id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0906.4237 | Elias C. Vagenas | M. R. Setare and Elias C. Vagenas | Non-minimal coupling of the phantom field and cosmic acceleration | 9 pages, no figures; (v2) title slightly changed, one reference and
acknowledgments added, no change in physics | Astrophys.Space Sci.330:145-150,2010 | 10.1007/s10509-010-0369-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the recent interest in phantom fields as candidates for the dark
energy component, we investigate the consequences of the phantom field when is
minimally coupled to gravity. In particular, the necessary (but insufficient)
conditions for the acceleration and superacceleration of the universe are
obtained when the non-minimal coupling term is taken into account. Furthermore,
the necessary condition for the cosmic acceleration is derived when the phantom
field is non-minimally coupled to gravity and baryonic matter is included.
| [
{
"created": "Tue, 23 Jun 2009 12:14:56 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Mar 2010 18:43:48 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Setare",
"M. R.",
""
],
[
"Vagenas",
"Elias C.",
""
]
] | Motivated by the recent interest in phantom fields as candidates for the dark energy component, we investigate the consequences of the phantom field when is minimally coupled to gravity. In particular, the necessary (but insufficient) conditions for the acceleration and superacceleration of the universe are obtained when the non-minimal coupling term is taken into account. Furthermore, the necessary condition for the cosmic acceleration is derived when the phantom field is non-minimally coupled to gravity and baryonic matter is included. |
1106.4427 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Cosmological apparent and trapping horizons | 18 pages, 2 tables, no figures, to appear in Phys. Rev. D | Phys.Rev.D84:024003,2011 | 10.1103/PhysRevD.84.024003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of particle, event, and apparent horizons in FLRW space are
discussed. The apparent horizon is trapping when the Ricci curvature is
positive. This simple criterion coincides with the condition for the
Kodama-Hayward apparent horizon temperature to be positive, and also
discriminates between timelike and spacelike character of the apparent horizon.
We discuss also the entropy of apparent cosmological horizons in extended
theories of gravity and we use the generalized 2nd law to discard an exact
solution of Brans-Dicke gravity as unphysical.
| [
{
"created": "Wed, 22 Jun 2011 12:09:33 GMT",
"version": "v1"
}
] | 2011-08-08 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | The dynamics of particle, event, and apparent horizons in FLRW space are discussed. The apparent horizon is trapping when the Ricci curvature is positive. This simple criterion coincides with the condition for the Kodama-Hayward apparent horizon temperature to be positive, and also discriminates between timelike and spacelike character of the apparent horizon. We discuss also the entropy of apparent cosmological horizons in extended theories of gravity and we use the generalized 2nd law to discard an exact solution of Brans-Dicke gravity as unphysical. |
2202.00178 | Arianna Renzini | Arianna I. Renzini, Boris Goncharov, Alexander C. Jenkins, Pat M.
Meyers | Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and
Future Prospects | 71 pages, 14 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The collection of individually resolvable gravitational wave (GW) events
makes up a tiny fraction of all GW signals which reach our detectors, while
most lie below the confusion limit and go undetected. Like voices in a crowded
room, the collection of unresolved signals gives rise to a background which is
well-described via stochastic variables, and hence referred to as the
stochastic GW background (SGWB). In this review, we provide an overview of
stochastic GW signals, and characterise them based on features of interest such
as generation processes and observational properties. We then review the
current detection strategies for stochastic backgrounds, offering a
ready-to-use manual for stochastic GW searches in real data. In the process, we
distinguish between interferometric measurements of GWs, either by ground-based
or space-based laser interferometers, and timing-residuals analyses with pulsar
timing arrays (PTAs). These detection methods have been applied to real data
both by the large GW collaborations and smaller research groups, and the most
recent and instructive results are reported here. We close this review with an
outlook on future observations with third generation detectors, space-based
interferometers, and potential non-interferometric detection methods proposed
in the literature.
| [
{
"created": "Tue, 1 Feb 2022 01:25:53 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2022 22:08:11 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Renzini",
"Arianna I.",
""
],
[
"Goncharov",
"Boris",
""
],
[
"Jenkins",
"Alexander C.",
""
],
[
"Meyers",
"Pat M.",
""
]
] | The collection of individually resolvable gravitational wave (GW) events makes up a tiny fraction of all GW signals which reach our detectors, while most lie below the confusion limit and go undetected. Like voices in a crowded room, the collection of unresolved signals gives rise to a background which is well-described via stochastic variables, and hence referred to as the stochastic GW background (SGWB). In this review, we provide an overview of stochastic GW signals, and characterise them based on features of interest such as generation processes and observational properties. We then review the current detection strategies for stochastic backgrounds, offering a ready-to-use manual for stochastic GW searches in real data. In the process, we distinguish between interferometric measurements of GWs, either by ground-based or space-based laser interferometers, and timing-residuals analyses with pulsar timing arrays (PTAs). These detection methods have been applied to real data both by the large GW collaborations and smaller research groups, and the most recent and instructive results are reported here. We close this review with an outlook on future observations with third generation detectors, space-based interferometers, and potential non-interferometric detection methods proposed in the literature. |
gr-qc/9605024 | Jai-chan Hwang | J. Hwang | Evolution of Structures in Generalized Gravity Theories | 9 pages, revtex, no figures | Class.Quant.Grav.14:1981-1991,1997 | 10.1088/0264-9381/14/7/029 | null | gr-qc | null | A broad class of generalized Einstein's gravity can be cast into Einstein's
gravity with a minimally coupled scalar field using suitable conformal
rescaling of the metric. Using this conformal equivalence between the theories,
we derive the equations for the background and the perturbations, and the
general asymptotic solutions for the perturbations in the generalized
Einstein's gravity from the simple results known in the minimally coupled
scalar field. Results for the scalar and tensor perturbations can be presented
in unified forms. The large scale evolutions for both modes are characterized
by corresponding conserved quantities. We also present the normalization
condition for canonical quantization.
| [
{
"created": "Sun, 12 May 1996 05:18:58 GMT",
"version": "v1"
}
] | 2011-09-30 | [
[
"Hwang",
"J.",
""
]
] | A broad class of generalized Einstein's gravity can be cast into Einstein's gravity with a minimally coupled scalar field using suitable conformal rescaling of the metric. Using this conformal equivalence between the theories, we derive the equations for the background and the perturbations, and the general asymptotic solutions for the perturbations in the generalized Einstein's gravity from the simple results known in the minimally coupled scalar field. Results for the scalar and tensor perturbations can be presented in unified forms. The large scale evolutions for both modes are characterized by corresponding conserved quantities. We also present the normalization condition for canonical quantization. |
1401.3276 | Juan Betancort-Rijo | Juan Betancort-Rijo (1,2) and Felipe Jimenez Ibarra (2) ((1) Instituto
de Astrofisica de Canarias, La Laguna, Tenerife, Spain (2) Departamento de
Astrofisica, Universidad de La Laguna, Tenerife, Spain) | Einstein's first gravitational field equation 101 years latter | null | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review and strengthen the arguments given by Einstein to derive his first
gravitational field equation for static fields and show that, although it was
ultimately rejected, it follows from General Relativity (GR) for negligible
pressure. Using this equation and considerations folowing directly from the
equivalence principle (EP), we show how Schwarzschild metric and other vacum
metrics can be obtained immediately. With this results and some basic
principles, we obtain the metric in the general spherically symmetric case and
the corresponding hydrostatic equilibrium equation. For this metrics we obtain
the motion equations in a simple and exact manner that clearly shows the three
sources of difference (implied by various aspects of the EP) with respect to
the Newtonian case and use them to study the classical tests of GR. We comment
on the origin of the problems of Einstein first theory of gravity and discuss
how, by removing it the theory could be made consistent and extended to include
rotations, we also comments on various conceptual issues of GR as the origin of
the gravitational effect of pressure.
| [
{
"created": "Fri, 10 Jan 2014 18:58:12 GMT",
"version": "v1"
}
] | 2014-01-15 | [
[
"Betancort-Rijo",
"Juan",
""
],
[
"Ibarra",
"Felipe Jimenez",
""
]
] | We review and strengthen the arguments given by Einstein to derive his first gravitational field equation for static fields and show that, although it was ultimately rejected, it follows from General Relativity (GR) for negligible pressure. Using this equation and considerations folowing directly from the equivalence principle (EP), we show how Schwarzschild metric and other vacum metrics can be obtained immediately. With this results and some basic principles, we obtain the metric in the general spherically symmetric case and the corresponding hydrostatic equilibrium equation. For this metrics we obtain the motion equations in a simple and exact manner that clearly shows the three sources of difference (implied by various aspects of the EP) with respect to the Newtonian case and use them to study the classical tests of GR. We comment on the origin of the problems of Einstein first theory of gravity and discuss how, by removing it the theory could be made consistent and extended to include rotations, we also comments on various conceptual issues of GR as the origin of the gravitational effect of pressure. |
0704.3184 | Alexander Burinskii | Alexander Burinskii | Kerr-Schild Photonlike Metric Solutions | 6 p, Revtex4 | null | null | null | gr-qc hep-th | null | The charged and spinning lightlike solutions are obtained in the Kerr-Schild
formalism. In particular, one of them may be considered as an ultrarelativistic
boost of the Kerr-Newman solution along the direction of angular momentum. The
Kerr singular ring disappears, however, there remains a finite parameter $a$
which determines spin by the Kerr relation $J=ma$. By $J=\hbar$, the parameter
$a$ is de Broglie wavelength of the corresponding photon. Electromagnetic field
is aligned to the Kerr null congruence. Some of the presented solutions contain
singular beam pulse (pp-strings) like the considered recently `gyratons'.
| [
{
"created": "Tue, 24 Apr 2007 13:01:59 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Apr 2007 11:18:01 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Mar 2008 13:18:54 GMT",
"version": "v3"
}
] | 2008-03-20 | [
[
"Burinskii",
"Alexander",
""
]
] | The charged and spinning lightlike solutions are obtained in the Kerr-Schild formalism. In particular, one of them may be considered as an ultrarelativistic boost of the Kerr-Newman solution along the direction of angular momentum. The Kerr singular ring disappears, however, there remains a finite parameter $a$ which determines spin by the Kerr relation $J=ma$. By $J=\hbar$, the parameter $a$ is de Broglie wavelength of the corresponding photon. Electromagnetic field is aligned to the Kerr null congruence. Some of the presented solutions contain singular beam pulse (pp-strings) like the considered recently `gyratons'. |
1611.05337 | Sharmanthie Fernando | Sharmanthie Fernando | Bardeen-de Sitter black holes | 20 pages with 12 figures, Accepted to be published in International
Journal of Modern Physics D | International Journal of Modern Physics D, vol: 26, no: 07,
1750071 (2017) | 10.1142/S0218271817500717 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a regular black hole with a positive cosmological
constant. The regular black hole considered is the well known Bardeen black
hole and it is a solution to the Einstein equations coupled to non-linear
electrodynamics with a magnetic monopole. The paper discuss the properties of
the Bardeen-de Sitter black hole. We have computed the grey body factors and
partial absorption cross sections for massless scalar field impinges on this
black hole with the third order WKB approximation. A detailed discussion on how
the behavior of the grey body factors depend on the parameters of the theory
such as the mass, charge and the cosmological constant is given. Possible
extensions of the work is discussed at the end of the paper.
| [
{
"created": "Wed, 16 Nov 2016 15:55:28 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2016 15:12:34 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Jan 2017 20:32:04 GMT",
"version": "v3"
}
] | 2017-06-15 | [
[
"Fernando",
"Sharmanthie",
""
]
] | In this paper we present a regular black hole with a positive cosmological constant. The regular black hole considered is the well known Bardeen black hole and it is a solution to the Einstein equations coupled to non-linear electrodynamics with a magnetic monopole. The paper discuss the properties of the Bardeen-de Sitter black hole. We have computed the grey body factors and partial absorption cross sections for massless scalar field impinges on this black hole with the third order WKB approximation. A detailed discussion on how the behavior of the grey body factors depend on the parameters of the theory such as the mass, charge and the cosmological constant is given. Possible extensions of the work is discussed at the end of the paper. |
gr-qc/9805083 | Marek Pawlowski | L. N. Gyngazov, M. Pawlowski, V. N. Pervushin, V. I. Smirichinski | Proper Time Dynamics in General Relativity and Conformal Unified Theory | 20 pages, latex, no figures, submited to General Relativity and
Garvitation | Gen.Rel.Grav.30:1749-1773,1998 | 10.1023/A:1026667111744 | JINR E2-98-114 | gr-qc | null | The paper is devoted to the description a measurable time-interval (``proper
time'') in the Hamiltonian version of general relativity with the Dirac-ADM
metric. To separate the dynamical parameter of evolution from the space metric
we use the Lichnerowicz conformally invariant variables. In terms of these
variables GR is equivalent to the conformally invariant
Penrose-Chernicov-Tagirov theory of a scalar field the role of which is played
by the scale factor multiplied on the Planck constant. Identification of this
scalar field with the modulus of the Higgs field in the standard model of
electroweak and strong interactions allows us to formulate an example of
conformally invariant unified theory where the vacuum averaging of the scalar
field is determined by cosmological integrals of motion of the Universe
evolution.
| [
{
"created": "Thu, 21 May 1998 13:11:59 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Gyngazov",
"L. N.",
""
],
[
"Pawlowski",
"M.",
""
],
[
"Pervushin",
"V. N.",
""
],
[
"Smirichinski",
"V. I.",
""
]
] | The paper is devoted to the description a measurable time-interval (``proper time'') in the Hamiltonian version of general relativity with the Dirac-ADM metric. To separate the dynamical parameter of evolution from the space metric we use the Lichnerowicz conformally invariant variables. In terms of these variables GR is equivalent to the conformally invariant Penrose-Chernicov-Tagirov theory of a scalar field the role of which is played by the scale factor multiplied on the Planck constant. Identification of this scalar field with the modulus of the Higgs field in the standard model of electroweak and strong interactions allows us to formulate an example of conformally invariant unified theory where the vacuum averaging of the scalar field is determined by cosmological integrals of motion of the Universe evolution. |
1505.04434 | Joan Sola | Spyros Basilakos, Nick E. Mavromatos and Joan Sola | Starobinsky-like inflation and running vacuum in the context of
Supergravity | Version accepted in Universe | null | null | LCTS/2015-11 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the primeval inflationary phase of the early Universe within a
quantum field theoretical (QFT) framework that can be viewed as the effective
action of vacuum decay in the early times. Interestingly enough, the model
accounts for the "graceful exit" of the inflationary phase into the standard
radiation regime. The underlying QFT framework considered here is Supergravity
(SUGRA), more specifically an existing formulation in which the
Starobinsky-type inflation (de-Sitter background) emerges from the quantum
corrections to the effective action after integrating out the gravitino fields
in their (dynamically induced) massive phase. We also demonstrate that the
structure of the effective action in this model is consistent with the generic
idea of renormalization group (RG) running of the cosmological parameters,
specifically it follows from the corresponding RG equation for the vacuum
energy density as a function of the Hubble rate, $\rho_{\Lambda}(H)$. Overall
our combined approach amounts to a concrete-model realization of inflation
triggered by vacuum decay in a fundamental physics context which, as it turns
out, can also be extended for the remaining epochs of the cosmological
evolution until the current dark energy era.
| [
{
"created": "Sun, 17 May 2015 18:56:31 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Feb 2016 13:45:56 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Jul 2016 19:29:03 GMT",
"version": "v3"
}
] | 2016-07-22 | [
[
"Basilakos",
"Spyros",
""
],
[
"Mavromatos",
"Nick E.",
""
],
[
"Sola",
"Joan",
""
]
] | We describe the primeval inflationary phase of the early Universe within a quantum field theoretical (QFT) framework that can be viewed as the effective action of vacuum decay in the early times. Interestingly enough, the model accounts for the "graceful exit" of the inflationary phase into the standard radiation regime. The underlying QFT framework considered here is Supergravity (SUGRA), more specifically an existing formulation in which the Starobinsky-type inflation (de-Sitter background) emerges from the quantum corrections to the effective action after integrating out the gravitino fields in their (dynamically induced) massive phase. We also demonstrate that the structure of the effective action in this model is consistent with the generic idea of renormalization group (RG) running of the cosmological parameters, specifically it follows from the corresponding RG equation for the vacuum energy density as a function of the Hubble rate, $\rho_{\Lambda}(H)$. Overall our combined approach amounts to a concrete-model realization of inflation triggered by vacuum decay in a fundamental physics context which, as it turns out, can also be extended for the remaining epochs of the cosmological evolution until the current dark energy era. |
1411.4735 | Pardyumn Kumar Sahoo | P.K. Sahoo, B. Mishra and S.K. Tripathy | Kaluza-Klein cosmological model in $f(R,T)$ gravity with $\Lambda(T)$ | 10 pages, 9 figures | Indian Journal of Physics, Vol 94(4), 485-493, 2016 | 10.1007/s12648-015-0759-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of Kaluza-Klein cosmological models in $f(R,T)$ theory of gravity
have been investigated. In the work, we have considered the functional $f(R,T)$
to be in the form $f(R,T)=f(R)+f(T)$ with $f(R)=\lambda R$ and $f(T)=\lambda
T$. Such a choice of the functional $f(R,T)$ leads to an evolving effective
cosmological constant $\Lambda$ which depends on the stress energy tensor. The
source of the matter field is taken to be a perfect cosmic fluid. The exact
solutions of the field equations are obtained by considering a constant
deceleration parameter which leads two different aspects of the volumetric
expansion namely a power law and an exponential volumetric expansion. Keeping
an eye on the accelerating nature of the universe in the present epoch, the
dynamics and physical behaviour of the models have been discussed. From
statefinder diagnostic pair we found that the model with exponential volumetric
expansion behaves more like a $\Lambda$CDM model.
| [
{
"created": "Tue, 18 Nov 2014 05:08:55 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Nov 2014 05:14:24 GMT",
"version": "v2"
}
] | 2016-07-14 | [
[
"Sahoo",
"P. K.",
""
],
[
"Mishra",
"B.",
""
],
[
"Tripathy",
"S. K.",
""
]
] | A class of Kaluza-Klein cosmological models in $f(R,T)$ theory of gravity have been investigated. In the work, we have considered the functional $f(R,T)$ to be in the form $f(R,T)=f(R)+f(T)$ with $f(R)=\lambda R$ and $f(T)=\lambda T$. Such a choice of the functional $f(R,T)$ leads to an evolving effective cosmological constant $\Lambda$ which depends on the stress energy tensor. The source of the matter field is taken to be a perfect cosmic fluid. The exact solutions of the field equations are obtained by considering a constant deceleration parameter which leads two different aspects of the volumetric expansion namely a power law and an exponential volumetric expansion. Keeping an eye on the accelerating nature of the universe in the present epoch, the dynamics and physical behaviour of the models have been discussed. From statefinder diagnostic pair we found that the model with exponential volumetric expansion behaves more like a $\Lambda$CDM model. |
1607.04070 | Kimet Jusufi | Kimet Jusufi | Quantum Corrected Schwarzschild Thin Shell Wormhole | 8 pages, 4 figures, accepted for publication in EPJC | Eur. Phys. J. C (2016) 76: 608 | 10.1140/epjc/s10052-016-4456-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Ali and Khalil \cite{Farag Ali}, based on the Bohmian quantum
mechanics derived a quantum corrected version of the Schwarzschild metric. In
this paper, we construct a quantum corrected Schwarzschild thin shell wormhole
(QSTSW) and investigate the stability of this wormhole. First we compute the
surface stress at the wormhole throat by applying the Darmois-Israel formalism
to the modified Schwarzschild metric and show that exotic matter is required at
the throat to keep the wormhole stable. We then study the stability analysis of
the wormhole by considering phantom-energy for the exotic matter, generalized
Chaplygin gas (GCG), and the linearized stability analysis. It is argued that,
quantum corrections can affect the stability domain of the wormhole.
| [
{
"created": "Thu, 14 Jul 2016 10:24:38 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Oct 2016 11:23:49 GMT",
"version": "v2"
}
] | 2016-11-08 | [
[
"Jusufi",
"Kimet",
""
]
] | Recently, Ali and Khalil \cite{Farag Ali}, based on the Bohmian quantum mechanics derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois-Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to keep the wormhole stable. We then study the stability analysis of the wormhole by considering phantom-energy for the exotic matter, generalized Chaplygin gas (GCG), and the linearized stability analysis. It is argued that, quantum corrections can affect the stability domain of the wormhole. |
2310.08141 | Samuel Blitz | Samuel Blitz and David McNutt | Horizons that Gyre and Gimble: A Differential Characterization of Null
Hypersurfaces | 18 pages, significant changes | null | null | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | Motivated by the thermodynamics of black hole solutions conformal to
stationary solutions, we study the geometric invariant theory of null
hypersurfaces. It is well-known that a null hypersurface in a Lorentzian
manifold can be treated as a Carrollian geometry. Additional structure can be
added to this geometry by choosing a connection which yields a Carrollian
manifold. In the literature various authors have introduced Koszul connections
to study the study the physics on these hypersurfaces. In this paper we examine
the various Carrollian geometries and their relationship to null hypersurface
embeddings. We specify the geometric data required to construct a rigid
Carrollian geometry, and we argue that a connection with torsion is the most
natural object to study Carrollian manifolds. We then use this connection to
develop a hypersurface calculus suitable for a study of intrinsic and extrinsic
differential invariants on embedded null hypersurfaces; motivating examples are
given, including geometric invariants preserved under conformal
transformations.
| [
{
"created": "Thu, 12 Oct 2023 08:55:34 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Mar 2024 10:11:35 GMT",
"version": "v2"
}
] | 2024-03-19 | [
[
"Blitz",
"Samuel",
""
],
[
"McNutt",
"David",
""
]
] | Motivated by the thermodynamics of black hole solutions conformal to stationary solutions, we study the geometric invariant theory of null hypersurfaces. It is well-known that a null hypersurface in a Lorentzian manifold can be treated as a Carrollian geometry. Additional structure can be added to this geometry by choosing a connection which yields a Carrollian manifold. In the literature various authors have introduced Koszul connections to study the study the physics on these hypersurfaces. In this paper we examine the various Carrollian geometries and their relationship to null hypersurface embeddings. We specify the geometric data required to construct a rigid Carrollian geometry, and we argue that a connection with torsion is the most natural object to study Carrollian manifolds. We then use this connection to develop a hypersurface calculus suitable for a study of intrinsic and extrinsic differential invariants on embedded null hypersurfaces; motivating examples are given, including geometric invariants preserved under conformal transformations. |
1703.05316 | S Habib Mazharimousavi | S. Habib Mazharimousavi, Z. Amirabi and M. Halilsoy | Magnetic Morris-Thorne wormhole in 2+1-dimensions | 8 pages, one figure published version | Gen Relativ Gravit 48, 143 (2016) | 10.1007/s10714-016-2139-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of $2+1-$dimensional gravity coupled to a particular nonlinear
electrodynamics (NED), we obtain a class of traversable / Morris-Thorne type
wormhole solutions. The problem is reduced to a single function dependence in
which the shape function acts as generator to the wormholes. The field ansatz
is pure magnetic and the nonlinear Lagrangian is $\sqrt{F_{\mu \nu }F^{\mu \nu
}}$ i.e. the square root of the Maxwell Lagrangian. In $2+1-$dimensions the
source-free pure magnetic non-linear Maxwell equation with square-root
Lagrangian is trivially satisfied. The exotic energy density is found
explicitly and the flare-out conditions are emphasized.
| [
{
"created": "Wed, 15 Mar 2017 12:49:29 GMT",
"version": "v1"
}
] | 2017-03-17 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Amirabi",
"Z.",
""
],
[
"Halilsoy",
"M.",
""
]
] | In the context of $2+1-$dimensional gravity coupled to a particular nonlinear electrodynamics (NED), we obtain a class of traversable / Morris-Thorne type wormhole solutions. The problem is reduced to a single function dependence in which the shape function acts as generator to the wormholes. The field ansatz is pure magnetic and the nonlinear Lagrangian is $\sqrt{F_{\mu \nu }F^{\mu \nu }}$ i.e. the square root of the Maxwell Lagrangian. In $2+1-$dimensions the source-free pure magnetic non-linear Maxwell equation with square-root Lagrangian is trivially satisfied. The exotic energy density is found explicitly and the flare-out conditions are emphasized. |
2202.02238 | Yaser Tavakoli | Yaser Tavakoli, Ahad K. Ardabili, Mariam Bouhmadi-L\'opez and Paulo
Vargas Moniz | Role of Gauss-Bonnet corrections in a DGP brane gravitational collapse | 28 pages, 5 figures (version published in PRD) | Phys. Rev. D 105, 084050 (2022) | 10.1103/PhysRevD.105.084050 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | An Oppenheimer-Snyder (OS)-type collapse is considered for a
Dvali-Gabadadze-Porrati (DGP) brane, whereas a Gauss-Bonnet (GB) term is
provided for the bulk. We study the combined effect of the DGP induced gravity
plus the GB curvature, regarding any modification of the general relativistic
OS dynamics. Our paper has a twofold objective. On the one hand, we investigate
the nature of singularities that may arise at the collapse end state. It is
shown that all dynamical scenarios for the contracting brane would end in one
of the following cases, depending on conditions imposed: either a central
shell-focusing singularity or what we designate as a "sudden collapse
singularity." On the other hand, we also study the deviations of the exterior
spacetime from the standard Schwarzschild geometry, which emerges in our
modified OS scenario. Our purpose is to investigate whether a black hole always
forms regarding this brane world model. We find situations where a naked
singularity emerges instead.
| [
{
"created": "Fri, 4 Feb 2022 17:16:26 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2022 16:23:13 GMT",
"version": "v2"
}
] | 2022-04-27 | [
[
"Tavakoli",
"Yaser",
""
],
[
"Ardabili",
"Ahad K.",
""
],
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Moniz",
"Paulo Vargas",
""
]
] | An Oppenheimer-Snyder (OS)-type collapse is considered for a Dvali-Gabadadze-Porrati (DGP) brane, whereas a Gauss-Bonnet (GB) term is provided for the bulk. We study the combined effect of the DGP induced gravity plus the GB curvature, regarding any modification of the general relativistic OS dynamics. Our paper has a twofold objective. On the one hand, we investigate the nature of singularities that may arise at the collapse end state. It is shown that all dynamical scenarios for the contracting brane would end in one of the following cases, depending on conditions imposed: either a central shell-focusing singularity or what we designate as a "sudden collapse singularity." On the other hand, we also study the deviations of the exterior spacetime from the standard Schwarzschild geometry, which emerges in our modified OS scenario. Our purpose is to investigate whether a black hole always forms regarding this brane world model. We find situations where a naked singularity emerges instead. |
gr-qc/0508029 | Volker Perlick | Volker Perlick | Fermat Principle in Finsler Spacetimes | 18 pages, submitted to Gen. Rel. Grav | Gen.Rel.Grav. 38 (2006) 365-380 | 10.1007/s10714-005-0225-6 | null | gr-qc | null | It is shown that, on a manifold with a Finsler metric of Lorentzian
signature, the lightlike geodesics satisfy the following variational principle.
Among all lightlike curves from a point (emission event) to a timelike curve
(worldline of receiver), the lightlike geodesics make the arrival time
stationary. Here ``arrival time'' refers to a parametrization of the timelike
curve. This variational principle can be applied (i) to the vacuum light rays
in an alternative spacetime theory, based on Finsler geometry, and (ii) to
light rays in an anisotropic non-dispersive medium with a general-relativistic
spacetime as background.
| [
{
"created": "Mon, 8 Aug 2005 19:57:34 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Perlick",
"Volker",
""
]
] | It is shown that, on a manifold with a Finsler metric of Lorentzian signature, the lightlike geodesics satisfy the following variational principle. Among all lightlike curves from a point (emission event) to a timelike curve (worldline of receiver), the lightlike geodesics make the arrival time stationary. Here ``arrival time'' refers to a parametrization of the timelike curve. This variational principle can be applied (i) to the vacuum light rays in an alternative spacetime theory, based on Finsler geometry, and (ii) to light rays in an anisotropic non-dispersive medium with a general-relativistic spacetime as background. |
gr-qc/0003099 | Eric Chassande-Mottin | E. Chassande-Mottin and S. V. Dhurandhar | Adaptive filtering techniques for gravitational wave interferometric
data: Removing long-term sinusoidal disturbances and oscillatory transients | 16 pages, 9 figures, submitted to Phys. Rev. D | Phys.Rev. D63 (2001) 042004 | 10.1103/PhysRevD.63.042004 | null | gr-qc | null | It is known by the experience gained from the gravitational wave detector
proto-types that the interferometric output signal will be corrupted by a
significant amount of non-Gaussian noise, large part of it being essentially
composed of long-term sinusoids with slowly varying envelope (such as violin
resonances in the suspensions, or main power harmonics) and short-term ringdown
noise (which may emanate from servo control systems, electronics in a
non-linear state, etc.). Since non-Gaussian noise components make the detection
and estimation of the gravitational wave signature more difficult, a denoising
algorithm based on adaptive filtering techniques (LMS methods) is proposed to
separate and extract them from the stationary and Gaussian background noise.
The strength of the method is that it does not require any precise model on the
observed data: the signals are distinguished on the basis of their
autocorrelation time. We believe that the robustness and simplicity of this
method make it useful for data preparation and for the understanding of the
first interferometric data. We present the detailed structure of the algorithm
and its application to both simulated data and real data from the LIGO 40meter
proto-type.
| [
{
"created": "Mon, 27 Mar 2000 17:12:45 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Chassande-Mottin",
"E.",
""
],
[
"Dhurandhar",
"S. V.",
""
]
] | It is known by the experience gained from the gravitational wave detector proto-types that the interferometric output signal will be corrupted by a significant amount of non-Gaussian noise, large part of it being essentially composed of long-term sinusoids with slowly varying envelope (such as violin resonances in the suspensions, or main power harmonics) and short-term ringdown noise (which may emanate from servo control systems, electronics in a non-linear state, etc.). Since non-Gaussian noise components make the detection and estimation of the gravitational wave signature more difficult, a denoising algorithm based on adaptive filtering techniques (LMS methods) is proposed to separate and extract them from the stationary and Gaussian background noise. The strength of the method is that it does not require any precise model on the observed data: the signals are distinguished on the basis of their autocorrelation time. We believe that the robustness and simplicity of this method make it useful for data preparation and for the understanding of the first interferometric data. We present the detailed structure of the algorithm and its application to both simulated data and real data from the LIGO 40meter proto-type. |
gr-qc/9502009 | Robert C. Myers | TED JACOBSON, GUNGWON KANG and ROBERT C. MYERS | BLACK HOLE ENTROPY IN HIGHER CURVATURE GRAVITY | 18 pages, LaTeX, Based on talks presented at the 16th Annual MRST
Meeting and at the Heat Kernel Techniques and Quantum Gravity Meeting, very
minor corrections made for some typo's in the original version. | null | null | McGill/95--04; UMDGR--95-092 | gr-qc hep-th | null | We discuss some recent results on black hole thermodynamics within the
context of effective gravitational actions including higher-curvature
interactions. Wald's derivation of the First Law demonstrates that black hole
entropy can always be expressed as a local geometric density integrated over a
space-like cross-section of the horizon. In certain cases, it can also be shown
that these entropy expressions satisfy a Second Law. One such simple example is
considered from the class of higher curvature theories where the Lagrangian
consists of a polynomial in the Ricci scalar.
| [
{
"created": "Thu, 2 Feb 1995 23:22:03 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Feb 1995 19:41:31 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"JACOBSON",
"TED",
""
],
[
"KANG",
"GUNGWON",
""
],
[
"MYERS",
"ROBERT C.",
""
]
] | We discuss some recent results on black hole thermodynamics within the context of effective gravitational actions including higher-curvature interactions. Wald's derivation of the First Law demonstrates that black hole entropy can always be expressed as a local geometric density integrated over a space-like cross-section of the horizon. In certain cases, it can also be shown that these entropy expressions satisfy a Second Law. One such simple example is considered from the class of higher curvature theories where the Lagrangian consists of a polynomial in the Ricci scalar. |
2311.07921 | Susobhan Mandal | Susobhan Mandal, Tausif Parvez, S. Shankaranarayanan | From Horndeski action to the Callan-Giddings-Harvey-Strominger model and
beyond | V2: Version accepted in PRD Letters. The title is modified. 34 Pages,
4 figures (including supplementary material) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The knowledge of what entered black hole (BH) is completely lost as it
evaporates. This contradicts the unitarity principle of quantum mechanics and
is referred to as the information loss paradox. Understanding the end stages of
BH evaporation is key to resolving this paradox. As a first step, we need to
have exact models that can mimic 4-D BHs in General relativity in classical
limit and have a systematic way to include high-energy corrections. While there
are various models in the literature, there is no systematic procedure by which
one can study high-energy corrections. In this work, for the first time, we
obtain Callan, Giddings, Harvey, and Strominger (CGHS) -- a (1+1)-D -- model
from 4-D Horndeski action -- the most general scalar-tensor theory that does
not lead to Ostrogradsky ghosts. We then show that 4-D Horndeski action can
systematically provide a route to include higher-derivative terms relevant at
the end stages of black hole evaporation. We derive the leading order Hawking
flux while discussing some intriguing characteristics of the corrected CGHS
models. We compare our results with other works and discuss the implications
for primordial BHs.
| [
{
"created": "Tue, 14 Nov 2023 05:45:25 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jan 2024 13:14:59 GMT",
"version": "v2"
}
] | 2024-01-19 | [
[
"Mandal",
"Susobhan",
""
],
[
"Parvez",
"Tausif",
""
],
[
"Shankaranarayanan",
"S.",
""
]
] | The knowledge of what entered black hole (BH) is completely lost as it evaporates. This contradicts the unitarity principle of quantum mechanics and is referred to as the information loss paradox. Understanding the end stages of BH evaporation is key to resolving this paradox. As a first step, we need to have exact models that can mimic 4-D BHs in General relativity in classical limit and have a systematic way to include high-energy corrections. While there are various models in the literature, there is no systematic procedure by which one can study high-energy corrections. In this work, for the first time, we obtain Callan, Giddings, Harvey, and Strominger (CGHS) -- a (1+1)-D -- model from 4-D Horndeski action -- the most general scalar-tensor theory that does not lead to Ostrogradsky ghosts. We then show that 4-D Horndeski action can systematically provide a route to include higher-derivative terms relevant at the end stages of black hole evaporation. We derive the leading order Hawking flux while discussing some intriguing characteristics of the corrected CGHS models. We compare our results with other works and discuss the implications for primordial BHs. |
0711.0428 | Joseph Samuel | Joseph Samuel and Sutirtha Roy Chowdhury | Geometric flows and black hole entropy | 11 pages, no figures | Class.Quant.Grav.24:F47-F54,2007 | 10.1088/0264-9381/24/11/F01 | null | gr-qc | null | Perelman has given a gradient formulation for the Ricci flow, introducing an
``entropy function'' which increases monotonically along the flow.We pursue a
thermodynamic analogy and apply Ricci flow ideas to general relativity. We
investigate whether Perelman's entropy is related to
(Bekenstein-Hawking)geometric entropy as familiar from black hole
thermodynamics. From a study of the fixed points of the flow we conclude that
Perelman entropy is not connected to geometric entropy. However, we notice that
there is a very similar flow which DOES appear to be connected to geometric
entropy. The new flow may find applications in black hole physics suggesting
for instance, new approaches to the Penrose inequality.
| [
{
"created": "Sat, 3 Nov 2007 05:34:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Samuel",
"Joseph",
""
],
[
"Chowdhury",
"Sutirtha Roy",
""
]
] | Perelman has given a gradient formulation for the Ricci flow, introducing an ``entropy function'' which increases monotonically along the flow.We pursue a thermodynamic analogy and apply Ricci flow ideas to general relativity. We investigate whether Perelman's entropy is related to (Bekenstein-Hawking)geometric entropy as familiar from black hole thermodynamics. From a study of the fixed points of the flow we conclude that Perelman entropy is not connected to geometric entropy. However, we notice that there is a very similar flow which DOES appear to be connected to geometric entropy. The new flow may find applications in black hole physics suggesting for instance, new approaches to the Penrose inequality. |
1110.6238 | Y. M. Cho | Y. M. Cho and Franklin H. Cho | Knot Topology of Vacuum Space-Time and Vacuum Decomposition of
Einstein's Theory | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Viewing Einstein's theory as the gauge theory of Lorentz group, we construct
the most general vacuum connections which have vanishing curvature tensor and
show that the vacuum space-time can be classified by the knot topology
$\pi_3(S^3)\simeq \pi_3(S^2)$ of $\pi_3(SO(3,1))$. With this we obtain the
gauge independent vacuum decomposition of Einstein's theory to the vacuum and
gauge covariant physical parts. We discuss the physical implications of our
result in quantum gravity.
| [
{
"created": "Fri, 28 Oct 2011 03:37:12 GMT",
"version": "v1"
}
] | 2011-10-31 | [
[
"Cho",
"Y. M.",
""
],
[
"Cho",
"Franklin H.",
""
]
] | Viewing Einstein's theory as the gauge theory of Lorentz group, we construct the most general vacuum connections which have vanishing curvature tensor and show that the vacuum space-time can be classified by the knot topology $\pi_3(S^3)\simeq \pi_3(S^2)$ of $\pi_3(SO(3,1))$. With this we obtain the gauge independent vacuum decomposition of Einstein's theory to the vacuum and gauge covariant physical parts. We discuss the physical implications of our result in quantum gravity. |
2005.05785 | Adriano Barreto | Adriano B. Barreto and Gilberto M. Kremer | Cosmological Solutions for the Geometrical Scalar-Tensor with the
Potential Determined by the Noether Symmetry Approach | 14 pages, 3 figures | Symmetry 2020, 12(7), 1110 | 10.3390/sym12071110 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we consider a scale-tensor theory in which the space-time is
endowed with a Weyl integrable geometrical structure due to the Palatini
variational method. Since the scalar field has a geometrical nature (related to
non-metricity), the theory is known as \textit{Geometrical Scalar-Tensor}. On
the framework of Weyl transformations, a non-minimally coupled scalar-tensor
theory on the Jordan frame corresponds to a minimally coupled Einstein-Hilbert
action on the Einstein frame. The scalar potential is selected by the Noether
symmetry approach in order to obtain conserved quantities for the FRW
cosmological model. Exact solutions are obtained and analyzed in the context of
the cosmological scenarios consistent with an expanding universe. A particular
case is matched in each frame and the role of scalar field as a dark energy
component is discussed.
| [
{
"created": "Tue, 12 May 2020 14:07:12 GMT",
"version": "v1"
}
] | 2020-07-06 | [
[
"Barreto",
"Adriano B.",
""
],
[
"Kremer",
"Gilberto M.",
""
]
] | In this work we consider a scale-tensor theory in which the space-time is endowed with a Weyl integrable geometrical structure due to the Palatini variational method. Since the scalar field has a geometrical nature (related to non-metricity), the theory is known as \textit{Geometrical Scalar-Tensor}. On the framework of Weyl transformations, a non-minimally coupled scalar-tensor theory on the Jordan frame corresponds to a minimally coupled Einstein-Hilbert action on the Einstein frame. The scalar potential is selected by the Noether symmetry approach in order to obtain conserved quantities for the FRW cosmological model. Exact solutions are obtained and analyzed in the context of the cosmological scenarios consistent with an expanding universe. A particular case is matched in each frame and the role of scalar field as a dark energy component is discussed. |
1307.5461 | Florian Girelli | Maite Dupuis, Florian Girelli | Quantum hyperbolic geometry in loop quantum gravity with cosmological
constant | 6pages, 1 figure | null | 10.1103/PhysRevD.87.121502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Quantum Gravity (LQG) is an attempt to describe the quantum gravity
regime. Introducing a non-zero cosmological constant $\Lambda$ in this context
has been a withstanding problem. Other approaches, such as Chern-Simons
gravity, suggest that quantum groups can be used to introduce $\Lambda$ in the
game. Not much is known when defining LQG with a quantum group. Tensor
operators can be used to construct observables in any type of discrete quantum
gauge theory with a classical/quantum gauge group. We illustrate this by
constructing explicitly geometric observables for LQG defined with a quantum
group and show for the first time that they encode a quantized hyperbolic
geometry. This is a novel argument pointing out the usefulness of quantum
groups as encoding a non-zero cosmological constant. We conclude by discussing
how tensor operators provide the right formalism to unlock the LQG formulation
with a non-zero cosmological constant.
| [
{
"created": "Sat, 20 Jul 2013 20:57:13 GMT",
"version": "v1"
}
] | 2013-07-24 | [
[
"Dupuis",
"Maite",
""
],
[
"Girelli",
"Florian",
""
]
] | Loop Quantum Gravity (LQG) is an attempt to describe the quantum gravity regime. Introducing a non-zero cosmological constant $\Lambda$ in this context has been a withstanding problem. Other approaches, such as Chern-Simons gravity, suggest that quantum groups can be used to introduce $\Lambda$ in the game. Not much is known when defining LQG with a quantum group. Tensor operators can be used to construct observables in any type of discrete quantum gauge theory with a classical/quantum gauge group. We illustrate this by constructing explicitly geometric observables for LQG defined with a quantum group and show for the first time that they encode a quantized hyperbolic geometry. This is a novel argument pointing out the usefulness of quantum groups as encoding a non-zero cosmological constant. We conclude by discussing how tensor operators provide the right formalism to unlock the LQG formulation with a non-zero cosmological constant. |
gr-qc/0305072 | Vishnu Jejjala | Vishnu Jejjala, Robert G. Leigh, Djordje Minic | Deconstructing the Cosmological Constant | Fourth Prize, 2003 Gravity Research Foundation Essay Contest; 7
pages, LaTeX | Gen.Rel.Grav. 35 (2003) 2089-2095 | 10.1023/A:1027337303968 | VPI-IPPAP-03-07, CERN-TH/2003-109 | gr-qc hep-ph hep-th | null | Deconstruction provides a novel way of dealing with the notoriously difficult
ultraviolet problems of four-dimensional gravity. This approach also naturally
leads to a new perspective on the holographic principle, tying it to the
fundamental requirements of unitarity and diffeomorphism invariance, as well as
to a new viewpoint on the cosmological constant problem. The numerical
smallness of the cosmological constant is implied by a unique combination of
holography and supersymmetry, opening a new window into the fundamental physics
of the vacuum.
| [
{
"created": "Mon, 19 May 2003 20:20:50 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Jejjala",
"Vishnu",
""
],
[
"Leigh",
"Robert G.",
""
],
[
"Minic",
"Djordje",
""
]
] | Deconstruction provides a novel way of dealing with the notoriously difficult ultraviolet problems of four-dimensional gravity. This approach also naturally leads to a new perspective on the holographic principle, tying it to the fundamental requirements of unitarity and diffeomorphism invariance, as well as to a new viewpoint on the cosmological constant problem. The numerical smallness of the cosmological constant is implied by a unique combination of holography and supersymmetry, opening a new window into the fundamental physics of the vacuum. |
gr-qc/9805092 | null | A. Dobado and A.L. Maroto | Non-local gravitational effective action and particle production | 8 pages, Latex. Contribution to the Proceedings of the International
Seminar on Mathematical Cosmology, Potsdam (Germany), March 30 - April 4,
1998 | null | null | FT-UCM/10-98 | gr-qc | null | We study the effective action for gravity obtained after the integration of
scalar matter fields, using the local momentum representation based on the
Riemann normal coordinates expansion. By considering this expansion around
different space-time points, we also compute the non-local terms together with
the more usual divergent ones. We discuss the applicability of our results to
the calculation of particle production rates in cosmological backgrounds and
compare this method with the traditional Bogolyubov transformations.
| [
{
"created": "Tue, 26 May 1998 15:21:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dobado",
"A.",
""
],
[
"Maroto",
"A. L.",
""
]
] | We study the effective action for gravity obtained after the integration of scalar matter fields, using the local momentum representation based on the Riemann normal coordinates expansion. By considering this expansion around different space-time points, we also compute the non-local terms together with the more usual divergent ones. We discuss the applicability of our results to the calculation of particle production rates in cosmological backgrounds and compare this method with the traditional Bogolyubov transformations. |
gr-qc/9805056 | null | M. Brunetti, E. Coccia, V. Fafone, F. Fucito | Gravitational Wave Radiation from Compact Binary Systems in the
Jordan-Brans-Dicke Theory | 24 pages, 3 figures, some references added with comments | Phys.Rev. D59 (1999) 044027 | 10.1103/PhysRevD.59.044027 | ROM2F/98/11 | gr-qc astro-ph hep-th | null | In this paper we analyze the signal emitted by a compact binary system in the
Jordan-Brans-Dicke theory. We compute the scalar and tensor components of the
power radiated by the source and study the scalar waveform. Eventually we
consider the detectability of the scalar component of the radiation by
interferometers and resonant-mass detectors.
| [
{
"created": "Thu, 14 May 1998 08:12:50 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Sep 1998 07:54:42 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Brunetti",
"M.",
""
],
[
"Coccia",
"E.",
""
],
[
"Fafone",
"V.",
""
],
[
"Fucito",
"F.",
""
]
] | In this paper we analyze the signal emitted by a compact binary system in the Jordan-Brans-Dicke theory. We compute the scalar and tensor components of the power radiated by the source and study the scalar waveform. Eventually we consider the detectability of the scalar component of the radiation by interferometers and resonant-mass detectors. |
2104.14318 | Sergi Nadal-Gisbert | Antonio Ferreiro, Sergi Nadal-Gisbert and Jos\'e Navarro-Salas | Renormalization, running couplings and decoupling for the Yukawa model
in curved spacetime | New references and comments added | Phys. Rev. D 104, 025003 (2021) | 10.1103/PhysRevD.104.025003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The decoupling of heavy fields as required by the Appelquist-Carazzone
theorem plays a fundamental role in the construction of any effective field
theory. However, it is not a trivial task to implement a renormalization
prescription that produces the expected decoupling of massive fields, and it is
even more difficult in curved spacetime. Focused on this idea, we consider the
renormalization of the one-loop effective action for the Yukawa interaction
with a background scalar field in curved space. We compute the beta functions
within a generalized DeWitt-Schwinger subtraction procedure and discuss the
decoupling in the running of the coupling constants. For the case of a
quantized scalar field, all the beta function exhibit decoupling, including
also the gravitational ones. For a quantized Dirac field, decoupling appears
almost for all the beta functions. We obtain the anomalous result that the mass
of the background scalar field does not decouple.
| [
{
"created": "Thu, 29 Apr 2021 13:04:42 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Apr 2021 08:42:27 GMT",
"version": "v2"
},
{
"created": "Wed, 5 May 2021 08:59:53 GMT",
"version": "v3"
}
] | 2021-07-07 | [
[
"Ferreiro",
"Antonio",
""
],
[
"Nadal-Gisbert",
"Sergi",
""
],
[
"Navarro-Salas",
"José",
""
]
] | The decoupling of heavy fields as required by the Appelquist-Carazzone theorem plays a fundamental role in the construction of any effective field theory. However, it is not a trivial task to implement a renormalization prescription that produces the expected decoupling of massive fields, and it is even more difficult in curved spacetime. Focused on this idea, we consider the renormalization of the one-loop effective action for the Yukawa interaction with a background scalar field in curved space. We compute the beta functions within a generalized DeWitt-Schwinger subtraction procedure and discuss the decoupling in the running of the coupling constants. For the case of a quantized scalar field, all the beta function exhibit decoupling, including also the gravitational ones. For a quantized Dirac field, decoupling appears almost for all the beta functions. We obtain the anomalous result that the mass of the background scalar field does not decouple. |
2404.15948 | Abhishek Chowdhury | Abhishek Chowdhury | Warp Drives and Martel-Poisson charts | 9 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We extend the construction of the Alcubierre-Natario class of warp drives to
an infinite class of spacetimes with similar properties. This is achieved by
utilising the Martel-Poisson charts which closely resemble the Weak
Painleve-Gullstrand form for various background metrics (Mink, AdS, dS). The
highlight of this construction is the non-flat intrinsic metric which in
three-dimensional spacetimes introduces conical singularities at the origin and
in higher dimensions generates a non-zero Ricci scalar for the spatial
hypersurfaces away from the origin. We analyse the expansion/contraction of
space and negative energy densities associated with this class of warp drives
and find interesting deviations due to the global imprints of the conical
defects. Several generalizations are also discussed.
| [
{
"created": "Wed, 24 Apr 2024 16:09:44 GMT",
"version": "v1"
}
] | 2024-04-25 | [
[
"Chowdhury",
"Abhishek",
""
]
] | We extend the construction of the Alcubierre-Natario class of warp drives to an infinite class of spacetimes with similar properties. This is achieved by utilising the Martel-Poisson charts which closely resemble the Weak Painleve-Gullstrand form for various background metrics (Mink, AdS, dS). The highlight of this construction is the non-flat intrinsic metric which in three-dimensional spacetimes introduces conical singularities at the origin and in higher dimensions generates a non-zero Ricci scalar for the spatial hypersurfaces away from the origin. We analyse the expansion/contraction of space and negative energy densities associated with this class of warp drives and find interesting deviations due to the global imprints of the conical defects. Several generalizations are also discussed. |
gr-qc/9908063 | Mauricio Bellini | Mauricio Bellini (Departamento de Fisica, Fac. de Cs. Exactas y Nat.,
Universidad Nacional de Mar del Plata) | Primordial fluctuations in the warm inflation scenario with a more
realistic coarse - grained field | 11 pages, no figures (revtex file) | Nucl.Phys. B563 (1999) 245-258 | 10.1016/S0550-3213(99)00537-4 | null | gr-qc | null | I study a semiclassical approach to warm inflation scenario introduced in
previous works. In this work, I define the fluctuations for the matter field by
means of a new coarse - grained field with a suppression factor G. This field
describes the matter field fluctuations on the now observable scale of the
universe. The power spectrum for the fluctuations of the matter field is
analyzed in both, de Sitter and power - law expansions for the universe. The
constraint for the spectral index gives a constraint for the mass of the matter
field in the de Sitter expansion and a constraint for the friction parameter in
the power - law expansion for the universe.
| [
{
"created": "Tue, 24 Aug 1999 21:19:27 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 1999 19:00:31 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Jan 2000 22:09:19 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Bellini",
"Mauricio",
"",
"Departamento de Fisica, Fac. de Cs. Exactas y Nat.,\n Universidad Nacional de Mar del Plata"
]
] | I study a semiclassical approach to warm inflation scenario introduced in previous works. In this work, I define the fluctuations for the matter field by means of a new coarse - grained field with a suppression factor G. This field describes the matter field fluctuations on the now observable scale of the universe. The power spectrum for the fluctuations of the matter field is analyzed in both, de Sitter and power - law expansions for the universe. The constraint for the spectral index gives a constraint for the mass of the matter field in the de Sitter expansion and a constraint for the friction parameter in the power - law expansion for the universe. |
2309.17404 | Nicholas Loutrel | Nicholas Loutrel, Richard Brito, Andrea Maselli, Paolo Pani | Relevance of Precession for Tests of the Black Hole No Hair Theorems | 14 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The multipole moments of black holes in general relativity obey certain
consistency relations known as the no-hair theorems. The details of this
multipolar structure are imprinted into the gravitational waves emitted by
binary black holes, particularly if the binary is precessing. If black holes do
not obey the vacuum field equations of general relativity, then the no-hair
theorems may be broken, and the observed gravitational waves will be modified,
thus providing an important test of the no-hair theorems. Recently, analytic
solutions to the precession dynamics and inspiral waveforms were computed
within the context of binaries possessing non-axisymmetric mass quadrupole
moments, which are parametrized by a modulus $q_{m}$ and phase $a_{m}$ with $m
= 1,2$ the azimuthal spherical harmonic number. Here, we use a Fisher analysis
to study plausible constraints one may obtain on generic, non-axisymmetry
quadrupole configurations using current and future ground-based detectors. For
non-precessing binaries, we generically find that no meaningful constraints can
be placed on the non-axisymmetry parameters $(q_{m}, a_{m})$ due to the
presence of strong degeneracies with other waveform parameters. For precessing
configurations, the exact value of the uncertainty is strongly dependent on the
sky location, system orientation relative to the line of sight, and initial
inclination angle of the orbital angular momentum. After averaging over these
parameters, we find that with GWTC-3-like events, one should be able to
plausibly constraint non-axisymmetric mass quadrupole deviations to $\Delta
q_{m} \sim 10^{-2}$ for LIGO at design sensitivity, and $\Delta q_{m} \sim
10^{-4}$ for the same sources with Einstein Telescope and Cosmic Explorer.
| [
{
"created": "Fri, 29 Sep 2023 17:04:07 GMT",
"version": "v1"
}
] | 2023-10-02 | [
[
"Loutrel",
"Nicholas",
""
],
[
"Brito",
"Richard",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
]
] | The multipole moments of black holes in general relativity obey certain consistency relations known as the no-hair theorems. The details of this multipolar structure are imprinted into the gravitational waves emitted by binary black holes, particularly if the binary is precessing. If black holes do not obey the vacuum field equations of general relativity, then the no-hair theorems may be broken, and the observed gravitational waves will be modified, thus providing an important test of the no-hair theorems. Recently, analytic solutions to the precession dynamics and inspiral waveforms were computed within the context of binaries possessing non-axisymmetric mass quadrupole moments, which are parametrized by a modulus $q_{m}$ and phase $a_{m}$ with $m = 1,2$ the azimuthal spherical harmonic number. Here, we use a Fisher analysis to study plausible constraints one may obtain on generic, non-axisymmetry quadrupole configurations using current and future ground-based detectors. For non-precessing binaries, we generically find that no meaningful constraints can be placed on the non-axisymmetry parameters $(q_{m}, a_{m})$ due to the presence of strong degeneracies with other waveform parameters. For precessing configurations, the exact value of the uncertainty is strongly dependent on the sky location, system orientation relative to the line of sight, and initial inclination angle of the orbital angular momentum. After averaging over these parameters, we find that with GWTC-3-like events, one should be able to plausibly constraint non-axisymmetric mass quadrupole deviations to $\Delta q_{m} \sim 10^{-2}$ for LIGO at design sensitivity, and $\Delta q_{m} \sim 10^{-4}$ for the same sources with Einstein Telescope and Cosmic Explorer. |
1704.03232 | Runqiu Yang | Shan-Ming Ruan and Run-Qiu Yang | Comments on Joint Terms in Gravitational Action | Published version with little modifications compared with previous
one | Class. Quantum Grav. 34 (2017) 175017 (18pp) | 10.1088/1361-6382/aa8053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper compares three different methods about computing joint terms in
on-shell action of gravity, which are identifying the joint term by the
variational principle in Dirichlet boundary condition, treating the joint term
as the limit contribution of smooth boundary and finding the joint term by
local SO(1,$d-1$) transformation. In general metric gravitational theory, we
show that the differences between these joint terms are some variational
invariants under fixed boundary condition. We also give an explicit condition
to judge the existence of joint term determined by variational principle and
apply it into general relativity as an example.
| [
{
"created": "Tue, 11 Apr 2017 10:36:39 GMT",
"version": "v1"
},
{
"created": "Thu, 4 May 2017 03:54:02 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Aug 2017 13:46:25 GMT",
"version": "v3"
}
] | 2017-08-17 | [
[
"Ruan",
"Shan-Ming",
""
],
[
"Yang",
"Run-Qiu",
""
]
] | This paper compares three different methods about computing joint terms in on-shell action of gravity, which are identifying the joint term by the variational principle in Dirichlet boundary condition, treating the joint term as the limit contribution of smooth boundary and finding the joint term by local SO(1,$d-1$) transformation. In general metric gravitational theory, we show that the differences between these joint terms are some variational invariants under fixed boundary condition. We also give an explicit condition to judge the existence of joint term determined by variational principle and apply it into general relativity as an example. |
0903.1122 | Chad Galley | Chad R. Galley and Manuel Tiglio | Radiation reaction and gravitational waves in the effective field theory
approach | 23 pages, 8 figures | Phys.Rev.D79:124027,2009 | 10.1103/PhysRevD.79.124027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the contribution to the Lagrangian from the leading order (2.5
post-Newtonian) radiation reaction and the quadrupolar gravitational waves
emitted from a binary system using the effective field theory (EFT) approach of
Goldberger and Rothstein. We use an initial value formulation of the underlying
(quantum) framework to implement retarded boundary conditions and describe
these real-time dissipative processes. We also demonstrate why the usual
scattering formalism of quantum field theory inadequately accounts for these.
The methods discussed here should be useful for deriving real-time quantities
(including radiation reaction forces and gravitational wave emission) and
hereditary terms in the post-Newtonian approximation (including memory, tail
and other causal, history-dependent integrals) within the EFT approach. We also
provide a consistent formulation of the radiation sector in the equivalent
effective field theory approach of Kol and Smolkin.
| [
{
"created": "Thu, 5 Mar 2009 22:27:39 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Galley",
"Chad R.",
""
],
[
"Tiglio",
"Manuel",
""
]
] | We compute the contribution to the Lagrangian from the leading order (2.5 post-Newtonian) radiation reaction and the quadrupolar gravitational waves emitted from a binary system using the effective field theory (EFT) approach of Goldberger and Rothstein. We use an initial value formulation of the underlying (quantum) framework to implement retarded boundary conditions and describe these real-time dissipative processes. We also demonstrate why the usual scattering formalism of quantum field theory inadequately accounts for these. The methods discussed here should be useful for deriving real-time quantities (including radiation reaction forces and gravitational wave emission) and hereditary terms in the post-Newtonian approximation (including memory, tail and other causal, history-dependent integrals) within the EFT approach. We also provide a consistent formulation of the radiation sector in the equivalent effective field theory approach of Kol and Smolkin. |
0709.1625 | Mairi Sakellariadou | William Nelson and Mairi Sakellariadou (King's College, University of
London, U.K.) | On the possibility of Dark Energy from corrections to the Wheeler-De
Witt equation | 4 pages, 1 figure. Minor modifications to match version to appear in
Phys. Let. B | Phys.Lett.B661:37-41,2008 | 10.1016/j.physletb.2008.01.060 | null | gr-qc astro-ph hep-ph hep-th | null | We present a method for approximating the effective consequence of generic
quantum gravity corrections to the Wheeler-DeWitt equation. We show that in
many cases these corrections can produce departures from classical physics at
large scales and that this behaviour can be interpreted as additional matter
components. This opens up the possibility that dark energy (and possible dark
matter) could be large scale manifestations of quantum gravity corrections to
classical general relativity. As a specific example we examine the first order
corrections to the Wheeler-De Witt equation arising from loop quantum cosmology
in the absence of lattice refinement and show how the ultimate breakdown in
large scale physics occurs.
| [
{
"created": "Tue, 11 Sep 2007 13:50:18 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jan 2008 07:23:42 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Nelson",
"William",
"",
"King's College, University of\n London, U.K."
],
[
"Sakellariadou",
"Mairi",
"",
"King's College, University of\n London, U.K."
]
] | We present a method for approximating the effective consequence of generic quantum gravity corrections to the Wheeler-DeWitt equation. We show that in many cases these corrections can produce departures from classical physics at large scales and that this behaviour can be interpreted as additional matter components. This opens up the possibility that dark energy (and possible dark matter) could be large scale manifestations of quantum gravity corrections to classical general relativity. As a specific example we examine the first order corrections to the Wheeler-De Witt equation arising from loop quantum cosmology in the absence of lattice refinement and show how the ultimate breakdown in large scale physics occurs. |
1812.06151 | David Benisty | David Benisty, Eduardo Guendelman, Zbigniew Haba | Unification of DE-DM from Diffusive Cosmology | Accepted for publishing in Phys. Rev. D | Phys. Rev. D 99, 123521 (2019) | 10.1103/PhysRevD.99.123521 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generalized ideas of unified dark matter and dark energy in the context of
dynamical space time theories with a diffusive transfer of energy are studied.
The dynamical space-time theories are introduced a vector field whose equation
of motion guarantees a conservation of a certain Energy Momentum tensor, which
may be related, but in general is not the same as the gravitational Energy
Momentum tensor. This particular energy momentum tensor is built from a general
combination of scalar fields derivatives as the kinetic terms, and possibly
potentials for the scalar field. By demanding that the dynamical space vector
field be the gradient of a scalar the dynamical space time theory becomes a
theory for diffusive interacting dark energy and dark matter. These
generalizations produce non-conserved energy momentum tensors instead of
conserved energy momentum tensors which leads at the end to a formulation for
interacting DE-DM. We solved analytically the theories and we show that the
$\Lambda$CDM is a fixed point of these theories at large times. A particular
case has asymptotic correspondence to previously studied non-Lagrangian
formulations of diffusive exchange between dark energy dark matter.
| [
{
"created": "Fri, 14 Dec 2018 20:15:55 GMT",
"version": "v1"
},
{
"created": "Wed, 29 May 2019 22:52:21 GMT",
"version": "v2"
}
] | 2019-06-26 | [
[
"Benisty",
"David",
""
],
[
"Guendelman",
"Eduardo",
""
],
[
"Haba",
"Zbigniew",
""
]
] | Generalized ideas of unified dark matter and dark energy in the context of dynamical space time theories with a diffusive transfer of energy are studied. The dynamical space-time theories are introduced a vector field whose equation of motion guarantees a conservation of a certain Energy Momentum tensor, which may be related, but in general is not the same as the gravitational Energy Momentum tensor. This particular energy momentum tensor is built from a general combination of scalar fields derivatives as the kinetic terms, and possibly potentials for the scalar field. By demanding that the dynamical space vector field be the gradient of a scalar the dynamical space time theory becomes a theory for diffusive interacting dark energy and dark matter. These generalizations produce non-conserved energy momentum tensors instead of conserved energy momentum tensors which leads at the end to a formulation for interacting DE-DM. We solved analytically the theories and we show that the $\Lambda$CDM is a fixed point of these theories at large times. A particular case has asymptotic correspondence to previously studied non-Lagrangian formulations of diffusive exchange between dark energy dark matter. |
gr-qc/9406019 | null | A. Connes and C. Rovelli | Von Neumann Algebra Automorphisms and Time-Thermodynamics Relation in
General Covariant Quantum Theories | 25 pages, LaTex | Class.Quant.Grav.11:2899-2918,1994 | 10.1088/0264-9381/11/12/007 | null | gr-qc | null | We consider the cluster of problems raised by the relation between the notion
of time, gravitational theory, quantum theory and thermodynamics; in
particular, we address the problem of relating the "timelessness" of the
hypothetical fundamental general covariant quantum field theory with the
"evidence" of the flow of time. By using the algebraic formulation of quantum
theory, we propose a unifying perspective on these problems, based on the
hypothesis that in a generally covariant quantum theory the physical time-flow
is not a universal property of the mechanical theory, but rather it is
determined by the thermodynamical state of the system ("thermal time
hypothesis"). We implement this hypothesis by using a key structural property
of von Neumann algebras: the Tomita-Takesaki theorem, which allows to derive a
time-flow, namely a one-parameter group of automorphisms of the observable
algebra, from a generic thermal physical state. We study this time-flow, its
classical limit, and we relate it to various characteristic theoretical facts,
as the Unruh temperature and the Hawking radiation. We also point out the
existence of a state-independent notion of "time", given by the canonical
one-parameter subgroup of outer automorphisms provided by the Cocycle
Radon-Nikodym theorem.
| [
{
"created": "Tue, 14 Jun 1994 09:15:26 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Connes",
"A.",
""
],
[
"Rovelli",
"C.",
""
]
] | We consider the cluster of problems raised by the relation between the notion of time, gravitational theory, quantum theory and thermodynamics; in particular, we address the problem of relating the "timelessness" of the hypothetical fundamental general covariant quantum field theory with the "evidence" of the flow of time. By using the algebraic formulation of quantum theory, we propose a unifying perspective on these problems, based on the hypothesis that in a generally covariant quantum theory the physical time-flow is not a universal property of the mechanical theory, but rather it is determined by the thermodynamical state of the system ("thermal time hypothesis"). We implement this hypothesis by using a key structural property of von Neumann algebras: the Tomita-Takesaki theorem, which allows to derive a time-flow, namely a one-parameter group of automorphisms of the observable algebra, from a generic thermal physical state. We study this time-flow, its classical limit, and we relate it to various characteristic theoretical facts, as the Unruh temperature and the Hawking radiation. We also point out the existence of a state-independent notion of "time", given by the canonical one-parameter subgroup of outer automorphisms provided by the Cocycle Radon-Nikodym theorem. |
1706.04287 | Y. Jack Ng | Y. Jack Ng | Effective Cosmological Constant and Dark Energy | 12 pages, to appear in Proc. BASIC 2017 Conference; a large part of
section 5 (addendum) is taken from "Modified Dark Matter: Relating Dark
Energy, Dark Matter and Baryonic Matter" by D. Edmonds et al. (in
preparation) | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two very different methods are used to estimate the magnitude of the
effective cosmological constant / dark energy (for the present cosmic epoch).
Their results agree with each other and are in agreement with observations. One
method makes use of unimodular gravity and causal set theory, while the other
one employs arguments involving spacetime foam and holography. I also motivate
and discuss the possibility that quanta of (both) dark energy (and dark matter
in the Modified Dark Matter model) are extended/non-local, obeying infinite
statistics, also known as quantum Boltzmann statistics. Such quanta out-number
ordinary particles obeying Bose-Einstein or Fermi-Dirac statistics by a factor
of $\sim 10^{30}$.
| [
{
"created": "Wed, 14 Jun 2017 00:19:57 GMT",
"version": "v1"
}
] | 2017-06-15 | [
[
"Ng",
"Y. Jack",
""
]
] | Two very different methods are used to estimate the magnitude of the effective cosmological constant / dark energy (for the present cosmic epoch). Their results agree with each other and are in agreement with observations. One method makes use of unimodular gravity and causal set theory, while the other one employs arguments involving spacetime foam and holography. I also motivate and discuss the possibility that quanta of (both) dark energy (and dark matter in the Modified Dark Matter model) are extended/non-local, obeying infinite statistics, also known as quantum Boltzmann statistics. Such quanta out-number ordinary particles obeying Bose-Einstein or Fermi-Dirac statistics by a factor of $\sim 10^{30}$. |
gr-qc/0606122 | Juan Pablo Beltr\'an Almeida jalmeida | R. Aldrovandi, J. P. Beltran Almeida and J. G. Pereira | de Sitter special relativity | V2: Some presentation changes; a new section introduced, with a
discussion about possible phenomenological consequences; new references
added; version to be published in Classical and Quantum Gravity | Class.Quant.Grav.24:1385-1404,2007 | 10.1088/0264-9381/24/6/002 | null | gr-qc hep-th | null | A special relativity based on the de Sitter group is introduced, which is the
theory that might hold up in the presence of a non-vanishing cosmological
constant. Like ordinary special relativity, it retains the quotient character
of spacetime, and a notion of homogeneity. As a consequence, the underlying
spacetime will be a de Sitter spacetime, whose associated kinematics will
differ from that of ordinary special relativity. The corresponding modified
notions of energy and momentum are obtained, and the exact relationship between
them, which is invariant under a re-scaling of the involved quantities,
explicitly exhibited. Since the de Sitter group can be considered a particular
deformation of the Poincar\'e group, this theory turns out to be a specific
kind of deformed (or doubly) special relativity. Some experimental
consequences, as well as the causal structure of spacetime--modified by the
presence of the de Sitter horizon--are briefly discussed.
| [
{
"created": "Wed, 28 Jun 2006 20:38:20 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2007 12:26:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Aldrovandi",
"R.",
""
],
[
"Almeida",
"J. P. Beltran",
""
],
[
"Pereira",
"J. G.",
""
]
] | A special relativity based on the de Sitter group is introduced, which is the theory that might hold up in the presence of a non-vanishing cosmological constant. Like ordinary special relativity, it retains the quotient character of spacetime, and a notion of homogeneity. As a consequence, the underlying spacetime will be a de Sitter spacetime, whose associated kinematics will differ from that of ordinary special relativity. The corresponding modified notions of energy and momentum are obtained, and the exact relationship between them, which is invariant under a re-scaling of the involved quantities, explicitly exhibited. Since the de Sitter group can be considered a particular deformation of the Poincar\'e group, this theory turns out to be a specific kind of deformed (or doubly) special relativity. Some experimental consequences, as well as the causal structure of spacetime--modified by the presence of the de Sitter horizon--are briefly discussed. |
0711.4897 | Cl\'audio Nassif Cruz | Claudio Nassif | Deformed special relativity with an invariant minimum speed and its
cosmological implications | 7 pages, 3 figures. arXiv admin note: substantial text overlap with
arXiv:0705.4315, arXiv:0709.1727 | Pramana Journal of Physics, Vol.71, No.1, p.1-13 (2008);
correlated paper in:
http://www.worldscientific.com/worldscinet/ijmpd?journalTabs=read | 10.1007/s12043-008-0136-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper aims to introduce a new symmetry principle in the space-time
geometry through the elimination of the classical idea of rest and by including
a universal minimum limit of speed in the subatomic world. Such a limit,
unattainable by particles, represents a preferred reference frame associated
with a universal background field that breaks Lorentz symmetry. Thus the
structure of space-time is extended due to the presence of a vacuum energy
density, which leads to a negative pressure at cosmological scales. The tiny
values of the cosmological constant and the vacuum energy density shall be
successfully obtained, being in good agreement with current observational
results.
| [
{
"created": "Fri, 30 Nov 2007 10:14:14 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Dec 2007 22:58:36 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Feb 2008 17:55:51 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Feb 2008 12:49:10 GMT",
"version": "v4"
},
{
"cr... | 2016-11-08 | [
[
"Nassif",
"Claudio",
""
]
] | The paper aims to introduce a new symmetry principle in the space-time geometry through the elimination of the classical idea of rest and by including a universal minimum limit of speed in the subatomic world. Such a limit, unattainable by particles, represents a preferred reference frame associated with a universal background field that breaks Lorentz symmetry. Thus the structure of space-time is extended due to the presence of a vacuum energy density, which leads to a negative pressure at cosmological scales. The tiny values of the cosmological constant and the vacuum energy density shall be successfully obtained, being in good agreement with current observational results. |
1205.6012 | Andres Anabalon | Andres Anabalon and Julio Oliva | Exact Hairy Black Holes and their Modification to the Universal Law of
Gravitation | Two new references, 10 pages, 2 figures | null | 10.1103/PhysRevD.86.107501 | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper two things are done. First, it is pointed out the existence of
exact asymptotically flat, spherically symmetric black holes when a self
interacting, minimally coupled scalar field is the source of the energy
momentum of the Einstein equations in four dimensions. The scalar field
potential is the recently found to be compatible with the hairy generalization
of the Plebanski-Demianski solution of general relativity. This paper describes
the spherically symmetric solutions that smoothly connect the Schwarzschild
black hole with its hairy counterpart. The geometry and scalar field are
everywhere regular except at the usual Schwarzschild like singularity inside
the black hole. The scalar field energy momentum tensor satisfies the null
energy condition in the static region of the spacetime. The first law holds
when the parameters of the scalar field potential are fixed under
thermodynamical variation. Secondly, it is shown that an extra, dimensionless
parameter, present in the hairy solution, allows to modify the gravitational
field of a spherically symmetric black hole in a remarkable way. When the
dimensionless parameter is increased, the scalar field generates a flat
gravitational potential, that however asymptotically matches the Schwarzschild
gravitational field. Finally, it is shown that a positive cosmological constant
can render the scalar field potential convex if the parameters are within a
specific rank.
| [
{
"created": "Mon, 28 May 2012 01:06:11 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jun 2012 16:49:10 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Anabalon",
"Andres",
""
],
[
"Oliva",
"Julio",
""
]
] | In this paper two things are done. First, it is pointed out the existence of exact asymptotically flat, spherically symmetric black holes when a self interacting, minimally coupled scalar field is the source of the energy momentum of the Einstein equations in four dimensions. The scalar field potential is the recently found to be compatible with the hairy generalization of the Plebanski-Demianski solution of general relativity. This paper describes the spherically symmetric solutions that smoothly connect the Schwarzschild black hole with its hairy counterpart. The geometry and scalar field are everywhere regular except at the usual Schwarzschild like singularity inside the black hole. The scalar field energy momentum tensor satisfies the null energy condition in the static region of the spacetime. The first law holds when the parameters of the scalar field potential are fixed under thermodynamical variation. Secondly, it is shown that an extra, dimensionless parameter, present in the hairy solution, allows to modify the gravitational field of a spherically symmetric black hole in a remarkable way. When the dimensionless parameter is increased, the scalar field generates a flat gravitational potential, that however asymptotically matches the Schwarzschild gravitational field. Finally, it is shown that a positive cosmological constant can render the scalar field potential convex if the parameters are within a specific rank. |
2310.12237 | Reyhan Kaya | Reyhan Kaya, Hasan Tuncay \"Oz\c{c}elik | Self-interacting scalar field in (2+1) dimensions Einstein gravity with
torsion | 17 pages, 25 figures | Eur. Phys. J. C 84 (2024) 528 | 10.1140/epjc/s10052-024-12912-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a massless real self-interacting scalar field $\varphi$
non-minimally coupled to Einstein gravity with torsion in (2+1) space-time
dimensions in the presence of cosmological constant. The field equations with a
self-interaction potential $V(\varphi)$ including $\varphi^{n}$ terms are
derived by a variational principle. By numerically solving these field
equations with the 4th Runge-Kutta method, the circularly symmetric rotating
solutions for (2+1) dimensions Einstein gravity with torsion are obtained.
Exact analytical solutions to the field equations are derived for the proposed
metric in the absence of both torsion and angular momentum. We find that the
self-interacting potential only exists for $n=6$. We also study the motion of
massive and massless particles in (2+1) Einstein gravity with torsion coupled
to a self-interacting scalar field. The effect of torsion on the behavior of
the effective potentials of the particles is analyzed numerically.
| [
{
"created": "Wed, 18 Oct 2023 18:22:57 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Kaya",
"Reyhan",
""
],
[
"Özçelik",
"Hasan Tuncay",
""
]
] | We study a massless real self-interacting scalar field $\varphi$ non-minimally coupled to Einstein gravity with torsion in (2+1) space-time dimensions in the presence of cosmological constant. The field equations with a self-interaction potential $V(\varphi)$ including $\varphi^{n}$ terms are derived by a variational principle. By numerically solving these field equations with the 4th Runge-Kutta method, the circularly symmetric rotating solutions for (2+1) dimensions Einstein gravity with torsion are obtained. Exact analytical solutions to the field equations are derived for the proposed metric in the absence of both torsion and angular momentum. We find that the self-interacting potential only exists for $n=6$. We also study the motion of massive and massless particles in (2+1) Einstein gravity with torsion coupled to a self-interacting scalar field. The effect of torsion on the behavior of the effective potentials of the particles is analyzed numerically. |
1004.3200 | Rudranil Basu | Rudranil Basu, Ayan Chatterjee and Amit Ghosh | Local symmetries of non-expanding horizons | 4 pages, revtex4, no figure. Few typos corrected | null | 10.1088/0264-9381/29/23/235010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Local symmetries of a non-expanding horizon has been investigated in the 1st
order formulation of gravity. When applied to a spherically symmetric isolated
horizon only a U(1) subgroup of the Lorentz group survives as residual local
symmetry that one can make use of in constructing an effective theory on the
horizon.
| [
{
"created": "Mon, 19 Apr 2010 14:07:11 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Apr 2010 11:19:09 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Basu",
"Rudranil",
""
],
[
"Chatterjee",
"Ayan",
""
],
[
"Ghosh",
"Amit",
""
]
] | Local symmetries of a non-expanding horizon has been investigated in the 1st order formulation of gravity. When applied to a spherically symmetric isolated horizon only a U(1) subgroup of the Lorentz group survives as residual local symmetry that one can make use of in constructing an effective theory on the horizon. |
gr-qc/0403110 | Salvatore Antoci | S. Antoci | Proposal for an Interpretation of the Hermitian Theory of Relativity | 13 pages, corrected misprint | Gen.Rel.Grav. 19 (1987) 665-679 | null | null | gr-qc astro-ph | null | The equilibrium conditions for charges and currents, apparent in exact
solutions of the field equations, lead one to regard the Hermitian theory of
relativity as the theory of a field endowed with two sources: electromagnetic
and colour four-currents.
| [
{
"created": "Mon, 29 Mar 2004 14:55:54 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2004 18:12:45 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Antoci",
"S.",
""
]
] | The equilibrium conditions for charges and currents, apparent in exact solutions of the field equations, lead one to regard the Hermitian theory of relativity as the theory of a field endowed with two sources: electromagnetic and colour four-currents. |
0911.5419 | Alexander Petrov Nikolaevich | A.N.Petrov | On creating mass/matter by extra dimensions in the Einstein-Gauss-Bonnet
gravity | 15 pages, no figures, minor changes related to the Journal
publication with adding two references in footnotes | Grav.Cosmol.16:34-41,2010 | 10.1134/S0202289310010056 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Kaluza-Klein (KK) black hole solutions in the Einstein-Gauss-Bonnet (EGB)
gravity in $D$ dimensions obtained in the current series of the works by Maeda,
Dadhich and Molina are examined. Interpreting their solutions, the authors
claim that the mass/matter is created by the extra dimensions. To support this
claim, one needs to show that such objects have classically defined masses. We
calculate the mass and mass flux for 3D KK black holes in 6D EGB gravity whose
properties are sufficiently physically interesting. Superpotentials for
arbitrary types of perturbations on arbitrary curved backgrounds, recently
obtained by the author, are used, and acceptable mass and mass flux are
obtained. A possibility of considering the KK created matter as dark matter in
the Universe is discussed.
| [
{
"created": "Sat, 28 Nov 2009 19:27:39 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Oct 2010 12:25:46 GMT",
"version": "v2"
}
] | 2010-10-19 | [
[
"Petrov",
"A. N.",
""
]
] | Kaluza-Klein (KK) black hole solutions in the Einstein-Gauss-Bonnet (EGB) gravity in $D$ dimensions obtained in the current series of the works by Maeda, Dadhich and Molina are examined. Interpreting their solutions, the authors claim that the mass/matter is created by the extra dimensions. To support this claim, one needs to show that such objects have classically defined masses. We calculate the mass and mass flux for 3D KK black holes in 6D EGB gravity whose properties are sufficiently physically interesting. Superpotentials for arbitrary types of perturbations on arbitrary curved backgrounds, recently obtained by the author, are used, and acceptable mass and mass flux are obtained. A possibility of considering the KK created matter as dark matter in the Universe is discussed. |
gr-qc/9712090 | Sibel Baskal | S. Baskal (Dept. of Physics, Middle East Technical University) | Radiation in Yang-Mills formulation of gravity and a generalized pp-wave
metric | 5 pages; e mail: baskal@newton.physics.metu.edu.tr | Prog.Theor.Phys.102:803-807,1999 | 10.1143/PTP.102.803 | null | gr-qc | null | The variational methods implemented on a quadratic Yang-Mills type Lagrangian
yield two sets of equations interpreted as the field equations and the
energy-momentum tensor for the gravitational field. A covariant condition is
imposed on the energy-momentum tensor to represent the radiation field. A
generalized pp-wave metric is found to simultaneously satisfy both the field
equations and the radiation condition. The result is compared with that of
Lichn\'{e}rowicz.
| [
{
"created": "Tue, 23 Dec 1997 17:58:53 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Baskal",
"S.",
"",
"Dept. of Physics, Middle East Technical University"
]
] | The variational methods implemented on a quadratic Yang-Mills type Lagrangian yield two sets of equations interpreted as the field equations and the energy-momentum tensor for the gravitational field. A covariant condition is imposed on the energy-momentum tensor to represent the radiation field. A generalized pp-wave metric is found to simultaneously satisfy both the field equations and the radiation condition. The result is compared with that of Lichn\'{e}rowicz. |
0905.1501 | Valentin Bonzom | Valentin Bonzom | Spin foam models for quantum gravity from lattice path integrals | 19 pages, 1 figure | Phys. Rev. D80:064028, 2009 | 10.1103/PhysRevD.80.064028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin foam models for quantum gravity are derived from lattice path integrals.
The setting involves variables from both lattice BF theory and Regge calculus.
The action consists in a Regge action, which depends on areas, dihedral angles
and includes the Immirzi parameter. In addition, a measure is inserted to
ensure a consistent gluing of simplices, so that the amplitude is dominated by
configurations which satisfy the parallel transport relations. We explicitly
compute the path integral as a sum over spin foams for a generic measure. The
Freidel-Krasnov and Engle-Pereira-Rovelli models correspond to a special choice
of gluing. In this case, the equations of motion describe genuine geometries,
where the constraints of area-angle Regge calculus are satisfied. Furthermore,
the Immirzi parameter drops out of the on-shell action, and stationarity with
respect to area variations requires spacetime geometry to be flat.
| [
{
"created": "Sun, 10 May 2009 19:50:20 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 2009 08:58:20 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Bonzom",
"Valentin",
""
]
] | Spin foam models for quantum gravity are derived from lattice path integrals. The setting involves variables from both lattice BF theory and Regge calculus. The action consists in a Regge action, which depends on areas, dihedral angles and includes the Immirzi parameter. In addition, a measure is inserted to ensure a consistent gluing of simplices, so that the amplitude is dominated by configurations which satisfy the parallel transport relations. We explicitly compute the path integral as a sum over spin foams for a generic measure. The Freidel-Krasnov and Engle-Pereira-Rovelli models correspond to a special choice of gluing. In this case, the equations of motion describe genuine geometries, where the constraints of area-angle Regge calculus are satisfied. Furthermore, the Immirzi parameter drops out of the on-shell action, and stationarity with respect to area variations requires spacetime geometry to be flat. |
1903.00265 | Guillermo A. Mena Marugan | Alejandro Garc\'ia-Quismondo and Guillermo A. Mena Marug\'an | The Martin-Benito-Mena Marugan-Olmedo prescription for the
Dapor-Liegener model of Loop Quantum Cosmology | 15 pages, published in Physical Review D | Phys. Rev. D 99, 083505 (2019) | 10.1103/PhysRevD.99.083505 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, an alternative Hamiltonian constraint for Loop Quantum Cosmology
has been put forward by Dapor and Liegener, inspired by previous work on
regularization due to Thiemann. Here, we quantize this Hamiltonian following a
prescription for cosmology proposed by Mart\'{\i}n-Benito, Mena Marug\'an, and
Olmedo. To this effect, we first regularize the Euclidean and Lorentzian parts
of the Hamiltonian constraint separately in the case of a Bianchi I cosmology.
This allows us to identify a natural symmetrization of the Hamiltonian which is
apparent in anisotropic scenarios. Preserving this symmetrization in isotropic
regimes, we then determine the Hamiltonian constraint corresponding to a
Friedmann-Lema\^itre-Robertson-Walker cosmology, which we proceed to quantize.
We compute the action of this Hamiltonian operator in the volume eigenbasis and
show that it takes the form of a fourth-order difference equation, unlike in
standard Loop Quantum Cosmology, where it is known to be of second order. We
investigate the superselection sectors of our constraint operator, proving that
they are semilattices supported only on either the positive or the negative
semiaxis, depending on the triad orientation. Remarkably, the decoupling
between semiaxes allows us to write a closed expression for the generalized
eigenfunctions of the geometric part of the constraint. This expression is
totally determined by the values at the two points of the semilattice that are
closest to the origin, namely the two contributions with smallest eigenvolume.
This is in clear contrast with the situation found for the standard Hamiltonian
of Loop Quantum Cosmology, where only the smallest value is free. This result
indicates that the degeneracy of the new geometric Hamiltonian operator is
equal to two, doubling the possible number of solutions with respect to the
conventional quantization considered until now.
| [
{
"created": "Fri, 1 Mar 2019 12:28:31 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2019 10:02:21 GMT",
"version": "v2"
}
] | 2019-05-15 | [
[
"García-Quismondo",
"Alejandro",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | Recently, an alternative Hamiltonian constraint for Loop Quantum Cosmology has been put forward by Dapor and Liegener, inspired by previous work on regularization due to Thiemann. Here, we quantize this Hamiltonian following a prescription for cosmology proposed by Mart\'{\i}n-Benito, Mena Marug\'an, and Olmedo. To this effect, we first regularize the Euclidean and Lorentzian parts of the Hamiltonian constraint separately in the case of a Bianchi I cosmology. This allows us to identify a natural symmetrization of the Hamiltonian which is apparent in anisotropic scenarios. Preserving this symmetrization in isotropic regimes, we then determine the Hamiltonian constraint corresponding to a Friedmann-Lema\^itre-Robertson-Walker cosmology, which we proceed to quantize. We compute the action of this Hamiltonian operator in the volume eigenbasis and show that it takes the form of a fourth-order difference equation, unlike in standard Loop Quantum Cosmology, where it is known to be of second order. We investigate the superselection sectors of our constraint operator, proving that they are semilattices supported only on either the positive or the negative semiaxis, depending on the triad orientation. Remarkably, the decoupling between semiaxes allows us to write a closed expression for the generalized eigenfunctions of the geometric part of the constraint. This expression is totally determined by the values at the two points of the semilattice that are closest to the origin, namely the two contributions with smallest eigenvolume. This is in clear contrast with the situation found for the standard Hamiltonian of Loop Quantum Cosmology, where only the smallest value is free. This result indicates that the degeneracy of the new geometric Hamiltonian operator is equal to two, doubling the possible number of solutions with respect to the conventional quantization considered until now. |
2212.04657 | Michael LaHaye | Michael LaHaye, Huan Yang, B\'eatrice Bonga, and Zhenwei Lyu | Efficient fully precessing gravitational waveforms for binaries with
neutron stars | Corrected minor typos and a typo in Fig 9 resulting in the incorrect
placement in the images | null | 10.1103/PhysRevD.108.043018 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We construct an efficient frequency domain waveform for generic circular
compact object binaries that include neutron stars. The orbital precession is
solved on the radiation reaction timescale (and then transformed to the
frequency domain), which is used to map the non-precessional waveform from the
source frame of the binary to the lab frame. The treatment of orbital
precession is different from that for precessional binary black holes, as
$\chi_{\rm eff}$ is no longer conserved due to the spin-induced quadrupole
moments of neutron stars. We show that the new waveform achieves $\le 10^{-4}$
mismatch compared with waveforms generated by numerically evolved precession
for neutron star-black hole systems for $\ge 90\%$ configurations with
component mass/spin magnitude assumed in the analysis and randomized initial
spin directions. We expect this waveform to be useful to test the nature of the
mass-gap objects similar to the one discovered in GW 190814 by measuring their
spin-induced quadrupole moments, as it is possible that these mass-gap objects
are rapidly spinning. It is also applicable for the tests of black hole
mimickers in precessional binary black hole events, if the black hole mimicker
candidates have nontrivial spin-induced quadrupole moments.
| [
{
"created": "Fri, 9 Dec 2022 03:58:45 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Dec 2022 04:49:59 GMT",
"version": "v2"
}
] | 2023-08-28 | [
[
"LaHaye",
"Michael",
""
],
[
"Yang",
"Huan",
""
],
[
"Bonga",
"Béatrice",
""
],
[
"Lyu",
"Zhenwei",
""
]
] | We construct an efficient frequency domain waveform for generic circular compact object binaries that include neutron stars. The orbital precession is solved on the radiation reaction timescale (and then transformed to the frequency domain), which is used to map the non-precessional waveform from the source frame of the binary to the lab frame. The treatment of orbital precession is different from that for precessional binary black holes, as $\chi_{\rm eff}$ is no longer conserved due to the spin-induced quadrupole moments of neutron stars. We show that the new waveform achieves $\le 10^{-4}$ mismatch compared with waveforms generated by numerically evolved precession for neutron star-black hole systems for $\ge 90\%$ configurations with component mass/spin magnitude assumed in the analysis and randomized initial spin directions. We expect this waveform to be useful to test the nature of the mass-gap objects similar to the one discovered in GW 190814 by measuring their spin-induced quadrupole moments, as it is possible that these mass-gap objects are rapidly spinning. It is also applicable for the tests of black hole mimickers in precessional binary black hole events, if the black hole mimicker candidates have nontrivial spin-induced quadrupole moments. |
1601.00838 | Cosimo Bambi | Jiachen Jiang, Cosimo Bambi, James F. Steiner | Testing the Kerr nature of black hole candidates using iron line
reverberation mapping in the CPR framework | 10 pages, 6 figures. v2: refereed version | Phys. Rev. D 93, 123008 (2016) | 10.1103/PhysRevD.93.123008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The iron K$\alpha$ line commonly observed in the X-ray spectrum of black hole
candidates is produced by X-ray fluorescence of the inner accretion disk. This
line can potentially be quite a powerful tool to probe the spacetime geometry
around these objects and test the Kerr black hole hypothesis. In a previous
paper, we studied the ability to constrain possible deviations from the Kerr
solution from the standard time-integrated iron line spectrum within the
Cardoso-Pani-Rico framework. In the present work, we expand on that study and
consider iron line reverberation mapping in the CPR framework. That is, we
consider the time-evolution of the iron line profile in response to
fluctuations in the X-ray primary source. Our simulations clearly show that the
time information in reverberation mapping can better constrain the background
metric than the time-integrated approach, and this is true, notably, for the
deformation parameter $\epsilon^r_3$, which is only weakly informed by a
time-integrated observation.
| [
{
"created": "Tue, 5 Jan 2016 14:30:09 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jun 2016 04:13:49 GMT",
"version": "v2"
}
] | 2016-06-17 | [
[
"Jiang",
"Jiachen",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Steiner",
"James F.",
""
]
] | The iron K$\alpha$ line commonly observed in the X-ray spectrum of black hole candidates is produced by X-ray fluorescence of the inner accretion disk. This line can potentially be quite a powerful tool to probe the spacetime geometry around these objects and test the Kerr black hole hypothesis. In a previous paper, we studied the ability to constrain possible deviations from the Kerr solution from the standard time-integrated iron line spectrum within the Cardoso-Pani-Rico framework. In the present work, we expand on that study and consider iron line reverberation mapping in the CPR framework. That is, we consider the time-evolution of the iron line profile in response to fluctuations in the X-ray primary source. Our simulations clearly show that the time information in reverberation mapping can better constrain the background metric than the time-integrated approach, and this is true, notably, for the deformation parameter $\epsilon^r_3$, which is only weakly informed by a time-integrated observation. |
gr-qc/9212003 | null | Carl H. Brans and Duane Randall | Exotic Differentiable Structures and General Relativity | 11 pages, LaTeX | null | 10.1007/BF00758828 | null | gr-qc | null | We review recent developments in differential topology with special concern
for their possible significance to physical theories, especially general
relativity. In particular we are concerned here with the discovery of the
existence of non-standard (``fake'' or ``exotic'') differentiable structures on
topologically simple manifolds such as $S^7$, \R and $S^3\times {\bf R^1}.$
Because of the technical difficulties involved in the smooth case, we begin
with an easily understood toy example looking at the role which the choice of
complex structures plays in the formulation of two-dimensional vacuum
electrostatics. We then briefly review the mathematical formalisms involved
with differentiable structures on topological manifolds, diffeomorphisms and
their significance for physics. We summarize the important work of Milnor,
Freedman, Donaldson, and others in developing exotic differentiable structures
on well known topological manifolds. Finally, we discuss some of the geometric
implications of these results and propose some conjectures on possible physical
implications of these new manifolds which have never before been considered as
physical models.
| [
{
"created": "Thu, 3 Dec 1992 19:59:17 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Brans",
"Carl H.",
""
],
[
"Randall",
"Duane",
""
]
] | We review recent developments in differential topology with special concern for their possible significance to physical theories, especially general relativity. In particular we are concerned here with the discovery of the existence of non-standard (``fake'' or ``exotic'') differentiable structures on topologically simple manifolds such as $S^7$, \R and $S^3\times {\bf R^1}.$ Because of the technical difficulties involved in the smooth case, we begin with an easily understood toy example looking at the role which the choice of complex structures plays in the formulation of two-dimensional vacuum electrostatics. We then briefly review the mathematical formalisms involved with differentiable structures on topological manifolds, diffeomorphisms and their significance for physics. We summarize the important work of Milnor, Freedman, Donaldson, and others in developing exotic differentiable structures on well known topological manifolds. Finally, we discuss some of the geometric implications of these results and propose some conjectures on possible physical implications of these new manifolds which have never before been considered as physical models. |
gr-qc/0501046 | Eran Rosenthal | Eran Rosenthal | Regularization of second-order scalar perturbation produced by a
point-particle with a nonlinear coupling | 14 pages | Class.Quant.Grav. 22 (2005) S859 | 10.1088/0264-9381/22/15/013 | null | gr-qc | null | Accurate calculation of the motion of a compact object in a background
spacetime induced by a supermassive black hole is required for the future
detection of such binary systems by the gravitational-wave detector LISA.
Reaching the desired accuracy requires calculation of the second-order
gravitational perturbations produced by the compact object. At the point
particle limit the second-order gravitational perturbation equations turn out
to have highly singular source terms, for which the standard retarded solutions
diverge. Here we study a simplified scalar toy-model in which a point particle
induces a nonlinear scalar field in a given curved spacetime. The corresponding
second-order scalar perturbation equation in this model is found to have a
similar singular source term, and therefore its standard retarded solutions
diverge. We develop a regularization method for constructing well-defined
causal solutions for this equation. Notably these solutions differ from the
standard retarded solutions, which are ill-defined in this case.
| [
{
"created": "Thu, 13 Jan 2005 23:34:28 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Rosenthal",
"Eran",
""
]
] | Accurate calculation of the motion of a compact object in a background spacetime induced by a supermassive black hole is required for the future detection of such binary systems by the gravitational-wave detector LISA. Reaching the desired accuracy requires calculation of the second-order gravitational perturbations produced by the compact object. At the point particle limit the second-order gravitational perturbation equations turn out to have highly singular source terms, for which the standard retarded solutions diverge. Here we study a simplified scalar toy-model in which a point particle induces a nonlinear scalar field in a given curved spacetime. The corresponding second-order scalar perturbation equation in this model is found to have a similar singular source term, and therefore its standard retarded solutions diverge. We develop a regularization method for constructing well-defined causal solutions for this equation. Notably these solutions differ from the standard retarded solutions, which are ill-defined in this case. |
gr-qc/0212095 | Robert van den Hoogen | R. J. van den Hoogen and J. Ibanez | Bianchi II Brane-world Cosmologies (${\cal U}\geq 0$) | 30 pages, 28 eps figures, Revtex | Phys.Rev. D67 (2003) 083510 | 10.1103/PhysRevD.67.083510 | null | gr-qc | null | The asymptotic properties of the Bianchi type II cosmological model in the
Brane-world scenario are investigated. The matter content is assumed to be a
combination of a perfect fluid and a minimimally coupled scalar field that is
restricted to the Brane. The isotropic braneworld solution is determined to
represent the initial singularity in all brane-world cosmologies. Additionally,
it is shown that it is the kinetic energy of the scalar field which dominates
the initial dynamics in these brane-world cosmologies. It is important to note
that, the dynamics of these brane-world cosmologies is not necessarily
asymptotic to general relativistic cosmologies to the future in the case of a
zero four-dimensional cosmological constant.
| [
{
"created": "Mon, 23 Dec 2002 15:29:02 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hoogen",
"R. J. van den",
""
],
[
"Ibanez",
"J.",
""
]
] | The asymptotic properties of the Bianchi type II cosmological model in the Brane-world scenario are investigated. The matter content is assumed to be a combination of a perfect fluid and a minimimally coupled scalar field that is restricted to the Brane. The isotropic braneworld solution is determined to represent the initial singularity in all brane-world cosmologies. Additionally, it is shown that it is the kinetic energy of the scalar field which dominates the initial dynamics in these brane-world cosmologies. It is important to note that, the dynamics of these brane-world cosmologies is not necessarily asymptotic to general relativistic cosmologies to the future in the case of a zero four-dimensional cosmological constant. |
1511.08740 | A. N. Ivanov | A. N. Ivanov and M. Wellenzohn | Effective Low-Energy Potential for Slow Dirac Fermions in
Einstein-Cartan Gravity with Torsion and Chameleon | 16 pages, no figures, the paper is accepted for publication in
Physical Review D | null | 10.1103/PhysRevD.92.125004 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the most general effective low-energy potential to order O(1/m) for
slow Dirac fermions with mass m, coupled to gravitational, chameleon and
torsion fields in the Einstein-Cartan gravity. The obtained results can be
applied to the experimental analysis of gravitational, chameleon and torsion
interactions in terrestrial laboratories. We discuss the use of rotating
coordinate systems, caused by rotations of devices, for measurements of the
torsion vector and tensor components, caused by minimal torsion--fermion
couplings (Ivanov and Wellenzohn, Phys. Rev. D92, 065006 (2015)). Using the
most general form of a metric tensor of curved spacetimes in rotating
coordinate systems, proposed by Obukhov, Silenko, and Teryaev (Phys. Rev. D84,
024025 (2011)), we extend this metric by the inclusion of the chameleon field
and calculate the set of vierbein fields, in terms of which Dirac fermions
couple to torsion vector and tensor components through minimal torsion-fermion
couplings. For such a set of vierbein fields we discuss a part of the effective
low-energy potential for slow Dirac fermions, coupled to gravitational,
chameleon and torsion fields to order O(1) in the large fermion mass expansion.
| [
{
"created": "Tue, 24 Nov 2015 10:41:14 GMT",
"version": "v1"
}
] | 2016-01-20 | [
[
"Ivanov",
"A. N.",
""
],
[
"Wellenzohn",
"M.",
""
]
] | We derive the most general effective low-energy potential to order O(1/m) for slow Dirac fermions with mass m, coupled to gravitational, chameleon and torsion fields in the Einstein-Cartan gravity. The obtained results can be applied to the experimental analysis of gravitational, chameleon and torsion interactions in terrestrial laboratories. We discuss the use of rotating coordinate systems, caused by rotations of devices, for measurements of the torsion vector and tensor components, caused by minimal torsion--fermion couplings (Ivanov and Wellenzohn, Phys. Rev. D92, 065006 (2015)). Using the most general form of a metric tensor of curved spacetimes in rotating coordinate systems, proposed by Obukhov, Silenko, and Teryaev (Phys. Rev. D84, 024025 (2011)), we extend this metric by the inclusion of the chameleon field and calculate the set of vierbein fields, in terms of which Dirac fermions couple to torsion vector and tensor components through minimal torsion-fermion couplings. For such a set of vierbein fields we discuss a part of the effective low-energy potential for slow Dirac fermions, coupled to gravitational, chameleon and torsion fields to order O(1) in the large fermion mass expansion. |
2407.16992 | Jungjai Lee | Yongjun Yun and Jungjai Lee | Holographic Dark Energy with Torsion | 11 pages, No figures, to be published in JKPS | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the holographic dark energy model with axial torsion which
satisfy the cosmological principle. Subsequently, by using the torsional
analogues of Friedmann equations for the new equation from Einstein-Cartan
gravity theory, we obtain the equation of state for dark energy in this model.
We find that the extended holographic dark energy from the particle horizon as
the infrared (IR) cut-off does not give the accelerating expansion of the
universe. Also, employing the future event horizon as IR cut-off still achieves
the accelerating expansion of the universe. In contrast, there is a possibility
that the Hubble radius as IR cut-off achieves to the accelerating expansion of
the universe in superluminal region for axial torsion. More precisely, the
current value of ratio for torsion to the matter density, $\gamma^{0}=0.5$
gives the equation of state of dark energy $\omega_{\Lambda}\cong-1$.
| [
{
"created": "Wed, 24 Jul 2024 04:24:27 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2024 06:25:46 GMT",
"version": "v2"
}
] | 2024-07-26 | [
[
"Yun",
"Yongjun",
""
],
[
"Lee",
"Jungjai",
""
]
] | We consider the holographic dark energy model with axial torsion which satisfy the cosmological principle. Subsequently, by using the torsional analogues of Friedmann equations for the new equation from Einstein-Cartan gravity theory, we obtain the equation of state for dark energy in this model. We find that the extended holographic dark energy from the particle horizon as the infrared (IR) cut-off does not give the accelerating expansion of the universe. Also, employing the future event horizon as IR cut-off still achieves the accelerating expansion of the universe. In contrast, there is a possibility that the Hubble radius as IR cut-off achieves to the accelerating expansion of the universe in superluminal region for axial torsion. More precisely, the current value of ratio for torsion to the matter density, $\gamma^{0}=0.5$ gives the equation of state of dark energy $\omega_{\Lambda}\cong-1$. |
1108.1178 | Daniele Oriti | Aristide Baratin and Daniele Oriti | Quantum simplicial geometry in the group field theory formalism:
reconsidering the Barrett-Crane model | revtex, 24 pages | New J.Phys. 13 (2011) 125011 | 10.1088/1367-2630/13/12/125011 | LPT-ORSAY 11-121 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A dual formulation of group field theories, obtained by a Fourier transform
mapping functions on a group to functions on its Lie algebra, has been proposed
recently. In the case of the Ooguri model for SO(4) BF theory, the variables of
the dual field variables are thus so(4) bivectors, which have a direct
interpretation as the discrete B variables. Here we study a modification of the
model by means of a constraint operator implementing the simplicity of the
bivectors, in such a way that projected fields describe metric tetrahedra. This
involves a extension of the usual GFT framework, where boundary operators are
labelled by projected spin network states. By construction, the Feynman
amplitudes are simplicial path integrals for constrained BF theory. We show
that the spin foam formulation of these amplitudes corresponds to a variant of
the Barrett-Crane model for quantum gravity. We then re-examin the arguments
against the Barrett-Crane model(s), in light of our construction.
| [
{
"created": "Thu, 4 Aug 2011 19:48:32 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Nov 2011 22:41:02 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Baratin",
"Aristide",
""
],
[
"Oriti",
"Daniele",
""
]
] | A dual formulation of group field theories, obtained by a Fourier transform mapping functions on a group to functions on its Lie algebra, has been proposed recently. In the case of the Ooguri model for SO(4) BF theory, the variables of the dual field variables are thus so(4) bivectors, which have a direct interpretation as the discrete B variables. Here we study a modification of the model by means of a constraint operator implementing the simplicity of the bivectors, in such a way that projected fields describe metric tetrahedra. This involves a extension of the usual GFT framework, where boundary operators are labelled by projected spin network states. By construction, the Feynman amplitudes are simplicial path integrals for constrained BF theory. We show that the spin foam formulation of these amplitudes corresponds to a variant of the Barrett-Crane model for quantum gravity. We then re-examin the arguments against the Barrett-Crane model(s), in light of our construction. |
2307.10464 | Michail Chabanov | Michail Chabanov and Luciano Rezzolla | Impact of bulk viscosity on the post-merger gravitational-wave signal
from merging neutron stars | 8 pages, 2 figures | null | null | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the violent post-merger of binary neutron-star mergers strong oscillations
are present that impact the emitted gravitational-wave (GW) signal. The
frequencies, temperatures and densities involved in these oscillations allow
for violations of the chemical equilibrium promoted by weak-interactions, thus
leading to a nonzero bulk viscosity that can impact dynamics and GW signals. We
present the first simulations of binary neutron-star mergers employing the
self-consistent and second-order formulation of the equations of relativistic
hydrodynamics for dissipative fluids proposed by M\"uller, Israel and Stewart.
With the spirit of obtaining a first assessment of the impact of bulk viscosity
on the structure and radiative efficiency of the merger remnant we adopt a
simplified approach for the viscosity, which we assume to be constant within
the stars, but which we vary in strength for different binaries, thus exploring
the possible behaviours and obtaining strict upper limits. In this way, we find
that large bulk viscosities are very effective at damping the
collision-and-bounce oscillations that characterize the dynamics of the stellar
cores right after the merger. As a result, the $m=2$ deformations and the
gravitational-radiation efficiency of the remnant are considerably reduced,
with qualitative and quantitative changes in the post-merger spectrum that can
be large in the case of the most extreme configurations. Overall, our crude but
self-consistent results indicate that bulk viscosity reduces the energy
radiated in GWs by $\lesssim 1\%$ in the (realistic) scenario of small
viscosity, and by $\lesssim 15\%$ in the (unrealistic) scenario of large
viscosity.
| [
{
"created": "Wed, 19 Jul 2023 21:22:51 GMT",
"version": "v1"
}
] | 2023-07-21 | [
[
"Chabanov",
"Michail",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | In the violent post-merger of binary neutron-star mergers strong oscillations are present that impact the emitted gravitational-wave (GW) signal. The frequencies, temperatures and densities involved in these oscillations allow for violations of the chemical equilibrium promoted by weak-interactions, thus leading to a nonzero bulk viscosity that can impact dynamics and GW signals. We present the first simulations of binary neutron-star mergers employing the self-consistent and second-order formulation of the equations of relativistic hydrodynamics for dissipative fluids proposed by M\"uller, Israel and Stewart. With the spirit of obtaining a first assessment of the impact of bulk viscosity on the structure and radiative efficiency of the merger remnant we adopt a simplified approach for the viscosity, which we assume to be constant within the stars, but which we vary in strength for different binaries, thus exploring the possible behaviours and obtaining strict upper limits. In this way, we find that large bulk viscosities are very effective at damping the collision-and-bounce oscillations that characterize the dynamics of the stellar cores right after the merger. As a result, the $m=2$ deformations and the gravitational-radiation efficiency of the remnant are considerably reduced, with qualitative and quantitative changes in the post-merger spectrum that can be large in the case of the most extreme configurations. Overall, our crude but self-consistent results indicate that bulk viscosity reduces the energy radiated in GWs by $\lesssim 1\%$ in the (realistic) scenario of small viscosity, and by $\lesssim 15\%$ in the (unrealistic) scenario of large viscosity. |
1011.5475 | Reiner Birkl | Reiner Birkl, Nikolaos Stergioulas, Ewald M\"uller | Stationary, Axisymmetric Neutron Stars with Meridional Circulation in
General Relativity | null | Phys.Rev.D84:023003,2011 | 10.1103/PhysRevD.84.023003 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first stationary, axisymmetric neutron star models with
meridional circulation in general relativity. For that purpose, we developed
GRNS, a new code based on a fixed point iteration. We find a two-dimensional
set of meridional circulation modes, which differ by the number of vortices in
the stream lines of the neutron star fluid. For expected maximal meridional
circulation velocities of about 1000 km/s, the vortices cause surface
deformations of about a percent. The deformations depend on the shape of the
vortices close to the surface and increase with the meridional circulation
velocity. We also computed models of rotating neutron stars with meridional
circulation, where neither the surface rotates nor does the rotation velocity
exceed the circulation velocity.
| [
{
"created": "Wed, 24 Nov 2010 20:00:22 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Birkl",
"Reiner",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Müller",
"Ewald",
""
]
] | We present the first stationary, axisymmetric neutron star models with meridional circulation in general relativity. For that purpose, we developed GRNS, a new code based on a fixed point iteration. We find a two-dimensional set of meridional circulation modes, which differ by the number of vortices in the stream lines of the neutron star fluid. For expected maximal meridional circulation velocities of about 1000 km/s, the vortices cause surface deformations of about a percent. The deformations depend on the shape of the vortices close to the surface and increase with the meridional circulation velocity. We also computed models of rotating neutron stars with meridional circulation, where neither the surface rotates nor does the rotation velocity exceed the circulation velocity. |
1804.10746 | Shibei Kong | Chao-Guang Huang, Shibei Kong | Hamiltonian Analysis of 4-dimensional Spacetime in Bondi-like
Coordinates | null | 2018 Chinese Phys. C 42 105101 | 10.1088/1674-1137/42/10/105101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the Hamiltonian formulation of gravity in 4-dimensional spacetime
under Bondi-like coordinates{v, r, x^a, a=2, 3}. In Bondi-like coordinates, the
3-dimensional hypersurface is a null hypersurface and the evolution direction
is the advanced time v. The internal symmetry group SO(1,3) of the
4-dimensional spacetime is decomposed into SO(1,1), SO(2), and T^\pm(2), whose
Lie algebra so(1,3) is decomposed into so(1,1), so(2), t^\pm(2)
correspondingly. The SO(1,1) symmetry is very obvious in this kind of
decomposition, which is very useful in so(1,1) BF theory. General relativity
can be reformulated as the 4-dimensional coframe (e^I_\mu) and connection
({\omega}^{IJ}_\mu) dynamics of gravity based on this kind of decomposition in
the Bondi-like coordinate system. The coframe consists of 2 null 1-forms e^-,
e^+ and 2 spacelike 1-forms e^2, e^3. The Palatini action is used. The
Hamiltonian analysis is conducted by the Dirac's methods. The consistency
analysis of constraints has been done completely. There are 2 scalar
constraints and one 2-dimensional vector constraint. The torsion-free
conditions are acquired from the consistency conditions of the primary
constraints about {\pi}^\mu_{IJ}. The consistency conditions of the primary
constraints {\pi}^0_{IJ}=0 can be reformulated as Gauss constraints. The
conditions of the Lagrange multipliers have been acquired. The Poisson brackets
among the constraints have been calculated. There are 46 constraints including
6 first class constraints {\pi}^0_{IJ}=0 and 40 second class constraints. The
local physical degrees of freedom is 2. The integrability conditions of
Lagrange multipliers n_0, l_0, and e^A_0 are Ricci identities. The equations of
motion of the canonical variables have also been shown.
| [
{
"created": "Sat, 28 Apr 2018 05:36:05 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jul 2018 11:02:18 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Oct 2018 17:45:46 GMT",
"version": "v3"
}
] | 2018-10-09 | [
[
"Huang",
"Chao-Guang",
""
],
[
"Kong",
"Shibei",
""
]
] | We discuss the Hamiltonian formulation of gravity in 4-dimensional spacetime under Bondi-like coordinates{v, r, x^a, a=2, 3}. In Bondi-like coordinates, the 3-dimensional hypersurface is a null hypersurface and the evolution direction is the advanced time v. The internal symmetry group SO(1,3) of the 4-dimensional spacetime is decomposed into SO(1,1), SO(2), and T^\pm(2), whose Lie algebra so(1,3) is decomposed into so(1,1), so(2), t^\pm(2) correspondingly. The SO(1,1) symmetry is very obvious in this kind of decomposition, which is very useful in so(1,1) BF theory. General relativity can be reformulated as the 4-dimensional coframe (e^I_\mu) and connection ({\omega}^{IJ}_\mu) dynamics of gravity based on this kind of decomposition in the Bondi-like coordinate system. The coframe consists of 2 null 1-forms e^-, e^+ and 2 spacelike 1-forms e^2, e^3. The Palatini action is used. The Hamiltonian analysis is conducted by the Dirac's methods. The consistency analysis of constraints has been done completely. There are 2 scalar constraints and one 2-dimensional vector constraint. The torsion-free conditions are acquired from the consistency conditions of the primary constraints about {\pi}^\mu_{IJ}. The consistency conditions of the primary constraints {\pi}^0_{IJ}=0 can be reformulated as Gauss constraints. The conditions of the Lagrange multipliers have been acquired. The Poisson brackets among the constraints have been calculated. There are 46 constraints including 6 first class constraints {\pi}^0_{IJ}=0 and 40 second class constraints. The local physical degrees of freedom is 2. The integrability conditions of Lagrange multipliers n_0, l_0, and e^A_0 are Ricci identities. The equations of motion of the canonical variables have also been shown. |
1709.02657 | Sabine Hossenfelder | Sabine Hossenfelder, Ricardo Gallego Torrom\'e | General Relativity with Local Space-time Defects | 15 pages, 2 figures, replaced with published version | null | 10.1088/1361-6382/aad38c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity is incomplete because it cannot describe quantum effects
of space-time. The complete theory of quantum gravity is not yet known and to
date no observational evidence exists that space-time is quantized. However, in
most approaches to quantum gravity the space-time manifold of general
relativity is only an effective limit that, among other things like higher
curvature terms, should receive corrections stemming from space-time defects.
We here develop a modification of general relativity that describes local
space-time defects and solve the Friedmann equations. From this, we obtain the
time-dependence of the density of defects. It turns out that the defects'
density dilutes quickly, somewhat faster even than radiation.
| [
{
"created": "Fri, 8 Sep 2017 11:45:14 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jul 2018 16:16:37 GMT",
"version": "v2"
}
] | 2018-07-17 | [
[
"Hossenfelder",
"Sabine",
""
],
[
"Torromé",
"Ricardo Gallego",
""
]
] | General relativity is incomplete because it cannot describe quantum effects of space-time. The complete theory of quantum gravity is not yet known and to date no observational evidence exists that space-time is quantized. However, in most approaches to quantum gravity the space-time manifold of general relativity is only an effective limit that, among other things like higher curvature terms, should receive corrections stemming from space-time defects. We here develop a modification of general relativity that describes local space-time defects and solve the Friedmann equations. From this, we obtain the time-dependence of the density of defects. It turns out that the defects' density dilutes quickly, somewhat faster even than radiation. |
gr-qc/9904069 | Mayburov S. N. | S. Mayburov (Lebedev Inst. of Physics, Moscow) | Quantum Space-Time and Reference Frames in ADM Canonical Gravity | 19 pages, Latex, Talk given at 'Quantum Field Theory under External
Conditions' conference, Leipzig, September 1998, to appear in proceedings | null | null | null | gr-qc | null | The quantum space-time model which accounts material Reference Frames (RF)
quantum effects considered for flat space-time and ADM canonical gravity. As
was shown by Aharonov for RF - free material object its c.m. nonrelativistic
motion in vacuum described by Schrodinger wave packet evolution which modify
space coordinate operator of test particle in this RF and changes its
Heisenberg uncertainty relations. In the relativistic case we show that Lorentz
transformations between two RFs include the quantum corrections for RFs
momentum uncertainty and in general can be formulated as the quantum space-time
transformations. As the result for moving RF its Lorentz time boost acquires
quantum fluctuations which calculated solving relativistic Heisenberg equations
for the quantum clocks models. It permits to calculate RF proper time for the
arbitrary RF quantum motion including quantum gravity metrics fluctuations.
Space-time structure of canonical Quantum Gravity and its observables evolution
for RF proper time discussed in this quantum space-time transformations
framework.
| [
{
"created": "Tue, 27 Apr 1999 12:50:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mayburov",
"S.",
"",
"Lebedev Inst. of Physics, Moscow"
]
] | The quantum space-time model which accounts material Reference Frames (RF) quantum effects considered for flat space-time and ADM canonical gravity. As was shown by Aharonov for RF - free material object its c.m. nonrelativistic motion in vacuum described by Schrodinger wave packet evolution which modify space coordinate operator of test particle in this RF and changes its Heisenberg uncertainty relations. In the relativistic case we show that Lorentz transformations between two RFs include the quantum corrections for RFs momentum uncertainty and in general can be formulated as the quantum space-time transformations. As the result for moving RF its Lorentz time boost acquires quantum fluctuations which calculated solving relativistic Heisenberg equations for the quantum clocks models. It permits to calculate RF proper time for the arbitrary RF quantum motion including quantum gravity metrics fluctuations. Space-time structure of canonical Quantum Gravity and its observables evolution for RF proper time discussed in this quantum space-time transformations framework. |
1104.3654 | Valery Kiselev | V.V.Kiselev, S.A.Timofeev | Cosmological extrapolation of MOND | 20 pages, 5 figures, comments added | Class.Quant.Grav. 29 (2012) 065015 | 10.1088/0264-9381/29/6/065015 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regime of MOND, which is used in astronomy to describe the gravitating
systems of island type without the need to postulate the existence of a
hypothetical dark matter, is generalized to the case of homogeneous
distribution of usual matter by introducing a linear dependence of the critical
acceleration on the size of region under consideration. We show that such the
extrapolation of MOND in cosmology is consistent with both the observed
dependence of brightness on the redshift for type Ia supernovae and the
parameters of large-scale structure of Universe in the evolution, that is
determined by the presence of a cosmological constant, the ordinary matter of
baryons and electrons as well as the photon and neutrino radiation without any
dark matter.
| [
{
"created": "Tue, 19 Apr 2011 07:02:06 GMT",
"version": "v1"
},
{
"created": "Wed, 4 May 2011 13:34:07 GMT",
"version": "v2"
},
{
"created": "Tue, 31 May 2011 11:32:39 GMT",
"version": "v3"
}
] | 2019-11-28 | [
[
"Kiselev",
"V. V.",
""
],
[
"Timofeev",
"S. A.",
""
]
] | Regime of MOND, which is used in astronomy to describe the gravitating systems of island type without the need to postulate the existence of a hypothetical dark matter, is generalized to the case of homogeneous distribution of usual matter by introducing a linear dependence of the critical acceleration on the size of region under consideration. We show that such the extrapolation of MOND in cosmology is consistent with both the observed dependence of brightness on the redshift for type Ia supernovae and the parameters of large-scale structure of Universe in the evolution, that is determined by the presence of a cosmological constant, the ordinary matter of baryons and electrons as well as the photon and neutrino radiation without any dark matter. |
1202.2893 | Alexandre Le Tiec | Alexandre Le Tiec | Spacetime Symmetries and Kepler's Third Law | 11 pages, 3 figures; minor changes and text improvements; matches
version to appear in Class. Quant. Grav | Class.Quant.Grav.29:217002,2012 | 10.1088/0264-9381/29/21/217002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The curved spacetime geometry of a system of two point masses moving on a
circular orbit has a helical symmetry. We show how Kepler's third law for
circular motion, and its generalization in post-Newtonian theory, can be
recovered from a simple, covariant condition on the norm of the associated
helical Killing vector field. This unusual derivation can be used to illustrate
some concepts of prime importance in a general relativity course, including
those of Killing field, covariance, coordinate dependence, and gravitational
redshift.
| [
{
"created": "Mon, 13 Feb 2012 23:15:34 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Sep 2012 19:54:30 GMT",
"version": "v2"
}
] | 2013-08-26 | [
[
"Tiec",
"Alexandre Le",
""
]
] | The curved spacetime geometry of a system of two point masses moving on a circular orbit has a helical symmetry. We show how Kepler's third law for circular motion, and its generalization in post-Newtonian theory, can be recovered from a simple, covariant condition on the norm of the associated helical Killing vector field. This unusual derivation can be used to illustrate some concepts of prime importance in a general relativity course, including those of Killing field, covariance, coordinate dependence, and gravitational redshift. |
1607.01234 | Yadao Solanke | Y. S. Solanke, D. D.Pawar and V. J. Dagwal | Role of the constant deceleration parameter in cosmological models with
perfect fluid and dark energy | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main purpose of the present paper is to investigate LRS Bianchi type I
metric in the presence of perfect fluid and dark energy. In order to obtain a
deterministic solution of the field equations we have assumed that, the two
sources of the perfect fluid and dark energy interact minimally with separate
conservation of their energy momentum tensors. The EoS parameter of the perfect
fluid is also assumed to be constant. In addition to these we have used a
special law of variation of Hubble parameter proposed by Berman that yields
constant deceleration parameter. For two different values of the constant
deceleration parameters we have obtained two different cosmological models. The
physical behaviors of both the models have been discussed by using some
physical parameters.
| [
{
"created": "Tue, 5 Jul 2016 12:58:00 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Mar 2020 06:57:45 GMT",
"version": "v2"
}
] | 2020-03-06 | [
[
"Solanke",
"Y. S.",
""
],
[
"Pawar",
"D. D.",
""
],
[
"Dagwal",
"V. J.",
""
]
] | The main purpose of the present paper is to investigate LRS Bianchi type I metric in the presence of perfect fluid and dark energy. In order to obtain a deterministic solution of the field equations we have assumed that, the two sources of the perfect fluid and dark energy interact minimally with separate conservation of their energy momentum tensors. The EoS parameter of the perfect fluid is also assumed to be constant. In addition to these we have used a special law of variation of Hubble parameter proposed by Berman that yields constant deceleration parameter. For two different values of the constant deceleration parameters we have obtained two different cosmological models. The physical behaviors of both the models have been discussed by using some physical parameters. |
1011.3667 | Benjamin Bahr | Benjamin Bahr, Bianca Dittrich, Song He | Coarse graining free theories with gauge symmetries: the linearized case | 31 pages, 3 pictures, title changed, reference updated | New J.Phys.13:045009,2011 | 10.1088/1367-2630/13/4/045009 | null | gr-qc hep-lat | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Discretizations of continuum theories often do not preserve the gauge
symmetry content. This occurs in particular for diffeomorphism symmetry in
general relativity, which leads to severe difficulties both in canonical and
covariant quantization approaches. We discuss here the method of perfect
actions, which attempts to restore gauge symmetries by mirroring exactly
continuum physics on a lattice via a coarse graining process. Analytical
results can only be obtained via a perturbative approach, for which we consider
the first steps, namely the coarse graining of the linearized theory. The
linearized gauge symmetries are exact also in the discretized theory, hence we
develop a formalism to deal with gauge systems. Finally we provide a
discretization of linearized gravity as well as a coarse graining map and show
that with this choice the 3D linearized gravity action is invariant under
coarse graining.
| [
{
"created": "Tue, 16 Nov 2010 12:11:21 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2011 13:00:39 GMT",
"version": "v2"
}
] | 2011-06-10 | [
[
"Bahr",
"Benjamin",
""
],
[
"Dittrich",
"Bianca",
""
],
[
"He",
"Song",
""
]
] | Discretizations of continuum theories often do not preserve the gauge symmetry content. This occurs in particular for diffeomorphism symmetry in general relativity, which leads to severe difficulties both in canonical and covariant quantization approaches. We discuss here the method of perfect actions, which attempts to restore gauge symmetries by mirroring exactly continuum physics on a lattice via a coarse graining process. Analytical results can only be obtained via a perturbative approach, for which we consider the first steps, namely the coarse graining of the linearized theory. The linearized gauge symmetries are exact also in the discretized theory, hence we develop a formalism to deal with gauge systems. Finally we provide a discretization of linearized gravity as well as a coarse graining map and show that with this choice the 3D linearized gravity action is invariant under coarse graining. |
2303.02990 | Vladimir Folomeev | Vladimir Dzhunushaliev, Vladimir Folomeev, and Dina Zholdakhmet | Spinor domain wall and test fermions on an arbitrary domain wall | 18 pages, 4 figures, minor corrections to content, version published
in EPJC | Eur.Phys.J. C 83, 550 (2023) | 10.1140/epjc/s10052-023-11742-1 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a spinor domain wall embedded in a five-dimensional spacetime
with a nondiagonal metric. The corresponding plane symmetric solutions for
linear and nonlinear spinor fields with different parameters are obtained. It
is shown that in the general case the metric functions and spinor fields do not
possess $Z_2$ symmetry with respect to the domain wall. We study the angular
momentum density of the domain wall arising because of the presence of the
spinor field creating the wall. The properties of test fermions located on an
arbitrary domain wall are considered. The concepts of the ``second spin''
(arising due to the properties of the Lorentz group generators in a
five-dimensional spacetime) and of the ``second magnetic field'' (representing
the components $F_{i 5}$ of the electromagnetic field five-tensor) are
introduced. We find eigenspinors of the ``second spin'' and show that some of
them represent the Bell states. In the nonrelativistic limit we derive the
Pauli equation for the test fermions on the domain wall which contains an extra
term describing the interaction of a spin-$1/2$ particle with the ``second
magnetic field''; this allows the possibility of an experimental verification
of the existence of extra dimensions.
| [
{
"created": "Mon, 6 Mar 2023 09:35:19 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jul 2023 03:42:56 GMT",
"version": "v2"
}
] | 2023-07-31 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
],
[
"Zholdakhmet",
"Dina",
""
]
] | We consider a spinor domain wall embedded in a five-dimensional spacetime with a nondiagonal metric. The corresponding plane symmetric solutions for linear and nonlinear spinor fields with different parameters are obtained. It is shown that in the general case the metric functions and spinor fields do not possess $Z_2$ symmetry with respect to the domain wall. We study the angular momentum density of the domain wall arising because of the presence of the spinor field creating the wall. The properties of test fermions located on an arbitrary domain wall are considered. The concepts of the ``second spin'' (arising due to the properties of the Lorentz group generators in a five-dimensional spacetime) and of the ``second magnetic field'' (representing the components $F_{i 5}$ of the electromagnetic field five-tensor) are introduced. We find eigenspinors of the ``second spin'' and show that some of them represent the Bell states. In the nonrelativistic limit we derive the Pauli equation for the test fermions on the domain wall which contains an extra term describing the interaction of a spin-$1/2$ particle with the ``second magnetic field''; this allows the possibility of an experimental verification of the existence of extra dimensions. |
gr-qc/9810053 | Dmitriy Yu. Shabalkin | Dmitriy Yu. Shabalkin | On the method of effective nonlinear sigma model in plane- and
axially-symmetric vacuum spacetimes | 5 pages, LaTex, submitted to Gravitation and Cosmology | Grav.Cosmol. 4 (1999) 16 | null | UlSU/LFR-9802 | gr-qc | null | In present article effective nonlinear sigma model (NSM) is considered.
Einstein equation solution, corresponded to the chiral fields determined by
functional parameter method, are presented.
Effective NSM of stationary axially-symmetric gravitational field is
constructed. Motion equations are solved exactly by functional parameter
method. Einstein equations solution are constructed.
For particular dependences of functional parameter graphics of solutions are
presented. Metric coefficients behaviour is shown to be similar as functional
parameter one.
| [
{
"created": "Fri, 16 Oct 1998 14:07:22 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Shabalkin",
"Dmitriy Yu.",
""
]
] | In present article effective nonlinear sigma model (NSM) is considered. Einstein equation solution, corresponded to the chiral fields determined by functional parameter method, are presented. Effective NSM of stationary axially-symmetric gravitational field is constructed. Motion equations are solved exactly by functional parameter method. Einstein equations solution are constructed. For particular dependences of functional parameter graphics of solutions are presented. Metric coefficients behaviour is shown to be similar as functional parameter one. |
1001.3407 | Jose Geraldo Pereira | H. I. Arcos, Tiago Gribl Lucas, J. G. Pereira | Consistent Gravitationally-Coupled Spin-2 Field Theory | 16 pages, no figures. V2: Presentation changes, including addition of
a new sub-section, aiming at clarifying the text; version accepted for
publication in Class. Quantum Grav. | Class.Quant.Grav.27:145007,2010 | 10.1088/0264-9381/27/14/145007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the translational gauge structure of teleparallel gravity, the
theory for a fundamental massless spin-2 field is constructed. Accordingly,
instead of being represented by a symmetric second-rank tensor, the fundamental
spin-2 field is assumed to be represented by a spacetime (world) vector field
assuming values in the Lie algebra of the translation group. The flat-space
theory naturally emerges in the Fierz formalism and is found to be equivalent
to the usual metric-based theory. However, the gravitationally coupled theory,
with gravitation itself described by teleparallel gravity, is shown not to
present the consistency problems of the spin-2 theory constructed on the basis
of general relativity.
| [
{
"created": "Tue, 19 Jan 2010 21:00:21 GMT",
"version": "v1"
},
{
"created": "Wed, 5 May 2010 11:14:59 GMT",
"version": "v2"
}
] | 2013-02-28 | [
[
"Arcos",
"H. I.",
""
],
[
"Lucas",
"Tiago Gribl",
""
],
[
"Pereira",
"J. G.",
""
]
] | Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed to be represented by a spacetime (world) vector field assuming values in the Lie algebra of the translation group. The flat-space theory naturally emerges in the Fierz formalism and is found to be equivalent to the usual metric-based theory. However, the gravitationally coupled theory, with gravitation itself described by teleparallel gravity, is shown not to present the consistency problems of the spin-2 theory constructed on the basis of general relativity. |
1705.08602 | Sourav Bhattacharya | Md Sabir Ali and Sourav Bhattacharya | Light bending, static dark energy and related uniqueness of
Schwarzschild-de Sitter spacetime | v2, 18pp, 1 fig; title changed, added references, discussions and
clarifications; improved presentation, main results unchanged; accepted in
PRD | Phys. Rev. D 97 (2018) 024029 | 10.1103/PhysRevD.97.024029 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the Schwarzschild-de Sitter spacetime is static inside the cosmological
event horizon, if the dark energy state parameter is sufficiently close to
$-1$, apparently one could still expect an effectively static geometry, in the
attraction dominated region inside the maximum turn around radius, $R_{\rm TA,
max}$, of a cosmic structure. We take the first order metric derived recently
assuming a static and ideal dark energy fluid with equation of state
$P(r)=\alpha\rho(r)$ as a source in Ref. [1], which reproduced the expression
for $R_{\rm TA, max}$ found earlier in the cosmological McVittie spacetime.
Here we show that the equality originates from the equivalence of geodesic
motion in these two backgrounds, in the non-relativistic regime. We extend this
metric up to the third order and compute the bending of light using the
Rindler-Ishak method. For $ \alpha\neq -1$, a dark energy dependent term
appears in the bending equation, unlike the case of the cosmological constant,
$\alpha=-1$. Due to this new term in particular, existing data for the light
bending at galactic scales yields, $(1+\alpha)\lesssim {\cal O}(10^{-14})$,
thereby practically ruling out any such static and inhomogeneous dark energy
fluid we started with. Implication of this result pertaining the uniqueness of
the Schwarzschild-de Sitter spacetime in such inhomogeneous dark energy
background is discussed.
| [
{
"created": "Wed, 24 May 2017 04:23:13 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jan 2018 04:33:42 GMT",
"version": "v2"
}
] | 2018-01-25 | [
[
"Ali",
"Md Sabir",
""
],
[
"Bhattacharya",
"Sourav",
""
]
] | Since the Schwarzschild-de Sitter spacetime is static inside the cosmological event horizon, if the dark energy state parameter is sufficiently close to $-1$, apparently one could still expect an effectively static geometry, in the attraction dominated region inside the maximum turn around radius, $R_{\rm TA, max}$, of a cosmic structure. We take the first order metric derived recently assuming a static and ideal dark energy fluid with equation of state $P(r)=\alpha\rho(r)$ as a source in Ref. [1], which reproduced the expression for $R_{\rm TA, max}$ found earlier in the cosmological McVittie spacetime. Here we show that the equality originates from the equivalence of geodesic motion in these two backgrounds, in the non-relativistic regime. We extend this metric up to the third order and compute the bending of light using the Rindler-Ishak method. For $ \alpha\neq -1$, a dark energy dependent term appears in the bending equation, unlike the case of the cosmological constant, $\alpha=-1$. Due to this new term in particular, existing data for the light bending at galactic scales yields, $(1+\alpha)\lesssim {\cal O}(10^{-14})$, thereby practically ruling out any such static and inhomogeneous dark energy fluid we started with. Implication of this result pertaining the uniqueness of the Schwarzschild-de Sitter spacetime in such inhomogeneous dark energy background is discussed. |
gr-qc/0206066 | Edward Teo | Edward Teo and K.F. Wong | Quantum interest in two dimensions | 17 pages, 4 figures; final version to appear in PRD | Phys.Rev. D66 (2002) 064007 | 10.1103/PhysRevD.66.064007 | null | gr-qc | null | The quantum interest conjecture of Ford and Roman asserts that any
negative-energy pulse must necessarily be followed by an over-compensating
positive-energy one within a certain maximum time delay. Furthermore, the
minimum amount of over-compensation increases with the separation between the
pulses. In this paper, we first study the case of a negative-energy square
pulse followed by a positive-energy one for a minimally coupled, massless
scalar field in two-dimensional Minkowski space. We obtain explicit expressions
for the maximum time delay and the amount of over-compensation needed, using a
previously developed eigenvalue approach. These results are then used to give a
proof of the quantum interest conjecture for massless scalar fields in two
dimensions, valid for general energy distributions.
| [
{
"created": "Fri, 21 Jun 2002 03:20:57 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2002 06:58:16 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Teo",
"Edward",
""
],
[
"Wong",
"K. F.",
""
]
] | The quantum interest conjecture of Ford and Roman asserts that any negative-energy pulse must necessarily be followed by an over-compensating positive-energy one within a certain maximum time delay. Furthermore, the minimum amount of over-compensation increases with the separation between the pulses. In this paper, we first study the case of a negative-energy square pulse followed by a positive-energy one for a minimally coupled, massless scalar field in two-dimensional Minkowski space. We obtain explicit expressions for the maximum time delay and the amount of over-compensation needed, using a previously developed eigenvalue approach. These results are then used to give a proof of the quantum interest conjecture for massless scalar fields in two dimensions, valid for general energy distributions. |
2002.03402 | Marios Bounakis | Marios Bounakis and Gerasimos Rigopoulos | Feynman Rules for Stochastic Inflationary Correlators | 30 pages | JCAP05(2020)046 | 10.1088/1475-7516/2020/05/046 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We elaborate on the functional integral describing the stochastic dynamics of
a spectator field during inflation, comparing its diagrammatic expansion to
that obtained directly from a perturbative solution of the corresponding
Langevin equation. We state Feynman rules for computing arbitrary temporal
$n$-point functions and perform some illustrative computations for a
$\lambda\phi^4$ interaction, paying attention to the role played by a
functional Jacobian determinant in the path integral. We also briefly consider
the case when the field contributes to the expansion rate, making the noise
multiplicative, which introduces additional vertices.
| [
{
"created": "Sun, 9 Feb 2020 17:32:13 GMT",
"version": "v1"
}
] | 2020-06-02 | [
[
"Bounakis",
"Marios",
""
],
[
"Rigopoulos",
"Gerasimos",
""
]
] | We elaborate on the functional integral describing the stochastic dynamics of a spectator field during inflation, comparing its diagrammatic expansion to that obtained directly from a perturbative solution of the corresponding Langevin equation. We state Feynman rules for computing arbitrary temporal $n$-point functions and perform some illustrative computations for a $\lambda\phi^4$ interaction, paying attention to the role played by a functional Jacobian determinant in the path integral. We also briefly consider the case when the field contributes to the expansion rate, making the noise multiplicative, which introduces additional vertices. |
2008.10884 | Salvatore Capozziello | Artyom V. Astashenok, Salvatore Capozziello, Sergei D. Odintsov,
Vasilis K. Oikonomou | Extended Gravity Description for the GW190814 Supermassive Neutron Star | 8 pages, 3 figures | null | 10.1016/j.physletb.2020.135910 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Very recently a compact object with a mass in the range $2.50\div 2.67\,
M_{\odot}$ has been discovered via gravitational waves detection of a compact
binary coalescence. The mass of this object makes it among the heaviest neutron
star never detected or the lightest black hole ever observed. Here we show that
a neutron star with this observed mass, can be consistently explained with the
mass-radius relation obtained by Extended Theories of Gravity. Furthermore,
equations of state, consistent with LIGO observational constraints, are
adopted. We consider also the influence of rotation and show that masses of
rotating neutron stars can exceed $2.6 M_\odot$ for some equations of state
compatible with LIGO data.
| [
{
"created": "Tue, 25 Aug 2020 08:40:16 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Astashenok",
"Artyom V.",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Oikonomou",
"Vasilis K.",
""
]
] | Very recently a compact object with a mass in the range $2.50\div 2.67\, M_{\odot}$ has been discovered via gravitational waves detection of a compact binary coalescence. The mass of this object makes it among the heaviest neutron star never detected or the lightest black hole ever observed. Here we show that a neutron star with this observed mass, can be consistently explained with the mass-radius relation obtained by Extended Theories of Gravity. Furthermore, equations of state, consistent with LIGO observational constraints, are adopted. We consider also the influence of rotation and show that masses of rotating neutron stars can exceed $2.6 M_\odot$ for some equations of state compatible with LIGO data. |
gr-qc/0506079 | John Hartnett | Moshe Carmeli, John G. Hartnett, Firmin J. Oliveira | The Cosmic Time in Terms of the Redshift | 3 pages, 3 figures | Found.Phys.Lett. 19 (2006) 277-283 | 10.1007/s10702-006-0518-3 | null | gr-qc | null | In cosmology one labels the time t since the Big Bang in terms of the
redshift of light emitted at t, as we see it now. In this Note we derive a
formula that relates t to z which is valid for all redshifts. One can go back
in time as far as one wishes, but not to the Big Bang at which the redshift
tends to infinity.
| [
{
"created": "Tue, 14 Jun 2005 04:06:13 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2005 06:46:39 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Carmeli",
"Moshe",
""
],
[
"Hartnett",
"John G.",
""
],
[
"Oliveira",
"Firmin J.",
""
]
] | In cosmology one labels the time t since the Big Bang in terms of the redshift of light emitted at t, as we see it now. In this Note we derive a formula that relates t to z which is valid for all redshifts. One can go back in time as far as one wishes, but not to the Big Bang at which the redshift tends to infinity. |
gr-qc/0109024 | Peter Dunsby | G. F. R. Ellis, P. McEwan, W. Stoeger and P. Dunsby | Causality in Inflationary Universes with Positive Spatial Curvature | 13 pages RevTex4, 4 figures. Changes to the abstract and the section
on Realistic Estimates | Gen.Rel.Grav. 34 (2002) 1461-1481 | 10.1023/A:1020039120851 | null | gr-qc | null | We show that in the case of positively-curved Friedmann-Lema\^{\i}tre
universes $(k=+1)$, an inflationary period in the early universe will for most
initial conditions not solve the horizon problem, no matter how long inflation
lasts. It will only do so for cases where inflation starts in an almost static
state, corresponding to an extremely high value of $\Omega_{\Lambda}$,
$\Omega_{\Lambda} \gg 1$, at the beginning of inflation. For smaller values, it
is not possible to solve the horizon problem because the relevant integral
asymptotes to a finite value (as happens also in the de Sitter universe in a
$k=+1$ frame). Thus, for these cases, the causal problems associated with the
near-isotropy of the Cosmic Background Radiation have to be solved already in
the Planck era. Furthermore both compact space sections and event horizons will
exist in these universes even if the present cosmological constant dies away in
the far future, raising potential problems for M-theory as a theory of gravity.
| [
{
"created": "Thu, 6 Sep 2001 15:22:26 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Feb 2002 13:33:26 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Ellis",
"G. F. R.",
""
],
[
"McEwan",
"P.",
""
],
[
"Stoeger",
"W.",
""
],
[
"Dunsby",
"P.",
""
]
] | We show that in the case of positively-curved Friedmann-Lema\^{\i}tre universes $(k=+1)$, an inflationary period in the early universe will for most initial conditions not solve the horizon problem, no matter how long inflation lasts. It will only do so for cases where inflation starts in an almost static state, corresponding to an extremely high value of $\Omega_{\Lambda}$, $\Omega_{\Lambda} \gg 1$, at the beginning of inflation. For smaller values, it is not possible to solve the horizon problem because the relevant integral asymptotes to a finite value (as happens also in the de Sitter universe in a $k=+1$ frame). Thus, for these cases, the causal problems associated with the near-isotropy of the Cosmic Background Radiation have to be solved already in the Planck era. Furthermore both compact space sections and event horizons will exist in these universes even if the present cosmological constant dies away in the far future, raising potential problems for M-theory as a theory of gravity. |
0911.2340 | Abhas Mitra | Abhas Mitra | Einstein energy associated with the Friedmann -Robertson -Walker metric | By mistake a marginally different earlier version was loaded, now the
journal version is uploaded | Gen.Rel.Grav.42:443-469,2010 | 10.1007/s10714-009-0863-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following Einstein's definition of Lagrangian density and gravitational field
energy density (Einstein, A., Ann. Phys. Lpz., 49, 806 (1916); Einstein, A.,
Phys. Z., 19, 115 (1918); Pauli, W., {\it Theory of Relativity}, B.I.
Publications, Mumbai, 1963, Trans. by G. Field), Tolman derived a general
formula for the total matter plus gravitational field energy ($P_0$) of an
arbitrary system (Tolman, R.C., Phys. Rev., 35(8), 875 (1930); Tolman, R.C.,
{\it Relativity, Thermodynamics & Cosmology}, Clarendon Press, Oxford, 1962));
Xulu, S.S., arXiv:hep-th/0308070 (2003)). For a static isolated system, in
quasi-Cartesian coordinates, this formula leads to the well known result $P_0 =
\int \sqrt{-g} (T_0^0 - T_1^1 -T_2^2 -T_3^3) ~d^3 x$, where $g$ is the
determinant of the metric tensor and $T^a_b$ is the energy momentum tensor of
the {\em matter}. Though in the literature, this is known as "Tolman Mass", it
must be realized that this is essentially "Einstein Mass" because the
underlying pseudo-tensor here is due to Einstein. In fact, Landau -Lifshitz
obtained the same expression for the "inertial mass" of a static isolated
system without using any pseudo-tensor at all and which points to physical
significance and correctness of Einstein Mass (Landau, L.D., and Lifshitz,
E.M., {\it The Classical Theory of Fields}, Pergamon Press, Oxford, 2th ed.,
1962)! For the first time we apply this general formula to find an expression
for $P_0$ for the Friedmann- Robertson -Walker (FRW) metric by using the same
quasi-Cartesian basis. As we analyze this new result, physically, a spatially
flat model having no cosmological constant is suggested. Eventually, it is seen
that conservation of $P_0$ is honoured only in the a static limit.
| [
{
"created": "Thu, 12 Nov 2009 09:49:12 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Nov 2009 11:30:19 GMT",
"version": "v2"
}
] | 2010-02-23 | [
[
"Mitra",
"Abhas",
""
]
] | Following Einstein's definition of Lagrangian density and gravitational field energy density (Einstein, A., Ann. Phys. Lpz., 49, 806 (1916); Einstein, A., Phys. Z., 19, 115 (1918); Pauli, W., {\it Theory of Relativity}, B.I. Publications, Mumbai, 1963, Trans. by G. Field), Tolman derived a general formula for the total matter plus gravitational field energy ($P_0$) of an arbitrary system (Tolman, R.C., Phys. Rev., 35(8), 875 (1930); Tolman, R.C., {\it Relativity, Thermodynamics & Cosmology}, Clarendon Press, Oxford, 1962)); Xulu, S.S., arXiv:hep-th/0308070 (2003)). For a static isolated system, in quasi-Cartesian coordinates, this formula leads to the well known result $P_0 = \int \sqrt{-g} (T_0^0 - T_1^1 -T_2^2 -T_3^3) ~d^3 x$, where $g$ is the determinant of the metric tensor and $T^a_b$ is the energy momentum tensor of the {\em matter}. Though in the literature, this is known as "Tolman Mass", it must be realized that this is essentially "Einstein Mass" because the underlying pseudo-tensor here is due to Einstein. In fact, Landau -Lifshitz obtained the same expression for the "inertial mass" of a static isolated system without using any pseudo-tensor at all and which points to physical significance and correctness of Einstein Mass (Landau, L.D., and Lifshitz, E.M., {\it The Classical Theory of Fields}, Pergamon Press, Oxford, 2th ed., 1962)! For the first time we apply this general formula to find an expression for $P_0$ for the Friedmann- Robertson -Walker (FRW) metric by using the same quasi-Cartesian basis. As we analyze this new result, physically, a spatially flat model having no cosmological constant is suggested. Eventually, it is seen that conservation of $P_0$ is honoured only in the a static limit. |
gr-qc/9805039 | Shinji Mukohyama | Shinji Mukohyama | Comments on entanglement entropy | Latex, 24 pages, proofs of some equations are added in appendices;
Accepted for publication in Physical Review D | Phys. Rev. D 58, 104023 (1998) | 10.1103/PhysRevD.58.104023 | YITP-98-30 | gr-qc | null | A new interpretation of entanglement entropy is proposed: entanglement
entropy of a pure state with respect to a division of a Hilbert space into two
subspaces 1 and 2 is an amount of information, which can be transmitted through
1 and 2 from a system interacting with 1 to another system interacting with 2.
The transmission medium is quantum entanglement between 1 and 2. In order to
support the interpretation, suggestive arguments are given: variational
principles in entanglement thermodynamics and quantum teleportation. It is
shown that a quantum state having maximal entanglement entropy plays an
important role in quantum teleportation. Hence, the entanglement entropy is, in
some sense, an index of efficiency of quantum teleportation. Finally,
implications for the information loss problem and Hawking radiation are
discussed.
| [
{
"created": "Tue, 12 May 1998 05:47:08 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 1998 10:45:51 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Sep 1998 07:51:59 GMT",
"version": "v3"
}
] | 2016-08-25 | [
[
"Mukohyama",
"Shinji",
""
]
] | A new interpretation of entanglement entropy is proposed: entanglement entropy of a pure state with respect to a division of a Hilbert space into two subspaces 1 and 2 is an amount of information, which can be transmitted through 1 and 2 from a system interacting with 1 to another system interacting with 2. The transmission medium is quantum entanglement between 1 and 2. In order to support the interpretation, suggestive arguments are given: variational principles in entanglement thermodynamics and quantum teleportation. It is shown that a quantum state having maximal entanglement entropy plays an important role in quantum teleportation. Hence, the entanglement entropy is, in some sense, an index of efficiency of quantum teleportation. Finally, implications for the information loss problem and Hawking radiation are discussed. |
2110.13132 | Amjad Ashoorioon | Amjad Ashoorioon and Mohammad Bagher Jahani Poshteh and Robert B. Mann | Lensing Signatures of a Slowly-Accelerated Black Hole | v3: 14 pages, 12 figures, extended version of the upcoming PRL paper | Phys.Rev.D 107 (2023) 044031 | 10.1103/PhysRevD.107.044031 | IPM/P-2021/38 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accelerating black holes, connected to cosmic strings could evolve to
supermassive black holes. However, if they are going to take part in structure
formation and resides at the center of galaxies, their acceleration should be
small. This slow acceleration does not change the shadow or image position in
gravitational lensing effect significantly. However we show that the time delay
associated to these images change significantly. This is in contrast with when
the theory governing the strong gravitational field around the black hole is
different from general relativity, where not only the differential time delays
but the angular position of images would be different. We conclude that, if the
observed angular position of images are compatible with the prediction of
general relativity, a possible deviation in the differential time delays
between the observed values and those predicted by general relativity, could be
due to the acceleration of the black hole.
| [
{
"created": "Mon, 25 Oct 2021 17:57:13 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2022 20:35:16 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Oct 2022 15:53:07 GMT",
"version": "v3"
}
] | 2023-02-17 | [
[
"Ashoorioon",
"Amjad",
""
],
[
"Poshteh",
"Mohammad Bagher Jahani",
""
],
[
"Mann",
"Robert B.",
""
]
] | Accelerating black holes, connected to cosmic strings could evolve to supermassive black holes. However, if they are going to take part in structure formation and resides at the center of galaxies, their acceleration should be small. This slow acceleration does not change the shadow or image position in gravitational lensing effect significantly. However we show that the time delay associated to these images change significantly. This is in contrast with when the theory governing the strong gravitational field around the black hole is different from general relativity, where not only the differential time delays but the angular position of images would be different. We conclude that, if the observed angular position of images are compatible with the prediction of general relativity, a possible deviation in the differential time delays between the observed values and those predicted by general relativity, could be due to the acceleration of the black hole. |
0904.2240 | Xiangdong Zhang | Xiangdong Zhang, Xiaoning Wu and Sijie Gao | On Newman-Penrose constants of stationary electrovacuum spacetimes | 11pages, no figures accepted by PRD | Phys.Rev.D79:104001,2009 | 10.1103/PhysRevD.79.104001 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | A theorem related to the Newman-Penrose constants is proven. The theorem
states that all the Newman-Penrose constants of asymptotically flat,
stationary, asymptotically algebraically special electrovacuum spacetimes are
zero. Straightforward application of this theorem shows that all the
Newman-Penrose constants of the Kerr-Newman spacetime must vanish.
| [
{
"created": "Wed, 15 Apr 2009 05:52:34 GMT",
"version": "v1"
}
] | 2009-10-29 | [
[
"Zhang",
"Xiangdong",
""
],
[
"Wu",
"Xiaoning",
""
],
[
"Gao",
"Sijie",
""
]
] | A theorem related to the Newman-Penrose constants is proven. The theorem states that all the Newman-Penrose constants of asymptotically flat, stationary, asymptotically algebraically special electrovacuum spacetimes are zero. Straightforward application of this theorem shows that all the Newman-Penrose constants of the Kerr-Newman spacetime must vanish. |
gr-qc/0102081 | null | Wu Shuang-Qing and Cai Xu | Hawking Radiation of Dirac Particles in a Variable-mass Kerr Black Hole | 6 pages, revtex (12pt), no figure. Chin. Phys. Lett. 18 (2001) 485
(in press) | Chin.Phys.Lett. 18 (2001) 485 | 10.1088/0256-307X/18/4/306 | null | gr-qc | null | Hawking effect of Dirac particles in a variable-mass Kerr space-time is
investigated by using method of the generalized tortoise coordinate
transformation. The location and the temperature of event horizon of the
non-stationary Kerr black hole are derived. It is shown that the temperature
and the shape of event horizon depend not only on the time but also on the
polar angle. However, our results demonstrate that the Fermi-Dirac spectrum
displays a new spin-rotation effect which is absent from that of Bose-Einstein
distribution.
| [
{
"created": "Mon, 19 Feb 2001 07:34:57 GMT",
"version": "v1"
}
] | 2017-02-08 | [
[
"Shuang-Qing",
"Wu",
""
],
[
"Xu",
"Cai",
""
]
] | Hawking effect of Dirac particles in a variable-mass Kerr space-time is investigated by using method of the generalized tortoise coordinate transformation. The location and the temperature of event horizon of the non-stationary Kerr black hole are derived. It is shown that the temperature and the shape of event horizon depend not only on the time but also on the polar angle. However, our results demonstrate that the Fermi-Dirac spectrum displays a new spin-rotation effect which is absent from that of Bose-Einstein distribution. |
1106.6355 | Tyson Littenberg | Tyson B. Littenberg | A detection pipeline for galactic binaries in LISA data | 12 pages, 8 figures | null | 10.1103/PhysRevD.84.063009 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Galaxy is suspected to contain hundreds of millions of binary white dwarf
systems, a large fraction of which will have sufficiently small orbital period
to emit gravitational radiation in band for space-based gravitational wave
detectors such as the Laser Interferometer Space Antenna (LISA). LISA's main
science goal is the detection of cosmological events (supermassive black hole
mergers, etc.) however the gravitational signal from the galaxy will be the
dominant contribution to the data -- including instrumental noise -- over
approximately two decades in frequency. The catalogue of detectable binary
systems will serve as an unparalleled means of studying the Galaxy.
Furthermore, to maximize the scientific return from the mission, the data must
be "cleansed" of the galactic foreground. We will present an algorithm that can
accurately resolve and subtract >10000 of these sources from simulated data
supplied by the Mock LISA Data Challenge Task Force. Using the time evolution
of the gravitational wave frequency, we will reconstruct the position of the
recovered binaries and show how LISA will sample the entire compact binary
population in the Galaxy.
| [
{
"created": "Thu, 30 Jun 2011 19:55:49 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Littenberg",
"Tyson B.",
""
]
] | The Galaxy is suspected to contain hundreds of millions of binary white dwarf systems, a large fraction of which will have sufficiently small orbital period to emit gravitational radiation in band for space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). LISA's main science goal is the detection of cosmological events (supermassive black hole mergers, etc.) however the gravitational signal from the galaxy will be the dominant contribution to the data -- including instrumental noise -- over approximately two decades in frequency. The catalogue of detectable binary systems will serve as an unparalleled means of studying the Galaxy. Furthermore, to maximize the scientific return from the mission, the data must be "cleansed" of the galactic foreground. We will present an algorithm that can accurately resolve and subtract >10000 of these sources from simulated data supplied by the Mock LISA Data Challenge Task Force. Using the time evolution of the gravitational wave frequency, we will reconstruct the position of the recovered binaries and show how LISA will sample the entire compact binary population in the Galaxy. |
gr-qc/0009080 | Eduardo Sergio Santini | N. Pinto-Neto and E. Sergio Santini (CBPF-Rio de Janeiro) | The Consistency of Causal Quantum Geometrodynamics and Quantum Field
Theory | Final version. See also http://www.cosmologia.cbpf.br | Gen.Rel.Grav. 34 (2002) 505-532 | 10.1023/A:1015592724845 | null | gr-qc hep-th quant-ph | null | We consider quantum geometrodynamics and parametrized quantum field theories
in the framework of the Bohm-de Broglie interpretation. In the first case, and
following the lines of our previous work [1], where a hamiltonian formalism for
the bohmian trajectories was constructed, we show the consistency of the theory
for any quantum potential, completing the scenarios for canonical quantum
cosmology presented there. In the latter case, we prove the consistency of
scalar field theory in Minkowski spacetime for any quantum potential, and we
show, using this alternative hamiltonian method, a concrete example where
Lorentz invariance of individual events is broken.
| [
{
"created": "Fri, 22 Sep 2000 17:36:27 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Oct 2001 14:04:11 GMT",
"version": "v2"
},
{
"created": "Mon, 27 May 2002 15:52:22 GMT",
"version": "v3"
}
] | 2013-06-21 | [
[
"Pinto-Neto",
"N.",
"",
"CBPF-Rio de Janeiro"
],
[
"Santini",
"E. Sergio",
"",
"CBPF-Rio de Janeiro"
]
] | We consider quantum geometrodynamics and parametrized quantum field theories in the framework of the Bohm-de Broglie interpretation. In the first case, and following the lines of our previous work [1], where a hamiltonian formalism for the bohmian trajectories was constructed, we show the consistency of the theory for any quantum potential, completing the scenarios for canonical quantum cosmology presented there. In the latter case, we prove the consistency of scalar field theory in Minkowski spacetime for any quantum potential, and we show, using this alternative hamiltonian method, a concrete example where Lorentz invariance of individual events is broken. |
1906.11552 | Cem Yeti\c{s}mi\c{s}o\u{g}lu | Tekin Dereli, Cem Yeti\c{s}mi\c{s}o\u{g}lu | Weyl Covariant Quadratic Curvature Gravity in 3-Dimensional
Riemann-Cartan-Weyl Space-Times | arXiv admin note: text overlap with arXiv:1904.08124 | Phys. Rev. D 100, 044010 (2019) | 10.1103/PhysRevD.100.044010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss locally Weyl (scale) covariant generalisation of quadratic
curvature gravity theory in three dimensions using Riemann-Cartan-Weyl
space-times. We show that this procedure of Weyl gauging yields a consistent
generalisation for a particular class of quadratic curvature gravity theories
which includes the New Massive Gravity theory.
| [
{
"created": "Thu, 27 Jun 2019 11:25:32 GMT",
"version": "v1"
}
] | 2019-08-14 | [
[
"Dereli",
"Tekin",
""
],
[
"Yetişmişoğlu",
"Cem",
""
]
] | We discuss locally Weyl (scale) covariant generalisation of quadratic curvature gravity theory in three dimensions using Riemann-Cartan-Weyl space-times. We show that this procedure of Weyl gauging yields a consistent generalisation for a particular class of quadratic curvature gravity theories which includes the New Massive Gravity theory. |
gr-qc/9704079 | Jan Ambjorn | J. Ambjorn, J. Nielsen, J. Rolf and G. Savvidy | Spikes in Quantum Regge Calculus | 20 pages, Latex2e, 11 figures | Class.Quant.Grav. 14 (1997) 3225-3241 | 10.1088/0264-9381/14/12/009 | NBI-HE-97-20 and DEMO-HEP-97-10 | gr-qc hep-lat hep-th | null | We demonstrate by explicit calculation of the DeWitt-like measure in
two-dimensional quantum Regge gravity that it is highly non-local and that the
average values of link lengths $l, <l^n>$, do not exist for sufficient high
powers of $n$. Thus the concept of length has no natural definition in this
formalism and a generic manifold degenerates into spikes. This might explain
the failure of quantum Regge calculus to reproduce the continuum results of
two-dimensional quantum gravity. It points to severe problems for the Regge
approach in higher dimensions.
| [
{
"created": "Mon, 28 Apr 1997 14:53:09 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Ambjorn",
"J.",
""
],
[
"Nielsen",
"J.",
""
],
[
"Rolf",
"J.",
""
],
[
"Savvidy",
"G.",
""
]
] | We demonstrate by explicit calculation of the DeWitt-like measure in two-dimensional quantum Regge gravity that it is highly non-local and that the average values of link lengths $l, <l^n>$, do not exist for sufficient high powers of $n$. Thus the concept of length has no natural definition in this formalism and a generic manifold degenerates into spikes. This might explain the failure of quantum Regge calculus to reproduce the continuum results of two-dimensional quantum gravity. It points to severe problems for the Regge approach in higher dimensions. |
gr-qc/0604077 | Jeferson Oliveira de | Jeferson de Oliveira | Spin Zero Perturbation in the Kerr-Randall-Sundrum Space-Time | Master Degree Thesis (Advisor: Elcio Abdalla), 110 pages, 7 figures,
in portuguese | null | null | null | gr-qc | null | This dissertation aims at studying the braneworld models in the context
proposed by Randall and Sundrum. The focus is on the spin-0 perturbations in
the Kerr space-time as a 4-dimensional braneworld.
The work deals the main aspects of Einstein General Relativity as well as
perturbations of black holes metrics. We also review the Randall-Sundrum models
and their motivations and attempts to describe braneworld black holes. In the
end the Kerr-Randall-Sundrum black string scalar perturbation and superradiance
are obtained.
| [
{
"created": "Tue, 18 Apr 2006 17:49:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Oliveira",
"Jeferson",
""
]
] | This dissertation aims at studying the braneworld models in the context proposed by Randall and Sundrum. The focus is on the spin-0 perturbations in the Kerr space-time as a 4-dimensional braneworld. The work deals the main aspects of Einstein General Relativity as well as perturbations of black holes metrics. We also review the Randall-Sundrum models and their motivations and attempts to describe braneworld black holes. In the end the Kerr-Randall-Sundrum black string scalar perturbation and superradiance are obtained. |
1903.04379 | Ujjal Debnath | Ujjal Debnath | Thermodynamic Black Hole with Modified Chaplygin Gas as a Heat Engine | 6 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We assume that the negative cosmological constant as a thermodynamical
pressure and the asymptotically anti-de Sitter (AdS) black hole thermodynamics
with modified Chaplygin gas. We have written the mass of the black hole,
volume, entropy and temperature due to the thermodynamic system. We find a new
solution of Einstein's field equations of AdS black hole with modified
Chaplygin gas as a thermodynamic system. We also examine the weak, strong and
dominant energy conditions for the source fluid of black hole. We also show
that the thermodynamic black hole with Chaplygin gas can be considered as a
heat engine and then we calculate work done and its efficiency by this system.
| [
{
"created": "Mon, 11 Mar 2019 15:43:54 GMT",
"version": "v1"
}
] | 2019-03-12 | [
[
"Debnath",
"Ujjal",
""
]
] | We assume that the negative cosmological constant as a thermodynamical pressure and the asymptotically anti-de Sitter (AdS) black hole thermodynamics with modified Chaplygin gas. We have written the mass of the black hole, volume, entropy and temperature due to the thermodynamic system. We find a new solution of Einstein's field equations of AdS black hole with modified Chaplygin gas as a thermodynamic system. We also examine the weak, strong and dominant energy conditions for the source fluid of black hole. We also show that the thermodynamic black hole with Chaplygin gas can be considered as a heat engine and then we calculate work done and its efficiency by this system. |
gr-qc/0201096 | Jorge Stephany | D.E.Diaz and J.Stephany | Radiative Processes of the DeWitt-Takagi Detector | 6 pages, 2 figures | Rev.Mex.Fis. 29S3 (2003) 120-122 | null | SB/F/02-297 | gr-qc hep-th | null | We examine the excitation of a uniformly accelerated DeWitt-Takagi detector
coupled quadratically to a Majorana-Dirac field. We obtain the transition
probability from the ground state of the detector and the vacuum state of the
field to an excited state with the emission of a Minkowski pair of quanta, in
terms of elementary processes of absorption and scattering of Rindler quanta
from the Fulling-Davies-Unruh thermal bath in the co-accelerated frame.
| [
{
"created": "Wed, 30 Jan 2002 21:34:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Diaz",
"D. E.",
""
],
[
"Stephany",
"J.",
""
]
] | We examine the excitation of a uniformly accelerated DeWitt-Takagi detector coupled quadratically to a Majorana-Dirac field. We obtain the transition probability from the ground state of the detector and the vacuum state of the field to an excited state with the emission of a Minkowski pair of quanta, in terms of elementary processes of absorption and scattering of Rindler quanta from the Fulling-Davies-Unruh thermal bath in the co-accelerated frame. |
gr-qc/9407018 | Herbert Balasin | P.C.Aichelburg and H.Balasin | A Note on the Symmetries of the Gravitational Field of a Massless
Particle | 10pages, amslatex, TUW-94-12 and UWThPh-1994-27 | Class.Quant.Grav.11:L121-L123,1994 | 10.1088/0264-9381/11/10/001 | null | gr-qc | null | It is shown that the metric of a massless particle obtained from boosting the
Schwarzschild metric to the velocity of light, has four Killing vectors
corresponding to an $E(2)\times \RR$ symmetry-group. This is in agreement with
the expectations based on flat-space kinematics but is in contrast to previous
statements in the literature \cite{Schueck}. Moreover, it also goes beyond the
general Jordan-Ehlers-Kundt-(JEK)-classification of gravitational pp-waves as
given in \cite{JEK}.
| [
{
"created": "Fri, 15 Jul 1994 09:27:37 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Aichelburg",
"P. C.",
""
],
[
"Balasin",
"H.",
""
]
] | It is shown that the metric of a massless particle obtained from boosting the Schwarzschild metric to the velocity of light, has four Killing vectors corresponding to an $E(2)\times \RR$ symmetry-group. This is in agreement with the expectations based on flat-space kinematics but is in contrast to previous statements in the literature \cite{Schueck}. Moreover, it also goes beyond the general Jordan-Ehlers-Kundt-(JEK)-classification of gravitational pp-waves as given in \cite{JEK}. |
1303.6250 | Daniela Pugliese Dr | Daniela Pugliese, Hernando Quevedo, and Remo Ruffini | Equatorial circular orbits of neutral test particles in the Kerr--Newman
spacetime | 28 pages, 26 figures, 6 tables. This work follows the papers:
DOI:10.1103/PhysRevD.84.044030; DOI:10.1103/PhysRevD.83.104052;
DOI:10.1103/PhysRevD.83.024021 This is a revised version to meet the
published article | Phys. Rev. D 88, 024042 (2013) | 10.1103/PhysRevD.88.024042 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a detailed analysis of the orbital circular motion of electrically
neutral test particles on the equatorial plane of the Kerr-Newman spacetime.
Many details of the motion in the cases of black hole and naked singularity
sources are pointed out. We identify four different types of orbital regions,
which depend on the properties of the orbital angular momentum, and define four
different kinds of naked singularities, according to the values of the
charge-to-mass ratio of the source. It is shown that the presence of a
particular type of counter-rotating test particles is sufficient to uniquely
identify naked singularities. It is pointed out that the structure of the
stability regions can be used to differentiate between black holes and naked
singularities.
| [
{
"created": "Mon, 25 Mar 2013 18:57:47 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Jul 2013 14:33:46 GMT",
"version": "v2"
}
] | 2013-07-31 | [
[
"Pugliese",
"Daniela",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Ruffini",
"Remo",
""
]
] | We present a detailed analysis of the orbital circular motion of electrically neutral test particles on the equatorial plane of the Kerr-Newman spacetime. Many details of the motion in the cases of black hole and naked singularity sources are pointed out. We identify four different types of orbital regions, which depend on the properties of the orbital angular momentum, and define four different kinds of naked singularities, according to the values of the charge-to-mass ratio of the source. It is shown that the presence of a particular type of counter-rotating test particles is sufficient to uniquely identify naked singularities. It is pointed out that the structure of the stability regions can be used to differentiate between black holes and naked singularities. |
1508.00441 | Daniele Vernieri | Salvatore Capozziello, S. J. Gabriele Gionti, Daniele Vernieri | String duality transformations in $f(R)$ gravity from Noether symmetry
approach | v1: 13 pages; v2: minor rephrasings, published version | JCAP 1601, 015 (2016) | 10.1088/1475-7516/2016/01/015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We select $f(R)$ gravity models that undergo scale factor duality
transformations. As a starting point, we consider the tree-level effective
gravitational action of bosonic String Theory coupled with the dilaton field.
This theory inherits the Busher's duality of its parent String Theory. Using
conformal transformations of the metric tensor, it is possible to map the
tree-level dilaton-graviton string effective action into $f(R)$ gravity,
relating the dilaton field to the Ricci scalar curvature. Furthermore, the
duality can be framed under the standard of Noether symmetries and exact
cosmological solutions are derived. Using suitable changes of variables, the
string-based $f(R)$ Lagrangians are shown in cases where the duality
transformation becomes a parity inversion.
| [
{
"created": "Mon, 3 Aug 2015 15:01:06 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Feb 2016 16:36:51 GMT",
"version": "v2"
}
] | 2016-02-10 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Gionti",
"S. J. Gabriele",
""
],
[
"Vernieri",
"Daniele",
""
]
] | We select $f(R)$ gravity models that undergo scale factor duality transformations. As a starting point, we consider the tree-level effective gravitational action of bosonic String Theory coupled with the dilaton field. This theory inherits the Busher's duality of its parent String Theory. Using conformal transformations of the metric tensor, it is possible to map the tree-level dilaton-graviton string effective action into $f(R)$ gravity, relating the dilaton field to the Ricci scalar curvature. Furthermore, the duality can be framed under the standard of Noether symmetries and exact cosmological solutions are derived. Using suitable changes of variables, the string-based $f(R)$ Lagrangians are shown in cases where the duality transformation becomes a parity inversion. |
1104.2851 | Mario Lubini | M. Lubini, C. Tortora, J. N\"af, Ph. Jetzer and S. Capozziello | Probing the dark matter issue in f(R)-gravity via gravitational lensing | 7 pages, accepted for publication in EPJC | Eur. Phys. J. C (2011) 71, 1834 | 10.1140/epjc/s10052-011-1834-8 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a general class of analytic f(R)-gravity theories, we discuss the weak
field limit in view of gravitational lensing. Though an additional Yukawa term
in the gravitational potential modifies dynamics with respect to the standard
Newtonian limit of General Relativity, the motion of massless particles results
unaffected thanks to suitable cancellations in the post-Newtonian limit. Thus,
all the lensing observables are equal to the ones known from General
Relativity. Since f(R)-gravity is claimed, among other things, to be a possible
solution to overcome for the need of dark matter in virialized systems, we
discuss the impact of our results on the dynamical and gravitational lensing
analyses. In this framework, dynamics could, in principle, be able to reproduce
the astrophysical observations without recurring to dark matter, but in the
case of gravitational lensing we find that dark matter is an unavoidable
ingredient. Another important implication is that gravitational lensing, in the
post-Newtonian limit, is not able to constrain these extended theories, since
their predictions do not differ from General Relativity.
| [
{
"created": "Thu, 14 Apr 2011 18:05:07 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2011 13:10:05 GMT",
"version": "v2"
}
] | 2012-02-09 | [
[
"Lubini",
"M.",
""
],
[
"Tortora",
"C.",
""
],
[
"Näf",
"J.",
""
],
[
"Jetzer",
"Ph.",
""
],
[
"Capozziello",
"S.",
""
]
] | For a general class of analytic f(R)-gravity theories, we discuss the weak field limit in view of gravitational lensing. Though an additional Yukawa term in the gravitational potential modifies dynamics with respect to the standard Newtonian limit of General Relativity, the motion of massless particles results unaffected thanks to suitable cancellations in the post-Newtonian limit. Thus, all the lensing observables are equal to the ones known from General Relativity. Since f(R)-gravity is claimed, among other things, to be a possible solution to overcome for the need of dark matter in virialized systems, we discuss the impact of our results on the dynamical and gravitational lensing analyses. In this framework, dynamics could, in principle, be able to reproduce the astrophysical observations without recurring to dark matter, but in the case of gravitational lensing we find that dark matter is an unavoidable ingredient. Another important implication is that gravitational lensing, in the post-Newtonian limit, is not able to constrain these extended theories, since their predictions do not differ from General Relativity. |
gr-qc/0209090 | Chris Doran | Anthony Lasenby, Chris Doran, Jonathan Pritchard, Alejandro Caceres
and Sam Dolan | Bound states and decay times of fermions in a Schwarzschild black hole
background | 27 pages, 14 figures, fully revised version | Phys.Rev.D72:105014,2005 | 10.1103/PhysRevD.72.105014 | null | gr-qc astro-ph hep-th | null | We compute the spectrum of normalizable fermion bound states in a
Schwarzschild black hole background. The eigenstates have complex energies. The
real part of the energies, for small couplings, closely follow a hydrogen-like
spectrum. The imaginary parts give decay times for the various states, due to
the absorption properties of the hole, with states closer to the hole having
shorter half-lives. As the coupling increases, the spectrum departs from that
of the hydrogen atom, as states close to the horizon become unfavourable.
Beyond a certain coupling the 1S1/2 state is no longer the ground state, which
shifts to the 2P3/2 state, and then to states of successively greater angular
momentum. For each positive energy state a negative energy counterpart exists,
with opposite sign of its real energy, and the same decay factor. It follows
that the Dirac sea of negative energy states is decaying, which may provide a
physical contribution to Hawking radiation.
| [
{
"created": "Tue, 24 Sep 2002 15:13:45 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2005 14:30:15 GMT",
"version": "v2"
}
] | 2011-06-24 | [
[
"Lasenby",
"Anthony",
""
],
[
"Doran",
"Chris",
""
],
[
"Pritchard",
"Jonathan",
""
],
[
"Caceres",
"Alejandro",
""
],
[
"Dolan",
"Sam",
""
]
] | We compute the spectrum of normalizable fermion bound states in a Schwarzschild black hole background. The eigenstates have complex energies. The real part of the energies, for small couplings, closely follow a hydrogen-like spectrum. The imaginary parts give decay times for the various states, due to the absorption properties of the hole, with states closer to the hole having shorter half-lives. As the coupling increases, the spectrum departs from that of the hydrogen atom, as states close to the horizon become unfavourable. Beyond a certain coupling the 1S1/2 state is no longer the ground state, which shifts to the 2P3/2 state, and then to states of successively greater angular momentum. For each positive energy state a negative energy counterpart exists, with opposite sign of its real energy, and the same decay factor. It follows that the Dirac sea of negative energy states is decaying, which may provide a physical contribution to Hawking radiation. |
1208.4481 | Narayan Banerjee | Barun Majumder and Narayan Banerjee | Perfect Fluid Quantum Anisotropic Universe: Merits and Challenges | 13 pages, 4 figures; Accepted for publication in Gen Relativ Gravit | null | 10.1007/s10714-012-1446-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper deals with quantization of perfect fluid anisotropic
cosmological models. Bianchi type V and IX models are discussed following
Schutz's method of expressing fluid velocities in terms of six potentials. The
wave functions are found for several examples of equations of state. In one
case a complete wave packet could be formed analytically. The initial
singularity of a zero proper volume can be avoided in this case, but it is
plagued by the usual problem of non-unitarity of anisotropic quantum
cosmological models. It is seen that a particular operator ordering alleviates
this problem.
| [
{
"created": "Wed, 22 Aug 2012 11:47:28 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Majumder",
"Barun",
""
],
[
"Banerjee",
"Narayan",
""
]
] | The present paper deals with quantization of perfect fluid anisotropic cosmological models. Bianchi type V and IX models are discussed following Schutz's method of expressing fluid velocities in terms of six potentials. The wave functions are found for several examples of equations of state. In one case a complete wave packet could be formed analytically. The initial singularity of a zero proper volume can be avoided in this case, but it is plagued by the usual problem of non-unitarity of anisotropic quantum cosmological models. It is seen that a particular operator ordering alleviates this problem. |
2001.08759 | Merced Montesinos | Merced Montesinos, Rodrigo Romero, Diego Gonzalez | The gauge symmetries of f(R) gravity with torsion in the Cartan
formalism | It contains a detailed derivation of the generalization of
3-dimensional "local translations" for 4-dimensional first-order general
relativity | Class. Quantum Grav. 37, 045008 (2020) | 10.1088/1361-6382/ab6272 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First-order general relativity in $n$ dimensions ($n \geq 3$) has an internal
gauge symmetry that is the higher-dimensional generalization of
three-dimensional local translations. We report the extension of this symmetry
for $n$-dimensional f(R) gravity with torsion in the Cartan formalism. The new
symmetry arises from the direct application of the converse of Noether's second
theorem to the action principle of f(R) gravity with torsion. We show that
infinitesimal diffeomorphisms can be written as a linear combination of the new
internal gauge symmetry, local Lorentz transformations, and terms proportional
to the variational derivatives of the f(R) action. It means that the new
internal symmetry together with local Lorentz transformations can be used to
describe the full gauge symmetry of f(R) gravity with torsion, and thus
diffeomorphisms become a derived symmetry in this setting.
| [
{
"created": "Thu, 23 Jan 2020 19:00:10 GMT",
"version": "v1"
}
] | 2020-01-27 | [
[
"Montesinos",
"Merced",
""
],
[
"Romero",
"Rodrigo",
""
],
[
"Gonzalez",
"Diego",
""
]
] | First-order general relativity in $n$ dimensions ($n \geq 3$) has an internal gauge symmetry that is the higher-dimensional generalization of three-dimensional local translations. We report the extension of this symmetry for $n$-dimensional f(R) gravity with torsion in the Cartan formalism. The new symmetry arises from the direct application of the converse of Noether's second theorem to the action principle of f(R) gravity with torsion. We show that infinitesimal diffeomorphisms can be written as a linear combination of the new internal gauge symmetry, local Lorentz transformations, and terms proportional to the variational derivatives of the f(R) action. It means that the new internal symmetry together with local Lorentz transformations can be used to describe the full gauge symmetry of f(R) gravity with torsion, and thus diffeomorphisms become a derived symmetry in this setting. |
1912.12981 | Philippe G. LeFloch | Bruno Le Floch and Philippe G. LeFloch | Compensated compactness and corrector stress tensor for the Einstein
equations in T2 symmetry | 6 pages | Port. Math. 77 (2020), 409-421 | 10.4171/PM/2057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Einstein equations in T2 symmetry, either for vacuum
spacetimes or coupled to the Euler equations for a compressible fluid, and we
introduce the notion of T2 areal flows on T3 with finite total energy. By
uncovering a hidden structure of the Einstein equations, we establish a
compensated compactness framework and solve the global evolution problem for
vacuum spacetimes as well as for self-gravitating compressible fluids. We study
the stability and instability of such flows and prove that, when the initial
data are well-prepared, any family of T2 areal flows is sequentially compact in
a natural topology. In order to handle general initial data we propose a
relaxed notion of T2 areal flows endowed with a corrector stress tensor (as we
call it) which is a bounded measure generated by geometric oscillations and
concentrations propagating at the speed of light. This generalizes a result for
vacuum spacetimes in: Le Floch B. and LeFloch P.G., Arch. Rational Mech. Anal.
233 (2019), 45-86. In addition, we determine the global geometry of the
corresponding future Cauchy developments and we prove that the area of the T2
orbits generically approaches infinity in the future-expanding regime. In the
future-contracting regime, the volume of the T3 spacelike slices approaches
zero and, for generic initial data, the area of the orbits of symmetry
approaches zero in Gowdy symmetric matter spacetimes and in T2 vacuum
spacetimes.
| [
{
"created": "Mon, 30 Dec 2019 16:15:41 GMT",
"version": "v1"
}
] | 2021-01-05 | [
[
"Floch",
"Bruno Le",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We consider the Einstein equations in T2 symmetry, either for vacuum spacetimes or coupled to the Euler equations for a compressible fluid, and we introduce the notion of T2 areal flows on T3 with finite total energy. By uncovering a hidden structure of the Einstein equations, we establish a compensated compactness framework and solve the global evolution problem for vacuum spacetimes as well as for self-gravitating compressible fluids. We study the stability and instability of such flows and prove that, when the initial data are well-prepared, any family of T2 areal flows is sequentially compact in a natural topology. In order to handle general initial data we propose a relaxed notion of T2 areal flows endowed with a corrector stress tensor (as we call it) which is a bounded measure generated by geometric oscillations and concentrations propagating at the speed of light. This generalizes a result for vacuum spacetimes in: Le Floch B. and LeFloch P.G., Arch. Rational Mech. Anal. 233 (2019), 45-86. In addition, we determine the global geometry of the corresponding future Cauchy developments and we prove that the area of the T2 orbits generically approaches infinity in the future-expanding regime. In the future-contracting regime, the volume of the T3 spacelike slices approaches zero and, for generic initial data, the area of the orbits of symmetry approaches zero in Gowdy symmetric matter spacetimes and in T2 vacuum spacetimes. |
2301.04187 | V Gayathri | V. Gayathri, Daniel Wysocki, Y. Yang, R. O Shaughnessy, Z. Haiman, H.
Tagawa, and I. Bartos | Gravitational wave source populations: Disentangling an AGN component | 7 pages, 4 figures, and 1 table | null | 10.3847/2041-8213/acbfb8 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The astrophysical origin of the over 90 compact binary mergers discovered by
the LIGO and Virgo gravitational wave observatories is an open question. While
the unusual mass and spin of some of the discovered objects constrain
progenitor scenarios, the observed mergers are consistent with multiple
interpretations. A promising approach to solve this question is to consider the
observed distributions of binary properties and compare them to expectations
from different origin scenarios. Here we describe a new hierarchical population
analysis framework to assess the relative contribution of different formation
channels simultaneously. For this study we considered binary formation in AGN
disks along with phenomenological models, but the same framework can be
extended to other models. We find that high-mass and high-mass-ratio binaries
appear more likely to have an AGN origin compared to the same origin as
lower-mass events. Future observations of high-mass black hole mergers could
further disentangle the AGN component from other channels.
| [
{
"created": "Tue, 10 Jan 2023 19:50:32 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Gayathri",
"V.",
""
],
[
"Wysocki",
"Daniel",
""
],
[
"Yang",
"Y.",
""
],
[
"Shaughnessy",
"R. O",
""
],
[
"Haiman",
"Z.",
""
],
[
"Tagawa",
"H.",
""
],
[
"Bartos",
"I.",
""
]
] | The astrophysical origin of the over 90 compact binary mergers discovered by the LIGO and Virgo gravitational wave observatories is an open question. While the unusual mass and spin of some of the discovered objects constrain progenitor scenarios, the observed mergers are consistent with multiple interpretations. A promising approach to solve this question is to consider the observed distributions of binary properties and compare them to expectations from different origin scenarios. Here we describe a new hierarchical population analysis framework to assess the relative contribution of different formation channels simultaneously. For this study we considered binary formation in AGN disks along with phenomenological models, but the same framework can be extended to other models. We find that high-mass and high-mass-ratio binaries appear more likely to have an AGN origin compared to the same origin as lower-mass events. Future observations of high-mass black hole mergers could further disentangle the AGN component from other channels. |
1906.00011 | Antonios Tsokaros A. | Antonios Tsokaros, Milton Ruiz, Vasileios Paschalidis, Stuart L.
Shapiro, K\=oji Ury\=u | Effect of spin on the inspiral of binary neutron stars | 11 pages, 6 figures | Phys. Rev. D 100, 024061 (2019) | 10.1103/PhysRevD.100.024061 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform long-term simulations of spinning binary neutron stars, with our
highest dimensionless spin being $\chi \sim 0.32$. To assess the importance of
spin during the inspiral we vary the spin, and also use two equations of state,
one that consists of plain nuclear matter and produces compact stars (SLy), and
a hybrid one that contains both nuclear and quark matter and leads to larger
stars (ALF2). Using high resolution that has grid spacing $\Delta x\sim 98$ m
on the finest refinement level, we find that the effects of spin in the phase
evolution of a binary system can be larger than the one that comes from tidal
forces. Our calculations demonstrate explicitly that although tidal effects are
dominant for small spins ($\lesssim 0.1$), this is no longer true when the
spins are larger, but still much smaller than the Keplerian limit.
| [
{
"created": "Fri, 31 May 2019 18:00:02 GMT",
"version": "v1"
}
] | 2019-08-07 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Ruiz",
"Milton",
""
],
[
"Paschalidis",
"Vasileios",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Uryū",
"Kōji",
""
]
] | We perform long-term simulations of spinning binary neutron stars, with our highest dimensionless spin being $\chi \sim 0.32$. To assess the importance of spin during the inspiral we vary the spin, and also use two equations of state, one that consists of plain nuclear matter and produces compact stars (SLy), and a hybrid one that contains both nuclear and quark matter and leads to larger stars (ALF2). Using high resolution that has grid spacing $\Delta x\sim 98$ m on the finest refinement level, we find that the effects of spin in the phase evolution of a binary system can be larger than the one that comes from tidal forces. Our calculations demonstrate explicitly that although tidal effects are dominant for small spins ($\lesssim 0.1$), this is no longer true when the spins are larger, but still much smaller than the Keplerian limit. |
1006.2978 | Nils Andersson | C.S. Lopez-Monsalvo and N. Andersson | Thermal Dynamics in General Relativity | null | Proc.Roy.Soc.Lond.A467:738-759,2010 | 10.1098/rspa.2010.0308 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a relativistic model for heat conduction, building on a convective
variational approach to multi-fluid systems where the entropy is treated as a
distinct dynamical entity. We demonstrate how this approach leads to a
relativistic version of the Cattaneo equation, encoding the finite thermal
relaxation time that is required to satisfy causality. We also show that the
model naturally includes the non-equilibrium Gibbs relation that is a key
ingredient in most approaches to extended thermodynamics. Focussing on the pure
heat conduction problem, we compare the variational results to the second-order
model developed by Israel and Stewart. The comparison shows that, despite the
very different philosophies behind the two approaches, the two models are
equivalent at first order deviations from thermal equilibrium. Finally, we
complete the picture by working out the non-relativistic limit of our results,
making contact with recent work in that regime.
| [
{
"created": "Tue, 15 Jun 2010 13:12:37 GMT",
"version": "v1"
}
] | 2011-02-11 | [
[
"Lopez-Monsalvo",
"C. S.",
""
],
[
"Andersson",
"N.",
""
]
] | We discuss a relativistic model for heat conduction, building on a convective variational approach to multi-fluid systems where the entropy is treated as a distinct dynamical entity. We demonstrate how this approach leads to a relativistic version of the Cattaneo equation, encoding the finite thermal relaxation time that is required to satisfy causality. We also show that the model naturally includes the non-equilibrium Gibbs relation that is a key ingredient in most approaches to extended thermodynamics. Focussing on the pure heat conduction problem, we compare the variational results to the second-order model developed by Israel and Stewart. The comparison shows that, despite the very different philosophies behind the two approaches, the two models are equivalent at first order deviations from thermal equilibrium. Finally, we complete the picture by working out the non-relativistic limit of our results, making contact with recent work in that regime. |
2303.13917 | Tiago Fernandes | Tiago S. Fernandes and Samuel J. Vieira and Antonio Onofre and Juan
Calder\'on Bustillo and Alejandro Torres-Forn\'e and Jos\'e A. Font | Convolutional Neural Networks for the classification of glitches in
gravitational-wave data streams | 15 pages, 14 figures | null | 10.1088/1361-6382/acf26c | null | gr-qc astro-ph.IM cs.CV cs.LG | http://creativecommons.org/licenses/by/4.0/ | We investigate the use of Convolutional Neural Networks (including the modern
ConvNeXt network family) to classify transient noise signals (i.e.~glitches)
and gravitational waves in data from the Advanced LIGO detectors. First, we use
models with a supervised learning approach, both trained from scratch using the
Gravity Spy dataset and employing transfer learning by fine-tuning pre-trained
models in this dataset. Second, we also explore a self-supervised approach,
pre-training models with automatically generated pseudo-labels. Our findings
are very close to existing results for the same dataset, reaching values for
the F1 score of 97.18% (94.15%) for the best supervised (self-supervised)
model. We further test the models using actual gravitational-wave signals from
LIGO-Virgo's O3 run. Although trained using data from previous runs (O1 and
O2), the models show good performance, in particular when using transfer
learning. We find that transfer learning improves the scores without the need
for any training on real signals apart from the less than 50 chirp examples
from hardware injections present in the Gravity Spy dataset. This motivates the
use of transfer learning not only for glitch classification but also for signal
classification.
| [
{
"created": "Fri, 24 Mar 2023 11:12:37 GMT",
"version": "v1"
}
] | 2023-08-28 | [
[
"Fernandes",
"Tiago S.",
""
],
[
"Vieira",
"Samuel J.",
""
],
[
"Onofre",
"Antonio",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Torres-Forné",
"Alejandro",
""
],
[
"Font",
"José A.",
""
]
] | We investigate the use of Convolutional Neural Networks (including the modern ConvNeXt network family) to classify transient noise signals (i.e.~glitches) and gravitational waves in data from the Advanced LIGO detectors. First, we use models with a supervised learning approach, both trained from scratch using the Gravity Spy dataset and employing transfer learning by fine-tuning pre-trained models in this dataset. Second, we also explore a self-supervised approach, pre-training models with automatically generated pseudo-labels. Our findings are very close to existing results for the same dataset, reaching values for the F1 score of 97.18% (94.15%) for the best supervised (self-supervised) model. We further test the models using actual gravitational-wave signals from LIGO-Virgo's O3 run. Although trained using data from previous runs (O1 and O2), the models show good performance, in particular when using transfer learning. We find that transfer learning improves the scores without the need for any training on real signals apart from the less than 50 chirp examples from hardware injections present in the Gravity Spy dataset. This motivates the use of transfer learning not only for glitch classification but also for signal classification. |
gr-qc/0607053 | J. Fernando Barbero G. | J. Fernando Barbero G., I\~naki Garay, Eduardo J. S. Villase\~nor | Probing Quantized Einstein-Rosen Waves with Massless Scalar Matter | Accepted for publication in Physical Review D | Phys.Rev.D74:044004,2006 | 10.1103/PhysRevD.74.044004 | null | gr-qc | null | The purpose of this paper is to discuss in detail the use of scalar matter
coupled to linearly polarized Einstein-Rosen waves as a probe to study quantum
gravity in the restricted setting provided by this symmetry reduction of
general relativity. We will obtain the relevant Hamiltonian and quantize it
with the techniques already used for the purely gravitational case. Finally we
will discuss the use of particle-like modes of the quantized fields to
operationally explore some of the features of quantum gravity within this
framework. Specifically we will study two-point functions, the Newton-Wigner
propagator, and radial wave functions for one-particle states.
| [
{
"created": "Thu, 13 Jul 2006 08:58:23 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Garay",
"Iñaki",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | The purpose of this paper is to discuss in detail the use of scalar matter coupled to linearly polarized Einstein-Rosen waves as a probe to study quantum gravity in the restricted setting provided by this symmetry reduction of general relativity. We will obtain the relevant Hamiltonian and quantize it with the techniques already used for the purely gravitational case. Finally we will discuss the use of particle-like modes of the quantized fields to operationally explore some of the features of quantum gravity within this framework. Specifically we will study two-point functions, the Newton-Wigner propagator, and radial wave functions for one-particle states. |
1602.07478 | Xiangdong Zhang | You Ding and Xiangdong Zhang | 2+1 dimensional loop quantum cosmology of Bianchi I models | 11 pages | International Journal of Modern Physics A, Vol. 35, No. 29,
2050185 (2020) | 10.1142/S0217751X20501857 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the anisotropic Bianchi I loop quantum cosmology in 2+1 dimensions.
Both the $\mubar$ and $\mubar'$ schemes are considered in the present paper and
the following expected results are established: (i) the massless scalar field
again play the role of emergent time variables and serves as an internal clock;
(ii) By imposing the fundamental discreteness of length operator, the total
Hamiltonian constraint is obtained and gives rise the evolution as a difference
equation; and (iii) the exact solutions of Friedmann equation are constructed
rigorously for both classical and effective level. The investigation extends
the domain of validity of loop quantum cosmology to beyond the four dimensions.
| [
{
"created": "Wed, 24 Feb 2016 12:30:30 GMT",
"version": "v1"
}
] | 2020-10-23 | [
[
"Ding",
"You",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | We study the anisotropic Bianchi I loop quantum cosmology in 2+1 dimensions. Both the $\mubar$ and $\mubar'$ schemes are considered in the present paper and the following expected results are established: (i) the massless scalar field again play the role of emergent time variables and serves as an internal clock; (ii) By imposing the fundamental discreteness of length operator, the total Hamiltonian constraint is obtained and gives rise the evolution as a difference equation; and (iii) the exact solutions of Friedmann equation are constructed rigorously for both classical and effective level. The investigation extends the domain of validity of loop quantum cosmology to beyond the four dimensions. |
2011.00661 | Bogar D\'iaz | J. Fernando Barbero G., Bogar D\'iaz, Juan Margalef-Bentabol and
Eduardo J.S. Villase\~nor | Concise symplectic formulation for tetrad gravity | 5 pages | Physical Review D, 103 (2021) 024051 | 10.1103/PhysRevD.103.024051 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a simple symplectic formulation for tetrad gravity that leads to
the real Ashtekar variables in a direct and transparent way. It also sheds
light on the role of the Immirzi parameter and the time gauge.
| [
{
"created": "Mon, 2 Nov 2020 00:54:37 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2021 20:18:18 GMT",
"version": "v2"
}
] | 2021-03-18 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Díaz",
"Bogar",
""
],
[
"Margalef-Bentabol",
"Juan",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We discuss a simple symplectic formulation for tetrad gravity that leads to the real Ashtekar variables in a direct and transparent way. It also sheds light on the role of the Immirzi parameter and the time gauge. |
1805.00592 | Francisco Tello Ortiz | E. Morales and Francisco Tello-Ortiz | Charged anisotropic compact objects by gravitational decoupling | null | null | 10.1140/epjc/s10052-018-6102-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present article, we have constructed a static charged anisotropic
compact star model of Einstein field equations for a spherically symmetric
space-time geometry. Specifically, we have extended the charged isotropic
Heintzmann solution to an anisotropic domain. To address this work, we have
employed the gravitational decoupling through the so called minimal geometric
deformation approach. The charged anisotropic model is representing the
realistic compact objects such as $RXJ1856-37$ and $SAX J1808.4-3658(SS2)$. We
have reported our results in details for the compact star $RXJ1856-37$ on the
ground of physical properties such as pressure, density, velocity of sound,
energy conditions, stability conditions, Tolman-Oppenheimer-Volkoff equation
and redshift etc.
| [
{
"created": "Wed, 2 May 2018 01:22:59 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jul 2018 19:54:21 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Morales",
"E.",
""
],
[
"Tello-Ortiz",
"Francisco",
""
]
] | In the present article, we have constructed a static charged anisotropic compact star model of Einstein field equations for a spherically symmetric space-time geometry. Specifically, we have extended the charged isotropic Heintzmann solution to an anisotropic domain. To address this work, we have employed the gravitational decoupling through the so called minimal geometric deformation approach. The charged anisotropic model is representing the realistic compact objects such as $RXJ1856-37$ and $SAX J1808.4-3658(SS2)$. We have reported our results in details for the compact star $RXJ1856-37$ on the ground of physical properties such as pressure, density, velocity of sound, energy conditions, stability conditions, Tolman-Oppenheimer-Volkoff equation and redshift etc. |
2405.18420 | Marko Stojanovic | Goran S. Djordjevic, Neven Bili\'c, Dragoljub D. Dimitrijevic, Milan
Milosevic, Marko Stojanovic | On attractor behavior in braneworld constant-roll inflation | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We investigate in detail the attractor behavior of some inflationary models
based on braneworld dynamics under the constant-roll condition. We describe the
dynamics of the models, assuming that the second slow-roll parameter remains
constant during inflation. We show that the dynamics of the considered models
have the property of a cosmological attractor.
| [
{
"created": "Tue, 28 May 2024 17:58:08 GMT",
"version": "v1"
}
] | 2024-05-29 | [
[
"Djordjevic",
"Goran S.",
""
],
[
"Bilić",
"Neven",
""
],
[
"Dimitrijevic",
"Dragoljub D.",
""
],
[
"Milosevic",
"Milan",
""
],
[
"Stojanovic",
"Marko",
""
]
] | We investigate in detail the attractor behavior of some inflationary models based on braneworld dynamics under the constant-roll condition. We describe the dynamics of the models, assuming that the second slow-roll parameter remains constant during inflation. We show that the dynamics of the considered models have the property of a cosmological attractor. |
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