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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1402.1038 | Norbert Bodendorfer | Norbert Bodendorfer | A note on entanglement entropy and quantum geometry | 14 pages. v2: journal version. Comment added | Class. Quantum Grav. 31 (2014) 214004 | 10.1088/0264-9381/31/21/214004 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been argued that the entropy which one is computing in the isolated
horizon framework of loop quantum gravity is closely related to the
entanglement entropy of the gravitational field and that the calculation
performed is not restricted to horizons. We recall existing work on this issue
and explain how recent work on generalising these computations to arbitrary
spacetime dimensions D+1>2 supports this point of view and makes the duality
between entanglement entropy and the entropy computed from counting boundary
states manifest. In a certain semiclassical regime in 3+1 dimensions, this
entropy is given by the Bekenstein-Hawking formula.
| [
{
"created": "Wed, 5 Feb 2014 13:45:26 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Nov 2014 11:31:58 GMT",
"version": "v2"
}
] | 2014-11-25 | [
[
"Bodendorfer",
"Norbert",
""
]
] | It has been argued that the entropy which one is computing in the isolated horizon framework of loop quantum gravity is closely related to the entanglement entropy of the gravitational field and that the calculation performed is not restricted to horizons. We recall existing work on this issue and explain how recent work on generalising these computations to arbitrary spacetime dimensions D+1>2 supports this point of view and makes the duality between entanglement entropy and the entropy computed from counting boundary states manifest. In a certain semiclassical regime in 3+1 dimensions, this entropy is given by the Bekenstein-Hawking formula. |
1303.0174 | Jean-Philippe Bruneton | Jean-Philippe Bruneton | MG13 Proceedings: A lattice Universe as a toy-model for inhomogeneous
cosmology | 3 pages, no figures. Prepared for MG13 conference | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly report on a previously found new, approximate, solution to
Einstein field equations, describing a cubic lattice of spherical masses. This
model mimics in a satisfactory way a Universe which can be strongly
inhomogeneous at small scales, but quite homogeneous at large ones. As a
consequence of field equations, the lattice Universe is found to expand or
contract in the same way as the solution of a Friedmann Universe filled with
dust having the same average density. The study of observables indicates
however the possible existence of a fitting problem, i.e. the fact that the
Friedmann model obtained from past-lightcone observables does not match with
the one obtained by smoothing the matter content of the Universe.
| [
{
"created": "Fri, 1 Mar 2013 14:10:47 GMT",
"version": "v1"
}
] | 2013-03-04 | [
[
"Bruneton",
"Jean-Philippe",
""
]
] | We briefly report on a previously found new, approximate, solution to Einstein field equations, describing a cubic lattice of spherical masses. This model mimics in a satisfactory way a Universe which can be strongly inhomogeneous at small scales, but quite homogeneous at large ones. As a consequence of field equations, the lattice Universe is found to expand or contract in the same way as the solution of a Friedmann Universe filled with dust having the same average density. The study of observables indicates however the possible existence of a fitting problem, i.e. the fact that the Friedmann model obtained from past-lightcone observables does not match with the one obtained by smoothing the matter content of the Universe. |
1612.07970 | Ernesto Barrientos | E. Barrientos, S. Mendoza | MOND as the weak field limit of an extended metric theory of gravity
with torsion | 10 pages | Eur. Phys. J. Plus (2017) 132: 361 | 10.1140/epjp/i2017-11642-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we construct a relativistic extended metric theory of
gravity, for which its weak field limit reduces to the non-relativistic
MOdified Newtonian Dynamics regime of gravity. The theory is fully covariant
and the way to achieve this is to introduce torsion in the description of
gravity as well as with the addition of a particular function of the matter
lagrangian into the gravitational action.
| [
{
"created": "Fri, 23 Dec 2016 13:49:48 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2017 16:07:02 GMT",
"version": "v2"
}
] | 2017-09-01 | [
[
"Barrientos",
"E.",
""
],
[
"Mendoza",
"S.",
""
]
] | In this article we construct a relativistic extended metric theory of gravity, for which its weak field limit reduces to the non-relativistic MOdified Newtonian Dynamics regime of gravity. The theory is fully covariant and the way to achieve this is to introduce torsion in the description of gravity as well as with the addition of a particular function of the matter lagrangian into the gravitational action. |
1805.03936 | Hemza Azri | Hemza Azri | Cosmological Implications of Affine Gravity | Ph.D thesis; 109 pages; 18 figures; 3 tables | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main aim of this thesis is to reveal some interesting aspects of the
purely affine theory of gravity and its cosmological implication. A particular
attention will be devoted to its consequences when applied to cosmological
inflation. Primarily, affine spacetime, composed of geodesics with no notion of
length and angle, accommodates gravity but not matter. The thesis study is
expected to reveal salient properties of matter dynamics in affine spacetime
and may reveal an intimate connection between vacuum state and metrical
gravity. An interesting application of the framework is the inflationary
regime, where it is shown that affine gravity prefers only a unique metric
tensor such that the transition from nonminimal to minimal coupling of the
inflaton is performed only via redefinition of the latter. This allows us to
avoid the use of the so called conformal frames. In fact, unlike metric
gravity, the metric tensor in affine gravity is generated and not postulated a
priori, thus this tensor is absent in the actions and conformal transformation
does not make sense. Last but not least, we try to show how metric gravity can
be induced through a simple structure that contains only affine connection and
scalar fields. General relativity arises classically only at the vacuum, and
this view of gravity may be considered as a new way to inducing metric
elasticity of space, not through quantum corrections as in standard induced
gravity, but only classically. The thesis is concluded by analyzing affine
gravity in a particular higher-dimensional manifold (product of two spaces) in
an attempt to understand both, the cosmological constant and matter
dynamically.
| [
{
"created": "Thu, 10 May 2018 12:26:45 GMT",
"version": "v1"
}
] | 2018-05-11 | [
[
"Azri",
"Hemza",
""
]
] | The main aim of this thesis is to reveal some interesting aspects of the purely affine theory of gravity and its cosmological implication. A particular attention will be devoted to its consequences when applied to cosmological inflation. Primarily, affine spacetime, composed of geodesics with no notion of length and angle, accommodates gravity but not matter. The thesis study is expected to reveal salient properties of matter dynamics in affine spacetime and may reveal an intimate connection between vacuum state and metrical gravity. An interesting application of the framework is the inflationary regime, where it is shown that affine gravity prefers only a unique metric tensor such that the transition from nonminimal to minimal coupling of the inflaton is performed only via redefinition of the latter. This allows us to avoid the use of the so called conformal frames. In fact, unlike metric gravity, the metric tensor in affine gravity is generated and not postulated a priori, thus this tensor is absent in the actions and conformal transformation does not make sense. Last but not least, we try to show how metric gravity can be induced through a simple structure that contains only affine connection and scalar fields. General relativity arises classically only at the vacuum, and this view of gravity may be considered as a new way to inducing metric elasticity of space, not through quantum corrections as in standard induced gravity, but only classically. The thesis is concluded by analyzing affine gravity in a particular higher-dimensional manifold (product of two spaces) in an attempt to understand both, the cosmological constant and matter dynamically. |
2211.14760 | Masroor C. Pookkillath | Antonio De Felice, Kei-ichi Maeda, Shinji Mukohyama, Masroor C.
Pookkillath | Gravitational collapse and formation of a black hole in a type II
minimally modified gravity theory | 22 pages, 9 figures | null | 10.1088/1475-7516/2023/03/030 | YITP-22-142, IPMU22-0062 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the spherically symmetric collapse of a cloud of dust in VCDM, a
class of gravitational theories with two local physical degrees of freedom. We
find that the collapse corresponds to a particular foliation of the
Oppenheimer-Snyder solution in general relativity (GR) which is endowed with a
constant trace for the extrinsic curvature relative to the time $t$ constant
foliation. For this solution, we find that the final state of the collapse
leads to a static configuration with the lapse function vanishing at a radius
inside the apparent horizon. Such a point is reached in an infinite time-$t$
interval, $t$ being the cosmological time, i.e. the time of an observer located
far away from the collapsing cloud. The presence of this vanishing lapse
endpoint implies the necessity of a UV completion to describe the physics
inside the resulting black hole. On the other hand, since the corresponding
cosmic time $t$ is infinite, VCDM can safely describe the whole history of the
universe at large scales without knowledge of the unknown UV completion,
despite the presence of the so-called shadowy mode.
| [
{
"created": "Sun, 27 Nov 2022 08:23:40 GMT",
"version": "v1"
}
] | 2023-03-22 | [
[
"De Felice",
"Antonio",
""
],
[
"Maeda",
"Kei-ichi",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Pookkillath",
"Masroor C.",
""
]
] | We study the spherically symmetric collapse of a cloud of dust in VCDM, a class of gravitational theories with two local physical degrees of freedom. We find that the collapse corresponds to a particular foliation of the Oppenheimer-Snyder solution in general relativity (GR) which is endowed with a constant trace for the extrinsic curvature relative to the time $t$ constant foliation. For this solution, we find that the final state of the collapse leads to a static configuration with the lapse function vanishing at a radius inside the apparent horizon. Such a point is reached in an infinite time-$t$ interval, $t$ being the cosmological time, i.e. the time of an observer located far away from the collapsing cloud. The presence of this vanishing lapse endpoint implies the necessity of a UV completion to describe the physics inside the resulting black hole. On the other hand, since the corresponding cosmic time $t$ is infinite, VCDM can safely describe the whole history of the universe at large scales without knowledge of the unknown UV completion, despite the presence of the so-called shadowy mode. |
2311.03474 | Giorgio Mentasti | Giorgio Mentasti and Carlo R. Contaldi | Observing gravitational waves with solar system astrometry | 5 pages, 1 figure | null | null | null | gr-qc astro-ph.CO astro-ph.EP astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The subtle influence of gravitational waves on the apparent positioning of
celestial bodies offers novel observational windows. We calculate the expected
astrometric signal induced by an isotropic Stochastic Gravitational Wave
Background (SGWB) in the short distance limit. Our focus is on the resultant
proper motion of Solar System objects, a signal on the same time scales
addressed by Pulsar Timing Arrays (PTA). We derive the corresponding
astrometric deflection patterns, finding that they manifest as distinctive
dipole and quadrupole correlations, or in some cases, may not be present. Our
analysis encompasses both Einsteinian and non-Einsteinian polarisations. We
estimate the upper limits for the amplitude of a scale-invariant SGWB that
could be obtained by tracking the proper motions of large numbers of solar
system objects such as asteroids. With the Gaia satellite and the Vera C. Rubin
Observatory poised to track an extensive sample of asteroids-ranging from
$O(10^5)$ to $O(10^6)$, we highlight the significant future potential for
similar surveys to contribute to our understanding of the SGWB.
| [
{
"created": "Mon, 6 Nov 2023 19:23:06 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Feb 2024 19:48:19 GMT",
"version": "v2"
}
] | 2024-02-27 | [
[
"Mentasti",
"Giorgio",
""
],
[
"Contaldi",
"Carlo R.",
""
]
] | The subtle influence of gravitational waves on the apparent positioning of celestial bodies offers novel observational windows. We calculate the expected astrometric signal induced by an isotropic Stochastic Gravitational Wave Background (SGWB) in the short distance limit. Our focus is on the resultant proper motion of Solar System objects, a signal on the same time scales addressed by Pulsar Timing Arrays (PTA). We derive the corresponding astrometric deflection patterns, finding that they manifest as distinctive dipole and quadrupole correlations, or in some cases, may not be present. Our analysis encompasses both Einsteinian and non-Einsteinian polarisations. We estimate the upper limits for the amplitude of a scale-invariant SGWB that could be obtained by tracking the proper motions of large numbers of solar system objects such as asteroids. With the Gaia satellite and the Vera C. Rubin Observatory poised to track an extensive sample of asteroids-ranging from $O(10^5)$ to $O(10^6)$, we highlight the significant future potential for similar surveys to contribute to our understanding of the SGWB. |
2211.13111 | Shao-Jiang Wang | Wang-Wei Yu, Shao-Jiang Wang | Searching for double-peak and doubly broken gravitational-wave spectra
from Advanced LIGO-Virgo's first three observing runs | v1, 5 pages + references, 5 figures, 1 table; v2, 11 pages, 6
figures, 1 table, version accepted for publication in Physical Review D; v3,
to match the published version | Phys. Rev. D 108 (2023) 6, 063526 | 10.1103/PhysRevD.108.063526 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current LIGO-Virgo observing run has been pushing the sensitivity limit
to touch the stochastic gravitational-wave backgrounds (SGWBs). However, no
significant detection has been reported to date for any single dominated source
of SGWBs with a single broken-power-law (BPL) spectrum. Nevertheless, it could
equally well escape from existing Bayesian searches from, for example, two
comparable dominated sources with two separate BPL spectra (double-peak case)
or a single source with its power-law behavior in the spectrum broken twice
(doubly broken case). In this paper, we put constraints on these two cases but
specifically for the model with cosmological first-order phase transitions from
Advanced LIGO-Virgo's first three observing runs. We found strong negative
evidence for the double-peak case and hence place 95\% C.L. upper limits
$\Omega_\mathrm{BPL,1}<5.8\times10^{-8}$ and
$\Omega_\mathrm{BPL,2}<4.4\times10^{-8}$ on the two BPL spectra amplitudes with
respect to the unresolved compact binary coalescence (CBC) amplitude
$\Omega_\mathrm{CBC}<5.6\times10^{-9}$. We further found weak negative evidence
for the doubly broken case and hence place 95\% C.L. upper limit
$\Omega_\mathrm{DB}<1.2\times10^{-7}$ on the overall amplitude of the doubly
broken spectrum with respect to $\Omega_\mathrm{CBC}<6.0\times10^{-9}$. In
particular, the results from the double-peak case have marginally ruled out the
strong super-cooling first-order phase transitions at LIGO-Virgo band.
| [
{
"created": "Wed, 23 Nov 2022 16:51:08 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Sep 2023 17:19:57 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Sep 2023 15:23:34 GMT",
"version": "v3"
}
] | 2023-09-29 | [
[
"Yu",
"Wang-Wei",
""
],
[
"Wang",
"Shao-Jiang",
""
]
] | The current LIGO-Virgo observing run has been pushing the sensitivity limit to touch the stochastic gravitational-wave backgrounds (SGWBs). However, no significant detection has been reported to date for any single dominated source of SGWBs with a single broken-power-law (BPL) spectrum. Nevertheless, it could equally well escape from existing Bayesian searches from, for example, two comparable dominated sources with two separate BPL spectra (double-peak case) or a single source with its power-law behavior in the spectrum broken twice (doubly broken case). In this paper, we put constraints on these two cases but specifically for the model with cosmological first-order phase transitions from Advanced LIGO-Virgo's first three observing runs. We found strong negative evidence for the double-peak case and hence place 95\% C.L. upper limits $\Omega_\mathrm{BPL,1}<5.8\times10^{-8}$ and $\Omega_\mathrm{BPL,2}<4.4\times10^{-8}$ on the two BPL spectra amplitudes with respect to the unresolved compact binary coalescence (CBC) amplitude $\Omega_\mathrm{CBC}<5.6\times10^{-9}$. We further found weak negative evidence for the doubly broken case and hence place 95\% C.L. upper limit $\Omega_\mathrm{DB}<1.2\times10^{-7}$ on the overall amplitude of the doubly broken spectrum with respect to $\Omega_\mathrm{CBC}<6.0\times10^{-9}$. In particular, the results from the double-peak case have marginally ruled out the strong super-cooling first-order phase transitions at LIGO-Virgo band. |
gr-qc/0412058 | Valery Kiselev | A.A.Logunov, M.A.Mestverishvili, V.V.Kiselev | Black holes: a prediction of theory or phantasy? | Eq.(5) gives the strict inequality for a velocity of massive
particle. It is not correct because the observer on the horizon of black hole
is light-like, hence, the corresponding relative velocity reaches the unit
limit. Second, the trajectory satisfies the Hamilton-Jacobi equation, that
means that the massive particle is always on the mass-shell. The conclusion
(page 6) is erroneous | Phys.Part.Nucl. 37 (2006) 317-320; Fiz.Elem.Chast.Atom.Yadra 37
(2006) 597-604 | null | null | gr-qc | null | We argue for black holes do not represent a strict consequence of general
relativity.
| [
{
"created": "Mon, 13 Dec 2004 08:59:42 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Dec 2021 15:57:56 GMT",
"version": "v2"
}
] | 2021-12-21 | [
[
"Logunov",
"A. A.",
""
],
[
"Mestverishvili",
"M. A.",
""
],
[
"Kiselev",
"V. V.",
""
]
] | We argue for black holes do not represent a strict consequence of general relativity. |
gr-qc/9307004 | Adam Helfer | Adam D. Helfer | A Phase Space for Gravitational Radiation | 21 pages | Commun.Math.Phys.170:483-502,1995 | 10.1007/BF02099146 | null | gr-qc | null | We give a new definition, based on considerations of well-posedness for a
certain asymptotic initial value problem, of the phase space for the radiative
degrees of freedom of the gravitational field in exact General Relativity. This
space fibres over the space of final states, with the fibres being the purely
radiative degrees of freedom. The symplectic form is rigorously identified.
The infrared sectors are shown to be the level surfaces of a moment map of an
action of the quotient group Supertranslations/Translations. A similar result
holds for Electromagnetism in Minkowski space.
| [
{
"created": "Wed, 7 Jul 1993 23:20:41 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Helfer",
"Adam D.",
""
]
] | We give a new definition, based on considerations of well-posedness for a certain asymptotic initial value problem, of the phase space for the radiative degrees of freedom of the gravitational field in exact General Relativity. This space fibres over the space of final states, with the fibres being the purely radiative degrees of freedom. The symplectic form is rigorously identified. The infrared sectors are shown to be the level surfaces of a moment map of an action of the quotient group Supertranslations/Translations. A similar result holds for Electromagnetism in Minkowski space. |
1003.4295 | Vitor Cardoso | Mariam Bouhmadi-Lopez, Vitor Cardoso, Andrea Nerozzi, Jorge V. Rocha | Black holes die hard: can one spin-up a black hole past extremality? | 10 pages, 7 figures. RevTex4. | null | 10.1103/PhysRevD.81.084051 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A possible process to destroy a black hole consists on throwing point
particles with sufficiently large angular momentum into the black hole. In the
case of Kerr black holes, it was shown by Wald that particles with dangerously
large angular momentum are simply not captured by the hole, and thus the event
horizon is not destroyed. Here we reconsider this gedanken experiment for a
variety of black hole geometries, from black holes in higher dimensions to
black rings. We show that this particular way of destroying a black hole does
not succeed and that Cosmic Censorship is preserved.
| [
{
"created": "Mon, 22 Mar 2010 22:25:04 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Nerozzi",
"Andrea",
""
],
[
"Rocha",
"Jorge V.",
""
]
] | A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for a variety of black hole geometries, from black holes in higher dimensions to black rings. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved. |
0811.3368 | Alexis Larranaga | Alexis Larranaga, Luz Angela Garcia | Thermodynamics of the Three-dimensional Black Hole with a Coulomb-like
Field | 8 pages | EJTP, 9, 27. 121-130 (2012) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the thermodynamical properties of the
(2+1)dimensional black hole with a Coulomb-like electric field and the
differential form of the first law of thermodynamics is derived considering a
virtual displacement of its event horizon. This approach shows that it is
possible to give a thermodynamical interpretation to the field equations near
the horizon. The Lambda=0 solution is studied and its interesting
thermodynamical properties are commented.
| [
{
"created": "Thu, 20 Nov 2008 17:19:30 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Nov 2008 05:42:40 GMT",
"version": "v2"
}
] | 2012-11-07 | [
[
"Larranaga",
"Alexis",
""
],
[
"Garcia",
"Luz Angela",
""
]
] | In this paper, we study the thermodynamical properties of the (2+1)dimensional black hole with a Coulomb-like electric field and the differential form of the first law of thermodynamics is derived considering a virtual displacement of its event horizon. This approach shows that it is possible to give a thermodynamical interpretation to the field equations near the horizon. The Lambda=0 solution is studied and its interesting thermodynamical properties are commented. |
1909.13467 | Pavel Krtous | Pavel Krtou\v{s}, Andrei Zelnikov | Thermodynamics of two black holes | 8 pages, 2 figure; v2: significant modifications; v3: minor typo and
reference corrections | JHEP02(2020)164 | 10.1007/JHEP02(2020)164 | Alberta Thy 11-19 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a system of two charged non-rotating black holes separated by a
strut. Using the exact solution of the Einstein-Maxwell equations, which
describes this system, we construct a consistent form of the first law of
thermodynamics. We derive thermodynamic parameters related to the strut in an
explicit form. The intensive thermodynamical quantity associated with the strut
is its tension. We call the corresponding extensive quantity the
thermodynamical length and we provide an explicit expression and interpretation
for it.
| [
{
"created": "Mon, 30 Sep 2019 06:06:22 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jan 2020 02:19:32 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Feb 2020 16:17:33 GMT",
"version": "v3"
}
] | 2020-02-27 | [
[
"Krtouš",
"Pavel",
""
],
[
"Zelnikov",
"Andrei",
""
]
] | We study a system of two charged non-rotating black holes separated by a strut. Using the exact solution of the Einstein-Maxwell equations, which describes this system, we construct a consistent form of the first law of thermodynamics. We derive thermodynamic parameters related to the strut in an explicit form. The intensive thermodynamical quantity associated with the strut is its tension. We call the corresponding extensive quantity the thermodynamical length and we provide an explicit expression and interpretation for it. |
gr-qc/9705006 | Rafael D. Sorkin | Rafael D. Sorkin (ICN-UNAM and Syracuse University) | The Statistical Mechanics of Black Hole Thermodynamics | 21 pages, plainTeX, no figures. (Only nontrivial change from original
version is rewriting to improve clarity.) | in Black Holes and Relativistic Stars, edited by R.M. Wald
(University of Chicago Press, 1998) | null | null | gr-qc hep-th | null | Although we have convincing evidence that a black hole bears an entropy
proportional to its surface (horizon) area, the ``statistical mechanical''
explanation of this entropy remains unknown. Two basic questions in this
connection are: what is the microscopic origin of the entropy, and why does the
law of entropy increase continue to hold when the horizon entropy is included?
After a review of some of the difficulties in answering these questions, I
propose an explanation of the law of entropy increase which comes near to a
proof in the context of the ``semi-classical'' approximation, and which also
provides a proof in full quantum gravity under the assumption that the latter
fulfills certain natural expectations, like the existence of a conserved energy
definable at infinity. This explanation seems to require a fundamental
spacetime discreteness in order for the entropy to be consistently finite, and
I recall briefly some of the ideas for what the discreteness might be. If such
ideas are right, then our knowledge of the horizon entropy will allow us to
``count the atoms of spacetime''.
| [
{
"created": "Mon, 5 May 1997 15:08:17 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Dec 1997 10:08:58 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Sorkin",
"Rafael D.",
"",
"ICN-UNAM and Syracuse University"
]
] | Although we have convincing evidence that a black hole bears an entropy proportional to its surface (horizon) area, the ``statistical mechanical'' explanation of this entropy remains unknown. Two basic questions in this connection are: what is the microscopic origin of the entropy, and why does the law of entropy increase continue to hold when the horizon entropy is included? After a review of some of the difficulties in answering these questions, I propose an explanation of the law of entropy increase which comes near to a proof in the context of the ``semi-classical'' approximation, and which also provides a proof in full quantum gravity under the assumption that the latter fulfills certain natural expectations, like the existence of a conserved energy definable at infinity. This explanation seems to require a fundamental spacetime discreteness in order for the entropy to be consistently finite, and I recall briefly some of the ideas for what the discreteness might be. If such ideas are right, then our knowledge of the horizon entropy will allow us to ``count the atoms of spacetime''. |
0908.0219 | Rong-Gen Cai | Zhong-Hua Li, Rong-Gen Cai | Critical Dimension for Stable Self-gravitating Stars in AdS | Revtex, 11 pages with 7 eps figures | Commun.Theor.Phys.52:255-260,2009 | 10.1088/0253-6102/52/2/13 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We study the self-gravitating stars with a linear equation of state, $P=a
\rho$, in AdS space, where $a$ is a constant parameter. There exists a critical
dimension, beyond which the stars are always stable with any central energy
density; below which there exists a maximal mass configuration for a certain
central energy density and when the central energy density continues to
increase, the configuration becomes unstable. We find that the critical
dimension depends on the parameter $a$, it runs from $d=11.1429$ to 10.1291 as
$a$ varies from $a=0$ to 1. The lowest integer dimension for a dynamically
stable self-gravitating configuration should be $d=12$ for any $a \in [0,1]$
rather than $d=11$, the latter is the case of self-gravitating radiation
configurations in AdS space.
| [
{
"created": "Mon, 3 Aug 2009 10:19:56 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Li",
"Zhong-Hua",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | We study the self-gravitating stars with a linear equation of state, $P=a \rho$, in AdS space, where $a$ is a constant parameter. There exists a critical dimension, beyond which the stars are always stable with any central energy density; below which there exists a maximal mass configuration for a certain central energy density and when the central energy density continues to increase, the configuration becomes unstable. We find that the critical dimension depends on the parameter $a$, it runs from $d=11.1429$ to 10.1291 as $a$ varies from $a=0$ to 1. The lowest integer dimension for a dynamically stable self-gravitating configuration should be $d=12$ for any $a \in [0,1]$ rather than $d=11$, the latter is the case of self-gravitating radiation configurations in AdS space. |
2301.01329 | Rodrigo Maier | Rodrigo Maier | Stellar Instability from Parametric Resonance | Accepted for publication in Classical and Quantum Gravity | null | 10.1088/1361-6382/acafd3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we examine the stability of stellar configurations in which the
interior solution is described by a closed FLRW geometry sourced with a charged
pressureless fluid and radiation. An interacting vacuum component and a
conformally coupled massive scalar field are also included. Given a simple
factor for the energy transfer between the pressureless fluid and the vacuum
component we obtain bounded interior oscillatory solutions. We show that in
proper domains of the parameter space the interior dynamics is highly unstable
so that the break of the KAM tori leads to a disruptive ejection of mass. For
such configurations the interior solution asymptotically matches an exterior
Reissner-Nordstr\"om-de Sitter spacetime.
| [
{
"created": "Tue, 3 Jan 2023 19:31:51 GMT",
"version": "v1"
}
] | 2023-01-25 | [
[
"Maier",
"Rodrigo",
""
]
] | In this paper we examine the stability of stellar configurations in which the interior solution is described by a closed FLRW geometry sourced with a charged pressureless fluid and radiation. An interacting vacuum component and a conformally coupled massive scalar field are also included. Given a simple factor for the energy transfer between the pressureless fluid and the vacuum component we obtain bounded interior oscillatory solutions. We show that in proper domains of the parameter space the interior dynamics is highly unstable so that the break of the KAM tori leads to a disruptive ejection of mass. For such configurations the interior solution asymptotically matches an exterior Reissner-Nordstr\"om-de Sitter spacetime. |
gr-qc/0604057 | Joan Sola | Javier Grande, Joan Sola, Hrvoje Stefancic | LXCDM: a cosmon model solution to the cosmological coincidence problem? | LaTeX, 53 pages, 15 figures. Comments and references added. Version
accepted in JCAP | JCAP0608:011,2006 | 10.1088/1475-7516/2006/08/011 | UB-ECM-PF-06/12 | gr-qc astro-ph hep-ph hep-th | null | We consider the possibility that the total dark energy (DE) of the Universe
is made out of two dynamical components of different nature: a variable
cosmological term, Lambda, and a dynamical ``cosmon'', X, possibly interacting
with Lambda but not with matter -- which remains conserved. We call this
scenario the LXCDM model. One possibility for X would be a scalar field, but it
is not the only one. The overall equation of state (EOS) of the LXCDM model can
effectively appear as quintessence or phantom energy depending on the mixture
of the two components. Both the dynamics of Lambda and of X could be linked to
high energy effects near the Planck scale. In the case of Lambda it may be
related to the running of this parameter under quantum effects, whereas X might
be identified with some fundamental field (say, a dilaton) left over as a
low-energy ``relic'' by e.g. string theory. We find that the dynamics of the
LXCDM model can trigger a future stopping of the Universe expansion and can
keep the ratio rho_D/rho_m (DE density to matter-radiation density) bounded and
of order 1. Therefore, the model could explain the so-called ``cosmological
coincidence problem''. This is in part related to the possibility that the
present value of the cosmological term can be Lambda<0 in this framework (the
current total DE density nevertheless being positive). However, a cosmic halt
could occur even if Lambda>0 because of the peculiar behavior of X as ``Phantom
Matter''. We describe various cosmological scenarios made possible by the
composite and dynamical nature of LXCDM, and discuss in detail their impact on
the cosmological coincidence problem.
| [
{
"created": "Tue, 11 Apr 2006 21:40:04 GMT",
"version": "v1"
},
{
"created": "Tue, 2 May 2006 21:19:53 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Aug 2006 16:32:37 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Grande",
"Javier",
""
],
[
"Sola",
"Joan",
""
],
[
"Stefancic",
"Hrvoje",
""
]
] | We consider the possibility that the total dark energy (DE) of the Universe is made out of two dynamical components of different nature: a variable cosmological term, Lambda, and a dynamical ``cosmon'', X, possibly interacting with Lambda but not with matter -- which remains conserved. We call this scenario the LXCDM model. One possibility for X would be a scalar field, but it is not the only one. The overall equation of state (EOS) of the LXCDM model can effectively appear as quintessence or phantom energy depending on the mixture of the two components. Both the dynamics of Lambda and of X could be linked to high energy effects near the Planck scale. In the case of Lambda it may be related to the running of this parameter under quantum effects, whereas X might be identified with some fundamental field (say, a dilaton) left over as a low-energy ``relic'' by e.g. string theory. We find that the dynamics of the LXCDM model can trigger a future stopping of the Universe expansion and can keep the ratio rho_D/rho_m (DE density to matter-radiation density) bounded and of order 1. Therefore, the model could explain the so-called ``cosmological coincidence problem''. This is in part related to the possibility that the present value of the cosmological term can be Lambda<0 in this framework (the current total DE density nevertheless being positive). However, a cosmic halt could occur even if Lambda>0 because of the peculiar behavior of X as ``Phantom Matter''. We describe various cosmological scenarios made possible by the composite and dynamical nature of LXCDM, and discuss in detail their impact on the cosmological coincidence problem. |
1106.0091 | Hossein Farajollahi | H. Farajollahi, A. Salehi | A new approach in stability analysis: case study: tachyon cosmology with
non-minimally coupled scalar field-matter | 21 pages, 30 figures; accepted for publication in Phys. Rev. D | Phys.Rev.D83:124042,2011 | 10.1103/PhysRevD.83.124042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the general properties of attractors in a cosmological model with
tachyonic potential and a scalar field non-minimally coupled to matter. A
general analytic formulation is given to derive fixed points with a discussion
on their stability. We also check the consistency of the model by fitting it to
the supernovae type Ia data.
| [
{
"created": "Wed, 1 Jun 2011 04:53:07 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2011 05:46:55 GMT",
"version": "v2"
}
] | 2011-07-08 | [
[
"Farajollahi",
"H.",
""
],
[
"Salehi",
"A.",
""
]
] | We study the general properties of attractors in a cosmological model with tachyonic potential and a scalar field non-minimally coupled to matter. A general analytic formulation is given to derive fixed points with a discussion on their stability. We also check the consistency of the model by fitting it to the supernovae type Ia data. |
gr-qc/0507102 | Bruno Giacomazzo | B. Giacomazzo (1) and L. Rezzolla (1 and 2) ((1) SISSA and INFN, (2)
Louisiana State University) | The Exact Solution of the Riemann Problem in Relativistic MHD | 36 pages, 13 figures. Minor changes to match published version | J. Fluid Mech. 562(2006), 223-259 | 10.1017/S0022112006001145 | null | gr-qc astro-ph | null | We discuss the procedure for the exact solution of the Riemann problem in
special relativistic magnetohydrodynamics (MHD). We consider both initial
states leading to a set of only three waves analogous to the ones in
relativistic hydrodynamics, as well as generic initial states leading to the
full set of seven MHD waves. Because of its generality, the solution presented
here could serve as an important test for those numerical codes solving the MHD
equations in relativistic regimes.
| [
{
"created": "Mon, 25 Jul 2005 14:52:02 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jul 2006 17:21:28 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Giacomazzo",
"B.",
"",
"1 and 2"
],
[
"Rezzolla",
"L.",
"",
"1 and 2"
]
] | We discuss the procedure for the exact solution of the Riemann problem in special relativistic magnetohydrodynamics (MHD). We consider both initial states leading to a set of only three waves analogous to the ones in relativistic hydrodynamics, as well as generic initial states leading to the full set of seven MHD waves. Because of its generality, the solution presented here could serve as an important test for those numerical codes solving the MHD equations in relativistic regimes. |
2307.02026 | W{\l}odzimierz Piechocki | A. G\'o\'zd\'z, J. J. Ostrowski, A. P\c{e}drak, W. Piechocki | Quantum system ascribed to the Oppenheimer-Snyder model of massive star | 29 pages, one figure, version accepted for publication in EPJC | null | null | null | gr-qc math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/4.0/ | We quantize the Oppenheimer-Snyder model of black hole using the integral
quantization method. We treat spatial and temporal coordinates on the same
footing both at classical and quantum levels. Our quantization resolves or
smears the singularities of the classical curvature invariants. Quantum
trajectories with bounces can replace singular classical ones. The considered
quantum black hole may have finite bouncing time. As a byproduct, we obtain the
resolution of the gravitational singularity of the Schwarzschild black hole at
quantum level.
| [
{
"created": "Wed, 5 Jul 2023 05:23:56 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2023 07:17:46 GMT",
"version": "v2"
}
] | 2023-11-30 | [
[
"Góźdź",
"A.",
""
],
[
"Ostrowski",
"J. J.",
""
],
[
"Pȩdrak",
"A.",
""
],
[
"Piechocki",
"W.",
""
]
] | We quantize the Oppenheimer-Snyder model of black hole using the integral quantization method. We treat spatial and temporal coordinates on the same footing both at classical and quantum levels. Our quantization resolves or smears the singularities of the classical curvature invariants. Quantum trajectories with bounces can replace singular classical ones. The considered quantum black hole may have finite bouncing time. As a byproduct, we obtain the resolution of the gravitational singularity of the Schwarzschild black hole at quantum level. |
2111.04752 | Isabel Su\'arez Fern\'andez | Isabel Su\'arez Fern\'andez, Thomas W. Baumgarte and David Hilditch | Comparison of linear Brill and Teukolsky waves | 10 pages, 4 figures | null | 10.1103/PhysRevD.104.124036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by studies of critical phenomena in the gravitational collapse of
vacuum gravitational waves we compare, at the linear level, two common
approaches to constructing gravitational-wave initial data. Specifically, we
construct analytical, linear Brill wave initial data and compare these with
Teukolsky waves in an attempt to understand the different numerical behavior
observed in dynamical (nonlinear) evolutions of these two different sets of
data. In general, the Brill waves indeed feature higher multipole moments than
the quadrupolar Teukolsky waves, which might have provided an explanation for
the differences observed in the dynamical evolution of the two types of waves.
However, we also find that, for a common choice of the Brill-wave seed
function, all higher-order moments vanish identically, rendering the (linear)
Brill initial data surprisingly similar to the Teukolsky data for a similarly
common choice of its seed function.
| [
{
"created": "Mon, 8 Nov 2021 19:00:02 GMT",
"version": "v1"
}
] | 2021-12-22 | [
[
"Fernández",
"Isabel Suárez",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Hilditch",
"David",
""
]
] | Motivated by studies of critical phenomena in the gravitational collapse of vacuum gravitational waves we compare, at the linear level, two common approaches to constructing gravitational-wave initial data. Specifically, we construct analytical, linear Brill wave initial data and compare these with Teukolsky waves in an attempt to understand the different numerical behavior observed in dynamical (nonlinear) evolutions of these two different sets of data. In general, the Brill waves indeed feature higher multipole moments than the quadrupolar Teukolsky waves, which might have provided an explanation for the differences observed in the dynamical evolution of the two types of waves. However, we also find that, for a common choice of the Brill-wave seed function, all higher-order moments vanish identically, rendering the (linear) Brill initial data surprisingly similar to the Teukolsky data for a similarly common choice of its seed function. |
1903.07098 | Ozay Gurtug | O. Gurtug and M. Mangut | Effect of power-law Maxwell field to the gravitational lensing | 12 pages 5 figures, final version published in Physical Review D | Phys. Rev. D 99, 084003 (2019) | 10.1103/PhysRevD.99.084003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we extend the gravitational bending of light studies in
Kottler metrics to comprise nonlinear electrodynamics within the framework of
Einstein - power - Maxwell theory. We show that the closest approach distance
and the gravitational bending of light are affected from the presence of charge
for particular values of the power parameter $k$, which is defined by means of
energy conditions. It is shown that the bending angle of light is stronger in
the case of a strong electric field, which is the case for $k=1.2$.
| [
{
"created": "Sun, 17 Mar 2019 14:33:59 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2019 10:20:20 GMT",
"version": "v2"
}
] | 2019-04-11 | [
[
"Gurtug",
"O.",
""
],
[
"Mangut",
"M.",
""
]
] | In this paper, we extend the gravitational bending of light studies in Kottler metrics to comprise nonlinear electrodynamics within the framework of Einstein - power - Maxwell theory. We show that the closest approach distance and the gravitational bending of light are affected from the presence of charge for particular values of the power parameter $k$, which is defined by means of energy conditions. It is shown that the bending angle of light is stronger in the case of a strong electric field, which is the case for $k=1.2$. |
2304.11498 | Alejandro Casallas-Lagos | Alejandro Casallas Lagos, Javier M. Antelis, Claudia Moreno, Michele
Zanolin, Anthony Mezzacappa and Marek J. Szczepa\'nczyk | Characterizing the gravitational wave temporal evolution of the gmode
fundamental resonant frequency for a core collapse supernova: A neural
network approach | 14 pages, 9 figures, 6 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a methodology based on the implementation of a fully connected
neural network to estimate the gravitational wave (GW) temporal evolution of
the gmode fundamental resonant frequency for a Core Collapse Supernova (CCSN).
To perform the estimation, we construct a training data set, using synthetic
waveforms, that serves to train the ML algorithm, and then use several CCSN
waveforms to test the model. According to the results obtained from the
implementation of our model, we provide numerical evidence to support the
classification of progenitors according to their degree of rotation. The
relative error associated with the estimate of the slope of the resonant
frequency versus time for the GW from CCSN signals is within $13\%$ for the
tested candidates included in this study. This method of classification does
not require priors or templates, it is based on physical modelling, and can be
combined with studies that classify the progenitor with other physical
features.
| [
{
"created": "Sat, 22 Apr 2023 23:18:08 GMT",
"version": "v1"
}
] | 2023-04-25 | [
[
"Lagos",
"Alejandro Casallas",
""
],
[
"Antelis",
"Javier M.",
""
],
[
"Moreno",
"Claudia",
""
],
[
"Zanolin",
"Michele",
""
],
[
"Mezzacappa",
"Anthony",
""
],
[
"Szczepańczyk",
"Marek J.",
""
]
] | We present a methodology based on the implementation of a fully connected neural network to estimate the gravitational wave (GW) temporal evolution of the gmode fundamental resonant frequency for a Core Collapse Supernova (CCSN). To perform the estimation, we construct a training data set, using synthetic waveforms, that serves to train the ML algorithm, and then use several CCSN waveforms to test the model. According to the results obtained from the implementation of our model, we provide numerical evidence to support the classification of progenitors according to their degree of rotation. The relative error associated with the estimate of the slope of the resonant frequency versus time for the GW from CCSN signals is within $13\%$ for the tested candidates included in this study. This method of classification does not require priors or templates, it is based on physical modelling, and can be combined with studies that classify the progenitor with other physical features. |
1606.06096 | Anuradha Gupta | Sukanta Bose, Sanjeev Dhurandhar, Anuradha Gupta, Andrew Lundgren | Towards mitigating the effect of sine-Gaussian noise transients on
searches for gravitational waves from compact binary coalescences | 18 pages, 13 figures. v2: title changed, minor changes to the text,
matches published version (abstract is shortened to comply with the arXiv's
1920 characters limitation) | Phys. Rev. D 94, 122004 (2016) | 10.1103/PhysRevD.94.122004 | LIGO-P1600145 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave (GW) signals were recently detected directly by LIGO from
the coalescences of two black hole pairs. These detections have strengthened
our belief that compact binary coalescences (CBCs) are the most promising GW
detection prospects accessible to ground-based interferometric detectors. For
detecting CBC signals it is of vital importance to characterize and identify
non-Gaussian and non-stationary noise in these detectors. In this work we model
two important classes of transient artifacts that contribute to this noise and
adversely affect the detector sensitivity to CBC signals. One of them is the
sine-Gaussian glitch, characterized by a central frequency $f_0$ and a quality
factor $Q$ and the other is the chirping sine-Gaussian glitch, which is
characterized by $f_0$, $Q$ as well as a chirp parameter. We study the response
a bank of compact binary inspiral templates has to these two families of
glitches when they are used to match-filter data containing any of these
glitches. Two important characteristics of this response are the distributions
of the signal-to-noise ratio and the timelag of individual templates. We show
how these distributions differ from those when the detector data has a real CBC
signal instead of a glitch. We argue that these distinctions can be utilized to
develop useful signal-artifact vetos that add negligibly to the computational
cost of a CBC search. Specifically, we show how $f_0$ of a glitch can be used
to set adaptive time-windows around it so that any template trigger occurring
in that window can be quarantined for further vetting of its supposed
astrophysical nature. Second, we recommend focusing efforts on reducing the
incidence of glitches with low $f_0$ values because they create CBC triggers
with the longest timelags. This work allows us to associate such triggers with
the glitches which otherwise would have escaped attention.
| [
{
"created": "Mon, 20 Jun 2016 12:52:42 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2016 07:30:38 GMT",
"version": "v2"
}
] | 2016-12-28 | [
[
"Bose",
"Sukanta",
""
],
[
"Dhurandhar",
"Sanjeev",
""
],
[
"Gupta",
"Anuradha",
""
],
[
"Lundgren",
"Andrew",
""
]
] | Gravitational wave (GW) signals were recently detected directly by LIGO from the coalescences of two black hole pairs. These detections have strengthened our belief that compact binary coalescences (CBCs) are the most promising GW detection prospects accessible to ground-based interferometric detectors. For detecting CBC signals it is of vital importance to characterize and identify non-Gaussian and non-stationary noise in these detectors. In this work we model two important classes of transient artifacts that contribute to this noise and adversely affect the detector sensitivity to CBC signals. One of them is the sine-Gaussian glitch, characterized by a central frequency $f_0$ and a quality factor $Q$ and the other is the chirping sine-Gaussian glitch, which is characterized by $f_0$, $Q$ as well as a chirp parameter. We study the response a bank of compact binary inspiral templates has to these two families of glitches when they are used to match-filter data containing any of these glitches. Two important characteristics of this response are the distributions of the signal-to-noise ratio and the timelag of individual templates. We show how these distributions differ from those when the detector data has a real CBC signal instead of a glitch. We argue that these distinctions can be utilized to develop useful signal-artifact vetos that add negligibly to the computational cost of a CBC search. Specifically, we show how $f_0$ of a glitch can be used to set adaptive time-windows around it so that any template trigger occurring in that window can be quarantined for further vetting of its supposed astrophysical nature. Second, we recommend focusing efforts on reducing the incidence of glitches with low $f_0$ values because they create CBC triggers with the longest timelags. This work allows us to associate such triggers with the glitches which otherwise would have escaped attention. |
1706.04434 | Christian Corda Prof. | Y. Heydarzade, H. Hadi, C. Corda and F. Darabi | Braneworld Black Holes and Entropy Bounds | 13 pages, accepted for publication in Physics Letters B | Physics Letters B 776, 457 (2018) | 10.1016/j.physletb.2017.11.061 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bousso's D-bound entropy for the various possible black hole solutions on
a 4-dimensional brane is checked. It is found that the D-bound entropy here is
apparently different from that of obtained for the 4-dimensional black hole
solutions. This difference is interpreted as the extra loss of information,
associated to the extra dimension, when an extra-dimensional black hole is
moved outward the observer's cosmological horizon. Also, it is discussed that
N-bound entropy is hold for the possible solutions here. Finally, by adopting
the recent Bohr-like approach to black hole quantum physics for the excited
black holes, the obtained results are written also in terms of the black hole
excited states.
| [
{
"created": "Tue, 13 Jun 2017 15:54:19 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Nov 2017 20:28:49 GMT",
"version": "v2"
}
] | 2017-12-25 | [
[
"Heydarzade",
"Y.",
""
],
[
"Hadi",
"H.",
""
],
[
"Corda",
"C.",
""
],
[
"Darabi",
"F.",
""
]
] | The Bousso's D-bound entropy for the various possible black hole solutions on a 4-dimensional brane is checked. It is found that the D-bound entropy here is apparently different from that of obtained for the 4-dimensional black hole solutions. This difference is interpreted as the extra loss of information, associated to the extra dimension, when an extra-dimensional black hole is moved outward the observer's cosmological horizon. Also, it is discussed that N-bound entropy is hold for the possible solutions here. Finally, by adopting the recent Bohr-like approach to black hole quantum physics for the excited black holes, the obtained results are written also in terms of the black hole excited states. |
2403.10240 | Maria Caruana | Maria Caruana, Gabriel Farrugia, Jackson Levi Said, and Joseph Sultana | Spatial Dependence of the Growth Factor in Scalar-Tensor Cosmology | null | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Scalar-tensor theories have taken on a key role in attempts to confront the
growing open questions in standard cosmology. It is important to understand
entirely their dynamics at perturbative level including any possible spatial
dependence in their growth of large scale structures. In this work, we
investigate the spatial dependence of the growth rate of scalar-tensor theories
through the M\'{e}sz\'{a}ros equation. We confirm that at subhorizon level this
dependence does not play a major role for viable models. However, we establish
conditions on which this criterion is met which may be important for developing
new models. In our work, we consider three specific models that exhibit spatial
dependence of the growth rate at subhorizon modes, which may also be important
for early Universe models.
| [
{
"created": "Fri, 15 Mar 2024 12:21:16 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 20:35:49 GMT",
"version": "v2"
}
] | 2024-04-04 | [
[
"Caruana",
"Maria",
""
],
[
"Farrugia",
"Gabriel",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Sultana",
"Joseph",
""
]
] | Scalar-tensor theories have taken on a key role in attempts to confront the growing open questions in standard cosmology. It is important to understand entirely their dynamics at perturbative level including any possible spatial dependence in their growth of large scale structures. In this work, we investigate the spatial dependence of the growth rate of scalar-tensor theories through the M\'{e}sz\'{a}ros equation. We confirm that at subhorizon level this dependence does not play a major role for viable models. However, we establish conditions on which this criterion is met which may be important for developing new models. In our work, we consider three specific models that exhibit spatial dependence of the growth rate at subhorizon modes, which may also be important for early Universe models. |
1203.3563 | Marcello Ortaggio | Sigbj{\o}rn Hervik, Marcello Ortaggio, Lode Wylleman | Minimal tensors and purely electric or magnetic spacetimes of arbitrary
dimension | 43 pages. v2: new proposition 4.10; some text reshuffled (former sec.
2 is now an appendix); references added; some footnotes cancelled, others
incorporated into the main text; some typos fixed and a few more minor
changes made | Class. Quantum Grav. 30 (2013) 165014 | 10.1088/0264-9381/30/16/165014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider time reversal transformations to obtain twofold orthogonal
splittings of any tensor on a Lorentzian space of arbitrary dimension n.
Applied to the Weyl tensor of a spacetime, this leads to a definition of its
electric and magnetic parts relative to an observer (i.e., a unit timelike
vector field u), in any n. We study the cases where one of these parts vanishes
in particular, i.e., purely electric (PE) or magnetic (PM) spacetimes. We
generalize several results from four to higher dimensions and discuss new
features of higher dimensions. We prove that the only permitted Weyl types are
G, I_i and D, and discuss the possible relation of u with the WANDs; we provide
invariant conditions that characterize PE/PM spacetimes, such as Bel-Debever
criteria, or constraints on scalar invariants, and connect the PE/PM parts to
the kinematic quantities of u; we present conditions under which direct product
spacetimes (and certain warps) are PE/PM, which enables us to construct
explicit examples. In particular, it is also shown that all static spacetimes
are necessarily PE, while stationary spacetimes (e.g., spinning black holes)
are in general neither PE nor PM. Ample classes of PE spacetimes exist, but PM
solutions are elusive, and we prove that PM Einstein spacetimes of type D do
not exist, for any n. Finally, we derive corresponding results for the
electric/magnetic parts of the Riemann tensor. This also leads to first
examples of PM spacetimes in higher dimensions. We also note in passing that
PE/PM Weyl tensors provide examples of minimal tensors, and we make the
connection hereof with the recently proved alignment theorem. This in turn
sheds new light on classification of the Weyl tensors based on null alignment,
providing a further invariant characterization that distinguishes the types
G/I/D from the types II/III/N.
| [
{
"created": "Thu, 15 Mar 2012 21:04:19 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Dec 2012 21:15:34 GMT",
"version": "v2"
}
] | 2013-07-30 | [
[
"Hervik",
"Sigbjørn",
""
],
[
"Ortaggio",
"Marcello",
""
],
[
"Wylleman",
"Lode",
""
]
] | We consider time reversal transformations to obtain twofold orthogonal splittings of any tensor on a Lorentzian space of arbitrary dimension n. Applied to the Weyl tensor of a spacetime, this leads to a definition of its electric and magnetic parts relative to an observer (i.e., a unit timelike vector field u), in any n. We study the cases where one of these parts vanishes in particular, i.e., purely electric (PE) or magnetic (PM) spacetimes. We generalize several results from four to higher dimensions and discuss new features of higher dimensions. We prove that the only permitted Weyl types are G, I_i and D, and discuss the possible relation of u with the WANDs; we provide invariant conditions that characterize PE/PM spacetimes, such as Bel-Debever criteria, or constraints on scalar invariants, and connect the PE/PM parts to the kinematic quantities of u; we present conditions under which direct product spacetimes (and certain warps) are PE/PM, which enables us to construct explicit examples. In particular, it is also shown that all static spacetimes are necessarily PE, while stationary spacetimes (e.g., spinning black holes) are in general neither PE nor PM. Ample classes of PE spacetimes exist, but PM solutions are elusive, and we prove that PM Einstein spacetimes of type D do not exist, for any n. Finally, we derive corresponding results for the electric/magnetic parts of the Riemann tensor. This also leads to first examples of PM spacetimes in higher dimensions. We also note in passing that PE/PM Weyl tensors provide examples of minimal tensors, and we make the connection hereof with the recently proved alignment theorem. This in turn sheds new light on classification of the Weyl tensors based on null alignment, providing a further invariant characterization that distinguishes the types G/I/D from the types II/III/N. |
2008.13350 | Ryotaro Kase | Ryotaro Kase, Shinji Tsujikawa | Instability of compact stars with a nonminimal scalar-derivative
coupling | 17 pages, 8 figures, published version | JCAP01(2021)008 | 10.1088/1475-7516/2021/01/008 | WUCG-20-06 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a theory in which a scalar field $\phi$ has a nonminimal derivative
coupling to the Einstein tensor $G_{\mu \nu}$ of the form $\phi\,G_{\mu
\nu}\nabla^{\mu}\nabla^{\nu} \phi$, it is known that there exists a branch of
static and spherically-symmetric relativistic stars endowed with a scalar hair
in their interiors. We study the stability of such hairy solutions with a
radial field dependence $\phi(r)$ against odd- and even-parity perturbations.
We show that, for the star compactness ${\cal C}$ smaller than $1/3$, they are
prone to Laplacian instabilities of the even-parity perturbation associated
with the scalar-field propagation along an angular direction. Even for ${\cal
C}>1/3$, the hairy star solutions are subject to ghost instabilities. We also
find that even the other branch with a vanishing background field derivative is
unstable for a positive perfect-fluid pressure, due to nonstandard propagation
of the field perturbation $\delta \phi$ inside the star. Thus, there are no
stable star configurations in derivative coupling theory without a standard
kinetic term, including both relativistic and nonrelativistic compact objects.
| [
{
"created": "Mon, 31 Aug 2020 04:10:06 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Sep 2020 08:51:32 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jan 2021 01:05:03 GMT",
"version": "v3"
}
] | 2021-01-08 | [
[
"Kase",
"Ryotaro",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | For a theory in which a scalar field $\phi$ has a nonminimal derivative coupling to the Einstein tensor $G_{\mu \nu}$ of the form $\phi\,G_{\mu \nu}\nabla^{\mu}\nabla^{\nu} \phi$, it is known that there exists a branch of static and spherically-symmetric relativistic stars endowed with a scalar hair in their interiors. We study the stability of such hairy solutions with a radial field dependence $\phi(r)$ against odd- and even-parity perturbations. We show that, for the star compactness ${\cal C}$ smaller than $1/3$, they are prone to Laplacian instabilities of the even-parity perturbation associated with the scalar-field propagation along an angular direction. Even for ${\cal C}>1/3$, the hairy star solutions are subject to ghost instabilities. We also find that even the other branch with a vanishing background field derivative is unstable for a positive perfect-fluid pressure, due to nonstandard propagation of the field perturbation $\delta \phi$ inside the star. Thus, there are no stable star configurations in derivative coupling theory without a standard kinetic term, including both relativistic and nonrelativistic compact objects. |
0712.3643 | Shih-Yuin Lin | B. L. Hu and Shih-Yuin Lin | Black Hole Information in a Detector (Atom) - Field Analog | 13 pages, 4 figures; Invited plenary talk at the workshop ``From
Quantum to Emergent Gravity: Theory and Phenomenology", Trieste, Italy, June
11-15, 2007 | PoS QG-Ph:019,2007 | null | null | gr-qc | null | This is a synopsis of our recent work on quantum entanglement, recoherence
and information flow between an uniformly accelerated detector and a massless
quantum scalar field. The availability of exact solutions to this model enables
us to explore the black hole information issue with some quantifiable results
and new insights. To the extent this model can be used as an analog to the
system of a black hole interacting with a quantum field, our result seems to
suggest in the prevalent non-Markovian regime, assuming unitarity for the
combined system, that black hole information is not lost but transferred to the
quantum field degrees of freedom. This combined system will evolve into a
highly entangled state between a remnant of large area (in Bekenstein's black
hole atom analog) without any information of its initial state, while the
quantum field is imbued with complex information content not-so-easily
retrievable by a local observer.
| [
{
"created": "Fri, 21 Dec 2007 09:09:46 GMT",
"version": "v1"
}
] | 2009-12-15 | [
[
"Hu",
"B. L.",
""
],
[
"Lin",
"Shih-Yuin",
""
]
] | This is a synopsis of our recent work on quantum entanglement, recoherence and information flow between an uniformly accelerated detector and a massless quantum scalar field. The availability of exact solutions to this model enables us to explore the black hole information issue with some quantifiable results and new insights. To the extent this model can be used as an analog to the system of a black hole interacting with a quantum field, our result seems to suggest in the prevalent non-Markovian regime, assuming unitarity for the combined system, that black hole information is not lost but transferred to the quantum field degrees of freedom. This combined system will evolve into a highly entangled state between a remnant of large area (in Bekenstein's black hole atom analog) without any information of its initial state, while the quantum field is imbued with complex information content not-so-easily retrievable by a local observer. |
1808.07246 | Abolhassan Mohammadi | Abolhassan Mohammadi, Tayeb Golanbari, and Khaled Saaidi | Observational constraints on DBI constant-roll inflation | 32 pages, 9 figures | Physics of the Dark Universe 27, 100456 (2020) | 10.1016/j.dark.2019.100456 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the constant-roll approach, DBI inflationary scenario will be studied
and it is sought to compare the result with observational data. By considering
the cosmological perturbations of the model, it is realized that some extra
terms appear in the amplitude of scalar perturbations which indicate that there
shuold be a modified version of the scalar spectral index and tensor-to-scalar
ratio. In order to compare the model with observational data, some specific
functions of scalar field are assumed for the function $f(\phi)$ function. For
the power-law and exponential functions, a constant slow-roll parameter
$\epsilon$ is obtained which produced difficulties for the graceful exit from
inflation. Then, a product of linear and exponential function, and also a
hyperbolic function of scalar field are selected for $f(\phi)$ that result in a
$\epsilon$ with an end for accelerated expansion phase. Considering the scalar
spectral index, the amplitude of scalar perturbations and tensor-to-scalar
ratio shows that for some values of the constant $\eta = \beta$ there could be
a good consistency between the model predictions and observational data. In
addition, based on the form of the equation of motion of the scalar field, a
new interesting definition for the second slow-roll parameters is presented and
the behavior of the perturbations is reconsidered. The results come to good
consistency with data. Finally, the attractor behavior of these two cases is
investigated and it is determined that this feature could be satisfied.
| [
{
"created": "Wed, 22 Aug 2018 07:04:22 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Nov 2019 17:45:48 GMT",
"version": "v2"
}
] | 2020-05-12 | [
[
"Mohammadi",
"Abolhassan",
""
],
[
"Golanbari",
"Tayeb",
""
],
[
"Saaidi",
"Khaled",
""
]
] | Using the constant-roll approach, DBI inflationary scenario will be studied and it is sought to compare the result with observational data. By considering the cosmological perturbations of the model, it is realized that some extra terms appear in the amplitude of scalar perturbations which indicate that there shuold be a modified version of the scalar spectral index and tensor-to-scalar ratio. In order to compare the model with observational data, some specific functions of scalar field are assumed for the function $f(\phi)$ function. For the power-law and exponential functions, a constant slow-roll parameter $\epsilon$ is obtained which produced difficulties for the graceful exit from inflation. Then, a product of linear and exponential function, and also a hyperbolic function of scalar field are selected for $f(\phi)$ that result in a $\epsilon$ with an end for accelerated expansion phase. Considering the scalar spectral index, the amplitude of scalar perturbations and tensor-to-scalar ratio shows that for some values of the constant $\eta = \beta$ there could be a good consistency between the model predictions and observational data. In addition, based on the form of the equation of motion of the scalar field, a new interesting definition for the second slow-roll parameters is presented and the behavior of the perturbations is reconsidered. The results come to good consistency with data. Finally, the attractor behavior of these two cases is investigated and it is determined that this feature could be satisfied. |
1506.02631 | Vuk Mandic | K. Crocker, V. Mandic, T. Regimbau, K. Belczynski, W. Gladysz, K.
Olive, T. Prestegard, E. Vangioni | A Model of the Stochastic Gravitational-Wave Background due to Core
Collapse to Black Holes | null | Phys. Rev. D 92, 063005 (2015) | 10.1103/PhysRevD.92.063005 | FTPI-MINN-15/28, UMN-TH-3440/15, LIGO-P1500077 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superposition of gravitational waves generated by astrophysical sources is
expected to give rise to the stochastic gravitational-wave background. We focus
on the background generated by the ring-down of black holes produced in the
stellar core collapse events across the universe. We systematically study the
parameter space in this model, including the most recent information about the
star formation rate and about the population of black holes as a function of
redshift and of metallicity. We investigate the accessibility of this
gravitational wave background to the upcoming gravitational-wave detectors,
such as Advanced LIGO and Einstein Telescope.
| [
{
"created": "Mon, 8 Jun 2015 19:36:04 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Crocker",
"K.",
""
],
[
"Mandic",
"V.",
""
],
[
"Regimbau",
"T.",
""
],
[
"Belczynski",
"K.",
""
],
[
"Gladysz",
"W.",
""
],
[
"Olive",
"K.",
""
],
[
"Prestegard",
"T.",
""
],
[
"Vangioni",
"E.",
""
]
] | Superposition of gravitational waves generated by astrophysical sources is expected to give rise to the stochastic gravitational-wave background. We focus on the background generated by the ring-down of black holes produced in the stellar core collapse events across the universe. We systematically study the parameter space in this model, including the most recent information about the star formation rate and about the population of black holes as a function of redshift and of metallicity. We investigate the accessibility of this gravitational wave background to the upcoming gravitational-wave detectors, such as Advanced LIGO and Einstein Telescope. |
2309.01709 | Hao-Jui Kuan | Hao-Jui Kuan, Karim Van Aelst, Alan Tsz-Lok Lam, Masaru Shibata | Binary neutron star mergers in massive scalar-tensor theory:
Quasi-equilibrium states and dynamical enhancement of the scalarization | 14 pages, 8 figures, 1 table. Submitted to PRD | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study quasi-equilibrium sequences of binary neutron stars in the framework
of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive
scalar field, paying particular attention to the case where neutron stars are
already spontaneously scalarized at distant orbits, i.e., in the high coupling
constant case. Although scalar effects are largely quenched when the separation
$a$ is $\gtrsim 3$--$6$ times of the Compton length-scale that is defined by
the scalar mass, we show that the interaction between the scalar fields of the
two neutron stars generates a scalar cloud surrounding the binary at the price
of orbital energy when $a \lesssim 3$--$6$ times of the Compton length-scale.
This enables us to constrain the scalar mass $m_\phi$ from gravitational-wave
observations of binary neutron star mergers by inspecting the dephasing due to
such phenomenon. In particular, the event GW170817 is suggestive of a
constraint of $m_\phi \gtrsim 10^{-11}$ eV and the coupling strength should be
mild if the neutron stars in this system were spontaneously scalarized.
| [
{
"created": "Mon, 4 Sep 2023 16:42:23 GMT",
"version": "v1"
}
] | 2023-09-06 | [
[
"Kuan",
"Hao-Jui",
""
],
[
"Van Aelst",
"Karim",
""
],
[
"Lam",
"Alan Tsz-Lok",
""
],
[
"Shibata",
"Masaru",
""
]
] | We study quasi-equilibrium sequences of binary neutron stars in the framework of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive scalar field, paying particular attention to the case where neutron stars are already spontaneously scalarized at distant orbits, i.e., in the high coupling constant case. Although scalar effects are largely quenched when the separation $a$ is $\gtrsim 3$--$6$ times of the Compton length-scale that is defined by the scalar mass, we show that the interaction between the scalar fields of the two neutron stars generates a scalar cloud surrounding the binary at the price of orbital energy when $a \lesssim 3$--$6$ times of the Compton length-scale. This enables us to constrain the scalar mass $m_\phi$ from gravitational-wave observations of binary neutron star mergers by inspecting the dephasing due to such phenomenon. In particular, the event GW170817 is suggestive of a constraint of $m_\phi \gtrsim 10^{-11}$ eV and the coupling strength should be mild if the neutron stars in this system were spontaneously scalarized. |
2306.05210 | Felipe Asenjo | Felipe A. Asenjo and Sergio A. Hojman | Time-domain supersymmetry for massless scalar and electromagnetic fields
in anisotropic cosmologies | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that any cosmological anisotropic model produces supersymmetric
theories for both massless scalar and electromagnetic fields. This
supersymmetric theory is the time-domain analogue of a supersymmetric quantum
mechanical theory. In this case, the variations of the anisotropic scale
factors of the Universe are responsible for triggering the supersymmetry. For
scalar fields, the superpartner fields evolve in two different cosmological
scenarios (Universes). On the other hand, for propagating electromagnetic
fields, supersymmetry is manifested through its polarization degrees of freedom
in one Universe. In this case, polarization degrees of freedom of
electromagnetic waves, which are orthogonal to its propagation direction,
become superpartners from each other. This behavior can be measured, for
example, through the rotation of the plane of polarization of cosmological
light.
| [
{
"created": "Thu, 8 Jun 2023 14:09:27 GMT",
"version": "v1"
}
] | 2023-06-09 | [
[
"Asenjo",
"Felipe A.",
""
],
[
"Hojman",
"Sergio A.",
""
]
] | It is shown that any cosmological anisotropic model produces supersymmetric theories for both massless scalar and electromagnetic fields. This supersymmetric theory is the time-domain analogue of a supersymmetric quantum mechanical theory. In this case, the variations of the anisotropic scale factors of the Universe are responsible for triggering the supersymmetry. For scalar fields, the superpartner fields evolve in two different cosmological scenarios (Universes). On the other hand, for propagating electromagnetic fields, supersymmetry is manifested through its polarization degrees of freedom in one Universe. In this case, polarization degrees of freedom of electromagnetic waves, which are orthogonal to its propagation direction, become superpartners from each other. This behavior can be measured, for example, through the rotation of the plane of polarization of cosmological light. |
1106.3877 | Sujoy Modak Dr. | Rabin Banerjee, Sujoy Kumar Modak, Dibakar Roychowdhury | A unified picture of phase transition: from liquid-vapour systems to AdS
black holes | v3; JHEP style, 11 pages, 1 figure; title is changed, paper rewritten
but basic results are unchanged, to appear in JHEP | JHEP 1210:125,2012 | 10.1007/JHEP10(2012)125 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on fundamental concepts of thermodynamics we examine phase transitions
in black holes defined in Anti-de Sitter (AdS) spaces. The method is in line
with that used a long ago to understand the liquid-vapour phase transition
where the first order derivatives of Gibbs potential are discontinuous and
Clausius-Clapeyron equation is satisfied. The idea here is to consider the AdS
black holes as grand-canonical ensembles and study phase transition defined by
the discontinuity of second order derivatives of Gibbs potential. We
analytically check that this phase transition between the `smaller' and
`larger' mass black holes obey Ehrenfest relations defined at the critical
point and hence confirm a second order phase transition. This include both the
rotating and charged black holes in Einstein gravity.
| [
{
"created": "Mon, 20 Jun 2011 12:17:48 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jul 2011 12:14:43 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Sep 2012 07:13:08 GMT",
"version": "v3"
}
] | 2012-10-23 | [
[
"Banerjee",
"Rabin",
""
],
[
"Modak",
"Sujoy Kumar",
""
],
[
"Roychowdhury",
"Dibakar",
""
]
] | Based on fundamental concepts of thermodynamics we examine phase transitions in black holes defined in Anti-de Sitter (AdS) spaces. The method is in line with that used a long ago to understand the liquid-vapour phase transition where the first order derivatives of Gibbs potential are discontinuous and Clausius-Clapeyron equation is satisfied. The idea here is to consider the AdS black holes as grand-canonical ensembles and study phase transition defined by the discontinuity of second order derivatives of Gibbs potential. We analytically check that this phase transition between the `smaller' and `larger' mass black holes obey Ehrenfest relations defined at the critical point and hence confirm a second order phase transition. This include both the rotating and charged black holes in Einstein gravity. |
gr-qc/0307082 | Eric Gourgoulhon | S. Bonazzola, E. Gourgoulhon, P. Grandclement, J. Novak (LUTH, CNRS,
Observatoire de Paris) | A constrained scheme for Einstein equations based on Dirac gauge and
spherical coordinates | Difference w.r.t. v1: Major revision: improved presentation of the
tensor wave equation and addition of the first results from a numerical
implementation; w.r.t. v2: Minor changes: improved conclusion and figures;
w.r.t. v3: Minors changes, 1 figure added; 25 pages, 13 figures, REVTeX,
accepted for publication in Phys. Rev. D | Phys.Rev. D70 (2004) 104007 | 10.1103/PhysRevD.70.104007 | null | gr-qc | null | We propose a new formulation for 3+1 numerical relativity, based on a
constrained scheme and a generalization of Dirac gauge to spherical
coordinates. This is made possible thanks to the introduction of a flat
3-metric on the spatial hypersurfaces t=const, which corresponds to the
asymptotic structure of the physical 3-metric induced by the spacetime metric.
Thanks to the joint use of Dirac gauge, maximal slicing and spherical
components of tensor fields, the ten Einstein equations are reduced to a system
of five quasi-linear elliptic equations (including the Hamiltonian and momentum
constraints) coupled to two quasi-linear scalar wave equations. The remaining
three degrees of freedom are fixed by the Dirac gauge. Indeed this gauge allows
a direct computation of the spherical components of the conformal metric from
the two scalar potentials which obey the wave equations. We present some
numerical evolution of 3-D gravitational wave spacetimes which demonstrates the
stability of the proposed scheme.
| [
{
"created": "Thu, 17 Jul 2003 13:01:14 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 2004 21:24:45 GMT",
"version": "v2"
},
{
"created": "Sat, 31 Jul 2004 20:49:38 GMT",
"version": "v3"
},
{
"created": "Tue, 21 Sep 2004 09:45:58 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Bonazzola",
"S.",
"",
"LUTH, CNRS,\n Observatoire de Paris"
],
[
"Gourgoulhon",
"E.",
"",
"LUTH, CNRS,\n Observatoire de Paris"
],
[
"Grandclement",
"P.",
"",
"LUTH, CNRS,\n Observatoire de Paris"
],
[
"Novak",
"J.",
"",
"LUTH, CNRS,\n Observatoire de Paris"
]
] | We propose a new formulation for 3+1 numerical relativity, based on a constrained scheme and a generalization of Dirac gauge to spherical coordinates. This is made possible thanks to the introduction of a flat 3-metric on the spatial hypersurfaces t=const, which corresponds to the asymptotic structure of the physical 3-metric induced by the spacetime metric. Thanks to the joint use of Dirac gauge, maximal slicing and spherical components of tensor fields, the ten Einstein equations are reduced to a system of five quasi-linear elliptic equations (including the Hamiltonian and momentum constraints) coupled to two quasi-linear scalar wave equations. The remaining three degrees of freedom are fixed by the Dirac gauge. Indeed this gauge allows a direct computation of the spherical components of the conformal metric from the two scalar potentials which obey the wave equations. We present some numerical evolution of 3-D gravitational wave spacetimes which demonstrates the stability of the proposed scheme. |
gr-qc/0301090 | S. Shankaranarayanan | S. Shankaranarayanan | Temperature and entropy of Schwarzschild-de Sitter space-time | Final version; To appear in Phys. Rev. D; 12 pages, 1 figure,
RevTex-4; Typos corrected; References added | Phys.Rev. D67 (2003) 084026 | 10.1103/PhysRevD.67.084026 | null | gr-qc hep-th | null | In the light of recent interest in quantum gravity in de Sitter space, we
investigate semi-classical aspects of 4-dimensional Schwarzschild-de Sitter
space-time using the method of complex paths. The standard semi-classical
techniques (such as Bogoliubov coefficients and Euclidean field theory) have
been useful to study quantum effects in space-times with single horizons;
however, none of these approaches seem to work for Schwarzschild-de Sitter or,
in general, for space-times with multiple horizons. We extend the method of
complex paths to space-times with multiple horizons and obtain the spectrum of
particles produced in these space-times. We show that the temperature of
radiation in these space-times is proportional to the effective surface gravity
-- inverse harmonic sum of surface gravity of each horizon. For the
Schwarzschild-de Sitter, we apply the method of complex paths to three
different coordinate systems -- spherically symmetric, Painleve and Lemaitre.
We show that the equilibrium temperature in Schwarzschild-de Sitter is the
harmonic mean of cosmological and event horizon temperatures. We obtain
Bogoliubov coefficients for space-times with multiple horizons by analyzing the
mode functions of the quantum fields near the horizons. We propose a new
definition of entropy for space-times with multiple horizons analogous to the
entropic definition for space-times with a single horizon. We define entropy
for these space-times to be inversely proportional to the square of the
effective surface gravity. We show that this definition of entropy for
Schwarzschild-de Sitter satisfies the D-bound conjecture.
| [
{
"created": "Wed, 22 Jan 2003 18:56:15 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Apr 2003 12:50:19 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Shankaranarayanan",
"S.",
""
]
] | In the light of recent interest in quantum gravity in de Sitter space, we investigate semi-classical aspects of 4-dimensional Schwarzschild-de Sitter space-time using the method of complex paths. The standard semi-classical techniques (such as Bogoliubov coefficients and Euclidean field theory) have been useful to study quantum effects in space-times with single horizons; however, none of these approaches seem to work for Schwarzschild-de Sitter or, in general, for space-times with multiple horizons. We extend the method of complex paths to space-times with multiple horizons and obtain the spectrum of particles produced in these space-times. We show that the temperature of radiation in these space-times is proportional to the effective surface gravity -- inverse harmonic sum of surface gravity of each horizon. For the Schwarzschild-de Sitter, we apply the method of complex paths to three different coordinate systems -- spherically symmetric, Painleve and Lemaitre. We show that the equilibrium temperature in Schwarzschild-de Sitter is the harmonic mean of cosmological and event horizon temperatures. We obtain Bogoliubov coefficients for space-times with multiple horizons by analyzing the mode functions of the quantum fields near the horizons. We propose a new definition of entropy for space-times with multiple horizons analogous to the entropic definition for space-times with a single horizon. We define entropy for these space-times to be inversely proportional to the square of the effective surface gravity. We show that this definition of entropy for Schwarzschild-de Sitter satisfies the D-bound conjecture. |
2104.03253 | Aron Wall | Aron C. Wall | Violation of Unitarity in Gravitational Subregions | 8 pages, 3 figs. Submitted to the Gravity Research Foundation 2021
Essay Competition | Int. J. Mod. Phys. D 30, 2142014 (2021) | 10.1142/S0218271821420141 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This essay contends that in quantum gravity, some spatial regions do not
admit a unitary Hilbert space. Because the gravitational path integral
spontaneously breaks CPT symmetry, "states" with negative probability can be
identified on either side of trapped surfaces. I argue that these negative norm
states are tolerable, by analogy to quantum mechanics. This viewpoint suggests
a resolution of the firewall paradox, similar to black hole complementarity.
Implications for cosmology are briefly discussed.
| [
{
"created": "Wed, 7 Apr 2021 16:56:39 GMT",
"version": "v1"
}
] | 2022-07-04 | [
[
"Wall",
"Aron C.",
""
]
] | This essay contends that in quantum gravity, some spatial regions do not admit a unitary Hilbert space. Because the gravitational path integral spontaneously breaks CPT symmetry, "states" with negative probability can be identified on either side of trapped surfaces. I argue that these negative norm states are tolerable, by analogy to quantum mechanics. This viewpoint suggests a resolution of the firewall paradox, similar to black hole complementarity. Implications for cosmology are briefly discussed. |
2210.01184 | Albert Munyeshyaka Mr | Albert Munyeshyaka, Joseph Ntahompagaze, Tom Mutabazi, Manasse.R
Mbonye, Abraham Ayirwanda, Fidele Twagirayezu and Amare Abebe | Perturbations in the interacting vacuum | 28 pages, 13 figures | Int. J. Mod. Phys. D 32 12 (2023) | 10.1142/S0219887823500470 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this study, we present the evolution of cosmological perturbations in a
universe consisting of standard matter and interacting vacuum. We use the $1 +
3$ covariant formalism in perturbation framework and consider two different
models for the interacting vacuum namely a linear interacting model and
interaction with creation pressure model. For both models, we derive the
evolution equations governing the growth of linear perturbations for both
radiation and dust dominated Universe. We find numerical solutions in
appropriate limits namely long and short wavelengths. For both models, the
perturbations grow with time (decay with redshift), showing that structure
formation is possible in an accelerated cosmic background. The perturbation
amplitudes and their relative scalings with those of standard model of
cosmology depend on the values of the interaction parameters considered, and in
a way that can be used to constrain the models using existing and future large
scale structure data. In the vanishing limits of the coupling parameters of the
interaction, we show that standard cosmology, both background and perturbed, is
recovered.
| [
{
"created": "Mon, 3 Oct 2022 18:54:50 GMT",
"version": "v1"
}
] | 2024-01-15 | [
[
"Munyeshyaka",
"Albert",
""
],
[
"Ntahompagaze",
"Joseph",
""
],
[
"Mutabazi",
"Tom",
""
],
[
"Mbonye",
"Manasse. R",
""
],
[
"Ayirwanda",
"Abraham",
""
],
[
"Twagirayezu",
"Fidele",
""
],
[
"Abebe",
"Amare",
""
]
] | In this study, we present the evolution of cosmological perturbations in a universe consisting of standard matter and interacting vacuum. We use the $1 + 3$ covariant formalism in perturbation framework and consider two different models for the interacting vacuum namely a linear interacting model and interaction with creation pressure model. For both models, we derive the evolution equations governing the growth of linear perturbations for both radiation and dust dominated Universe. We find numerical solutions in appropriate limits namely long and short wavelengths. For both models, the perturbations grow with time (decay with redshift), showing that structure formation is possible in an accelerated cosmic background. The perturbation amplitudes and their relative scalings with those of standard model of cosmology depend on the values of the interaction parameters considered, and in a way that can be used to constrain the models using existing and future large scale structure data. In the vanishing limits of the coupling parameters of the interaction, we show that standard cosmology, both background and perturbed, is recovered. |
1001.2287 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | The Jebsen-Birkhoff theorem in alternative gravity | 10 pages, no figures, to appear in Phys. Rev. D | Phys.Rev.D81:044002,2010 | 10.1103/PhysRevD.81.044002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the validity, or lack thereof, of the Jebsen-Birkhoff theorem in
scalar-tensor theories by generalizing it and regarding the Brans-Dicke-like
scalar as effective matter. Both the Jordan and Einstein frames are discussed
and an apparent contradiction between static spherical solutions of
scalar-tensor gravity and Hawking's theorem on Brans-Dicke black holes is
clarified. The results are applied to metric and Palatini f(R) gravity.
| [
{
"created": "Wed, 13 Jan 2010 20:03:07 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | We discuss the validity, or lack thereof, of the Jebsen-Birkhoff theorem in scalar-tensor theories by generalizing it and regarding the Brans-Dicke-like scalar as effective matter. Both the Jordan and Einstein frames are discussed and an apparent contradiction between static spherical solutions of scalar-tensor gravity and Hawking's theorem on Brans-Dicke black holes is clarified. The results are applied to metric and Palatini f(R) gravity. |
0811.4076 | Betti Hartmann | Betti Hartmann (Jacobs University Bremen, Germany) | Non-abelian black holes and black strings in higher dimensions | 8 pages; prepared as contribution to the proceedings of the Spanish
Relativity Meeting (ERE), Salamanca, 2008 | AIP Conf.Proc.1122:137-144,2009 | 10.1063/1.3141235 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the properties of static, higher dimensional black hole solutions
in theories where non-abelian gauge fields are minimally coupled to gravity. It
is shown that black holes with hyperspherically symmetric horizon topology do
not exist in $d > 4$, but that hyperspherically symmetric black holes can be
constructed numerically in generalized Einstein-Yang-Mills models.
5-dimensional black strings with horizon topology S^2 x S^1 are also discussed.
These are so-called undeformed and deformed non-abelian black strings, which
are translationally invariant and correspond to 4-dimensional non-abelian black
holes trivially extended into one extra dimensions. The fact that black strings
can be deformed, i.e. axially symmetric for constant values of the extra
coordinate is a new feature as compared to black string solutions of Einstein
(-Maxwell) theory. It is argued that these non-abelian black strings are
thermodynamically unstable.
| [
{
"created": "Tue, 25 Nov 2008 12:54:39 GMT",
"version": "v1"
}
] | 2009-07-24 | [
[
"Hartmann",
"Betti",
"",
"Jacobs University Bremen, Germany"
]
] | We review the properties of static, higher dimensional black hole solutions in theories where non-abelian gauge fields are minimally coupled to gravity. It is shown that black holes with hyperspherically symmetric horizon topology do not exist in $d > 4$, but that hyperspherically symmetric black holes can be constructed numerically in generalized Einstein-Yang-Mills models. 5-dimensional black strings with horizon topology S^2 x S^1 are also discussed. These are so-called undeformed and deformed non-abelian black strings, which are translationally invariant and correspond to 4-dimensional non-abelian black holes trivially extended into one extra dimensions. The fact that black strings can be deformed, i.e. axially symmetric for constant values of the extra coordinate is a new feature as compared to black string solutions of Einstein (-Maxwell) theory. It is argued that these non-abelian black strings are thermodynamically unstable. |
gr-qc/9706008 | Serge Massar | S. Massar and R. Parentani | Particle creation and non-adiabatic transitions in quantum cosmology | 27 pages, Latex | Nucl.Phys. B513 (1998) 375-401 | 10.1016/S0550-3213(97)00718-9 | TAUP 2429-97 | gr-qc | null | The aim of this paper is to compute transitions amplitudes in quantum
cosmology, and in particular pair creation amplitudes and radiative
transitions. To this end, we apply a double adiabatic development to the
solutions of the Wheeler-DeWitt equation restricted to mini-superspace wherein
gravity is described by the scale factor $a$. The first development consists in
working with instantaneous eigenstates, in $a$, of the matter Hamiltonian. The
second development is applied to the gravitational part of the wave function
and generalizes the usual WKB approximation. We then obtain an exact equation
which replaces the Wheeler-DeWitt equation and determines the evolution, i.e.
the dependence in $a$, of the coefficients of this double expansion. When
working in the gravitational adiabatic approximation, the simplified equation
delivers the unitary evolution of transition amplitudes occurring among
instantaneous eigenstates. Upon abandoning this approximation, one finds that
there is an additional coupling among matter states living in expanding and
contracting universes. Moreover one has to face also the Klein paradox, i.e.
the generation of backward waves from an initially forward wave. The
interpretation and the consequences of these unusual features are only sketched
in the present paper. Finally, the examples of pair creation and radiative
transitions are analyzed in detail to establish when and how the above
mentioned unitary evolution coincides with the Schr\" odinger evolution.
| [
{
"created": "Tue, 3 Jun 1997 12:40:39 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Massar",
"S.",
""
],
[
"Parentani",
"R.",
""
]
] | The aim of this paper is to compute transitions amplitudes in quantum cosmology, and in particular pair creation amplitudes and radiative transitions. To this end, we apply a double adiabatic development to the solutions of the Wheeler-DeWitt equation restricted to mini-superspace wherein gravity is described by the scale factor $a$. The first development consists in working with instantaneous eigenstates, in $a$, of the matter Hamiltonian. The second development is applied to the gravitational part of the wave function and generalizes the usual WKB approximation. We then obtain an exact equation which replaces the Wheeler-DeWitt equation and determines the evolution, i.e. the dependence in $a$, of the coefficients of this double expansion. When working in the gravitational adiabatic approximation, the simplified equation delivers the unitary evolution of transition amplitudes occurring among instantaneous eigenstates. Upon abandoning this approximation, one finds that there is an additional coupling among matter states living in expanding and contracting universes. Moreover one has to face also the Klein paradox, i.e. the generation of backward waves from an initially forward wave. The interpretation and the consequences of these unusual features are only sketched in the present paper. Finally, the examples of pair creation and radiative transitions are analyzed in detail to establish when and how the above mentioned unitary evolution coincides with the Schr\" odinger evolution. |
1002.1818 | J\"org Hennig | J\"org Hennig and Gernot Neugebauer | Non-existence of stationary two-black-hole configurations | Proceedings of the 12th Marcel Grossmann Meeting (Paris, July 12-18,
2009), 3 pages | null | null | AEI-2010-021 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We resume former discussions of the question, whether the spin-spin repulsion
and the gravitational attraction of two aligned sub-extremal black holes can
balance each other. To answer the question we formulate a boundary value
problem for two separate (Killing-) horizons and apply the inverse (scattering)
method to solve it. Making use of a universal inequality between angular
momentum and horizon area that has to be satisfied by every sub-extremal black
hole, we prove the non-existence of the equilibrium situation in question.
| [
{
"created": "Tue, 9 Feb 2010 10:48:37 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jun 2010 13:23:51 GMT",
"version": "v2"
}
] | 2010-06-08 | [
[
"Hennig",
"Jörg",
""
],
[
"Neugebauer",
"Gernot",
""
]
] | We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned sub-extremal black holes can balance each other. To answer the question we formulate a boundary value problem for two separate (Killing-) horizons and apply the inverse (scattering) method to solve it. Making use of a universal inequality between angular momentum and horizon area that has to be satisfied by every sub-extremal black hole, we prove the non-existence of the equilibrium situation in question. |
1206.5658 | Martin Kolo\v{s} | Z. Stuchl\'ik and M. Kolo\v{s} | Acceleration of string loops in the Schwarzschild-de Sitter geometry | 12 pages, 7 figures | Physical Review D, vol. 85, Issue 6, id. 065022, 2012 | 10.1103/PhysRevD.85.065022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study acceleration of current-carrying string loops governed by the
presence of an outer tension barrier and an inner angular momentum barrier in
the field of Schwarzschild-de Sitter black holes. We restrict attention to the
axisymmetric motion of string loops with energy high enough, when the string
loop can overcome the gravitational attraction and escape to infinity. We
demonstrate that string loops can be scattered near the black hole horizon, and
the energy of string oscillations can be efficiently converted to the energy of
their linear motion. Such a transmutation effect can potentially represent
acceleration of jets in active galactic nuclei and microquasars. We give the
conditions limiting energy available for conversion onto the jetlike motion.
Surprisingly, we are able to show that string loops starting from rest can be
accelerated up to velocities v\simc even in the field of Schwarzschild black
holes, if their angular momentum parameter is low enough. Such loops could
serve as an explanation of highly relativistic jets observed in some quasars
and active galactic nuclei. The cosmic repulsion becomes important behind the
so-called static radius where it accelerates the linear motion of the string
loops up to velocity v=c that is reached at the cosmic horizon of the
Schwarzschild-de Sitter spacetimes independently of the angular momentum
parameter of the strings.
| [
{
"created": "Mon, 25 Jun 2012 12:04:38 GMT",
"version": "v1"
}
] | 2012-06-26 | [
[
"Stuchlík",
"Z.",
""
],
[
"Kološ",
"M.",
""
]
] | We study acceleration of current-carrying string loops governed by the presence of an outer tension barrier and an inner angular momentum barrier in the field of Schwarzschild-de Sitter black holes. We restrict attention to the axisymmetric motion of string loops with energy high enough, when the string loop can overcome the gravitational attraction and escape to infinity. We demonstrate that string loops can be scattered near the black hole horizon, and the energy of string oscillations can be efficiently converted to the energy of their linear motion. Such a transmutation effect can potentially represent acceleration of jets in active galactic nuclei and microquasars. We give the conditions limiting energy available for conversion onto the jetlike motion. Surprisingly, we are able to show that string loops starting from rest can be accelerated up to velocities v\simc even in the field of Schwarzschild black holes, if their angular momentum parameter is low enough. Such loops could serve as an explanation of highly relativistic jets observed in some quasars and active galactic nuclei. The cosmic repulsion becomes important behind the so-called static radius where it accelerates the linear motion of the string loops up to velocity v=c that is reached at the cosmic horizon of the Schwarzschild-de Sitter spacetimes independently of the angular momentum parameter of the strings. |
1005.3250 | Jong-Ping Hsu | Jong-Ping Hsu | Yang-Mills Gravity in Flat Space-time, II. Gravitational Radiations and
Lee-Yang Force for Accelerated Cosmic Expansion | 19 pages | Int.J.Mod.Phys.A24:5217-5233,2009 | 10.1142/S0217751X0904765X | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within Yang-Mills gravity with translation group $T(4)$ in flat space-time,
the invariant action involving quadratic translation gauge-curvature leads to
quadrupole radiations which are shown to be consistent with experiments. The
radiation power turns out to be the same as that in Einstein's gravity to the
second-order approximation. We also discuss an interesting physical reason for
the accelerated cosmic expansion based on the long-range Lee-Yang force of
$U_{b}(1)$ gauge field associated with the established conservation law of
baryon number. We show that the Lee-Yang force can be related to a linear
potential $\propto r$, provided the gauge field satisfies a fourth-order
differential equation. Furthermore, we consider an experimental test of the
Lee-Yang force related to the accelerated cosmic expansion. The necessity of
generalizing Lorentz transformations for accelerated frames of reference and
accelerated Wu-Doppler effects are briefly discussed.
| [
{
"created": "Tue, 18 May 2010 17:00:45 GMT",
"version": "v1"
}
] | 2010-05-25 | [
[
"Hsu",
"Jong-Ping",
""
]
] | Within Yang-Mills gravity with translation group $T(4)$ in flat space-time, the invariant action involving quadratic translation gauge-curvature leads to quadrupole radiations which are shown to be consistent with experiments. The radiation power turns out to be the same as that in Einstein's gravity to the second-order approximation. We also discuss an interesting physical reason for the accelerated cosmic expansion based on the long-range Lee-Yang force of $U_{b}(1)$ gauge field associated with the established conservation law of baryon number. We show that the Lee-Yang force can be related to a linear potential $\propto r$, provided the gauge field satisfies a fourth-order differential equation. Furthermore, we consider an experimental test of the Lee-Yang force related to the accelerated cosmic expansion. The necessity of generalizing Lorentz transformations for accelerated frames of reference and accelerated Wu-Doppler effects are briefly discussed. |
1306.6724 | Dario Bettoni | Dario Bettoni, Stefano Liberati | Disformal invariance of second order tensor-scalar theories: framing the
Horndeski action | 17 pages, one table, more references, typos corrected | Phys. Rev. D 88, 084020 (2013) | 10.1103/PhysRevD.88.084020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Horndeski action is the most general one involving a metric and a scalar
field that leads to second order field equations in four dimensions. Being the
natural extension of the well known Scalar-Tensor theories, its structure and
properties are worth analysing along the experience accumulated in the latter
context. Here we argue that disformal transformations play, for the Horndeski
theory, a similar role to that of conformal transformations for Scalar-Tensor
theories a l`a Brans-Dicke. We identify the most general transformation
preserving second order field equations and discuss the issue of viable frames
for this kind of theories, in particular the possibility to cast the action in
the so called Einstein frame. Finally, we investigate the physical equivalence
of such frames and their reciprocal relationship.
| [
{
"created": "Fri, 28 Jun 2013 06:20:03 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Oct 2013 10:37:11 GMT",
"version": "v2"
}
] | 2013-10-22 | [
[
"Bettoni",
"Dario",
""
],
[
"Liberati",
"Stefano",
""
]
] | The Horndeski action is the most general one involving a metric and a scalar field that leads to second order field equations in four dimensions. Being the natural extension of the well known Scalar-Tensor theories, its structure and properties are worth analysing along the experience accumulated in the latter context. Here we argue that disformal transformations play, for the Horndeski theory, a similar role to that of conformal transformations for Scalar-Tensor theories a l`a Brans-Dicke. We identify the most general transformation preserving second order field equations and discuss the issue of viable frames for this kind of theories, in particular the possibility to cast the action in the so called Einstein frame. Finally, we investigate the physical equivalence of such frames and their reciprocal relationship. |
1801.02118 | Chen Songbai | Mingzhi Wang, Songbai Chen, Jiliang Jing | Chaotic shadow of a non-Kerr rotating compact object with quadrupole
mass moment | 23 pages, 12 figures, Accepted by PRD for publication | Phys. Rev. D 98, 104040 (2018) | 10.1103/PhysRevD.98.104040 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied numerically the shadows of a non-Kerr rotating compact object
with quadrupole mass moment, which belongs to Manko-Novikov family. The
non-integrable photon motion caused by quadrupole mass moment affects sharply
the shadow of the compact object. As the deviation parameter related to
quadrupole mass moment is negative, the shadow of compact object is prolate and
there are two disconnected main shadows with eyebrows located symmetrically on
both sides of the equatorial plane. As the deviation parameter is positive, the
shadow becomes oblate and the main shadow is joined together in the equatorial
plane. Moreover, in this positive cases, there is a disorder region in the left
of shadow which increases with the quadrupole-deviation parameter.
Interestingly, we also find that Einstein ring is broken as the deviation from
Kerr metric is larger than a certain critical value. This critical value
decreases with the rotation parameter of black hole. Especially, the observer
on the direction of rotation axis will find some concentric bright rings in the
black disc. Finally, supposing that the gravitational field of the supermassive
central object of the galaxy described by this metric, we estimated the
numerical values of the observables for the black hole shadow.
| [
{
"created": "Sun, 7 Jan 2018 03:15:51 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2018 03:24:15 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Nov 2018 09:19:42 GMT",
"version": "v3"
}
] | 2018-11-29 | [
[
"Wang",
"Mingzhi",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We have studied numerically the shadows of a non-Kerr rotating compact object with quadrupole mass moment, which belongs to Manko-Novikov family. The non-integrable photon motion caused by quadrupole mass moment affects sharply the shadow of the compact object. As the deviation parameter related to quadrupole mass moment is negative, the shadow of compact object is prolate and there are two disconnected main shadows with eyebrows located symmetrically on both sides of the equatorial plane. As the deviation parameter is positive, the shadow becomes oblate and the main shadow is joined together in the equatorial plane. Moreover, in this positive cases, there is a disorder region in the left of shadow which increases with the quadrupole-deviation parameter. Interestingly, we also find that Einstein ring is broken as the deviation from Kerr metric is larger than a certain critical value. This critical value decreases with the rotation parameter of black hole. Especially, the observer on the direction of rotation axis will find some concentric bright rings in the black disc. Finally, supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the observables for the black hole shadow. |
gr-qc/9708064 | Ronggen Cai | Rong-Gen Cai, Jeong-Young Ji | Hairs on the cosmological horizon | Revtex, no figures, 16 pages | Phys.Rev. D58 (1998) 024002 | 10.1103/PhysRevD.58.024002 | SNUTP 97-120 | gr-qc | null | We investigate the possibility of having hairs on the cosmological horizon.
The cosmological horizon shares similar properties of black hole horizons in
the aspect of having hairs on the horizons. For those theories admitting haired
black hole solutions, the nontrivial matter fields may reach and extend beyond
the cosmological horizon. For Q-stars and boson stars, the matter fields cannot
reach the cosmological horizon. The no short hair conjecture keeps valid,
despite the asymptotic behavior (de Sitter or anti-de Sitter) of black hole
solutions. We prove the no scalar hair theorem for anti-de Sitter black holes.
Using the Bekenstein's identity method, we also prove the no scalar hair
theorem for the de Sitter space and de Sitter black holes if the scalar
potential is convex.
| [
{
"created": "Tue, 26 Aug 1997 12:47:18 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Sep 1997 00:41:36 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Jul 1998 08:14:30 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Ji",
"Jeong-Young",
""
]
] | We investigate the possibility of having hairs on the cosmological horizon. The cosmological horizon shares similar properties of black hole horizons in the aspect of having hairs on the horizons. For those theories admitting haired black hole solutions, the nontrivial matter fields may reach and extend beyond the cosmological horizon. For Q-stars and boson stars, the matter fields cannot reach the cosmological horizon. The no short hair conjecture keeps valid, despite the asymptotic behavior (de Sitter or anti-de Sitter) of black hole solutions. We prove the no scalar hair theorem for anti-de Sitter black holes. Using the Bekenstein's identity method, we also prove the no scalar hair theorem for the de Sitter space and de Sitter black holes if the scalar potential is convex. |
1209.2144 | Naresh Dadhich | Naresh Dadhich | A curious spacetime entirely free of centrifugal acceleration | 3 pages, latex | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Einstein gravity, besides the usual gravitational and centrifugal
potential there is an additional attractive term that couples these two
together. It is fun to enquire whether the latter could fully counteract the
centrifugal repulsion everywhere making the spacetime completely free of the
centrifugal acceleration. We present here such a curious spacetime metric and
it produces a global monopole like stresses going as $~1/r^2$ in an AdS
spacetime.
| [
{
"created": "Fri, 7 Sep 2012 09:30:31 GMT",
"version": "v1"
}
] | 2012-09-12 | [
[
"Dadhich",
"Naresh",
""
]
] | In the Einstein gravity, besides the usual gravitational and centrifugal potential there is an additional attractive term that couples these two together. It is fun to enquire whether the latter could fully counteract the centrifugal repulsion everywhere making the spacetime completely free of the centrifugal acceleration. We present here such a curious spacetime metric and it produces a global monopole like stresses going as $~1/r^2$ in an AdS spacetime. |
1711.02898 | Balendra Pratap Singh | Balendra Pratap Singh | Rotating charged black holes shadow in quintessence | 15 pages, 7 figures | Annals of Physics, 168892 (2022) | 10.1016/j.aop.2022.168892 | Report-no:YAPHY_168892 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the shadow of rotating charge black holes in the presence of
quintessence. The shadow of a rotating black hole is a distorted circle and in
our study, we find that the shape and size of the black hole shadow depend upon
four parameters, i.e., charge $q$, spin parameter $a$, quintessential field
parameter $\omega_q$ and normalization factor $c$. The parameter $\omega_q$ can
take the value between $-1<\omega_q<-1/3$ and related with pressure $p$ and
density $\rho_q$ by the equation of state $p=\omega_q \rho_q$. We derive the
complete geodesic structure of photon near black hole using the Hamilton-Jacobi
equation and Carter constant separable method. We relate celestial coordinate
to geodesics equation and plot the contour of the black hole shadow for the
case $\omega_q=-2/3$. We compare our results with the standard Kerr-Newman
black hole and find that for a fix value of $a$ and $q$, the black hole shadow
decreases and get distorted with $c$. The area of the photon sphere is equal to
the high-energy absorption cross section due to the optical properties of the
black hole. On the basis of this assumption we calculate the energy emission
rate of the black hole.
| [
{
"created": "Wed, 8 Nov 2017 10:31:04 GMT",
"version": "v1"
},
{
"created": "Wed, 4 May 2022 09:29:36 GMT",
"version": "v2"
}
] | 2022-05-05 | [
[
"Singh",
"Balendra Pratap",
""
]
] | We study the shadow of rotating charge black holes in the presence of quintessence. The shadow of a rotating black hole is a distorted circle and in our study, we find that the shape and size of the black hole shadow depend upon four parameters, i.e., charge $q$, spin parameter $a$, quintessential field parameter $\omega_q$ and normalization factor $c$. The parameter $\omega_q$ can take the value between $-1<\omega_q<-1/3$ and related with pressure $p$ and density $\rho_q$ by the equation of state $p=\omega_q \rho_q$. We derive the complete geodesic structure of photon near black hole using the Hamilton-Jacobi equation and Carter constant separable method. We relate celestial coordinate to geodesics equation and plot the contour of the black hole shadow for the case $\omega_q=-2/3$. We compare our results with the standard Kerr-Newman black hole and find that for a fix value of $a$ and $q$, the black hole shadow decreases and get distorted with $c$. The area of the photon sphere is equal to the high-energy absorption cross section due to the optical properties of the black hole. On the basis of this assumption we calculate the energy emission rate of the black hole. |
gr-qc/0703133 | Mikhail Iofa | Mikhail Z. Iofa | A note on cosmology in a brane model | 10 pages LaTex | null | null | null | gr-qc astro-ph | null | We study some aspects of cosmology in a five-dimensional model with matter,
radiation and cosmological constant on the four-dimensional brane(s) and
without matter in the bulk. The action of the model does not contain explicit
curvature terms on the the brane(s). We obtain solution of the generalized
Friedman equation as a function of dimensionless ratio of the scales $b^2 =
\frac{\mu M^2_{pl}}{M^3}$ ($\mu$ is the scale in the warp factor in the 5D
metric which is taken of order $10^{3\div 4}GeV$, $M\geq\mu$ is the $5D$
fundamental scale). We assume that there is a hierarchy between 4D and 5D
scales. For $b^2 =O(1)$ the age of the Universe is found comparable, but below
the current experimental value, for $b^2\gg 1$ it is obtained much smaller than
the experimental bound. Because time dependence of temperature of the Universe
in the 5D model is different from that in the standard cosmology, the abundance
of ${}^4$He produced in the primordial nucleosynthesis is obtained about three
times more than in the standard cosmology.
| [
{
"created": "Tue, 27 Mar 2007 14:36:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Iofa",
"Mikhail Z.",
""
]
] | We study some aspects of cosmology in a five-dimensional model with matter, radiation and cosmological constant on the four-dimensional brane(s) and without matter in the bulk. The action of the model does not contain explicit curvature terms on the the brane(s). We obtain solution of the generalized Friedman equation as a function of dimensionless ratio of the scales $b^2 = \frac{\mu M^2_{pl}}{M^3}$ ($\mu$ is the scale in the warp factor in the 5D metric which is taken of order $10^{3\div 4}GeV$, $M\geq\mu$ is the $5D$ fundamental scale). We assume that there is a hierarchy between 4D and 5D scales. For $b^2 =O(1)$ the age of the Universe is found comparable, but below the current experimental value, for $b^2\gg 1$ it is obtained much smaller than the experimental bound. Because time dependence of temperature of the Universe in the 5D model is different from that in the standard cosmology, the abundance of ${}^4$He produced in the primordial nucleosynthesis is obtained about three times more than in the standard cosmology. |
1711.00996 | Changjun Gao | Changjun Gao, Youjun Lu, Shuang Yu, You-Gen Shen | Black hole and cosmos with multiple horizons and multiple singularities
in vector-tensor theories | 14 pages, 7 figures. The Penrose diagrams are corrected. PRD accepted | Phys. Rev. D 97, 104013 (2018) | 10.1103/PhysRevD.97.104013 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A stationary and spherically symmetric black hole (For example,
Reissner-Nordstrom black hole or Kerr-Newman black hole) has at most one
singularity and two horizons. One horizon is the outer event horizon and the
other is the inner Cauchy horizon. Can we construct static and spherically
symmetric black hole solutions with N horizons and M singularities? De Sitter
cosmos has only one apparent horizon. Can we construct cosmos solutions with N
horizons? In this article, we present the static and spherically symmetric
black hole and cosmos solutions with N horizons and M singularities in the
vector-tensor theories. Following these motivations, we also construct the
black hole solutions with a firewall. The deviation of these black hole
solutions from the usual ones can be potentially tested by future measurements
of gravitational waves.
| [
{
"created": "Fri, 3 Nov 2017 02:14:19 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Nov 2017 05:03:36 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Nov 2017 03:06:08 GMT",
"version": "v3"
},
{
"created": "Mon, 13 Nov 2017 00:24:12 GMT",
"version": "v4"
},
{
"created": "Tue, 20 Mar 2018 00:54:39 GMT",
"version": "v5"
},
{
"created": "Wed, 21 Mar 2018 06:57:27 GMT",
"version": "v6"
},
{
"created": "Thu, 22 Mar 2018 01:06:45 GMT",
"version": "v7"
},
{
"created": "Tue, 17 Apr 2018 02:55:25 GMT",
"version": "v8"
},
{
"created": "Wed, 25 Apr 2018 02:27:18 GMT",
"version": "v9"
}
] | 2018-05-23 | [
[
"Gao",
"Changjun",
""
],
[
"Lu",
"Youjun",
""
],
[
"Yu",
"Shuang",
""
],
[
"Shen",
"You-Gen",
""
]
] | A stationary and spherically symmetric black hole (For example, Reissner-Nordstrom black hole or Kerr-Newman black hole) has at most one singularity and two horizons. One horizon is the outer event horizon and the other is the inner Cauchy horizon. Can we construct static and spherically symmetric black hole solutions with N horizons and M singularities? De Sitter cosmos has only one apparent horizon. Can we construct cosmos solutions with N horizons? In this article, we present the static and spherically symmetric black hole and cosmos solutions with N horizons and M singularities in the vector-tensor theories. Following these motivations, we also construct the black hole solutions with a firewall. The deviation of these black hole solutions from the usual ones can be potentially tested by future measurements of gravitational waves. |
0911.4232 | Yousuke Itoh | Yousuke Itoh | Third-and-a-half order post-Newtonian equations of motion for
relativistic compact binaries using the strong field point particle limit | 38 pages, no figures. Accepted for publication in Phys. Rev. D | Phys.Rev.D80:124003,2009 | 10.1103/PhysRevD.80.124003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report our rederivation of the equations of motion for relativistic
compact binaries through the third-and-a-half post-Newtonian (3.5 PN) order
approximation to general relativity using the strong field point particle limit
to describe self-gravitating stars instead of the Dirac delta functional. The
computation is done in harmonic coordinates. Our equations of motion describe
the orbital motion of the binary consisting of spherically symmetric
non-rotating stars. The resulting equations of motion fully agree with the 3.5
PN equations of motion derived in the previous works. We also show that the
locally defined energy of the star has a simple relation with its mass up to
the 3.5 PN order.
| [
{
"created": "Sun, 22 Nov 2009 06:03:07 GMT",
"version": "v1"
}
] | 2010-10-12 | [
[
"Itoh",
"Yousuke",
""
]
] | We report our rederivation of the equations of motion for relativistic compact binaries through the third-and-a-half post-Newtonian (3.5 PN) order approximation to general relativity using the strong field point particle limit to describe self-gravitating stars instead of the Dirac delta functional. The computation is done in harmonic coordinates. Our equations of motion describe the orbital motion of the binary consisting of spherically symmetric non-rotating stars. The resulting equations of motion fully agree with the 3.5 PN equations of motion derived in the previous works. We also show that the locally defined energy of the star has a simple relation with its mass up to the 3.5 PN order. |
gr-qc/9712086 | Jutta Kunz | Burkhard Kleihaus and Jutta Kunz (Universit\"at Oldenburg) | Static Axially Symmetric Einstein-Yang-Mills-Dilaton Solutions: II.Black
Hole Solutions | 41 pages including 45 postscript figures, RevTex format | Phys.Rev. D57 (1998) 6138-6157 | 10.1103/PhysRevD.57.6138 | null | gr-qc hep-th | null | We discuss the new class of static axially symmetric black hole solutions
obtained recently in Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton
theory. These black hole solutions are asymptotically flat and they possess a
regular event horizon. The event horizon is almost spherically symmetric with a
slight elongation along the symmetry axis. The energy density of the matter
fields is angle-dependent at the horizon. The static axially symmetric black
hole solutions satisfy a simple relation between mass, dilaton charge, entropy
and temperature. The black hole solutions are characterized by two integers,
the winding number $n$ and the node number $k$ of the purely magnetic gauge
field. With increasing node number the magnetically neutral black hole
solutions form sequences tending to limiting solutions with magnetic charge
$n$, corresponding to Einstein-Maxwell-dilaton black hole solutions for finite
dilaton coupling constant and to Reissner-Nordstr\o m black hole solutions for
vanishing dilaton coupling constant.
| [
{
"created": "Mon, 22 Dec 1997 16:49:28 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Kleihaus",
"Burkhard",
"",
"Universität Oldenburg"
],
[
"Kunz",
"Jutta",
"",
"Universität Oldenburg"
]
] | We discuss the new class of static axially symmetric black hole solutions obtained recently in Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theory. These black hole solutions are asymptotically flat and they possess a regular event horizon. The event horizon is almost spherically symmetric with a slight elongation along the symmetry axis. The energy density of the matter fields is angle-dependent at the horizon. The static axially symmetric black hole solutions satisfy a simple relation between mass, dilaton charge, entropy and temperature. The black hole solutions are characterized by two integers, the winding number $n$ and the node number $k$ of the purely magnetic gauge field. With increasing node number the magnetically neutral black hole solutions form sequences tending to limiting solutions with magnetic charge $n$, corresponding to Einstein-Maxwell-dilaton black hole solutions for finite dilaton coupling constant and to Reissner-Nordstr\o m black hole solutions for vanishing dilaton coupling constant. |
2004.03641 | David Brown | J. David Brown | Elasticity Theory in General Relativity | 12 pages, 2 figures, to be published in Classical and Quantum Gravity | null | 10.1088/1361-6382/abe1ff | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general relativistic theory of elasticity is reviewed from a Lagrangian,
as opposed to Eulerian, perspective. The equations of motion and
stress-energy-momentum tensor for a hyperelastic body are derived from the
gauge-invariant action principle first considered by DeWitt. This action is a
natural extension of the action for a single relativistic particle. The central
object in the Lagrangian treatment is the Landau-Lifshitz radar metric, which
is the relativistic version of the right Cauchy-Green deformation tensor. We
also introduce relativistic definitions of the deformation gradient, Green
strain, and first and second Piola-Kirchhoff stress tensors. A gauge-fixed
description of relativistic hyperelasticity is also presented, and the
nonrelativistic theory is derived in the limit as the speed of light becomes
infinite.
| [
{
"created": "Tue, 7 Apr 2020 18:26:40 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2021 20:13:53 GMT",
"version": "v2"
}
] | 2021-06-09 | [
[
"Brown",
"J. David",
""
]
] | The general relativistic theory of elasticity is reviewed from a Lagrangian, as opposed to Eulerian, perspective. The equations of motion and stress-energy-momentum tensor for a hyperelastic body are derived from the gauge-invariant action principle first considered by DeWitt. This action is a natural extension of the action for a single relativistic particle. The central object in the Lagrangian treatment is the Landau-Lifshitz radar metric, which is the relativistic version of the right Cauchy-Green deformation tensor. We also introduce relativistic definitions of the deformation gradient, Green strain, and first and second Piola-Kirchhoff stress tensors. A gauge-fixed description of relativistic hyperelasticity is also presented, and the nonrelativistic theory is derived in the limit as the speed of light becomes infinite. |
1405.2133 | Dimitry Ayzenberg | Dimitry Ayzenberg and Nicolas Yunes | Slowly-Rotating Black Holes in Einstein-Dilaton-Gauss-Bonnet Gravity:
Quadratic Order in Spin Solutions | 13 pages, 1 figure. Updated to published version. Typos fixed | Phys. Rev. D 90, 044066 (2014) | 10.1103/PhysRevD.90.044066 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a stationary and axisymmetric black hole solution in
Einstein-Dilaton-Gauss-Bonnet gravity to quadratic order in the ratio of the
spin angular momentum to the black hole mass squared. This solution introduces
new corrections to previously found nonspinning and linear-in-spin solutions.
The location of the event horizon and the ergosphere are modified, as well as
the quadrupole moment. The new solution is of Petrov type I, although lower
order in spin solutions are of Petrov type D. There are no closed timelike
curves or spacetime regions that violate causality outside of the event horizon
in the new solution. We calculate the modifications to the binding energy,
Kepler's third law, and properties of the innermost stable circular orbit.
These modifications are important for determining how the electromagnetic
properties of accretion disks around supermassive black holes are changed from
those expected in general relativity.
| [
{
"created": "Fri, 9 May 2014 02:39:49 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Aug 2014 17:13:21 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Feb 2015 23:18:37 GMT",
"version": "v3"
},
{
"created": "Mon, 23 Feb 2015 05:20:15 GMT",
"version": "v4"
}
] | 2015-02-24 | [
[
"Ayzenberg",
"Dimitry",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We derive a stationary and axisymmetric black hole solution in Einstein-Dilaton-Gauss-Bonnet gravity to quadratic order in the ratio of the spin angular momentum to the black hole mass squared. This solution introduces new corrections to previously found nonspinning and linear-in-spin solutions. The location of the event horizon and the ergosphere are modified, as well as the quadrupole moment. The new solution is of Petrov type I, although lower order in spin solutions are of Petrov type D. There are no closed timelike curves or spacetime regions that violate causality outside of the event horizon in the new solution. We calculate the modifications to the binding energy, Kepler's third law, and properties of the innermost stable circular orbit. These modifications are important for determining how the electromagnetic properties of accretion disks around supermassive black holes are changed from those expected in general relativity. |
1311.5261 | Diego S\'aez-G\'omez | Ratbay Myrzakulov, Diego Saez-Gomez and Petr Tsyba | Cosmological solutions in F(T) gravity with the presence of spinor
fields | 10 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of spinor fields is considered in the framework of some
extensions of teleparallel gravity, where the Weitzenb\"ock connection is
assumed. Some well known models as the Chaplygin gas and its generalizations
are reconstructed in terms of a spinor field in the framework of teleparallel
gravity. In addition, the {\Lambda}CDM model is also realized with the presence
of a spinor field where a simple self-intercating term is considered and the
corresponding action is reconstructed. Other cosmological solutions and the
reconstruction of the gravitational action in terms of the scalar torsion is
studied.
| [
{
"created": "Wed, 20 Nov 2013 23:05:40 GMT",
"version": "v1"
}
] | 2013-11-22 | [
[
"Myrzakulov",
"Ratbay",
""
],
[
"Saez-Gomez",
"Diego",
""
],
[
"Tsyba",
"Petr",
""
]
] | The presence of spinor fields is considered in the framework of some extensions of teleparallel gravity, where the Weitzenb\"ock connection is assumed. Some well known models as the Chaplygin gas and its generalizations are reconstructed in terms of a spinor field in the framework of teleparallel gravity. In addition, the {\Lambda}CDM model is also realized with the presence of a spinor field where a simple self-intercating term is considered and the corresponding action is reconstructed. Other cosmological solutions and the reconstruction of the gravitational action in terms of the scalar torsion is studied. |
gr-qc/9302032 | null | J. W. Moffat | Do Black Holes Exist? | 10 pages, UTPT-93-04 | null | null | null | gr-qc | null | The problem of information loss in black hole formation and the associated
violations of basic laws of physics, such as conservation of energy, causality
and unitarity, are avoided in the nonsymmetric gravitational theory, if the NGT
charge of a black hole and its mass satisfy an inequality that does not violate
any known experimental data and allows the existence of white dwarfs and
neutron stars.
| [
{
"created": "Mon, 22 Feb 1993 23:28:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Moffat",
"J. W.",
""
]
] | The problem of information loss in black hole formation and the associated violations of basic laws of physics, such as conservation of energy, causality and unitarity, are avoided in the nonsymmetric gravitational theory, if the NGT charge of a black hole and its mass satisfy an inequality that does not violate any known experimental data and allows the existence of white dwarfs and neutron stars. |
1509.03895 | Chien-Hao Liu | Chien-Hao Liu | Quantum fluctuations, conformal deformations, and Gromov's topology ---
Wheeler, DeWitt, and Wilson meeting Gromov | 23+2 pages, 8 figures. Two brief notes after the first posting are
added on p.23: One on a historical account linking to the related work of
David Edwards in 1968; and the other on the proof of the Main Theorem and an
inflation scenario in cosmology | null | null | null | gr-qc hep-th math.DG math.GT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The moduli space of isometry classes of Riemannian structures on a smooth
manifold was emphasized by J.A.Wheeler in his superspace formalism of quantum
gravity. A natural question concerning it is: What is a natural topology on
such moduli space that reflects best quantum fluctuations of the geometries
within the Planck's scale? This very question has been addressed by B.DeWitt
and others. In this article we introduce Gromov's $\varepsilon$-approximation
topology on the above moduli space for a closed smooth manifold. After giving
readers some feel of this topology, we prove that each conformal class in the
moduli space is dense with respect to this topology. Implication of this
phenomenon to quantum gravity is yet to be explored. When going further to
general metric spaces, Gromov's geometries-at-large-scale based on his
topologies remind one of K.Wilson's theory of renormalization group. We discuss
some features of both and pose a question on whether both can be merged into a
single unified theory.
| [
{
"created": "Sun, 13 Sep 2015 20:33:01 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Oct 2015 00:29:27 GMT",
"version": "v2"
}
] | 2015-10-08 | [
[
"Liu",
"Chien-Hao",
""
]
] | The moduli space of isometry classes of Riemannian structures on a smooth manifold was emphasized by J.A.Wheeler in his superspace formalism of quantum gravity. A natural question concerning it is: What is a natural topology on such moduli space that reflects best quantum fluctuations of the geometries within the Planck's scale? This very question has been addressed by B.DeWitt and others. In this article we introduce Gromov's $\varepsilon$-approximation topology on the above moduli space for a closed smooth manifold. After giving readers some feel of this topology, we prove that each conformal class in the moduli space is dense with respect to this topology. Implication of this phenomenon to quantum gravity is yet to be explored. When going further to general metric spaces, Gromov's geometries-at-large-scale based on his topologies remind one of K.Wilson's theory of renormalization group. We discuss some features of both and pose a question on whether both can be merged into a single unified theory. |
1601.06864 | E M Howard Dr. | E. M. Howard | Causal structure of general relativistic spacetimes | 4 pages, 1 figure, Conference, 24/26 November 2009, Perth, WA | AIP Conf. Proc. 1246, 127 (2010) | 10.1063/1.3460187 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present some of the recent results and open questions on the causality
problem in General Relativity. The concept of singularity is intimately
connected with future trapped surface and inner event horizon formation. We
offer a brief overview of the Hawking Penrose singularity theorems and discuss
a few open problems concerning the future Cauchy development (domain of
dependence), breakdown criteria and energy conditions for the horizon
stability. A key question is whether causality violating regions, generating a
Cauchy horizon are allowed.
We raise several questions concerning the invisibility and stability of
closed trapped surfaces from future null infinity and derive the imprisonment
conditions. We provide an new perspective of the causal boundaries and
spacelike conformal boundary extensions for time oriented Lorentzian manifolds
and more exotic settings.
| [
{
"created": "Tue, 26 Jan 2016 02:04:48 GMT",
"version": "v1"
}
] | 2016-01-27 | [
[
"Howard",
"E. M.",
""
]
] | We present some of the recent results and open questions on the causality problem in General Relativity. The concept of singularity is intimately connected with future trapped surface and inner event horizon formation. We offer a brief overview of the Hawking Penrose singularity theorems and discuss a few open problems concerning the future Cauchy development (domain of dependence), breakdown criteria and energy conditions for the horizon stability. A key question is whether causality violating regions, generating a Cauchy horizon are allowed. We raise several questions concerning the invisibility and stability of closed trapped surfaces from future null infinity and derive the imprisonment conditions. We provide an new perspective of the causal boundaries and spacelike conformal boundary extensions for time oriented Lorentzian manifolds and more exotic settings. |
2407.20345 | Raissa Mendes | Raissa F. P. Mendes, Caroline F. Sodr\'e, Felipe T. Falciano | Exceeding the conformal limit inside rotating neutron stars:
Implications to modified theories of gravity | 10 pages, 7 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | At the supranuclear densities achieved inside a neutron star, matter may
exhibit extreme properties. In particular, it may be the case that a suitable
average of the speed of sound squared exceeds the so-called conformal limit,
i.e., $\langle c_s^2 \rangle > 1/3$, a condition that is equivalent to the
positiveness of the trace of the energy-momentum tensor at the stellar center.
This property, that holds for highly compact neutron stars obeying many (but
not any) realistic equations of state, would turn these objects into
interesting laboratories for tests of several scalar extensions of general
relativity. In this paper, we investigate how rapid rotation influences the
superconformality of the averaged speed of sound squared and modified gravity
effects that depend thereupon, paying particular attention to scalar-tensor
theories prone to the spontaneous scalarization effect.
| [
{
"created": "Mon, 29 Jul 2024 18:00:55 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Mendes",
"Raissa F. P.",
""
],
[
"Sodré",
"Caroline F.",
""
],
[
"Falciano",
"Felipe T.",
""
]
] | At the supranuclear densities achieved inside a neutron star, matter may exhibit extreme properties. In particular, it may be the case that a suitable average of the speed of sound squared exceeds the so-called conformal limit, i.e., $\langle c_s^2 \rangle > 1/3$, a condition that is equivalent to the positiveness of the trace of the energy-momentum tensor at the stellar center. This property, that holds for highly compact neutron stars obeying many (but not any) realistic equations of state, would turn these objects into interesting laboratories for tests of several scalar extensions of general relativity. In this paper, we investigate how rapid rotation influences the superconformality of the averaged speed of sound squared and modified gravity effects that depend thereupon, paying particular attention to scalar-tensor theories prone to the spontaneous scalarization effect. |
0803.3559 | {\L}ukasz Szulc | Lukasz Szulc | Loop Quantum Cosmology of Diagonal Bianchi Type I model: simplifications
and scaling problems | 11 pages, 12 figures, version to appear in PRD | Phys.Rev.D78:064035,2008 | 10.1103/PhysRevD.78.064035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A simplified theory of the diagonal Bianchi type I model coupled with a
massless scalar field in loop quantum cosmology is constructed according to the
$\bar{\mu}$ scheme. Kinematical and physical sectors of the theory are under
good analytical control as well as the scalar constraint operator. Although it
is possible to compute numerically the nonsingular evolution of the three
gravitational degrees of freedom, the naive implementation of the $\bar{\mu}$
scheme to the diagonal Bianchi type I model is problematic. The lack of the
full invariance of the theory with respect to the fiducial cell and fiducial
metric scaling causes serious problems in the semiclassical limit of the
theory. Because of this behavior it is very difficult to extract reasonable
physics from the model. The weaknesses of the implementation of the $\bar{\mu}$
scheme to the Bianchi I model do not imply limitations of the $\bar{\mu}$
scheme in the isotropic case.
| [
{
"created": "Tue, 25 Mar 2008 13:31:49 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Aug 2008 11:34:29 GMT",
"version": "v2"
}
] | 2009-02-20 | [
[
"Szulc",
"Lukasz",
""
]
] | A simplified theory of the diagonal Bianchi type I model coupled with a massless scalar field in loop quantum cosmology is constructed according to the $\bar{\mu}$ scheme. Kinematical and physical sectors of the theory are under good analytical control as well as the scalar constraint operator. Although it is possible to compute numerically the nonsingular evolution of the three gravitational degrees of freedom, the naive implementation of the $\bar{\mu}$ scheme to the diagonal Bianchi type I model is problematic. The lack of the full invariance of the theory with respect to the fiducial cell and fiducial metric scaling causes serious problems in the semiclassical limit of the theory. Because of this behavior it is very difficult to extract reasonable physics from the model. The weaknesses of the implementation of the $\bar{\mu}$ scheme to the Bianchi I model do not imply limitations of the $\bar{\mu}$ scheme in the isotropic case. |
1706.05455 | Seth Hopper | Seth Hopper | Unbound motion on a Schwarzschild background: Practical approaches to
frequency domain computations | 12 pages, 3 figures | Phys. Rev. D 97, 064007 (2018) | 10.1103/PhysRevD.97.064007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational perturbations due to a point particle moving on a static black
hole background are naturally described in Regge-Wheeler gauge. The first-order
field equations reduce to a single master wave equation for each radiative
mode. The master function satisfying this wave equation is a linear combination
of the metric perturbation amplitudes with a source term arising from the
stress-energy tensor of the point particle. The original master functions were
found by Regge and Wheeler (odd parity) and Zerilli (even parity). Subsequent
work by Moncrief and then Cunningham, Price and Moncrief introduced new master
variables which allow time domain reconstruction of the metric perturbation
amplitudes. Here I explore the relationship between these different functions
and develop a general procedure for deriving new higher-order master functions
from ones already known. The benefit of higher-order functions is that their
source terms always converge faster at large distance than their lower-order
counterparts. This makes for a dramatic improvement in both the speed and
accuracy of frequency domain codes when analyzing unbound motion.
| [
{
"created": "Sat, 17 Jun 2017 00:06:53 GMT",
"version": "v1"
}
] | 2018-03-21 | [
[
"Hopper",
"Seth",
""
]
] | Gravitational perturbations due to a point particle moving on a static black hole background are naturally described in Regge-Wheeler gauge. The first-order field equations reduce to a single master wave equation for each radiative mode. The master function satisfying this wave equation is a linear combination of the metric perturbation amplitudes with a source term arising from the stress-energy tensor of the point particle. The original master functions were found by Regge and Wheeler (odd parity) and Zerilli (even parity). Subsequent work by Moncrief and then Cunningham, Price and Moncrief introduced new master variables which allow time domain reconstruction of the metric perturbation amplitudes. Here I explore the relationship between these different functions and develop a general procedure for deriving new higher-order master functions from ones already known. The benefit of higher-order functions is that their source terms always converge faster at large distance than their lower-order counterparts. This makes for a dramatic improvement in both the speed and accuracy of frequency domain codes when analyzing unbound motion. |
gr-qc/0409097 | Parthasarathi Majumdar | Ashok Chatterjee and Parthasarathi Majumdar | Mass and charge fluctuations and black hole entropy | 8 pages revtex, no figures | Phys.Rev. D71 (2005) 024003 | 10.1103/PhysRevD.71.024003 | null | gr-qc | null | The effects of thermal fluctuations of the mass (horizon area) and electric
charge, on the entropy of non-rotating charged {\it macroscopic} black holes,
are analyzed using a grand canonical ensemble. Restricting to Gaussian
fluctuations around equilibrium, and assuming a power law type of relation
between the black hole mass, charge and horizon area, characterized by two real
positive indices, the grand canonical entropy is shown to acquire a logarithmic
correction with a positive coefficient proportional to the sum of the indices.
However, the root mean squared fluctuations of mass and charge relative to the
mean values of these quantities turn out to be independent of the details of
the assumed mass-area relation. We also comment on possible cancellation
between log (area) corrections arising due to {\it fixed area} quantum
spacetime fluctuations and that due to thermal fluctuations of the area and
other quantities.
| [
{
"created": "Mon, 27 Sep 2004 09:25:09 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Chatterjee",
"Ashok",
""
],
[
"Majumdar",
"Parthasarathi",
""
]
] | The effects of thermal fluctuations of the mass (horizon area) and electric charge, on the entropy of non-rotating charged {\it macroscopic} black holes, are analyzed using a grand canonical ensemble. Restricting to Gaussian fluctuations around equilibrium, and assuming a power law type of relation between the black hole mass, charge and horizon area, characterized by two real positive indices, the grand canonical entropy is shown to acquire a logarithmic correction with a positive coefficient proportional to the sum of the indices. However, the root mean squared fluctuations of mass and charge relative to the mean values of these quantities turn out to be independent of the details of the assumed mass-area relation. We also comment on possible cancellation between log (area) corrections arising due to {\it fixed area} quantum spacetime fluctuations and that due to thermal fluctuations of the area and other quantities. |
1601.04666 | Michael Cole | Michael J. Cole, Juan A. Valiente Kroon | Killing spinors as a characterisation of rotating black hole spacetimes | 18 pages | null | 10.1088/0264-9381/33/12/125019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the implications of the existence of Killing spinors in a
spacetime. In particular, we show that in vacuum and electrovacuum a Killing
spinor, along with some assumptions on the associated Killing vector in an
asymptotic region, guarantees that the spacetime is locally isometric to the
Kerr or Kerr-Newman solutions. We show that the characterisation of these
spacetimes in terms of Killing spinors is an alternative expression of
characterisation results of Mars (Kerr) and Wong (Kerr-Newman) involving
restrictions on the Weyl curvature and matter content.
| [
{
"created": "Mon, 18 Jan 2016 19:38:17 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2016 15:43:42 GMT",
"version": "v2"
}
] | 2016-05-25 | [
[
"Cole",
"Michael J.",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | We investigate the implications of the existence of Killing spinors in a spacetime. In particular, we show that in vacuum and electrovacuum a Killing spinor, along with some assumptions on the associated Killing vector in an asymptotic region, guarantees that the spacetime is locally isometric to the Kerr or Kerr-Newman solutions. We show that the characterisation of these spacetimes in terms of Killing spinors is an alternative expression of characterisation results of Mars (Kerr) and Wong (Kerr-Newman) involving restrictions on the Weyl curvature and matter content. |
1606.08569 | Daria Tretyakova | D.A. Tretyakova | Horndeski black hole observational properties | 16 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine geodesics for scalar-tensor black holes in the Horndeski-Galileon
non-minimal kinetic coupling framework. Our analysis shows that bound orbits
may not be present within some model parameters range. Using the observational
data we pose bounds on possible solution parameter values, as well as initial
model parameters.
| [
{
"created": "Tue, 28 Jun 2016 06:20:36 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Jul 2016 08:28:07 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Oct 2016 09:21:36 GMT",
"version": "v3"
}
] | 2016-10-13 | [
[
"Tretyakova",
"D. A.",
""
]
] | We examine geodesics for scalar-tensor black holes in the Horndeski-Galileon non-minimal kinetic coupling framework. Our analysis shows that bound orbits may not be present within some model parameters range. Using the observational data we pose bounds on possible solution parameter values, as well as initial model parameters. |
2309.14318 | Hirotaka Yoshino | Hirotaka Yoshino | Distorted static photon surfaces in perturbed Reissner-Nordstr\"om
spacetimes | 40 pages , 5 figures | null | null | OCU-PHYS-585, AP-GR-194 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The photon surface is defined as a timelike surface $S$ such that any photon
emitted in arbitrary tangential direction to $S$ from an arbitrary point on $S$
continues to propagate on $S$. In this paper, we examine whether a static
photon surface can be present in distorted electrovacuum spacetimes with
perturbative approach, by constructing analytic solutions to the equations for
static perturbations of a Reissner-Nordstr\"om spacetime that are regular
outside the background photon surface. For each of the $\ell\ge 2$ modes, there
are two physical solutions to the perturbative equations that correspond to
adding the multipole moments of mass and electric charge, respectively. By
adjusting the ratio of the amplitudes of the two solutions appropriately, it is
possible to realize a distorted photon surface. In the case of $\ell=1$,
although there is only one physical solution to the perturbative equations,
there is also a degree of freedom to shift the coordinate position of the
photon surface, and this enables the formation of a photon surface. Such a
photon surface has a spherically symmetric spatial section, but it is also
distorted in the three-dimensional sense. Our results show that distorted
static photon surfaces can be formed at least at the level of the first-order
perturbations, and imply that the uniqueness of the photon surface may not hold
in electrovacuum spacetimes.
| [
{
"created": "Mon, 25 Sep 2023 17:43:19 GMT",
"version": "v1"
}
] | 2023-09-26 | [
[
"Yoshino",
"Hirotaka",
""
]
] | The photon surface is defined as a timelike surface $S$ such that any photon emitted in arbitrary tangential direction to $S$ from an arbitrary point on $S$ continues to propagate on $S$. In this paper, we examine whether a static photon surface can be present in distorted electrovacuum spacetimes with perturbative approach, by constructing analytic solutions to the equations for static perturbations of a Reissner-Nordstr\"om spacetime that are regular outside the background photon surface. For each of the $\ell\ge 2$ modes, there are two physical solutions to the perturbative equations that correspond to adding the multipole moments of mass and electric charge, respectively. By adjusting the ratio of the amplitudes of the two solutions appropriately, it is possible to realize a distorted photon surface. In the case of $\ell=1$, although there is only one physical solution to the perturbative equations, there is also a degree of freedom to shift the coordinate position of the photon surface, and this enables the formation of a photon surface. Such a photon surface has a spherically symmetric spatial section, but it is also distorted in the three-dimensional sense. Our results show that distorted static photon surfaces can be formed at least at the level of the first-order perturbations, and imply that the uniqueness of the photon surface may not hold in electrovacuum spacetimes. |
gr-qc/0401117 | John W. Moffat | J. W. Moffat | Quantum Gravity Momentum Representation and Maximum Invariant Energy | 16 pages, LateX file, no figures | Int. J. Geometric Methods in Mod. Phys., 13(1), 1650005 (2016) | 10.1142/S0219887816500055 | null | gr-qc astro-ph hep-ph hep-th | null | We use the idea of the symmetry between the spacetime coordinates x^\mu and
the energy-momentum p^\mu in quantum theory to construct a momentum space
quantum gravity geometry with a metric s_{\mu\nu} and a curvature
P^\lambda_{\mu\nu\rho}. For a closed maximally symmetric momentum space with a
constant 3-curvature, the volume of the p-space admits a cutoff with an
invariant maximum momentum a. A Wheeler-DeWitt-type wave equation is obtained
in the momentum space representation. The vacuum energy density and the
self-energy of a charged particle are shown to be finite, and modifications of
the electromagnetic radiation density and the entropy density of a system of
particles occur for high frequencies.
| [
{
"created": "Thu, 29 Jan 2004 00:57:21 GMT",
"version": "v1"
}
] | 2016-03-08 | [
[
"Moffat",
"J. W.",
""
]
] | We use the idea of the symmetry between the spacetime coordinates x^\mu and the energy-momentum p^\mu in quantum theory to construct a momentum space quantum gravity geometry with a metric s_{\mu\nu} and a curvature P^\lambda_{\mu\nu\rho}. For a closed maximally symmetric momentum space with a constant 3-curvature, the volume of the p-space admits a cutoff with an invariant maximum momentum a. A Wheeler-DeWitt-type wave equation is obtained in the momentum space representation. The vacuum energy density and the self-energy of a charged particle are shown to be finite, and modifications of the electromagnetic radiation density and the entropy density of a system of particles occur for high frequencies. |
2208.09024 | Lukasz Bratek | {\L}ukasz Bratek, Joanna Ja{\l}ocha, Marek Kutschera | Cylindrically symmetric radial accretion onto a Levi-Civita string-like
source | This is not the final published version | Phys. Rev. D 105, 023013 (2022) | 10.1103/PhysRevD.105.023013 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Radial steady-state accretion of polytropic matter is investigated under
cylindrical symmetry in the Levi-Civita background metric. The model can be
considered as a cylindrical analog of Bondi accretion in strong gravitational
field. As a byproduct of this study, the issue of defining the line mass
density is addressed and the role of the metric free parameters is discussed on
the example of physical observables. The form of radial accretion equations is
insensitive to the structure of the interior solution. Accordingly, the
accretion solution analysis can be limited to a special Wilson form of
Levi-Civita metric describing a structureless homogeneous string.
| [
{
"created": "Thu, 18 Aug 2022 18:57:13 GMT",
"version": "v1"
}
] | 2022-08-22 | [
[
"Bratek",
"Łukasz",
""
],
[
"Jałocha",
"Joanna",
""
],
[
"Kutschera",
"Marek",
""
]
] | Radial steady-state accretion of polytropic matter is investigated under cylindrical symmetry in the Levi-Civita background metric. The model can be considered as a cylindrical analog of Bondi accretion in strong gravitational field. As a byproduct of this study, the issue of defining the line mass density is addressed and the role of the metric free parameters is discussed on the example of physical observables. The form of radial accretion equations is insensitive to the structure of the interior solution. Accordingly, the accretion solution analysis can be limited to a special Wilson form of Levi-Civita metric describing a structureless homogeneous string. |
1809.01385 | Muzaffer Adak | Muzaffer Adak | Gauge Approach to The Symmetric Teleparallel Gravity | This is the improved version of our manuscript arXiv:0810.2388v1. To
appear in International Journal of Geometric Methods in Modern Physics | Int. J. Geomet. Meth. Modern Phys. 15 (2018) 1850198 | 10.1142/S0219887818501980 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a gauge invariant gravity model in a non-Riemannian geometry in
which the curvature and the torsion both are zero, the nonmetricity is nonzero.
We also argue that only a metric ansatz is enough to start finding solutions to
the field equations. As an application we obtain explicitly a conformally flat
solution.
| [
{
"created": "Wed, 5 Sep 2018 08:40:07 GMT",
"version": "v1"
}
] | 2020-11-24 | [
[
"Adak",
"Muzaffer",
""
]
] | We discuss a gauge invariant gravity model in a non-Riemannian geometry in which the curvature and the torsion both are zero, the nonmetricity is nonzero. We also argue that only a metric ansatz is enough to start finding solutions to the field equations. As an application we obtain explicitly a conformally flat solution. |
gr-qc/0503013 | Donald Salisbury | J. M. Pons and D. C. Salisbury | The issue of time in generally covariant theories and the Komar-Bergmann
approach to observables in general relativity | null | Phys.Rev. D71 (2005) 124012 | 10.1103/PhysRevD.71.124012 | null | gr-qc | null | Diffeomorphism-induced symmetry transformations and time evolution are
distinct operations in generally covariant theories formulated in phase space.
Time is not frozen. Diffeomorphism invariants are consequently not necessarily
constants of the motion. Time-dependent invariants arise through the choice of
an intrinsic time, or equivalently through the imposition of time-dependent
gauge fixation conditions. One example of such a time-dependent gauge fixing is
the Komar-Bergmann use of Weyl curvature scalars in general relativity. An
analogous gauge fixing is also imposed for the relativistic free particle and
the resulting complete set time-dependent invariants for this exactly solvable
model are displayed. In contrast with the free particle case, we show that
gauge invariants that are simultaneously constants of motion cannot exist in
general relativity. They vary with intrinsic time.
| [
{
"created": "Thu, 3 Mar 2005 19:05:48 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Pons",
"J. M.",
""
],
[
"Salisbury",
"D. C.",
""
]
] | Diffeomorphism-induced symmetry transformations and time evolution are distinct operations in generally covariant theories formulated in phase space. Time is not frozen. Diffeomorphism invariants are consequently not necessarily constants of the motion. Time-dependent invariants arise through the choice of an intrinsic time, or equivalently through the imposition of time-dependent gauge fixation conditions. One example of such a time-dependent gauge fixing is the Komar-Bergmann use of Weyl curvature scalars in general relativity. An analogous gauge fixing is also imposed for the relativistic free particle and the resulting complete set time-dependent invariants for this exactly solvable model are displayed. In contrast with the free particle case, we show that gauge invariants that are simultaneously constants of motion cannot exist in general relativity. They vary with intrinsic time. |
gr-qc/0606132 | Jaap Eldering | Jaap Eldering | The polygon model for 2+1D gravity: the constraint algebra and problems
of quantization | 69 pages, 22 figures, LaTeX, Master thesis | null | null | null | gr-qc | null | In this Master thesis we consider 't Hooft's polygon model for 2+1D gravity.
After a detailed review of the polygon model in the classical context, we
discuss problems associated with its quantization and calculate the explicitly
the full Poisson structure of the constraints.
The calculation of the Poisson structure in chapter 6 introduces corrections
and generalizations to earlier published results. We show that the full Poisson
structure closes on shell, but not off shell. An attempt is made to interpret
the gauge orbits generated by the constraints.
| [
{
"created": "Fri, 30 Jun 2006 10:14:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Eldering",
"Jaap",
""
]
] | In this Master thesis we consider 't Hooft's polygon model for 2+1D gravity. After a detailed review of the polygon model in the classical context, we discuss problems associated with its quantization and calculate the explicitly the full Poisson structure of the constraints. The calculation of the Poisson structure in chapter 6 introduces corrections and generalizations to earlier published results. We show that the full Poisson structure closes on shell, but not off shell. An attempt is made to interpret the gauge orbits generated by the constraints. |
1405.4155 | Alessandro D.A.M. Spallicci di Filottrano | Alessandro D.A.M. Spallicci, P. Ritter, S. Aoudia | Self-force driven motion in curved spacetimes | To appear in Int. J. Geom. Meth. Mod. Phys | 2014, Int. J. Geom. Meth. Mod. Phys., 11, 1450072 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We adopt the Dirac-Detweiler-Whiting radiative and regular effective field in
curved spacetime. Thereby, we derive straightforwardly the first order
perturbative correction to the geodesic of the background in a covariant form,
for the extreme mass ratio two-body problem. The correction contains the
self-force contribution and a background metric dependent term.
| [
{
"created": "Fri, 16 May 2014 13:00:25 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Spallicci",
"Alessandro D. A. M.",
""
],
[
"Ritter",
"P.",
""
],
[
"Aoudia",
"S.",
""
]
] | We adopt the Dirac-Detweiler-Whiting radiative and regular effective field in curved spacetime. Thereby, we derive straightforwardly the first order perturbative correction to the geodesic of the background in a covariant form, for the extreme mass ratio two-body problem. The correction contains the self-force contribution and a background metric dependent term. |
1805.01097 | Lu\'is Filipe Costa | L. Filipe O. Costa, Rita Franco, Vitor Cardoso | Gravitational Magnus effect | 28 pages, 9 figures. References added, matches the final published
version | Phys. Rev. D 98, 024026 (2018) | 10.1103/PhysRevD.98.024026 | null | gr-qc astro-ph.HE hep-th physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that a spinning body moving in a fluid suffers a force
orthogonal to its velocity and rotation axis --- it is called the Magnus
effect. Recent simulations of spinning black holes and (indirect) theoretical
predictions, suggest that a somewhat analogous effect may occur for purely
gravitational phenomena. The magnitude and precise direction of this
"gravitational Magnus effect" is still the subject of debate. Starting from the
rigorous equations of motion for spinning bodies in General Relativity
(Mathisson-Papapetrou equations), we show that indeed such an effect takes
place and is a fundamental part of the spin-curvature force. The effect arises
whenever there is a current of mass/energy, non-parallel to a body's spin. We
compute the effect explicitly for some astrophysical systems of interest: a
galactic dark matter halo, a black hole accretion disk, and the
Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime. It is seen to lead to
secular orbital precessions potentially observable by future astrometric
experiments and gravitational-wave detectors. Finally, we consider also the
reciprocal problem: the "force" exerted by the body on the surrounding matter,
and show that (from this perspective) the effect is due to the body's
gravitomagnetic field. We compute it rigorously, showing the matching with its
reciprocal, and clarifying common misconceptions in the literature regarding
the action-reaction law in post-Newtonian gravity.
| [
{
"created": "Thu, 3 May 2018 03:25:23 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jul 2018 22:22:47 GMT",
"version": "v2"
}
] | 2018-07-27 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Franco",
"Rita",
""
],
[
"Cardoso",
"Vitor",
""
]
] | It is well known that a spinning body moving in a fluid suffers a force orthogonal to its velocity and rotation axis --- it is called the Magnus effect. Recent simulations of spinning black holes and (indirect) theoretical predictions, suggest that a somewhat analogous effect may occur for purely gravitational phenomena. The magnitude and precise direction of this "gravitational Magnus effect" is still the subject of debate. Starting from the rigorous equations of motion for spinning bodies in General Relativity (Mathisson-Papapetrou equations), we show that indeed such an effect takes place and is a fundamental part of the spin-curvature force. The effect arises whenever there is a current of mass/energy, non-parallel to a body's spin. We compute the effect explicitly for some astrophysical systems of interest: a galactic dark matter halo, a black hole accretion disk, and the Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime. It is seen to lead to secular orbital precessions potentially observable by future astrometric experiments and gravitational-wave detectors. Finally, we consider also the reciprocal problem: the "force" exerted by the body on the surrounding matter, and show that (from this perspective) the effect is due to the body's gravitomagnetic field. We compute it rigorously, showing the matching with its reciprocal, and clarifying common misconceptions in the literature regarding the action-reaction law in post-Newtonian gravity. |
1505.01565 | Habibollah Razmi | S. Karbasi and H. Razmi | Spherical "Top-Hat" Collapse in a Modified Chaplygin Gas Dominated
Universe | 16 pages, 16 figures | International Journal of Modern Physics D, Vol. 24, No. 7, 1550050
(2015) | 10.1142/S0218271815500509 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering perturbation growth in spherical Top-Hat model of structure
formation in a generalized Chaplygin gas dominated universe, we want to study
this scenario with a modified Chaplygin gas model. The evolution of background
and collapsed region parameters are found for different cases. The stability of
the model and the collapse time rate are considered in different cases. The
turn-around redshifts are also computed; the results are in relatively good
agreement with current observational data.
| [
{
"created": "Wed, 6 May 2015 12:04:48 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 2015 07:23:37 GMT",
"version": "v2"
}
] | 2015-05-11 | [
[
"Karbasi",
"S.",
""
],
[
"Razmi",
"H.",
""
]
] | Considering perturbation growth in spherical Top-Hat model of structure formation in a generalized Chaplygin gas dominated universe, we want to study this scenario with a modified Chaplygin gas model. The evolution of background and collapsed region parameters are found for different cases. The stability of the model and the collapse time rate are considered in different cases. The turn-around redshifts are also computed; the results are in relatively good agreement with current observational data. |
gr-qc/0312034 | Clemens Heuson | Clemens Heuson | Noncommutative Space-Time in DSR theories | 5 pages, no figures | null | null | null | gr-qc | null | Space-time coordinates in DSR theories with two invariant scales based on a
dispersion relation with an energy independent speed of light are introduced by
the demand, that boost and rotation generators are invariant under a
transformation from SR to DSR variables. This turns out to be equivalent to a
recent suggestion postulating the existence of plane wave solutions in DSR
theories. The momentum space representation of coordinates is derived, yielding
a noncommutative space-time and the deformed algebra.
| [
{
"created": "Fri, 5 Dec 2003 10:21:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Heuson",
"Clemens",
""
]
] | Space-time coordinates in DSR theories with two invariant scales based on a dispersion relation with an energy independent speed of light are introduced by the demand, that boost and rotation generators are invariant under a transformation from SR to DSR variables. This turns out to be equivalent to a recent suggestion postulating the existence of plane wave solutions in DSR theories. The momentum space representation of coordinates is derived, yielding a noncommutative space-time and the deformed algebra. |
2109.09865 | Jose Jovel | Norman Cruz, Esteban Gonz\'alez, and Jos\'e Jovel | Singularities and Soft-Big Bang in a viscous $\Lambda$CDM model | 17 pages, 13 figures | null | 10.1103/PhysRevD.105.024047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we explore the different types of singularities that arise in
the $\Lambda$CDM model when dissipative processes are considered, in the
framework of the Eckart's theory. In particular, we study the late-time
behavior of $\Lambda$CDM model with viscous cold dark matter (CDM) and an
early-time viscous radiation domination era with cosmological constant (CC).
The fluids are described by the barotropic equation of state (EoS)
$p=(\gamma-1)\rho$, where $p$ is the equilibrium pressure of the fluid, $\rho$
their energy density, and $\gamma$ is the barotropic index. We explore two
particular cases for the bulk viscosity $\xi$, a constant bulk viscosity
$\xi=\xi_{0}$, and a bulk viscosity proportional to the energy density of the
fluid $\xi=\xi_{0}\rho$. Due to some previous investigations that have explored
to describe the behavior of the universe with a negative CC, we extend our
analysis to this case. We found that future singularities like Big-Rip are
allowed but without having a phantom EoS associated to the DE fluid. Big-Crunch
singularities also appears when a negative CC is present, but also de Sitter
and even Big-Rip types are allowed due to the negative pressure of the
viscosity, which opens the possibility of an accelerated expansion in AdS
cosmologies. We also discuss a very particular solution without Big Bang
singularity that arises in the early-time radiation dominant era of our model
known as Soft-Big Bang.
| [
{
"created": "Mon, 20 Sep 2021 22:19:13 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2022 22:37:22 GMT",
"version": "v2"
}
] | 2022-02-02 | [
[
"Cruz",
"Norman",
""
],
[
"González",
"Esteban",
""
],
[
"Jovel",
"José",
""
]
] | In this paper we explore the different types of singularities that arise in the $\Lambda$CDM model when dissipative processes are considered, in the framework of the Eckart's theory. In particular, we study the late-time behavior of $\Lambda$CDM model with viscous cold dark matter (CDM) and an early-time viscous radiation domination era with cosmological constant (CC). The fluids are described by the barotropic equation of state (EoS) $p=(\gamma-1)\rho$, where $p$ is the equilibrium pressure of the fluid, $\rho$ their energy density, and $\gamma$ is the barotropic index. We explore two particular cases for the bulk viscosity $\xi$, a constant bulk viscosity $\xi=\xi_{0}$, and a bulk viscosity proportional to the energy density of the fluid $\xi=\xi_{0}\rho$. Due to some previous investigations that have explored to describe the behavior of the universe with a negative CC, we extend our analysis to this case. We found that future singularities like Big-Rip are allowed but without having a phantom EoS associated to the DE fluid. Big-Crunch singularities also appears when a negative CC is present, but also de Sitter and even Big-Rip types are allowed due to the negative pressure of the viscosity, which opens the possibility of an accelerated expansion in AdS cosmologies. We also discuss a very particular solution without Big Bang singularity that arises in the early-time radiation dominant era of our model known as Soft-Big Bang. |
gr-qc/0508104 | Johan Noldus | Johan Noldus | Towards a fully consistent relativistic quantum mechanics and a change
of perspective on quantum gravity | 17 pages, no figures, entire subsection added. submitted to CQG | null | null | null | gr-qc quant-ph | null | This paper can be seen as an exercise in how to adapt quantum mechanics from
a strict relativistic perspective while being respectful and critical towards
the experimental achievements of the contemporary theory. The result is a fully
observer independent relativistic quantum mechanics for N particle systems
without tachyonic solutions. A remaining worry for the moment is Bell's
theorem.
| [
{
"created": "Fri, 26 Aug 2005 12:46:01 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2005 21:38:42 GMT",
"version": "v2"
},
{
"created": "Sat, 10 Sep 2005 09:33:54 GMT",
"version": "v3"
},
{
"created": "Mon, 10 Oct 2005 17:24:46 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Noldus",
"Johan",
""
]
] | This paper can be seen as an exercise in how to adapt quantum mechanics from a strict relativistic perspective while being respectful and critical towards the experimental achievements of the contemporary theory. The result is a fully observer independent relativistic quantum mechanics for N particle systems without tachyonic solutions. A remaining worry for the moment is Bell's theorem. |
0906.1442 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | Is it possible to see the infinite future of the Universe when falling
into a black hole? | 12 pages, 2 figures; Methodological Notes | Usp.Fiz.Nauk 179:279-283,2009 | 10.3367/UFNe.0179.200903d.0279 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A possibility to see the infinite future of the Universe by an astronaut
falling into a black hole is discussed and ruled out.
| [
{
"created": "Mon, 8 Jun 2009 09:13:38 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | A possibility to see the infinite future of the Universe by an astronaut falling into a black hole is discussed and ruled out. |
gr-qc/9402006 | Juan Pablo | Wojciech Hubert Zurek and Juan Pablo Paz | Decoherence, Chaos, and the Second Law | 13 Pages, 2 Figures available upon request, Preprint LA-UR-93-, The
new version contains the text, the previous one had only the Macros: sorry! | Phys.Rev.Lett.72:2508,1994 | 10.1103/PhysRevLett.72.2508 | null | gr-qc hep-th | null | We investigate implications of decoherence for quantum systems which are
classically chaotic. We show that, in open systems, the rate of von Neumann
entropy production quickly reaches an asymptotic value which is: (i)
independent of the system-environment coupling, (ii) dictated by the dynamics
of the system, and (iii) dominated by the largest Lyapunov exponent. These
results shed a new light on the correspondence between quantum and classical
dynamics as well as on the origins of the ``arrow of time.''
| [
{
"created": "Wed, 2 Feb 1994 17:33:22 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Feb 1994 19:18:39 GMT",
"version": "v2"
}
] | 2011-08-04 | [
[
"Zurek",
"Wojciech Hubert",
""
],
[
"Paz",
"Juan Pablo",
""
]
] | We investigate implications of decoherence for quantum systems which are classically chaotic. We show that, in open systems, the rate of von Neumann entropy production quickly reaches an asymptotic value which is: (i) independent of the system-environment coupling, (ii) dictated by the dynamics of the system, and (iii) dominated by the largest Lyapunov exponent. These results shed a new light on the correspondence between quantum and classical dynamics as well as on the origins of the ``arrow of time.'' |
1302.6920 | Lorenzo Iorio | L. Iorio | A possible new test of general relativity with Juno | LaTex2e, 16 pages, no tables, 2 figures, 39 references. Version
published in Classical and Quantum Gravity (CQG) | Class. Quant. Gravit.30:195011,2013 | 10.1088/0264-9381/30/19/195011 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The expansion in multipoles of the gravitational potential of a rotating body
affects the orbital motion of a test particle orbiting it with long-term
perturbations both at a classical and at a relativistic level. In this
preliminary sensitivity analysis, we show that, for the first time, the J2 c^-2
effects could be measured by the ongoing Juno mission in the gravitational
field of Jupiter during its yearlong science phase (10 November 2016-5 October
2017) thanks to its high eccentricity (e=0.947) and to the huge oblateness of
Jupiter (J2=1.47 10^-2). The semi-major axis a and the perijove \omega\ of Juno
are expected to be shifted by \Delta a =700-900 m and \Delta\omega = 50-60
milliarcseconds, respectively, over 1-2 yr. A numerical analysis shows also
that the expected J2c^-2 range-rate signal for Juno should be as large as 280
microns per second during a typical 6 h pass at its closest approach.
Independent analyses previously performed by other researchers about the
measurability of the Lense-Thirring effect showed that the radio science
apparatus of Juno should reach an accuracy in Doppler range-rate measurements
of 1-5 microns per second over such passes. The range-rate signature of the
classical even zonal perturbations is different from the 1PN one. Thus, further
investigations, based on covariance analyses of simulated Doppler data and
dedicated parameters estimation, are worth of further consideration. It turns
out that the J2 c^-2 effects cannot be responsible of the flyby anomaly in the
gravitational field of the Earth. A dedicated spacecraft in a 6678 km X 57103
km polar orbit would experience a geocentric J2 c^-2 range-rate shift of 0.4 mm
s^-1.
| [
{
"created": "Wed, 27 Feb 2013 16:52:00 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Mar 2013 16:10:41 GMT",
"version": "v2"
},
{
"created": "Fri, 3 May 2013 20:42:37 GMT",
"version": "v3"
},
{
"created": "Fri, 9 Aug 2013 16:53:32 GMT",
"version": "v4"
},
{
"created": "Sat, 7 Sep 2013 14:21:48 GMT",
"version": "v5"
}
] | 2013-09-10 | [
[
"Iorio",
"L.",
""
]
] | The expansion in multipoles of the gravitational potential of a rotating body affects the orbital motion of a test particle orbiting it with long-term perturbations both at a classical and at a relativistic level. In this preliminary sensitivity analysis, we show that, for the first time, the J2 c^-2 effects could be measured by the ongoing Juno mission in the gravitational field of Jupiter during its yearlong science phase (10 November 2016-5 October 2017) thanks to its high eccentricity (e=0.947) and to the huge oblateness of Jupiter (J2=1.47 10^-2). The semi-major axis a and the perijove \omega\ of Juno are expected to be shifted by \Delta a =700-900 m and \Delta\omega = 50-60 milliarcseconds, respectively, over 1-2 yr. A numerical analysis shows also that the expected J2c^-2 range-rate signal for Juno should be as large as 280 microns per second during a typical 6 h pass at its closest approach. Independent analyses previously performed by other researchers about the measurability of the Lense-Thirring effect showed that the radio science apparatus of Juno should reach an accuracy in Doppler range-rate measurements of 1-5 microns per second over such passes. The range-rate signature of the classical even zonal perturbations is different from the 1PN one. Thus, further investigations, based on covariance analyses of simulated Doppler data and dedicated parameters estimation, are worth of further consideration. It turns out that the J2 c^-2 effects cannot be responsible of the flyby anomaly in the gravitational field of the Earth. A dedicated spacecraft in a 6678 km X 57103 km polar orbit would experience a geocentric J2 c^-2 range-rate shift of 0.4 mm s^-1. |
gr-qc/9601035 | Yoav Peleg | Sukanta Bose, Leonard Parker and Yoav Peleg (UWM) | Validity of the Semiclassical Approximation and Back=reaction | RevTex, 14 pages + 1 figure (uucompressed) | Phys.Rev. D53 (1996) 7089-7093 | 10.1103/PhysRevD.53.7089 | WISC-MILW-96-TH-10 | gr-qc hep-th | null | Studying two-dimensional evaporating dilatonic black holes, we show that the
semiclassical approximation, based on the background field approach, is valid
everywhere in regions of weak curvature (including the horizon), as long as one
takes into account the effects of back-reaction of the Hawking radiation on the
background geometry.
| [
{
"created": "Mon, 22 Jan 1996 21:42:47 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Bose",
"Sukanta",
"",
"UWM"
],
[
"Parker",
"Leonard",
"",
"UWM"
],
[
"Peleg",
"Yoav",
"",
"UWM"
]
] | Studying two-dimensional evaporating dilatonic black holes, we show that the semiclassical approximation, based on the background field approach, is valid everywhere in regions of weak curvature (including the horizon), as long as one takes into account the effects of back-reaction of the Hawking radiation on the background geometry. |
2208.02599 | Andronikos Paliathanasis | Andronikos Paliathanasis | New exact and analytic solutions in Weyl Integrable cosmology from
Noether symmetry analysis | 16 pages, 1 Fig. to appear in Physica Scripta | null | 10.1088/1402-4896/ac8702 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a cosmological model in a
Friedmann--Lema\^{\i}tre--Robertson--Walker background space with an ideal gas
defined in Weyl Integrable gravity. In the Einstein-Weyl theory a scalar field
is introduced in a geometric way. Furthermore, the scalar field and the ideal
gas interact in the gravitational Action Integral. Furthermore, we introduce a
potential term for the scalar field potential and we show that the field
equations admit a minisuperspace description. Noether's theorem is applied for
the constraint of the potential function and the corresponding conservation
laws are constructed. Finally, we solve the Hamilton-Jacobi equation for the
cosmological model and we derive a family of new solutions in Weyl Integrable
cosmology. Some closed-form expressions for the Hubble function are presented.
| [
{
"created": "Thu, 4 Aug 2022 11:55:27 GMT",
"version": "v1"
}
] | 2022-08-24 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We consider a cosmological model in a Friedmann--Lema\^{\i}tre--Robertson--Walker background space with an ideal gas defined in Weyl Integrable gravity. In the Einstein-Weyl theory a scalar field is introduced in a geometric way. Furthermore, the scalar field and the ideal gas interact in the gravitational Action Integral. Furthermore, we introduce a potential term for the scalar field potential and we show that the field equations admit a minisuperspace description. Noether's theorem is applied for the constraint of the potential function and the corresponding conservation laws are constructed. Finally, we solve the Hamilton-Jacobi equation for the cosmological model and we derive a family of new solutions in Weyl Integrable cosmology. Some closed-form expressions for the Hubble function are presented. |
1711.09484 | Osvaldo Pablo Santillan | Juan M. Armaleo, J. Osorio Morales and O. Santillan | Gauss-Bonnet models with cosmological constant and non zero spatial
curvature in $D=4$ | Grammar corrected and some confusing notation was modified. 24 pages | null | 10.1140/epjc/s10052-018-5558-x | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper the possibility of eternal universes in Gauss-Bonnet
theories of gravity in four dimensions is analysed. It is shown that, for zero
spatial curvature and zero cosmological constant, if the coupling is such that
$0<f'(\phi)\leq c \exp(\frac{\sqrt{8}}{\sqrt{10}}\phi)$, then there are
solutions that are eternal. Similar conclusions are found when a cosmological
constant turned on. These conclusions are not generalized for the case when the
spatial curvature is present, but we are able to find some general results
about the possible nature of the singularities. The presented results correct
some dubious arguments in [54], although the same conclusions are reached. On
the other hand, these past results are considerably generalized to a wide class
of situations which were not considered in [54].
| [
{
"created": "Sun, 26 Nov 2017 23:02:15 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Jan 2018 19:56:52 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Armaleo",
"Juan M.",
""
],
[
"Morales",
"J. Osorio",
""
],
[
"Santillan",
"O.",
""
]
] | In the present paper the possibility of eternal universes in Gauss-Bonnet theories of gravity in four dimensions is analysed. It is shown that, for zero spatial curvature and zero cosmological constant, if the coupling is such that $0<f'(\phi)\leq c \exp(\frac{\sqrt{8}}{\sqrt{10}}\phi)$, then there are solutions that are eternal. Similar conclusions are found when a cosmological constant turned on. These conclusions are not generalized for the case when the spatial curvature is present, but we are able to find some general results about the possible nature of the singularities. The presented results correct some dubious arguments in [54], although the same conclusions are reached. On the other hand, these past results are considerably generalized to a wide class of situations which were not considered in [54]. |
1006.3130 | Subenoy Chakraborty | Ritabrata Biswas, Nairwita Mazumder, Subenoy Chakraborty | Accretion of Holographic Dark Energy : Dependency only upon Horizon
Radius of Expanding Universe | 11 pages | Astrophys.Space Sci.335:603-609,2011 | 10.1007/s10509-011-0772-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we deal with accretion of dark energy in the holographic dark
energy model for a general non-rotating static spherically symmetric black
hole. The mass of the black hole increases or decreases depending on the nature
of the holographic dark energy (quintessence or phantom) as well as on some
integration parameters. It is to be illustrated that the enhancement or
reduction of mass of a black hole is independent of the mass or size of the
black hole itself. Rather it depends only upon the radius of the event horizon
of the universe. Finally, the generalized second law of thermodynamics has been
studied on the event horizon to be assured that the law holds even if when the
black hole mass is decreasing though it is engrossing some mass.
| [
{
"created": "Wed, 16 Jun 2010 03:58:53 GMT",
"version": "v1"
},
{
"created": "Wed, 4 May 2011 12:14:21 GMT",
"version": "v2"
}
] | 2011-09-12 | [
[
"Biswas",
"Ritabrata",
""
],
[
"Mazumder",
"Nairwita",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this paper we deal with accretion of dark energy in the holographic dark energy model for a general non-rotating static spherically symmetric black hole. The mass of the black hole increases or decreases depending on the nature of the holographic dark energy (quintessence or phantom) as well as on some integration parameters. It is to be illustrated that the enhancement or reduction of mass of a black hole is independent of the mass or size of the black hole itself. Rather it depends only upon the radius of the event horizon of the universe. Finally, the generalized second law of thermodynamics has been studied on the event horizon to be assured that the law holds even if when the black hole mass is decreasing though it is engrossing some mass. |
2008.10474 | Chikun Ding | Chikun Ding, Xiongwen Chen | Slowly rotating Einstein-bumblebee black hole solution and its greybody
factor in a Lorentz violation model | 17 pages, 3 figures. Accepted by Chin. Phys. C | Chin. Phys. C 45 025106 2021 | 10.1088/1674-1137/abce51 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain an exact slowly rotating Einstein-bumblebee black hole solution by
solving the corresponding $rr$ and $t\phi$ components of the gravitational
field equations in both cases: A, $b_\mu=(0,b(r),0,0)$; B,
$b_\mu=(0,b(r),\mathfrak{b}(\theta),0)$. Then we check the other gravitational
field equations and the bumblebee field motion equations by using this
solution. We find that in the case A, there exists a slowly rotating black hole
solution indeed for arbitrary LV (Lorentz violation) coupling constant $\ell$;
however as in the case B, there exists this slowly rotating solution if and
only if the coupling constant $\ell$ is as small as or smaller than the angular
momentum $a$. Till now there seems to be no full rotating black hole solution,
so one can't use the Newman-Janis algorithm to generate a rotating solution in
Einstein-bumblebee theory. It is similar as that in Einstein-aether theory
where there exists only some slowly rotating black hole solutions. In order to
study the effects of this Lorentz symmetry broken, we consider the black hole
greybody factor and find that when angular index $l=0$, the LV constant $\ell$
decreases the effective potential and enhances the absorption probability,
which is similar to that of the non-minimal derivative coupling theory.
| [
{
"created": "Fri, 21 Aug 2020 00:38:34 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2020 07:57:28 GMT",
"version": "v2"
}
] | 2021-02-19 | [
[
"Ding",
"Chikun",
""
],
[
"Chen",
"Xiongwen",
""
]
] | We obtain an exact slowly rotating Einstein-bumblebee black hole solution by solving the corresponding $rr$ and $t\phi$ components of the gravitational field equations in both cases: A, $b_\mu=(0,b(r),0,0)$; B, $b_\mu=(0,b(r),\mathfrak{b}(\theta),0)$. Then we check the other gravitational field equations and the bumblebee field motion equations by using this solution. We find that in the case A, there exists a slowly rotating black hole solution indeed for arbitrary LV (Lorentz violation) coupling constant $\ell$; however as in the case B, there exists this slowly rotating solution if and only if the coupling constant $\ell$ is as small as or smaller than the angular momentum $a$. Till now there seems to be no full rotating black hole solution, so one can't use the Newman-Janis algorithm to generate a rotating solution in Einstein-bumblebee theory. It is similar as that in Einstein-aether theory where there exists only some slowly rotating black hole solutions. In order to study the effects of this Lorentz symmetry broken, we consider the black hole greybody factor and find that when angular index $l=0$, the LV constant $\ell$ decreases the effective potential and enhances the absorption probability, which is similar to that of the non-minimal derivative coupling theory. |
0808.0318 | Kourosh Nozari | Kourosh Nozari, N. Behrouz, T. Azizi and B. Fazlpour | Crossing the Cosmological Constant Line on a Warped DGP Brane | 28 pages, 8 figures, 2 tables, revised version to appear in Prog.
Theor. Phys | Prog.Theor.Phys.122:735-754,2009 | 10.1143/PTP.122.735 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study dynamics of the equation of state parameter for a dark energy
component non-minimally coupled to induced gravity on a warped DGP brane. We
show that there are appropriate domains of the model parameters space that
account for crossing of the phantom divide line. This crossing, which is
possible for both branches of the scenario, depends explicitly on the values of
the non-minimal coupling and warp factor. The effect of warp factor appears in
the value of the redshift parameter at which phantom divide line crossing
occurs.
| [
{
"created": "Sun, 3 Aug 2008 12:15:07 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Dec 2008 08:41:32 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Jun 2009 13:15:24 GMT",
"version": "v3"
}
] | 2010-05-12 | [
[
"Nozari",
"Kourosh",
""
],
[
"Behrouz",
"N.",
""
],
[
"Azizi",
"T.",
""
],
[
"Fazlpour",
"B.",
""
]
] | We study dynamics of the equation of state parameter for a dark energy component non-minimally coupled to induced gravity on a warped DGP brane. We show that there are appropriate domains of the model parameters space that account for crossing of the phantom divide line. This crossing, which is possible for both branches of the scenario, depends explicitly on the values of the non-minimal coupling and warp factor. The effect of warp factor appears in the value of the redshift parameter at which phantom divide line crossing occurs. |
2007.08038 | Mingzhe Li | Mingzhe Li, Haomin Rao, Dehao Zhao | A simple parity violating gravity model without ghost instability | The version matches the one to appear in JCAP | null | 10.1088/1475-7516/2020/11/023 | USTC-ICTS/PCFT-20-19 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider a parity violating gravity model without higher
derivatives, thus ghost free. This model is constructed from the tetrad and its
derivatives and coupled to a dynamical scalar field, like axion. It can be
reduced from the Nieh-Yan term within the framework of teleparallel gravity. We
apply this model to cosmology and investigate its consequences on cosmological
perturbation theory. We find that the coupled dynamical scalar field lost its
independent dynamics at the linear order and the parity violating term itself
behaves like a viscosity. For gravitational waves, this model produces velocity
difference between left- and right-handed polarizations, but generates no
amplitude discrepancy.
| [
{
"created": "Wed, 15 Jul 2020 23:59:03 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Jul 2020 08:06:07 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Oct 2020 04:24:39 GMT",
"version": "v3"
}
] | 2020-11-25 | [
[
"Li",
"Mingzhe",
""
],
[
"Rao",
"Haomin",
""
],
[
"Zhao",
"Dehao",
""
]
] | In this paper we consider a parity violating gravity model without higher derivatives, thus ghost free. This model is constructed from the tetrad and its derivatives and coupled to a dynamical scalar field, like axion. It can be reduced from the Nieh-Yan term within the framework of teleparallel gravity. We apply this model to cosmology and investigate its consequences on cosmological perturbation theory. We find that the coupled dynamical scalar field lost its independent dynamics at the linear order and the parity violating term itself behaves like a viscosity. For gravitational waves, this model produces velocity difference between left- and right-handed polarizations, but generates no amplitude discrepancy. |
1403.0109 | Amalaya Khurshudyan | Martiros Khurshudyan | Toy models of Universe with an Effective varying $\Lambda$-Term in Lyra
Manifold | null | Advances in High Energy Physics Volume 2015 (2015), Article ID
796168 | 10.1155/2015/796168 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We are interested by the study of several toy models of the Universe in
presence of interacting quintessence DE models. Models are considered in the
cosmology with an Effective varying $\Lambda$-Term in Lyra Manifold. The
motivation of the phenomenological models discussed in this paper is to obtain
corresponding models to describe and understand an accelerated expansion of the
Universe for the later stage of evolution. Phenomenology of the models
describes by the phenomenological forms of $\Lambda(t)$ ($8 \pi G =c =1$).
Concerning to the mathematical hardness we discuss results numerically and
graphically. Obtained results give us hope that proposed models can work as
good models for old Universe and in good agreement with observational data.
| [
{
"created": "Sat, 1 Mar 2014 17:54:34 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Khurshudyan",
"Martiros",
""
]
] | We are interested by the study of several toy models of the Universe in presence of interacting quintessence DE models. Models are considered in the cosmology with an Effective varying $\Lambda$-Term in Lyra Manifold. The motivation of the phenomenological models discussed in this paper is to obtain corresponding models to describe and understand an accelerated expansion of the Universe for the later stage of evolution. Phenomenology of the models describes by the phenomenological forms of $\Lambda(t)$ ($8 \pi G =c =1$). Concerning to the mathematical hardness we discuss results numerically and graphically. Obtained results give us hope that proposed models can work as good models for old Universe and in good agreement with observational data. |
1802.06553 | Raihaneh Moti | R. Moti and A. Shojai (Tehran U.) | On the quantum improved Schwarzschild black hole | null | Int.J.Mod.Phys. A35 (2020) 2050016 | 10.1142/S0217751X20500165 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Deriving the gravitational effective action directly from exact
renormalization group is very complicated, if not impossible. Hence, to study
the effects of running gravitational coupling which tends to a non--Gaussian UV
fixed point (as it is supposed by the asymptotic safety conjecture), two steps
are usually adopted. Cutoff identification and improvement of the gravitational
coupling to the running one. As suggested in [1], a function of all independent
curvature invariants seems to be the best choice for cutoff identification of
gravitational quantum fluctuations in curved spacetime and makes the action
improvement, which saves the general covariance of theory, possible. Here, we
choose Ricci tensor square for this purpose and then the equation of motion of
improved gravitational action and its spherically symmetric vacuum solution are
obtained. Indeed, its effect on the massive particles' trajectory and the black
hole thermodynamics are studied.
| [
{
"created": "Mon, 19 Feb 2018 09:00:59 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2019 08:39:12 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Feb 2020 17:36:45 GMT",
"version": "v3"
}
] | 2020-04-29 | [
[
"Moti",
"R.",
"",
"Tehran U."
],
[
"Shojai",
"A.",
"",
"Tehran U."
]
] | Deriving the gravitational effective action directly from exact renormalization group is very complicated, if not impossible. Hence, to study the effects of running gravitational coupling which tends to a non--Gaussian UV fixed point (as it is supposed by the asymptotic safety conjecture), two steps are usually adopted. Cutoff identification and improvement of the gravitational coupling to the running one. As suggested in [1], a function of all independent curvature invariants seems to be the best choice for cutoff identification of gravitational quantum fluctuations in curved spacetime and makes the action improvement, which saves the general covariance of theory, possible. Here, we choose Ricci tensor square for this purpose and then the equation of motion of improved gravitational action and its spherically symmetric vacuum solution are obtained. Indeed, its effect on the massive particles' trajectory and the black hole thermodynamics are studied. |
1706.00622 | Charles Hellaby | Charles Hellaby | Frame Rotation in the Szekeres Spacetimes | 21 pages, no figures. V2 has a few minor corrections | Classical and Quantum Gravity, 34, 145006, 1-20 (2017) | 10.1088/1361-6382/aa76f8 | uct-cosmology-2017-06-02-12-49 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Szekeres metric is an inhomogeneous cosmological model without any
symmetries. The standard Riemann-type coordinates can be transformed into
spherical-type coordinates, but the metric is no longer diagonal, and the
constant "radius" 2-spheres, 2-hyperboloids or 2-planes are known to be
"non-concentric". Since the transformation into spherical-type coordinates is
"radius" dependent, we question whether these coordinates have the same
orientation on each 2-surface. To answer this question, we set up an
orthonormal tetrad (ONT), and investigate its variation. We find that a
relative rotation of the tetrad is generic, and it can increase systematically
under conditions that are not very restrictive. We search for paths along which
the tetrad is constant, and find they only exist under very restrictive
conditions. In the process, we create a systematic method for defining an ONT
with chosen properties from a given metric.
| [
{
"created": "Fri, 2 Jun 2017 10:51:02 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jun 2017 14:59:18 GMT",
"version": "v2"
}
] | 2017-06-27 | [
[
"Hellaby",
"Charles",
""
]
] | The Szekeres metric is an inhomogeneous cosmological model without any symmetries. The standard Riemann-type coordinates can be transformed into spherical-type coordinates, but the metric is no longer diagonal, and the constant "radius" 2-spheres, 2-hyperboloids or 2-planes are known to be "non-concentric". Since the transformation into spherical-type coordinates is "radius" dependent, we question whether these coordinates have the same orientation on each 2-surface. To answer this question, we set up an orthonormal tetrad (ONT), and investigate its variation. We find that a relative rotation of the tetrad is generic, and it can increase systematically under conditions that are not very restrictive. We search for paths along which the tetrad is constant, and find they only exist under very restrictive conditions. In the process, we create a systematic method for defining an ONT with chosen properties from a given metric. |
1901.04300 | Antonella Cid | Fabiola Arevalo, Antonella Cid, Luis P. Chimento and Patricio Mella | On sign-changeable interaction in FLRW cosmology | 8 figures | null | 10.1140/epjc/s10052-019-6872-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate an interacting two-fluid model in a spatially flat
Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe, when the energy transfer
between these two dark components is produced by a factorisable nonlinear
sign-changeable interaction depending linearly on the energy density and
quadratically on the deceleration parameter. We solve the source equation and
obtain the effective energy densities of the dark sector and their components.
We show that the effective equation of state of the dark sector includes some
of the several kind of Chaplygin gas equations of state as well as a
generalization of the polytropic equation of state. We use bayesian statistics
methods to constrain free parameters in the models during its most recent
evolution considering supernovae type Ia and measurements of the Hubble
expansion rate. The resulting constraints provide new information on
sign-changeable interactions, its equivalences and compatibility with previous
models and novel late time universe dynamics.
| [
{
"created": "Fri, 4 Jan 2019 21:29:53 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Arevalo",
"Fabiola",
""
],
[
"Cid",
"Antonella",
""
],
[
"Chimento",
"Luis P.",
""
],
[
"Mella",
"Patricio",
""
]
] | We investigate an interacting two-fluid model in a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe, when the energy transfer between these two dark components is produced by a factorisable nonlinear sign-changeable interaction depending linearly on the energy density and quadratically on the deceleration parameter. We solve the source equation and obtain the effective energy densities of the dark sector and their components. We show that the effective equation of state of the dark sector includes some of the several kind of Chaplygin gas equations of state as well as a generalization of the polytropic equation of state. We use bayesian statistics methods to constrain free parameters in the models during its most recent evolution considering supernovae type Ia and measurements of the Hubble expansion rate. The resulting constraints provide new information on sign-changeable interactions, its equivalences and compatibility with previous models and novel late time universe dynamics. |
1505.00481 | Gines Perez Teruel | Gin\'es R. P\'erez Teruel | Non-linear energy conservation theorem in the framework of Special
Relativity | null | Eur. J. Phys. 36 045009 (2015) | 10.1088/0143-0807/36/4/045009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we revisit the study of the gravitational interaction in the
context of the Special Theory of Relativity. It is found that, as long as the
equivalence principle is respected, a relativistic non-linear energy
conservation theorem arises in a natural way. We interpret that this non-linear
conservation law stresses the non-linear character of the gravitational
interaction.The theorem reproduces the energy conservation theorem of Newtonian
mechanics in the corresponding low energy limit, but also allows to derive some
standard results of post-Newtonian gravity, such as the formula of the
gravitational redshift. Guided by this conservation law, we develop a
Lagrangian formalism for a particle in a gravitational field. We realize that
the Lagrangian can be written in an explicit covariant fashion, and turns out
to be the geodesic Lagrangian of a curved Lorentzian manifold. Therefore, any
attempt to describe gravity within the Special Theory, leads outside their own
domains towards a curved space-time. Thus, the pedagogical content of the paper
may be useful as a starting point to discuss the problem of Gravitation in the
context of the Special Theory, as a preliminary step before introducing General
Relativity.
| [
{
"created": "Sun, 3 May 2015 21:43:54 GMT",
"version": "v1"
}
] | 2015-05-05 | [
[
"Teruel",
"Ginés R. Pérez",
""
]
] | In this work we revisit the study of the gravitational interaction in the context of the Special Theory of Relativity. It is found that, as long as the equivalence principle is respected, a relativistic non-linear energy conservation theorem arises in a natural way. We interpret that this non-linear conservation law stresses the non-linear character of the gravitational interaction.The theorem reproduces the energy conservation theorem of Newtonian mechanics in the corresponding low energy limit, but also allows to derive some standard results of post-Newtonian gravity, such as the formula of the gravitational redshift. Guided by this conservation law, we develop a Lagrangian formalism for a particle in a gravitational field. We realize that the Lagrangian can be written in an explicit covariant fashion, and turns out to be the geodesic Lagrangian of a curved Lorentzian manifold. Therefore, any attempt to describe gravity within the Special Theory, leads outside their own domains towards a curved space-time. Thus, the pedagogical content of the paper may be useful as a starting point to discuss the problem of Gravitation in the context of the Special Theory, as a preliminary step before introducing General Relativity. |
1303.5602 | Supriya Pan | Supriya Pan and Subenoy Chakraborty | Will there be again a transition from acceleration to deceleration in
course of the dark energy evolution of the universe? | 15 pages, 3 figures, 1 table | Eur. Phys. J. C (2013) 73:2575 | 10.1140/epjc/s10052-013-2575-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we consider the evolution of the interactive dark fluids in the
background of homogeneous and isotropic FRW model of the universe. The dark
fluids consist of a warm dark matter and a dark energy and both are described
as perfect fluid with barotropic equation of state. The dark species interact
non-gravitationally through an additional term in the energy conservation
equations. An autonomous system is formed in the energy density spaces and
fixed points are analyzed. A general expression for the deceleration parameter
has been obtained and it is possible to have more than one zero of the
deceleration parameter. Finally, vanishing of the deceleration parameter has
been examined with some examples.
| [
{
"created": "Fri, 22 Mar 2013 12:57:38 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Apr 2013 11:07:46 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Sep 2013 11:16:28 GMT",
"version": "v3"
}
] | 2013-10-01 | [
[
"Pan",
"Supriya",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this work we consider the evolution of the interactive dark fluids in the background of homogeneous and isotropic FRW model of the universe. The dark fluids consist of a warm dark matter and a dark energy and both are described as perfect fluid with barotropic equation of state. The dark species interact non-gravitationally through an additional term in the energy conservation equations. An autonomous system is formed in the energy density spaces and fixed points are analyzed. A general expression for the deceleration parameter has been obtained and it is possible to have more than one zero of the deceleration parameter. Finally, vanishing of the deceleration parameter has been examined with some examples. |
2107.05609 | Maximiliano Isi | Maximiliano Isi and Will M. Farr | Analyzing black-hole ringdowns | 34 pages and 35 figures, plus appendices | null | null | LIGO-P2100227 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | A perturbed black hole rings down by emitting gravitational waves in tones
with specific frequencies and durations. Such tones encode prized information
about the geometry of the source spacetime and the fundamental nature of
gravity, making the measurement of black hole ringdowns a key goal of
gravitational wave astronomy. However, this task is plagued by technical
challenges that invalidate the naive application of standard data analysis
methods and complicate sensitivity projections. In this paper, we provide a
comprehensive account of the formalism required to properly carry out ringdown
analyses, examining in detail the foundations of recent observational results,
and providing a framework for future measurements. We build on those insights
to clarify the concepts of ringdown detectability and resolvability -- touching
on the drawbacks of both Bayes factors and naive Fisher matrix approaches --
and find that overly pessimistic heuristics have led previous works to
underestimate the role of ringdown overtones for black hole spectroscopy. We
put our framework to work on the analysis of a variety of simulated signals in
colored noise, including analytic injections and a numerical relativity
simulation consistent with GW150914. We demonstrate that we can use tones of
the quadrupolar angular harmonic to test the no-hair theorem at current
sensitivity, with precision comparable to published constraints from real data.
Finally, we assess the role of modeling systematics, and project measurements
for future, louder signals. We release ringdown, a Python library for analyzing
black hole ringdowns using the the methods discussed in this paper, under a
permissive open-source license at https://github.com/maxisi/ringdown
| [
{
"created": "Mon, 12 Jul 2021 17:45:56 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jul 2021 19:32:35 GMT",
"version": "v2"
}
] | 2021-07-15 | [
[
"Isi",
"Maximiliano",
""
],
[
"Farr",
"Will M.",
""
]
] | A perturbed black hole rings down by emitting gravitational waves in tones with specific frequencies and durations. Such tones encode prized information about the geometry of the source spacetime and the fundamental nature of gravity, making the measurement of black hole ringdowns a key goal of gravitational wave astronomy. However, this task is plagued by technical challenges that invalidate the naive application of standard data analysis methods and complicate sensitivity projections. In this paper, we provide a comprehensive account of the formalism required to properly carry out ringdown analyses, examining in detail the foundations of recent observational results, and providing a framework for future measurements. We build on those insights to clarify the concepts of ringdown detectability and resolvability -- touching on the drawbacks of both Bayes factors and naive Fisher matrix approaches -- and find that overly pessimistic heuristics have led previous works to underestimate the role of ringdown overtones for black hole spectroscopy. We put our framework to work on the analysis of a variety of simulated signals in colored noise, including analytic injections and a numerical relativity simulation consistent with GW150914. We demonstrate that we can use tones of the quadrupolar angular harmonic to test the no-hair theorem at current sensitivity, with precision comparable to published constraints from real data. Finally, we assess the role of modeling systematics, and project measurements for future, louder signals. We release ringdown, a Python library for analyzing black hole ringdowns using the the methods discussed in this paper, under a permissive open-source license at https://github.com/maxisi/ringdown |
2101.02125 | Giacomo Gradenigo | Giacomo Gradenigo, Roberto Livi | Symplectic quantization I: dynamics of quantum fluctuations in a
relativistic field theory | 7 pages | Found. Phys. 51, 66 (2021) | 10.1007/s10701-021-00470-9 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose here a new symplectic quantization scheme, where quantum
fluctuations of a scalar field theory stem from two main assumptions:
relativistic invariance and equiprobability of the field configurations with
identical value of the action. In this approach the fictitious time of
stochastic quantization becomes a genuine additional time variable, with
respect to the coordinate time of relativity. This proper time is associated to
a symplectic evolution in the action space, which allows one to investigate not
only asymptotic, i.e. equilibrium, properties of the theory, but also its
non-equilibrium transient evolution. In this paper, which is the first one in a
series of two, we introduce a formalism which will be applied to general
relativity in the companion work "Symplectic quantization II".
| [
{
"created": "Wed, 6 Jan 2021 16:35:32 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jan 2021 12:21:06 GMT",
"version": "v2"
},
{
"created": "Thu, 27 May 2021 20:45:18 GMT",
"version": "v3"
}
] | 2021-06-03 | [
[
"Gradenigo",
"Giacomo",
""
],
[
"Livi",
"Roberto",
""
]
] | We propose here a new symplectic quantization scheme, where quantum fluctuations of a scalar field theory stem from two main assumptions: relativistic invariance and equiprobability of the field configurations with identical value of the action. In this approach the fictitious time of stochastic quantization becomes a genuine additional time variable, with respect to the coordinate time of relativity. This proper time is associated to a symplectic evolution in the action space, which allows one to investigate not only asymptotic, i.e. equilibrium, properties of the theory, but also its non-equilibrium transient evolution. In this paper, which is the first one in a series of two, we introduce a formalism which will be applied to general relativity in the companion work "Symplectic quantization II". |
gr-qc/0507129 | Filimonova Irina V | V. Aldaya, E. Sanchez-Sastre | Lagrangian Formalism on Jet-Gauge and Jet-Diffeomorphism Groups: Towards
a Unification of Gravity with Internal Gauge Interactions | Plenary talk presented at Workshop on High Energy Physics&Field
Theory (Protvino, Russia, 2004) | null | null | HEPFT/2004/10 | gr-qc | null | In this talk the description of gauge theories associated with internal
symmetries is extended to the case in which the symmetry group is the
space-time translation group (recovering Einstein's theory) using the standard
jet-bundle formalism. We also reformulate these theories introducing the idea
of jet-gauge and jet-diffeomorphism groups. Finally, we attempt to a simple,
yet non-trivial, mixing of gravity and electromagnetism (or more general
internal interaction) by turning to gauge symmetry a central extension of the
Poincare group.
| [
{
"created": "Fri, 29 Jul 2005 07:16:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Aldaya",
"V.",
""
],
[
"Sanchez-Sastre",
"E.",
""
]
] | In this talk the description of gauge theories associated with internal symmetries is extended to the case in which the symmetry group is the space-time translation group (recovering Einstein's theory) using the standard jet-bundle formalism. We also reformulate these theories introducing the idea of jet-gauge and jet-diffeomorphism groups. Finally, we attempt to a simple, yet non-trivial, mixing of gravity and electromagnetism (or more general internal interaction) by turning to gauge symmetry a central extension of the Poincare group. |
0708.1233 | Gaurang Mahajan | Gaurang Mahajan, T. Padmanabhan | Particle creation, classicality and related issues in quantum field
theory: I. Formalism and toy models | RevTeX 4; 32 pages; 28 figures; first of a series of two papers, the
second being arXiv:0708.1237 [gr-qc]; high resolution figures available from
the authors on request | Gen.Rel.Grav. 40 (2008) 661-708 | 10.1007/s10714-007-0526-z | null | gr-qc astro-ph hep-th | null | The quantum theory of a harmonic oscillator with a time dependent frequency
arises in several important physical problems, especially in the study of
quantum field theory in an external background. While the mathematics of this
system is straightforward, several conceptual issues arise in such a study. We
present a general formalism to address some of the conceptual issues like the
emergence of classicality, definition of particle content, back reaction etc.
In particular, we parametrize the wave function in terms of a complex number
(which we call excitation parameter) and express all physically relevant
quantities in terms it. Many of the notions -- like those of particle number
density, effective Lagrangian etc., which are usually defined using asymptotic
in-out states -- are generalized as time-dependent concepts and we show that
these generalized definitions lead to useful and reasonable results. Having
developed the general formalism we apply it to several examples. Exact analytic
expressions are found for a particular toy model and approximate analytic
solutions are obtained in the extreme cases of adiabatic and highly
non-adiabatic evolution. We then work out the exact results numerically for a
variety of models and compare them with the analytic results and
approximations. The formalism is useful in addressing the question of emergence
of classicality of the quantum state, its relation to particle production and
to clarify several conceptual issues related to this. In Paper II
(arXiv:0708.1237), which is a sequel to this, the formalism will be applied to
analyze the corresponding issues in the context of quantum field theory in
background cosmological models and electric fields.
| [
{
"created": "Thu, 9 Aug 2007 10:16:29 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Mahajan",
"Gaurang",
""
],
[
"Padmanabhan",
"T.",
""
]
] | The quantum theory of a harmonic oscillator with a time dependent frequency arises in several important physical problems, especially in the study of quantum field theory in an external background. While the mathematics of this system is straightforward, several conceptual issues arise in such a study. We present a general formalism to address some of the conceptual issues like the emergence of classicality, definition of particle content, back reaction etc. In particular, we parametrize the wave function in terms of a complex number (which we call excitation parameter) and express all physically relevant quantities in terms it. Many of the notions -- like those of particle number density, effective Lagrangian etc., which are usually defined using asymptotic in-out states -- are generalized as time-dependent concepts and we show that these generalized definitions lead to useful and reasonable results. Having developed the general formalism we apply it to several examples. Exact analytic expressions are found for a particular toy model and approximate analytic solutions are obtained in the extreme cases of adiabatic and highly non-adiabatic evolution. We then work out the exact results numerically for a variety of models and compare them with the analytic results and approximations. The formalism is useful in addressing the question of emergence of classicality of the quantum state, its relation to particle production and to clarify several conceptual issues related to this. In Paper II (arXiv:0708.1237), which is a sequel to this, the formalism will be applied to analyze the corresponding issues in the context of quantum field theory in background cosmological models and electric fields. |
1405.2783 | Christian Gr\~Af | C. Gr\"af, B. W. Barr, A. S. Bell, F. Campbell, A. V. Cumming, S. L.
Danilishin, N. A. Gordon, G. D. Hammond, J. Hennig, E. A. Houston, S. H.
Huttner, R. A. Jones, S. S. Leavey, H. L\"uck, J. Macarthur, M. Marwick, S.
Rigby, R. Schilling, B. Sorazu, A. Spencer, S. Steinlechner, K. A. Strain and
S. Hild | Design of a speed meter interferometer proof-of-principle experiment | Revised version: 16 pages, 6 figures | Class. Quantum Grav. 31 215009 (2014) | 10.1088/0264-9381/31/21/215009 | null | gr-qc physics.optics quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The second generation of large scale interferometric gravitational wave
detectors will be limited by quantum noise over a wide frequency range in their
detection band. Further sensitivity improvements for future upgrades or new
detectors beyond the second generation motivate the development of measurement
schemes to mitigate the impact of quantum noise in these instruments. Two
strands of development are being pursued to reach this goal, focusing both on
modifications of the well-established Michelson detector configuration and
development of different detector topologies. In this paper, we present the
design of the world's first Sagnac speed meter interferometer which is
currently being constructed at the University of Glasgow. With this
proof-of-principle experiment we aim to demonstrate the theoretically predicted
lower quantum noise in a Sagnac interferometer compared to an equivalent
Michelson interferometer, to qualify Sagnac speed meters for further research
towards an implementation in a future generation large scale gravitational wave
detector, such as the planned Einstein Telescope observatory.
| [
{
"created": "Mon, 12 May 2014 14:38:18 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Sep 2014 15:49:14 GMT",
"version": "v2"
}
] | 2016-08-08 | [
[
"Gräf",
"C.",
""
],
[
"Barr",
"B. W.",
""
],
[
"Bell",
"A. S.",
""
],
[
"Campbell",
"F.",
""
],
[
"Cumming",
"A. V.",
""
],
[
"Danilishin",
"S. L.",
""
],
[
"Gordon",
"N. A.",
""
],
[
"Hammond",
"G. D.",
""
],
[
"Hennig",
"J.",
""
],
[
"Houston",
"E. A.",
""
],
[
"Huttner",
"S. H.",
""
],
[
"Jones",
"R. A.",
""
],
[
"Leavey",
"S. S.",
""
],
[
"Lück",
"H.",
""
],
[
"Macarthur",
"J.",
""
],
[
"Marwick",
"M.",
""
],
[
"Rigby",
"S.",
""
],
[
"Schilling",
"R.",
""
],
[
"Sorazu",
"B.",
""
],
[
"Spencer",
"A.",
""
],
[
"Steinlechner",
"S.",
""
],
[
"Strain",
"K. A.",
""
],
[
"Hild",
"S.",
""
]
] | The second generation of large scale interferometric gravitational wave detectors will be limited by quantum noise over a wide frequency range in their detection band. Further sensitivity improvements for future upgrades or new detectors beyond the second generation motivate the development of measurement schemes to mitigate the impact of quantum noise in these instruments. Two strands of development are being pursued to reach this goal, focusing both on modifications of the well-established Michelson detector configuration and development of different detector topologies. In this paper, we present the design of the world's first Sagnac speed meter interferometer which is currently being constructed at the University of Glasgow. With this proof-of-principle experiment we aim to demonstrate the theoretically predicted lower quantum noise in a Sagnac interferometer compared to an equivalent Michelson interferometer, to qualify Sagnac speed meters for further research towards an implementation in a future generation large scale gravitational wave detector, such as the planned Einstein Telescope observatory. |
0808.1262 | Giovanni Marozzi Dr. | S. E. Joras and G. Marozzi | Trans-Planckian Physics from a Nonlinear Dispersion Relation | 11 pages, 10 figures. Some changes made, comments and references
added, a figure added, typos corrected, conclusions unchanged, version
accepted for pubblication in Phys. Rev. D | Phys.Rev.D79:023514,2009 | 10.1103/PhysRevD.79.023514 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a particular nonlinear dispersion relation $\omega_p(k_p)$ -- a
series expansion in the physical wavenumber $k_p$ -- for modeling first-order
corrections in the equation of motion of a test scalar field in a de Sitter
spacetime from trans-Planckian physics in cosmology. Using both a numerical
approach and a semianalytical one, we show that the WKB approximation
previously adopted in the literature should be used with caution, since it
holds only when the comoving wavenumber $k\gg aH$. We determine the amplitude
and behavior of the corrections on the power spectrum for this test field.
Furthermore, we consider also a more realistic model of inflation, the
power-law model, using only a numerical approach to determine the corrections
on the power spectrum.
| [
{
"created": "Fri, 8 Aug 2008 18:16:23 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jan 2009 16:56:00 GMT",
"version": "v2"
}
] | 2009-02-26 | [
[
"Joras",
"S. E.",
""
],
[
"Marozzi",
"G.",
""
]
] | We study a particular nonlinear dispersion relation $\omega_p(k_p)$ -- a series expansion in the physical wavenumber $k_p$ -- for modeling first-order corrections in the equation of motion of a test scalar field in a de Sitter spacetime from trans-Planckian physics in cosmology. Using both a numerical approach and a semianalytical one, we show that the WKB approximation previously adopted in the literature should be used with caution, since it holds only when the comoving wavenumber $k\gg aH$. We determine the amplitude and behavior of the corrections on the power spectrum for this test field. Furthermore, we consider also a more realistic model of inflation, the power-law model, using only a numerical approach to determine the corrections on the power spectrum. |
2311.03274 | Abhishek Sharma | Abhishek Sharma, Soumen Roy, and Anand S. Sengupta | Template bank to search for exotic gravitational wave signals from
astrophysical compact binaries | 16 pages, 8 figures | Physical Review D (Vol. 109, No. 12), 2024 | 10.1103/PhysRevD.109.124049 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modeled searches of gravitational wave signals from compact binary mergers
rely on template waveforms determined by the theory of general relativity (GR).
Once a signal is detected, one generally performs the model agnostic test of
GR, either looking for consistency between the GR waveform and data or
introducing phenomenological deviations to detect the departure from GR. The
non-trivial presence of beyond-GR physics can alter the waveform and could be
missed by the GR template-based searches. A recent study [Phys. Rev. D 107,
024017 (2023)] targeted the binary black hole merger, assuming the parametrized
deviation in lower post-Newtonian terms and demonstrated a mild effect on the
search sensitivity. Surprisingly, for the search space of binary neutron star
(BNS) systems where component masses range from 1 to $2.4\:\rm{M}_\odot$ and
parametrized deviations span $1\sigma$ width of the deviation parameters
measured from the GW170817 event, the GR template bank is highly ineffectual
for detecting the non-GR signals. Here, we present a new hybrid method to
construct a non-GR template bank for the BNS search space. The hybrid method
uses the geometric approach of three-dimensional lattice placement to cover
most of the parameter space volume, followed by the random method to cover the
boundary regions of parameter space. We find that the non-GR bank size is
$\sim$15 times larger than the conventional GR bank and is effectual towards
detecting non-GR signals in the target search space.
| [
{
"created": "Mon, 6 Nov 2023 17:17:01 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2024 18:04:19 GMT",
"version": "v2"
}
] | 2024-06-27 | [
[
"Sharma",
"Abhishek",
""
],
[
"Roy",
"Soumen",
""
],
[
"Sengupta",
"Anand S.",
""
]
] | Modeled searches of gravitational wave signals from compact binary mergers rely on template waveforms determined by the theory of general relativity (GR). Once a signal is detected, one generally performs the model agnostic test of GR, either looking for consistency between the GR waveform and data or introducing phenomenological deviations to detect the departure from GR. The non-trivial presence of beyond-GR physics can alter the waveform and could be missed by the GR template-based searches. A recent study [Phys. Rev. D 107, 024017 (2023)] targeted the binary black hole merger, assuming the parametrized deviation in lower post-Newtonian terms and demonstrated a mild effect on the search sensitivity. Surprisingly, for the search space of binary neutron star (BNS) systems where component masses range from 1 to $2.4\:\rm{M}_\odot$ and parametrized deviations span $1\sigma$ width of the deviation parameters measured from the GW170817 event, the GR template bank is highly ineffectual for detecting the non-GR signals. Here, we present a new hybrid method to construct a non-GR template bank for the BNS search space. The hybrid method uses the geometric approach of three-dimensional lattice placement to cover most of the parameter space volume, followed by the random method to cover the boundary regions of parameter space. We find that the non-GR bank size is $\sim$15 times larger than the conventional GR bank and is effectual towards detecting non-GR signals in the target search space. |
gr-qc/9908065 | Djordje Sijacki | I. Miskovic and Dj. Sijacki | Dirac-like Affine Fields in 3D | 4 pages, TeX; Talk given at the XI Yugoslav Symposium on Nuclear and
Particle Physics, Studenica, September 1998 | SFIN, XI A2 (1998) | null | null | gr-qc | null | A generalization of the Dirac field equation in three-dimensional Minkowski
space-time to the case of the $\bar{SL}(3,R)$ $\subset$ $\bar{SA}(3,R)$
symmetry is considered. Constraints that ensure a correct physical
interpretation of the corresponding particle states are presented. Dirac-like
equations based on both multiplicity-free and generic infinite-component
$\bar{SL}(3,R)$ representations are outlined.
| [
{
"created": "Wed, 25 Aug 1999 12:26:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Miskovic",
"I.",
""
],
[
"Sijacki",
"Dj.",
""
]
] | A generalization of the Dirac field equation in three-dimensional Minkowski space-time to the case of the $\bar{SL}(3,R)$ $\subset$ $\bar{SA}(3,R)$ symmetry is considered. Constraints that ensure a correct physical interpretation of the corresponding particle states are presented. Dirac-like equations based on both multiplicity-free and generic infinite-component $\bar{SL}(3,R)$ representations are outlined. |
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