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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0904.0414 | Jeffrey Winicour | Jeffrey Winicour | Geometrization of metric boundary data for Einstein's equations | Article to appear in Gen. Rel. Grav. volume in memory of Juergen
Ehlers | Gen.Rel.Grav.41:1909-1926,2009 | 10.1007/s10714-009-0801-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The principle part of Einstein equations in the harmonic gauge consists of a
constrained system of 10 curved space wave equations for the components of the
space-time metric. A well-posed initial boundary value problem based upon a new
formulation of constraint-preserving boundary conditions of the Sommerfeld type
has recently been established for such systems. In this paper these boundary
conditions are recast in a geometric form. This serves as a first step toward
their application to other metric formulations of Einstein's equations.
| [
{
"created": "Thu, 2 Apr 2009 16:13:35 GMT",
"version": "v1"
}
] | 2009-09-28 | [
[
"Winicour",
"Jeffrey",
""
]
] | The principle part of Einstein equations in the harmonic gauge consists of a constrained system of 10 curved space wave equations for the components of the space-time metric. A well-posed initial boundary value problem based upon a new formulation of constraint-preserving boundary conditions of the Sommerfeld type has recently been established for such systems. In this paper these boundary conditions are recast in a geometric form. This serves as a first step toward their application to other metric formulations of Einstein's equations. |
2105.03433 | Justin Feng | Justin C. Feng, Jos\'e P. S. Lemos, Richard A. Matzner | Self-collision of a portal wormhole | 12 pages, 8 figures | Physical Review D 103, 124037 (2021) | 10.1103/PhysRevD.103.124037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the self-collision of portals in classical general relativity.
Portals are wormholes supported by a single loop of negative mass cosmic
string, and being wormholes, portals have a nontrivial topology. Portals can be
constructed so that the curvature is zero everywhere outside the cosmic string,
with vanishing ADM mass. The conical singularities of these wormholes can be
smoothed, yielding a spatial topology of $S^2 \times S^1$ with a point
corresponding to spatial infinity removed. If one attempts to collide the
mouths of a smoothed portal to induce self-annihilation, one naively might
think that a Euclidean topology is recovered, which would violate the classical
no topology change theorems. We consider a particular limit of smoothed portals
supported by an anisotropic fluid, and find that while the portal mouths do not
experience an acceleration as they are brought close together, a curvature
singularity forms in the limit that the separation distance vanishes. We find
that in general relativity, the interaction between portal mouths is not
primarily gravitational in nature, but depends critically on matter
interactions.
| [
{
"created": "Fri, 7 May 2021 18:00:00 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jun 2021 16:04:07 GMT",
"version": "v2"
}
] | 2021-06-15 | [
[
"Feng",
"Justin C.",
""
],
[
"Lemos",
"José P. S.",
""
],
[
"Matzner",
"Richard A.",
""
]
] | We consider the self-collision of portals in classical general relativity. Portals are wormholes supported by a single loop of negative mass cosmic string, and being wormholes, portals have a nontrivial topology. Portals can be constructed so that the curvature is zero everywhere outside the cosmic string, with vanishing ADM mass. The conical singularities of these wormholes can be smoothed, yielding a spatial topology of $S^2 \times S^1$ with a point corresponding to spatial infinity removed. If one attempts to collide the mouths of a smoothed portal to induce self-annihilation, one naively might think that a Euclidean topology is recovered, which would violate the classical no topology change theorems. We consider a particular limit of smoothed portals supported by an anisotropic fluid, and find that while the portal mouths do not experience an acceleration as they are brought close together, a curvature singularity forms in the limit that the separation distance vanishes. We find that in general relativity, the interaction between portal mouths is not primarily gravitational in nature, but depends critically on matter interactions. |
2402.07620 | Christian Boehmer | Sudan Hansraj, Chevarra Hansraj, Njabulo Mkhize, Abdelghani Errehymy,
Christian G. Boehmer | Generating exact polytropes in non-conservative unimodular geometries | 14 pages, 2 figures | Physics of the Dark Universe 44 (2024) 101443 | 10.1016/j.dark.2024.101443 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The trace-free Einstein equations contain one equation less than the complete
field equations. In a static and spherically symmetric spacetime, the number of
field equations is thus reduced to two. The equation of pressure isotropy of
general relativity, however, is preserved thus showing that any known perfect
fluid spacetime is a suitable candidate for the trace-free scenario. The extra
freedom in imposing two constraints may now be exploited to include polytopes,
something that is difficult in general relativity. The point here is that using
any known exact solution one can find a polytropic star for various values of
the polytropic index. One arrives at Tolman-Oppenheimer-Volkoff type equations
and can study their solutions explicitly. Two examples of well-known stellar
distributions that generate polytropes with physically reasonable behaviour are
discussed. These models are regular, exhibit a sound speed that is never
superluminal and are adiabatically stable in the sense of Chandrasekhar. We
investigate a compactness measure confirming that our results are consistent
with some observational data.
| [
{
"created": "Mon, 12 Feb 2024 12:54:10 GMT",
"version": "v1"
}
] | 2024-03-27 | [
[
"Hansraj",
"Sudan",
""
],
[
"Hansraj",
"Chevarra",
""
],
[
"Mkhize",
"Njabulo",
""
],
[
"Errehymy",
"Abdelghani",
""
],
[
"Boehmer",
"Christian G.",
""
]
] | The trace-free Einstein equations contain one equation less than the complete field equations. In a static and spherically symmetric spacetime, the number of field equations is thus reduced to two. The equation of pressure isotropy of general relativity, however, is preserved thus showing that any known perfect fluid spacetime is a suitable candidate for the trace-free scenario. The extra freedom in imposing two constraints may now be exploited to include polytopes, something that is difficult in general relativity. The point here is that using any known exact solution one can find a polytropic star for various values of the polytropic index. One arrives at Tolman-Oppenheimer-Volkoff type equations and can study their solutions explicitly. Two examples of well-known stellar distributions that generate polytropes with physically reasonable behaviour are discussed. These models are regular, exhibit a sound speed that is never superluminal and are adiabatically stable in the sense of Chandrasekhar. We investigate a compactness measure confirming that our results are consistent with some observational data. |
0912.4816 | Pradip Mukherjee | Pradip Mukherjee | Poincare gauge theory from higher derivative matter lagrangean | Some modifications of text,typos corrected, 8 pages, latex This
version to be published in Classical and Quantum Gravity | Class.Quant.Grav.27:215008,2010 | 10.1088/0264-9381/27/21/215008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from matter lagrangean containing higher order derivative than the
first, we construct the Poincare gauge theory by localising the Poincare
symmetry of the matter theory. The construction is shown to follow the usual
geometric procedure of gravitational coupling, thereby buttressing the
geometric interpretation of the Poincare gauge theory.
| [
{
"created": "Thu, 24 Dec 2009 09:21:21 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jun 2010 18:38:37 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Aug 2010 15:44:47 GMT",
"version": "v3"
}
] | 2010-11-04 | [
[
"Mukherjee",
"Pradip",
""
]
] | Starting from matter lagrangean containing higher order derivative than the first, we construct the Poincare gauge theory by localising the Poincare symmetry of the matter theory. The construction is shown to follow the usual geometric procedure of gravitational coupling, thereby buttressing the geometric interpretation of the Poincare gauge theory. |
2207.08270 | Sandro D. P. Vitenti | Mariana Penna-Lima, Nelson Pinto-Neto, Sandro D. P. Vitenti | New formalism to define vacuum states for scalar fields in curved
space-times | 31 pages, 6 figures | null | 10.1103/PhysRevD.107.065019 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of finding a vacuum definition for a single quantum field in
curved space-times is discussed under a new geometrical perspective. The phase
space dynamics of the quantum field modes are mapped to curves in a
2-dimensional hyperbolic metric space, in which distances between neighbor
points are shown to be proportional to the Bogoliubov coefficients associated
with their corresponding mode solutions in phase space. The vacuum state for
each mode is then defined as the unique trajectory from which all mapped phase
space solutions move within thin annular regions around it. This property
implies the stability of the vacuum state: solutions evolved from a point in
this trajectory stay close to it as both evolve, and the particle creation is
therefore minimized. The new approach is applied to the well-known cases of the
time-independent dynamics, where the solutions draw circles around this curve,
and when the adiabatic approximation is valid. The analysis is then extended to
time-dependent cases in which the adiabatic approximation is not applicable, in
the super-Hubble or low-frequency regimes. It is shown that stability
trajectories can also be found in these situations, and stable quantum vacua
can be obtained. This new formalism is applied to two situations: de Sitter
space, where the Bunch-Davies vacuum is obtained in a completely different
manner through an analysis in the super-Hubble regime, and in the context of
cosmological bouncing models, in which the contracting phase is dominated by a
cosmological constant in the asymptotic past. A new vacuum state for
cosmological perturbations is proposed in this situation.
| [
{
"created": "Sun, 17 Jul 2022 19:43:32 GMT",
"version": "v1"
}
] | 2023-04-12 | [
[
"Penna-Lima",
"Mariana",
""
],
[
"Pinto-Neto",
"Nelson",
""
],
[
"Vitenti",
"Sandro D. P.",
""
]
] | The problem of finding a vacuum definition for a single quantum field in curved space-times is discussed under a new geometrical perspective. The phase space dynamics of the quantum field modes are mapped to curves in a 2-dimensional hyperbolic metric space, in which distances between neighbor points are shown to be proportional to the Bogoliubov coefficients associated with their corresponding mode solutions in phase space. The vacuum state for each mode is then defined as the unique trajectory from which all mapped phase space solutions move within thin annular regions around it. This property implies the stability of the vacuum state: solutions evolved from a point in this trajectory stay close to it as both evolve, and the particle creation is therefore minimized. The new approach is applied to the well-known cases of the time-independent dynamics, where the solutions draw circles around this curve, and when the adiabatic approximation is valid. The analysis is then extended to time-dependent cases in which the adiabatic approximation is not applicable, in the super-Hubble or low-frequency regimes. It is shown that stability trajectories can also be found in these situations, and stable quantum vacua can be obtained. This new formalism is applied to two situations: de Sitter space, where the Bunch-Davies vacuum is obtained in a completely different manner through an analysis in the super-Hubble regime, and in the context of cosmological bouncing models, in which the contracting phase is dominated by a cosmological constant in the asymptotic past. A new vacuum state for cosmological perturbations is proposed in this situation. |
2402.17388 | Guillem Dom\`enech | Guillem Dom\`enech | GW Backgrounds associated with PBHs | To appear [with updates] in the book "Primordial Black Holes", ed.
Chris Byrnes, Gabriele Franciolini, Tomohiro Harada, Paolo Pani, Misao
Sasaki; Springer (2024). I tried to show the generation of induced GWs with
new illustrations, two of them in real space. So, any comments are welcome,
especially about the illustrations | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | PBH formation requires high-density regions in the (random) density field
filling the primordial universe. While only the largest (and so rarest)
overdensities collapse to form PBHs, the rest cause large anisotropic stresses,
which are the source of GWs. We provide an overview of the theoretical aspects
of the GW backgrounds associated with PBHs from large primordial fluctuations.
We consider GW backgrounds associated with PBH formation, PBH reheating and
unresolved PBH binaries. We present several graphical summaries and
illustrations for the busy reader.
| [
{
"created": "Tue, 27 Feb 2024 10:29:35 GMT",
"version": "v1"
}
] | 2024-02-28 | [
[
"Domènech",
"Guillem",
""
]
] | PBH formation requires high-density regions in the (random) density field filling the primordial universe. While only the largest (and so rarest) overdensities collapse to form PBHs, the rest cause large anisotropic stresses, which are the source of GWs. We provide an overview of the theoretical aspects of the GW backgrounds associated with PBHs from large primordial fluctuations. We consider GW backgrounds associated with PBH formation, PBH reheating and unresolved PBH binaries. We present several graphical summaries and illustrations for the busy reader. |
1706.01328 | Yoshimasa Kurihara | Yoshimasa Kurihara | Characteristic classes in general relativity on a modified Poincare
curvature bundle | 12 pages, no figure | Journal of Mathematical Physics 58 , 092502 (2017) | 10.1063/1.4990708 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Characteristic classes in space-time manifolds are discussed for both even-
and odd-dimensional spacetimes. In particular, it is shown that the
Einstein--Hilbert action is equivalent to a second Chern-class on a modified
Poincare bundle in four dimensions. Consequently, the cosmological constant and
the trace of an energy-momentum tensor become divisible modulo R/Z.
| [
{
"created": "Thu, 1 Jun 2017 00:15:58 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jun 2017 06:45:58 GMT",
"version": "v2"
}
] | 2018-07-06 | [
[
"Kurihara",
"Yoshimasa",
""
]
] | Characteristic classes in space-time manifolds are discussed for both even- and odd-dimensional spacetimes. In particular, it is shown that the Einstein--Hilbert action is equivalent to a second Chern-class on a modified Poincare bundle in four dimensions. Consequently, the cosmological constant and the trace of an energy-momentum tensor become divisible modulo R/Z. |
1207.2510 | Jose Wadih Maluf Dr. | J. W. Maluf, S. C. Ulhoa and J. F. da Rocha-Neto | Gravitational waves and the breaking of parallelograms in space-time | 19 pages, 2 figures. The article has been substantially enlarged. We
established a connection between our results and the Fermilab Holometer
experiment. Published by the General Relativity and Gravitation | null | 10.1007/s10714-013-1517-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that plane-fronted gravitational waves induce the breaking of
parallelograms in space-time, in the context of the teleparallel equivalent of
general relativity (TEGR). The breaking of parallelograms can be shown by
considering a thought experiment that consists of a simple physical
configuration, similar to the experimental setup that is expected to lead to
the measurement of gravitational waves with the use of laser interferometers.
An incident beam of light splits into two beams running along perpendicular
arms, endowed with fixed mirrors at the extremes. The reflected light beams are
detected at the same point of the splitting. Along each arm, the two light
beams define two null vectors: the forward vector and the reflected vector. We
show that the sum of these four vectors, the forward and reflected null vectors
along the two arms, do form a parallelogram in flat space-time, but not in the
presence of plane-fronted gravitational waves. The non-closure of the
parallelogram is a manifestation of the torsion of the space-time, and in this
context indicates the existence of gravitational waves.
| [
{
"created": "Tue, 10 Jul 2012 23:16:43 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2013 12:09:59 GMT",
"version": "v2"
}
] | 2013-03-28 | [
[
"Maluf",
"J. W.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
]
] | We show that plane-fronted gravitational waves induce the breaking of parallelograms in space-time, in the context of the teleparallel equivalent of general relativity (TEGR). The breaking of parallelograms can be shown by considering a thought experiment that consists of a simple physical configuration, similar to the experimental setup that is expected to lead to the measurement of gravitational waves with the use of laser interferometers. An incident beam of light splits into two beams running along perpendicular arms, endowed with fixed mirrors at the extremes. The reflected light beams are detected at the same point of the splitting. Along each arm, the two light beams define two null vectors: the forward vector and the reflected vector. We show that the sum of these four vectors, the forward and reflected null vectors along the two arms, do form a parallelogram in flat space-time, but not in the presence of plane-fronted gravitational waves. The non-closure of the parallelogram is a manifestation of the torsion of the space-time, and in this context indicates the existence of gravitational waves. |
gr-qc/0608034 | Pavel Krtous | Pavel Krtous | Electromagnetic field near cosmic string | 12 pages, 8 figures (low-resolution figures; for the version with
high-resolution figures see http://utf.mff.cuni.cz/~krtous/papers/), v2: two
references added, typos corrected | Phys.Rev. D74 (2006) 065006 | 10.1103/PhysRevD.74.065006 | null | gr-qc astro-ph hep-th | null | The retarded Green function of the electromagnetic field in spacetime of a
straight thin cosmic string is found. It splits into a geodesic part
(corresponding to the propagation along null rays) and to the field scattered
on the string. With help of the Green function the electric and magnetic fields
of simple sources are constructed. It is shown that these sources are
influenced by the cosmic string through a self-interaction with their field.
The distant field of static sources is studied and it is found that it has a
different multipole structure than in Minkowski spacetime. On the other hand,
the string suppresses the electric and magnetic field of distant sources--the
field is expelled from regions near the string.
| [
{
"created": "Mon, 7 Aug 2006 13:33:53 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Sep 2006 08:17:03 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Krtous",
"Pavel",
""
]
] | The retarded Green function of the electromagnetic field in spacetime of a straight thin cosmic string is found. It splits into a geodesic part (corresponding to the propagation along null rays) and to the field scattered on the string. With help of the Green function the electric and magnetic fields of simple sources are constructed. It is shown that these sources are influenced by the cosmic string through a self-interaction with their field. The distant field of static sources is studied and it is found that it has a different multipole structure than in Minkowski spacetime. On the other hand, the string suppresses the electric and magnetic field of distant sources--the field is expelled from regions near the string. |
1508.05853 | Eduardo Bittencourt | Mario Novello and Eduardo Bittencourt | Metric Relativity and the Dynamical Bridge: highlights of Riemannian
geometry in physics | 121 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an overview of recent developments concerning modifications of the
geometry of space-time to describe various physical processes of interactions
among classical and quantum configurations. We concentrate in two main lines of
research: the Metric Relativity and the Dynamical Bridge.
| [
{
"created": "Fri, 21 Aug 2015 10:25:27 GMT",
"version": "v1"
}
] | 2015-08-25 | [
[
"Novello",
"Mario",
""
],
[
"Bittencourt",
"Eduardo",
""
]
] | We present an overview of recent developments concerning modifications of the geometry of space-time to describe various physical processes of interactions among classical and quantum configurations. We concentrate in two main lines of research: the Metric Relativity and the Dynamical Bridge. |
1711.01111 | Miguel Sabido | J. L. Lopez, M. Sabido and C. Yee-Romero | Phase space deformations in phantom cosmology | 6 pages, 2 figures. v2: version to appear in Phys. Dark Univ | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the physical consequences of making general phase space
deformations on the minisuperspace of phantom cosmology. Based on the principle
of physically equivalent descriptions in the deformed theory, we investigate
for what values of the deformation parameters the arising descriptions are
physically equivalent. We also construct and solve the quantum model and derive
the semiclassical dynamics.
| [
{
"created": "Fri, 3 Nov 2017 11:38:45 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2018 10:50:02 GMT",
"version": "v2"
}
] | 2018-01-11 | [
[
"Lopez",
"J. L.",
""
],
[
"Sabido",
"M.",
""
],
[
"Yee-Romero",
"C.",
""
]
] | We discuss the physical consequences of making general phase space deformations on the minisuperspace of phantom cosmology. Based on the principle of physically equivalent descriptions in the deformed theory, we investigate for what values of the deformation parameters the arising descriptions are physically equivalent. We also construct and solve the quantum model and derive the semiclassical dynamics. |
2005.00602 | Paul Ramond | Paul Ramond, Alexandre Le Tiec | Multipolar Particles in Helically Symmetric Spacetimes | 37 pages, 2 figures | Class. Quantum Grav. 38, 135022 (2021) | 10.1088/1361-6382/abebef | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a binary system of spinning compact objects with internal
structure, moving along an exactly circular orbit, and modelled within the
multipolar gravitational skeleton formalism, up to quadrupolar order. We prove
that the worldline of each multipolar particle is an integral curve of the
helical Killing vector field, and that the 4-velocity, 4-momentum, spin tensor
and quadrupole tensor of each particle are Lie-dragged along those worldlines.
The geometrical framework developed in this paper paves the way to an extension
of the first law of compact-object binary mechanics up to quadrupolar order.
| [
{
"created": "Fri, 1 May 2020 20:50:24 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Mar 2021 15:25:48 GMT",
"version": "v2"
}
] | 2022-04-27 | [
[
"Ramond",
"Paul",
""
],
[
"Tiec",
"Alexandre Le",
""
]
] | We consider a binary system of spinning compact objects with internal structure, moving along an exactly circular orbit, and modelled within the multipolar gravitational skeleton formalism, up to quadrupolar order. We prove that the worldline of each multipolar particle is an integral curve of the helical Killing vector field, and that the 4-velocity, 4-momentum, spin tensor and quadrupole tensor of each particle are Lie-dragged along those worldlines. The geometrical framework developed in this paper paves the way to an extension of the first law of compact-object binary mechanics up to quadrupolar order. |
gr-qc/0407067 | Andrei Galiautdinov | Andrei Galiautdinov | Modified Einstein equations | 3 pages, no figures; some changes; typos corrected | null | null | null | gr-qc | null | Standard general relativity fails to take into account the changes in
coordinates induced by the variation of metric in the Hilbert action principle.
We propose to include such changes by introducing a fundamental compensating
tensor field and modifying the usual variational procedure.
| [
{
"created": "Mon, 19 Jul 2004 17:16:11 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jul 2004 20:30:42 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Jul 2004 16:27:01 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Galiautdinov",
"Andrei",
""
]
] | Standard general relativity fails to take into account the changes in coordinates induced by the variation of metric in the Hilbert action principle. We propose to include such changes by introducing a fundamental compensating tensor field and modifying the usual variational procedure. |
gr-qc/0407023 | Jean-Paul Mbelek | J.P. Mbelek | General relativity and quintessence explain the Pioneer anomaly | 14 pages, no figure | null | null | null | gr-qc astro-ph physics.space-ph | null | The anomalous time depending blueshift, the so-called "Pioneer anomaly", that
was detected in the radio-metric data from Pioneer 10/11, Ulysses and Galileo
spacecraft may not result from a real change of velocity. Rather, the Pioneer
anomaly may be understood within the framework of general relativity as a time
depending gravitational frequency shift accounting for the time dependence of
the density of the dark energy when the latter is identified with quintessence.
Thus, instead of being in conflict with Einstein equivalence principle, the
main Pioneer anomaly appears merely as a new validation of general relativity
in the weak field and low velocity limit.
| [
{
"created": "Tue, 6 Jul 2004 17:16:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mbelek",
"J. P.",
""
]
] | The anomalous time depending blueshift, the so-called "Pioneer anomaly", that was detected in the radio-metric data from Pioneer 10/11, Ulysses and Galileo spacecraft may not result from a real change of velocity. Rather, the Pioneer anomaly may be understood within the framework of general relativity as a time depending gravitational frequency shift accounting for the time dependence of the density of the dark energy when the latter is identified with quintessence. Thus, instead of being in conflict with Einstein equivalence principle, the main Pioneer anomaly appears merely as a new validation of general relativity in the weak field and low velocity limit. |
1010.1383 | Tomas Ortin | Tomas Ortin | Supersymmetric solutions of 4-dimensional supergravities | Latex2e, 14 pages. Contribution to the Proceedings of the IV Mexican
Meeting in Mathematical and Experimental Physics held at El Colegio Nacional,
M\'exico DF. July 19th to 23rd, 2010 | null | 10.1063/1.3531629 | IFT-UAM/CSIC-10-52 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review some general and recent results on the characterization and
construction of timelike supersymmetric solutions of 4-dimensional supergravity
theories.
| [
{
"created": "Thu, 7 Oct 2010 10:03:43 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Ortin",
"Tomas",
""
]
] | We review some general and recent results on the characterization and construction of timelike supersymmetric solutions of 4-dimensional supergravity theories. |
1507.04703 | Ivan Agullo | Ivan Agullo | Loop quantum cosmology, non-Gaussianity, and CMB power asymmetry | 7 pages, 3 figure | Phys. Rev. D 92, 064038 (2015) | 10.1103/PhysRevD.92.064038 | LSU-REL-071615 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that the anomalous power asymmetry observed in the cosmic microwave
background (CMB) may have originated in a cosmic bounce preceding inflation. In
loop quantum cosmology (LQC) the big bang singularity is generically replaced
by a bounce due to quantum gravitational effects. We compute the spectrum of
inflationary non-Gaussianity and show that strong correlation between
observable scales and modes with longer (super-horizon) wavelength arise as a
consequence of the evolution of perturbations across the LQC bounce. These
correlations are strongly scale dependent and induce a dipole-dominated
modulation on large angular scales in the CMB, in agreement with observations.
| [
{
"created": "Thu, 16 Jul 2015 18:59:14 GMT",
"version": "v1"
}
] | 2015-09-30 | [
[
"Agullo",
"Ivan",
""
]
] | We argue that the anomalous power asymmetry observed in the cosmic microwave background (CMB) may have originated in a cosmic bounce preceding inflation. In loop quantum cosmology (LQC) the big bang singularity is generically replaced by a bounce due to quantum gravitational effects. We compute the spectrum of inflationary non-Gaussianity and show that strong correlation between observable scales and modes with longer (super-horizon) wavelength arise as a consequence of the evolution of perturbations across the LQC bounce. These correlations are strongly scale dependent and induce a dipole-dominated modulation on large angular scales in the CMB, in agreement with observations. |
1811.08864 | Nasr Ahmed | Nasr Ahmed and Sultan Z. Alamri | A stable flat entropy-corrected FRW universe | 17 pages, 18 figures | null | 10.1142/S0219887819501597 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a general entropy-corrected FRW cosmological model has been
presented in which a deceleration-to-acceleration transition occurs according
to recent observations. We found that the case for the flat universe ($k=0$),
supported by observations, is the most stable one where it successfully passes
all stability tests. The stability of the model has been studied through
testing the sound speed, the classical and the new nonlinear energy conditions.
The model predicts a positive pressure during the early-time decelerating
epoch, and a negative pressure during the late-time accelerating epoch in a
good agreement with cosmic history and dark energy assumption. We have
investigated all possible values of the prefactors $\alpha$ and $\beta$ in the
corrected entropy-area relation to find the best values required for a stable
flat universe. We have also made use of the evolution of the equation of state
parameters $\omega(t)$ in predicting the correct values of $\alpha$ and
$\beta$. The jerk and density parameters have been calculated where a good
agreement with observations and $\Lambda$CDM model has been obtained. Two dark
energy proposals have been investigated in this model, the entropy-corrected
holographic dark energy and the modified holographic Ricci dark energy.
| [
{
"created": "Wed, 21 Nov 2018 18:19:57 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2019 17:40:07 GMT",
"version": "v2"
}
] | 2019-10-23 | [
[
"Ahmed",
"Nasr",
""
],
[
"Alamri",
"Sultan Z.",
""
]
] | In this paper, a general entropy-corrected FRW cosmological model has been presented in which a deceleration-to-acceleration transition occurs according to recent observations. We found that the case for the flat universe ($k=0$), supported by observations, is the most stable one where it successfully passes all stability tests. The stability of the model has been studied through testing the sound speed, the classical and the new nonlinear energy conditions. The model predicts a positive pressure during the early-time decelerating epoch, and a negative pressure during the late-time accelerating epoch in a good agreement with cosmic history and dark energy assumption. We have investigated all possible values of the prefactors $\alpha$ and $\beta$ in the corrected entropy-area relation to find the best values required for a stable flat universe. We have also made use of the evolution of the equation of state parameters $\omega(t)$ in predicting the correct values of $\alpha$ and $\beta$. The jerk and density parameters have been calculated where a good agreement with observations and $\Lambda$CDM model has been obtained. Two dark energy proposals have been investigated in this model, the entropy-corrected holographic dark energy and the modified holographic Ricci dark energy. |
1209.2317 | Michael Stone | Michael Stone | An analogue of Hawking radiation in the quantum Hall effect | 16 pages, five figures | Class. Quantum Grav. 30 085003 (2013) | 10.1088/0264-9381/30/8/085003 | null | gr-qc cond-mat.mes-hall | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the identification of the edge mode of the filling fraction $\nu=1$
quantum Hall phase with a 1+1 dimensional chiral Dirac fermion to construct an
analogue model for a chiral fermion in a space-time geometry possessing an
event horizon. By solving the model in the lowest Landau level, we show that
the event horizon emits particles and holes with a thermal spectrum. Each
emitted quasiparticle is correlated with an opposite-energy partner on the
other side of the event horizon. Once we trace out these "unobservable"
partners, we are left with a thermal density matrix.
| [
{
"created": "Tue, 11 Sep 2012 13:38:06 GMT",
"version": "v1"
}
] | 2013-08-22 | [
[
"Stone",
"Michael",
""
]
] | We use the identification of the edge mode of the filling fraction $\nu=1$ quantum Hall phase with a 1+1 dimensional chiral Dirac fermion to construct an analogue model for a chiral fermion in a space-time geometry possessing an event horizon. By solving the model in the lowest Landau level, we show that the event horizon emits particles and holes with a thermal spectrum. Each emitted quasiparticle is correlated with an opposite-energy partner on the other side of the event horizon. Once we trace out these "unobservable" partners, we are left with a thermal density matrix. |
2112.12518 | Jitendra Kumar Dr. | Jitendra Kumar and Puja Bharti | The classification of interior solutions of anisotropic fluid
configurations | null | null | null | null | gr-qc astro-ph.HE astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | The Einstein-Maxwell (or Einstein) system of field equations plays a
substantial role in the modeling of compact stars. Although due to its
non-linearity getting an exact solution for the system of field equations is a
difficult task, the solutions of field equations have a long and rich history.
It took a year for Karl Schwarzschild to obtain the first exact solution of
Einstein's field equations since general theory of relativity was published.
The number of viable solutions has been growing since then. Many authors have
adopted several methods to obtain the solution. Different models have been
constructed for a variety of applications. To produce feasible models of
compact stars, a considerable amount of effort has been applied in gaining an
understanding of the properties of anisotropic matter. Theoretical study
indicates that pressure within compact stars with extreme internal density and
strong gravity is mostly anisotropic. Anisotropy was found sufficient for the
study of compact stars with the dense nuclear matter. It is claimed that it is
important to consider the pressure experienced to be anisotropic whenever
relativistic fluids are involved. In this review article, we have discussed
different ways of generating a static spherically symmetric anisotropic fluid
model. The purpose of the article is to present a simple classification scheme
for static and spherically symmetric anisotropic fluid solutions. The known
solutions are reviewed and compartmentalized as per the proposed scheme so that
we can illustrate general ideas about these solutions without being exhaustive.
| [
{
"created": "Wed, 22 Dec 2021 06:34:21 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jan 2022 09:10:58 GMT",
"version": "v2"
}
] | 2022-01-26 | [
[
"Kumar",
"Jitendra",
""
],
[
"Bharti",
"Puja",
""
]
] | The Einstein-Maxwell (or Einstein) system of field equations plays a substantial role in the modeling of compact stars. Although due to its non-linearity getting an exact solution for the system of field equations is a difficult task, the solutions of field equations have a long and rich history. It took a year for Karl Schwarzschild to obtain the first exact solution of Einstein's field equations since general theory of relativity was published. The number of viable solutions has been growing since then. Many authors have adopted several methods to obtain the solution. Different models have been constructed for a variety of applications. To produce feasible models of compact stars, a considerable amount of effort has been applied in gaining an understanding of the properties of anisotropic matter. Theoretical study indicates that pressure within compact stars with extreme internal density and strong gravity is mostly anisotropic. Anisotropy was found sufficient for the study of compact stars with the dense nuclear matter. It is claimed that it is important to consider the pressure experienced to be anisotropic whenever relativistic fluids are involved. In this review article, we have discussed different ways of generating a static spherically symmetric anisotropic fluid model. The purpose of the article is to present a simple classification scheme for static and spherically symmetric anisotropic fluid solutions. The known solutions are reviewed and compartmentalized as per the proposed scheme so that we can illustrate general ideas about these solutions without being exhaustive. |
gr-qc/9703051 | Haret Rosu | B. Roy Frieden, H.C. Rosu | Fisher's arrow of `time' in cosmological coherent phase space | 10 pages, LaTex, Honorable Mention at GRF-1997 | Mod.Phys.Lett. A13 (1998) 39-46 | 10.1142/S0217732398000073 | null | gr-qc | null | Fisher's arrow of `time' in a cosmological phase space defined as in quantum
optics (i.e., whose points are coherent states) is introduced as follows.
Assuming that the phase space evolution of the universe starts from an initial
squeezed cosmological state towards a final thermal one, a Fokker-Planck
equation for the time-dependent, cosmological Q phase space probability
distribution can be written down. Next, using some recent results in the
literature, we derive an information arrow of time for the Fisher phase space
cosmological entropy based on the Q function. We also mention the application
of Fisher's arrow of time to stochastic inflation models
| [
{
"created": "Wed, 19 Mar 1997 21:22:47 GMT",
"version": "v1"
},
{
"created": "Wed, 21 May 1997 17:37:01 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Dec 1997 14:48:44 GMT",
"version": "v3"
},
{
"created": "Sat, 7 Feb 1998 19:58:15 GMT",
"version": "v4"
}
] | 2009-10-30 | [
[
"Frieden",
"B. Roy",
""
],
[
"Rosu",
"H. C.",
""
]
] | Fisher's arrow of `time' in a cosmological phase space defined as in quantum optics (i.e., whose points are coherent states) is introduced as follows. Assuming that the phase space evolution of the universe starts from an initial squeezed cosmological state towards a final thermal one, a Fokker-Planck equation for the time-dependent, cosmological Q phase space probability distribution can be written down. Next, using some recent results in the literature, we derive an information arrow of time for the Fisher phase space cosmological entropy based on the Q function. We also mention the application of Fisher's arrow of time to stochastic inflation models |
gr-qc/9808026 | Gian Paolo Vacca | G.L. Alberghi, R. Casadio, G.P. Vacca, G. Venturi | Gravitational Collapse of a Shell of Quantized Matter | 20 pages, 1 eps figure. Problem with figure fixed | Class.Quant.Grav.16:131-147,1999 | 10.1088/0264-9381/16/1/010 | null | gr-qc astro-ph hep-ph | null | The semi-classical collapse, including lowest order back-reaction, of a thin
shell of self-gravitating quantized matter is illustrated. The conditions for
which self-gravitating matter forms a thin shell are first discussed and an
effective Lagrangian for such matter is obtained. The matter-gravity system is
then quantized, the semi-classical limit for gravitation is taken and the
method of adiabatic invariants is applied to the resulting time dependent
matter Hamiltonian. The governing equations are integrated numerically, for
suitable initial conditions, in order to illustrate the effect of
back-reaction, due to the creation of matter, in slowing down the collapse near
the horizon.
| [
{
"created": "Mon, 10 Aug 1998 12:22:53 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Aug 1998 09:56:31 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Alberghi",
"G. L.",
""
],
[
"Casadio",
"R.",
""
],
[
"Vacca",
"G. P.",
""
],
[
"Venturi",
"G.",
""
]
] | The semi-classical collapse, including lowest order back-reaction, of a thin shell of self-gravitating quantized matter is illustrated. The conditions for which self-gravitating matter forms a thin shell are first discussed and an effective Lagrangian for such matter is obtained. The matter-gravity system is then quantized, the semi-classical limit for gravitation is taken and the method of adiabatic invariants is applied to the resulting time dependent matter Hamiltonian. The governing equations are integrated numerically, for suitable initial conditions, in order to illustrate the effect of back-reaction, due to the creation of matter, in slowing down the collapse near the horizon. |
1910.03298 | Ilya Peshkov M. | Evgeniy Romenski and Ilya Peshkov and Michael Dumbser and and
Francesco Fambri | A new continuum model for general relativistic viscous heat-conducting
media | Accepted for publication in Phil. Trans. R. Soc. A. (before author
proofs) 21 pages, 1 figure | null | 10.1098/rsta.2019.0175 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The lack of formulation of macroscopic equations for irreversible dynamics of
viscous heat-conducting media compatible with the causality principle of
Einstein's Special Relativity and the Euler-Lagrange structure of General
Relativity is a long-lasting problem. In this paper, we propose a possible
solution to this problem in the framework of SHTC equations. The approach does
not rely on postulates of equilibrium irreversible thermodynamics but treats
irreversible processes from the non-equilibrium point of view. Thus, each
transfer process is characterized by a characteristic velocity of perturbation
propagation in the non-equilibrium state, as well as by an intrinsic
time/length scale of the dissipative dynamics. The resulting system of
governing equations is formulated as a first-order system of hyperbolic
equations with relaxation-type irreversible terms. Via a formal asymptotic
analysis, we demonstrate that classical transport coefficients such as the
viscosity and heat conductivity are recovered in leading terms of our theory as
effective transport coefficients. Some numerical examples are presented in
order to demonstrate the viability of the approach.
| [
{
"created": "Tue, 8 Oct 2019 09:38:07 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Feb 2020 12:18:31 GMT",
"version": "v2"
}
] | 2020-03-31 | [
[
"Romenski",
"Evgeniy",
""
],
[
"Peshkov",
"Ilya",
""
],
[
"Dumbser",
"Michael",
""
],
[
"Fambri",
"and Francesco",
""
]
] | The lack of formulation of macroscopic equations for irreversible dynamics of viscous heat-conducting media compatible with the causality principle of Einstein's Special Relativity and the Euler-Lagrange structure of General Relativity is a long-lasting problem. In this paper, we propose a possible solution to this problem in the framework of SHTC equations. The approach does not rely on postulates of equilibrium irreversible thermodynamics but treats irreversible processes from the non-equilibrium point of view. Thus, each transfer process is characterized by a characteristic velocity of perturbation propagation in the non-equilibrium state, as well as by an intrinsic time/length scale of the dissipative dynamics. The resulting system of governing equations is formulated as a first-order system of hyperbolic equations with relaxation-type irreversible terms. Via a formal asymptotic analysis, we demonstrate that classical transport coefficients such as the viscosity and heat conductivity are recovered in leading terms of our theory as effective transport coefficients. Some numerical examples are presented in order to demonstrate the viability of the approach. |
1712.03066 | Simpliciano Castardelli Reis | Simpliciano Castardelli dos Reis and Ilya L.Shapiro | Cosmic anisotropy with Reduced Relativistic Gas | 18 pages, 4 figures. Added small Appendix and a few extra references,
slightly extended discussion on the possible application of the results.
Version accepted in European Journal of Physics C, with LaTeX format modified
accordingly | Eur.Phys.J. C78 (2018) no.2, 145 | 10.1140/epjc/s10052-018-5618-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of cosmological anisotropies is investigated for Bianchi type I
universe filled by a relativistic matter represented by the reduced
relativistic gas model (RRG), with equation of state interpolating between
radiation and matter. Previously it was shown that the interpolation is
observed in the background cosmological solutions for homogeneous and isotropic
universe and also for the linear cosmological perturbations. We extend the
application of RRG to the Bianchi type I anisotropic model and find that the
solutions evolve to the isotropic universe with the pressureless matter
contents.
| [
{
"created": "Fri, 8 Dec 2017 14:01:19 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 2018 00:18:56 GMT",
"version": "v2"
}
] | 2019-08-20 | [
[
"Reis",
"Simpliciano Castardelli dos",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | The dynamics of cosmological anisotropies is investigated for Bianchi type I universe filled by a relativistic matter represented by the reduced relativistic gas model (RRG), with equation of state interpolating between radiation and matter. Previously it was shown that the interpolation is observed in the background cosmological solutions for homogeneous and isotropic universe and also for the linear cosmological perturbations. We extend the application of RRG to the Bianchi type I anisotropic model and find that the solutions evolve to the isotropic universe with the pressureless matter contents. |
1204.2177 | Christian Fr{\o}nsdal | Christian Fronsdal, Thomas J. Wilcox | An equation of state for dark matter in the Milky Way | 19 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dark matter, believed to be present in many galaxies, is interpreted as a
hydrodynamical system in interaction with the gravitational field and with
nothing else. The gravitational field of our Galaxy can be inferred from
observation of orbital velocities of the visible stars, in a first
approximation in which the field is taken to be due to the distribution of dark
matter only. An equation of state is determined by the gravitational field via
the equations of motion.
To arrive at an estimate of the distribution of dark matter in our galaxy,
and simultaneously learn something about the gravitational field in the inner
regions, the following strategy was adopted: 1. The observed rotation curves
suggest an expression for the newtonian potential, valid in the outer region.
2. The assumption of a quasi stationary, spherically symmetric distribution of
dark matter then leads to a unique equation of state. 3. This equation of state
is assumed to be valid all the way to the center (though of course the
newtonian approximation is not). 4. Using this equation of state, together with
Einstein's equations and the relativistic hydrostatic condition, we calculate
the metric and the matter density throughout the galaxy. The solutions are
regular all the way to the center; there is no indication of a structure of the
type of a Black Hole.
The equation of state that is thus determined experimentally is of the type
used by Chandrasekhar and others for the degenerate Fermi gas. In the
approximation of weak fields the associated "sinh-Emden" equation has a global,
nonsingular solution.
| [
{
"created": "Sun, 8 Apr 2012 21:56:13 GMT",
"version": "v1"
}
] | 2012-04-11 | [
[
"Fronsdal",
"Christian",
""
],
[
"Wilcox",
"Thomas J.",
""
]
] | Dark matter, believed to be present in many galaxies, is interpreted as a hydrodynamical system in interaction with the gravitational field and with nothing else. The gravitational field of our Galaxy can be inferred from observation of orbital velocities of the visible stars, in a first approximation in which the field is taken to be due to the distribution of dark matter only. An equation of state is determined by the gravitational field via the equations of motion. To arrive at an estimate of the distribution of dark matter in our galaxy, and simultaneously learn something about the gravitational field in the inner regions, the following strategy was adopted: 1. The observed rotation curves suggest an expression for the newtonian potential, valid in the outer region. 2. The assumption of a quasi stationary, spherically symmetric distribution of dark matter then leads to a unique equation of state. 3. This equation of state is assumed to be valid all the way to the center (though of course the newtonian approximation is not). 4. Using this equation of state, together with Einstein's equations and the relativistic hydrostatic condition, we calculate the metric and the matter density throughout the galaxy. The solutions are regular all the way to the center; there is no indication of a structure of the type of a Black Hole. The equation of state that is thus determined experimentally is of the type used by Chandrasekhar and others for the degenerate Fermi gas. In the approximation of weak fields the associated "sinh-Emden" equation has a global, nonsingular solution. |
2304.06895 | Yu-Xiao Liu | Sen Yang, Wen-Di Guo, Qin Tan, Yu-Xiao Liu | Axial gravitational quasinormal modes of a self-dual black hole in loop
quantum gravity | 14 pages, 3 figures, 5 tables | Phys.Rev.D 108 (2023) 2, 024055 | 10.1103/PhysRevD.108.024055 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the axial gravitational quasinormal modes of a self-dual black hole
in loop quantum gravity. Considering the axial perturbation of the background
spacetime, we obtain the Schr\"{o}dinger-like master equation. Then we
calculate the quasinormal frequencies with the Wentzel-Kramers-Brillouin
approximation and the asymptotic iteration method. We also investigate the
numerical evolution of an initial wave packet on the self-dual black hole
spacetime. We find the quantum correction parameter $P$ positively affects the
absolute values of both the real and imaginary parts of quasinormal
frequencies. We derive the relation between the parameters of the circular null
geodesics and quasinormal frequencies in the eikonal limit for the self-dual
black hole, and numerically verify this relation.
| [
{
"created": "Fri, 14 Apr 2023 02:09:14 GMT",
"version": "v1"
},
{
"created": "Fri, 5 May 2023 14:34:02 GMT",
"version": "v2"
}
] | 2024-02-21 | [
[
"Yang",
"Sen",
""
],
[
"Guo",
"Wen-Di",
""
],
[
"Tan",
"Qin",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | We study the axial gravitational quasinormal modes of a self-dual black hole in loop quantum gravity. Considering the axial perturbation of the background spacetime, we obtain the Schr\"{o}dinger-like master equation. Then we calculate the quasinormal frequencies with the Wentzel-Kramers-Brillouin approximation and the asymptotic iteration method. We also investigate the numerical evolution of an initial wave packet on the self-dual black hole spacetime. We find the quantum correction parameter $P$ positively affects the absolute values of both the real and imaginary parts of quasinormal frequencies. We derive the relation between the parameters of the circular null geodesics and quasinormal frequencies in the eikonal limit for the self-dual black hole, and numerically verify this relation. |
1504.08226 | Jonas Mureika | Jonas R. Mureika, John W. Moffat, Mir Faizal | Black Hole Thermodynamics in MOdified Gravity (MOG) | Title changed slightly; new section on BH entropy corrections added;
matches version published in PLB | Phys. Lett. B 757, 528 (2016) | 10.1016/j.physletb.2016.04.041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the thermodynamical properties of black holes in a modified theory
of gravity, which was initially proposed to obtain correct dynamics of galaxies
and galaxy clusters without dark matter. The thermodynamics of non-rotating and
rotating black hole solutions resembles similar solutions in Einstein-Maxwell
theory with the electric charge being replaced by a new mass dependent
gravitational charge $Q = \sqrt{\alpha G_N}M$. This new mass dependent charge
modifies the effective Newtonian constant from $G_N$ to $G = G_N(1+\alpha)$,
and this in turn critically affects the thermodynamics of the black holes. We
also investigate the thermodynamics of regular solutions, and explore the
limiting case when no horizons forms. So, it is possible that the modified
gravity can lead to the absence of black hole horizons in our universe.
Finally, we analyze corrections to the thermodynamics of a non-rotating black
hole and obtain the usual logarithmic correction term.
| [
{
"created": "Tue, 3 Mar 2015 19:09:53 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2016 18:33:05 GMT",
"version": "v2"
}
] | 2016-05-20 | [
[
"Mureika",
"Jonas R.",
""
],
[
"Moffat",
"John W.",
""
],
[
"Faizal",
"Mir",
""
]
] | We analyze the thermodynamical properties of black holes in a modified theory of gravity, which was initially proposed to obtain correct dynamics of galaxies and galaxy clusters without dark matter. The thermodynamics of non-rotating and rotating black hole solutions resembles similar solutions in Einstein-Maxwell theory with the electric charge being replaced by a new mass dependent gravitational charge $Q = \sqrt{\alpha G_N}M$. This new mass dependent charge modifies the effective Newtonian constant from $G_N$ to $G = G_N(1+\alpha)$, and this in turn critically affects the thermodynamics of the black holes. We also investigate the thermodynamics of regular solutions, and explore the limiting case when no horizons forms. So, it is possible that the modified gravity can lead to the absence of black hole horizons in our universe. Finally, we analyze corrections to the thermodynamics of a non-rotating black hole and obtain the usual logarithmic correction term. |
gr-qc/9712001 | James Hartle | James B. Hartle (University of California, Santa Barbara) | Quantum Pasts and the Utility of History | 22pages, uses REVTEX 3.0 | Phys.Scripta T76 (1998) 67 | 10.1238/Physica.Topical.076a00067 | null | gr-qc quant-ph | null | From data in the present we can predict the future and retrodict the past.
These predictions and retrodictions are for histories -- most simply time
sequences of events. Quantum mechanics gives probabilities for individual
histories in a decoherent set of alternative histories. This paper discusses
several issues connected with the distinction between prediction and
retrodiction in quantum cosmology: the difference between classical and quantum
retrodiction, the permanence of the past, why we predict the future but
remember the past, the nature and utility of reconstructing the past(s), and
information theoretic measures of the utility of history. (Talk presented at
the Nobel Symposium: Modern Studies of Basic Quantum Concepts and Phenomena,
Gimo, Sweden, June 13-17, 1997)
| [
{
"created": "Tue, 2 Dec 1997 00:46:12 GMT",
"version": "v1"
}
] | 2014-01-15 | [
[
"Hartle",
"James B.",
"",
"University of California, Santa Barbara"
]
] | From data in the present we can predict the future and retrodict the past. These predictions and retrodictions are for histories -- most simply time sequences of events. Quantum mechanics gives probabilities for individual histories in a decoherent set of alternative histories. This paper discusses several issues connected with the distinction between prediction and retrodiction in quantum cosmology: the difference between classical and quantum retrodiction, the permanence of the past, why we predict the future but remember the past, the nature and utility of reconstructing the past(s), and information theoretic measures of the utility of history. (Talk presented at the Nobel Symposium: Modern Studies of Basic Quantum Concepts and Phenomena, Gimo, Sweden, June 13-17, 1997) |
1510.07490 | Sunil Maharaj | Naresh Dadhich, Sudan Hansraj, Sunil D. Maharaj | Universality of isothermal fluid spheres in Lovelock gravity | 11 pages | Phys. Rev. D 93, 044072 (2016) | 10.1103/PhysRevD.93.044072 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show universality of isothermal fluid spheres in pure Lovelock gravity
where the equation of motion has only one $N$th order term coming from the
corresponding Lovelock polynomial action of degree $N$. Isothermality is
characterized by the equation of state, $p = \alpha \rho$ and the property,
$\rho \sim 1/r^{2N}$. Then the solution describing isothermal spheres, which
exist only for the pure Lovelock equation, is of the same form for the general
Lovelock degree $N$ in all dimenions $d \geq 2N+2$. We further prove that the
necessary and sufficient condition for the isothermal sphere is that its metric
is conformal to the massless global monopole or the solid angle deficit metric,
and this feature is also universal.
| [
{
"created": "Mon, 26 Oct 2015 14:26:21 GMT",
"version": "v1"
}
] | 2016-03-09 | [
[
"Dadhich",
"Naresh",
""
],
[
"Hansraj",
"Sudan",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | We show universality of isothermal fluid spheres in pure Lovelock gravity where the equation of motion has only one $N$th order term coming from the corresponding Lovelock polynomial action of degree $N$. Isothermality is characterized by the equation of state, $p = \alpha \rho$ and the property, $\rho \sim 1/r^{2N}$. Then the solution describing isothermal spheres, which exist only for the pure Lovelock equation, is of the same form for the general Lovelock degree $N$ in all dimenions $d \geq 2N+2$. We further prove that the necessary and sufficient condition for the isothermal sphere is that its metric is conformal to the massless global monopole or the solid angle deficit metric, and this feature is also universal. |
2106.05062 | Deepen Garg | Deepen Garg and I. Y. Dodin | Gauge-invariant gravitational waves in matter beyond linearized gravity | null | Class. Quantum Grav. 40 215002 (2023) | 10.1088/1361-6382/acfc0e | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Modeling the propagation of gravitational waves (GWs) through matter is
complicated by the gauge freedom of linearized gravity in that once
nonlinearities are taken into consideration, gauge artifacts can cause spurious
acceleration of the matter. To eliminate these artifacts, we propose how to
keep the theory of dispersive GWs gauge-invariant beyond the linear
approximation and, in particular, obtain an unambiguous gauge-invariant
expression for the energy--momentum of a GW in dispersive medium. Using
analytic tools from plasma physics, we propose an exactly gauge-invariant
``quasilinear'' theory, in which GWs are governed by linear equations and also
affect the background metric on scales large compared to their wavelength. As a
corollary, the gauge-invariant geometrical optics of linear dispersive GWs in a
general background is formulated. As an example, we show how the well-known
properties of vacuum GWs are naturally and concisely yielded by our theory in a
manifestly gauge-invariant form. We also show how the gauge invariance can be
maintained within a given accuracy to an arbitrary order in the GW amplitude.
These results are intended to form a physically meaningful framework for
studying dispersive GWs in matter.
| [
{
"created": "Wed, 9 Jun 2021 13:32:56 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Dec 2022 13:52:05 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Sep 2023 22:05:20 GMT",
"version": "v3"
}
] | 2024-02-28 | [
[
"Garg",
"Deepen",
""
],
[
"Dodin",
"I. Y.",
""
]
] | Modeling the propagation of gravitational waves (GWs) through matter is complicated by the gauge freedom of linearized gravity in that once nonlinearities are taken into consideration, gauge artifacts can cause spurious acceleration of the matter. To eliminate these artifacts, we propose how to keep the theory of dispersive GWs gauge-invariant beyond the linear approximation and, in particular, obtain an unambiguous gauge-invariant expression for the energy--momentum of a GW in dispersive medium. Using analytic tools from plasma physics, we propose an exactly gauge-invariant ``quasilinear'' theory, in which GWs are governed by linear equations and also affect the background metric on scales large compared to their wavelength. As a corollary, the gauge-invariant geometrical optics of linear dispersive GWs in a general background is formulated. As an example, we show how the well-known properties of vacuum GWs are naturally and concisely yielded by our theory in a manifestly gauge-invariant form. We also show how the gauge invariance can be maintained within a given accuracy to an arbitrary order in the GW amplitude. These results are intended to form a physically meaningful framework for studying dispersive GWs in matter. |
0809.4076 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev, Vladimir Folomeev and Masato Minamitsuji | Thick de Sitter brane solutions in higher dimensions | typos corrected | Phys.Rev.D79:024001,2009 | 10.1103/PhysRevD.79.024001 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present thick de Sitter brane solutions which are supported by two
interacting {\it phantom} scalar fields in five-, six- and seven-dimensional
spacetime. It is shown that for all cases regular solutions with anti-de Sitter
asymptotic (5D problem) and a flat asymptotic far from the brane (6D and 7D
cases) exist. We also discuss the stability of our solutions.
| [
{
"created": "Wed, 24 Sep 2008 03:38:49 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Oct 2008 04:55:40 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Jan 2009 07:48:14 GMT",
"version": "v3"
}
] | 2009-01-22 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
],
[
"Minamitsuji",
"Masato",
""
]
] | We present thick de Sitter brane solutions which are supported by two interacting {\it phantom} scalar fields in five-, six- and seven-dimensional spacetime. It is shown that for all cases regular solutions with anti-de Sitter asymptotic (5D problem) and a flat asymptotic far from the brane (6D and 7D cases) exist. We also discuss the stability of our solutions. |
gr-qc/9701041 | Roberto De Pietri | Roberto De Pietri (University of Parma) | Spin Networks and Recoupling in Loop Quantum Gravity | 8 pages, LaTeX3e, To appear in the Proceedings of the 2nd Conference
on Constrained Dynamics and Quantum Gravity, Santa Margherita, Italy, 17-21
September 1996 | Nucl.Phys.Proc.Suppl. 57 (1997) 251-254 | 10.1016/S0920-5632(97)00397-6 | University of Parma UPRF-97-01 | gr-qc | null | I discuss the role played by the spin-network basis and recoupling theory (in
its graphical tangle-theoretic formulation) and their use for performing
explicit calculations in loop quantum gravity. In particular, I show that
recoupling theory allows the derivation of explicit expressions for the
eingenvalues of the quantum volume operator. An important side result of these
computations is the determination of a scalar product with respect to which
area and volume operators are symmetric, and the spin network states are
orthonormal.
| [
{
"created": "Sat, 18 Jan 1997 12:53:33 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"De Pietri",
"Roberto",
"",
"University of Parma"
]
] | I discuss the role played by the spin-network basis and recoupling theory (in its graphical tangle-theoretic formulation) and their use for performing explicit calculations in loop quantum gravity. In particular, I show that recoupling theory allows the derivation of explicit expressions for the eingenvalues of the quantum volume operator. An important side result of these computations is the determination of a scalar product with respect to which area and volume operators are symmetric, and the spin network states are orthonormal. |
1106.6036 | Bahram Mashhoon | B. Mashhoon and P. S. Wesson | Mach's Principle and Higher-Dimensional Dynamics | 16 pages, accepted for publication in Annalen der Physik; Revised
Version: minor improvements | Annalen Phys.524:63-70,2012 | 10.1002/andp.201100100 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly discuss the current status of Mach's principle in general
relativity and point out that its last vestige, namely, the gravitomagnetic
field associated with rotation, has recently been measured for the earth in the
GP-B experiment. Furthermore, in his analysis of the foundations of Newtonian
mechanics, Mach provided an operational definition for inertial mass and
pointed out that time and space are conceptually distinct from their
operational definitions by means of masses. Mach recognized that this
circumstance is due to the lack of any a priori connection between the inertial
mass of a body and its Newtonian state in space and time. One possible way to
improve upon this situation in classical physics is to associate mass with an
extra dimension. Indeed, Einstein's theory of gravitation can be locally
embedded in a Ricci-flat 5D manifold such that the 4D energy-momentum tensor
appears to originate from the existence of the extra dimension. An outline of
such a 5D Machian extension of Einstein's general relativity is presented.
| [
{
"created": "Wed, 29 Jun 2011 19:42:50 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2011 20:43:05 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Dec 2011 19:50:42 GMT",
"version": "v3"
}
] | 2015-05-28 | [
[
"Mashhoon",
"B.",
""
],
[
"Wesson",
"P. S.",
""
]
] | We briefly discuss the current status of Mach's principle in general relativity and point out that its last vestige, namely, the gravitomagnetic field associated with rotation, has recently been measured for the earth in the GP-B experiment. Furthermore, in his analysis of the foundations of Newtonian mechanics, Mach provided an operational definition for inertial mass and pointed out that time and space are conceptually distinct from their operational definitions by means of masses. Mach recognized that this circumstance is due to the lack of any a priori connection between the inertial mass of a body and its Newtonian state in space and time. One possible way to improve upon this situation in classical physics is to associate mass with an extra dimension. Indeed, Einstein's theory of gravitation can be locally embedded in a Ricci-flat 5D manifold such that the 4D energy-momentum tensor appears to originate from the existence of the extra dimension. An outline of such a 5D Machian extension of Einstein's general relativity is presented. |
gr-qc/0212074 | Martinetti | P. Martinetti, C. Rovelli | Diamonds's Temperature: Unruh effect for bounded trajectories and
thermal time hypothesis | One reference corrected | Class.Quant.Grav. 20 (2003) 4919-4932 | 10.1088/0264-9381/20/22/015 | null | gr-qc hep-th math-ph math.MP | null | We study the Unruh effect for an observer with a finite lifetime, using the
thermal time hypothesis. The thermal time hypothesis maintains that: (i) time
is the physical quantity determined by the flow defined by a state over an
observable algebra, and (ii) when this flow is proportional to a geometric flow
in spacetime, temperature is the ratio between flow parameter and proper time.
An eternal accelerated Unruh observer has access to the local algebra
associated to a Rindler wedge. The flow defined by the Minkowski vacuum of a
field theory over this algebra is proportional to a flow in spacetime and the
associated temperature is the Unruh temperature. An observer with a finite
lifetime has access to the local observable algebra associated to a finite
spacetime region called a "diamond". The flow defined by the Minkowski vacuum
of a (four dimensional, conformally invariant) quantum field theory over this
algebra is also proportional to a flow in spacetime. The associated temperature
generalizes the Unruh temperature to finite lifetime observers.
Furthermore, this temperature does not vanish even in the limit in which the
acceleration is zero. The temperature associated to an inertial observer with
lifetime T, which we denote as "diamond's temperature", is 2hbar/(pi k_b
T).This temperature is related to the fact that a finite lifetime observer does
not have access to all the degrees of freedom of the quantum field theory.
| [
{
"created": "Tue, 17 Dec 2002 19:57:23 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Mar 2003 18:04:30 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Jan 2004 21:22:49 GMT",
"version": "v3"
},
{
"created": "Mon, 2 Feb 2004 12:21:48 GMT",
"version": "v4"
}
] | 2009-11-07 | [
[
"Martinetti",
"P.",
""
],
[
"Rovelli",
"C.",
""
]
] | We study the Unruh effect for an observer with a finite lifetime, using the thermal time hypothesis. The thermal time hypothesis maintains that: (i) time is the physical quantity determined by the flow defined by a state over an observable algebra, and (ii) when this flow is proportional to a geometric flow in spacetime, temperature is the ratio between flow parameter and proper time. An eternal accelerated Unruh observer has access to the local algebra associated to a Rindler wedge. The flow defined by the Minkowski vacuum of a field theory over this algebra is proportional to a flow in spacetime and the associated temperature is the Unruh temperature. An observer with a finite lifetime has access to the local observable algebra associated to a finite spacetime region called a "diamond". The flow defined by the Minkowski vacuum of a (four dimensional, conformally invariant) quantum field theory over this algebra is also proportional to a flow in spacetime. The associated temperature generalizes the Unruh temperature to finite lifetime observers. Furthermore, this temperature does not vanish even in the limit in which the acceleration is zero. The temperature associated to an inertial observer with lifetime T, which we denote as "diamond's temperature", is 2hbar/(pi k_b T).This temperature is related to the fact that a finite lifetime observer does not have access to all the degrees of freedom of the quantum field theory. |
2105.09192 | Hamid Reza Sepangi | Mohaddese Heydari-Fard, Malihe Heydari-Fard, Hamid Reza Sepangi | Thin accretion disks around rotating black holes in $4D$
Einstein-Gauss-Bonnet gravity | 18 pages, 8 figures, to appear in EPJC | EPJC (2021) 81:473 | 10.1140/epjc/s10052-021-09266-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Kumar and Ghosh have derived Kerr-like rotating black hole
solutions in the framework of four-dimensional Einstein-Gauss-Bonnet theory of
gravity and investigated the black hole shadow. Using the steady-state
Novikov-Thorne model, we study thin accretion disk processes for such rotating
black holes including the energy flux, temperature distribution, emission
spectrum, energy conversion efficiency as well as the radius of the innermost
stable circular orbit. We also study the effects of the Gauss-Bonnet coupling
parameter $\alpha$ on these quantities. The results are compared to slowly
rotating relativistic Kerr black holes which show that for a positive
Gauss-Bonnet coupling, thin accretion disks around rotating black holes in
four-dimensional Einstein-Gauss-Bonnet gravity are hotter and more efficient
than that for Kerr black holes with the same rotation parameter $a$, while for
a negative coupling they are cooler and less efficient. Thus the accretion disk
processes may be considered as tools for testing Einstein-Gauss-Bonnet gravity
using astrophysical observations.
| [
{
"created": "Wed, 19 May 2021 15:11:10 GMT",
"version": "v1"
}
] | 2021-06-16 | [
[
"Heydari-Fard",
"Mohaddese",
""
],
[
"Heydari-Fard",
"Malihe",
""
],
[
"Sepangi",
"Hamid Reza",
""
]
] | Recently, Kumar and Ghosh have derived Kerr-like rotating black hole solutions in the framework of four-dimensional Einstein-Gauss-Bonnet theory of gravity and investigated the black hole shadow. Using the steady-state Novikov-Thorne model, we study thin accretion disk processes for such rotating black holes including the energy flux, temperature distribution, emission spectrum, energy conversion efficiency as well as the radius of the innermost stable circular orbit. We also study the effects of the Gauss-Bonnet coupling parameter $\alpha$ on these quantities. The results are compared to slowly rotating relativistic Kerr black holes which show that for a positive Gauss-Bonnet coupling, thin accretion disks around rotating black holes in four-dimensional Einstein-Gauss-Bonnet gravity are hotter and more efficient than that for Kerr black holes with the same rotation parameter $a$, while for a negative coupling they are cooler and less efficient. Thus the accretion disk processes may be considered as tools for testing Einstein-Gauss-Bonnet gravity using astrophysical observations. |
1608.08656 | Andrei Lebed G | Andrei G. Lebed | Breakdown of the Equivalence between Gravitational Mass and Energy for a
Quantum Body: Theory and Suggested Experiments | Review: 15 pages, no figures | International Journal of Modern Physics D, vol. 24, 1530027 (2015) | 10.1142/S021827181530027X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review recent theoretical results, obtained for the equivalence between
gravitational mass and energy of a composite quantum body as well as for its
breakdown at macroscopic and microscopic levels. In particular, we discuss that
the expectation values of passive and active gravitational masses operators are
equivalent to the expectation value of energy for electron stationary quantum
states in a hydrogen atom. On the other hand, for superpositions of the
stationary quantum states, inequivalence between the gravitational masses and
energy appears at a macroscopic level. It reveals itself as time-dependent
oscillations of the expectation values of passive and active gravitational
masses, which can be, in principle, experimentally measured. Inequivalence
between passive gravitational mass and energy at a microscopic level can be
experimentally observed as unusual electromagnetic radiation, emitted by a
macroscopic ensemble of the atoms. We propose the corresponding experiment,
which can be done on the Earth's orbit, using small spacecraft. If such
experiment is done it would be the first direct observation of quantum effects
in general relativity.
| [
{
"created": "Tue, 30 Aug 2016 20:53:59 GMT",
"version": "v1"
}
] | 2016-09-07 | [
[
"Lebed",
"Andrei G.",
""
]
] | We review recent theoretical results, obtained for the equivalence between gravitational mass and energy of a composite quantum body as well as for its breakdown at macroscopic and microscopic levels. In particular, we discuss that the expectation values of passive and active gravitational masses operators are equivalent to the expectation value of energy for electron stationary quantum states in a hydrogen atom. On the other hand, for superpositions of the stationary quantum states, inequivalence between the gravitational masses and energy appears at a macroscopic level. It reveals itself as time-dependent oscillations of the expectation values of passive and active gravitational masses, which can be, in principle, experimentally measured. Inequivalence between passive gravitational mass and energy at a microscopic level can be experimentally observed as unusual electromagnetic radiation, emitted by a macroscopic ensemble of the atoms. We propose the corresponding experiment, which can be done on the Earth's orbit, using small spacecraft. If such experiment is done it would be the first direct observation of quantum effects in general relativity. |
gr-qc/0207108 | J. Ponce de Leon | J. Ponce de Leon | Mass and Charge in Brane-World and Non-Compact Kaluza-Klein Theories in
5 Dim | V2: References added, discussion extended. V3 is identical to V2,
references updated. To appear in General Relativity and Gravitation | Gen.Rel.Grav. 35 (2003) 1365-1384 | 10.1023/A:1024526400349 | null | gr-qc | null | In classical Kaluza-Klein theory, with compactified extra dimensions and
without scalar field, the rest mass as well as the electric charge of test
particles are constants of motion. We show that in the case of a large extra
dimension this is no longer so. We propose the Hamilton-Jacobi formalism,
instead of the geodesic equation, for the study of test particles moving in a
five-dimensional background metric. This formalism has a number of advantages:
(i) it provides a clear and invariant definition of rest mass, without the
ambiguities associated with the choice of the parameters used along the motion
in 5D and 4D, (ii) the electromagnetic field can be easily incorporated in the
discussion, and (iii) we avoid the difficulties associated with the "splitting"
of the geodesic equation. For particles moving in a general 5D metric, we show
how the effective rest mass, as measured by an observer in 4D, varies as a
consequence of the large extra dimension. Also, the fifth component of the
momentum changes along the motion. This component can be identified with the
electric charge of test particles. With this interpretation, both the rest mass
and the charge vary along the trajectory. The constant of motion is now a
combination of these quantities. We study the cosmological variations of charge
and rest mass in a five-dimensional bulk metric which is used to embed the
standard k = 0 FRW universes. The time variations in the fine structure
"constant" and the Thomson cross section are also discussed.
| [
{
"created": "Sun, 28 Jul 2002 09:25:14 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Sep 2002 12:42:52 GMT",
"version": "v2"
},
{
"created": "Fri, 9 May 2003 07:05:47 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"de Leon",
"J. Ponce",
""
]
] | In classical Kaluza-Klein theory, with compactified extra dimensions and without scalar field, the rest mass as well as the electric charge of test particles are constants of motion. We show that in the case of a large extra dimension this is no longer so. We propose the Hamilton-Jacobi formalism, instead of the geodesic equation, for the study of test particles moving in a five-dimensional background metric. This formalism has a number of advantages: (i) it provides a clear and invariant definition of rest mass, without the ambiguities associated with the choice of the parameters used along the motion in 5D and 4D, (ii) the electromagnetic field can be easily incorporated in the discussion, and (iii) we avoid the difficulties associated with the "splitting" of the geodesic equation. For particles moving in a general 5D metric, we show how the effective rest mass, as measured by an observer in 4D, varies as a consequence of the large extra dimension. Also, the fifth component of the momentum changes along the motion. This component can be identified with the electric charge of test particles. With this interpretation, both the rest mass and the charge vary along the trajectory. The constant of motion is now a combination of these quantities. We study the cosmological variations of charge and rest mass in a five-dimensional bulk metric which is used to embed the standard k = 0 FRW universes. The time variations in the fine structure "constant" and the Thomson cross section are also discussed. |
1911.07520 | Hrishikesh Chakrabarty | Kimet Jusufi, Mubasher Jamil, Hrishikesh Chakrabarty, Qiang Wu, Cosimo
Bambi and Anzhong Wang | Rotating regular black holes in conformal massive gravity | 17 pages, 28 figures, Accepted for Publication (Phys.Rev.D) | Phys. Rev. D 101, 044035 (2020) | 10.1103/PhysRevD.101.044035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we use a suitable conformal rescaling to construct static and
rotating regular black holes in conformal massive gravity. The new metric is
characterized by the mass $M$, the "scalar charge" $Q$, the angular momentum
parameter $a$, the "hair parameter" $\lambda$, and the conformal scale factor
encoded in the parameter $L$. We explore the shadow images and the deflection
angles of relativistic massive particles in the spacetime geometry of a
rotating regular black hole. For $\lambda \neq 0$ and $Q > 0$, the shadow is
larger than the shadow of a Kerr black hole. In particular, if $\lambda < 0$,
the shadow radius increases considerably. For $\lambda \neq 0$ and $Q < 0$, the
shadow is smaller than the shadow of a Kerr black hole. Additionally we put
observational constraints on the parameter $ Q $ using the latest Event Horizon
Telescope (EHT) observation of the supermassive black hole M87*. Lastly, using
the Gauss-Bonnet theorem, we show that the deflection angle of massive
particles is strongly affected by the parameter $L$. The deflection angle might
be used to distinguish rotating regular black holes from rotating singular
black holes.
| [
{
"created": "Mon, 18 Nov 2019 10:07:08 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jan 2020 13:54:17 GMT",
"version": "v2"
}
] | 2020-02-18 | [
[
"Jusufi",
"Kimet",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Chakrabarty",
"Hrishikesh",
""
],
[
"Wu",
"Qiang",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper, we use a suitable conformal rescaling to construct static and rotating regular black holes in conformal massive gravity. The new metric is characterized by the mass $M$, the "scalar charge" $Q$, the angular momentum parameter $a$, the "hair parameter" $\lambda$, and the conformal scale factor encoded in the parameter $L$. We explore the shadow images and the deflection angles of relativistic massive particles in the spacetime geometry of a rotating regular black hole. For $\lambda \neq 0$ and $Q > 0$, the shadow is larger than the shadow of a Kerr black hole. In particular, if $\lambda < 0$, the shadow radius increases considerably. For $\lambda \neq 0$ and $Q < 0$, the shadow is smaller than the shadow of a Kerr black hole. Additionally we put observational constraints on the parameter $ Q $ using the latest Event Horizon Telescope (EHT) observation of the supermassive black hole M87*. Lastly, using the Gauss-Bonnet theorem, we show that the deflection angle of massive particles is strongly affected by the parameter $L$. The deflection angle might be used to distinguish rotating regular black holes from rotating singular black holes. |
2007.16139 | Jean-Philippe Nicolas | Dietrich H\"afner, Mokdad Mokdad, Jean-Philippe Nicolas | Scattering theory for Dirac fields inside a Reissner-Nordstr\"om-type
black hole | 18 pages, 1 figure | J. Math. Phys. 62, 081503 (2021) | 10.1063/5.0055920 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show asymptotic completeness for the massive charged Dirac equation
between the black hole and Cauchy horizons of a sub-extremal ((Anti-) De
Sitter) Reissner-Nordstr\"om black hole.
| [
{
"created": "Fri, 31 Jul 2020 15:38:05 GMT",
"version": "v1"
}
] | 2022-04-14 | [
[
"Häfner",
"Dietrich",
""
],
[
"Mokdad",
"Mokdad",
""
],
[
"Nicolas",
"Jean-Philippe",
""
]
] | We show asymptotic completeness for the massive charged Dirac equation between the black hole and Cauchy horizons of a sub-extremal ((Anti-) De Sitter) Reissner-Nordstr\"om black hole. |
2311.16085 | Marine Prunier Mrs | Marine Prunier, Gonzalo Morr\'as, Jos\'e Francisco Nu\~no Siles,
Sebastien Clesse, Juan Garc\'ia-Bellido and Ester Ruiz Morales | Analysis of the subsolar-mass black hole candidate SSM200308 from the
second part of the third observing run of Advanced LIGO-Virgo | 7 pages, 4 figures, comments welcome | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A follow-up of a subsolar black hole candidate identified in the second part
of the third observing run of the LIGO-Virgo-KAGRA collaboration is carried
out. With a search signal-to-noise ratio of $8.90$ and a false-alarm rate of 1
per 5 years, close to the usual thresholds for claiming a gravitational-wave
event, we cannot exclude a noise origin. A complete Bayesian parameter
estimation of this candidate, denoted SSM200308, reveals that if the signal
originates from a compact binary coalescence, the component masses are $m_1=
0.62^{+0.46}_{-0.20} M_{\odot}$ and $m_2 = 0.27^{+0.12}_{-0.10} M_{\odot}$ (90%
credible intervals) with at least one component being firmly subsolar, below
the minimum mass of a neutron star. This discards the hypothesis that the
signal comes from a standard binary neutron star. The signal coherence test
between the two LIGO detectors brings support to a compact object coalescence
origin.
| [
{
"created": "Mon, 27 Nov 2023 18:54:18 GMT",
"version": "v1"
}
] | 2023-11-28 | [
[
"Prunier",
"Marine",
""
],
[
"Morrás",
"Gonzalo",
""
],
[
"Siles",
"José Francisco Nuño",
""
],
[
"Clesse",
"Sebastien",
""
],
[
"García-Bellido",
"Juan",
""
],
[
"Morales",
"Ester Ruiz",
""
]
] | A follow-up of a subsolar black hole candidate identified in the second part of the third observing run of the LIGO-Virgo-KAGRA collaboration is carried out. With a search signal-to-noise ratio of $8.90$ and a false-alarm rate of 1 per 5 years, close to the usual thresholds for claiming a gravitational-wave event, we cannot exclude a noise origin. A complete Bayesian parameter estimation of this candidate, denoted SSM200308, reveals that if the signal originates from a compact binary coalescence, the component masses are $m_1= 0.62^{+0.46}_{-0.20} M_{\odot}$ and $m_2 = 0.27^{+0.12}_{-0.10} M_{\odot}$ (90% credible intervals) with at least one component being firmly subsolar, below the minimum mass of a neutron star. This discards the hypothesis that the signal comes from a standard binary neutron star. The signal coherence test between the two LIGO detectors brings support to a compact object coalescence origin. |
1207.2504 | Steven Carlip | S. Carlip | Challenges for Emergent Gravity | 18 pages; v2: added discussion of TDiff invariance, emergence of
diffeomorphism invariance, and more references | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The idea of gravity as an "emergent" phenomenon has gained popularity in
recent years. I discuss some of the obstacles that any such model must overcome
in order to agree with the observational underpinnings of general relativity.
| [
{
"created": "Tue, 10 Jul 2012 22:35:23 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jul 2012 23:04:42 GMT",
"version": "v2"
}
] | 2012-07-23 | [
[
"Carlip",
"S.",
""
]
] | The idea of gravity as an "emergent" phenomenon has gained popularity in recent years. I discuss some of the obstacles that any such model must overcome in order to agree with the observational underpinnings of general relativity. |
2304.12640 | Jose Luis Hernandez-Pastora | J.L. Hern\'andez-Pastora and L. Herrera | Non-spherical sources of Schwarzschild space-time | 16 pages, 4 figures, to appear in EPJC | Eur. Phys. J. C (2023) 83:375 | 10.1140/epjc/s10052-023-11552-5 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | While it is known that any spherical fluid distribution may only source the
spherically symmetric Schwarzschild space-time, the inverse is not true. Thus,
in this manuscript, we find exact axially symmetric and static fluid (interior)
solutions to Einstein equations, which match smoothly on the boundary surface
to the Schwarzschild (exterior) space-time, even though the fluid distribution
is not endowed with spherical symmetry. The solutions are obtained by using the
general approach outlined in [1], and satisfy the usual requirements imposed to
any physically admissible interior solution. A discussion about the physical
and geometric properties of the source is presented. The relativistic multipole
moments (RMM) are explicitly calculated in terms of the physical variables,
allowing to prove that spherical sources can only match to the Schwarzschild
space-time. The complexity of the source is evaluated through the complexity
factors. It is shown that there is only one independent complexity factor, as
in the spherically symmetric case.
| [
{
"created": "Tue, 25 Apr 2023 08:11:59 GMT",
"version": "v1"
}
] | 2023-05-09 | [
[
"Hernández-Pastora",
"J. L.",
""
],
[
"Herrera",
"L.",
""
]
] | While it is known that any spherical fluid distribution may only source the spherically symmetric Schwarzschild space-time, the inverse is not true. Thus, in this manuscript, we find exact axially symmetric and static fluid (interior) solutions to Einstein equations, which match smoothly on the boundary surface to the Schwarzschild (exterior) space-time, even though the fluid distribution is not endowed with spherical symmetry. The solutions are obtained by using the general approach outlined in [1], and satisfy the usual requirements imposed to any physically admissible interior solution. A discussion about the physical and geometric properties of the source is presented. The relativistic multipole moments (RMM) are explicitly calculated in terms of the physical variables, allowing to prove that spherical sources can only match to the Schwarzschild space-time. The complexity of the source is evaluated through the complexity factors. It is shown that there is only one independent complexity factor, as in the spherically symmetric case. |
1809.07781 | Cormac Breen | Cormac Breen, Peter Taylor | Vacuum polarization for varying quantum scalar field parameters in
Schwarzschild-anti-de Sitter spacetime | 15 pages, 9 figures | Phys. Rev. D 98, 105006 (2018) | 10.1103/PhysRevD.98.105006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Equipped with new powerful and efficient methods for computing quantum
expectation values in static-spherically symmetric spacetimes in arbitrary
dimensions, we perform an in-depth investigation of how the quantum vacuum
polarization varies with the parameters in the theory. In particular, we
compute and compare the vacuum polarization for a quantum scalar field in the
Schwarzschild anti-de Sitter black hole spacetime for a range of values of the
field mass and field coupling constant as well as the black hole mass and
number of spacetime dimensions. In addition, a new approximation for the vacuum
polarization in asymptotically anti-de Sitter black hole spacetimes is
presented.
| [
{
"created": "Thu, 20 Sep 2018 18:01:00 GMT",
"version": "v1"
}
] | 2018-11-21 | [
[
"Breen",
"Cormac",
""
],
[
"Taylor",
"Peter",
""
]
] | Equipped with new powerful and efficient methods for computing quantum expectation values in static-spherically symmetric spacetimes in arbitrary dimensions, we perform an in-depth investigation of how the quantum vacuum polarization varies with the parameters in the theory. In particular, we compute and compare the vacuum polarization for a quantum scalar field in the Schwarzschild anti-de Sitter black hole spacetime for a range of values of the field mass and field coupling constant as well as the black hole mass and number of spacetime dimensions. In addition, a new approximation for the vacuum polarization in asymptotically anti-de Sitter black hole spacetimes is presented. |
2112.09589 | Peter Horvathy | P.-M. Zhang, Q.-L. Zhao, P. A. Horvathy | Gravitational Waves and Conformal Time Transformations | Reorganised and refined. Title shortened. 27 pages, 4 double figures.
The Conclusion expanded with an Outlook for further research and additional
references . Accepted for publication in Ann. Phys. (N.Y.) | null | 10.1016/j.aop.2022.168833 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent interest in the "memory effect" prompted us to revisit the relation of
gravitational aves and oscillators. 50 years ago Niederer [1] found that an
isotropic harmonic oscillator with a constant frequency can be mapped onto a
free particle. Later Takagi [2] has shown that "time-dependent scaling" extends
the oscillator versus free particle correspondence to a time-dependent
frequency when the scale factor satisfies a Sturm-Liouville equation. More
recently Gibbons [3] pointed out that time redefinition is conveniently studied
in terms of the Schwarzian derivative. The oscillator versus free particle
correspondence "Eisenhart-Duval lifts" to a conformal transformation between
Bargmann spaces [4-7]. These methods are extended to spacetimes which are not
conformally flat and have a time-dependent profile, and can then be applied to
the geodesic motion in a plane gravitational wave.
| [
{
"created": "Fri, 17 Dec 2021 16:03:10 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jan 2022 16:04:48 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Feb 2022 08:23:25 GMT",
"version": "v3"
},
{
"created": "Fri, 11 Mar 2022 17:33:34 GMT",
"version": "v4"
}
] | 2022-05-04 | [
[
"Zhang",
"P. -M.",
""
],
[
"Zhao",
"Q. -L.",
""
],
[
"Horvathy",
"P. A.",
""
]
] | Recent interest in the "memory effect" prompted us to revisit the relation of gravitational aves and oscillators. 50 years ago Niederer [1] found that an isotropic harmonic oscillator with a constant frequency can be mapped onto a free particle. Later Takagi [2] has shown that "time-dependent scaling" extends the oscillator versus free particle correspondence to a time-dependent frequency when the scale factor satisfies a Sturm-Liouville equation. More recently Gibbons [3] pointed out that time redefinition is conveniently studied in terms of the Schwarzian derivative. The oscillator versus free particle correspondence "Eisenhart-Duval lifts" to a conformal transformation between Bargmann spaces [4-7]. These methods are extended to spacetimes which are not conformally flat and have a time-dependent profile, and can then be applied to the geodesic motion in a plane gravitational wave. |
2007.03401 | Yujie Tan | Cheng-Gang Qin, Yu-Jie Tan, Ya-Fen Chen, and Cheng-Gang Shao | Light propagation in the field of the N-body system and the application
in the TianQin mission | null | null | 10.1103/PhysRevD.100.064063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given the high-precision modern space mission, a precise relativistic
modeling of observations is required. By solving the eikonal equation with the
post-Newtonian approximation, the light propagation is determined by the
iterative method in the gravitational field of an isolated, gravitationally
bound N-body system. Different from the traditional $N$ bodies that are
independent with each other in the system, our system includes the velocities,
accelerations, gravitational interactions and tidal deformations of the
gravitational bodies. The light delays of these factors then are precisely
determined by the analytical solutions. These delays are significant and are
likely to reach a detectable level for the \emph{strong} gravitational fields,
such as binary pulsars and some gravitational wave sources. The result's
application in the vicinity of the Earth provides a relativistic framework for
modern space missions. From the relativistic analysis in the TianQin mission,
we find the possible tests for the alternative gravitational theories, such as
a possible determination for the post-Newtonian parameter $\gamma$ in the level
of some scalar-tensor theories of gravity.
| [
{
"created": "Tue, 7 Jul 2020 13:10:07 GMT",
"version": "v1"
}
] | 2020-07-08 | [
[
"Qin",
"Cheng-Gang",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Chen",
"Ya-Fen",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | Given the high-precision modern space mission, a precise relativistic modeling of observations is required. By solving the eikonal equation with the post-Newtonian approximation, the light propagation is determined by the iterative method in the gravitational field of an isolated, gravitationally bound N-body system. Different from the traditional $N$ bodies that are independent with each other in the system, our system includes the velocities, accelerations, gravitational interactions and tidal deformations of the gravitational bodies. The light delays of these factors then are precisely determined by the analytical solutions. These delays are significant and are likely to reach a detectable level for the \emph{strong} gravitational fields, such as binary pulsars and some gravitational wave sources. The result's application in the vicinity of the Earth provides a relativistic framework for modern space missions. From the relativistic analysis in the TianQin mission, we find the possible tests for the alternative gravitational theories, such as a possible determination for the post-Newtonian parameter $\gamma$ in the level of some scalar-tensor theories of gravity. |
0902.2304 | Supratik Pal Dr | Sudipta Das, Subir Ghosh, Jan-Willem van Holten, Supratik Pal | Generalized particle dynamics: modifying the motion of particles and
branes | 17 pages, 2 figures. Minor revisions. To appear in JHEP | JHEP 0904:115,2009; Erratum-ibid.1103:118,2011 | 10.1088/1126-6708/2009/04/115 10.1007/JHEP03(2011)118 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a generalized dynamics for particles moving in a symmetric
space-time, i.e. a space-time admitting one or more Killing vectors. The
generalization implies that the effective mass of particles becomes dynamical.
We apply this generalized dynamics to the motion of test particles in a static,
spherically symmetric metric. A significant consequence of the new framework is
to generate an effective negative pressure on a cosmological surface whose
expansion is manifest by the particle trajectory via embedding geometry
\cite{bwg,embed2,embed,pal}. This formalism thus may give rise to a source for
dark energy in modeling the late accelerating universe.
| [
{
"created": "Fri, 13 Feb 2009 12:46:32 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Apr 2009 11:47:03 GMT",
"version": "v2"
}
] | 2011-03-31 | [
[
"Das",
"Sudipta",
""
],
[
"Ghosh",
"Subir",
""
],
[
"van Holten",
"Jan-Willem",
""
],
[
"Pal",
"Supratik",
""
]
] | We construct a generalized dynamics for particles moving in a symmetric space-time, i.e. a space-time admitting one or more Killing vectors. The generalization implies that the effective mass of particles becomes dynamical. We apply this generalized dynamics to the motion of test particles in a static, spherically symmetric metric. A significant consequence of the new framework is to generate an effective negative pressure on a cosmological surface whose expansion is manifest by the particle trajectory via embedding geometry \cite{bwg,embed2,embed,pal}. This formalism thus may give rise to a source for dark energy in modeling the late accelerating universe. |
1103.2149 | Priscilla Canizares | Priscilla Canizares and Carlos F. Sopuerta | Time-domain modelling of Extreme-Mass-Ratio Inspirals for the Laser
Interferometer Space Antenna | 4 pages, 2 figures, JPCS latex style. Submitted to JPCS (special
issue for the proceedings of the Spanish Relativity Meeting (ERE2010)) | J.Phys.Conf.Ser.314:012075,2011 | 10.1088/1742-6596/314/1/012075 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When a stellar-mass compact object is captured by a supermassive black hole
located in a galactic centre, the system losses energy and angular momentum by
the emission of gravitational waves. Subsequently, the stellar compact object
evolves inspiraling until plunging onto the massive black hole. These EMRI
systems are expected to be one of the main sources of gravitational waves for
the future space-based Laser Interferometer Space Antenna (LISA). However, the
detection of EMRI signals will require of very accurate theoretical templates
taking into account the gravitational self-force, which is the responsible of
the stellar-compact object inspiral. Due to its potential applicability on
EMRIs, the obtention of an efficient method to compute the scalar self-force
acting on a point-like particle orbiting around a massive black hole is being
object of increasing interest. We present here a review of our time-domain
numerical technique to compute the self-force acting on a point-like particle
and we show its suitability to deal with both circular and eccentric orbits.
| [
{
"created": "Thu, 10 Mar 2011 21:54:35 GMT",
"version": "v1"
}
] | 2011-09-28 | [
[
"Canizares",
"Priscilla",
""
],
[
"Sopuerta",
"Carlos F.",
""
]
] | When a stellar-mass compact object is captured by a supermassive black hole located in a galactic centre, the system losses energy and angular momentum by the emission of gravitational waves. Subsequently, the stellar compact object evolves inspiraling until plunging onto the massive black hole. These EMRI systems are expected to be one of the main sources of gravitational waves for the future space-based Laser Interferometer Space Antenna (LISA). However, the detection of EMRI signals will require of very accurate theoretical templates taking into account the gravitational self-force, which is the responsible of the stellar-compact object inspiral. Due to its potential applicability on EMRIs, the obtention of an efficient method to compute the scalar self-force acting on a point-like particle orbiting around a massive black hole is being object of increasing interest. We present here a review of our time-domain numerical technique to compute the self-force acting on a point-like particle and we show its suitability to deal with both circular and eccentric orbits. |
gr-qc/9806066 | David Polarski | Claus Kiefer, Julien Lesgourgues, David Polarski and Alexei A.
Starobinsky | The Coherence of Primordial Fluctuations Produced During Inflation | LaTeX (7 pages) | Class.Quant.Grav.15:L67-L72,1998 | 10.1088/0264-9381/15/10/002 | LMPT 06/98 | gr-qc astro-ph hep-th | null | The behaviour of quantum metric perturbations produced during inflation is
considered at the stage after the second Hubble radius crossing. It is shown
that the classical correlation between amplitude and momentum of a perturbation
mode, previously shown to emerge in the course of an effective
quantum-to-classical transition, is maintained for a sufficiently long time,
and we present the explicit form in which it takes place using the Wigner
function. We further show with a simple diffraction experiment that quantum
interference, non-expressible in terms of a classical stochastic description of
the perturbations, is essentially suppressed. Rescattering of the perturbations
leads to a comparatively slow decay of this correlation and to a complete
stochastization of the system.
| [
{
"created": "Mon, 15 Jun 1998 21:08:57 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Kiefer",
"Claus",
""
],
[
"Lesgourgues",
"Julien",
""
],
[
"Polarski",
"David",
""
],
[
"Starobinsky",
"Alexei A.",
""
]
] | The behaviour of quantum metric perturbations produced during inflation is considered at the stage after the second Hubble radius crossing. It is shown that the classical correlation between amplitude and momentum of a perturbation mode, previously shown to emerge in the course of an effective quantum-to-classical transition, is maintained for a sufficiently long time, and we present the explicit form in which it takes place using the Wigner function. We further show with a simple diffraction experiment that quantum interference, non-expressible in terms of a classical stochastic description of the perturbations, is essentially suppressed. Rescattering of the perturbations leads to a comparatively slow decay of this correlation and to a complete stochastization of the system. |
2207.09214 | Bin Wu | Bin Wu, Tomohiro Ishikawa, Shoki Iwaguchi, Ryuma Shimizu, Izumi
Watanabe, Yuki Kawasaki, Yuta Michimura, Shuichiro Yokoyama, Seiji Kawamura | Conceptual design and science cases of a juggled interferometer for
gravitational wave detection | 11 pages, 9 figures | null | 10.1103/PhysRevD.106.042007 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Juggled interferometer (JIFO) is an earth-based gravitational wave
detector using repeatedly free-falling test masses. With no worries of seismic
noise and suspension thermal noise, the JIFO can have much better sensitivity
at lower frequencies than the current earth-based gravitational wave detectors.
The data readout method of a JIFO could be challenging if one adopts the
fringe-locking method. We present a phase reconstruction method in this paper
by building up a complex function which has a fringe-independent
signal-to-noise ratio. Considering the displacement noise budget of the
Einstein Telescope (ET), we show that the juggled test masses significantly
improve the sensitivity at 0.1-2.5$\,$Hz even with discontinuous data. The
science cases brought with the improved sensitivity would include detecting
quasi-normal modes of black holes with $10^4-10^5\,M_{\odot}$, testing
Brans-Dicke theory with black-hole and neutron-star inspirals, and detecting
primordial-black-hole-related gravitational waves.
| [
{
"created": "Tue, 19 Jul 2022 12:01:17 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Wu",
"Bin",
""
],
[
"Ishikawa",
"Tomohiro",
""
],
[
"Iwaguchi",
"Shoki",
""
],
[
"Shimizu",
"Ryuma",
""
],
[
"Watanabe",
"Izumi",
""
],
[
"Kawasaki",
"Yuki",
""
],
[
"Michimura",
"Yuta",
""
],
[
"Yokoyama",
"Shuichiro",
""
],
[
"Kawamura",
"Seiji",
""
]
] | The Juggled interferometer (JIFO) is an earth-based gravitational wave detector using repeatedly free-falling test masses. With no worries of seismic noise and suspension thermal noise, the JIFO can have much better sensitivity at lower frequencies than the current earth-based gravitational wave detectors. The data readout method of a JIFO could be challenging if one adopts the fringe-locking method. We present a phase reconstruction method in this paper by building up a complex function which has a fringe-independent signal-to-noise ratio. Considering the displacement noise budget of the Einstein Telescope (ET), we show that the juggled test masses significantly improve the sensitivity at 0.1-2.5$\,$Hz even with discontinuous data. The science cases brought with the improved sensitivity would include detecting quasi-normal modes of black holes with $10^4-10^5\,M_{\odot}$, testing Brans-Dicke theory with black-hole and neutron-star inspirals, and detecting primordial-black-hole-related gravitational waves. |
1912.05824 | Shibendu Gupta Choudhury | Shibendu Gupta Choudhury, Soumya Chakrabarti, Ananda Dasgupta and
Narayan Banerjee | Self Similar Collapse and the Raychaudhuri equation | 7 pages, to appear in EPJC | Eur. Phys. J. C (2019) 79: 1027 | 10.1140/epjc/s10052-019-7559-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The role of the Raychaudhuri equation in studying gravitational collapse is
discussed. A self-similar distribution of a scalar field along with an
imperfect fluid in a conformally flat spacetime is considered for the purpose.
The general focusing condition is found out and verified against the available
exact solutions. The connection between the Raychaudhuri equation and the
critical phenomena is also explored.
| [
{
"created": "Thu, 12 Dec 2019 08:12:25 GMT",
"version": "v1"
}
] | 2019-12-30 | [
[
"Choudhury",
"Shibendu Gupta",
""
],
[
"Chakrabarti",
"Soumya",
""
],
[
"Dasgupta",
"Ananda",
""
],
[
"Banerjee",
"Narayan",
""
]
] | The role of the Raychaudhuri equation in studying gravitational collapse is discussed. A self-similar distribution of a scalar field along with an imperfect fluid in a conformally flat spacetime is considered for the purpose. The general focusing condition is found out and verified against the available exact solutions. The connection between the Raychaudhuri equation and the critical phenomena is also explored. |
gr-qc/0202004 | Leonid V. Verozub | L.V.Verozub | Metric-Field Approach to Gravitation and the Problem of the Universe
Acceleration | LaTex2e, 10 pages, 2 figures. To appear in the Proc.of the
Conf."Cosmology and Elementary particle physics" at Coral Gables, December
11-16,2001 | null | 10.1063/1.1492151 | null | gr-qc | null | A metric-field approach to gravitation is presented. It is based on an idea
of dependency of space-time properties on measuring instruments. Some bimetric
equations that realize this idea are considered. They were tested by the binary
pulsar PSR1913+16. The spherically - symmetric solution of the equations has no
event horizon and no physical singularity in the center. The proper energy of a
point particle is finite. There can exist supermassive compact configurations
of degenerated Fermi-gas which can be identified with observed objects in
galactic centers. The problem of the Universe acceleration has a natural
explanation.
| [
{
"created": "Sat, 2 Feb 2002 12:04:24 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Verozub",
"L. V.",
""
]
] | A metric-field approach to gravitation is presented. It is based on an idea of dependency of space-time properties on measuring instruments. Some bimetric equations that realize this idea are considered. They were tested by the binary pulsar PSR1913+16. The spherically - symmetric solution of the equations has no event horizon and no physical singularity in the center. The proper energy of a point particle is finite. There can exist supermassive compact configurations of degenerated Fermi-gas which can be identified with observed objects in galactic centers. The problem of the Universe acceleration has a natural explanation. |
1304.0210 | Patrick Sutton | Patrick J. Sutton | A Rule of Thumb for the Detectability of Gravitational-Wave Bursts | 8 pages, 1 figure | null | null | LIGO-P1000041-v3 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a simple relationship between the energy emitted in gravitational
waves for a narrowband source and the distance to which that emission can be
detected by a single detector. We consider linearly polarized, elliptically
polarized, and unpolarized gravitational waves, and emission patterns
appropriate for each of these cases. We ignore cosmological effects.
| [
{
"created": "Sun, 31 Mar 2013 14:28:40 GMT",
"version": "v1"
}
] | 2013-04-02 | [
[
"Sutton",
"Patrick J.",
""
]
] | We derive a simple relationship between the energy emitted in gravitational waves for a narrowband source and the distance to which that emission can be detected by a single detector. We consider linearly polarized, elliptically polarized, and unpolarized gravitational waves, and emission patterns appropriate for each of these cases. We ignore cosmological effects. |
0804.0594 | Bruno Giacomazzo | Luca Baiotti, Bruno Giacomazzo, Luciano Rezzolla | Accurate evolutions of inspiralling neutron-star binaries: prompt and
delayed collapse to black hole | 35 pages, 29 figures, corrected few typos to match the published
version. High-resolution figures and animations can be found at
http://numrel.aei.mpg.de/Visualisations/Archive/BinaryNeutronStars/Relativistic_Meudon/index.html | Phys.Rev.D78:084033,2008 | 10.1103/PhysRevD.78.084033 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary neutron-star (BNS) systems represent primary sources for the
gravitational-wave (GW) detectors. We present a systematic investigation in
full GR of the dynamics and GW emission from BNS which inspiral and merge,
producing a black hole (BH) surrounded by a torus. Our results represent the
state of the art from several points of view: (i) We use HRSC methods for the
hydrodynamics equations and high-order finite-differencing techniques for the
Einstein equations; (ii) We employ AMR techniques with "moving boxes"; (iii) We
use as initial data BNSs in irrotational quasi-circular orbits; (iv) We exploit
the isolated-horizon formalism to measure the properties of the BHs produced in
the merger; (v) Finally, we use two approaches, based either on gauge-invariant
perturbations or on Weyl scalars, to calculate the GWs. These techniques allow
us to perform accurate evolutions on timescales never reported before (ie ~30
ms) and to provide the first complete description of the inspiral and merger of
a BNS leading to the prompt or delayed formation of a BH and to its ringdown.
We consider either a polytropic or an ideal fluid EOS and show that already
with this idealized EOSs a very interesting phenomenology emerges. In
particular, we show that while high-mass binaries lead to the prompt formation
of a rapidly rotating BH surrounded by a dense torus, lower-mass binaries give
rise to a differentially rotating NS, which undergoes large oscillations and
emits large amounts of GWs. Eventually, also the NS collapses to a rotating BH
surrounded by a torus. Finally, we also show that the use of a non-isentropic
EOS leads to significantly different evolutions, giving rise to a delayed
collapse also with high-mass binaries, as well as to a more intense emission of
GWs and to a geometrically thicker torus.
| [
{
"created": "Thu, 3 Apr 2008 17:40:45 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 2008 19:51:32 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Oct 2008 13:34:23 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Baiotti",
"Luca",
""
],
[
"Giacomazzo",
"Bruno",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Binary neutron-star (BNS) systems represent primary sources for the gravitational-wave (GW) detectors. We present a systematic investigation in full GR of the dynamics and GW emission from BNS which inspiral and merge, producing a black hole (BH) surrounded by a torus. Our results represent the state of the art from several points of view: (i) We use HRSC methods for the hydrodynamics equations and high-order finite-differencing techniques for the Einstein equations; (ii) We employ AMR techniques with "moving boxes"; (iii) We use as initial data BNSs in irrotational quasi-circular orbits; (iv) We exploit the isolated-horizon formalism to measure the properties of the BHs produced in the merger; (v) Finally, we use two approaches, based either on gauge-invariant perturbations or on Weyl scalars, to calculate the GWs. These techniques allow us to perform accurate evolutions on timescales never reported before (ie ~30 ms) and to provide the first complete description of the inspiral and merger of a BNS leading to the prompt or delayed formation of a BH and to its ringdown. We consider either a polytropic or an ideal fluid EOS and show that already with this idealized EOSs a very interesting phenomenology emerges. In particular, we show that while high-mass binaries lead to the prompt formation of a rapidly rotating BH surrounded by a dense torus, lower-mass binaries give rise to a differentially rotating NS, which undergoes large oscillations and emits large amounts of GWs. Eventually, also the NS collapses to a rotating BH surrounded by a torus. Finally, we also show that the use of a non-isentropic EOS leads to significantly different evolutions, giving rise to a delayed collapse also with high-mass binaries, as well as to a more intense emission of GWs and to a geometrically thicker torus. |
gr-qc/0401051 | Kuiroukidis | A. Kuiroukidis and D.B. Papadopoulos (Thessaloniki) | Pre-Inflation in the Presence of Conformal Coupling | 11 pages, 5 figures, LaTeX, Accepted for publication in MPLA | Mod.Phys.Lett. A19 (2004) 807-816 | 10.1142/S0217732304013386 | null | gr-qc | null | We consider a massless scalar field, conformally coupled to the Ricci scalar
curvature, in the pre-inflation era of a closed FLRW Universe. The scalar field
potential can be of the form of the Coleman-Weinberg one-loop potential, which
is flat at the origin and drives the inflationary evolution. For positive
values of the conformal parameter \xi, less than the critical value xi_c=(1/6),
the model admits exact solutions with non-zero scale factor and zero initial
Hubble parameter. Thus these solutions can be matched smoothly to the so called
Pre-Big-Bang models. At the end of this pre-inflation era one can match
inflationary solutions by specifying the form of the potential and the whole
solution is of the class C^(1).
| [
{
"created": "Tue, 13 Jan 2004 10:13:00 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Kuiroukidis",
"A.",
"",
"Thessaloniki"
],
[
"Papadopoulos",
"D. B.",
"",
"Thessaloniki"
]
] | We consider a massless scalar field, conformally coupled to the Ricci scalar curvature, in the pre-inflation era of a closed FLRW Universe. The scalar field potential can be of the form of the Coleman-Weinberg one-loop potential, which is flat at the origin and drives the inflationary evolution. For positive values of the conformal parameter \xi, less than the critical value xi_c=(1/6), the model admits exact solutions with non-zero scale factor and zero initial Hubble parameter. Thus these solutions can be matched smoothly to the so called Pre-Big-Bang models. At the end of this pre-inflation era one can match inflationary solutions by specifying the form of the potential and the whole solution is of the class C^(1). |
1606.05211 | Emilio Elizalde | Emilio Elizalde, Andrey N. Makarenko | Singular inflation from Born-Infeld-f(R) gravity | 8 pages, 14 figures; version to appear in MPLA | null | 10.1142/S0217732316501492 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Accelerating dynamics from Born-Infeld-$f(R)$ gravity are studied in a
simplified conformal approach without matter. Explicit unification of inflation
with late-time acceleration is realized within this singular inflation
approach, which is similar to Odintsov-Oikonomou singular $f(R)$ inflation. Our
model turns out to be consistent with the latest release of Planck data.
| [
{
"created": "Thu, 16 Jun 2016 14:49:25 GMT",
"version": "v1"
}
] | 2016-08-17 | [
[
"Elizalde",
"Emilio",
""
],
[
"Makarenko",
"Andrey N.",
""
]
] | Accelerating dynamics from Born-Infeld-$f(R)$ gravity are studied in a simplified conformal approach without matter. Explicit unification of inflation with late-time acceleration is realized within this singular inflation approach, which is similar to Odintsov-Oikonomou singular $f(R)$ inflation. Our model turns out to be consistent with the latest release of Planck data. |
gr-qc/0202087 | Marc Mars | Marc Mars | Axially symmetric Einstein-Straus models | Latex, no figures | Phys.Rev. D57 (1998) 3389-3400 | 10.1103/PhysRevD.57.3389 | null | gr-qc | null | The existence of static and axially symmetric regions in a Friedman-Lemaitre
cosmology is investigated under the only assumption that the cosmic time and
the static time match properly on the boundary hypersurface. It turns out that
the most general form for the static region is a two-sphere with arbitrarily
changing radius which moves along the axis of symmetry in a determined way. The
geometry of the interior region is completely determined in terms of background
objects. When any of the most widely used energy-momentum contents for the
interior region is imposed, both the interior geometry and the shape of the
static region must become exactly spherically symmetric. This shows that the
Einstein-Straus model, which is the generally accepted answer for the null
influence of the cosmic expansion on the local physics, is not a robust model
and it is rather an exceptional and isolated situation. Hence, its suitability
for solving the interplay between cosmic expansion and local physics is
doubtful and more adequate models should be investigated.
| [
{
"created": "Sat, 23 Feb 2002 18:26:15 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Mars",
"Marc",
""
]
] | The existence of static and axially symmetric regions in a Friedman-Lemaitre cosmology is investigated under the only assumption that the cosmic time and the static time match properly on the boundary hypersurface. It turns out that the most general form for the static region is a two-sphere with arbitrarily changing radius which moves along the axis of symmetry in a determined way. The geometry of the interior region is completely determined in terms of background objects. When any of the most widely used energy-momentum contents for the interior region is imposed, both the interior geometry and the shape of the static region must become exactly spherically symmetric. This shows that the Einstein-Straus model, which is the generally accepted answer for the null influence of the cosmic expansion on the local physics, is not a robust model and it is rather an exceptional and isolated situation. Hence, its suitability for solving the interplay between cosmic expansion and local physics is doubtful and more adequate models should be investigated. |
1610.01246 | Zichang Huang | Muxin Han and Zichang Huang | SU(2) Flat Connection on Riemann Surface and Twisted Geometry with
Cosmological Constant | 10+2 pages, 21 figures | Phys. Rev. D 95, 044018 (2017) | 10.1103/PhysRevD.95.044018 | null | gr-qc hep-th math-ph math.GT math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | SU(2) flat connection on 2D Riemann surface is shown to relate to the
generalized twisted geometry in 3D space with cosmological constant. Various
flat connection quantities on Riemann surface are mapped to the geometrical
quantities in discrete 3D space. We propose that the moduli space of SU(2) flat
connections on Riemann surface generalizes the phase space of twisted geometry
or Loop Quantum Gravity to include the cosmological constant.
| [
{
"created": "Wed, 5 Oct 2016 01:18:25 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2017 05:19:39 GMT",
"version": "v2"
}
] | 2017-03-01 | [
[
"Han",
"Muxin",
""
],
[
"Huang",
"Zichang",
""
]
] | SU(2) flat connection on 2D Riemann surface is shown to relate to the generalized twisted geometry in 3D space with cosmological constant. Various flat connection quantities on Riemann surface are mapped to the geometrical quantities in discrete 3D space. We propose that the moduli space of SU(2) flat connections on Riemann surface generalizes the phase space of twisted geometry or Loop Quantum Gravity to include the cosmological constant. |
2010.07224 | Quentin Baghi | Quentin Baghi, James Ira Thorpe, Jacob Slutsky, John Baker | A statistical inference approach to time-delay interferometry for
gravitational-wave detection | More realistic gravitational-wave source used as a case study.
Figures 3-7 modified. Rationale and conclusions unchanged | Phys. Rev. D 103, 042006 (2021) | 10.1103/PhysRevD.103.042006 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The future space-based gravitational wave observatory LISA will consist of a
constellation of three spacecraft in a triangular constellation, connected by
laser interferometers with 2.5 million-kilometer arms. Among other challenges,
the success of the mission strongly depends on the quality of the cancellation
of laser frequency noise, whose power lies eight orders of magnitude above the
gravitational signal. The standard technique to perform noise removal is
time-delay interferometry (TDI). TDI constructs linear combinations of delayed
phasemeter measurements tailored to cancel laser noise terms. Previous work has
demonstrated the relationship between TDI and principal component analysis
(PCA). We build on this idea to develop an extension of TDI based on a model
likelihood that directly depends on the phasemeter measurements. Assuming
stationary Gaussian noise, we decompose the measurement covariance using PCA in
the frequency domain. We obtain a comprehensive and compact framework that we
call PCI for "principal component interferometry," and show that it provides an
optimal description of the LISA data analysis problem.
| [
{
"created": "Wed, 14 Oct 2020 16:38:49 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2022 07:59:40 GMT",
"version": "v2"
}
] | 2022-04-27 | [
[
"Baghi",
"Quentin",
""
],
[
"Thorpe",
"James Ira",
""
],
[
"Slutsky",
"Jacob",
""
],
[
"Baker",
"John",
""
]
] | The future space-based gravitational wave observatory LISA will consist of a constellation of three spacecraft in a triangular constellation, connected by laser interferometers with 2.5 million-kilometer arms. Among other challenges, the success of the mission strongly depends on the quality of the cancellation of laser frequency noise, whose power lies eight orders of magnitude above the gravitational signal. The standard technique to perform noise removal is time-delay interferometry (TDI). TDI constructs linear combinations of delayed phasemeter measurements tailored to cancel laser noise terms. Previous work has demonstrated the relationship between TDI and principal component analysis (PCA). We build on this idea to develop an extension of TDI based on a model likelihood that directly depends on the phasemeter measurements. Assuming stationary Gaussian noise, we decompose the measurement covariance using PCA in the frequency domain. We obtain a comprehensive and compact framework that we call PCI for "principal component interferometry," and show that it provides an optimal description of the LISA data analysis problem. |
gr-qc/0204080 | Jeremy S. Heyl | Ramesh Narayan (IAS and Harvard-Smithonian CfA) and Jeremy S. Heyl
(Harvard-Smithsonian CfA) | Evidence for the Black Hole Event Horizon | 10 pages, 1 figure; Invited contribution to the Coral Gables
Conference on High Energy Physics and Cosmology, December, 2001 (eds. B.
Kursunoglu and A. Perlmutter; American Institute of Physics Conference
Proceedings). After it is published, it will be found at
http://proceedings.aip.org/proceedings/ | null | 10.1063/1.1492161 | null | gr-qc astro-ph | null | Roughly a dozen X-ray binaries are presently known in which the compact
accreting primary stars are too massive to be neutron stars. These primaries
are identified as black holes, though there is as yet no definite proof that
any of the candidate black holes actually possesses an event horizon. We
discuss how Type I X-ray bursts may be used to verify the presence of the event
horizon in these objects. Type I bursts are caused by thermonuclear explosions
when gas accretes onto a compact star. The bursts are commonly seen in many
neutron star X-ray binaries, but they have never been seen in any black hole
X-ray binary. Our model calculations indicate that black hole candidates ought
to burst frequently if they have surfaces. Based on this, we argue that the
lack of bursts constitutes strong evidence for the presence of event horizons
in these objects.
| [
{
"created": "Fri, 26 Apr 2002 14:08:36 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Narayan",
"Ramesh",
"",
"IAS and Harvard-Smithonian CfA"
],
[
"Heyl",
"Jeremy S.",
"",
"Harvard-Smithsonian CfA"
]
] | Roughly a dozen X-ray binaries are presently known in which the compact accreting primary stars are too massive to be neutron stars. These primaries are identified as black holes, though there is as yet no definite proof that any of the candidate black holes actually possesses an event horizon. We discuss how Type I X-ray bursts may be used to verify the presence of the event horizon in these objects. Type I bursts are caused by thermonuclear explosions when gas accretes onto a compact star. The bursts are commonly seen in many neutron star X-ray binaries, but they have never been seen in any black hole X-ray binary. Our model calculations indicate that black hole candidates ought to burst frequently if they have surfaces. Based on this, we argue that the lack of bursts constitutes strong evidence for the presence of event horizons in these objects. |
2210.07525 | Subenoy Chakraborty | Dhritimalya Roy, Ayanendu Dutta, Subenoy Chakraborty | Does violation of Cosmic No-hair Conjecture guarantee the existence of
Wormhole? | null | Europhysics Letters 140, 19002 (2022) | 10.1209/0295-5075/ac969d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work investigates the interrelation between the validity (or
violation) of the cosmic no-hair conjecture and the existence (or
non-existence) of wormholes, both in Einstein's Gravity and in modified gravity
theories. It is found that the existence of wormholes implies a violation of
the cosmic no-hair conjecture, and the validity of the cosmic no-hair
conjecture implies the non-existence of wormholes but not the reverse way both
in Einstein's Gravity and in modified gravity theories. We will also re-visit
the gravitational entropy predictions of the wormhole and show how they are
connected.
| [
{
"created": "Fri, 14 Oct 2022 05:12:09 GMT",
"version": "v1"
}
] | 2022-10-17 | [
[
"Roy",
"Dhritimalya",
""
],
[
"Dutta",
"Ayanendu",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present work investigates the interrelation between the validity (or violation) of the cosmic no-hair conjecture and the existence (or non-existence) of wormholes, both in Einstein's Gravity and in modified gravity theories. It is found that the existence of wormholes implies a violation of the cosmic no-hair conjecture, and the validity of the cosmic no-hair conjecture implies the non-existence of wormholes but not the reverse way both in Einstein's Gravity and in modified gravity theories. We will also re-visit the gravitational entropy predictions of the wormhole and show how they are connected. |
2112.13049 | Shaoqi Hou | Shaoqi Hou, Tao Zhu, Zong-Hong Zhu | Conserved charges in Chern-Simons modified theory and memory effects | 34 pages. Minor changes according to Referee's suggestions | JCAP04(2022)032 | 10.1088/1475-7516/2022/04/032 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, conserved charges and fluxes at the future null infinity are
determined in the asymptotically flat spacetime for Chern-Simons modified
gravity. The flux-balance laws are used to constrain the memory effects. For
tensor memories, the Penrose's conformal completion method is used to analyze
the asymptotic structures and asymptotic symmetries, and then, conserved
charges for the Bondi-Metzner-Sachs algebra are constructed with the
Wald-Zoupas formalism. These charges take very similar forms to those in
Brans-Dicke theory. For the scalar memory, Chern-Simons modified gravity is
rewritten in the first-order formalism, and the scalar field is replaced by a
2-form field dual to it. With this dual formalism, the scalar memory is
described by the vacuum transition induced by the large gauge transformation of
the 2-form field.
| [
{
"created": "Fri, 24 Dec 2021 12:24:51 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Jan 2022 13:07:17 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Mar 2022 09:31:45 GMT",
"version": "v3"
}
] | 2022-04-22 | [
[
"Hou",
"Shaoqi",
""
],
[
"Zhu",
"Tao",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | In this work, conserved charges and fluxes at the future null infinity are determined in the asymptotically flat spacetime for Chern-Simons modified gravity. The flux-balance laws are used to constrain the memory effects. For tensor memories, the Penrose's conformal completion method is used to analyze the asymptotic structures and asymptotic symmetries, and then, conserved charges for the Bondi-Metzner-Sachs algebra are constructed with the Wald-Zoupas formalism. These charges take very similar forms to those in Brans-Dicke theory. For the scalar memory, Chern-Simons modified gravity is rewritten in the first-order formalism, and the scalar field is replaced by a 2-form field dual to it. With this dual formalism, the scalar memory is described by the vacuum transition induced by the large gauge transformation of the 2-form field. |
0803.3278 | Lorenzo Iorio | Lorenzo Iorio | Will the recently approved LARES mission be able to measure the
Lense-Thirring effect at 1%? | Latex, 15 pages, 1 table, no figures. Final version matching the
published one in General Relativity and Gravitation (GRG) | Gen.Rel.Grav.41:1717-1724,2009 | 10.1007/s10714-008-0742-1 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After the approval by the Italian Space Agency of the LARES satellite, which
should be launched at the end of 2009 with a VEGA rocket and whose claimed goal
is a about 1% measurement of the general relativistic gravitomagnetic
Lense-Thirring effect in the gravitational field of the spinning Earth, it is
of the utmost importance to reliably assess the total realistic accuracy that
can be reached by such a mission. The observable is a linear combination of the
nodes of the existing LAGEOS and LAGEOS II satellites and of LARES able to
cancel out the impact of the first two even zonal harmonic coefficients of the
multipolar expansion of the classical part of the terrestrial gravitational
potential representing a major source of systematic error. While LAGEOS and
LAGEOS II fly at altitudes of about 6000 km, LARES will be placed at an
altitude of 1450 km. Thus, it will be sensitive to much more even zonals than
LAGEOS and LAGEOS II. Their corrupting impact \delta\mu has been evaluated by
using the standard Kaula's approach up to degree L=70 along with the sigmas of
the covariance matrices of eight different global gravity solutions
(EIGEN-GRACE02S, EIGEN-CG03C, GGM02S, GGM03S, JEM01-RL03B, ITG-Grace02s,
ITG-Grace03, EGM2008) obtained by five institutions (GFZ, CSR, JPL, IGG, NGA)
with different techniques from long data sets of the dedicated GRACE mission.
It turns out \delta\mu about 100-1000% of the Lense-Thirring effect. An
improvement of 2-3 orders of magnitude in the determination of the high degree
even zonals would be required to constrain the bias to about 1-10%.
| [
{
"created": "Sat, 22 Mar 2008 22:54:21 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Apr 2008 10:00:31 GMT",
"version": "v2"
},
{
"created": "Thu, 29 May 2008 18:28:33 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Dec 2008 10:00:49 GMT",
"version": "v4"
},
{
"created": "Thu, 18 Dec 2008 13:52:23 GMT",
"version": "v5"
}
] | 2009-07-29 | [
[
"Iorio",
"Lorenzo",
""
]
] | After the approval by the Italian Space Agency of the LARES satellite, which should be launched at the end of 2009 with a VEGA rocket and whose claimed goal is a about 1% measurement of the general relativistic gravitomagnetic Lense-Thirring effect in the gravitational field of the spinning Earth, it is of the utmost importance to reliably assess the total realistic accuracy that can be reached by such a mission. The observable is a linear combination of the nodes of the existing LAGEOS and LAGEOS II satellites and of LARES able to cancel out the impact of the first two even zonal harmonic coefficients of the multipolar expansion of the classical part of the terrestrial gravitational potential representing a major source of systematic error. While LAGEOS and LAGEOS II fly at altitudes of about 6000 km, LARES will be placed at an altitude of 1450 km. Thus, it will be sensitive to much more even zonals than LAGEOS and LAGEOS II. Their corrupting impact \delta\mu has been evaluated by using the standard Kaula's approach up to degree L=70 along with the sigmas of the covariance matrices of eight different global gravity solutions (EIGEN-GRACE02S, EIGEN-CG03C, GGM02S, GGM03S, JEM01-RL03B, ITG-Grace02s, ITG-Grace03, EGM2008) obtained by five institutions (GFZ, CSR, JPL, IGG, NGA) with different techniques from long data sets of the dedicated GRACE mission. It turns out \delta\mu about 100-1000% of the Lense-Thirring effect. An improvement of 2-3 orders of magnitude in the determination of the high degree even zonals would be required to constrain the bias to about 1-10%. |
1707.02802 | {\L}ukasz Nakonieczny | {\L}ukasz Nakonieczny, Anna Nakonieczna and Marek Rogatko | Dark matter cosmic string in the gravitational field of a black hole | This is an author-created, uncopyedited version of an article
accepted for publication in Journal of Cosmology and Astroparticle Physics .
IOP Publishing Ltd is not responsible for any errors or omissions in this
version of the manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
doi.org/10.1088/1475-7516/2018/03/024. 28 pages, 8 figures | JCAP03(2018)024 | 10.1088/1475-7516/2018/03/024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examined analytically and proposed a numerical model of an Abelian Higgs
dark matter vortex in the spacetime of a stationary axisymmetric Kerr black
hole. In analytical calculations the dark matter sector was modeled by an
addition of a U (1)-gauge field coupled to the visible sector. The backreaction
analysis revealed that the impact of the dark vortex presence is far more
complicated than causing only a deficit angle. The vortex causes an ergosphere
shift and the event horizon velocity is also influenced by its presence. These
phenomena are more significant than in the case of a visible vortex sector. The
area of the event horizon of a black hole is diminished and this decline is
larger in comparison to the Kerr black hole with an Abelian Higgs vortex case.
After analyzing the gravitational properties for the general setup, we focused
on the subset of models that are motivated by particle physics. We retained the
Abelian Higgs model as a description of the dark matter sector (this sector
contained a heavy dark photon and an additional complex scalar) and added a
real scalar representing the real component of the Higgs doublet in the unitary
gauge, as well as an additional U (1)-gauge field representing an ordinary
electromagnetic field. Moreover, we considered two coupling channels between
the visible and dark sectors, which were the kinetic mixing between the gauge
fields and a quartic coupling between the scalar fields. After solving the
equations of motion for the matter fields numerically we analyzed properties of
the cosmic string in the dark matter sector and its influence on the visible
sector fields that are directly coupled to it. We found out that the presence
of the cosmic string induced spatial variation in the vacuum expectation value
of the Higgs field and a nonzero electromagnetic field around the black hole.
| [
{
"created": "Mon, 10 Jul 2017 11:31:33 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Feb 2018 11:27:49 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Mar 2018 08:14:34 GMT",
"version": "v3"
}
] | 2018-04-02 | [
[
"Nakonieczny",
"Łukasz",
""
],
[
"Nakonieczna",
"Anna",
""
],
[
"Rogatko",
"Marek",
""
]
] | We examined analytically and proposed a numerical model of an Abelian Higgs dark matter vortex in the spacetime of a stationary axisymmetric Kerr black hole. In analytical calculations the dark matter sector was modeled by an addition of a U (1)-gauge field coupled to the visible sector. The backreaction analysis revealed that the impact of the dark vortex presence is far more complicated than causing only a deficit angle. The vortex causes an ergosphere shift and the event horizon velocity is also influenced by its presence. These phenomena are more significant than in the case of a visible vortex sector. The area of the event horizon of a black hole is diminished and this decline is larger in comparison to the Kerr black hole with an Abelian Higgs vortex case. After analyzing the gravitational properties for the general setup, we focused on the subset of models that are motivated by particle physics. We retained the Abelian Higgs model as a description of the dark matter sector (this sector contained a heavy dark photon and an additional complex scalar) and added a real scalar representing the real component of the Higgs doublet in the unitary gauge, as well as an additional U (1)-gauge field representing an ordinary electromagnetic field. Moreover, we considered two coupling channels between the visible and dark sectors, which were the kinetic mixing between the gauge fields and a quartic coupling between the scalar fields. After solving the equations of motion for the matter fields numerically we analyzed properties of the cosmic string in the dark matter sector and its influence on the visible sector fields that are directly coupled to it. We found out that the presence of the cosmic string induced spatial variation in the vacuum expectation value of the Higgs field and a nonzero electromagnetic field around the black hole. |
1210.7968 | B\'arbara Montes N\'u\~nez | B. Montes N\'u\~nez, J. A. R. Cembranos and A. de la Cruz-Dombriz | On the collapse in fourth order gravities | 4 pages, 2 figures, Contribution to the Proceedings of Spanish
Relativity Meeting ERE2011, Madrid 2011 | AIP Conf.Proc. 1458 (2011) 491-494 | 10.1063/1.4734467 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational collapse in fourth order theories of gravity defined by an
arbitrary action of the scalar curvature shows significant deviations with
General Relativity. The presence of a new scalar mode produces a higher initial
contraction that favors the reduction of the collapsing time. However,
depending on the particular model, there are fundamental differences when the
modifications to the General Relativity collapse leave the linear regime. These
analyses can be used to exclude an important region of the parameter space
associated with alternative gravitational models.
| [
{
"created": "Tue, 30 Oct 2012 11:26:54 GMT",
"version": "v1"
}
] | 2012-10-31 | [
[
"Núñez",
"B. Montes",
""
],
[
"Cembranos",
"J. A. R.",
""
],
[
"de la Cruz-Dombriz",
"A.",
""
]
] | The gravitational collapse in fourth order theories of gravity defined by an arbitrary action of the scalar curvature shows significant deviations with General Relativity. The presence of a new scalar mode produces a higher initial contraction that favors the reduction of the collapsing time. However, depending on the particular model, there are fundamental differences when the modifications to the General Relativity collapse leave the linear regime. These analyses can be used to exclude an important region of the parameter space associated with alternative gravitational models. |
2110.08278 | Achim Kempf | Achim Kempf | Replacing the Notion of Spacetime Distance by the Notion of Correlation | 8 pages | Front. Phys., Vol.9, 655857 (2021) | 10.3389/fphy.2021.655857 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Spacetime is conventionally viewed as a stage on which actors, in the form of
fields, move. Here, we explore what may lie beyond this picture. The starting
point is the observation that quantum fluctuations of fields are the more
strongly correlated the shorter their spacetime distance. As a consequence, the
notion of spacetime distance, including the metric as its infinitesimal
version, can be replaced by the notion of correlation strength. This suggests a
new picture in which abstract (2-point and multi-point) correlators are the
primary structure. In general, these abstract correlators can only be described
as information theoretic structures and, in principle, they need not bear any
relationship to quantum fields or spacetimes. These correlators may allow
approximations, however, so that, in certain regimes, they can be
mathematically approximately represented as the 2-point and multi-point
functions of quantum fields living on a spacetime. In this way, the standard
picture of a curved spacetime with fields whose correlators arise from Feynman
rules would merely be a convenient approximate picture, while the underlying
picture is that of a spacetime-less and field-less information-theoretic
structure of abstract correlations.
| [
{
"created": "Fri, 15 Oct 2021 18:00:01 GMT",
"version": "v1"
}
] | 2021-10-19 | [
[
"Kempf",
"Achim",
""
]
] | Spacetime is conventionally viewed as a stage on which actors, in the form of fields, move. Here, we explore what may lie beyond this picture. The starting point is the observation that quantum fluctuations of fields are the more strongly correlated the shorter their spacetime distance. As a consequence, the notion of spacetime distance, including the metric as its infinitesimal version, can be replaced by the notion of correlation strength. This suggests a new picture in which abstract (2-point and multi-point) correlators are the primary structure. In general, these abstract correlators can only be described as information theoretic structures and, in principle, they need not bear any relationship to quantum fields or spacetimes. These correlators may allow approximations, however, so that, in certain regimes, they can be mathematically approximately represented as the 2-point and multi-point functions of quantum fields living on a spacetime. In this way, the standard picture of a curved spacetime with fields whose correlators arise from Feynman rules would merely be a convenient approximate picture, while the underlying picture is that of a spacetime-less and field-less information-theoretic structure of abstract correlations. |
1108.2779 | Brihaye Yves | Y. Brihaye | Charged, rotating black holes in Einstein-Gauss-Bonnet gravity | 14 pages, 10 figures, references added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Einstein-Gauss-Bonnet equations in five dimensions including
a negative cosmological constant and a Maxwell field. Using an appropriate
Ansatz for the metric and for the electromagnetic fields, we construct
numerically black holes with two equal angular momenta in the two orthogonal
space-like planes of space-time. Families of such solutions, labeled by the
angular momentum and by the electric charge are obtained for many
representative intervals of the Gauss-Bonnet coupling constant $\alpha$. It is
argued that, for fixed values of $\alpha$, the solutions terminate into
extremal black holes at ($\alpha$-dependent) critical values of the angular
momentum and/or of the electric charge. The influence of the Gauss-Bonnet
coupling constant, of the charge and of the cosmological constant on the
thermodynamics of the black holes and on their domain of existence is analyzed.
| [
{
"created": "Sat, 13 Aug 2011 08:59:42 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2011 10:53:01 GMT",
"version": "v2"
}
] | 2011-12-01 | [
[
"Brihaye",
"Y.",
""
]
] | We consider the Einstein-Gauss-Bonnet equations in five dimensions including a negative cosmological constant and a Maxwell field. Using an appropriate Ansatz for the metric and for the electromagnetic fields, we construct numerically black holes with two equal angular momenta in the two orthogonal space-like planes of space-time. Families of such solutions, labeled by the angular momentum and by the electric charge are obtained for many representative intervals of the Gauss-Bonnet coupling constant $\alpha$. It is argued that, for fixed values of $\alpha$, the solutions terminate into extremal black holes at ($\alpha$-dependent) critical values of the angular momentum and/or of the electric charge. The influence of the Gauss-Bonnet coupling constant, of the charge and of the cosmological constant on the thermodynamics of the black holes and on their domain of existence is analyzed. |
2407.12920 | Zhiyao Lu | Zhiyao Lu, Lian-Tao Wang, Huangyu Xiao | A New Probe of $\mu$Hz Gravitational Waves with FRB Timing | 17 pages, 6 figures | null | null | FERMILAB-PUB-24-0365-T | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM hep-ph | http://creativecommons.org/licenses/by/4.0/ | We propose Fast Radio Burst (FRB) timing, which uses the precision
measurements of the arrival time differences of repeated FRB signals along
multiple sightlines, as a new probe of gravitational waves (GWs) around nHz to
$\mu$Hz frequencies, with the highest frequency limited by FRB repeating
period. The anticipated experiment requires a sightline separation of tens of
AU, achieved by sending radio telescopes to space. We find the signal of
arrival time difference induced by GWs depends only on the local GWs in the
solar system and we can correlate the measurements from different FRB sources
or the same source with different repeaters, which leads to a better
sensitivity with a larger number of FRB repeaters detected. The projected
sensitivity shows this method is a competitive probe in the nHz to $\mu$Hz
frequency range. It can fill the '$\mu$Hz gap' between pulsar timing arrays and
Laser Interferometer Space Antenna (LISA) and is complementary to other
proposals of GW detection in this frequency band.
| [
{
"created": "Wed, 17 Jul 2024 18:00:14 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Lu",
"Zhiyao",
""
],
[
"Wang",
"Lian-Tao",
""
],
[
"Xiao",
"Huangyu",
""
]
] | We propose Fast Radio Burst (FRB) timing, which uses the precision measurements of the arrival time differences of repeated FRB signals along multiple sightlines, as a new probe of gravitational waves (GWs) around nHz to $\mu$Hz frequencies, with the highest frequency limited by FRB repeating period. The anticipated experiment requires a sightline separation of tens of AU, achieved by sending radio telescopes to space. We find the signal of arrival time difference induced by GWs depends only on the local GWs in the solar system and we can correlate the measurements from different FRB sources or the same source with different repeaters, which leads to a better sensitivity with a larger number of FRB repeaters detected. The projected sensitivity shows this method is a competitive probe in the nHz to $\mu$Hz frequency range. It can fill the '$\mu$Hz gap' between pulsar timing arrays and Laser Interferometer Space Antenna (LISA) and is complementary to other proposals of GW detection in this frequency band. |
gr-qc/0701102 | Slava G. Turyshev | Slava G. Turyshev and Michael Shao | The Laser Astrometric Test of Relativity: Science, Technology, and
Mission Design | 12 pages, 4 figures. To appear in the proceedings of the
International Workshop "From Quantum to Cosmos: Fundamental Physics Research
in Space", 21-24 May 2006, Warrenton, Virginia, USA
http://physics.jpl.nasa.gov/quantum-to-cosmos/ | Int.J.Mod.Phys.D16:2191-2203,2007 | 10.1142/S0218271807011747 | null | gr-qc | null | The Laser Astrometric Test of Relativity (LATOR) experiment is designed to
explore general theory of relativity in the close proximity to the Sun -- the
most intense gravitational environment in the solar system. Using independent
time-series of highly accurate measurements of the Shapiro time-delay
(interplanetary laser ranging accurate to 3 mm at 2 AU) and interferometric
astrometry (accurate to 0.01 picoradian), LATOR will measure gravitational
deflection of light by the solar gravity with accuracy of 1 part in a billion
-- a factor ~30,000 better than currently available. LATOR will perform series
of highly-accurate tests in its search for cosmological remnants of scalar
field in the solar system. We present science, technology and mission design
for the LATOR mission.
| [
{
"created": "Thu, 18 Jan 2007 07:52:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Shao",
"Michael",
""
]
] | The Laser Astrometric Test of Relativity (LATOR) experiment is designed to explore general theory of relativity in the close proximity to the Sun -- the most intense gravitational environment in the solar system. Using independent time-series of highly accurate measurements of the Shapiro time-delay (interplanetary laser ranging accurate to 3 mm at 2 AU) and interferometric astrometry (accurate to 0.01 picoradian), LATOR will measure gravitational deflection of light by the solar gravity with accuracy of 1 part in a billion -- a factor ~30,000 better than currently available. LATOR will perform series of highly-accurate tests in its search for cosmological remnants of scalar field in the solar system. We present science, technology and mission design for the LATOR mission. |
1807.00036 | Diogo Bragan\c{c}a | Diogo P. L. Bragan\c{c}a, Jos\'e P. S. Lemos | Stratified scalar field theories of gravitation with self-energy term
and effective particle Lagrangian | 12 pages | Eur. Phys. J. C 78:, 533 (2018) | 10.1140/epjc/s10052-018-6006-7 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a general stratified scalar theory of gravitation from a field
equation that accounts for the self-interaction of the field and a particle
Lagrangian, and calculate its post-Newtonian parameters. Using this general
framework, we analyze several specific scalar theories of gravitation and check
their predictions for the solar system post-Newtonian effects.
| [
{
"created": "Fri, 29 Jun 2018 18:50:42 GMT",
"version": "v1"
}
] | 2018-12-07 | [
[
"Bragança",
"Diogo P. L.",
""
],
[
"Lemos",
"José P. S.",
""
]
] | We construct a general stratified scalar theory of gravitation from a field equation that accounts for the self-interaction of the field and a particle Lagrangian, and calculate its post-Newtonian parameters. Using this general framework, we analyze several specific scalar theories of gravitation and check their predictions for the solar system post-Newtonian effects. |
0712.0687 | Ghanashyam Date | Kinjal Banerjee and Ghanashyam Date | Loop Quantization of Polarized Gowdy Model on $T^3$: Kinematical States
and Constraint Operators | 26 pages, no figures. Version 2 accepted for publication. This has
the sub-title changed, introduction modified for comments on references,
small errors corrected and references updated | Class.Quant.Grav.25:145004,2008 | 10.1088/0264-9381/25/14/145004 | IMSc/2007/12/16 | gr-qc hep-th | null | In this second paper on loop quantization of Gowdy model, we introduce the
kinematical Hilbert space on which appropriate holonomies and fluxes are well
represented. The quantization of the volume operator and the Gauss constraint
is straightforward. Imposition of the Gauss constraint can be done on the
kinematical Hilbert space to select subspace of gauge invariant states. We
carry out the quantization of the Hamiltonian constraint making specific
choices. Alternative choices are briefly discussed. It appears that to get
spatial correlations reflected in the Hamiltonian constraint, one may have to
adopt the so called `effective operator viewpoint'.
| [
{
"created": "Wed, 5 Dec 2007 10:47:23 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jun 2008 09:43:07 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Banerjee",
"Kinjal",
""
],
[
"Date",
"Ghanashyam",
""
]
] | In this second paper on loop quantization of Gowdy model, we introduce the kinematical Hilbert space on which appropriate holonomies and fluxes are well represented. The quantization of the volume operator and the Gauss constraint is straightforward. Imposition of the Gauss constraint can be done on the kinematical Hilbert space to select subspace of gauge invariant states. We carry out the quantization of the Hamiltonian constraint making specific choices. Alternative choices are briefly discussed. It appears that to get spatial correlations reflected in the Hamiltonian constraint, one may have to adopt the so called `effective operator viewpoint'. |
1005.5605 | Piero Nicolini | Leonardo Modesto and Piero Nicolini | Charged rotating noncommutative black holes | 13 pages, 3 figures, correction of a typesetting inattention, updated
reference list, version accepted for publication on Physical Review D | Phys.Rev.D82:104035,2010 | 10.1103/PhysRevD.82.104035 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we complete the program of the noncomutative geometry inspired
black holes, providing the richest possible solution, endowed with mass, charge
and angular momentum. After providing a prescription for employing the
Newman-Janis algorithm in the case of nonvanishing stress tensors, we find
regular axisymmetric charged black holes in the presence of a minimal length.
We study also the new thermodynamics and we determine the corresponding
higher-dimensional solutions. As a conclusion we make some consideration about
possible applications.
| [
{
"created": "Mon, 31 May 2010 07:02:31 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 2010 19:19:25 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Nov 2010 22:37:18 GMT",
"version": "v3"
}
] | 2010-12-13 | [
[
"Modesto",
"Leonardo",
""
],
[
"Nicolini",
"Piero",
""
]
] | In this paper we complete the program of the noncomutative geometry inspired black holes, providing the richest possible solution, endowed with mass, charge and angular momentum. After providing a prescription for employing the Newman-Janis algorithm in the case of nonvanishing stress tensors, we find regular axisymmetric charged black holes in the presence of a minimal length. We study also the new thermodynamics and we determine the corresponding higher-dimensional solutions. As a conclusion we make some consideration about possible applications. |
2401.05448 | Pardyumn Kumar Sahoo | Dheeraj Singh Rana, Raja Solanki, P.K. Sahoo | Phase-space analysis of the viscous fluid cosmological models in the
coincident $f(Q)$ gravity | Physics of the Dark Universe accepted version | Physics of the Dark Universe, 43 (2024) 101421 | 10.1016/j.dark.2024.101421 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this article, we consider a newly proposed parameterization of the
viscosity coefficient $\zeta$, specifically $\zeta=\bar{\zeta}_0 {\Omega^s_m} H
$, where $\bar{\zeta}_0 = \frac{\zeta_0}{{\Omega^s_{m_0}}} $ within the
coincident $f(Q)$ gravity formalism. We consider a non-linear function $f(Q)=
-Q +\alpha Q^n$, where $\alpha$ and $n$ are arbitrary model parameters, which
is a power-law correction to the STEGR scenario. We find an autonomous system
by invoking the dimensionless density parameters as the governing phase-space
variables. We discuss the physical significance of the model corresponding to
the parameter choices $n=-1$ and $n=2$ along with the exponent choices $s=0,
0.5$, and $1.05$. We find that model I shows the stable de-Sitter type or
stable phantom type (depending on the choice of exponent $s$) behavior with no
transition epoch, whereas model II shows the evolutionary phase from the
radiation epoch to the accelerated de-Sitter epoch via passing through the
matter-dominated epoch. Hence, we conclude that model I provides a good
description of the late-time cosmology but fails to describe the transition
epoch, whereas model II modifies the description in the context of the early
universe and provides a good description of the matter and radiation era along
with the transition phase.
| [
{
"created": "Tue, 9 Jan 2024 11:09:30 GMT",
"version": "v1"
}
] | 2024-01-17 | [
[
"Rana",
"Dheeraj Singh",
""
],
[
"Solanki",
"Raja",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this article, we consider a newly proposed parameterization of the viscosity coefficient $\zeta$, specifically $\zeta=\bar{\zeta}_0 {\Omega^s_m} H $, where $\bar{\zeta}_0 = \frac{\zeta_0}{{\Omega^s_{m_0}}} $ within the coincident $f(Q)$ gravity formalism. We consider a non-linear function $f(Q)= -Q +\alpha Q^n$, where $\alpha$ and $n$ are arbitrary model parameters, which is a power-law correction to the STEGR scenario. We find an autonomous system by invoking the dimensionless density parameters as the governing phase-space variables. We discuss the physical significance of the model corresponding to the parameter choices $n=-1$ and $n=2$ along with the exponent choices $s=0, 0.5$, and $1.05$. We find that model I shows the stable de-Sitter type or stable phantom type (depending on the choice of exponent $s$) behavior with no transition epoch, whereas model II shows the evolutionary phase from the radiation epoch to the accelerated de-Sitter epoch via passing through the matter-dominated epoch. Hence, we conclude that model I provides a good description of the late-time cosmology but fails to describe the transition epoch, whereas model II modifies the description in the context of the early universe and provides a good description of the matter and radiation era along with the transition phase. |
1412.6758 | Xavier Calmet | Xavier Calmet | Quantum black holes and effective quantum gravity approaches | 5 pages, written in 2013. To appear in the proceedings of the Karl
Schwarzschild Meeting (Frankfurt, July 22-26, 2013) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the text of the invited talk I have given at the Karl Schwarzschild
Meeting in Frankfurt in 2013.
| [
{
"created": "Sun, 21 Dec 2014 10:22:22 GMT",
"version": "v1"
}
] | 2014-12-23 | [
[
"Calmet",
"Xavier",
""
]
] | This is the text of the invited talk I have given at the Karl Schwarzschild Meeting in Frankfurt in 2013. |
1606.08296 | Fabien Nugier | Fabien Nugier | From GLC to double-null coordinates and illustration with static black
holes | 30 pages, 3 figures. Comments and references added. Paper published
in JCAP | JCAP09(2016)019 | 10.1088/1475-7516/2016/09/019 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a system of coordinates deriving directly from the so-called
Geodesic Light-Cone (GLC) coordinates and made of two null scalars intersecting
on a 2-dimensional sphere parameterized by two constant angles along geodesics.
These coordinates are shown to be equivalent to the well-known double-null
coordinates. As GLC, they present interesting properties for cosmology and
astrophysics. We discuss this latter topic for static black holes, showing
simple descriptions for the metric or particles and photons trajectories. We
also briefly comment on the time of flight of ultra-relativistic particles.
| [
{
"created": "Fri, 24 Jun 2016 11:54:15 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Sep 2016 04:41:41 GMT",
"version": "v2"
}
] | 2016-09-16 | [
[
"Nugier",
"Fabien",
""
]
] | We present a system of coordinates deriving directly from the so-called Geodesic Light-Cone (GLC) coordinates and made of two null scalars intersecting on a 2-dimensional sphere parameterized by two constant angles along geodesics. These coordinates are shown to be equivalent to the well-known double-null coordinates. As GLC, they present interesting properties for cosmology and astrophysics. We discuss this latter topic for static black holes, showing simple descriptions for the metric or particles and photons trajectories. We also briefly comment on the time of flight of ultra-relativistic particles. |
2305.19313 | Nicola Franchini | Nicola Franchini | Slow rotation black hole perturbation theory | 21 pages (12 + appendix and bibliography). Minor changes and
additions to the bibliography | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present a detailed analysis of first-order perturbations of
the Kerr metric in the slow-rotation limit. We perform the calculation by
perturbing the Schwarzschild metric plus up to second-order corrections in the
spin in the Regge-Wheeler gauge. The apparent coupling between different
angular momentum axial-led and polar-led modes can be removed by suitably
combining the perturbation equations and projecting them onto spin-weighted
spherical harmonics. In this way, we derive the corrections to the
Regge-Wheeler and the Zerilli equations up to second-order in the spin. We show
that the two potentials remain isospectral as in the non-rotating limit.
However, it is easy to demonstrate it only for a precise choice of the tortoise
coordinate. The isospectrality with slow-rotating Teukolsky equation is also
verified. We discuss the main implication of this result for the problem of
vacuum metric reconstruction, providing the transformation rule between
slow-spinning Teukolsky variables and metric perturbations. The existence of
this relation leaves us with the conjecture that a resummation of the expansion
in the spin is possible, leading to two decoupled differential equations for
perturbations of the Kerr metric.
| [
{
"created": "Tue, 30 May 2023 18:00:00 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2023 15:31:46 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Franchini",
"Nicola",
""
]
] | In this paper, we present a detailed analysis of first-order perturbations of the Kerr metric in the slow-rotation limit. We perform the calculation by perturbing the Schwarzschild metric plus up to second-order corrections in the spin in the Regge-Wheeler gauge. The apparent coupling between different angular momentum axial-led and polar-led modes can be removed by suitably combining the perturbation equations and projecting them onto spin-weighted spherical harmonics. In this way, we derive the corrections to the Regge-Wheeler and the Zerilli equations up to second-order in the spin. We show that the two potentials remain isospectral as in the non-rotating limit. However, it is easy to demonstrate it only for a precise choice of the tortoise coordinate. The isospectrality with slow-rotating Teukolsky equation is also verified. We discuss the main implication of this result for the problem of vacuum metric reconstruction, providing the transformation rule between slow-spinning Teukolsky variables and metric perturbations. The existence of this relation leaves us with the conjecture that a resummation of the expansion in the spin is possible, leading to two decoupled differential equations for perturbations of the Kerr metric. |
gr-qc/9902015 | Kirill Krasnov | Kirill Krasnov | Quanta of Geometry and Rotating Black Holes | 5 pages | Class.Quant.Grav.16:L15-L18,1999 | 10.1088/0264-9381/16/4/015 | CGPG-98/3-3 | gr-qc | null | In the loop approach to quantum gravity the spectra of operators
corresponding to such geometrical quantities as length, area and volume become
quantized. However, the size of arising quanta of geometry in Planck units is
not fixed by the theory itself: a free parameter, sometimes referred to as
Immirzi parameter, is known to affect the spectrum of all geometrical
operators. In this paper I propose an argument that fixes the value of this
parameter. I consider rotating black holes, in particular the extremal ones.
For such black holes the ``no naked singularity condition'' bounds the total
angular momentum J by A_H/8 pi G, where A_H is the horizon area and G Newton's
constant. A similar bound on J comes from the quantum theory. The requirement
that these two bounds are the same fixes the value of Immirzi parameter to be
unity. A byproduct of this argument is the picture of the quantum extremal
rotating black hole in which all the spin entering the extremal hole is
concentrated in a single puncture.
| [
{
"created": "Thu, 4 Feb 1999 05:03:51 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Krasnov",
"Kirill",
""
]
] | In the loop approach to quantum gravity the spectra of operators corresponding to such geometrical quantities as length, area and volume become quantized. However, the size of arising quanta of geometry in Planck units is not fixed by the theory itself: a free parameter, sometimes referred to as Immirzi parameter, is known to affect the spectrum of all geometrical operators. In this paper I propose an argument that fixes the value of this parameter. I consider rotating black holes, in particular the extremal ones. For such black holes the ``no naked singularity condition'' bounds the total angular momentum J by A_H/8 pi G, where A_H is the horizon area and G Newton's constant. A similar bound on J comes from the quantum theory. The requirement that these two bounds are the same fixes the value of Immirzi parameter to be unity. A byproduct of this argument is the picture of the quantum extremal rotating black hole in which all the spin entering the extremal hole is concentrated in a single puncture. |
gr-qc/9704078 | Smirichinskii V. I. | V.N.Pervushin, V.I Smirichinski | On the Cosmological Origin of the Homogeneous Scalar Field in Unified
Theories | 8 pages, Latex | null | null | JINR E2-97-155 | gr-qc | null | We consider the possibility of describing the Higgs effect in unified
theories without the Higgs potential in the presence of the Einstein gravity
with the conformal gravity-scalar coupling under the assumption of homogeneous
matter distribution.
The scalar field values can be found from the Friedmann equations for the
homogeneous Universe. The considered cosmological mechanism solves the vacuum
density problem (we got $\rho_\phi^{Cosmic}=10^{-34}\rho_{cr}$ instead of
$\rho_\phi^{Higgs}=10^{54}\rho_{cr}$),and exludes the monopole creation and the
domain walls.
| [
{
"created": "Mon, 28 Apr 1997 13:30:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pervushin",
"V. N.",
""
],
[
"Smirichinski",
"V. I",
""
]
] | We consider the possibility of describing the Higgs effect in unified theories without the Higgs potential in the presence of the Einstein gravity with the conformal gravity-scalar coupling under the assumption of homogeneous matter distribution. The scalar field values can be found from the Friedmann equations for the homogeneous Universe. The considered cosmological mechanism solves the vacuum density problem (we got $\rho_\phi^{Cosmic}=10^{-34}\rho_{cr}$ instead of $\rho_\phi^{Higgs}=10^{54}\rho_{cr}$),and exludes the monopole creation and the domain walls. |
2006.11281 | Yongqiang Wang | Hong-Bo Li, Yan-Bo Zeng, Yan Song, Yong-Qiang Wang | Self-interacting multistate boson stars | 21 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1906.00420 | null | 10.1007/JHEP04(2021)042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider rotating multistate boson stars with quartic
self-interactions. In contrast to the nodeless quartic-boson stars in
\cite{Herdeiro:2015tia}, the self-interacting multistate boson stars (SIMBSs)
have two types of nodes, including the $^1S^2S$ and $^1S^2P$ states. We show
the mass $M$ of SIMBSs as a function of the synchronized frequency $\omega$,
and the nonsynchronized frequency $\omega_2$ for three different cases.
Moreover, for the case of two coexisting states with self-interacting
potential, we study the mass $M$ of SIMBSs versus the angular momentum $J$ for
the synchronized frequency $\omega$ and the nonsynchronized frequency
$\omega_2$. Furthermore, for three different cases, we analyze the coexisting
phase with both the ground and first excited states for SIMBSs. We also
calculate the maximum value of coupling parameter $\Lambda$, and find the
coupling parameter $\Lambda$ exists the finite range.
| [
{
"created": "Fri, 19 Jun 2020 09:24:59 GMT",
"version": "v1"
}
] | 2021-04-21 | [
[
"Li",
"Hong-Bo",
""
],
[
"Zeng",
"Yan-Bo",
""
],
[
"Song",
"Yan",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we consider rotating multistate boson stars with quartic self-interactions. In contrast to the nodeless quartic-boson stars in \cite{Herdeiro:2015tia}, the self-interacting multistate boson stars (SIMBSs) have two types of nodes, including the $^1S^2S$ and $^1S^2P$ states. We show the mass $M$ of SIMBSs as a function of the synchronized frequency $\omega$, and the nonsynchronized frequency $\omega_2$ for three different cases. Moreover, for the case of two coexisting states with self-interacting potential, we study the mass $M$ of SIMBSs versus the angular momentum $J$ for the synchronized frequency $\omega$ and the nonsynchronized frequency $\omega_2$. Furthermore, for three different cases, we analyze the coexisting phase with both the ground and first excited states for SIMBSs. We also calculate the maximum value of coupling parameter $\Lambda$, and find the coupling parameter $\Lambda$ exists the finite range. |
gr-qc/9404015 | Ian Moss | Chris M. Chambers and Ian G. Moss | Stability of the Cauchy horizon in Kerr--de Sitter spacetimes | 21 pages, NCL93-TP10 (TeX) | Class.Quant.Grav.11:1035-1054,1994 | 10.1088/0264-9381/11/4/019 | null | gr-qc | null | We begin a program of work aimed at examining the interior of a rotating
black hole with a non--zero cosmological constant. The generalisation of
Teukolsky's equation for the radial mode functions is presented. It is shown
that the energy fluxes of scalar, electromagnetic and gravity waves are regular
at the Cauchy horizon whenever the surface gravity there is less than the
surface gravity at the cosmological horizon. This condition is narrowly
allowed, even when the cosmological constant is very small, thus permitting an
observer to pass through the hole, viewing the naked singularity along the way.
| [
{
"created": "Fri, 8 Apr 1994 16:21:27 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Chambers",
"Chris M.",
""
],
[
"Moss",
"Ian G.",
""
]
] | We begin a program of work aimed at examining the interior of a rotating black hole with a non--zero cosmological constant. The generalisation of Teukolsky's equation for the radial mode functions is presented. It is shown that the energy fluxes of scalar, electromagnetic and gravity waves are regular at the Cauchy horizon whenever the surface gravity there is less than the surface gravity at the cosmological horizon. This condition is narrowly allowed, even when the cosmological constant is very small, thus permitting an observer to pass through the hole, viewing the naked singularity along the way. |
1104.3488 | Barun Majumder | Barun Majumder | Effects of GUP in Quantum Cosmological Perfect Fluid Models | 10 pages. Accepted for publication in Physics Letters B | Physics Letters B 699 (2011) 315 - 319 | 10.1016/j.physletb.2011.04.030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Very recently authors in [5] proposed a new Generalized Uncertainty Principle
(or GUP) with a linear term in Plank length. In this Letter the effect of this
GUP is studied in quantum cosmological models with dust and cosmic string as
the perfect fluid. For the quantum mechanical description it is possible to
find the wave packet which resulted from the superposition of the stationary
wave functions of the Wheeler-deWitt equation. However the norm of the wave
packets turned out to be time dependent and hence the model became non-unitary.
The loss of unitarity is due to the fact that the presence of the linear term
in Plank length in the Generalized Uncertainty Principle made the Hamiltonian
non-Hermitian.
| [
{
"created": "Mon, 18 Apr 2011 14:06:17 GMT",
"version": "v1"
}
] | 2011-05-11 | [
[
"Majumder",
"Barun",
""
]
] | Very recently authors in [5] proposed a new Generalized Uncertainty Principle (or GUP) with a linear term in Plank length. In this Letter the effect of this GUP is studied in quantum cosmological models with dust and cosmic string as the perfect fluid. For the quantum mechanical description it is possible to find the wave packet which resulted from the superposition of the stationary wave functions of the Wheeler-deWitt equation. However the norm of the wave packets turned out to be time dependent and hence the model became non-unitary. The loss of unitarity is due to the fact that the presence of the linear term in Plank length in the Generalized Uncertainty Principle made the Hamiltonian non-Hermitian. |
1608.04723 | Parthapratim Pradhan | Parthapratim Pradhan | Extremal limits and Ba\~nados-Silk-West effect | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A fascinating property of extremal Kerr black hole (BH) is that it could be
act as a particle accelerator with infinite high center-of-mass (CM) energy
\cite{bsw}. In this note, we would like to discuss about such fascinating
result and to point out that this infinite energy at the event horizon comes
solely due \emph{to the singular nature of the extremal limit}. We also show
that a non-extremal Kerr BH can \emph{not} transform into extremal Kerr BH by
the Ba\~{n}ados-Silk-West mechanism. Moreover, we discuss about three possible
geometries (near extremal, purely extremal and near horizon of extremal Kerr)
of this mechanism. We further prove that near extremal geometry and near
horizon geometry, precisely extremal geometry of extremal Kerr BHs are
qualitatively different. Near extremal geometry and near horizon geometry gives
the CM energy is finite, whereas precisely extremal geometry gives the
diverging energy. Thus, we can argue that extremal Kerr BH and non-extremal
Kerr BH are quite distinct objects. Finally, we show that the CM energy of
collisions of particles not only diverges at infinite red-shift surface
($r_{+}$) but it could also diverges at the ISCO ($r_{isco}$) or at the
circular photon orbit ($r_{cpo}$) or at the marginally bound circular orbit
($r_{mbco}$) or at the Cauchy horizon i.e. at $r \equiv
r_{isco}=r_{cpo}=r_{mbco}=r_{+}=r_{-}=M$.
| [
{
"created": "Tue, 16 Aug 2016 19:39:30 GMT",
"version": "v1"
}
] | 2016-08-17 | [
[
"Pradhan",
"Parthapratim",
""
]
] | A fascinating property of extremal Kerr black hole (BH) is that it could be act as a particle accelerator with infinite high center-of-mass (CM) energy \cite{bsw}. In this note, we would like to discuss about such fascinating result and to point out that this infinite energy at the event horizon comes solely due \emph{to the singular nature of the extremal limit}. We also show that a non-extremal Kerr BH can \emph{not} transform into extremal Kerr BH by the Ba\~{n}ados-Silk-West mechanism. Moreover, we discuss about three possible geometries (near extremal, purely extremal and near horizon of extremal Kerr) of this mechanism. We further prove that near extremal geometry and near horizon geometry, precisely extremal geometry of extremal Kerr BHs are qualitatively different. Near extremal geometry and near horizon geometry gives the CM energy is finite, whereas precisely extremal geometry gives the diverging energy. Thus, we can argue that extremal Kerr BH and non-extremal Kerr BH are quite distinct objects. Finally, we show that the CM energy of collisions of particles not only diverges at infinite red-shift surface ($r_{+}$) but it could also diverges at the ISCO ($r_{isco}$) or at the circular photon orbit ($r_{cpo}$) or at the marginally bound circular orbit ($r_{mbco}$) or at the Cauchy horizon i.e. at $r \equiv r_{isco}=r_{cpo}=r_{mbco}=r_{+}=r_{-}=M$. |
gr-qc/0701051 | Stanislav Hled\'ik | Stanislav Hledik, Zdenek Stuchlik and Kristina Mrazova | Dynamical stability of fluid spheres in spacetimes with a nonzero
cosmological constant | 3 pages, 1 figure, to appear in "Proceedings of the 11th Marcel
Grossmann Meeting on General Relativity", eds H. Kleinert, R. T. Jantzen, R.
Ruffini | null | 10.1142/9789812834300_0097 | null | gr-qc | null | The Sturm-Liouville eigenvalue equation for eigenmodes of the radial
oscillations is determined for spherically symmetric perfect fluid
configurations in spacetimes with a nonzero cosmological constant and applied
in the cases of configurations with uniform distribution of energy density and
polytropic spheres. It is shown that a repulsive cosmological constant rises
the critical adiabatic index and decreases the critical radius under which the
dynamical instability occurs.
| [
{
"created": "Tue, 9 Jan 2007 13:14:13 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2007 16:28:08 GMT",
"version": "v2"
}
] | 2016-11-15 | [
[
"Hledik",
"Stanislav",
""
],
[
"Stuchlik",
"Zdenek",
""
],
[
"Mrazova",
"Kristina",
""
]
] | The Sturm-Liouville eigenvalue equation for eigenmodes of the radial oscillations is determined for spherically symmetric perfect fluid configurations in spacetimes with a nonzero cosmological constant and applied in the cases of configurations with uniform distribution of energy density and polytropic spheres. It is shown that a repulsive cosmological constant rises the critical adiabatic index and decreases the critical radius under which the dynamical instability occurs. |
0712.3685 | Jurjen Koksma | Jurjen F. Koksma (Utrecht University, ITP) Tomislav Prokopec (Utrecht
University, ITP) Gerasimos I. Rigopoulos (University of Helsinki, HIP) | The Scalar Field Kernel in Cosmological Spaces | 13 pages, 1 figure | Class.Quant.Grav.25:125009,2008 | 10.1088/0264-9381/25/12/125009 | ITP-UU-07/65, SPIN-07/50, HIP-2008-02/TH | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the quantum mechanical evolution operator in the Functional
Schrodinger picture - the kernel - for a scalar field in spatially homogeneous
FLRW spacetimes when the field is a) free and b) coupled to a spacetime
dependent source term. The essential element in the construction is the causal
propagator, linked to the commutator of two Heisenberg picture scalar fields.
We show that the kernels can be expressed solely in terms of the causal
propagator and derivatives of the causal propagator. Furthermore, we show that
our kernel reveals the standard light cone structure in FLRW spacetimes. We
finally apply the result to Minkowski spacetime, to de Sitter spacetime and
calculate the forward time evolution of the vacuum in a general FLRW spacetime.
| [
{
"created": "Fri, 21 Dec 2007 12:30:55 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jun 2008 13:27:25 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Koksma",
"Jurjen F.",
"",
"Utrecht University, ITP"
],
[
"Prokopec",
"Tomislav",
"",
"Utrecht\n University, ITP"
],
[
"Rigopoulos",
"Gerasimos I.",
"",
"University of Helsinki, HIP"
]
] | We construct the quantum mechanical evolution operator in the Functional Schrodinger picture - the kernel - for a scalar field in spatially homogeneous FLRW spacetimes when the field is a) free and b) coupled to a spacetime dependent source term. The essential element in the construction is the causal propagator, linked to the commutator of two Heisenberg picture scalar fields. We show that the kernels can be expressed solely in terms of the causal propagator and derivatives of the causal propagator. Furthermore, we show that our kernel reveals the standard light cone structure in FLRW spacetimes. We finally apply the result to Minkowski spacetime, to de Sitter spacetime and calculate the forward time evolution of the vacuum in a general FLRW spacetime. |
2102.05722 | Helios Sanchis-Alepuz | Georg Herzog and H\`elios Sanchis-Alepuz | Neutron Stars in Palatini $R+\alpha R^2$ and $R+\alpha R^2+\beta Q$
Theories | 13 pages, 18 figures. References added. Discussion around Fig. 18
extended. Agrees with published version | Eur.Phys.J.C 81 (2021) 10, 888 | 10.1140/epjc/s10052-021-09662-z | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | We study solutions of the stellar structure equations for spherically
symmetric objects in Palatini $f(R)=R+\alpha R^2$ and $f(R,Q)=R+\alpha
R^2+\beta Q$ in the mass-radius region associated to neutron stars. We
illustrate the potential impact of the $R^2$ and $Q$ terms by studying a range
of viable values of $\alpha$ and $\beta$. Similarly, we use different equations
of state (SLy, FPS, HS(DD2) and HS(TMA)) as a simple way to account for the
equation of state uncertainty. Our results show that for certain combinations
of the $\alpha$ and $\beta$ parameters and equation of state, the effect of
modifications of general relativity on the properties of stars is sizeable.
Therefore, with increasing accuracy in the determination of the equation of
state for neutron stars, astrophysical observations may serve as discriminators
of modifications of General Relativity.
| [
{
"created": "Wed, 10 Feb 2021 20:07:09 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jun 2021 07:24:58 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Oct 2021 06:05:57 GMT",
"version": "v3"
}
] | 2021-10-20 | [
[
"Herzog",
"Georg",
""
],
[
"Sanchis-Alepuz",
"Hèlios",
""
]
] | We study solutions of the stellar structure equations for spherically symmetric objects in Palatini $f(R)=R+\alpha R^2$ and $f(R,Q)=R+\alpha R^2+\beta Q$ in the mass-radius region associated to neutron stars. We illustrate the potential impact of the $R^2$ and $Q$ terms by studying a range of viable values of $\alpha$ and $\beta$. Similarly, we use different equations of state (SLy, FPS, HS(DD2) and HS(TMA)) as a simple way to account for the equation of state uncertainty. Our results show that for certain combinations of the $\alpha$ and $\beta$ parameters and equation of state, the effect of modifications of general relativity on the properties of stars is sizeable. Therefore, with increasing accuracy in the determination of the equation of state for neutron stars, astrophysical observations may serve as discriminators of modifications of General Relativity. |
1711.05419 | Canisius Bernard | Canisius Bernard | Analytical Study of a Kerr-Sen Black Hole and a Charged Massive Scalar
Field | 18 pages, no figures; v2: references are added, typos are corrected,
to be published in Physical Review D. The reference list is slightly
different from the journal version | Phys. Rev. D 96, 105025 (2017) | 10.1103/PhysRevD.96.105025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is reported that Kerr-Newman and Kerr-Sen black holes are unstable to
perturbations of charged massive scalar field. In this paper, we study
analytically the complex frequencies which characterize charged massive scalar
fields in a near-extremal Kerr-Sen black hole. For near-extremal Kerr-Sen black
holes and for charged massive scalar fields in the eikonal large-mass
$\mathcal{M}\gg \mu$ regime, where $\mathcal{M}$ is the mass of the black hole,
and $\mu$ is the mass of the charged scalar field, we have obtained a simple
expression for the dimensionless ratio $\omega_I /\left(\omega_R -
\omega_c\right)$, where $\omega_I$ and $\omega_R$ are, respectively, the
imaginary and real parts of the frequency of the modes, and $\omega_c$ is the
critical frequency for the onset of super-radiance. We have also found our
expression is consistent with the result of Hod [Phys. Rev. D 94, 044036
(2016)] for the case of a near-extremal Kerr-Newman black hole and the result
of Zouros and Eardly [Ann. Phys. (N.Y.) 118, 139 (1979)] for the case of
neutral scalar fields in the background of a near-extremal Kerr black hole.
| [
{
"created": "Wed, 15 Nov 2017 06:02:08 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Nov 2017 09:56:45 GMT",
"version": "v2"
}
] | 2017-11-30 | [
[
"Bernard",
"Canisius",
""
]
] | It is reported that Kerr-Newman and Kerr-Sen black holes are unstable to perturbations of charged massive scalar field. In this paper, we study analytically the complex frequencies which characterize charged massive scalar fields in a near-extremal Kerr-Sen black hole. For near-extremal Kerr-Sen black holes and for charged massive scalar fields in the eikonal large-mass $\mathcal{M}\gg \mu$ regime, where $\mathcal{M}$ is the mass of the black hole, and $\mu$ is the mass of the charged scalar field, we have obtained a simple expression for the dimensionless ratio $\omega_I /\left(\omega_R - \omega_c\right)$, where $\omega_I$ and $\omega_R$ are, respectively, the imaginary and real parts of the frequency of the modes, and $\omega_c$ is the critical frequency for the onset of super-radiance. We have also found our expression is consistent with the result of Hod [Phys. Rev. D 94, 044036 (2016)] for the case of a near-extremal Kerr-Newman black hole and the result of Zouros and Eardly [Ann. Phys. (N.Y.) 118, 139 (1979)] for the case of neutral scalar fields in the background of a near-extremal Kerr black hole. |
0804.1075 | Lior M. Burko | Jonathan L. Barton, David J. Lazar, Daniel J. Kennefick, Gaurav
Khanna, and Lior M. Burko | Computational Efficiency of Frequency-- and Time--Domain Calculations of
Extreme Mass--Ratio Binaries: Equatorial Orbits | 19 figures, 6 tables | Phys.Rev.D78:064042,2008 | 10.1103/PhysRevD.78.064042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waveforms and fluxes from extreme mass--ratio inspirals can be
computed using time--domain methods with accuracy that is fast approaching that
of frequency--domain methods. We study in detail the computational efficiency
of these methods for equatorial orbits of fast spinning Kerr black holes, and
find the number of modes needed in either method --as functions of the orbital
parameters-- in order to achieve a desired accuracy level. We then estimate the
total computation time and argue that for high eccentricity orbits the
time--domain approach is more efficient computationally. We suggest that in
practice low--$m$ modes are computed using the frequency--domain approach, and
high--$m$ modes are computed using the time--domain approach, where $m$ is the
azimuthal mode number.
| [
{
"created": "Mon, 7 Apr 2008 16:47:47 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Barton",
"Jonathan L.",
""
],
[
"Lazar",
"David J.",
""
],
[
"Kennefick",
"Daniel J.",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Burko",
"Lior M.",
""
]
] | Gravitational waveforms and fluxes from extreme mass--ratio inspirals can be computed using time--domain methods with accuracy that is fast approaching that of frequency--domain methods. We study in detail the computational efficiency of these methods for equatorial orbits of fast spinning Kerr black holes, and find the number of modes needed in either method --as functions of the orbital parameters-- in order to achieve a desired accuracy level. We then estimate the total computation time and argue that for high eccentricity orbits the time--domain approach is more efficient computationally. We suggest that in practice low--$m$ modes are computed using the frequency--domain approach, and high--$m$ modes are computed using the time--domain approach, where $m$ is the azimuthal mode number. |
1405.4143 | Liu Zhao | Hao Xu, Wei Xu and Liu Zhao | Extended phase space thermodynamics for third order Lovelock black holes
in diverse dimensions | pdflatex, 22 pages, 36 eps figures included. V2: minor corrections
and new references | null | 10.1140/epjc/s10052-014-3074-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Treating the cosmological constant as thermodynamic pressure and its
conjugate as thermodynamic volume, we investigate the critical behavior of the
third order Lovelock black holes in diverse dimensions. For black hole horizons
with different normalized sectional curvature $k=0,\pm1$, the corresponding
critical behaviors differ drastically. For $k=0$, there is no critical point in
the extended thermodynamic phase space. For $k=-1$, there is a single critical
point in any dimension $d\geq 7$, and for $k=+1$, there is a single critical
point in $7$ dimension and two critical points in $8,9,10,11$ dimensions. We
studied the corresponding phase structures in all possible cases.
| [
{
"created": "Fri, 16 May 2014 12:15:09 GMT",
"version": "v1"
},
{
"created": "Thu, 22 May 2014 02:17:41 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Xu",
"Hao",
""
],
[
"Xu",
"Wei",
""
],
[
"Zhao",
"Liu",
""
]
] | Treating the cosmological constant as thermodynamic pressure and its conjugate as thermodynamic volume, we investigate the critical behavior of the third order Lovelock black holes in diverse dimensions. For black hole horizons with different normalized sectional curvature $k=0,\pm1$, the corresponding critical behaviors differ drastically. For $k=0$, there is no critical point in the extended thermodynamic phase space. For $k=-1$, there is a single critical point in any dimension $d\geq 7$, and for $k=+1$, there is a single critical point in $7$ dimension and two critical points in $8,9,10,11$ dimensions. We studied the corresponding phase structures in all possible cases. |
gr-qc/0308079 | Fangyu Li | Fang-Yu Li, Meng-Xi Tang, and Dong-Ping Shi | Electromagnetic Response for High-Frequency Gravitational Waves in the
GHz to THz Band | 19 pages, 3 figures | Invited talk at the first international conference on
High-Frequency Gravitational Waves, Paper-03-108, May 2003, The MITRE
Corporation, Mclean, Viginia, USA | null | null | gr-qc | null | We consider the electromagnetic (EM) response of a Gaussian beam passing
through a static magnetic field to be the high-frequency gravitational waves
(HFGW) as generated by several devices discussed at this conference. It is
found that under the synchroresonance condition, the first-order perturbative
EM power fluxes will contain a ''left circular wave'' and a ''right circular
wave'' around the symmetrical axis of the Gaussian beam. However, the
perturbative effects produced by the states of + polarization and \times
polarization of the GW have a different physical behavior. For the HFGW of
$\nu_{g}=3GHz$, $h=10^{-30}$ (which corresponds to the power flux density $~
10^{-6} W m^{-2}$) to $\nu_{g}=1.3THz$, $ h=10^{-28}$ (which corresponds to the
power flux density $~10^{3} W m^{-2}$) expected by the HFGW generators
described at this conference, the corresponding perturbative photon fluxes
passing through a surface region of $10^{-2} m^{2}$ would be expected to be
$10^{3} s^{-1} - 10^{4} s^{-1}$. They are the orders of magnitude of the
perturbative photon flux we estimated using typical laboratory parameters that
could lead to the development of sensitive HFGW receivers. Moreover, we will
also discuss the relative background noise problems and the possibility of
displaying the HFGW. A laboratory test bed for juxtaposed HFGW generators and
our detecting scheme is explored and discussed.
| [
{
"created": "Mon, 25 Aug 2003 03:24:39 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Oct 2003 02:51:40 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Li",
"Fang-Yu",
""
],
[
"Tang",
"Meng-Xi",
""
],
[
"Shi",
"Dong-Ping",
""
]
] | We consider the electromagnetic (EM) response of a Gaussian beam passing through a static magnetic field to be the high-frequency gravitational waves (HFGW) as generated by several devices discussed at this conference. It is found that under the synchroresonance condition, the first-order perturbative EM power fluxes will contain a ''left circular wave'' and a ''right circular wave'' around the symmetrical axis of the Gaussian beam. However, the perturbative effects produced by the states of + polarization and \times polarization of the GW have a different physical behavior. For the HFGW of $\nu_{g}=3GHz$, $h=10^{-30}$ (which corresponds to the power flux density $~ 10^{-6} W m^{-2}$) to $\nu_{g}=1.3THz$, $ h=10^{-28}$ (which corresponds to the power flux density $~10^{3} W m^{-2}$) expected by the HFGW generators described at this conference, the corresponding perturbative photon fluxes passing through a surface region of $10^{-2} m^{2}$ would be expected to be $10^{3} s^{-1} - 10^{4} s^{-1}$. They are the orders of magnitude of the perturbative photon flux we estimated using typical laboratory parameters that could lead to the development of sensitive HFGW receivers. Moreover, we will also discuss the relative background noise problems and the possibility of displaying the HFGW. A laboratory test bed for juxtaposed HFGW generators and our detecting scheme is explored and discussed. |
2212.06162 | Giulia Capurri | Giulia Capurri, Andrea Lapi, Lumen Boco and Carlo Baccigalupi | Searching for anisotropic stochastic gravitational-wave backgrounds with
constellations of space-based interferometers | 17 pages, 9 figures, accepted by ApJ | null | 10.3847/1538-4357/acaaa3 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many recent works have shown that the angular resolution of ground-based
detectors is too poor to characterize the anisotropies of the stochastic
gravitational-wave background (SGWB). For this reason, we asked ourselves if a
constellation of space-based instruments could be more suitable. We consider
the Laser Interferometer Space Antenna (LISA), a constellation of multiple
LISA-like clusters, and the Deci-hertz Interferometer Gravitational-wave
Observatory (DECIGO). Specifically, we test whether these detector
constellations can probe the anisotropies of the SGWB. For this scope, we
considered the SGWB produced by two astrophysical sources: merging compact
binaries and a recently proposed scenario for massive black-hole seed formation
through multiple mergers of stellar remnants. We find that measuring the
angular power spectrum of the SGWB anisotropies is almost unattainable.
However, it turns out that it could be possible to probe the SGWB anisotropies
through cross-correlation with the CMB fluctuations. In particular, we find
that a constellation of two LISA-like detectors and CMB-S4 can marginally
constrain the cross-correlation between the CMB lensing convergence and the
SGWB produced by the black hole seed formation process. Moreover, we find that
DECIGO can probe the cross-correlation between the CMB lensing and the SGWB
from merging compact binaries.
| [
{
"created": "Mon, 12 Dec 2022 19:00:01 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Capurri",
"Giulia",
""
],
[
"Lapi",
"Andrea",
""
],
[
"Boco",
"Lumen",
""
],
[
"Baccigalupi",
"Carlo",
""
]
] | Many recent works have shown that the angular resolution of ground-based detectors is too poor to characterize the anisotropies of the stochastic gravitational-wave background (SGWB). For this reason, we asked ourselves if a constellation of space-based instruments could be more suitable. We consider the Laser Interferometer Space Antenna (LISA), a constellation of multiple LISA-like clusters, and the Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO). Specifically, we test whether these detector constellations can probe the anisotropies of the SGWB. For this scope, we considered the SGWB produced by two astrophysical sources: merging compact binaries and a recently proposed scenario for massive black-hole seed formation through multiple mergers of stellar remnants. We find that measuring the angular power spectrum of the SGWB anisotropies is almost unattainable. However, it turns out that it could be possible to probe the SGWB anisotropies through cross-correlation with the CMB fluctuations. In particular, we find that a constellation of two LISA-like detectors and CMB-S4 can marginally constrain the cross-correlation between the CMB lensing convergence and the SGWB produced by the black hole seed formation process. Moreover, we find that DECIGO can probe the cross-correlation between the CMB lensing and the SGWB from merging compact binaries. |
1906.05668 | Abdolhosein Khodam-Mohammadi | Z. Molavi and A. Khodam-Mohammadi | Observational Tests of Gauss-Bonnet Like Dark Energy Model | 19 pages, 6 figures | Eur. Phys. J. Plus (2019) 134: 254 | 10.1140/epjp/i2019-12723-x | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The consistency of some dynamical dark energy models based on Gauss-Bonnet
invariant, ${\cal G}$, is studied compared with cosmological observational
tests. The investigated models are modified form of Gauss Bonnet dark energy,
MGB-DE and two other versions which are interacting MGB and $n_0$MGB. The
energy density of proposed models are combinations of powers of the Hubble
rate, H, and its time derivative. To inquire the performance of MGB dark energy
models, we have used data analyzing methods and numerical solutions, in both
background and perturbed levels, based on recent observational data from SNIa,
Baryon Acoustic Oscillations (BAO), Hubble parameter, CMB data, and structure
formation data surveys. Employing joint data sets and comparing the results to
those of LCDM, show that all versions of MGB-DE predicts the expansion history
and evolution of structures appropriately as well as $\Lambda$CDM. If we use
pure late universe data set, we see that all models of MGB-DE are successful in
recent epoch, and there is not any significant evidence against or in favor of
$\Lambda$CDM, whereas for early universe, statistical results indicate a
significantly better agreement for $\Lambda$CDM as compared to all versions of
MGB-DE models.
| [
{
"created": "Tue, 11 Jun 2019 07:55:07 GMT",
"version": "v1"
}
] | 2019-06-14 | [
[
"Molavi",
"Z.",
""
],
[
"Khodam-Mohammadi",
"A.",
""
]
] | The consistency of some dynamical dark energy models based on Gauss-Bonnet invariant, ${\cal G}$, is studied compared with cosmological observational tests. The investigated models are modified form of Gauss Bonnet dark energy, MGB-DE and two other versions which are interacting MGB and $n_0$MGB. The energy density of proposed models are combinations of powers of the Hubble rate, H, and its time derivative. To inquire the performance of MGB dark energy models, we have used data analyzing methods and numerical solutions, in both background and perturbed levels, based on recent observational data from SNIa, Baryon Acoustic Oscillations (BAO), Hubble parameter, CMB data, and structure formation data surveys. Employing joint data sets and comparing the results to those of LCDM, show that all versions of MGB-DE predicts the expansion history and evolution of structures appropriately as well as $\Lambda$CDM. If we use pure late universe data set, we see that all models of MGB-DE are successful in recent epoch, and there is not any significant evidence against or in favor of $\Lambda$CDM, whereas for early universe, statistical results indicate a significantly better agreement for $\Lambda$CDM as compared to all versions of MGB-DE models. |
2004.00822 | Naoki Tsukamoto | Naoki Tsukamoto | Nonlogarithmic divergence of a deflection angle by a marginally unstable
photon sphere of the Damour-Solodukhin wormhole in a strong deflection limit | 13 pages, 3 figures, typos corrected, accepted for publication in
Physical Review D | Phys. Rev. D 101, 104021 (2020) | 10.1103/PhysRevD.101.104021 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Static, spherically symmetric black holes and compact objects without an
event horizon have unstable (stable) circular orbits of a light called photon
(antiphoton) sphere. A Damour-Solodukhin wormhole has been suggested as a
simple black hole mimicker and the difference of its metric tensors from a
black hole is described by a dimensionless parameter $\lambda$. The wormhole
with two flat regions has two photon spheres and an antiphoton sphere for
$\lambda<\sqrt{2}/2$ and a photon sphere for $\lambda \geq \sqrt{2}/2$. When
the parameter $\lambda$ is $\sqrt{2}/2$, the photon sphere is marginally
unstable because of degeneration of the photon spheres and antiphoton sphere.
We investigate gravitational lensing by the wormhole in weak and strong
gravitational fields. We find that the deflection angle of a light ray
reflected by the marginally unstable photon sphere diverges nonlogarithmically
in a strong deflection limit for $\lambda=\sqrt{2}/2$, while the deflection
angle reflected by the photon sphere diverges logarithmically for $\lambda \neq
\sqrt{2}/2$. We extend a strong deflection limit analysis for the
nonlogarithmic divergence case. We expect that our method can be applied for
gravitational lenses by marginally unstable photon spheres of various compact
objects.
| [
{
"created": "Thu, 2 Apr 2020 05:17:36 GMT",
"version": "v1"
},
{
"created": "Wed, 6 May 2020 16:28:47 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Sep 2022 13:23:44 GMT",
"version": "v3"
}
] | 2022-09-27 | [
[
"Tsukamoto",
"Naoki",
""
]
] | Static, spherically symmetric black holes and compact objects without an event horizon have unstable (stable) circular orbits of a light called photon (antiphoton) sphere. A Damour-Solodukhin wormhole has been suggested as a simple black hole mimicker and the difference of its metric tensors from a black hole is described by a dimensionless parameter $\lambda$. The wormhole with two flat regions has two photon spheres and an antiphoton sphere for $\lambda<\sqrt{2}/2$ and a photon sphere for $\lambda \geq \sqrt{2}/2$. When the parameter $\lambda$ is $\sqrt{2}/2$, the photon sphere is marginally unstable because of degeneration of the photon spheres and antiphoton sphere. We investigate gravitational lensing by the wormhole in weak and strong gravitational fields. We find that the deflection angle of a light ray reflected by the marginally unstable photon sphere diverges nonlogarithmically in a strong deflection limit for $\lambda=\sqrt{2}/2$, while the deflection angle reflected by the photon sphere diverges logarithmically for $\lambda \neq \sqrt{2}/2$. We extend a strong deflection limit analysis for the nonlogarithmic divergence case. We expect that our method can be applied for gravitational lenses by marginally unstable photon spheres of various compact objects. |
0710.4418 | Folkert Muller-Hoissen | Folkert Muller-Hoissen | Noncommutative Geometries and Gravity | 18 pages, to appear in the Proceedings of the Third Mexican Meeting
on Mathematical and Experimental Physics, Symposium on Gravitation and
Cosmology, Mexico City, 10-14 September 2007 | AIPConf.Proc.977:12-29,2008 | 10.1063/1.2902778 | null | gr-qc | null | We briefly review ideas about ``noncommutativity of space-time'' and
approaches toward a corresponding theory of gravity.
| [
{
"created": "Wed, 24 Oct 2007 09:50:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Muller-Hoissen",
"Folkert",
""
]
] | We briefly review ideas about ``noncommutativity of space-time'' and approaches toward a corresponding theory of gravity. |
2202.06125 | Zbigniew Haba | Z.Haba | Graviton noise:the Heisenberg picture | 15 pages | Int.Journ.Mod.Phys.D32,2350005(2023) | 10.1142/S0218271823500050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesic deviation equation for a quantum particle in a
linearized quantum gravitational field. Particle's Heisenberg equations of
motion are treated as stochastic equations with a quantum noise. We explore the
stochastic equation beyond its local approximation as a differential. We
discuss the squeezed states resulting from an inflationary evolution. We
calculate the noise in the thermal and squeezed states.
| [
{
"created": "Sat, 12 Feb 2022 18:58:17 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Sep 2022 20:17:13 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Mar 2023 15:29:38 GMT",
"version": "v3"
}
] | 2023-03-02 | [
[
"Haba",
"Z.",
""
]
] | We study the geodesic deviation equation for a quantum particle in a linearized quantum gravitational field. Particle's Heisenberg equations of motion are treated as stochastic equations with a quantum noise. We explore the stochastic equation beyond its local approximation as a differential. We discuss the squeezed states resulting from an inflationary evolution. We calculate the noise in the thermal and squeezed states. |
0905.3968 | Ken-Ichi Nakao | Ken-ichi Nakao, Tomohiro Harada, Yasunari Kurita, Yoshiyuki Morisawa | Relativistic Gravitational Collapse of a Cylindrical Shell of Dust II:
Settling Down Boundary Condition | 24 pages, 10 figures | Prog.Theor.Phys.122:521-541,2009 | 10.1143/PTP.122.521 | OCU-PHYS-306, AP-GR-63 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically study the dynamics of an imploding hollow cylinder composed of
dust. Since there is no cylindrical black hole in 4-dimensional spacetime with
physically reasonable energy conditions, a collapsed dust cylinder involves a
naked singularity accompanied by its causal future, or a fatal singularity
which terminates the history of the whole universe. In a previous paper, the
present authors have shown that if the dust is assumed to be composed of
collisionless particles such that these particles go through the symmetry axis
of the cylinder, then the scalar polynomial singularity formed on the symmetry
axis is so weak that almost all of geodesics are complete, and thus effectively
no singularity forms by the collapse of a hollow dust cylinder. By contrast, in
this paper, we assume that whole of the collapsed dust settles down on the
symmetry axis by changing its equation of state. Obtained solutions are the
straightforward extension of Morgan's null dust solution, in which no
gravitational radiation is emitted. However, in the present case with timelike
dust, infinite amount of $C$-energy initially stored in the system is released
through gravitational radiation. We also show that the gravitational waves
asymptotically behave in a self-similar manner.
| [
{
"created": "Mon, 25 May 2009 08:50:37 GMT",
"version": "v1"
}
] | 2009-11-19 | [
[
"Nakao",
"Ken-ichi",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Kurita",
"Yasunari",
""
],
[
"Morisawa",
"Yoshiyuki",
""
]
] | We numerically study the dynamics of an imploding hollow cylinder composed of dust. Since there is no cylindrical black hole in 4-dimensional spacetime with physically reasonable energy conditions, a collapsed dust cylinder involves a naked singularity accompanied by its causal future, or a fatal singularity which terminates the history of the whole universe. In a previous paper, the present authors have shown that if the dust is assumed to be composed of collisionless particles such that these particles go through the symmetry axis of the cylinder, then the scalar polynomial singularity formed on the symmetry axis is so weak that almost all of geodesics are complete, and thus effectively no singularity forms by the collapse of a hollow dust cylinder. By contrast, in this paper, we assume that whole of the collapsed dust settles down on the symmetry axis by changing its equation of state. Obtained solutions are the straightforward extension of Morgan's null dust solution, in which no gravitational radiation is emitted. However, in the present case with timelike dust, infinite amount of $C$-energy initially stored in the system is released through gravitational radiation. We also show that the gravitational waves asymptotically behave in a self-similar manner. |
2403.19383 | Maciej Ossowski | Jerzy Lewandowski, Maciej Ossowski | Vacuum Petrov type D horizons of non-trivial $U(1)$ bundle structure
over Riemann surfaces with genus $> 0$ | 24 pages, minor typos corrected, version published in PRD | Phys. Rev. D 110, 024071 (2024) | 10.1103/PhysRevD.110.024071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider isolated horizons (Killing horizons up to the second order) whose
null flow has the structure of a U(1) principal fiber bundle over a compact
Riemann surface. We impose the vacuum Einstein equations (with the cosmological
constant) and the condition that the spacetime Weyl tensor is of Petrov D type
on the geometry of the horizons. We derive all the solutions in the case when
the genus of the surface is $>1$. By doing so for all the non-trivial bundles,
we complete the classification. We construct the embedding spacetimes and show
that they are locally isometric to the toroidal or hyperbolic generalization of
the Taub-NUT-(anti-) de Sitter spacetimes for horizons of genus $1$ or $>1$
respectively, after performing Misner's identification of the spacetime. The
horizon bundle structure can be naturally extended to bundle structure defined
on the entire spacetime.
| [
{
"created": "Thu, 28 Mar 2024 12:45:34 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Aug 2024 10:25:49 GMT",
"version": "v2"
}
] | 2024-08-16 | [
[
"Lewandowski",
"Jerzy",
""
],
[
"Ossowski",
"Maciej",
""
]
] | We consider isolated horizons (Killing horizons up to the second order) whose null flow has the structure of a U(1) principal fiber bundle over a compact Riemann surface. We impose the vacuum Einstein equations (with the cosmological constant) and the condition that the spacetime Weyl tensor is of Petrov D type on the geometry of the horizons. We derive all the solutions in the case when the genus of the surface is $>1$. By doing so for all the non-trivial bundles, we complete the classification. We construct the embedding spacetimes and show that they are locally isometric to the toroidal or hyperbolic generalization of the Taub-NUT-(anti-) de Sitter spacetimes for horizons of genus $1$ or $>1$ respectively, after performing Misner's identification of the spacetime. The horizon bundle structure can be naturally extended to bundle structure defined on the entire spacetime. |
2009.01125 | Simone Speziale | Andrea Calcinari, Laurent Freidel, Etera Livine and Simone Speziale | Twisted Geometries Coherent States for Loop Quantum Gravity | 21 pages + Appendices. Various color figures. v2: minor corrections,
matches published version | null | 10.1088/1361-6382/abc273 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a new family of coherent states for loop quantum gravity,
inspired by the twisted geometry parametrization. We compute their peakedness
properties and compare them with the heat-kernel coherent states. They show
similar features for the area and the holonomy operators, but improved
peakedness in the direction of the flux. At the gauge-invariant level, the new
family is built from tensor products of coherent intertwiners. To study the
peakedness of the holonomy operator, we introduce a new shift operator based on
the harmonic oscillator representation associated with the twisted geometry
parametrization. The new shift operator captures the components of the holonomy
relevant to disentangle its action into a simple positive shift of the spins.
| [
{
"created": "Wed, 2 Sep 2020 15:04:30 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Oct 2020 18:59:52 GMT",
"version": "v2"
}
] | 2021-02-03 | [
[
"Calcinari",
"Andrea",
""
],
[
"Freidel",
"Laurent",
""
],
[
"Livine",
"Etera",
""
],
[
"Speziale",
"Simone",
""
]
] | We introduce a new family of coherent states for loop quantum gravity, inspired by the twisted geometry parametrization. We compute their peakedness properties and compare them with the heat-kernel coherent states. They show similar features for the area and the holonomy operators, but improved peakedness in the direction of the flux. At the gauge-invariant level, the new family is built from tensor products of coherent intertwiners. To study the peakedness of the holonomy operator, we introduce a new shift operator based on the harmonic oscillator representation associated with the twisted geometry parametrization. The new shift operator captures the components of the holonomy relevant to disentangle its action into a simple positive shift of the spins. |
1711.01067 | Mohammad Vahid Takook | M.V. Takook | Quantum de Sitter-black hole in ambient space formalism | 11 pages, Lecture presented at 5th Workshop and Seminar on Topics in
Theoretical Physics, Azarbaijan Shahid Madani University, IRAN, 23-25 August
(2017) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two important problems in studying the quantum black hole, namely the
construction of the Hilbert space and the definition of the time evolution
operator on such Hilbert space, are discussed using the de Sitter background
field method for an observer far from the black hole. This is achieved through
the ambient space formalism. Remarkably, in this approximation (distant
observer), the theory preserves unitarity and analyticity, it is free from any
infrared divergence, and it renders a quantum black hole entropy that turns out
to be finite.
| [
{
"created": "Fri, 3 Nov 2017 09:05:13 GMT",
"version": "v1"
}
] | 2017-11-06 | [
[
"Takook",
"M. V.",
""
]
] | Two important problems in studying the quantum black hole, namely the construction of the Hilbert space and the definition of the time evolution operator on such Hilbert space, are discussed using the de Sitter background field method for an observer far from the black hole. This is achieved through the ambient space formalism. Remarkably, in this approximation (distant observer), the theory preserves unitarity and analyticity, it is free from any infrared divergence, and it renders a quantum black hole entropy that turns out to be finite. |
gr-qc/0012089 | Niall O. Murchadha | Julian Barbour (College Farm), Brendan Foster (UMD), Niall \'O
Murchadha (UCC) | Relativity without relativity | minor revisions, accepted for publication by Classical and Quantum
Gravity | Class.Quant.Grav. 19 (2002) 3217-3248 | 10.1088/0264-9381/19/12/308 | null | gr-qc | null | We give a derivation of general relativity and the gauge principle that is
novel in presupposing neither spacetime nor the relativity principle. We
consider a class of actions defined on superspace with two key properties. The
first is 3-coordinate invariance. This is the only postulated symmetry, and it
leads to the standard momentum constraint. The second property is that the
Lagrangian is constructed from a `local' square root of an expression quadratic
in the velocities, `local' because it is taken before integration over 3-space.
It gives rise to quadratic constraints that do not correspond to any symmetry
and are not, in general, propagated by the Euler-Lagrange equations. Therefore
these actions are internally inconsistent. Only one action of this form is well
behaved: the Baierlein-Sharp-Wheeler reparametrisation-invariant action for GR.
From this viewpoint, spacetime symmetry is emergent. It appears as a `hidden'
symmetry in the (underdetermined) solutions of the evolution equations, without
being manifestly coded into the action itself. In addition, propagation of the
constraints acts as a striking selection mechanism beyond pure gravity. If a
scalar field is included in the configuration space, it must have the same
characteristic speed as gravity. Thus Einstein causality emerges. Finally,
self-consistency requires that any 3-vector field must satisfy Einstein
causality, the equivalence principle and, in addition, the Gauss constraint.
Therefore we recover the standard (massless) Maxwell equations.
| [
{
"created": "Thu, 21 Dec 2000 18:06:57 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2002 14:49:54 GMT",
"version": "v2"
},
{
"created": "Thu, 9 May 2002 20:08:05 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Barbour",
"Julian",
"",
"College Farm"
],
[
"Foster",
"Brendan",
"",
"UMD"
],
[
"Murchadha",
"Niall Ó",
"",
"UCC"
]
] | We give a derivation of general relativity and the gauge principle that is novel in presupposing neither spacetime nor the relativity principle. We consider a class of actions defined on superspace with two key properties. The first is 3-coordinate invariance. This is the only postulated symmetry, and it leads to the standard momentum constraint. The second property is that the Lagrangian is constructed from a `local' square root of an expression quadratic in the velocities, `local' because it is taken before integration over 3-space. It gives rise to quadratic constraints that do not correspond to any symmetry and are not, in general, propagated by the Euler-Lagrange equations. Therefore these actions are internally inconsistent. Only one action of this form is well behaved: the Baierlein-Sharp-Wheeler reparametrisation-invariant action for GR. From this viewpoint, spacetime symmetry is emergent. It appears as a `hidden' symmetry in the (underdetermined) solutions of the evolution equations, without being manifestly coded into the action itself. In addition, propagation of the constraints acts as a striking selection mechanism beyond pure gravity. If a scalar field is included in the configuration space, it must have the same characteristic speed as gravity. Thus Einstein causality emerges. Finally, self-consistency requires that any 3-vector field must satisfy Einstein causality, the equivalence principle and, in addition, the Gauss constraint. Therefore we recover the standard (massless) Maxwell equations. |
1111.4927 | Christian Corda cordac | C. Corda, D. Leiter, H. J. Mosquera Cuesta, S. Robertson, R. E. Schild | Farewell to black hole horizons and singularities? | Invited review, 11 pages. Paper dedicated to the Memory of Professor
Darryl Jay Leiter, February 25, 1937 - March 4, 2011 | Journal of Cosmology, 17, 13 (2011) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the fundamental issues which dominate the question about the
existence or non-existence of black hole horizons and singularities from both
of the theoretical and observational points of view, and discuss some of the
ways that black hole singularities can be prevented from forming at a classical
level, i.e. without arguments of quantum gravity. In this way, we argue that
black holes could have a different nature with respect the common belief. In
fact, even remaining very compact astrophysics objects, they could be devoid of
horizons and singularities. Our analysis represents a key point within the
debate on the path to unification of theories. As recently some scientists
partially retrieved the old Einstein's opinion that quantum mechanics has to be
subjected to a more general deterministic theory, a way to find solutions to
the problem of black hole horizons and singularities at a semi-classical level,
i.e. without discussions of quantum gravity, becomes a fundamental framework.
| [
{
"created": "Mon, 21 Nov 2011 16:51:44 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Nov 2011 09:00:22 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Nov 2011 06:45:10 GMT",
"version": "v3"
},
{
"created": "Wed, 30 Nov 2011 08:40:45 GMT",
"version": "v4"
}
] | 2011-12-01 | [
[
"Corda",
"C.",
""
],
[
"Leiter",
"D.",
""
],
[
"Cuesta",
"H. J. Mosquera",
""
],
[
"Robertson",
"S.",
""
],
[
"Schild",
"R. E.",
""
]
] | We consider the fundamental issues which dominate the question about the existence or non-existence of black hole horizons and singularities from both of the theoretical and observational points of view, and discuss some of the ways that black hole singularities can be prevented from forming at a classical level, i.e. without arguments of quantum gravity. In this way, we argue that black holes could have a different nature with respect the common belief. In fact, even remaining very compact astrophysics objects, they could be devoid of horizons and singularities. Our analysis represents a key point within the debate on the path to unification of theories. As recently some scientists partially retrieved the old Einstein's opinion that quantum mechanics has to be subjected to a more general deterministic theory, a way to find solutions to the problem of black hole horizons and singularities at a semi-classical level, i.e. without discussions of quantum gravity, becomes a fundamental framework. |
2007.10579 | Vladimir Folomeev | Vladimir Dzhunushaliev and Vladimir Folomeev | On the linear stability of polytropic fluid spheres in $R^2$ gravity | 8 pages, 2 figures, some corrections to content, new reference added,
version published in IJGMMP | International Journal of Geometric Methods in Modern Physics,
2050165 (2020) | 10.1142/S0219887820501650 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within $R^2$ gravity, we study the linear stability of strongly gravitating
spherically symmetric configurations supported by a polytropic fluid. All
calculations are carried out in the Jordan frame. It is demonstrated that, as
in general relativity, the transition from stable to unstable systems occurs at
the maximum of the curve mass-central density of the fluid.
| [
{
"created": "Tue, 21 Jul 2020 03:38:31 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Sep 2020 06:38:50 GMT",
"version": "v2"
}
] | 2020-09-29 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
]
] | Within $R^2$ gravity, we study the linear stability of strongly gravitating spherically symmetric configurations supported by a polytropic fluid. All calculations are carried out in the Jordan frame. It is demonstrated that, as in general relativity, the transition from stable to unstable systems occurs at the maximum of the curve mass-central density of the fluid. |
2406.10343 | Alexander Grant | Alexander M. Grant | Flux-balance laws for spinning bodies under the gravitational self-force | 22 pages, 1 figure | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of an extended, but still weakly gravitating body in general
relativity can often be determined by a set of conserved quantities. If they
are sufficient in number, this allows for a complete solution to the equations
of motion, much like for geodesic motion. Under the gravitational self-force
(relaxing the "weakly gravitating" assumption), these "conserved quantities"
evolve with time. This evolution can be calculated using the (local) self-force
on the body, but such an approach is computationally intensive. To avoid this,
one often instead uses flux-balance laws: relationships between the average
evolution (capturing the dissipative dynamics) and the values of the field far
away from the body, which are far easier to compute. In the absence of spin,
such a flux-balance law has been proven in [Isoyama et al., 2019] for any of
the conserved action variables appearing in a Hamiltonian formulation of
geodesic motion in the Kerr spacetime. In this paper, we attempt to extend this
flux-balance law to linear order in spin, in the context of an arbitrary black
hole spacetime, and in a way that directly relates the average rates of change
to the flux of a conserved current through the horizon and to infinity. In the
absence of spin, we reproduce results consistent with those in [Isoyama et al.,
2019]. To linear order in spin we show that most, but not all, constants of
motion at linear order in spin appear to possess flux-balance laws.
| [
{
"created": "Fri, 14 Jun 2024 18:00:05 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Grant",
"Alexander M.",
""
]
] | The motion of an extended, but still weakly gravitating body in general relativity can often be determined by a set of conserved quantities. If they are sufficient in number, this allows for a complete solution to the equations of motion, much like for geodesic motion. Under the gravitational self-force (relaxing the "weakly gravitating" assumption), these "conserved quantities" evolve with time. This evolution can be calculated using the (local) self-force on the body, but such an approach is computationally intensive. To avoid this, one often instead uses flux-balance laws: relationships between the average evolution (capturing the dissipative dynamics) and the values of the field far away from the body, which are far easier to compute. In the absence of spin, such a flux-balance law has been proven in [Isoyama et al., 2019] for any of the conserved action variables appearing in a Hamiltonian formulation of geodesic motion in the Kerr spacetime. In this paper, we attempt to extend this flux-balance law to linear order in spin, in the context of an arbitrary black hole spacetime, and in a way that directly relates the average rates of change to the flux of a conserved current through the horizon and to infinity. In the absence of spin, we reproduce results consistent with those in [Isoyama et al., 2019]. To linear order in spin we show that most, but not all, constants of motion at linear order in spin appear to possess flux-balance laws. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.