id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1007.3040 | Francisco Lobo | Nadiezhda Montelongo Garcia, Francisco S. N. Lobo | Wormhole geometries supported by a nonminimal curvature-matter coupling | 8 pages, 3 figures. V2: 9 pages, error and typos corrected;
discussion and references added; to appear in PRD | Phys.Rev.D82:104018,2010 | 10.1103/PhysRevD.82.104018 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormhole geometries in curvature-matter coupled modified gravity are
explored, by considering an explicit nonminimal coupling between an arbitrary
function of the scalar curvature, R, and the Lagrangian density of matter. It
is the effective stress-energy tensor containing the coupling between matter
and the higher order curvature derivatives that is responsible for the null
energy condition violation, and consequently for supporting the respective
wormhole geometries. The general restrictions imposed by the null energy
condition violation are presented in the presence of a nonminimal R-matter
coupling. Furthermore, obtaining exact solutions to the gravitational field
equations is extremely difficult due to the nonlinearity of the equations,
although the problem is mathematically well-defined. Thus, we outline several
approaches for finding wormhole solutions, and deduce an exact solution by
considering a linear R nonmiminal curvature-matter coupling and by considering
an explicit monotonically decreasing function for the energy density. Although
it is difficult to find exact solutions of matter threading the wormhole
satisfying the energy conditions at the throat, an exact solution is found
where the nonminimal coupling does indeed minimize the violation of the null
energy condition of normal matter at the throat.
| [
{
"created": "Sun, 18 Jul 2010 21:25:29 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Oct 2010 21:20:30 GMT",
"version": "v2"
}
] | 2010-11-09 | [
[
"Garcia",
"Nadiezhda Montelongo",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | Wormhole geometries in curvature-matter coupled modified gravity are explored, by considering an explicit nonminimal coupling between an arbitrary function of the scalar curvature, R, and the Lagrangian density of matter. It is the effective stress-energy tensor containing the coupling between matter and the higher order curvature derivatives that is responsible for the null energy condition violation, and consequently for supporting the respective wormhole geometries. The general restrictions imposed by the null energy condition violation are presented in the presence of a nonminimal R-matter coupling. Furthermore, obtaining exact solutions to the gravitational field equations is extremely difficult due to the nonlinearity of the equations, although the problem is mathematically well-defined. Thus, we outline several approaches for finding wormhole solutions, and deduce an exact solution by considering a linear R nonmiminal curvature-matter coupling and by considering an explicit monotonically decreasing function for the energy density. Although it is difficult to find exact solutions of matter threading the wormhole satisfying the energy conditions at the throat, an exact solution is found where the nonminimal coupling does indeed minimize the violation of the null energy condition of normal matter at the throat. |
1301.3049 | Lorenzo Sebastiani | K. Bamba (1), A. Lopez-Revelles (2, 5), R. Myrzakulov (6), S.D.
Odintsov (2, 3, 4, 6) and L. Sebastiani (5, 6) ((1) KMI, Nagoya University,
Nagoya, Japan, (2) ICE/CSIC-IEEC, Bellaterram, Barcelona, Spain, (3) ICREA,
Barcelona, Spain, (4) TSPU, Tomsk, Russia (5) Dipartimento di Fisica,
Universit`a di Trento, Italia, (6) Department of General & Theoretical
Physics, Eurasian National University, Astana, Kazakhstan) | The universe evolution in exponential $F(R)$-gravity | Proceedings of QFTG2013, published in TSPU Bulletin 3 (128), 2012, n
13 p.19-24 | TSPU Bulletin 2012 (2012) 13, 22-27 | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generic feature of viable exponential $F(R)$-gravity is investigated. An
additional modification to stabilize the effective dark energy oscillations
during matter era is proposed and applied to two viable models. An analysis on
the future evolution of the universe is performed. Furthermore, a unified model
for early and late-time acceleration is proposed and studied.
| [
{
"created": "Mon, 14 Jan 2013 16:46:27 GMT",
"version": "v1"
}
] | 2015-09-21 | [
[
"Bamba",
"K.",
""
],
[
"Lopez-Revelles",
"A.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Sebastiani",
"L.",
""
]
] | A generic feature of viable exponential $F(R)$-gravity is investigated. An additional modification to stabilize the effective dark energy oscillations during matter era is proposed and applied to two viable models. An analysis on the future evolution of the universe is performed. Furthermore, a unified model for early and late-time acceleration is proposed and studied. |
gr-qc/0504068 | Leonardo Gualtieri | Omar Benhar, Valeria Ferrari, Leonardo Gualtieri, Stefania Marassi | Perturbative approach to the structure of rapidly rotating neutron stars | 17 pages, 5 figures, minor changes to match version accepted by Phys.
Rev. D | Phys.Rev. D72 (2005) 044028 | 10.1103/PhysRevD.72.044028 | null | gr-qc astro-ph | null | We construct models of rotating stars using the perturbative approach
introduced by J. Hartle in 1967, and a set of equations of state proposed to
model hadronic interactions in the inner core of neutron stars. We integrate
the equations of stellar structure to third order in the angular velocity and
show, comparing our results to those obtained with fully non linear codes, to
what extent third order corrections are needed to accurately reproduce the
moment of inertia of a star which rotates at rates comparable to that of the
fastest isolated pulsars.
| [
{
"created": "Fri, 15 Apr 2005 11:38:37 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2005 12:54:57 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Benhar",
"Omar",
""
],
[
"Ferrari",
"Valeria",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Marassi",
"Stefania",
""
]
] | We construct models of rotating stars using the perturbative approach introduced by J. Hartle in 1967, and a set of equations of state proposed to model hadronic interactions in the inner core of neutron stars. We integrate the equations of stellar structure to third order in the angular velocity and show, comparing our results to those obtained with fully non linear codes, to what extent third order corrections are needed to accurately reproduce the moment of inertia of a star which rotates at rates comparable to that of the fastest isolated pulsars. |
2301.12370 | Omar Mustafa | Omar Mustafa | PDM KG-Coulombic particles in cosmic string rainbow gravity spacetime
and a uniform magnetic field | 14 pages, 8 figures. arXiv admin note: substantial text overlap with
arXiv:2301.05464 | Phys. Lett. B 839 (2023) 137793 | 10.1016/j.physletb.2023.137793 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Klein-Gordon (KG) particles in cosmic string rainbow gravity spacetime and a
uniform magnetic field are studied in the context of the so called,
metaphorically speaking, position-dependent mass (PDM) settings. We show that
the corresponding KG-equation collapses into a two-dimensional radial
Schr\"{o}dinger-Coulomb like model. The exact textbook solution of which is
used to find the energies and wave functions of KG-Coulombic particles (both
constant mass and PDM ones). In so doing, we consider, with $y=E/E_{P}$, four
pairs of rainbow functions: (a) $% g_{_{0}}\left( y\right) =1$, $g_{_{1}}\left(
y\right) =\sqrt{1-\epsilon y^{2}% }$, (b) $g_{_{0}}\left( y\right) =1$,
$g_{_{1}}\left( y\right) =\sqrt{% 1-\epsilon y}$, (c) $g_{_{0}}\left( y\right)
=g_{_{1}}\left( y\right) =\left( 1-\epsilon y\right) ^{-1}$, and (d) $g_{_{0}}(
y) =(e^{\epsilon y}-1) /\epsilon y$, $g_{_{1}}\left( y\right) =1$.
Interestingly, we observe that the first pair in (a) introduces the Planck
energy $E_{p}$ as a maximum possible KG-particle/antiparticle energy value.
| [
{
"created": "Sun, 29 Jan 2023 06:16:48 GMT",
"version": "v1"
}
] | 2023-04-17 | [
[
"Mustafa",
"Omar",
""
]
] | Klein-Gordon (KG) particles in cosmic string rainbow gravity spacetime and a uniform magnetic field are studied in the context of the so called, metaphorically speaking, position-dependent mass (PDM) settings. We show that the corresponding KG-equation collapses into a two-dimensional radial Schr\"{o}dinger-Coulomb like model. The exact textbook solution of which is used to find the energies and wave functions of KG-Coulombic particles (both constant mass and PDM ones). In so doing, we consider, with $y=E/E_{P}$, four pairs of rainbow functions: (a) $% g_{_{0}}\left( y\right) =1$, $g_{_{1}}\left( y\right) =\sqrt{1-\epsilon y^{2}% }$, (b) $g_{_{0}}\left( y\right) =1$, $g_{_{1}}\left( y\right) =\sqrt{% 1-\epsilon y}$, (c) $g_{_{0}}\left( y\right) =g_{_{1}}\left( y\right) =\left( 1-\epsilon y\right) ^{-1}$, and (d) $g_{_{0}}( y) =(e^{\epsilon y}-1) /\epsilon y$, $g_{_{1}}\left( y\right) =1$. Interestingly, we observe that the first pair in (a) introduces the Planck energy $E_{p}$ as a maximum possible KG-particle/antiparticle energy value. |
2305.11224 | Dongjun Li | Mathew W. Bub, Yanbei Chen, Yufeng Du, Dongjun Li, Yiwen Zhang,
Kathryn M. Zurek | Quantum Gravity Background in Next-Generation Gravitational Wave
Detectors | 19 pages, 9 figures | null | null | CALT-TH-2023-012 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effects of geontropic vacuum fluctuations in quantum gravity on
next-generation terrestrial gravitational wave detectors. If the VZ effect
proposed in Ref. [1], as modeled in Refs. [2, 3], appears in the upcoming
GQuEST experiment, we show that it will be a large background for astrophysical
gravitational wave searches in observatories like Cosmic Explorer and the
Einstein Telescope.
| [
{
"created": "Thu, 18 May 2023 18:00:05 GMT",
"version": "v1"
}
] | 2023-05-22 | [
[
"Bub",
"Mathew W.",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Du",
"Yufeng",
""
],
[
"Li",
"Dongjun",
""
],
[
"Zhang",
"Yiwen",
""
],
[
"Zurek",
"Kathryn M.",
""
]
] | We study the effects of geontropic vacuum fluctuations in quantum gravity on next-generation terrestrial gravitational wave detectors. If the VZ effect proposed in Ref. [1], as modeled in Refs. [2, 3], appears in the upcoming GQuEST experiment, we show that it will be a large background for astrophysical gravitational wave searches in observatories like Cosmic Explorer and the Einstein Telescope. |
0706.2749 | Khireddine Nouicer | Khireddine Nouicer | Black holes thermodynamics to all orders in the Planck length in extra
dimensions | 21 pages, 6 figures, 1 table; Figure 2 replaced and section 4
improved | Class.Quant.Grav.24:5917-5934,2007; Erratum-ibid.24:6435,2007 | 10.1088/0264-9381/24/23/014 10.1088/0264-9381/24/24/C02 | null | gr-qc | null | We investigate the effects to all orders in the Planck length, from a
generalized uncertainty principle, on the thermodynamic parameters of radiating
Schwarzschild black holes in a scenario with large extra dimesions. We show
that black holes in this framework are hotter, decay faster and are less
classical objects. Particularly, we show that the final stage of the radiation
process is a black hole remnant with zero entropy, zero heat capacity and non
zero finite temperature. We finally compare our results with the ones obtained
in the standard Hawking picture and with the generalized uncertainty principle
to leading order in the Planck length.
| [
{
"created": "Tue, 19 Jun 2007 09:44:51 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Nov 2007 11:57:33 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Nov 2007 12:20:45 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Nouicer",
"Khireddine",
""
]
] | We investigate the effects to all orders in the Planck length, from a generalized uncertainty principle, on the thermodynamic parameters of radiating Schwarzschild black holes in a scenario with large extra dimesions. We show that black holes in this framework are hotter, decay faster and are less classical objects. Particularly, we show that the final stage of the radiation process is a black hole remnant with zero entropy, zero heat capacity and non zero finite temperature. We finally compare our results with the ones obtained in the standard Hawking picture and with the generalized uncertainty principle to leading order in the Planck length. |
1602.00851 | Ichiro Oda | Ichiro Oda | Induced Gravity from Curvature Density Preserving Diffeomorphisms | 8 pages | null | null | DPUR/TH/46 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct not only an induced gravity model with the restricted
diffeomorphisms, that is, transverse diffeomorphisms which preserves the
curvature density, but also that with the full diffeomorphisms. By solving the
equations of motion, it turns out that these models produce Einstein's
equations with a certain Newton's constant in addition to the constraint for
the curvature density. In the limit of the infinite Newton constant, the models
give rise to induced gravity. Moreover, we discuss cosmological solutions on
the basis of the gravitational models at hand.
| [
{
"created": "Tue, 2 Feb 2016 09:39:53 GMT",
"version": "v1"
}
] | 2016-02-03 | [
[
"Oda",
"Ichiro",
""
]
] | We construct not only an induced gravity model with the restricted diffeomorphisms, that is, transverse diffeomorphisms which preserves the curvature density, but also that with the full diffeomorphisms. By solving the equations of motion, it turns out that these models produce Einstein's equations with a certain Newton's constant in addition to the constraint for the curvature density. In the limit of the infinite Newton constant, the models give rise to induced gravity. Moreover, we discuss cosmological solutions on the basis of the gravitational models at hand. |
1707.06458 | Katherine Jones-Smith | Lillie Ogden, Katherine Jones-Smith, Harsh Mathur and Kevin Rovelli | An Electrostatic Analogy for Symmetron Gravity | Matches journal version; notably this version has a clarified
discussion of the possibility of a net repulsive force in Section II F | Phys. Rev. D 96, 124029 (2017) | 10.1103/PhysRevD.96.124029 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The symmetron model is a scalar-tensor theory of gravity with a screening
mechanism that suppresses the effect of the symmetron field at high densities
characteristic of the solar system and laboratory scales but allows it to act
with gravitational strength at low density on the cosmological scale. We
elucidate the screening mechanism by showing that in the quasi-static Newtonian
limit there are precise analogies between symmetron gravity and electrostatics
for both strong and weak screening. For strong screening we find that large
dense bodies behave in a manner analogous to perfect conductors in
electrostatics. Based on this analogy we find that the symmetron field exhibits
a lightning rod effect wherein the field gradients are enhanced near the ends
of pointed or elongated objects. An ellipsoid placed in a uniform symmetron
gradient is shown to experience a torque. By symmetry there is no gravitational
torque in this case. Hence this effect unmasks the symmetron and might serve as
the basis for future laboratory experiments. The symmetron force between a
point mass and a large dense body includes a component corresponding to the
interaction of the point mass with its image in the larger body. None of these
effects have counterparts in the Newtonian limit of Einstein gravity. We
discuss the similarities between symmetron gravity and the chameleon model as
well as the differences between the two.
| [
{
"created": "Wed, 19 Jul 2017 16:10:53 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Aug 2017 03:46:42 GMT",
"version": "v2"
},
{
"created": "Sun, 31 Dec 2017 23:32:23 GMT",
"version": "v3"
}
] | 2018-01-03 | [
[
"Ogden",
"Lillie",
""
],
[
"Jones-Smith",
"Katherine",
""
],
[
"Mathur",
"Harsh",
""
],
[
"Rovelli",
"Kevin",
""
]
] | The symmetron model is a scalar-tensor theory of gravity with a screening mechanism that suppresses the effect of the symmetron field at high densities characteristic of the solar system and laboratory scales but allows it to act with gravitational strength at low density on the cosmological scale. We elucidate the screening mechanism by showing that in the quasi-static Newtonian limit there are precise analogies between symmetron gravity and electrostatics for both strong and weak screening. For strong screening we find that large dense bodies behave in a manner analogous to perfect conductors in electrostatics. Based on this analogy we find that the symmetron field exhibits a lightning rod effect wherein the field gradients are enhanced near the ends of pointed or elongated objects. An ellipsoid placed in a uniform symmetron gradient is shown to experience a torque. By symmetry there is no gravitational torque in this case. Hence this effect unmasks the symmetron and might serve as the basis for future laboratory experiments. The symmetron force between a point mass and a large dense body includes a component corresponding to the interaction of the point mass with its image in the larger body. None of these effects have counterparts in the Newtonian limit of Einstein gravity. We discuss the similarities between symmetron gravity and the chameleon model as well as the differences between the two. |
1304.4297 | Jos\'e Villanueva PhD | Marco Olivares, Germ\'an Rojas, Yerko V\'asquez and J. R. Villanueva | Particles motion on topological Lifshitz black holes in 3+1 dimensions | 8 figures | null | 10.1007/s10509-013-1496-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we study the causal structure of a topological black
hole presented by Mann R. B. JHEP 06, 075 (2009) by mean the standard
Lagrangian procedure, which allow us analyze qualitatively the behavior of test
particles using the effective potential. Then, the geodesic motion of massive
and massless particles is obtained analytically. We find that confined orbits
are forbidden on this spacetime, however radial photons can escape to infinity
in an infinite proper time but in a finite coordinate time, this correspond to
an interesting and novel result.
| [
{
"created": "Mon, 15 Apr 2013 23:46:39 GMT",
"version": "v1"
}
] | 2013-06-26 | [
[
"Olivares",
"Marco",
""
],
[
"Rojas",
"Germán",
""
],
[
"Vásquez",
"Yerko",
""
],
[
"Villanueva",
"J. R.",
""
]
] | In the present paper we study the causal structure of a topological black hole presented by Mann R. B. JHEP 06, 075 (2009) by mean the standard Lagrangian procedure, which allow us analyze qualitatively the behavior of test particles using the effective potential. Then, the geodesic motion of massive and massless particles is obtained analytically. We find that confined orbits are forbidden on this spacetime, however radial photons can escape to infinity in an infinite proper time but in a finite coordinate time, this correspond to an interesting and novel result. |
gr-qc/0404125 | Valerii Dryuma sem | V.Dryuma | On the Riemann Extension of the Schwarzschild Metric | 12 pages | Bul.Acad.Sti.Rep.Moldova (Fiz.Teh.) 3 (2003) 92-103 | null | null | gr-qc | null | Some solutions of the Einstein equations for the eight-dimensional Riemann
extension of the classical four-dimensional Schwarzschild metric are
considered.
| [
{
"created": "Fri, 30 Apr 2004 08:20:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dryuma",
"V.",
""
]
] | Some solutions of the Einstein equations for the eight-dimensional Riemann extension of the classical four-dimensional Schwarzschild metric are considered. |
1602.04395 | Yen Chin Ong | Yen Chin Ong | Black Hole: The Interior Spacetime | Proceedings for the 2nd LeCosPA Symposium: "Everything about Gravity:
Celebrating the Centenary of Einstein's General Relativity", based on a talk
given on 17 December 2015, Taipei | null | 10.1142/9789813203952_0081 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The information loss paradox is often discussed from the perspective of the
observers who stay outside of a black hole. However, the interior spacetime of
a black hole can be rather nontrivial. We discuss the open problems regarding
the volume of a black hole, and whether it plays any role in information
storage. We also emphasize the importance of resolving the black hole
singularity, if one were to resolve the information loss paradox.
| [
{
"created": "Sat, 13 Feb 2016 22:49:38 GMT",
"version": "v1"
}
] | 2019-02-27 | [
[
"Ong",
"Yen Chin",
""
]
] | The information loss paradox is often discussed from the perspective of the observers who stay outside of a black hole. However, the interior spacetime of a black hole can be rather nontrivial. We discuss the open problems regarding the volume of a black hole, and whether it plays any role in information storage. We also emphasize the importance of resolving the black hole singularity, if one were to resolve the information loss paradox. |
gr-qc/0507079 | Serguei Krasnikov | S. Krasnikov | Evaporation induced traversability of the Einstein--Rosen wormhole | v.2 A bit of discussion has been added and a few references v.3
Insignificant changes to match the published version | Phys.Rev. D73 (2006) 084006 | 10.1103/PhysRevD.73.084006 | null | gr-qc astro-ph hep-th | null | Suppose, the Universe comes into existence (as classical spacetime) already
with an empty spherically symmetric macroscopic wormhole present in it.
Classically the wormhole would evolve into a part of the Schwarzschild space
and thus would not allow any signal to traverse it. I consider semiclassical
corrections to that picture and build a model of an evaporating wormhole. The
model is based on the assumption that the vacuum polarization and its
backreaction on the geometry of the wormhole are weak. The lack of information
about the era preceding the emergence of the wormhole results in appearance of
three parameters which -- along with the initial mass -- determine the
evolution of the wormhole. For some values of these parameters the wormhole
turns out to be long-lived enough to be traversed and to transform into a time
machine.
| [
{
"created": "Mon, 18 Jul 2005 22:40:24 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Dec 2005 17:44:01 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Nov 2006 23:24:00 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Krasnikov",
"S.",
""
]
] | Suppose, the Universe comes into existence (as classical spacetime) already with an empty spherically symmetric macroscopic wormhole present in it. Classically the wormhole would evolve into a part of the Schwarzschild space and thus would not allow any signal to traverse it. I consider semiclassical corrections to that picture and build a model of an evaporating wormhole. The model is based on the assumption that the vacuum polarization and its backreaction on the geometry of the wormhole are weak. The lack of information about the era preceding the emergence of the wormhole results in appearance of three parameters which -- along with the initial mass -- determine the evolution of the wormhole. For some values of these parameters the wormhole turns out to be long-lived enough to be traversed and to transform into a time machine. |
gr-qc/0002073 | Sawa Manoff | S. Manoff | (^-L_n,g)-spaces. Length of a vector field and the angle between two
vector fields | 12 pages, LaTeX 2.09 | null | null | null | gr-qc | null | The notions of length of a vector field and cosine of the angle between two
vector fields over a differentiable manifold with contravariant and covariant
affine connections and metrics are introduced and considered. The change of the
length of a vector field and of the angle between two vector fields along a
contravariant vector field are found. The introduced notions are necessary for
investigations of different types of transports over a manifold of the above
mentioned type.
| [
{
"created": "Tue, 22 Feb 2000 12:32:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Manoff",
"S.",
""
]
] | The notions of length of a vector field and cosine of the angle between two vector fields over a differentiable manifold with contravariant and covariant affine connections and metrics are introduced and considered. The change of the length of a vector field and of the angle between two vector fields along a contravariant vector field are found. The introduced notions are necessary for investigations of different types of transports over a manifold of the above mentioned type. |
1212.6095 | Kostiantyn Ropotenko | K. Ropotenko | Black hole motion in Euclidean space as a diffusion process II | 5 pages, no figures; v3: a Kerr-Newman black holea is described by
the canonical density matrix for a particle moving in a potential, not by the
grand canonical density matrix; title, abstract and text slightly changed;
results remains unchanged | Phys. Rev. D 87, 044037 (2013) | 10.1103/PhysRevD.87.044037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A diffusion equation approach to black hole thermodynamics in Euclidean
sector is proposed. A diffusion equation for a generic in Euclidean sector is
derived from the Bloch equation. Black hole thermodynamics is also derived and
it is found, in particular, that the entropy of a generic Kerr-Newman black
hole is the same, apart from the logarithmic corrections, as the
Bekenstein-Hawking entropy of the black hole.
| [
{
"created": "Tue, 25 Dec 2012 22:50:44 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Dec 2012 17:47:20 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Jan 2013 14:21:33 GMT",
"version": "v3"
}
] | 2013-03-26 | [
[
"Ropotenko",
"K.",
""
]
] | A diffusion equation approach to black hole thermodynamics in Euclidean sector is proposed. A diffusion equation for a generic in Euclidean sector is derived from the Bloch equation. Black hole thermodynamics is also derived and it is found, in particular, that the entropy of a generic Kerr-Newman black hole is the same, apart from the logarithmic corrections, as the Bekenstein-Hawking entropy of the black hole. |
2302.14641 | Hebin Zheng | He-Bin Zheng, Ping-Hui Mou, Yun-Xian Chen and Guo-Ping Li | Shadow Thermodynamics of AdS Black Hole with the Nonlinear
Electrodynamics Term | 17 pages, 21 figures | null | 10.1088/1674-1056/acc806 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have creatively employed the shadow radius to study the
thermodynamics of a charged AdS black hole with a nonlinear
electrodynamics(NLED) term. First, the connection between the shadow radius and
event horizon is constructed with the aid of the geodesic analysis. It turns
out that the black hole shadow radius shows a positive correlation as a
function of the event horizon radius. Then in the shadow context, we found that
the black hole temperature and heat capacity can be presented by the shadow
radius. And further analysis shows that the shadow radius can do as well as the
event horizon in revealing black hole phase transition process. In this sense,
we constructed the thermal profile of the charged AdS black hole with inclusion
of the NLED effect. In P < Pc case, it is found that the N-type trend of the
temperature given by the shadow radius is always coincide with that obtained by
using the event horizon. So, we can concluded for the charged AdS black hole
that the phase transition process can be intuitively presented as the thermal
profile in the shadow context. Finally, the effects of NLED have been carefully
analysed through out the paper.
| [
{
"created": "Mon, 27 Feb 2023 11:51:49 GMT",
"version": "v1"
}
] | 2023-08-16 | [
[
"Zheng",
"He-Bin",
""
],
[
"Mou",
"Ping-Hui",
""
],
[
"Chen",
"Yun-Xian",
""
],
[
"Li",
"Guo-Ping",
""
]
] | In this paper, we have creatively employed the shadow radius to study the thermodynamics of a charged AdS black hole with a nonlinear electrodynamics(NLED) term. First, the connection between the shadow radius and event horizon is constructed with the aid of the geodesic analysis. It turns out that the black hole shadow radius shows a positive correlation as a function of the event horizon radius. Then in the shadow context, we found that the black hole temperature and heat capacity can be presented by the shadow radius. And further analysis shows that the shadow radius can do as well as the event horizon in revealing black hole phase transition process. In this sense, we constructed the thermal profile of the charged AdS black hole with inclusion of the NLED effect. In P < Pc case, it is found that the N-type trend of the temperature given by the shadow radius is always coincide with that obtained by using the event horizon. So, we can concluded for the charged AdS black hole that the phase transition process can be intuitively presented as the thermal profile in the shadow context. Finally, the effects of NLED have been carefully analysed through out the paper. |
gr-qc/9706010 | Nils Andersson | Nils Andersson and Kostas D. Kokkotas | Pulsation modes for increasingly relativistic polytropes | submitted to MNRAS | Mon.Not.Roy.Astron.Soc. 297 (1998) 493 | 10.1046/j.1365-8711.1998.01541.x | null | gr-qc | null | We present the results of a numerical study of the fluid $f$, $p$ and the
gravitational $w$ modes for increasingly relativistic nonrotating polytropes.
The results for $f$ and $w$-modes are in good agreement with previous data for
uniform density stars, which supports an understanding of the nature of the
gravitational wave modes based on the uniform density data. We show that the
$p$-modes can become extremely long-lived for some relativistic stars. This
effect is attributed to the change in the perturbed density distribution as the
star becomes more compact.
| [
{
"created": "Tue, 3 Jun 1997 15:09:00 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Andersson",
"Nils",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | We present the results of a numerical study of the fluid $f$, $p$ and the gravitational $w$ modes for increasingly relativistic nonrotating polytropes. The results for $f$ and $w$-modes are in good agreement with previous data for uniform density stars, which supports an understanding of the nature of the gravitational wave modes based on the uniform density data. We show that the $p$-modes can become extremely long-lived for some relativistic stars. This effect is attributed to the change in the perturbed density distribution as the star becomes more compact. |
2406.05771 | Gabriel Farrugia | Gabriel Farrugia, Carlos Gafa', Jackson Levi Said | White Dwarf Envelops and Temperature Corrections in Exponential $f(T)$
Gravity | 14 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Compact stars have long served as a test bed of gravitational models and
their coupling with stellar matter. In this work, we explore the behavior of an
exponential model in f(T) gravity through the Tolman-Oppenheimer-Volkoff
equation. This is performed for different envelope thicknesses. Finally,
constraints on the models parameters are obtained, which are comparable to the
results obtained using cosmological survey data. This consistency across the
strong astrophysical and weak cosmological scales shows reasonable viability of
the underlying model.
| [
{
"created": "Sun, 9 Jun 2024 13:03:14 GMT",
"version": "v1"
}
] | 2024-06-11 | [
[
"Farrugia",
"Gabriel",
""
],
[
"Gafa'",
"Carlos",
""
],
[
"Said",
"Jackson Levi",
""
]
] | Compact stars have long served as a test bed of gravitational models and their coupling with stellar matter. In this work, we explore the behavior of an exponential model in f(T) gravity through the Tolman-Oppenheimer-Volkoff equation. This is performed for different envelope thicknesses. Finally, constraints on the models parameters are obtained, which are comparable to the results obtained using cosmological survey data. This consistency across the strong astrophysical and weak cosmological scales shows reasonable viability of the underlying model. |
2209.01186 | Daniel Vanzella | Daniel A. T. Vanzella | Gravity theories with local energy-momentum exchange: a closer look at
Rastall-like gravity | 21 pages, 11 figures. New version: Title slightly changed; revised
(particularly Sec. IV) to make it clearer that the model is not equivalent to
Rastall's original theory and how it avoids the criticisms which are used to
dismiss the latter | null | 10.1088/1361-6382/ace58a | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Einstein's famous equivalence principle is certainly one of the most striking
features of the gravitational interaction. In a strict reading, it states that
the effects of gravity can be made to disappear $locally$ by a convenient
choice of reference frame. As a consequence, no covariantly-defined
gravitational force should exist and energy-momentum of all matter and
interaction fields combined, with gravity $excluded$, should be locally
conserved. Although elegant, this separate conservation law represents a strong
constraint on the dynamics of a gravitating system and it is only logical to
question its naturality and observational basis. This is the purpose of the
present work. For concreteness sake, we analyze, in the context of metric
theories of gravity, the simplest phenomenological model which allows for local
energy-momentum exchange between the spacetime and matter/interaction fields
while preserving the seemingly more natural principle of general covariance.
This concrete model turns out to be a generalization of the socalled Rastall's
theory, with one important advantage: criticisms made to the latter, which are
often used to dismiss it as a viable or interesting model, do not apply to the
former in a universe containing "dark" ingredients, such as ours -- a
connection which seems to have been overlooked thus far. We conclude by
exploring the consequences of our Rastall-like model to standard (astrophysical
and cosmological) gravitational scenarios.
| [
{
"created": "Fri, 2 Sep 2022 17:31:51 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Feb 2023 12:57:15 GMT",
"version": "v2"
}
] | 2023-08-02 | [
[
"Vanzella",
"Daniel A. T.",
""
]
] | Einstein's famous equivalence principle is certainly one of the most striking features of the gravitational interaction. In a strict reading, it states that the effects of gravity can be made to disappear $locally$ by a convenient choice of reference frame. As a consequence, no covariantly-defined gravitational force should exist and energy-momentum of all matter and interaction fields combined, with gravity $excluded$, should be locally conserved. Although elegant, this separate conservation law represents a strong constraint on the dynamics of a gravitating system and it is only logical to question its naturality and observational basis. This is the purpose of the present work. For concreteness sake, we analyze, in the context of metric theories of gravity, the simplest phenomenological model which allows for local energy-momentum exchange between the spacetime and matter/interaction fields while preserving the seemingly more natural principle of general covariance. This concrete model turns out to be a generalization of the socalled Rastall's theory, with one important advantage: criticisms made to the latter, which are often used to dismiss it as a viable or interesting model, do not apply to the former in a universe containing "dark" ingredients, such as ours -- a connection which seems to have been overlooked thus far. We conclude by exploring the consequences of our Rastall-like model to standard (astrophysical and cosmological) gravitational scenarios. |
1210.0396 | Supriya Pan | Supriya Pan, Subhra Bhattacharya, and Subenoy Chakraborty | An analytic model for interacting dark energy and its observational
constraints | 14 pages, 7 figures, Published version | Mon. Not. R. Astron. Soc, 452, 3038-3046 (2015) | 10.1093/mnras/stv1495 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with a theoretical model for interacting dark energy. The
interaction between the cold dark matter (dust) and the dark energy has been
assumed to be non-gravitational in nature. Exact analytic cosmological
solutions are obtained both for constant and variable equation of state for
dark energy. It is found that, for very small value of the coupling parameter
(in the interaction term), the model asymptotically extends up to $\Lambda$CDM,
while the model can enter into the phantom domain asymptotically, if the
coupling parameter is not so small. Both the solutions are then analyzed with
194 Supernovae Type Ia data. The best fit parameters are shown with 1$\sigma$
and 2$\sigma$ confidence intervals. Finally, we have discussed the cosmographic
parameters for both the cases.
| [
{
"created": "Fri, 28 Sep 2012 05:28:30 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Nov 2012 13:25:39 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Feb 2013 12:14:40 GMT",
"version": "v3"
},
{
"created": "Wed, 2 Apr 2014 06:48:48 GMT",
"version": "v4"
},
{
"cr... | 2015-07-31 | [
[
"Pan",
"Supriya",
""
],
[
"Bhattacharya",
"Subhra",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The paper deals with a theoretical model for interacting dark energy. The interaction between the cold dark matter (dust) and the dark energy has been assumed to be non-gravitational in nature. Exact analytic cosmological solutions are obtained both for constant and variable equation of state for dark energy. It is found that, for very small value of the coupling parameter (in the interaction term), the model asymptotically extends up to $\Lambda$CDM, while the model can enter into the phantom domain asymptotically, if the coupling parameter is not so small. Both the solutions are then analyzed with 194 Supernovae Type Ia data. The best fit parameters are shown with 1$\sigma$ and 2$\sigma$ confidence intervals. Finally, we have discussed the cosmographic parameters for both the cases. |
0902.0697 | Tomasz Pawlowski | David Brizuela, Guillermo A. Mena Marugan, Tomasz Pawlowski | Big Bounce and inhomogeneities | RevTex4, 4 pages, 2 figures | Class.Quant.Grav.27:052001,2010 | 10.1088/0264-9381/27/5/052001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of an inhomogeneous universe is studied with the methods of Loop
Quantum Cosmology as an example of the quantization of vacuum cosmological
spacetimes containing gravitational waves (Gowdy spacetimes). The analysis
performed at the effective level shows that: (i) The initial Big Bang
singularity is replaced (as in the case of homogeneous cosmological models) by
a Big Bounce, joining deterministically two large universes, (ii) the universe
size at the bounce is at least of the same order of magnitude as that of the
background homogeneous universe, (iii) for each gravitational wave mode, the
difference in amplitude at very early and very late times has a vanishing
statistical average when the bounce dynamics is strongly dominated by the
inhomogeneities, whereas this average is positive when the dynamics is in a
near-vacuum regime, so that statistically the inhomogeneities are amplified.
| [
{
"created": "Wed, 4 Feb 2009 14:24:49 GMT",
"version": "v1"
}
] | 2010-02-17 | [
[
"Brizuela",
"David",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | The dynamics of an inhomogeneous universe is studied with the methods of Loop Quantum Cosmology as an example of the quantization of vacuum cosmological spacetimes containing gravitational waves (Gowdy spacetimes). The analysis performed at the effective level shows that: (i) The initial Big Bang singularity is replaced (as in the case of homogeneous cosmological models) by a Big Bounce, joining deterministically two large universes, (ii) the universe size at the bounce is at least of the same order of magnitude as that of the background homogeneous universe, (iii) for each gravitational wave mode, the difference in amplitude at very early and very late times has a vanishing statistical average when the bounce dynamics is strongly dominated by the inhomogeneities, whereas this average is positive when the dynamics is in a near-vacuum regime, so that statistically the inhomogeneities are amplified. |
1904.05652 | Zhi-Peng Li | Zhi-Peng Li and Yun-Song Piao | Mixing of gravitational wave echoes | 18 pages, 10 figures | Phys. Rev. D 100, 044023 (2019) | 10.1103/PhysRevD.100.044023 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave (GW) echoes, if they exist, would be a probe to the
near-horizon quantum structure of black hole (BH), which has motivated the
searching for the echo signals in GW data. We point out that the echo
phenomenology related with the potential structure might be not so simple as
expected. In particular, if the near-horizon regime of BH is modelled as a
multiple-barriers filter, the late-time GW ringdown waveform will exhibit the
mixing of echoes, even the superpositions. As a result, the amplitudes of
successive echoes might not drop sequentially.
| [
{
"created": "Thu, 11 Apr 2019 12:10:13 GMT",
"version": "v1"
}
] | 2019-08-21 | [
[
"Li",
"Zhi-Peng",
""
],
[
"Piao",
"Yun-Song",
""
]
] | Gravitational wave (GW) echoes, if they exist, would be a probe to the near-horizon quantum structure of black hole (BH), which has motivated the searching for the echo signals in GW data. We point out that the echo phenomenology related with the potential structure might be not so simple as expected. In particular, if the near-horizon regime of BH is modelled as a multiple-barriers filter, the late-time GW ringdown waveform will exhibit the mixing of echoes, even the superpositions. As a result, the amplitudes of successive echoes might not drop sequentially. |
1403.7377 | Clifford M. Will | Clifford M. Will | The Confrontation between General Relativity and Experiment | 113 pages, 10 figures, an update of the 2006 Living Review
arXiv:gr-qc/0510072 ; submitted to Living Reviews in Relativity | Living Rev. Relativity 17 (2014), 4 | 10.12942/lrr-2014-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The status of experimental tests of general relativity and of theoretical
frameworks for analyzing them are reviewed and updated. Einstein's equivalence
principle (EEP) is well supported by experiments such as the Eotvos experiment,
tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP
and of the inverse square law are searching for new interactions arising from
unification or quantum gravity. Tests of general relativity at the
post-Newtonian level have reached high precision, including the light
deflection, the Shapiro time delay, the perihelion advance of Mercury, the
Nordtvedt effect in lunar motion, and frame-dragging. Gravitational-wave
damping has been detected in an amount that agrees with general relativity to
better than half a percent using the Hulse-Taylor binary pulsar, and a growing
family of other binary pulsar systems is yielding new tests, especially of
strong-field effects. Current and future tests of relativity will center on
strong gravity and gravitational waves.
| [
{
"created": "Fri, 28 Mar 2014 14:04:31 GMT",
"version": "v1"
}
] | 2014-08-06 | [
[
"Will",
"Clifford M.",
""
]
] | The status of experimental tests of general relativity and of theoretical frameworks for analyzing them are reviewed and updated. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational-wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves. |
gr-qc/0408028 | Ralf Schutzhold | G\"unter Plunien, Marcus Ruser, and Ralf Sch\"utzhold | A relativistic toy model for back-reaction | 8 pages RevTeX, 4 figures | Class.Quant.Grav.24:4361-4376,2007 | 10.1088/0264-9381/24/17/006 | null | gr-qc quant-ph | null | We consider a quantized massless and minimally coupled scalar field on a
circular closed string with a time-dependent radius $R(t)$, whose undisturbed
dynamics is governed by the Nambu-Goto action. Within the semi-classical
treatment, the back-reaction of the quantum field onto the string dynamics is
taken into account in terms of the renormalized expectation value of the
energy-momentum tensor including the trace anomaly. The results indicate that
the back-reaction could prevent the collapse of the circle $R\downarrow0$ --
however, the semi-classical picture fails to describe the string dynamics at
the turning point (i.e., possible bounce) at finite values of $R$ and $\dot R$.
The fate of the closed string after that point (e.g., oscillation or eternal
acceleration) cannot be determined within the semi-classical picture and thus
probably requires the full quantum treatment. PACS: 04.62.+v, 03.70.+k,
11.15.Kc, 04.60.-m.
| [
{
"created": "Tue, 10 Aug 2004 16:50:47 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Plunien",
"Günter",
""
],
[
"Ruser",
"Marcus",
""
],
[
"Schützhold",
"Ralf",
""
]
] | We consider a quantized massless and minimally coupled scalar field on a circular closed string with a time-dependent radius $R(t)$, whose undisturbed dynamics is governed by the Nambu-Goto action. Within the semi-classical treatment, the back-reaction of the quantum field onto the string dynamics is taken into account in terms of the renormalized expectation value of the energy-momentum tensor including the trace anomaly. The results indicate that the back-reaction could prevent the collapse of the circle $R\downarrow0$ -- however, the semi-classical picture fails to describe the string dynamics at the turning point (i.e., possible bounce) at finite values of $R$ and $\dot R$. The fate of the closed string after that point (e.g., oscillation or eternal acceleration) cannot be determined within the semi-classical picture and thus probably requires the full quantum treatment. PACS: 04.62.+v, 03.70.+k, 11.15.Kc, 04.60.-m. |
2309.11958 | Syed Masood A. S. Bukhari | Syed Masood A. S. Bukhari and Li-Gang Wang | Seeing dark matter via acceleration radiation | 8 pages, 6 figures | Phys. Rev. D 109 (2024),04 045009 | 10.1103/PhysRevD.109.045009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Despite constituting a noteworthy $\sim 27\%$ share of the total energy
budget of our Universe, dark matter (DM) has thus far eluded direct
observations. Owing to its pervasive nature, there is a sincere expectation
that astrophysical black holes (BHs) encompassed by DM should leave distinctive
imprints on the gravitational waves arising from BH mergers. Theoretical models
of DM present a diverse landscape of possibilities, with perfect fluid dark
matter (PFDM) emerging as a recent and notably intriguing candidate model. In
this work, utilizing the established quantum optical approach, we investigate
the possibility of catching DM signatures via acceleration radiation emitted by
a freely-falling detector (e.g. an atom) within a PFDM-surrounded Schwarzschild
BH. The setup involves a Casimir-type apparatus where the detector interacts
with the field, and this situation induces excitations in the detector in a
manner consistent with Unruh effect. We observe that our DM candidate, while
making classical contributions to spacetime geometry, has the potential to
leave quantum imprints in the radiation flux. Notably, it is observed that, in
comparison to a pure Schwarzschild BH, PFDM can markedly reduce particle
emission as long as its density remains below a critical threshold, and vice
versa. Given the lessons we have learnt from realizing cosmological phenomena
in simulated laboratory conditions, there is a remote possibility that such
study may perhaps provide insights (to whatever degree !) into the future
table-top experiments in analogue gravity paradigm.
| [
{
"created": "Thu, 21 Sep 2023 10:20:51 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Oct 2023 06:07:03 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Feb 2024 14:01:07 GMT",
"version": "v3"
}
] | 2024-02-20 | [
[
"Bukhari",
"Syed Masood A. S.",
""
],
[
"Wang",
"Li-Gang",
""
]
] | Despite constituting a noteworthy $\sim 27\%$ share of the total energy budget of our Universe, dark matter (DM) has thus far eluded direct observations. Owing to its pervasive nature, there is a sincere expectation that astrophysical black holes (BHs) encompassed by DM should leave distinctive imprints on the gravitational waves arising from BH mergers. Theoretical models of DM present a diverse landscape of possibilities, with perfect fluid dark matter (PFDM) emerging as a recent and notably intriguing candidate model. In this work, utilizing the established quantum optical approach, we investigate the possibility of catching DM signatures via acceleration radiation emitted by a freely-falling detector (e.g. an atom) within a PFDM-surrounded Schwarzschild BH. The setup involves a Casimir-type apparatus where the detector interacts with the field, and this situation induces excitations in the detector in a manner consistent with Unruh effect. We observe that our DM candidate, while making classical contributions to spacetime geometry, has the potential to leave quantum imprints in the radiation flux. Notably, it is observed that, in comparison to a pure Schwarzschild BH, PFDM can markedly reduce particle emission as long as its density remains below a critical threshold, and vice versa. Given the lessons we have learnt from realizing cosmological phenomena in simulated laboratory conditions, there is a remote possibility that such study may perhaps provide insights (to whatever degree !) into the future table-top experiments in analogue gravity paradigm. |
0710.4445 | A. I. Nikishov | A.I.Nikishov | On two pictures in the heuristic approach to gravity | 4 pages | null | null | null | gr-qc | null | We examine the heuristic approach to constant gravitational field by Dehnen,
H\"onl and Westpfahl, extending it everywhere beyond linear approximation. Then
it becomes flexible to accommodate possible modifications of General
Relativity. We have found that two pictures introduced in the related paper by
Thirring are helpful in better understanding some features of gravitation. In
particular, this approach suggest that the privileged system for constant
gravitational field must be the isotropic one and that the requirement of gauge
invariance in gravitation theory may be a luxury; it is sufficient to take care
that the nonphysical degrees of freedom do not invalidate calculations. It
follows from this approach that gravitational constant should depend on
gravitational field and some universality in the form of metric of an
asymmetric body is suggested.
| [
{
"created": "Wed, 24 Oct 2007 12:08:16 GMT",
"version": "v1"
}
] | 2007-10-25 | [
[
"Nikishov",
"A. I.",
""
]
] | We examine the heuristic approach to constant gravitational field by Dehnen, H\"onl and Westpfahl, extending it everywhere beyond linear approximation. Then it becomes flexible to accommodate possible modifications of General Relativity. We have found that two pictures introduced in the related paper by Thirring are helpful in better understanding some features of gravitation. In particular, this approach suggest that the privileged system for constant gravitational field must be the isotropic one and that the requirement of gauge invariance in gravitation theory may be a luxury; it is sufficient to take care that the nonphysical degrees of freedom do not invalidate calculations. It follows from this approach that gravitational constant should depend on gravitational field and some universality in the form of metric of an asymmetric body is suggested. |
1201.6414 | Ben Whale | B. E. Whale | The dependence of the abstract boundary classification on a set of
curves II: How the classification changes when the bounded parameter property
satisfying set of curves changes | 24 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The abstract boundary uses sets of curves with the bounded parameter property
(b.p.p.) to classify the elements of the abstract boundary into regular points,
singular points, points at infinity and so on. Building on the material of Part
one of this two part series, we show how this classification changes when the
set of b.p.p. satisfying curves changes.
| [
{
"created": "Tue, 31 Jan 2012 01:36:04 GMT",
"version": "v1"
}
] | 2012-02-01 | [
[
"Whale",
"B. E.",
""
]
] | The abstract boundary uses sets of curves with the bounded parameter property (b.p.p.) to classify the elements of the abstract boundary into regular points, singular points, points at infinity and so on. Building on the material of Part one of this two part series, we show how this classification changes when the set of b.p.p. satisfying curves changes. |
1201.4545 | \"Ozg\"ur Akarsu | Ozgur Akarsu, Tekin Dereli | A four-dimensional {\Lambda}CDM-type cosmological model induced from
higher dimensions using a kinematical constraint | 12 pages, 8 figures; matches the version published in General
Relativity and Gravitation | General Relativity and Gravitation 45 (2013) 1211-1226 | 10.1007/s10714-013-1521-1 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of cosmological solutions of higher dimensional Einstein field
equations with the energy-momentum tensor of a homogeneous, isotropic fluid as
the source are considered with an anisotropic metric that includes the direct
sum of a 3-dimensional (physical, flat) external space metric and an
n-dimensional (compact, flat) internal space metric. A simple kinematical
constraint is postulated that correlates the expansion rates of the external
and internal spaces in terms of a real parameter {\lambda}. A specific solution
for which both the external and internal spaces expand at different rates is
given analytically for n=3. Assuming that the internal dimensions were at
Planck length scales when the external space starts with a Big Bang (t=0), they
expand only 1.49 times and stay at Planck length scales even in the present age
of the universe (13.7 Gyr). The effective four dimensional universe would
exhibit a behavior consistent with our current understanding of the observed
universe. It would start in a stiff fluid dominated phase and evolve through
radiation dominated and pressureless matter dominated phases, eventually going
into a de Sitter phase at late times.
| [
{
"created": "Sun, 22 Jan 2012 09:47:57 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jan 2013 18:01:31 GMT",
"version": "v2"
},
{
"created": "Sun, 31 Mar 2013 19:58:58 GMT",
"version": "v3"
}
] | 2013-10-24 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Dereli",
"Tekin",
""
]
] | A class of cosmological solutions of higher dimensional Einstein field equations with the energy-momentum tensor of a homogeneous, isotropic fluid as the source are considered with an anisotropic metric that includes the direct sum of a 3-dimensional (physical, flat) external space metric and an n-dimensional (compact, flat) internal space metric. A simple kinematical constraint is postulated that correlates the expansion rates of the external and internal spaces in terms of a real parameter {\lambda}. A specific solution for which both the external and internal spaces expand at different rates is given analytically for n=3. Assuming that the internal dimensions were at Planck length scales when the external space starts with a Big Bang (t=0), they expand only 1.49 times and stay at Planck length scales even in the present age of the universe (13.7 Gyr). The effective four dimensional universe would exhibit a behavior consistent with our current understanding of the observed universe. It would start in a stiff fluid dominated phase and evolve through radiation dominated and pressureless matter dominated phases, eventually going into a de Sitter phase at late times. |
2105.06670 | Bing-Yu Su | Bing-Yu Su and Nan Li | On the dual relation in the Hawking--Page phase transition of the black
holes in a cavity | 18 pages, 3 figures | Nucl. Phys. B 979 (2022) 115782 | 10.1016/j.nuclphysb.2022.115782 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hawking--Page phase transitions of the $d$-dimensional Schwarzschild and
charged black holes are explored in a cavity. The phase transition temperature
$T_{\rm HP}$, the minimum black hole temperature $T_0$, and the Gibbs free
energy $G$ are systematically calculated. A dual relation for the Schwarzschild
black holes in the anti-de Sitter space, $T_{\rm HP}(d)=T_0(d+1)$, is found to
be also approximately valid in the cavity case to a high precision, and this
relation can be further generalized to the charged black holes in a suitable
form. Our work reveals the universal properties of the black holes in different
extended phase spaces and motivates further studies on their thermodynamic
behaviors that are sensitive to specific boundary conditions, like the terminal
points in the $G$--$T$ curves.
| [
{
"created": "Fri, 14 May 2021 07:03:23 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Apr 2022 07:27:11 GMT",
"version": "v2"
}
] | 2022-04-25 | [
[
"Su",
"Bing-Yu",
""
],
[
"Li",
"Nan",
""
]
] | The Hawking--Page phase transitions of the $d$-dimensional Schwarzschild and charged black holes are explored in a cavity. The phase transition temperature $T_{\rm HP}$, the minimum black hole temperature $T_0$, and the Gibbs free energy $G$ are systematically calculated. A dual relation for the Schwarzschild black holes in the anti-de Sitter space, $T_{\rm HP}(d)=T_0(d+1)$, is found to be also approximately valid in the cavity case to a high precision, and this relation can be further generalized to the charged black holes in a suitable form. Our work reveals the universal properties of the black holes in different extended phase spaces and motivates further studies on their thermodynamic behaviors that are sensitive to specific boundary conditions, like the terminal points in the $G$--$T$ curves. |
gr-qc/0411076 | Frederic P. Schuller | Frederic P. Schuller, Mattias N.R. Wohlfarth | Classical limit of quantum gravity in an accelerating universe | 11 pages, no figures | Phys.Lett. B612 (2005) 93-99 | 10.1016/j.physletb.2005.03.009 | null | gr-qc hep-th | null | A one-parameter deformation of Einstein?Hilbert gravity with an inverse
Riemann curvature term is derived as the classical limit of quantum gravity
compatible with an accelerating universe. This result is based on the
investigation of semi-classical theories with sectional curvature bounds which
are shown not to admit static spherically symmetric black holes if otherwise of
phenomenological interest. We discuss the impact on the canonical quantization
of gravity, and observe that worldsheet string theory is not affected.
| [
{
"created": "Mon, 15 Nov 2004 21:53:06 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2005 16:21:50 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Apr 2005 23:41:10 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Schuller",
"Frederic P.",
""
],
[
"Wohlfarth",
"Mattias N. R.",
""
]
] | A one-parameter deformation of Einstein?Hilbert gravity with an inverse Riemann curvature term is derived as the classical limit of quantum gravity compatible with an accelerating universe. This result is based on the investigation of semi-classical theories with sectional curvature bounds which are shown not to admit static spherically symmetric black holes if otherwise of phenomenological interest. We discuss the impact on the canonical quantization of gravity, and observe that worldsheet string theory is not affected. |
gr-qc/0309039 | Alessandro D. A. M. Spallicci | Alessandro D.A.M. Spallicci, Sofiane Aoudia (Observatoire de la Cote
d'Azur, Nice) | Perturbation method in the assessment of radiation reaction in the
capture of stars by black holes | 10 pages, no figures. Email: spallicci@obs-nice.fr To appear on
Classical and Quantum Gravity March 2004 | Class.Quant.Grav. 21 (2004) S563-S572 | 10.1088/0264-9381/21/5/027 | null | gr-qc astro-ph math-ph math.MP | null | This work deals with the motion of a radially falling star in Schwarzschild
geometry and correctly identifies radiation reaction terms by the perturbative
method. The results are: i) identification of all terms up to first order in
perturbations, second in trajectory deviation, and mixed terms including lowest
order radiation reaction terms; ii) renormalisation of all divergent terms by
the $\zeta$ Riemann and Hurwitz functions. The work implements a method
previously identified by one of the authors and corrects some current
misconceptions and results.
| [
{
"created": "Sun, 7 Sep 2003 08:54:49 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Dec 2003 14:37:53 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Spallicci",
"Alessandro D. A. M.",
"",
"Observatoire de la Cote\n d'Azur, Nice"
],
[
"Aoudia",
"Sofiane",
"",
"Observatoire de la Cote\n d'Azur, Nice"
]
] | This work deals with the motion of a radially falling star in Schwarzschild geometry and correctly identifies radiation reaction terms by the perturbative method. The results are: i) identification of all terms up to first order in perturbations, second in trajectory deviation, and mixed terms including lowest order radiation reaction terms; ii) renormalisation of all divergent terms by the $\zeta$ Riemann and Hurwitz functions. The work implements a method previously identified by one of the authors and corrects some current misconceptions and results. |
2304.06641 | Mushtaq Ahmad Sial | Mushtaq Ahmad, M. Farasat Shamir, G. Mustafa | $f(\mathcal{G},\mathrm{\textit{T}})$ Gravity Bouncing Universe with
Cosmological Parameters | 12 pages, 10 figures | Chin. J. Phys. 71 (2021) 770 | 10.1016/j.cjph.2021.04.009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In recent few years, the Gauss-Bonnet $f(\mathcal{G},\mathrm{\textit{T}})$
theory of gravity has fascinated considerable researchers owing to its coupling
of trace of the stress-energy tensor $T$ with the Gauss-Bonnet term
$\mathcal{G}$. In this context, we focuss ourselves to study bouncing universe
with in $f(\mathcal{G},\mathrm{\textit{T}})$ gravity background. Some important
preliminaries are presented along with the discussion of cosmological
parameters to develop a minimal background about
$f(\mathcal{G},\mathrm{\textit{T}})$ theory of gravity. The exact bouncing
solutions with physical analysis are provided with the choice of two equation
of state parameters. It is shown that the results do agree with the present
values of deceleration, jerk and snap parameters. Moreover, it is concluded
that the model parameters are quite important for the validity of conservation
equation (as the matter coupled theories do not obey the usual conservation
law).
| [
{
"created": "Thu, 13 Apr 2023 16:11:06 GMT",
"version": "v1"
}
] | 2023-04-14 | [
[
"Ahmad",
"Mushtaq",
""
],
[
"Shamir",
"M. Farasat",
""
],
[
"Mustafa",
"G.",
""
]
] | In recent few years, the Gauss-Bonnet $f(\mathcal{G},\mathrm{\textit{T}})$ theory of gravity has fascinated considerable researchers owing to its coupling of trace of the stress-energy tensor $T$ with the Gauss-Bonnet term $\mathcal{G}$. In this context, we focuss ourselves to study bouncing universe with in $f(\mathcal{G},\mathrm{\textit{T}})$ gravity background. Some important preliminaries are presented along with the discussion of cosmological parameters to develop a minimal background about $f(\mathcal{G},\mathrm{\textit{T}})$ theory of gravity. The exact bouncing solutions with physical analysis are provided with the choice of two equation of state parameters. It is shown that the results do agree with the present values of deceleration, jerk and snap parameters. Moreover, it is concluded that the model parameters are quite important for the validity of conservation equation (as the matter coupled theories do not obey the usual conservation law). |
2407.20621 | Giuseppe Gaetano Luciano Dr | Yassine Sekhmani, Dhruba Jyoti Gogoi, Ratbay Myrzakulov, Giuseppe
Gaetano Luciano and Javlon Rayimbaev | Four $\mathbb{S}\mathbb{T}\mathbb{U}$ Black Holes Shadows | 32 pages, 14 labeled figures, accepted for publication in Classical
and Quantum Gravity | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we examine the optical behaviors and thermodynamic phase
structures using shadow analysis for four $\mathbb{S}\mathbb{T}\mathbb{U}$
black holes. The study is conducted for four cases of charge configurations on
the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$. As a matter of
fact, both the electric charge as a parameter and the parameter space
$\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ affect the geometry of the black hole
shadow, particularly the size of the shadow. We also introduce a constraint on
the charge of the black hole from the observational results of the M87$^\star$
{\color{black}and Sgr A$^\star$} shadow. Furthermore, we show that the electric
charge and the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ have a
non-trivial impact on the variation of the energy emission rate. Interestingly
enough, we find novel scenarios in which the evaporation is slower, which
causes the lifetime of the black holes to be considerably elongated. On the
other side, the phase structure of four $\mathbb{S}\mathbb{T}\mathbb{U}$ black
holes is explored for two cases of electric charge configuration. The findings
show a perfect correlation between the shadow and event horizon radii. This
correlation is, in fact, helpful in discovering the phase transition in terms
of the shadow radius. In addition, the microstructure is being analyzed in
terms of shadow analysis, providing similar behavior to the ordinary situation
of the Ruppeiner formalism.
| [
{
"created": "Tue, 30 Jul 2024 07:55:26 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Sekhmani",
"Yassine",
""
],
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Rayimbaev",
"Javlon",
""
]
] | In this work, we examine the optical behaviors and thermodynamic phase structures using shadow analysis for four $\mathbb{S}\mathbb{T}\mathbb{U}$ black holes. The study is conducted for four cases of charge configurations on the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$. As a matter of fact, both the electric charge as a parameter and the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ affect the geometry of the black hole shadow, particularly the size of the shadow. We also introduce a constraint on the charge of the black hole from the observational results of the M87$^\star$ {\color{black}and Sgr A$^\star$} shadow. Furthermore, we show that the electric charge and the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ have a non-trivial impact on the variation of the energy emission rate. Interestingly enough, we find novel scenarios in which the evaporation is slower, which causes the lifetime of the black holes to be considerably elongated. On the other side, the phase structure of four $\mathbb{S}\mathbb{T}\mathbb{U}$ black holes is explored for two cases of electric charge configuration. The findings show a perfect correlation between the shadow and event horizon radii. This correlation is, in fact, helpful in discovering the phase transition in terms of the shadow radius. In addition, the microstructure is being analyzed in terms of shadow analysis, providing similar behavior to the ordinary situation of the Ruppeiner formalism. |
1907.07586 | Christos Tsagas | J.D. Barrow, C.G. Tsagas, G. Fanaras | Friedmann-like universes with weak torsion: a dynamical system approach | Minor changes. Published in EPJC | Eur. Phys. J. C 79, 764 (2019) | 10.1140/epjc/s10052-019-7270-x | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Friedmann-like universes with torsion and take a step towards
studying their stability. In so doing, we apply dynamical-system techniques to
an autonomous system of differential equations, which monitors the evolution of
these models via the associated density parameters. Assuming relatively weak
torsion, we identify the system's equilibrium points. These are found to
represent homogeneous and isotropic spacetimes with nonzero torsion that
undergo accelerated expansion. We then examine the linear stability of the
aforementioned fixed points. Our results indicate that Friedmann-like
cosmologies with weak torsion are generally stable attractors, either
asymptotically or in the Lyapunov sense. In addition, depending on the equation
of state of the matter, the equilibrium states can also act as intermediate
saddle points, marking a transition from a torsional to a torsion-free
universe.
| [
{
"created": "Wed, 17 Jul 2019 15:31:37 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2019 14:55:49 GMT",
"version": "v2"
}
] | 2019-10-02 | [
[
"Barrow",
"J. D.",
""
],
[
"Tsagas",
"C. G.",
""
],
[
"Fanaras",
"G.",
""
]
] | We consider Friedmann-like universes with torsion and take a step towards studying their stability. In so doing, we apply dynamical-system techniques to an autonomous system of differential equations, which monitors the evolution of these models via the associated density parameters. Assuming relatively weak torsion, we identify the system's equilibrium points. These are found to represent homogeneous and isotropic spacetimes with nonzero torsion that undergo accelerated expansion. We then examine the linear stability of the aforementioned fixed points. Our results indicate that Friedmann-like cosmologies with weak torsion are generally stable attractors, either asymptotically or in the Lyapunov sense. In addition, depending on the equation of state of the matter, the equilibrium states can also act as intermediate saddle points, marking a transition from a torsional to a torsion-free universe. |
1606.00852 | Arvin Ravanpak | H. Farajollahi, A. Ravanpak, M. Abolghasemi | Thermodynamics and holography of tachyon cosmology | null | Gen. Relativ. Gravit., Volume 45, Issue 2, pp 465-476 (2013) | 10.1007/s10714-012-1481-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, we have investigated the dynamics of the universe in tachyon
cosmology with non-minimal coupling to matter \cite{faraj}-\cite{faraj3}. In
particular, for the interacting holographic dark energy (IHDE), the model is
studied in \cite{Ravanpak}. In the current work, a significant observational
program has been conducted to unveil the model's thermodynamic properties. Our
result shows that the IHDE version of our model better fits the observational
data than $\Lambda$CDM model. The first and generalized second thermodynamics
laws for the universe enveloped by cosmological apparent and event horizon are
revisited. From the results, both first and generalized second laws,
constrained by the observational data, are satisfied on cosmological apparent
horizon.In addition, the total entropy is verified with the observation only if
the horizon of the universe is taken as apparent horizon. Then, due to validity
of generalized second law, the current cosmic acceleration is also predicted.
| [
{
"created": "Thu, 2 Jun 2016 20:13:11 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jul 2016 06:54:45 GMT",
"version": "v2"
}
] | 2016-07-26 | [
[
"Farajollahi",
"H.",
""
],
[
"Ravanpak",
"A.",
""
],
[
"Abolghasemi",
"M.",
""
]
] | Recently, we have investigated the dynamics of the universe in tachyon cosmology with non-minimal coupling to matter \cite{faraj}-\cite{faraj3}. In particular, for the interacting holographic dark energy (IHDE), the model is studied in \cite{Ravanpak}. In the current work, a significant observational program has been conducted to unveil the model's thermodynamic properties. Our result shows that the IHDE version of our model better fits the observational data than $\Lambda$CDM model. The first and generalized second thermodynamics laws for the universe enveloped by cosmological apparent and event horizon are revisited. From the results, both first and generalized second laws, constrained by the observational data, are satisfied on cosmological apparent horizon.In addition, the total entropy is verified with the observation only if the horizon of the universe is taken as apparent horizon. Then, due to validity of generalized second law, the current cosmic acceleration is also predicted. |
gr-qc/0306062 | Akira Ohashi | Akira Ohashi | Multipole particle in relativity | 22 pages, 2 figures. Accepted for publication in Phys. Rev. D | Phys.Rev. D68 (2003) 044009 | 10.1103/PhysRevD.68.044009 | null | gr-qc | null | We discuss the motion of extended objects in a spacetime by considering a
gravitational field created by these objects. We define multipole moments of
the objects as a classification by Lie group SO(3). Then, we construct an
energy-momentum tensor for the objects and derive equations of motion from it.
As a result, we reproduce the Papapetrou equations for a spinning particle.
Furthermore, we will show that we can obtain more simple equations than the
Papapetrou equations by changing the center-of-mass.
| [
{
"created": "Mon, 16 Jun 2003 07:44:15 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ohashi",
"Akira",
""
]
] | We discuss the motion of extended objects in a spacetime by considering a gravitational field created by these objects. We define multipole moments of the objects as a classification by Lie group SO(3). Then, we construct an energy-momentum tensor for the objects and derive equations of motion from it. As a result, we reproduce the Papapetrou equations for a spinning particle. Furthermore, we will show that we can obtain more simple equations than the Papapetrou equations by changing the center-of-mass. |
2009.03905 | Emanuele Berti | Emanuele Berti, Lucas G. Collodel, Burkhard Kleihaus, Jutta Kunz | Spin-induced black hole scalarization in Einstein-scalar-Gauss-Bonnet
theory | 5 pages, 3 figures. Matches version published in PRL and fixes a
small typo (F_0 should read F_1 in equation 6) | Phys. Rev. Lett. 126, 011104 (2021) | 10.1103/PhysRevLett.126.011104 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct black hole solutions with spin-induced scalarization in a class
of models where a scalar field is quadratically coupled to the topological
Gauss-Bonnet term. Starting from the tachyonically unstable Kerr solutions, we
obtain families of scalarized black holes such that the scalar field has either
even or odd parity, and we investigate their domain of existence. The
scalarized black holes can violate the Kerr rotation bound. We identify
"critical" families of scalarized black hole solutions such that the expansion
of the metric functions and of the scalar field at the horizon no longer allows
for real coefficients. For the quadratic coupling considered here, solutions
with spin-induced scalarization are entropically favored over Kerr solutions
with the same mass and angular momentum.
| [
{
"created": "Tue, 8 Sep 2020 18:00:02 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Jan 2021 18:12:12 GMT",
"version": "v2"
}
] | 2021-01-12 | [
[
"Berti",
"Emanuele",
""
],
[
"Collodel",
"Lucas G.",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We construct black hole solutions with spin-induced scalarization in a class of models where a scalar field is quadratically coupled to the topological Gauss-Bonnet term. Starting from the tachyonically unstable Kerr solutions, we obtain families of scalarized black holes such that the scalar field has either even or odd parity, and we investigate their domain of existence. The scalarized black holes can violate the Kerr rotation bound. We identify "critical" families of scalarized black hole solutions such that the expansion of the metric functions and of the scalar field at the horizon no longer allows for real coefficients. For the quadratic coupling considered here, solutions with spin-induced scalarization are entropically favored over Kerr solutions with the same mass and angular momentum. |
2006.14628 | Elisa Maggio | Elisa Maggio, Luca Buoninfante, Anupam Mazumdar, Paolo Pani | How does a dark compact object ringdown? | 11+7 pages, 8 figures. v2: minor revisions to match the version to
appear in PRD | Phys. Rev. D 102, 064053 (2020) | 10.1103/PhysRevD.102.064053 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generic feature of nearly out-of-equilibrium dissipative systems is that
they resonate through a set of quasinormal modes. Black holes - the absorbing
objects par excellence - are no exception. When formed in a merger, black holes
vibrate in a process called "ringdown", which leaves the gravitational-wave
footprint of the event horizon. In some models of quantum gravity which attempt
to solve the information-loss paradox and the singularities of General
Relativity, black holes are replaced by regular, horizonless objects with a
tiny effective reflectivity. Motivated by these scenarios, here we develop a
generic framework to the study of the ringdown of a compact object with various
shades of darkness. By extending the black-hole membrane paradigm, we map the
interior of any compact object in terms of the bulk and shear viscosities of a
fictitious fluid located at the surface, with the black-hole limit being a
single point in a three-dimensional parameter space. We unveil some remarkable
features of the ringdown and some universal properties of the light ring in
this framework. We also identify the region of the parameter space which can be
probed by current and future gravitational-wave detectors. A general feature is
the appearance of mode doublets which are degenerate only in the black-hole
limit. We argue that the merger event GW150914 already imposes a strong lower
bound on the compactness of the merger remnant of approximately 99% of the
black-hole compactness. This places model-independent constraints on black-hole
alternatives such as diffuse "fuzzballs" and nonlocal stars.
| [
{
"created": "Thu, 25 Jun 2020 18:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2020 21:29:00 GMT",
"version": "v2"
}
] | 2020-09-23 | [
[
"Maggio",
"Elisa",
""
],
[
"Buoninfante",
"Luca",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Pani",
"Paolo",
""
]
] | A generic feature of nearly out-of-equilibrium dissipative systems is that they resonate through a set of quasinormal modes. Black holes - the absorbing objects par excellence - are no exception. When formed in a merger, black holes vibrate in a process called "ringdown", which leaves the gravitational-wave footprint of the event horizon. In some models of quantum gravity which attempt to solve the information-loss paradox and the singularities of General Relativity, black holes are replaced by regular, horizonless objects with a tiny effective reflectivity. Motivated by these scenarios, here we develop a generic framework to the study of the ringdown of a compact object with various shades of darkness. By extending the black-hole membrane paradigm, we map the interior of any compact object in terms of the bulk and shear viscosities of a fictitious fluid located at the surface, with the black-hole limit being a single point in a three-dimensional parameter space. We unveil some remarkable features of the ringdown and some universal properties of the light ring in this framework. We also identify the region of the parameter space which can be probed by current and future gravitational-wave detectors. A general feature is the appearance of mode doublets which are degenerate only in the black-hole limit. We argue that the merger event GW150914 already imposes a strong lower bound on the compactness of the merger remnant of approximately 99% of the black-hole compactness. This places model-independent constraints on black-hole alternatives such as diffuse "fuzzballs" and nonlocal stars. |
2303.09699 | Nicolas R. Bertini | Nicolas R. Bertini, Hermano Velten | Fully conservative $f(R,T)$ gravity and Solar System constraints | 15 pages, thirteen references added and text improvements. Typos
corrected. Accepted in PRD | Phys. Rev. D 107, 124005 (2023) | 10.1103/PhysRevD.107.124005 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The $f(R,T)$ gravity is a model whose action contains an arbitrary function
of the Ricci scalar $R$ and the trace of the energy-momentum tensor $T$. We
consider the separable model $f (R, T ) = \chi(R) + \varphi(T )$ and shown
that, for perfect fluids, the dynamical equations are sufficient to determine
how $\varphi$ depends on $T$, independently of the matter state equation and
the geometry of space-time. Imposing the energy-momentum tensor conservation we
obtain that $\varphi$ must be linear in $T$. However, the $T$ dependence is
severely constrained using the full Will-Nordtvedt version of the parameterized
post-Newtonian (PPN) formalism. The result of the PPN analysis is discussed and
in addition it is shown that the diffeomorphism invariance of the matter action
imposes strong constraints on conservative versions of $f(R,T)$ gravity.
| [
{
"created": "Fri, 17 Mar 2023 00:05:58 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2023 17:37:46 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Jun 2023 23:58:38 GMT",
"version": "v3"
}
] | 2023-06-29 | [
[
"Bertini",
"Nicolas R.",
""
],
[
"Velten",
"Hermano",
""
]
] | The $f(R,T)$ gravity is a model whose action contains an arbitrary function of the Ricci scalar $R$ and the trace of the energy-momentum tensor $T$. We consider the separable model $f (R, T ) = \chi(R) + \varphi(T )$ and shown that, for perfect fluids, the dynamical equations are sufficient to determine how $\varphi$ depends on $T$, independently of the matter state equation and the geometry of space-time. Imposing the energy-momentum tensor conservation we obtain that $\varphi$ must be linear in $T$. However, the $T$ dependence is severely constrained using the full Will-Nordtvedt version of the parameterized post-Newtonian (PPN) formalism. The result of the PPN analysis is discussed and in addition it is shown that the diffeomorphism invariance of the matter action imposes strong constraints on conservative versions of $f(R,T)$ gravity. |
2310.09224 | ChengGang Qin | Cheng-Gang Qin, Jun Ke, Qin Li, Ya-Fen Chen, Jie Luo, Yu-Jie Tan, and
Cheng-Gang Shao | Testing Lorentz symmetry with space-based gravitational-wave detectors | 17 pages, 10 figures | Classical and Quantum Gravity 40(2023)205005 | 10.1088/1361-6382/acf7a6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lorentz symmetry (LS), one of the most fundamental physical symmetries, has
been extensively studied in the context of quantum gravity and unification
theories. Many of these theories predict a LS violation, which could arise from
the discreteness of spacetime, or extra dimensions. Standard-model extension
(SME) is an effective field theory to describe Lorentz violation whose effects
can be explored using precision instruments such as atomic clocks and
gravitational-wave (GW) detectors. Considering the pure-gravity sector and
matter-gravity coupling sector in the SME, we studied the leading
Lorentz-violating modifications to the time delay of light and the relativistic
frequency shift of the clock in the space-based GW detectors. We found that the
six data streams from the GW mission can construct various combinations of
measurement signals, such as single-arm round-trip path, interference path,
triangular round-trip path, etc. These measurements are sensitive to the
different combinations of SME coefficients and provide novel linear
combinations of SME coefficients different from previous studies. Based on the
orbits of TianQin, LISA, and Taiji missions, we calculated the response of
Lorentz-violating effects on the combinations of the measurement signal data
streams. Our results allow us to estimate the sensitivities for SME
coefficients: $10^{-6}$ for the gravity sector coefficient $\bar{s}^{TT}$,
$10^{-6}$ for matter-gravity coupling coefficients
$(\bar{a}^{(e+p)}_{\text{eff}})_{T}$ and $\bar{c}^{(e+p)}_{TT}$, and $10^{-5}$
for $(\bar{a}^{n}_{\text{eff}})_{T}$ and $\bar{c}^{n}_{TT}$.
| [
{
"created": "Fri, 13 Oct 2023 16:21:33 GMT",
"version": "v1"
}
] | 2023-10-16 | [
[
"Qin",
"Cheng-Gang",
""
],
[
"Ke",
"Jun",
""
],
[
"Li",
"Qin",
""
],
[
"Chen",
"Ya-Fen",
""
],
[
"Luo",
"Jie",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | Lorentz symmetry (LS), one of the most fundamental physical symmetries, has been extensively studied in the context of quantum gravity and unification theories. Many of these theories predict a LS violation, which could arise from the discreteness of spacetime, or extra dimensions. Standard-model extension (SME) is an effective field theory to describe Lorentz violation whose effects can be explored using precision instruments such as atomic clocks and gravitational-wave (GW) detectors. Considering the pure-gravity sector and matter-gravity coupling sector in the SME, we studied the leading Lorentz-violating modifications to the time delay of light and the relativistic frequency shift of the clock in the space-based GW detectors. We found that the six data streams from the GW mission can construct various combinations of measurement signals, such as single-arm round-trip path, interference path, triangular round-trip path, etc. These measurements are sensitive to the different combinations of SME coefficients and provide novel linear combinations of SME coefficients different from previous studies. Based on the orbits of TianQin, LISA, and Taiji missions, we calculated the response of Lorentz-violating effects on the combinations of the measurement signal data streams. Our results allow us to estimate the sensitivities for SME coefficients: $10^{-6}$ for the gravity sector coefficient $\bar{s}^{TT}$, $10^{-6}$ for matter-gravity coupling coefficients $(\bar{a}^{(e+p)}_{\text{eff}})_{T}$ and $\bar{c}^{(e+p)}_{TT}$, and $10^{-5}$ for $(\bar{a}^{n}_{\text{eff}})_{T}$ and $\bar{c}^{n}_{TT}$. |
2309.08694 | Marina Cort\^es | Vasco Gil Gomes, Marina Cort\^es, Andrew R. Liddle | Higher Dimensional Energetic Causal Sets | 17 pages, 19 figures, additional discussion and references. Matches
the journal submitted version and includes a new section connecting
perspectives in quantum gravity with those in the artificial general
intelligence (AGI) debate. This allows us to take a position in the AGI
debate based in arguments of the ECS programme and its main foundational
principle: that of fundamental causality | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The energetic causal set (ECS) program of Cort\^es and Smolin, whose
distinguishing feature is the foundational time irreversibility of the
evolution equations of quantum gravity, was initiated ten years ago. The model
showed the emergence of a time-reversible phase from the time-irreversible
foundational regime, but originally only had one spatial dimension. The
extension to two and more spatial dimensions has posed a substantial challenge,
the higher-dimensional set of solutions having measure zero (requiring
infinitely-specified initial conditions). This challenge is overcome here with
the extension of the ECS to 2+1 dimensions, invoking a finite interaction
cross-section to determine generation of new events and including an adjustable
fundamental stochasticity. As in the 1+1 dimensional case, we successfully
observe a phase transition into a time-symmetric phase, here through the
emergence of crystal-like structures. Due to the irreversible evolution we also
witness the discrete dynamical systems behaviour of the 1d+1 case explored in
later articles of the ECS program, in which the model is captured in and out of
the limit cycles which here take the form of lattice crystals. In a companion
paper we carry out a detailed parameter investigation and study the causal
network underlying the set, explaining the emergence of the time-symmetric
phase. In a final section we propose a view of science as a (potential) unifier
of threads, and present one such perspective unifying aspects of quantum
gravity, biology, and artificial general intelligence (AGI).
| [
{
"created": "Fri, 15 Sep 2023 18:36:59 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Sep 2023 11:20:55 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Nov 2023 18:48:19 GMT",
"version": "v3"
}
] | 2023-11-30 | [
[
"Gomes",
"Vasco Gil",
""
],
[
"Cortês",
"Marina",
""
],
[
"Liddle",
"Andrew R.",
""
]
] | The energetic causal set (ECS) program of Cort\^es and Smolin, whose distinguishing feature is the foundational time irreversibility of the evolution equations of quantum gravity, was initiated ten years ago. The model showed the emergence of a time-reversible phase from the time-irreversible foundational regime, but originally only had one spatial dimension. The extension to two and more spatial dimensions has posed a substantial challenge, the higher-dimensional set of solutions having measure zero (requiring infinitely-specified initial conditions). This challenge is overcome here with the extension of the ECS to 2+1 dimensions, invoking a finite interaction cross-section to determine generation of new events and including an adjustable fundamental stochasticity. As in the 1+1 dimensional case, we successfully observe a phase transition into a time-symmetric phase, here through the emergence of crystal-like structures. Due to the irreversible evolution we also witness the discrete dynamical systems behaviour of the 1d+1 case explored in later articles of the ECS program, in which the model is captured in and out of the limit cycles which here take the form of lattice crystals. In a companion paper we carry out a detailed parameter investigation and study the causal network underlying the set, explaining the emergence of the time-symmetric phase. In a final section we propose a view of science as a (potential) unifier of threads, and present one such perspective unifying aspects of quantum gravity, biology, and artificial general intelligence (AGI). |
gr-qc/9703046 | S. M. Goncalves | Sergio M.C.V. Goncalves and Ian G. Moss | Scalar Curvature Fluctuations on the Four-Sphere | 8 pages, RevTeX, 2 eps figures. Submitted to Phys. Lett. B | Phys.Lett. B401 (1997) 254-257 | 10.1016/S0370-2693(97)00397-3 | null | gr-qc | null | Two-point functions of the scalar curvature for metric fluctuations on the
four-sphere are analysed. The two-point function for points separated by a
fixed distance and for metrics of fixed volume is calculated using spacetime
foam methods. This result can be used for comparison between the continuum
approach to quantum gravity and numerical quantum gravity on the lattice.
Pacs numbers: 04.60.Gw, 04.60.Nc, 04.62.+v
| [
{
"created": "Tue, 18 Mar 1997 14:17:50 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Goncalves",
"Sergio M. C. V.",
""
],
[
"Moss",
"Ian G.",
""
]
] | Two-point functions of the scalar curvature for metric fluctuations on the four-sphere are analysed. The two-point function for points separated by a fixed distance and for metrics of fixed volume is calculated using spacetime foam methods. This result can be used for comparison between the continuum approach to quantum gravity and numerical quantum gravity on the lattice. Pacs numbers: 04.60.Gw, 04.60.Nc, 04.62.+v |
0707.3387 | Rodrigo Holanda | R. F. L. Holanda, S. H. Pereira | On the dynamics of the universe in $D$ spatial dimensions | 10 pages, 2 figures, Revista Mexicana de Astronom\'ia y Astrof\'isica
(in Press). arXiv admin note: text overlap with arXiv:astro-ph/0109215 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present the equations of the evolution of the universe in
$D$ spatial dimensions, as a generalization of the work of Lima \citep{lima}.
We discuss the Friedmann-Robertson-Walker cosmological equations in $D$ spatial
dimensions for a simple fluid with equation of state $p=\omega_{D}\rho$. It is
possible to reduce the multidimensional equations to the equation of a point
particle system subject to a linear force. This force can be expressed as an
oscillator equation, anti-oscillator or a free particle equation, depending on
the $k$ parameter of the spatial curvature. An interesting result is the
independence on the dimension $D$ in a de Sitter evolution. We also stress the
generality of this procedure with a cosmological $\Lambda$ term. A more
interesting result is that the reduction of the dimensionality leads naturally
to an accelerated expansion of the scale factor in the plane case.
| [
{
"created": "Mon, 23 Jul 2007 18:17:10 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jul 2012 21:45:20 GMT",
"version": "v2"
}
] | 2012-07-09 | [
[
"Holanda",
"R. F. L.",
""
],
[
"Pereira",
"S. H.",
""
]
] | In this paper we present the equations of the evolution of the universe in $D$ spatial dimensions, as a generalization of the work of Lima \citep{lima}. We discuss the Friedmann-Robertson-Walker cosmological equations in $D$ spatial dimensions for a simple fluid with equation of state $p=\omega_{D}\rho$. It is possible to reduce the multidimensional equations to the equation of a point particle system subject to a linear force. This force can be expressed as an oscillator equation, anti-oscillator or a free particle equation, depending on the $k$ parameter of the spatial curvature. An interesting result is the independence on the dimension $D$ in a de Sitter evolution. We also stress the generality of this procedure with a cosmological $\Lambda$ term. A more interesting result is that the reduction of the dimensionality leads naturally to an accelerated expansion of the scale factor in the plane case. |
1302.3275 | Xuefeng Zhang PhD | Xuefeng Zhang and Daniel Finley | CR Structures and Twisting Vacuum Spacetimes with Two Killing Vectors
and Cosmological Constant: Type II and More Special | 22 pages | Class. Quantum Grav. (2013) 30 115006 | 10.1088/0264-9381/30/11/115006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the CR formalism of algebraically special spacetimes by Hill,
Lewandowski and Nurowski, we derive a nonlinear system of two real ODEs, of
which the general solution determines a twisting type II (or more special)
vacuum spacetime with two Killing vectors (commuting or not) and at most seven
real parameters in addition to the cosmological constant Lambda. To demonstrate
a broad range of interesting spacetimes that these ODEs can capture, special
solutions of various Petrov types are presented and described as they appear in
this approach. They include Kerr-NUT, Kerr and Debney/Demia\'{n}ski's type II,
Lun's type II and III (subclasses of Held-Robinson), MacCallum and Siklos' type
III (Lambda<0), and the type N solutions (Lambda<>0) we found in an earlier
paper, along with a new class of type II solutions as a nontrivial limit of
Kerr and Debney's type II solutions. Also, we discuss a situation in which the
two ODEs can be reduced to one. However, constructing the general solution
still remains an open problem.
| [
{
"created": "Wed, 13 Feb 2013 23:52:19 GMT",
"version": "v1"
}
] | 2013-05-23 | [
[
"Zhang",
"Xuefeng",
""
],
[
"Finley",
"Daniel",
""
]
] | Based on the CR formalism of algebraically special spacetimes by Hill, Lewandowski and Nurowski, we derive a nonlinear system of two real ODEs, of which the general solution determines a twisting type II (or more special) vacuum spacetime with two Killing vectors (commuting or not) and at most seven real parameters in addition to the cosmological constant Lambda. To demonstrate a broad range of interesting spacetimes that these ODEs can capture, special solutions of various Petrov types are presented and described as they appear in this approach. They include Kerr-NUT, Kerr and Debney/Demia\'{n}ski's type II, Lun's type II and III (subclasses of Held-Robinson), MacCallum and Siklos' type III (Lambda<0), and the type N solutions (Lambda<>0) we found in an earlier paper, along with a new class of type II solutions as a nontrivial limit of Kerr and Debney's type II solutions. Also, we discuss a situation in which the two ODEs can be reduced to one. However, constructing the general solution still remains an open problem. |
2002.07554 | Carlos Palenzuela | S.L. Liebling, C. Palenzuela and L. Lehner | Towards fidelity and scalability in non-vacuum mergers | 10 pages, 8 figures | null | 10.1088/1361-6382/ab8fcd | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of two fiducial configurations for binary neutron
stars using two different general relativistic hydrodynamics(GRHD), distributed
adaptive mesh codes. One code, HAD, has for many years been used to study
mergers of compact object binaries, while a new code, MHDuet, has been recently
developed with the experience gained with the older one as well as several
novel features for scalability improvements. As such, we examine the
performance of each, placing particular focus on future requirements for the
extraction of gravitational wave signatures of non-vacuum binaries.
| [
{
"created": "Tue, 18 Feb 2020 13:48:28 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"Liebling",
"S. L.",
""
],
[
"Palenzuela",
"C.",
""
],
[
"Lehner",
"L.",
""
]
] | We study the evolution of two fiducial configurations for binary neutron stars using two different general relativistic hydrodynamics(GRHD), distributed adaptive mesh codes. One code, HAD, has for many years been used to study mergers of compact object binaries, while a new code, MHDuet, has been recently developed with the experience gained with the older one as well as several novel features for scalability improvements. As such, we examine the performance of each, placing particular focus on future requirements for the extraction of gravitational wave signatures of non-vacuum binaries. |
2111.06303 | Norbert Van den Bergh | Norbert Van den Bergh and John Carminati | Comment on "Shear-free barotropic perfect fluids cannot rotate and
expand simultaneously" by R. Goswami and G.F.R. Ellis | 3 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out an error in a recent paper by Goswami and Ellis. As a
consequence the question of whether shear-free barotropic perfect fluids (with
$p+\mu\neq 0$) can or cannot rotate and expand simultaneously, is still wide
open
| [
{
"created": "Thu, 11 Nov 2021 16:48:13 GMT",
"version": "v1"
}
] | 2021-11-12 | [
[
"Bergh",
"Norbert Van den",
""
],
[
"Carminati",
"John",
""
]
] | We point out an error in a recent paper by Goswami and Ellis. As a consequence the question of whether shear-free barotropic perfect fluids (with $p+\mu\neq 0$) can or cannot rotate and expand simultaneously, is still wide open |
2404.18875 | Alice Bonino | Alice Bonino, Patricia Schmidt, Geraint Pratten | Mapping eccentricity evolutions between numerical relativity and
effective-one-body gravitational waveforms | 25 pages, 14 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Orbital eccentricity in compact binaries is considered to be a key tracer of
their astrophysical origin, and can be inferred from gravitational-wave
observations due to its imprint on the emitted signal. For a robust
measurement, accurate waveform models are needed. However, ambiguities in the
definition of eccentricity can obfuscate the physical meaning and result in
seemingly discrepant measurements. In this work we present a suite of 28 new
numerical relativity simulations of eccentric, aligned-spin binary black holes
with mass ratios between 1 and 6 and initial post-Newtonian eccentricities
between 0.05 and 0.3. We then develop a robust pipeline for measuring the
eccentricity evolution as a function of frequency from gravitational-wave
observables that is applicable even to signals that span at least $\gtrsim 7$
orbits. We assess the reliability of our procedure and quantify its robustness
under different assumptions on the data. Using the eccentricity measured at the
first apastron, we initialise effective-one-body waveforms and quantify how the
precision in the eccentricity measurement, and therefore the choice of the
initial conditions, impacts the agreement with the numerical data. We find that
even small deviations in the initial eccentricity can lead to non-negligible
differences in the phase and amplitude of the waveforms. However, we
demonstrate that we can reliably map the eccentricities between the simulation
data and analytic models, which is crucial for robustly building eccentric
hybrid waveforms, and to improve the accuracy of eccentric waveform models in
the strong-field regime.
| [
{
"created": "Mon, 29 Apr 2024 17:09:15 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Bonino",
"Alice",
""
],
[
"Schmidt",
"Patricia",
""
],
[
"Pratten",
"Geraint",
""
]
] | Orbital eccentricity in compact binaries is considered to be a key tracer of their astrophysical origin, and can be inferred from gravitational-wave observations due to its imprint on the emitted signal. For a robust measurement, accurate waveform models are needed. However, ambiguities in the definition of eccentricity can obfuscate the physical meaning and result in seemingly discrepant measurements. In this work we present a suite of 28 new numerical relativity simulations of eccentric, aligned-spin binary black holes with mass ratios between 1 and 6 and initial post-Newtonian eccentricities between 0.05 and 0.3. We then develop a robust pipeline for measuring the eccentricity evolution as a function of frequency from gravitational-wave observables that is applicable even to signals that span at least $\gtrsim 7$ orbits. We assess the reliability of our procedure and quantify its robustness under different assumptions on the data. Using the eccentricity measured at the first apastron, we initialise effective-one-body waveforms and quantify how the precision in the eccentricity measurement, and therefore the choice of the initial conditions, impacts the agreement with the numerical data. We find that even small deviations in the initial eccentricity can lead to non-negligible differences in the phase and amplitude of the waveforms. However, we demonstrate that we can reliably map the eccentricities between the simulation data and analytic models, which is crucial for robustly building eccentric hybrid waveforms, and to improve the accuracy of eccentric waveform models in the strong-field regime. |
gr-qc/0303044 | Carlos Augusto Romero Filho | F. Dahia, E. M. Monte and C. Romero | Fifth force from fifth dimension: a comparison between two different
approaches | l7 pages - Typeset using REVTEX | Mod.Phys.Lett. A18 (2003) 1773-1782 | 10.1142/S0217732303011484 | null | gr-qc hep-th | null | We investigate the dynamics of particles moving in a spacetime augmented by
one extra dimension in the context of the induced matter theory of gravity. We
examine the appearance of a fifth force as an effect caused by the extra
dimension and discuss two different approaches to the fifth force formalism. We
then give two examples of application of both approaches by considering the
case of a Ricci-flat warped-product manifold and a generalized Randall-Sundrum
space.
| [
{
"created": "Tue, 11 Mar 2003 17:49:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Dahia",
"F.",
""
],
[
"Monte",
"E. M.",
""
],
[
"Romero",
"C.",
""
]
] | We investigate the dynamics of particles moving in a spacetime augmented by one extra dimension in the context of the induced matter theory of gravity. We examine the appearance of a fifth force as an effect caused by the extra dimension and discuss two different approaches to the fifth force formalism. We then give two examples of application of both approaches by considering the case of a Ricci-flat warped-product manifold and a generalized Randall-Sundrum space. |
1601.06467 | Mihalis Dafermos | Mihalis Dafermos, Gustav Holzegel and Igor Rodnianski | The linear stability of the Schwarzschild solution to gravitational
perturbations | 146 pages, 4 figures | Acta Math., 222 (2019), 1-214 | 10.4310/ACTA.2019.v222.n1.a1 | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove in this paper the linear stability of the celebrated Schwarzschild
family of black holes in general relativity: Solutions to the linearisation of
the Einstein vacuum equations around a Schwarzschild metric arising from
regular initial data remain globally bounded on the black hole exterior and in
fact decay to a linearised Kerr metric. We express the equations in a suitable
double null gauge. To obtain decay, one must in fact add a residual pure gauge
solution which we prove to be itself quantitatively controlled from initial
data. Our result a fortiori includes decay statements for general solutions of
the Teukolsky equation (satisfied by gauge-invariant null-decomposed curvature
components). These latter statements are in fact deduced in the course of the
proof by exploiting associated quantities shown to satisfy the Regge--Wheeler
equation, for which appropriate decay can be obtained easily by adapting
previous work on the linear scalar wave equation. The bounds on the rate of
decay to linearised Kerr are inverse polynomial, suggesting that dispersion is
sufficient to control the non-linearities of the Einstein equations in a
potential future proof of nonlinear stability. This paper is self-contained and
includes a physical-space derivation of the equations of linearised gravity
around Schwarzschild from the full non-linear Einstein vacuum equations
expressed in a double null gauge.
| [
{
"created": "Mon, 25 Jan 2016 02:38:24 GMT",
"version": "v1"
}
] | 2019-08-27 | [
[
"Dafermos",
"Mihalis",
""
],
[
"Holzegel",
"Gustav",
""
],
[
"Rodnianski",
"Igor",
""
]
] | We prove in this paper the linear stability of the celebrated Schwarzschild family of black holes in general relativity: Solutions to the linearisation of the Einstein vacuum equations around a Schwarzschild metric arising from regular initial data remain globally bounded on the black hole exterior and in fact decay to a linearised Kerr metric. We express the equations in a suitable double null gauge. To obtain decay, one must in fact add a residual pure gauge solution which we prove to be itself quantitatively controlled from initial data. Our result a fortiori includes decay statements for general solutions of the Teukolsky equation (satisfied by gauge-invariant null-decomposed curvature components). These latter statements are in fact deduced in the course of the proof by exploiting associated quantities shown to satisfy the Regge--Wheeler equation, for which appropriate decay can be obtained easily by adapting previous work on the linear scalar wave equation. The bounds on the rate of decay to linearised Kerr are inverse polynomial, suggesting that dispersion is sufficient to control the non-linearities of the Einstein equations in a potential future proof of nonlinear stability. This paper is self-contained and includes a physical-space derivation of the equations of linearised gravity around Schwarzschild from the full non-linear Einstein vacuum equations expressed in a double null gauge. |
0705.0246 | Valerio Bozza | V. Bozza, G. Scarpetta | Strong deflection limit of black hole gravitational lensing with
arbitrary source distances | 20 pages, 8 figures, appendix added. In press on Physical Review D | Phys.Rev.D76:083008,2007 | 10.1103/PhysRevD.76.083008 | null | gr-qc astro-ph | null | The gravitational field of supermassive black holes is able to strongly bend
light rays emitted by nearby sources. When the deflection angle exceeds $\pi$,
gravitational lensing can be analytically approximated by the so-called strong
deflection limit. In this paper we remove the conventional assumption of
sources very far from the black hole, considering the distance of the source as
an additional parameter in the lensing problem to be treated exactly. We find
expressions for critical curves, caustics and all lensing observables valid for
any position of the source up to the horizon. After analyzing the spherically
symmetric case we focus on the Kerr black hole, for which we present an
analytical 3-dimensional description of the higher order caustic tubes.
| [
{
"created": "Wed, 2 May 2007 10:39:43 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Sep 2007 10:44:36 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bozza",
"V.",
""
],
[
"Scarpetta",
"G.",
""
]
] | The gravitational field of supermassive black holes is able to strongly bend light rays emitted by nearby sources. When the deflection angle exceeds $\pi$, gravitational lensing can be analytically approximated by the so-called strong deflection limit. In this paper we remove the conventional assumption of sources very far from the black hole, considering the distance of the source as an additional parameter in the lensing problem to be treated exactly. We find expressions for critical curves, caustics and all lensing observables valid for any position of the source up to the horizon. After analyzing the spherically symmetric case we focus on the Kerr black hole, for which we present an analytical 3-dimensional description of the higher order caustic tubes. |
1708.03757 | Chunshan Lin | Chunshan Lin, Shinji Mukohyama | A Class of Minimally Modified Gravity Theories | 20 pages, no figure | null | 10.1088/1475-7516/2017/10/033 | YITP17-83, IPMU17-0111 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the Hamiltonian structure of a class of gravitational theories
whose actions are linear in the lapse function. We derive the necessary and
sufficient condition for a theory in this class to have two or less local
physical degrees of freedom. As an application we then find several concrete
examples of modified gravity theories in which the total number of local
physical degrees of freedom in the gravity sector is two.
| [
{
"created": "Sat, 12 Aug 2017 09:31:49 GMT",
"version": "v1"
}
] | 2017-11-01 | [
[
"Lin",
"Chunshan",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | We investigate the Hamiltonian structure of a class of gravitational theories whose actions are linear in the lapse function. We derive the necessary and sufficient condition for a theory in this class to have two or less local physical degrees of freedom. As an application we then find several concrete examples of modified gravity theories in which the total number of local physical degrees of freedom in the gravity sector is two. |
gr-qc/9912064 | Petr Hajicek | P. Hajicek (University of Berne) | What simplified models say about unitarity and gravitational collapse | 17 pages, uses amstex, no figures | Nucl.Phys.Proc.Suppl. 88 (2000) 114-123 | 10.1016/S0920-5632(00)00759-3 | BUTP-99/29 | gr-qc | null | This paper is an extended version of a talk at the conference Constrained
Dynamics and Quantum Gravity QG99. It reviews some work on the quantum collapse
of the spherically symmetric gravitating thin shell of zero rest mass. Recent
results on Kucha\v{r} decomposition are applied. The constructed version of
quantum mechanics is unitary, although the shell falls under its Schwarzschild
radius if its energy is high enough. Rather that a permanent black hole,
something like a transient black and white hole pair seems to be created in
such a case.
| [
{
"created": "Wed, 15 Dec 1999 14:34:41 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Hajicek",
"P.",
"",
"University of Berne"
]
] | This paper is an extended version of a talk at the conference Constrained Dynamics and Quantum Gravity QG99. It reviews some work on the quantum collapse of the spherically symmetric gravitating thin shell of zero rest mass. Recent results on Kucha\v{r} decomposition are applied. The constructed version of quantum mechanics is unitary, although the shell falls under its Schwarzschild radius if its energy is high enough. Rather that a permanent black hole, something like a transient black and white hole pair seems to be created in such a case. |
gr-qc/0608072 | Santiago Esteban Perez Bergliaffa | Santiago Esteban Perez Bergliaffa | Constraining f(R) theories with the energy conditions | 4 pages, 3 figures | Phys.Lett. B642 (2006) 311-314 | 10.1016/j.physletb.2006.10.003 | null | gr-qc | null | A new method to constrain gravitational theories depending on the Ricci
scalar is presented. It is based on the weak energy condition and yields limits
on the parameters of a given theory through the current values of the
derivatives of the scale factor of the Friedmann-Robertson-Walker geometry. A
further constraint depending on the current value of the snap is also given.
Actual constraints (and the corresponding error propagation analysis) are
calculated for two examples, which show that the method is useful in limiting
the possible $f(R)$ theories.
| [
{
"created": "Tue, 15 Aug 2006 18:34:37 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Bergliaffa",
"Santiago Esteban Perez",
""
]
] | A new method to constrain gravitational theories depending on the Ricci scalar is presented. It is based on the weak energy condition and yields limits on the parameters of a given theory through the current values of the derivatives of the scale factor of the Friedmann-Robertson-Walker geometry. A further constraint depending on the current value of the snap is also given. Actual constraints (and the corresponding error propagation analysis) are calculated for two examples, which show that the method is useful in limiting the possible $f(R)$ theories. |
gr-qc/0409112 | Ulvi Yurtsever | Ulvi Yurtsever and George Hockney | Signaling, Entanglement, and Quantum Evolution Beyond Cauchy Horizons | Combined, revised, and expanded version of quant-ph/0312160 and
hep-th/0402060; 13 pages, RevTeX, 2 eps figures | Class.Quant.Grav. 22 (2005) 295-312 | 10.1088/0264-9381/22/2/004 | null | gr-qc hep-th quant-ph | null | Consider a bipartite entangled system half of which falls through the event
horizon of an evaporating black hole, while the other half remains coherently
accessible to experiments in the exterior region. Beyond complete evaporation,
the evolution of the quantum state past the Cauchy horizon cannot remain
unitary, raising the questions: How can this evolution be described as a
quantum map, and how is causality preserved? What are the possible effects of
such nonstandard quantum evolution maps on the behavior of the entangled
laboratory partner? More generally, the laws of quantum evolution under extreme
conditions in remote regions (not just in evaporating black-hole interiors, but
possibly near other naked singularities and regions of extreme spacetime
structure) remain untested by observation, and might conceivably be non-unitary
or even nonlinear, raising the same questions about the evolution of entangled
states. The answers to these questions are subtle, and are linked in unexpected
ways to the fundamental laws of quantum mechanics. We show that terrestrial
experiments can be designed to probe and constrain exactly how the laws of
quantum evolution might be altered, either by black-hole evaporation, or by
other extreme processes in remote regions possibly governed by unknown physics.
| [
{
"created": "Wed, 29 Sep 2004 08:16:42 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Yurtsever",
"Ulvi",
""
],
[
"Hockney",
"George",
""
]
] | Consider a bipartite entangled system half of which falls through the event horizon of an evaporating black hole, while the other half remains coherently accessible to experiments in the exterior region. Beyond complete evaporation, the evolution of the quantum state past the Cauchy horizon cannot remain unitary, raising the questions: How can this evolution be described as a quantum map, and how is causality preserved? What are the possible effects of such nonstandard quantum evolution maps on the behavior of the entangled laboratory partner? More generally, the laws of quantum evolution under extreme conditions in remote regions (not just in evaporating black-hole interiors, but possibly near other naked singularities and regions of extreme spacetime structure) remain untested by observation, and might conceivably be non-unitary or even nonlinear, raising the same questions about the evolution of entangled states. The answers to these questions are subtle, and are linked in unexpected ways to the fundamental laws of quantum mechanics. We show that terrestrial experiments can be designed to probe and constrain exactly how the laws of quantum evolution might be altered, either by black-hole evaporation, or by other extreme processes in remote regions possibly governed by unknown physics. |
2310.04221 | Ekapong Hirunsirisawat | Chatchai Promsiri, Weerawit Horinouchi, Ekapong Hirunsirisawat | Remarks on the light ring images and the optical appearance of hairy
black holes in Einstein-Maxwell-dilaton gravity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The behaviors of null geodesics in the spherical symmetric black holes in
Einstein-Maxwell-dilaton (EMD) theory with coupling function
$f(\Phi)=e^{-2\alpha \Phi}$ are meticulously analyzed. We investigate the
effects of coupling constant $\alpha$ on the effective potential of photon
trajectories within three ranges, namely $0<\alpha <1$, $\alpha =1$ and $\alpha
>1$. We find that the thicknesses of lensing and photon rings are smaller at
larger $\alpha$ and fixed electric charge in the unit of mass $q$, whereas they
are larger at fixed $\alpha$ and larger $q$. Remarkably, the behaviors of
photon trajectories are found to be more interesting when $\alpha>1$. Namely,
the radius of the black hole shadow $R_\text{s}$ becomes to be smaller than the
photon sphere radius $r_\text{ph}$ when $\alpha > 1$ and $q>q^*$. Moreover,
$R_\text{s}$ goes to zero as $q$ saturates the extremal limit, beyond which the
photon orbit becomes absent. %This tends to be consistent with the result of
Wilczek. Furthermore, we construct the optical appearance of black holes
surrounded by optically and geometrically thin accretion disks with three
emission models. Our results indicate that the observed flux originating from
the lensing and photon rings exhibits suppression as $\alpha$ increases, while
it undergoes amplification with the increasing parameter $q$.
| [
{
"created": "Fri, 6 Oct 2023 13:09:50 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Oct 2023 13:37:56 GMT",
"version": "v2"
}
] | 2023-10-20 | [
[
"Promsiri",
"Chatchai",
""
],
[
"Horinouchi",
"Weerawit",
""
],
[
"Hirunsirisawat",
"Ekapong",
""
]
] | The behaviors of null geodesics in the spherical symmetric black holes in Einstein-Maxwell-dilaton (EMD) theory with coupling function $f(\Phi)=e^{-2\alpha \Phi}$ are meticulously analyzed. We investigate the effects of coupling constant $\alpha$ on the effective potential of photon trajectories within three ranges, namely $0<\alpha <1$, $\alpha =1$ and $\alpha >1$. We find that the thicknesses of lensing and photon rings are smaller at larger $\alpha$ and fixed electric charge in the unit of mass $q$, whereas they are larger at fixed $\alpha$ and larger $q$. Remarkably, the behaviors of photon trajectories are found to be more interesting when $\alpha>1$. Namely, the radius of the black hole shadow $R_\text{s}$ becomes to be smaller than the photon sphere radius $r_\text{ph}$ when $\alpha > 1$ and $q>q^*$. Moreover, $R_\text{s}$ goes to zero as $q$ saturates the extremal limit, beyond which the photon orbit becomes absent. %This tends to be consistent with the result of Wilczek. Furthermore, we construct the optical appearance of black holes surrounded by optically and geometrically thin accretion disks with three emission models. Our results indicate that the observed flux originating from the lensing and photon rings exhibits suppression as $\alpha$ increases, while it undergoes amplification with the increasing parameter $q$. |
gr-qc/0209027 | Lorenzo Iorio | Lorenzo Iorio, David M. Lucchesi | LAGEOS-type Satellites in Critical Supplementary Orbit Configuration and
the Lense-Thirring Effect Detection | LaTex2e, 20 pages, 7 Tables, 6 Figures. Changes in Introduction,
Conclusions, reference added, accepted for publication in Classical and
Quantum Gravity | Class.Quant.Grav. 20 (2003) 2477-2490 | 10.1088/0264-9381/20/13/302 | null | gr-qc astro-ph physics.space-ph | null | In this paper we analyze quantitatively the concept of LAGEOS--type
satellites in critical supplementary orbit configuration (CSOC) which has
proven capable of yielding various observables for many tests of General
Relativity in the terrestrial gravitational field, with particular emphasis on
the measurement of the Lense--Thirring effect.
| [
{
"created": "Mon, 9 Sep 2002 10:27:54 GMT",
"version": "v1"
},
{
"created": "Sat, 17 May 2003 13:36:05 GMT",
"version": "v2"
},
{
"created": "Tue, 20 May 2003 13:44:26 GMT",
"version": "v3"
}
] | 2007-11-12 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Lucchesi",
"David M.",
""
]
] | In this paper we analyze quantitatively the concept of LAGEOS--type satellites in critical supplementary orbit configuration (CSOC) which has proven capable of yielding various observables for many tests of General Relativity in the terrestrial gravitational field, with particular emphasis on the measurement of the Lense--Thirring effect. |
2005.03690 | Ernesto F. Eiroa | Javier Bad\'ia, Ernesto F. Eiroa | Influence of an anisotropic matter field on the shadow of a rotating
black hole | 14 pages, 5 figures; v2: extended and improved version, new
references added | Phys. Rev. D 102, 024066 (2020) | 10.1103/PhysRevD.102.024066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the shadow produced by rotating black holes with
charge in the presence of an anisotropic matter field. We obtain the apparent
shape and the corresponding observables characterizing the size, oblateness,
and deviation of the center, for different values of the parameters of the
model. We compare the new results with those corresponding to the Kerr-Newmann
spacetime and we also discuss the observational prospects in this case.
| [
{
"created": "Thu, 7 May 2020 18:27:52 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 16:11:20 GMT",
"version": "v2"
}
] | 2020-07-24 | [
[
"Badía",
"Javier",
""
],
[
"Eiroa",
"Ernesto F.",
""
]
] | In this paper, we study the shadow produced by rotating black holes with charge in the presence of an anisotropic matter field. We obtain the apparent shape and the corresponding observables characterizing the size, oblateness, and deviation of the center, for different values of the parameters of the model. We compare the new results with those corresponding to the Kerr-Newmann spacetime and we also discuss the observational prospects in this case. |
0710.0814 | Jannie Leach | Naureen Goheer, Jannie A. Leach and Peter K.S. Dunsby | Dynamical systems analysis of anisotropic cosmologies in $R^n$-gravity | 21pages, revised to match published version | Class.Quant.Grav.24:5689-5708,2007 | 10.1088/0264-9381/24/22/026 | null | gr-qc astro-ph math.DS | null | In this paper we study the dynamics of {\it orthogonal spatially homogeneous}
Bianchi cosmologies in $R^n$-gravity. We construct a compact state space by
dividing the state space into different sectors. We perform a detailed analysis
of the cosmological behaviour in terms of the parameter $n$, determining all
the equilibrium points, their stability and corresponding cosmological
evolution. In particular, the appropriately compactified state space allows us
to investigate static and bouncing solutions. We find no Einstein static
solutions, but there do exist cosmologies with bounce behaviours. We also
investigate the isotropisation of these models and find that all isotropic
points are flat Friedmann like.
| [
{
"created": "Wed, 3 Oct 2007 15:47:31 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2007 15:55:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Goheer",
"Naureen",
""
],
[
"Leach",
"Jannie A.",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | In this paper we study the dynamics of {\it orthogonal spatially homogeneous} Bianchi cosmologies in $R^n$-gravity. We construct a compact state space by dividing the state space into different sectors. We perform a detailed analysis of the cosmological behaviour in terms of the parameter $n$, determining all the equilibrium points, their stability and corresponding cosmological evolution. In particular, the appropriately compactified state space allows us to investigate static and bouncing solutions. We find no Einstein static solutions, but there do exist cosmologies with bounce behaviours. We also investigate the isotropisation of these models and find that all isotropic points are flat Friedmann like. |
gr-qc/9809043 | Saulo Carneiro | Saulo Carneiro | A Godel-Friedman cosmology? | Extended version, accepted for publication in Physical Review D | Phys.Rev. D61 (2000) 083506 | 10.1103/PhysRevD.61.083506 | null | gr-qc astro-ph hep-th | null | Based on the mathematical similarity between the Friedman open metric and
Godel's metric in the case of nearby distances, we investigate a new scenario
for the Universe's evolution, where the present Friedman universe originates
from a primordial Godel universe by a phase transition during which the
cosmological constant vanishes. Using Hubble's constant and the present matter
density as input, we show that the radius and density of the primordial Godel
universe are close, in order of magnitude, to the present values, and that the
time of expansion coincides with the age of the Universe in the standard
Friedman model. In addition, the conservation of angular momentum provides, in
this context, a possible origin for the rotation of galaxies, leading to a
relation between the masses and spins corroborated by observational data.
| [
{
"created": "Fri, 11 Sep 1998 19:55:13 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Feb 2000 16:05:09 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Carneiro",
"Saulo",
""
]
] | Based on the mathematical similarity between the Friedman open metric and Godel's metric in the case of nearby distances, we investigate a new scenario for the Universe's evolution, where the present Friedman universe originates from a primordial Godel universe by a phase transition during which the cosmological constant vanishes. Using Hubble's constant and the present matter density as input, we show that the radius and density of the primordial Godel universe are close, in order of magnitude, to the present values, and that the time of expansion coincides with the age of the Universe in the standard Friedman model. In addition, the conservation of angular momentum provides, in this context, a possible origin for the rotation of galaxies, leading to a relation between the masses and spins corroborated by observational data. |
gr-qc/0105050 | Dragovich | G.S. Djordjevic, B. Dragovich, Lj.D. Nesic and I.V. Volovich | p-Adic and Adelic Minisuperspace Quantum Cosmology | 20 pages, Extended version which will be published in
Int.J.Mod.Phys.A | Int.J.Mod.Phys. A17 (2002) 1413-1434 | 10.1142/S0217751X02009734 | null | gr-qc | null | We consider the formulation and some elaboration of p-adic and adelic quantum
cosmology. The adelic generalization of the Hartle-Hawking proposal does not
work in models with matter fields. p-Adic and adelic minisuperspace quantum
cosmology is well defined as an ordinary application of p-adic and adelic
quantum mechanics. It is illustrated by a few minisuperspace cosmological
models in one, two and three minisuperspace dimensions. As a result of p-adic
quantum effects and the adelic approach, these models exhibit some discreteness
of the minisuperspace and cosmological constant. In particular, discreteness of
the de Sitter space and its cosmological constant is emphasized.
| [
{
"created": "Tue, 15 May 2001 11:16:39 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2002 11:26:44 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Djordjevic",
"G. S.",
""
],
[
"Dragovich",
"B.",
""
],
[
"Nesic",
"Lj. D.",
""
],
[
"Volovich",
"I. V.",
""
]
] | We consider the formulation and some elaboration of p-adic and adelic quantum cosmology. The adelic generalization of the Hartle-Hawking proposal does not work in models with matter fields. p-Adic and adelic minisuperspace quantum cosmology is well defined as an ordinary application of p-adic and adelic quantum mechanics. It is illustrated by a few minisuperspace cosmological models in one, two and three minisuperspace dimensions. As a result of p-adic quantum effects and the adelic approach, these models exhibit some discreteness of the minisuperspace and cosmological constant. In particular, discreteness of the de Sitter space and its cosmological constant is emphasized. |
2304.13087 | Hryhorii Ovcharenko | H.V.Ovcharenko, O.B.Zaslavskii | Ba\~{n}ados-Silk-West effect with finite forces near different types of
horizons: general classification of scenarios | 39 pages, 2 figures. Section XII and refs. 22 - 26 added | Phys. Rev. D 108, 064029 (2023) | 10.1103/PhysRevD.108.064029 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If two particles move towards a black hole and collide in the vicinity of the
horizon, under certain conditions their energy $E_{c.m.}$ in the center of mass
frame can grow unbounded. This is the Ba\~{n}ados-Silk-West (BSW) effect.
Usually, this effect is considered for extremal horizons and geodesic (or
electrogedesic) trajectories. We study this effect in a more general context,
when both geometric and dynamic factors are taken into account. We consider
generic axially symmetric rotating black holes. The near-horizon behavior of
metric coefficients is determined by three numbers $p,~q,$ $k$ that appear in
the Taylor expansions for different types of a horizon$.$ This includes
nonextremal, extremal and ultraextremal horizons. We also give general
classification of possible trajectories that include so-called usual,
subcritical, critical and ultracritical ones depending on the near-horizon
behavior of the radial component of the four-velocity. We assume that particles
move not freely but under the action of some unspecified force. We find when
the finiteness of a force and the BSW effect are compatible with each other.
The BSW effect implies that one of two particles has fine-tuned parameters. We
show that such a particle always requires an infinite proper time for reaching
the horizon. Otherwise, either a force becomes infinite or a horizon fails to
be regular. This realizes the so-called principle of kinematic censorship that
forbids literally infinite $E_{c.m.}$ in any act of collision. The obtained
general results are illustrated for the Kerr-Newman-(anti-)de Sitter metric
used as an example. The description of diversity of trajectories suggested in
our work can be of use also in other contexts, beyond the BSW effect. In
particular, we find the relation between a force and the type of a trajectory.
| [
{
"created": "Tue, 25 Apr 2023 18:40:10 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Sep 2023 18:09:16 GMT",
"version": "v2"
}
] | 2023-09-19 | [
[
"Ovcharenko",
"H. V.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | If two particles move towards a black hole and collide in the vicinity of the horizon, under certain conditions their energy $E_{c.m.}$ in the center of mass frame can grow unbounded. This is the Ba\~{n}ados-Silk-West (BSW) effect. Usually, this effect is considered for extremal horizons and geodesic (or electrogedesic) trajectories. We study this effect in a more general context, when both geometric and dynamic factors are taken into account. We consider generic axially symmetric rotating black holes. The near-horizon behavior of metric coefficients is determined by three numbers $p,~q,$ $k$ that appear in the Taylor expansions for different types of a horizon$.$ This includes nonextremal, extremal and ultraextremal horizons. We also give general classification of possible trajectories that include so-called usual, subcritical, critical and ultracritical ones depending on the near-horizon behavior of the radial component of the four-velocity. We assume that particles move not freely but under the action of some unspecified force. We find when the finiteness of a force and the BSW effect are compatible with each other. The BSW effect implies that one of two particles has fine-tuned parameters. We show that such a particle always requires an infinite proper time for reaching the horizon. Otherwise, either a force becomes infinite or a horizon fails to be regular. This realizes the so-called principle of kinematic censorship that forbids literally infinite $E_{c.m.}$ in any act of collision. The obtained general results are illustrated for the Kerr-Newman-(anti-)de Sitter metric used as an example. The description of diversity of trajectories suggested in our work can be of use also in other contexts, beyond the BSW effect. In particular, we find the relation between a force and the type of a trajectory. |
2010.00451 | Salvatore Capozziello | Salvatore Capozziello, Maurizio Capriolo, Loredana Caso | Gravitational Waves in Higher Order Teleparallel Gravity | 27 pages, accepted for publication in Classical and Quantum Gravity | null | 10.1088/1361-6382/abbe71 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The teleparallel equivalent of higher order Lagrangians like $L_{\Box
R}=-R+a_{0}R^{2}+a_{1}R\Box R$ can be obtained by means of the boundary term
$B=2\nabla_{\mu}T^{\mu}$. In this perspective, we derive the field equations in
presence of matter for higher-order teleparallel gravity considering, in
particular, sixth-order theories where the $\Box$ operator is linearly
included. In the weak field approximation, gravitational wave solutions for
these theories are derived. Three states of polarization are found: the two
standard $+$ and $\times$ polarizations, namely 2-helicity massless transverse
tensor polarizations, and a 0-helicity massive, with partly transverse and
partly longitudinal scalar polarization. Moreover, these gravitational waves
exhibit four oscillation modes related to four degrees of freedom: the two
classical $+$ and $\times$ tensor modes of frequency $\omega_{1}$, related to
the standard Einstein waves with $k^{2}_{1}=0$; two mixed
longitudinal-transverse scalar modes for each frequencies $\omega_{2}$ and
$\omega_{3}$, related to two different 4-wave vectors, $k^{2}_{2}=M_{2}^{2}$
and $k^{2}_{3}=M^{2}_{3}$. The four degrees of freedom are the amplitudes of
each individual mode, i.e. $\hat{\epsilon}^{(+)}\left(\omega_{1}\right)$,
$\hat{\epsilon}^{(\times)}\left(\omega_{1}\right)$,
$\hat{B}_{2}\left(\mathbf{k}\right)$, and $\hat{B}_{3}\left(\mathbf{k}\right)$.
| [
{
"created": "Thu, 1 Oct 2020 14:46:06 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Capriolo",
"Maurizio",
""
],
[
"Caso",
"Loredana",
""
]
] | The teleparallel equivalent of higher order Lagrangians like $L_{\Box R}=-R+a_{0}R^{2}+a_{1}R\Box R$ can be obtained by means of the boundary term $B=2\nabla_{\mu}T^{\mu}$. In this perspective, we derive the field equations in presence of matter for higher-order teleparallel gravity considering, in particular, sixth-order theories where the $\Box$ operator is linearly included. In the weak field approximation, gravitational wave solutions for these theories are derived. Three states of polarization are found: the two standard $+$ and $\times$ polarizations, namely 2-helicity massless transverse tensor polarizations, and a 0-helicity massive, with partly transverse and partly longitudinal scalar polarization. Moreover, these gravitational waves exhibit four oscillation modes related to four degrees of freedom: the two classical $+$ and $\times$ tensor modes of frequency $\omega_{1}$, related to the standard Einstein waves with $k^{2}_{1}=0$; two mixed longitudinal-transverse scalar modes for each frequencies $\omega_{2}$ and $\omega_{3}$, related to two different 4-wave vectors, $k^{2}_{2}=M_{2}^{2}$ and $k^{2}_{3}=M^{2}_{3}$. The four degrees of freedom are the amplitudes of each individual mode, i.e. $\hat{\epsilon}^{(+)}\left(\omega_{1}\right)$, $\hat{\epsilon}^{(\times)}\left(\omega_{1}\right)$, $\hat{B}_{2}\left(\mathbf{k}\right)$, and $\hat{B}_{3}\left(\mathbf{k}\right)$. |
gr-qc/0109057 | Alejandro Corichi | A. Corichi, G. Cruz, A. Minzoni, P. Padilla, M Rosenbaum, M.P. Ryan,
N.F. Smyth, T. Vukasinac | Quantum Collapse of a Small Dust Shell | 23 pages, 8 figures, Revtex4 file | Phys.Rev. D65 (2002) 064006 | 10.1103/PhysRevD.65.064006 | ICN-UNAM-01-18 | gr-qc hep-th | null | The full quantum mechanical collapse of a small relativistic dust shell is
studied analytically, asymptotically and numerically starting from the exact
finite dimensional classical reduced Hamiltonian recently derived by
H\'aj{\'\i}\v{c}ek and Kucha\v{r}. The formulation of the quantum mechanics
encounters two problems. The first is the multivalued nature of the Hamiltonian
and the second is the construction of an appropriate self adjoint momentum
operator in the space of the shell motion which is confined to a half line. The
first problem is solved by identifying and neglecting orbits of small action in
order to obtain a single valued Hamiltonian. The second problem is solved by
introducing an appropriate lapse function. The resulting quantum mechanics is
then studied by means of analytical and numerical techniques. We find that the
region of total collapse has very small probability. We also find that the
solution concentrates around the classical Schwarzschild radius. The present
work obtains from first principles a quantum mechanics for the shell and
provides numerical solutions, whose behavior is explained by a detailed WKB
analysis for a wide class of collapsing shells.
| [
{
"created": "Mon, 17 Sep 2001 22:06:15 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Corichi",
"A.",
""
],
[
"Cruz",
"G.",
""
],
[
"Minzoni",
"A.",
""
],
[
"Padilla",
"P.",
""
],
[
"Rosenbaum",
"M",
""
],
[
"Ryan",
"M. P.",
""
],
[
"Smyth",
"N. F.",
""
],
[
"Vukasinac",
"T.",
... | The full quantum mechanical collapse of a small relativistic dust shell is studied analytically, asymptotically and numerically starting from the exact finite dimensional classical reduced Hamiltonian recently derived by H\'aj{\'\i}\v{c}ek and Kucha\v{r}. The formulation of the quantum mechanics encounters two problems. The first is the multivalued nature of the Hamiltonian and the second is the construction of an appropriate self adjoint momentum operator in the space of the shell motion which is confined to a half line. The first problem is solved by identifying and neglecting orbits of small action in order to obtain a single valued Hamiltonian. The second problem is solved by introducing an appropriate lapse function. The resulting quantum mechanics is then studied by means of analytical and numerical techniques. We find that the region of total collapse has very small probability. We also find that the solution concentrates around the classical Schwarzschild radius. The present work obtains from first principles a quantum mechanics for the shell and provides numerical solutions, whose behavior is explained by a detailed WKB analysis for a wide class of collapsing shells. |
0809.0998 | Matteo Luca Ruggiero | Donato Bini, Andrea Geralico, Matteo Luca Ruggiero, Angelo Tartaglia | Emission vs Fermi coordinates: applications to relativistic positioning
systems | 12 pages iop style, 2 eps figures, to appear on Classical and Quantum
Gravity, 2008 | Class.Quant.Grav.25:205011,2008 | 10.1088/0264-9381/25/20/205011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A 4-dimensional relativistic positioning system for a general spacetime is
constructed by using the so called "emission coordinates". The results apply in
a small region around the world line of an accelerated observer carrying a
Fermi triad, as described by the Fermi metric. In the case of a Schwarzschild
spacetime modeling the gravitational field around the Earth and an observer at
rest at a fixed spacetime point, these coordinates realize a relativistic
positioning system alternative to the current GPS system. The latter is indeed
essentially conceived as Newtonian, so that it necessarily needs taking into
account at least the most important relativistic effects through Post-Newtonian
corrections to work properly. Previous results concerning emission coordinates
in flat spacetime are thus extended to this more general situation.
Furthermore, the mapping between spacetime coordinates and emission coordinates
is completely determined by means of the world function, which in the case of a
Fermi metric can be explicitly obtained.
| [
{
"created": "Fri, 5 Sep 2008 10:13:27 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Tartaglia",
"Angelo",
""
]
] | A 4-dimensional relativistic positioning system for a general spacetime is constructed by using the so called "emission coordinates". The results apply in a small region around the world line of an accelerated observer carrying a Fermi triad, as described by the Fermi metric. In the case of a Schwarzschild spacetime modeling the gravitational field around the Earth and an observer at rest at a fixed spacetime point, these coordinates realize a relativistic positioning system alternative to the current GPS system. The latter is indeed essentially conceived as Newtonian, so that it necessarily needs taking into account at least the most important relativistic effects through Post-Newtonian corrections to work properly. Previous results concerning emission coordinates in flat spacetime are thus extended to this more general situation. Furthermore, the mapping between spacetime coordinates and emission coordinates is completely determined by means of the world function, which in the case of a Fermi metric can be explicitly obtained. |
1303.1544 | Manuel Kraemer | Manuel Kraemer | Can one observe quantum-gravitational effects in the cosmic microwave
background? | 3 pages, submitted to the Proceedings of the 13th Marcel Grossmann
Meeting, Stockholm, July 2012 | null | 10.1142/9789814623995_0241 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to find the correct theory of quantum gravity, one has to look for
observational effects in any candidate theory. Here, we focus on canonical
quantum gravity and calculate the quantum-gravitational contributions to the
anisotropy spectrum of the cosmic microwave background that arise from a
semiclassical approximation to the Wheeler-DeWitt equation. While the resulting
modification of the power spectrum at large scales is too weak to be
observable, we find an upper bound on the energy scale of inflation.
| [
{
"created": "Wed, 6 Mar 2013 21:04:44 GMT",
"version": "v1"
}
] | 2016-05-20 | [
[
"Kraemer",
"Manuel",
""
]
] | In order to find the correct theory of quantum gravity, one has to look for observational effects in any candidate theory. Here, we focus on canonical quantum gravity and calculate the quantum-gravitational contributions to the anisotropy spectrum of the cosmic microwave background that arise from a semiclassical approximation to the Wheeler-DeWitt equation. While the resulting modification of the power spectrum at large scales is too weak to be observable, we find an upper bound on the energy scale of inflation. |
0906.2622 | Meng-Sen Ma | Chao-Guang Huang, Meng-Sen Ma | On Torsion-free Vacuum Solutions of the Model of de Sitter Gauge Theory
of Gravity (II) | 4 pafes,0 figure | Front.Phys.China 4:525-529,2009 | 10.1007/s11467-009-0063-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that all torsion-free vacuum solutions of the model of dS gauge
theory of gravity are the vacuum solutions of Einstein field equations with the
same positive cosmological constant. Furthermore, for the gravitational
theories with more general quadratic gravitational Lagrangian ($F^2+T^2$), the
torsion-free vacuum solutions are also the vacuum solutions of Einstein field
equations.
| [
{
"created": "Mon, 15 Jun 2009 07:31:45 GMT",
"version": "v1"
}
] | 2009-10-02 | [
[
"Huang",
"Chao-Guang",
""
],
[
"Ma",
"Meng-Sen",
""
]
] | It is shown that all torsion-free vacuum solutions of the model of dS gauge theory of gravity are the vacuum solutions of Einstein field equations with the same positive cosmological constant. Furthermore, for the gravitational theories with more general quadratic gravitational Lagrangian ($F^2+T^2$), the torsion-free vacuum solutions are also the vacuum solutions of Einstein field equations. |
2204.03056 | Gaoping Long | Gaoping Long | Twisted geometry coherent states in all dimensional loop quantum
gravity: II. Ehrenfest Property | null | null | 10.1103/PhysRevD.106.066021 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In the preceding paper of this series of articles we constructed the twisted
geometry coherent states in all dimensional loop quantum gravity and
established their peakedness properties. In this paper we establish the
"Ehrenfest property" of these coherent states which are labelled by the twisted
geometry parameters. By this we mean that the expectation values of the
polynomials of the elementary operators as well as the operators which are not
polynomial functions of the elementary operators, reproduce, to zeroth order in
$\hbar$, the values of the corresponding classical functions at the twisted
geometry space point where the coherent state is peaked.
| [
{
"created": "Wed, 6 Apr 2022 19:46:51 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Apr 2022 19:20:46 GMT",
"version": "v2"
}
] | 2022-10-05 | [
[
"Long",
"Gaoping",
""
]
] | In the preceding paper of this series of articles we constructed the twisted geometry coherent states in all dimensional loop quantum gravity and established their peakedness properties. In this paper we establish the "Ehrenfest property" of these coherent states which are labelled by the twisted geometry parameters. By this we mean that the expectation values of the polynomials of the elementary operators as well as the operators which are not polynomial functions of the elementary operators, reproduce, to zeroth order in $\hbar$, the values of the corresponding classical functions at the twisted geometry space point where the coherent state is peaked. |
2309.16315 | Nobuyoshi Komatsu | Nobuyoshi Komatsu | Cosmological model based on both holographic-like connection and
Padmanabhan's holographic equipartition law | Final version accepted for publication in PRD. [13 pages, 1 figure] | Phys. Rev. D 109, 023505 (2024) | 10.1103/PhysRevD.109.023505 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | A cosmological model based on holographic scenarios is formulated in a flat
Friedmann-Robertson-Walker universe. To formulate this model, the cosmological
horizon is assumed to have a general entropy and a general temperature
(including Bekenstein-Hawking entropy and Gibbons-Hawking temperature,
respectively). In addition, a holographic-like connection [Eur. Phys. J. C 83,
690 (2023) (arXiv:2212.05822)] and Padmanabhan's holographic equipartition law
are assumed for the entropy and temperature, and the Friedmann and acceleration
equations are derived from these. The derived Friedmann and acceleration
equations include both the entropy and the temperature and are slightly
complicated, but can be combined into a single simple equation, corresponding
to a similar equation that describes the background evolution of the universe
in time-varying $\Lambda (t)$ cosmologies. The simple equation depends on the
entropy but not on the temperature because the temperatures in the Friedmann
and acceleration equations cancel each other. These results imply that the
holographic-like connection should be consistent with Padmanabhan's holographic
equipartition law through the present model and that the entropy plays a more
important role. When the Gibbons-Hawking temperature is used as the
temperature, the Friedmann and acceleration equations are found to be
equivalent to those for a $\Lambda(t)$ model. A particular case of the present
model is also examined, applying a power-law corrected entropy.
| [
{
"created": "Thu, 28 Sep 2023 10:10:11 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Dec 2023 22:56:48 GMT",
"version": "v2"
}
] | 2024-01-09 | [
[
"Komatsu",
"Nobuyoshi",
""
]
] | A cosmological model based on holographic scenarios is formulated in a flat Friedmann-Robertson-Walker universe. To formulate this model, the cosmological horizon is assumed to have a general entropy and a general temperature (including Bekenstein-Hawking entropy and Gibbons-Hawking temperature, respectively). In addition, a holographic-like connection [Eur. Phys. J. C 83, 690 (2023) (arXiv:2212.05822)] and Padmanabhan's holographic equipartition law are assumed for the entropy and temperature, and the Friedmann and acceleration equations are derived from these. The derived Friedmann and acceleration equations include both the entropy and the temperature and are slightly complicated, but can be combined into a single simple equation, corresponding to a similar equation that describes the background evolution of the universe in time-varying $\Lambda (t)$ cosmologies. The simple equation depends on the entropy but not on the temperature because the temperatures in the Friedmann and acceleration equations cancel each other. These results imply that the holographic-like connection should be consistent with Padmanabhan's holographic equipartition law through the present model and that the entropy plays a more important role. When the Gibbons-Hawking temperature is used as the temperature, the Friedmann and acceleration equations are found to be equivalent to those for a $\Lambda(t)$ model. A particular case of the present model is also examined, applying a power-law corrected entropy. |
2105.14985 | Zhi-Wei Wang | Zhi-Wei Wang and Samuel L. Braunstein | Noether charge astronomy | 15 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Noether's theorem identifies fundamental conserved quantities, called Noether
charges, from a Hamiltonian. To-date Noether charges remain largely elusive
within theories of gravity: We do not know how to directly measure them, and
their physical interpretation remains unsettled in general spacetimes. Here we
show that the surface gravity as naturally defined for a family of observers in
arbitrarily dynamical spacetimes is a directly measurable Noether charge. This
Noether charge reduces to the accepted value on stationary horizons, and, when
integrated over a closed surface, yields an energy with the characteristics of
gravitating mass. Stokes' theorem then identifies the gravitating energy
density as the time-component of a locally conserved Noether current in general
spacetimes. Our conclusion, that this Noether charge is extractable from
astronomical observations, holds the potential for determining the detailed
distribution of the gravitating mass in galaxies, galaxy clusters and beyond.
| [
{
"created": "Mon, 31 May 2021 14:13:59 GMT",
"version": "v1"
}
] | 2021-06-01 | [
[
"Wang",
"Zhi-Wei",
""
],
[
"Braunstein",
"Samuel L.",
""
]
] | Noether's theorem identifies fundamental conserved quantities, called Noether charges, from a Hamiltonian. To-date Noether charges remain largely elusive within theories of gravity: We do not know how to directly measure them, and their physical interpretation remains unsettled in general spacetimes. Here we show that the surface gravity as naturally defined for a family of observers in arbitrarily dynamical spacetimes is a directly measurable Noether charge. This Noether charge reduces to the accepted value on stationary horizons, and, when integrated over a closed surface, yields an energy with the characteristics of gravitating mass. Stokes' theorem then identifies the gravitating energy density as the time-component of a locally conserved Noether current in general spacetimes. Our conclusion, that this Noether charge is extractable from astronomical observations, holds the potential for determining the detailed distribution of the gravitating mass in galaxies, galaxy clusters and beyond. |
1410.2718 | Narayan Banerjee | Sridip Pal and Narayan Banerjee | Addressing the issue of non-unitarity in anisotropic quantum cosmology | 6 two column pages, no figure, accepted for publication in Physical
Review D | null | 10.1103/PhysRevD.90.104001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we show that the widely believed pathology of the
non-unitarity of anisotropic quantum cosmological models cannot be a generic
problem. We exhibit a non trivial example, a Bianchi-I model with an
ultrarelativistic fluid, that has a well behaved time independent norm. We also
show that a suitable operator ordering should produce time independent norms
for the wave packets in the case of other more realistic fluids as well.
| [
{
"created": "Fri, 10 Oct 2014 09:17:31 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Pal",
"Sridip",
""
],
[
"Banerjee",
"Narayan",
""
]
] | In the present work we show that the widely believed pathology of the non-unitarity of anisotropic quantum cosmological models cannot be a generic problem. We exhibit a non trivial example, a Bianchi-I model with an ultrarelativistic fluid, that has a well behaved time independent norm. We also show that a suitable operator ordering should produce time independent norms for the wave packets in the case of other more realistic fluids as well. |
gr-qc/0102047 | Sergio Dain | Sergio Dain and Helmut Friedrich | Asymptotically Flat Initial Data with Prescribed Regularity at Infinity | Latex 2e, 47 pages, no figures | Commun.Math.Phys. 222 (2001) 569-609 | 10.1007/s002200100524 | null | gr-qc | null | We prove the existence of a large class of asymptotically flat initial data
with non-vanishing mass and angular momentum for which the metric and the
extrinsic curvature have asymptotic expansions at space-like infinity in terms
of powers of a radial coordinate.
| [
{
"created": "Mon, 12 Feb 2001 15:35:25 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Dain",
"Sergio",
""
],
[
"Friedrich",
"Helmut",
""
]
] | We prove the existence of a large class of asymptotically flat initial data with non-vanishing mass and angular momentum for which the metric and the extrinsic curvature have asymptotic expansions at space-like infinity in terms of powers of a radial coordinate. |
0803.1823 | Joel Saavedra | Joel Saavedra and Yerko V\'asquez | Effective gravitational equations on brane world with induced gravity
described by $f(R)$ term | 8 pages, disscusion improved, version accepted by JCAP | null | 10.1088/1475-7516/2009/04/013 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study a generalization of DGP scenarios, where the induced
gravity is given by a $f(R)$ term. We obtain the effective gravitational
equations and the effective FLRW cosmological equation on the brane of this
model. We show that this generalization has also two regime, a 5D regime a low
energies that has a self-accelerated branch of interest for cosmology and a 4D
regime at high energies that it is described a modified gravitational theory.
| [
{
"created": "Wed, 12 Mar 2008 19:02:30 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jul 2008 15:21:28 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Apr 2009 01:33:29 GMT",
"version": "v3"
}
] | 2009-11-13 | [
[
"Saavedra",
"Joel",
""
],
[
"Vásquez",
"Yerko",
""
]
] | In this article we study a generalization of DGP scenarios, where the induced gravity is given by a $f(R)$ term. We obtain the effective gravitational equations and the effective FLRW cosmological equation on the brane of this model. We show that this generalization has also two regime, a 5D regime a low energies that has a self-accelerated branch of interest for cosmology and a 4D regime at high energies that it is described a modified gravitational theory. |
gr-qc/0605131 | Hirotaka Yoshino | Hirotaka Yoshino, Robert B. Mann | Black hole formation in the head-on collision of ultrarelativistic
charges | 24 pages, 6 figures, published version | Phys.Rev. D74 (2006) 044003 | 10.1103/PhysRevD.74.044003 | null | gr-qc hep-ph hep-th | null | We study black hole formation in the head-on collision of ultrarelativistic
charges. The metric of charged particles is obtained by boosting the
Reissner-Nordstr\"om spacetime to the speed of light. Using the slice at the
instant of collision, we study formation of the apparent horizon (AH) and
derive a condition indicating that a critical value of the electric charge is
necessary for formation to take place. Evaluating this condition for
characteristic values at the LHC, we find that the presence of charge decreases
the black hole production rate in accelerators. We comment on possible
limitations of our approach.
| [
{
"created": "Fri, 26 May 2006 14:11:14 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jul 2006 14:51:28 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Aug 2006 07:46:17 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Mann",
"Robert B.",
""
]
] | We study black hole formation in the head-on collision of ultrarelativistic charges. The metric of charged particles is obtained by boosting the Reissner-Nordstr\"om spacetime to the speed of light. Using the slice at the instant of collision, we study formation of the apparent horizon (AH) and derive a condition indicating that a critical value of the electric charge is necessary for formation to take place. Evaluating this condition for characteristic values at the LHC, we find that the presence of charge decreases the black hole production rate in accelerators. We comment on possible limitations of our approach. |
2111.02404 | Wenshuai Liu | Wenshuai Liu | Detection of extremely low frequency gravitational wave using
gravitational lens: The general case | 4 pages, 1 figure. Submitted to Physical Review D. arXiv admin note:
text overlap with arXiv:2111.02007 | null | null | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effect of gravitational wave of extremely low frequency on time delays
between different locations on the Einstein ring in a lens system with an
aligned source-deflector-observer configuration is investigated. The observer
will observe an Einstein ring from the lens system aligned in a highly
symmetric configuration. Time delays between different locations on the
Einstein ring cannot emerge without gravitational wave of cosmological
wavelength propagating through the lens system. Otherwise, different locations
on the Einstein ring will show time delays. Our previous studies showed that
time delays from different locations on the Einstein ring in the presence of
gravitational wave of cosmological wavelength present a special relationship.
But this result is limited to a specific aligned source-deflector-observer
configuration where the source and the observer are equidistant from the
deflector and the gravitational wave has special direction of propagation and
polarization. In order to investigate the property in the general case, we
extend to the general condition that the source and the observer aren't
equidistant from the deflector and the direction and polarization of the
gravitational wave is arbitrary in the present work. Results in this work show
that time delays between different locations on the Einstein ring with the
general condition present the same relationship as that in our previous
studies.
| [
{
"created": "Wed, 3 Nov 2021 04:07:35 GMT",
"version": "v1"
}
] | 2021-11-05 | [
[
"Liu",
"Wenshuai",
""
]
] | The effect of gravitational wave of extremely low frequency on time delays between different locations on the Einstein ring in a lens system with an aligned source-deflector-observer configuration is investigated. The observer will observe an Einstein ring from the lens system aligned in a highly symmetric configuration. Time delays between different locations on the Einstein ring cannot emerge without gravitational wave of cosmological wavelength propagating through the lens system. Otherwise, different locations on the Einstein ring will show time delays. Our previous studies showed that time delays from different locations on the Einstein ring in the presence of gravitational wave of cosmological wavelength present a special relationship. But this result is limited to a specific aligned source-deflector-observer configuration where the source and the observer are equidistant from the deflector and the gravitational wave has special direction of propagation and polarization. In order to investigate the property in the general case, we extend to the general condition that the source and the observer aren't equidistant from the deflector and the direction and polarization of the gravitational wave is arbitrary in the present work. Results in this work show that time delays between different locations on the Einstein ring with the general condition present the same relationship as that in our previous studies. |
gr-qc/0511048 | Yosef Zlochower | M. Campanelli, C. O. Lousto, P. Marronetti, Y. Zlochower | Accurate Evolutions of Orbiting Black-Hole Binaries Without Excision | 4 pages, revtex4, 3 figs, references added, typos fixed | Phys.Rev.Lett.96:111101,2006 | 10.1103/PhysRevLett.96.111101 | null | gr-qc astro-ph | null | We present a new algorithm for evolving orbiting black-hole binaries that
does not require excision or a corotating shift. Our algorithm is based on a
novel technique to handle the singular puncture conformal factor. This system,
based on the BSSN formulation of Einstein's equations, when used with a
`pre-collapsed' initial lapse, is non-singular at the start of the evolution,
and remains non-singular and stable provided that a good choice is made for the
gauge. As a test case, we use this technique to fully evolve orbiting
black-hole binaries from near the Innermost Stable Circular Orbit (ISCO)
regime. We show fourth order convergence of waveforms and compute the radiated
gravitational energy and angular momentum from the plunge. These results are in
good agreement with those predicted by the Lazarus approach.
| [
{
"created": "Wed, 9 Nov 2005 20:30:35 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Nov 2005 22:32:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Campanelli",
"M.",
""
],
[
"Lousto",
"C. O.",
""
],
[
"Marronetti",
"P.",
""
],
[
"Zlochower",
"Y.",
""
]
] | We present a new algorithm for evolving orbiting black-hole binaries that does not require excision or a corotating shift. Our algorithm is based on a novel technique to handle the singular puncture conformal factor. This system, based on the BSSN formulation of Einstein's equations, when used with a `pre-collapsed' initial lapse, is non-singular at the start of the evolution, and remains non-singular and stable provided that a good choice is made for the gauge. As a test case, we use this technique to fully evolve orbiting black-hole binaries from near the Innermost Stable Circular Orbit (ISCO) regime. We show fourth order convergence of waveforms and compute the radiated gravitational energy and angular momentum from the plunge. These results are in good agreement with those predicted by the Lazarus approach. |
2202.09382 | Katerina Chatziioannou | Marcella Wijngaarden, Katerina Chatziioannou, Andreas Bauswein, James
A. Clark, Neil J. Cornish | Probing neutron stars with the full pre-merger and post-merger
gravitational wave signal from binary coalescences | 18 pages, 17 figures, final published version | null | 10.1103/PhysRevD.105.104019 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The gravitational wave signal emitted during the coalescence of two neutron
stars carries information about the stars' internal structure. During the long
inspiral phase the main matter observable is the tidal interaction between the
binary components, an effect that can be parametrically modeled with
compact-binary solutions to General Relativity. After the binary merger the
main observable is frequency modes of the remnant, most commonly giving rise to
a short-duration signal accessible only through numerical simulations. The
complicated morphology and the decreasing detector sensitivity in the relevant
frequencies currently hinder detection of the post-merger signal and motivate
separate analyses for the pre-merger and post-merger data. However, planned and
ongoing detector improvements could soon put the post-merger signal within
reach. In this study we target the whole pre-merger and post-merger signal
without an artificial separation at the binary merger. We construct a hybrid
analysis that models the inspiral with templates based on analytical
calculations and calibrated to numerical relativity and the post-merger signal
with a flexible morphology-independent analysis. Applying this analysis to
GW170817 we find, as expected, that the post-merger signal remains undetected.
We further study simulated signals and find that we can reconstruct the full
signal and simultaneously estimate both the pre-merger tidal deformation and
the post-merger signal frequency content. Our analysis allows us to study
neutron star physics using all the data available and directly test the
pre-merger and post-merger signal for consistency thus probing effects such as
the onset of the hadron-quark phase transition.
| [
{
"created": "Fri, 18 Feb 2022 19:06:05 GMT",
"version": "v1"
},
{
"created": "Wed, 11 May 2022 18:48:30 GMT",
"version": "v2"
}
] | 2022-05-13 | [
[
"Wijngaarden",
"Marcella",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Bauswein",
"Andreas",
""
],
[
"Clark",
"James A.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | The gravitational wave signal emitted during the coalescence of two neutron stars carries information about the stars' internal structure. During the long inspiral phase the main matter observable is the tidal interaction between the binary components, an effect that can be parametrically modeled with compact-binary solutions to General Relativity. After the binary merger the main observable is frequency modes of the remnant, most commonly giving rise to a short-duration signal accessible only through numerical simulations. The complicated morphology and the decreasing detector sensitivity in the relevant frequencies currently hinder detection of the post-merger signal and motivate separate analyses for the pre-merger and post-merger data. However, planned and ongoing detector improvements could soon put the post-merger signal within reach. In this study we target the whole pre-merger and post-merger signal without an artificial separation at the binary merger. We construct a hybrid analysis that models the inspiral with templates based on analytical calculations and calibrated to numerical relativity and the post-merger signal with a flexible morphology-independent analysis. Applying this analysis to GW170817 we find, as expected, that the post-merger signal remains undetected. We further study simulated signals and find that we can reconstruct the full signal and simultaneously estimate both the pre-merger tidal deformation and the post-merger signal frequency content. Our analysis allows us to study neutron star physics using all the data available and directly test the pre-merger and post-merger signal for consistency thus probing effects such as the onset of the hadron-quark phase transition. |
gr-qc/9710069 | Roberto A. Sussman | Roberto A. Sussman | Ideal gas sources for the Lemaitre-Tolman-Bondi metrics | 7 pages, Plain TeX with IOP macros, important corrections to previous
version, 3 figures (to appear in Classical and Quantum Gravity, June 1998) | null | 10.1088/0264-9381/15/6/023 | null | gr-qc astro-ph physics.flu-dyn | null | New exact solutions emerge by replacing the dust source of the
Lem\^aitre-Tolman-Bondi metrics with a viscous fluid satisfying the monatomic
gas equation of state. The solutions have a consistent thermodynamical
interpretation. The most general transport equation of Extended Irreversible
Thermodynamics is satisfied, with phenomenological coefficients bearing a close
resemblance to those characterizing a non relativistic Maxwell-Bolzmann gas.
| [
{
"created": "Tue, 14 Oct 1997 01:50:06 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Mar 1998 23:36:51 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Sussman",
"Roberto A.",
""
]
] | New exact solutions emerge by replacing the dust source of the Lem\^aitre-Tolman-Bondi metrics with a viscous fluid satisfying the monatomic gas equation of state. The solutions have a consistent thermodynamical interpretation. The most general transport equation of Extended Irreversible Thermodynamics is satisfied, with phenomenological coefficients bearing a close resemblance to those characterizing a non relativistic Maxwell-Bolzmann gas. |
0707.3341 | Lukasz Andrzej Glinka | Lukasz-Andrzej Glinka | Quantum Information from Graviton-Matter Gas | This is a contribution to the Proc. of the Seventh International
Conference ''Symmetry in Nonlinear Mathematical Physics'' (June 24-30, 2007,
Kyiv, Ukraine), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA/ | SIGMA 3:087,2007 | 10.3842/SIGMA.2007.087 | null | gr-qc cond-mat.stat-mech hep-th math-ph math.MP quant-ph | null | We present basics of conceptually new-type way for explaining of the origin,
evolution and current physical properties of our Universe from the
graviton-matter gas viewpoint. Quantization method for the Friedmann-Lemaitre
Universe based on the canonical Hamilton equations of motion is proposed and
quantum information theory way to physics of the Universe is showed. The
current contribution from the graviton-matter gas temperature in quintessence
approximation is discussed.
| [
{
"created": "Mon, 23 Jul 2007 09:06:48 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jul 2007 17:18:16 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Jul 2007 13:25:12 GMT",
"version": "v3"
},
{
"created": "Mon, 20 Aug 2007 15:11:57 GMT",
"version": "v4"
},
{
"c... | 2008-12-19 | [
[
"Glinka",
"Lukasz-Andrzej",
""
]
] | We present basics of conceptually new-type way for explaining of the origin, evolution and current physical properties of our Universe from the graviton-matter gas viewpoint. Quantization method for the Friedmann-Lemaitre Universe based on the canonical Hamilton equations of motion is proposed and quantum information theory way to physics of the Universe is showed. The current contribution from the graviton-matter gas temperature in quintessence approximation is discussed. |
1410.4043 | Sunil Maharaj | Sushant G. Ghosh, Sunil D. Maharaj | Radiating Kerr-like regular black hole | 9 pages. arXiv admin note: text overlap with arXiv:1208.3028 | Eur. Phys. J. C 75, 7 (2015) | 10.1140/epjc/s10052-014-3222-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a radiating regular rotating black hole solution, radiating
Kerr-like regular black hole solution. We achieve this by starting from the
Hayward regular black hole solution via a complex transformation suggested by
Newman-Janis. The radiating Kerr metric, the Kerr-like regular black hole and
the standard Kerr metric are regained in the appropriate limits. The structure
of the horizon-like surfaces are also determined.
| [
{
"created": "Wed, 15 Oct 2014 12:49:13 GMT",
"version": "v1"
}
] | 2015-12-31 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | We derive a radiating regular rotating black hole solution, radiating Kerr-like regular black hole solution. We achieve this by starting from the Hayward regular black hole solution via a complex transformation suggested by Newman-Janis. The radiating Kerr metric, the Kerr-like regular black hole and the standard Kerr metric are regained in the appropriate limits. The structure of the horizon-like surfaces are also determined. |
1905.00818 | Patricia Schmidt | Patricia Schmidt, Tanja Hinderer | Frequency domain model of $f$-mode dynamic tides in gravitational
waveforms from compact binary inspirals | 7 pages, 3 figures; matches published version | Phys. Rev. D 100, 021501 (2019) | 10.1103/PhysRevD.100.021501 | LIGO-P1900130 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detection of gravitational waves (GWs) from the neutron star
binary inspiral GW170817 has opened a unique avenue to probe matter and
fundamental interactions in previously unexplored regimes. Extracting
information on neutron star matter from the observed GWs requires robust and
computationally efficient theoretical waveform models. We develop an
approximate frequency-domain GW phase model of a main GW signature of matter:
dynamic tides associated with the neutron stars' fundamental oscillation modes
($f$-modes). We focus on nonspinning objects on circular orbits and demonstrate
that, despite its mathematical simplicity, the new "$f$-mode tidal" (fmtidal)
model is in good agreement with the effective-one-body dynamical tides model up
to GW frequencies of $\gtrsim 1$ kHz and gives physical meaning to part of the
phenomenology captured in tidal models tuned to numerical-relativity. The
advantages of the fmtidal model are that it makes explicit the dependence of
the GW phasing on the characteristic equation-of-state parameters, i.e., tidal
deformabilities and $f$-mode frequencies; it is computationally efficient; and
it can readily be added to any frequency-domain baseline waveform. The fmtidal
model is easily amenable to future improvements and provides the means for a
first step towards independently measuring additional fundamental properties of
neutron star matter beyond the tidal deformability as well as performing novel
tests of general relativity from GW observations.
| [
{
"created": "Thu, 2 May 2019 15:48:59 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Oct 2019 08:48:58 GMT",
"version": "v2"
}
] | 2019-10-07 | [
[
"Schmidt",
"Patricia",
""
],
[
"Hinderer",
"Tanja",
""
]
] | The recent detection of gravitational waves (GWs) from the neutron star binary inspiral GW170817 has opened a unique avenue to probe matter and fundamental interactions in previously unexplored regimes. Extracting information on neutron star matter from the observed GWs requires robust and computationally efficient theoretical waveform models. We develop an approximate frequency-domain GW phase model of a main GW signature of matter: dynamic tides associated with the neutron stars' fundamental oscillation modes ($f$-modes). We focus on nonspinning objects on circular orbits and demonstrate that, despite its mathematical simplicity, the new "$f$-mode tidal" (fmtidal) model is in good agreement with the effective-one-body dynamical tides model up to GW frequencies of $\gtrsim 1$ kHz and gives physical meaning to part of the phenomenology captured in tidal models tuned to numerical-relativity. The advantages of the fmtidal model are that it makes explicit the dependence of the GW phasing on the characteristic equation-of-state parameters, i.e., tidal deformabilities and $f$-mode frequencies; it is computationally efficient; and it can readily be added to any frequency-domain baseline waveform. The fmtidal model is easily amenable to future improvements and provides the means for a first step towards independently measuring additional fundamental properties of neutron star matter beyond the tidal deformability as well as performing novel tests of general relativity from GW observations. |
gr-qc/0201090 | B. V. Ivanov | B.V.Ivanov | Maximum bounds on the surface redshift of anisotropic stars | 5 pages, Revtex, journal version, accepted in Phys. Rev. D | Phys.Rev. D65 (2002) 104011 | 10.1103/PhysRevD.65.104011 | null | gr-qc astro-ph | null | It is shown that for realistic anisotropic star models the surface redshift
can not exceed the values 3.842 or 5.211 when the tangential pressure satisfies
the strong or the dominant energy condition respectively. Both values are
higher than 2, the bound in the perfect fluid case.
| [
{
"created": "Tue, 29 Jan 2002 10:54:52 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2002 13:21:35 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Ivanov",
"B. V.",
""
]
] | It is shown that for realistic anisotropic star models the surface redshift can not exceed the values 3.842 or 5.211 when the tangential pressure satisfies the strong or the dominant energy condition respectively. Both values are higher than 2, the bound in the perfect fluid case. |
0706.0283 | Tomasz Stachowiak | Marek Szydlowski, Wlodzimierz Godlowski, Tomasz Stachowiak | Testing and selection of cosmological models with $(1+z)^6$ corrections | 19 pages, 1 figure. Version 2 generally revised and accepted for
publication | Phys.Rev.D77:043530,2008 | 10.1103/PhysRevD.77.043530 | null | gr-qc | null | In the paper we check whether the contribution of $(-)(1+z)^6$ type in the
Friedmann equation can be tested. We consider some astronomical tests to
constrain the density parameters in such models. We describe different
interpretations of such an additional term: geometric effects of Loop Quantum
Cosmology, effects of braneworld cosmological models, non-standard cosmological
models in metric-affine gravity, and models with spinning fluid. Kinematical
(or geometrical) tests based on null geodesics are insufficient to separate
individual matter components when they behave like perfect fluid and scale in
the same way. Still, it is possible to measure their overall effect. We use
recent measurements of the coordinate distances from the Fanaroff-Riley type
IIb (FRIIb) radio galaxy (RG) data, supernovae type Ia (SNIa) data, baryon
oscillation peak and cosmic microwave background radiation (CMBR) observations
to obtain stronger bounds for the contribution of the type considered. We
demonstrate that, while $\rho^2$ corrections are very small, they can be tested
by astronomical observations -- at least in principle. Bayesian criteria of
model selection (the Bayesian factor, AIC, and BIC) are used to check if
additional parameters are detectable in the present epoch. As it turns out, the
$\Lambda$CDM model is favoured over the bouncing model driven by loop quantum
effects. Or, in other words, the bounds obtained from cosmography are very
weak, and from the point of view of the present data this model is
indistinguishable from the $\Lambda$CDM one.
| [
{
"created": "Sat, 2 Jun 2007 18:42:54 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Mar 2008 18:20:33 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Mar 2008 12:13:20 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Szydlowski",
"Marek",
""
],
[
"Godlowski",
"Wlodzimierz",
""
],
[
"Stachowiak",
"Tomasz",
""
]
] | In the paper we check whether the contribution of $(-)(1+z)^6$ type in the Friedmann equation can be tested. We consider some astronomical tests to constrain the density parameters in such models. We describe different interpretations of such an additional term: geometric effects of Loop Quantum Cosmology, effects of braneworld cosmological models, non-standard cosmological models in metric-affine gravity, and models with spinning fluid. Kinematical (or geometrical) tests based on null geodesics are insufficient to separate individual matter components when they behave like perfect fluid and scale in the same way. Still, it is possible to measure their overall effect. We use recent measurements of the coordinate distances from the Fanaroff-Riley type IIb (FRIIb) radio galaxy (RG) data, supernovae type Ia (SNIa) data, baryon oscillation peak and cosmic microwave background radiation (CMBR) observations to obtain stronger bounds for the contribution of the type considered. We demonstrate that, while $\rho^2$ corrections are very small, they can be tested by astronomical observations -- at least in principle. Bayesian criteria of model selection (the Bayesian factor, AIC, and BIC) are used to check if additional parameters are detectable in the present epoch. As it turns out, the $\Lambda$CDM model is favoured over the bouncing model driven by loop quantum effects. Or, in other words, the bounds obtained from cosmography are very weak, and from the point of view of the present data this model is indistinguishable from the $\Lambda$CDM one. |
gr-qc/9303006 | null | Sean A. Hayward | General Laws of Black-Hole Dynamics | 16 pages | null | 10.1103/PhysRevD.49.6467 | null | gr-qc | null | A general definition of a black hole is given, and general `laws of
black-hole dynamics' derived. The definition involves something similar to an
apparent horizon, a trapping horizon, defined as a hypersurface foliated by
marginal surfaces of one of four non-degenerate types, described as future or
past, and outer or inner. If the boundary of an inextendible trapped region is
suitably regular, then it is a (possibly degenerate) trapping horizon. The
future outer trapping horizon provides the definition of a black hole. Outer
marginal surfaces have spherical or planar topology. Trapping horizons are null
only in the instantaneously stationary case, and otherwise outer trapping
horizons are spatial and inner trapping horizons are Lorentzian. Future outer
trapping horizons have non-decreasing area form, constant only in the null
case---the `second law'. A definition of the trapping gravity of an outer
trapping horizon is given, generalizing surface gravity. The total trapping
gravity of a compact outer marginal surface has an upper bound, attained if and
only if the trapping gravity is constant---the `zeroth law'. The variation of
the area form along an outer trapping horizon is determined by the trapping
gravity and an energy flux---the `first law'.
| [
{
"created": "Tue, 2 Mar 1993 15:27:53 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Mar 1993 14:51:54 GMT",
"version": "v2"
},
{
"created": "Wed, 25 May 1994 06:08:20 GMT",
"version": "v3"
}
] | 2009-10-22 | [
[
"Hayward",
"Sean A.",
""
]
] | A general definition of a black hole is given, and general `laws of black-hole dynamics' derived. The definition involves something similar to an apparent horizon, a trapping horizon, defined as a hypersurface foliated by marginal surfaces of one of four non-degenerate types, described as future or past, and outer or inner. If the boundary of an inextendible trapped region is suitably regular, then it is a (possibly degenerate) trapping horizon. The future outer trapping horizon provides the definition of a black hole. Outer marginal surfaces have spherical or planar topology. Trapping horizons are null only in the instantaneously stationary case, and otherwise outer trapping horizons are spatial and inner trapping horizons are Lorentzian. Future outer trapping horizons have non-decreasing area form, constant only in the null case---the `second law'. A definition of the trapping gravity of an outer trapping horizon is given, generalizing surface gravity. The total trapping gravity of a compact outer marginal surface has an upper bound, attained if and only if the trapping gravity is constant---the `zeroth law'. The variation of the area form along an outer trapping horizon is determined by the trapping gravity and an energy flux---the `first law'. |
gr-qc/9710056 | Dr John W. Barrett | John W. Barrett, Martin Rocek, Ruth M. Williams | A note on area variables in Regge calculus | 4 pages, amstex. Revision has minor changes and more precise
conclusions | Class.Quant.Grav. 16 (1999) 1373-1376 | 10.1088/0264-9381/16/4/025 | ITP-SB-97-59 | gr-qc | null | We consider the possibility of setting up a new version of Regge calculus in
four dimensions with areas of triangles as the basic variables rather than the
edge-lengths. The difficulties and restrictions of this approach are discussed.
| [
{
"created": "Fri, 10 Oct 1997 08:53:21 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 1999 10:38:54 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Barrett",
"John W.",
""
],
[
"Rocek",
"Martin",
""
],
[
"Williams",
"Ruth M.",
""
]
] | We consider the possibility of setting up a new version of Regge calculus in four dimensions with areas of triangles as the basic variables rather than the edge-lengths. The difficulties and restrictions of this approach are discussed. |
gr-qc/9412063 | Thibault Damour | T. Damour | Photon rockets and gravitational radiation | 21 pages, LATEX, submitted to Class. Quant. Grav | Class.Quant.Grav.12:725-738,1995 | 10.1088/0264-9381/12/3/011 | IHES/P/94/60 | gr-qc | null | The absence of gravitational radiation in Kinnersley's ``photon rocket''
solution of Einstein's equations is clarified by studying the mathematically
well-defined problem of point-like photon rockets in Minkowski space (i.e.
massive particles emitting null fluid anisotro\-pically and accelerating
because of the recoil). We explicitly compute the (uniquely defined) {\it
linearized} retarded gravitational waves emitted by such objects, which are the
coherent superposition of the gravitational waves generated by the motion of
the massive point-like rocket and of those generated by the energy-momentum
distribution of the photon fluid. In the special case (corresponding to
Kinnersley's solution) where the anisotropy of the photon emission is purely
dipolar we find that the gravitational wave amplitude generated by the
energy-momentum of the photons exactly cancels the usual $1/r$ gravitational
wave amplitude generated by the accelerated motion of the rocket. More general
photon anisotropies would, however, generate genuine gravitational radiation at
infinity. Our explicit calculations show the compatibility between the
non-radiative character of Kinnersley's solution and the currently used
gravitational wave generation formalisms based on post-Minkowskian perturbation
theory.
| [
{
"created": "Wed, 21 Dec 1994 09:58:33 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Damour",
"T.",
""
]
] | The absence of gravitational radiation in Kinnersley's ``photon rocket'' solution of Einstein's equations is clarified by studying the mathematically well-defined problem of point-like photon rockets in Minkowski space (i.e. massive particles emitting null fluid anisotro\-pically and accelerating because of the recoil). We explicitly compute the (uniquely defined) {\it linearized} retarded gravitational waves emitted by such objects, which are the coherent superposition of the gravitational waves generated by the motion of the massive point-like rocket and of those generated by the energy-momentum distribution of the photon fluid. In the special case (corresponding to Kinnersley's solution) where the anisotropy of the photon emission is purely dipolar we find that the gravitational wave amplitude generated by the energy-momentum of the photons exactly cancels the usual $1/r$ gravitational wave amplitude generated by the accelerated motion of the rocket. More general photon anisotropies would, however, generate genuine gravitational radiation at infinity. Our explicit calculations show the compatibility between the non-radiative character of Kinnersley's solution and the currently used gravitational wave generation formalisms based on post-Minkowskian perturbation theory. |
1907.12968 | Nasr Ahmed | Nasr Ahmed and Anirudh Pradhan | Crossing the phantom divide line in universal extra dimensions | 9 pages, 6 figures, 1 table | null | 10.1016/j.newast.2020.101406 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmic acceleration and the evolution of dark energy
across the cosmological constant boundary in universal extra dimensions UED. We
adopt an empirical approach to solve the higher-dimensional cosmological
equations so that the deceleration parameter $q$ is consistent with
observations. The expressions for the jerk and deceleration parameters are
independent of the number of dimensions $n$. The behavior of pressure in $4$D
shows a positive-to-negative transition corresponding to the
deceleration-to-acceleration cosmic transition. This pressure behavior helps in
providing an explanation to the cosmic deceleration-acceleration transition
although the reason behind the transition itself remains unknown. In the
conventional $4$D cosmology, there is a no-go theorem prevents the EoS
parameter of a single perfect fluid in FRW geometry to cross the $\omega=-1$
boundary. The current model includes a single homogenous but anisotropic
perfect fluid in a homogenous FRW metric with two different scale factors in
the ordinary $4$D and the UED. In contrast to the conventional $4$D cosmology,
we have found that the dark energy evolution in UED shows $\omega=-1$ crossing.
however, the no-go theorem is still respected in $4$D where the EoS parameter
doesn't cross the $\omega=-1$ boundary.
| [
{
"created": "Mon, 29 Jul 2019 13:32:13 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Dec 2019 15:33:44 GMT",
"version": "v2"
}
] | 2020-05-27 | [
[
"Ahmed",
"Nasr",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | We investigate the cosmic acceleration and the evolution of dark energy across the cosmological constant boundary in universal extra dimensions UED. We adopt an empirical approach to solve the higher-dimensional cosmological equations so that the deceleration parameter $q$ is consistent with observations. The expressions for the jerk and deceleration parameters are independent of the number of dimensions $n$. The behavior of pressure in $4$D shows a positive-to-negative transition corresponding to the deceleration-to-acceleration cosmic transition. This pressure behavior helps in providing an explanation to the cosmic deceleration-acceleration transition although the reason behind the transition itself remains unknown. In the conventional $4$D cosmology, there is a no-go theorem prevents the EoS parameter of a single perfect fluid in FRW geometry to cross the $\omega=-1$ boundary. The current model includes a single homogenous but anisotropic perfect fluid in a homogenous FRW metric with two different scale factors in the ordinary $4$D and the UED. In contrast to the conventional $4$D cosmology, we have found that the dark energy evolution in UED shows $\omega=-1$ crossing. however, the no-go theorem is still respected in $4$D where the EoS parameter doesn't cross the $\omega=-1$ boundary. |
2205.04761 | Yang Zhang | Xuan Ye, Yang Zhang and Bo Wang | Point-splitting regularization of the stress tensor of a coupling scalar
field in de Sitter space | 33 pages, 22 figures, published | JCAP 09 (2022) 020 | 10.1088/1475-7516/2022/09/020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform the point-splitting regularization on the vacuum stress tensor of
a coupling scalar field in de Sitter space under the guidance from the
adiabatically regularized Green's function. For the massive scalar field with
the minimal coupling $\xi=0$, the 2nd order point-splitting regularization
yields a finite vacuum stress tensor with a positive, constant energy density,
which can be identified as the cosmological constant that drives de Sitter
inflation. For the coupling $\xi\ne 0$, we find that, even if the regularized
Green's function is continuous, UV and IR convergent, the point-splitting
regularization does not automatically lead to an appropriate stress tensor. The
coupling $\xi R$ causes log divergent terms, as well as higher-order finite
terms which depend upon the path of the coincidence limit. After removing these
unwanted terms by extra treatments, the 2nd-order regularization for small
couplings $\xi \in(0,\frac{1}{7.04})$, and respectively the 0th-order
regularization for the conformal coupling $\xi=\frac16$, yield a finite,
constant vacuum stress tensor, in analogy to the case $\xi=0$. For the massless
field with $\xi=0$ or $\xi=\frac16$, the point-splitting regularization yields
a vanishing vacuum stress tensor, and there is no conformal trace anomaly for
$\xi=\frac16$. If the 4th-order regularization were taken, the regularized
energy density for general $\xi$ would be negative, which is inconsistent with
the de Sitter inflation, and the regularized Green's function would be singular
at the zero mass, which is unphysical. In all these cases, the stress tensor
from the point-splitting regularization is equal to that from the adiabatic
one.
| [
{
"created": "Tue, 10 May 2022 09:15:29 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Sep 2022 11:47:24 GMT",
"version": "v2"
}
] | 2022-09-13 | [
[
"Ye",
"Xuan",
""
],
[
"Zhang",
"Yang",
""
],
[
"Wang",
"Bo",
""
]
] | We perform the point-splitting regularization on the vacuum stress tensor of a coupling scalar field in de Sitter space under the guidance from the adiabatically regularized Green's function. For the massive scalar field with the minimal coupling $\xi=0$, the 2nd order point-splitting regularization yields a finite vacuum stress tensor with a positive, constant energy density, which can be identified as the cosmological constant that drives de Sitter inflation. For the coupling $\xi\ne 0$, we find that, even if the regularized Green's function is continuous, UV and IR convergent, the point-splitting regularization does not automatically lead to an appropriate stress tensor. The coupling $\xi R$ causes log divergent terms, as well as higher-order finite terms which depend upon the path of the coincidence limit. After removing these unwanted terms by extra treatments, the 2nd-order regularization for small couplings $\xi \in(0,\frac{1}{7.04})$, and respectively the 0th-order regularization for the conformal coupling $\xi=\frac16$, yield a finite, constant vacuum stress tensor, in analogy to the case $\xi=0$. For the massless field with $\xi=0$ or $\xi=\frac16$, the point-splitting regularization yields a vanishing vacuum stress tensor, and there is no conformal trace anomaly for $\xi=\frac16$. If the 4th-order regularization were taken, the regularized energy density for general $\xi$ would be negative, which is inconsistent with the de Sitter inflation, and the regularized Green's function would be singular at the zero mass, which is unphysical. In all these cases, the stress tensor from the point-splitting regularization is equal to that from the adiabatic one. |
1601.01215 | Muhammad Sharif | M. Sharif and Iqra Nawazish | Study of Some Chaotic Inflationary Models in f(R) Gravity | 26 pages, 7 figures, final accepted version | Astrophys. Space Sci. 363(2018)73 | 10.1007/s10509-018-3292-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss inflationary scenario via scalar field and fluid
cosmology for anisotropic homogeneous universe model in $f(R)$ gravity. We
consider an equation of state which corresponds to quasi-de Sitter expansion
and investigate the effect of anisotropy parameter for different values of
deviation parameter. We evaluate potential models like linear, quadratic and
quartic which correspond to chaotic inflation. We construct the observational
parameters for power-law model of $f(R)$ gravity and construct the graphical
analysis of tensor-scalar ratio and spectral index which indicates consistency
of these parameters with Planck 2015 data.
| [
{
"created": "Fri, 1 Jan 2016 04:57:05 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Apr 2018 02:37:43 GMT",
"version": "v2"
}
] | 2018-04-11 | [
[
"Sharif",
"M.",
""
],
[
"Nawazish",
"Iqra",
""
]
] | In this paper, we discuss inflationary scenario via scalar field and fluid cosmology for anisotropic homogeneous universe model in $f(R)$ gravity. We consider an equation of state which corresponds to quasi-de Sitter expansion and investigate the effect of anisotropy parameter for different values of deviation parameter. We evaluate potential models like linear, quadratic and quartic which correspond to chaotic inflation. We construct the observational parameters for power-law model of $f(R)$ gravity and construct the graphical analysis of tensor-scalar ratio and spectral index which indicates consistency of these parameters with Planck 2015 data. |
0906.1981 | Leonardo Fernandez-Jambrina | L. Fern\'andez-Jambrina | Multipole corrections to perihelion and node line precession | 5 pp, sprocl.sty, Proceedings of ERE'00 | null | 10.1142/9789812810021_0029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this talk relativistic corrections due to Geroch-Hansen multipoles for
perihelion precession and node line precession of orbits in a stationary
axially symmetric vacuum spacetime endowed with a plane of symmetry will be
shown. Patterns of regularity will be discussed.
| [
{
"created": "Wed, 10 Jun 2009 17:37:36 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Fernández-Jambrina",
"L.",
""
]
] | In this talk relativistic corrections due to Geroch-Hansen multipoles for perihelion precession and node line precession of orbits in a stationary axially symmetric vacuum spacetime endowed with a plane of symmetry will be shown. Patterns of regularity will be discussed. |
1506.02498 | Saibal Ray | S.K. Maurya, Y.K. Gupta, Saibal Ray and Sourav Roy Chowdhury | Spherically symmetric electromagnetic mass models of embedding class one | 21 pages, 9 figures, 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we consider the static spherically symmetric spacetime metric
of embedding class one. Specifically three new electromagnetic mass models are
derived where the solutions are entirely dependent on the electromagnetic
field, such that the physical parameters, like density, pressure etc. do vanish
for the vanishing charge. We have analyzed schematically all these three sets
of solutions related to electromagnetic mass models by plotting graphs and
shown that they can pass through all the physical tests performed by us. To
validate these special type of solutions related to electromagnetic mass models
a comparison has been done with that of compact stars and shown exclusively the
feasibility of the models.
| [
{
"created": "Sat, 30 May 2015 18:15:51 GMT",
"version": "v1"
}
] | 2015-06-09 | [
[
"Maurya",
"S. K.",
""
],
[
"Gupta",
"Y. K.",
""
],
[
"Ray",
"Saibal",
""
],
[
"Chowdhury",
"Sourav Roy",
""
]
] | In this article we consider the static spherically symmetric spacetime metric of embedding class one. Specifically three new electromagnetic mass models are derived where the solutions are entirely dependent on the electromagnetic field, such that the physical parameters, like density, pressure etc. do vanish for the vanishing charge. We have analyzed schematically all these three sets of solutions related to electromagnetic mass models by plotting graphs and shown that they can pass through all the physical tests performed by us. To validate these special type of solutions related to electromagnetic mass models a comparison has been done with that of compact stars and shown exclusively the feasibility of the models. |
1808.05280 | Joseph Rizcallah | Vladimir V. Kassandrov, Joseph A. Rizcallah and Nina V. Markova | Twistor structures and boost-invariant solutions to field equations | 10 pages, 1 figure | Gravitation and Cosmology, Vol. 23, No. 4, 300-304 (2017) | 10.1134/S0202289317040119 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a brief overview of a non-Lagrangian approach to field theory based
on a generalization of the Kerr-Penrose theorem and algebraic twistor
equations. Explicit algorithms for obtaining the set of fundamental (Maxwell,
SL(2, C)-Yang-Mills, spinor Weyl and curvature) fields associated with every
solution of the basic system of algebraic equations are reviewed. The notion of
a boost-invariant solution is introduced, and the unique axially-symmetric and
boost-invariant solution which can be generated by twistor functions is
obtained, together with the associated fields. It is found that this solution
possesses a wide variety of point-, string- and membrane-like singularities
exhibiting nontrivial dynamics and transmutations.
| [
{
"created": "Wed, 15 Aug 2018 20:25:15 GMT",
"version": "v1"
}
] | 2018-08-17 | [
[
"Kassandrov",
"Vladimir V.",
""
],
[
"Rizcallah",
"Joseph A.",
""
],
[
"Markova",
"Nina V.",
""
]
] | We give a brief overview of a non-Lagrangian approach to field theory based on a generalization of the Kerr-Penrose theorem and algebraic twistor equations. Explicit algorithms for obtaining the set of fundamental (Maxwell, SL(2, C)-Yang-Mills, spinor Weyl and curvature) fields associated with every solution of the basic system of algebraic equations are reviewed. The notion of a boost-invariant solution is introduced, and the unique axially-symmetric and boost-invariant solution which can be generated by twistor functions is obtained, together with the associated fields. It is found that this solution possesses a wide variety of point-, string- and membrane-like singularities exhibiting nontrivial dynamics and transmutations. |
gr-qc/9311006 | I. Racz | Istvan Racz | On Einstein's equations for spacetimes admitting a non-null Killing
field | 23 pages, TeX | J.Math.Phys. 38 (1997) 4237-4254 | 10.1063/1.532092 | ESI Preprint Series No. 168/94 | gr-qc | null | We consider the 3-dimensional formulation of Einstein's theory for spacetimes
possessing a non-null Killing field $\xi^a$. It is known that for the vacuum
case some of the basic field equations are deducible from the others. It will
be shown here how this result can be generalized for the case of essentially
arbitrary matter fields. The systematic study of the structure of the
fundamental field equations is carried out. In particular, the existence of
geometrically preferred reference systems is shown. Using local coordinates of
this type two approaches are presented resulting resolvent systems of partial
differential equations for the basic field variables. Finally, the above
results are applied for perfect fluid spacetimes describing possible
equilibrium configurations of relativistic dissipative fluids.
| [
{
"created": "Thu, 4 Nov 1993 14:06:00 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 1997 02:27:15 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Racz",
"Istvan",
""
]
] | We consider the 3-dimensional formulation of Einstein's theory for spacetimes possessing a non-null Killing field $\xi^a$. It is known that for the vacuum case some of the basic field equations are deducible from the others. It will be shown here how this result can be generalized for the case of essentially arbitrary matter fields. The systematic study of the structure of the fundamental field equations is carried out. In particular, the existence of geometrically preferred reference systems is shown. Using local coordinates of this type two approaches are presented resulting resolvent systems of partial differential equations for the basic field variables. Finally, the above results are applied for perfect fluid spacetimes describing possible equilibrium configurations of relativistic dissipative fluids. |
2103.14087 | S. I. Kruglov | S. I. Kruglov | Remarks on nonsingular models of Hayward and magnetized black hole with
rational nonlinear electrodynamics | 16 pages, 6 figures, 1 table, published in Gravitation and Cosmology | Gravitation and Cosmology, 2021, Vol. 27, No. 1, pp. 78-84 | 10.1134/S0202289321010126 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Hayward black hole and magnetically charged black hole based on rational
nonlinear electrodynamics with the Lagrangian ${\cal L} = -{\cal
F}/(1+2\beta{\cal F})$ (${\cal F}$ is a field invariant) are considered. It was
shown that the metric function in both models possesses a de Sitter core
without singularities as $r\rightarrow 0$. The behavior of the Hawking
temperature and the heat capacity in these models are similar. The phase
transitions take place when the Hawking temperature has a maximum, and black
holes are thermodynamically stable at some event horizon radii when the heat
capacity is positive. We show that the source of gravity in the Hayward model
is questionable.
| [
{
"created": "Thu, 25 Mar 2021 19:05:26 GMT",
"version": "v1"
}
] | 2023-11-28 | [
[
"Kruglov",
"S. I.",
""
]
] | A Hayward black hole and magnetically charged black hole based on rational nonlinear electrodynamics with the Lagrangian ${\cal L} = -{\cal F}/(1+2\beta{\cal F})$ (${\cal F}$ is a field invariant) are considered. It was shown that the metric function in both models possesses a de Sitter core without singularities as $r\rightarrow 0$. The behavior of the Hawking temperature and the heat capacity in these models are similar. The phase transitions take place when the Hawking temperature has a maximum, and black holes are thermodynamically stable at some event horizon radii when the heat capacity is positive. We show that the source of gravity in the Hayward model is questionable. |
1909.01278 | Tim Dietrich | Tim Dietrich and Katy Clough | Cooling binary neutron star remnants via nucleon-nucleon-axion
bremsstrahlung | null | Phys. Rev. D 100, 083005 (2019) | 10.1103/PhysRevD.100.083005 | null | gr-qc astro-ph.HE hep-ph nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The QCD axion is a hypothetical particle motivated by the Strong CP problem
of particle physics. One of the primary ways in which its existence can be
inferred is via its function as an additional cooling channel in stars, with
some of the strongest constraints coming from the supernova observation
SN1987A. Multimessenger observations of binary neutron star mergers (such as
those of GW170817, AT2017gfo, and GRB170817A) may provide another scenario in
which such constraints could be obtained. In particular, the axion could
potentially alter the lifetime, the ejection of material, and the emitted
gravitational wave signal of the postmerger remnant. In this article, we
perform numerical relativity simulations of a binary neutron star merger,
including a phenomenological description of the nucleon-nucleon-axion
bremsstrahlung to quantify the effects of such a cooling channel on the
dynamical evolution. While our simulations show a difference in the temperature
profile of the merger remnant, the imprint of the axion via
nucleon-nucleon-axion bremsstrahlung on the emitted gravitational wave signal
and the ejecta mass is too small to improve constraints on the axion mass with
current or future planned detectors. Whilst we consider a limited number of
cases, and a simplified cooling model, these broadly represent the "best case"
scenario, thus, a more thorough investigation is unlikely to change the
conclusions, at least for this particular interaction channel.
| [
{
"created": "Tue, 3 Sep 2019 16:19:23 GMT",
"version": "v1"
}
] | 2019-10-16 | [
[
"Dietrich",
"Tim",
""
],
[
"Clough",
"Katy",
""
]
] | The QCD axion is a hypothetical particle motivated by the Strong CP problem of particle physics. One of the primary ways in which its existence can be inferred is via its function as an additional cooling channel in stars, with some of the strongest constraints coming from the supernova observation SN1987A. Multimessenger observations of binary neutron star mergers (such as those of GW170817, AT2017gfo, and GRB170817A) may provide another scenario in which such constraints could be obtained. In particular, the axion could potentially alter the lifetime, the ejection of material, and the emitted gravitational wave signal of the postmerger remnant. In this article, we perform numerical relativity simulations of a binary neutron star merger, including a phenomenological description of the nucleon-nucleon-axion bremsstrahlung to quantify the effects of such a cooling channel on the dynamical evolution. While our simulations show a difference in the temperature profile of the merger remnant, the imprint of the axion via nucleon-nucleon-axion bremsstrahlung on the emitted gravitational wave signal and the ejecta mass is too small to improve constraints on the axion mass with current or future planned detectors. Whilst we consider a limited number of cases, and a simplified cooling model, these broadly represent the "best case" scenario, thus, a more thorough investigation is unlikely to change the conclusions, at least for this particular interaction channel. |
1812.04753 | Chul-Moon Yoo | Chul-Moon Yoo and Ken-ichi Nakao | Constant-mean-curvature Slicing of the Swiss-cheese Universe | 14 pages, 1 figure | Gen.Rel.Grav. 51 (2019) no.9, 114 | 10.1007/s10714-019-2596-0 | OCU-PHYS 493, AP-GR 152, NITEP 4 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A sequence of Constant-Mean-Curvature(CMC) slices in the Swiss-Cheese(SC)
Universe is investigated. We focus on the CMC slices which smoothly connect to
the homogeneous time slices in the Einstein-de Sitter region in the SC
universe. It is shown that the slices do not pass through the black hole region
but white hole region.
| [
{
"created": "Wed, 12 Dec 2018 00:35:55 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2019 00:50:36 GMT",
"version": "v2"
}
] | 2019-09-11 | [
[
"Yoo",
"Chul-Moon",
""
],
[
"Nakao",
"Ken-ichi",
""
]
] | A sequence of Constant-Mean-Curvature(CMC) slices in the Swiss-Cheese(SC) Universe is investigated. We focus on the CMC slices which smoothly connect to the homogeneous time slices in the Einstein-de Sitter region in the SC universe. It is shown that the slices do not pass through the black hole region but white hole region. |
gr-qc/0204063 | Ettore Minguzzi | E. Minguzzi | Simultaneity and generalized connections in general relativity | RevTeX, 9 pages, 2 figures, 1 table. Previous title "The gauge nature
of simultaneity". Classical and Quantum Gravity
http://www.iop.org/EJ/journal/CQG | Class.Quant.Grav. 20 (2003) 2443-2456 | 10.1088/0264-9381/20/11/332 | null | gr-qc | null | Stationary extended frames in general relativity are considered. The
requirement of stationarity allows to treat the spacetime as a principal fiber
bundle over the one-dimensional group of time translations. Over this bundle a
connection form establishes the simultaneity between neighboring events
accordingly with the Einstein synchronization convention. The mathematics
involved is that of gauge theories where a gauge choice is interpreted as a
global simultaneity convention. Then simultaneity in non-stationary frames is
investigated: it turns to be described by a gauge theory in a fiber bundle
without structure group, the curvature being given by the Fr\"olicher-Nijenhuis
bracket of the connection. The Bianchi identity of this gauge theory is a
differential relation between the vorticity field and the acceleration field.
In order for the simultaneity connection to be principal, a necessary and
sufficient condition on the 4-velocity of the observers is given.
| [
{
"created": "Fri, 19 Apr 2002 13:18:17 GMT",
"version": "v1"
},
{
"created": "Fri, 23 May 2003 12:23:03 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Minguzzi",
"E.",
""
]
] | Stationary extended frames in general relativity are considered. The requirement of stationarity allows to treat the spacetime as a principal fiber bundle over the one-dimensional group of time translations. Over this bundle a connection form establishes the simultaneity between neighboring events accordingly with the Einstein synchronization convention. The mathematics involved is that of gauge theories where a gauge choice is interpreted as a global simultaneity convention. Then simultaneity in non-stationary frames is investigated: it turns to be described by a gauge theory in a fiber bundle without structure group, the curvature being given by the Fr\"olicher-Nijenhuis bracket of the connection. The Bianchi identity of this gauge theory is a differential relation between the vorticity field and the acceleration field. In order for the simultaneity connection to be principal, a necessary and sufficient condition on the 4-velocity of the observers is given. |
1804.11230 | Scientific Information Service CERN | V.A. Rubakov (Moscow, INR and Moscow State U.) | Cosmology | 56 pages, presented at the 2nd Asia-Europe-Pacific School of
High-Energy Physics, Puri, India, 04 - 17 Nov 2014. arXiv admin note:
substantial text overlap with arXiv:1504.03587 | CERN Yellow Report CERN-2017-005-SP pp. 239-294 | 10.23730/CYRSP-2017-002.239 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Cosmology and particle physics are deeply interrelated. Among the common
problems are dark energy, dark matter and baryon asymmetry of the Universe. We
discuss these problems in general terms, and concentrate on several particular
hypotheses. On the dark matter side, we consider weakly interacting massive
particles and axions/axion-like particles as cold dark matter, sterile
neutrinos and gravitinos as warm dark matter. On the baryon asymmetry side, we
discuss electroweak baryogenesis as a still-viable mechanism. We briefly
describe diverse experimental and observational approaches towards checking
these hypotheses. We then turn to the earliest cosmology. We give arguments
showing that the hot stage was preceded by another epoch at which density
perturbations and possibly primordial gravity waves were generated. The best
guess here is inflation, which is consistent with everything we know of density
perturbations, but there are alternative scenarios. Future measurements of the
properties of density perturbations and possible discovery of primordial
gravity waves have strong potential in this regard.
| [
{
"created": "Mon, 30 Apr 2018 14:30:16 GMT",
"version": "v1"
}
] | 2018-05-01 | [
[
"Rubakov",
"V. A.",
"",
"Moscow, INR and Moscow State U."
]
] | Cosmology and particle physics are deeply interrelated. Among the common problems are dark energy, dark matter and baryon asymmetry of the Universe. We discuss these problems in general terms, and concentrate on several particular hypotheses. On the dark matter side, we consider weakly interacting massive particles and axions/axion-like particles as cold dark matter, sterile neutrinos and gravitinos as warm dark matter. On the baryon asymmetry side, we discuss electroweak baryogenesis as a still-viable mechanism. We briefly describe diverse experimental and observational approaches towards checking these hypotheses. We then turn to the earliest cosmology. We give arguments showing that the hot stage was preceded by another epoch at which density perturbations and possibly primordial gravity waves were generated. The best guess here is inflation, which is consistent with everything we know of density perturbations, but there are alternative scenarios. Future measurements of the properties of density perturbations and possible discovery of primordial gravity waves have strong potential in this regard. |
0711.4416 | Silke Weinfurtner | Silke Weinfurtner | Emergent spacetimes | PhD thesis at Victoria University of Wellington, New Zealand
(Advisor: Prof. Matt Visser), 234 pages | null | null | null | gr-qc | null | We discuss the possibility that spacetime geometry may be an emergent
phenomenon. This idea has been motivated by the Analogue Gravity programme.
These are systems where the kinematics of small perturbations are dominated by
an effective gravitational field. In these models there is no obvious
connection between the "gravitational" field tensor and the Einstein equations,
as the emergent spacetime geometry arises as a consequence of linearising
around some classical field. After a brief introduction on this topic, we
present our recent contributions to the field.
| [
{
"created": "Wed, 28 Nov 2007 03:56:46 GMT",
"version": "v1"
}
] | 2007-11-29 | [
[
"Weinfurtner",
"Silke",
""
]
] | We discuss the possibility that spacetime geometry may be an emergent phenomenon. This idea has been motivated by the Analogue Gravity programme. These are systems where the kinematics of small perturbations are dominated by an effective gravitational field. In these models there is no obvious connection between the "gravitational" field tensor and the Einstein equations, as the emergent spacetime geometry arises as a consequence of linearising around some classical field. After a brief introduction on this topic, we present our recent contributions to the field. |
1609.06891 | Edward Wilson-Ewing | Stefano Bianco, Victor Nicolai Friedhoff, Edward Wilson-Ewing | Modified dispersion relations, inflation and scale invariance | 9 pages. v2: Clarifications and references added | Phys. Rev. D 97, 046006 (2018) | 10.1103/PhysRevD.97.046006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a certain type of modified dispersion relations, the vacuum quantum state
for very short wavelength cosmological perturbations is scale-invariant and it
has been suggested that this may be the source of the scale-invariance observed
in the temperature anisotropies in the cosmic microwave background. We point
out that for this scenario to be possible, it is necessary to redshift these
short wavelength modes to cosmological scales in such a way that the
scale-invariance is not lost. This requires non-trivial background dynamics
before the onset of standard radiation-dominated cosmology; we demonstrate that
one possible solution is inflation with a sufficiently large Hubble rate, for
this slow roll is not necessary. In addition, we also show that if the
slow-roll condition is added to inflation with a large Hubble rate, then for
any power law modified dispersion relation quantum vacuum fluctuations become
nearly scale-invariant when they exit the Hubble radius.
| [
{
"created": "Thu, 22 Sep 2016 10:05:34 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2018 14:50:54 GMT",
"version": "v2"
}
] | 2018-02-28 | [
[
"Bianco",
"Stefano",
""
],
[
"Friedhoff",
"Victor Nicolai",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to redshift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This requires non-trivial background dynamics before the onset of standard radiation-dominated cosmology; we demonstrate that one possible solution is inflation with a sufficiently large Hubble rate, for this slow roll is not necessary. In addition, we also show that if the slow-roll condition is added to inflation with a large Hubble rate, then for any power law modified dispersion relation quantum vacuum fluctuations become nearly scale-invariant when they exit the Hubble radius. |
1603.06641 | Andre Landulfo | Andre G. S. Landulfo | Nonperturbative approach to relativistic quantum communication channels | 12 pages, Reference added, typos corrected. Minor changes to match
the published version | Phys. Rev. D 93, 104019 (2016) | 10.1103/PhysRevD.93.104019 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the transmission of both classical and quantum information
between two arbitrary observers in globally hyperbolic spacetimes using a
quantum field as a communication channel. The field is supposed to be in some
arbitrary quasifree state and no choice of representation of its canonical
commutation relations is made. Both sender and receiver possess some localized
two-level quantum system with which they can interact with the quantum field to
prepare the input and receive the output of the channel, respectively. The
interaction between the two-level systems and the quantum field is such that
one can trace out the field degrees of freedom exactly and thus obtain the
quantum channel in a nonperturbative way. We end the paper determining the
unassisted as well as the entanglement-assisted classical and quantum channel
capacities.
| [
{
"created": "Mon, 21 Mar 2016 22:58:34 GMT",
"version": "v1"
},
{
"created": "Mon, 2 May 2016 15:03:44 GMT",
"version": "v2"
},
{
"created": "Tue, 10 May 2016 21:30:19 GMT",
"version": "v3"
}
] | 2016-05-12 | [
[
"Landulfo",
"Andre G. S.",
""
]
] | We investigate the transmission of both classical and quantum information between two arbitrary observers in globally hyperbolic spacetimes using a quantum field as a communication channel. The field is supposed to be in some arbitrary quasifree state and no choice of representation of its canonical commutation relations is made. Both sender and receiver possess some localized two-level quantum system with which they can interact with the quantum field to prepare the input and receive the output of the channel, respectively. The interaction between the two-level systems and the quantum field is such that one can trace out the field degrees of freedom exactly and thus obtain the quantum channel in a nonperturbative way. We end the paper determining the unassisted as well as the entanglement-assisted classical and quantum channel capacities. |
1706.07379 | Martin Bojowald | Martin Bojowald, Suddhasattwa Brahma and Juan D. Reyes | Comment on "New variables for 1+1 dimensional gravity" | 4 pages | Class. Quantum Grav. 34 (2017) 138001 | 10.1088/1361-6382/aa7011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The results reported by Gambini, Pullin and Rastgoo in (2010 Class. Quantum
Grav. 27 025002) are special cases of a general treatment of canonical
variables for dilaton gravity models published in (2009 Class. Quantum Grav. 26
035018).
| [
{
"created": "Thu, 22 Jun 2017 16:04:01 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Bojowald",
"Martin",
""
],
[
"Brahma",
"Suddhasattwa",
""
],
[
"Reyes",
"Juan D.",
""
]
] | The results reported by Gambini, Pullin and Rastgoo in (2010 Class. Quantum Grav. 27 025002) are special cases of a general treatment of canonical variables for dilaton gravity models published in (2009 Class. Quantum Grav. 26 035018). |
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