id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2102.03211 | Ion I. Cotaescu | Ion I. Cotaescu | Kinematics in spatially flat FLRW space-time | 20 pages | null | 10.1088/1674-1137/ac1576 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The kinematics on spatially flat FLRW space-times is presented for the first
time in co-moving local charts with physical coordinates, i. e. the cosmic time
and Painlev\' e-type Cartesian space coordinates. It is shown that there exists
a conserved momentum which determines the form of the covariant four-momentum
on geodesics in terms of physical coordinates. Moreover, with the help of the
conserved momentum one identifies the peculiar momentum separating the peculiar
and recessional motions without ambiguities. It is shown that the energy and
peculiar momentum satisfy the mass-shell condition of special relativity while
the recessional momentum does not produce energy. In this framework, the
measurements of the kinetic quantities along geodesic performed by different
observers are analysed pointing out an energy loss of the massive particles
similar to that giving the photon redshift. The examples of the kinematics on
the de Sitter expanding universe and a new Milne-type space-time are
extensively analysed.
| [
{
"created": "Fri, 5 Feb 2021 14:54:58 GMT",
"version": "v1"
}
] | 2021-10-27 | [
[
"Cotaescu",
"Ion I.",
""
]
] | The kinematics on spatially flat FLRW space-times is presented for the first time in co-moving local charts with physical coordinates, i. e. the cosmic time and Painlev\' e-type Cartesian space coordinates. It is shown that there exists a conserved momentum which determines the form of the covariant four-momentum on geodesics in terms of physical coordinates. Moreover, with the help of the conserved momentum one identifies the peculiar momentum separating the peculiar and recessional motions without ambiguities. It is shown that the energy and peculiar momentum satisfy the mass-shell condition of special relativity while the recessional momentum does not produce energy. In this framework, the measurements of the kinetic quantities along geodesic performed by different observers are analysed pointing out an energy loss of the massive particles similar to that giving the photon redshift. The examples of the kinematics on the de Sitter expanding universe and a new Milne-type space-time are extensively analysed. |
2306.11451 | Javier Relancio | F. Mercati, J.J. Relancio | Relative Locality in curved spacetimes and event horizons | 20 pages, 3 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the past decade, significant efforts have been devoted to the study of
Relative Locality, which aims to generalize the kinematics of relativistic
particles to a nonlocal framework by introducing a nontrivial geometry for
momentum space. This paper builds upon a recent proposal to extend the theory
to curved spacetimes and investigates the behavior of horizons in certain
spacetimes with this nonlocality framework. Specifically, we examine whether
nonlocality effects weaken or destroy the notion of horizon in these
spacetimes. Our analysis indicates that, in the chosen models, the nonlocality
effects do not disrupt the notion of horizon and that it remains as robust as
it is in General Relativity.
| [
{
"created": "Tue, 20 Jun 2023 11:09:11 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Mercati",
"F.",
""
],
[
"Relancio",
"J. J.",
""
]
] | In the past decade, significant efforts have been devoted to the study of Relative Locality, which aims to generalize the kinematics of relativistic particles to a nonlocal framework by introducing a nontrivial geometry for momentum space. This paper builds upon a recent proposal to extend the theory to curved spacetimes and investigates the behavior of horizons in certain spacetimes with this nonlocality framework. Specifically, we examine whether nonlocality effects weaken or destroy the notion of horizon in these spacetimes. Our analysis indicates that, in the chosen models, the nonlocality effects do not disrupt the notion of horizon and that it remains as robust as it is in General Relativity. |
2308.00302 | Buddhadeb Ghosh | Abhijit Let, Arunoday Sarkar, Chitrak Sarkar and Buddhadeb Ghosh | Non-perturbative stabilization of two K\"ahler moduli in type-IIB/F
theory and the inflaton potential | 7 pages, 4 figures and 3 tables | 2023 EPL 143 39001 | 10.1209/0295-5075/acec09 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider a combination of perturbative and non-perturbative corrections in
K\"ahler moduli stabilizations in the configuration of three magnetised
intersecting D7 branes in the type-IIB/F theory, compactified on the 6d T^6/Z_N
orbifold of Calabi-Yau three-fold (CY_3). Two of the K\"ahler moduli are
stabilized non-perturbatively, out of the three which get perturbative
corrections up to one-loop-order multi-graviton scattering amplitudes in the
large volume scenario. In this framework, the dS vacua are achieved through all
K\"ahler moduli stabilizations by considering the D-term. We obtain inflaton
potentials of slow-roll plateau-type, which are expected by recent cosmological
observations. Calculations of cosmological parameters with the potentials yield
experimentally favoured values.
| [
{
"created": "Tue, 1 Aug 2023 05:50:10 GMT",
"version": "v1"
}
] | 2023-08-11 | [
[
"Let",
"Abhijit",
""
],
[
"Sarkar",
"Arunoday",
""
],
[
"Sarkar",
"Chitrak",
""
],
[
"Ghosh",
"Buddhadeb",
""
]
] | We consider a combination of perturbative and non-perturbative corrections in K\"ahler moduli stabilizations in the configuration of three magnetised intersecting D7 branes in the type-IIB/F theory, compactified on the 6d T^6/Z_N orbifold of Calabi-Yau three-fold (CY_3). Two of the K\"ahler moduli are stabilized non-perturbatively, out of the three which get perturbative corrections up to one-loop-order multi-graviton scattering amplitudes in the large volume scenario. In this framework, the dS vacua are achieved through all K\"ahler moduli stabilizations by considering the D-term. We obtain inflaton potentials of slow-roll plateau-type, which are expected by recent cosmological observations. Calculations of cosmological parameters with the potentials yield experimentally favoured values. |
2308.03926 | Ali Kaya | Ali Kaya | Big-Bang is a Boundary Condition | v2: 16 pages, Revtex 4-1, to appear in Annals of Physics | null | 10.1016/j.aop.2023.169526 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a common expectation that the big-bang singularity must be resolved
in quantum gravity but it is not clear how this can be achieved. A major
obstacle here is the difficulty of interpreting wave-functions in quantum
gravity. The standard quantum mechanical framework requires a notion of time
evolution and a proper definition of an invariant inner product having a
probability interpretation, both of which are seemingly problematic in quantum
gravity. We show that these two issues can actually be solved by introducing
the embedding coordinates as dynamical variables \`a la Isham and Kuchar. The
extended theory is identical to general relativity but has a larger group of
gauge symmetries. The Wheeler-DeWitt equations describe the change of the
wave-function from one arbitrary spacelike slice to another, however the
constraint algebra makes this evolution purely kinematical and furthermore
enforces the wave-function to be constrained in the subspace of zero-energy
states. An inner product can also be introduced having all the necessary
requirements. In this formalism big-bang appears as a finite field space
boundary on which certain boundary conditions must be imposed for mathematical
consistency. We explicitly illustrate this point both in the full theory and in
the minisuperspace approximation.
| [
{
"created": "Mon, 7 Aug 2023 22:06:13 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Nov 2023 17:46:11 GMT",
"version": "v2"
}
] | 2023-11-07 | [
[
"Kaya",
"Ali",
""
]
] | There is a common expectation that the big-bang singularity must be resolved in quantum gravity but it is not clear how this can be achieved. A major obstacle here is the difficulty of interpreting wave-functions in quantum gravity. The standard quantum mechanical framework requires a notion of time evolution and a proper definition of an invariant inner product having a probability interpretation, both of which are seemingly problematic in quantum gravity. We show that these two issues can actually be solved by introducing the embedding coordinates as dynamical variables \`a la Isham and Kuchar. The extended theory is identical to general relativity but has a larger group of gauge symmetries. The Wheeler-DeWitt equations describe the change of the wave-function from one arbitrary spacelike slice to another, however the constraint algebra makes this evolution purely kinematical and furthermore enforces the wave-function to be constrained in the subspace of zero-energy states. An inner product can also be introduced having all the necessary requirements. In this formalism big-bang appears as a finite field space boundary on which certain boundary conditions must be imposed for mathematical consistency. We explicitly illustrate this point both in the full theory and in the minisuperspace approximation. |
0902.1664 | David Garfinkle | David Garfinkle | Matters of Gravity, The Newsletter of the Topical Group in Gravitation
of the American Physical Society, Volume 33, Winter 2009 | 13 pages, latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | GGR News:
o GGR program at the APS meeting in Denver, by David Garfinkle
o we hear that ..., by David Garfinkle
o 400 years ago, by David Garfinkle
Conference reports:
o The 24th Texas Symposium on Relativistic Astrophysics, by Scott Hughes
o Loop Quantum Cosmology Workshop, by Parampreet Singh
| [
{
"created": "Mon, 9 Feb 2009 16:11:59 GMT",
"version": "v1"
}
] | 2009-02-11 | [
[
"Garfinkle",
"David",
""
]
] | GGR News: o GGR program at the APS meeting in Denver, by David Garfinkle o we hear that ..., by David Garfinkle o 400 years ago, by David Garfinkle Conference reports: o The 24th Texas Symposium on Relativistic Astrophysics, by Scott Hughes o Loop Quantum Cosmology Workshop, by Parampreet Singh |
1511.07935 | Xin-Zhou Li | Chao-jun Feng, Fei-fei Ge, Xin-zhou Li, Rui-hui Lin and Xiang-hua Zhai | Towards realistic $f(T)$ models with nonminimal torsion-matter coupling
extension | 12 pages, 5 figures | Phys. Rev. D 92 (2015) 104038 | 10.1103/PhysRevD.92.104038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the observation data of SNeIa, CMB and BAO, we establish two concrete
$f(T)$ models with nonminimal torsion-matter coupling extension. We study in
detail the cosmological implication of our models and find they are successful
in describing the observation of the Universe, its large scale structure and
evolution. In other words, these models do not change the successful aspects of
$\Lambda$CDM scenario under the error band of fitting values as describing the
evolution history of the Universe including radiation-dominated era,
matter-dominated era and the present accelerating expansion. Meanwhile, the
significant advantage of these models is that they could avoid the cosmological
constant problem of $\Lambda$CDM. A joint analysis is performed by using the
data of CMB+BAO+JLA, which leads to $\Omega_{m0}=0.255\pm 0.010,
\Omega_{b0}h^2=0.0221\pm 0.0003$ and $H_0=68.54\pm 1.27$ for model I and
$\Omega_{m0}=0.306\pm 0.010, \Omega_{b0}h^2=0.0225\pm 0.0003$ and $H_0=60.97\pm
0.44$ for model II at 1$\sigma$ confidence level. The evolution of the
decelaration parameter $q(a)$ and the effective equation of state $w_{DE}(a)$
are displayed. Furthermore, The resulted age of the Universe from our models is
consistent with the ages of the oldest globular clusters. As for the fate of
the Universe, model I results in a de Sitter accelerating phase while model II
appears a power-law one, even though $w_{DE0}< -1$ makes model I look like a
phantom at present time.
| [
{
"created": "Wed, 25 Nov 2015 02:19:07 GMT",
"version": "v1"
}
] | 2015-11-26 | [
[
"Feng",
"Chao-jun",
""
],
[
"Ge",
"Fei-fei",
""
],
[
"Li",
"Xin-zhou",
""
],
[
"Lin",
"Rui-hui",
""
],
[
"Zhai",
"Xiang-hua",
""
]
] | Using the observation data of SNeIa, CMB and BAO, we establish two concrete $f(T)$ models with nonminimal torsion-matter coupling extension. We study in detail the cosmological implication of our models and find they are successful in describing the observation of the Universe, its large scale structure and evolution. In other words, these models do not change the successful aspects of $\Lambda$CDM scenario under the error band of fitting values as describing the evolution history of the Universe including radiation-dominated era, matter-dominated era and the present accelerating expansion. Meanwhile, the significant advantage of these models is that they could avoid the cosmological constant problem of $\Lambda$CDM. A joint analysis is performed by using the data of CMB+BAO+JLA, which leads to $\Omega_{m0}=0.255\pm 0.010, \Omega_{b0}h^2=0.0221\pm 0.0003$ and $H_0=68.54\pm 1.27$ for model I and $\Omega_{m0}=0.306\pm 0.010, \Omega_{b0}h^2=0.0225\pm 0.0003$ and $H_0=60.97\pm 0.44$ for model II at 1$\sigma$ confidence level. The evolution of the decelaration parameter $q(a)$ and the effective equation of state $w_{DE}(a)$ are displayed. Furthermore, The resulted age of the Universe from our models is consistent with the ages of the oldest globular clusters. As for the fate of the Universe, model I results in a de Sitter accelerating phase while model II appears a power-law one, even though $w_{DE0}< -1$ makes model I look like a phantom at present time. |
1112.5836 | Mariam Bouhmadi-Lopez | Moulay-Hicham Belkacemi, Mariam Bouhmadi-Lopez, Ahmed Errahmani, and
Taoufiq Ouali | The holographic induced gravity model with a Ricci dark energy:
smoothing the little rip and big rip through Gauss-Bonnet effects? | 11 pages, 8 figures. RevTex4-1. Comments and references added.
Version accepted in PRD | Phys. Rev. D 85, 083503 (2012) | 10.1103/PhysRevD.85.083503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an holographic brane-world model of the Dvali-Gabadadze-Porrati
(DGP) scenario with and without a Gauss-Bonnet term (GB) in the bulk. We show
that an holographic dark energy component with the Ricci scale as the infra-red
cutoff can describe the late-time acceleration of the universe. In addition, we
show that the dimensionless holographic parameter is very important in
characterising the DGP branches, and in determining the behaviour of the Ricci
dark energy as well as the asymptotic behaviour of the brane. On the one hand,
in the DGP scenario the Ricci dark energy will exhibit a phantom-like behaviour
with no big rip if the holographic parameter is strictly larger than 1/2. For
smaller values, the brane hits a big rip or a little rip. On the other hand, we
have shown that the introduction of the GB term avoids the big rip and little
rip singularities on both branches but cannot avoid the appearance of a big
freeze singularity for some values of the holographic parameter on the normal
branch, however, these values are very unlikely because they lead to a very
negative equation of state at the present and therefore we can speak in
practice of singularity avoidance. At this regard, the equation of state
parameter of the Ricci dark energy plays a crucial role, even more important
than the GB parameter, in rejecting the parameter space where future
singularities appear.
| [
{
"created": "Mon, 26 Dec 2011 10:31:45 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2012 14:03:33 GMT",
"version": "v2"
}
] | 2012-04-13 | [
[
"Belkacemi",
"Moulay-Hicham",
""
],
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Errahmani",
"Ahmed",
""
],
[
"Ouali",
"Taoufiq",
""
]
] | We present an holographic brane-world model of the Dvali-Gabadadze-Porrati (DGP) scenario with and without a Gauss-Bonnet term (GB) in the bulk. We show that an holographic dark energy component with the Ricci scale as the infra-red cutoff can describe the late-time acceleration of the universe. In addition, we show that the dimensionless holographic parameter is very important in characterising the DGP branches, and in determining the behaviour of the Ricci dark energy as well as the asymptotic behaviour of the brane. On the one hand, in the DGP scenario the Ricci dark energy will exhibit a phantom-like behaviour with no big rip if the holographic parameter is strictly larger than 1/2. For smaller values, the brane hits a big rip or a little rip. On the other hand, we have shown that the introduction of the GB term avoids the big rip and little rip singularities on both branches but cannot avoid the appearance of a big freeze singularity for some values of the holographic parameter on the normal branch, however, these values are very unlikely because they lead to a very negative equation of state at the present and therefore we can speak in practice of singularity avoidance. At this regard, the equation of state parameter of the Ricci dark energy plays a crucial role, even more important than the GB parameter, in rejecting the parameter space where future singularities appear. |
2207.14423 | Dicong Liang | Dicong Liang, Rui Xu, Xuchen Lu and Lijing Shao | Polarizations of Gravitational Waves in the Bumblebee Gravity Model | 16 pages, no figures | Phys. Rev. D 106 (2022) 124019 | 10.1103/PhysRevD.106.124019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lorentz violation modifies the dispersion relation of gravitational waves
(GWs), and induces birefringence and anisotropy in propagation. Our study shows
that Lorentz violation can also activate multiple polarizations of GWs. We use
the gauge invariants to investigate the polarizations of GWs in the bumblebee
gravity model, and obtain the following results. (i) For a vector background
$b^\mu$ with only a nonzero temporal component $b^t$, there are five
independent propagating degrees of freedom (DOFs), which is simlar to the
Einstein-aether theory. (ii) The presence of a spatial component in the
background defines a preferred spatial direction which breaks rotational
symmetry. We denote $\hat{\bf b}$ as the direction of the spatial part of the
background and $b_s$ as its length. If GWs propagate along $\hat{\bf b}$, the
polarization content is similar to the purely timelike case. (iii) If the
propagation direction of GWs is separated by an angle $\beta$ to $\hat{\bf b}$,
and $\beta=\arccos(b^t/b_s)$, there are only two tensor polarizations. (iv) If
$\beta\neq \arccos(b^t/b_s)$, there are only two independent DOFs, and the
vector and scalar modes degenerate with the tensor modes. The tensor
perturbations can activate a mixture of all six polarizations simultaneously.
Finally, we point out the difference in GWs between the bumblebee gravity model
and the minimal Standard-Model Extension framework in the linearized regime.
Current observations have placed stringent constraints on the anisotropy
induced by the background, while our theoretical study still reveals some novel
phenomena and provides more understanding about the interaction between the
Lorentz-violating vector field and gravity.
| [
{
"created": "Fri, 29 Jul 2022 01:01:43 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2022 14:07:06 GMT",
"version": "v2"
}
] | 2022-12-20 | [
[
"Liang",
"Dicong",
""
],
[
"Xu",
"Rui",
""
],
[
"Lu",
"Xuchen",
""
],
[
"Shao",
"Lijing",
""
]
] | Lorentz violation modifies the dispersion relation of gravitational waves (GWs), and induces birefringence and anisotropy in propagation. Our study shows that Lorentz violation can also activate multiple polarizations of GWs. We use the gauge invariants to investigate the polarizations of GWs in the bumblebee gravity model, and obtain the following results. (i) For a vector background $b^\mu$ with only a nonzero temporal component $b^t$, there are five independent propagating degrees of freedom (DOFs), which is simlar to the Einstein-aether theory. (ii) The presence of a spatial component in the background defines a preferred spatial direction which breaks rotational symmetry. We denote $\hat{\bf b}$ as the direction of the spatial part of the background and $b_s$ as its length. If GWs propagate along $\hat{\bf b}$, the polarization content is similar to the purely timelike case. (iii) If the propagation direction of GWs is separated by an angle $\beta$ to $\hat{\bf b}$, and $\beta=\arccos(b^t/b_s)$, there are only two tensor polarizations. (iv) If $\beta\neq \arccos(b^t/b_s)$, there are only two independent DOFs, and the vector and scalar modes degenerate with the tensor modes. The tensor perturbations can activate a mixture of all six polarizations simultaneously. Finally, we point out the difference in GWs between the bumblebee gravity model and the minimal Standard-Model Extension framework in the linearized regime. Current observations have placed stringent constraints on the anisotropy induced by the background, while our theoretical study still reveals some novel phenomena and provides more understanding about the interaction between the Lorentz-violating vector field and gravity. |
0901.3827 | Belinch\'on Jos\'e Antonio | Jos\'e Antonio Belinch\'on | Bianchi II with time varying constants. Self-similar approach | 10 pages. RevTeX4 | Astrophys.Space Sci.323:185-195,2009 | 10.1007/s10509-009-0050-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a perfect fluid Bianchi II models with time varying constants under
the self-similarity approach. In the first of the studied model, we consider
that only vary $G$ and $\Lambda.$ The obtained solution is more general that
the obtained one for the classical solution since it is valid for an equation
of state $\omega\in(-1,\infty) $ while in the classical solution
$\omega\in(-1/3,1) .$ Taking into account the current observations, we conclude
that $G$ must be a growing time function while $\Lambda$ is a positive
decreasing function. In the second of the studied models we consider a variable
speed of light (VSL). We obtain a similar solution as in the first model
arriving to the conclusions that $c$ must be a growing time function if
$\Lambda$ is a positive decreasing function.
| [
{
"created": "Sat, 24 Jan 2009 11:45:55 GMT",
"version": "v1"
}
] | 2009-08-11 | [
[
"Belinchón",
"José Antonio",
""
]
] | We study a perfect fluid Bianchi II models with time varying constants under the self-similarity approach. In the first of the studied model, we consider that only vary $G$ and $\Lambda.$ The obtained solution is more general that the obtained one for the classical solution since it is valid for an equation of state $\omega\in(-1,\infty) $ while in the classical solution $\omega\in(-1/3,1) .$ Taking into account the current observations, we conclude that $G$ must be a growing time function while $\Lambda$ is a positive decreasing function. In the second of the studied models we consider a variable speed of light (VSL). We obtain a similar solution as in the first model arriving to the conclusions that $c$ must be a growing time function if $\Lambda$ is a positive decreasing function. |
1712.04827 | Luigi Pilo | Marco Celoria, Denis Comelli, Luigi Pilo | Self-gravitating $\Lambda$-media | 17 pages+ 3 pdf figures. Expanded version published on JCAP | JCAP 1901 (2019) no.01, 057 | 10.1088/1475-7516/2019/01/057 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the question whether a medium featuring $p + \rho = 0$, dubbed
$\Lambda$- medium, has to be necessarily a cosmological constant. By using
effective field theory, we show that this is not the case for a class of media
comprising perfect fluids, solids and special super solids, providing an
explicit construction. The low energy excitations are non trivial and lensing,
the growth of large scale structures can be used to clearly distinguish
$\Lambda$-media from a cosmological constant.
| [
{
"created": "Wed, 13 Dec 2017 15:55:03 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Apr 2019 21:20:46 GMT",
"version": "v2"
}
] | 2019-04-16 | [
[
"Celoria",
"Marco",
""
],
[
"Comelli",
"Denis",
""
],
[
"Pilo",
"Luigi",
""
]
] | We address the question whether a medium featuring $p + \rho = 0$, dubbed $\Lambda$- medium, has to be necessarily a cosmological constant. By using effective field theory, we show that this is not the case for a class of media comprising perfect fluids, solids and special super solids, providing an explicit construction. The low energy excitations are non trivial and lensing, the growth of large scale structures can be used to clearly distinguish $\Lambda$-media from a cosmological constant. |
1807.09801 | Sourya Ray | David Kastor, Sourya Ray, Jennie Traschen | Black Hole Enthalpy and Scalar Fields | 24 pages | null | 10.1088/1361-6382/aaf663 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mass of an AdS black hole represents its enthalpy, which in addition to
internal energy, generally includes the energy required to assemble the system
in its environment. In this paper, we consider black holes immersed in a more
complex environment, generated by a scalar field with an exponential potential.
In the analogue of the AdS vacuum, which we call dilaton-AdS, the scalar field
has non-trivial behavior, breaking the hyperscaling symmetry of AdS and
modifying the asymptotic form of the spacetime. We find that the scalar field
falloff at infinity makes novel contributions to the ADM mass and spatial
tensions of dilaton-AdS black holes. We derive a first law and Smarr formula
for planar dilaton-AdS black holes. We study the analogue of thermodynamic
volume in this system and show that the mass of a black hole again represents
its enthalpy.
| [
{
"created": "Wed, 25 Jul 2018 18:03:35 GMT",
"version": "v1"
}
] | 2019-01-09 | [
[
"Kastor",
"David",
""
],
[
"Ray",
"Sourya",
""
],
[
"Traschen",
"Jennie",
""
]
] | The mass of an AdS black hole represents its enthalpy, which in addition to internal energy, generally includes the energy required to assemble the system in its environment. In this paper, we consider black holes immersed in a more complex environment, generated by a scalar field with an exponential potential. In the analogue of the AdS vacuum, which we call dilaton-AdS, the scalar field has non-trivial behavior, breaking the hyperscaling symmetry of AdS and modifying the asymptotic form of the spacetime. We find that the scalar field falloff at infinity makes novel contributions to the ADM mass and spatial tensions of dilaton-AdS black holes. We derive a first law and Smarr formula for planar dilaton-AdS black holes. We study the analogue of thermodynamic volume in this system and show that the mass of a black hole again represents its enthalpy. |
1802.00313 | Sayani Maity | Sayani Maity and Prabir Rudra | Gravitational Baryogenesis in Ho$\check{r}$ava-Lifshitz gravity | null | null | 10.1142/S0217732319502031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we intend to address the matter-antimatter asymmetry via the
gravitational baryogenesis mechanism in the background of a quantum theory of
gravity. We investigate this mechanism under the framework of
Ho$\check{r}$ava-Lifshitz gravity. We will compute the baryon-to-entropy ratio
in the chosen framework and investigate its physical viability against the
observational bounds. We also conduct the above study for various sources of
matter like scalar field and Chaplygin gas as specific examples. We speculate
that quantum corrections from the background geometry will lead to interesting
results.
| [
{
"created": "Wed, 31 Jan 2018 11:01:17 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Feb 2018 08:03:52 GMT",
"version": "v2"
}
] | 2019-10-02 | [
[
"Maity",
"Sayani",
""
],
[
"Rudra",
"Prabir",
""
]
] | In this work we intend to address the matter-antimatter asymmetry via the gravitational baryogenesis mechanism in the background of a quantum theory of gravity. We investigate this mechanism under the framework of Ho$\check{r}$ava-Lifshitz gravity. We will compute the baryon-to-entropy ratio in the chosen framework and investigate its physical viability against the observational bounds. We also conduct the above study for various sources of matter like scalar field and Chaplygin gas as specific examples. We speculate that quantum corrections from the background geometry will lead to interesting results. |
2304.02219 | Keita Takizawa | Keita Takizawa, Hideki Asada | Gravitational lens on a static optical constant-curvature background:
Its application to Weyl gravity model | 12 pages, 4 figures, the differences between the present result and
the previous literature clarified, title and text improved, accepted for PRD | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | This paper extends the de-Sitter/anti-de Sitter (dS/AdS) background method
based on the optical metric for gravitational lens [Phys. Rev. D 105, 084022
(2022)] to a static optical constant-curvature (SOCC) background. It is shown
that the exact lens equation on the SOCC background can be written in the same
form as that for either Minkowski, dS or AdS background in terms of flat,
spherical or hyperbolic trigonometry, depending on the Gaussian curvature of
the equatorial plane in the SOCC background. To exemplify the SOCC method, we
consider the gravitational lens in Mannheim-Kazanas (MK) solution of Weyl
gravity, which includes Rindler and de Sitter terms. In the zero mass limit,
the deflection angle of light for the MK solution in the literature diverges to
infinity. This is because there is a self-contradiction in their perturbative
approximations of the MK metric and the orbit equation. The SOCC method
incorporates the long-distance curvature effect into the background. Thereby
the SOCC expression for the deflection angle of light in the MK solution is
finite also in the zero mass limit.
| [
{
"created": "Wed, 5 Apr 2023 04:16:50 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Oct 2023 04:17:13 GMT",
"version": "v2"
}
] | 2023-10-30 | [
[
"Takizawa",
"Keita",
""
],
[
"Asada",
"Hideki",
""
]
] | This paper extends the de-Sitter/anti-de Sitter (dS/AdS) background method based on the optical metric for gravitational lens [Phys. Rev. D 105, 084022 (2022)] to a static optical constant-curvature (SOCC) background. It is shown that the exact lens equation on the SOCC background can be written in the same form as that for either Minkowski, dS or AdS background in terms of flat, spherical or hyperbolic trigonometry, depending on the Gaussian curvature of the equatorial plane in the SOCC background. To exemplify the SOCC method, we consider the gravitational lens in Mannheim-Kazanas (MK) solution of Weyl gravity, which includes Rindler and de Sitter terms. In the zero mass limit, the deflection angle of light for the MK solution in the literature diverges to infinity. This is because there is a self-contradiction in their perturbative approximations of the MK metric and the orbit equation. The SOCC method incorporates the long-distance curvature effect into the background. Thereby the SOCC expression for the deflection angle of light in the MK solution is finite also in the zero mass limit. |
gr-qc/9610069 | Carsten Gundlach | Carsten Gundlach | Echoing and scaling in Einstein-Yang-Mills critical collapse | 13 pages, Revtex, one important reference corrected | Phys.Rev. D55 (1997) 6002-6013 | 10.1103/PhysRevD.55.6002 | null | gr-qc | null | We confirm recent numerical results of echoing and mass scaling in the
gravitational collapse of a spherical Yang-Mills field by constructing the
critical solution and its perturbations as an eigenvalue problem. Because the
field equations are not scale-invariant, the Yang-Mills critical solution is
asymptotically, rather than exactly, self-similar, but the methods for dealing
with discrete self-similarity developed for the real scalar field can be
generalized. We find an echoing period Delta = 0.73784 +/- 0.00002 and critical
exponent for the black hole mass gamma = 0.1964 +/- 0.0007.
| [
{
"created": "Wed, 30 Oct 1996 19:01:15 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 1996 15:58:06 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Gundlach",
"Carsten",
""
]
] | We confirm recent numerical results of echoing and mass scaling in the gravitational collapse of a spherical Yang-Mills field by constructing the critical solution and its perturbations as an eigenvalue problem. Because the field equations are not scale-invariant, the Yang-Mills critical solution is asymptotically, rather than exactly, self-similar, but the methods for dealing with discrete self-similarity developed for the real scalar field can be generalized. We find an echoing period Delta = 0.73784 +/- 0.00002 and critical exponent for the black hole mass gamma = 0.1964 +/- 0.0007. |
1303.2471 | Miroslav Shaltev | Miroslav Shaltev and Reinhard Prix | Fully coherent follow-up of continuous gravitational-wave candidates | 12 pages, 5 figures | null | 10.1103/PhysRevD.87.084057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The search for continuous gravitational waves from unknown isolated sources
is computationally limited due to the enormous parameter space that needs to be
covered and the weakness of the expected signals. Therefore semi-coherent
search strategies have been developed and applied in distributed computing
environments such as Einstein@Home, in order to narrow down the parameter space
and identify interesting candidates. However, in order to optimally confirm or
dismiss a candidate as a possible gravitational-wave signal, a fully-coherent
follow-up using all the available data is required.
We present a general method and implementation of a direct (2-stage)
transition to a fully-coherent follow-up on semi-coherent candidates. This
method is based on a grid-less Mesh Adaptive Direct Search (MADS) algorithm
using the F-statistic. We demonstrate the detection power and computing cost of
this follow-up procedure using extensive Monte-Carlo simulations on (simulated)
semi-coherent candidates from a directed as well as from an all-sky search
setup.
| [
{
"created": "Mon, 11 Mar 2013 10:11:02 GMT",
"version": "v1"
}
] | 2013-11-26 | [
[
"Shaltev",
"Miroslav",
""
],
[
"Prix",
"Reinhard",
""
]
] | The search for continuous gravitational waves from unknown isolated sources is computationally limited due to the enormous parameter space that needs to be covered and the weakness of the expected signals. Therefore semi-coherent search strategies have been developed and applied in distributed computing environments such as Einstein@Home, in order to narrow down the parameter space and identify interesting candidates. However, in order to optimally confirm or dismiss a candidate as a possible gravitational-wave signal, a fully-coherent follow-up using all the available data is required. We present a general method and implementation of a direct (2-stage) transition to a fully-coherent follow-up on semi-coherent candidates. This method is based on a grid-less Mesh Adaptive Direct Search (MADS) algorithm using the F-statistic. We demonstrate the detection power and computing cost of this follow-up procedure using extensive Monte-Carlo simulations on (simulated) semi-coherent candidates from a directed as well as from an all-sky search setup. |
gr-qc/0404031 | Giovanni Imponente | Giovanni Imponente and Giovanni Montani | Inhomogeneous de Sitter Solution with Scalar Field and Perturbations
Spectrum | 9 pages, no figures, to appear on Mod.Phys.Lett. A | Mod.Phys.Lett. A19 (2004) 1281-1290 | 10.1142/S0217732304014057 | null | gr-qc astro-ph | null | We provide an inhomogeneous solution concerning the dynamics of a real self
interacting scalar field minimally coupled to gravity in a region of the
configuration space where it performs a slow rolling on a plateau of its
potential. During the inhomogeneous de Sitter phase the scalar field dominant
term is a function of the spatial coordinates only. This solution specialized
nearby the FLRW model allows a classical origin for the inhomogeneous
perturbations spectrum.
| [
{
"created": "Wed, 7 Apr 2004 10:52:03 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Imponente",
"Giovanni",
""
],
[
"Montani",
"Giovanni",
""
]
] | We provide an inhomogeneous solution concerning the dynamics of a real self interacting scalar field minimally coupled to gravity in a region of the configuration space where it performs a slow rolling on a plateau of its potential. During the inhomogeneous de Sitter phase the scalar field dominant term is a function of the spatial coordinates only. This solution specialized nearby the FLRW model allows a classical origin for the inhomogeneous perturbations spectrum. |
2408.02235 | Tian-Yong Cao | Tian-Yong Cao, Ankit Kumar, and Shu-Xu Yi | Constraining gravitational wave velocities using gravitational and
electromagnetic wave observations of white dwarf binaries | 10 pages, 10 figures | Monthly Notices of the Royal Astronomical Society, 2024: stae1755 | 10.1093/mnras/stae1755 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although the general theory of relativity (GR) predicts that gravitational
waves (GWs) have exactly the same propagation velocity as electromagnetic (EM)
waves, many theories of gravity beyond GR expect otherwise. Accurate
measurement of the difference in their propagation speed, or a tight constraint
on it, could be crucial to validate or put limits on theories beyond GR. The
proposed future space-borne GW detectors are poised to detect a substantial
number of Galactic white dwarf binaries (GWDBs), which emit the GW as
semi-monochromatic signals. Concurrently, these GWDBs can also be identified as
optical variable sources. Here we proposed that allocating a GWDB's optical
light curve and contemporaneous GW signal can be used to trace the difference
between the velocity of GW and EM waves. Simulating GW and EM wave data from 14
verification binaries (VBs), our method constrains propagation-originated phase
differences, limiting the discrepancy between the speed of light ($c$) and GW
($c_{GW}$). Through the utilization of LISA's design sensitivity and the
current precision in optical observation on GWDB, our study reveals that a
four-year observation of the 14 recognized VBs results in a joint constraint
that confines $\Delta c/c$ ($\Delta c = c_{\mathrm{GW}} - c$) to the range of
$-2.1\times10^{-12}$ and $4.8\times10^{-12}$. Additionally, by incorporating
this constraint on $c_{\mathrm{GW}}$, we are able to establish boundaries for
the mass of the graviton, limiting it to
$m_{\mathrm{g}}\le3\times10^{-23}\,e\mathrm{V}/c^{2}$, and for the parameter
associated with local Lorentz violation, $\bar{s}_{00}$, constrained within the
range of $-3.4\times10^{-11}\le\bar{s}_{00}\le1.5\times10^{-11}$.
| [
{
"created": "Mon, 5 Aug 2024 04:56:20 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Cao",
"Tian-Yong",
""
],
[
"Kumar",
"Ankit",
""
],
[
"Yi",
"Shu-Xu",
""
]
] | Although the general theory of relativity (GR) predicts that gravitational waves (GWs) have exactly the same propagation velocity as electromagnetic (EM) waves, many theories of gravity beyond GR expect otherwise. Accurate measurement of the difference in their propagation speed, or a tight constraint on it, could be crucial to validate or put limits on theories beyond GR. The proposed future space-borne GW detectors are poised to detect a substantial number of Galactic white dwarf binaries (GWDBs), which emit the GW as semi-monochromatic signals. Concurrently, these GWDBs can also be identified as optical variable sources. Here we proposed that allocating a GWDB's optical light curve and contemporaneous GW signal can be used to trace the difference between the velocity of GW and EM waves. Simulating GW and EM wave data from 14 verification binaries (VBs), our method constrains propagation-originated phase differences, limiting the discrepancy between the speed of light ($c$) and GW ($c_{GW}$). Through the utilization of LISA's design sensitivity and the current precision in optical observation on GWDB, our study reveals that a four-year observation of the 14 recognized VBs results in a joint constraint that confines $\Delta c/c$ ($\Delta c = c_{\mathrm{GW}} - c$) to the range of $-2.1\times10^{-12}$ and $4.8\times10^{-12}$. Additionally, by incorporating this constraint on $c_{\mathrm{GW}}$, we are able to establish boundaries for the mass of the graviton, limiting it to $m_{\mathrm{g}}\le3\times10^{-23}\,e\mathrm{V}/c^{2}$, and for the parameter associated with local Lorentz violation, $\bar{s}_{00}$, constrained within the range of $-3.4\times10^{-11}\le\bar{s}_{00}\le1.5\times10^{-11}$. |
2311.15585 | Zhixiang Ren | Tianyu Zhao, Ruijun Shi, Yue Zhou, Zhoujian Cao, Zhixiang Ren | Dawning of a New Era in Gravitational Wave Data Analysis: Unveiling
Cosmic Mysteries via Artificial Intelligence -- A Systematic Review | null | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Background: Artificial intelligence (AI), with its vast capabilities, has
become an integral part of our daily interactions, particularly with the rise
of sophisticated models like Large Language Models. These advancements have not
only transformed human-machine interactions but have also paved the way for
significant breakthroughs in various scientific domains. Aim of review: This
review is centered on elucidating the profound impact of AI, especially deep
learning, in the field of gravitational wave data analysis (GWDA). We aim to
highlight the challenges faced by traditional GWDA methodologies and how AI
emerges as a beacon of hope, promising enhanced accuracy, real-time processing,
and adaptability. Key scientific concepts of review: Gravitational wave (GW)
waveform modeling stands as a cornerstone in the realm of GW research, serving
as a sophisticated method to simulate and interpret the intricate patterns and
signatures of these cosmic phenomena. This modeling provides a deep
understanding of the astrophysical events that produce gravitational waves.
Next in line is GW signal detection, a refined technique that meticulously
combs through extensive datasets, distinguishing genuine gravitational wave
signals from the cacophony of background noise. This detection process is
pivotal in ensuring the authenticity of observed events. Complementing this is
the GW parameter estimation, a method intricately designed to decode the
detected signals, extracting crucial parameters that offer insights into the
properties and origins of the waves. Lastly, the integration of AI for GW
science has emerged as a transformative force. AI methodologies harness vast
computational power and advanced algorithms to enhance the efficiency,
accuracy, and adaptability of data analysis in GW research, heralding a new era
of innovation and discovery in the field.
| [
{
"created": "Mon, 27 Nov 2023 07:21:24 GMT",
"version": "v1"
}
] | 2023-11-28 | [
[
"Zhao",
"Tianyu",
""
],
[
"Shi",
"Ruijun",
""
],
[
"Zhou",
"Yue",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Ren",
"Zhixiang",
""
]
] | Background: Artificial intelligence (AI), with its vast capabilities, has become an integral part of our daily interactions, particularly with the rise of sophisticated models like Large Language Models. These advancements have not only transformed human-machine interactions but have also paved the way for significant breakthroughs in various scientific domains. Aim of review: This review is centered on elucidating the profound impact of AI, especially deep learning, in the field of gravitational wave data analysis (GWDA). We aim to highlight the challenges faced by traditional GWDA methodologies and how AI emerges as a beacon of hope, promising enhanced accuracy, real-time processing, and adaptability. Key scientific concepts of review: Gravitational wave (GW) waveform modeling stands as a cornerstone in the realm of GW research, serving as a sophisticated method to simulate and interpret the intricate patterns and signatures of these cosmic phenomena. This modeling provides a deep understanding of the astrophysical events that produce gravitational waves. Next in line is GW signal detection, a refined technique that meticulously combs through extensive datasets, distinguishing genuine gravitational wave signals from the cacophony of background noise. This detection process is pivotal in ensuring the authenticity of observed events. Complementing this is the GW parameter estimation, a method intricately designed to decode the detected signals, extracting crucial parameters that offer insights into the properties and origins of the waves. Lastly, the integration of AI for GW science has emerged as a transformative force. AI methodologies harness vast computational power and advanced algorithms to enhance the efficiency, accuracy, and adaptability of data analysis in GW research, heralding a new era of innovation and discovery in the field. |
gr-qc/0312121 | Sergio M. C. V. Goncalves | Sergio M. C. V. Goncalves | No-horizon theorem for vacuum gravity with spacelike G1 isometry groups | 6 pages, revtex4; published in Phys. Rev. D Rapid Comm | Phys.Rev. D68 (2003) 101502 | 10.1103/PhysRevD.68.101502 | null | gr-qc | null | We show that (3+1) vacuum spacetimes admitting a global, spacelike,
one-parameter Lie group of isometries of translational type cannot contain
apparent horizons. The only assumption made is that of the existence of a
global spacelike Killing vector field with infinite open orbits; the
four-dimensional vacuum spacetime metric is otherwise arbitrary. This result
may thus be viewed as a hoop conjecture theorem for vacuum gravity with one
spacelike translational Killing symmetry.
| [
{
"created": "Tue, 30 Dec 2003 19:43:53 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Goncalves",
"Sergio M. C. V.",
""
]
] | We show that (3+1) vacuum spacetimes admitting a global, spacelike, one-parameter Lie group of isometries of translational type cannot contain apparent horizons. The only assumption made is that of the existence of a global spacelike Killing vector field with infinite open orbits; the four-dimensional vacuum spacetime metric is otherwise arbitrary. This result may thus be viewed as a hoop conjecture theorem for vacuum gravity with one spacelike translational Killing symmetry. |
0705.2851 | Yoshiaki Himemoto | Takeshi Chiba, Yoshiaki Himemoto, Masahide Yamaguchi, Jun'ichi
Yokoyama | Effective Search Templates for a Primordial Stochastic Gravitational
Wave Background | 13 pages, 4 figures, final version to be published in PRD | Phys.Rev.D76:043516,2007 | 10.1103/PhysRevD.76.043516 | null | gr-qc astro-ph hep-ph | null | We calculate the signal-to-noise ratio (SNR) of the stochastic
gravitational-wave background in an extreme case that its spectrum has a sharp
falloff with its amplitude close to the detection threshold. Such a spectral
feature is a characteristic imprint of the change in the number of relativistic
degrees of freedom on the stochastic background generated during inflation in
the early Universe. We find that, although SNR is maximal with the correct
template which is proportional to the assumed real spectrum, its sensitivity to
the shape of template is fairly weak indicating that a simple power-law
template is sufficient to detect the signature.
| [
{
"created": "Mon, 21 May 2007 12:48:37 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Aug 2007 15:04:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Chiba",
"Takeshi",
""
],
[
"Himemoto",
"Yoshiaki",
""
],
[
"Yamaguchi",
"Masahide",
""
],
[
"Yokoyama",
"Jun'ichi",
""
]
] | We calculate the signal-to-noise ratio (SNR) of the stochastic gravitational-wave background in an extreme case that its spectrum has a sharp falloff with its amplitude close to the detection threshold. Such a spectral feature is a characteristic imprint of the change in the number of relativistic degrees of freedom on the stochastic background generated during inflation in the early Universe. We find that, although SNR is maximal with the correct template which is proportional to the assumed real spectrum, its sensitivity to the shape of template is fairly weak indicating that a simple power-law template is sufficient to detect the signature. |
gr-qc/0509071 | Stephane Fay | Stephane Fay and Thierry Lehner | Bianchi type IX asymptotical behaviours with a massive scalar field:
chaos strikes back | 31 pages, 7 figures (low resolution) | Gen.Rel.Grav.37:1097-1117,2005 | 10.1007/s10714-005-0093-0 | null | gr-qc | null | We use numerical integrations to study the asymptotical behaviour of a
homogeneous but anisotropic Bianchi type IX model in General Relativity with a
massive scalar field. As it is well known, for a Brans-Dicke theory, the
asymptotical behaviour of the metric functions is ruled only by the Brans-Dicke
coupling constant with respect to the value -3/2. In this paper we examine if
such a condition still exists with a massive scalar field. We also show that,
contrary to what occurs for a massless scalar field, the singularity
oscillatory approach may exist in presence of a massive scalar field having a
positive energy density.
| [
{
"created": "Fri, 16 Sep 2005 17:10:46 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Fay",
"Stephane",
""
],
[
"Lehner",
"Thierry",
""
]
] | We use numerical integrations to study the asymptotical behaviour of a homogeneous but anisotropic Bianchi type IX model in General Relativity with a massive scalar field. As it is well known, for a Brans-Dicke theory, the asymptotical behaviour of the metric functions is ruled only by the Brans-Dicke coupling constant with respect to the value -3/2. In this paper we examine if such a condition still exists with a massive scalar field. We also show that, contrary to what occurs for a massless scalar field, the singularity oscillatory approach may exist in presence of a massive scalar field having a positive energy density. |
1303.0849 | Norman Metzner | Paul Tod, Norman Metzner, Lionel Mason | Twistor Construction of Higher-Dimensional Black Holes - Part II:
Examples | 35 pages, 5 figures | Class. Quantum Grav. 30 (2013) 095002 | 10.1088/0264-9381/30/9/095002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the twistor construction for higher-dimensional black holes to known
examples in five space-time dimensions. First the patching matrices are
calculated from the explicit metric for these examples. Then an ansatz is
proposed for obtaining the patching matrix instead from the data of rod
structure and angular momenta. The ansatz is tested on examples with up to
three nuts, and these are shown to give flat space, the Myers-Perry solution
and the black ring, as expected. Rules for the transition between different
adaptations of the patching matrix and for the elimination of conical
singularities are developed and seen to work.
| [
{
"created": "Mon, 4 Mar 2013 21:03:33 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Tod",
"Paul",
""
],
[
"Metzner",
"Norman",
""
],
[
"Mason",
"Lionel",
""
]
] | We apply the twistor construction for higher-dimensional black holes to known examples in five space-time dimensions. First the patching matrices are calculated from the explicit metric for these examples. Then an ansatz is proposed for obtaining the patching matrix instead from the data of rod structure and angular momenta. The ansatz is tested on examples with up to three nuts, and these are shown to give flat space, the Myers-Perry solution and the black ring, as expected. Rules for the transition between different adaptations of the patching matrix and for the elimination of conical singularities are developed and seen to work. |
gr-qc/0212044 | Kenneth Nordtvedt | Kenneth Nordtvedt | Space-Time Variation of Physical Constants and the Equivalence Principle | 5 pages, PCTex32.v3.4 | null | 10.1142/S0217751X02011655 | null | gr-qc | null | Location dependence of physical parameters such as the electromagnetic fine
structure constant and Newton's G produce body accelerations which violate
universality of free fall rates testable with laboratory and space experiments.
Theoretically related cosmological time variation of these same parameters are
also constrained by experiments such as lunar laser ranging, and these time
variations produce accelerations of bodies relative to a preferred cosmological
frame.
| [
{
"created": "Tue, 10 Dec 2002 03:01:59 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Nordtvedt",
"Kenneth",
""
]
] | Location dependence of physical parameters such as the electromagnetic fine structure constant and Newton's G produce body accelerations which violate universality of free fall rates testable with laboratory and space experiments. Theoretically related cosmological time variation of these same parameters are also constrained by experiments such as lunar laser ranging, and these time variations produce accelerations of bodies relative to a preferred cosmological frame. |
1807.00987 | Jonghyun Sim | Jonghyun Sim, Jiwon Park, Tae Hoon Lee | Dynamical analysis of Brans-Dicke Universe with inverse power-law
effective potential | 20 pages, 9 figures, 2 tables, accepted for publication in MPLA | null | 10.1142/S0217732320500947 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Brans-Dicke cosmology with an inverse power-law effective potential.
By using dynamical analyses, we search for fixed points corresponding to the
radiation-like matter and dark energy-dominated era of our Universe, and the
stability of fixed points is also investigated. We find phase space
trajectories which are attracted to the stable point of the dark
energy-dominated era from unstable fixed points like matter-dominated era of
the Universe. The dark energy comes from effective potentials of the
Brans-Dicke field, whose variation (related to the time-variation of the
gravitational coupling constant) is shown to be in good agreement with
observational data.
| [
{
"created": "Tue, 3 Jul 2018 06:09:38 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 11:53:55 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Feb 2019 12:35:22 GMT",
"version": "v3"
},
{
"created": "Sun, 2 Feb 2020 06:44:50 GMT",
"version": "v4"
}
] | 2020-02-04 | [
[
"Sim",
"Jonghyun",
""
],
[
"Park",
"Jiwon",
""
],
[
"Lee",
"Tae Hoon",
""
]
] | We study Brans-Dicke cosmology with an inverse power-law effective potential. By using dynamical analyses, we search for fixed points corresponding to the radiation-like matter and dark energy-dominated era of our Universe, and the stability of fixed points is also investigated. We find phase space trajectories which are attracted to the stable point of the dark energy-dominated era from unstable fixed points like matter-dominated era of the Universe. The dark energy comes from effective potentials of the Brans-Dicke field, whose variation (related to the time-variation of the gravitational coupling constant) is shown to be in good agreement with observational data. |
gr-qc/9712085 | Frans Pretorius | F. Pretorius, D. Vollick and W. Israel | An Operational Approach To Black Hole Entropy | 15 pages, LaTeX, submitted to Phys. Rev. D | Phys.Rev. D57 (1998) 6311-6316 | 10.1103/PhysRevD.57.6311 | null | gr-qc | null | In this paper we calculate the entropy of a thin spherical shell that
contracts reversibly from infinity down to its event horizon. We find that, for
a broad class of equations of state, the entropy of a non-extremal shell is
one-quarter of its area in the black hole limit. The considerations in this
paper suggest the following operational definition for the entropy of a black
hole: $S_{BH}$ is the equilibrium thermodynamic entropy that would be stored in
the material which gathers to form the black hole, if all of this material were
compressed into a thin layer near its gravitational radius. Since the entropy
for a given mass and area is maximized for thermal equilibrium we expect that
this is the maximum entropy that could be stored in the material before it
crosses the horizon. In the case of an extremal black hole the shell model does
not assign an unambiguous value to the entropy.
| [
{
"created": "Mon, 22 Dec 1997 09:03:17 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Pretorius",
"F.",
""
],
[
"Vollick",
"D.",
""
],
[
"Israel",
"W.",
""
]
] | In this paper we calculate the entropy of a thin spherical shell that contracts reversibly from infinity down to its event horizon. We find that, for a broad class of equations of state, the entropy of a non-extremal shell is one-quarter of its area in the black hole limit. The considerations in this paper suggest the following operational definition for the entropy of a black hole: $S_{BH}$ is the equilibrium thermodynamic entropy that would be stored in the material which gathers to form the black hole, if all of this material were compressed into a thin layer near its gravitational radius. Since the entropy for a given mass and area is maximized for thermal equilibrium we expect that this is the maximum entropy that could be stored in the material before it crosses the horizon. In the case of an extremal black hole the shell model does not assign an unambiguous value to the entropy. |
2312.16681 | Dario Sauro | Riccardo Martini, Gregorio Paci, Dario Sauro | Radiative corrections to the Starobinsky Lagrangian from Torsion
fluctuations | 26 pages | null | null | null | gr-qc hep-ph hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the running of the $R^2$ coupling in the Starobinsky Lagrangian
that stems from integrating out quantum torsion fluctuations on a maximally
symmetric Euclidean background. Our analysis is performed in a manifestly
covariant way, exploiting both the recently-introduced spin-parity
decomposition of torsion perturbations and the heat kernel technique. The
Lagrangian we start with is the most general one involving kinetic terms and
couplings to the scalar curvature that is compatible with a gauge-like symmetry
for the torsion. The latter removes the twice-longitudinal vector mode from the
spectrum, and it yields operators of maximum rank four.
| [
{
"created": "Wed, 27 Dec 2023 18:51:46 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Martini",
"Riccardo",
""
],
[
"Paci",
"Gregorio",
""
],
[
"Sauro",
"Dario",
""
]
] | We derive the running of the $R^2$ coupling in the Starobinsky Lagrangian that stems from integrating out quantum torsion fluctuations on a maximally symmetric Euclidean background. Our analysis is performed in a manifestly covariant way, exploiting both the recently-introduced spin-parity decomposition of torsion perturbations and the heat kernel technique. The Lagrangian we start with is the most general one involving kinetic terms and couplings to the scalar curvature that is compatible with a gauge-like symmetry for the torsion. The latter removes the twice-longitudinal vector mode from the spectrum, and it yields operators of maximum rank four. |
1207.7250 | Tetsuya Shiromizu | Tetsuya Shiromizu, Seiju Ohashi and Ryotaku Suzuki | A no-go on strictly stationary spacetimes in four/higher dimensions | 8 pages | null | 10.1103/PhysRevD.86.064041 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that strictly stationary spacetimes cannot have non-trivial
configurations of form fields/complex scalar fields and then the spacetime
should be exactly Minkowski or anti-deSitter spacetimes depending on the
presence of negative cosmological constant. That is, self-gravitating complex
scalar fields and form fields cannot exist.
| [
{
"created": "Tue, 31 Jul 2012 14:06:40 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Ohashi",
"Seiju",
""
],
[
"Suzuki",
"Ryotaku",
""
]
] | We show that strictly stationary spacetimes cannot have non-trivial configurations of form fields/complex scalar fields and then the spacetime should be exactly Minkowski or anti-deSitter spacetimes depending on the presence of negative cosmological constant. That is, self-gravitating complex scalar fields and form fields cannot exist. |
1110.6095 | Thomas L. Wilson | Thomas L. Wilson | A New Interpretation of Einstein's Cosmological Constant | 59 pages, 2 figures, 1 table | null | null | NASA-JSC Report Theor-Wil-04-2011 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new approach to the cosmological constant problem is proposed by modifying
Einstein's theory of general relativity, using instead a scalar-tensor theory
of gravitation. This theory of gravity crucially incorporates the concept of
quantum symmetry breaking. The role of the cosmological constant $\lambda$ as a
graviton mass in the weak-field limit is necessarily utilized. Because
$\lambda$ takes on two values as a broken symmetry, so does the graviton mass
-- one of which cannot be zero. Gravity now exhibits both long- and short-range
forces, by introducing hadron bags into strong interaction physics using a
nonlinear, self-interacting scalar $\sigma$-field coupled to the gravitational
Lagrangian.
| [
{
"created": "Tue, 25 Oct 2011 21:24:20 GMT",
"version": "v1"
}
] | 2011-10-28 | [
[
"Wilson",
"Thomas L.",
""
]
] | A new approach to the cosmological constant problem is proposed by modifying Einstein's theory of general relativity, using instead a scalar-tensor theory of gravitation. This theory of gravity crucially incorporates the concept of quantum symmetry breaking. The role of the cosmological constant $\lambda$ as a graviton mass in the weak-field limit is necessarily utilized. Because $\lambda$ takes on two values as a broken symmetry, so does the graviton mass -- one of which cannot be zero. Gravity now exhibits both long- and short-range forces, by introducing hadron bags into strong interaction physics using a nonlinear, self-interacting scalar $\sigma$-field coupled to the gravitational Lagrangian. |
gr-qc/0206077 | Claudio Dappiaggi | M. Carfora, C. Dappiaggi, A. Marzuoli | The modular geometry of Random Regge Triangulations | 36 pages corrected typos, enhanced introduction | Class.Quant.Grav. 19 (2002) 5195-5220 | 10.1088/0264-9381/19/20/312 | DFNT/T 2002/09 | gr-qc hep-th math-ph math.MP | null | We show that the introduction of triangulations with variable connectivity
and fluctuating egde-lengths (Random Regge Triangulations) allows for a
relatively simple and direct analyisis of the modular properties of 2
dimensional simplicial quantum gravity. In particular, we discuss in detail an
explicit bijection between the space of possible random Regge triangulations
(of given genus g and with N vertices) and a suitable decorated version of the
(compactified) moduli space of genus g Riemann surfaces with N punctures. Such
an analysis allows us to associate a Weil-Petersson metric with the set of
random Regge triangulations and prove that the corresponding volume provides
the dynamical triangulation partition function for pure gravity.
| [
{
"created": "Wed, 26 Jun 2002 13:48:10 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Sep 2002 13:39:03 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Carfora",
"M.",
""
],
[
"Dappiaggi",
"C.",
""
],
[
"Marzuoli",
"A.",
""
]
] | We show that the introduction of triangulations with variable connectivity and fluctuating egde-lengths (Random Regge Triangulations) allows for a relatively simple and direct analyisis of the modular properties of 2 dimensional simplicial quantum gravity. In particular, we discuss in detail an explicit bijection between the space of possible random Regge triangulations (of given genus g and with N vertices) and a suitable decorated version of the (compactified) moduli space of genus g Riemann surfaces with N punctures. Such an analysis allows us to associate a Weil-Petersson metric with the set of random Regge triangulations and prove that the corresponding volume provides the dynamical triangulation partition function for pure gravity. |
gr-qc/0508093 | Anthony N. Aguirre | Anthony Aguirre, Matthew C. Johnson | Dynamics and instability of false vacuum bubbles | 16 PRD-style pages including 11 embedded figures; accepted by PRD.
Revised version includes new solution, discussion of 'thermal activation',
added reference, fixed typos | Phys.Rev. D72 (2005) 103525 | 10.1103/PhysRevD.72.103525 | null | gr-qc hep-th | null | This paper examines the classical dynamics of false vacuum regions embedded
in surrounding regions of true vacuum, in the thin-wall limit. The dynamics of
all generally relativistically allowed solutions -- most but not all of which
have been previously studied -- are derived, enumerated, and interpreted. We
comment on the relation of these solutions to possible mechanisms whereby
inflating regions may be spawned from non-inflating ones. We then calculate the
dynamics of first order deviations from spherical symmetry, finding that many
solutions are unstable to such aspherical perturbations. The parameter space in
which the perturbations on bound solutions inevitably become nonlinear is
mapped. This instability has consequences for the Farhi-Guth-Guven mechanism
for baby universe production via quantum tunneling.
| [
{
"created": "Mon, 22 Aug 2005 20:25:19 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Nov 2005 21:43:31 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Aguirre",
"Anthony",
""
],
[
"Johnson",
"Matthew C.",
""
]
] | This paper examines the classical dynamics of false vacuum regions embedded in surrounding regions of true vacuum, in the thin-wall limit. The dynamics of all generally relativistically allowed solutions -- most but not all of which have been previously studied -- are derived, enumerated, and interpreted. We comment on the relation of these solutions to possible mechanisms whereby inflating regions may be spawned from non-inflating ones. We then calculate the dynamics of first order deviations from spherical symmetry, finding that many solutions are unstable to such aspherical perturbations. The parameter space in which the perturbations on bound solutions inevitably become nonlinear is mapped. This instability has consequences for the Farhi-Guth-Guven mechanism for baby universe production via quantum tunneling. |
1205.5715 | Mitsuhiro Matsumoto | Mitsuhiro Matsumoto, Hirotaka Yoshino, Hideo Kodama | Time evolution of a thin black ring via Hawking radiation | 28 pages, 6 figures | Phys. Rev. D 89, 044016 (2014) | 10.1103/PhysRevD.89.044016 | KEK-TH-1550 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black objects lose their mass and angular momenta through evaporation by
Hawking radiation, and the investigation of their time evolution has a long
history. In this paper, we study this problem for a five-dimensional doubly
spinning black ring. The black ring is assumed to emit only massless scalar
particles. We consider a thin black ring with a small thickness parameter,
$\lambda\ll 1$, which can be approximated by a boosted Kerr string locally. We
show that a thin black ring evaporates with fixing its thickness parameter
$\lambda$. Further, in the case of an Emparan-Reall black ring, we derive
analytic formulas for the time evolution, which has one parameter to be
evaluated numerically. We find that the lifetime of a thin black ring is
shorter by a factor of $O(\lambda^2)$ compared to a five-dimensional
Schwarzschild black hole with the same initial mass. We also study detailed
properties of the Hawking radiation from the thin black ring, including the
energy and angular spectra of emitted particles.
| [
{
"created": "Fri, 25 May 2012 14:52:32 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Dec 2013 09:16:16 GMT",
"version": "v2"
}
] | 2014-02-19 | [
[
"Matsumoto",
"Mitsuhiro",
""
],
[
"Yoshino",
"Hirotaka",
""
],
[
"Kodama",
"Hideo",
""
]
] | Black objects lose their mass and angular momenta through evaporation by Hawking radiation, and the investigation of their time evolution has a long history. In this paper, we study this problem for a five-dimensional doubly spinning black ring. The black ring is assumed to emit only massless scalar particles. We consider a thin black ring with a small thickness parameter, $\lambda\ll 1$, which can be approximated by a boosted Kerr string locally. We show that a thin black ring evaporates with fixing its thickness parameter $\lambda$. Further, in the case of an Emparan-Reall black ring, we derive analytic formulas for the time evolution, which has one parameter to be evaluated numerically. We find that the lifetime of a thin black ring is shorter by a factor of $O(\lambda^2)$ compared to a five-dimensional Schwarzschild black hole with the same initial mass. We also study detailed properties of the Hawking radiation from the thin black ring, including the energy and angular spectra of emitted particles. |
1905.01479 | Jian-Yang Zhu | Xi-Bin Li and Jian-Yang Zhu | Thermal effect on primordial black holes in standard Higgs minimum
double-well potential | 9 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We attempt a new scheme to combine the Higgs field in the minimal standard
model and the statistic physics with thermal effect together. By introducing
the stochastic differential equation in FRW metric frame which is something
like the warm inflation model but not exactly the same. By using the previous
researches on Fokker-Planck equation with double-well potential, we find the
abundance of primordial black holes (PBHs) dominate at a special mass and the
PBHs with extremely large or extremely small mass could be almost excluded. In
addition, two perturbed model within this frame are employed, one is the model
with symmetry breaking and another is stochastic resonance. The former may
increase the probability to the generation of PBHs, while the latter may both
increase and decrease the probability. Finally, we also discuss the possibility
on extension this scenario to other models.
| [
{
"created": "Sat, 4 May 2019 11:52:10 GMT",
"version": "v1"
}
] | 2019-05-07 | [
[
"Li",
"Xi-Bin",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | We attempt a new scheme to combine the Higgs field in the minimal standard model and the statistic physics with thermal effect together. By introducing the stochastic differential equation in FRW metric frame which is something like the warm inflation model but not exactly the same. By using the previous researches on Fokker-Planck equation with double-well potential, we find the abundance of primordial black holes (PBHs) dominate at a special mass and the PBHs with extremely large or extremely small mass could be almost excluded. In addition, two perturbed model within this frame are employed, one is the model with symmetry breaking and another is stochastic resonance. The former may increase the probability to the generation of PBHs, while the latter may both increase and decrease the probability. Finally, we also discuss the possibility on extension this scenario to other models. |
1612.01823 | Breno Giacchini | Breno L. Giacchini | Experimental limits on the free parameters of higher-derivative gravity | 4 pages. Contribution to the proceedings of the 14th Marcel Grossmann
Meeting, Rome 12-18 July 2015 | The Fourteenth Marcel Grossmann Meeting: pp. 1340-1345 (2017) | 10.1142/9789813226609_0109 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fourth-derivative gravity has two free parameters, $\alpha$ and $\beta$,
which couple the curvature-squared terms $R^2$ and $R_{\mu\nu}^2$. Relativistic
effects and short-range laboratory experiments can be used to provide upper
limits to these constants. In this work we briefly review both types of
experimental results in the context of higher-derivative gravity. The strictest
limit follows from the second kind of test. Interestingly enough, the bound on
$\beta$ due to semiclassical light deflection at the solar limb is only one
order of magnitude larger.
| [
{
"created": "Tue, 6 Dec 2016 14:29:37 GMT",
"version": "v1"
}
] | 2017-12-12 | [
[
"Giacchini",
"Breno L.",
""
]
] | Fourth-derivative gravity has two free parameters, $\alpha$ and $\beta$, which couple the curvature-squared terms $R^2$ and $R_{\mu\nu}^2$. Relativistic effects and short-range laboratory experiments can be used to provide upper limits to these constants. In this work we briefly review both types of experimental results in the context of higher-derivative gravity. The strictest limit follows from the second kind of test. Interestingly enough, the bound on $\beta$ due to semiclassical light deflection at the solar limb is only one order of magnitude larger. |
1804.05744 | Gerard Hooft 't | Gerard t Hooft | What happens in a black hole when a particle meets its antipode | 15 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The notion of antipodal identification on the black hole horizon is further
explained and elaborated. Contrasting with numerous attempts in the literature
to make fuzzy, poorly motivated models for black holes, we explain how, with an
absolute minimum of assumptions, known laws of local physics suffice to
calculate the unitary evolution law for a Schwarzschild black hole. Earlier
work by the author, which explains how firewalls can and must be avoided, while
also the information paradox disappears, ran into its one remaining problem:
how to explain it better to the community. Antipodal identification is a
natural way to replace thermally mixed states by pure quantum states, without
the need to hide our ignorance in "chaos". We do encounter a strange looking
sign switch in the relation of particles to their antipodes near the horizon.
This sign switch is necessary to recover complete unitarity without any loss of
information anywhere, while restoring locality. Although there are some
important remaining problems, we advertise our approach as a healthy
alternative to the reliance on AdS/CFT conjectures, which, we claim, do not
guarantee to provide reliable answers.
| [
{
"created": "Mon, 16 Apr 2018 15:38:51 GMT",
"version": "v1"
}
] | 2018-04-17 | [
[
"Hooft",
"Gerard t",
""
]
] | The notion of antipodal identification on the black hole horizon is further explained and elaborated. Contrasting with numerous attempts in the literature to make fuzzy, poorly motivated models for black holes, we explain how, with an absolute minimum of assumptions, known laws of local physics suffice to calculate the unitary evolution law for a Schwarzschild black hole. Earlier work by the author, which explains how firewalls can and must be avoided, while also the information paradox disappears, ran into its one remaining problem: how to explain it better to the community. Antipodal identification is a natural way to replace thermally mixed states by pure quantum states, without the need to hide our ignorance in "chaos". We do encounter a strange looking sign switch in the relation of particles to their antipodes near the horizon. This sign switch is necessary to recover complete unitarity without any loss of information anywhere, while restoring locality. Although there are some important remaining problems, we advertise our approach as a healthy alternative to the reliance on AdS/CFT conjectures, which, we claim, do not guarantee to provide reliable answers. |
gr-qc/0610022 | Shankaranarayanan S | Saurya Das (Lethbridge U), S. Shankaranarayanan (AEI, Golm) | Entanglement as a source of black hole entropy | 12 pages, latex, 5 figures. Invited talk by SD at `Recent
Developments in Gravity' (NEB XII), Nafplion, Greece, 30 June 2006. To appear
in Journal of Physics: Conference Series; V2: References added, Minor changes
to match published version | J.Phys.Conf.Ser.68:012015,2007 | 10.1088/1742-6596/68/1/012015 | AEI-2006-075 | gr-qc hep-th quant-ph | null | We review aspects of black hole thermodynamics, and show how entanglement of
a quantum field between the inside and outside of a horizon can account for the
area-proportionality of black hole entropy, provided the field is in its ground
state. We show that the result continues to hold for Coherent States and
Squeezed States, while for Excited States, the entropy scales as a power of
area less than unity. We also identify location of the degrees of freedom which
give rise to the above entropy.
| [
{
"created": "Fri, 6 Oct 2006 06:38:19 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Jun 2007 15:13:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Das",
"Saurya",
"",
"Lethbridge U"
],
[
"Shankaranarayanan",
"S.",
"",
"AEI, Golm"
]
] | We review aspects of black hole thermodynamics, and show how entanglement of a quantum field between the inside and outside of a horizon can account for the area-proportionality of black hole entropy, provided the field is in its ground state. We show that the result continues to hold for Coherent States and Squeezed States, while for Excited States, the entropy scales as a power of area less than unity. We also identify location of the degrees of freedom which give rise to the above entropy. |
1312.3147 | Alexander Kamenshchik | A.O. Barvinsky and A.Yu. Kamenshchik | Selection rules for the Wheeler-DeWitt equation in quantum cosmology | final version, to appear in Physical Review D | Physical Review D 89 (2014) 043526 | 10.1103/PhysRevD.89.043526 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Selection of physically meaningful solutions of the Wheeler-DeWitt equation
for the wavefunction in quantum cosmology, can be attained by a reduction of
the theory to the sector of true physical degrees of freedom and their
canonical quantization. The resulting physical wavefunction unitarily evolving
in the time variable introduced within this reduction can then be raised to the
level of the cosmological wavefunction in superspace of 3-metrics. We apply
this technique in several simple minisuperspace models and discuss both at
classical and quantum level physical reduction in {\em extrinsic} time -- the
time variable determined in terms of extrinsic curvature. Only this extrinsic
time gauge can be consistently used in vicinity of turning points and bounces
where the scale factor reaches extremum. Since the 3-metric scale factor is
canonically dual to extrinsic time variable, the transition from the physical
wavefunction to the wavefunction in superspace represents a kind of the
generalized Fourier transform. This transformation selects square integrable
solutions of the Wheeler-DeWitt equation, which guarantee Hermiticity of
canonical operators of the Dirac quantization scheme. Semiclassically this
means that wavefunctions are represented by oscillating waves in classically
allowed domains of superspace and exponentially fall off in classically
forbidden (underbarrier) regions. This is explicitly demonstrated in flat FRW
model with a scalar field having a constant negative potential and for the case
of phantom scalar field with a positive potential. The FRW model of a scalar
field with a vanishing potential does not lead to selection rules for solutions
of the Wheeler-DeWitt equation, but this does not violate Hermiticity
properties, because all these solutions are anyway of plane wave type and
describe cosmological dynamics without turning points and bounces.
| [
{
"created": "Wed, 11 Dec 2013 12:52:46 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jan 2014 08:46:21 GMT",
"version": "v2"
}
] | 2014-05-06 | [
[
"Barvinsky",
"A. O.",
""
],
[
"Kamenshchik",
"A. Yu.",
""
]
] | Selection of physically meaningful solutions of the Wheeler-DeWitt equation for the wavefunction in quantum cosmology, can be attained by a reduction of the theory to the sector of true physical degrees of freedom and their canonical quantization. The resulting physical wavefunction unitarily evolving in the time variable introduced within this reduction can then be raised to the level of the cosmological wavefunction in superspace of 3-metrics. We apply this technique in several simple minisuperspace models and discuss both at classical and quantum level physical reduction in {\em extrinsic} time -- the time variable determined in terms of extrinsic curvature. Only this extrinsic time gauge can be consistently used in vicinity of turning points and bounces where the scale factor reaches extremum. Since the 3-metric scale factor is canonically dual to extrinsic time variable, the transition from the physical wavefunction to the wavefunction in superspace represents a kind of the generalized Fourier transform. This transformation selects square integrable solutions of the Wheeler-DeWitt equation, which guarantee Hermiticity of canonical operators of the Dirac quantization scheme. Semiclassically this means that wavefunctions are represented by oscillating waves in classically allowed domains of superspace and exponentially fall off in classically forbidden (underbarrier) regions. This is explicitly demonstrated in flat FRW model with a scalar field having a constant negative potential and for the case of phantom scalar field with a positive potential. The FRW model of a scalar field with a vanishing potential does not lead to selection rules for solutions of the Wheeler-DeWitt equation, but this does not violate Hermiticity properties, because all these solutions are anyway of plane wave type and describe cosmological dynamics without turning points and bounces. |
2308.02375 | Polina Dyadina | P.I. Dyadina, N.A. Avdeev | Thin accretion disk signatures in hybrid metric-Palatini gravity | 21 pages, 14 figures | Eur. Phys. J. C 84, 103 (2024) | 10.1140/epjc/s10052-024-12465-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, accretion onto a static spherically symmetric black hole
in the hybrid metric-Palatini gravity is considered. The Novikov-Thorne model
for a relativistic thin accretion disk is used. The energy flux, temperature
distribution, emission spectrum and energy conversion efficiency of accretion
disks around such black holes are numerically calculated. A comparison with the
results for a Schwarzschild black hole is made and conclusions about the
viability of the model are drawn. As a result, it is obtained that the
accretion disks around black holes in hybrid metric-Palatini gravity are colder
and less luminous than in general relativity.
| [
{
"created": "Fri, 4 Aug 2023 15:15:34 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Sep 2023 18:27:04 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Feb 2024 10:33:49 GMT",
"version": "v3"
}
] | 2024-02-05 | [
[
"Dyadina",
"P. I.",
""
],
[
"Avdeev",
"N. A.",
""
]
] | In the present work, accretion onto a static spherically symmetric black hole in the hybrid metric-Palatini gravity is considered. The Novikov-Thorne model for a relativistic thin accretion disk is used. The energy flux, temperature distribution, emission spectrum and energy conversion efficiency of accretion disks around such black holes are numerically calculated. A comparison with the results for a Schwarzschild black hole is made and conclusions about the viability of the model are drawn. As a result, it is obtained that the accretion disks around black holes in hybrid metric-Palatini gravity are colder and less luminous than in general relativity. |
gr-qc/0108084 | Satoshi Yamaguchi | Satoshi Yamaguchi (Kyoto Univ.) | Enhancon and Resolution of Singularity | 10 pages, LaTeX, 8 figures, talk at the Meeting of Frontier of
Cosmology and Gravitation, Kyoto, Japan, 25-27 April 2001, v2: minor changes,
typos corrected | null | null | KUCP-0194 | gr-qc | null | We review the enhancon mechanism proposed by Johnson, Peet and Polchinski. If
we consider the D6-brane wrapped on K3, then there appear a naked singularity
called ``repulson'' in the supergravity solution. But this singularity is
resolved by a shell structure called ``enhancon''. In the interior of the
enhancon, the abelian gauge symmetry is enhanced to a nonabelian one, and
ordinary supergravity is no more reliable. We also review the interpretation of
enhancon as fuzzy sphere. This paper is the contribution to the proceedings of
"Frontier of Cosmology and Gravitation", April 25-27 2001, YITP.
| [
{
"created": "Fri, 31 Aug 2001 08:08:04 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Sep 2001 08:30:51 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Yamaguchi",
"Satoshi",
"",
"Kyoto Univ."
]
] | We review the enhancon mechanism proposed by Johnson, Peet and Polchinski. If we consider the D6-brane wrapped on K3, then there appear a naked singularity called ``repulson'' in the supergravity solution. But this singularity is resolved by a shell structure called ``enhancon''. In the interior of the enhancon, the abelian gauge symmetry is enhanced to a nonabelian one, and ordinary supergravity is no more reliable. We also review the interpretation of enhancon as fuzzy sphere. This paper is the contribution to the proceedings of "Frontier of Cosmology and Gravitation", April 25-27 2001, YITP. |
1909.07807 | Faizuddin Ahmed | Faizuddin Ahmed | Comment on "Ground state of a bosonic massive charged particle in the
presence of external fields in a G\"{o}del-type space-time [Eur. Phys. J.
Plus (2018) 133 : 530]" | This is a comment on article arXiv:1807.02838 [hep-th]; overall
presentation improved, accepted for publication in EPJ Plus | Eur. Phys. J. Plus (2020) 135 (02):174 | 10.1140/epjp/s13360-020-00196-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out incorrect equations derived in a paper published in this journal
Ref. [1] (E. O. Silva, Eur. Phys. J. Plus (2018) 133 : 530) for the
Klein-Gordon equation with the Aharonov-Bohm and Coulomb potentials in a
G\"{o}del-type space-time. We derive the final form of the radial wave equation
of the Klein-Gordon equation in the Som-Raychaudhuri space-time with these
potentials and show that the derive equation here jeopardize the equations
obtained in Ref. [1] and therefore, the energy eigenvalues presented there is
incorrect.
| [
{
"created": "Sun, 15 Sep 2019 12:40:54 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Sep 2019 10:35:41 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Feb 2020 04:22:06 GMT",
"version": "v3"
}
] | 2020-02-04 | [
[
"Ahmed",
"Faizuddin",
""
]
] | We point out incorrect equations derived in a paper published in this journal Ref. [1] (E. O. Silva, Eur. Phys. J. Plus (2018) 133 : 530) for the Klein-Gordon equation with the Aharonov-Bohm and Coulomb potentials in a G\"{o}del-type space-time. We derive the final form of the radial wave equation of the Klein-Gordon equation in the Som-Raychaudhuri space-time with these potentials and show that the derive equation here jeopardize the equations obtained in Ref. [1] and therefore, the energy eigenvalues presented there is incorrect. |
2212.06103 | Raimon Luna | Raimon Luna, Juan Calder\'on Bustillo, Juan Jos\'e Seoane Mart\'inez,
Alejandro Torres-Forn\'e, Jos\'e A. Font | Solving the Teukolsky equation with physics-informed neural networks | 12 pages, 7 figures. v2: Matches published version, minor typos
corrected | Phys.Rev.D 107 (2023) 6, 064025 | 10.1103/PhysRevD.107.064025 | null | gr-qc astro-ph.HE physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use physics-informed neural networks (PINNs) to compute the first
quasi-normal modes of the Kerr geometry via the Teukolsky equation. This
technique allows us to extract the complex frequencies and separation constants
of the equation without the need for sophisticated numerical techniques, and
with an almost immediate implementation under the \texttt{PyTorch} framework.
We are able to compute the oscillation frequencies and damping times for
arbitrary black hole spins and masses, with accuracy typically below the
percentual level as compared to the accepted values in the literature. We find
that PINN-computed quasi-normal modes are indistinguishable from those obtained
through existing methods at signal-to-noise ratios (SNRs) larger than 100,
making the former reliable for gravitational-wave data analysis in the mid
term, before the arrival of third-generation detectors like LISA or the
Einstein Telescope, where SNRs of ${\cal O}(1000)$ might be achieved.
| [
{
"created": "Mon, 12 Dec 2022 18:23:41 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2024 17:17:05 GMT",
"version": "v2"
}
] | 2024-04-09 | [
[
"Luna",
"Raimon",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Martínez",
"Juan José Seoane",
""
],
[
"Torres-Forné",
"Alejandro",
""
],
[
"Font",
"José A.",
""
]
] | We use physics-informed neural networks (PINNs) to compute the first quasi-normal modes of the Kerr geometry via the Teukolsky equation. This technique allows us to extract the complex frequencies and separation constants of the equation without the need for sophisticated numerical techniques, and with an almost immediate implementation under the \texttt{PyTorch} framework. We are able to compute the oscillation frequencies and damping times for arbitrary black hole spins and masses, with accuracy typically below the percentual level as compared to the accepted values in the literature. We find that PINN-computed quasi-normal modes are indistinguishable from those obtained through existing methods at signal-to-noise ratios (SNRs) larger than 100, making the former reliable for gravitational-wave data analysis in the mid term, before the arrival of third-generation detectors like LISA or the Einstein Telescope, where SNRs of ${\cal O}(1000)$ might be achieved. |
2003.12999 | Sijie Gao | Chengcheng Liu and Sijie Gao | Overcharging magnetized black holes at linear order and the weak cosmic
censorship conjecture | 13 pages, 1 figure | Phys. Rev. D 101, 124067 (2020) | 10.1103/PhysRevD.101.124067 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Evidences have been found that the weak cosmic censorship conjecture could be
violated if test particles with charge and angular momentum are injected into a
black hole. However, second-order corrections and fine-tunings on the
particle's parameters are required in previous studies, indicating that
self-force and radiative effects must be taken into account. In this paper, we
first consider a magnetically charged particle falling into an extremal Bardeen
black hole, which is regular (with no singularity) and has a magnetic monopole
at the center. We then investigate a general class of magnetic black holes with
or without singularities. In all the cases, we show that the test particle with
magnetic charge could overcharge the black hole, causing possible violation of
the weak cosmic censorship conjecture. In contrast to previous arguments in the
literature, second-order corrections are not necessary in our analysis and the
results are not sensitive to the particle's parameters. Our work indicates that
the self-force effect, which is related to the second-order correction, may not
help rescue the weak cosmic censorship conjecture in our examples.
| [
{
"created": "Sun, 29 Mar 2020 10:53:56 GMT",
"version": "v1"
}
] | 2020-07-08 | [
[
"Liu",
"Chengcheng",
""
],
[
"Gao",
"Sijie",
""
]
] | Evidences have been found that the weak cosmic censorship conjecture could be violated if test particles with charge and angular momentum are injected into a black hole. However, second-order corrections and fine-tunings on the particle's parameters are required in previous studies, indicating that self-force and radiative effects must be taken into account. In this paper, we first consider a magnetically charged particle falling into an extremal Bardeen black hole, which is regular (with no singularity) and has a magnetic monopole at the center. We then investigate a general class of magnetic black holes with or without singularities. In all the cases, we show that the test particle with magnetic charge could overcharge the black hole, causing possible violation of the weak cosmic censorship conjecture. In contrast to previous arguments in the literature, second-order corrections are not necessary in our analysis and the results are not sensitive to the particle's parameters. Our work indicates that the self-force effect, which is related to the second-order correction, may not help rescue the weak cosmic censorship conjecture in our examples. |
1908.07103 | Zack Carson | Zack Carson and Kent Yagi | Parameterized and Consistency Tests of Gravity with Gravitational Waves:
Current and Future | To appear in the proceedings of the conference 'Recent Progress in
Relativistic Astrophysics', Shanghai, China, 6-8 May 2019; Fixed error on
Fig. 4 axis label; Updated DECIGO noise curve; Fixed typo in equations | null | 10.3390/proceedings2019017005 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave observations offer unique opportunities to probe gravity
in the strong and dynamical regime, which was difficult to access previously.
We here review two theory-agnostic ways to carry out tests of general
relativity with gravitational waves, namely (i) parameterized waveform tests
and (ii) consistency tests between the inspiral and merger-ringdown portions.
For each method, we explain the formalism, followed by results from existing
events, and finally we discuss future prospects with upgraded detectors,
including the possibility of using multi-band gravitational-wave observations
with ground-based and space-borne interferometers. We show that such future
observations have the potential to improve upon current bounds on theories
beyond general relativity by many orders of magnitude. We conclude by listing
several open questions that remain to be addressed.
| [
{
"created": "Mon, 19 Aug 2019 23:20:15 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Sep 2019 04:00:21 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Oct 2019 22:35:17 GMT",
"version": "v3"
},
{
"created": "Sat, 26 Oct 2019 02:27:25 GMT",
"version": "v4"
}
] | 2020-05-19 | [
[
"Carson",
"Zack",
""
],
[
"Yagi",
"Kent",
""
]
] | Gravitational wave observations offer unique opportunities to probe gravity in the strong and dynamical regime, which was difficult to access previously. We here review two theory-agnostic ways to carry out tests of general relativity with gravitational waves, namely (i) parameterized waveform tests and (ii) consistency tests between the inspiral and merger-ringdown portions. For each method, we explain the formalism, followed by results from existing events, and finally we discuss future prospects with upgraded detectors, including the possibility of using multi-band gravitational-wave observations with ground-based and space-borne interferometers. We show that such future observations have the potential to improve upon current bounds on theories beyond general relativity by many orders of magnitude. We conclude by listing several open questions that remain to be addressed. |
gr-qc/0110101 | null | Sergei Kopeikin and Bahram Mashhoon (Department of Physics and
Astronomy, University of Missouri-Columbia) | Gravitomagnetic Effects in the Propagation of Electromagnetic Waves in
Variable Gravitational Fields of Arbitrary-Moving and Spinning Bodies | 36 pages, 1 figure, submitted to Phys. Rev. D | Phys.Rev.D65:064025,2002 | 10.1103/PhysRevD.65.064025 | null | gr-qc astro-ph | null | Propagation of light in the gravitational field of self-gravitating spinning
bodies moving with arbitrary velocities is discussed. The gravitational field
is assumed to be "weak" everywhere. Equations of motion of a light ray are
solved in the first post-Minkowskian approximation that is linear with respect
to the universal gravitational constant $G$. We do not restrict ourselves with
the approximation of gravitational lens so that the solution of light geodesics
is applicable for arbitrary locations of source of light and observer. This
formalism is applied for studying corrections to the Shapiro time delay in
binary pulsars caused by the rotation of pulsar and its companion. We also
derive the correction to the light deflection angle caused by rotation of
gravitating bodies in the solar system (Sun, planets) or a gravitational lens.
The gravitational shift of frequency due to the combined translational and
rotational motions of light-ray-deflecting bodies is analyzed as well. We give
a general derivation of the formula describing the relativistic rotation of the
plane of polarization of electromagnetic waves (Skrotskii effect). This formula
is valid for arbitrary translational and rotational motion of gravitating
bodies and greatly extends the results of previous researchers. Finally, we
discuss the Skrotskii effect for gravitational waves emitted by localized
sources such as a binary system. The theoretical results of this paper can be
applied for studying various relativistic effects in microarcsecond space
astrometry and developing corresponding algorithms for data processing in space
astrometric missions such as FAME, SIM, and GAIA.
| [
{
"created": "Tue, 23 Oct 2001 23:45:30 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Oct 2001 14:53:42 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Kopeikin",
"Sergei",
"",
"Department of Physics and\n Astronomy, University of Missouri-Columbia"
],
[
"Mashhoon",
"Bahram",
"",
"Department of Physics and\n Astronomy, University of Missouri-Columbia"
]
] | Propagation of light in the gravitational field of self-gravitating spinning bodies moving with arbitrary velocities is discussed. The gravitational field is assumed to be "weak" everywhere. Equations of motion of a light ray are solved in the first post-Minkowskian approximation that is linear with respect to the universal gravitational constant $G$. We do not restrict ourselves with the approximation of gravitational lens so that the solution of light geodesics is applicable for arbitrary locations of source of light and observer. This formalism is applied for studying corrections to the Shapiro time delay in binary pulsars caused by the rotation of pulsar and its companion. We also derive the correction to the light deflection angle caused by rotation of gravitating bodies in the solar system (Sun, planets) or a gravitational lens. The gravitational shift of frequency due to the combined translational and rotational motions of light-ray-deflecting bodies is analyzed as well. We give a general derivation of the formula describing the relativistic rotation of the plane of polarization of electromagnetic waves (Skrotskii effect). This formula is valid for arbitrary translational and rotational motion of gravitating bodies and greatly extends the results of previous researchers. Finally, we discuss the Skrotskii effect for gravitational waves emitted by localized sources such as a binary system. The theoretical results of this paper can be applied for studying various relativistic effects in microarcsecond space astrometry and developing corresponding algorithms for data processing in space astrometric missions such as FAME, SIM, and GAIA. |
2112.12048 | Fabrizio Corelli | Fabrizio Corelli | Instability of Schwarzschild Black Holes in Einstein-scalar-Gauss-Bonnet
Gravity: Perturbative Approach and Time-Domain Analysis | 81 pages, 13 figures, Master thesis defended at Sapienza University
of Rome on 20th October 2020 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the instability of Schwarzschild black holes and the appearance of
scalarized solutions in Einstein-scalar-Gauss-Bonnet gravity performing a
time-domain analysis in a perturbative scheme. First we consider a quadratic
coupling function and we perform an expansion for a small perturbation of the
scalar field around the Schwarzschild solution up to the second order; we do
not observe any stable scalarized configuration, in agreement with previous
studies. We then consider the cases of quartic and exponential coupling, using
an expansion for small values of the Newton's constant, in order to include the
nonlinear terms introduced by the coupling in the field equations; in this case
we observe the appearance of stable scalarized solutions different from those
found in literature. The discrepancy can be an artifact of the perturbative
approach.
| [
{
"created": "Wed, 22 Dec 2021 17:18:04 GMT",
"version": "v1"
}
] | 2021-12-23 | [
[
"Corelli",
"Fabrizio",
""
]
] | We study the instability of Schwarzschild black holes and the appearance of scalarized solutions in Einstein-scalar-Gauss-Bonnet gravity performing a time-domain analysis in a perturbative scheme. First we consider a quadratic coupling function and we perform an expansion for a small perturbation of the scalar field around the Schwarzschild solution up to the second order; we do not observe any stable scalarized configuration, in agreement with previous studies. We then consider the cases of quartic and exponential coupling, using an expansion for small values of the Newton's constant, in order to include the nonlinear terms introduced by the coupling in the field equations; in this case we observe the appearance of stable scalarized solutions different from those found in literature. The discrepancy can be an artifact of the perturbative approach. |
2104.06691 | Xiongjun Fang | Wei Yang, Xiongjun Fang, Jiliang Jing | Consistency between dynamical and thermodynamical stabilities for
charged self-gravitating perfect fluid | 9 pages | General Relativity and Gravitation (2021) 53:81 | 10.1007/s10714-021-02852-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entropy principle shows that, for self-gravitating perfect fluid, the
Einstein field equations can be derived from the extrema of the total entropy,
and the thermodynamical stability criterion are equivalent to the dynamical
stability criterion. In this paper, we recast the dynamical criterion for the
charged self-gravitating perfect fluid in Einstein-Maxwell theory, and further
give the criterion of the star with barotropic condition. In order to obtain
the thermodynamical stability criterion, first we get the general formula of
the second variation of the total entropy for charged perfect fluid case, and
then obtain the thermodynamical criterion for radial perturbation. We show that
these two stability criterion are the same, which suggest that the inherent
connection between gravity and thermodynamic even when the electric field is
taken into account.
| [
{
"created": "Wed, 14 Apr 2021 08:34:04 GMT",
"version": "v1"
}
] | 2021-08-27 | [
[
"Yang",
"Wei",
""
],
[
"Fang",
"Xiongjun",
""
],
[
"Jing",
"Jiliang",
""
]
] | The entropy principle shows that, for self-gravitating perfect fluid, the Einstein field equations can be derived from the extrema of the total entropy, and the thermodynamical stability criterion are equivalent to the dynamical stability criterion. In this paper, we recast the dynamical criterion for the charged self-gravitating perfect fluid in Einstein-Maxwell theory, and further give the criterion of the star with barotropic condition. In order to obtain the thermodynamical stability criterion, first we get the general formula of the second variation of the total entropy for charged perfect fluid case, and then obtain the thermodynamical criterion for radial perturbation. We show that these two stability criterion are the same, which suggest that the inherent connection between gravity and thermodynamic even when the electric field is taken into account. |
1811.11600 | Xiaoning Wu | Xiaoning Wu and Xiao Zhang | Energy-momentum in general relativity | 21 pages | Published on Memorial Volume for Yi-Shi Duan. Edited by Mo-Lin Ge,
Rong-Gen Cai, Yu-Xiao Liu. pp 189-209. World Scientific 2018 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly review of the definitions of the total energy, the total linear
momentum and the angular momentum of gravitational field when the cosmological
constant is zero. In particular, we show pseudo-tensor's definition of the
energy and the momentum given by Prof. Duan in 1963 agree with the ADM total
energy-momentum and the Bondi energy-momentum at spatial and null infinity
respectively. We also review the relevant energy-momentum inequalities.
Finally, we provide a short review of the positive energy theorem and the
peeling property of the Newmann-Penrose quantities when the cosmological
constant is positive.
| [
{
"created": "Wed, 28 Nov 2018 14:49:41 GMT",
"version": "v1"
}
] | 2018-11-29 | [
[
"Wu",
"Xiaoning",
""
],
[
"Zhang",
"Xiao",
""
]
] | We briefly review of the definitions of the total energy, the total linear momentum and the angular momentum of gravitational field when the cosmological constant is zero. In particular, we show pseudo-tensor's definition of the energy and the momentum given by Prof. Duan in 1963 agree with the ADM total energy-momentum and the Bondi energy-momentum at spatial and null infinity respectively. We also review the relevant energy-momentum inequalities. Finally, we provide a short review of the positive energy theorem and the peeling property of the Newmann-Penrose quantities when the cosmological constant is positive. |
2401.12330 | Narasimha Reddy Gosala | Narasimha Reddy Gosala, Arundhati Dasgupta | Effect of Gravitational Waves on Yang-Mills condensates | 26 pages, 20 figures; Includes a discussion on motivation and
implications of YM fields in the context of cosmology in the introduction and
conclusion; typos corrected; Additional references included | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article, we investigate the interactions of a Yang-Mills (YM) wave
fluctuation of a classical isotropic, homogeneous YM condensate, which models
gluon plasma, with a Gravitational Wave (GW). We re-analyse the study of
fluctuations of the gluon plasma using vector decomposition of the gauge field
into scalar, longitudinal, and transverse modes. We find that there is an
energy transfer between isotropic gluon condensate and plasmon modes, but the
effect is delayed, and dependent on the initial conditions. We also studied
quarks in the background of YM condensate and GW. We find that the quarks break
the isotropy of the condensate and the GW couples quarks of different flavours
of the SU(2) group. The GW induces flavour fluctuations, and this has
interesting implications for experimental observations and quark-gluon plasma
physics.
| [
{
"created": "Mon, 22 Jan 2024 19:45:11 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Feb 2024 17:22:13 GMT",
"version": "v2"
}
] | 2024-02-23 | [
[
"Gosala",
"Narasimha Reddy",
""
],
[
"Dasgupta",
"Arundhati",
""
]
] | In this article, we investigate the interactions of a Yang-Mills (YM) wave fluctuation of a classical isotropic, homogeneous YM condensate, which models gluon plasma, with a Gravitational Wave (GW). We re-analyse the study of fluctuations of the gluon plasma using vector decomposition of the gauge field into scalar, longitudinal, and transverse modes. We find that there is an energy transfer between isotropic gluon condensate and plasmon modes, but the effect is delayed, and dependent on the initial conditions. We also studied quarks in the background of YM condensate and GW. We find that the quarks break the isotropy of the condensate and the GW couples quarks of different flavours of the SU(2) group. The GW induces flavour fluctuations, and this has interesting implications for experimental observations and quark-gluon plasma physics. |
1706.06400 | Andronikos Paliathanasis | Andronikos Paliathanasis | Analytic Solution of the Starobinsky Model for Inflation | 5 pages, references added, to appear in EPJC | Eur. Phys. J. C 77, 438 (2017) | 10.1140/epjc/s10052-017-5009-0 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the field equations of the Starobinsky model for inflation in a
Friedmann-Lema\^{\i}tre-Robertson-Walker constitute an integrable system as the
field equations pass the singularity test. The analytical solution in terms of
a Painlev\'{e} Series for the Starobinsky model is presented for the case of
zero and nonzero spatial curvature. In both cases the leading-order term
describes the radiation era provided by the corresponding higher-order theory.
| [
{
"created": "Tue, 20 Jun 2017 13:06:09 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jun 2017 15:26:30 GMT",
"version": "v2"
}
] | 2017-07-05 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We prove that the field equations of the Starobinsky model for inflation in a Friedmann-Lema\^{\i}tre-Robertson-Walker constitute an integrable system as the field equations pass the singularity test. The analytical solution in terms of a Painlev\'{e} Series for the Starobinsky model is presented for the case of zero and nonzero spatial curvature. In both cases the leading-order term describes the radiation era provided by the corresponding higher-order theory. |
2107.08352 | Yan-Gang Miao | Xin-Chang Cai, Yan-Gang Miao | Can we know about black hole thermodynamics through shadows? | v1: 31 pages, 11 figures, a new paper regarding shadow and
thermodynamics for both spherically symmetric and rotating black holes,
substantial new results for rotating black holes, only a small part of
discussions on shadow and scalar curvature for spherically symmetric black
holes overlapping with arXiv:2101.10780; v4: clarifications added, typos
corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the relationship between shadow radius and microstructure for
a general static spherically symmetric black hole and confirm their close
connection. In this regard, we take the Reissner-Nordstr\"om (AdS) black hole
as an example to do the concrete analysis. On the other hand, we study for the
Kerr (AdS) black hole the relationship between its shadow and thermodynamics in
the aspects of phase transition and microstructure. Our results for the Kerr
(AdS) black hole show that the shadow radius $r_{\rm sh}$, the deformation
parameters $\delta_s$ and $k_s$, and the circularity deviation $\Delta C$ can
reflect the black hole thermodynamics. In addition, we give the constraints to
the relaxation time of the M$87^{*}$ black hole by combining its shadow data
and the Bekenstein-Hod universal bounds when the M$87^{*}$ is regarded as the
Reissner-Nordstr\"om or Kerr black hole. We predict that the minimum relaxation
times of M$87^{*}$ black hole and Sgr $A^{*}$ black hole are approximately 3
days and 2.64 minutes, respectively. Finally, we draw the first graph of the
minimum relaxation time $\tau_{\rm min}$ with respect to the maximum shadow
radius $ r_{\rm sh}^{\rm max}$ at different mass levels.
| [
{
"created": "Sun, 18 Jul 2021 03:14:35 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jul 2021 03:07:42 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Jul 2021 10:01:30 GMT",
"version": "v3"
},
{
"created": "Fri, 12 Nov 2021 07:23:03 GMT",
"version": "v4"
}
] | 2021-11-15 | [
[
"Cai",
"Xin-Chang",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | We investigate the relationship between shadow radius and microstructure for a general static spherically symmetric black hole and confirm their close connection. In this regard, we take the Reissner-Nordstr\"om (AdS) black hole as an example to do the concrete analysis. On the other hand, we study for the Kerr (AdS) black hole the relationship between its shadow and thermodynamics in the aspects of phase transition and microstructure. Our results for the Kerr (AdS) black hole show that the shadow radius $r_{\rm sh}$, the deformation parameters $\delta_s$ and $k_s$, and the circularity deviation $\Delta C$ can reflect the black hole thermodynamics. In addition, we give the constraints to the relaxation time of the M$87^{*}$ black hole by combining its shadow data and the Bekenstein-Hod universal bounds when the M$87^{*}$ is regarded as the Reissner-Nordstr\"om or Kerr black hole. We predict that the minimum relaxation times of M$87^{*}$ black hole and Sgr $A^{*}$ black hole are approximately 3 days and 2.64 minutes, respectively. Finally, we draw the first graph of the minimum relaxation time $\tau_{\rm min}$ with respect to the maximum shadow radius $ r_{\rm sh}^{\rm max}$ at different mass levels. |
1905.09850 | Yuri Bonder | Y. Bonder and C. Corral | Symmetries in the SME gravity sector: A study in the first-order
formalism | Presented at the Eighth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 12-16, 2019 | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method to find the symmetries of a theory in the first order formalism of
gravity is presented. This method is applied to the minimal gravity sector of
the Standard Model Extension. It is argued that no inconsistencies arise when
Lorentz violation is explicit and the relation between Lorentz violation and
invariance under (active) diffeomorphisms is clearly exposed.
| [
{
"created": "Thu, 23 May 2019 18:11:39 GMT",
"version": "v1"
}
] | 2019-05-27 | [
[
"Bonder",
"Y.",
""
],
[
"Corral",
"C.",
""
]
] | A method to find the symmetries of a theory in the first order formalism of gravity is presented. This method is applied to the minimal gravity sector of the Standard Model Extension. It is argued that no inconsistencies arise when Lorentz violation is explicit and the relation between Lorentz violation and invariance under (active) diffeomorphisms is clearly exposed. |
1609.08268 | Chad Galley | Chad R. Galley and Ira Z. Rothstein | Deriving analytic solutions for compact binary inspirals without
recourse to adiabatic approximations | 18 pages, 2 figures | Phys. Rev. D 95, 104054 (2017) | 10.1103/PhysRevD.95.104054 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We utilize the dynamical renormalization group formalism to calculate the
real space trajectory of a compact binary inspiral for long times via a
systematic resummation of secularly growing terms. This method generates closed
form solutions without orbit averaging, and the accuracy can be systematically
improved. The expansion parameter is $v^5 \nu \Omega(t-t_0)$ where $t_0$ is the
initial time, $t$ is the time elapsed, and $\Omega$ and $v$ are the angular
orbital frequency and initial speed, respectively, and $\nu$ is the binary's
symmetric mass ratio. We demonstrate how to apply the renormalization group
method to resum solutions beyond leading order in two ways. First, we calculate
the second order corrections of the leading radiation reaction force, which
involves highly non-trivial checks of the formalism (i.e. its
renormalizability). Second, we show how to systematically include
post-Newtonian corrections to the radiation reaction force. By avoiding orbit
averaging we gain predictive power and eliminate ambiguities in the initial
conditions. Finally, we discuss how this methodology can be used to find
analytic solutions to the spin equations of motion that are valid over long
times.
| [
{
"created": "Tue, 27 Sep 2016 06:03:02 GMT",
"version": "v1"
}
] | 2017-06-07 | [
[
"Galley",
"Chad R.",
""
],
[
"Rothstein",
"Ira Z.",
""
]
] | We utilize the dynamical renormalization group formalism to calculate the real space trajectory of a compact binary inspiral for long times via a systematic resummation of secularly growing terms. This method generates closed form solutions without orbit averaging, and the accuracy can be systematically improved. The expansion parameter is $v^5 \nu \Omega(t-t_0)$ where $t_0$ is the initial time, $t$ is the time elapsed, and $\Omega$ and $v$ are the angular orbital frequency and initial speed, respectively, and $\nu$ is the binary's symmetric mass ratio. We demonstrate how to apply the renormalization group method to resum solutions beyond leading order in two ways. First, we calculate the second order corrections of the leading radiation reaction force, which involves highly non-trivial checks of the formalism (i.e. its renormalizability). Second, we show how to systematically include post-Newtonian corrections to the radiation reaction force. By avoiding orbit averaging we gain predictive power and eliminate ambiguities in the initial conditions. Finally, we discuss how this methodology can be used to find analytic solutions to the spin equations of motion that are valid over long times. |
1404.0862 | Qasem Exirifard | Qasem Exirifard | Gauge Vectors-Tensor Gravity | 7 pages, dynamical stability of the theory proved | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review and extend the Gauge Vectors-Tensor gravity: a covariant theory of
gravity composed of a metric and gauge fields, leading to simple second order
partial differential equations of motion, whose Newtonian and strong limits
coincide to those of the Einsten-Hilbert action but the physics of its very
weak fields should be identified through observation.
We show that GVT is at least as dynamically stable as the Einstein-Hilbert
gravity. It accommodates the MOND paradigm. We study its gravitational light
deflection. We show that the post Newtonian parameter of $\gamma$ vanishes in
the MOND regime of GVT gravity. Since $\Lambda$CDM assumes that $\gamma=1$,
this suggests to observationally measure the $\gamma$ parameter in the weak
regime of gravity as either a test for $\Lambda$CDM or GVT models
| [
{
"created": "Thu, 3 Apr 2014 11:25:35 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Jun 2014 11:04:51 GMT",
"version": "v2"
}
] | 2014-06-03 | [
[
"Exirifard",
"Qasem",
""
]
] | We review and extend the Gauge Vectors-Tensor gravity: a covariant theory of gravity composed of a metric and gauge fields, leading to simple second order partial differential equations of motion, whose Newtonian and strong limits coincide to those of the Einsten-Hilbert action but the physics of its very weak fields should be identified through observation. We show that GVT is at least as dynamically stable as the Einstein-Hilbert gravity. It accommodates the MOND paradigm. We study its gravitational light deflection. We show that the post Newtonian parameter of $\gamma$ vanishes in the MOND regime of GVT gravity. Since $\Lambda$CDM assumes that $\gamma=1$, this suggests to observationally measure the $\gamma$ parameter in the weak regime of gravity as either a test for $\Lambda$CDM or GVT models |
1906.05633 | Aurelien Barrau | Flora Moulin, Aur\'elien Barrau | Analytical proof of the isospectrality of quasinormal modes for
Schwarzschild-de Sitter and Schwarzschild-Anti de Sitter spacetimes | null | null | 10.1007/s10714-020-02737-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deep reason why the equations describing axial and polar perturbations of
Schwarzschild black holes have the same spectrum is far from trivial. In this
article, we revisit the original proof and try to make it clearer. Still
focusing on uncharged and non-rotating black holes, we extend the results to
spacetimes including a cosmological constant, which have so far mostly been
investigated numerically from this perspective.
| [
{
"created": "Thu, 13 Jun 2019 12:31:47 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Feb 2020 13:55:25 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Sep 2020 17:27:36 GMT",
"version": "v3"
}
] | 2020-09-09 | [
[
"Moulin",
"Flora",
""
],
[
"Barrau",
"Aurélien",
""
]
] | The deep reason why the equations describing axial and polar perturbations of Schwarzschild black holes have the same spectrum is far from trivial. In this article, we revisit the original proof and try to make it clearer. Still focusing on uncharged and non-rotating black holes, we extend the results to spacetimes including a cosmological constant, which have so far mostly been investigated numerically from this perspective. |
1204.0407 | Marc Casals | Marc Casals and Brien C. Nolan | A Kirchhoff integral approach to the calculation of Green's functions
beyond the normal neighbourhood | 32 pages, 5 figures. Minor modifications throughout in version 2 | null | 10.1103/PhysRevD.86.024038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new method for investigating the global properties of the
retarded Green's function $G_R(x',x)$ for fields propagating on an arbitrary
globally hyperbolic spacetime. Our method combines the Hadamard form for $G_R$
(this form is only valid within a normal neighbourhood of $x$) together with
Kirchhoff's integral representation for the field in order to calculate $G_R$
outside the maximal normal neighbourhood of $x$. As an example, we apply this
method to the case of a scalar field on a black hole toy-model spacetime, the
Pleba{\'n}ski-Hacyan spacetime, $\mathbb{M}_2\times\mathbb{S}^2$. The method
allows us to determine in an exact manner that the singularity structure of the
`direct' term in the Hadamard form for $G_R(x',x)$ changes from a form
$\delta(\sigma)$ to `$1/\pi\sigma$' after the null geodesic joining $x$ and
$x'$ has crossed a caustic point, where $\sigma$ is the world function.
Furthermore, there is a change of form from a $\theta(-\sigma)$ to a
`$-\ln|\sigma|/\pi$' in the `tail' term, which has not been explicitly noted
before in the literature. We complement the results from the Kirchhoff integral
method with an analysis for large-$\ell$ of the Green function modes. This
analysis allows us to determine the singularity structure after null geodesics
have crossed an arbitrary number of caustics, although it raises a causality
issue which the Kirchhoff integral method resolves. Because of the similarity
in the caustic structure of the spacetimes, we expect our main results for wave
propagation to also be valid on Schwarzschild spacetime.
| [
{
"created": "Mon, 2 Apr 2012 13:46:43 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Apr 2012 19:26:14 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Casals",
"Marc",
""
],
[
"Nolan",
"Brien C.",
""
]
] | We propose a new method for investigating the global properties of the retarded Green's function $G_R(x',x)$ for fields propagating on an arbitrary globally hyperbolic spacetime. Our method combines the Hadamard form for $G_R$ (this form is only valid within a normal neighbourhood of $x$) together with Kirchhoff's integral representation for the field in order to calculate $G_R$ outside the maximal normal neighbourhood of $x$. As an example, we apply this method to the case of a scalar field on a black hole toy-model spacetime, the Pleba{\'n}ski-Hacyan spacetime, $\mathbb{M}_2\times\mathbb{S}^2$. The method allows us to determine in an exact manner that the singularity structure of the `direct' term in the Hadamard form for $G_R(x',x)$ changes from a form $\delta(\sigma)$ to `$1/\pi\sigma$' after the null geodesic joining $x$ and $x'$ has crossed a caustic point, where $\sigma$ is the world function. Furthermore, there is a change of form from a $\theta(-\sigma)$ to a `$-\ln|\sigma|/\pi$' in the `tail' term, which has not been explicitly noted before in the literature. We complement the results from the Kirchhoff integral method with an analysis for large-$\ell$ of the Green function modes. This analysis allows us to determine the singularity structure after null geodesics have crossed an arbitrary number of caustics, although it raises a causality issue which the Kirchhoff integral method resolves. Because of the similarity in the caustic structure of the spacetimes, we expect our main results for wave propagation to also be valid on Schwarzschild spacetime. |
gr-qc/9802031 | Marcelo Jose Reboucas | A. Bernui, G.I. Gomero, M.J. Reboucas, A.F.F. Teixeira | Radiation Damping in FRW Space-times with Different Topologies | 13 pages, RevTeX, 5 figures, To appear in Phys. Rev. D 15, vol. 57
(1998) | Phys.Rev. D57 (1998) 4699-4706 | 10.1103/PhysRevD.57.4699 | CBPF-NF-027/97 | gr-qc astro-ph hep-ph hep-th | null | We study the role played by the compactness and the degree of connectedness
in the time evolution of the energy of a radiating system in the
Friedmann-Robertson-Walker (FRW) space-times whose $t=const $ spacelike
sections are the Euclidean 3-manifold ${\cal R}^3$ and six topologically
non-equivalent flat orientable compact multiply connected Riemannian
3-manifolds. An exponential damping of the energy $E(t)$ is present in the
${\cal R}^3$ case, whereas for the six compact flat 3-spaces it is found
basically the same pattern for the evolution of the energy, namely relative
minima and maxima occurring at different times (depending on the degree of
connectedness) followed by a growth of $E(t)$. Likely reasons for this
divergent behavior of $E(t)$ in these compact flat 3-manifolds are discussed
and further developments are indicated. A misinterpretation of Wolf's results
regarding one of the six orientable compact flat 3-manifolds is also indicated
and rectified.
| [
{
"created": "Fri, 13 Feb 1998 20:37:18 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bernui",
"A.",
""
],
[
"Gomero",
"G. I.",
""
],
[
"Reboucas",
"M. J.",
""
],
[
"Teixeira",
"A. F. F.",
""
]
] | We study the role played by the compactness and the degree of connectedness in the time evolution of the energy of a radiating system in the Friedmann-Robertson-Walker (FRW) space-times whose $t=const $ spacelike sections are the Euclidean 3-manifold ${\cal R}^3$ and six topologically non-equivalent flat orientable compact multiply connected Riemannian 3-manifolds. An exponential damping of the energy $E(t)$ is present in the ${\cal R}^3$ case, whereas for the six compact flat 3-spaces it is found basically the same pattern for the evolution of the energy, namely relative minima and maxima occurring at different times (depending on the degree of connectedness) followed by a growth of $E(t)$. Likely reasons for this divergent behavior of $E(t)$ in these compact flat 3-manifolds are discussed and further developments are indicated. A misinterpretation of Wolf's results regarding one of the six orientable compact flat 3-manifolds is also indicated and rectified. |
2011.08878 | Sarah Habib | Sarah Habib, Antoni Ramos-Buades, E. A. Huerta, Sascha Husa, Roland
Haas, Zachariah Etienne | Initial Data and Eccentricity Reduction Toolkit for Binary Black Hole
Numerical Relativity Waveforms | 11 pages, 1 figure, 1 table. Open source software available at:
https://github.com/NCSAGravity/eccred | null | 10.1088/1361-6382/abe691 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The production of numerical relativity waveforms that describe quasicircular
binary black hole mergers requires high-quality initial data, and an algorithm
to iteratively reduce residual eccentricity. To date, these tools remain closed
source, or in commercial software that prevents their use in high performance
computing platforms. To address these limitations, and to ensure that the
broader numerical relativity community has access to these tools, herein we
provide all the required elements to produce high-quality numerical relativity
simulations in supercomputer platforms, namely: open source parameter files to
numerical simulate spinning black hole binaries with asymmetric mass-ratios;
open source $\texttt{Python}$ tools to produce high-quality initial data for
numerical relativity simulations of spinning black hole binaries on
quasi-circular orbits; open source $\texttt{Python}$ tools for eccentricity
reduction, both as stand-alone software and deployed in the $\texttt{Einstein
Toolkit}$'s software infrastructure. This open source toolkit fills in a
critical void in the literature at a time when numerical relativity has an ever
increasing role in the study and interpretation of gravitational wave sources.
As part of our community building efforts, and to streamline and accelerate the
use of these resources, we provide tutorials that describe, step by step, how
to obtain and use these open source numerical relativity tools.
| [
{
"created": "Tue, 17 Nov 2020 19:10:03 GMT",
"version": "v1"
}
] | 2021-06-09 | [
[
"Habib",
"Sarah",
""
],
[
"Ramos-Buades",
"Antoni",
""
],
[
"Huerta",
"E. A.",
""
],
[
"Husa",
"Sascha",
""
],
[
"Haas",
"Roland",
""
],
[
"Etienne",
"Zachariah",
""
]
] | The production of numerical relativity waveforms that describe quasicircular binary black hole mergers requires high-quality initial data, and an algorithm to iteratively reduce residual eccentricity. To date, these tools remain closed source, or in commercial software that prevents their use in high performance computing platforms. To address these limitations, and to ensure that the broader numerical relativity community has access to these tools, herein we provide all the required elements to produce high-quality numerical relativity simulations in supercomputer platforms, namely: open source parameter files to numerical simulate spinning black hole binaries with asymmetric mass-ratios; open source $\texttt{Python}$ tools to produce high-quality initial data for numerical relativity simulations of spinning black hole binaries on quasi-circular orbits; open source $\texttt{Python}$ tools for eccentricity reduction, both as stand-alone software and deployed in the $\texttt{Einstein Toolkit}$'s software infrastructure. This open source toolkit fills in a critical void in the literature at a time when numerical relativity has an ever increasing role in the study and interpretation of gravitational wave sources. As part of our community building efforts, and to streamline and accelerate the use of these resources, we provide tutorials that describe, step by step, how to obtain and use these open source numerical relativity tools. |
1208.5102 | Kent Yagi | Kent Yagi, Nicolas Yunes, Takahiro Tanaka | Gravitational Waves from Quasi-Circular Black Hole Binaries in Dynamical
Chern-Simons Gravity | 6 pages, 1 figure; errors corrected in Eqs. (8) and (9) | Phys. Rev. Lett. 109, 251105 (2012) | 10.1103/PhysRevLett.109.251105 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical Chern-Simons gravity cannot be strongly constrained with current
experiments because it reduces to General Relativity in the weak-field limit.
This theory, however, introduces modifications in the non-linear, dynamical
regime, and thus, it could be greatly constrained with gravitational waves from
the late inspiral of black hole binaries. We complete the first self-consistent
calculation of such gravitational waves in this theory. For favorable
spin-orientations, advanced ground-based detectors may improve existing
solar-system constraints by 6 orders of magnitude.
| [
{
"created": "Sat, 25 Aug 2012 05:26:17 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Feb 2013 06:02:22 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Apr 2016 15:22:59 GMT",
"version": "v3"
},
{
"created": "Thu, 2 Jan 2020 06:36:50 GMT",
"version": "v4"
}
] | 2020-01-03 | [
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Dynamical Chern-Simons gravity cannot be strongly constrained with current experiments because it reduces to General Relativity in the weak-field limit. This theory, however, introduces modifications in the non-linear, dynamical regime, and thus, it could be greatly constrained with gravitational waves from the late inspiral of black hole binaries. We complete the first self-consistent calculation of such gravitational waves in this theory. For favorable spin-orientations, advanced ground-based detectors may improve existing solar-system constraints by 6 orders of magnitude. |
0805.1241 | Jorge P\'aramos | O. Bertolami and J. P\'aramos | On the non-minimal gravitational coupling to matter | 11 pages | Class.Quant.Grav.25:245017,2008 | 10.1088/0264-9381/25/24/245017 | DF/IST-2.2008 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The connection between $f(R)$ theories of gravity and scalar-tensor models
with a "physical" metric coupled to the scalar field is well known. In this
work, we pursue the equivalence between a suitable scalar theory and a model
that generalises the $f(R)$ scenario, encompassing both a non-trivial scalar
curvature term and a non-minimum coupling of the scalar curvature and matter.
This equivalence allows for the calculation of the PPN parameters $\beta$ and
$\gamma$ and, eventually, a solution to the debate concerning the weak-field
limit of $f(R)$ theories.
| [
{
"created": "Thu, 8 May 2008 20:25:18 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Aug 2008 19:08:17 GMT",
"version": "v2"
}
] | 2009-01-01 | [
[
"Bertolami",
"O.",
""
],
[
"Páramos",
"J.",
""
]
] | The connection between $f(R)$ theories of gravity and scalar-tensor models with a "physical" metric coupled to the scalar field is well known. In this work, we pursue the equivalence between a suitable scalar theory and a model that generalises the $f(R)$ scenario, encompassing both a non-trivial scalar curvature term and a non-minimum coupling of the scalar curvature and matter. This equivalence allows for the calculation of the PPN parameters $\beta$ and $\gamma$ and, eventually, a solution to the debate concerning the weak-field limit of $f(R)$ theories. |
1105.4336 | Daniele Malafarina | Pankaj S. Joshi and Daniele Malafarina | Instability of black hole formation under small pressure perturbations | 7 pages, 1 figure, several modifications to match published version
on GRG | null | 10.1007/s10714-012-1471-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate here the spectrum of gravitational collapse endstates when
arbitrarily small perfect fluid pressures are introduced in the classic black
hole formation scenario as described by Oppenheimer, Snyder and Datt (OSD) [1].
This extends a previous result on tangential pressures [2] to the more
physically realistic scenario of perfect fluid collapse. The existence of
classes of pressure perturbations is shown explicitly, which has the property
that injecting any smallest pressure changes the final fate of the dynamical
collapse from a black hole to a naked singularity. It is therefore seen that
any smallest neighborhood of the OSD model, in the space of initial data,
contains collapse evolutions that go to a naked singularity outcome. This gives
an intriguing insight on the nature of naked singularity formation in
gravitational collapse.
| [
{
"created": "Sun, 22 May 2011 13:13:45 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2012 08:34:03 GMT",
"version": "v2"
}
] | 2012-11-15 | [
[
"Joshi",
"Pankaj S.",
""
],
[
"Malafarina",
"Daniele",
""
]
] | We investigate here the spectrum of gravitational collapse endstates when arbitrarily small perfect fluid pressures are introduced in the classic black hole formation scenario as described by Oppenheimer, Snyder and Datt (OSD) [1]. This extends a previous result on tangential pressures [2] to the more physically realistic scenario of perfect fluid collapse. The existence of classes of pressure perturbations is shown explicitly, which has the property that injecting any smallest pressure changes the final fate of the dynamical collapse from a black hole to a naked singularity. It is therefore seen that any smallest neighborhood of the OSD model, in the space of initial data, contains collapse evolutions that go to a naked singularity outcome. This gives an intriguing insight on the nature of naked singularity formation in gravitational collapse. |
2010.04006 | Hossein Ghaffarnejad | Hossein Ghaffarnejad and Elham Ghasemi Kordkheilee | Thermodynamics phase transition of Anti de Sitter Schwarzschild
scalar-tensor-vector-Black Holes | 21 pages, 4 figures | Iranian Journal of Astronomy and Astrophysics 2023 | 10.22128/ijaa.2022.592.1124 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Instead of scalar tensor gravity models which is applicable for description
of cosmic inflation with unknown dark sector of matter/energy, at presentense
there are presented different alternative scalar tensor vector gravities where
meaningful dynamical vector fields can support cosmic inflation well without to
use dark matter/energy concept. One of these gravity models was presented by
Moffat which its modified Schwarzschild black hole solution is used to study
thermodynamic phase transition in presence of the AdS space pressure in this
article. To do so we obtained an equation of state which asymptotically reaches
to equation of state of ideal gas for large black holes but for small scale
black holes we obtained a critical point at phase space where the black hole
can be exhibit with a phase transition at processes of isotherm and isobaric.
By looking at diagrams of the Gibbs free energy and the heat capacity at
constant pressure which are plotted versus the temperature and the specific
volume one can see an inflection point which means that the phase transition is
type of second order. In fact there is small to large phase transition for the
black hole which is equivalent to the Van der Waals liquid-gas phase transition
in ordinary thermodynamic systems. The phase transition is happened below the
critical point in phase space when the gravitational charge of the black hole
is equal to its mass.
| [
{
"created": "Wed, 7 Oct 2020 17:33:06 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Dec 2020 23:29:21 GMT",
"version": "v2"
}
] | 2023-01-24 | [
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Kordkheilee",
"Elham Ghasemi",
""
]
] | Instead of scalar tensor gravity models which is applicable for description of cosmic inflation with unknown dark sector of matter/energy, at presentense there are presented different alternative scalar tensor vector gravities where meaningful dynamical vector fields can support cosmic inflation well without to use dark matter/energy concept. One of these gravity models was presented by Moffat which its modified Schwarzschild black hole solution is used to study thermodynamic phase transition in presence of the AdS space pressure in this article. To do so we obtained an equation of state which asymptotically reaches to equation of state of ideal gas for large black holes but for small scale black holes we obtained a critical point at phase space where the black hole can be exhibit with a phase transition at processes of isotherm and isobaric. By looking at diagrams of the Gibbs free energy and the heat capacity at constant pressure which are plotted versus the temperature and the specific volume one can see an inflection point which means that the phase transition is type of second order. In fact there is small to large phase transition for the black hole which is equivalent to the Van der Waals liquid-gas phase transition in ordinary thermodynamic systems. The phase transition is happened below the critical point in phase space when the gravitational charge of the black hole is equal to its mass. |
2112.11851 | Maximilian K\"olsch | Maximilian K\"olsch, Tim Dietrich, Maximiliano Ujevic, Bernd Bruegmann | Investigating the mass-ratio dependence of the prompt-collapse threshold
with numerical-relativity simulations | 26 pages, 18 figures, 16 tables | null | 10.1103/PhysRevD.106.044026 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The next observing runs of advanced gravitational-wave detectors will lead to
a variety of binary neutron star detections and numerous possibilities for
multi-messenger observations of binary neutron star systems. In this context a
clear understanding of the merger process and the possibility of prompt black
hole formation after merger is important, as the amount of ejected material
strongly depends on the merger dynamics. These dynamics are primarily affected
by the total mass of the binary, however, the mass ratio also influences the
postmerger evolution. To determine the effect of the mass ratio, we investigate
the parameter space around the prompt-collapse threshold with a new set of
fully relativistic simulations. The simulations cover three equations of state
and seven mass ratios in the range of $1.0 \leq q \leq 1.75$, with five to
seven simulations of binary systems of different total mass in each case. The
threshold mass is determined through an empirical relation based on the
collapse-time, which allows us to investigate effects of the mass-ratio on the
threshold mass and also on the properties of the remnant system. Furthermore,
we model effects of mass ratio and equation of state on tidal parameters of
threshold configurations.
| [
{
"created": "Wed, 22 Dec 2021 12:58:07 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Kölsch",
"Maximilian",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Ujevic",
"Maximiliano",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | The next observing runs of advanced gravitational-wave detectors will lead to a variety of binary neutron star detections and numerous possibilities for multi-messenger observations of binary neutron star systems. In this context a clear understanding of the merger process and the possibility of prompt black hole formation after merger is important, as the amount of ejected material strongly depends on the merger dynamics. These dynamics are primarily affected by the total mass of the binary, however, the mass ratio also influences the postmerger evolution. To determine the effect of the mass ratio, we investigate the parameter space around the prompt-collapse threshold with a new set of fully relativistic simulations. The simulations cover three equations of state and seven mass ratios in the range of $1.0 \leq q \leq 1.75$, with five to seven simulations of binary systems of different total mass in each case. The threshold mass is determined through an empirical relation based on the collapse-time, which allows us to investigate effects of the mass-ratio on the threshold mass and also on the properties of the remnant system. Furthermore, we model effects of mass ratio and equation of state on tidal parameters of threshold configurations. |
1510.00595 | Cl\'audio Nassif Cruz | Cl\'audio Nassif | An explanation for the tiny value of the cosmological constant and the
low vacuum energy density | 26 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1211.3612, arXiv:0805.1201, arXiv:0711.4897, arXiv:1308.5258 | General Relativity and Gravitation Vol.47, 9, p.1-34 (2015) | 10.1007/s10714-015-1939-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper aims to provide an explanation for the tiny value of the
cosmological constant and the low vacuum energy density to represent the dark
energy. To accomplish this, we will search for a fundamental principle of
symmetry in space-time by means of the elimination of the classical idea of
rest, by including an invariant minimum limit of speed in the subatomic world.
Such a minimum speed, unattainable by particles, represents a preferred
reference frame associated with a background field that breaks down the Lorentz
symmetry. The metric of the flat space-time shall include the presence of a
uniform vacuum energy density, which leads to a negative pressure at
cosmological length scales. Thus, the equation of state for the cosmological
constant [$p$(pressure)$=- \epsilon$ (energy density)] naturally emerges from
such a space-time with an energy barrier of a minimum speed. The tiny values of
the cosmological constant and the vacuum energy density will be successfully
obtained, being in agreement with the observational results of Perlmutter,
Schmidt and Riess.
| [
{
"created": "Mon, 28 Sep 2015 21:42:00 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Nov 2016 18:37:54 GMT",
"version": "v2"
}
] | 2016-11-14 | [
[
"Nassif",
"Cláudio",
""
]
] | The paper aims to provide an explanation for the tiny value of the cosmological constant and the low vacuum energy density to represent the dark energy. To accomplish this, we will search for a fundamental principle of symmetry in space-time by means of the elimination of the classical idea of rest, by including an invariant minimum limit of speed in the subatomic world. Such a minimum speed, unattainable by particles, represents a preferred reference frame associated with a background field that breaks down the Lorentz symmetry. The metric of the flat space-time shall include the presence of a uniform vacuum energy density, which leads to a negative pressure at cosmological length scales. Thus, the equation of state for the cosmological constant [$p$(pressure)$=- \epsilon$ (energy density)] naturally emerges from such a space-time with an energy barrier of a minimum speed. The tiny values of the cosmological constant and the vacuum energy density will be successfully obtained, being in agreement with the observational results of Perlmutter, Schmidt and Riess. |
gr-qc/0207001 | J. Ponce de Leon | J. Ponce de Leon | Variation of G, $\Lambda_{(4)}$ and Vacuum Energy From Brane-World
Models | In version 2 an error noticed by the author is fixed, and the
corresponding changes are made. Version 3 is identical to v2, except for a
couple of typos corrected. V3 will appear in Mod. Phys. Lett. A | Mod.Phys.Lett. A17 (2002) 2425-2441 | 10.1142/S0217732302009143 | null | gr-qc | null | In brane-world theory in five dimensions, the bulk metric is usually written
in gaussian coordinates, where $g_{4\mu} = 0$ and $g_{44} = - 1$. However, the
choice $g_{44} = - 1$ is an external condition, not a requirement of the field
equations. In this paper we study the consequences of having $g_{44} = \epsilon
\Phi^2$, where $\epsilon = \pm 1$ and $\Phi$ is a scalar function varying with
time, $\dot{\Phi} \neq 0$. This varying field entails the possibility of
variable fundamental physical "constants". These variations are different from
those predicted in scalar-tensor and multidimensional theories. We solve the
five-dimensional equations for a {\em fixed} brane and use the brane-world
paradigm to determine the fundamental parameters in the theory, which are the
vacuum energy $\sigma$, the gravitational coupling $G$ and the cosmological
term $\Lambda_{(4)}$. We present specific models where these physical
quantities are variable functions of time. Different scenarios are possible but
we discuss with some detail a model for which $\dot{G}/G \sim H$ and
$\Lambda_{(4)} \sim H^2$, which seems to be favored by observations. Our
results are not in contradiction to previous ones in the literature. In
particular, to those where the brane is described as a domain wall moving in a
static $Sch-AdS$ bulk. Indeed these latter models in RS scenarios describe the
same spacetime as other solutions (with fixed brane) in gaussian coordinates
with $\dot{\Phi} = 0 $. We conclude that the introduction of a time-varying
$\Phi$ in brane-world theory yields a number of models that show variation in
the fundamental physical "constants" and exhibit reasonable physical
properties.
| [
{
"created": "Sat, 29 Jun 2002 07:25:51 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Nov 2002 22:57:05 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Nov 2002 22:20:27 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"de Leon",
"J. Ponce",
""
]
] | In brane-world theory in five dimensions, the bulk metric is usually written in gaussian coordinates, where $g_{4\mu} = 0$ and $g_{44} = - 1$. However, the choice $g_{44} = - 1$ is an external condition, not a requirement of the field equations. In this paper we study the consequences of having $g_{44} = \epsilon \Phi^2$, where $\epsilon = \pm 1$ and $\Phi$ is a scalar function varying with time, $\dot{\Phi} \neq 0$. This varying field entails the possibility of variable fundamental physical "constants". These variations are different from those predicted in scalar-tensor and multidimensional theories. We solve the five-dimensional equations for a {\em fixed} brane and use the brane-world paradigm to determine the fundamental parameters in the theory, which are the vacuum energy $\sigma$, the gravitational coupling $G$ and the cosmological term $\Lambda_{(4)}$. We present specific models where these physical quantities are variable functions of time. Different scenarios are possible but we discuss with some detail a model for which $\dot{G}/G \sim H$ and $\Lambda_{(4)} \sim H^2$, which seems to be favored by observations. Our results are not in contradiction to previous ones in the literature. In particular, to those where the brane is described as a domain wall moving in a static $Sch-AdS$ bulk. Indeed these latter models in RS scenarios describe the same spacetime as other solutions (with fixed brane) in gaussian coordinates with $\dot{\Phi} = 0 $. We conclude that the introduction of a time-varying $\Phi$ in brane-world theory yields a number of models that show variation in the fundamental physical "constants" and exhibit reasonable physical properties. |
gr-qc/9607012 | Alessando Fabbri | R. Balbinot and A. Fabbri | Two-dimensional black holes in accelerated frames: quantum aspects | 18 pages, harvmac, 2 figures | Class.Quant.Grav. 14 (1997) 463-476 | 10.1088/0264-9381/14/2/019 | SISSA-ISAS/100/96/EP | gr-qc | null | By considering charged black hole solutions of a one parameter family of two
dimensional dilaton gravity theories, one finds the existence of quantum
mechanically stable gravitational kinks with a simple mass to charge relation.
Unlike their Einsteinian counterpart (i.e. extreme Reissner-Nordstr\"om), these
have nonvanishing horizon surface gravity.
| [
{
"created": "Thu, 4 Jul 1996 17:10:56 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Balbinot",
"R.",
""
],
[
"Fabbri",
"A.",
""
]
] | By considering charged black hole solutions of a one parameter family of two dimensional dilaton gravity theories, one finds the existence of quantum mechanically stable gravitational kinks with a simple mass to charge relation. Unlike their Einsteinian counterpart (i.e. extreme Reissner-Nordstr\"om), these have nonvanishing horizon surface gravity. |
2104.00804 | Alex Pandya | Alex Pandya, Frans Pretorius | A numerical exploration of first-order relativistic hydrodynamics | 24 pages, 11 figures; updated to match accepted version (PRD) | Phys. Rev. D 104, 023015 (2021) | 10.1103/PhysRevD.104.023015 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first numerical solutions of the causal, stable relativistic
Navier-Stokes equations as formulated by Bemfica, Disconzi, Noronha, and Kovtun
(BDNK). For this initial investigation we restrict to plane-symmetric
configurations of a conformal fluid in Minkowski spacetime. We consider
evolution of three classes of initial data: a smooth (initially) stationary
concentration of energy, a standard shock tube setup, and a smooth shockwave
setup. We compare these solutions to those obtained with the
Muller-Israel-Stewart (MIS) formalism, variants of which are the common tools
used to model relativistic, viscous fluids. We find that for the two smooth
initial data cases, simple finite difference methods are adequate to obtain
stable, convergent solutions to the BDNK equations. For low viscosity, the MIS
and BDNK evolutions show good agreement. At high viscosity the solutions begin
to differ in regions with large gradients, and there the BDNK solutions can (as
expected) exhibit violation of the weak energy condition. This behavior is
transient, and the solutions evolve toward a hydrodynamic regime in a way
reminiscent of an approach to a universal attractor. For the shockwave problem,
we give evidence that if a hydrodynamic frame is chosen so that the maximum
characteristic speed of the BDNK system is the speed of light (or larger),
arbitrarily strong shockwaves are smoothly resolved. Regarding the shock tube
problem, it is unclear whether discontinuous initial data is mathematically
well-posed for the BDNK system, even in a weak sense. Nevertheless we attempt
numerical solution, and then need to treat the perfect fluid terms using
high-resolution shock-capturing methods. When such methods can successfully
evolve the solution beyond the initial time, subsequent evolution agrees with
corresponding MIS solutions, as well as the perfect fluid solution in the limit
of zero viscosity.
| [
{
"created": "Thu, 1 Apr 2021 23:36:29 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jun 2021 15:48:31 GMT",
"version": "v2"
}
] | 2021-07-21 | [
[
"Pandya",
"Alex",
""
],
[
"Pretorius",
"Frans",
""
]
] | We present the first numerical solutions of the causal, stable relativistic Navier-Stokes equations as formulated by Bemfica, Disconzi, Noronha, and Kovtun (BDNK). For this initial investigation we restrict to plane-symmetric configurations of a conformal fluid in Minkowski spacetime. We consider evolution of three classes of initial data: a smooth (initially) stationary concentration of energy, a standard shock tube setup, and a smooth shockwave setup. We compare these solutions to those obtained with the Muller-Israel-Stewart (MIS) formalism, variants of which are the common tools used to model relativistic, viscous fluids. We find that for the two smooth initial data cases, simple finite difference methods are adequate to obtain stable, convergent solutions to the BDNK equations. For low viscosity, the MIS and BDNK evolutions show good agreement. At high viscosity the solutions begin to differ in regions with large gradients, and there the BDNK solutions can (as expected) exhibit violation of the weak energy condition. This behavior is transient, and the solutions evolve toward a hydrodynamic regime in a way reminiscent of an approach to a universal attractor. For the shockwave problem, we give evidence that if a hydrodynamic frame is chosen so that the maximum characteristic speed of the BDNK system is the speed of light (or larger), arbitrarily strong shockwaves are smoothly resolved. Regarding the shock tube problem, it is unclear whether discontinuous initial data is mathematically well-posed for the BDNK system, even in a weak sense. Nevertheless we attempt numerical solution, and then need to treat the perfect fluid terms using high-resolution shock-capturing methods. When such methods can successfully evolve the solution beyond the initial time, subsequent evolution agrees with corresponding MIS solutions, as well as the perfect fluid solution in the limit of zero viscosity. |
0804.4348 | Sergei Rubin | S. G. Rubin | Cascade Birth of Universes in Multidimensional Spaces | 10 p., minor corrections | Sov.Phys.JETP.106:715,2008; J.Exp.Theor.Phys.106:714-722,2008 | 10.1134/S1063776108040109 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formation mechanism of universes with distinctly different properties is
considered within the framework of pure gravity in a space of D > 4 dimensions.
The emergence of the Planck scale and its relationship to the inflaton mass are
discussed.
| [
{
"created": "Mon, 28 Apr 2008 14:38:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rubin",
"S. G.",
""
]
] | The formation mechanism of universes with distinctly different properties is considered within the framework of pure gravity in a space of D > 4 dimensions. The emergence of the Planck scale and its relationship to the inflaton mass are discussed. |
1812.11557 | Salvatore Capozziello | Salvatore Capozziello, Maurizio Capriolo, Loredana Caso | Weak field limit and gravitational waves in higher-order gravity | 21 pages, to appear in Int.J.Geom.Meth.Mod.Phys | Int.J.Geom.Meth.Mod.Phys. (2019) | 10.1142/S0219887819500476 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the weak field limit for a gravitational Lagrangian density
$L_{g}=(R+a_{0}R^{2}+\sum_{k=1}^{p} a_{k}R\Box^{k}R)\sqrt{-g}$ where
higher-order derivative terms in the Ricci scalar $R$ are taken into account.
The interest for this kind of effective theories comes out from the
consideration of the infrared and ultraviolet behaviors of gravitational field
and, in general, from the formulation of quantum field theory in curved
spacetimes. Here, we obtain solutions in weak field regime both in vacuum and
in the presence of matter and derive gravitational waves considering the
contribution of $R\Box^{k}R$ terms. By using a suitable set of coefficients
$a_{k}$, it is possible to find up to $(p+2)$ normal modes of oscillation with
six polarization states with helicity 0 or 2. Here $p$ is the higher order term
in the $\Box$ operator appearing in the gravitational Lagrangian. More
specifically: the mode $\omega_{1}$, with $k^{2}=0$, has transverse
polarizations $\epsilon_{\mu\nu}^{\left(+\right)}$ and
$\epsilon_{\mu\nu}^{\left(\times\right)}$ with helicity 2; the $(p+1)$ modes
$\omega_{m}$, with $k^{2}\neq0$, have transverse polarizations
$\epsilon_{\mu\nu}^{\left(1\right)}$ and non-transverse ones
$\epsilon_{\mu\nu}^{\left(\text{TT}\right)}$,
$\epsilon_{\mu\nu}^{\left(\text{TS}\right)}$,
$\epsilon_{\mu\nu}^{\left(L\right)}$ with helicity 0.
| [
{
"created": "Sun, 30 Dec 2018 15:31:27 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Jan 2019 15:32:45 GMT",
"version": "v2"
}
] | 2019-02-11 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Capriolo",
"Maurizio",
""
],
[
"Caso",
"Loredana",
""
]
] | We derive the weak field limit for a gravitational Lagrangian density $L_{g}=(R+a_{0}R^{2}+\sum_{k=1}^{p} a_{k}R\Box^{k}R)\sqrt{-g}$ where higher-order derivative terms in the Ricci scalar $R$ are taken into account. The interest for this kind of effective theories comes out from the consideration of the infrared and ultraviolet behaviors of gravitational field and, in general, from the formulation of quantum field theory in curved spacetimes. Here, we obtain solutions in weak field regime both in vacuum and in the presence of matter and derive gravitational waves considering the contribution of $R\Box^{k}R$ terms. By using a suitable set of coefficients $a_{k}$, it is possible to find up to $(p+2)$ normal modes of oscillation with six polarization states with helicity 0 or 2. Here $p$ is the higher order term in the $\Box$ operator appearing in the gravitational Lagrangian. More specifically: the mode $\omega_{1}$, with $k^{2}=0$, has transverse polarizations $\epsilon_{\mu\nu}^{\left(+\right)}$ and $\epsilon_{\mu\nu}^{\left(\times\right)}$ with helicity 2; the $(p+1)$ modes $\omega_{m}$, with $k^{2}\neq0$, have transverse polarizations $\epsilon_{\mu\nu}^{\left(1\right)}$ and non-transverse ones $\epsilon_{\mu\nu}^{\left(\text{TT}\right)}$, $\epsilon_{\mu\nu}^{\left(\text{TS}\right)}$, $\epsilon_{\mu\nu}^{\left(L\right)}$ with helicity 0. |
2109.03113 | Hai-Tian Wang | Hai-Tian Wang, Yi-Ming Hu, Peng-Cheng Li, and Yi-Zhong Fan | Probing chromatic onsets of gravitational wave overtones | 6 pages, 3 figures, 1 table, accepted by PRD | null | 10.1103/PhysRevD.105.043012 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ringdown data of both GW150914 and GW190521\_074359 (GW190521r) show
evidence supporting the presence of overtone. Previous studies all adopt a
fundamental assumption, which were motivated more by convenience than by first
principles, that the first overtone and the fundamental mode share a same
onset. In this work, for the first time we relax such assumption, and we aim to
probe the possible chromatic onsets of these two components within the GW150914
and GW190521r ringdown data. For both events, we bound the onset lags to be
$\Delta t_0\geq 5M_f$ at probabilities of $\geq 94.7\%$, where $M_f$ is the
mass of the remnant black hole formed in the merger. This result moderately
favours the non-simultaneous excitation between the fundamental mode and the
first overtone in the ringdown.
| [
{
"created": "Tue, 7 Sep 2021 14:21:48 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jan 2022 09:29:12 GMT",
"version": "v2"
}
] | 2022-02-22 | [
[
"Wang",
"Hai-Tian",
""
],
[
"Hu",
"Yi-Ming",
""
],
[
"Li",
"Peng-Cheng",
""
],
[
"Fan",
"Yi-Zhong",
""
]
] | The ringdown data of both GW150914 and GW190521\_074359 (GW190521r) show evidence supporting the presence of overtone. Previous studies all adopt a fundamental assumption, which were motivated more by convenience than by first principles, that the first overtone and the fundamental mode share a same onset. In this work, for the first time we relax such assumption, and we aim to probe the possible chromatic onsets of these two components within the GW150914 and GW190521r ringdown data. For both events, we bound the onset lags to be $\Delta t_0\geq 5M_f$ at probabilities of $\geq 94.7\%$, where $M_f$ is the mass of the remnant black hole formed in the merger. This result moderately favours the non-simultaneous excitation between the fundamental mode and the first overtone in the ringdown. |
1707.09505 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | Back reaction of the gravitational radiation on the metric of spacetime | 9 pages, no figures. New version matches the published version,
includes adding references and corrections mainly in section 4 | Int. J. Mod. Phys. D 27 (2018) 1850071 | 10.1142/S0218271818500712 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of back reaction of the gravitational radiation of the two
merging black holes on the metric of the spacetime is investigated. It is shown
for some models that large energy density of the gravitational waves close to
the merger can lead to the disappearance of the visible accretion disc of the
merged pair of black holes.
| [
{
"created": "Sat, 29 Jul 2017 12:40:19 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Mar 2018 11:13:55 GMT",
"version": "v2"
}
] | 2018-03-07 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | The problem of back reaction of the gravitational radiation of the two merging black holes on the metric of the spacetime is investigated. It is shown for some models that large energy density of the gravitational waves close to the merger can lead to the disappearance of the visible accretion disc of the merged pair of black holes. |
1612.04124 | Nelson Videla Dr. | Nelson Videla | Hamilton-Jacobi approach for quasi-exponential inflation: predictions
and constraints after Planck 2015 results | 21 pages, 4 figures, typos corrected, version accepted for
publication in EPJC. arXiv admin note: text overlap with arXiv:1606.04888 | null | 10.1140/epjc/s10052-017-4711-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we study the consequences of considering an inflationary
universe model in which the Hubble rate has a quasi-exponential dependence in
the inflaton field, given by $H(\phi)=H_{inf}\exp
\left[\frac{\frac{\phi}{m_p}}{p\left(1+\frac{\phi}{m_p}\right)}\right]$. We
analyze the inflation dynamics under the Hamilton-Jacobi approach, which allows
us to consider $H(\phi)$, rather than $V(\phi)$, as the fundamental quantity to
be specified. By comparing the theoretical predictions of the model together
with the allowed contour plots in the $n_s-r$ plane and the amplitude of
primordial scalar perturbations from the latest Planck data, the parameters
charactering this model are constrained. The model predicts values for the
tensor-to-scalar ratio $r$ and for the running of the scalar spectral index
$dn_s/ d\ln k$ consistent with the current bounds imposed by Planck, and we
conclude that the model is viable.
| [
{
"created": "Tue, 13 Dec 2016 12:25:52 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2017 17:52:00 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Feb 2017 13:19:14 GMT",
"version": "v3"
}
] | 2017-04-05 | [
[
"Videla",
"Nelson",
""
]
] | In the present work we study the consequences of considering an inflationary universe model in which the Hubble rate has a quasi-exponential dependence in the inflaton field, given by $H(\phi)=H_{inf}\exp \left[\frac{\frac{\phi}{m_p}}{p\left(1+\frac{\phi}{m_p}\right)}\right]$. We analyze the inflation dynamics under the Hamilton-Jacobi approach, which allows us to consider $H(\phi)$, rather than $V(\phi)$, as the fundamental quantity to be specified. By comparing the theoretical predictions of the model together with the allowed contour plots in the $n_s-r$ plane and the amplitude of primordial scalar perturbations from the latest Planck data, the parameters charactering this model are constrained. The model predicts values for the tensor-to-scalar ratio $r$ and for the running of the scalar spectral index $dn_s/ d\ln k$ consistent with the current bounds imposed by Planck, and we conclude that the model is viable. |
2305.07060 | Carlos M. Reyes | Carlos M. Reyes and Marco Schreck | The boundary of the gravitational Standard-Model Extension | 17 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modification of General Relativity that is based on the gravitational
Standard-Model Extension and incorporates nondynamical background fields has
recently been studied via the ADM formalism. Our objective in this paper is to
develop a better understanding of the additional contributions that arise on
the spacetime boundary $\partial M$. An extension of the previously introduced
boundary terms, which are relevant in the context of asymptotically flat
spacetimes, follows from the decomposition of $\partial M$ into timelike and
spacelike hypersurfaces. Furthermore, we present an alternative method of
deriving the field equations satisfied by the induced metric on the purely
spacelike hypersurfaces of the foliated spacetime. This leads to the dynamical
part of the Einstein equations modified by the background fields. Our results
have the potential to be applicable in various contexts such as modified black
holes and cosmology.
| [
{
"created": "Thu, 11 May 2023 18:00:06 GMT",
"version": "v1"
}
] | 2023-05-15 | [
[
"Reyes",
"Carlos M.",
""
],
[
"Schreck",
"Marco",
""
]
] | A modification of General Relativity that is based on the gravitational Standard-Model Extension and incorporates nondynamical background fields has recently been studied via the ADM formalism. Our objective in this paper is to develop a better understanding of the additional contributions that arise on the spacetime boundary $\partial M$. An extension of the previously introduced boundary terms, which are relevant in the context of asymptotically flat spacetimes, follows from the decomposition of $\partial M$ into timelike and spacelike hypersurfaces. Furthermore, we present an alternative method of deriving the field equations satisfied by the induced metric on the purely spacelike hypersurfaces of the foliated spacetime. This leads to the dynamical part of the Einstein equations modified by the background fields. Our results have the potential to be applicable in various contexts such as modified black holes and cosmology. |
1105.3704 | Norbert Bodendorfer | Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn | New Variables for Classical and Quantum Gravity in all Dimensions II.
Lagrangian Analysis | 42 pages. v2: Journal version. Some nonessential sign errors in
section 2 corrected. Minor clarifications | Class. Quantum Grav. 30 (2013) 045002 | 10.1088/0264-9381/30/4/045002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We rederive the results of our companion paper, for matching spacetime and
internal signature, by applying in detail the Dirac algorithm to the Palatini
action. While the constraint set of the Palatini action contains second class
constraints, by an appeal to the method of gauge unfixing, we map the second
class system to an equivalent first class system which turns out to be
identical to the first class constraint system obtained via the extension of
the ADM phase space performed in our companion paper. Central to our analysis
is again the appropriate treatment of the simplicity constraint. Remarkably,
the simplicity constraint invariant extension of the Hamiltonian constraint,
that is a necessary step in the gauge unfixing procedure, involves a correction
term which is precisely the one found in the companion paper and which makes
sure that the Hamiltonian constraint derived from the Palatini Lagrangian
coincides with the ADM Hamiltonian constraint when Gauss and simplicity
constraints are satisfied. We therefore have rederived our new connection
formulation of General Relativity from an independent starting point, thus
confirming the consistency of this framework.
| [
{
"created": "Wed, 18 May 2011 18:24:59 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2013 18:40:52 GMT",
"version": "v2"
}
] | 2013-02-13 | [
[
"Bodendorfer",
"Norbert",
""
],
[
"Thiemann",
"Thomas",
""
],
[
"Thurn",
"Andreas",
""
]
] | We rederive the results of our companion paper, for matching spacetime and internal signature, by applying in detail the Dirac algorithm to the Palatini action. While the constraint set of the Palatini action contains second class constraints, by an appeal to the method of gauge unfixing, we map the second class system to an equivalent first class system which turns out to be identical to the first class constraint system obtained via the extension of the ADM phase space performed in our companion paper. Central to our analysis is again the appropriate treatment of the simplicity constraint. Remarkably, the simplicity constraint invariant extension of the Hamiltonian constraint, that is a necessary step in the gauge unfixing procedure, involves a correction term which is precisely the one found in the companion paper and which makes sure that the Hamiltonian constraint derived from the Palatini Lagrangian coincides with the ADM Hamiltonian constraint when Gauss and simplicity constraints are satisfied. We therefore have rederived our new connection formulation of General Relativity from an independent starting point, thus confirming the consistency of this framework. |
gr-qc/0702138 | Hideaki Kudoh | Yu-ichi Takamizu, Hideaki Kudoh, Kei-ichi Maeda | Dynamics of colliding branes and black brane production | 5 pages, 5 figures references added | Phys.Rev.D75:061304,2007 | 10.1103/PhysRevD.75.061304 | null | gr-qc astro-ph hep-ph hep-th | null | We study the dynamics of colliding domain walls including self-gravity. The
initial data is set up by applying a BPS domain wall in five-dimensional
supergravity, and we evolve the system determining the final outcome of
collisions. After a collision, a spacelike curvature singularity covered by a
horizon is formed in the bulk, resulting in a black brane with trapped domain
walls. This is a generic consequence of collisions, except for non-relativistic
weak field cases, in which the walls pass through one another or multiple
bounces take place without singularity formation. These results show that
incorporating the self-gravity drastically changes a naive picture of colliding
branes.
| [
{
"created": "Mon, 26 Feb 2007 21:28:53 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Apr 2007 10:00:25 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Takamizu",
"Yu-ichi",
""
],
[
"Kudoh",
"Hideaki",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We study the dynamics of colliding domain walls including self-gravity. The initial data is set up by applying a BPS domain wall in five-dimensional supergravity, and we evolve the system determining the final outcome of collisions. After a collision, a spacelike curvature singularity covered by a horizon is formed in the bulk, resulting in a black brane with trapped domain walls. This is a generic consequence of collisions, except for non-relativistic weak field cases, in which the walls pass through one another or multiple bounces take place without singularity formation. These results show that incorporating the self-gravity drastically changes a naive picture of colliding branes. |
gr-qc/9812051 | WU Zhong Chao | Wu Zhong Chao (Beijing Normal University) | Entropy of Constrained Gravitational Instanton | 8 pages | Gen.Rel.Grav. 31 (1999) 1097-1103 | null | Beijing preprint 98-110 | gr-qc | null | The seeds for quantum creations of universes are constrained gravitational
instantons. For all compact constrained instantons with U(1) isometry, the
period $\beta$ of the group parameter $\tau$ is identified as the reciprocal of
the temperature. If $\beta$ remains a free parameter under the constraints,
then the Euclidean action becomes the negative of the "entropy". As examples,
we perform the calculations for the Taub-NUT and Taub-bolt-type models and
study the quantum creation of the Taub-NUT universe.
| [
{
"created": "Tue, 15 Dec 1998 17:12:16 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Dec 1998 19:03:42 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Chao",
"Wu Zhong",
"",
"Beijing Normal University"
]
] | The seeds for quantum creations of universes are constrained gravitational instantons. For all compact constrained instantons with U(1) isometry, the period $\beta$ of the group parameter $\tau$ is identified as the reciprocal of the temperature. If $\beta$ remains a free parameter under the constraints, then the Euclidean action becomes the negative of the "entropy". As examples, we perform the calculations for the Taub-NUT and Taub-bolt-type models and study the quantum creation of the Taub-NUT universe. |
0710.0819 | Jannie Leach | Naureen Goheer, Jannie A. Leach and Peter K.S. Dunsby | Compactifying the state space for alternative theories of gravity | 18 pages, revised to match published version | Class.Quant.Grav.25:035013,2008 | 10.1088/0264-9381/25/3/035013 | null | gr-qc astro-ph math.DS | null | In this paper we address important issues surrounding the choice of variables
when performing a dynamical systems analysis of alternative theories of
gravity. We discuss the advantages and disadvantages of compactifying the state
space, and illustrate this using two examples. We first show how to define a
compact state space for the class of LRS Bianchi type I models in $R^n$-gravity
and compare to a non--compact expansion--normalised approach. In the second
example we consider the flat Friedmann matter subspace of the previous example,
and compare the compact analysis to studies where non-compact
non--expansion--normalised variables were used. In both examples we comment on
the existence of bouncing or recollapsing orbits as well as the existence of
static models.
| [
{
"created": "Wed, 3 Oct 2007 17:38:23 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Jan 2008 14:49:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Goheer",
"Naureen",
""
],
[
"Leach",
"Jannie A.",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | In this paper we address important issues surrounding the choice of variables when performing a dynamical systems analysis of alternative theories of gravity. We discuss the advantages and disadvantages of compactifying the state space, and illustrate this using two examples. We first show how to define a compact state space for the class of LRS Bianchi type I models in $R^n$-gravity and compare to a non--compact expansion--normalised approach. In the second example we consider the flat Friedmann matter subspace of the previous example, and compare the compact analysis to studies where non-compact non--expansion--normalised variables were used. In both examples we comment on the existence of bouncing or recollapsing orbits as well as the existence of static models. |
1612.08187 | Manuel Hohmann | Manuel Hohmann, Christian Pfeifer | Geodesics and the magnitude-redshift relation on cosmologically
symmetric Finsler spacetimes | 34 pages, no figures; journal version | Phys. Rev. D 95, 104021 (2017) | 10.1103/PhysRevD.95.104021 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the geodesic motion of both massive test particles, following
timelike geodesics, and light, following null geodesics, on Finsler spacetimes
with cosmological symmetry. Using adapted coordinates on the tangent bundle of
the spacetime manifold, we derive the general form of the geodesic equation.
Further, we derive a complete set of constants of motion. As an application of
these findings, we derive the magnitude-redshift relation for light propagating
on a cosmologically symmetric Finsler background, both for a general Finsler
spacetime and for particular examples, such as spacetimes equipped with
Bogoslovsky and Randers length measures. Our results allow a confrontation of
these geometries with observations of the magnitude and redshift of supernovae.
| [
{
"created": "Sat, 24 Dec 2016 14:42:08 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jan 2017 18:24:46 GMT",
"version": "v2"
},
{
"created": "Sun, 28 May 2017 05:55:16 GMT",
"version": "v3"
}
] | 2017-05-30 | [
[
"Hohmann",
"Manuel",
""
],
[
"Pfeifer",
"Christian",
""
]
] | We discuss the geodesic motion of both massive test particles, following timelike geodesics, and light, following null geodesics, on Finsler spacetimes with cosmological symmetry. Using adapted coordinates on the tangent bundle of the spacetime manifold, we derive the general form of the geodesic equation. Further, we derive a complete set of constants of motion. As an application of these findings, we derive the magnitude-redshift relation for light propagating on a cosmologically symmetric Finsler background, both for a general Finsler spacetime and for particular examples, such as spacetimes equipped with Bogoslovsky and Randers length measures. Our results allow a confrontation of these geometries with observations of the magnitude and redshift of supernovae. |
2211.10876 | Omar Mustafa | Omar Mustafa | On the Klein-Gordon G\"{u}rses-oscillators and
pseudo-G\"{u}rses-oscillators: vorticity-energy correlations and spacetime
associated degeneracies | 8 pages, 2 figures | Mod. Phys. Lett. A 39 (2024) 2350204 | 10.1142/S0217732323502048 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We discuss KG-oscillators in the (1+2)-dimensional G\"{u}rses spacetime and
under position-dependent mass (PDM) settings. We observe that the KG-G\"{u}rses
oscillators are introduced as a byproduct of the very nature of the G\"{u}rses
spacetime structure. We report that the energy levels of such KG-G\"{u}rses
oscillators admit vorticity-energy correlations as well as spacetime associated
degeneracies (STAD). We discuss KG-G\"{u}rses oscillators' results reported by
Ahmed \cite{Ahmed1 2019} and pinpoint his improper treatment of this model so
that his results should be redirected to those reported in this study.
Moreover, we introduce a new set of KG pseudo-G\"{u}rses oscillators that
admits isospectrality and invariance with the KG-G\"{u}rses oscillators and
inherits the same vorticity-energy correlations as well as STADs.
| [
{
"created": "Sun, 20 Nov 2022 05:40:39 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Mustafa",
"Omar",
""
]
] | We discuss KG-oscillators in the (1+2)-dimensional G\"{u}rses spacetime and under position-dependent mass (PDM) settings. We observe that the KG-G\"{u}rses oscillators are introduced as a byproduct of the very nature of the G\"{u}rses spacetime structure. We report that the energy levels of such KG-G\"{u}rses oscillators admit vorticity-energy correlations as well as spacetime associated degeneracies (STAD). We discuss KG-G\"{u}rses oscillators' results reported by Ahmed \cite{Ahmed1 2019} and pinpoint his improper treatment of this model so that his results should be redirected to those reported in this study. Moreover, we introduce a new set of KG pseudo-G\"{u}rses oscillators that admits isospectrality and invariance with the KG-G\"{u}rses oscillators and inherits the same vorticity-energy correlations as well as STADs. |
gr-qc/9906122 | Julio Cesar Fabris | C.P. Constantinidis(1), J.C. Fabris(1), R.G. Furtado(1) and M.
Picco(1,2) ((1) DF-UFES, Brazil, (2) LPTHE, UPMC, France) | Regular Bouncing Cosmological Solutions in Effective Actions in Four
Dimensions | Latex file, 10 pages, no figure | Phys.Rev. D61 (2000) 043503 | 10.1103/PhysRevD.61.043503 | null | gr-qc | null | We study cosmological scenarios resulting from effective actions in four
dimensions which are, under some assumptions, connected with multidimensional,
supergravity and string theories. These effective actions are labeled by the
parameters $\omega$, the dilaton coupling constant, and $n$ which establishes
the coupling between the dilaton and a scalar field originated from the gauge
field existing in the original theories. There is a large class of bouncing as
well as Friedmann-like solutions. We investigate under which conditions
bouncing regular solutions can be obtained. In the case of the string effective
action, regularity is obtained through the inclusion of contributions from the
Ramond-Ramond sector of superstring.
| [
{
"created": "Wed, 30 Jun 1999 14:14:52 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Constantinidis",
"C. P.",
"",
"DF-UFES, Brazil"
],
[
"Fabris",
"J. C.",
"",
"DF-UFES, Brazil"
],
[
"Furtado",
"R. G.",
"",
"DF-UFES, Brazil"
],
[
"Picco",
"M.",
"",
"DF-UFES, Brazil",
"LPTHE, UPMC, France"
]
] | We study cosmological scenarios resulting from effective actions in four dimensions which are, under some assumptions, connected with multidimensional, supergravity and string theories. These effective actions are labeled by the parameters $\omega$, the dilaton coupling constant, and $n$ which establishes the coupling between the dilaton and a scalar field originated from the gauge field existing in the original theories. There is a large class of bouncing as well as Friedmann-like solutions. We investigate under which conditions bouncing regular solutions can be obtained. In the case of the string effective action, regularity is obtained through the inclusion of contributions from the Ramond-Ramond sector of superstring. |
1501.03148 | Alexander Shatskiy Doctor | Alexander Shatskiy, I.D. Novikov and Alexandr Malinovsky | Spectrum for the electric dipole which nonradially falling into a black
hole | 15 pages, 3 figures. To appear in IJMPD, 2015 | null | 10.1142/S0218271815500753 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The electromagnetic bremsstrahlung spectrum for the dipole which falling by a
spiral orbit into the Schwarzschild black hole was found. The characteristic
features in this electromagnetic spectrum can be used for determine of the
black hole mass by the new way. This new way (if implemented) provides higher
accuracy in determining of the black hole mass. Also these features in the
spectrum can be used for determine of the certain characteristics in the black
hole magnetosphere or in the accretion disk characteristics around the black
hole. It is also shown that the asymptotic behavior of this spectrum (at high
frequencies) is practically independent from the impact parameter of the
falling dipole.
| [
{
"created": "Sun, 28 Dec 2014 17:02:38 GMT",
"version": "v1"
},
{
"created": "Tue, 26 May 2015 14:00:47 GMT",
"version": "v2"
}
] | 2015-08-26 | [
[
"Shatskiy",
"Alexander",
""
],
[
"Novikov",
"I. D.",
""
],
[
"Malinovsky",
"Alexandr",
""
]
] | The electromagnetic bremsstrahlung spectrum for the dipole which falling by a spiral orbit into the Schwarzschild black hole was found. The characteristic features in this electromagnetic spectrum can be used for determine of the black hole mass by the new way. This new way (if implemented) provides higher accuracy in determining of the black hole mass. Also these features in the spectrum can be used for determine of the certain characteristics in the black hole magnetosphere or in the accretion disk characteristics around the black hole. It is also shown that the asymptotic behavior of this spectrum (at high frequencies) is practically independent from the impact parameter of the falling dipole. |
0707.1816 | {\L}ukasz Szulc | Lukasz Szulc | Open FRW model in Loop Quantum Cosmology | 12 pages, no figures, latex | Class.Quant.Grav.24:6191-6200,2007 | 10.1088/0264-9381/24/24/003 | null | gr-qc | null | Open FRW model in Loop Quantum Cosmology is under consideration. The left and
right invariant vector fields and holonomies along them are studied. It is
shown that in the hyperbolic geometry of $k=-1$ it is possible to construct a
suitable loop which provides us with quantum scalar constraint originally
introduced by Vandersloot. The quantum scalar constraint operator with negative
cosmological constant is proved to be essentially self-adjoint.
| [
{
"created": "Thu, 12 Jul 2007 15:51:37 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jul 2007 08:44:09 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Oct 2007 13:05:18 GMT",
"version": "v3"
},
{
"created": "Tue, 29 Jan 2008 16:57:08 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Szulc",
"Lukasz",
""
]
] | Open FRW model in Loop Quantum Cosmology is under consideration. The left and right invariant vector fields and holonomies along them are studied. It is shown that in the hyperbolic geometry of $k=-1$ it is possible to construct a suitable loop which provides us with quantum scalar constraint originally introduced by Vandersloot. The quantum scalar constraint operator with negative cosmological constant is proved to be essentially self-adjoint. |
1301.5558 | Steinar Johannesen | Oyvind Gron and Steinar Johannesen | Different representations of the Levi-Civita Bertotti Robinson solution | 58 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Levi-Civita Bertotti Robinson (LBR) spacetime is investigated in various
coordinate systems. By means of a general formalism for constructing
coordinates in conformally flat spacetimes, coordinate transformations between
the different coordinate systems are deduced. We discuss the motion of the
reference frames in which the different coordinate systems are comoving.
Furthermore we characterize the motion of the different reference frames by
their normalized timelike Killing vector fields, i.e. by the four velocity
fields of the reference particles. We also deduce the formulae in the different
coordinate systems for the embedding of the LBR spacetime in a flat
6-dimensional manifold. In particular we discuss a scenario with a spherical
domain wall having LBR spacetime outside the wall and flat spacetime inside. We
also discuss the internal flat spacetime using the same coordinate systems as
in the external LBR spacetime with continuous metric at the wall. Among the
different cases one represents a Milne-LBR universe model with a part of the
Milne universe inside the wall and an infinitely extended LBR universe outside
it. In an appendix we define combinations of trigonometric and hyperbolic
functions that we call k-functions and present a new k-function calculus.
| [
{
"created": "Wed, 23 Jan 2013 16:42:22 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2013 18:30:26 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Mar 2013 15:31:11 GMT",
"version": "v3"
}
] | 2013-03-07 | [
[
"Gron",
"Oyvind",
""
],
[
"Johannesen",
"Steinar",
""
]
] | The Levi-Civita Bertotti Robinson (LBR) spacetime is investigated in various coordinate systems. By means of a general formalism for constructing coordinates in conformally flat spacetimes, coordinate transformations between the different coordinate systems are deduced. We discuss the motion of the reference frames in which the different coordinate systems are comoving. Furthermore we characterize the motion of the different reference frames by their normalized timelike Killing vector fields, i.e. by the four velocity fields of the reference particles. We also deduce the formulae in the different coordinate systems for the embedding of the LBR spacetime in a flat 6-dimensional manifold. In particular we discuss a scenario with a spherical domain wall having LBR spacetime outside the wall and flat spacetime inside. We also discuss the internal flat spacetime using the same coordinate systems as in the external LBR spacetime with continuous metric at the wall. Among the different cases one represents a Milne-LBR universe model with a part of the Milne universe inside the wall and an infinitely extended LBR universe outside it. In an appendix we define combinations of trigonometric and hyperbolic functions that we call k-functions and present a new k-function calculus. |
1501.04990 | Bivudutta Mishra Dr. | S. K. Tripathy, B. Mishra, G. K. Pandey, A. K. Singh, T. Kumar,
S.S.Xulu | Energy and momentum of Bianchi Type VI_h Universes | null | Advances in High Energy Physics, 2015, 705262(2015) | 10.1155/2015/705262 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the energy and momentum of the Bianchi type VI_h universes using
different prescriptions for the energy-momentum complexes in the framework of
general relativity. The energy and momentum of the Bianchi VI_h universe are
found to be zero for the parameter h = -1 of the metric. The vanishing of these
results support the conjecture of Tryon that Universe must have a zero net
value for all conserved quantities.This also supports the work of Nathan Rosen
with the Robertson-Walker metric. Moreover, it raises an interesting question:
"Why h=-1 case is so special?"
| [
{
"created": "Mon, 19 Jan 2015 10:14:39 GMT",
"version": "v1"
}
] | 2017-05-10 | [
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
],
[
"Pandey",
"G. K.",
""
],
[
"Singh",
"A. K.",
""
],
[
"Kumar",
"T.",
""
],
[
"Xulu",
"S. S.",
""
]
] | We obtain the energy and momentum of the Bianchi type VI_h universes using different prescriptions for the energy-momentum complexes in the framework of general relativity. The energy and momentum of the Bianchi VI_h universe are found to be zero for the parameter h = -1 of the metric. The vanishing of these results support the conjecture of Tryon that Universe must have a zero net value for all conserved quantities.This also supports the work of Nathan Rosen with the Robertson-Walker metric. Moreover, it raises an interesting question: "Why h=-1 case is so special?" |
gr-qc/0609045 | David Garfinkle | David Garfinkle | Matters of Gravity, The Newsletter of the Topical Group in Gravitation
of the American Physical Society, Volume 28, Fall 2006 | 20 pages. David Garfinkle (Editor) | null | null | null | gr-qc | null | Research Briefs:
Singularity Avoidance in Canonical Quantum Gravity, by Viqar Husain
What's New in LIGO, by David Shoemaker
Conference reports:
Scanning New Horizons: GR Beyond 4 dimensions, by Donald Marolf
Quantum Gravity in the Americas III, by Jorge Pullin
New Frontiers in Numerical Relativity, by Luciano Rezzolla
Teaching General Relativity to Undergraduates, by Greg Comer
Ninth Capra Meeting on Radiation Reaction, by Lior Burko
| [
{
"created": "Wed, 13 Sep 2006 16:13:05 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Garfinkle",
"David",
""
]
] | Research Briefs: Singularity Avoidance in Canonical Quantum Gravity, by Viqar Husain What's New in LIGO, by David Shoemaker Conference reports: Scanning New Horizons: GR Beyond 4 dimensions, by Donald Marolf Quantum Gravity in the Americas III, by Jorge Pullin New Frontiers in Numerical Relativity, by Luciano Rezzolla Teaching General Relativity to Undergraduates, by Greg Comer Ninth Capra Meeting on Radiation Reaction, by Lior Burko |
2105.12766 | Miguel Cruz | Azucena Bola\~nos, Miguel Cruz, Samuel Lepe and David Rogelio
M\'arquez-Castillo | Holographic dark energy in curved spacetime for interacting fluids | 26 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore the scope of two holographic dark energy models
within the interacting scenario for the dark sector and spatial curvature. For
one holographic model we consider the usual formula for the dark energy density
with the Hubble scale and the second model is given in terms of a function
instead of a constant parameter as in the usual holographic formula. In this
description both holographic models admit a future singularity. The use of
recent cosmological data is considered only to support the physical results of
our proposal. The interaction term for each holographic model, $Q$, keeps
positive along the cosmic evolution and are not given a priori, they are
reconstructed from the dynamics of the model. The temperatures for the
components of the dark sector are computed and exhibit a growing behavior in
both scenarios. The cosmic evolution in this context it is not adiabatic and
the second law it is fulfilled only under certain well-established conditions
for the temperatures of the cosmic components and positive $Q$-terms.
| [
{
"created": "Wed, 26 May 2021 18:06:24 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jun 2021 01:17:38 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Nov 2021 00:49:40 GMT",
"version": "v3"
},
{
"created": "Wed, 23 Feb 2022 02:45:28 GMT",
"version": "v4"
},
{
"c... | 2023-05-10 | [
[
"Bolaños",
"Azucena",
""
],
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Márquez-Castillo",
"David Rogelio",
""
]
] | In this work we explore the scope of two holographic dark energy models within the interacting scenario for the dark sector and spatial curvature. For one holographic model we consider the usual formula for the dark energy density with the Hubble scale and the second model is given in terms of a function instead of a constant parameter as in the usual holographic formula. In this description both holographic models admit a future singularity. The use of recent cosmological data is considered only to support the physical results of our proposal. The interaction term for each holographic model, $Q$, keeps positive along the cosmic evolution and are not given a priori, they are reconstructed from the dynamics of the model. The temperatures for the components of the dark sector are computed and exhibit a growing behavior in both scenarios. The cosmic evolution in this context it is not adiabatic and the second law it is fulfilled only under certain well-established conditions for the temperatures of the cosmic components and positive $Q$-terms. |
1311.5325 | Jian-Yang Zhu | Kui Xiao, Xiao-Kai He and Jian-Yang Zhu | Note on the super inflation in loop quantum cosmology | 9 pages, 4 figures. Physics Letters B, online publication complete:
13-NOV-2013 | Physics Letters B 727, 349-356 (2013) | 10.1016/j.physletb.2013.10.071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phenomenological effect of the super-inflation in loop quantum cosmology
(LQC) is discussed. We investigate the case that the Universe is filled with
the interacting field between massive scalar field and radiation. Considering
the damping coefficient $\Gamma$ as a constant, the changes of the scale factor
during super-inflation with four different initial conditions are discussed,
and we find that the changes of the scale factor depends on the initial values
of energy density of the scalar field and radiation at the bounce point. But no
matter which initial condition is chosen, the radiation always dominated at the
late time. Moreover, we investigate whether the super-inflation can provide
enough e-folding number. For the super-inflation starts from the quantum bounce
point, the initial value of Hubble parameter $H(t_i)\sim0$, then it is possible
to solve the flatness problem and horizon problem. As an example, following the
method of \cite{Amoros-prd} to calculate particle horizon on the condition that
the radiation dominated at bounce point, and we find that the Universe has had
enough time to be homogeneous and isotopic.
| [
{
"created": "Thu, 21 Nov 2013 07:57:09 GMT",
"version": "v1"
}
] | 2013-11-28 | [
[
"Xiao",
"Kui",
""
],
[
"He",
"Xiao-Kai",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | Phenomenological effect of the super-inflation in loop quantum cosmology (LQC) is discussed. We investigate the case that the Universe is filled with the interacting field between massive scalar field and radiation. Considering the damping coefficient $\Gamma$ as a constant, the changes of the scale factor during super-inflation with four different initial conditions are discussed, and we find that the changes of the scale factor depends on the initial values of energy density of the scalar field and radiation at the bounce point. But no matter which initial condition is chosen, the radiation always dominated at the late time. Moreover, we investigate whether the super-inflation can provide enough e-folding number. For the super-inflation starts from the quantum bounce point, the initial value of Hubble parameter $H(t_i)\sim0$, then it is possible to solve the flatness problem and horizon problem. As an example, following the method of \cite{Amoros-prd} to calculate particle horizon on the condition that the radiation dominated at bounce point, and we find that the Universe has had enough time to be homogeneous and isotopic. |
gr-qc/0209049 | Zhongchao Wu | Zhong Chao Wu (Zhejiang U. of Technology) | Dispelling the Anthropic Principle from the Dimensionality Arguments | 7 pages, Essay | Chin.Phys.Lett. 19 (2002) 1749 | 10.1088/0256-307X/19/12/303 | ZUT-02-1 | gr-qc astro-ph hep-ph hep-th | null | It is shown that in d=11 supergravity, under a very reasonable ansatz, the
nearly flat spacetime in which we are living must be 4-dimensional without
appealing to the Anthropic Principle. Can we dispel the Anthropic Principle
completely from cosmology?
| [
{
"created": "Mon, 16 Sep 2002 16:55:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Wu",
"Zhong Chao",
"",
"Zhejiang U. of Technology"
]
] | It is shown that in d=11 supergravity, under a very reasonable ansatz, the nearly flat spacetime in which we are living must be 4-dimensional without appealing to the Anthropic Principle. Can we dispel the Anthropic Principle completely from cosmology? |
1709.02276 | Fay\c{c}al Hammad | Fay\c{c}al Hammad | Density perturbations in $f(R,\phi)$-gravity with an application to the
(varying power)-law model | 12 pp. Matches the published version | Phys. Rev. D 96, 064006 (2017) | 10.1103/PhysRevD.96.064006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Density perturbations in the cosmic microwave background within general
$f(R,\phi)$ models of gravity are investigated. The general dynamical equations
for the tensor and scalar modes in any $f(R,\phi)$ gravity model are derived.
An application of the equations to the (varying power)-law modified gravity
toy-model is then made. Formulas and numerical values for the tensor-to-scalar
ratio, the scalar tilt and the tensor tilt are all obtained within this
specific model. While the model cannot provide a theoretical reason for the
value of the energy scale at which inflation should occur, it is found, based
on the latest observations of the density perturbations in the sky, that the
model requires inflation to occur at an energy scale less than the GUT-scale;
namely, $\sim10^{14}\,{\rm GeV}$. The different energy intervals examined here
show that the density perturbations recently obtained from observations are
recovered naturally, with very high precision, and without fine tuning the
model's parameters.
| [
{
"created": "Wed, 6 Sep 2017 17:20:27 GMT",
"version": "v1"
}
] | 2017-10-11 | [
[
"Hammad",
"Fayçal",
""
]
] | Density perturbations in the cosmic microwave background within general $f(R,\phi)$ models of gravity are investigated. The general dynamical equations for the tensor and scalar modes in any $f(R,\phi)$ gravity model are derived. An application of the equations to the (varying power)-law modified gravity toy-model is then made. Formulas and numerical values for the tensor-to-scalar ratio, the scalar tilt and the tensor tilt are all obtained within this specific model. While the model cannot provide a theoretical reason for the value of the energy scale at which inflation should occur, it is found, based on the latest observations of the density perturbations in the sky, that the model requires inflation to occur at an energy scale less than the GUT-scale; namely, $\sim10^{14}\,{\rm GeV}$. The different energy intervals examined here show that the density perturbations recently obtained from observations are recovered naturally, with very high precision, and without fine tuning the model's parameters. |
1503.05102 | Patryk Mach | Patryk Mach | Homoclinic accretion solutions in the Schwarzschild-anti-de Sitter
spacetime | 6 pages, 2 figures, to appear in Physical Review D | null | 10.1103/PhysRevD.91.084016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this paper is to clarify the distinction between homoclinic and
standard (global) Bondi-type accretion solutions in the Schwarzschild-anti-de
Sitter spacetime. The homoclinic solutions have recently been discovered
numerically for polytropic equations of state. Here I show that they exist also
for certain isothermal (linear) equations of state, and an analytic solution of
this type is obtained. It is argued that the existence of such solutions is
generic, although for sufficiently relativistic matter models (photon gas,
ultra-hard equation of state) there exist global solutions that can be
continued to infinity, similarly to standard Michel's solutions in the
Schwarzschild spacetime. In contrast to that global solutions should not exist
for matter models with a non-vanishing rest-mass component, and this is
demonstrated for polytropes. For homoclinic isothermal solutions I derive an
upper bound on the mass of the black hole for which stationary transonic
accretion is allowed.
| [
{
"created": "Tue, 17 Mar 2015 15:52:08 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Mach",
"Patryk",
""
]
] | The aim of this paper is to clarify the distinction between homoclinic and standard (global) Bondi-type accretion solutions in the Schwarzschild-anti-de Sitter spacetime. The homoclinic solutions have recently been discovered numerically for polytropic equations of state. Here I show that they exist also for certain isothermal (linear) equations of state, and an analytic solution of this type is obtained. It is argued that the existence of such solutions is generic, although for sufficiently relativistic matter models (photon gas, ultra-hard equation of state) there exist global solutions that can be continued to infinity, similarly to standard Michel's solutions in the Schwarzschild spacetime. In contrast to that global solutions should not exist for matter models with a non-vanishing rest-mass component, and this is demonstrated for polytropes. For homoclinic isothermal solutions I derive an upper bound on the mass of the black hole for which stationary transonic accretion is allowed. |
2307.00063 | David Brizuela | Martin Bojowald, David Brizuela, Paula Calizaya Cabrera, Sara F. Uria | The chaotic behavior of the Bianchi IX model under the influence of
quantum effects | 22 pages, 4 figures. Version accepted for publication | Phys.Rev.D 109 (2024) 4, 044038 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quantum analysis of the vacuum Bianchi IX model is performed, focusing in
particular on the chaotic nature of the system. The framework constructed here
is general enough for the results to apply in the context of any theory of
quantum gravity, since it includes only minimal approximations that make it
possible to encode the information of all quantum degrees of freedom in the
fluctuations of the usual anisotropy parameters. These fluctuations are
described as canonical variables that extend the classical phase space. In this
way, standard methods for dynamical systems can be applied to study the chaos
of the model. Two specific methods are applied that are suitable for
time-reparameterization invariant systems. First, a generalized version of the
Misner-Chitre variables is constructed, which provides an isomorphism between
the quantum Bianchi IX dynamics and the geodesic flow on a suitable Riemannian
manifold, extending, in this way, the usual billiard picture. Secondly, the
fractal dimension of the boundary between points with different outcomes in the
space of initial data is numerically analyzed. While the quantum system remains
chaotic, the main conclusion is that its strength is considerably diminished by
quantum effects as compared to its classical counterpart.
| [
{
"created": "Fri, 30 Jun 2023 18:06:07 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2024 10:10:18 GMT",
"version": "v2"
}
] | 2024-04-17 | [
[
"Bojowald",
"Martin",
""
],
[
"Brizuela",
"David",
""
],
[
"Cabrera",
"Paula Calizaya",
""
],
[
"Uria",
"Sara F.",
""
]
] | A quantum analysis of the vacuum Bianchi IX model is performed, focusing in particular on the chaotic nature of the system. The framework constructed here is general enough for the results to apply in the context of any theory of quantum gravity, since it includes only minimal approximations that make it possible to encode the information of all quantum degrees of freedom in the fluctuations of the usual anisotropy parameters. These fluctuations are described as canonical variables that extend the classical phase space. In this way, standard methods for dynamical systems can be applied to study the chaos of the model. Two specific methods are applied that are suitable for time-reparameterization invariant systems. First, a generalized version of the Misner-Chitre variables is constructed, which provides an isomorphism between the quantum Bianchi IX dynamics and the geodesic flow on a suitable Riemannian manifold, extending, in this way, the usual billiard picture. Secondly, the fractal dimension of the boundary between points with different outcomes in the space of initial data is numerically analyzed. While the quantum system remains chaotic, the main conclusion is that its strength is considerably diminished by quantum effects as compared to its classical counterpart. |
2407.04975 | Gideon Koekoek | Richard Kerner, Gideon Koekoek, Julia Schuring, Jan-Willem van Holten | Polar magnetic fields in black-hole space-times | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | To model magnetic fields of compact objects we solve the Maxwell equations in
the background of the exterior static Schwarzschild and slowly rotating Kerr
space-times. We impose the boundary condition that the electromagnetic fields
are to vanish at infinity. A full set of solutions is obtained, describing
axially symmetric magnetic fields, supplemented by axial electric fields in the
case of non-vanishing rotation of the gravitational background. We study the
motion of charged test particles in these combined gravitational and
electromagnetic fields, in particular considering the conditions for circular
equatorial orbits. Such orbits always exist in odd-multipole magnetic fields,
and they can exist for particular radii in a combination of two or more
even-multipole magnetic fields. Combinations of several odd-multipole fields
can give rise to radial variation in the field orientation and the direction of
motion of charged particles. Deviations from circularity are described using a
perturbative approach. This also allows to study the stability of the parent
circular orbits.
| [
{
"created": "Sat, 6 Jul 2024 06:55:52 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Kerner",
"Richard",
""
],
[
"Koekoek",
"Gideon",
""
],
[
"Schuring",
"Julia",
""
],
[
"van Holten",
"Jan-Willem",
""
]
] | To model magnetic fields of compact objects we solve the Maxwell equations in the background of the exterior static Schwarzschild and slowly rotating Kerr space-times. We impose the boundary condition that the electromagnetic fields are to vanish at infinity. A full set of solutions is obtained, describing axially symmetric magnetic fields, supplemented by axial electric fields in the case of non-vanishing rotation of the gravitational background. We study the motion of charged test particles in these combined gravitational and electromagnetic fields, in particular considering the conditions for circular equatorial orbits. Such orbits always exist in odd-multipole magnetic fields, and they can exist for particular radii in a combination of two or more even-multipole magnetic fields. Combinations of several odd-multipole fields can give rise to radial variation in the field orientation and the direction of motion of charged particles. Deviations from circularity are described using a perturbative approach. This also allows to study the stability of the parent circular orbits. |
0708.0723 | Salvatore Capozziello | S. Capozziello, A. Stabile, A. Troisi | The Newtonian Limit of F(R) gravity | 16 pages | Phys.Rev.D76:104019,2007 | 10.1103/PhysRevD.76.104019 | null | gr-qc astro-ph | null | A general analytic procedure is developed to deal with the Newtonian limit of
$f(R)$ gravity. A discussion comparing the Newtonian and the post-Newtonian
limit of these models is proposed in order to point out the differences between
the two approaches. We calculate the post-Newtonian parameters of such theories
without any redefinition of the degrees of freedom, in particular, without
adopting some scalar fields and without any change from Jordan to Einstein
frame. Considering the Taylor expansion of a generic $f(R)$ theory, it is
possible to obtain general solutions in term of the metric coefficients up to
the third order of approximation. In particular, the solution relative to the
$g_{tt}$ component gives a gravitational potential always corrected with
respect to the Newtonian one of the linear theory $f(R)=R$. Furthermore, we
show that the Birkhoff theorem is not a general result for $f(R)$-gravity since
time-dependent evolution for spherically symmetric solutions can be achieved
depending on the order of perturbations. Finally, we discuss the
post-Minkowskian limit and the emergence of massive gravitational wave
solutions.
| [
{
"created": "Mon, 6 Aug 2007 08:46:02 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Aug 2007 08:22:24 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Capozziello",
"S.",
""
],
[
"Stabile",
"A.",
""
],
[
"Troisi",
"A.",
""
]
] | A general analytic procedure is developed to deal with the Newtonian limit of $f(R)$ gravity. A discussion comparing the Newtonian and the post-Newtonian limit of these models is proposed in order to point out the differences between the two approaches. We calculate the post-Newtonian parameters of such theories without any redefinition of the degrees of freedom, in particular, without adopting some scalar fields and without any change from Jordan to Einstein frame. Considering the Taylor expansion of a generic $f(R)$ theory, it is possible to obtain general solutions in term of the metric coefficients up to the third order of approximation. In particular, the solution relative to the $g_{tt}$ component gives a gravitational potential always corrected with respect to the Newtonian one of the linear theory $f(R)=R$. Furthermore, we show that the Birkhoff theorem is not a general result for $f(R)$-gravity since time-dependent evolution for spherically symmetric solutions can be achieved depending on the order of perturbations. Finally, we discuss the post-Minkowskian limit and the emergence of massive gravitational wave solutions. |
1912.06891 | Olivier Minazzoli | Olivier Minazzoli | Strong lensing in multimessenger astronomy as a test of the equivalence
principle | 3 pages. Few improvements of the text in this new version | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Standard Shapiro delay-based test of the equivalence principle, which are
grounded on the measurement of two arrival times from a unique source but from
messengers with different properties, cannot produce a reliable quantitative
test of the Einstein equivalence principle. Essentially because they are based
on the estimation for different messengers of the one-way propagation time
between the emission and the observation that is not an observable per se. As a
consequence, such tests are extremely model dependent, at best. In what
follows, I argue that the differential arrival times for strongly lensed
multimessengers can be used to define a new test of the Einstein equivalence
principle that is both well-defined from a relativistic point of view and model
independent---because it is entirely based on actual observables.
| [
{
"created": "Sat, 14 Dec 2019 17:42:40 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Feb 2020 09:56:19 GMT",
"version": "v2"
}
] | 2020-02-14 | [
[
"Minazzoli",
"Olivier",
""
]
] | Standard Shapiro delay-based test of the equivalence principle, which are grounded on the measurement of two arrival times from a unique source but from messengers with different properties, cannot produce a reliable quantitative test of the Einstein equivalence principle. Essentially because they are based on the estimation for different messengers of the one-way propagation time between the emission and the observation that is not an observable per se. As a consequence, such tests are extremely model dependent, at best. In what follows, I argue that the differential arrival times for strongly lensed multimessengers can be used to define a new test of the Einstein equivalence principle that is both well-defined from a relativistic point of view and model independent---because it is entirely based on actual observables. |
1712.06072 | Sai Wang | Sai Wang | Exploring the CPT violation and birefringence of gravitational waves
with ground- and space-based gravitational-wave interferometers | Preprint, 16 pages, 1 figure, 1 table, 2 appendices. All comments are
welcome | null | 10.1140/epjc/s10052-020-7812-2 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the gravitational sector, we study the CPT violation and birefringence of
gravitational waves. In presence of the CPT violation, a relative dephasing is
generated between two circular polarization states of gravitational waves. This
effect induces the birefringence of gravitational waves. We predict the
gravitational waveform corrected by it and estimate the expected constraints on
it from Advanced Laser Interferometer Gravitational-Wave Observatory, Einstein
Telescope and Laser Interferometer Space Antenna.
| [
{
"created": "Sun, 17 Dec 2017 08:42:26 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Dec 2017 03:42:21 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Dec 2017 12:11:06 GMT",
"version": "v3"
},
{
"created": "Tue, 19 Nov 2019 10:38:38 GMT",
"version": "v4"
}
] | 2020-03-13 | [
[
"Wang",
"Sai",
""
]
] | In the gravitational sector, we study the CPT violation and birefringence of gravitational waves. In presence of the CPT violation, a relative dephasing is generated between two circular polarization states of gravitational waves. This effect induces the birefringence of gravitational waves. We predict the gravitational waveform corrected by it and estimate the expected constraints on it from Advanced Laser Interferometer Gravitational-Wave Observatory, Einstein Telescope and Laser Interferometer Space Antenna. |
gr-qc/0211082 | Roy Maartens | George Ellis, Roy Maartens | The Emergent Universe: inflationary cosmology with no singularity | minor changes; version to appear in Class Q Grav | Class.Quant.Grav.21:223-232,2004 | 10.1088/0264-9381/21/1/015 | null | gr-qc astro-ph | null | Observations indicate that the universe is effectively flat, but they do not
rule out a closed universe. The role of positive curvature is negligible at
late times, but can be crucial in the early universe. In particular, positive
curvature allows for cosmologies that originate as Einstein static universes,
and then inflate and later reheat to a hot big bang era. These cosmologies have
no singularity, no "beginning of time", and no horizon problem. If the initial
radius is chosen to be above the Planck scale, then they also have no quantum
gravity era, and are described by classical general relativity throughout their
history.
| [
{
"created": "Mon, 25 Nov 2002 14:53:59 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Jun 2003 12:12:08 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Aug 2003 14:17:19 GMT",
"version": "v3"
},
{
"created": "Sat, 25 Oct 2003 10:15:41 GMT",
"version": "v4"
}
] | 2010-04-06 | [
[
"Ellis",
"George",
""
],
[
"Maartens",
"Roy",
""
]
] | Observations indicate that the universe is effectively flat, but they do not rule out a closed universe. The role of positive curvature is negligible at late times, but can be crucial in the early universe. In particular, positive curvature allows for cosmologies that originate as Einstein static universes, and then inflate and later reheat to a hot big bang era. These cosmologies have no singularity, no "beginning of time", and no horizon problem. If the initial radius is chosen to be above the Planck scale, then they also have no quantum gravity era, and are described by classical general relativity throughout their history. |
2009.03625 | Marko Sossich | Petar Pavlovi\'c and Marko Sossich | Dynamic properties of cyclic cosmologies | 45 pages, 6 figures | Phys. Rev. D 103, 023529 (2021) | 10.1103/PhysRevD.103.023529 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our first goal in this work is to study general and model-independent
properties of cyclic cosmologies. The large number of studies of bouncing
cosmologies and different cyclic scenarios published recently calls for a
proper understanding of the universal properties of cyclic models. We thus
first review and further elaborate the common physical and geometrical
properties of various classes of cyclic models and then discuss how cyclic
Universe can be treated as a dynamic system. We then discuss how two theorems
from dynamic systems analysis can be used to ensure the existence of cyclic
cosmological solutions under certain conditions on the field equations. After
this we proceed towards our second goal which is the application of the
obtained results to different frameworks of modified gravity theories: $f(R)$
gravity, dynamic dark energy and $f(T)$ gravity. We discuss the general
requirements for the existence of cyclic solutions in these theories and also
obtain various examples of cyclic cosmologies, while discussing their basic
properties.
| [
{
"created": "Tue, 8 Sep 2020 10:05:14 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Sep 2020 09:01:49 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Oct 2021 12:32:54 GMT",
"version": "v3"
}
] | 2021-10-11 | [
[
"Pavlović",
"Petar",
""
],
[
"Sossich",
"Marko",
""
]
] | Our first goal in this work is to study general and model-independent properties of cyclic cosmologies. The large number of studies of bouncing cosmologies and different cyclic scenarios published recently calls for a proper understanding of the universal properties of cyclic models. We thus first review and further elaborate the common physical and geometrical properties of various classes of cyclic models and then discuss how cyclic Universe can be treated as a dynamic system. We then discuss how two theorems from dynamic systems analysis can be used to ensure the existence of cyclic cosmological solutions under certain conditions on the field equations. After this we proceed towards our second goal which is the application of the obtained results to different frameworks of modified gravity theories: $f(R)$ gravity, dynamic dark energy and $f(T)$ gravity. We discuss the general requirements for the existence of cyclic solutions in these theories and also obtain various examples of cyclic cosmologies, while discussing their basic properties. |
1712.09977 | Stefanos Aretakis | Yannis Angelopoulos, Stefanos Aretakis, Dejan Gajic | Logarithmic corrections in the asymptotic expansion for the radiation
field along null infinity | 32 pages, 4 figures | Journal of Hyperbolic Differential Equations, 16 (01), 1-34 (2019) | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the second-order asymptotics for the radiation field of spherically
symmetric solutions to the wave equation on spherically symmetric and
asymptotically flat backgrounds including the Schwarzschild and sub-extremal
Reissner-Nordstrom families of black holes. These terms appear as logarithmic
corrections to the leading-order asymptotic terms which were rigorously derived
in our previous work. Such corrections were heuristically and numerically
derived in the physics literature in the case of a non-vanishing Newman-Penrose
constant. In this case, our results provide a rigorous confirmation of the
existence of these corrections. On the other hand, the precise logarithmic
corrections for compactly supported initial data (and hence with a vanishing
Newman-Penrose constant) explicitly obtained here appear to be new.
| [
{
"created": "Thu, 28 Dec 2017 18:38:53 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Mar 2021 22:18:26 GMT",
"version": "v2"
}
] | 2021-03-03 | [
[
"Angelopoulos",
"Yannis",
""
],
[
"Aretakis",
"Stefanos",
""
],
[
"Gajic",
"Dejan",
""
]
] | We obtain the second-order asymptotics for the radiation field of spherically symmetric solutions to the wave equation on spherically symmetric and asymptotically flat backgrounds including the Schwarzschild and sub-extremal Reissner-Nordstrom families of black holes. These terms appear as logarithmic corrections to the leading-order asymptotic terms which were rigorously derived in our previous work. Such corrections were heuristically and numerically derived in the physics literature in the case of a non-vanishing Newman-Penrose constant. In this case, our results provide a rigorous confirmation of the existence of these corrections. On the other hand, the precise logarithmic corrections for compactly supported initial data (and hence with a vanishing Newman-Penrose constant) explicitly obtained here appear to be new. |
2406.15843 | Antoine Rignon-Bret | Antoine Rignon-Bret | Black hole thermodynamic potentials for asymptotic observers | 25 pages + references, 6 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The generalized second law states the total entropy of any closed system as
the universe cannot decrease if we include black hole entropy. From the point
of view of an asymptotic observer, a black hole can be described at late time
as an open system at fixed temperature which can radiate energy and entropy to
infinity. I argue that for massless free quantum fields propagating on a black
hole background, we can define a black hole dynamical free energy using
observables defined at future null infinity which decreases on successive cross
sections. The proof of this spontaneous evolution law is similar to Wall's
derivation of the generalized second law and relies on the monotonicity
properties of the relative entropy. I discuss first the simpler case of the
Schwarzschild background in which the grey body factor are neglected and show
that in this case the free energy only depends on the Bondi mass, the Hawking
temperature and the von Neumann entropy of the propagating quantum fields. Then
I argue that taking into account the grey body factors adds a new term to the
thermodynamic potential involving the number of particles detected at future
null infinity conjugated to a chemical potential. Finally, I discuss the case
of the Kerr black hole for which an angular momentum piece needs to be added to
the free energy.
| [
{
"created": "Sat, 22 Jun 2024 13:14:13 GMT",
"version": "v1"
}
] | 2024-06-25 | [
[
"Rignon-Bret",
"Antoine",
""
]
] | The generalized second law states the total entropy of any closed system as the universe cannot decrease if we include black hole entropy. From the point of view of an asymptotic observer, a black hole can be described at late time as an open system at fixed temperature which can radiate energy and entropy to infinity. I argue that for massless free quantum fields propagating on a black hole background, we can define a black hole dynamical free energy using observables defined at future null infinity which decreases on successive cross sections. The proof of this spontaneous evolution law is similar to Wall's derivation of the generalized second law and relies on the monotonicity properties of the relative entropy. I discuss first the simpler case of the Schwarzschild background in which the grey body factor are neglected and show that in this case the free energy only depends on the Bondi mass, the Hawking temperature and the von Neumann entropy of the propagating quantum fields. Then I argue that taking into account the grey body factors adds a new term to the thermodynamic potential involving the number of particles detected at future null infinity conjugated to a chemical potential. Finally, I discuss the case of the Kerr black hole for which an angular momentum piece needs to be added to the free energy. |
2011.09266 | Anil Yadav dr | Anil Kumar Yadav, A. M. Alshehri, Nafis Ahmad, G. K. Goswami, Mukesh
Kumar | Transitioning Universe with hybrid scalar field in Bianchi I space-time | 11 pages, 9 figures | Physics of the Dark Universe 31 (2021) 100738 | 10.1016/j.dark.2020.100738 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate a Bianchi type I transitioning Universe in
Brans-Dicke theory. To get an explicit solution of the field equations, we
assume scalar field as $\phi = \phi_{0}\left[t^{\alpha}exp(\beta
t)\right]^{\delta}$ with $\phi_{0}$, $\alpha$, $\beta$ and $\delta$ as
constants. The values of $\alpha$ and $\beta$ are obtained by probing the
proposed model with recent observational Hubble data (OHD) points. The
interacting and non-interacting scenarios between dark matter and dark energy
of the derived Universe within the framework of Brans-Dicke gravity are
investigated. The $om(z)$ analysis of the Universe in derived model shows that
the Universe is filled with dynamical dark energy with its equation of state
parameter $\omega_{de} > -1$. Hence the Universe behaves like a quintessence
model at present epoch. Some physical properties of the Universe are also
discussed.
| [
{
"created": "Mon, 16 Nov 2020 15:08:59 GMT",
"version": "v1"
}
] | 2020-11-19 | [
[
"Yadav",
"Anil Kumar",
""
],
[
"Alshehri",
"A. M.",
""
],
[
"Ahmad",
"Nafis",
""
],
[
"Goswami",
"G. K.",
""
],
[
"Kumar",
"Mukesh",
""
]
] | In this paper we investigate a Bianchi type I transitioning Universe in Brans-Dicke theory. To get an explicit solution of the field equations, we assume scalar field as $\phi = \phi_{0}\left[t^{\alpha}exp(\beta t)\right]^{\delta}$ with $\phi_{0}$, $\alpha$, $\beta$ and $\delta$ as constants. The values of $\alpha$ and $\beta$ are obtained by probing the proposed model with recent observational Hubble data (OHD) points. The interacting and non-interacting scenarios between dark matter and dark energy of the derived Universe within the framework of Brans-Dicke gravity are investigated. The $om(z)$ analysis of the Universe in derived model shows that the Universe is filled with dynamical dark energy with its equation of state parameter $\omega_{de} > -1$. Hence the Universe behaves like a quintessence model at present epoch. Some physical properties of the Universe are also discussed. |
gr-qc/9602057 | Jacob D. Bekenstein | Avraham E. Mayo and Jacob D. Bekenstein | No hair for spherical black holes: charged and nonminimally coupled
scalar field with self--interaction | 30 pages, RevTeX. Sec.IV corrected, simplified and shortened.
Corrections to Sec.IIA between Eqs. 2.7 and Eq.2.1. First two paragraphs of
Sec. VC new. To appear Phys. Rev. D, Oct. 15, 1996 | Phys.Rev. D54 (1996) 5059-5069 | 10.1103/PhysRevD.54.5059 | null | gr-qc astro-ph hep-th | null | We prove three theorems in general relativity which rule out classical scalar
hair of static, spherically symmetric, possibly electrically charged black
holes. We first generalize Bekenstein's no--hair theorem for a multiplet of
minimally coupled real scalar fields with not necessarily quadratic action to
the case of a charged black hole. We then use a conformal map of the geometry
to convert the problem of a charged (or neutral) black hole with hair in the
form of a neutral self--interacting scalar field nonminimally coupled to
gravity to the preceding problem, thus establishing a no--hair theorem for the
cases with nonminimal coupling parameter $\xi<0$ or $\xi\geq {1\over 2}$. The
proof also makes use of a causality requirement on the field configuration.
Finally, from the required behavior of the fields at the horizon and infinity
we exclude hair of a charged black hole in the form of a charged
self--interacting scalar field nonminimally coupled to gravity for any $\xi$.
| [
{
"created": "Wed, 28 Feb 1996 08:12:00 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Aug 1996 09:37:00 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Mayo",
"Avraham E.",
""
],
[
"Bekenstein",
"Jacob D.",
""
]
] | We prove three theorems in general relativity which rule out classical scalar hair of static, spherically symmetric, possibly electrically charged black holes. We first generalize Bekenstein's no--hair theorem for a multiplet of minimally coupled real scalar fields with not necessarily quadratic action to the case of a charged black hole. We then use a conformal map of the geometry to convert the problem of a charged (or neutral) black hole with hair in the form of a neutral self--interacting scalar field nonminimally coupled to gravity to the preceding problem, thus establishing a no--hair theorem for the cases with nonminimal coupling parameter $\xi<0$ or $\xi\geq {1\over 2}$. The proof also makes use of a causality requirement on the field configuration. Finally, from the required behavior of the fields at the horizon and infinity we exclude hair of a charged black hole in the form of a charged self--interacting scalar field nonminimally coupled to gravity for any $\xi$. |
1706.08889 | Alexey Toporensky | D.M. Chirkov, A.V. Toporensky | On stable exponential cosmological solutions in the EGB model with a
$\Lambda$-term in dimensions D = 5,6,7,8 | 11 pages, no figures. arXiv admin note: text overlap with
arXiv:1612.08451 by other authors | Gravitation and Cosmology 23, 4, 359 (2017) | 10.1134/S0202289317040077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A $D$-dimensional Einstein-Gauss-Bonnet (EGB) flat cosmological model with a
cosmological term $\Lambda$ is considered. We focus on solutions with
exponential dependence of scale factor on time. Using previously developed
general analysis of stability of such solutions done by V.D.Ivashchuk (2016) we
apply the criterion from that paper to all known exponential solutions up to
dimensionality 7+1. We show that this criterion which guarantees stability of
solution under consideration is fulfilled for all combination of coupling
constant of the theory except for some discrete set.
| [
{
"created": "Mon, 26 Jun 2017 16:07:26 GMT",
"version": "v1"
}
] | 2018-07-16 | [
[
"Chirkov",
"D. M.",
""
],
[
"Toporensky",
"A. V.",
""
]
] | A $D$-dimensional Einstein-Gauss-Bonnet (EGB) flat cosmological model with a cosmological term $\Lambda$ is considered. We focus on solutions with exponential dependence of scale factor on time. Using previously developed general analysis of stability of such solutions done by V.D.Ivashchuk (2016) we apply the criterion from that paper to all known exponential solutions up to dimensionality 7+1. We show that this criterion which guarantees stability of solution under consideration is fulfilled for all combination of coupling constant of the theory except for some discrete set. |
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