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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1805.09459 | Edward Anderson | Edward Anderson | Absolute versus Relational Debate: a Modern Global Version | 22 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Suppose one seeks to free oneself from a symmetric absolute space by
quotienting out its symmetry group. This in general however fails to erase all
memory of this absolute space's symmetry properties. Stratification is one
major reason for this, which is present in both a) Kendall-type Shape Theory
and subsequent Relational Mechanics, and b) General Relativity configuration
spaces. We consider the alternative starting point with a generic absolute
space, meaning with no nontrivial generalized Killing vectors whatsoever. In
this approach, generically Shape-and-Scale Theory is but trivially realized,
there is no separate Shape Theory and indeed no stratification. While the GR
configuration space version of these considerations was already expounded in
1996 by Fischer and Moncrief, the Kendall-type shape theory version is new to
the current article. In each case, this amounts to admitting some small
deformation by which symmetry's hard consequences at the level of reduced
configuration spaces are warded off.We end by discussing the senses in which
each of the above two strategies retain absolutist features, each's main known
technical advantages and disadvantages, and the desirability of replacing
Kendall-type Shape Theory with a Local-and-Approximate Shape Theory. This
article is in honour of Prof. Niall \'{o} Murchadha, on the occasion of his
Festschrift.
| [
{
"created": "Thu, 24 May 2018 00:15:53 GMT",
"version": "v1"
}
] | 2018-05-25 | [
[
"Anderson",
"Edward",
""
]
] | Suppose one seeks to free oneself from a symmetric absolute space by quotienting out its symmetry group. This in general however fails to erase all memory of this absolute space's symmetry properties. Stratification is one major reason for this, which is present in both a) Kendall-type Shape Theory and subsequent Relational Mechanics, and b) General Relativity configuration spaces. We consider the alternative starting point with a generic absolute space, meaning with no nontrivial generalized Killing vectors whatsoever. In this approach, generically Shape-and-Scale Theory is but trivially realized, there is no separate Shape Theory and indeed no stratification. While the GR configuration space version of these considerations was already expounded in 1996 by Fischer and Moncrief, the Kendall-type shape theory version is new to the current article. In each case, this amounts to admitting some small deformation by which symmetry's hard consequences at the level of reduced configuration spaces are warded off.We end by discussing the senses in which each of the above two strategies retain absolutist features, each's main known technical advantages and disadvantages, and the desirability of replacing Kendall-type Shape Theory with a Local-and-Approximate Shape Theory. This article is in honour of Prof. Niall \'{o} Murchadha, on the occasion of his Festschrift. |
2202.08293 | Stephen Taylor | Stephen R. Taylor, Joseph Simon, Levi Schult, Nihan Pol, William G.
Lamb | A Parallelized Bayesian Approach To Accelerated Gravitational-Wave
Background Characterization | 14 pages, 6 figures. Matches version accepted by PRD | null | 10.1103/PhysRevD.105.084049 | null | gr-qc astro-ph.GA astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characterization of nanohertz-frequency gravitational waves (GWs) with
pulsar-timing arrays requires a continual expansion of datasets and monitored
pulsars. Whereas detection of the stochastic GW background is predicated on
measuring a distinctive pattern of inter-pulsar correlations, characterizing
the background's spectrum is driven by information encoded in the power spectra
of the individual pulsars' time series. We propose a new technique for rapid
Bayesian characterization of the stochastic GW background that is fully
parallelized over pulsar datasets. This Factorized Likelihood (FL) technique
empowers a modular approach to parameter estimation of the GW background,
multi-stage model selection of a spectrally-common stochastic process and
quadrupolar inter-pulsar correlations, and statistical cross-validation of
measured signals between independent pulsar sub-arrays. We demonstrate the
equivalence of this technique's efficacy with the full pulsar-timing array
likelihood, yet at a fraction of the required time. Our technique is fast,
easily implemented, and trivially allows for new data and pulsars to be
combined with legacy datasets without re-analysis of the latter.
| [
{
"created": "Wed, 16 Feb 2022 19:01:54 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2022 01:40:42 GMT",
"version": "v2"
}
] | 2022-05-11 | [
[
"Taylor",
"Stephen R.",
""
],
[
"Simon",
"Joseph",
""
],
[
"Schult",
"Levi",
""
],
[
"Pol",
"Nihan",
""
],
[
"Lamb",
"William G.",
""
]
] | The characterization of nanohertz-frequency gravitational waves (GWs) with pulsar-timing arrays requires a continual expansion of datasets and monitored pulsars. Whereas detection of the stochastic GW background is predicated on measuring a distinctive pattern of inter-pulsar correlations, characterizing the background's spectrum is driven by information encoded in the power spectra of the individual pulsars' time series. We propose a new technique for rapid Bayesian characterization of the stochastic GW background that is fully parallelized over pulsar datasets. This Factorized Likelihood (FL) technique empowers a modular approach to parameter estimation of the GW background, multi-stage model selection of a spectrally-common stochastic process and quadrupolar inter-pulsar correlations, and statistical cross-validation of measured signals between independent pulsar sub-arrays. We demonstrate the equivalence of this technique's efficacy with the full pulsar-timing array likelihood, yet at a fraction of the required time. Our technique is fast, easily implemented, and trivially allows for new data and pulsars to be combined with legacy datasets without re-analysis of the latter. |
0806.2515 | Ion I. Cotaescu | Ion I. Cotaescu and Cosmin Crucean | The quantum theory of the free Maxwell field on the de Sitter expanding
universe | 17 pages no figures | Prog.Theor.Phys.124:1051-1066,2010 | 10.1143/PTP.124.1051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of the free Maxwell field in two moving frames on the de Sitter
spacetime is investigated pointing out that the conserved momentum and energy
operators do not commute to each other. This leads us to consider new plane
waves solutions of the Maxwell equation which are eigenfunctions of the energy
operator. Such particular solutions complete the theory in which only the
solutions of given momentum were considered so far. The energy eigenfunctions
can be obtained thanks to our new time-evolution picture proposed previously
for the scalar and Dirac fields. Considering both these types of modes, it is
shown that the second quantization of the free electromagnetic potential in the
Coulomb gauge can be done in a canonical manner as in special relativity. The
principal conserved one-particle operators associated to Killing vectors are
derived, concentrating on the energy, momentum and total angular momentum
operators.
| [
{
"created": "Mon, 16 Jun 2008 07:58:32 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Oct 2008 07:48:23 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Sep 2010 08:50:35 GMT",
"version": "v3"
},
{
"created": "Mon, 22 Nov 2010 10:38:27 GMT",
"version": "v4"
}
] | 2011-03-15 | [
[
"Cotaescu",
"Ion I.",
""
],
[
"Crucean",
"Cosmin",
""
]
] | The theory of the free Maxwell field in two moving frames on the de Sitter spacetime is investigated pointing out that the conserved momentum and energy operators do not commute to each other. This leads us to consider new plane waves solutions of the Maxwell equation which are eigenfunctions of the energy operator. Such particular solutions complete the theory in which only the solutions of given momentum were considered so far. The energy eigenfunctions can be obtained thanks to our new time-evolution picture proposed previously for the scalar and Dirac fields. Considering both these types of modes, it is shown that the second quantization of the free electromagnetic potential in the Coulomb gauge can be done in a canonical manner as in special relativity. The principal conserved one-particle operators associated to Killing vectors are derived, concentrating on the energy, momentum and total angular momentum operators. |
2301.03901 | Farruh Atamurotov | A. Ditta, G. Mustafa, G. Abbas, Farruh Atamurotov, Kimet Jusufi | Constraining study of circular orbits and accretion disk around
nonlinear electrodynamics black hole | 22 pages, 13 figures | null | 10.1088/1475-7516/2023/08/002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The very latest observation of $M87$ supermassive black hole (BH) by the
Event Horizon Telescope (EHT) provides the accretion onto BHs is an interesting
study in the theory of gravity. We study the geodesics structure and accretion
near a nonlinear electrodynamics BH in strong and weak field approximations.
These approximations provide the disc-like structure under the geodesic motion
and accretion around the BH. Near the equatorial plane, we provide some new
reasons to make circular orbits and accretion of test particles around the BH.
Then we investigate perturbations, the critical speed of the fluid and the mass
accretion rate of particles around the central object. The physical validity of
this study shows that the parameter $\beta$ and $Q$ play an important role in
the circular orbits and the mass accretion rate in strong and weak field
approximations.
| [
{
"created": "Tue, 10 Jan 2023 10:58:06 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Mar 2023 17:29:14 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Jun 2023 16:19:00 GMT",
"version": "v3"
}
] | 2023-08-09 | [
[
"Ditta",
"A.",
""
],
[
"Mustafa",
"G.",
""
],
[
"Abbas",
"G.",
""
],
[
"Atamurotov",
"Farruh",
""
],
[
"Jusufi",
"Kimet",
""
]
] | The very latest observation of $M87$ supermassive black hole (BH) by the Event Horizon Telescope (EHT) provides the accretion onto BHs is an interesting study in the theory of gravity. We study the geodesics structure and accretion near a nonlinear electrodynamics BH in strong and weak field approximations. These approximations provide the disc-like structure under the geodesic motion and accretion around the BH. Near the equatorial plane, we provide some new reasons to make circular orbits and accretion of test particles around the BH. Then we investigate perturbations, the critical speed of the fluid and the mass accretion rate of particles around the central object. The physical validity of this study shows that the parameter $\beta$ and $Q$ play an important role in the circular orbits and the mass accretion rate in strong and weak field approximations. |
2108.07269 | Zheng-Wen Long | Xin-Dong Du and Chao-Yun Long | The Influence of Approximation in Generalized Uncertainty Principle on
Black Hole Evaporation | null | JCAP04(2022)031 | 10.1088/1475-7516/2022/04/031 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized uncertainty principle is often used to modify various
thermodynamics systems by regarding the greater-than-equal relation as an
approximate relation. We give a method to improve this approximation and
compare the differences between the original and improved methods during the
evaporation of black hole from two aspects of positive and negative parameters.
Finally, we prove the rationality of the improved method and give some guiding
opinions.
| [
{
"created": "Mon, 16 Aug 2021 04:37:50 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Aug 2021 14:51:24 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Aug 2021 13:44:19 GMT",
"version": "v3"
},
{
"created": "Thu, 26 Aug 2021 12:28:14 GMT",
"version": "v4"
},
{
"created": "Thu, 18 Nov 2021 12:53:23 GMT",
"version": "v5"
},
{
"created": "Thu, 21 Apr 2022 01:33:10 GMT",
"version": "v6"
}
] | 2022-10-13 | [
[
"Du",
"Xin-Dong",
""
],
[
"Long",
"Chao-Yun",
""
]
] | The generalized uncertainty principle is often used to modify various thermodynamics systems by regarding the greater-than-equal relation as an approximate relation. We give a method to improve this approximation and compare the differences between the original and improved methods during the evaporation of black hole from two aspects of positive and negative parameters. Finally, we prove the rationality of the improved method and give some guiding opinions. |
gr-qc/9608018 | Jai-chan Hwang | J. Hwang | Cosmological Perturbations with Multiple Scalar Fields | 2 pages, revtex, no figures | null | null | null | gr-qc | null | In this brief note we present a set of equations describing the evolution of
perturbed scalar fields in a cosmological spacetime with multiple scalar
fields. We take into account of the simultaneously excited full metric
perturbations in the context of the uniform-curvature gauge which is known to
be the best choice. The equations presented in a compact form will be useful
for handling the structure formation processes under the multiple episodes of
inflation.
| [
{
"created": "Thu, 8 Aug 1996 07:06:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hwang",
"J.",
""
]
] | In this brief note we present a set of equations describing the evolution of perturbed scalar fields in a cosmological spacetime with multiple scalar fields. We take into account of the simultaneously excited full metric perturbations in the context of the uniform-curvature gauge which is known to be the best choice. The equations presented in a compact form will be useful for handling the structure formation processes under the multiple episodes of inflation. |
1711.02442 | Georgios Loukes-Gerakopoulos | Ond\v{r}ej Zelenka and Georgios Lukes-Gerakopoulos | Chaotic motion in the Johannsen-Psaltis spacetime | 8 pages, 3 figures, submitted to the proceedings of RAGtime 19, Opava
23.-26.10.2017 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Johannsen-Psaltis spacetime is a perturbation of the Kerr spacetime
designed to avoid pathologies like naked singularities and closed timelike
curves. This spacetime depends not only on the mass and the spin of the compact
object, but also on extra parameters, making the spacetime deviate from Kerr;
in this work we consider only the lowest order physically meaningful extra
parameter. We use numerical examples to show that geodesic motion in this
spacetime can exhibit chaotic behavior. We study the corresponding phase space
by using Poincar\'{e} sections and rotation numbers to show chaotic behavior,
and we use Lyapunov exponents to directly estimate the sensitivity to initial
conditions for chaotic orbits.
| [
{
"created": "Tue, 7 Nov 2017 12:45:28 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Nov 2017 14:26:24 GMT",
"version": "v2"
}
] | 2017-11-09 | [
[
"Zelenka",
"Ondřej",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
]
] | The Johannsen-Psaltis spacetime is a perturbation of the Kerr spacetime designed to avoid pathologies like naked singularities and closed timelike curves. This spacetime depends not only on the mass and the spin of the compact object, but also on extra parameters, making the spacetime deviate from Kerr; in this work we consider only the lowest order physically meaningful extra parameter. We use numerical examples to show that geodesic motion in this spacetime can exhibit chaotic behavior. We study the corresponding phase space by using Poincar\'{e} sections and rotation numbers to show chaotic behavior, and we use Lyapunov exponents to directly estimate the sensitivity to initial conditions for chaotic orbits. |
1809.00913 | Juan Ram\'on Mu\~noz de Nova | Juan Ram\'on Mu\~noz de Nova, Katrine Golubkov, Victor I. Kolobov, and
Jeff Steinhauer | Observation of thermal Hawking radiation at the Hawking temperature in
an analogue black hole | 11 pages, 4 figures. Minor improvements added with respect to v1 | Nature 569, 688-691 (2019) | 10.1038/s41586-019-1241-0 | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We measure the correlation spectrum of the Hawking radiation emitted by an
analogue black hole and find it to be thermal at the Hawking temperature
implied by the analogue surface gravity. The Hawking radiation is in the regime
of linear dispersion, in analogy with a real black hole. Furthermore, the
radiation inside of the black hole is seen to be composed of negative-energy
partners only. This work confirms the prediction of Hawking's theory regarding
the value of the Hawking temperature, as well as the thermality of the
spectrum. The thermality of Hawking radiation is the root of the information
paradox. The correlations between the Hawking and partner particles imply that
the analogue black hole has no analogue firewall.
| [
{
"created": "Tue, 4 Sep 2018 12:10:51 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Sep 2018 16:44:00 GMT",
"version": "v2"
}
] | 2019-09-24 | [
[
"de Nova",
"Juan Ramón Muñoz",
""
],
[
"Golubkov",
"Katrine",
""
],
[
"Kolobov",
"Victor I.",
""
],
[
"Steinhauer",
"Jeff",
""
]
] | We measure the correlation spectrum of the Hawking radiation emitted by an analogue black hole and find it to be thermal at the Hawking temperature implied by the analogue surface gravity. The Hawking radiation is in the regime of linear dispersion, in analogy with a real black hole. Furthermore, the radiation inside of the black hole is seen to be composed of negative-energy partners only. This work confirms the prediction of Hawking's theory regarding the value of the Hawking temperature, as well as the thermality of the spectrum. The thermality of Hawking radiation is the root of the information paradox. The correlations between the Hawking and partner particles imply that the analogue black hole has no analogue firewall. |
2107.12111 | Chris Van Den Broeck | Pawan Kumar Gupta, Thomas F.M. Spieksma, Peter T.H. Pang, Gideon
Koekoek, Chris Van Den Broeck | Bounding dark charges on binary black holes using gravitational waves | 11 pages, 8 captioned figures | Phys. Rev. D 104, 063041 (2021) | 10.1103/PhysRevD.104.063041 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | In models of minicharged dark matter associated with a hidden $U(1)$
symmetry, astrophysical black holes may acquire a "dark" charge, in such a way
that the inspiral dynamics of binary black holes can be formally described by
an Einstein-Maxwell theory. Charges enter the gravitational wave signal
predominantly through a dipole term, but their effect is known to effectively
first post-Newtonian order in the phase, which enables measuring the size of
the charge-to-mass ratios, $|q_i/m_i|$, $i = 1,2$, of the individual black
holes in a binary. We set up a Bayesian analysis to discover, or constrain,
dark charges on binary black holes. After testing our framework in simulations,
we apply it to selected binary black hole signals from the second Gravitational
Wave Transient Catalog (GWTC-2), namely those with low masses so that most of
the signal-to-noise ratio is in the inspiral regime. We find no evidence for
charges on the black holes, and place typical 1-$\sigma$ bounds on the
charge-to-mass ratios of $|q_i/m_i| \lesssim 0.2 - 0.3$.
| [
{
"created": "Mon, 26 Jul 2021 11:08:45 GMT",
"version": "v1"
}
] | 2021-09-29 | [
[
"Gupta",
"Pawan Kumar",
""
],
[
"Spieksma",
"Thomas F. M.",
""
],
[
"Pang",
"Peter T. H.",
""
],
[
"Koekoek",
"Gideon",
""
],
[
"Broeck",
"Chris Van Den",
""
]
] | In models of minicharged dark matter associated with a hidden $U(1)$ symmetry, astrophysical black holes may acquire a "dark" charge, in such a way that the inspiral dynamics of binary black holes can be formally described by an Einstein-Maxwell theory. Charges enter the gravitational wave signal predominantly through a dipole term, but their effect is known to effectively first post-Newtonian order in the phase, which enables measuring the size of the charge-to-mass ratios, $|q_i/m_i|$, $i = 1,2$, of the individual black holes in a binary. We set up a Bayesian analysis to discover, or constrain, dark charges on binary black holes. After testing our framework in simulations, we apply it to selected binary black hole signals from the second Gravitational Wave Transient Catalog (GWTC-2), namely those with low masses so that most of the signal-to-noise ratio is in the inspiral regime. We find no evidence for charges on the black holes, and place typical 1-$\sigma$ bounds on the charge-to-mass ratios of $|q_i/m_i| \lesssim 0.2 - 0.3$. |
gr-qc/0402109 | A. Lewis Licht | A. Lewis Licht | Gravitational Waves on Conductors | 19 pages, revtex4, more realistic value used for the estimated high
frequency cosmic gravitational wave amplitude | null | null | null | gr-qc | null | We consider a gravitational wave of arbitrary frequency incident on a normal
or a super-conductor. The gravitationally induced fields inside the conductor
are derived. The outward propagating EM waves are calculated for a low
frequency wave on a small sphere and for a high frequency wave incident on a
large disk. We estimate for both targets the GW to EM conversion efficiencies
and also the magnitude of the superconductor's phase perturbation.
| [
{
"created": "Wed, 25 Feb 2004 00:56:36 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Mar 2004 23:09:36 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Licht",
"A. Lewis",
""
]
] | We consider a gravitational wave of arbitrary frequency incident on a normal or a super-conductor. The gravitationally induced fields inside the conductor are derived. The outward propagating EM waves are calculated for a low frequency wave on a small sphere and for a high frequency wave incident on a large disk. We estimate for both targets the GW to EM conversion efficiencies and also the magnitude of the superconductor's phase perturbation. |
gr-qc/9801078 | Beverly K. Berger | Beverly K. Berger (Oakland) and Vincent Moncrief (Yale) | Numerical Evidence that the Singularity in Polarized U(1) Symmetric
Cosmologies on $T^3 \times R$ is Velocity Dominated | 8 pages, RevTex, 4 figures, uses epsf | Phys.Rev. D57 (1998) 7235-7240 | 10.1103/PhysRevD.57.7235 | null | gr-qc | null | Numerical evidence supports the conjecture that polarized U(1) symmetric
cosmologies have asymptotically velocity term dominated singularities.
| [
{
"created": "Thu, 22 Jan 1998 21:17:47 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Berger",
"Beverly K.",
"",
"Oakland"
],
[
"Moncrief",
"Vincent",
"",
"Yale"
]
] | Numerical evidence supports the conjecture that polarized U(1) symmetric cosmologies have asymptotically velocity term dominated singularities. |
2312.02862 | Amodio Carleo | Amodio Carleo | Constraints on non-local gravity from binary pulsars gravitational
emission | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Non-local theories of gravity are considered extended theories of gravity,
meaning that when the non-local terms are canceled out, the limit of General
Relativity (GR) is obtained. Several reasons have led us to consider this
theory with increasing interest, but primarily non-locality emerges in a
natural way as a side effect of the introduction of quantum corrections to GR,
the purpose of which was to cure the singularity problem, both at astrophysical
and cosmological level. In this paper we studied a peculiar case of the so
called Deser-Woodard theory consisting in the addition of a non-local term to
the Hilbert-Einstein lagrangian, and we derived for the first time contraints
on the dimensionaless non-local parameter A by exploiting the predicted
gravitational wave emission in three binary pulsars, namely PSR J1012+5307, PSR
J0348+0432 and PSR $J1738+0333. We discovered that the instantaneous flux
strongly depends on A and that the best constraints (0.12 < A < 0.16) come from
PSR J1012+5307, for which the GR prediction is outside the observational
ranges. However, since for PSR J1012 + 5307 scintillation is suspected, as
emerged in a recent census by LOFAR, corruptions in pulsar timing could be
hidden. We finally comment on the usability and reliability of this type of
test for extended theories of gravity.
| [
{
"created": "Tue, 5 Dec 2023 16:15:39 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Carleo",
"Amodio",
""
]
] | Non-local theories of gravity are considered extended theories of gravity, meaning that when the non-local terms are canceled out, the limit of General Relativity (GR) is obtained. Several reasons have led us to consider this theory with increasing interest, but primarily non-locality emerges in a natural way as a side effect of the introduction of quantum corrections to GR, the purpose of which was to cure the singularity problem, both at astrophysical and cosmological level. In this paper we studied a peculiar case of the so called Deser-Woodard theory consisting in the addition of a non-local term to the Hilbert-Einstein lagrangian, and we derived for the first time contraints on the dimensionaless non-local parameter A by exploiting the predicted gravitational wave emission in three binary pulsars, namely PSR J1012+5307, PSR J0348+0432 and PSR $J1738+0333. We discovered that the instantaneous flux strongly depends on A and that the best constraints (0.12 < A < 0.16) come from PSR J1012+5307, for which the GR prediction is outside the observational ranges. However, since for PSR J1012 + 5307 scintillation is suspected, as emerged in a recent census by LOFAR, corruptions in pulsar timing could be hidden. We finally comment on the usability and reliability of this type of test for extended theories of gravity. |
gr-qc/9411021 | Hernando Quevedo | Hernando Quevedo and Roberto Sussman | Thermodynamics of the Stephani Universes | 25 pages, Plain.TeX, four figures | J.Math.Phys. 36 (1995) 1353-1377 | 10.1063/1.531126 | null | gr-qc | null | We examine the consistency of the thermodynamics of the most general class of
conformally flat solution with an irrotational perfect fluid source (the
Stephani Universes). For the case when the isometry group has dimension
$r\ge2$, the Gibbs-Duhem relation is always integrable, but if $r<2$ it is only
integrable for the particular subclass (containing FRW cosmologies)
characterized by $r=1$ and by admitting a conformal motion parallel to the
4-velocity. We provide explicit forms of the state variables and equations of
state linking them. These formal thermodynamic relations are determined up to
an arbitrary function of time which reduces to the FRW scale factor in the FRW
limit of the solutions. We show that a formal identification of this free
parameter with a FRW scale factor determined by FRW dynamics leads to an
unphysical temperature evolution law. If this parameter is not identified with
a FRW scale factor, it is possible to find examples of solutions and formal
equations of state complying with suitable energy conditions and reasonable
asymptotic behavior and temperature laws.
| [
{
"created": "Tue, 8 Nov 1994 16:45:18 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Quevedo",
"Hernando",
""
],
[
"Sussman",
"Roberto",
""
]
] | We examine the consistency of the thermodynamics of the most general class of conformally flat solution with an irrotational perfect fluid source (the Stephani Universes). For the case when the isometry group has dimension $r\ge2$, the Gibbs-Duhem relation is always integrable, but if $r<2$ it is only integrable for the particular subclass (containing FRW cosmologies) characterized by $r=1$ and by admitting a conformal motion parallel to the 4-velocity. We provide explicit forms of the state variables and equations of state linking them. These formal thermodynamic relations are determined up to an arbitrary function of time which reduces to the FRW scale factor in the FRW limit of the solutions. We show that a formal identification of this free parameter with a FRW scale factor determined by FRW dynamics leads to an unphysical temperature evolution law. If this parameter is not identified with a FRW scale factor, it is possible to find examples of solutions and formal equations of state complying with suitable energy conditions and reasonable asymptotic behavior and temperature laws. |
0903.5527 | Leonardo Fernandez-Jambrina | L. Fern\'andez-Jambrina, R. Lazkoz | Geodesic Behaviour around Cosmological Milestones | 9 pp. Uses jpconf.cls. Published in XXIXth Spanish Relativity Meeting
(ERE 2006): Einstein's Legacy: from the Theoretical Paradise to Astrophysical
Observations. Eds: P. Apostolopoulos, C. Bona, J. Carot, Ll. Mas, A.M.
Sintes, J. Stela | J.Phys.Conf.Ser.66:012015,2007 | 10.1088/1742-6596/66/1/012015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we provide a thorough classification of
Friedman-Lema\^itre-Robertson-Walker (FLRW) cosmological models in terms of the
strong or weak character of their singularities according to the usual
definitions. The classification refers to a generalised Puiseux power expansion
of the scale factor of the model around a singular event.
| [
{
"created": "Tue, 31 Mar 2009 17:45:37 GMT",
"version": "v1"
}
] | 2010-12-17 | [
[
"Fernández-Jambrina",
"L.",
""
],
[
"Lazkoz",
"R.",
""
]
] | In this paper we provide a thorough classification of Friedman-Lema\^itre-Robertson-Walker (FLRW) cosmological models in terms of the strong or weak character of their singularities according to the usual definitions. The classification refers to a generalised Puiseux power expansion of the scale factor of the model around a singular event. |
gr-qc/9701026 | Claude Barrabes | C. Barrabes and G.F. Bressange | Singular Hypersurfaces in Scalar-Tensor Theories of Gravity | 38 pages, latex, no figures, to appear in Classical and Quantum
Gravity | Class.Quant.Grav.14:805-824,1997 | 10.1088/0264-9381/14/3/021 | null | gr-qc | null | We study singular hypersurfaces in tensor multi-scalar theories of gravity.
We derive in a distributional and then in an intrinsic way, the general
equations of junction valid for all types of hypersurfaces, in particular for
lightlike shells and write the general equations of evolution for these
objects. We apply this formalism to various examples in static spherically
symmetric spacetimes, and to the study of planar domain walls and plane
impulsive waves.
| [
{
"created": "Mon, 13 Jan 1997 15:20:32 GMT",
"version": "v1"
}
] | 2011-05-12 | [
[
"Barrabes",
"C.",
""
],
[
"Bressange",
"G. F.",
""
]
] | We study singular hypersurfaces in tensor multi-scalar theories of gravity. We derive in a distributional and then in an intrinsic way, the general equations of junction valid for all types of hypersurfaces, in particular for lightlike shells and write the general equations of evolution for these objects. We apply this formalism to various examples in static spherically symmetric spacetimes, and to the study of planar domain walls and plane impulsive waves. |
2102.10419 | Michail Chabanov | Michail Chabanov, Luciano Rezzolla, Dirk H. Rischke | General-relativistic hydrodynamics of non-perfect fluids: 3+1
conservative formulation and application to viscous black-hole accretion | 54 pages, 5 figures, matches accepted version in MNRAS | null | 10.1093/mnras/stab1384 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the relativistic hydrodynamics of non-perfect fluids with the
goal of determining a formulation that is suited for numerical integration in
special-relativistic and general-relativistic scenarios. To this end, we review
the various formulations of relativistic second-order dissipative hydrodynamics
proposed so far and present in detail a particular formulation that is fully
general, causal, and can be cast into a 3+1 flux-conservative form, as the one
employed in modern numerical-relativity codes. As an example, we employ a
variant of this formulation restricted to a relaxation-type equation for the
bulk viscosity in the general-relativistic magnetohydrodynamics code
$\texttt{BHAC}$. After adopting the formulation for a series of standard and
non-standard tests in 1+1-dimensional special-relativistic hydrodynamics, we
consider a novel general-relativistic scenario, namely, the stationary,
spherically symmetric, viscous accretion onto a black hole. The newly developed
solution $-$ which can exhibit even considerable deviations from the inviscid
counterpart $-$ can be used as a testbed for numerical codes simulating
non-perfect fluids on curved backgrounds.
| [
{
"created": "Sat, 20 Feb 2021 18:54:11 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Feb 2023 18:01:59 GMT",
"version": "v2"
}
] | 2023-02-27 | [
[
"Chabanov",
"Michail",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Rischke",
"Dirk H.",
""
]
] | We consider the relativistic hydrodynamics of non-perfect fluids with the goal of determining a formulation that is suited for numerical integration in special-relativistic and general-relativistic scenarios. To this end, we review the various formulations of relativistic second-order dissipative hydrodynamics proposed so far and present in detail a particular formulation that is fully general, causal, and can be cast into a 3+1 flux-conservative form, as the one employed in modern numerical-relativity codes. As an example, we employ a variant of this formulation restricted to a relaxation-type equation for the bulk viscosity in the general-relativistic magnetohydrodynamics code $\texttt{BHAC}$. After adopting the formulation for a series of standard and non-standard tests in 1+1-dimensional special-relativistic hydrodynamics, we consider a novel general-relativistic scenario, namely, the stationary, spherically symmetric, viscous accretion onto a black hole. The newly developed solution $-$ which can exhibit even considerable deviations from the inviscid counterpart $-$ can be used as a testbed for numerical codes simulating non-perfect fluids on curved backgrounds. |
2105.14621 | Lorenzo Gavassino | Lorenzo Gavassino, Marco Antonelli and Brynmor Haskell | Thermodynamic stability implies causality | Main Article (6 pages, 2 figures) + Supplementary Material (8 pages,
2 figures) | Physical Review Letters 128, 010606 (Published 6 January 2022) | 10.1103/PhysRevLett.128.010606 | null | gr-qc astro-ph.HE hep-ph physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stability conditions of a relativistic hydrodynamic theory can be derived
directly from the requirement that the entropy should be maximised in
equilibrium. Here we use a simple geometrical argument to prove that, if the
hydrodynamic theory is stable according to this entropic criterion, then
localised perturbations to the equilibrium state cannot propagate outside their
future light-cone. In other words, within relativistic hydrodynamics, acausal
theories must be thermodynamically unstable, at least close to equilibrium. We
show that the physical origin of this deep connection between stability and
causality lies in the relationship between entropy and information. Our result
may be interpreted as an ``equilibrium conservation theorem'', which
generalizes the Hawking-Ellis vacuum conservation theorem to finite temperature
and chemical potential.
| [
{
"created": "Sun, 30 May 2021 20:45:36 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Dec 2021 21:55:40 GMT",
"version": "v2"
}
] | 2022-01-11 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Haskell",
"Brynmor",
""
]
] | The stability conditions of a relativistic hydrodynamic theory can be derived directly from the requirement that the entropy should be maximised in equilibrium. Here we use a simple geometrical argument to prove that, if the hydrodynamic theory is stable according to this entropic criterion, then localised perturbations to the equilibrium state cannot propagate outside their future light-cone. In other words, within relativistic hydrodynamics, acausal theories must be thermodynamically unstable, at least close to equilibrium. We show that the physical origin of this deep connection between stability and causality lies in the relationship between entropy and information. Our result may be interpreted as an ``equilibrium conservation theorem'', which generalizes the Hawking-Ellis vacuum conservation theorem to finite temperature and chemical potential. |
1608.02777 | Saulo Pereira H | S. H. Pereira, S. S. A. Pinho, J. M. Hoff da Silva, and J. F. Jesus | $\Lambda(t)$ cosmology induced by a slowly varying Elko field | 15 pages, 4 figures; New section on evolution of density
perturbations added | JCAP01(2017)055 | 10.1088/1475-7516/2017/01/055 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work the exact Friedmann-Robertson-Walker equations for an Elko
spinor field coupled to gravity in an Einstein-Cartan framework are presented.
The torsion functions coupling the Elko field spin-connection to gravity can be
exactly solved and the FRW equations for the system assume a relatively simple
form. In the limit of a slowly varying Elko spinor field there is a relevant
contribution to the field equations acting exactly as a time varying
cosmological model $\Lambda(t)=\Lambda_*+3\beta H^2$, where $\Lambda_*$ and
$\beta$ are constants. Observational data using distance luminosity from
magnitudes of supernovae constraint the parameters $\Omega_m$ and $\beta$,
which leads to a lower limit to the Elko mass. Such model mimics, then, the
effects of a dark energy fluid, here sourced by the Elko spinor field. The
density perturbations in the linear regime were also studied in the
pseudo-Newtonian formalism.
| [
{
"created": "Tue, 9 Aug 2016 12:08:34 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Dec 2016 19:16:40 GMT",
"version": "v2"
}
] | 2017-09-13 | [
[
"Pereira",
"S. H.",
""
],
[
"Pinho",
"S. S. A.",
""
],
[
"da Silva",
"J. M. Hoff",
""
],
[
"Jesus",
"J. F.",
""
]
] | In this work the exact Friedmann-Robertson-Walker equations for an Elko spinor field coupled to gravity in an Einstein-Cartan framework are presented. The torsion functions coupling the Elko field spin-connection to gravity can be exactly solved and the FRW equations for the system assume a relatively simple form. In the limit of a slowly varying Elko spinor field there is a relevant contribution to the field equations acting exactly as a time varying cosmological model $\Lambda(t)=\Lambda_*+3\beta H^2$, where $\Lambda_*$ and $\beta$ are constants. Observational data using distance luminosity from magnitudes of supernovae constraint the parameters $\Omega_m$ and $\beta$, which leads to a lower limit to the Elko mass. Such model mimics, then, the effects of a dark energy fluid, here sourced by the Elko spinor field. The density perturbations in the linear regime were also studied in the pseudo-Newtonian formalism. |
2407.08728 | Isaac Chun Fung Wong | Isaac C. F. Wong, Peter T. H. Pang, Milan Wils, Francesco Cireddu,
Walter Del Pozzo, Tjonnie G. F. Li | The Potential Impact of Noise Correlation in Next-generation
Gravitational Wave Detectors | 10 pages, 2 figures | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Building upon the statistical formulation for parameter estimation in the
presence of correlated noise proposed by Cireddu et al., we present an initial
study to incorporate the effects of correlated noise into the analyses of
various detector designs' performance. We consider a two L-shaped detector
configuration located in the European Union, and compare the expectation of
parameter estimation between the non-colocated and a hypothetical colocated
configurations. In our study, we posit the existence of low-frequency
correlated noise within the $5\text{ Hz}$ to $10\text{ Hz}$ range for the
colocated detector configuration, with a varying degree of correlation. In this
specific detector setup, our observations indicate an enhancement in the
precision of intrinsic parameter measurements as the degree of correlation
increases. This trend suggests that higher degrees of noise correlation may
beneficially influence the accuracy of parameter estimation. In particular,
when the noise is highly correlated, the uncertainty on chirp mass decreases by
up to $30\%$. The absence of an inter-European baseline does hinder the
estimation of the extrinsic parameters. However, given a realistic global
network with the additional detector located in the United States, the
uncertainty of extrinsic parameters is significantly reduced. This reduction is
further amplified as the degree of noise correlation increases. When noise
correlation exceeds a certain level, the colocated configuration outperforms
the non-colocated one, reducing the $90\%$ credible area of sky location by up
to $10\%$. We conclude that noise correlation significantly impacts detector
performance, potentially altering both quantitative and qualitative outcomes.
Thus, we recommend including noise correlation in comprehensive assessments of
third-generation gravitational wave detector designs.
| [
{
"created": "Thu, 11 Jul 2024 17:57:50 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Wong",
"Isaac C. F.",
""
],
[
"Pang",
"Peter T. H.",
""
],
[
"Wils",
"Milan",
""
],
[
"Cireddu",
"Francesco",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Li",
"Tjonnie G. F.",
""
]
] | Building upon the statistical formulation for parameter estimation in the presence of correlated noise proposed by Cireddu et al., we present an initial study to incorporate the effects of correlated noise into the analyses of various detector designs' performance. We consider a two L-shaped detector configuration located in the European Union, and compare the expectation of parameter estimation between the non-colocated and a hypothetical colocated configurations. In our study, we posit the existence of low-frequency correlated noise within the $5\text{ Hz}$ to $10\text{ Hz}$ range for the colocated detector configuration, with a varying degree of correlation. In this specific detector setup, our observations indicate an enhancement in the precision of intrinsic parameter measurements as the degree of correlation increases. This trend suggests that higher degrees of noise correlation may beneficially influence the accuracy of parameter estimation. In particular, when the noise is highly correlated, the uncertainty on chirp mass decreases by up to $30\%$. The absence of an inter-European baseline does hinder the estimation of the extrinsic parameters. However, given a realistic global network with the additional detector located in the United States, the uncertainty of extrinsic parameters is significantly reduced. This reduction is further amplified as the degree of noise correlation increases. When noise correlation exceeds a certain level, the colocated configuration outperforms the non-colocated one, reducing the $90\%$ credible area of sky location by up to $10\%$. We conclude that noise correlation significantly impacts detector performance, potentially altering both quantitative and qualitative outcomes. Thus, we recommend including noise correlation in comprehensive assessments of third-generation gravitational wave detector designs. |
0910.4372 | Neil J. Cornish | Neil J. Cornish | Alternative derivation of the response of interferometric gravitational
wave detectors | 2 pages | Phys.Rev.D80:087101,2009 | 10.1103/PhysRevD.80.087101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been pointed out by Finn that the long-standing derivation of
the response of an interferometric gravitational wave detector contains several
errors. Here I point out that a contemporaneous derivation of the gravitational
wave response for spacecraft doppler tracking and pulsar timing avoids these
pitfalls, and when adapted to describe interferometers, recovers a simplified
version of Finn's derivation. This simplified derivation may be useful for
pedagogical purposes.
| [
{
"created": "Thu, 22 Oct 2009 17:35:35 GMT",
"version": "v1"
}
] | 2009-11-05 | [
[
"Cornish",
"Neil J.",
""
]
] | It has recently been pointed out by Finn that the long-standing derivation of the response of an interferometric gravitational wave detector contains several errors. Here I point out that a contemporaneous derivation of the gravitational wave response for spacecraft doppler tracking and pulsar timing avoids these pitfalls, and when adapted to describe interferometers, recovers a simplified version of Finn's derivation. This simplified derivation may be useful for pedagogical purposes. |
2303.15546 | Lee Smolin | Lee Smolin | The path integral formulation of energetic causal set models of the
universe | 13 pages, 4 Figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | I study several aspects of the path(st) integral we formulated in previous
papers on energetic causal sets with Cortes and others. The focus here is on
quantum field theories, including the standard model of particle physics. I
show that the the theory can be extended to a quantum field theory, cut off in
momentum space. Fields of spin 0, 1/2 and 1 may be naturally included, which
allows us to formulate the standard model in this framework. The theory is at
first formulated in momentum space. Under certain conditions, spacetime can
emerge in a semiclassical limit. The theory comes with a $uv$ cutoff in
momentum space, $\mu$, hence that is also a scale for lorentz invariance to
break down. Traditionally, m is taken to be. a Planck energy, but we explore as
a possibility making m smaller.
| [
{
"created": "Mon, 27 Mar 2023 18:54:02 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Smolin",
"Lee",
""
]
] | I study several aspects of the path(st) integral we formulated in previous papers on energetic causal sets with Cortes and others. The focus here is on quantum field theories, including the standard model of particle physics. I show that the the theory can be extended to a quantum field theory, cut off in momentum space. Fields of spin 0, 1/2 and 1 may be naturally included, which allows us to formulate the standard model in this framework. The theory is at first formulated in momentum space. Under certain conditions, spacetime can emerge in a semiclassical limit. The theory comes with a $uv$ cutoff in momentum space, $\mu$, hence that is also a scale for lorentz invariance to break down. Traditionally, m is taken to be. a Planck energy, but we explore as a possibility making m smaller. |
1301.5314 | Naresh Dadhich | Naresh Dadhich | A novel derivation of the rotating black hole metric | 4 pages, to agree with the published version except one additional
reference, pubmished | Gen. Relativ. Grav. (2013) 45:2383-2388 | 10.1007/s10714-013-1594-x | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the rotating black hole metric by appealing to ellipsoidal symmetry
of space and a general guiding principle of incorporation of the Newtonian
acceleration for massive and no acceleration for massless particles.
| [
{
"created": "Tue, 22 Jan 2013 05:31:33 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Sep 2013 08:31:36 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Oct 2013 06:29:14 GMT",
"version": "v3"
}
] | 2013-10-15 | [
[
"Dadhich",
"Naresh",
""
]
] | We derive the rotating black hole metric by appealing to ellipsoidal symmetry of space and a general guiding principle of incorporation of the Newtonian acceleration for massive and no acceleration for massless particles. |
0908.2651 | Enrico Rodrigo | Enrico Rodrigo | Denouement of a Wormhole-Brane Encounter | 12 pages, 2 figures, accepted by Int. J. Mod. Phys. D | Int.J.Mod.Phys.D18:1809-1819,2009 | 10.1142/S0218271809015333 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Higher-dimensional black holes have long been considered within the context
of brane worlds. Recently, it was shown that the brane-world ethos also permits
the consideration of higher-dimensional wormholes. When such a wormhole,
preexisting in the bulk, impinges upon our universe, taken to be a
positive-tension 3-brane, it can induce the creation in our universe of a
wormhole of ordinary dimensionality. The throat of this wormhole might fully
constrict, pinch off, and thus birth a baby universe. Alternatively, the
induced wormhole might persist. I show that persistence is more likely and note
that the persistent wormhole manifests as a particle-like object whose
interaction with cosmic matter is purely gravitational. I consider briefly the
viability of this object as a dark matter candidate.
| [
{
"created": "Tue, 18 Aug 2009 22:30:36 GMT",
"version": "v1"
}
] | 2009-12-17 | [
[
"Rodrigo",
"Enrico",
""
]
] | Higher-dimensional black holes have long been considered within the context of brane worlds. Recently, it was shown that the brane-world ethos also permits the consideration of higher-dimensional wormholes. When such a wormhole, preexisting in the bulk, impinges upon our universe, taken to be a positive-tension 3-brane, it can induce the creation in our universe of a wormhole of ordinary dimensionality. The throat of this wormhole might fully constrict, pinch off, and thus birth a baby universe. Alternatively, the induced wormhole might persist. I show that persistence is more likely and note that the persistent wormhole manifests as a particle-like object whose interaction with cosmic matter is purely gravitational. I consider briefly the viability of this object as a dark matter candidate. |
1407.2816 | Adam D. Helfer | Adam D. Helfer | Energy-momentum and asymptotic geometry | 22 pages, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.90.044005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I show that radiative space-times are not asymptotically flat; rather, the
radiation field gives rise to holonomy at null infinity. (This was noted
earlier, by Bramson.) This means that, when gravitational radiation is present,
asymptotically covariantly constant vector fields do not exist. On the other
hand, according to the Bondi-Sachs construction, a weaker class of
asymptotically constant vectors does exist. Reconciling these concepts leads to
a measure of the scattering of matter by gravitational waves, that is, bulk
exchanges of energy-momentum between the waves and matter. Because these bulk
effects are potentially larger than the tidal ones which have usually been
studied, they may affect the waves' propagation more significantly, and the
question of matter's transparency to gravitational radiation should be
revisited. While in many cases there is reason to think the waves will be only
slightly affected, some situations are identified in which the energy-momentum
exchanges can be substantial enough that a closer investigation should be made.
In particular, the work here suggests that gravitational waves produced when
relativistic jets are formed might be substantially affected by passing through
an inhomogeneous medium.
| [
{
"created": "Thu, 10 Jul 2014 14:55:25 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Helfer",
"Adam D.",
""
]
] | I show that radiative space-times are not asymptotically flat; rather, the radiation field gives rise to holonomy at null infinity. (This was noted earlier, by Bramson.) This means that, when gravitational radiation is present, asymptotically covariantly constant vector fields do not exist. On the other hand, according to the Bondi-Sachs construction, a weaker class of asymptotically constant vectors does exist. Reconciling these concepts leads to a measure of the scattering of matter by gravitational waves, that is, bulk exchanges of energy-momentum between the waves and matter. Because these bulk effects are potentially larger than the tidal ones which have usually been studied, they may affect the waves' propagation more significantly, and the question of matter's transparency to gravitational radiation should be revisited. While in many cases there is reason to think the waves will be only slightly affected, some situations are identified in which the energy-momentum exchanges can be substantial enough that a closer investigation should be made. In particular, the work here suggests that gravitational waves produced when relativistic jets are formed might be substantially affected by passing through an inhomogeneous medium. |
gr-qc/0503123 | Noriko Shiiki | Noriko Shiiki and Nobuyuki Sawado | Regular and Black Hole Solutions in the Einstein-Skyrme Theory with
Negative Cosmological Constant | 10 pages, 9 figures, comments and one reference added, to appear in
Class.Quant.Grav | Class.Quant.Grav. 22 (2005) 3561-3574 | 10.1088/0264-9381/22/17/015 | null | gr-qc | null | We study spherically symmetric regular and black hole solutions in the
Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field
configuration depends on the value of the cosmological constant in a similar
manner to effectively varying the gravitational constant. We find the maximum
value of the cosmological constant above which there exists no solution. The
properties of the solutions are discussed in comparison with the asymptotically
flat solutions. The stability is investigated in detail by solving the linearly
perturbed equation numerically. We show that there exists a critical value of
the cosmological constant above which the solution in the branch representing
unstable configuration in the asymptotically flat spacetime turns to be
linearly stable.
| [
{
"created": "Thu, 31 Mar 2005 10:48:53 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jul 2005 04:25:01 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Shiiki",
"Noriko",
""
],
[
"Sawado",
"Nobuyuki",
""
]
] | We study spherically symmetric regular and black hole solutions in the Einstein-Skyrme theory with a negative cosmological constant. The Skyrme field configuration depends on the value of the cosmological constant in a similar manner to effectively varying the gravitational constant. We find the maximum value of the cosmological constant above which there exists no solution. The properties of the solutions are discussed in comparison with the asymptotically flat solutions. The stability is investigated in detail by solving the linearly perturbed equation numerically. We show that there exists a critical value of the cosmological constant above which the solution in the branch representing unstable configuration in the asymptotically flat spacetime turns to be linearly stable. |
2308.01078 | S. N Sajadi | S.N. Sajadi, Robert B. Mann, H. Sheikhahmadi, M. Khademi | Black hole solutions to Einstein-Bel-Robinson gravity | Major changes, with significant corrections and new solutions
presented; figure added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study the physical properties of black holes in the
framework of the recently proposed Einstien-Bel-Robinson gravity. We show that
interestingly the theory propagates a transverse and massive graviton on a
maximally symmetric background with positive energy. There is also a single
ghost-free branch that returns to the Einstein case when \beta\to 0. We find
new black hole solutions to the equations, both approximate and exact, the
latter being a constant curvature black hole solution, and discuss
inconsistencies with metrics that were previously claimed to be approximate
solutions to the equations. We obtain the conserved charges of the theory and
briefly study the thermodynamics of the black hole solutions.
| [
{
"created": "Wed, 2 Aug 2023 11:03:25 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jan 2024 19:54:00 GMT",
"version": "v2"
}
] | 2024-01-30 | [
[
"Sajadi",
"S. N.",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Sheikhahmadi",
"H.",
""
],
[
"Khademi",
"M.",
""
]
] | In this paper, we study the physical properties of black holes in the framework of the recently proposed Einstien-Bel-Robinson gravity. We show that interestingly the theory propagates a transverse and massive graviton on a maximally symmetric background with positive energy. There is also a single ghost-free branch that returns to the Einstein case when \beta\to 0. We find new black hole solutions to the equations, both approximate and exact, the latter being a constant curvature black hole solution, and discuss inconsistencies with metrics that were previously claimed to be approximate solutions to the equations. We obtain the conserved charges of the theory and briefly study the thermodynamics of the black hole solutions. |
2002.07907 | Ra\'ul Ag\"uero-Santacruz | Raul Aguero-Santacruz and David Bermudez | Hawking radiation in optics and beyond | 20 pages, 8 figures, 64 references. Contribution to: "The next
generation of analogue gravity experiments" at the Royal Society on December
2019 | null | 10.1098/rsta.2019.0223 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation was originally proposed in astrophysics, but it has been
generalized and extended to other physical systems receiving the name of
analogue Hawking radiation. In the last two decades, several attempts have been
made to measure it in a laboratory, one of the most successful systems is in
optics. Light interacting in a dielectric material causes an analogue Hawking
effect, in fact, its stimulated version has already been detected and the
search for the spontaneous signal is currently ongoing. We briefly review the
general derivation of Hawking radiation, then we focus on the optical analogue
and present some novel numerical results. Finally, we call for a generalization
of the term Hawking radiation.
| [
{
"created": "Tue, 18 Feb 2020 22:22:33 GMT",
"version": "v1"
}
] | 2021-03-17 | [
[
"Aguero-Santacruz",
"Raul",
""
],
[
"Bermudez",
"David",
""
]
] | Hawking radiation was originally proposed in astrophysics, but it has been generalized and extended to other physical systems receiving the name of analogue Hawking radiation. In the last two decades, several attempts have been made to measure it in a laboratory, one of the most successful systems is in optics. Light interacting in a dielectric material causes an analogue Hawking effect, in fact, its stimulated version has already been detected and the search for the spontaneous signal is currently ongoing. We briefly review the general derivation of Hawking radiation, then we focus on the optical analogue and present some novel numerical results. Finally, we call for a generalization of the term Hawking radiation. |
2407.04452 | Marie-No\"elle C\'el\'erier | Marie-No\"elle C\'el\'erier | Precision cosmology with exact inhomogeneous solutions of General
Relativity: the Szekeres models | 20 pages, no figure | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The exact Friedman solution to the field equations of General Relativity (GR)
describing an homogeneous and isotropic universe together with its linear and
higher-order perturbations are the theoretical roots of the current standard
model of cosmology. However, despite its global successes, this standard model
currently faces a number of tensions and anomalies, which occur mostly from a
mismatch between early and late cosmic time region depictions. Actually, in the
era of precision cosmology, the late inhomogeneities in the densities of the
Universe components can no more be neglected. Moreover, since GR is
fundamentally nonlinear, any linear perturbation theory is doomed to fail at
reproducing precisely its features, while higher-order perturbed FLRW models
cannot either claim the status of exact solution to Einstein's field equations.
Fortunately, other GR solutions exist which are best suited for this purpose,
e. g., exact inhomogeneous solutions able to represent a matter-cosmological
constant dominated universe region. Among these, the Szekeres solution, which
is devoid of any symmetry, appears as a proper tool for this purpose. Moreover,
since these solutions possess the FLRW model as a homogeneous limit, they can
be very smoothly matched to the standard representation at the
inhomogeneity-homogeneity transition. In this paper, the Szekeres solution and
its main interesting properties, as well as the equations needed to use this
solution in a cosmological context are presented. Then the prospects for a
broader use of its abilities are sketched out. In particular, the use of neural
networks is proposed to allow, in the future, the fitting of the huge amount of
data becoming available to constrain the arbitrary functions and the constant
parameters characterizing the Szekeres model, running for representing our late
Universe with an increased precision.
| [
{
"created": "Fri, 5 Jul 2024 12:06:33 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2024 07:54:40 GMT",
"version": "v2"
}
] | 2024-07-22 | [
[
"Célérier",
"Marie-Noëlle",
""
]
] | The exact Friedman solution to the field equations of General Relativity (GR) describing an homogeneous and isotropic universe together with its linear and higher-order perturbations are the theoretical roots of the current standard model of cosmology. However, despite its global successes, this standard model currently faces a number of tensions and anomalies, which occur mostly from a mismatch between early and late cosmic time region depictions. Actually, in the era of precision cosmology, the late inhomogeneities in the densities of the Universe components can no more be neglected. Moreover, since GR is fundamentally nonlinear, any linear perturbation theory is doomed to fail at reproducing precisely its features, while higher-order perturbed FLRW models cannot either claim the status of exact solution to Einstein's field equations. Fortunately, other GR solutions exist which are best suited for this purpose, e. g., exact inhomogeneous solutions able to represent a matter-cosmological constant dominated universe region. Among these, the Szekeres solution, which is devoid of any symmetry, appears as a proper tool for this purpose. Moreover, since these solutions possess the FLRW model as a homogeneous limit, they can be very smoothly matched to the standard representation at the inhomogeneity-homogeneity transition. In this paper, the Szekeres solution and its main interesting properties, as well as the equations needed to use this solution in a cosmological context are presented. Then the prospects for a broader use of its abilities are sketched out. In particular, the use of neural networks is proposed to allow, in the future, the fitting of the huge amount of data becoming available to constrain the arbitrary functions and the constant parameters characterizing the Szekeres model, running for representing our late Universe with an increased precision. |
2405.16031 | Jianbo Lu | Jianbo Lu, Yongxin Guo and G. Y. Chee | Lorentz group in gravity theories | 35 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, it is argued that in gravity theories the local Lorentz group
can not be considered as a gauge group in the sense of Yang-Mills theories, the
Lorentz connection is not a gauge potential but an artificial force, the
inertial force. A genuine gravity theory should be a translation gauge theory,
though a unnormal gauge theory. All the three theories of the Geometrical
Trinity of Gravity are translation gauge theories. A real gravity theory should
get rid of "gauging" Lorentz group. The covariantization of the teleparallel
gravity is not necessary physically.
| [
{
"created": "Sat, 25 May 2024 03:08:16 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Lu",
"Jianbo",
""
],
[
"Guo",
"Yongxin",
""
],
[
"Chee",
"G. Y.",
""
]
] | In this paper, it is argued that in gravity theories the local Lorentz group can not be considered as a gauge group in the sense of Yang-Mills theories, the Lorentz connection is not a gauge potential but an artificial force, the inertial force. A genuine gravity theory should be a translation gauge theory, though a unnormal gauge theory. All the three theories of the Geometrical Trinity of Gravity are translation gauge theories. A real gravity theory should get rid of "gauging" Lorentz group. The covariantization of the teleparallel gravity is not necessary physically. |
1606.08775 | Mauricio Bellini | Juan Ignacio Musmarra, Mariano Anabitarte, Mauricio Bellini (IFIMAR -
CONICET & UNMdP) | Mass density of the Earth from a Gravito-Electro-Magnetic 5D vacuum | 9 pages, 2 figures | null | 10.1139/cjp-2017-0118 | null | gr-qc astro-ph.EP physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the mass density of the Earth using a Gravito-Electro-Magnetic
theory on an extended 5D Schwarzschild-de Sitter metric, in which we define the
vacuum. Our results are in very good agreement with that of the
Dziewonski-Anderson model.
| [
{
"created": "Tue, 28 Jun 2016 16:16:32 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Musmarra",
"Juan Ignacio",
"",
"IFIMAR -\n CONICET & UNMdP"
],
[
"Anabitarte",
"Mariano",
"",
"IFIMAR -\n CONICET & UNMdP"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR -\n CONICET & UNMdP"
]
] | We calculate the mass density of the Earth using a Gravito-Electro-Magnetic theory on an extended 5D Schwarzschild-de Sitter metric, in which we define the vacuum. Our results are in very good agreement with that of the Dziewonski-Anderson model. |
gr-qc/9504002 | J. Anandan | Jeeva Anandan | TOPOLOGICAL PHASES AND THEIR DUALITY IN ELECTROMAGNETIC AND
GRAVITATIONAL FIELDS | 17 pages, tex, no figures | null | null | null | gr-qc | null | The duality found by Aharonov and Casher for topological phases in the
electromagnetic field is generalized to an arbitrary linear interaction. This
provides a heuristic principle for obtaining a new solution of the field
equations from a known solution. This is applied to the general relativistic
Sagnac phase shift due to the gravitational field in the interference of mass
or energy around a line source that has angular momentum and the dual phase
shift in the interference of a spin around a line mass. These topological
phases are treated both in the linearized limit of general relativity and the
exact solutions for which the gravitational sources are cosmic strings
containing torsion and curvature, which do not have a Newtonian limit.
| [
{
"created": "Mon, 3 Apr 1995 22:34:16 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Apr 1995 14:13:51 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Anandan",
"Jeeva",
""
]
] | The duality found by Aharonov and Casher for topological phases in the electromagnetic field is generalized to an arbitrary linear interaction. This provides a heuristic principle for obtaining a new solution of the field equations from a known solution. This is applied to the general relativistic Sagnac phase shift due to the gravitational field in the interference of mass or energy around a line source that has angular momentum and the dual phase shift in the interference of a spin around a line mass. These topological phases are treated both in the linearized limit of general relativity and the exact solutions for which the gravitational sources are cosmic strings containing torsion and curvature, which do not have a Newtonian limit. |
0711.1057 | Ujjal Debnath | Soma Nath, Ujjal Debnath and Subenoy Chakraborty | Junction Conditions and Consequences of Quasi-Spherical Space-Time with
Electro-Magnetic Field and Vaidya Matric | 8 latex pages, RevTex style, no figures | Astrophys.SpaceSci.313:431-436,2008 | 10.1007/s10509-007-9713-3 | null | gr-qc | null | In this work the junction conditions between the exterior
Reissner-Nordstrom-Vaidya space-time with the interior quasi-spherical Szekeres
space-time have been studied for analyzing gravitational collapse in the
presence of a magneto-hydrodynamic fluid undergoing dissipation in the form of
heat flow. We have discussed about the apparent horizon and have evaluated the
time difference between the formation of apparent horizon and central
singularity.
| [
{
"created": "Wed, 7 Nov 2007 10:17:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nath",
"Soma",
""
],
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this work the junction conditions between the exterior Reissner-Nordstrom-Vaidya space-time with the interior quasi-spherical Szekeres space-time have been studied for analyzing gravitational collapse in the presence of a magneto-hydrodynamic fluid undergoing dissipation in the form of heat flow. We have discussed about the apparent horizon and have evaluated the time difference between the formation of apparent horizon and central singularity. |
1304.3591 | Yasuo Ezawa | Yasuo Ezawa and Yoshiaki Ohkuwa | Refined form of the paper "Canonical formalism of the f(R)-type gravity
in terms of Lie derivatives" | We refined and compactified the presentation of the previous paper
[arXiv:gr-qc/0507060] | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We refine the presentation of the previous paper of our group, Y.Ezawa et
al., Class. Quantum Grav. {\bf 23} (2006), 3205 [arXiv:gr-qc/0507060]. In that
paper, we proposed a canonical formalism of f(R)-type generalized gravity by
using the Lie derivatives instead of the time derivatives. However, the use of
the Lie derivatives was not sufficient. In this note, we make use of the Lie
derivatives as far as possible, so that no time derivatives are used.
| [
{
"created": "Fri, 12 Apr 2013 10:20:34 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Sep 2013 10:51:24 GMT",
"version": "v2"
}
] | 2013-09-17 | [
[
"Ezawa",
"Yasuo",
""
],
[
"Ohkuwa",
"Yoshiaki",
""
]
] | We refine the presentation of the previous paper of our group, Y.Ezawa et al., Class. Quantum Grav. {\bf 23} (2006), 3205 [arXiv:gr-qc/0507060]. In that paper, we proposed a canonical formalism of f(R)-type generalized gravity by using the Lie derivatives instead of the time derivatives. However, the use of the Lie derivatives was not sufficient. In this note, we make use of the Lie derivatives as far as possible, so that no time derivatives are used. |
gr-qc/0602045 | Gustav Holzegel | Gustav Holzegel | A Note on the Instability of Lorentzian Taub-NUT-Space | 13 pages, no figures | Class.Quant.Grav. 23 (2006) 3951-3962 | 10.1088/0264-9381/23/11/017 | DAMTP-2006-16 | gr-qc hep-th | null | I show that there are no SU(2)-invariant (time-dependent) tensorial
perturbations of Lorentzian Taub-NUT space. It follows that the spacetime is
unstable at the linear level against generic perturbations. I speculate that
this fact is responsible for so far unsuccessful attempts to define a sensible
thermodynamics for NUT-charged spacetimes.
| [
{
"created": "Mon, 13 Feb 2006 14:28:16 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Holzegel",
"Gustav",
""
]
] | I show that there are no SU(2)-invariant (time-dependent) tensorial perturbations of Lorentzian Taub-NUT space. It follows that the spacetime is unstable at the linear level against generic perturbations. I speculate that this fact is responsible for so far unsuccessful attempts to define a sensible thermodynamics for NUT-charged spacetimes. |
gr-qc/9504046 | null | H. T. Cho and A. D. Speliotopoulos | Gravitational Waves in Bianchi Type-I Universes I: The Classical Theory | 34 papers, written in ReVTeX, submitted to Physical Review D | Phys.Rev. D52 (1995) 5445-5458 | 10.1103/PhysRevD.52.5445 | IP-ASTP-08-95 | gr-qc astro-ph hep-th | null | The propagation of classical gravitational waves in Bianchi Type-I universes
is studied. We find that gravitational waves in Bianchi Type-I universes are
not equivalent to two minimally coupled massless scalar fields as it is for the
Robertson-Walker universe. Due to its tensorial nature, the gravitational wave
is much more sensitive to the anisotropy of the spacetime than the scalar field
is and it gains an effective mass term. Moreover, we find a coupling between
the two polarization states of the gravitational wave which is also not present
in the Robertson-Walker universe.
| [
{
"created": "Thu, 27 Apr 1995 01:06:08 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Cho",
"H. T.",
""
],
[
"Speliotopoulos",
"A. D.",
""
]
] | The propagation of classical gravitational waves in Bianchi Type-I universes is studied. We find that gravitational waves in Bianchi Type-I universes are not equivalent to two minimally coupled massless scalar fields as it is for the Robertson-Walker universe. Due to its tensorial nature, the gravitational wave is much more sensitive to the anisotropy of the spacetime than the scalar field is and it gains an effective mass term. Moreover, we find a coupling between the two polarization states of the gravitational wave which is also not present in the Robertson-Walker universe. |
0911.3090 | Kazuhiro Agatsuma | Kazuhiro Agatsuma, Koji Arai, Masa-Katsu Fujimoto, Seiji Kawamura,
Kazuaki Kuroda, Osamu Miyakawa, Shinji Miyoki, Masatake Ohashi, Toshikazu
Suzuki, Ryutaro Takahashi, Daisuke Tatsumi, Souichi Telada, Takashi Uchiyama,
Kazuhiro Yamamoto, and CLIO collaborators | Thermal-noise-limited underground interferometer CLIO | 10 pages, 6 figures, Proceedings of the 8th Edoardo Amaldi Conference
on Gravitational Waves | Class. Quantum Grav. 27 (2010) 084022 | 10.1088/0264-9381/27/8/084022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on the current status of CLIO (Cryogenic Laser Interferometer
Observatory), which is a prototype interferometer for LCGT (Large Scale
Cryogenic Gravitational-Wave Telescope). LCGT is a Japanese next-generation
interferometric gravitational wave detector featuring the use of cryogenic
mirrors and a quiet underground site. The main purpose of CLIO is to
demonstrate a reduction of the mirror thermal noise by cooling the sapphire
mirrors. CLIO is located in an underground site of the Kamioka mine, 1000 m
deep from the mountain top, to verify its advantages. After a few years of
commissioning work, we have achieved a thermal-noise-limited sensitivity at
room temperature. One of the main results of noise hunting was the elimination
of thermal noise caused by a conductive coil-holder coupled with a pendulum
through magnets.
| [
{
"created": "Mon, 16 Nov 2009 17:29:51 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jan 2010 14:36:23 GMT",
"version": "v2"
}
] | 2014-01-28 | [
[
"Agatsuma",
"Kazuhiro",
""
],
[
"Arai",
"Koji",
""
],
[
"Fujimoto",
"Masa-Katsu",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Kuroda",
"Kazuaki",
""
],
[
"Miyakawa",
"Osamu",
""
],
[
"Miyoki",
"Shinji",
""
],
[
"Ohashi",
"Masatake",
""
],
[
"Suzuki",
"Toshikazu",
""
],
[
"Takahashi",
"Ryutaro",
""
],
[
"Tatsumi",
"Daisuke",
""
],
[
"Telada",
"Souichi",
""
],
[
"Uchiyama",
"Takashi",
""
],
[
"Yamamoto",
"Kazuhiro",
""
],
[
"collaborators",
"CLIO",
""
]
] | We report on the current status of CLIO (Cryogenic Laser Interferometer Observatory), which is a prototype interferometer for LCGT (Large Scale Cryogenic Gravitational-Wave Telescope). LCGT is a Japanese next-generation interferometric gravitational wave detector featuring the use of cryogenic mirrors and a quiet underground site. The main purpose of CLIO is to demonstrate a reduction of the mirror thermal noise by cooling the sapphire mirrors. CLIO is located in an underground site of the Kamioka mine, 1000 m deep from the mountain top, to verify its advantages. After a few years of commissioning work, we have achieved a thermal-noise-limited sensitivity at room temperature. One of the main results of noise hunting was the elimination of thermal noise caused by a conductive coil-holder coupled with a pendulum through magnets. |
gr-qc/0408027 | Pedro Jose Pompeia P. J. Pompeia | B. M. Pimentel, P. J. Pompeia, J. F. da Rocha-Neto | The Hamilton-Jacobi Approach to Teleparallelism | 12 pages, no figure | Nuovo Cim.B120:981-992,2005 | 10.1393/ncb/i2005-10085-4 | null | gr-qc | null | We intend to analyse the constraint structure of Teleparallelism employing
the Hamilton-Jacobi formalism for singular systems. This study is conducted
without using an ADM 3+1 decomposition and without fixing time gauge condition.
It can be verified that the field equations constitute an integrable system.
| [
{
"created": "Tue, 10 Aug 2004 13:25:27 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jul 2005 18:02:04 GMT",
"version": "v2"
}
] | 2010-11-11 | [
[
"Pimentel",
"B. M.",
""
],
[
"Pompeia",
"P. J.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
]
] | We intend to analyse the constraint structure of Teleparallelism employing the Hamilton-Jacobi formalism for singular systems. This study is conducted without using an ADM 3+1 decomposition and without fixing time gauge condition. It can be verified that the field equations constitute an integrable system. |
1512.06253 | Oldrich Semerak | Old\v{r}ich Semer\'ak | Spinning particles in vacuum spacetimes of different curvature types:
Natural reference tetrads, and massless particles | 12 pages, no figures | Phys. Rev. D 92, 124036 (2015) | 10.1103/PhysRevD.92.124036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous paper, we considered the motion of massive spinning test
particles in the "pole-dipole" approximation, as described by the
Mathisson--Papapetrou--Dixon (MPD) equations, and examined its properties in
dependence on the spin supplementary condition. We decomposed the equations in
the orthonormal tetrad based on the time-like vector fixing the spin condition
and on the corresponding spin, while representing the curvature in terms of the
Weyl scalars obtained in the Newman--Penrose (NP) null tetrad naturally
associated with the orthonormal one; the projections thus obtained did not
contain the Weyl scalars $\Psi_0$ and $\Psi_4$. In the present paper, we choose
the interpretation tetrad in a different way, attaching it to the tangent
$u^\mu$ of the world-line representing the history of the spinning body.
Actually {\em two} tetrads are suggested, both given "intrinsically" by the
problem and each of them incompatible with one specific spin condition. The
decomposition of the MPD equation, again supplemented by writing its right-hand
side in terms of the Weyl scalars, is slightly less efficient than in the
massive case, because $u^\mu$ cannot be freely chosen (in contrast to $V^\mu$)
and so the $u^\mu$-based tetrad is less flexible. In the second part of this
paper, a similar analysis is performed for massless spinning particles; in
particular, a certain "intrinsic" interpretation tetrad is again found. The
respective decomposition of the MPD equation of motion is considerably simpler
than in the massive case, containing only $\Psi_1$ and $\Psi_2$ scalars and not
the cosmological constant. An option to span the spin-bivector eigen-plane,
besides the world-line null tangent, by a main principal null direction of the
Weyl tensor can lead to an even simpler result.
| [
{
"created": "Sat, 19 Dec 2015 14:09:35 GMT",
"version": "v1"
}
] | 2015-12-22 | [
[
"Semerák",
"Oldřich",
""
]
] | In a previous paper, we considered the motion of massive spinning test particles in the "pole-dipole" approximation, as described by the Mathisson--Papapetrou--Dixon (MPD) equations, and examined its properties in dependence on the spin supplementary condition. We decomposed the equations in the orthonormal tetrad based on the time-like vector fixing the spin condition and on the corresponding spin, while representing the curvature in terms of the Weyl scalars obtained in the Newman--Penrose (NP) null tetrad naturally associated with the orthonormal one; the projections thus obtained did not contain the Weyl scalars $\Psi_0$ and $\Psi_4$. In the present paper, we choose the interpretation tetrad in a different way, attaching it to the tangent $u^\mu$ of the world-line representing the history of the spinning body. Actually {\em two} tetrads are suggested, both given "intrinsically" by the problem and each of them incompatible with one specific spin condition. The decomposition of the MPD equation, again supplemented by writing its right-hand side in terms of the Weyl scalars, is slightly less efficient than in the massive case, because $u^\mu$ cannot be freely chosen (in contrast to $V^\mu$) and so the $u^\mu$-based tetrad is less flexible. In the second part of this paper, a similar analysis is performed for massless spinning particles; in particular, a certain "intrinsic" interpretation tetrad is again found. The respective decomposition of the MPD equation of motion is considerably simpler than in the massive case, containing only $\Psi_1$ and $\Psi_2$ scalars and not the cosmological constant. An option to span the spin-bivector eigen-plane, besides the world-line null tangent, by a main principal null direction of the Weyl tensor can lead to an even simpler result. |
gr-qc/0610089 | Arunava Bhadra Dr. | A. Bhadra, K. Sarkar and K. K. Nandi | Testing gravity at the Second post-Newtonian level through gravitational
deflection of massive particles | 5 pages, couple of equations of the previous version are corrected | Phys.Rev.D75:123004,2007 | 10.1103/PhysRevD.75.123004 | null | gr-qc | null | Expression for second post-Newtonian level gravitational deflection angle of
massive particles is obtained in a model independent framework. Several of its
important implications including the possibility of testing gravitational
theories at that level are discussed.
| [
{
"created": "Wed, 18 Oct 2006 11:07:46 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Dec 2006 08:08:52 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bhadra",
"A.",
""
],
[
"Sarkar",
"K.",
""
],
[
"Nandi",
"K. K.",
""
]
] | Expression for second post-Newtonian level gravitational deflection angle of massive particles is obtained in a model independent framework. Several of its important implications including the possibility of testing gravitational theories at that level are discussed. |
gr-qc/9709081 | Mikhail Volkov | O. Sarbach, N. Straumann, and M. S. Volkov | Internal structure of Einstein-Yang-Mills-Dilaton black holes | 6 pages, LaTeX, 4 eps figures, Talk given at the International
Workshop on the Internal Structure of Black Holes and Spacetime
Singularities, Haifa, Israel, June 29 - July 3, 1997 | null | null | null | gr-qc | null | We study the interior structure of the Einstein-Yang-Mills-Dilaton black
holes as a function of the dilaton coupling constant $\gamma\in [0,1]$. For
$\gamma\neq 0$ the solutions have no internal Cauchy horizons and the field
amplitudes follow a power law behavior near the singularity. As $\gamma$
decreases, the solutions develop more and more oscillation cycles in the
interior region, whose number becomes infinite in the limit $\gamma\to 0$.
| [
{
"created": "Tue, 30 Sep 1997 13:14:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sarbach",
"O.",
""
],
[
"Straumann",
"N.",
""
],
[
"Volkov",
"M. S.",
""
]
] | We study the interior structure of the Einstein-Yang-Mills-Dilaton black holes as a function of the dilaton coupling constant $\gamma\in [0,1]$. For $\gamma\neq 0$ the solutions have no internal Cauchy horizons and the field amplitudes follow a power law behavior near the singularity. As $\gamma$ decreases, the solutions develop more and more oscillation cycles in the interior region, whose number becomes infinite in the limit $\gamma\to 0$. |
1503.02480 | Sasa Ilijic | Dubravko Horvat, Sasa Ilijic, Anamarija Kirin, Zoran Narancic | Note on the charged boson stars with torsion-coupled field | 11 pages, 2 figures, v2: appendix added, matches published version | Phys. Rev. D 92, 024045 (2015) | 10.1103/PhysRevD.92.024045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of the extended teleparallel gravity, a new class of
boson stars has recently been constructed by introducing the nonminimal
coupling of the scalar field to the torsion scalar. An interesting feature of
these static, spherical, self-gravitating configurations of the massive complex
scalar field is their central region with outwardly increasing energy density,
surrounded by a thick shell within which the joining with the usual
asymptotically Schwarzschild tail takes place. In this work we extend the
original model with the $U(1)$ gauge field and we find that the combined effect
of the charge and coupling of the field to torsion leads to a significant
increase of the maximal mass and the particle number that can be supported
against gravity. We also show that some charged configurations preserve the
property of having the outwardly increasing energy density over the central
region, regardless of the fact that charging the configurations affects the
anisotropy of the pressures in the opposite way relative to that of the
field-to-torsion coupling terms.
| [
{
"created": "Mon, 9 Mar 2015 14:09:38 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Aug 2015 07:38:44 GMT",
"version": "v2"
}
] | 2015-08-31 | [
[
"Horvat",
"Dubravko",
""
],
[
"Ilijic",
"Sasa",
""
],
[
"Kirin",
"Anamarija",
""
],
[
"Narancic",
"Zoran",
""
]
] | Within the framework of the extended teleparallel gravity, a new class of boson stars has recently been constructed by introducing the nonminimal coupling of the scalar field to the torsion scalar. An interesting feature of these static, spherical, self-gravitating configurations of the massive complex scalar field is their central region with outwardly increasing energy density, surrounded by a thick shell within which the joining with the usual asymptotically Schwarzschild tail takes place. In this work we extend the original model with the $U(1)$ gauge field and we find that the combined effect of the charge and coupling of the field to torsion leads to a significant increase of the maximal mass and the particle number that can be supported against gravity. We also show that some charged configurations preserve the property of having the outwardly increasing energy density over the central region, regardless of the fact that charging the configurations affects the anisotropy of the pressures in the opposite way relative to that of the field-to-torsion coupling terms. |
1904.06325 | Avneet Singh | Avneet Singh, Maria Alessandra Papa, Vladimir Dergachev | Characterizing the sensitivity of isolated continuous gravitational wave
searches to binary orbits | 12 pages, 10 figures, 2 tables; v1: initial submission; v2: journal
submission (minor typos fixed); v3: published version; v4: typos corrected,
references updated | Phys. Rev. D 100, 024058 (2019) | 10.1103/PhysRevD.100.024058 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Broadband all-sky searches for continuous gravitational waves (CW) from
isolated neutron stars typically yield a number of significant candidates that
are discarded through hierarchical semi-coherent and coherent follow-up
searches. However, these searches target purely isolated sources and do not
take into account possible phase modulations to the signals due to companion
objects in binary orbits. If the source object is in a binary orbit, the
signal-to-noise ratio (SNR) of a signal will diminish due to the mismatch
between the signal waveform and the template waveform used in the search. In
this paper, we investigate the sensitivity of CW searches to signals from
sources in binary systems over an exhaustive range of binary orbits. We use
Monte-Carlo simulations to constrain the ranges of binary orbital parameters
that leave a CW signal from a source in a binary orbit visible in a search for
signals from an isolated source (isolated searches), and consequently tighten
the parameter space explorable with dedicated searches for signals from sources
in binary systems (binary searches).
| [
{
"created": "Fri, 12 Apr 2019 17:04:53 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Apr 2019 22:43:35 GMT",
"version": "v2"
},
{
"created": "Tue, 30 Jul 2019 16:47:01 GMT",
"version": "v3"
},
{
"created": "Wed, 28 Jul 2021 08:02:55 GMT",
"version": "v4"
}
] | 2021-07-29 | [
[
"Singh",
"Avneet",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Dergachev",
"Vladimir",
""
]
] | Broadband all-sky searches for continuous gravitational waves (CW) from isolated neutron stars typically yield a number of significant candidates that are discarded through hierarchical semi-coherent and coherent follow-up searches. However, these searches target purely isolated sources and do not take into account possible phase modulations to the signals due to companion objects in binary orbits. If the source object is in a binary orbit, the signal-to-noise ratio (SNR) of a signal will diminish due to the mismatch between the signal waveform and the template waveform used in the search. In this paper, we investigate the sensitivity of CW searches to signals from sources in binary systems over an exhaustive range of binary orbits. We use Monte-Carlo simulations to constrain the ranges of binary orbital parameters that leave a CW signal from a source in a binary orbit visible in a search for signals from an isolated source (isolated searches), and consequently tighten the parameter space explorable with dedicated searches for signals from sources in binary systems (binary searches). |
0804.1053 | Thierry Barbot | Thierry Barbot (UMPA-ENSL), Fran\c{c}ois B\'eguin (LM-Orsay),
Abdelghani Zeghib (UMPA-ENSL) | Prescribing Gauss curvature of surfaces in 3-dimensional spacetimes,
Application to the Minkowski problem in the Minkowski space | null | Universit\'e de Grenoble. Annales de l'Institut Fourier 61, 2
(2011) 511-591 | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the existence of surfaces with constant or prescribed Gauss
curvature in certain Lorentzian spacetimes. We prove in particular that every
(non-elementary) 3-dimensional maximal globally hyperbolic spatially compact
spacetime with constant non-negative curvature is foliated by compact spacelike
surfaces with constant Gauss curvature. In the constant negative curvature
case, such a foliation exists outside the convex core. The existence of these
foliations, together with a theorem of C. Gerhardt, yield several corollaries.
For example, they allow to solve the Minkowski problem in the 3-dimensional
Minkowski space for datas that are invariant under the action of a co-compact
Fuchsian group.
| [
{
"created": "Mon, 7 Apr 2008 15:06:03 GMT",
"version": "v1"
}
] | 2013-01-18 | [
[
"Barbot",
"Thierry",
"",
"UMPA-ENSL"
],
[
"Béguin",
"François",
"",
"LM-Orsay"
],
[
"Zeghib",
"Abdelghani",
"",
"UMPA-ENSL"
]
] | We study the existence of surfaces with constant or prescribed Gauss curvature in certain Lorentzian spacetimes. We prove in particular that every (non-elementary) 3-dimensional maximal globally hyperbolic spatially compact spacetime with constant non-negative curvature is foliated by compact spacelike surfaces with constant Gauss curvature. In the constant negative curvature case, such a foliation exists outside the convex core. The existence of these foliations, together with a theorem of C. Gerhardt, yield several corollaries. For example, they allow to solve the Minkowski problem in the 3-dimensional Minkowski space for datas that are invariant under the action of a co-compact Fuchsian group. |
1812.09056 | Claudio Paganini | Claudio F Paganini | Proposal 42 -- A new Storyline for the Universe based on the Causal
Fermion Systems Framework | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on preliminary results from the Causal Fermion Systems framework
regarding the matter-antimatter asymmetry in the universe, I propose a novel
story line for the universe that would, if correct, resolve a number of
problems in cosmology. First and foremost, the here-presented arguments suggest
to identify cold dark matter as third generation (anti-)neutrino
mass-eigenstates $\nu_3$. Furthermore, the proposal suggests a new look at the
problem of initial conditions. Last but not least, the proposal also provides a
new angle on the cosmological constant.
| [
{
"created": "Fri, 21 Dec 2018 11:22:21 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Oct 2019 13:58:47 GMT",
"version": "v2"
}
] | 2019-10-25 | [
[
"Paganini",
"Claudio F",
""
]
] | Based on preliminary results from the Causal Fermion Systems framework regarding the matter-antimatter asymmetry in the universe, I propose a novel story line for the universe that would, if correct, resolve a number of problems in cosmology. First and foremost, the here-presented arguments suggest to identify cold dark matter as third generation (anti-)neutrino mass-eigenstates $\nu_3$. Furthermore, the proposal suggests a new look at the problem of initial conditions. Last but not least, the proposal also provides a new angle on the cosmological constant. |
0909.3986 | Christian Boehmer | Christian G. Boehmer, Francisco S. N. Lobo | Stability of the Einstein static universe in IR modified Ho\v{r}ava
gravity | 9 pages, 5 figures; references added | Eur.Phys.J.C70:1111-1118,2010 | 10.1140/epjc/s10052-010-1503-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Horava proposed a power counting renormalizable theory for
(3+1)-dimensional quantum gravity, which reduces to Einstein gravity with a
non-vanishing cosmological constant in IR, but possesses improved UV behaviors.
In this work, we analyze the stability of the Einstein static universe by
considering linear homogeneous perturbations in the context of an IR
modification of Horava gravity, which implies a `soft' breaking of the
`detailed balance' condition. The stability regions of the Einstein static
universe are parameterized by the linear equation of state parameter w=p/\rho
and the parameters appearing in the Horava theory, and it is shown that a large
class of stable solutions exists in the respective parameter space.
| [
{
"created": "Tue, 22 Sep 2009 16:52:45 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Oct 2009 15:59:33 GMT",
"version": "v2"
}
] | 2011-02-09 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | Recently, Horava proposed a power counting renormalizable theory for (3+1)-dimensional quantum gravity, which reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but possesses improved UV behaviors. In this work, we analyze the stability of the Einstein static universe by considering linear homogeneous perturbations in the context of an IR modification of Horava gravity, which implies a `soft' breaking of the `detailed balance' condition. The stability regions of the Einstein static universe are parameterized by the linear equation of state parameter w=p/\rho and the parameters appearing in the Horava theory, and it is shown that a large class of stable solutions exists in the respective parameter space. |
1806.02094 | Prado Martin-Moruno | Prado Martin-Moruno, Matt Visser | Hawking-Ellis type III spacetime geometry | 22 pages, 1 figure | null | 10.1088/1361-6382/aad473 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The type III (and the "essential core" type III$_0$) stress-energy tensors in
the Hawking-Ellis (Segre-Plebanski) classification stand out in that there is
to date no known source (either classical or semi-classical) leading to type
III stress-energy. (In contrast the Hawking-Ells types I and II occur
classically, and type IV is known to occur semi-classically). We instead start
by asking the obverse question: What sort of spacetime (assuming the Einstein
equations) needs a type III stress-energy to support it? One key observation is
that type III is incompatible with either planar or spherical symmetry, so one
should be looking at spacetimes of low symmetry (or no symmetry). Finding such
a type III spacetime is a matter of somehow finding an appropriate ansatz for
the metric, calculating the Einstein tensor, and analyzing the pattern of
(Lorentz invariant) eigenvalues and eigenvectors. Herein we report some
(partial) success along these lines - we explicitly exhibit several (somewhat
unnatural) spacetime geometries with a type III Einstein tensor. We then build
an explicit but somewhat odd Lagrangian model leading (in Minkowski space) to
type III stress-energy. While we still have no fully acceptable general
physical model for type III stress-energy, we can at least say something about
what such a stress-energy tensor would entail.
| [
{
"created": "Wed, 6 Jun 2018 10:06:45 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Martin-Moruno",
"Prado",
""
],
[
"Visser",
"Matt",
""
]
] | The type III (and the "essential core" type III$_0$) stress-energy tensors in the Hawking-Ellis (Segre-Plebanski) classification stand out in that there is to date no known source (either classical or semi-classical) leading to type III stress-energy. (In contrast the Hawking-Ells types I and II occur classically, and type IV is known to occur semi-classically). We instead start by asking the obverse question: What sort of spacetime (assuming the Einstein equations) needs a type III stress-energy to support it? One key observation is that type III is incompatible with either planar or spherical symmetry, so one should be looking at spacetimes of low symmetry (or no symmetry). Finding such a type III spacetime is a matter of somehow finding an appropriate ansatz for the metric, calculating the Einstein tensor, and analyzing the pattern of (Lorentz invariant) eigenvalues and eigenvectors. Herein we report some (partial) success along these lines - we explicitly exhibit several (somewhat unnatural) spacetime geometries with a type III Einstein tensor. We then build an explicit but somewhat odd Lagrangian model leading (in Minkowski space) to type III stress-energy. While we still have no fully acceptable general physical model for type III stress-energy, we can at least say something about what such a stress-energy tensor would entail. |
0708.1153 | Yuri Obukhov | Yuri N. Obukhov, Friedrich W. Hehl | Electrodynamics of moving magnetoelectric media: variational approach | Revtex, 18 pages, no figures, | Phys.Lett.A371:11-19,2007 | 10.1016/j.physleta.2007.08.026 | null | gr-qc cond-mat.other physics.class-ph | null | Recently, Feigel has predicted a new effect in magnetoelectric media. The
theoretical evaluation of this effect requires a careful analysis of a dynamics
of the moving magnetoelectric medium and, in particular, the derivation of the
energy-momentum of the electromagnetic field in such a medium. Then, one can
proceed with the study of the wave propagation in this medium and derive the
mechanical quantities such as the energy, the momentum, and their fluxes and
the corresponding forces. In this paper, we develop a consistent
general-relativistic variational approach to the moving dielectric and magnetic
medium with and without magnetoelectric properties. The old experiments in
which the light pressure was measured in fluids are reanalysed in our new
framework.
| [
{
"created": "Wed, 8 Aug 2007 18:07:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | Recently, Feigel has predicted a new effect in magnetoelectric media. The theoretical evaluation of this effect requires a careful analysis of a dynamics of the moving magnetoelectric medium and, in particular, the derivation of the energy-momentum of the electromagnetic field in such a medium. Then, one can proceed with the study of the wave propagation in this medium and derive the mechanical quantities such as the energy, the momentum, and their fluxes and the corresponding forces. In this paper, we develop a consistent general-relativistic variational approach to the moving dielectric and magnetic medium with and without magnetoelectric properties. The old experiments in which the light pressure was measured in fluids are reanalysed in our new framework. |
0901.3511 | Alberto Vecchiato | Mariateresa Crosta (1), Alberto Vecchiato (1) ((1) INAF - Astronomical
Observatory of Torino) | Physical Reference Frames and Astrometric Measurements of Star Direction
in General Relativity \\I. Stellar Aberration | 22 pages, 2 figures. Submitted to Phys. Rev. D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The high accuracy of modern space astrometry requires the use of General
Relativity to model the propagation of stellar light through the gravitational
field encountered from a source to a given observer inside the Solar System. In
this sense relativistic astrometry is part of fundamental physics. The general
relativistic definition of astrometric measurement needs an appropriate use of
the concept of reference frame, which should then be linked to the conventions
of the IAU Resolutions (2000), which fix the celestial coordinate system. A
consistent definition of the astrometric observables in the context of General
Relativity is also essential to find uniquely the stellar coordinates and
proper motion, this being the main physical task of the inverse ray tracing
problem. Aim of this work is to set the level of reciprocal consistency of two
relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to garantee a
physically correct definition of light direction to a star, an essential item
for deducing the star coordinates and proper motion within the same level of
measurement accuracy.
| [
{
"created": "Thu, 22 Jan 2009 16:21:13 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Feb 2009 12:51:36 GMT",
"version": "v2"
}
] | 2009-02-17 | [
[
"Crosta",
"Mariateresa",
""
],
[
"Vecchiato",
"Alberto",
""
]
] | The high accuracy of modern space astrometry requires the use of General Relativity to model the propagation of stellar light through the gravitational field encountered from a source to a given observer inside the Solar System. In this sense relativistic astrometry is part of fundamental physics. The general relativistic definition of astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU Resolutions (2000), which fix the celestial coordinate system. A consistent definition of the astrometric observables in the context of General Relativity is also essential to find uniquely the stellar coordinates and proper motion, this being the main physical task of the inverse ray tracing problem. Aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to garantee a physically correct definition of light direction to a star, an essential item for deducing the star coordinates and proper motion within the same level of measurement accuracy. |
1701.02239 | Mubasher Jamil | Mustapha Azreg-A\"inou, Sebastian Bahamonde, Mubasher Jamil | Strong Gravitational Lensing by a Charged Kiselev Black Hole | 14 pages, 5 figures, accepted for publication in Eur. Phys. J. C | Eur. Phys. J. C (2017) 77: 414 | 10.1140/epjc/s10052-017-4969-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravitational lensing scenario where the lens is a spherically
symmetric charged black hole (BH) surrounded by quintessence matter. The null
geodesic equations in the curved background of the black hole are derived. The
resulting trajectory equation is solved analytically via perturbation and
series methods for special choice of parameters and the distance of the closest
approach to black hole is calculated. We also derive the lens equation giving
the bending angle of light in the curved background. In the strong field
approximation, the solution of the lens equation is also obtained for all
values of the quintessence parameter $w_q$. For all $w_q$, we show that there
are no stable closed null orbits and that corrections to the deflection angle
for the Reissner-Nordstr\"om black hole when the observer and the source are at
large, but finite, distances from the lens do not depend on the charge up to
the inverse of the distances squared. A part of the present work, analyzed
however with a different approach, is the extension of {\it Phys. Rev. D
\textbf{92}, 084042 (2015)} where the uncharged case has been treated
| [
{
"created": "Thu, 5 Jan 2017 05:15:04 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jun 2017 05:11:02 GMT",
"version": "v2"
}
] | 2017-06-21 | [
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Bahamonde",
"Sebastian",
""
],
[
"Jamil",
"Mubasher",
""
]
] | We study the gravitational lensing scenario where the lens is a spherically symmetric charged black hole (BH) surrounded by quintessence matter. The null geodesic equations in the curved background of the black hole are derived. The resulting trajectory equation is solved analytically via perturbation and series methods for special choice of parameters and the distance of the closest approach to black hole is calculated. We also derive the lens equation giving the bending angle of light in the curved background. In the strong field approximation, the solution of the lens equation is also obtained for all values of the quintessence parameter $w_q$. For all $w_q$, we show that there are no stable closed null orbits and that corrections to the deflection angle for the Reissner-Nordstr\"om black hole when the observer and the source are at large, but finite, distances from the lens do not depend on the charge up to the inverse of the distances squared. A part of the present work, analyzed however with a different approach, is the extension of {\it Phys. Rev. D \textbf{92}, 084042 (2015)} where the uncharged case has been treated |
0707.2613 | Hongwei Yu | Hongwei Yu, Wenting Zhou | Do static atoms outside a Schwarzschild black hole spontaneously excite? | 15 pages, no figures, to be published in PRD | Phys.Rev.D76:044023,2007 | 10.1103/PhysRevD.76.044023 | null | gr-qc hep-th | null | The spontaneous excitation of a two-level atom held static outside a four
dimensional Schwarzschild black hole and in interaction with a massless scalar
field in the Boulware, Unruh and Hartle-Hawking vacuum is investigated and the
contributions of the vacuum fluctuations and radiation reaction to the rate of
change of the mean atomic energy are calculated separately. We find that for
the Boulware vacuum, the spontaneous excitation does not occur and the ground
state atoms are stable, while the spontaneous emission rate for excited atoms
in the Boulware vacuum, which is well-behaved at the event horizon, is not the
same as that in the usual Minkowski vacuum. However, both for the Unruh vacuum
and the Hartle-Hawking vacuum, our results show that the atom would
spontaneously excite, as if there were an outgoing thermal flux of radiation or
as if it were in a thermal bath of radiation at a proper temperature which
reduces to the Hawking temperature in the spatial asymptotic region, depending
on whether the scalar field is in the Unruh or Hartle-Hawking vacuum.
| [
{
"created": "Wed, 18 Jul 2007 00:20:27 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Yu",
"Hongwei",
""
],
[
"Zhou",
"Wenting",
""
]
] | The spontaneous excitation of a two-level atom held static outside a four dimensional Schwarzschild black hole and in interaction with a massless scalar field in the Boulware, Unruh and Hartle-Hawking vacuum is investigated and the contributions of the vacuum fluctuations and radiation reaction to the rate of change of the mean atomic energy are calculated separately. We find that for the Boulware vacuum, the spontaneous excitation does not occur and the ground state atoms are stable, while the spontaneous emission rate for excited atoms in the Boulware vacuum, which is well-behaved at the event horizon, is not the same as that in the usual Minkowski vacuum. However, both for the Unruh vacuum and the Hartle-Hawking vacuum, our results show that the atom would spontaneously excite, as if there were an outgoing thermal flux of radiation or as if it were in a thermal bath of radiation at a proper temperature which reduces to the Hawking temperature in the spatial asymptotic region, depending on whether the scalar field is in the Unruh or Hartle-Hawking vacuum. |
0911.3759 | Anil Yadav dr | Anil Kumar Yadav | Thermodynamical Behaviour of Inhomogeneous Universe with Varying
$\Lambda$ in Presence of Electromagnetic Field | 19 pages, 2 figures | Int. J. Theor. Phys. 49:1140-1154, 2010 | 10.1007/s10773-010-0295-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermodynamical Behaviour of Inhomogeneous Universe with Varying $ \Lambda $
in Presence of Electromagnetic Field is obtained. $ F_{12} $ is the
non-vanishing component of electromagnetic field tensor. To get a deterministic
solution, it is assumed that the free gravitational field is Petrov type-II
non-degenerate.The value of cosmological constant is found to be small and
pasitive supported by recent results from the supernovae observations recently
obtained by High-Z Supernovae Ia Team and Supernovae Cosmological Project. A
relation between cosmological constant and thermodynamical quantities is
established. Some physical and geometric properties of the model are also
discussed.
| [
{
"created": "Thu, 19 Nov 2009 16:47:33 GMT",
"version": "v1"
}
] | 2010-04-22 | [
[
"Yadav",
"Anil Kumar",
""
]
] | Thermodynamical Behaviour of Inhomogeneous Universe with Varying $ \Lambda $ in Presence of Electromagnetic Field is obtained. $ F_{12} $ is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, it is assumed that the free gravitational field is Petrov type-II non-degenerate.The value of cosmological constant is found to be small and pasitive supported by recent results from the supernovae observations recently obtained by High-Z Supernovae Ia Team and Supernovae Cosmological Project. A relation between cosmological constant and thermodynamical quantities is established. Some physical and geometric properties of the model are also discussed. |
gr-qc/9910027 | Soumya D. Mohanty | Soumya D. Mohanty (Center for Gravitational Physics and Geometry, Penn
State) | A Robust Test for Detecting Non-Stationarity in Data from Gravitational
Wave Detectors | Final version as published | Phys.Rev.D61:122002,2000 | 10.1103/PhysRevD.61.122002 | CGPG-99/10-1 | gr-qc astro-ph physics.data-an | null | It is difficult to choose detection thresholds for tests of non-stationarity
that assume {\em a priori} a noise model if the data is statistically
uncharacterized to begin with. This is a potentially serious problem when an
automated analysis is required, as would be the case for the huge data sets
that large interferometric gravitational wave detectors will produce. A
solution is proposed in the form of a {\em robust} time-frequency test for
detecting non-stationarity whose threshold for a specified false alarm rate is
almost independent of the statistical nature of the ambient stationary noise.
The efficiency of this test in detecting bursts is compared with that of an
ideal test that requires prior information about both the statistical
distribution of the noise and also the frequency band of the burst. When
supplemented with an approximate knowledge of the burst duration, this test can
detect, at the same false alarm rate and detection probability, bursts that are
about 3 times larger in amplitude than those that the ideal test can detect.
Apart from being robust, this test has properties which make it suitable as an
online monitor of stationarity.
| [
{
"created": "Thu, 7 Oct 1999 14:58:14 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Nov 1999 18:39:06 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Jun 2000 18:15:31 GMT",
"version": "v3"
}
] | 2009-12-30 | [
[
"Mohanty",
"Soumya D.",
"",
"Center for Gravitational Physics and Geometry, Penn\n State"
]
] | It is difficult to choose detection thresholds for tests of non-stationarity that assume {\em a priori} a noise model if the data is statistically uncharacterized to begin with. This is a potentially serious problem when an automated analysis is required, as would be the case for the huge data sets that large interferometric gravitational wave detectors will produce. A solution is proposed in the form of a {\em robust} time-frequency test for detecting non-stationarity whose threshold for a specified false alarm rate is almost independent of the statistical nature of the ambient stationary noise. The efficiency of this test in detecting bursts is compared with that of an ideal test that requires prior information about both the statistical distribution of the noise and also the frequency band of the burst. When supplemented with an approximate knowledge of the burst duration, this test can detect, at the same false alarm rate and detection probability, bursts that are about 3 times larger in amplitude than those that the ideal test can detect. Apart from being robust, this test has properties which make it suitable as an online monitor of stationarity. |
2109.15054 | Parth Bambhaniya | Parth Bambhaniya, Saurabh K, Kimet Jusufi, Pankaj S. Joshi | Thin accretion disk in the Simpson-Visser black-bounce and wormhole
spacetimes | 9 pages, 8 figures | Published in Phys. Rev. D, 2022 | 10.1103/PhysRevD.105.023021 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We compare the optical appearance of a thin accretion disk in the
Simpson-Visser spacetime to the Schwarzschild black hole case in this paper. We
calculate and illustrate the red-shift and observed flux distributions as
viewed by distant observers at various inclination angles. Simpson-Visser
family of metrics create Novikov-Thorne (NT) accretion disks images that nearly
look like a Schwarzschild black hole's NT accretion disk. We have studied also
the embedding diagram, the electromagnetic properties of the accretion disk
such as the temperature and the radiation flux of the energy by the accretion
disk and the accretion efficiency. Compared to the Schwarzschild black hole, we
find that the temperature, radiation flux of the energy, and the luminosity of
the accretion disk increase by increasing the regularization parameter $'l'$.
We conclude that, based on astrophysical observational signatures in the
properties of the electromagnetic spectrum, we can distinguish the wormhole
geometries from the regular black holes (black-bounce) and the Schwarzschild
black hole.
| [
{
"created": "Thu, 30 Sep 2021 12:16:58 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Jan 2022 12:13:16 GMT",
"version": "v2"
}
] | 2022-02-01 | [
[
"Bambhaniya",
"Parth",
""
],
[
"K",
"Saurabh",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We compare the optical appearance of a thin accretion disk in the Simpson-Visser spacetime to the Schwarzschild black hole case in this paper. We calculate and illustrate the red-shift and observed flux distributions as viewed by distant observers at various inclination angles. Simpson-Visser family of metrics create Novikov-Thorne (NT) accretion disks images that nearly look like a Schwarzschild black hole's NT accretion disk. We have studied also the embedding diagram, the electromagnetic properties of the accretion disk such as the temperature and the radiation flux of the energy by the accretion disk and the accretion efficiency. Compared to the Schwarzschild black hole, we find that the temperature, radiation flux of the energy, and the luminosity of the accretion disk increase by increasing the regularization parameter $'l'$. We conclude that, based on astrophysical observational signatures in the properties of the electromagnetic spectrum, we can distinguish the wormhole geometries from the regular black holes (black-bounce) and the Schwarzschild black hole. |
2304.14430 | Hiroki Takeda | Hiroki Takeda, Yusuke Manita, Hidetoshi Omiya, Takahiro Tanaka | Scalar polarization window in gravitational-wave signals | 18 pages | Prog Theor Exp Phys (2023) | 10.1093/ptep/ptad082 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar polarization modes of gravitational waves, which are often introduced
in the context of the viable extension of gravity, have been actively searched.
However, couplings of the scalar modes to the matter are strongly constrained
by the fifth-force experiments. Thus, the amplitude of scalar polarization in
the observed gravitational-wave signal must be significantly suppressed
compared to that of the tensor modes. Here, we discuss the implications of the
experiments in the solar system on the detectability of scalar modes in
gravitational waves from compact binary coalescences, taking into account the
whole processes from the generation to the observation of gravitational waves.
We first claim that the energy carried by the scalar modes at the generation
is, at most, that of the tensor modes from the observed phase evolution of the
inspiral gravitational waves. Next, we formulate general gravitational-wave
propagation and point out that the energy flux hardly changes through
propagation as long as the background changes slowly compared to the wavelength
of the propagating waves. Finally, we show that the possible magnitude of
scalar polarization modes detected by the ground-based gravitational-wave
telescopes is already severely constrained by the existing gravity tests in the
solar system.
| [
{
"created": "Thu, 27 Apr 2023 18:00:00 GMT",
"version": "v1"
}
] | 2023-07-19 | [
[
"Takeda",
"Hiroki",
""
],
[
"Manita",
"Yusuke",
""
],
[
"Omiya",
"Hidetoshi",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Scalar polarization modes of gravitational waves, which are often introduced in the context of the viable extension of gravity, have been actively searched. However, couplings of the scalar modes to the matter are strongly constrained by the fifth-force experiments. Thus, the amplitude of scalar polarization in the observed gravitational-wave signal must be significantly suppressed compared to that of the tensor modes. Here, we discuss the implications of the experiments in the solar system on the detectability of scalar modes in gravitational waves from compact binary coalescences, taking into account the whole processes from the generation to the observation of gravitational waves. We first claim that the energy carried by the scalar modes at the generation is, at most, that of the tensor modes from the observed phase evolution of the inspiral gravitational waves. Next, we formulate general gravitational-wave propagation and point out that the energy flux hardly changes through propagation as long as the background changes slowly compared to the wavelength of the propagating waves. Finally, we show that the possible magnitude of scalar polarization modes detected by the ground-based gravitational-wave telescopes is already severely constrained by the existing gravity tests in the solar system. |
1107.5274 | Simone Speziale | Mait\'e Dupuis, Laurent Freidel, Etera R. Livine, Simone Speziale | Holomorphic Lorentzian Simplicity Constraints | 20 pages. v2: explicit counting of the holomorphic constraints added,
and minor amendments | null | 10.1063/1.3692327 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop an Hamiltonian representation of the sl(2,C) algebra on a phase
space consisting of N copies of twistors, or bi-spinors. We identify a complete
set of global invariants, and show that they generate a closed algebra
including gl(N,C) as a subalgebra. Then, we define the linear and quadratic
simplicity constraints which reduce the spinor variables to (framed) 3d
spacelike polyhedra embedded in Minkowski spacetime. Finally, we introduce a
new version of the simplicity constraints which (i) are holomorphic and (ii)
Poisson-commute with each other, and show their equivalence to the linear and
quadratic constraints.
| [
{
"created": "Tue, 26 Jul 2011 17:52:57 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2012 12:54:16 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"Dupuis",
"Maité",
""
],
[
"Freidel",
"Laurent",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Speziale",
"Simone",
""
]
] | We develop an Hamiltonian representation of the sl(2,C) algebra on a phase space consisting of N copies of twistors, or bi-spinors. We identify a complete set of global invariants, and show that they generate a closed algebra including gl(N,C) as a subalgebra. Then, we define the linear and quadratic simplicity constraints which reduce the spinor variables to (framed) 3d spacelike polyhedra embedded in Minkowski spacetime. Finally, we introduce a new version of the simplicity constraints which (i) are holomorphic and (ii) Poisson-commute with each other, and show their equivalence to the linear and quadratic constraints. |
1911.05561 | Fabrizio De Marchi | Fabrizio De Marchi and Gael Cascioli | Testing General Relativity in the Solar System: present and future
perspectives | 18 pages, 5 figures | null | 10.1088/1361-6382/ab6ae0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The increasing precision of spacecraft radiometric tracking data experienced
in the last number of years, coupled with the huge amount of data collected and
the long baselines of the available datasets, has made the direct observation
of Solar System dynamics possible, and in particular relativistic effects,
through the measurement of some key parameters as the post-Newtonian
parameters, the Nordtvedt parameter "eta" and the graviton mass. In this work
we investigate the potentialities of the datasets provided by the most
promising past, present and future interplanetary missions to draw a realistic
picture of the knowledge that can be reached in the next 10-15 years. To this
aim, we update the semi-analytical model originally developed for the
BepiColombo mission, to take into account planet-planet relativistic
interactions and eccentricity-induced effects and validate it against
well-established numerical models to assess the precision of the retrieval of
the parameters of interest. Before the analysis of the results we give a review
of some of the hypotheses and constrained analysis schemes that have been
proposed until now to overcome geometrical weaknessess and model degeneracies,
proving that these strategies introduce model inconsistencies. Finally we apply
our semi-analytical model to perform a covariance analysis on three samples of
interplanetary missions: 1) those for which data are available now (e.g.
Cassini, MESSENGER, MRO, Juno), 2) in the next years (BepiColombo) and 3) still
to be launched as JUICE and VERITAS (this latter is waiting for the approval).
| [
{
"created": "Wed, 13 Nov 2019 15:49:45 GMT",
"version": "v1"
}
] | 2020-06-17 | [
[
"De Marchi",
"Fabrizio",
""
],
[
"Cascioli",
"Gael",
""
]
] | The increasing precision of spacecraft radiometric tracking data experienced in the last number of years, coupled with the huge amount of data collected and the long baselines of the available datasets, has made the direct observation of Solar System dynamics possible, and in particular relativistic effects, through the measurement of some key parameters as the post-Newtonian parameters, the Nordtvedt parameter "eta" and the graviton mass. In this work we investigate the potentialities of the datasets provided by the most promising past, present and future interplanetary missions to draw a realistic picture of the knowledge that can be reached in the next 10-15 years. To this aim, we update the semi-analytical model originally developed for the BepiColombo mission, to take into account planet-planet relativistic interactions and eccentricity-induced effects and validate it against well-established numerical models to assess the precision of the retrieval of the parameters of interest. Before the analysis of the results we give a review of some of the hypotheses and constrained analysis schemes that have been proposed until now to overcome geometrical weaknessess and model degeneracies, proving that these strategies introduce model inconsistencies. Finally we apply our semi-analytical model to perform a covariance analysis on three samples of interplanetary missions: 1) those for which data are available now (e.g. Cassini, MESSENGER, MRO, Juno), 2) in the next years (BepiColombo) and 3) still to be launched as JUICE and VERITAS (this latter is waiting for the approval). |
1002.3605 | Arturo Avelino Huerta | Arturo Avelino and Ulises Nucamendi | Exploring a matter-dominated model with bulk viscosity to drive the
accelerated expansion of the Universe | 27 pages, 14 figures and 2 tables. Related works: arXiv:0811.3253v2,
arXiv:0801.1686 and arXiv:0810.0303. The irrelevant cases of the analysis of
the model were removed. Results unchanged | JCAP 1008:009,2010 | 10.1088/1475-7516/2010/08/009 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the viability of a bulk viscous matter-dominated Universe to
explain the present accelerated expansion of the Universe. The model is
composed by a pressureless fluid with bulk viscosity of the form \zeta =
\zeta_0 + \zeta_1 * H where \zeta_0 and \zeta_1 are constants and H is the
Hubble parameter. The pressureless fluid characterizes both the baryon and dark
matter components. We study the behavior of the Universe according to this
model analyzing the scale factor as well as some curvature scalars and the
matter density. On the other hand, we compute the best estimated values of
\zeta_0 and \zeta_1 using the type Ia Supernovae (SNe Ia) probe. We find that
from all the possible scenarios for the Universe, the preferred one by the best
estimated values of (\zeta_0, \zeta_1) is that of an expanding Universe
beginning with a Big- Bang, followed by a decelerated expansion at early times,
and with a smooth transition in recent times to an accelerated expansion epoch
that is going to continue forever. The predicted age of the Universe is a
little smaller than the mean value of the observational constraint coming from
the oldest globular clusters but it is still inside of the confidence interval
of this constraint. A drawback of the model is the violation of the local
second law of thermodynamics in redshifts z >= 1. However, when we assume
\zeta_1 = 0, the simple model \zeta = \zeta_0 evaluated at the best estimated
value for \zeta_0 satisfies the local second law of thermodynamics, the age of
the Universe is in perfect agreement with the constraint of globular clusters,
and it also has a Big-Bang, followed by a decelerated expansion with the smooth
transition to an accelerated expansion epoch in late times, that is going to
continue forever.
| [
{
"created": "Thu, 18 Feb 2010 20:11:13 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Aug 2010 23:25:46 GMT",
"version": "v2"
}
] | 2010-10-25 | [
[
"Avelino",
"Arturo",
""
],
[
"Nucamendi",
"Ulises",
""
]
] | We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity of the form \zeta = \zeta_0 + \zeta_1 * H where \zeta_0 and \zeta_1 are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. On the other hand, we compute the best estimated values of \zeta_0 and \zeta_1 using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (\zeta_0, \zeta_1) is that of an expanding Universe beginning with a Big- Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z >= 1. However, when we assume \zeta_1 = 0, the simple model \zeta = \zeta_0 evaluated at the best estimated value for \zeta_0 satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever. |
1712.08462 | Yuan K. Ha | Yuan K. Ha | The Horizon Energy of a Black Hole | Contributed paper to the Fourteenth Marcel Grossmann Meeting on
General Relativity, University of Rome "La Sapienza", Italy, 12 - 18 July
2015 (7 pages) arXiv admin note: text overlap with arXiv:1706.01768 | null | 10.1142/9789813226609_0324 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the energy distribution of a black hole in various spacetimes
as reckoned by a distant observer using the quasi-local energy approach. In
each case the horizon mass of a black hole: neutral, charged or rotating, is
found to be twice the irreducible mass observed at infinity. This is known as
the Horizon Mass Theorem. As a consequence, the electrostatic energy and the
rotational energy of a general black hole are all external quantities. Matter
carrying charges and spins could only lie outside the horizon. This result
could resolve several long-standing paradoxes related to known black hole
properties; such as why entropy is proportional to area and not to volume, the
information loss problem, the firewall problem, the internal structure and the
thin shell model of a black hole.
| [
{
"created": "Tue, 19 Dec 2017 23:36:26 GMT",
"version": "v1"
}
] | 2019-02-27 | [
[
"Ha",
"Yuan K.",
""
]
] | We investigate the energy distribution of a black hole in various spacetimes as reckoned by a distant observer using the quasi-local energy approach. In each case the horizon mass of a black hole: neutral, charged or rotating, is found to be twice the irreducible mass observed at infinity. This is known as the Horizon Mass Theorem. As a consequence, the electrostatic energy and the rotational energy of a general black hole are all external quantities. Matter carrying charges and spins could only lie outside the horizon. This result could resolve several long-standing paradoxes related to known black hole properties; such as why entropy is proportional to area and not to volume, the information loss problem, the firewall problem, the internal structure and the thin shell model of a black hole. |
2209.09328 | Angela D. V. Di Virgilio dr | Carlo Altucci, Francesco Bajardi Emilio Barchiesi, Andrea Basti,
Nicol\`o Beverini, Thomas Braun, Giorgio Carelli, Salvatore Capozziello,
Donatella Ciampini, Fabrizio Dav\`i, Gaetano De Luca, Roberto Devoti, Rita Di
Giovambattista, Giuseppe Di Somma, Giuseppe Di Stefano, Angela D.V. Di
Virgilio, Daniela Famiani, Alberto Frepoli, Francesco Fuso, Ivan Giorgio,
Aladino Govoni, Gaetano Lambiase, Enrico Maccioni, Paolo Marsili, Alessia
Mercuri, Fabio Morsani, Antonello Ortolan, Alberto Porzio, Matteo Luca
Ruggiero, Marco Tallini, Jay Tasson, Emilio Turco, Raffaele Velotta | GINGER | 21 pages, 9 figures | Math. Mech. Compl. Sys. 11 (2023) 203-234 | 10.2140/memocs.2023.11.203 | null | gr-qc physics.geo-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we outline the scientific objectives, the experimental layout,
and the collaborations envisaged for the GINGER (Gyroscopes IN GEneral
Relativity) project. The GINGER project brings together different scientific
disciplines aiming at building an array of Ring Laser Gyroscopes (RLGs),
exploiting the Sagnac effect, to measure continuously, with sensitivity better
than picorad/ s, large bandwidth (ca. 1 kHz), and high dynamic range, the
absolute angular rotation rate of the Earth. In the paper, we address the
feasibility of the apparatus with respect to the ambitious specifications
above, as well as prove how such an apparatus, which will be able to detect
strong Earthquakes, very weak geodetic signals, as well as general relativity
effects like Lense-Thirring and De Sitter, will help scientific advancements in
Theoretical Physics, Geophysics, and Geodesy, among other scientific fields.
| [
{
"created": "Mon, 19 Sep 2022 20:11:23 GMT",
"version": "v1"
}
] | 2023-11-15 | [
[
"Altucci",
"Carlo",
""
],
[
"Barchiesi",
"Francesco Bajardi Emilio",
""
],
[
"Basti",
"Andrea",
""
],
[
"Beverini",
"Nicolò",
""
],
[
"Braun",
"Thomas",
""
],
[
"Carelli",
"Giorgio",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Ciampini",
"Donatella",
""
],
[
"Davì",
"Fabrizio",
""
],
[
"De Luca",
"Gaetano",
""
],
[
"Devoti",
"Roberto",
""
],
[
"Di Giovambattista",
"Rita",
""
],
[
"Di Somma",
"Giuseppe",
""
],
[
"Di Stefano",
"Giuseppe",
""
],
[
"Di Virgilio",
"Angela D. V.",
""
],
[
"Famiani",
"Daniela",
""
],
[
"Frepoli",
"Alberto",
""
],
[
"Fuso",
"Francesco",
""
],
[
"Giorgio",
"Ivan",
""
],
[
"Govoni",
"Aladino",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Maccioni",
"Enrico",
""
],
[
"Marsili",
"Paolo",
""
],
[
"Mercuri",
"Alessia",
""
],
[
"Morsani",
"Fabio",
""
],
[
"Ortolan",
"Antonello",
""
],
[
"Porzio",
"Alberto",
""
],
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Tallini",
"Marco",
""
],
[
"Tasson",
"Jay",
""
],
[
"Turco",
"Emilio",
""
],
[
"Velotta",
"Raffaele",
""
]
] | In this paper, we outline the scientific objectives, the experimental layout, and the collaborations envisaged for the GINGER (Gyroscopes IN GEneral Relativity) project. The GINGER project brings together different scientific disciplines aiming at building an array of Ring Laser Gyroscopes (RLGs), exploiting the Sagnac effect, to measure continuously, with sensitivity better than picorad/ s, large bandwidth (ca. 1 kHz), and high dynamic range, the absolute angular rotation rate of the Earth. In the paper, we address the feasibility of the apparatus with respect to the ambitious specifications above, as well as prove how such an apparatus, which will be able to detect strong Earthquakes, very weak geodetic signals, as well as general relativity effects like Lense-Thirring and De Sitter, will help scientific advancements in Theoretical Physics, Geophysics, and Geodesy, among other scientific fields. |
2201.04629 | Ekim Taylan Han{\i}meli | Ekim Taylan Han{\i}meli, Isaac Tutusaus, Brahim Lamine, Alain
Blanchard | Can Dark Energy Emerge from a Varying $G$ and Spacetime Geometry? | Prepared for the proceedings of Alternative Gravities and Fundamental
Cosmology - ALTECOSMOFUN'21 (https://indico.cern.ch/event/873762/)
conference. Matches the version published at Universe Special Issue:
Alternative Gravities and Fundamental Cosmology | Universe 2022, 8, 148 | 10.3390/universe8030148 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerated expansion of the universe implies the existence of an energy
contribution known as dark energy. Associated with the cosmological constant in
the standard model of cosmology, the nature of this dark energy is still
unknown. We will discuss an alternative gravity model in which this dark energy
contribution emerges naturally, as a result of allowing for a time-dependence
on the gravitational constant, $G$, in Einstein's field equations. With this
modification, Bianchi's identities require an additional tensor field to be
introduced so that the usual conservation equation for matter and radiation is
satisfied. The equation of state of this tensor field is obtained using
additional constraints, coming from the assumption that this tensor field
represents the space-time response to the variation of $G$. We will also
present the predictions of this model for the late-universe data, and show that
the energy contribution of this new tensor is able to explain the accelerated
expansion of the universe without the addition of a cosmological constant.
Unlike many other alternative gravities with varying gravitational strength,
the predicted $G$ evolution is also consistent with local observations and
therefore this model does not require screening. We will finish by discussing
possible other implications this approach might have for cosmology and some
future prospects.
| [
{
"created": "Wed, 12 Jan 2022 09:18:15 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2022 09:02:45 GMT",
"version": "v2"
}
] | 2022-03-01 | [
[
"Hanımeli",
"Ekim Taylan",
""
],
[
"Tutusaus",
"Isaac",
""
],
[
"Lamine",
"Brahim",
""
],
[
"Blanchard",
"Alain",
""
]
] | The accelerated expansion of the universe implies the existence of an energy contribution known as dark energy. Associated with the cosmological constant in the standard model of cosmology, the nature of this dark energy is still unknown. We will discuss an alternative gravity model in which this dark energy contribution emerges naturally, as a result of allowing for a time-dependence on the gravitational constant, $G$, in Einstein's field equations. With this modification, Bianchi's identities require an additional tensor field to be introduced so that the usual conservation equation for matter and radiation is satisfied. The equation of state of this tensor field is obtained using additional constraints, coming from the assumption that this tensor field represents the space-time response to the variation of $G$. We will also present the predictions of this model for the late-universe data, and show that the energy contribution of this new tensor is able to explain the accelerated expansion of the universe without the addition of a cosmological constant. Unlike many other alternative gravities with varying gravitational strength, the predicted $G$ evolution is also consistent with local observations and therefore this model does not require screening. We will finish by discussing possible other implications this approach might have for cosmology and some future prospects. |
gr-qc/9506076 | null | Giampiero Esposito, Hugo A. Morales-Tecotl, Giuseppe Pollifrone | Boundary Terms for Massless Fermionic Fields | 8 pages, plain-tex, recently appearing in Foundations of Physics
Letters, volume 7, pages 303-308, year 1994 | Found.Phys.Lett. 7 (1994) 303-308 | null | DSF 93/27 | gr-qc | null | Local supersymmetry leads to boundary conditions for fermionic fields in
one-loop quantum cosmology involving the Euclidean normal to the boundary and a
pair of independent spinor fields. This paper studies the corresponding
classical properties, i.e. the classical boundary-value problem and boundary
terms in the variational problem. Interestingly, a link is found with the
classical boundary-value problem when spectral boundary conditions are imposed
on a 3-sphere in the massless case. Moreover, the boundary term in the action
functional is derived.
| [
{
"created": "Thu, 29 Jun 1995 12:38:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Esposito",
"Giampiero",
""
],
[
"Morales-Tecotl",
"Hugo A.",
""
],
[
"Pollifrone",
"Giuseppe",
""
]
] | Local supersymmetry leads to boundary conditions for fermionic fields in one-loop quantum cosmology involving the Euclidean normal to the boundary and a pair of independent spinor fields. This paper studies the corresponding classical properties, i.e. the classical boundary-value problem and boundary terms in the variational problem. Interestingly, a link is found with the classical boundary-value problem when spectral boundary conditions are imposed on a 3-sphere in the massless case. Moreover, the boundary term in the action functional is derived. |
2005.07294 | Lior M. Burko | Lior M. Burko, Gaurav Khanna, and Subir Sabharwal | Scalar and gravitational hair for extreme Kerr black holes | 4 pages, 5 figures | Phys. Rev. D 103, 021502 (2021) | 10.1103/PhysRevD.103.L021502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For scalar perturbations of an extreme Reissner-Nordstr{\" o}m black hole we
show numerically that the Ori pre-factor equals the Aretakis conserved charge.
We demonstrate a linear relation of a generalized Ori pre-factor -- a certain
expression obtained from the late-time expansion or the perturbation field at
finite distances -- and the Aretakis conserved charge for a family of scalar or
gravitational perturbations of an extreme Kerr black hole, whose members vary
only in the radial location of the center of the initial packet. We infer that
it can be established that there is an Aretakis conserved charge for scalar or
gravitational perturbations of extreme Kerr black holes. This conclusion, in
addition to the calculation of the Aretakis charge, can be made from
measurements at a finite distance: Extreme Kerr black holes have gravitational
hair that can be measured at finite distances. This gravitational hair can in
principle be detected by gravitational-wave detectors.
| [
{
"created": "Thu, 14 May 2020 23:28:46 GMT",
"version": "v1"
}
] | 2021-09-08 | [
[
"Burko",
"Lior M.",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Sabharwal",
"Subir",
""
]
] | For scalar perturbations of an extreme Reissner-Nordstr{\" o}m black hole we show numerically that the Ori pre-factor equals the Aretakis conserved charge. We demonstrate a linear relation of a generalized Ori pre-factor -- a certain expression obtained from the late-time expansion or the perturbation field at finite distances -- and the Aretakis conserved charge for a family of scalar or gravitational perturbations of an extreme Kerr black hole, whose members vary only in the radial location of the center of the initial packet. We infer that it can be established that there is an Aretakis conserved charge for scalar or gravitational perturbations of extreme Kerr black holes. This conclusion, in addition to the calculation of the Aretakis charge, can be made from measurements at a finite distance: Extreme Kerr black holes have gravitational hair that can be measured at finite distances. This gravitational hair can in principle be detected by gravitational-wave detectors. |
gr-qc/9511062 | Fintan Ryan | Fintan D. Ryan | Effect of gravitational radiation reaction on nonequatorial orbits
around a Kerr black hole | Uses REVTEX 3.0 | Phys.Rev.D53:3064-3069,1996 | 10.1103/PhysRevD.53.3064 | null | gr-qc | null | The effect of gravitational radiation reaction on orbits around a spinning
black hole is analyzed. Such orbits possess three constants of motion: $\iota$,
$e$, and $a$, which correspond, in the Newtonian limit of the orbit being an
ellipse, to the inclination angle of the orbital plane to the hole's equatorial
plane, the eccentricity, and the semi-major axis length, respectively. First,
it is argued that circular orbits ($e=0$) remain circular under gravitational
radiation reaction. Second, for elliptical orbits (removing the restriction of
$e=0$), the evolution of $\iota$, $e$, and $a$ is computed to leading order in
$S$ (the magnitude of the spin angular momentum of the hole) and in $M/a$,
where $M$ is the mass of the black hole. As $a$ decreases, $\iota$ increases
and $e$ decreases.
| [
{
"created": "Wed, 22 Nov 1995 20:21:53 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Ryan",
"Fintan D.",
""
]
] | The effect of gravitational radiation reaction on orbits around a spinning black hole is analyzed. Such orbits possess three constants of motion: $\iota$, $e$, and $a$, which correspond, in the Newtonian limit of the orbit being an ellipse, to the inclination angle of the orbital plane to the hole's equatorial plane, the eccentricity, and the semi-major axis length, respectively. First, it is argued that circular orbits ($e=0$) remain circular under gravitational radiation reaction. Second, for elliptical orbits (removing the restriction of $e=0$), the evolution of $\iota$, $e$, and $a$ is computed to leading order in $S$ (the magnitude of the spin angular momentum of the hole) and in $M/a$, where $M$ is the mass of the black hole. As $a$ decreases, $\iota$ increases and $e$ decreases. |
1808.03635 | Zhen Zhong | Yuyu Mo, Yu Tian, Bin Wang, Hongbao Zhang, and Zhen Zhong | Strong cosmic censorship for the massless charged scalar field in the
Reissner-Nordstrom-de Sitter spacetime | figures refined and added, references updated and added, version to
appear in Physical Review D | Phys. Rev. D 98, 124025 (2018) | 10.1103/PhysRevD.98.124025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been shown that the strong cosmic censorship conjecture can
be violated by the massless neutral scalar field in the nearly extremal
Reissner-Nordstrom-de Sitter black hole. However, the formation of such a black
hole by gravitational collapse necessitates the presence of the charged sector
on top of the Einstein-Maxwell system. Thus we numerically calculate the
quasi-normal modes for a massless charged scalar field in the
Reissner-Nordstrom-de Sitter spacetime by generalizing the characteristic
formulation to the charged case. As a result, the strong cosmic censorship
turns out to be recovered by our massless charged scalar field except in the
highly extremal limit $Q\rightarrow Q_m$, where the violation still occurs when
the scalar field is appropriately charged.
| [
{
"created": "Fri, 10 Aug 2018 17:47:21 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Dec 2018 04:35:24 GMT",
"version": "v2"
}
] | 2018-12-26 | [
[
"Mo",
"Yuyu",
""
],
[
"Tian",
"Yu",
""
],
[
"Wang",
"Bin",
""
],
[
"Zhang",
"Hongbao",
""
],
[
"Zhong",
"Zhen",
""
]
] | It has recently been shown that the strong cosmic censorship conjecture can be violated by the massless neutral scalar field in the nearly extremal Reissner-Nordstrom-de Sitter black hole. However, the formation of such a black hole by gravitational collapse necessitates the presence of the charged sector on top of the Einstein-Maxwell system. Thus we numerically calculate the quasi-normal modes for a massless charged scalar field in the Reissner-Nordstrom-de Sitter spacetime by generalizing the characteristic formulation to the charged case. As a result, the strong cosmic censorship turns out to be recovered by our massless charged scalar field except in the highly extremal limit $Q\rightarrow Q_m$, where the violation still occurs when the scalar field is appropriately charged. |
2111.00542 | Vincenzo Ventriglia | Vincenzo Ventriglia | Gravitational self-force and conservative effects: a testing ground for
theories of gravity | 10 pages, 3 figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Considering extreme-mass-ratio inspirals along with the conservative dynamics
of gravitational self-force, we compare viable theories of gravity. In
particular, by examining a Schwarzschild background we analyse the
self-force-induced corrections to gauge-invariant benchmarks given by the
orbital frequency at the ISCO and the spin-precession rate. Moreover, following
an established indication of modifications to the equations of motion in
extended theories of gravity, we exploit a phenomenological approach, relying
on the variability of the gravitational constant G, to incorporate these
modifications. We find that conservative effects shape up to be a test-bed for
theories of gravity, allowing us to contrast General Relativity with competing
theories. By examining strong-field constraints, we highlight a wide margin of
investigation in the context of LISA Mission.
| [
{
"created": "Sun, 31 Oct 2021 16:46:33 GMT",
"version": "v1"
}
] | 2021-11-08 | [
[
"Ventriglia",
"Vincenzo",
""
]
] | Considering extreme-mass-ratio inspirals along with the conservative dynamics of gravitational self-force, we compare viable theories of gravity. In particular, by examining a Schwarzschild background we analyse the self-force-induced corrections to gauge-invariant benchmarks given by the orbital frequency at the ISCO and the spin-precession rate. Moreover, following an established indication of modifications to the equations of motion in extended theories of gravity, we exploit a phenomenological approach, relying on the variability of the gravitational constant G, to incorporate these modifications. We find that conservative effects shape up to be a test-bed for theories of gravity, allowing us to contrast General Relativity with competing theories. By examining strong-field constraints, we highlight a wide margin of investigation in the context of LISA Mission. |
1208.3034 | Aaron Zimmerman | Fan Zhang, Aaron Zimmerman, David A. Nichols, Yanbei Chen, Geoffrey
Lovelace, Keith D. Matthews, Robert Owen, Kip S. Thorne | Visualizing Spacetime Curvature via Frame-Drag Vortexes and Tidal
Tendexes II. Stationary Black Holes | 19 pages, 7 figures, v2: Changed to reflect published version
(changes made to color scales in Figs 5, 6, and 7 for consistent
conventions). v3: Fixed Ref 4 | Phys. Rev. D 86, 084049 (2012) | 10.1103/PhysRevD.86.084049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When one splits spacetime into space plus time, the Weyl curvature tensor
(which equals the Riemann tensor in vacuum) splits into two spatial, symmetric,
traceless tensors: the tidal field $E$, which produces tidal forces, and the
frame-drag field $B$, which produces differential frame dragging. In recent
papers, we and colleagues have introduced ways to visualize these two fields:
tidal tendex lines (integral curves of the three eigenvector fields of $E$) and
their tendicities (eigenvalues of these eigenvector fields); and the
corresponding entities for the frame-drag field: frame-drag vortex lines and
their vorticities. These entities fully characterize the vacuum Riemann tensor.
In this paper, we compute and depict the tendex and vortex lines, and their
tendicities and vorticities, outside the horizons of stationary (Schwarzschild
and Kerr) black holes; and we introduce and depict the black holes' horizon
tendicity and vorticity (the normal-normal components of $E$ and $B$ on the
horizon). For Schwarzschild and Kerr black holes, the horizon tendicity is
proportional to the horizon's intrinsic scalar curvature, and the horizon
vorticity is proportional to an extrinsic scalar curvature. We show that, for
horizon-penetrating time slices, all these entities ($E$, $B$, the tendex lines
and vortex lines, the lines' tendicities and vorticities, and the horizon
tendicities and vorticities) are affected only weakly by changes of slicing and
changes of spatial coordinates, within those slicing and coordinate choices
that are commonly used for black holes. [Abstract is abbreviated.]
| [
{
"created": "Wed, 15 Aug 2012 05:53:06 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Dec 2012 22:05:55 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Jan 2013 16:32:10 GMT",
"version": "v3"
}
] | 2013-02-01 | [
[
"Zhang",
"Fan",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Nichols",
"David A.",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Lovelace",
"Geoffrey",
""
],
[
"Matthews",
"Keith D.",
""
],
[
"Owen",
"Robert",
""
],
[
"Thorne",
"Kip S.",
""
]
] | When one splits spacetime into space plus time, the Weyl curvature tensor (which equals the Riemann tensor in vacuum) splits into two spatial, symmetric, traceless tensors: the tidal field $E$, which produces tidal forces, and the frame-drag field $B$, which produces differential frame dragging. In recent papers, we and colleagues have introduced ways to visualize these two fields: tidal tendex lines (integral curves of the three eigenvector fields of $E$) and their tendicities (eigenvalues of these eigenvector fields); and the corresponding entities for the frame-drag field: frame-drag vortex lines and their vorticities. These entities fully characterize the vacuum Riemann tensor. In this paper, we compute and depict the tendex and vortex lines, and their tendicities and vorticities, outside the horizons of stationary (Schwarzschild and Kerr) black holes; and we introduce and depict the black holes' horizon tendicity and vorticity (the normal-normal components of $E$ and $B$ on the horizon). For Schwarzschild and Kerr black holes, the horizon tendicity is proportional to the horizon's intrinsic scalar curvature, and the horizon vorticity is proportional to an extrinsic scalar curvature. We show that, for horizon-penetrating time slices, all these entities ($E$, $B$, the tendex lines and vortex lines, the lines' tendicities and vorticities, and the horizon tendicities and vorticities) are affected only weakly by changes of slicing and changes of spatial coordinates, within those slicing and coordinate choices that are commonly used for black holes. [Abstract is abbreviated.] |
gr-qc/0511012 | Harry I. Ringermacher | Harry I. Ringermacher, Lawrence R. Mead | Induced matter: Curved N-manifolds encapsulated in Riemann-flat N+1
dimensional space | 3 pages | J.Math.Phys. 46 (2005) 102501 | 10.1063/1.2042968 | null | gr-qc | null | Liko and Wesson have recently introduced a new 5-dimensional induced matter
solution of the Einstein equations, a negative curvature Robertson-Walker space
embedded in a Riemann flat 5-dimensional manifold. We show that this solution
is a special case of a more general theorem prescribing the structure of
certain N+1-dimensional Riemann flat spaces which are all solutions of the
Einstein equations. These solutions encapsulate N-dimensional curved manifolds.
Such spaces are said to "induce matter" in the sub-manifolds by virtue of their
geometric structure alone. We prove that the N-manifold can be any maximally
symmetric space.
| [
{
"created": "Wed, 2 Nov 2005 21:36:35 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ringermacher",
"Harry I.",
""
],
[
"Mead",
"Lawrence R.",
""
]
] | Liko and Wesson have recently introduced a new 5-dimensional induced matter solution of the Einstein equations, a negative curvature Robertson-Walker space embedded in a Riemann flat 5-dimensional manifold. We show that this solution is a special case of a more general theorem prescribing the structure of certain N+1-dimensional Riemann flat spaces which are all solutions of the Einstein equations. These solutions encapsulate N-dimensional curved manifolds. Such spaces are said to "induce matter" in the sub-manifolds by virtue of their geometric structure alone. We prove that the N-manifold can be any maximally symmetric space. |
1310.2160 | Pedro da Cunha Ferreira | Pedro C. Ferreira, Diego Pav\'on, and Joel C. Carvalho | On detecting interactions in the dark sector with H(z) data | 10 pages | Phys. Rev. D 88, 083503 (2013) | 10.1103/PhysRevD.88.083503 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An interesting approach to the cosmological coincidence problem is to allow
dark matter and dark energy interact with each other also nongravitationally.
We consider two general Ans\"{a}tze for such an interaction and appraise their
ability to address the coincidence problem. We determine the average accuracy
required on the cosmic expansion rate data to distinguish interacting
cosmological models from the conventional $\Lambda$CDM scenario. We find that
among the planned surveys the Wide Field Infrared Survey Telescope has the best
chance to detect an interaction, though at a low significance level. To
unambiguously determine the existence of an interaction one must, therefore,
combine the said expansion data with other probes.
| [
{
"created": "Tue, 8 Oct 2013 14:47:38 GMT",
"version": "v1"
}
] | 2013-10-10 | [
[
"Ferreira",
"Pedro C.",
""
],
[
"Pavón",
"Diego",
""
],
[
"Carvalho",
"Joel C.",
""
]
] | An interesting approach to the cosmological coincidence problem is to allow dark matter and dark energy interact with each other also nongravitationally. We consider two general Ans\"{a}tze for such an interaction and appraise their ability to address the coincidence problem. We determine the average accuracy required on the cosmic expansion rate data to distinguish interacting cosmological models from the conventional $\Lambda$CDM scenario. We find that among the planned surveys the Wide Field Infrared Survey Telescope has the best chance to detect an interaction, though at a low significance level. To unambiguously determine the existence of an interaction one must, therefore, combine the said expansion data with other probes. |
gr-qc/9903020 | Alena Pravdova | J. Bicak, A. Pravdova | Axisymmetric electrovacuum spacetimes with a translational Killing
vector at null infinity | 15 pages, RevTeX, submitted to Class. Quantum Grav | Class.Quant.Grav. 16 (1999) 2023-2041 | 10.1088/0264-9381/16/6/329 | null | gr-qc | null | By using the Bondi-Sachs-van der Burg formalism we analyze the asymptotic
properties at null infinity of axisymmetric electrovacuum spacetimes with a
translational Killing vector and, in general, an infinite ``cosmic string''
(represented by a conical singularity) along the axis. Such spacetimes admit
only a local null infinity. There is a non-vanishing news function due to the
existence of the string even though there is no radiation.
We prove that if null infinity has a smooth compact cross section and the
spacetime is not flat in a neighbourhood of null infinity, then the
translational Killing vector must be timelike and the spacetime is stationary.
The other case in which an additional symmetry of axisymmetric spacetimes
admits compact cross sections of null infinity is the boost symmetry, which
leads to radiative spacetimes representing ``uniformly accelerated objects''.
These cases were analyzed in detail in our previous works. If the translational
Killing vector is spacelike or null, corresponding to cylindrical or plane
waves, some complete generators of null infinity are ``singular'' but null
infinity itself can be smooth apart from these generators.
As two explicit examples of local null infinity, Schwarzschild spacetime with
a string and a class of cylindrical waves with a string are discussed in detail
in the Appendix.
| [
{
"created": "Fri, 5 Mar 1999 13:33:03 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bicak",
"J.",
""
],
[
"Pravdova",
"A.",
""
]
] | By using the Bondi-Sachs-van der Burg formalism we analyze the asymptotic properties at null infinity of axisymmetric electrovacuum spacetimes with a translational Killing vector and, in general, an infinite ``cosmic string'' (represented by a conical singularity) along the axis. Such spacetimes admit only a local null infinity. There is a non-vanishing news function due to the existence of the string even though there is no radiation. We prove that if null infinity has a smooth compact cross section and the spacetime is not flat in a neighbourhood of null infinity, then the translational Killing vector must be timelike and the spacetime is stationary. The other case in which an additional symmetry of axisymmetric spacetimes admits compact cross sections of null infinity is the boost symmetry, which leads to radiative spacetimes representing ``uniformly accelerated objects''. These cases were analyzed in detail in our previous works. If the translational Killing vector is spacelike or null, corresponding to cylindrical or plane waves, some complete generators of null infinity are ``singular'' but null infinity itself can be smooth apart from these generators. As two explicit examples of local null infinity, Schwarzschild spacetime with a string and a class of cylindrical waves with a string are discussed in detail in the Appendix. |
1512.06472 | Chengyong Zhang | Cheng-Yong Zhang, Shao-Jun Zhang, De-Cheng Zou, Bin Wang | Charged scalar gravitational collapse in de Sitter spacetime | 16pages, 8 figures. Accepted by PRD | Phys. Rev. D 93, 064036 (2016) | 10.1103/PhysRevD.93.064036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the charged scalar collapse in de Sitter spacetimes. With the
electric charge, there is one more competitor to join the competition of
dynamics in the gravitational collapse. We find that two factors can influence
the electric charge. If we just adjust the charge conjugation, the electric
charge effect is always perturbative at the black hole threshold. The electric
charge can also be influenced by the initial conditions of perturbations. These
initial parameters can be tuned to control the competition in dynamics and
present us new and rich physics in the process of gravitational collapse. We
give physical explanations on these phenomena found in dynamics. Furthermore we
show that the properties of the gravitational collapse are universal and do not
depend on spacetime dimensions.
| [
{
"created": "Mon, 21 Dec 2015 02:19:43 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Jan 2016 17:42:58 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Feb 2016 09:27:52 GMT",
"version": "v3"
}
] | 2016-08-22 | [
[
"Zhang",
"Cheng-Yong",
""
],
[
"Zhang",
"Shao-Jun",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Wang",
"Bin",
""
]
] | We study the charged scalar collapse in de Sitter spacetimes. With the electric charge, there is one more competitor to join the competition of dynamics in the gravitational collapse. We find that two factors can influence the electric charge. If we just adjust the charge conjugation, the electric charge effect is always perturbative at the black hole threshold. The electric charge can also be influenced by the initial conditions of perturbations. These initial parameters can be tuned to control the competition in dynamics and present us new and rich physics in the process of gravitational collapse. We give physical explanations on these phenomena found in dynamics. Furthermore we show that the properties of the gravitational collapse are universal and do not depend on spacetime dimensions. |
2407.12914 | Chen Yuan | Chong-Zhi Li, Chen Yuan and Qing-guo Huang | Gravitational Waves Induced by Scalar Perturbations with a Broken
Power-law Peak | 18 pages, 6 figures, first version | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an analytical approximation for the energy spectrum of the scalar
induced gravitational waves (SIGWs) generated by a broken power-law power
spectrum, and find that both the asymptotic power-law tails and the
intermediate peak contribute distinct features to the SIGW spectrum. Moreover,
the broken power-law power spectrum has abundant near-peak features and our
results can be used as a near-peak approximation that covers a wide range of
models. Our analytical approximation is useful in the rapid generation of the
SIGW energy spectrum, which is beneficial for gravitational wave data analysis.
| [
{
"created": "Wed, 17 Jul 2024 18:00:02 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Li",
"Chong-Zhi",
""
],
[
"Yuan",
"Chen",
""
],
[
"Huang",
"Qing-guo",
""
]
] | We propose an analytical approximation for the energy spectrum of the scalar induced gravitational waves (SIGWs) generated by a broken power-law power spectrum, and find that both the asymptotic power-law tails and the intermediate peak contribute distinct features to the SIGW spectrum. Moreover, the broken power-law power spectrum has abundant near-peak features and our results can be used as a near-peak approximation that covers a wide range of models. Our analytical approximation is useful in the rapid generation of the SIGW energy spectrum, which is beneficial for gravitational wave data analysis. |
0906.3826 | Joel Saavedra | Sergio del Campo, Ramon Herrera, Pedro Labrana and Joel Saavedra | Closed inflationary universe in Patch Cosmology | 21 pages, 4 figures. Accepted by Annals of Physics | Annals Phys.324:1823-1836,2009 | 10.1016/j.aop.2009.06.003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study closed inflationary universe models using the
Gauss-Bonnet Brane. We determine and characterize the existence of a universe
with $\Omega > 1$, with an appropriate period of inflation. We have found that
this model is less restrictive in comparison with the standard approach where a
scalar field is considered. We use recent astronomical observations to
constrain the parameters appearing in the model.
| [
{
"created": "Sat, 20 Jun 2009 20:28:54 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"del Campo",
"Sergio",
""
],
[
"Herrera",
"Ramon",
""
],
[
"Labrana",
"Pedro",
""
],
[
"Saavedra",
"Joel",
""
]
] | In this article we study closed inflationary universe models using the Gauss-Bonnet Brane. We determine and characterize the existence of a universe with $\Omega > 1$, with an appropriate period of inflation. We have found that this model is less restrictive in comparison with the standard approach where a scalar field is considered. We use recent astronomical observations to constrain the parameters appearing in the model. |
0704.1733 | Orfeu Bertolami | Orfeu Bertolami, Christian G. Boehmer, Tiberiu Harko, Francisco S.N.
Lobo | Extra force in $f(R)$ modified theories of gravity | Revtex4 file, 5 pages. Version to appear in Physical Review D | Phys.Rev.D75:104016,2007 | 10.1103/PhysRevD.75.104016 | null | gr-qc astro-ph hep-th | null | The equation of motion for test particles in $f(R)$ modified theories of
gravity is derived. By considering an explicit coupling between an arbitrary
function of the scalar curvature, $R$, and the Lagrangian density of matter, it
is shown that an extra force arises. This extra force is orthogonal to the
four-velocity and the corresponding acceleration law is obtained in the weak
field limit. Connections with MOND and with the Pioneer anomaly are further
discussed.
| [
{
"created": "Fri, 13 Apr 2007 11:49:59 GMT",
"version": "v1"
},
{
"created": "Thu, 24 May 2007 12:03:50 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Boehmer",
"Christian G.",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | The equation of motion for test particles in $f(R)$ modified theories of gravity is derived. By considering an explicit coupling between an arbitrary function of the scalar curvature, $R$, and the Lagrangian density of matter, it is shown that an extra force arises. This extra force is orthogonal to the four-velocity and the corresponding acceleration law is obtained in the weak field limit. Connections with MOND and with the Pioneer anomaly are further discussed. |
2208.05778 | Dr. Goutam Manna | Saibal Ray, Arijit Panda, Bivash Majumder, Md. Rabiul Islam and Goutam
Manna | Collapsing scenario for the k-essence emergent generalised Vaidya
spacetime in the context of massive gravity's rainbow | 20 pages, 5 figures, to be published in Chinese Physics C | null | 10.1088/1674-1137/ac8868 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-sa/4.0/ | In this paper, we study the collapsing scenario for the k-essence emergent
Vaidya spacetime in the context of massive gravity's rainbow. For this study,
we consider that the background metric is Vaidya spacetime in massive gravity's
rainbow. We show that the k-essence emergent gravity metric resembles closely
to the new type of generalized Vaidya massive gravity metric with the rainbow
deformations for null fluid collapse where we consider the k-essence scalar
field as a function solely of the advanced or the retarded time. The k-essence
emergent Vaidya massive gravity rainbow mass function is also different. This
new type k-essence emergent Vaidya massive gravity rainbow metric has satisfied
the required energy conditions. The existence of the locally naked central
singularity, the strength and the strongness of the singularities for the
rainbow deformations of the k-essence emergent Vaidya massive gravity metric
are the interesting outcomes of the present work.
| [
{
"created": "Wed, 10 Aug 2022 12:51:08 GMT",
"version": "v1"
}
] | 2022-08-12 | [
[
"Ray",
"Saibal",
""
],
[
"Panda",
"Arijit",
""
],
[
"Majumder",
"Bivash",
""
],
[
"Islam",
"Md. Rabiul",
""
],
[
"Manna",
"Goutam",
""
]
] | In this paper, we study the collapsing scenario for the k-essence emergent Vaidya spacetime in the context of massive gravity's rainbow. For this study, we consider that the background metric is Vaidya spacetime in massive gravity's rainbow. We show that the k-essence emergent gravity metric resembles closely to the new type of generalized Vaidya massive gravity metric with the rainbow deformations for null fluid collapse where we consider the k-essence scalar field as a function solely of the advanced or the retarded time. The k-essence emergent Vaidya massive gravity rainbow mass function is also different. This new type k-essence emergent Vaidya massive gravity rainbow metric has satisfied the required energy conditions. The existence of the locally naked central singularity, the strength and the strongness of the singularities for the rainbow deformations of the k-essence emergent Vaidya massive gravity metric are the interesting outcomes of the present work. |
2207.00059 | Waleed El Hanafy | Adel Awad, Alexey Golovnev, Mar\'ia-Jos\'e Guzm\'an, and Waleed El
Hanafy | Revisiting diagonal tetrads: New Black Hole solutions in $f(T)$ gravity | pdfLaTeX, 21 pages, one figure. Submitted to EPJC | Eur. Phys. J. C (2022) 82:972 | 10.1140/epjc/s10052-022-10939-0 | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We study various forms of diagonal tetrads that accommodate Black Hole
solutions in $f(T)$ gravity with certain symmetries. As is well-known, vacuum
spherically symmetric diagonal tetrads lead to rather boring cases of constant
torsion scalars. We extend this statement to other possible horizon topologies,
namely, spherical, hyperbolic and planar horizons. All such cases are forced to
have constant torsion scalars to satisfy the anti-symmetric part of the field
equations. We give a full classification of possible vacuum static solutions of
this sort. Furthermore, we discuss addition of time-dependence in all the above
cases. We also show that if all the components of a diagonal tetrad depend only
on one coordinate, then the anti-symmetric part of the field equations is
automatically satisfied. This result applies to the flat horizon case with
Cartesian coordinates. For solutions with a planar symmetry (or a flat
horizon), one can naturally use Cartesian coordinates on the horizon. In this
case, we show that the presence of matter is required for existence of
non-trivial solutions. This is a novel and very interesting feature of these
constructions. We present two new exact solutions, the first is a magnetic
Black Hole which is the magnetic dual of a known electrically charged Black
Hole in literature. The second is a dyonic Black Hole with electric and
magnetic charges. We present some features of these Black holes, namely,
extremality conditions, mass, behavior of torsion and curvature scalars near
the singularity.
| [
{
"created": "Thu, 30 Jun 2022 18:49:44 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Oct 2022 15:54:15 GMT",
"version": "v2"
}
] | 2022-11-08 | [
[
"Awad",
"Adel",
""
],
[
"Golovnev",
"Alexey",
""
],
[
"Guzmán",
"María-José",
""
],
[
"Hanafy",
"Waleed El",
""
]
] | We study various forms of diagonal tetrads that accommodate Black Hole solutions in $f(T)$ gravity with certain symmetries. As is well-known, vacuum spherically symmetric diagonal tetrads lead to rather boring cases of constant torsion scalars. We extend this statement to other possible horizon topologies, namely, spherical, hyperbolic and planar horizons. All such cases are forced to have constant torsion scalars to satisfy the anti-symmetric part of the field equations. We give a full classification of possible vacuum static solutions of this sort. Furthermore, we discuss addition of time-dependence in all the above cases. We also show that if all the components of a diagonal tetrad depend only on one coordinate, then the anti-symmetric part of the field equations is automatically satisfied. This result applies to the flat horizon case with Cartesian coordinates. For solutions with a planar symmetry (or a flat horizon), one can naturally use Cartesian coordinates on the horizon. In this case, we show that the presence of matter is required for existence of non-trivial solutions. This is a novel and very interesting feature of these constructions. We present two new exact solutions, the first is a magnetic Black Hole which is the magnetic dual of a known electrically charged Black Hole in literature. The second is a dyonic Black Hole with electric and magnetic charges. We present some features of these Black holes, namely, extremality conditions, mass, behavior of torsion and curvature scalars near the singularity. |
0905.0896 | Ricardo E. Gamboa Saravi | Ricardo E. Gamboa Saravi | The Gravitational Field of a Plane Slab | 24 pages, 5 figures, accepted for publication in the International
Journal of Modern Physics A | Int.J.Mod.Phys.A24:5381-5405,2009 | 10.1142/S0217751X09046096 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We discuss the exact solution of Einstein's equation corresponding to a
static and plane symmetric distribution of matter with constant positive
density located below $z=0$ matched to vacuum solutions.
| [
{
"created": "Thu, 7 May 2009 14:38:03 GMT",
"version": "v1"
}
] | 2009-11-30 | [
[
"Saravi",
"Ricardo E. Gamboa",
""
]
] | We discuss the exact solution of Einstein's equation corresponding to a static and plane symmetric distribution of matter with constant positive density located below $z=0$ matched to vacuum solutions. |
1207.5833 | Antonios Tsokaros A. | Antonios Tsokaros, Koji Uryu | Binary black hole circular orbits computed with COCAL | 12 pages, 3 figures. Presented at the Tercentenary of the
Laplace-Runge-Lenz vector conference. This paper is dedicated to Peter Leach
on the occasion of his seventieth birthday | Journal of Engineering Mathematics 82, 1, 133-141 (2013) | 10.1007/s10665-012-9585-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present our first results of binary black hole circular
orbits using {\sc cocal}, the Compact Object CALculator. Using the 3+1
decomposition five equations are being solved under the assumptions of
conformal flatness and maximal slicing. Excision is used and the appropriate
apparent horizon boundary conditions are applied. The orbital velocity is
determined by imposing a Schwarzschild behaviour at infinity. A sequence of
equal mass black holes is obtained and its main physical characteristics are
calculated.
| [
{
"created": "Tue, 24 Jul 2012 21:39:59 GMT",
"version": "v1"
}
] | 2016-03-04 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Uryu",
"Koji",
""
]
] | In this work we present our first results of binary black hole circular orbits using {\sc cocal}, the Compact Object CALculator. Using the 3+1 decomposition five equations are being solved under the assumptions of conformal flatness and maximal slicing. Excision is used and the appropriate apparent horizon boundary conditions are applied. The orbital velocity is determined by imposing a Schwarzschild behaviour at infinity. A sequence of equal mass black holes is obtained and its main physical characteristics are calculated. |
2309.04572 | Delilah Gates | Delilah E. A. Gates and Shahar Hadar | Signatures of particle collisions near extreme black holes | 11 pages, 4 figures | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finite-energy particles in free fall can collide with diverging
center-of-mass energy near rapidly rotating black holes. What are the most
salient observational signatures of this remarkable geometric effect? Here we
revisit the problem from the standpoint of the near-horizon extreme Kerr
geometry, where these collisions naturally take place. It is shown that the
ingoing particle kinematics admits a simple, universal form. Given a scattering
cross section, determination of emission properties is reduced to evaluation of
particular integrals on the sky of a near-horizon orbiting particle. We
subsequently apply this scheme to the example of single-photon bremsstrahlung,
substantiating past results which indicate that ejected particles are
observable, but their energies are bounded by the rest masses of the colliding
particles. Our framework is readily applicable for any scattering process.
| [
{
"created": "Fri, 8 Sep 2023 20:04:25 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"Gates",
"Delilah E. A.",
""
],
[
"Hadar",
"Shahar",
""
]
] | Finite-energy particles in free fall can collide with diverging center-of-mass energy near rapidly rotating black holes. What are the most salient observational signatures of this remarkable geometric effect? Here we revisit the problem from the standpoint of the near-horizon extreme Kerr geometry, where these collisions naturally take place. It is shown that the ingoing particle kinematics admits a simple, universal form. Given a scattering cross section, determination of emission properties is reduced to evaluation of particular integrals on the sky of a near-horizon orbiting particle. We subsequently apply this scheme to the example of single-photon bremsstrahlung, substantiating past results which indicate that ejected particles are observable, but their energies are bounded by the rest masses of the colliding particles. Our framework is readily applicable for any scattering process. |
gr-qc/9612054 | Michael P. Ryan | A. A. Minzoni, Marcos Rosenbaum, Michael P. Ryan, Jr | Variational Approach to Gaussian Approximate Coherent States: Quantum
Mechanics and Minisuperspace Field Theory | 26 pages, Plain TeX, no figures | Phys.Rev. D56 (1997) 2144-2154 | 10.1103/PhysRevD.56.2144 | null | gr-qc hep-th quant-ph | null | This paper has a dual purpose. One aim is to study the evolution of coherent
states in ordinary quantum mechanics. This is done by means of a Hamiltonian
approach to the evolution of the parameters that define the state. The
stability of the solutions is studied. The second aim is to apply these
techniques to the study of the stability of minisuperspace solutions in field
theory. For a $\lambda \varphi^4$ theory we show, both by means of perturbation
theory and rigorously by means of theorems of the K.A.M. type, that the
homogeneous minisuperspace sector is indeed stable for positive values of the
parameters that define the field theory.
| [
{
"created": "Wed, 18 Dec 1996 20:17:05 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Minzoni",
"A. A.",
""
],
[
"Rosenbaum",
"Marcos",
""
],
[
"Ryan,",
"Michael P.",
"Jr"
]
] | This paper has a dual purpose. One aim is to study the evolution of coherent states in ordinary quantum mechanics. This is done by means of a Hamiltonian approach to the evolution of the parameters that define the state. The stability of the solutions is studied. The second aim is to apply these techniques to the study of the stability of minisuperspace solutions in field theory. For a $\lambda \varphi^4$ theory we show, both by means of perturbation theory and rigorously by means of theorems of the K.A.M. type, that the homogeneous minisuperspace sector is indeed stable for positive values of the parameters that define the field theory. |
gr-qc/9909080 | Shane L. Larson | Shane L. Larson, William A. Hiscock and Ronald W. Hellings | Sensitivity curves for spaceborne gravitational wave interferometers | 27 pages + 5 figures, REVTeX, accepted for publication in Phys Rev D;
Update reflects referees comments, figure 3 clarified, figure 5 corrected for
LISA baseline | Phys.Rev.D62:062001,2000 | 10.1103/PhysRevD.62.062001 | MSUPHY99.04 | gr-qc astro-ph | null | To determine whether particular sources of gravitational radiation will be
detectable by a specific gravitational wave detector, it is necessary to know
the sensitivity limits of the instrument. These instrumental sensitivities are
often depicted (after averaging over source position and polarization) by
graphing the minimal values of the gravitational wave amplitude detectable by
the instrument versus the frequency of the gravitational wave. This paper
describes in detail how to compute such a sensitivity curve given a set of
specifications for a spaceborne laser interferometer gravitational wave
observatory. Minor errors in the prior literature are corrected, and the first
(mostly) analytic calculation of the gravitational wave transfer function is
presented. Example sensitivity curve calculations are presented for the
proposed LISA interferometer. We find that previous treatments of LISA have
underestimated its sensitivity by a factor of $\sqrt{3}$.
| [
{
"created": "Sun, 26 Sep 1999 20:38:47 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2000 22:40:20 GMT",
"version": "v2"
}
] | 2009-12-30 | [
[
"Larson",
"Shane L.",
""
],
[
"Hiscock",
"William A.",
""
],
[
"Hellings",
"Ronald W.",
""
]
] | To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic calculation of the gravitational wave transfer function is presented. Example sensitivity curve calculations are presented for the proposed LISA interferometer. We find that previous treatments of LISA have underestimated its sensitivity by a factor of $\sqrt{3}$. |
2307.02580 | Sanjib Katuwal | Sanjib Katuwal | Quantum Gravitational Corrections to Electromagnetism And Backreaction | PhD thesis, 112 pages, 33 figures and 1 table | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | This dissertation examines the impact of quantum gravity on electromagnetism
and its backreaction, using perturbative general relativity as an effective
field theory. Our analysis involves quantum-correcting Maxwell's equations to
obtain a gauge-independent, real, and causal effective field equation that
describes quantum gravitational effects on electromagnetism. Additionally, we
present a perturbative mechanism through which quantum gravity induces a
dimension six coupling between a massive scalar and electromagnetism. To
investigate the effects of electromagnetism on the gravitational sector, we
derive an exact, dimensionally regulated, Fourier mode sum for the Lorentz
gauge propagator of a massive photon on an arbitrary cosmological background
supported by a scalar inflaton. This allows us to calculate the effective
potential induced by photons. Finally, we use a similar Fourier mode sum for a
time-dependent mass to study the effective force on the inflaton 0-mode and its
impact on reheating.
| [
{
"created": "Wed, 5 Jul 2023 18:26:06 GMT",
"version": "v1"
}
] | 2023-07-07 | [
[
"Katuwal",
"Sanjib",
""
]
] | This dissertation examines the impact of quantum gravity on electromagnetism and its backreaction, using perturbative general relativity as an effective field theory. Our analysis involves quantum-correcting Maxwell's equations to obtain a gauge-independent, real, and causal effective field equation that describes quantum gravitational effects on electromagnetism. Additionally, we present a perturbative mechanism through which quantum gravity induces a dimension six coupling between a massive scalar and electromagnetism. To investigate the effects of electromagnetism on the gravitational sector, we derive an exact, dimensionally regulated, Fourier mode sum for the Lorentz gauge propagator of a massive photon on an arbitrary cosmological background supported by a scalar inflaton. This allows us to calculate the effective potential induced by photons. Finally, we use a similar Fourier mode sum for a time-dependent mass to study the effective force on the inflaton 0-mode and its impact on reheating. |
2403.00021 | Kayoomars Karami | Milad Solbi and Kayoomars Karami | Primordial black holes in non-minimal coupling Gauss-Bonnet inflation in
light of the NANOGrav 15 year data | 37 pages, 10 figures, 5 tables | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Here, we investigate the formation of primordial black holes (PBHs) in
non-minimal coupling Gauss-Bonnet inflationary model in the presence of
power-law potentials. We employ a two part coupling function to enhance
primordial curvatures at small scales as well as satisfy Planck measurements at
the CMB scale. Moreover, our model satisfies the swampland criteria. We find
PBHs with different mass scales and demonstrate that PBHs with masses around
$\mathcal{O}(10^{-14})M_{\odot}$ can account for almost all of the dark matter
in the universe. In addition, we investigate the implications of the reheating
stage and show that the PBHs in our model are generated during the
radiation-dominated era. Furthermore, we investigate the production of
scalar-induced gravitational waves (GWs). More interestingly enough, is that
for the specific cases $D_{\rm n}$ in our model, the GWs can be considered as a
source of NANOGrav signal. %evaluate the idea that the induced GWs propagating
concurrently with the PBH production are the source of NANOGrav signal. Also,
we conclude that the GWs energy density parameter at the nano-Hz regime can be
parameterized as $\Omega_{\rm GW_0} (f) \sim f^{5-\gamma}$, where the obtained
$\gamma$ is consistent with the NANOGrav 15 years data.
| [
{
"created": "Wed, 28 Feb 2024 09:40:41 GMT",
"version": "v1"
}
] | 2024-03-04 | [
[
"Solbi",
"Milad",
""
],
[
"Karami",
"Kayoomars",
""
]
] | Here, we investigate the formation of primordial black holes (PBHs) in non-minimal coupling Gauss-Bonnet inflationary model in the presence of power-law potentials. We employ a two part coupling function to enhance primordial curvatures at small scales as well as satisfy Planck measurements at the CMB scale. Moreover, our model satisfies the swampland criteria. We find PBHs with different mass scales and demonstrate that PBHs with masses around $\mathcal{O}(10^{-14})M_{\odot}$ can account for almost all of the dark matter in the universe. In addition, we investigate the implications of the reheating stage and show that the PBHs in our model are generated during the radiation-dominated era. Furthermore, we investigate the production of scalar-induced gravitational waves (GWs). More interestingly enough, is that for the specific cases $D_{\rm n}$ in our model, the GWs can be considered as a source of NANOGrav signal. %evaluate the idea that the induced GWs propagating concurrently with the PBH production are the source of NANOGrav signal. Also, we conclude that the GWs energy density parameter at the nano-Hz regime can be parameterized as $\Omega_{\rm GW_0} (f) \sim f^{5-\gamma}$, where the obtained $\gamma$ is consistent with the NANOGrav 15 years data. |
1107.1840 | Jinn-Ouk Gong | Jinn-Ouk Gong, Jai-chan Hwang, Wan Il Park, Misao Sasaki and Yong-Seon
Song | Conformal invariance of curvature perturbation | 15 pages, 1 figure | null | 10.1088/1475-7516/2011/09/023 | CERN-PH-TH/2011-123, YITP-11-57 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that in the single component situation all perturbation variables in
the comoving gauge are conformally invariant to all perturbation orders.
Generally we identify a special time slicing, the uniform-conformal
transformation slicing, where all perturbations are again conformally invariant
to all perturbation orders. We apply this result to the delta N formalism, and
show its conformal invariance.
| [
{
"created": "Sun, 10 Jul 2011 07:22:14 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Gong",
"Jinn-Ouk",
""
],
[
"Hwang",
"Jai-chan",
""
],
[
"Park",
"Wan Il",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Song",
"Yong-Seon",
""
]
] | We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a special time slicing, the uniform-conformal transformation slicing, where all perturbations are again conformally invariant to all perturbation orders. We apply this result to the delta N formalism, and show its conformal invariance. |
1706.00160 | Vee-Liem Saw | Vee-Liem Saw | Asymptotically simple spacetimes and mass loss due to gravitational
waves | 41 pages, 2 figures | International Journal of Modern Physics D, Vol. 26, No. 16 (2017),
1730027 | 10.1142/S0218271817300270 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological constant $\Lambda$ used to be a freedom in Einstein's theory
of general relativity, where one had a proclivity to set it to zero purely for
convenience. The signs of $\Lambda$ or $\Lambda$ being zero would describe
universes with different properties. For instance, the conformal structure of
spacetime directly depends on $\Lambda$: null infinity $\mathcal{I}$ is a
spacelike, null, or timelike hypersurface, if $\Lambda>0$, $\Lambda=0$, or
$\Lambda<0$, respectively. Recent observations of distant supernovae have
taught us that our universe expands at an accelerated rate, and this can be
accounted for by choosing $\Lambda>0$ in Einstein's theory of general
relativity. A quantity that depends on the conformal structure of spacetime,
especially on the nature of $\mathcal{I}$, is the Bondi mass which in turn
dictates the mass loss of an isolated gravitating system due to energy carried
away by gravitational waves. This problem of extending the Bondi mass to a
universe with $\Lambda>0$ has spawned intense research activity over the past
several years. Some aspects include a closer inspection on the conformal
properties, working with linearisation, attempts using a Hamiltonian
formulation based on "linearised" asymptotic symmetries, as well as obtaining
the general asymptotic solutions of de Sitter-like spacetimes. We consolidate
on the progress thus far from the various approaches that have been undertaken,
as well as discuss the current open problems and possible directions in this
area.
| [
{
"created": "Thu, 1 Jun 2017 04:16:19 GMT",
"version": "v1"
}
] | 2017-08-22 | [
[
"Saw",
"Vee-Liem",
""
]
] | The cosmological constant $\Lambda$ used to be a freedom in Einstein's theory of general relativity, where one had a proclivity to set it to zero purely for convenience. The signs of $\Lambda$ or $\Lambda$ being zero would describe universes with different properties. For instance, the conformal structure of spacetime directly depends on $\Lambda$: null infinity $\mathcal{I}$ is a spacelike, null, or timelike hypersurface, if $\Lambda>0$, $\Lambda=0$, or $\Lambda<0$, respectively. Recent observations of distant supernovae have taught us that our universe expands at an accelerated rate, and this can be accounted for by choosing $\Lambda>0$ in Einstein's theory of general relativity. A quantity that depends on the conformal structure of spacetime, especially on the nature of $\mathcal{I}$, is the Bondi mass which in turn dictates the mass loss of an isolated gravitating system due to energy carried away by gravitational waves. This problem of extending the Bondi mass to a universe with $\Lambda>0$ has spawned intense research activity over the past several years. Some aspects include a closer inspection on the conformal properties, working with linearisation, attempts using a Hamiltonian formulation based on "linearised" asymptotic symmetries, as well as obtaining the general asymptotic solutions of de Sitter-like spacetimes. We consolidate on the progress thus far from the various approaches that have been undertaken, as well as discuss the current open problems and possible directions in this area. |
gr-qc/0612023 | Edwin J. Son | Wontae Kim, Edwin J. Son | Future singularity free accelerating expansion with the modified Poisson
brackets | 13 pages, 2 figures; v2. to appear in Phys. Rev. D | Phys.Rev.D75:024025,2007 | 10.1103/PhysRevD.75.024025 | null | gr-qc | null | We show that the second accelerating expansion of the universe appears
smoothly from the decelerating universe remarkably after the initial inflation
in the two-dimensional soluble semi-classical dilaton gravity along with the
modified Poisson brackets of noncommutativity between the relevant fields.
However, the ordinary solution coming from the equations of motion following
the conventional Poisson algebra describes permanent accelerating universe
without any phase change. In this modified model, it turns out that the phase
transition is related to the noncommutative Poisson algebra.
| [
{
"created": "Mon, 4 Dec 2006 03:52:53 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jan 2007 01:11:56 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Kim",
"Wontae",
""
],
[
"Son",
"Edwin J.",
""
]
] | We show that the second accelerating expansion of the universe appears smoothly from the decelerating universe remarkably after the initial inflation in the two-dimensional soluble semi-classical dilaton gravity along with the modified Poisson brackets of noncommutativity between the relevant fields. However, the ordinary solution coming from the equations of motion following the conventional Poisson algebra describes permanent accelerating universe without any phase change. In this modified model, it turns out that the phase transition is related to the noncommutative Poisson algebra. |
1506.00725 | Jonathan Ziprick | Viqar Husain, Jonathan Ziprick | 3D gravity with dust: classical and quantum theory | 14 pages | Phys. Rev. D 91, 124074 (2015) | 10.1103/PhysRevD.91.124074 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Einstein gravity and dust system in three spacetime dimensions
as an example of a non-perturbative quantum gravity model with local degrees of
freedom. We derive the Hamiltonian theory in the dust time gauge and show that
it has a rich class of exact solutions. These include the
Ba\~nados-Teitelboim-Zanelli black hole, static solutions with naked
singularities and travelling wave solutions with dynamical horizons. We give a
complete quantization of the wave sector of the theory, including a definition
of a self-adjoint spacetime metric operator. This operator is used to
demonstrate the quantization of deficit angle and the fluctuation of dynamical
horizons.
| [
{
"created": "Tue, 2 Jun 2015 02:08:10 GMT",
"version": "v1"
}
] | 2015-07-08 | [
[
"Husain",
"Viqar",
""
],
[
"Ziprick",
"Jonathan",
""
]
] | We study the Einstein gravity and dust system in three spacetime dimensions as an example of a non-perturbative quantum gravity model with local degrees of freedom. We derive the Hamiltonian theory in the dust time gauge and show that it has a rich class of exact solutions. These include the Ba\~nados-Teitelboim-Zanelli black hole, static solutions with naked singularities and travelling wave solutions with dynamical horizons. We give a complete quantization of the wave sector of the theory, including a definition of a self-adjoint spacetime metric operator. This operator is used to demonstrate the quantization of deficit angle and the fluctuation of dynamical horizons. |
0802.3341 | Jennifer Seiler | Jennifer Seiler, Bela Szilagyi, Denis Pollney, and Luciano Rezzolla | Constraint-preserving boundary treatment for a harmonic formulation of
the Einstein equations | 18 pages, 7 figures, accepted in CQG | Class.Quant.Grav.25:175020,2008 | 10.1088/0264-9381/25/17/175020 | AEI-2008-007 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a set of well-posed constraint-preserving boundary conditions for
a first-order in time, second-order in space, harmonic formulation of the
Einstein equations. The boundary conditions are tested using robust stability,
linear and nonlinear waves, and are found to be both less reflective and
constraint preserving than standard Sommerfeld-type boundary conditions.
| [
{
"created": "Fri, 22 Feb 2008 16:00:35 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jul 2008 17:55:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Seiler",
"Jennifer",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Pollney",
"Denis",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | We present a set of well-posed constraint-preserving boundary conditions for a first-order in time, second-order in space, harmonic formulation of the Einstein equations. The boundary conditions are tested using robust stability, linear and nonlinear waves, and are found to be both less reflective and constraint preserving than standard Sommerfeld-type boundary conditions. |
gr-qc/0609088 | Petarpa Boonserm | Petarpa Boonserm (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington), and Silke Weinfurtner (Victoria
University of Wellington) | Solution generating theorems for perfect fluid spheres | 8 pages, no figures, to appear in the proceedings of the NEB XII
Conference (Recent Developments in Gravity), 29 June - 2 July, 2006, Napflio,
Greece | J.Phys.Conf.Ser.68:012055,2007 | 10.1088/1742-6596/68/1/012055 | null | gr-qc | null | The first static spherically symmetric perfect fluid solution with constant
density was found by Schwarzschild in 1918. Generically, perfect fluid spheres
are interesting because they are first approximations to any attempt at
building a realistic model for a general relativistic star. Over the past 90
years a confusing tangle of specific perfect fluid spheres has been discovered,
with most of these examples seemingly independent from each other. To bring
some order to this collection, we develop several new transformation theorems
that map perfect fluid spheres into perfect fluid spheres. These transformation
theorems sometimes lead to unexpected connections between previously known
perfect fluid spheres, sometimes lead to new previously unknown perfect fluid
spheres, and in general can be used to develop a systematic way of classifying
the set of all perfect fluid spheres. In addition, we develop new ``solution
generating'' theorems for the TOV, whereby any given solution can be
``deformed'' to a new solution. Because these TOV-based theorems work directly
in terms of the pressure profile and density profile it is relatively easy to
impose regularity conditions at the centre of the fluid sphere.
| [
{
"created": "Wed, 20 Sep 2006 23:43:49 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Boonserm",
"Petarpa",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
],
[
"Weinfurtner",
"Silke",
"",
"Victoria\n University of Wellington"
]
] | The first static spherically symmetric perfect fluid solution with constant density was found by Schwarzschild in 1918. Generically, perfect fluid spheres are interesting because they are first approximations to any attempt at building a realistic model for a general relativistic star. Over the past 90 years a confusing tangle of specific perfect fluid spheres has been discovered, with most of these examples seemingly independent from each other. To bring some order to this collection, we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres. In addition, we develop new ``solution generating'' theorems for the TOV, whereby any given solution can be ``deformed'' to a new solution. Because these TOV-based theorems work directly in terms of the pressure profile and density profile it is relatively easy to impose regularity conditions at the centre of the fluid sphere. |
2003.02862 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Bl\'azquez-Salcedo, Daniela D. Doneva, Sarah Kahlen, Jutta
Kunz, Petya Nedkova, Stoytcho S. Yazadjiev | Axial perturbations of the scalarized Einstein-Gauss-Bonnet black holes | 17 pages, 6 figures | Phys. Rev. D 101, 104006 (2020) | 10.1103/PhysRevD.101.104006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the axial perturbations of spontaneously scalarized black holes in
Einstein-Gauss-Bonnet (EGB) theories. We consider the nodeless solutions of the
fundamental branch of the model studied in [1], which possesses a region of
radially stable configurations, as shown in [2]. Here we show that almost all
of the radially stable black holes are also stable under axial perturbations.
When the axial potential is no longer strictly positive, we make use of the
S-deformation method to show stability. As for the radial perturbations,
hyperbolicity is lost below a certain critical horizon size for a fixed
coupling constant. In the stable region, we determine the spectrum of the
quasinormal modes by time evolution and by solving the associated
time-independent eigenvalue problem.
| [
{
"created": "Thu, 5 Mar 2020 19:00:55 GMT",
"version": "v1"
}
] | 2020-05-13 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Kahlen",
"Sarah",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Nedkova",
"Petya",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | We study the axial perturbations of spontaneously scalarized black holes in Einstein-Gauss-Bonnet (EGB) theories. We consider the nodeless solutions of the fundamental branch of the model studied in [1], which possesses a region of radially stable configurations, as shown in [2]. Here we show that almost all of the radially stable black holes are also stable under axial perturbations. When the axial potential is no longer strictly positive, we make use of the S-deformation method to show stability. As for the radial perturbations, hyperbolicity is lost below a certain critical horizon size for a fixed coupling constant. In the stable region, we determine the spectrum of the quasinormal modes by time evolution and by solving the associated time-independent eigenvalue problem. |
gr-qc/0407111 | I. B. Khriplovich | I.B. Khriplovich | Quasinormal modes, quantized black holes, and correspondence principle | 2 pages; a new argument added | Int.J.Mod.Phys. D14 (2005) 181 | 10.1142/S0218271805005980 | null | gr-qc hep-th | null | Contrary to the wide-spread belief, the correspondence principle does not
dictate any relation between the asymptotics of quasinormal modes and the
spectrum of quantized black holes. Moreover, this belief is in conflict with
simple physical arguments.
| [
{
"created": "Thu, 29 Jul 2004 07:22:37 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Sep 2004 04:56:37 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Khriplovich",
"I. B.",
""
]
] | Contrary to the wide-spread belief, the correspondence principle does not dictate any relation between the asymptotics of quasinormal modes and the spectrum of quantized black holes. Moreover, this belief is in conflict with simple physical arguments. |
gr-qc/9605027 | Kostas Kokkotas | B.R. Iyer (Bangalore) and K.D. Kokkotas (Jena) | Workshop on gravitational waves | 18 pages, kluwer.sty, no figures | in Gravitation and Cosmology, Eds S.Dhurandhar and T.Padmanabhan,
Kluwer Academic Publishers (1997), page 261 | 10.1007/978-94-011-5812-1_18 | null | gr-qc | null | In this article we summarise the proceedings of the Workshop on Gravitational
Waves held during ICGC-95. In the first part we present the discussions on 3PN
calculations (L. Blanchet, P. Jaranowski), black hole perturbation theory (M.
Sasaki, J. Pullin), numerical relativity (E. Seidel), data analysis (B.S.
Sathyaprakash), detection of gravitational waves from pulsars (S. Dhurandhar),
and the limit on rotation of relativistic stars (J. Friedman). In the second
part we briefly discuss the contributed papers which were mainly on detectors
and detection techniques of gravitational waves.
| [
{
"created": "Wed, 15 May 1996 06:50:44 GMT",
"version": "v1"
}
] | 2022-03-09 | [
[
"Iyer",
"B. R.",
"",
"Bangalore"
],
[
"Kokkotas",
"K. D.",
"",
"Jena"
]
] | In this article we summarise the proceedings of the Workshop on Gravitational Waves held during ICGC-95. In the first part we present the discussions on 3PN calculations (L. Blanchet, P. Jaranowski), black hole perturbation theory (M. Sasaki, J. Pullin), numerical relativity (E. Seidel), data analysis (B.S. Sathyaprakash), detection of gravitational waves from pulsars (S. Dhurandhar), and the limit on rotation of relativistic stars (J. Friedman). In the second part we briefly discuss the contributed papers which were mainly on detectors and detection techniques of gravitational waves. |
1004.0882 | Gerasimos Rigopoulos | Tomislav Prokopec and Gerasimos Rigopoulos | Path Integral for Inflationary Perturbations | (v1) 28 pages, no figures; (v2) 29 pages, minor changes, matches
published version | Phys.Rev.D82:023529,2010 | 10.1103/PhysRevD.82.023529 | HIP-2010-12/TH, ITP-UU-10-12, SPIN-10-10 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum theory of cosmological perturbations in single field inflation is
formulated in terms of a path integral. Starting from a canonical formulation,
we show how the free propagators can be obtained from the well known
gauge-invariant quadratic action for scalar and tensor perturbations, and
determine the interactions to arbitrary order. This approach does not require
the explicit solution of the energy and momentum constraints, a novel feature
which simplifies the determination of the interaction vertices. The constraints
and the necessary imposition of gauge conditions is reflected in the appearance
of various commuting and anti-commuting auxiliary fields in the action. These
auxiliary fields are not propagating physical degrees of freedom but need to be
included in internal lines and loops in a diagrammatic expansion. To illustrate
the formalism we discuss the tree-level 3-point and 4-point functions of the
inflaton perturbations, reproducing the results already obtained by the methods
used in the current literature. Loop calculations are left for future work.
| [
{
"created": "Tue, 6 Apr 2010 16:04:26 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Dec 2010 12:48:14 GMT",
"version": "v2"
}
] | 2010-12-14 | [
[
"Prokopec",
"Tomislav",
""
],
[
"Rigopoulos",
"Gerasimos",
""
]
] | The quantum theory of cosmological perturbations in single field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anti-commuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level 3-point and 4-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work. |
gr-qc/0407078 | Gregory B. Cook | Gregory B. Cook, Harald P. Pfeiffer | Excision boundary conditions for black hole initial data | 23 pages, 23 figures, revtex4, corrected typos, added reference,
minor content changes including additional post-Newtonian comparison. Version
accepted by PRD | Phys.Rev. D70 (2004) 104016 | 10.1103/PhysRevD.70.104016 | null | gr-qc | null | We define and extensively test a set of boundary conditions that can be
applied at black hole excision surfaces when the Hamiltonian and momentum
constraints of general relativity are solved within the conformal thin-sandwich
formalism. These boundary conditions have been designed to result in black
holes that are in quasiequilibrium and are completely general in the sense that
they can be applied with any conformal three-geometry and slicing condition.
Furthermore, we show that they retain precisely the freedom to specify an
arbitrary spin on each black hole. Interestingly, we have been unable to find a
boundary condition on the lapse that can be derived from a quasiequilibrium
condition. Rather, we find evidence that the lapse boundary condition is part
of the initial temporal gauge choice. To test these boundary conditions, we
have extensively explored the case of a single black hole and the case of a
binary system of equal-mass black holes, including the computation of
quasi-circular orbits and the determination of the inner-most stable circular
orbit. Our tests show that the boundary conditions work well.
| [
{
"created": "Wed, 21 Jul 2004 19:34:41 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jul 2004 15:49:41 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Sep 2004 14:24:14 GMT",
"version": "v3"
},
{
"created": "Fri, 1 Apr 2005 19:53:58 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Cook",
"Gregory B.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We define and extensively test a set of boundary conditions that can be applied at black hole excision surfaces when the Hamiltonian and momentum constraints of general relativity are solved within the conformal thin-sandwich formalism. These boundary conditions have been designed to result in black holes that are in quasiequilibrium and are completely general in the sense that they can be applied with any conformal three-geometry and slicing condition. Furthermore, we show that they retain precisely the freedom to specify an arbitrary spin on each black hole. Interestingly, we have been unable to find a boundary condition on the lapse that can be derived from a quasiequilibrium condition. Rather, we find evidence that the lapse boundary condition is part of the initial temporal gauge choice. To test these boundary conditions, we have extensively explored the case of a single black hole and the case of a binary system of equal-mass black holes, including the computation of quasi-circular orbits and the determination of the inner-most stable circular orbit. Our tests show that the boundary conditions work well. |
1709.06118 | Carlos A. R. Herdeiro | Pedro V. P. Cunha, Jos\'e A. Font, Carlos Herdeiro, Eugen Radu,
Nicolas Sanchis-Gual, Miguel Zilh\~ao | Lensing and dynamics of ultra-compact bosonic stars | 13 pages, 9 figures | Phys. Rev. D 96, 104040 (2017) | 10.1103/PhysRevD.96.104040 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spherically symmetric bosonic stars are one of the few examples of
gravitating solitons that are known to form dynamically, via a classical
process of (incomplete) gravitational collapse. As stationary solutions of the
Einstein--Klein-Gordon or the Einstein--Proca theory, bosonic stars may also
become sufficiently compact to develop light rings and hence mimic, in
principle, gravitational-wave observational signatures of black holes (BHs). In
this paper, we discuss how these horizonless ultra-compact objects (UCOs) are
actually distinct from BHs, both phenomenologically and dynamically. In the
electromagnetic channel, the light ring associated phenomenology reveals
remarkable lensing patterns, quite distinct from a standard BH shadow, with an
infinite number of Einstein rings accumulating in the vicinity of the light
ring, both inside and outside the latter. The strong lensing region, moreover,
can be considerably smaller than the shadow of a BH with a comparable mass.
Dynamically, we investigate the fate of such UCOs under perturbations, via
fully non-linear numerical simulations and observe that, in all cases, they
decay into a Schwarzschild BH within a time scale of $\mathcal{O}(M)$, where
$M$ is the mass of the bosonic star. Both these studies reinforce how difficult
it is for horizonless UCOs to mimic BH phenomenology and dynamics, in all its
aspects.
| [
{
"created": "Mon, 18 Sep 2017 18:35:39 GMT",
"version": "v1"
}
] | 2017-11-29 | [
[
"Cunha",
"Pedro V. P.",
""
],
[
"Font",
"José A.",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Zilhão",
"Miguel",
""
]
] | Spherically symmetric bosonic stars are one of the few examples of gravitating solitons that are known to form dynamically, via a classical process of (incomplete) gravitational collapse. As stationary solutions of the Einstein--Klein-Gordon or the Einstein--Proca theory, bosonic stars may also become sufficiently compact to develop light rings and hence mimic, in principle, gravitational-wave observational signatures of black holes (BHs). In this paper, we discuss how these horizonless ultra-compact objects (UCOs) are actually distinct from BHs, both phenomenologically and dynamically. In the electromagnetic channel, the light ring associated phenomenology reveals remarkable lensing patterns, quite distinct from a standard BH shadow, with an infinite number of Einstein rings accumulating in the vicinity of the light ring, both inside and outside the latter. The strong lensing region, moreover, can be considerably smaller than the shadow of a BH with a comparable mass. Dynamically, we investigate the fate of such UCOs under perturbations, via fully non-linear numerical simulations and observe that, in all cases, they decay into a Schwarzschild BH within a time scale of $\mathcal{O}(M)$, where $M$ is the mass of the bosonic star. Both these studies reinforce how difficult it is for horizonless UCOs to mimic BH phenomenology and dynamics, in all its aspects. |
gr-qc/0405045 | Bruce Allen | Bruce Allen | A chi-squared time-frequency discriminator for gravitational wave
detection | 18 pages, five figures, RevTex4 | Phys.Rev.D71:062001,2005 | 10.1103/PhysRevD.71.062001 | null | gr-qc | null | Searches for known waveforms in gravitational wave detector data are often
done using matched filtering. When used on real instrumental data, matched
filtering often does not perform as well as might be expected, because
non-stationary and non-Gaussian detector noise produces large spurious filter
outputs (events). This paper describes a chi-squared time-frequency test which
is one way to discriminate such spurious events from the events that would be
produced by genuine signals. The method works well only for broad-band signals.
The case where the filter template does not exactly match the signal waveform
is also considered, and upper bounds are found for the expected value of
chi-squared.
| [
{
"created": "Fri, 7 May 2004 21:10:42 GMT",
"version": "v1"
},
{
"created": "Fri, 28 May 2004 18:32:40 GMT",
"version": "v2"
}
] | 2011-07-18 | [
[
"Allen",
"Bruce",
""
]
] | Searches for known waveforms in gravitational wave detector data are often done using matched filtering. When used on real instrumental data, matched filtering often does not perform as well as might be expected, because non-stationary and non-Gaussian detector noise produces large spurious filter outputs (events). This paper describes a chi-squared time-frequency test which is one way to discriminate such spurious events from the events that would be produced by genuine signals. The method works well only for broad-band signals. The case where the filter template does not exactly match the signal waveform is also considered, and upper bounds are found for the expected value of chi-squared. |
1910.08831 | Scott Melville | Anne-Christine Davis and Scott Melville | Novel Screening with Two Bodies: Summing the ladder in disformal
scalar-tensor theories | 42 pages, 6 figures, 1 appendix | JCAP 09 (2020) 013 | 10.1088/1475-7516/2020/09/013 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When augmenting our cosmological models or gravitational theories with an
additional light scalar field, any coupling between matter and this scalar can
affect the orbital motion of binary systems. Ordinarily, the new force mediated
by the scalar can be naturally the same order of magnitude as the usual
gravitational force and therefore is tightly constrained. We show that a
disformal coupling between the scalar and matter can lead to a novel screening
mechanism in which these fifth forces are suppressed by several orders of
magnitude at sufficiently small separations and large relative velocities (such
as solar system scales). This is a result of resumming a class of ladder
diagrams, which suppresses the propagation of scalar signals between the two
bodies. Moreover, we are able to relate potential ambiguities in this
resummation to non-perturbative effects (which are invisible to perturbation
theory). As a result, solar system tests and future gravitational wave
observations can now be used to place meaningful constraints on scalar-tensor
theories with disformal couplings. We exemplify this using observational bounds
on the precession of planetary orbits.
| [
{
"created": "Sat, 19 Oct 2019 20:03:42 GMT",
"version": "v1"
}
] | 2021-02-16 | [
[
"Davis",
"Anne-Christine",
""
],
[
"Melville",
"Scott",
""
]
] | When augmenting our cosmological models or gravitational theories with an additional light scalar field, any coupling between matter and this scalar can affect the orbital motion of binary systems. Ordinarily, the new force mediated by the scalar can be naturally the same order of magnitude as the usual gravitational force and therefore is tightly constrained. We show that a disformal coupling between the scalar and matter can lead to a novel screening mechanism in which these fifth forces are suppressed by several orders of magnitude at sufficiently small separations and large relative velocities (such as solar system scales). This is a result of resumming a class of ladder diagrams, which suppresses the propagation of scalar signals between the two bodies. Moreover, we are able to relate potential ambiguities in this resummation to non-perturbative effects (which are invisible to perturbation theory). As a result, solar system tests and future gravitational wave observations can now be used to place meaningful constraints on scalar-tensor theories with disformal couplings. We exemplify this using observational bounds on the precession of planetary orbits. |
gr-qc/9909015 | Rod Aros | Rodrigo Aros, Mauricio Contreras, Rodrigo Olea, Ricardo Troncoso and
Jorge Zanelli | Conserved charges for gravity with locally AdS asymptotics | 5 pages, 2 Columns, revtex. Last version for Phys. Rev. Lett | Phys.Rev.Lett.84:1647-1650,2000 | 10.1103/PhysRevLett.84.1647 | CECS-PHY-99/14 | gr-qc hep-th | null | A new formula for the conserved charges in 3+1 gravity for spacetimes with
local AdS asymptotic geometry is proposed. It is shown that requiring the
action to have an extremum for this class of asymptotia sets the boundary term
that must be added to the Lagrangian as the Euler density with a fixed weight
factor. The resulting action gives rise to the mass and angular momentum as
Noether charges associated to the asymptotic Killing vectors without requiring
specification of a reference background in order to have a convergent
expression. A consequence of this definition is that any negative constant
curvature spacetime has vanishing Noether charges. These results remain valid
in the limit of vanishing cosmological constant.
| [
{
"created": "Sat, 4 Sep 1999 00:26:47 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Dec 1999 00:22:28 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Aros",
"Rodrigo",
""
],
[
"Contreras",
"Mauricio",
""
],
[
"Olea",
"Rodrigo",
""
],
[
"Troncoso",
"Ricardo",
""
],
[
"Zanelli",
"Jorge",
""
]
] | A new formula for the conserved charges in 3+1 gravity for spacetimes with local AdS asymptotic geometry is proposed. It is shown that requiring the action to have an extremum for this class of asymptotia sets the boundary term that must be added to the Lagrangian as the Euler density with a fixed weight factor. The resulting action gives rise to the mass and angular momentum as Noether charges associated to the asymptotic Killing vectors without requiring specification of a reference background in order to have a convergent expression. A consequence of this definition is that any negative constant curvature spacetime has vanishing Noether charges. These results remain valid in the limit of vanishing cosmological constant. |
1406.1124 | Morgan Lynch | Morgan H. Lynch | Acceleration-induced scalar field transitions of n-particle multiplicity | 24 pages, 13 figures. Accepted for publication in Phys. Rev. D | Phys. Rev. D 90, 024049 (2014) | 10.1103/PhysRevD.90.024049 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we calculate the effect of acceleration on the decay and
excitation rates of scalar fields into a final state of arbitrary multiplicity.
The analysis is carried out using standard field operators as well as an
Unruh-DeWitt detector. Using the equivalence of the two methods, we show how to
correctly setup the computation and interpret the results in terms of the
particle content of the initial and final state Rindler and Minkowski
spacetimes. We find the dominant transition pathway, and thus final state
multiplicity, is acceleration dependent. The formalisms developed are then used
to analyze the electron and muon system. We compute the transition rates and
lifetimes for accelerated electrons and muons as well as the branching
fractions for muon decay.
| [
{
"created": "Wed, 4 Jun 2014 17:52:14 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jun 2014 20:03:43 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Lynch",
"Morgan H.",
""
]
] | In this paper we calculate the effect of acceleration on the decay and excitation rates of scalar fields into a final state of arbitrary multiplicity. The analysis is carried out using standard field operators as well as an Unruh-DeWitt detector. Using the equivalence of the two methods, we show how to correctly setup the computation and interpret the results in terms of the particle content of the initial and final state Rindler and Minkowski spacetimes. We find the dominant transition pathway, and thus final state multiplicity, is acceleration dependent. The formalisms developed are then used to analyze the electron and muon system. We compute the transition rates and lifetimes for accelerated electrons and muons as well as the branching fractions for muon decay. |
2210.15246 | Srijit Bhattacharjee | Ayon Tarafdar and Srijit Bhattacharjee | Slowly evolving horizons in Einstein gravity and beyond | Section II is extended. Minor corrections and more clarifications
added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study event horizon candidates for slowly evolving dynamical black holes
in General Relativity and Einstein-Gauss-Bonnet (EGB) gravity. Such a type of
horizon candidate has been termed as slowly evolving null surface (SENS). It
signifies a near-equilibrium state of a dynamic black hole. We demonstrate the
time evolution of such surfaces for three different metrics. First, we locate
such a surface for a charged Vaidya metric and show that the parameter space of
the black hole gets constrained to allow a physically admissible slowly
evolving null surface. We then consider a supertranslated Vaidya solution that
contains a non-spherical horizon and study the properties of the SENS. This
spacetime generates a non-vanishing shear at the SENS due to the presence of
the supertranslation field. The SENS for a spherically symmetric Vaidya-like
solution in EGB gravity yields a bound on the accretion rate that depends on
the size of the horizon. We also show that the first and second laws of black
hole mechanics can be established for these slowly evolving surfaces.
| [
{
"created": "Thu, 27 Oct 2022 08:07:35 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jan 2023 18:25:08 GMT",
"version": "v2"
}
] | 2023-02-01 | [
[
"Tarafdar",
"Ayon",
""
],
[
"Bhattacharjee",
"Srijit",
""
]
] | We study event horizon candidates for slowly evolving dynamical black holes in General Relativity and Einstein-Gauss-Bonnet (EGB) gravity. Such a type of horizon candidate has been termed as slowly evolving null surface (SENS). It signifies a near-equilibrium state of a dynamic black hole. We demonstrate the time evolution of such surfaces for three different metrics. First, we locate such a surface for a charged Vaidya metric and show that the parameter space of the black hole gets constrained to allow a physically admissible slowly evolving null surface. We then consider a supertranslated Vaidya solution that contains a non-spherical horizon and study the properties of the SENS. This spacetime generates a non-vanishing shear at the SENS due to the presence of the supertranslation field. The SENS for a spherically symmetric Vaidya-like solution in EGB gravity yields a bound on the accretion rate that depends on the size of the horizon. We also show that the first and second laws of black hole mechanics can be established for these slowly evolving surfaces. |
1208.4440 | Takashi Tamaki | Takashi Tamaki, Nobuyuki Sakai | Unified pictures of Q-balls and Q-tubes | 11 pages, 14 figures | null | 10.1103/PhysRevD.86.105011 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While Q-balls have been investigated intensively for many years, another type
of nontopological solutions, Q-tubes, have not been understood very well. In
this paper we make a comparative study of Q-balls and Q-tubes. First, we
investigate their equilibrium solutions for four types of potentials. We find,
for example, that in some models the charge-energy relation is similar between
Q-balls and Q-tubes while in other models the relation is quite different
between them. To understand what determines the charge-energy relation, which
is a key of stability of the equilibrium solutions, we establish an analytical
method to obtain the two limit values of the energy and the charge. Our
prescription indicates how the existent domain of solutions and their stability
depends on their shape as well as potentials, which would also be useful for a
future study of Q-objects in higher-dimensional spacetime.
| [
{
"created": "Wed, 22 Aug 2012 08:05:47 GMT",
"version": "v1"
}
] | 2015-03-20 | [
[
"Tamaki",
"Takashi",
""
],
[
"Sakai",
"Nobuyuki",
""
]
] | While Q-balls have been investigated intensively for many years, another type of nontopological solutions, Q-tubes, have not been understood very well. In this paper we make a comparative study of Q-balls and Q-tubes. First, we investigate their equilibrium solutions for four types of potentials. We find, for example, that in some models the charge-energy relation is similar between Q-balls and Q-tubes while in other models the relation is quite different between them. To understand what determines the charge-energy relation, which is a key of stability of the equilibrium solutions, we establish an analytical method to obtain the two limit values of the energy and the charge. Our prescription indicates how the existent domain of solutions and their stability depends on their shape as well as potentials, which would also be useful for a future study of Q-objects in higher-dimensional spacetime. |
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