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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0606054 | Alexander Feinstein | Alexander Feinstein | Formation of a Black String in a Higher Dimensional Vacuum Gravitational
Collapse | Minor changes. A reference added. Matches the print version. To
appear in Phys. Lett. A | Phys.Lett.A372:4337-4339,2008 | 10.1016/j.physleta.2008.03.063 | null | gr-qc hep-th | null | We present a solution to the vacuum Einstein Equations which represents a
collapse of a gravitational wave in 5 dimensions. Depending on the focal length
of the wave, the collapse results, either in a black string covered by a
horizon, or in a naked singularity which can be removed.
| [
{
"created": "Mon, 12 Jun 2006 20:08:49 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Mar 2008 07:56:50 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Feinstein",
"Alexander",
""
]
] | We present a solution to the vacuum Einstein Equations which represents a collapse of a gravitational wave in 5 dimensions. Depending on the focal length of the wave, the collapse results, either in a black string covered by a horizon, or in a naked singularity which can be removed. |
2211.11821 | Paulo Jos\'e Ferreira Porf\'irio Da Silva | A. A. Ara\'ujo Filho, J. R. Nascimento, A. Yu. Petrov, P. J.
Porf\'irio | Vacuum solution within a metric-affine bumblebee gravity | 28 pages, 1 figure, version accepted to PRD | Phys. Rev. D 108, 085010 (2023) | 10.1103/PhysRevD.108.085010 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a metric-affine extension to the gravitational sector of the
Standard-Model Extension for the Lorentz-violating coefficients $u$ and
$s^{\mu\nu}$. The general results, which are applied to a specific model called
metric--affine bumblebee gravity, are obtained. A Schwarzschild-like solution,
incorporating effects of the Lorentz symmetry breaking through coefficient
$X=\xi b^2$, is found. Furthermore, a complete study of the geodesics
trajectories of particles has been accomplished in this background, emphasizing
the departure from general relativity. We also compute the advance of Mercury's
perihelion and the deflection of light within the context of the weak field
approximation, and we verify that there exist two new contributions ascribed to
the Lorentz symmetry breaking. As a phenomenological application, we compare
our theoretical results with observational data in order to estimate the
coefficient $X$.
| [
{
"created": "Mon, 21 Nov 2022 19:42:26 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Sep 2023 15:44:12 GMT",
"version": "v2"
}
] | 2023-10-18 | [
[
"Filho",
"A. A. Araújo",
""
],
[
"Nascimento",
"J. R.",
""
],
[
"Petrov",
"A. Yu.",
""
],
[
"Porfírio",
"P. J.",
""
]
] | We consider a metric-affine extension to the gravitational sector of the Standard-Model Extension for the Lorentz-violating coefficients $u$ and $s^{\mu\nu}$. The general results, which are applied to a specific model called metric--affine bumblebee gravity, are obtained. A Schwarzschild-like solution, incorporating effects of the Lorentz symmetry breaking through coefficient $X=\xi b^2$, is found. Furthermore, a complete study of the geodesics trajectories of particles has been accomplished in this background, emphasizing the departure from general relativity. We also compute the advance of Mercury's perihelion and the deflection of light within the context of the weak field approximation, and we verify that there exist two new contributions ascribed to the Lorentz symmetry breaking. As a phenomenological application, we compare our theoretical results with observational data in order to estimate the coefficient $X$. |
2108.08729 | Kai Shi | Kai Shi, Yu Tian, Xiaoning Wu, Hongbao Zhang, and Chuanjia Zhu | Thermodynamic equilibrium condition and the first law of thermodynamics
for charged perfect fluids in electromagnetic and gravitational fields | typos corrected, clarifications made, version to appear in CQG | Class. Quantum Grav. 39 (2022) 085004 | 10.1088/1361-6382/ac5378 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a proof of the necessary and sufficient condition on the profile
of the temperature, chemical potential, and angular velocity for a charged
perfect fluid in dynamic equilibrium to be in thermodynamic equilibrium not
only in fixed but also in dynamical electromagnetic and gravitational fields.
In passing, we also present the corresponding expression for the first law of
thermodynamics for such a charged star.
| [
{
"created": "Thu, 19 Aug 2021 15:00:11 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 13:54:22 GMT",
"version": "v2"
}
] | 2022-03-30 | [
[
"Shi",
"Kai",
""
],
[
"Tian",
"Yu",
""
],
[
"Wu",
"Xiaoning",
""
],
[
"Zhang",
"Hongbao",
""
],
[
"Zhu",
"Chuanjia",
""
]
] | We provide a proof of the necessary and sufficient condition on the profile of the temperature, chemical potential, and angular velocity for a charged perfect fluid in dynamic equilibrium to be in thermodynamic equilibrium not only in fixed but also in dynamical electromagnetic and gravitational fields. In passing, we also present the corresponding expression for the first law of thermodynamics for such a charged star. |
1607.05985 | ChengGang Shao | Pengshun Luo, Jianbo Wang, Shengguo Guan, Wenjie Wu, Zhaoyang Tian,
Shanqing Yang, Chenggang Shao, Jun Luo | Test of non-Newtonian gravitational force at micrometer range | Presented at the Seventh Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 20-24, 2016 | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report an experimental test of non-Newtonian gravitational forces at mi-
crometer range. To experimentally subtract off the Casimir force and the
electrostatic force background, differential force measurements were performed
by sensing the lateral force between a gold sphere and a density modulated
source mass using a soft cantilever. The current sensitivity is limited by the
patch electrostatic force, which is further improved by two dimensional (2D)
force mapping. The preliminary result sets a model independent constraint on
the Yukawa type force at this range.
| [
{
"created": "Mon, 18 Jul 2016 09:20:18 GMT",
"version": "v1"
}
] | 2016-07-21 | [
[
"Luo",
"Pengshun",
""
],
[
"Wang",
"Jianbo",
""
],
[
"Guan",
"Shengguo",
""
],
[
"Wu",
"Wenjie",
""
],
[
"Tian",
"Zhaoyang",
""
],
[
"Yang",
"Shanqing",
""
],
[
"Shao",
"Chenggang",
""
],
[
"Luo",
"Jun",
""
]
] | We report an experimental test of non-Newtonian gravitational forces at mi- crometer range. To experimentally subtract off the Casimir force and the electrostatic force background, differential force measurements were performed by sensing the lateral force between a gold sphere and a density modulated source mass using a soft cantilever. The current sensitivity is limited by the patch electrostatic force, which is further improved by two dimensional (2D) force mapping. The preliminary result sets a model independent constraint on the Yukawa type force at this range. |
1009.5831 | Md. Rahman Atiqur | M. Atiqur Rahman | Waves in General Relativistic Two-fluid Plasma around a Schwarzschild
Black Hole | 7 pages; Astrophys Space Sci (2012). arXiv admin note: substantial
text overlap with arXiv:1008.4838 | Astrophys. Space Sci. 341 (2012) 477 | 10.1007/s10509-012-1114-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Waves propagating in the relativistic electron-positron or ions plasma are
investigated in a frame of two-fluid equations using the 3+1 formalism of
general relativity developed by Thorne, Price and Macdonald (TPM). The plasma
is assumed to be freefalling in the radial direction toward the event horizon
due to the strong gravitational field of a Schwarzschild black hole. The local
dispersion relations for transverse and longitudinal waves have been derived,
in analogy with the special relativistic formulation as explained in an earlier
paper, to take account of relativistic effects due to the event horizon using
WKB approximation
| [
{
"created": "Wed, 29 Sep 2010 10:10:54 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jan 2011 06:32:41 GMT",
"version": "v2"
},
{
"created": "Wed, 16 May 2012 12:22:28 GMT",
"version": "v3"
}
] | 2012-11-12 | [
[
"Rahman",
"M. Atiqur",
""
]
] | Waves propagating in the relativistic electron-positron or ions plasma are investigated in a frame of two-fluid equations using the 3+1 formalism of general relativity developed by Thorne, Price and Macdonald (TPM). The plasma is assumed to be freefalling in the radial direction toward the event horizon due to the strong gravitational field of a Schwarzschild black hole. The local dispersion relations for transverse and longitudinal waves have been derived, in analogy with the special relativistic formulation as explained in an earlier paper, to take account of relativistic effects due to the event horizon using WKB approximation |
1210.0722 | Sujoy Modak Dr. | Sujoy Kumar Modak | Generalized Smarr formula as a local identity for arbitrary dimensional
black holes | 5 pages, no figures, prepared for the proceedings of COSGRAV-12,
Kolkata 7-11 February 2012, to appear in Journal of Physics: Conference
Series (JPCS) | Journal of Physics: Conference Series 405, 012023 (2012) | 10.1088/1742-6596/405/1/012023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a method based on Killing symmetries and Komar conserved charges
to generalize Smarr mass formula for arbitrary dimensional charged, rotating
spacetime. We derive a local identity defined at the event horizon of the
rotating black hole in Einstein-Maxwell gravity which reproduces the
generalized Smarr formula as a by-product. The advantages of this new identity
are the following: (i) unlike Smarr formula, which is non-local, this identity
is purely local and hence a switchover between horizon and infinity is
unnecessary and (ii) the new identity could be mapped with the recent
investigations on emergent gravity.
| [
{
"created": "Tue, 2 Oct 2012 10:05:29 GMT",
"version": "v1"
}
] | 2012-12-18 | [
[
"Modak",
"Sujoy Kumar",
""
]
] | We discuss a method based on Killing symmetries and Komar conserved charges to generalize Smarr mass formula for arbitrary dimensional charged, rotating spacetime. We derive a local identity defined at the event horizon of the rotating black hole in Einstein-Maxwell gravity which reproduces the generalized Smarr formula as a by-product. The advantages of this new identity are the following: (i) unlike Smarr formula, which is non-local, this identity is purely local and hence a switchover between horizon and infinity is unnecessary and (ii) the new identity could be mapped with the recent investigations on emergent gravity. |
1108.2821 | Andrei Mironov | A.Mironov, A.Morozov and T.N.Tomaras | Geodesic deviation and particle creation in curved spacetimes | 5 pages | Pisma v ZhETF (JETP Letters) vol. 94, issue 11, page 872 (2011) | 10.1134/S0021364011230081 | FIAN/TD-15/11; ITEP/TH-25/11; CCTP-2011-26 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quantum mechanical picture, relating accelerated geodesic deviation to
creation of massive particles via quantum tunneling in curved background
spacetimes, is presented. The effect is analogous to pair production by an
electric field and leads naturally to production of massive particles in de
Sitter and superluminal FRW spacetimes. The probability of particle production
in de Sitter space per unit volume and time is computed in a leading
semiclassical approximation and shown to coincide with the previously obtained
expression.
| [
{
"created": "Sat, 13 Aug 2011 21:04:05 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Mironov",
"A.",
""
],
[
"Morozov",
"A.",
""
],
[
"Tomaras",
"T. N.",
""
]
] | A quantum mechanical picture, relating accelerated geodesic deviation to creation of massive particles via quantum tunneling in curved background spacetimes, is presented. The effect is analogous to pair production by an electric field and leads naturally to production of massive particles in de Sitter and superluminal FRW spacetimes. The probability of particle production in de Sitter space per unit volume and time is computed in a leading semiclassical approximation and shown to coincide with the previously obtained expression. |
gr-qc/9609029 | Yasusada Nambu | Yasusada Nambu and Atsushi Taruya | Evolution of Cosmological Perturbation in Reheating Phase of the
Universe | 10 pages, 1 figures | Prog.Theor.Phys. 97 (1997) 83-89 | 10.1143/PTP.97.83 | null | gr-qc astro-ph | null | The evolution of the cosmological perturbation during the oscillatory stage
of the scalar field is investigated. For the power law potential of the
inflaton field, the evolution equation of the Mukhanov's gauge invariant
variable is reduced to the Mathieu equation and the density perturbation grows
by the parametric resonance.
| [
{
"created": "Thu, 12 Sep 1996 09:45:55 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Nambu",
"Yasusada",
""
],
[
"Taruya",
"Atsushi",
""
]
] | The evolution of the cosmological perturbation during the oscillatory stage of the scalar field is investigated. For the power law potential of the inflaton field, the evolution equation of the Mukhanov's gauge invariant variable is reduced to the Mathieu equation and the density perturbation grows by the parametric resonance. |
1711.11381 | Gonzalo Quiroga | L. A. G\'omez L\'opez, and G. D. Quiroga | Asymptotic structure of spacetime and the Newman-Penrose formalism: a
brief review | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief review about the Newman-Penrose formalism and the asymptotic
structure of the spacetime is given. The goal of this review is to describe the
latest developments in these topics and make a summary of the most important
articles published by Newman and collaborators. Additionally, we discuss some
aspects of this approach, and we compute the spin coefficients and the Weyl
scalars for a general stationary axisymmetric spacetimes in a tetrad basis
different from that defined by the principal null geodesic directions.
| [
{
"created": "Thu, 30 Nov 2017 13:30:26 GMT",
"version": "v1"
}
] | 2017-12-01 | [
[
"López",
"L. A. Gómez",
""
],
[
"Quiroga",
"G. D.",
""
]
] | A brief review about the Newman-Penrose formalism and the asymptotic structure of the spacetime is given. The goal of this review is to describe the latest developments in these topics and make a summary of the most important articles published by Newman and collaborators. Additionally, we discuss some aspects of this approach, and we compute the spin coefficients and the Weyl scalars for a general stationary axisymmetric spacetimes in a tetrad basis different from that defined by the principal null geodesic directions. |
2402.03914 | Aneta Wojnar | Eva Lope-Oter, Aneta Wojnar | Twin Stars in General Relativity and Extended Theories of Gravity | 21 pages, 14 figures, 5 tables | null | null | null | gr-qc astro-ph.HE hep-th nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore gravity-independent equations of state for neutron stars,
particularly focusing on twin stars. Examining four categories, we emphasize
their behavior in both General Relativity and Palatini gravity. Additionally,
we discuss a subcategory of type I, which, in the context of General
Relativity, does not exhibit twin star phenomena, yet demonstrates this
phenomenon in modified gravity. Furthermore, we briefly address challenges
associated with the negative trace of the energy-momentum tensor, prevalent in
both theories.
| [
{
"created": "Tue, 6 Feb 2024 11:28:51 GMT",
"version": "v1"
}
] | 2024-02-07 | [
[
"Lope-Oter",
"Eva",
""
],
[
"Wojnar",
"Aneta",
""
]
] | We explore gravity-independent equations of state for neutron stars, particularly focusing on twin stars. Examining four categories, we emphasize their behavior in both General Relativity and Palatini gravity. Additionally, we discuss a subcategory of type I, which, in the context of General Relativity, does not exhibit twin star phenomena, yet demonstrates this phenomenon in modified gravity. Furthermore, we briefly address challenges associated with the negative trace of the energy-momentum tensor, prevalent in both theories. |
1210.0897 | Ujjal Debnath | Ujjal Debnath | Thermodynamics in Higher Dimensional Vaidya Space-Time | 10 pages, 4 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have considered the Vaidya spacetime in null radiating fluid
with perfect fluid in higher dimension and have found the solution for
barotropic fluid. We have shown that the Einstein's field equations can be
obtained from Unified first law i.e., field equations and unified first law are
equivalent. The first law of thermodynamics has also been constructed by
Unified first law. From this, the variation of entropy function has been
derived on the horizon. The variation of entropy function inside the horizon
has been derived using Gibb's law of thermodynamics. So the total variation of
entropy function has been constructed at apparent and event horizons both. If
we do not assume the first law, then the entropy on the both horizons can be
considered by area law and the variation of total entropy has been found at
both the horizons. Also the validity of generalized second law (GSL) of
thermodynamics has been examined at both apparent and event horizons by using
the first law and the area law separately. When we use first law of
thermodynamics and Bekenstein-Hawking area law of thermodynamics, the GSL for
apparent horizon in any dimensions are satisfied, but the GSL for event horizon
can not be satisfied in any dimensions.
| [
{
"created": "Tue, 2 Oct 2012 07:06:31 GMT",
"version": "v1"
}
] | 2012-10-04 | [
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have considered the Vaidya spacetime in null radiating fluid with perfect fluid in higher dimension and have found the solution for barotropic fluid. We have shown that the Einstein's field equations can be obtained from Unified first law i.e., field equations and unified first law are equivalent. The first law of thermodynamics has also been constructed by Unified first law. From this, the variation of entropy function has been derived on the horizon. The variation of entropy function inside the horizon has been derived using Gibb's law of thermodynamics. So the total variation of entropy function has been constructed at apparent and event horizons both. If we do not assume the first law, then the entropy on the both horizons can be considered by area law and the variation of total entropy has been found at both the horizons. Also the validity of generalized second law (GSL) of thermodynamics has been examined at both apparent and event horizons by using the first law and the area law separately. When we use first law of thermodynamics and Bekenstein-Hawking area law of thermodynamics, the GSL for apparent horizon in any dimensions are satisfied, but the GSL for event horizon can not be satisfied in any dimensions. |
2202.01015 | Celio Muniz | Roberto V. Maluf and Celio R. Muniz | Comment on "Greybody radiation and quasinormal modes of Kerr-like black
hole in Bumblebee gravity model" | 3 pages. Published in The European Physics Journal C | Eur.Phys.J.C., (2022) 82:94 | 10.1140/epjc/s10052-022-10039-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the paper "Greybody radiation and quasinormal modes of
Kerr-like black hole in Bumblebee gravity model", Eur. Phys. J. C 81, 501
(2021). arXiv:2102.06303, recently published in this journal is based on an
incorrect result obtained by Ding et al., Eur. Phys. J. C 80, 178 (2020).
arXiv:1910.02674, for a Kerr-like black hole solution.
| [
{
"created": "Wed, 2 Feb 2022 13:19:35 GMT",
"version": "v1"
}
] | 2022-02-03 | [
[
"Maluf",
"Roberto V.",
""
],
[
"Muniz",
"Celio R.",
""
]
] | It is shown that the paper "Greybody radiation and quasinormal modes of Kerr-like black hole in Bumblebee gravity model", Eur. Phys. J. C 81, 501 (2021). arXiv:2102.06303, recently published in this journal is based on an incorrect result obtained by Ding et al., Eur. Phys. J. C 80, 178 (2020). arXiv:1910.02674, for a Kerr-like black hole solution. |
2106.15425 | Sergio Gimeno-Soler | Sergio Gimeno-Soler, Jos\'e A. Font, Carlos Herdeiro, Eugen Radu | Magnetized accretion disks around Kerr black holes with scalar hair --
Nonconstant angular momentum disks | 21 pages, 10 figures | null | 10.1103/PhysRevD.104.103008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new equilibrium solutions of stationary models of magnetized thick
disks (or tori) around Kerr black holes with synchronised scalar hair. The
models reported here largely extend our previous results based on constant
radial distributions of the specific angular momentum along the equatorial
plane. We introduce a new way to prescribe the distribution of the disk's
angular momentum based on a combination of two previous proposals and compute
the angular momentum distribution outside the equatorial plane by resorting to
the construction of von Zeipel cylinders. We find that the effect of the scalar
hair on the black hole spacetime can yield significant differences in the disk
morphology and properties compared to what is found if the spacetime is purely
Kerr. Some of the tori built within the most extreme, background hairy black
hole spacetime of our sample exhibit the appearance of two maxima in the
gravitational energy density which impacts the radial profile distributions of
the disk's thermodynamical quantities. The models reported in this paper can be
used as initial data for numerical evolutions with GRMHD codes to study their
stability properties. Moreover, they can be employed as illuminating sources to
build shadows of Kerr black holes with scalar hair which might help further
constrain the no-hair hypothesis as new observational data is collected.
| [
{
"created": "Tue, 29 Jun 2021 13:54:13 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jul 2021 10:27:24 GMT",
"version": "v2"
}
] | 2021-11-24 | [
[
"Gimeno-Soler",
"Sergio",
""
],
[
"Font",
"José A.",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
]
] | We present new equilibrium solutions of stationary models of magnetized thick disks (or tori) around Kerr black holes with synchronised scalar hair. The models reported here largely extend our previous results based on constant radial distributions of the specific angular momentum along the equatorial plane. We introduce a new way to prescribe the distribution of the disk's angular momentum based on a combination of two previous proposals and compute the angular momentum distribution outside the equatorial plane by resorting to the construction of von Zeipel cylinders. We find that the effect of the scalar hair on the black hole spacetime can yield significant differences in the disk morphology and properties compared to what is found if the spacetime is purely Kerr. Some of the tori built within the most extreme, background hairy black hole spacetime of our sample exhibit the appearance of two maxima in the gravitational energy density which impacts the radial profile distributions of the disk's thermodynamical quantities. The models reported in this paper can be used as initial data for numerical evolutions with GRMHD codes to study their stability properties. Moreover, they can be employed as illuminating sources to build shadows of Kerr black holes with scalar hair which might help further constrain the no-hair hypothesis as new observational data is collected. |
1103.3230 | Langmann Edwin | Edwin Langmann, Martin Sundin | Extrinsic curvature effects in brane-world scenarios | 24 pages; v2: typos corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider models of bosons on curved 3+1 dimensional space-time embedded in
a higher dimensional flat ambient space. We propose to derive (rather than
postulate) equations of motions by assuming that a standard Klein-Gordon field
on ambient space is restricted to space-time by a strong confining potential.
This leads to a modified Klein-Gordon equation on space-time which includes, in
addition to the standard terms, a term with a so-called induced potential which
depends on intrinsic- and extrinsic curvature of the embedded space-time but
not on the details of the confining potential. We compute this induced
potential for natural, simple embeddings of Schwarzschild- and Robertson-Walker
space-times. We also discuss possible observable implications of our results
and, in particular, propose and study an extension of a standard model of
cosmological inflation taking into account extrinsic curvature effects. We show
that the modified model allows for a solution where the scaling function
vanishes like a power law with exponent 0.6830.. at some initial time.
| [
{
"created": "Wed, 16 Mar 2011 16:57:52 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2011 09:12:18 GMT",
"version": "v2"
}
] | 2011-04-01 | [
[
"Langmann",
"Edwin",
""
],
[
"Sundin",
"Martin",
""
]
] | We consider models of bosons on curved 3+1 dimensional space-time embedded in a higher dimensional flat ambient space. We propose to derive (rather than postulate) equations of motions by assuming that a standard Klein-Gordon field on ambient space is restricted to space-time by a strong confining potential. This leads to a modified Klein-Gordon equation on space-time which includes, in addition to the standard terms, a term with a so-called induced potential which depends on intrinsic- and extrinsic curvature of the embedded space-time but not on the details of the confining potential. We compute this induced potential for natural, simple embeddings of Schwarzschild- and Robertson-Walker space-times. We also discuss possible observable implications of our results and, in particular, propose and study an extension of a standard model of cosmological inflation taking into account extrinsic curvature effects. We show that the modified model allows for a solution where the scaling function vanishes like a power law with exponent 0.6830.. at some initial time. |
2212.13043 | Xue Zheng Zhu | Xuezheng Zhu | Spatially covariant gravity: Degeneracy condition and mimetic
formulation | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make a perturbative analysis of spatially covariant gravity only
respecting spatial symmetries, of which the Lagrangian includes the dynamic
lapse function and the coupling term of spatial curvature and extrinsic
curvature. We show that the theory propagates 2 scalar degrees of freedom, as
long as the kinetic terms are degenerate, it propagates a single scalar mode at
the linear order. Then we calculate the scalar and tensor power spectra.
Finally, we study cosmological perturbations in mimetic gravity in the presence
of spatially covariant gravity. The original spatially covariant theory
propagates 2 scalar degrees of freedom, and it will propagate only one scalar
degree of freedom after adding the mimetic constraint.
| [
{
"created": "Mon, 26 Dec 2022 08:51:04 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2022 03:46:10 GMT",
"version": "v2"
}
] | 2022-12-29 | [
[
"Zhu",
"Xuezheng",
""
]
] | We make a perturbative analysis of spatially covariant gravity only respecting spatial symmetries, of which the Lagrangian includes the dynamic lapse function and the coupling term of spatial curvature and extrinsic curvature. We show that the theory propagates 2 scalar degrees of freedom, as long as the kinetic terms are degenerate, it propagates a single scalar mode at the linear order. Then we calculate the scalar and tensor power spectra. Finally, we study cosmological perturbations in mimetic gravity in the presence of spatially covariant gravity. The original spatially covariant theory propagates 2 scalar degrees of freedom, and it will propagate only one scalar degree of freedom after adding the mimetic constraint. |
1005.1637 | Carlos Peralta | B. Rodr\'iguez-Mueller, C. Peralta, W. Barreto and L. Rosales | Heat flow in the postquasistatic approximation | 5 pages, 5 figures | Phys.Rev.D82:044003,2010 | 10.1103/PhysRevD.82.044003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the postquasistatic approximation to study the evolution of
spherically symmetric fluid distributions undergoing dissipation in the form of
radial heat flow. For a model which corresponds to an incompressible fluid
departing from the static equilibrium, it is not possible to go far from the
initial state after the emission of a small amount of energy. Initially
collapsing distributions of matter are not permitted. Emission of energy can be
considered as a mechanism to avoid the collapse. If the distribution collapses
initially and emits one hundredth of the initial mass only the outermost layers
evolve. For a model which corresponds to a highly compressed Fermi gas, only
the outermost shell can evolve with a shorter hydrodynamic time scale.
| [
{
"created": "Mon, 10 May 2010 19:57:51 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Aug 2010 18:44:48 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Rodríguez-Mueller",
"B.",
""
],
[
"Peralta",
"C.",
""
],
[
"Barreto",
"W.",
""
],
[
"Rosales",
"L.",
""
]
] | We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model which corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model which corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale. |
2408.07674 | Yeinzon Rodriguez Garcia | Jhan N. Martinez (1), Jose F. Rodriguez (1,2), Laura M. Becerra (2,3),
Yeinzon Rodriguez (1,4), Gabriel Gomez (5) ((1) Universidad Industrial de
Santander, (2) ICRANet, (3) Universidad Mayor, (4) Universidad Antonio
Narino, (5) Universidad de Santiago de Chile) | Neutron stars in the generalized SU(2) Proca theory | LaTeX file in RevTeX 4.1 style, 14 pages, 9 figures | null | null | PI/UAN-2024-727FT | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized SU(2) Proca theory is a vector-tensor modified gravity theory
characterized by an action that remains invariant under both diffeomorphisms
and global internal transformations of the SU(2) group. This study aims to
further explore the physical properties of the theory within astrophysical
contexts. Previous investigations have unveiled intriguing astrophysical
solutions, including particle-like configurations and black holes. The purpose
of this work is to constrain the theory's free parameters by modeling realistic
neutron stars. To that end, we have assumed solutions that are static,
spherically symmetric, and have adopted the t'Hooft-Polyakov magnetic monopole
configuration for the vector fields. Employing both analytical techniques, such
as asymptotic expansions, and numerical methods involving solving boundary
value problems, we have obtained neutron star solutions whose baryonic matter
is described by realistic equations of state for nuclear matter. Furthermore,
we have constructed mass-radius relations which reveal that neutron stars
exhibit greater compactness in comparison with general relativity predictions
for most of the solutions we have found and for the employed equations of
state. Finally, we have found out solutions where the mass of the star is
greater than $\sim$ 2.5 $M_\odot$; this result poses an alternative in the
exploration of the mass gap of compact stellar objects.
| [
{
"created": "Wed, 14 Aug 2024 17:17:31 GMT",
"version": "v1"
}
] | 2024-08-15 | [
[
"Martinez",
"Jhan N.",
""
],
[
"Rodriguez",
"Jose F.",
""
],
[
"Becerra",
"Laura M.",
""
],
[
"Rodriguez",
"Yeinzon",
""
],
[
"Gomez",
"Gabriel",
""
]
] | The generalized SU(2) Proca theory is a vector-tensor modified gravity theory characterized by an action that remains invariant under both diffeomorphisms and global internal transformations of the SU(2) group. This study aims to further explore the physical properties of the theory within astrophysical contexts. Previous investigations have unveiled intriguing astrophysical solutions, including particle-like configurations and black holes. The purpose of this work is to constrain the theory's free parameters by modeling realistic neutron stars. To that end, we have assumed solutions that are static, spherically symmetric, and have adopted the t'Hooft-Polyakov magnetic monopole configuration for the vector fields. Employing both analytical techniques, such as asymptotic expansions, and numerical methods involving solving boundary value problems, we have obtained neutron star solutions whose baryonic matter is described by realistic equations of state for nuclear matter. Furthermore, we have constructed mass-radius relations which reveal that neutron stars exhibit greater compactness in comparison with general relativity predictions for most of the solutions we have found and for the employed equations of state. Finally, we have found out solutions where the mass of the star is greater than $\sim$ 2.5 $M_\odot$; this result poses an alternative in the exploration of the mass gap of compact stellar objects. |
1203.3171 | Ahmed Youssef | Ahmed Youssef | Do scale-invariant fluctuations imply the breaking of de Sitter
invariance? | 4 pages | null | 10.1016/j.physletb.2012.11.023 | MaPhy-AvH/2012-05 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantization of the massless minimally coupled (mmc) scalar field in de
Sitter spacetime is known to be a non-trivial problem due to the appearance of
strong infrared (IR) effects. In particular, the scale-invariance of the CMB
power-spectrum - certainly one of the most successful predictions of modern
cosmology - is widely believed to be inconsistent with a de Sitter invariant
mmc two-point function.
Using a Cesaro-summability technique to properly define an otherwise
divergent Fourier transform, we show in this Letter that de Sitter symmetry
breaking is \emph{not} a necessary consequence of the scale-invariant
fluctuation spectrum. We also generalize our result to the tachyonic scalar
fields, i.e the discrete series of representations of the de Sitter group, that
suffer from similar strong IR effects.
| [
{
"created": "Wed, 14 Mar 2012 18:38:20 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Youssef",
"Ahmed",
""
]
] | The quantization of the massless minimally coupled (mmc) scalar field in de Sitter spacetime is known to be a non-trivial problem due to the appearance of strong infrared (IR) effects. In particular, the scale-invariance of the CMB power-spectrum - certainly one of the most successful predictions of modern cosmology - is widely believed to be inconsistent with a de Sitter invariant mmc two-point function. Using a Cesaro-summability technique to properly define an otherwise divergent Fourier transform, we show in this Letter that de Sitter symmetry breaking is \emph{not} a necessary consequence of the scale-invariant fluctuation spectrum. We also generalize our result to the tachyonic scalar fields, i.e the discrete series of representations of the de Sitter group, that suffer from similar strong IR effects. |
1606.07611 | Eric Huguet | E. Huguet, J. Queva and J. Renaud | Massive scalar field on (A)dS space from a massless conformal field in
$\mathbb{R}^6$ | Revtex 4.1, 6 pages. In v3: New material added (references, relation
with mass ladder operator), accepted in JMP | J. Math. Phys. 61, 053506 (2020) | 10.1063/1.5132893 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how the equations for the scalar field (including the massive,
massless, minimally and conformally coupled cases) on de Sitter and Anti-de
Sitter spaces can be obtained from both the SO$(2,4)$-invariant equation
$\square \phi = 0$ in $\mathbb{R}^6$ and two geometrical constraints defining
the (A)dS space. Apart from the equation in $\mathbb{R}^6$, the results only
follow from the geometry.
| [
{
"created": "Fri, 24 Jun 2016 09:10:29 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Jul 2017 12:09:40 GMT",
"version": "v2"
},
{
"created": "Mon, 4 May 2020 08:25:46 GMT",
"version": "v3"
}
] | 2020-08-11 | [
[
"Huguet",
"E.",
""
],
[
"Queva",
"J.",
""
],
[
"Renaud",
"J.",
""
]
] | We show how the equations for the scalar field (including the massive, massless, minimally and conformally coupled cases) on de Sitter and Anti-de Sitter spaces can be obtained from both the SO$(2,4)$-invariant equation $\square \phi = 0$ in $\mathbb{R}^6$ and two geometrical constraints defining the (A)dS space. Apart from the equation in $\mathbb{R}^6$, the results only follow from the geometry. |
1211.6884 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado G\'omez-Lobo and Jos\'e M. M. Senovilla | A set of invariant quality factors measuring the deviation from the Kerr
metric | 34 pages, 6 figures. References added, acknowledgments section
expanded. Presentation improved and role of the Killing vector change of
scale clarified. To appear in General Relativity and Gravitation | null | 10.1007/s10714-013-1518-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A number of scalar invariant characterizations of the Kerr solution are
presented. These characterizations come in the form of {\em quality factors}
defined in stationary space-times. A quality factor is a scalar quantity
varying in the interval $[0,1]$ with the value 1 being attained if and only if
the space-time is locally isometric to the Kerr solution. No knowledge of the
Kerr solution is required to compute these quality factors. A number of
different possibilities arise depending on whether the space-time is Ricci-flat
and asymptotically flat, just Ricci-flat, or Ricci non-flat. In each situation
a number of quality factors are constructed and analysed. The relevance of
these quality factors is clear in any situation where one seeks a rigorous
formulation of the statement that a space-time is "close" to the Kerr solution,
such as: its non-linear stability problem, the asymptotic settlement of a
radiating isolated system undergoing gravitational collapse, or in the
formulation of some uniqueness results.
| [
{
"created": "Thu, 29 Nov 2012 11:27:50 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2013 20:54:52 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Mar 2013 09:39:23 GMT",
"version": "v3"
}
] | 2013-03-08 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | A number of scalar invariant characterizations of the Kerr solution are presented. These characterizations come in the form of {\em quality factors} defined in stationary space-times. A quality factor is a scalar quantity varying in the interval $[0,1]$ with the value 1 being attained if and only if the space-time is locally isometric to the Kerr solution. No knowledge of the Kerr solution is required to compute these quality factors. A number of different possibilities arise depending on whether the space-time is Ricci-flat and asymptotically flat, just Ricci-flat, or Ricci non-flat. In each situation a number of quality factors are constructed and analysed. The relevance of these quality factors is clear in any situation where one seeks a rigorous formulation of the statement that a space-time is "close" to the Kerr solution, such as: its non-linear stability problem, the asymptotic settlement of a radiating isolated system undergoing gravitational collapse, or in the formulation of some uniqueness results. |
0705.0674 | Simone Speziale | Etera R. Livine and Simone Speziale | A new spinfoam vertex for quantum gravity | 17+8 pages, 6 figures. v2 updated references | Phys.Rev.D76:084028,2007 | 10.1103/PhysRevD.76.084028 | pi-qg-45 | gr-qc hep-th | null | We introduce a new spinfoam vertex to be used in models of 4d quantum gravity
based on SU(2) and SO(4) BF theory plus constraints. It can be seen as the
conventional vertex of SU(2) BF theory, the 15j symbol, in a particular basis
constructed using SU(2) coherent states. This basis makes the geometric
interpretation of the variables transparent: they are the vectors normal to the
triangles within each tetrahedron. We study the condition under which these
states can be considered semiclassical, and we show that the semiclassical ones
dominate the evaluation of quantum correlations. Finally, we describe how the
constraints reducing BF to gravity can be directly written in terms of the new
variables, and how the semiclassicality of the states might improve
understanding the correct way to implement the constraints.
| [
{
"created": "Fri, 4 May 2007 16:45:38 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Aug 2007 15:36:13 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Livine",
"Etera R.",
""
],
[
"Speziale",
"Simone",
""
]
] | We introduce a new spinfoam vertex to be used in models of 4d quantum gravity based on SU(2) and SO(4) BF theory plus constraints. It can be seen as the conventional vertex of SU(2) BF theory, the 15j symbol, in a particular basis constructed using SU(2) coherent states. This basis makes the geometric interpretation of the variables transparent: they are the vectors normal to the triangles within each tetrahedron. We study the condition under which these states can be considered semiclassical, and we show that the semiclassical ones dominate the evaluation of quantum correlations. Finally, we describe how the constraints reducing BF to gravity can be directly written in terms of the new variables, and how the semiclassicality of the states might improve understanding the correct way to implement the constraints. |
1411.3073 | Ryan Lang | Ryan N. Lang | Compact binary systems in scalar-tensor gravity. III. Scalar waves and
energy flux | 35 pages | Phys. Rev. D 91, 084027 (2015) | 10.1103/PhysRevD.91.084027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the scalar waveform generated by a binary of nonspinning compact
objects (black holes or neutron stars) in a general class of scalar-tensor
theories of gravity. The waveform is accurate to 1.5 post-Newtonian order
[$O((v/c)^3)$] beyond the leading-order tensor gravitational waves (the
"Newtonian quadrupole"). To solve the scalar-tensor field equations, we adapt
the direct integration of the relaxed Einstein equations formalism developed by
Will, Wiseman, and Pati. The internal gravity of the compact objects is treated
with an approach developed by Eardley. We find that the scalar waves are
described by the same small set of parameters which describes the equations of
motion and tensor waves. For black hole--black hole binaries, the scalar
waveform vanishes, as expected from previous results which show that these
systems in scalar-tensor theory are indistinguishable from their general
relativistic counterparts. For black hole--neutron star binaries, the scalar
waveform simplifies considerably from the generic case, essentially depending
on only a single parameter up to first post-Newtonian order. With both the
tensor and scalar waveforms in hand, we calculate the total energy flux carried
by the outgoing waves. This quantity is computed to first post-Newtonian order
relative to the "quadrupole formula" and agrees with previous, lower order
calculations.
| [
{
"created": "Wed, 12 Nov 2014 05:33:28 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 2015 22:35:22 GMT",
"version": "v2"
}
] | 2015-05-12 | [
[
"Lang",
"Ryan N.",
""
]
] | We derive the scalar waveform generated by a binary of nonspinning compact objects (black holes or neutron stars) in a general class of scalar-tensor theories of gravity. The waveform is accurate to 1.5 post-Newtonian order [$O((v/c)^3)$] beyond the leading-order tensor gravitational waves (the "Newtonian quadrupole"). To solve the scalar-tensor field equations, we adapt the direct integration of the relaxed Einstein equations formalism developed by Will, Wiseman, and Pati. The internal gravity of the compact objects is treated with an approach developed by Eardley. We find that the scalar waves are described by the same small set of parameters which describes the equations of motion and tensor waves. For black hole--black hole binaries, the scalar waveform vanishes, as expected from previous results which show that these systems in scalar-tensor theory are indistinguishable from their general relativistic counterparts. For black hole--neutron star binaries, the scalar waveform simplifies considerably from the generic case, essentially depending on only a single parameter up to first post-Newtonian order. With both the tensor and scalar waveforms in hand, we calculate the total energy flux carried by the outgoing waves. This quantity is computed to first post-Newtonian order relative to the "quadrupole formula" and agrees with previous, lower order calculations. |
2002.10922 | Abraham Harte | Abraham I. Harte and Michael T. Gaffney | Extended-body effects and rocket-free orbital maneuvering | 11 pages, 4 figures, considerably expanded discussion | Acta Astronautica 178, 625 (2020) | 10.1016/j.actaastro.2020.09.038 | null | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The trajectory of a spherical object which falls freely in a gravitational
field is fixed by its initial position and velocity. However, an object which
can control its shape can also control its motion: Except where forbidden by
symmetries and their associated conservation laws, a shape-changing (but
rocket-free) spacecraft can have complete control over its trajectory. We
discuss a general formalism which allows rocket-free maneuvers to be understood
without constructing detailed interior models. A spacecraft's interior is
abstracted to the specification of a quadrupole moment, and in some cases, it
is only a single eigenvalue of that moment which is relevant. For orbits around
a spherically-symmetric mass, we show that appropriately varying the relevant
eigenvalue allows the energy and eccentricity of an orbit to be increased or
decreased and its apsides to be rotated arbitrarily. Strategies are identified
which optimize these maneuvers. In other contexts, we show that extended-body
effects can be used to stabilize orbits which would otherwise be unstable.
| [
{
"created": "Tue, 25 Feb 2020 14:54:22 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2020 10:01:01 GMT",
"version": "v2"
}
] | 2020-10-22 | [
[
"Harte",
"Abraham I.",
""
],
[
"Gaffney",
"Michael T.",
""
]
] | The trajectory of a spherical object which falls freely in a gravitational field is fixed by its initial position and velocity. However, an object which can control its shape can also control its motion: Except where forbidden by symmetries and their associated conservation laws, a shape-changing (but rocket-free) spacecraft can have complete control over its trajectory. We discuss a general formalism which allows rocket-free maneuvers to be understood without constructing detailed interior models. A spacecraft's interior is abstracted to the specification of a quadrupole moment, and in some cases, it is only a single eigenvalue of that moment which is relevant. For orbits around a spherically-symmetric mass, we show that appropriately varying the relevant eigenvalue allows the energy and eccentricity of an orbit to be increased or decreased and its apsides to be rotated arbitrarily. Strategies are identified which optimize these maneuvers. In other contexts, we show that extended-body effects can be used to stabilize orbits which would otherwise be unstable. |
1812.08643 | Benjamin Lackey | Benjamin D. Lackey, Michael P\"urrer, Andrea Taracchini, Sylvain
Marsat | Surrogate model for an aligned-spin effective one body waveform model of
binary neutron star inspirals using Gaussian process regression | 19 pages, 10 figures, submitted to PRD | Phys. Rev. D 100, 024002 (2019) | 10.1103/PhysRevD.100.024002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fast and accurate waveform models are necessary for measuring the properties
of inspiraling binary neutron star systems such as GW170817. We present a
frequency-domain surrogate version of the aligned-spin binary neutron star
waveform model using the effective one body formalism known as SEOBNRv4T. This
model includes the quadrupolar and octopolar adiabatic and dynamical tides. The
version presented here is improved by the inclusion of the spin-induced
quadrupole moment effect, and completed by a prescription for tapering the end
of the waveform to qualitatively reproduce numerical relativity simulations.
The resulting model has 14 intrinsic parameters. We reduce its dimensionality
by using universal relations that approximate all matter effects in terms of
the leading quadrupolar tidal parameters. The implementation of the time-domain
model can take up to an hour to evaluate using a starting frequency of 20Hz,
and this is too slow for many parameter estimation codes that require $O(10^7)$
sequential waveform evaluations. We therefore construct a fast and faithful
frequency-domain surrogate of this model using Gaussian process regression. The
resulting surrogate has a maximum mismatch of $4.5\times 10^{-4}$ for the
Advanced LIGO detector, and requires 0.13s to evaluate for a waveform with a
starting frequency of 20Hz. Finally, we perform an end-to-end test of the
surrogate with a set of parameter estimation runs, and find that the surrogate
accurately recovers the parameters of injected waveforms.
| [
{
"created": "Thu, 20 Dec 2018 15:44:27 GMT",
"version": "v1"
}
] | 2019-07-10 | [
[
"Lackey",
"Benjamin D.",
""
],
[
"Pürrer",
"Michael",
""
],
[
"Taracchini",
"Andrea",
""
],
[
"Marsat",
"Sylvain",
""
]
] | Fast and accurate waveform models are necessary for measuring the properties of inspiraling binary neutron star systems such as GW170817. We present a frequency-domain surrogate version of the aligned-spin binary neutron star waveform model using the effective one body formalism known as SEOBNRv4T. This model includes the quadrupolar and octopolar adiabatic and dynamical tides. The version presented here is improved by the inclusion of the spin-induced quadrupole moment effect, and completed by a prescription for tapering the end of the waveform to qualitatively reproduce numerical relativity simulations. The resulting model has 14 intrinsic parameters. We reduce its dimensionality by using universal relations that approximate all matter effects in terms of the leading quadrupolar tidal parameters. The implementation of the time-domain model can take up to an hour to evaluate using a starting frequency of 20Hz, and this is too slow for many parameter estimation codes that require $O(10^7)$ sequential waveform evaluations. We therefore construct a fast and faithful frequency-domain surrogate of this model using Gaussian process regression. The resulting surrogate has a maximum mismatch of $4.5\times 10^{-4}$ for the Advanced LIGO detector, and requires 0.13s to evaluate for a waveform with a starting frequency of 20Hz. Finally, we perform an end-to-end test of the surrogate with a set of parameter estimation runs, and find that the surrogate accurately recovers the parameters of injected waveforms. |
1202.0966 | Fay\c{c}al Hammad | Fay\c{c}al Hammad | Erratum to: An Entropy Functional for Riemann-Cartan Space-Times | 15 pages. These are the preprints of the original paper and its
erratum published in Int. J. Theor. Phys | Int J Theor Phys 51 (2012) 362-373; Erratum - Int J Theor Phys. 52
(2013) 4592-4593 | 10.1007/s10773-011-0913-9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We correct the entropy functional constructed in Int. J. Theor. Phys. 51:362
(2012). The 'on-shell' functional one obtains from this correct functional
possesses a holographic structure without imposing any constraint on the
spin-angular momentum tensor of matter, in contrast to the conclusion made in
the above paper.
| [
{
"created": "Sun, 5 Feb 2012 14:48:17 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Dec 2013 18:53:08 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Dec 2013 07:33:59 GMT",
"version": "v3"
}
] | 2013-12-06 | [
[
"Hammad",
"Fayçal",
""
]
] | We correct the entropy functional constructed in Int. J. Theor. Phys. 51:362 (2012). The 'on-shell' functional one obtains from this correct functional possesses a holographic structure without imposing any constraint on the spin-angular momentum tensor of matter, in contrast to the conclusion made in the above paper. |
1710.05971 | Muhammad Sharif | M. Sharif and S. Mumtaz | Dynamical Instability of Charged Gaseous Cylinder | 7 pages, 4 figures | Mon. Notices Roy. Astron. Soc. 471(2017)1215-1221 | 10.1093/mnras/stx1695 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss dynamical instability of charged dissipative
cylinder under radial oscillations. For this purpose, we follow the Eulerian
and Lagrangian approaches to evaluate linearized perturbed equation of motion.
We formulate perturbed pressure in terms of adiabatic index by applying the
conservation of baryon numbers. A variational principle is established to
determine characteristic frequencies of oscillation which define stability
criteria for gaseous cylinder. We compute the ranges of radii as well as
adiabatic index for both charged and uncharged cases in Newtonian and
post-Newtonian limits. We conclude that dynamical instability occurs in the
presence of charge if the gaseous cylinder contracts to the radius $R_{*}$.
| [
{
"created": "Thu, 12 Oct 2017 05:35:25 GMT",
"version": "v1"
}
] | 2017-10-25 | [
[
"Sharif",
"M.",
""
],
[
"Mumtaz",
"S.",
""
]
] | In this paper, we discuss dynamical instability of charged dissipative cylinder under radial oscillations. For this purpose, we follow the Eulerian and Lagrangian approaches to evaluate linearized perturbed equation of motion. We formulate perturbed pressure in terms of adiabatic index by applying the conservation of baryon numbers. A variational principle is established to determine characteristic frequencies of oscillation which define stability criteria for gaseous cylinder. We compute the ranges of radii as well as adiabatic index for both charged and uncharged cases in Newtonian and post-Newtonian limits. We conclude that dynamical instability occurs in the presence of charge if the gaseous cylinder contracts to the radius $R_{*}$. |
0912.3011 | Robert C. Helling | Robert C. Helling | Higher curvature counter terms cause the bounce in loop cosmology | Added references | null | null | LMU-ASC 58/09 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the loop approach to the quantisation of gravity, one uses a Hilbert space
which is too singular for some operators to be realised as derivatives. This is
usually addressed by instead using finite difference operators at the Planck
scale, a process known as ``polymerisation''. In the symmetry reduced example
of loop cosmology, we study an ambiguity in the regularisation which we relate
to the ambiguity of fixing the coefficients of infinitely many higher curvature
counter terms augmenting the Einstein-Hilbert action. Thus the situation is
comparable to he one in a naive perturbative treatment of quantum gravity with
a cut-off where the necessary presence of infinitely many higher derivative
terms compromises predictability. As a by-product, we demonstrate in an
appendix that it is possible to have higher curvature actions for gravity which
still lead to first order equations of motion like in the Friedmann case.
| [
{
"created": "Tue, 15 Dec 2009 21:33:23 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Dec 2009 17:51:58 GMT",
"version": "v2"
}
] | 2009-12-17 | [
[
"Helling",
"Robert C.",
""
]
] | In the loop approach to the quantisation of gravity, one uses a Hilbert space which is too singular for some operators to be realised as derivatives. This is usually addressed by instead using finite difference operators at the Planck scale, a process known as ``polymerisation''. In the symmetry reduced example of loop cosmology, we study an ambiguity in the regularisation which we relate to the ambiguity of fixing the coefficients of infinitely many higher curvature counter terms augmenting the Einstein-Hilbert action. Thus the situation is comparable to he one in a naive perturbative treatment of quantum gravity with a cut-off where the necessary presence of infinitely many higher derivative terms compromises predictability. As a by-product, we demonstrate in an appendix that it is possible to have higher curvature actions for gravity which still lead to first order equations of motion like in the Friedmann case. |
1703.10070 | Sharmanthie Fernando | Nora Breton, Tyler Clark and Sharmanthie Fernando | Quasinormal modes and absorption cross sections of Born-Infeld-de Sitter
black holes | Accepted to be published in International Journal of Modern Physics D | International Journal of Modern Physics D 26, no:10, 1750112
(2017) | 10.1142/S0218271817501127 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have studied QNM modes and absorption cross sections of
Born-Infeld-de Sitter black holes. WKB approximation is employed to compute the
QNM modes of massless scalar fields. We have also used null geodesics to
compute quasi-normal modes in the eikonal approximation. In the eikonal limit
QNMs of black holes are determined by the parameters of the circular null
geodesics. Unstable circular null orbits are derived from the effective metric
which is obeyed by light rays under the influence of a nonlinear
electromagnetic field. Comparison is shown with the QNM of the linear
electromagnetic counterpart, the Reissner-Nordstr\"{o}m black hole.
Furthermore, the null geodesics are employed to compute the absorption cross
sections in the high frequency limit via the sinc approximation.
| [
{
"created": "Wed, 29 Mar 2017 14:37:25 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Mar 2017 17:47:13 GMT",
"version": "v2"
}
] | 2018-07-31 | [
[
"Breton",
"Nora",
""
],
[
"Clark",
"Tyler",
""
],
[
"Fernando",
"Sharmanthie",
""
]
] | In this paper, we have studied QNM modes and absorption cross sections of Born-Infeld-de Sitter black holes. WKB approximation is employed to compute the QNM modes of massless scalar fields. We have also used null geodesics to compute quasi-normal modes in the eikonal approximation. In the eikonal limit QNMs of black holes are determined by the parameters of the circular null geodesics. Unstable circular null orbits are derived from the effective metric which is obeyed by light rays under the influence of a nonlinear electromagnetic field. Comparison is shown with the QNM of the linear electromagnetic counterpart, the Reissner-Nordstr\"{o}m black hole. Furthermore, the null geodesics are employed to compute the absorption cross sections in the high frequency limit via the sinc approximation. |
1805.04133 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es, Guillermo A. Mena Marug\'an and Santiago
Prado Loy | Backreaction of fermionic perturbations in the Hamiltonian of hybrid
loop quantum cosmology | 20 pages, matches published version | Phys. Rev. D 98, 063535 (2018) | 10.1103/PhysRevD.98.063535 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the freedom available in hybrid loop quantum cosmology to define
canonical variables for the matter content and investigate whether this can be
used to derive a quantum field theory with good properties for the matter
sector. We study a primordial, inflationary, cosmological spacetime with
inhomogeneous perturbations at lowest nontrivial order, and focus our attention
on the contribution of minimally coupled fermionic perturbations of Dirac type.
Within the framework of the hybrid quantization, we analyze the different
possible separations of the homogeneous background and the inhomogeneous
perturbations, by means of canonical transformations that mix the two separated
sectors. These possibilities provide a family of sets of annihilation and
creationlike fermionic variables, each of them with a different associated
contribution to the total Hamiltonian. In all cases, imposing the quantum
constraints and introducing a Born-Oppenheimer approximation, one can derive a
Schr\"odinger equation for the fermionic part of the wave functions. The
resulting evolution turns out to be generated, for each of the allowed choices
of variables, by a version of the fermionic contribution to the Hamiltonian
which is obtained by evaluating all the dependence on the homogeneous geometry
at quantum expectation values. This equation contains a term that encodes the
backreaction of the fermionic perturbations on the quantum dynamics of the
homogeneous sector. We analyze this backreaction by solving the associated
Heisenberg evolution of the fermionic annihilation and creation operators.
Then, we identify the conditions that the choice of those operators must
satisfy in order to lead to a finite backreaction. Finally, we discuss further
restrictions on this choice so that the fermionic Hamiltonian that dictates the
Schr\"odinger dynamics is densely defined in Fock space.
| [
{
"created": "Thu, 10 May 2018 18:53:52 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Oct 2018 08:35:37 GMT",
"version": "v2"
}
] | 2018-10-02 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Loy",
"Santiago Prado",
""
]
] | We discuss the freedom available in hybrid loop quantum cosmology to define canonical variables for the matter content and investigate whether this can be used to derive a quantum field theory with good properties for the matter sector. We study a primordial, inflationary, cosmological spacetime with inhomogeneous perturbations at lowest nontrivial order, and focus our attention on the contribution of minimally coupled fermionic perturbations of Dirac type. Within the framework of the hybrid quantization, we analyze the different possible separations of the homogeneous background and the inhomogeneous perturbations, by means of canonical transformations that mix the two separated sectors. These possibilities provide a family of sets of annihilation and creationlike fermionic variables, each of them with a different associated contribution to the total Hamiltonian. In all cases, imposing the quantum constraints and introducing a Born-Oppenheimer approximation, one can derive a Schr\"odinger equation for the fermionic part of the wave functions. The resulting evolution turns out to be generated, for each of the allowed choices of variables, by a version of the fermionic contribution to the Hamiltonian which is obtained by evaluating all the dependence on the homogeneous geometry at quantum expectation values. This equation contains a term that encodes the backreaction of the fermionic perturbations on the quantum dynamics of the homogeneous sector. We analyze this backreaction by solving the associated Heisenberg evolution of the fermionic annihilation and creation operators. Then, we identify the conditions that the choice of those operators must satisfy in order to lead to a finite backreaction. Finally, we discuss further restrictions on this choice so that the fermionic Hamiltonian that dictates the Schr\"odinger dynamics is densely defined in Fock space. |
gr-qc/9511022 | null | Dieter R. Brill | Multi-Black-Hole Geometries in (2+1)-Dimensional Gravity | LaTeX, 10 pages, 3 figures in LaTeX picture environment | Phys.Rev.D53:4133-4176,1996 | 10.1103/PhysRevD.53.4133 | UMDGR 96-47 | gr-qc hep-th | null | Generalizations of the Black Hole geometry of Ba\~nados, Teitelboim and
Zanelli (BTZ) are presented. The theory is three-dimensional vacuum Einstein
theory with a negative cosmological constant. The $n$-black-hole solution has
$n$ asymptotically anti-de Sitter ``exterior" regions that join in one
``interior" region. The geometry of each exterior region is identical to that
of a BTZ geometry; in particular, each contains a black hole horizon that
surrounds (as judged from that exterior) all the other horizons. The interior
region acts as a closed universe containing $n$ black holes. The initial state
and its time development are discussed in some detail for the simple case when
the angular momentum parameters of all the black holes vanish. A procedure to
construct $n$ black holes with angular momentum (for $n \geq 4$) is also given.
| [
{
"created": "Mon, 6 Nov 1995 18:05:25 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Brill",
"Dieter R.",
""
]
] | Generalizations of the Black Hole geometry of Ba\~nados, Teitelboim and Zanelli (BTZ) are presented. The theory is three-dimensional vacuum Einstein theory with a negative cosmological constant. The $n$-black-hole solution has $n$ asymptotically anti-de Sitter ``exterior" regions that join in one ``interior" region. The geometry of each exterior region is identical to that of a BTZ geometry; in particular, each contains a black hole horizon that surrounds (as judged from that exterior) all the other horizons. The interior region acts as a closed universe containing $n$ black holes. The initial state and its time development are discussed in some detail for the simple case when the angular momentum parameters of all the black holes vanish. A procedure to construct $n$ black holes with angular momentum (for $n \geq 4$) is also given. |
1703.02779 | Nadereh Namavarian | Nadereh Namavarian | Trace anomaly and invariance under transformation of units | 8 pages | Phys. Rev. D 95, 104015 (2017) | 10.1103/PhysRevD.95.104015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Paying attention to conformal invariance as the invariance under local
transformations of units of measure, we take a conformal invariant quantum
field as a quantum matter theory in which one has the freedom to choose the
values of units of mass, length and time arbitrarily at each point. To be able
to have this view, it is necessary that the background on which the quantum
field is based be conformal invariant as well. Consequently, defining the
unambiguous expectation value of the energy-momentum tensor of such a quantum
field through the Wald renormalizing prescription necessitates breaking down
the conformal symmetry of the background. Then, noticing the field equations
suitable for describing the back-reaction effect, we show that the existence of
trace anomaly, known for indicating the brokenness of conformal symmetry in
quantum field theory, can also indicate the above gravitational conformal
symmetry brokenness
| [
{
"created": "Wed, 8 Mar 2017 10:43:18 GMT",
"version": "v1"
}
] | 2017-05-17 | [
[
"Namavarian",
"Nadereh",
""
]
] | Paying attention to conformal invariance as the invariance under local transformations of units of measure, we take a conformal invariant quantum field as a quantum matter theory in which one has the freedom to choose the values of units of mass, length and time arbitrarily at each point. To be able to have this view, it is necessary that the background on which the quantum field is based be conformal invariant as well. Consequently, defining the unambiguous expectation value of the energy-momentum tensor of such a quantum field through the Wald renormalizing prescription necessitates breaking down the conformal symmetry of the background. Then, noticing the field equations suitable for describing the back-reaction effect, we show that the existence of trace anomaly, known for indicating the brokenness of conformal symmetry in quantum field theory, can also indicate the above gravitational conformal symmetry brokenness |
gr-qc/9711071 | Wang Bin | Ru-Keng Su, Bin Wang, P.K.N.Yu and E.C.M.Young | A possible explanation of the clash for black hole entropy in the
extremal limit | 9 pages, Latex, no figures | null | null | null | gr-qc | null | It is shown that the classical entropy of the extremal black hole depends on
two different limits procedures. If we first take the extremal limit and then
the boundary limit, the entropy is zero; if we do it the other way round, we
get the Bekenstein-Hawking entropy. By means of the brick wall model, the
quantum entropy of scalar field in the extremal black hole background has been
calculated for the above two different limits procedures. A possible
explanation which considers the quantum effect for the clash of black hole
entropy in the extremal limit is given.
| [
{
"created": "Mon, 24 Nov 1997 09:05:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Su",
"Ru-Keng",
""
],
[
"Wang",
"Bin",
""
],
[
"Yu",
"P. K. N.",
""
],
[
"Young",
"E. C. M.",
""
]
] | It is shown that the classical entropy of the extremal black hole depends on two different limits procedures. If we first take the extremal limit and then the boundary limit, the entropy is zero; if we do it the other way round, we get the Bekenstein-Hawking entropy. By means of the brick wall model, the quantum entropy of scalar field in the extremal black hole background has been calculated for the above two different limits procedures. A possible explanation which considers the quantum effect for the clash of black hole entropy in the extremal limit is given. |
0812.3438 | R. Aldrovandi | R. Aldrovandi and J. G. Pereira | De Sitter Special Relativity: Effects on Cosmology | 12 pages | Grav.Cosmol.15:287-294,2009 | 10.1134/S020228930904001X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main consequences of de Sitter Special Relativity to the Standard
Cosmological Model of Physical Cosmology are examined. The cosmological
constant Lambda appears, in this theory, as a manifestation of the proper
conformal current, which must be added to the usual energy-momentum density. As
that conformal current itself vanishes in absence of sources, Lambda is
ultimately dependent on the matter content, and can in principle be calculated.
A present-day value very close to that given by the crossed supernova/BBR data
is obtained through simple and reasonable approximations. Also a primeval
inflation of polynomial type is found, and the usual notion of co-moving
observer is slightly modified.
| [
{
"created": "Thu, 18 Dec 2008 00:31:51 GMT",
"version": "v1"
}
] | 2010-01-08 | [
[
"Aldrovandi",
"R.",
""
],
[
"Pereira",
"J. G.",
""
]
] | The main consequences of de Sitter Special Relativity to the Standard Cosmological Model of Physical Cosmology are examined. The cosmological constant Lambda appears, in this theory, as a manifestation of the proper conformal current, which must be added to the usual energy-momentum density. As that conformal current itself vanishes in absence of sources, Lambda is ultimately dependent on the matter content, and can in principle be calculated. A present-day value very close to that given by the crossed supernova/BBR data is obtained through simple and reasonable approximations. Also a primeval inflation of polynomial type is found, and the usual notion of co-moving observer is slightly modified. |
2101.09524 | \"Ozg\"ur \"Okc\"u | \"Ozg\"ur \"Okc\"u, Ekrem Aydiner | Observational Tests of the Generalized Uncertainty Principle: Shapiro
Time Delay, Gravitational Redshift, and Geodetic Precession | 17 pages, 1 figure, 1 table. Accepted for publication in Nuclear
Physics B | null | 10.1016/j.nuclphysb.2021.115324 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is based on the study of the paper of Scardigli and Casadio [Eur.
Phys. J. C (2015) 75:425] where the authors computed the light deflection and
perihelion precession for the Generalized Uncertainty Principle (GUP) modified
Schwarzschild metric. In the present work, we computed the gravitational tests
such as Shapiro time delay, gravitational redshift, and geodetic precession for
the GUP modified Schwarzschild metric. Using the results of Solar system
experiments and observations, we obtain upper bounds for the GUP parameter
$\beta$. Finally, we compare our bounds with other bounds in the literature.
| [
{
"created": "Sat, 23 Jan 2021 15:35:42 GMT",
"version": "v1"
}
] | 2021-01-26 | [
[
"Ökcü",
"Özgür",
""
],
[
"Aydiner",
"Ekrem",
""
]
] | This paper is based on the study of the paper of Scardigli and Casadio [Eur. Phys. J. C (2015) 75:425] where the authors computed the light deflection and perihelion precession for the Generalized Uncertainty Principle (GUP) modified Schwarzschild metric. In the present work, we computed the gravitational tests such as Shapiro time delay, gravitational redshift, and geodetic precession for the GUP modified Schwarzschild metric. Using the results of Solar system experiments and observations, we obtain upper bounds for the GUP parameter $\beta$. Finally, we compare our bounds with other bounds in the literature. |
2007.10336 | Alexandru Lupsasca | Samuel E. Gralla, Alexandru Lupsasca | On the Observable Shape of Black Hole Photon Rings | 16 pages, 8 figures | null | 10.1103/PhysRevD.102.124003 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the prospect of measuring a black hole photon ring, in previous
work we explored the interferometric signature produced by a bright, narrow
curve in the sky. Interferometric observations of such a curve measure its
"projected position function" $\mathbf{r}\cdot\hat{\mathbf{n}}$, where
$\mathbf{r}$ parameterizes the curve and $\hat{\mathbf{n}}$ denotes its unit
normal vector. In this paper, we show by explicit construction that a curve can
be fully reconstructed from its projected position, completing the argument
that space interferometry can in principle determine the detailed photon ring
shape. In practice, near-term observations may be limited to the visibility
amplitude alone, which contains incomplete shape information: for convex
curves, the amplitude only encodes the set of projected diameters (or "widths")
of the shape. We explore the freedom in reconstructing a convex curve from its
widths, giving insight into the shape information probed by technically
plausible future astronomical measurements. Finally, we consider the Kerr
"critical curve" in this framework and present some new results on its shape.
We analytically show that the critical curve is an ellipse at small spin or
inclination, while at extremal spin it becomes the convex hull of a Cartesian
oval. We find a simple oval shape, the "phoval", which reproduces the critical
curve with high fidelity over the whole parameter range.
| [
{
"created": "Mon, 20 Jul 2020 18:00:00 GMT",
"version": "v1"
}
] | 2020-12-09 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Lupsasca",
"Alexandru",
""
]
] | Motivated by the prospect of measuring a black hole photon ring, in previous work we explored the interferometric signature produced by a bright, narrow curve in the sky. Interferometric observations of such a curve measure its "projected position function" $\mathbf{r}\cdot\hat{\mathbf{n}}$, where $\mathbf{r}$ parameterizes the curve and $\hat{\mathbf{n}}$ denotes its unit normal vector. In this paper, we show by explicit construction that a curve can be fully reconstructed from its projected position, completing the argument that space interferometry can in principle determine the detailed photon ring shape. In practice, near-term observations may be limited to the visibility amplitude alone, which contains incomplete shape information: for convex curves, the amplitude only encodes the set of projected diameters (or "widths") of the shape. We explore the freedom in reconstructing a convex curve from its widths, giving insight into the shape information probed by technically plausible future astronomical measurements. Finally, we consider the Kerr "critical curve" in this framework and present some new results on its shape. We analytically show that the critical curve is an ellipse at small spin or inclination, while at extremal spin it becomes the convex hull of a Cartesian oval. We find a simple oval shape, the "phoval", which reproduces the critical curve with high fidelity over the whole parameter range. |
1606.04226 | Davide Gerosa | Davide Gerosa, Christopher J. Moore | Black hole kicks as new gravitational wave observables | 6 pages, 3 figures. Accepted for publication in Physical Review
Letters | Phys. Rev. Lett. 117, 011101 (2016) | 10.1103/PhysRevLett.117.011101 | LIGO-P1600118 | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generic black hole binaries radiate gravitational waves anisotropically,
imparting a recoil, or kick, velocity to the merger remnant. If a component of
the kick along the line of sight is present, gravitational waves emitted during
the final orbits and merger will be gradually Doppler shifted as the kick
builds up. We develop a simple prescription to capture this effect in existing
waveform models, showing that future gravitational wave experiments will be
able to perform direct measurements, not only of the black hole kick velocity,
but also of its accumulation profile. In particular, the eLISA space mission
will measure supermassive black hole kick velocities as low as ~500 km/s, which
are expected to be a common outcome of black hole binary coalescence following
galaxy mergers. Black hole kicks thus constitute a promising new observable in
the growing field of gravitational wave astronomy.
| [
{
"created": "Tue, 14 Jun 2016 07:26:10 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jun 2016 17:43:17 GMT",
"version": "v2"
}
] | 2016-06-30 | [
[
"Gerosa",
"Davide",
""
],
[
"Moore",
"Christopher J.",
""
]
] | Generic black hole binaries radiate gravitational waves anisotropically, imparting a recoil, or kick, velocity to the merger remnant. If a component of the kick along the line of sight is present, gravitational waves emitted during the final orbits and merger will be gradually Doppler shifted as the kick builds up. We develop a simple prescription to capture this effect in existing waveform models, showing that future gravitational wave experiments will be able to perform direct measurements, not only of the black hole kick velocity, but also of its accumulation profile. In particular, the eLISA space mission will measure supermassive black hole kick velocities as low as ~500 km/s, which are expected to be a common outcome of black hole binary coalescence following galaxy mergers. Black hole kicks thus constitute a promising new observable in the growing field of gravitational wave astronomy. |
1306.5177 | Sante Carloni Dr | C. Garc\'ia-Meca, S. Carloni, C. Barcel\'o, G. Jannes, J.
S\'anchez-Dehesa, A. Mart\'inez | Analogue Transformations in Physics and their Application to Acoustics | 29 pages, 11 figures, published on Scientific Reports | Scientific Reports 3, 2009 (2013) | 10.1038/srep02009 | null | gr-qc cond-mat.mes-hall cond-mat.mtrl-sci | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Transformation optics has shaped up a revolutionary electromagnetic design
paradigm, enabling scientists to build astonishing devices such as invisibility
cloaks. Unfortunately, the application of transformation techniques to other
branches of physics is often constrained by the structure of the field
equations. We develop here a complete transformation method using the idea of
analogue spacetimes. The method is general and could be considered as a new
paradigm for controlling waves in different branches of physics, from acoustics
in quantum fluids to graphene electronics. As an application, we derive an
"analogue transformation acoustics" formalism that naturally allows the use of
transformations mixing space and time or involving moving fluids, both of which
were impossible with the standard approach. To demonstrate the power of our
method, we give an explicit design of a spacetime compressor for acoustic waves
and a carpet cloak for a moving aircraft.
| [
{
"created": "Fri, 21 Jun 2013 15:46:42 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jun 2015 14:45:16 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"García-Meca",
"C.",
""
],
[
"Carloni",
"S.",
""
],
[
"Barceló",
"C.",
""
],
[
"Jannes",
"G.",
""
],
[
"Sánchez-Dehesa",
"J.",
""
],
[
"Martínez",
"A.",
""
]
] | Transformation optics has shaped up a revolutionary electromagnetic design paradigm, enabling scientists to build astonishing devices such as invisibility cloaks. Unfortunately, the application of transformation techniques to other branches of physics is often constrained by the structure of the field equations. We develop here a complete transformation method using the idea of analogue spacetimes. The method is general and could be considered as a new paradigm for controlling waves in different branches of physics, from acoustics in quantum fluids to graphene electronics. As an application, we derive an "analogue transformation acoustics" formalism that naturally allows the use of transformations mixing space and time or involving moving fluids, both of which were impossible with the standard approach. To demonstrate the power of our method, we give an explicit design of a spacetime compressor for acoustic waves and a carpet cloak for a moving aircraft. |
0704.3936 | Leonardo Fernandez-Jambrina | L. Fernandez-Jambrina | Hidden past of dark energy cosmological models | 6 pages, 1 figure, RevTeX4, new references and comments added | Phys.Lett.B656:9-14,2007 | 10.1016/j.physletb.2007.08.091 | null | gr-qc astro-ph hep-th | null | In this paper we analyse the possibility of having homogeneous isotropic
cosmological models with observers reaching $t=\infty$ in finite proper time.
It is shown that just observationally-suggested dark energy models with
$w\in(-5/3,-1)$ show this feature and that they are endowed with an exotic
curvature singularity. Furthermore, it is shown that non-accelerated observers
in these models may experience a duration of the universe as short as desired
by increasing their linear momentum. A subdivision of phantom models in two
families according to this behavior is suggested.
| [
{
"created": "Mon, 30 Apr 2007 13:30:04 GMT",
"version": "v1"
},
{
"created": "Thu, 3 May 2007 10:08:42 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Sep 2007 17:05:12 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Fernandez-Jambrina",
"L.",
""
]
] | In this paper we analyse the possibility of having homogeneous isotropic cosmological models with observers reaching $t=\infty$ in finite proper time. It is shown that just observationally-suggested dark energy models with $w\in(-5/3,-1)$ show this feature and that they are endowed with an exotic curvature singularity. Furthermore, it is shown that non-accelerated observers in these models may experience a duration of the universe as short as desired by increasing their linear momentum. A subdivision of phantom models in two families according to this behavior is suggested. |
1003.5690 | Alexander Zhuk | Maxim Eingorn, Alexander Zhuk | Classical tests of multidimensional gravity: negative result | 18 pages, LaTex | Class.Quant.Grav.27:205014,2010 | 10.1088/0264-9381/27/20/205014 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Kaluza-Klein model with toroidal extra dimensions, we obtain the metric
coefficients in a weak-field approximation for delta-shaped matter sources.
These metric coefficients are applied to calculate the formulas for frequency
shift, perihelion shift, deflection of light and parameterized post-Newtonian
(PPN) parameters. In the leading order of approximation, the formula for
frequency shift coincides with well-known general relativity expression.
However, for perihelion shift, light deflection and PPN parameter $\gamma $ we
obtain formulas $D\pi r_g/[(D-2)a(1-e^2)]$, $(D-1)r_g/[(D-2)\rho]$ and
$1/(D-2)$ respectively, where $D$ is a total number of spatial dimensions.
These expressions demonstrate good agreement with experimental data only in the
case of ordinary three-dimensional $(D=3)$ space. This result does not depend
on the size of the extra dimensions. Therefore, in the considered
multidimensional Kaluza-Klein models the point-like masses cannot produce the
gravitational field which corresponds to the classical gravitational tests.
| [
{
"created": "Mon, 29 Mar 2010 21:51:07 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Oct 2010 15:09:49 GMT",
"version": "v2"
}
] | 2010-10-29 | [
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | In Kaluza-Klein model with toroidal extra dimensions, we obtain the metric coefficients in a weak-field approximation for delta-shaped matter sources. These metric coefficients are applied to calculate the formulas for frequency shift, perihelion shift, deflection of light and parameterized post-Newtonian (PPN) parameters. In the leading order of approximation, the formula for frequency shift coincides with well-known general relativity expression. However, for perihelion shift, light deflection and PPN parameter $\gamma $ we obtain formulas $D\pi r_g/[(D-2)a(1-e^2)]$, $(D-1)r_g/[(D-2)\rho]$ and $1/(D-2)$ respectively, where $D$ is a total number of spatial dimensions. These expressions demonstrate good agreement with experimental data only in the case of ordinary three-dimensional $(D=3)$ space. This result does not depend on the size of the extra dimensions. Therefore, in the considered multidimensional Kaluza-Klein models the point-like masses cannot produce the gravitational field which corresponds to the classical gravitational tests. |
1905.10414 | Nils A. Nilsson | Nils A. Nilsson, Kellie O'Neal-Ault, Quentin G. Bailey | A 3+1 Decomposition of the Minimal Standard-Model Extension
Gravitational Sector | Presented at the Eighth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 12-16, 2019 | CPT and Lorentz Symmetry, pp. 198-200 (2020) | 10.1142/9789811213984_0050 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 3+1 (ADM) formulation of General Relativity is used in, for example,
canonical quantum gravity and numerical relativity. Here we present a 3+1
decomposition of the minimal Standard-Model Extension gravity Lagrangian. By
choosing the leaves of foliation to lie along a timelike vector field we write
the theory in a form which will allow for comparison and matching to other
gravity models.
| [
{
"created": "Fri, 24 May 2019 19:14:02 GMT",
"version": "v1"
}
] | 2020-04-21 | [
[
"Nilsson",
"Nils A.",
""
],
[
"O'Neal-Ault",
"Kellie",
""
],
[
"Bailey",
"Quentin G.",
""
]
] | The 3+1 (ADM) formulation of General Relativity is used in, for example, canonical quantum gravity and numerical relativity. Here we present a 3+1 decomposition of the minimal Standard-Model Extension gravity Lagrangian. By choosing the leaves of foliation to lie along a timelike vector field we write the theory in a form which will allow for comparison and matching to other gravity models. |
1607.03923 | S. I. Kruglov | S.I. Kruglov | Nonlinear Electromagnetic Fields As a Source of Universe Acceleration | 20 pages, 4 figures, to appear in IJMPA | null | 10.1142/S0217751X16500585 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model of nonlinear electromagnetic fields with a dimensional parameter
$\beta$ is proposed. From PVLAS experiment the bound on the parameter $\beta$
was obtained. Electromagnetic fields are coupled with the gravitation field and
we show that the universe accelerates due to nonlinear electromagnetic fields.
The magnetic universe is considered and the stochastic magnetic field is a
background. After inflation the universe decelerates and approaches to the
radiation era. The range of the scale factor, when the causality of the model
and a classical stability take place, was obtained. The spectral index, the
tensor-to-scalar ratio, and the running of the spectral index were estimated
which are in approximate agreement with the PLANCK, WMAP, and BICEP2 data.
| [
{
"created": "Fri, 8 Apr 2016 16:12:17 GMT",
"version": "v1"
}
] | 2016-07-15 | [
[
"Kruglov",
"S. I.",
""
]
] | A model of nonlinear electromagnetic fields with a dimensional parameter $\beta$ is proposed. From PVLAS experiment the bound on the parameter $\beta$ was obtained. Electromagnetic fields are coupled with the gravitation field and we show that the universe accelerates due to nonlinear electromagnetic fields. The magnetic universe is considered and the stochastic magnetic field is a background. After inflation the universe decelerates and approaches to the radiation era. The range of the scale factor, when the causality of the model and a classical stability take place, was obtained. The spectral index, the tensor-to-scalar ratio, and the running of the spectral index were estimated which are in approximate agreement with the PLANCK, WMAP, and BICEP2 data. |
gr-qc/0405025 | Frank Potter | Franklin Potter and Howard G. Preston | Gravitational Lensing by Galaxy Quantization States | 6 pages | null | null | null | gr-qc | null | We show how our theory of large-scale gravitational quantization explains the
large angle gravitational lensing by galaxies without requiring "dark matter".
A galaxy is treated as a collective system of billions of stars in each
quantization state with each star experiencing an average gravitational
environment analogous to that for nucleons in the atomic nucleus. Consequently,
each star is in an approximate finite depth square well type of gravitational
potential. The "effective potential" is shown to be about ten times greater
than the Newtonian gravitational potential, so the gravitational lensing
effects of a galaxy are about ten times greater also, in agreement with the
measured gravitational lensing.
| [
{
"created": "Thu, 6 May 2004 02:16:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Potter",
"Franklin",
""
],
[
"Preston",
"Howard G.",
""
]
] | We show how our theory of large-scale gravitational quantization explains the large angle gravitational lensing by galaxies without requiring "dark matter". A galaxy is treated as a collective system of billions of stars in each quantization state with each star experiencing an average gravitational environment analogous to that for nucleons in the atomic nucleus. Consequently, each star is in an approximate finite depth square well type of gravitational potential. The "effective potential" is shown to be about ten times greater than the Newtonian gravitational potential, so the gravitational lensing effects of a galaxy are about ten times greater also, in agreement with the measured gravitational lensing. |
gr-qc/9905100 | Paul Matthew Saffin | J. D. Barrow, Y. Gaspar and P. M. Saffin | Some exact non-vacuum Bianchi VI0 and VII0 instantons | latex, 15 pages with 3 eps figures | Class.Quant.Grav. 17 (2000) 1435-1445 | 10.1088/0264-9381/17/6/308 | DAMTP-1999-71 | gr-qc astro-ph | null | We report some new exact instantons in general relativity. These solutions
are K\"ahler and fall into the symmetry classes of Bianchi types VI0 and VII0,
with matter content of a stiff fluid. The qualitative behaviour of the
solutions is presented, and we compare it to the known results of the
corresponding self-dual Bianchi solutions. We also give axisymmetric Bianchi
VII0 solutions with an electromagnetic field.
| [
{
"created": "Thu, 27 May 1999 17:54:30 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Barrow",
"J. D.",
""
],
[
"Gaspar",
"Y.",
""
],
[
"Saffin",
"P. M.",
""
]
] | We report some new exact instantons in general relativity. These solutions are K\"ahler and fall into the symmetry classes of Bianchi types VI0 and VII0, with matter content of a stiff fluid. The qualitative behaviour of the solutions is presented, and we compare it to the known results of the corresponding self-dual Bianchi solutions. We also give axisymmetric Bianchi VII0 solutions with an electromagnetic field. |
2403.12634 | Patrick Bourg | Patrick Bourg, Benjamin Leather, Marc Casals, Adam Pound, Barry
Wardell | Implementation of a GHZ-Teukolsky puncture scheme for gravitational
self-force calculations | 30 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Post-adiabatic models of extreme- and intermediate-mass-ratio inspirals will
require calculations of second-order gravitational self-force effects in the
spacetime of a spinning, Kerr black hole. We take a step toward such
calculations by implementing the recently formulated Teukolsky puncture scheme
with Green-Hollands-Zimmerman metric reconstruction [CQG 39, 015019 (2022)].
This scheme eliminates the critical obstacle of gauge singularities that arise
in the standard no-string metric reconstruction. Our first proof-of-principle
implementation is limited to the simple case of circular orbits in
Schwarzschild spacetime, but the method also applies to generic orbits on a
Kerr background. We conclude with a discussion of various approaches to the
second-order self-force problem in Kerr.
| [
{
"created": "Tue, 19 Mar 2024 11:04:46 GMT",
"version": "v1"
}
] | 2024-03-20 | [
[
"Bourg",
"Patrick",
""
],
[
"Leather",
"Benjamin",
""
],
[
"Casals",
"Marc",
""
],
[
"Pound",
"Adam",
""
],
[
"Wardell",
"Barry",
""
]
] | Post-adiabatic models of extreme- and intermediate-mass-ratio inspirals will require calculations of second-order gravitational self-force effects in the spacetime of a spinning, Kerr black hole. We take a step toward such calculations by implementing the recently formulated Teukolsky puncture scheme with Green-Hollands-Zimmerman metric reconstruction [CQG 39, 015019 (2022)]. This scheme eliminates the critical obstacle of gauge singularities that arise in the standard no-string metric reconstruction. Our first proof-of-principle implementation is limited to the simple case of circular orbits in Schwarzschild spacetime, but the method also applies to generic orbits on a Kerr background. We conclude with a discussion of various approaches to the second-order self-force problem in Kerr. |
2105.12283 | Luis L\'opez | Nora Bret\'on and L. A. L\'opez | Birefringence and QuasiNormal Modes of the Einstein-Euler-Heisenberg
Black Hole | null | Phys. Rev. D 104, 024064 (2021) | 10.1103/PhysRevD.104.024064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this contribution we study the birefringence and the quasinormal modes
(QNM) in the eikonal approximation, of the Einstein-Euler-Heisenberg black hole
(EEH-BH) . The EEH-BH is an exact solution of the Einstein equations coupled to
the Euler-Heisenberg nonlinear electrodynamics. It is well known that in the
presence of strong electromagnetic fields light rays modify their trajectories
and do follow the null geodesics of an effective metric as a result of the
nonlinear interaction between light and the intense magnetic or electric
background. In the Euler-Heisenberg theory the phenomenon of birefringence
arises and then exist two possible light trajectories for polarized light in
the vicinity of the EEH-BH. On the other hand, using the correspondence between
the parameters of the null unstable geodesics and the quasinormal modes in the
eikonal approximation. We determine these QNM for both, the electric and the
magnetic EEH-BH and compare them with its linear counterpart, the
Reissner-Nordstr\"{o}m black hole, since there are two effective metrics, to
each one corresponds one null geodesic that renders two possible QNM from the
same compact object.
| [
{
"created": "Wed, 26 May 2021 01:07:32 GMT",
"version": "v1"
}
] | 2021-08-04 | [
[
"Bretón",
"Nora",
""
],
[
"López",
"L. A.",
""
]
] | In this contribution we study the birefringence and the quasinormal modes (QNM) in the eikonal approximation, of the Einstein-Euler-Heisenberg black hole (EEH-BH) . The EEH-BH is an exact solution of the Einstein equations coupled to the Euler-Heisenberg nonlinear electrodynamics. It is well known that in the presence of strong electromagnetic fields light rays modify their trajectories and do follow the null geodesics of an effective metric as a result of the nonlinear interaction between light and the intense magnetic or electric background. In the Euler-Heisenberg theory the phenomenon of birefringence arises and then exist two possible light trajectories for polarized light in the vicinity of the EEH-BH. On the other hand, using the correspondence between the parameters of the null unstable geodesics and the quasinormal modes in the eikonal approximation. We determine these QNM for both, the electric and the magnetic EEH-BH and compare them with its linear counterpart, the Reissner-Nordstr\"{o}m black hole, since there are two effective metrics, to each one corresponds one null geodesic that renders two possible QNM from the same compact object. |
gr-qc/0003029 | Jeffrey Winicour | Jeffrey Winicour | A New Way to Make Waves | In Proceeding of CIMENICS 2000, The Vth International Congress on
Numerical Methods in Engineering and Applied Science (Puerto La Cruz,
Venezuela, March 2000) | null | null | null | gr-qc | null | I describe a new algorithm for solving nonlinear wave equations. In this
approach, evolution takes place on characteristic hypersurfaces. The algorithm
is directly applicable to electromagnetic, Yang-Mills and gravitational fields
and other systems described by second differential order hyperbolic equations.
The basic ideas should also be applicable to hydrodynamics. It is an especially
accurate and efficient way for simulating waves in regions where the
characteristics are well behaved. A prime application of the algorithm is to
Cauchy-characteristic matching, in which this new approach is matched to a
standard Cauchy evolution to obtain a global solution. In a model problem of a
nonlinear wave, this proves to be more accurate and efficient than any other
present method of assigning Cauchy outer boundary conditions. The approach was
developed to compute the gravitational wave signal produced by collisions of
two black holes. An application to colliding black holes is presented.
| [
{
"created": "Wed, 8 Mar 2000 10:58:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Winicour",
"Jeffrey",
""
]
] | I describe a new algorithm for solving nonlinear wave equations. In this approach, evolution takes place on characteristic hypersurfaces. The algorithm is directly applicable to electromagnetic, Yang-Mills and gravitational fields and other systems described by second differential order hyperbolic equations. The basic ideas should also be applicable to hydrodynamics. It is an especially accurate and efficient way for simulating waves in regions where the characteristics are well behaved. A prime application of the algorithm is to Cauchy-characteristic matching, in which this new approach is matched to a standard Cauchy evolution to obtain a global solution. In a model problem of a nonlinear wave, this proves to be more accurate and efficient than any other present method of assigning Cauchy outer boundary conditions. The approach was developed to compute the gravitational wave signal produced by collisions of two black holes. An application to colliding black holes is presented. |
2110.02713 | Hamid Reza Sepangi | Mohaddese Heydari-Fard, Malihe Heydari-Fard, Hamid Reza Sepangi | On null geodesics and shadow of hairy black holes in
Einstein-Maxwell-dilaton gravity | 19 pages, 13 figures, to appear in PRD | Phys. Rev. D 105, 124009 (2022) | 10.1103/PhysRevD.105.124009 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | The time-like and null-like geodesics around compact objects are some of the
best tools to classify and understand the structure of a space-time. In this
paper, we study the null geodesics around charged static dilaton black holes in
Einstein-Maxwell-dilaton gravity. The physical parameters for non-radial
geodesics including the effective potential, effective force, radius of the
photon sphere and impact parameter are obtained and effects of the charge
parameter and dilaton coupling constant on these quantities are studied.
Possible photon motions for different values of the impact parameter are
analyzed and unstable circular orbits and unbounded orbits are plotted. These
results are compared to that of the Schwarzschild, Reissner-Nordstrom and
Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black holes. Also, we study
the shadow cast by a dilaton black hole and investigate how the dilaton
coupling affects the size of the black hole shadow. Finally, as an application
of null geodesics, we calculate the deflection of light and investigate the
effects of the model parameters on the bending angle.
| [
{
"created": "Wed, 6 Oct 2021 13:00:45 GMT",
"version": "v1"
},
{
"created": "Thu, 12 May 2022 11:26:28 GMT",
"version": "v2"
}
] | 2022-06-22 | [
[
"Heydari-Fard",
"Mohaddese",
""
],
[
"Heydari-Fard",
"Malihe",
""
],
[
"Sepangi",
"Hamid Reza",
""
]
] | The time-like and null-like geodesics around compact objects are some of the best tools to classify and understand the structure of a space-time. In this paper, we study the null geodesics around charged static dilaton black holes in Einstein-Maxwell-dilaton gravity. The physical parameters for non-radial geodesics including the effective potential, effective force, radius of the photon sphere and impact parameter are obtained and effects of the charge parameter and dilaton coupling constant on these quantities are studied. Possible photon motions for different values of the impact parameter are analyzed and unstable circular orbits and unbounded orbits are plotted. These results are compared to that of the Schwarzschild, Reissner-Nordstrom and Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black holes. Also, we study the shadow cast by a dilaton black hole and investigate how the dilaton coupling affects the size of the black hole shadow. Finally, as an application of null geodesics, we calculate the deflection of light and investigate the effects of the model parameters on the bending angle. |
1701.07934 | Ramon Herrera | Ramon Herrera | G-Warm inflation | 23 pages, 4 figures, Accepted for publication in JCAP | null | 10.1088/1475-7516/2017/05/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A warm inflationary universe in the context of Galileon model or G-model is
studied. Under a general formalism we study the inflationary dynamics and the
cosmological perturbations considering a coupling of the form
$G(\phi,X)=g(\phi)\,X$. As a concrete example, we consider an exponential
potential together with the cases in which the dissipation and Galilean
coefficients are constants. Also, we study the weak regime given by the
condition $R<1+3gH\dot{\phi}$, and the strong regime in which
$1<R+3gH\dot{\phi}$.Additionally, we obtain constraints on the parameters
during the evolution of G-warm inflation, assuming the condition for warm
inflation in which the temperature $T>H$, the conditions for the weak and
strong regimes, together with the consistency relation $r=r(n_s)$ from Planck
data.
| [
{
"created": "Fri, 27 Jan 2017 03:41:09 GMT",
"version": "v1"
},
{
"created": "Wed, 10 May 2017 18:42:35 GMT",
"version": "v2"
}
] | 2017-05-24 | [
[
"Herrera",
"Ramon",
""
]
] | A warm inflationary universe in the context of Galileon model or G-model is studied. Under a general formalism we study the inflationary dynamics and the cosmological perturbations considering a coupling of the form $G(\phi,X)=g(\phi)\,X$. As a concrete example, we consider an exponential potential together with the cases in which the dissipation and Galilean coefficients are constants. Also, we study the weak regime given by the condition $R<1+3gH\dot{\phi}$, and the strong regime in which $1<R+3gH\dot{\phi}$.Additionally, we obtain constraints on the parameters during the evolution of G-warm inflation, assuming the condition for warm inflation in which the temperature $T>H$, the conditions for the weak and strong regimes, together with the consistency relation $r=r(n_s)$ from Planck data. |
gr-qc/9806018 | Scott A. Hughes | Scott A. Hughes and Kip S. Thorne | Seismic gravity-gradient noise in interferometric gravitational-wave
detectors | 30 pages, Revtex, 12 figures, submitted to Phys Rev D | Phys.Rev.D58:122002,1998 | 10.1103/PhysRevD.58.122002 | GRP-500 | gr-qc | null | When ambient seismic waves pass near an interferometric gravitational-wave
detector, they induce density perturbations in the earth which produce
fluctuating gravitational forces on the interferometer's test masses. These
forces mimic a stochastic background of gravitational waves and thus constitute
noise. We compute this noise using the theory of multimode Rayleigh and Love
waves propagating in a layered medium that approximates the geological strata
at the LIGO sites. We characterize the noise by a transfer function $T(f)
\equiv \tilde x(f)/\tilde W(f)$ from the spectrum of direction averaged ground
motion $\tilde W(f)$ to the spectrum of test mass motion $\tilde x(f) = L\tilde
h(f)$ (where $L$ is the length of the interferometer's arms, and $\tilde h(f)$
is the spectrum of gravitational-wave noise). This paper's primary foci are (i)
a study of how $T(f)$ depends on the various seismic modes; (ii) an attempt to
estimate which modes are excited at the LIGO sites at quiet and noisy times;
and (iii) a corresponding estimate of the seismic gravity-gradient noise level.
At quiet times the noise is below the benchmark noise level of ``advanced LIGO
interferometers'' (although not by much near 10 Hz); it may significantly
exceed this level at noisy times. The lower edge of our quiet-time noise is a
limit beyond which there is little gain from further improvements in vibration
isolation and thermal noise, unless one also reduces seismic gravity-gradient
noise. Two methods of reduction are discussed: monitoring the earth's density
perturbations, computing their gravitational forces, and correcting the data
for those forces; and constructing narrow moats around the interferometers'
test masses to shield out the fundamental-mode Rayleigh waves, which we suspect
dominate at quiet times.
| [
{
"created": "Wed, 3 Jun 1998 22:08:25 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Hughes",
"Scott A.",
""
],
[
"Thorne",
"Kip S.",
""
]
] | When ambient seismic waves pass near an interferometric gravitational-wave detector, they induce density perturbations in the earth which produce fluctuating gravitational forces on the interferometer's test masses. These forces mimic a stochastic background of gravitational waves and thus constitute noise. We compute this noise using the theory of multimode Rayleigh and Love waves propagating in a layered medium that approximates the geological strata at the LIGO sites. We characterize the noise by a transfer function $T(f) \equiv \tilde x(f)/\tilde W(f)$ from the spectrum of direction averaged ground motion $\tilde W(f)$ to the spectrum of test mass motion $\tilde x(f) = L\tilde h(f)$ (where $L$ is the length of the interferometer's arms, and $\tilde h(f)$ is the spectrum of gravitational-wave noise). This paper's primary foci are (i) a study of how $T(f)$ depends on the various seismic modes; (ii) an attempt to estimate which modes are excited at the LIGO sites at quiet and noisy times; and (iii) a corresponding estimate of the seismic gravity-gradient noise level. At quiet times the noise is below the benchmark noise level of ``advanced LIGO interferometers'' (although not by much near 10 Hz); it may significantly exceed this level at noisy times. The lower edge of our quiet-time noise is a limit beyond which there is little gain from further improvements in vibration isolation and thermal noise, unless one also reduces seismic gravity-gradient noise. Two methods of reduction are discussed: monitoring the earth's density perturbations, computing their gravitational forces, and correcting the data for those forces; and constructing narrow moats around the interferometers' test masses to shield out the fundamental-mode Rayleigh waves, which we suspect dominate at quiet times. |
2106.05829 | Sebastian Szybka | Krzysztof G{\l}\'od, Szymon Sikora, Sebastian J. Szybka | Example of cross-polarized standing gravitational waves | 19 pages, 6 figures; improved version | Phys. Rev. D 106, 124022 (2022) | 10.1103/PhysRevD.106.124022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a cosmological counterpart of the cylindrical Halilsoy solution to
illustrate properties of cross-polarized standing gravitational waves.
| [
{
"created": "Thu, 10 Jun 2021 15:48:19 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Dec 2022 20:48:50 GMT",
"version": "v2"
}
] | 2022-12-23 | [
[
"Głód",
"Krzysztof",
""
],
[
"Sikora",
"Szymon",
""
],
[
"Szybka",
"Sebastian J.",
""
]
] | We use a cosmological counterpart of the cylindrical Halilsoy solution to illustrate properties of cross-polarized standing gravitational waves. |
gr-qc/9809023 | Peter H\"ubner | Othmar Brodbeck, Simonetta Frittelli, Peter Huebner, Oscar A. Reula | Einstein's Equations with Asymptotically Stable Constraint Propagation | 23 pages, submitted to JMP, added reference for section 2 | J.Math.Phys. 40 (1999) 909-923 | 10.1063/1.532694 | AEI preprint 091 | gr-qc | null | We introduce a proposal to modify Einstein's equations by embedding them in a
larger symmetric hyperbolic system. The additional dynamical variables of the
modified system are essentially first integrals of the original constraints.
The extended system of equations reproduces the usual dynamics on the
constraint surface of general relativity, and therefore naturally includes the
solutions to Einstein gravity. The main feature of this extended system is
that, at least for a linearized version of it, the constraint surface is an
attractor of the time evolution. This feature suggests that this system may be
a useful alternative to Einstein's equations when obtaining numerical solutions
to full, non-linear gravity.
| [
{
"created": "Fri, 4 Sep 1998 12:33:53 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 1998 09:45:39 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Brodbeck",
"Othmar",
""
],
[
"Frittelli",
"Simonetta",
""
],
[
"Huebner",
"Peter",
""
],
[
"Reula",
"Oscar A.",
""
]
] | We introduce a proposal to modify Einstein's equations by embedding them in a larger symmetric hyperbolic system. The additional dynamical variables of the modified system are essentially first integrals of the original constraints. The extended system of equations reproduces the usual dynamics on the constraint surface of general relativity, and therefore naturally includes the solutions to Einstein gravity. The main feature of this extended system is that, at least for a linearized version of it, the constraint surface is an attractor of the time evolution. This feature suggests that this system may be a useful alternative to Einstein's equations when obtaining numerical solutions to full, non-linear gravity. |
1405.3915 | T. P. Singh | Anushrut Sharma and Tejinder P. Singh | How the quantum emerges from gravity | 6 pages. Honorable mention in the Gravity Research Foundation 2014
Essay Contest. Based on the more detailed paper arXiv:1403.2231 | Int. J. Mod. Phys. 23, 1442007 (2014) | 10.1142/S0218271814420073 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of a massive, relativistic spinning particle could be described
either by the Dirac equation or by the Kerr solution of Einstein equations.
However, one does not know a priori as to which of the two systems of equations
should be used in a given situation, and the choice is dictated by experiments.
It is expected that the Dirac equation holds for microscopic masses, and the
Kerr solution for macroscopic masses. This suggests that Einstein gravity and
the Dirac theory are limiting cases of a common underlying theoretical
framework. Here we propose that such a framework is provided by a geometric
theory of gravity on a Riemann-Cartan spacetime, which includes torsion. The
Dirac equation emerges as the torsion dominated, gravity-free limit of this
framework.
| [
{
"created": "Thu, 15 May 2014 17:08:56 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Sharma",
"Anushrut",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | The dynamics of a massive, relativistic spinning particle could be described either by the Dirac equation or by the Kerr solution of Einstein equations. However, one does not know a priori as to which of the two systems of equations should be used in a given situation, and the choice is dictated by experiments. It is expected that the Dirac equation holds for microscopic masses, and the Kerr solution for macroscopic masses. This suggests that Einstein gravity and the Dirac theory are limiting cases of a common underlying theoretical framework. Here we propose that such a framework is provided by a geometric theory of gravity on a Riemann-Cartan spacetime, which includes torsion. The Dirac equation emerges as the torsion dominated, gravity-free limit of this framework. |
1903.10411 | Alessia Platania | Alessia Platania | Dynamical renormalization of black-hole spacetimes | 7 pages, 1 figure | null | 10.1140/epjc/s10052-019-6990-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a black-hole spacetime which includes the running of the
gravitational coupling in a self-consistent way. Starting from a classical
Schwarzschild black hole, the backreaction effects produced by the running
Newton's coupling are taken into account iteratively. The sequence, described
by a simple recurrence relation, flows towards a self-consistent solution that
can be derived analytically. As a key result, if the gravitational
renormalization group flow attains a non-trivial fixed point at high energies,
the sequence converges to a "renormalized" black-hole spacetime of the
Dymnikova-type, which is free of singularities.
| [
{
"created": "Mon, 25 Mar 2019 15:50:33 GMT",
"version": "v1"
}
] | 2019-06-26 | [
[
"Platania",
"Alessia",
""
]
] | We construct a black-hole spacetime which includes the running of the gravitational coupling in a self-consistent way. Starting from a classical Schwarzschild black hole, the backreaction effects produced by the running Newton's coupling are taken into account iteratively. The sequence, described by a simple recurrence relation, flows towards a self-consistent solution that can be derived analytically. As a key result, if the gravitational renormalization group flow attains a non-trivial fixed point at high energies, the sequence converges to a "renormalized" black-hole spacetime of the Dymnikova-type, which is free of singularities. |
2407.11185 | Emilio Rub\'in de Celis | Cecilia Tomasini, Claudio Simeone and Emilio Rub\'in de Celis | Tides and traversability in gravastars and other related geometries | 14 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tidal effects related to the traversability across thin shells are examined
in spherically symmetric geometries. We focus mainly on shells separating inner
from outer regions of gravastars (de Sitter -- i.e., $\Lambda>0$ -- interior
and Schwarzschild exterior of mass parameter $M$), but we also examine other
related geometries by including the possibility of a negative cosmological
constant and, besides, non trivial topologies where the shell separates two
outer regions. The analysis is developed for radially traversing objects and
for tides in both radial and transverse directions, which present difficulties
of somewhat different nature. Transverse tides are unavoidable across shells
which satisfy the flare-out condition, while shells in trivial topologies, i.e.
geometries with one asymptotic region, are more indulgent with the issue of
insurmountable tides. Besides, contradicting other cases analyzed in previous
works, we find that large radial tides cannot be avoided when traveling across
the shell in the gravastar solution, but in non-trivial topologies they can. We
study with special attention the traversability in practice of the transition
layer in the thin-shell gravastar solution. In particular, a finite object
which traverses radially the shell in a gravastar with $\sqrt{\Lambda}\ll 1/M$
undergoes a compression effect in both the transverse and the radial directions
due to the tides associated to the thin layer. The results are interpreted in
terms of the total momentum transfer obtained by integrating the travel time of
the object.
| [
{
"created": "Mon, 15 Jul 2024 19:16:28 GMT",
"version": "v1"
}
] | 2024-07-17 | [
[
"Tomasini",
"Cecilia",
""
],
[
"Simeone",
"Claudio",
""
],
[
"de Celis",
"Emilio Rubín",
""
]
] | Tidal effects related to the traversability across thin shells are examined in spherically symmetric geometries. We focus mainly on shells separating inner from outer regions of gravastars (de Sitter -- i.e., $\Lambda>0$ -- interior and Schwarzschild exterior of mass parameter $M$), but we also examine other related geometries by including the possibility of a negative cosmological constant and, besides, non trivial topologies where the shell separates two outer regions. The analysis is developed for radially traversing objects and for tides in both radial and transverse directions, which present difficulties of somewhat different nature. Transverse tides are unavoidable across shells which satisfy the flare-out condition, while shells in trivial topologies, i.e. geometries with one asymptotic region, are more indulgent with the issue of insurmountable tides. Besides, contradicting other cases analyzed in previous works, we find that large radial tides cannot be avoided when traveling across the shell in the gravastar solution, but in non-trivial topologies they can. We study with special attention the traversability in practice of the transition layer in the thin-shell gravastar solution. In particular, a finite object which traverses radially the shell in a gravastar with $\sqrt{\Lambda}\ll 1/M$ undergoes a compression effect in both the transverse and the radial directions due to the tides associated to the thin layer. The results are interpreted in terms of the total momentum transfer obtained by integrating the travel time of the object. |
gr-qc/9412009 | Jacques Legare | J. Legare and J.W. Moffat | Field Equations and Conservation Laws in the Nonsymmetric Gravitational
Theory | 16 pages, RevTeX. Additional equations supplied | null | 10.1007/BF02105322 | UTPT-94-36 | gr-qc | null | The field equations in the nonsymmetric gravitational theory are derived from
a Lagrangian density using a first-order formalism. Using the general
covariance of the Lagrangian density, conservation laws and tensor identities
are derived. Among these are the generalized Bianchi identities and the law of
energy-momentum conservation. The Lagrangian density is expanded to
second-order, and treated as an ``Einstein plus fields'' theory. From this, it
is deduced that the energy is positive in the radiation zone.
| [
{
"created": "Fri, 2 Dec 1994 14:40:58 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Dec 1994 21:20:56 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Legare",
"J.",
""
],
[
"Moffat",
"J. W.",
""
]
] | The field equations in the nonsymmetric gravitational theory are derived from a Lagrangian density using a first-order formalism. Using the general covariance of the Lagrangian density, conservation laws and tensor identities are derived. Among these are the generalized Bianchi identities and the law of energy-momentum conservation. The Lagrangian density is expanded to second-order, and treated as an ``Einstein plus fields'' theory. From this, it is deduced that the energy is positive in the radiation zone. |
1207.0230 | Douglas A. Singleton | Sujoy Kumar Modak and Douglas Singleton | Inflation with a graceful exit and entrance driven by Hawking radiation | 19 pages, 2 figures revtex, matches PRD published version | Phys.Rev. D86 (2012) 123515 | 10.1103/PhysRevD.86.123515 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a model for cosmological inflation which has a natural "turn on"
and a natural "turn off" mechanism. In our model inflation is driven by the
Hawking-like radiation that occurs in Friedman-Robertson-Walker (FRW)
space-time. This Hawking-like radiation results in an effective negative
pressure "fluid" which leads to a rapid period of expansion in the very early
Universe. As the Universe expands the FRW Hawking temperature decreases and the
inflationary expansion turns off and makes a natural transition to the power
law expansion of a radiation dominated universe. The "turn on" mechanism is
more speculative, but is based on the common hypothesis that in a quantum
theory of gravity at very high temperatures/high densities Hawking radiation
will stop. Applying this speculation to the very early Universe implies that
the Hawking-like radiation of the FRW space-time will be turned off and
therefore the inflation driven by this radiation will turn off.
| [
{
"created": "Sun, 1 Jul 2012 17:26:55 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2012 20:23:09 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Modak",
"Sujoy Kumar",
""
],
[
"Singleton",
"Douglas",
""
]
] | We present a model for cosmological inflation which has a natural "turn on" and a natural "turn off" mechanism. In our model inflation is driven by the Hawking-like radiation that occurs in Friedman-Robertson-Walker (FRW) space-time. This Hawking-like radiation results in an effective negative pressure "fluid" which leads to a rapid period of expansion in the very early Universe. As the Universe expands the FRW Hawking temperature decreases and the inflationary expansion turns off and makes a natural transition to the power law expansion of a radiation dominated universe. The "turn on" mechanism is more speculative, but is based on the common hypothesis that in a quantum theory of gravity at very high temperatures/high densities Hawking radiation will stop. Applying this speculation to the very early Universe implies that the Hawking-like radiation of the FRW space-time will be turned off and therefore the inflation driven by this radiation will turn off. |
gr-qc/9905051 | Hans-Juergen Schmidt | Hans - Juergen Schmidt | The classical solutions of two-dimensional gravity | 11 pages, LaTeX, no figures, Gen.Rel.Grav. in print | Gen.Rel.Grav.31:1187-1210,1999 | 10.1023/A:1026708320831 | Preprint UNIPO-MATH-98-June-8 | gr-qc | null | The solutions of two-dimensional gravity following from a non-linear
Lagrangian L = f(R) are classified, and their symmetry and singularity
properties are described. Then a conformal transformation is applied to rewrite
these solutions as analogous solutions of two-dimensional Einstein-dilaton
gravity and vice versa.
| [
{
"created": "Sat, 15 May 1999 08:12:59 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Schmidt",
"Hans - Juergen",
""
]
] | The solutions of two-dimensional gravity following from a non-linear Lagrangian L = f(R) are classified, and their symmetry and singularity properties are described. Then a conformal transformation is applied to rewrite these solutions as analogous solutions of two-dimensional Einstein-dilaton gravity and vice versa. |
1911.01846 | Sergey S. Kokarev | Sergey S. Kokarev | Dynamic general covariance of physical systems | The matter of a talk, prepared for 3-d Russian conference
"Foundations of fundamental physics and mathematics" (29-30.11.2019) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One unusual property of dynamic systems, whose state is characterized by a
set of scalar dynamic variables satisfying a system of differential equations
of a general form, is considered. This property is related to the behavior of
equations (optionally covariant) with respect to coordinate diffeomorphisms:
the equations, in a sense, retain their form on their solutions. More
precisely, non-covariant addends to the equations of such systems always
exactly reduced in any order of perturbation theory by solutions of unperturbed
(initial) equations. This property demonstrated by a set of simple illustrative
examples. Various aspects of the dynamic covariance are discussed.
| [
{
"created": "Sat, 2 Nov 2019 18:56:22 GMT",
"version": "v1"
}
] | 2019-11-06 | [
[
"Kokarev",
"Sergey S.",
""
]
] | One unusual property of dynamic systems, whose state is characterized by a set of scalar dynamic variables satisfying a system of differential equations of a general form, is considered. This property is related to the behavior of equations (optionally covariant) with respect to coordinate diffeomorphisms: the equations, in a sense, retain their form on their solutions. More precisely, non-covariant addends to the equations of such systems always exactly reduced in any order of perturbation theory by solutions of unperturbed (initial) equations. This property demonstrated by a set of simple illustrative examples. Various aspects of the dynamic covariance are discussed. |
2403.02089 | Guangzhou Guo | Guangzhou Guo, Peng Wang, and Yupeng Zhang | Nonlinear Stability of Black Holes with a Stable Light Ring | v1: 26 pages, 6 figures; v2: references added | null | null | CTP-SCU/2024002 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, ultracompact objects have been found to be susceptible to a new
nonlinear instability, known as the light-ring instability, triggered by stable
light rings. This discovery raises concerns about the viability of these
objects as alternatives to black holes. In this work, we investigate the
presence of the light-ring instability in scalarized Reissner-Nordstr\"om black
holes, which have been previously shown to admit stable light rings. We employ
fully nonlinear numerical evolutions of both scalarized black holes with and
without stable light rings, perturbing them initially with spherically
symmetric scalar perturbations. Our simulations demonstrate the long-term
stability of these scalarized black holes, suggesting that the presence of a
stable light ring may not necessarily induce the light-ring instability.
| [
{
"created": "Mon, 4 Mar 2024 14:45:55 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Mar 2024 08:36:24 GMT",
"version": "v2"
}
] | 2024-03-12 | [
[
"Guo",
"Guangzhou",
""
],
[
"Wang",
"Peng",
""
],
[
"Zhang",
"Yupeng",
""
]
] | Recently, ultracompact objects have been found to be susceptible to a new nonlinear instability, known as the light-ring instability, triggered by stable light rings. This discovery raises concerns about the viability of these objects as alternatives to black holes. In this work, we investigate the presence of the light-ring instability in scalarized Reissner-Nordstr\"om black holes, which have been previously shown to admit stable light rings. We employ fully nonlinear numerical evolutions of both scalarized black holes with and without stable light rings, perturbing them initially with spherically symmetric scalar perturbations. Our simulations demonstrate the long-term stability of these scalarized black holes, suggesting that the presence of a stable light ring may not necessarily induce the light-ring instability. |
1801.03044 | Ben Kain | Ben Kain | Stability and Critical Behavior of Gravitational Monopoles | 16 pages, 10 figures | Phys. Rev. D 97, 024012 (2018) | 10.1103/PhysRevD.97.024012 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I dynamically evolve spherically symmetric spacetimes containing
gravitational 't Hooft-Polyakov monopoles and determine the stable end states
of the evolutions. I do so to study stability and critical behavior of the
well-known static gravitational monopole solutions. For the static solutions,
there exist regions of parameter space where two static monopole black holes
and the static Reissner-Nordstrom black hole have the same mass. I find strong
evidence that one of the static monopole black hole solutions is a critical
solution, to which near-critical solutions are dynamically attracted before
evolving to one of the other two static solutions as end states. I also discuss
the no-hair conjecture for this model in the context of collapse.
| [
{
"created": "Tue, 9 Jan 2018 17:22:34 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Kain",
"Ben",
""
]
] | I dynamically evolve spherically symmetric spacetimes containing gravitational 't Hooft-Polyakov monopoles and determine the stable end states of the evolutions. I do so to study stability and critical behavior of the well-known static gravitational monopole solutions. For the static solutions, there exist regions of parameter space where two static monopole black holes and the static Reissner-Nordstrom black hole have the same mass. I find strong evidence that one of the static monopole black hole solutions is a critical solution, to which near-critical solutions are dynamically attracted before evolving to one of the other two static solutions as end states. I also discuss the no-hair conjecture for this model in the context of collapse. |
1905.00045 | Tommi Markkanen | Jos\'e Eliel Camargo-Molina, Tommi Markkanen and Pat Scott | Dark energy without fine tuning | v2: 13 pages, minor improvements, version accepted in JHEP | JHEP 1901 (2019) 044 | 10.1007/JHEP10(2019)044 | IMPERIAL/TP/2019/TM/04 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a two-field model that realises inflation and the observed density
of dark energy today, whilst solving the fine-tuning problems inherent in
quintessence models. One field acts as the inflaton, generically driving the
other to a saddle-point of the potential, from which it acts as a quintessence
field following electroweak symmetry breaking. The model exhibits essentially
no sensitivity to the initial value of the quintessence field, naturally
suppresses its interactions with other fields, and automatically endows it with
a small effective mass in the late Universe. The magnitude of dark energy today
is fixed by the height of the saddle point in the potential, which is dictated
entirely by the scale of electroweak symmetry breaking.
| [
{
"created": "Tue, 30 Apr 2019 18:06:40 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Sep 2019 18:09:52 GMT",
"version": "v2"
}
] | 2019-10-14 | [
[
"Camargo-Molina",
"José Eliel",
""
],
[
"Markkanen",
"Tommi",
""
],
[
"Scott",
"Pat",
""
]
] | We present a two-field model that realises inflation and the observed density of dark energy today, whilst solving the fine-tuning problems inherent in quintessence models. One field acts as the inflaton, generically driving the other to a saddle-point of the potential, from which it acts as a quintessence field following electroweak symmetry breaking. The model exhibits essentially no sensitivity to the initial value of the quintessence field, naturally suppresses its interactions with other fields, and automatically endows it with a small effective mass in the late Universe. The magnitude of dark energy today is fixed by the height of the saddle point in the potential, which is dictated entirely by the scale of electroweak symmetry breaking. |
1309.0067 | Md. Rahman Atiqur | M. Ilias Hossain, M. Atiqur Rahman | Hawking radiation of Reissner-Nordstrom-de Sitter black hole by
Hamilton-Jacobi method | 10 pages | null | 10.1007/s10509-013-1505-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Refs. (M. Atiqur Rahman, M. Ilias Hossain (2012) Phys. Lett. B {\bf 712}
1), we have developed Hamilton-Jacobi method for dynamical spacetime and
discussed Hawking radiation of Schwarzschild-de Sitter black hole by massive
particle tunneling method. In this letter, we have investigated the hawking
purely thermal and nonthermal radiations of Reissner-Nordstr\"{o}m-de Sitter
(RNdS) black hole. We have considered energy and angular momentum as conserved
and shown that the tunneling rate is related to the change of
Bekenstein-Hawking entropy and the derived emission spectrum deviates from the
pure thermal spectrum. The results we have obtained for RNdS black hole is also
in accordance with Parikh and Wilczek\rq s opinion and recovered the new result
for Hawking radiation of RNdS black hole.
| [
{
"created": "Sat, 31 Aug 2013 05:37:10 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Hossain",
"M. Ilias",
""
],
[
"Rahman",
"M. Atiqur",
""
]
] | In Refs. (M. Atiqur Rahman, M. Ilias Hossain (2012) Phys. Lett. B {\bf 712} 1), we have developed Hamilton-Jacobi method for dynamical spacetime and discussed Hawking radiation of Schwarzschild-de Sitter black hole by massive particle tunneling method. In this letter, we have investigated the hawking purely thermal and nonthermal radiations of Reissner-Nordstr\"{o}m-de Sitter (RNdS) black hole. We have considered energy and angular momentum as conserved and shown that the tunneling rate is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum. The results we have obtained for RNdS black hole is also in accordance with Parikh and Wilczek\rq s opinion and recovered the new result for Hawking radiation of RNdS black hole. |
gr-qc/0309009 | Rafael Sorkin | Rafael D. Sorkin | Causal Sets: Discrete Gravity (Notes for the Valdivia Summer School) | plainTeX, 27 pages, no figures To appear in the proceedings of the
Valdivia Summer School, edited by A. Gomberoff and D. Marolf | null | null | SU-GP-2003/1-2 | gr-qc astro-ph hep-th | null | These are lecture notes on causal set theory prepared in Jan. 2002 for a
Summer School in Valdivia, Chile. In some places, they are more complete, in
others much less so, regrettably. An extensive set of references and a glossary
of terms can be found at the end of the notes.
| [
{
"created": "Mon, 1 Sep 2003 23:44:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sorkin",
"Rafael D.",
""
]
] | These are lecture notes on causal set theory prepared in Jan. 2002 for a Summer School in Valdivia, Chile. In some places, they are more complete, in others much less so, regrettably. An extensive set of references and a glossary of terms can be found at the end of the notes. |
2206.11932 | Ethan Payne | Ethan Payne, Sophie Hourihane, Jacob Golomb, Rhiannon Udall, Derek
Davis, Katerina Chatziioannou | The curious case of GW200129: interplay between spin-precession
inference and data-quality issues | 17 pages, 14 figures, 2 tables. Data release:
https://zenodo.org/record/7259655 | Phys. Rev. D 106, 104017 (2022) | 10.1103/PhysRevD.106.104017 | LIGO DCC: P2200185 | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Measurement of spin-precession in black hole binary mergers observed with
gravitational waves is an exciting milestone as it relates to both general
relativistic dynamics and astrophysical binary formation scenarios. In this
study, we revisit the evidence for spin-precession in GW200129 and localize its
origin to data in LIGO Livingston in the 20--50\,Hz frequency range where the
signal amplitude is lower than expected from a non-precessing binary given all
the other data. These data are subject to known data quality issues as a glitch
was subtracted from the detector's strain data. The lack of evidence for
spin-precession in LIGO Hanford leads to a noticeable inconsistency between the
inferred binary mass ratio and precessing spin in the two LIGO detectors,
something not expected from solely different Gaussian noise realizations. We
revisit the LIGO Livingston glitch mitigation and show that the difference
between a spin-precessing and a non-precessing interpretation for GW200129 is
smaller than the statistical and systematic uncertainty of the glitch
subtraction, finding that the support for spin-precession depends sensitively
on the glitch modeling. We also investigate the signal-to-noise ratio $\sim7$
trigger in the less sensitive Virgo detector. Though not influencing the
spin-precession studies, the Virgo trigger is grossly inconsistent with the
ones in LIGO Hanford and LIGO Livingston as it points to a much heavier system.
We interpret the Virgo data in the context of further data quality issues.
While our results do not disprove the presence of spin-precession in GW200129,
we argue that any such inference is contingent upon the statistical and
systematic uncertainty of the glitch mitigation. Our study highlights the role
of data quality investigations when inferring subtle effects such as
spin-precession for short signals such as the ones produced by high-mass
systems.
| [
{
"created": "Thu, 23 Jun 2022 18:27:14 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Nov 2022 21:50:29 GMT",
"version": "v2"
}
] | 2022-11-23 | [
[
"Payne",
"Ethan",
""
],
[
"Hourihane",
"Sophie",
""
],
[
"Golomb",
"Jacob",
""
],
[
"Udall",
"Rhiannon",
""
],
[
"Davis",
"Derek",
""
],
[
"Chatziioannou",
"Katerina",
""
]
] | Measurement of spin-precession in black hole binary mergers observed with gravitational waves is an exciting milestone as it relates to both general relativistic dynamics and astrophysical binary formation scenarios. In this study, we revisit the evidence for spin-precession in GW200129 and localize its origin to data in LIGO Livingston in the 20--50\,Hz frequency range where the signal amplitude is lower than expected from a non-precessing binary given all the other data. These data are subject to known data quality issues as a glitch was subtracted from the detector's strain data. The lack of evidence for spin-precession in LIGO Hanford leads to a noticeable inconsistency between the inferred binary mass ratio and precessing spin in the two LIGO detectors, something not expected from solely different Gaussian noise realizations. We revisit the LIGO Livingston glitch mitigation and show that the difference between a spin-precessing and a non-precessing interpretation for GW200129 is smaller than the statistical and systematic uncertainty of the glitch subtraction, finding that the support for spin-precession depends sensitively on the glitch modeling. We also investigate the signal-to-noise ratio $\sim7$ trigger in the less sensitive Virgo detector. Though not influencing the spin-precession studies, the Virgo trigger is grossly inconsistent with the ones in LIGO Hanford and LIGO Livingston as it points to a much heavier system. We interpret the Virgo data in the context of further data quality issues. While our results do not disprove the presence of spin-precession in GW200129, we argue that any such inference is contingent upon the statistical and systematic uncertainty of the glitch mitigation. Our study highlights the role of data quality investigations when inferring subtle effects such as spin-precession for short signals such as the ones produced by high-mass systems. |
gr-qc/0612159 | A. Yu. Ignatiev | A. Yu. Ignatiev | Is violation of Newton's second law possible? | 10 pages; minor changes to match the published version | Phys.Rev.Lett.98:101101,2007 | 10.1103/PhysRevLett.98.101101 | null | gr-qc astro-ph | null | Astrophysical observations (usually explained by dark matter) suggest that
classical mechanics could break down when the acceleration becomes extremely
small (the approach known as modified Newtonian dynamics, or MOND). I present
the first analysis of MOND manifestations in terrestrial (rather than
astrophysical) settings. A new effect is reported: around each equinox date, 2
spots emerge on the Earth where static bodies experience spontaneous
acceleration due to the possible violation of Newton's second law. Preliminary
estimates indicate that an experimental search for this effect can be feasible.
| [
{
"created": "Mon, 25 Dec 2006 07:02:09 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Mar 2007 11:49:29 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ignatiev",
"A. Yu.",
""
]
] | Astrophysical observations (usually explained by dark matter) suggest that classical mechanics could break down when the acceleration becomes extremely small (the approach known as modified Newtonian dynamics, or MOND). I present the first analysis of MOND manifestations in terrestrial (rather than astrophysical) settings. A new effect is reported: around each equinox date, 2 spots emerge on the Earth where static bodies experience spontaneous acceleration due to the possible violation of Newton's second law. Preliminary estimates indicate that an experimental search for this effect can be feasible. |
gr-qc/0606005 | Kayll Lake | Kayll Lake | Static Ricci-flat 5-manifolds admitting the 2-sphere | Generalize, in a straightforward way, to higher dimensions | Class.Quant.Grav. 23 (2006) 5871-5881 | 10.1088/0264-9381/23/20/009 | null | gr-qc hep-th | null | We examine, in a purely geometrical way, static Ricci-flat 5-manifolds
admitting the 2-sphere and an additional hypersurface-orthogonal Killing
vector. These are widely studied in the literature, from different physical
approaches, and known variously as the Kramer - Gross - Perry - Davidson - Owen
solutions. The 2-fold infinity of cases that result are studied by way of new
coordinates (which are in most cases global) and the cases likely to be of
interest in any physical approach are distinguished on the basis of the
nakedness and geometrical mass of their associated singularities. It is argued
that the entire class of solutions has to be considered unstable about the
exceptional solutions: the black string and soliton cases. Any physical theory
which admits the non-exceptional solutions as the external vacuua of a
collapsing object has to accept the possibility of collapse to zero volume
leaving behind the weakest possible, albeit naked, geometrical singularities at
the origin.Finally, it is pointed out that these types of solutions generalize,
in a straightforward way, to higher dimensions.
| [
{
"created": "Thu, 1 Jun 2006 18:10:15 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2006 19:05:48 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Lake",
"Kayll",
""
]
] | We examine, in a purely geometrical way, static Ricci-flat 5-manifolds admitting the 2-sphere and an additional hypersurface-orthogonal Killing vector. These are widely studied in the literature, from different physical approaches, and known variously as the Kramer - Gross - Perry - Davidson - Owen solutions. The 2-fold infinity of cases that result are studied by way of new coordinates (which are in most cases global) and the cases likely to be of interest in any physical approach are distinguished on the basis of the nakedness and geometrical mass of their associated singularities. It is argued that the entire class of solutions has to be considered unstable about the exceptional solutions: the black string and soliton cases. Any physical theory which admits the non-exceptional solutions as the external vacuua of a collapsing object has to accept the possibility of collapse to zero volume leaving behind the weakest possible, albeit naked, geometrical singularities at the origin.Finally, it is pointed out that these types of solutions generalize, in a straightforward way, to higher dimensions. |
2210.11853 | Benjamin Koch | Pedro D. Alvarez, Benjamin Koch, Cristobal Laporte, and Angel Rincon | Cosmological constraints on scale-dependent cosmology | 18 pages, 12 figures, accepted for publication in Physics of the Dark
Universe | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper examines a cosmological model of scale-dependent gravity. The
gravitational action is taken to be the Einstein-Hilbert term supplemented with
a cosmological constant, where the couplings, $G_k$ and $\Lambda_k$, run with
the energy scale $k$. % Also, notice that, by construction, our formalism
recovers general relativity when in the limit of constant Newton's coupling. %
Two sub-models based on the scale-dependent cosmological model are confronted
with recent observational data from:
i) the Hubble parameter $H(z)$,
ii) distance modulus $\mu(z)$, and iii) baryon acoustic scale evolution as
functions of redshift (BAO). % The viability of the model is discussed,
obtaining the best-fit parameters and the maximum likelihood contours for these
observables. Finally, a joint analysis is performed for $H(z)$+$\mu(z)$+BAO.
| [
{
"created": "Fri, 21 Oct 2022 10:20:37 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 2024 08:53:26 GMT",
"version": "v2"
}
] | 2024-05-29 | [
[
"Alvarez",
"Pedro D.",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Laporte",
"Cristobal",
""
],
[
"Rincon",
"Angel",
""
]
] | This paper examines a cosmological model of scale-dependent gravity. The gravitational action is taken to be the Einstein-Hilbert term supplemented with a cosmological constant, where the couplings, $G_k$ and $\Lambda_k$, run with the energy scale $k$. % Also, notice that, by construction, our formalism recovers general relativity when in the limit of constant Newton's coupling. % Two sub-models based on the scale-dependent cosmological model are confronted with recent observational data from: i) the Hubble parameter $H(z)$, ii) distance modulus $\mu(z)$, and iii) baryon acoustic scale evolution as functions of redshift (BAO). % The viability of the model is discussed, obtaining the best-fit parameters and the maximum likelihood contours for these observables. Finally, a joint analysis is performed for $H(z)$+$\mu(z)$+BAO. |
2009.05663 | Stanislav Komarov | Stanislav Komarov and Alexander Gorbatsievich | Reconstruction of a star motion in the vicinity of a Schwarzschild black
hole by redshift of the spectrum | 24 pages, 10 figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the time evolution of the redshift of the spectrum of
electromagnetic radiation that is emitted by the star that moves in the
vicinity of supermassive black hole. For the case of Schwarzschild black hole
we solve this problem exactly in General Theory of Relativity. Also we
formulate an approach that gives possibilities to solve the inverse problem:
reconstruction of motion of a star in the vicinity of black hole using the
redshift data. This approach consists of two steps. The first step gives
possibilities to find unique solution for the integrals of motion of the star
by solution of a system of non-linear equations, rather than the direct
application of standard statistical methods. For this purpose we consider
properties of congruences of isotropic geodesics that connect of the worldline
of the source and the worldline of the observer. The second step is the
application of standard least squares method in order to obtain more accurate
solution. This approach is used on the numerical model of the star in the
vicinity of the Center of our Galaxy.
| [
{
"created": "Fri, 11 Sep 2020 21:24:16 GMT",
"version": "v1"
}
] | 2020-09-15 | [
[
"Komarov",
"Stanislav",
""
],
[
"Gorbatsievich",
"Alexander",
""
]
] | We investigate the time evolution of the redshift of the spectrum of electromagnetic radiation that is emitted by the star that moves in the vicinity of supermassive black hole. For the case of Schwarzschild black hole we solve this problem exactly in General Theory of Relativity. Also we formulate an approach that gives possibilities to solve the inverse problem: reconstruction of motion of a star in the vicinity of black hole using the redshift data. This approach consists of two steps. The first step gives possibilities to find unique solution for the integrals of motion of the star by solution of a system of non-linear equations, rather than the direct application of standard statistical methods. For this purpose we consider properties of congruences of isotropic geodesics that connect of the worldline of the source and the worldline of the observer. The second step is the application of standard least squares method in order to obtain more accurate solution. This approach is used on the numerical model of the star in the vicinity of the Center of our Galaxy. |
1806.08087 | Bahram Mashhoon | Bahram Mashhoon | General Relativistic Gravity Gradiometry | 18 pages, invited contribution to appear in "Relativistic Geodesy:
Foundations and Applications", D. Puetzfeld et al. (eds.), 2018; v2: matches
version published in: D. Puetzfeld and C. L\"ammerzahl (eds.) "Relativistic
Geodesy" (Springer, Cham, 2019), pp. 143-157 | Fundamental Theories of Physics 196 (2019) 143-157 | 10.1007/978-3-030-11500-5_5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity gradiometry within the framework of the general theory of relativity
involves the measurement of the elements of the relativistic tidal matrix,
which is theoretically obtained via the projection of the spacetime curvature
tensor upon the nonrotating orthonormal tetrad frame of a geodesic observer.
The behavior of the measured components of the curvature tensor under Lorentz
boosts is briefly described in connection with the existence of certain special
tidal directions. Relativistic gravity gradiometry in the exterior
gravitational field of a rotating mass is discussed and a gravitomagnetic beat
effect along an inclined spherical geodesic orbit is elucidated.
| [
{
"created": "Thu, 21 Jun 2018 07:07:40 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Feb 2019 20:41:24 GMT",
"version": "v2"
}
] | 2020-07-29 | [
[
"Mashhoon",
"Bahram",
""
]
] | Gravity gradiometry within the framework of the general theory of relativity involves the measurement of the elements of the relativistic tidal matrix, which is theoretically obtained via the projection of the spacetime curvature tensor upon the nonrotating orthonormal tetrad frame of a geodesic observer. The behavior of the measured components of the curvature tensor under Lorentz boosts is briefly described in connection with the existence of certain special tidal directions. Relativistic gravity gradiometry in the exterior gravitational field of a rotating mass is discussed and a gravitomagnetic beat effect along an inclined spherical geodesic orbit is elucidated. |
1006.4587 | Sabine Hossenfelder | Sabine Hossenfelder | Reply to arXiv:1006.2126 by Giovanni Amelino-Camelia et al | Update in reply to update of arXiv:1006.2126 | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was previously shown that models with deformations of special relativity
that have an energy-dependent yet observer-independent speed of light suffer
from nonlocal effects that are in conflict with observation to very high
precision. In a recent preprint it has been claimed that this conclusion is
false. This claim was made by writing down expressions for modified
Lorentz-transformations the use of which does not reproduce the result. I will
show here that the failure to reproduce the result is not a consequence of a
novel and improved calculation, but a consequence of repeating the same
calculation but making an assumption that is in conflict with the assumptions
made to produce the original scenario. I will here explain what the physical
meaning of either assumption is and why the original assumption is the
physically meaningful one. I will then further explain why even making the
differing assumption does not remove but merely shift the problem and why the
bound derived by Amelino-Camelia et al is wrong.
| [
{
"created": "Wed, 23 Jun 2010 16:47:47 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jul 2010 05:29:24 GMT",
"version": "v2"
}
] | 2010-07-08 | [
[
"Hossenfelder",
"Sabine",
""
]
] | It was previously shown that models with deformations of special relativity that have an energy-dependent yet observer-independent speed of light suffer from nonlocal effects that are in conflict with observation to very high precision. In a recent preprint it has been claimed that this conclusion is false. This claim was made by writing down expressions for modified Lorentz-transformations the use of which does not reproduce the result. I will show here that the failure to reproduce the result is not a consequence of a novel and improved calculation, but a consequence of repeating the same calculation but making an assumption that is in conflict with the assumptions made to produce the original scenario. I will here explain what the physical meaning of either assumption is and why the original assumption is the physically meaningful one. I will then further explain why even making the differing assumption does not remove but merely shift the problem and why the bound derived by Amelino-Camelia et al is wrong. |
gr-qc/0005069 | Alicia M. Sintes | J. Carot, A.M. Sintes | Self-similar static solutions admitting a two-space of constant
curvature | 6 pages | Class.Quant.Grav.11:L125-L128,1994 | 10.1088/0264-9381/11/11/001 | null | gr-qc | null | A recent result by Haggag and Hajj-Boutros is reviewed within the framework
of self-similar space-times, extending, in some sense, their results and
presenting a family of metrics consisting of all the static spherically
symmetric perfect fluid solutions admitting a homothety.
| [
{
"created": "Tue, 16 May 2000 15:41:41 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Carot",
"J.",
""
],
[
"Sintes",
"A. M.",
""
]
] | A recent result by Haggag and Hajj-Boutros is reviewed within the framework of self-similar space-times, extending, in some sense, their results and presenting a family of metrics consisting of all the static spherically symmetric perfect fluid solutions admitting a homothety. |
2404.13643 | Pramit Rej | Pramit Rej and Akashdip Karmakar | Well behaved class of Heintzmann's solution within $f(R,\,T)$ framework | 19 Pages. 10 Figures, 4 tables (Accepted for publication in The
European Physical Journal Plus on 23.07.2024) | The European Physical Journal Plus 139 (8), 686 (2024) | 10.1140/epjp/s13360-024-05487-3 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The primary objective of this paper is to develop a well-behaved class of
Heintzmann IIa [{\em H. Heintzmann, Z. Physik 228, 489-493 (1969)}] solution in
the context of $f(R,\, T)$ gravity. In the $f(R, T)$ framework, the
gravitational action includes both the Ricci scalar ($R$) and the trace of the
energy-momentum tensor ($T$). We chose a particular $f(R,\,T)$ model s.t.
$f(R,\,T) = R+2 \chi T$, where $\chi$ is known as the coupling parameter. This
solution describes a novel isotropic compact fluid sphere with positively
finite central pressure and density in this extended theory of gravity. The
results obtained analytically are better described by graphical representations
of the physical parameters for various values of the coupling parameter $\chi$.
The solution for a specific compact object, Vela X-1, with radius $\mathfrak{R}
= 9.56_{-0.08}^{+0.08}$ km and mass $\mathcal{M} = 1.77 \pm
0.08~\mathcal{M}_{\odot}$ [{\em M. L. Rawls et al. ApJ, 730, 25 (2011)}], is
shown here. We analyze the fundamental physical attributes of the star, which
reveals the influence of the coupling parameter $\chi$ on the values of
substance parameters. This helps us to make a fruitful comparison of this
modified $f(R,\, T)$ gravity with the standard GR and notice that it holds good
for stable compact objects. In this framework, the star under our consideration
exhibits a stable structure consistent with the Heintzmann IIa {\em ansatz}.
From all of our obtained graphical and numerical results, we can ultimately
conclude that our reported model is physically admissible and satisfies all the
physical criteria for an acceptable model.
| [
{
"created": "Sun, 21 Apr 2024 12:40:18 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2024 02:53:50 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Rej",
"Pramit",
""
],
[
"Karmakar",
"Akashdip",
""
]
] | The primary objective of this paper is to develop a well-behaved class of Heintzmann IIa [{\em H. Heintzmann, Z. Physik 228, 489-493 (1969)}] solution in the context of $f(R,\, T)$ gravity. In the $f(R, T)$ framework, the gravitational action includes both the Ricci scalar ($R$) and the trace of the energy-momentum tensor ($T$). We chose a particular $f(R,\,T)$ model s.t. $f(R,\,T) = R+2 \chi T$, where $\chi$ is known as the coupling parameter. This solution describes a novel isotropic compact fluid sphere with positively finite central pressure and density in this extended theory of gravity. The results obtained analytically are better described by graphical representations of the physical parameters for various values of the coupling parameter $\chi$. The solution for a specific compact object, Vela X-1, with radius $\mathfrak{R} = 9.56_{-0.08}^{+0.08}$ km and mass $\mathcal{M} = 1.77 \pm 0.08~\mathcal{M}_{\odot}$ [{\em M. L. Rawls et al. ApJ, 730, 25 (2011)}], is shown here. We analyze the fundamental physical attributes of the star, which reveals the influence of the coupling parameter $\chi$ on the values of substance parameters. This helps us to make a fruitful comparison of this modified $f(R,\, T)$ gravity with the standard GR and notice that it holds good for stable compact objects. In this framework, the star under our consideration exhibits a stable structure consistent with the Heintzmann IIa {\em ansatz}. From all of our obtained graphical and numerical results, we can ultimately conclude that our reported model is physically admissible and satisfies all the physical criteria for an acceptable model. |
2307.11303 | Naoki Tsukamoto | Naoki Tsukamoto | Comment on "Horizon-scale tests of gravity theories and fundamental
physics from the Event Horizon Telescope image of Sagittarius A*" | 3 pages, no figure, minor changes, accepted for publication in
Classical and Quantum Gravity | Class. Quantum Grav. 40, 228001(2023) | 10.1088/1361-6382/acfb6e | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Vagnozzi et al. constrained the additional parameter of spacetimes with a
photon sphere from the observation of the shadow of Sagittarius A* under the
assumption that a distance to the Sagittarius A* and its mass parameter was
estimated from other observations. They claimed that a Damour-Solodukhin
wormhole with an additional parameter $\lambda$ is not an asymptotically-flat
spacetime and that they gave the first robust observational constraint on the
parameter $\lambda$ of the Damour-Solodukhin wormhole. However, they overlooked
the fact that: (A) the Damour-Solodukhin wormhole spacetime is asymptotically
flat, (B) the throat of the Damour-Solodukhin wormhole works as an effective
photon sphere for $\lambda>\sqrt{2}/2$, and (C) not only a usual mass parameter
but also the parameter $\lambda$ contributes the mass of the Damour-Solodukhin
wormhole. Because of the overlook (C), we realize that their constraint on the
parameter $\lambda$ is invalid. This is because their method corresponds to the
following way: They estimated the mass parameter from the other observations
under the assumption $\lambda=0$ even though the value of the parameter
$\lambda$ strongly affects the determination of the mass parameter, and then,
they used the value of the mass parameter to constrain $\lambda$ from the
observation of the shadow. We conclude that we should constrain the mass
parameter and $\lambda$ from the shadow observation and other observations
without the assumption $\lambda=0$.
| [
{
"created": "Fri, 21 Jul 2023 02:22:50 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jul 2023 06:53:47 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Sep 2023 13:23:19 GMT",
"version": "v3"
}
] | 2023-10-19 | [
[
"Tsukamoto",
"Naoki",
""
]
] | Vagnozzi et al. constrained the additional parameter of spacetimes with a photon sphere from the observation of the shadow of Sagittarius A* under the assumption that a distance to the Sagittarius A* and its mass parameter was estimated from other observations. They claimed that a Damour-Solodukhin wormhole with an additional parameter $\lambda$ is not an asymptotically-flat spacetime and that they gave the first robust observational constraint on the parameter $\lambda$ of the Damour-Solodukhin wormhole. However, they overlooked the fact that: (A) the Damour-Solodukhin wormhole spacetime is asymptotically flat, (B) the throat of the Damour-Solodukhin wormhole works as an effective photon sphere for $\lambda>\sqrt{2}/2$, and (C) not only a usual mass parameter but also the parameter $\lambda$ contributes the mass of the Damour-Solodukhin wormhole. Because of the overlook (C), we realize that their constraint on the parameter $\lambda$ is invalid. This is because their method corresponds to the following way: They estimated the mass parameter from the other observations under the assumption $\lambda=0$ even though the value of the parameter $\lambda$ strongly affects the determination of the mass parameter, and then, they used the value of the mass parameter to constrain $\lambda$ from the observation of the shadow. We conclude that we should constrain the mass parameter and $\lambda$ from the shadow observation and other observations without the assumption $\lambda=0$. |
1512.05329 | Dra\v{z}en Glavan | Dra\v{z}en Glavan, Tomislav Prokopec, Tomo Takahashi | Late-time quantum backreaction of a very light nonminimally coupled
scalar | 66 pages, 6 figures | Phys. Rev. D 94, 084053 (2016) | 10.1103/PhysRevD.94.084053 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the backreaction of the quantum fluctuations of a very light
($m \!\lesssim\! H_{\text{today}}$) nonminimally coupled spectator scalar field
on the expansion dynamics of the Universe. The one-loop expectation value of
the energy momentum tensor of these fluctuations, as a measure of the
backreaction, is computed throughout the expansion history from the early
inflationary universe until the onset of recent acceleration today. We show
that, when the nonminimal coupling $\xi$ to Ricci curvature is negative ($\xi_c
\!=\! 1/6$ corresponding to conformal coupling), the quantum backreaction grows
exponentially during inflation, such that it can grow large enough rather
quickly (within a few hundred e-foldings) to survive until late time and
constitute a contribution of the cosmological constant type of the right
magnitude to appreciably alter the expansion dynamics. The unique feature of
this model is in that, under rather generic assumptions, inflation provides
natural explanation for the initial conditions needed to explain the late-time
accelerated expansion of the Universe, making it a particularly attractive
model of dark energy.
| [
{
"created": "Wed, 16 Dec 2015 20:52:33 GMT",
"version": "v1"
}
] | 2016-11-02 | [
[
"Glavan",
"Dražen",
""
],
[
"Prokopec",
"Tomislav",
""
],
[
"Takahashi",
"Tomo",
""
]
] | We investigate the backreaction of the quantum fluctuations of a very light ($m \!\lesssim\! H_{\text{today}}$) nonminimally coupled spectator scalar field on the expansion dynamics of the Universe. The one-loop expectation value of the energy momentum tensor of these fluctuations, as a measure of the backreaction, is computed throughout the expansion history from the early inflationary universe until the onset of recent acceleration today. We show that, when the nonminimal coupling $\xi$ to Ricci curvature is negative ($\xi_c \!=\! 1/6$ corresponding to conformal coupling), the quantum backreaction grows exponentially during inflation, such that it can grow large enough rather quickly (within a few hundred e-foldings) to survive until late time and constitute a contribution of the cosmological constant type of the right magnitude to appreciably alter the expansion dynamics. The unique feature of this model is in that, under rather generic assumptions, inflation provides natural explanation for the initial conditions needed to explain the late-time accelerated expansion of the Universe, making it a particularly attractive model of dark energy. |
1206.2591 | Muhammad Sharif | M. Sharif and Wajiha Javed | Fermions Tunneling from Charged Accelerating and Rotating Black Holes
with NUT Parameter | 21 pages, no figure | Eur. Phys. J. C 72(2012)1997 | 10.1140/epjc/s10052-012-1997-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to the study of Hawking radiation as a tunneling of
charged fermions through event horizons of a pair of charged accelerating and
rotating black holes with NUT parameter. We evaluate tunneling probabilities of
outgoing charged particles by using the semiclassical WKB approximation to the
general covariant Dirac equation. The Hawking temperature corresponding to this
pair of black holes is also investigated. For the zero NUT parameter, we find
results consistent with those already available in the literature.
| [
{
"created": "Wed, 16 May 2012 02:02:18 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Sharif",
"M.",
""
],
[
"Javed",
"Wajiha",
""
]
] | This paper is devoted to the study of Hawking radiation as a tunneling of charged fermions through event horizons of a pair of charged accelerating and rotating black holes with NUT parameter. We evaluate tunneling probabilities of outgoing charged particles by using the semiclassical WKB approximation to the general covariant Dirac equation. The Hawking temperature corresponding to this pair of black holes is also investigated. For the zero NUT parameter, we find results consistent with those already available in the literature. |
1912.12465 | Antonio Enea Romano | Brayan Yamid Del Valle Mazo, Antonio Enea Romano, Maryi Alejandra
Carvajal Quintero | Combining gravitational and electromagnetic waves observations to
investigate local structure and the Hubble tension | revised version for JCAP resubmission | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent estimations of the Hubble parameter $H_0$ based on gravitational waves
(GW) observations can be used to shed some light on the discrepancy between the
value of the Hubble parameter $H_0^P$ obtained from large scale observations
such as the Planck mission, and the small scale value $H_0^R$, obtained from
low redshift supernovae (SNe).
In order to investigate the origin of this discrepancy we perform a combined
analysis of the luminosity distance of SNe and GW sources, using different
methods, finding that the impact of the GW data is very limited, due to the
small number of data points, and their large errors. We analyze separately data
from the Pantheon and the Union 2.1 catalogues, finding that a model with
$H_0^P$ and a small local void can fit the data as well as a homogeneous model
with $H_0^R$, resolving the apparent $H_0$ tension. We find that there is a
significant difference between the size and depth of the inhomogeneity obtained
using the two datasets, which could be due to the different sky coverage of the
two catalogues. For Pantheon we obtain evidence of a local inhomogeneity with a
density contrast $\delta_v=-0.155 \pm 0.026$, extending up to a redshift of
$z_v = 0.056 \pm 0.0002$, while for Union 2.1 we obtain $\delta_v=-0.461 \pm
0.032$ and $z_v= 0.081\pm 0.008$. We also perform some analysis using redshift
shell averaged data, and obtain approximately the same results, hinting to the
fact that the effects of the monopole component of the local inhomogeneity are
the dominant ones
| [
{
"created": "Sat, 28 Dec 2019 14:46:52 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Mar 2020 13:45:46 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Dec 2020 20:09:56 GMT",
"version": "v3"
},
{
"created": "Sun, 20 Jun 2021 16:20:51 GMT",
"version": "v4"
}
] | 2021-06-22 | [
[
"Mazo",
"Brayan Yamid Del Valle",
""
],
[
"Romano",
"Antonio Enea",
""
],
[
"Quintero",
"Maryi Alejandra Carvajal",
""
]
] | Recent estimations of the Hubble parameter $H_0$ based on gravitational waves (GW) observations can be used to shed some light on the discrepancy between the value of the Hubble parameter $H_0^P$ obtained from large scale observations such as the Planck mission, and the small scale value $H_0^R$, obtained from low redshift supernovae (SNe). In order to investigate the origin of this discrepancy we perform a combined analysis of the luminosity distance of SNe and GW sources, using different methods, finding that the impact of the GW data is very limited, due to the small number of data points, and their large errors. We analyze separately data from the Pantheon and the Union 2.1 catalogues, finding that a model with $H_0^P$ and a small local void can fit the data as well as a homogeneous model with $H_0^R$, resolving the apparent $H_0$ tension. We find that there is a significant difference between the size and depth of the inhomogeneity obtained using the two datasets, which could be due to the different sky coverage of the two catalogues. For Pantheon we obtain evidence of a local inhomogeneity with a density contrast $\delta_v=-0.155 \pm 0.026$, extending up to a redshift of $z_v = 0.056 \pm 0.0002$, while for Union 2.1 we obtain $\delta_v=-0.461 \pm 0.032$ and $z_v= 0.081\pm 0.008$. We also perform some analysis using redshift shell averaged data, and obtain approximately the same results, hinting to the fact that the effects of the monopole component of the local inhomogeneity are the dominant ones |
gr-qc/9408023 | Albrecht | Andreas Albrecht | The Theory of Everything vs the Theory of Anything | 13 pages plain LaTeX, no figures. To appear in the proceedings of
``The Birth of the Universe and Fundamental Forces'', Rome, May 1994, F.
Occhionero Editor, Springer Verlag. Imperial/TP/93-94/56 REVISED 10/94: Minor
improvements, more referneces, no major changes | Lect.Notes Phys.455:323-332,1995 | 10.1007/3-540-60024-8_126 | null | gr-qc astro-ph hep-th | null | To what extent can our limited set of observations be used to pin down the
specifics of a ``Theory of Everything''? In the limit where the links are
arbitrarily tenuous, a ``Theory of Everything'' might become a ``Theory of
Anything''. A clear understanding of what we can and can not expect to learn
about the universe is particularly important in the field of particle
cosmology. The aim of this article is to draw attention to some key issues
which arise in this context, in the hopes of fostering further discussion. In
particular, I explore the idea that a variety of different inflaton potentials
may contribute to worlds ``like ours''. A careful examination of the
conditional probability questions we can ask might give a physical measure of
what is ``natural'' for an inflation potential which is quite different from
those previously used.
| [
{
"created": "Thu, 18 Aug 1994 08:03:40 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Nov 1994 19:34:00 GMT",
"version": "v2"
}
] | 2018-05-02 | [
[
"Albrecht",
"Andreas",
""
]
] | To what extent can our limited set of observations be used to pin down the specifics of a ``Theory of Everything''? In the limit where the links are arbitrarily tenuous, a ``Theory of Everything'' might become a ``Theory of Anything''. A clear understanding of what we can and can not expect to learn about the universe is particularly important in the field of particle cosmology. The aim of this article is to draw attention to some key issues which arise in this context, in the hopes of fostering further discussion. In particular, I explore the idea that a variety of different inflaton potentials may contribute to worlds ``like ours''. A careful examination of the conditional probability questions we can ask might give a physical measure of what is ``natural'' for an inflation potential which is quite different from those previously used. |
1010.5149 | Lorenzo Sindoni | Daniele Oriti and Lorenzo Sindoni | Towards classical geometrodynamics from Group Field Theory hydrodynamics | revtex4, 32 pages. Contribution submitted to the focus issue of the
New Journal of Physics on "Classical and Quantum Analogues for Gravitational
Phenomena and Related Effects", R. Schuetzhold, U. Leonhardt and C. Maia,
Eds; v2: typos corrected, references updated, to match the published version | New J.Phys.13:025006,2011 | 10.1088/1367-2630/13/2/025006 | AEI-2010-157 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We take the first steps towards identifying the hydrodynamics of group field
theories (GFTs) and relating this hydrodynamic regime to classical
geometrodynamics of continuum space. We apply to GFT mean field theory
techniques borrowed from the theory of Bose condensates, alongside standard GFT
and spin foam techniques. The mean field configuration we study is, in turn,
obtained from loop quantum gravity coherent states. We work in the context of
2d and 3d GFT models, in euclidean signature, both ordinary and colored, as
examples of a procedure that has a more general validity. We also extract the
effective dynamics of the system around the mean field configurations, and
discuss the role of GFT symmetries in going from microscopic to effective
dynamics. In the process, we obtain additional insights on the GFT formalism
itself.
| [
{
"created": "Mon, 25 Oct 2010 14:49:18 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Feb 2011 11:35:09 GMT",
"version": "v2"
}
] | 2011-02-18 | [
[
"Oriti",
"Daniele",
""
],
[
"Sindoni",
"Lorenzo",
""
]
] | We take the first steps towards identifying the hydrodynamics of group field theories (GFTs) and relating this hydrodynamic regime to classical geometrodynamics of continuum space. We apply to GFT mean field theory techniques borrowed from the theory of Bose condensates, alongside standard GFT and spin foam techniques. The mean field configuration we study is, in turn, obtained from loop quantum gravity coherent states. We work in the context of 2d and 3d GFT models, in euclidean signature, both ordinary and colored, as examples of a procedure that has a more general validity. We also extract the effective dynamics of the system around the mean field configurations, and discuss the role of GFT symmetries in going from microscopic to effective dynamics. In the process, we obtain additional insights on the GFT formalism itself. |
gr-qc/0606020 | Thomas Buchert | Thomas Buchert (Univ. Bielefeld & ASC Munich, Germany), Julien Larena
and Jean-Michel Alimi (LUTH, Obs. de Paris--Meudon, France) | Correspondence between kinematical backreaction and scalar field
cosmologies - the `morphon field' | 36 pages and 6 Figures, matches published version in Class.Quant.Grav | Class.Quant.Grav.23:6379-6408,2006 | 10.1088/0264-9381/23/22/018 | null | gr-qc astro-ph hep-th | null | Spatially averaged inhomogeneous cosmologies in classical general relativity
can be written in the form of effective Friedmann equations with sources that
include backreaction terms. In this paper we propose to describe these
backreaction terms with the help of a homogeneous scalar field evolving in a
potential; we call it the `morphon field'. This new field links classical
inhomogeneous cosmologies to scalar field cosmologies, allowing to reinterpret,
e.g., quintessence scenarios by routing the physical origin of the scalar field
source to inhomogeneities in the Universe. We investigate a one-parameter
family of scaling solutions to the backreaction problem. Subcases of these
solutions (all without an assumed cosmological constant) include
scale-dependent models with Friedmannian kinematics that can mimic the presence
of a cosmological constant or a time-dependent cosmological term. We explicitly
reconstruct the scalar field potential for the scaling solutions, and discuss
those cases that provide a solution to the Dark Energy and coincidence
problems. In this approach, Dark Energy emerges from morphon fields, a
mechanism that can be understood through the proposed correspondence: the
averaged cosmology is characterized by a weak decay (quintessence) or growth
(phantom quintessence) of kinematical fluctuations, fed by `curvature energy'
that is stored in the averaged 3-Ricci curvature. We find that the late-time
trajectories of those models approach attractors that lie in the future of a
state that is predicted by observational constraints.
| [
{
"created": "Sat, 3 Jun 2006 15:13:26 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Sep 2006 09:59:38 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Buchert",
"Thomas",
"",
"Univ. Bielefeld & ASC Munich, Germany"
],
[
"Larena",
"Julien",
"",
"LUTH, Obs. de Paris--Meudon, France"
],
[
"Alimi",
"Jean-Michel",
"",
"LUTH, Obs. de Paris--Meudon, France"
]
] | Spatially averaged inhomogeneous cosmologies in classical general relativity can be written in the form of effective Friedmann equations with sources that include backreaction terms. In this paper we propose to describe these backreaction terms with the help of a homogeneous scalar field evolving in a potential; we call it the `morphon field'. This new field links classical inhomogeneous cosmologies to scalar field cosmologies, allowing to reinterpret, e.g., quintessence scenarios by routing the physical origin of the scalar field source to inhomogeneities in the Universe. We investigate a one-parameter family of scaling solutions to the backreaction problem. Subcases of these solutions (all without an assumed cosmological constant) include scale-dependent models with Friedmannian kinematics that can mimic the presence of a cosmological constant or a time-dependent cosmological term. We explicitly reconstruct the scalar field potential for the scaling solutions, and discuss those cases that provide a solution to the Dark Energy and coincidence problems. In this approach, Dark Energy emerges from morphon fields, a mechanism that can be understood through the proposed correspondence: the averaged cosmology is characterized by a weak decay (quintessence) or growth (phantom quintessence) of kinematical fluctuations, fed by `curvature energy' that is stored in the averaged 3-Ricci curvature. We find that the late-time trajectories of those models approach attractors that lie in the future of a state that is predicted by observational constraints. |
0908.0379 | Jozef Skakala | Jozef Skakala (Victoria University of Wellington) | New ideas about multiplication of tensorial distributions | 37 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a need in general relativity for a consistent and useful
mathematical theory defining the multiplication of tensor distributions in a
geometric (diffeomorphism invariant) way. Significant progress has been made
through the concept of Colombeau algebras, and the construction of full
Colombeau algebras on differential manifolds for arbitrary tensors. Despite the
fact that this goal was achieved, it does not incorporate clearly enough the
concept of covariant derivative and hence is of a limited use. We take a
different approach: we consider any type of preference for smooth distributions
(on a smooth manifold) as nonintuitive, which means all our approach must be
based fully on the Colombeau equivalence relation as the fundamental feature of
the theory. After taking this approach we very naturally obtain a canonical and
geometric theory defining tensorial operations with tensorial distributions,
including covariant derivative. This also happens because we no longer need any
explicit canonical geometric construction of Colombeau algebras. The big
advantage of our approach lies also in the fact that it brings a physical
insight into the mathematical concepts used and naturally leads to formulation
of physics on (what we call) piecewise smooth manifolds, rather than on smooth
manifold. This brings to the language of physics much higher symmetry (in the
same way as turning from Poincare invariance to diffeomorphism invariance), and
is compatible with our intuition, that "pointwise" properties in some
metaphorical sense "do not matter".
| [
{
"created": "Tue, 4 Aug 2009 03:15:18 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Mar 2010 04:11:00 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Dec 2010 03:14:57 GMT",
"version": "v3"
},
{
"created": "Thu, 21 Apr 2011 05:00:14 GMT",
"version": "v4"
},
{
"created": "Fri, 9 Dec 2011 15:03:24 GMT",
"version": "v5"
}
] | 2011-12-12 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
]
] | There is a need in general relativity for a consistent and useful mathematical theory defining the multiplication of tensor distributions in a geometric (diffeomorphism invariant) way. Significant progress has been made through the concept of Colombeau algebras, and the construction of full Colombeau algebras on differential manifolds for arbitrary tensors. Despite the fact that this goal was achieved, it does not incorporate clearly enough the concept of covariant derivative and hence is of a limited use. We take a different approach: we consider any type of preference for smooth distributions (on a smooth manifold) as nonintuitive, which means all our approach must be based fully on the Colombeau equivalence relation as the fundamental feature of the theory. After taking this approach we very naturally obtain a canonical and geometric theory defining tensorial operations with tensorial distributions, including covariant derivative. This also happens because we no longer need any explicit canonical geometric construction of Colombeau algebras. The big advantage of our approach lies also in the fact that it brings a physical insight into the mathematical concepts used and naturally leads to formulation of physics on (what we call) piecewise smooth manifolds, rather than on smooth manifold. This brings to the language of physics much higher symmetry (in the same way as turning from Poincare invariance to diffeomorphism invariance), and is compatible with our intuition, that "pointwise" properties in some metaphorical sense "do not matter". |
gr-qc/0511102 | D. Petroff | David Petroff, Marcus Ansorg | The Extreme Distortion of Black Holes due to Matter | 3 pages, 2 figures, v2: minor changes, one reference added | null | null | null | gr-qc | null | A highly accurate computer program is used to study axially symmetric and
stationary spacetimes containing a Black Hole surrounded by a ring of matter.
It is shown that the matter ring affects the properties of the Black Hole
drastically. In particular, the absolute value of the ratio of the Black Hole's
angular momentum to the square of its mass not only exceeds one, but can be
greater than ten thousand (|J|/M^2 > 10^4). Indeed, the numerical evidence
suggests that this quantity is unbounded.
| [
{
"created": "Thu, 17 Nov 2005 14:16:40 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Nov 2005 15:06:05 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Petroff",
"David",
""
],
[
"Ansorg",
"Marcus",
""
]
] | A highly accurate computer program is used to study axially symmetric and stationary spacetimes containing a Black Hole surrounded by a ring of matter. It is shown that the matter ring affects the properties of the Black Hole drastically. In particular, the absolute value of the ratio of the Black Hole's angular momentum to the square of its mass not only exceeds one, but can be greater than ten thousand (|J|/M^2 > 10^4). Indeed, the numerical evidence suggests that this quantity is unbounded. |
1506.03492 | Davide Gerosa | Davide Gerosa, Michael Kesden, Ulrich Sperhake, Emanuele Berti,
Richard O'Shaughnessy | Multi-timescale analysis of phase transitions in precessing black-hole
binaries | Accepted for publication in PRD. Animations available at
http://davidegerosa.com/spinprecession/ | Phys. Rev. D 92, 064016 (2015) | 10.1103/PhysRevD.92.064016 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of precessing binary black holes (BBHs) in the post-Newtonian
regime has a strong timescale hierarchy: the orbital timescale is very short
compared to the spin-precession timescale which, in turn, is much shorter than
the radiation-reaction timescale on which the orbit is shrinking due to
gravitational-wave emission. We exploit this timescale hierarchy to develop a
multi-scale analysis of BBH dynamics elaborating on the analysis of Kesden et
al. (2015). We solve the spin-precession equations analytically on the
precession time and then implement a quasi-adiabatic approach to evolve these
solutions on the longer radiation-reaction time. This procedure leads to an
innovative "precession-averaged" post-Newtonian approach to studying precessing
BBHs. We use our new solutions to classify BBH spin precession into three
distinct morphologies, then investigate phase transitions between these
morphologies as BBHs inspiral. These precession-averaged post-Newtonian
inspirals can be efficiently calculated from arbitrarily large separations,
thus making progress towards bridging the gap between astrophysics and
numerical relativity.
| [
{
"created": "Wed, 10 Jun 2015 21:45:08 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2015 16:19:33 GMT",
"version": "v2"
}
] | 2015-09-16 | [
[
"Gerosa",
"Davide",
""
],
[
"Kesden",
"Michael",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Berti",
"Emanuele",
""
],
[
"O'Shaughnessy",
"Richard",
""
]
] | The dynamics of precessing binary black holes (BBHs) in the post-Newtonian regime has a strong timescale hierarchy: the orbital timescale is very short compared to the spin-precession timescale which, in turn, is much shorter than the radiation-reaction timescale on which the orbit is shrinking due to gravitational-wave emission. We exploit this timescale hierarchy to develop a multi-scale analysis of BBH dynamics elaborating on the analysis of Kesden et al. (2015). We solve the spin-precession equations analytically on the precession time and then implement a quasi-adiabatic approach to evolve these solutions on the longer radiation-reaction time. This procedure leads to an innovative "precession-averaged" post-Newtonian approach to studying precessing BBHs. We use our new solutions to classify BBH spin precession into three distinct morphologies, then investigate phase transitions between these morphologies as BBHs inspiral. These precession-averaged post-Newtonian inspirals can be efficiently calculated from arbitrarily large separations, thus making progress towards bridging the gap between astrophysics and numerical relativity. |
1907.08681 | Sofie Marie Koksbang | S. M. Koksbang | Towards statistically homogeneous and isotropic perfect fluid universes
with cosmic backreaction | 35 pages, 10 captioned figures. Submitted for publication. v2: Typo
in eq. 1 corrected and text added to explain figure. No changes to results.
Matches publishd version | Class. Quantum Grav. 36 185004, 2019 | 10.1088/1361-6382/ab376c | HIP-2019-25/TH | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method for constructing statistically homogeneous and isotropic perfect
fluid universe models with significant cosmic backreaction is proposed. The
method is illustrated using a simplified model constructed as a Swiss-cheese
model with Lemaitre-Tolman-Bondi structures. The model exhibits significant
cosmic backreaction and is used to study methods proposed in the literature for
relating volume averaged quantities with observations. The comparison shows a
poor agreement between exact redshift-distance relations and the relations
predicted by schemes based on volume averages. Most of these deviations are,
however, clearly exaggerated by peculiarities of the example model, such as
large local expansion rates.
| [
{
"created": "Thu, 18 Jul 2019 11:24:52 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2019 07:38:43 GMT",
"version": "v2"
}
] | 2019-08-22 | [
[
"Koksbang",
"S. M.",
""
]
] | A method for constructing statistically homogeneous and isotropic perfect fluid universe models with significant cosmic backreaction is proposed. The method is illustrated using a simplified model constructed as a Swiss-cheese model with Lemaitre-Tolman-Bondi structures. The model exhibits significant cosmic backreaction and is used to study methods proposed in the literature for relating volume averaged quantities with observations. The comparison shows a poor agreement between exact redshift-distance relations and the relations predicted by schemes based on volume averages. Most of these deviations are, however, clearly exaggerated by peculiarities of the example model, such as large local expansion rates. |
1712.09554 | Indrani Banerjee | Indrani Banerjee, Bhaswati Mandal and Soumitra SenGupta | In quest of axionic hairs in quasars | v2, Revised, accepted for publication in JCAP, 19 pages, 3 figures | null | 10.1088/1475-7516/2018/03/039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of axionic field can provide plausible explanation to several
long standing problems in physics such as dark matter and dark energy. The
pseudo-scalar axion whose derivative corresponds to the Hodge dual of the
Kalb-Ramond field strength in four dimensions plays crucial roles in explaining
several astrophysical and cosmological observations. Therefore, the detection
of axionic hairs/Kalb-Ramond field which appears as closed string excitations
in the heterotic string spectrum may provide a profound insight to our
understanding of the current universe. The current level of precision achieved
in solar-system based tests employed to test general relativity, is not
sufficient to detect the presence of axion. However, the near horizon regime of
quasars where the curvature effects are maximum seems to be a natural
laboratory to probe such additions to the matter sector. The continuum spectrum
emitted from the accretion disk around quasars encapsulates the imprints of the
background spacetime and hence acts as a storehouse of information regarding
the nature of gravitational interaction in extreme situations. The surfeit of
data available in the electromagnetic domain provides a further motivation to
explore such systems. Using the optical data for eighty Palomar Green quasars
we demonstrate that the theoretical estimates of optical luminosity explain the
observations best when the axionic field is assumed to be absent. However,
axion which violates the energy condition seems to be favored by observations
which has several interesting consequences. Error estimators, including reduced
$\chi^{2}$, Nash-Sutcliffe efficiency, index of agreement and modified versions
of the last two are used to solidify our conclusion and the implications of our
result are discussed.
| [
{
"created": "Wed, 27 Dec 2017 11:31:50 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Feb 2018 07:50:50 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Mar 2018 05:11:57 GMT",
"version": "v3"
}
] | 2018-04-11 | [
[
"Banerjee",
"Indrani",
""
],
[
"Mandal",
"Bhaswati",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | The presence of axionic field can provide plausible explanation to several long standing problems in physics such as dark matter and dark energy. The pseudo-scalar axion whose derivative corresponds to the Hodge dual of the Kalb-Ramond field strength in four dimensions plays crucial roles in explaining several astrophysical and cosmological observations. Therefore, the detection of axionic hairs/Kalb-Ramond field which appears as closed string excitations in the heterotic string spectrum may provide a profound insight to our understanding of the current universe. The current level of precision achieved in solar-system based tests employed to test general relativity, is not sufficient to detect the presence of axion. However, the near horizon regime of quasars where the curvature effects are maximum seems to be a natural laboratory to probe such additions to the matter sector. The continuum spectrum emitted from the accretion disk around quasars encapsulates the imprints of the background spacetime and hence acts as a storehouse of information regarding the nature of gravitational interaction in extreme situations. The surfeit of data available in the electromagnetic domain provides a further motivation to explore such systems. Using the optical data for eighty Palomar Green quasars we demonstrate that the theoretical estimates of optical luminosity explain the observations best when the axionic field is assumed to be absent. However, axion which violates the energy condition seems to be favored by observations which has several interesting consequences. Error estimators, including reduced $\chi^{2}$, Nash-Sutcliffe efficiency, index of agreement and modified versions of the last two are used to solidify our conclusion and the implications of our result are discussed. |
gr-qc/0607065 | Lars Andersson | Lars Andersson (UM and AEI) | On the relation between mathematical and numerical relativity | 12 pages | Class.Quant.Grav.23:S307-S318,2006 | 10.1088/0264-9381/23/16/S02 | AEI-2006-055 | gr-qc | null | The large scale binary black hole effort in numerical relativity has led to
an increasing distinction between numerical and mathematical relativity. This
note discusses this situation and gives some examples of succesful interactions
between numerical and mathematical methods is general relativity.
| [
{
"created": "Mon, 17 Jul 2006 18:17:47 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Andersson",
"Lars",
"",
"UM and AEI"
]
] | The large scale binary black hole effort in numerical relativity has led to an increasing distinction between numerical and mathematical relativity. This note discusses this situation and gives some examples of succesful interactions between numerical and mathematical methods is general relativity. |
2303.05430 | Giampiero Esposito Dr. | Giampiero Esposito | DeWitt boundary condition in one-loop quantum cosmology | In the final version, the presentation has been improved | null | 10.3390/universe9040187 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | DeWitt's suggestion that the wave function of the universe should vanish at
the classical big-bang singularity is here considered within the framework of
one-loop quantum cosmology. For pure gravity at one loop about a flat
four-dimensional background bounded by a 3-sphere, three choices of boundary
conditions are considered: vanishing of the linearized magnetic curvature when
only transverse-traceless gravitational modes are quantized; a one-parameter
family of mixed boundary conditions for gravitational and ghost modes;
diffeomorphism invariant boundary conditions for metric perturbations and ghost
modes. A positive zeta(0) value in these cases ensures that, when the 3-sphere
boundary approaches zero, the resulting one-loop wave function approaches zero.
This property may be interpreted by saying that, in the limit of small
three-geometry, the resulting one-loop wave function describes a
singularity-free universe. This property holds for one-loop functional
integrals, which are not necessarily equivalent to solutions of the quantum
constraint equations.
| [
{
"created": "Thu, 9 Mar 2023 17:22:17 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Apr 2023 15:04:41 GMT",
"version": "v2"
}
] | 2023-04-18 | [
[
"Esposito",
"Giampiero",
""
]
] | DeWitt's suggestion that the wave function of the universe should vanish at the classical big-bang singularity is here considered within the framework of one-loop quantum cosmology. For pure gravity at one loop about a flat four-dimensional background bounded by a 3-sphere, three choices of boundary conditions are considered: vanishing of the linearized magnetic curvature when only transverse-traceless gravitational modes are quantized; a one-parameter family of mixed boundary conditions for gravitational and ghost modes; diffeomorphism invariant boundary conditions for metric perturbations and ghost modes. A positive zeta(0) value in these cases ensures that, when the 3-sphere boundary approaches zero, the resulting one-loop wave function approaches zero. This property may be interpreted by saying that, in the limit of small three-geometry, the resulting one-loop wave function describes a singularity-free universe. This property holds for one-loop functional integrals, which are not necessarily equivalent to solutions of the quantum constraint equations. |
2103.11708 | David Senjaya | David Senjaya | Canonical Quantization of Static and Rotating Black Hole as A
Gravitational Atom | Cancelled for publication | null | null | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | Gravitational field is usually neglected in calculation of atomic energy
levels as its effect is much weaker than the electromagnetic field, but that is
not the case for a particle orbiting a black hole. In this work, canonical
quantization of a particle under a gravitational field exerted by this tiny but
very massive object, both static and rotating-is carried out. By using this
method, very rare exact result of the particles quantized energy can be
discovered. The presence of a very strong attractive field and the horizon make
the energy complex valued and force the corresponding wave function to be a
quasi-bound state. Moreover, by taking a small scale limit, the system becomes
a gravitational atom in sense that hydrogenic atoms energy levels and wave
functions can be recovered. Obtaining these exact solutions for fundamental
black holes effectively empowers us to deal with more complex black holes such
as cosmological black holes or black hole solutions emerging from modified
gravity.
| [
{
"created": "Mon, 22 Mar 2021 10:25:34 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2023 10:30:09 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Senjaya",
"David",
""
]
] | Gravitational field is usually neglected in calculation of atomic energy levels as its effect is much weaker than the electromagnetic field, but that is not the case for a particle orbiting a black hole. In this work, canonical quantization of a particle under a gravitational field exerted by this tiny but very massive object, both static and rotating-is carried out. By using this method, very rare exact result of the particles quantized energy can be discovered. The presence of a very strong attractive field and the horizon make the energy complex valued and force the corresponding wave function to be a quasi-bound state. Moreover, by taking a small scale limit, the system becomes a gravitational atom in sense that hydrogenic atoms energy levels and wave functions can be recovered. Obtaining these exact solutions for fundamental black holes effectively empowers us to deal with more complex black holes such as cosmological black holes or black hole solutions emerging from modified gravity. |
2404.17846 | Zeeshan Gul | M. Zeeshan Gul and M. Sharif | Spherically Symmetric Wormhole Solutions admitting Karmarkar Condition | 31 pages, 26 figures | Phys. Scr. 99(2024)055036 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigated the viable traversable wormhole solutions through
Karmarkar condition in the context of $f(\mathcal{G},T)$ theory. A static
spherical spacetime with anisotropic matter configuration is used to study the
wormhole geometry. Karmarkar condition is used to develop a viable shape
function for a static wormhole structure. A wormhole geometry is constructed
using the resulting shape function that satisfies all the required conditions
and connects the asymptotically flat regions of the spacetime. To assess the
viability of traversable wormhole geometries, the energy conditions are
analyzed by various models of this theory. Further, their stable state is
investigated through sound speed and adiabatic index. This investigation
demonstrates the presence of viable traversable wormhole solutions in the
modified theory.
| [
{
"created": "Sat, 27 Apr 2024 09:48:34 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Gul",
"M. Zeeshan",
""
],
[
"Sharif",
"M.",
""
]
] | This paper investigated the viable traversable wormhole solutions through Karmarkar condition in the context of $f(\mathcal{G},T)$ theory. A static spherical spacetime with anisotropic matter configuration is used to study the wormhole geometry. Karmarkar condition is used to develop a viable shape function for a static wormhole structure. A wormhole geometry is constructed using the resulting shape function that satisfies all the required conditions and connects the asymptotically flat regions of the spacetime. To assess the viability of traversable wormhole geometries, the energy conditions are analyzed by various models of this theory. Further, their stable state is investigated through sound speed and adiabatic index. This investigation demonstrates the presence of viable traversable wormhole solutions in the modified theory. |
0705.3340 | Stefan Hollands | Stefan Hollands | Renormalized Quantum Yang-Mills Fields in Curved Spacetime | Latex 144pp, no figures, review style presentation; v2: equations
corrected, details in proof of Ward-identity added, discussion of state
space, refs. added; v3: typos corrected, details added in renormalization
section, one subsection removed; v4 BRST-invariant state, typos corrected,
background field discussion clarified, hyperref feature added | Rev.Math.Phys.20:1033-1172,2008 | 10.1142/S0129055X08003420 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a proof that quantum Yang-Mills theory can be consistently defined
as a renormalized, perturbative quantum field theory on an arbitrary globally
hyperbolic curved, Lorentzian spacetime. To this end, we construct the
non-commutative algebra of observables, in the sense of formal power series, as
well as a space of corresponding quantum states. The algebra contains all gauge
invariant, renormalized, interacting quantum field operators (polynomials in
the field strength and its derivatives), and all their relations such as
commutation relations or operator product expansion. It can be viewed as a
deformation quantization of the Poisson algebra of classical Yang-Mills theory
equipped with the Peierls bracket. The algebra is constructed as the cohomology
of an auxiliary algebra describing a gauge fixed theory with ghosts and
anti-fields. A key technical difficulty is to establish a suitable hierarchy of
Ward identities at the renormalized level that ensure conservation of the
interacting BRST-current, and that the interacting BRST-charge is nilpotent.
The algebra of physical interacting field observables is obtained as the
cohomology of this charge. As a consequence of our constructions, we can prove
that the operator product expansion closes on the space of gauge invariant
operators. Similarly, the renormalization group flow is proved not to leave the
space of gauge invariant operators.
| [
{
"created": "Wed, 23 May 2007 11:33:38 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2007 13:03:52 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Feb 2008 16:27:04 GMT",
"version": "v3"
},
{
"created": "Wed, 14 Mar 2018 07:47:21 GMT",
"version": "v4"
}
] | 2018-03-15 | [
[
"Hollands",
"Stefan",
""
]
] | We present a proof that quantum Yang-Mills theory can be consistently defined as a renormalized, perturbative quantum field theory on an arbitrary globally hyperbolic curved, Lorentzian spacetime. To this end, we construct the non-commutative algebra of observables, in the sense of formal power series, as well as a space of corresponding quantum states. The algebra contains all gauge invariant, renormalized, interacting quantum field operators (polynomials in the field strength and its derivatives), and all their relations such as commutation relations or operator product expansion. It can be viewed as a deformation quantization of the Poisson algebra of classical Yang-Mills theory equipped with the Peierls bracket. The algebra is constructed as the cohomology of an auxiliary algebra describing a gauge fixed theory with ghosts and anti-fields. A key technical difficulty is to establish a suitable hierarchy of Ward identities at the renormalized level that ensure conservation of the interacting BRST-current, and that the interacting BRST-charge is nilpotent. The algebra of physical interacting field observables is obtained as the cohomology of this charge. As a consequence of our constructions, we can prove that the operator product expansion closes on the space of gauge invariant operators. Similarly, the renormalization group flow is proved not to leave the space of gauge invariant operators. |
gr-qc/0504115 | Alan Coley | A.A. Coley, N. Pelavas and R.M. Zalaletdinov | Cosmological Solutions in Macroscopic Gravity | 5 pages | Phys.Rev.Lett. 95 (2005) 151102 | 10.1103/PhysRevLett.95.151102 | null | gr-qc astro-ph | null | In the macroscopic gravity approach to the averaging problem in cosmology,
the Einstein field equations on cosmological scales are modified by appropriate
gravitational correlation terms. We present exact cosmological solutions to the
equations of macroscopic gravity for a spatially homogeneous and isotropic
macroscopic space-time and find that the correlation tensor is of the form of a
spatial curvature term. We briefly discuss the physical consequences of these
results.
| [
{
"created": "Sat, 23 Apr 2005 18:11:53 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Oct 2005 17:19:49 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Coley",
"A. A.",
""
],
[
"Pelavas",
"N.",
""
],
[
"Zalaletdinov",
"R. M.",
""
]
] | In the macroscopic gravity approach to the averaging problem in cosmology, the Einstein field equations on cosmological scales are modified by appropriate gravitational correlation terms. We present exact cosmological solutions to the equations of macroscopic gravity for a spatially homogeneous and isotropic macroscopic space-time and find that the correlation tensor is of the form of a spatial curvature term. We briefly discuss the physical consequences of these results. |
gr-qc/0605024 | Lars Samuelsson | Brandon Carter and Lars Samuelsson | Relativistic mechanics of neutron superfluid in (magneto) elastic star
crust | 29 pages, Latex. V. 2. Minor changes, matches published version | Class.Quant.Grav. 23 (2006) 5367-5388 | 10.1088/0264-9381/23/17/015 | null | gr-qc astro-ph | null | At densities below the neutron drip threshold, a purely elastic solid model
(including, if necessary, a frozen-in magnetic field) can provide an adequate
description of a neutron star crust, but at higher densities it will be
necessary to allow for the penetration of the solid lattice by an independently
moving current of superfluid neutrons. In order to do this, the previously
available category of relativistic elasticity models is combined here with a
separately developed category of relativistic superfluidity models in a unified
treatment based on the use of an appropriate Lagrangian master function. As
well as models of the purely variational kind, in which the vortices flow
freely with the fluid, such a master function also provides a corresponding
category of non-dissipative models in which the vortices are pinned to the
solid structure.
| [
{
"created": "Wed, 3 May 2006 22:31:49 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Aug 2006 16:30:26 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Carter",
"Brandon",
""
],
[
"Samuelsson",
"Lars",
""
]
] | At densities below the neutron drip threshold, a purely elastic solid model (including, if necessary, a frozen-in magnetic field) can provide an adequate description of a neutron star crust, but at higher densities it will be necessary to allow for the penetration of the solid lattice by an independently moving current of superfluid neutrons. In order to do this, the previously available category of relativistic elasticity models is combined here with a separately developed category of relativistic superfluidity models in a unified treatment based on the use of an appropriate Lagrangian master function. As well as models of the purely variational kind, in which the vortices flow freely with the fluid, such a master function also provides a corresponding category of non-dissipative models in which the vortices are pinned to the solid structure. |
2310.04759 | Sohan Kumar Jha | Sohan Kumar Jha | Shadow, quasinormal modes, greybody bounds, and Hawking sparsity of Loop
Quantum Gravity motivated non-rotating black hole | Accepted for publication in Eur.Phy.Jour.C | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider Loop Quantum Gravity(LQG) motivated $4D$ polymerized black hole
and study shadow, quasinormal modes, and Hawking radiation. We obtain
analytical expressions of photonsphere radius and shadow radius and study their
qualitative and quantitative nature of variation with respect to the LQG
parameter $\alpha$. We also show shadows of the black hole for various values
of $\alpha$. Our study reveals that both radii increase with an increase in the
parameter value. We, then, study quasinormal modes for scalar and
electromagnetic perturbations using the $6th$ order WKB method. Our study
reveals that the LQG parameter impacts quasinormal modes. We observe that the
oscillation of gravitational wave(GW) and decay rate decrease as $\alpha$
increases. At the same time, the error associated with the $6th$ order WKB
method increases with an increase in $\alpha$. The ringdown waveform for
electromagnetic and scalar perturbations is shown. We also study greybody
bounds, power spectrum, and sparsity of Hawking radiation. Greybody bounds for
electromagnetic perturbations do not depend on $\alpha$. For scalar
perturbation, greybody bounds increase as the LQG parameter increases, but the
variation with $\alpha$ is very small. The peak of the power spectrum as well
as total power emitted decrease as we increase the value of $\alpha$. Also, the
sparsity of Hawking radiation gets significantly impacted by quantum
correction. Finally, we obtain the area spectrum of the black hole. It is found
to be significantly different than that for the Schwarzschild black hole.
| [
{
"created": "Sat, 7 Oct 2023 09:42:28 GMT",
"version": "v1"
}
] | 2023-10-10 | [
[
"Jha",
"Sohan Kumar",
""
]
] | We consider Loop Quantum Gravity(LQG) motivated $4D$ polymerized black hole and study shadow, quasinormal modes, and Hawking radiation. We obtain analytical expressions of photonsphere radius and shadow radius and study their qualitative and quantitative nature of variation with respect to the LQG parameter $\alpha$. We also show shadows of the black hole for various values of $\alpha$. Our study reveals that both radii increase with an increase in the parameter value. We, then, study quasinormal modes for scalar and electromagnetic perturbations using the $6th$ order WKB method. Our study reveals that the LQG parameter impacts quasinormal modes. We observe that the oscillation of gravitational wave(GW) and decay rate decrease as $\alpha$ increases. At the same time, the error associated with the $6th$ order WKB method increases with an increase in $\alpha$. The ringdown waveform for electromagnetic and scalar perturbations is shown. We also study greybody bounds, power spectrum, and sparsity of Hawking radiation. Greybody bounds for electromagnetic perturbations do not depend on $\alpha$. For scalar perturbation, greybody bounds increase as the LQG parameter increases, but the variation with $\alpha$ is very small. The peak of the power spectrum as well as total power emitted decrease as we increase the value of $\alpha$. Also, the sparsity of Hawking radiation gets significantly impacted by quantum correction. Finally, we obtain the area spectrum of the black hole. It is found to be significantly different than that for the Schwarzschild black hole. |
1802.09107 | W. G. Unruh | William G Unruh | Prehawking radiation | 4pp, 1figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the 2-D quantum energy momentum tensor expectation value near a black
hole, the value near a collapsing shell which stops collapsing just outside the
putative horizon is calculated and shown not to have any evidence of preHawking
radiation.
| [
{
"created": "Sun, 25 Feb 2018 23:50:27 GMT",
"version": "v1"
}
] | 2018-02-27 | [
[
"Unruh",
"William G",
""
]
] | Using the 2-D quantum energy momentum tensor expectation value near a black hole, the value near a collapsing shell which stops collapsing just outside the putative horizon is calculated and shown not to have any evidence of preHawking radiation. |
gr-qc/0605082 | Roman Konoplya | R. A. Konoplya, A. Zhidenko | Perturbations and quasi-normal modes of black holes in Einstein-Aether
theory | 6 pages, 3 figures, RevTex, to be published in Phys. Lett. B | Phys.Lett. B644 (2007) 186-191 | 10.1016/j.physletb.2006.11.036 | null | gr-qc | null | We develop a new method for calculation of quasi-normal modes of black holes,
when the effective potential, which governs black hole perturbations, is known
only numerically in some region near the black hole. This method can be applied
to perturbations of a wide class of numerical black hole solutions. We apply it
to the black holes in the Einstein-Aether theory, a theory where general
relativity is coupled to a unit time-like vector field, in order to observe
local Lorentz symmetry violation. We found that in the non-reduced
Einstein-Aether theory, real oscillation frequency and damping rate of
quasi-normal modes are larger than those of Schwarzschild black holes in the
Einstein theory.
| [
{
"created": "Fri, 12 May 2006 22:22:19 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jul 2006 13:02:00 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Aug 2006 21:40:30 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Oct 2006 14:21:54 GMT",
"version": "v4"
},
{
"created": "Sun, 19 Nov 2006 18:43:06 GMT",
"version": "v5"
}
] | 2009-11-11 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | We develop a new method for calculation of quasi-normal modes of black holes, when the effective potential, which governs black hole perturbations, is known only numerically in some region near the black hole. This method can be applied to perturbations of a wide class of numerical black hole solutions. We apply it to the black holes in the Einstein-Aether theory, a theory where general relativity is coupled to a unit time-like vector field, in order to observe local Lorentz symmetry violation. We found that in the non-reduced Einstein-Aether theory, real oscillation frequency and damping rate of quasi-normal modes are larger than those of Schwarzschild black holes in the Einstein theory. |
1004.1790 | Olga Babourova Valer'evna | Olga V. Babourova, Boris N. Frolov | Interaction of the 4-rotational gauge field with orbital momentum,
gravidiamagnetic effect, and orbit experiment "Gravity Probe B" | 4 pages, 0 figures Some missprints in the text were corrected | Phys.Rev.D82:027503,2010 | 10.1103/PhysRevD.82.027503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct interaction of the 4-rotational (Lorentzian) gauge field with the
angular orbital momentum of an external field is considered. This interaction
appears in a new Poincar\'{e} gauge theory of gravitation, in which tetrads are
not true gauge fields, but represent some functions of the translational and
4-rotational gauge fields. The given interaction leads to a new effect: the
existence of an electronic orbits precession under the action of an intensive
external gravitational field (gravidiamagnetic effect), and also substantiates
the existence of the direct interaction of the proper angular momentum of a
gyroscope with the torsion field, which theoretically can be generated by the
rotational angular momentum of the planet the Earth. The latter interaction can
be detected by the experiment Gravity Probe B on the satellite orbit.
| [
{
"created": "Sun, 11 Apr 2010 11:09:11 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jun 2010 12:38:50 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Babourova",
"Olga V.",
""
],
[
"Frolov",
"Boris N.",
""
]
] | The direct interaction of the 4-rotational (Lorentzian) gauge field with the angular orbital momentum of an external field is considered. This interaction appears in a new Poincar\'{e} gauge theory of gravitation, in which tetrads are not true gauge fields, but represent some functions of the translational and 4-rotational gauge fields. The given interaction leads to a new effect: the existence of an electronic orbits precession under the action of an intensive external gravitational field (gravidiamagnetic effect), and also substantiates the existence of the direct interaction of the proper angular momentum of a gyroscope with the torsion field, which theoretically can be generated by the rotational angular momentum of the planet the Earth. The latter interaction can be detected by the experiment Gravity Probe B on the satellite orbit. |
1308.0018 | Sam Dolan Dr | Caio F. B. Macedo, Luiz C. S. Leite, Ednilton S. Oliveira, Sam R.
Dolan, Lu\'is C. B. Crispino | Absorption of planar massless scalar waves by Kerr black holes | 11 pages, 10 figures | null | 10.1103/PhysRevD.88.064033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider planar massless scalar waves impinging upon a Kerr black hole,
for general angles of incidence. We compute the absorption cross section via
the partial wave approach, and present a gallery of results. In the
low-frequency regime, we show that the cross section approaches the horizon
area; in the high-frequency regime, we show that the cross section approaches
the geodesic capture cross section. In the aligned case, we extend the complex
angular momentum method to obtain a `sinc' approximation, which relates the
regular high-frequency oscillations in the cross section to the properties of
the polar null orbit. In the non-aligned case, we show, via a semi-analytic
approximation, that the reduction in symmetry generates a richer, less regular
absorption cross section. We separate the absorption cross section into
corotating and counterrotating contributions, showing that the absorption is
larger for counterrotating waves, as expected.
| [
{
"created": "Wed, 31 Jul 2013 20:01:02 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Macedo",
"Caio F. B.",
""
],
[
"Leite",
"Luiz C. S.",
""
],
[
"Oliveira",
"Ednilton S.",
""
],
[
"Dolan",
"Sam R.",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | We consider planar massless scalar waves impinging upon a Kerr black hole, for general angles of incidence. We compute the absorption cross section via the partial wave approach, and present a gallery of results. In the low-frequency regime, we show that the cross section approaches the horizon area; in the high-frequency regime, we show that the cross section approaches the geodesic capture cross section. In the aligned case, we extend the complex angular momentum method to obtain a `sinc' approximation, which relates the regular high-frequency oscillations in the cross section to the properties of the polar null orbit. In the non-aligned case, we show, via a semi-analytic approximation, that the reduction in symmetry generates a richer, less regular absorption cross section. We separate the absorption cross section into corotating and counterrotating contributions, showing that the absorption is larger for counterrotating waves, as expected. |
1002.0538 | Albert V. Minkevich | A. V. Minkevich | De Sitter spacetime with torsion as physical spacetime in the vacuum | 8 pages | Modern Physics Letters A, vol.26, No. 4 (2011) 259-266 | 10.1142/S0217732311034797 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Homogeneous isotropic models built in the framework of the Poincar\'e gauge
theory of gravity (PGTG) based on general expression of gravitational
Lagrangian without cosmological constant are analyzed. It is shown that the
physical spacetime in the vacuum in the frame of PGTG can have the structure of
flat de Sitter spacetime with torsion. Some physical consequences of obtained
conclusion are discussed.
| [
{
"created": "Tue, 2 Feb 2010 17:03:36 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Feb 2011 08:21:19 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Minkevich",
"A. V.",
""
]
] | Homogeneous isotropic models built in the framework of the Poincar\'e gauge theory of gravity (PGTG) based on general expression of gravitational Lagrangian without cosmological constant are analyzed. It is shown that the physical spacetime in the vacuum in the frame of PGTG can have the structure of flat de Sitter spacetime with torsion. Some physical consequences of obtained conclusion are discussed. |
1507.08419 | Avisa Behboodi | A. Behboodi, S. Akhshabi, K. Nozari | Scalar perturbation potentials in a homogeneous and isotropic
Weitzenb\"ock geometry | 16 pages, 6 figures | null | 10.1142/S0218271816500875 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the fully gauge invariant cosmological perturbation equations in
teleparallel gravity by using the gauge covariant version of the Stewart lemma
for obtaining the variations in tetrad perturbations. In teleparallel theory,
perturbations are the result of small fluctuations in the tetrad field. The
tetrad transforms as a vector in both its holonomic and anholonomic indices. As
a result, in the gauge invariant formalism, physical degrees of freedom are
those combinations of perturbation parameters which remain invariant under a
diffeomorphism in the coordinate frame, followed by an arbitrary rotation of
the local inertial (Lorentz) frame. We derive these gauge invariant
perturbation potentials for scalar perturbations and present the gauge
invariant field equations governing their evolution.
| [
{
"created": "Thu, 30 Jul 2015 08:47:06 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Dec 2015 13:23:08 GMT",
"version": "v2"
},
{
"created": "Mon, 30 May 2016 18:24:16 GMT",
"version": "v3"
}
] | 2016-05-31 | [
[
"Behboodi",
"A.",
""
],
[
"Akhshabi",
"S.",
""
],
[
"Nozari",
"K.",
""
]
] | We describe the fully gauge invariant cosmological perturbation equations in teleparallel gravity by using the gauge covariant version of the Stewart lemma for obtaining the variations in tetrad perturbations. In teleparallel theory, perturbations are the result of small fluctuations in the tetrad field. The tetrad transforms as a vector in both its holonomic and anholonomic indices. As a result, in the gauge invariant formalism, physical degrees of freedom are those combinations of perturbation parameters which remain invariant under a diffeomorphism in the coordinate frame, followed by an arbitrary rotation of the local inertial (Lorentz) frame. We derive these gauge invariant perturbation potentials for scalar perturbations and present the gauge invariant field equations governing their evolution. |
gr-qc/0107025 | Hector Hernandez | H. Hernandez, L.A. Nunez | Nonlocal Equation of State in Anisotropic Static Fluid Spheres in
General Relativity | 21 pages, 1 figure, minor changes in the text, references added, two
new solutions studied | Can.J.Phys. 82 (2004) 29-51 | 10.1139/p03-124 | null | gr-qc | null | We show that it is possible to obtain credible static anisotropic spherically
symmetric matter configurations starting from known density profiles and
satisfying a nonlocal equation of state. These particular types of equation of
state describe, at a given point, the components of the corresponding
energy-momentum tensor not only as a function at that point, but as a
functional throughout the enclosed configuration. To establish the physical
plausibility of the proposed family of solutions satisfying nonlocal equation
of state, we study the constraints imposed by the junction and energy
conditions on these bounded matter distributions.
We also show that it is possible to obtain physically plausible static
anisotropic spherically symmetric matter configurations, having nonlocal
equations of state\textit{,}concerning the particular cases where the radial
pressure vanishes and, other where the tangential pressures vanishes. The later
very particular type of relativistic sphere with vanishing tangential stresses
is inspired by some of the models proposed to describe extremely magnetized
neutron stars (magnetars) during the transverse quantum collapse.
| [
{
"created": "Fri, 6 Jul 2001 16:33:21 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2002 15:48:27 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Hernandez",
"H.",
""
],
[
"Nunez",
"L. A.",
""
]
] | We show that it is possible to obtain credible static anisotropic spherically symmetric matter configurations starting from known density profiles and satisfying a nonlocal equation of state. These particular types of equation of state describe, at a given point, the components of the corresponding energy-momentum tensor not only as a function at that point, but as a functional throughout the enclosed configuration. To establish the physical plausibility of the proposed family of solutions satisfying nonlocal equation of state, we study the constraints imposed by the junction and energy conditions on these bounded matter distributions. We also show that it is possible to obtain physically plausible static anisotropic spherically symmetric matter configurations, having nonlocal equations of state\textit{,}concerning the particular cases where the radial pressure vanishes and, other where the tangential pressures vanishes. The later very particular type of relativistic sphere with vanishing tangential stresses is inspired by some of the models proposed to describe extremely magnetized neutron stars (magnetars) during the transverse quantum collapse. |
2309.02658 | Manuel Rodrigues | Ednaldo L. B. Junior, Francisco S. N. Lobo, Manuel E. Rodrigues and
Henrique A. Vieira | Gravitational lens effect of a holonomy corrected Schwarzschild black
hole | 26 pages, 17 figures | Phys.Rev.D 109 (2024) 2, 024004 | 10.1103/PhysRevD.109.024004 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the gravitational lensing effect for the Schwarzschild
solution with holonomy corrections. We use two types of approximation methods
to calculate the deflection angle, namely the weak and strong field limits. For
the first method, we calculate the deflection angle up to the fifth order of
approximation and show the influence of the parameter $\lambda$ (in terms of
loop quantum gravity) on it. In addition, we construct expressions for the
magnification, the position of the lensed images and the time delay as
functions of the coefficients from the deflection angle expansion. We find that
$\lambda$ increases the deflection angle. In the strong field limit, we use a
logarithmic approximation to compute the deflection angle. We then write four
observables, in terms of the coefficients $b_1$, $b_2$ and $u_m$, namely: the
asymptotic position approached by a set of images $\theta_{\infty}$, the
distance between the first image and the others $s$, the ratio between the flux
of the first image and the flux of all other images $r_m$, and the time delay
between two photons $\Delta T_{2,1}$. We then use the experimental data of the
black hole Sagittarius $A^{\star}$ and calculate the observables and the
coefficients of the logarithmic expansion. We find that the parameter $\lambda$
increases the deflection angle, the separation between the lensed images and
the delay time between them. In contrast, it decreases the brightness of the
first image compared to the others.
| [
{
"created": "Wed, 6 Sep 2023 02:07:06 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2024 15:53:18 GMT",
"version": "v2"
}
] | 2024-01-10 | [
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Rodrigues",
"Manuel E.",
""
],
[
"Vieira",
"Henrique A.",
""
]
] | In this paper we study the gravitational lensing effect for the Schwarzschild solution with holonomy corrections. We use two types of approximation methods to calculate the deflection angle, namely the weak and strong field limits. For the first method, we calculate the deflection angle up to the fifth order of approximation and show the influence of the parameter $\lambda$ (in terms of loop quantum gravity) on it. In addition, we construct expressions for the magnification, the position of the lensed images and the time delay as functions of the coefficients from the deflection angle expansion. We find that $\lambda$ increases the deflection angle. In the strong field limit, we use a logarithmic approximation to compute the deflection angle. We then write four observables, in terms of the coefficients $b_1$, $b_2$ and $u_m$, namely: the asymptotic position approached by a set of images $\theta_{\infty}$, the distance between the first image and the others $s$, the ratio between the flux of the first image and the flux of all other images $r_m$, and the time delay between two photons $\Delta T_{2,1}$. We then use the experimental data of the black hole Sagittarius $A^{\star}$ and calculate the observables and the coefficients of the logarithmic expansion. We find that the parameter $\lambda$ increases the deflection angle, the separation between the lensed images and the delay time between them. In contrast, it decreases the brightness of the first image compared to the others. |
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