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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1701.03657 | Marko Sossich | Petar Pavlovic and Marko Sossich | Cyclic cosmology in modified gravity | 33 pages, 11 figures | Phys. Rev. D 95, 103519 (2017) | 10.1103/PhysRevD.95.103519 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we propose a new general model of eternal cyclic Universe. We
start from the assumption that quantum gravity corrections can be effectively
accounted by the addition of higher order curvature terms in the Lagrangian
density for gravity. It is also taken into account that coefficients associated
with these curvature corrections will in general be dependent on a curvature
regime. We therewith assume no new ingredients, such as extra dimensions, new
scalar fields, phantom energy or special space-time geometries. Evolution of
the Universe in this framework is studied and general properties of each phase
of the cycle - cosmological bounce, low curvature ($\Lambda$CDM) phase,
destruction of bounded systems and contracting phase - are analysed in detail.
Focusing on some simple special cases, we obtain analytical and numerical
solutions for the each phase confirming our analysis.
| [
{
"created": "Fri, 13 Jan 2017 13:15:44 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jan 2017 16:39:16 GMT",
"version": "v2"
},
{
"created": "Sat, 3 Jun 2017 13:14:09 GMT",
"version": "v3"
}
] | 2017-06-06 | [
[
"Pavlovic",
"Petar",
""
],
[
"Sossich",
"Marko",
""
]
] | In this work we propose a new general model of eternal cyclic Universe. We start from the assumption that quantum gravity corrections can be effectively accounted by the addition of higher order curvature terms in the Lagrangian density for gravity. It is also taken into account that coefficients associated with these curvature corrections will in general be dependent on a curvature regime. We therewith assume no new ingredients, such as extra dimensions, new scalar fields, phantom energy or special space-time geometries. Evolution of the Universe in this framework is studied and general properties of each phase of the cycle - cosmological bounce, low curvature ($\Lambda$CDM) phase, destruction of bounded systems and contracting phase - are analysed in detail. Focusing on some simple special cases, we obtain analytical and numerical solutions for the each phase confirming our analysis. |
gr-qc/0602014 | Mauricio Bellini | Mauricio Bellini (Mar del Plata University & CONICET) | Cosmological expansion governed by a scalar field from a 5D vacuum | version accepted in Phys. Lett. B | Phys.Lett. B637 (2006) 16-20 | 10.1016/j.physletb.2006.04.033 | null | gr-qc astro-ph hep-ph hep-th | null | We consider a single field governed expansion of the universe from a five
dimensional (5D) vacuum state. Under an appropiate change of variables the
universe can be viewed in a effective manner as expanding in 4D with an
effective equation of state which describes different epochs of its evolution.
In the example here worked the universe fistly describes an inflationary phase,
followed by a decelerated expansion. Thereafter, the universe is accelerated
and describes a quintessential expansion to finally, in the future, be vacuum
dominated.
| [
{
"created": "Thu, 2 Feb 2006 22:24:32 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2006 14:01:29 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Apr 2006 19:42:10 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Bellini",
"Mauricio",
"",
"Mar del Plata University & CONICET"
]
] | We consider a single field governed expansion of the universe from a five dimensional (5D) vacuum state. Under an appropiate change of variables the universe can be viewed in a effective manner as expanding in 4D with an effective equation of state which describes different epochs of its evolution. In the example here worked the universe fistly describes an inflationary phase, followed by a decelerated expansion. Thereafter, the universe is accelerated and describes a quintessential expansion to finally, in the future, be vacuum dominated. |
1603.05537 | Diego S\'aez-G\'omez | Alvaro de la Cruz-Dombriz (ACGC, U. of Cape Town), Emilio Elizalde
(ICE-CSIC/IEEC), Sergei D. Odintsov (ICE-CSIC/IEEC and ICREA) and Diego
Saez-Gomez (IA, U. of Lisbon) | Spotting deviations from R^2 inflation | 24 pages, 1 figure, minor changes, version matching published
version, conclusions unchanged. arXiv admin note: text overlap with
arXiv:1411.1636 by other authors | JCAP 05 (2016) 060 | 10.1088/1475-7516/2016/05/060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the soundness of inflationary scenarios in theories beyond the
Starobinsky model, namely a class of theories described by arbitrary functions
of the Ricci scalar and the K-essence field. We discuss the pathologies
associated with higher-order equations of motion which will be shown to
constrain the stability of this class of theories. We provide a general
framework to calculate the slow-roll parameters and the corresponding mappings
to the theory parameters. For paradigmatic gravitational models within the
class of theories under consideration we illustrate the power of the
Planck/Bicep2 latest results to constrain such gravitational Lagrangians.
Finally, bounds for potential deviations from Starobinsky-like inflation are
derived.
| [
{
"created": "Thu, 17 Mar 2016 15:22:03 GMT",
"version": "v1"
},
{
"created": "Wed, 25 May 2016 16:13:47 GMT",
"version": "v2"
}
] | 2016-06-09 | [
[
"de la Cruz-Dombriz",
"Alvaro",
"",
"ACGC, U. of Cape Town"
],
[
"Elizalde",
"Emilio",
"",
"ICE-CSIC/IEEC"
],
[
"Odintsov",
"Sergei D.",
"",
"ICE-CSIC/IEEC and ICREA"
],
[
"Saez-Gomez",
"Diego",
"",
"IA, U. of Lisbon"
]
] | We discuss the soundness of inflationary scenarios in theories beyond the Starobinsky model, namely a class of theories described by arbitrary functions of the Ricci scalar and the K-essence field. We discuss the pathologies associated with higher-order equations of motion which will be shown to constrain the stability of this class of theories. We provide a general framework to calculate the slow-roll parameters and the corresponding mappings to the theory parameters. For paradigmatic gravitational models within the class of theories under consideration we illustrate the power of the Planck/Bicep2 latest results to constrain such gravitational Lagrangians. Finally, bounds for potential deviations from Starobinsky-like inflation are derived. |
0811.1712 | Abdullah Vercin | \"O. A\c{c}{\i}k, \"U. Ertem, M. \"Onder and A. Ver\c{c}in | Basic Gravitational Currents and Killing-Yano Forms | 11 pages | Gen. Relativ. Gravit., 42, 2543 (2010) | 10.1007/s10714-010-1075-4 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that for each Killing-Yano (KY)-form accepted by an
$n$-dimensional (pseudo)Riemannian manifold of arbitrary signature, two basic
gravitational currents can be defined. Conservation of the currents are
explicitly proved by showing co-exactness of the one and co-closedness of the
other. Some general geometrical facts implied by these conservation laws are
also elucidated. In particular, the conservation of the one-form currents
implies that the scalar curvature of the manifold is a flow invariant for all
of its Killing vector fields. It also directly follows that, while all KY-forms
and their Hodge duals on a constant curvature manifold are the eigenforms of
the Laplace-Beltrami operator, for an Einstein manifold this is certain only
for KY 1-forms, $(n-1)$-forms and their Hodge duals.
| [
{
"created": "Tue, 11 Nov 2008 14:24:49 GMT",
"version": "v1"
}
] | 2016-02-10 | [
[
"Açık",
"Ö.",
""
],
[
"Ertem",
"Ü.",
""
],
[
"Önder",
"M.",
""
],
[
"Verçin",
"A.",
""
]
] | It has been shown that for each Killing-Yano (KY)-form accepted by an $n$-dimensional (pseudo)Riemannian manifold of arbitrary signature, two basic gravitational currents can be defined. Conservation of the currents are explicitly proved by showing co-exactness of the one and co-closedness of the other. Some general geometrical facts implied by these conservation laws are also elucidated. In particular, the conservation of the one-form currents implies that the scalar curvature of the manifold is a flow invariant for all of its Killing vector fields. It also directly follows that, while all KY-forms and their Hodge duals on a constant curvature manifold are the eigenforms of the Laplace-Beltrami operator, for an Einstein manifold this is certain only for KY 1-forms, $(n-1)$-forms and their Hodge duals. |
2302.06401 | Andrea Pierfrancesco Sanna | Mariano Cadoni, Andrea Pierfrancesco Sanna | Nonsingular black holes from conformal symmetries | 6 pages, no figures, some discussions improved, matches the version
accepted for pubblication in CQG | Classical & Quantum Gravity, 40 (2023), no. 14, 145012 | 10.1088/1361-6382/acde3c | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We derive the form of the metric for static, nonsingular black holes with a
de Sitter core, representing a deformation of the Schwarzschild solution, by
assuming that the gravitational sources describe a flow between two conformal
points, at small and great distances. The resulting black-hole metric turns out
to be a particular case of the Fan $\&$ Wang metric, whose parameters have been
recently constrained by using the data of the S$2$ star orbits around the
galactic centre SgrA$^\ast$.
| [
{
"created": "Mon, 13 Feb 2023 14:40:11 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2023 07:26:07 GMT",
"version": "v2"
}
] | 2023-06-30 | [
[
"Cadoni",
"Mariano",
""
],
[
"Sanna",
"Andrea Pierfrancesco",
""
]
] | We derive the form of the metric for static, nonsingular black holes with a de Sitter core, representing a deformation of the Schwarzschild solution, by assuming that the gravitational sources describe a flow between two conformal points, at small and great distances. The resulting black-hole metric turns out to be a particular case of the Fan $\&$ Wang metric, whose parameters have been recently constrained by using the data of the S$2$ star orbits around the galactic centre SgrA$^\ast$. |
2101.08409 | Qiming Fu | Qi-Ming Fu, Li Zhao, and Yu-Xiao Liu | Weak deflection angle by electrically and magnetically charged black
holes from nonlinear electrodynamics | null | Phys. Rev. D 104, 024033 (2021) | 10.1103/PhysRevD.104.024033 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Nonlinear electrodynamic (NLED) theories are well-motivated for their
extensions to classical electrodynamics in the strong field regime, and have
been extensively investigated in seeking for regular black hole solutions. In
this paper, we focus on two spherically symmetric and static black hole
solutions based on two types of NLED models: the Euler-Heisenberg NLED model
and the Bronnikov NLED model, and calculate the weak deflection angle of light
by these two black holes with the help of the Gauss-Bonnet theorem. We
investigate the effects of the one-loop corrections to quantum electrodynamics
on the deflection angle and analyse the behavior of the deflection angle by a
regular magnetically charged black hole. It is found that the weak deflection
angle of the electrically charged Einstein-Euler-Heisenberg black hole
increases with the one-loop corrections and the regular magnetically charged
black hole based on the Bronnikov NLED model has a smaller deflection angle
than the singular one. Besides, we also calculate the deflection angle of light
by the geodesic method for verification. In addition, we discuss the effects of
a cold non-magnetized plasma on the deflection angle and find that the
deflection angle increases with the plasma parameter.
| [
{
"created": "Thu, 21 Jan 2021 02:39:42 GMT",
"version": "v1"
}
] | 2021-07-21 | [
[
"Fu",
"Qi-Ming",
""
],
[
"Zhao",
"Li",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Nonlinear electrodynamic (NLED) theories are well-motivated for their extensions to classical electrodynamics in the strong field regime, and have been extensively investigated in seeking for regular black hole solutions. In this paper, we focus on two spherically symmetric and static black hole solutions based on two types of NLED models: the Euler-Heisenberg NLED model and the Bronnikov NLED model, and calculate the weak deflection angle of light by these two black holes with the help of the Gauss-Bonnet theorem. We investigate the effects of the one-loop corrections to quantum electrodynamics on the deflection angle and analyse the behavior of the deflection angle by a regular magnetically charged black hole. It is found that the weak deflection angle of the electrically charged Einstein-Euler-Heisenberg black hole increases with the one-loop corrections and the regular magnetically charged black hole based on the Bronnikov NLED model has a smaller deflection angle than the singular one. Besides, we also calculate the deflection angle of light by the geodesic method for verification. In addition, we discuss the effects of a cold non-magnetized plasma on the deflection angle and find that the deflection angle increases with the plasma parameter. |
1406.0152 | Roberto Chan | G. Pinheiro and R. Chan | Radiating Gravitational Collapse with an Initial Inhomogeneous Energy
Density Distribution | 22 pages, 12 figures. This paper has already been published in GRG
(2011). arXiv admin note: substantial text overlap with arXiv:1301.2540 | General Relativity and Gravitation 43, 145 (2011) | 10.1007/s10714-010-1132-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new model is proposed to a collapsing star consisting of an initial
inhomogeneous energy density and anisotropic pressure fluid with shear, radial
heat flow and outgoing radiation. In previous papers one of us has always
assumed an initial star with homogeneous energy density. The aim of this work
is to generalize the previous models by introducing an initial inhomogeneous
energy density and compare it to the initial homogeneous energy density
collapse model. We will show the differences between these models in the
evolution of all physical quantities that characterizes the gravitational
collapse. The behavior of the energy density, pressure, mass, luminosity and
the effective adiabatic index is analyzed. The pressure of the star, at the
beginning of the collapse, is isotropic but due to the presence of the shear
the pressure becomes more and more anisotropic. The black hole is never formed
because the apparent horizon formation condition is never satisfied, in
contrast of the previous model where a black hole is formed. An observer at
infinity sees a radial point source radiating exponentially until reaches the
time of maximum luminosity and suddenly the star turns off. In contrast of the
former model where the luminosity also increases exponentially, reaching a
maximum and after it decreases until the formation of the black hole. The
effective adiabatic index is always positive without any discontinuity in
contrast of the former model where there is a discontinuity around the time of
maximum luminosity. The collapse is about three thousand times slower than in
the case where the energy density is initially homogeneous.
| [
{
"created": "Sun, 1 Jun 2014 09:37:47 GMT",
"version": "v1"
}
] | 2014-06-03 | [
[
"Pinheiro",
"G.",
""
],
[
"Chan",
"R.",
""
]
] | A new model is proposed to a collapsing star consisting of an initial inhomogeneous energy density and anisotropic pressure fluid with shear, radial heat flow and outgoing radiation. In previous papers one of us has always assumed an initial star with homogeneous energy density. The aim of this work is to generalize the previous models by introducing an initial inhomogeneous energy density and compare it to the initial homogeneous energy density collapse model. We will show the differences between these models in the evolution of all physical quantities that characterizes the gravitational collapse. The behavior of the energy density, pressure, mass, luminosity and the effective adiabatic index is analyzed. The pressure of the star, at the beginning of the collapse, is isotropic but due to the presence of the shear the pressure becomes more and more anisotropic. The black hole is never formed because the apparent horizon formation condition is never satisfied, in contrast of the previous model where a black hole is formed. An observer at infinity sees a radial point source radiating exponentially until reaches the time of maximum luminosity and suddenly the star turns off. In contrast of the former model where the luminosity also increases exponentially, reaching a maximum and after it decreases until the formation of the black hole. The effective adiabatic index is always positive without any discontinuity in contrast of the former model where there is a discontinuity around the time of maximum luminosity. The collapse is about three thousand times slower than in the case where the energy density is initially homogeneous. |
2309.15488 | She-Sheng Xue | She-Sheng Xue | Holographic massive plasma state in Friedman Universe: cosmological
fine-tuning and coincidence problems | 27 pages and 7 captioned figures. Final version to appear in JCAP
(2024) | JCAP (2024) | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Massive particle and antiparticle pair production and oscillation on the
horizon form a holographic and massive pair plasma state in the Friedman
Universe. Via this state, the Einstein cosmology term (dark energy) interacts
with matter and radiation and is time-varying $\tilde\Lambda$ in the Universe's
evolution. It is determined by a close set of ordinary differential equations
for dark energy, matter, and radiation energy densities. The solutions are
unique, provided the initial conditions given by observations. In inflation and
reheating, dark energy density decreases from the inflation scale, converting
to matter and radiation energy densities. In standard cosmology, matter and
radiation energy densities convert to dark energy density, reaching the present
Universe. By comparing with $\Lambda$CDM, quintessence and dark energy
interacting models, we show that these results can be the possible solutions
for cosmological fine-tuning and coincidence problems.
| [
{
"created": "Wed, 27 Sep 2023 08:35:48 GMT",
"version": "v1"
},
{
"created": "Fri, 17 May 2024 15:17:18 GMT",
"version": "v2"
}
] | 2024-05-21 | [
[
"Xue",
"She-Sheng",
""
]
] | Massive particle and antiparticle pair production and oscillation on the horizon form a holographic and massive pair plasma state in the Friedman Universe. Via this state, the Einstein cosmology term (dark energy) interacts with matter and radiation and is time-varying $\tilde\Lambda$ in the Universe's evolution. It is determined by a close set of ordinary differential equations for dark energy, matter, and radiation energy densities. The solutions are unique, provided the initial conditions given by observations. In inflation and reheating, dark energy density decreases from the inflation scale, converting to matter and radiation energy densities. In standard cosmology, matter and radiation energy densities convert to dark energy density, reaching the present Universe. By comparing with $\Lambda$CDM, quintessence and dark energy interacting models, we show that these results can be the possible solutions for cosmological fine-tuning and coincidence problems. |
gr-qc/0103086 | Hiroko Koyama | Hiroko Koyama and Akira Tomimatsu | Asymptotic tails of massive scalar fields in Schwarzschild background | 21 pages, 2 figures, accepted for publication in Phys.Rev.D | Phys.Rev. D64 (2001) 044014 | 10.1103/PhysRevD.64.044014 | DPNU-01-04 | gr-qc | null | We investigate the asymptotic tail behavior of massive scalar fields in
Schwarzschild background. It is shown that the oscillatory tail of the scalar
field has the decay rate of $t^{-5/6}$ at asymptotically late times, and the
oscillation with the period $2\pi/m$ for the field mass $m$ is modulated by the
long-term phase shift. These behaviors are qualitatively similar to those found
in nearly extreme Reissner-Nordstr\"{o}m background, which are discussed in
terms of a resonant backscattering due to the space-time curvature.
| [
{
"created": "Fri, 23 Mar 2001 07:19:51 GMT",
"version": "v1"
},
{
"created": "Fri, 4 May 2001 06:04:40 GMT",
"version": "v2"
}
] | 2007-10-02 | [
[
"Koyama",
"Hiroko",
""
],
[
"Tomimatsu",
"Akira",
""
]
] | We investigate the asymptotic tail behavior of massive scalar fields in Schwarzschild background. It is shown that the oscillatory tail of the scalar field has the decay rate of $t^{-5/6}$ at asymptotically late times, and the oscillation with the period $2\pi/m$ for the field mass $m$ is modulated by the long-term phase shift. These behaviors are qualitatively similar to those found in nearly extreme Reissner-Nordstr\"{o}m background, which are discussed in terms of a resonant backscattering due to the space-time curvature. |
gr-qc/0312115 | John W. Moffat | J. W. Moffat | Cosmological Constant Problem | 8 pages. No figures. Latex file. Talk given at QFEXT03, University of
Oklahoma, Norman, Oklahoma, September 15-19, 2003. To be published in the
proceedings by Rinton Press | null | null | null | gr-qc astro-ph hep-ph hep-th | null | The cosmological constant problem is reviewed and a possible quantum gravity
resolution is proposed. A space satellite E\"otv\"os experiment for zero-point
vacuum energy is proposed to see whether Casimir vacuum energy falls in a
gravitational field at the same rate as ordinary matter.
| [
{
"created": "Sun, 28 Dec 2003 21:18:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Moffat",
"J. W.",
""
]
] | The cosmological constant problem is reviewed and a possible quantum gravity resolution is proposed. A space satellite E\"otv\"os experiment for zero-point vacuum energy is proposed to see whether Casimir vacuum energy falls in a gravitational field at the same rate as ordinary matter. |
gr-qc/0607064 | {\O}ystein Rudjord | Oystein Rudjord, Oyvind Gron | The Weyl curvature conjecture and black hole entropy | 10 pages, 2 figures, typesetting revtex4 | Phys.Scripta77:055901,2008 | 10.1088/0031-8949/77/05/055901 | null | gr-qc | null | The universe today, with structure such as stars, galaxies and black holes,
seems to have evolved from a very homogeneous initial state. From this it
appears as if the entropy of the universe is decreasing, in violation of the
second law of thermodynamics. It has been suggested by Roger Penrose
\cite{grossmann:penrose:wcc} that this inconsistency can be solved if one
assigns an entropy to the spacetime geometry. He also pointed out that the Weyl
tensor has the properties one would expect to find in a description of a
gravitational entropy. In this article we make an attempt to use this so-called
Weyl curvature conjecture to describe the Hawking-Bekenstein entropy of black
holes and the entropy of horizons due to a cosmological constant.
| [
{
"created": "Mon, 17 Jul 2006 14:49:44 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rudjord",
"Oystein",
""
],
[
"Gron",
"Oyvind",
""
]
] | The universe today, with structure such as stars, galaxies and black holes, seems to have evolved from a very homogeneous initial state. From this it appears as if the entropy of the universe is decreasing, in violation of the second law of thermodynamics. It has been suggested by Roger Penrose \cite{grossmann:penrose:wcc} that this inconsistency can be solved if one assigns an entropy to the spacetime geometry. He also pointed out that the Weyl tensor has the properties one would expect to find in a description of a gravitational entropy. In this article we make an attempt to use this so-called Weyl curvature conjecture to describe the Hawking-Bekenstein entropy of black holes and the entropy of horizons due to a cosmological constant. |
gr-qc/0608036 | Farrukh Fattoyev Jabborovich | B. J. Ahmedov, N. I. Rakhmatov | Concerning Measurement of Gravitomagnetism in Electromagnetic Systems | 12 pages, 1 figure | Found.Phys. 33 (2003) 625-639 | null | null | gr-qc astro-ph | null | Measurement of gravitomagnetic field is of fundamental importance as a test
of general relativity. Here we present a new theoretical project for performing
such a measurement based on detection of the electric field arising from the
interplay between the gravitomagnetic and magnetic fields in the stationary
axial-symmetric gravitational field of a slowly rotating massive body. Finally
it is shown that precise magnetometers based on superconducting quantum
interferometers could not be designed for measurement of the
gravitomagnetically induced magnetic field in the cavity of a charged capacitor
since they measure the circulation of a vector potential of electromagnetic
field, i.e., an invariant quantity including the sum of electric and magnetic
fields, and the general-relativistic magnetic part will be totally cancelled by
the electric one which is in good agreement with the experimental results.
| [
{
"created": "Mon, 7 Aug 2006 19:21:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ahmedov",
"B. J.",
""
],
[
"Rakhmatov",
"N. I.",
""
]
] | Measurement of gravitomagnetic field is of fundamental importance as a test of general relativity. Here we present a new theoretical project for performing such a measurement based on detection of the electric field arising from the interplay between the gravitomagnetic and magnetic fields in the stationary axial-symmetric gravitational field of a slowly rotating massive body. Finally it is shown that precise magnetometers based on superconducting quantum interferometers could not be designed for measurement of the gravitomagnetically induced magnetic field in the cavity of a charged capacitor since they measure the circulation of a vector potential of electromagnetic field, i.e., an invariant quantity including the sum of electric and magnetic fields, and the general-relativistic magnetic part will be totally cancelled by the electric one which is in good agreement with the experimental results. |
1910.08538 | Grigoris Panotopoulos | Grigoris Panotopoulos and \'Angel Rinc\'on | Quasinormal modes of five-dimensional black holes in non-commutative
geometry | References added, to appear soon in EPJ Plus. Analysis similar to
arXiv:1904.10847, albeit in a different context | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the spectrum of quasinormal frequencies of five-dimensional black
holes obtained in noncommutative geometry. In particular, we study scalar
perturbations of a massive scalar field adopting the 6th order WKB
approximation. We investigate in detail the impact of the mass of the scalar
field, the angular degree and the overtone number on the spectrum. All modes
are found to be stable.
| [
{
"created": "Fri, 18 Oct 2019 01:26:20 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2019 15:24:51 GMT",
"version": "v2"
}
] | 2019-12-24 | [
[
"Panotopoulos",
"Grigoris",
""
],
[
"Rincón",
"Ángel",
""
]
] | We compute the spectrum of quasinormal frequencies of five-dimensional black holes obtained in noncommutative geometry. In particular, we study scalar perturbations of a massive scalar field adopting the 6th order WKB approximation. We investigate in detail the impact of the mass of the scalar field, the angular degree and the overtone number on the spectrum. All modes are found to be stable. |
2207.03508 | Javier Roulet | Javier Roulet, Seth Olsen, Jonathan Mushkin, Tousif Islam, Tejaswi
Venumadhav, Barak Zackay and Matias Zaldarriaga | Removing degeneracy and multimodality in gravitational wave source
parameters | 17 pages, 13 figures, 1 table. Matches version accepted for
publication in Phys. Rev. D | null | 10.1103/PhysRevD.106.123015 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasicircular binary black hole mergers are described by 15 parameters, of
which gravitational wave observations can typically constrain only $\sim 10$
independent combinations to varying degree. In this work, we devise coordinates
that remove correlations, and disentangle well- and poorly-measured quantities.
Additionally, we identify approximate discrete symmetries in the posterior as
the primary cause of multimodality, and design a method to tackle this type of
multimodality. The resulting posteriors have little structure and can be
sampled efficiently and robustly. We provide a Python package for parameter
estimation, cogwheel, that implements these methods together with other
algorithms for accelerating the inference process. One of the coordinates we
introduce is a spin azimuth that is measured remarkably well in several events.
We suggest this might be a sensitive indicator of orbital precession, and we
anticipate that it will shed light on the occurrence of spin-orbit misalignment
in nature.
| [
{
"created": "Thu, 7 Jul 2022 18:00:15 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Nov 2022 23:16:18 GMT",
"version": "v2"
}
] | 2022-12-28 | [
[
"Roulet",
"Javier",
""
],
[
"Olsen",
"Seth",
""
],
[
"Mushkin",
"Jonathan",
""
],
[
"Islam",
"Tousif",
""
],
[
"Venumadhav",
"Tejaswi",
""
],
[
"Zackay",
"Barak",
""
],
[
"Zaldarriaga",
"Matias",
""
]
] | Quasicircular binary black hole mergers are described by 15 parameters, of which gravitational wave observations can typically constrain only $\sim 10$ independent combinations to varying degree. In this work, we devise coordinates that remove correlations, and disentangle well- and poorly-measured quantities. Additionally, we identify approximate discrete symmetries in the posterior as the primary cause of multimodality, and design a method to tackle this type of multimodality. The resulting posteriors have little structure and can be sampled efficiently and robustly. We provide a Python package for parameter estimation, cogwheel, that implements these methods together with other algorithms for accelerating the inference process. One of the coordinates we introduce is a spin azimuth that is measured remarkably well in several events. We suggest this might be a sensitive indicator of orbital precession, and we anticipate that it will shed light on the occurrence of spin-orbit misalignment in nature. |
gr-qc/0407094 | Keye Martin | Keye Martin and Prakash Panangaden | A domain of spacetime intervals in general relativity | 25 pages | Commun.Math.Phys. 267 (2006) 563-586 | 10.1007/s00220-006-0066-5 | null | gr-qc | null | Beginning from only a countable dense set of events and the causality
relation, it is possible to reconstruct a globally hyperbolic spacetime in a
purely order theoretic manner. The ultimate reason for this is that globally
hyperbolic spacetimes belong to a category that is equivalent to a special
category of domains called interval domains.
| [
{
"created": "Mon, 26 Jul 2004 03:12:55 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Martin",
"Keye",
""
],
[
"Panangaden",
"Prakash",
""
]
] | Beginning from only a countable dense set of events and the causality relation, it is possible to reconstruct a globally hyperbolic spacetime in a purely order theoretic manner. The ultimate reason for this is that globally hyperbolic spacetimes belong to a category that is equivalent to a special category of domains called interval domains. |
1003.0112 | David Campo | David Campo, Nathaniel Obadia | Why does the Unruh effect rely on Lorentz invariance, while Hawking
radiation does not ? | null | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that without Lorentz invariance, the Unruh effect does not exist. We
use modified dispersion relations and describe in turn: the non-thermal nature
of the vacuum (defined in the preferred frame) restricted to the Rindler wedge,
the loss of the KMS property of the Wigthman function, the transition
amplitudes and transition rates of a uniformaly accelerated detector. This
situation seems to contrast with the Hawking radiation of acoustic black holes,
which under certain assumptions has been shown to be robust to a breaking of
Lorentz symmetry. We explain this discrepancy.
| [
{
"created": "Sat, 27 Feb 2010 16:43:54 GMT",
"version": "v1"
}
] | 2010-03-02 | [
[
"Campo",
"David",
""
],
[
"Obadia",
"Nathaniel",
""
]
] | We show that without Lorentz invariance, the Unruh effect does not exist. We use modified dispersion relations and describe in turn: the non-thermal nature of the vacuum (defined in the preferred frame) restricted to the Rindler wedge, the loss of the KMS property of the Wigthman function, the transition amplitudes and transition rates of a uniformaly accelerated detector. This situation seems to contrast with the Hawking radiation of acoustic black holes, which under certain assumptions has been shown to be robust to a breaking of Lorentz symmetry. We explain this discrepancy. |
gr-qc/9507023 | Pavel Krtous | Pavel Krtou\v{s} | Particle Interpretations and Green Functions for a Free Scalar Field | 28 pages; LaTeX2e document; it uses amsmath.sty, amsfonts.sty,
amssymb.sty, cite.sty and ifthen.sty packages; There exists a broader version
of this paper with additional review material available from
http://fermi.phys.ualberta.ca/~krtous/Physics/pigf/pigf.html or by e-mail
from the Author | null | null | null | gr-qc | null | The formalism of Ashtekar and Magnon \cite{AshtekarMagnon:1975} for the
definition of particles in quantum field theory in curved spacetime is further
developed. The relation between basic objects of this formalism (e.g., the
complex structure) and different Green functions is found. It allows one to
derive composition laws for Green functions. The relation of two definitions of
particles is reformulated in the formalism and the base-independent Bogoljubov
transformation is expressed using quantities which are derivable directly from
the ``in-out'' Green function.
| [
{
"created": "Tue, 11 Jul 1995 23:48:04 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 1995 17:20:08 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Krtouš",
"Pavel",
""
]
] | The formalism of Ashtekar and Magnon \cite{AshtekarMagnon:1975} for the definition of particles in quantum field theory in curved spacetime is further developed. The relation between basic objects of this formalism (e.g., the complex structure) and different Green functions is found. It allows one to derive composition laws for Green functions. The relation of two definitions of particles is reformulated in the formalism and the base-independent Bogoljubov transformation is expressed using quantities which are derivable directly from the ``in-out'' Green function. |
1807.06959 | Tim Dietrich | Tim Dietrich and Serguei Ossokine and Katy Clough | Full 3D Numerical Relativity Simulations of Neutron Star -- Boson Star
Collisions with BAM | null | null | 10.1088/1361-6382/aaf43e | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the first direct detections of gravitational waves (GWs) from the
coalescence of compact binaries observed by the advanced LIGO and VIRGO
interferometers, the era of GW astronomy has begun. Whilst there is strong
evidence that the observed GWs are connected to the merger of two black holes
(BH) or two neutron stars (NS), future detections may present a less consistent
picture. Indeed, the possibility that the observed GW signal was created by a
merger of exotic compact objects (ECOs) such as boson stars (BS) or axion stars
(AS) has not yet been fully excluded. For a detailed understanding of the late
stages of the coalescence full 3D numerical relativity simulations are
essential. In this paper, we extend the infrastructure of the numerical
relativity code BAM, to permit the simultaneous simulation of baryonic matter
with bosonic scalar fields, thus enabling the study of BS-BS, BS-NS, and BS-BH
mergers. We present a large number of single star evolutions to test the newly
implemented routines, and to quantify the numerical challenges of such
simulations, which we find to partially differ from the default NS case. We
also compare head-on BS-BS simulations with independent numerical relativity
codes, namely the SpEC and the GRChombo codes, and find good general agreement.
Finally, we present what are, to the best of our knowledge, the first full NR
simulations of BS-NS mergers, a first step towards identifying the hallmarks of
BS-NS interactions in the strong gravity regime, as well as possible GW and
electromagnetic observables.
| [
{
"created": "Wed, 18 Jul 2018 14:22:20 GMT",
"version": "v1"
}
] | 2019-01-09 | [
[
"Dietrich",
"Tim",
""
],
[
"Ossokine",
"Serguei",
""
],
[
"Clough",
"Katy",
""
]
] | With the first direct detections of gravitational waves (GWs) from the coalescence of compact binaries observed by the advanced LIGO and VIRGO interferometers, the era of GW astronomy has begun. Whilst there is strong evidence that the observed GWs are connected to the merger of two black holes (BH) or two neutron stars (NS), future detections may present a less consistent picture. Indeed, the possibility that the observed GW signal was created by a merger of exotic compact objects (ECOs) such as boson stars (BS) or axion stars (AS) has not yet been fully excluded. For a detailed understanding of the late stages of the coalescence full 3D numerical relativity simulations are essential. In this paper, we extend the infrastructure of the numerical relativity code BAM, to permit the simultaneous simulation of baryonic matter with bosonic scalar fields, thus enabling the study of BS-BS, BS-NS, and BS-BH mergers. We present a large number of single star evolutions to test the newly implemented routines, and to quantify the numerical challenges of such simulations, which we find to partially differ from the default NS case. We also compare head-on BS-BS simulations with independent numerical relativity codes, namely the SpEC and the GRChombo codes, and find good general agreement. Finally, we present what are, to the best of our knowledge, the first full NR simulations of BS-NS mergers, a first step towards identifying the hallmarks of BS-NS interactions in the strong gravity regime, as well as possible GW and electromagnetic observables. |
2405.11395 | Kamel Ourabah | Kamel Ourabah | Jeans analysis in fractional gravity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It has recently been demonstrated [A. Giusti, Phys. Rev. D 101, 124029
(2020)] that characteristic traits of Milgrom's modified Newtonian dynamics
(MOND) can be replicated from an entirely distinct framework: a fractional
variant of Newtonian mechanics. To further assess its validity, this proposal
needs to be tested in relevant astrophysical scenarios. Here, we investigate
its implications on Jeans gravitational instability and related phenomena. We
examine scenarios involving classical matter confined by gravity and extend our
analysis to the quantum domain, through a Schr\"odinger-Newton approach. We
also derive a generalized Lane-Emden equation associated with fractional
gravity. Through comparisons between the derived stability criteria and the
observed stability of Bok globules, we establish constraints on the theory's
parameters to align with observational data.
| [
{
"created": "Sat, 18 May 2024 21:23:23 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Ourabah",
"Kamel",
""
]
] | It has recently been demonstrated [A. Giusti, Phys. Rev. D 101, 124029 (2020)] that characteristic traits of Milgrom's modified Newtonian dynamics (MOND) can be replicated from an entirely distinct framework: a fractional variant of Newtonian mechanics. To further assess its validity, this proposal needs to be tested in relevant astrophysical scenarios. Here, we investigate its implications on Jeans gravitational instability and related phenomena. We examine scenarios involving classical matter confined by gravity and extend our analysis to the quantum domain, through a Schr\"odinger-Newton approach. We also derive a generalized Lane-Emden equation associated with fractional gravity. Through comparisons between the derived stability criteria and the observed stability of Bok globules, we establish constraints on the theory's parameters to align with observational data. |
2304.00183 | Reggie Pantig | Gaetano Lambiase, Reggie C. Pantig, Dhruba Jyoti Gogoi, Ali \"Ovg\"un | Investigating the Connection between Generalized Uncertainty Principle
and Asymptotically Safe Gravity in Black Hole Signatures through Shadow and
Quasinormal Modes | 19 pages, 8 figures | Eur. Phys. J. C (2023) 83:679 | 10.1140/epjc/s10052-023-11848-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The links between the deformation parameter $\beta$ of the generalized
uncertainty principle (GUP) to the two free parameters $\hat{\omega}$ and
$\gamma$ of the running Newtonian coupling constant of the Asymptotic Safe
gravity (ASG) program, has been conducted recently in [Phys.Rev.D 105 (2022)
12, 124054]. In this paper, we test these findings by calculating and examining
the shadow and quasinormal modes of black holes and demonstrate that the
approach provides a theoretical framework for exploring the interplay between
quantum gravity and GUP. Our results confirm the consistency of ASG and GUP and
offer new insights into the nature of black holes and their signatures. The
implications of these findings for future studies in quantum gravity are also
discussed.
| [
{
"created": "Sat, 1 Apr 2023 00:18:35 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"Lambiase",
"Gaetano",
""
],
[
"Pantig",
"Reggie C.",
""
],
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Övgün",
"Ali",
""
]
] | The links between the deformation parameter $\beta$ of the generalized uncertainty principle (GUP) to the two free parameters $\hat{\omega}$ and $\gamma$ of the running Newtonian coupling constant of the Asymptotic Safe gravity (ASG) program, has been conducted recently in [Phys.Rev.D 105 (2022) 12, 124054]. In this paper, we test these findings by calculating and examining the shadow and quasinormal modes of black holes and demonstrate that the approach provides a theoretical framework for exploring the interplay between quantum gravity and GUP. Our results confirm the consistency of ASG and GUP and offer new insights into the nature of black holes and their signatures. The implications of these findings for future studies in quantum gravity are also discussed. |
1208.5266 | Mauricio Bellini | Luz Marina Reyes, Claudia Moreno, Jos\'e Edgar Madriz Aguilar
(Departamento de Matem\'aticas, CUCEI, Universidad de Guadalajara), Mauricio
Bellini (IFIMAR, Universidad Nacional de Mar del Plata and CONICET) | Gravitational waves during inflation from a 5D large-scale repulsive
gravity model | Improved version, accepted in Physics Letters B | null | 10.1016/j.physletb.2012.09.024 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate, in the transverse traceless (TT) gauge, the generation of the
relic background of gravitational waves, generated during an early inflationary
stage, on the framework of a large-scale repulsive gravity model. We calculate
the spectrum of the tensor metric fluctuations of an effective 4D
Schwarzschild-de-Sitter metric, which is obtained after implementing a planar
coordinate transformation on a 5D Ricci-flat metric solution, in the context of
a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is
nearly scale invariant under certain conditions. One interesting aspect of this
model is that is possible to derive dynamical field equations for the tensor
metric fluctuations, valid not just at cosmological scales, but also at
astrophysical scales, from the same theoretical model. The astrophysical and
cosmological scales are determined by the gravity- antigravity radius, which is
a natural length scale of the model, that indicates when gravity becomes
repulsive in nature.
| [
{
"created": "Sun, 26 Aug 2012 23:33:42 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Sep 2012 16:41:17 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Reyes",
"Luz Marina",
"",
"Departamento de Matemáticas, CUCEI, Universidad de Guadalajara"
],
[
"Moreno",
"Claudia",
"",
"Departamento de Matemáticas, CUCEI, Universidad de Guadalajara"
],
[
"Aguilar",
"José Edgar Madriz",
"",
"Departamento de Matemáticas, CUCEI, Universidad de Guadalajara"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR, Universidad Nacional de Mar del Plata and CONICET"
]
] | We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during an early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de-Sitter metric, which is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that is possible to derive dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity- antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature. |
1412.5482 | Yu Zhang | En-Kun Li, Yu Zhang, and Jin-Ling Geng | Modified holographic Ricci dark energy coupled to interacting
relativistic and non-relativistic dark matter in the nonflat universe | 14 pages, 8 figures | Phys. Rev. D 90, 083534 (2014) | 10.1103/PhysRevD.90.083534 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The modified holographic Ricci dark energy coupled to interacting
relativistic and non-relativistic dark matter is considered in the nonflat
Friedmann-Robertson-Walker universe. Through examining the deceleration
parameter, one can find that the transition time of the Universe from
decelerating to accelerating phase in the interacting holographic Ricci dark
energy model is close to that in the $\Lambda$ cold dark matter model. The
evolution of modified holographic Ricci dark energy's state parameter and the
evolution of dark matter and dark energy's densities shows that the dark energy
holds the dominant position from the near past to the future. By studying the
statefinder diagnostic and the evolution of the total pressure, one can find
that this model could explain the Universe's transition from the radiation to
accelerating expansion stage through the dust stage. According to the $Om$
diagnostic, it is easy to find that when the interaction is weak and the
proportion of relativistic dark matter in total dark matter is small, this
model is phantom-like. Through our studying, we find the interaction and the
relativistic dark matter's proportion all have great influence on the evolution
of the Universe.
| [
{
"created": "Tue, 16 Dec 2014 13:45:48 GMT",
"version": "v1"
}
] | 2014-12-18 | [
[
"Li",
"En-Kun",
""
],
[
"Zhang",
"Yu",
""
],
[
"Geng",
"Jin-Ling",
""
]
] | The modified holographic Ricci dark energy coupled to interacting relativistic and non-relativistic dark matter is considered in the nonflat Friedmann-Robertson-Walker universe. Through examining the deceleration parameter, one can find that the transition time of the Universe from decelerating to accelerating phase in the interacting holographic Ricci dark energy model is close to that in the $\Lambda$ cold dark matter model. The evolution of modified holographic Ricci dark energy's state parameter and the evolution of dark matter and dark energy's densities shows that the dark energy holds the dominant position from the near past to the future. By studying the statefinder diagnostic and the evolution of the total pressure, one can find that this model could explain the Universe's transition from the radiation to accelerating expansion stage through the dust stage. According to the $Om$ diagnostic, it is easy to find that when the interaction is weak and the proportion of relativistic dark matter in total dark matter is small, this model is phantom-like. Through our studying, we find the interaction and the relativistic dark matter's proportion all have great influence on the evolution of the Universe. |
2110.01879 | Koustav Chandra | Koustav Chandra, Archana Pai, V. Villa-Ortega, T. Dent, C. McIsaac, I.
W. Harry, G. S. Cabourn Davies and K. Soni | Salient features of the optimised PyCBC IMBH search | 9 pages, Conference proceedings of Sixteenth Marcel Grossmann Meeting
- MG16 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Matched-filter based PyCBC searches have successfully detected $\sim
\mathcal{O}(50)$ compact binary merger signals in the LIGO-Virgo data. While
most PyCBC searches have been designed to detect stellar-mass binaries, we
present here a new search that is optimised to detect short-duration \ac{GW}
signals emitted by intermediate-mass black hole mergers. When applied to the
first half of the third observation run data, the optimised search
re-identified the \ac{IMBH} binary event, GW190521, with a false alarm rate of
1 in 727 yrs, significantly lower than the previous PyCBC search result of 1 in
0.94 yr. Analysis of simulated signals from \ac{IMBH} binaries with generically
spinning components shows an increase in sensitivity by a factor of 1.2 to 3
over previous PyCBC searches.
| [
{
"created": "Tue, 5 Oct 2021 08:47:21 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Oct 2021 05:19:24 GMT",
"version": "v2"
}
] | 2021-10-07 | [
[
"Chandra",
"Koustav",
""
],
[
"Pai",
"Archana",
""
],
[
"Villa-Ortega",
"V.",
""
],
[
"Dent",
"T.",
""
],
[
"McIsaac",
"C.",
""
],
[
"Harry",
"I. W.",
""
],
[
"Davies",
"G. S. Cabourn",
""
],
[
"Soni",
"K.",
""
]
] | Matched-filter based PyCBC searches have successfully detected $\sim \mathcal{O}(50)$ compact binary merger signals in the LIGO-Virgo data. While most PyCBC searches have been designed to detect stellar-mass binaries, we present here a new search that is optimised to detect short-duration \ac{GW} signals emitted by intermediate-mass black hole mergers. When applied to the first half of the third observation run data, the optimised search re-identified the \ac{IMBH} binary event, GW190521, with a false alarm rate of 1 in 727 yrs, significantly lower than the previous PyCBC search result of 1 in 0.94 yr. Analysis of simulated signals from \ac{IMBH} binaries with generically spinning components shows an increase in sensitivity by a factor of 1.2 to 3 over previous PyCBC searches. |
1510.08828 | Simone Speziale | Tommaso De Lorenzo, Andrea Giusti, Simone Speziale | Non-singular rotating black hole with a time delay in the center | 15 pages, many figures; v2: updated references | General Relativity and Gravitation 48 (March 2016) | 10.1007/s10714-016-2026-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As proposed by Bambi and Modesto, rotating non-singular black holes can be
constructed via the Newman-Janis algorithm. Here we show that if one starts
with a modified Hayward black hole with a time delay in the centre, the
algorithm succeeds in producing a rotating metric, but curvature divergences
reappear. To preserve finiteness, the time delay must be introduced directly at
the level of the non-singular rotating metric. This is possible thanks to the
deformation of the inner stationarity limit surface caused by the
regularisation, and in more than one way. We outline three different
possibilities, distinguished by the angular velocity of the event horizon.
Along the way, we provide additional results on the Bambi-Modesto rotating
Hayward metric, such as the structure of the regularisation occurring at the
centre, the behaviour of the quantum gravity scale alike an electric charge in
decreasing the angular momentum of the extremal black hole configuration, or
details on the deformation of the ergosphere.
| [
{
"created": "Thu, 29 Oct 2015 19:23:38 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2016 09:07:36 GMT",
"version": "v2"
}
] | 2017-09-06 | [
[
"De Lorenzo",
"Tommaso",
""
],
[
"Giusti",
"Andrea",
""
],
[
"Speziale",
"Simone",
""
]
] | As proposed by Bambi and Modesto, rotating non-singular black holes can be constructed via the Newman-Janis algorithm. Here we show that if one starts with a modified Hayward black hole with a time delay in the centre, the algorithm succeeds in producing a rotating metric, but curvature divergences reappear. To preserve finiteness, the time delay must be introduced directly at the level of the non-singular rotating metric. This is possible thanks to the deformation of the inner stationarity limit surface caused by the regularisation, and in more than one way. We outline three different possibilities, distinguished by the angular velocity of the event horizon. Along the way, we provide additional results on the Bambi-Modesto rotating Hayward metric, such as the structure of the regularisation occurring at the centre, the behaviour of the quantum gravity scale alike an electric charge in decreasing the angular momentum of the extremal black hole configuration, or details on the deformation of the ergosphere. |
1401.0714 | Sharmanthie Fernando | Sharmanthie Fernando | Cold, ultracold and Nariai black holes with quintessence | 22 pages and 18 figures | General Relativity and Gravitation (45) 2053 (2013) | 10.1007/s10714-013-1578-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the properties of the charged black hole surrounded
by the quintessence. The solution space for the horizons for various values of
the mass $M$, charge $Q$, and the quintessence parameter $\alpha$ are studied
in detail. Special focus in given to the degenerate horizons: we obtain cold,
ultracold and Nariai black holes which has similar topologies as for the
Reissner-Nordstrom-de Sitter black holes. We also study the lukewarm black hole
with the quintessence in this paper.
| [
{
"created": "Fri, 3 Jan 2014 20:46:46 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Fernando",
"Sharmanthie",
""
]
] | In this paper, we study the properties of the charged black hole surrounded by the quintessence. The solution space for the horizons for various values of the mass $M$, charge $Q$, and the quintessence parameter $\alpha$ are studied in detail. Special focus in given to the degenerate horizons: we obtain cold, ultracold and Nariai black holes which has similar topologies as for the Reissner-Nordstrom-de Sitter black holes. We also study the lukewarm black hole with the quintessence in this paper. |
1204.3455 | Hubert F M Goenner | Hubert Goenner | Some remarks on the genesis of scalar-tensor theories | 24 pages | null | 10.1007/s10714-012-1378-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Between 1941 and 1962, scalar-tensor theories of gravitation were suggested
four times by different scientists in four different countries. The earliest
originator, the Swiss mathematician W. Scherrer, was virtually unknown until
now whereas the chronologically latest pair gave their names to a multitude of
publications on Brans-Dicke theory. P. Jordan, one of the pioneers of quantum
mechanics theory, and Y. Thiry, a student of the mathematician A. Lichnerowicz,
known by his book on celestial mechanics, complete the quartet. Diverse
motivations for and conceptual interpretations of their theories will be
discussed as well as relations among them. Also, external factors like
language, citation habits, or closeness to the mainstream are considered. It
will become clear why Brans-Dicke theory, although structurally a d\'ej\`a-vu,
superseded all the other approaches.
| [
{
"created": "Mon, 16 Apr 2012 11:47:19 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Goenner",
"Hubert",
""
]
] | Between 1941 and 1962, scalar-tensor theories of gravitation were suggested four times by different scientists in four different countries. The earliest originator, the Swiss mathematician W. Scherrer, was virtually unknown until now whereas the chronologically latest pair gave their names to a multitude of publications on Brans-Dicke theory. P. Jordan, one of the pioneers of quantum mechanics theory, and Y. Thiry, a student of the mathematician A. Lichnerowicz, known by his book on celestial mechanics, complete the quartet. Diverse motivations for and conceptual interpretations of their theories will be discussed as well as relations among them. Also, external factors like language, citation habits, or closeness to the mainstream are considered. It will become clear why Brans-Dicke theory, although structurally a d\'ej\`a-vu, superseded all the other approaches. |
gr-qc/0507003 | Bahtiyar Ozgur Sarioglu | Serkay Olmez, Ozgur Sarioglu, Bayram Tekin | Mass and angular momentum of asymptotically AdS or flat solutions in the
topologically massive gravity | REVTEX4, 8 pages, no figures, added 2 references and a few clarifying
remarks | Class.Quant.Grav. 22 (2005) 4355-4362 | 10.1088/0264-9381/22/20/014 | null | gr-qc hep-th | null | We study the conserved charges of supersymmetric solutions in the
topologically massive gravity theory for both asymptotically flat and constant
curvature geometries.
| [
{
"created": "Fri, 1 Jul 2005 12:06:53 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jul 2005 07:24:49 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Sep 2005 14:19:37 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Olmez",
"Serkay",
""
],
[
"Sarioglu",
"Ozgur",
""
],
[
"Tekin",
"Bayram",
""
]
] | We study the conserved charges of supersymmetric solutions in the topologically massive gravity theory for both asymptotically flat and constant curvature geometries. |
gr-qc/9507036 | Hideo Kodama | Hideo Kodama | Dynamics of Totally Constrained Systems I. Classical Theory | 31 pages, LaTeX file | Prog.Theor.Phys. 94 (1995) 475-502 | 10.1143/PTP.94.475 | YITP/U-95-18 | gr-qc | null | This is the first of a series of papers in which a new formulation of quantum
theory is developed for totally constrained systems, that is, canonical systems
in which the hamiltonian is written as a linear combination of constraints
$h_\alpha$ with arbitrary coefficients. The main purpose of the present paper
is to make clear that classical dynamics of a totally constrained system is
nothing but the foliation of the constraint submanifold in phase space by the
involutive system of infinitesimal canonical transformations $Y_\alpha$
generated by the constraint functions. From this point of view it is shown that
statistical dynamics for an ensemble of a totally constrained system can be
formulated in terms of a relative distribution function without gauge fixing or
reduction. There the key role is played by the fact that the canonical measure
in phase space and the vector fields $Y_\alpha$ induce natural conservative
measures on acausal submanifolds, which are submanifolds transversal to the
dynamical foliation. Further it is shown that the structure coefficients
$c^\gamma_{\alpha\beta}$ defined by $\{h_\alpha,h_\beta\}=\sum_\gamma
c^\gamma_{\alpha\beta}h_\gamma$ should weakly commute with $h_\alpha$,
$\sum_\gamma\{h_\gamma,c^\gamma_{\alpha\beta}\}\approx0$, in order that the
description in terms of the relative distribution function is consistent. The
overall picture on the classical dynamics given in this paper provides the
basic motivation for the quantum formulation developed in the subsequent
papers.
| [
{
"created": "Mon, 17 Jul 1995 11:05:27 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Kodama",
"Hideo",
""
]
] | This is the first of a series of papers in which a new formulation of quantum theory is developed for totally constrained systems, that is, canonical systems in which the hamiltonian is written as a linear combination of constraints $h_\alpha$ with arbitrary coefficients. The main purpose of the present paper is to make clear that classical dynamics of a totally constrained system is nothing but the foliation of the constraint submanifold in phase space by the involutive system of infinitesimal canonical transformations $Y_\alpha$ generated by the constraint functions. From this point of view it is shown that statistical dynamics for an ensemble of a totally constrained system can be formulated in terms of a relative distribution function without gauge fixing or reduction. There the key role is played by the fact that the canonical measure in phase space and the vector fields $Y_\alpha$ induce natural conservative measures on acausal submanifolds, which are submanifolds transversal to the dynamical foliation. Further it is shown that the structure coefficients $c^\gamma_{\alpha\beta}$ defined by $\{h_\alpha,h_\beta\}=\sum_\gamma c^\gamma_{\alpha\beta}h_\gamma$ should weakly commute with $h_\alpha$, $\sum_\gamma\{h_\gamma,c^\gamma_{\alpha\beta}\}\approx0$, in order that the description in terms of the relative distribution function is consistent. The overall picture on the classical dynamics given in this paper provides the basic motivation for the quantum formulation developed in the subsequent papers. |
1706.01244 | Kimet Jusufi | Kimet Jusufi | Deflection Angle of Light by Wormholes using the Gauss-Bonnet Theorem | Accepted for publication in International Journal of Geometric
Methods in Modern Physics | Int. J. Geom. Methods Mod. Phys. Vol. 14 (2017) 1750179 | 10.1142/S0219887817501791 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we have investigated the deflection angle of light by
wormholes using a new geometrical method known as Gibbons-Werner method (GW).
In particular we have calculated the deflection angle of light in the weak
limit approximation in two wormhole spacetime geometries: Ellis wormhole and
Janis-Newman-Winnicour (JNW) wormhole. We have employed the famous Gauss-Bonnet
theorem (GBT) to the Ellis wormhole optical geometry and JNW wormhole optical
geometry, respectively. By using GBT, we computed the deflection angles in
leading orders by these wormholes and our results were compared with the ones
in the literature.
| [
{
"created": "Mon, 5 Jun 2017 09:08:41 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Aug 2017 15:45:41 GMT",
"version": "v2"
}
] | 2017-08-22 | [
[
"Jusufi",
"Kimet",
""
]
] | In this letter, we have investigated the deflection angle of light by wormholes using a new geometrical method known as Gibbons-Werner method (GW). In particular we have calculated the deflection angle of light in the weak limit approximation in two wormhole spacetime geometries: Ellis wormhole and Janis-Newman-Winnicour (JNW) wormhole. We have employed the famous Gauss-Bonnet theorem (GBT) to the Ellis wormhole optical geometry and JNW wormhole optical geometry, respectively. By using GBT, we computed the deflection angles in leading orders by these wormholes and our results were compared with the ones in the literature. |
0911.4583 | Brett McInnes | Brett McInnes | Decoupling Inflation From the String Scale | 24 pages, 5 eps figures, references added, stylistic changes, version
to appear in Classical and Quantum Gravity | Class.Quant.Grav.27:165001,2010 | 10.1088/0264-9381/27/16/165001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When Inflation is embedded in a fundamental theory, such as string theory, it
typically begins when the Universe is already substantially larger than the
fundamental scale [such as the one defined by the string length scale]. This is
naturally explained by postulating a pre-inflationary era, during which the
size of the Universe grew from the fundamental scale to the initial
inflationary scale. The problem then arises of maintaining the [presumed]
initial spatial homogeneity throughout this era, so that, when it terminates,
Inflation is able to begin in its potential-dominated state. Linde has proposed
that a spacetime with compact negatively curved spatial sections can achieve
this, by means of chaotic mixing. Such a compactification will however lead to
a Casimir energy, which can lead to effects that defeat the purpose unless the
coupling to gravity is suppressed. We estimate the value of this coupling
required by the proposal, and use it to show that the pre-inflationary
spacetime is stable, despite the violation of the Null Energy Condition
entailed by the Casimir energy.
| [
{
"created": "Tue, 24 Nov 2009 09:39:51 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2010 04:27:07 GMT",
"version": "v2"
}
] | 2010-09-03 | [
[
"McInnes",
"Brett",
""
]
] | When Inflation is embedded in a fundamental theory, such as string theory, it typically begins when the Universe is already substantially larger than the fundamental scale [such as the one defined by the string length scale]. This is naturally explained by postulating a pre-inflationary era, during which the size of the Universe grew from the fundamental scale to the initial inflationary scale. The problem then arises of maintaining the [presumed] initial spatial homogeneity throughout this era, so that, when it terminates, Inflation is able to begin in its potential-dominated state. Linde has proposed that a spacetime with compact negatively curved spatial sections can achieve this, by means of chaotic mixing. Such a compactification will however lead to a Casimir energy, which can lead to effects that defeat the purpose unless the coupling to gravity is suppressed. We estimate the value of this coupling required by the proposal, and use it to show that the pre-inflationary spacetime is stable, despite the violation of the Null Energy Condition entailed by the Casimir energy. |
1703.10391 | Mercedes Martin-Benito | Beatriz Elizaga Navascu\'es, Mercedes Mart\'in-Benito and Guillermo A.
Mena Marug\'an | Fermions in Hybrid Loop Quantum Cosmology | 29 pages. It matches published version | Phys. Rev. D 96, 044023 (2017) | 10.1103/PhysRevD.96.044023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work pioneers the quantization of primordial fermion perturbations in
hybrid Loop Quantum Cosmology (LQC). We consider a Dirac field coupled to a
spatially flat, homogeneous, and isotropic cosmology, sourced by a scalar
inflaton, and treat the Dirac field as a perturbation. We describe the
inhomogeneities of this field in terms of creation and annihilation variables,
chosen to admit a unitary evolution if the Dirac fermion were treated as a test
field. Considering instead the full system, we truncate its action at quadratic
perturbative order and construct a canonical formulation. In particular this
implies that, in the global Hamiltonian constraint of the model, the
contribution of the homogeneous sector is corrected with a quadratic
perturbative term. We then adopt the hybrid LQC approach to quantize the full
model, combining the loop representation of the homogeneous geometry with the
Fock quantization of the inhomogeneities. We assume a Born-Oppenheimer ansatz
for physical states and show how to obtain a Schr\"odinger equation for the
quantum evolution of the perturbations, where the role of time is played by the
homogeneous inflaton. We prove that the resulting quantum evolution of the
Dirac field is indeed unitary, despite the fact that the underlying homogeneous
geometry has been quantized as well. Remarkably, in such evolution, the fermion
field couples to an infinite sequence of quantum moments of the homogeneous
geometry. Moreover, the evolved Fock vacuum of our fermion perturbations is
shown to be an exact solution of the Schr\"odinger equation. Finally, we
discuss in detail the quantum backreaction that the fermion field introduces in
the global Hamiltonian constraint. For completeness, our quantum study includes
since the beginning (gauge-invariant) scalar and tensor perturbations, that
were studied in previous works.
| [
{
"created": "Thu, 30 Mar 2017 10:31:21 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Sep 2017 11:44:01 GMT",
"version": "v2"
}
] | 2017-09-08 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Martín-Benito",
"Mercedes",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | This work pioneers the quantization of primordial fermion perturbations in hybrid Loop Quantum Cosmology (LQC). We consider a Dirac field coupled to a spatially flat, homogeneous, and isotropic cosmology, sourced by a scalar inflaton, and treat the Dirac field as a perturbation. We describe the inhomogeneities of this field in terms of creation and annihilation variables, chosen to admit a unitary evolution if the Dirac fermion were treated as a test field. Considering instead the full system, we truncate its action at quadratic perturbative order and construct a canonical formulation. In particular this implies that, in the global Hamiltonian constraint of the model, the contribution of the homogeneous sector is corrected with a quadratic perturbative term. We then adopt the hybrid LQC approach to quantize the full model, combining the loop representation of the homogeneous geometry with the Fock quantization of the inhomogeneities. We assume a Born-Oppenheimer ansatz for physical states and show how to obtain a Schr\"odinger equation for the quantum evolution of the perturbations, where the role of time is played by the homogeneous inflaton. We prove that the resulting quantum evolution of the Dirac field is indeed unitary, despite the fact that the underlying homogeneous geometry has been quantized as well. Remarkably, in such evolution, the fermion field couples to an infinite sequence of quantum moments of the homogeneous geometry. Moreover, the evolved Fock vacuum of our fermion perturbations is shown to be an exact solution of the Schr\"odinger equation. Finally, we discuss in detail the quantum backreaction that the fermion field introduces in the global Hamiltonian constraint. For completeness, our quantum study includes since the beginning (gauge-invariant) scalar and tensor perturbations, that were studied in previous works. |
1911.04723 | Guang-Zhen Kang | Guang-Zhen Kang, De-Sheng Zhang, Long Du, Dan Shan and Hong-Shi Zong | Cosmic Acceleration Caused by the Extra-Dimensional Evolution in a
Generalized Randall-Sundrum Model | 7 pages, 3 figures | null | 10.1088/1674-1137/abadec | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a $(n+1)$-dimensional generalized Randall-Sundrum model with
an anisotropic metric which has three different scale factors. One obtain a
positive effective cosmological constant $\Omega_{eff}\sim10^{-124}$ (in Planck
unit) which only need a solution $kr\simeq50-80$ without fine tuning, and both
the visible and hidden brane tensions are positive which results in the two
branes to be stable. Then, we find that the Hubble parameter is seem to be a
constant in a large region near its minimum, thus causing the acceleration of
the universe. Therefore, the fine tuning problem also can be solved in this
model. Meanwhile, the scale of extra dimensions is smaller than the observed
scale but greater than the Planck length. This demonstrates that the observed
present acceleration of the universe is caused by the extra-dimensional
evolution rather than dark energy.
| [
{
"created": "Tue, 12 Nov 2019 07:58:31 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Kang",
"Guang-Zhen",
""
],
[
"Zhang",
"De-Sheng",
""
],
[
"Du",
"Long",
""
],
[
"Shan",
"Dan",
""
],
[
"Zong",
"Hong-Shi",
""
]
] | We investigate a $(n+1)$-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors. One obtain a positive effective cosmological constant $\Omega_{eff}\sim10^{-124}$ (in Planck unit) which only need a solution $kr\simeq50-80$ without fine tuning, and both the visible and hidden brane tensions are positive which results in the two branes to be stable. Then, we find that the Hubble parameter is seem to be a constant in a large region near its minimum, thus causing the acceleration of the universe. Therefore, the fine tuning problem also can be solved in this model. Meanwhile, the scale of extra dimensions is smaller than the observed scale but greater than the Planck length. This demonstrates that the observed present acceleration of the universe is caused by the extra-dimensional evolution rather than dark energy. |
1710.03827 | Gil de Oliveira-Neto | G. Oliveira-Neto, L. G. Martins, G. A. Monerat and E. V. Corr\^ea
Silva | DeBroglie-Bohm interpretation of a Ho\v{r}ava-Lifshitz quantum cosmology
model | 12 pages and 2 figures | Mod. Phys. Lett. A, Vol. 33, No. 2 (2018) 1850014 | 10.1142/S0217732318500141 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present letter, we consider the DeBroglie-Bohm interpretation of a
Ho\v{r}ava-Lifshitz quantum cosmology model in the presence of a radiation
perfect fluid. We compute the Bohm's trajectories for the scale factor and show
that it never goes to zero. That result gives a strong indication that this
model is free from singularities, at the quantum level. We also compute the
quantum potential. That quantity helps understanding why the scale factor never
vanishes.
| [
{
"created": "Tue, 10 Oct 2017 21:23:07 GMT",
"version": "v1"
}
] | 2018-01-17 | [
[
"Oliveira-Neto",
"G.",
""
],
[
"Martins",
"L. G.",
""
],
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
]
] | In the present letter, we consider the DeBroglie-Bohm interpretation of a Ho\v{r}ava-Lifshitz quantum cosmology model in the presence of a radiation perfect fluid. We compute the Bohm's trajectories for the scale factor and show that it never goes to zero. That result gives a strong indication that this model is free from singularities, at the quantum level. We also compute the quantum potential. That quantity helps understanding why the scale factor never vanishes. |
gr-qc/0512030 | Joan Sola | Joan Sola | Cosmology with running parameters | Talk given at TAUP 2005, Zaragoza, Spain, 10-14 Sep 2005 | J.Phys.Conf.Ser. 39 (2006) 179 | 10.1088/1742-6596/39/1/044 | null | gr-qc astro-ph hep-ph hep-th | null | The experimental evidence that the equation of state (EOS) of the dark energy
(DE) could be evolving with time/redshift (including the possibility that it
might behave phantom-like near our time) suggests that there might be dynamical
DE fields that could explain this behavior. We propose, instead, that a
variable cosmological term (including perhaps a variable Newton's gravitational
coupling too) may account in a natural way for all these features.
| [
{
"created": "Mon, 5 Dec 2005 20:32:56 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sola",
"Joan",
""
]
] | The experimental evidence that the equation of state (EOS) of the dark energy (DE) could be evolving with time/redshift (including the possibility that it might behave phantom-like near our time) suggests that there might be dynamical DE fields that could explain this behavior. We propose, instead, that a variable cosmological term (including perhaps a variable Newton's gravitational coupling too) may account in a natural way for all these features. |
2012.11536 | Daniele Oriti | Marco Finocchiaro, Yoobin Jeong, Daniele Oriti | Quantum geometric maps and their properties | 26 pages | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum geometric maps, which relate SU(2) spin networks and Lorentz
covariant projected spin networks, are an important ingredient of spin foam
models (and tensorial group field theories) for 4-dimensional quantum gravity.
We give a general definition of such maps, that encompasses all current spin
foam models, and we investigate their properties at such a general level. We
then specialize the definition to see how the precise implementation of
simplicity constraints affects features of the quantum geometric maps in
specific models.
| [
{
"created": "Mon, 21 Dec 2020 17:56:33 GMT",
"version": "v1"
}
] | 2020-12-22 | [
[
"Finocchiaro",
"Marco",
""
],
[
"Jeong",
"Yoobin",
""
],
[
"Oriti",
"Daniele",
""
]
] | Quantum geometric maps, which relate SU(2) spin networks and Lorentz covariant projected spin networks, are an important ingredient of spin foam models (and tensorial group field theories) for 4-dimensional quantum gravity. We give a general definition of such maps, that encompasses all current spin foam models, and we investigate their properties at such a general level. We then specialize the definition to see how the precise implementation of simplicity constraints affects features of the quantum geometric maps in specific models. |
gr-qc/9410023 | Ted Jacobson | Ted Jacobson and Shankar Venkataramani | Topology of Event Horizons and Topological Censorship | 11 pages, plain latex (minor revision: $\Sigma$ replaced by its
closure in various places.) | Class.Quant.Grav.12:1055-1062,1995 | 10.1088/0264-9381/12/4/012 | UMDGR-95-019 | gr-qc hep-th | null | We prove that, under certain conditions, the topology of the event horizon of
a four dimensional asymptotically flat black hole spacetime must be a 2-sphere.
No stationarity assumption is made. However, in order for the theorem to apply,
the horizon topology must be unchanging for long enough to admit a certain kind
of cross section. We expect this condition is generically satisfied if the
topology is unchanging for much longer than the light-crossing time of the
black hole. More precisely, let $M$ be a four dimensional asymptotically flat
spacetime satisfying the averaged null energy condition, and suppose that the
domain of outer communication $\C_K$ to the future of a cut $K$ of $\Sm$ is
globally hyperbolic. Suppose further that a Cauchy surface $\Sigma$ for $\C_K$
is a topological 3-manifold with compact boundary $\partial\S$ in $M$, and
$\S'$ is a compact submanifold of $\bS$ with spherical boundary in $\S$ (and
possibly other boundary components in $M/\S$). Then we prove that the homology
group $H_1(\Sigma',Z)$ must be finite. This implies that either $\partial\S'$
consists of a disjoint union of 2-spheres, or $\S'$ is nonorientable and
$\partial\S'$ contains a projective plane. Further,
$\partial\S=\partial\Ip[K]\cap\partial\Im[\Sp]$, and $\partial \Sigma$ will be
a cross section of the horizon as long as no generator of $\partial\Ip[K]$
becomes a generator of $\partial\Im[\Sp]$. In this case, if $\S$ is orientable,
the horizon cross section must consist of a disjoint union of 2-spheres.}
| [
{
"created": "Tue, 18 Oct 1994 04:26:56 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 1994 20:23:53 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Jacobson",
"Ted",
""
],
[
"Venkataramani",
"Shankar",
""
]
] | We prove that, under certain conditions, the topology of the event horizon of a four dimensional asymptotically flat black hole spacetime must be a 2-sphere. No stationarity assumption is made. However, in order for the theorem to apply, the horizon topology must be unchanging for long enough to admit a certain kind of cross section. We expect this condition is generically satisfied if the topology is unchanging for much longer than the light-crossing time of the black hole. More precisely, let $M$ be a four dimensional asymptotically flat spacetime satisfying the averaged null energy condition, and suppose that the domain of outer communication $\C_K$ to the future of a cut $K$ of $\Sm$ is globally hyperbolic. Suppose further that a Cauchy surface $\Sigma$ for $\C_K$ is a topological 3-manifold with compact boundary $\partial\S$ in $M$, and $\S'$ is a compact submanifold of $\bS$ with spherical boundary in $\S$ (and possibly other boundary components in $M/\S$). Then we prove that the homology group $H_1(\Sigma',Z)$ must be finite. This implies that either $\partial\S'$ consists of a disjoint union of 2-spheres, or $\S'$ is nonorientable and $\partial\S'$ contains a projective plane. Further, $\partial\S=\partial\Ip[K]\cap\partial\Im[\Sp]$, and $\partial \Sigma$ will be a cross section of the horizon as long as no generator of $\partial\Ip[K]$ becomes a generator of $\partial\Im[\Sp]$. In this case, if $\S$ is orientable, the horizon cross section must consist of a disjoint union of 2-spheres.} |
1310.6858 | Giovanni Acquaviva | Giovanni Acquaviva | Tunnelling methods and Unruh-DeWitt detectors in curved spacetimes | Contribution for the Proceedings of the Karl Schwarzschild Meeting
2013 (Frankfurt, July 22-26 2013) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this contribution we describe some interesting interplay between quantum
theory, general relativity and thermodynamics. In order to highlight the
connection between these theories, we describe two approaches that allow to
calculate thermal features as perceived by different observers in curved
spacetimes: the tunnelling method and the Unruh-DeWitt detector. In this
context, the semi-classical tunnelling approach is applied to the issue of
Hawking radiation and allows the calculation of the horizon temperature in a
wide variety of scenarios. The Unruh-DeWitt model is instead a quantum
field-theoretical approach that should give a more exact answer in terms of
transition rates between energy levels of an idealized detector.
| [
{
"created": "Fri, 25 Oct 2013 09:23:43 GMT",
"version": "v1"
}
] | 2013-10-28 | [
[
"Acquaviva",
"Giovanni",
""
]
] | In this contribution we describe some interesting interplay between quantum theory, general relativity and thermodynamics. In order to highlight the connection between these theories, we describe two approaches that allow to calculate thermal features as perceived by different observers in curved spacetimes: the tunnelling method and the Unruh-DeWitt detector. In this context, the semi-classical tunnelling approach is applied to the issue of Hawking radiation and allows the calculation of the horizon temperature in a wide variety of scenarios. The Unruh-DeWitt model is instead a quantum field-theoretical approach that should give a more exact answer in terms of transition rates between energy levels of an idealized detector. |
1408.4945 | Andrea Geralico | Donato Bini, Andrea Geralico, Robert T. Jantzen, Oldrich Semer\'ak,
Luigi Stella | The general relativistic Poynting-Robertson effect. II: A photon flux
with nonzero angular momentum | 22 pages, 4 figures; published version | Class. Quantum Grav. 28, 035008 (2011) | 10.1088/0264-9381/28/3/035008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the motion of a test particle in a stationary, axially and
reflection symmetric spacetime of a central compact object, as affected by
interaction with a test radiation field of the same symmetries. Considering the
radiation flux with fixed but arbitrary (non-zero) angular momentum, we extend
previous results limited to an equatorial motion within a zero-angular-momentum
photon flux in the Kerr and Schwarzschild backgrounds. While a unique
equilibrium circular orbit exists if the photon flux has zero angular momentum,
multiple such orbits appear if the photon angular momentum is sufficiently
high.
| [
{
"created": "Thu, 21 Aug 2014 10:44:51 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Jantzen",
"Robert T.",
""
],
[
"Semerák",
"Oldrich",
""
],
[
"Stella",
"Luigi",
""
]
] | We study the motion of a test particle in a stationary, axially and reflection symmetric spacetime of a central compact object, as affected by interaction with a test radiation field of the same symmetries. Considering the radiation flux with fixed but arbitrary (non-zero) angular momentum, we extend previous results limited to an equatorial motion within a zero-angular-momentum photon flux in the Kerr and Schwarzschild backgrounds. While a unique equilibrium circular orbit exists if the photon flux has zero angular momentum, multiple such orbits appear if the photon angular momentum is sufficiently high. |
gr-qc/0502067 | Mark Hannam | Mark D. Hannam, Gregory B. Cook | Conformal thin-sandwich puncture initial data for boosted black holes | 12 pages, 11 figures | Phys.Rev. D71 (2005) 084023 | 10.1103/PhysRevD.71.084023 | null | gr-qc | null | We apply the puncture approach to conformal thin-sandwich black-hole initial
data. We solve numerically the conformal thin-sandwich puncture (CTSP)
equations for a single black hole with non-zero linear momentum. We show that
conformally flat solutions for a boosted black hole have the same maximum
gravitational radiation content as the corresponding Bowen-York solution in the
conformal transverse-traceless decomposition. We find that the physical
properties of these data are independent of the free slicing parameter.
| [
{
"created": "Mon, 14 Feb 2005 18:38:31 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2005 22:11:57 GMT",
"version": "v2"
},
{
"created": "Mon, 23 May 2005 20:11:19 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Hannam",
"Mark D.",
""
],
[
"Cook",
"Gregory B.",
""
]
] | We apply the puncture approach to conformal thin-sandwich black-hole initial data. We solve numerically the conformal thin-sandwich puncture (CTSP) equations for a single black hole with non-zero linear momentum. We show that conformally flat solutions for a boosted black hole have the same maximum gravitational radiation content as the corresponding Bowen-York solution in the conformal transverse-traceless decomposition. We find that the physical properties of these data are independent of the free slicing parameter. |
2302.05413 | Antonio Enea Romano | Antonio Enea Romano, Mairi Sakellariadou | The mirage of luminal modified gravitational-wave propagation | Version accepted in Phys. Rev. Lett | Phys. Rev. Lett. 130, 231401, 2023 | 10.1103/PhysRevLett.130.231401 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Using conformal invariance of gravitational waves, we show that for a luminal
modified gravity theory, the gravitational-wave propagation and luminosity
distance are the same as in general relativity. The relation between the
gravitational-wave and electromagnetic-wave luminosity distance gets however
modified for electromagnetism minimally coupled to the Jordan frame metric.
Using effective field theory we show that the modified relation obtained for
luminal theories is also valid for non-luminal theories with Jordan frame
matter-gravity coupling.We generalise our analysis to a time-dependent speed of
gravitational waves with matter minimally coupled to either the Jordan or
Einstein frame metrics.
| [
{
"created": "Fri, 10 Feb 2023 18:29:06 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2023 17:15:18 GMT",
"version": "v2"
},
{
"created": "Sat, 10 Jun 2023 15:22:33 GMT",
"version": "v3"
}
] | 2023-12-08 | [
[
"Romano",
"Antonio Enea",
""
],
[
"Sakellariadou",
"Mairi",
""
]
] | Using conformal invariance of gravitational waves, we show that for a luminal modified gravity theory, the gravitational-wave propagation and luminosity distance are the same as in general relativity. The relation between the gravitational-wave and electromagnetic-wave luminosity distance gets however modified for electromagnetism minimally coupled to the Jordan frame metric. Using effective field theory we show that the modified relation obtained for luminal theories is also valid for non-luminal theories with Jordan frame matter-gravity coupling.We generalise our analysis to a time-dependent speed of gravitational waves with matter minimally coupled to either the Jordan or Einstein frame metrics. |
1610.02636 | Zhong-Ying Fan | Zhong-Ying Fan and Xiaobao Wang | Construction of Regular Black Holes in General Relativity | 18 pages,1 figure;minor corrections, references added,published
version | Phys. Rev. D 94, 124027 (2016) | 10.1103/PhysRevD.94.124027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general procedure for constructing exact black hole solutions
with electric or magnetic charges in General Relativity coupled to a nonlinear
electrodynamics. We obtain a variety of two-parameter family spherically
symmetric black hole solutions. In particular, the singularity at the central
of the space-time can be cancelled in the parameters space and the black hole
solutions become regular everywhere in the space-time. We study the global
properties of the solutions and derive the first law of thermodynamics. We also
generalize the procedure to include a cosmological constant and construct
regular black hole solutions that are asymptotic to anti-de Sitter space-time.
| [
{
"created": "Sun, 9 Oct 2016 07:15:39 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Oct 2016 02:27:37 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Dec 2016 15:12:24 GMT",
"version": "v3"
}
] | 2016-12-28 | [
[
"Fan",
"Zhong-Ying",
""
],
[
"Wang",
"Xiaobao",
""
]
] | We present a general procedure for constructing exact black hole solutions with electric or magnetic charges in General Relativity coupled to a nonlinear electrodynamics. We obtain a variety of two-parameter family spherically symmetric black hole solutions. In particular, the singularity at the central of the space-time can be cancelled in the parameters space and the black hole solutions become regular everywhere in the space-time. We study the global properties of the solutions and derive the first law of thermodynamics. We also generalize the procedure to include a cosmological constant and construct regular black hole solutions that are asymptotic to anti-de Sitter space-time. |
0706.2621 | George Bogoslovsky | George Bogoslovsky | Some physical displays of the space anisotropy relevant to the
feasibility of its being detected at a laboratory | 11 pages, to appear in Proc. Int. Conf. "Physical Interpretations of
Relativity Theory" | null | null | null | gr-qc | null | The impact of local space anisotropy on the transverse Doppler effect is
examined. Two types of laboratory experiments aimed at seeking and measuring
the local space anisotropy are proposed. In terms of the conventional special
relativity theory, which treats 3D space to be locally isotropic, the
experiments are of the type of ``null-experiments''. In the first-type
experiments, a feasible Doppler shift of frequency is measured by the
M\"ossbauer effect, with the M\"ossbauer source and absorber being located at
two identical and diametrically opposed distances from the center of a rapidly
rotating rotor, while the $\gamma$-quanta are recorded by two stationary and
oppositely positioned proportional counters. Either of the counters records
only those $\gamma$-quanta that passed through the absorber at the moment of
the passage of the latter near a counter. The second-type experiments are made
using the latest radio physics techniques for generating monochromatic
oscillations and for recording weak signals. The effect expected due to space
anisotropy consists in frequency modulation of the harmonic oscillations coming
to a receiver that rotates at a constant velocity around the monochromatic wave
emitter. In this case the modulation depth proves to be proportional to the
space anisotropy magnitude.
| [
{
"created": "Mon, 18 Jun 2007 15:21:13 GMT",
"version": "v1"
}
] | 2007-06-19 | [
[
"Bogoslovsky",
"George",
""
]
] | The impact of local space anisotropy on the transverse Doppler effect is examined. Two types of laboratory experiments aimed at seeking and measuring the local space anisotropy are proposed. In terms of the conventional special relativity theory, which treats 3D space to be locally isotropic, the experiments are of the type of ``null-experiments''. In the first-type experiments, a feasible Doppler shift of frequency is measured by the M\"ossbauer effect, with the M\"ossbauer source and absorber being located at two identical and diametrically opposed distances from the center of a rapidly rotating rotor, while the $\gamma$-quanta are recorded by two stationary and oppositely positioned proportional counters. Either of the counters records only those $\gamma$-quanta that passed through the absorber at the moment of the passage of the latter near a counter. The second-type experiments are made using the latest radio physics techniques for generating monochromatic oscillations and for recording weak signals. The effect expected due to space anisotropy consists in frequency modulation of the harmonic oscillations coming to a receiver that rotates at a constant velocity around the monochromatic wave emitter. In this case the modulation depth proves to be proportional to the space anisotropy magnitude. |
1810.08550 | Daniel Litim | Kevin G. Falls, Daniel F. Litim, Jan Schr\"oder | Aspects of asymptotic safety for quantum gravity | 29 pages, 7 figures, v2: explanations added, to appear with PRD | Phys. Rev. D 99, 126015 (2019) | 10.1103/PhysRevD.99.126015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study fixed points of quantum gravity with renormalisation group methods,
and a procedure to remove convergence-limiting poles from the flow. The setup
is tested within the $f(R)$ approximation for gravity by solving exact
recursive relations up to order $R^{70}$ in the Ricci scalar, combined with
resummations and numerical integration. Results include fixed points, scaling
exponents, gap in the eigenvalue spectrum, dimensionality of the UV critical
surface, fingerprints for weak coupling, and quantum equations of motion. Our
findings strengthen the view that ``most of quantum gravity'' is rather weakly
coupled. Another novelty are a pair of de Sitter solutions for quantum
cosmology, whose occurrence is traced back to the removal of poles. We also
address slight disparities of results in the literature, and give bounds on the
number of fundamentally free parameters of quantum gravity.
| [
{
"created": "Fri, 19 Oct 2018 15:28:29 GMT",
"version": "v1"
},
{
"created": "Wed, 29 May 2019 17:13:54 GMT",
"version": "v2"
}
] | 2019-07-03 | [
[
"Falls",
"Kevin G.",
""
],
[
"Litim",
"Daniel F.",
""
],
[
"Schröder",
"Jan",
""
]
] | We study fixed points of quantum gravity with renormalisation group methods, and a procedure to remove convergence-limiting poles from the flow. The setup is tested within the $f(R)$ approximation for gravity by solving exact recursive relations up to order $R^{70}$ in the Ricci scalar, combined with resummations and numerical integration. Results include fixed points, scaling exponents, gap in the eigenvalue spectrum, dimensionality of the UV critical surface, fingerprints for weak coupling, and quantum equations of motion. Our findings strengthen the view that ``most of quantum gravity'' is rather weakly coupled. Another novelty are a pair of de Sitter solutions for quantum cosmology, whose occurrence is traced back to the removal of poles. We also address slight disparities of results in the literature, and give bounds on the number of fundamentally free parameters of quantum gravity. |
gr-qc/0502044 | Sergey Cherkas L. | S.L. Cherkas and V.L. Kalashnikov | Quantum evolution of the Universe from $\tau=0$ in the constrained
quasi-Heisenberg picture | Lecture at the VIIIth International School-seminar "The Actual
Problems of Microworld Physics", Gomel, Belarus, July 25-August 5, 2005. 20
pages | Proc. VIIIth International School-seminar "The Actual Problems of
Microworld Physics" (Gomel), Dubna 2007, v. I, p. 208-222. | null | null | gr-qc | null | The Heisenberg picture of the minisuperspace model is considered. The
suggested quantization scheme interprets all the observables including the
Universe scale factor as the (quasi)Heisenberg operators. The operators arise
as a result of the re-quantization of the Heisenberg operators that is required
to obtain the hermitian theory. It is shown that the DeWitt constraint H=0 on
the physical states of the Universe does not prevent a time-evolution of the
(quasi)Heisenberg operators and their mean values. Mean value of an observable,
which is singular in a classical theory, is also singular in a quantum case.
The (quasi)Heisenberg operator equations are solved in an analytical form in a
first order on the interaction constant for the quadratic inflationary
potential. Operator solutions are used to evaluate the observables mean values
and dispersions. A late stage of the inflation is considered numerically in the
framework of the Wigner-Weyl phase-space formalism. It is found that the
dispersions of the observables do not vanish at the inflation end.
| [
{
"created": "Thu, 10 Feb 2005 14:47:29 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2005 07:23:55 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Sep 2005 15:16:16 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Sep 2005 09:55:46 GMT",
"version": "v4"
},
{
"created": "Wed, 21 Sep 2005 05:34:12 GMT",
"version": "v5"
}
] | 2011-11-09 | [
[
"Cherkas",
"S. L.",
""
],
[
"Kalashnikov",
"V. L.",
""
]
] | The Heisenberg picture of the minisuperspace model is considered. The suggested quantization scheme interprets all the observables including the Universe scale factor as the (quasi)Heisenberg operators. The operators arise as a result of the re-quantization of the Heisenberg operators that is required to obtain the hermitian theory. It is shown that the DeWitt constraint H=0 on the physical states of the Universe does not prevent a time-evolution of the (quasi)Heisenberg operators and their mean values. Mean value of an observable, which is singular in a classical theory, is also singular in a quantum case. The (quasi)Heisenberg operator equations are solved in an analytical form in a first order on the interaction constant for the quadratic inflationary potential. Operator solutions are used to evaluate the observables mean values and dispersions. A late stage of the inflation is considered numerically in the framework of the Wigner-Weyl phase-space formalism. It is found that the dispersions of the observables do not vanish at the inflation end. |
gr-qc/9604053 | Vladimir M. Khatsymovsky | V.M.Khatsymovsky | Ashtekar Constraint Surface as Projection of Hilbert-Palatini One | 9 pages of LaTeX file | Phys.Lett. B394 (1997) 57-61 | 10.1016/S0370-2693(96)01691-7 | null | gr-qc | null | The Hilbert-Palatini (HP) Lagrangian of general relativity being written in
terms of selfdual and antiselfdual variables contains Ashtekar Lagrangian
(which governs the dynamics of the selfdual sector of the theory on condition
that the dynamics of antiselfdual sector is not fixed). We show that
nonequivalence of the Ashtekar and HP quantum theories is due to the specific
form (of the "loose relation" type) of constraints which relate self- and
antiselfdual variables so that the procedure of (canonical) quantisation of
such the theory is noncommutative with the procedure of excluding antiselfdual
variables.
| [
{
"created": "Mon, 29 Apr 1996 10:46:38 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | The Hilbert-Palatini (HP) Lagrangian of general relativity being written in terms of selfdual and antiselfdual variables contains Ashtekar Lagrangian (which governs the dynamics of the selfdual sector of the theory on condition that the dynamics of antiselfdual sector is not fixed). We show that nonequivalence of the Ashtekar and HP quantum theories is due to the specific form (of the "loose relation" type) of constraints which relate self- and antiselfdual variables so that the procedure of (canonical) quantisation of such the theory is noncommutative with the procedure of excluding antiselfdual variables. |
1910.00428 | Mehrab Momennia | Mehrab Momennia, Seyed Hossein Hendi | Quasinormal modes of black holes in Weyl gravity: Electromagnetic and
gravitational perturbations | 15 pages with 3 captioned figures. Published version | Eur. Phys. J. C 80 (2020) 505 | 10.1140/epjc/s10052-020-8051-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent reported gravitational wave detection motivates one to investigate
the properties of different black hole models, especially their behavior under
(axial) gravitational perturbation. Here, we study the quasinormal modes of
black holes in Weyl gravity. We derive the master equation describing the
quasinormal radiation by using a relation between the Schwarzschild-anti de
Sitter black holes and Weyl solutions, and also the conformal invariance
property of the Weyl action. It will be observed that the quasinormal mode
spectra of the Weyl solutions deviate from those of the Schwarzschild black
hole due to the presence of an additional linear $r$-term in the metric
function. We also consider the evolution of the Maxwell field on the background
spacetime and obtain the master equation of electromagnetic perturbations.
Then, we use the WKB approximation and asymptotic iteration method to calculate
the quasinormal frequencies. Finally, the time evolution of modes is studied
through the time-domain integration of the master equation.
| [
{
"created": "Mon, 30 Sep 2019 06:45:55 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jul 2020 12:11:40 GMT",
"version": "v2"
}
] | 2022-08-09 | [
[
"Momennia",
"Mehrab",
""
],
[
"Hendi",
"Seyed Hossein",
""
]
] | The recent reported gravitational wave detection motivates one to investigate the properties of different black hole models, especially their behavior under (axial) gravitational perturbation. Here, we study the quasinormal modes of black holes in Weyl gravity. We derive the master equation describing the quasinormal radiation by using a relation between the Schwarzschild-anti de Sitter black holes and Weyl solutions, and also the conformal invariance property of the Weyl action. It will be observed that the quasinormal mode spectra of the Weyl solutions deviate from those of the Schwarzschild black hole due to the presence of an additional linear $r$-term in the metric function. We also consider the evolution of the Maxwell field on the background spacetime and obtain the master equation of electromagnetic perturbations. Then, we use the WKB approximation and asymptotic iteration method to calculate the quasinormal frequencies. Finally, the time evolution of modes is studied through the time-domain integration of the master equation. |
2404.12223 | Songbai Chen | Zelin Zhang, Songbai Chen, Jiliang Jing | Images of Kerr-MOG black holes surrounded by geometrically thick
magnetized equilibrium tori | 13 pages,7 figures | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We adopt general relativistic ray-tracing (GRRT) schemes to study images of
Kerr-MOG black holes surrounded by geometrically thick magnetized equilibrium
tori, which belong to steady-state solutions of thick accretion disks within
the framework of general relativistic magnetohydrodynamics (GRMHD). The black
hole possesses an extra dimensionless MOG parameter described its deviation
from usual Kerr one. Our results show that the presence of the MOG parameter
leads to smaller disks in size, but enhances the total flux density and peak
brightness in their images. Combining with observation data of black hole M87*
from the Event Horizon Telescope (EHT), we make a constraint on parameters of
the Kerr-MOG black hole and find that the presence of the MOG parameter
broadens the allowable range of black hole spin.
| [
{
"created": "Thu, 18 Apr 2024 14:38:05 GMT",
"version": "v1"
}
] | 2024-04-19 | [
[
"Zhang",
"Zelin",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We adopt general relativistic ray-tracing (GRRT) schemes to study images of Kerr-MOG black holes surrounded by geometrically thick magnetized equilibrium tori, which belong to steady-state solutions of thick accretion disks within the framework of general relativistic magnetohydrodynamics (GRMHD). The black hole possesses an extra dimensionless MOG parameter described its deviation from usual Kerr one. Our results show that the presence of the MOG parameter leads to smaller disks in size, but enhances the total flux density and peak brightness in their images. Combining with observation data of black hole M87* from the Event Horizon Telescope (EHT), we make a constraint on parameters of the Kerr-MOG black hole and find that the presence of the MOG parameter broadens the allowable range of black hole spin. |
2110.10002 | Diego Rubiera-Garcia | Gonzalo J. Olmo, Diego Rubiera-Garcia, Diego S\'aez-Chill\'on G\'omez | New light rings from multiple critical curves as observational
signatures of black hole mimickers | 6 pages, 5 figures | null | 10.1016/j.physletb.2022.137045 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We argue that the appearance of additional light rings in a shadow
observation - beyond the infinite sequence of exponentially demagnified
self-similar rings foreseen in the Kerr solution - would make a compelling case
for the existence of black hole mimickers having multiple critical curves. We
support this claim by discussing three different scenarios of spherically
symmetric wormhole geometries having two such critical curves, and explicitly
work out the optical appearance of one such object when surrounded by an
optically and geometrically thin accretion disk.
| [
{
"created": "Tue, 19 Oct 2021 14:12:50 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
]
] | We argue that the appearance of additional light rings in a shadow observation - beyond the infinite sequence of exponentially demagnified self-similar rings foreseen in the Kerr solution - would make a compelling case for the existence of black hole mimickers having multiple critical curves. We support this claim by discussing three different scenarios of spherically symmetric wormhole geometries having two such critical curves, and explicitly work out the optical appearance of one such object when surrounded by an optically and geometrically thin accretion disk. |
0709.1011 | Takashi Tamaki | Takashi Tamaki, Umpei Miyamoto | Generic features of Einstein-Aether black holes | 9 pages, 9 figures, basic equations and their analytic arguments are
added | Phys.Rev.D77:024026,2008 | 10.1103/PhysRevD.77.024026 | null | gr-qc hep-ph hep-th | null | We reconsider spherically symmetric black hole solutions in Einstein-Aether
theory with the condition that this theory has identical PPN parameters as
those for general relativity, which is the main difference from the previous
research. In contrast with previous study, we allow superluminal propagation of
a spin-0 Aether-gravity wave mode. As a result, we obtain black holes having a
spin-0 "horizon" inside an event horizon. We allow a singularity at a spin-0
"horizon" since it is concealed by the event horizon. If we allow such a
configuration, the kinetic term of the Aether field can be large enough for
black holes to be significantly different from Schwarzschild black holes with
respect to ADM mass, innermost stable circular orbit, Hawking temperature, and
so on. We also discuss whether or not the above features can be seen in more
generic vector-tensor theories.
| [
{
"created": "Fri, 7 Sep 2007 07:33:44 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Sep 2007 05:30:16 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Nov 2007 02:27:15 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Tamaki",
"Takashi",
""
],
[
"Miyamoto",
"Umpei",
""
]
] | We reconsider spherically symmetric black hole solutions in Einstein-Aether theory with the condition that this theory has identical PPN parameters as those for general relativity, which is the main difference from the previous research. In contrast with previous study, we allow superluminal propagation of a spin-0 Aether-gravity wave mode. As a result, we obtain black holes having a spin-0 "horizon" inside an event horizon. We allow a singularity at a spin-0 "horizon" since it is concealed by the event horizon. If we allow such a configuration, the kinetic term of the Aether field can be large enough for black holes to be significantly different from Schwarzschild black holes with respect to ADM mass, innermost stable circular orbit, Hawking temperature, and so on. We also discuss whether or not the above features can be seen in more generic vector-tensor theories. |
1811.10713 | Maria Okounkova | Maria Okounkova, Mark A. Scheel, Saul A. Teukolsky | Evolving Metric Perturbations in dynamical Chern-Simons Gravity | 15 pages, 11 figures Updated to match version accepted to Phys Rev D | Phys. Rev. D 99, 044019 (2019) | 10.1103/PhysRevD.99.044019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a well-posed constraint-preserving scheme for evolving first-order
metric perturbations on an arbitrary background with arbitrary source. We use
this scheme to evolve the leading-order metric perturbation in order-reduced
dynamical Chern-Simons gravity (dCS) on a Kerr background. In particular we
test the stability of stationary dCS data on a Kerr background with stationary
first-order dCS scalar field source. We find that the leading-order metric
perturbation numerically exhibits linear growth, but that the level of this
growth converges to zero with numerical resolution. This analysis shows that
spinning black holes in dCS gravity are numerically stable to leading-order
perturbations in the metric.
| [
{
"created": "Mon, 26 Nov 2018 22:07:20 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2019 21:32:04 GMT",
"version": "v2"
}
] | 2019-02-20 | [
[
"Okounkova",
"Maria",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present a well-posed constraint-preserving scheme for evolving first-order metric perturbations on an arbitrary background with arbitrary source. We use this scheme to evolve the leading-order metric perturbation in order-reduced dynamical Chern-Simons gravity (dCS) on a Kerr background. In particular we test the stability of stationary dCS data on a Kerr background with stationary first-order dCS scalar field source. We find that the leading-order metric perturbation numerically exhibits linear growth, but that the level of this growth converges to zero with numerical resolution. This analysis shows that spinning black holes in dCS gravity are numerically stable to leading-order perturbations in the metric. |
2001.02755 | Kristina Giesel | Kristina Giesel and David Winnekens | Coherent States on the Circle: Semiclassical Matrix Elements in the
Context of Kummer Functions and the Zak transformation | 28 pages, extended section Vi, updated references | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend former results for coherent states on the circle in the literature
in two ways. On the one hand, we show that expectation values of fractional
powers of momentum operators can be computed exactly analytically by means of
Kummer's confluent hypergeometric functions. Earlier, these expectation values
have only been obtained by using suitable estimates. On the other hand, we
consider the Zak transformation not only to map harmonic oscillator coherent
states to coherent states on the circle as it has been discussed before, but we
also use the properties of the Zak transformation to derive a relation between
matrix elements with respect to coherent states in L2(R) and L2(S1). This
provides an alternative way for computing semiclassical matrix elements for
coherent states on the circle. In certain aspects, this method simplifies the
semiclassical computations in particular if one is only interested in the
classical limit, that is the zeroth order term in the semiclassical expansion.
| [
{
"created": "Wed, 8 Jan 2020 21:54:59 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2021 08:17:42 GMT",
"version": "v2"
}
] | 2021-09-27 | [
[
"Giesel",
"Kristina",
""
],
[
"Winnekens",
"David",
""
]
] | We extend former results for coherent states on the circle in the literature in two ways. On the one hand, we show that expectation values of fractional powers of momentum operators can be computed exactly analytically by means of Kummer's confluent hypergeometric functions. Earlier, these expectation values have only been obtained by using suitable estimates. On the other hand, we consider the Zak transformation not only to map harmonic oscillator coherent states to coherent states on the circle as it has been discussed before, but we also use the properties of the Zak transformation to derive a relation between matrix elements with respect to coherent states in L2(R) and L2(S1). This provides an alternative way for computing semiclassical matrix elements for coherent states on the circle. In certain aspects, this method simplifies the semiclassical computations in particular if one is only interested in the classical limit, that is the zeroth order term in the semiclassical expansion. |
1303.5376 | Carl Kent | Carl Kent, Elizabeth Winstanley | Scalar field Hadamard renormalisation in $AdS_{n}$ | 3 pages, proceedings of the 13th Marcel Grossmann Meeting, Stockholm,
Sweden, July 1-7, 2012 | Proceedings of the Thirteenth Marcel Grossman Meeting on General
Relativity, pp. 1959-1961 | 10.1142/9789814623995_0328 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We outline an analytic method for computing the renormalised vacuum
expectation value of the quadratic fluctuations and stress-energy tensor
associated with a quantised scalar field propagating on $AdS_{n}$. Explicit
results have been obtained using Hadamard renormalisation in the case of a
massive neutral scalar field with arbitrary coupling to the curvature, for
$n=2$ to $n=11$ inclusive.
| [
{
"created": "Thu, 21 Mar 2013 19:30:15 GMT",
"version": "v1"
}
] | 2015-03-16 | [
[
"Kent",
"Carl",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] | We outline an analytic method for computing the renormalised vacuum expectation value of the quadratic fluctuations and stress-energy tensor associated with a quantised scalar field propagating on $AdS_{n}$. Explicit results have been obtained using Hadamard renormalisation in the case of a massive neutral scalar field with arbitrary coupling to the curvature, for $n=2$ to $n=11$ inclusive. |
1312.0846 | D. C. Robinson | D.C.Robinson | Generalized forms and gravitation | 23 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The algebra and calculus of generalized differential forms are reviewed and
employed to construct a class of generalized connections and to investigate
their properties. The class includes generalized connections which are flat
when Einstein's vacuum field equations are satisfied. Generalized Chern-Simons
action principles are formulated and it is shown that certain of these have
Einstein's vacuum field equations as Euler-Lagrange equations.
| [
{
"created": "Tue, 3 Dec 2013 15:09:07 GMT",
"version": "v1"
}
] | 2013-12-04 | [
[
"Robinson",
"D. C.",
""
]
] | The algebra and calculus of generalized differential forms are reviewed and employed to construct a class of generalized connections and to investigate their properties. The class includes generalized connections which are flat when Einstein's vacuum field equations are satisfied. Generalized Chern-Simons action principles are formulated and it is shown that certain of these have Einstein's vacuum field equations as Euler-Lagrange equations. |
1806.06572 | Benoit Mours | D. Estevez, B. Lieunard, F. Marion, B. Mours, L. Rolland, D. Verkindt | First Tests of a Newtonian Calibrator on an Interferometric
Gravitational Wave Detector | null | Class.Quant.Grav. 35 (2018) no.23, 235009 | 10.1088/1361-6382/aae95f | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ongoing improvements of the advanced gravitational wave (GW) detectors
are setting challenging requirements on instrument calibration. We report tests
of a calibration technique, based on the well-known gravitation force, which
has been applied for the first time on a large interferometer. The results
obtained with Advanced Virgo are in good agreement with the predictions and
with the usual calibration method. This technique is expected to lead to
accurate absolute calibration at the sub-percent level in the coming years,
matching the needs of the blooming GW science.
| [
{
"created": "Mon, 18 Jun 2018 09:34:05 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Aug 2018 17:02:52 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Dec 2018 06:59:59 GMT",
"version": "v3"
}
] | 2018-12-21 | [
[
"Estevez",
"D.",
""
],
[
"Lieunard",
"B.",
""
],
[
"Marion",
"F.",
""
],
[
"Mours",
"B.",
""
],
[
"Rolland",
"L.",
""
],
[
"Verkindt",
"D.",
""
]
] | The ongoing improvements of the advanced gravitational wave (GW) detectors are setting challenging requirements on instrument calibration. We report tests of a calibration technique, based on the well-known gravitation force, which has been applied for the first time on a large interferometer. The results obtained with Advanced Virgo are in good agreement with the predictions and with the usual calibration method. This technique is expected to lead to accurate absolute calibration at the sub-percent level in the coming years, matching the needs of the blooming GW science. |
2407.15191 | Hayato Motohashi | Hayato Motohashi | Resonant excitation of quasinormal modes of black holes | 9 pages, 4 figures, dataset available at
https://doi.org/10.5281/zenodo.12696857 | null | null | null | gr-qc astro-ph.HE cond-mat.mes-hall hep-th physics.optics | http://creativecommons.org/licenses/by/4.0/ | We elucidate that a distinctive resonant excitation between quasinormal modes
(QNMs) of black holes emerges as a universal phenomenon at avoided crossing
near exceptional point through high-precision numerical analysis and theory of
QNMs based on the framework of non-Hermitian physics. This resonant phenomenon
not only allows us to decipher a long-standing mystery concerning the peculiar
behaviors of QNMs but also stands as a novel beacon for characterizing black
hole spacetime geometry. Our findings pave the way for rigorous examinations of
black holes and the exploration of new physics in gravity.
| [
{
"created": "Sun, 21 Jul 2024 15:11:34 GMT",
"version": "v1"
}
] | 2024-07-24 | [
[
"Motohashi",
"Hayato",
""
]
] | We elucidate that a distinctive resonant excitation between quasinormal modes (QNMs) of black holes emerges as a universal phenomenon at avoided crossing near exceptional point through high-precision numerical analysis and theory of QNMs based on the framework of non-Hermitian physics. This resonant phenomenon not only allows us to decipher a long-standing mystery concerning the peculiar behaviors of QNMs but also stands as a novel beacon for characterizing black hole spacetime geometry. Our findings pave the way for rigorous examinations of black holes and the exploration of new physics in gravity. |
1604.07568 | Tuan Do | Tuan Q. Do | Higher dimensional massive bigravity | Minor revision with 20 two-column pages, no figure. Some statements
have been revised/added appropriately after receiving some comments.
Calculations are unchanged. Comments are welcome | Phys. Rev. D 94, 044022 (2016) | 10.1103/PhysRevD.94.044022 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study higher dimensional scenarios of massive bigravity, which is a very
interesting extension of nonlinear massive gravity since its reference metric
is assumed to be full dynamical. In particular, the Einstein field equations
along with the following constraint equations for both physical and reference
metrics of a five-dimensional massive bigravity will be addressed. Then, we
study some well-known cosmological spacetimes such as the
Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and
Schwarzschild-Tangherlini metrics for the five-dimensional massive bigravity.
As a result, we find that massive graviton terms will serve as effective
cosmological constants in both physical and reference sectors if a special
scenario, in which reference metrics are chosen to be proportional to physical
ones, is considered for all mentioned metrics. Thanks to the constancy property
of massive graviton terms, consistent cosmological solutions will be figured
out accordingly.
| [
{
"created": "Tue, 26 Apr 2016 08:38:53 GMT",
"version": "v1"
},
{
"created": "Thu, 5 May 2016 08:30:46 GMT",
"version": "v2"
},
{
"created": "Mon, 16 May 2016 18:11:36 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Jun 2016 15:18:18 GMT",
"version": "v4"
}
] | 2016-08-15 | [
[
"Do",
"Tuan Q.",
""
]
] | We study higher dimensional scenarios of massive bigravity, which is a very interesting extension of nonlinear massive gravity since its reference metric is assumed to be full dynamical. In particular, the Einstein field equations along with the following constraint equations for both physical and reference metrics of a five-dimensional massive bigravity will be addressed. Then, we study some well-known cosmological spacetimes such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini metrics for the five-dimensional massive bigravity. As a result, we find that massive graviton terms will serve as effective cosmological constants in both physical and reference sectors if a special scenario, in which reference metrics are chosen to be proportional to physical ones, is considered for all mentioned metrics. Thanks to the constancy property of massive graviton terms, consistent cosmological solutions will be figured out accordingly. |
1907.07967 | Stephen McCormick | Stephen McCormick | On the charged Riemannian Penrose inequality with charged matter | V2: Updated to agree with published version (various small
clarifications added). 18 pages, comments very welcome :) | Class. Quantum Grav. 37 015007 (2020) | 10.1088/1361-6382/ab50a8 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Throughout the literature on the charged Riemannian Penrose inequality, it is
generally assumed that there is no charged matter present; that is, the
electric field is divergence-free. The aim of this article is to clarify when
the charged Riemannian Penrose inequality holds in the presence of charged
matter, and when it does not.
First we revisit Jang's proof of the charged Riemannian Penrose inequality to
show that under suitable conditions on the charged matter, this argument still
carries though. In particular, a charged Riemannian Penrose inequality is
obtained from this argument when charged matter is present provided that the
charge density does not change sign. Moreover, we show that such hypotheses on
the sign of the charge are in fact required by constructing counterexamples to
the charged Riemannian Penrose inequality when these conditions are violated.
We conclude by comparing this counterexample to another version of the
Riemannian Penrose inequality with charged matter existing in the literature.
| [
{
"created": "Thu, 18 Jul 2019 10:23:20 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jun 2021 14:06:21 GMT",
"version": "v2"
}
] | 2021-06-30 | [
[
"McCormick",
"Stephen",
""
]
] | Throughout the literature on the charged Riemannian Penrose inequality, it is generally assumed that there is no charged matter present; that is, the electric field is divergence-free. The aim of this article is to clarify when the charged Riemannian Penrose inequality holds in the presence of charged matter, and when it does not. First we revisit Jang's proof of the charged Riemannian Penrose inequality to show that under suitable conditions on the charged matter, this argument still carries though. In particular, a charged Riemannian Penrose inequality is obtained from this argument when charged matter is present provided that the charge density does not change sign. Moreover, we show that such hypotheses on the sign of the charge are in fact required by constructing counterexamples to the charged Riemannian Penrose inequality when these conditions are violated. We conclude by comparing this counterexample to another version of the Riemannian Penrose inequality with charged matter existing in the literature. |
2301.08709 | Loris Del Grosso | L. Del Grosso, G. Franciolini, P. Pani, A. Urbano | Fermion soliton stars | 16 pages, 5 figures. v2: matches version accepted in PRD. v3: final
plots, matches PRD version | Phys. Rev. D 108, 044024 (2023) | 10.1103/PhysRevD.108.044024 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A real scalar field coupled to a fermion via a Yukawa term can evade no-go
theorems preventing solitonic solutions. For the first time, we study this
model within General Relativity without approximations, finding static and
spherically symmetric solutions that describe fermion soliton stars. The Yukawa
coupling provides an effective mass for the fermion, which is key to the
existence of self-gravitating relativistic solutions. We systematically study
this novel family of solutions and present their mass-radius diagram and
maximum compactness, which is close to (but smaller than) that of the
corresponding Schwarzschild photon sphere. Finally, we discuss the ranges of
the parameters of the fundamental theory in which the latter might have
interesting astrophysical implications, including compact (sub)solar and
supermassive fermion soliton stars for a standard gas of degenerate neutrons
and electrons, respectively.
| [
{
"created": "Fri, 20 Jan 2023 18:10:26 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jul 2023 15:11:45 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Aug 2023 10:22:14 GMT",
"version": "v3"
}
] | 2023-08-31 | [
[
"Del Grosso",
"L.",
""
],
[
"Franciolini",
"G.",
""
],
[
"Pani",
"P.",
""
],
[
"Urbano",
"A.",
""
]
] | A real scalar field coupled to a fermion via a Yukawa term can evade no-go theorems preventing solitonic solutions. For the first time, we study this model within General Relativity without approximations, finding static and spherically symmetric solutions that describe fermion soliton stars. The Yukawa coupling provides an effective mass for the fermion, which is key to the existence of self-gravitating relativistic solutions. We systematically study this novel family of solutions and present their mass-radius diagram and maximum compactness, which is close to (but smaller than) that of the corresponding Schwarzschild photon sphere. Finally, we discuss the ranges of the parameters of the fundamental theory in which the latter might have interesting astrophysical implications, including compact (sub)solar and supermassive fermion soliton stars for a standard gas of degenerate neutrons and electrons, respectively. |
1207.0876 | Amir H. Abbassi | Amir H. Abbassi, J. Khodagholizadeh, Amir M. Abbassi | Gravitational Waves in a Spatially Closed deSitter Spacetime | 16 pages,no figures | Eur.Phys.J.C(2013)73:2592 | 10.1140/epjc/s10052-013-2592-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbation of gravitational fields may be decomposed into scalar,vector and
tensor components.In this paper we concern with the evolution of tensor mode
perturbations in a spatially closed deSitter background of RW form. It may be
thought as gravitional waves in a classical description. The chosen background
has the advantage of to be maximally extended and symmetric. The spatially flat
models commonly emerge from inflationary scenarios are not completely
extended.We first derive the general weak field equations.Then the form of the
field equations in two special cases, planar and spherical waves are obtained
and their solutions are presented. We conclued with discussing the significance
of the results and their implications.
| [
{
"created": "Wed, 4 Jul 2012 01:55:48 GMT",
"version": "v1"
},
{
"created": "Sun, 18 May 2014 05:51:26 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Abbassi",
"Amir H.",
""
],
[
"Khodagholizadeh",
"J.",
""
],
[
"Abbassi",
"Amir M.",
""
]
] | Perturbation of gravitational fields may be decomposed into scalar,vector and tensor components.In this paper we concern with the evolution of tensor mode perturbations in a spatially closed deSitter background of RW form. It may be thought as gravitional waves in a classical description. The chosen background has the advantage of to be maximally extended and symmetric. The spatially flat models commonly emerge from inflationary scenarios are not completely extended.We first derive the general weak field equations.Then the form of the field equations in two special cases, planar and spherical waves are obtained and their solutions are presented. We conclued with discussing the significance of the results and their implications. |
gr-qc/9801043 | Renaud Parentani | S. Massar and R. Parentani | On the Gravitational Back Reaction to Hawking Radiation | 12 pages, latex | null | null | THU-98/03 | gr-qc | null | We show that a surface term should be added to the Einstein-Hilbert action in
order to properly describe quantum transitions occurring around a black hole.
The introduction of this boundary term has been advocated by Teitelboim and
collaborators and it has been used in the computation of the black hole
entropy. Here, we use it to compute the gravitational corrections to the
transition amplitudes giving rise to Hawking radiation. This surface term
implies that the probability to emit a particle is given by $e^{- \Delta A/4}$
where $\Delta A$ is the change in the area of the black hole horizon induced by
the emission. Its inclusion at the level of the amplitudes therefore relates
quantum black hole radiation to the first law of black hole dynamics. In both
cases indeed, the term expressing the change in area directly results from the
same boundary term introduced for the same reason: to obtain a well defined
action principle.
| [
{
"created": "Tue, 13 Jan 1998 13:03:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Massar",
"S.",
""
],
[
"Parentani",
"R.",
""
]
] | We show that a surface term should be added to the Einstein-Hilbert action in order to properly describe quantum transitions occurring around a black hole. The introduction of this boundary term has been advocated by Teitelboim and collaborators and it has been used in the computation of the black hole entropy. Here, we use it to compute the gravitational corrections to the transition amplitudes giving rise to Hawking radiation. This surface term implies that the probability to emit a particle is given by $e^{- \Delta A/4}$ where $\Delta A$ is the change in the area of the black hole horizon induced by the emission. Its inclusion at the level of the amplitudes therefore relates quantum black hole radiation to the first law of black hole dynamics. In both cases indeed, the term expressing the change in area directly results from the same boundary term introduced for the same reason: to obtain a well defined action principle. |
1404.1024 | Minas Tsoukalas | Christos Charmousis, Theodoros Kolyvaris, Eleftherios Papantonopoulos
and Minas Tsoukalas | Black Holes in Bi-scalar Extensions of Horndeski Theories | v2, 16 pages, minor corrections, version accepted to JHEP | null | 10.1007/JHEP07(2014)085 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study certain bi-scalar-tensor theories emanating from conformal symmetry
requirements of Horndeski's four-dimensional action. The former scalar is a
Galileon with shift symmetry whereas the latter scalar is adjusted to have a
higher order conformal coupling. Employing technics from local Weyl geometry
certain Galileon higher order terms are thus constructed to be conformally
invariant. The combined shift and partial conformal symmetry of the action,
allow us to construct exact black hole solutions. The black holes initially
found are of planar horizon geometry embedded in anti de Sitter space and can
accommodate electric charge. The conformally coupled scalar comes with an
additional independent charge and it is well-defined on the horizon whereas
additional regularity of the Galileon field is achieved allowing for time
dependence. Guided by our results in adS space-time we then consider a higher
order version of the BBMB action and construct asymptotically flat, regular,
hairy black holes. The addition of the Galileon field is seen to cure the BBMB
scalar horizon singularity while allowing for the presence of primary scalar
hair seen as an independent integration constant along-side the mass of the
black hole.
| [
{
"created": "Thu, 3 Apr 2014 17:58:33 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jul 2014 15:51:50 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Charmousis",
"Christos",
""
],
[
"Kolyvaris",
"Theodoros",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Tsoukalas",
"Minas",
""
]
] | We study certain bi-scalar-tensor theories emanating from conformal symmetry requirements of Horndeski's four-dimensional action. The former scalar is a Galileon with shift symmetry whereas the latter scalar is adjusted to have a higher order conformal coupling. Employing technics from local Weyl geometry certain Galileon higher order terms are thus constructed to be conformally invariant. The combined shift and partial conformal symmetry of the action, allow us to construct exact black hole solutions. The black holes initially found are of planar horizon geometry embedded in anti de Sitter space and can accommodate electric charge. The conformally coupled scalar comes with an additional independent charge and it is well-defined on the horizon whereas additional regularity of the Galileon field is achieved allowing for time dependence. Guided by our results in adS space-time we then consider a higher order version of the BBMB action and construct asymptotically flat, regular, hairy black holes. The addition of the Galileon field is seen to cure the BBMB scalar horizon singularity while allowing for the presence of primary scalar hair seen as an independent integration constant along-side the mass of the black hole. |
gr-qc/9403064 | Melnikov Vitaly Nikolaevich | V. D. Ivashchuk and V. N. Melnikov | Multidimensional Cosmology with $m$-Component Perfect Fluid | 16 pages. RGA-CSVR-002/94 | Int.J.Mod.Phys.D3:795-812,1994 | 10.1142/S0218271894000897 | null | gr-qc | null | A cosmological model describing the evolution of $n$ Einstein spaces $(n>1)$
with $m$-component perfect-fluid matter is considered. When all spaces are
Ricci-flat and for any $\alpha$-th component the pressures in all spaces are
proportional to the density: $p_{i}^{(\alpha)} = (1- h_{i}^{(\alpha)})
\rho^{(\alpha)}$, $h_{i}^{(\alpha)}$ = const, the Einstein and Wheeler-DeWitt
equations are integrated in the cases: i) $m=1$, for all $h_{i}^{(\alpha)}$;
ii) $m > 1$, for some special sets of $h_{i}^{(\alpha)}$. For $m=1$ the quantum
wormhole solutions are also obtained. \\
| [
{
"created": "Thu, 31 Mar 1994 15:28:05 GMT",
"version": "v1"
}
] | 2011-04-20 | [
[
"Ivashchuk",
"V. D.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | A cosmological model describing the evolution of $n$ Einstein spaces $(n>1)$ with $m$-component perfect-fluid matter is considered. When all spaces are Ricci-flat and for any $\alpha$-th component the pressures in all spaces are proportional to the density: $p_{i}^{(\alpha)} = (1- h_{i}^{(\alpha)}) \rho^{(\alpha)}$, $h_{i}^{(\alpha)}$ = const, the Einstein and Wheeler-DeWitt equations are integrated in the cases: i) $m=1$, for all $h_{i}^{(\alpha)}$; ii) $m > 1$, for some special sets of $h_{i}^{(\alpha)}$. For $m=1$ the quantum wormhole solutions are also obtained. \\ |
gr-qc/0103106 | David Kastor | Jennie Traschen and Daniel Fox | Tension Perturbations of Black Brane Spacetimes | 21 pages, o figures, harvmac | Class.Quant.Grav. 21 (2004) 289-306 | 10.1088/0264-9381/21/1/021 | null | gr-qc hep-th | null | We consider black-brane spacetimes that have at least one spatial translation
Killing field that is tangent to the brane. A new parameter, the tension of a
spacetime, is defined. The tension parameter is associated with spatial
translations in much the same way that the ADM mass is associated with the time
translation Killing field. In this work, we explore the implications of the
spatial translation symmetry for small perturbations around a background black
brane. For static charged black branes we derive a law which relates the
tension perturbation to the surface gravity times the change in the the horizon
area, plus terms that involve variations in the charges and currents. We find
that as a black brane evaporates the tension decreases. We also give a simple
derivation of a first law for black brane spacetimes. These constructions hold
when the background stress-energy is governed by a Hamiltonian, and the results
include arbitrary perturbative stress-energy sources.
| [
{
"created": "Wed, 28 Mar 2001 17:19:51 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Sep 2003 15:04:52 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Traschen",
"Jennie",
""
],
[
"Fox",
"Daniel",
""
]
] | We consider black-brane spacetimes that have at least one spatial translation Killing field that is tangent to the brane. A new parameter, the tension of a spacetime, is defined. The tension parameter is associated with spatial translations in much the same way that the ADM mass is associated with the time translation Killing field. In this work, we explore the implications of the spatial translation symmetry for small perturbations around a background black brane. For static charged black branes we derive a law which relates the tension perturbation to the surface gravity times the change in the the horizon area, plus terms that involve variations in the charges and currents. We find that as a black brane evaporates the tension decreases. We also give a simple derivation of a first law for black brane spacetimes. These constructions hold when the background stress-energy is governed by a Hamiltonian, and the results include arbitrary perturbative stress-energy sources. |
2004.05636 | Rikpratik Sengupta | Rikpratik Sengupta, B C Paul, Prasenjit Pal | Skyrme Fluid in Anisotropic Universe | 24 pages, 10 figures | Pramana J. Phys. (2022) 96 | 10.1007/s12043-022-02368-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological solutions are obtained in an anisotropic Kantowski-Sachs (KS)
and Bianchi Type-I universes considering a cosmological constant with Skyrme
fluid. Interestingly, the solutions obtained here in both the KS and Bianchi-I
anisotropic universes are found isotropize at late time due to the presence of
the Skyrme fluid even in the absence of $\Lambda$ term or any inflationary
mechanism involving the inflaton field. A comparative study of both the
anisotropic cosmological models are carried out here and found that Bianchi-I
universe admits oscillatory solutions for a given matter configuration. We also
note that the emergent universe model can be obtained with Skyrme fluid. The
anisotropy, deceleration and jerk parameters have been studied along with the
linear perturbative stability to explore efficacy of the model. Both the
cosmological models are stable in the absence of cosmological constant besides
their compatibility with observational data. Thus, we claim Skyrme fluid a
possible source for isotropization of an anisotropic universe via accelerated
expansion, which is capable of reproducing some observed features of the
universe.
| [
{
"created": "Sun, 12 Apr 2020 15:45:11 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jul 2021 07:44:15 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Feb 2022 15:51:55 GMT",
"version": "v3"
}
] | 2022-06-09 | [
[
"Sengupta",
"Rikpratik",
""
],
[
"Paul",
"B C",
""
],
[
"Pal",
"Prasenjit",
""
]
] | Cosmological solutions are obtained in an anisotropic Kantowski-Sachs (KS) and Bianchi Type-I universes considering a cosmological constant with Skyrme fluid. Interestingly, the solutions obtained here in both the KS and Bianchi-I anisotropic universes are found isotropize at late time due to the presence of the Skyrme fluid even in the absence of $\Lambda$ term or any inflationary mechanism involving the inflaton field. A comparative study of both the anisotropic cosmological models are carried out here and found that Bianchi-I universe admits oscillatory solutions for a given matter configuration. We also note that the emergent universe model can be obtained with Skyrme fluid. The anisotropy, deceleration and jerk parameters have been studied along with the linear perturbative stability to explore efficacy of the model. Both the cosmological models are stable in the absence of cosmological constant besides their compatibility with observational data. Thus, we claim Skyrme fluid a possible source for isotropization of an anisotropic universe via accelerated expansion, which is capable of reproducing some observed features of the universe. |
1307.3542 | Jeremy D. Schnittman | Jeremy D. Schnittman (GSFC) | Astrophysics of Super-massive Black Hole Mergers | Invited article for the focus issue on astrophysical black holes in
Classical and Quantum Gravity, guest editors: D. Merritt and L. Rezzolla | null | 10.1088/0264-9381/30/24/244007 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present here an overview of recent work in the subject of astrophysical
manifestations of super-massive black hole (SMBH) mergers. This is a field that
has been traditionally driven by theoretical work, but in recent years has also
generated a great deal of interest and excitement in the observational
astronomy community. In particular, the electromagnetic (EM) counterparts to
SMBH mergers provide the means to detect and characterize these highly
energetic events at cosmological distances, even in the absence of a
space-based gravitational-wave observatory. In addition to providing a
mechanism for observing SMBH mergers, EM counterparts also give important
information about the environments in which these remarkable events take place,
thus teaching us about the mechanisms through which galaxies form and evolve
symbiotically with their central black holes.
| [
{
"created": "Fri, 12 Jul 2013 19:06:27 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Schnittman",
"Jeremy D.",
"",
"GSFC"
]
] | We present here an overview of recent work in the subject of astrophysical manifestations of super-massive black hole (SMBH) mergers. This is a field that has been traditionally driven by theoretical work, but in recent years has also generated a great deal of interest and excitement in the observational astronomy community. In particular, the electromagnetic (EM) counterparts to SMBH mergers provide the means to detect and characterize these highly energetic events at cosmological distances, even in the absence of a space-based gravitational-wave observatory. In addition to providing a mechanism for observing SMBH mergers, EM counterparts also give important information about the environments in which these remarkable events take place, thus teaching us about the mechanisms through which galaxies form and evolve symbiotically with their central black holes. |
1509.06746 | Gabor Kunstatter | Gabor Kunstatter, Hideki Maeda, and Tim Taves | New 2D dilaton gravity for nonsingular black holes | Fully revised version, including covariant field equations, 38 pages,
extended version of arXiv:1509.04243 with details of derivations and proofs | Class. Quant. Grav. 33 (2016) 105005 | 10.1088/0264-9381/33/10/105005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a two-dimensional action that is an extension of spherically
symmetric Einstein-Lanczos-Lovelock gravity. The action contains arbitrary
functions of the areal radius and the norm squared of its gradient, but the
field equations are second order and obey Birkhoff's theorem. In complete
analogy with spherically symmetric Einstein-Lanczos-Lovelock gravity, the field
equations admit the generalized Misner-Sharp mass as the first integral that
determines the form of the vacuum solution. The arbitrary functions in the
action allow for vacuum solutions that describe a larger class of interesting
nonsingular black-hole spacetimes than previously available.
| [
{
"created": "Tue, 22 Sep 2015 20:12:56 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Dec 2015 02:07:43 GMT",
"version": "v2"
}
] | 2017-06-13 | [
[
"Kunstatter",
"Gabor",
""
],
[
"Maeda",
"Hideki",
""
],
[
"Taves",
"Tim",
""
]
] | We construct a two-dimensional action that is an extension of spherically symmetric Einstein-Lanczos-Lovelock gravity. The action contains arbitrary functions of the areal radius and the norm squared of its gradient, but the field equations are second order and obey Birkhoff's theorem. In complete analogy with spherically symmetric Einstein-Lanczos-Lovelock gravity, the field equations admit the generalized Misner-Sharp mass as the first integral that determines the form of the vacuum solution. The arbitrary functions in the action allow for vacuum solutions that describe a larger class of interesting nonsingular black-hole spacetimes than previously available. |
0801.4829 | Francois Limousin | Dorota Gondek-Rosinska (LUTH), Francois Limousin (LUTH) | The final phase of inspiral of strange quark star binaries | null | null | null | null | gr-qc | null | We present calculations of the final phase of inspiral of irrotational
strange star binaries. Two types of equation of state at zero temperature are
used - the MIT bag model and the Dey et al. 1998 model of strange quark matter.
We study the precoalescence stage within the Isenberg-Wilson-Mathews
approximation of General Relativity using a multidomain spectral method. The
gravitational-radiation driven evolution of the binary system is approximated
by a sequence of quasi-equilibrium configurations at a fixed baryon number and
with decreasing separation. We find that the innermost stable circular orbit
(ISCO) is determined always by an orbital instability for binaries consisting
of two stars built predominantly of strange quark matter independently on the
total mass of a binary system and compactness parameter of each star. In
contrast, for neutron stars described by baryonic equation of state without
exotic phases the ISCO is given by the mass-shedding limit. The gravitational
wave frequency at the ISCO, which marks the end of the inspiral phase, is
always higher than 1.1kHz for equal masses irrotational strange quark stars
with the total mass-energy of a binary system greater than $2 M_\odot$. We find
that the dependence of the frequency of gravitational waves at the ISCO on the
compactness parameter for the equal mass binaries can be described by the same
simple analytical formulae for broad ranges of masses independently on a
strange star model. Detailed comparisons with binary neutrons star models, as
well as with the third order Post-Newtonian point-mass binaries are given. The
difference in the phase, for two $1.35 M_\odot$ strange stars, between our
numerical results and 3PN is $\sim 40 %$ for the last two orbits of inspiral.
| [
{
"created": "Thu, 31 Jan 2008 07:12:14 GMT",
"version": "v1"
}
] | 2008-02-01 | [
[
"Gondek-Rosinska",
"Dorota",
"",
"LUTH"
],
[
"Limousin",
"Francois",
"",
"LUTH"
]
] | We present calculations of the final phase of inspiral of irrotational strange star binaries. Two types of equation of state at zero temperature are used - the MIT bag model and the Dey et al. 1998 model of strange quark matter. We study the precoalescence stage within the Isenberg-Wilson-Mathews approximation of General Relativity using a multidomain spectral method. The gravitational-radiation driven evolution of the binary system is approximated by a sequence of quasi-equilibrium configurations at a fixed baryon number and with decreasing separation. We find that the innermost stable circular orbit (ISCO) is determined always by an orbital instability for binaries consisting of two stars built predominantly of strange quark matter independently on the total mass of a binary system and compactness parameter of each star. In contrast, for neutron stars described by baryonic equation of state without exotic phases the ISCO is given by the mass-shedding limit. The gravitational wave frequency at the ISCO, which marks the end of the inspiral phase, is always higher than 1.1kHz for equal masses irrotational strange quark stars with the total mass-energy of a binary system greater than $2 M_\odot$. We find that the dependence of the frequency of gravitational waves at the ISCO on the compactness parameter for the equal mass binaries can be described by the same simple analytical formulae for broad ranges of masses independently on a strange star model. Detailed comparisons with binary neutrons star models, as well as with the third order Post-Newtonian point-mass binaries are given. The difference in the phase, for two $1.35 M_\odot$ strange stars, between our numerical results and 3PN is $\sim 40 %$ for the last two orbits of inspiral. |
1301.2214 | Jonathan Engle | Jonathan Engle | Corrigendum: The Plebanski sectors of the EPRL vertex | Corrigendum to arXiv:1107.0709, 4 pages | null | 10.1088/0264-9381/30/4/049501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We correct what amounts to a sign error in the proof of part (i.) of theorem
3 in Class.Quant.Grav.28 225003 (arXiv:1107.0709). The Plebanski sectors
isolated by the linear simplicity constraints do not change --- they are still
the three sectors (deg), (II+), and (II-). What changes is the characterization
of the continuum Plebanski two-form corresponding to the first two terms in the
asymptotics of the EPRL vertex amplitude for Regge-like boundary data. These
two terms do not correspond to Plebanski sectors (II+) and (II-), but rather to
the two possible signs of the product of the sign of the sector --- +1 for
(II+) and -1 for (II-) --- and the sign of the orientation
$\epsilon_{IJKL}B^{IJ} \wedge B^{KL}$ determined by $B^{IJ}$. This is
consistent with what one would expect, as this is exactly the sign which
classically relates the BF action, in Plebanski sectors (II+) and (II-), to the
Einstein-Hilbert action, whose discretization is the Regge action appearing in
the asymptotics.
| [
{
"created": "Thu, 10 Jan 2013 18:46:27 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Engle",
"Jonathan",
""
]
] | We correct what amounts to a sign error in the proof of part (i.) of theorem 3 in Class.Quant.Grav.28 225003 (arXiv:1107.0709). The Plebanski sectors isolated by the linear simplicity constraints do not change --- they are still the three sectors (deg), (II+), and (II-). What changes is the characterization of the continuum Plebanski two-form corresponding to the first two terms in the asymptotics of the EPRL vertex amplitude for Regge-like boundary data. These two terms do not correspond to Plebanski sectors (II+) and (II-), but rather to the two possible signs of the product of the sign of the sector --- +1 for (II+) and -1 for (II-) --- and the sign of the orientation $\epsilon_{IJKL}B^{IJ} \wedge B^{KL}$ determined by $B^{IJ}$. This is consistent with what one would expect, as this is exactly the sign which classically relates the BF action, in Plebanski sectors (II+) and (II-), to the Einstein-Hilbert action, whose discretization is the Regge action appearing in the asymptotics. |
gr-qc/9810050 | Vladimir Dzhunushaliev | V. Dzhunushaliev and D. Singleton | Einstein-Cartan-Heisenberg Theory of Gravity with Dynamical Torsion | 15 pp., LATEX, references added, and discussion of several points
changed/expanded | Phys.Lett. A257 (1999) 7-13 | 10.1016/S0375-9601(99)00282-0 | null | gr-qc hep-th | null | On the basis of an algebraic relation between torsion and a classical spinor
field a new interpretation of Einstein-Cartan gravity interacting with
classical spinor field is proposed. In this approach the spinor field becomes
an auxiliary field and the dynamical equation for this field (the Heisenberg
equation) is a dynamical, gravitational equation for torsion. The simplest
version of this theory is examined where the metric degrees of freedom are
frozen and only torsion plays a role. A spherically symmetric solution of this
theory is examined. This solution can be interpreted, in the spirit of
Wheeler's ideas of ``charge without charge'' and ``mass without mass'', as a
geometrical model for an uncharged and massless particle with spin (``spin
without spin'').
| [
{
"created": "Thu, 15 Oct 1998 09:21:19 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jun 1999 17:53:47 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Dzhunushaliev",
"V.",
""
],
[
"Singleton",
"D.",
""
]
] | On the basis of an algebraic relation between torsion and a classical spinor field a new interpretation of Einstein-Cartan gravity interacting with classical spinor field is proposed. In this approach the spinor field becomes an auxiliary field and the dynamical equation for this field (the Heisenberg equation) is a dynamical, gravitational equation for torsion. The simplest version of this theory is examined where the metric degrees of freedom are frozen and only torsion plays a role. A spherically symmetric solution of this theory is examined. This solution can be interpreted, in the spirit of Wheeler's ideas of ``charge without charge'' and ``mass without mass'', as a geometrical model for an uncharged and massless particle with spin (``spin without spin''). |
gr-qc/9904023 | Jacques Renaud | J-P. Gazeau, J. Renaud, M. V. Takook | Gupta-Bleuler quantization for minimally coupled scalar fields in de
Sitter space | 20 pages, appear in class. quantum grav | Class.Quant.Grav. 17 (2000) 1415-1434 | 10.1088/0264-9381/17/6/307 | null | gr-qc | null | We present in this paper a fully covariant quantization of the
minimally-coupled massless field on de Sitter space. We thus obtain a formalism
free of any infrared (e.g logarithmic) divergence. Our method is based on a
rigorous group theoretical approach combined with a suitable adaptation (Krein
spaces) of the Wightman-G\"{a}rding axiomatic for massless fields
(Gupta-Bleuler scheme). We make explicit the correspondence between unitary
irreducible representations of the de Sitter group and the field theory on de
Sitter space-time. The minimally-coupled massless field is associated with a
representation which is the lowest term of the discrete series of unitary
representations of the de Sitter group. In spite of the presence of negative
norm modes in the theory, no negative energy can be measured: expressions as
$\le n_{k_1}n_{k_2}...|T_{00}|n_{k_1}n_{k_2}...\re$ are always positive.
| [
{
"created": "Thu, 8 Apr 1999 18:55:54 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jan 2000 12:54:32 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Gazeau",
"J-P.",
""
],
[
"Renaud",
"J.",
""
],
[
"Takook",
"M. V.",
""
]
] | We present in this paper a fully covariant quantization of the minimally-coupled massless field on de Sitter space. We thus obtain a formalism free of any infrared (e.g logarithmic) divergence. Our method is based on a rigorous group theoretical approach combined with a suitable adaptation (Krein spaces) of the Wightman-G\"{a}rding axiomatic for massless fields (Gupta-Bleuler scheme). We make explicit the correspondence between unitary irreducible representations of the de Sitter group and the field theory on de Sitter space-time. The minimally-coupled massless field is associated with a representation which is the lowest term of the discrete series of unitary representations of the de Sitter group. In spite of the presence of negative norm modes in the theory, no negative energy can be measured: expressions as $\le n_{k_1}n_{k_2}...|T_{00}|n_{k_1}n_{k_2}...\re$ are always positive. |
gr-qc/9709068 | Max Banados | Maximo Banados and Mauricio Contreras | Darboux coordinates for (first order) tetrad gravity | 12 pages, Latex. Minor presentation changes and some references
added. Version to appear in Classical and Quantum Gravity | Class.Quant.Grav. 15 (1998) 1527-1534 | 10.1088/0264-9381/15/6/009 | null | gr-qc hep-th | null | The Hamiltonian form of the Hilbert action in the first order tetrad
formalism is examined. We perform a non-linear field redefinition of the
canonical variables isolating the part of the spin connection which is
canonically conjugate to the tetrad. The geometrical meaning of the constraints
written in these new variables is examined.
| [
{
"created": "Thu, 25 Sep 1997 23:18:44 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Sep 1997 16:39:29 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Feb 1998 23:57:09 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Banados",
"Maximo",
""
],
[
"Contreras",
"Mauricio",
""
]
] | The Hamiltonian form of the Hilbert action in the first order tetrad formalism is examined. We perform a non-linear field redefinition of the canonical variables isolating the part of the spin connection which is canonically conjugate to the tetrad. The geometrical meaning of the constraints written in these new variables is examined. |
1009.3293 | Valerio Ferroni | Valerio Ferroni and Alexander Silbergleit | Electrostatic Patch Effect in Cylindrical Geometry. II. Forces | 32 pages, 10 Figures. Submitted to Classical and Quantum Gravity | Class.Quant.Grav.28:145002,2011 | 10.1088/0264-9381/28/14/145002 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue our study of patch effect (PE) for two close cylindrical
conductors with parallel axes, slightly shifted against each other in the
radial and by any length in the axial direction, started in [1], where the
potential and energy in the gap were calculated to the second order in the
small transverse shift, and to lowest order in the gap to cylinder radius
ratio. Based on these results, here we derive and analyze PE force. It consists
of three parts: the usual capacitor force due to the uniform potential
difference, the one from the interaction between the voltage patches and the
uniform voltage difference, and the force due to patch interaction, entirely
independent of the uniform voltage. General formulas for these forces are
found, and their general properties are described. A convenient model of a
localized patch is then suggested that allows us to calculate all the forces in
a closed elementary form. Using this, a detailed analysis of the patch
interaction for one pair of patches is carried out, and the dependence of
forces on the patch parameters (width and strength) and their mutual position
is examined. We also give various estimates of the axial patch effect force
important for the Satellite Test of the Equivalence Principle (STEP), and
recommend intensive pre-flight simulations employing our results.
| [
{
"created": "Thu, 16 Sep 2010 22:09:35 GMT",
"version": "v1"
}
] | 2011-06-07 | [
[
"Ferroni",
"Valerio",
""
],
[
"Silbergleit",
"Alexander",
""
]
] | We continue our study of patch effect (PE) for two close cylindrical conductors with parallel axes, slightly shifted against each other in the radial and by any length in the axial direction, started in [1], where the potential and energy in the gap were calculated to the second order in the small transverse shift, and to lowest order in the gap to cylinder radius ratio. Based on these results, here we derive and analyze PE force. It consists of three parts: the usual capacitor force due to the uniform potential difference, the one from the interaction between the voltage patches and the uniform voltage difference, and the force due to patch interaction, entirely independent of the uniform voltage. General formulas for these forces are found, and their general properties are described. A convenient model of a localized patch is then suggested that allows us to calculate all the forces in a closed elementary form. Using this, a detailed analysis of the patch interaction for one pair of patches is carried out, and the dependence of forces on the patch parameters (width and strength) and their mutual position is examined. We also give various estimates of the axial patch effect force important for the Satellite Test of the Equivalence Principle (STEP), and recommend intensive pre-flight simulations employing our results. |
2310.12185 | Kyriakos Papadopoulos | Markus Fr\"ob, Albert Much and Kyriakos Papadopoulos | Relative Entropy in de Sitter is a Noether Charge | null | Phys. Rev. D 108 (2023) 105004 | 10.1103/PhysRevD.108.105004 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the relative entropy between the vacuum and a coherent state for a
massive scalar field in de Sitter spacetime, using Tomita-Takesaki modular
theory and the Araki-Uhlmann formula for the relative entropy. Embedding de
Sitter spacetime as a hyperboloid in the ambient Minkowski space, we can
restrict the Minkowski wedge and the corresponding modular operator to de
Sitter, and we verify that this construction gives the correct modular flow. We
check that the relative entropy is positive and jointly convex, relate it to
the Noether charge of translations along the trajectories of the modular flow,
and determine the local temperature as seen by an observer that moves along
these trajectories.
| [
{
"created": "Wed, 18 Oct 2023 04:51:52 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Nov 2023 13:03:59 GMT",
"version": "v2"
}
] | 2023-11-22 | [
[
"Fröb",
"Markus",
""
],
[
"Much",
"Albert",
""
],
[
"Papadopoulos",
"Kyriakos",
""
]
] | We compute the relative entropy between the vacuum and a coherent state for a massive scalar field in de Sitter spacetime, using Tomita-Takesaki modular theory and the Araki-Uhlmann formula for the relative entropy. Embedding de Sitter spacetime as a hyperboloid in the ambient Minkowski space, we can restrict the Minkowski wedge and the corresponding modular operator to de Sitter, and we verify that this construction gives the correct modular flow. We check that the relative entropy is positive and jointly convex, relate it to the Noether charge of translations along the trajectories of the modular flow, and determine the local temperature as seen by an observer that moves along these trajectories. |
1811.10873 | M. Umair Shahzad | M. Umair Shahzad, Abdul Jawad | Thermodynamics of Black holes With Higher Order Corrected Entropy | 23 pages, 10 figures, accepted for publication by Canadian Journal of
Physics. arXiv admin note: text overlap with arXiv:1701.08650 by other
authors | null | 10.1139/cjp-2018-0091 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For analyzing the thermodynamical behavior of two well-known black holes such
as RN-AdS black hole with global monopole and $f(R)$ black hole, we consider
the higher order logarithmic corrected entropy. We develop various
thermodynamical properties such as, entropy, specific heats, pressure, Gibb's
and Helmhotz free energies for both black holes in the presence of corrected
entropy. The versatile study on the stability of black holes is being made by
using various frameworks such as the ratio of heat capacities ($\gamma$), grand
canonical and canonical ensembles, and phase transition in view of higher order
logarithmic corrected entropy. It is observed that both black holes exhibit
more stability (locally as well as globally) for growing values of cosmological
constant and higher order correction terms.
| [
{
"created": "Tue, 27 Nov 2018 08:46:01 GMT",
"version": "v1"
}
] | 2018-11-28 | [
[
"Shahzad",
"M. Umair",
""
],
[
"Jawad",
"Abdul",
""
]
] | For analyzing the thermodynamical behavior of two well-known black holes such as RN-AdS black hole with global monopole and $f(R)$ black hole, we consider the higher order logarithmic corrected entropy. We develop various thermodynamical properties such as, entropy, specific heats, pressure, Gibb's and Helmhotz free energies for both black holes in the presence of corrected entropy. The versatile study on the stability of black holes is being made by using various frameworks such as the ratio of heat capacities ($\gamma$), grand canonical and canonical ensembles, and phase transition in view of higher order logarithmic corrected entropy. It is observed that both black holes exhibit more stability (locally as well as globally) for growing values of cosmological constant and higher order correction terms. |
1111.3676 | Sergey Manida | Sergey N. Manida | Generalized Relativistic Kinematics | null | Theor.Math.Phys., 169(2): 1643-1655 (2011) | 10.1007/s11232-011-0141-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a method for deforming an extended Galilei algebra that leads to a
nonstandard realization of the Poincar\'e group with the Fock-Lorentz linear
fractional transformations. The invariant parameter in these transformations
has the dimension of length. Combining this deformation with the standard one
(with an invariant velocity $c$) leads to the algebra of the symmetry group of
the anti-de Sitter space in Beltrami coordinates. In this case, the action for
free point particles contains the dimensional constants $R$ and $c$. The limit
transitions lead to the ordinary ($R\to \infty$) or alternative ($c\to \infty$)
but nevertheless relativistic kinematics.
| [
{
"created": "Tue, 15 Nov 2011 22:07:18 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Manida",
"Sergey N.",
""
]
] | We propose a method for deforming an extended Galilei algebra that leads to a nonstandard realization of the Poincar\'e group with the Fock-Lorentz linear fractional transformations. The invariant parameter in these transformations has the dimension of length. Combining this deformation with the standard one (with an invariant velocity $c$) leads to the algebra of the symmetry group of the anti-de Sitter space in Beltrami coordinates. In this case, the action for free point particles contains the dimensional constants $R$ and $c$. The limit transitions lead to the ordinary ($R\to \infty$) or alternative ($c\to \infty$) but nevertheless relativistic kinematics. |
1212.5150 | Martin Bojowald | Martin Bojowald | A loop quantum multiverse? | 10 pages, 9 figures, based on a plenary talk given at Multicosmofun
'12, Szeczin, Poland | AIP Conf. Proc. 1514 (2013) 21-30 | 10.1063/1.4791718 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inhomogeneous space-times in loop quantum cosmology have come under better
control with recent advances in effective methods. Even highly inhomogeneous
situations, for which multiverse scenarios provide extreme examples, can now be
considered at least qualitatively.
| [
{
"created": "Thu, 20 Dec 2012 17:19:02 GMT",
"version": "v1"
}
] | 2013-11-13 | [
[
"Bojowald",
"Martin",
""
]
] | Inhomogeneous space-times in loop quantum cosmology have come under better control with recent advances in effective methods. Even highly inhomogeneous situations, for which multiverse scenarios provide extreme examples, can now be considered at least qualitatively. |
2207.04279 | Giorgio Immirzi | Yogendra Srivastava, Giorgio Immirzi, John Swain, Orland Panella,
Simone Pacetti | General Relativity versus Dark Matter for rotating galaxies | 22 pages, 4 figures; v2, minor corrections, e-mails added | null | 10.1140/epjc/s10052-022-11031-3 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A very general class of axially-symmetric metrics in general relativity (GR)
that includes rotations is used to discuss the dynamics of
rotationally-supported galaxies. The exact vacuum solutions of the Einstein
equations for this extended Weyl class of metrics allow us to deduce rigorously
the following: (i) GR rotational velocity always exceeds the Newtonian velocity
(thanks to Lenz's law in GR); (ii) A non-vanishing intrinsic angular momentum
($J$) for a galaxy demands the asymptotic constancy of the Weyl (vectorial)
length parameter ($a$) -a behavior identical to that found for the Kerr metric;
(iii) Asymptotic constancy of the same parameter $a$ also demands a plateau in
the rotational velocity. Unlike the Kerr metric, the extended Weyl metric can
and has been continued within the galaxy and it has been shown under what
conditions Gau\ss\ \&\ Amp\'ere laws emerge along with Ludwig's extended GEM
theory with its attendant non-linear rate equations for the velocity field.
Better estimates (than that from the Newtonian theory) for the escape velocity
of the Sun and a reasonable rotation curve \&\ $J$ for our own galaxy has been
presented.
| [
{
"created": "Sat, 9 Jul 2022 14:40:34 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jul 2022 16:36:21 GMT",
"version": "v2"
}
] | 2023-02-15 | [
[
"Srivastava",
"Yogendra",
""
],
[
"Immirzi",
"Giorgio",
""
],
[
"Swain",
"John",
""
],
[
"Panella",
"Orland",
""
],
[
"Pacetti",
"Simone",
""
]
] | A very general class of axially-symmetric metrics in general relativity (GR) that includes rotations is used to discuss the dynamics of rotationally-supported galaxies. The exact vacuum solutions of the Einstein equations for this extended Weyl class of metrics allow us to deduce rigorously the following: (i) GR rotational velocity always exceeds the Newtonian velocity (thanks to Lenz's law in GR); (ii) A non-vanishing intrinsic angular momentum ($J$) for a galaxy demands the asymptotic constancy of the Weyl (vectorial) length parameter ($a$) -a behavior identical to that found for the Kerr metric; (iii) Asymptotic constancy of the same parameter $a$ also demands a plateau in the rotational velocity. Unlike the Kerr metric, the extended Weyl metric can and has been continued within the galaxy and it has been shown under what conditions Gau\ss\ \&\ Amp\'ere laws emerge along with Ludwig's extended GEM theory with its attendant non-linear rate equations for the velocity field. Better estimates (than that from the Newtonian theory) for the escape velocity of the Sun and a reasonable rotation curve \&\ $J$ for our own galaxy has been presented. |
1504.08156 | Antonin Coutant | Antonin Coutant | Semiclassical momentum representation in quantum cosmology | 21 pages, 3 figures. Several clarifications, Sec.IV.C added. Typo
corrected, matches published version | Phys. Rev. D 93, 043520 (2016) | 10.1103/PhysRevD.93.043520 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that the standard WKB approximation fails to provide
semiclassical solutions in the vicinity of turning points. However, turning
points arise in many cosmological scenarios. In a previous work, we obtained a
new class of semiclassical solutions of the Wheeler-deWitt equation using the
conjugate momentum to the geometric variable. We present here a detailed study
of their main properties. We carefully compare them to usual WKB solutions and
turning point resolutions using Airy functions. We show that the momentum
representation possesses many advantages that are absent in other apporaches.
In particular, this framework has a key application in tackling the problem of
time. It allows us to use curvature as a time variable, and control the
corresponding domain of validity, i.e. under which conditions it provides a
good clock. We consider several applications, and in particular show how this
allows us to obtain semiclassical solutions of the Wheeler-DeWitt equation
parametrized by York time.
| [
{
"created": "Thu, 30 Apr 2015 10:30:24 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2015 11:56:40 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Feb 2016 12:31:33 GMT",
"version": "v3"
}
] | 2016-02-12 | [
[
"Coutant",
"Antonin",
""
]
] | It is well-known that the standard WKB approximation fails to provide semiclassical solutions in the vicinity of turning points. However, turning points arise in many cosmological scenarios. In a previous work, we obtained a new class of semiclassical solutions of the Wheeler-deWitt equation using the conjugate momentum to the geometric variable. We present here a detailed study of their main properties. We carefully compare them to usual WKB solutions and turning point resolutions using Airy functions. We show that the momentum representation possesses many advantages that are absent in other apporaches. In particular, this framework has a key application in tackling the problem of time. It allows us to use curvature as a time variable, and control the corresponding domain of validity, i.e. under which conditions it provides a good clock. We consider several applications, and in particular show how this allows us to obtain semiclassical solutions of the Wheeler-DeWitt equation parametrized by York time. |
1903.06471 | Suman Ghosh | Suman Ghosh | Renormalized stress tensor of a quantized massless scalar field in
warped cosmological braneworld background | 17+1 preprint pages. To appear in EPJC | null | 10.1140/epjc/s10052-019-6760-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Energy momentum tensor of a conformally coupled quantum scalar field in five
dimensional warped cosmological spacetimes is studied. We look at situations
where the four dimensional part represents a cosmological thick brane and the
scale of the extra dimension is time dependent. Renormalization of the
components of the energy momentum tensor is achieved using adiabatic
regularization method. The resulting energy and pressure densities explicitly
show the effects of warping and the dynamic extra dimension on the created
matter. We discussed how the created matter may accumulate to form thick branes
along the extra dimension.
| [
{
"created": "Fri, 15 Mar 2019 11:33:46 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Ghosh",
"Suman",
""
]
] | Energy momentum tensor of a conformally coupled quantum scalar field in five dimensional warped cosmological spacetimes is studied. We look at situations where the four dimensional part represents a cosmological thick brane and the scale of the extra dimension is time dependent. Renormalization of the components of the energy momentum tensor is achieved using adiabatic regularization method. The resulting energy and pressure densities explicitly show the effects of warping and the dynamic extra dimension on the created matter. We discussed how the created matter may accumulate to form thick branes along the extra dimension. |
0711.4644 | Steve Drasco | Steve Drasco | Verifying black hole orbits with gravitational spectroscopy | 18 pages, expanded section on detection algorithms and made minor
edits. Final published version | Phys.Rev.D79:104016,2009 | 10.1103/PhysRevD.79.104016 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from test masses bound to geodesic orbits of rotating
black holes are simulated, using Teukolsky's black hole perturbation formalism,
for about ten thousand generic orbital configurations. Each binary radiates
power exclusively in modes with frequencies that are
integer-linear-combinations of the orbit's three fundamental frequencies. The
following general spectral properties are found with a survey of orbits: (i)
99% of the radiated power is typically carried by a few hundred modes, and at
most by about a thousand modes, (ii) the dominant frequencies can be grouped
into a small number of families defined by fixing two of the three integer
frequency multipliers, and (iii) the specifics of these trends can be
qualitatively inferred from the geometry of the orbit under consideration.
Detections using triperiodic analytic templates modeled on these general
properties would constitute a verification of radiation from an adiabatic
sequence of black hole orbits and would recover the evolution of the
fundamental orbital frequencies. In an analogy with ordinary spectroscopy, this
would compare to observing the Bohr model's atomic hydrogen spectrum without
being able to rule out alternative atomic theories or nuclei. The suitability
of such a detection technique is demonstrated using snapshots computed at
12-hour intervals throughout the last three years before merger of a kludged
inspiral. Because of circularization, the number of excited modes decreases as
the binary evolves. A hypothetical detection algorithm that tracks mode
families dominating the first 12 hours of the inspiral would capture 98% of the
total power over the remaining three years.
| [
{
"created": "Thu, 29 Nov 2007 02:48:55 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 2009 04:51:14 GMT",
"version": "v2"
}
] | 2009-07-30 | [
[
"Drasco",
"Steve",
""
]
] | Gravitational waves from test masses bound to geodesic orbits of rotating black holes are simulated, using Teukolsky's black hole perturbation formalism, for about ten thousand generic orbital configurations. Each binary radiates power exclusively in modes with frequencies that are integer-linear-combinations of the orbit's three fundamental frequencies. The following general spectral properties are found with a survey of orbits: (i) 99% of the radiated power is typically carried by a few hundred modes, and at most by about a thousand modes, (ii) the dominant frequencies can be grouped into a small number of families defined by fixing two of the three integer frequency multipliers, and (iii) the specifics of these trends can be qualitatively inferred from the geometry of the orbit under consideration. Detections using triperiodic analytic templates modeled on these general properties would constitute a verification of radiation from an adiabatic sequence of black hole orbits and would recover the evolution of the fundamental orbital frequencies. In an analogy with ordinary spectroscopy, this would compare to observing the Bohr model's atomic hydrogen spectrum without being able to rule out alternative atomic theories or nuclei. The suitability of such a detection technique is demonstrated using snapshots computed at 12-hour intervals throughout the last three years before merger of a kludged inspiral. Because of circularization, the number of excited modes decreases as the binary evolves. A hypothetical detection algorithm that tracks mode families dominating the first 12 hours of the inspiral would capture 98% of the total power over the remaining three years. |
1511.05107 | Paolo Glorioso | Paolo Glorioso | Classification of certain asymptotically AdS space-times with Ricci-flat
boundary | 30 pages; v2: two references added, typos corrected, some
explanations improved; v.3: title changed, minor modifications of the
abstract, improved introduction of secs. II and V, three references added,
two typos corrected (published version) | JHEP 1612 (2016) 126 | 10.1007/JHEP12(2016)126 | MIT-CTP/4736 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We classify solutions to Einstein's equations in AdS with Ricci-flat boundary
metric and with covariantly constant boundary stress tensor, which in general
is not diagonalizable, i.e. it does not admit a reference frame. New solutions
are found, and in the context of the AdS/CFT duality they should describe a
boundary QFT in certain non-equilibrium steady states. Further imposing the
absence of scalar curvature singularities leads to a subset of metrics that can
be seen as null deformations of AdS or of the AdS soliton. We also outline the
procedure of solving the equations when a scalar is coupled to the metric,
which holographically leads to non-Lorentz-invariant RG flows.
| [
{
"created": "Mon, 16 Nov 2015 19:59:41 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Dec 2015 20:33:47 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Jan 2017 18:37:24 GMT",
"version": "v3"
}
] | 2017-01-30 | [
[
"Glorioso",
"Paolo",
""
]
] | We classify solutions to Einstein's equations in AdS with Ricci-flat boundary metric and with covariantly constant boundary stress tensor, which in general is not diagonalizable, i.e. it does not admit a reference frame. New solutions are found, and in the context of the AdS/CFT duality they should describe a boundary QFT in certain non-equilibrium steady states. Further imposing the absence of scalar curvature singularities leads to a subset of metrics that can be seen as null deformations of AdS or of the AdS soliton. We also outline the procedure of solving the equations when a scalar is coupled to the metric, which holographically leads to non-Lorentz-invariant RG flows. |
gr-qc/9608041 | Karen Brewster | Abhay Ashtekar, Jiri Bicak, Bernd G. Schmidt | Behavior of Einstein-Rosen Waves at Null Infinity | 16 pages, REVETEX, CGPG-96/5-2 | Phys.Rev. D55 (1997) 687-694 | 10.1103/PhysRevD.55.687 | null | gr-qc | null | The asymptotic behavior of Einstein-Rosen waves at null infinity in 4
dimensions is investigated in {\it all} directions by exploiting the relation
between the 4-dimensional space-time and the 3-dimensional symmetry reduction
thereof. Somewhat surprisingly, the behavior in a generic direction is {\it
better} than that in directions orthogonal to the symmetry axis. The geometric
origin of this difference can be understood most clearly from the 3-dimensional
perspective.
| [
{
"created": "Fri, 16 Aug 1996 17:49:29 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Bicak",
"Jiri",
""
],
[
"Schmidt",
"Bernd G.",
""
]
] | The asymptotic behavior of Einstein-Rosen waves at null infinity in 4 dimensions is investigated in {\it all} directions by exploiting the relation between the 4-dimensional space-time and the 3-dimensional symmetry reduction thereof. Somewhat surprisingly, the behavior in a generic direction is {\it better} than that in directions orthogonal to the symmetry axis. The geometric origin of this difference can be understood most clearly from the 3-dimensional perspective. |
1904.04883 | Oswaldo Duarte Miranda odm | Eunice Bezerra and Oswaldo D. Miranda | Mimetic gravity: mimicking the dynamics of the primeval universe in the
context of loop quantum cosmology | 13 pages, 2 figures | Eur. Phys. J. C, 79 4 (2019) 310 [published online April 6] | 10.1140/epjc/s10052-019-6823-3 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mimetic gravity can be described as a formulation capable of mimicking
different evolutionary scenarios regarding the universe dynamics.
Notwithstanding its initial aim of producing a similar evolution to the one
expected from the dark components of the standard cosmology, a recent
association with loop quantum cosmology could also provide interesting results.
In this work, we reinterpret the physics behind the curvature potential of
mimetic gravity description of loop quantum cosmology. Furthermore, we also
test the compatibility of our formulation for a Higgs-type field, proving that
the mimetic curvature potential can mimic the dynamics from a Higgs
inflationary model. Additionally, we discuss possible scenarios that emerge
from the relationship between matter and mimetic curvature and, within certain
limits, describe results for the primeval universe dynamics obtained by other
authors.
| [
{
"created": "Tue, 9 Apr 2019 19:50:58 GMT",
"version": "v1"
}
] | 2019-05-01 | [
[
"Bezerra",
"Eunice",
""
],
[
"Miranda",
"Oswaldo D.",
""
]
] | Mimetic gravity can be described as a formulation capable of mimicking different evolutionary scenarios regarding the universe dynamics. Notwithstanding its initial aim of producing a similar evolution to the one expected from the dark components of the standard cosmology, a recent association with loop quantum cosmology could also provide interesting results. In this work, we reinterpret the physics behind the curvature potential of mimetic gravity description of loop quantum cosmology. Furthermore, we also test the compatibility of our formulation for a Higgs-type field, proving that the mimetic curvature potential can mimic the dynamics from a Higgs inflationary model. Additionally, we discuss possible scenarios that emerge from the relationship between matter and mimetic curvature and, within certain limits, describe results for the primeval universe dynamics obtained by other authors. |
gr-qc/0008038 | Matthias Arnsdorf | Matthias Arnsdorf | Loop Quantum Gravity and Asymptotically Flat Spaces | 15 pages, based on talk presented at the MG IX meeting in Rome, July
2000 | null | null | null | gr-qc | null | After motivating why the study of asymptotically flat spaces is important in
loop quantum gravity, we review the extension of the standard framework of this
theory to the asymptotically flat sector based on the GNS construction. In
particular, we provide a general procedure for constructing new Hilbert spaces
for loop quantum gravity on non-compact spatial manifolds. States in these
Hilbert spaces can be interpreted as describing fluctuations around fiducial
fixed backgrounds. When the backgrounds are chosen to approximate classical
asymptotically flat 3-geometries this gives a natural framework in which to
discuss physical applications of loop quantum gravity, especially its
semi-classical limit. We present three general proposals for the construction
of suitable backgrounds, including one approach that can lead to quantum
gravity on anti-DeSitter space as described by the Chern-Simons state.
| [
{
"created": "Tue, 15 Aug 2000 15:24:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arnsdorf",
"Matthias",
""
]
] | After motivating why the study of asymptotically flat spaces is important in loop quantum gravity, we review the extension of the standard framework of this theory to the asymptotically flat sector based on the GNS construction. In particular, we provide a general procedure for constructing new Hilbert spaces for loop quantum gravity on non-compact spatial manifolds. States in these Hilbert spaces can be interpreted as describing fluctuations around fiducial fixed backgrounds. When the backgrounds are chosen to approximate classical asymptotically flat 3-geometries this gives a natural framework in which to discuss physical applications of loop quantum gravity, especially its semi-classical limit. We present three general proposals for the construction of suitable backgrounds, including one approach that can lead to quantum gravity on anti-DeSitter space as described by the Chern-Simons state. |
1804.05846 | Troels Harmark | Gianluca Grignani, Troels Harmark, Marta Orselli | On the existence of the Blandford-Znajek monopole for a slowly rotating
Kerr black hole | 8 pages, pdflatex. v2: minor typos corrected, conclusion improved,
acknowledgments added. v3: published version, references added, MAE
explanation and conclusions slightly expanded | Phys. Rev. D 98, 084056 (2018) | 10.1103/PhysRevD.98.084056 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Blandford-Znajek monopole is a conjectured solution of force-free
electrodynamics in the vicinity of a slowly rotating Kerr black hole,
supposedly defined as a perturbation in small angular momentum. It is used to
argue for the extraction of energy from rotating black holes by the
Blandford-Znajek process. We set up a careful analysis of the perturbative
definition of the Blandford-Znajek monopole, showing in particular that the
regime in which it is defined allows to use the technique of matched asymptotic
expansions. Our conclusion is that the Blandford-Znajek monopole, as it is
defined, is not consistent with demanding physically reasonable boundary
conditions far away from the event horizon. This puts into question the
existence of the Blandford-Znajek monopole, at least in the limit of slow
rotation of the Kerr black hole.
| [
{
"created": "Mon, 16 Apr 2018 18:00:01 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jun 2018 12:32:39 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Oct 2018 13:17:45 GMT",
"version": "v3"
}
] | 2018-11-07 | [
[
"Grignani",
"Gianluca",
""
],
[
"Harmark",
"Troels",
""
],
[
"Orselli",
"Marta",
""
]
] | The Blandford-Znajek monopole is a conjectured solution of force-free electrodynamics in the vicinity of a slowly rotating Kerr black hole, supposedly defined as a perturbation in small angular momentum. It is used to argue for the extraction of energy from rotating black holes by the Blandford-Znajek process. We set up a careful analysis of the perturbative definition of the Blandford-Znajek monopole, showing in particular that the regime in which it is defined allows to use the technique of matched asymptotic expansions. Our conclusion is that the Blandford-Znajek monopole, as it is defined, is not consistent with demanding physically reasonable boundary conditions far away from the event horizon. This puts into question the existence of the Blandford-Znajek monopole, at least in the limit of slow rotation of the Kerr black hole. |
gr-qc/0302054 | Yoshiaki Himemoto | Yoshiaki Himemoto and Misao Sasaki | Braneworld inflation driven by dynamics of a bulk scalar field | 10 pages, 1 figure, 1 reference added, typos corrected, to be
published in Progress of Theoretical Physics Supplement No. 148 "Brane World:
New Perspective in Cosmology" | Prog.Theor.Phys.Suppl.148:235-244,2003 | 10.1143/PTPS.148.235 | null | gr-qc astro-ph hep-ph hep-th | null | We review a viable alternative scenario of the inflationary universe in the
context of the Randall-Sundrum (RS) braneworld. In this scenario, the dynamics
of a 5-dimensional scalar field, which we call a bulk scalar field, plays the
central role. Focusing on the second (single-brane) RS model, we discuss
braneworld inflation driven by a bulk scalar field without introducing an
inflaton on the brane. As a toy model, for the bulk scalar field, we consider a
minimally coupled massive scalar field in the 5-dimensional spacetime, and look
for a perturbative solution of the field equation in the anti-de Sitter
background with an inflating brane. For a suitable range of the model
parameters, we find a solution that realizes slow-roll inflation on the brane.
When the Hubble parameter on the brane and the mass of a bulk scalar field are
much smaller than a typical 5-dimensional mass scale, it is found that this
proposed inflation scenario reproduces the standard inflation scenario in the
4-dimensional theory.
| [
{
"created": "Thu, 13 Feb 2003 13:51:45 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Feb 2003 08:54:38 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Himemoto",
"Yoshiaki",
""
],
[
"Sasaki",
"Misao",
""
]
] | We review a viable alternative scenario of the inflationary universe in the context of the Randall-Sundrum (RS) braneworld. In this scenario, the dynamics of a 5-dimensional scalar field, which we call a bulk scalar field, plays the central role. Focusing on the second (single-brane) RS model, we discuss braneworld inflation driven by a bulk scalar field without introducing an inflaton on the brane. As a toy model, for the bulk scalar field, we consider a minimally coupled massive scalar field in the 5-dimensional spacetime, and look for a perturbative solution of the field equation in the anti-de Sitter background with an inflating brane. For a suitable range of the model parameters, we find a solution that realizes slow-roll inflation on the brane. When the Hubble parameter on the brane and the mass of a bulk scalar field are much smaller than a typical 5-dimensional mass scale, it is found that this proposed inflation scenario reproduces the standard inflation scenario in the 4-dimensional theory. |
0803.4459 | Lars Andersson | Lars Andersson | Report on GRG18, Session A3, Mathematical Studies of the Field Equations | 12 pages | Class.Quant.Grav.25:114016,2008 | 10.1088/0264-9381/25/11/114016 | AEI-2008-020 | gr-qc | http://creativecommons.org/licenses/by/3.0/ | In this report I will give a summary of some of the main topics covered in
Session A3, mathematical studies of the field equations, at GRG18, Sydney.
Unfortunately, due to length constraints, some of the topics covered at the
session will be very briefly mentioned or left out altogether. The summary is
mainly based on extended abstracts submitted by the speakers and some of those
who presented posters at the session. I would like to thank all participants
for their contributions and help with this summary.
| [
{
"created": "Mon, 31 Mar 2008 13:40:27 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Apr 2008 08:13:29 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Andersson",
"Lars",
""
]
] | In this report I will give a summary of some of the main topics covered in Session A3, mathematical studies of the field equations, at GRG18, Sydney. Unfortunately, due to length constraints, some of the topics covered at the session will be very briefly mentioned or left out altogether. The summary is mainly based on extended abstracts submitted by the speakers and some of those who presented posters at the session. I would like to thank all participants for their contributions and help with this summary. |
1006.3743 | Deborah A. Konkowski | D.A. Konkowski, T.M. Helliwell | Quantum particle behavior in classically singular spacetimes | 3 pages, no figures, submitted to Proceedings of the 12th Marcel
Grossmann Meeting on General Relativity and Gravitation, Paris, July 13-18,
2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the classical and quantum singularity structure of a broad class of
spacetimes with asymptotically power-law behavior near the origin. Quantum
considerations "heal" a large class of scalar curvature singularities.
| [
{
"created": "Fri, 18 Jun 2010 16:23:00 GMT",
"version": "v1"
}
] | 2010-06-21 | [
[
"Konkowski",
"D. A.",
""
],
[
"Helliwell",
"T. M.",
""
]
] | We review the classical and quantum singularity structure of a broad class of spacetimes with asymptotically power-law behavior near the origin. Quantum considerations "heal" a large class of scalar curvature singularities. |
1112.6318 | Ziyang Hu | Ziyang Hu | The implications of Galilean invariance for classical point particle
lagrangians | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the implications of the requirement of Galilean invariance for
classical point particle lagrangians, in which the space is not assumed to be
flat to begin with. We show that for the free, time-independent lagrangian,
this requirement is equivalent to the existence of gradient Killing vectors on
space, which is in turn equivalent to the condition that the space is a direct
product, which is totally flat in the Galilean invariant direction. We then
consider more general cases and see that there is no simple generalisation to
these cases.
| [
{
"created": "Thu, 29 Dec 2011 14:28:49 GMT",
"version": "v1"
}
] | 2011-12-30 | [
[
"Hu",
"Ziyang",
""
]
] | We explore the implications of the requirement of Galilean invariance for classical point particle lagrangians, in which the space is not assumed to be flat to begin with. We show that for the free, time-independent lagrangian, this requirement is equivalent to the existence of gradient Killing vectors on space, which is in turn equivalent to the condition that the space is a direct product, which is totally flat in the Galilean invariant direction. We then consider more general cases and see that there is no simple generalisation to these cases. |
2107.07146 | Naoki Tsukamoto | Naoki Tsukamoto | Gravitational lensing by a photon sphere in a Reissner-Nordstr\"{o}m
naked singularity spacetime in strong deflection limits | 11 pages, 7 figures, calculations are fixed, accepted to be published
in Physical Review D | Phys. Rev. D. 104, 124016 (2021) | 10.1103/PhysRevD.104.124016 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate gravitational lensing by a photon sphere in a
Reissner-Nordstr\"{o}m naked singularity spacetime in strong deflection limits.
Because of the nonexistence of an event horizon and the existence of a
potential barrier near an antiphoton sphere, infinite numbers of images
slightly inside and outside of a photon sphere can appear. We obtain the
analytic expressions of the factors of logarithmic divergent terms and the
constant terms of the deflection angles in the strong deflection limits not
only the for the little outside but also the barely inside of the photon sphere
without Taylor expansions in the power of an electric charge. We can
distinguish between a Reissner-Nordstr\"{o}m black hole spacetime and the naked
singularity spacetime since the images little inside of the photon sphere
around the naked singularity are significantly brighter than the image barely
outside of the photon sphere around the black hole and the naked singularity.
| [
{
"created": "Thu, 15 Jul 2021 06:21:48 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jul 2021 15:33:30 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Jul 2021 09:54:34 GMT",
"version": "v3"
},
{
"created": "Wed, 21 Jul 2021 09:48:31 GMT",
"version": "v4"
},
{
"created": "Sat, 27 Nov 2021 10:50:35 GMT",
"version": "v5"
}
] | 2021-12-06 | [
[
"Tsukamoto",
"Naoki",
""
]
] | We investigate gravitational lensing by a photon sphere in a Reissner-Nordstr\"{o}m naked singularity spacetime in strong deflection limits. Because of the nonexistence of an event horizon and the existence of a potential barrier near an antiphoton sphere, infinite numbers of images slightly inside and outside of a photon sphere can appear. We obtain the analytic expressions of the factors of logarithmic divergent terms and the constant terms of the deflection angles in the strong deflection limits not only the for the little outside but also the barely inside of the photon sphere without Taylor expansions in the power of an electric charge. We can distinguish between a Reissner-Nordstr\"{o}m black hole spacetime and the naked singularity spacetime since the images little inside of the photon sphere around the naked singularity are significantly brighter than the image barely outside of the photon sphere around the black hole and the naked singularity. |
gr-qc/0306078 | Yonatan Oren | Yonatan Oren and Tsvi Piran | On the Collapse of Charged Scalar Fields | Accepted for publication in Phys. Rev. D | Phys.Rev. D68 (2003) 044013 | 10.1103/PhysRevD.68.044013 | null | gr-qc | null | We explore numerically the evolution of a collapsing spherical shell of
charged, massless scalar field. We obtain an external \RN space-time, and an
inner space-time that is bounded by a singularity on the Cauchy Horizon. We
compare these results with previous analysis and discuss some of the numerical
problems encountered.
| [
{
"created": "Tue, 17 Jun 2003 10:18:27 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Oren",
"Yonatan",
""
],
[
"Piran",
"Tsvi",
""
]
] | We explore numerically the evolution of a collapsing spherical shell of charged, massless scalar field. We obtain an external \RN space-time, and an inner space-time that is bounded by a singularity on the Cauchy Horizon. We compare these results with previous analysis and discuss some of the numerical problems encountered. |
2002.03551 | Puskar Mondal | Puskar Mondal | Big-bang limit of $2+1$ gravity and Thurston boundary of Teichm\"uller
space | 46 pages | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the asymptotic behavior of the solution curves of the dynamics of
spacetimes of the topological type $\Sigma_{p}\times \mathbb{R}$, $p>1$, where
$\Sigma_{p}$ is a closed Riemann surface of genus $p$, in the regime of $2+1$
dimensional classical general relativity. The configuration space of the gauge
fixed dynamics is identified with the Teichm\"uller space
($\mathcal{T}\Sigma_{p}\approx \mathbb{R}^{6p-6}$) of $\Sigma_{p}$. Utilizing
the properties of the Dirichlet energy of certain harmonic maps, estimates
derived from the associated elliptic equations in conjunction with a few
standard results of the theory of the compact Riemann surfaces, we prove that
every non-trivial solution curve runs off the edge of the Teichm\"uller space
at the limit of the big bang singularity and approaches the space of projective
measured laminations/foliations ($\mathcal{PML}$ $\mathcal{PMF}$), the Thurston
boundary of the Teichm\"uller space.
| [
{
"created": "Mon, 10 Feb 2020 05:20:21 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Feb 2020 21:51:26 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Feb 2020 16:10:17 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Jul 2020 21:47:55 GMT",
"version": "v4"
},
{
"created": "Sat, 17 Oct 2020 02:51:42 GMT",
"version": "v5"
},
{
"created": "Fri, 18 Feb 2022 03:00:43 GMT",
"version": "v6"
},
{
"created": "Thu, 2 Nov 2023 15:52:33 GMT",
"version": "v7"
},
{
"created": "Tue, 16 Jan 2024 07:11:29 GMT",
"version": "v8"
}
] | 2024-01-17 | [
[
"Mondal",
"Puskar",
""
]
] | We study the asymptotic behavior of the solution curves of the dynamics of spacetimes of the topological type $\Sigma_{p}\times \mathbb{R}$, $p>1$, where $\Sigma_{p}$ is a closed Riemann surface of genus $p$, in the regime of $2+1$ dimensional classical general relativity. The configuration space of the gauge fixed dynamics is identified with the Teichm\"uller space ($\mathcal{T}\Sigma_{p}\approx \mathbb{R}^{6p-6}$) of $\Sigma_{p}$. Utilizing the properties of the Dirichlet energy of certain harmonic maps, estimates derived from the associated elliptic equations in conjunction with a few standard results of the theory of the compact Riemann surfaces, we prove that every non-trivial solution curve runs off the edge of the Teichm\"uller space at the limit of the big bang singularity and approaches the space of projective measured laminations/foliations ($\mathcal{PML}$ $\mathcal{PMF}$), the Thurston boundary of the Teichm\"uller space. |
gr-qc/0501098 | Fu-Wen Shu | Fu-Wen Shu, You-Gen Shen | Quasinormal modes in Schwarschild black holes due to arbitrary spin
fields | 11 pages, 3 figures | Phys.Lett.B619:340-346,2005 | 10.1016/j.physletb.2005.05.077 | null | gr-qc | null | The Newman-Penrose formalism is used to deal with the massless scalar,
neutrino, electromagnetic, gravitino and gravitational quasinormal modes (QNMs)
in Schwarzschild black holes in a united form. The quasinormal mode frequencies
evaluated by using the 3rd-order WKB potential approximation show that the
boson perturbations and the fermion perturbations behave in a contrary way for
the variation of the oscillation frequencies with spin, while this is no longer
true for the damping's, which variate with $s$ in a same way both for boson and
fermion perturbations.
| [
{
"created": "Sun, 30 Jan 2005 18:23:17 GMT",
"version": "v1"
},
{
"created": "Tue, 31 May 2005 14:27:20 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Shu",
"Fu-Wen",
""
],
[
"Shen",
"You-Gen",
""
]
] | The Newman-Penrose formalism is used to deal with the massless scalar, neutrino, electromagnetic, gravitino and gravitational quasinormal modes (QNMs) in Schwarzschild black holes in a united form. The quasinormal mode frequencies evaluated by using the 3rd-order WKB potential approximation show that the boson perturbations and the fermion perturbations behave in a contrary way for the variation of the oscillation frequencies with spin, while this is no longer true for the damping's, which variate with $s$ in a same way both for boson and fermion perturbations. |
2205.06094 | Theodoros Papanikolaou | Theodoros Papanikolaou, Charalampos Tzerefos, Spyros Basilakos,
Emmanuel N. Saridakis | No constraints for $f(T)$ gravity from gravitational waves induced from
primordial black hole fluctuations | Published in Eur. Phys. J. C. arXiv admin note: text overlap with
arXiv:2112.15059 | Eur.Phys.J.C 83 (2023) | 10.1140/epjc/s10052-022-11157-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black hole (PBH) fluctuations can induce a stochastic
gravitational wave background at second order, and since this procedure is
sensitive to the underlying gravitational theory it can be used as a novel tool
to test general relativity and extract constraints on possible modified gravity
deviations. We apply this formalism in the framework of $f(T)$ gravity,
considering three viable mono-parametric models. In particular, we investigate
the induced modifications at the level of the gravitational-wave source, which
is encoded in terms of the power spectrum of the PBH gravitational potential,
as well as at the level of their propagation, described in terms of the Green
function which quantifies the propagator of the tensor perturbations. We find
that, within the observationally allowed range of the $f(T)$ model-parameters,
the obtained deviations from general relativity, both at the levels of source
and propagation, are practically negligible. Hence, we conclude that realistic
and viable $f(T)$ theories can safely pass the primordial black hole
constraints, which may offer an additional argument in their favor.
| [
{
"created": "Thu, 12 May 2022 14:00:16 GMT",
"version": "v1"
},
{
"created": "Tue, 16 May 2023 14:22:04 GMT",
"version": "v2"
}
] | 2023-05-17 | [
[
"Papanikolaou",
"Theodoros",
""
],
[
"Tzerefos",
"Charalampos",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | Primordial black hole (PBH) fluctuations can induce a stochastic gravitational wave background at second order, and since this procedure is sensitive to the underlying gravitational theory it can be used as a novel tool to test general relativity and extract constraints on possible modified gravity deviations. We apply this formalism in the framework of $f(T)$ gravity, considering three viable mono-parametric models. In particular, we investigate the induced modifications at the level of the gravitational-wave source, which is encoded in terms of the power spectrum of the PBH gravitational potential, as well as at the level of their propagation, described in terms of the Green function which quantifies the propagator of the tensor perturbations. We find that, within the observationally allowed range of the $f(T)$ model-parameters, the obtained deviations from general relativity, both at the levels of source and propagation, are practically negligible. Hence, we conclude that realistic and viable $f(T)$ theories can safely pass the primordial black hole constraints, which may offer an additional argument in their favor. |
gr-qc/0612028 | Lukasz Andrzej Glinka | B.M. Barbashov, L.A. Glinka, V.N. Pervushin, A.F. Zakharov | Hamiltonian General Relativity in CMB frame | 16 pages, 4 figures | null | null | null | gr-qc | null | A collection of requirements to the General Relativity that follow from the
WMAP observations of the Cosmic Microwave Background radiation anisotropy as an
inertial frame are discussed. These obligations include the separation of both
the CMB frame from the diffeomorphisms and the diffeo-invariant cosmic
evolution from the local scalar metric component in the manner compatible with
the canonical Hamiltonian approach to the Einstein--Hilbert theory with the
energy constraints. The solution of these constraints in classical and quantum
theories and a fit of units of measurements are discussed in the light of the
last Supernovae data.
| [
{
"created": "Tue, 5 Dec 2006 10:11:40 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2006 13:28:43 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Barbashov",
"B. M.",
""
],
[
"Glinka",
"L. A.",
""
],
[
"Pervushin",
"V. N.",
""
],
[
"Zakharov",
"A. F.",
""
]
] | A collection of requirements to the General Relativity that follow from the WMAP observations of the Cosmic Microwave Background radiation anisotropy as an inertial frame are discussed. These obligations include the separation of both the CMB frame from the diffeomorphisms and the diffeo-invariant cosmic evolution from the local scalar metric component in the manner compatible with the canonical Hamiltonian approach to the Einstein--Hilbert theory with the energy constraints. The solution of these constraints in classical and quantum theories and a fit of units of measurements are discussed in the light of the last Supernovae data. |
1909.04205 | Ben Kain | Ben Kain | Are gravitating magnetic monopoles stable? | 12 pages, 5 figures | Phys. Rev. D 100, 063003 (2019) | 10.1103/PhysRevD.100.063003 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitating Julia-Zee dyon is a particle-like solution with both electric
and magnetic charge. It is found in the Einstein-Yang-Mills-Higgs system of
SU(2) with a scalar field in the adjoint representation coupled to gravity.
Within the magnetic ansatz this system is reduced from describing dyons to
describing the gravitating 't Hooft-Polyakov magnetic monopole. The stability
of the well-known static gravitating magnetic monopole solutions with respect
to perturbations within the magnetic ansatz--so-called magnetic
perturbations--is well studied, but their stability with respect to
perturbations outside the magnetic ansatz--so-called sphaleronic
perturbations--is not. I undertake a purely numerical study by adding
sphaleronic perturbations to gravitating magnetic monopole solutions and then
dynamically evolving the system. For large perturbations I find that the system
heads toward a dyon configuration, as expected. For sufficiently small
perturbations, however, the system oscillates about the magnetic ansatz in a
manner consistent with oscillations about a stable equilibrium.
| [
{
"created": "Tue, 10 Sep 2019 00:30:51 GMT",
"version": "v1"
}
] | 2019-09-25 | [
[
"Kain",
"Ben",
""
]
] | The gravitating Julia-Zee dyon is a particle-like solution with both electric and magnetic charge. It is found in the Einstein-Yang-Mills-Higgs system of SU(2) with a scalar field in the adjoint representation coupled to gravity. Within the magnetic ansatz this system is reduced from describing dyons to describing the gravitating 't Hooft-Polyakov magnetic monopole. The stability of the well-known static gravitating magnetic monopole solutions with respect to perturbations within the magnetic ansatz--so-called magnetic perturbations--is well studied, but their stability with respect to perturbations outside the magnetic ansatz--so-called sphaleronic perturbations--is not. I undertake a purely numerical study by adding sphaleronic perturbations to gravitating magnetic monopole solutions and then dynamically evolving the system. For large perturbations I find that the system heads toward a dyon configuration, as expected. For sufficiently small perturbations, however, the system oscillates about the magnetic ansatz in a manner consistent with oscillations about a stable equilibrium. |
gr-qc/0007029 | Salvatore Capozziello | S.Capozziello, A. Feoli, G. Lambiase, G. Papini | Thin shell quantization in Weyl spacetime | 9 pages, Latex, to appear in Phys. Lett. A | Phys.Lett. A273 (2000) 25-30 | 10.1016/S0375-9601(00)00478-3 | null | gr-qc | null | We study the problem of quantization of thin shells in a Weyl-Dirac theory by
deriving a Wheeler-DeWitt equation from the dynamics. Solutions are found which
have interpretations in both cosmology and particle physics.
| [
{
"created": "Fri, 14 Jul 2000 09:42:41 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Capozziello",
"S.",
""
],
[
"Feoli",
"A.",
""
],
[
"Lambiase",
"G.",
""
],
[
"Papini",
"G.",
""
]
] | We study the problem of quantization of thin shells in a Weyl-Dirac theory by deriving a Wheeler-DeWitt equation from the dynamics. Solutions are found which have interpretations in both cosmology and particle physics. |
gr-qc/9712021 | N. K. Dadhich | Naresh Dadhich | A duality relation : global monopole and texture | 10 pages, LaTeX version | null | null | IUCAA-60/97 | gr-qc | null | We resolve the entire gravitational field;i.e. the Riemann curvature into its
electric and magnetic parts. In general, the vacuum Einstein equation is
symmetric in active and passive electric parts. However it turns out that the
Schwarzschild solution, which is the unique spherically symmetric vacuum
solutions can be characterised by a slightly more general equation which is not
symmetric. Then the duality transformation, implying interchange of active and
passive parts will relate the Schwarzschlid particle with the one with global
monopole charge. That is the two are dual of each-other. It further turns out
that flat spacetime is dual to massless global monopole and global texture
spacetimes.
| [
{
"created": "Wed, 3 Dec 1997 05:10:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dadhich",
"Naresh",
""
]
] | We resolve the entire gravitational field;i.e. the Riemann curvature into its electric and magnetic parts. In general, the vacuum Einstein equation is symmetric in active and passive electric parts. However it turns out that the Schwarzschild solution, which is the unique spherically symmetric vacuum solutions can be characterised by a slightly more general equation which is not symmetric. Then the duality transformation, implying interchange of active and passive parts will relate the Schwarzschlid particle with the one with global monopole charge. That is the two are dual of each-other. It further turns out that flat spacetime is dual to massless global monopole and global texture spacetimes. |
1802.01801 | Vladimir Folomeev | Vladimir Folomeev | Anisotropic neutron stars in $R^2$ gravity | 14 pages, 4 figures, minor corrections to content, new references
added, version published in PRD | Phys. Rev. D 97, 124009 (2018) | 10.1103/PhysRevD.97.124009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider static neutron stars within the framework of $R^2$ gravity. The
neutron fluid is described by three different types of realistic equations of
state (soft, moderately stiff, and stiff). Using the observational data on the
neutron star mass-radius relation, it is demonstrated that the characteristics
of the objects supported by the isotropic fluid agree with the observations
only if one uses the soft equation of state. We show that the inclusion of the
fluid anisotropy enables one also to employ more stiff equations of state to
model configurations that will satisfy the observational constraints
sufficiently. Also, using the standard thin accretion disk model, we
demonstrate potentially observable differences, which allow us to distinguish
the neutron stars constructed within the modified gravity framework from those
described in Einstein's general relativity.
| [
{
"created": "Tue, 6 Feb 2018 05:13:45 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jun 2018 10:49:34 GMT",
"version": "v2"
}
] | 2018-06-08 | [
[
"Folomeev",
"Vladimir",
""
]
] | We consider static neutron stars within the framework of $R^2$ gravity. The neutron fluid is described by three different types of realistic equations of state (soft, moderately stiff, and stiff). Using the observational data on the neutron star mass-radius relation, it is demonstrated that the characteristics of the objects supported by the isotropic fluid agree with the observations only if one uses the soft equation of state. We show that the inclusion of the fluid anisotropy enables one also to employ more stiff equations of state to model configurations that will satisfy the observational constraints sufficiently. Also, using the standard thin accretion disk model, we demonstrate potentially observable differences, which allow us to distinguish the neutron stars constructed within the modified gravity framework from those described in Einstein's general relativity. |
2204.10734 | Sumanta Chakraborty | Sumanta Chakraborty and Naresh Dadhich | Universality of the Buchdahl sphere | Published version, 20 pages, 2 figures | Eur. Phys. J. C 83, 677 (2023) | 10.1140/epjc/s10052-023-11793-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Buchdahl sphere, the limiting stable isotropic stellar structure without
exotic matter, plays a very important role in our understanding of how compact
an astrophysical object can be. Here, we show certain universal properties
associated with the Buchdahl sphere, in the sense that these properties will
not change with the inclusion of electric charge in the stellar structure, or,
will hold good in the pure Lovelock theories of gravity as well. Using these
universalities, we have proposed a Buchdahl limit for a slowly-rotating stellar
configuration, for the first time. Finally, the universality of the Buchdahl
sphere in terms of the gravitational and non-gravitational field energies, as
well as for the photon sphere have also been discussed.
| [
{
"created": "Fri, 22 Apr 2022 14:45:13 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Aug 2023 02:38:51 GMT",
"version": "v2"
}
] | 2023-08-22 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Dadhich",
"Naresh",
""
]
] | Buchdahl sphere, the limiting stable isotropic stellar structure without exotic matter, plays a very important role in our understanding of how compact an astrophysical object can be. Here, we show certain universal properties associated with the Buchdahl sphere, in the sense that these properties will not change with the inclusion of electric charge in the stellar structure, or, will hold good in the pure Lovelock theories of gravity as well. Using these universalities, we have proposed a Buchdahl limit for a slowly-rotating stellar configuration, for the first time. Finally, the universality of the Buchdahl sphere in terms of the gravitational and non-gravitational field energies, as well as for the photon sphere have also been discussed. |
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