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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1304.2836 | Emanuele Berti | Emanuele Berti, Vitor Cardoso, Leonardo Gualtieri, Michael Horbatsch,
Ulrich Sperhake | Numerical simulations of single and binary black holes in scalar-tensor
theories: circumventing the no-hair theorem | 21 pages, 6 figures, matches version accepted in Physical Review D | null | 10.1103/PhysRevD.87.124020 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor theories are a compelling alternative to general relativity and
one of the most accepted extensions of Einstein's theory. Black holes in these
theories have no hair, but could grow "wigs" supported by time-dependent
boundary conditions or spatial gradients. Time-dependent or spatially varying
fields lead in general to nontrivial black hole dynamics, with potentially
interesting experimental consequences. We carry out a numerical investigation
of the dynamics of single and binary black holes in the presence of scalar
fields. In particular we study gravitational and scalar radiation from
black-hole binaries in a constant scalar-field gradient, and we compare our
numerical findings to analytical models. In the single black hole case we find
that, after a short transient, the scalar field relaxes to static
configurations, in agreement with perturbative calculations. Furthermore we
predict analytically (and verify numerically) that accelerated black holes in a
scalar-field gradient emit scalar radiation. For a quasicircular black-hole
binary, our analytical and numerical calculations show that the dominant
component of the scalar radiation is emitted at twice the binary's orbital
frequency.
| [
{
"created": "Wed, 10 Apr 2013 03:22:25 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jun 2013 09:36:26 GMT",
"version": "v2"
}
] | 2013-06-26 | [
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Horbatsch",
"Michael",
""
],
[
"Sperhake",
"Ulrich",
""
]
] | Scalar-tensor theories are a compelling alternative to general relativity and one of the most accepted extensions of Einstein's theory. Black holes in these theories have no hair, but could grow "wigs" supported by time-dependent boundary conditions or spatial gradients. Time-dependent or spatially varying fields lead in general to nontrivial black hole dynamics, with potentially interesting experimental consequences. We carry out a numerical investigation of the dynamics of single and binary black holes in the presence of scalar fields. In particular we study gravitational and scalar radiation from black-hole binaries in a constant scalar-field gradient, and we compare our numerical findings to analytical models. In the single black hole case we find that, after a short transient, the scalar field relaxes to static configurations, in agreement with perturbative calculations. Furthermore we predict analytically (and verify numerically) that accelerated black holes in a scalar-field gradient emit scalar radiation. For a quasicircular black-hole binary, our analytical and numerical calculations show that the dominant component of the scalar radiation is emitted at twice the binary's orbital frequency. |
2002.12073 | Lucila Kraiselburd | Carolina Negrelli, Lucila Kraiselburd, Susana J. Landau and Marcelo
Salgado | Solar System tests and chameleon effect in f (R) gravity | accepted in Phys. Rev. D | Phys. Rev. D 101, 064005 (2020) | 10.1103/PhysRevD.101.064005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a novel and self-consistent approach that avoids the scalar-tensor
identification in the Einstein frame, we reanalyze the viability of f(R)
gravity within the context of solar-system tests. In order to do so, we depart
from a simple but fully relativistic system of differential equations that
describe a compact object in a static and spherically symmetric spacetime, and
then we make suitable linearizations that apply to nonrelativistic objects such
as the Sun. We then show clearly under which conditions the emerging
chameleonlike mechanism can lead to a post-Newtonian parameter {\gamma}
compatible with the observational bounds. To illustrate this method, we use
several specific f(R) models proposed to explain the current acceleration of
the Universe, and we show which of them are able to satisfy those bounds.
| [
{
"created": "Thu, 27 Feb 2020 13:04:26 GMT",
"version": "v1"
}
] | 2020-03-06 | [
[
"Negrelli",
"Carolina",
""
],
[
"Kraiselburd",
"Lucila",
""
],
[
"Landau",
"Susana J.",
""
],
[
"Salgado",
"Marcelo",
""
]
] | Using a novel and self-consistent approach that avoids the scalar-tensor identification in the Einstein frame, we reanalyze the viability of f(R) gravity within the context of solar-system tests. In order to do so, we depart from a simple but fully relativistic system of differential equations that describe a compact object in a static and spherically symmetric spacetime, and then we make suitable linearizations that apply to nonrelativistic objects such as the Sun. We then show clearly under which conditions the emerging chameleonlike mechanism can lead to a post-Newtonian parameter {\gamma} compatible with the observational bounds. To illustrate this method, we use several specific f(R) models proposed to explain the current acceleration of the Universe, and we show which of them are able to satisfy those bounds. |
gr-qc/0512153 | Jingyi Zhang | Jingyi Zhang, Zheng Zhao | Charged particles' tunnelling from the Kerr-Newman black hole | 6 pages | Phys.Lett. B638 (2006) 110-113 | 10.1016/j.physletb.2006.05.059 | null | gr-qc | null | In this letter, Parikh-Wilczek tunnelling framework, which treats Hawking
radiation as a tunnelling process, is extended, and the emission rate of a
charged particle tunnelling from the Kerr-Newman black hole is calculated. The
emission spectrum takes the same functional form as that of uncharged particles
and consists with an underlying unitary theory but deviates from the pure
thermal spectrum. Moreover, our calculation indicates that the emission process
is treated as a reversible process in the Parikh-Wilczek tunnelling framework,
and the information conservation is a natural result of the first law of black
hole thermodynamics.
| [
{
"created": "Tue, 27 Dec 2005 13:37:50 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Zhang",
"Jingyi",
""
],
[
"Zhao",
"Zheng",
""
]
] | In this letter, Parikh-Wilczek tunnelling framework, which treats Hawking radiation as a tunnelling process, is extended, and the emission rate of a charged particle tunnelling from the Kerr-Newman black hole is calculated. The emission spectrum takes the same functional form as that of uncharged particles and consists with an underlying unitary theory but deviates from the pure thermal spectrum. Moreover, our calculation indicates that the emission process is treated as a reversible process in the Parikh-Wilczek tunnelling framework, and the information conservation is a natural result of the first law of black hole thermodynamics. |
gr-qc/0202084 | V. L. Kalashnikov | V. L. Kalashnikov | Constraints on the Cosmological Parameters in the Relativistic Theory of
Gravitation | 6 pages, 2 figures, LaTeX2e, commented Maple 6 worksheet is
accessible on http://www.geocities.com/optomaplev | null | null | null | gr-qc | null | The causality principle imposes the constraints on the cosmological
parameters in the relativistic theory of gravitation. As a result, X-matter
causes the quite definite cosmological scenario with the alternate acceleration
and deceleration and the final recollapse
| [
{
"created": "Fri, 22 Feb 2002 17:22:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kalashnikov",
"V. L.",
""
]
] | The causality principle imposes the constraints on the cosmological parameters in the relativistic theory of gravitation. As a result, X-matter causes the quite definite cosmological scenario with the alternate acceleration and deceleration and the final recollapse |
2312.04260 | Paolo Massimo Bassani | Paolo Massimo Bassani | Varying Constants and the Brans-Dicke theory: a new landscape in
cosmological energy conservation | null | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We develop the Brans-Dicke theory of gravity in the context of varying
constants of Nature. Using the unimodular formalism of General Relativity, we
create a platform to provide physical relational times giving the evolution of
physical constants. We therefore review the ideas and experiments behind
varying constants, mostly focusing on the speed of light and the gravitational
constant. Then, we apply this idea to the energy conservation in cosmology,
illustrating the arising patterns. Motivated by a varying gravitational
constant resulting from Mach's principle, we develop the unimodular formalism
of varying constants in the Brans-Dicke theory. Doing so, we obtain several
original results, some of which can be compared with phenomenological
observation. Finally, we suggest how a varying Brans-Dicke parameter could be
linked to the Cosmological Constant problem.
| [
{
"created": "Thu, 7 Dec 2023 12:37:49 GMT",
"version": "v1"
}
] | 2023-12-08 | [
[
"Bassani",
"Paolo Massimo",
""
]
] | We develop the Brans-Dicke theory of gravity in the context of varying constants of Nature. Using the unimodular formalism of General Relativity, we create a platform to provide physical relational times giving the evolution of physical constants. We therefore review the ideas and experiments behind varying constants, mostly focusing on the speed of light and the gravitational constant. Then, we apply this idea to the energy conservation in cosmology, illustrating the arising patterns. Motivated by a varying gravitational constant resulting from Mach's principle, we develop the unimodular formalism of varying constants in the Brans-Dicke theory. Doing so, we obtain several original results, some of which can be compared with phenomenological observation. Finally, we suggest how a varying Brans-Dicke parameter could be linked to the Cosmological Constant problem. |
1511.04252 | Alessandro D.A.M. Spallicci di Filottrano | P. Ritter, S. Aoudia, A. Spallicci, S. Cordier | Indirect (source-free) integration method. I. Wave-forms from geodesic
generic orbits of EMRIs | To appear in Int. J. Geom. Meth. Mod Phys | 2016, Int. J. Geom. Meth. Mod. Phys., 13, 1650021 | 10.1142/S0219887816500213 | null | gr-qc astro-ph.HE math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Regge-Wheeler-Zerilli (RWZ) wave-equation describes Schwarzschild-Droste
black hole perturbations. The source term contains a Dirac distribution and its
derivative. We have previously designed a method of integration in time domain.
It consists of a finite difference scheme where analytic expressions, dealing
with the wave-function discontinuity through the jump conditions, replace the
direct integration of the source and the potential. Herein, we successfully
apply the same method to the geodesic generic orbits of EMRI (Extreme Mass
Ratio Inspiral) sources, at second order. An EMRI is a Compact Star (CS)
captured by a Super Massive Black Hole (SMBH). These are considered the best
probes for testing gravitation in strong regime. The gravitational wave-forms,
the radiated energy and angular momentum at infinity are computed and
extensively compared with other methods, for different orbits (circular,
elliptic, parabolic, including zoom-whirl).
| [
{
"created": "Fri, 13 Nov 2015 11:55:57 GMT",
"version": "v1"
}
] | 2016-03-22 | [
[
"Ritter",
"P.",
""
],
[
"Aoudia",
"S.",
""
],
[
"Spallicci",
"A.",
""
],
[
"Cordier",
"S.",
""
]
] | The Regge-Wheeler-Zerilli (RWZ) wave-equation describes Schwarzschild-Droste black hole perturbations. The source term contains a Dirac distribution and its derivative. We have previously designed a method of integration in time domain. It consists of a finite difference scheme where analytic expressions, dealing with the wave-function discontinuity through the jump conditions, replace the direct integration of the source and the potential. Herein, we successfully apply the same method to the geodesic generic orbits of EMRI (Extreme Mass Ratio Inspiral) sources, at second order. An EMRI is a Compact Star (CS) captured by a Super Massive Black Hole (SMBH). These are considered the best probes for testing gravitation in strong regime. The gravitational wave-forms, the radiated energy and angular momentum at infinity are computed and extensively compared with other methods, for different orbits (circular, elliptic, parabolic, including zoom-whirl). |
1911.11438 | Li Zhao | Chen Yang, Zi-Qi Chen, and Li Zhao | Kalb-Ramond field localization on a de Sitter Thick Brane | 16 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the localization of Kalb-Ramond (KR) tensorial gauge
field on a non-flat de Sitter thick brane. The localization and resonance of KR
gauge field are discussed for three kinds of couplings. For the first coupling
there is no localized tensorial zero mode. For the other two couplings, the
zero mode of KR field can be localized under certain condition. There are
resonant KK modes on the thick brane for the third case. Furthermore, we mainly
analyze the effects of three parameters on the localization and resonant mode
for KR field.
| [
{
"created": "Tue, 26 Nov 2019 10:20:07 GMT",
"version": "v1"
}
] | 2019-11-27 | [
[
"Yang",
"Chen",
""
],
[
"Chen",
"Zi-Qi",
""
],
[
"Zhao",
"Li",
""
]
] | In this paper, we study the localization of Kalb-Ramond (KR) tensorial gauge field on a non-flat de Sitter thick brane. The localization and resonance of KR gauge field are discussed for three kinds of couplings. For the first coupling there is no localized tensorial zero mode. For the other two couplings, the zero mode of KR field can be localized under certain condition. There are resonant KK modes on the thick brane for the third case. Furthermore, we mainly analyze the effects of three parameters on the localization and resonant mode for KR field. |
2212.10853 | Gael SERVIGNAT | Ga\"el Servignat (LUTH (UMR\_8102)), Jerome Novak (LUTH (UMR\_8102)),
Isabel Cordero-Carri\'on | A new formulation of general-relativistic hydrodynamic equations using
primitive variables | null | 2023 Class. Quantum Grav. 40 105002 | 10.1088/1361-6382/acc828 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the derivation of hydrodynamical equations for a perfect fluid in
General Relativity, within the 3+1 decomposition of spacetime framework, using
only primitive variables. Primitive variables are opposed to conserved
variables, as defined in the widely used Valencia formulation of the same
hydrodynamical equations. The equations are derived in a covariant way, so that
they can be used to describe any configuration of the perfect fluid. Once
derived, the equations are tested numerically. We implement them in an
evolution code for spherically symmetric self-gravitating compact objects. The
code uses pseudospectral methods for both the metric and the hydrodynamics.
First, convergence tests are performed, then the frequencies of radial modes of
polytropes are recovered with and without the Cowling approximation, and
finally the performance of our code in the black hole collapse and migration
tests are described. The results of the tests and the comparison with a
reference corecollapse and neutron star oscillations code suggests that not
only our code can handle very strong gravitational fields, but also that this
new formulation helps gaining a significant amount of computational time in
hydrodynamical simulations of smooth flows in General Relativity.
| [
{
"created": "Wed, 21 Dec 2022 08:57:07 GMT",
"version": "v1"
}
] | 2023-04-17 | [
[
"Servignat",
"Gaël",
"",
"LUTH"
],
[
"Novak",
"Jerome",
"",
"LUTH"
],
[
"Cordero-Carrión",
"Isabel",
""
]
] | We present the derivation of hydrodynamical equations for a perfect fluid in General Relativity, within the 3+1 decomposition of spacetime framework, using only primitive variables. Primitive variables are opposed to conserved variables, as defined in the widely used Valencia formulation of the same hydrodynamical equations. The equations are derived in a covariant way, so that they can be used to describe any configuration of the perfect fluid. Once derived, the equations are tested numerically. We implement them in an evolution code for spherically symmetric self-gravitating compact objects. The code uses pseudospectral methods for both the metric and the hydrodynamics. First, convergence tests are performed, then the frequencies of radial modes of polytropes are recovered with and without the Cowling approximation, and finally the performance of our code in the black hole collapse and migration tests are described. The results of the tests and the comparison with a reference corecollapse and neutron star oscillations code suggests that not only our code can handle very strong gravitational fields, but also that this new formulation helps gaining a significant amount of computational time in hydrodynamical simulations of smooth flows in General Relativity. |
gr-qc/9806116 | Andrzej Borowiec | A. Borowiec and M. Francaviglia | Alternative Lagrangians for Einstein Metrics | 9 pages in LaTeX (sprocl.sty). Extended version; misprints removed,
comments and references added. To appear in Proc. Int. Sem. Math. Cosmol.,
Potsdam, 1998, M. Rainer and H.-J. Schmidt (eds.), WSPC Singapore | null | null | null | gr-qc | null | We shall use the variational decomposition technique in order to calculate
equations of motion and Noether energy-momentum complex for some classes of
non-linear gravitational Lagrangians within the first-order (Palatini)
formalism. In particular, a complex space-time appears as a solution of our
variational problem.
| [
{
"created": "Tue, 30 Jun 1998 11:17:41 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 1998 11:44:48 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Borowiec",
"A.",
""
],
[
"Francaviglia",
"M.",
""
]
] | We shall use the variational decomposition technique in order to calculate equations of motion and Noether energy-momentum complex for some classes of non-linear gravitational Lagrangians within the first-order (Palatini) formalism. In particular, a complex space-time appears as a solution of our variational problem. |
2002.09613 | Philip Chang | Philip Chang, Zachariah Etienne | General Relativistic Hydrodynamics on a Moving-mesh I: Static Spacetimes | 10 pages, 4 figures, accepted version, update description of Riemann
solver | null | 10.1093/mnras/staa1532 | null | gr-qc astro-ph.IM physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first-ever moving-mesh general relativistic hydrodynamics
solver for static spacetimes as implemented in the code, MANGA. Our
implementation builds on the architectures of MANGA and the numerical
relativity Python package NRPy+. We review the general algorithm to solve these
equations and, in particular, detail the time stepping; Riemann solution across
moving faces; conversion between primitive and conservative variables;
validation and correction of hydrodynamic variables; and mapping of the metric
to a Voronoi moving-mesh grid.
We present test results for the numerical integration of an unmagnetized
Tolman-Oppenheimer-Volkoff star for 24 dynamical times. We demonstrate that at
a resolution of $10^6$ mesh generating points, the star is stable and its
central density drifts downward by 2% over this timescale. At a lower
resolution the central density drift increases in a manner consistent with the
adopted second order spatial reconstruction scheme. These results agree well
with the exact solutions, and we find the error behavior to be similar to
Eulerian codes with second-order spatial reconstruction. We also demonstrate
that the new code recovers the fundamental mode frequency for the same TOV star
but with its initial pressure depleted by 10%
| [
{
"created": "Sat, 22 Feb 2020 03:46:12 GMT",
"version": "v1"
},
{
"created": "Thu, 28 May 2020 17:21:12 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Chang",
"Philip",
""
],
[
"Etienne",
"Zachariah",
""
]
] | We present the first-ever moving-mesh general relativistic hydrodynamics solver for static spacetimes as implemented in the code, MANGA. Our implementation builds on the architectures of MANGA and the numerical relativity Python package NRPy+. We review the general algorithm to solve these equations and, in particular, detail the time stepping; Riemann solution across moving faces; conversion between primitive and conservative variables; validation and correction of hydrodynamic variables; and mapping of the metric to a Voronoi moving-mesh grid. We present test results for the numerical integration of an unmagnetized Tolman-Oppenheimer-Volkoff star for 24 dynamical times. We demonstrate that at a resolution of $10^6$ mesh generating points, the star is stable and its central density drifts downward by 2% over this timescale. At a lower resolution the central density drift increases in a manner consistent with the adopted second order spatial reconstruction scheme. These results agree well with the exact solutions, and we find the error behavior to be similar to Eulerian codes with second-order spatial reconstruction. We also demonstrate that the new code recovers the fundamental mode frequency for the same TOV star but with its initial pressure depleted by 10% |
0712.0085 | Laszlo B. Szabados | Laszlo B Szabados | On some global problems in the tetrad approach to quasi-local quantities | 13 pages, a more detailed discussion of the problems is given,
Theorems 3.1 and 3.2 are modified slightly, the proof of Theorem 4.3 is
improved, 5 references are added, misprints are corrected. Appearing in
Class. Quantum Grav | Class.Quant.Grav.25:195004,2008 | 10.1088/0264-9381/25/19/195004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The potential global topological obstructions to the tetrad approach to
finding the quasi-local conserved quantities, associated with closed,
orientable spacelike 2-surfaces S, are investigated. First we show that the
Lorentz frame bundle is always globally trivializable over an open
neighbourhood U of any such S if an open neighbourhood of S is space and time
orientable, and hence a globally trivializable SL(2,C) spin frame bundle can
also be introduced over U. Then it is shown that all the spin frames belonging
to the same spinor structure on S have always the same homotopy class. On the
other hand, on a 2-surface with genus g, there are $2^{2g}$ homotopically
different Lorentz frame fields, and there is a natural one-to-one
correspondence between these homotopy classes and the different SL(2,C) spinor
structures.
| [
{
"created": "Sat, 1 Dec 2007 14:48:39 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Aug 2008 16:08:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Szabados",
"Laszlo B",
""
]
] | The potential global topological obstructions to the tetrad approach to finding the quasi-local conserved quantities, associated with closed, orientable spacelike 2-surfaces S, are investigated. First we show that the Lorentz frame bundle is always globally trivializable over an open neighbourhood U of any such S if an open neighbourhood of S is space and time orientable, and hence a globally trivializable SL(2,C) spin frame bundle can also be introduced over U. Then it is shown that all the spin frames belonging to the same spinor structure on S have always the same homotopy class. On the other hand, on a 2-surface with genus g, there are $2^{2g}$ homotopically different Lorentz frame fields, and there is a natural one-to-one correspondence between these homotopy classes and the different SL(2,C) spinor structures. |
gr-qc/0702062 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay | Gravity induced neutrino-antineutrino oscillation: CPT and lepton number
non-conservation under gravity | 15 pages; Accepted for publication in Classical and Quantum Gravity | Class.Quant.Grav.24:1433-1442,2007 | 10.1088/0264-9381/24/6/004 | null | gr-qc astro-ph hep-ph | null | We introduce a new effect in the neutrino oscillation phase which shows the
neutrino-antineutrino oscillation is possible under gravity even if the rest
masses of the corresponding eigenstates are same. This is due to CPT violation
and possible to demonstrate if the neutrino mass eigenstates are expressed as a
combination of neutrino and antineutrino eigenstates, as of the neutral kaon
system, with the plausible breaking of lepton number conservation. For Majorana
neutrinos, this oscillation is expected to affect significantly the inner edge
of neutrino dominated accretion disks around a compact object by influencing
the neutrino sphere which controls the accretion dynamics, and then the related
type-II supernova evolution and the r-process nucleosynthesis. On the other
hand, in early universe, in presence of various lepton number violating
processes, this oscillation, we argue, might lead to neutrino asymmetry which
resulted baryogenesis from the B-L symmetry by electro-weak sphaleron
processes.
| [
{
"created": "Sat, 10 Feb 2007 07:20:01 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mukhopadhyay",
"Banibrata",
""
]
] | We introduce a new effect in the neutrino oscillation phase which shows the neutrino-antineutrino oscillation is possible under gravity even if the rest masses of the corresponding eigenstates are same. This is due to CPT violation and possible to demonstrate if the neutrino mass eigenstates are expressed as a combination of neutrino and antineutrino eigenstates, as of the neutral kaon system, with the plausible breaking of lepton number conservation. For Majorana neutrinos, this oscillation is expected to affect significantly the inner edge of neutrino dominated accretion disks around a compact object by influencing the neutrino sphere which controls the accretion dynamics, and then the related type-II supernova evolution and the r-process nucleosynthesis. On the other hand, in early universe, in presence of various lepton number violating processes, this oscillation, we argue, might lead to neutrino asymmetry which resulted baryogenesis from the B-L symmetry by electro-weak sphaleron processes. |
2112.02444 | Larry Ford | L. H. Ford | Cosmological Particle Production: A Review | 28 pages, 3 figures, contains some material adapted from
arXiv:gr-qc/9707062 | Rep. Prog. Phys. 84, 116901 (2021) | 10.1088/1361-6633/ac1b23 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article will review quantum particle creation in expanding universes.
The emphasis will be on the basic physical principles and on selected
applications to cosmological models. The needed formalism of quantum field
theory in curved spacetime will be summarized, and applied to the example of
scalar particle creation in a spatially flat universe. Estimates for the
creation rate will be given and applied to inflationary cosmology models.
Analog models which illustrate the same physical principles and may be
experimentally realizable are also discussed.
| [
{
"created": "Sat, 4 Dec 2021 23:09:33 GMT",
"version": "v1"
}
] | 2021-12-07 | [
[
"Ford",
"L. H.",
""
]
] | This article will review quantum particle creation in expanding universes. The emphasis will be on the basic physical principles and on selected applications to cosmological models. The needed formalism of quantum field theory in curved spacetime will be summarized, and applied to the example of scalar particle creation in a spatially flat universe. Estimates for the creation rate will be given and applied to inflationary cosmology models. Analog models which illustrate the same physical principles and may be experimentally realizable are also discussed. |
1312.6451 | P. A. Gonzalez | Marcela Catalan, Eduardo Cisternas, P. A. Gonzalez and Yerko Vasquez | Dirac quasinormal modes for a 4-dimensional Lifshitz Black Hole | Version accepted for publication in EPJC. arXiv admin note: text
overlap with arXiv:1306.5974 | null | 10.1140/epjc/s10052-014-2813-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quasinormal modes of fermionic perturbations for an
asymptotically Lifshitz black hole in 4-dimensions with dynamical exponent z=2
and plane topology for the transverse section, and we find analytically and
numerically the quasinormal modes for massless fermionic fields by using the
improved asymptotic iteration method and the Horowitz-Hubeny method. The
quasinormal frequencies are purely imaginary and negative, which guarantees the
stability of these black holes under massless fermionic field perturbations.
Remarkably, both numerical methods yield consistent results; i.e., both methods
converge to the exact quasinormal frequencies; however, the improved asymptotic
iteration method converges in a fewer number of iterations. Also, we find
analytically the quasinormal modes for massive fermionic fields for the mode
with lowest angular momentum. In this case, the quasinormal frequencies are
purely imaginary and negative, which guarantees the stability of these black
holes under fermionic field perturbations. Moreover, we show that the lowest
quasinormal frequencies have real and imaginary parts for the mode with higher
angular momentum by using the improved asymptotic iteration method.
| [
{
"created": "Mon, 23 Dec 2013 01:26:58 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Mar 2014 14:59:26 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Catalan",
"Marcela",
""
],
[
"Cisternas",
"Eduardo",
""
],
[
"Gonzalez",
"P. A.",
""
],
[
"Vasquez",
"Yerko",
""
]
] | We study the quasinormal modes of fermionic perturbations for an asymptotically Lifshitz black hole in 4-dimensions with dynamical exponent z=2 and plane topology for the transverse section, and we find analytically and numerically the quasinormal modes for massless fermionic fields by using the improved asymptotic iteration method and the Horowitz-Hubeny method. The quasinormal frequencies are purely imaginary and negative, which guarantees the stability of these black holes under massless fermionic field perturbations. Remarkably, both numerical methods yield consistent results; i.e., both methods converge to the exact quasinormal frequencies; however, the improved asymptotic iteration method converges in a fewer number of iterations. Also, we find analytically the quasinormal modes for massive fermionic fields for the mode with lowest angular momentum. In this case, the quasinormal frequencies are purely imaginary and negative, which guarantees the stability of these black holes under fermionic field perturbations. Moreover, we show that the lowest quasinormal frequencies have real and imaginary parts for the mode with higher angular momentum by using the improved asymptotic iteration method. |
gr-qc/0609020 | Philippe Grandclement | Philippe Grandclement (LUTH) | Introduction to spectral methods | 20 pages, 15 figures | Stellar fluid dynamics and numerical simulations: from the sun to
neutron stars, France (2006) 153 | 10.1051/eas:2006112 | null | gr-qc math.SP physics.comp-ph | null | This proceeding is intended to be a first introduction to spectral methods.
It is written around some simple problems that are solved explicitly and in
details and that aim at demonstrating the power of those methods. The
mathematical foundation of the spectral approximation is first introduced,
based on the Gauss quadratures. The two usual basis of Legendre and Chebyshev
polynomials are then presented. The next section is devoted to one dimensional
equation solvers using only one domain. Three different methods are described.
Techniques using several domains are shown in the last section of this paper
and their various merits discussed.
| [
{
"created": "Wed, 6 Sep 2006 10:01:17 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Grandclement",
"Philippe",
"",
"LUTH"
]
] | This proceeding is intended to be a first introduction to spectral methods. It is written around some simple problems that are solved explicitly and in details and that aim at demonstrating the power of those methods. The mathematical foundation of the spectral approximation is first introduced, based on the Gauss quadratures. The two usual basis of Legendre and Chebyshev polynomials are then presented. The next section is devoted to one dimensional equation solvers using only one domain. Three different methods are described. Techniques using several domains are shown in the last section of this paper and their various merits discussed. |
gr-qc/0211099 | Ujjal Debnath | Asit Banerjee, Ujjal Debnath and Subenoy Chakraborty | Naked Singularities in Higher Dimensional Gravitational Collapse | 7 Latex pages, No figure, Revtex style | Int.J.Mod.Phys. D12 (2003) 1255-1264 | 10.1142/S021827180300375X | null | gr-qc | null | Spherically symmetric inhomogeneous dust collapse has been studied in higher
dimensional space-time and the factors responsible for the appearance of a
naked singularity are analyzed in the region close to the centre for the
marginally bound case. It is clearly demonstrated that in the former case naked
singularities do not appear in the space-time having more than five dimension,
which appears to a strong result. The non-marginally bound collapse is also
examined in five dimensions and the role of shear in developing naked
singularities in this space-time is discussed in details. The five dimensional
space-time is chosen in the later case because we have exact solution in closed
form only in five dimension and not in any other case.
| [
{
"created": "Thu, 28 Nov 2002 12:18:53 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Feb 2003 10:53:20 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Banerjee",
"Asit",
""
],
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | Spherically symmetric inhomogeneous dust collapse has been studied in higher dimensional space-time and the factors responsible for the appearance of a naked singularity are analyzed in the region close to the centre for the marginally bound case. It is clearly demonstrated that in the former case naked singularities do not appear in the space-time having more than five dimension, which appears to a strong result. The non-marginally bound collapse is also examined in five dimensions and the role of shear in developing naked singularities in this space-time is discussed in details. The five dimensional space-time is chosen in the later case because we have exact solution in closed form only in five dimension and not in any other case. |
gr-qc/9509056 | Sergey V. Sushkov | Sushkov Sergei | Chronology Protection and Quantized Fields: Complex Automorphic Scalar
Field in Misner Space | 7 pages, LaTeX, two figures are available in PCX or postscript format
upon request, to appear in Proceedings of the 3rd Friedmann Seminar | Class.Quant.Grav.14:523-534,1997 | 10.1088/0264-9381/14/2/025 | null | gr-qc | null | The renormalized stress-energy tensor $\langle T_{\mu\nu}\rangle$ of the
quantized complex massless scalar field which obeys the automorphic condition
in Misner space is obtained. It is shown that there exists the special value of
the automorphic parameter for which $\langle T_{\mu\nu}\rangle$ is regular on
the chronology horizon and, so, can not act as a protector of chronology
through a back reaction on a spacetime metric. However, it is shown that, at
the same time, the value of field square $\langle\phi^2\rangle$, which
characterizes the quantum field fluctuations, is divergent on the chronology
horizon. The assumption is suggested that the infinitely growing quantum field
fluctuations, which appear if a (self)interaction of the scalar field is taken
into account, would prevent the chronology horizon formation.
| [
{
"created": "Thu, 28 Sep 1995 05:02:45 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Sergei",
"Sushkov",
""
]
] | The renormalized stress-energy tensor $\langle T_{\mu\nu}\rangle$ of the quantized complex massless scalar field which obeys the automorphic condition in Misner space is obtained. It is shown that there exists the special value of the automorphic parameter for which $\langle T_{\mu\nu}\rangle$ is regular on the chronology horizon and, so, can not act as a protector of chronology through a back reaction on a spacetime metric. However, it is shown that, at the same time, the value of field square $\langle\phi^2\rangle$, which characterizes the quantum field fluctuations, is divergent on the chronology horizon. The assumption is suggested that the infinitely growing quantum field fluctuations, which appear if a (self)interaction of the scalar field is taken into account, would prevent the chronology horizon formation. |
1803.03703 | Yousef Bisabr | Yousef Bisabr | Gravitational Coupling and the Cosmological Constant | 7 pages, no figure. To appear in IJMPD | Int. J. Mod. Phys. D 27, 1850086 (2018) | 10.1142/S0218271818500864 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We deal with a dynamical mechanism in which a large cosmological constant, as
suggested by inflationary scenarios, decays due to expansion of the universe.
This mechanism has its origin in the gravitational coupling of the vacuum
density. We assume that the vacuum couples anomalously to gravity that is the
metric tensor that appears the gravitational part is not the same as that
appears the matter part as suggested by weak equivalence principle. Instead,
the two metric tensors are taken to be conformally related. We show that this
provides a dynamical mechanism which works during expansion of the universe. We
also consider some observational consequences of such a gravitational model.
| [
{
"created": "Fri, 9 Mar 2018 21:48:03 GMT",
"version": "v1"
}
] | 2018-06-05 | [
[
"Bisabr",
"Yousef",
""
]
] | We deal with a dynamical mechanism in which a large cosmological constant, as suggested by inflationary scenarios, decays due to expansion of the universe. This mechanism has its origin in the gravitational coupling of the vacuum density. We assume that the vacuum couples anomalously to gravity that is the metric tensor that appears the gravitational part is not the same as that appears the matter part as suggested by weak equivalence principle. Instead, the two metric tensors are taken to be conformally related. We show that this provides a dynamical mechanism which works during expansion of the universe. We also consider some observational consequences of such a gravitational model. |
1606.08451 | Adam Levi | Adam Levi, Amos Ori | Mode-sum regularization of $\left\langle \phi^{2} \right\rangle$ in the
angular-splitting method | 34 pages, 12 figures. Submitted to Phys. Rev. D | Phys. Rev. D 94, 044054 (2016) | 10.1103/PhysRevD.94.044054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The computation of the renormalized stress-energy tensor or
$\left\langle\phi^{2}\right\rangle_{ren}$ in curved spacetime is a challenging
task, at both the conceptual and technical levels. Recently we developed a new
approach to compute such renormalized quantities in asymptotically-flat curved
spacetimes, based on the point-splitting procedure. Our approach requires the
spacetime to admit some symmetry. We already implemented this approach to
compute $\left\langle \phi^{2}\right\rangle _{ren}$ in a stationary spacetime
using t-splitting, namely splitting in the time-translation direction. Here we
present the angular-splitting version of this approach, aimed for computing
renormalized quantities in a general (possibly dynamical) spherically-symmetric
spacetime. To illustrate how the angular-splitting method works, we use it here
to compute $\left\langle \phi^{2}\right\rangle _{ren}$ for a quantum massless
scalar field in Schwarzschild background, in various quantum states (Boulware,
Unruh, and Hartle-Hawking states). We find excellent agreement with the results
obtained from the t-splitting variant, and also with other methods. Our main
goal in pursuing this new mode-sum approach was to enable the computation of
the renormalized stress-energy tensor in a dynamical spherically symmetric
background, e.g. an evaporating black hole. The angular-splitting variant
presented here is most suitable to this purpose.
| [
{
"created": "Mon, 27 Jun 2016 20:00:06 GMT",
"version": "v1"
}
] | 2016-08-30 | [
[
"Levi",
"Adam",
""
],
[
"Ori",
"Amos",
""
]
] | The computation of the renormalized stress-energy tensor or $\left\langle\phi^{2}\right\rangle_{ren}$ in curved spacetime is a challenging task, at both the conceptual and technical levels. Recently we developed a new approach to compute such renormalized quantities in asymptotically-flat curved spacetimes, based on the point-splitting procedure. Our approach requires the spacetime to admit some symmetry. We already implemented this approach to compute $\left\langle \phi^{2}\right\rangle _{ren}$ in a stationary spacetime using t-splitting, namely splitting in the time-translation direction. Here we present the angular-splitting version of this approach, aimed for computing renormalized quantities in a general (possibly dynamical) spherically-symmetric spacetime. To illustrate how the angular-splitting method works, we use it here to compute $\left\langle \phi^{2}\right\rangle _{ren}$ for a quantum massless scalar field in Schwarzschild background, in various quantum states (Boulware, Unruh, and Hartle-Hawking states). We find excellent agreement with the results obtained from the t-splitting variant, and also with other methods. Our main goal in pursuing this new mode-sum approach was to enable the computation of the renormalized stress-energy tensor in a dynamical spherically symmetric background, e.g. an evaporating black hole. The angular-splitting variant presented here is most suitable to this purpose. |
2007.00285 | Tetsuya Shiromizu | Tetsuya Shiromizu and Diego Soligon | The positive mass theorem in Kaluza-Klein picture | 8 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider Schoen and Yau's proof of the positive mass theorem from the
extra dimensional point of view, and we introduce a modified argument to prove
the theorem in the Kaluza-Klein picture. We consider in this study an
alternative condition to Jang's equation, which makes the argument more
physically intuitive.
| [
{
"created": "Wed, 1 Jul 2020 07:22:55 GMT",
"version": "v1"
}
] | 2020-07-02 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Soligon",
"Diego",
""
]
] | We reconsider Schoen and Yau's proof of the positive mass theorem from the extra dimensional point of view, and we introduce a modified argument to prove the theorem in the Kaluza-Klein picture. We consider in this study an alternative condition to Jang's equation, which makes the argument more physically intuitive. |
2007.01732 | Leonardo Campanelli | Leonardo Campanelli | Creation of Universes from the Third-Quantized Vacuum | 12 pages, 7 figures, accepted for publication in Physical Review D | Phys. Rev. D 102, 043514 (2020) | 10.1103/PhysRevD.102.043514 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the average numbers of closed, flat, and open universes
spontaneously created from nothing in third quantization. The creation of
universes is exponentially suppressed for large values of the kinetic energy of
the inflaton, while for small kinetic energies it is exponentially favoured for
closed universes over flat and open ones: For a scale of inflation less than
about $2 \times 10^{16}$GeV, the ratio of the number of closed universes to
either the number of flat or open universes is \begin{equation}
\frac{n_{closed}}{n_{flat,open}} \gtrsim 10^{10^{10}} . \nonumber
\end{equation}
| [
{
"created": "Fri, 3 Jul 2020 14:54:30 GMT",
"version": "v1"
}
] | 2020-08-19 | [
[
"Campanelli",
"Leonardo",
""
]
] | We calculate the average numbers of closed, flat, and open universes spontaneously created from nothing in third quantization. The creation of universes is exponentially suppressed for large values of the kinetic energy of the inflaton, while for small kinetic energies it is exponentially favoured for closed universes over flat and open ones: For a scale of inflation less than about $2 \times 10^{16}$GeV, the ratio of the number of closed universes to either the number of flat or open universes is \begin{equation} \frac{n_{closed}}{n_{flat,open}} \gtrsim 10^{10^{10}} . \nonumber \end{equation} |
2405.06921 | Anxianyi Xiong | Anxianyi Xiong, Xin-zhe Zhang, Taotao Qiu | Perturbations of Mimetic Curvaton | null | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mimetic gravity theory is one of the interesting modified gravity
theories, which aims to unify the matter component of our universe within the
power of gravity. The mimetic-like theory can also be responsible for
primordial perturbations production, e.g., when the mimetic field is set to be
like a curvaton field, and the adiabatic perturbation can thus be generated
from the isocurvature perturbation via usual curvaton mechanism [1]. In the
original mimetic curvaton model, the parameter $\lambda$ was purely an
algebraic multiplier, lack of any perturbed dynamics. In the current paper, we
treat $\lambda$ as an auxiliary field, with its perturbation $\delta\lambda$
evolving alongside. We show that, with such a consideration, the adiabatic
perturbation can still be generated from the curvaton mechanism, and becomes
scale invariant with different field space configurations.
| [
{
"created": "Sat, 11 May 2024 05:45:17 GMT",
"version": "v1"
}
] | 2024-05-14 | [
[
"Xiong",
"Anxianyi",
""
],
[
"Zhang",
"Xin-zhe",
""
],
[
"Qiu",
"Taotao",
""
]
] | The mimetic gravity theory is one of the interesting modified gravity theories, which aims to unify the matter component of our universe within the power of gravity. The mimetic-like theory can also be responsible for primordial perturbations production, e.g., when the mimetic field is set to be like a curvaton field, and the adiabatic perturbation can thus be generated from the isocurvature perturbation via usual curvaton mechanism [1]. In the original mimetic curvaton model, the parameter $\lambda$ was purely an algebraic multiplier, lack of any perturbed dynamics. In the current paper, we treat $\lambda$ as an auxiliary field, with its perturbation $\delta\lambda$ evolving alongside. We show that, with such a consideration, the adiabatic perturbation can still be generated from the curvaton mechanism, and becomes scale invariant with different field space configurations. |
1404.4099 | Hartmut Abele | T. Jenke, G. Cronenberg, J. Burgd\"orfer, L.A. Chizhova, P.
Geltenbort, A.N. Ivanov, T. Lauer, T. Lins, S. Rotter, H. Saul, U. Schmidt,
H. Abele | Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter
Scenarios | 5 pages, 4 figures | Phys. Rev. Lett. 112, 151105 (2014) | 10.1103/PhysRevLett.112.151105 | null | gr-qc nucl-ex quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on precision resonance spectroscopy measurements of quantum states
of ultracold neutrons confined above the surface of a horizontal mirror by the
gravity potential of the Earth. Resonant transitions between several of the
lowest quantum states are observed for the first time. These measurements
demonstrate, that Newton's inverse square law of Gravity is understood at
micron distances on an energy scale of~$10^{-14}$~eV. At this level of
precision we are able to provide constraints on any possible gravity-like
interaction. In particular, a dark energy chameleon field is excluded for
values of the coupling constant~$\beta > 5.8\times10^8$ at~95% confidence
level~(C.L.), and an attractive (repulsive) dark matter axion-like spin-mass
coupling is excluded for the coupling strength $g_sg_p >
3.7\times10^{-16}$~($5.3\times10^{-16}$)~at a Yukawa length of~$\lambda =
20$~{\textmu}m~(95% (C.L.).
| [
{
"created": "Tue, 15 Apr 2014 22:24:59 GMT",
"version": "v1"
}
] | 2014-10-08 | [
[
"Jenke",
"T.",
""
],
[
"Cronenberg",
"G.",
""
],
[
"Burgdörfer",
"J.",
""
],
[
"Chizhova",
"L. A.",
""
],
[
"Geltenbort",
"P.",
""
],
[
"Ivanov",
"A. N.",
""
],
[
"Lauer",
"T.",
""
],
[
"Lins",
"T.",
""
],
[
"Rotter",
"S.",
""
],
[
"Saul",
"H.",
""
],
[
"Schmidt",
"U.",
""
],
[
"Abele",
"H.",
""
]
] | We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of the Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate, that Newton's inverse square law of Gravity is understood at micron distances on an energy scale of~$10^{-14}$~eV. At this level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant~$\beta > 5.8\times10^8$ at~95% confidence level~(C.L.), and an attractive (repulsive) dark matter axion-like spin-mass coupling is excluded for the coupling strength $g_sg_p > 3.7\times10^{-16}$~($5.3\times10^{-16}$)~at a Yukawa length of~$\lambda = 20$~{\textmu}m~(95% (C.L.). |
1508.01079 | Paul Frampton | Paul Howard Frampton | Scale Invariant Density Perturbations from Cyclic Cosmology | 11 pages, LaTeX | null | 10.1142/S0217732316500760 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown how quantum fluctuations of the radiation during the contraction
era of a CBE (Comes Back Empty) cyclic cosmology can provide density
fluctuations which re-enter the horizon during the subsequent expansion era and
at lowest order are scale invariant, in a Harrison-Zel'dovich-Peebles sense, as
necessary to be consistent with observations of large scale structure.
| [
{
"created": "Tue, 4 Aug 2015 16:27:28 GMT",
"version": "v1"
}
] | 2016-05-25 | [
[
"Frampton",
"Paul Howard",
""
]
] | It is shown how quantum fluctuations of the radiation during the contraction era of a CBE (Comes Back Empty) cyclic cosmology can provide density fluctuations which re-enter the horizon during the subsequent expansion era and at lowest order are scale invariant, in a Harrison-Zel'dovich-Peebles sense, as necessary to be consistent with observations of large scale structure. |
1804.00988 | Ernesto Contreras | Ernesto Contreras and Pedro Bargue\~no | A self-sustained traversable scale-dependent wormhole | Accepted in Int. J. Mod. Phys. D | International Journal of Modern Physics D Vol. 27, No. 9 (2018)
1850101 | 10.1142/S0218271818501018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A self--sustained traversable wormhole is obtained as a vacuum solution of a
scale-dependent gravitational theory. Comparison with other approaches towards
wormhole self--sustainability are presented, with emphasis on the running of
the gravitational coupling and on a possible effective description of gravity
near the Planck scale.
| [
{
"created": "Tue, 3 Apr 2018 14:24:20 GMT",
"version": "v1"
}
] | 2019-04-01 | [
[
"Contreras",
"Ernesto",
""
],
[
"Bargueño",
"Pedro",
""
]
] | A self--sustained traversable wormhole is obtained as a vacuum solution of a scale-dependent gravitational theory. Comparison with other approaches towards wormhole self--sustainability are presented, with emphasis on the running of the gravitational coupling and on a possible effective description of gravity near the Planck scale. |
1207.5472 | Diego S\'aez-G\'omez | Diego S\'aez-G\'omez (University of the Basque Country) | Cosmological evolution, future singularities, Little Rip and Pseudo-Rip
in viable f(R) theories and their scalar-tensor counterpart | 20 pages. Extended version, new figures and additional analysis.
Version to be published in Class. Quant. Grav | Class. Quantum Grav. 30, 095008, 2013 | 10.1088/0264-9381/30/9/095008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified f(R) gravity is one of the most promising candidates for dark
energy, and even for the unification of the whole cosmological evolution,
including the inflationary phase. Within this class of theories, the so-called
viable modified gravities represent realistic theories that are capable of
reproducing late-time acceleration, and satisfy strong constraints at local
scales, where General Relativity is recovered. The present manuscript deals
with the analysis of the cosmological evolution for some of these models, which
indicates that the evolution may enter into a phantom phase, but the behavior
may be asymptotically stable. Furthermore, the scalar-tensor equivalence of
f(R) gravity is considered, which provides useful information about the
possibility of the occurrence of a future singularity. The so-called Little Rip
and Pseudo-Rip are also studied in the framework of this class of modified
gravities.
| [
{
"created": "Mon, 23 Jul 2012 18:15:10 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2013 13:06:28 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Sáez-Gómez",
"Diego",
"",
"University of the Basque Country"
]
] | Modified f(R) gravity is one of the most promising candidates for dark energy, and even for the unification of the whole cosmological evolution, including the inflationary phase. Within this class of theories, the so-called viable modified gravities represent realistic theories that are capable of reproducing late-time acceleration, and satisfy strong constraints at local scales, where General Relativity is recovered. The present manuscript deals with the analysis of the cosmological evolution for some of these models, which indicates that the evolution may enter into a phantom phase, but the behavior may be asymptotically stable. Furthermore, the scalar-tensor equivalence of f(R) gravity is considered, which provides useful information about the possibility of the occurrence of a future singularity. The so-called Little Rip and Pseudo-Rip are also studied in the framework of this class of modified gravities. |
gr-qc/9804005 | Vojtich Pravda | J. Bicak and V. Pravda | Curvature invariants in type N spacetimes | 17 pages, to appear in Class. Quantum Grav | Class.Quant.Grav.15:1539-1555,1998 | 10.1088/0264-9381/15/6/011 | null | gr-qc | null | Scalar curvature invariants are studied in type N solutions of vacuum
Einstein's equations with in general non-vanishing cosmological constant
Lambda. Zero-order invariants which include only the metric and Weyl (Riemann)
tensor either vanish, or are constants depending on Lambda. Even all
higher-order invariants containing covariant derivatives of the Weyl (Riemann)
tensor are shown to be trivial if a type N spacetime admits a non-expanding and
non-twisting null geodesic congruence.
However, in the case of expanding type N spacetimes we discover a
non-vanishing scalar invariant which is quartic in the second derivatives of
the Riemann tensor.
We use this invariant to demonstrate that both linearized and the third order
type N twisting solutions recently discussed in literature contain
singularities at large distances and thus cannot describe radiation fields
outside bounded sources.
| [
{
"created": "Thu, 2 Apr 1998 14:54:24 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 1998 15:20:20 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bicak",
"J.",
""
],
[
"Pravda",
"V.",
""
]
] | Scalar curvature invariants are studied in type N solutions of vacuum Einstein's equations with in general non-vanishing cosmological constant Lambda. Zero-order invariants which include only the metric and Weyl (Riemann) tensor either vanish, or are constants depending on Lambda. Even all higher-order invariants containing covariant derivatives of the Weyl (Riemann) tensor are shown to be trivial if a type N spacetime admits a non-expanding and non-twisting null geodesic congruence. However, in the case of expanding type N spacetimes we discover a non-vanishing scalar invariant which is quartic in the second derivatives of the Riemann tensor. We use this invariant to demonstrate that both linearized and the third order type N twisting solutions recently discussed in literature contain singularities at large distances and thus cannot describe radiation fields outside bounded sources. |
1511.07095 | Woei Chet Lim | Alan Coley and Woei Chet Lim | Spikes and matter inhomogeneities in massless scalar field models | 24 pages, 3 figures | Class. Quantum Grav. 33 (2016) 015009 | 10.1088/0264-9381/33/1/015009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We shall discuss the general relativistic generation of spikes in a massless
scalar field or stiff perfect fluid model. We first investigate orthogonally
transitive (OT) $G_2$ stiff fluid spike models both heuristically and
numerically, and give a new exact OT $G_2$ stiff fluid spike solution. We then
present a new two-parameter family of non-OT $G_2$ stiff fluid spike solutions,
obtained by the generalization of non-OT $G_2$ vacuum spike solutions to the
stiff fluid case by applying Geroch's transformation on a Jacobs seed. The
dynamics of these new stiff fluid spike solutions is qualitatively different
from that of the vacuum spike solutions, in that the matter (stiff fluid) feels
the spike directly and the stiff fluid spike solution can end up with a
permanent spike. We then derive the evolution equations of non-OT $G_2$ stiff
fluid models, including a second perfect fluid, in full generality, and briefly
discuss some of their qualitative properties and their potential numerical
analysis. Finally, we discuss how a fluid, and especially a stiff fluid or
massless scalar field, affects the physics of the generation of spikes.
| [
{
"created": "Mon, 23 Nov 2015 02:14:21 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jan 2017 22:50:56 GMT",
"version": "v2"
}
] | 2017-01-12 | [
[
"Coley",
"Alan",
""
],
[
"Lim",
"Woei Chet",
""
]
] | We shall discuss the general relativistic generation of spikes in a massless scalar field or stiff perfect fluid model. We first investigate orthogonally transitive (OT) $G_2$ stiff fluid spike models both heuristically and numerically, and give a new exact OT $G_2$ stiff fluid spike solution. We then present a new two-parameter family of non-OT $G_2$ stiff fluid spike solutions, obtained by the generalization of non-OT $G_2$ vacuum spike solutions to the stiff fluid case by applying Geroch's transformation on a Jacobs seed. The dynamics of these new stiff fluid spike solutions is qualitatively different from that of the vacuum spike solutions, in that the matter (stiff fluid) feels the spike directly and the stiff fluid spike solution can end up with a permanent spike. We then derive the evolution equations of non-OT $G_2$ stiff fluid models, including a second perfect fluid, in full generality, and briefly discuss some of their qualitative properties and their potential numerical analysis. Finally, we discuss how a fluid, and especially a stiff fluid or massless scalar field, affects the physics of the generation of spikes. |
gr-qc/9601037 | Erik Martinez | Erik A. Martinez (Center for Gravitational Physics and Geometry, Penn
State, USA) | Fundamental thermodynamical equation of a self-gravitating system | 30 pages, Revtex, no figures; Introduction rewritten and small
changes included throughout to improve presentation; to appear in Physical
Review D | Phys.Rev. D53 (1996) 7062-7072 | 10.1103/PhysRevD.53.7062 | CGPG-96/1-6 | gr-qc hep-th | null | The features of the fundamental thermodynamical relation (expressing entropy
as function of state variables) that arise from the self-gravitating character
of a system are analyzed. The models studied include not only a spherically
symmetric hot matter shell with constant particle number but also a black hole
characterized by a general thermal equation of state. These examples illustrate
the formal structure of thermodynamics developed by Callen as applied to a
gravitational configuration as well as the phenomenological manner in which
Einstein equations largely determine the thermodynamical equations of state. We
consider in detail the thermodynamics and quasi-static collapse of a
self-gravitating shell. This includes a discussion of intrinsic stability for a
one-parameter family of thermal equations of state and the interpretation of
the Bekenstein bound. The entropy growth associated with a collapsing sequence
of equilibrium states of a shell is computed under different boundary
conditions in the quasi-static approximation and compared with black hole
entropy. Although explicit expressions involve empirical coefficients, these
are constrained by physical conditions of thermodynamical origin. The absence
of a Gibbs-Duhem relation and the associated scaling laws for self-gravitating
matter systems are presented.
| [
{
"created": "Tue, 23 Jan 1996 14:18:37 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Apr 1996 14:23:26 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Martinez",
"Erik A.",
"",
"Center for Gravitational Physics and Geometry, Penn\n State, USA"
]
] | The features of the fundamental thermodynamical relation (expressing entropy as function of state variables) that arise from the self-gravitating character of a system are analyzed. The models studied include not only a spherically symmetric hot matter shell with constant particle number but also a black hole characterized by a general thermal equation of state. These examples illustrate the formal structure of thermodynamics developed by Callen as applied to a gravitational configuration as well as the phenomenological manner in which Einstein equations largely determine the thermodynamical equations of state. We consider in detail the thermodynamics and quasi-static collapse of a self-gravitating shell. This includes a discussion of intrinsic stability for a one-parameter family of thermal equations of state and the interpretation of the Bekenstein bound. The entropy growth associated with a collapsing sequence of equilibrium states of a shell is computed under different boundary conditions in the quasi-static approximation and compared with black hole entropy. Although explicit expressions involve empirical coefficients, these are constrained by physical conditions of thermodynamical origin. The absence of a Gibbs-Duhem relation and the associated scaling laws for self-gravitating matter systems are presented. |
1905.08512 | Giovanni Acquaviva | Morteza Kerachian, Giovanni Acquaviva, Georgios Lukes-Gerakopoulos | Classes of non-minimally coupled scalar fields in spatially curved FRW
spacetimes | 13 pages, 7 figures | Phys. Rev. D 99, 123516 (2019) | 10.1103/PhysRevD.99.123516 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we perform a dynamical analysis of a broad class of
non-minimally coupled real scalar fields in the Friedmann-Robertson-Walker
(FRW) spacetime framework. The first part of our study concerns the dynamics of
an unspecified positive potential in a spatially curved FRW spacetime, for
which we define a new set of dimensionless variables and a new evolution
parameter. In the framework of this general setup we have recognized several
general features of the system, like symmetries, invariant subsets and critical
points, and provide their cosmological interpretation. The second part of our
work focuses on flat FRW cases for which the tracker parameter is constant,
i.e. we examine specific classes of potentials. After analyzing these cases
dynamically, we discuss their physical interpretation.
| [
{
"created": "Tue, 21 May 2019 09:27:06 GMT",
"version": "v1"
}
] | 2019-06-18 | [
[
"Kerachian",
"Morteza",
""
],
[
"Acquaviva",
"Giovanni",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
]
] | In this work we perform a dynamical analysis of a broad class of non-minimally coupled real scalar fields in the Friedmann-Robertson-Walker (FRW) spacetime framework. The first part of our study concerns the dynamics of an unspecified positive potential in a spatially curved FRW spacetime, for which we define a new set of dimensionless variables and a new evolution parameter. In the framework of this general setup we have recognized several general features of the system, like symmetries, invariant subsets and critical points, and provide their cosmological interpretation. The second part of our work focuses on flat FRW cases for which the tracker parameter is constant, i.e. we examine specific classes of potentials. After analyzing these cases dynamically, we discuss their physical interpretation. |
1804.05382 | Jos\'e Tom\'as G\'alvez Ghersi | Aditya Dhumuntarao, Jos\'e Tom\'as G\'alvez Ghersi, Niayesh Afshordi | Instantaneous Temperatures \`a la Hadamard: Towards a generalized
Stefan-Boltzmann law for curved spacetime | REVTeX 4.1, 10 pages, 2 figures. Considered effects from higher order
terms in the quasi-local expansion. Minor typos fixed, conclusions revised | null | null | SCG-2018-04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the celebrated Unruh effect, we learn that a uniformly accelerating
detector in a Minkowski vacuum spacetime registers a constant temperature.
Building on prior work, we present a technique based on derivative couplings of
the two-point Wightman function and the Hadamard renormalization procedure to
define an instantaneous temperature for a massive scalar field, non-minimally
coupled to gravity. We find the temperature contains local contributions from
the acceleration of the detector, the curvature of spacetime, and the
renormalized stress-energy tensor of the field. Our result, which can be
considered as a generalized Stefan-Boltzmann law for curved spacetimes, agrees
with the familiar expressions found in 4D Rindler, thermal Minkowski, and de
Sitter.
| [
{
"created": "Sun, 15 Apr 2018 17:09:23 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Apr 2018 20:03:01 GMT",
"version": "v2"
}
] | 2018-04-19 | [
[
"Dhumuntarao",
"Aditya",
""
],
[
"Ghersi",
"José Tomás Gálvez",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | In the celebrated Unruh effect, we learn that a uniformly accelerating detector in a Minkowski vacuum spacetime registers a constant temperature. Building on prior work, we present a technique based on derivative couplings of the two-point Wightman function and the Hadamard renormalization procedure to define an instantaneous temperature for a massive scalar field, non-minimally coupled to gravity. We find the temperature contains local contributions from the acceleration of the detector, the curvature of spacetime, and the renormalized stress-energy tensor of the field. Our result, which can be considered as a generalized Stefan-Boltzmann law for curved spacetimes, agrees with the familiar expressions found in 4D Rindler, thermal Minkowski, and de Sitter. |
2209.04429 | Martin Bojowald | Martin Bojowald and Freddy Hancock | Quasiclassical model of inhomogeneous cosmology | 43 pages, 11 figures | Class. Quantum Grav. 40 (2023) 155012 | 10.1088/1361-6382/acdd45 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fluctuation terms and higher moments of a quantum state imply corrections to
the classical equations of motion that may have implications in early-universe
cosmology, for instance in the state-dependent form of effective potentials. In
addition, space-time properties are relevant in cosmology, in particular when
combined with quantum corrections required to maintain general covariance in a
consistent way. Here, an extension of previous investigations of static
quasiclassical space-time models to dynamical ones is presented, describing the
evolution of 1-dimensional space as in the classical Lemaitre--Tolman--Bondi
models. The corresponding spatial metric has two independent components, both
of which are in general subject to quantum fluctuations. The main result is
that individual moments from both components are indeed required for general
covariance to be maintained at a semiclassical level, while quantum
correlations between the components are less relevant.
| [
{
"created": "Fri, 9 Sep 2022 17:41:25 GMT",
"version": "v1"
}
] | 2023-07-10 | [
[
"Bojowald",
"Martin",
""
],
[
"Hancock",
"Freddy",
""
]
] | Fluctuation terms and higher moments of a quantum state imply corrections to the classical equations of motion that may have implications in early-universe cosmology, for instance in the state-dependent form of effective potentials. In addition, space-time properties are relevant in cosmology, in particular when combined with quantum corrections required to maintain general covariance in a consistent way. Here, an extension of previous investigations of static quasiclassical space-time models to dynamical ones is presented, describing the evolution of 1-dimensional space as in the classical Lemaitre--Tolman--Bondi models. The corresponding spatial metric has two independent components, both of which are in general subject to quantum fluctuations. The main result is that individual moments from both components are indeed required for general covariance to be maintained at a semiclassical level, while quantum correlations between the components are less relevant. |
2305.12771 | Uwe R. Fischer | Sang-Shin Baak, Satadal Datta, Uwe R. Fischer | Petrov classification of analogue spacetimes | 11 pages, 2 figures; added section with general considerations on
possible Petrov types of Painlev\'e-Gullstrand geometries, to appear in
Classical and Quantum Gravity | Class. Quantum Grav. 40, 215001 (2023) | 10.1088/1361-6382/acf08e | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In an effort to invariantly characterize the conformal curvature structure of
analogue spacetimes built from a nonrelativistic fluid background, we determine
the Petrov type of a variety of laboratory geometries. Starting from the
simplest examples, we increase the complexity of the background, and thereby
determine how the laboratory fluid symmetry affects the corresponding Petrov
type in the analogue spacetime realm of the sound waves. We find that for more
complex flows isolated hypersurfaces develop, which are of a Petrov type
differing from that of the surrounding fluid. {Finally, we demonstrate that
within the incompressible background approximation, as well as for all
compressible quasi-one-dimensional flows, the only possible Petrov types are
the algebraically general type I and the algebraically special types O and D.
| [
{
"created": "Mon, 22 May 2023 07:01:13 GMT",
"version": "v1"
},
{
"created": "Wed, 31 May 2023 04:55:16 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Aug 2023 09:41:21 GMT",
"version": "v3"
}
] | 2023-10-06 | [
[
"Baak",
"Sang-Shin",
""
],
[
"Datta",
"Satadal",
""
],
[
"Fischer",
"Uwe R.",
""
]
] | In an effort to invariantly characterize the conformal curvature structure of analogue spacetimes built from a nonrelativistic fluid background, we determine the Petrov type of a variety of laboratory geometries. Starting from the simplest examples, we increase the complexity of the background, and thereby determine how the laboratory fluid symmetry affects the corresponding Petrov type in the analogue spacetime realm of the sound waves. We find that for more complex flows isolated hypersurfaces develop, which are of a Petrov type differing from that of the surrounding fluid. {Finally, we demonstrate that within the incompressible background approximation, as well as for all compressible quasi-one-dimensional flows, the only possible Petrov types are the algebraically general type I and the algebraically special types O and D. |
1507.05099 | Marcus Werner | Marcus C. Werner | A geometrical approach to gravitational lensing magnification | 4 pages, for the Proceedings of the 14th Marcel Grossmann Meeting,
based on gr-qc/1507.02765 | null | null | null | gr-qc astro-ph.GA math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard definition of gravitational lensing magnification is generalized
to Lorentzian spacetimes, and it is shown how it can be interpreted
geometrically in terms of the van Vleck determinant and the exponential map.
This is joint work with Amir B. Aazami (Kavli IPMU, University of Tokyo).
| [
{
"created": "Fri, 17 Jul 2015 20:02:54 GMT",
"version": "v1"
}
] | 2015-07-21 | [
[
"Werner",
"Marcus C.",
""
]
] | The standard definition of gravitational lensing magnification is generalized to Lorentzian spacetimes, and it is shown how it can be interpreted geometrically in terms of the van Vleck determinant and the exponential map. This is joint work with Amir B. Aazami (Kavli IPMU, University of Tokyo). |
2308.15354 | Zheng Wu | Zheng Wu, Hui-Min Fan, Yi-Ming Hu, Ik Siong Heng | Searching for gravitational-wave bursts with space-borne detectors | 13 pages, 9 figures, comments welcome | the 15 May 2024 issue of Physical Review D (Vol. 109, No. 10) | 10.1103/PhysRevD.109.103004 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The millihertz gravitational wave band is expected to be opened by
space-borne detectors like TianQin. Various mechanisms can produce short
outbursts of gravitational waves, whose actual waveform can be hard to model.
In order to identify such gravitational wave bursts and not to misclassify them
as noise transients, we proposed a proof-of-principle energy excess method,
that utilized the signal-insensitive channel to veto noise transients. We
perform a test on simulated data, and for bursts with a signal-to-noise ratio
of 20, even with the contamination of noise transient, our methods can reach a
detection efficiency of 97.4% under a false alarm rate of once per year.
However, more frequent occurrences of noise transients would lower the
detection efficiency.
| [
{
"created": "Tue, 29 Aug 2023 14:49:28 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2024 07:55:57 GMT",
"version": "v2"
}
] | 2024-05-15 | [
[
"Wu",
"Zheng",
""
],
[
"Fan",
"Hui-Min",
""
],
[
"Hu",
"Yi-Ming",
""
],
[
"Heng",
"Ik Siong",
""
]
] | The millihertz gravitational wave band is expected to be opened by space-borne detectors like TianQin. Various mechanisms can produce short outbursts of gravitational waves, whose actual waveform can be hard to model. In order to identify such gravitational wave bursts and not to misclassify them as noise transients, we proposed a proof-of-principle energy excess method, that utilized the signal-insensitive channel to veto noise transients. We perform a test on simulated data, and for bursts with a signal-to-noise ratio of 20, even with the contamination of noise transient, our methods can reach a detection efficiency of 97.4% under a false alarm rate of once per year. However, more frequent occurrences of noise transients would lower the detection efficiency. |
gr-qc/0004046 | Jelle Boersma | Jelle P. Boersma | Variational dynamics in open spacetimes | 21 pages, Latex, no figures | Phys.Rev. D60 (1999) 084013 | 10.1103/PhysRevD.60.084013 | null | gr-qc | null | We study the effect of non-vanishing surface terms at spatial infinity on the
dynamics of a scalar field in an open FLRW spacetime. Starting from the
path-integral formulation of quantum field theory we argue that classical
physics is described by field configurations which extremize the action
functional in the space of field configurations for which the variation of the
action is well defined. Since these field configurations are not required to
vanish outside a bounded domain, there is generally a non-vanishing
contribution of a surface term to the variation of the action. We then
investigate whether this surface term has an effect on the dynamics of the
action-extremizing field configurations. This question appears to be
surprisingly nontrivial in the case of the open FLRW geometry, since surface
terms tend to grow as fast as volume terms in the infinite volume limit. We
find that surface terms can be important for the dynamics of the field at a
classical and at a quantum level, when there are supercurvature perturbations.
| [
{
"created": "Fri, 14 Apr 2000 11:21:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Boersma",
"Jelle P.",
""
]
] | We study the effect of non-vanishing surface terms at spatial infinity on the dynamics of a scalar field in an open FLRW spacetime. Starting from the path-integral formulation of quantum field theory we argue that classical physics is described by field configurations which extremize the action functional in the space of field configurations for which the variation of the action is well defined. Since these field configurations are not required to vanish outside a bounded domain, there is generally a non-vanishing contribution of a surface term to the variation of the action. We then investigate whether this surface term has an effect on the dynamics of the action-extremizing field configurations. This question appears to be surprisingly nontrivial in the case of the open FLRW geometry, since surface terms tend to grow as fast as volume terms in the infinite volume limit. We find that surface terms can be important for the dynamics of the field at a classical and at a quantum level, when there are supercurvature perturbations. |
1908.05332 | Arvin Ravanpak | Arvin Ravanpak, Golnaz Farpour Fadakar | Interacting Agegraphic Dark Energy Model in DGP Braneworld Cosmology:
Dynamical System Approach | null | Mod. Phys. Lett. A 34, 1950105 (2019) | 10.1142/S0217732319501050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A proposal to study the effect of interaction in an agegraphic dark energy
model in DGP brane-world cosmology is presented in this manuscript. After
explaining the details, we proceed to apply the dynamical system approach to
the model to analyze its stability. We first, constrain model parameters with a
variety of independent observational data such as cosmic microwave background
anisotropies, baryon acoustic oscillation peaks and observational Hubble data.
Then, we obtain the critical points related to different cosmological epochs.
In particular, we conclude that in the presence of interaction, dark energy
dominated era could be a stable point if model parameters $n$ and $\beta$, obey
a given constraint. Also, big rip singularity is avoidable in this model.
| [
{
"created": "Wed, 14 Aug 2019 20:10:40 GMT",
"version": "v1"
}
] | 2019-08-16 | [
[
"Ravanpak",
"Arvin",
""
],
[
"Fadakar",
"Golnaz Farpour",
""
]
] | A proposal to study the effect of interaction in an agegraphic dark energy model in DGP brane-world cosmology is presented in this manuscript. After explaining the details, we proceed to apply the dynamical system approach to the model to analyze its stability. We first, constrain model parameters with a variety of independent observational data such as cosmic microwave background anisotropies, baryon acoustic oscillation peaks and observational Hubble data. Then, we obtain the critical points related to different cosmological epochs. In particular, we conclude that in the presence of interaction, dark energy dominated era could be a stable point if model parameters $n$ and $\beta$, obey a given constraint. Also, big rip singularity is avoidable in this model. |
1610.05753 | Parthapratim Pradhan | Parthapratim Pradhan | Enthalpy, Geometric Volume and Logarithmic correction to Entropy for
Van-der-Waals Black Hole | EPL version, 7 pages, 5 figures | EPL, 116 (2016) 10001 | 10.1209/0295-5075/116/10001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the negative cosmological constant is treated as a dynamical pressure and
if the volume be its thermodynamically conjugate variable then the
gravitational mass can be expressed as the total gravitational enthalpy rather
than the energy. Under these circumstances, a new phenomena emerges in the
context of extended phase space thermodynamics. We \emph{examine} here these
features for recently discovered Van-der-Waal (VDW) black hole (BH)
\cite{mann15} which is analogous to the VDW fluid. We show that the
thermodynamic volume is \emph{greater} than the naive geometric volume. We also
show that the \emph{Smarr-Gibbs-Duhem} relation is satisfied for this BH.
Furthermore, by computing the thermal specific heat we find the local
thermodynamic stability criterion for this BH. It has been observed that the BH
does \emph{not} possess any kind of second order phase transition. This is an
interesting feature of VDW BH by its own right. Moreover, we also derive
\emph{Cosmic-Censorship-Inequality} for this class of BH. In addition finally,
we compute the \emph{logarithmic correction} to the entropy of this BH due to
the quantum fluctuations around the thermal equilibrium.
| [
{
"created": "Tue, 18 Oct 2016 19:35:03 GMT",
"version": "v1"
}
] | 2016-11-08 | [
[
"Pradhan",
"Parthapratim",
""
]
] | If the negative cosmological constant is treated as a dynamical pressure and if the volume be its thermodynamically conjugate variable then the gravitational mass can be expressed as the total gravitational enthalpy rather than the energy. Under these circumstances, a new phenomena emerges in the context of extended phase space thermodynamics. We \emph{examine} here these features for recently discovered Van-der-Waal (VDW) black hole (BH) \cite{mann15} which is analogous to the VDW fluid. We show that the thermodynamic volume is \emph{greater} than the naive geometric volume. We also show that the \emph{Smarr-Gibbs-Duhem} relation is satisfied for this BH. Furthermore, by computing the thermal specific heat we find the local thermodynamic stability criterion for this BH. It has been observed that the BH does \emph{not} possess any kind of second order phase transition. This is an interesting feature of VDW BH by its own right. Moreover, we also derive \emph{Cosmic-Censorship-Inequality} for this class of BH. In addition finally, we compute the \emph{logarithmic correction} to the entropy of this BH due to the quantum fluctuations around the thermal equilibrium. |
2309.13894 | Fil Simovic | Fil Simovic | Black Holes, Equilibrium, and Cosmology | 9 pages, 1 figure. Honorable Mention for the Gravity Research
Foundation 2023 Awards for Essays on Gravitation | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We trace the origins and development of black hole thermodynamics across the
past half-century, emphasizing the framework's relation to classical
thermodynamics, and the vital role played by the notions of equilibrium,
stationarity, and symmetry. We discuss different interpretations of the first
law of black hole mechanics, and assess the validity of its mechanical,
process-based interpretation for evaporating black holes. We bring these ideas
to the cosmological realm, and highlight the various difficulties that arise
when formulating thermodynamics for black holes in asymptotically de Sitter
backgrounds. We discuss a number of proposed solutions and the open questions
that arise therein.
| [
{
"created": "Mon, 25 Sep 2023 06:19:37 GMT",
"version": "v1"
}
] | 2023-09-26 | [
[
"Simovic",
"Fil",
""
]
] | We trace the origins and development of black hole thermodynamics across the past half-century, emphasizing the framework's relation to classical thermodynamics, and the vital role played by the notions of equilibrium, stationarity, and symmetry. We discuss different interpretations of the first law of black hole mechanics, and assess the validity of its mechanical, process-based interpretation for evaporating black holes. We bring these ideas to the cosmological realm, and highlight the various difficulties that arise when formulating thermodynamics for black holes in asymptotically de Sitter backgrounds. We discuss a number of proposed solutions and the open questions that arise therein. |
1304.2796 | Krzysztof Urbanowski | K. Urbanowski and M. Szydlowski | Cosmology with a decaying vacuum | 4 pages, 2 figures, based on a talk given at Multiverse and
Fundamental Cosmology (Multicosmofun'12), Szczecin, Poland, 10-14 September
2012. arXiv admin note: text overlap with arXiv:1006.2417 by other authors | AIP Conf. Proc. 1514, 143 (2013) | 10.1063/1.4791743 | null | gr-qc astro-ph.HE hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Properties of unstable false vacuum states are analyzed from the point of
view of the quantum theory of unstable states. Some of false vacuum states
survive up to times when their survival probability has a non-exponential form.
At times much latter than the transition time, when contributions to the
survival probability of its exponential and non-exponential parts are
comparable, the survival probability as a function of time t has an inverse
power-like form. We show that at this time region the instantaneous energy of
the false vacuum states tends to the energy of the true vacuum state as
$1/t^{2}$ for $t \to \infty$.
| [
{
"created": "Wed, 10 Apr 2013 11:25:42 GMT",
"version": "v1"
}
] | 2013-04-11 | [
[
"Urbanowski",
"K.",
""
],
[
"Szydlowski",
"M.",
""
]
] | Properties of unstable false vacuum states are analyzed from the point of view of the quantum theory of unstable states. Some of false vacuum states survive up to times when their survival probability has a non-exponential form. At times much latter than the transition time, when contributions to the survival probability of its exponential and non-exponential parts are comparable, the survival probability as a function of time t has an inverse power-like form. We show that at this time region the instantaneous energy of the false vacuum states tends to the energy of the true vacuum state as $1/t^{2}$ for $t \to \infty$. |
2107.04467 | Guangzhou Guo | Guangzhou Guo, Peng Wang, Houwen Wu and Haitang Yang | Thermodynamics and Phase Structure of an Einstein-Maxwell-scalar Model
in Extended Phase Space | v1: 16 pages, 9 figures; v2: 16 pages, 9 figures, references added | null | 10.1103/PhysRevD.105.064069 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study thermodynamics and phase structure of asymptotically
AdS hairy and Reissner-Nordstr\"{o}m-AdS (RNAdS) black holes in the extended
phase space, where the cosmological constant is interpreted as a thermal
pressure. The RNAdS and hairy black holes are black hole solutions of an
Einstein-Maxwell-scalar (EMS) model with a non-minimal coupling between the
scalar and electromagnetic fields. The Smarr relation, the first law of
thermodynamics and the free energy are derived for black hole solutions in the
EMS model. Moreover, the phase structure of the RNAdS and hairy black holes is
investigated in canonical and grand canonical ensembles. Interestingly, RNAdS
BH/hairy BH/RNAdS BH reentrant phase transitions, consisting of zeroth-order
and second-order phase transitions, are found in both ensembles.
| [
{
"created": "Fri, 9 Jul 2021 14:33:41 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jul 2021 13:07:13 GMT",
"version": "v2"
}
] | 2022-04-13 | [
[
"Guo",
"Guangzhou",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | In this paper, we study thermodynamics and phase structure of asymptotically AdS hairy and Reissner-Nordstr\"{o}m-AdS (RNAdS) black holes in the extended phase space, where the cosmological constant is interpreted as a thermal pressure. The RNAdS and hairy black holes are black hole solutions of an Einstein-Maxwell-scalar (EMS) model with a non-minimal coupling between the scalar and electromagnetic fields. The Smarr relation, the first law of thermodynamics and the free energy are derived for black hole solutions in the EMS model. Moreover, the phase structure of the RNAdS and hairy black holes is investigated in canonical and grand canonical ensembles. Interestingly, RNAdS BH/hairy BH/RNAdS BH reentrant phase transitions, consisting of zeroth-order and second-order phase transitions, are found in both ensembles. |
gr-qc/9405006 | null | B.A.C.C. Bassett, P.K.S. Dunsby and G.F.R. Ellis | Shrinking and the True Power Spectrum at Decoupling | 21 pages, Latex, postscript figures available on request, revised and
enlarged to include a discussion of the doppler peaks | null | null | UCT preprint-94/4 | gr-qc astro-ph | null | In this paper we examine the change in the estimated spatial power spectra at
decoupling due to the effects of our clumpy universe which modify observational
distances. We find that scales at decoupling can be significantly underestmated
in our approximation of neglecting the shear of the ray bundle. We compare our
results with other work on lensing and speculate on the implications for
structure formation. In particular we examine a proposal to use the position of
the first Doppler peak to determine $\Omega$, and find that shrinking will
modify the esimated curvature, so that it must be included to obtain an
accurate estimate of $\Omega$. Finally we consider future applications and
improvements of our results.
| [
{
"created": "Tue, 3 May 1994 16:32:41 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Oct 1994 13:04:32 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Oct 1994 20:06:06 GMT",
"version": "v3"
}
] | 2009-09-25 | [
[
"Bassett",
"B. A. C. C.",
""
],
[
"Dunsby",
"P. K. S.",
""
],
[
"Ellis",
"G. F. R.",
""
]
] | In this paper we examine the change in the estimated spatial power spectra at decoupling due to the effects of our clumpy universe which modify observational distances. We find that scales at decoupling can be significantly underestmated in our approximation of neglecting the shear of the ray bundle. We compare our results with other work on lensing and speculate on the implications for structure formation. In particular we examine a proposal to use the position of the first Doppler peak to determine $\Omega$, and find that shrinking will modify the esimated curvature, so that it must be included to obtain an accurate estimate of $\Omega$. Finally we consider future applications and improvements of our results. |
1610.03102 | Andrei Lebed G | Andrei G. Lebed | Inequivalence Between Passive Gravitational Mass and Energy for a
Quantum Body: Theory and Suggested Experiment | Presentation at the 21st International Conference on General
Relativity and Gravitation (New York, USA; July 2016) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, we have suggested some semi-quantitative Hamiltonian for an
electron in a hydrogen atom in a weak gravitational field, which takes into
account quantum effects of electron motion in the atom. We have shown that this
Hamiltonian predicts breakdown of the equivalence between passive electron
gravitational mass and its energy. Moreover, as has been shown by us, the
latter phenomenon can be experimentally observed as unusual emission of
radiation from an ensemble of the atoms, provided that they are moved in the
Earth's gravitational field with constant velocity by some spacecraft. In this
article, we derive the above-mentioned Hamiltonian from the Dirac equation in a
curved spacetime. It is shown that it exactly coincides with the
semi-quantitative Hamiltonian, used in our previous papers. We extend the
obtained Hamiltonian to the case of a spacecraft, containing a macroscopic
ensemble of the atoms and moving with a constant velocity in the Earth's
gravitational field. On this basis, we discuss some idealized and realistic
experiments on the Earth's orbit. If such (realistic) experiment is done, it
will be the first direct observation of quantum effects in the General
Relativity.
| [
{
"created": "Mon, 10 Oct 2016 21:40:02 GMT",
"version": "v1"
}
] | 2016-10-12 | [
[
"Lebed",
"Andrei G.",
""
]
] | Recently, we have suggested some semi-quantitative Hamiltonian for an electron in a hydrogen atom in a weak gravitational field, which takes into account quantum effects of electron motion in the atom. We have shown that this Hamiltonian predicts breakdown of the equivalence between passive electron gravitational mass and its energy. Moreover, as has been shown by us, the latter phenomenon can be experimentally observed as unusual emission of radiation from an ensemble of the atoms, provided that they are moved in the Earth's gravitational field with constant velocity by some spacecraft. In this article, we derive the above-mentioned Hamiltonian from the Dirac equation in a curved spacetime. It is shown that it exactly coincides with the semi-quantitative Hamiltonian, used in our previous papers. We extend the obtained Hamiltonian to the case of a spacecraft, containing a macroscopic ensemble of the atoms and moving with a constant velocity in the Earth's gravitational field. On this basis, we discuss some idealized and realistic experiments on the Earth's orbit. If such (realistic) experiment is done, it will be the first direct observation of quantum effects in the General Relativity. |
gr-qc/0208037 | Dimitar Mladenov | A.M. Khvedelidze and D.M. Mladenov | Bianchi type I cosmology and the Euler-Calogero-Sutherland model | 13 pages, LaTeX, no figures. V2: Title and abstract slightly changed,
typos corrected. V3: Minor changes, version to appear in Physical Review D | Phys.Rev. D66 (2002) 123504 | 10.1103/PhysRevD.66.123504 | null | gr-qc hep-th math-ph math.MP nlin.SI | null | The Bianchi type I cosmological model is brought into a form where the
evolution of observables is governed by the unconstrained Hamiltonian that
coincides with the Hamiltonian describing the relative motion of particles in
the integrable three-body hyperbolic Euler-Calogero-Sutherland system.
| [
{
"created": "Wed, 14 Aug 2002 15:19:00 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Sep 2002 18:07:36 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Dec 2002 15:57:05 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Khvedelidze",
"A. M.",
""
],
[
"Mladenov",
"D. M.",
""
]
] | The Bianchi type I cosmological model is brought into a form where the evolution of observables is governed by the unconstrained Hamiltonian that coincides with the Hamiltonian describing the relative motion of particles in the integrable three-body hyperbolic Euler-Calogero-Sutherland system. |
1211.7099 | Yosef Zlochower | Carlos O. Lousto, Yosef Zlochower | Nonlinear Gravitational Recoil from the Mergers of Precessing Black-Hole
Binaries | Fix sign error in table 1. Repeated terms dropped in table 5 | Phys. Rev. D 87, 084027 (2013) | 10.1103/PhysRevD.87.084027 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present results from an extensive study of 88 precessing, equal-mass
black-hole binaries with large spins (83 with intrinsic spins of 0.8 and 5 with
intrinsic spins of 0.9)and use these data to model new nonlinear contributions
to the gravitational recoil imparted to the merged black hole. We find a new
effect, the cross kick, that enhances the recoil for partially aligned binaries
beyond the hangup kick effect. This has the consequence of increasing the
probabilities of recoils larger than 2000 km/s by nearly a factor two, and,
consequently, of black holes getting ejected from galaxies, as well as the
observation of large differential redshifts/blueshifts in the cores of recently
merged galaxies.
| [
{
"created": "Thu, 29 Nov 2012 21:46:07 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Feb 2013 20:17:17 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Mar 2013 18:05:17 GMT",
"version": "v3"
},
{
"created": "Sun, 12 Jan 2014 16:24:36 GMT",
"version": "v4"
}
] | 2014-01-14 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Zlochower",
"Yosef",
""
]
] | We present results from an extensive study of 88 precessing, equal-mass black-hole binaries with large spins (83 with intrinsic spins of 0.8 and 5 with intrinsic spins of 0.9)and use these data to model new nonlinear contributions to the gravitational recoil imparted to the merged black hole. We find a new effect, the cross kick, that enhances the recoil for partially aligned binaries beyond the hangup kick effect. This has the consequence of increasing the probabilities of recoils larger than 2000 km/s by nearly a factor two, and, consequently, of black holes getting ejected from galaxies, as well as the observation of large differential redshifts/blueshifts in the cores of recently merged galaxies. |
1501.02963 | Alejandro Perez | J. Fernando Barbero G. and Alejandro Perez | Quantum Geometry and Black Holes | Contribution to appear in the World Scientific series "100 Years of
General Relativity" edited by A. Ashtekar and J. Pullin | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an overall picture of the advances in the description of black
hole physics from the perspective of loop quantum gravity. After an
introduction that discusses the main conceptual issues we present some details
about the classical and quantum geometry of isolated horizons and their quantum
geometry and then use this scheme to give a natural definition of the entropy
of black holes. The entropy computations can be neatly expressed in the form of
combinatorial problems solvable with the help of methods based on number theory
and the use of generating functions. The recovery of the Bekenstein-Hawking law
and corrections to it is explained in some detail. After this, due attention is
paid to the discussion of semiclassical issues. An important point in this
respect is the proper interpretation of the horizon area as the energy that
should appear in the statistical-mechanical treatment of the black hole model
presented here. The chapter ends with a comparison between the microscopic and
semiclassical approaches to the computation of the entropy and discusses a
number of issues regarding the relation between entanglement and statistical
entropy and the possibility of comparing the subdominant (logarithmic)
corrections to the entropy obtained with the help of the Euclidean path
integral with the ones obtained in the present framework.
| [
{
"created": "Tue, 13 Jan 2015 11:28:01 GMT",
"version": "v1"
}
] | 2015-01-14 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Perez",
"Alejandro",
""
]
] | We present an overall picture of the advances in the description of black hole physics from the perspective of loop quantum gravity. After an introduction that discusses the main conceptual issues we present some details about the classical and quantum geometry of isolated horizons and their quantum geometry and then use this scheme to give a natural definition of the entropy of black holes. The entropy computations can be neatly expressed in the form of combinatorial problems solvable with the help of methods based on number theory and the use of generating functions. The recovery of the Bekenstein-Hawking law and corrections to it is explained in some detail. After this, due attention is paid to the discussion of semiclassical issues. An important point in this respect is the proper interpretation of the horizon area as the energy that should appear in the statistical-mechanical treatment of the black hole model presented here. The chapter ends with a comparison between the microscopic and semiclassical approaches to the computation of the entropy and discusses a number of issues regarding the relation between entanglement and statistical entropy and the possibility of comparing the subdominant (logarithmic) corrections to the entropy obtained with the help of the Euclidean path integral with the ones obtained in the present framework. |
gr-qc/0106040 | Eugen Radu | J.J. van der Bij and Eugen Radu (Faculty of Physics,
Albert-Ludwigs-University, Freiburg, Germany) | Gravitating sphalerons and sphaleron black holes in asymptotically
anti-de Sitter spacetime | 30 pages, LaTeX, 8 Encapsulated PostScript figures | Phys.Rev. D64 (2001) 064020 | 10.1103/PhysRevD.64.064020 | Freiburg-THEP 01/02 | gr-qc | null | Numerical arguments are presented for the existence of spherically symmetric
regular and black hole solutions of the EYMH equations with a negative
cosmological constant. These solutions approach asymptotically the anti-de
Sitter spacetime. The main properties of the solutions and the differences with
respect to the asymptotically flat case are discussed. The instability of the
gravitating sphaleron solutions is also proven.
| [
{
"created": "Mon, 11 Jun 2001 16:45:30 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"van der Bij",
"J. J.",
"",
"Faculty of Physics,\n Albert-Ludwigs-University, Freiburg, Germany"
],
[
"Radu",
"Eugen",
"",
"Faculty of Physics,\n Albert-Ludwigs-University, Freiburg, Germany"
]
] | Numerical arguments are presented for the existence of spherically symmetric regular and black hole solutions of the EYMH equations with a negative cosmological constant. These solutions approach asymptotically the anti-de Sitter spacetime. The main properties of the solutions and the differences with respect to the asymptotically flat case are discussed. The instability of the gravitating sphaleron solutions is also proven. |
1103.3149 | Adriano Contillo | Adriano Contillo | Inflation in asymptotically safe f(R) theory | Presented at 14th Conference on Recent Developments in Gravity: NEB
14, Ioannina, Greece, 8-11 Jun 2010 | J.Phys.Conf.Ser.283:012009,2011 | 10.1088/1742-6596/283/1/012009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the existence of inflationary solutions in a class of
renormalization group improved polynomial f(R) theories, which have been
studied recently in the context of the asymptotic safety scenario for quantum
gravity. These theories seem to possess a nontrivial ultraviolet fixed point,
where the dimensionful couplings scale according to their canonical
dimensionality. Assuming that the cutoff is proportional to the Hubble
parameter, we obtain modified Friedmann equations which admit both power law
and exponential solutions. We establish that for sufficiently high order
polynomial the solutions are reliable, in the sense that considering still
higher order polynomials is very unlikely to change the solution.
| [
{
"created": "Wed, 16 Mar 2011 11:32:46 GMT",
"version": "v1"
}
] | 2011-07-22 | [
[
"Contillo",
"Adriano",
""
]
] | We discuss the existence of inflationary solutions in a class of renormalization group improved polynomial f(R) theories, which have been studied recently in the context of the asymptotic safety scenario for quantum gravity. These theories seem to possess a nontrivial ultraviolet fixed point, where the dimensionful couplings scale according to their canonical dimensionality. Assuming that the cutoff is proportional to the Hubble parameter, we obtain modified Friedmann equations which admit both power law and exponential solutions. We establish that for sufficiently high order polynomial the solutions are reliable, in the sense that considering still higher order polynomials is very unlikely to change the solution. |
1707.06930 | Abhik Kumar Sanyal Dr. | Abhik Kumar Sanyal | Semiclassical gravity with a nonminimally coupled scalar field | 8, pages, 0 figures | International Journal of Modern Physics A, Vol. 10, No. 15,
2231-2240 (1995) | 10.1142/S0217751X9500108X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Semiclassical approximation to the Wheeler-DeWitt equation which corresponds
to gravity with a minimally coupled scalar field has been performed. To the
leading order, vacuum Einstein's equation along with the functional Schrodinger
equation for the matter field, propagating in the background of classical
curved space are obtained. The Schrodinger equation is solved for a quartic
potential. It is observed that the wave-functional admits the wormhole boundary
condition even for large negative values of the coupling constant epsilon. For
conformal coupling epsilon = 1/6, the Hawking-Page wormhole solution is
recovered.
| [
{
"created": "Fri, 21 Jul 2017 15:18:09 GMT",
"version": "v1"
}
] | 2017-07-26 | [
[
"Sanyal",
"Abhik Kumar",
""
]
] | Semiclassical approximation to the Wheeler-DeWitt equation which corresponds to gravity with a minimally coupled scalar field has been performed. To the leading order, vacuum Einstein's equation along with the functional Schrodinger equation for the matter field, propagating in the background of classical curved space are obtained. The Schrodinger equation is solved for a quartic potential. It is observed that the wave-functional admits the wormhole boundary condition even for large negative values of the coupling constant epsilon. For conformal coupling epsilon = 1/6, the Hawking-Page wormhole solution is recovered. |
gr-qc/0203067 | Mario La Camera | A. G. Agnese and M. La Camera | Traceless stress-energy and traversable wormholes | revtex4, 7 pages, 1 figure | Nuovo Cim.B117:647-652,2002 | null | null | gr-qc | null | A one-parameter family of static and spherically symmetric solutions to
Einstein equations with a traceless energy-momentum tensor is found. When the
nonzero parameter $\beta$ lies in the open interval $(0,1)$ one obtains
traversable Lorentzian wormholes. One also obtains naked singularities when
either $\beta < 0$ or $\beta > 1$ and the Schwarzschild black hole for $\beta =
1$.
| [
{
"created": "Wed, 20 Mar 2002 15:00:17 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Agnese",
"A. G.",
""
],
[
"La Camera",
"M.",
""
]
] | A one-parameter family of static and spherically symmetric solutions to Einstein equations with a traceless energy-momentum tensor is found. When the nonzero parameter $\beta$ lies in the open interval $(0,1)$ one obtains traversable Lorentzian wormholes. One also obtains naked singularities when either $\beta < 0$ or $\beta > 1$ and the Schwarzschild black hole for $\beta = 1$. |
1810.00003 | Liang Dai | Liang Dai, Shun-Sheng Li, Barak Zackay, Shude Mao, Youjun Lu | Detecting Lensing-Induced Diffraction in Astrophysical Gravitational
Waves | 14 pages including references; 8 figures; comments are welcome | Phys. Rev. D 98, 104029 (2018) | 10.1103/PhysRevD.98.104029 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted from compact binary coalescence can be subject to
wave diffraction if they are gravitationally lensed by an intervening mass
clump whose Schwarzschild timescale matches the wave period. Waves in the
ground-based frequency band $f\sim 10$--$10^3\,$Hz are sensitive to clumps with
masses $M_E \sim 10^2$--$10^3\,M_\odot$ enclosed within the impact parameter.
These can be the central parts of low mass $M_L \sim 10^3$--$10^6\,M_\odot$
dark matter halos, which are predicted in Cold Dark Matter scenarios but are
challenging to observe. Neglecting finely-tuned impact parameters, we focus on
lenses aligned generally on the Einstein scale for which multiple lensed images
may not form in the case of an extended lens. In this case, diffraction induces
amplitude and phase modulations whose sizes $\sim 10\%$--$20\%$ are small
enough so that standard matched filtering with unlensed waveforms do not
degrade, but are still detectable for events with high signal-to-noise ratio.
We develop and test an agnostic detection method based on dynamic programming,
which does not require a detailed model of the lensed waveforms. For
pseudo-Jaffe lenses aligned up to the Einstein radius, we demonstrate that a
pair of fully upgraded aLIGO/Virgo detectors can extract diffraction imprints
from binary black hole mergers out to $z_s \sim 0.2$--$0.3$. The prospect will
improve dramatically for a third-generation detector for which binary black
hole mergers out to $z_s \sim 2$--$4$ will all become valuable sources.
| [
{
"created": "Fri, 28 Sep 2018 18:00:00 GMT",
"version": "v1"
}
] | 2018-11-28 | [
[
"Dai",
"Liang",
""
],
[
"Li",
"Shun-Sheng",
""
],
[
"Zackay",
"Barak",
""
],
[
"Mao",
"Shude",
""
],
[
"Lu",
"Youjun",
""
]
] | Gravitational waves emitted from compact binary coalescence can be subject to wave diffraction if they are gravitationally lensed by an intervening mass clump whose Schwarzschild timescale matches the wave period. Waves in the ground-based frequency band $f\sim 10$--$10^3\,$Hz are sensitive to clumps with masses $M_E \sim 10^2$--$10^3\,M_\odot$ enclosed within the impact parameter. These can be the central parts of low mass $M_L \sim 10^3$--$10^6\,M_\odot$ dark matter halos, which are predicted in Cold Dark Matter scenarios but are challenging to observe. Neglecting finely-tuned impact parameters, we focus on lenses aligned generally on the Einstein scale for which multiple lensed images may not form in the case of an extended lens. In this case, diffraction induces amplitude and phase modulations whose sizes $\sim 10\%$--$20\%$ are small enough so that standard matched filtering with unlensed waveforms do not degrade, but are still detectable for events with high signal-to-noise ratio. We develop and test an agnostic detection method based on dynamic programming, which does not require a detailed model of the lensed waveforms. For pseudo-Jaffe lenses aligned up to the Einstein radius, we demonstrate that a pair of fully upgraded aLIGO/Virgo detectors can extract diffraction imprints from binary black hole mergers out to $z_s \sim 0.2$--$0.3$. The prospect will improve dramatically for a third-generation detector for which binary black hole mergers out to $z_s \sim 2$--$4$ will all become valuable sources. |
gr-qc/9802012 | Felix Finster | Felix Finster, Joel Smoller, and Shing-Tung Yau | Particle-Like Solutions of the Einstein-Dirac-Maxwell Equations | 7 pages, LaTeX, 3 PostScript figures (published version) | Phys.Lett.A259:431-436,1999 | 10.1016/S0375-9601(99)00457-0 | null | gr-qc hep-th | null | We consider the coupled Einstein-Dirac-Maxwell equations for a static,
spherically symmetric system of two fermions in a singlet spinor state.
Soliton-like solutions are constructed numerically. The stability and the
properties of the ground state solutions are discussed for different values of
the electromagnetic coupling constant. We find solutions even when the
electromagnetic coupling is so strong that the total interaction is repulsive
in the Newtonian limit. Our solutions are regular and well-behaved; this shows
that the combined electromagnetic and gravitational self-interaction of the
Dirac particles is finite.
| [
{
"created": "Tue, 3 Feb 1998 21:38:22 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Feb 1998 14:51:36 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Aug 1999 21:46:24 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Finster",
"Felix",
""
],
[
"Smoller",
"Joel",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | We consider the coupled Einstein-Dirac-Maxwell equations for a static, spherically symmetric system of two fermions in a singlet spinor state. Soliton-like solutions are constructed numerically. The stability and the properties of the ground state solutions are discussed for different values of the electromagnetic coupling constant. We find solutions even when the electromagnetic coupling is so strong that the total interaction is repulsive in the Newtonian limit. Our solutions are regular and well-behaved; this shows that the combined electromagnetic and gravitational self-interaction of the Dirac particles is finite. |
1110.3095 | Jose Wadih Maluf Dr. | J. W. Maluf and F. F. Faria | Conformally invariant teleparallel theories of gravity | 10 pages, no figures. We discuss the construction of the teleparallel
version of the Weyl Lagrangian | Phys. Rev. D 85, 027502 (2012) | 10.1103/PhysRevD.85.027502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the construction of conformal theories of gravity in the realm of
teleparallel theories. We first present a family of conformal theories which
are quadratic in the torsion tensor and are constructed out of the tetrad field
and of a scalar field. For a particular value of a coupling constant, and in
the gauge where the scalar field is restricted to assume a constant value, the
theory reduces to the teleparallel equivalent of general relativity, and the
tetrad field satisfies Einstein's equations. A second theory is formulated out
of the tetrad field only, and is not equivalent to the usual Weyl Lagrangian.
Therefore the latter is not the unique genuinely geometrical construction that
yields a conformally invariant action. The teleparallel framework allows more
possibilities for conformal theories of gravity.
| [
{
"created": "Thu, 13 Oct 2011 23:48:55 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Oct 2011 22:18:51 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Jan 2012 18:32:48 GMT",
"version": "v3"
}
] | 2012-01-19 | [
[
"Maluf",
"J. W.",
""
],
[
"Faria",
"F. F.",
""
]
] | We analyze the construction of conformal theories of gravity in the realm of teleparallel theories. We first present a family of conformal theories which are quadratic in the torsion tensor and are constructed out of the tetrad field and of a scalar field. For a particular value of a coupling constant, and in the gauge where the scalar field is restricted to assume a constant value, the theory reduces to the teleparallel equivalent of general relativity, and the tetrad field satisfies Einstein's equations. A second theory is formulated out of the tetrad field only, and is not equivalent to the usual Weyl Lagrangian. Therefore the latter is not the unique genuinely geometrical construction that yields a conformally invariant action. The teleparallel framework allows more possibilities for conformal theories of gravity. |
1611.05523 | Andrew J. S. Hamilton | Andrew J. S. Hamilton | A covariant Hamiltonian tetrad approach to numerical relativity | v1: 14 pages. v2: 15 pages. v3: 21 pages, extensive revision, added
discussion of WEBB formalism | Phys. Rev. D 96, 124027 (2017) | 10.1103/PhysRevD.96.124027 | Phys. Rev. D 96, 124027 (2017) | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Hamiltonian approach to the equations of general relativity is proposed
using the powerful mathematical language of multivector-valued differential
forms. In the approach, the gravitational coordinates are the 12 spatial
components of the line interval (the vierbein) including their antisymmetric
parts, and their 12 conjugate momenta. A feature of the proposed formalism is
that it allows Lorentz gauge freedoms to be imposed on the Lorentz connections
rather than on the vierbein, which may facilitate numerical integration in some
challenging problems. The 40 Hamilton's equations comprise 12 + 12 = 24
equations of motion, 10 constraint equations (first class constraints, which
must be arranged on the initial hypersurface of constant time, but which are
guaranteed thereafter by conservation laws), and 6 identities (second class
constraints). The 6 identities define a trace-free spatial tensor that is the
gravitational analog of the magnetic field of electromagnetism. If the
gravitational magnetic field is promoted to an independent field satisfying its
own equation of motion, then the system becomes the WEBB system, which is known
to be strongly hyperbolic. Some other approaches, including ADM, BSSN, WEBB,
and Loop Quantum Gravity, are translated into the language of
multivector-valued forms, bringing out their underlying mathematical structure.
| [
{
"created": "Thu, 17 Nov 2016 01:25:30 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Mar 2017 21:43:44 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Dec 2017 00:29:04 GMT",
"version": "v3"
}
] | 2017-12-27 | [
[
"Hamilton",
"Andrew J. S.",
""
]
] | A Hamiltonian approach to the equations of general relativity is proposed using the powerful mathematical language of multivector-valued differential forms. In the approach, the gravitational coordinates are the 12 spatial components of the line interval (the vierbein) including their antisymmetric parts, and their 12 conjugate momenta. A feature of the proposed formalism is that it allows Lorentz gauge freedoms to be imposed on the Lorentz connections rather than on the vierbein, which may facilitate numerical integration in some challenging problems. The 40 Hamilton's equations comprise 12 + 12 = 24 equations of motion, 10 constraint equations (first class constraints, which must be arranged on the initial hypersurface of constant time, but which are guaranteed thereafter by conservation laws), and 6 identities (second class constraints). The 6 identities define a trace-free spatial tensor that is the gravitational analog of the magnetic field of electromagnetism. If the gravitational magnetic field is promoted to an independent field satisfying its own equation of motion, then the system becomes the WEBB system, which is known to be strongly hyperbolic. Some other approaches, including ADM, BSSN, WEBB, and Loop Quantum Gravity, are translated into the language of multivector-valued forms, bringing out their underlying mathematical structure. |
2407.08777 | Andrew R. Liddle | Marina Cort\^es and Andrew R Liddle | Hawking evaporation and the Landauer Principle | 4 pages. Title modified, additional discussion and references | null | null | null | gr-qc cond-mat.stat-mech quant-ph | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We show that Hawking black-hole evaporation saturates the Landauer Principle
of information thermodynamics. Our result implies that information loss
experienced by a black hole during Hawking evaporation takes place as
efficiently as possible. We also extend the analysis to the case of Barrow
entropy as a phenomenological realization of a fractal event horizon, where the
Landauer Principle informs amongst different options for the black hole
temperature. To our knowledge, this work is the first identification of the two
results as expressions of the same process.
| [
{
"created": "Thu, 11 Jul 2024 18:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2024 17:14:32 GMT",
"version": "v2"
}
] | 2024-08-13 | [
[
"Cortês",
"Marina",
""
],
[
"Liddle",
"Andrew R",
""
]
] | We show that Hawking black-hole evaporation saturates the Landauer Principle of information thermodynamics. Our result implies that information loss experienced by a black hole during Hawking evaporation takes place as efficiently as possible. We also extend the analysis to the case of Barrow entropy as a phenomenological realization of a fractal event horizon, where the Landauer Principle informs amongst different options for the black hole temperature. To our knowledge, this work is the first identification of the two results as expressions of the same process. |
1711.07198 | Cosimo Bambi | Hrishikesh Chakrabarty, Carlos A. Benavides-Gallego, Cosimo Bambi,
Leonardo Modesto | Unattainable extended spacetime regions in conformal gravity | 1+10 pages, 2 figures. v2: refereed version | JHEP 1803:013,2018 | 10.1007/JHEP03(2018)013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Janis-Newman-Winicour metric is a solution of Einstein's gravity
minimally coupled to a real massless scalar field. The $\gamma$-metric is
instead a vacuum solution of Einstein's gravity. These spacetimes have no
horizon and possess a naked singularity at a finite value of the radial
coordinate, where curvature invariants diverge and the spacetimes are
geodetically incomplete. In this paper, we reconsider these solutions in the
framework of conformal gravity and we show that it is possible to solve the
spacetime singularities with a suitable choice of the conformal factor. Now
curvature invariants remain finite over the whole spacetime. Massive particles
never reach the previous singular surface and massless particles can never do
it with a finite value of their affine parameter. Our results support the
conjecture according to which conformal gravity can fix the singularity problem
that plagues Einstein's gravity.
| [
{
"created": "Mon, 20 Nov 2017 08:35:47 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Feb 2018 18:08:16 GMT",
"version": "v2"
}
] | 2018-03-08 | [
[
"Chakrabarty",
"Hrishikesh",
""
],
[
"Benavides-Gallego",
"Carlos A.",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Modesto",
"Leonardo",
""
]
] | The Janis-Newman-Winicour metric is a solution of Einstein's gravity minimally coupled to a real massless scalar field. The $\gamma$-metric is instead a vacuum solution of Einstein's gravity. These spacetimes have no horizon and possess a naked singularity at a finite value of the radial coordinate, where curvature invariants diverge and the spacetimes are geodetically incomplete. In this paper, we reconsider these solutions in the framework of conformal gravity and we show that it is possible to solve the spacetime singularities with a suitable choice of the conformal factor. Now curvature invariants remain finite over the whole spacetime. Massive particles never reach the previous singular surface and massless particles can never do it with a finite value of their affine parameter. Our results support the conjecture according to which conformal gravity can fix the singularity problem that plagues Einstein's gravity. |
2004.07396 | Filipe Mena | Jo\~ao L. Costa and Filipe C. Mena | Global solutions to the spherically symmetric Einstein-scalar field
system with a positive cosmological constant in Bondi coordinates | 25 pages, to appear in Journal of Hyperbolic Differential Equations | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a characteristic initial value problem, with initial data given
on a future null cone, for the Einstein (massless) scalar field system with a
positive cosmological constant, in Bondi coordinates. We prove that, for small
data, this system has a unique global classical solution which is causally
geodesically complete to the future and decays polynomially in radius and
exponentially in Bondi time, approaching the de Sitter solution.
| [
{
"created": "Wed, 15 Apr 2020 23:45:43 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Dec 2020 13:25:59 GMT",
"version": "v2"
}
] | 2020-12-29 | [
[
"Costa",
"João L.",
""
],
[
"Mena",
"Filipe C.",
""
]
] | We consider a characteristic initial value problem, with initial data given on a future null cone, for the Einstein (massless) scalar field system with a positive cosmological constant, in Bondi coordinates. We prove that, for small data, this system has a unique global classical solution which is causally geodesically complete to the future and decays polynomially in radius and exponentially in Bondi time, approaching the de Sitter solution. |
0902.3224 | Jonathan Ziprick | J. Ziprick, G. Kunstatter | Dynamical Singularity Resolution in Spherically Symmetric Black Hole
Formation | 10 pages, 5 figures | Phys.Rev.D80:024032,2009 | 10.1103/PhysRevD.80.024032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study numerically the effects of loop quantum gravity motivated
corrections on massless scalar field collapse in Painlev\'e-Gullstrand
coordinates. Near criticality, the system exhibits Choptuik scaling with the
added features of a mass gap and a new scaling relationship dependant upon the
quantum length scale. The quantum corrected collapse exhibits a radiation-like
phase which resolves the singularity: the black hole consists of a compact
region of space-time bounded by a single, smooth trapping horizon. The
"evaporation" is not complete but leaves behind an outward moving remnant.
| [
{
"created": "Wed, 18 Feb 2009 19:32:06 GMT",
"version": "v1"
}
] | 2009-08-11 | [
[
"Ziprick",
"J.",
""
],
[
"Kunstatter",
"G.",
""
]
] | We study numerically the effects of loop quantum gravity motivated corrections on massless scalar field collapse in Painlev\'e-Gullstrand coordinates. Near criticality, the system exhibits Choptuik scaling with the added features of a mass gap and a new scaling relationship dependant upon the quantum length scale. The quantum corrected collapse exhibits a radiation-like phase which resolves the singularity: the black hole consists of a compact region of space-time bounded by a single, smooth trapping horizon. The "evaporation" is not complete but leaves behind an outward moving remnant. |
2304.08012 | De-Cheng Zou | Meng-Yun Lai, De-Cheng Zou, Rui-Hong Yue and Yun Soo Myung | Nonlinearly scalarized rotating black holes in
Einstein-scalar-Gauss-Bonnet theory | 23 pages, 8 figures and 2 tables | Phys.Rev.D 108,084007(2023) | 10.1103/PhysRevD.108.084007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss a fully nonlinear mechanism for the formation of
scalarized rotating black holes in Einstein-scalar-Gauss-Bonnet gravity, where
Kerr black holes are linearly stable, but unstable against nonlinear scalar
perturbations. With the help of the pseudospectral method, we obtain a spectrum
of nonlinearly scalarized rotating black hole solutions with multiple
scalarized branches. Moreover, we investigate the thermodynamic properties of
nonlinearly scalarized rotating black holes and find the phase transition
between Kerr and these scalarized black holes.
| [
{
"created": "Mon, 17 Apr 2023 06:22:15 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Oct 2023 05:41:44 GMT",
"version": "v2"
}
] | 2023-10-09 | [
[
"Lai",
"Meng-Yun",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Yue",
"Rui-Hong",
""
],
[
"Myung",
"Yun Soo",
""
]
] | In this paper, we discuss a fully nonlinear mechanism for the formation of scalarized rotating black holes in Einstein-scalar-Gauss-Bonnet gravity, where Kerr black holes are linearly stable, but unstable against nonlinear scalar perturbations. With the help of the pseudospectral method, we obtain a spectrum of nonlinearly scalarized rotating black hole solutions with multiple scalarized branches. Moreover, we investigate the thermodynamic properties of nonlinearly scalarized rotating black holes and find the phase transition between Kerr and these scalarized black holes. |
1901.01031 | Rocco D'Agostino | Kuantay Boshkayev, Rocco D'Agostino, Orlando Luongo | Extended logotropic fluids as unified dark energy models | 6 pages, 3 figures | null | 10.1140/epjc/s10052-019-6854-9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We here study extended classes of logotropic fluids as \textit{unified dark
energy models}. Under the hypothesis of the Anton-Schmidt scenario, we consider
the universe obeying a single fluid whose pressure evolves through a
logarithmic equation of state. This result is in analogy with crystals under
isotropic stresses. Thus, we investigate thermodynamic and dynamical
consequences by integrating the speed of sound to obtain the pressure in terms
of the density, leading to an extended version of the Anton-Schmidt cosmic
fluids. Within this picture, we get significant outcomes expanding the
Anton-Schmidt pressure in the infrared regime. The low-energy case becomes
relevant for the universe to accelerate without any cosmological constant. We
therefore derive the effective representation of our fluid in terms of a
Lagrangian $\mathcal{L}=\mathcal{L}(X)$, depending on the kinetic term $X$
only. We analyze both the relativistic and non-relativistic limits. In the
non-relativistic limit we construct both the Hamiltonian and Lagrangian in
terms of density $\rho$ and scalar field $\vartheta$, whereas in the
relativistic case no analytical expression for the Lagrangian can be found.
Thus, we obtain the potential as a function of $\rho$, under the hypothesis of
irrotational perfect fluid. We demonstrate that the model represents a natural
generalization of \emph{logotropic dark energy models}. Finally, we analyze an
extended class of generalized Chaplygin gas models with one extra parameter
$\beta$. Interestingly, we find that the Lagrangians of this scenario and the
pure logotropic one coincide in the non-relativistic regime.
| [
{
"created": "Fri, 4 Jan 2019 09:42:41 GMT",
"version": "v1"
}
] | 2019-04-16 | [
[
"Boshkayev",
"Kuantay",
""
],
[
"D'Agostino",
"Rocco",
""
],
[
"Luongo",
"Orlando",
""
]
] | We here study extended classes of logotropic fluids as \textit{unified dark energy models}. Under the hypothesis of the Anton-Schmidt scenario, we consider the universe obeying a single fluid whose pressure evolves through a logarithmic equation of state. This result is in analogy with crystals under isotropic stresses. Thus, we investigate thermodynamic and dynamical consequences by integrating the speed of sound to obtain the pressure in terms of the density, leading to an extended version of the Anton-Schmidt cosmic fluids. Within this picture, we get significant outcomes expanding the Anton-Schmidt pressure in the infrared regime. The low-energy case becomes relevant for the universe to accelerate without any cosmological constant. We therefore derive the effective representation of our fluid in terms of a Lagrangian $\mathcal{L}=\mathcal{L}(X)$, depending on the kinetic term $X$ only. We analyze both the relativistic and non-relativistic limits. In the non-relativistic limit we construct both the Hamiltonian and Lagrangian in terms of density $\rho$ and scalar field $\vartheta$, whereas in the relativistic case no analytical expression for the Lagrangian can be found. Thus, we obtain the potential as a function of $\rho$, under the hypothesis of irrotational perfect fluid. We demonstrate that the model represents a natural generalization of \emph{logotropic dark energy models}. Finally, we analyze an extended class of generalized Chaplygin gas models with one extra parameter $\beta$. Interestingly, we find that the Lagrangians of this scenario and the pure logotropic one coincide in the non-relativistic regime. |
1311.1286 | Collin Capano | Collin Capano, Yi Pan, and Alessandra Buonanno | Impact of Higher Harmonics in Searching for Gravitational Waves from
Non-Spinning Binary Black Holes | 22 pages, 11 figures. Version approved by journal | Phys. Rev. D 89, 102003 (2014) | 10.1103/PhysRevD.89.102003 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current searches for gravitational waves from coalescing binary black holes
(BBH) use templates that only include the dominant harmonic. In this study we
use effective-one-body multipolar waveforms calibrated to numerical-relativity
simulations to quantify the effect of neglecting sub-dominant harmonics on the
sensitivity of searches. We consider both signal-to-noise ratio (SNR) and the
signal-based vetoes that are used to re-weight SNR. We find that neglecting
sub-dominant modes when searching for non-spinning BBHs with component masses
$3\,M_{\odot} \leq m_1, m_2 \leq 200\,M_{\odot}$ and total mass $M <
360\,M_{\odot}$ in advanced LIGO results in a negligible reduction of the
re-weighted SNR at detection thresholds. Sub-dominant modes therefore have no
effect on the detection rates predicted for advanced LIGO. Furthermore, we find
that if sub-dominant modes are included in templates the sensitivity of the
search becomes worse if we use current search priors, due to an increase in
false alarm probability. Templates would need to be weighted differently than
what is currently done to compensate for the increase in false alarms. If we
split the template bank such that sub-dominant modes are only used when $M
\gtrsim 100\,M_{\odot}$ and mass ratio $q \gtrsim 4$, we find that the
sensitivity does improve for these intermediate mass-ratio BBHs, but the
sensitive volume associated with these systems is still small compared to
equal-mass systems. Using sub-dominant modes is therefore unlikely to
substantially increase the probability of detecting gravitational waves from
non-spinning BBH signals unless there is a relatively large population of
intermediate mass-ratio BBHs in the universe.
| [
{
"created": "Wed, 6 Nov 2013 04:42:18 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Mar 2014 16:11:32 GMT",
"version": "v2"
}
] | 2014-05-28 | [
[
"Capano",
"Collin",
""
],
[
"Pan",
"Yi",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | Current searches for gravitational waves from coalescing binary black holes (BBH) use templates that only include the dominant harmonic. In this study we use effective-one-body multipolar waveforms calibrated to numerical-relativity simulations to quantify the effect of neglecting sub-dominant harmonics on the sensitivity of searches. We consider both signal-to-noise ratio (SNR) and the signal-based vetoes that are used to re-weight SNR. We find that neglecting sub-dominant modes when searching for non-spinning BBHs with component masses $3\,M_{\odot} \leq m_1, m_2 \leq 200\,M_{\odot}$ and total mass $M < 360\,M_{\odot}$ in advanced LIGO results in a negligible reduction of the re-weighted SNR at detection thresholds. Sub-dominant modes therefore have no effect on the detection rates predicted for advanced LIGO. Furthermore, we find that if sub-dominant modes are included in templates the sensitivity of the search becomes worse if we use current search priors, due to an increase in false alarm probability. Templates would need to be weighted differently than what is currently done to compensate for the increase in false alarms. If we split the template bank such that sub-dominant modes are only used when $M \gtrsim 100\,M_{\odot}$ and mass ratio $q \gtrsim 4$, we find that the sensitivity does improve for these intermediate mass-ratio BBHs, but the sensitive volume associated with these systems is still small compared to equal-mass systems. Using sub-dominant modes is therefore unlikely to substantially increase the probability of detecting gravitational waves from non-spinning BBH signals unless there is a relatively large population of intermediate mass-ratio BBHs in the universe. |
1303.0531 | Giampiero Esposito Dr. | Donato Bini, Giampiero Esposito, Claus Kiefer, Manuel Kraemer,
Francesco Pessina | On the modification of the cosmic microwave background anisotropy
spectrum from canonical quantum gravity | 13 pages, 7 figures. The presentation has been improved | Physical Review D87, 104008 (2013) | 10.1103/PhysRevD.87.104008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We evaluate the modifications to the cosmic microwave background anisotropy
spectrum that result from a semiclassical expansion of the Wheeler-DeWitt
equation. Recently, such an investigation in the case of a real scalar field
coupled to gravity, has led to the prediction that the power at large scales is
suppressed. We make here a more general analysis and show that there is an
ambiguity in the choice of solution to the equations describing the quantum
gravitational effects. Whereas one of the two solutions describes a suppression
of power, the other one describes an enhancement. We investigate possible
criteria for an appropriate choice of solution. The absolute value of the
correction term is in both cases of the same order and currently not
observable. We also obtain detailed formulae for arbitrary values of a complex
parameter occurring in the general solution of the nonlinear equations of the
model. We finally discuss the modification of the spectral index connected with
the power spectrum and comment on the possibility of a quantum-gravity induced
unitarity violation.
| [
{
"created": "Sun, 3 Mar 2013 17:11:56 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2013 06:08:50 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Bini",
"Donato",
""
],
[
"Esposito",
"Giampiero",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Kraemer",
"Manuel",
""
],
[
"Pessina",
"Francesco",
""
]
] | We evaluate the modifications to the cosmic microwave background anisotropy spectrum that result from a semiclassical expansion of the Wheeler-DeWitt equation. Recently, such an investigation in the case of a real scalar field coupled to gravity, has led to the prediction that the power at large scales is suppressed. We make here a more general analysis and show that there is an ambiguity in the choice of solution to the equations describing the quantum gravitational effects. Whereas one of the two solutions describes a suppression of power, the other one describes an enhancement. We investigate possible criteria for an appropriate choice of solution. The absolute value of the correction term is in both cases of the same order and currently not observable. We also obtain detailed formulae for arbitrary values of a complex parameter occurring in the general solution of the nonlinear equations of the model. We finally discuss the modification of the spectral index connected with the power spectrum and comment on the possibility of a quantum-gravity induced unitarity violation. |
2404.17798 | Patrick Das Gupta | Patrick Das Gupta | Torsion and Chern-Simons gravity in 4D space-times from a
Geometrodynamical four-form | To appear in the Proceedings of the Third Minkowski Meeting that was
held at Albena (Bulgaria) in September, 2023 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The space-time geometry in any inertial frame is described by the
line-element $ds^2= \eta_{\mu \nu} dx^\mu dx^\nu$. Now, not only the Minkowski
metric $\eta_{\mu \nu} $ is invariant under proper Lorentz transformations, the
totally antisymmetric Levi-Civita tensor $e_{\mu \nu \alpha \beta} $ too is. In
general relativity (GR), $\eta_{\mu \nu} $ of the flat space-time gets
generalized to a dynamical, space-time dependent metric tensor $ g_{\mu \nu} $
that characterizes a curved space-time geometry. In the present study, it is
put forward that the flat space-time Levi-Civita tensor gets elevated to a
dynamical four-form field $\tilde {w} $ in curved space-time manifolds, i.e.
$e_{\mu \nu \alpha \beta} \rightarrow w_{\mu \nu \alpha \beta} (x) = \phi (x) \
e_{\mu \nu \alpha \beta} $, so that $\tilde {w} = {1\over {4!}} \ w_{\mu \nu
\rho \sigma} \ \tilde{d} x^\mu \wedge \tilde{d} x^\nu \wedge \tilde{d} x^\rho
\wedge \tilde{d} x^\sigma$. It is shown that this geometrodynamical four-form
field extends GR by leading naturally to a torsion in the theory as well as to
a Chern-Simons gravity. It is demonstrated that the scalar-density $\phi (x)$
associated with $\tilde {w} $ may be used to construct a generalized exterior
derivative that converts a p-form density to a (p+1)-form density of identical
weight.
It is argued that the scalar-density $\phi (x)$ associated with $\tilde {w}$
corresponds to an axion-like pseudo-scalar field in the Minkowski space-time,
and that it can also masquerade as dark matter. Thereafter, we provide a simple
semi-classical analysis in which a self-gravitating Bose-Einstein condensate of
such ultra-light pseudo-scalars leads to the formation of a supermassive black
hole. A brief analysis of propagation of weak gravitational waves in the
presence of $\tilde{w} $ is also considered in this article.
| [
{
"created": "Sat, 27 Apr 2024 06:36:04 GMT",
"version": "v1"
},
{
"created": "Wed, 8 May 2024 06:45:34 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jul 2024 06:16:10 GMT",
"version": "v3"
}
] | 2024-07-08 | [
[
"Gupta",
"Patrick Das",
""
]
] | The space-time geometry in any inertial frame is described by the line-element $ds^2= \eta_{\mu \nu} dx^\mu dx^\nu$. Now, not only the Minkowski metric $\eta_{\mu \nu} $ is invariant under proper Lorentz transformations, the totally antisymmetric Levi-Civita tensor $e_{\mu \nu \alpha \beta} $ too is. In general relativity (GR), $\eta_{\mu \nu} $ of the flat space-time gets generalized to a dynamical, space-time dependent metric tensor $ g_{\mu \nu} $ that characterizes a curved space-time geometry. In the present study, it is put forward that the flat space-time Levi-Civita tensor gets elevated to a dynamical four-form field $\tilde {w} $ in curved space-time manifolds, i.e. $e_{\mu \nu \alpha \beta} \rightarrow w_{\mu \nu \alpha \beta} (x) = \phi (x) \ e_{\mu \nu \alpha \beta} $, so that $\tilde {w} = {1\over {4!}} \ w_{\mu \nu \rho \sigma} \ \tilde{d} x^\mu \wedge \tilde{d} x^\nu \wedge \tilde{d} x^\rho \wedge \tilde{d} x^\sigma$. It is shown that this geometrodynamical four-form field extends GR by leading naturally to a torsion in the theory as well as to a Chern-Simons gravity. It is demonstrated that the scalar-density $\phi (x)$ associated with $\tilde {w} $ may be used to construct a generalized exterior derivative that converts a p-form density to a (p+1)-form density of identical weight. It is argued that the scalar-density $\phi (x)$ associated with $\tilde {w}$ corresponds to an axion-like pseudo-scalar field in the Minkowski space-time, and that it can also masquerade as dark matter. Thereafter, we provide a simple semi-classical analysis in which a self-gravitating Bose-Einstein condensate of such ultra-light pseudo-scalars leads to the formation of a supermassive black hole. A brief analysis of propagation of weak gravitational waves in the presence of $\tilde{w} $ is also considered in this article. |
2004.12970 | Rahul Kumar | Rahul Kumar, Shafqat Ul Islam, and Sushant G. Ghosh | Gravitational lensing by charged black hole in regularized $4D$
Einstein-Gauss-Bonnet gravity | 13 pages, 10 figures, and 1 table. Typos corrected and minor changes
made. Version accepted in EPJC | null | 10.1140/epjc/s10052-020-08606-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among the higher curvature gravities, the most extensively studied theory is
the so-called Einstein-Gauss-Bonnet (EGB) gravity, whose Lagrangian contains
Einstein term with the GB combination of quadratic curvature terms, and the GB
term yields nontrivial gravitational dynamics in $ D\geq5$. Recently there has
been a surge of interest in regularizing, a $ D \to 4 $ limit of, the EGB
gravity, and the resulting regularized $4D$ EGB gravity valid in $4D$. We
consider gravitational lensing by Charged black holes in the $4D$ EGB gravity
theory to calculate the light deflection coefficients in strong-field limits
$\bar{a}$ and $\bar{b}$, while the former increases with increasing GB
parameter $\alpha$ and charge $q$, later decrease. We also find a decrease in
the deflection angle $\alpha_D$, angular position $\theta_{\infty}$ decreases
more slowly and impact parameter for photon orbits $u_{m}$ more quickly, but
angular separation $s$ increases more rapidly with $\alpha$ and charge $q$. We
compare our results with those for analogous black holes in General Relativity
(GR) and also the formalism is applied to discuss the astrophysical
consequences in the case of the supermassive black holes Sgr A* and M87*.
| [
{
"created": "Mon, 27 Apr 2020 17:24:24 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Oct 2020 11:30:37 GMT",
"version": "v2"
}
] | 2020-12-30 | [
[
"Kumar",
"Rahul",
""
],
[
"Islam",
"Shafqat Ul",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | Among the higher curvature gravities, the most extensively studied theory is the so-called Einstein-Gauss-Bonnet (EGB) gravity, whose Lagrangian contains Einstein term with the GB combination of quadratic curvature terms, and the GB term yields nontrivial gravitational dynamics in $ D\geq5$. Recently there has been a surge of interest in regularizing, a $ D \to 4 $ limit of, the EGB gravity, and the resulting regularized $4D$ EGB gravity valid in $4D$. We consider gravitational lensing by Charged black holes in the $4D$ EGB gravity theory to calculate the light deflection coefficients in strong-field limits $\bar{a}$ and $\bar{b}$, while the former increases with increasing GB parameter $\alpha$ and charge $q$, later decrease. We also find a decrease in the deflection angle $\alpha_D$, angular position $\theta_{\infty}$ decreases more slowly and impact parameter for photon orbits $u_{m}$ more quickly, but angular separation $s$ increases more rapidly with $\alpha$ and charge $q$. We compare our results with those for analogous black holes in General Relativity (GR) and also the formalism is applied to discuss the astrophysical consequences in the case of the supermassive black holes Sgr A* and M87*. |
2201.01939 | Brett McInnes | Brett McInnes | Planar Black Holes as a Route to Understanding the Weak Gravity
Conjecture | Non-dependence of results on energy conditions stressed; 18 pages, no
figures; version appearing in NPB | Nuclear Physics B Volume 983 (2022) 115933 Volume 983, October
2022, 115933 | 10.1016/j.nuclphysb.2022.115933 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One version of the Weak Gravity Conjecture requires that it should be
possible for an extremal black hole to emit a smaller black hole: that is, the
original black hole bifurcates. For asymptotically flat and asymptotically AdS
Reissner-Nordstr\"{o}m black holes with spherical event horizons, such a
bifurcation reduces the total classical entropy of the system, and so it is
apparently forbidden by the second law of thermodynamics. It may well be
possible to remedy this by taking other (for example, quantum-gravitational)
effects into account, but it is difficult to understand this in a quantitative
way. In the case of asymptotically AdS Reissner-Nordstr\"{o}m black holes with
\emph{planar} event horizons, however, one can show that bifurcations are
definitely compatible with the second law. (Naked singularities, generated by
the bifurcation, may play an important role here.) Furthermore, in this case
one can exhibit a detailed mechanism explaining precisely why planar black
holes must indeed be unstable (through emission of branes) when they are
sufficiently close to extremality. Thus planar black holes can improve our
understanding of the WGC.
| [
{
"created": "Thu, 6 Jan 2022 06:51:33 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2022 07:56:42 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Aug 2022 05:32:51 GMT",
"version": "v3"
}
] | 2022-08-31 | [
[
"McInnes",
"Brett",
""
]
] | One version of the Weak Gravity Conjecture requires that it should be possible for an extremal black hole to emit a smaller black hole: that is, the original black hole bifurcates. For asymptotically flat and asymptotically AdS Reissner-Nordstr\"{o}m black holes with spherical event horizons, such a bifurcation reduces the total classical entropy of the system, and so it is apparently forbidden by the second law of thermodynamics. It may well be possible to remedy this by taking other (for example, quantum-gravitational) effects into account, but it is difficult to understand this in a quantitative way. In the case of asymptotically AdS Reissner-Nordstr\"{o}m black holes with \emph{planar} event horizons, however, one can show that bifurcations are definitely compatible with the second law. (Naked singularities, generated by the bifurcation, may play an important role here.) Furthermore, in this case one can exhibit a detailed mechanism explaining precisely why planar black holes must indeed be unstable (through emission of branes) when they are sufficiently close to extremality. Thus planar black holes can improve our understanding of the WGC. |
gr-qc/0306031 | Eugene J. Surowitz | E. L. Schucking, E. J. Surowitz, J. Zhao | A Diagram for Bianchi A-Types | 15 Latex pages, 3 encapsulated postscript figures, GRG in print | Gen.Rel.Grav. vol.35 #9 (2003) 1521-1530 | 10.1023/A:1025757215254 | null | gr-qc | null | A diagram for Bianchi spaces with vanishing vector of structure constants
(type A in the Ellis-MacCallum classification) illustrates the relations among
their different types under similarity transformations. The Ricci coefficients
and the Ricci tensor are related by a Cremona transformation.
| [
{
"created": "Mon, 9 Jun 2003 19:18:10 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jun 2003 20:02:16 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Schucking",
"E. L.",
""
],
[
"Surowitz",
"E. J.",
""
],
[
"Zhao",
"J.",
""
]
] | A diagram for Bianchi spaces with vanishing vector of structure constants (type A in the Ellis-MacCallum classification) illustrates the relations among their different types under similarity transformations. The Ricci coefficients and the Ricci tensor are related by a Cremona transformation. |
1603.07864 | Farhad Darabi | F. Darabi, F. Felegary, M. R. Setare | Cosmological Dynamics of Interacting Logarithmic Entropy Corrected
Holographic Dark Energy Model | 8 pages, Published online, Int. J. Mod. Phys. D (2016) | Int. J. Mod. Phys. D, 1650104 (2016) | 10.1142/S0218271816501042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological dynamics of interacting Logarithmic Entropy
Corrected Holographic Dark Energy model with Cold Dark Matter. Fixed points are
determined and their corresponding cosmological models are presented. Moreover,
the dynamical properties of these fixed points are derived.
| [
{
"created": "Fri, 25 Mar 2016 10:01:20 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Aug 2016 10:27:22 GMT",
"version": "v2"
}
] | 2016-09-27 | [
[
"Darabi",
"F.",
""
],
[
"Felegary",
"F.",
""
],
[
"Setare",
"M. R.",
""
]
] | We investigate the cosmological dynamics of interacting Logarithmic Entropy Corrected Holographic Dark Energy model with Cold Dark Matter. Fixed points are determined and their corresponding cosmological models are presented. Moreover, the dynamical properties of these fixed points are derived. |
1409.0809 | Pierre-Andr\'e Mandrin Ph.D. | Pierre A. Mandrin | An improved derivation of minimum information quantum gravity | 21 pages. v2: more details in the proof of the space-time structure;
text improved; some parts transfered to appendix, added by summaries of some
previously published concepts, a few formulations more comprehensive.
Prepared for submission to Annals of Physics. v3: Minor revision (boundary
law: "non-thin-layers", clean notation; Legendre transf.: tetrad bath; proof
local trivializ. on subsystems) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Minimum information quantum gravity (MIQG) is a theory of quantum gravity
which requires no explicit microscopic quantum structure. In this article, it
is shown that the MIQG action can be derived using a more elegant and
straight-forward method than in the first existence proof. The required
assumptions are dramatically reduced. In particular, former assumptions
referring to the existence of quantum boxes, the exact differential of the
entropy variation and the role of the boundary can be omitted. Moreover, the
open problem of the quantum occupation number per box is solved. Thus, the
arguments in favour of MIQG become even more stringent. The remaining
assumptions are 1. the principle of optimisation of the resulting per imposed
degrees of freedom, 2. abstract quantum number conservation, 3. the validity of
the laws of thermodynamics, 4. identification of a macroscopic parameterisation
with space-time and 5. unspecific interactions. Although the requirements are
reduced, all former results remain valid. In particular, all well established
physics as special cases (Quantum Field Theory, QFT, and General Relativity,
GR) follow and all measurable quantities may be computed.
| [
{
"created": "Tue, 2 Sep 2014 18:07:50 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Oct 2014 15:04:53 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Jan 2015 20:07:39 GMT",
"version": "v3"
}
] | 2015-01-05 | [
[
"Mandrin",
"Pierre A.",
""
]
] | Minimum information quantum gravity (MIQG) is a theory of quantum gravity which requires no explicit microscopic quantum structure. In this article, it is shown that the MIQG action can be derived using a more elegant and straight-forward method than in the first existence proof. The required assumptions are dramatically reduced. In particular, former assumptions referring to the existence of quantum boxes, the exact differential of the entropy variation and the role of the boundary can be omitted. Moreover, the open problem of the quantum occupation number per box is solved. Thus, the arguments in favour of MIQG become even more stringent. The remaining assumptions are 1. the principle of optimisation of the resulting per imposed degrees of freedom, 2. abstract quantum number conservation, 3. the validity of the laws of thermodynamics, 4. identification of a macroscopic parameterisation with space-time and 5. unspecific interactions. Although the requirements are reduced, all former results remain valid. In particular, all well established physics as special cases (Quantum Field Theory, QFT, and General Relativity, GR) follow and all measurable quantities may be computed. |
1103.5183 | Kentaro Tanabe | Kentaro Tanabe, Tetsuya Shiromizu | Asymptotic structure at timelike infinity: higher orders | 19 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bearing the final fate of gravitational collapse in mind, we study the
asymptotic structures at timelike infinity in four dimensions. Assuming that
spacetimes are asymptotically stationary, we will examine the asymptotic
structure of asymptotic stationary spacetimes in a systematic way. Then we see
that the asymptotic stationarity strongly restricts the asymptotic structure at
timelike infinity. We also observe that the resulted asymptotic form of the
metric have the deviation from the Kerr black hole spacetime without assuming
of the presence of some additional asymptotic symmetries.
| [
{
"created": "Sun, 27 Mar 2011 04:43:36 GMT",
"version": "v1"
}
] | 2011-03-29 | [
[
"Tanabe",
"Kentaro",
""
],
[
"Shiromizu",
"Tetsuya",
""
]
] | Bearing the final fate of gravitational collapse in mind, we study the asymptotic structures at timelike infinity in four dimensions. Assuming that spacetimes are asymptotically stationary, we will examine the asymptotic structure of asymptotic stationary spacetimes in a systematic way. Then we see that the asymptotic stationarity strongly restricts the asymptotic structure at timelike infinity. We also observe that the resulted asymptotic form of the metric have the deviation from the Kerr black hole spacetime without assuming of the presence of some additional asymptotic symmetries. |
1106.2278 | Evan Halstead | Evan Halstead and Peng Hao | Time Evolution of Temperature and Entropy of a Gravitationally
Collapsing Cylinder | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the time evolution of the temperature and entropy of a
gravitationally collapsing cylinder, represented by an infinitely thin domain
wall, as seen by an asymptotic observer. Previous work has shown that the
entropy of a spherically symmetric collapsing domain approaches a constant, and
we follow this procedure using a (3+1) BTZ metric to see if a different
topology will yield different results. We do this by coupling a scalar field to
the background of the domain wall and analyzing the spectrum of radiation as a
function of time. We find that the spectrum is quasi-thermal, with the degree
of thermality increasing as the domain wall approaches the horizon. The thermal
distribution allows for the determination of the temperature as a function of
time, and we find that the late time temperature is very close to the Hawking
temperature and that it also exhibits the proper scaling with the mass. From
the temperature we find the entropy. Since the collapsing domain wall is what
forms a black hole, we can compare the results to those of the standard
entropy-area relation. We find that the entropy does in fact approach a
constant that is close to the Hawking entropy. However, the time dependence of
the entropy shows that the entropy decreases with time, indicating that a (3+1)
BTZ domain wall will not collapse spontaneously.
| [
{
"created": "Sun, 12 Jun 2011 05:26:25 GMT",
"version": "v1"
}
] | 2011-06-14 | [
[
"Halstead",
"Evan",
""
],
[
"Hao",
"Peng",
""
]
] | We investigate the time evolution of the temperature and entropy of a gravitationally collapsing cylinder, represented by an infinitely thin domain wall, as seen by an asymptotic observer. Previous work has shown that the entropy of a spherically symmetric collapsing domain approaches a constant, and we follow this procedure using a (3+1) BTZ metric to see if a different topology will yield different results. We do this by coupling a scalar field to the background of the domain wall and analyzing the spectrum of radiation as a function of time. We find that the spectrum is quasi-thermal, with the degree of thermality increasing as the domain wall approaches the horizon. The thermal distribution allows for the determination of the temperature as a function of time, and we find that the late time temperature is very close to the Hawking temperature and that it also exhibits the proper scaling with the mass. From the temperature we find the entropy. Since the collapsing domain wall is what forms a black hole, we can compare the results to those of the standard entropy-area relation. We find that the entropy does in fact approach a constant that is close to the Hawking entropy. However, the time dependence of the entropy shows that the entropy decreases with time, indicating that a (3+1) BTZ domain wall will not collapse spontaneously. |
2301.02722 | Gabriel S\'anchez-P\'erez | Marc Mars and Gabriel S\'anchez-P\'erez | Covariant definition of Double Null Data and geometric uniqueness of the
characteristic initial value problem | 36 pages, 1 figure | Journal of Physics A: Mathematical and Theoretical, Volume 56,
Number 25, 2023 | 10.1088/1751-8121/acd312 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characteristic Cauchy problem of the Einstein field equations has been
recently addressed from a completely abstract viewpoint by means of
hypersurface data and, in particular, via the notion of double null data.
However, this definition was given in a partially gauge-fixed form. In this
paper we generalize the notion of double null data in a fully diffeomorphism
and gauge covariant way, and show that the definition is complete by proving
that no extra conditions are needed to embed the double null data in some
spacetime. The second aim of the paper is to show that the characteristic
Cauchy problem satisfies a geometric uniqueness property. Specifically, we
introduce a natural notion of isometry at the abstract level such that two
double null data that are isometric in this sense give rise to isometric
spacetimes.
| [
{
"created": "Fri, 6 Jan 2023 21:40:10 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2023 11:45:36 GMT",
"version": "v2"
}
] | 2023-05-31 | [
[
"Mars",
"Marc",
""
],
[
"Sánchez-Pérez",
"Gabriel",
""
]
] | The characteristic Cauchy problem of the Einstein field equations has been recently addressed from a completely abstract viewpoint by means of hypersurface data and, in particular, via the notion of double null data. However, this definition was given in a partially gauge-fixed form. In this paper we generalize the notion of double null data in a fully diffeomorphism and gauge covariant way, and show that the definition is complete by proving that no extra conditions are needed to embed the double null data in some spacetime. The second aim of the paper is to show that the characteristic Cauchy problem satisfies a geometric uniqueness property. Specifically, we introduce a natural notion of isometry at the abstract level such that two double null data that are isometric in this sense give rise to isometric spacetimes. |
0906.3751 | Tomasz Pawlowski | Mercedes Martin-Benito, Guillermo A. Mena Marugan, Tomasz Pawlowski | Physical evolution in Loop Quantum Cosmology: The example of vacuum
Bianchi I | RevTex4, 22 pages, 4 figures | Phys.Rev.D80:084038,2009 | 10.1103/PhysRevD.80.084038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the vacuum Bianchi I model as an example to investigate the concept of
physical evolution in Loop Quantum Cosmology (LQC) in the absence of the
massless scalar field which has been used so far in the literature as an
internal time. In order to retrieve the system dynamics when no such a suitable
clock field is present, we explore different constructions of families of
unitarily related partial observables. These observables are parameterized,
respectively, by: (i) one of the components of the densitized triad, and (ii)
its conjugate momentum; each of them playing the role of an evolution
parameter. Exploiting the properties of the considered example, we investigate
in detail the domains of applicability of each construction. In both cases the
observables possess a neat physical interpretation only in an approximate
sense. However, whereas in case (i) such interpretation is reasonably accurate
only for a portion of the evolution of the universe, in case (ii) it remains so
during all the evolution (at least in the physically interesting cases). The
constructed families of observables are next used to describe the evolution of
the Bianchi I universe. The performed analysis confirms the robustness of the
bounces, also in absence of matter fields, as well as the preservation of the
semiclassicality through them. The concept of evolution studied here and the
presented construction of observables are applicable to a wide class of models
in LQC, including quantizations of the Bianchi I model obtained with other
prescriptions for the improved dynamics.
| [
{
"created": "Mon, 22 Jun 2009 16:03:35 GMT",
"version": "v1"
}
] | 2009-11-05 | [
[
"Martin-Benito",
"Mercedes",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | We use the vacuum Bianchi I model as an example to investigate the concept of physical evolution in Loop Quantum Cosmology (LQC) in the absence of the massless scalar field which has been used so far in the literature as an internal time. In order to retrieve the system dynamics when no such a suitable clock field is present, we explore different constructions of families of unitarily related partial observables. These observables are parameterized, respectively, by: (i) one of the components of the densitized triad, and (ii) its conjugate momentum; each of them playing the role of an evolution parameter. Exploiting the properties of the considered example, we investigate in detail the domains of applicability of each construction. In both cases the observables possess a neat physical interpretation only in an approximate sense. However, whereas in case (i) such interpretation is reasonably accurate only for a portion of the evolution of the universe, in case (ii) it remains so during all the evolution (at least in the physically interesting cases). The constructed families of observables are next used to describe the evolution of the Bianchi I universe. The performed analysis confirms the robustness of the bounces, also in absence of matter fields, as well as the preservation of the semiclassicality through them. The concept of evolution studied here and the presented construction of observables are applicable to a wide class of models in LQC, including quantizations of the Bianchi I model obtained with other prescriptions for the improved dynamics. |
2004.07420 | Jens Boos | Jens Boos, Jose Pinedo Soto, Valeri P. Frolov | Ultrarelativistic spinning objects in non-local ghost-free gravity | v2: 13 pages, 2 figures, matches published version, title changed
slightly and references added; v1: 13 pages, 2 figures, computer algebra code
available at http://spintwo.net/static/2020.04.14/ | Phys. Rev. D 101, 124065 (2020) | 10.1103/PhysRevD.101.124065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravitational field of ultrarelativistic spinning objects
(gyratons) in a modified gravity theory with higher derivatives. In particular,
we focus on a special class of such theories with an infinite number of
derivatives known as "ghost-free gravity" that include a non-local form factor
such as $\exp(-\Box\ell^2)$, where $\ell$ is the scale of non-locality. First,
we obtain solutions of the linearized ghost-free equations for stationary
spinning objects. To obtain gyraton solutions we boost these metrics and take
their Penrose limit. This approach allows us to perform calculations for any
number of spacetime dimensions. All solutions are regular at the gyraton axis.
In four dimensions, when the scale non-locality $\ell$ tends to zero, the
obtained gyraton solutions correctly reproduce the Aichelburg--Sexl metric and
its generalization to spinning sources found earlier by Bonnor. We also study
the properties of the obtained four-dimensional and higher-dimensional
ghost-free gyraton metrics and briefly discuss their possible applications.
| [
{
"created": "Thu, 16 Apr 2020 02:12:36 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jun 2020 15:12:51 GMT",
"version": "v2"
}
] | 2020-07-08 | [
[
"Boos",
"Jens",
""
],
[
"Soto",
"Jose Pinedo",
""
],
[
"Frolov",
"Valeri P.",
""
]
] | We study the gravitational field of ultrarelativistic spinning objects (gyratons) in a modified gravity theory with higher derivatives. In particular, we focus on a special class of such theories with an infinite number of derivatives known as "ghost-free gravity" that include a non-local form factor such as $\exp(-\Box\ell^2)$, where $\ell$ is the scale of non-locality. First, we obtain solutions of the linearized ghost-free equations for stationary spinning objects. To obtain gyraton solutions we boost these metrics and take their Penrose limit. This approach allows us to perform calculations for any number of spacetime dimensions. All solutions are regular at the gyraton axis. In four dimensions, when the scale non-locality $\ell$ tends to zero, the obtained gyraton solutions correctly reproduce the Aichelburg--Sexl metric and its generalization to spinning sources found earlier by Bonnor. We also study the properties of the obtained four-dimensional and higher-dimensional ghost-free gyraton metrics and briefly discuss their possible applications. |
gr-qc/0504091 | Suresh Maran k | Suresh K Maran | The Area Metric Reality Constraint in Classical General Relativity | The title has been changed. A new section on the simplicial
discretization of the area metric reality constraint and GR actions has been
introduced. Certain errors in field equations has been corrected. English has
been improved, sections edited and reorganized | null | null | null | gr-qc | null | A classical foundation for an idea of reality condition in the context of
spin foams (Barrett-Crane models) is developed. I extract classical real
general relativity (all signatures) from complex general relativity by imposing
the area metric reality constraint; the area metric is real iff a
non-degenerate metric is real or imaginary. First I review the Plebanski theory
of complex general relativity starting from a complex vectorial action. Then I
modify the theory by adding a Lagrange multiplier to impose the area metric
reality condition and derive classical real general relativity. I investigate
two types of action: Complex and Real. All the non-trivial solutions of the
field equations of the theory with the complex action correspond to real
general relativity. Half the non-trivial solutions of the field equations of
the theory with the real action correspond to real general relativity.
Discretization of the area metric reality constraint in the context of
Barrett-Crane theory is discussed. In the context of Barrett-Crane theory the
area metric reality condition is equivalent to the condition that the scalar
products of the bivectors associated to the triangles of a four simplex be
real. The Plebanski formalism for the degenerate case and Palatini formalism
are also briefly discussed by including the area metric reality condition.
| [
{
"created": "Wed, 20 Apr 2005 19:32:15 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2005 19:25:51 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Sep 2005 18:44:43 GMT",
"version": "v3"
},
{
"created": "Sun, 25 Sep 2005 21:48:15 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Maran",
"Suresh K",
""
]
] | A classical foundation for an idea of reality condition in the context of spin foams (Barrett-Crane models) is developed. I extract classical real general relativity (all signatures) from complex general relativity by imposing the area metric reality constraint; the area metric is real iff a non-degenerate metric is real or imaginary. First I review the Plebanski theory of complex general relativity starting from a complex vectorial action. Then I modify the theory by adding a Lagrange multiplier to impose the area metric reality condition and derive classical real general relativity. I investigate two types of action: Complex and Real. All the non-trivial solutions of the field equations of the theory with the complex action correspond to real general relativity. Half the non-trivial solutions of the field equations of the theory with the real action correspond to real general relativity. Discretization of the area metric reality constraint in the context of Barrett-Crane theory is discussed. In the context of Barrett-Crane theory the area metric reality condition is equivalent to the condition that the scalar products of the bivectors associated to the triangles of a four simplex be real. The Plebanski formalism for the degenerate case and Palatini formalism are also briefly discussed by including the area metric reality condition. |
2011.05145 | Varun Behera | Varun Nagesh Jolly Behera, Anik Kumar Samanta, Aurobinda Routray | Frequency Estimation of Gravitational Waves from a Binary Black Hole
Merger | arXiv admin note: text overlap with arXiv:1609.05933,
arXiv:1810.00040 by other authors | null | null | null | gr-qc astro-ph.HE physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a collection of literature reviews and some initial work on the
estimation of the frequency of gravitational waves from a binary black hole
merger for low SNR. This document provides a starting point, with a broad
overview of the prerequisites required for the follow-up work on frequency
estimation.
| [
{
"created": "Mon, 9 Nov 2020 05:59:01 GMT",
"version": "v1"
}
] | 2020-11-11 | [
[
"Behera",
"Varun Nagesh Jolly",
""
],
[
"Samanta",
"Anik Kumar",
""
],
[
"Routray",
"Aurobinda",
""
]
] | This is a collection of literature reviews and some initial work on the estimation of the frequency of gravitational waves from a binary black hole merger for low SNR. This document provides a starting point, with a broad overview of the prerequisites required for the follow-up work on frequency estimation. |
2004.04700 | R Loll | N. Klitgaard, R. Loll, Marcus Reitz and Reiko Toriumi | Geometric flux formula for the gravitational Wilson loop | 36 pages, 5 figures; minor text changes, clarifying the role of
diffeomorphism invariance; agrees with published version | Classical and Quantum Gravity (2020) | 10.1088/1361-6382/abb874 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finding diffeomorphism-invariant observables to characterize the properties
of gravity and spacetime at the Planck scale is essential for making progress
in quantum gravity. The holonomy and Wilson loop of the Levi-Civita connection
are potentially interesting ingredients in the construction of quantum
curvature observables. Motivated by recent developments in nonperturbative
quantum gravity, we establish new relations in three and four dimensions
between the holonomy of a finite loop and certain curvature integrals over the
surface spanned by the loop. They are much simpler than a gravitational version
of the nonabelian Stokes' theorem, but require the presence of totally geodesic
surfaces in the manifold, which follows from the existence of suitable Killing
vectors. We show that the relations are invariant under smooth surface
deformations, due to the presence of a conserved geometric flux.
| [
{
"created": "Thu, 9 Apr 2020 17:28:58 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 2020 11:32:41 GMT",
"version": "v2"
}
] | 2020-09-24 | [
[
"Klitgaard",
"N.",
""
],
[
"Loll",
"R.",
""
],
[
"Reitz",
"Marcus",
""
],
[
"Toriumi",
"Reiko",
""
]
] | Finding diffeomorphism-invariant observables to characterize the properties of gravity and spacetime at the Planck scale is essential for making progress in quantum gravity. The holonomy and Wilson loop of the Levi-Civita connection are potentially interesting ingredients in the construction of quantum curvature observables. Motivated by recent developments in nonperturbative quantum gravity, we establish new relations in three and four dimensions between the holonomy of a finite loop and certain curvature integrals over the surface spanned by the loop. They are much simpler than a gravitational version of the nonabelian Stokes' theorem, but require the presence of totally geodesic surfaces in the manifold, which follows from the existence of suitable Killing vectors. We show that the relations are invariant under smooth surface deformations, due to the presence of a conserved geometric flux. |
0907.4851 | Dr. Anirudh Pradhan | Anirudh Pradhan, Shyam Sundar Kumhar, Padmini Yadav and Kanti Jotania | A New Class of LRS Bianchi Type ${\rm VI}_{0}$ Universes with Free
Gravitational Field and Decaying Vacuum Energy Density | 16 pages, 9 figures, minor corrections in figures. arXiv admin note:
text overlap with arXiv:gr-qc/0010016 by other author | Int. J. Math. Eng. Sci. (IJMES), 1:74-89, 2012 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new class of LRS Bianchi type ${\rm VI}_{0}$ cosmological models with free
gravitational fields and a variable cosmological term is investigated in
presence of perfect fluid as well as bulk viscous fluid. To get the
deterministic solution we have imposed the two different conditions over the
free gravitational fields. In first case we consider the free gravitational
field as magnetic type whereas in second case `gravitational wrench' of unit
`pitch" is supposed to be present in free gravitational field. The viscosity
coefficient of bulk viscous fluid is assumed to be a power function of mass
density. The cosmological constant $\Lambda$ is found to be a decreasing
function of time and positive which is corroborated by results from recent
supernovae Ia observations. The physical and geometric aspects of the models
are discussed.
| [
{
"created": "Tue, 28 Jul 2009 07:33:36 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2012 13:09:32 GMT",
"version": "v2"
}
] | 2012-04-13 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Kumhar",
"Shyam Sundar",
""
],
[
"Yadav",
"Padmini",
""
],
[
"Jotania",
"Kanti",
""
]
] | A new class of LRS Bianchi type ${\rm VI}_{0}$ cosmological models with free gravitational fields and a variable cosmological term is investigated in presence of perfect fluid as well as bulk viscous fluid. To get the deterministic solution we have imposed the two different conditions over the free gravitational fields. In first case we consider the free gravitational field as magnetic type whereas in second case `gravitational wrench' of unit `pitch" is supposed to be present in free gravitational field. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. The cosmological constant $\Lambda$ is found to be a decreasing function of time and positive which is corroborated by results from recent supernovae Ia observations. The physical and geometric aspects of the models are discussed. |
1204.3566 | Jozef Skakala | Jozef Skakala | Quasi-normal modes, area spectra and multi-horizon spacetimes | 8 pages, v2: no physics changed, some references added, few sentences
added in the discussion parts | JHEP 1206:094, 2012 | 10.1007/JHEP06(2012)094 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest an interpretation for the highly damped QNM frequencies of the
spherically symmetric multi-horizon spacetimes (Reissner-Nordstrom,
Schwarzschild-deSitter, Reissner-Nordstrom-deSitter) following Maggiore's
proposal about the link between the asymptotic QNM frequencies and the black
hole thermodynamics. We show that the behavior of the asymptotic frequencies is
easy to understand if one assumes that all of the horizons have the same
equispaced area spectra. The QNM analysis is then consistent with the choice of
the area spectra to be the one originally proposed for the black hole's horizon
by Bekenstein: A=8\pi n (in Planck units). The interpretation of the highly
damped QNM frequencies in the multi-horizon case is based on the similar
grounds as in the single horizon (Schwarzschild) case, but it has some new
features that are discussed in the paper.
| [
{
"created": "Mon, 16 Apr 2012 16:48:44 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Apr 2012 20:16:46 GMT",
"version": "v2"
}
] | 2012-06-21 | [
[
"Skakala",
"Jozef",
""
]
] | We suggest an interpretation for the highly damped QNM frequencies of the spherically symmetric multi-horizon spacetimes (Reissner-Nordstrom, Schwarzschild-deSitter, Reissner-Nordstrom-deSitter) following Maggiore's proposal about the link between the asymptotic QNM frequencies and the black hole thermodynamics. We show that the behavior of the asymptotic frequencies is easy to understand if one assumes that all of the horizons have the same equispaced area spectra. The QNM analysis is then consistent with the choice of the area spectra to be the one originally proposed for the black hole's horizon by Bekenstein: A=8\pi n (in Planck units). The interpretation of the highly damped QNM frequencies in the multi-horizon case is based on the similar grounds as in the single horizon (Schwarzschild) case, but it has some new features that are discussed in the paper. |
1609.08604 | Rodrigo Panosso Macedo | Yu-Chun Pynn, Rodrigo Panosso Macedo, Martin Breithaupt, Stefan
Palenta, Reinhard Meinel | Gyromagnetic factor of rotating disks of electrically charged dust in
general relativity | 10 pages, 4 figures (typos corrected) | Phys. Rev. D 94, 104035 (2016) | 10.1103/PhysRevD.94.104035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculated the dimensionless gyromagnetic ratio ("$g$-factor") of
self-gravitating, uniformly rotating disks of dust with a constant specific
charge $\epsilon$. These disk solutions to the Einstein-Maxwell equations
depend on $\epsilon$ and a "relativity parameter" $\gamma$ ($0<\gamma\le 1$) up
to a scaling parameter. Accordingly, the $g$-factor is a function
$g=g(\gamma,\epsilon)$. The Newtonian limit is characterized by $\gamma \ll 1$,
whereas $\gamma\to 1$ leads to a black-hole limit. The $g$-factor, for all
$\epsilon$, approaches the values $g=1$ as $\gamma\to 0$ and $g=2$ as
$\gamma\to 1$.
| [
{
"created": "Tue, 27 Sep 2016 19:59:57 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Oct 2016 08:02:40 GMT",
"version": "v2"
}
] | 2016-11-16 | [
[
"Pynn",
"Yu-Chun",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Breithaupt",
"Martin",
""
],
[
"Palenta",
"Stefan",
""
],
[
"Meinel",
"Reinhard",
""
]
] | We calculated the dimensionless gyromagnetic ratio ("$g$-factor") of self-gravitating, uniformly rotating disks of dust with a constant specific charge $\epsilon$. These disk solutions to the Einstein-Maxwell equations depend on $\epsilon$ and a "relativity parameter" $\gamma$ ($0<\gamma\le 1$) up to a scaling parameter. Accordingly, the $g$-factor is a function $g=g(\gamma,\epsilon)$. The Newtonian limit is characterized by $\gamma \ll 1$, whereas $\gamma\to 1$ leads to a black-hole limit. The $g$-factor, for all $\epsilon$, approaches the values $g=1$ as $\gamma\to 0$ and $g=2$ as $\gamma\to 1$. |
gr-qc/0501091 | Aleksandar Mikovic | A. Mikovic | New Spin Foam Models of Quantum Gravity | 9 pages, talk given at the Workshop on Quantum Gravity and
Noncommutative geometry, Lusofona University, 20 - 23 July 2004, Lisbon | Mod.Phys.Lett.A20:1305,2005 | 10.1142/S0217732305017779 | null | gr-qc | null | We give a brief and a critical review of the Barret-Crane spin foam models of
quantum gravity. Then we describe two new spin foam models which are obtained
by direct quantization of General Relativity and do not have some of the
drawbacks of the Barret-Crane models. These are the model of spin foam
invariants for the embedded spin networks in loop quantum gravity and the spin
foam model based on the integration of the tetrads in the path integral for the
Palatini action.
| [
{
"created": "Fri, 28 Jan 2005 11:04:40 GMT",
"version": "v1"
}
] | 2009-01-16 | [
[
"Mikovic",
"A.",
""
]
] | We give a brief and a critical review of the Barret-Crane spin foam models of quantum gravity. Then we describe two new spin foam models which are obtained by direct quantization of General Relativity and do not have some of the drawbacks of the Barret-Crane models. These are the model of spin foam invariants for the embedded spin networks in loop quantum gravity and the spin foam model based on the integration of the tetrads in the path integral for the Palatini action. |
gr-qc/0611127 | Ignacio Navarro | I. Navarro, K. Van Acoleyen | f(R) actions, cosmic acceleration and local tests of gravity | 26 pages | JCAP 0702:022,2007 | 10.1088/1475-7516/2007/02/022 | DAMTP-2006-115 | gr-qc astro-ph hep-ph hep-th | null | We study spherically symmetric solutions in f(R) theories and its
compatibility with local tests of gravity. We start by clarifying the range of
validity of the weak field expansion and show that for many models proposed to
address the Dark Energy problem this expansion breaks down in realistic
situations. This invalidates the conclusions of several papers that make
inappropriate use of this expansion. For the stable models that modify gravity
only at small curvatures we find that when the asymptotic background curvature
is large we approximately recover the solutions of Einstein gravity through the
so-called Chameleon mechanism, as a result of the non-linear dynamics of the
extra scalar degree of freedom contained in the metric. In these models one
would observe a transition from Einstein to scalar-tensor gravity as the
Universe expands and the background curvature diminishes. Assuming an adiabatic
evolution we estimate the redshift at which this transition would take place
for a source with given mass and radius. We also show that models of dynamical
Dark Energy claimed to be compatible with tests of gravity because the mass of
the scalar is large in vacuum (e.g. those that also include R^2 corrections in
the action), are not viable.
| [
{
"created": "Thu, 23 Nov 2006 19:21:58 GMT",
"version": "v1"
}
] | 2010-10-27 | [
[
"Navarro",
"I.",
""
],
[
"Van Acoleyen",
"K.",
""
]
] | We study spherically symmetric solutions in f(R) theories and its compatibility with local tests of gravity. We start by clarifying the range of validity of the weak field expansion and show that for many models proposed to address the Dark Energy problem this expansion breaks down in realistic situations. This invalidates the conclusions of several papers that make inappropriate use of this expansion. For the stable models that modify gravity only at small curvatures we find that when the asymptotic background curvature is large we approximately recover the solutions of Einstein gravity through the so-called Chameleon mechanism, as a result of the non-linear dynamics of the extra scalar degree of freedom contained in the metric. In these models one would observe a transition from Einstein to scalar-tensor gravity as the Universe expands and the background curvature diminishes. Assuming an adiabatic evolution we estimate the redshift at which this transition would take place for a source with given mass and radius. We also show that models of dynamical Dark Energy claimed to be compatible with tests of gravity because the mass of the scalar is large in vacuum (e.g. those that also include R^2 corrections in the action), are not viable. |
1907.06463 | Davide Batic | Davide Batic and N. G. Kelkar and Marek Nowakowski and Karlus Redway | Perturbing microscopic black holes inspired by noncommutativity | 14 pages, 6 figures, reference added | The European Physical Journal C 79: 581 (2019) | 10.1140/epjc/s10052-019-7084-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We probe into the instabilities of microscopic quantum black holes. For this
purpose, we study the quasinormal modes (QNMs) for a massless scalar
perturbation of the noncommutative geometry inspired Schwarzschild black hole.
By means of a sixth order Wentzel-Kramers-Brillouin (WKB) approximation we show
that the widely used WKB method does not converge in the critical cases where
instabilities show up at the third order. By employing the inverted potential
method, we demonstrate that the instabilities are an artifact of the WKB
method. Finally, we discuss the usefulness of the asymptotic iteration method
to find the QNMs.
| [
{
"created": "Mon, 15 Jul 2019 12:20:44 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2019 16:45:37 GMT",
"version": "v2"
}
] | 2019-07-24 | [
[
"Batic",
"Davide",
""
],
[
"Kelkar",
"N. G.",
""
],
[
"Nowakowski",
"Marek",
""
],
[
"Redway",
"Karlus",
""
]
] | We probe into the instabilities of microscopic quantum black holes. For this purpose, we study the quasinormal modes (QNMs) for a massless scalar perturbation of the noncommutative geometry inspired Schwarzschild black hole. By means of a sixth order Wentzel-Kramers-Brillouin (WKB) approximation we show that the widely used WKB method does not converge in the critical cases where instabilities show up at the third order. By employing the inverted potential method, we demonstrate that the instabilities are an artifact of the WKB method. Finally, we discuss the usefulness of the asymptotic iteration method to find the QNMs. |
2407.01673 | Sijia Wang | Sijia Wang, Mar\'ia Rosa Preciado-Rivas, Massimilano Spadafora, Robert
B. Mann | Singular Excitement Beyond the Horizon of a Rotating Black Hole | null | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Previous studies have shown that an Unruh-DeWitt (UDW) detector, when coupled
linearly to a massless scalar field and permitted to fall radially into certain
black holes, will exhibit non-monotonicity in its transition properties near
the horizon. Specifically, the transition probability of a detector freely
falling into a (3+1)-dimensional Schawrzschild black hole, when considering the
Unruh and Hartle-Hawking vacuum states, was shown to possess a local extremum
at horizon crossing [K.K. Ng et al., New J. Phys. 24 (2022) 103018]. The
transition rate of a detector falling into a static (2+1)-dimensional
Ba\~nados-Teitelboim-Zanelli (BTZ) black hole, for the Hartle-Hawking state,
was also found to have multiple local extrema near the horizon under certain
parameter settings [M.R. Preciado-Rivas et al., arXiv:2402.14908v1]. These
discoveries are of interest, as they suggest that the event horizon of a black
hole may be distinguishable to a local probe when QFT effects are included. In
this paper, we explore the problem of a UDW detector falling freely into a
rotating BTZ black hole. We numerically compute the detector's transition rate
for different values of black hole mass, black hole angular momentum, detector
energy gap, and field boundary conditions at infinity. Our results lead to a
more generalized description of the behaviour of particle detectors in BTZ
black hole spacetime, from which the previous non-rotating BTZ case can be
retrieved in the limit as angular momentum vanishes.
| [
{
"created": "Mon, 1 Jul 2024 18:00:01 GMT",
"version": "v1"
}
] | 2024-07-08 | [
[
"Wang",
"Sijia",
""
],
[
"Preciado-Rivas",
"María Rosa",
""
],
[
"Spadafora",
"Massimilano",
""
],
[
"Mann",
"Robert B.",
""
]
] | Previous studies have shown that an Unruh-DeWitt (UDW) detector, when coupled linearly to a massless scalar field and permitted to fall radially into certain black holes, will exhibit non-monotonicity in its transition properties near the horizon. Specifically, the transition probability of a detector freely falling into a (3+1)-dimensional Schawrzschild black hole, when considering the Unruh and Hartle-Hawking vacuum states, was shown to possess a local extremum at horizon crossing [K.K. Ng et al., New J. Phys. 24 (2022) 103018]. The transition rate of a detector falling into a static (2+1)-dimensional Ba\~nados-Teitelboim-Zanelli (BTZ) black hole, for the Hartle-Hawking state, was also found to have multiple local extrema near the horizon under certain parameter settings [M.R. Preciado-Rivas et al., arXiv:2402.14908v1]. These discoveries are of interest, as they suggest that the event horizon of a black hole may be distinguishable to a local probe when QFT effects are included. In this paper, we explore the problem of a UDW detector falling freely into a rotating BTZ black hole. We numerically compute the detector's transition rate for different values of black hole mass, black hole angular momentum, detector energy gap, and field boundary conditions at infinity. Our results lead to a more generalized description of the behaviour of particle detectors in BTZ black hole spacetime, from which the previous non-rotating BTZ case can be retrieved in the limit as angular momentum vanishes. |
1004.1805 | Kayoomars Karami | K. Karami, M.S. Khaledian | Reconstructing f(R) modified gravity from ordinary and entropy-corrected
versions of the holographic and new agegraphic dark energy models | 17 pages, accepted for publication in JHEP | JHEP 1103:086,2011 | 10.1007/JHEP03(2011)086 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here, we peruse cosmological usage of the most promising candidates of dark
energy in the framework of f(R) theory. We reconstruct the different f(R)
modified gravity models in the spatially flat FRW universe according to the
ordinary and entropy-corrected versions of the holographic and new agegraphic
dark energy models, which describe accelerated expansion of the universe. We
also obtain the equation of state parameter of the corresponding f(R)-gravity
models. We conclude that the holographic and new agegraphic f(R)-gravity models
can behave like phantom or quintessence models. Whereas the equation of state
parameter of the entropy-corrected models can transit from quintessence state
to phantom regime as indicated by recent observations.
| [
{
"created": "Sun, 11 Apr 2010 12:57:36 GMT",
"version": "v1"
},
{
"created": "Mon, 10 May 2010 07:43:26 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Mar 2011 18:23:28 GMT",
"version": "v3"
}
] | 2011-07-18 | [
[
"Karami",
"K.",
""
],
[
"Khaledian",
"M. S.",
""
]
] | Here, we peruse cosmological usage of the most promising candidates of dark energy in the framework of f(R) theory. We reconstruct the different f(R) modified gravity models in the spatially flat FRW universe according to the ordinary and entropy-corrected versions of the holographic and new agegraphic dark energy models, which describe accelerated expansion of the universe. We also obtain the equation of state parameter of the corresponding f(R)-gravity models. We conclude that the holographic and new agegraphic f(R)-gravity models can behave like phantom or quintessence models. Whereas the equation of state parameter of the entropy-corrected models can transit from quintessence state to phantom regime as indicated by recent observations. |
gr-qc/0307093 | Michael A. Ivanov | Michael A. Ivanov | A fine quantum mechanism of classical gravity | 9 pages, LaTeX. Contribution to the Tenth Marcel Grossmann Meeting
(MG10), 20-26 July 2003, Rio de Janeiro, Brazil | In the book in Russian "Searches for a mechanism of gravity", Eds.
M.A. Ivanov and L.A. Savrov, Nizhny Novgorod, Yu.A. Nickolaev Publisher,
2004, pp 274-281 | null | null | gr-qc | null | It is shown that screening the background of super-strong interacting
gravitons ensures the Newtonian attraction, if a part of single gravitons is
pairing and graviton pairs are destructed by collisions with a body. If the
considered quantum mechanism of classical gravity is realized in the nature,
than an existence of black holes contradicts to the equivalence principle. In
such the model, Newton's constant is proportional to $H^{2}/T^{4},$ where $H$
is the Hubble constant, $T$ is an equivalent temperature of the graviton
background. The estimate of the Hubble constant is obtained for the Newtonian
limit: $H=3.026 \cdot 10^{-18} s^{-1}$ (or $94.576 km \cdot s^{-1} \cdot
Mpc^{-1}$).
| [
{
"created": "Mon, 21 Jul 2003 14:36:06 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Ivanov",
"Michael A.",
""
]
] | It is shown that screening the background of super-strong interacting gravitons ensures the Newtonian attraction, if a part of single gravitons is pairing and graviton pairs are destructed by collisions with a body. If the considered quantum mechanism of classical gravity is realized in the nature, than an existence of black holes contradicts to the equivalence principle. In such the model, Newton's constant is proportional to $H^{2}/T^{4},$ where $H$ is the Hubble constant, $T$ is an equivalent temperature of the graviton background. The estimate of the Hubble constant is obtained for the Newtonian limit: $H=3.026 \cdot 10^{-18} s^{-1}$ (or $94.576 km \cdot s^{-1} \cdot Mpc^{-1}$). |
1405.7702 | Shahar Hod | Shahar Hod | Onset of superradiant instabilities in the hydrodynamic vortex model | 5 pages | Physical Review D 90, 027501B (2014) | 10.1103/PhysRevD.90.027501 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The hydrodynamic vortex, an effective spacetime geometry for propagating
sound waves, is studied analytically. In contrast with the familiar Kerr
black-hole spacetime, the hydrodynamic vortex model is described by an
effective acoustic geometry which has no horizons. However, this acoustic
spacetime possesses an ergoregion, a property which it shares with the rotating
Kerr spacetime. It has recently been shown numerically that this physical
system is linearly unstable due to the superradiant scattering of sound waves
in the ergoregion of the effective spacetime. In the present study we use
analytical tools in order to explore the onset of these superradiant
instabilities which characterize the effective spacetime geometry. In
particular, we derive a simple analytical formula which describes the physical
properties of the hydrodynamic vortex system in its critical
(marginally-stable) state, the state which marks the boundary between stable
and unstable fluid configurations. The analytically derived formula is shown to
agree with the recently published numerical data for the hydrodynamic vortex
system.
| [
{
"created": "Thu, 29 May 2014 20:00:15 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jul 2014 20:06:30 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Hod",
"Shahar",
""
]
] | The hydrodynamic vortex, an effective spacetime geometry for propagating sound waves, is studied analytically. In contrast with the familiar Kerr black-hole spacetime, the hydrodynamic vortex model is described by an effective acoustic geometry which has no horizons. However, this acoustic spacetime possesses an ergoregion, a property which it shares with the rotating Kerr spacetime. It has recently been shown numerically that this physical system is linearly unstable due to the superradiant scattering of sound waves in the ergoregion of the effective spacetime. In the present study we use analytical tools in order to explore the onset of these superradiant instabilities which characterize the effective spacetime geometry. In particular, we derive a simple analytical formula which describes the physical properties of the hydrodynamic vortex system in its critical (marginally-stable) state, the state which marks the boundary between stable and unstable fluid configurations. The analytically derived formula is shown to agree with the recently published numerical data for the hydrodynamic vortex system. |
gr-qc/0506053 | Valery Kiselev | V.V.Kiselev | Entropy of BTZ black hole and its spectrum by quantum radial geodesics
behind horizons | 6 pages, 2 eps-figures, revtex4 class | Phys.Rev. D73 (2006) 104018 | 10.1103/PhysRevD.73.104018 | null | gr-qc astro-ph hep-th | null | In the framework of thermal quantization of radial geodesics completely
confined behind the horizons we calculate the entropy of BTZ black hole in
agreement with the Bekenstein--Hawking relation. Particles in the BTZ black
hole occupy the only quantum ground level. The quantization allow us to find a
linear dependence of black hole mass versus its orbital momentum.
| [
{
"created": "Thu, 9 Jun 2005 07:29:53 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Kiselev",
"V. V.",
""
]
] | In the framework of thermal quantization of radial geodesics completely confined behind the horizons we calculate the entropy of BTZ black hole in agreement with the Bekenstein--Hawking relation. Particles in the BTZ black hole occupy the only quantum ground level. The quantization allow us to find a linear dependence of black hole mass versus its orbital momentum. |
2012.04450 | Bayram Tekin | Emel Altas, Bayram Tekin | Approximate analytical description of apparent horizons for initial data
with momentum and spin | 11 pages, 1 figure, v2 matches the published form | Phys. Rev. D 103, 084036 (2021) | 10.1103/PhysRevD.103.084036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct analytical initial data for a slowly moving and rotating black
hole for generic orientations of the linear momentum and the spin. We solve the
Hamiltonian constraint approximately and work out the properties of the
apparent horizon and show the dependence of its shape on the angle between the
spin and the linear momentum. In particular a dimple, whose location depends on
the mentioned angle, arises on the 2-sphere geometry of the apparent horizon.
We exclusively work in the case of conformally flat initial metrics.
| [
{
"created": "Tue, 8 Dec 2020 14:37:42 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Apr 2021 07:21:36 GMT",
"version": "v2"
}
] | 2021-04-23 | [
[
"Altas",
"Emel",
""
],
[
"Tekin",
"Bayram",
""
]
] | We construct analytical initial data for a slowly moving and rotating black hole for generic orientations of the linear momentum and the spin. We solve the Hamiltonian constraint approximately and work out the properties of the apparent horizon and show the dependence of its shape on the angle between the spin and the linear momentum. In particular a dimple, whose location depends on the mentioned angle, arises on the 2-sphere geometry of the apparent horizon. We exclusively work in the case of conformally flat initial metrics. |
2408.06582 | Mian Zhu | Mian Zhu and Taotao Qiu | Interpretating Pulsar Timing Array data of Gravitational Waves with
Ekpyrosis-Bouncing Cosmology | 24 pages, 4 figures and 1 table | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent pulsar timing array (PTA) experiments have reported strong evidence of
the stochastic gravitational wave background (SGWB). If interpreted as
primordial Gravitational Waves (pGWs), the signal favors a strongly blue-tilted
spectrum. On the other hand, the Ekpyrosis-bouncing cosmology with a strongly
blue-tilted GW spectrum, i.e., $n_T \simeq 2$, offers a potential explanation
for the observed SGWB signal. In this paper, we construct a concrete
Ekpyrosis-bouncing model, and show its capacity to intepret the PTA result
without pathologies. Both tensor and scalar perturbations are analysed with
constraints from the current observations.
| [
{
"created": "Tue, 13 Aug 2024 02:42:21 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Zhu",
"Mian",
""
],
[
"Qiu",
"Taotao",
""
]
] | Recent pulsar timing array (PTA) experiments have reported strong evidence of the stochastic gravitational wave background (SGWB). If interpreted as primordial Gravitational Waves (pGWs), the signal favors a strongly blue-tilted spectrum. On the other hand, the Ekpyrosis-bouncing cosmology with a strongly blue-tilted GW spectrum, i.e., $n_T \simeq 2$, offers a potential explanation for the observed SGWB signal. In this paper, we construct a concrete Ekpyrosis-bouncing model, and show its capacity to intepret the PTA result without pathologies. Both tensor and scalar perturbations are analysed with constraints from the current observations. |
1111.3605 | Jonathan R. Gair | Jonathan R Gair, Nicolas Yunes and Carl M Bender | Resonances in Extreme Mass-Ratio Inspirals: Asymptotic and
Hyperasymptotic Analysis | 12 pages, 3 figures, submitted to JMP | null | 10.1063/1.3691226 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An expected source of gravitational waves for future detectors in space are
the inspirals of small compact objects into much more massive black holes.
These sources have the potential to provide a wealth of information about
astronomy and fundamental physics. On short timescales the orbit of the small
object is approximately geodesic. Generic geodesics for a Kerr black hole
spacetime have a complete set of integrals and can be characterized by three
frequencies of the motion. Over the course of an inspiral, a typical system
will pass through resonances where two of these frequencies become
commensurate. The effect of the resonance will be to alter significantly the
rate of inspiral for the duration of the resonance. Understanding the impact of
these resonances on gravitational wave phasing is important to detect and
exploit these signals for astrophysics and fundamental physics. Two
differential equations that might describe the passage of an inspiral through
such a resonance are investigated. These differ depending on whether it is the
phase or the frequency components of a Fourier expansion of the motion that are
taken to be continuous through the resonance. Asymptotic and hyperasymptotic
analysis are used to find the late-time analytic behavior of the solution for a
system that has passed through a resonance. Linearly growing (weak resonances)
or linearly decaying (strong resonances) solutions are found depending on the
strength of the resonance. In the weak-resonance case, frequency resonances
leave an imprint (a resonant memory) on the gravitational frequency evolution.
The transition between weak and strong resonances is characterized by a
square-root singularity, and as one approaches this transition from above, the
solutions to the frequency resonance equation bunch up into families
exponentially fast.
| [
{
"created": "Tue, 15 Nov 2011 18:22:23 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Gair",
"Jonathan R",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Bender",
"Carl M",
""
]
] | An expected source of gravitational waves for future detectors in space are the inspirals of small compact objects into much more massive black holes. These sources have the potential to provide a wealth of information about astronomy and fundamental physics. On short timescales the orbit of the small object is approximately geodesic. Generic geodesics for a Kerr black hole spacetime have a complete set of integrals and can be characterized by three frequencies of the motion. Over the course of an inspiral, a typical system will pass through resonances where two of these frequencies become commensurate. The effect of the resonance will be to alter significantly the rate of inspiral for the duration of the resonance. Understanding the impact of these resonances on gravitational wave phasing is important to detect and exploit these signals for astrophysics and fundamental physics. Two differential equations that might describe the passage of an inspiral through such a resonance are investigated. These differ depending on whether it is the phase or the frequency components of a Fourier expansion of the motion that are taken to be continuous through the resonance. Asymptotic and hyperasymptotic analysis are used to find the late-time analytic behavior of the solution for a system that has passed through a resonance. Linearly growing (weak resonances) or linearly decaying (strong resonances) solutions are found depending on the strength of the resonance. In the weak-resonance case, frequency resonances leave an imprint (a resonant memory) on the gravitational frequency evolution. The transition between weak and strong resonances is characterized by a square-root singularity, and as one approaches this transition from above, the solutions to the frequency resonance equation bunch up into families exponentially fast. |
gr-qc/9901014 | David Wands | Robert J. van den Hoogen, Alan A. Coley and David Wands | Scaling Solutions in Robertson-Walker Spacetimes | 8 pages, no figures, latex with revtex | Class.Quant.Grav.16:1843-1851,1999 | 10.1088/0264-9381/16/6/317 | null | gr-qc | null | We investigate the stability of cosmological scaling solutions describing a
barotropic fluid with $p=(\gamma-1)\rho$ and a non-interacting scalar field
$\phi$ with an exponential potential $V(\phi)=V_0\e^{-\kappa\phi}$. We study
homogeneous and isotropic spacetimes with non-zero spatial curvature and find
three possible asymptotic future attractors in an ever-expanding universe. One
is the zero-curvature power-law inflation solution where $\Omega_\phi=1$
($\gamma<2/3,\kappa^2<3\gamma$ and $\gamma>2/3,\kappa^2<2$). Another is the
zero-curvature scaling solution, first identified by Wetterich, where the
energy density of the scalar field is proportional to that of matter with
$\Omega_\phi=3\gamma/\kappa^2$ ($\gamma<2/3,\kappa^2>3\gamma$). We find that
this matter scaling solution is unstable to curvature perturbations for
$\gamma>2/3$. The third possible future asymptotic attractor is a solution with
negative spatial curvature where the scalar field energy density remains
proportional to the curvature with $\Omega_\phi=2/\kappa^2$
($\gamma>2/3,\kappa^2>2$). We find that solutions with $\Omega_\phi=0$ are
never late-time attractors.
| [
{
"created": "Thu, 7 Jan 1999 10:14:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hoogen",
"Robert J. van den",
""
],
[
"Coley",
"Alan A.",
""
],
[
"Wands",
"David",
""
]
] | We investigate the stability of cosmological scaling solutions describing a barotropic fluid with $p=(\gamma-1)\rho$ and a non-interacting scalar field $\phi$ with an exponential potential $V(\phi)=V_0\e^{-\kappa\phi}$. We study homogeneous and isotropic spacetimes with non-zero spatial curvature and find three possible asymptotic future attractors in an ever-expanding universe. One is the zero-curvature power-law inflation solution where $\Omega_\phi=1$ ($\gamma<2/3,\kappa^2<3\gamma$ and $\gamma>2/3,\kappa^2<2$). Another is the zero-curvature scaling solution, first identified by Wetterich, where the energy density of the scalar field is proportional to that of matter with $\Omega_\phi=3\gamma/\kappa^2$ ($\gamma<2/3,\kappa^2>3\gamma$). We find that this matter scaling solution is unstable to curvature perturbations for $\gamma>2/3$. The third possible future asymptotic attractor is a solution with negative spatial curvature where the scalar field energy density remains proportional to the curvature with $\Omega_\phi=2/\kappa^2$ ($\gamma>2/3,\kappa^2>2$). We find that solutions with $\Omega_\phi=0$ are never late-time attractors. |
0902.2720 | Sebastiano Bernuzzi | Sebastiano Bernuzzi, Luca Baiotti, Giovanni Corvino, Roberto De
Pietri, Alessandro Nagar | Gravitational-wave extraction from neutron-star oscillations | null | Proceedings of the Third Stueckelberg Workshop on Relativistic
Field Theories, 2010, Cambridge Scientific Publishers, p.97 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare different gravitational-wave extraction methods used in
three-dimensional nonlinear simulations against linear simulations of
perturbations of spherical spacetimes with matter. We present results from
fully general-relativistic simulations of a system composed by an oscillating
and non-rotating star emitting gravitational radiation. Results about the onset
of non-linear effects are also shown.
| [
{
"created": "Mon, 16 Feb 2009 16:03:13 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Feb 2009 17:05:23 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Aug 2011 16:40:17 GMT",
"version": "v3"
}
] | 2015-03-13 | [
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Baiotti",
"Luca",
""
],
[
"Corvino",
"Giovanni",
""
],
[
"De Pietri",
"Roberto",
""
],
[
"Nagar",
"Alessandro",
""
]
] | We compare different gravitational-wave extraction methods used in three-dimensional nonlinear simulations against linear simulations of perturbations of spherical spacetimes with matter. We present results from fully general-relativistic simulations of a system composed by an oscillating and non-rotating star emitting gravitational radiation. Results about the onset of non-linear effects are also shown. |
1708.05360 | Joel Franklin | E. Banyas, J. Franklin | The (Weak) Gravitational Field of a Dirac Monopole | to appear, Classical and Quantum Gravity | Classical and Quantum Gravity 34, 195004, 2017 | 10.1088/1361-6382/aa8657 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish the gravitational detectability of a Dirac monopole using a
weak-field limit of general relativity, which can be developed from the
Newtonian gravitational potential by including energy as a source. The
resulting potential matches (by construction) the weak-field limit of two
different solutions to Einstein's equations of general relativity: one
associated with the magnetically monopolar spray of field lines emerging from
the half-infinite solenoid that makes up the Dirac monopole, the other
associated with the field-energetic source of the solenoid itself (the Dirac
string). The string's gravitational effect dominates, and we suggest that the
primary strong-field contribution of the Dirac configuration is that of a
half-infinite line of energy, whose GR solution is known.
| [
{
"created": "Thu, 17 Aug 2017 16:49:19 GMT",
"version": "v1"
}
] | 2017-09-22 | [
[
"Banyas",
"E.",
""
],
[
"Franklin",
"J.",
""
]
] | We establish the gravitational detectability of a Dirac monopole using a weak-field limit of general relativity, which can be developed from the Newtonian gravitational potential by including energy as a source. The resulting potential matches (by construction) the weak-field limit of two different solutions to Einstein's equations of general relativity: one associated with the magnetically monopolar spray of field lines emerging from the half-infinite solenoid that makes up the Dirac monopole, the other associated with the field-energetic source of the solenoid itself (the Dirac string). The string's gravitational effect dominates, and we suggest that the primary strong-field contribution of the Dirac configuration is that of a half-infinite line of energy, whose GR solution is known. |
1508.03331 | Ram Gopal Vishwakarma | Ram Gopal Vishwakarma | A Machian Approach to General Relativity | Int. J. Geom. Methods Mod. Phys. (in press) | null | 10.1142/S0219887815501169 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mach's principle is surely one of those tantalizingly beautiful concepts in
physics which remain elusive. Though General Relativity (GR) was conceived in
the spirit of realizing it, the theory failed to fulfill this expectation.
Here a study on the implications of imposing Mach's principle on GR with an
insight that spacetime has no independent existence without a material
background, is presented. This inclusion of the principle in GR turns out to be
unexpectedly rewarding. The resulting theory solves many mysteries and averts
lingering problems of the conventional forms of GR and cosmology.
| [
{
"created": "Wed, 12 Aug 2015 23:11:45 GMT",
"version": "v1"
}
] | 2015-08-19 | [
[
"Vishwakarma",
"Ram Gopal",
""
]
] | Mach's principle is surely one of those tantalizingly beautiful concepts in physics which remain elusive. Though General Relativity (GR) was conceived in the spirit of realizing it, the theory failed to fulfill this expectation. Here a study on the implications of imposing Mach's principle on GR with an insight that spacetime has no independent existence without a material background, is presented. This inclusion of the principle in GR turns out to be unexpectedly rewarding. The resulting theory solves many mysteries and averts lingering problems of the conventional forms of GR and cosmology. |
2103.03083 | Muhammad Sharif | M. Sharif and M. Zeeshan Gul | Noether Symmetry Approach in Energy-Momentum Squared Gravity | 22 pages, 5 figures | Physica Scripta 96(2021)025002 | 10.1088/1402-4896/abcd67 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the newly developed $f(R,\mathbf{T}^2)$ theory
($R$ is the Ricci scalar and $\mathbf{T}^2=T_{\alpha\beta}T^{\alpha\beta},~T
_{\alpha\beta}$ demonstrates the energy-momentum tensor) to explore some viable
cosmological models. For this purpose, we use the Noether symmetry approach in
the context of flat Friedmann-Robertson-Walker (FRW) universe. We solve the
Noether equations of this modified theory for two types of models and obtain
the symmetry generators as well as corresponding conserved quantities. We also
evaluate exact solutions and investigate their physical behavior via different
cosmological parameters. For the prospective models, the graphical behavior of
these parameters indicate consistency with recent observations representing
accelerated expansion of the universe. In the first case, we take a special
model of this theory and obtain new class of exact solutions with the help of
conserved quantities. Secondly, we consider minimal and non-minimal coupling
models of $f(R,\mathbf{T} ^{2})$ gravity. We conclude that conserved quantities
are very useful to derive the exact solutions that are used to study the cosmic
accelerated expansion.
| [
{
"created": "Wed, 3 Mar 2021 10:05:35 GMT",
"version": "v1"
}
] | 2021-03-10 | [
[
"Sharif",
"M.",
""
],
[
"Gul",
"M. Zeeshan",
""
]
] | In this paper, we investigate the newly developed $f(R,\mathbf{T}^2)$ theory ($R$ is the Ricci scalar and $\mathbf{T}^2=T_{\alpha\beta}T^{\alpha\beta},~T _{\alpha\beta}$ demonstrates the energy-momentum tensor) to explore some viable cosmological models. For this purpose, we use the Noether symmetry approach in the context of flat Friedmann-Robertson-Walker (FRW) universe. We solve the Noether equations of this modified theory for two types of models and obtain the symmetry generators as well as corresponding conserved quantities. We also evaluate exact solutions and investigate their physical behavior via different cosmological parameters. For the prospective models, the graphical behavior of these parameters indicate consistency with recent observations representing accelerated expansion of the universe. In the first case, we take a special model of this theory and obtain new class of exact solutions with the help of conserved quantities. Secondly, we consider minimal and non-minimal coupling models of $f(R,\mathbf{T} ^{2})$ gravity. We conclude that conserved quantities are very useful to derive the exact solutions that are used to study the cosmic accelerated expansion. |
1006.4435 | Sebastein Clesse | Sebastien Clesse | Initial conditions in hybrid inflation: exploration by MCMC technique | Proceedings of the 45th Rencontres de Moriond conference, March 13 -
20, 2010, La Thuile, Italy | null | null | ulb-th/10-16, CP3-10-23 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In hybrid inflation, initial field values leading to sufficiently long
inflation were thought be fine-tuned in a narrow band along the inflationary
valley. A re-analysis of this problem has shown that there exists a non
negligible proportion of successful initial conditions exterior to the valley,
organized in a complex structure with fractal boundaries, and whose origin has
been explained. Their existence in a large part of the parameter space has been
demonstrated using a bayesian Monte-Carlo-Markov-Chain (MCMC) method, and
natural bounds on potential parameters have been established. Moreover, these
results are shown to be valid not only for the original hybrid model, but also
for other hybrid realizations in various frameworks.
| [
{
"created": "Wed, 23 Jun 2010 07:30:04 GMT",
"version": "v1"
}
] | 2010-06-24 | [
[
"Clesse",
"Sebastien",
""
]
] | In hybrid inflation, initial field values leading to sufficiently long inflation were thought be fine-tuned in a narrow band along the inflationary valley. A re-analysis of this problem has shown that there exists a non negligible proportion of successful initial conditions exterior to the valley, organized in a complex structure with fractal boundaries, and whose origin has been explained. Their existence in a large part of the parameter space has been demonstrated using a bayesian Monte-Carlo-Markov-Chain (MCMC) method, and natural bounds on potential parameters have been established. Moreover, these results are shown to be valid not only for the original hybrid model, but also for other hybrid realizations in various frameworks. |
1511.00247 | Giulio D'Odorico | Giulio D'Odorico and Frank Saueressig | Quantum Phase Transitions in the BKL Universe | 4 pages, 2 figures | Phys. Rev. D 92, 124068 (2015) | 10.1103/PhysRevD.92.124068 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study quantum corrections to the classical Bianchi I and Bianchi IX
universes. The modified dynamics is well-motivated from the asymptotic safety
program where the short-distance behavior of gravity is governed by a
non-trivial renormalization group fixed point. The correction terms induce a
phase transition in the dynamics of the model, changing the classical, chaotic
Kasner oscillations into a uniform approach to a point singularity. The
resulting implications for the microscopic structure of spacetime are
discussed.
| [
{
"created": "Sun, 1 Nov 2015 13:30:50 GMT",
"version": "v1"
}
] | 2016-01-06 | [
[
"D'Odorico",
"Giulio",
""
],
[
"Saueressig",
"Frank",
""
]
] | We study quantum corrections to the classical Bianchi I and Bianchi IX universes. The modified dynamics is well-motivated from the asymptotic safety program where the short-distance behavior of gravity is governed by a non-trivial renormalization group fixed point. The correction terms induce a phase transition in the dynamics of the model, changing the classical, chaotic Kasner oscillations into a uniform approach to a point singularity. The resulting implications for the microscopic structure of spacetime are discussed. |
gr-qc/9612065 | Jai-chan Hwang | J. Hwang and H. Noh | Density Spectrums from Kinetic Inflations | 8 pages, revtex, no figures | null | null | null | gr-qc | null | The pole-like accelerated expansion stages purely driven by the coupling
between the gravity and the dilaton field without referring to the potential
term can be realized in a class of generalized gravity theories. We consider
three such scenarios based on the scalar-tensor gravity, the induced gravity
and the string theory. Quantum fluctuations during the expansion stages
(including more general situations) can be derived in exact analytic forms.
Assuming that the pole-like acceleration stage provides a viable inflation
scenario in the early universe we derive the generated classical density
spectrums. The generated classical density field shows a generic tilted
spectrum with $n \simeq 4$ which differs from the observed spectrum supporting
$n \simeq 1$.
| [
{
"created": "Mon, 30 Dec 1996 02:18:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hwang",
"J.",
""
],
[
"Noh",
"H.",
""
]
] | The pole-like accelerated expansion stages purely driven by the coupling between the gravity and the dilaton field without referring to the potential term can be realized in a class of generalized gravity theories. We consider three such scenarios based on the scalar-tensor gravity, the induced gravity and the string theory. Quantum fluctuations during the expansion stages (including more general situations) can be derived in exact analytic forms. Assuming that the pole-like acceleration stage provides a viable inflation scenario in the early universe we derive the generated classical density spectrums. The generated classical density field shows a generic tilted spectrum with $n \simeq 4$ which differs from the observed spectrum supporting $n \simeq 1$. |
1809.08792 | Mehdi Rezaei | Mohammad Malekjani, Mehdi Rezaei and Iman A. Akhlaghi | Can Holographic dark energy models fit the observational data? | 12 pages, 4 figures, 6 tables, Accepted in PRD | null | 10.1103/PhysRevD.98.063533 | Phys. Rev. D 98, 063533 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate the holographic dark energy models with slowly
time-varying model parameter defined based on the current Hubble horizon length
scale. While the previous studies on the three popular holographic dark energy
models defined based on the future event horizon, Ricci scale and
Granda-Oliveros IR cutoffs showed that these models cannot fit the
observational data [1], in this work we show that the holographic dark energy
models with time-varying model parameter defined on the current Hubble radius
are well favored by observations. Using the standard $\chi^2$ minimization in
the context of Markov Chain Monte Carlo method, we compare the ability of
holographic dark energy models with time-varying $c^2$ parameter constructed on
the current Hubble length scale against different sets of observational data
namely expansion data, growth rate data and expansion+growth rate data
respectively. Based on the values of Akaike and Bayesian information criteria,
we find that these types of holographic dark energy models are well fitted to
both expansion and growth rate observations as equal to $\Lambda$CDM cosmology.
We also put constraints on the cosmological parameters and show that the
transition epoch form early decelerated to current accelerated expansion
calculated in holographic dark energy models with time-varying model parameter
defined on the Hubble length is consistent with observations.
| [
{
"created": "Mon, 24 Sep 2018 08:03:59 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Oct 2018 20:26:52 GMT",
"version": "v2"
}
] | 2019-05-07 | [
[
"Malekjani",
"Mohammad",
""
],
[
"Rezaei",
"Mehdi",
""
],
[
"Akhlaghi",
"Iman A.",
""
]
] | In this work we investigate the holographic dark energy models with slowly time-varying model parameter defined based on the current Hubble horizon length scale. While the previous studies on the three popular holographic dark energy models defined based on the future event horizon, Ricci scale and Granda-Oliveros IR cutoffs showed that these models cannot fit the observational data [1], in this work we show that the holographic dark energy models with time-varying model parameter defined on the current Hubble radius are well favored by observations. Using the standard $\chi^2$ minimization in the context of Markov Chain Monte Carlo method, we compare the ability of holographic dark energy models with time-varying $c^2$ parameter constructed on the current Hubble length scale against different sets of observational data namely expansion data, growth rate data and expansion+growth rate data respectively. Based on the values of Akaike and Bayesian information criteria, we find that these types of holographic dark energy models are well fitted to both expansion and growth rate observations as equal to $\Lambda$CDM cosmology. We also put constraints on the cosmological parameters and show that the transition epoch form early decelerated to current accelerated expansion calculated in holographic dark energy models with time-varying model parameter defined on the Hubble length is consistent with observations. |
2103.06411 | Luis L\'opez | L. A. L\'opez and Omar Pedraza | Effects of quintessence on scattering and absorption sections of black
holes | null | null | 10.1007/s12648-022-02373-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Basing on the ideas used by Kiselev, we study three black holes surrounded by
quintessence and the effects of quintessence on the classical and semiclassical
scattering cross-sections. In contrast, the absorption section is studied with
the sinc approximation in the eikonal limit. For Schwarzschild,
Reissner-Nordstr\"{o}m and Bardeen black holes surrounded by quintessence, the
values critical of charges and the normalization factor are obtained. We also
described the horizons and the extremal condition of the black holes surrounded
by quintessence. By setting for the quintessence state parameter in two the
particular cases w=-2/3 and w=-1/2.
| [
{
"created": "Thu, 11 Mar 2021 01:53:32 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Apr 2022 20:53:04 GMT",
"version": "v2"
}
] | 2022-06-08 | [
[
"López",
"L. A.",
""
],
[
"Pedraza",
"Omar",
""
]
] | Basing on the ideas used by Kiselev, we study three black holes surrounded by quintessence and the effects of quintessence on the classical and semiclassical scattering cross-sections. In contrast, the absorption section is studied with the sinc approximation in the eikonal limit. For Schwarzschild, Reissner-Nordstr\"{o}m and Bardeen black holes surrounded by quintessence, the values critical of charges and the normalization factor are obtained. We also described the horizons and the extremal condition of the black holes surrounded by quintessence. By setting for the quintessence state parameter in two the particular cases w=-2/3 and w=-1/2. |
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