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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2112.01747 | Yan-Gang Miao | Yang Guo, Yan-Gang Miao | Charged black-bounce spacetimes: Photon rings, shadows and observational
appearances | v1: 10 pages, 6 figures; v2: references added; v3: 12 pages, 7
figures, clarifications and references added, final version to appear in
Nuclear Physics B | Nucl. Phys. B 983 (2022) 115938 | 10.1016/j.nuclphysb.2022.115938 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The photon ring, shadow and observational appearance of the emission
originating near a charged black-bounce are investigated. Based on the geodesic
analysis, we determine the upper and lower limits of critical impact parameters
of a charged black-bounce. In particular, we find that the charged black-bounce
shares the same critical impact parameter with the Reissner-Nordst\"om black
hole. In addition, we classify the light trajectories coming from the region
near the charged black-bounce by utilizing the rays tracing procedure, and then
investigate the observational appearance of the emissions from a thin disk
accretion and a spherically symmetric infalling accretion. We reveal that a
large charge increases the observed intensity but decreases the apparent size
of shadows, and that the photon ring presents the intrinsic property of a
spacetime geometry, which is independent of the types of the two accretions.
Our results are in good agreement with the recent observations.
| [
{
"created": "Fri, 3 Dec 2021 07:00:23 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Dec 2021 09:09:37 GMT",
"version": "v2"
},
{
"created": "Sun, 7 Aug 2022 10:40:07 GMT",
"version": "v3"
}
] | 2022-08-23 | [
[
"Guo",
"Yang",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | The photon ring, shadow and observational appearance of the emission originating near a charged black-bounce are investigated. Based on the geodesic analysis, we determine the upper and lower limits of critical impact parameters of a charged black-bounce. In particular, we find that the charged black-bounce shares the same critical impact parameter with the Reissner-Nordst\"om black hole. In addition, we classify the light trajectories coming from the region near the charged black-bounce by utilizing the rays tracing procedure, and then investigate the observational appearance of the emissions from a thin disk accretion and a spherically symmetric infalling accretion. We reveal that a large charge increases the observed intensity but decreases the apparent size of shadows, and that the photon ring presents the intrinsic property of a spacetime geometry, which is independent of the types of the two accretions. Our results are in good agreement with the recent observations. |
1409.2407 | Sebastian Steinhaus | Bianca Dittrich, Sebastian Mizera, Sebastian Steinhaus | Decorated tensor network renormalization for lattice gauge theories and
spin foam models | 20 pages, 13 figures. v2: extended explanation of tensor network
algorithm with focus on Abelian case | New J.Phys. 18 (2016) no.5, 053009 | 10.1088/1367-2630/18/5/053009 | null | gr-qc cond-mat.str-el hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tensor network techniques have proved to be powerful tools that can be
employed to explore the large scale dynamics of lattice systems. Nonetheless,
the redundancy of degrees of freedom in lattice gauge theories (and related
models) poses a challenge for standard tensor network algorithms. We
accommodate for such systems by introducing an additional structure decorating
the tensor network. This allows to explicitly preserve the gauge symmetry of
the system under coarse graining and straightforwardly interpret the fixed
point tensors. We propose and test (for models with finite Abelian groups) a
coarse graining algorithm for lattice gauge theories based on decorated tensor
networks. We also point out that decorated tensor networks are applicable to
other models as well, where they provide the advantage to give immediate access
to certain expectation values and correlation functions.
| [
{
"created": "Mon, 8 Sep 2014 15:53:31 GMT",
"version": "v1"
},
{
"created": "Fri, 6 May 2016 16:17:44 GMT",
"version": "v2"
}
] | 2016-05-12 | [
[
"Dittrich",
"Bianca",
""
],
[
"Mizera",
"Sebastian",
""
],
[
"Steinhaus",
"Sebastian",
""
]
] | Tensor network techniques have proved to be powerful tools that can be employed to explore the large scale dynamics of lattice systems. Nonetheless, the redundancy of degrees of freedom in lattice gauge theories (and related models) poses a challenge for standard tensor network algorithms. We accommodate for such systems by introducing an additional structure decorating the tensor network. This allows to explicitly preserve the gauge symmetry of the system under coarse graining and straightforwardly interpret the fixed point tensors. We propose and test (for models with finite Abelian groups) a coarse graining algorithm for lattice gauge theories based on decorated tensor networks. We also point out that decorated tensor networks are applicable to other models as well, where they provide the advantage to give immediate access to certain expectation values and correlation functions. |
gr-qc/0506084 | Jerzy Kowalski-Glikman | Katarzyna Imilkowska and Jerzy Kowalski-Glikman | Doubly Special Relativity as a Limit of Gravity | 26 pages, Submitted to Lecture Notes in Physics | Lect.NotesPhys.702:279-298,2006 | 10.1007/3-540-34523-X_10 | null | gr-qc | null | Doubly Special Relativity (DSR) is a theory with two observer-independent
scales, of velocity and mass, which is expected to replace Special Relativity
at ultra-high energies. In these notes we first discuss the postulates of DSR,
and then turn to presenting arguments supporting the hypothesis that DSR can be
regarded as a flat space, semiclassical limit of gravity. The notes are based
on the talk presented at the conference ``Special Relativity -- Will it Survive
the Next 100 Years?''
| [
{
"created": "Wed, 15 Jun 2005 09:37:57 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 2005 07:19:17 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Imilkowska",
"Katarzyna",
""
],
[
"Kowalski-Glikman",
"Jerzy",
""
]
] | Doubly Special Relativity (DSR) is a theory with two observer-independent scales, of velocity and mass, which is expected to replace Special Relativity at ultra-high energies. In these notes we first discuss the postulates of DSR, and then turn to presenting arguments supporting the hypothesis that DSR can be regarded as a flat space, semiclassical limit of gravity. The notes are based on the talk presented at the conference ``Special Relativity -- Will it Survive the Next 100 Years?'' |
2407.20476 | Sebastiano Segreto | Sebastiano Segreto, Giovanni Montani | Mixmaster Universe in a 2D non-commutative GUP framework | 23 pages, 3 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we examine the dynamical aspects of the cosmological Mixmaster
model within the framework of non-commutative generalized uncertainty principle
(GUP) theories. The theory is formulated classically by introducing a
well-defined symplectic form that differs from the ordinary one, thereby
inducing a general deformation of the Poisson brackets describing a precise
class of GUP theories. In this general setting, we first investigate the
behavior of the Bianchi I and Bianchi II models using Misner variables. Then,
we study the Bianchi IX model in the Mixmaster approximation, which is
well-known for accurately reproducing the dynamics of the point-particle
Universe approaching the cosmological singularity. We derive the corresponding
Belinsky-Khalatnikov-Lifshitz (BKL) map and then, by selecting a specific GUP
model associated with string theory, we explicitly investigate its resulting
features shaped by the non-commutative GUP scheme. Our findings reveal that the
chaotic and ergodic behavior typically observed in the standard BKL map, which
characterizes the point-Universe's approach to the singularity, is replaced by
quasi-periodic orbits in the parameter space of the theory. This corresponds to
an oscillatory behavior of the Universe's scale factors, dependent on the
initial conditions.
| [
{
"created": "Tue, 30 Jul 2024 00:28:18 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Segreto",
"Sebastiano",
""
],
[
"Montani",
"Giovanni",
""
]
] | In this work, we examine the dynamical aspects of the cosmological Mixmaster model within the framework of non-commutative generalized uncertainty principle (GUP) theories. The theory is formulated classically by introducing a well-defined symplectic form that differs from the ordinary one, thereby inducing a general deformation of the Poisson brackets describing a precise class of GUP theories. In this general setting, we first investigate the behavior of the Bianchi I and Bianchi II models using Misner variables. Then, we study the Bianchi IX model in the Mixmaster approximation, which is well-known for accurately reproducing the dynamics of the point-particle Universe approaching the cosmological singularity. We derive the corresponding Belinsky-Khalatnikov-Lifshitz (BKL) map and then, by selecting a specific GUP model associated with string theory, we explicitly investigate its resulting features shaped by the non-commutative GUP scheme. Our findings reveal that the chaotic and ergodic behavior typically observed in the standard BKL map, which characterizes the point-Universe's approach to the singularity, is replaced by quasi-periodic orbits in the parameter space of the theory. This corresponds to an oscillatory behavior of the Universe's scale factors, dependent on the initial conditions. |
1704.05378 | Sergey Chervon | Sergey V. Chervon and Igor V. Fomin | On calculation of the cosmological parameters in exact models of
inflation | 5 pages, publication of 2008, minor corrections | Grav. & Cosmol. v.14, (2008) 163 | 10.1134/S0202289308020060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a method of calculating the key cosmological parameters on the
basis of a selected scale factor by using exact solutions of the background
equations. We specify the formulas for calculating the power spectrum, the
spectral indices and their ratios, and the ratio of squared amplitudes of
scalar and tensor perturbations. We obtain, for the first time, expressions for
the basic cosmological parameters in terms of the scalar factor value at the
instant of crossing the cosmological horizon. In this case, the cosmological
parameters are calculated for a wide class of exact models. They are compared
with their analogs derived in the slow-rolling approximation.
| [
{
"created": "Tue, 18 Apr 2017 14:51:45 GMT",
"version": "v1"
}
] | 2017-04-19 | [
[
"Chervon",
"Sergey V.",
""
],
[
"Fomin",
"Igor V.",
""
]
] | We discuss a method of calculating the key cosmological parameters on the basis of a selected scale factor by using exact solutions of the background equations. We specify the formulas for calculating the power spectrum, the spectral indices and their ratios, and the ratio of squared amplitudes of scalar and tensor perturbations. We obtain, for the first time, expressions for the basic cosmological parameters in terms of the scalar factor value at the instant of crossing the cosmological horizon. In this case, the cosmological parameters are calculated for a wide class of exact models. They are compared with their analogs derived in the slow-rolling approximation. |
gr-qc/0401098 | Bernd Reimann | Bernd Reimann, Bernd Bruegmann | Late Time Analysis for Maximal Slicing of Reissner-Nordstr\"om Puncture
Evolutions | 22 pages, 4 figures, changes in Sec. IV B, as published in Phys. Rev.
D | Phys.Rev.D69:124009,2004 | 10.1103/PhysRevD.69.124009 | AEI-2003-107, CGPG-03/12-1 | gr-qc | null | We perform an analytic late time analysis for maximal slicing of the
Reissner-Nordstr\"om black hole spacetime. In particular, we discuss the
collapse of the lapse in terms of its late time behavior at the throat and at
the event horizon for the even and the puncture lapse. In the latter case we
also determine the value of the lapse at the puncture. Furthermore, in the
limit of late times slice stretching effects are studied as they arise for
maximal slicing of puncture evolutions. We perform numerical experiments for a
Schwarzschild black hole with puncture lapse and find agreement with the
analytical results.
| [
{
"created": "Fri, 23 Jan 2004 18:25:26 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jun 2004 16:48:02 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Reimann",
"Bernd",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | We perform an analytic late time analysis for maximal slicing of the Reissner-Nordstr\"om black hole spacetime. In particular, we discuss the collapse of the lapse in terms of its late time behavior at the throat and at the event horizon for the even and the puncture lapse. In the latter case we also determine the value of the lapse at the puncture. Furthermore, in the limit of late times slice stretching effects are studied as they arise for maximal slicing of puncture evolutions. We perform numerical experiments for a Schwarzschild black hole with puncture lapse and find agreement with the analytical results. |
2309.02709 | Soham Chatterjee | Sagnik Roy, Soham Chatterjee and Ratna Koley | Shadow of higher dimensional collapsing dark star and blackhole | 15 pages, 4 figures | Eur.Phys.J.C 84 (2024) 1, 47 | 10.1140/epjc/s10052-023-12379-w | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The shadow of a black hole or a collapsing star is of great importance as we
can extract important properties of the object and of the surrounding spacetime
from the shadow profile. It can also be used to distinguish different types of
black holes and ultra compact objects. In this work, we have analytically
calculated the shadow of a higher dimensional collapsing dark star, described
by higher dimensional Vaidya metric, by choosing a slightly generalized version
of Misner--Sharp mass function. We have also numerically investigated the
properties of the shadows of the black holes and the collapsing stars for a
slightly more general mass function. Examining the potential influence of extra
spatial dimensions on the shadow, we have explored the possibility of
distinguishing higher dimensions from the standard four-dimensional spacetime.
| [
{
"created": "Wed, 6 Sep 2023 04:43:26 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jul 2024 13:14:38 GMT",
"version": "v2"
}
] | 2024-07-08 | [
[
"Roy",
"Sagnik",
""
],
[
"Chatterjee",
"Soham",
""
],
[
"Koley",
"Ratna",
""
]
] | The shadow of a black hole or a collapsing star is of great importance as we can extract important properties of the object and of the surrounding spacetime from the shadow profile. It can also be used to distinguish different types of black holes and ultra compact objects. In this work, we have analytically calculated the shadow of a higher dimensional collapsing dark star, described by higher dimensional Vaidya metric, by choosing a slightly generalized version of Misner--Sharp mass function. We have also numerically investigated the properties of the shadows of the black holes and the collapsing stars for a slightly more general mass function. Examining the potential influence of extra spatial dimensions on the shadow, we have explored the possibility of distinguishing higher dimensions from the standard four-dimensional spacetime. |
1611.01062 | Jeremy Sakstein | Jeremy Sakstein, Michael Kenna-Allison, Kazuya Koyama | Stellar Pulsations in Beyond Horndeski Gravity Theories | 13 pages, 4 figures, 1 table. Updated to reflect published version.
Minor changes from previous version | JCAP03(2017)007 | 10.1088/1475-7516/2017/03/007 | null | gr-qc astro-ph.CO astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories of gravity in the beyond Horndeski class recover the predictions of
general relativity in the solar system whilst admitting novel cosmologies,
including late-time de Sitter solutions in the absence of a cosmological
constant. Deviations from Newton's law are predicted inside astrophysical
bodies, which allow for falsifiable, smoking-gun tests of the theory. In this
work we study the pulsations of stars by deriving and solving the wave equation
governing linear adiabatic oscillations to find the modified period of
pulsation. Using both semi-analytic and numerical models, we perform a
preliminary survey of the stellar zoo in an attempt to identify the best
candidate objects for testing the theory. Brown dwarfs and Cepheid stars are
found to be particularly sensitive objects and we discuss the possibility of
using both to test the theory.
| [
{
"created": "Thu, 3 Nov 2016 15:28:29 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Nov 2016 15:20:47 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Feb 2017 14:14:58 GMT",
"version": "v3"
}
] | 2017-03-08 | [
[
"Sakstein",
"Jeremy",
""
],
[
"Kenna-Allison",
"Michael",
""
],
[
"Koyama",
"Kazuya",
""
]
] | Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory. |
1203.3799 | Muhammad Sharif | M. Sharif and M. Azam | Effects of Electromagnetic Field on the Dynamical Instability of
Cylindrical Collapse | null | JCAP 02(2012)043 | 10.1088/1475-7516/2012/02/043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The objective of this paper is to discuss the dynamical instability in the
context of Newtonian and post Newtonian regimes. For this purpose, we consider
non-viscous heat conducting charged isotropic fluid as a collapsing matter with
cylindrical symmetry. Darmois junction conditions are formulated. The
perturbation scheme is applied to investigate the influence of dissipation and
electromagnetic field on the dynamical instability. We conclude that the
adiabatic index $\Gamma$ has smaller value for such a fluid in cylindrically
symmetric than isotropic sphere.
| [
{
"created": "Fri, 16 Mar 2012 02:09:07 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Sharif",
"M.",
""
],
[
"Azam",
"M.",
""
]
] | The objective of this paper is to discuss the dynamical instability in the context of Newtonian and post Newtonian regimes. For this purpose, we consider non-viscous heat conducting charged isotropic fluid as a collapsing matter with cylindrical symmetry. Darmois junction conditions are formulated. The perturbation scheme is applied to investigate the influence of dissipation and electromagnetic field on the dynamical instability. We conclude that the adiabatic index $\Gamma$ has smaller value for such a fluid in cylindrically symmetric than isotropic sphere. |
gr-qc/0201039 | Peter Leifer | P. Leifer | Super-Relativity and State-Dependent Gauge Fields | 20 pages, LaTeX, submitted to the Foundations of Physics Letters,
some formulas improved, minor grammatical changes | null | null | null | gr-qc hep-th quant-ph | null | State-dependent gauge principle invoked to realize the relativity to a
measuring device, has been proposed. Self-consistent global (cosmic) potential
forms the state space of the fundamental field and its connection, agreed with
Fubini-Study metric of $CP(N-1)$, serves as state-dependent gauge potential. In
this framework the linearity of the ordinary quantum mechanics appears as a
`tangent approximation' to the totally nonlinear underlying pre-dynamical
`functional' field theory on $CP(N-1)$.
| [
{
"created": "Fri, 11 Jan 2002 20:01:27 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Jan 2002 08:40:29 GMT",
"version": "v2"
},
{
"created": "Sun, 27 Jan 2002 18:56:53 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Leifer",
"P.",
""
]
] | State-dependent gauge principle invoked to realize the relativity to a measuring device, has been proposed. Self-consistent global (cosmic) potential forms the state space of the fundamental field and its connection, agreed with Fubini-Study metric of $CP(N-1)$, serves as state-dependent gauge potential. In this framework the linearity of the ordinary quantum mechanics appears as a `tangent approximation' to the totally nonlinear underlying pre-dynamical `functional' field theory on $CP(N-1)$. |
gr-qc/9412022 | Harald Mueller | Harald F. Muller and Christoph Schmid | Non--Gaussian Primordial Fluctuations | 9 pages, uses AMSTex, 1 figure (not included) | null | null | ETH-TH/94-35 | gr-qc astro-ph | null | We analyze the non--Gaussian primordial fluctuations which are inescapably
contributed by scalar fields $\Phi$ with vanishing expectation values,
$\langle\Phi\rangle=0$, present during inflation in addition to the inflaton
field. For simplicity we take $\Phi$ to be non--interacting and minimally
coupled to gravity. $\Phi$ is a Gaussian variable, but the energy density
fluctuations contributed by such a field are $\chi^2$--distributed. We compute
the three--point function $\xxxT$ for the configuration of an equilateral
triangle (with side length $\ell$) and the skewness $\dddRR$, {\it i.e.} the
third moment of the one--point probability distribution of the spatially
smeared energy density contrast $\de_R$, where $R$ is the smearing scale. The
relative magnitudes of the non--Gaussian effects,
$[\xi^{(N)}]^{1/N}/[\xi^{(2)}]^{1/2}$, do not grow in time. They are given by
numerical constants of order unity, independent of the scale $\ell$. The
"bi--skewness" $\dddRS$ is positive. For smearing lengths $R\ll S$ this shows
that in our model (in contrast to Gaussian models) voids are more quiet than
high--density regions.
| [
{
"created": "Wed, 7 Dec 1994 15:36:34 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Muller",
"Harald F.",
""
],
[
"Schmid",
"Christoph",
""
]
] | We analyze the non--Gaussian primordial fluctuations which are inescapably contributed by scalar fields $\Phi$ with vanishing expectation values, $\langle\Phi\rangle=0$, present during inflation in addition to the inflaton field. For simplicity we take $\Phi$ to be non--interacting and minimally coupled to gravity. $\Phi$ is a Gaussian variable, but the energy density fluctuations contributed by such a field are $\chi^2$--distributed. We compute the three--point function $\xxxT$ for the configuration of an equilateral triangle (with side length $\ell$) and the skewness $\dddRR$, {\it i.e.} the third moment of the one--point probability distribution of the spatially smeared energy density contrast $\de_R$, where $R$ is the smearing scale. The relative magnitudes of the non--Gaussian effects, $[\xi^{(N)}]^{1/N}/[\xi^{(2)}]^{1/2}$, do not grow in time. They are given by numerical constants of order unity, independent of the scale $\ell$. The "bi--skewness" $\dddRS$ is positive. For smearing lengths $R\ll S$ this shows that in our model (in contrast to Gaussian models) voids are more quiet than high--density regions. |
2109.02424 | Shanika Galaudage | Shanika Galaudage and Colm Talbot and Tushar Nagar and Deepnika Jain
and Eric Thrane and Ilya Mandel | Building better spin models for merging binary black holes: Evidence for
non-spinning and rapidly spinning nearly aligned sub-populations | 13 pages, 6 figures | null | 10.3847/2041-8213/ac2f3c | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent work paints a conflicting portrait of the distribution of black hole
spins in merging binaries measured with gravitational waves. Some analyses find
that a significant fraction of merging binaries contain at least one black hole
with a spin tilt $>90^\circ$ with respect to the orbital angular momentum
vector, which has been interpreted as a signature for dynamical assembly. Other
analyses find the data are consistent with a bimodal population in which some
binaries contain black holes with negligible spin while the rest contain black
holes with spin vectors preferentially aligned with the orbital angular
momentum vector. In this work, we scrutinize models for the distribution of
black hole spins to pinpoint possible failure modes in which the model yields a
faulty conclusion. We reanalyze data from the second LIGO--Virgo
gravitational-wave transient catalog (GWTC-2) using a revised spin model, which
allows for a sub-population of black holes with negligible spins. In agreement
with recent results by Roulet et al., we show that the GWTC-2 detections are
consistent with two distinct sub-populations. We estimate that $29-75\%$ (90\%
credible interval) of merging binaries contain black holes with negligible spin
$\chi \approx 0$. The remaining binaries are part of a second sub-population in
which the spin vectors are preferentially (but not exactly) aligned to the
orbital angular momentum. The black holes in this second sub-population are
characterized by spins of $\chi\sim0.45$. We suggest that the inferred spin
distribution is consistent with the hypothesis that all merging binaries form
via the field formation scenario.
| [
{
"created": "Fri, 3 Sep 2021 02:42:02 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Sep 2021 10:12:54 GMT",
"version": "v2"
},
{
"created": "Sat, 23 Apr 2022 13:26:46 GMT",
"version": "v3"
}
] | 2022-04-26 | [
[
"Galaudage",
"Shanika",
""
],
[
"Talbot",
"Colm",
""
],
[
"Nagar",
"Tushar",
""
],
[
"Jain",
"Deepnika",
""
],
[
"Thrane",
"Eric",
""
],
[
"Mandel",
"Ilya",
""
]
] | Recent work paints a conflicting portrait of the distribution of black hole spins in merging binaries measured with gravitational waves. Some analyses find that a significant fraction of merging binaries contain at least one black hole with a spin tilt $>90^\circ$ with respect to the orbital angular momentum vector, which has been interpreted as a signature for dynamical assembly. Other analyses find the data are consistent with a bimodal population in which some binaries contain black holes with negligible spin while the rest contain black holes with spin vectors preferentially aligned with the orbital angular momentum vector. In this work, we scrutinize models for the distribution of black hole spins to pinpoint possible failure modes in which the model yields a faulty conclusion. We reanalyze data from the second LIGO--Virgo gravitational-wave transient catalog (GWTC-2) using a revised spin model, which allows for a sub-population of black holes with negligible spins. In agreement with recent results by Roulet et al., we show that the GWTC-2 detections are consistent with two distinct sub-populations. We estimate that $29-75\%$ (90\% credible interval) of merging binaries contain black holes with negligible spin $\chi \approx 0$. The remaining binaries are part of a second sub-population in which the spin vectors are preferentially (but not exactly) aligned to the orbital angular momentum. The black holes in this second sub-population are characterized by spins of $\chi\sim0.45$. We suggest that the inferred spin distribution is consistent with the hypothesis that all merging binaries form via the field formation scenario. |
1803.02339 | Eric Ling | Piotr T. Chru\'sciel, Gregory J. Galloway, Eric Ling | Weakly trapped surfaces in asymptotically de Sitter spacetimes | 9 pages, 4 figures; v2: figure corrected, references added. Version
to appear in CQG | null | 10.1088/1361-6382/aac30d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is a standard fact that trapped or marginally trapped surfaces are not
visible from conformal infinity, under the usual set of conditions on matter
fields and the conformal completion, provided that the cosmological constant is
non-positive. In this note we show that the situation is more delicate in the
presence of a positive cosmological constant: we present examples of visible
marginally trapped surfaces, and we provide a set of natural conditions which
guarantee non-visibility.
| [
{
"created": "Tue, 6 Mar 2018 18:55:12 GMT",
"version": "v1"
},
{
"created": "Wed, 9 May 2018 17:32:10 GMT",
"version": "v2"
}
] | 2018-05-10 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Galloway",
"Gregory J.",
""
],
[
"Ling",
"Eric",
""
]
] | It is a standard fact that trapped or marginally trapped surfaces are not visible from conformal infinity, under the usual set of conditions on matter fields and the conformal completion, provided that the cosmological constant is non-positive. In this note we show that the situation is more delicate in the presence of a positive cosmological constant: we present examples of visible marginally trapped surfaces, and we provide a set of natural conditions which guarantee non-visibility. |
1707.02873 | Parbati Sahoo | Parbati Sahoo, Raghavender Reddy | LRS Bianchi type-I bulk viscous cosmological models in $f(R,T)$ gravity | 7 pages, 3 figure, This work accepted for publication in Astrophysics
journal with issue 1 for 2018 | Astrophysics, 61 ,1 , 2018, pp. 153-162 | 10.1007/s10511-018-9522-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied the locally rotationally symmetric (LRS) Bianchi type-I
cosmological model in $f(R,T)$ gravity ($R$ is the Ricci scalar and $T$ is the
trace of the stress energy tensor) with Bulk viscous fluid as matter content.
The model is constructed for the linear form $f(R,T)=R+2f(T)$. The exact
solution of field equations is obtained by using a time varying deceleration
parameter $q$ for a suitable choice of the function $f(T)$. In this work, the
bulk viscous pressure $\bar{p}$ is found to be negative and energy density
$\rho$ is found to be positive. The obtained model is anisotropic, accelerating
and compatible with the results of astronomical observations. Also, some
important features of physical parameters of this model have been discussed.
| [
{
"created": "Fri, 7 Jul 2017 11:42:33 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2017 12:03:32 GMT",
"version": "v2"
}
] | 2018-03-29 | [
[
"Sahoo",
"Parbati",
""
],
[
"Reddy",
"Raghavender",
""
]
] | We have studied the locally rotationally symmetric (LRS) Bianchi type-I cosmological model in $f(R,T)$ gravity ($R$ is the Ricci scalar and $T$ is the trace of the stress energy tensor) with Bulk viscous fluid as matter content. The model is constructed for the linear form $f(R,T)=R+2f(T)$. The exact solution of field equations is obtained by using a time varying deceleration parameter $q$ for a suitable choice of the function $f(T)$. In this work, the bulk viscous pressure $\bar{p}$ is found to be negative and energy density $\rho$ is found to be positive. The obtained model is anisotropic, accelerating and compatible with the results of astronomical observations. Also, some important features of physical parameters of this model have been discussed. |
gr-qc/0308049 | Ralf Schutzhold | R. Sch\"utzhold and W. G. Unruh | Large-scale non-locality in "doubly special relativity" with an
energy-dependent speed of light | 5 pages RevTeX, several modifications | JETP Lett. 78 (2003) 431-435; Pisma Zh.Eksp.Teor.Fiz. 78 (2003)
899-903 | 10.1134/1.1633311 | null | gr-qc hep-th | null | There are two major alternatives for violating the (usual) Lorentz invariance
at large (Planckian) energies or momenta - either not all inertial frames (in
the Planck regime) are equivalent (e.g., there is an effectively preferred
frame) or the transformations from one frame to another are (non-linearly)
deformed (``doubly special relativity''). We demonstrate that the natural (and
reasonable) assumption of an energy-dependent speed of light in the latter
method goes along with violations of locality/separability (and even
translational invariance) on macroscopic scales.
PACS: 03.30.+p, 11.30.Cp, 04.60.-m, 04.50.+h.
| [
{
"created": "Thu, 14 Aug 2003 22:22:03 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Aug 2003 20:55:12 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Schützhold",
"R.",
""
],
[
"Unruh",
"W. G.",
""
]
] | There are two major alternatives for violating the (usual) Lorentz invariance at large (Planckian) energies or momenta - either not all inertial frames (in the Planck regime) are equivalent (e.g., there is an effectively preferred frame) or the transformations from one frame to another are (non-linearly) deformed (``doubly special relativity''). We demonstrate that the natural (and reasonable) assumption of an energy-dependent speed of light in the latter method goes along with violations of locality/separability (and even translational invariance) on macroscopic scales. PACS: 03.30.+p, 11.30.Cp, 04.60.-m, 04.50.+h. |
2402.12342 | Gustav Uhre Jakobsen | Alessandra Buonanno, Gustav Uhre Jakobsen, Gustav Mogull | Post-Minkowskian Theory Meets the Spinning Effective-One-Body Approach
for Two-Body Scattering | 25 pages, 10 figures, 8 tables, 1 ancillary file | null | null | HU-EP-24/07-RTG | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Effective-one-body (EOB) waveforms employed by the LIGO-Virgo-KAGRA
Collaboration have primarily been developed by resumming the post-Newtonian
expansion of the relativistic two-body problem. Given the recent significant
advancements in post-Minkowskian (PM) theory and gravitational self-force
formalism, there is considerable interest in creating waveform models that
integrate information from various perturbative methods in innovative ways.
This becomes particularly crucial when tackling the accuracy challenge posed by
upcoming ground-based detectors (such as the Einstein Telescope and Cosmic
Explorer) and space-based detectors (such as LISA, TianQin or Taiji) expected
to operate in the next decade. In this context, we present the derivation of
the first spinning EOB Hamiltonian that incorporates PM results up to
three-loop order: the SEOB-PM model. The model accounts for the complete
hyperbolic motion, encompassing nonlocal-in-time tails. To evaluate its
accuracy, we compare its predictions for the conservative scattering angle,
augmented with dissipative contributions, against numerical-relativity data of
non-spinning and spinning equal-mass black holes. We observe very good
agreement, comparable, and in some cases slightly better to the recently
proposed $w_{\rm EOB}$-potential model, of which the SEOB-PM model is a
resummation around the probe limit. Indeed, in the probe limit, the SEOB-PM
Hamiltonian and scattering angles reduce to the one of a test mass in Kerr
spacetime. Once complemented with nonlocal-in-time contributions for bound
orbits, the SEOB-PM Hamiltonian can be utilized to generate waveform models for
spinning black holes on quasi-circular orbits.
| [
{
"created": "Mon, 19 Feb 2024 18:15:09 GMT",
"version": "v1"
}
] | 2024-02-20 | [
[
"Buonanno",
"Alessandra",
""
],
[
"Jakobsen",
"Gustav Uhre",
""
],
[
"Mogull",
"Gustav",
""
]
] | Effective-one-body (EOB) waveforms employed by the LIGO-Virgo-KAGRA Collaboration have primarily been developed by resumming the post-Newtonian expansion of the relativistic two-body problem. Given the recent significant advancements in post-Minkowskian (PM) theory and gravitational self-force formalism, there is considerable interest in creating waveform models that integrate information from various perturbative methods in innovative ways. This becomes particularly crucial when tackling the accuracy challenge posed by upcoming ground-based detectors (such as the Einstein Telescope and Cosmic Explorer) and space-based detectors (such as LISA, TianQin or Taiji) expected to operate in the next decade. In this context, we present the derivation of the first spinning EOB Hamiltonian that incorporates PM results up to three-loop order: the SEOB-PM model. The model accounts for the complete hyperbolic motion, encompassing nonlocal-in-time tails. To evaluate its accuracy, we compare its predictions for the conservative scattering angle, augmented with dissipative contributions, against numerical-relativity data of non-spinning and spinning equal-mass black holes. We observe very good agreement, comparable, and in some cases slightly better to the recently proposed $w_{\rm EOB}$-potential model, of which the SEOB-PM model is a resummation around the probe limit. Indeed, in the probe limit, the SEOB-PM Hamiltonian and scattering angles reduce to the one of a test mass in Kerr spacetime. Once complemented with nonlocal-in-time contributions for bound orbits, the SEOB-PM Hamiltonian can be utilized to generate waveform models for spinning black holes on quasi-circular orbits. |
2211.05097 | Alisha Marriott-Best | Alisha Marriott-Best | Quantum Cosmology of the Nothing | Submitted as dissertation for MSc | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Quantum cosmology uses a wave function to model the universe, but finding
solutions for this poses a problem as it is difficult to define the boundary
conditions or identify the correct path for a path integral. We begin the
discussion by going over various proposals and look at how bubble universe
nucleation can be used as an analogy for the tunneling wave function. We review
how the Hartle-Hawking wave function and tunneling wave functions are
equivalent. This leads into how the transition between the decelerated and
accelerated expansion is formulated as a bounce in connection space. This is
done in a toy model Universe that contains only radiation and a cosmological
constant $\Lambda$. The wave function is a superposition on an incident wave, a
reflected wave, and an evanescent wave; when it is constructed from wave
packets. Using the toy model, we introduce the new concept of the universe
tunneling to a different classical region during this bounce in connection
space. This concept is explored by deriving the wave function of the evanescent
wave $\psi_{ev}$ in order to calculate $|\psi|^2$ to give an indication of the
probability of the universe tunneling to another classical region.
| [
{
"created": "Tue, 8 Nov 2022 11:45:58 GMT",
"version": "v1"
}
] | 2022-11-10 | [
[
"Marriott-Best",
"Alisha",
""
]
] | Quantum cosmology uses a wave function to model the universe, but finding solutions for this poses a problem as it is difficult to define the boundary conditions or identify the correct path for a path integral. We begin the discussion by going over various proposals and look at how bubble universe nucleation can be used as an analogy for the tunneling wave function. We review how the Hartle-Hawking wave function and tunneling wave functions are equivalent. This leads into how the transition between the decelerated and accelerated expansion is formulated as a bounce in connection space. This is done in a toy model Universe that contains only radiation and a cosmological constant $\Lambda$. The wave function is a superposition on an incident wave, a reflected wave, and an evanescent wave; when it is constructed from wave packets. Using the toy model, we introduce the new concept of the universe tunneling to a different classical region during this bounce in connection space. This concept is explored by deriving the wave function of the evanescent wave $\psi_{ev}$ in order to calculate $|\psi|^2$ to give an indication of the probability of the universe tunneling to another classical region. |
2106.05479 | Jonathan Luk | Jonathan Luk and Maxime Van de Moortel | Nonlinear interaction of three impulsive gravitational waves II: the
wave estimates | Part II to arXiv:2101.08353; 95 pages, 2 figures; version accepted
for publication | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the second and last paper of a series aimed at solving the local
Cauchy problem for polarized $\mathbb U(1)$ symmetric solutions to the Einstein
vacuum equations featuring the nonlinear interaction of three small amplitude
impulsive gravitational waves. Such solutions are characterized by their three
singular "wave-fronts" across which the curvature tensor is allowed to admit a
delta singularity.
Under polarized $\mathbb U(1)$ symmetry, the Einstein vacuum equations reduce
to the Einstein-scalar field system in $(2+1)$ dimensions. In this paper, we
focus on the wave estimates for the scalar field in the reduced system. The
scalar field terms are the most singular ones in the problem, with the scalar
field only being Lipschitz initially. We use geometric commutators to prove
energy estimates which reflect that the singularities are localized, and that
the scalar field obeys additional fractional-derivative regularity, as well as
regularity along appropriately defined "good directions". The main challenge is
to carry out all these estimates using only the low-regularity properties of
the metric. Finally, we prove an anisotropic Sobolev embedding lemma, which
when combined with our energy estimates shows that the scalar field is
everywhere Lipschitz, and that it obeys additional $C^{1,\theta}$ estimates
away from the most singular region.
| [
{
"created": "Thu, 10 Jun 2021 03:34:21 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Mar 2023 04:01:59 GMT",
"version": "v2"
}
] | 2023-03-28 | [
[
"Luk",
"Jonathan",
""
],
[
"Van de Moortel",
"Maxime",
""
]
] | This is the second and last paper of a series aimed at solving the local Cauchy problem for polarized $\mathbb U(1)$ symmetric solutions to the Einstein vacuum equations featuring the nonlinear interaction of three small amplitude impulsive gravitational waves. Such solutions are characterized by their three singular "wave-fronts" across which the curvature tensor is allowed to admit a delta singularity. Under polarized $\mathbb U(1)$ symmetry, the Einstein vacuum equations reduce to the Einstein-scalar field system in $(2+1)$ dimensions. In this paper, we focus on the wave estimates for the scalar field in the reduced system. The scalar field terms are the most singular ones in the problem, with the scalar field only being Lipschitz initially. We use geometric commutators to prove energy estimates which reflect that the singularities are localized, and that the scalar field obeys additional fractional-derivative regularity, as well as regularity along appropriately defined "good directions". The main challenge is to carry out all these estimates using only the low-regularity properties of the metric. Finally, we prove an anisotropic Sobolev embedding lemma, which when combined with our energy estimates shows that the scalar field is everywhere Lipschitz, and that it obeys additional $C^{1,\theta}$ estimates away from the most singular region. |
0808.1039 | Vladimir Khatsymovsky | V.M. Khatsymovsky | Gravity action on discontinuous metrics | 6 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider minisuperspace gravity system described by piecewise flat metric
discontinuous on three-dimensional faces (tetrahedra). There are infinite terms
in the Einstein action. However, starting from proper regularization, these
terms in the exponential of path integral result in pre-exponent factor with
$\delta$-functions requiring vanishing metric discontinuities. Thereby path
integral measure in Regge calculus is related to path integral measure in Regge
calculus where length of an edge is not constrained to be the same for all the
4-tetrahedra containing this edge, i.e. in Regge calculus with independent
4-tetrahedra. The result obtained is in accordance with our previous one
obtained from symmetry considerations.
| [
{
"created": "Thu, 7 Aug 2008 14:39:34 GMT",
"version": "v1"
}
] | 2008-10-09 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | We consider minisuperspace gravity system described by piecewise flat metric discontinuous on three-dimensional faces (tetrahedra). There are infinite terms in the Einstein action. However, starting from proper regularization, these terms in the exponential of path integral result in pre-exponent factor with $\delta$-functions requiring vanishing metric discontinuities. Thereby path integral measure in Regge calculus is related to path integral measure in Regge calculus where length of an edge is not constrained to be the same for all the 4-tetrahedra containing this edge, i.e. in Regge calculus with independent 4-tetrahedra. The result obtained is in accordance with our previous one obtained from symmetry considerations. |
2109.10022 | Satish Kumar Saravanan | Satish Kumar Saravanan | Spin-induced motion in black hole spacetime | 27 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the covariant hamiltonian formalism, we study the dynamics of
spinning test bodies in the Kerr and Schwarzschild spacetimes. For the first
time, we derive the exact solution of circular orbits in the Kerr plane without
truncating the spin of the particle or black hole. A large class of noncircular
bound orbits has been developed by using the world line perturbation theory. It
is found that the spinning body possesses a double frequency, and thus, in
addition to the angular shift, the periastron varies radially proportional to
the alignment and magnitude of spins. By using the method of stability
analysis, we predict the radius of the innermost stable circular orbit (ISCO)
as a function of particle and black hole spin. Furthermore, extending the
perturbative technique for generic orientation of spin in Schwarzschild
spacetime leads to the development of nonplanar bound orbits and the prediction
of fully relativistic precessional frequency of the orbital plane.
| [
{
"created": "Tue, 21 Sep 2021 08:25:54 GMT",
"version": "v1"
}
] | 2021-09-22 | [
[
"Saravanan",
"Satish Kumar",
""
]
] | Based on the covariant hamiltonian formalism, we study the dynamics of spinning test bodies in the Kerr and Schwarzschild spacetimes. For the first time, we derive the exact solution of circular orbits in the Kerr plane without truncating the spin of the particle or black hole. A large class of noncircular bound orbits has been developed by using the world line perturbation theory. It is found that the spinning body possesses a double frequency, and thus, in addition to the angular shift, the periastron varies radially proportional to the alignment and magnitude of spins. By using the method of stability analysis, we predict the radius of the innermost stable circular orbit (ISCO) as a function of particle and black hole spin. Furthermore, extending the perturbative technique for generic orientation of spin in Schwarzschild spacetime leads to the development of nonplanar bound orbits and the prediction of fully relativistic precessional frequency of the orbital plane. |
2109.13293 | Damianos Iosifidis | Damianos Iosifidis | Quadratic Metric-Affine Gravity: Solving for the Affine-Connection | 14 pages, no figures | null | 10.1140/epjc/s10052-022-10499-3 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider the most general 11 parameter parity even quadratic Metric-Affine
Theory whose action consists of the usual Einstein-Hilbert plus the 11
quadratic terms in torsion, non-metricity as well as their mixing. By following
a certain procedure and using a simple trick we are able to find the unique
solution of the affine connection in terms of an arbitrary hypermomentum. Given
a fairly general non-degeneracy condition our result provides the exact form of
the affine connection for all types of matter. Subsequently we compute the
forms of torsion and non-metricity in terms of their sources (hypermomentum
tensor) and also express the metric field equations in effectively Einstein's
GR with modified source terms that depend on the hypermomentum and its
derivatives. We show that in the absence of matter the Theory always reduces to
GR. Finally we generalize our result and find the form of the connection for a
wider class of quadratic Theories.
| [
{
"created": "Mon, 27 Sep 2021 18:29:09 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Iosifidis",
"Damianos",
""
]
] | We consider the most general 11 parameter parity even quadratic Metric-Affine Theory whose action consists of the usual Einstein-Hilbert plus the 11 quadratic terms in torsion, non-metricity as well as their mixing. By following a certain procedure and using a simple trick we are able to find the unique solution of the affine connection in terms of an arbitrary hypermomentum. Given a fairly general non-degeneracy condition our result provides the exact form of the affine connection for all types of matter. Subsequently we compute the forms of torsion and non-metricity in terms of their sources (hypermomentum tensor) and also express the metric field equations in effectively Einstein's GR with modified source terms that depend on the hypermomentum and its derivatives. We show that in the absence of matter the Theory always reduces to GR. Finally we generalize our result and find the form of the connection for a wider class of quadratic Theories. |
gr-qc/9702022 | Robert Manuel Wald | Robert M. Wald | Black Holes and Thermodynamics | 26 pages, plain LaTeX; to appear in the proceedings of the Symposium
on Black Holes and Relativistic Stars (in honor of S. Chandrasekhar),
December 14-15, 1996 | null | null | null | gr-qc hep-th | null | We review the remarkable relationship between the laws of black hole
mechanics and the ordinary laws of thermodynamics. It is emphasized that - in
analogy with the laws of thermodynamics - the validity the laws of black hole
mechanics does not appear to depend upon the details of the underlying
dynamical theory (i.e., upon the particular field equations of general
relativity). It also is emphasized that a number of unresolved issues arise in
``ordinary thermodynamics'' in the context of general relativity. Thus, a
deeper understanding of the relationship between black holes and thermodynamics
may provide us with an opportunity not only to gain a better understanding of
the nature of black holes in quantum gravity, but also to better understand
some aspects of the fundamental nature of thermodynamics itself.
| [
{
"created": "Tue, 11 Feb 1997 23:02:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wald",
"Robert M.",
""
]
] | We review the remarkable relationship between the laws of black hole mechanics and the ordinary laws of thermodynamics. It is emphasized that - in analogy with the laws of thermodynamics - the validity the laws of black hole mechanics does not appear to depend upon the details of the underlying dynamical theory (i.e., upon the particular field equations of general relativity). It also is emphasized that a number of unresolved issues arise in ``ordinary thermodynamics'' in the context of general relativity. Thus, a deeper understanding of the relationship between black holes and thermodynamics may provide us with an opportunity not only to gain a better understanding of the nature of black holes in quantum gravity, but also to better understand some aspects of the fundamental nature of thermodynamics itself. |
gr-qc/0305036 | Karim . A. Malik | Karim A. Malik, Maria Rodriguez-Martinez, and David Langlois | Defining perturbations on submanifolds | 9 pages, 2 figures, Revtex4 | Phys.Rev. D68 (2003) 123517 | 10.1103/PhysRevD.68.123517 | null | gr-qc astro-ph hep-th | null | We study the definition of perturbations in the presence of a submanifold,
like e.g. a brane. In the standard theory of cosmological perturbations, one
compares quantities at the same coordinate points in the non-perturbed and the
perturbed manifolds, identified via a (non-unique) mapping between the two
manifolds. In the presence of a physical submanifold one needs to modify this
definition in order to evaluate perturbations of quantities at the submanifold
location. As an application, we compute the perturbed metric and the extrinsic
curvature tensors at the brane position in a general gauge.
| [
{
"created": "Fri, 9 May 2003 16:46:25 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Malik",
"Karim A.",
""
],
[
"Rodriguez-Martinez",
"Maria",
""
],
[
"Langlois",
"David",
""
]
] | We study the definition of perturbations in the presence of a submanifold, like e.g. a brane. In the standard theory of cosmological perturbations, one compares quantities at the same coordinate points in the non-perturbed and the perturbed manifolds, identified via a (non-unique) mapping between the two manifolds. In the presence of a physical submanifold one needs to modify this definition in order to evaluate perturbations of quantities at the submanifold location. As an application, we compute the perturbed metric and the extrinsic curvature tensors at the brane position in a general gauge. |
2012.14084 | Shyam Das | Shyam Das, Bikash Chandra Paul, Ranjan Sharma | Gravitational collapse of anisotropic stars | 15 pages, 3 figures, Accepted for publication in INJP | null | 10.1007/s12648-020-01931-z | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We study the gravitational collapse of a spherically symmetric anisotropic
relativistic star within Einstein theory of gravity making use of one of our
recently developed collapsing stellar models [{\it Astrophys. Space Sci.}
{\bf361} 99 (2016)]. The final state of continual gravitational collapse of a
massive star under regular initial conditions is analyzed in terms of the
formation of black holes. To study the evolution of an anisotropic star
undergoing gravitational collapse, it is assumed that the dissipation process
happens in the form of radial heat-flux. The interior space-time is described
by static metric matched at the boundary with Vaidya metric that describes the
exterior to the radiating star. The initial static configuration is described
by the relativistic solution obtained by Paul and Deb [{\it Astrophys. Space
Sci.} {\bf354} 421 (2014)]. The impact of anisotropy on the dynamical
gravitational collapse of a massive star is studied. The relativistic causal
heat transport equation of the Maxwell-Cattaneo equation is utilized to show
the dependence of anisotropy on the temperature profile of the collapsing
system.
| [
{
"created": "Mon, 28 Dec 2020 03:53:00 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"Das",
"Shyam",
""
],
[
"Paul",
"Bikash Chandra",
""
],
[
"Sharma",
"Ranjan",
""
]
] | We study the gravitational collapse of a spherically symmetric anisotropic relativistic star within Einstein theory of gravity making use of one of our recently developed collapsing stellar models [{\it Astrophys. Space Sci.} {\bf361} 99 (2016)]. The final state of continual gravitational collapse of a massive star under regular initial conditions is analyzed in terms of the formation of black holes. To study the evolution of an anisotropic star undergoing gravitational collapse, it is assumed that the dissipation process happens in the form of radial heat-flux. The interior space-time is described by static metric matched at the boundary with Vaidya metric that describes the exterior to the radiating star. The initial static configuration is described by the relativistic solution obtained by Paul and Deb [{\it Astrophys. Space Sci.} {\bf354} 421 (2014)]. The impact of anisotropy on the dynamical gravitational collapse of a massive star is studied. The relativistic causal heat transport equation of the Maxwell-Cattaneo equation is utilized to show the dependence of anisotropy on the temperature profile of the collapsing system. |
2304.11616 | Gopi Kant Goswami Dr | Anirudh Pradhan, Gopikant Goswami, Aroonkumar Beesham | Reconstruction of an Observationally Constrained $f(R, T)$ gravity model | 25 pages, 11 figures, 2 tables | International Journal of Geometric Mathods in Modern Physics 2023 | 10.1142/S0219887823501694 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, an attempt is made to construct a
Friedmann-Lemaitre-Robertson-Walker model in $f(R,T)$ gravity with a perfect
fluid that yields acceleration at late times. We take $f(R,T)$ as $R$ + $8\pi
\mu T$. As in the $\Lambda$CDM model, we take the matter to consist of two
components, viz., $\Omega_m$ and $\Omega_{\mu}$ such that $\Omega_m$ +
$\Omega_{\mu}$=1. The parameter $\Omega_m$ is the matter density (baryons +
dark matter), and $\Omega_{\mu}$ is the density associated with the Ricci
scalar $R$ and the trace $T$ of the energy momentum tensor, which we shall call
dominant matter. We find that at present $\Omega_{\mu}$ is dominant over
$\Omega_m$, and that the two are in the ratio 3:1 to 3:2 according to the three
data sets: (i) 77 Hubble OHD data set (ii) 580 SNIa supernova distance modulus
data set and (iii) 66 pantheon SNIa data which include high red shift data in
the range $0\leq z\leq 2.36$. We have also calculated the pressures and
densities associated with the two matter densities, viz., $p_{\mu}$,
$\rho_{\mu}$, $p_m$ and $\rho_m$, respectively. It is also found that at
present, $\rho_{\mu}$ is greater than $\rho_m$. The negative dominant matter
pressure $p_{\mu}$ creates acceleration in the universe. Our deceleration and
snap parameters show a change from negative to positive, whereas the jerk
parameter is always positive. This means that the universe is at present
accelerating and in the past it was decelerating. State finder diagnostics
indicate that our model is at present a dark energy quintessence model. The
various other physical and geometric properties of the model are also
discussed.
| [
{
"created": "Sun, 23 Apr 2023 11:13:56 GMT",
"version": "v1"
}
] | 2023-04-25 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Goswami",
"Gopikant",
""
],
[
"Beesham",
"Aroonkumar",
""
]
] | In this paper, an attempt is made to construct a Friedmann-Lemaitre-Robertson-Walker model in $f(R,T)$ gravity with a perfect fluid that yields acceleration at late times. We take $f(R,T)$ as $R$ + $8\pi \mu T$. As in the $\Lambda$CDM model, we take the matter to consist of two components, viz., $\Omega_m$ and $\Omega_{\mu}$ such that $\Omega_m$ + $\Omega_{\mu}$=1. The parameter $\Omega_m$ is the matter density (baryons + dark matter), and $\Omega_{\mu}$ is the density associated with the Ricci scalar $R$ and the trace $T$ of the energy momentum tensor, which we shall call dominant matter. We find that at present $\Omega_{\mu}$ is dominant over $\Omega_m$, and that the two are in the ratio 3:1 to 3:2 according to the three data sets: (i) 77 Hubble OHD data set (ii) 580 SNIa supernova distance modulus data set and (iii) 66 pantheon SNIa data which include high red shift data in the range $0\leq z\leq 2.36$. We have also calculated the pressures and densities associated with the two matter densities, viz., $p_{\mu}$, $\rho_{\mu}$, $p_m$ and $\rho_m$, respectively. It is also found that at present, $\rho_{\mu}$ is greater than $\rho_m$. The negative dominant matter pressure $p_{\mu}$ creates acceleration in the universe. Our deceleration and snap parameters show a change from negative to positive, whereas the jerk parameter is always positive. This means that the universe is at present accelerating and in the past it was decelerating. State finder diagnostics indicate that our model is at present a dark energy quintessence model. The various other physical and geometric properties of the model are also discussed. |
gr-qc/0001020 | Sergiu Vacaru | Sergiu I. Vacaru | Locally Anisotropic Black Holes in Einstein Gravity | latex209, version 4, misprints corrected | Chapter 4 in: "Clifford and Riemann Finsler Structures in
Geometric Mechanics and Gravity, Selected Works by S. Vacaru, P. Stavrinos,
E. Gaburov and D. Gonta (Geometry Balkan Press, 2006)
http://www.mathem.pub.ro/dgds/mono/va-t.pdf | null | null | gr-qc astro-ph hep-ph hep-th | null | By applying the method of moving frames modelling one and two dimensional
local anisotropies we construct new solutions of Einstein equations on
pseudo-Riemannian spacetimes. The first class of solutions describes
non-trivial deformations of static spherically symmetric black holes to locally
anisotropic ones which have elliptic (in three dimensions) and ellipsoidal,
toroidal and elliptic and another forms of cylinder symmetries (in four
dimensions). The second class consists from black holes with oscillating
elliptic horizons.
| [
{
"created": "Sat, 8 Jan 2000 11:12:04 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jan 2000 13:07:01 GMT",
"version": "v2"
},
{
"created": "Mon, 8 May 2000 11:55:37 GMT",
"version": "v3"
}
] | 2016-08-31 | [
[
"Vacaru",
"Sergiu I.",
""
]
] | By applying the method of moving frames modelling one and two dimensional local anisotropies we construct new solutions of Einstein equations on pseudo-Riemannian spacetimes. The first class of solutions describes non-trivial deformations of static spherically symmetric black holes to locally anisotropic ones which have elliptic (in three dimensions) and ellipsoidal, toroidal and elliptic and another forms of cylinder symmetries (in four dimensions). The second class consists from black holes with oscillating elliptic horizons. |
2309.05695 | Johanna N. Borissova | Johanna Borissova | Suppression of spacetime singularities in quantum gravity | v1: 10 pages, 3 figures; v2: 12 pages, clarifications & discussions
added, matches version accepted for publication in CQG | null | 10.1088/1361-6382/ad46c0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the requirement of suppressing spacetime geometries with a
curvature singularity via destructive interference in the Lorentzian
gravitational path integral as a constraint on the microscopic action for
gravity. Based on simple examples of static spherically symmetric spacetimes,
we demonstrate that complete singularity suppression in the path integral
stipulates that the action for gravity be of infinite order in the curvature.
| [
{
"created": "Mon, 11 Sep 2023 18:00:00 GMT",
"version": "v1"
},
{
"created": "Sat, 4 May 2024 23:02:36 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Borissova",
"Johanna",
""
]
] | We investigate the requirement of suppressing spacetime geometries with a curvature singularity via destructive interference in the Lorentzian gravitational path integral as a constraint on the microscopic action for gravity. Based on simple examples of static spherically symmetric spacetimes, we demonstrate that complete singularity suppression in the path integral stipulates that the action for gravity be of infinite order in the curvature. |
2405.18508 | Rishabh Kumar Singh | Shailesh Kumar, Rishabh Kumar Singh, Abhishek Chowdhuri, Arpan
Bhattacharyya | Exploring waveforms with non-GR deviations for extreme mass-ratio
inspirals | 26 pages, 3 Figures | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fundamental process of detecting and examining the polarization modes of
gravitational waves plays a pivotal role in enhancing our grasp on the precise
mechanisms behind their generation. A thorough investigation is essential for
delving deeper into the essence of gravitational waves and rigorously
evaluating and validating the range of modified gravity theories. In this line
of interest, a general description of black holes in theories beyond general
relativity can serve a meaningful purpose where distinct deviation parameters
can be mapped to solutions representing distinct theories. Employing a refined
version of the deformed Kerr geometry, which is free from pathological
behaviours such as unphysical divergences in the metric, we explore an extreme
mass-ratio inspiral system, wherein a stellar-mass object perturbs a
supermassive black hole. We compute the effects of deformation parameters on
gravitational wave fluxes, orbital evolution and phase dynamics with leading
order post-Newtonian corrections. With the waveform analysis, we assess the
plausibility of detecting deviations from general relativity through
observations facilitated by the Laser Interferometer Space Antenna (LISA),
simultaneously constraining the extent of these deviations. Therefore, this
analysis provides an understanding while highlighting the essential role of
observations in advancing gravitational phenomena beyond general relativity.
| [
{
"created": "Tue, 28 May 2024 18:24:17 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Kumar",
"Shailesh",
""
],
[
"Singh",
"Rishabh Kumar",
""
],
[
"Chowdhuri",
"Abhishek",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | The fundamental process of detecting and examining the polarization modes of gravitational waves plays a pivotal role in enhancing our grasp on the precise mechanisms behind their generation. A thorough investigation is essential for delving deeper into the essence of gravitational waves and rigorously evaluating and validating the range of modified gravity theories. In this line of interest, a general description of black holes in theories beyond general relativity can serve a meaningful purpose where distinct deviation parameters can be mapped to solutions representing distinct theories. Employing a refined version of the deformed Kerr geometry, which is free from pathological behaviours such as unphysical divergences in the metric, we explore an extreme mass-ratio inspiral system, wherein a stellar-mass object perturbs a supermassive black hole. We compute the effects of deformation parameters on gravitational wave fluxes, orbital evolution and phase dynamics with leading order post-Newtonian corrections. With the waveform analysis, we assess the plausibility of detecting deviations from general relativity through observations facilitated by the Laser Interferometer Space Antenna (LISA), simultaneously constraining the extent of these deviations. Therefore, this analysis provides an understanding while highlighting the essential role of observations in advancing gravitational phenomena beyond general relativity. |
1802.09123 | Ismael Delgado Gaspar PhD | Ismael Delgado Gaspar, Juan Carlos Hidalgo, Roberto A. Sussman, Israel
Quiros | Black hole formation from the gravitational collapse of a non-spherical
network of structures | Matches published version. 11 pages, 5 figures. Minor but important
corrections were incorporated | Phys. Rev. D 97, 104029 (2018) | 10.1103/PhysRevD.97.104029 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the gravitational collapse and black hole formation of multiple
non--spherical configurations constructed from Szekeres dust models with
positive spatial curvature that smoothly match to a Schwarzschild exterior.
These configurations are made of an almost spherical central core region
surrounded by a network of "pancake-like" overdensities and voids with spatial
positions prescribed through standard initial conditions. We show that a full
collapse into a focusing singularity, without shell crossings appearing before
the formation of an apparent horizon, is not possible unless the full
configuration becomes exactly or almost spherical. Seeking for black hole
formation, we demand that shell crossings are covered by the apparent horizon.
This requires very special fine-tuned initial conditions that impose very
strong and unrealistic constraints on the total black hole mass and full
collapse time. As a consequence, non-spherical non-rotating dust sources cannot
furnish even minimally realistic toy models of black hole formation at
astrophysical scales: demanding realistic collapse time scales yields huge
unrealistic black hole masses, while simulations of typical astrophysical black
hole masses collapse in unrealistically small times. We note, however, that the
resulting time--mass constraint is compatible with early Universe models of
primordial black hole formation, suitable in early dust-like environments.
Finally, we argue that the shell crossings appearing when non-spherical dust
structures collapse are an indicator that such structures do not form galactic
mass black holes but virialise into stable stationary objects.
| [
{
"created": "Mon, 26 Feb 2018 01:37:17 GMT",
"version": "v1"
},
{
"created": "Mon, 21 May 2018 16:38:09 GMT",
"version": "v2"
}
] | 2018-05-22 | [
[
"Gaspar",
"Ismael Delgado",
""
],
[
"Hidalgo",
"Juan Carlos",
""
],
[
"Sussman",
"Roberto A.",
""
],
[
"Quiros",
"Israel",
""
]
] | We examine the gravitational collapse and black hole formation of multiple non--spherical configurations constructed from Szekeres dust models with positive spatial curvature that smoothly match to a Schwarzschild exterior. These configurations are made of an almost spherical central core region surrounded by a network of "pancake-like" overdensities and voids with spatial positions prescribed through standard initial conditions. We show that a full collapse into a focusing singularity, without shell crossings appearing before the formation of an apparent horizon, is not possible unless the full configuration becomes exactly or almost spherical. Seeking for black hole formation, we demand that shell crossings are covered by the apparent horizon. This requires very special fine-tuned initial conditions that impose very strong and unrealistic constraints on the total black hole mass and full collapse time. As a consequence, non-spherical non-rotating dust sources cannot furnish even minimally realistic toy models of black hole formation at astrophysical scales: demanding realistic collapse time scales yields huge unrealistic black hole masses, while simulations of typical astrophysical black hole masses collapse in unrealistically small times. We note, however, that the resulting time--mass constraint is compatible with early Universe models of primordial black hole formation, suitable in early dust-like environments. Finally, we argue that the shell crossings appearing when non-spherical dust structures collapse are an indicator that such structures do not form galactic mass black holes but virialise into stable stationary objects. |
1405.0540 | Sergio Ulhoa | S. C. Ulhoa and R. G. G. Amorim | On Teleparallel Quantum Gravity in Schwarzschild Space-Time | Accepted in Advances in High Energy Physics | Advances in High Energy Physics, Volume 2014 (2014), Article ID
812691, 6 pages | 10.1155/2014/812691 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we present the quantization process for Schwarzschild
space-time in the context of Teleparallel gravity. In order to achieve such a
goal we use the Weyl formalism that establishes a well defined correspondence
between classical quantities which are realized by functions and quantum ones
which are realized by operators. In the process of quantization we introduce a
fundamental constant that is used to construct what we call the quantum of
matter by the imposition of periodic conditions over the eigenfunction.
| [
{
"created": "Fri, 2 May 2014 23:34:10 GMT",
"version": "v1"
}
] | 2014-07-18 | [
[
"Ulhoa",
"S. C.",
""
],
[
"Amorim",
"R. G. G.",
""
]
] | In this article we present the quantization process for Schwarzschild space-time in the context of Teleparallel gravity. In order to achieve such a goal we use the Weyl formalism that establishes a well defined correspondence between classical quantities which are realized by functions and quantum ones which are realized by operators. In the process of quantization we introduce a fundamental constant that is used to construct what we call the quantum of matter by the imposition of periodic conditions over the eigenfunction. |
gr-qc/0512085 | Sigbjorn Hervik | A.A. Coley, S. Hervik, W.C. Lim | Tilt and phantom cosmology | 9 pages, v2: more discussion, added references | Phys.Lett. B638 (2006) 310-313 | 10.1016/j.physletb.2006.05.048 | null | gr-qc astro-ph hep-th | null | We show that in tilting perfect fluid cosmological models with an
ultra-radiative equation of state, generically the tilt becomes extreme at late
times and, as the tilt instability sets in, observers moving with the tilting
fluid will experience singular behaviour in which infinite expansion is reached
within a finite proper time, similar to that of phantom cosmology (but without
the need for exotic forms of matter).
| [
{
"created": "Wed, 14 Dec 2005 14:30:14 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jul 2006 15:45:58 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Coley",
"A. A.",
""
],
[
"Hervik",
"S.",
""
],
[
"Lim",
"W. C.",
""
]
] | We show that in tilting perfect fluid cosmological models with an ultra-radiative equation of state, generically the tilt becomes extreme at late times and, as the tilt instability sets in, observers moving with the tilting fluid will experience singular behaviour in which infinite expansion is reached within a finite proper time, similar to that of phantom cosmology (but without the need for exotic forms of matter). |
gr-qc/0107084 | F. Ya. Khalili | F.Ya.Khalili | Frequency-dependent rigidity in large-scale interferometric
gravitational-wave detectors | 11 pages, 6 figures, corrected typos | Phys.Lett. A288 (2001) 251-256 | 10.1016/S0375-9601(01)00550-3 | null | gr-qc | null | Electromagnetic rigidity which exists in large-scale optical resonators if
pumping frequency is detuned from the eigenfrequency of resonator have
sophisticated spectral dependence which allows to obtain sensitivity better
than the Standard Quantum Limits both for the free test mass and the harmonic
oscillator.
| [
{
"created": "Thu, 26 Jul 2001 07:51:44 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2001 09:44:10 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Khalili",
"F. Ya.",
""
]
] | Electromagnetic rigidity which exists in large-scale optical resonators if pumping frequency is detuned from the eigenfrequency of resonator have sophisticated spectral dependence which allows to obtain sensitivity better than the Standard Quantum Limits both for the free test mass and the harmonic oscillator. |
gr-qc/0210110 | Sabine Hossenfelder | Sabine Hossenfelder, Dominik J. Schwarz, Walter Greiner | Particle production in time-dependent gravitational fields: the
expanding mass shell | 19 pages, 8 figures | Class.Quant.Grav. 20 (2003) 2337-2354 | 10.1088/0264-9381/20/11/325 | null | gr-qc | null | We compute the production of particles from the gravitational field of an
expanding mass shell. Contrary to the situation of Hawking radiation and the
production of cosmological perturbations during cosmological inflation, the
example of an expanding mass shell has no horizon and no singularity. We apply
the method of `ray-tracing', first introduced by Hawking, and calculate the
energy spectrum of the produced particles. The result depends on three
parameters: the expansion velocity of the mass shell, its radius, and its mass.
Contrary to the situation of a collapsing mass shell, the energy spectrum is
non-thermal. Invoking time reversal we reproduce Hawking's thermal spectrum in
a certain limit.
| [
{
"created": "Thu, 31 Oct 2002 19:40:52 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hossenfelder",
"Sabine",
""
],
[
"Schwarz",
"Dominik J.",
""
],
[
"Greiner",
"Walter",
""
]
] | We compute the production of particles from the gravitational field of an expanding mass shell. Contrary to the situation of Hawking radiation and the production of cosmological perturbations during cosmological inflation, the example of an expanding mass shell has no horizon and no singularity. We apply the method of `ray-tracing', first introduced by Hawking, and calculate the energy spectrum of the produced particles. The result depends on three parameters: the expansion velocity of the mass shell, its radius, and its mass. Contrary to the situation of a collapsing mass shell, the energy spectrum is non-thermal. Invoking time reversal we reproduce Hawking's thermal spectrum in a certain limit. |
gr-qc/9509027 | R. R. Caldwell | R. R. Caldwell | On the Evolution of Scalar Metric Perturbations in an Inflationary
Cosmology | uuencoded, compressed postscript, 15 pages including 3 figures | Class.Quant.Grav. 13 (1996) 2437-2448 | 10.1088/0264-9381/13/9/009 | DAMTP-R95/45 | gr-qc astro-ph | null | We further clarify how scalar metric perturbations are amplified in an
inflationary cosmology. We first construct a simple, analytic model of an
inflationary cosmology in which the expansion scale factor evolves continuously
from an inflationary era to a radiation-dominated era. From this model, it is
clear to see how scalar perturbations are amplified. Second, we examine the
recent claims of Grishchuk, and the reply by Deruelle and Mukhanov, regarding
the evolution of scalar perturbations through an abrupt transition in the
equation of state of the cosmological fluid. We demonstrate that the ``standard
results'' regarding the amplification of scalar, density perturbations from
inflation are valid.
| [
{
"created": "Fri, 15 Sep 1995 12:14:25 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Caldwell",
"R. R.",
""
]
] | We further clarify how scalar metric perturbations are amplified in an inflationary cosmology. We first construct a simple, analytic model of an inflationary cosmology in which the expansion scale factor evolves continuously from an inflationary era to a radiation-dominated era. From this model, it is clear to see how scalar perturbations are amplified. Second, we examine the recent claims of Grishchuk, and the reply by Deruelle and Mukhanov, regarding the evolution of scalar perturbations through an abrupt transition in the equation of state of the cosmological fluid. We demonstrate that the ``standard results'' regarding the amplification of scalar, density perturbations from inflation are valid. |
gr-qc/0611054 | Jose Edgar Madriz Aguilar | Jose Edgar Madriz Aguilar and Mauricio Bellini | Inflation from the bang of a white hole induced from a 6D vacuum state | 9 pages, 1 figure Accepted for publication in Physics Letters B | Phys.Lett.B648:19-27,2007 | 10.1016/j.physletb.2007.02.062 | null | gr-qc astro-ph hep-th | null | Using ideas of STM theory, but starting from a 6D vacuum state, we propose an
inflationary model where the universe emerges from the blast of a white hole.
Under this approach, the expansion is affected by a geometrical deformation
induced by the gravitational attraction of the hole, which should be
responsible for the k_{R}-non invariant spectrum of galaxies (and likewise of
the matter density) today observed.
| [
{
"created": "Wed, 8 Nov 2006 20:41:13 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jan 2007 14:18:07 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Feb 2007 15:14:29 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Aguilar",
"Jose Edgar Madriz",
""
],
[
"Bellini",
"Mauricio",
""
]
] | Using ideas of STM theory, but starting from a 6D vacuum state, we propose an inflationary model where the universe emerges from the blast of a white hole. Under this approach, the expansion is affected by a geometrical deformation induced by the gravitational attraction of the hole, which should be responsible for the k_{R}-non invariant spectrum of galaxies (and likewise of the matter density) today observed. |
gr-qc/9410041 | Carlos O. Lousto | C.O.Lousto and N.S\'anchez | Scattering Processes at the Planck Scale | 31 pages, TeX, report UAB-FT-353. To appear in the proceedings of the
2nd. Journee Cosmologie, Paris, 2nd-4th June 1994. "Second Paris Cosmology
Colloquium", H.J. de Vega and N. S\'anchez Eds., pp 339-370, World Sci. Pub.
Co., Singapore (1995) | "Second Paris Cosmology Colloquium", World Sci. (1995) | null | null | gr-qc astro-ph hep-th | null | The ultrarelativistic limit of the Kerr - Newman geometry is studied in
detail. We find the gravitational shock wave background associated with this
limit. We study the scattering of scalar fields in the gravitational shock wave
geometries and compare this with the scattering by ultrarelativistic extended
sources and with the scattering of fundamental strings.
We also study planckian energy string collisions in flat spacetime as the
scattering of a string in the effective curved background produced by the
others as the impact parameter $b$ decreases. We find the effective energy
density distribution generated by these collisions. The effective metric
generated by these collisions is a gravitational shock wave with profile
$f(\rho)\sim p\rho^{4-D}$, for large impact parameter $b$. For intermediate
$b$, $f(\rho)\sim q\rho^2$, corresponding to an extended source of momentum
$q$.
We finally study the emergence of string instabilities in $D$ - dimensional
black hole spacetimes and De Sitter space. We solve the first order string
fluctuations around the center of mass motion at spatial infinity, near the
horizon and at the spacetime singularity. We find that the time components are
always well behaved in the three regions and in the three backgrounds. The
radial components are unstable: imaginary frequencies develop in the
oscillatory modes near the horizon, and the evolution is like $(\tau-\tau_0)^
{-P}$, $(P>0)$, near the spacetime singularity, $r\to0$, where the world -
sheet time $(\tau-\tau_0)\to0$, and the proper string length grows infinitely.
| [
{
"created": "Fri, 28 Oct 1994 16:45:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lousto",
"C. O.",
""
],
[
"Sánchez",
"N.",
""
]
] | The ultrarelativistic limit of the Kerr - Newman geometry is studied in detail. We find the gravitational shock wave background associated with this limit. We study the scattering of scalar fields in the gravitational shock wave geometries and compare this with the scattering by ultrarelativistic extended sources and with the scattering of fundamental strings. We also study planckian energy string collisions in flat spacetime as the scattering of a string in the effective curved background produced by the others as the impact parameter $b$ decreases. We find the effective energy density distribution generated by these collisions. The effective metric generated by these collisions is a gravitational shock wave with profile $f(\rho)\sim p\rho^{4-D}$, for large impact parameter $b$. For intermediate $b$, $f(\rho)\sim q\rho^2$, corresponding to an extended source of momentum $q$. We finally study the emergence of string instabilities in $D$ - dimensional black hole spacetimes and De Sitter space. We solve the first order string fluctuations around the center of mass motion at spatial infinity, near the horizon and at the spacetime singularity. We find that the time components are always well behaved in the three regions and in the three backgrounds. The radial components are unstable: imaginary frequencies develop in the oscillatory modes near the horizon, and the evolution is like $(\tau-\tau_0)^ {-P}$, $(P>0)$, near the spacetime singularity, $r\to0$, where the world - sheet time $(\tau-\tau_0)\to0$, and the proper string length grows infinitely. |
0810.1074 | Ramon Herrera | Ramon Herrera | Tachyon-Chaplygin inflation on the brane | 15 pages, 3 figures, Accepted for publication in General Relativity
and Gravitation | Gen.Rel.Grav.41:1259-1271,2009 | 10.1007/s10714-008-0703-8 | null | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tachyon-Brane inflationary universe model in the context of a Chaplygin gas
equation of state is studied. General conditions for this model to be
realizable are discussed. In the high-energy limit and by using an exponential
potential we describe in great details the characteristic of this model. Recent
observational data from the Wilkinson Microwave Anisotropy Probe experiment are
employed to restrict the parameters of the model.
| [
{
"created": "Mon, 6 Oct 2008 22:47:00 GMT",
"version": "v1"
}
] | 2009-11-18 | [
[
"Herrera",
"Ramon",
""
]
] | Tachyon-Brane inflationary universe model in the context of a Chaplygin gas equation of state is studied. General conditions for this model to be realizable are discussed. In the high-energy limit and by using an exponential potential we describe in great details the characteristic of this model. Recent observational data from the Wilkinson Microwave Anisotropy Probe experiment are employed to restrict the parameters of the model. |
1406.6057 | Francesco Pannarale | Francesco Pannarale and Frank Ohme | Prospects for joint gravitational-wave and electromagnetic observations
of neutron-star--black-hole coalescing binaries | 5 pages, 3 figures; matches published version | ApJ, 791, L7 (2014) | 10.1088/2041-8205/791/1/L7 | LIGO-P1400096 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Coalescing neutron-star-black-hole (NS-BH) binaries are a promising source of
gravitational-wave (GW) signals detectable with large-scale laser
interferometers such as Advanced LIGO and Virgo. They are also one of the main
short gamma-ray burst (SGRB) progenitor candidates. If the BH tidally disrupts
its companion, an SGRB may be ignited when a sufficiently massive accretion
disk forms around the remnant BH. Detecting an NS-BH coalescence both in the GW
and electromagnetic (EM) spectrum offers a wealth of information about the
nature of the source. How much can actually be inferred from a joint detection
is unclear, however, as a mass/spin degeneracy may reduce the GW measurement
accuracy. To shed light on this problem and on the potential of joint EM+GW
observations, we here combine recent semi-analytical predictions for the
remnant disk mass with estimates of the parameter-space portion that is
selected by a GW detection. We identify cases in which an SGRB ignition is
supported, others in which it can be excluded, and finally others in which the
outcome depends on the chosen model for the currently unknown NS equation of
state. We pinpoint a range of systems that would allow us to place lower bounds
on the equation of state stiffness if both the GW emission and its EM
counterpart are observed. The methods we develop can broaden the scope of
existing GW detection and parameter-estimation algorithms and could allow us to
disregard about half of the templates in an NS-BH search following an SGRB
trigger, increasing its speed and sensitivity.
| [
{
"created": "Mon, 23 Jun 2014 20:00:31 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jul 2014 08:21:23 GMT",
"version": "v2"
}
] | 2014-07-25 | [
[
"Pannarale",
"Francesco",
""
],
[
"Ohme",
"Frank",
""
]
] | Coalescing neutron-star-black-hole (NS-BH) binaries are a promising source of gravitational-wave (GW) signals detectable with large-scale laser interferometers such as Advanced LIGO and Virgo. They are also one of the main short gamma-ray burst (SGRB) progenitor candidates. If the BH tidally disrupts its companion, an SGRB may be ignited when a sufficiently massive accretion disk forms around the remnant BH. Detecting an NS-BH coalescence both in the GW and electromagnetic (EM) spectrum offers a wealth of information about the nature of the source. How much can actually be inferred from a joint detection is unclear, however, as a mass/spin degeneracy may reduce the GW measurement accuracy. To shed light on this problem and on the potential of joint EM+GW observations, we here combine recent semi-analytical predictions for the remnant disk mass with estimates of the parameter-space portion that is selected by a GW detection. We identify cases in which an SGRB ignition is supported, others in which it can be excluded, and finally others in which the outcome depends on the chosen model for the currently unknown NS equation of state. We pinpoint a range of systems that would allow us to place lower bounds on the equation of state stiffness if both the GW emission and its EM counterpart are observed. The methods we develop can broaden the scope of existing GW detection and parameter-estimation algorithms and could allow us to disregard about half of the templates in an NS-BH search following an SGRB trigger, increasing its speed and sensitivity. |
gr-qc/0108015 | Massimo Giovannini | Danilo Babusci (INFN, Frascati) and Massimo Giovannini (Institute for
Theoretical Physics, Lausanne University) | Response of VIRGO detectors to pre-big-bang gravitons | 23 pages in Latex style | Int.J.Mod.Phys. D10 (2001) 477-500 | 10.1142/S0218271801001165 | International Journal of Modern Physics D, Vol. 10, No. 4 (2001)
477-500 | gr-qc astro-ph hep-ph | null | The sensitivity achievable by a pair of VIRGO detectors to stochastic and
isotropic gravitational wave backgrounds produced in pre-big-bang models is
discussed in view of the development of a second VIRGO interferometer. We
describe a semi-analytical technique allowing to compute the signal-to-noise
ratio for (monotonic or non-monotonic) logarithmic energy spectra of relic
gravitons of arbitrary slope. We apply our results to the case of two
correlated and coaligned VIRGO detectors and we compute their achievable
sensitivities. We perform our calculations both for the usual case of minimal
string cosmological scenario and in the case of a non-minimal scenario where a
long dilaton dominated phase is present prior to the onset of the ordinary
radiation dominated phase. In this framework, we investigate possible
improvements of the achievable sensitivities by selective reduction of the
thermal contributions (pendulum and pendulum's internal modes) to the noise
power spectra of the detectors. Since a reduction of the shot noise does not
increase significantly the expected sensitivity of a VIRGO pair (in spite of
the relative spatial location of the two detectors) our findings support the
experimental efforts directed towards a substantial reduction of thermal noise.
| [
{
"created": "Sat, 4 Aug 2001 16:51:03 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Babusci",
"Danilo",
"",
"INFN, Frascati"
],
[
"Giovannini",
"Massimo",
"",
"Institute for\n Theoretical Physics, Lausanne University"
]
] | The sensitivity achievable by a pair of VIRGO detectors to stochastic and isotropic gravitational wave backgrounds produced in pre-big-bang models is discussed in view of the development of a second VIRGO interferometer. We describe a semi-analytical technique allowing to compute the signal-to-noise ratio for (monotonic or non-monotonic) logarithmic energy spectra of relic gravitons of arbitrary slope. We apply our results to the case of two correlated and coaligned VIRGO detectors and we compute their achievable sensitivities. We perform our calculations both for the usual case of minimal string cosmological scenario and in the case of a non-minimal scenario where a long dilaton dominated phase is present prior to the onset of the ordinary radiation dominated phase. In this framework, we investigate possible improvements of the achievable sensitivities by selective reduction of the thermal contributions (pendulum and pendulum's internal modes) to the noise power spectra of the detectors. Since a reduction of the shot noise does not increase significantly the expected sensitivity of a VIRGO pair (in spite of the relative spatial location of the two detectors) our findings support the experimental efforts directed towards a substantial reduction of thermal noise. |
gr-qc/9209006 | null | Boro Grubisic and Vincent Moncrief | Asymptotic Behavior of the $T^3 \times R$ Gowdy Spacetimes | 30 pages | Phys.Rev. D47 (1993) 2371-2382 | 10.1103/PhysRevD.47.2371 | null | gr-qc | null | We present new evidence in support of the Penrose's strong cosmic censorship
conjecture in the class of Gowdy spacetimes with $T^3$ spatial topology.
Solving Einstein's equations perturbatively to all orders we show that
asymptotically close to the boundary of the maximal Cauchy development the
dominant term in the expansion gives rise to curvature singularity for almost
all initial data. The dominant term, which we call the ``geodesic loop
solution'', is a solution of the Einstein's equations with all space
derivatives dropped. We also describe the extent to which our perturbative
results can be rigorously justified.
| [
{
"created": "Wed, 16 Sep 1992 03:31:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Grubisic",
"Boro",
""
],
[
"Moncrief",
"Vincent",
""
]
] | We present new evidence in support of the Penrose's strong cosmic censorship conjecture in the class of Gowdy spacetimes with $T^3$ spatial topology. Solving Einstein's equations perturbatively to all orders we show that asymptotically close to the boundary of the maximal Cauchy development the dominant term in the expansion gives rise to curvature singularity for almost all initial data. The dominant term, which we call the ``geodesic loop solution'', is a solution of the Einstein's equations with all space derivatives dropped. We also describe the extent to which our perturbative results can be rigorously justified. |
gr-qc/0501011 | Christian Koenigsdoerffer | Christian Koenigsdoerffer, Achamveedu Gopakumar | Post-Newtonian accurate parametric solution to the dynamics of spinning
compact binaries in eccentric orbits: The leading order spin-orbit
interaction | 18 pages, accepted by Phys. Rev. D | Phys.Rev. D71 (2005) 024039 | 10.1103/PhysRevD.71.024039 | null | gr-qc | null | We derive Keplerian-type parametrization for the solution of post-Newtonian
(PN) accurate conservative dynamics of spinning compact binaries moving in
eccentric orbits. The PN accurate dynamics that we consider consists of the
third post-Newtonian accurate conservative orbital dynamics influenced by the
leading order spin effects, namely the leading order spin-orbit interactions.
The orbital elements of the representation are explicitly given in terms of the
conserved orbital energy, angular momentum and a quantity that characterizes
the leading order spin-orbit interactions in Arnowitt, Deser, and Misner-type
coordinates. Our parametric solution is applicable in the following two
distinct cases: (i) the binary consists of equal mass compact objects, having
two arbitrary spins, and (ii) the binary consists of compact objects of
arbitrary mass, where only one of them is spinning with an arbitrary spin. As
an application of our parametrization, we present gravitational wave
polarizations, whose amplitudes are restricted to the leading quadrupolar
order, suitable to describe gravitational radiation from spinning compact
binaries moving in eccentric orbits. The present parametrization will be
required to construct `ready to use' reference templates for gravitational
waves from spinning compact binaries in inspiralling eccentric orbits. Our
parametric solution for the post-Newtonian accurate conservative dynamics of
spinning compact binaries clearly indicates, for the cases considered, the
absence of chaos in these systems. Finally, we note that our parametrization
provides the first step in deriving a fully second post-Newtonian accurate
`timing formula', that may be useful for the radio observations of relativistic
binary pulsars like J0737-3039.
| [
{
"created": "Wed, 5 Jan 2005 13:28:06 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Koenigsdoerffer",
"Christian",
""
],
[
"Gopakumar",
"Achamveedu",
""
]
] | We derive Keplerian-type parametrization for the solution of post-Newtonian (PN) accurate conservative dynamics of spinning compact binaries moving in eccentric orbits. The PN accurate dynamics that we consider consists of the third post-Newtonian accurate conservative orbital dynamics influenced by the leading order spin effects, namely the leading order spin-orbit interactions. The orbital elements of the representation are explicitly given in terms of the conserved orbital energy, angular momentum and a quantity that characterizes the leading order spin-orbit interactions in Arnowitt, Deser, and Misner-type coordinates. Our parametric solution is applicable in the following two distinct cases: (i) the binary consists of equal mass compact objects, having two arbitrary spins, and (ii) the binary consists of compact objects of arbitrary mass, where only one of them is spinning with an arbitrary spin. As an application of our parametrization, we present gravitational wave polarizations, whose amplitudes are restricted to the leading quadrupolar order, suitable to describe gravitational radiation from spinning compact binaries moving in eccentric orbits. The present parametrization will be required to construct `ready to use' reference templates for gravitational waves from spinning compact binaries in inspiralling eccentric orbits. Our parametric solution for the post-Newtonian accurate conservative dynamics of spinning compact binaries clearly indicates, for the cases considered, the absence of chaos in these systems. Finally, we note that our parametrization provides the first step in deriving a fully second post-Newtonian accurate `timing formula', that may be useful for the radio observations of relativistic binary pulsars like J0737-3039. |
1409.1523 | Mariusz Dabrowski P. | Adam Balcerzak, Mariusz P. Dabrowski, Tomasz Denkiewicz, David
Polarski, Denis Puy | A critical assessment of some inhomogeneous pressure Stephani models | REVTEX4-1, 12 pages, 6 figures, explanatory material added, version
to appear in PRD, conclusions and results unchanged | Phys. Rev. D 91, 083506 (2015) | 10.1103/PhysRevD.91.083506 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/3.0/ | We consider spherically symmetric inhomogeneous pressure Stephani universes,
the center of symmetry being our location. The main feature of these models is
that comoving observers do not follow geodesics. In particular, comoving
perfect fluids have necessarily a radially dependent pressure. We consider a
subclass of these models characterized by some inhomogeneity parameter $\beta$.
We show that also the velocity of sound, like the (effective) equation of state
parameter, of comoving perfect fluids acquire away from the origin a time and
radial dependent change proportional to $\beta$. In order to produce a
realistic universe accelerating at late times without dark energy component one
must take $\beta < 0$. The redshift gets a modified dependence on the scale
factor $a(t)$ with a relative modification of $-9\%$ peaking at $z\sim 4$ and
vanishing at the big-bang and today on our past lightcone. The equation of
state parameter and the speed of sound of dustlike matter (corresponding to a
vanishing pressure at the center of symmetry $r=0$) behave in a similar way and
away from the center of symmetry they become negative -- a property usually
encountered for the dark energy component only. In order to mimic the observed
late-time accelerated expansion, the matter component must significantly depart
from standard dust, presumably ruling this subclass of Stephani models out as a
realistic cosmology. The only way to accept these models is to keep all
standard matter components of the universe including dark energy and take an
inhomogeneity parameter $\beta$ small enough.
| [
{
"created": "Tue, 2 Sep 2014 21:55:27 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Dec 2014 00:12:02 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Mar 2015 13:55:45 GMT",
"version": "v3"
}
] | 2015-04-08 | [
[
"Balcerzak",
"Adam",
""
],
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Denkiewicz",
"Tomasz",
""
],
[
"Polarski",
"David",
""
],
[
"Puy",
"Denis",
""
]
] | We consider spherically symmetric inhomogeneous pressure Stephani universes, the center of symmetry being our location. The main feature of these models is that comoving observers do not follow geodesics. In particular, comoving perfect fluids have necessarily a radially dependent pressure. We consider a subclass of these models characterized by some inhomogeneity parameter $\beta$. We show that also the velocity of sound, like the (effective) equation of state parameter, of comoving perfect fluids acquire away from the origin a time and radial dependent change proportional to $\beta$. In order to produce a realistic universe accelerating at late times without dark energy component one must take $\beta < 0$. The redshift gets a modified dependence on the scale factor $a(t)$ with a relative modification of $-9\%$ peaking at $z\sim 4$ and vanishing at the big-bang and today on our past lightcone. The equation of state parameter and the speed of sound of dustlike matter (corresponding to a vanishing pressure at the center of symmetry $r=0$) behave in a similar way and away from the center of symmetry they become negative -- a property usually encountered for the dark energy component only. In order to mimic the observed late-time accelerated expansion, the matter component must significantly depart from standard dust, presumably ruling this subclass of Stephani models out as a realistic cosmology. The only way to accept these models is to keep all standard matter components of the universe including dark energy and take an inhomogeneity parameter $\beta$ small enough. |
gr-qc/0608117 | Pablo Laguna | Pablo Laguna | Numerical Analysis of the Big Bounce in Loop Quantum Cosmology | 5 pages, 3 figures, new title, replaced with version accepted for
publication | Phys.Rev.D75:024033,2007 | 10.1103/PhysRevD.75.024033 | null | gr-qc astro-ph | null | Loop quantum cosmology homogeneous models with a massless scalar field show
that the big-bang singularity can be replaced by a big quantum bounce. To gain
further insight on the nature of this bounce, we study the semi-discrete loop
quantum gravity Hamiltonian constraint equation from the point of view of
numerical analysis. For illustration purposes, we establish a numerical analogy
between the quantum bounces and reflections in finite difference
discretizations of wave equations triggered by the use of nonuniform grids or,
equivalently, reflections found when solving numerically wave equations with
varying coefficients. We show that the bounce is closely related to the method
for the temporal update of the system and demonstrate that explicit
time-updates in general yield bounces. Finally, we present an example of an
implicit time-update devoid of bounces and show back-in-time, deterministic
evolutions that reach and partially jump over the big-bang singularity.
| [
{
"created": "Mon, 28 Aug 2006 11:48:38 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2007 14:27:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Laguna",
"Pablo",
""
]
] | Loop quantum cosmology homogeneous models with a massless scalar field show that the big-bang singularity can be replaced by a big quantum bounce. To gain further insight on the nature of this bounce, we study the semi-discrete loop quantum gravity Hamiltonian constraint equation from the point of view of numerical analysis. For illustration purposes, we establish a numerical analogy between the quantum bounces and reflections in finite difference discretizations of wave equations triggered by the use of nonuniform grids or, equivalently, reflections found when solving numerically wave equations with varying coefficients. We show that the bounce is closely related to the method for the temporal update of the system and demonstrate that explicit time-updates in general yield bounces. Finally, we present an example of an implicit time-update devoid of bounces and show back-in-time, deterministic evolutions that reach and partially jump over the big-bang singularity. |
2201.06988 | Aurelien Barrau | Aur\'elien Barrau | The holographic space-time and black hole remnants as dark matter | null | null | 10.1016/j.physletb.2022.137061 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The holographic space-time approach to inflation provides a well defined and
self-contained framework to study the early universe. Based on a quasi-local
quantum gravity theory generalizing string theory beyond AdS backgrounds, it
addresses fundamental questions like the arrow of time and the entropy of the
initial cosmological state. It was recently argued that it also provides a
naturel explanation for dark matter in the form of primordial black holes. The
orignal idea however suffers from troubles that can be cured by considering
instead Planck relics. This possibility is investigated and paths for
observational confirmation are pointed out.
| [
{
"created": "Tue, 18 Jan 2022 13:49:41 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Barrau",
"Aurélien",
""
]
] | The holographic space-time approach to inflation provides a well defined and self-contained framework to study the early universe. Based on a quasi-local quantum gravity theory generalizing string theory beyond AdS backgrounds, it addresses fundamental questions like the arrow of time and the entropy of the initial cosmological state. It was recently argued that it also provides a naturel explanation for dark matter in the form of primordial black holes. The orignal idea however suffers from troubles that can be cured by considering instead Planck relics. This possibility is investigated and paths for observational confirmation are pointed out. |
1809.00920 | Carsten van de Bruck | Carsten van de Bruck and Chris Longden | Einstein-Gauss-Bonnet gravity with extra dimensions | 23 pages, 1 figure | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a theory of modified gravity possessing d extra spatial
dimensions with a maximally symmetric metric and a scale factor, whose
(4+d)-dimensional gravitational action contains terms proportional to quadratic
curvature scalars. Constructing the 4D effective field theory by dimensional
reduction, we find that a special case of our action where the additional terms
appear in the well-known Gauss-Bonnet combination is of special interest as it
uniquely produces a Horndeski scalar-tensor theory in the 4D effective action.
We further consider the possibility of achieving stabilised extra dimensions in
this scenario, as a function of the number and curvature of extra dimensions,
as well as the strength of the Gauss-Bonnet coupling. Further questions that
remain to be answered such as the influence of matter-coupling are briefly
discussed.
| [
{
"created": "Tue, 4 Sep 2018 12:36:09 GMT",
"version": "v1"
}
] | 2018-09-05 | [
[
"van de Bruck",
"Carsten",
""
],
[
"Longden",
"Chris",
""
]
] | We consider a theory of modified gravity possessing d extra spatial dimensions with a maximally symmetric metric and a scale factor, whose (4+d)-dimensional gravitational action contains terms proportional to quadratic curvature scalars. Constructing the 4D effective field theory by dimensional reduction, we find that a special case of our action where the additional terms appear in the well-known Gauss-Bonnet combination is of special interest as it uniquely produces a Horndeski scalar-tensor theory in the 4D effective action. We further consider the possibility of achieving stabilised extra dimensions in this scenario, as a function of the number and curvature of extra dimensions, as well as the strength of the Gauss-Bonnet coupling. Further questions that remain to be answered such as the influence of matter-coupling are briefly discussed. |
2211.00616 | Gabriele Benomio | Gabriele Benomio | A new gauge for gravitational perturbations of Kerr spacetimes II: The
linear stability of Schwarzschild revisited | 50 pages | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://creativecommons.org/publicdomain/zero/1.0/ | We present a new proof of linear stability of the Schwarzschild solution to
gravitational perturbations. Our approach employs the system of linearised
gravity in the new geometric gauge of \cite{benomio_kerr}, specialised to the
$|a|=0$ case. The proof fundamentally relies on the novel structure of the
transport equations in the system. Indeed, while exploiting the well-known
decoupling of two gauge invariant linearised quantities into spin $\pm 2$
Teukolsky equations, we make enhanced use of the red-shifted transport
equations and their stabilising properties to control the gauge dependent part
of the system. As a result, an initial-data gauge normalisation suffices to
establish both orbital and asymptotic stability for all the linearised
quantities in the system.
The absence of future gauge normalisations is a novel element in the linear
stability analysis of black hole spacetimes in geometric gauges governed by
transport equations. In particular, our approach simplifies the proof of
\cite{DHR}, which requires a future normalised (double-null) gauge to establish
asymptotic stability for the full system.
| [
{
"created": "Tue, 1 Nov 2022 17:31:21 GMT",
"version": "v1"
}
] | 2022-11-02 | [
[
"Benomio",
"Gabriele",
""
]
] | We present a new proof of linear stability of the Schwarzschild solution to gravitational perturbations. Our approach employs the system of linearised gravity in the new geometric gauge of \cite{benomio_kerr}, specialised to the $|a|=0$ case. The proof fundamentally relies on the novel structure of the transport equations in the system. Indeed, while exploiting the well-known decoupling of two gauge invariant linearised quantities into spin $\pm 2$ Teukolsky equations, we make enhanced use of the red-shifted transport equations and their stabilising properties to control the gauge dependent part of the system. As a result, an initial-data gauge normalisation suffices to establish both orbital and asymptotic stability for all the linearised quantities in the system. The absence of future gauge normalisations is a novel element in the linear stability analysis of black hole spacetimes in geometric gauges governed by transport equations. In particular, our approach simplifies the proof of \cite{DHR}, which requires a future normalised (double-null) gauge to establish asymptotic stability for the full system. |
1701.00796 | Tahereh Azizi | Tahereh Azizi and Miysam Gorjizadeh | Energy conditions in f(T) gravity with higher-derivative torsion terms | null | null | 10.1209/0295-5075/117/60003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the energy conditions in the framework of the modi- fied gravity
with higher-derivative torsional terms in the action. We discuss the viability
of the model by studying the energy conditions in terms of the cosmographical
parameters like Hubble, deceleration, jerk, snap and lerk parameters. In
particular, We consider two spe- cific models that are proposed in literature
and examine the viability bounds imposed by the weak energy condition.
| [
{
"created": "Tue, 3 Jan 2017 19:37:29 GMT",
"version": "v1"
}
] | 2017-06-07 | [
[
"Azizi",
"Tahereh",
""
],
[
"Gorjizadeh",
"Miysam",
""
]
] | We study the energy conditions in the framework of the modi- fied gravity with higher-derivative torsional terms in the action. We discuss the viability of the model by studying the energy conditions in terms of the cosmographical parameters like Hubble, deceleration, jerk, snap and lerk parameters. In particular, We consider two spe- cific models that are proposed in literature and examine the viability bounds imposed by the weak energy condition. |
1307.3933 | Dirk Puetzfeld | Dirk Puetzfeld, Yuri N. Obukhov | Unraveling gravity beyond Einstein with extended test bodies | 4 pages, 2 figures, to appear in Phys. Lett. A | Physics Letters A 377 (2013) 2447 | 10.1016/j.physleta.2013.07.024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of test bodies in gravity is tightly linked to the conservation
laws. This well-known fact in the context of General Relativity is also valid
for gravitational theories which go beyond Einstein's theory. Here we derive
the equations of motion for test bodies for a very large class of gravitational
theories with a general nonminimal coupling to matter. These equations form the
basis for future systematic tests of alternative gravity theories. Our
treatment is covariant and generalizes the classic Mathisson-Papapetrou-Dixon
result for spinning (extended) test bodies. The equations of motion for
structureless test bodies turn out to be surprisingly simple, despite the very
general nature of the theories considered.
| [
{
"created": "Mon, 15 Jul 2013 13:35:35 GMT",
"version": "v1"
}
] | 2013-09-09 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] | The motion of test bodies in gravity is tightly linked to the conservation laws. This well-known fact in the context of General Relativity is also valid for gravitational theories which go beyond Einstein's theory. Here we derive the equations of motion for test bodies for a very large class of gravitational theories with a general nonminimal coupling to matter. These equations form the basis for future systematic tests of alternative gravity theories. Our treatment is covariant and generalizes the classic Mathisson-Papapetrou-Dixon result for spinning (extended) test bodies. The equations of motion for structureless test bodies turn out to be surprisingly simple, despite the very general nature of the theories considered. |
1408.3446 | Bruno Carneiro da Cunha | Nicol\'as Avil\'an, Andr\'es F. Reyes-Lega and Bruno Carneiro da Cunha | Coupling the Sorkin-Johnston State to Gravity | 8 pages, 1 figure. RevTeX 4.1 | Phys. Rev. D 90, 084036 (2014) | 10.1103/PhysRevD.90.084036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the dynamics of the Sorkin-Johnston (SJ) state for a massless
scalar field in two dimensions. We conduct a study of the renormalized
stress-tensor by a subtraction procedure, and compare the results with those of
the conformal vacuum, with an important contribution from correction term. We
find a large trace anomaly and compute backreaction effects to two dimensional
(Liouville) gravity. We find a natural interpretation for the mirror behavior
of the SJ state described in previous works.
| [
{
"created": "Fri, 15 Aug 2014 00:03:13 GMT",
"version": "v1"
}
] | 2014-10-29 | [
[
"Avilán",
"Nicolás",
""
],
[
"Reyes-Lega",
"Andrés F.",
""
],
[
"da Cunha",
"Bruno Carneiro",
""
]
] | We consider the dynamics of the Sorkin-Johnston (SJ) state for a massless scalar field in two dimensions. We conduct a study of the renormalized stress-tensor by a subtraction procedure, and compare the results with those of the conformal vacuum, with an important contribution from correction term. We find a large trace anomaly and compute backreaction effects to two dimensional (Liouville) gravity. We find a natural interpretation for the mirror behavior of the SJ state described in previous works. |
1209.3441 | Helgi Freyr R\'unarsson | Helgi Freyr R\'unarsson | Conformal isometry of the lukewarm Reissner-Nordstr\"om-de Sitter
spacetime | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the extremal Reissner-Nordstr\"om black hole possesses a
discrete conformal isometry that exchanges the black hole horizon with
infinity. It is also known that the Reissner-Nordstr\"om-de Sitter spacetime
posseses a similar discrete conformal isometry which exchanges the event
horizon of the black hole with the cosmological horizon. In this short paper we
will continue this line of thought and extend the conformal isometry of the
latter spacetime and give an unphysical interpretation of the negative root.
| [
{
"created": "Sat, 15 Sep 2012 21:44:32 GMT",
"version": "v1"
}
] | 2012-09-18 | [
[
"Rúnarsson",
"Helgi Freyr",
""
]
] | It is known that the extremal Reissner-Nordstr\"om black hole possesses a discrete conformal isometry that exchanges the black hole horizon with infinity. It is also known that the Reissner-Nordstr\"om-de Sitter spacetime posseses a similar discrete conformal isometry which exchanges the event horizon of the black hole with the cosmological horizon. In this short paper we will continue this line of thought and extend the conformal isometry of the latter spacetime and give an unphysical interpretation of the negative root. |
gr-qc/9705062 | Vladimir | V.I. Tkach and J.J. Rosales | Supersymmetric Action for FRW Model with Complex Matter Field | 11 pages, Latex | null | null | null | gr-qc | null | On the basis of the local n=2 supersymmetry we construct the supersymmetric
action for a set of complex scalar supermultiplets in the FRW model. This
action corresponds to the dilaton-axion and chiral components of supergravity
theory.
| [
{
"created": "Thu, 22 May 1997 18:15:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tkach",
"V. I.",
""
],
[
"Rosales",
"J. J.",
""
]
] | On the basis of the local n=2 supersymmetry we construct the supersymmetric action for a set of complex scalar supermultiplets in the FRW model. This action corresponds to the dilaton-axion and chiral components of supergravity theory. |
2403.02415 | Matthias Koschnitzke | Mateja Bo\v{s}kovi\'c, Matthias Koschnitzke, Rafael A. Porto | Signatures of ultralight bosons in the orbital eccentricity of binary
black holes | 5 pages + 9 pages appendices and references, 8 figures | null | null | DESY-24-030 | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that the existence of clouds of ultralight particles surrounding
black holes during their cosmological history as members of a binary system can
leave a measurable imprint on the distribution of masses and orbital
eccentricities observable with future gravitational-wave detectors. Notably, we
find that for nonprecessing binaries with chirp masses ${\cal M} \lesssim
10\,M_\odot$, formed exclusively in isolation, larger-than-expected values of
the eccentricity, i.e. $e\gtrsim 10^{-2}$ at gravitational-wave frequencies
$f_{\rm GW} \simeq 10^{-2}\,$Hz, would provide tantalizing evidence for a new
particle of mass between $[0.5,2.5] \times 10^{-12}\,$eV in nature. The
predicted evolution of the eccentricity can also drastically affect the in-band
phase evolution and peak frequency. These results constitute unique signatures
of boson clouds of ultralight particles in the dynamics of binary black holes,
which will be readily accessible with the Laser Interferometer Space Antenna,
as well as future mid-band and Deci-hertz detectors.
| [
{
"created": "Mon, 4 Mar 2024 19:10:10 GMT",
"version": "v1"
}
] | 2024-03-06 | [
[
"Bošković",
"Mateja",
""
],
[
"Koschnitzke",
"Matthias",
""
],
[
"Porto",
"Rafael A.",
""
]
] | We show that the existence of clouds of ultralight particles surrounding black holes during their cosmological history as members of a binary system can leave a measurable imprint on the distribution of masses and orbital eccentricities observable with future gravitational-wave detectors. Notably, we find that for nonprecessing binaries with chirp masses ${\cal M} \lesssim 10\,M_\odot$, formed exclusively in isolation, larger-than-expected values of the eccentricity, i.e. $e\gtrsim 10^{-2}$ at gravitational-wave frequencies $f_{\rm GW} \simeq 10^{-2}\,$Hz, would provide tantalizing evidence for a new particle of mass between $[0.5,2.5] \times 10^{-12}\,$eV in nature. The predicted evolution of the eccentricity can also drastically affect the in-band phase evolution and peak frequency. These results constitute unique signatures of boson clouds of ultralight particles in the dynamics of binary black holes, which will be readily accessible with the Laser Interferometer Space Antenna, as well as future mid-band and Deci-hertz detectors. |
0905.1243 | Lars Andersson | Lars Andersson (AEI and UM) and Berndt G. Schmidt (AEI) | Static self-gravitating many-body systems in Einstein gravity | 15 pages | Class.Quant.Grav.26:165007,2009 | 10.1088/0264-9381/26/16/165007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the problem of constructing static, elastic, many-body systems in
Einstein gravity. The solutions constructed are deformations of static
many-body configurations in Newtonian gravity. No symmetry assumptions are
made.
| [
{
"created": "Fri, 8 May 2009 12:42:57 GMT",
"version": "v1"
}
] | 2009-09-28 | [
[
"Andersson",
"Lars",
"",
"AEI and UM"
],
[
"Schmidt",
"Berndt G.",
"",
"AEI"
]
] | We consider the problem of constructing static, elastic, many-body systems in Einstein gravity. The solutions constructed are deformations of static many-body configurations in Newtonian gravity. No symmetry assumptions are made. |
gr-qc/9303001 | Robert Brandenberger | R. Brandenberger (Brown), V. Mukhanov (ETH Zuerich) and A. Sornborger
(Brown) | A Cosmological Theory without Singularities | 25 pages, 11 figures (available as hard copies from the authors),
uses phyzzx, BROWN-HET-891 | Phys.Rev. D48 (1993) 1629-1642 | 10.1103/PhysRevD.48.1629 | null | gr-qc astro-ph hep-th | null | A theory of gravitation is constructed in which all homogeneous and isotropic
solutions are nonsingular, and in which all curvature invariants are bounded.
All solutions for which curvature invariants approach their limiting values
approach de Sitter space. The action for this theory is obtained by a higher
derivative modification of Einstein's theory. We expect that our model can
easily be generalized to solve the singularity problem also for anisotropic
cosmologies.
| [
{
"created": "Mon, 1 Mar 1993 20:27:54 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Brandenberger",
"R.",
"",
"Brown"
],
[
"Mukhanov",
"V.",
"",
"ETH Zuerich"
],
[
"Sornborger",
"A.",
"",
"Brown"
]
] | A theory of gravitation is constructed in which all homogeneous and isotropic solutions are nonsingular, and in which all curvature invariants are bounded. All solutions for which curvature invariants approach their limiting values approach de Sitter space. The action for this theory is obtained by a higher derivative modification of Einstein's theory. We expect that our model can easily be generalized to solve the singularity problem also for anisotropic cosmologies. |
2309.03991 | Nikolaos Stergioulas | Ioannis Liodis, Evaggelos Smirniotis, Nikolaos Stergioulas | A neural-network-based surrogate model for the properties of neutron
stars in 4D Einstein-Gauss-Bonnet gravity | 12 pages, 8 figures | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Machine learning and artificial neural networks (ANNs) have increasingly
become integral to data analysis research in astrophysics due to the growing
demand for fast calculations resulting from the abundance of observational
data. Simultaneously, neutron stars and black holes have been extensively
examined within modified theories of gravity since they enable the exploration
of the strong field regime of gravity. In this study, we employ ANNs to develop
a surrogate model for a numerical iterative method to solve the structure
equations of NSs within a specific 4D Einstein-Gauss-Bonnet gravity framework.
We have trained highly accurate surrogate models, each corresponding to one of
twenty realistic EoSs. The resulting ANN models predict the mass and radius of
individual NS models between 10 and 100 times faster than the numerical solver.
In the case of batch processing, we demonstrated that the speed up is several
orders of magnitude higher. We have trained additional models where the radius
is predicted for specific masses. Here, the speed up is considerably higher
since the original numerical code that constructs the equilibrium models would
have to do additional iterations to find a model with a specific mass. Our ANN
models can be used to speed up Bayesian inference, where the mass and radius of
equilibrium models in this theory of gravity are required.
| [
{
"created": "Thu, 7 Sep 2023 19:47:11 GMT",
"version": "v1"
}
] | 2023-09-11 | [
[
"Liodis",
"Ioannis",
""
],
[
"Smirniotis",
"Evaggelos",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | Machine learning and artificial neural networks (ANNs) have increasingly become integral to data analysis research in astrophysics due to the growing demand for fast calculations resulting from the abundance of observational data. Simultaneously, neutron stars and black holes have been extensively examined within modified theories of gravity since they enable the exploration of the strong field regime of gravity. In this study, we employ ANNs to develop a surrogate model for a numerical iterative method to solve the structure equations of NSs within a specific 4D Einstein-Gauss-Bonnet gravity framework. We have trained highly accurate surrogate models, each corresponding to one of twenty realistic EoSs. The resulting ANN models predict the mass and radius of individual NS models between 10 and 100 times faster than the numerical solver. In the case of batch processing, we demonstrated that the speed up is several orders of magnitude higher. We have trained additional models where the radius is predicted for specific masses. Here, the speed up is considerably higher since the original numerical code that constructs the equilibrium models would have to do additional iterations to find a model with a specific mass. Our ANN models can be used to speed up Bayesian inference, where the mass and radius of equilibrium models in this theory of gravity are required. |
1902.08323 | Paul Chesler | Paul M. Chesler, Ramesh Narayan and Erik Curiel | Singularities in Reissner-Nordstr\"om black holes | 17 pages, 3 figures, clarifications and an appendix with numerics
added, published version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black holes produced by the collapse of a spherically symmetric
charged scalar field in asymptotically flat space. We employ a late time
expansion and show decaying fluxes of radiation through the event horizon imply
the black hole must contain a null singularity on the Cauchy horizon and a
central spacelike singularity.
| [
{
"created": "Fri, 22 Feb 2019 00:49:56 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Nov 2019 20:40:41 GMT",
"version": "v2"
}
] | 2019-12-03 | [
[
"Chesler",
"Paul M.",
""
],
[
"Narayan",
"Ramesh",
""
],
[
"Curiel",
"Erik",
""
]
] | We study black holes produced by the collapse of a spherically symmetric charged scalar field in asymptotically flat space. We employ a late time expansion and show decaying fluxes of radiation through the event horizon imply the black hole must contain a null singularity on the Cauchy horizon and a central spacelike singularity. |
gr-qc/9704076 | N. K. Dadhich | Naresh Dadhich and K. Narayan | An ansatz for spacetimes of zero gravitational mass : global monopoles
and textures | 9 pages, LaTeX version | Gen.Rel.Grav. 30 (1998) 1133 | 10.1023/A:1026660907760 | IUCAA-32/97 | gr-qc | null | We propose a geometric ansatz, a restriction on Euclidean / Minkowski
distance in the embedding space being propotional to distance in the embedded
space, to generate spacetimes with vanishing gravitational mass ($R_{ik} u^i
u^k = 0, u_i u^i = 1 $). It turns out that these spacetimes can represent
global monopoles and textures. Thus the ansatz is a prescription to generate
zero mass spacetimes that could describe topological defects, global monopoles
and textures.
| [
{
"created": "Mon, 28 Apr 1997 11:30:12 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Dadhich",
"Naresh",
""
],
[
"Narayan",
"K.",
""
]
] | We propose a geometric ansatz, a restriction on Euclidean / Minkowski distance in the embedding space being propotional to distance in the embedded space, to generate spacetimes with vanishing gravitational mass ($R_{ik} u^i u^k = 0, u_i u^i = 1 $). It turns out that these spacetimes can represent global monopoles and textures. Thus the ansatz is a prescription to generate zero mass spacetimes that could describe topological defects, global monopoles and textures. |
gr-qc/0309082 | Burkhard Kleihaus | Burkhard Kleihaus, Jutta Kunz, Francisco Navarro-L\'erida | Stationary Black Holes with Static and Counterrotating Horizons | 4 pages, 6 figures | Phys.Rev.D69:081501,2004 | 10.1103/PhysRevD.69.081501 | null | gr-qc | null | We show that rotating dyonic black holes with static and counterrotating
horizon exist in Einstein-Maxwell-dilaton theory when the dilaton coupling
constant exceeds the Kaluza-Klein value. The black holes with static horizon
bifurcate from the static black holes. Their mass decreases with increasing
angular momentum, their horizons are prolate.
| [
{
"created": "Wed, 17 Sep 2003 12:45:25 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lérida",
"Francisco",
""
]
] | We show that rotating dyonic black holes with static and counterrotating horizon exist in Einstein-Maxwell-dilaton theory when the dilaton coupling constant exceeds the Kaluza-Klein value. The black holes with static horizon bifurcate from the static black holes. Their mass decreases with increasing angular momentum, their horizons are prolate. |
1009.5189 | Georgios Kraniotis | G. V. Kraniotis | Precise analytic treatment of Kerr and Kerr-(anti) de Sitter black holes
as gravitational lenses | 42 pages, 4 figures | Class.Quant.Grav.28:085021,2011 | 10.1088/0264-9381/28/8/085021 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The null geodesic equations that describe motion of photons in Kerr spacetime
are solved exactly in the presence of the cosmological constant $\Lambda$. The
exact solution for the deflection angle for generic light orbits (i.e.
non-polar, non-equatorial) is calculated in terms of the generalized
hypergeometric functions of Appell and Lauricella. We then consider the more
involved issue in which the black hole acts as a `gravitational lens'. The
constructed Kerr black hole gravitational lens geometry consists of an observer
and a source located far away and placed at arbitrary inclination with respect
to the black hole's equatorial plane. The resulting lens equations are solved
elegantly in terms of Appell-Lauricella hypergeometric functions and the
Weierstrass elliptic function. We then, systematically, apply our closed form
solutions for calculating the image and source positions of generic photon
orbits that solve the lens equations and reach an observer located at various
values of the polar angle for various values of the Kerr parameter and the
first integrals of motion. In this framework, the magnification factors for
generic orbits are calculated in closed analytic form for the first time. The
exercise is repeated with the appropriate modifications for the case of a
non-zero cosmological constant.
| [
{
"created": "Mon, 27 Sep 2010 08:48:25 GMT",
"version": "v1"
}
] | 2011-04-08 | [
[
"Kraniotis",
"G. V.",
""
]
] | The null geodesic equations that describe motion of photons in Kerr spacetime are solved exactly in the presence of the cosmological constant $\Lambda$. The exact solution for the deflection angle for generic light orbits (i.e. non-polar, non-equatorial) is calculated in terms of the generalized hypergeometric functions of Appell and Lauricella. We then consider the more involved issue in which the black hole acts as a `gravitational lens'. The constructed Kerr black hole gravitational lens geometry consists of an observer and a source located far away and placed at arbitrary inclination with respect to the black hole's equatorial plane. The resulting lens equations are solved elegantly in terms of Appell-Lauricella hypergeometric functions and the Weierstrass elliptic function. We then, systematically, apply our closed form solutions for calculating the image and source positions of generic photon orbits that solve the lens equations and reach an observer located at various values of the polar angle for various values of the Kerr parameter and the first integrals of motion. In this framework, the magnification factors for generic orbits are calculated in closed analytic form for the first time. The exercise is repeated with the appropriate modifications for the case of a non-zero cosmological constant. |
1108.0060 | Rodrigo P. Macedo | Jos\'e Luis Jaramillo and Rodrigo P. Macedo and Philipp Moesta and
Luciano Rezzolla | Black-hole horizons as probes of black-hole dynamics I: post-merger
recoil in head-on collisions | final version published on PRD | Phys. Rev. D 85, 084030 (2012) | 10.1103/PhysRevD.85.084030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The understanding of strong-field dynamics near black-hole horizons is a
long-standing and challenging prob- lem in general relativity. Recent advances
in numerical relativity and in the geometric characterization of black- hole
horizons open new avenues into the problem. In this first paper in a series of
two, we focus on the analysis of the recoil occurring in the merger of binary
black holes, extending the analysis initiated in [1] with Robinson- Trautman
spacetimes. More specifically, we probe spacetime dynamics through the
correlation of quantities defined at the black-hole horizon and at null
infinity. The geometry of these hypersurfaces responds to bulk gravitational
fields acting as test screens in a scattering perspective of spacetime
dynamics. Within a 3 + 1 approach we build an effective-curvature vector from
the intrinsic geometry of dynamical-horizon sections and correlate its
evolution with the flux of Bondi linear momentum at large distances. We employ
this setup to study numerically the head-on collision of nonspinning black
holes and demonstrate its validity to track the qualita- tive aspects of recoil
dynamics at infinity. We also make contact with the suggestion that the
antikick can be described in terms of a "slowness parameter" and how this can
be computed from the local properties of the horizon. In a companion paper [2]
we will further elaborate on the geometric aspects of this approach and on its
relation with other approaches to characterize dynamical properties of
black-hole horizons.
| [
{
"created": "Sat, 30 Jul 2011 11:24:31 GMT",
"version": "v1"
},
{
"created": "Sat, 5 May 2012 13:38:17 GMT",
"version": "v2"
}
] | 2012-05-08 | [
[
"Jaramillo",
"José Luis",
""
],
[
"Macedo",
"Rodrigo P.",
""
],
[
"Moesta",
"Philipp",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | The understanding of strong-field dynamics near black-hole horizons is a long-standing and challenging prob- lem in general relativity. Recent advances in numerical relativity and in the geometric characterization of black- hole horizons open new avenues into the problem. In this first paper in a series of two, we focus on the analysis of the recoil occurring in the merger of binary black holes, extending the analysis initiated in [1] with Robinson- Trautman spacetimes. More specifically, we probe spacetime dynamics through the correlation of quantities defined at the black-hole horizon and at null infinity. The geometry of these hypersurfaces responds to bulk gravitational fields acting as test screens in a scattering perspective of spacetime dynamics. Within a 3 + 1 approach we build an effective-curvature vector from the intrinsic geometry of dynamical-horizon sections and correlate its evolution with the flux of Bondi linear momentum at large distances. We employ this setup to study numerically the head-on collision of nonspinning black holes and demonstrate its validity to track the qualita- tive aspects of recoil dynamics at infinity. We also make contact with the suggestion that the antikick can be described in terms of a "slowness parameter" and how this can be computed from the local properties of the horizon. In a companion paper [2] we will further elaborate on the geometric aspects of this approach and on its relation with other approaches to characterize dynamical properties of black-hole horizons. |
1503.00920 | Angelo Tartaglia | Angelo Tartaglia | Testing General Relativity | The paper will appear on Proceedings of Science: Gran Sasso Summer
Institute 2014 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This lecture will present a review of the past and present tests of the
General Relativity theory. The essentials of the theory will be recalled and
the measurable effects will be listed and analyzed. The main historical
confirmations of General Relativity will be described. Then, the present
situation will be reviewed presenting a number of examples. The opportunities
given by astrophysical and astrometric observations will be shortly discussed.
Coming to terrestrial experiments the attention will be specially focused on
ringlasers and a dedicated experiment for the Gran Sasso Laboratories, named by
the acronym GINGER, will be presented. Mention will also be made of
alternatives to the use of light, such as particle beams and superfluid rings.
| [
{
"created": "Tue, 3 Mar 2015 12:44:02 GMT",
"version": "v1"
}
] | 2015-03-04 | [
[
"Tartaglia",
"Angelo",
""
]
] | This lecture will present a review of the past and present tests of the General Relativity theory. The essentials of the theory will be recalled and the measurable effects will be listed and analyzed. The main historical confirmations of General Relativity will be described. Then, the present situation will be reviewed presenting a number of examples. The opportunities given by astrophysical and astrometric observations will be shortly discussed. Coming to terrestrial experiments the attention will be specially focused on ringlasers and a dedicated experiment for the Gran Sasso Laboratories, named by the acronym GINGER, will be presented. Mention will also be made of alternatives to the use of light, such as particle beams and superfluid rings. |
2201.08726 | Geanderson Carvalho | G.A. Carvalho, R. Lobato, P.H.R.S. Moraes, D. Deb and M. Malheiro | Quark stars with 2.6 $M_\odot$ in a non-minimal geometry-matter coupling
theory of gravity | null | null | 10.1140/epjc/s10052-022-11058-6 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work analyses the hydrostatic equilibrium configurations of strange
stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. Those
stars are made of strange quark matter, whose distribution is governed by the
MIT equation of state. The non-minimal GMC theory is described by the following
gravitational action: $f(R,L)=R/2+L+\sigma RL$, where $R$ represents the
curvature scalar, $L$ is the matter Lagrangian density, and $\sigma$ is the
coupling parameter. When considering this theory, the strange stars become
larger and more massive. In particular, when $\sigma=50$ km$^2$, the theory can
achieve the 2.6 $M_\odot$, which is suitable for describing the pulsars PSR
J2215+5135 and PSR J1614-2230, and the mass of the secondary object in the
GW190814 event. The 2.6 $M_\odot$ is a value hardly achievable in General
Relativity even considering fast rotation effects, and is also compatible with
the mass of PSR J0952-0607 ($M = 2.35 \pm 0.17 ~M_\odot$), the heaviest and
fastest pulsar in the disk of the Milky Way, recently measured, supporting the
possible existence of strange quark matter in its composition. The non-minimal
GMC theory can also give feasible results to describe the macroscopical
features of strange star candidates.
| [
{
"created": "Fri, 21 Jan 2022 14:43:54 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Sep 2022 14:13:45 GMT",
"version": "v2"
}
] | 2022-12-21 | [
[
"Carvalho",
"G. A.",
""
],
[
"Lobato",
"R.",
""
],
[
"Moraes",
"P. H. R. S.",
""
],
[
"Deb",
"D.",
""
],
[
"Malheiro",
"M.",
""
]
] | This work analyses the hydrostatic equilibrium configurations of strange stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. Those stars are made of strange quark matter, whose distribution is governed by the MIT equation of state. The non-minimal GMC theory is described by the following gravitational action: $f(R,L)=R/2+L+\sigma RL$, where $R$ represents the curvature scalar, $L$ is the matter Lagrangian density, and $\sigma$ is the coupling parameter. When considering this theory, the strange stars become larger and more massive. In particular, when $\sigma=50$ km$^2$, the theory can achieve the 2.6 $M_\odot$, which is suitable for describing the pulsars PSR J2215+5135 and PSR J1614-2230, and the mass of the secondary object in the GW190814 event. The 2.6 $M_\odot$ is a value hardly achievable in General Relativity even considering fast rotation effects, and is also compatible with the mass of PSR J0952-0607 ($M = 2.35 \pm 0.17 ~M_\odot$), the heaviest and fastest pulsar in the disk of the Milky Way, recently measured, supporting the possible existence of strange quark matter in its composition. The non-minimal GMC theory can also give feasible results to describe the macroscopical features of strange star candidates. |
gr-qc/9511064 | Ulf Nilsson | Ulf Nilsson, Claes Uggla | Spatially self-similar locally rotationally symmetric perfect fluid
models | 27 pages, pictures available at
ftp://vanosf.physto.se/pub/figures/ssslrs.tar.gz | Class.Quant.Grav. 13 (1996) 1601-1622 | 10.1088/0264-9381/13/6/024 | null | gr-qc | null | Einstein's field equations for spatially self-similar locally rotationally
symmetric perfect fluid models are investigated. The field equations are
rewritten as a first order system of autonomous ordinary differential
equations. Dimensionless variables are chosen in such a way that the number of
equations in the coupled system of differential equations is reduced as far as
possible. The system is subsequently analyzed qualitatively for some of the
models. The nature of the singularities occurring in the models is discussed.
| [
{
"created": "Fri, 24 Nov 1995 09:00:49 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Nilsson",
"Ulf",
""
],
[
"Uggla",
"Claes",
""
]
] | Einstein's field equations for spatially self-similar locally rotationally symmetric perfect fluid models are investigated. The field equations are rewritten as a first order system of autonomous ordinary differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system of differential equations is reduced as far as possible. The system is subsequently analyzed qualitatively for some of the models. The nature of the singularities occurring in the models is discussed. |
1806.02533 | Richard Woodard | Z. H. Liao (NCKU), S. P. Miao (NCKU) and R. P. Woodard (Florida) | Cosmological Coleman-Weinberg Potentials and Inflation | 11 pages, 3 figures, uses LaTeX2e Version 2 extensively revised for
publication, contains a new section connecting reheating and fine tuning and
an extended discussion of the late time de Sitter phase approached by all
fermion models | Phys. Rev. D 99, 103522 (2019) | 10.1103/PhysRevD.99.103522 | UFIFT-QG-18-04 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an additional fine-tuning problem which afflicts scalar-driven
models of inflation. The problem is that successful reheating requires the
inflaton be coupled to ordinary matter, and quantum fluctuations of this matter
induces Coleman-Weinberg potentials which are not Planck-suppressed. Unlike the
flat space case, these potentials depend upon a still-unknown, nonlocal
functional of the metric which reduces to the Hubble parameter for de Sitter.
Such a potential cannot be completely subtracted off by any local action. In a
simple model we numerically consider one possible subtraction scheme in which
the correction is locally subtracted at the beginning of inflation. For
fermions the effect is to make the universe approach de Sitter with a smaller
Hubble parameter. For gauge bosons the effect is to make inflation end almost
instantly unless the gauge charge is unacceptably small.
| [
{
"created": "Thu, 7 Jun 2018 06:47:42 GMT",
"version": "v1"
},
{
"created": "Tue, 21 May 2019 04:24:11 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Liao",
"Z. H.",
"",
"NCKU"
],
[
"Miao",
"S. P.",
"",
"NCKU"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] | We consider an additional fine-tuning problem which afflicts scalar-driven models of inflation. The problem is that successful reheating requires the inflaton be coupled to ordinary matter, and quantum fluctuations of this matter induces Coleman-Weinberg potentials which are not Planck-suppressed. Unlike the flat space case, these potentials depend upon a still-unknown, nonlocal functional of the metric which reduces to the Hubble parameter for de Sitter. Such a potential cannot be completely subtracted off by any local action. In a simple model we numerically consider one possible subtraction scheme in which the correction is locally subtracted at the beginning of inflation. For fermions the effect is to make the universe approach de Sitter with a smaller Hubble parameter. For gauge bosons the effect is to make inflation end almost instantly unless the gauge charge is unacceptably small. |
gr-qc/9606038 | Daniel Sudarsky | Marcelo Salgado, Daniel Sudarsky, and Hernando Quevedo | Galactic periodicity and the oscillating G model | Latex file 29 pages with no figures. Please contact M.Salgado for
figures. A more careful study of the model appears in gr-qc/9606039 | Phys.Rev. D53 (1996) 6771-6783 | 10.1103/PhysRevD.53.6771 | null | gr-qc | null | We consider the model involving the oscillation of the effective
gravitational constant that has been put forward in an attempt to reconcile the
observed periodicity in the galaxy number distribution with the standard
cosmological models. This model involves a highly nonlinear dynamics which we
analyze numerically. We carry out a detailed study of the bound that
nucleosynthesis imposes on this model. The analysis shows that for any assumed
value for $\Omega$ (the total energy density) one can fix the value of
$\Omega_{\rm bar}$ (the baryonic energy density) in such a way as to
accommodate the observational constraints coming from the $^4{\rm He}$
primordial abundance. In particular, if we impose the inflationary value
$\Omega=1$ the resulting baryonic energy density turns out to be $\Omega_{\rm
bar}\sim 0.021$. This result lies in the very narrow range $0.016 \leq
\Omega_{\rm bar} \leq 0.026$ allowed by the observed values of the primordial
abundances of the other light elements. The remaining fraction of $\Omega$
corresponds to dark matter represented by a scalar field.
| [
{
"created": "Fri, 14 Jun 1996 23:01:18 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Salgado",
"Marcelo",
""
],
[
"Sudarsky",
"Daniel",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We consider the model involving the oscillation of the effective gravitational constant that has been put forward in an attempt to reconcile the observed periodicity in the galaxy number distribution with the standard cosmological models. This model involves a highly nonlinear dynamics which we analyze numerically. We carry out a detailed study of the bound that nucleosynthesis imposes on this model. The analysis shows that for any assumed value for $\Omega$ (the total energy density) one can fix the value of $\Omega_{\rm bar}$ (the baryonic energy density) in such a way as to accommodate the observational constraints coming from the $^4{\rm He}$ primordial abundance. In particular, if we impose the inflationary value $\Omega=1$ the resulting baryonic energy density turns out to be $\Omega_{\rm bar}\sim 0.021$. This result lies in the very narrow range $0.016 \leq \Omega_{\rm bar} \leq 0.026$ allowed by the observed values of the primordial abundances of the other light elements. The remaining fraction of $\Omega$ corresponds to dark matter represented by a scalar field. |
gr-qc/9511063 | Rafael D. Sorkin | Rafael D. Sorkin (Syracuse University and UNAM) | A Specimen of Theory Construction from Quantum Gravity | 16 pages, plainTeX. Figures not included but available on request
from the Author. To be published in: "The Creation of Ideas in Physics", ed.
Jarrett Leplin, (Kluwer Academic Publishers, Dordrecht, 1995) | in The Creation of Ideas in Physics: Studies for a Methodology of
Theory Construction (Proceedings of the Thirteenth Annual Symposium in
Philosophy, held Greensboro, North Carolina, March, 1989) (Number 55 in the
University of Western Ontario Series in Philosophy of Science) edited by
J.~Leplin, pp. 167-179 (Kluwer Academic Publishers, Dordrecht, 1995) | null | null | gr-qc hep-th | null | I describe the history of my attempts to arrive at a discrete substratum
underlying the spacetime manifold, culminating in the hypothesis that the basic
structure has the form of a partial-order (i.e. that it is a causal set).
| [
{
"created": "Thu, 23 Nov 1995 08:43:21 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Sorkin",
"Rafael D.",
"",
"Syracuse University and UNAM"
]
] | I describe the history of my attempts to arrive at a discrete substratum underlying the spacetime manifold, culminating in the hypothesis that the basic structure has the form of a partial-order (i.e. that it is a causal set). |
gr-qc/0003111 | Robert Paternoga | Robert Paternoga, Robert Graham | Triad representation of the Chern-Simons state in quantum gravity | Latex, 30 pages, 1 figure, to appear in Phys. Rev. D | Phys.Rev. D62 (2000) 084005 | 10.1103/PhysRevD.62.084005 | null | gr-qc | null | We investigate a triad representation of the Chern-Simons state of quantum
gravity with a non-vanishing cosmological constant. It is shown that the
Chern-Simons state, which is a well-known exact wavefunctional within the
Ashtekar theory, can be transformed to the real triad representation by means
of a suitably generalized Fourier transformation, yielding a complex integral
representation for the corresponding state in the triad variables. It is found
that topologically inequivalent choices for the complex integration contour
give rise to linearly independent wavefunctionals in the triad representation,
which all arise from the one Chern-Simons state in the Ashtekar variables. For
a suitable choice of the normalization factor, these states turn out to be
gauge-invariant under arbitrary, even topologically non-trivial
gauge-transformations. Explicit analytical expressions for the wavefunctionals
in the triad representation can be obtained in several interesting asymptotic
parameter regimes, and the associated semiclassical 4-geometries are discussed.
In restriction to Bianchi-type homogeneous 3-metrics, we compare our results
with earlier discussions of homogeneous cosmological models. Moreover, we
define an inner product on the Hilbert space of quantum gravity, and choose a
natural gauge-condition fixing the time-gauge. With respect to this particular
inner product, the Chern-Simons state of quantum gravity turns out to be a
non-normalizable wavefunctional.
| [
{
"created": "Thu, 30 Mar 2000 15:18:47 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Paternoga",
"Robert",
""
],
[
"Graham",
"Robert",
""
]
] | We investigate a triad representation of the Chern-Simons state of quantum gravity with a non-vanishing cosmological constant. It is shown that the Chern-Simons state, which is a well-known exact wavefunctional within the Ashtekar theory, can be transformed to the real triad representation by means of a suitably generalized Fourier transformation, yielding a complex integral representation for the corresponding state in the triad variables. It is found that topologically inequivalent choices for the complex integration contour give rise to linearly independent wavefunctionals in the triad representation, which all arise from the one Chern-Simons state in the Ashtekar variables. For a suitable choice of the normalization factor, these states turn out to be gauge-invariant under arbitrary, even topologically non-trivial gauge-transformations. Explicit analytical expressions for the wavefunctionals in the triad representation can be obtained in several interesting asymptotic parameter regimes, and the associated semiclassical 4-geometries are discussed. In restriction to Bianchi-type homogeneous 3-metrics, we compare our results with earlier discussions of homogeneous cosmological models. Moreover, we define an inner product on the Hilbert space of quantum gravity, and choose a natural gauge-condition fixing the time-gauge. With respect to this particular inner product, the Chern-Simons state of quantum gravity turns out to be a non-normalizable wavefunctional. |
gr-qc/0603119 | Roberto Giambo' | R. Giambo', F. Giannoni, G. Magli | A variational approach to homogeneous scalar fields in General
Relativity | null | null | null | null | gr-qc math.FA | null | A result of existence of homogeneous scalar field solutions between
prescribed configurations is given, using a modified version of
Euler--Maupertuis least action variational principle. Solutions are obtained as
limit of approximating variational problems, solved using techniques introduced
by Rabinowitz.
| [
{
"created": "Wed, 29 Mar 2006 15:36:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Giambo'",
"R.",
""
],
[
"Giannoni",
"F.",
""
],
[
"Magli",
"G.",
""
]
] | A result of existence of homogeneous scalar field solutions between prescribed configurations is given, using a modified version of Euler--Maupertuis least action variational principle. Solutions are obtained as limit of approximating variational problems, solved using techniques introduced by Rabinowitz. |
gr-qc/0411083 | Sasha Kozyreva v. | L. Bezrukov (1), S. Popov (2), V. Rudenko (2), A. Serdobolskii (2), M.
Skvortsov (3) ((1) Institute for Nuclear Research of Russian Academy of
Sciences, Moscow, (2) Sternberg Astronomical Institute of Moscow State
University, Moscow, (3) Institute of Laser Physics of Siberian Branch of
Russian Academy of Sciences, Novosibirsk) | Gravitational wave experiments and Baksan project "OGRAN" | 14 pages, 5 figures, The talk at the Gamov Memorial International
Conference dedicated to 100-th anniversary of George Gamow. Odessa, Ukraine,
August 8-14 2004. To be published in the Proceedings (Cambridge Scientific
Publications) | null | null | null | gr-qc | null | A brief sketch of the present status of gravitational wave experiments is
given. Attention is concentrated to recent observations with the gravitational
detector network. The project OGRAN for a combined optic-interferometrical and
acoustical gravitation wave antenna planned for installation into underground
facilities of the Baksan Neutrino Observatory is presented. We describe general
principles of the apparatus, expected sensitivity and current characteristics
of the antenna prototype; some ways for sensitivity improvement are also
discussed.
| [
{
"created": "Tue, 16 Nov 2004 19:54:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bezrukov",
"L.",
""
],
[
"Popov",
"S.",
""
],
[
"Rudenko",
"V.",
""
],
[
"Serdobolskii",
"A.",
""
],
[
"Skvortsov",
"M.",
""
]
] | A brief sketch of the present status of gravitational wave experiments is given. Attention is concentrated to recent observations with the gravitational detector network. The project OGRAN for a combined optic-interferometrical and acoustical gravitation wave antenna planned for installation into underground facilities of the Baksan Neutrino Observatory is presented. We describe general principles of the apparatus, expected sensitivity and current characteristics of the antenna prototype; some ways for sensitivity improvement are also discussed. |
1406.2850 | Branislav Cvetkovi\'c | M. Blagojevi\'c and B. Cvetkovi\'c | Gravitational waves with torsion in 3D | LaTeX, 15 pages, 4 figures; v2 minor changes | Phys. Rev. D 90 (2014), 044006 | 10.1103/PhysRevD.90.044006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational waves with torsion as exact vacuum solutions of
three-dimensional gravity with propagating torsion. The new solutions are a
natural generalization of the plane-fronted gravitational waves in general
relativity with a cosmological constant, in the presence of matter.
| [
{
"created": "Wed, 11 Jun 2014 10:24:35 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Sep 2014 22:24:45 GMT",
"version": "v2"
}
] | 2014-09-16 | [
[
"Blagojević",
"M.",
""
],
[
"Cvetković",
"B.",
""
]
] | We study gravitational waves with torsion as exact vacuum solutions of three-dimensional gravity with propagating torsion. The new solutions are a natural generalization of the plane-fronted gravitational waves in general relativity with a cosmological constant, in the presence of matter. |
1712.08752 | Ben David Normann Mr. | Ben David Normann, Sigbj{\o}rn Hervik, Angelo Ricciardone and Mikjel
Thorsrud | Bianchi cosmologies with $p$-form gauge fields | 42 pages, 6 figures, 6 tables in text. V2: minor changes, matches the
version published in CQG | Class. Quantum Grav. 35 (2018) 095004 | 10.1088/1361-6382/aab3a7 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper the dynamics of free gauge fields in Bianchi type I-VII$_{h}$
space-times is investigated. The general equations for a matter sector
consisting of a $p$-form field strength ($p\,\in\,\{1,3\}$), a cosmological
constant ($4$-form) and perfect fluid in Bianchi type I-VII$_{h}$ space-times
are computed using the orthonormal frame method. The number of independent
components of a $p$-form in all Bianchi types I-IX are derived and, by means of
the dynamical systems approach, the behaviour of such fields in Bianchi type I
and V are studied. Both a local and a global analysis are performed and strong
global results regarding the general behaviour are obtained. New self-similar
cosmological solutions appear both in Bianchi type I and Bianchi type V, in
particular, a one-parameter family of self-similar solutions,"Wonderland
($\lambda$)" appears generally in type V and in type I for $\lambda=0$.
Depending on the value of the equation of state parameter other new stable
solutions are also found ("The Rope" and "The Edge") containing a purely
spatial field strength that rotates relative to the co-moving inertial tetrad.
Using monotone functions, global results are given and the conditions under
which exact solutions are (global) attractors are found.
| [
{
"created": "Sat, 23 Dec 2017 10:37:26 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Apr 2018 16:40:03 GMT",
"version": "v2"
}
] | 2018-04-10 | [
[
"Normann",
"Ben David",
""
],
[
"Hervik",
"Sigbjørn",
""
],
[
"Ricciardone",
"Angelo",
""
],
[
"Thorsrud",
"Mikjel",
""
]
] | In this paper the dynamics of free gauge fields in Bianchi type I-VII$_{h}$ space-times is investigated. The general equations for a matter sector consisting of a $p$-form field strength ($p\,\in\,\{1,3\}$), a cosmological constant ($4$-form) and perfect fluid in Bianchi type I-VII$_{h}$ space-times are computed using the orthonormal frame method. The number of independent components of a $p$-form in all Bianchi types I-IX are derived and, by means of the dynamical systems approach, the behaviour of such fields in Bianchi type I and V are studied. Both a local and a global analysis are performed and strong global results regarding the general behaviour are obtained. New self-similar cosmological solutions appear both in Bianchi type I and Bianchi type V, in particular, a one-parameter family of self-similar solutions,"Wonderland ($\lambda$)" appears generally in type V and in type I for $\lambda=0$. Depending on the value of the equation of state parameter other new stable solutions are also found ("The Rope" and "The Edge") containing a purely spatial field strength that rotates relative to the co-moving inertial tetrad. Using monotone functions, global results are given and the conditions under which exact solutions are (global) attractors are found. |
gr-qc/0607114 | Gamal Nashed G.L. | Gamal G.L Nashed | Reissner-Nordstr\"om anti-de Sitter black holes and energy | 1 page Latex. Letter will appear in the European Journal of physics | Eur.Phys.J.C48:303,2006 | 10.1140/epjc/s10052-006-0011-y | null | gr-qc | null | We show that the tetrad field whose metric gives the Reissner-Nordstr\"om
anti-de Sitter black holes gives the correct value of energy in M{\o}ller
tetrad theory of gravitation.
| [
{
"created": "Wed, 26 Jul 2006 10:23:06 GMT",
"version": "v1"
}
] | 2011-01-27 | [
[
"Nashed",
"Gamal G. L",
""
]
] | We show that the tetrad field whose metric gives the Reissner-Nordstr\"om anti-de Sitter black holes gives the correct value of energy in M{\o}ller tetrad theory of gravitation. |
2104.00802 | Djordje Minic | Laurent Freidel, Jerzy Kowalski-Glikman, Robert G. Leigh and Djordje
Minic | Quantum Gravity Phenomenology in the Infrared | 10 pages;This paper has been awarded the Second Prize in the 2021
Essay Competition of the Gravity Research Foundation (typos corrected) | null | 10.1142/S0218271821410029 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity effects are traditionally tied to short distances and high
energies. In this essay we argue that, perhaps surprisingly, quantum gravity
may have important consequences for the phenomenology of the infrared. We
center our discussion around a conception of quantum gravity involving a notion
of quantum spacetime that arises in metastring theory. This theory allows for
an evolution of a cosmological Universe in which string-dual degrees of freedom
decouple as the Universe ages. Importantly such an implementation of quantum
gravity allows for the inclusion of a fundamental length scale without
introducing the fundamental breaking of Lorentz symmetry. The mechanism seems
to have potential for an entirely novel source for dark matter/energy. The
simplest observational consequences of this scenario may very well be residual
infrared modifications that emerge through the evolution of the Universe.
| [
{
"created": "Thu, 1 Apr 2021 23:34:35 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2022 22:31:59 GMT",
"version": "v2"
}
] | 2022-05-19 | [
[
"Freidel",
"Laurent",
""
],
[
"Kowalski-Glikman",
"Jerzy",
""
],
[
"Leigh",
"Robert G.",
""
],
[
"Minic",
"Djordje",
""
]
] | Quantum gravity effects are traditionally tied to short distances and high energies. In this essay we argue that, perhaps surprisingly, quantum gravity may have important consequences for the phenomenology of the infrared. We center our discussion around a conception of quantum gravity involving a notion of quantum spacetime that arises in metastring theory. This theory allows for an evolution of a cosmological Universe in which string-dual degrees of freedom decouple as the Universe ages. Importantly such an implementation of quantum gravity allows for the inclusion of a fundamental length scale without introducing the fundamental breaking of Lorentz symmetry. The mechanism seems to have potential for an entirely novel source for dark matter/energy. The simplest observational consequences of this scenario may very well be residual infrared modifications that emerge through the evolution of the Universe. |
1603.06608 | Aaron Levy | Aaron M. Levy and Gustavo Turiaci | Warm Ekpyrosis | 10 pages, 5 figures. References added | Phys. Rev. D 94, 083514 (2016) | 10.1103/PhysRevD.94.083514 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a mechanism to generate a nearly scale-invariant spectrum of
adiabatic scalar perturbations about a stable, ekpyrotic background. The key
ingredient is a coupling between a single ekpyrotic field and a perfect fluid
of ultra-relativistic matter. This coupling introduces a friction term into the
equation of motion for the field, opposing the Hubble anti-friction, which can
be chosen such that an exactly scale-invariant (or nearly scale-invariant)
spectrum of adiabatic density perturbations is continuously produced throughout
the ekpyrotic phase. This mechanism eliminates the need for a second (entropic)
scalar field and hence any need for introducing a second phase for converting
entropic into curvature fluctuations. It also reduces the constraints on the
equation of state during the ekpyrotic phase and, thereby, the need for
parametric fine-tuning.
| [
{
"created": "Mon, 21 Mar 2016 20:45:57 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Apr 2016 17:34:59 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Levy",
"Aaron M.",
""
],
[
"Turiaci",
"Gustavo",
""
]
] | We propose a mechanism to generate a nearly scale-invariant spectrum of adiabatic scalar perturbations about a stable, ekpyrotic background. The key ingredient is a coupling between a single ekpyrotic field and a perfect fluid of ultra-relativistic matter. This coupling introduces a friction term into the equation of motion for the field, opposing the Hubble anti-friction, which can be chosen such that an exactly scale-invariant (or nearly scale-invariant) spectrum of adiabatic density perturbations is continuously produced throughout the ekpyrotic phase. This mechanism eliminates the need for a second (entropic) scalar field and hence any need for introducing a second phase for converting entropic into curvature fluctuations. It also reduces the constraints on the equation of state during the ekpyrotic phase and, thereby, the need for parametric fine-tuning. |
2311.07749 | Shant Baghram | Javad Tabatabaei, Abdolali Banihashemi, Shant Baghram, Bahram Mashhoon | Local Limit of Nonlocal Gravity: Cosmological Perturbations | 37 pages, 3 figure, 1 table; v2: expanded version accepted for
publication in ApJ | Astrophys. J. 965, 116 (2024) | 10.3847/1538-4357/ad2e04 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We explore the cosmological implications of the local limit of nonlocal
gravity, which is a classical generalization of Einstein's theory of
gravitation within the framework of teleparallelism. An appropriate solution of
this theory is the modified Cartesian flat cosmological model. The main purpose
of this paper is to study linear perturbations about the orthonormal tetrad
frame field adapted to the standard comoving observers in this model. The
observational viability of the perturbed model is examined using all available
data regarding the cosmic microwave background. The implications of the
linearly perturbed modified Cartesian flat model are examined and it is shown
that the model is capable of alleviating the $H_0$ tension.
| [
{
"created": "Mon, 13 Nov 2023 21:06:19 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Feb 2024 17:49:35 GMT",
"version": "v2"
}
] | 2024-04-17 | [
[
"Tabatabaei",
"Javad",
""
],
[
"Banihashemi",
"Abdolali",
""
],
[
"Baghram",
"Shant",
""
],
[
"Mashhoon",
"Bahram",
""
]
] | We explore the cosmological implications of the local limit of nonlocal gravity, which is a classical generalization of Einstein's theory of gravitation within the framework of teleparallelism. An appropriate solution of this theory is the modified Cartesian flat cosmological model. The main purpose of this paper is to study linear perturbations about the orthonormal tetrad frame field adapted to the standard comoving observers in this model. The observational viability of the perturbed model is examined using all available data regarding the cosmic microwave background. The implications of the linearly perturbed modified Cartesian flat model are examined and it is shown that the model is capable of alleviating the $H_0$ tension. |
1609.04418 | Claudio Cremaschini | Claudio Cremaschini and Massimo Tessarotto | Synchronous Lagrangian variational principles in General Relativity | null | The European Physical Journal Plus 130, 123 (2015) | 10.1140/epjp/i2015-15123-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of formulating synchronous variational principles in the context
of General Relativity is discussed. Based on the analogy with classical
relativistic particle dynamics, the existence of variational principles is
pointed out in relativistic classical field theory which are either
asynchronous or synchronous. The historical Einstein-Hilbert and Palatini
variational formulations are found to belong to the first category.
Nevertheless, it is shown that an alternative route exists which permits one to
cast these principles in terms of equivalent synchronous Lagrangian variational
formulations. The advantage is twofold. First, synchronous approaches allow one
to overcome the lack of gauge symmetry of the asynchronous principles. Second,
the property of manifest covariance of the theory is also restored at all
levels, including the symbolic Euler-Lagrange equations, with the variational
Lagrangian density being now identified with a $4-$scalar. As an application, a
joint synchronous variational principle holding both for the non-vacuum
Einstein and Maxwell equations is displayed, with the matter source being
described by means of a Vlasov kinetic treatment.
| [
{
"created": "Wed, 14 Sep 2016 20:03:45 GMT",
"version": "v1"
}
] | 2016-09-16 | [
[
"Cremaschini",
"Claudio",
""
],
[
"Tessarotto",
"Massimo",
""
]
] | The problem of formulating synchronous variational principles in the context of General Relativity is discussed. Based on the analogy with classical relativistic particle dynamics, the existence of variational principles is pointed out in relativistic classical field theory which are either asynchronous or synchronous. The historical Einstein-Hilbert and Palatini variational formulations are found to belong to the first category. Nevertheless, it is shown that an alternative route exists which permits one to cast these principles in terms of equivalent synchronous Lagrangian variational formulations. The advantage is twofold. First, synchronous approaches allow one to overcome the lack of gauge symmetry of the asynchronous principles. Second, the property of manifest covariance of the theory is also restored at all levels, including the symbolic Euler-Lagrange equations, with the variational Lagrangian density being now identified with a $4-$scalar. As an application, a joint synchronous variational principle holding both for the non-vacuum Einstein and Maxwell equations is displayed, with the matter source being described by means of a Vlasov kinetic treatment. |
gr-qc/9802034 | Mikhail Altaisky | Mikhail V. Altaisky (Joint Institute for Nuclear Research) and
B.G.Sidharth (B.M.Birla Science Centre) | p-Adic physics below and above Planck scales | 8 pages, RevTeX, 2 encapsulated postscript figures, Invited paper to
appear in the special issue of the Journal of Chaos, Solitons and Fractals on
: "Superstrings, M, F, S ...Theory" M. S. El Naschie, C. Castro, Editors | null | 10.1016/S0960-0779(98)00089-7 | BSC-CAMCS-98-01-01 | gr-qc | null | We present a rewiew and also new possible applications of $p$-adic numbers to
pre-spacetime physics. It is shown that instead of the extension $R^n\to
Q_p^n$, which is usually implied in $p$-adic quantum field theory, it is
possible to build a model based on the $R^n\to Q_p$, where p=n+2 extension and
get rid of loop divergences. It is also shown that the concept of mass
naturally arises in $p$-adic models as inverse transition probability with a
dimensional constant of proportionality.
| [
{
"created": "Mon, 16 Feb 1998 10:35:04 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Altaisky",
"Mikhail V.",
"",
"Joint Institute for Nuclear Research"
],
[
"Sidharth",
"B. G.",
"",
"B.M.Birla Science Centre"
]
] | We present a rewiew and also new possible applications of $p$-adic numbers to pre-spacetime physics. It is shown that instead of the extension $R^n\to Q_p^n$, which is usually implied in $p$-adic quantum field theory, it is possible to build a model based on the $R^n\to Q_p$, where p=n+2 extension and get rid of loop divergences. It is also shown that the concept of mass naturally arises in $p$-adic models as inverse transition probability with a dimensional constant of proportionality. |
gr-qc/0107082 | Jeremy D. Schnittman | Jeremy D. Schnittman and Frederic A. Rasio | Ruling Out Chaos in Compact Binary Systems | 8 pages, 4 figures, submitted to Phys. Rev. Lett | Phys.Rev.Lett. 87 (2001) 121101 | 10.1103/PhysRevLett.87.121101 | null | gr-qc astro-ph | null | We investigate the orbits of compact binary systems during the final inspiral
period before coalescence by integrating numerically the second-order
post-Newtonian equations of motion. We include spin-orbit and spin-spin
coupling terms, which, according to a recent study by Levin [J. Levin, Phys.
Rev. Lett. 84, 3515 (2000)], may cause the orbits to become chaotic. To examine
this claim, we study the divergence of initially nearby phase-space
trajectories and attempt to measure the Lyapunov exponent gamma. Even for
systems with maximally spinning objects and large spin-orbit misalignment
angles, we find no chaotic behavior. For all the systems we consider, we can
place a strict lower limit on the divergence time t_L=1/gamma that is many
times greater than the typical inspiral time, suggesting that chaos should not
adversely affect the detection of inspiral events by upcoming
gravitational-wave detectors.
| [
{
"created": "Wed, 25 Jul 2001 20:58:53 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Schnittman",
"Jeremy D.",
""
],
[
"Rasio",
"Frederic A.",
""
]
] | We investigate the orbits of compact binary systems during the final inspiral period before coalescence by integrating numerically the second-order post-Newtonian equations of motion. We include spin-orbit and spin-spin coupling terms, which, according to a recent study by Levin [J. Levin, Phys. Rev. Lett. 84, 3515 (2000)], may cause the orbits to become chaotic. To examine this claim, we study the divergence of initially nearby phase-space trajectories and attempt to measure the Lyapunov exponent gamma. Even for systems with maximally spinning objects and large spin-orbit misalignment angles, we find no chaotic behavior. For all the systems we consider, we can place a strict lower limit on the divergence time t_L=1/gamma that is many times greater than the typical inspiral time, suggesting that chaos should not adversely affect the detection of inspiral events by upcoming gravitational-wave detectors. |
1601.01265 | Sarita Rani | J. K. Singh, Sarita Rani | The Bianchi type-V Dark Energy Cosmology in Self Interacting Brans Dicke
Theory of Gravity | 17 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1206.0391 by other authors | null | 10.1134/S0040577917120121 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper deals with a spatially homogeneous and totally anisotropic Bianchi
type-V cosmological model within the framework of self interacting Brans Dicke
theory of gravity in the background of anisotropic dark energy (DE) with
variable equation of state (EoS) parameter and constant deceleration parameter.
Constant deceleration parameter leads to two models of universe, i.e. power law
model and exponential model. EoS parameter {\omega} and its existing range for
the models is in good agreement with the most recent observational data. We
notice that {\omega} given by (37) i.e {\omega}(t) = log(k1t) is more suitable
in explaining the evolution of the universe. The physical behaviors of the
solutions have also been discussed using some physical quantities. Finally, we
observe that despite having several prominent features, both of the DE models
discussed fail in details.
| [
{
"created": "Mon, 4 Jan 2016 10:11:55 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Singh",
"J. K.",
""
],
[
"Rani",
"Sarita",
""
]
] | This paper deals with a spatially homogeneous and totally anisotropic Bianchi type-V cosmological model within the framework of self interacting Brans Dicke theory of gravity in the background of anisotropic dark energy (DE) with variable equation of state (EoS) parameter and constant deceleration parameter. Constant deceleration parameter leads to two models of universe, i.e. power law model and exponential model. EoS parameter {\omega} and its existing range for the models is in good agreement with the most recent observational data. We notice that {\omega} given by (37) i.e {\omega}(t) = log(k1t) is more suitable in explaining the evolution of the universe. The physical behaviors of the solutions have also been discussed using some physical quantities. Finally, we observe that despite having several prominent features, both of the DE models discussed fail in details. |
2302.12739 | Adam Bac | Adam Bac, Wojciech Kami\'nski, Jerzy Lewandowski, Michalina Broda | Symplectic charges in the Yang-Mills theory of the normal conformal
Cartan connection: applications to gravity | 29 pages, 0 figures | Phys. Rev. D 108 (2023) 024009 | 10.1103/PhysRevD.108.024009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that a source-free Yang-Mills theory with the normal conformal
Cartan connection used as the gauge potential gives rise to equations of motion
equivalent to the vanishing of the Bach tensor. We investigate the conformally
invariant presymplectic potential current obtained from this theory and find
that on the solutions to the Einstein field equations, it can be decomposed
into a topological term derived from the Euler density and a part proportional
to the potential of the standard Einstein-Hilbert Lagrangian. The pullback of
our potential to the asymptotic boundary of asymptotically de Sitter spacetimes
turns out to coincide with the current obtained from the holographically
renormalized gravitational action. This provides an alternative derivation of a
symplectic structure on scri without resorting to holographic techniques. We
also calculate our current at the null infinity of asymptotically flat
spacetimes and in particular show that it vanishes for variations induced by
the BMS symmetries. In addition, we calculate the Noether currents and charges
corresponding to gauge transformations and diffeomorphisms.
| [
{
"created": "Fri, 24 Feb 2023 16:50:57 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Mar 2023 09:13:23 GMT",
"version": "v2"
},
{
"created": "Sun, 30 Jul 2023 16:26:47 GMT",
"version": "v3"
}
] | 2023-08-01 | [
[
"Bac",
"Adam",
""
],
[
"Kamiński",
"Wojciech",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Broda",
"Michalina",
""
]
] | It is known that a source-free Yang-Mills theory with the normal conformal Cartan connection used as the gauge potential gives rise to equations of motion equivalent to the vanishing of the Bach tensor. We investigate the conformally invariant presymplectic potential current obtained from this theory and find that on the solutions to the Einstein field equations, it can be decomposed into a topological term derived from the Euler density and a part proportional to the potential of the standard Einstein-Hilbert Lagrangian. The pullback of our potential to the asymptotic boundary of asymptotically de Sitter spacetimes turns out to coincide with the current obtained from the holographically renormalized gravitational action. This provides an alternative derivation of a symplectic structure on scri without resorting to holographic techniques. We also calculate our current at the null infinity of asymptotically flat spacetimes and in particular show that it vanishes for variations induced by the BMS symmetries. In addition, we calculate the Noether currents and charges corresponding to gauge transformations and diffeomorphisms. |
gr-qc/0508075 | Dr. Bikash Chandra Paul | Dilip Paul and Bikash Chandra Paul (North Bengal University) | Probability for Primordial Black Holes Pair in 1/R Gravity | 15 pages, no figure. submitted to Phys. Rev. D | Phys.Rev. D72 (2005) 064012 | 10.1103/PhysRevD.72.064012 | null | gr-qc | null | The probability for quantum creation of an inflationary universe with a pair
of black holes in 1/R - gravitational theory has been studied. Considering a
gravitational action which includes a cosmological constant ($\Lambda$) in
addition to $ \delta R^{- 1} $ term, the probability has been evaluated in a
semiclassical approximation with Hartle-Hawking boundary condition. We obtain
instanton solutions determined by the parameters $\delta$ and $\Lambda$
satisfying the constraint $ \delta \leq \frac{4 \Lambda^{2}}{3}$. However, we
note that two different classes of instanton solutions exists in the region $0
< \delta < \frac{4 \Lambda^{2}}{3}$. The probabilities of creation of such
configurations are evaluated. It is found that the probability of creation of a
universe with a pair of black holes is strongly suppressed with a positive
cosmological constant except in one case when $0 < \delta < \Lambda^{2}$. It is
also found that gravitational instanton solution is permitted even with
$\Lambda = 0$ but one has to consider $\delta < 0$. However, in the later case
a universe with a pair of black holes is less probable.
| [
{
"created": "Thu, 18 Aug 2005 10:53:06 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Paul",
"Dilip",
"",
"North Bengal University"
],
[
"Paul",
"Bikash Chandra",
"",
"North Bengal University"
]
] | The probability for quantum creation of an inflationary universe with a pair of black holes in 1/R - gravitational theory has been studied. Considering a gravitational action which includes a cosmological constant ($\Lambda$) in addition to $ \delta R^{- 1} $ term, the probability has been evaluated in a semiclassical approximation with Hartle-Hawking boundary condition. We obtain instanton solutions determined by the parameters $\delta$ and $\Lambda$ satisfying the constraint $ \delta \leq \frac{4 \Lambda^{2}}{3}$. However, we note that two different classes of instanton solutions exists in the region $0 < \delta < \frac{4 \Lambda^{2}}{3}$. The probabilities of creation of such configurations are evaluated. It is found that the probability of creation of a universe with a pair of black holes is strongly suppressed with a positive cosmological constant except in one case when $0 < \delta < \Lambda^{2}$. It is also found that gravitational instanton solution is permitted even with $\Lambda = 0$ but one has to consider $\delta < 0$. However, in the later case a universe with a pair of black holes is less probable. |
1305.6759 | Paolo Pani | Paolo Pani | Advanced Methods in Black-Hole Perturbation Theory | Lecture notes from the NRHEP spring school held at IST-Lisbon, March
2013. Extra material and notebooks available online at
http://blackholes.ist.utl.pt/nrhep2/. To be published by IJMPA (V. Cardoso,
L. Gualtieri, C. Herdeiro and U. Sperhake, Eds., 2013); v2: references
updated, published version | International Journal of Modern Physics A, Vol. 28 (2013) 1340018 | 10.1142/S0217751X13400186 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black-hole perturbation theory is a useful tool to investigate issues in
astrophysics, high-energy physics, and fundamental problems in gravity. It is
often complementary to fully-fledged nonlinear evolutions and instrumental to
interpret some results of numerical simulations. Several modern applications
require advanced tools to investigate the linear dynamics of generic small
perturbations around stationary black holes. Here, we present an overview of
these applications and introduce extensions of the standard semianalytical
methods to construct and solve the linearized field equations in curved
spacetime. Current state-of-the-art techniques are pedagogically explained and
exciting open problems are presented.
| [
{
"created": "Wed, 29 May 2013 11:10:22 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Sep 2013 11:05:54 GMT",
"version": "v2"
}
] | 2013-09-10 | [
[
"Pani",
"Paolo",
""
]
] | Black-hole perturbation theory is a useful tool to investigate issues in astrophysics, high-energy physics, and fundamental problems in gravity. It is often complementary to fully-fledged nonlinear evolutions and instrumental to interpret some results of numerical simulations. Several modern applications require advanced tools to investigate the linear dynamics of generic small perturbations around stationary black holes. Here, we present an overview of these applications and introduce extensions of the standard semianalytical methods to construct and solve the linearized field equations in curved spacetime. Current state-of-the-art techniques are pedagogically explained and exciting open problems are presented. |
0808.1709 | Dong-han Yeom | Sungwook E. Hong, Dong-il Hwang, Ewan D. Stewart, Dong-han Yeom | The causal structure of dynamical charged black holes | 23 pages, 23 figures | Class.Quant.Grav.27:045014,2010 | 10.1088/0264-9381/27/4/045014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the causal structure of dynamical charged black holes, with a
sufficient number of massless fields, using numerical simulations. Neglecting
Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature
singularity due to mass inflation. When we include Hawking radiation, the inner
horizon becomes space-like and is separated from the Cauchy horizon, which is
parallel to the out-going null direction. Since a charged black hole must
eventually transit to a neutral black hole, we studied the neutralization of
the black hole and observed that the inner horizon evolves into a space-like
singularity, generating a Cauchy horizon which is parallel to the in-going null
direction. Since the mass function is finite around the inner horizon, the
inner horizon is regular and penetrable in a general relativistic sense.
However, since the curvature functions become trans-Planckian, we cannot
saymore about the region beyond the inner horizon, and it is natural to say
that there is a 'physical' space-like singularity. However, if we assume an
exponentially large number of massless scalar fields, our results can be
extended beyond the inner horizon. In this case, strong cosmic censorship and
black hole complementarity can be violated.
| [
{
"created": "Tue, 12 Aug 2008 19:44:17 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Nov 2009 06:53:00 GMT",
"version": "v2"
},
{
"created": "Sat, 30 Jan 2010 17:10:05 GMT",
"version": "v3"
}
] | 2014-11-18 | [
[
"Hong",
"Sungwook E.",
""
],
[
"Hwang",
"Dong-il",
""
],
[
"Stewart",
"Ewan D.",
""
],
[
"Yeom",
"Dong-han",
""
]
] | We study the causal structure of dynamical charged black holes, with a sufficient number of massless fields, using numerical simulations. Neglecting Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature singularity due to mass inflation. When we include Hawking radiation, the inner horizon becomes space-like and is separated from the Cauchy horizon, which is parallel to the out-going null direction. Since a charged black hole must eventually transit to a neutral black hole, we studied the neutralization of the black hole and observed that the inner horizon evolves into a space-like singularity, generating a Cauchy horizon which is parallel to the in-going null direction. Since the mass function is finite around the inner horizon, the inner horizon is regular and penetrable in a general relativistic sense. However, since the curvature functions become trans-Planckian, we cannot saymore about the region beyond the inner horizon, and it is natural to say that there is a 'physical' space-like singularity. However, if we assume an exponentially large number of massless scalar fields, our results can be extended beyond the inner horizon. In this case, strong cosmic censorship and black hole complementarity can be violated. |
gr-qc/0412029 | Glenn Barnich | G. Barnich and G.Compere | Generalized Smarr relation for Kerr AdS black holes from improved
surface integrals | 21 pages Latex file, 1 figure; discussion on integrability rectified,
typo in (2.14) corrected | Phys.Rev.D71:044016,2005; Erratum-ibid.D71:029904,2006 | 10.1103/PhysRevD.71.044016 10.1103/PhysRevD.71.029904 | ULB-TH/04-31 | gr-qc hep-th | null | By using suitably improved surface integrals, we give a unified geometric
derivation of the generalized Smarr relation for higher dimensional Kerr black
holes which is valid both in flat and in anti-de Sitter backgrounds. The
improvement of the surface integrals, which allows one to use them
simultaneously at infinity and on the horizon, consists in integrating them
along a path in solution space. Path independence of the improved charges is
discussed and explicitly proved for the higher dimensional Kerr AdS black
holes. It is also shown that the charges for these black holes can be correctly
computed from the standard Hamiltonian or Lagrangian surface integrals.
| [
{
"created": "Tue, 7 Dec 2004 12:39:11 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Dec 2005 16:44:51 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Barnich",
"G.",
""
],
[
"Compere",
"G.",
""
]
] | By using suitably improved surface integrals, we give a unified geometric derivation of the generalized Smarr relation for higher dimensional Kerr black holes which is valid both in flat and in anti-de Sitter backgrounds. The improvement of the surface integrals, which allows one to use them simultaneously at infinity and on the horizon, consists in integrating them along a path in solution space. Path independence of the improved charges is discussed and explicitly proved for the higher dimensional Kerr AdS black holes. It is also shown that the charges for these black holes can be correctly computed from the standard Hamiltonian or Lagrangian surface integrals. |
1208.3376 | Nan Li | Nan Li, Thomas Buchert, Akio Hosoya, Masaaki Morita, Dominik J.
Schwarz | Relative information entropy and Weyl curvature of the inhomogeneous
Universe | 8 pages, matches the published version in Physical Review D | Phys.Rev.D86: 083539,2012 | 10.1103/PhysRevD.86.083539 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Penrose conjectured a connection between entropy and Weyl curvature of the
Universe. This is plausible, as the almost homogeneous and isotropic Universe
at the onset of structure formation has negligible Weyl curvature, which then
grows (relative to the Ricci curvature) due to the formation of large-scale
structure and thus reminds us of the second law of thermodynamics. We study two
scalar measures to quantify the deviations from a homogeneous and isotropic
space-time, the relative information entropy and a Weyl tensor invariant, and
show their relation to the averaging problem. We calculate these two quantities
up to second order in standard cosmological perturbation theory and find that
they are correlated and can be linked via the kinematic backreaction of a
spatially averaged universe model.
| [
{
"created": "Thu, 16 Aug 2012 14:08:46 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Dec 2012 00:54:48 GMT",
"version": "v2"
}
] | 2013-06-13 | [
[
"Li",
"Nan",
""
],
[
"Buchert",
"Thomas",
""
],
[
"Hosoya",
"Akio",
""
],
[
"Morita",
"Masaaki",
""
],
[
"Schwarz",
"Dominik J.",
""
]
] | Penrose conjectured a connection between entropy and Weyl curvature of the Universe. This is plausible, as the almost homogeneous and isotropic Universe at the onset of structure formation has negligible Weyl curvature, which then grows (relative to the Ricci curvature) due to the formation of large-scale structure and thus reminds us of the second law of thermodynamics. We study two scalar measures to quantify the deviations from a homogeneous and isotropic space-time, the relative information entropy and a Weyl tensor invariant, and show their relation to the averaging problem. We calculate these two quantities up to second order in standard cosmological perturbation theory and find that they are correlated and can be linked via the kinematic backreaction of a spatially averaged universe model. |
gr-qc/9309002 | Steve Carlip | Steven Carlip | Notes on the (2+1)-Dimensional Wheeler-DeWitt Equation | 11 pages, LaTeX, UCD-93-25 and NSF-ITP-93-115 | Class.Quant.Grav.11:31-40,1994 | 10.1088/0264-9381/11/1/007 | null | gr-qc | null | In contrast to other approaches to (2+1)-dimensional quantum gravity, the
Wheeler-DeWitt equation appears to be too complicated to solve explicitly, even
for simple spacetime topologies. Nevertheless, it is possible to obtain a good
deal of information about solutions and their interpretation. In particular,
strong evidence is presented that Wheeler-DeWitt quantization is not equivalent
to reduced phase space quantization.
| [
{
"created": "Thu, 2 Sep 1993 01:01:39 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"Steven",
""
]
] | In contrast to other approaches to (2+1)-dimensional quantum gravity, the Wheeler-DeWitt equation appears to be too complicated to solve explicitly, even for simple spacetime topologies. Nevertheless, it is possible to obtain a good deal of information about solutions and their interpretation. In particular, strong evidence is presented that Wheeler-DeWitt quantization is not equivalent to reduced phase space quantization. |
1607.07461 | Peter K.F. Kuhfittig | Peter K. F. Kuhfittig | Stable phantom-energy wormholes admitting conformal motions | 8 pages, no figures | Int. J. Mod. Phys. D, Vol. 26, 1750025, 2017 | 10.1142/S0218271817500250 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been argued that wormholes are as good a prediction of Einstein's
theory as black holes but the theoretical construction requires a reverse
strategy, specifying the desired geometric properties of the wormhole and
leaving open the determination of the stress-energy tensor. We begin by
confirming an earlier result by the author showing that a complete wormhole
solution can be obtained by adopting the equation of state $p=\omega\rho$ and
assuming that the wormhole admits a one-parameter group of conformal motions.
The main purpose of this paper is to use the assumption of conformal symmetry
to show that the wormhole is stable to linearized radial perturbations whenever
$-1.5<\omega <-1$.
| [
{
"created": "Mon, 25 Jul 2016 20:14:52 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Aug 2016 17:17:58 GMT",
"version": "v2"
}
] | 2017-02-15 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | It has been argued that wormholes are as good a prediction of Einstein's theory as black holes but the theoretical construction requires a reverse strategy, specifying the desired geometric properties of the wormhole and leaving open the determination of the stress-energy tensor. We begin by confirming an earlier result by the author showing that a complete wormhole solution can be obtained by adopting the equation of state $p=\omega\rho$ and assuming that the wormhole admits a one-parameter group of conformal motions. The main purpose of this paper is to use the assumption of conformal symmetry to show that the wormhole is stable to linearized radial perturbations whenever $-1.5<\omega <-1$. |
1707.02817 | Reza Saffari | Sara Rezvanjou, Reza Saffari, Mozhgan Masoudi and Saheb Soroushfar | Particle Dynamics Around the Black String | 38 pages, 33 figures, Accepted for Publication in Classical and
Quantum Gravity | null | 10.1088/1361-6382/ab9934 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, some dynamical properties of neutral and charged particles
around a weakly magnetized five-dimensional static black string have been
studied. The perturbation method was also used to calculate the Innermost
Stable Circular Orbit (ISCO) of this metric in the presence of a magnetic
field. The escape velocity of neutral and charged particles around the black
string was derived. In the next step, the analytical solutions of the equations
of motion were discussed and some possible orbits for particles in the black
string space-time were plotted. Interestingly, it was found that adding an
extra dimension has a slight influence on the effective potential and one term
of the effective force. The magnitude of the new constant of motion $(J)$
affects both the shape of the potential and existence of the stable circular
orbits. In conclusion, by comparing a black hole and a black string, it is
realized that the value of a new constant of motion causes slight but
interesting differences.
| [
{
"created": "Mon, 10 Jul 2017 12:09:23 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Aug 2017 07:37:31 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Jan 2018 19:34:36 GMT",
"version": "v3"
},
{
"created": "Thu, 1 Feb 2018 08:58:58 GMT",
"version": "v4"
},
{
"created": "Sat, 21 Sep 2019 17:32:24 GMT",
"version": "v5"
},
{
"created": "Mon, 8 Jun 2020 06:35:47 GMT",
"version": "v6"
}
] | 2020-06-09 | [
[
"Rezvanjou",
"Sara",
""
],
[
"Saffari",
"Reza",
""
],
[
"Masoudi",
"Mozhgan",
""
],
[
"Soroushfar",
"Saheb",
""
]
] | In this paper, some dynamical properties of neutral and charged particles around a weakly magnetized five-dimensional static black string have been studied. The perturbation method was also used to calculate the Innermost Stable Circular Orbit (ISCO) of this metric in the presence of a magnetic field. The escape velocity of neutral and charged particles around the black string was derived. In the next step, the analytical solutions of the equations of motion were discussed and some possible orbits for particles in the black string space-time were plotted. Interestingly, it was found that adding an extra dimension has a slight influence on the effective potential and one term of the effective force. The magnitude of the new constant of motion $(J)$ affects both the shape of the potential and existence of the stable circular orbits. In conclusion, by comparing a black hole and a black string, it is realized that the value of a new constant of motion causes slight but interesting differences. |
1809.03303 | Pardyumn Kumar Sahoo | P.K. Sahoo, P.H.R.S. Moraes, Parbati Sahoo, Binaya K. Bishi | $f(R,T)=f(R)+\lambda T$ gravity models as alternatives to cosmic
acceleration | 11 pages, 20 figures, Accepted version in EPJ C | Eur. Phys. J. C (2018) 78:736 | 10.1140/epjc/s10052-018-6211-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article presents cosmological models that arise in a subclass of
$f(R,T)=f(R)+f(T)$ gravity models, with different $f(R)$ functions and fixed
$T$-dependence. That is, the gravitational lagrangian is considered as
$f(R,T)=f(R)+\lambda T$, with constant $\lambda$. Here $R$ and $T$ represent
the Ricci scalar and trace of the stress-energy tensor, respectively. The
modified gravitational field equations are obtained through the metric
formalism for the Friedmann-Lema\^itre-Robertson-Walker metric with signature
$(+,-,-,-)$. We work with $f(R)=R+\alpha R^2-\frac{\mu^4}{R}$,
$f(R)=R+k\ln(\gamma R)$ and $f(R)=R+me^{[-nR]}$, with $\alpha, \mu, k, \gamma,
m$ and $n$ all free parameters, which lead to three different cosmological
models for our Universe. For the choice of $\lambda=0$, this reduces to widely
discussed $f(R)$ gravity models. This manuscript clearly describes the effects
of adding the trace of the energy-momentum tensor in the $f(R)$ lagrangian. The
exact solution of the modified field equations are obtained under the hybrid
expansion law. Also we present the Om diagnostic analysis for the discussed
models.
| [
{
"created": "Wed, 5 Sep 2018 14:09:20 GMT",
"version": "v1"
}
] | 2018-09-18 | [
[
"Sahoo",
"P. K.",
""
],
[
"Moraes",
"P. H. R. S.",
""
],
[
"Sahoo",
"Parbati",
""
],
[
"Bishi",
"Binaya K.",
""
]
] | This article presents cosmological models that arise in a subclass of $f(R,T)=f(R)+f(T)$ gravity models, with different $f(R)$ functions and fixed $T$-dependence. That is, the gravitational lagrangian is considered as $f(R,T)=f(R)+\lambda T$, with constant $\lambda$. Here $R$ and $T$ represent the Ricci scalar and trace of the stress-energy tensor, respectively. The modified gravitational field equations are obtained through the metric formalism for the Friedmann-Lema\^itre-Robertson-Walker metric with signature $(+,-,-,-)$. We work with $f(R)=R+\alpha R^2-\frac{\mu^4}{R}$, $f(R)=R+k\ln(\gamma R)$ and $f(R)=R+me^{[-nR]}$, with $\alpha, \mu, k, \gamma, m$ and $n$ all free parameters, which lead to three different cosmological models for our Universe. For the choice of $\lambda=0$, this reduces to widely discussed $f(R)$ gravity models. This manuscript clearly describes the effects of adding the trace of the energy-momentum tensor in the $f(R)$ lagrangian. The exact solution of the modified field equations are obtained under the hybrid expansion law. Also we present the Om diagnostic analysis for the discussed models. |
gr-qc/0301129 | Gerard Clement | Gerard Clement | Black hole mass and angular momentum in 2+1 gravity | 23 pages, 3 references added, to be published in Physical Review D | Phys.Rev. D68 (2003) 024032 | 10.1103/PhysRevD.68.024032 | LAPTH-962/03 | gr-qc hep-th | null | We propose a new definition for the mass and angular momentum of neutral or
electrically charged black holes in 2+1 gravity with two Killing vectors. These
finite conserved quantities, associated with the SL(2,R) invariance of the
reduced mechanical system, are shown to be identical to the quasilocal
conserved quantities for an improved gravitational action corresponding to
mixed boundary conditions. They obey a general Smarr-like formula and, in all
cases investigated, are consistent with the first law of black hole
thermodynamics. Our framework is applied to the computation of the mass and
angular momentum of black hole solutions to several field-theoretical models.
| [
{
"created": "Fri, 31 Jan 2003 15:46:18 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2003 15:14:27 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Jun 2003 08:23:18 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Clement",
"Gerard",
""
]
] | We propose a new definition for the mass and angular momentum of neutral or electrically charged black holes in 2+1 gravity with two Killing vectors. These finite conserved quantities, associated with the SL(2,R) invariance of the reduced mechanical system, are shown to be identical to the quasilocal conserved quantities for an improved gravitational action corresponding to mixed boundary conditions. They obey a general Smarr-like formula and, in all cases investigated, are consistent with the first law of black hole thermodynamics. Our framework is applied to the computation of the mass and angular momentum of black hole solutions to several field-theoretical models. |
gr-qc/0504024 | Wu Ning | Ning Wu | Non-Relativistic Limit of Dirac Equations in Gravitational Field and
Quantum Effects of Gravity | 12 pages, no figure | Commun.Theor.Phys.45:452-456,2006 | 10.1088/0253-6102/45/3/016 | null | gr-qc | null | Based on unified theory of electromagnetic interactions and gravitational
interactions, the non-relativistic limit of the equation of motion of a charged
Dirac particle in gravitational field is studied. From the Schrodinger equation
obtained from this non-relativistic limit, we could see that the classical
Newtonian gravitational potential appears as a part of the potential in the
Schrodinger equation, which can explain the gravitational phase effects found
in COW experiments. And because of this Newtonian gravitational potential, a
quantum particle in earth's gravitational field may form a gravitationally
bound quantized state, which had already been detected in experiments. Three
different kinds of phase effects related to gravitational interactions are
discussed in this paper, and these phase effects should be observable in some
astrophysical processes. Besides, there exists direct coupling between
gravitomagnetic field and quantum spin, radiation caused by this coupling can
be used to directly determine the gravitomagnetic field on the surface of a
star.
| [
{
"created": "Wed, 6 Apr 2005 14:48:15 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Apr 2005 15:02:05 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Wu",
"Ning",
""
]
] | Based on unified theory of electromagnetic interactions and gravitational interactions, the non-relativistic limit of the equation of motion of a charged Dirac particle in gravitational field is studied. From the Schrodinger equation obtained from this non-relativistic limit, we could see that the classical Newtonian gravitational potential appears as a part of the potential in the Schrodinger equation, which can explain the gravitational phase effects found in COW experiments. And because of this Newtonian gravitational potential, a quantum particle in earth's gravitational field may form a gravitationally bound quantized state, which had already been detected in experiments. Three different kinds of phase effects related to gravitational interactions are discussed in this paper, and these phase effects should be observable in some astrophysical processes. Besides, there exists direct coupling between gravitomagnetic field and quantum spin, radiation caused by this coupling can be used to directly determine the gravitomagnetic field on the surface of a star. |
2006.03581 | William Barker Mr | W. E. V. Barker, A. N. Lasenby, M. P. Hobson, W. J. Handley | Mapping Poincar\'{e} gauge cosmology to Horndeski theory for emergent
dark energy | 11 pages, 2 figures. Results previously presented at DAMTP on
14/02/20. Added substantial introduction to Poincar\'e gauge theory and its
perturbative renormalisability. Added various references. Incorporated
supplemental material into main text (previously hosted on GitHub). Titular
change. Results unaffected. Accepted for publication by Phys. Rev. D | Phys. Rev. D 102, 084002 (2020) | 10.1103/PhysRevD.102.084002 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ten-parameter, quadratic Poincar\'e gauge theory of gravity is a
plausible alternative to general relativity. We show that the rich background
cosmology of the gauge theory is described by a non-canonical bi-scalar-tensor
theory in the Jordan frame: the `metrical analogue'. This provides a unified
framework for future investigation by the broader community. For many parameter
choices, the non-canonical term reduces to a Cuscuton field of the form
$\smash{\sqrt{|X^{\phi\phi}|}}$. The Einstein-Cartan-Kibble-Sciama theory maps
to a pure quadratic Cuscuton, whereas the teleparallel theory maps to the
Einstein-Hilbert Lagrangian. We apply the metrical analogue to novel unitary
and power-counting-renormalisable cases of Poincar\'e gauge theory. These
theories support the concordance $\Lambda$CDM background cosmology up to an
optional, effective dark radiation component, we explain this behaviour in
terms of a stalled Cuscuton. We also obtain two dark energy solutions from one
of these cases: accelerated expansion from a negative bare cosmological
constant whose magnitude is screened, and emergent dark energy to replace
vanishing bare cosmological constant in $\Lambda$CDM.
| [
{
"created": "Fri, 5 Jun 2020 17:54:04 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 2020 14:11:36 GMT",
"version": "v2"
}
] | 2020-10-07 | [
[
"Barker",
"W. E. V.",
""
],
[
"Lasenby",
"A. N.",
""
],
[
"Hobson",
"M. P.",
""
],
[
"Handley",
"W. J.",
""
]
] | The ten-parameter, quadratic Poincar\'e gauge theory of gravity is a plausible alternative to general relativity. We show that the rich background cosmology of the gauge theory is described by a non-canonical bi-scalar-tensor theory in the Jordan frame: the `metrical analogue'. This provides a unified framework for future investigation by the broader community. For many parameter choices, the non-canonical term reduces to a Cuscuton field of the form $\smash{\sqrt{|X^{\phi\phi}|}}$. The Einstein-Cartan-Kibble-Sciama theory maps to a pure quadratic Cuscuton, whereas the teleparallel theory maps to the Einstein-Hilbert Lagrangian. We apply the metrical analogue to novel unitary and power-counting-renormalisable cases of Poincar\'e gauge theory. These theories support the concordance $\Lambda$CDM background cosmology up to an optional, effective dark radiation component, we explain this behaviour in terms of a stalled Cuscuton. We also obtain two dark energy solutions from one of these cases: accelerated expansion from a negative bare cosmological constant whose magnitude is screened, and emergent dark energy to replace vanishing bare cosmological constant in $\Lambda$CDM. |
0812.1081 | Joel Saavedra | Sergio del Campo, Ramon Herrera and Joel Saavedra | Tachyon warm inflationary universe model in the weak dissipative regime | 9 pages, accepted by European Physical Journal C | Eur.Phys.J.C59:913-916,2009 | 10.1140/epjc/s10052-008-0848-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Warm inflationary universe model in a tachyon field theory is studied in the
weak dissipative regime. We develop our model for an exponential potential and
the dissipation parameter $\Gamma=\Gamma_0$=constant. We describe scalar and
tensor perturbations for this scenario.
| [
{
"created": "Fri, 5 Dec 2008 15:34:45 GMT",
"version": "v1"
}
] | 2009-12-04 | [
[
"del Campo",
"Sergio",
""
],
[
"Herrera",
"Ramon",
""
],
[
"Saavedra",
"Joel",
""
]
] | Warm inflationary universe model in a tachyon field theory is studied in the weak dissipative regime. We develop our model for an exponential potential and the dissipation parameter $\Gamma=\Gamma_0$=constant. We describe scalar and tensor perturbations for this scenario. |
2212.13802 | F\'elix-Louis Juli\'e | F\'elix-Louis Juli\'e, Vishal Baibhav, Emanuele Berti, Alessandra
Buonanno | Third post-Newtonian effective-one-body Hamiltonian in scalar-tensor and
Einstein-scalar-Gauss-Bonnet gravity | Minor changes to match published version. Results unchanged | Phys. Rev. D 107, 104044 (2023) | 10.1103/PhysRevD.107.104044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We build an effective-one-body (EOB) Hamiltonian at third post-Newtonian
(3PN) order in scalar-tensor (ST) and Einstein-scalar-Gauss-Bonnet (ESGB)
theories of gravity. The latter is an extension of general relativity that
predicts scalar hair for black holes. We start from the known two-body
Lagrangian at 3PN order, and use order-reduction methods to construct its
ordinary Hamiltonian counterpart. We then reduce the conservative two-body
dynamics to the (nongeodesic) motion of a test particle in an effective metric
by means of canonical transformations. The resulting EOB Hamiltonian is a
modification of the general relativistic Hamiltonian, and already at 3PN order,
it must account for nonlocal-in-time tail contributions. We include the latter
beyond circular orbits and up to sixth order in the binary's orbital
eccentricity. We finally calculate the orbital frequency at the innermost
stable circular orbit (ISCO) of binary black holes in the shift-symmetric ESGB
model. Our work extends F.L. Juli\'e and N. Deruelle [Phys. Rev. D 95, 124054
(2017)], and it is an essential step toward the accurate modeling of
gravitational waveforms beyond general relativity.
| [
{
"created": "Wed, 28 Dec 2022 12:48:53 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 2023 20:25:59 GMT",
"version": "v2"
}
] | 2023-06-08 | [
[
"Julié",
"Félix-Louis",
""
],
[
"Baibhav",
"Vishal",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | We build an effective-one-body (EOB) Hamiltonian at third post-Newtonian (3PN) order in scalar-tensor (ST) and Einstein-scalar-Gauss-Bonnet (ESGB) theories of gravity. The latter is an extension of general relativity that predicts scalar hair for black holes. We start from the known two-body Lagrangian at 3PN order, and use order-reduction methods to construct its ordinary Hamiltonian counterpart. We then reduce the conservative two-body dynamics to the (nongeodesic) motion of a test particle in an effective metric by means of canonical transformations. The resulting EOB Hamiltonian is a modification of the general relativistic Hamiltonian, and already at 3PN order, it must account for nonlocal-in-time tail contributions. We include the latter beyond circular orbits and up to sixth order in the binary's orbital eccentricity. We finally calculate the orbital frequency at the innermost stable circular orbit (ISCO) of binary black holes in the shift-symmetric ESGB model. Our work extends F.L. Juli\'e and N. Deruelle [Phys. Rev. D 95, 124054 (2017)], and it is an essential step toward the accurate modeling of gravitational waveforms beyond general relativity. |
0810.2006 | Mohammad Nouri-Zonoz | H. Miraghaei and M. Nouri-Zonoz | Classical tests of general relativity in the Newtonian limit of
Schwarzschild-de Sitter spacetime | 12 pages, Revtex, 1 figure | Gen.Rel.Grav.42:2947-2956,2010 | 10.1007/s10714-010-1052-y | IPM/A-2008/001 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been shown that despite previous claims the cosmological
constant affects light bending. In the present article we study light bending
and the advance of Mercury's perihelion in the context of the Newtonian limit
of Schwarzschild-de Sitter spacetime employing the special relativistic
equivalence of mass and energy. In both cases, up to a constant factor, we find
the same results as in the full general relativistic treatment of the same
phenomena. These approximate and intuitive arguments demonstrate clearly what
effects should have been expected from the presence of $\Lambda$ in the general
relativistic treatment of these phenomena.
| [
{
"created": "Sat, 11 Oct 2008 06:54:56 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Nov 2008 13:43:37 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Dec 2008 08:16:17 GMT",
"version": "v3"
},
{
"created": "Thu, 1 Jan 2009 11:06:25 GMT",
"version": "v4"
},
{
"created": "Sat, 4 Jul 2009 12:39:41 GMT",
"version": "v5"
}
] | 2010-11-09 | [
[
"Miraghaei",
"H.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | Recently it has been shown that despite previous claims the cosmological constant affects light bending. In the present article we study light bending and the advance of Mercury's perihelion in the context of the Newtonian limit of Schwarzschild-de Sitter spacetime employing the special relativistic equivalence of mass and energy. In both cases, up to a constant factor, we find the same results as in the full general relativistic treatment of the same phenomena. These approximate and intuitive arguments demonstrate clearly what effects should have been expected from the presence of $\Lambda$ in the general relativistic treatment of these phenomena. |
1611.05766 | Mariafelicia De Laurentis Professor | Mariafelicia De Laurentis, Oliver Porth, Luke Bovard, Bobomurat
Ahmedov, Ahmadjon Abdujabbarov | Constraining alternative theories of gravity using GW$150914$ and
GW$151226$ | 11 pages, 3 figures, accepted for publication in Phys. Rev. D. arXiv
admin note: text overlap with arXiv:gr-qc/0412088 by other authors | null | 10.1103/PhysRevD.94.124038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recently reported gravitational wave events GW$150914$ and GW$151226$
caused by the mergers of binary black holes
[arXiv:1602.03841],[arXiv:1606.04855],[arXiv:1606.04856] provide a formidable
way to set constraints on alternative metric theories of gravity in the strong
field regime. In this paper, we develop an approach where an arbitrary theory
of gravity can be parametrised by an effective coupling $G_{eff}$ and an
effective gravitational potential $\Phi(r)$. The standard Newtonian limit of
General Relativity is recovered as soon as $G_{eff}\rightarrow G_N$ and
$\Phi(r)\rightarrow \Phi_{N}$. The upper bound on the graviton mass and the
gravitational interaction length, reported by the LIGO-VIRGO collaboration, can
be directly recast in terms of the parameters of the theory which allows an
analysis where the gravitational wave frequency modulation sets constraints on
the range of possible alternative models of gravity. Numerical results based on
published parameters for the binary black hole mergers are also reported.
Comparison of the observed phase of the GW$150914$ and GW$151226$ with the
modulated phase in alternative theories of gravity does not give reasonable
constraints due the large uncertainties in the estimated parameters for the
coalescing black holes. In addition to these general considerations, we obtain
limits for the frequency dependence of the $\alpha$ parameter in scalar tensor
theories of gravity.
| [
{
"created": "Wed, 16 Nov 2016 16:23:00 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Porth",
"Oliver",
""
],
[
"Bovard",
"Luke",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
]
] | The recently reported gravitational wave events GW$150914$ and GW$151226$ caused by the mergers of binary black holes [arXiv:1602.03841],[arXiv:1606.04855],[arXiv:1606.04856] provide a formidable way to set constraints on alternative metric theories of gravity in the strong field regime. In this paper, we develop an approach where an arbitrary theory of gravity can be parametrised by an effective coupling $G_{eff}$ and an effective gravitational potential $\Phi(r)$. The standard Newtonian limit of General Relativity is recovered as soon as $G_{eff}\rightarrow G_N$ and $\Phi(r)\rightarrow \Phi_{N}$. The upper bound on the graviton mass and the gravitational interaction length, reported by the LIGO-VIRGO collaboration, can be directly recast in terms of the parameters of the theory which allows an analysis where the gravitational wave frequency modulation sets constraints on the range of possible alternative models of gravity. Numerical results based on published parameters for the binary black hole mergers are also reported. Comparison of the observed phase of the GW$150914$ and GW$151226$ with the modulated phase in alternative theories of gravity does not give reasonable constraints due the large uncertainties in the estimated parameters for the coalescing black holes. In addition to these general considerations, we obtain limits for the frequency dependence of the $\alpha$ parameter in scalar tensor theories of gravity. |
gr-qc/0205056 | T. P. Singh | T. P. Singh (Tata Institute of Fundamental Research) | Quantum mechanics without spacetime II : noncommutative geometry and the
free point particle | 8 pages | Gen.Rel.Grav. 35 (2003) 869-876 | 10.1023/A:1022999205139 | null | gr-qc hep-th quant-ph | null | In a recent paper we have suggested that a formulation of quantum mechanics
should exist, which does not require the concept of time, and that the
appropriate mathematical language for such a formulation is noncommutative
differential geometry. In the present paper we discuss this formulation for the
free point particle, by introducing a commutation relation for a set of
noncommuting coordinates. The sought for background independent quantum
mechanics is derived from this commutation relation for the coordinates. We
propose that the basic equations are invariant under automorphisms which map
one set of coordinates to another- this is a natural generalization of
diffeomorphism invariance when one makes a transition to noncommutative
geometry. The background independent description becomes equivalent to standard
quantum mechanics if a spacetime manifold exists, because of the proposed
automorphism invariance. The suggested basic equations also give a quantum
gravitational description of the free particle.
| [
{
"created": "Wed, 15 May 2002 04:28:32 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Singh",
"T. P.",
"",
"Tata Institute of Fundamental Research"
]
] | In a recent paper we have suggested that a formulation of quantum mechanics should exist, which does not require the concept of time, and that the appropriate mathematical language for such a formulation is noncommutative differential geometry. In the present paper we discuss this formulation for the free point particle, by introducing a commutation relation for a set of noncommuting coordinates. The sought for background independent quantum mechanics is derived from this commutation relation for the coordinates. We propose that the basic equations are invariant under automorphisms which map one set of coordinates to another- this is a natural generalization of diffeomorphism invariance when one makes a transition to noncommutative geometry. The background independent description becomes equivalent to standard quantum mechanics if a spacetime manifold exists, because of the proposed automorphism invariance. The suggested basic equations also give a quantum gravitational description of the free particle. |
2308.06803 | Luca Guido Molinari | Carlo Alberto Mantica and Luca Guido Molinari | A note on Harada's Conformal Killing gravity | 5 pages. Last section improved, new references and remark 3 added | Phys. Rev. D 108, 124029 (2023) | 10.1103/PhysRevD.108.124029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that "Gravity at cosmological distances: Explaining the accelerating
expansion without dark energy" recently proposed by J. Harada [6] is equivalent
to the Einstein equation extended by the presence of an arbitrary conformal
Killing tensor. This turns Harada's equations of third order in the derivatives
of the metric tensor to second order, and offers a simple strategy of solution
that shortcuts Harada's derivation and obtains both modified Friedmann
equations. An application is presented for the case of flat space and constant
curvature.
| [
{
"created": "Sun, 13 Aug 2023 16:13:52 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Oct 2023 17:25:24 GMT",
"version": "v2"
}
] | 2023-12-18 | [
[
"Mantica",
"Carlo Alberto",
""
],
[
"Molinari",
"Luca Guido",
""
]
] | We show that "Gravity at cosmological distances: Explaining the accelerating expansion without dark energy" recently proposed by J. Harada [6] is equivalent to the Einstein equation extended by the presence of an arbitrary conformal Killing tensor. This turns Harada's equations of third order in the derivatives of the metric tensor to second order, and offers a simple strategy of solution that shortcuts Harada's derivation and obtains both modified Friedmann equations. An application is presented for the case of flat space and constant curvature. |
1710.10429 | Mohammad Atazadeh | F. Darabi, K. Atazadeh, Y. Heydarzade | Einstein Static Universe in Rastall Theory of Gravity | 9 pages, 1 figure | Eur. Phys. J. Plus (2018) 133: 249 | 10.1140/epjp/i2018-12083-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate stability of the Einstein static solution against homogeneous
scalar, vector and tensor perturbations in the context of Rastall theory of
gravity. We show that this solution in the presence of perfect fluid and vacuum
energy originating from conformally-invariant fields is stable. Using the fix
point method and taking linear homogeneous perturbations, we find that the
scale factor of Einstein static universe for closed deformed isotropic and
homogeneous FLRW universe depends on the coupling parameter $\lambda$ between
the energy-momentum tensor and the gradient of Ricci scalar. Thus, in the
present model and in presence of vacuum energy, our universe can stay at the
Einstein static state past-eternally, which means that the big bang singularity
may be resolved successfully in the context of Einstein static universe in
Rastall theory.
| [
{
"created": "Sat, 28 Oct 2017 09:05:20 GMT",
"version": "v1"
}
] | 2018-07-10 | [
[
"Darabi",
"F.",
""
],
[
"Atazadeh",
"K.",
""
],
[
"Heydarzade",
"Y.",
""
]
] | We investigate stability of the Einstein static solution against homogeneous scalar, vector and tensor perturbations in the context of Rastall theory of gravity. We show that this solution in the presence of perfect fluid and vacuum energy originating from conformally-invariant fields is stable. Using the fix point method and taking linear homogeneous perturbations, we find that the scale factor of Einstein static universe for closed deformed isotropic and homogeneous FLRW universe depends on the coupling parameter $\lambda$ between the energy-momentum tensor and the gradient of Ricci scalar. Thus, in the present model and in presence of vacuum energy, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity may be resolved successfully in the context of Einstein static universe in Rastall theory. |
1304.1160 | Paolo Pani | Paolo Pani, Emanuele Berti, Leonardo Gualtieri | Gravito-Electromagnetic Perturbations of Kerr-Newman Black Holes:
Stability and Isospectrality in the Slow-Rotation Limit | 5 pages, 2 figures. Mathematica notebook with derivation of the axial
and polar equations available at http://blackholes.ist.utl.pt/?page=Files and
at http://www.phy.olemiss.edu/~berti/qnms.html; v2: Discussion improved.
Matches version to be published in PRL | null | 10.1103/PhysRevLett.110.241103 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The most general stationary black-hole solution of Einstein-Maxwell theory in
vacuum is the Kerr-Newman metric, specified by three parameters: mass M, spin J
and charge Q. Within classical general relativity, the most important and
challenging open problem in black-hole perturbation theory is the study of
gravitational and electromagnetic fields in the Kerr-Newman geometry, because
of the indissoluble coupling of the perturbation functions. Here we circumvent
this long-standing problem by working in the slow-rotation limit. We compute
the quasinormal modes up to linear order in J for any value of Q and provide
the first, fully-consistent stability analysis of the Kerr-Newman metric. For
scalar perturbations the quasinormal modes can be computed exactly, and we
demonstrate that the method is accurate within 3% for spins J/Jmax<~0.5, where
Jmax is the maximum allowed spin for any value of Q. Quite remarkably, we find
numerical evidence that the axial and polar sectors of the
gravito-electromagnetic perturbations are isospectral to linear order in the
spin. The extension of our results to nonasymptotically flat space-times could
be useful in the context of gauge/gravity dualities and string theory.
| [
{
"created": "Wed, 3 Apr 2013 20:00:04 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2013 15:04:11 GMT",
"version": "v2"
}
] | 2013-06-19 | [
[
"Pani",
"Paolo",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Gualtieri",
"Leonardo",
""
]
] | The most general stationary black-hole solution of Einstein-Maxwell theory in vacuum is the Kerr-Newman metric, specified by three parameters: mass M, spin J and charge Q. Within classical general relativity, the most important and challenging open problem in black-hole perturbation theory is the study of gravitational and electromagnetic fields in the Kerr-Newman geometry, because of the indissoluble coupling of the perturbation functions. Here we circumvent this long-standing problem by working in the slow-rotation limit. We compute the quasinormal modes up to linear order in J for any value of Q and provide the first, fully-consistent stability analysis of the Kerr-Newman metric. For scalar perturbations the quasinormal modes can be computed exactly, and we demonstrate that the method is accurate within 3% for spins J/Jmax<~0.5, where Jmax is the maximum allowed spin for any value of Q. Quite remarkably, we find numerical evidence that the axial and polar sectors of the gravito-electromagnetic perturbations are isospectral to linear order in the spin. The extension of our results to nonasymptotically flat space-times could be useful in the context of gauge/gravity dualities and string theory. |
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