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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1812.06126 | Shawn Rosofsky | Shawn Rosofsky, Roman Gold, Cecilia Chirenti, E. A. Huerta and M.
Coleman Miller | Probing neutron star structure via f-mode oscillations and damping in
dynamical spacetime models | 14 pages, 12 figures, 1 appendix. Submitted to PRD | Phys. Rev. D 99, 084024 (2019) | 10.1103/PhysRevD.99.084024 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave and electromagnetic observations can provide new insights
into the nature of matter at supra-nuclear densities inside neutron stars.
Improvements in electromagnetic and gravitational wave sensing instruments
continue to enhance the accuracy with which they can measure the masses, radii,
and tidal deformability of neutron stars. These better measurements place
tighter constraints on the equation of state of cold matter above nuclear
density. In this article, we discuss a complementary approach to get insights
into the structure of neutron stars by providing a model prediction for
non-linear fundamental eigenmodes (f-modes) and their decay over time, which
are thought to be induced by time-dependent tides in neutron star binaries.
Building on pioneering studies that relate the properties of f-modes to the
structure of neutron stars, we systematically study this link in the
non-perturbative regime using models that utilize numerical relativity. Using a
suite of fully relativistic numerical relativity simulations of oscillating TOV
stars, we establish blueprints for the numerical accuracy needed to accurately
compute the frequency and damping times of f-mode oscillations, which we expect
to be a good guide for the requirements in the binary case. We show that the
resulting f-mode frequencies match established results from linear perturbation
theory, but the damping times within numerical errors depart from linear
predictions. This work lays the foundation for upcoming studies aimed at a
comparison of theoretical models of f-mode signatures in gravitational waves,
and their uncertainties with actual gravitational wave data, searching for
neutron star binaries on highly eccentric orbits, and probing neutron star
structure at high densities.
| [
{
"created": "Fri, 14 Dec 2018 19:27:43 GMT",
"version": "v1"
}
] | 2019-04-24 | [
[
"Rosofsky",
"Shawn",
""
],
[
"Gold",
"Roman",
""
],
[
"Chirenti",
"Cecilia",
""
],
[
"Huerta",
"E. A.",
""
],
[
"Miller",
"M. Coleman",
""
]
] | Gravitational wave and electromagnetic observations can provide new insights into the nature of matter at supra-nuclear densities inside neutron stars. Improvements in electromagnetic and gravitational wave sensing instruments continue to enhance the accuracy with which they can measure the masses, radii, and tidal deformability of neutron stars. These better measurements place tighter constraints on the equation of state of cold matter above nuclear density. In this article, we discuss a complementary approach to get insights into the structure of neutron stars by providing a model prediction for non-linear fundamental eigenmodes (f-modes) and their decay over time, which are thought to be induced by time-dependent tides in neutron star binaries. Building on pioneering studies that relate the properties of f-modes to the structure of neutron stars, we systematically study this link in the non-perturbative regime using models that utilize numerical relativity. Using a suite of fully relativistic numerical relativity simulations of oscillating TOV stars, we establish blueprints for the numerical accuracy needed to accurately compute the frequency and damping times of f-mode oscillations, which we expect to be a good guide for the requirements in the binary case. We show that the resulting f-mode frequencies match established results from linear perturbation theory, but the damping times within numerical errors depart from linear predictions. This work lays the foundation for upcoming studies aimed at a comparison of theoretical models of f-mode signatures in gravitational waves, and their uncertainties with actual gravitational wave data, searching for neutron star binaries on highly eccentric orbits, and probing neutron star structure at high densities. |
gr-qc/0102028 | Jian Dai | Jian Dai, Xing-Chang Song (Theory Group, Department of Physics, Peking
University) | Vacuum Solutions of Classical Gravity on Cyclic Groups from
Noncommutative Geometry | Latex 7 pages; no figures. Significant modifications being given,
with references added | Commun.Theor.Phys. 37 (2002) 11-14 | 10.1088/0253-6102/37/1/11 | null | gr-qc hep-lat hep-th | null | Based on the observation that the moduli of a link variable on a cyclic group
modify Connes' distance on this group, we construct several action functionals
for this link variable within the framework of noncommutative geometry. After
solving the equations of motion, we find that one type of action gives
nontrivial vacuum solution for gravity on this cyclic group in a broad range of
coupling constants and that such solutions can be expressed with Chebyshev's
polynomials.
| [
{
"created": "Wed, 7 Feb 2001 16:30:17 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2001 09:37:19 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Feb 2001 14:28:26 GMT",
"version": "v3"
},
{
"created": "Wed, 4 Apr 2001 18:22:02 GMT",
"version": "v4"
}
] | 2018-01-17 | [
[
"Dai",
"Jian",
"",
"Theory Group, Department of Physics, Peking\n University"
],
[
"Song",
"Xing-Chang",
"",
"Theory Group, Department of Physics, Peking\n University"
]
] | Based on the observation that the moduli of a link variable on a cyclic group modify Connes' distance on this group, we construct several action functionals for this link variable within the framework of noncommutative geometry. After solving the equations of motion, we find that one type of action gives nontrivial vacuum solution for gravity on this cyclic group in a broad range of coupling constants and that such solutions can be expressed with Chebyshev's polynomials. |
2108.01774 | Iara Ota | Iara Ota and Cecilia Chirenti | Black hole spectroscopy horizons for current and future gravitational
wave detectors | 19 pages, 17 figures, version accepted for publication on PRD | Phys. Rev. D 105, 044015 (2022) | 10.1103/PhysRevD.105.044015 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole spectroscopy is the proposal to observe multiple quasinormal modes
in the ringdown of a binary black hole merger. In addition to the fundamental
quadrupolar mode, overtones and higher harmonics may be present and detectable
in the gravitational wave signal, allowing for tests of the no-hair theorem. We
analyze in detail the strengths and weaknesses of the standard Rayleigh
criterion supplied with a Fisher matrix error estimation, and we find that the
criterion is useful, but too restrictive. Therefore we motivate the use of a
conservative high Bayes factor threshold to obtain the black hole spectroscopy
horizons of current and future detectors, i.e., the distance (averaged in sky
location and binary inclination) up to which one or more additional modes can
be detected and confidently distinguished from each other. We set up all of our
searches for additional modes starting at $t = 10(M_1+M_2)$ after the peak
amplitude in simulated signals of circular nonspinning binaries. An agnostic
multimode analysis allows us to rank the subdominant modes: for nearly equal
mass binaries we find $(\ell, m, n) = (2,2,1)$ and $(3,3,0)$ and, for very
asymmetric binaries, $(3,3,0)$ and $(4,4,0)$, for the secondary and tertiary
modes, respectively. At the current estimated rates for heavy stellar mass
binary black hole mergers, with primary masses between 45 and 100 solar masses,
we expect an event rate of mergers within our conservative estimate for the
$(2,2,1)$ spectroscopy horizon of $0.03 - 0.10\ {\rm yr}^{-1}$ for LIGO at
design sensitivity and $(0.6 - 2.4) \times 10^3\ {\rm yr}^{-1}$ for the future
third generation ground-based detector Cosmic Explorer.
| [
{
"created": "Tue, 3 Aug 2021 22:15:38 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jan 2022 00:05:31 GMT",
"version": "v2"
}
] | 2022-02-14 | [
[
"Ota",
"Iara",
""
],
[
"Chirenti",
"Cecilia",
""
]
] | Black hole spectroscopy is the proposal to observe multiple quasinormal modes in the ringdown of a binary black hole merger. In addition to the fundamental quadrupolar mode, overtones and higher harmonics may be present and detectable in the gravitational wave signal, allowing for tests of the no-hair theorem. We analyze in detail the strengths and weaknesses of the standard Rayleigh criterion supplied with a Fisher matrix error estimation, and we find that the criterion is useful, but too restrictive. Therefore we motivate the use of a conservative high Bayes factor threshold to obtain the black hole spectroscopy horizons of current and future detectors, i.e., the distance (averaged in sky location and binary inclination) up to which one or more additional modes can be detected and confidently distinguished from each other. We set up all of our searches for additional modes starting at $t = 10(M_1+M_2)$ after the peak amplitude in simulated signals of circular nonspinning binaries. An agnostic multimode analysis allows us to rank the subdominant modes: for nearly equal mass binaries we find $(\ell, m, n) = (2,2,1)$ and $(3,3,0)$ and, for very asymmetric binaries, $(3,3,0)$ and $(4,4,0)$, for the secondary and tertiary modes, respectively. At the current estimated rates for heavy stellar mass binary black hole mergers, with primary masses between 45 and 100 solar masses, we expect an event rate of mergers within our conservative estimate for the $(2,2,1)$ spectroscopy horizon of $0.03 - 0.10\ {\rm yr}^{-1}$ for LIGO at design sensitivity and $(0.6 - 2.4) \times 10^3\ {\rm yr}^{-1}$ for the future third generation ground-based detector Cosmic Explorer. |
0806.2634 | Albert Roura | Guillem P\'erez-Nadal, Albert Roura, Enric Verdaguer | Backreaction from non-conformal quantum fields in de Sitter spacetime | 31 pages | Class.Quant.Grav.25:154013,2008 | 10.1088/0264-9381/25/15/154013 | LA-UR-08-0557 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the backreaction on the mean field geometry due to a non-conformal
quantum field in a Robertson-Walker background. In the regime of small mass and
small deviation from conformal coupling, we compute perturbatively the
expectation value of the stress tensor of the field for a variety of vacuum
states, and use it to obtain explicitly the semiclassical gravity solutions for
isotropic perturbations around de Sitter spacetime, which is found to be
stable. Our results show clearly the crucial role of the non-local terms that
appear in the effective action: they cancel the contribution from local terms
proportional to the logarithm of the scale factor which would otherwise become
dominant at late times and prevent the existence of a stable self-consistent de
Sitter solution. Finally, the opposite regime of a strongly non-conformal field
with a large mass is also considered.
| [
{
"created": "Mon, 16 Jun 2008 18:07:58 GMT",
"version": "v1"
}
] | 2009-12-02 | [
[
"Pérez-Nadal",
"Guillem",
""
],
[
"Roura",
"Albert",
""
],
[
"Verdaguer",
"Enric",
""
]
] | We study the backreaction on the mean field geometry due to a non-conformal quantum field in a Robertson-Walker background. In the regime of small mass and small deviation from conformal coupling, we compute perturbatively the expectation value of the stress tensor of the field for a variety of vacuum states, and use it to obtain explicitly the semiclassical gravity solutions for isotropic perturbations around de Sitter spacetime, which is found to be stable. Our results show clearly the crucial role of the non-local terms that appear in the effective action: they cancel the contribution from local terms proportional to the logarithm of the scale factor which would otherwise become dominant at late times and prevent the existence of a stable self-consistent de Sitter solution. Finally, the opposite regime of a strongly non-conformal field with a large mass is also considered. |
1606.08505 | Peter Zimmerman | Marc Casals, Samuel E. Gralla, and Peter Zimmerman | Horizon Instability of Extremal Kerr Black Holes: Nonaxisymmetric Modes
and Enhanced Growth Rate | 7 pages. 1 figure | Phys. Rev. D 94, 064003 (2016) | 10.1103/PhysRevD.94.064003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the horizon instability of the extremal Kerr black hole is
associated with a singular branch point in the Green function at the
superradiant bound frequency. We study generic initial data supported away from
the horizon and find an enhanced growth rate due to nonaxisymmetric modes. The
growth is controlled by the conformal weight of each mode. We speculate on
connections to near-extremal black holes and holographic duality.
| [
{
"created": "Mon, 27 Jun 2016 22:38:46 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jul 2016 19:45:45 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Jul 2016 13:19:32 GMT",
"version": "v3"
}
] | 2016-09-07 | [
[
"Casals",
"Marc",
""
],
[
"Gralla",
"Samuel E.",
""
],
[
"Zimmerman",
"Peter",
""
]
] | We show that the horizon instability of the extremal Kerr black hole is associated with a singular branch point in the Green function at the superradiant bound frequency. We study generic initial data supported away from the horizon and find an enhanced growth rate due to nonaxisymmetric modes. The growth is controlled by the conformal weight of each mode. We speculate on connections to near-extremal black holes and holographic duality. |
gr-qc/9606083 | Benni Reznik | B. Reznik | Trans-Planckian Tail in a Theory with a Cutoff | 17 pages, RevTex | Phys.Rev. D55 (1997) 2152-2158 | 10.1103/PhysRevD.55.2152 | null | gr-qc hep-th quant-ph | null | Trans-planckian frequencies can be mimicked outside a black-hole horizon as a
tail of an exponentially large amplitude wave that is mostly hidden behind the
horizon. The present proposal requires implementing a final state condition.
This condition involves only frequencies below the cutoff scale. It may be
interpreted as a condition on the singularity. Despite the introduction of the
cutoff, the Hawking radiation is restored for static observers. Freely falling
observers see empty space outside the horizon, but are "heated" as they cross
the horizon.
| [
{
"created": "Fri, 28 Jun 1996 04:50:55 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Reznik",
"B.",
""
]
] | Trans-planckian frequencies can be mimicked outside a black-hole horizon as a tail of an exponentially large amplitude wave that is mostly hidden behind the horizon. The present proposal requires implementing a final state condition. This condition involves only frequencies below the cutoff scale. It may be interpreted as a condition on the singularity. Despite the introduction of the cutoff, the Hawking radiation is restored for static observers. Freely falling observers see empty space outside the horizon, but are "heated" as they cross the horizon. |
1506.01282 | Xiongjun Fang | Xiongjun Fang, Sijie Gao | Proof of entropy principle in Einstein-Maxwell theory | LaTex, 16 pages, some minor changes and simplified derivations,
references added, matches published version | Phys. Rev. D 92, 024044 (2015) | 10.1103/PhysRevD.92.024044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a static self-gravitating charged perfect fluid system in the
Einstein-Maxwell theory. Assume Maxwell's equation and the Einstein constraint
equation are satisfied, and the temperature of the fluid obeys Tolman's law.
Then we prove that the total entropy of the fluid achieves an extremum implies
other components of Einstein's equation for any variations of metric and
electrical potential with fixed boundary values. Conversely, if Einstein's
equation and Maxwell's equations hold, the total entropy achieves an extremum.
Our work suggests that the maximum entropy principle is consistent with
Einstein's equation when electric field is taken into account.
| [
{
"created": "Wed, 3 Jun 2015 15:36:46 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jun 2015 14:00:30 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Aug 2015 09:33:41 GMT",
"version": "v3"
}
] | 2015-08-04 | [
[
"Fang",
"Xiongjun",
""
],
[
"Gao",
"Sijie",
""
]
] | We consider a static self-gravitating charged perfect fluid system in the Einstein-Maxwell theory. Assume Maxwell's equation and the Einstein constraint equation are satisfied, and the temperature of the fluid obeys Tolman's law. Then we prove that the total entropy of the fluid achieves an extremum implies other components of Einstein's equation for any variations of metric and electrical potential with fixed boundary values. Conversely, if Einstein's equation and Maxwell's equations hold, the total entropy achieves an extremum. Our work suggests that the maximum entropy principle is consistent with Einstein's equation when electric field is taken into account. |
1204.3654 | William C. C. Lima | A. G. S. Landulfo, W. C. C. Lima, G. E. A. Matsas, and D. A. T.
Vanzella | Particle creation due to tachyonic instability in relativistic stars | 12 pages, 2 figures, discussion improved: paragraph added at the end
of Sec. V B (published version) | Phys.Rev.D86:104025,2012 | 10.1103/PhysRevD.86.104025 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dense enough compact objects were recently shown to lead to an exponentially
fast increase of the vacuum energy density for some free scalar fields properly
coupled to the spacetime curvature as a consequence of a tachyonic-like
instability. Once the effect is triggered, the star energy density would be
overwhelmed by the vacuum energy density in a few milliseconds. This demands
that eventually geometry and field evolve to a new configuration to bring the
vacuum back to a stationary regime. Here, we show that the vacuum fluctuations
built up during the unstable epoch lead to particle creation in the final
stationary state when the tachyonic instability ceases. The amount of created
particles depends mostly on the duration of the unstable epoch and final
stationary configuration, which are open issues at this point. We emphasize
that the particle creation coming from the tachyonic instability will occur
even in the adiabatic limit, where the spacetime geometry changes arbitrarily
slowly, and therefore is quite distinct from the usual particle creation due to
the change in the background geometry.
| [
{
"created": "Mon, 16 Apr 2012 21:07:08 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2012 15:56:16 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Nov 2012 17:35:18 GMT",
"version": "v3"
}
] | 2012-11-22 | [
[
"Landulfo",
"A. G. S.",
""
],
[
"Lima",
"W. C. C.",
""
],
[
"Matsas",
"G. E. A.",
""
],
[
"Vanzella",
"D. A. T.",
""
]
] | Dense enough compact objects were recently shown to lead to an exponentially fast increase of the vacuum energy density for some free scalar fields properly coupled to the spacetime curvature as a consequence of a tachyonic-like instability. Once the effect is triggered, the star energy density would be overwhelmed by the vacuum energy density in a few milliseconds. This demands that eventually geometry and field evolve to a new configuration to bring the vacuum back to a stationary regime. Here, we show that the vacuum fluctuations built up during the unstable epoch lead to particle creation in the final stationary state when the tachyonic instability ceases. The amount of created particles depends mostly on the duration of the unstable epoch and final stationary configuration, which are open issues at this point. We emphasize that the particle creation coming from the tachyonic instability will occur even in the adiabatic limit, where the spacetime geometry changes arbitrarily slowly, and therefore is quite distinct from the usual particle creation due to the change in the background geometry. |
2402.01818 | Omar Nemoul | Omar Nemoul, Hichem Guergouri, and Jamal Mimouni | Studying the Behavior of Radial Free Geodesics in {\Lambda}CDM Model | 28 pages, 6 figures, and 1 table | null | 10.1142/S0219887824501342 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents an analytical study of the behavior of radial
free-geodesics in the Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime
within the Lambda Cold Dark Matter ({\Lambda}CDM) model. Using the radial free
motion solutions, we provide two methods for characterizing the geodesics and
defines a general formula that encapsulates all possible solutions, determined
by two initial conditions. We show that the past light cone, event horizon, and
particle horizon, can be considered as special cases of this overarching
formula. Furthermore, the paper explores the free geodesics within the
currently accepted cosmological model based on the recent Planck results,
thoroughly examining the various possible geodesic scenarios.
| [
{
"created": "Fri, 2 Feb 2024 15:19:31 GMT",
"version": "v1"
}
] | 2024-02-06 | [
[
"Nemoul",
"Omar",
""
],
[
"Guergouri",
"Hichem",
""
],
[
"Mimouni",
"Jamal",
""
]
] | This paper presents an analytical study of the behavior of radial free-geodesics in the Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime within the Lambda Cold Dark Matter ({\Lambda}CDM) model. Using the radial free motion solutions, we provide two methods for characterizing the geodesics and defines a general formula that encapsulates all possible solutions, determined by two initial conditions. We show that the past light cone, event horizon, and particle horizon, can be considered as special cases of this overarching formula. Furthermore, the paper explores the free geodesics within the currently accepted cosmological model based on the recent Planck results, thoroughly examining the various possible geodesic scenarios. |
gr-qc/9411066 | null | Jacek Jezierski | On the relation between metric and spin--2 form. of lin. Ein. theory | 20 pages, latex | Gen.Rel.Grav.27:821-843,1995 | 10.1007/BF02113066 | null | gr-qc | null | A twenty--dimensional space of charged solutions of spin--2 equations is
proposed. The relation with extended (via dilatation) Poincar\'e group is
analyzed. Locally, each solution of the theory may be described in terms of a
potential, which can be interpreted as a metric tensor satisfying linearized
Einstein equations. Globally, the non--singular metric tensor exists if and
only if 10 among the above 20 charges do vanish. The situation is analogous to
that in classical electrodynamics, where vanishing of magnetic monopole implies
the global existence of the electro--magnetic potentials. The notion of {\em
asymptotic conformal Yano--Killing tensor} is defined and used as a basic
concept to introduce an inertial frame in General Relativity via asymptotic
conditions at spatial infinity. The introduced class of asymptotically flat
solutions is free of supertranslation ambiguities.
| [
{
"created": "Mon, 28 Nov 1994 15:09:20 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Jezierski",
"Jacek",
""
]
] | A twenty--dimensional space of charged solutions of spin--2 equations is proposed. The relation with extended (via dilatation) Poincar\'e group is analyzed. Locally, each solution of the theory may be described in terms of a potential, which can be interpreted as a metric tensor satisfying linearized Einstein equations. Globally, the non--singular metric tensor exists if and only if 10 among the above 20 charges do vanish. The situation is analogous to that in classical electrodynamics, where vanishing of magnetic monopole implies the global existence of the electro--magnetic potentials. The notion of {\em asymptotic conformal Yano--Killing tensor} is defined and used as a basic concept to introduce an inertial frame in General Relativity via asymptotic conditions at spatial infinity. The introduced class of asymptotically flat solutions is free of supertranslation ambiguities. |
2211.03512 | Zhen-Ming Xu | Zhen-Ming Xu, Bin Wu, and Wen-Li Yang | Rate of the phase transition for a charged anti-de Sitter black hole | 8 pages, 3 figures, match the published version | SCIENCE CHINA Physics, Mechanics & Astronomy, 66(4), 240411 (2023) | 10.1007/s11433-022-2022-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phase transition is a core content of black hole thermodynamics. This study
adopted the Kramer's escape rate method for describing the Brownian motion of
particles in an external field to investigate the intensity of the phase
transition between small and large black hole states. Some existing studies
mostly focused on the formal analysis of the thermodynamic phase transition of
black holes, but they neglected the detailed description of the phase
transition process. Our results show that the phase transition between small
and large black holes for charged anti-de Sitter (AdS) black holes presents
serious asymmetric features, and the overall process is dominated by the
transition from a small black hole to a large black hole. This study filled a
research gap of a stochastic process analysis on the issue of the first-order
phase transition rate in the AdS black hole.
| [
{
"created": "Tue, 1 Nov 2022 08:04:03 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2023 03:26:54 GMT",
"version": "v2"
}
] | 2023-03-07 | [
[
"Xu",
"Zhen-Ming",
""
],
[
"Wu",
"Bin",
""
],
[
"Yang",
"Wen-Li",
""
]
] | Phase transition is a core content of black hole thermodynamics. This study adopted the Kramer's escape rate method for describing the Brownian motion of particles in an external field to investigate the intensity of the phase transition between small and large black hole states. Some existing studies mostly focused on the formal analysis of the thermodynamic phase transition of black holes, but they neglected the detailed description of the phase transition process. Our results show that the phase transition between small and large black holes for charged anti-de Sitter (AdS) black holes presents serious asymmetric features, and the overall process is dominated by the transition from a small black hole to a large black hole. This study filled a research gap of a stochastic process analysis on the issue of the first-order phase transition rate in the AdS black hole. |
1501.06724 | Jorge Rocha | Jorge V. Rocha | Gravitational collapse with rotating thin shells and cosmic censorship | 11 pages, 2 figures, proceedings of the VII Black Holes Workshop; v2:
references updated and minor corrections, matches version to be published in
International Journal of Modern Physics D | International Journal of Modern Physics D, Vol. 24, No. 9 (2015)
1542002 | 10.1142/S021827181542002X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational collapse of matter in the presence of rotation is a mostly
unexplored topic but it might have important implications for cosmic
censorship. Recently a convenient setup was identified to address this problem,
by considering thin matter shells at the interface between two equal angular
momenta Myers-Perry spacetimes in five dimensions. This note provides more
details about the matching of such cohomogeneity-1 spacetimes and extends the
results obtained therein to arbitrary higher odd dimensions. It is also pointed
out that oscillatory orbits for shells in asymptotically flat spacetimes can be
naturally obtained if the matter has a negative pressure component.
| [
{
"created": "Tue, 27 Jan 2015 10:25:47 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Mar 2015 11:32:26 GMT",
"version": "v2"
}
] | 2015-04-14 | [
[
"Rocha",
"Jorge V.",
""
]
] | Gravitational collapse of matter in the presence of rotation is a mostly unexplored topic but it might have important implications for cosmic censorship. Recently a convenient setup was identified to address this problem, by considering thin matter shells at the interface between two equal angular momenta Myers-Perry spacetimes in five dimensions. This note provides more details about the matching of such cohomogeneity-1 spacetimes and extends the results obtained therein to arbitrary higher odd dimensions. It is also pointed out that oscillatory orbits for shells in asymptotically flat spacetimes can be naturally obtained if the matter has a negative pressure component. |
2011.05055 | Guillaume Boileau | Guillaume Boileau, Nelson Christensen, Renate Meyer, Neil J. Cornish | Spectral separation of the stochastic gravitational-wave background for
LISA: observing both cosmological and astrophysical backgrounds | The paper has been corrected | Phys. Rev. D 103, 103529 (2021) | 10.1103/PhysRevD.103.103529 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the goal of attempting to observe a stochastic gravitational wave
background (SGWB) with LISA, the spectral separability of the cosmological and
astrophysical backgrounds is important to estimate. We attempt to determine the
level with which a cosmological background can be observed given the predicted
astrophysical background level. We predict detectable limits for the future
LISA measurement of the SGWB. Adaptive Markov chain Monte-Carlo methods are
used to produce estimates with the simulated data from the LISA Data challenge
(LDC). We also calculate the Cramer-Rao lower bound on the variance of the SGWB
parameter uncertainties based on the inverse Fisher Information using the
Whittle Likelihood. The estimation of the parameters is done with the 3 LISA
channels $A$, $E$, and $T$. We simultaneously estimate the noise using a LISA
noise model. Assuming the expected astrophysical background, a cosmological
background energy density of around $\Omega_{GW,Cosmo} \approx 1 \times
10^{-12}$ to $1 \times 10^{-13}$ can be detected by LISA.
| [
{
"created": "Tue, 10 Nov 2020 11:40:57 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2021 11:33:04 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Oct 2021 11:21:26 GMT",
"version": "v3"
}
] | 2021-10-08 | [
[
"Boileau",
"Guillaume",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Meyer",
"Renate",
""
],
[
"Cornish",
"Neil J.",
""
]
] | With the goal of attempting to observe a stochastic gravitational wave background (SGWB) with LISA, the spectral separability of the cosmological and astrophysical backgrounds is important to estimate. We attempt to determine the level with which a cosmological background can be observed given the predicted astrophysical background level. We predict detectable limits for the future LISA measurement of the SGWB. Adaptive Markov chain Monte-Carlo methods are used to produce estimates with the simulated data from the LISA Data challenge (LDC). We also calculate the Cramer-Rao lower bound on the variance of the SGWB parameter uncertainties based on the inverse Fisher Information using the Whittle Likelihood. The estimation of the parameters is done with the 3 LISA channels $A$, $E$, and $T$. We simultaneously estimate the noise using a LISA noise model. Assuming the expected astrophysical background, a cosmological background energy density of around $\Omega_{GW,Cosmo} \approx 1 \times 10^{-12}$ to $1 \times 10^{-13}$ can be detected by LISA. |
gr-qc/9311015 | Bill Pezzaglia | William Pezzaglia and Alfred Differ | A Clifford Dyadic Superfield from Bilateral Interactions of Geometric
Multispin Dirac Theory | 10 pages LaTex (kluwer.sty macro), report# clf-alg/pezz9304, [Summary
of talk Sept. 22, 1993 at Ixtapa-Zihuatanejo, Mexico, XXIIth International
Conference on Differential Geometric Methods in Theoretical Physics] | null | null | null | gr-qc hep-th | null | Multivector quantum mechanics utilizes wavefunctions which are Clifford
aggregates (e.g. sum of scalar, vector, bivector). This is equivalent to multi-
spinors constructed of Dirac matrices, with the representation independent form
of the generators geometrically interpreted as the basis vectors of spacetime.
Multiple generations of particles appear as left ideals of the algebra, coupled
only by now-allowed right-side applied (dextral) operations. A generalized
bilateral (two-sided operation) coupling is proposed which includes the above
mentioned dextrad field, and the spin-gauge interaction as particular cases.
This leads to a new principle of {\it poly-dimensional covariance}, in which
physical laws are invariant under the reshuffling of coordinate geometry. Such
a multigeometric superfield equation is proposed, which is sourced by a
bilateral current. In order to express the superfield in representation and
coordinate free form, we introduce Eddington E-F {\it double-frame} numbers.
Symmetric tensors can now be represented as 4D ``dyads", which actually are
elements of a global 8D Clifford algebra. As a restricted example, the dyadic
field created by the Greider-Ross multivector current (of a Dirac electron)
describes both electromagnetic and Morris- Greider gravitational interactions.
[to appear in Proceedings edited by J. Keller, UNAM, Mexico (Kluwer Academic
Publ)]
| [
{
"created": "Tue, 9 Nov 1993 12:25:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pezzaglia",
"William",
""
],
[
"Differ",
"Alfred",
""
]
] | Multivector quantum mechanics utilizes wavefunctions which are Clifford aggregates (e.g. sum of scalar, vector, bivector). This is equivalent to multi- spinors constructed of Dirac matrices, with the representation independent form of the generators geometrically interpreted as the basis vectors of spacetime. Multiple generations of particles appear as left ideals of the algebra, coupled only by now-allowed right-side applied (dextral) operations. A generalized bilateral (two-sided operation) coupling is proposed which includes the above mentioned dextrad field, and the spin-gauge interaction as particular cases. This leads to a new principle of {\it poly-dimensional covariance}, in which physical laws are invariant under the reshuffling of coordinate geometry. Such a multigeometric superfield equation is proposed, which is sourced by a bilateral current. In order to express the superfield in representation and coordinate free form, we introduce Eddington E-F {\it double-frame} numbers. Symmetric tensors can now be represented as 4D ``dyads", which actually are elements of a global 8D Clifford algebra. As a restricted example, the dyadic field created by the Greider-Ross multivector current (of a Dirac electron) describes both electromagnetic and Morris- Greider gravitational interactions. [to appear in Proceedings edited by J. Keller, UNAM, Mexico (Kluwer Academic Publ)] |
2201.01138 | Lang Liu | Lang Liu and Sang Pyo Kim | Gravitational and electromagnetic radiations from binary black holes
with electric and magnetic charges | Proceedings for the 17th Italian-Korean Symposium on Relativistic
Astrophysics, Korea, August 2-6, 2021; 12 pages, 5 figures; Talk based on
arXiv:2008.02326 and arXiv:2011.13586 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Maxwell theory has black hole solutions with electric and
magnetic charges. In the standard model for particle physics, dyons with
electric and magnetic charges would have been formed in the early universe. We
derive the equations of motion of black hole binaries with electric and
magnetic charges and explore some features of static orbits. We calculate the
total emission rates of energy and angular momentum due to gravitational and
electromagnetic radiations from dyonic binary black holes in different cases.
It is shown that the emission rates of energy and angular momentum due to
gravitational and electromagnetic radiations have the same dependence on the
conic angle for different orbits. Moreover, we obtain the evolutions of orbits
and find that a circular orbit remains circular while an elliptic orbit becomes
quasi-circular due to electromagnetic and gravitational radiations. Our results
provide rich information about black hole binaries with electric and magnetic
charges and can be used to test black holes with magnetic charges.
| [
{
"created": "Tue, 4 Jan 2022 13:55:53 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"Liu",
"Lang",
""
],
[
"Kim",
"Sang Pyo",
""
]
] | The Einstein-Maxwell theory has black hole solutions with electric and magnetic charges. In the standard model for particle physics, dyons with electric and magnetic charges would have been formed in the early universe. We derive the equations of motion of black hole binaries with electric and magnetic charges and explore some features of static orbits. We calculate the total emission rates of energy and angular momentum due to gravitational and electromagnetic radiations from dyonic binary black holes in different cases. It is shown that the emission rates of energy and angular momentum due to gravitational and electromagnetic radiations have the same dependence on the conic angle for different orbits. Moreover, we obtain the evolutions of orbits and find that a circular orbit remains circular while an elliptic orbit becomes quasi-circular due to electromagnetic and gravitational radiations. Our results provide rich information about black hole binaries with electric and magnetic charges and can be used to test black holes with magnetic charges. |
2408.07789 | Saeed Haddadi | Hazhir Dolatkhah, Artur Czerwinski, Asad Ali, Saif Al-Kuwari, and
Saeed Haddadi | Tripartite measurement uncertainty in Schwarzschild space-time | 8 pages, 6 figures. All comments are welcome | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | The effect of Hawking radiation on tripartite measurement uncertainty in a
Schwarzschild black hole background is analyzed in this study. Two scenarios
are examined: in the first, quantum memory particles approach a Schwarzschild
black hole and are positioned near the event horizon, while the particle being
measured remains in the asymptotically flat region. In the second scenario, the
measured particle moves toward the black hole, and the quantum memories stay in
the asymptotically flat region. The study considers two initial quantum states:
GHZ and W states. The findings reveal that in both cases, measurement
uncertainty increases steadily with rising Hawking temperature. When comparing
the GHZ and W states, the GHZ state initially exhibits lower measurement
uncertainty at low Hawking temperatures than the W state, indicating greater
resilience to Hawking radiation. Additionally, when the quantum memories remain
in the asymptotically flat region while the measured particle falls toward the
black hole, the uncertainties for GHZ and W states do not align at high
temperatures. The GHZ state consistently demonstrates lower measurement
uncertainty, showcasing its superior robustness against Hawking radiation.
| [
{
"created": "Wed, 14 Aug 2024 20:03:01 GMT",
"version": "v1"
}
] | 2024-08-16 | [
[
"Dolatkhah",
"Hazhir",
""
],
[
"Czerwinski",
"Artur",
""
],
[
"Ali",
"Asad",
""
],
[
"Al-Kuwari",
"Saif",
""
],
[
"Haddadi",
"Saeed",
""
]
] | The effect of Hawking radiation on tripartite measurement uncertainty in a Schwarzschild black hole background is analyzed in this study. Two scenarios are examined: in the first, quantum memory particles approach a Schwarzschild black hole and are positioned near the event horizon, while the particle being measured remains in the asymptotically flat region. In the second scenario, the measured particle moves toward the black hole, and the quantum memories stay in the asymptotically flat region. The study considers two initial quantum states: GHZ and W states. The findings reveal that in both cases, measurement uncertainty increases steadily with rising Hawking temperature. When comparing the GHZ and W states, the GHZ state initially exhibits lower measurement uncertainty at low Hawking temperatures than the W state, indicating greater resilience to Hawking radiation. Additionally, when the quantum memories remain in the asymptotically flat region while the measured particle falls toward the black hole, the uncertainties for GHZ and W states do not align at high temperatures. The GHZ state consistently demonstrates lower measurement uncertainty, showcasing its superior robustness against Hawking radiation. |
2011.12734 | Abbas Mirahmadi | Abbas Mirahmadi | Analytical Study of Gravitational Waves | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of the present thesis is to review the Blanchet-Damour approach to
analytical study of gravitational waves emitted by localized perfect fluid
sources. It is assumed these perfect fluids are such that it is possible to
define small parameters for asymptotic expansions. Asymptotic expansions in
this approach are called post-Minkowskian and post-Newtonian expansions. By
plugging these expansions into the Einstein field equation, post-Minkowskian
and post-Newtonian equations are obtained. The usual methods for solving these
equations are to use the retarded and Poisson integrals. However, they cannot
provide solutions up to any arbitrary order in these cases because of their
divergence. In fact, these divergences motivated Blanchet and Damour to employ
a new approach to solve the post-Minkowskian and post-Newtonian equations. They
obtained the general solutions by means of a specific process of analytic
continuation. These solutions have some unknown terms that if one determines,
the gravitational field is described everywhere in $\mathbb{R}^3$. A matching
procedure, which depends deeply on analytic continuation, is used to determine
these unknown terms.
| [
{
"created": "Tue, 24 Nov 2020 17:15:38 GMT",
"version": "v1"
}
] | 2020-11-26 | [
[
"Mirahmadi",
"Abbas",
""
]
] | The aim of the present thesis is to review the Blanchet-Damour approach to analytical study of gravitational waves emitted by localized perfect fluid sources. It is assumed these perfect fluids are such that it is possible to define small parameters for asymptotic expansions. Asymptotic expansions in this approach are called post-Minkowskian and post-Newtonian expansions. By plugging these expansions into the Einstein field equation, post-Minkowskian and post-Newtonian equations are obtained. The usual methods for solving these equations are to use the retarded and Poisson integrals. However, they cannot provide solutions up to any arbitrary order in these cases because of their divergence. In fact, these divergences motivated Blanchet and Damour to employ a new approach to solve the post-Minkowskian and post-Newtonian equations. They obtained the general solutions by means of a specific process of analytic continuation. These solutions have some unknown terms that if one determines, the gravitational field is described everywhere in $\mathbb{R}^3$. A matching procedure, which depends deeply on analytic continuation, is used to determine these unknown terms. |
gr-qc/9912076 | Konstantina Savvidou | Konstantina Savvidou | Continuous Time in Consistent Histories | 95 pages, Latex, A PhD thesis, submitted at Imperial College, London,
UK. It provides a thorough review of the HPO consistent histories programme | null | null | null | gr-qc | null | We discuss the case of histories labelled by a continuous time parameter in
the {\em History Projection Operator} consistent-histories quantum theory. We
describe how the appropriate representation of the history algebra may be
chosen by requiring the existence of projection operators that represent
propositions about time averages of the energy. We define the action operator
for the consistent histories formalism, as the quantum analogue of the
classical action functional, for the simple harmonic oscillator case. We show
that the action operator is the generator of two types of time transformations
that may be related to the two laws of time-evolution of the standard quantum
theory: the `state-vector reduction' and the unitary time-evolution. We
construct the corresponding classical histories and demonstrate the relevance
with the quantum histories; we demonstrate how the requirement of the temporal
logic structure of the theory is sufficient for the definition of classical
histories. Furthermore, we show the relation of the action operator to the
decoherence functional which describes the dynamics of the system. Finally, the
discussion is extended to give a preliminary account of quantum field theory in
this approach to the consistent histories formalism.
| [
{
"created": "Fri, 17 Dec 1999 20:47:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Savvidou",
"Konstantina",
""
]
] | We discuss the case of histories labelled by a continuous time parameter in the {\em History Projection Operator} consistent-histories quantum theory. We describe how the appropriate representation of the history algebra may be chosen by requiring the existence of projection operators that represent propositions about time averages of the energy. We define the action operator for the consistent histories formalism, as the quantum analogue of the classical action functional, for the simple harmonic oscillator case. We show that the action operator is the generator of two types of time transformations that may be related to the two laws of time-evolution of the standard quantum theory: the `state-vector reduction' and the unitary time-evolution. We construct the corresponding classical histories and demonstrate the relevance with the quantum histories; we demonstrate how the requirement of the temporal logic structure of the theory is sufficient for the definition of classical histories. Furthermore, we show the relation of the action operator to the decoherence functional which describes the dynamics of the system. Finally, the discussion is extended to give a preliminary account of quantum field theory in this approach to the consistent histories formalism. |
1004.4440 | Jiliang Jing | Chikun Ding, Songbai Chen, Jiliang Jing | Analytical expressions for greybody factor and dynamic evolution for
scalar field in Ho\v{r}ava-Lifshitz black hole | 13 pages, 4 figures, Accepted for publication in PRD | Phys.Rev.D82:024031,2010 | 10.1103/PhysRevD.82.024031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the propagation and evolution for a massless scalar field in
the background of $\lambda=1/2$ Ho\v{r}ava-Lifshitz black hole with the
condition of detailed balance. We fortunately obtain an exact solution for the
Klein-Gordon equation. Then, we find an analytical expression for the greybody
factor which is valid for any frequency; and also exactly show that the
perturbation decays without any oscillation. All of these can help us to
understand more about the Ho\v{r}ava-Lifshitz gravity.
| [
{
"created": "Mon, 26 Apr 2010 09:13:48 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 2010 15:17:56 GMT",
"version": "v2"
}
] | 2010-09-10 | [
[
"Ding",
"Chikun",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We investigate the propagation and evolution for a massless scalar field in the background of $\lambda=1/2$ Ho\v{r}ava-Lifshitz black hole with the condition of detailed balance. We fortunately obtain an exact solution for the Klein-Gordon equation. Then, we find an analytical expression for the greybody factor which is valid for any frequency; and also exactly show that the perturbation decays without any oscillation. All of these can help us to understand more about the Ho\v{r}ava-Lifshitz gravity. |
1511.08926 | Seema Satin | Seema Satin | Noise Kernel for Reissner Nordstrom Metric: Results at Cauchy Horizon | null | null | 10.1103/PhysRevD.93.084007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain point separated Noise Kernel for the Reissner Nordstr\"{o}m
metric.The Noise Kernel defines the fluctuations of the quantum stress tensor
and is of central importance to Semiclassical Stochastic Gravity.The metric is
modeled as gravitationally collapsing spacetime, by using suitable coordinate
transformations, defined earlier. The fluctuations of the quantum stress
tensor, at the final stage of collapse are then analysed for both, the naked
singularity and black hole end states. The behavior of this Noise Kernel, at
the Cauchy Horizon for naked singularity shows markedly different behaviour
from self similar Tolman Bondi metric, which was obtained earlier. In the
latter a very unique divergence was seen, which does not appear for the
Reissner Nordstr\"{o}m metric, here . It is known that the quantum stress
tensor itself, diverges at the Cauchy Horizon (CH) for both of these metrics .
In contrast, it can now be seen that the the fluctuations of the stress tensor
behave differently for the two cases. We give a discussion and further
directions for investigations of this interesting behaviour in the two cases
(regarding the collapse scenario).
| [
{
"created": "Sat, 28 Nov 2015 20:46:19 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Jan 2016 07:21:06 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Feb 2016 10:46:16 GMT",
"version": "v3"
}
] | 2016-05-04 | [
[
"Satin",
"Seema",
""
]
] | We obtain point separated Noise Kernel for the Reissner Nordstr\"{o}m metric.The Noise Kernel defines the fluctuations of the quantum stress tensor and is of central importance to Semiclassical Stochastic Gravity.The metric is modeled as gravitationally collapsing spacetime, by using suitable coordinate transformations, defined earlier. The fluctuations of the quantum stress tensor, at the final stage of collapse are then analysed for both, the naked singularity and black hole end states. The behavior of this Noise Kernel, at the Cauchy Horizon for naked singularity shows markedly different behaviour from self similar Tolman Bondi metric, which was obtained earlier. In the latter a very unique divergence was seen, which does not appear for the Reissner Nordstr\"{o}m metric, here . It is known that the quantum stress tensor itself, diverges at the Cauchy Horizon (CH) for both of these metrics . In contrast, it can now be seen that the the fluctuations of the stress tensor behave differently for the two cases. We give a discussion and further directions for investigations of this interesting behaviour in the two cases (regarding the collapse scenario). |
2108.05330 | Dong-han Yeom | Suddhasattwa Brahma, Che-Yu Chen, Dong-han Yeom | Annihilation-to-nothing: DeWitt boundary condition inside a black hole | 24 pages, 9 figures | Eur.Phys.J. C82, 772 (2022) | 10.1140/epjc/s10052-022-10730-1 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In canonical quantum gravity, the wave function for a hypersurface inside a
Schwarzschild black hole can be obtained by solving the Wheeler-DeWitt
equation. What is of prime importance is the behavior of the wave function for
the future boundary near the singularity, and the DeWitt boundary condition
implies that it should vanish here. In this paper, we provide several
generalizations, and new interpretations, of the DeWitt boundary condition.
First, we summarize existing works on the wave function inside the black hole
to justify the DeWitt boundary condition. Next, we investigate the wave
function for the collapsing null shell to show that due to the reflection
symmetry in space and time, there exists a destructive interference near the
singularity and hence a vanishing boundary condition can be natural. If we
extend this point of view to the black hole spacetime itself, then the DeWitt
boundary condition is equivalent to saying that there exists a symmetric
anti-black hole contribution, such that eventually these two geometries are
annihilated-to-nothing near the quantum transition surface. This symmetric
model can be realized within black hole models of loop quantum gravity with a
novel interpretation for the arrow(s) of time.
| [
{
"created": "Wed, 11 Aug 2021 17:13:34 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Sep 2022 04:40:50 GMT",
"version": "v2"
}
] | 2022-09-05 | [
[
"Brahma",
"Suddhasattwa",
""
],
[
"Chen",
"Che-Yu",
""
],
[
"Yeom",
"Dong-han",
""
]
] | In canonical quantum gravity, the wave function for a hypersurface inside a Schwarzschild black hole can be obtained by solving the Wheeler-DeWitt equation. What is of prime importance is the behavior of the wave function for the future boundary near the singularity, and the DeWitt boundary condition implies that it should vanish here. In this paper, we provide several generalizations, and new interpretations, of the DeWitt boundary condition. First, we summarize existing works on the wave function inside the black hole to justify the DeWitt boundary condition. Next, we investigate the wave function for the collapsing null shell to show that due to the reflection symmetry in space and time, there exists a destructive interference near the singularity and hence a vanishing boundary condition can be natural. If we extend this point of view to the black hole spacetime itself, then the DeWitt boundary condition is equivalent to saying that there exists a symmetric anti-black hole contribution, such that eventually these two geometries are annihilated-to-nothing near the quantum transition surface. This symmetric model can be realized within black hole models of loop quantum gravity with a novel interpretation for the arrow(s) of time. |
1201.4630 | Anzhong Wang | Yongqing Huang, Anzhong Wang, and Qiang Wu | Inflation in general covariant theory of gravity | 19 pages, 0 figures. Version published in JCAP, 10 (2012) 010 | null | 10.1088/1475-7516/2012/10/010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study inflation in the framework of the nonrelativistic
general covariant theory of the Ho\v{r}ava-Lifshitz gravity with the
projectability condition and an arbitrary coupling constant $\lambda$. We find
that the Friedmann-Robterson-Walker (FRW) universe is necessarily flat in such
a setup. We work out explicitly the linear perturbations of the flat FRW
universe without specifying to a particular gauge, and find that the
perturbations are different from those obtained in general relativity, because
of the presence of the high-order spatial derivative terms. Applied the general
formulas to a single scalar field, we show that in the sub-horizon regions, the
metric and scalar field are tightly coupled and have the same oscillating
frequencies. In the super-horizon regions, the perturbations become adiabatic,
and the comoving curvature perturbation is constant. We also calculate the
power spectra and indices of both the scalar and tensor perturbations, and
express them explicitly in terms of the slow roll parameters and the coupling
constants of the high-order spatial derivative terms. In particular, we find
that the perturbations, of both scalar and tensor, are almost scale-invariant,
and the spectrum indices are the same as those given in GR, but the ratio of
the scalar and tensor power spectra depends on the high-order spatial
derivative terms, and can be different from that of GR significantly.
| [
{
"created": "Mon, 23 Jan 2012 06:03:31 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Oct 2012 03:17:14 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Huang",
"Yongqing",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Wu",
"Qiang",
""
]
] | In this paper, we study inflation in the framework of the nonrelativistic general covariant theory of the Ho\v{r}ava-Lifshitz gravity with the projectability condition and an arbitrary coupling constant $\lambda$. We find that the Friedmann-Robterson-Walker (FRW) universe is necessarily flat in such a setup. We work out explicitly the linear perturbations of the flat FRW universe without specifying to a particular gauge, and find that the perturbations are different from those obtained in general relativity, because of the presence of the high-order spatial derivative terms. Applied the general formulas to a single scalar field, we show that in the sub-horizon regions, the metric and scalar field are tightly coupled and have the same oscillating frequencies. In the super-horizon regions, the perturbations become adiabatic, and the comoving curvature perturbation is constant. We also calculate the power spectra and indices of both the scalar and tensor perturbations, and express them explicitly in terms of the slow roll parameters and the coupling constants of the high-order spatial derivative terms. In particular, we find that the perturbations, of both scalar and tensor, are almost scale-invariant, and the spectrum indices are the same as those given in GR, but the ratio of the scalar and tensor power spectra depends on the high-order spatial derivative terms, and can be different from that of GR significantly. |
1905.00064 | Roman Konoplya | R. A. Konoplya | Shadow of a black hole surrounded by dark matter | 7 pages, 6 figures, revtex, the published version | Physics Letters B 795 (2019) pp. 1-6 | 10.1016/j.physletb.2019.05.043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a simple spherical model consisting of a Schwarzschild black hole
of mass $M$ and a dark matter of mass $\Delta M$ around it. The general formula
for the radius of black-hole shadow has been derived in this case. It is shown
that the change of the shadow is not negligible, once the effective radius of
the dark matter halo is of order $\sim \sqrt{3 M \Delta M}$. For this to
happen, for example, for the galactic black hole, the dark matter must be
concentrated near the black hole. For small deviations from the Schwarzschild
limit, the dominant contribution into the size of a shadow is due to the dark
matter under the photon sphere, but at larger deviations, the matter outside
the photon sphere cannot be ignored.
| [
{
"created": "Tue, 30 Apr 2019 19:08:54 GMT",
"version": "v1"
},
{
"created": "Sun, 5 May 2019 22:01:17 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Jun 2019 14:46:43 GMT",
"version": "v3"
}
] | 2019-06-05 | [
[
"Konoplya",
"R. A.",
""
]
] | We consider a simple spherical model consisting of a Schwarzschild black hole of mass $M$ and a dark matter of mass $\Delta M$ around it. The general formula for the radius of black-hole shadow has been derived in this case. It is shown that the change of the shadow is not negligible, once the effective radius of the dark matter halo is of order $\sim \sqrt{3 M \Delta M}$. For this to happen, for example, for the galactic black hole, the dark matter must be concentrated near the black hole. For small deviations from the Schwarzschild limit, the dominant contribution into the size of a shadow is due to the dark matter under the photon sphere, but at larger deviations, the matter outside the photon sphere cannot be ignored. |
1905.07277 | Shilpa Kastha | Shilpa Kastha, Anuradha Gupta, K. G. Arun, B. S. Sathyaprakash and
Chris Van Den Broeck | Testing the multipole structure and conservative dynamics of compact
binaries using gravitational wave observations: The spinning case | 16 pages, 8 figures, Mathematica readable supplemental material file
for all the inputs to calculate the parametrized waveform is with the source | Phys. Rev. D 100, 044007 (2019) | 10.1103/PhysRevD.100.044007 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In an earlier work [S. Kastha et al., PRD {\bf 98}, 124033 (2018)], we
developed the {\it parametrized multipolar gravitational wave phasing formula}
to test general relativity, for the non-spinning compact binaries in
quasi-circular orbit. In this paper, we extend the method and include the
important effect of spins in the inspiral dynamics. Furthermore, we consider
parametric scaling of PN coefficients of the conserved energy for the compact
binary, resulting in the parametrized phasing formula for non-precessing
spinning compact binaries in quasi-circular orbit. We also compute the
projected accuracies with which the second and third generation ground-based
gravitational wave detector networks as well as the planned space-based
detector LISA will be able to measure the multipole deformation parameters and
the binding energy parameters. Based on different source configurations, we
find that a network of third-generation detectors would have comparable ability
to that of LISA in constraining the conservative and dissipative dynamics of
the compact binary systems. This parametrized multipolar waveform would be
extremely useful not only in deriving the first upper limits on any deviations
of the multipole and the binding energy coefficients from general relativity
using the gravitational wave detections, but also for science case studies of
next generation gravitational wave detectors.
| [
{
"created": "Fri, 17 May 2019 14:04:57 GMT",
"version": "v1"
}
] | 2019-08-14 | [
[
"Kastha",
"Shilpa",
""
],
[
"Gupta",
"Anuradha",
""
],
[
"Arun",
"K. G.",
""
],
[
"Sathyaprakash",
"B. S.",
""
],
[
"Broeck",
"Chris Van Den",
""
]
] | In an earlier work [S. Kastha et al., PRD {\bf 98}, 124033 (2018)], we developed the {\it parametrized multipolar gravitational wave phasing formula} to test general relativity, for the non-spinning compact binaries in quasi-circular orbit. In this paper, we extend the method and include the important effect of spins in the inspiral dynamics. Furthermore, we consider parametric scaling of PN coefficients of the conserved energy for the compact binary, resulting in the parametrized phasing formula for non-precessing spinning compact binaries in quasi-circular orbit. We also compute the projected accuracies with which the second and third generation ground-based gravitational wave detector networks as well as the planned space-based detector LISA will be able to measure the multipole deformation parameters and the binding energy parameters. Based on different source configurations, we find that a network of third-generation detectors would have comparable ability to that of LISA in constraining the conservative and dissipative dynamics of the compact binary systems. This parametrized multipolar waveform would be extremely useful not only in deriving the first upper limits on any deviations of the multipole and the binding energy coefficients from general relativity using the gravitational wave detections, but also for science case studies of next generation gravitational wave detectors. |
gr-qc/0105086 | Mohammad Nouri-Zonoz | Mohammad Nouri-Zonoz and Ali Reza Tavanfar | Plane symmetric analogue of NUT space | 16 pages, REVTex format, typos corrected,reference added and a
conclusion corrected | Class.Quant.Grav.18:4293-4302,2001 | 10.1088/0264-9381/18/20/308 | IPM/P-2001/010 | gr-qc | null | In this article on the basis of a new definition of spacetime symmetry, which
is in accordance with the symmetry of the curvature invariants, we investigate
exact vacuum solutions of Einstein field equations corresponding to both static
and stationary plane symmetric spacetimes using the concepts of the
(1+3)-decomposition or threading formalism. Demanding the presence of a plane
symmetric gravitomagnetic field we find a family of two parameter (m and l)
solutions, every member of which being the plane symmetric analogue of NUT
space.
| [
{
"created": "Thu, 24 May 2001 11:24:22 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jun 2001 12:41:26 GMT",
"version": "v2"
},
{
"created": "Sat, 9 Jun 2001 11:29:02 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Nouri-Zonoz",
"Mohammad",
""
],
[
"Tavanfar",
"Ali Reza",
""
]
] | In this article on the basis of a new definition of spacetime symmetry, which is in accordance with the symmetry of the curvature invariants, we investigate exact vacuum solutions of Einstein field equations corresponding to both static and stationary plane symmetric spacetimes using the concepts of the (1+3)-decomposition or threading formalism. Demanding the presence of a plane symmetric gravitomagnetic field we find a family of two parameter (m and l) solutions, every member of which being the plane symmetric analogue of NUT space. |
1605.01587 | Hang Liu | Hang Liu and Xin-he Meng | Angular Momentum-Free of the Entropy Relations for Rotating Kaluza-Klein
Black Holes | Final version, accepted for publication by International Journal of
Theoretical Physics | Int.J.Theor.Phys. 56 (2017) no.2, 437-449 | 10.1007/s10773-016-3185-6 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on a mathematical lemma related to the Vandermonde determinant and two
theorems derived from the first law of black hole thermodynamics, we
investigate the angular momentum independence of the entropy sum as well as the
entropy product of general rotating Kaluza-Klein black holes in higher
dimensions. We show that for both non-charged rotating Kaluza-Klein black holes
and non-charged rotating Kaluza-Klein-AdS black holes, the angular momentum of
the black holes will not be present in entropy sum relation in dimensions
$d\geq4$, while the independence of angular momentum of the entropy product
holds provided that the black holes possess at least one zero rotation
parameter $a_j$ = 0 in higher dimensions $d\geq5$, which means that the
cosmological constant does not affect the angular momentum-free property of
entropy sum and entropy product under the circumstances that charge $\delta=0$.
For the reason that the entropy relations of charged rotating Kaluza-Klein
black holes as well as the non-charged rotating Kaluza-Klein black holes in
asymptotically flat spacetime act the same way, it is found that the charge has
no effect in the angular momentum-independence of entropy sum and product in
asymptotically flat spactime.
| [
{
"created": "Thu, 5 May 2016 13:40:56 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2016 09:54:42 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Nov 2016 11:19:46 GMT",
"version": "v3"
}
] | 2017-08-28 | [
[
"Liu",
"Hang",
""
],
[
"Meng",
"Xin-he",
""
]
] | Based on a mathematical lemma related to the Vandermonde determinant and two theorems derived from the first law of black hole thermodynamics, we investigate the angular momentum independence of the entropy sum as well as the entropy product of general rotating Kaluza-Klein black holes in higher dimensions. We show that for both non-charged rotating Kaluza-Klein black holes and non-charged rotating Kaluza-Klein-AdS black holes, the angular momentum of the black holes will not be present in entropy sum relation in dimensions $d\geq4$, while the independence of angular momentum of the entropy product holds provided that the black holes possess at least one zero rotation parameter $a_j$ = 0 in higher dimensions $d\geq5$, which means that the cosmological constant does not affect the angular momentum-free property of entropy sum and entropy product under the circumstances that charge $\delta=0$. For the reason that the entropy relations of charged rotating Kaluza-Klein black holes as well as the non-charged rotating Kaluza-Klein black holes in asymptotically flat spacetime act the same way, it is found that the charge has no effect in the angular momentum-independence of entropy sum and product in asymptotically flat spactime. |
1010.3630 | Horace W. Crater | Horace W. Crater, Jesse Labello, and Steve Rubenstein | Schwarzschild Solution of the Generally Covariant Quaternionic Field
Equations of Sachs | 23 pages, appendix added | Eur.Phys.J.Plus 126:16,2011 | 10.1140/epjp/i2011-11016-x | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Sachs has derived quaternion field equations that fully exploit the
underlying symmetry of the principle of general relativity, one in which the
fundamental 10 component metric field is replaced by a 16 component four-vector
quaternion. Instead of the 10 field equations of Einstein's tensor formulation,
these equations are 16 in number corresponding to the 16 analytic parametric
functions {\partial}x^{{\mu}'}/{\partial}x^{{\nu}} of the Einstein Lie Group.
The difference from the Einstein equations is that these equations are not
covariant with respect to reflections in space-time, as a consequence of their
underlying quaternionic structure. These equations can be combined into a part
that is even and a part that is odd with respect to spatial or temporal
reflections. This paper constructs a four-vector quaternion solution of the
quaternionic field equation of Sachs that corresponds to a spherically
symmetric static metric. We show that the equations for this four-vector
quaternion corresponding to a vacuum solution lead to differential equations
that are identical to the corresponding Schwarzschild equations for the metric
tensor components.
| [
{
"created": "Mon, 18 Oct 2010 15:37:45 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Nov 2010 01:32:59 GMT",
"version": "v2"
}
] | 2011-04-20 | [
[
"Crater",
"Horace W.",
""
],
[
"Labello",
"Jesse",
""
],
[
"Rubenstein",
"Steve",
""
]
] | Sachs has derived quaternion field equations that fully exploit the underlying symmetry of the principle of general relativity, one in which the fundamental 10 component metric field is replaced by a 16 component four-vector quaternion. Instead of the 10 field equations of Einstein's tensor formulation, these equations are 16 in number corresponding to the 16 analytic parametric functions {\partial}x^{{\mu}'}/{\partial}x^{{\nu}} of the Einstein Lie Group. The difference from the Einstein equations is that these equations are not covariant with respect to reflections in space-time, as a consequence of their underlying quaternionic structure. These equations can be combined into a part that is even and a part that is odd with respect to spatial or temporal reflections. This paper constructs a four-vector quaternion solution of the quaternionic field equation of Sachs that corresponds to a spherically symmetric static metric. We show that the equations for this four-vector quaternion corresponding to a vacuum solution lead to differential equations that are identical to the corresponding Schwarzschild equations for the metric tensor components. |
1005.2095 | Luis Rosales | L. Rosales, W. Barreto, C. Peralta and B. Rodr\'i guez-Mueller | Nonadiabatic charged spherical evolution in the postquasistatic
approximation | 11 pages, 16 Figures. Accepted for publication in Phys Rev D | Phys.Rev.D82:084014,2010 | 10.1103/PhysRevD.82.084014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the postquasistatic approximation, an iterative method for the
evolution of self-gravitating spheres of matter, to study the evolution of
dissipative and electrically charged distributions in General Relativity. We
evolve nonadiabatic distributions assuming an equation of state that accounts
for the anisotropy induced by the electric charge. Dissipation is described by
streaming out or diffusion approximations. We match the interior solution, in
noncomoving coordinates, with the Vaidya-Reissner-Nordstr\"om exterior
solution. Two models are considered: i) a Schwarzschild-like shell in the
diffusion limit; ii) a Schwarzschild-like interior in the free streaming limit.
These toy models tell us something about the nature of the dissipative and
electrically charged collapse. Diffusion stabilizes the gravitational collapse
producing a spherical shell whose contraction is halted in a short
characteristic hydrodynamic time. The streaming out radiation provides a more
efficient mechanism for emission of energy, redistributing the electric charge
on the whole sphere, while the distribution collapses indefinitely with a
longer hydrodynamic time scale.
| [
{
"created": "Wed, 12 May 2010 13:34:54 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Sep 2010 05:20:32 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Rosales",
"L.",
""
],
[
"Barreto",
"W.",
""
],
[
"Peralta",
"C.",
""
],
[
"guez-Mueller",
"B. Rodrí",
""
]
] | We apply the postquasistatic approximation, an iterative method for the evolution of self-gravitating spheres of matter, to study the evolution of dissipative and electrically charged distributions in General Relativity. We evolve nonadiabatic distributions assuming an equation of state that accounts for the anisotropy induced by the electric charge. Dissipation is described by streaming out or diffusion approximations. We match the interior solution, in noncomoving coordinates, with the Vaidya-Reissner-Nordstr\"om exterior solution. Two models are considered: i) a Schwarzschild-like shell in the diffusion limit; ii) a Schwarzschild-like interior in the free streaming limit. These toy models tell us something about the nature of the dissipative and electrically charged collapse. Diffusion stabilizes the gravitational collapse producing a spherical shell whose contraction is halted in a short characteristic hydrodynamic time. The streaming out radiation provides a more efficient mechanism for emission of energy, redistributing the electric charge on the whole sphere, while the distribution collapses indefinitely with a longer hydrodynamic time scale. |
2008.09098 | Supriya Pan | H. B. Benaoum, Weiqiang Yang, Supriya Pan and Eleonora Di Valentino | Modified Emergent Dark Energy and its Astronomical Constraints | 10 pages, 4 Figures and 2 Tables; typos corrected; comments are
welcome | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a modified form of the Phenomenologically Emergent Dark Energy
(PEDE) model by showing a very elegant approach. The model is named as Modified
Emergent Dark Energy (MEDE) to distinguish from PEDE model and it includes
$\Lambda$CDM, PEDE model, Chevallier-Polarski-Linder model and other
cosmological models of interest. We show that the present article offers a very
fantastic route to construct other PEDE models in a simple but very elegant
way. The model has seven free parameters where the six parameters are the same
as in $\Lambda$CDM or PEDE model and the remaining one parameter `$\alpha$'
quantifies the generalization. The present model predicts that dark energy
equation of state at present assumes, $w_{\rm DE}\; (z=0) = -1 -
\frac{\alpha}{3 \ln (10)}$ and in the far future (i.e., for $z \longrightarrow
-1$), it will evolve asymptotically to $w_{\rm DE} \longrightarrow -1$. We
perform a very robust observational analysis of the model using various
observational datasets including cosmic microwave background radiation, baryon
acoustic oscillations distance measurements, a local value of the Hubble
constant and the pantheon sample of Supernovae Type Ia. We find that the $H_0$
tension here is alleviated but not solved, while the only free parameter,
$\alpha$ could recover the $\Lambda$CDM or PEDE for different datasets. In
summary, the present article describes a novel route to construct other
modified versions of the PEDE model in a very simplified manner.
| [
{
"created": "Thu, 20 Aug 2020 17:38:45 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Aug 2020 09:18:28 GMT",
"version": "v2"
}
] | 2020-08-24 | [
[
"Benaoum",
"H. B.",
""
],
[
"Yang",
"Weiqiang",
""
],
[
"Pan",
"Supriya",
""
],
[
"Di Valentino",
"Eleonora",
""
]
] | We introduce a modified form of the Phenomenologically Emergent Dark Energy (PEDE) model by showing a very elegant approach. The model is named as Modified Emergent Dark Energy (MEDE) to distinguish from PEDE model and it includes $\Lambda$CDM, PEDE model, Chevallier-Polarski-Linder model and other cosmological models of interest. We show that the present article offers a very fantastic route to construct other PEDE models in a simple but very elegant way. The model has seven free parameters where the six parameters are the same as in $\Lambda$CDM or PEDE model and the remaining one parameter `$\alpha$' quantifies the generalization. The present model predicts that dark energy equation of state at present assumes, $w_{\rm DE}\; (z=0) = -1 - \frac{\alpha}{3 \ln (10)}$ and in the far future (i.e., for $z \longrightarrow -1$), it will evolve asymptotically to $w_{\rm DE} \longrightarrow -1$. We perform a very robust observational analysis of the model using various observational datasets including cosmic microwave background radiation, baryon acoustic oscillations distance measurements, a local value of the Hubble constant and the pantheon sample of Supernovae Type Ia. We find that the $H_0$ tension here is alleviated but not solved, while the only free parameter, $\alpha$ could recover the $\Lambda$CDM or PEDE for different datasets. In summary, the present article describes a novel route to construct other modified versions of the PEDE model in a very simplified manner. |
2401.16126 | Ebrahim Yusofi Ramneti | S. Ahmadi, E. Yusofi, and M. A. Ramzanpour | Incorporating the Cosmological Constant in a Modified Uncertainty
Principle | 8 pages, 2 tables | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This study explores the cosmological constant problem and modified
uncertainty principle within a unified framework inspired by a void-dominated
scenario. In a recent paper~\cite{Yusofi:2022hgg}, voids were modeled as
spherical bubbles of similar average sizes, and the surface energy on the
voids' borders was calculated across various scales in a heuristic manner. We
show that this results in a significant discrepancy of approximately
$\mathcal{O}(+122)$ between the cosmological constant values from the minimum
to the maximum radii of bubbles. Furthermore, when considering the generalized
form of the uncertainty principle with both minimum and maximum lengths, i.e.
$\Delta X \Delta P \geq \frac{\hbar}{2} \frac{1}{1- \beta \Delta P^2}
\frac{1}{1- \alpha \Delta X^2}$, a similar order of discrepancy is observed
between $\alpha_{\rm max}$ and $\alpha_{\rm min}$, indicating that
$\alpha\propto\beta^{-1}\propto\Lambda\propto{\rm length}^{-2}~(m^{-2})$. As a
primary outcome of this finding, we offer a novel uncertainty principle that
incorporates a non-zero cosmological constant.
| [
{
"created": "Mon, 29 Jan 2024 12:51:31 GMT",
"version": "v1"
},
{
"created": "Sat, 11 May 2024 12:03:16 GMT",
"version": "v2"
}
] | 2024-05-14 | [
[
"Ahmadi",
"S.",
""
],
[
"Yusofi",
"E.",
""
],
[
"Ramzanpour",
"M. A.",
""
]
] | This study explores the cosmological constant problem and modified uncertainty principle within a unified framework inspired by a void-dominated scenario. In a recent paper~\cite{Yusofi:2022hgg}, voids were modeled as spherical bubbles of similar average sizes, and the surface energy on the voids' borders was calculated across various scales in a heuristic manner. We show that this results in a significant discrepancy of approximately $\mathcal{O}(+122)$ between the cosmological constant values from the minimum to the maximum radii of bubbles. Furthermore, when considering the generalized form of the uncertainty principle with both minimum and maximum lengths, i.e. $\Delta X \Delta P \geq \frac{\hbar}{2} \frac{1}{1- \beta \Delta P^2} \frac{1}{1- \alpha \Delta X^2}$, a similar order of discrepancy is observed between $\alpha_{\rm max}$ and $\alpha_{\rm min}$, indicating that $\alpha\propto\beta^{-1}\propto\Lambda\propto{\rm length}^{-2}~(m^{-2})$. As a primary outcome of this finding, we offer a novel uncertainty principle that incorporates a non-zero cosmological constant. |
gr-qc/9612021 | Stephen R. Lau | W. Kummer and S. R. Lau (Technische Universitaet Wien) | Boundary Conditions and Quasilocal Energy in the Canonical Formulation
of All 1+1 Models of Gravity | REVTeX, 41 pages, 2 Postscript figures, 10 macros | Annals Phys.258:37-80,1997 | 10.1006/aphy.1997.5687 | TUW-96-27 | gr-qc | null | Within a first-order framework, we comprehensively examine the role played by
boundary conditions in the canonical formulation of a completely general
two-dimensional gravity model. Our analysis particularly elucidates the
perennial themes of mass and energy. The gravity models for which our arguments
are valid include theories with dynamical torsion and so-called generalized
dilaton theories (GDTs). Our analysis of the canonical action principle (i)
provides a rigorous correspondence between the most general first-order
two-dimensional Einstein-Cartan model (ECM) and GDT and (ii) allows us to
extract in a virtually simultaneous manner the ``true degrees of freedom'' for
both ECMs and GDTs. For all such models, the existence of an absolutely
conserved (in vacuo) quantity C is a generic feature, with (minus) C
corresponding to the black-hole mass parameter in the important special cases
of spherically symmetric four-dimensional general relativity and standard
two-dimensional dilaton gravity. The mass C also includes (minimally coupled)
matter into a ``universal mass function.'' We place particular emphasis on the
(quite general) class of models within GDT possessing a Minkowski-like
groundstate solution (allowing comparison between $C$ and the
Arnowitt-Deser-Misner mass for such models).
| [
{
"created": "Mon, 9 Dec 1996 17:59:31 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Kummer",
"W.",
"",
"Technische Universitaet Wien"
],
[
"Lau",
"S. R.",
"",
"Technische Universitaet Wien"
]
] | Within a first-order framework, we comprehensively examine the role played by boundary conditions in the canonical formulation of a completely general two-dimensional gravity model. Our analysis particularly elucidates the perennial themes of mass and energy. The gravity models for which our arguments are valid include theories with dynamical torsion and so-called generalized dilaton theories (GDTs). Our analysis of the canonical action principle (i) provides a rigorous correspondence between the most general first-order two-dimensional Einstein-Cartan model (ECM) and GDT and (ii) allows us to extract in a virtually simultaneous manner the ``true degrees of freedom'' for both ECMs and GDTs. For all such models, the existence of an absolutely conserved (in vacuo) quantity C is a generic feature, with (minus) C corresponding to the black-hole mass parameter in the important special cases of spherically symmetric four-dimensional general relativity and standard two-dimensional dilaton gravity. The mass C also includes (minimally coupled) matter into a ``universal mass function.'' We place particular emphasis on the (quite general) class of models within GDT possessing a Minkowski-like groundstate solution (allowing comparison between $C$ and the Arnowitt-Deser-Misner mass for such models). |
2007.09408 | Hexu Zhang | He-Xu Zhang, Yuan Chen, Tian-Chi Ma, Peng-Zhang He, and Jian-Bo Deng | Bardeen black hole surrounded by perfect fluid dark matter | It is to be published in Chinese Physics C | null | 10.1088/1674-1137/abe84c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an exact solution of the spherically symmetric Bardeen black hole
surrounded by perfect fluid dark matter (PFDM). By treating the magnetic charge
$g$ and dark matter parameter $\alpha$ as thermodynamic variables, we find that
the thermodynamic first law and the corresponding Smarr formula are satisfied.
The thermodynamic stability of the black hole is also studied. The result show
that, there exists a critical radius $r_{+}^{C}$, where the heat capacity
diverges, suggesting that the black hole is thermodynamically stable in the
range $0<r_{+}<r_{+}^{C}$. In addition, the critical radius $r_{+}^{C}$
increases with the magnetic charge $g$ and decreases with the dark matter
parameter $\alpha$. Applying the Newman-Janis algorithm, we generalize the
spherically symmetric solution to the corresponding rotating black hole. With
the metric at hand, the horizons and ergospheres are studied. It turns out that
for a fixed dark matter parameter $\alpha$, in a certain range, with the
increase of the rotation parameter $a$ and magnetic charge $g$, the Cauchy
horizon radius increases while the event horizon radius decreases. Finally, we
investigate the energy extraction by the Penrose process in rotating Bardeen
black hole surrounded by PFDM.
| [
{
"created": "Sat, 18 Jul 2020 11:18:44 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Feb 2021 20:50:57 GMT",
"version": "v2"
}
] | 2021-05-26 | [
[
"Zhang",
"He-Xu",
""
],
[
"Chen",
"Yuan",
""
],
[
"Ma",
"Tian-Chi",
""
],
[
"He",
"Peng-Zhang",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | We derive an exact solution of the spherically symmetric Bardeen black hole surrounded by perfect fluid dark matter (PFDM). By treating the magnetic charge $g$ and dark matter parameter $\alpha$ as thermodynamic variables, we find that the thermodynamic first law and the corresponding Smarr formula are satisfied. The thermodynamic stability of the black hole is also studied. The result show that, there exists a critical radius $r_{+}^{C}$, where the heat capacity diverges, suggesting that the black hole is thermodynamically stable in the range $0<r_{+}<r_{+}^{C}$. In addition, the critical radius $r_{+}^{C}$ increases with the magnetic charge $g$ and decreases with the dark matter parameter $\alpha$. Applying the Newman-Janis algorithm, we generalize the spherically symmetric solution to the corresponding rotating black hole. With the metric at hand, the horizons and ergospheres are studied. It turns out that for a fixed dark matter parameter $\alpha$, in a certain range, with the increase of the rotation parameter $a$ and magnetic charge $g$, the Cauchy horizon radius increases while the event horizon radius decreases. Finally, we investigate the energy extraction by the Penrose process in rotating Bardeen black hole surrounded by PFDM. |
1005.2740 | Dana Levanony | Dana Levanony and Amos Ori | Interior design of a two-dimensional semiclassical black hole: Quantum
transition across the singularity | Accepted to Phys. Rev. D | Phys.Rev.D81:104036,2010 | 10.1103/PhysRevD.81.104036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the internal structure of a two-dimensional dilatonic evaporating
black hole, based on the CGHS model. At the semiclassical level, a (weak)
spacelike singularity was previously found to develop inside the black hole. We
employ here a simplified quantum formulation of spacetime dynamics in the
neighborhood of this singularity, using a minisuperspace-like approach. Quantum
evolution is found to be regular and well-defined at the semiclassical
singularity. A well-localized initial wave-packet propagating towards the
singularity bounces off the latter and retains its well-localized form. Our
simplified quantum treatment thus suggests that spacetime may extend
semiclassically beyond the singularity, and also signifies the specific
extension.
| [
{
"created": "Sun, 16 May 2010 12:01:16 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Levanony",
"Dana",
""
],
[
"Ori",
"Amos",
""
]
] | We study the internal structure of a two-dimensional dilatonic evaporating black hole, based on the CGHS model. At the semiclassical level, a (weak) spacelike singularity was previously found to develop inside the black hole. We employ here a simplified quantum formulation of spacetime dynamics in the neighborhood of this singularity, using a minisuperspace-like approach. Quantum evolution is found to be regular and well-defined at the semiclassical singularity. A well-localized initial wave-packet propagating towards the singularity bounces off the latter and retains its well-localized form. Our simplified quantum treatment thus suggests that spacetime may extend semiclassically beyond the singularity, and also signifies the specific extension. |
2404.13447 | G\'abor Zsolt T\'oth | Istvan Racz, Gabor Zsolt Toth | Numerical investigation of the late-time tails of the solutions of the
Fackerell-Ipser equation | 28 pages, LaTeX | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The late-time behaviour of the solutions of the Fackerell-Ipser equation
(which is a wave equation for the spin-zero component of the electromagnetic
field strength tensor) on the closure of the domain of outer communication of
sub-extremal Kerr spacetime is studied numerically. Within the Kerr family, the
case of Schwarzschild background is also considered. Horizon-penetrating
compactified hyperboloidal coordinates are used, which allow the behaviour of
the solutions to be observed at the event horizon and at future null infinity
as well. For the initial data, pure multipole configurations that have compact
support and are either stationary or non-stationary are taken. It is found that
with such initial data the solutions of the Fackerell-Ipser equation converge
at late times either to a known static solution (up to a constant factor) or to
zero. As the limit is approached, the solutions exhibit a quasinormal ringdown
and finally a power-law decay. The exponents characterizing the power-law decay
of the spherical harmonic components of the field variable are extracted from
the numerical data for various values of the parameters of the initial data,
and based on the results a proposal for a Price's law relevant to the
Fackerell-Ipser equation is made. Certain conserved energy and angular momentum
currents are used to verify the numerical implementation of the underlying
mathematical model. In the construction of these currents a discrete symmetry
of the Fackerell-Ipser equation, which is the product of an equatorial
reflection and a complex conjugation, is also taken into account.
| [
{
"created": "Sat, 20 Apr 2024 19:13:39 GMT",
"version": "v1"
}
] | 2024-04-23 | [
[
"Racz",
"Istvan",
""
],
[
"Toth",
"Gabor Zsolt",
""
]
] | The late-time behaviour of the solutions of the Fackerell-Ipser equation (which is a wave equation for the spin-zero component of the electromagnetic field strength tensor) on the closure of the domain of outer communication of sub-extremal Kerr spacetime is studied numerically. Within the Kerr family, the case of Schwarzschild background is also considered. Horizon-penetrating compactified hyperboloidal coordinates are used, which allow the behaviour of the solutions to be observed at the event horizon and at future null infinity as well. For the initial data, pure multipole configurations that have compact support and are either stationary or non-stationary are taken. It is found that with such initial data the solutions of the Fackerell-Ipser equation converge at late times either to a known static solution (up to a constant factor) or to zero. As the limit is approached, the solutions exhibit a quasinormal ringdown and finally a power-law decay. The exponents characterizing the power-law decay of the spherical harmonic components of the field variable are extracted from the numerical data for various values of the parameters of the initial data, and based on the results a proposal for a Price's law relevant to the Fackerell-Ipser equation is made. Certain conserved energy and angular momentum currents are used to verify the numerical implementation of the underlying mathematical model. In the construction of these currents a discrete symmetry of the Fackerell-Ipser equation, which is the product of an equatorial reflection and a complex conjugation, is also taken into account. |
1509.02658 | Saurya Das | Saurya Das | Bose-Einstein condensation as an alternative to inflation | This essay received an Honorable Mention in the 2015 Gravity Research
Foundation Essay Competition | Int. J. Mod. Phys. D, Vol.24 (2015) 1544001 | 10.1142/S0218271815440010 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently shown that gravitons with a very small mass should have
formed a Bose-Einstein condensate in the very early Universe, whose density and
quantum potential can account for the dark matter and dark energy in the
Universe respectively. Here we show that the condensation can also naturally
explain the observed large scale homogeneity and isotropy of the Universe.
Furthermore gravitons continue to fall into their ground state within the
condensate at every epoch, accounting for the observed flatness of space at
cosmological distances scales. Finally, we argue that the density perturbations
due to quantum fluctuations within the condensate give rise to a scale
invariant spectrum. This therefore provides a viable alternative to inflation,
which is not associated with the well-known problems associated with the
latter.
| [
{
"created": "Wed, 9 Sep 2015 07:13:27 GMT",
"version": "v1"
}
] | 2015-10-13 | [
[
"Das",
"Saurya",
""
]
] | It was recently shown that gravitons with a very small mass should have formed a Bose-Einstein condensate in the very early Universe, whose density and quantum potential can account for the dark matter and dark energy in the Universe respectively. Here we show that the condensation can also naturally explain the observed large scale homogeneity and isotropy of the Universe. Furthermore gravitons continue to fall into their ground state within the condensate at every epoch, accounting for the observed flatness of space at cosmological distances scales. Finally, we argue that the density perturbations due to quantum fluctuations within the condensate give rise to a scale invariant spectrum. This therefore provides a viable alternative to inflation, which is not associated with the well-known problems associated with the latter. |
0902.2921 | Tomohiro Takahashi | Tomohiro Takahashi and Jiro Soda | Stability of Lovelock Black Holes under Tensor Perturbations | 22 pages, 7 figures;v3:references added | Phys.Rev.D79:104025,2009 | 10.1103/PhysRevD.79.104025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of static black holes in the third order Lovelock
theory. We derive a master equation for tensor perturbations. Using the master
equation, we analyze the stability of Lovelock black holes mainly in seven and
eight dimensions. We find there are cases where the linear analysis breaks
down. If we restrict ourselves to the regime where the linear analysis is
legitimate, black holes are always stable in seven dimensions. However, in
eight dimensions, there exists a critical mass below which black holes are
unstable. Combining our result in the third order Lovelock theory with the
previous one in Einstein-Gauss-Bonnet theory, we conjecture that small black
holes are unstable in any dimensions. The instability found in this paper will
be important for the analysis of black holes at the LHC.
| [
{
"created": "Tue, 17 Feb 2009 13:35:43 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Feb 2009 11:00:03 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Feb 2009 08:20:50 GMT",
"version": "v3"
}
] | 2009-07-30 | [
[
"Takahashi",
"Tomohiro",
""
],
[
"Soda",
"Jiro",
""
]
] | We study the stability of static black holes in the third order Lovelock theory. We derive a master equation for tensor perturbations. Using the master equation, we analyze the stability of Lovelock black holes mainly in seven and eight dimensions. We find there are cases where the linear analysis breaks down. If we restrict ourselves to the regime where the linear analysis is legitimate, black holes are always stable in seven dimensions. However, in eight dimensions, there exists a critical mass below which black holes are unstable. Combining our result in the third order Lovelock theory with the previous one in Einstein-Gauss-Bonnet theory, we conjecture that small black holes are unstable in any dimensions. The instability found in this paper will be important for the analysis of black holes at the LHC. |
2112.08406 | Ricard Aguilera-Miret | Ricard Aguilera-Miret, Daniele Vigan\`o, Carlos Palenzuela | Universality of the turbulent magnetic field in hypermassive neutron
stars produced by binary mergers | 8 pages, 5 figures | null | 10.3847/2041-8213/ac50a7 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-sa/4.0/ | The detection of a binary neutron star merger in 2017 through both
gravitational waves and electromagnetic emission opened a new era of
multimessenger astronomy. The understanding of the magnetic field amplification
triggered by the Kelvin-Helmholtz instability during the merger is still a
numerically unresolved problem because of the relevant small scales involved.
One of the uncertainties comes from the simplifications usually assumed in the
initial magnetic topology of merging neutron stars. We perform high-resolution,
convergent large-eddy simulations of binary neutron star mergers, following the
newly formed remnant for up to $30$ milliseconds. Here we specifically focus on
the comparison between simulations with different initial magnetic
configurations, going beyond the widespread-used aligned dipole confined within
each star. The results obtained show that the initial topology is quickly
forgotten, in a timescale of few miliseconds after the merger. Moreover, at the
end of the simulations, the average intensity ($B\sim 10^{16}$ G) and the
spectral distribution of magnetic energy over spatial scales barely depend on
the initial configuration. This is expected due to the small-scale efficient
dynamo involved, and thus it holds as long as: (i) the initial large-scale
magnetic field is not unrealistically high (as often imposed in mergers
studies); (ii) the turbulent instability is numerically (at least partially)
resolved, so that the amplified magnetic energy is distributed across a wide
range of scales and becomes orders-of-magnitude larger than the initial one.
| [
{
"created": "Wed, 15 Dec 2021 19:00:37 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2022 10:51:24 GMT",
"version": "v2"
}
] | 2022-03-29 | [
[
"Aguilera-Miret",
"Ricard",
""
],
[
"Viganò",
"Daniele",
""
],
[
"Palenzuela",
"Carlos",
""
]
] | The detection of a binary neutron star merger in 2017 through both gravitational waves and electromagnetic emission opened a new era of multimessenger astronomy. The understanding of the magnetic field amplification triggered by the Kelvin-Helmholtz instability during the merger is still a numerically unresolved problem because of the relevant small scales involved. One of the uncertainties comes from the simplifications usually assumed in the initial magnetic topology of merging neutron stars. We perform high-resolution, convergent large-eddy simulations of binary neutron star mergers, following the newly formed remnant for up to $30$ milliseconds. Here we specifically focus on the comparison between simulations with different initial magnetic configurations, going beyond the widespread-used aligned dipole confined within each star. The results obtained show that the initial topology is quickly forgotten, in a timescale of few miliseconds after the merger. Moreover, at the end of the simulations, the average intensity ($B\sim 10^{16}$ G) and the spectral distribution of magnetic energy over spatial scales barely depend on the initial configuration. This is expected due to the small-scale efficient dynamo involved, and thus it holds as long as: (i) the initial large-scale magnetic field is not unrealistically high (as often imposed in mergers studies); (ii) the turbulent instability is numerically (at least partially) resolved, so that the amplified magnetic energy is distributed across a wide range of scales and becomes orders-of-magnitude larger than the initial one. |
0905.4916 | Carlo Rovelli | Kirill Krasnov, Carlo Rovelli | Black holes in full quantum gravity | 5 pages | Class.Quant.Grav.26:245009,2009 | 10.1088/0264-9381/26/24/245009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum black holes have been studied extensively in quantum gravity and
string theory, using various semiclassical or background dependent approaches.
We explore the possibility of studying black holes in the full non-perturbative
quantum theory, without recurring to semiclassical considerations, and in the
context of loop quantum gravity. We propose a definition of a quantum black
hole as the collection of the quantum degrees of freedom that do not influence
observables at infinity. From this definition, it follows that for an observer
at infinity a black hole is described by an SU(2) intertwining operator. The
dimension of the Hilbert space of such intertwiners grows exponentially with
the horizon area. These considerations shed some light on the physical nature
of the microstates contributing to the black hole entropy. In particular, it
can be seen that the microstates being counted for the entropy have the
interpretation of describing different horizon shapes. The space of black hole
microstates described here is related to the one arrived at recently by Engle,
Noui and Perez, and sometime ago by Smolin, but obtained here directly within
the full quantum theory.
| [
{
"created": "Fri, 29 May 2009 16:20:04 GMT",
"version": "v1"
}
] | 2010-02-22 | [
[
"Krasnov",
"Kirill",
""
],
[
"Rovelli",
"Carlo",
""
]
] | Quantum black holes have been studied extensively in quantum gravity and string theory, using various semiclassical or background dependent approaches. We explore the possibility of studying black holes in the full non-perturbative quantum theory, without recurring to semiclassical considerations, and in the context of loop quantum gravity. We propose a definition of a quantum black hole as the collection of the quantum degrees of freedom that do not influence observables at infinity. From this definition, it follows that for an observer at infinity a black hole is described by an SU(2) intertwining operator. The dimension of the Hilbert space of such intertwiners grows exponentially with the horizon area. These considerations shed some light on the physical nature of the microstates contributing to the black hole entropy. In particular, it can be seen that the microstates being counted for the entropy have the interpretation of describing different horizon shapes. The space of black hole microstates described here is related to the one arrived at recently by Engle, Noui and Perez, and sometime ago by Smolin, but obtained here directly within the full quantum theory. |
gr-qc/0312085 | David B. Malament | David B. Malament | On the Time Reversal Invariance of Classical Electromagnetic Theory | 24 pages, 3 figure, forthcoming in Studies in History and Philosophy
of Modern Physics | Stud.Hist.Philos.Mod.Phys. 35 (2004) 295-315 | null | null | gr-qc | null | David Albert claims that classical electromagnetic theory is not time
reversal invariant. He acknowledges that all physics books say that it is, but
claims they are "simply wrong" because they rely on an incorrect account of how
the time reversal operator acts on magnetic fields. On that account, electric
fields are left intact by the operator, but magnetic fields are inverted.
Albert sees no reason for the asymmetric treatment, and insists that neither
field should be inverted. I argue, to the contrary, that the inversion of
magnetic fields makes good sense and is, in fact, forced by elementary
geometric considerations. I also suggest a way of thinking about the time
reversal invariance of classical electromagnetic theory -- one that makes use
of the invariant four-dimensional formulation of the theory -- that makes no
reference to magnetic fields at all. It is my hope that it will be of interest
in its own right, Albert aside. It has the advantage that it allows for
arbitrary curvature in the background spacetime structure, and is therefore
suitable for the framework of general relativity. The only assumption one needs
is temporal orientability.
| [
{
"created": "Thu, 18 Dec 2003 14:43:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Malament",
"David B.",
""
]
] | David Albert claims that classical electromagnetic theory is not time reversal invariant. He acknowledges that all physics books say that it is, but claims they are "simply wrong" because they rely on an incorrect account of how the time reversal operator acts on magnetic fields. On that account, electric fields are left intact by the operator, but magnetic fields are inverted. Albert sees no reason for the asymmetric treatment, and insists that neither field should be inverted. I argue, to the contrary, that the inversion of magnetic fields makes good sense and is, in fact, forced by elementary geometric considerations. I also suggest a way of thinking about the time reversal invariance of classical electromagnetic theory -- one that makes use of the invariant four-dimensional formulation of the theory -- that makes no reference to magnetic fields at all. It is my hope that it will be of interest in its own right, Albert aside. It has the advantage that it allows for arbitrary curvature in the background spacetime structure, and is therefore suitable for the framework of general relativity. The only assumption one needs is temporal orientability. |
2402.07981 | Conor Dyson | Conor Dyson, Jaime Redondo-Yuste, Maarten van de Meent, Vitor Cardoso | Relativistic aerodynamics of spinning black holes | 15 pages, 8 figures, minor update to text and references | Phys. Rev. D 109, 104038 (2024) | 10.1103/PhysRevD.109.104038 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Astrophysical black holes do not exist in vacuum, and their motion is
affected by the galactic environment. As a black hole moves it attracts stars
and matter, creating a wake that, in turn, exerts an effective friction slowing
down the black hole. This force is known as dynamical friction, and has
significant consequences, ranging from the formation of supermassive black hole
binaries to modifications in the phase of binary mergers. In this work we
explore the motion of spinning black holes on a medium. We find that the
classical drag along the velocity direction is modified and two novel forces
appear: a rotational force, which in the context of fluid dynamics is dubbed
the Magnus force, and a lift, orthogonal to the direction of motion. We develop
a first-principles fully-relativistic treatment of these spin-induced
aerodynamic forces in two types of environment: i) collisionless corpuscular
matter and ii) a light scalar field, exploring the differences between both
cases. In both cases we find that the total rotational force acts precisely in
the opposite direction as compared to the classical set-up of a spinning ball
moving through a fluid. Finally, we comment on the consequences of these new
effects for astrophysics and gravitational wave observations.
| [
{
"created": "Mon, 12 Feb 2024 19:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Feb 2024 07:53:22 GMT",
"version": "v2"
}
] | 2024-06-11 | [
[
"Dyson",
"Conor",
""
],
[
"Redondo-Yuste",
"Jaime",
""
],
[
"van de Meent",
"Maarten",
""
],
[
"Cardoso",
"Vitor",
""
]
] | Astrophysical black holes do not exist in vacuum, and their motion is affected by the galactic environment. As a black hole moves it attracts stars and matter, creating a wake that, in turn, exerts an effective friction slowing down the black hole. This force is known as dynamical friction, and has significant consequences, ranging from the formation of supermassive black hole binaries to modifications in the phase of binary mergers. In this work we explore the motion of spinning black holes on a medium. We find that the classical drag along the velocity direction is modified and two novel forces appear: a rotational force, which in the context of fluid dynamics is dubbed the Magnus force, and a lift, orthogonal to the direction of motion. We develop a first-principles fully-relativistic treatment of these spin-induced aerodynamic forces in two types of environment: i) collisionless corpuscular matter and ii) a light scalar field, exploring the differences between both cases. In both cases we find that the total rotational force acts precisely in the opposite direction as compared to the classical set-up of a spinning ball moving through a fluid. Finally, we comment on the consequences of these new effects for astrophysics and gravitational wave observations. |
gr-qc/9807007 | E. Montanari | Mirco Calura, Enrico Montanari and Pierluigi Fortini (University of
Ferrara and INFN sezione di Ferrara, Italy) | Lagrangian planetary equations in Schwarzschild space--time | 7 pages; revtex; accepted for publication in Class. Quantum Grav | Class.Quant.Grav. 15 (1998) 3121-3129 | 10.1088/0264-9381/15/10/015 | null | gr-qc astro-ph | null | We have developed a method to study the effects of a perturbation to the
motion of a test point--like object in a Schwarzschild spacetime. Such a method
is the extension of the Lagrangian planetary equations of classical celestial
mechanics into the framework of the full theory of general relativity. The
method provides a natural approach to account for relativistic effects in the
unperturbed problem in an exact way.
| [
{
"created": "Thu, 2 Jul 1998 17:31:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Calura",
"Mirco",
"",
"University of\n Ferrara and INFN sezione di Ferrara, Italy"
],
[
"Montanari",
"Enrico",
"",
"University of\n Ferrara and INFN sezione di Ferrara, Italy"
],
[
"Fortini",
"Pierluigi",
"",
"University of\n Ferrara and INFN sezione di ... | We have developed a method to study the effects of a perturbation to the motion of a test point--like object in a Schwarzschild spacetime. Such a method is the extension of the Lagrangian planetary equations of classical celestial mechanics into the framework of the full theory of general relativity. The method provides a natural approach to account for relativistic effects in the unperturbed problem in an exact way. |
1704.08402 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | Black hole entropy emission property | 4 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we examine the entropy emission property of black holes. When
the greybody factor is considered, it is found that Schwarzschild black hole is
a one-dimensional entropy emitter, which is independent of the spacetime
dimension and the spin of the emitted quanta. However, when generalized to
other black holes with two or more parameters, the result shows that the
one-dimensional entropy emission property will be violated. Thus our result
implies that not all black holes behave as one-dimensional entropy emitters.
| [
{
"created": "Thu, 27 Apr 2017 01:24:15 GMT",
"version": "v1"
}
] | 2017-04-28 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | In this work, we examine the entropy emission property of black holes. When the greybody factor is considered, it is found that Schwarzschild black hole is a one-dimensional entropy emitter, which is independent of the spacetime dimension and the spin of the emitted quanta. However, when generalized to other black holes with two or more parameters, the result shows that the one-dimensional entropy emission property will be violated. Thus our result implies that not all black holes behave as one-dimensional entropy emitters. |
2011.14239 | Joel Saavedra | Ramon Becar, P.A. Gonzalez, Joel Saavedra, Yerko Vasquez and Bin Wang | Phase transitions in four-dimensional AdS black holes with a nonlinear
electrodynamics source | 19 pages, 8 figures. Some references added and minor revision | null | 10.1088/1572-9494/ac3073 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we consider black hole solutions to Einstein theory coupled to a
nonlinear power-law electromagnetic field with a fixed exponent value. We study
the extended phase space thermodynamics in canonical and grand canonical
ensembles where the varying cosmological constant plays the role of an
effective thermodynamic pressure. We examine thermodynamical phase transitions
in such black hols and find that both first and second order phase transitions
can occur in the canonical ensemble, while for the grand canonical ensemble the
Hawking-Page and second order phase transitions are allowed.
| [
{
"created": "Sun, 29 Nov 2020 00:10:45 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Dec 2020 17:31:09 GMT",
"version": "v2"
}
] | 2021-12-08 | [
[
"Becar",
"Ramon",
""
],
[
"Gonzalez",
"P. A.",
""
],
[
"Saavedra",
"Joel",
""
],
[
"Vasquez",
"Yerko",
""
],
[
"Wang",
"Bin",
""
]
] | In this work we consider black hole solutions to Einstein theory coupled to a nonlinear power-law electromagnetic field with a fixed exponent value. We study the extended phase space thermodynamics in canonical and grand canonical ensembles where the varying cosmological constant plays the role of an effective thermodynamic pressure. We examine thermodynamical phase transitions in such black hols and find that both first and second order phase transitions can occur in the canonical ensemble, while for the grand canonical ensemble the Hawking-Page and second order phase transitions are allowed. |
gr-qc/9608011 | Joseph David Romano | Karel V. Kuchar, Joseph D. Romano, Madhavan Varadarajan | Dirac Constraint Quantization of a Dilatonic Model of Gravitational
Collapse | 37 pages, LATEX, no figures, submitted to Physical Review D | Phys.Rev.D55:795-808,1997 | 10.1103/PhysRevD.55.795 | null | gr-qc | null | We present an anomaly-free Dirac constraint quantization of the
string-inspired dilatonic gravity (the CGHS model) in an open 2-dimensional
spacetime. We show that the quantum theory has the same degrees of freedom as
the classical theory; namely, all the modes of the scalar field on an auxiliary
flat background, supplemented by a single additional variable corresponding to
the primordial component of the black hole mass. The functional Heisenberg
equations of motion for these dynamical variables and their canonical
conjugates are linear, and they have exactly the same form as the corresponding
classical equations. A canonical transformation brings us back to the physical
geometry and induces its quantization.
| [
{
"created": "Mon, 5 Aug 1996 15:21:45 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Kuchar",
"Karel V.",
""
],
[
"Romano",
"Joseph D.",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | We present an anomaly-free Dirac constraint quantization of the string-inspired dilatonic gravity (the CGHS model) in an open 2-dimensional spacetime. We show that the quantum theory has the same degrees of freedom as the classical theory; namely, all the modes of the scalar field on an auxiliary flat background, supplemented by a single additional variable corresponding to the primordial component of the black hole mass. The functional Heisenberg equations of motion for these dynamical variables and their canonical conjugates are linear, and they have exactly the same form as the corresponding classical equations. A canonical transformation brings us back to the physical geometry and induces its quantization. |
1305.3085 | Hamid Reza Sepangi | Amir Hadi Ziaie, Paulo Vargas Moniz, Arash Ranjbar, Hamid Reza Sepangi | Einstein-Cartan gravitational collapse of a homogeneous Weyssenhoff
fluid | 23 pages, 11 figures | Eur. Phys. J. C74 (2014) 3154 | 10.1140/epjc/s10052-014-3154-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the gravitational collapse of a spherically symmetric homogeneous
matter distribution consisting of a Weyssenhoff fluid in the presence of a
negative cosmological constant. Our aim is to investigate the effects of
torsion and spin averaged terms on the final outcome of the collapse. For a
specific interior spacetime setup, namely the homogeneous and isotropic FLRW
metric, we obtain two classes of solutions to the field equations where
depending on the relation between spin source parameters, $(i)$ the collapse
procedure culminates in a spacetime singularity or $(ii)$ it is replaced by a
non-singular bounce. We show that, under certain conditions, for a specific
subset of the former solutions, the formation of trapped surfaces is prevented
and thus the resulted singularity could be naked. The curvature singularity
that forms could be gravitationally strong in the sense of Tipler. Our
numerical analysis for the latter solutions shows that the collapsing dynamical
process experiences four phases, so that two of which occur at the pre-bounce
and the other two at post-bounce regimes. We further observe that there can be
found a minimum radius for the apparent horizon curve, such that the main
outcome of which is that there exists an upper bound for the size of the
collapsing body, below which no horizon forms throughout the whole scenario.
| [
{
"created": "Tue, 14 May 2013 09:57:25 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jun 2013 13:17:48 GMT",
"version": "v2"
},
{
"created": "Sun, 16 Feb 2014 12:25:12 GMT",
"version": "v3"
},
{
"created": "Sun, 3 Aug 2014 07:22:18 GMT",
"version": "v4"
}
] | 2017-04-19 | [
[
"Ziaie",
"Amir Hadi",
""
],
[
"Moniz",
"Paulo Vargas",
""
],
[
"Ranjbar",
"Arash",
""
],
[
"Sepangi",
"Hamid Reza",
""
]
] | We consider the gravitational collapse of a spherically symmetric homogeneous matter distribution consisting of a Weyssenhoff fluid in the presence of a negative cosmological constant. Our aim is to investigate the effects of torsion and spin averaged terms on the final outcome of the collapse. For a specific interior spacetime setup, namely the homogeneous and isotropic FLRW metric, we obtain two classes of solutions to the field equations where depending on the relation between spin source parameters, $(i)$ the collapse procedure culminates in a spacetime singularity or $(ii)$ it is replaced by a non-singular bounce. We show that, under certain conditions, for a specific subset of the former solutions, the formation of trapped surfaces is prevented and thus the resulted singularity could be naked. The curvature singularity that forms could be gravitationally strong in the sense of Tipler. Our numerical analysis for the latter solutions shows that the collapsing dynamical process experiences four phases, so that two of which occur at the pre-bounce and the other two at post-bounce regimes. We further observe that there can be found a minimum radius for the apparent horizon curve, such that the main outcome of which is that there exists an upper bound for the size of the collapsing body, below which no horizon forms throughout the whole scenario. |
2310.15157 | Indrajit Sen | Indrajit Sen, Stephon Alexander, Justin Dressel | A Realist Interpretation of Unitarity in Quantum Gravity | Matches published version | Sen et al 2024 Class. Quantum Grav. 41 115005 | 10.1088/1361-6382/ad3eda | null | gr-qc astro-ph.CO hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Unitarity is a difficult concept to implement in canonical quantum gravity
because of state non-normalizability and the problem of time. We take a realist
approach based on pilot-wave theory to address this issue in the Ashtekar
formulation of the Wheeler-DeWitt equation. We use the postulate of a definite
configuration in the theory to define a global time for the
gravitational-fermionic system recently discussed in (Phys. Rev. D 106.10
(2022): 106012), by parameterizing a variation of a Weyl-spinor that depends on
the Kodama state. The total Hamiltonian constraint yields a time-dependent
Schrodinger equation, without semi-classical approximations, which we use to
derive a local continuity equation over the configuration space. We implement
the reality conditions at the level of the guidance equation, and obtain a real
spin-connection, extrinsic curvature and triad along the system trajectory. We
obtain quantum corrections to deSitter spacetime from the guidance equation.
The non-normalizable Kodama state is naturally factored out of the full quantum
state in the conserved current density, opening the possibility for
quantum-mechanical unitarity. We also give a pilot-wave generalisation of the
notion of unitarity applicable to non-normalizable states, and show the
existence of equilibrium density for our system. Lastly, we find unitary states
in mini-superspace by finding an approximate solution to the Hamiltonian
constraint.
| [
{
"created": "Mon, 23 Oct 2023 17:56:28 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Oct 2023 07:29:22 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Nov 2023 18:38:33 GMT",
"version": "v3"
},
{
"created": "Sun, 5 May 2024 17:10:10 GMT",
"version": "v4"
}
] | 2024-05-07 | [
[
"Sen",
"Indrajit",
""
],
[
"Alexander",
"Stephon",
""
],
[
"Dressel",
"Justin",
""
]
] | Unitarity is a difficult concept to implement in canonical quantum gravity because of state non-normalizability and the problem of time. We take a realist approach based on pilot-wave theory to address this issue in the Ashtekar formulation of the Wheeler-DeWitt equation. We use the postulate of a definite configuration in the theory to define a global time for the gravitational-fermionic system recently discussed in (Phys. Rev. D 106.10 (2022): 106012), by parameterizing a variation of a Weyl-spinor that depends on the Kodama state. The total Hamiltonian constraint yields a time-dependent Schrodinger equation, without semi-classical approximations, which we use to derive a local continuity equation over the configuration space. We implement the reality conditions at the level of the guidance equation, and obtain a real spin-connection, extrinsic curvature and triad along the system trajectory. We obtain quantum corrections to deSitter spacetime from the guidance equation. The non-normalizable Kodama state is naturally factored out of the full quantum state in the conserved current density, opening the possibility for quantum-mechanical unitarity. We also give a pilot-wave generalisation of the notion of unitarity applicable to non-normalizable states, and show the existence of equilibrium density for our system. Lastly, we find unitary states in mini-superspace by finding an approximate solution to the Hamiltonian constraint. |
gr-qc/0104065 | Valentin Kuzmichev | V. E. Kuzmichev and V. V. Kuzmichev (Bogolyubov Institute for
Theoretical Physics) | Properties of the quasistationary universe in context of the Big-bang
cosmology problems | 21 pages, 1 EPS figure, 1 table; revised subsection 3.7 | null | null | null | gr-qc astro-ph hep-th | null | Old and new puzzles of cosmology are reexamined from the point of view of
quantum theory of the universe developed here. It is shown that in proposed
approach the difficulties of the standard cosmology do not arise. The theory
predicts the observed dimensions of the nonhomogeneities of matter density and
the amplitude of the fluctuations of the cosmic background radiation
temperature in the Universe and points to a new quantum mechanism of their
origin. It allows to obtain the value of the deceleration parameter which is in
good agreement with the recent SNe Ia measurements. The theory explains the
large value of entropy of the Universe and describes other parameters.
| [
{
"created": "Thu, 19 Apr 2001 08:17:00 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2001 07:36:55 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kuzmichev",
"V. E.",
"",
"Bogolyubov Institute for\n Theoretical Physics"
],
[
"Kuzmichev",
"V. V.",
"",
"Bogolyubov Institute for\n Theoretical Physics"
]
] | Old and new puzzles of cosmology are reexamined from the point of view of quantum theory of the universe developed here. It is shown that in proposed approach the difficulties of the standard cosmology do not arise. The theory predicts the observed dimensions of the nonhomogeneities of matter density and the amplitude of the fluctuations of the cosmic background radiation temperature in the Universe and points to a new quantum mechanism of their origin. It allows to obtain the value of the deceleration parameter which is in good agreement with the recent SNe Ia measurements. The theory explains the large value of entropy of the Universe and describes other parameters. |
2205.02794 | Anisur Rahaman | Himangshu Barman, Mohamed Moussa, Homa Shababi, Anisur Rahaman | Thermodynamics of a Schwarzschild-like black hole with a minimum
observable length and the radiation process of a thin accretion disc around
it | 20 pages latex 11 figures and 2 tables, Title changes and a
considerably large part is added. arXiv admin note: text overlap with
2203.09252; text overlap with arXiv:2106.03140, arXiv:2101.07917 by other
authors without attribution | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study quantum gravity effects on the thermodynamic character and the
radiation process of the thin accretion disks around Schwarzschild-like black
hole. The quantum gravity correction is invoked through the framework of
generalization of uncertainty which is equivalent to the renormalization group
improved quantum gravity and maintain the limit of the asymptotically safe
preposition of gravity. It admits a free parameter that encodes the quantum
effects on the spacetime geometry. It allows us to study how the thermal
properties of the black hole itself and the the accretion around it disk are
modified in the quantum regime. We computed explicitly the entropy,
temperature, free energy, and enthalpy of the modified black hole and show its
variation with with the free parameter that encodes the quantum effects. We
explicitly make estimations of quantum correction to the time averaged energy
flux, the temperature of the disk, the differential luminosity, and the
conversion efficiency of accreting mass into radiation. We observe a
conspicuous shifting of the radius of the innermost stable circular orbit
(ISCO) toward small values together with an enhancement of the maximum of the
values of the average thermal radiation and greater conversion efficiency of
accreting mass into radiation compared to the classical gravity scenario.
| [
{
"created": "Thu, 5 May 2022 17:13:35 GMT",
"version": "v1"
},
{
"created": "Tue, 10 May 2022 14:02:07 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Nov 2022 08:25:30 GMT",
"version": "v3"
}
] | 2022-12-07 | [
[
"Barman",
"Himangshu",
""
],
[
"Moussa",
"Mohamed",
""
],
[
"Shababi",
"Homa",
""
],
[
"Rahaman",
"Anisur",
""
]
] | We study quantum gravity effects on the thermodynamic character and the radiation process of the thin accretion disks around Schwarzschild-like black hole. The quantum gravity correction is invoked through the framework of generalization of uncertainty which is equivalent to the renormalization group improved quantum gravity and maintain the limit of the asymptotically safe preposition of gravity. It admits a free parameter that encodes the quantum effects on the spacetime geometry. It allows us to study how the thermal properties of the black hole itself and the the accretion around it disk are modified in the quantum regime. We computed explicitly the entropy, temperature, free energy, and enthalpy of the modified black hole and show its variation with with the free parameter that encodes the quantum effects. We explicitly make estimations of quantum correction to the time averaged energy flux, the temperature of the disk, the differential luminosity, and the conversion efficiency of accreting mass into radiation. We observe a conspicuous shifting of the radius of the innermost stable circular orbit (ISCO) toward small values together with an enhancement of the maximum of the values of the average thermal radiation and greater conversion efficiency of accreting mass into radiation compared to the classical gravity scenario. |
gr-qc/0007040 | Reboucas | M.J. Reboucas | Distinguishing Marks of Simply-connected Universes | 13 pages, 4 figures, LaTeX2e. To appear in Int. J. Mod. Phys. D
(2000) | Int.J.Mod.Phys. D9 (2000) 561 | 10.1142/S0218271800000669 | CBPF-NF-031/00 | gr-qc astro-ph hep-th math-ph math.MP | null | A statistical quantity suitable for distinguishing simply-connected
Robertson-Walker (RW) universes is introduced, and its explicit expressions for
the three possible classes of simply-connected RW universes with an uniform
distribution of matter are determined. Graphs of the distinguishing mark for
each class of RW universes are presented and analyzed.There sprout from our
results an improvement on the procedure to extract the topological signature of
multiply-connected RW universes, and a refined understanding of that
topological signature of these universes studied in previous works.
| [
{
"created": "Tue, 18 Jul 2000 01:56:48 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Reboucas",
"M. J.",
""
]
] | A statistical quantity suitable for distinguishing simply-connected Robertson-Walker (RW) universes is introduced, and its explicit expressions for the three possible classes of simply-connected RW universes with an uniform distribution of matter are determined. Graphs of the distinguishing mark for each class of RW universes are presented and analyzed.There sprout from our results an improvement on the procedure to extract the topological signature of multiply-connected RW universes, and a refined understanding of that topological signature of these universes studied in previous works. |
gr-qc/0107024 | Wolfgang Graf | Wolfgang Graf | Nonanalytic extensions of the extreme Reissner-Nordstroem metric in
terms of weak solutions | 28 pages, 4 figures, IOP macros (MYIOPART.CLS). Added appendix plus
two references. Accepted for publication by Class. Quant. Gravity | Class.Quant.Grav. 18 (2001) 5371-5394 | 10.1088/0264-9381/18/24/304 | UWThPh-2001-26 | gr-qc | null | A basic extension of the exterior part of the extreme Reissner-Nordstroem
solution in terms of a continuous metric and gauge potential is constructed.
This extension is not smooth at the null hypersurface given by the
Cauchy-Killing horizon which separates isometric copies of the exterior metric.
The Maxwell-Einstein system of equations is satisfied only in a weak sense. The
manifold is topologically incomplete and the spherical symmetry is globally
broken down to an axial symmetry. This behaviour can be attributed to the
effect of a 'topological string', in the sense of a infinitesimally thin closed
stringlike object 'sitting on the rim' of the black hole and holding it open by
means of an accompanying impulsive gravitational wave. The resulting
differentiable manifold and the corresponding horizons are not anymore simply
connected, being 'pierced' by the strings.
| [
{
"created": "Fri, 6 Jul 2001 15:28:19 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Nov 2001 22:45:02 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Graf",
"Wolfgang",
""
]
] | A basic extension of the exterior part of the extreme Reissner-Nordstroem solution in terms of a continuous metric and gauge potential is constructed. This extension is not smooth at the null hypersurface given by the Cauchy-Killing horizon which separates isometric copies of the exterior metric. The Maxwell-Einstein system of equations is satisfied only in a weak sense. The manifold is topologically incomplete and the spherical symmetry is globally broken down to an axial symmetry. This behaviour can be attributed to the effect of a 'topological string', in the sense of a infinitesimally thin closed stringlike object 'sitting on the rim' of the black hole and holding it open by means of an accompanying impulsive gravitational wave. The resulting differentiable manifold and the corresponding horizons are not anymore simply connected, being 'pierced' by the strings. |
gr-qc/0201067 | Spiros Cotsakis | Spiros Cotsakis | Cosmological Singularities | 41 pages, 11pt. To be published in the Springer LNP Proceedings of
the First Aegean Summer School of Cosmology held on Samos, Greece, in
September 21-29, 2001 | Lect.Notes Phys. 592 (2002) 59-94 | null | null | gr-qc | null | An overview is provided of the singularity theorems in cosmological contexts
at a level suitable for advanced graduate students. The necessary background
from tensor and causal geometry to understand the theorems is supplied, the
mathematical notion of a cosmology is described in some detail and issues
related to the range of validity of general relativity are also discussed.
| [
{
"created": "Mon, 21 Jan 2002 10:16:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cotsakis",
"Spiros",
""
]
] | An overview is provided of the singularity theorems in cosmological contexts at a level suitable for advanced graduate students. The necessary background from tensor and causal geometry to understand the theorems is supplied, the mathematical notion of a cosmology is described in some detail and issues related to the range of validity of general relativity are also discussed. |
2307.08103 | Jiaming Shi | Jiaming Shi | Cosmological constraints in covariant $f(Q)$ gravity with different
connections | 14 pages, 6 figures, 3 tables | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been shown that the cosmological dynamics of covariant $f(Q)$
gravity depend on different affine connections. In this paper, two specific
$f(Q)$ models are investigated with SNe+CC+BAO+QSO observational data, and the
spatial curvature of the universe is studied in covariant $f(Q)$ gravity. It is
found that the parameters $\mathcal{X}_0$ and $\mathcal{X}'_0$ characterizing
affine connections significantly affect the behavior of the effective equation
of state $w_Q$ and may drive it across the phantom divide line. These results
imply some inertial effects of the universe change the cosmic dynamics. However
based on the Bayesian evidence, the zero inertial effect is more favored in the
flat universe. Moreover, a closed universe is favored not only in the
$\Lambda$CDM model but also in covariant $f(Q)$ gravity. The $f(Q)$ models have
less support evidence than the $\Lambda$CDM model in the non-flat universe.
| [
{
"created": "Sun, 16 Jul 2023 17:05:45 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jul 2023 05:22:03 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Oct 2023 00:03:10 GMT",
"version": "v3"
}
] | 2023-10-24 | [
[
"Shi",
"Jiaming",
""
]
] | Recently it has been shown that the cosmological dynamics of covariant $f(Q)$ gravity depend on different affine connections. In this paper, two specific $f(Q)$ models are investigated with SNe+CC+BAO+QSO observational data, and the spatial curvature of the universe is studied in covariant $f(Q)$ gravity. It is found that the parameters $\mathcal{X}_0$ and $\mathcal{X}'_0$ characterizing affine connections significantly affect the behavior of the effective equation of state $w_Q$ and may drive it across the phantom divide line. These results imply some inertial effects of the universe change the cosmic dynamics. However based on the Bayesian evidence, the zero inertial effect is more favored in the flat universe. Moreover, a closed universe is favored not only in the $\Lambda$CDM model but also in covariant $f(Q)$ gravity. The $f(Q)$ models have less support evidence than the $\Lambda$CDM model in the non-flat universe. |
2308.05084 | Fernando Carneiro | S. C. Ulhoa, F. L. Carneiro and J. W. Maluf | On the Thermodynamics of Gravitational Radiation | 10 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This article deals with the thermodynamics of gravitational radiation arising
from the Bondi-Sachs space-time. The equation of state found allows us to
conclude that the dependence of the energy density on the temperature is a
quadratic power of the latter. Such a conclusion is possible once the
consequences of the first law of thermodynamics are analyzed. Then, in analogy
to electromagnetic radiation, the same approach as used by Planck to obtain the
quantum of energy of the gravitational radiation is proposed. An energy for the
graviton proportional to the cubic frequency is found. The graviton is here
understood as the quantum of gravitational energy.
| [
{
"created": "Wed, 9 Aug 2023 17:27:07 GMT",
"version": "v1"
}
] | 2023-08-10 | [
[
"Ulhoa",
"S. C.",
""
],
[
"Carneiro",
"F. L.",
""
],
[
"Maluf",
"J. W.",
""
]
] | This article deals with the thermodynamics of gravitational radiation arising from the Bondi-Sachs space-time. The equation of state found allows us to conclude that the dependence of the energy density on the temperature is a quadratic power of the latter. Such a conclusion is possible once the consequences of the first law of thermodynamics are analyzed. Then, in analogy to electromagnetic radiation, the same approach as used by Planck to obtain the quantum of energy of the gravitational radiation is proposed. An energy for the graviton proportional to the cubic frequency is found. The graviton is here understood as the quantum of gravitational energy. |
2108.00766 | Jie Jiang | Jie Jiang, Aofei Sang, Ming Zhang | First Law of Black Hole in the Gravitational Electromagnetic System | 14 pages | JHEP 09 (2021) 199 | 10.1007/JHEP09(2021)199 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | After considering the quantum corrections of Einstein-Maxwell theory, the
effective theory will contain some higher-curvature terms and nonminimally
coupled electromagnetic fields. In this paper, we study the first law of black
holes in the gravitational electromagnetic system with the Lagrangian
$\math{L}(g_{ab}, R_{abcd}, F_{ab})$. Firstly, we calculate the Noether charge
and the variational identity in this theory, and then generically derive the
first law of thermodynamics for an asymptotically flat stationary
axisymmetrical symmetric black hole without the requirement that the
electromagnetic field is smooth on the bifurcation surface. Our results
indicate that the first law of black hole thermodynamics might be valid for the
Einstein-Maxwell theory with some quantum corrections in the effective region.
| [
{
"created": "Mon, 2 Aug 2021 10:23:11 GMT",
"version": "v1"
}
] | 2021-10-05 | [
[
"Jiang",
"Jie",
""
],
[
"Sang",
"Aofei",
""
],
[
"Zhang",
"Ming",
""
]
] | After considering the quantum corrections of Einstein-Maxwell theory, the effective theory will contain some higher-curvature terms and nonminimally coupled electromagnetic fields. In this paper, we study the first law of black holes in the gravitational electromagnetic system with the Lagrangian $\math{L}(g_{ab}, R_{abcd}, F_{ab})$. Firstly, we calculate the Noether charge and the variational identity in this theory, and then generically derive the first law of thermodynamics for an asymptotically flat stationary axisymmetrical symmetric black hole without the requirement that the electromagnetic field is smooth on the bifurcation surface. Our results indicate that the first law of black hole thermodynamics might be valid for the Einstein-Maxwell theory with some quantum corrections in the effective region. |
1812.05074 | S. Danial Forghani | S. Danial Forghani, S. Habib Mazharimousavi, and M. Halilsoy | Thin-Shells and Thin-Shell Wormholes in New Massive Gravity | 11 pages, no figure | Eur. Phys. J. C (2019) 79: 449 | 10.1140/epjc/s10052-019-6964-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within 2+1-dimensional cosmological new massive gravity, we consider
thin-shell and thin-shell wormhole construction. For this, we introduce first,
the junction conditions apt for the fourth order terms in the action of the
theory. Then, by employing some specific static solutions in new massive
gravity, we study the characteristics of associated thin-shells and thin-shell
wormholes. Our finding suggests that, firstly, there cannot exist any
thin-shells regarding our chosen solutions of cosmological new massive gravity,
and secondly, the constructed thin-shell wormhole does not need to be
symmetric. More importantly, the thin-shell wormhole, if ever forms, possesses
null energy density and null angular pressure on its throat which preferable to
their negative-valued counterparts.
| [
{
"created": "Wed, 12 Dec 2018 18:24:57 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Feb 2019 12:25:42 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Mar 2019 12:35:29 GMT",
"version": "v3"
},
{
"created": "Mon, 13 May 2019 15:37:34 GMT",
"version": "v4"
}
] | 2019-06-04 | [
[
"Forghani",
"S. Danial",
""
],
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | Within 2+1-dimensional cosmological new massive gravity, we consider thin-shell and thin-shell wormhole construction. For this, we introduce first, the junction conditions apt for the fourth order terms in the action of the theory. Then, by employing some specific static solutions in new massive gravity, we study the characteristics of associated thin-shells and thin-shell wormholes. Our finding suggests that, firstly, there cannot exist any thin-shells regarding our chosen solutions of cosmological new massive gravity, and secondly, the constructed thin-shell wormhole does not need to be symmetric. More importantly, the thin-shell wormhole, if ever forms, possesses null energy density and null angular pressure on its throat which preferable to their negative-valued counterparts. |
2007.02369 | Emilio Elizalde | Emilio Elizalde, Martiros Khurshudyan | Interplay between Swampland and Bayesian Machine Learning in
constraining cosmological models | 12 pages, 4 figures, 2 tables | null | 10.1140/epjc/s10052-021-09130-8 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Constraints on a dark energy dominated Universe are obtained from an
interplay between Bayesian Machine Learning and string Swampland criteria. The
approach here differs from previous studies, since in the generative process
Swampland criteria are used and, only later, the results of the fit are
validated, by using observational data-sets. A generative process based
Bayesian Learning approach is applied to two models and the results are
validated by means of available $H(z)$ data. For the first model, a
parametrization of the Hubble constant is considered and, for the second, a
parametrization of the deceleration parameter. This study is motivated by a
recent work, where constraints on string Swampland criteria have been obtained
from a Gaussian Process and $H(z)$ data. However, the results obtained here are
fully independent of the observational data and allow to estimate how the
high-redshift behavior of the Universe will affect the low-redshift one.
Moreover, both parameterizations in the generative process, for the Hubble and
for the deceleration parameters, are independent of the dark energy model. The
outcome, both data- and dark energy model-independent, may highlight, in the
future, the borders of the Swampland for the low-redshift Universe and help to
develop new string-theory motivated dark-energy models. The string Swampland
criteria considered might be in tension with recent observations indicating
that phantom dark energy cannot be in the Swampland. Finally, a spontaneous
sign switch in the dark energy equation of state parameter is observed when the
field traverses are in the $z\in[0,5]$ redshift range, a remarkable phenomenon
requiring further analysis.
| [
{
"created": "Sun, 5 Jul 2020 15:53:27 GMT",
"version": "v1"
}
] | 2021-05-05 | [
[
"Elizalde",
"Emilio",
""
],
[
"Khurshudyan",
"Martiros",
""
]
] | Constraints on a dark energy dominated Universe are obtained from an interplay between Bayesian Machine Learning and string Swampland criteria. The approach here differs from previous studies, since in the generative process Swampland criteria are used and, only later, the results of the fit are validated, by using observational data-sets. A generative process based Bayesian Learning approach is applied to two models and the results are validated by means of available $H(z)$ data. For the first model, a parametrization of the Hubble constant is considered and, for the second, a parametrization of the deceleration parameter. This study is motivated by a recent work, where constraints on string Swampland criteria have been obtained from a Gaussian Process and $H(z)$ data. However, the results obtained here are fully independent of the observational data and allow to estimate how the high-redshift behavior of the Universe will affect the low-redshift one. Moreover, both parameterizations in the generative process, for the Hubble and for the deceleration parameters, are independent of the dark energy model. The outcome, both data- and dark energy model-independent, may highlight, in the future, the borders of the Swampland for the low-redshift Universe and help to develop new string-theory motivated dark-energy models. The string Swampland criteria considered might be in tension with recent observations indicating that phantom dark energy cannot be in the Swampland. Finally, a spontaneous sign switch in the dark energy equation of state parameter is observed when the field traverses are in the $z\in[0,5]$ redshift range, a remarkable phenomenon requiring further analysis. |
1004.0760 | Anil Zenginoglu C | Anil Zenginoglu and Lawrence E. Kidder | Hyperboloidal evolution of test fields in three spatial dimensions | 10 pages, 8 figures | Phys.Rev.D81:124010,2010 | 10.1103/PhysRevD.81.124010 | CSCAMM-10-01 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the numerical implementation of a clean solution to the outer
boundary and radiation extraction problems within the 3+1 formalism for
hyperbolic partial differential equations on a given background. Our approach
is based on compactification at null infinity in hyperboloidal scri fixing
coordinates. We report numerical tests for the particular example of a scalar
wave equation on Minkowski and Schwarzschild backgrounds. We address issues
related to the implementation of the hyperboloidal approach for the Einstein
equations, such as nonlinear source functions, matching, and evaluation of
formally singular terms at null infinity.
| [
{
"created": "Tue, 6 Apr 2010 03:06:25 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Zenginoglu",
"Anil",
""
],
[
"Kidder",
"Lawrence E.",
""
]
] | We present the numerical implementation of a clean solution to the outer boundary and radiation extraction problems within the 3+1 formalism for hyperbolic partial differential equations on a given background. Our approach is based on compactification at null infinity in hyperboloidal scri fixing coordinates. We report numerical tests for the particular example of a scalar wave equation on Minkowski and Schwarzschild backgrounds. We address issues related to the implementation of the hyperboloidal approach for the Einstein equations, such as nonlinear source functions, matching, and evaluation of formally singular terms at null infinity. |
2302.07096 | Subhayan Maity | Subhayan Maity and Subenoy Chakraborty | Does diffusion mechanism favor the emergent scenario of the universe? | null | International Journal of Modern Physics A , Vol.37,No.3 (2022)
2250016 | 10.1142/S0217751X22500166 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present work, the flat FLRW Universe has been modelled with cosmic
matter in the form of diffusive barotropic fluid. The diffusive fluid undergoes
dissipation due to diffusion mechanism in the form of cosmological scalar
field. From the perspective of non-equilibrium thermodynamics, the evolution
equations of the universe have been formulated. By a suitable choice of the
cosmological scalar field, emergent scenario of the universe has been obtained.
| [
{
"created": "Mon, 13 Feb 2023 05:09:30 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Maity",
"Subhayan",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In the present work, the flat FLRW Universe has been modelled with cosmic matter in the form of diffusive barotropic fluid. The diffusive fluid undergoes dissipation due to diffusion mechanism in the form of cosmological scalar field. From the perspective of non-equilibrium thermodynamics, the evolution equations of the universe have been formulated. By a suitable choice of the cosmological scalar field, emergent scenario of the universe has been obtained. |
2110.14772 | Ricardo Gallego Torrom\'e | Ricardo Gallego Torrom\'e | On Penrose's theory of objective gravitationally induced wave function
reduction | Accepted for publication in International Journal of Geometric
Methods in Modern Physics. arXiv admin note: substantial text overlap with
arXiv:1402.5070 | null | 10.1142/S0219887822500207 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formal structure of Penrose's gravitationally induced reduction of the
wave function mechanism is analyzed. It is shown that pushing Penrose's
argument forward leads to the interpretation of quantum coherence in
microscopic systems as an observable signature violation of general covariance.
We discuss potential avenues to avoid this conclusion, among them emergent
quantum mechanics and super-determinism.
| [
{
"created": "Wed, 27 Oct 2021 21:06:01 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Torromé",
"Ricardo Gallego",
""
]
] | The formal structure of Penrose's gravitationally induced reduction of the wave function mechanism is analyzed. It is shown that pushing Penrose's argument forward leads to the interpretation of quantum coherence in microscopic systems as an observable signature violation of general covariance. We discuss potential avenues to avoid this conclusion, among them emergent quantum mechanics and super-determinism. |
2201.10381 | Naresh Dadhich | Naresh Dadhich | Maximum Force for Black Holes and Buchdahl Stars | 5 pages, Abstract is revamped, some references are added and the CAS
grant his acknowledged. No change in the results. Accepted for publication in
PRD | Phys. Rev. {\bf D105}, 0640044 (2022) | 10.1103/PhysRevD.105.064044 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole and Buchdahl star are identified respectively by $\Phi(R)=1/2,
4/9$ where $g_{tt}=1-2\Phi(R)$ for a spherically symmetric static metric. We
investigate the maximum force for black hole and Buchdahl star when one of the
participating objects is charged and/or rotating while the other is neutral and
non-rotating. It turns out that the maximum force between two Schwarzschild
objects is universal, given in terms of the fundamental constant velocity of
light and the gravitational constant in general relativity (GR) in the usual
four dimensional spacetime. In general this feature uniquely picks out the pure
Lovelock gravity (having only one $N$th order term in action which includes GR
in the linear order $N=1$) and the dimensional spectrum, $D=3N+1$, where $N$ is
degree of the Lovelock polynomial action.
| [
{
"created": "Mon, 24 Jan 2022 05:59:56 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2022 01:15:41 GMT",
"version": "v2"
}
] | 2022-08-12 | [
[
"Dadhich",
"Naresh",
""
]
] | Black hole and Buchdahl star are identified respectively by $\Phi(R)=1/2, 4/9$ where $g_{tt}=1-2\Phi(R)$ for a spherically symmetric static metric. We investigate the maximum force for black hole and Buchdahl star when one of the participating objects is charged and/or rotating while the other is neutral and non-rotating. It turns out that the maximum force between two Schwarzschild objects is universal, given in terms of the fundamental constant velocity of light and the gravitational constant in general relativity (GR) in the usual four dimensional spacetime. In general this feature uniquely picks out the pure Lovelock gravity (having only one $N$th order term in action which includes GR in the linear order $N=1$) and the dimensional spectrum, $D=3N+1$, where $N$ is degree of the Lovelock polynomial action. |
1611.04084 | Nobuyoshi Komatsu | Nobuyoshi Komatsu | Cosmological model from the holographic equipartition law with a
modified R\'{e}nyi entropy | Final version accepted for publication in EPJC. The titile is revised
and references are added. [12 pages, 4 figures] | Eur. Phys. J. C 77, 229 (2017) | 10.1140/epjc/s10052-017-4800-2 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological equations were recently derived by Padmanabhan from the
expansion of cosmic space due to the difference between the degrees of freedom
on the surface and in the bulk in a region of space. In this study, a modified
R\'{e}nyi entropy is applied to Padmanabhan's `holographic equipartition law',
by regarding the Bekenstein--Hawking entropy as a nonextensive Tsallis entropy
and using a logarithmic formula of the original R\'{e}nyi entropy.
Consequently, the acceleration equation including an extra driving term (such
as a time-varying cosmological term) can be derived in a homogeneous,
isotropic, and spatially flat universe. When a specific condition is
mathematically satisfied, the extra driving term is found to be constant-like
as if it is a cosmological constant. Interestingly, the order of the
constant-like term is naturally consistent with the order of the cosmological
constant measured by observations, because the specific condition constrains
the value of the constant-like term.
| [
{
"created": "Sun, 13 Nov 2016 05:19:52 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Mar 2017 23:07:41 GMT",
"version": "v2"
}
] | 2017-04-14 | [
[
"Komatsu",
"Nobuyoshi",
""
]
] | Cosmological equations were recently derived by Padmanabhan from the expansion of cosmic space due to the difference between the degrees of freedom on the surface and in the bulk in a region of space. In this study, a modified R\'{e}nyi entropy is applied to Padmanabhan's `holographic equipartition law', by regarding the Bekenstein--Hawking entropy as a nonextensive Tsallis entropy and using a logarithmic formula of the original R\'{e}nyi entropy. Consequently, the acceleration equation including an extra driving term (such as a time-varying cosmological term) can be derived in a homogeneous, isotropic, and spatially flat universe. When a specific condition is mathematically satisfied, the extra driving term is found to be constant-like as if it is a cosmological constant. Interestingly, the order of the constant-like term is naturally consistent with the order of the cosmological constant measured by observations, because the specific condition constrains the value of the constant-like term. |
1308.5959 | Ernesto F. Eiroa | Ernesto F. Eiroa, Carlos M. Sendra | Regular phantom black hole gravitational lensing | 14 pages, 4 figures; v2: improved and extended version, new
references added. Accepted for publication in Phys. Rev. D | Phys. Rev. D 88, 103007 (2013) | 10.1103/PhysRevD.88.103007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study regular and asymptotically flat phantom black holes as gravitational
lenses. We obtain the deflection angle in both the weak and the strong
deflection limits, from which we calculate the positions, magnifications, and
time delays of the images. We compare our results with those corresponding to
the Schwarzschild solution and to the vacuum Brans-Dicke black hole.
| [
{
"created": "Tue, 27 Aug 2013 19:42:14 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Nov 2013 19:34:05 GMT",
"version": "v2"
}
] | 2013-11-27 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Sendra",
"Carlos M.",
""
]
] | We study regular and asymptotically flat phantom black holes as gravitational lenses. We obtain the deflection angle in both the weak and the strong deflection limits, from which we calculate the positions, magnifications, and time delays of the images. We compare our results with those corresponding to the Schwarzschild solution and to the vacuum Brans-Dicke black hole. |
1807.06128 | Milinda Fernando | Milinda Fernando, David Neilsen, Hyun Lim, Eric Hirschmann and Hari
Sundar | Massively Parallel Simulations of Binary Black Hole
Intermediate-Mass-Ratio Inspirals | null | SIAM Journal on Scientific Computing 2019 | 10.1137/18M1196972 | null | gr-qc astro-ph.HE | http://creativecommons.org/publicdomain/zero/1.0/ | We present a highly-scalable framework that targets problems of interest to
the numerical relativity and broader astrophysics communities. This framework
combines a parallel octree-refined adaptive mesh with a wavelet adaptive
multiresolution and a physics module to solve the Einstein equations of general
relativity in the BSSN formulation. The goal of this work is to perform
advanced, massively parallel numerical simulations of Intermediate Mass Ratio
Inspirals (IMRIs) of binary black holes with mass ratios on the order of 100:1.
These studies will be used to generate waveforms as used in LIGO data analysis
and to calibrate semi-analytical approximate methods. Our framework consists of
a distributed memory octree-based adaptive meshing framework in conjunction
with a node-local code generator. The code generator makes our code portable
across different architectures. The equations corresponding to the target
application are written in symbolic notation and generators for different
architectures can be added independent of the application. Additionally, this
symbolic interface also makes our code extensible, and as such has been
designed to easily accommodate many existing algorithms in astrophysics for
plasma dynamics and radiation hydrodynamics. Our adaptive meshing algorithms
and data-structures have been optimized for modern architectures with deep
memory hierarchies. This enables our framework to have achieve excellent
performance and scalability on modern leadership architectures. We demonstrate
excellent weak scalability up to 131K cores on ORNL's Titan for binary mergers
for mass ratios up to 100.
| [
{
"created": "Mon, 16 Jul 2018 21:54:42 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Jan 2019 19:05:19 GMT",
"version": "v2"
}
] | 2019-04-10 | [
[
"Fernando",
"Milinda",
""
],
[
"Neilsen",
"David",
""
],
[
"Lim",
"Hyun",
""
],
[
"Hirschmann",
"Eric",
""
],
[
"Sundar",
"Hari",
""
]
] | We present a highly-scalable framework that targets problems of interest to the numerical relativity and broader astrophysics communities. This framework combines a parallel octree-refined adaptive mesh with a wavelet adaptive multiresolution and a physics module to solve the Einstein equations of general relativity in the BSSN formulation. The goal of this work is to perform advanced, massively parallel numerical simulations of Intermediate Mass Ratio Inspirals (IMRIs) of binary black holes with mass ratios on the order of 100:1. These studies will be used to generate waveforms as used in LIGO data analysis and to calibrate semi-analytical approximate methods. Our framework consists of a distributed memory octree-based adaptive meshing framework in conjunction with a node-local code generator. The code generator makes our code portable across different architectures. The equations corresponding to the target application are written in symbolic notation and generators for different architectures can be added independent of the application. Additionally, this symbolic interface also makes our code extensible, and as such has been designed to easily accommodate many existing algorithms in astrophysics for plasma dynamics and radiation hydrodynamics. Our adaptive meshing algorithms and data-structures have been optimized for modern architectures with deep memory hierarchies. This enables our framework to have achieve excellent performance and scalability on modern leadership architectures. We demonstrate excellent weak scalability up to 131K cores on ORNL's Titan for binary mergers for mass ratios up to 100. |
gr-qc/0002004 | Pia Astone | P. Astone, S. Frasca, G. Pizzella | Background Estimation in a Gravitational Wave Experiment | Latex file. 6 pages, 3 figures. Submitted to the proceeding of the 3
GWDAW workshop (Rome, dic 1999) (International journal of Modern physics D) | Int.J.Mod.Phys. D9 (2000) 341-346 | 10.1142/S0218271800000396 | null | gr-qc | null | The problem to estimate the background due to accidental coincidences in the
search for coincidences in gravitational wave experiments is discussed. The use
of delayed coincidences obtained by orderly shifting the event times of one of
the two detectors is shown to be the most correct
| [
{
"created": "Tue, 1 Feb 2000 12:38:00 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Astone",
"P.",
""
],
[
"Frasca",
"S.",
""
],
[
"Pizzella",
"G.",
""
]
] | The problem to estimate the background due to accidental coincidences in the search for coincidences in gravitational wave experiments is discussed. The use of delayed coincidences obtained by orderly shifting the event times of one of the two detectors is shown to be the most correct |
gr-qc/9902063 | Mauro Francaviglia | L. Fatibene, M. Ferraris, M. Francaviglia, M. Raiteri | Remarks on Conserved Quantities and Entropy of BTZ Black Hole Solutions.
Part I: the General Setting | PlainTEX, 16 pages. Revised version 1.1 | Phys.Rev. D60 (1999) 124012 | 10.1103/PhysRevD.60.124012 | null | gr-qc | null | The BTZ stationary black hole solution is considered and its mass and angular
momentum are calculated by means of Noether theorem. In particular, relative
conserved quantities with respect to a suitably fixed background are discussed.
Entropy is then computed in a geometric and macroscopic framework, so that it
satisfies the first principle of thermodynamics. In order to compare this more
general framework to the prescription by Wald et al. we construct the maximal
extension of the BTZ horizon by means of Kruskal-like coordinates. A discussion
about the different features of the two methods for computing entropy is
finally developed.
| [
{
"created": "Mon, 22 Feb 1999 09:21:35 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 1999 07:32:07 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Fatibene",
"L.",
""
],
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | The BTZ stationary black hole solution is considered and its mass and angular momentum are calculated by means of Noether theorem. In particular, relative conserved quantities with respect to a suitably fixed background are discussed. Entropy is then computed in a geometric and macroscopic framework, so that it satisfies the first principle of thermodynamics. In order to compare this more general framework to the prescription by Wald et al. we construct the maximal extension of the BTZ horizon by means of Kruskal-like coordinates. A discussion about the different features of the two methods for computing entropy is finally developed. |
1809.06611 | Masato Minamitsuji | Masato Minamitsuji and Hayato Motohashi | Stealth Schwarzschild solution in shift symmetry breaking theories | 16 pages, no figure | Phys. Rev. D 98, 084027 (2018) | 10.1103/PhysRevD.98.084027 | YITP-18-104 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find stealth Schwarzschild solutions with a nontrivial profile of the
scalar field regular on the horizon in the Einstein gravity coupled to the
scalar field with the k-essence and/or generalized cubic galileon terms, which
is a subclass of the Horndeski theory breaking the shift symmetry, where the
propagation speed of gravitational waves coincides with the speed of light.
After deriving sufficient conditions for the shift symmetry breaking theory to
allow a general Ricci-flat metric solution with a nontrivial scalar field
profile, we focus on the stealth Schwarzschild solution with the scalar field
with or without time dependence. For the profile $\phi=\phi_0(r)$, we
explicitly obtain two types of stealth Schwarzschild solutions, one of which is
regular on the event horizon. The linear perturbation analysis clarifies that
the kinetic term of the scalar mode identically vanishes, indicating that the
scalar mode is strongly coupled. The absence of the kinetic term of the scalar
mode in the quadratic action would inevitably arise for the stealth
Schwarzschild solutions in the theory with a general scalar field profile
depending only on the spatial coordinates. On the other hand, for the
time-dependent scalar field profile, we clarify that there does not exist a
stealth Schwarzschild solution in the shift symmetry breaking theories.
| [
{
"created": "Tue, 18 Sep 2018 09:32:25 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Oct 2018 09:48:58 GMT",
"version": "v2"
}
] | 2019-05-08 | [
[
"Minamitsuji",
"Masato",
""
],
[
"Motohashi",
"Hayato",
""
]
] | We find stealth Schwarzschild solutions with a nontrivial profile of the scalar field regular on the horizon in the Einstein gravity coupled to the scalar field with the k-essence and/or generalized cubic galileon terms, which is a subclass of the Horndeski theory breaking the shift symmetry, where the propagation speed of gravitational waves coincides with the speed of light. After deriving sufficient conditions for the shift symmetry breaking theory to allow a general Ricci-flat metric solution with a nontrivial scalar field profile, we focus on the stealth Schwarzschild solution with the scalar field with or without time dependence. For the profile $\phi=\phi_0(r)$, we explicitly obtain two types of stealth Schwarzschild solutions, one of which is regular on the event horizon. The linear perturbation analysis clarifies that the kinetic term of the scalar mode identically vanishes, indicating that the scalar mode is strongly coupled. The absence of the kinetic term of the scalar mode in the quadratic action would inevitably arise for the stealth Schwarzschild solutions in the theory with a general scalar field profile depending only on the spatial coordinates. On the other hand, for the time-dependent scalar field profile, we clarify that there does not exist a stealth Schwarzschild solution in the shift symmetry breaking theories. |
gr-qc/9812072 | Junya Hashida | J. Hashida, S. Mukaigawa, T. Muta, K. Ohkura and K. Yamamoto | A Model of Curvature-Induced Phase Transitions in Inflationary Universe | 12 pages, 3 figures, REVTeX | Phys.Rev.D59:101302,1999 | 10.1103/PhysRevD.59.101302 | HUPD-9832 | gr-qc hep-ph | null | Chiral phase transitions driven by space-time curvature effects are
investigated in de Sitter space in the supersymmetric Nambu-Jona-Lasinio model
with soft supersymmetry breaking. The model is considered to be suitable for
the analysis of possible phase transitions in inflationary universe. It is
found that a restoration of the broken chiral symmetry takes place in two
patterns for increasing curvature : the first order and second order phase
transition respectively depending on initial settings of the four-body
interaction parameter and the soft supersymmetry breaking parameter. The
critical curves expressing the phase boundaries in these parameters are
obtained. Cosmological implications of the result are discussed in connection
with bubble formations and the creation of cosmic strings during the
inflationary era.
| [
{
"created": "Mon, 21 Dec 1998 08:58:18 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Hashida",
"J.",
""
],
[
"Mukaigawa",
"S.",
""
],
[
"Muta",
"T.",
""
],
[
"Ohkura",
"K.",
""
],
[
"Yamamoto",
"K.",
""
]
] | Chiral phase transitions driven by space-time curvature effects are investigated in de Sitter space in the supersymmetric Nambu-Jona-Lasinio model with soft supersymmetry breaking. The model is considered to be suitable for the analysis of possible phase transitions in inflationary universe. It is found that a restoration of the broken chiral symmetry takes place in two patterns for increasing curvature : the first order and second order phase transition respectively depending on initial settings of the four-body interaction parameter and the soft supersymmetry breaking parameter. The critical curves expressing the phase boundaries in these parameters are obtained. Cosmological implications of the result are discussed in connection with bubble formations and the creation of cosmic strings during the inflationary era. |
1301.5460 | Hamid Reza Sepangi | F. Kheyri, M. Khodadi and H. R. Sepangi | Horava-Lifshitz early universe phase transition beyond detailed balance | 14 pages, 11 figures, to appear in Eur. Phys. J. C. arXiv admin note:
text overlap with arXiv:0912.2541, arXiv:0807.3066, arXiv:1005.3508,
arXiv:1011.4230 by other authors | Eur. Phys. J. C. 73 (2013) 2286 | 10.1140/epjc/s10052-013-2286-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The early universe is believed to have undergone a QCD phase transition to
hadrons at about $10\mu s$ after the big bang. We study such a transition in
the context of the non-detailed balance Horava-Lifshitz theory by investigating
the effects of the dynamical coupling constant $\lambda$ in a flat universe.
The evolution of the relevant physical quantities, namely the energy density
$\rho$, temperature $T$, scale factor $a$ and the Hubble parameter $H$ is
investigated before, during and after the phase transition, assumed to be of
first order. Also, in view of the recent lattice QCD simulations data, we study
a cross-over phase transition of the early universe whose results are based on
two different sets of lattice data.
| [
{
"created": "Wed, 23 Jan 2013 10:25:22 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Jan 2013 15:16:32 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Kheyri",
"F.",
""
],
[
"Khodadi",
"M.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | The early universe is believed to have undergone a QCD phase transition to hadrons at about $10\mu s$ after the big bang. We study such a transition in the context of the non-detailed balance Horava-Lifshitz theory by investigating the effects of the dynamical coupling constant $\lambda$ in a flat universe. The evolution of the relevant physical quantities, namely the energy density $\rho$, temperature $T$, scale factor $a$ and the Hubble parameter $H$ is investigated before, during and after the phase transition, assumed to be of first order. Also, in view of the recent lattice QCD simulations data, we study a cross-over phase transition of the early universe whose results are based on two different sets of lattice data. |
gr-qc/0509065 | Douglas A. Singleton | V. D. Ivashchuk, V. N. Melnikov, and D. Singleton | On avoiding cosmological oscillating behavior for S-brane solutions with
diagonal metrics | Corrected typos, published in Phys. Rev. D72, 103511 (2005) | Phys.Rev. D72 (2005) 103511 | 10.1103/PhysRevD.72.103511 | null | gr-qc hep-th | null | In certain string inspired higher dimensional cosmological models it has been
conjectured that there is generic, chaotic oscillating behavior near the
initial singularity -- the Kasner parameters which characterize the asymptotic
form of the metric "jump" between different, locally constant values and
exhibit a never-ending oscillation as one approaches the singularity. In this
paper we investigate a class of cosmological solutions with form fields and
diagonal metrics which have a "maximal" number of composite electric S-branes.
We look at two explicit examples in D=4 and D=5 dimensions that do not have
chaotic oscillating behavior near the singularity. When the composite branes
are replaced by non-composite branes chaotic oscillating
| [
{
"created": "Fri, 16 Sep 2005 04:32:49 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Oct 2005 17:19:37 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Dec 2005 01:22:46 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Ivashchuk",
"V. D.",
""
],
[
"Melnikov",
"V. N.",
""
],
[
"Singleton",
"D.",
""
]
] | In certain string inspired higher dimensional cosmological models it has been conjectured that there is generic, chaotic oscillating behavior near the initial singularity -- the Kasner parameters which characterize the asymptotic form of the metric "jump" between different, locally constant values and exhibit a never-ending oscillation as one approaches the singularity. In this paper we investigate a class of cosmological solutions with form fields and diagonal metrics which have a "maximal" number of composite electric S-branes. We look at two explicit examples in D=4 and D=5 dimensions that do not have chaotic oscillating behavior near the singularity. When the composite branes are replaced by non-composite branes chaotic oscillating |
gr-qc/9409045 | Tatsuhiko Koike | Tatsuhiko Koike and Takashi Mishima | An Analytic Model with Critical Behavior in Black Hole Formation | 21pp., ReVTeX, 7 figures (postscript, compressed and uuencoded),
TIT/HEP-266/COSMO-46 | Phys.Rev. D51 (1995) 4045-4053 | 10.1103/PhysRevD.51.4045 | null | gr-qc hep-th | null | A simple analytic model is presented which exhibits a critical behavior in
black hole formation, namely, collapse of a thin shell coupled with outgoing
null fluid. It is seen that the critical behavior is caused by the
gravitational nonlinearity near the event horizon. We calculate the value of
the critical exponent analytically and find that it is very dependent on the
coupling constants of the system.
| [
{
"created": "Wed, 21 Sep 1994 08:37:57 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Sep 1994 21:35:25 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Koike",
"Tatsuhiko",
""
],
[
"Mishima",
"Takashi",
""
]
] | A simple analytic model is presented which exhibits a critical behavior in black hole formation, namely, collapse of a thin shell coupled with outgoing null fluid. It is seen that the critical behavior is caused by the gravitational nonlinearity near the event horizon. We calculate the value of the critical exponent analytically and find that it is very dependent on the coupling constants of the system. |
0802.0112 | Olivier Piguet | Clisthenis P. Constantinidis, Jose Andre Lourenco, Ivan Morales,
Olivier Piguet and Alex Rios | Canonical Analysis of the Jackiw-Teitelboim Model in the Temporal Gauge.
I. The Classical Theory | 15 pages, Latex. Misprint corrections | Class.Quant.Grav.25:125003,2008 | 10.1088/0264-9381/25/12/125003 | null | gr-qc | null | As a preparation for its quantization in the loop formalism, the
2-dimensional gravitation model of Jackiw and Teitelboim is analysed in the
classical canonical formalism. The dynamics is of pure constraints as it is
well-known. A partial gauge fixing of the temporal type being performed, the
resulting second class constraints are sorted out and the corresponding Dirac
bracket algebra is worked out. Dirac observables of this classical theory are
then calculated.
| [
{
"created": "Fri, 1 Feb 2008 12:37:18 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Feb 2008 23:51:31 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Constantinidis",
"Clisthenis P.",
""
],
[
"Lourenco",
"Jose Andre",
""
],
[
"Morales",
"Ivan",
""
],
[
"Piguet",
"Olivier",
""
],
[
"Rios",
"Alex",
""
]
] | As a preparation for its quantization in the loop formalism, the 2-dimensional gravitation model of Jackiw and Teitelboim is analysed in the classical canonical formalism. The dynamics is of pure constraints as it is well-known. A partial gauge fixing of the temporal type being performed, the resulting second class constraints are sorted out and the corresponding Dirac bracket algebra is worked out. Dirac observables of this classical theory are then calculated. |
1909.13629 | Ming Zhang | Ming Zhang | Information paradox and corrected thermodynamics for black holes | 7 pages | Phys.Lett. B799 (2019) 135063 | 10.1016/j.physletb.2019.135063 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We generally consider that entropy and temperature of a spherically symmetric
black hole are corrected by quantum effect. We calculate interior entropy
variation of massless scalar field and compare it with corrected
Bekenstein-Hawking entropy variation for the evaporating black hole. We find
that the corrected ratio between them is greater than the uncorrected one. The
information paradox is then discussed.
| [
{
"created": "Mon, 30 Sep 2019 12:35:48 GMT",
"version": "v1"
}
] | 2019-12-10 | [
[
"Zhang",
"Ming",
""
]
] | We generally consider that entropy and temperature of a spherically symmetric black hole are corrected by quantum effect. We calculate interior entropy variation of massless scalar field and compare it with corrected Bekenstein-Hawking entropy variation for the evaporating black hole. We find that the corrected ratio between them is greater than the uncorrected one. The information paradox is then discussed. |
1504.07204 | Pedro Moraes | J. R. L. Santos and P. H. R. S. Moraes | Fast-roll solutions from two scalar fields inflation | 8 pages, 8 figures, new updates | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One common approach for cosmic inflation consists in couple Einstein's
gravity with a scalar field, often referred to inflaton field. In order to
derive analytic simple scenarios, we usually work in the {\it slow-roll}
regime. In such an approximation one considers the scalar field potentials to
be nearly flat. It is possible to directly generalize such an approach for
hybrid inflationary models, where the inflaton sector is composed of two or
more scalar fields. However, the Friedmann equations and the equations of
motion for such hybrid models are often hard to be analytically solved. Another
recent path to describe cosmic inflation is through the so-called {\it
fast-roll} regime, where one considers exactly flat potentials. Our purpose in
this work is to obtain solutions for a hybrid inflaton model in the fast-roll
regime. Cosmological interpretations through the behavior of Hubble, slow-roll,
and equation of state parameters are also presented.
| [
{
"created": "Mon, 27 Apr 2015 18:49:19 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Dec 2020 19:04:46 GMT",
"version": "v2"
}
] | 2021-01-01 | [
[
"Santos",
"J. R. L.",
""
],
[
"Moraes",
"P. H. R. S.",
""
]
] | One common approach for cosmic inflation consists in couple Einstein's gravity with a scalar field, often referred to inflaton field. In order to derive analytic simple scenarios, we usually work in the {\it slow-roll} regime. In such an approximation one considers the scalar field potentials to be nearly flat. It is possible to directly generalize such an approach for hybrid inflationary models, where the inflaton sector is composed of two or more scalar fields. However, the Friedmann equations and the equations of motion for such hybrid models are often hard to be analytically solved. Another recent path to describe cosmic inflation is through the so-called {\it fast-roll} regime, where one considers exactly flat potentials. Our purpose in this work is to obtain solutions for a hybrid inflaton model in the fast-roll regime. Cosmological interpretations through the behavior of Hubble, slow-roll, and equation of state parameters are also presented. |
gr-qc/0402075 | I.-chin Wang | I.-Chin Wang | Dust and Radiation Quantum Perfect Fluid Cosmology : Selection of Time
Variable | 5 pages, revtex4 type | Gen.Rel.Grav. 37 (2005) 971-976 | 10.1007/s10714-005-0080-5 | null | gr-qc | null | We studied the expectation value of the scale factor in radiation and dust
quantum perfect fluid cosmology. We used Schutz variational formalism to
describe perfect fluid and selected the conjugate coordinate of perfect fluid
be dynamical variable. After quantization and solving the Wheeler-DeWitt
equation can obtain the exact solution. By superposition of the exact solution,
we obtained one wave packets and used it to compute the expectation value of
the scale factor. We found that if one select different dynamical variable be
the time variable in each of these two systems, the expectation value of the
scale factor of these two systems can fit in with the prediction of General
Relativity. Therefore we thought that the selection of reference time can be
different for different quantum perfect fluid systems.
| [
{
"created": "Mon, 16 Feb 2004 12:46:28 GMT",
"version": "v1"
},
{
"created": "Thu, 20 May 2004 03:55:52 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Wang",
"I. -Chin",
""
]
] | We studied the expectation value of the scale factor in radiation and dust quantum perfect fluid cosmology. We used Schutz variational formalism to describe perfect fluid and selected the conjugate coordinate of perfect fluid be dynamical variable. After quantization and solving the Wheeler-DeWitt equation can obtain the exact solution. By superposition of the exact solution, we obtained one wave packets and used it to compute the expectation value of the scale factor. We found that if one select different dynamical variable be the time variable in each of these two systems, the expectation value of the scale factor of these two systems can fit in with the prediction of General Relativity. Therefore we thought that the selection of reference time can be different for different quantum perfect fluid systems. |
2111.09495 | Georgios Mavrogiannis | Georgios Mavrogiannis | Quasilinear wave equations on Schwarzschild-de Sitter | 40 pages, 2 figures | null | null | null | gr-qc math-ph math.AP math.MP | http://creativecommons.org/licenses/by/4.0/ | We give an elementary new argument for global existence and exponential decay
of solutions of quasilinear wave equations on Schwarzschild-de Sitter black
hole backgrounds, for appropriately small initial data. The core of the
argument is entirely local, based on time translation invariant energy
estimates in spacetime slabs of fixed time length. Global existence then
follows simply by iterating this local result in consecutive spacetime slabs.
We infer that an appropriate future energy flux decays exponentially with
respect to the energy flux of the initial data.
| [
{
"created": "Thu, 18 Nov 2021 03:10:50 GMT",
"version": "v1"
}
] | 2021-11-19 | [
[
"Mavrogiannis",
"Georgios",
""
]
] | We give an elementary new argument for global existence and exponential decay of solutions of quasilinear wave equations on Schwarzschild-de Sitter black hole backgrounds, for appropriately small initial data. The core of the argument is entirely local, based on time translation invariant energy estimates in spacetime slabs of fixed time length. Global existence then follows simply by iterating this local result in consecutive spacetime slabs. We infer that an appropriate future energy flux decays exponentially with respect to the energy flux of the initial data. |
1609.05933 | Eliu Huerta | E. A. Huerta, Prayush Kumar, Bhanu Agarwal, Daniel George, Hsi-Yu
Schive, Harald P. Pfeiffer, Roland Haas, Wei Ren, Tony Chu, Michael Boyle,
Daniel A. Hemberger, Lawrence E. Kidder, Mark A. Scheel and Bela Szilagyi | Complete waveform model for compact binaries on eccentric orbits | 31 pages, 19 figures, 3 appendices. Submitted to Phys Rev D. v2:
direct comparison to eccentric numerical relativity simulations, not used for
calibration of the model, included. References added. Accepted to Phys Rev D | Phys. Rev. D 95, 024038 (2017) | 10.1103/PhysRevD.95.024038 | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a time domain waveform model that describes the
inspiral-merger-ringdown (IMR) of compact binary systems whose components are
non-spinning, and which evolve on orbits with low to moderate eccentricity. The
inspiral evolution is described using third order post-Newtonian equations both
for the equations of motion of the binary, and its far-zone radiation field.
This latter component also includes instantaneous, tails and tails-of-tails
contributions, and a contribution due to non-linear memory. This framework
reduces to the post-Newtonian approximant TaylorT4 at third post-Newtonian
order in the zero eccentricity limit. To improve phase accuracy, we incorporate
higher-order post-Newtonian corrections for the energy flux of quasi-circular
binaries and gravitational self-force corrections to the binding energy of
compact binaries. This enhanced inspiral evolution prescription is combined
with an analytical prescription for the merger-ringdown evolution using a
catalog of numerical relativity simulations. This IMR waveform model reproduces
effective-one-body waveforms for systems with mass-ratios between 1 to 15 in
the zero eccentricity limit. Using a set of eccentric numerical relativity
simulations, not used during calibration, we show that our eccentric model
accurately reproduces the features of eccentric compact binary coalescence
throughout the merger. Using this model we show that the gravitational wave
transients GW150914 and GW151226 can be effectively recovered with template
banks of quasi-circular, spin-aligned waveforms if the eccentricity $e_0$ of
these systems when they enter the aLIGO band at a gravitational wave frequency
of 14 Hz satisfies $e_0^{\rm GW150914}\leq0.15$ and $e_0^{\rm
GW151226}\leq0.1$.
| [
{
"created": "Mon, 19 Sep 2016 20:44:41 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Feb 2017 22:48:05 GMT",
"version": "v2"
}
] | 2017-02-03 | [
[
"Huerta",
"E. A.",
""
],
[
"Kumar",
"Prayush",
""
],
[
"Agarwal",
"Bhanu",
""
],
[
"George",
"Daniel",
""
],
[
"Schive",
"Hsi-Yu",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Haas",
"Roland",
""
],
[
... | We present a time domain waveform model that describes the inspiral-merger-ringdown (IMR) of compact binary systems whose components are non-spinning, and which evolve on orbits with low to moderate eccentricity. The inspiral evolution is described using third order post-Newtonian equations both for the equations of motion of the binary, and its far-zone radiation field. This latter component also includes instantaneous, tails and tails-of-tails contributions, and a contribution due to non-linear memory. This framework reduces to the post-Newtonian approximant TaylorT4 at third post-Newtonian order in the zero eccentricity limit. To improve phase accuracy, we incorporate higher-order post-Newtonian corrections for the energy flux of quasi-circular binaries and gravitational self-force corrections to the binding energy of compact binaries. This enhanced inspiral evolution prescription is combined with an analytical prescription for the merger-ringdown evolution using a catalog of numerical relativity simulations. This IMR waveform model reproduces effective-one-body waveforms for systems with mass-ratios between 1 to 15 in the zero eccentricity limit. Using a set of eccentric numerical relativity simulations, not used during calibration, we show that our eccentric model accurately reproduces the features of eccentric compact binary coalescence throughout the merger. Using this model we show that the gravitational wave transients GW150914 and GW151226 can be effectively recovered with template banks of quasi-circular, spin-aligned waveforms if the eccentricity $e_0$ of these systems when they enter the aLIGO band at a gravitational wave frequency of 14 Hz satisfies $e_0^{\rm GW150914}\leq0.15$ and $e_0^{\rm GW151226}\leq0.1$. |
2010.05126 | John Westernacher-Schneider | John Ryan Westernacher-Schneider | Extremely High-Order Convergence in Simulations of Relativistic Stars | Pdf ~1 Mb. 13 page body, 2 pages of appendices. Video content
available at https://youtu.be/rBpz-aVNSLo . v2: added references and
footnote, minor style change | null | 10.1088/1361-6382/ac0234 | null | gr-qc astro-ph.HE physics.comp-ph physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a road towards obtaining gravitational waveforms from inspiraling
material binaries with an accuracy viable for third-generation gravitational
wave detectors, without necessarily advancing computational hardware or
massively-parallel software infrastructure. We demonstrate a proof-of-principle
1+1-dimensional numerical implementation that exhibits up to 7th-order
convergence for highly dynamic barotropic stars in curved spacetime, and
numerical errors up to 6 orders of magnitude smaller than a standard method.
Aside from high-order interpolation errors (Runge's phenomenon), there are no
obvious fundamental obstacles to obtaining convergence of even higher order.
The implementation uses a novel surface-tracking method, where the surface is
evolved and high-order accurate boundary conditions are imposed there.
Computational memory does not need to be allocated to fluid variables in the
vacuum region of spacetime. We anticipate the application of this new method to
full $3\! +\! 1$-dimensional simulations of the inspiral phase of compact
binary systems with at least one material body. The additional challenge of a
deformable surface must be addressed in multiple spatial dimensions, but it is
also an opportunity to input more precise surface tension physics.
| [
{
"created": "Sun, 11 Oct 2020 01:10:36 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2021 03:54:27 GMT",
"version": "v2"
}
] | 2021-07-07 | [
[
"Westernacher-Schneider",
"John Ryan",
""
]
] | We provide a road towards obtaining gravitational waveforms from inspiraling material binaries with an accuracy viable for third-generation gravitational wave detectors, without necessarily advancing computational hardware or massively-parallel software infrastructure. We demonstrate a proof-of-principle 1+1-dimensional numerical implementation that exhibits up to 7th-order convergence for highly dynamic barotropic stars in curved spacetime, and numerical errors up to 6 orders of magnitude smaller than a standard method. Aside from high-order interpolation errors (Runge's phenomenon), there are no obvious fundamental obstacles to obtaining convergence of even higher order. The implementation uses a novel surface-tracking method, where the surface is evolved and high-order accurate boundary conditions are imposed there. Computational memory does not need to be allocated to fluid variables in the vacuum region of spacetime. We anticipate the application of this new method to full $3\! +\! 1$-dimensional simulations of the inspiral phase of compact binary systems with at least one material body. The additional challenge of a deformable surface must be addressed in multiple spatial dimensions, but it is also an opportunity to input more precise surface tension physics. |
2012.13788 | Serge Repin Mr. | I. D. Novikov, D. I. Novikov, S. V. Repin | Disintegration and expansion of wormholes | null | Phys. Rev. D, vol. 102, issue 12, article id. 124073 (2020) | 10.1103/PhysRevD.102.124073 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the process of catastrophic expansion of a spacelike wormhole
after a violation of its equilibrium state. The dynamics of deformation of the
comoving reference frame is investigated. We show that the deformation has a
very specific anisotropic feature. The statement made earlier by other authors,
that in the process of expanding the wormhole connecting two universes these
universes ultimately unite into one universe, is not correct. We show that the
transverse size of the wormhole (its throat) increases and the length of the
corridor decreases which does not correspond to the de Sitter model.
| [
{
"created": "Sat, 26 Dec 2020 17:47:42 GMT",
"version": "v1"
}
] | 2021-06-08 | [
[
"Novikov",
"I. D.",
""
],
[
"Novikov",
"D. I.",
""
],
[
"Repin",
"S. V.",
""
]
] | We consider the process of catastrophic expansion of a spacelike wormhole after a violation of its equilibrium state. The dynamics of deformation of the comoving reference frame is investigated. We show that the deformation has a very specific anisotropic feature. The statement made earlier by other authors, that in the process of expanding the wormhole connecting two universes these universes ultimately unite into one universe, is not correct. We show that the transverse size of the wormhole (its throat) increases and the length of the corridor decreases which does not correspond to the de Sitter model. |
gr-qc/9411025 | Mark Scheel | Mark A. Scheel, Stuart L. Shapiro, and Saul A. Teukolsky | Collapse to Black Holes in Brans-Dicke Theory: I. Horizon Boundary
Conditions for Dynamical Spacetimes | 46 pages including figures, uuencoded gz-compressed postscript,
Submitted to Phys Rev D | Phys.Rev. D51 (1995) 4208-4235 | 10.1103/PhysRevD.51.4208 | CRSR-1085 | gr-qc | null | We present a new numerical code that evolves a spherically symmetric
configuration of collisionless matter in the Brans-Dicke theory of gravitation.
In this theory the spacetime is dynamical even in spherical symmetry, where it
can contain gravitational radiation. Our code is capable of accurately tracking
collapse to a black hole in a dynamical spacetime arbitrarily far into the
future, without encountering either coordinate pathologies or spacetime
singularities. This is accomplished by truncating the spacetime at a spherical
surface inside the apparent horizon, and subsequently solving the evolution and
constraint equations only in the exterior region. We use our code to address a
number of long-standing theoretical questions about collapse to black holes in
Brans-Dicke theory.
| [
{
"created": "Thu, 10 Nov 1994 14:22:53 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Scheel",
"Mark A.",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present a new numerical code that evolves a spherically symmetric configuration of collisionless matter in the Brans-Dicke theory of gravitation. In this theory the spacetime is dynamical even in spherical symmetry, where it can contain gravitational radiation. Our code is capable of accurately tracking collapse to a black hole in a dynamical spacetime arbitrarily far into the future, without encountering either coordinate pathologies or spacetime singularities. This is accomplished by truncating the spacetime at a spherical surface inside the apparent horizon, and subsequently solving the evolution and constraint equations only in the exterior region. We use our code to address a number of long-standing theoretical questions about collapse to black holes in Brans-Dicke theory. |
gr-qc/9811020 | Garcia | L.C.Garcia de Andrade | Distributional Torsion of Cosmic Walls crossed by Cosmic Strings | 6 pages Latex | null | null | null | gr-qc | null | Distributional sources of cosmic walls crossed by cosmic strings from
Riemann-Cartan (RC) Geometry. The matter density of the planar wall is maximum
at the point where the cosmic string crosses the cosmic wall. Cartan torsion is
has a support on the cosmic string given by the Dirac $ \delta $-function. Off
the sources are left with a torsionless vacuum.
| [
{
"created": "Fri, 6 Nov 1998 03:58:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Distributional sources of cosmic walls crossed by cosmic strings from Riemann-Cartan (RC) Geometry. The matter density of the planar wall is maximum at the point where the cosmic string crosses the cosmic wall. Cartan torsion is has a support on the cosmic string given by the Dirac $ \delta $-function. Off the sources are left with a torsionless vacuum. |
1607.03441 | Rafael Nunes | Rafael C. Nunes | Gravitationally induced particle production and its impact on structure
formation | 14 pages, 12 figures, Published version in General Relativity and
Gravitation. arXiv admin note: text overlap with arXiv:1503.04113; text
overlap with arXiv:1204.3789, arXiv:astro-ph/0308118 by other authors | Gen. Rel. Grav. 48 (2016) 107 | 10.1007/s10714-016-2104-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the influence of a continuous particles creation
processes on the linear and nonlinear matter clustering, and its consequences
on the weak lensing effect induced by structure formation. We study the line of
sight behavior of the contribution to the bispectrum signal at a given angular
multipole $l$, showing that the scale where the nonlinear growth overcomes the
linear effect depends strongly of particles creation rate.
| [
{
"created": "Tue, 12 Jul 2016 17:14:39 GMT",
"version": "v1"
}
] | 2016-07-13 | [
[
"Nunes",
"Rafael C.",
""
]
] | In this paper we investigate the influence of a continuous particles creation processes on the linear and nonlinear matter clustering, and its consequences on the weak lensing effect induced by structure formation. We study the line of sight behavior of the contribution to the bispectrum signal at a given angular multipole $l$, showing that the scale where the nonlinear growth overcomes the linear effect depends strongly of particles creation rate. |
2109.13544 | Vyacheslav Dokuchaev | Victor A. Berezin and Vyacheslav I. Dokuchaev | Supervisor of the Universe | 7 pages, published version of the invited paper for the Special Issue
"Light on Dark Worlds - A Themed Issue in Honor of Professor Maxim Yu.
Khlopov on the Occasion of His 70th Birthday" | Physics 2021, 3(4), 814-820 | 10.3390/physics3040051 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, conformal invariant gravitation, based on Weyl geometry, is
considered. In addition to the gravitational and matter action integrals, the
interaction between the Weyl vector (entered in Weyl geometry) and the vector,
representing the world line of the independent observer, are introduced. It is
shown that the very existence of such an interaction selects the exponentially
growing scale factor solutions among the cosmological vacuums.
| [
{
"created": "Tue, 28 Sep 2021 07:56:37 GMT",
"version": "v1"
}
] | 2021-09-29 | [
[
"Berezin",
"Victor A.",
""
],
[
"Dokuchaev",
"Vyacheslav I.",
""
]
] | In this paper, conformal invariant gravitation, based on Weyl geometry, is considered. In addition to the gravitational and matter action integrals, the interaction between the Weyl vector (entered in Weyl geometry) and the vector, representing the world line of the independent observer, are introduced. It is shown that the very existence of such an interaction selects the exponentially growing scale factor solutions among the cosmological vacuums. |
gr-qc/9901041 | Linux User Rhs | O. Bertolami and D.F. Mota | Seed Magnetic Fields from the Breaking of Lorentz Invariance | 6 pages, plain Latex (requires mprocl.sty file available at
http://www.indiana.edu/~cpt98/proceedings.html). Talk delivered by O.B. at
the Meeting on CPT and Lorentz Symmetry, Bloomington, USA, November 1998 | null | null | null | gr-qc astro-ph hep-ph | null | Spontaneous breaking of Lorentz invariance may take place in string theories,
possibly endowing the photon with a mass. This leads to the breaking of the
conformal symmetry of the electromagnetic action allowing for the generation
within inflationary scenarios of magnetic fields over $Mpc$ scales. We show
that the generated fields are consistent with amplification by the galactic
dynamo processes and can be as large as to explain the observed galactic
magnetic fields through the collapse of protogalactic clouds.
| [
{
"created": "Thu, 14 Jan 1999 15:06:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bertolami",
"O.",
""
],
[
"Mota",
"D. F.",
""
]
] | Spontaneous breaking of Lorentz invariance may take place in string theories, possibly endowing the photon with a mass. This leads to the breaking of the conformal symmetry of the electromagnetic action allowing for the generation within inflationary scenarios of magnetic fields over $Mpc$ scales. We show that the generated fields are consistent with amplification by the galactic dynamo processes and can be as large as to explain the observed galactic magnetic fields through the collapse of protogalactic clouds. |
1707.07612 | Brien C. Nolan | Brien C. Nolan | Local properties and global structure of McVittie spacetimes with
non-flat FLRW backgrounds | 46 + 4 pages, 7 figures | null | 10.1088/1361-6382/aa903c | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | McVittie spacetimes embed the vacuum Schwarzschild(-(anti) de Sitter)
spacetime in an isotropic FLRW background universe. We study the global
structure of McVittie spacetimes with spatially non-flat FLRW backgrounds. This
requires the extension of the definition of such spacetimes, previously given
only for the flat and open cases, to the closed case. We revisit this
definition and show how it gives rise to a unique spacetime (given the FLRW
background, the mass parameter $M$ and the cosmological constant $\Lambda$) in
the open and flat cases. In the closed case, an additional free function of the
cosmic time arises. We derive some basic results on the metric, curvature and
matter content of McVittie spacetimes and derive a representation of the line
element that makes the study of their global properties possible. In the closed
case (independently of the free function mentioned above), the spacetime is
confined (at each instant of time) to a region bounded by a minimum and a
maximum area radius, and is bounded either to the future or to the past by a
scalar curvature singularity. This allowed region only exists when the
background scale factor is above a certain minimum. In the open case, radial
null geodesics originate in finite affine time in the past at a boundary formed
by the union of the Big Bang singularity of the FLRW background and a
non-singular hypersurface of varying causal character. Furthermore, in the case
of eternally expanding open universes, we show that black holes are ubiquitous:
ingoing radial null geodesics extend in finite affine time to a hypersurface
that forms the boundary of the region from which photons can escape to future
null infinity. We revisit the black hole interpretation of McVittie spacetimes
in the spatially flat case, and show that this interpretation holds also in the
case of a vanishing cosmological constant, contrary to a previous claim of
ours.
| [
{
"created": "Mon, 24 Jul 2017 15:49:11 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2017 11:03:15 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Nolan",
"Brien C.",
""
]
] | McVittie spacetimes embed the vacuum Schwarzschild(-(anti) de Sitter) spacetime in an isotropic FLRW background universe. We study the global structure of McVittie spacetimes with spatially non-flat FLRW backgrounds. This requires the extension of the definition of such spacetimes, previously given only for the flat and open cases, to the closed case. We revisit this definition and show how it gives rise to a unique spacetime (given the FLRW background, the mass parameter $M$ and the cosmological constant $\Lambda$) in the open and flat cases. In the closed case, an additional free function of the cosmic time arises. We derive some basic results on the metric, curvature and matter content of McVittie spacetimes and derive a representation of the line element that makes the study of their global properties possible. In the closed case (independently of the free function mentioned above), the spacetime is confined (at each instant of time) to a region bounded by a minimum and a maximum area radius, and is bounded either to the future or to the past by a scalar curvature singularity. This allowed region only exists when the background scale factor is above a certain minimum. In the open case, radial null geodesics originate in finite affine time in the past at a boundary formed by the union of the Big Bang singularity of the FLRW background and a non-singular hypersurface of varying causal character. Furthermore, in the case of eternally expanding open universes, we show that black holes are ubiquitous: ingoing radial null geodesics extend in finite affine time to a hypersurface that forms the boundary of the region from which photons can escape to future null infinity. We revisit the black hole interpretation of McVittie spacetimes in the spatially flat case, and show that this interpretation holds also in the case of a vanishing cosmological constant, contrary to a previous claim of ours. |
2106.05812 | Shreyansh Shankar Dave | Shreyansh S. Dave and Sanatan Digal | Field excitation in fuzzy dark matter near a strong gravitational wave
source | 11 pages, 5 figures | Phys. Rev. D 105, 024039 (2022) | 10.1103/PhysRevD.105.024039 | null | gr-qc astro-ph.HE hep-ph hep-th nucl-th | http://creativecommons.org/licenses/by/4.0/ | The axion-like particles with ultralight mass ($\sim10^{-22}$eV) can be a
possible candidate of dark matter, known as the fuzzy dark matter (FDM). These
particles form Bose-Einstein condensate in the early Universe which can explain
the dark matter density distribution in galaxies at the present time. We study
the time evolution of ultralight axion-like field in the near region of a
strong gravitational wave (GW) source, such as binary black hole merger. We
show that GWs can lead to the generation of field excitations in a spherical
shell about the source that eventually propagate out of the shell to minimize
the energy density of the field configuration. These excitations are generated
toward the end of the merger and in some cases even in the ringdown phase of
the merger, therefore it can provide a qualitatively distinct prediction for
changes in the GW waveform due to the presence of FDM. This would be helpful in
investigating the existence of FDM in galaxies.
| [
{
"created": "Thu, 10 Jun 2021 15:29:23 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Nov 2021 12:20:34 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Jan 2022 17:38:47 GMT",
"version": "v3"
}
] | 2022-01-14 | [
[
"Dave",
"Shreyansh S.",
""
],
[
"Digal",
"Sanatan",
""
]
] | The axion-like particles with ultralight mass ($\sim10^{-22}$eV) can be a possible candidate of dark matter, known as the fuzzy dark matter (FDM). These particles form Bose-Einstein condensate in the early Universe which can explain the dark matter density distribution in galaxies at the present time. We study the time evolution of ultralight axion-like field in the near region of a strong gravitational wave (GW) source, such as binary black hole merger. We show that GWs can lead to the generation of field excitations in a spherical shell about the source that eventually propagate out of the shell to minimize the energy density of the field configuration. These excitations are generated toward the end of the merger and in some cases even in the ringdown phase of the merger, therefore it can provide a qualitatively distinct prediction for changes in the GW waveform due to the presence of FDM. This would be helpful in investigating the existence of FDM in galaxies. |
2002.05012 | Jorge Delgado B.S. | Jorge F. M. Delgado, Carlos A. R. Herdeiro, Eugen Radu | Spinning black holes in shift-symmetric Horndeski theory | 29 pages, 8 figures | null | 10.1007/JHEP04(2020)180 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct spinning black holes (BHs) in shift-symmetric Horndeski theory.
This is an Einstein-scalar-Gauss-Bonnet model wherein the (real) scalar field
couples linearly to the Gauss-Bonnet curvature squared combination. The BH
solutions constructed are stationary, axially symmetric and asymptotically
flat. They possess a non-trivial scalar field outside their regular event
horizon; thus they have scalar hair. The scalar "charge" is not, however, an
independent macroscopic degree of freedom. It is proportional to the Hawking
temperature, as in the static limit, wherein the BHs reduce to the spherical
solutions found by Sotirou and Zhou. The spinning BHs herein are found by
solving non-perturbatively the field equations, numerically. We present an
overview of the parameter space of the solutions together with a study of their
basic geometric and phenomenological properties. These solutions are compared
with the spinning BHs in the Einstein-dilaton-Gauss-Bonnet model and the Kerr
BH of vacuum General Relativity. As for the former, and in contrast with the
latter, there is a minimal BH size and small violations of the Kerr bound.
Phenomenological differences with respect to either the former or the latter,
however, are small for illustrative observables, being of the order of a few
percent, at most.
| [
{
"created": "Wed, 12 Feb 2020 14:21:04 GMT",
"version": "v1"
}
] | 2020-05-20 | [
[
"Delgado",
"Jorge F. M.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | We construct spinning black holes (BHs) in shift-symmetric Horndeski theory. This is an Einstein-scalar-Gauss-Bonnet model wherein the (real) scalar field couples linearly to the Gauss-Bonnet curvature squared combination. The BH solutions constructed are stationary, axially symmetric and asymptotically flat. They possess a non-trivial scalar field outside their regular event horizon; thus they have scalar hair. The scalar "charge" is not, however, an independent macroscopic degree of freedom. It is proportional to the Hawking temperature, as in the static limit, wherein the BHs reduce to the spherical solutions found by Sotirou and Zhou. The spinning BHs herein are found by solving non-perturbatively the field equations, numerically. We present an overview of the parameter space of the solutions together with a study of their basic geometric and phenomenological properties. These solutions are compared with the spinning BHs in the Einstein-dilaton-Gauss-Bonnet model and the Kerr BH of vacuum General Relativity. As for the former, and in contrast with the latter, there is a minimal BH size and small violations of the Kerr bound. Phenomenological differences with respect to either the former or the latter, however, are small for illustrative observables, being of the order of a few percent, at most. |
2103.15040 | Leonardo Balart | Leonardo Balart, Sharmanthie Fernando | Thermodynamics and Heat Engines of Black Holes with Born-Infeld-type
Electrodynamics | 17 pages, 7 figures | Mod.Phys.Lett.A 36 (2021) 15, 2150102 | 10.1142/S0217732321501029 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we have studied electrically charged black holes in a new model
of nonlinear electrodynamics introduced by Kruglov in Ref. [1]. There are two
parameters for the theory and the black hole could have up to two horizons.
Thermodynamics is studied in the extended phase space where the pressure is
proportional to the cosmological constant. First law and the Smarr formula are
derived. There are phase transitions similar to the Van der Waals liquid-gas
phase transitions. Black hole is also studied as a heat engine and have
discussed how the parameters in the nonlinear electrodynamics theory effect the
efficiency of the heat engine.
| [
{
"created": "Sun, 28 Mar 2021 04:04:23 GMT",
"version": "v1"
}
] | 2021-10-19 | [
[
"Balart",
"Leonardo",
""
],
[
"Fernando",
"Sharmanthie",
""
]
] | In this paper we have studied electrically charged black holes in a new model of nonlinear electrodynamics introduced by Kruglov in Ref. [1]. There are two parameters for the theory and the black hole could have up to two horizons. Thermodynamics is studied in the extended phase space where the pressure is proportional to the cosmological constant. First law and the Smarr formula are derived. There are phase transitions similar to the Van der Waals liquid-gas phase transitions. Black hole is also studied as a heat engine and have discussed how the parameters in the nonlinear electrodynamics theory effect the efficiency of the heat engine. |
1009.1791 | Laura Nuttall | Laura K Nuttall, Patrick J Sutton | Identifying the Host Galaxy of Gravitational Wave Signals | 5 pages, 2 figures | Phys.Rev.D82:102002,2010 | 10.1103/PhysRevD.82.102002 | LIGO-P1000087-v3 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the goals of the current LIGO-GEO-Virgo science run is to identify
transient gravitational wave (GW) signals in near real time to allow follow-up
electromagnetic (EM) observations. An EM counterpart could increase the
confidence of the GW detection and provide insight into the nature of the
source. Current GW-EM campaigns target potential host galaxies based on overlap
with the GW sky error box. We propose a new statistic to identify the most
likely host galaxy, ranking galaxies based on their position, distance, and
luminosity. We test our statistic with Monte Carlo simulations of GWs produced
by coalescing binaries of neutron stars (NS) and black holes (BH), one of the
most promising sources for ground-based GW detectors. Considering signals
accessible to current detectors, we find that when imaging a single galaxy, our
statistic correctly identifies the true host ~20% to ~50% of the time,
depending on the masses of the binary components. With five narrow-field images
the probability of imaging the true host increases to ~50% to ~80%. When
collectively imaging groups of galaxies using large field-of-view telescopes,
the probability improves to ~30% to ~60% for a single image and to ~70% to ~90%
for five images. For the advanced generation of detectors (c. 2015+), and
considering binaries within 100 Mpc (the reach of the galaxy catalogue used),
the probability is ~40% for one narrow-field image, ~75% for five narrow-field
images, ~65% for one wide-field image, and ~95% for five wide-field images,
irrespective of binary type.
| [
{
"created": "Thu, 9 Sep 2010 14:21:32 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Oct 2010 13:28:05 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Nov 2011 15:40:41 GMT",
"version": "v3"
}
] | 2011-11-30 | [
[
"Nuttall",
"Laura K",
""
],
[
"Sutton",
"Patrick J",
""
]
] | One of the goals of the current LIGO-GEO-Virgo science run is to identify transient gravitational wave (GW) signals in near real time to allow follow-up electromagnetic (EM) observations. An EM counterpart could increase the confidence of the GW detection and provide insight into the nature of the source. Current GW-EM campaigns target potential host galaxies based on overlap with the GW sky error box. We propose a new statistic to identify the most likely host galaxy, ranking galaxies based on their position, distance, and luminosity. We test our statistic with Monte Carlo simulations of GWs produced by coalescing binaries of neutron stars (NS) and black holes (BH), one of the most promising sources for ground-based GW detectors. Considering signals accessible to current detectors, we find that when imaging a single galaxy, our statistic correctly identifies the true host ~20% to ~50% of the time, depending on the masses of the binary components. With five narrow-field images the probability of imaging the true host increases to ~50% to ~80%. When collectively imaging groups of galaxies using large field-of-view telescopes, the probability improves to ~30% to ~60% for a single image and to ~70% to ~90% for five images. For the advanced generation of detectors (c. 2015+), and considering binaries within 100 Mpc (the reach of the galaxy catalogue used), the probability is ~40% for one narrow-field image, ~75% for five narrow-field images, ~65% for one wide-field image, and ~95% for five wide-field images, irrespective of binary type. |
gr-qc/9908038 | Steven L. Liebling | Dieter Maison and Steven L. Liebling | Some Remarks on Gravitational Global Monopoles | 9 pages, 5 figures | Phys.Rev.Lett. 83 (1999) 5218-5221 | 10.1103/PhysRevLett.83.5218 | MPI-PhT/99-31 | gr-qc | null | Using mainly analytical arguments, we derive the exact relation
$\eta_{max}=\sqrt{3/8\pi}$ for the maximal vacuum value of the Higgs field for
static gravitational global monopoles. For this value, the global monopole
bifurcates with the de Sitter solution obtained for vanishing Higgs field. In
addition, we analyze the stability properties of the solutions.
| [
{
"created": "Wed, 11 Aug 1999 20:11:01 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Maison",
"Dieter",
""
],
[
"Liebling",
"Steven L.",
""
]
] | Using mainly analytical arguments, we derive the exact relation $\eta_{max}=\sqrt{3/8\pi}$ for the maximal vacuum value of the Higgs field for static gravitational global monopoles. For this value, the global monopole bifurcates with the de Sitter solution obtained for vanishing Higgs field. In addition, we analyze the stability properties of the solutions. |
gr-qc/0701136 | Wen Zhao | Wen Zhao, Donghui Xu | Evolution of magnetic component in Yang-Mills condensate dark energy
models | 12 pages, 4 figures, minor typos corrected | Int.J.Mod.Phys.D16:1735-1744,2007 | 10.1142/S0218271807011048 | Int.J.Mod.Phys.D 16 (2007) 1735-1744 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of the electric and magnetic components in an effective
Yang-Mills condensate dark energy model is investigated. If the electric field
is dominant, the magnetic component disappears with the expansion of the
Universe. The total YM condensate tracks the radiation in the earlier Universe,
and later it becomes $w_y\sim-1$ thus is similar to the cosmological constant.
So the cosmic coincidence problem can be avoided in this model. However, if the
magnetic field is dominant, $w_y>1/3$ holds for all time, suggesting that it
cannot be a candidate for the dark energy in this case.
| [
{
"created": "Thu, 25 Jan 2007 02:27:24 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jan 2007 01:45:14 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Apr 2007 00:29:35 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Jun 2007 00:45:21 GMT",
"version": "v4"
},
{
"c... | 2009-04-10 | [
[
"Zhao",
"Wen",
""
],
[
"Xu",
"Donghui",
""
]
] | The evolution of the electric and magnetic components in an effective Yang-Mills condensate dark energy model is investigated. If the electric field is dominant, the magnetic component disappears with the expansion of the Universe. The total YM condensate tracks the radiation in the earlier Universe, and later it becomes $w_y\sim-1$ thus is similar to the cosmological constant. So the cosmic coincidence problem can be avoided in this model. However, if the magnetic field is dominant, $w_y>1/3$ holds for all time, suggesting that it cannot be a candidate for the dark energy in this case. |
1706.05035 | John W. Moffat | J. W. Moffat | Misaligned Spin Merging Black Holes in Modified Gravity (MOG) | 4 pages, no figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A promising signature of coalescing black holes is their spin angular
distribution. We consider the aLIGO collaboration gravitational wave
measurements of the binary black hole spins and the predicted modified gravity
(MOG) preference for misaligned spins of the coalescing black holes. In MOG,
during the merger of two black holes, the enhanced strength of gravitation
reduces the effective spin parameter $\chi_{\rm eff}\sim 0$ in agreement with
the measured spin misalignment of the merging black holes observed in the
gravitational wave detections by the aLIGO collaboration.
| [
{
"created": "Thu, 15 Jun 2017 18:38:06 GMT",
"version": "v1"
}
] | 2017-06-19 | [
[
"Moffat",
"J. W.",
""
]
] | A promising signature of coalescing black holes is their spin angular distribution. We consider the aLIGO collaboration gravitational wave measurements of the binary black hole spins and the predicted modified gravity (MOG) preference for misaligned spins of the coalescing black holes. In MOG, during the merger of two black holes, the enhanced strength of gravitation reduces the effective spin parameter $\chi_{\rm eff}\sim 0$ in agreement with the measured spin misalignment of the merging black holes observed in the gravitational wave detections by the aLIGO collaboration. |
1310.6252 | Peter Kazinski | P.O. Kazinski | Comment on "Quantum versus classical instability of scalar fields in
curved backgrounds" | 5 pp | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I show that the claim of the paper [arXiv:1310.2185] on the absence of
instability for a minimally coupled scalar field on a static spherically
symmetric gravitational background is incorrect.
| [
{
"created": "Wed, 23 Oct 2013 15:07:22 GMT",
"version": "v1"
}
] | 2013-10-24 | [
[
"Kazinski",
"P. O.",
""
]
] | I show that the claim of the paper [arXiv:1310.2185] on the absence of instability for a minimally coupled scalar field on a static spherically symmetric gravitational background is incorrect. |
gr-qc/0112005 | Sascha Husa | Sascha Husa | Semiglobal Numerical Calculations of Asymptotically Minkowski Spacetimes | 6 pages, published in "Relativistic Astrophysics: 20th Texas
Symposium", ed. by J. Craig Wheeler and Hugo Martel, AIP Conference
Proceedings 586 (Austin, Texas, 10-15 Dec. 2000) | null | 10.1063/1.1419646 | null | gr-qc | null | This talk reports on recent progress toward the semiglobal study of
asymptotically flat spacetimes within numerical relativity. The development of
a 3D solver for asymptotically Minkowski-like hyperboloidal initial data has
rendered possible the application of Friedrich's conformal field equations to
astrophysically interesting spacetimes. As a first application, the whole
future of a hyperboloidal set of weak initial data has been studied, including
future null and timelike infinity. Using this example we sketch the numerical
techniques employed and highlight some of the unique capabilities of the
numerical code. We conclude with implications for future work.
| [
{
"created": "Thu, 6 Dec 2001 16:52:42 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Husa",
"Sascha",
""
]
] | This talk reports on recent progress toward the semiglobal study of asymptotically flat spacetimes within numerical relativity. The development of a 3D solver for asymptotically Minkowski-like hyperboloidal initial data has rendered possible the application of Friedrich's conformal field equations to astrophysically interesting spacetimes. As a first application, the whole future of a hyperboloidal set of weak initial data has been studied, including future null and timelike infinity. Using this example we sketch the numerical techniques employed and highlight some of the unique capabilities of the numerical code. We conclude with implications for future work. |
0808.2284 | Shinji Tsujikawa | Takashi Tamaki, Shinji Tsujikawa | Revisiting chameleon gravity - thin-shells and no-shells with
appropriate boundary conditions | 14 pages, no figures | Phys.Rev.D78:084028,2008 | 10.1103/PhysRevD.78.084028 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive analytic solutions of a chameleon scalar field $\phi$ that couples
to a non-relativistic matter in the weak gravitational background of a
spherically symmetric body, paying particular attention to a field mass $m_A$
inside of the body. The standard thin-shell field profile is recovered by
taking the limit $m_A*r_c \to \infty$, where $r_c$ is a radius of the body. We
show the existence of "no-shell" solutions where the field is nearly frozen in
the whole interior of the body, which does not necessarily correspond to the
"zero-shell" limit of thin-shell solutions. In the no-shell case, under the
condition $m_A*r_c \gg 1$, the effective coupling of $\phi$ with matter takes
the same asymptotic form as that in the thin-shell case. We study experimental
bounds coming from the violation of equivalence principle as well as
solar-system tests for a number of models including $f(R)$ gravity and find
that the field is in either the thin-shell or the no-shell regime under such
constraints, depending on the shape of scalar-field potentials. We also show
that, for the consistency with local gravity constraints, the field at the
center of the body needs to be extremely close to the value $\phi_A$ at the
extremum of an effective potential induced by the matter coupling.
| [
{
"created": "Sun, 17 Aug 2008 07:25:53 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Tamaki",
"Takashi",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We derive analytic solutions of a chameleon scalar field $\phi$ that couples to a non-relativistic matter in the weak gravitational background of a spherically symmetric body, paying particular attention to a field mass $m_A$ inside of the body. The standard thin-shell field profile is recovered by taking the limit $m_A*r_c \to \infty$, where $r_c$ is a radius of the body. We show the existence of "no-shell" solutions where the field is nearly frozen in the whole interior of the body, which does not necessarily correspond to the "zero-shell" limit of thin-shell solutions. In the no-shell case, under the condition $m_A*r_c \gg 1$, the effective coupling of $\phi$ with matter takes the same asymptotic form as that in the thin-shell case. We study experimental bounds coming from the violation of equivalence principle as well as solar-system tests for a number of models including $f(R)$ gravity and find that the field is in either the thin-shell or the no-shell regime under such constraints, depending on the shape of scalar-field potentials. We also show that, for the consistency with local gravity constraints, the field at the center of the body needs to be extremely close to the value $\phi_A$ at the extremum of an effective potential induced by the matter coupling. |
2209.07978 | Betti Hartmann | Y. Brihaye (University of Mons, Belgium), F. Console (University of
S\~ao Paulo, Brazil), B. Hartmann (University College London, UK) | Charged and radially excited boson stars (in Anti-de Sitter) | null | null | 10.1103/PhysRevD.106.104058 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We study charged and radially excited boson stars in both asymptotically flat
as well as asymptotically Anti-de Sitter space-time. We demonstrate that two
different types of radially excited solutions exist~: one that persists in the
linear limit of small scalar fields, in which analytical arguments suggest the
existence of these solutions, and one that appears only in the highly
non-linear regime of the model. We also demonstrate that the formation of wavy
scalar hair discussed previously for black holes and boson stars in
asymptotically flat space-time persists for asymptotically Anti-de Sitter
space-time.
| [
{
"created": "Fri, 16 Sep 2022 14:44:18 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Brihaye",
"Y.",
"",
"University of Mons, Belgium"
],
[
"Console",
"F.",
"",
"University of\n São Paulo, Brazil"
],
[
"Hartmann",
"B.",
"",
"University College London, UK"
]
] | We study charged and radially excited boson stars in both asymptotically flat as well as asymptotically Anti-de Sitter space-time. We demonstrate that two different types of radially excited solutions exist~: one that persists in the linear limit of small scalar fields, in which analytical arguments suggest the existence of these solutions, and one that appears only in the highly non-linear regime of the model. We also demonstrate that the formation of wavy scalar hair discussed previously for black holes and boson stars in asymptotically flat space-time persists for asymptotically Anti-de Sitter space-time. |
1401.6662 | Sergey Kozyrev | Sergey M. Kozyrev | Stability of composite vacuum Heckmann wormholes in Brans-Dicke theory | 13 pages. arXiv admin note: substantial text overlap with
arXiv:1109.2273 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper discusses linearized (spherically symmetric) perturbation of
static Heckmann composite thin shell wormholes in Brans-Dicke gravity. The
equation of state $P= \beta^2 \sigma$ at the throat is linearized around the
static solution where $\sigma$ energy density of the shell and $P$ the presume.
We have shown that this thin shell wormholes is stable within the range
$0\leq\beta<1$ and with all values of $\omega$ except $\omega=-2$.
| [
{
"created": "Sun, 26 Jan 2014 16:03:50 GMT",
"version": "v1"
}
] | 2014-01-28 | [
[
"Kozyrev",
"Sergey M.",
""
]
] | This paper discusses linearized (spherically symmetric) perturbation of static Heckmann composite thin shell wormholes in Brans-Dicke gravity. The equation of state $P= \beta^2 \sigma$ at the throat is linearized around the static solution where $\sigma$ energy density of the shell and $P$ the presume. We have shown that this thin shell wormholes is stable within the range $0\leq\beta<1$ and with all values of $\omega$ except $\omega=-2$. |
1412.4801 | Alex Va\~n\'o-Vi\~nuales | Alex Va\~n\'o-Vi\~nuales and Sascha Husa | Unconstrained hyperboloidal evolution of black holes in spherical
symmetry with GBSSN and Z4c | 6 pages, 5 figures | null | 10.1088/1742-6596/600/1/012061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider unconstrained evolution schemes for the hyperboloidal initial
value problem in numerical relativity as a promising candidate for the
optimally efficient numerical treatment of radiating compact objects. Here,
spherical symmetry already poses nontrivial problems and constitutes an
important first step to regularize the resulting singular PDEs. We evolve the
Einstein equations in their generalized BSSN and Z4 formulations coupled to a
massless self-gravitating scalar field. Stable numerical evolutions are
achieved for black hole initial data, and critically rely on the construction
of appropriate gauge conditions.
| [
{
"created": "Mon, 15 Dec 2014 21:07:26 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Vañó-Viñuales",
"Alex",
""
],
[
"Husa",
"Sascha",
""
]
] | We consider unconstrained evolution schemes for the hyperboloidal initial value problem in numerical relativity as a promising candidate for the optimally efficient numerical treatment of radiating compact objects. Here, spherical symmetry already poses nontrivial problems and constitutes an important first step to regularize the resulting singular PDEs. We evolve the Einstein equations in their generalized BSSN and Z4 formulations coupled to a massless self-gravitating scalar field. Stable numerical evolutions are achieved for black hole initial data, and critically rely on the construction of appropriate gauge conditions. |
gr-qc/9802016 | null | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Indeterministic Quantum Gravity and Cosmology IX. Nonreality of
Many-Place Gravitational Autolocalization: Why a Ball Is Not Located in
Different Places at Once | 5 pages, LATEX 2.09 | null | null | IP 2/98 | gr-qc quant-ph | null | This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034,
gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038,
gr-qc/9708014], being an immediate continuation and supplement to the last of
them, where gravitational autolocalization of a body has been considered. A
resulting solution, which describes a one-place location, has been called
gravilon. Here it is shown that a gravilon is the only solution, i.e., that
many-place gravitational autolocalization is unreal. This is closely related to
nonreality of tunneling in the conditions under consideration.
| [
{
"created": "Sun, 8 Feb 1998 10:19:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] | This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038, gr-qc/9708014], being an immediate continuation and supplement to the last of them, where gravitational autolocalization of a body has been considered. A resulting solution, which describes a one-place location, has been called gravilon. Here it is shown that a gravilon is the only solution, i.e., that many-place gravitational autolocalization is unreal. This is closely related to nonreality of tunneling in the conditions under consideration. |
1111.1879 | Benjamin Bahr | Benjamin Bahr, Rodolfo Gambini, Jorge Pullin | Discretisations, Constraints and Diffeomorphisms in Quantum Gravity | Contribution for a special issue of SIGMA on Loop Quantum Gravity and
Cosmology | SIGMA 8 (2012), 002, 29 pages | 10.3842/SIGMA.2012.002 | null | gr-qc hep-lat hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | In this review we discuss the interplay between discretization, constraint
implementation, and diffeomorphism symmetry in Loop Quantum Gravity and Spin
Foam models. To this end we review the Consistent Discretizations approach,
which is an application of the master constraint program to construct the
physical Hilbert space of the canonical theory, as well as the Perfect Actions
approach, which aims at finding a path integral measure with the correct
symmetry behavior under diffeomorphisms.
| [
{
"created": "Tue, 8 Nov 2011 12:05:25 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Jan 2012 08:56:36 GMT",
"version": "v2"
}
] | 2012-01-10 | [
[
"Bahr",
"Benjamin",
""
],
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | In this review we discuss the interplay between discretization, constraint implementation, and diffeomorphism symmetry in Loop Quantum Gravity and Spin Foam models. To this end we review the Consistent Discretizations approach, which is an application of the master constraint program to construct the physical Hilbert space of the canonical theory, as well as the Perfect Actions approach, which aims at finding a path integral measure with the correct symmetry behavior under diffeomorphisms. |
2212.07130 | Vitalii Vertogradov | Vitalii Vertogradov, Dmitriy Kudryavcev | Generalized Vaidya spacetime: horizons, conformal symmetries, surface
gravity and diagonalization | 21 pages, submitted to theoretical and mathematical physics | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper the different properties of generalized Vaidya spacetime are
considered. We located and compared different types of horizons. We show that
the apparent horizon can contain the event horizon. The locations of all types
of horizons are compared with ones in usual Vaidya spacetime. Also, we consider
the conformal Killing vector and transform the metric to conformally-static
coordinates. We introduce a new constant of motion along null and timelike
geodesics, which is generated by homothetic Killing vector. The
conformally-static coordinates allow to diagonalize the generalized Vaidya
spacetime. The surface gravity has been calculated for the dust and stiff fluid
cases.
| [
{
"created": "Wed, 14 Dec 2022 09:36:24 GMT",
"version": "v1"
}
] | 2022-12-15 | [
[
"Vertogradov",
"Vitalii",
""
],
[
"Kudryavcev",
"Dmitriy",
""
]
] | In this paper the different properties of generalized Vaidya spacetime are considered. We located and compared different types of horizons. We show that the apparent horizon can contain the event horizon. The locations of all types of horizons are compared with ones in usual Vaidya spacetime. Also, we consider the conformal Killing vector and transform the metric to conformally-static coordinates. We introduce a new constant of motion along null and timelike geodesics, which is generated by homothetic Killing vector. The conformally-static coordinates allow to diagonalize the generalized Vaidya spacetime. The surface gravity has been calculated for the dust and stiff fluid cases. |
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