 97/24 | gr-qc | null | We describe the first discrete-time 4-dimensional numerical application of
Regge calculus. The spacetime is represented as a complex of 4-dimensional
simplices, and the geometry interior to each 4-simplex is flat Minkowski
spacetime. This simplicial spacetime is constructed so as to be foliated with a
one parameter family of spacelike hypersurfaces built of tetrahedra. We
implement a novel two-surface initial-data prescription for Regge calculus, and
provide the first fully 4-dimensional application of an implicit decoupled
evolution scheme (the ``Sorkin evolution scheme''). We benchmark this code on
the Kasner cosmology --- a cosmology which embodies generic features of the
collapse of many cosmological models. We (1) reproduce the continuum solution
with a fractional error in the 3-volume of 10^{-5} after 10000 evolution steps,
(2) demonstrate stable evolution, (3) preserve the standard deviation of
spatial homogeneity to less than 10^{-10} and (4) explicitly display the
existence of diffeomorphism freedom in Regge calculus. We also present the
second-order convergence properties of the solution to the continuum.
| [
{
"created": "Fri, 13 Jun 1997 01:48:01 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jan 1998 03:13:06 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Gentle",
"Adrian P.",
""
],
[
"Miller",
"Warner A.",
""
]
] | We describe the first discrete-time 4-dimensional numerical application of Regge calculus. The spacetime is represented as a complex of 4-dimensional simplices, and the geometry interior to each 4-simplex is flat Minkowski spacetime. This simplicial spacetime is constructed so as to be foliated with a one parameter family of spacelike hypersurfaces built of tetrahedra. We implement a novel two-surface initial-data prescription for Regge calculus, and provide the first fully 4-dimensional application of an implicit decoupled evolution scheme (the ``Sorkin evolution scheme''). We benchmark this code on the Kasner cosmology --- a cosmology which embodies generic features of the collapse of many cosmological models. We (1) reproduce the continuum solution with a fractional error in the 3-volume of 10^{-5} after 10000 evolution steps, (2) demonstrate stable evolution, (3) preserve the standard deviation of spatial homogeneity to less than 10^{-10} and (4) explicitly display the existence of diffeomorphism freedom in Regge calculus. We also present the second-order convergence properties of the solution to the continuum. |
2110.05396 | Iarley P. Lobo Dr | Iarley P. Lobo, Luis C. N. Santos, V. B. Bezerra, J. P. Morais
Gra\c{c}a and H. Moradpour | The extended phase space thermodynamics of Planck-scale-corrected
Reissner-Nordstr\"om-anti-de Sitter black hole | 13 pages, 7 figures. Matches published version | Nuclear Physics B 972 (2021) 115568 | 10.1016/j.nuclphysb.2021.115568 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We analyze the effect of Planck-scale modified radiation equation of state on
the Reissner-Nodstr\"om-anti-de Sitter black hole inspired by Kiselev's ansatz.
Deformed thermodynamic quantities are found, phase transitions and black holes
as heat engines are described for the Carnot and square cycles. Non-trivial
differences between linear and quadratic Planck-scale corrections are discussed
in detail.
| [
{
"created": "Mon, 11 Oct 2021 16:34:48 GMT",
"version": "v1"
}
] | 2021-10-12 | [
[
"Lobo",
"Iarley P.",
""
],
[
"Santos",
"Luis C. N.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Graça",
"J. P. Morais",
""
],
[
"Moradpour",
"H.",
""
]
] | We analyze the effect of Planck-scale modified radiation equation of state on the Reissner-Nodstr\"om-anti-de Sitter black hole inspired by Kiselev's ansatz. Deformed thermodynamic quantities are found, phase transitions and black holes as heat engines are described for the Carnot and square cycles. Non-trivial differences between linear and quadratic Planck-scale corrections are discussed in detail. |
1704.08163 | Giorgio Papini | Giorgio Papini | Classical and Quantum Aspects of Particle Propagation in External
Gravitational Fields | 8 pages | null | 10.1142/S0218271817501371 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the study of covariant wave equations, linear gravity manifests itself
through the metric deviation $\gamma_{\mu\nu}$ and a two-point vector potential
$K_{\lambda}$ itself constructed from $\gamma_{\mu\nu}$ and its derivatives.
The simultaneous presence of the two gravitational potentials is non
contradictory. Particles also assume the character of quasiparticles and
$K_{\lambda}$ carries information about the matter with which it interacts. We
consider the influence of $K_{\lambda}$ on the dispersion relations of the
particles involved, the particles' motion, quantum tunneling through a horizon,
radiation, energy-momentum dissipation and flux quantization. % No {\it REVTEX}
limit to number of lines.
| [
{
"created": "Wed, 26 Apr 2017 15:31:52 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Papini",
"Giorgio",
""
]
] | In the study of covariant wave equations, linear gravity manifests itself through the metric deviation $\gamma_{\mu\nu}$ and a two-point vector potential $K_{\lambda}$ itself constructed from $\gamma_{\mu\nu}$ and its derivatives. The simultaneous presence of the two gravitational potentials is non contradictory. Particles also assume the character of quasiparticles and $K_{\lambda}$ carries information about the matter with which it interacts. We consider the influence of $K_{\lambda}$ on the dispersion relations of the particles involved, the particles' motion, quantum tunneling through a horizon, radiation, energy-momentum dissipation and flux quantization. % No {\it REVTEX} limit to number of lines. |
2206.07500 | Mohammad Nouri-Zonoz | M. Nouri-Zonoz, A. Parvizi and H. Forghani | Metamaterial analog of a black hole shadow: An exact ray-tracing
simulation based on the spacetime index of refraction | 14 pages, 7 figures, typos corrected and the resolution of last
figure is enhanced | null | 10.1103/PhysRevD.106.124013 | null | gr-qc physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter first we show that the equation of null geodesics in
spherically symmetric spacetimes in isotropic coordinates is identical to the
equation of light ray trajectories in isotropic media in flat spacetime. Based
on this analogy we introduce an exact simulation of the light ray trajectories
both in these spacetimes and in their metamaterial analogs in terms of the
spacetime index of refraction. As unstable light trajectories, the photon
spheres form in these metamaterial analogs at {\it exactly} the same radial
distances as expected from the corresponding black hole geometries. Using the
same ray-tracing simulation we find the analog of a simple black hole shadow
formed by the metamaterial analog of a Schwarzschild black hole, eclipsing a
line of light sources near its analog horizon.
| [
{
"created": "Wed, 15 Jun 2022 12:51:11 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2022 21:20:51 GMT",
"version": "v2"
}
] | 2022-12-21 | [
[
"Nouri-Zonoz",
"M.",
""
],
[
"Parvizi",
"A.",
""
],
[
"Forghani",
"H.",
""
]
] | In this letter first we show that the equation of null geodesics in spherically symmetric spacetimes in isotropic coordinates is identical to the equation of light ray trajectories in isotropic media in flat spacetime. Based on this analogy we introduce an exact simulation of the light ray trajectories both in these spacetimes and in their metamaterial analogs in terms of the spacetime index of refraction. As unstable light trajectories, the photon spheres form in these metamaterial analogs at {\it exactly} the same radial distances as expected from the corresponding black hole geometries. Using the same ray-tracing simulation we find the analog of a simple black hole shadow formed by the metamaterial analog of a Schwarzschild black hole, eclipsing a line of light sources near its analog horizon. |
2008.12251 | Pisin Chen | Kuan-Nan Lin, Chih-En Chou, Pisin Chen | Particle Production by a Relativistic Semi-Transparent Mirror in 1+3D
Minkowski Spacetime | 9 pages, 3 figures | Phys. Rev. D 103, 025014 (2021) | 10.1103/PhysRevD.103.025014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Production of scalar particles by a relativistic, semi-transparent mirror in
1+3D Minkowski spacetime based on the Barton-Calogeracos (BC) action is
investigated. The corresponding Bogoliubov coefficients are derived for a
mirror with arbitrary trajectory. In particular, we apply our derived formula
to the gravitational collapse trajectory. In addition, we identify the relation
between the particle spectrum and the particle production probability, and we
demonstrate the equivalence between our approach and the existing approach in
the literature, which is restricted to 1+1D. In short, our treatment extends
the study to 1+3D spacetime. Lastly, we offer a third approach for finding the
particle spectrum using the S-matrix formalism.
| [
{
"created": "Thu, 27 Aug 2020 16:47:24 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Aug 2020 07:41:36 GMT",
"version": "v2"
}
] | 2021-01-20 | [
[
"Lin",
"Kuan-Nan",
""
],
[
"Chou",
"Chih-En",
""
],
[
"Chen",
"Pisin",
""
]
] | Production of scalar particles by a relativistic, semi-transparent mirror in 1+3D Minkowski spacetime based on the Barton-Calogeracos (BC) action is investigated. The corresponding Bogoliubov coefficients are derived for a mirror with arbitrary trajectory. In particular, we apply our derived formula to the gravitational collapse trajectory. In addition, we identify the relation between the particle spectrum and the particle production probability, and we demonstrate the equivalence between our approach and the existing approach in the literature, which is restricted to 1+1D. In short, our treatment extends the study to 1+3D spacetime. Lastly, we offer a third approach for finding the particle spectrum using the S-matrix formalism. |
1902.03590 | John W. Barrett | John W. Barrett, Paul Druce and Lisa Glaser | Spectral estimators for finite non-commutative geometries | 27 pages, final version with typos and references corrected | null | 10.1088/1751-8121/ab22f8 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A finite non-commutative geometry consists of a fuzzy space together with a
Dirac operator satisfying the axioms of a real spectral triple. This paper
addreses the question of how to extract information about these geometries from
the spectrum of the Dirac operator. Since the Dirac operator is a
finite-dimensional matrix, the usual asymptotics of the eigenvalues makes no
sense and is replaced by measurements of the spectrum at a finite energy scale.
The spectral dimension of the square of the Dirac operator is improved to
provide a new spectral measure of the dimension of a space called the spectral
variance. Similarly, the volume of a space can be computed from the spectrum
once the dimension is known. Two methods of doing this are investigated: the
well-known Dixmier trace and a recent improvement due to Abel Stern. Finally,
the distance between two geometries is investigated by comparing the spectral
zeta functions using the method of Cornelissen and Kontogeorgis. All of these
techniques are tested on the explicit examples of the fuzzy spheres and fuzzy
tori, which can be regarded as approximations of the usual Riemannian sphere
and flat tori. Then they are applied to characterise some random fuzzy spaces
using data generated by a Monte Carlo simulation.
| [
{
"created": "Sun, 10 Feb 2019 12:59:46 GMT",
"version": "v1"
},
{
"created": "Mon, 20 May 2019 17:24:28 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jun 2019 13:54:24 GMT",
"version": "v3"
}
] | 2019-09-04 | [
[
"Barrett",
"John W.",
""
],
[
"Druce",
"Paul",
""
],
[
"Glaser",
"Lisa",
""
]
] | A finite non-commutative geometry consists of a fuzzy space together with a Dirac operator satisfying the axioms of a real spectral triple. This paper addreses the question of how to extract information about these geometries from the spectrum of the Dirac operator. Since the Dirac operator is a finite-dimensional matrix, the usual asymptotics of the eigenvalues makes no sense and is replaced by measurements of the spectrum at a finite energy scale. The spectral dimension of the square of the Dirac operator is improved to provide a new spectral measure of the dimension of a space called the spectral variance. Similarly, the volume of a space can be computed from the spectrum once the dimension is known. Two methods of doing this are investigated: the well-known Dixmier trace and a recent improvement due to Abel Stern. Finally, the distance between two geometries is investigated by comparing the spectral zeta functions using the method of Cornelissen and Kontogeorgis. All of these techniques are tested on the explicit examples of the fuzzy spheres and fuzzy tori, which can be regarded as approximations of the usual Riemannian sphere and flat tori. Then they are applied to characterise some random fuzzy spaces using data generated by a Monte Carlo simulation. |
0905.4530 | Silke Weinfurtner | Silke Weinfurtner (University of British Columbia), Angela White
(Newcastle University), and Matt Visser (Victoria University of Wellington) | Signature-change events in emergent spacetimes with anisotropic scaling | Based on a presentation by Silke Weinfurtner at the NEB XIII
conference in Thessaloniki in June 2008; 9 pages | J.Phys.Conf.Ser.189:012046,2009 | 10.1088/1742-6596/189/1/012046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the behaviour of quantum fields coupled to a spacetime
geometry exhibiting finite regions of Euclidean (Riemannian) signature.
Although from a gravity perspective this situation might seem somewhat far
fetched, we will demonstrate its direct physical relevance for an explicitly
realizable condensed matter system whose linearized perturbations experience an
effective emergent spacetime geometry with externally controllable signature.
This effective geometry is intrinsically quantum in origin, and its signature
is determined by the details of the microscopic structure. At the level of the
effective field theory arising from our condensed matter system we encounter
explicit anisotropic scaling in time and space. Here Lorentz symmetry is an
emergent symmetry in the infrared. This anisotropic scaling of time and space
cures some of the technical problems that arise when working within a canonical
quantisation scheme obeying strict Lorentz invariance at all scales, and so is
helpful in permitting signature change events to take place.
| [
{
"created": "Thu, 28 May 2009 00:17:45 GMT",
"version": "v1"
}
] | 2009-11-05 | [
[
"Weinfurtner",
"Silke",
"",
"University of British Columbia"
],
[
"White",
"Angela",
"",
"Newcastle University"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | We investigate the behaviour of quantum fields coupled to a spacetime geometry exhibiting finite regions of Euclidean (Riemannian) signature. Although from a gravity perspective this situation might seem somewhat far fetched, we will demonstrate its direct physical relevance for an explicitly realizable condensed matter system whose linearized perturbations experience an effective emergent spacetime geometry with externally controllable signature. This effective geometry is intrinsically quantum in origin, and its signature is determined by the details of the microscopic structure. At the level of the effective field theory arising from our condensed matter system we encounter explicit anisotropic scaling in time and space. Here Lorentz symmetry is an emergent symmetry in the infrared. This anisotropic scaling of time and space cures some of the technical problems that arise when working within a canonical quantisation scheme obeying strict Lorentz invariance at all scales, and so is helpful in permitting signature change events to take place. |
1604.02143 | Rajeev Kumar Jain | Debika Chowdhury, L. Sriramkumar and Rajeev Kumar Jain | Duality and scale invariant magnetic fields from bouncing universes | v1: 17 pages, 5 figures; v2: 14 pages, 5 figures, bouncing model
details and discussion extended, references added, to appear in Phys. Rev. D | Phys. Rev. D 94, 083512 (2016) | 10.1103/PhysRevD.94.083512 | CP3-Origins-2016-018 DNRF90 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, we had numerically shown that, for a non-minimal coupling that is a
simple power of the scale factor, scale invariant magnetic fields arise in a
class of bouncing universes. In this work, we {\it analytically} evaluate the
spectrum of magnetic and electric fields generated in a sub-class of such
models. We illustrate that, for cosmological scales which have wavenumbers much
smaller than the wavenumber associated with the bounce, the shape of the
spectrum is preserved across the bounce. Using the analytic solutions obtained,
we also illustrate that the problem of backreaction is severe at the bounce.
Finally, we show that the power spectrum of the magnetic field remains
invariant under a two parameter family of transformations of the non-minimal
coupling function.
| [
{
"created": "Thu, 7 Apr 2016 13:13:22 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2016 23:39:37 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Chowdhury",
"Debika",
""
],
[
"Sriramkumar",
"L.",
""
],
[
"Jain",
"Rajeev Kumar",
""
]
] | Recently, we had numerically shown that, for a non-minimal coupling that is a simple power of the scale factor, scale invariant magnetic fields arise in a class of bouncing universes. In this work, we {\it analytically} evaluate the spectrum of magnetic and electric fields generated in a sub-class of such models. We illustrate that, for cosmological scales which have wavenumbers much smaller than the wavenumber associated with the bounce, the shape of the spectrum is preserved across the bounce. Using the analytic solutions obtained, we also illustrate that the problem of backreaction is severe at the bounce. Finally, we show that the power spectrum of the magnetic field remains invariant under a two parameter family of transformations of the non-minimal coupling function. |
2108.13484 | Roldao da Rocha | Roldao da Rocha | AdS graviton stars and differential configurational entropy | 6 pages, 1 figure | Phys. Lett. B 823 (2021) 136729 | 10.1016/j.physletb.2021.136729 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | AdS graviton stars are studied in the differential configurational entropy
setup, as solutions of the effective Einstein field equations that backreact to
compactification. With the critical central density of AdS graviton stars, the
differential configurational entropy is derived and computed, presenting global
minima for a wide range of stellar mass magnitude orders. It indicates insular
domains of configurational stability for AdS graviton stars near astrophysical
neutron star densities. Other relevant features are also reported.
| [
{
"created": "Mon, 30 Aug 2021 19:13:56 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2021 17:02:48 GMT",
"version": "v2"
}
] | 2021-10-20 | [
[
"da Rocha",
"Roldao",
""
]
] | AdS graviton stars are studied in the differential configurational entropy setup, as solutions of the effective Einstein field equations that backreact to compactification. With the critical central density of AdS graviton stars, the differential configurational entropy is derived and computed, presenting global minima for a wide range of stellar mass magnitude orders. It indicates insular domains of configurational stability for AdS graviton stars near astrophysical neutron star densities. Other relevant features are also reported. |
0705.0720 | Paul Halpern | Paul Halpern | Energy Distribution of a Charged Black Hole with a Minimally Coupled
Scalar Field | 11 pages; To appear in Astrophysics and Space Science | Astrophys.SpaceSci.313:357-361,2008 | 10.1007/s10509-007-9704-4 | null | gr-qc astro-ph | null | Using three different energy-momentum complexes, the Einstein,
Landau-Lifshitz, and Papapetrou prescriptions, we calculate the energy of an
electrically charged black hole exact solution with a self-interacting,
minimally-coupled scalar field and the asymptotic region locally an
Anti-deSitter spacetime. Writing the metric in Kerr-Schild Cartesian
coordinates, we demonstrate that this metric belongs to the Kerr-Schild class
of solutions. Applying each of the three energy-momentum prescriptions and
comparing the results, we find consistency among these complexes, suggesting
their utility as localized measures of energy.
| [
{
"created": "Sat, 5 May 2007 01:25:14 GMT",
"version": "v1"
},
{
"created": "Wed, 30 May 2007 15:28:27 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Nov 2007 02:08:17 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Halpern",
"Paul",
""
]
] | Using three different energy-momentum complexes, the Einstein, Landau-Lifshitz, and Papapetrou prescriptions, we calculate the energy of an electrically charged black hole exact solution with a self-interacting, minimally-coupled scalar field and the asymptotic region locally an Anti-deSitter spacetime. Writing the metric in Kerr-Schild Cartesian coordinates, we demonstrate that this metric belongs to the Kerr-Schild class of solutions. Applying each of the three energy-momentum prescriptions and comparing the results, we find consistency among these complexes, suggesting their utility as localized measures of energy. |
1111.4595 | Nikodem Poplawski | Nikodem Poplawski | Nonsingular, big-bounce cosmology from spinor-torsion coupling | 7 pages; published version | Phys. Rev. D 85, 107502 (2012) | 10.1103/PhysRevD.85.107502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of
general relativity that the affine connection be symmetric by regarding its
antisymmetric part, the torsion tensor, as a dynamical variable. The minimal
coupling between the torsion tensor and Dirac spinors generates a spin-spin
interaction which is significant in fermionic matter at extremely high
densities. We show that such an interaction averts the unphysical big-bang
singularity, replacing it with a cusp-like bounce at a finite minimum scale
factor, before which the Universe was contracting. This scenario also explains
why the present Universe at largest scales appears spatially flat, homogeneous
and isotropic.
| [
{
"created": "Sun, 20 Nov 2011 00:01:39 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jul 2012 23:19:54 GMT",
"version": "v2"
}
] | 2012-07-06 | [
[
"Poplawski",
"Nikodem",
""
]
] | The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic. |
2109.00564 | Che-Yu Chen | Che-Yu Chen, Hsiang-Yi Karen Yang | Curved accretion disks around rotating black holes without reflection
symmetry | 23 pages, 5 figures, version to appear in EPJC | Eur. Phys. J. C (2022) 82:307 | 10.1140/epjc/s10052-022-10263-7 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rotating black holes without equatorial reflection symmetry can naturally
arise in effective low-energy theories of fundamental quantum gravity, in
particular, when parity-violating interactions are introduced. Adopting a
theory-agnostic approach and considering a recently proposed Kerr-like black
hole model, we investigate the structure and properties of accretion disk
around a rotating black hole without reflection symmetry. In the absence of
reflection symmetry, the accretion disk is in general a curved surface in
shape, rather than a flat disk lying on the equatorial plane. Furthermore, the
parameter $\epsilon$ that controls the reflection asymmetry would shrink the
size of the prograde innermost stable circular orbits, and enhance the
efficiency of the black hole in converting rest-mass energy to radiation during
accretion. The retrograde innermost stable circular orbits are stretched but
the effects are substantially suppressed. In addition, we find that spin
measurements based on the gravitational redshift observations of the disk,
assuming a Kerr geometry, may overestimate the true spin values if the central
object is actually a Kerr-like black hole with conspicuous equatorial
reflection asymmetry. The qualitative results that the accretion disk becomes
curved and the prograde innermost stable circular orbits are shrunk turn out to
be generic in our model when the reflection asymmetry is small.
| [
{
"created": "Wed, 1 Sep 2021 18:26:55 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Oct 2021 01:24:20 GMT",
"version": "v2"
},
{
"created": "Sun, 27 Mar 2022 18:43:59 GMT",
"version": "v3"
}
] | 2022-04-11 | [
[
"Chen",
"Che-Yu",
""
],
[
"Yang",
"Hsiang-Yi Karen",
""
]
] | Rotating black holes without equatorial reflection symmetry can naturally arise in effective low-energy theories of fundamental quantum gravity, in particular, when parity-violating interactions are introduced. Adopting a theory-agnostic approach and considering a recently proposed Kerr-like black hole model, we investigate the structure and properties of accretion disk around a rotating black hole without reflection symmetry. In the absence of reflection symmetry, the accretion disk is in general a curved surface in shape, rather than a flat disk lying on the equatorial plane. Furthermore, the parameter $\epsilon$ that controls the reflection asymmetry would shrink the size of the prograde innermost stable circular orbits, and enhance the efficiency of the black hole in converting rest-mass energy to radiation during accretion. The retrograde innermost stable circular orbits are stretched but the effects are substantially suppressed. In addition, we find that spin measurements based on the gravitational redshift observations of the disk, assuming a Kerr geometry, may overestimate the true spin values if the central object is actually a Kerr-like black hole with conspicuous equatorial reflection asymmetry. The qualitative results that the accretion disk becomes curved and the prograde innermost stable circular orbits are shrunk turn out to be generic in our model when the reflection asymmetry is small. |
1805.00240 | Bobir Toshmatov | Bobir Toshmatov, Zden\v{e}k Stuchl\'ik, Jan Schee, Bobomurat Ahmedov | Electromagnetic perturbations of black holes in general relativity
coupled to nonlinear electrodynamics | 11 pages, 9 figures | Phys. Rev. D 97, 084058 (2018) | 10.1103/PhysRevD.97.084058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The electromagnetic (EM) perturbations of the black hole solutions in general
relativity coupled to nonlinear electrodynamics (NED) are studied for both
electrically and magnetically charged black holes, assuming that the EM
perturbations do not alter the spacetime geometry. It is shown that the
effective potentials of the electrically and magnetically charged black holes
related to test perturbative NED EM fields are related to the effective metric
governing the photon motion, contrary to the effective potential of the linear
electrodynamic (Maxwell) field that is related to the spacetime metric.
Consequently, corresponding quasinormal (QN) frequencies differ as well. As a
special case, we study new family of the NED black hole solutions which tend in
the weak field limit to the Maxwell field, giving the Reissner-Nordstr\"{o}m
(RN) black hole solution. We compare the NED Maxwellian black hole QN spectra
with the RN black hole QN spectra.
| [
{
"created": "Tue, 1 May 2018 08:56:40 GMT",
"version": "v1"
}
] | 2018-05-02 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Stuchlík",
"Zdeněk",
""
],
[
"Schee",
"Jan",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | The electromagnetic (EM) perturbations of the black hole solutions in general relativity coupled to nonlinear electrodynamics (NED) are studied for both electrically and magnetically charged black holes, assuming that the EM perturbations do not alter the spacetime geometry. It is shown that the effective potentials of the electrically and magnetically charged black holes related to test perturbative NED EM fields are related to the effective metric governing the photon motion, contrary to the effective potential of the linear electrodynamic (Maxwell) field that is related to the spacetime metric. Consequently, corresponding quasinormal (QN) frequencies differ as well. As a special case, we study new family of the NED black hole solutions which tend in the weak field limit to the Maxwell field, giving the Reissner-Nordstr\"{o}m (RN) black hole solution. We compare the NED Maxwellian black hole QN spectra with the RN black hole QN spectra. |
2002.00980 | Basem Mahmoud El-Menoufi | Basem Kamal El-Menoufi and Sonali Mohapatra | What can Black Holes teach us about the IR and UV? | 6 pages. To appear in Physical Review D | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Combining insights from both the effective field theory of quantum gravity
and black hole thermodynamics, we derive two novel consistency relations to be
satisfied by any quantum theory of gravity. First, we show that a particular
combination of the number of massless (light) fields in the theory must take
integer values. Second, we show that, once the massless spectrum is fixed, the
Wilson coefficient of the Kretschmann scalar in the low-energy effective theory
is fully determined by the logarithm of a single natural number.
| [
{
"created": "Mon, 3 Feb 2020 19:01:09 GMT",
"version": "v1"
}
] | 2020-02-05 | [
[
"El-Menoufi",
"Basem Kamal",
""
],
[
"Mohapatra",
"Sonali",
""
]
] | Combining insights from both the effective field theory of quantum gravity and black hole thermodynamics, we derive two novel consistency relations to be satisfied by any quantum theory of gravity. First, we show that a particular combination of the number of massless (light) fields in the theory must take integer values. Second, we show that, once the massless spectrum is fixed, the Wilson coefficient of the Kretschmann scalar in the low-energy effective theory is fully determined by the logarithm of a single natural number. |
2405.13737 | Iris van Gemeren | Iris van Gemeren, Tanja Hinderer, Stefan Vandoren | Massive scalar clouds and black hole spacetimes in Gauss-Bonnet gravity | 17 pages + appendix, 12 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static black holes in scalar-Gauss-Bonnet (sGB) gravity with a
massive scalar field as an example of higher curvature gravity. The scalar mass
introduces an additional scale and leads to a strong suppression of the scalar
field beyond its Compton wavelength. We numerically compute sGB black hole
spacetimes and scalar configurations and also compare with perturbative results
for small couplings, where we focus on a dilatonic coupling function. We
analyze the constraints on the parameters from requiring the curvature
singularity to be located inside the black hole horizon $r_h$ and the relation
to the regularity condition for the scalar field. For scalar field masses $m
r_h \gtrsim 10^{-1}$, this leads to a new and currently most stringent bound on
sGB coupling constant $\alpha$ of $\alpha/r_h^2 \sim 10^{-1}$ in the context of
stellar mass black holes. Lastly, we look at several properties of the black
hole configurations relevant for further work on observational consequences,
including the scalar monopole charge, Arnowitt Deser Misner mass, curvature
invariants and the frequencies of the innermost stable circular orbit and light
ring.
| [
{
"created": "Wed, 22 May 2024 15:29:44 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"van Gemeren",
"Iris",
""
],
[
"Hinderer",
"Tanja",
""
],
[
"Vandoren",
"Stefan",
""
]
] | We study static black holes in scalar-Gauss-Bonnet (sGB) gravity with a massive scalar field as an example of higher curvature gravity. The scalar mass introduces an additional scale and leads to a strong suppression of the scalar field beyond its Compton wavelength. We numerically compute sGB black hole spacetimes and scalar configurations and also compare with perturbative results for small couplings, where we focus on a dilatonic coupling function. We analyze the constraints on the parameters from requiring the curvature singularity to be located inside the black hole horizon $r_h$ and the relation to the regularity condition for the scalar field. For scalar field masses $m r_h \gtrsim 10^{-1}$, this leads to a new and currently most stringent bound on sGB coupling constant $\alpha$ of $\alpha/r_h^2 \sim 10^{-1}$ in the context of stellar mass black holes. Lastly, we look at several properties of the black hole configurations relevant for further work on observational consequences, including the scalar monopole charge, Arnowitt Deser Misner mass, curvature invariants and the frequencies of the innermost stable circular orbit and light ring. |
1307.5029 | Norbert Bodendorfer | Norbert Bodendorfer | Black hole entropy from loop quantum gravity in higher dimensions | 6 pages. v3: journal version, minor clarifications | Phys. Lett. B 726: 887-891 (2013) | 10.1016/j.physletb.2013.09.043 | IGC-13/7-4 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a derivation for computing black hole entropy for spherical
non-rotating isolated horizons from loop quantum gravity in four and higher
dimensions. The state counting problem effectively reduces to the well studied
3+1-dimensional one based on an SU(2)-Chern-Simons theory, differing only in
the precise form of the area spectrum.
| [
{
"created": "Thu, 18 Jul 2013 18:14:42 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2013 17:46:41 GMT",
"version": "v2"
},
{
"created": "Fri, 25 Oct 2013 14:11:39 GMT",
"version": "v3"
}
] | 2013-10-28 | [
[
"Bodendorfer",
"Norbert",
""
]
] | We propose a derivation for computing black hole entropy for spherical non-rotating isolated horizons from loop quantum gravity in four and higher dimensions. The state counting problem effectively reduces to the well studied 3+1-dimensional one based on an SU(2)-Chern-Simons theory, differing only in the precise form of the area spectrum. |
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