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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0001055 | Julio Cesar Fabris | A.B. Batista, J.C. Fabris and R. de S\'a Ribeiro | A remark on Brans-Dicke dust cosmological solutions with negative
$\omega$ | Latex file, 6 pages | Gen.Rel.Grav. 33 (2001) 1237-1244 | 10.1023/A:1012089402583 | null | gr-qc | null | Analysing the Brans-Dicke solutions for the dust phase, we show that, for
negative values of $\omega$, they contain scenarios that display an initial
subluminal expansion followed by an inflationary phase. We discuss these
solutions with respect to the results of the observation of high redshif
supernova as well as the age problem and structure formation. We stablish
possible connections of these solutions with those emerging from string
effective models.
| [
{
"created": "Wed, 19 Jan 2000 21:50:17 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Batista",
"A. B.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Ribeiro",
"R. de Sá",
""
]
] | Analysing the Brans-Dicke solutions for the dust phase, we show that, for negative values of $\omega$, they contain scenarios that display an initial subluminal expansion followed by an inflationary phase. We discuss these solutions with respect to the results of the observation of high redshif supernova as well as the age problem and structure formation. We stablish possible connections of these solutions with those emerging from string effective models. |
gr-qc/0309027 | Robert T. Jantzen | Robert T. Jantzen | Exact Cosmological Solutions of Gravitational Theories | 11 latex article style pages | Phys.Lett.B186:290-296,1987 | 10.1016/0370-2693(87)90297-8 | null | gr-qc | null | A global picture is drawn tying together most exact cosmological solutions of
gravitational theories in four or more spacetime dimensions.
| [
{
"created": "Thu, 4 Sep 2003 15:19:22 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Jantzen",
"Robert T.",
""
]
] | A global picture is drawn tying together most exact cosmological solutions of gravitational theories in four or more spacetime dimensions. |
gr-qc/9911024 | Gianluca Gemme | Ph. Bernard, G. Gemme, R. Parodi and E. Picasso | Two Coupled Superconducting Cavities as a Gravitational Wave Detector:
First Experimental Results | 7 pages, 3 figures. Presented at the 9th Workshop on RF
Superconductivity, November 1-5, 1999, Santa Fe, New Mexico, USA | null | null | null | gr-qc | null | First experimental results of a feasibility study of a gravitational wave
detector based on two coupled superconducting cavities are presented. Basic
physical principles underlying the detector behaviour and sensitivity limits
are discussed. The detector layout is described in detail and its rf properties
are showed. The limit sensitivity to small harmonic displacements at the
detection frequency (around 1 MHz) is showed. The system performance as a
potential g.w. detector is discussed and future developments are foreseen.
| [
{
"created": "Mon, 8 Nov 1999 13:17:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bernard",
"Ph.",
""
],
[
"Gemme",
"G.",
""
],
[
"Parodi",
"R.",
""
],
[
"Picasso",
"E.",
""
]
] | First experimental results of a feasibility study of a gravitational wave detector based on two coupled superconducting cavities are presented. Basic physical principles underlying the detector behaviour and sensitivity limits are discussed. The detector layout is described in detail and its rf properties are showed. The limit sensitivity to small harmonic displacements at the detection frequency (around 1 MHz) is showed. The system performance as a potential g.w. detector is discussed and future developments are foreseen. |
0808.4034 | Riccardo Sturani | Umberto Cannella and Riccardo Sturani (University of Geneva) | Classical energy momentum tensor renormalisation via effective field
theory methods | 20 pages, 6 figures. Sec. IV improved in v2. New introduction in v3.
Typos corrected and one reference added in v4, published version | Gen.Rel.Grav.42:2491-2509,2010 | 10.1007/s10714-010-0998-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the Effective Field Theory approach to General Relativity,
introduced by Goldberger and Rothstein, to study point-like and string-like
sources in the context of scalar-tensor theories of gravity. Within this
framework we compute the classical energy-momentum tensor renormalization to
first Post-Newtonian order or, in the case of extra scalar fields, up to first
order in the (non-derivative) trilinear interaction terms: this allows to write
down the corrections to the standard (Newtonian) gravitational potential and to
the extra-scalar potential. In the case of one-dimensional extended sources we
give an alternative derivation of the renormalization of the string tension
enabling a re-analysis of the discrepancy between the results obtained by
Dabholkar and Harvey in one paper and by Buonanno and Damour in another,
already discussed in the latter.
| [
{
"created": "Fri, 29 Aug 2008 07:15:40 GMT",
"version": "v1"
},
{
"created": "Mon, 18 May 2009 20:58:08 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Nov 2009 13:41:36 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Sep 2010 22:47:30 GMT",
"version": "v4"
}
] | 2014-11-18 | [
[
"Cannella",
"Umberto",
"",
"University of Geneva"
],
[
"Sturani",
"Riccardo",
"",
"University of Geneva"
]
] | We apply the Effective Field Theory approach to General Relativity, introduced by Goldberger and Rothstein, to study point-like and string-like sources in the context of scalar-tensor theories of gravity. Within this framework we compute the classical energy-momentum tensor renormalization to first Post-Newtonian order or, in the case of extra scalar fields, up to first order in the (non-derivative) trilinear interaction terms: this allows to write down the corrections to the standard (Newtonian) gravitational potential and to the extra-scalar potential. In the case of one-dimensional extended sources we give an alternative derivation of the renormalization of the string tension enabling a re-analysis of the discrepancy between the results obtained by Dabholkar and Harvey in one paper and by Buonanno and Damour in another, already discussed in the latter. |
1301.7652 | Alexandros P. Kouretsis | A.P. Kouretsis, M. Stathakopoulos and P.C. Stavrinos | Relativistic Finsler geometry | references added, Contribution to the proceedings of "Modern
Mathematical Methods in Science and Technology 2012 (M3ST2012)", Kalamata,
Greece, August, 2012 | null | 10.1002/mma.2919 | null | gr-qc astro-ph.CO math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly review some basic concepts of parallel displacement in Finsler
geometry. In general relativity, the parallel translation of objects along the
congruence of the fundamental observer corresponds to the evolution in time. By
dropping the quadratic restriction on the measurement of an infinitesimal
distance, the geometry is generalized to a Finsler structure. Apart from
curvature a new property of the manifold complicates the geometrodynamics, the
color. The color brings forth an intrinsic local anisotropy and many quantities
depend on position and to a "supporting" direction. We discuss this direction
dependence and some physical interpretations. Also, we highlight that in
Finsler geometry the parallel displacement isn't necessarily always along the
"supporting" direction. The latter is a fundamental congruence of the manifold
and induces a natural 1+3 decomposition. Its internal deformation is given
through the evolution of the irreducible components of vorticity, shear and
expansion.
| [
{
"created": "Thu, 31 Jan 2013 15:44:03 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Feb 2013 16:58:10 GMT",
"version": "v2"
}
] | 2013-12-18 | [
[
"Kouretsis",
"A. P.",
""
],
[
"Stathakopoulos",
"M.",
""
],
[
"Stavrinos",
"P. C.",
""
]
] | We briefly review some basic concepts of parallel displacement in Finsler geometry. In general relativity, the parallel translation of objects along the congruence of the fundamental observer corresponds to the evolution in time. By dropping the quadratic restriction on the measurement of an infinitesimal distance, the geometry is generalized to a Finsler structure. Apart from curvature a new property of the manifold complicates the geometrodynamics, the color. The color brings forth an intrinsic local anisotropy and many quantities depend on position and to a "supporting" direction. We discuss this direction dependence and some physical interpretations. Also, we highlight that in Finsler geometry the parallel displacement isn't necessarily always along the "supporting" direction. The latter is a fundamental congruence of the manifold and induces a natural 1+3 decomposition. Its internal deformation is given through the evolution of the irreducible components of vorticity, shear and expansion. |
2108.11936 | Martin Bojowald | Martin Bojowald | Space-time physics in background-independent theories of quantum gravity | 28 pages, 4 figures | Universe 7 (2021) 251 | 10.3390/universe7070251 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Background independence is often emphasized as an important property of a
quantum theory of gravity that takes seriously the geometrical nature of
general relativity. In a background-independent formulation, quantum gravity
should determine not only the dynamics of space-time but also its geometry,
which may have equally important implications for claims of potential physical
observations. One of the leading candidates for background-independent quantum
gravity is loop quantum gravity. By combining and interpreting several recent
results, it is shown here how the canonical nature of this theory makes it
possible to perform a complete space-time analysis in various models that have
been proposed in this setting. In spite of the background-independent starting
point, all these models turn out to be non-geometrical and even inconsistent to
varying degrees, unless strong modifications of Riemannian geometry are taken
into account. This outcome leads to several implications for potential
observations as well as lessons for other background-independent approaches.
| [
{
"created": "Thu, 26 Aug 2021 17:48:06 GMT",
"version": "v1"
}
] | 2021-08-27 | [
[
"Bojowald",
"Martin",
""
]
] | Background independence is often emphasized as an important property of a quantum theory of gravity that takes seriously the geometrical nature of general relativity. In a background-independent formulation, quantum gravity should determine not only the dynamics of space-time but also its geometry, which may have equally important implications for claims of potential physical observations. One of the leading candidates for background-independent quantum gravity is loop quantum gravity. By combining and interpreting several recent results, it is shown here how the canonical nature of this theory makes it possible to perform a complete space-time analysis in various models that have been proposed in this setting. In spite of the background-independent starting point, all these models turn out to be non-geometrical and even inconsistent to varying degrees, unless strong modifications of Riemannian geometry are taken into account. This outcome leads to several implications for potential observations as well as lessons for other background-independent approaches. |
2004.00671 | Maria Okounkova | Maria Okounkova | Revisiting non-linearity in binary black hole mergers | 8 pages, 5 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, it has been shown that with the inclusion of overtones, the
post-merger gravitational waveform at infinity of a binary black hole system is
well-modelled using pure linear theory. However, given that a binary black hole
merger is expected to be highly non-linear, where do these non-linearities,
which do not make it out to infinity, go? We visualize quantities measuring
non-linearity in the strong-field region of a numerical relativity binary black
hole merger in order to begin to answer this question.
| [
{
"created": "Wed, 1 Apr 2020 19:25:28 GMT",
"version": "v1"
}
] | 2020-04-03 | [
[
"Okounkova",
"Maria",
""
]
] | Recently, it has been shown that with the inclusion of overtones, the post-merger gravitational waveform at infinity of a binary black hole system is well-modelled using pure linear theory. However, given that a binary black hole merger is expected to be highly non-linear, where do these non-linearities, which do not make it out to infinity, go? We visualize quantities measuring non-linearity in the strong-field region of a numerical relativity binary black hole merger in order to begin to answer this question. |
1602.06253 | Magd Elias Kahil | M. I. Wanas, M. E. Kahil and Mona M. Kamal | An AP-Structure with Finslerian Flavor: Path Equations | null | null | 10.1134/S0202289316040162 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bazanski approach for deriving paths is applied to Finsler geometry. The
approach is generalized and applied to a new developed geometry called
"Absolute parallelism with a Finslerian Flavor" (FAP). A sets of path equations
is derived for the FAP. This is the horizontal (h) set. A striking feature
appears in this set, that is: the coefficient of torsion term, in the set,
jumps by a step of one-half from one equation to the other. This is tempting to
believe that the h-set admits some quantum features. Comparisons with the
corresponding sets in other geometries are given. Conditions to reduce the set
of path equations obtained, to well known path equations in some geometries are
summarized in a schematic diagram.
| [
{
"created": "Fri, 19 Feb 2016 18:53:01 GMT",
"version": "v1"
}
] | 2016-12-07 | [
[
"Wanas",
"M. I.",
""
],
[
"Kahil",
"M. E.",
""
],
[
"Kamal",
"Mona M.",
""
]
] | The Bazanski approach for deriving paths is applied to Finsler geometry. The approach is generalized and applied to a new developed geometry called "Absolute parallelism with a Finslerian Flavor" (FAP). A sets of path equations is derived for the FAP. This is the horizontal (h) set. A striking feature appears in this set, that is: the coefficient of torsion term, in the set, jumps by a step of one-half from one equation to the other. This is tempting to believe that the h-set admits some quantum features. Comparisons with the corresponding sets in other geometries are given. Conditions to reduce the set of path equations obtained, to well known path equations in some geometries are summarized in a schematic diagram. |
1401.5286 | Farzaneh Atyabi | K. Kaviani and F. Atyabi | If the spin of gravitational field depends on spacetime dimension | 5 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this manuscript a different perspective on gravitational field has been
proposed, suggesting different features of gravity depending on spacetime
dimension, which can explain preventing the formation of singularity inside
blackholes and also suggest interpreting spin-1 fields emerged in theories with
dimensional reduction mechanism, as different aspects of gravitational field.
| [
{
"created": "Tue, 21 Jan 2014 12:15:30 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2015 14:02:19 GMT",
"version": "v2"
}
] | 2015-04-15 | [
[
"Kaviani",
"K.",
""
],
[
"Atyabi",
"F.",
""
]
] | In this manuscript a different perspective on gravitational field has been proposed, suggesting different features of gravity depending on spacetime dimension, which can explain preventing the formation of singularity inside blackholes and also suggest interpreting spin-1 fields emerged in theories with dimensional reduction mechanism, as different aspects of gravitational field. |
1405.2640 | Jiliang Jing | Zixu Zhao and Jiliang Jing | Ehrenfest scheme for complex thermodynamic systems in full phase space | 9 pages | JHEP 11 (2014) 037 | 10.1007/JHEP11(2014)037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a thermodynamic system with multiple pairs of intensive/extensive
variables and the thermodynamical coefficients attain finite or infinite values
on the phase boundary, we obtain the two classes of Ehrenfest equations in the
full phase space, and find that the rank of the matrix for these equations can
tell us the dimensions of the phase boundary. We also apply this treatment to
the RN-AdS black hole.
| [
{
"created": "Mon, 12 May 2014 06:48:56 GMT",
"version": "v1"
},
{
"created": "Thu, 15 May 2014 03:32:36 GMT",
"version": "v2"
},
{
"created": "Sat, 7 Jun 2014 01:42:24 GMT",
"version": "v3"
},
{
"created": "Fri, 20 Jun 2014 13:51:12 GMT",
"version": "v4"
}
] | 2014-11-20 | [
[
"Zhao",
"Zixu",
""
],
[
"Jing",
"Jiliang",
""
]
] | For a thermodynamic system with multiple pairs of intensive/extensive variables and the thermodynamical coefficients attain finite or infinite values on the phase boundary, we obtain the two classes of Ehrenfest equations in the full phase space, and find that the rank of the matrix for these equations can tell us the dimensions of the phase boundary. We also apply this treatment to the RN-AdS black hole. |
gr-qc/9907102 | L. Raul Abramo | L. R. Abramo (1) and F. Finelli (2) ((1) University of Florida and
University of Munich, (2) University of Bologna, Brown University and
Istituto Te.S.R.E.) | Back Reaction of Gravitational Radiation on the Schwarzschild Black Hole | 13 pages, LaTex; one reference updated; submitted to Class. Q. Grav | Gen.Rel.Grav. 33 (2001) 339-352 | 10.1023/A:1002757419086 | HET-BROWN-1149 | gr-qc | null | We address some of the issues that appear in the study of back reaction in
Schwarzschild backgrounds. Our main object is the effective energy-momentum
tensor (EEMT) of gravitational perturbations. It is commonly held that only
asymptotically flat or radiation gauges can be employed for these purposes. We
show that the traditional Regge-Wheeler gauge for the perturbations of the
Schwarszchild metric can also be used for computing physical quantities both at
the horizon and at infinity. In particular, we find that the physically
relevant components of the EEMT of gravitational perturbations have the same
asymptotic behaviour as the stress-energy tensor of a scalar field in the
Schwarzschild background, even though some of the metric components themselves
diverge.
| [
{
"created": "Thu, 29 Jul 1999 14:31:56 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Aug 1999 12:53:01 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Abramo",
"L. R.",
""
],
[
"Finelli",
"F.",
""
]
] | We address some of the issues that appear in the study of back reaction in Schwarzschild backgrounds. Our main object is the effective energy-momentum tensor (EEMT) of gravitational perturbations. It is commonly held that only asymptotically flat or radiation gauges can be employed for these purposes. We show that the traditional Regge-Wheeler gauge for the perturbations of the Schwarszchild metric can also be used for computing physical quantities both at the horizon and at infinity. In particular, we find that the physically relevant components of the EEMT of gravitational perturbations have the same asymptotic behaviour as the stress-energy tensor of a scalar field in the Schwarzschild background, even though some of the metric components themselves diverge. |
gr-qc/0311049 | Slava G. Turyshev | Slava G. Turyshev, Michael Shao and Kenneth Nordtvedt Jr | New Concept for Testing General Relativity: The Laser Astrometric Test
of Relativity (LATOR) Mission | 11 pages, 4 figures, invited talk presented at AIAA Meeting "Space
2003", 23 September 2003, Long Beach, CA | Astron.Nachr. 325 (2004) 267-277 | 10.1002/asna.200310205 | null | gr-qc | null | This paper discusses new Fundamental physics experiment that will test
relativistic gravity at the accuracy better than the effects of the second
order in the gravitational field strength, ~G^2. The Laser Astrometric Test Of
Relativity (LATOR) mission uses laser interferometry between two
micro-spacecraft whose lines of sight pass close by the Sun to accurately
measure deflection of light in the solar gravity. The key element of the
experimental design is a redundant geometry optical truss provided by a
long-baseline (100 m) multi-channel stellar optical interferometer placed on
the International Space Station (ISS). The spatial interferometer is used for
measuring the angles between the two spacecraft and for orbit determination
purposes. LATOR will not only improve the value of the parameterized
post-Newtonian (PPN) $\gamma$ to unprecedented levels of accuracy of 1 part in
10e8, it will also reach ability to measure effects of the next post-Newtonian
order (1/c^4) of light deflection resulting from gravity's intrinsic
non-linearity. The solar quadrupole moment parameter, J2, will be measured with
high precision, as well as a variety of other relativistic effects including
Lense-Thirring precession. LATOR will lead to very robust advances in the tests
of Fundamental physics: this mission could discover a violation or extension of
general relativity, or reveal the presence of an additional long range
interaction in the physical law. There are no analogs to the LATOR experiment;
it is unique and is a natural culmination of solar system gravity experiments.
| [
{
"created": "Sat, 15 Nov 2003 04:11:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Shao",
"Michael",
""
],
[
"Nordtvedt",
"Kenneth",
"Jr"
]
] | This paper discusses new Fundamental physics experiment that will test relativistic gravity at the accuracy better than the effects of the second order in the gravitational field strength, ~G^2. The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station (ISS). The spatial interferometer is used for measuring the angles between the two spacecraft and for orbit determination purposes. LATOR will not only improve the value of the parameterized post-Newtonian (PPN) $\gamma$ to unprecedented levels of accuracy of 1 part in 10e8, it will also reach ability to measure effects of the next post-Newtonian order (1/c^4) of light deflection resulting from gravity's intrinsic non-linearity. The solar quadrupole moment parameter, J2, will be measured with high precision, as well as a variety of other relativistic effects including Lense-Thirring precession. LATOR will lead to very robust advances in the tests of Fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity experiments. |
1704.07955 | Jos\'e A. Zapata | Homero G. D\'iaz-Mar\'in, Jos\'e A. Zapata | Observable currents and a covariant Poisson algebra of physical
observables | null | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observable currents are locally defined gauge invariant conserved currents;
physical observables may be calculated integrating them on appropriate
hypersurfaces. Due to the conservation law the hypersurfaces become irrelevant
up to homology, and the main objects of interest become the observable currents
them selves. Gauge inequivalent solutions can be distinguished by means of
observable currents. With the aim of modeling spacetime local physics, we work
on spacetime domains $U\subset M$ which may have boundaries and corners.
Hamiltonian observable currents are those satisfying ${\sf
d_v}F=-\iota_V\Omega_L+{\sf d_h}\sigma^F$ and a certain boundary condition. The
family of Hamiltonian observable currents is endowed with a bracket that gives
it a structure which generalizes a Lie algebra in which the Jacobi relation is
modified by the presence of a boundary term. If the domain of interest has no
boundaries the resulting algebra of observables is a Lie algebra. In the
resulting framework algebras of observable currents are associated to bounded
domains, and the local algebras obey interesting gluing properties. These
results are due to considering currents that defined only locally in field
space and to a revision of the concept of gauge invariance in bounded spacetime
domains. A perturbation of the field on a bounded spacetime domain is regarded
as gauge if: (i) the "first order holographic imprint" that it leaves in any
hypersurface locally splitting a spacetime domain into two subdomains is
negligible according to the linearized gluing field equation, and (ii) the
perturbation vanishes at the boundary of the domain. A current is gauge
invariant if the variation in them induced by any gauge perturbation vanishes
up to boundary terms.
| [
{
"created": "Wed, 26 Apr 2017 02:45:46 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2017 23:03:06 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Aug 2018 19:04:44 GMT",
"version": "v3"
}
] | 2018-08-03 | [
[
"Díaz-Marín",
"Homero G.",
""
],
[
"Zapata",
"José A.",
""
]
] | Observable currents are locally defined gauge invariant conserved currents; physical observables may be calculated integrating them on appropriate hypersurfaces. Due to the conservation law the hypersurfaces become irrelevant up to homology, and the main objects of interest become the observable currents them selves. Gauge inequivalent solutions can be distinguished by means of observable currents. With the aim of modeling spacetime local physics, we work on spacetime domains $U\subset M$ which may have boundaries and corners. Hamiltonian observable currents are those satisfying ${\sf d_v}F=-\iota_V\Omega_L+{\sf d_h}\sigma^F$ and a certain boundary condition. The family of Hamiltonian observable currents is endowed with a bracket that gives it a structure which generalizes a Lie algebra in which the Jacobi relation is modified by the presence of a boundary term. If the domain of interest has no boundaries the resulting algebra of observables is a Lie algebra. In the resulting framework algebras of observable currents are associated to bounded domains, and the local algebras obey interesting gluing properties. These results are due to considering currents that defined only locally in field space and to a revision of the concept of gauge invariance in bounded spacetime domains. A perturbation of the field on a bounded spacetime domain is regarded as gauge if: (i) the "first order holographic imprint" that it leaves in any hypersurface locally splitting a spacetime domain into two subdomains is negligible according to the linearized gluing field equation, and (ii) the perturbation vanishes at the boundary of the domain. A current is gauge invariant if the variation in them induced by any gauge perturbation vanishes up to boundary terms. |
1109.4629 | Martin Kober | Martin Kober | Generalized Quantization Principle in Canonical Quantum Gravity and
Application to Quantum Cosmology | 11 pages | Int.J.Mod.Phys.A27:1250106,2012 | 10.1142/S0217751X12501060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper is considered a generalized quantization principle for the
gravitational field in canonical quantum gravity, especially with respect to
quantum geometrodynamics. This assumption can be interpreted as a transfer from
the generalized uncertainty principle in quantum mechanics, which is postulated
as generalization of the Heisenberg algebra to introduce a minimal length, to a
corresponding quantization principle concerning the quantities of quantum
gravity. According to this presupposition there have to be given generalized
representations of the operators referring to the observables in the canonical
approach of a quantum description of general relativity. This also leads to
generalized constraints for the states and thus to a generalized Wheeler DeWitt
equation determining a new dynamical behaviour. As a special manifestation of
this modified canonical theory of quantum gravity there is explored quantum
cosmology. The generalized cosmological Wheeler DeWitt equation corresponding
to the application of the generalized quantization principle to the
cosmological degree of freedom is solved by using Sommerfelds polynomial
method.
| [
{
"created": "Wed, 21 Sep 2011 08:58:23 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Mar 2012 23:21:49 GMT",
"version": "v2"
},
{
"created": "Sun, 5 Aug 2012 13:29:17 GMT",
"version": "v3"
}
] | 2012-08-07 | [
[
"Kober",
"Martin",
""
]
] | In this paper is considered a generalized quantization principle for the gravitational field in canonical quantum gravity, especially with respect to quantum geometrodynamics. This assumption can be interpreted as a transfer from the generalized uncertainty principle in quantum mechanics, which is postulated as generalization of the Heisenberg algebra to introduce a minimal length, to a corresponding quantization principle concerning the quantities of quantum gravity. According to this presupposition there have to be given generalized representations of the operators referring to the observables in the canonical approach of a quantum description of general relativity. This also leads to generalized constraints for the states and thus to a generalized Wheeler DeWitt equation determining a new dynamical behaviour. As a special manifestation of this modified canonical theory of quantum gravity there is explored quantum cosmology. The generalized cosmological Wheeler DeWitt equation corresponding to the application of the generalized quantization principle to the cosmological degree of freedom is solved by using Sommerfelds polynomial method. |
1412.4366 | Jian-Yang Zhu | Xiao-Min Zhang and Jian-Yang Zhu | Primordial non-Gaussianity in noncanonical warm inflation | 7 pages, 2 figures | Phys. Rev. D 91, 063510 (2015) | 10.1103/PhysRevD.91.063510 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the bispectrum of the primordial curvature perturbation on
uniform-density hypersurfaces generated by a kind of the noncanonical warm
inflation, wherein the inflation is provided by a noncanonical scalar inflaton
field that is coupled to radiation through a thermal dissipation effect. We
obtain an analytic form for the nonlinear parameter $f_{NL}$ that describes the
non-Gaussianity in first-order cosmological perturbation theory and analyse the
magnitude of this nonlinear parameter. We make a comparison between our result
and those of the standard inflation and the canonical warm inflation. We also
discuss when the contribution to the non-Gaussianity due to the second-order
perturbation theory becomes more important and what effect can be observed. We
take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how
the sound speed and the thermal dissipation strength to decide the
non-Gaussianity and to get a lower bound of the sound speed constrained by
PLANCK.
| [
{
"created": "Sun, 14 Dec 2014 14:45:23 GMT",
"version": "v1"
}
] | 2015-04-09 | [
[
"Zhang",
"Xiao-Min",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | We study the bispectrum of the primordial curvature perturbation on uniform-density hypersurfaces generated by a kind of the noncanonical warm inflation, wherein the inflation is provided by a noncanonical scalar inflaton field that is coupled to radiation through a thermal dissipation effect. We obtain an analytic form for the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in first-order cosmological perturbation theory and analyse the magnitude of this nonlinear parameter. We make a comparison between our result and those of the standard inflation and the canonical warm inflation. We also discuss when the contribution to the non-Gaussianity due to the second-order perturbation theory becomes more important and what effect can be observed. We take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how the sound speed and the thermal dissipation strength to decide the non-Gaussianity and to get a lower bound of the sound speed constrained by PLANCK. |
2104.04596 | Toral Gupta | Toral Gupta, Mario Herrero-Valea, Diego Blas, Enrico Barausse, Neil
Cornish, Kent Yagi, Nicol\'as Yunes | New binary pulsar constraints on Einstein-{\ae}ther theory after
GW170817 | 43 pages, 8 figures; minor changes to match version published in CQG | Class. Quantum Grav. 38 195003 (2021) | 10.1088/1361-6382/ac1a69 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The timing of millisecond pulsars has long been used as an exquisitely
precise tool for testing the building blocks of general relativity, including
the strong equivalence principle and Lorentz symmetry. Observations of binary
systems involving at least one millisecond pulsar have been used to place
bounds on the parameters of Einstein-{\ae}ther theory, a gravitational theory
that violates Lorentz symmetry at low energies via a preferred and dynamical
time threading of the spacetime manifold. However, these studies did not cover
the region of parameter space that is still viable after the recent bounds on
the speed of gravitational waves from GW170817/GRB170817A. The restricted
coverage was due to limitations in the methods used to compute the pulsar
sensitivities, which parameterize violations of the strong-equivalence
principle in these systems. We extend here the calculation of pulsar
sensitivities to the parameter space of Einstein-{\ae}ther theory that remains
viable after GW170817/GRB170817A. We show that observations of the damping of
the period of quasi-circular binary pulsars and of the triple system PSR
J0337+1715 further constrain the viable parameter space by about an order of
magnitude over previous constraints.
| [
{
"created": "Fri, 9 Apr 2021 20:55:18 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Aug 2021 18:36:28 GMT",
"version": "v2"
}
] | 2021-08-31 | [
[
"Gupta",
"Toral",
""
],
[
"Herrero-Valea",
"Mario",
""
],
[
"Blas",
"Diego",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Cornish",
"Neil",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The timing of millisecond pulsars has long been used as an exquisitely precise tool for testing the building blocks of general relativity, including the strong equivalence principle and Lorentz symmetry. Observations of binary systems involving at least one millisecond pulsar have been used to place bounds on the parameters of Einstein-{\ae}ther theory, a gravitational theory that violates Lorentz symmetry at low energies via a preferred and dynamical time threading of the spacetime manifold. However, these studies did not cover the region of parameter space that is still viable after the recent bounds on the speed of gravitational waves from GW170817/GRB170817A. The restricted coverage was due to limitations in the methods used to compute the pulsar sensitivities, which parameterize violations of the strong-equivalence principle in these systems. We extend here the calculation of pulsar sensitivities to the parameter space of Einstein-{\ae}ther theory that remains viable after GW170817/GRB170817A. We show that observations of the damping of the period of quasi-circular binary pulsars and of the triple system PSR J0337+1715 further constrain the viable parameter space by about an order of magnitude over previous constraints. |
gr-qc/0606038 | Alan Macdonald | Alan Macdonald | Comment on "The Cosmic Time in Terms of the Redshift", by Carmeli et al | 2 pages, to appear Found. Phys. Lett | Found.Phys.Lett.19:631-632,2006 | 10.1007/s10702-006-1017-2 | null | gr-qc | null | The time-redshift relation of Carmeli et al. differs from that of the
standard flat LambdaCDM model by more than 500 million years for 1 < z < 4.5.
| [
{
"created": "Thu, 8 Jun 2006 22:56:05 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Macdonald",
"Alan",
""
]
] | The time-redshift relation of Carmeli et al. differs from that of the standard flat LambdaCDM model by more than 500 million years for 1 < z < 4.5. |
1001.1990 | Eric Greenwood | Eric Greenwood | Quantum Mechanical Effects in Gravitational Collapse | PhD thesis, 137 pages, 26 Figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis we investigate quantum mechanical effects to various aspects
of gravitational collapse. These quantum mechanical effects are implemented in
the context of the Functional Schr\"odinger formalism. The Functional
Schr\"odinger formalism allows us to investigate the time-dependent evolutions
of the quantum mechanical effects, which is beyond the scope of the usual
methods used to investigate the quantum mechanical corrections of gravitational
collapse. Utilizing the time-dependent nature of the Functional Schr\"odinger
formalism, we study the quantization of a spherically symmetric domain wall
from the view point of an asymptotic and infalling observer, in the absence of
radiation. To build a more realistic picture, we then study the time-dependent
nature of the induced radiation during the collapse using a semi-classical
approach. Using the domain wall and the induced radiation, we then study the
time-dependent evolution of the entropy of the domain wall. Finally we make
some remarks about the possible inclusion of backreaction into the system.
| [
{
"created": "Tue, 12 Jan 2010 19:33:34 GMT",
"version": "v1"
}
] | 2010-01-13 | [
[
"Greenwood",
"Eric",
""
]
] | In this thesis we investigate quantum mechanical effects to various aspects of gravitational collapse. These quantum mechanical effects are implemented in the context of the Functional Schr\"odinger formalism. The Functional Schr\"odinger formalism allows us to investigate the time-dependent evolutions of the quantum mechanical effects, which is beyond the scope of the usual methods used to investigate the quantum mechanical corrections of gravitational collapse. Utilizing the time-dependent nature of the Functional Schr\"odinger formalism, we study the quantization of a spherically symmetric domain wall from the view point of an asymptotic and infalling observer, in the absence of radiation. To build a more realistic picture, we then study the time-dependent nature of the induced radiation during the collapse using a semi-classical approach. Using the domain wall and the induced radiation, we then study the time-dependent evolution of the entropy of the domain wall. Finally we make some remarks about the possible inclusion of backreaction into the system. |
1607.01702 | Parthapratim Pradhan | Parthapratim Pradhan | CFT and Logarithmic Corrections to the Black Hole Entropy Product
Formula | Version accepted in AHEP | Advances in High Energy Physics Volume 2017 (2017), Article ID
2367387, 8 pages | 10.1155/2017/2367387 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the logarithmic corrections to the black hole (BH) entropy product
formula of outer horizon and inner horizon by taking into account the
\emph{effects of statistical quantum fluctuations around the thermal
equilibrium} and \emph{via conformal field theory} (CFT). We argue that
logarithmic corrections to the BH entropy product formula when calculated using
CFT and taking into the effects of quantum fluctuations around the thermal
equilibrium, the formula should \emph{not be universal} and it should also
\emph{not be quantized}. These results have been explicitly checked by giving
several examples.
| [
{
"created": "Wed, 6 Jul 2016 16:43:27 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Aug 2017 16:13:05 GMT",
"version": "v2"
}
] | 2017-08-08 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We examine the logarithmic corrections to the black hole (BH) entropy product formula of outer horizon and inner horizon by taking into account the \emph{effects of statistical quantum fluctuations around the thermal equilibrium} and \emph{via conformal field theory} (CFT). We argue that logarithmic corrections to the BH entropy product formula when calculated using CFT and taking into the effects of quantum fluctuations around the thermal equilibrium, the formula should \emph{not be universal} and it should also \emph{not be quantized}. These results have been explicitly checked by giving several examples. |
2110.01121 | Thomas Berry | Thomas Berry | Mimicking Black Holes in General Relativity | Masters thesis | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The central theme of this thesis is the study and analysis of black hole
mimickers. The concept of a black hole mimicker is introduced, and various
mimicker spacetime models are examined within the framework of classical
general relativity. The mimickers examined fall into the classes of regular
black holes and traversable wormholes under spherical symmetry. The regular
black holes examined can be further categorised as static spacetimes, however
the traversable wormhole is allowed to have a dynamic (non-static) throat.
Astrophysical observables are calculated for a recently proposed regular black
hole model containing an exponential suppression of the Misner-Sharp
quasi-local mass. This same regular black hole model is then used to construct
a wormhole via the ''cut- and-paste'' technique. The resulting wormhole is then
analysed within the Darmois-Israel thin-shell formalism, and a linearised
stability analysis of the (dynamic) wormhole throat is undertaken. Yet another
regular black hole model spacetime is proposed, extending a previous work which
attempted to construct a regular black hole through a quantum ''deformation''
of the Schwarzschild spacetime. The resulting spacetime is again analysed
within the framework of classical general relativity. In addition to the study
of black hole mimickers, I start with a brief overview of the theory of special
relativity where a new and novel result is presented for the combination of
relativistic velocities in general directions using quaternions. This is
succeed by an introduction to concepts in differential geometry needed for the
successive introduction to the theory of general relativity. A thorough
discussion of the concept of spacetime singularities is then provided, before
analysing the specific black hole mimickers discussed above.
| [
{
"created": "Thu, 30 Sep 2021 07:15:15 GMT",
"version": "v1"
}
] | 2021-10-05 | [
[
"Berry",
"Thomas",
""
]
] | The central theme of this thesis is the study and analysis of black hole mimickers. The concept of a black hole mimicker is introduced, and various mimicker spacetime models are examined within the framework of classical general relativity. The mimickers examined fall into the classes of regular black holes and traversable wormholes under spherical symmetry. The regular black holes examined can be further categorised as static spacetimes, however the traversable wormhole is allowed to have a dynamic (non-static) throat. Astrophysical observables are calculated for a recently proposed regular black hole model containing an exponential suppression of the Misner-Sharp quasi-local mass. This same regular black hole model is then used to construct a wormhole via the ''cut- and-paste'' technique. The resulting wormhole is then analysed within the Darmois-Israel thin-shell formalism, and a linearised stability analysis of the (dynamic) wormhole throat is undertaken. Yet another regular black hole model spacetime is proposed, extending a previous work which attempted to construct a regular black hole through a quantum ''deformation'' of the Schwarzschild spacetime. The resulting spacetime is again analysed within the framework of classical general relativity. In addition to the study of black hole mimickers, I start with a brief overview of the theory of special relativity where a new and novel result is presented for the combination of relativistic velocities in general directions using quaternions. This is succeed by an introduction to concepts in differential geometry needed for the successive introduction to the theory of general relativity. A thorough discussion of the concept of spacetime singularities is then provided, before analysing the specific black hole mimickers discussed above. |
2403.20011 | Sunil Maurya DR. | S. K. Maurya, Ksh. Newton Singh, G. Mustafa, M. Govender, Abdelghani
Errehymy, Abdul Aziz | Influence of pressure anisotropy and non-metricity parameter on
mass-radius relation and stability of millisecond pulsar in $f(Q)$ gravity | 6 figures and 2 tables (Submssion for JCAP) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this study we explore the astrophysical implications of pressure
anisotropy on the physical characteristics of millisecond pulsars within the
framework of $f(Q)$ gravity. Starting off with the field equations for
anisotropic matter distributions, we adopt the physically salient
Durgapal-Fuloria ansatz together with a well-motivated anisotropic factor for
the interior matter distribution. This leads to a nonlinear second order
differential equation which is integrated to give the complete gravitational
and thermodynamical properties of the stellar object. The resulting model is
subjected to rigorous tests to ensure that it qualifies as a physically viable
compact object within the $f(Q)$-gravity framework. We study in detail two
factors, one being non-metricity (gravitational interaction) and the other the
pressure anisotropy (matter variation) and their contributions to the mass,
radius and stability of the star. Our analyses indicate that our models are
well-behaved, singularity-free and can account for the existence of a wide
range of observed pulsars with masses ranging from 2.08 to 2.67 $M_{\odot}$,
with the upper value being in the so-called {\em mass gap} regime observed in
gravitational events such as GW190814. A novel finding of this work is
two-fold: an increase in the non-metricity factor (fixed anisotropy) leads to a
spectrum of pulsars with radii ranging from a minimum of 10 km whereas a
variation in anisotropy (fixed non-metricity) restricts the radii to a narrow
window between ($12 - 13.2$) km for a 450 Hz pulsar. In addition, contributions
from anisotropy outweigh the impact of nonmetricity in predicting the masses of
pulsars with the ratio, $\left(\frac{M_\Delta}{M_Q}\right)_{max} \approx 2.43 $
for low mass pulsars.
| [
{
"created": "Fri, 29 Mar 2024 06:52:53 GMT",
"version": "v1"
}
] | 2024-04-01 | [
[
"Maurya",
"S. K.",
""
],
[
"Singh",
"Ksh. Newton",
""
],
[
"Mustafa",
"G.",
""
],
[
"Govender",
"M.",
""
],
[
"Errehymy",
"Abdelghani",
""
],
[
"Aziz",
"Abdul",
""
]
] | In this study we explore the astrophysical implications of pressure anisotropy on the physical characteristics of millisecond pulsars within the framework of $f(Q)$ gravity. Starting off with the field equations for anisotropic matter distributions, we adopt the physically salient Durgapal-Fuloria ansatz together with a well-motivated anisotropic factor for the interior matter distribution. This leads to a nonlinear second order differential equation which is integrated to give the complete gravitational and thermodynamical properties of the stellar object. The resulting model is subjected to rigorous tests to ensure that it qualifies as a physically viable compact object within the $f(Q)$-gravity framework. We study in detail two factors, one being non-metricity (gravitational interaction) and the other the pressure anisotropy (matter variation) and their contributions to the mass, radius and stability of the star. Our analyses indicate that our models are well-behaved, singularity-free and can account for the existence of a wide range of observed pulsars with masses ranging from 2.08 to 2.67 $M_{\odot}$, with the upper value being in the so-called {\em mass gap} regime observed in gravitational events such as GW190814. A novel finding of this work is two-fold: an increase in the non-metricity factor (fixed anisotropy) leads to a spectrum of pulsars with radii ranging from a minimum of 10 km whereas a variation in anisotropy (fixed non-metricity) restricts the radii to a narrow window between ($12 - 13.2$) km for a 450 Hz pulsar. In addition, contributions from anisotropy outweigh the impact of nonmetricity in predicting the masses of pulsars with the ratio, $\left(\frac{M_\Delta}{M_Q}\right)_{max} \approx 2.43 $ for low mass pulsars. |
1105.4929 | Pankaj Jain | Pankaj Jain, Purnendu Karmakar, Subhadip Mitra, Sukanta Panda, Naveen
K. Singh | Cosmological Perturbation Analysis in a Scale Invariant Model of Gravity | 9 pages, 1 figure | Class.Quant.Grav.28:215010,2011 | 10.1088/0264-9381/28/21/215010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a model for gravity that is invariant under global scale
transformations. It includes one extra real scalar field coupled non-minimally
to the gravity fields. In this model all the dimensionful parameters like the
gravitational constant and the cosmological constant etc. are generated by a
solution of the classical equations of motion which breaks scale invariance. In
this paper we demonstrate the stability of such a solution against small
perturbations in a flat FRW background by making a perturbative expansion
around this solution and solving the resulting equations linear in the
perturbations.
| [
{
"created": "Wed, 25 May 2011 04:23:13 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Feb 2012 15:45:11 GMT",
"version": "v2"
}
] | 2012-02-06 | [
[
"Jain",
"Pankaj",
""
],
[
"Karmakar",
"Purnendu",
""
],
[
"Mitra",
"Subhadip",
""
],
[
"Panda",
"Sukanta",
""
],
[
"Singh",
"Naveen K.",
""
]
] | We consider a model for gravity that is invariant under global scale transformations. It includes one extra real scalar field coupled non-minimally to the gravity fields. In this model all the dimensionful parameters like the gravitational constant and the cosmological constant etc. are generated by a solution of the classical equations of motion which breaks scale invariance. In this paper we demonstrate the stability of such a solution against small perturbations in a flat FRW background by making a perturbative expansion around this solution and solving the resulting equations linear in the perturbations. |
gr-qc/9901008 | Daniel Augusto Turolla Vanzella | George E.A. Matsas and Daniel A.T. Vanzella | Decay of protons and neutrons induced by acceleration | 18 pages (REVTEX), 3 figures | Phys.Rev. D59 (1999) 094004 | 10.1103/PhysRevD.59.094004 | IFT-P.007/99 | gr-qc hep-ph hep-th | null | We investigate the decay of accelerated protons and neutrons. Calculations
are carried out in the inertial and coaccelerated frames. Particle
interpretation of these processes are quite different in each frame but the
decay rates are verified to agree in both cases. For sake of simplicity our
calculations are performed in a two-dimensional spacetime since our conclusions
are not conceptually affected by this.
| [
{
"created": "Tue, 5 Jan 1999 16:08:05 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Matsas",
"George E. A.",
""
],
[
"Vanzella",
"Daniel A. T.",
""
]
] | We investigate the decay of accelerated protons and neutrons. Calculations are carried out in the inertial and coaccelerated frames. Particle interpretation of these processes are quite different in each frame but the decay rates are verified to agree in both cases. For sake of simplicity our calculations are performed in a two-dimensional spacetime since our conclusions are not conceptually affected by this. |
gr-qc/9710015 | Chris Chambers | Chris M. Chambers (Montana State), Patrick R. Brady (CalTech), William
Krivan (Utah) and Pablo Laguna (Penn. State) | Some Cosmological Tails of Collapse | 3 pages (including 2 postscript figures), Latex. Uses mprocl.sty
(included). To appear in the proceedings of `The Eight Marcel Grossmann
Meeting on General Relativity', 22-27 June 1997, The Hebrew University,
Jerusalem, Israel | null | null | MSUPHY9720 | gr-qc | null | We summarize the results of an investigation into the late time behavior of
massless scalar fields propagating on spherically symmetric black hole
spacetimes with a non-zero cosmological constant. The compatibility of these
results with the `minimal requirement' of Brady and Poisson is commented upon.
| [
{
"created": "Thu, 2 Oct 1997 18:37:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chambers",
"Chris M.",
"",
"Montana State"
],
[
"Brady",
"Patrick R.",
"",
"CalTech"
],
[
"Krivan",
"William",
"",
"Utah"
],
[
"Laguna",
"Pablo",
"",
"Penn. State"
]
] | We summarize the results of an investigation into the late time behavior of massless scalar fields propagating on spherically symmetric black hole spacetimes with a non-zero cosmological constant. The compatibility of these results with the `minimal requirement' of Brady and Poisson is commented upon. |
1805.12593 | Kazuharu Bamba | G.G.L. Nashed and Kazuharu Bamba | Spherically symmetric charged black hole in conformal teleparallel
equivalent of general relativity | 11 pages, no figure, version accepted for publication in JCAP | Journal of Cosmology and Astroparticle Physics 09 (2018) 020 | 10.1088/1475-7516/2018/09/020 | FU-PCG-35 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study 4-dimensional non-charged and charged spherically symmetric
spacetimes in conformal teleparallel equivalent of general relativity. We apply
the gravitational field equations in non-charged and charged spacetimes to the
diagonal and non-diagonal vierbeins and derive their sets of the non-linear
differential equations. It is demonstrated that the Schwarzschild, for the
non-charged case, and the Reissner-Nordstr\"om, for the charged case, are the
only black hole solutions for the spherically symmetric case in the framework
of the conformal teleparallel equivalent of general relativity theory. As a
result, it is found that in the conformal teleparallel equivalent of general
relativity theory, the scalar field cannot have any effect for the spherically
symmetric manifold.
| [
{
"created": "Tue, 29 May 2018 14:20:58 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Aug 2018 15:26:00 GMT",
"version": "v2"
}
] | 2018-09-17 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | We study 4-dimensional non-charged and charged spherically symmetric spacetimes in conformal teleparallel equivalent of general relativity. We apply the gravitational field equations in non-charged and charged spacetimes to the diagonal and non-diagonal vierbeins and derive their sets of the non-linear differential equations. It is demonstrated that the Schwarzschild, for the non-charged case, and the Reissner-Nordstr\"om, for the charged case, are the only black hole solutions for the spherically symmetric case in the framework of the conformal teleparallel equivalent of general relativity theory. As a result, it is found that in the conformal teleparallel equivalent of general relativity theory, the scalar field cannot have any effect for the spherically symmetric manifold. |
1701.09169 | Naoki Tsukamoto | Naoki Tsukamoto | Retrolensing by a wormhole at deflection angles $\pi$ and $3\pi$ | 20 pages, 6 figures, title changed, minor correction, accepted for
publication in Physical Review D | Phys. Rev. D 95, 084021 (2017) | 10.1103/PhysRevD.95.084021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deflection angle of a light ray can be arbitrarily large near a light
sphere. The time-symmetrical shape of light curves of a pair of light rays
reflected by a light sphere of a lens object does not depend on the details of
the lens object. We consider retrolensing light curves of sunlight with
deflection angles $\pi$ and $3\pi$ by an Ellis wormhole, which is the simplest
Morris-Thorne wormhole. If an Ellis wormhole with a throat parameter
$a=10^{11}$ km is $100$ pc away from an observer and if the Ellis wormhole, the
observer, and the sun are aligned perfectly in this order, the apparent
magnitudes of a pair of light rays with deflection angles $\pi$ and $3\pi$
become $11$ and $18$, respectively. The two pairs of light rays make a
superposed light curve with two separable peaks and they break down time
symmetry of a retrolensing light curve. The observation of the two separated
peaks of the light curves gives us information on the details of the lens
object. If the observer can also separate the pair of the images with the
deflection angle $\pi$ into a double image, he or she can say whether the
retrolensing is caused by an Ellis wormhole or a Schwarzschild black hole.
| [
{
"created": "Tue, 31 Jan 2017 18:32:19 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Apr 2017 13:56:33 GMT",
"version": "v2"
}
] | 2017-04-14 | [
[
"Tsukamoto",
"Naoki",
""
]
] | The deflection angle of a light ray can be arbitrarily large near a light sphere. The time-symmetrical shape of light curves of a pair of light rays reflected by a light sphere of a lens object does not depend on the details of the lens object. We consider retrolensing light curves of sunlight with deflection angles $\pi$ and $3\pi$ by an Ellis wormhole, which is the simplest Morris-Thorne wormhole. If an Ellis wormhole with a throat parameter $a=10^{11}$ km is $100$ pc away from an observer and if the Ellis wormhole, the observer, and the sun are aligned perfectly in this order, the apparent magnitudes of a pair of light rays with deflection angles $\pi$ and $3\pi$ become $11$ and $18$, respectively. The two pairs of light rays make a superposed light curve with two separable peaks and they break down time symmetry of a retrolensing light curve. The observation of the two separated peaks of the light curves gives us information on the details of the lens object. If the observer can also separate the pair of the images with the deflection angle $\pi$ into a double image, he or she can say whether the retrolensing is caused by an Ellis wormhole or a Schwarzschild black hole. |
gr-qc/9510028 | Chris Isham | P. Hajicek and C.J. Isham | The symplectic geometry of a parametrized scalar field on a curved
background | 30 pages, revtex | J.Math.Phys. 37 (1996) 3505-3521 | 10.1063/1.531578 | IMPERIAL/TP/95--96/1 | gr-qc | null | We study the real, massive Klein-Gordon field on a $C^\infty$
globally-hyperbolic background space-time with compact Cauchy hypersurfaces. In
particular, the parametrization of this system as initiated by Dirac and
Kucha\v{r} is put on a rigorous basis. The discussion is focussed on the
structure of the set of spacelike embeddings of the Cauchy manifold into the
space-time, and on the associated $e$-tensor density bundles and their tangent
and cotangent bundles. The dynamics of the field is expressed as a set of
automorphisms of the space of initial data in which each pair of embeddings
defines one such automorphism. Using these results, the extended phase space of
the system is shown to be a weak-symplectic manifold, and the Kucha\v{r}
constraint is shown to define a smooth constraint submanifold which is foliated
smoothly by the constraint orbits. The pull-back of the symplectic form to the
constraint surface is a presymplectic form which is singular on the tangent
spaces to the constraint orbits. Thus, the geometric structure of this
infinite-dimensional system is analogous to that of a finite-dimensional,
first-class parametrized system, and hence many of the results for the latter
can be transferred to the infinite-dimensional case without difficulty.
| [
{
"created": "Mon, 16 Oct 1995 20:56:51 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Hajicek",
"P.",
""
],
[
"Isham",
"C. J.",
""
]
] | We study the real, massive Klein-Gordon field on a $C^\infty$ globally-hyperbolic background space-time with compact Cauchy hypersurfaces. In particular, the parametrization of this system as initiated by Dirac and Kucha\v{r} is put on a rigorous basis. The discussion is focussed on the structure of the set of spacelike embeddings of the Cauchy manifold into the space-time, and on the associated $e$-tensor density bundles and their tangent and cotangent bundles. The dynamics of the field is expressed as a set of automorphisms of the space of initial data in which each pair of embeddings defines one such automorphism. Using these results, the extended phase space of the system is shown to be a weak-symplectic manifold, and the Kucha\v{r} constraint is shown to define a smooth constraint submanifold which is foliated smoothly by the constraint orbits. The pull-back of the symplectic form to the constraint surface is a presymplectic form which is singular on the tangent spaces to the constraint orbits. Thus, the geometric structure of this infinite-dimensional system is analogous to that of a finite-dimensional, first-class parametrized system, and hence many of the results for the latter can be transferred to the infinite-dimensional case without difficulty. |
2403.07302 | Rudeep Gaur | Rudeep Gaur (Victoria University of Wellington) | The Kerr Memory Effect at Null Infinity | 15 pages (2 references added on request) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the memory effect due to a gravitational wave striking a Kerr
black hole as seen by an observer at null infinity. This is done by working in
Bondi--Sachs coordinates. It was shown by Hawking, Perry, and Strominger (HPS)
that the memory effect due to a gravitational shockwave is seen as a pure BMS
supertranslation from null infinity. Hence, it is of interest to compute the
supertranslated Kerr solution in Bondi--Sachs coordinates. Finally, the
gravitational wave is said to implant soft supertranslation hair on the event
horizon of the black hole which carries superrotation charge. We will
explicitly calculate the change in superrotation charge on the event horizon
due to the supertranslation hair.
| [
{
"created": "Tue, 12 Mar 2024 04:07:19 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2024 21:12:00 GMT",
"version": "v2"
}
] | 2024-03-29 | [
[
"Gaur",
"Rudeep",
"",
"Victoria University of Wellington"
]
] | We compute the memory effect due to a gravitational wave striking a Kerr black hole as seen by an observer at null infinity. This is done by working in Bondi--Sachs coordinates. It was shown by Hawking, Perry, and Strominger (HPS) that the memory effect due to a gravitational shockwave is seen as a pure BMS supertranslation from null infinity. Hence, it is of interest to compute the supertranslated Kerr solution in Bondi--Sachs coordinates. Finally, the gravitational wave is said to implant soft supertranslation hair on the event horizon of the black hole which carries superrotation charge. We will explicitly calculate the change in superrotation charge on the event horizon due to the supertranslation hair. |
2105.06636 | Sumanta Chakraborty | Indrani Banerjee, Sumanta Chakraborty and Soumitra SenGupta | Looking for extra dimensions in the observed quasi-periodic oscillations
of black holes | Published version, 37 pages, 9 figures | JCAP09(2021)037 | 10.1088/1475-7516/2021/09/037 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-periodic oscillations, often present in the power density spectrum of
accretion disk around black holes, are useful probes for the understanding of
gravitational interaction in the near-horizon regime of black holes. Since the
presence of an extra spatial dimension modifies the near horizon geometry of
black holes, it is expected that the study of these quasi-periodic oscillations
may shed some light on the possible existence of these extra dimensions.
Intriguingly, most of the extra dimensional models, which are of significant
interest to the scientific community, predicts the existence of a tidal charge
parameter in black hole spacetimes. This tidal charge parameter can have an
overall negative sign and is a distinctive signature of the extra dimensions.
Motivated by this, we have studied the quasi-periodic oscillations for a
rotating braneworld black hole using the available theoretical models.
Subsequently, we have used the observations of the quasi-periodic oscillations
from available black hole sources, e.g., GRO J1655 -- 40, XTE J1550 -- 564, GRS
1915 + 105, H 1743 + 322 and Sgr A* and have compared them with the predictions
from the relevant theoretical models, in order to estimate the tidal charge
parameter. It turns out that among the 11 theoretical models considered here, 8
of them predict a negative value for the tidal charge parameter, while for the
others negative values of the tidal charge parameter are also well within the
1-$\sigma$ confidence interval.
| [
{
"created": "Fri, 14 May 2021 04:13:19 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 2021 03:56:19 GMT",
"version": "v2"
}
] | 2021-09-29 | [
[
"Banerjee",
"Indrani",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | Quasi-periodic oscillations, often present in the power density spectrum of accretion disk around black holes, are useful probes for the understanding of gravitational interaction in the near-horizon regime of black holes. Since the presence of an extra spatial dimension modifies the near horizon geometry of black holes, it is expected that the study of these quasi-periodic oscillations may shed some light on the possible existence of these extra dimensions. Intriguingly, most of the extra dimensional models, which are of significant interest to the scientific community, predicts the existence of a tidal charge parameter in black hole spacetimes. This tidal charge parameter can have an overall negative sign and is a distinctive signature of the extra dimensions. Motivated by this, we have studied the quasi-periodic oscillations for a rotating braneworld black hole using the available theoretical models. Subsequently, we have used the observations of the quasi-periodic oscillations from available black hole sources, e.g., GRO J1655 -- 40, XTE J1550 -- 564, GRS 1915 + 105, H 1743 + 322 and Sgr A* and have compared them with the predictions from the relevant theoretical models, in order to estimate the tidal charge parameter. It turns out that among the 11 theoretical models considered here, 8 of them predict a negative value for the tidal charge parameter, while for the others negative values of the tidal charge parameter are also well within the 1-$\sigma$ confidence interval. |
1705.06988 | Hafiza Rizwana Kausar | Hafiza Rizwana Kausar | Behaviour of Charged Collapsing Fluids after Hydrostatic Equilibrium in
R^n Gravity | Accepted for publication in European Physical Journal C | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to study the transport equation and its coupling
with Maxwell equation in the framework of R^n gravity. Using
Muller-Israel-Stewart theory for the conduction of dissipative fluids, we
analyze the temperature, heat flux, viscosity and thermal conductivity in the
scenario of relaxation time. All these thermodynamical variables are appeared
in the form of a single factor whose influence is discussed on the evolution of
relativistic model for the heat conducting collapsing star.
| [
{
"created": "Thu, 18 May 2017 06:46:49 GMT",
"version": "v1"
}
] | 2017-05-22 | [
[
"Kausar",
"Hafiza Rizwana",
""
]
] | The purpose of this paper is to study the transport equation and its coupling with Maxwell equation in the framework of R^n gravity. Using Muller-Israel-Stewart theory for the conduction of dissipative fluids, we analyze the temperature, heat flux, viscosity and thermal conductivity in the scenario of relaxation time. All these thermodynamical variables are appeared in the form of a single factor whose influence is discussed on the evolution of relativistic model for the heat conducting collapsing star. |
gr-qc/9612010 | Simonetta Frittelli | Simonetta Frittelli, Carlos N. Kozameh, Ezra T. Newman, Carlo Rovelli,
Ranjeet S. Tate (University of Pittsburgh) | On the quantization of the Null-Surface formulation of GR | 24 pages, Revtex | Phys.Rev. D56 (1997) 889-907 | 10.1103/PhysRevD.56.889 | null | gr-qc | null | We define and discuss various quantum operators that describe the geometry of
spacetime in quantum general relativity. These are obtained by combining the
Null-Surface Formulation of general relativity, recently developed, with
asymptotic quantization. One of the operators defined describes a ``fuzzy''
quantum light cone structure. Others, denoted ``spacetime-point operators'',
characterize geometrically-defined physical points. We discuss the
interpretation of these operators. This seems to suggest a picture of quantum
spacetime as made of ``fuzzy'' physical points. We derive the commutation
algebra of the quantum spacetime point operators in the linearization around
flat space.
| [
{
"created": "Tue, 3 Dec 1996 19:44:38 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Frittelli",
"Simonetta",
"",
"University of Pittsburgh"
],
[
"Kozameh",
"Carlos N.",
"",
"University of Pittsburgh"
],
[
"Newman",
"Ezra T.",
"",
"University of Pittsburgh"
],
[
"Rovelli",
"Carlo",
"",
"University of Pittsburgh"
],
[... | We define and discuss various quantum operators that describe the geometry of spacetime in quantum general relativity. These are obtained by combining the Null-Surface Formulation of general relativity, recently developed, with asymptotic quantization. One of the operators defined describes a ``fuzzy'' quantum light cone structure. Others, denoted ``spacetime-point operators'', characterize geometrically-defined physical points. We discuss the interpretation of these operators. This seems to suggest a picture of quantum spacetime as made of ``fuzzy'' physical points. We derive the commutation algebra of the quantum spacetime point operators in the linearization around flat space. |
2312.03760 | Dr. Sudhaker Upadhyay | Amit Kumar, Dharm Veer Singh, Yerlan Myrzakulov, Gulmira Yergaliyeva
and Sudhaker Upadhyay | Exact Solution of Bardeen Black Hole in Einstein-Gauss-Bonnet gravity | 22 pages, 22 pages, published in EPJP | Eur. Phys. J. Plus (2023) 138:1071 | 10.1140/epjp/s13360-023-04718-3 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We have obtained a new exact regular black hole solution for the EGB gravity
coupled with nonlinear electrodynamics in AdS space. The numerical analysis of
horizon structure suggests two horizons exist: Cauchy and event. We also study
the thermal properties of this black hole, which satisfy the modified first law
of thermodynamics. Moreover, we analyse the local and global stability of the
black hole. The $P-V$ criticality and phase transition are also discussed. The
critical exponents for the present model exactly match the mean field theory.
| [
{
"created": "Tue, 5 Dec 2023 16:43:09 GMT",
"version": "v1"
}
] | 2023-12-08 | [
[
"Kumar",
"Amit",
""
],
[
"Singh",
"Dharm Veer",
""
],
[
"Myrzakulov",
"Yerlan",
""
],
[
"Yergaliyeva",
"Gulmira",
""
],
[
"Upadhyay",
"Sudhaker",
""
]
] | We have obtained a new exact regular black hole solution for the EGB gravity coupled with nonlinear electrodynamics in AdS space. The numerical analysis of horizon structure suggests two horizons exist: Cauchy and event. We also study the thermal properties of this black hole, which satisfy the modified first law of thermodynamics. Moreover, we analyse the local and global stability of the black hole. The $P-V$ criticality and phase transition are also discussed. The critical exponents for the present model exactly match the mean field theory. |
1804.03535 | Changjun Gao | Changjun Gao | Extending Horndeski theories into Lovelock gravity | 9 pages,8 figures. errors corrected, references added | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Horndeski theories are extended into the Lovelock gravity theory. When
the canonical scalar field is uniquely kinetically coupled to the Lovelock
tensors, it is named after Lovelock scalar field. The Lovelock scalar field
model is a subclass of the new Horndeski theories. A most attractive feature of
the Lovelock scalar field is its equation of motion is second order. So it is
free of ghosts. We study the cosmology of Lovelock scalar field in the
background of $7$ dimensional spacetime and present a class of cosmic
solutions. These solutions reveal the physics of the scalar field is rather
rich and merit further study.
| [
{
"created": "Tue, 10 Apr 2018 13:50:05 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Apr 2018 01:50:51 GMT",
"version": "v2"
},
{
"created": "Thu, 17 May 2018 01:40:40 GMT",
"version": "v3"
}
] | 2018-05-18 | [
[
"Gao",
"Changjun",
""
]
] | The Horndeski theories are extended into the Lovelock gravity theory. When the canonical scalar field is uniquely kinetically coupled to the Lovelock tensors, it is named after Lovelock scalar field. The Lovelock scalar field model is a subclass of the new Horndeski theories. A most attractive feature of the Lovelock scalar field is its equation of motion is second order. So it is free of ghosts. We study the cosmology of Lovelock scalar field in the background of $7$ dimensional spacetime and present a class of cosmic solutions. These solutions reveal the physics of the scalar field is rather rich and merit further study. |
gr-qc/9303014 | null | Istvan Racz | Maxwell Fields in Spacetimes Admitting Non-Null Killing Vectors | 7 pages,PACS numbers: 04.20.Cv, 04.20.Me, 04.40.+c | Class.Quant.Grav.10:L167-L172,1993 | 10.1088/0264-9381/10/9/010 | null | gr-qc | null | We consider source-free electromagnetic fields in spacetimes possessing a
non-null Killing vector field, $\xi^a$. We assume further that the
electromagnetic field tensor, $F_{ab}$, is invariant under the action of the
isometry group induced by $\xi^a$. It is proved that whenever the two
potentials associated with the electromagnetic field are functionally
independent the entire content of Maxwell's equations is equivalent to the
relation $\n^aT_{ab}=0$. Since this relation is implied by Einstein's equation
we argue that it is enough to solve merely Einstein's equation for these
electrovac spacetimes because the relevant equations of motion will be
satisfied automatically. It is also shown that for the exceptional case of
functionally related potentials $\n^aT_{ab}=0$ implies along with one of the
relevant equations of motion that the complementary equation concerning the
electromagnetic field is satisfied.
| [
{
"created": "Wed, 10 Mar 1993 15:24:01 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Racz",
"Istvan",
""
]
] | We consider source-free electromagnetic fields in spacetimes possessing a non-null Killing vector field, $\xi^a$. We assume further that the electromagnetic field tensor, $F_{ab}$, is invariant under the action of the isometry group induced by $\xi^a$. It is proved that whenever the two potentials associated with the electromagnetic field are functionally independent the entire content of Maxwell's equations is equivalent to the relation $\n^aT_{ab}=0$. Since this relation is implied by Einstein's equation we argue that it is enough to solve merely Einstein's equation for these electrovac spacetimes because the relevant equations of motion will be satisfied automatically. It is also shown that for the exceptional case of functionally related potentials $\n^aT_{ab}=0$ implies along with one of the relevant equations of motion that the complementary equation concerning the electromagnetic field is satisfied. |
2102.07494 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev and Vladimir Folomeev | Masking singularities in Weyl gravity and Ricci flows | 10 pages | null | 10.1140/epjc/s10052-021-09188-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within vacuum Weyl gravity, we obtain a solution by which, using different
choices of the conformal factor, we derive metrics describing (i)~a bounce of
the universe; (ii)~toroidal and spherical wormholes; and (iii)~a change in
metric signature. It is demonstrated that singularities occurring in these
systems are "masked". We give a simple explanation of the possibility of
masking the singularities within Weyl gravity. It is shown that in the first
and third cases the three-dimensional metrics form Ricci flows. The question of
the possible applicability of conformal Weyl gravity as some phenomenological
theory in an approximate description of quantum gravity is discussed.
| [
{
"created": "Mon, 15 Feb 2021 11:58:36 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2021 05:47:52 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
]
] | Within vacuum Weyl gravity, we obtain a solution by which, using different choices of the conformal factor, we derive metrics describing (i)~a bounce of the universe; (ii)~toroidal and spherical wormholes; and (iii)~a change in metric signature. It is demonstrated that singularities occurring in these systems are "masked". We give a simple explanation of the possibility of masking the singularities within Weyl gravity. It is shown that in the first and third cases the three-dimensional metrics form Ricci flows. The question of the possible applicability of conformal Weyl gravity as some phenomenological theory in an approximate description of quantum gravity is discussed. |
0905.2542 | E. Kyriakopoulos | E. Kyriakopoulos | Rotating Black Hole Solutions with Axion Dilaton and Two Vector Fields
and Solutions with Metric and Fields of the Same Form | 50 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present two rotating black hole solutions with axion $\xi$, dilaton $\phi$
and two U(1) vector fields. By applying the "Newman-Janis trick" to a metric
with 3 arbitrary parameters we find a rotating metric $g_{\mu\nu}$ with 4 such
parameters $(M, a, Q_E, Q_M)$, and then a solution with this $g_{\mu\nu}$ as
metric. Our solution is asymptotically flat and has angular momentum $J=M a$,
gyromagnetic ratio $g=2$, two horizons, the singularities of Kerr's solution,
axion and dilaton singular only for $r=a\cos\theta=0$. Applying to the solution
we have found the $S-$duality transformation we get a new solution, whose
axion, dilaton and vector fields have one more parameter. The metric, each
vector field and the $\lambda=\xi+ie^{-2\phi}$ of our solutions and the
solution of : Sen for $Q_E$, Sen for $Q_E$ and $Q_M$, Kerr-Newman for $Q_E$ and
$Q_M$, Kerr, Ref. 9, STW, GM-GHS, Reissner-Nordstr\"{o}m,Schwarzschild are the
same function of $a$, and two functions $\rho^2=r(r+b)+a^2\cos^2\theta$ and
$\Delta=\rho^2-2Mr+c$, of $a$, $b$ and two functions, and of $a$, $b$ and $d$
respectively, where $a$, $b$, $c$ and $d$ are constants. It is shown that from
our solutions a number of known solutions can be obtained, which together with
our solutions are listed in an Appendix. Also it is shown that all solutions
which are mentioned in the paper satisfy all energy conditions, and mass
formulae are obtained for them.
| [
{
"created": "Fri, 15 May 2009 12:57:08 GMT",
"version": "v1"
}
] | 2009-05-18 | [
[
"Kyriakopoulos",
"E.",
""
]
] | We present two rotating black hole solutions with axion $\xi$, dilaton $\phi$ and two U(1) vector fields. By applying the "Newman-Janis trick" to a metric with 3 arbitrary parameters we find a rotating metric $g_{\mu\nu}$ with 4 such parameters $(M, a, Q_E, Q_M)$, and then a solution with this $g_{\mu\nu}$ as metric. Our solution is asymptotically flat and has angular momentum $J=M a$, gyromagnetic ratio $g=2$, two horizons, the singularities of Kerr's solution, axion and dilaton singular only for $r=a\cos\theta=0$. Applying to the solution we have found the $S-$duality transformation we get a new solution, whose axion, dilaton and vector fields have one more parameter. The metric, each vector field and the $\lambda=\xi+ie^{-2\phi}$ of our solutions and the solution of : Sen for $Q_E$, Sen for $Q_E$ and $Q_M$, Kerr-Newman for $Q_E$ and $Q_M$, Kerr, Ref. 9, STW, GM-GHS, Reissner-Nordstr\"{o}m,Schwarzschild are the same function of $a$, and two functions $\rho^2=r(r+b)+a^2\cos^2\theta$ and $\Delta=\rho^2-2Mr+c$, of $a$, $b$ and two functions, and of $a$, $b$ and $d$ respectively, where $a$, $b$, $c$ and $d$ are constants. It is shown that from our solutions a number of known solutions can be obtained, which together with our solutions are listed in an Appendix. Also it is shown that all solutions which are mentioned in the paper satisfy all energy conditions, and mass formulae are obtained for them. |
2001.10914 | Marta Colleoni | Cecilio Garc\'ia-Quir\'os, Marta Colleoni, Sascha Husa, H\'ector
Estell\'es, Geraint Pratten, Antoni Ramos-Buades, Maite Mateu-Lucena, and
Rafel Jaume | IMRPhenomXHM: A multi-mode frequency-domain model for the gravitational
wave signal from non-precessing black-hole binaries | 30 pages, 23 figures. Updated to match published version | Phys. Rev. D 102, 064002 (2020) | 10.1103/PhysRevD.102.064002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the IMRPhenomXHM frequency domain phenomenological waveform model
for the inspiral, merger and ringdown of quasi-circular non-precessing black
hole binaries. The model extends the IMRPhenomXAS waveform model, which
describes the dominant quadrupole modes $\ell = |m| = 2$, to the harmonics
$(\ell, |m|)=(2,1), (3,3), (3,2), (4,4)$, and includes mode mixing effects for
the $(3,2)$ spherical harmonic. IMRPhenomXHM is calibrated against hybrid
waveforms, which match an inspiral phase described by the effective-one-body
model and post-Newtonian amplitudes for the subdominant harmonics to numerical
relativity waveforms and numerical solutions to the perturbative Teukolsky
equation for large mass ratios up to 1000.
A computationally efficient implementation of the model is available as part
of the LSC Algorithm Library Suite.
| [
{
"created": "Wed, 29 Jan 2020 16:01:33 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 12:27:51 GMT",
"version": "v2"
}
] | 2020-11-04 | [
[
"García-Quirós",
"Cecilio",
""
],
[
"Colleoni",
"Marta",
""
],
[
"Husa",
"Sascha",
""
],
[
"Estellés",
"Héctor",
""
],
[
"Pratten",
"Geraint",
""
],
[
"Ramos-Buades",
"Antoni",
""
],
[
"Mateu-Lucena",
"Maite",
... | We present the IMRPhenomXHM frequency domain phenomenological waveform model for the inspiral, merger and ringdown of quasi-circular non-precessing black hole binaries. The model extends the IMRPhenomXAS waveform model, which describes the dominant quadrupole modes $\ell = |m| = 2$, to the harmonics $(\ell, |m|)=(2,1), (3,3), (3,2), (4,4)$, and includes mode mixing effects for the $(3,2)$ spherical harmonic. IMRPhenomXHM is calibrated against hybrid waveforms, which match an inspiral phase described by the effective-one-body model and post-Newtonian amplitudes for the subdominant harmonics to numerical relativity waveforms and numerical solutions to the perturbative Teukolsky equation for large mass ratios up to 1000. A computationally efficient implementation of the model is available as part of the LSC Algorithm Library Suite. |
2304.11458 | Roberto Capuzzo-Dolcetta | Roberto Capuzzo-Dolcetta (1) and Matteo Sadun Bordoni (1 and 2) ((1)
Dep. of Physics, Sapienza Univ. of Rome, P.le A. Moro 5, Rome, Italy, (2)
Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1,
85748 Garching, Germany) | Orbital precession of stars in the Galactic center | 12 pages, 8 figures, 7 tables. Submitted to Monthly Notices of the
Royal Astronomical Society | null | 10.1093/mnras/stad1317 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The region around the center of our Galaxy is very dense of stars. The
kinematics of inner moving stars in the Galaxy (the so called S-stars) has been
deeply studied by different research groups leading to the conclusion of the
existence of a very compact object (Sgr A$^*$, likely a supermassive black
hole) responsible for their high speed. Here we start from the observational
evidence of orbital apsidal line precession for the S2 (also called S0-2) star
to investigate on a theoretical side what level of quality in such regime of
relatively strong gravitational field is reached in the orbit angular
precession determination when using a direct orbital integration of the star
motion subjected to an acceleration computed in the post-Newtonian (PN) scheme
up to different orders. This approach, although approximated and limited to
particle speed not exceeding $\sim \ 0.3 c$, allows the inclusion of various
effects, like that of a possible spin of the central massive object. Our
results show that the inclusion of PN terms above the standard 1PN term (the
one corresponding to the classic Einstein-Schwarzschild estimate of pericenter
advance) is compulsory to determine angular precession at sufficient level of
accuracy for those penetrating stars that would allow to pick contemporary the
value of the mass and of the spin of a rotating (Kerr-like) super massive black
hole (SMBH). We discuss how future observational data, together with a proper
modelization, could allow the determination of both mass and spin of the SMBH
of our Galaxy.
| [
{
"created": "Sat, 22 Apr 2023 18:12:47 GMT",
"version": "v1"
}
] | 2023-05-10 | [
[
"Capuzzo-Dolcetta",
"Roberto",
"",
"1 and 2"
],
[
"Bordoni",
"Matteo Sadun",
"",
"1 and 2"
]
] | The region around the center of our Galaxy is very dense of stars. The kinematics of inner moving stars in the Galaxy (the so called S-stars) has been deeply studied by different research groups leading to the conclusion of the existence of a very compact object (Sgr A$^*$, likely a supermassive black hole) responsible for their high speed. Here we start from the observational evidence of orbital apsidal line precession for the S2 (also called S0-2) star to investigate on a theoretical side what level of quality in such regime of relatively strong gravitational field is reached in the orbit angular precession determination when using a direct orbital integration of the star motion subjected to an acceleration computed in the post-Newtonian (PN) scheme up to different orders. This approach, although approximated and limited to particle speed not exceeding $\sim \ 0.3 c$, allows the inclusion of various effects, like that of a possible spin of the central massive object. Our results show that the inclusion of PN terms above the standard 1PN term (the one corresponding to the classic Einstein-Schwarzschild estimate of pericenter advance) is compulsory to determine angular precession at sufficient level of accuracy for those penetrating stars that would allow to pick contemporary the value of the mass and of the spin of a rotating (Kerr-like) super massive black hole (SMBH). We discuss how future observational data, together with a proper modelization, could allow the determination of both mass and spin of the SMBH of our Galaxy. |
1012.2327 | Mayeul Arminjon | Mayeul Arminjon and Frank Reifler | Four-vector vs. four-scalar representation of the Dirac wave function | 30 pages (standard 12pt). v2: version accepted for publication in
Int. J. Geom. Meth. Mod. Phys. Some emphasis and a clarification in Sect.
2.1. The Appendix now proves that the complex tangent bundle is a spinor
bundle according to precisely the definition given in Sect. 2.1. Proof of the
main Theorem 2 made easier to follow | Int. J. Geom. Meth. Mod. Phys., Vol. 9, 1250026 (2012) | 10.1142/S0219887812500260 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a Minkowski spacetime, one may transform the Dirac wave function under the
spin group, as one transforms coordinates under the Poincar\'e group. This is
not an option in a curved spacetime. Therefore, in the equation proposed
independently by Fock and Weyl, the four complex components of the Dirac wave
function transform as scalars under a general coordinate transformation. Recent
work has shown that a covariant complex four-vector representation is also
possible. Using notions of vector bundle theory, we describe these two
representations in a unified framework. We prove theorems that relate together
the different representations and the different choices of connections within
each representation. As a result, either of the two representations can account
for a variety of inequivalent, linear, covariant Dirac equations in a curved
spacetime that reduce to the original Dirac equation in a Minkowski spacetime.
In particular, we show that the standard Dirac equation in a curved spacetime,
with any choice of the tetrad field, is equivalent to a particular realization
of the covariant Dirac equation for a complex four-vector wave function.
| [
{
"created": "Fri, 10 Dec 2010 17:33:16 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2011 14:00:33 GMT",
"version": "v2"
}
] | 2012-04-30 | [
[
"Arminjon",
"Mayeul",
""
],
[
"Reifler",
"Frank",
""
]
] | In a Minkowski spacetime, one may transform the Dirac wave function under the spin group, as one transforms coordinates under the Poincar\'e group. This is not an option in a curved spacetime. Therefore, in the equation proposed independently by Fock and Weyl, the four complex components of the Dirac wave function transform as scalars under a general coordinate transformation. Recent work has shown that a covariant complex four-vector representation is also possible. Using notions of vector bundle theory, we describe these two representations in a unified framework. We prove theorems that relate together the different representations and the different choices of connections within each representation. As a result, either of the two representations can account for a variety of inequivalent, linear, covariant Dirac equations in a curved spacetime that reduce to the original Dirac equation in a Minkowski spacetime. In particular, we show that the standard Dirac equation in a curved spacetime, with any choice of the tetrad field, is equivalent to a particular realization of the covariant Dirac equation for a complex four-vector wave function. |
1901.03972 | Bruno Barros | Bruno J. Barros | Kinetically coupled dark energy | 11 pages, 5 figures. V2: Matches published version | Phys. Rev. D 99, 064051 (2019) | 10.1103/PhysRevD.99.064051 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main goal of this work is to propose a generalized model of interacting
dark energy which allows for the kinetic term of a scalar field to couple to
the matter species a priori in the action. We derive the modified field
equations, and present novel cosmological solutions for a specific coupled
model. One alluring consequence is the emergence of solutions allowing for an
early scaling regime, possible due to two novel critical points, followed by a
period of accelerated expansion. Using a dynamical system analysis, we show
that the presence of the coupling may alter the dynamical nature of the
critical points and can be used to enlarge the existence and stability regions
of these. Using constraints from Planck data we are able to find an upper bound
on the coupling parameter. Finally, it is shown how this theory encapsulates a
wide variety of dark energy models already present in the literature.
| [
{
"created": "Sun, 6 Jan 2019 16:50:58 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Mar 2019 15:07:22 GMT",
"version": "v2"
}
] | 2019-04-01 | [
[
"Barros",
"Bruno J.",
""
]
] | The main goal of this work is to propose a generalized model of interacting dark energy which allows for the kinetic term of a scalar field to couple to the matter species a priori in the action. We derive the modified field equations, and present novel cosmological solutions for a specific coupled model. One alluring consequence is the emergence of solutions allowing for an early scaling regime, possible due to two novel critical points, followed by a period of accelerated expansion. Using a dynamical system analysis, we show that the presence of the coupling may alter the dynamical nature of the critical points and can be used to enlarge the existence and stability regions of these. Using constraints from Planck data we are able to find an upper bound on the coupling parameter. Finally, it is shown how this theory encapsulates a wide variety of dark energy models already present in the literature. |
2102.00340 | David Ramos-Salamanca | D. Ramos-Salamanca, L. A. N\'u\~nez, J. Ospino | Physical acceptability conditions for realistic neutron star equations
of state | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We select 37 most common and realistic dense matter equation of states to
integrate the general relativistic stellar structure equations for static
spherically symmetric matter configurations. For all these models, we check the
compliance of the acceptability conditions that every stellar model should
satisfy. It was found that some of the non-relativistic equation of states
violate the causality and/or the dominant energy condition and that adiabatic
instabilities appear in the inner crust for all equation of state considered.
| [
{
"created": "Sat, 30 Jan 2021 23:55:45 GMT",
"version": "v1"
}
] | 2021-02-02 | [
[
"Ramos-Salamanca",
"D.",
""
],
[
"Núñez",
"L. A.",
""
],
[
"Ospino",
"J.",
""
]
] | We select 37 most common and realistic dense matter equation of states to integrate the general relativistic stellar structure equations for static spherically symmetric matter configurations. For all these models, we check the compliance of the acceptability conditions that every stellar model should satisfy. It was found that some of the non-relativistic equation of states violate the causality and/or the dominant energy condition and that adiabatic instabilities appear in the inner crust for all equation of state considered. |
0705.1511 | Burkhard Kleihaus | Burkhard Kleihaus, Jutta Kunz, Francisco Navarro-L\'erida, Ulrike
Neemann | Stationary Dyonic Regular and Black Hole Solutions | 23 pages, 4 figures | Gen.Rel.Grav.40:1279-1310,2008 | 10.1007/s10714-007-0604-2 | null | gr-qc | null | We consider globally regular and black hole solutions in SU(2)
Einstein-Yang-Mills-Higgs theory, coupled to a dilaton field. The basic
solutions represent magnetic monopoles, monopole-antimonopole systems or black
holes with monopole or dipole hair. When the globally regular solutions carry
additionally electric charge, an angular momentum density results, except in
the simplest spherically symmetric case. We evaluate the global charges of the
solutions and their effective action, and analyze their dependence on the
gravitational coupling strength. We show, that in the presence of a dilaton
field, the black hole solutions satisfy a generalized Smarr type mass formula.
| [
{
"created": "Thu, 10 May 2007 17:16:05 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lérida",
"Francisco",
""
],
[
"Neemann",
"Ulrike",
""
]
] | We consider globally regular and black hole solutions in SU(2) Einstein-Yang-Mills-Higgs theory, coupled to a dilaton field. The basic solutions represent magnetic monopoles, monopole-antimonopole systems or black holes with monopole or dipole hair. When the globally regular solutions carry additionally electric charge, an angular momentum density results, except in the simplest spherically symmetric case. We evaluate the global charges of the solutions and their effective action, and analyze their dependence on the gravitational coupling strength. We show, that in the presence of a dilaton field, the black hole solutions satisfy a generalized Smarr type mass formula. |
gr-qc/0603008 | Etera R. Livine | Etera R. Livine, Daniel R. Terno | Reconstructing Quantum Geometry from Quantum Information: Area
Renormalisation, Coarse-Graining and Entanglement on Spin Networks | 27 pages, 12 figures, RevTex4 | null | null | null | gr-qc | null | After a brief review of spin networks and their interpretation as wave
functions for the (space) geometry, we discuss the renormalisation of the area
operator in loop quantum gravity. In such a background independent framework,
we propose to probe the structure of a surface through the analysis of the
coarse-graining and renormalisation flow(s) of its area. We further introduce a
procedure to coarse-grain spin network states and we quantitatively study the
decrease in the number of degrees of freedom during this process. Finally, we
use these coarse-graining tools to define the correlation and entanglement
between parts of a spin network and discuss their potential interpretation as a
natural measure of distance in such a state of quantum geometry.
| [
{
"created": "Fri, 3 Mar 2006 13:59:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Livine",
"Etera R.",
""
],
[
"Terno",
"Daniel R.",
""
]
] | After a brief review of spin networks and their interpretation as wave functions for the (space) geometry, we discuss the renormalisation of the area operator in loop quantum gravity. In such a background independent framework, we propose to probe the structure of a surface through the analysis of the coarse-graining and renormalisation flow(s) of its area. We further introduce a procedure to coarse-grain spin network states and we quantitatively study the decrease in the number of degrees of freedom during this process. Finally, we use these coarse-graining tools to define the correlation and entanglement between parts of a spin network and discuss their potential interpretation as a natural measure of distance in such a state of quantum geometry. |
gr-qc/9408007 | Renate Loll | R. Loll | Independent Loop Invariants for 2+1 Gravity | 11pp, 2 figures (postscript, compressed and uu-encoded), TeX,
Pennsylvania State University, CGPG-94/7-1 | Class.Quant.Grav.12:1655-1662,1995 | 10.1088/0264-9381/12/7/008 | null | gr-qc | null | We identify an explicit set of complete and independent Wilson loop
invariants for 2+1 gravity on a three-manifold $M=\R\times\Sigma^g$, with
$\Sigma^g$ a compact oriented Riemann surface of arbitrary genus $g$. In the
derivation we make use of a global cross section of the $PSU(1,1)$-principal
bundle over Teichm\"uller space given in terms of Fenchel-Nielsen coordinates.
| [
{
"created": "Wed, 3 Aug 1994 22:47:43 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Loll",
"R.",
""
]
] | We identify an explicit set of complete and independent Wilson loop invariants for 2+1 gravity on a three-manifold $M=\R\times\Sigma^g$, with $\Sigma^g$ a compact oriented Riemann surface of arbitrary genus $g$. In the derivation we make use of a global cross section of the $PSU(1,1)$-principal bundle over Teichm\"uller space given in terms of Fenchel-Nielsen coordinates. |
gr-qc/0112004 | Robin W. Tucker | R W Tucker and C Wang | Gravitational Wave Induced Vibrations of Slender Structures in Space | 26 pages, 3 Figures | Gen.Rel.Grav. 35 (2003) 2137-2158 | 10.1023/A:1027397522624 | null | gr-qc | null | This paper explores the interaction of weak gravitational fields with slender
elastic materials in space and estimates their sensitivities for the detection
of gravitational waves with frequencies between $10^{-4}$ and 1 Hz. The dynamic
behaviour of such slender structures is ideally suited to analysis by the
simple theory of Cosserat rods. Such a description offers a clean conceptual
separation of the vibrations induced by bending, shear, twist and extension and
the response to gravitational tidal accelerations can be reliably estimated in
terms of the constitutive properties of the structure. The sensitivity
estimates are based on a truncation of the theory in the presence of thermally
induced homogeneous Gaussian stochastic forces.
| [
{
"created": "Thu, 6 Dec 2001 14:48:05 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Tucker",
"R W",
""
],
[
"Wang",
"C",
""
]
] | This paper explores the interaction of weak gravitational fields with slender elastic materials in space and estimates their sensitivities for the detection of gravitational waves with frequencies between $10^{-4}$ and 1 Hz. The dynamic behaviour of such slender structures is ideally suited to analysis by the simple theory of Cosserat rods. Such a description offers a clean conceptual separation of the vibrations induced by bending, shear, twist and extension and the response to gravitational tidal accelerations can be reliably estimated in terms of the constitutive properties of the structure. The sensitivity estimates are based on a truncation of the theory in the presence of thermally induced homogeneous Gaussian stochastic forces. |
0812.4333 | Piotr Bizon | Piotr Bizo\'n, Tadeusz Chmaj, Andrzej Rostworowski | Late-time tails of a self-gravitating massless scalar field, revisited | 10 pages, 6 figures, one reference added, updated to conform with
published version | Class.Quant.Grav.26:175006,2009 | 10.1088/0264-9381/26/17/175006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the nonlinear origin of the power-law tail in the long-time
evolution of a spherically symmetric self-gravitating massless scalar field in
even-dimensional spacetimes. Using third-order perturbation method, we derive
explicit expressions for the tail (the decay rate and the amplitude) for
solutions starting from small initial data and we verify this prediction via
numerical integration of the Einstein-scalar field equations in four and six
dimensions. Our results show that the coincidence of decay rates of linear and
nonlinear tails in four dimensions (which has misguided some tail hunters in
the past) is in a sense accidental and does not hold in higher dimensions.
| [
{
"created": "Tue, 23 Dec 2008 14:50:06 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jul 2009 15:57:17 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Aug 2009 05:26:46 GMT",
"version": "v3"
}
] | 2010-05-12 | [
[
"Bizoń",
"Piotr",
""
],
[
"Chmaj",
"Tadeusz",
""
],
[
"Rostworowski",
"Andrzej",
""
]
] | We discuss the nonlinear origin of the power-law tail in the long-time evolution of a spherically symmetric self-gravitating massless scalar field in even-dimensional spacetimes. Using third-order perturbation method, we derive explicit expressions for the tail (the decay rate and the amplitude) for solutions starting from small initial data and we verify this prediction via numerical integration of the Einstein-scalar field equations in four and six dimensions. Our results show that the coincidence of decay rates of linear and nonlinear tails in four dimensions (which has misguided some tail hunters in the past) is in a sense accidental and does not hold in higher dimensions. |
0905.4179 | J\"org Hennig | Gernot Neugebauer and J\"org Hennig | Non-existence of stationary two-black-hole configurations | 15 pages, 3 figures; Contribution to Juergen Ehlers Memorial Issue
(GeRG journal) | Gen.Rel.Grav.41:2113-2130,2009 | 10.1007/s10714-009-0840-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We resume former discussions of the question, whether the spin-spin repulsion
and the gravitational attraction of two aligned black holes can balance each
other. To answer the question we formulate a boundary value problem for two
separate (Killing-) horizons and apply the inverse (scattering) method to solve
it. Making use of results of Manko, Ruiz and Sanabria-G\'omez and a novel black
hole criterion, we prove the non-existence of the equilibrium situation in
question.
| [
{
"created": "Tue, 26 May 2009 11:54:17 GMT",
"version": "v1"
},
{
"created": "Fri, 29 May 2009 08:51:20 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Jun 2009 14:09:43 GMT",
"version": "v3"
}
] | 2010-04-30 | [
[
"Neugebauer",
"Gernot",
""
],
[
"Hennig",
"Jörg",
""
]
] | We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned black holes can balance each other. To answer the question we formulate a boundary value problem for two separate (Killing-) horizons and apply the inverse (scattering) method to solve it. Making use of results of Manko, Ruiz and Sanabria-G\'omez and a novel black hole criterion, we prove the non-existence of the equilibrium situation in question. |
gr-qc/0104054 | Jljing | Jiliang Jing, Mu-Lin Yan | Quantum entropy of the Kerr black hole arising from gravitational
perturbation | 8 pages, 1 figure, Latex. to appear in Phys. Rev. D | Phys.Rev. D64 (2001) 064015 | 10.1103/PhysRevD.64.064015 | null | gr-qc hep-th | null | The quantum entropy of the Kerr black hole arising from gravitational
perturbation is investigated by using Null tetrad and \'t Hooft\'s brick-wall
model. It is shown that effect of the graviton\'s spins on the subleading
correction is dependent of the square of the spins and the angular momentum per
unit mass of the black hole, and contribution of the logarithmic term to the
entropy will be positive, zero, and negative for different value of $a/r_+$.
| [
{
"created": "Tue, 17 Apr 2001 23:54:46 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jun 2001 14:46:08 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Jing",
"Jiliang",
""
],
[
"Yan",
"Mu-Lin",
""
]
] | The quantum entropy of the Kerr black hole arising from gravitational perturbation is investigated by using Null tetrad and \'t Hooft\'s brick-wall model. It is shown that effect of the graviton\'s spins on the subleading correction is dependent of the square of the spins and the angular momentum per unit mass of the black hole, and contribution of the logarithmic term to the entropy will be positive, zero, and negative for different value of $a/r_+$. |
gr-qc/0303070 | Ken D. Olum | Ken D. Olum | Conflict between anthropic reasoning and observation | 7 pages, RevTeX. v2: New "lost colony" section. Corresponds to
published version | Analysis 64 (2004),1 | null | null | gr-qc physics.soc-ph | null | Anthropic reasoning often begins with the premise that we should expect to
find ourselves typical among all intelligent observers. However, in the
infinite universe predicted by inflation, there are some civilizations which
have spread across their galaxies and contain huge numbers of individuals.
Unless the proportion of such large civilizations is unreasonably tiny, most
observers belong to them. Thus anthropic reasoning predicts that we should find
ourselves in such a large civilization, while in fact we do not. There must be
an important flaw in our understanding of the structure of the universe and the
range of development of civilizations, or in the process of anthropic
reasoning.
| [
{
"created": "Wed, 19 Mar 2003 15:14:13 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Feb 2004 16:04:23 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Olum",
"Ken D.",
""
]
] | Anthropic reasoning often begins with the premise that we should expect to find ourselves typical among all intelligent observers. However, in the infinite universe predicted by inflation, there are some civilizations which have spread across their galaxies and contain huge numbers of individuals. Unless the proportion of such large civilizations is unreasonably tiny, most observers belong to them. Thus anthropic reasoning predicts that we should find ourselves in such a large civilization, while in fact we do not. There must be an important flaw in our understanding of the structure of the universe and the range of development of civilizations, or in the process of anthropic reasoning. |
gr-qc/0611113 | Sante Carloni | Sante Carloni, Peter K. S. Dunsby, Claudio Rubano | Gauge invariant perturbations of Scalar-Tensor Cosmologies: The vacuum
case | 19 pages, 3 figures, accepted for publication on PRD | Phys.Rev.D74:123513,2006 | 10.1103/PhysRevD.74.123513 | null | gr-qc astro-ph | null | The covariant gauge invariant perturbation theory of scalar cosmological
perturbations is developed for a general Scalar-Tensor
Friedmann-Lemaitre-Robertson-Walker cosmology in a vacuum. The perturbation
equations are then solved exactly in the long wavelength limit for a specific
coupling, potential and background. Differences with the minimally coupled case
are briefly discussed.
| [
{
"created": "Wed, 22 Nov 2006 09:29:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Carloni",
"Sante",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Rubano",
"Claudio",
""
]
] | The covariant gauge invariant perturbation theory of scalar cosmological perturbations is developed for a general Scalar-Tensor Friedmann-Lemaitre-Robertson-Walker cosmology in a vacuum. The perturbation equations are then solved exactly in the long wavelength limit for a specific coupling, potential and background. Differences with the minimally coupled case are briefly discussed. |
2406.12281 | Gabriel Luis Dizon | Gabriel Luis Dizon (1) and Reinabelle Reyes (1) ((1) National
Institute of Physics, University of the Philippines - Diliman, Philippines) | Projected gravitational wave constraints on primordial black hole
abundance for extended mass distributions | 15 pages, 7 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We investigate the projected minimum constraints set by next-generation
gravitational wave detectors Einstein Telescope and LISA on the abundance of
primordial black holes relative to dark matter for extended primordial black
hole mass distributions. We consider broad power law distributions for a range
of negative and positive exponents $\gamma$ and use the IMRPhenomXAS waveforms
to simulate binary sources up to mass ratios $q = 1000$ and redshifts $z=300$.
Our results show that power law mass distributions loosen the $f_\mathrm{PBH}$
constraint for increasing power law exponents, suggesting that extended
distributions do not help in evading existing constraints. Interestingly, very
negative values of $\gamma$ yield constraints close to ones derived from a
monochromatic distribution.
| [
{
"created": "Tue, 18 Jun 2024 05:19:17 GMT",
"version": "v1"
}
] | 2024-06-19 | [
[
"Dizon",
"Gabriel Luis",
""
],
[
"Reyes",
"Reinabelle",
""
]
] | We investigate the projected minimum constraints set by next-generation gravitational wave detectors Einstein Telescope and LISA on the abundance of primordial black holes relative to dark matter for extended primordial black hole mass distributions. We consider broad power law distributions for a range of negative and positive exponents $\gamma$ and use the IMRPhenomXAS waveforms to simulate binary sources up to mass ratios $q = 1000$ and redshifts $z=300$. Our results show that power law mass distributions loosen the $f_\mathrm{PBH}$ constraint for increasing power law exponents, suggesting that extended distributions do not help in evading existing constraints. Interestingly, very negative values of $\gamma$ yield constraints close to ones derived from a monochromatic distribution. |
1012.4216 | Muxin Han | Muxin Han | 4-dimensional Spin-foam Model with Quantum Lorentz Group | 23 pages, 3 figures, references added | J. Math. Phys. 52, 072501 (2011) | 10.1063/1.3606592 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum group deformation of the Lorentzian EPRL spin-foam
model. The construction uses the harmonic analysis on the quantum Lorentz
group. We show that the quantum group spin-foam model so defined is free of the
infra-red divergence, thus gives a finite partition function on a fixed
triangulation. We expect this quantum group spin-foam model is a spin-foam
quantization of discrete gravity with a cosmological constant.
| [
{
"created": "Sun, 19 Dec 2010 23:06:15 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Dec 2010 10:38:06 GMT",
"version": "v2"
},
{
"created": "Sun, 23 Oct 2011 01:53:46 GMT",
"version": "v3"
}
] | 2011-10-25 | [
[
"Han",
"Muxin",
""
]
] | We study the quantum group deformation of the Lorentzian EPRL spin-foam model. The construction uses the harmonic analysis on the quantum Lorentz group. We show that the quantum group spin-foam model so defined is free of the infra-red divergence, thus gives a finite partition function on a fixed triangulation. We expect this quantum group spin-foam model is a spin-foam quantization of discrete gravity with a cosmological constant. |
1903.11519 | \"Ozg\"ur Akarsu | Ozgur Akarsu, John D. Barrow, Charles V. R. Board, N. Merve Uzun, J.
Alberto Vazquez | Screening $\Lambda$ in a new modified gravity model | 17 pages, 11 figures, 1 table; matches the version published in EPJC | Eur. Phys. J. C 79 (2019) 846 | 10.1140/epjc/s10052-019-7333-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a new model of Energy-Momentum Squared Gravity (EMSG), called
Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term
$f(T_{\mu\nu}T^{\mu\nu})=\alpha \ln(\lambda\,T_{\mu\nu}T^{\mu\nu})$, envisaged
as a correction, to the Einstein-Hilbert action with cosmological constant
$\Lambda$. The choice of this modification is made as a specific way of
including new terms in the right-hand side of the Einstein field equations,
resulting in constant effective inertial mass density and, importantly, leading
to an explicit exact solution of the matter energy density in terms of
redshift. We look for viable cosmologies, in particular, an extension of the
standard $\Lambda$CDM model. EMLG provides an effective dynamical dark energy
passing below zero at large redshifts, accommodating a mechanism for screening
$\Lambda$ in this region, in line with suggestions for alleviating some of the
tensions that arise between observational data sets within the standard
$\Lambda$CDM model. We present a detailed theoretical investigation of the
model and then constrain the free parameter $\alpha'$, a normalisation of
$\alpha$, using the latest observational data. The data does not rule out the
$\Lambda$CDM limit of our model ($\alpha'= 0$), but prefers slightly negative
values of the EMLG model parameter ($\alpha'= -0.032\pm 0.043$), which leads to
the screening of $\Lambda$. We also discuss how EMLG relaxes the persistent
tension that appears in the measurements of $H_0$ within the standard
$\Lambda$CDM model.
| [
{
"created": "Wed, 27 Mar 2019 16:15:59 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Mar 2019 13:17:39 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Oct 2019 13:36:23 GMT",
"version": "v3"
}
] | 2019-10-16 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Barrow",
"John D.",
""
],
[
"Board",
"Charles V. R.",
""
],
[
"Uzun",
"N. Merve",
""
],
[
"Vazquez",
"J. Alberto",
""
]
] | We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term $f(T_{\mu\nu}T^{\mu\nu})=\alpha \ln(\lambda\,T_{\mu\nu}T^{\mu\nu})$, envisaged as a correction, to the Einstein-Hilbert action with cosmological constant $\Lambda$. The choice of this modification is made as a specific way of including new terms in the right-hand side of the Einstein field equations, resulting in constant effective inertial mass density and, importantly, leading to an explicit exact solution of the matter energy density in terms of redshift. We look for viable cosmologies, in particular, an extension of the standard $\Lambda$CDM model. EMLG provides an effective dynamical dark energy passing below zero at large redshifts, accommodating a mechanism for screening $\Lambda$ in this region, in line with suggestions for alleviating some of the tensions that arise between observational data sets within the standard $\Lambda$CDM model. We present a detailed theoretical investigation of the model and then constrain the free parameter $\alpha'$, a normalisation of $\alpha$, using the latest observational data. The data does not rule out the $\Lambda$CDM limit of our model ($\alpha'= 0$), but prefers slightly negative values of the EMLG model parameter ($\alpha'= -0.032\pm 0.043$), which leads to the screening of $\Lambda$. We also discuss how EMLG relaxes the persistent tension that appears in the measurements of $H_0$ within the standard $\Lambda$CDM model. |
gr-qc/0007022 | S. Shankarnarayanan | S. Shankaranarayanan, K. Srinivasan, T. Padmanabhan | Method of complex paths and general covariance of Hawking radiation | 9 pages, uses MPLA Style file, Accepted for publication in Mod. Phys.
Letts. A | Mod.Phys.Lett. A16 (2001) 571-578 | 10.1142/S0217732301003632 | IUCAA Preprint 27/2000 - July 2000 | gr-qc hep-th | null | We apply the technique of complex paths to obtain Hawking radiation in
different coordinate representations of the Schwarzschild space-time. The
coordinate representations we consider do not possess a singularity at the
horizon unlike the standard Schwarzschild coordinate. However, the event
horizon manifests itself as a singularity in the expression for the
semi-classical action. This singularity is regularized by using the method of
complex paths and we find that Hawking radiation is recovered in these
coordinates indicating the covariance of Hawking radiation. This also shows
that there is no correspondence between the particles detected by the model
detector and the particle spectrum obtained by the quantum field theoretic
analysis -- a result known in other contexts as well.
| [
{
"created": "Tue, 11 Jul 2000 17:30:47 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Mar 2001 15:22:57 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Shankaranarayanan",
"S.",
""
],
[
"Srinivasan",
"K.",
""
],
[
"Padmanabhan",
"T.",
""
]
] | We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semi-classical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation. This also shows that there is no correspondence between the particles detected by the model detector and the particle spectrum obtained by the quantum field theoretic analysis -- a result known in other contexts as well. |
1901.00813 | Annegret Burtscher | Annegret Burtscher, Michael K.-H. Kiessling, A. Shadi Tahvildar-Zadeh | Weak second Bianchi identity for static, spherically symmetric
spacetimes with timelike singularities | 23 pages; added Corollary 2.2, removed Appendix. Final version, to
appear in CQG | Classical and Quantum Gravity, Volume 38, Number 18 (2021),
185001, 31 pages | 10.1088/1361-6382/ac1853 | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The (twice-contracted) second Bianchi identity is a differential curvature
identity that holds on any smooth manifold with a metric. In the case when such
a metric is Lorentzian and solves Einstein's equations with an (in this case
inevitably smooth) energy-momentum-stress tensor of a "matter field" as the
source of spacetime curvature, this identity implies the physical laws of
energy and momentum conservation for the "matter field". The present work
inquires into whether such a Bianchi identity can still hold in a weak sense
for spacetimes with curvature singularities associated with timelike
singularities in the "matter field". Sufficient conditions that establish a
distributional version of the twice-contracted second Bianchi identity are
found. In our main theorem, a large class of spherically symmetric static
Lorentzian metrics with timelike one-dimensional singularities is identified,
for which this identity holds. As an important first application we show that
the well-known Reissner-Weyl-Nordstr\"om spacetime of a point charge does not
belong to this class, but that Hoffmann's spacetime of a point charge with
negative bare mass in the Born-Infeld electromagnetic vacuum does.
| [
{
"created": "Thu, 3 Jan 2019 16:48:38 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Apr 2021 21:27:16 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Aug 2021 13:29:42 GMT",
"version": "v3"
}
] | 2021-08-24 | [
[
"Burtscher",
"Annegret",
""
],
[
"Kiessling",
"Michael K. -H.",
""
],
[
"Tahvildar-Zadeh",
"A. Shadi",
""
]
] | The (twice-contracted) second Bianchi identity is a differential curvature identity that holds on any smooth manifold with a metric. In the case when such a metric is Lorentzian and solves Einstein's equations with an (in this case inevitably smooth) energy-momentum-stress tensor of a "matter field" as the source of spacetime curvature, this identity implies the physical laws of energy and momentum conservation for the "matter field". The present work inquires into whether such a Bianchi identity can still hold in a weak sense for spacetimes with curvature singularities associated with timelike singularities in the "matter field". Sufficient conditions that establish a distributional version of the twice-contracted second Bianchi identity are found. In our main theorem, a large class of spherically symmetric static Lorentzian metrics with timelike one-dimensional singularities is identified, for which this identity holds. As an important first application we show that the well-known Reissner-Weyl-Nordstr\"om spacetime of a point charge does not belong to this class, but that Hoffmann's spacetime of a point charge with negative bare mass in the Born-Infeld electromagnetic vacuum does. |
gr-qc/0604017 | Hannes Helgason | Emmanuel J. Candes, Philip R. Charlton and Hannes Helgason | Detecting Highly Oscillatory Signals by Chirplet Path Pursuit | null | Appl.Comput.Harmon.Anal.24:14-40,2008 | null | null | gr-qc math.ST stat.TH | null | This paper considers the problem of detecting nonstationary phenomena, and
chirps in particular, from very noisy data. Chirps are waveforms of the very
general form A(t) exp(i\lambda \phi(t)), where \lambda is a (large) base
frequency, the phase \phi(t) is time-varying and the amplitude A(t) is slowly
varying. Given a set of noisy measurements, we would like to test whether there
is signal or whether the data is just noise. One particular application of note
in conjunction with this problem is the detection of gravitational waves
predicted by Einstein's Theory of General Relativity.
We introduce detection strategies which are very sensitive and more flexible
than existing feature detectors. The idea is to use structured algorithms which
exploit information in the so-called chirplet graph to chain chirplets together
adaptively as to form chirps with polygonal instantaneous frequency. We then
search for the path in the graph which provides the best trade-off between
complexity and goodness of fit. Underlying our methodology is the idea that
while the signal may be extremely weak so that none of the individual empirical
coefficients is statistically significant, one can still reliably detect by
combining several coefficients into a coherent chain. This strategy is general
and may be applied in many other detection problems. We complement our study
with numerical experiments showing that our algorithms are so sensitive that
they seem to detect signals whenever their strength makes them detectable.
| [
{
"created": "Wed, 5 Apr 2006 01:25:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Candes",
"Emmanuel J.",
""
],
[
"Charlton",
"Philip R.",
""
],
[
"Helgason",
"Hannes",
""
]
] | This paper considers the problem of detecting nonstationary phenomena, and chirps in particular, from very noisy data. Chirps are waveforms of the very general form A(t) exp(i\lambda \phi(t)), where \lambda is a (large) base frequency, the phase \phi(t) is time-varying and the amplitude A(t) is slowly varying. Given a set of noisy measurements, we would like to test whether there is signal or whether the data is just noise. One particular application of note in conjunction with this problem is the detection of gravitational waves predicted by Einstein's Theory of General Relativity. We introduce detection strategies which are very sensitive and more flexible than existing feature detectors. The idea is to use structured algorithms which exploit information in the so-called chirplet graph to chain chirplets together adaptively as to form chirps with polygonal instantaneous frequency. We then search for the path in the graph which provides the best trade-off between complexity and goodness of fit. Underlying our methodology is the idea that while the signal may be extremely weak so that none of the individual empirical coefficients is statistically significant, one can still reliably detect by combining several coefficients into a coherent chain. This strategy is general and may be applied in many other detection problems. We complement our study with numerical experiments showing that our algorithms are so sensitive that they seem to detect signals whenever their strength makes them detectable. |
1010.4512 | Thomas Buchert | Thomas Buchert and Nathaniel Obadia | Effective inhomogeneous inflation: curvature inhomogeneities of the
Einstein vacuum | 9 pages, 2 figures, to appear in Class. Quant. Grav. as Fast Track
Communication | Class.Quant.Grav.28:162002,2011 | 10.1088/0264-9381/28/16/162002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spatially averaged inhomogeneous universe models and argue that,
already in the absence of sources, an effective scalar field arises through
foliating and spatially averaging inhomogeneous geometrical curvature
invariants of the Einstein vacuum. This scalar field (the `morphon') acts as an
inflaton, if we prescribe a potential of some generic form. We show that, for
any initially negative average spatial curvature, the morphon is driven through
an inflationary phase and leads - on average - to a spatially flat, homogeneous
and isotropic universe model, providing initial conditions for pre-heating and,
by the same mechanism, a possibly natural self-exit.
| [
{
"created": "Thu, 21 Oct 2010 16:16:38 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2011 10:58:14 GMT",
"version": "v2"
}
] | 2011-07-26 | [
[
"Buchert",
"Thomas",
""
],
[
"Obadia",
"Nathaniel",
""
]
] | We consider spatially averaged inhomogeneous universe models and argue that, already in the absence of sources, an effective scalar field arises through foliating and spatially averaging inhomogeneous geometrical curvature invariants of the Einstein vacuum. This scalar field (the `morphon') acts as an inflaton, if we prescribe a potential of some generic form. We show that, for any initially negative average spatial curvature, the morphon is driven through an inflationary phase and leads - on average - to a spatially flat, homogeneous and isotropic universe model, providing initial conditions for pre-heating and, by the same mechanism, a possibly natural self-exit. |
gr-qc/9910084 | Matthias Arnsdorf | Matthias Arnsdorf | Approximating Connections in Loop Quantum Gravity | 12 pages, 2 figures | null | null | null | gr-qc | null | We discuss the action of the configuration operators of loop quantum gravity.
In particular, we derive the generalised eigenbasis for the Wilson loop
operator and show that the transformation between this basis and the
spin-network basis is given by an expansion in terms of Chebyshev polynomials.
These results are used to construct states which approximate connections on the
background 3-manifold in an analogous way that the weave states reproduce area
and volumes of a given 3-metric. This should be necessary for the construction
of genuine semi-classical states that are peaked both in the configuration and
momentum variables.
| [
{
"created": "Mon, 25 Oct 1999 11:41:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arnsdorf",
"Matthias",
""
]
] | We discuss the action of the configuration operators of loop quantum gravity. In particular, we derive the generalised eigenbasis for the Wilson loop operator and show that the transformation between this basis and the spin-network basis is given by an expansion in terms of Chebyshev polynomials. These results are used to construct states which approximate connections on the background 3-manifold in an analogous way that the weave states reproduce area and volumes of a given 3-metric. This should be necessary for the construction of genuine semi-classical states that are peaked both in the configuration and momentum variables. |
1307.1812 | Alexander Zhidenko | R. A. Konoplya and A. Zhidenko | A massive charged scalar field in the Kerr-Newman background I:
quasinormal modes, late-time tails and stability | 13 pages, 10 figures | Phys. Rev. D 88, 024054 (2013) | 10.1103/PhysRevD.88.024054 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | So far analysis of the quasinormal spectrum of a massive charged scalar field
in the black hole background has been limited by the regime of small \mu M and
qQ, where \mu, q (M, Q) are mass and charge of the field (black hole). Here we
shall present a comprehensive picture of quasinormal modes, late-time tails and
stability of a massive charged scalar field around Kerr-Newman black holes for
any physically meaningful values of the parameters. We shall show that despite
presence of the two mechanisms of superradiance (owing to black hole's rotation
and charge) and the massive term creating growing bound states, there is no
indication of instability under quasinormal modes' boundary conditions. We have
shown that for some moderate values of qQ dominant quasinormal modes may have
arbitrarily small real oscillation frequencies Re(\omega). An analytic formula
for the quasinormal modes has been derived in the regime of large qQ. The
larger the field's charge, the sooner asymptotic tails dominate in a signal,
making it difficult to extract quasinormal frequencies from a time-domain
profile. Analytic expressions for intermediate and asymptotically late-time
tails have been found for the Reissner-Nordstr\"om black hole. For the near
extremal Kerr-Newman black holes we have obtained a more general picture of the
mode branching found recently for massless fields [arXiv:1212.3271] in the Kerr
background.
| [
{
"created": "Sat, 6 Jul 2013 19:56:33 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Aug 2013 15:49:11 GMT",
"version": "v2"
}
] | 2013-08-06 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | So far analysis of the quasinormal spectrum of a massive charged scalar field in the black hole background has been limited by the regime of small \mu M and qQ, where \mu, q (M, Q) are mass and charge of the field (black hole). Here we shall present a comprehensive picture of quasinormal modes, late-time tails and stability of a massive charged scalar field around Kerr-Newman black holes for any physically meaningful values of the parameters. We shall show that despite presence of the two mechanisms of superradiance (owing to black hole's rotation and charge) and the massive term creating growing bound states, there is no indication of instability under quasinormal modes' boundary conditions. We have shown that for some moderate values of qQ dominant quasinormal modes may have arbitrarily small real oscillation frequencies Re(\omega). An analytic formula for the quasinormal modes has been derived in the regime of large qQ. The larger the field's charge, the sooner asymptotic tails dominate in a signal, making it difficult to extract quasinormal frequencies from a time-domain profile. Analytic expressions for intermediate and asymptotically late-time tails have been found for the Reissner-Nordstr\"om black hole. For the near extremal Kerr-Newman black holes we have obtained a more general picture of the mode branching found recently for massless fields [arXiv:1212.3271] in the Kerr background. |
2405.09095 | Elliot Marshall | Florian Beyer, Elliot Marshall, Todd A. Oliynyk | Past instability of FLRW solutions of the Einstein-Euler-scalar field
equations for linear equations of state $p=K\rho$ with $0 \leq K<1/3$ | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using numerical methods, we examine, under a Gowdy symmetry assumption, the
dynamics of nonlinearly perturbed FLRW fluid solutions of the
Einstein-Euler-scalar field equations in the contracting direction for linear
equations of state $p = K\rho$ and sound speeds $0\leq K<1/3$. This article
builds upon the numerical work from \cite{BMO:2023} in which perturbations of
FLRW solutions to the Einstein-Euler equations with positive cosmological
constant in the expanding time direction were studied. The numerical results
presented here confirm that the instabilities observed in
\cite{BMO:2023,MarshallOliynyk:2022} for $1/3<K<1$, first conjectured to occur
in the expanding direction by Rendall in \cite{Rendall:2004}, are also present
in the contracting direction over the complementary parameter range $0\leq
K<1/3$. Our numerical solutions show that the fractional density gradient of
the nonlinear perturbations develop steep gradients near a finite number of
spatial points and become unbounded towards the big bang. This behaviour, and
in particular the characteristic profile of the fractional density gradient
near the big bang, is strikingly similar to what was observed in the expanding
direction near timelike infinity in the article \cite{BMO:2023}.
| [
{
"created": "Wed, 15 May 2024 05:13:08 GMT",
"version": "v1"
}
] | 2024-05-16 | [
[
"Beyer",
"Florian",
""
],
[
"Marshall",
"Elliot",
""
],
[
"Oliynyk",
"Todd A.",
""
]
] | Using numerical methods, we examine, under a Gowdy symmetry assumption, the dynamics of nonlinearly perturbed FLRW fluid solutions of the Einstein-Euler-scalar field equations in the contracting direction for linear equations of state $p = K\rho$ and sound speeds $0\leq K<1/3$. This article builds upon the numerical work from \cite{BMO:2023} in which perturbations of FLRW solutions to the Einstein-Euler equations with positive cosmological constant in the expanding time direction were studied. The numerical results presented here confirm that the instabilities observed in \cite{BMO:2023,MarshallOliynyk:2022} for $1/3<K<1$, first conjectured to occur in the expanding direction by Rendall in \cite{Rendall:2004}, are also present in the contracting direction over the complementary parameter range $0\leq K<1/3$. Our numerical solutions show that the fractional density gradient of the nonlinear perturbations develop steep gradients near a finite number of spatial points and become unbounded towards the big bang. This behaviour, and in particular the characteristic profile of the fractional density gradient near the big bang, is strikingly similar to what was observed in the expanding direction near timelike infinity in the article \cite{BMO:2023}. |
2301.02672 | Jakob Stegmann | Jakob Stegmann, Sander M. Vermeulen | Detecting the heterodyning of gravitational waves | 12 pages, 6 figures, 1 table | Classical and Quantum Gravity, Volume 41, Number 17 (2024) | 10.1088/1361-6382/ad682c | null | gr-qc astro-ph.HE astro-ph.IM astro-ph.SR | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Gravitational waves modulate the apparent frequencies of other periodic
signals. Low-frequency gravitational waves could therefore be detected by
observing frequency modulations in signals from higher-frequency sources, e.g.,
those from binary white dwarfs detected with the LISA gravitational-wave
detector. We propose a concrete method to extract these modulations by
coherently adding the cross-spectra of a large number of well-resolved
quasi-monochromatic signals. We apply this method to the case of LISA, and find
this method would enable the detection of background gravitational wave strain
amplitudes of, e.g., $A\simeq10^{-10}$ at a frequency $F\simeq10^{-8}\,\rm Hz$,
given current projections for the number and properties of Galactic binary
white dwarfs and the sensitivity of the instrument. We also estimate (to within
an order of magnitude) that this method could potentially compete with that of
current Pulsar Timing Arrays when using signals from binary neutron stars such
as those expected to be observed with proposed detectors like DECIGO. Our
results show that gravitational-wave detectors could be sensitive at
frequencies outside of their designed bandwidth using the same infrastructure,
which has the potential to open up unexplored and otherwise inaccessible parts
of the gravitational wave spectrum.
| [
{
"created": "Fri, 6 Jan 2023 19:00:00 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2024 08:04:31 GMT",
"version": "v2"
}
] | 2024-08-09 | [
[
"Stegmann",
"Jakob",
""
],
[
"Vermeulen",
"Sander M.",
""
]
] | Gravitational waves modulate the apparent frequencies of other periodic signals. Low-frequency gravitational waves could therefore be detected by observing frequency modulations in signals from higher-frequency sources, e.g., those from binary white dwarfs detected with the LISA gravitational-wave detector. We propose a concrete method to extract these modulations by coherently adding the cross-spectra of a large number of well-resolved quasi-monochromatic signals. We apply this method to the case of LISA, and find this method would enable the detection of background gravitational wave strain amplitudes of, e.g., $A\simeq10^{-10}$ at a frequency $F\simeq10^{-8}\,\rm Hz$, given current projections for the number and properties of Galactic binary white dwarfs and the sensitivity of the instrument. We also estimate (to within an order of magnitude) that this method could potentially compete with that of current Pulsar Timing Arrays when using signals from binary neutron stars such as those expected to be observed with proposed detectors like DECIGO. Our results show that gravitational-wave detectors could be sensitive at frequencies outside of their designed bandwidth using the same infrastructure, which has the potential to open up unexplored and otherwise inaccessible parts of the gravitational wave spectrum. |
1806.09162 | Nishanth Abu Gudapati | Nishanth Gudapati | A Conserved Energy for Axially Symmetric Newman-Penrose-Maxwell Scalars
on Kerr Black Holes | null | null | 10.1098/rspa.2018.0686 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that there exists a 1-parameter family of positive-definite and
conserved energy functionals for axially symmetric Newman-Penrose-Maxwell
scalars on the maximal spacelike hypersurfaces in the exterior of Kerr black
holes. It is also shown that the Poisson bracket within this 1-parameter family
of energies vanishes on the maximal hypersurfaces.
| [
{
"created": "Sun, 24 Jun 2018 15:21:47 GMT",
"version": "v1"
}
] | 2019-03-06 | [
[
"Gudapati",
"Nishanth",
""
]
] | We show that there exists a 1-parameter family of positive-definite and conserved energy functionals for axially symmetric Newman-Penrose-Maxwell scalars on the maximal spacelike hypersurfaces in the exterior of Kerr black holes. It is also shown that the Poisson bracket within this 1-parameter family of energies vanishes on the maximal hypersurfaces. |
1509.05827 | Vasilis Oikonomou | V.K. Oikonomou | Singular Bouncing Cosmology from Gauss-Bonnet Modified Gravity | Significantly expanded perturbations section, important references
added, PRD accepted | Phys. Rev. D 92, 124027 (2015) | 10.1103/PhysRevD.92.124027 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study how a cosmological bounce with a Type IV singularity at the bouncing
point, can be generated by a classical vacuum $F(G)$ gravity. We focus our
investigation on the behavior of the vacuum $F(G)$ theory near the Type IV
singular bouncing point and also we address the stability of the resulting
solution, by treating the equations of motion as a dynamical system. In
addition, we investigate how the scalar perturbations of the background metric
evolve, emphasizing to cosmological times near the Type IV singular bouncing
point. Finally, we also investigate which mimetic vacuum $F(G)$ gravity can
describe the singular bounce cosmology.
| [
{
"created": "Sat, 19 Sep 2015 00:05:55 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Nov 2015 21:28:23 GMT",
"version": "v2"
}
] | 2015-12-23 | [
[
"Oikonomou",
"V. K.",
""
]
] | We study how a cosmological bounce with a Type IV singularity at the bouncing point, can be generated by a classical vacuum $F(G)$ gravity. We focus our investigation on the behavior of the vacuum $F(G)$ theory near the Type IV singular bouncing point and also we address the stability of the resulting solution, by treating the equations of motion as a dynamical system. In addition, we investigate how the scalar perturbations of the background metric evolve, emphasizing to cosmological times near the Type IV singular bouncing point. Finally, we also investigate which mimetic vacuum $F(G)$ gravity can describe the singular bounce cosmology. |
1106.4225 | Matthew P. Masarik | Matthew P. Masarik | The Wave Equation in a General Spherically Symmetric Black Hole Geometry | Editorial revisions made to first version; this version contains no
substantive changes | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Cauchy problem for the wave equation in a general class of
spherically symmetric black hole geometries. Under certain mild conditions on
the far-field decay and the singularity, we show that there is a unique
globally smooth solution to the Cauchy problem for the wave equation with data
compactly supported away from the horizon that is compactly supported for all
times and \emph{decays in $L^{\infty}_{\text{loc}}$ as $t$ tends to infinity}.
We obtain as a corollary that in the geometry of black hole solutions of the
SU(2) Einstein/Yang-Mills equations, solutions to the wave equation with
compactly supported initial data decay as $t$ goes to infinity.
| [
{
"created": "Tue, 21 Jun 2011 15:12:13 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Sep 2011 00:16:26 GMT",
"version": "v2"
}
] | 2011-09-14 | [
[
"Masarik",
"Matthew P.",
""
]
] | We consider the Cauchy problem for the wave equation in a general class of spherically symmetric black hole geometries. Under certain mild conditions on the far-field decay and the singularity, we show that there is a unique globally smooth solution to the Cauchy problem for the wave equation with data compactly supported away from the horizon that is compactly supported for all times and \emph{decays in $L^{\infty}_{\text{loc}}$ as $t$ tends to infinity}. We obtain as a corollary that in the geometry of black hole solutions of the SU(2) Einstein/Yang-Mills equations, solutions to the wave equation with compactly supported initial data decay as $t$ goes to infinity. |
gr-qc/9307007 | null | P.F. Gonz\'alez-D\'iaz | 2D dilaton-gravity from 5D Einstein equations | 9, IMAFF-Rc-04-93# | null | null | null | gr-qc | null | A semiclassical two-dimensional dilaton-gravity model is obtained by
dimensional reduction of the spherically symmetric five-dimensional Einstein
equations and used to investigate black hole evaporation. It is shown that this
model prevents the formation of naked singularity and allows spacetime
wormholes to contribute the process of formation and evaporation of black
holes.
| [
{
"created": "Fri, 9 Jul 1993 12:03:12 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 1993 12:40:14 GMT",
"version": "v2"
}
] | 2016-08-14 | [
[
"González-Díaz",
"P. F.",
""
]
] | A semiclassical two-dimensional dilaton-gravity model is obtained by dimensional reduction of the spherically symmetric five-dimensional Einstein equations and used to investigate black hole evaporation. It is shown that this model prevents the formation of naked singularity and allows spacetime wormholes to contribute the process of formation and evaporation of black holes. |
gr-qc/0105104 | Hans-Juergen Schmidt | H.-J. Schmidt | Inhomogeneous Cosmological Models Containing Homogeneous Inner
Hypersurface Geometry. Changes of the Bianchi Type | 10 pages, LaTeX, 1 figure | Astron.Nachr.303:227-230,1982 | 10.1002/asna.2103030403 | UNIPO-MATH-01-May-23 | gr-qc | null | There are investigated such cosmological models which instead of the usual
spatial homogeneity property only fulfil the condition that in a certain
synchronized system of reference all spacelike sections t = const. are
homogeneous manifolds. This allows time-dependent changes of the BIANCHI type.
Discussing differential geometrical theorems it is shown which of them are
permitted. Besides the trivial case of changing into type I there exist some
possible changes between other types. However, physical reasons like energy
inequalities partially exclude them.
| [
{
"created": "Mon, 28 May 2001 07:30:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Schmidt",
"H. -J.",
""
]
] | There are investigated such cosmological models which instead of the usual spatial homogeneity property only fulfil the condition that in a certain synchronized system of reference all spacelike sections t = const. are homogeneous manifolds. This allows time-dependent changes of the BIANCHI type. Discussing differential geometrical theorems it is shown which of them are permitted. Besides the trivial case of changing into type I there exist some possible changes between other types. However, physical reasons like energy inequalities partially exclude them. |
1203.3766 | Michael Reiterer | Michael Reiterer (ETH Zurich), Eugene Trubowitz (ETH Zurich) | Choptuik's critical spacetime exists | 46 pages | Commun. Math. Phys. 368, 143-186 (2019) | 10.1007/s00220-019-03413-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | About twenty years ago, Choptuik studied numerically the gravitational
collapse (Einstein field equations) of a massless scalar field in spherical
symmetry, and found strong evidence for a universal, self-similar solution at
the threshold of black hole formation. We prove rigorously the existence of a
real analytic solution, that we interpret as the solution observed by Choptuik.
Our construction covers an open neighborhood of the past light cone of the
singularity. The proof is computer assisted. Starting from an explicit
approximate solution, we show that nearby there is a true solution. The source
code and a high precision data file (about 80 significant decimal digits, with
rigorous error bounds) are included. We do not study perturbations.
| [
{
"created": "Fri, 16 Mar 2012 17:14:00 GMT",
"version": "v1"
}
] | 2020-05-08 | [
[
"Reiterer",
"Michael",
"",
"ETH Zurich"
],
[
"Trubowitz",
"Eugene",
"",
"ETH Zurich"
]
] | About twenty years ago, Choptuik studied numerically the gravitational collapse (Einstein field equations) of a massless scalar field in spherical symmetry, and found strong evidence for a universal, self-similar solution at the threshold of black hole formation. We prove rigorously the existence of a real analytic solution, that we interpret as the solution observed by Choptuik. Our construction covers an open neighborhood of the past light cone of the singularity. The proof is computer assisted. Starting from an explicit approximate solution, we show that nearby there is a true solution. The source code and a high precision data file (about 80 significant decimal digits, with rigorous error bounds) are included. We do not study perturbations. |
gr-qc/0605034 | Alfredo L\'opez Ortega | A. L\'opez-Ortega | Electromagnetic quasinormal modes of D-dimensional black holes | 24 pages, 1 figure. Some changes made according to referee's
suggestions. Matches published version in GRG | Gen.Rel.Grav.38:1747-1770,2006 | 10.1007/s10714-006-0358-2 | null | gr-qc | null | Using the monodromy method we calculate the asymptotic quasinormal (QN)
frequencies of an electromagnetic field moving in D-dimensional Schwarzschild
and Schwarzschild de Sitter (SdS) black holes ($D\geq 4$). For the
D-dimensional Schwarzschild anti-de Sitter (SadS) black hole we also compute
these frequencies with a similar method. Moreover, we calculate the
electromagnetic normal modes of the D-dimensional anti-de Sitter (AdS)
spacetime.
| [
{
"created": "Fri, 5 May 2006 19:37:13 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Nov 2006 09:45:33 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"López-Ortega",
"A.",
""
]
] | Using the monodromy method we calculate the asymptotic quasinormal (QN) frequencies of an electromagnetic field moving in D-dimensional Schwarzschild and Schwarzschild de Sitter (SdS) black holes ($D\geq 4$). For the D-dimensional Schwarzschild anti-de Sitter (SadS) black hole we also compute these frequencies with a similar method. Moreover, we calculate the electromagnetic normal modes of the D-dimensional anti-de Sitter (AdS) spacetime. |
2408.03725 | Yi Zhang | Xianfu Su, Dongze He, Yi Zhang | Two novel $f(Q)$ models | 10 pages, 4 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/publicdomain/zero/1.0/ | We propose two novel models in the framework of $f(Q)$ gravity to explain our
accelerated universe, namely the exponential $f(Q)_{EXP}$ model and the
hyperbolic tangent $f(Q)_{HT}$ model. The current cosmological electromagnetic
observations including the cosmic microwave background anisotropies (CMB), the
baryon acoustic oscillations(BAO), the type Ia supernovae (SN) and the direct
measurements of H(z), combined with the simulated gravitational-wave data are
used to constrain the $f(Q)$ models. We find that the Hubble tension can be
significantly alleviated to $1.40\sigma$ level in the $f(Q)_{EXP}$ model. The
fitting $\chi^2$ of the $f(Q)_{HT}$ model is $9.75\sigma$ poorer than that of
the $f(Q)_{EXP}$ model, implying the $f(Q)_{HT}$ model would be excluded by
future gravitational-wave observation.
| [
{
"created": "Wed, 7 Aug 2024 12:29:46 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2024 08:50:26 GMT",
"version": "v2"
}
] | 2024-08-09 | [
[
"Su",
"Xianfu",
""
],
[
"He",
"Dongze",
""
],
[
"Zhang",
"Yi",
""
]
] | We propose two novel models in the framework of $f(Q)$ gravity to explain our accelerated universe, namely the exponential $f(Q)_{EXP}$ model and the hyperbolic tangent $f(Q)_{HT}$ model. The current cosmological electromagnetic observations including the cosmic microwave background anisotropies (CMB), the baryon acoustic oscillations(BAO), the type Ia supernovae (SN) and the direct measurements of H(z), combined with the simulated gravitational-wave data are used to constrain the $f(Q)$ models. We find that the Hubble tension can be significantly alleviated to $1.40\sigma$ level in the $f(Q)_{EXP}$ model. The fitting $\chi^2$ of the $f(Q)_{HT}$ model is $9.75\sigma$ poorer than that of the $f(Q)_{EXP}$ model, implying the $f(Q)_{HT}$ model would be excluded by future gravitational-wave observation. |
2307.04073 | Arthur Garnier | Arthur Garnier | Motion equations in a Kerr-Newman-de Sitter spacetime: some methods of
integration and application to black holes shadowing in Scilab | null | Classical and Quantum Gravity, Volume 40, Number 13 (2023) | 10.1088/1361-6382/accbfe | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we recall some basic facts about the Kerr--Newman--(anti) de
Sitter (KNdS) spacetime and review several formulations and integration methods
for the geodesic equation of a test particle in such a spacetime. In
particular, we introduce some basic general symplectic integrators in the
Hamiltonian formalism and we re-derive the separated motion equations using
Carter's method.
After this theoretical background, we explain how to ray-trace a KNdS black
hole, equipped with a thin accretion disk, using Scilab. We compare the
accuracy and execution time of the previous methods, concluding that the Carter
equations is the best one. Then, inspired by Hagihara, we apply Weierstrass'
elliptic functions to the non-rotating case, yielding a fairly fast shadowing
program for such a spacetime.
We provide some illustrations of the code, including a depiction of the
effects of the cosmological constant on shadows and accretion disk, as well as
a simulation of M87*.
| [
{
"created": "Sun, 9 Jul 2023 00:46:09 GMT",
"version": "v1"
}
] | 2023-07-11 | [
[
"Garnier",
"Arthur",
""
]
] | In this paper, we recall some basic facts about the Kerr--Newman--(anti) de Sitter (KNdS) spacetime and review several formulations and integration methods for the geodesic equation of a test particle in such a spacetime. In particular, we introduce some basic general symplectic integrators in the Hamiltonian formalism and we re-derive the separated motion equations using Carter's method. After this theoretical background, we explain how to ray-trace a KNdS black hole, equipped with a thin accretion disk, using Scilab. We compare the accuracy and execution time of the previous methods, concluding that the Carter equations is the best one. Then, inspired by Hagihara, we apply Weierstrass' elliptic functions to the non-rotating case, yielding a fairly fast shadowing program for such a spacetime. We provide some illustrations of the code, including a depiction of the effects of the cosmological constant on shadows and accretion disk, as well as a simulation of M87*. |
2301.08421 | Jian-Pin Wu | Guoyang Fu, Dan Zhang, Peng Liu, Xiao-Mei Kuang, Jian-Pin Wu | Peculiar properties in quasi-normal spectra from loop quantum gravity
effect | 33 pages,10 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quasi-normal mode (QNM) spectra for scalar and
electromagnetic fields over a covairant loop quantum gravity black hole
(LQG-BH). For the fundamental modes, the LQG effect reduces the oscillations in
the scalar field, however it induces stronger oscillations in the
electromagnetic field, comparing to the classical case. Under the scalar field
perturbation, the system enjoys faster decaying modes with more oscillations
than the electromagnetic field. Some peculiar phenomena emerge in the QNM
spectra with higher overtones. A notable feature is the substantial divergence
observed in the first several overtones from their Schwarzschild counterparts,
with this discrepancy magnifying as the overtone number increases. Another
remarkable phenomenon in higher overtones is that the QNFs of the scalar field
with $l=0$ exhibit an oscillatory behavior as the quantum parameter $r_0$
increases significantly. These oscillations intensify with the rising overtone
number. We hypothesize that this oscillatory pattern may be associated with the
extremal effect.
| [
{
"created": "Fri, 20 Jan 2023 04:35:46 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Nov 2023 02:19:54 GMT",
"version": "v2"
}
] | 2023-11-22 | [
[
"Fu",
"Guoyang",
""
],
[
"Zhang",
"Dan",
""
],
[
"Liu",
"Peng",
""
],
[
"Kuang",
"Xiao-Mei",
""
],
[
"Wu",
"Jian-Pin",
""
]
] | We investigate the quasi-normal mode (QNM) spectra for scalar and electromagnetic fields over a covairant loop quantum gravity black hole (LQG-BH). For the fundamental modes, the LQG effect reduces the oscillations in the scalar field, however it induces stronger oscillations in the electromagnetic field, comparing to the classical case. Under the scalar field perturbation, the system enjoys faster decaying modes with more oscillations than the electromagnetic field. Some peculiar phenomena emerge in the QNM spectra with higher overtones. A notable feature is the substantial divergence observed in the first several overtones from their Schwarzschild counterparts, with this discrepancy magnifying as the overtone number increases. Another remarkable phenomenon in higher overtones is that the QNFs of the scalar field with $l=0$ exhibit an oscillatory behavior as the quantum parameter $r_0$ increases significantly. These oscillations intensify with the rising overtone number. We hypothesize that this oscillatory pattern may be associated with the extremal effect. |
1010.2777 | Geoffrey Lovelace | Geoffrey Lovelace, Mark A. Scheel, and Bela Szilagyi | Simulating merging binary black holes with nearly extremal spins | 4 pages, 2 figures, updated with version accepted for publication in
Phys. Rev. D, removed a plot that was incorrectly included at the end of the
article in version v2 | Phys.Rev.D83:024010,2011 | 10.1103/PhysRevD.83.024010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrophysically realistic black holes may have spins that are nearly extremal
(i.e., close to 1 in dimensionless units). Numerical simulations of binary
black holes are important tools both for calibrating analytical templates for
gravitational-wave detection and for exploring the nonlinear dynamics of curved
spacetime. However, all previous simulations of binary-black-hole inspiral,
merger, and ringdown have been limited by an apparently insurmountable barrier:
the merging holes' spins could not exceed 0.93, which is still a long way from
the maximum possible value in terms of the physical effects of the spin. In
this paper, we surpass this limit for the first time, opening the way to
explore numerically the behavior of merging, nearly extremal black holes.
Specifically, using an improved initial-data method suitable for binary black
holes with nearly extremal spins, we simulate the inspiral (through 12.5
orbits), merger and ringdown of two equal-mass black holes with equal spins of
magnitude 0.95 antialigned with the orbital angular momentum.
| [
{
"created": "Wed, 13 Oct 2010 21:13:40 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2011 15:51:03 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Jan 2011 04:47:15 GMT",
"version": "v3"
}
] | 2015-03-17 | [
[
"Lovelace",
"Geoffrey",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilagyi",
"Bela",
""
]
] | Astrophysically realistic black holes may have spins that are nearly extremal (i.e., close to 1 in dimensionless units). Numerical simulations of binary black holes are important tools both for calibrating analytical templates for gravitational-wave detection and for exploring the nonlinear dynamics of curved spacetime. However, all previous simulations of binary-black-hole inspiral, merger, and ringdown have been limited by an apparently insurmountable barrier: the merging holes' spins could not exceed 0.93, which is still a long way from the maximum possible value in terms of the physical effects of the spin. In this paper, we surpass this limit for the first time, opening the way to explore numerically the behavior of merging, nearly extremal black holes. Specifically, using an improved initial-data method suitable for binary black holes with nearly extremal spins, we simulate the inspiral (through 12.5 orbits), merger and ringdown of two equal-mass black holes with equal spins of magnitude 0.95 antialigned with the orbital angular momentum. |
0904.3810 | Ryuichi Fujita | Ryuichi Fujita, Wataru Hikida and Hideyuki Tagoshi | An Efficient Numerical Method for Computing Gravitational Waves Induced
by a Particle Moving on Eccentric Inclined Orbits around a Kerr Black Hole | Reference added in section 1 | Prog. Theor. Phys.121:843-874, 2009 | 10.1143/PTP.121.843 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a numerical code to compute gravitational waves induced by a
particle moving on eccentric inclined orbits around a Kerr black hole. For such
systems, the black hole perturbation method is applicable. The gravitational
waves can be evaluated by solving the Teukolsky equation with a point like
source term, which is computed from the stress-energy tensor of a test particle
moving on generic bound geodesic orbits. In our previous papers, we computed
the homogeneous solutions of the Teukolsky equation using a formalism developed
by Mano, Suzuki and Takasugi and showed that we could compute gravitational
waves efficiently and very accurately in the case of circular orbits on the
equatorial plane. Here, we apply this method to eccentric inclined orbits. The
geodesics around a Kerr black hole have three constants of motion: energy,
angular momentum and the Carter constant. We compute the rates of change of the
Carter constant as well as those of energy and angular momentum. This is the
first time that the rate of change of the Carter constant has been evaluated
accurately. We also treat the case of highly eccentric orbits with $e=0.9$. To
confirm the accuracy of our codes, several tests are performed. We find that
the accuracy is only limited by the truncation of $\ell$-, $k$- and $n$-modes,
where $\ell$ is the index of the spin-weighted spheroidal harmonics, and $n$
and $k$ are the harmonics of the radial and polar motion, respectively. When we
set the maximum of $\ell$ to 20, we obtain a relative accuracy of $10^{-5}$
even in the highly eccentric case of $e=0.9$. The accuracy is better for lower
eccentricity. Our numerical code is expected to be useful for computing
templates of the extreme mass ratio inspirals, which is one of the main targets
of the Laser Interferometer Space Antenna (LISA).
| [
{
"created": "Fri, 24 Apr 2009 07:27:26 GMT",
"version": "v1"
},
{
"created": "Wed, 20 May 2009 11:26:59 GMT",
"version": "v2"
}
] | 2009-08-05 | [
[
"Fujita",
"Ryuichi",
""
],
[
"Hikida",
"Wataru",
""
],
[
"Tagoshi",
"Hideyuki",
""
]
] | We develop a numerical code to compute gravitational waves induced by a particle moving on eccentric inclined orbits around a Kerr black hole. For such systems, the black hole perturbation method is applicable. The gravitational waves can be evaluated by solving the Teukolsky equation with a point like source term, which is computed from the stress-energy tensor of a test particle moving on generic bound geodesic orbits. In our previous papers, we computed the homogeneous solutions of the Teukolsky equation using a formalism developed by Mano, Suzuki and Takasugi and showed that we could compute gravitational waves efficiently and very accurately in the case of circular orbits on the equatorial plane. Here, we apply this method to eccentric inclined orbits. The geodesics around a Kerr black hole have three constants of motion: energy, angular momentum and the Carter constant. We compute the rates of change of the Carter constant as well as those of energy and angular momentum. This is the first time that the rate of change of the Carter constant has been evaluated accurately. We also treat the case of highly eccentric orbits with $e=0.9$. To confirm the accuracy of our codes, several tests are performed. We find that the accuracy is only limited by the truncation of $\ell$-, $k$- and $n$-modes, where $\ell$ is the index of the spin-weighted spheroidal harmonics, and $n$ and $k$ are the harmonics of the radial and polar motion, respectively. When we set the maximum of $\ell$ to 20, we obtain a relative accuracy of $10^{-5}$ even in the highly eccentric case of $e=0.9$. The accuracy is better for lower eccentricity. Our numerical code is expected to be useful for computing templates of the extreme mass ratio inspirals, which is one of the main targets of the Laser Interferometer Space Antenna (LISA). |
gr-qc/0702108 | Hamid Reza Sepangi | N. Khosravi, S. Jalalzadeh and H. R. Sepangi | Stabilization of internal space in noncommutative multidimensional
cosmology | 8 pages, 1 figure, to appear in IJMPD | Int.J.Mod.PHys.D16:1187-1196,2007 | 10.1142/S0218271807010651 | null | gr-qc hep-th | null | We study the cosmological aspects of a noncommutative, multidimensional
universe where the matter source is assumed to be a scalar field which does not
commute with the internal scale factor. We show that such noncommutativity
results in the internal dimensions being stabilized
| [
{
"created": "Tue, 20 Feb 2007 06:53:49 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Khosravi",
"N.",
""
],
[
"Jalalzadeh",
"S.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | We study the cosmological aspects of a noncommutative, multidimensional universe where the matter source is assumed to be a scalar field which does not commute with the internal scale factor. We show that such noncommutativity results in the internal dimensions being stabilized |
0704.1457 | T. Damour | Thibault Damour | Chaos and Symmetry in String Cosmology | 14 pages, one diagram; invited talk at the 11th Marcel Grossmann
Meeting on Recent Developments in General Relativity, Berlin, Germany, 23-29
July 2006 | null | 10.1142/9789812834300_0003 | null | gr-qc | null | We review the recently discovered interplay between chaos and symmetry in the
general inhomogeneous solution of many string-related Einstein-matter systems
in the vicinity of a cosmological singularity. The
Belinsky-Khalatnikov-Lifshitz-type chaotic behaviour is found, for many
Einstein-matter models (notably those related to the low-energy limit of
superstring theory and M-theory), to be connected with certain
(infinite-dimensional) hyperbolic Kac-Moody algebras. In particular, the
billiard chambers describing the asymptotic cosmological behaviour of pure
Einstein gravity in spacetime dimension d+1, or the metric-three-form system of
11-dimensional supergravity, are found to be identical to the Weyl chambers of
the Lorentzian Kac-Moody algebras AE_d, or E_{10}, respectively. This suggests
that these Kac-Moody algebras are hidden symmetries of the corresponding
models. There even exists some evidence of a hidden equivalence between the
general solution of the Einstein-three-form system and a null geodesic in the
infinite dimensional coset space E_{10} / K(E_{10}), where K(E_{10}) is the
maximal compact subgroup of E_{10}.
| [
{
"created": "Wed, 11 Apr 2007 17:10:40 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Damour",
"Thibault",
""
]
] | We review the recently discovered interplay between chaos and symmetry in the general inhomogeneous solution of many string-related Einstein-matter systems in the vicinity of a cosmological singularity. The Belinsky-Khalatnikov-Lifshitz-type chaotic behaviour is found, for many Einstein-matter models (notably those related to the low-energy limit of superstring theory and M-theory), to be connected with certain (infinite-dimensional) hyperbolic Kac-Moody algebras. In particular, the billiard chambers describing the asymptotic cosmological behaviour of pure Einstein gravity in spacetime dimension d+1, or the metric-three-form system of 11-dimensional supergravity, are found to be identical to the Weyl chambers of the Lorentzian Kac-Moody algebras AE_d, or E_{10}, respectively. This suggests that these Kac-Moody algebras are hidden symmetries of the corresponding models. There even exists some evidence of a hidden equivalence between the general solution of the Einstein-three-form system and a null geodesic in the infinite dimensional coset space E_{10} / K(E_{10}), where K(E_{10}) is the maximal compact subgroup of E_{10}. |
1009.1727 | Tom\'a\v{s} M\'alek | Tom\'a\v{s} M\'alek, Vojt\v{e}ch Pravda | Kerr-Schild spacetimes with (A)dS background | 17 pages, minor changes | Class. Quantum Grav.28:125011, 2011;
Class.Quant.Grav.28:125011,2011 | 10.1088/0264-9381/28/12/125011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General properties of Kerr-Schild spacetimes with (A)dS background in
arbitrary dimension are studied. It is shown that the geodetic Kerr-Schild
vector k is a multiple WAND of the spacetime. Einstein Kerr-Schild spacetimes
with non-expanding k are shown to be of Weyl type N, while the expanding
spacetimes are of type II or D. It is shown that this class of spacetimes obeys
the optical constraint. This allows us to solve Sachs equation, determine
r-dependence of boost weight zero components of the Weyl tensor and discuss
curvature singularities.
| [
{
"created": "Thu, 9 Sep 2010 10:20:36 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jan 2011 18:15:35 GMT",
"version": "v2"
},
{
"created": "Thu, 12 May 2011 10:04:18 GMT",
"version": "v3"
}
] | 2011-05-13 | [
[
"Málek",
"Tomáš",
""
],
[
"Pravda",
"Vojtěch",
""
]
] | General properties of Kerr-Schild spacetimes with (A)dS background in arbitrary dimension are studied. It is shown that the geodetic Kerr-Schild vector k is a multiple WAND of the spacetime. Einstein Kerr-Schild spacetimes with non-expanding k are shown to be of Weyl type N, while the expanding spacetimes are of type II or D. It is shown that this class of spacetimes obeys the optical constraint. This allows us to solve Sachs equation, determine r-dependence of boost weight zero components of the Weyl tensor and discuss curvature singularities. |
gr-qc/9910077 | Janos Kannar | H. Friedrich and J. Kannar | Bondi-type systems near space-like infinity and the calculation of the
NP-constants | 35 pages | J.Math.Phys. 41 (2000) 2195-2232 | 10.1063/1.533235 | null | gr-qc | null | We relate Bondi systems near space-like infinity to another type of gauge
conditions. While the former are based on null infinity, the latter are defined
in terms of Einstein propagation, the conformal structure, and data on some
Cauchy hypersurface. For a certain class of time symmetric space-times we study
an expansion which allows us to determine the behavior of various fields
arising in Bondi systems in the region of space-time where null infinity
touches space-like infinity. The coefficients of these expansions can be read
off from the initial data. We obtain in particular expressions for the
constants discovered by Newman and Penrose (NP-constants) in terms of the
initial data. For this purpose we calculate a certain expansion up to 3rd
order.
| [
{
"created": "Fri, 22 Oct 1999 12:55:48 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Friedrich",
"H.",
""
],
[
"Kannar",
"J.",
""
]
] | We relate Bondi systems near space-like infinity to another type of gauge conditions. While the former are based on null infinity, the latter are defined in terms of Einstein propagation, the conformal structure, and data on some Cauchy hypersurface. For a certain class of time symmetric space-times we study an expansion which allows us to determine the behavior of various fields arising in Bondi systems in the region of space-time where null infinity touches space-like infinity. The coefficients of these expansions can be read off from the initial data. We obtain in particular expressions for the constants discovered by Newman and Penrose (NP-constants) in terms of the initial data. For this purpose we calculate a certain expansion up to 3rd order. |
2402.02424 | Tayyab Naseer | M. Sharif, Tayyab Naseer | Influence of $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ Gravity on
Cylindrical Collapse | 23 pages, no figure | Indian J. Phys. 97(2023)2853-2863 | 10.1007/s12648-023-02630-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article examines the dynamics of gravitational collapse in
$f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where
$\mathcal{Q}=\mathcal{R}_{\mathrm{ab}}\mathcal{T}^{\mathrm{ab}}$. We consider
self-gravitating anisotropic cylindrical geometry whose interior is filled with
dissipative matter configuration and match it with exterior cylindrically
symmetric spacetime at the hypersurface through junction conditions. We employ
the Misner-Sharp and M\"{u}ler-Israel Stewart formalisms to derive the
dynamical as well as transport equations corresponding to the model
$\mathcal{R}+\Phi\sqrt{\mathcal{T}}+\Psi\mathcal{Q}$, where $\Phi$ and $\Psi$
are arbitrary coupling constants. We then establish some relations between
these equations through which the impact of effective matter variables, heat
dissipation and the bulk viscosity on the collapse rate is studied. Further, we
express the Weyl scalar in terms of the effective matter sector. We also obtain
the conformal flatness by applying some restrictions on the considered model
and taking dust configuration into the account. Finally, we investigate various
cases to check whether the modified corrections increase or decrease the
collapse rate.
| [
{
"created": "Sun, 4 Feb 2024 09:40:52 GMT",
"version": "v1"
}
] | 2024-02-06 | [
[
"Sharif",
"M.",
""
],
[
"Naseer",
"Tayyab",
""
]
] | This article examines the dynamics of gravitational collapse in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where $\mathcal{Q}=\mathcal{R}_{\mathrm{ab}}\mathcal{T}^{\mathrm{ab}}$. We consider self-gravitating anisotropic cylindrical geometry whose interior is filled with dissipative matter configuration and match it with exterior cylindrically symmetric spacetime at the hypersurface through junction conditions. We employ the Misner-Sharp and M\"{u}ler-Israel Stewart formalisms to derive the dynamical as well as transport equations corresponding to the model $\mathcal{R}+\Phi\sqrt{\mathcal{T}}+\Psi\mathcal{Q}$, where $\Phi$ and $\Psi$ are arbitrary coupling constants. We then establish some relations between these equations through which the impact of effective matter variables, heat dissipation and the bulk viscosity on the collapse rate is studied. Further, we express the Weyl scalar in terms of the effective matter sector. We also obtain the conformal flatness by applying some restrictions on the considered model and taking dust configuration into the account. Finally, we investigate various cases to check whether the modified corrections increase or decrease the collapse rate. |
gr-qc/0103030 | Sergio Dain | Sergio Dain | Initial data for a head on collision of two Kerr-like black holes with
close limit | 15 pages, no figures, Latex2e | Phys.Rev. D64 (2001) 124002 | 10.1103/PhysRevD.64.124002 | null | gr-qc | null | We prove the existence of a family of initial data for the Einstein vacuum
equation which can be interpreted as the data for two Kerr-like black holes in
arbitrary location and with spin in arbitrary direction. This family of initial
data has the following properties: (i) When the mass parameter of one of them
is zero or when the distance between them goes to infinity, it reduces exactly
to the Kerr initial data. (ii) When the distance between them is zero, we
obtain exactly a Kerr initial data with mass and angular momentum equal to the
sum of the mass and angular momentum parameters of each of them. The initial
data depends smoothly on the distance, the mass and the angular momentum
parameters.
| [
{
"created": "Fri, 9 Mar 2001 14:58:19 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Dain",
"Sergio",
""
]
] | We prove the existence of a family of initial data for the Einstein vacuum equation which can be interpreted as the data for two Kerr-like black holes in arbitrary location and with spin in arbitrary direction. This family of initial data has the following properties: (i) When the mass parameter of one of them is zero or when the distance between them goes to infinity, it reduces exactly to the Kerr initial data. (ii) When the distance between them is zero, we obtain exactly a Kerr initial data with mass and angular momentum equal to the sum of the mass and angular momentum parameters of each of them. The initial data depends smoothly on the distance, the mass and the angular momentum parameters. |
0807.0854 | Marcus Werner | G W Gibbons, M C Werner | Applications of the Gauss-Bonnet theorem to gravitational lensing | 10 pages, 1 figure, IoP style | Class.Quant.Grav.25:235009,2008 | 10.1088/0264-9381/25/23/235009 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this geometrical approach to gravitational lensing theory, we apply the
Gauss-Bonnet theorem to the optical metric of a lens, modelled as a static,
spherically symmetric, perfect non-relativistic fluid, in the weak deflection
limit. We find that the focusing of the light rays emerges here as a
topological effect, and we introduce a new method to calculate the deflection
angle from the Gaussian curvature of the optical metric. As examples, the
Schwarzschild lens, the Plummer sphere and the singular isothermal sphere are
discussed within this framework.
| [
{
"created": "Sat, 5 Jul 2008 12:24:21 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Gibbons",
"G W",
""
],
[
"Werner",
"M C",
""
]
] | In this geometrical approach to gravitational lensing theory, we apply the Gauss-Bonnet theorem to the optical metric of a lens, modelled as a static, spherically symmetric, perfect non-relativistic fluid, in the weak deflection limit. We find that the focusing of the light rays emerges here as a topological effect, and we introduce a new method to calculate the deflection angle from the Gaussian curvature of the optical metric. As examples, the Schwarzschild lens, the Plummer sphere and the singular isothermal sphere are discussed within this framework. |
1210.1485 | Florian Girelli | Florian Girelli, Franz Hinterleitner and Seth A. Major | Loop Quantum Gravity Phenomenology: Linking Loops to Observational
Physics | Invited review for SIGMA Special Issue "Loop Quantum Gravity and
Cosmology" | SIGMA 8 (2012), 098, 73 pages | 10.3842/SIGMA.2012.098 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Research during the last decade demonstrates that effects originating on the
Planck scale are currently being tested in multiple observational contexts. In
this review we discuss quantum gravity phenomenological models and their
possible links to loop quantum gravity. Particle frameworks, including
kinematic models, broken and deformed Poincar\'e symmetry, non-commutative
geometry, relative locality and generalized uncertainty principle, and field
theory frameworks, including Lorentz violating operators in effective field
theory and non-commutative field theory, are discussed. The arguments relating
loop quantum gravity to models with modified dispersion relations are reviewed,
as well as, arguments supporting the preservation of local Lorentz invariance.
The phenomenology related to loop quantum cosmology is briefly reviewed, with a
focus on possible effects that might be tested in the near future. As the
discussion makes clear, there remains much interesting work to do in
establishing the connection between the fundamental theory of loop quantum
gravity and these specific phenomenological models, in determining
observational consequences of the characteristic aspects of loop quantum
gravity, and in further refining current observations. Open problems related to
these developments are highlighted. characteristic aspects of loop quantum
gravity, and in further refining current observations. Open problems related to
these developments are highlighted.
| [
{
"created": "Thu, 4 Oct 2012 15:26:17 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2012 06:22:50 GMT",
"version": "v2"
}
] | 2012-12-14 | [
[
"Girelli",
"Florian",
""
],
[
"Hinterleitner",
"Franz",
""
],
[
"Major",
"Seth A.",
""
]
] | Research during the last decade demonstrates that effects originating on the Planck scale are currently being tested in multiple observational contexts. In this review we discuss quantum gravity phenomenological models and their possible links to loop quantum gravity. Particle frameworks, including kinematic models, broken and deformed Poincar\'e symmetry, non-commutative geometry, relative locality and generalized uncertainty principle, and field theory frameworks, including Lorentz violating operators in effective field theory and non-commutative field theory, are discussed. The arguments relating loop quantum gravity to models with modified dispersion relations are reviewed, as well as, arguments supporting the preservation of local Lorentz invariance. The phenomenology related to loop quantum cosmology is briefly reviewed, with a focus on possible effects that might be tested in the near future. As the discussion makes clear, there remains much interesting work to do in establishing the connection between the fundamental theory of loop quantum gravity and these specific phenomenological models, in determining observational consequences of the characteristic aspects of loop quantum gravity, and in further refining current observations. Open problems related to these developments are highlighted. characteristic aspects of loop quantum gravity, and in further refining current observations. Open problems related to these developments are highlighted. |
1404.1435 | Chul-Moon Yoo | Chul-Moon Yoo and Hirotada Okawa | Black Hole Universe with $\Lambda$ | 14 pages, 9 figures | Phys. Rev. D 89, 123502 (2014) | 10.1103/PhysRevD.89.123502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time evolution of a black hole lattice universe with a positive cosmological
constant $\Lambda$ is simulated. The vacuum Einstein equations are numerically
solved in a cubic box with a black hole in the center. Periodic boundary
conditions on all pairs of opposite faces are imposed. Configurations of
marginally trapped surfaces are analyzed. We describe the time evolution of not
only black hole horizons, but also cosmological horizons. Defining the
effective scale factor by using the area of a surface of the cubic box, we
compare it with that in the spatially flat dust dominated FLRW universe with
the same value of $\Lambda$. It is found that the behaviour of the effective
scale factor is well approximated by that in the FLRW universe. Our result
suggests that local inhomogeneities do not significantly affect the global
expansion law of the universe irrespective of the value of $\Lambda$.
| [
{
"created": "Sat, 5 Apr 2014 05:27:18 GMT",
"version": "v1"
}
] | 2014-06-11 | [
[
"Yoo",
"Chul-Moon",
""
],
[
"Okawa",
"Hirotada",
""
]
] | Time evolution of a black hole lattice universe with a positive cosmological constant $\Lambda$ is simulated. The vacuum Einstein equations are numerically solved in a cubic box with a black hole in the center. Periodic boundary conditions on all pairs of opposite faces are imposed. Configurations of marginally trapped surfaces are analyzed. We describe the time evolution of not only black hole horizons, but also cosmological horizons. Defining the effective scale factor by using the area of a surface of the cubic box, we compare it with that in the spatially flat dust dominated FLRW universe with the same value of $\Lambda$. It is found that the behaviour of the effective scale factor is well approximated by that in the FLRW universe. Our result suggests that local inhomogeneities do not significantly affect the global expansion law of the universe irrespective of the value of $\Lambda$. |
1303.2410 | Michel Miranda | Galaxia Miranda, Tonatiuh Matos and Nadiezhda Motelongo Garc\'ia | Kerr-Like Phantom Wormhole | null | Gen. Rel. Grav. 46, (2014), 1613 | 10.1007/s10714-013-1613-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study a Kerr-like wormhole with phantom matter as source. It
has three parameters: mass, angular momentum and scalar field charge. This
wormhole has a naked ring singularity, other wise it is regular everywhere. The
mean feature of this wormhole is that the mouth of the throat lie on a sphere
of the same radius as the ring singularity an avoids any observer to see or to
reach the singularity, it behaves like an anti-horizon. We analyse the
geodesics of the wormhole and find that an observer can go through the
geodesics without troubles, but the equator presents an infinity potential
barrier which avoids to reach the throat. From an analysis of the Riemann
tensor we obtain that the tidal forces permits the wormhole to be traversable
for an observer like a human being.
| [
{
"created": "Mon, 11 Mar 2013 02:13:19 GMT",
"version": "v1"
}
] | 2021-02-09 | [
[
"Miranda",
"Galaxia",
""
],
[
"Matos",
"Tonatiuh",
""
],
[
"García",
"Nadiezhda Motelongo",
""
]
] | In this work we study a Kerr-like wormhole with phantom matter as source. It has three parameters: mass, angular momentum and scalar field charge. This wormhole has a naked ring singularity, other wise it is regular everywhere. The mean feature of this wormhole is that the mouth of the throat lie on a sphere of the same radius as the ring singularity an avoids any observer to see or to reach the singularity, it behaves like an anti-horizon. We analyse the geodesics of the wormhole and find that an observer can go through the geodesics without troubles, but the equator presents an infinity potential barrier which avoids to reach the throat. From an analysis of the Riemann tensor we obtain that the tidal forces permits the wormhole to be traversable for an observer like a human being. |
2110.00722 | Sebastian Murk | Pravin K. Dahal, Sebastian Murk, Daniel R. Terno | Semiclassical black holes and horizon singularities | 12 pages, 3 figures. Published version. Invited contribution to the
special topic collection "Celebrating Sir Roger Penrose's Nobel Prize"
published in AVS Quantum Science. Comments welcome! | AVS Quantum Sci. 4, 015606 (2022) | 10.1116/5.0073598 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In spherical symmetry, solutions of the semiclassical Einstein equations
belong to one of two possible classes. Both classes contain solutions that --
depending on the dynamic behavior of the horizon -- describe evaporating
physical black holes or expanding white holes (trapped/anti-trapped regions
that form in finite time of a distant observer). These solutions are
real-valued only if the null energy condition (NEC) is violated in the vicinity
of the Schwarzschild sphere. We review their properties and describe the only
consistent black hole formation scenario. While the curvature scalars are
finite on the outer apparent/anti-trapping horizon, it is still a weakly
singular surface. This singularity manifests itself in a mild firewall. Near
the inner apparent horizon, the NEC is satisfied. Models of static regular
black holes are known to be unstable, but since dynamic models of regular black
holes are severely constrained by self-consistency requirements, their
stability requires further investigation.
| [
{
"created": "Sat, 2 Oct 2021 04:02:44 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Dec 2021 10:29:10 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Mar 2022 11:22:00 GMT",
"version": "v3"
}
] | 2022-03-10 | [
[
"Dahal",
"Pravin K.",
""
],
[
"Murk",
"Sebastian",
""
],
[
"Terno",
"Daniel R.",
""
]
] | In spherical symmetry, solutions of the semiclassical Einstein equations belong to one of two possible classes. Both classes contain solutions that -- depending on the dynamic behavior of the horizon -- describe evaporating physical black holes or expanding white holes (trapped/anti-trapped regions that form in finite time of a distant observer). These solutions are real-valued only if the null energy condition (NEC) is violated in the vicinity of the Schwarzschild sphere. We review their properties and describe the only consistent black hole formation scenario. While the curvature scalars are finite on the outer apparent/anti-trapping horizon, it is still a weakly singular surface. This singularity manifests itself in a mild firewall. Near the inner apparent horizon, the NEC is satisfied. Models of static regular black holes are known to be unstable, but since dynamic models of regular black holes are severely constrained by self-consistency requirements, their stability requires further investigation. |
gr-qc/0509121 | Brendan Foster | Brendan Z. Foster | Noether charges and black hole mechanics in Einstein-aether theory | 14 pages; v2: minor comments added | Phys.Rev. D73 (2006) 024005 | 10.1103/PhysRevD.73.024005 | null | gr-qc hep-th | null | The Noether charge method for defining the Hamiltonian of a
diffeomorphism-invariant field theory is applied to "Einstein-aether" theory,
in which gravity couples to a dynamical, timelike, unit-norm vector field.
Using the method, expressions are obtained for the total energy, momentum, and
angular momentum of an Einstein-aether space-time. The method is also used to
discuss the mechanics of Einstein-aether black holes. The derivation of Wald,
and Iyer and Wald, of the first law of black hole thermodynamics fails for this
theory, because the unit vector is necessarily singular at the bifurcation
surface of the Killing horizon. A general identity relating variations of
energy and angular momentum to a surface integral at the horizon is obtained,
but a thermodynamic interpretation, including a definitive expression for the
black hole entropy, is not found.
| [
{
"created": "Thu, 29 Sep 2005 19:10:03 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Dec 2005 20:30:56 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Foster",
"Brendan Z.",
""
]
] | The Noether charge method for defining the Hamiltonian of a diffeomorphism-invariant field theory is applied to "Einstein-aether" theory, in which gravity couples to a dynamical, timelike, unit-norm vector field. Using the method, expressions are obtained for the total energy, momentum, and angular momentum of an Einstein-aether space-time. The method is also used to discuss the mechanics of Einstein-aether black holes. The derivation of Wald, and Iyer and Wald, of the first law of black hole thermodynamics fails for this theory, because the unit vector is necessarily singular at the bifurcation surface of the Killing horizon. A general identity relating variations of energy and angular momentum to a surface integral at the horizon is obtained, but a thermodynamic interpretation, including a definitive expression for the black hole entropy, is not found. |
1111.3167 | Pedro Fraz\~ao | Orfeu Bertolami, Pedro Fraz\~ao, Jorge P\'aramos | Mimicking dark matter in galaxy clusters through a non-minimal
gravitational coupling with matter | 15 pages, 19 figures; published version | Phys. Rev. D 86, 044034 (2012) | 10.1103/PhysRevD.86.044034 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, one shows that a specific non-minimal coupling between the
scalar curvature and matter can mimic the dark matter component of galaxy
clusters. For this purpose, one assesses the Abell cluster A586, a massive
nearby relaxed cluster of galaxies in virial equilibrium, where direct mass
estimates and strong-lensing determinations are possible. One then extends the
dark matter mimicking to a large sample of galaxy clusters whose density
profiles are obtained from the Chandra high quality data, also in virial
equilibrium. The total density, which generally follows a cusped profile and
reveals a very small baryonic component, can be effectively described within
this framework.
| [
{
"created": "Mon, 14 Nov 2011 10:41:17 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2013 17:58:09 GMT",
"version": "v2"
}
] | 2013-01-31 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Frazão",
"Pedro",
""
],
[
"Páramos",
"Jorge",
""
]
] | In this work, one shows that a specific non-minimal coupling between the scalar curvature and matter can mimic the dark matter component of galaxy clusters. For this purpose, one assesses the Abell cluster A586, a massive nearby relaxed cluster of galaxies in virial equilibrium, where direct mass estimates and strong-lensing determinations are possible. One then extends the dark matter mimicking to a large sample of galaxy clusters whose density profiles are obtained from the Chandra high quality data, also in virial equilibrium. The total density, which generally follows a cusped profile and reveals a very small baryonic component, can be effectively described within this framework. |
1903.10496 | David D. K. Chow | David D. K. Chow | Characterization of three-dimensional Lorentzian metrics that admit four
Killing vectors | 15 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider three-dimensional Lorentzian metrics that locally admit four
independent Killing vectors. Their classification is summarized, and conditions
for characterizing them are found. These consist of algebraic classification of
the traceless Ricci tensor, and other conditions satisfied by the curvature and
its derivative.
| [
{
"created": "Mon, 25 Mar 2019 17:52:57 GMT",
"version": "v1"
}
] | 2019-03-26 | [
[
"Chow",
"David D. K.",
""
]
] | We consider three-dimensional Lorentzian metrics that locally admit four independent Killing vectors. Their classification is summarized, and conditions for characterizing them are found. These consist of algebraic classification of the traceless Ricci tensor, and other conditions satisfied by the curvature and its derivative. |
2404.17904 | Faisal Javed | G. Mustafa, Faisal Javed, Arfa Waseem, S.K. Maurya, Ghulam Fatima | Imprints of dark energy models on structural properties of charged
gravastars in extended teleparallel gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A gravastar comprises three distinct sections: the interior zone, the middle
shell, and its outer region. By considering a specific extended teleparallel
gravity model that incorporates conformal Killing vectors and provides the
field equations. We observe that the interior part exhibits a repellent force
acting on the shell. This is based on the assumption that pressure is analogous
to negative energy density. The middle shell consists of ultrarelativistic
plasma and pressure, which is directly proportional to the matter density and
counteracts the repellent force exerted by the inner zone. In the outer zone,
we compute the precise solution in a vacuum and then connect these spacetimes
using junction conditions to investigate stability limits. We aim to
investigate the influence of dark energy models on the stable characteristics
of gravastar configurations. It is worth noting that the phantom field exhibits
the highest stable configurations for all physically viable selections of
physical parameters. We additionally investigate the influence of physical
parameters on the correct length, entropy, and energy of the gravastar.
| [
{
"created": "Sat, 27 Apr 2024 13:26:41 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Mustafa",
"G.",
""
],
[
"Javed",
"Faisal",
""
],
[
"Waseem",
"Arfa",
""
],
[
"Maurya",
"S. K.",
""
],
[
"Fatima",
"Ghulam",
""
]
] | A gravastar comprises three distinct sections: the interior zone, the middle shell, and its outer region. By considering a specific extended teleparallel gravity model that incorporates conformal Killing vectors and provides the field equations. We observe that the interior part exhibits a repellent force acting on the shell. This is based on the assumption that pressure is analogous to negative energy density. The middle shell consists of ultrarelativistic plasma and pressure, which is directly proportional to the matter density and counteracts the repellent force exerted by the inner zone. In the outer zone, we compute the precise solution in a vacuum and then connect these spacetimes using junction conditions to investigate stability limits. We aim to investigate the influence of dark energy models on the stable characteristics of gravastar configurations. It is worth noting that the phantom field exhibits the highest stable configurations for all physically viable selections of physical parameters. We additionally investigate the influence of physical parameters on the correct length, entropy, and energy of the gravastar. |
2405.13096 | Esmaeil Ebrahimi | Esmaeil Ebrahimi, Ahmad Sheykhi | Ghost Dark Energy in Tsallis and Barrow Cosmology | 14 pages, 31 figures | Published in: Phys.Dark Univ. 45 (2024) 101518 | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | According to the thermodynamics-gravity conjecture, any modification to the
entropy expression leads to the modified cosmological field equations. Based on
this, we investigate the cosmological consequences of the modified Friedmann
equations when the entropy associated with the horizon is in the form of
Tsallis/Barrow entropy and the dark energy (DE) component is in the form of
ghost dark energy (GDE). We perform a dynamical system analysis and see that
the Tsallis GDE(TGDE) and Barrow GDE(BGDE) can exhibit a correct phase space
evolution for suitable range of the free parameters($0<\Delta<1$ for BGDE and
$\beta<3/2$ for TGDE). We find that in BGDE and TGDE (with $Q=3b^2
H(\rho_D+\rho_m)$), there exist an early radiation dominated phase of expansion
which is absent for GDE model in standard cosmology. It is worth mentioning
that seeking an unstable phase of matter dominated in TGDE leads to a new
constraint on $\beta$($<3/2$). Using the resulting range of free parameters
from latter step we find that both models are capable to explain the cosmic
evolution from deceleration to an accelerated phase. We observe that increasing
$\Delta$ ($\beta$) parameters leads to a delay in the cosmic phase transition.
We conclude that BGDE and TGDE are viable cosmological models which predict a
consistent phase transition of the cosmic expansion for suitable ranges of the
parameters. We also calculate the squared sound speed for both models and find
out that they are unstable against perturbations...
| [
{
"created": "Tue, 21 May 2024 13:58:28 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Ebrahimi",
"Esmaeil",
""
],
[
"Sheykhi",
"Ahmad",
""
]
] | According to the thermodynamics-gravity conjecture, any modification to the entropy expression leads to the modified cosmological field equations. Based on this, we investigate the cosmological consequences of the modified Friedmann equations when the entropy associated with the horizon is in the form of Tsallis/Barrow entropy and the dark energy (DE) component is in the form of ghost dark energy (GDE). We perform a dynamical system analysis and see that the Tsallis GDE(TGDE) and Barrow GDE(BGDE) can exhibit a correct phase space evolution for suitable range of the free parameters($0<\Delta<1$ for BGDE and $\beta<3/2$ for TGDE). We find that in BGDE and TGDE (with $Q=3b^2 H(\rho_D+\rho_m)$), there exist an early radiation dominated phase of expansion which is absent for GDE model in standard cosmology. It is worth mentioning that seeking an unstable phase of matter dominated in TGDE leads to a new constraint on $\beta$($<3/2$). Using the resulting range of free parameters from latter step we find that both models are capable to explain the cosmic evolution from deceleration to an accelerated phase. We observe that increasing $\Delta$ ($\beta$) parameters leads to a delay in the cosmic phase transition. We conclude that BGDE and TGDE are viable cosmological models which predict a consistent phase transition of the cosmic expansion for suitable ranges of the parameters. We also calculate the squared sound speed for both models and find out that they are unstable against perturbations... |
1004.3102 | Pedro Montero | Pedro J. Montero, Jose A. Font and Masaru Shibata | Influence of self-gravity on the runaway instability of black hole-torus
systems | To appear on Phys.Rev.Lett | Phys.Rev.Lett.104:191101,2010 | 10.1103/PhysRevLett.104.191101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Results from the first fully general relativistic numerical simulations in
axisymmetry of a system formed by a black hole surrounded by a self-gravitating
torus in equilibrium are presented, aiming to assess the influence of the torus
self-gravity on the onset of the runaway instability. We consider several
models with varying torus-to-black hole mass ratio and angular momentum
distribution orbiting in equilibrium around a non-rotating black hole. The tori
are perturbed to induce the mass transfer towards the black hole. Our numerical
simulations show that all models exhibit a persistent phase of axisymmetric
oscillations around their equilibria for several dynamical timescales without
the appearance of the runaway instability, indicating that the self-gravity of
the torus does not play a critical role favoring the onset of the instability,
at least during the first few dynamical timescales.
| [
{
"created": "Mon, 19 Apr 2010 06:22:47 GMT",
"version": "v1"
}
] | 2010-05-25 | [
[
"Montero",
"Pedro J.",
""
],
[
"Font",
"Jose A.",
""
],
[
"Shibata",
"Masaru",
""
]
] | Results from the first fully general relativistic numerical simulations in axisymmetry of a system formed by a black hole surrounded by a self-gravitating torus in equilibrium are presented, aiming to assess the influence of the torus self-gravity on the onset of the runaway instability. We consider several models with varying torus-to-black hole mass ratio and angular momentum distribution orbiting in equilibrium around a non-rotating black hole. The tori are perturbed to induce the mass transfer towards the black hole. Our numerical simulations show that all models exhibit a persistent phase of axisymmetric oscillations around their equilibria for several dynamical timescales without the appearance of the runaway instability, indicating that the self-gravity of the torus does not play a critical role favoring the onset of the instability, at least during the first few dynamical timescales. |
1308.1859 | Julio Cesar Fabris | J.C. Fabris, O.F. Piattella, I.G. Salako, J. Tossa, H.E.S. Velten | A note on acoustic black holes in neo-Newtonian theory | Latex file, 10 pages. Some discussions extended. Accepted for
publication in MPLA | Modern Physics Letters A28, 1350169(2013) | 10.1142/S0217732313501691 | null | gr-qc astro-ph.HE hep-th physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Newtonian fluid dynamics allows the construction of acoustic metrics from
which black hole configurations can be studied. However, relativistic pressure
effects are neglected within Newtonian theory. We study acoustic black holes in
the framework of neo-Newtonian hydrodynamics, which is designed to take into
account relativistic inertial effects of the pressure $p$. Within this new
hydrodynamical context we show how $p$ can influence the formation of the
acoustic horizons.
| [
{
"created": "Thu, 8 Aug 2013 14:15:01 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Oct 2013 14:21:39 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Fabris",
"J. C.",
""
],
[
"Piattella",
"O. F.",
""
],
[
"Salako",
"I. G.",
""
],
[
"Tossa",
"J.",
""
],
[
"Velten",
"H. E. S.",
""
]
] | Newtonian fluid dynamics allows the construction of acoustic metrics from which black hole configurations can be studied. However, relativistic pressure effects are neglected within Newtonian theory. We study acoustic black holes in the framework of neo-Newtonian hydrodynamics, which is designed to take into account relativistic inertial effects of the pressure $p$. Within this new hydrodynamical context we show how $p$ can influence the formation of the acoustic horizons. |
1210.0730 | Timothy Clifton | Timothy Clifton, Peter Dunsby, Rituparno Goswami and Anne Marie Nzioki | On the absence of the usual weak-field limit, and the impossibility of
embedding some known solutions for isolated masses in cosmologies with f(R)
dark energy | 12 pages. Corrections made in Eqs. (6)-(9) | Phys. Rev. D 87, 063517 (2013) | 10.1103/PhysRevD.87.063517 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of matching different regions of spacetime in order to construct
inhomogeneous cosmological models is investigated in the context of Lagrangian
theories of gravity constructed from general analytic functions f(R), and from
non-analytic theories with f(R)=R^n. In all of the cases studied, we find that
it is impossible to satisfy the required junction conditions without the
large-scale behaviour reducing to that expected from Einstein's equations with
a cosmological constant. For theories with analytic f(R) this suggests that the
usual treatment of weak-field systems as perturbations about Minkowski space
may not be compatible with late-time acceleration driven by anything other than
a constant term of the form f(0), which acts like a cosmological constant. In
the absence of Minkowski space as a suitable background for weak-field systems,
one must then choose and justify some other solution to perform perturbative
analyses around. For theories with f(R)=R^n we find that no known spherically
symmetric vacuum solutions can be matched to an expanding FLRW background. This
includes the absence of any Einstein-Straus-like embeddings of the
Schwarzschild exterior solution in FLRW spacetimes.
| [
{
"created": "Tue, 2 Oct 2012 10:50:08 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Mar 2013 10:28:03 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Apr 2013 14:05:36 GMT",
"version": "v3"
}
] | 2013-04-24 | [
[
"Clifton",
"Timothy",
""
],
[
"Dunsby",
"Peter",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Nzioki",
"Anne Marie",
""
]
] | The problem of matching different regions of spacetime in order to construct inhomogeneous cosmological models is investigated in the context of Lagrangian theories of gravity constructed from general analytic functions f(R), and from non-analytic theories with f(R)=R^n. In all of the cases studied, we find that it is impossible to satisfy the required junction conditions without the large-scale behaviour reducing to that expected from Einstein's equations with a cosmological constant. For theories with analytic f(R) this suggests that the usual treatment of weak-field systems as perturbations about Minkowski space may not be compatible with late-time acceleration driven by anything other than a constant term of the form f(0), which acts like a cosmological constant. In the absence of Minkowski space as a suitable background for weak-field systems, one must then choose and justify some other solution to perform perturbative analyses around. For theories with f(R)=R^n we find that no known spherically symmetric vacuum solutions can be matched to an expanding FLRW background. This includes the absence of any Einstein-Straus-like embeddings of the Schwarzschild exterior solution in FLRW spacetimes. |
2306.12234 | Hippolyte Quelquejay Leclere | Hippolyte Quelquejay Leclere, Pierre Auclair, Stanislav Babak,
Aur\'elien Chalumeau, Dani\`ele A. Steer, J. Antoniadis, A.-S. Bak Nielsen,
C. G. Bassa, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay,
R. N. Caballero, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, G.
Desvignes, M. Falxa, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov,
E. Graikou, J.-M. Grie{\ss}meier, L. Guillemot, Y. J. Guo, H. Hu, F. Iraci,
D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, R.
Karuppusamy, E. F. Keane, M. J. Keith, M. Kramer, M. A. Krishnakumar, K.
Lackeos, K. J. Lee, K. Liu, Y. Liu, A. G. Lyne, J. W. McKee, R. A. Main, M.
B. Mickaliger, I. C. Ni\c{t}u, A. Parthasarathy, B. B. P. Perera, D.
Perrodin, A. Petiteau, N. K. Porayko, A. Possenti, A. Samajdar, S. A.
Sanidas, A. Sesana, G. Shaifullah, L. Speri, R. Spiewak, B. W. Stappers, S.
C. Susarla, G. Theureau, C. Tiburzi, E. van der Wateren, A. Vecchio, V.
Venkatraman Krishnan, J. P. W. Verbiest, J. Wang, L. Wang and Z. Wu | Practical approaches to analyzing PTA data: Cosmic strings with six
pulsars | 14 pages, 6 figures; typo corrected in (5) | Phys. Rev. D 108 (2023), 123527 | 10.1103/PhysRevD.108.123527 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We search for a stochastic gravitational wave background (SGWB) generated by
a network of cosmic strings using six millisecond pulsars from Data Release 2
(DR2) of the European Pulsar Timing Array (EPTA). We perform a Bayesian
analysis considering two models for the network of cosmic string loops, and
compare it to a simple power-law model which is expected from the population of
supermassive black hole binaries. Our main strong assumption is that the
previously reported common red noise process is a SGWB. We find that the
one-parameter cosmic string model is slightly favored over a power-law model
thanks to its simplicity. If we assume a two-component stochastic signal in the
data (supermassive black hole binary population and the signal from cosmic
strings), we get a $95\%$ upper limit on the string tension of $\log_{10}(G\mu)
< -9.9$ ($-10.5$) for the two cosmic string models we consider. In extended
two-parameter string models, we were unable to constrain the number of kinks.
We test two approximate and fast Bayesian data analysis methods against the
most rigorous analysis and find consistent results. These two fast and
efficient methods are applicable to all SGWBs, independent of their source, and
will be crucial for analysis of extended data sets.
| [
{
"created": "Wed, 21 Jun 2023 12:53:02 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 2023 17:00:31 GMT",
"version": "v2"
},
{
"created": "Fri, 3 May 2024 09:58:29 GMT",
"version": "v3"
}
] | 2024-05-06 | [
[
"Leclere",
"Hippolyte Quelquejay",
""
],
[
"Auclair",
"Pierre",
""
],
[
"Babak",
"Stanislav",
""
],
[
"Chalumeau",
"Aurélien",
""
],
[
"Steer",
"Danièle A.",
""
],
[
"Antoniadis",
"J.",
""
],
[
"Nielsen",
"A. -... | We search for a stochastic gravitational wave background (SGWB) generated by a network of cosmic strings using six millisecond pulsars from Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA). We perform a Bayesian analysis considering two models for the network of cosmic string loops, and compare it to a simple power-law model which is expected from the population of supermassive black hole binaries. Our main strong assumption is that the previously reported common red noise process is a SGWB. We find that the one-parameter cosmic string model is slightly favored over a power-law model thanks to its simplicity. If we assume a two-component stochastic signal in the data (supermassive black hole binary population and the signal from cosmic strings), we get a $95\%$ upper limit on the string tension of $\log_{10}(G\mu) < -9.9$ ($-10.5$) for the two cosmic string models we consider. In extended two-parameter string models, we were unable to constrain the number of kinks. We test two approximate and fast Bayesian data analysis methods against the most rigorous analysis and find consistent results. These two fast and efficient methods are applicable to all SGWBs, independent of their source, and will be crucial for analysis of extended data sets. |
1309.4756 | Alberto Diez-Tejedor | Alberto Diez-Tejedor | Note on scalars, perfect fluids, constrained field theories, and all
that | 5 pages, 1 figure. Accepted for publication in Phys. Lett. B | Phys. Lett. B 727, 27-30 (2013) | 10.1016/j.physletb.2013.10.030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relation of a scalar field with a perfect fluid has generated some debate
along the last few years. In this paper we argue that shift-invariant scalar
fields can describe accurately the potential flow of an isentropic perfect
fluid, but, in general, the identification is possible only for a finite period
of time. After that period in the evolution the dynamics of the scalar field
and the perfect fluid branch off. The Lagrangian density for the
velocity-potential can be read directly from the expression relating the
pressure with the Taub charge and the entropy per particle in the fluid,
whereas the other quantities of interest can be obtained from the thermodynamic
relations.
| [
{
"created": "Wed, 18 Sep 2013 19:19:24 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Nov 2013 22:24:32 GMT",
"version": "v2"
}
] | 2013-11-22 | [
[
"Diez-Tejedor",
"Alberto",
""
]
] | The relation of a scalar field with a perfect fluid has generated some debate along the last few years. In this paper we argue that shift-invariant scalar fields can describe accurately the potential flow of an isentropic perfect fluid, but, in general, the identification is possible only for a finite period of time. After that period in the evolution the dynamics of the scalar field and the perfect fluid branch off. The Lagrangian density for the velocity-potential can be read directly from the expression relating the pressure with the Taub charge and the entropy per particle in the fluid, whereas the other quantities of interest can be obtained from the thermodynamic relations. |
1009.3225 | Lorenzo Iorio | L. Iorio, H.I.M. Lichtenegger, M.L. Ruggiero, C. Corda | Phenomenology of the Lense-Thirring effect in the Solar System | LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in
Astrophysics and Space Science (ApSS). Some uncited references in the text
now correctly quoted. One reference added. A footnote added | Astrophys. Space Sci. 331:351-395, 2011 | 10.1007/s10509-010-0489-5 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent years have seen increasing efforts to directly measure some aspects of
the general relativistic gravitomagnetic interaction in several astronomical
scenarios in the solar system. After briefly overviewing the concept of
gravitomagnetism from a theoretical point of view, we review the performed or
proposed attempts to detect the Lense-Thirring effect affecting the orbital
motions of natural and artificial bodies in the gravitational fields of the
Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of
the impact of several sources of systematic uncertainties of dynamical origin
to realistically elucidate the present and future perspectives in directly
measuring such an elusive relativistic effect.
| [
{
"created": "Thu, 16 Sep 2010 17:15:17 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2010 16:27:21 GMT",
"version": "v2"
}
] | 2011-01-04 | [
[
"Iorio",
"L.",
""
],
[
"Lichtenegger",
"H. I. M.",
""
],
[
"Ruggiero",
"M. L.",
""
],
[
"Corda",
"C.",
""
]
] | Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect. |
1811.02289 | Saulo Carneiro | J. A. de Freitas Pacheco, S. Carneiro and J. C. Fabris | Gravitational waves from binary axionic black holes | 6 pages, 2 figures. Version to appear in Eur. Phys. J. C | Eur. Phys. J. C (2019) 79: 426 | 10.1140/epjc/s10052-019-6940-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper we have shown that a minimally coupled, self-interacting
scalar field of mass $m$ can form black holes of mass $M=\sqrt{3}/(4m)$ (in
Planck units). If dark matter is composed by axions, they can form miniclusters
that for QCD axions have masses below this value. In this work it is shown that
for a scenario in which the axion mass depends on the temperature as $m \propto
T^{-6}$, minicluster masses above $0.32\,M_\odot$, corresponding to an axion
mass of $3\times 10^{-10}$ eV, exceed $M$ and can collapse into black holes. If
a fraction of these black holes is in binary systems, gravitational waves
emitted during the inspiral phase could be detected by advanced interferometers
like LIGO or VIRGO and by the planned Einstein Telescope. For a detection rate
of one event per year, the lower limits on the binary fraction are $10^{-4}$
and $10^{-6}$ for LIGO and Einstein Telescope respectively.
| [
{
"created": "Tue, 6 Nov 2018 11:18:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 May 2019 18:15:51 GMT",
"version": "v2"
}
] | 2019-05-23 | [
[
"Pacheco",
"J. A. de Freitas",
""
],
[
"Carneiro",
"S.",
""
],
[
"Fabris",
"J. C.",
""
]
] | In a recent paper we have shown that a minimally coupled, self-interacting scalar field of mass $m$ can form black holes of mass $M=\sqrt{3}/(4m)$ (in Planck units). If dark matter is composed by axions, they can form miniclusters that for QCD axions have masses below this value. In this work it is shown that for a scenario in which the axion mass depends on the temperature as $m \propto T^{-6}$, minicluster masses above $0.32\,M_\odot$, corresponding to an axion mass of $3\times 10^{-10}$ eV, exceed $M$ and can collapse into black holes. If a fraction of these black holes is in binary systems, gravitational waves emitted during the inspiral phase could be detected by advanced interferometers like LIGO or VIRGO and by the planned Einstein Telescope. For a detection rate of one event per year, the lower limits on the binary fraction are $10^{-4}$ and $10^{-6}$ for LIGO and Einstein Telescope respectively. |
2001.07081 | Serhii E. Samokhvalov | S. E. Samokhvalov | About the symmetry of general relativity | 29 pages, references added, typos corrected, version accepted in JGSP | J. Geom. Symmetry Phys. 55 (2020), 75--103 | 10.7546/jgsp-55-2020-75-103 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we use generalized deformed gauge groups for investigation of
symmetry of general relativity (GR). GR is formulated in generalized reference
frames, which are represented by (anholonomic in general case) affine frame
fields. The general principle of relativity is extended to the requirement of
invariance of the theory with respect to transitions between generalized
reference frames, that is, with respect to the group $GL^g$ of local linear
transformations of affine frame fields. GR is interpreted as the gauge theory
of the gauge group of translations $T^g_M$, and therefore is invariant under
the space-time diffeomorphisms. The groups $GL^g$ and $T^g_M$ are united into
group $S^g_M$, which is their semidirect product and is the complete symmetry
group of the general relativity in an affine frame (GRAF).
The consequence of $GL^g$-invariance of GRAF is the Palatini equation, which
in the absence of torsion goes into the metricity condition, and vice versa,
that is, is fulfilled identically in the Riemannian space. The consequence of
the $T^g_M$-invariance of GRAF is representation of the Einstein equation in
the superpotential form, that is, in the form of dynamic Maxwell equations (or
Young-Mills equations). Deformation of the group $S^g_M$ leads to
renormalisation of energy-momentum of the gravitation field. At the end we show
that by limiting admissible reference frames (by $GL^g$-gauge fixing) from
GRAF, in addition to Einstein gravity, one can obtain other local equivalent
formulations of GR: general relativity in an orthonormal frame or teleparallel
equivalent of general relativity, dilaton gravity, unimodular gravity, etc.
| [
{
"created": "Mon, 20 Jan 2020 12:36:38 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 2020 03:17:55 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Apr 2020 08:44:11 GMT",
"version": "v3"
}
] | 2020-06-09 | [
[
"Samokhvalov",
"S. E.",
""
]
] | In this work we use generalized deformed gauge groups for investigation of symmetry of general relativity (GR). GR is formulated in generalized reference frames, which are represented by (anholonomic in general case) affine frame fields. The general principle of relativity is extended to the requirement of invariance of the theory with respect to transitions between generalized reference frames, that is, with respect to the group $GL^g$ of local linear transformations of affine frame fields. GR is interpreted as the gauge theory of the gauge group of translations $T^g_M$, and therefore is invariant under the space-time diffeomorphisms. The groups $GL^g$ and $T^g_M$ are united into group $S^g_M$, which is their semidirect product and is the complete symmetry group of the general relativity in an affine frame (GRAF). The consequence of $GL^g$-invariance of GRAF is the Palatini equation, which in the absence of torsion goes into the metricity condition, and vice versa, that is, is fulfilled identically in the Riemannian space. The consequence of the $T^g_M$-invariance of GRAF is representation of the Einstein equation in the superpotential form, that is, in the form of dynamic Maxwell equations (or Young-Mills equations). Deformation of the group $S^g_M$ leads to renormalisation of energy-momentum of the gravitation field. At the end we show that by limiting admissible reference frames (by $GL^g$-gauge fixing) from GRAF, in addition to Einstein gravity, one can obtain other local equivalent formulations of GR: general relativity in an orthonormal frame or teleparallel equivalent of general relativity, dilaton gravity, unimodular gravity, etc. |
gr-qc/9910062 | Murat Ozer | Murat \"Ozer | On the Equivalence Principle and a Unified Description of Gravitation
and Electromagnetism | A new argument that produces the $g_{00}$ of the metric outside a
charged sphere is presented. Existing experimental evidences for the
electromagnetic equivalence principle introduced are pointed out. A new
footnote has been added | null | null | null | gr-qc astro-ph hep-ph math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We first investigate the form the General Relativity Theory would have taken
had the gravitational mass and the inertial mass of material objects been
different. We then extend this analysis to electromagnetism and postulate an
equivalence principle for the electromagnetic field. We argue that to each
particle with a different electric charge-to-mass ratio in superimposed
gravitational and electromagnetic fields there corresponds a spacetime manifold
whose metric tensor $g_{\mu\nu}$ describes the dynamical actions of gravitation
and electromagnetism. The electric field outside a charged sphere asserts
itself independently rather than contributing to the gravitational field. The
contribution of the electric field to the spacetime metric outside the charged
sphere is shown to be similar to the gravitational one in the Schwartzschild
metric but with a charge-to-mass ratio dependence of the test particle instead
of the Reissner - Nordstr\"om metric, resulting in a unified description of
gravitation and electromagnetism. We point out that there are existing
experiments whose results can be explained by the equivalence principle for the
electromagnetic field presented here. Additional experimental predictions of
the theory are mentioned.
| [
{
"created": "Tue, 19 Oct 1999 12:26:32 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Oct 1999 15:44:53 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Feb 2000 17:17:13 GMT",
"version": "v3"
},
{
"created": "Mon, 18 Dec 2017 11:09:09 GMT",
"version": "v4"
},
{
"c... | 2020-01-09 | [
[
"Özer",
"Murat",
""
]
] | We first investigate the form the General Relativity Theory would have taken had the gravitational mass and the inertial mass of material objects been different. We then extend this analysis to electromagnetism and postulate an equivalence principle for the electromagnetic field. We argue that to each particle with a different electric charge-to-mass ratio in superimposed gravitational and electromagnetic fields there corresponds a spacetime manifold whose metric tensor $g_{\mu\nu}$ describes the dynamical actions of gravitation and electromagnetism. The electric field outside a charged sphere asserts itself independently rather than contributing to the gravitational field. The contribution of the electric field to the spacetime metric outside the charged sphere is shown to be similar to the gravitational one in the Schwartzschild metric but with a charge-to-mass ratio dependence of the test particle instead of the Reissner - Nordstr\"om metric, resulting in a unified description of gravitation and electromagnetism. We point out that there are existing experiments whose results can be explained by the equivalence principle for the electromagnetic field presented here. Additional experimental predictions of the theory are mentioned. |
gr-qc/0510030 | Peter D'Eath | A.N.St.J.Farley and P.D.D'Eath | Spin-1 Amplitudes in Black-Hole Evaporation | null | null | 10.1088/0264-9381/22/14/010 | null | gr-qc | null | Our earlier work on the quantum amplitude for a scalar field in black-hole
evaporation, following gravitational collapse, is here extended to Maxwell
theory. Boundary data are specified on initial and final space-like
hypersurfaces $\Sigma_{I,F}$, separated by a large Lorentzian proper-time
interval $T$, as measured at spatial infinity. The initial boundary data may be
chosen (say) to be spherically symmetric, corresponding to a nearly-spherical
configuration prior to gravitational collapse. The final data include the
intrinsic 3-metric and scalar field, restricted to $\Sigma_F$, in addition to
spin-1 data, naturally taken to be the magnetic field $B_i$ on $\Sigma_{I,F}
(i=1,2,3)$. For a locally-supersymmetric theory, the quantum amplitude should
be proportional to $\exp(iS_{\rm class})$, apart from corrections which are
very small when the frequencies in the boundary data are small compared to the
Planck scale. Here, $S_{\rm class}$ is the action of the classical solution.
The Lorentzian amplitude is found by taking the limit $\theta\to 0_+$. By a
method similar to that used in the spin-0 case, one obtains the quantum
amplitude for photon data on $\Sigma_F$. The magnetic boundary conditions are
related by supersymmetry to the natural spin-2 (gravitational-wave) boundary
conditions, which involve fixing the magnetic part of the Weyl tensor.
| [
{
"created": "Fri, 7 Oct 2005 17:28:40 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Farley",
"A. N. St. J.",
""
],
[
"D'Eath",
"P. D.",
""
]
] | Our earlier work on the quantum amplitude for a scalar field in black-hole evaporation, following gravitational collapse, is here extended to Maxwell theory. Boundary data are specified on initial and final space-like hypersurfaces $\Sigma_{I,F}$, separated by a large Lorentzian proper-time interval $T$, as measured at spatial infinity. The initial boundary data may be chosen (say) to be spherically symmetric, corresponding to a nearly-spherical configuration prior to gravitational collapse. The final data include the intrinsic 3-metric and scalar field, restricted to $\Sigma_F$, in addition to spin-1 data, naturally taken to be the magnetic field $B_i$ on $\Sigma_{I,F} (i=1,2,3)$. For a locally-supersymmetric theory, the quantum amplitude should be proportional to $\exp(iS_{\rm class})$, apart from corrections which are very small when the frequencies in the boundary data are small compared to the Planck scale. Here, $S_{\rm class}$ is the action of the classical solution. The Lorentzian amplitude is found by taking the limit $\theta\to 0_+$. By a method similar to that used in the spin-0 case, one obtains the quantum amplitude for photon data on $\Sigma_F$. The magnetic boundary conditions are related by supersymmetry to the natural spin-2 (gravitational-wave) boundary conditions, which involve fixing the magnetic part of the Weyl tensor. |
1605.05066 | Lavinia Heisenberg | Antonio De Felice, Lavinia Heisenberg, Ryotaro Kase, Shinji Mukohyama,
Shinji Tsujikawa and Ying-li Zhang | Effective gravitational couplings for cosmological perturbations in
generalized Proca theories | 23 pages, 3 figures | Phys. Rev. D 94, 044024 (2016) | 10.1103/PhysRevD.94.044024 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the finite interactions of the generalized Proca theory including
the sixth-order Lagrangian and derive the full linear perturbation equations of
motion on the flat Friedmann-Lema\^{i}tre-Robertson-Walker background in the
presence of a matter perfect fluid. By construction, the propagating degrees of
freedom (besides the matter perfect fluid) are two transverse vector
perturbations, one longitudinal scalar, and two tensor polarizations. The
Lagrangians associated with intrinsic vector modes neither affect the
background equations of motion nor the second-order action of tensor
perturbations, but they do give rise to non-trivial modifications to the
no-ghost condition of vector perturbations and to the propagation speeds of
vector and scalar perturbations. We derive the effective gravitational coupling
$G_{\rm eff}$ with matter density perturbations under a quasi-static
approximation on scales deep inside the sound horizon. We find that the
existence of intrinsic vector modes allows a possibility for reducing $G_{\rm
eff}$. In fact, within the parameter space, $G_{\rm eff}$ can be even smaller
than the Newton gravitational constant $G$ at the late cosmological epoch, with
a peculiar phantom dark energy equation of state (without ghosts). The
modifications to the slip parameter $\eta$ and the evolution of growth rate
$f\sigma_8$ are discussed as well. Thus, dark energy models in the framework of
generalized Proca theories can be observationally distinguished from the
$\Lambda$CDM model according to both cosmic growth and expansion history.
Furthermore, we study the evolution of vector perturbations and show that
outside the vector sound horizon the perturbations are nearly frozen and start
to decay with oscillations after the horizon entry.
| [
{
"created": "Tue, 17 May 2016 09:07:52 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Aug 2016 06:44:57 GMT",
"version": "v2"
}
] | 2016-08-17 | [
[
"De Felice",
"Antonio",
""
],
[
"Heisenberg",
"Lavinia",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Tsujikawa",
"Shinji",
""
],
[
"Zhang",
"Ying-li",
""
]
] | We consider the finite interactions of the generalized Proca theory including the sixth-order Lagrangian and derive the full linear perturbation equations of motion on the flat Friedmann-Lema\^{i}tre-Robertson-Walker background in the presence of a matter perfect fluid. By construction, the propagating degrees of freedom (besides the matter perfect fluid) are two transverse vector perturbations, one longitudinal scalar, and two tensor polarizations. The Lagrangians associated with intrinsic vector modes neither affect the background equations of motion nor the second-order action of tensor perturbations, but they do give rise to non-trivial modifications to the no-ghost condition of vector perturbations and to the propagation speeds of vector and scalar perturbations. We derive the effective gravitational coupling $G_{\rm eff}$ with matter density perturbations under a quasi-static approximation on scales deep inside the sound horizon. We find that the existence of intrinsic vector modes allows a possibility for reducing $G_{\rm eff}$. In fact, within the parameter space, $G_{\rm eff}$ can be even smaller than the Newton gravitational constant $G$ at the late cosmological epoch, with a peculiar phantom dark energy equation of state (without ghosts). The modifications to the slip parameter $\eta$ and the evolution of growth rate $f\sigma_8$ are discussed as well. Thus, dark energy models in the framework of generalized Proca theories can be observationally distinguished from the $\Lambda$CDM model according to both cosmic growth and expansion history. Furthermore, we study the evolution of vector perturbations and show that outside the vector sound horizon the perturbations are nearly frozen and start to decay with oscillations after the horizon entry. |
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