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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1607.05524 | Sourav Dutta | Sourav Dutta and Subenoy Chakraborty | Answer to the Comments on the paper "A study of phantom scalar field
cosmology using Lie and Noether symmetries" by A. Paliathanasis, et al.
arXiv:1605.05147 | null | null | 10.1142/S021827181675002X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a short communication in reference to the comments in (arXiv:
1605.05147) of our paper in Int. J. Mod. Phys. D 25, 1650051 (2016). We have
tried to answer to the comments or criticism in the paper.
| [
{
"created": "Tue, 19 Jul 2016 11:23:17 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Dutta",
"Sourav",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | This is a short communication in reference to the comments in (arXiv: 1605.05147) of our paper in Int. J. Mod. Phys. D 25, 1650051 (2016). We have tried to answer to the comments or criticism in the paper. |
1301.4553 | Abhishek Majhi | Abhishek Majhi, Parthasarathi Majumdar | Quantum Hairs and Entropy of Quantum Isolated Horizon from Chern-Simons
Theory | 11 pages, version accepted for publication in Classical and Quantum
Gravity | Class. Quantum Grav. 31 (2014) 195003 | 10.1088/0264-9381/31/19/195003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We articulate the fact that the loop quantum gravity description of the
quantum macrostates of black hole horizons, modeled as Quantum Isolated
Horizons (QIHs), is completely characterized in terms of two independent
integer-valued `quantum hairs', viz,. the coupling constant $(k)$ of the
quantum $SU(2)$ Chern-Simons theory describing QIH dynamics, and the number of
punctures $(N)$ produced by the bulk spin network edges piercing the isolated
horizon (which act as pointlike sources for the Chern- Simons fields). We
demonstrate that the microcanonical entropy of macroscopic (both parameters
assuming very large values) QIHs can be obtained directly from the microstates
of this Chern-Simons theory, using standard statistical mechanical methods,
without having to additionally postulate the horizon as an ideal gas of
punctures, or incorporate any additional classical or semi-classical input from
general relativity vis-a-vis the functional dependence of the IH mass on its
area, or indeed, without having to restrict to any special class of spins.
Requiring the validity of the Bekenstein-Hawking area law relates these two
parameters (as an equilibrium `equation of state') and consequently allows the
Barbero-Immirzi parameter to take any real and positive value depending on the
value of $k/N$. The logarithmic correction to the area law obtained a decade
ago by R. Kaul and one of us (P.M.), ensues straightforwardly, with precisely
the coefficient -3/2, making it a signature of the loop quantum gravity
approach to black hole entropy.
| [
{
"created": "Sat, 19 Jan 2013 10:10:24 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Mar 2014 14:39:26 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Aug 2014 14:07:29 GMT",
"version": "v3"
}
] | 2014-09-16 | [
[
"Majhi",
"Abhishek",
""
],
[
"Majumdar",
"Parthasarathi",
""
]
] | We articulate the fact that the loop quantum gravity description of the quantum macrostates of black hole horizons, modeled as Quantum Isolated Horizons (QIHs), is completely characterized in terms of two independent integer-valued `quantum hairs', viz,. the coupling constant $(k)$ of the quantum $SU(2)$ Chern-Simons theory describing QIH dynamics, and the number of punctures $(N)$ produced by the bulk spin network edges piercing the isolated horizon (which act as pointlike sources for the Chern- Simons fields). We demonstrate that the microcanonical entropy of macroscopic (both parameters assuming very large values) QIHs can be obtained directly from the microstates of this Chern-Simons theory, using standard statistical mechanical methods, without having to additionally postulate the horizon as an ideal gas of punctures, or incorporate any additional classical or semi-classical input from general relativity vis-a-vis the functional dependence of the IH mass on its area, or indeed, without having to restrict to any special class of spins. Requiring the validity of the Bekenstein-Hawking area law relates these two parameters (as an equilibrium `equation of state') and consequently allows the Barbero-Immirzi parameter to take any real and positive value depending on the value of $k/N$. The logarithmic correction to the area law obtained a decade ago by R. Kaul and one of us (P.M.), ensues straightforwardly, with precisely the coefficient -3/2, making it a signature of the loop quantum gravity approach to black hole entropy. |
2205.06329 | Marco Schreck MS | Carlos M. Reyes, Marco Schreck, Alex Soto | Cosmology in the presence of diffeomorphism-violating, nondynamical
background fields | 18 pages, 2 figures | null | 10.1103/PhysRevD.106.023524 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider diffeomorphism violation, which is parameterized by nondynamical
background fields of the gravitational Standard-Model Extension (SME), and
study its effects on the time evolution of the Universe. Our goal is to
identify background field configurations that imply stages of accelerated
expansion without exotic forms of matter and radiation present. Although our
approach gives rise to a set of restrictive conditions, configurations are
encountered that exhibit this property or show other interesting behaviors. The
findings of our article, which is among the first to apply the SME to a
cosmological setting, provide an initial understanding of how to technically
incorporate background fields into the cosmological evolution equations and
what their phenomenological impact may be.
| [
{
"created": "Thu, 12 May 2022 19:38:20 GMT",
"version": "v1"
}
] | 2022-08-03 | [
[
"Reyes",
"Carlos M.",
""
],
[
"Schreck",
"Marco",
""
],
[
"Soto",
"Alex",
""
]
] | We consider diffeomorphism violation, which is parameterized by nondynamical background fields of the gravitational Standard-Model Extension (SME), and study its effects on the time evolution of the Universe. Our goal is to identify background field configurations that imply stages of accelerated expansion without exotic forms of matter and radiation present. Although our approach gives rise to a set of restrictive conditions, configurations are encountered that exhibit this property or show other interesting behaviors. The findings of our article, which is among the first to apply the SME to a cosmological setting, provide an initial understanding of how to technically incorporate background fields into the cosmological evolution equations and what their phenomenological impact may be. |
2204.11676 | Diego S\'aez-Chill\'on G\'omez | Diego \'Alvarez-Ortega, Gonzalo J. Olmo, Diego Rubiera-Garc\'ia and
Diego S\'aez-Chill\'on G\'omez | Eternal vs singular observers in interacting dark energy-dark matter
models | 14 pages, 3 figures | null | 10.1103/PhysRevD.106.023523 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interacting dark energy-dark matter models have been widely analyzed in the
literature in an attempt to find traces of new physics beyond the usual
cosmological ($\Lambda$CDM) models. Such a coupling between both dark
components is usually introduced in a phenomenological way through a flux in
the continuity equation. However, models with a Lagrangian formulation are also
possible. A class of the latter assumes a conformal/disformal coupling that
leads to a fifth force on the dark matter component, which consequently does
not follow the same geodesics as the other (baryonic, radiation, and dark
energy) matter sources. Here we analyze how the usual cosmological
singularities of the standard matter frame are seen from the dark matter one,
concluding that by choosing an appropriate coupling, dark matter observers will
see no singularities but a non-beginning, non-ending universe. By considering
two simple phenomenological models we show that such a type of coupling can fit
observational data as well as the usual $\Lambda$CDM model.
| [
{
"created": "Mon, 25 Apr 2022 14:12:57 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Álvarez-Ortega",
"Diego",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-García",
"Diego",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
]
] | Interacting dark energy-dark matter models have been widely analyzed in the literature in an attempt to find traces of new physics beyond the usual cosmological ($\Lambda$CDM) models. Such a coupling between both dark components is usually introduced in a phenomenological way through a flux in the continuity equation. However, models with a Lagrangian formulation are also possible. A class of the latter assumes a conformal/disformal coupling that leads to a fifth force on the dark matter component, which consequently does not follow the same geodesics as the other (baryonic, radiation, and dark energy) matter sources. Here we analyze how the usual cosmological singularities of the standard matter frame are seen from the dark matter one, concluding that by choosing an appropriate coupling, dark matter observers will see no singularities but a non-beginning, non-ending universe. By considering two simple phenomenological models we show that such a type of coupling can fit observational data as well as the usual $\Lambda$CDM model. |
gr-qc/0512026 | Iver. H. Brevik | Iver Brevik, Jon-Mattis Borven, and Sebastian Ng | Viscous Brane Cosmology with a Brane-Bulk Energy Interchange Term | 12 pages, latex, no figures | Gen.Rel.Grav.38:907-915,2006 | 10.1007/s10714-006-0271-8 | null | gr-qc hep-th | null | We assume a flat brane located at y=0, surrounded by an AdS space, and
consider the 5D Einstein equations when the energy flux component of the
energy-momentum tensor is related to the Hubble parameter through a constant Q.
We calculate the metric tensor, as well as the Hubble parameter on the brane,
when Q is small. As a special case, if the brane is tensionless, the influence
from Q on the Hubble parameter is absent. We also consider the emission of
gravitons from the brane, by means of the Boltzmann equation. Comparing the
energy conservation equation derived herefrom with the energy conservation
equation for a viscous fluid on the brane, we find that the entropy change for
the fluid in the emission process has to be negative. This peculiar effect is
related to the fluid on the brane being a non-closed thermodynamic system. The
negative entropy property for non-closed systems is encountered in other areas
in physics also, in particular, in connection with the Casimir effect at finite
temperature.
| [
{
"created": "Mon, 5 Dec 2005 10:22:46 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Brevik",
"Iver",
""
],
[
"Borven",
"Jon-Mattis",
""
],
[
"Ng",
"Sebastian",
""
]
] | We assume a flat brane located at y=0, surrounded by an AdS space, and consider the 5D Einstein equations when the energy flux component of the energy-momentum tensor is related to the Hubble parameter through a constant Q. We calculate the metric tensor, as well as the Hubble parameter on the brane, when Q is small. As a special case, if the brane is tensionless, the influence from Q on the Hubble parameter is absent. We also consider the emission of gravitons from the brane, by means of the Boltzmann equation. Comparing the energy conservation equation derived herefrom with the energy conservation equation for a viscous fluid on the brane, we find that the entropy change for the fluid in the emission process has to be negative. This peculiar effect is related to the fluid on the brane being a non-closed thermodynamic system. The negative entropy property for non-closed systems is encountered in other areas in physics also, in particular, in connection with the Casimir effect at finite temperature. |
2406.17402 | Jiawei Hu | Di Hao, Jiawei Hu, Hongwei Yu | Quantum gravitomagnetic interaction | 18 pages, 1 figure | Phys. Rev. D 109, 126016 (2024) | 10.1103/PhysRevD.109.126016 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of linearized quantum gravity, we study the quantum
gravitational interaction between two nonpointlike objects induced by
fluctuating gravitomagnetic fields in vacuum. We find that, in addition to the
quantum gravitational interaction induced by fluctuating gravitoelectric fields
previously studied, there exists a quantum gravitomagnetic interaction. This
interaction originates from the interaction between the instantaneous localized
mass currents in nonpointlike objects induced by the fluctuating
gravitomagnetic fields. Using fourth-order perturbation theory, we derive the
explicit form of the quantum gravitomagnetic interaction energy, which shows an
$r^{-10}$ dependence in the near regime and an $r^{-11}$ dependence in the far
regime, where $r$ is the distance between the two objects. This interaction
energy is expected to be significant when the gravitomagnetic polarizability of
the objects is large.
| [
{
"created": "Tue, 25 Jun 2024 09:25:04 GMT",
"version": "v1"
}
] | 2024-06-26 | [
[
"Hao",
"Di",
""
],
[
"Hu",
"Jiawei",
""
],
[
"Yu",
"Hongwei",
""
]
] | In the framework of linearized quantum gravity, we study the quantum gravitational interaction between two nonpointlike objects induced by fluctuating gravitomagnetic fields in vacuum. We find that, in addition to the quantum gravitational interaction induced by fluctuating gravitoelectric fields previously studied, there exists a quantum gravitomagnetic interaction. This interaction originates from the interaction between the instantaneous localized mass currents in nonpointlike objects induced by the fluctuating gravitomagnetic fields. Using fourth-order perturbation theory, we derive the explicit form of the quantum gravitomagnetic interaction energy, which shows an $r^{-10}$ dependence in the near regime and an $r^{-11}$ dependence in the far regime, where $r$ is the distance between the two objects. This interaction energy is expected to be significant when the gravitomagnetic polarizability of the objects is large. |
gr-qc/0010106 | Sarah Beryl Melisande Bell | Sarah B. M. Bell, John P. Cullerne and Bernard M. Diaz (Department of
Computer Science I. Q. Group, University of Liverpool, United Kingdom) | A new approach to quantum gravity: an overview | This paper has been superceded by quant-ph/0104017, quant-ph/0104018,
quant-ph/0110162 and physics/0211108. Proceedings of the Vigier 2000
Symposium, August 21-25, 2000, University of California, Berkeley, CA USA. 9
pages | null | null | null | gr-qc | null | We quantise General Relativity for a class of energy-momentum-stress tensors.
| [
{
"created": "Sat, 28 Oct 2000 17:23:12 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2001 17:50:17 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Nov 2002 20:28:04 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Bell",
"Sarah B. M.",
"",
"Department of\n Computer Science I. Q. Group, University of Liverpool, United Kingdom"
],
[
"Cullerne",
"John P.",
"",
"Department of\n Computer Science I. Q. Group, University of Liverpool, United Kingdom"
],
[
"Diaz",
"Bernard M.",
... | We quantise General Relativity for a class of energy-momentum-stress tensors. |
2312.16589 | Susobhan Mandal | Golam Mortuza Hossain, Susobhan Mandal | Effects of magnetic field on the equation of state in curved spacetime
of a neutron star | 8 pages, 4 figures, revtex4 | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutron stars are known to have strong magnetic fields reaching as high as
$10^{15}$ Gauss, besides having strongly curved interior spacetime. So for
computing an equation of state for neutron-star matter, the effect of magnetic
field as well as curved spacetime should be taken into account. In this
article, we compute the equation of state for an ensemble of degenerate
fermions in the curved spacetime of a neutron star in presence of a magnetic
field. We show that the effect of curved spacetime on the equation of state is
relatively stronger than the effect of observed strengths of magnetic field.
Besides, a thin layer containing only spin-up neutrons is shown to form at the
boundary of a degenerate neutron star.
| [
{
"created": "Wed, 27 Dec 2023 14:30:46 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Hossain",
"Golam Mortuza",
""
],
[
"Mandal",
"Susobhan",
""
]
] | Neutron stars are known to have strong magnetic fields reaching as high as $10^{15}$ Gauss, besides having strongly curved interior spacetime. So for computing an equation of state for neutron-star matter, the effect of magnetic field as well as curved spacetime should be taken into account. In this article, we compute the equation of state for an ensemble of degenerate fermions in the curved spacetime of a neutron star in presence of a magnetic field. We show that the effect of curved spacetime on the equation of state is relatively stronger than the effect of observed strengths of magnetic field. Besides, a thin layer containing only spin-up neutrons is shown to form at the boundary of a degenerate neutron star. |
gr-qc/0401082 | Roberto Aloisio | R. Aloisio, P. Blasi, A. Galante and A.F. Grillo | Phenomenology of Space Time Fluctuations | 18 pages, 1 figure, talk given at the 10th Marcel Grossman Meeting
(Rio de Janeiro, July 20 - 26, 2003) | null | 10.1142/9789812704030_0285 | null | gr-qc astro-ph | null | Quantum gravitational effects may induce stochastic fluctuations in the
structure of space-time, to produce a characteristic foamy structure. It has
been known for some time now that these fluctuations may have observable
consequences for the propagation of cosmic ray particles over cosmological
distances. While invoked as a possible explanation for the detection of the
puzzling cosmic rays with energies in excess of the threshold for photopion
production (the so-called super-GZK particles), we demonstrate here that lower
energy observations may provide strong constraints on the role of a fluctuating
space-time structure. We note also that the same fluctuations, if they exist,
imply that some decay reactions normally forbidden by elementary conservation
laws, become kinematically allowed, inducing the decay of particles that are
seen to be stable in our universe. Due to the strength of the prediction, we
are led to consider this finding as the most severe constraint on the classes
of models that may describe the effects of gravity on the structure of
space-time. We also propose and discuss several potential loopholes of our
approach, that may affect our conclusions. In particular, we try to identify
the situations in which despite a fluctuating energy-momentum of the particles,
the reactions mentioned above may not take place.
| [
{
"created": "Mon, 19 Jan 2004 18:12:31 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Aloisio",
"R.",
""
],
[
"Blasi",
"P.",
""
],
[
"Galante",
"A.",
""
],
[
"Grillo",
"A. F.",
""
]
] | Quantum gravitational effects may induce stochastic fluctuations in the structure of space-time, to produce a characteristic foamy structure. It has been known for some time now that these fluctuations may have observable consequences for the propagation of cosmic ray particles over cosmological distances. While invoked as a possible explanation for the detection of the puzzling cosmic rays with energies in excess of the threshold for photopion production (the so-called super-GZK particles), we demonstrate here that lower energy observations may provide strong constraints on the role of a fluctuating space-time structure. We note also that the same fluctuations, if they exist, imply that some decay reactions normally forbidden by elementary conservation laws, become kinematically allowed, inducing the decay of particles that are seen to be stable in our universe. Due to the strength of the prediction, we are led to consider this finding as the most severe constraint on the classes of models that may describe the effects of gravity on the structure of space-time. We also propose and discuss several potential loopholes of our approach, that may affect our conclusions. In particular, we try to identify the situations in which despite a fluctuating energy-momentum of the particles, the reactions mentioned above may not take place. |
2008.07396 | Arick Shao | Arick Shao | The Near-Boundary Geometry of Einstein-Vacuum Asymptotically Anti-de
Sitter Spacetimes | 46 pages. Accepted version - some typos corrected | null | 10.1088/1361-6382/abc81a | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geometry of a general class of vacuum asymptotically Anti-de
Sitter spacetimes near the conformal boundary. In particular, the spacetime is
only assumed to have finite regularity, and it is allowed to have arbitrary
boundary topology and geometry. For the main results, we derive limits at the
conformal boundary of various geometric quantities, and we use these limits to
construct partial Fefferman--Graham expansions from the boundary. The results
of this article will be applied, in upcoming papers, toward proving symmetry
extension and gravity--boundary correspondence theorems for vacuum
asymptotically Anti-de Sitter spacetimes.
| [
{
"created": "Mon, 17 Aug 2020 15:10:45 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2020 00:41:04 GMT",
"version": "v2"
}
] | 2020-11-18 | [
[
"Shao",
"Arick",
""
]
] | We study the geometry of a general class of vacuum asymptotically Anti-de Sitter spacetimes near the conformal boundary. In particular, the spacetime is only assumed to have finite regularity, and it is allowed to have arbitrary boundary topology and geometry. For the main results, we derive limits at the conformal boundary of various geometric quantities, and we use these limits to construct partial Fefferman--Graham expansions from the boundary. The results of this article will be applied, in upcoming papers, toward proving symmetry extension and gravity--boundary correspondence theorems for vacuum asymptotically Anti-de Sitter spacetimes. |
0704.3372 | Norbert Van den Bergh | Norbert Van den Bergh, John Carminati, Hamid Reza Karimian | Shearfree perfect fluids with solenoidal magnetic curvature and a
gamma-law equation of state | 11 pages | Class.Quant.Grav.24:3735-3744,2007 | 10.1088/0264-9381/24/14/012 | null | gr-qc | null | We show that shearfree perfect fluids obeying an equation of state p=(gamma
-1) mu are non-rotating or non-expanding under the assumption that the spatial
divergence of the magnetic part of the Weyl tensor is zero.
| [
{
"created": "Wed, 25 Apr 2007 13:49:55 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bergh",
"Norbert Van den",
""
],
[
"Carminati",
"John",
""
],
[
"Karimian",
"Hamid Reza",
""
]
] | We show that shearfree perfect fluids obeying an equation of state p=(gamma -1) mu are non-rotating or non-expanding under the assumption that the spatial divergence of the magnetic part of the Weyl tensor is zero. |
0812.2671 | Philippe G. LeFloch | Philippe G. LeFloch | Injectivity radius and optimal regularity of Lorentzian manifolds with
bounded curvature | 13 pages | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review recent work on the local geometry and optimal regularity of
Lorentzian manifolds with bounded curvature. Our main results provide an
estimate of the injectivity radius of an observer, and a local canonical
foliations by CMC (Constant Mean Curvature) hypersurfaces, together with
spatially harmonic coordinates. In contrast with earlier results based on a
global bound for derivatives of the curvature, our method requires only a
sup-norm bound on the curvature near the given observer.
| [
{
"created": "Sun, 14 Dec 2008 19:34:26 GMT",
"version": "v1"
}
] | 2008-12-20 | [
[
"LeFloch",
"Philippe G.",
""
]
] | We review recent work on the local geometry and optimal regularity of Lorentzian manifolds with bounded curvature. Our main results provide an estimate of the injectivity radius of an observer, and a local canonical foliations by CMC (Constant Mean Curvature) hypersurfaces, together with spatially harmonic coordinates. In contrast with earlier results based on a global bound for derivatives of the curvature, our method requires only a sup-norm bound on the curvature near the given observer. |
1705.05340 | Oliver Janssen | Juan Diaz Dorronsoro, Jonathan J. Halliwell, James B. Hartle, Thomas
Hertog and Oliver Janssen | The Real No-Boundary Wave Function in Lorentzian Quantum Cosmology | 1 + 10.5 + 2.5 pages, 2 figures. v2: minor changes and added
references | Phys. Rev. D 96, 043505 (2017) | 10.1103/PhysRevD.96.043505 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the standard no-boundary wave function has a natural
expression in terms of a Lorentzian path integral with its contour defined by
Picard-Lefschetz theory. The wave function is real, satisfies the
Wheeler-DeWitt equation and predicts an ensemble of asymptotically classical,
inflationary universes with nearly-Gaussian fluctuations and with a smooth
semiclassical origin.
| [
{
"created": "Mon, 15 May 2017 17:15:09 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2017 22:51:50 GMT",
"version": "v2"
}
] | 2017-08-16 | [
[
"Dorronsoro",
"Juan Diaz",
""
],
[
"Halliwell",
"Jonathan J.",
""
],
[
"Hartle",
"James B.",
""
],
[
"Hertog",
"Thomas",
""
],
[
"Janssen",
"Oliver",
""
]
] | It is shown that the standard no-boundary wave function has a natural expression in terms of a Lorentzian path integral with its contour defined by Picard-Lefschetz theory. The wave function is real, satisfies the Wheeler-DeWitt equation and predicts an ensemble of asymptotically classical, inflationary universes with nearly-Gaussian fluctuations and with a smooth semiclassical origin. |
gr-qc/0604120 | Luca Lusanna | Luca Lusanna (INFN, Firenze) | The Chrono-geometrical Structure of Special and General Relativity: a
Re-Visitation of Canonical Geometrodynamics | 33 pages, Lectures given at the 42nd Karpacz Winter School of
Theoretical Physics, "Current Mathematical Topics in Gravitation and
Cosmology", Ladek, Poland, 6-11 February 2006 | ECONFC0602061:05,2006; Int.J.Geom.Meth.Mod.Phys.4:79-114,2007 | 10.1142/S0219887807001874 | null | gr-qc astro-ph hep-th | null | A modern re-visitation of the consequences of the lack of an intrinsic notion
of instantaneous 3-space in relativistic theories leads to a reformulation of
their kinematical basis emphasizing the role of non-inertial frames centered on
an arbitrary accelerated observer. In special relativity the exigence of
predictability implies the adoption of the 3+1 point of view, which leads to a
well posed initial value problem for field equations in a framework where the
change of the convention of synchronization of distant clocks is realized by
means of a gauge transformation. This point of view is also at the heart of the
canonical approach to metric and tetrad gravity in globally hyperbolic
asymptotically flat space-times, where the use of Shanmugadhasan canonical
transformations allows the separation of the physical degrees of freedom of the
gravitational field (the tidal effects) from the arbitrary gauge variables.
Since a global vision of the equivalence principle implies that only global
non-inertial frames can exist in general relativity, the gauge variables are
naturally interpreted as generalized relativistic inertial effects, which have
to be fixed to get a deterministic evolution in a given non-inertial frame. As
a consequence, in each Einstein's space-time in this class the whole
chrono-geometrical structure, including also the clock synchronization
convention, is dynamically determined and a new approach to the Hole Argument
leads to the conclusion that "gravitational field" and "space-time" are two
faces of the same entity. This view allows to get a classical scenario for the
unification of the four interactions in a scheme suited to the description of
the solar system or our galaxy with a deperametrization to special relativity
and the subsequent possibility to take the non-relativistic limit.
| [
{
"created": "Thu, 27 Apr 2006 14:34:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lusanna",
"Luca",
"",
"INFN, Firenze"
]
] | A modern re-visitation of the consequences of the lack of an intrinsic notion of instantaneous 3-space in relativistic theories leads to a reformulation of their kinematical basis emphasizing the role of non-inertial frames centered on an arbitrary accelerated observer. In special relativity the exigence of predictability implies the adoption of the 3+1 point of view, which leads to a well posed initial value problem for field equations in a framework where the change of the convention of synchronization of distant clocks is realized by means of a gauge transformation. This point of view is also at the heart of the canonical approach to metric and tetrad gravity in globally hyperbolic asymptotically flat space-times, where the use of Shanmugadhasan canonical transformations allows the separation of the physical degrees of freedom of the gravitational field (the tidal effects) from the arbitrary gauge variables. Since a global vision of the equivalence principle implies that only global non-inertial frames can exist in general relativity, the gauge variables are naturally interpreted as generalized relativistic inertial effects, which have to be fixed to get a deterministic evolution in a given non-inertial frame. As a consequence, in each Einstein's space-time in this class the whole chrono-geometrical structure, including also the clock synchronization convention, is dynamically determined and a new approach to the Hole Argument leads to the conclusion that "gravitational field" and "space-time" are two faces of the same entity. This view allows to get a classical scenario for the unification of the four interactions in a scheme suited to the description of the solar system or our galaxy with a deperametrization to special relativity and the subsequent possibility to take the non-relativistic limit. |
1406.5909 | Ettore Minguzzi | E. Minguzzi | Completeness of Cauchy horizon generators | 14 pages. v2: corrected some typos | J. Math. Phys. 55 (2014) 082503 | 10.1063/1.4893877 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is proved that every compactly generated future Cauchy horizon has past
complete generators, and dually. No condition on the differentiability of the
horizon is imposed.
| [
{
"created": "Mon, 23 Jun 2014 14:05:01 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Oct 2014 15:15:47 GMT",
"version": "v2"
}
] | 2014-10-02 | [
[
"Minguzzi",
"E.",
""
]
] | It is proved that every compactly generated future Cauchy horizon has past complete generators, and dually. No condition on the differentiability of the horizon is imposed. |
2210.13877 | Samuele Marco Silveravalle | Samuele Silveravalle, Alessandro Zuccotti | The phase diagram of Einstein-Weyl gravity | 10 pages, 7 figures | Phys.Rev.D 107 (2023) 6, 064029 | 10.1103/PhysRevD.107.064029 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thanks to their interpretation as first order correction of General
Relativity at high energies, quadratic theories of gravity gained much
attention in recent times. Particular attention has been drawn to the
Einstein-Weyl theory, where the addition of the squared Weyl tensor to the
action opens the possibility of having non-Schwarzschild black holes in the
classical spectrum of the theory. Static and spherically symmetric solutions of
this theory have been studied and classified in terms of their small scales
behaviour; however, a classification of these solutions in terms of the
asymptotic gravitational field is still lacking. In this paper we address this
point and present a phase diagram of the theory, where the different types of
solutions are shown in terms of their mass and the strength of a Yukawa-like
correction to the gravitational field. In particular we will show that, in the
case of compact stars, different equations of state imply different Yukawa
corrections to the gravitational potential, with possible phenomenological
implications.
| [
{
"created": "Tue, 25 Oct 2022 10:05:35 GMT",
"version": "v1"
}
] | 2023-03-17 | [
[
"Silveravalle",
"Samuele",
""
],
[
"Zuccotti",
"Alessandro",
""
]
] | Thanks to their interpretation as first order correction of General Relativity at high energies, quadratic theories of gravity gained much attention in recent times. Particular attention has been drawn to the Einstein-Weyl theory, where the addition of the squared Weyl tensor to the action opens the possibility of having non-Schwarzschild black holes in the classical spectrum of the theory. Static and spherically symmetric solutions of this theory have been studied and classified in terms of their small scales behaviour; however, a classification of these solutions in terms of the asymptotic gravitational field is still lacking. In this paper we address this point and present a phase diagram of the theory, where the different types of solutions are shown in terms of their mass and the strength of a Yukawa-like correction to the gravitational field. In particular we will show that, in the case of compact stars, different equations of state imply different Yukawa corrections to the gravitational potential, with possible phenomenological implications. |
2012.02723 | Shahab Shahidi | Jin-Zhao Yang, Shahab Shahidi, Tiberiu Harko and Shi-Dong Liang | Black hole solutions in modified gravity induced by quantum metric
fluctuations | 23 pages, 30 figures, Accepted for publication in Physics of the Dark
Universe | Phys. Dark Univ. 31 (2021) 100756 | 10.1016/j.dark.2020.100756 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inclusion of the quantum fluctuations of the metric in the geometric
action is a promising avenue for the understanding of the quantum properties of
gravity. In this approach the metric is decomposed in the sum of a classical
and of a fluctuating part, of quantum origin, which can be generally expressed
in terms of an arbitrary second order tensor, constructed from the metric, and
from the thermodynamic quantities describing matter fields. In the present
paper we investigate the effects of the quantum fluctuations on the spherically
symmetric static black hole solutions of the modified field equations, obtained
from a variational principle, by assuming that the quantum correction tensor is
given by the coupling of a scalar field to the metric tensor. After
reformulating the field equations in a dimensionless form, and by introducing a
suitable independent radial coordinate, we obtain their solutions numerically.
We detect the formation of a black hole from the presence of a singularity in
the metric tensor components. Several models, corresponding to different
functional forms of the scalar field potential, are considered. The
thermodynamic properties of the black hole solutions (horizon temperature,
specific heat, entropy and evaporation time due to Hawking luminosity) are also
investigated.
| [
{
"created": "Fri, 4 Dec 2020 17:14:09 GMT",
"version": "v1"
}
] | 2021-04-19 | [
[
"Yang",
"Jin-Zhao",
""
],
[
"Shahidi",
"Shahab",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Liang",
"Shi-Dong",
""
]
] | The inclusion of the quantum fluctuations of the metric in the geometric action is a promising avenue for the understanding of the quantum properties of gravity. In this approach the metric is decomposed in the sum of a classical and of a fluctuating part, of quantum origin, which can be generally expressed in terms of an arbitrary second order tensor, constructed from the metric, and from the thermodynamic quantities describing matter fields. In the present paper we investigate the effects of the quantum fluctuations on the spherically symmetric static black hole solutions of the modified field equations, obtained from a variational principle, by assuming that the quantum correction tensor is given by the coupling of a scalar field to the metric tensor. After reformulating the field equations in a dimensionless form, and by introducing a suitable independent radial coordinate, we obtain their solutions numerically. We detect the formation of a black hole from the presence of a singularity in the metric tensor components. Several models, corresponding to different functional forms of the scalar field potential, are considered. The thermodynamic properties of the black hole solutions (horizon temperature, specific heat, entropy and evaporation time due to Hawking luminosity) are also investigated. |
gr-qc/0105016 | Eric Poisson | William G. Laarakkers and Eric Poisson | Radiative falloff in Einstein-Straus spacetime | ReVTeX, 12 pages, 14 figures | Phys.Rev. D64 (2001) 084008 | 10.1103/PhysRevD.64.084008 | null | gr-qc | null | The Einstein-Straus spacetime describes a nonrotating black hole immersed in
a matter-dominated cosmology. It is constructed by scooping out a spherical
ball of the dust and replacing it with a vacuum region containing a black hole
of the same mass. The metric is smooth at the boundary, which is comoving with
the rest of the universe. We study the evolution of a massless scalar field in
the Einstein-Straus spacetime, with a special emphasis on its late-time
behavior. This is done by numerically integrating the scalar wave equation in a
double-null coordinate system that covers both portions (vacuum and dust) of
the spacetime. We show that the field's evolution is governed mostly by the
strong concentration of curvature near the black hole, and the discontinuity in
the dust's mass density at the boundary; these give rise to a rather complex
behavior at late times. Contrary to what it would do in an asymptotically-flat
spacetime, the field does not decay in time according to an inverse power-law.
| [
{
"created": "Thu, 3 May 2001 19:37:22 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Laarakkers",
"William G.",
""
],
[
"Poisson",
"Eric",
""
]
] | The Einstein-Straus spacetime describes a nonrotating black hole immersed in a matter-dominated cosmology. It is constructed by scooping out a spherical ball of the dust and replacing it with a vacuum region containing a black hole of the same mass. The metric is smooth at the boundary, which is comoving with the rest of the universe. We study the evolution of a massless scalar field in the Einstein-Straus spacetime, with a special emphasis on its late-time behavior. This is done by numerically integrating the scalar wave equation in a double-null coordinate system that covers both portions (vacuum and dust) of the spacetime. We show that the field's evolution is governed mostly by the strong concentration of curvature near the black hole, and the discontinuity in the dust's mass density at the boundary; these give rise to a rather complex behavior at late times. Contrary to what it would do in an asymptotically-flat spacetime, the field does not decay in time according to an inverse power-law. |
1702.07743 | Mart\'in G. Richarte MR | Mauricio Cataldo, Luis P. Chimento, and Mart\'in G. Richarte | Finite time future singularities in the interacting dark sector | 12 pages, 2 figures. Accepted for its publication in Physical Review
D | null | 10.1103/PhysRevD.95.063510 | Phys. Rev. D 95, 063510 (2017) | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a piecewise model that gives a physical viable realization of
finite-time future singularity for a spatially flat Friedmann-Robertson-Walker
universe within the interacting dark matter--dark energy framework, with the
latter one in the form of a variable vacuum energy. The scale factor solutions
provided by the model are accommodated in several branches defined in four
regions delimited by the scale factor and the effective energy density. A
branch starts from a big bang singularity and describes an expanding
matter-dominated universe until the sudden future singularity occurs. Then, an
expanding branch emerges from a past singularity, reaches a maximum, reverses
its expansion and possibly collapses into itself while another expanding branch
emerges from the latter singularity and has a stable de Sitter phase which is
intrinsically stable. We obtain a different piecewise scale factor which
describes a contracting de Sitter universe in the distant past until the
finite-time future singularity happens. It emerges and continues in a
contracting phase, bounces at the minimum, reverses, and enters into a stable
de Sitter phase without a dramatic final. Also, we explore the aforesaid cosmic
scenarios by focusing on the leading contributions of some physical quantities
near the sudden future singularity and applying the geometric Tipler and
Kr\'olak criteria in order to inspect the behavior of timelike geodesic curves
around such singularity.
| [
{
"created": "Fri, 24 Feb 2017 20:02:04 GMT",
"version": "v1"
}
] | 2017-03-14 | [
[
"Cataldo",
"Mauricio",
""
],
[
"Chimento",
"Luis P.",
""
],
[
"Richarte",
"Martín G.",
""
]
] | We construct a piecewise model that gives a physical viable realization of finite-time future singularity for a spatially flat Friedmann-Robertson-Walker universe within the interacting dark matter--dark energy framework, with the latter one in the form of a variable vacuum energy. The scale factor solutions provided by the model are accommodated in several branches defined in four regions delimited by the scale factor and the effective energy density. A branch starts from a big bang singularity and describes an expanding matter-dominated universe until the sudden future singularity occurs. Then, an expanding branch emerges from a past singularity, reaches a maximum, reverses its expansion and possibly collapses into itself while another expanding branch emerges from the latter singularity and has a stable de Sitter phase which is intrinsically stable. We obtain a different piecewise scale factor which describes a contracting de Sitter universe in the distant past until the finite-time future singularity happens. It emerges and continues in a contracting phase, bounces at the minimum, reverses, and enters into a stable de Sitter phase without a dramatic final. Also, we explore the aforesaid cosmic scenarios by focusing on the leading contributions of some physical quantities near the sudden future singularity and applying the geometric Tipler and Kr\'olak criteria in order to inspect the behavior of timelike geodesic curves around such singularity. |
2401.00990 | Yan Peng | Yan Peng | Analytical investigations on the Maxwell electromagnetic invariant in
the spinning and charged horizonless star background | 6 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study properties of the Maxwell electromagnetic invariant in the external
region of spinning and charged horizonless stars. We analytically find that the
minimum negative value of the Maxwell electromagnetic invariant is obtained on
the equator of the star surface. We are interested in scalar fields
non-minimally coupled to the Maxwell electromagnetic invariant. The negative
enough Maxwell electromagnetic invariant can lead to a negative effective mass
term, which forms a binding potential well for the scalar field. It means that
the scalar field coupled to the Maxwell electromagnetic invariant may mostly
exist around the surface of the star on the equator.
| [
{
"created": "Tue, 2 Jan 2024 01:59:52 GMT",
"version": "v1"
}
] | 2024-01-03 | [
[
"Peng",
"Yan",
""
]
] | We study properties of the Maxwell electromagnetic invariant in the external region of spinning and charged horizonless stars. We analytically find that the minimum negative value of the Maxwell electromagnetic invariant is obtained on the equator of the star surface. We are interested in scalar fields non-minimally coupled to the Maxwell electromagnetic invariant. The negative enough Maxwell electromagnetic invariant can lead to a negative effective mass term, which forms a binding potential well for the scalar field. It means that the scalar field coupled to the Maxwell electromagnetic invariant may mostly exist around the surface of the star on the equator. |
1904.05431 | Lucila Kraiselburd | Lucila Kraiselburd, Susana J. Landau, Marcelo Salgado, Daniel Sudarsky
and H\'ector Vucetich | Thick shell regime in the chameleon two-body problem | 12 pages, 6 figures, accepted by PRD | Phys. Rev. D 99, 083516 (2019) | 10.1103/PhysRevD.99.083516 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous paper [Phys. Rev. D 97, 104044 (2018)] we pointed out some
shortcomings of the standard approach to chameleon theories consisting in
treating the small bodies used to test the weak equivalence principle (WEP) as
test particles, whose presence do not modify the chameleon field configuration.
In that paper we developed an alternative method to determine the relevant
field configuration which takes into account the influence of both test and
source bodies, and computed the chamaleon mediated force. Relying on that
analysis we showed that the effective acceleration of test bodies is
composition dependent even when the model is based on universal couplings. In
this paper, we improve our method by using a more suitable approximation for
the effective chameleon potential in situations where the bodies are in the
so-called "thick shell regime". We then find new and more restrictive bounds on
the model' s parametres by confronting the new theoretical predictions with the
empirical bounds on E\"otv\"os parameter comming from the lunar laser ranging
experiments.
| [
{
"created": "Wed, 10 Apr 2019 20:46:21 GMT",
"version": "v1"
}
] | 2019-04-22 | [
[
"Kraiselburd",
"Lucila",
""
],
[
"Landau",
"Susana J.",
""
],
[
"Salgado",
"Marcelo",
""
],
[
"Sudarsky",
"Daniel",
""
],
[
"Vucetich",
"Héctor",
""
]
] | In a previous paper [Phys. Rev. D 97, 104044 (2018)] we pointed out some shortcomings of the standard approach to chameleon theories consisting in treating the small bodies used to test the weak equivalence principle (WEP) as test particles, whose presence do not modify the chameleon field configuration. In that paper we developed an alternative method to determine the relevant field configuration which takes into account the influence of both test and source bodies, and computed the chamaleon mediated force. Relying on that analysis we showed that the effective acceleration of test bodies is composition dependent even when the model is based on universal couplings. In this paper, we improve our method by using a more suitable approximation for the effective chameleon potential in situations where the bodies are in the so-called "thick shell regime". We then find new and more restrictive bounds on the model' s parametres by confronting the new theoretical predictions with the empirical bounds on E\"otv\"os parameter comming from the lunar laser ranging experiments. |
1303.0666 | Johannes Hartung | Johannes Hartung and Jan Steinhoff and Gerhard Sch\"afer | Recent progress in spin calculations in the post-Newtonian framework and
applications | 3 pages, Proceedings of the 13th Marcel Grossmann Meeting | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently we derived the next-to-next-to-leading order post-Newtonian
Hamiltonians at spin-orbit and spin(1)-spin(2) level for a binary system of
compact objects. In this talk the derivation of them will be shortly outlined
at an introductory level. We will also discuss some checks of our (complicated
and long) results in the first part of the talk. In the second part we will
show how to apply our results to the calculation of the last stable circular
orbit of such a binary system of black holes or neutron stars.
| [
{
"created": "Mon, 4 Mar 2013 10:34:27 GMT",
"version": "v1"
}
] | 2013-03-05 | [
[
"Hartung",
"Johannes",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Schäfer",
"Gerhard",
""
]
] | Recently we derived the next-to-next-to-leading order post-Newtonian Hamiltonians at spin-orbit and spin(1)-spin(2) level for a binary system of compact objects. In this talk the derivation of them will be shortly outlined at an introductory level. We will also discuss some checks of our (complicated and long) results in the first part of the talk. In the second part we will show how to apply our results to the calculation of the last stable circular orbit of such a binary system of black holes or neutron stars. |
1606.09286 | Alexander B. Balakin | Alexander B. Balakin | Axionic extension of the Einstein-aether theory | 15 pages, 0 figures, accepted for publication in Physical Review D | Phys. Rev. D (2016) 94, 024021 | 10.1103/PhysRevD.94.024021 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the Einstein-aether theory to take into account the interaction
between a pseudoscalar field, which describes the axionic dark matter, and a
time-like dynamic unit vector field, which characterizes the velocity of the
aether motion. The Lagrangian of the Einstein-aether-axion theory includes
cross-terms based on the axion field and its gradient four-vector, on the
covariant derivative of the aether velocity four-vector, and on the Riemann
tensor and its convolutions. We follow the principles of the Effective Field
theory, and include into the Lagrangian of interactions all possible terms up
to the second order in the covariant derivative. Interpretation of new
couplings is given in terms of irreducible parts of the covariant derivative of
the aether velocity, namely, the acceleration four-vector, the shear and
vorticity tensors, and the expansion scalar. A spatially isotropic and
homogeneous cosmological model with dynamic unit vector field and axionic dark
matter is considered as an application of the established theory; new exact
solutions are discussed, which describe models with a Big Rip, Pseudo Rip and
de Sitter-type asymptotic behavior.
| [
{
"created": "Wed, 29 Jun 2016 21:00:59 GMT",
"version": "v1"
}
] | 2016-07-11 | [
[
"Balakin",
"Alexander B.",
""
]
] | We extend the Einstein-aether theory to take into account the interaction between a pseudoscalar field, which describes the axionic dark matter, and a time-like dynamic unit vector field, which characterizes the velocity of the aether motion. The Lagrangian of the Einstein-aether-axion theory includes cross-terms based on the axion field and its gradient four-vector, on the covariant derivative of the aether velocity four-vector, and on the Riemann tensor and its convolutions. We follow the principles of the Effective Field theory, and include into the Lagrangian of interactions all possible terms up to the second order in the covariant derivative. Interpretation of new couplings is given in terms of irreducible parts of the covariant derivative of the aether velocity, namely, the acceleration four-vector, the shear and vorticity tensors, and the expansion scalar. A spatially isotropic and homogeneous cosmological model with dynamic unit vector field and axionic dark matter is considered as an application of the established theory; new exact solutions are discussed, which describe models with a Big Rip, Pseudo Rip and de Sitter-type asymptotic behavior. |
gr-qc/0407037 | Daniele Malafarina | L. Herrera, G. Magli, D. Malafarina | Non-spherical sources of static gravitational fields: investigating the
boundaries of the no-hair theorem | 10 pages, 2 figures | Gen.Rel.Grav.37:1371-1383,2005 | 10.1007/s10714-005-0120-1 | null | gr-qc | null | A new, globally regular model describing a static, non spherical gravitating
object in General Relativity is presented. The model is composed by a vacuum
Weyl--Levi-Civita special field - the so called gamma metric - generated by a
regular static distribution of mass-energy. Standard requirements of physical
reasonableness such as, energy, matching and regularity conditions are
satisfied. The model is used as a toy in investigating various issues related
to the directional behavior of naked singularities in static spacetimes and the
blackhole (Schwarschild) limit.
| [
{
"created": "Fri, 9 Jul 2004 09:49:56 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Herrera",
"L.",
""
],
[
"Magli",
"G.",
""
],
[
"Malafarina",
"D.",
""
]
] | A new, globally regular model describing a static, non spherical gravitating object in General Relativity is presented. The model is composed by a vacuum Weyl--Levi-Civita special field - the so called gamma metric - generated by a regular static distribution of mass-energy. Standard requirements of physical reasonableness such as, energy, matching and regularity conditions are satisfied. The model is used as a toy in investigating various issues related to the directional behavior of naked singularities in static spacetimes and the blackhole (Schwarschild) limit. |
gr-qc/0606035 | Alexander Burinskii | Alexander Burinskii | Kerr geometry beyond the Quantum theory | 13 pages, 3 figures, based on the invited talk given at the workshop
`Beyond the Quantum',v. 2. added new results, title is changed | null | 10.1142/9789812771186_0026 | null | gr-qc hep-th quant-ph | null | The Dirac electron theory and QED do not take into account gravitational
field, while the corresponding Kerr-Newman solution with parameters of electron
has very strong stringy, topological and non-local action on the Compton
distances, polarizing space-time and deforming the Coulomb field. We discuss
the relation of the electron to the Kerr's microgeon model and argue that the
Kerr geometry may be hidden beyond the Quantum Theory. In particular, we show
that the Foldi-Wouthuysen `mean-position' operator of the Dirac electron is
related to a complex representation of the Kerr geometry, and to a complex
stringy source. Therefore, the complex Kerr geometry may be hidden beyond the
Dirac equation.
| [
{
"created": "Thu, 8 Jun 2006 12:58:02 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Oct 2006 12:56:29 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Burinskii",
"Alexander",
""
]
] | The Dirac electron theory and QED do not take into account gravitational field, while the corresponding Kerr-Newman solution with parameters of electron has very strong stringy, topological and non-local action on the Compton distances, polarizing space-time and deforming the Coulomb field. We discuss the relation of the electron to the Kerr's microgeon model and argue that the Kerr geometry may be hidden beyond the Quantum Theory. In particular, we show that the Foldi-Wouthuysen `mean-position' operator of the Dirac electron is related to a complex representation of the Kerr geometry, and to a complex stringy source. Therefore, the complex Kerr geometry may be hidden beyond the Dirac equation. |
0906.2754 | Alfredo Lopez Ortega | A. Lopez-Ortega | The Dirac equation in D-dimensional spherically symmetric spacetimes | 10 pages, 2 figures | Lat. Am. Jour. Phys. Educ. 3 (2009) 578. | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We expound in detail a method frequently used to reduce the Dirac equation in
D-dimensional (D >= 4) spherically symmetric spacetimes to a pair of coupled
partial differential equations in two variables. As a simple application of
these results we exactly calculate the quasinormal frequencies of the uncharged
Dirac field propagating in the D-dimensional Nariai spacetime.
| [
{
"created": "Mon, 15 Jun 2009 18:31:41 GMT",
"version": "v1"
}
] | 2010-02-03 | [
[
"Lopez-Ortega",
"A.",
""
]
] | We expound in detail a method frequently used to reduce the Dirac equation in D-dimensional (D >= 4) spherically symmetric spacetimes to a pair of coupled partial differential equations in two variables. As a simple application of these results we exactly calculate the quasinormal frequencies of the uncharged Dirac field propagating in the D-dimensional Nariai spacetime. |
2211.10481 | Michael Grayson | Michael Grayson, Charlie Rackson | Maximal energy extraction through information gathering | 6 pages, 1 figure | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the maximal non-equilibrium work that can be extracted from any
mass using information about its micro-state. This is done through the use of
black hole thermodynamics in the context of the thermodynamics of information.
The non-equilibrium work that can be obtained by knowing the exact micro-state
is found to be $\frac{1}{2} Mc^{2}$. This is calculated using the entropy of an
eternal, uncharged, non rotating black hole. This is derivation helps elucidate
the relativity of entropy and its relationship to general relativity and time.
| [
{
"created": "Fri, 18 Nov 2022 19:31:48 GMT",
"version": "v1"
}
] | 2022-11-22 | [
[
"Grayson",
"Michael",
""
],
[
"Rackson",
"Charlie",
""
]
] | We calculate the maximal non-equilibrium work that can be extracted from any mass using information about its micro-state. This is done through the use of black hole thermodynamics in the context of the thermodynamics of information. The non-equilibrium work that can be obtained by knowing the exact micro-state is found to be $\frac{1}{2} Mc^{2}$. This is calculated using the entropy of an eternal, uncharged, non rotating black hole. This is derivation helps elucidate the relativity of entropy and its relationship to general relativity and time. |
gr-qc/0102088 | Thomas Filk | Thomas Filk | Proper time and Minkowski structure on causal graphs | 15 pages, 4 figures | Class.Quant.Grav.18:2785-2796,2001 | 10.1088/0264-9381/18/14/311 | Freiburg preprint THEP 01/03 | gr-qc | null | For causal graphs we propose a definition of proper time which for small
scales is based on the concept of volume, while for large scales the usual
definition of length is applied. The scale where the change from "volume" to
"length" occurs is related to the size of a dynamical clock and defines a
natural cut-off for this type of clock. By changing the cut-off volume we may
probe the geometry of the causal graph on different scales and therey define a
continuum limit. This provides an alternative to the standard coarse graining
procedures. For regular causal lattice (like e.g. the 2-dim. light-cone
lattice) this concept can be proven to lead to a Minkowski structure. An
illustrative example of this approach is provided by the breather solutions of
the Sine-Gordon model on a 2-dimensional light-cone lattice.
| [
{
"created": "Tue, 20 Feb 2001 21:47:01 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Filk",
"Thomas",
""
]
] | For causal graphs we propose a definition of proper time which for small scales is based on the concept of volume, while for large scales the usual definition of length is applied. The scale where the change from "volume" to "length" occurs is related to the size of a dynamical clock and defines a natural cut-off for this type of clock. By changing the cut-off volume we may probe the geometry of the causal graph on different scales and therey define a continuum limit. This provides an alternative to the standard coarse graining procedures. For regular causal lattice (like e.g. the 2-dim. light-cone lattice) this concept can be proven to lead to a Minkowski structure. An illustrative example of this approach is provided by the breather solutions of the Sine-Gordon model on a 2-dimensional light-cone lattice. |
1603.08112 | Deng Wang | Deng Wang and Xin-He Meng | Observational constraints and differential diagnosis for cosmic
evolutionary models | null | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have proposed a plotting method based on the " natural
plotting rule " (NPR) which can be used to distinguish different cosmological
scenarios more efficiently and obtain more useful information. By using the
NPR, we have avoided the blindness to use different diagnostics when
discovering that some scenarios can be hardly differentiated from each other,
and develop a logical line to adopt different diagnostics. As a concrete
instance, we take this method based on the NPR to distinguish several
Cardassian scenarios from the base cosmology scenario, and one from the other.
We place constraints on three Cardassian cosmological scenarios and their flat
versions by utilizing the Type Ia supernovae (SNe Ia), baryonic acoustic
oscillations (BAO), cosmic microwave background (CMB) radiation, observational
Hubble parameter (OHD) data-sets as well as the single data point from the
newest event GW150914, and discover that our results are more stringent than
previous results for constraining the cosmological parameters of the Cardassian
scenarios. We find that the flat original Cardassian (FOC) and original
Cardassian (OC) scenarios can only be distinguished in the plane of
$\{\Omega_m,S_3^{(1)}\}$ at the present epoch, however, if applying the NPR to
plot hierarchically for these Cardassian scenarios in the plane of
$\{S_3^{(1)},S_4^{(1)}\}$, we can obtain more detailed information and
distinguish the two scenarios better than before. More importantly, from the
planes of $\{S_4,S_4^{(2)}\}$, $\{S_5^{(1)},S_5^{(2)}\}$,
$\{S_3^{(2)},S_4^{(2)}\}$, $\{\Omega_m,S_3^{(1)}\}$,$\{z,\omega\}$
$\{\epsilon(z),S_3^{(1)}\}$ and $\{z,Om\}$, we dsicover that the flat modified
polytropic Cardassian (FMPC) scenario can be directly removed from the possible
candidates of dark energy phenomenon, since its evolutional behavior deviates
from the base cosmology scenario too much.
| [
{
"created": "Sat, 26 Mar 2016 14:40:58 GMT",
"version": "v1"
}
] | 2016-03-29 | [
[
"Wang",
"Deng",
""
],
[
"Meng",
"Xin-He",
""
]
] | In this paper, we have proposed a plotting method based on the " natural plotting rule " (NPR) which can be used to distinguish different cosmological scenarios more efficiently and obtain more useful information. By using the NPR, we have avoided the blindness to use different diagnostics when discovering that some scenarios can be hardly differentiated from each other, and develop a logical line to adopt different diagnostics. As a concrete instance, we take this method based on the NPR to distinguish several Cardassian scenarios from the base cosmology scenario, and one from the other. We place constraints on three Cardassian cosmological scenarios and their flat versions by utilizing the Type Ia supernovae (SNe Ia), baryonic acoustic oscillations (BAO), cosmic microwave background (CMB) radiation, observational Hubble parameter (OHD) data-sets as well as the single data point from the newest event GW150914, and discover that our results are more stringent than previous results for constraining the cosmological parameters of the Cardassian scenarios. We find that the flat original Cardassian (FOC) and original Cardassian (OC) scenarios can only be distinguished in the plane of $\{\Omega_m,S_3^{(1)}\}$ at the present epoch, however, if applying the NPR to plot hierarchically for these Cardassian scenarios in the plane of $\{S_3^{(1)},S_4^{(1)}\}$, we can obtain more detailed information and distinguish the two scenarios better than before. More importantly, from the planes of $\{S_4,S_4^{(2)}\}$, $\{S_5^{(1)},S_5^{(2)}\}$, $\{S_3^{(2)},S_4^{(2)}\}$, $\{\Omega_m,S_3^{(1)}\}$,$\{z,\omega\}$ $\{\epsilon(z),S_3^{(1)}\}$ and $\{z,Om\}$, we dsicover that the flat modified polytropic Cardassian (FMPC) scenario can be directly removed from the possible candidates of dark energy phenomenon, since its evolutional behavior deviates from the base cosmology scenario too much. |
gr-qc/0612191 | Yoshiharu Tanaka | Yoshiharu Tanaka, Misao Sasaki | Gradient expansion approach to nonlinear superhorizon perturbations | 15 pages, no figures. V2: minor changes, typos corrected; V3:Section
I, Introduction and minor change to match version to appear in Prog. Theor.
Phys. | Prog.Theor.Phys.117:633-654,2007 | 10.1143/PTP.117.633 | YITP-06-69 | gr-qc astro-ph hep-th | null | Using the gradient expansion approach, we formulate a nonlinear cosmological
perturbation theory on super-horizon scales valid to $O(\epsilon^2)$, where
$\epsilon$ is the expansion parameter associated with a spatial derivative. For
simplicity, we focus on the case of a single perfect fluid, but we take into
account not only scalar but also vector and tensor modes. We derive the general
solution under the uniform-Hubble time-slicing. In doing so, we identify the
scalar, vector and tensor degrees of freedom contained in the solution. We then
consider the coordinate transformation to the synchronous gauge in order to
compare our result with the previous result given in the literature. In
particular, we find that the tensor mode is invariant to $O(\epsilon^2)$ under
the coordinate transformation.
| [
{
"created": "Fri, 29 Dec 2006 15:15:18 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jan 2007 07:45:01 GMT",
"version": "v2"
},
{
"created": "Sat, 31 Mar 2007 12:18:58 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Tanaka",
"Yoshiharu",
""
],
[
"Sasaki",
"Misao",
""
]
] | Using the gradient expansion approach, we formulate a nonlinear cosmological perturbation theory on super-horizon scales valid to $O(\epsilon^2)$, where $\epsilon$ is the expansion parameter associated with a spatial derivative. For simplicity, we focus on the case of a single perfect fluid, but we take into account not only scalar but also vector and tensor modes. We derive the general solution under the uniform-Hubble time-slicing. In doing so, we identify the scalar, vector and tensor degrees of freedom contained in the solution. We then consider the coordinate transformation to the synchronous gauge in order to compare our result with the previous result given in the literature. In particular, we find that the tensor mode is invariant to $O(\epsilon^2)$ under the coordinate transformation. |
1804.09573 | Lee Smolin | Stephon Alexander and Lee Smolin | The Equivalence Principle and the Emergence of Flat Rotation Curves | 10 pages LaTeX | null | null | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explain flat rotation curves and the baryonic Tully-Fisher relation by a
combination of three hypotheses. The first is a formulation of the equivalence
principle for gravitationally bound quantum $N$ body systems, while the second
is a second order phase transition hypothesized to arise from a competition
between the effects of Unruh and deSitter radiation experienced by a static
observer in a galaxy. The third is a light dark matter particle, coupled to a
dark photon.
The phase transition is triggered in a ring where the Unruh temperature of a
static observer falls below the deSitter temperature, thus explaining the
apparent coincidence that Milgrom's $a_0 \approx a_\Lambda = c^2
\sqrt{\frac{\Lambda}{3}}$
This phase transition drives the dark matter particles to a regime
characterized by a broken $U(1)$ invariance and an approximate scale
invariance. In this regime, the dark matter condenses to a super-current
characterized by a differentially rotating ring with a flat rotation curve,
coupled to a dark magnetic field. The baryonic Tully Fisher relation is a
direct consequence of the approximate scale invariance.
| [
{
"created": "Wed, 25 Apr 2018 13:53:13 GMT",
"version": "v1"
}
] | 2018-04-26 | [
[
"Alexander",
"Stephon",
""
],
[
"Smolin",
"Lee",
""
]
] | We explain flat rotation curves and the baryonic Tully-Fisher relation by a combination of three hypotheses. The first is a formulation of the equivalence principle for gravitationally bound quantum $N$ body systems, while the second is a second order phase transition hypothesized to arise from a competition between the effects of Unruh and deSitter radiation experienced by a static observer in a galaxy. The third is a light dark matter particle, coupled to a dark photon. The phase transition is triggered in a ring where the Unruh temperature of a static observer falls below the deSitter temperature, thus explaining the apparent coincidence that Milgrom's $a_0 \approx a_\Lambda = c^2 \sqrt{\frac{\Lambda}{3}}$ This phase transition drives the dark matter particles to a regime characterized by a broken $U(1)$ invariance and an approximate scale invariance. In this regime, the dark matter condenses to a super-current characterized by a differentially rotating ring with a flat rotation curve, coupled to a dark magnetic field. The baryonic Tully Fisher relation is a direct consequence of the approximate scale invariance. |
gr-qc/0309119 | Charles Hellaby | Andrzej Krasinski and Charles Hellaby | Formation of a galaxy with a central black hole in the Lemaitre-Tolman
model | REVTeX, 22 pages including 11 figures (25 figure files). Replacement
has minor changes in response to the referee, and editorial corrections. To
appear in PRD | Phys.Rev.D69:043502,2004 | 10.1103/PhysRevD.69.043502 | uct-cosmology-03/03 | gr-qc | null | We construct two models of the formation a galaxy with a central black hole,
starting from a small initial fluctuation at recombination. This is an
application of previously developed methods to find a Lemaitre-Tolman model
that evolves from a given initial density or velocity profile to a given final
density profile. We show that the black hole itself could be either a collapsed
object, or a non-vacuum generalisation of a full Schwarzschild-Kruskal-Szekeres
wormhole. Particular attention is paid to the black hole's apparent and event
horizons.
| [
{
"created": "Thu, 25 Sep 2003 11:07:59 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jan 2004 14:19:31 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Krasinski",
"Andrzej",
""
],
[
"Hellaby",
"Charles",
""
]
] | We construct two models of the formation a galaxy with a central black hole, starting from a small initial fluctuation at recombination. This is an application of previously developed methods to find a Lemaitre-Tolman model that evolves from a given initial density or velocity profile to a given final density profile. We show that the black hole itself could be either a collapsed object, or a non-vacuum generalisation of a full Schwarzschild-Kruskal-Szekeres wormhole. Particular attention is paid to the black hole's apparent and event horizons. |
2103.04627 | Soham Bhattacharyya | Soham Bhattacharyya | The Equivalence and/or the Effacing principle in $ f\left(R\right) $
theories of gravity | 15 pages. Version as accepted in the European Physical Journal C | null | 10.1140/epjc/s10052-022-10574-9 | null | gr-qc astro-ph.GA hep-th | http://creativecommons.org/licenses/by/4.0/ | The Einstein-Hilbert action of general theory of relativity (GR) is the
integral of the scalar curvature $R$. It is a theory that is drawn from the
Equivalence principle, and has predictions that come out as a consequence of
the principle, in observables. Testing such observables to find
confirmation/infirmation of the principle have formed a significant chunk of
tests of GR itself. It is expected that quantum corrections to GR may add
additional higher powers of $R$ to the Einstein-Hilbert action, or more
generally, modifying the action into a generic class of functions of the Ricci
scalar. Testing the fate of the prized equivalence principle, in such modified
theories of gravity, hence become important in order to obtain a more generic
theory of gravitation, and consequently, of gravitating objects. In this study,
it is shown that a Post-Newtonian (PN) expansion of a class of $
f\left(R\right) $ theories lead to a sequence of solutions to the two-body
problem, which follows the equivalence principle (EP) at the Newtonian order,
and generalizes to the 'effacing principle' at a higher PN order.
| [
{
"created": "Mon, 8 Mar 2021 09:24:24 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jan 2022 09:14:02 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jul 2022 05:08:38 GMT",
"version": "v3"
}
] | 2022-07-15 | [
[
"Bhattacharyya",
"Soham",
""
]
] | The Einstein-Hilbert action of general theory of relativity (GR) is the integral of the scalar curvature $R$. It is a theory that is drawn from the Equivalence principle, and has predictions that come out as a consequence of the principle, in observables. Testing such observables to find confirmation/infirmation of the principle have formed a significant chunk of tests of GR itself. It is expected that quantum corrections to GR may add additional higher powers of $R$ to the Einstein-Hilbert action, or more generally, modifying the action into a generic class of functions of the Ricci scalar. Testing the fate of the prized equivalence principle, in such modified theories of gravity, hence become important in order to obtain a more generic theory of gravitation, and consequently, of gravitating objects. In this study, it is shown that a Post-Newtonian (PN) expansion of a class of $ f\left(R\right) $ theories lead to a sequence of solutions to the two-body problem, which follows the equivalence principle (EP) at the Newtonian order, and generalizes to the 'effacing principle' at a higher PN order. |
1105.0749 | Domenico Giulini J.W. | Domenico Giulini | Equivalence principle, quantum mechanics, and atom-interferometric tests | 26 pages, 3 figures. Written up version of a talk delivered on
October 1st 2010 at the Regensburg conference on Quantum Field Theory and
Gravity. Version 2: references updated and typos eliminated | In: F. Finster et al. (editors), Quantum Field Theory and Gravity,
pp. 345-370, Birkhaeuser series, Springer Verlag, Basel, 2012 | null | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | That gravitation can be understood as purely metric phenomenon depends
crucially on the validity of a number of hypotheses which are summarised by the
Einstein Equivalence Principle, the least well tested part of which being the
Universality of Gravitational Redshift. A recent and currently widely debated
proposal (Nature 463 (2010) 926-929) to re-interpret some 10-year old
experiments in atom interferometry would imply, if tenable, substantial
reductions on upper bounds for possible violations of the Universality of
Gravitational Redshift by four orders of magnitude. This interpretation,
however, is problematic and raises various compatibility issues concerning
basic principles of General Relativity and Quantum Mechanics. I review some
relevant aspects of the equivalence principle and its import into quantum
mechanics, and then turn to the problems raised by the mentioned proposal. I
conclude that this proposal is too problematic to warrant the claims that were
launched with it.
| [
{
"created": "Wed, 4 May 2011 07:56:53 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Dec 2011 16:22:31 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Giulini",
"Domenico",
""
]
] | That gravitation can be understood as purely metric phenomenon depends crucially on the validity of a number of hypotheses which are summarised by the Einstein Equivalence Principle, the least well tested part of which being the Universality of Gravitational Redshift. A recent and currently widely debated proposal (Nature 463 (2010) 926-929) to re-interpret some 10-year old experiments in atom interferometry would imply, if tenable, substantial reductions on upper bounds for possible violations of the Universality of Gravitational Redshift by four orders of magnitude. This interpretation, however, is problematic and raises various compatibility issues concerning basic principles of General Relativity and Quantum Mechanics. I review some relevant aspects of the equivalence principle and its import into quantum mechanics, and then turn to the problems raised by the mentioned proposal. I conclude that this proposal is too problematic to warrant the claims that were launched with it. |
gr-qc/0503064 | Satsuki Shimono | Satsuki Shimono, Takeshi Chiba | Numerical Solutions of Inflating Higher Dimensional Global Defects | 6 pages, 7 figures, ReVTeX4, Accepted for publication in PRD | Phys.Rev. D71 (2005) 084002 | 10.1103/PhysRevD.71.084002 | null | gr-qc astro-ph hep-th | null | We find numerical solutions of Einstein equations and scalar field equation
for a global defect in higher dimensional spacetimes ($\geq 6$). We examine in
detail the relation among the expansion rate $H$ and the symmetry-breaking
scale $\eta$ and the number of extra dimensions $n$ for these solutions. We
find that even if the extra dimensions do not have a cigar geometry, the
expansion rate $H$ grows as $\eta$ increases, which is opposite to what is
needed for the recently proposed mechanism for solving the cosmological
constant problem. We also find that the expansion rate $H$ decreases as $n$
increases.
| [
{
"created": "Tue, 15 Mar 2005 07:43:04 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2005 14:30:14 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Shimono",
"Satsuki",
""
],
[
"Chiba",
"Takeshi",
""
]
] | We find numerical solutions of Einstein equations and scalar field equation for a global defect in higher dimensional spacetimes ($\geq 6$). We examine in detail the relation among the expansion rate $H$ and the symmetry-breaking scale $\eta$ and the number of extra dimensions $n$ for these solutions. We find that even if the extra dimensions do not have a cigar geometry, the expansion rate $H$ grows as $\eta$ increases, which is opposite to what is needed for the recently proposed mechanism for solving the cosmological constant problem. We also find that the expansion rate $H$ decreases as $n$ increases. |
1801.01787 | Ryotaro Kase | Ryotaro Kase, Masato Minamitsuji, Shinji Tsujikawa, and Ying-li Zhang | Black hole perturbations in vector-tensor theories: The odd-mode
analysis | 26 pages, 4 figures, published version | JCAP02(2018)048 | 10.1088/1475-7516/2018/02/048 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In generalized Proca theories with vector-field derivative couplings, a bunch
of hairy black hole solutions have been derived on a static and spherically
symmetric background. In this paper, we formulate the odd-parity black hole
perturbations in generalized Proca theories by expanding the corresponding
action up to second order and investigate whether or not black holes with
vector hair suffer ghost or Laplacian instabilities. We show that the models
with cubic couplings $G_3(X)$, where $X=-A_{\mu}A^{\mu}/2$ with a vector field
$A_{\mu}$, do not provide any additional stability condition as in General
Relativity. On the other hand, the exact charged stealth Schwarzschild solution
with a nonvanishing longitudinal vector component $A_1$, which originates from
the coupling to the Einstein tensor $G^{\mu\nu}A_\mu A_\nu$ equivalent to the
quartic coupling $G_4(X)$ containing a linear function of $X$, is unstable in
the vicinity of the event horizon. The same instability problem also persists
for hairy black holes arising from general quartic power-law couplings $G_4(X)
\supset \beta_4 X^n$ with the nonvanishing $A_1$, while the other branch with
$A_1=0$ can be consistent with conditions for the absence of ghost and
Laplacian instabilities. We also discuss the case of other exact and numerical
black hole solutions associated with intrinsic vector-field derivative
couplings and show that there exists a wide range of parameter spaces in which
the solutions suffer neither ghost nor Laplacian instabilities against
odd-parity perturbations.
| [
{
"created": "Fri, 5 Jan 2018 15:17:45 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Feb 2018 03:20:48 GMT",
"version": "v2"
}
] | 2018-02-27 | [
[
"Kase",
"Ryotaro",
""
],
[
"Minamitsuji",
"Masato",
""
],
[
"Tsujikawa",
"Shinji",
""
],
[
"Zhang",
"Ying-li",
""
]
] | In generalized Proca theories with vector-field derivative couplings, a bunch of hairy black hole solutions have been derived on a static and spherically symmetric background. In this paper, we formulate the odd-parity black hole perturbations in generalized Proca theories by expanding the corresponding action up to second order and investigate whether or not black holes with vector hair suffer ghost or Laplacian instabilities. We show that the models with cubic couplings $G_3(X)$, where $X=-A_{\mu}A^{\mu}/2$ with a vector field $A_{\mu}$, do not provide any additional stability condition as in General Relativity. On the other hand, the exact charged stealth Schwarzschild solution with a nonvanishing longitudinal vector component $A_1$, which originates from the coupling to the Einstein tensor $G^{\mu\nu}A_\mu A_\nu$ equivalent to the quartic coupling $G_4(X)$ containing a linear function of $X$, is unstable in the vicinity of the event horizon. The same instability problem also persists for hairy black holes arising from general quartic power-law couplings $G_4(X) \supset \beta_4 X^n$ with the nonvanishing $A_1$, while the other branch with $A_1=0$ can be consistent with conditions for the absence of ghost and Laplacian instabilities. We also discuss the case of other exact and numerical black hole solutions associated with intrinsic vector-field derivative couplings and show that there exists a wide range of parameter spaces in which the solutions suffer neither ghost nor Laplacian instabilities against odd-parity perturbations. |
1807.10630 | Bogeun Gwak | Bogeun Gwak | Weak Cosmic Censorship Conjecture in Kerr-(Anti-)de Sitter Black Hole
with Scalar Field | 20 pages, 3 figures, published in JHEP | JHEP 1809 (2018) 081 | 10.1007/JHEP09(2018)081 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the weak cosmic censorship conjecture in Kerr-(anti-)de Sitter
black holes under the scattering of a scalar field. We test the conjecture in
terms of whether the black hole can exceed the extremal condition with respect
to its change caused by the energy and angular momentum fluxes of the scalar
field. Without imposing the laws of thermodynamics, we prove that the
conjecture is valid in all the initial states of the black hole (non-extremal,
near-extremal, and extremal black holes). The validity in the case of the
near-extremal black hole is different from the results of similar tests
conducted by adding a particle because the fluxes represent the energy and
angular momentum transferred to the black hole during the time interval not
included in the tests involving the particle. Using the time interval, we show
that the angular velocity of the black hole with the scalar field of a constant
state takes a long time for saturation to the frequency of the scalar field.
| [
{
"created": "Fri, 27 Jul 2018 13:58:08 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Sep 2018 10:43:44 GMT",
"version": "v2"
}
] | 2018-09-18 | [
[
"Gwak",
"Bogeun",
""
]
] | We investigate the weak cosmic censorship conjecture in Kerr-(anti-)de Sitter black holes under the scattering of a scalar field. We test the conjecture in terms of whether the black hole can exceed the extremal condition with respect to its change caused by the energy and angular momentum fluxes of the scalar field. Without imposing the laws of thermodynamics, we prove that the conjecture is valid in all the initial states of the black hole (non-extremal, near-extremal, and extremal black holes). The validity in the case of the near-extremal black hole is different from the results of similar tests conducted by adding a particle because the fluxes represent the energy and angular momentum transferred to the black hole during the time interval not included in the tests involving the particle. Using the time interval, we show that the angular velocity of the black hole with the scalar field of a constant state takes a long time for saturation to the frequency of the scalar field. |
1008.1577 | Neil J. Cornish | Tyson B. Littenberg and Neil J. Cornish | Separating Gravitational Wave Signals from Instrument Artifacts | 21 pages, 18 figures | Phys.Rev.D82:103007,2010 | 10.1103/PhysRevD.82.103007 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Central to the gravitational wave detection problem is the challenge of
separating features in the data produced by astrophysical sources from features
produced by the detector. Matched filtering provides an optimal solution for
Gaussian noise, but in practice, transient noise excursions or ``glitches''
complicate the analysis. Detector diagnostics and coincidence tests can be used
to veto many glitches which may otherwise be misinterpreted as gravitational
wave signals. The glitches that remain can lead to long tails in the matched
filter search statistics and drive up the detection threshold. Here we describe
a Bayesian approach that incorporates a more realistic model for the instrument
noise allowing for fluctuating noise levels that vary independently across
frequency bands, and deterministic ``glitch fitting'' using wavelets as
``glitch templates'', the number of which is determined by a trans-dimensional
Markov chain Monte Carlo algorithm. We demonstrate the method's effectiveness
on simulated data containing low amplitude gravitational wave signals from
inspiraling binary black hole systems, and simulated non-stationary and
non-Gaussian noise comprised of a Gaussian component with the standard
LIGO/Virgo spectrum, and injected glitches of various amplitude, prevalence,
and variety. Glitch fitting allows us to detect significantly weaker signals
than standard techniques.
| [
{
"created": "Mon, 9 Aug 2010 20:00:01 GMT",
"version": "v1"
}
] | 2010-12-09 | [
[
"Littenberg",
"Tyson B.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | Central to the gravitational wave detection problem is the challenge of separating features in the data produced by astrophysical sources from features produced by the detector. Matched filtering provides an optimal solution for Gaussian noise, but in practice, transient noise excursions or ``glitches'' complicate the analysis. Detector diagnostics and coincidence tests can be used to veto many glitches which may otherwise be misinterpreted as gravitational wave signals. The glitches that remain can lead to long tails in the matched filter search statistics and drive up the detection threshold. Here we describe a Bayesian approach that incorporates a more realistic model for the instrument noise allowing for fluctuating noise levels that vary independently across frequency bands, and deterministic ``glitch fitting'' using wavelets as ``glitch templates'', the number of which is determined by a trans-dimensional Markov chain Monte Carlo algorithm. We demonstrate the method's effectiveness on simulated data containing low amplitude gravitational wave signals from inspiraling binary black hole systems, and simulated non-stationary and non-Gaussian noise comprised of a Gaussian component with the standard LIGO/Virgo spectrum, and injected glitches of various amplitude, prevalence, and variety. Glitch fitting allows us to detect significantly weaker signals than standard techniques. |
1906.05406 | Gabriel R. Bengochea | Gabriel R. Bengochea, Gabriel Le\'on, Elias Okon, Daniel Sudarsky | Can the quantum vacuum fluctuations really solve the cosmological
constant problem? | 12 pages. Minor changes, comments added in Conclusions and new
references. Accepted for publication in EPJC | Eur. Phys. J. C 80, 18 (2020) | 10.1140/epjc/s10052-019-7554-1 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been argued that a correct reading of the quantum
fluctuations of the vacuum could lead to a solution to the cosmological
constant problem. In this work we critically examine such a proposal, finding
it questionable due to conceptual and self-consistency problems, as well as
issues with the actual calculations. We conclude that the proposal is
inadequate as a solution to the cosmological constant problem.
| [
{
"created": "Wed, 12 Jun 2019 22:17:44 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Dec 2019 04:10:54 GMT",
"version": "v2"
}
] | 2020-01-15 | [
[
"Bengochea",
"Gabriel R.",
""
],
[
"León",
"Gabriel",
""
],
[
"Okon",
"Elias",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | Recently it has been argued that a correct reading of the quantum fluctuations of the vacuum could lead to a solution to the cosmological constant problem. In this work we critically examine such a proposal, finding it questionable due to conceptual and self-consistency problems, as well as issues with the actual calculations. We conclude that the proposal is inadequate as a solution to the cosmological constant problem. |
1310.3124 | Herbert Balasin | Herbert Balasin | Timescape realized | 15 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a concrete proposal to realize the observer dependence of
expansion redshift employing a map that relates static to conformally static
geometries. This provides a manifest realization of Wiltshire's proposal for
observer selection which serves as a model to explain accelerated expansion
| [
{
"created": "Fri, 11 Oct 2013 13:56:45 GMT",
"version": "v1"
}
] | 2013-10-14 | [
[
"Balasin",
"Herbert",
""
]
] | We discuss a concrete proposal to realize the observer dependence of expansion redshift employing a map that relates static to conformally static geometries. This provides a manifest realization of Wiltshire's proposal for observer selection which serves as a model to explain accelerated expansion |
1310.8596 | Eugen Radu | Burkhard Kleihaus, Jutta Kunz and Eugen Radu | The Gregory-Laflamme instability and non-uniform generalizations of NUT
strings | 10 pages, 3 figures | null | 10.1016/j.physletb.2014.01.012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore via linearized perturbation theory the Gregory-Laflamme
instability of the NUT string (i.e the D=4 Lorentzian NUT solution uplifted to
five dimensions). Our results indicate that the Gregory-Laflamme instability
persists in the presence of a NUT charge $n$, the critical length of the
extra-dimension increasing with $n$ for the same value of mass. The non-uniform
branch of NUT strings is numerically extended into the full nonlinear regime.
| [
{
"created": "Thu, 31 Oct 2013 17:11:06 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Radu",
"Eugen",
""
]
] | We explore via linearized perturbation theory the Gregory-Laflamme instability of the NUT string (i.e the D=4 Lorentzian NUT solution uplifted to five dimensions). Our results indicate that the Gregory-Laflamme instability persists in the presence of a NUT charge $n$, the critical length of the extra-dimension increasing with $n$ for the same value of mass. The non-uniform branch of NUT strings is numerically extended into the full nonlinear regime. |
1609.03159 | Kevin Croker | K.A.S. Croker | A Smolin-like branching multiverse from multiscalar-tensor theory | 14 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We implement a Smolin-like branching multiverse through a directed, acyclic
graph of $N$ metrics. Our gravitational and matter actions are
indistinguishable from $N$ decoupled statements of General Relativity, if one
varies with respect to metric degrees of freedom. We replace $N-1$ metrics with
scalar fields by conformally relating each metric to its unique graph
predecessor. Varying with respect to the $N-1$ scalar fields gives a
multiscalar-tensor model which naturally features dark matter candidates.
Building atop an argument of Chapline and Laughlin, branching is accomplished
with the emergence of order parameters during gravitational collapse: we
bootstrap a suitably defined $N$ scalar field model with initial data from an
$N-1$ field model. We focus on the nearest-neighbour approximation, determine
conditions for dynamical stability, and compute the equations of motion. The
model features a novel screening property where the scalar fields actively
adjust to decouple themselves from the stress, oscillating about the requisite
values. In the Newtonian limit, these background values for the scalar fields
exactly reproduce Newton's law of gravitation.
| [
{
"created": "Sun, 11 Sep 2016 13:22:08 GMT",
"version": "v1"
}
] | 2016-09-13 | [
[
"Croker",
"K. A. S.",
""
]
] | We implement a Smolin-like branching multiverse through a directed, acyclic graph of $N$ metrics. Our gravitational and matter actions are indistinguishable from $N$ decoupled statements of General Relativity, if one varies with respect to metric degrees of freedom. We replace $N-1$ metrics with scalar fields by conformally relating each metric to its unique graph predecessor. Varying with respect to the $N-1$ scalar fields gives a multiscalar-tensor model which naturally features dark matter candidates. Building atop an argument of Chapline and Laughlin, branching is accomplished with the emergence of order parameters during gravitational collapse: we bootstrap a suitably defined $N$ scalar field model with initial data from an $N-1$ field model. We focus on the nearest-neighbour approximation, determine conditions for dynamical stability, and compute the equations of motion. The model features a novel screening property where the scalar fields actively adjust to decouple themselves from the stress, oscillating about the requisite values. In the Newtonian limit, these background values for the scalar fields exactly reproduce Newton's law of gravitation. |
gr-qc/9903071 | Manoelito M. de Souza | Manoelito M. de Souza, Robson N. Silveira | Gauss vs Coulomb and the Cosmological Mass-deficit Problem | 7 pages 1 ps figure | null | null | null | gr-qc astro-ph hep-th | null | In a previous work General Relativity has been presented as a microscopic
theory of finite and discrete point-like fields that we associate to a
classical description of gravitons. The standard macroscopic continuous field
is retrieved as an average-valued field through an integration over these
gravitons. Here we discuss extreme alternative (the Gauss's and the Coulomb's)
ways of obtaining and interpreting the averaged fields, how they depend on the
kind of measurements involved, and how do they fit with the experimental data.
The field measurements in the classical tests of general relativity correspond
to the Coulomb's mode whereas the determination of the overall spacetime
curvature in a cosmological scale is clearly a Gauss's mode. As a natural
consequence there is no missing mass and, therefore, no such a need of dark
mass as the value predicted by General Relativity, in the context of the
Gauss's mode, agrees with the observed one.
| [
{
"created": "Thu, 18 Mar 1999 20:40:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Souza",
"Manoelito M.",
""
],
[
"Silveira",
"Robson N.",
""
]
] | In a previous work General Relativity has been presented as a microscopic theory of finite and discrete point-like fields that we associate to a classical description of gravitons. The standard macroscopic continuous field is retrieved as an average-valued field through an integration over these gravitons. Here we discuss extreme alternative (the Gauss's and the Coulomb's) ways of obtaining and interpreting the averaged fields, how they depend on the kind of measurements involved, and how do they fit with the experimental data. The field measurements in the classical tests of general relativity correspond to the Coulomb's mode whereas the determination of the overall spacetime curvature in a cosmological scale is clearly a Gauss's mode. As a natural consequence there is no missing mass and, therefore, no such a need of dark mass as the value predicted by General Relativity, in the context of the Gauss's mode, agrees with the observed one. |
1412.5803 | Nicolas Chamel | N. Chamel | On the Lie subalgebra of Killing-Milne and Killing-Cartan vector fields
in Newtonian space-time | 8 pages | Int. J. Mod. Phys. D24, No. 2 (2015) 1550018 | 10.1142/S0218271815500182 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Galilean (and more generally Milne) invariance of Newtonian theory allows
for Killing vector fields of a general kind, whereby the Lie derivative of a
field is not required to vanish but only to be cancellable by some
infinitesimal Galilean (respectively Milne) gauge transformation. In this
paper, it is shown that both the Killing-Milne vector fields, which preserve
the background Newtonian space-time structure, and the Killing-Cartan vector
fields, which in addition preserve the gravitational field, form a Lie
subalgebra.
| [
{
"created": "Thu, 18 Dec 2014 11:07:10 GMT",
"version": "v1"
}
] | 2014-12-19 | [
[
"Chamel",
"N.",
""
]
] | The Galilean (and more generally Milne) invariance of Newtonian theory allows for Killing vector fields of a general kind, whereby the Lie derivative of a field is not required to vanish but only to be cancellable by some infinitesimal Galilean (respectively Milne) gauge transformation. In this paper, it is shown that both the Killing-Milne vector fields, which preserve the background Newtonian space-time structure, and the Killing-Cartan vector fields, which in addition preserve the gravitational field, form a Lie subalgebra. |
2009.00043 | Neil J. Cornish | Neil J. Cornish | Time-Frequency Analysis of Gravitational Wave Data | 20 pages, 22 figures | null | 10.1103/PhysRevD.102.124038 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Data from gravitational wave detectors are recorded as time series that
include contributions from myriad noise sources in addition to any
gravitational wave signals. When regularly sampled data are available, such as
for ground based and future space based interferometers, analyses are typically
performed in the frequency domain, where stationary (time invariant) noise
processes can be modeled very efficiently. In reality, detector noise is not
stationary due to a combination of short duration noise transients and longer
duration drifts in the power spectrum. This non-stationarity produces
correlations across samples at different frequencies, obviating the main
advantage of a frequency domain analysis. Here an alternative time-frequency
approach to gravitational wave data analysis is proposed that uses discrete,
orthogonal wavelet wavepackets. The time domain data is mapped onto a uniform
grid of time-frequency pixels. For locally stationary noise - that is, noise
with an adiabatically varying spectrum - the time-frequency pixels are
uncorrelated, which greatly simplifies the calculation of quantities such as
the likelihood. Moreover, the gravitational wave signals from binary systems
can be compactly represented as a collection of lines in time-frequency space,
resulting in a computational cost for computing waveforms and likelihoods that
scales as the square root of the number of time samples, as opposed to the
linear scaling for time or frequency based analyses. Key to this approach is
having fast methods for computing binary signals directly in the wavelet
domain. Multiple fast transform methods are developed in detail.
| [
{
"created": "Mon, 31 Aug 2020 18:22:27 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Oct 2020 20:09:19 GMT",
"version": "v2"
}
] | 2020-12-23 | [
[
"Cornish",
"Neil J.",
""
]
] | Data from gravitational wave detectors are recorded as time series that include contributions from myriad noise sources in addition to any gravitational wave signals. When regularly sampled data are available, such as for ground based and future space based interferometers, analyses are typically performed in the frequency domain, where stationary (time invariant) noise processes can be modeled very efficiently. In reality, detector noise is not stationary due to a combination of short duration noise transients and longer duration drifts in the power spectrum. This non-stationarity produces correlations across samples at different frequencies, obviating the main advantage of a frequency domain analysis. Here an alternative time-frequency approach to gravitational wave data analysis is proposed that uses discrete, orthogonal wavelet wavepackets. The time domain data is mapped onto a uniform grid of time-frequency pixels. For locally stationary noise - that is, noise with an adiabatically varying spectrum - the time-frequency pixels are uncorrelated, which greatly simplifies the calculation of quantities such as the likelihood. Moreover, the gravitational wave signals from binary systems can be compactly represented as a collection of lines in time-frequency space, resulting in a computational cost for computing waveforms and likelihoods that scales as the square root of the number of time samples, as opposed to the linear scaling for time or frequency based analyses. Key to this approach is having fast methods for computing binary signals directly in the wavelet domain. Multiple fast transform methods are developed in detail. |
1302.1762 | Steven Willison | Steven Willison | AdS spacetimes and isometric embeddings | To appear in the proceedings of the conference: "Relativity and
Gravitation, 100 Years after Einstein in Prague." We give a brief review of
the results obtained in [arXiv:1011.3883[gr-qc]]. Lemma 2.2, is a new result | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An algebraic global isometric embedding of the nonrotating BTZ black hole is
presented. The ambient spacetime is $\mathbb{M}^{2,3}$, the 3+2 dimensional
flat spacetime. We also present the analogous embedding for the Euclidean BTZ
spacetime and by performing a kind of double analytic continuation construct a
1-parameter family of embeddings of cosmological AdS spacetime into
$\mathbb{M}^{2,3}$ which coincide asymptotically with the embedded BTZ manifold
of the appropriate mass. Finally we note that the family of embeddings of
cosmological AdS$_{n}$ into $\mathbb{M}^{2,n}$ generalises to higher
dimensions.
| [
{
"created": "Thu, 7 Feb 2013 14:37:51 GMT",
"version": "v1"
}
] | 2013-02-08 | [
[
"Willison",
"Steven",
""
]
] | An algebraic global isometric embedding of the nonrotating BTZ black hole is presented. The ambient spacetime is $\mathbb{M}^{2,3}$, the 3+2 dimensional flat spacetime. We also present the analogous embedding for the Euclidean BTZ spacetime and by performing a kind of double analytic continuation construct a 1-parameter family of embeddings of cosmological AdS spacetime into $\mathbb{M}^{2,3}$ which coincide asymptotically with the embedded BTZ manifold of the appropriate mass. Finally we note that the family of embeddings of cosmological AdS$_{n}$ into $\mathbb{M}^{2,n}$ generalises to higher dimensions. |
1912.01971 | Caio Ribeiro | C. C. H. Ribeiro and D. A. T. Vanzella | Analogues of gravity-induced instabilities in anisotropic metamaterials | null | Phys. Rev. Research 2, 013281 (2020) | 10.1103/PhysRevResearch.2.013281 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of field theory in curved spacetimes, it is known that
suitable background spacetime geometries can trigger instabilities of fields,
leading to exponential growth of their (quantum and classical) fluctuations ---
a phenomenon called $\textit{vacuum awakening}$ in the quantum context, which
in some classical scenarios seeds $\textit{spontaneous
scalarization/vectorization}$. Despite its conceptual interest, an actual
observation in nature of this effect is uncertain since it depends on the
existence of fields with appropriate masses and couplings in strong-gravity
regimes. Here, we propose analogues for this gravity-induced instability based
on nonlinear optics of metamaterials which could, in principle, be observed in
laboratory.
| [
{
"created": "Wed, 4 Dec 2019 13:42:14 GMT",
"version": "v1"
}
] | 2020-03-18 | [
[
"Ribeiro",
"C. C. H.",
""
],
[
"Vanzella",
"D. A. T.",
""
]
] | In the context of field theory in curved spacetimes, it is known that suitable background spacetime geometries can trigger instabilities of fields, leading to exponential growth of their (quantum and classical) fluctuations --- a phenomenon called $\textit{vacuum awakening}$ in the quantum context, which in some classical scenarios seeds $\textit{spontaneous scalarization/vectorization}$. Despite its conceptual interest, an actual observation in nature of this effect is uncertain since it depends on the existence of fields with appropriate masses and couplings in strong-gravity regimes. Here, we propose analogues for this gravity-induced instability based on nonlinear optics of metamaterials which could, in principle, be observed in laboratory. |
2406.12933 | Michael Gammon | Michael Gammon, Robert B. Mann, Sarah Rourke | Charged Quark Stars and Extreme Compact Objects in Regularized 4D
Einstein-Gauss-Bonnet Gravity | arXiv admin note: substantial text overlap with arXiv:2309.00703 | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Since the derivation of a well-defined $D\rightarrow 4$ limit for 4
dimensional Einstein Gauss-Bonnet (4DEGB) gravity coupled to a scalar field,
there has been interest in testing it as an alternative to Einstein's general
theory of relativity. Using the Tolman-Oppenheimer-Volkoff (TOV) equations
modified for charge and 4DEGB gravity, we model the stellar structure of
charged, non-interacting quark stars. We find that increasing the Gauss-Bonnet
coupling constant $\alpha$ or the charge $Q$ both tend to increase the
mass-radius profiles of quark stars described by this theory, allowing a given
central pressure to support larger quark stars in general. We also derive a
generalization of the Buchdahl bound for charged stars in 4DEGB gravity. As in
the uncharged case, we find that quark stars can exist below the general
relativistic Buchdahl bound (BB) and Schwarzschild radius $R=2M$, due to the
lack of a mass gap between black holes and compact stars in the 4DEGB theory.
Even for $\alpha$ well within current observational constraints, we find that
quark star solutions in this theory can describe Extreme Compact Charged
Objects (ECCOs), objects whose radii are smaller than what is allowed by
general relativity.
| [
{
"created": "Sun, 16 Jun 2024 20:28:09 GMT",
"version": "v1"
}
] | 2024-06-21 | [
[
"Gammon",
"Michael",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Rourke",
"Sarah",
""
]
] | Since the derivation of a well-defined $D\rightarrow 4$ limit for 4 dimensional Einstein Gauss-Bonnet (4DEGB) gravity coupled to a scalar field, there has been interest in testing it as an alternative to Einstein's general theory of relativity. Using the Tolman-Oppenheimer-Volkoff (TOV) equations modified for charge and 4DEGB gravity, we model the stellar structure of charged, non-interacting quark stars. We find that increasing the Gauss-Bonnet coupling constant $\alpha$ or the charge $Q$ both tend to increase the mass-radius profiles of quark stars described by this theory, allowing a given central pressure to support larger quark stars in general. We also derive a generalization of the Buchdahl bound for charged stars in 4DEGB gravity. As in the uncharged case, we find that quark stars can exist below the general relativistic Buchdahl bound (BB) and Schwarzschild radius $R=2M$, due to the lack of a mass gap between black holes and compact stars in the 4DEGB theory. Even for $\alpha$ well within current observational constraints, we find that quark star solutions in this theory can describe Extreme Compact Charged Objects (ECCOs), objects whose radii are smaller than what is allowed by general relativity. |
gr-qc/0511154 | Jeffrey Winicour | Maria C. Babiuc, Bela Szilagyi and Jeffrey Winicour | Testing numerical relativity with the shifted gauge wave | Submitted to special numerical relativity issue of Classical and
Quantum Gravity | Class.Quant.Grav.23:S319-S342,2006 | 10.1088/0264-9381/23/16/S03 | null | gr-qc | null | Computational methods are essential to provide waveforms from coalescing
black holes, which are expected to produce strong signals for the gravitational
wave observatories being developed. Although partial simulations of the
coalescence have been reported, scientifically useful waveforms have so far not
been delivered. The goal of the AppleswithApples (AwA) Alliance is to design,
coordinate and document standardized code tests for comparing numerical
relativity codes. The first round of AwA tests have now being completed and the
results are being analyzed. These initial tests are based upon periodic
boundary conditions designed to isolate performance of the main evolution code.
Here we describe and carry out an additional test with periodic boundary
conditions which deals with an essential feature of the black hole excision
problem, namely a non-vanishing shift. The test is a shifted version of the
existing AwA gauge wave test. We show how a shift introduces an exponentially
growing instability which violates the constraints of a standard harmonic
formulation of Einstein's equations. We analyze the Cauchy problem in a
harmonic gauge and discuss particular options for suppressing instabilities in
the gauge wave tests. We implement these techniques in a finite difference
evolution algorithm and present test results. Although our application here is
limited to a model problem, the techniques should benefit the simulation of
black holes using harmonic evolution codes.
| [
{
"created": "Tue, 29 Nov 2005 09:45:12 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Feb 2006 22:22:41 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Babiuc",
"Maria C.",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | Computational methods are essential to provide waveforms from coalescing black holes, which are expected to produce strong signals for the gravitational wave observatories being developed. Although partial simulations of the coalescence have been reported, scientifically useful waveforms have so far not been delivered. The goal of the AppleswithApples (AwA) Alliance is to design, coordinate and document standardized code tests for comparing numerical relativity codes. The first round of AwA tests have now being completed and the results are being analyzed. These initial tests are based upon periodic boundary conditions designed to isolate performance of the main evolution code. Here we describe and carry out an additional test with periodic boundary conditions which deals with an essential feature of the black hole excision problem, namely a non-vanishing shift. The test is a shifted version of the existing AwA gauge wave test. We show how a shift introduces an exponentially growing instability which violates the constraints of a standard harmonic formulation of Einstein's equations. We analyze the Cauchy problem in a harmonic gauge and discuss particular options for suppressing instabilities in the gauge wave tests. We implement these techniques in a finite difference evolution algorithm and present test results. Although our application here is limited to a model problem, the techniques should benefit the simulation of black holes using harmonic evolution codes. |
1904.03502 | Dimitris Kallifatides | Dimitris S. Kallifatides | Primordial Black Hole Remnants as Dark Energy and an Instability of De
Sitter Space towards Power-Law Accelerating Expansion | 19 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from a discussion of the black hole information loss paradox, we
argue that Primordial Black Hole Remnants (PBHRs) of Planck mass, should they
exist, are a plausible candidate for dark energy. We call this proposal the
PBHR model. We also find an instability of de Sitter space towards a space with
power-law accelerating expansion, the time dependence of the cosmological
constant and the resulting form of the metric, and propose that this is the
dominant instability of de Sitter space. We conjecture that a similar
instability does not afflict a space sourced by PBHRs. We find that the PBHR
model satisfies the upper limits on $\beta$, the fraction of the Universe's
mass in PBHs at their formation time, for a fair range of initial PBH masses.
We derive information on the present day gravitational wave background due to
the PBHs in our scenario.
| [
{
"created": "Sat, 6 Apr 2019 17:44:01 GMT",
"version": "v1"
}
] | 2019-04-09 | [
[
"Kallifatides",
"Dimitris S.",
""
]
] | Starting from a discussion of the black hole information loss paradox, we argue that Primordial Black Hole Remnants (PBHRs) of Planck mass, should they exist, are a plausible candidate for dark energy. We call this proposal the PBHR model. We also find an instability of de Sitter space towards a space with power-law accelerating expansion, the time dependence of the cosmological constant and the resulting form of the metric, and propose that this is the dominant instability of de Sitter space. We conjecture that a similar instability does not afflict a space sourced by PBHRs. We find that the PBHR model satisfies the upper limits on $\beta$, the fraction of the Universe's mass in PBHs at their formation time, for a fair range of initial PBH masses. We derive information on the present day gravitational wave background due to the PBHs in our scenario. |
0802.3712 | David Garfinkle | David Garfinkle, Greg Comer | Matters of Gravity, The Newsletter of the Topical Group in Gravitation
of the American Physical Society, Volume 31, Winter 2008 | 14 pages, latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | GGR News: GGR program at the APS meeting in St. Louis we hear that... by
David Garfinkle 100 years ago, by David Garfinkle
Research Briefs: The Torsion Pendulum's Contribution to Dark Energy, by Bill
Hamilton
Conference Reports: 10th Capra Meeting on Radiation Reaction, by Carlos
Sopuerta Quantum Gravity in the Southern Cone IV, by Rafael A. Porto
| [
{
"created": "Mon, 25 Feb 2008 22:38:44 GMT",
"version": "v1"
}
] | 2008-02-27 | [
[
"Garfinkle",
"David",
""
],
[
"Comer",
"Greg",
""
]
] | GGR News: GGR program at the APS meeting in St. Louis we hear that... by David Garfinkle 100 years ago, by David Garfinkle Research Briefs: The Torsion Pendulum's Contribution to Dark Energy, by Bill Hamilton Conference Reports: 10th Capra Meeting on Radiation Reaction, by Carlos Sopuerta Quantum Gravity in the Southern Cone IV, by Rafael A. Porto |
1903.00990 | Thomas P. Kling | Thomas Kling, Eric Grotzke, Kevin Roebuck, Harry Waite | Examining the Kerr Metric through Wave Fronts of Null Geodesics | This is a post-peer-review, pre-copyedit version of an article
published in General Relativity and Gravitation. The final authenticated
version is available online at: https://doi.org/10.1007/s10714-019-2518-1 | General Relativity and Gravitation (2019) 51:32 | 10.1007/s10714-019-2518-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the singularities of the wave fronts of null geodesics from point
sources in the Kerr Metric. We find that the wave fronts develop a tube like
structure that collapses non-symmetrically, leading to cusp features in the
wave front singularities. As the wave front advances, the cusps trace out an
astroidal shaped caustic tube, which had been discovered previously using lens
mapping and geodesic deviation methods. Thus, the wave front approach in this
study helps to complete a picture of caustics and gravitational lensing in the
Kerr geometry.
| [
{
"created": "Sun, 3 Mar 2019 21:10:21 GMT",
"version": "v1"
}
] | 2019-03-05 | [
[
"Kling",
"Thomas",
""
],
[
"Grotzke",
"Eric",
""
],
[
"Roebuck",
"Kevin",
""
],
[
"Waite",
"Harry",
""
]
] | We examine the singularities of the wave fronts of null geodesics from point sources in the Kerr Metric. We find that the wave fronts develop a tube like structure that collapses non-symmetrically, leading to cusp features in the wave front singularities. As the wave front advances, the cusps trace out an astroidal shaped caustic tube, which had been discovered previously using lens mapping and geodesic deviation methods. Thus, the wave front approach in this study helps to complete a picture of caustics and gravitational lensing in the Kerr geometry. |
gr-qc/9501003 | Lior M. Burko | Lior M. Burko, Amos Ori | Are physical objects necessarily burnt up by the blue sheet inside a
black hole? | 13 pages, ordinary LaTex. Accepted for Physical Review Letters. | Phys.Rev.Lett. 74 (1995) 1064-1066 | 10.1103/PhysRevLett.74.1064 | Technion preprint no. TECHNION-PH-94-17 | gr-qc | null | The electromagnetic radiation that falls into a Reissner-Nordstrom black hole
develops a ``blue sheet'' of infinite energy density at the Cauchy horizon. We
consider classical electromagnetic fields (that were produced during the
collapse and then backscattered into the black hole), and investigate the
blue-sheet effects of these fields on infalling objects within a simplified
model. These effects are found to be finite and even negligible for typical
parameters.
| [
{
"created": "Sun, 8 Jan 1995 08:38:52 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Burko",
"Lior M.",
""
],
[
"Ori",
"Amos",
""
]
] | The electromagnetic radiation that falls into a Reissner-Nordstrom black hole develops a ``blue sheet'' of infinite energy density at the Cauchy horizon. We consider classical electromagnetic fields (that were produced during the collapse and then backscattered into the black hole), and investigate the blue-sheet effects of these fields on infalling objects within a simplified model. These effects are found to be finite and even negligible for typical parameters. |
1912.07049 | Sergey Yu. Vernov | S.Yu. Vernov, V.R. Ivanov, E.O. Pozdeeva | Superpotential method for $F(R)$ cosmological models | 10 pages, references added | Phys. Part. Nuclei 51 (2020) 744 | 10.1134/S1063779620040735 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the $F(R)$ gravity models with exact particular solutions using
the conformal transformation and the superpotential method for the
corresponding models in the Einstein frame. The functions $F(R)$ are obtained
explicitly. We consider exact solutions for the obtained $R^2$ gravity model
with the cosmological constant in detail.
| [
{
"created": "Sun, 15 Dec 2019 14:27:17 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Dec 2019 11:27:14 GMT",
"version": "v2"
}
] | 2020-10-06 | [
[
"Vernov",
"S. Yu.",
""
],
[
"Ivanov",
"V. R.",
""
],
[
"Pozdeeva",
"E. O.",
""
]
] | We construct the $F(R)$ gravity models with exact particular solutions using the conformal transformation and the superpotential method for the corresponding models in the Einstein frame. The functions $F(R)$ are obtained explicitly. We consider exact solutions for the obtained $R^2$ gravity model with the cosmological constant in detail. |
1001.2886 | Lorenzo Fatibene | L. Fatibene, M. Francaviglia, S. Mercadante | Noether Symmetries and Covariant Conservation Laws in Classical,
Relativistic and Quantum Physics | 27 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the Lagrangian formulation of Noether symmetries (as well as
"generalized Noether symmetries") in the framework of Calculus of Variations in
Jet Bundles, with a special attention to so-called "Natural Theories" and
"Gauge-Natural Theories", that include all relevant Field Theories and physical
applications (from Mechanics to General Relativity, to Gauge Theories,
Supersymmetric Theories, Spinors and so on). It is discussed how the use of
Poincare'-Cartan forms and decompositions of natural (or gauge-natural)
variational operators give rise to notions such as "generators of Noether
symmetries", energy and reduced energy flow, Bianchi identities, weak and
strong conservation laws, covariant conservation laws, Hamiltonian-like
conservation laws (such as, e.g., so-called ADM laws in General Relativity)
with emphasis on the physical interpretation of the quantities calculated in
specific cases (energy, angular momentum, entropy, etc.). A few substantially
new and very recent applications/examples are presented to better show the
power of the methods introduced: one in Classical Mechanics (definition of
strong conservation laws in a frame-independent setting and a discussion on the
way in which conserved quantities depend on the choice of an observer); one in
Classical Field Theories (energy and entropy in General Relativity, in its
standard formulation, in its spin-frame formulation, in its first order
formulation "`a la Palatini" and in its extensions to Non-Linear Gravity
Theories); one in Quantum Field Theories (applications to conservation laws in
Loop Quantum Gravity via spin connections and Barbero-Immirzi connections).
| [
{
"created": "Sun, 17 Jan 2010 10:54:45 GMT",
"version": "v1"
}
] | 2010-01-19 | [
[
"Fatibene",
"L.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Mercadante",
"S.",
""
]
] | We review the Lagrangian formulation of Noether symmetries (as well as "generalized Noether symmetries") in the framework of Calculus of Variations in Jet Bundles, with a special attention to so-called "Natural Theories" and "Gauge-Natural Theories", that include all relevant Field Theories and physical applications (from Mechanics to General Relativity, to Gauge Theories, Supersymmetric Theories, Spinors and so on). It is discussed how the use of Poincare'-Cartan forms and decompositions of natural (or gauge-natural) variational operators give rise to notions such as "generators of Noether symmetries", energy and reduced energy flow, Bianchi identities, weak and strong conservation laws, covariant conservation laws, Hamiltonian-like conservation laws (such as, e.g., so-called ADM laws in General Relativity) with emphasis on the physical interpretation of the quantities calculated in specific cases (energy, angular momentum, entropy, etc.). A few substantially new and very recent applications/examples are presented to better show the power of the methods introduced: one in Classical Mechanics (definition of strong conservation laws in a frame-independent setting and a discussion on the way in which conserved quantities depend on the choice of an observer); one in Classical Field Theories (energy and entropy in General Relativity, in its standard formulation, in its spin-frame formulation, in its first order formulation "`a la Palatini" and in its extensions to Non-Linear Gravity Theories); one in Quantum Field Theories (applications to conservation laws in Loop Quantum Gravity via spin connections and Barbero-Immirzi connections). |
0911.4932 | Kayoomars Karami | K. Karami, J. Fehri | Holographic dark energy in a non-flat universe with Granda-Oliveros
cut-off | 11 pages, 5 figures | Int.J.Theor.Phys.49:1118-1126,2010 | 10.1007/s10773-010-0291-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by Granda and Oliveros (GO) model, we generalize their work to the
non-flat case. We obtain the evolution of the dark energy density, the
deceleration and the equation of state parameters for the holographic dark
energy model in a non-flat universe with GO cut-off. In the limiting case of a
flat universe, i.e. $k = 0$, all results given in GO model are obtained.
| [
{
"created": "Wed, 25 Nov 2009 18:39:14 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Nov 2009 14:52:15 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Apr 2010 06:33:19 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Karami",
"K.",
""
],
[
"Fehri",
"J.",
""
]
] | Motivated by Granda and Oliveros (GO) model, we generalize their work to the non-flat case. We obtain the evolution of the dark energy density, the deceleration and the equation of state parameters for the holographic dark energy model in a non-flat universe with GO cut-off. In the limiting case of a flat universe, i.e. $k = 0$, all results given in GO model are obtained. |
2205.02712 | Benrong Mu | Siyuan Hui, Benrong Mu, Yuzhou Tao, Jun Tao | Thermodynamics of the RN-AdS black hole with cloud of strings and
quintessence in stationary and free-fall frame in rainbow gravity | 14 pages, 5 figures, 1 table | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the thermodynamic properties of the RN-AdS
black hole with cloud of strings and quintessence in rainbow gravity with the
stationary (ST) orthonormal frame and the free-fall (FF) orthonormal frame.
After the SF and the FF rainbow metric is obtained, we get the Hawking
temperature and the entropy, and their physical meanings are discussed. We find
that, for the ST rainbow RN-AdS black hole with cloud of strings and
quintessence, the effect of rainbow gravity is to increase the Hawking
temperature but decrease the entropy of the black hole. However, for the FF
rainbow case, rainbow gravity turns out to decrease the Hawking temperature but
increase the entropy of the black hole, which seems that the effects rainbow
gravity has are quite model-dependent.
| [
{
"created": "Thu, 5 May 2022 15:32:56 GMT",
"version": "v1"
}
] | 2022-05-06 | [
[
"Hui",
"Siyuan",
""
],
[
"Mu",
"Benrong",
""
],
[
"Tao",
"Yuzhou",
""
],
[
"Tao",
"Jun",
""
]
] | In this paper, we investigate the thermodynamic properties of the RN-AdS black hole with cloud of strings and quintessence in rainbow gravity with the stationary (ST) orthonormal frame and the free-fall (FF) orthonormal frame. After the SF and the FF rainbow metric is obtained, we get the Hawking temperature and the entropy, and their physical meanings are discussed. We find that, for the ST rainbow RN-AdS black hole with cloud of strings and quintessence, the effect of rainbow gravity is to increase the Hawking temperature but decrease the entropy of the black hole. However, for the FF rainbow case, rainbow gravity turns out to decrease the Hawking temperature but increase the entropy of the black hole, which seems that the effects rainbow gravity has are quite model-dependent. |
0911.5041 | Alessandro Nagar | Thibault Damour, Alessandro Nagar | Effective One Body description of tidal effects in inspiralling compact
binaries | 21 pages, 5 figures. Submitted to Phys. Rev. D | Phys.Rev.D81:084016,2010 | 10.1103/PhysRevD.81.084016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The late part of the gravitational wave signal of binary neutron star
inspirals can in principle yield crucial information on the nuclear equation of
state via its dependence on relativistic tidal parameters. In the hope of
analytically describing the gravitational wave phasing during the late inspiral
(essentially up to contact) we propose an extension of the effective one body
(EOB) formalism which includes tidal effects. We compare the prediction of this
tidal-EOB formalism to recently computed nonconformally flat quasi-equilibrium
circular sequences of binary neutron star systems. Our analysis suggests the
importance of higher-order (post-Newtonian) corrections to tidal effects, even
beyond the first post-Newtonian order, and their tendency to {\it
significantly} increase the ``effective tidal polarizability'' of neutron
stars. We compare the EOB predictions to some recently advocated, nonresummed,
post-Newtonian based (``Taylor-T4'') description of the phasing of inspiralling
systems. This comparison shows the strong sensitivity of the late-inspiral
phasing to the choice of the analytical model, but raises the hope that a
sufficiently accurate numerical--relativity--``calibrated'' EOB model might
give us a reliable handle on the nuclear equation of state
| [
{
"created": "Fri, 27 Nov 2009 14:53:45 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Damour",
"Thibault",
""
],
[
"Nagar",
"Alessandro",
""
]
] | The late part of the gravitational wave signal of binary neutron star inspirals can in principle yield crucial information on the nuclear equation of state via its dependence on relativistic tidal parameters. In the hope of analytically describing the gravitational wave phasing during the late inspiral (essentially up to contact) we propose an extension of the effective one body (EOB) formalism which includes tidal effects. We compare the prediction of this tidal-EOB formalism to recently computed nonconformally flat quasi-equilibrium circular sequences of binary neutron star systems. Our analysis suggests the importance of higher-order (post-Newtonian) corrections to tidal effects, even beyond the first post-Newtonian order, and their tendency to {\it significantly} increase the ``effective tidal polarizability'' of neutron stars. We compare the EOB predictions to some recently advocated, nonresummed, post-Newtonian based (``Taylor-T4'') description of the phasing of inspiralling systems. This comparison shows the strong sensitivity of the late-inspiral phasing to the choice of the analytical model, but raises the hope that a sufficiently accurate numerical--relativity--``calibrated'' EOB model might give us a reliable handle on the nuclear equation of state |
0908.1326 | Clovis Jacinto de Matos | Clovis Jacinto de Matos | Gravitoelectromagnetism in (Anti) de Sitter Spacetime | 12 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of a non-zero cosmological term in Einstein field equations can
be interpreted as the physical possibility for preferred reference frames
without breaking of general covariance. This possibility is used in the process
of linearizing Einstein field equations in a de Sitter background, and in
formulating the resulting equations in the framework of
gravitoelectromagnetism. It is proposed that this set of equations only applies
to the physical vacuum and not to baryonic (normal) matter.
| [
{
"created": "Mon, 10 Aug 2009 14:00:45 GMT",
"version": "v1"
}
] | 2009-08-11 | [
[
"de Matos",
"Clovis Jacinto",
""
]
] | The presence of a non-zero cosmological term in Einstein field equations can be interpreted as the physical possibility for preferred reference frames without breaking of general covariance. This possibility is used in the process of linearizing Einstein field equations in a de Sitter background, and in formulating the resulting equations in the framework of gravitoelectromagnetism. It is proposed that this set of equations only applies to the physical vacuum and not to baryonic (normal) matter. |
gr-qc/9503017 | Mariusz Dabrowski | Mariusz P. Dabrowski | Oscillating Friedman Cosmology | Latex file, 27 pages, figures available on request | Annals Phys.248:199-219,1996 | 10.1006/aphy.1996.0057 | null | gr-qc | null | The non-singular, oscillating Friedman cosmology within the framework of
General Relativity is considered. The general oscillatory solution given in
terms of elliptic functions and the conditions for its existence are discussed.
It is shown that the wall-like-matter and the small, but negative cosmological
constant are required for oscillations. The oscillations can , in principle, be
deep enough to allow standard hot universe processes like recombination and
nucleosynthesis. It is shown that the wall-like-matter and string-like-matter
can be interpreted as scalar fields with some potentials. This may give another
candidate for the dark matter which may be compatible with observational data.
For an exact elementary oscillatory solution it is shown that the associated
scalar field potential is oscillating as well.
| [
{
"created": "Thu, 9 Mar 1995 12:41:58 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Dabrowski",
"Mariusz P.",
""
]
] | The non-singular, oscillating Friedman cosmology within the framework of General Relativity is considered. The general oscillatory solution given in terms of elliptic functions and the conditions for its existence are discussed. It is shown that the wall-like-matter and the small, but negative cosmological constant are required for oscillations. The oscillations can , in principle, be deep enough to allow standard hot universe processes like recombination and nucleosynthesis. It is shown that the wall-like-matter and string-like-matter can be interpreted as scalar fields with some potentials. This may give another candidate for the dark matter which may be compatible with observational data. For an exact elementary oscillatory solution it is shown that the associated scalar field potential is oscillating as well. |
1405.1644 | Caixia Gao | Caixia Gao, Robert H. Brandenberger, Yifu Cai, Pisin Chen | Cosmological Perturbations in Unimodular Gravity | null | null | 10.1088/1475-7516/2014/09/021 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological perturbation theory within the framework of unimodular
gravity. We show that the Lagrangian constraint on the determinant of the
metric required by unimodular gravity leads to an extra constraint on the gauge
freedom of the metric perturbations. Although the main equation of motion for
the gravitational potential remains the same, the shift variable, which is
gauge artifact in General Relativity, cannot be set to zero in unimodular
gravity. This non-vanishing shift variable affects the propagation of photons
throughout the cosmological evolution and therefore modifies the Sachs-Wolfe
relation between the relativistic gravitational potential and the microwave
temperature anisotropies. However, for adiabatic fluctuations the difference
between the result in General Relativity and unimodular gravity is suppressed
on large angular scales. Thus, no strong constraints on the theory can be
derived.
| [
{
"created": "Wed, 7 May 2014 15:30:39 GMT",
"version": "v1"
},
{
"created": "Sat, 31 May 2014 18:29:08 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Gao",
"Caixia",
""
],
[
"Brandenberger",
"Robert H.",
""
],
[
"Cai",
"Yifu",
""
],
[
"Chen",
"Pisin",
""
]
] | We study cosmological perturbation theory within the framework of unimodular gravity. We show that the Lagrangian constraint on the determinant of the metric required by unimodular gravity leads to an extra constraint on the gauge freedom of the metric perturbations. Although the main equation of motion for the gravitational potential remains the same, the shift variable, which is gauge artifact in General Relativity, cannot be set to zero in unimodular gravity. This non-vanishing shift variable affects the propagation of photons throughout the cosmological evolution and therefore modifies the Sachs-Wolfe relation between the relativistic gravitational potential and the microwave temperature anisotropies. However, for adiabatic fluctuations the difference between the result in General Relativity and unimodular gravity is suppressed on large angular scales. Thus, no strong constraints on the theory can be derived. |
gr-qc/0306086 | Kahil | M.I.Wanas, M.Melek and M.E.Kahil | SN1987A: Temporal Models | 7 pages LaTex file, published in the Proceedings of MG IX, Vol. 2,
p.1100, World Scientific Pub.(2002) | null | null | null | gr-qc astro-ph | null | It is well known that carriers of astrophysical information are massless
spinning particles. These carriers are photons, neutrinos and, expectedly,
gravitons. All these particles are emitted during supernova events. Information
carried by these particles characterize their sources, but such information are
affected by the trajectories of the carriers. Recently, it is shown that these
trajectories are spin dependent. Knowing these trajectories and the arrival
times of such particles to the detectors, a spin dependent model is constructed
and compared with the conventional spin independent model.
| [
{
"created": "Thu, 19 Jun 2003 10:55:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wanas",
"M. I.",
""
],
[
"Melek",
"M.",
""
],
[
"Kahil",
"M. E.",
""
]
] | It is well known that carriers of astrophysical information are massless spinning particles. These carriers are photons, neutrinos and, expectedly, gravitons. All these particles are emitted during supernova events. Information carried by these particles characterize their sources, but such information are affected by the trajectories of the carriers. Recently, it is shown that these trajectories are spin dependent. Knowing these trajectories and the arrival times of such particles to the detectors, a spin dependent model is constructed and compared with the conventional spin independent model. |
1403.3074 | Ion I. Cotaescu | Ion I. Cotaescu | Accelerated frames in de Sitter spacetime | 5 pages no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a definition of the accelerated frames in de Sitter spacetime
whose metric recovers the Rindler approach in the flat limit. Unfortunately,
this metric has no a satisfactory limit for vanishing acceleration such that
its physical meaning remains obscure.
| [
{
"created": "Tue, 11 Mar 2014 16:15:33 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Mar 2014 06:37:57 GMT",
"version": "v2"
},
{
"created": "Fri, 30 May 2014 16:02:47 GMT",
"version": "v3"
},
{
"created": "Fri, 11 Jul 2014 07:48:42 GMT",
"version": "v4"
},
{
"c... | 2014-07-18 | [
[
"Cotaescu",
"Ion I.",
""
]
] | We propose a definition of the accelerated frames in de Sitter spacetime whose metric recovers the Rindler approach in the flat limit. Unfortunately, this metric has no a satisfactory limit for vanishing acceleration such that its physical meaning remains obscure. |
2111.01828 | Pierre-Henri Chavanis | Pierre-Henri Chavanis | Cosmological models based on a complex scalar field with a power-law
potential associated with a polytropic equation of state | null | null | 10.1103/PhysRevD.106.043502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct cosmological models based on a complex scalar field with a
power-law potential
$V=\frac{K}{\gamma-1}(\frac{m}{\hbar})^{2\gamma}|\varphi|^{2\gamma}$ associated
with a polytropic equation of state $P=K\rho^{\gamma}$ (the potential
associated with an isothermal equation of state $P=\rho k_B T/m$ is $V=\frac{m
k_B T}{\hbar^2}|\varphi|^2 [\ln(m^2|\varphi|^2/\rho_*\hbar^2)-1]$ and the
potential associated with a logotropic equation of state $P=A\ln(\rho/\rho_P)$
is $V=-A[\ln(m^2|\varphi|^2/\hbar^2\rho_P)+1]$). We consider a fast oscillation
regime of ``spintessence'' where the equations of the problem can be
simplified. We study all possible cases with arbitrary (positive and negative)
values of the polytropic constant and polytropic index. The $\Lambda$CDM model,
the Chaplygin gas model and the Bose-Einstein condensate model are recovered as
particular cases of our study corresponding to a constant potential
($\gamma=0$), an inverse square-law potential ($\gamma=-1$), and a quartic
potential ($\gamma=2$). We also derive the two-fluid representation of the
Chaplygin gas model.
| [
{
"created": "Tue, 2 Nov 2021 18:27:48 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Chavanis",
"Pierre-Henri",
""
]
] | We construct cosmological models based on a complex scalar field with a power-law potential $V=\frac{K}{\gamma-1}(\frac{m}{\hbar})^{2\gamma}|\varphi|^{2\gamma}$ associated with a polytropic equation of state $P=K\rho^{\gamma}$ (the potential associated with an isothermal equation of state $P=\rho k_B T/m$ is $V=\frac{m k_B T}{\hbar^2}|\varphi|^2 [\ln(m^2|\varphi|^2/\rho_*\hbar^2)-1]$ and the potential associated with a logotropic equation of state $P=A\ln(\rho/\rho_P)$ is $V=-A[\ln(m^2|\varphi|^2/\hbar^2\rho_P)+1]$). We consider a fast oscillation regime of ``spintessence'' where the equations of the problem can be simplified. We study all possible cases with arbitrary (positive and negative) values of the polytropic constant and polytropic index. The $\Lambda$CDM model, the Chaplygin gas model and the Bose-Einstein condensate model are recovered as particular cases of our study corresponding to a constant potential ($\gamma=0$), an inverse square-law potential ($\gamma=-1$), and a quartic potential ($\gamma=2$). We also derive the two-fluid representation of the Chaplygin gas model. |
2303.04399 | Sayantani Datta | Sayantani Datta | Enhancing the performance of multiparameter tests of general relativity
with LISA using Principal Component Analysis | null | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Laser Interferometer Space Antenna (LISA) will provide us with a unique
opportunity to observe the early inspiral phase of supermassive binary black
holes (SMBBHs) in the mass range of $10^5-10^6\,M_{\odot}$, that lasts for
several years. It will also detect the merger and ringdown phases of these
sources. Therefore, such sources are extremely useful for multiparameter tests
of general relativity (GR), where parametrized deviations from GR at multiple
post-Newtonian orders are simultaneously measured, thus allowing for a rigorous
test of GR. However, the correlations of the deviation parameters with the
intrinsic parameters of the system make multiparameter tests extremely
challenging to perform. We demonstrate the use of principal component analysis
(PCA) to obtain a new set of deviation parameters, which are best-measured
orthogonal linear combinations of the original deviation parameters. With the
observation of an SMBBH of total redshifted mass,
$\sim\mathrm{7\times10^5\,M_{\odot}}$ at a luminosity distance of 3 Gpc, we can
estimate the five most dominant PCA parameters, with 1-$\sigma$ statistical
uncertainty of $\lesssim 0.2$. The two most dominant PCA parameters can be
bounded to $\sim \mathcal{O}(10^{-4})$, while the third and fourth-dominant
ones to $\sim \mathcal{O}(10^{-3})$. Measurement of the PCA parameters with
such unprecedented precision with LISA makes them an excellent probe to test
the overall PN structure of the GW phase evolution.
| [
{
"created": "Wed, 8 Mar 2023 06:20:17 GMT",
"version": "v1"
}
] | 2023-03-09 | [
[
"Datta",
"Sayantani",
""
]
] | The Laser Interferometer Space Antenna (LISA) will provide us with a unique opportunity to observe the early inspiral phase of supermassive binary black holes (SMBBHs) in the mass range of $10^5-10^6\,M_{\odot}$, that lasts for several years. It will also detect the merger and ringdown phases of these sources. Therefore, such sources are extremely useful for multiparameter tests of general relativity (GR), where parametrized deviations from GR at multiple post-Newtonian orders are simultaneously measured, thus allowing for a rigorous test of GR. However, the correlations of the deviation parameters with the intrinsic parameters of the system make multiparameter tests extremely challenging to perform. We demonstrate the use of principal component analysis (PCA) to obtain a new set of deviation parameters, which are best-measured orthogonal linear combinations of the original deviation parameters. With the observation of an SMBBH of total redshifted mass, $\sim\mathrm{7\times10^5\,M_{\odot}}$ at a luminosity distance of 3 Gpc, we can estimate the five most dominant PCA parameters, with 1-$\sigma$ statistical uncertainty of $\lesssim 0.2$. The two most dominant PCA parameters can be bounded to $\sim \mathcal{O}(10^{-4})$, while the third and fourth-dominant ones to $\sim \mathcal{O}(10^{-3})$. Measurement of the PCA parameters with such unprecedented precision with LISA makes them an excellent probe to test the overall PN structure of the GW phase evolution. |
1601.01262 | Ondrej Kop\'a\v{c}ek | Ond\v{r}ej Kop\'a\v{c}ek, Vladim\'ir Karas, Ji\v{r}\'i Kov\'a\v{r} and
Zden\v{e}k Stuchl\'ik | Application of a symplectic integrator in a non-integrable relativistic
system | 11 pages, 5 figures, 2 tables, prepared in 2011 for the Proceedings
of RAGtime 10-13: Workshops on black holes and neutron stars (Opava,
September 15 - 17, 2010) | in Proc. of RAGtime 10-13, eds. Z. Stuchl\'{i}k, G. T\"{o}r\"{o}k,
T. Pech\'{a}\v{c}ek, 2014 (Silesian University in Opava), pp. 123-132, ISBN
978-80-7510-125-9 | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a detailed comparison of several integration schemes applied to
the dynamic system consisting of a charged particle on the Kerr background
endowed with the axisymmetric electromagnetic test field. In particular, we
compare the performance of the symplectic integrator with several
non-symplectic routines and discuss under which circumstances we should choose
the symplectic one and when we should switch to some other scheme. We are
basically concerned with two crucial, yet opposing aspects - accuracy of the
integration and CPU time consumption. The latter is generally less critical in
our application while the highest possible accuracy is strongly demanded.
| [
{
"created": "Sun, 3 Jan 2016 23:17:18 GMT",
"version": "v1"
}
] | 2018-03-02 | [
[
"Kopáček",
"Ondřej",
""
],
[
"Karas",
"Vladimír",
""
],
[
"Kovář",
"Jiří",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | We present a detailed comparison of several integration schemes applied to the dynamic system consisting of a charged particle on the Kerr background endowed with the axisymmetric electromagnetic test field. In particular, we compare the performance of the symplectic integrator with several non-symplectic routines and discuss under which circumstances we should choose the symplectic one and when we should switch to some other scheme. We are basically concerned with two crucial, yet opposing aspects - accuracy of the integration and CPU time consumption. The latter is generally less critical in our application while the highest possible accuracy is strongly demanded. |
gr-qc/0607013 | Jan Ambjorn | J. Ambjorn, R. Janik, W. Westra and S. Zohren | The emergence of background geometry from quantum fluctuations | 12 pages | Phys.Lett. B641 (2006) 94-98 | 10.1016/j.physletb.2006.08.021 | null | gr-qc hep-th | null | We show how the quantization of two-dimensional gravity leads to an
(Euclidean) quantum space-time where the average geometry is that of constant
negative curvature and where the Hartle-Hawking boundary condition arises
naturally.
| [
{
"created": "Tue, 4 Jul 2006 20:13:11 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ambjorn",
"J.",
""
],
[
"Janik",
"R.",
""
],
[
"Westra",
"W.",
""
],
[
"Zohren",
"S.",
""
]
] | We show how the quantization of two-dimensional gravity leads to an (Euclidean) quantum space-time where the average geometry is that of constant negative curvature and where the Hartle-Hawking boundary condition arises naturally. |
2306.15982 | Dirk Puetzfeld | Peter A. Hogan, Dirk Puetzfeld | Plane fronted electromagnetic waves and an asymptotic limit of
Li\'enard--Wiechert fields | 11 pages, 2 figures | Int. J. Mod. Phys. D, Vol. 33, No. 02, 2450009 (2024) | 10.1142/S0218271824500093 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Colliding or noncolliding plane fronted electromagnetic or gravitational
waves are the asymptotic limit of Robinson--Trautman spherical electromagnetic
or gravitational waves. Noncolliding plane fronted waves contain no information
about their sources whereas colliding waves contain information about possibly
the motion of their sources. As a first step to investigate the latter
phenomenon we construct an asymptotic limit of Li\'enard--Wiechert
electromagnetic fields in the context of Minkowskian space--time. This has the
advantage that the source is well known and the calculations can be carried out
in full detail. The final result is an algebraically general Maxwell field
which consists of colliding plane fronted waves in a subregion of Minkowskian
space--time and an interesting byproduct is a novel perspective on a Maxwell
field originally discovered by Bateman.
| [
{
"created": "Wed, 28 Jun 2023 07:35:47 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 17:36:26 GMT",
"version": "v2"
}
] | 2024-04-03 | [
[
"Hogan",
"Peter A.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | Colliding or noncolliding plane fronted electromagnetic or gravitational waves are the asymptotic limit of Robinson--Trautman spherical electromagnetic or gravitational waves. Noncolliding plane fronted waves contain no information about their sources whereas colliding waves contain information about possibly the motion of their sources. As a first step to investigate the latter phenomenon we construct an asymptotic limit of Li\'enard--Wiechert electromagnetic fields in the context of Minkowskian space--time. This has the advantage that the source is well known and the calculations can be carried out in full detail. The final result is an algebraically general Maxwell field which consists of colliding plane fronted waves in a subregion of Minkowskian space--time and an interesting byproduct is a novel perspective on a Maxwell field originally discovered by Bateman. |
2107.02441 | Stefan Czimek | Stefanos Aretakis, Stefan Czimek, Igor Rodnianski | The characteristic gluing problem for the Einstein equations and
applications | 31 pages, 12 figures | null | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we introduce the characteristic gluing problem for the Einstein
vacuum equations. We present a codimension-$10$ gluing construction for
characteristic initial data which are close to the Minkowski data and we show
that the $10$-dimensional obstruction space consists of gauge-invariant charges
which are conserved by the linearized null constraint equations. By relating
these $10$ charges to the ADM energy, linear momentum, angular momentum and the
center-of-mass we prove that asymptotically flat data can be characteristically
glued (including the $10$ charges) to the data of a suitably chosen Kerr
spacetime, obtaining as a corollary an alternative proof of the Corvino--Schoen
spacelike gluing construction. Moreover, we derive a localized version of our
construction where the given data restricted on an angular sector is
characteristically glued to the Minkowski data restricted on another angular
sector. As a corollary we obtain an alternative proof of the Carlotto-Schoen
localized spacelike gluing construction. Our method yields no loss of decay in
the transition region, resolving an open problem. We also discuss a number of
other applications.
| [
{
"created": "Tue, 6 Jul 2021 07:39:14 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Aretakis",
"Stefanos",
""
],
[
"Czimek",
"Stefan",
""
],
[
"Rodnianski",
"Igor",
""
]
] | In this paper we introduce the characteristic gluing problem for the Einstein vacuum equations. We present a codimension-$10$ gluing construction for characteristic initial data which are close to the Minkowski data and we show that the $10$-dimensional obstruction space consists of gauge-invariant charges which are conserved by the linearized null constraint equations. By relating these $10$ charges to the ADM energy, linear momentum, angular momentum and the center-of-mass we prove that asymptotically flat data can be characteristically glued (including the $10$ charges) to the data of a suitably chosen Kerr spacetime, obtaining as a corollary an alternative proof of the Corvino--Schoen spacelike gluing construction. Moreover, we derive a localized version of our construction where the given data restricted on an angular sector is characteristically glued to the Minkowski data restricted on another angular sector. As a corollary we obtain an alternative proof of the Carlotto-Schoen localized spacelike gluing construction. Our method yields no loss of decay in the transition region, resolving an open problem. We also discuss a number of other applications. |
gr-qc/0406002 | Oleg Karpov | O.B. Karpov | The Papapetrou equations and supplementary conditions | 7 pages, Latex2e, amsmath, to appear in Grav. Cosmol | null | null | null | gr-qc | null | On the bases of the Papapetrou equations with various supplementary
conditions and other approaches a comparative analysis of the equations of
motion of rotating bodies in general relativity is made. The motion of a body
with vertical spin in a circular orbit is considered. An expression for the
spin-orbit force in a post-Newtonian approximation is investigated.
| [
{
"created": "Tue, 1 Jun 2004 19:29:22 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jun 2004 07:03:06 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Karpov",
"O. B.",
""
]
] | On the bases of the Papapetrou equations with various supplementary conditions and other approaches a comparative analysis of the equations of motion of rotating bodies in general relativity is made. The motion of a body with vertical spin in a circular orbit is considered. An expression for the spin-orbit force in a post-Newtonian approximation is investigated. |
2106.02236 | Yujie Tan | Pan-Pan Wang, Yu-Jie Tan, Wei-Liang Qian and Cheng-Gang Shao | Refined clock-jitter reduction in the Sagnac-type time-delay
interferometry combinations | null | Phys. Rev. D 104, 082002 (2021) | 10.1103/PhysRevD.104.082002 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The ongoing development of the space-based laser interferometer missions is
aiming at unprecedented gravitational wave detections in the millihertz
frequency band. The spaceborne nature of the experimental setups leads to a
degree of subtlety regarding the otherwise overwhelming laser frequency noise.
The cancellation of the latter is accomplished through the time-delay
interferometry technique. Moreover, to eventually achieve the desired noise
level, the phase fluctuations of the onboard ultra-stable oscillator must also
be suppressed. This can be fulfilled by introducing sideband signals which, in
turn, give rise to an improved cancellation scheme accounting for the
clock-jitter noise. Nonetheless, for certain Sagnac-type interferometry
layouts, it can be shown that resultant residual clock noise found in the
literature can be further improved. In this regard, we propose refined
cancellation combinations for two specific clock noise patterns. This is
achieved by employing the so-called geometric time-delay interferometry
interpretation. It is shown that for specific Sagnac combinations, the residual
noise diminishes significantly to attain the experimentally acceptable
sensitivity level. Moreover, we argue that the derived combination, in addition
to the existing ones in the literature, furnishes a general-purpose
cancellation scheme that serves for arbitrary time-delay interferometry
combinations. The subsequential residual noise will only involve factors
proportional to the commutators between the delay operators. Our arguments
reside in the form of the clock noise expressed in terms of the coefficients of
the generating set of the first module of syzygies, the linear combination of
which originally constitutes the very solution for laser noise reduction.
| [
{
"created": "Fri, 4 Jun 2021 03:36:37 GMT",
"version": "v1"
}
] | 2021-10-04 | [
[
"Wang",
"Pan-Pan",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Qian",
"Wei-Liang",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | The ongoing development of the space-based laser interferometer missions is aiming at unprecedented gravitational wave detections in the millihertz frequency band. The spaceborne nature of the experimental setups leads to a degree of subtlety regarding the otherwise overwhelming laser frequency noise. The cancellation of the latter is accomplished through the time-delay interferometry technique. Moreover, to eventually achieve the desired noise level, the phase fluctuations of the onboard ultra-stable oscillator must also be suppressed. This can be fulfilled by introducing sideband signals which, in turn, give rise to an improved cancellation scheme accounting for the clock-jitter noise. Nonetheless, for certain Sagnac-type interferometry layouts, it can be shown that resultant residual clock noise found in the literature can be further improved. In this regard, we propose refined cancellation combinations for two specific clock noise patterns. This is achieved by employing the so-called geometric time-delay interferometry interpretation. It is shown that for specific Sagnac combinations, the residual noise diminishes significantly to attain the experimentally acceptable sensitivity level. Moreover, we argue that the derived combination, in addition to the existing ones in the literature, furnishes a general-purpose cancellation scheme that serves for arbitrary time-delay interferometry combinations. The subsequential residual noise will only involve factors proportional to the commutators between the delay operators. Our arguments reside in the form of the clock noise expressed in terms of the coefficients of the generating set of the first module of syzygies, the linear combination of which originally constitutes the very solution for laser noise reduction. |
0806.2702 | Christian Corda | Christian Corda | "Magnetic" components of gravitational waves and response functions of
interferometers | Review commissioned by Nova Science Publishers, to appear in the
edited collection "Interferometers: Research, Technology and Applications" | Handbook of Interferometers... ISBN 978-1-60741-050-8 c 2009 Nova
Science Publishers, Inc. Editors: D. Halsey and W. Raynor, pp. 23-53 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, arising from an enlighting analysis of Baskaran and Grishchuk in
Class. Quant. Grav. 21, 4041-4061 (2004), some papers in the literature have
shown the presence and importance of the so-called "magnetic" components of
gravitational waves (GWs), which have to be taken into account in the context
of the total response functions of interferometers for GWs propagating from
arbitrary directions. In Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) and
Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007) accurate response functions for
the Virgo and LIGO interferometers have been analysed. However, some results
which have been shown in Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) look
in contrast with the results which have been shown in Int. J. Mod. Phys. D 16,
9, 1497-1517 (2007). In fact, in Int. Journ. Mod. Phys. A 22, 13, 2361-2381
(2007) it was claimed that the "magnetic" component of GWs could, in principle,
extend the frequency range of Earth based interferometers, while in Int. J.
Mod. Phys. D 16, 9, 1497-1517 (2007) such a possibility has been banned. This
contrast has been partially solved in the Proceedings of the XLIInd Rencontres
de Moriond, Gravitational Waves and Experimental Gravity, La Thuile, Val
d'Aosta Italy (March 12-18 2007). The aim of this review paper is to re-analyse
all the framework of the "magnetic" components of GWs with the goal of solving
the mentioned contrast in definitive way. Accurate response funtions for the
Virgo and LIGO interferometers will be also re-discussed in detail.
| [
{
"created": "Tue, 17 Jun 2008 05:45:30 GMT",
"version": "v1"
}
] | 2010-01-25 | [
[
"Corda",
"Christian",
""
]
] | Recently, arising from an enlighting analysis of Baskaran and Grishchuk in Class. Quant. Grav. 21, 4041-4061 (2004), some papers in the literature have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) and Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007) accurate response functions for the Virgo and LIGO interferometers have been analysed. However, some results which have been shown in Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) look in contrast with the results which have been shown in Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007). In fact, in Int. Journ. Mod. Phys. A 22, 13, 2361-2381 (2007) it was claimed that the "magnetic" component of GWs could, in principle, extend the frequency range of Earth based interferometers, while in Int. J. Mod. Phys. D 16, 9, 1497-1517 (2007) such a possibility has been banned. This contrast has been partially solved in the Proceedings of the XLIInd Rencontres de Moriond, Gravitational Waves and Experimental Gravity, La Thuile, Val d'Aosta Italy (March 12-18 2007). The aim of this review paper is to re-analyse all the framework of the "magnetic" components of GWs with the goal of solving the mentioned contrast in definitive way. Accurate response funtions for the Virgo and LIGO interferometers will be also re-discussed in detail. |
2407.16414 | Leigh Smith | Leigh Smith, Sayantan Ghosh, Jiyoon Sun, V. Gayathri, Ik Siong Heng,
Archana Pai | The enhancement of Gaussian mixture modelling as an application to the
coherent WaveBurst algorithm in the search for short gravitational wave
transients | 14 pages, 8 figures | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | We present an enhanced method for the application of Gaussian Mixture
Modelling (GMM) to the coherent WaveBurst (cWB) algorithm in the search for
short-duration gravitational wave (GW) transients. The supervised Machine
Learning method of GMM allows for the multi-dimensional distributions of noise
and signal to be modelled over a set of representative attributes, which aids
in the classification of GW signals against noise transients (glitches) in the
data. We demonstrate that updating the approach to model construction
eliminates bias previously seen in the GMM analysis, increasing the robustness
and sensitivity of the analysis over a wider range of burst source populations.
The enhanced methodology is applied to the generic burst all-sky short search
in the LIGO-Virgo full third observing run (O3), marking the first application
of GMM to the 3 detector Livingston-Hanford-Virgo network. For both 2- and 3-
detector networks, we observe comparable sensitivities to an array of generic
signal morphologies, with significant sensitivity improvements to waveforms in
the low Quality factor parameter space at false alarm rates of 1 per 100 years.
This proves that GMM can effectively mitigate blip glitches, which are one of
the most problematic sources of noise for un-modelled GW searches. The cWB-GMM
search recovers similar numbers of compact binary coalescence (CBC) events as
other cWB post-production methods, and concludes on no new gravitational wave
detection after known CBC events are removed.
| [
{
"created": "Tue, 23 Jul 2024 11:58:10 GMT",
"version": "v1"
}
] | 2024-07-24 | [
[
"Smith",
"Leigh",
""
],
[
"Ghosh",
"Sayantan",
""
],
[
"Sun",
"Jiyoon",
""
],
[
"Gayathri",
"V.",
""
],
[
"Heng",
"Ik Siong",
""
],
[
"Pai",
"Archana",
""
]
] | We present an enhanced method for the application of Gaussian Mixture Modelling (GMM) to the coherent WaveBurst (cWB) algorithm in the search for short-duration gravitational wave (GW) transients. The supervised Machine Learning method of GMM allows for the multi-dimensional distributions of noise and signal to be modelled over a set of representative attributes, which aids in the classification of GW signals against noise transients (glitches) in the data. We demonstrate that updating the approach to model construction eliminates bias previously seen in the GMM analysis, increasing the robustness and sensitivity of the analysis over a wider range of burst source populations. The enhanced methodology is applied to the generic burst all-sky short search in the LIGO-Virgo full third observing run (O3), marking the first application of GMM to the 3 detector Livingston-Hanford-Virgo network. For both 2- and 3- detector networks, we observe comparable sensitivities to an array of generic signal morphologies, with significant sensitivity improvements to waveforms in the low Quality factor parameter space at false alarm rates of 1 per 100 years. This proves that GMM can effectively mitigate blip glitches, which are one of the most problematic sources of noise for un-modelled GW searches. The cWB-GMM search recovers similar numbers of compact binary coalescence (CBC) events as other cWB post-production methods, and concludes on no new gravitational wave detection after known CBC events are removed. |
gr-qc/0301120 | Lee Lindblom | Lee Lindblom and Mark A. Scheel | Dynamical Gauge Conditions for the Einstein Evolution Equations | New appendix on constraint evolution added | Phys.Rev. D67 (2003) 124005 | 10.1103/PhysRevD.67.124005 | null | gr-qc | null | The Einstein evolution equations have been written in a number of symmetric
hyperbolic forms when the gauge fields--the densitized lapse and the shift--are
taken to be fixed functions of the coordinates. Extended systems of evolution
equations are constructed here by adding the gauge degrees of freedom to the
set of dynamical fields, thus forming symmetric hyperbolic systems for the
combined evolution of the gravitational and the gauge fields. The associated
characteristic speeds can be made causal (i.e. less than or equal to the speed
of light) by adjusting 14 free parameters in these new systems. And 21
additional free parameters are available, for example to optimize the stability
of numerical evolutions. The gauge evolution equations in these systems are
generalizations of the ``K-driver'' and ``Gamma-driver'' conditions that have
been used with some success in numerical black hole evolutions.
| [
{
"created": "Wed, 29 Jan 2003 20:58:32 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Apr 2003 23:13:04 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Lindblom",
"Lee",
""
],
[
"Scheel",
"Mark A.",
""
]
] | The Einstein evolution equations have been written in a number of symmetric hyperbolic forms when the gauge fields--the densitized lapse and the shift--are taken to be fixed functions of the coordinates. Extended systems of evolution equations are constructed here by adding the gauge degrees of freedom to the set of dynamical fields, thus forming symmetric hyperbolic systems for the combined evolution of the gravitational and the gauge fields. The associated characteristic speeds can be made causal (i.e. less than or equal to the speed of light) by adjusting 14 free parameters in these new systems. And 21 additional free parameters are available, for example to optimize the stability of numerical evolutions. The gauge evolution equations in these systems are generalizations of the ``K-driver'' and ``Gamma-driver'' conditions that have been used with some success in numerical black hole evolutions. |
1103.4765 | Martin Reiris | Martin Reiris | Static solutions from the point of view of comparison geometry | 41 pages | null | 10.1063/1.3668045 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze (the harmonic map representation of) static solutions of the
Einstein Equations in dimension three from the point of view of comparison
geometry. We find simple monotonic quantities capturing sharply the influence
of the Lapse function on the focussing of geodesics. This allows, in
particular, a sharp estimation of the Laplacian of the distance function to a
given (hyper)-surface. We apply the technique to asymptotically flat solutions
with regular and connected horizons and, after a detailed analysis of the
distance function to the horizon, we recover the Penrose inequality and the
uniqueness of the Schwarzschild solution. The proof of this last result does
not require proving conformal flatness at any intermediate step.
| [
{
"created": "Thu, 24 Mar 2011 13:45:01 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Reiris",
"Martin",
""
]
] | We analyze (the harmonic map representation of) static solutions of the Einstein Equations in dimension three from the point of view of comparison geometry. We find simple monotonic quantities capturing sharply the influence of the Lapse function on the focussing of geodesics. This allows, in particular, a sharp estimation of the Laplacian of the distance function to a given (hyper)-surface. We apply the technique to asymptotically flat solutions with regular and connected horizons and, after a detailed analysis of the distance function to the horizon, we recover the Penrose inequality and the uniqueness of the Schwarzschild solution. The proof of this last result does not require proving conformal flatness at any intermediate step. |
1712.08148 | Boris Bolliet | Ivan Agullo, Boris Bolliet, V. Sreenath | Non-Gaussianity in Loop Quantum Cosmology | Minor updates: current version matches the accepted PRD manuscript | Phys. Rev. D 97, 066021 (2018) | 10.1103/PhysRevD.97.066021 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the phenomenology of loop quantum cosmology (LQC) to second order
in perturbations. Our motivation is twofold. On the one hand, since LQC
predicts a cosmic bounce that takes place at the Planck scale, the second order
contributions could be large enough to jeopardize the validity of the
perturbative expansion on which previous results rest. On the other hand, the
upper bounds on primordial non-Gaussianity obtained by the Planck Collaboration
are expected to play a significant role on explorations of the LQC
phenomenology. We find that the bounce in LQC produces an enhancement of
non-Gaussianity of several orders of magnitude, on length scales that were
larger than the curvature radius at the bounce. Nonetheless, we find that one
can still rely on the perturbative expansion to make predictions about
primordial perturbations. We discuss the consequences of our results for LQC
and its predictions for the cosmic microwave background.
| [
{
"created": "Thu, 21 Dec 2017 18:37:22 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jan 2018 15:42:49 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Feb 2018 12:43:08 GMT",
"version": "v3"
}
] | 2018-04-04 | [
[
"Agullo",
"Ivan",
""
],
[
"Bolliet",
"Boris",
""
],
[
"Sreenath",
"V.",
""
]
] | We extend the phenomenology of loop quantum cosmology (LQC) to second order in perturbations. Our motivation is twofold. On the one hand, since LQC predicts a cosmic bounce that takes place at the Planck scale, the second order contributions could be large enough to jeopardize the validity of the perturbative expansion on which previous results rest. On the other hand, the upper bounds on primordial non-Gaussianity obtained by the Planck Collaboration are expected to play a significant role on explorations of the LQC phenomenology. We find that the bounce in LQC produces an enhancement of non-Gaussianity of several orders of magnitude, on length scales that were larger than the curvature radius at the bounce. Nonetheless, we find that one can still rely on the perturbative expansion to make predictions about primordial perturbations. We discuss the consequences of our results for LQC and its predictions for the cosmic microwave background. |
1303.4462 | Hiromi Saida | Hiromi Saida | Nontriviality in Black Hole Thermodynamics: towards physically and
mathematically rigorous foundation as phenomenology | Submitted to Prog.Theor.Exp.Phys.(PTEP), 35 pages, 7figures | null | null | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Comparing black hole thermodynamics with the axiomatic formulation of
thermodynamics for laboratory systems, it is found that some basic assumptions
(required by experimental facts) in laboratory thermodynamics do not hold for
black hole thermodynamics. Hence, at present, it is not obvious whether black
hole thermodynamics retains some crucial theorems of laboratory thermodynamics
(e.g. Carnot's theorem, increase of entropy by arbitrary adiabatic process, and
uniqueness of entropy) whose proofs use the basic assumptions which do not hold
for black holes. This paper aims to clarify such nontriviality in black hole
thermodynamics, and propose a suitable set of basic assumptions in black hole
thermodynamics, which are regarded as the rigorous foundation of black hole
thermodynamics as phenomenology.
| [
{
"created": "Tue, 19 Mar 2013 01:09:17 GMT",
"version": "v1"
}
] | 2013-03-20 | [
[
"Saida",
"Hiromi",
""
]
] | Comparing black hole thermodynamics with the axiomatic formulation of thermodynamics for laboratory systems, it is found that some basic assumptions (required by experimental facts) in laboratory thermodynamics do not hold for black hole thermodynamics. Hence, at present, it is not obvious whether black hole thermodynamics retains some crucial theorems of laboratory thermodynamics (e.g. Carnot's theorem, increase of entropy by arbitrary adiabatic process, and uniqueness of entropy) whose proofs use the basic assumptions which do not hold for black holes. This paper aims to clarify such nontriviality in black hole thermodynamics, and propose a suitable set of basic assumptions in black hole thermodynamics, which are regarded as the rigorous foundation of black hole thermodynamics as phenomenology. |
2209.01008 | Sergey L Cherkas | Sergey L. Cherkas and Vladimir L. Kalashnikov | Vacuum polarization instead of "dark matter" in a galaxy | 16 pages, 6 figures | Universe 8(9), 456 (2022) | 10.3390/universe8090456 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We considered a vacuum polarization inside a galaxy in the eikonal
approximation and found that two possible types of polarization exist. The
first type is described by the equation of state $p=\rho/3$, similar to
radiation. Using the conformally-unimodular metric allows constructing a
nonsingular solution for this vacuum ``substance'', if a compact astrophysical
object exists in the galaxy's center. As a result, a ``dark'' galactical halo
appears that increases the rotation velocity of a test particle as a function
of the distance from a galactic center. The second type of vacuum polarization
has a more complicated equation of state. As a static physical effect, it
produces renormalization of the gravitational constant, thus, causing no static
halo. However, a nonstationary polarization of the second type, resulting from
an exponential increase (or decrease) of the galactic nuclei mass with time in
some hypothetical time-dependent process, produces a gravitational potential
looking like a dark matter halo.
| [
{
"created": "Thu, 1 Sep 2022 12:21:31 GMT",
"version": "v1"
}
] | 2022-09-05 | [
[
"Cherkas",
"Sergey L.",
""
],
[
"Kalashnikov",
"Vladimir L.",
""
]
] | We considered a vacuum polarization inside a galaxy in the eikonal approximation and found that two possible types of polarization exist. The first type is described by the equation of state $p=\rho/3$, similar to radiation. Using the conformally-unimodular metric allows constructing a nonsingular solution for this vacuum ``substance'', if a compact astrophysical object exists in the galaxy's center. As a result, a ``dark'' galactical halo appears that increases the rotation velocity of a test particle as a function of the distance from a galactic center. The second type of vacuum polarization has a more complicated equation of state. As a static physical effect, it produces renormalization of the gravitational constant, thus, causing no static halo. However, a nonstationary polarization of the second type, resulting from an exponential increase (or decrease) of the galactic nuclei mass with time in some hypothetical time-dependent process, produces a gravitational potential looking like a dark matter halo. |
1303.6050 | Dirk Puetzfeld | Yuri N. Obukhov, Dirk Puetzfeld | Conservation laws in gravitational theories with general nonminimal
coupling | 6 pages, RevTex format | Phys. Rev. D 87, 081502 (2013) | 10.1103/PhysRevD.87.081502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the Lagrange-Noether methods to derive the conservation laws for
models in which matter interacts nonminimally with the gravitational field. The
nonminimal coupling function can depend arbitrarily on the gravitational field
strength. The obtained result generalizes earlier findings. The generalized
conservation laws provide the basis for the derivation of the equations of
motion for the nonminimally coupled test bodies.
| [
{
"created": "Mon, 25 Mar 2013 08:32:45 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Apr 2013 08:16:38 GMT",
"version": "v2"
}
] | 2013-04-19 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | We use the Lagrange-Noether methods to derive the conservation laws for models in which matter interacts nonminimally with the gravitational field. The nonminimal coupling function can depend arbitrarily on the gravitational field strength. The obtained result generalizes earlier findings. The generalized conservation laws provide the basis for the derivation of the equations of motion for the nonminimally coupled test bodies. |
gr-qc/9602028 | Winfried Zimdahl | Josep Triginer, Winfried Zimdahl, Diego Pavon | Kinetic theory for particle production | 19 pages, Latex file, to appear in Class.Quantum Grav | Class.Quant.Grav. 13 (1996) 403-416 | 10.1088/0264-9381/13/3/008 | null | gr-qc astro-ph | null | Recently, the phenomenological description of cosmological particle
production processes in terms of effective viscous pressures has attracted some
attention. Using a simple creation rate model we discuss the question to what
extent this approach is compatible with the kinetic theory of a relativistic
gas. We find the effective viscous pressure approach to be consistent with this
model for homogeneous spacetimes but not for inhomogeneous ones.
| [
{
"created": "Tue, 13 Feb 1996 13:05:46 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Triginer",
"Josep",
""
],
[
"Zimdahl",
"Winfried",
""
],
[
"Pavon",
"Diego",
""
]
] | Recently, the phenomenological description of cosmological particle production processes in terms of effective viscous pressures has attracted some attention. Using a simple creation rate model we discuss the question to what extent this approach is compatible with the kinetic theory of a relativistic gas. We find the effective viscous pressure approach to be consistent with this model for homogeneous spacetimes but not for inhomogeneous ones. |
2012.04140 | Irvin Martinez | Irvin Martinez and Amanda Weltman | Effective field theory for compact object evolution in binary inspirals | 20 pages, 8 figures. Improved GW extraction and deepened discussion | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Using the effective field theory framework for extended objects we describe
the evolution of spinning compact objects in the late inspiral of the
coalescence of a binary, before the plunge and merger, by including leading
order corrections due to spin, tides, dissipation and gravitational wave
radiation. Our implementation is of particular relevance for probing the
stellar structure of compact objects with gravitational wave observations. A
spinning compact object in the effective field theory framework is described as
a spinning point particle, with its finite size effects encoded in higher order
operators in the effective action, operators which have coefficients that
encapsulates the internal structure of the star. For the inspiral regime
described by non-relativistic general relativity, post-Newtonian corrections to
each term of the action can be obtained in a diagrammatic approach, including
gravitational radiation effects. Taking into account the aforementioned
ingredients of the effective theory, we solve for the dynamics of the inspiral
of binary systems using an algorithm for point particle simulations. We extract
the gravitational wave as a function of the orbital frequency, input that is
generated numerically and then evaluated in the analytic function of the
waveform. By performing illustrative numerical experiments of systems that the
LIGO-Virgo observatories have already detected, we show the role of the stellar
structure and its coefficients in the phase evolution of the waveform, as well
as the order in which they arise and the sensitivity required for the
gravitational wave observatories to measure them. If these coefficients are to
be measured, tight constraints on fundamental physics can be placed.
| [
{
"created": "Tue, 8 Dec 2020 00:59:44 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jan 2022 17:24:01 GMT",
"version": "v2"
}
] | 2022-01-07 | [
[
"Martinez",
"Irvin",
""
],
[
"Weltman",
"Amanda",
""
]
] | Using the effective field theory framework for extended objects we describe the evolution of spinning compact objects in the late inspiral of the coalescence of a binary, before the plunge and merger, by including leading order corrections due to spin, tides, dissipation and gravitational wave radiation. Our implementation is of particular relevance for probing the stellar structure of compact objects with gravitational wave observations. A spinning compact object in the effective field theory framework is described as a spinning point particle, with its finite size effects encoded in higher order operators in the effective action, operators which have coefficients that encapsulates the internal structure of the star. For the inspiral regime described by non-relativistic general relativity, post-Newtonian corrections to each term of the action can be obtained in a diagrammatic approach, including gravitational radiation effects. Taking into account the aforementioned ingredients of the effective theory, we solve for the dynamics of the inspiral of binary systems using an algorithm for point particle simulations. We extract the gravitational wave as a function of the orbital frequency, input that is generated numerically and then evaluated in the analytic function of the waveform. By performing illustrative numerical experiments of systems that the LIGO-Virgo observatories have already detected, we show the role of the stellar structure and its coefficients in the phase evolution of the waveform, as well as the order in which they arise and the sensitivity required for the gravitational wave observatories to measure them. If these coefficients are to be measured, tight constraints on fundamental physics can be placed. |
0805.1201 | Cl\'audio Nassif Cruz | Claudio Nassif | Deformed Special Relativity with an energy barrier of a minimum speed | 14 pages, 4 figures | International Journal of Modern Physics D 19, 5, p.539-564 (2010) | 10.1142/S021827181001652X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This research aims to introduce a new principle in the flat space-time
geometry through the elimination of the classical idea of rest and by including
a universal minimum limit of speed in the quantum world. This limit,
unattainable by the particles, represents a preferred inertial reference frame
associated with a universal background field that breaks Lorentz symmetry.
There emerges a new relativistic dynamics where a minimum speed forms an
inferior energy barrier. One of the interesting consequences of the existence
of such a minimum speed is that it prevents the absolute zero temperature for
an ultracold gas according to the third law of thermodynamics. So we will be
able to provide a fundamental dynamical explanation for the third law through a
connection between such a phenomenological law and the new relativistic
dynamics with a minimum speed.
| [
{
"created": "Thu, 8 May 2008 17:15:13 GMT",
"version": "v1"
},
{
"created": "Fri, 9 May 2008 16:46:11 GMT",
"version": "v2"
},
{
"created": "Sun, 11 May 2008 22:17:31 GMT",
"version": "v3"
},
{
"created": "Sun, 25 May 2008 14:09:05 GMT",
"version": "v4"
},
{
"cre... | 2017-11-23 | [
[
"Nassif",
"Claudio",
""
]
] | This research aims to introduce a new principle in the flat space-time geometry through the elimination of the classical idea of rest and by including a universal minimum limit of speed in the quantum world. This limit, unattainable by the particles, represents a preferred inertial reference frame associated with a universal background field that breaks Lorentz symmetry. There emerges a new relativistic dynamics where a minimum speed forms an inferior energy barrier. One of the interesting consequences of the existence of such a minimum speed is that it prevents the absolute zero temperature for an ultracold gas according to the third law of thermodynamics. So we will be able to provide a fundamental dynamical explanation for the third law through a connection between such a phenomenological law and the new relativistic dynamics with a minimum speed. |
2106.01622 | Lijing Shao | Minghao Guo, Junjie Zhao, Lijing Shao | Extended reduced-order surrogate models for scalar-tensor gravity in the
strong field and applications to binary pulsars and gravitational waves | 15 pages, 11 figures, 2 tables; accepted by PRD | Phys. Rev. D 104, 104065 (2021) | 10.1103/PhysRevD.104.104065 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Statistically sound tests of scalar-tensor gravity theories in the
strong-field regime usually involves computationally intensive calculations. In
this study, we construct a reduced order surrogate model for the scalar-tensor
gravity of Damour and Esposito-Far\`ese (DEF) with spontaneous scalarization
phenomena developed for neutron stars (NSs). This model allows us to perform a
rapid and comprehensive prediction of NS properties, including mass, radius,
moment of inertia, effective scalar coupling, and two extra coupling
parameters. We code the model in the pySTGROMX package, as an extension of our
previous work, that speeds up the calculations at two and even three orders of
magnitude and yet still keeps accuracy of $\sim1\%$. Using the model, we can
calculate all the post-Keplerian parameters in the timing of binary pulsars
conveniently, which provides a quick approach for us to place comprehensive
constraints on the DEF theory. We perform Markov-chain Monte Carlo simulations
with the model to constrain the parameters of the DEF theory with well-timed
binary pulsars. Utilizing five NS-white dwarf and three NS-NS binaries, we
obtain the most stringent constraints on the DEF theory up to now. Our work
provides a public tool for quick evaluation of NSs' derived parameters to test
gravity in the strong-field regime.
| [
{
"created": "Thu, 3 Jun 2021 06:46:17 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Oct 2021 02:13:38 GMT",
"version": "v2"
}
] | 2021-12-01 | [
[
"Guo",
"Minghao",
""
],
[
"Zhao",
"Junjie",
""
],
[
"Shao",
"Lijing",
""
]
] | Statistically sound tests of scalar-tensor gravity theories in the strong-field regime usually involves computationally intensive calculations. In this study, we construct a reduced order surrogate model for the scalar-tensor gravity of Damour and Esposito-Far\`ese (DEF) with spontaneous scalarization phenomena developed for neutron stars (NSs). This model allows us to perform a rapid and comprehensive prediction of NS properties, including mass, radius, moment of inertia, effective scalar coupling, and two extra coupling parameters. We code the model in the pySTGROMX package, as an extension of our previous work, that speeds up the calculations at two and even three orders of magnitude and yet still keeps accuracy of $\sim1\%$. Using the model, we can calculate all the post-Keplerian parameters in the timing of binary pulsars conveniently, which provides a quick approach for us to place comprehensive constraints on the DEF theory. We perform Markov-chain Monte Carlo simulations with the model to constrain the parameters of the DEF theory with well-timed binary pulsars. Utilizing five NS-white dwarf and three NS-NS binaries, we obtain the most stringent constraints on the DEF theory up to now. Our work provides a public tool for quick evaluation of NSs' derived parameters to test gravity in the strong-field regime. |
gr-qc/9606053 | null | Kosaburo Hashiguchi | Invalidity of the relativity principle and a proposal of the twofold
metric principle | 53 pages | null | null | null | gr-qc | null | I show that all inertial systems are not equivalent, and the Lorentz
transformation is not the space-time transformation over two inertial systems
moving with relative constant velocity. To do this, I consider imaginary
signals travelling over any inertial system K with arbitrarily large
velocities. The travelling of an imaginary signal over K is just a time lapse
over K. Then I present an example to show that all coordinate systems are not
equivalent when the related theory is restricted over tensor-based coordinate
transformations, i.e., the genereal relativity principle is not valid. Instead
of the relativity principle, I propose the twofold metric principle which may
be roughly stated to assert that the set of equations H(v) describing the
motion of a material body with velocity v> 0 can be obtained from the
corresponding set of equations H(0) for velocity v=0 by replacing, in each
differential equation in H(0), each infinitesimal time variable dt with dt /
\beta(v) , each maximal velocity-critical infinitesimal length variable dr with
beta(v) dr, and each zero velocity-critical infinitesimal length variable dx
with dx, where beta(v) = 1/ sqrt {1- v^2/c^2}. By depending on the twofold
metric principle and the energy-velocity equation, I derive beta(v)mc^2, the
twofold Schwarzshild metric, the centennial procession of planatery orbits and
deflection of light. We also present a reason why the Michelson-Morley
experiment is observed. Several other topics are also studied.
| [
{
"created": "Wed, 19 Jun 1996 05:57:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hashiguchi",
"Kosaburo",
""
]
] | I show that all inertial systems are not equivalent, and the Lorentz transformation is not the space-time transformation over two inertial systems moving with relative constant velocity. To do this, I consider imaginary signals travelling over any inertial system K with arbitrarily large velocities. The travelling of an imaginary signal over K is just a time lapse over K. Then I present an example to show that all coordinate systems are not equivalent when the related theory is restricted over tensor-based coordinate transformations, i.e., the genereal relativity principle is not valid. Instead of the relativity principle, I propose the twofold metric principle which may be roughly stated to assert that the set of equations H(v) describing the motion of a material body with velocity v> 0 can be obtained from the corresponding set of equations H(0) for velocity v=0 by replacing, in each differential equation in H(0), each infinitesimal time variable dt with dt / \beta(v) , each maximal velocity-critical infinitesimal length variable dr with beta(v) dr, and each zero velocity-critical infinitesimal length variable dx with dx, where beta(v) = 1/ sqrt {1- v^2/c^2}. By depending on the twofold metric principle and the energy-velocity equation, I derive beta(v)mc^2, the twofold Schwarzshild metric, the centennial procession of planatery orbits and deflection of light. We also present a reason why the Michelson-Morley experiment is observed. Several other topics are also studied. |
2012.06484 | Joel Berg\'e | Joel Berg\'e, Quentin Baghi, Emilie Hardy, Gilles M\'etris, Alain
Robert, Manuel Rodrigues, Pierre Touboul, Ratana Chhun, Pierre-Yves Guidotti,
Sandrine Pires, Serge Reynaud, Laura Serron, Jean-Michel Travert | MICROSCOPE mission: Data analysis principle | References updated | Class. Quantum Grav. 39 (2022) 204007 | 10.1088/1361-6382/ac0235 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | After performing highly sensitive acceleration measurements during two years
of drag-free flight around the Earth, MICROSCOPE provided the best constraint
on the Weak Equivalence Principle (WEP) to date. Beside being a technological
challenge, this experiment required a specialised data analysis pipeline to
look for a potential small signal buried in the noise, possibly plagued by
instrumental defects, missing data and glitches. This paper describes the
frequency-domain iterative least-square technique that we developed for
MICROSCOPE. In particular, using numerical simulations, we prove that our
estimator is unbiased and provides correct error bars. This paper therefore
justifies the robustness of the WEP measurements given by MICROSCOPE.
| [
{
"created": "Fri, 11 Dec 2020 16:48:37 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Dec 2020 12:41:53 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Bergé",
"Joel",
""
],
[
"Baghi",
"Quentin",
""
],
[
"Hardy",
"Emilie",
""
],
[
"Métris",
"Gilles",
""
],
[
"Robert",
"Alain",
""
],
[
"Rodrigues",
"Manuel",
""
],
[
"Touboul",
"Pierre",
""
],
[
"Ch... | After performing highly sensitive acceleration measurements during two years of drag-free flight around the Earth, MICROSCOPE provided the best constraint on the Weak Equivalence Principle (WEP) to date. Beside being a technological challenge, this experiment required a specialised data analysis pipeline to look for a potential small signal buried in the noise, possibly plagued by instrumental defects, missing data and glitches. This paper describes the frequency-domain iterative least-square technique that we developed for MICROSCOPE. In particular, using numerical simulations, we prove that our estimator is unbiased and provides correct error bars. This paper therefore justifies the robustness of the WEP measurements given by MICROSCOPE. |
gr-qc/0402111 | Alejandro Perez | Karim Noui and Alejandro Perez | Three dimensional loop quantum gravity: coupling to point particles | Typos corrected and references added | Class.Quant.Grav. 22 (2005) 4489-4514 | 10.1088/0264-9381/22/21/005 | null | gr-qc hep-th | null | We consider the coupling between three dimensional gravity with zero
cosmological constant and massive spinning point particles. First, we study the
classical canonical analysis of the coupled system. Then, we go to the
Hamiltonian quantization generalizing loop quantum gravity techniques. We give
a complete description of the kinematical Hilbert space of the coupled system.
Finally, we define the physical Hilbert space of the system of self-gravitating
massive spinning point particles using Rovelli's generalized projection
operator which can be represented as a sum over spin foam amplitudes. In
addition we provide an explicit expression of the (physical) distance operator
between two particles which is defined as a Dirac observable.
| [
{
"created": "Wed, 25 Feb 2004 03:36:01 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Mar 2004 20:54:33 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Noui",
"Karim",
""
],
[
"Perez",
"Alejandro",
""
]
] | We consider the coupling between three dimensional gravity with zero cosmological constant and massive spinning point particles. First, we study the classical canonical analysis of the coupled system. Then, we go to the Hamiltonian quantization generalizing loop quantum gravity techniques. We give a complete description of the kinematical Hilbert space of the coupled system. Finally, we define the physical Hilbert space of the system of self-gravitating massive spinning point particles using Rovelli's generalized projection operator which can be represented as a sum over spin foam amplitudes. In addition we provide an explicit expression of the (physical) distance operator between two particles which is defined as a Dirac observable. |
gr-qc/0506111 | Manasse R. Mbonye | Manasse R. Mbonye and Demosthenes Kazanas | A non-singular black hole model as a possible end-product of
gravitational collapse | 12 Pages, 1 figure. Accepted for publication in Phys. Rev. D | Phys.Rev. D72 (2005) 024016 | 10.1103/PhysRevD.72.024016 | null | gr-qc astro-ph hep-th | null | In this paper we present a non-singular black hole model as a possible
end-product of gravitational collapse. The depicted spacetime which is type
[II,(II)], by Petrov classification, is an exact solution of the Einstein
equations and contains two horizons. The equation of state in the radial
direction, is a well-behaved function of the density and smoothly reproduces
vacuum-like behavior near r=0 while tending to a polytrope at larger r, low
density, values. The final equilibrium configuration comprises of a de
Sitter-like inner core surrounded by a family of 2-surfaces of matter fields
with variable equation of state. The fields are all concentrated in the
vicinity of the radial center r=0. The solution depicts a spacetime that is
asymptotically Schwarzschild at large r, while it becomes de Sitter-like for
vanishing r. Possible physical interpretations of the macro-state of the black
hole interior in the model are offered. We find that the possible state admits
two equally viable interpretations, namely either a quintessential intermediary
region or a phase transition in which a two-fluid system is in both dynamic and
thermodynamic equilibrium. We estimate the ratio of pure matter present to the
total energy and in both (interpretations) cases find it to be virtually the
same, being 0.83. Finally, the well-behaved dependence of the density and
pressure on the radial coordinate provides some insight on dealing with the
information loss paradox.
| [
{
"created": "Wed, 22 Jun 2005 22:45:31 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jun 2005 20:02:17 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Mbonye",
"Manasse R.",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] | In this paper we present a non-singular black hole model as a possible end-product of gravitational collapse. The depicted spacetime which is type [II,(II)], by Petrov classification, is an exact solution of the Einstein equations and contains two horizons. The equation of state in the radial direction, is a well-behaved function of the density and smoothly reproduces vacuum-like behavior near r=0 while tending to a polytrope at larger r, low density, values. The final equilibrium configuration comprises of a de Sitter-like inner core surrounded by a family of 2-surfaces of matter fields with variable equation of state. The fields are all concentrated in the vicinity of the radial center r=0. The solution depicts a spacetime that is asymptotically Schwarzschild at large r, while it becomes de Sitter-like for vanishing r. Possible physical interpretations of the macro-state of the black hole interior in the model are offered. We find that the possible state admits two equally viable interpretations, namely either a quintessential intermediary region or a phase transition in which a two-fluid system is in both dynamic and thermodynamic equilibrium. We estimate the ratio of pure matter present to the total energy and in both (interpretations) cases find it to be virtually the same, being 0.83. Finally, the well-behaved dependence of the density and pressure on the radial coordinate provides some insight on dealing with the information loss paradox. |
2301.10773 | Eduardo Velasco-Aja Mr. | Enrique \'Alvarez, Jesus Anero and Eduardo Velasco-Aja | Variations on the Goroff-Sagnotti operator | 12 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The effect of modifying General Relativity with the addition of some higher
dimensional operators, generalizations of the Goroff-Sagnotti operator, is
discussed. We determine in particular, the general solution of the classical
equations of motion, assuming it to be spherically symmetric, not necessarily
static. Even in the non-spherically symmetric case, we present a necessary
condition for an algebraically generic spacetime to solve the corresponding
equations of motion. Some examples of an application of said condition are
explicitly worked out.
| [
{
"created": "Wed, 25 Jan 2023 15:21:29 GMT",
"version": "v1"
}
] | 2023-01-27 | [
[
"Álvarez",
"Enrique",
""
],
[
"Anero",
"Jesus",
""
],
[
"Velasco-Aja",
"Eduardo",
""
]
] | The effect of modifying General Relativity with the addition of some higher dimensional operators, generalizations of the Goroff-Sagnotti operator, is discussed. We determine in particular, the general solution of the classical equations of motion, assuming it to be spherically symmetric, not necessarily static. Even in the non-spherically symmetric case, we present a necessary condition for an algebraically generic spacetime to solve the corresponding equations of motion. Some examples of an application of said condition are explicitly worked out. |
2302.09870 | Anna Liu | Anna Liu, Isaac C. F. Wong, Samson H. W. Leong, Anupreeta More, Otto
A. Hannuksela, Tjonnie G. F. Li | Exploring the hidden Universe: A novel phenomenological approach for
recovering arbitrary gravitational-wave millilensing configurations | 12 pages, 8 figures | null | 10.1093/mnras/stad1302 | null | gr-qc astro-ph.HE hep-ph | http://creativecommons.org/licenses/by/4.0/ | Since the first detection of gravitational waves in 2015, gravitational-wave
astronomy has emerged as a rapidly advancing field that holds great potential
for studying the cosmos, from probing the properties of black holes to testing
the limits of our current understanding of gravity. One important aspect of
gravitational-wave astronomy is the phenomenon of gravitational lensing, where
massive intervening objects can bend and magnify gravitational waves, providing
a unique way to probe the distribution of matter in the universe, as well as
finding applications to fundamental physics, astrophysics, and cosmology.
However, current models for gravitational-wave millilensing - a specific form
of lensing where small-scale astrophysical objects can split a gravitational
wave signal into multiple copies - are often limited to simple isolated lenses,
which is not realistic for complex lensing scenarios. In this paper, we present
a novel phenomenological approach to incorporate millilensing in data analysis
in a model-independent fashion. Our approach enables the recovery of arbitrary
lens configurations without the need for extensive computational lens modeling,
making it a more accurate and computationally efficient tool for studying the
distribution of matter in the universe using gravitational-wave signals. When
gravitational-wave lensing observations become possible, our method can provide
a powerful tool for studying complex lens configurations, including dark matter
subhalos and MACHOs.
| [
{
"created": "Mon, 20 Feb 2023 10:01:57 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Feb 2023 02:22:57 GMT",
"version": "v2"
}
] | 2023-05-17 | [
[
"Liu",
"Anna",
""
],
[
"Wong",
"Isaac C. F.",
""
],
[
"Leong",
"Samson H. W.",
""
],
[
"More",
"Anupreeta",
""
],
[
"Hannuksela",
"Otto A.",
""
],
[
"Li",
"Tjonnie G. F.",
""
]
] | Since the first detection of gravitational waves in 2015, gravitational-wave astronomy has emerged as a rapidly advancing field that holds great potential for studying the cosmos, from probing the properties of black holes to testing the limits of our current understanding of gravity. One important aspect of gravitational-wave astronomy is the phenomenon of gravitational lensing, where massive intervening objects can bend and magnify gravitational waves, providing a unique way to probe the distribution of matter in the universe, as well as finding applications to fundamental physics, astrophysics, and cosmology. However, current models for gravitational-wave millilensing - a specific form of lensing where small-scale astrophysical objects can split a gravitational wave signal into multiple copies - are often limited to simple isolated lenses, which is not realistic for complex lensing scenarios. In this paper, we present a novel phenomenological approach to incorporate millilensing in data analysis in a model-independent fashion. Our approach enables the recovery of arbitrary lens configurations without the need for extensive computational lens modeling, making it a more accurate and computationally efficient tool for studying the distribution of matter in the universe using gravitational-wave signals. When gravitational-wave lensing observations become possible, our method can provide a powerful tool for studying complex lens configurations, including dark matter subhalos and MACHOs. |
2104.11134 | Hyat Huang | Jinbo Yang and Hyat Huang | Trapping Horizons of the Evolving Charged Wormhole and Black Bounce | Matched the published version. Added Penrose diagrams | Phys. Rev. D 104, 084005 (2021) | 10.1103/PhysRevD.104.084005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain one family of dynamic solutions in the Einstein-Maxwell-scalar(EMS)
theory. Our solutions could describe the evolving charged black(white) hole or
wormhole and its transition, including the case of black bounce/wormhole
transition. We compare different wormhole throat definitions and suggest that
the usage of trapping horizons is the most suitable choice for tracking the
evolution of the dynamic black(white) hole and wormhole, and their conversion
in a unified framework. Then we research several evolving processes in the
appropriate parameters region, including the charge, the initial condition for
the scalar hair, and parameters in our EMS Lagrangian. The results show that
the appearance of a degenerate marginal trapped surface is the crucial event
for the conversion or transition, particularly in these cases: i) when the
evolving wormhole converts to a black hole, the surface emerges and splits into
two trapping horizons; ii) if the metric would become a black hole but finally
fails, two trapping horizons combine as the surface and then vanish; iii) if
the black bounce/wormhole transition happens, one single trapping horizon
changes its type.
| [
{
"created": "Thu, 22 Apr 2021 15:37:44 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Oct 2021 08:21:47 GMT",
"version": "v2"
}
] | 2021-10-14 | [
[
"Yang",
"Jinbo",
""
],
[
"Huang",
"Hyat",
""
]
] | We obtain one family of dynamic solutions in the Einstein-Maxwell-scalar(EMS) theory. Our solutions could describe the evolving charged black(white) hole or wormhole and its transition, including the case of black bounce/wormhole transition. We compare different wormhole throat definitions and suggest that the usage of trapping horizons is the most suitable choice for tracking the evolution of the dynamic black(white) hole and wormhole, and their conversion in a unified framework. Then we research several evolving processes in the appropriate parameters region, including the charge, the initial condition for the scalar hair, and parameters in our EMS Lagrangian. The results show that the appearance of a degenerate marginal trapped surface is the crucial event for the conversion or transition, particularly in these cases: i) when the evolving wormhole converts to a black hole, the surface emerges and splits into two trapping horizons; ii) if the metric would become a black hole but finally fails, two trapping horizons combine as the surface and then vanish; iii) if the black bounce/wormhole transition happens, one single trapping horizon changes its type. |
1204.3138 | Matt Visser | Matt Visser (Victoria University of Wellington) | Quantization of area for event and Cauchy horizons of the Kerr-Newman
black hole | v1: 15 pages; v2: 2 references added, no physics changes; v3: 16 now
pages, discussion of physical implications clarified, no calculational
changes, this version accepted for publication in JHEP | JHEP 1206 (2012) 023 | 10.1007/JHEP06(2012)023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on various string theoretic constructions, and various string-inspired
generalizations thereof, there have been repeated suggestions that the areas of
black hole event horizons might be quantized in a quite specific manner, in
terms of linear combinations of square roots of positive integers. It is
important to realise that there are significant physical constraints on such
integer-based proposals when one (somewhat speculatively) attempts to extend
them outside their original extremal and supersymmetric framework.
Specifically, in their most natural and direct physical interpretations, some
of the more speculative integer-based proposals for the quantization of horizon
areas fail for the ordinary Kerr-Newman black holes in (3+1) dimensions,
essentially because the fine structure constant is not an integer. A more
baroque interpretation involves asserting the fine structure constant is the
square root of a rational number; but such a proposal has its own problems.
Insofar as one takes (3+1) general relativity (plus the usual quantization of
angular momentum and electric charge) as being paramount, the known explicitly
calculable spectra of horizon areas for the physically compelling Kerr-Newman
spacetimes indicate that some caution is called for when assessing the
universality of some of the more speculative integer-based string-inspired
proposals.
| [
{
"created": "Sat, 14 Apr 2012 03:43:45 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Apr 2012 02:19:05 GMT",
"version": "v2"
},
{
"created": "Tue, 22 May 2012 21:58:51 GMT",
"version": "v3"
}
] | 2012-06-07 | [
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Based on various string theoretic constructions, and various string-inspired generalizations thereof, there have been repeated suggestions that the areas of black hole event horizons might be quantized in a quite specific manner, in terms of linear combinations of square roots of positive integers. It is important to realise that there are significant physical constraints on such integer-based proposals when one (somewhat speculatively) attempts to extend them outside their original extremal and supersymmetric framework. Specifically, in their most natural and direct physical interpretations, some of the more speculative integer-based proposals for the quantization of horizon areas fail for the ordinary Kerr-Newman black holes in (3+1) dimensions, essentially because the fine structure constant is not an integer. A more baroque interpretation involves asserting the fine structure constant is the square root of a rational number; but such a proposal has its own problems. Insofar as one takes (3+1) general relativity (plus the usual quantization of angular momentum and electric charge) as being paramount, the known explicitly calculable spectra of horizon areas for the physically compelling Kerr-Newman spacetimes indicate that some caution is called for when assessing the universality of some of the more speculative integer-based string-inspired proposals. |
1207.3770 | Laszlo Arpad Gergely | L. \'A. Gergely, T. Harko | Testing General Relativity With Laser Accelerated Electron Beams | Proceedings of LEI 2011 - Light at Extreme Intensities Conference,
Szeged, Hungary, 2011 | AIP Conf.Proc.1462:9-12,2012 | 10.1063/1.4736750 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electron accelerations of the order of $10^{21} g$ obtained by laser fields
open up the possibility of experimentally testing one of the cornerstones of
general relativity, the weak equivalence principle, which states that the local
effects of a gravitational field are indistinguishable from those sensed by a
properly accelerated observer in flat space-time. We illustrate how this can be
done by solving the Einstein equations in vacuum and integrating the geodesic
equations of motion for a uniformly accelerated particle.
| [
{
"created": "Mon, 16 Jul 2012 19:13:11 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Gergely",
"L. Á.",
""
],
[
"Harko",
"T.",
""
]
] | Electron accelerations of the order of $10^{21} g$ obtained by laser fields open up the possibility of experimentally testing one of the cornerstones of general relativity, the weak equivalence principle, which states that the local effects of a gravitational field are indistinguishable from those sensed by a properly accelerated observer in flat space-time. We illustrate how this can be done by solving the Einstein equations in vacuum and integrating the geodesic equations of motion for a uniformly accelerated particle. |
1311.7539 | Edward Porter | Edward K. Porter and J\'er\^ome Carr\'e | A Hamiltonian Monte Carlo method for Bayesian Inference of Supermassive
Black Hole Binaries | 16 pages, 8 figures | null | 10.1088/0264-9381/31/14/145004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the use of a Hamiltonian Monte Carlo to map out the posterior
density function for supermassive black hole binaries. While previous Markov
Chain Monte Carlo (MCMC) methods, such as Metropolis-Hastings MCMC, have been
successfully employed for a number of different gravitational wave sources,
these methods are essentially random walk algorithms. The Hamiltonian Monte
Carlo treats the inverse likelihood surface as a "gravitational potential" and
by introducing canonical positions and momenta, dynamically evolves the Markov
chain by solving Hamilton's equations of motion. We present an implementation
of the Hamiltonian Markov Chain that is faster, and more efficient by a factor
of approximately the dimension of the parameter space, than the standard MCMC.
| [
{
"created": "Fri, 29 Nov 2013 12:20:40 GMT",
"version": "v1"
}
] | 2019-08-19 | [
[
"Porter",
"Edward K.",
""
],
[
"Carré",
"Jérôme",
""
]
] | We investigate the use of a Hamiltonian Monte Carlo to map out the posterior density function for supermassive black hole binaries. While previous Markov Chain Monte Carlo (MCMC) methods, such as Metropolis-Hastings MCMC, have been successfully employed for a number of different gravitational wave sources, these methods are essentially random walk algorithms. The Hamiltonian Monte Carlo treats the inverse likelihood surface as a "gravitational potential" and by introducing canonical positions and momenta, dynamically evolves the Markov chain by solving Hamilton's equations of motion. We present an implementation of the Hamiltonian Markov Chain that is faster, and more efficient by a factor of approximately the dimension of the parameter space, than the standard MCMC. |
gr-qc/9411009 | Jemal Guven | Jemal Guven and Niall \'O Murchadha | The Constraints in Spherically Symmetric General Relativity I ---
Optical Scalars, Foliations, Bounds on the Configuration Space Variables and
the Positivity of the Quasi-Local Mass | 45 pages, Plain Tex, 1 figure available from the authors. | Phys.Rev. D52 (1995) 758-775 | 10.1103/PhysRevD.52.758 | ICN-UNAM 94-15 Revised Version | gr-qc | null | We examine the constraints of spherically symmetric general relativity with
one asymptotically flat region, exploiting both the traditional metric
variables and variables constructed from the optical scalars. With respect to
the latter variables, there exist two linear combinations of the Hamiltonian
and momentum constraints which are related by time reversal. We introduce a
one-parameter family of linear extrinsic time foliations of spacetime. The
values of the parameter yielding globally valid gauges correspond to the
vanishing of a timelike vector in the superspace of spherically symmetric
geometries. We define a quasi-local mass on spheres of fixed proper radius
which we prove is positive when the constraints are satisfied. Underpinning the
proof are various local bounds on the configuration variables. We prove that a
reasonable definition of the gravitational binding energy is always negative.
Finally, we provide a tentative characterization of the configuration space of
the theory in terms of closed bounded trajectories on the parameter space of
the optical scalars.
| [
{
"created": "Thu, 3 Nov 1994 17:30:37 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Apr 1995 00:02:05 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Guven",
"Jemal",
""
],
[
"Murchadha",
"Niall Ó",
""
]
] | We examine the constraints of spherically symmetric general relativity with one asymptotically flat region, exploiting both the traditional metric variables and variables constructed from the optical scalars. With respect to the latter variables, there exist two linear combinations of the Hamiltonian and momentum constraints which are related by time reversal. We introduce a one-parameter family of linear extrinsic time foliations of spacetime. The values of the parameter yielding globally valid gauges correspond to the vanishing of a timelike vector in the superspace of spherically symmetric geometries. We define a quasi-local mass on spheres of fixed proper radius which we prove is positive when the constraints are satisfied. Underpinning the proof are various local bounds on the configuration variables. We prove that a reasonable definition of the gravitational binding energy is always negative. Finally, we provide a tentative characterization of the configuration space of the theory in terms of closed bounded trajectories on the parameter space of the optical scalars. |
1410.5213 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo, M. K. Mak | Bianchi type I cosmological models in Eddington-inspired Born-Infeld
gravity | 23 pages, 12 figures; to appear in a Special Issue of Galaxies:
"Beyond Standard Gravity and Cosmology". V2: references added, 24 pages;
matches published version | Galaxies 2 (2014) 4, 496-519 | 10.3390/galaxies2040496 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the dynamics of a barotropic cosmological fluid in an
anisotropic, Bianchi type I space-time in Eddington-inspired Born-Infeld (EiBI)
gravity. By assuming an isotropic pressure distribution, we obtain the general
solution of the field equations in an exact parametric form. The behavior of
the geometric and thermodynamic parameters of the Bianchi type I Universe is
studied, by using both analytical and numerical methods, for some classes of
high density matter, described by the stiff causal, radiation, and pressureless
fluid equations of state. In all cases the study of the models with different
equations of state can be reduced to the integration of a highly nonlinear
second order ordinary differential equation for the energy density. The time
evolution of the anisotropic Bianchi type I Universe strongly depends on the
initial values of the energy density and of the Hubble function. An important
observational parameter, the mean anisotropy parameter is also studied in
detail, and we show that for the dust filled Universe the cosmological
evolution always ends into an isotropic phase, while for high density matter
filled universes the isotropization of Bianchi type I universes is essentially
determined by the initial conditions of the energy density.
| [
{
"created": "Mon, 20 Oct 2014 10:00:07 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Oct 2014 21:59:41 GMT",
"version": "v2"
}
] | 2014-10-30 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Mak",
"M. K.",
""
]
] | We consider the dynamics of a barotropic cosmological fluid in an anisotropic, Bianchi type I space-time in Eddington-inspired Born-Infeld (EiBI) gravity. By assuming an isotropic pressure distribution, we obtain the general solution of the field equations in an exact parametric form. The behavior of the geometric and thermodynamic parameters of the Bianchi type I Universe is studied, by using both analytical and numerical methods, for some classes of high density matter, described by the stiff causal, radiation, and pressureless fluid equations of state. In all cases the study of the models with different equations of state can be reduced to the integration of a highly nonlinear second order ordinary differential equation for the energy density. The time evolution of the anisotropic Bianchi type I Universe strongly depends on the initial values of the energy density and of the Hubble function. An important observational parameter, the mean anisotropy parameter is also studied in detail, and we show that for the dust filled Universe the cosmological evolution always ends into an isotropic phase, while for high density matter filled universes the isotropization of Bianchi type I universes is essentially determined by the initial conditions of the energy density. |
2209.04297 | Andreas G. A. Pithis | Luca Marchetti, Daniele Oriti, Andreas G. A. Pithis, Johannes
Th\"urigen | Phase transitions in TGFT: a Landau-Ginzburg analysis of Lorentzian
quantum geometric models | 41 + 20 pages, 2 figures; matches published version | J. High Energ. Phys. 2023, 74 (2023) | 10.1007/JHEP02(2023)074 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the tensorial group field theory (TGFT) approach to quantum gravity, the
basic quanta of the theory correspond to discrete building blocks of geometry.
It is expected that their collective dynamics gives rise to continuum spacetime
at a coarse grained level, via a process involving a phase transition. In this
work we show for the first time how phase transitions for realistic TGFT models
can be realized using Landau-Ginzburg mean-field theory. More precisely, we
consider models generating 4-dimensional Lorentzian triangulations formed by
spacelike tetrahedra whose quantum geometry is encoded in non-local degrees of
freedom on the non-compact group $\mathrm{SL}(2,\mathbb{C})$ and subject to
gauge and simplicity constraints. Further we include $\mathbb{R}$-valued
variables which may be interpreted as discretized scalar fields typically
employed as a matter reference frame. We apply the Ginzburg criterion finding
that fluctuations around the non-vanishing mean-field vacuum remain small at
large correlation lengths regardless of the combinatorics of the non-local
interaction validating the mean-field theory description of the phase
transition. This work represents a first crucial step to understand phase
transitions in compelling TGFT models for quantum gravity and paves the way for
a more complete analysis via functional renormalization group techniques.
Moreover, it supports the recent extraction of effective cosmological dynamics
from TGFTs in the context of a mean-field approximation.
| [
{
"created": "Fri, 9 Sep 2022 13:44:49 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Feb 2023 22:10:03 GMT",
"version": "v2"
}
] | 2023-02-14 | [
[
"Marchetti",
"Luca",
""
],
[
"Oriti",
"Daniele",
""
],
[
"Pithis",
"Andreas G. A.",
""
],
[
"Thürigen",
"Johannes",
""
]
] | In the tensorial group field theory (TGFT) approach to quantum gravity, the basic quanta of the theory correspond to discrete building blocks of geometry. It is expected that their collective dynamics gives rise to continuum spacetime at a coarse grained level, via a process involving a phase transition. In this work we show for the first time how phase transitions for realistic TGFT models can be realized using Landau-Ginzburg mean-field theory. More precisely, we consider models generating 4-dimensional Lorentzian triangulations formed by spacelike tetrahedra whose quantum geometry is encoded in non-local degrees of freedom on the non-compact group $\mathrm{SL}(2,\mathbb{C})$ and subject to gauge and simplicity constraints. Further we include $\mathbb{R}$-valued variables which may be interpreted as discretized scalar fields typically employed as a matter reference frame. We apply the Ginzburg criterion finding that fluctuations around the non-vanishing mean-field vacuum remain small at large correlation lengths regardless of the combinatorics of the non-local interaction validating the mean-field theory description of the phase transition. This work represents a first crucial step to understand phase transitions in compelling TGFT models for quantum gravity and paves the way for a more complete analysis via functional renormalization group techniques. Moreover, it supports the recent extraction of effective cosmological dynamics from TGFTs in the context of a mean-field approximation. |
gr-qc/0508027 | Peter Breitenlohner | Peter Breitenlohner (1), Dieter Maison (1), D. H. Tchrakian (2) ((1)
Max-Planck-Institut fuer Physik, Munich, Germany, (2) Department of
Mathematical Physics, National University of Ireland Maynooth, and School of
Theoretical Physics -- DIAS, Dublin, Ireland) | Regular solutions to higher order curvature Einstein--Yang-Mills systems
in higher dimensions | 34 pages, 12 figures | Class.Quant.Grav. 22 (2005) 5201-5222 | 10.1088/0264-9381/22/24/001 | MPP-2005-83 | gr-qc hep-th | null | We study regular, static, spherically symmetric solutions of Yang-Mills
theories employing higher order invariants of the field strength coupled to
gravity in $d$ dimensions. We consider models with only two such invariants
characterised by integers $p$ and $q$. These models depend on one dimensionless
parameter $\alpha$ leading to one-parameter families of regular solutions,
obtainable by numerical solution of the corresponding boundary value problem.
Much emphasis is put on an analytical understanding of the numerical results.
| [
{
"created": "Mon, 8 Aug 2005 12:00:07 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Breitenlohner",
"Peter",
""
],
[
"Maison",
"Dieter",
""
],
[
"Tchrakian",
"D. H.",
""
]
] | We study regular, static, spherically symmetric solutions of Yang-Mills theories employing higher order invariants of the field strength coupled to gravity in $d$ dimensions. We consider models with only two such invariants characterised by integers $p$ and $q$. These models depend on one dimensionless parameter $\alpha$ leading to one-parameter families of regular solutions, obtainable by numerical solution of the corresponding boundary value problem. Much emphasis is put on an analytical understanding of the numerical results. |
1406.4284 | Debraj Roy | Debraj Roy | Lagrangian analysis of `trivial' symmetries in models of gravity | 4 pages, LaTeX; Based on presentation at the conference "Relativity
and Gravitation: 100 Years after Einstein in Prague," held in Prague, June
2012 | Springer Proceedings in Physics, Relativity and Gravitation,
Volume 157, 2014, pp 309-313 | 10.1007/978-3-319-06761-2_43 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the differences between Poincare and canonical hamiltonian
symmetries in models of gravity through the corresponding Noether identities
and show that they are equivalent modulo trivial gauge symmetries.
| [
{
"created": "Tue, 17 Jun 2014 09:18:00 GMT",
"version": "v1"
}
] | 2014-06-18 | [
[
"Roy",
"Debraj",
""
]
] | We study the differences between Poincare and canonical hamiltonian symmetries in models of gravity through the corresponding Noether identities and show that they are equivalent modulo trivial gauge symmetries. |
gr-qc/9901087 | Alexander N. Linden | Alexander N. Linden | Near Field Behavior of Static Spherically Symmetric Solutions of
Einstein SU(2) Yang Mills Equations with Cosmological Constant | 27pages | null | null | null | gr-qc | null | We consider static spherically symmetric solutions of the Einstein equations
with cosmological constant coupled to the SU(2) Yang Mills equations. We prove
that most solutions can be continued back to the origin of spherical symmetry
and that the qualitative behavior of solutions near this origin does not depend
on the value of the cosmological constant.
| [
{
"created": "Fri, 29 Jan 1999 22:25:34 GMT",
"version": "v1"
},
{
"created": "Mon, 1 May 2000 21:25:08 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Linden",
"Alexander N.",
""
]
] | We consider static spherically symmetric solutions of the Einstein equations with cosmological constant coupled to the SU(2) Yang Mills equations. We prove that most solutions can be continued back to the origin of spherical symmetry and that the qualitative behavior of solutions near this origin does not depend on the value of the cosmological constant. |
gr-qc/0610085 | Alcides Garat | Alcides Garat | The Lorentz force equation as Fermi-Walker transport in geometrodynamics | There is a new abstract and the introduction has been modified. There
are two new sections: Frenet-Serret second version, and Fermi-Walker
projections. The conclusions have been substantially modified | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new tetrad introduced within the framework of geometrodynamics for non-null
electromagnetic fields allows for the geometrical analysis of the Lorentz force
equation and its solutions in curved spacetimes. When expressed in terms of
this new tetrad, the electromagnetic field displays explicitly maximum
simplification, and the degrees of freedom are manifestly revealed. In our
manuscript we are deducing the Lorentz force equation on purely Riemannian
geometrical grounds. The equation arises on the basis of Frenet-Serret analysis
through the use of our new tetrads and gauge invariance arguments only. The
force is deduced through a geometrical construction that precludes any other
mathematical form other than the one already accepted. Therefore, a significant
and fundamental result such as the first geometrical proof on the necessity of
the force in the equation to have the structure already accepted in physics and
not any other, is given. Through the use of the Frenet-Serret formulae and
gauge invariance arguments we are also able to express in terms of the new
tetrad vectors the Lorentz force equation as a generalized form of Fermi-Walker
transport.
| [
{
"created": "Tue, 17 Oct 2006 15:36:48 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Dec 2006 18:37:08 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Jun 2012 13:37:40 GMT",
"version": "v3"
}
] | 2012-07-25 | [
[
"Garat",
"Alcides",
""
]
] | A new tetrad introduced within the framework of geometrodynamics for non-null electromagnetic fields allows for the geometrical analysis of the Lorentz force equation and its solutions in curved spacetimes. When expressed in terms of this new tetrad, the electromagnetic field displays explicitly maximum simplification, and the degrees of freedom are manifestly revealed. In our manuscript we are deducing the Lorentz force equation on purely Riemannian geometrical grounds. The equation arises on the basis of Frenet-Serret analysis through the use of our new tetrads and gauge invariance arguments only. The force is deduced through a geometrical construction that precludes any other mathematical form other than the one already accepted. Therefore, a significant and fundamental result such as the first geometrical proof on the necessity of the force in the equation to have the structure already accepted in physics and not any other, is given. Through the use of the Frenet-Serret formulae and gauge invariance arguments we are also able to express in terms of the new tetrad vectors the Lorentz force equation as a generalized form of Fermi-Walker transport. |
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