id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9904050 | Siming Liu | Yunqiang Yu and Siming Liu | Relativistic Charged Balls | revtex, 11 pages | null | 10.1088/0253-6102/33/4/571 | null | gr-qc | null | It is proven that the relativistic charged ball with its charge less than its
mass (in natural units) cannot have a non-singular static configuration while
its radius approaches its external horizon size. This conclusion does not
depend on the details of charge distribution and the equation of state. The
involved assumptions are (1) the ball is made of perfect fluid, (2) the energy
density is everywhere non-negative.
| [
{
"created": "Tue, 20 Apr 1999 14:07:55 GMT",
"version": "v1"
}
] | 2018-01-17 | [
[
"Yu",
"Yunqiang",
""
],
[
"Liu",
"Siming",
""
]
] | It is proven that the relativistic charged ball with its charge less than its mass (in natural units) cannot have a non-singular static configuration while its radius approaches its external horizon size. This conclusion does not depend on the details of charge distribution and the equation of state. The involved assumptions are (1) the ball is made of perfect fluid, (2) the energy density is everywhere non-negative. |
1211.3612 | Cl\'audio Nassif Cruz | Cl\'audio Nassif | Doubly Special Relativity with a minimum speed and the search for a
quantum gravity at low energies | 11 pages and 4 figures. Accepted for publication in Int. Journal of
Modern Physics D. arXiv admin note: substantial text overlap with
arXiv:0805.1201, arXiv:0711.4897 | International Journal of Modern Physics D Vol.19, No.5, p.539
(2010) | 10.1142/S021827181001652X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This research aims to consider a new principle of symmetry in the space-time
by means of the elimination of the classical idea of rest including a universal
minimum limit of speed in the subatomic world. Such a limit, unattainable by
the particles, represents a preferred inertial reference frame associated with
a cosmological background field that breaks Lorentz symmetry. So there emerges
a modified relativistic dynamics with a minimum speed related to the Planck
length of the early universe, which leads us to search for a quantum gravity at
low energies.
| [
{
"created": "Thu, 15 Nov 2012 14:15:21 GMT",
"version": "v1"
}
] | 2012-11-28 | [
[
"Nassif",
"Cláudio",
""
]
] | This research aims to consider a new principle of symmetry in the space-time by means of the elimination of the classical idea of rest including a universal minimum limit of speed in the subatomic world. Such a limit, unattainable by the particles, represents a preferred inertial reference frame associated with a cosmological background field that breaks Lorentz symmetry. So there emerges a modified relativistic dynamics with a minimum speed related to the Planck length of the early universe, which leads us to search for a quantum gravity at low energies. |
gr-qc/0203014 | Michele Vallisneri | Massimo Pauri and Michele Vallisneri | Ephemeral point-events: is there a last remnant of physical objectivity? | LaTeX, natbib, 34 pages. Final journal version | Dialogos 79, 263-303 (2002) | null | null | gr-qc | null | For the past two decades, Einstein's Hole Argument (which deals with the
apparent indeterminateness of general relativity due to the general covariance
of the field equations) and its resolution in terms of Leibniz equivalence (the
statement that Riemannian geometries related by active diffeomorphisms
represent the same physical solution) have been the starting point for a lively
philosophical debate on the objectivity of the point-events of space-time. It
seems that Leibniz equivalence makes it impossible to consider the points of
the space-time manifold as physically individuated without recourse to
dynamical individuating fields. Various authors have posited that the metric
field itself can be used in this way, but nobody so far has considered the
problem of explicitly distilling the metrical fingerprint of point-events from
the gauge-dependent components of the metric field. Working in the Hamiltonian
formulation of general relativity, and building on the results of Lusanna and
Pauri (2002), we show how Bergmann and Komar's intrinsic pseudo-coordinates
(based on the value of curvature invariants) can be used to provide a physical
individuation of point-events in terms of the true degrees of freedom (the
Dirac observables) of the gravitational field, and we suggest how this
conceptual individuation could in principle be implemented with a well-defined
empirical procedure. We argue from these results that point-events retain a
significant kind of physical objectivity.
| [
{
"created": "Mon, 4 Mar 2002 23:42:18 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Apr 2002 17:47:52 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Apr 2002 15:59:50 GMT",
"version": "v3"
},
{
"created": "Wed, 16 Oct 2002 18:52:59 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Pauri",
"Massimo",
""
],
[
"Vallisneri",
"Michele",
""
]
] | For the past two decades, Einstein's Hole Argument (which deals with the apparent indeterminateness of general relativity due to the general covariance of the field equations) and its resolution in terms of Leibniz equivalence (the statement that Riemannian geometries related by active diffeomorphisms represent the same physical solution) have been the starting point for a lively philosophical debate on the objectivity of the point-events of space-time. It seems that Leibniz equivalence makes it impossible to consider the points of the space-time manifold as physically individuated without recourse to dynamical individuating fields. Various authors have posited that the metric field itself can be used in this way, but nobody so far has considered the problem of explicitly distilling the metrical fingerprint of point-events from the gauge-dependent components of the metric field. Working in the Hamiltonian formulation of general relativity, and building on the results of Lusanna and Pauri (2002), we show how Bergmann and Komar's intrinsic pseudo-coordinates (based on the value of curvature invariants) can be used to provide a physical individuation of point-events in terms of the true degrees of freedom (the Dirac observables) of the gravitational field, and we suggest how this conceptual individuation could in principle be implemented with a well-defined empirical procedure. We argue from these results that point-events retain a significant kind of physical objectivity. |
1701.06271 | Alexey Golovnev | Alexey Golovnev, Tomi Koivisto, Marit Sandstad | On the covariance of teleparallel gravity theories | 14 pages; final version accepted by CQG | Classical and Quantum Gravity 34 (2017) 145013 | 10.1088/1361-6382/aa7830 | NORDITA-2017-11 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The basics of teleparallel gravity and its extensions are reviewed with
particular emphasis on the problem of Lorentz-breaking choice of connection in
pure-tetrad versions of the theories. Various possible ways to covariantise
such models are discussed. A by-product is a new form of $f(T)$ field
equations.
| [
{
"created": "Mon, 23 Jan 2017 06:08:43 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jan 2017 10:52:07 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Feb 2017 13:58:49 GMT",
"version": "v3"
},
{
"created": "Fri, 23 Jun 2017 10:36:08 GMT",
"version": "v4"
}
] | 2017-06-30 | [
[
"Golovnev",
"Alexey",
""
],
[
"Koivisto",
"Tomi",
""
],
[
"Sandstad",
"Marit",
""
]
] | The basics of teleparallel gravity and its extensions are reviewed with particular emphasis on the problem of Lorentz-breaking choice of connection in pure-tetrad versions of the theories. Various possible ways to covariantise such models are discussed. A by-product is a new form of $f(T)$ field equations. |
gr-qc/9409039 | Ahmed Hindawi | F. I. Mikhail, M. I. Wanas, E. I. Lashin, and Ahmed Hindawi | Spherically Symmetric Solutions in M\o ller's Tetrad Theory of
Gravitation | LaTeX2e with AMS-LaTeX 1.2, 8 pages | Gen.Rel.Grav.26:869-876,1994 | 10.1007/BF02107145 | null | gr-qc | null | The general solution of M\o ller's field equations in case of spherical
symmetry is derived. The previously obtained solutions are verified as special
cases of the general solution.
| [
{
"created": "Mon, 19 Sep 1994 15:58:03 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Feb 1995 18:50:09 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Feb 1995 23:02:12 GMT",
"version": "v3"
},
{
"created": "Tue, 7 Nov 1995 21:12:14 GMT",
"version": "v4"
},
{
"cr... | 2008-11-26 | [
[
"Mikhail",
"F. I.",
""
],
[
"Wanas",
"M. I.",
""
],
[
"Lashin",
"E. I.",
""
],
[
"Hindawi",
"Ahmed",
""
]
] | The general solution of M\o ller's field equations in case of spherical symmetry is derived. The previously obtained solutions are verified as special cases of the general solution. |
2111.11995 | Roldao da Rocha | Roldao da Rocha | Gravitational decoupling of generalized Horndeski hybrid stars | 35 pages, 10 figures | Eur. Phys. J. C 82 (2022) 34 | 10.1140/epjc/s10052-021-09971-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational decoupled compact polytropic hybrid stars are here addressed in
generalized Horndeski scalar-tensor gravity. Additional physical properties of
hybrid stars are scrutinized and discussed in the gravitational decoupling
setup. The asymptotic value of the mass function, the compactness, and the
effective radius of gravitational decoupled hybrid stars are studied for both
cases of a bosonic and a fermionic prevalent core. These quantities are
presented and discussed as functions of Horndeski parameters, the decoupling
parameter, the adiabatic index, and the polytropic constant. Important
corrections to general relativity and generalized Horndeski scalar-tensor
gravity, induced by the gravitational decoupling, comply with available
observational data. Particular cases involving white dwarfs, boson stellar
configurations, neutron stars, and Einstein-Klein-Gordon solutions, formulated
in the gravitational decoupling context, are also scrutinized.
| [
{
"created": "Tue, 23 Nov 2021 16:51:30 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jan 2022 13:16:19 GMT",
"version": "v2"
}
] | 2022-01-14 | [
[
"da Rocha",
"Roldao",
""
]
] | Gravitational decoupled compact polytropic hybrid stars are here addressed in generalized Horndeski scalar-tensor gravity. Additional physical properties of hybrid stars are scrutinized and discussed in the gravitational decoupling setup. The asymptotic value of the mass function, the compactness, and the effective radius of gravitational decoupled hybrid stars are studied for both cases of a bosonic and a fermionic prevalent core. These quantities are presented and discussed as functions of Horndeski parameters, the decoupling parameter, the adiabatic index, and the polytropic constant. Important corrections to general relativity and generalized Horndeski scalar-tensor gravity, induced by the gravitational decoupling, comply with available observational data. Particular cases involving white dwarfs, boson stellar configurations, neutron stars, and Einstein-Klein-Gordon solutions, formulated in the gravitational decoupling context, are also scrutinized. |
gr-qc/9601031 | Andrew M. Abrahams | A.M. Abrahams and J.W. York, Jr | 3+1 General Relativity in Hyperbolic Form | 15 pages, latex, 2 figures | null | null | null | gr-qc | null | This paper focuses on the imposition of boundary conditions for numerical
relativity simulations of black holes. This issue is used to motivate the
discussion of a new hyperbolic formulation of 3+1 general relativity. The paper
will appear in the Proceedings of the Les Houches School on Astrophysical
Sources of Gravitational Radiation, 1995, edited by J.-A. Marck and J.-P.
Lasota to be published by Springer-Verlag.
| [
{
"created": "Sat, 20 Jan 1996 22:15:56 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Abrahams",
"A. M.",
""
],
[
"York,",
"J. W.",
"Jr"
]
] | This paper focuses on the imposition of boundary conditions for numerical relativity simulations of black holes. This issue is used to motivate the discussion of a new hyperbolic formulation of 3+1 general relativity. The paper will appear in the Proceedings of the Les Houches School on Astrophysical Sources of Gravitational Radiation, 1995, edited by J.-A. Marck and J.-P. Lasota to be published by Springer-Verlag. |
1611.04044 | Sina Bahrami | Sina Bahrami | Saturating The Bekenstein-Hawking Entropy Bound With Initial Data Sets
For Gravitational Collapse | null | Phys. Rev. D 95, 026006 (2017) | 10.1103/PhysRevD.95.026006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is possible to find initial states for gravitational collapse whose
entropy approximately saturates the Bekenstein-Hawking entropy of the final
black hole. The prototypical example of such a state is that envisaged by Zurek
and Thorne, and also by Susskind: for a black hole of mass $\sim M$ , a number
$\sim M^2$ of quanta with energies of order $1/M$ are accreted on a timescale
of order $\sim M^3$, an approximate time-reverse of Hawking evaporation. There
is lore that all initial states which saturate the Bekenstein-Hawking entropy
must involve a formation timescale of this order, $M^3$ , and not the much
shorter dynamical timescale $M$ . Counterexamples to this lore have been found
by Sorkin, Wald and Zhang, and also by Hsu and Reeb, in the form of
semiclassical initial data sets. However the spacetimes that correspond to
these counterexamples possess white holes in the past, as well as black holes
in the future, which casts doubt on their physical relevance. We modify the
counterexamples to eliminate the white holes, yielding formation timescales of
order $M^2$ , and argue that the lore is unfounded.
| [
{
"created": "Sat, 12 Nov 2016 21:25:31 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Dec 2016 03:03:50 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Feb 2017 02:30:57 GMT",
"version": "v3"
}
] | 2017-02-08 | [
[
"Bahrami",
"Sina",
""
]
] | It is possible to find initial states for gravitational collapse whose entropy approximately saturates the Bekenstein-Hawking entropy of the final black hole. The prototypical example of such a state is that envisaged by Zurek and Thorne, and also by Susskind: for a black hole of mass $\sim M$ , a number $\sim M^2$ of quanta with energies of order $1/M$ are accreted on a timescale of order $\sim M^3$, an approximate time-reverse of Hawking evaporation. There is lore that all initial states which saturate the Bekenstein-Hawking entropy must involve a formation timescale of this order, $M^3$ , and not the much shorter dynamical timescale $M$ . Counterexamples to this lore have been found by Sorkin, Wald and Zhang, and also by Hsu and Reeb, in the form of semiclassical initial data sets. However the spacetimes that correspond to these counterexamples possess white holes in the past, as well as black holes in the future, which casts doubt on their physical relevance. We modify the counterexamples to eliminate the white holes, yielding formation timescales of order $M^2$ , and argue that the lore is unfounded. |
2112.00311 | Hideki Asada | Keita Takizawa, Hideki Asada | Gravitational lens on de-Sitter background | 12 pages, 8 figures, typos corrected, 2 references added, accepted
for PRD | Phys. Rev. D 105, 084022 (2022) | 10.1103/PhysRevD.105.084022 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Gravitational lenses are examined in de-Sitter (dS) background, for which the
existence of the dS horizon is taken into account and hyperbolic trigonometry
is used together with the hyperbolic angular diameter distance. Spherical
trigonometry is used to discuss a gravitational lens in anti-de Sitter (AdS)
background. The difference in the form among the dS/AdS lens equations and the
exact lens equation in Minkowski background begins at the third order, when a
small angle approximation is used in terms of lens and source planes. The
angular separation of lensed images is decreased by the third-order deviation
in the dS lens equation, while it is increased in AdS. In the present framework
on the dS/AdS backgrounds, we discuss also the deflection angle of light, which
does not include any term of purely the cosmological constant. Despite the
different geometry, the deflection angle of light rays in hyperbolic and
spherical geometry can take the same form. Through a coupling of the
cosmological constant with lens mass, the separation angle of multiple images
is larger (smaller) in dS (AdS) than in the flat case, for a given mass, source
direction, and angular diameter distances among the lens, receiver and source.
| [
{
"created": "Wed, 1 Dec 2021 07:08:34 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2022 00:14:02 GMT",
"version": "v2"
}
] | 2022-06-08 | [
[
"Takizawa",
"Keita",
""
],
[
"Asada",
"Hideki",
""
]
] | Gravitational lenses are examined in de-Sitter (dS) background, for which the existence of the dS horizon is taken into account and hyperbolic trigonometry is used together with the hyperbolic angular diameter distance. Spherical trigonometry is used to discuss a gravitational lens in anti-de Sitter (AdS) background. The difference in the form among the dS/AdS lens equations and the exact lens equation in Minkowski background begins at the third order, when a small angle approximation is used in terms of lens and source planes. The angular separation of lensed images is decreased by the third-order deviation in the dS lens equation, while it is increased in AdS. In the present framework on the dS/AdS backgrounds, we discuss also the deflection angle of light, which does not include any term of purely the cosmological constant. Despite the different geometry, the deflection angle of light rays in hyperbolic and spherical geometry can take the same form. Through a coupling of the cosmological constant with lens mass, the separation angle of multiple images is larger (smaller) in dS (AdS) than in the flat case, for a given mass, source direction, and angular diameter distances among the lens, receiver and source. |
2203.01919 | David Kubiznak | David Kubiznak, Tayebeh Tahamtan, Otakar Svitek | Slowly rotating black holes in nonlinear electrodynamics | 11 pages, no figures v3: slightly extended version, added references | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how (at least in principle) one can construct electrically and
magnetically charged slowly rotating black hole solutions coupled to non-linear
electrodynamics (NLE). Our generalized Lense-Thirring ansatz is, apart from the
static metric function $f$ and the electrostatic potential $\phi$ inherited
from the corresponding spherical solution, characterized by two new functions
$h$ (in the metric) and $\omega$ (in the vector potential) encoding the effect
of rotation. In the linear Maxwell case, the rotating solutions are completely
characterized by static solution, featuring $h=(f-1)/r^2$ and $\omega=1$. We
show that when the first is imposed, the ansatz is inconsistent with any
restricted (see below) NLE but the Maxwell electrodynamics. In particular, this
implies that the (standard) Newman-Janis algorithm cannot be used to generate
rotating solutions for any restricted non-trivial NLE. We present a few
explicit examples of slowly rotating solutions in particular models of NLE, as
well as briefly discuss the NLE charged Taub-NUT spacetimes.
| [
{
"created": "Thu, 3 Mar 2022 18:52:27 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2022 09:53:07 GMT",
"version": "v2"
},
{
"created": "Thu, 12 May 2022 10:05:34 GMT",
"version": "v3"
}
] | 2022-05-13 | [
[
"Kubiznak",
"David",
""
],
[
"Tahamtan",
"Tayebeh",
""
],
[
"Svitek",
"Otakar",
""
]
] | We show how (at least in principle) one can construct electrically and magnetically charged slowly rotating black hole solutions coupled to non-linear electrodynamics (NLE). Our generalized Lense-Thirring ansatz is, apart from the static metric function $f$ and the electrostatic potential $\phi$ inherited from the corresponding spherical solution, characterized by two new functions $h$ (in the metric) and $\omega$ (in the vector potential) encoding the effect of rotation. In the linear Maxwell case, the rotating solutions are completely characterized by static solution, featuring $h=(f-1)/r^2$ and $\omega=1$. We show that when the first is imposed, the ansatz is inconsistent with any restricted (see below) NLE but the Maxwell electrodynamics. In particular, this implies that the (standard) Newman-Janis algorithm cannot be used to generate rotating solutions for any restricted non-trivial NLE. We present a few explicit examples of slowly rotating solutions in particular models of NLE, as well as briefly discuss the NLE charged Taub-NUT spacetimes. |
2312.11433 | David McNutt | C. Brown, M. Gorban, W. Julius, R. Radhakrishnan, G. Cleaver, and D.
McNutt | Killing Invariants: An approach to the sub-classification of geometries
with symmetry | 11 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In principle, the local classification of spacetimes is always possible using
the Cartan-Karlhede algorithm. However, in practice, the process of determining
equivalence of two spacetimes is potentially computationally difficult or not
at all possible. This difficulty will arise whenever the classifying invariants
are either high-degree rational functions or depend on transcendental functions
without standard inverses. In the case that spacetimes admit Killing vectors
with non-trivial orbits, we propose a new set of invariant quantities, called
Killing invariants. These invariants will allow for the sub-classification of
spacetimes admitting the same group of symmetries and will, in principle, be
substantially less complicated than any other known set. We apply this approach
to the class of static spherically symmetric geometries as an illustrative
example.
| [
{
"created": "Mon, 18 Dec 2023 18:34:58 GMT",
"version": "v1"
}
] | 2023-12-19 | [
[
"Brown",
"C.",
""
],
[
"Gorban",
"M.",
""
],
[
"Julius",
"W.",
""
],
[
"Radhakrishnan",
"R.",
""
],
[
"Cleaver",
"G.",
""
],
[
"McNutt",
"D.",
""
]
] | In principle, the local classification of spacetimes is always possible using the Cartan-Karlhede algorithm. However, in practice, the process of determining equivalence of two spacetimes is potentially computationally difficult or not at all possible. This difficulty will arise whenever the classifying invariants are either high-degree rational functions or depend on transcendental functions without standard inverses. In the case that spacetimes admit Killing vectors with non-trivial orbits, we propose a new set of invariant quantities, called Killing invariants. These invariants will allow for the sub-classification of spacetimes admitting the same group of symmetries and will, in principle, be substantially less complicated than any other known set. We apply this approach to the class of static spherically symmetric geometries as an illustrative example. |
1904.12803 | Daniel Kabat | Lam Hui, Daniel Kabat, Xinyu Li, Luca Santoni, Sam S. C. Wong | Black Hole Hair from Scalar Dark Matter | 34 pages. v2: references added, link to animation fixed. v3: minor
changes, more references, version to appear in JCAP | null | 10.1088/1475-7516/2019/06/038 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a black hole surrounded by scalar dark matter develops scalar
hair. This is the generalization of a phenomenon pointed out by Jacobson, that
a minimally coupled scalar with a non-trivial time dependence far away from the
black hole would endow the black hole with hair. In our case, the time
dependence arises from the oscillation of a scalar field with a non-zero mass.
We systematically explore the scalar profile around the black hole for
different scalar masses. In the small mass limit, the scalar field has a $1/r$
component at large radius $r$, consistent with Jacobson's result. In the large
mass limit (with the Compton wavelength of order of the horizon or smaller),
the scalar field has a $1/r^{3/4}$ profile yielding a pile-up close to the
horizon, while distinctive nodes occur for intermediate masses. Thus, the dark
matter profile around a black hole, while challenging to measure, contains
information about the dark matter particle mass. As an application, we consider
the case of the supermassive black hole at the center of M87, recently imaged
by the Event Horizon Telescope. Its horizon size is roughly the Compton
wavelength of a scalar particle of mass $10^{-20}$ eV. We consider the
implications of the expected scalar pile-up close to the horizon, for fuzzy
dark matter at a mass of $10^{-20}$ eV or below.
| [
{
"created": "Mon, 29 Apr 2019 16:33:34 GMT",
"version": "v1"
},
{
"created": "Wed, 8 May 2019 19:42:17 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Jun 2019 16:39:58 GMT",
"version": "v3"
}
] | 2019-06-26 | [
[
"Hui",
"Lam",
""
],
[
"Kabat",
"Daniel",
""
],
[
"Li",
"Xinyu",
""
],
[
"Santoni",
"Luca",
""
],
[
"Wong",
"Sam S. C.",
""
]
] | We show that a black hole surrounded by scalar dark matter develops scalar hair. This is the generalization of a phenomenon pointed out by Jacobson, that a minimally coupled scalar with a non-trivial time dependence far away from the black hole would endow the black hole with hair. In our case, the time dependence arises from the oscillation of a scalar field with a non-zero mass. We systematically explore the scalar profile around the black hole for different scalar masses. In the small mass limit, the scalar field has a $1/r$ component at large radius $r$, consistent with Jacobson's result. In the large mass limit (with the Compton wavelength of order of the horizon or smaller), the scalar field has a $1/r^{3/4}$ profile yielding a pile-up close to the horizon, while distinctive nodes occur for intermediate masses. Thus, the dark matter profile around a black hole, while challenging to measure, contains information about the dark matter particle mass. As an application, we consider the case of the supermassive black hole at the center of M87, recently imaged by the Event Horizon Telescope. Its horizon size is roughly the Compton wavelength of a scalar particle of mass $10^{-20}$ eV. We consider the implications of the expected scalar pile-up close to the horizon, for fuzzy dark matter at a mass of $10^{-20}$ eV or below. |
1807.01995 | Alessandro Casalino | Alessandro Casalino and Massimiliano Rinaldi | Testing Horndeski gravity as dark matter with $\texttt{hi_class}$ | 23 pages, 18 figures. References added, minor corrections, version
accepted for publication in Physics of The Dark Universe | Physics of the Dark Universe 23 (2019) 100243 | 10.1016/j.dark.2018.11.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a model of dark matter fluid based on a sector of Horndeski
gravity. The model is very successful, at the background level, in reproducing
the evolution of the Universe from early times to today. However, at the
perturbative level the model fails. To show this, we use the code
$\texttt{hi_class}$ and we compute the matter power spectrum and the cosmic
microwave background spectrum. Our results confirm, in a new and independent
way, that this sector of Horndeski gravity is not viable, in agreement with the
recent constraints coming from the measurement of the speed of gravitational
waves obtained from the observation of the neutron star merger event GW170817.
| [
{
"created": "Wed, 4 Jul 2018 09:16:21 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jul 2018 11:09:31 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Nov 2018 18:41:31 GMT",
"version": "v3"
}
] | 2019-01-10 | [
[
"Casalino",
"Alessandro",
""
],
[
"Rinaldi",
"Massimiliano",
""
]
] | We consider a model of dark matter fluid based on a sector of Horndeski gravity. The model is very successful, at the background level, in reproducing the evolution of the Universe from early times to today. However, at the perturbative level the model fails. To show this, we use the code $\texttt{hi_class}$ and we compute the matter power spectrum and the cosmic microwave background spectrum. Our results confirm, in a new and independent way, that this sector of Horndeski gravity is not viable, in agreement with the recent constraints coming from the measurement of the speed of gravitational waves obtained from the observation of the neutron star merger event GW170817. |
1710.04660 | Ivica Smoli\'c | Luka Gulin, Ivica Smoli\'c | Generalizations of the Smarr formula for black holes with nonlinear
electromagnetic fields | 20 pages, v3: slightly revised, published version | Class. Quantum Grav. 35 (2018) 025015 | 10.1088/1361-6382/aa9dfd | ZTF-EP-17-09 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a direct, geometric derivation of the generalized Smarr formula
for the stationary axially symmetric black holes with nonlinear electromagnetic
fields. The additional term is proven to be proportional to the integral of the
trace of the electromagnetic energy-momentum tensor and can be written as a
product of two conjugate variables. From the novel relation we can deduce all
previously proposed forms of the generalized Smarr formula, which were derived
only for the spherically symmetric black holes, and provide the lowest order
quantum correction to the classical relation from the Euler-Heisenberg
Lagrangian.
| [
{
"created": "Thu, 12 Oct 2017 18:00:00 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Oct 2017 18:00:06 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Jan 2018 19:22:44 GMT",
"version": "v3"
}
] | 2018-01-08 | [
[
"Gulin",
"Luka",
""
],
[
"Smolić",
"Ivica",
""
]
] | We present a direct, geometric derivation of the generalized Smarr formula for the stationary axially symmetric black holes with nonlinear electromagnetic fields. The additional term is proven to be proportional to the integral of the trace of the electromagnetic energy-momentum tensor and can be written as a product of two conjugate variables. From the novel relation we can deduce all previously proposed forms of the generalized Smarr formula, which were derived only for the spherically symmetric black holes, and provide the lowest order quantum correction to the classical relation from the Euler-Heisenberg Lagrangian. |
0809.4113 | Eduardo D\'iaz-Miguel | Eduardo D\'iaz-Miguel | The local deflection of light | 4 latex pages, 1 eps figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have derived the relationship between the radial proper distance, h, and
the polar angle, phi, for a light ray that is emitted and travels in the
neighborhood of the Earth's surface. General relativity predicts that, even
locally, the equation which relates these two physical magnitudes differs from
the one stated by the principle of equivalence. More precisely, we have proved
that, in the weak field limit, the local physical trajectory, h=h(phi), is the
one that would correspond to a massive Newtonian particle in a field two times
greater. Therefore, and contrary to the generally accepted fact, the principle
of equivalence gives only 1/2 part of the general relativity local deflection
of light.
| [
{
"created": "Wed, 24 Sep 2008 07:44:23 GMT",
"version": "v1"
}
] | 2008-09-25 | [
[
"Díaz-Miguel",
"Eduardo",
""
]
] | We have derived the relationship between the radial proper distance, h, and the polar angle, phi, for a light ray that is emitted and travels in the neighborhood of the Earth's surface. General relativity predicts that, even locally, the equation which relates these two physical magnitudes differs from the one stated by the principle of equivalence. More precisely, we have proved that, in the weak field limit, the local physical trajectory, h=h(phi), is the one that would correspond to a massive Newtonian particle in a field two times greater. Therefore, and contrary to the generally accepted fact, the principle of equivalence gives only 1/2 part of the general relativity local deflection of light. |
1311.3912 | Stanley P. Gudder | Stan Gudder | A covariant causal set approach to discrete quantum gravity | 23 pages, 6 tables; new version corrects some typos in the proof of
Theorem 6.1 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant causal set (c-causet) is a causal set that is invariant under
labeling. Such causets are well-behaved and have a rigid geometry that is
determined by a sequence of positive integers called the shell sequence. We
first consider the microscopic picture. In this picture, the vertices of a
c-causet have integer labels that are unique up to a label isomorphism. This
labeling enables us to define a natural metric $d(a,b)$ between time-like
separated vertices $a$ and $b$. The time metric $d(a,b)$ results in a natural
definition of a geodesic from $a$ to $b$. It turns out that there can be $n\ge
1$ such geodesics. Letting $a$ be the origin (the big bang), we define the
curvature $K(b)$ of $b$ to be $n-1$. Assuming that particles tend to move along
geodesics, $K(b)$ gives the tendency that vertex $b$ is occupied. In this way,
the mass distribution is determined by the geometry of the c-causet. We next
consider the macroscopic picture which describes the growth process of
c-causets. We propose that this process is governed by a quantum dynamics given
by complex amplitudes. At present, these amplitudes are unknown. But if they
can be found, they will determine the (approximate) geometry of the c-causet
describing our particular universe. As an illustration, we present a simple
example of an amplitude process that may have physical relevance. We also give
a discrete analogue of Einstein's field equations.
| [
{
"created": "Fri, 15 Nov 2013 16:34:24 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Nov 2013 00:49:00 GMT",
"version": "v2"
}
] | 2013-11-26 | [
[
"Gudder",
"Stan",
""
]
] | A covariant causal set (c-causet) is a causal set that is invariant under labeling. Such causets are well-behaved and have a rigid geometry that is determined by a sequence of positive integers called the shell sequence. We first consider the microscopic picture. In this picture, the vertices of a c-causet have integer labels that are unique up to a label isomorphism. This labeling enables us to define a natural metric $d(a,b)$ between time-like separated vertices $a$ and $b$. The time metric $d(a,b)$ results in a natural definition of a geodesic from $a$ to $b$. It turns out that there can be $n\ge 1$ such geodesics. Letting $a$ be the origin (the big bang), we define the curvature $K(b)$ of $b$ to be $n-1$. Assuming that particles tend to move along geodesics, $K(b)$ gives the tendency that vertex $b$ is occupied. In this way, the mass distribution is determined by the geometry of the c-causet. We next consider the macroscopic picture which describes the growth process of c-causets. We propose that this process is governed by a quantum dynamics given by complex amplitudes. At present, these amplitudes are unknown. But if they can be found, they will determine the (approximate) geometry of the c-causet describing our particular universe. As an illustration, we present a simple example of an amplitude process that may have physical relevance. We also give a discrete analogue of Einstein's field equations. |
2007.10601 | Rodrigo Lipparelli Fernandez | Rodrigo L. Fernandez | Cosmic Censorship Conjecture violation: A semiclassical approach | 80 pages, 25 figures, accepted PhD Thesis (Instituto de F\'isica,
UFRJ). Chapter 4 originated article published in arXiv:2007.06766 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Cosmic Censorship Conjecture (CCC) states that every singularity (except
the cosmological one) must appear "dressed" in the universe. This statement was
introduced by Roger Penrose (Penrose, 1969), meaning that every singularity
(except the Big Bang) in the universe must be hidden inside an Event Horizon.
Mathematically, this is described by the inequality $M^2 \geqslant Q^2 + a^2$
(in geometrized unit system), with $M$ being the mass of the black hole, $Q$
its charge and $a := J/M$ its specific angular momentum. Essentially, this
three quantities determines uniquely a black hole, as stated by the no-hair
theorem. We study the emission probability of a massive ($m_w$) uncharged
scalar wave packet, a semi-classical approximation for a particle, by a static,
charged black hole. We show that for a few values of the mass $\mathcal{M} :=
M+\delta M$ (where $M$ is the fixed value for the mass and $\delta M$ being a
small variation to $M$ in the order of $m_w$) with different values for $\delta
M$ and fixed charge $Q$ for the black hole, the emission probability tends to
zero once the Cosmic Censorship Conjecture is close to be violated, that is,
when the emitted packet is such that the new quantity $\mathcal{M}' :=
\mathcal{M}-m_w$ would violate the inequality $\mathcal{M}' > Q$.
| [
{
"created": "Tue, 21 Jul 2020 05:07:41 GMT",
"version": "v1"
}
] | 2020-07-22 | [
[
"Fernandez",
"Rodrigo L.",
""
]
] | The Cosmic Censorship Conjecture (CCC) states that every singularity (except the cosmological one) must appear "dressed" in the universe. This statement was introduced by Roger Penrose (Penrose, 1969), meaning that every singularity (except the Big Bang) in the universe must be hidden inside an Event Horizon. Mathematically, this is described by the inequality $M^2 \geqslant Q^2 + a^2$ (in geometrized unit system), with $M$ being the mass of the black hole, $Q$ its charge and $a := J/M$ its specific angular momentum. Essentially, this three quantities determines uniquely a black hole, as stated by the no-hair theorem. We study the emission probability of a massive ($m_w$) uncharged scalar wave packet, a semi-classical approximation for a particle, by a static, charged black hole. We show that for a few values of the mass $\mathcal{M} := M+\delta M$ (where $M$ is the fixed value for the mass and $\delta M$ being a small variation to $M$ in the order of $m_w$) with different values for $\delta M$ and fixed charge $Q$ for the black hole, the emission probability tends to zero once the Cosmic Censorship Conjecture is close to be violated, that is, when the emitted packet is such that the new quantity $\mathcal{M}' := \mathcal{M}-m_w$ would violate the inequality $\mathcal{M}' > Q$. |
gr-qc/9504019 | Bill Hiscock | Paul R. Anderson (Wake Forest University), William A. Hiscock and
Daniel J. Loranz (Montana State University) | Semiclassical Stability of the Extreme Reissner-Nordstrom Black Hole | 10 pages, REVTeX, 4 figures in separate uuencoded compressed file | Phys.Rev.Lett.74:4365-4368,1995 | 10.1103/PhysRevLett.74.4365 | null | gr-qc hep-th | null | The stress-energy tensor of a free quantized scalar field is calculated in
the extreme Reissner-Nordstr\"{o}m black hole spacetime in the zero temperature
vacuum state. The stress-energy appears to be regular on the event horizon,
contrary to the suggestion provided by two-dimensional calculations. An
analytic calculation on the event horizon for a thermal state shows that if the
temperature is nonzero then the stress-energy diverges strongly there.
| [
{
"created": "Thu, 13 Apr 1995 19:43:49 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Anderson",
"Paul R.",
"",
"Wake Forest University"
],
[
"Hiscock",
"William A.",
"",
"Montana State University"
],
[
"Loranz",
"Daniel J.",
"",
"Montana State University"
]
] | The stress-energy tensor of a free quantized scalar field is calculated in the extreme Reissner-Nordstr\"{o}m black hole spacetime in the zero temperature vacuum state. The stress-energy appears to be regular on the event horizon, contrary to the suggestion provided by two-dimensional calculations. An analytic calculation on the event horizon for a thermal state shows that if the temperature is nonzero then the stress-energy diverges strongly there. |
gr-qc/9507028 | Don N. Page | Don N. Page (University of Alberta, Edmonton, Canada) | Quantum Cosmology Lectures | LaTeX, 18 pages, lectures at the First Mexican School on Gravitation
and Mathematical Physics, December 12-16, 1994 | null | null | Alberta-Thy-15-95 | gr-qc | null | Quantum cosmology is the quantum theory of the entire universe. Although
strange at first sight, it is appropriate because (1) our world appears to be
fundamentally quantum, (2) the classical description of gravity breaks down at
singularities it would give at the beginning of the universe, and (3) our
universe has many properties that cannot be explained by a classical
description of them. A quantum state of the universe should obey certain
constraints, such as the Wheeler-DeWitt equations. One approach to interpreting
such a state is {\it Sensible Quantum Mechanics} (SQM), in which nothing is
probabilistic, except, in a certain frequency sense, conscious perceptions.
Sets of these perceptions can be deterministically realized with measures given
by expectation values of positive-operator-valued {\it awareness operators}.
These may be defined even when the quantum state itself is not normalizable,
though there still seem to be problems of divergences when one has an infinite
amount of inflation, producing infinitely large spatial volumes with presumably
infinite measures of perceptions. Ratios of the measures for sets of
perceptions (if finite) can be interpreted as frequency-type probabilities for
many actually existing sets rather than as propensities for potentialities to
be actualized, so there is nothing indeterministic in a specific SQM. One can
do a Bayesian analysis to test between different specific SQMs. One can also
make statistical predictions of what one might perceive within a specific SQM
by invoking the {\it Conditional Aesthemic Principle}: among the set of all
conscious perceptions, our perceptions are likely to be typical.
| [
{
"created": "Fri, 14 Jul 1995 00:26:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Page",
"Don N.",
"",
"University of Alberta, Edmonton, Canada"
]
] | Quantum cosmology is the quantum theory of the entire universe. Although strange at first sight, it is appropriate because (1) our world appears to be fundamentally quantum, (2) the classical description of gravity breaks down at singularities it would give at the beginning of the universe, and (3) our universe has many properties that cannot be explained by a classical description of them. A quantum state of the universe should obey certain constraints, such as the Wheeler-DeWitt equations. One approach to interpreting such a state is {\it Sensible Quantum Mechanics} (SQM), in which nothing is probabilistic, except, in a certain frequency sense, conscious perceptions. Sets of these perceptions can be deterministically realized with measures given by expectation values of positive-operator-valued {\it awareness operators}. These may be defined even when the quantum state itself is not normalizable, though there still seem to be problems of divergences when one has an infinite amount of inflation, producing infinitely large spatial volumes with presumably infinite measures of perceptions. Ratios of the measures for sets of perceptions (if finite) can be interpreted as frequency-type probabilities for many actually existing sets rather than as propensities for potentialities to be actualized, so there is nothing indeterministic in a specific SQM. One can do a Bayesian analysis to test between different specific SQMs. One can also make statistical predictions of what one might perceive within a specific SQM by invoking the {\it Conditional Aesthemic Principle}: among the set of all conscious perceptions, our perceptions are likely to be typical. |
0707.1122 | Rituparno Goswami | Rituparno Goswami | Gravitational collapse of dustlike matter with heat flux | 5 pages, Revtex4, 2 figures | null | null | null | gr-qc astro-ph hep-th | null | We present a new class of solutions to Einstein equations for the spherical
collapse of dustlike matter coupled with heat flux. In this family of solutions
spacetime shear is necessarily non-zero. Also these solutions have an
interesting property that there is always a bounce before the singularity,
which is caused entirely due to the dissipative processes. We show there exist
open sets of initial data for which the bounce occurs before any trapped
surface formation, making the star explode away to infinity. We also discuss
the role of heat flow in generating spacetime shear and in modifying the
effective inertial mass of the matter cloud.
| [
{
"created": "Mon, 9 Jul 2007 19:37:52 GMT",
"version": "v1"
}
] | 2007-07-11 | [
[
"Goswami",
"Rituparno",
""
]
] | We present a new class of solutions to Einstein equations for the spherical collapse of dustlike matter coupled with heat flux. In this family of solutions spacetime shear is necessarily non-zero. Also these solutions have an interesting property that there is always a bounce before the singularity, which is caused entirely due to the dissipative processes. We show there exist open sets of initial data for which the bounce occurs before any trapped surface formation, making the star explode away to infinity. We also discuss the role of heat flow in generating spacetime shear and in modifying the effective inertial mass of the matter cloud. |
1610.05299 | Alessia Platania | Alfio Bonanno, Benjamin Koch, Alessia Platania | Cosmic Censorship in Quantum Einstein Gravity | 10 pages, 6 figures; v3: version accepted for publication in CQG | null | 10.1088/1361-6382/aa6788 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum gravity modification of the Kuroda-Papapetrou model
induced by the running of the Newton's constant at high energy in Quantum
Einstein Gravity. We argue that although the antiscreening character of the
gravitational interaction favours the formation of a naked singularity, quantum
gravity effects turn the classical singularity into a "whimper" singularity
which remains naked for a finite amount of advanced time.
| [
{
"created": "Mon, 17 Oct 2016 20:00:00 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2017 19:00:00 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Apr 2017 18:00:00 GMT",
"version": "v3"
}
] | 2017-04-11 | [
[
"Bonanno",
"Alfio",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Platania",
"Alessia",
""
]
] | We study the quantum gravity modification of the Kuroda-Papapetrou model induced by the running of the Newton's constant at high energy in Quantum Einstein Gravity. We argue that although the antiscreening character of the gravitational interaction favours the formation of a naked singularity, quantum gravity effects turn the classical singularity into a "whimper" singularity which remains naked for a finite amount of advanced time. |
1312.5843 | Masahiro Shimano | Masahiro Shimano and Umpei Miyamoto | Naked singularity explosion in higher-dimensional dust collapse | 21 pages, 4 figures, accepted for publication in CQG | null | 10.1088/0264-9381/31/4/045002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of the large extra dimensions or TeV-scale gravity, it has
been argued that an effective naked singularity, called the visible border of
spacetime, would be generated by high-energy particle collisions. Motivated by
this interesting possibility, we investigate a particle creation by a naked
singularity in general dimensions, adopting a spherically symmetric
self-similar dust collapse as the simple model of a naked singularity
formation. The power and energy of the particle emission behave in two distinct
ways depending on a parameter in the model. In a generic case, the emission
power is proportional to the quadratic inverse of the remaining time to the
Cauchy horizon, which has been known for the four-dimensional case in the
literature. On the other hand, in a degenerate case the emission power is
proportional to the quartic inverse of the remaining time to the Cauchy
horizon, and depends on the total mass of a dust fluid in spite that the
central region of the collapse is scale-free due to the self-similarity. In the
both cases, within a test-field approximation the energy radiated before any
quantum gravitational effect dominates amounts to TeV. This suggests that a
backreaction is not ignorable in the TeV-scale gravity context, in contrast to
the similar phenomena in stellar collapse.
| [
{
"created": "Fri, 20 Dec 2013 08:14:35 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Shimano",
"Masahiro",
""
],
[
"Miyamoto",
"Umpei",
""
]
] | In the context of the large extra dimensions or TeV-scale gravity, it has been argued that an effective naked singularity, called the visible border of spacetime, would be generated by high-energy particle collisions. Motivated by this interesting possibility, we investigate a particle creation by a naked singularity in general dimensions, adopting a spherically symmetric self-similar dust collapse as the simple model of a naked singularity formation. The power and energy of the particle emission behave in two distinct ways depending on a parameter in the model. In a generic case, the emission power is proportional to the quadratic inverse of the remaining time to the Cauchy horizon, which has been known for the four-dimensional case in the literature. On the other hand, in a degenerate case the emission power is proportional to the quartic inverse of the remaining time to the Cauchy horizon, and depends on the total mass of a dust fluid in spite that the central region of the collapse is scale-free due to the self-similarity. In the both cases, within a test-field approximation the energy radiated before any quantum gravitational effect dominates amounts to TeV. This suggests that a backreaction is not ignorable in the TeV-scale gravity context, in contrast to the similar phenomena in stellar collapse. |
2405.07313 | Wenbin Lin | Yiknag Xiao, Wenbin Lin | Scattering cross section of the long gravitino wave in Schwarzschild
spacetime | 10 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The scattering problem of the gravitino wave in Schwarzschild spacetime is
explored. We employ the perturbative method to calculate the differential
scattering cross section in the long wavelength limit, and demonstrate that it
satisfies the same rule of the spin dependance as those of the scalar,
neutrino, electromagnetic waves.
| [
{
"created": "Sun, 12 May 2024 15:48:12 GMT",
"version": "v1"
}
] | 2024-05-14 | [
[
"Xiao",
"Yiknag",
""
],
[
"Lin",
"Wenbin",
""
]
] | The scattering problem of the gravitino wave in Schwarzschild spacetime is explored. We employ the perturbative method to calculate the differential scattering cross section in the long wavelength limit, and demonstrate that it satisfies the same rule of the spin dependance as those of the scalar, neutrino, electromagnetic waves. |
gr-qc/9807070 | Nikolaos Mavromatos | Nick E. Mavromatos and Richard J. Szabo | Spacetime Quantization from Non-abelian D-particle Dynamics | 8 pages LATEX, one eps figure incorporated | Phys.Rev. D59 (1999) 064016 | 10.1103/PhysRevD.59.064016 | OUTP-98-56P | gr-qc hep-th | null | We describe the short-distance properties of the spacetime of a system of
D-particles by viewing their matrix-valued coordinates as coupling constants of
a deformed worldsheet $\sigma$-model. We show that the Zamolodchikov metric on
the associated moduli space naturally encodes properties of the non-abelian
dynamics, and from this we derive new spacetime uncertainty relations directly
from the quantum string theory. The non-abelian uncertainties exhibit
decoherence effects which suggest the interplay of quantum gravity in multiple
D-particle dynamics.
| [
{
"created": "Sat, 25 Jul 1998 15:39:59 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mavromatos",
"Nick E.",
""
],
[
"Szabo",
"Richard J.",
""
]
] | We describe the short-distance properties of the spacetime of a system of D-particles by viewing their matrix-valued coordinates as coupling constants of a deformed worldsheet $\sigma$-model. We show that the Zamolodchikov metric on the associated moduli space naturally encodes properties of the non-abelian dynamics, and from this we derive new spacetime uncertainty relations directly from the quantum string theory. The non-abelian uncertainties exhibit decoherence effects which suggest the interplay of quantum gravity in multiple D-particle dynamics. |
1706.07658 | George Pappas Dr | Kostas Glampedakis, George Pappas, Hector O. Silva, Emanuele Berti | Post-Kerr black hole spectroscopy | null | Phys. Rev. D 96, 064054 (2017) | 10.1103/PhysRevD.96.064054 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the central goals of the newborn field of gravitational wave astronomy
is to test gravity in the highly nonlinear, strong field regime characterizing
the spacetime of black holes. In particular, "black hole spectroscopy" (the
observation and identification of black hole quasinormal mode frequencies in
the gravitational wave signal) is expected to become one of the main tools for
probing the structure and dynamics of Kerr black holes. In this paper we take a
significant step towards that goal by constructing a "post-Kerr" quasinormal
mode formalism. The formalism incorporates a parametrized but general
perturbative deviation from the Kerr metric and exploits the well-established
connection between the properties of the spacetime's circular null geodesics
and the fundamental quasinormal mode to provide approximate, eikonal limit
formulae for the modes' complex frequencies. The resulting algebraic toolkit
can be used in waveform templates for ringing black holes with the purpose of
measuring deviations from the Kerr metric. As a first illustrative application
of our framework, we consider the Johannsen-Psaltis deformed Kerr metric and
compute the resulting deviation in the quasinormal mode frequency relative to
the known Kerr result.
| [
{
"created": "Fri, 23 Jun 2017 12:17:31 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Pappas",
"George",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Berti",
"Emanuele",
""
]
] | One of the central goals of the newborn field of gravitational wave astronomy is to test gravity in the highly nonlinear, strong field regime characterizing the spacetime of black holes. In particular, "black hole spectroscopy" (the observation and identification of black hole quasinormal mode frequencies in the gravitational wave signal) is expected to become one of the main tools for probing the structure and dynamics of Kerr black holes. In this paper we take a significant step towards that goal by constructing a "post-Kerr" quasinormal mode formalism. The formalism incorporates a parametrized but general perturbative deviation from the Kerr metric and exploits the well-established connection between the properties of the spacetime's circular null geodesics and the fundamental quasinormal mode to provide approximate, eikonal limit formulae for the modes' complex frequencies. The resulting algebraic toolkit can be used in waveform templates for ringing black holes with the purpose of measuring deviations from the Kerr metric. As a first illustrative application of our framework, we consider the Johannsen-Psaltis deformed Kerr metric and compute the resulting deviation in the quasinormal mode frequency relative to the known Kerr result. |
1907.08714 | Fulvio Sbis\`a | Fulvio Sbis\`a, Pedro O. Baqui, Tays Miranda, Sergio E. Jor\'as and
Oliver F. Piattella | Neutron star masses in $R^{2}$-gravity | 26 pages, 15 figures, pdfLatex, one subsection added and other minor
changes, version accepted for publication | Physics of the Dark Universe 27C (2020) 100411 | 10.1016/j.dark.2019.100411 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the issue of the existence of inequivalent definitions of
gravitational mass in $R^{2}$-gravity. We present several definitions of
gravitational mass, and discuss the formal relations between them. We then
consider the concrete case of a static and spherically symmetric neutron star,
and solve numerically the equations of motion for several values of the free
parameter of the model. We compare the features of the mass-radius relations
obtained for each definition of gravitational mass, and we comment on their
dependence on the free parameter. We then argue that $R^{2}$-gravity is a
valuable proxy to discuss the existence of inequivalent definitions of
gravitational mass in a generic modified gravity theory, and present some
comments on the general case.
| [
{
"created": "Fri, 19 Jul 2019 22:31:46 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Nov 2019 17:57:26 GMT",
"version": "v2"
}
] | 2019-11-15 | [
[
"Sbisà",
"Fulvio",
""
],
[
"Baqui",
"Pedro O.",
""
],
[
"Miranda",
"Tays",
""
],
[
"Jorás",
"Sergio E.",
""
],
[
"Piattella",
"Oliver F.",
""
]
] | We address the issue of the existence of inequivalent definitions of gravitational mass in $R^{2}$-gravity. We present several definitions of gravitational mass, and discuss the formal relations between them. We then consider the concrete case of a static and spherically symmetric neutron star, and solve numerically the equations of motion for several values of the free parameter of the model. We compare the features of the mass-radius relations obtained for each definition of gravitational mass, and we comment on their dependence on the free parameter. We then argue that $R^{2}$-gravity is a valuable proxy to discuss the existence of inequivalent definitions of gravitational mass in a generic modified gravity theory, and present some comments on the general case. |
0901.3191 | Mahmood Roshan | Mahmood Roshan, Maryam Nouri, Fatimah Shojai | Cosmological solutions of time varying speed of light theories | 16 pages, final version accepted for publication in Physics Letters B | Phys.Lett.B672:197-202,2009 | 10.1016/j.physletb.2009.01.042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider scalar-tensor theory for describing varying speed of light in a
spatially flat FRW space-time. We find some exact solutions in the metric and
Palatini formalisms. Also we examine the dynamics of this theory by dynamical
system method assuming a $\Lambda$CDM background and we find some exact
solutions by considering the character of critical points of the theory in both
formalisms. We show that for any attractor the form of non-minimal coupling
coefficient is quadratic in terms of the scalar field $\Psi$. Also we show that
only attractors of the de Sitter era satisfy the horizon criteria.
| [
{
"created": "Wed, 21 Jan 2009 06:01:00 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Feb 2009 19:09:50 GMT",
"version": "v2"
}
] | 2010-04-23 | [
[
"Roshan",
"Mahmood",
""
],
[
"Nouri",
"Maryam",
""
],
[
"Shojai",
"Fatimah",
""
]
] | We consider scalar-tensor theory for describing varying speed of light in a spatially flat FRW space-time. We find some exact solutions in the metric and Palatini formalisms. Also we examine the dynamics of this theory by dynamical system method assuming a $\Lambda$CDM background and we find some exact solutions by considering the character of critical points of the theory in both formalisms. We show that for any attractor the form of non-minimal coupling coefficient is quadratic in terms of the scalar field $\Psi$. Also we show that only attractors of the de Sitter era satisfy the horizon criteria. |
1805.04729 | Jerzy Matyjasek | Jerzy Matyjasek and Dariusz Tryniecki | Vacuum polarization of massive fields in the spacetime of the
higher-dimensional black holes | null | null | 10.5506/APhysPolB.49.1737 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct and study the vacuum polarization, $\langle
\phi^{2}\rangle_{D},$ of the quantized massive scalar field with a general
curvature coupling parameter in higher-dimensional static and
spherically-symmetric black hole spacetimes, with a special emphasis put on the
electrically charged Tangherlini solutions and the extremal and ultraextremal
configurations. For $4 \leq D \leq 7$ the explicit analytic expressions for the
vacuum polarization are given. For the conformally coupled fields the relation
between the trace of the stress-energy tensor and the vacuum polarization is
examined, which requires knowledge of the higher-order terms in the
Schwinger-DeWitt expansion.
| [
{
"created": "Sat, 12 May 2018 14:57:11 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Matyjasek",
"Jerzy",
""
],
[
"Tryniecki",
"Dariusz",
""
]
] | We construct and study the vacuum polarization, $\langle \phi^{2}\rangle_{D},$ of the quantized massive scalar field with a general curvature coupling parameter in higher-dimensional static and spherically-symmetric black hole spacetimes, with a special emphasis put on the electrically charged Tangherlini solutions and the extremal and ultraextremal configurations. For $4 \leq D \leq 7$ the explicit analytic expressions for the vacuum polarization are given. For the conformally coupled fields the relation between the trace of the stress-energy tensor and the vacuum polarization is examined, which requires knowledge of the higher-order terms in the Schwinger-DeWitt expansion. |
1311.0592 | Yong-Wan Kim | Yong-Wan Kim, Jaedong Choi, Young-Jai Park | Local free-fall Temperature of GMGHS Black Holes | 18 pages, 2 figures, version to appear in PRD | Phys. Rev. D 89, 044004 (2014) | 10.1103/PhysRevD.89.044004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a (5+1)-dimensional global flat embedding of the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger spacetime in Einstein frame, and a
(5+2)-dimensional global flat embedding in string frame. We show that the local
free-fall temperatures for freely falling observers in each frames are finite
at the event horizons, while the local temperatures for fiducial observers are
divergent. We also observe that the local free-fall temperatures differ between
the two frames.
| [
{
"created": "Mon, 4 Nov 2013 06:40:48 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jan 2014 01:20:23 GMT",
"version": "v2"
}
] | 2014-02-12 | [
[
"Kim",
"Yong-Wan",
""
],
[
"Choi",
"Jaedong",
""
],
[
"Park",
"Young-Jai",
""
]
] | We obtain a (5+1)-dimensional global flat embedding of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger spacetime in Einstein frame, and a (5+2)-dimensional global flat embedding in string frame. We show that the local free-fall temperatures for freely falling observers in each frames are finite at the event horizons, while the local temperatures for fiducial observers are divergent. We also observe that the local free-fall temperatures differ between the two frames. |
2306.00062 | S. Q. Wu | Shuang-Qing Wu, Di Wu | Consistent mass formulas for higher even-dimensional
Reissner-Nordstr\"om-NUT-AdS spacetimes | 20 pages, revtex4-1.cls, match with the published version in PRD;
companion to 2209.01757 | Phys. Rev. D 108, 064035 (2023) | 10.1103/PhysRevD.108.064035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our previous work [D. Wu and S.-Q. Wu, Phys. Rev. D 108, 064034 (2023)],
we have formulated consistent thermodynamic first law and Bekenstein-Smarr mass
formulae for all higher even-dimensional uncharged Taub-NUT (AdS) spacetimes
through the inclusion of a secondary hair $J_n = Mn$ as did in the
four-dimensional NUT-charged cases [S.-Q. Wu and D. Wu, Phys. Rev. D 100,
101501(R) (2019)]. In this article, we will show that the corresponding
Reissner-Nordstr\"om(RN)-NUT (AdS) cases in all higher even-dimensions can be
coherently treated just like the uncharged cases if another secondary hair $Q_n
\propto qn$ is further introduced as did in the four-dimensional dyonic
NUT-charged case [D. Wu and S.-Q. Wu, Phys. Rev. D 105, 124013 (2022)]. As a
by-product of our consequence, it is also demonstrated that there is no need to
introduce the secondary hair $Q_n$ in the mass formulae for the
four-dimensional purely electric-charged RN-NUT (AdS) spacetimes.
| [
{
"created": "Wed, 31 May 2023 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Aug 2023 15:08:58 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Sep 2023 15:34:39 GMT",
"version": "v3"
}
] | 2023-09-19 | [
[
"Wu",
"Shuang-Qing",
""
],
[
"Wu",
"Di",
""
]
] | In our previous work [D. Wu and S.-Q. Wu, Phys. Rev. D 108, 064034 (2023)], we have formulated consistent thermodynamic first law and Bekenstein-Smarr mass formulae for all higher even-dimensional uncharged Taub-NUT (AdS) spacetimes through the inclusion of a secondary hair $J_n = Mn$ as did in the four-dimensional NUT-charged cases [S.-Q. Wu and D. Wu, Phys. Rev. D 100, 101501(R) (2019)]. In this article, we will show that the corresponding Reissner-Nordstr\"om(RN)-NUT (AdS) cases in all higher even-dimensions can be coherently treated just like the uncharged cases if another secondary hair $Q_n \propto qn$ is further introduced as did in the four-dimensional dyonic NUT-charged case [D. Wu and S.-Q. Wu, Phys. Rev. D 105, 124013 (2022)]. As a by-product of our consequence, it is also demonstrated that there is no need to introduce the secondary hair $Q_n$ in the mass formulae for the four-dimensional purely electric-charged RN-NUT (AdS) spacetimes. |
gr-qc/0609018 | Jos\'e Wadih Maluf | J. W. Maluf, S. C. Ulhoa, F. F. Faria and J. F. da Rocha-Neto | The angular momentum of the gravitational field and the Poincare group | 20 pages, no figures, accepted by Class. Quantum Gravity | Class.Quant.Grav. 23 (2006) 6245-6256 | 10.1088/0264-9381/23/22/011 | null | gr-qc | null | We redefine the gravitational angular momentum in the framework of the
teleparallel equivalent of general relativity. In similarity to the
gravitational energy-momentum, the new definition for the gravitational angular
momentum is coordinate independent. By considering the Poisson brackets in the
phase space of the theory, we find that the gravitational energy-momentum and
angular momentum correspond to a representation of the Poincar\'e group. This
result allows us to define Casimir type invariants for the gravitational field.
| [
{
"created": "Wed, 6 Sep 2006 00:16:02 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Maluf",
"J. W.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Faria",
"F. F.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
]
] | We redefine the gravitational angular momentum in the framework of the teleparallel equivalent of general relativity. In similarity to the gravitational energy-momentum, the new definition for the gravitational angular momentum is coordinate independent. By considering the Poisson brackets in the phase space of the theory, we find that the gravitational energy-momentum and angular momentum correspond to a representation of the Poincar\'e group. This result allows us to define Casimir type invariants for the gravitational field. |
2404.12811 | Felipe Agurto Sep\'ulveda Agurto-Sepulveda F | F. Agurto-Sep\'ulveda, J. Oliva, M. Oyarzo and D.R.G Schleicher | Black Hole shadows of $\alpha'$-corrected black holes | 14 pages, 8 figures. V2: small changes, references added, accepted in
PRD | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we study the qualitative features induces by corrections to GR
coming from String Theory, on the shadows of rotating black holes. We deal with
the slowly rotating black hole solutions up to order $\mathcal{O}(a^3)$, to
first order in $\alpha'$, including also the dilaton. We provide a detailed
characterization of the geometry, as well as the innermost stable circular
orbit (ISCO) and photon ring, and then we proceed to obtain the black hole
images within the relativistic thin-disk model. We characterize the images by
computing the diameter, displacement and asymmetry. A comparison with the Kerr
case, indicates that all these quantities grow due to the $\alpha'$ correction,
and that the departure from GR for different observable is enhanced depending
on the angle of view, namely for the diameter the maximum departure is obtained
when the system is face-on, while for the displacement and asymmetry the
departure from GR is maximized for edge-on point of view.
| [
{
"created": "Fri, 19 Apr 2024 11:48:29 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jun 2024 21:12:36 GMT",
"version": "v2"
}
] | 2024-06-26 | [
[
"Agurto-Sepúlveda",
"F.",
""
],
[
"Oliva",
"J.",
""
],
[
"Oyarzo",
"M.",
""
],
[
"Schleicher",
"D. R. G",
""
]
] | In this paper we study the qualitative features induces by corrections to GR coming from String Theory, on the shadows of rotating black holes. We deal with the slowly rotating black hole solutions up to order $\mathcal{O}(a^3)$, to first order in $\alpha'$, including also the dilaton. We provide a detailed characterization of the geometry, as well as the innermost stable circular orbit (ISCO) and photon ring, and then we proceed to obtain the black hole images within the relativistic thin-disk model. We characterize the images by computing the diameter, displacement and asymmetry. A comparison with the Kerr case, indicates that all these quantities grow due to the $\alpha'$ correction, and that the departure from GR for different observable is enhanced depending on the angle of view, namely for the diameter the maximum departure is obtained when the system is face-on, while for the displacement and asymmetry the departure from GR is maximized for edge-on point of view. |
gr-qc/0409057 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Consistent discretization and loop quantum geometry | 4 pages, Revtex, no figures | Phys.Rev.Lett. 94 (2005) 101302 | 10.1103/PhysRevLett.94.101302 | LSU-REL-091404 | gr-qc | null | We apply the ``consistent discretization'' approach to general relativity
leaving the spatial slices continuous. The resulting theory is free of the
diffeomorphism and Hamiltonian constraints, but one can impose the
diffeomorphism constraint to reduce its space of solutions and the constraint
is preserved exactly under the discrete evolution. One ends up with a theory
that has as physical space what is usually considered the kinematical space of
loop quantum geometry, given by diffeomorphism invariant spin networks endowed
with appropriate rigorously defined diffeomorphism invariant measures and inner
products. The dynamics can be implemented as a unitary transformation and the
problem of time explicitly solved or at least reduced to as a numerical
problem. We exhibit the technique explicitly in 2+1 dimensional gravity.
| [
{
"created": "Tue, 14 Sep 2004 19:03:00 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We apply the ``consistent discretization'' approach to general relativity leaving the spatial slices continuous. The resulting theory is free of the diffeomorphism and Hamiltonian constraints, but one can impose the diffeomorphism constraint to reduce its space of solutions and the constraint is preserved exactly under the discrete evolution. One ends up with a theory that has as physical space what is usually considered the kinematical space of loop quantum geometry, given by diffeomorphism invariant spin networks endowed with appropriate rigorously defined diffeomorphism invariant measures and inner products. The dynamics can be implemented as a unitary transformation and the problem of time explicitly solved or at least reduced to as a numerical problem. We exhibit the technique explicitly in 2+1 dimensional gravity. |
gr-qc/0010058 | Frederick J. Ernst | I. Hauser and F. J. Ernst | The monodromy matrix method of solving an exterior boundary value
problem for a given stationary axisymmetric perfect fluid solution | 29 pages LaTeX | Gen.Rel.Grav.33:1985-2014,2001 | 10.1023/A:1013003110831 | null | gr-qc | null | A procedure is described for matching a given stationary axisymmetric perfect
fluid solution to a not necessarily asymptotically flat vacuum exterior. Using
data on the zero pressure surface, the procedure yields the Ernst potential of
the matching vacuum metric on the symmetry axis. From this the full metric can
be constructed using a variety of well established procedures.
| [
{
"created": "Sun, 15 Oct 2000 16:02:20 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hauser",
"I.",
""
],
[
"Ernst",
"F. J.",
""
]
] | A procedure is described for matching a given stationary axisymmetric perfect fluid solution to a not necessarily asymptotically flat vacuum exterior. Using data on the zero pressure surface, the procedure yields the Ernst potential of the matching vacuum metric on the symmetry axis. From this the full metric can be constructed using a variety of well established procedures. |
2110.05982 | Theodoros Papanikolaou | Ilia Musco, Theodoros Papanikolaou | Primordial black hole formation for an anisotropic perfect fluid:
Initial conditions and estimation of the threshold | Published in Physical Review D, Version 4: 16 pages, 7 figures, minor
changes in Sec. III | Phys.Rev.D 106 (2022) 8, 083017 | 10.1103/PhysRevD.106.083017 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work investigates the formation of primordial black holes within a
radiation fluid with an anisotropic pressure. We focus our attention on the
initial conditions describing cosmological perturbations in the super horizon
regime, using a covariant form of the equation of state in terms of pressure
and energy density gradients. The effect of the anisotropy is to modify the
initial shape of the cosmological perturbations with respect to the isotropic
case. Using the dependence of the threshold $\delta_\mathrm{c}$ for primordial
black holes with respect to the shape of cosmological perturbations, we
estimate here how the threshold is varying with respect to the amplitude of the
anisotropy. If this variation is large enough it could lead to a significant
variation of the abundance of PBHs.
| [
{
"created": "Tue, 12 Oct 2021 13:19:06 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Oct 2021 16:12:12 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Jan 2022 17:32:21 GMT",
"version": "v3"
},
{
"created": "Mon, 24 Oct 2022 08:39:16 GMT",
"version": "v4"
}
] | 2022-10-25 | [
[
"Musco",
"Ilia",
""
],
[
"Papanikolaou",
"Theodoros",
""
]
] | This work investigates the formation of primordial black holes within a radiation fluid with an anisotropic pressure. We focus our attention on the initial conditions describing cosmological perturbations in the super horizon regime, using a covariant form of the equation of state in terms of pressure and energy density gradients. The effect of the anisotropy is to modify the initial shape of the cosmological perturbations with respect to the isotropic case. Using the dependence of the threshold $\delta_\mathrm{c}$ for primordial black holes with respect to the shape of cosmological perturbations, we estimate here how the threshold is varying with respect to the amplitude of the anisotropy. If this variation is large enough it could lead to a significant variation of the abundance of PBHs. |
2008.04906 | Jie Jiang | Jie Jiang and Ming Zhang | Testing the Weak Cosmic Censorship Conjecture in Lanczos-Lovelock
gravity | 9 pages,1 figures | Phys. Rev. D 102, 084033 (2020) | 10.1103/PhysRevD.102.084033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we test the weak cosmic censorship conjecture (WCCC) in the
nearly extremal static charged black holes of Lanczos-Lovelock-Maxwell gravity
based on the new version of gedanken experiments proposed by Sorce and Wald.
After introducing the null energy condition of the matter fields, we show that
the (nearly) extremal black holes can be destroyed under the first-order
approximation for the case with $S'(r_h)\leq 0$, where $S(r_h)$ is the entropy
of the background black hole geometry in Lanczos-Lovelock gravity. It implies
that the WCCC is violated in these situations. For the case with $S'(r_h)>0$,
the nearly extremal black holes cannot be overcharged by the new version of the
gedanken experiments for both first- and second-order approximations of
perturbation. These results indicate that the WCCC is satisfied in the
Lanczos-Lovelock gravity with the condition $S'(r_h)>0$. Our work also implies
that the WCCC will play a natural role to constrain the Lanczos-Lovelock
gravities. Finally, we also show that the destroy condition $S'(r_h)<0$ implies
that the nearly extremal black hole is thermodynamically unstable under the
first-order approximation.
| [
{
"created": "Tue, 11 Aug 2020 04:19:04 GMT",
"version": "v1"
}
] | 2020-10-16 | [
[
"Jiang",
"Jie",
""
],
[
"Zhang",
"Ming",
""
]
] | In this paper, we test the weak cosmic censorship conjecture (WCCC) in the nearly extremal static charged black holes of Lanczos-Lovelock-Maxwell gravity based on the new version of gedanken experiments proposed by Sorce and Wald. After introducing the null energy condition of the matter fields, we show that the (nearly) extremal black holes can be destroyed under the first-order approximation for the case with $S'(r_h)\leq 0$, where $S(r_h)$ is the entropy of the background black hole geometry in Lanczos-Lovelock gravity. It implies that the WCCC is violated in these situations. For the case with $S'(r_h)>0$, the nearly extremal black holes cannot be overcharged by the new version of the gedanken experiments for both first- and second-order approximations of perturbation. These results indicate that the WCCC is satisfied in the Lanczos-Lovelock gravity with the condition $S'(r_h)>0$. Our work also implies that the WCCC will play a natural role to constrain the Lanczos-Lovelock gravities. Finally, we also show that the destroy condition $S'(r_h)<0$ implies that the nearly extremal black hole is thermodynamically unstable under the first-order approximation. |
2205.15724 | Bijan Bagchi | Bijan Bagchi and Sauvik Sen | MOND and asymptotic safe gravity | Inconsistencies noticed in some of the equations | null | null | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | The modified Newtonian dynamics (MOND) paradigm is discussed in the context
of asymptotic safe gravity. We estimate quantum correction to the logarithmic
potential which is well known to account for the constancy of the circular
velocity $v$ of the spiral galaxies. We determine plausible bounds on $v$.
| [
{
"created": "Tue, 31 May 2022 12:14:24 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Aug 2022 06:59:12 GMT",
"version": "v2"
}
] | 2022-08-23 | [
[
"Bagchi",
"Bijan",
""
],
[
"Sen",
"Sauvik",
""
]
] | The modified Newtonian dynamics (MOND) paradigm is discussed in the context of asymptotic safe gravity. We estimate quantum correction to the logarithmic potential which is well known to account for the constancy of the circular velocity $v$ of the spiral galaxies. We determine plausible bounds on $v$. |
1801.03718 | Cedric Troessaert | Marc Henneaux and C\'edric Troessaert | BMS Group at Spatial Infinity: the Hamiltonian (ADM) approach | 26 pages | null | 10.1007/JHEP03(2018)147 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New boundary conditions for asymptotically flat spacetimes are given at
spatial infinity. These boundary conditions are invariant under the BMS group,
which acts non trivially. The boundary conditions fulfill all standard
consistency requirements: (i) they make the symplectic form finite; (ii) they
contain the Schwarzchild solution, the Kerr solution and their Poincar\'e
transforms, (iii) they make the Hamiltonian generators of the asymptotic
symmetries integrable and well-defined (finite). The boundary conditions differ
from the ones given earlier in the literature in the choice of the parity
conditions. It is this different choice of parity conditions that makes the
action of the BMS group non trivial. Our approach is purely Hamiltonian and
off-shell throughout.
| [
{
"created": "Thu, 11 Jan 2018 11:29:05 GMT",
"version": "v1"
}
] | 2018-04-18 | [
[
"Henneaux",
"Marc",
""
],
[
"Troessaert",
"Cédric",
""
]
] | New boundary conditions for asymptotically flat spacetimes are given at spatial infinity. These boundary conditions are invariant under the BMS group, which acts non trivially. The boundary conditions fulfill all standard consistency requirements: (i) they make the symplectic form finite; (ii) they contain the Schwarzchild solution, the Kerr solution and their Poincar\'e transforms, (iii) they make the Hamiltonian generators of the asymptotic symmetries integrable and well-defined (finite). The boundary conditions differ from the ones given earlier in the literature in the choice of the parity conditions. It is this different choice of parity conditions that makes the action of the BMS group non trivial. Our approach is purely Hamiltonian and off-shell throughout. |
1001.0297 | Asoke Sen Dr. | A. K. Sen | Towards a more exact value of deflection of light due to static
gravitational mass | submitted to GRG, Springer | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deflection of a ray of light passing close to a gravitational mass, is
generally calculated from the null geodesic which the light ray (photon)
follows. However, there is an alternate approach, where the effect of
gravitation on the ray of light is estimated by considering the ray to be
passing through a material medium. Calculations have been done in this paper,
following the later approach, to estimate the amount of deflection due to a
static non-rotating mass. The refractive index of such a material medium has
been calculated in a more rigorous manner in the present work and the final
value of amount of deflection calculated here is claimed to be more accurate
than all other values resulting from previous calculations.
| [
{
"created": "Sat, 2 Jan 2010 11:38:40 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Feb 2010 07:23:52 GMT",
"version": "v2"
}
] | 2010-02-08 | [
[
"Sen",
"A. K.",
""
]
] | The deflection of a ray of light passing close to a gravitational mass, is generally calculated from the null geodesic which the light ray (photon) follows. However, there is an alternate approach, where the effect of gravitation on the ray of light is estimated by considering the ray to be passing through a material medium. Calculations have been done in this paper, following the later approach, to estimate the amount of deflection due to a static non-rotating mass. The refractive index of such a material medium has been calculated in a more rigorous manner in the present work and the final value of amount of deflection calculated here is claimed to be more accurate than all other values resulting from previous calculations. |
1805.11569 | Adam D. Helfer | Adam D. Helfer | Black hole uniqueness and magnetic shear | 7 pages, 1 figure GRF 2018 submission | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A series of tantalizing results led to the black hole uniqueness conjecture:
isolated, realistic black holes should settle down to states characterized by
their spin, mass and charge. I argue that generically real black holes will
also possess a `magnetic' shear; equivalently, that the dominant contribution
to their long-range gravitational field should have a `magnetic' (odd-parity)
component. In fact, the Blandford-Znajek process, combined with the axial
anomaly and gravitational gyrotropy, would tend to leave a black hole in such a
state. It seems that the black-hole uniqueness conjecture may apply in a regime
around the hole, but as one approaches future null infinity the `magnetic'
effects become significant. In this far-field regime, the space-time will be
non-stationary, but there will be no radiation.
| [
{
"created": "Tue, 29 May 2018 16:27:18 GMT",
"version": "v1"
}
] | 2018-05-30 | [
[
"Helfer",
"Adam D.",
""
]
] | A series of tantalizing results led to the black hole uniqueness conjecture: isolated, realistic black holes should settle down to states characterized by their spin, mass and charge. I argue that generically real black holes will also possess a `magnetic' shear; equivalently, that the dominant contribution to their long-range gravitational field should have a `magnetic' (odd-parity) component. In fact, the Blandford-Znajek process, combined with the axial anomaly and gravitational gyrotropy, would tend to leave a black hole in such a state. It seems that the black-hole uniqueness conjecture may apply in a regime around the hole, but as one approaches future null infinity the `magnetic' effects become significant. In this far-field regime, the space-time will be non-stationary, but there will be no radiation. |
2105.08586 | Alexey Golovnev | Alexey Golovnev | Issues of Lorentz-invariance in f(T) gravity and calculations for
spherically symmetric solutions | 13 pages; some more explanations added | Classical and Quantum Gravity 38 (2021) 197001 | 10.1088/1361-6382/ac2136 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The f(T) gravity is nowadays being widely used for cosmological model
building, as well as for constructing spherically symmetric solutions. In its
classical pure tetrad formulation it violates the local Lorentz symmetry in the
space of tetrads. By using an appropriate spin connection it can be brought to
a formally Lorentz invariant shape. However, despite some mathematical elegance
obtained and new options of looking for non-standard couplings to matter
probably made possible, it is fully equivalent in itself to the initial
formulation. It seems that this fact, that the covariantisation does not in
principle change anything, is not understood well by the community. Therefore
we give a pedagogical introduction to these topics. And, on top of that, we
show that obtaining the explicit equations for spherically symmetric solutions
in f(T) gravity is not very difficult computationally and can be easily done
even without any computer at hand.
| [
{
"created": "Tue, 18 May 2021 15:14:15 GMT",
"version": "v1"
},
{
"created": "Fri, 21 May 2021 14:55:45 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Jul 2021 21:51:57 GMT",
"version": "v3"
}
] | 2021-09-24 | [
[
"Golovnev",
"Alexey",
""
]
] | The f(T) gravity is nowadays being widely used for cosmological model building, as well as for constructing spherically symmetric solutions. In its classical pure tetrad formulation it violates the local Lorentz symmetry in the space of tetrads. By using an appropriate spin connection it can be brought to a formally Lorentz invariant shape. However, despite some mathematical elegance obtained and new options of looking for non-standard couplings to matter probably made possible, it is fully equivalent in itself to the initial formulation. It seems that this fact, that the covariantisation does not in principle change anything, is not understood well by the community. Therefore we give a pedagogical introduction to these topics. And, on top of that, we show that obtaining the explicit equations for spherically symmetric solutions in f(T) gravity is not very difficult computationally and can be easily done even without any computer at hand. |
2109.02660 | Luc\'ia Men\'endez-Pidal | Steffen Gielen and Luc\'ia Men\'endez-Pidal | Unitarity, clock dependence and quantum recollapse in quantum cosmology | 53 pages, 12 figures, matches version accepted for publication | Class. Quantum Grav. 39 (2022), 075011 | 10.1088/1361-6382/ac504f | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We continue our analysis of a quantum cosmology model describing a flat
Friedmann--Lema\^itre--Robertson--Walker universe filled with a (free) massless
scalar field and an arbitrary perfect fluid. For positive energy density in the
scalar and fluid, each classical solution has a singularity and expands to
infinite volume. When quantising we view the cosmological dynamics in
relational terms, using one degree of freedom as a clock for the others. Three
natural candidates for this clock are the volume, a time variable conjugate to
the perfect fluid, and the scalar field. We have previously shown that
requiring unitary evolution in the "fluid" time leads to a boundary condition
at the singularity and generic singularity resolution, while in the volume time
semiclassical states follow the classical singular trajectories. Here we
analyse the third option of using the scalar field as a clock, finding further
dramatic differences to the previous cases: the boundary condition arising from
unitarity is now at infinity. Rather than singularity resolution, this theory
features a quantum recollapse of the universe at large volume, as was shown in
a similar context by Paw{\l}owski and Ashtekar. We illustrate the properties of
the theory analytically and numerically, showing that the ways in which the
different quantum theories do or do not depart from classical behaviour
directly arise from demanding unitarity with respect to different clocks. We
argue that using a Dirac quantisation would not resolve the issue. Our results
further illustrate the problem of time in quantum gravity.
| [
{
"created": "Mon, 6 Sep 2021 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jan 2022 14:19:46 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Apr 2022 16:18:00 GMT",
"version": "v3"
}
] | 2022-04-08 | [
[
"Gielen",
"Steffen",
""
],
[
"Menéndez-Pidal",
"Lucía",
""
]
] | We continue our analysis of a quantum cosmology model describing a flat Friedmann--Lema\^itre--Robertson--Walker universe filled with a (free) massless scalar field and an arbitrary perfect fluid. For positive energy density in the scalar and fluid, each classical solution has a singularity and expands to infinite volume. When quantising we view the cosmological dynamics in relational terms, using one degree of freedom as a clock for the others. Three natural candidates for this clock are the volume, a time variable conjugate to the perfect fluid, and the scalar field. We have previously shown that requiring unitary evolution in the "fluid" time leads to a boundary condition at the singularity and generic singularity resolution, while in the volume time semiclassical states follow the classical singular trajectories. Here we analyse the third option of using the scalar field as a clock, finding further dramatic differences to the previous cases: the boundary condition arising from unitarity is now at infinity. Rather than singularity resolution, this theory features a quantum recollapse of the universe at large volume, as was shown in a similar context by Paw{\l}owski and Ashtekar. We illustrate the properties of the theory analytically and numerically, showing that the ways in which the different quantum theories do or do not depart from classical behaviour directly arise from demanding unitarity with respect to different clocks. We argue that using a Dirac quantisation would not resolve the issue. Our results further illustrate the problem of time in quantum gravity. |
1311.2530 | Astrid Eichhorn | Astrid Eichhorn, Sebastian Mizera | Spectral dimension in causal set quantum gravity | 16 pages, 11 figures | null | 10.1088/0264-9381/31/12/125007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We evaluate the spectral dimension in causal set quantum gravity by
simulating random walks on causal sets. In contrast to other approaches to
quantum gravity, we find an increasing spectral dimension at small scales. This
observation can be connected to the non-locality of causal set theory that is
deeply rooted in its fundamentally Lorentzian nature. Based on its large-scale
behaviour, we conjecture that the spectral dimension can serve as a tool to
distinguish causal sets that approximate manifolds from those that do not. As a
new tool to probe quantum spacetime in different quantum gravity approaches, we
introduce a novel dimensional estimator, the causal spectral dimension, based
on the meeting probability of two random walkers, which respect the causal
structure of the quantum spacetime. We discuss a causal-set example, where the
spectral dimension and the causal spectral dimension differ, due to the
existence of a preferred foliation.
| [
{
"created": "Mon, 11 Nov 2013 18:54:20 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Mizera",
"Sebastian",
""
]
] | We evaluate the spectral dimension in causal set quantum gravity by simulating random walks on causal sets. In contrast to other approaches to quantum gravity, we find an increasing spectral dimension at small scales. This observation can be connected to the non-locality of causal set theory that is deeply rooted in its fundamentally Lorentzian nature. Based on its large-scale behaviour, we conjecture that the spectral dimension can serve as a tool to distinguish causal sets that approximate manifolds from those that do not. As a new tool to probe quantum spacetime in different quantum gravity approaches, we introduce a novel dimensional estimator, the causal spectral dimension, based on the meeting probability of two random walkers, which respect the causal structure of the quantum spacetime. We discuss a causal-set example, where the spectral dimension and the causal spectral dimension differ, due to the existence of a preferred foliation. |
1404.0476 | Luciano Vanzo | Luciano Vanzo | {\Lambda} may not be vacuum energy, after all | 5 pages, Essay written for the Gravity Research Foundation 2014
Awards for Essays on Gravitation | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest the possibility that the mysterious dark energy component driving
the acceleration of the Universe is the leading term, in the de Sitter
temperature, of the free energy density of space-time seen as a quantum gravity
coherent state of the gravitational field. The corresponding field theory
classically has positive pressure, and can be considered as living on the
Hubble horizon, or, alternatively, within the non compact part of the
Robertson-Walker metric, both manifolds being characterized by the same scale
and degrees of freedom. The equation of state is then recovered via the
conformal anomaly. No such interpretation seems to be available for negative
{\Lambda}.
| [
{
"created": "Wed, 2 Apr 2014 08:04:11 GMT",
"version": "v1"
}
] | 2014-04-03 | [
[
"Vanzo",
"Luciano",
""
]
] | We suggest the possibility that the mysterious dark energy component driving the acceleration of the Universe is the leading term, in the de Sitter temperature, of the free energy density of space-time seen as a quantum gravity coherent state of the gravitational field. The corresponding field theory classically has positive pressure, and can be considered as living on the Hubble horizon, or, alternatively, within the non compact part of the Robertson-Walker metric, both manifolds being characterized by the same scale and degrees of freedom. The equation of state is then recovered via the conformal anomaly. No such interpretation seems to be available for negative {\Lambda}. |
2403.00253 | Tayyab Naseer | M. Sharif, T. Naseer | Effects of
$f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\upsilon}\mathcal{T}^{\gamma\upsilon})$
Gravity on Anisotropic Charged Compact Structures | 30 pages, 8 figures | Chin. J. Phys. 73(2021)179-194 | 10.1016/j.cjph.2021.06.009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper focuses on the analysis of static spherically symmetric
anisotropic solutions in the presence of electromagnetic field through the
gravitational decoupling approach in
$f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\upsilon}\mathcal{T}^{\gamma\upsilon})$
gravity. We use geometric deformation only on radial metric function and obtain
two sets of the field equations. The first set deals with isotropic fluid while
the second set yields the influence of anisotropic source. We consider the
modified Krori-Barua charged isotropic solution for spherical self-gravitating
star to deal with the isotropic system. The second set of the field equations
is solved by taking two different constraints. We then investigate physical
acceptability of the obtained solutions through graphical analysis of the
effective physical variables and energy conditions. We also analyze the effects
of charge on different parameters, (i.e., mass, compactness and redshift) for
the resulting solutions. It is found that our both solutions are viable as well
as stable for specific values of the decoupling parameter $\varphi$ and charge.
We conclude that a self-gravitating star shows more stable behavior in this
gravity.
| [
{
"created": "Fri, 1 Mar 2024 03:36:35 GMT",
"version": "v1"
}
] | 2024-03-04 | [
[
"Sharif",
"M.",
""
],
[
"Naseer",
"T.",
""
]
] | This paper focuses on the analysis of static spherically symmetric anisotropic solutions in the presence of electromagnetic field through the gravitational decoupling approach in $f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\upsilon}\mathcal{T}^{\gamma\upsilon})$ gravity. We use geometric deformation only on radial metric function and obtain two sets of the field equations. The first set deals with isotropic fluid while the second set yields the influence of anisotropic source. We consider the modified Krori-Barua charged isotropic solution for spherical self-gravitating star to deal with the isotropic system. The second set of the field equations is solved by taking two different constraints. We then investigate physical acceptability of the obtained solutions through graphical analysis of the effective physical variables and energy conditions. We also analyze the effects of charge on different parameters, (i.e., mass, compactness and redshift) for the resulting solutions. It is found that our both solutions are viable as well as stable for specific values of the decoupling parameter $\varphi$ and charge. We conclude that a self-gravitating star shows more stable behavior in this gravity. |
1707.08568 | Hyerim Noh | Hyerim Noh, Jai-chan Hwang, Chan-Gyung Park | Axion as a cold dark matter candidate: Proof to fully nonlinear order | 6 pages, no figure | null | 10.3847/1538-4357/aa8366 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a proof of the axion as a cold dark matter candidate to the fully
nonlinear order perturbations based on Einstein's gravity. We consider the
axion as a coherently oscillating massive classical scalar field without
interaction. We present the fully nonlinear and exact, except for {\it
ignoring} the transverse-tracefree tensor-type perturbation, hydrodynamic
equations for an axion fluid in Einstein's gravity. We show that the axion has
the characteristic pressure and anisotropic stress, the latter starts to appear
from the second-order perturbation. But these terms do not directly affect the
hydrodynamic equations in our axion treatment. Instead, what behaves as the
effective pressure term in relativistic hydrodynamic equations is the perturbed
lapse function and the relativistic result coincides exactly with the one known
in the previous non-relativistic studies. The effective pressure term leads to
a Jeans scale which is of the solar-system scale for conventional axion mass.
As the fully nonlinear and relativistic hydrodynamic equations for an axion
fluid coincide exactly with the ones of a zero-pressure fluid in the
super-Jeans scale, we have proved the cold dark matter nature of such an axion
in that scale.
| [
{
"created": "Wed, 26 Jul 2017 07:36:04 GMT",
"version": "v1"
}
] | 2017-08-30 | [
[
"Noh",
"Hyerim",
""
],
[
"Hwang",
"Jai-chan",
""
],
[
"Park",
"Chan-Gyung",
""
]
] | We present a proof of the axion as a cold dark matter candidate to the fully nonlinear order perturbations based on Einstein's gravity. We consider the axion as a coherently oscillating massive classical scalar field without interaction. We present the fully nonlinear and exact, except for {\it ignoring} the transverse-tracefree tensor-type perturbation, hydrodynamic equations for an axion fluid in Einstein's gravity. We show that the axion has the characteristic pressure and anisotropic stress, the latter starts to appear from the second-order perturbation. But these terms do not directly affect the hydrodynamic equations in our axion treatment. Instead, what behaves as the effective pressure term in relativistic hydrodynamic equations is the perturbed lapse function and the relativistic result coincides exactly with the one known in the previous non-relativistic studies. The effective pressure term leads to a Jeans scale which is of the solar-system scale for conventional axion mass. As the fully nonlinear and relativistic hydrodynamic equations for an axion fluid coincide exactly with the ones of a zero-pressure fluid in the super-Jeans scale, we have proved the cold dark matter nature of such an axion in that scale. |
2304.03449 | Jin Jia | Jin Jia and Pin Yu | Remark on the nonlinear stability of Minkowski spacetime: a rigidity
theorem | references added, typos corrected | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the nonlinear stability of Minkowski spacetime, we show
that if the radiation field of the curvature tensor vanishes, the spacetime
must be flat.
| [
{
"created": "Fri, 7 Apr 2023 02:43:12 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2023 06:31:43 GMT",
"version": "v2"
}
] | 2023-04-11 | [
[
"Jia",
"Jin",
""
],
[
"Yu",
"Pin",
""
]
] | In the framework of the nonlinear stability of Minkowski spacetime, we show that if the radiation field of the curvature tensor vanishes, the spacetime must be flat. |
2106.08464 | Md Sabir Ali | Md Sabir Ali, and Shagun Kaushal | Gravitational lensing for stationary axisymmetric black holes in
Eddington-inspired Born-Infeld gravity | 29 pages, 7 figures, Accepted for publication in Physical Review D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent years witnessed a surge of interest of the lensing of the black
holes arising from general as well as other modified theories of gravity due to
the experimental data available from the EHT results. The EHT may open a new
door indicating the possible existence of the rotating black hole solutions in
modified theories of gravity in the strong field regime. With this motivation,
we investigate in the present paper the equatorial lensing $(\theta=\pi/2)$ by
a recently obtained exact rotating black holes solution in EiBI theory in both
the strong and weak field limits. Such black holes are the modification of
Kerr-Newman black holes in general relativity, characterized by their mass
($M$), the charge ($Q$), and the rotation parameter ($a$). and an additional
term $\epsilon$ accounting for the correction to the Kerr-Newman solutions. We
show numerically the variations of the impact parameter $u_m$, the light
deflection coefficients $p$ and $q$, the total azimuthal bending angle
$\alpha_D$ and find a close dependence of these quantities on the charge
parameter $r_q$, the correction term $\epsilon$ and the spin $a$. We also
calculate the angular position $\theta_\infty$, and the angular separation $s$,
and the magnification of the relativistic images. In addition, we also discuss
the weak lensing of the black holes in EiBI theory using the Gauss-Bonnet
theorem. We calculate the weak lensing parameter and find its variation with
different values of the parameters $r_q$ and $\epsilon$.
| [
{
"created": "Tue, 15 Jun 2021 22:16:25 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jan 2022 16:56:03 GMT",
"version": "v2"
}
] | 2022-01-19 | [
[
"Ali",
"Md Sabir",
""
],
[
"Kaushal",
"Shagun",
""
]
] | The recent years witnessed a surge of interest of the lensing of the black holes arising from general as well as other modified theories of gravity due to the experimental data available from the EHT results. The EHT may open a new door indicating the possible existence of the rotating black hole solutions in modified theories of gravity in the strong field regime. With this motivation, we investigate in the present paper the equatorial lensing $(\theta=\pi/2)$ by a recently obtained exact rotating black holes solution in EiBI theory in both the strong and weak field limits. Such black holes are the modification of Kerr-Newman black holes in general relativity, characterized by their mass ($M$), the charge ($Q$), and the rotation parameter ($a$). and an additional term $\epsilon$ accounting for the correction to the Kerr-Newman solutions. We show numerically the variations of the impact parameter $u_m$, the light deflection coefficients $p$ and $q$, the total azimuthal bending angle $\alpha_D$ and find a close dependence of these quantities on the charge parameter $r_q$, the correction term $\epsilon$ and the spin $a$. We also calculate the angular position $\theta_\infty$, and the angular separation $s$, and the magnification of the relativistic images. In addition, we also discuss the weak lensing of the black holes in EiBI theory using the Gauss-Bonnet theorem. We calculate the weak lensing parameter and find its variation with different values of the parameters $r_q$ and $\epsilon$. |
1412.0478 | Yosef Verbin | Y. Brihaye and Y. Verbin | Self-Gravitating Spherical Solutions of the non-minimally coupled
non-Abelian Higgs Model | null | Phys. Rev. D 91, 064021 (2015) | 10.1103/PhysRevD.91.064021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the Higgs Inflation scenario, we study static
spherically-symmetric solutions of the non-Abelian Higgs model coupled
non-minimally to Gravity. We find solutions for the self-gravitating sphaleron
as well as monopole-like solutions and study the impact of the non-minimal
coupling on their properties. Finally we discuss shortly the possibility that
these solutions interact gravitationally with star-like objects like boson
stars.
| [
{
"created": "Mon, 1 Dec 2014 13:49:41 GMT",
"version": "v1"
}
] | 2015-03-18 | [
[
"Brihaye",
"Y.",
""
],
[
"Verbin",
"Y.",
""
]
] | Motivated by the Higgs Inflation scenario, we study static spherically-symmetric solutions of the non-Abelian Higgs model coupled non-minimally to Gravity. We find solutions for the self-gravitating sphaleron as well as monopole-like solutions and study the impact of the non-minimal coupling on their properties. Finally we discuss shortly the possibility that these solutions interact gravitationally with star-like objects like boson stars. |
1907.05265 | Carlos A. Mar\'in V. | Carlos A. Mar\'in and Jorge Poveda | Light deflection around a spherical charged black hole to second order.
Multivariate Pad\'e approximants | 32 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1701.04434 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the Reissner-Nordstrom metric we obtain the higher-order terms for the
deflection of light around a massive-charged black hole using the
Lindstedt-Poincar\'e method to solve the equation of motion of a photon around
the compact object. The corrections are performed developing the expansion in
terms of $\epsilon=\frac{r_{c}}{b}$ and $\frac{\delta}{b}= \frac{Q^{2}}{6 \pi
\epsilon_{0}Mc^{2} b}$. Additionally, from the perturbation expansion, we
obtain multivariate Pad\'e approximants. We also show how these are a better
fit for the numerical data than the original formal Taylor series.
| [
{
"created": "Wed, 10 Jul 2019 17:35:44 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2019 17:33:49 GMT",
"version": "v2"
}
] | 2019-08-01 | [
[
"Marín",
"Carlos A.",
""
],
[
"Poveda",
"Jorge",
""
]
] | From the Reissner-Nordstrom metric we obtain the higher-order terms for the deflection of light around a massive-charged black hole using the Lindstedt-Poincar\'e method to solve the equation of motion of a photon around the compact object. The corrections are performed developing the expansion in terms of $\epsilon=\frac{r_{c}}{b}$ and $\frac{\delta}{b}= \frac{Q^{2}}{6 \pi \epsilon_{0}Mc^{2} b}$. Additionally, from the perturbation expansion, we obtain multivariate Pad\'e approximants. We also show how these are a better fit for the numerical data than the original formal Taylor series. |
1912.13035 | Michael Crescimanno | Martin D. Strong, Michael Crescimanno | Lagrange point stability for a rotating host mass binary | Version accepted for publication in PRD | Phys. Rev. D 102, 024052 (2020) | 10.1103/PhysRevD.102.024052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this new era of gravitational wave astrophysics, observations have
indicated the likely existence of black holes with significant spin. In order
to better understand the potential imprint orbital dynamics have on the
multi-messenger data, we include rotation of the primary mass to leading order
in the analysis of the stability boundary pertaining to the triangular
equilibrium points, L_4 and L_5, in the relativistic, restricted, circular
three body problem. For Lagrange point stability these rotation effects are of
the same order as the leading order relativistic corrections ignoring rotation
and make both L_4 and L_5 more stable for retrograde orbital motion.
| [
{
"created": "Mon, 30 Dec 2019 18:06:47 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jun 2020 18:45:40 GMT",
"version": "v2"
}
] | 2020-07-22 | [
[
"Strong",
"Martin D.",
""
],
[
"Crescimanno",
"Michael",
""
]
] | In this new era of gravitational wave astrophysics, observations have indicated the likely existence of black holes with significant spin. In order to better understand the potential imprint orbital dynamics have on the multi-messenger data, we include rotation of the primary mass to leading order in the analysis of the stability boundary pertaining to the triangular equilibrium points, L_4 and L_5, in the relativistic, restricted, circular three body problem. For Lagrange point stability these rotation effects are of the same order as the leading order relativistic corrections ignoring rotation and make both L_4 and L_5 more stable for retrograde orbital motion. |
1803.00348 | D\'aniel Barta | D\'aniel Barta, M\'aty\'as Vas\'uth | Fast prediction and evaluation of eccentric inspirals using
reduced-order models | null | Phys. Rev. D 97, 124011 (2018) | 10.1103/PhysRevD.97.124011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A large number of theoretically predicted waveforms are required by
matched-filtering searches for the gravitational-wave signals produced by
compact binary coalescence. In order to substantially alleviate the
computational burden in gravitational-wave searches and parameter estimation
without degrading the signal detectability, we propose a novel
reduced-order-model (ROM) approach with applications to adiabatic 3PN-accurate
inspiral waveforms of sources that evolve on either highly or slightly
eccentric orbits. We provide a singular-value decomposition-based reduced-basis
method in the frequency domain to generate reduced-order approximations of any
gravitational waves with acceptable accuracy and precision within the parameter
range of the model. We construct efficient reduced bases comprised of a
relatively small number of the most relevant waveforms over 3-dimensional
parameter-space covered by the template bank (total mass $2.15M_{\odot} \leq M
\leq 215M_{\odot}$, mass ratio $0.01 \leq q \leq 1$, and initial orbital
eccentricity $0 \leq e_{0} \leq 0.95$). The ROM is designed to predict signals
in the frequency band from 10 Hz to 2 kHz for aLIGO and aVirgo design
sensitivity. Beside moderating the data reduction, finer sampling of fiducial
templates improves the accuracy of surrogates. Considerable increase in the
speedup from several hundreds to thousands can be achieved by evaluating
surrogates for low-mass systems especially when combined with
high-eccentricity.
| [
{
"created": "Thu, 1 Mar 2018 12:51:26 GMT",
"version": "v1"
}
] | 2018-06-11 | [
[
"Barta",
"Dániel",
""
],
[
"Vasúth",
"Mátyás",
""
]
] | A large number of theoretically predicted waveforms are required by matched-filtering searches for the gravitational-wave signals produced by compact binary coalescence. In order to substantially alleviate the computational burden in gravitational-wave searches and parameter estimation without degrading the signal detectability, we propose a novel reduced-order-model (ROM) approach with applications to adiabatic 3PN-accurate inspiral waveforms of sources that evolve on either highly or slightly eccentric orbits. We provide a singular-value decomposition-based reduced-basis method in the frequency domain to generate reduced-order approximations of any gravitational waves with acceptable accuracy and precision within the parameter range of the model. We construct efficient reduced bases comprised of a relatively small number of the most relevant waveforms over 3-dimensional parameter-space covered by the template bank (total mass $2.15M_{\odot} \leq M \leq 215M_{\odot}$, mass ratio $0.01 \leq q \leq 1$, and initial orbital eccentricity $0 \leq e_{0} \leq 0.95$). The ROM is designed to predict signals in the frequency band from 10 Hz to 2 kHz for aLIGO and aVirgo design sensitivity. Beside moderating the data reduction, finer sampling of fiducial templates improves the accuracy of surrogates. Considerable increase in the speedup from several hundreds to thousands can be achieved by evaluating surrogates for low-mass systems especially when combined with high-eccentricity. |
1406.0822 | Xian Gao | Xian Gao | Unifying framework for scalar-tensor theories of gravity | 5 pages; v2 comments added; v3 published version | Phys. Rev. D 90, 081501 (2014) | 10.1103/PhysRevD.90.081501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general framework for effective theories propagating two tensor and one
scalar degrees of freedom is investigated. Geometrically, it describes
dynamical foliation of spacelike hypersurfaces coupled to a general background,
in which the scalar mode encodes the fluctuation of the hypersurfaces. Within
this framework, various models in the literature---including $k$-essence,
Horndeski theory, the effective field theory of inflation, ghost condensate as
well as the Ho\v{r}ava gravity---get unified. Our framework generalizes the
Horndeski theory in the sense that, it propagates the correct number of degrees
of freedom, although the equations of motion are generally higher order. We
also identify new operators beyond the Horndeski theory, which yield second
order equations of motion for linear perturbations around an a
Friedmann-Robertson-Walker background.
| [
{
"created": "Tue, 3 Jun 2014 19:28:38 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Aug 2014 15:34:49 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Oct 2014 13:32:37 GMT",
"version": "v3"
}
] | 2014-10-29 | [
[
"Gao",
"Xian",
""
]
] | A general framework for effective theories propagating two tensor and one scalar degrees of freedom is investigated. Geometrically, it describes dynamical foliation of spacelike hypersurfaces coupled to a general background, in which the scalar mode encodes the fluctuation of the hypersurfaces. Within this framework, various models in the literature---including $k$-essence, Horndeski theory, the effective field theory of inflation, ghost condensate as well as the Ho\v{r}ava gravity---get unified. Our framework generalizes the Horndeski theory in the sense that, it propagates the correct number of degrees of freedom, although the equations of motion are generally higher order. We also identify new operators beyond the Horndeski theory, which yield second order equations of motion for linear perturbations around an a Friedmann-Robertson-Walker background. |
1108.3962 | John Barrow | John D. Barrow and Kei Yamamoto | The Instabilities of Bianchi Type IX Einstein Static Universes | 11 pages, no figures + revisions | Phys. Rev. D 85, 083505 (2012) | 10.1103/PhysRevD.85.083505 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stability of the Einstein static universe as a non-LRS
Bianchi type IX solution of the Einstein equations in the presence of both
non-tilted and tilted fluids. We find that the static universe is unstable to
homogeneous perturbations of Bianchi type IX to the future and the past.
| [
{
"created": "Fri, 19 Aug 2011 13:24:46 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Feb 2012 11:47:44 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Barrow",
"John D.",
""
],
[
"Yamamoto",
"Kei",
""
]
] | We investigate the stability of the Einstein static universe as a non-LRS Bianchi type IX solution of the Einstein equations in the presence of both non-tilted and tilted fluids. We find that the static universe is unstable to homogeneous perturbations of Bianchi type IX to the future and the past. |
1701.06343 | John Barrow | John D. Barrow and G.W. Gibbons | A maximum magnetic moment to angular momentum conjecture | 24 pages, no figures; to appear in Phys Rev D, refs added and typos
corrected | Phys. Rev. D 95, 064040 (2017) | 10.1103/PhysRevD.95.064040 | null | gr-qc astro-ph.CO hep-th physics.hist-ph | http://creativecommons.org/licenses/by/4.0/ | Conjectures play a central role in theoretical physics, especially those that
assert an upper bound to some dimensionless ratio of physical quantities. In
this paper we introduce a new such conjecture bounding the ratio of the
magnetic moment to angular momentum in nature. We also discuss the current
status of some old bounds on dimensionless and dimensional quantities in
arbitrary spatial dimension. Our new conjecture is that the dimensionless
Schuster-Wilson-Blackett number, c{\mu}/JG^{(1/2)}, where {\mu} is the magnetic
moment and J is the angular momentum, is bounded above by a number of order
unity. We verify that such a bound holds for charged rotating black holes in
those theories for which exact solutions are available, including the
Einstein-Maxwell theory, Kaluza-Klein theory, the Kerr-Sen black hole, and the
so-called STU family of charged rotating supergravity black holes. We also
discuss the current status of the Maximum Tension Conjecture, the Dyson
Luminosity Bound, and Thorne's Hoop Conjecture.
| [
{
"created": "Mon, 23 Jan 2017 11:43:50 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2017 14:05:50 GMT",
"version": "v2"
}
] | 2017-03-29 | [
[
"Barrow",
"John D.",
""
],
[
"Gibbons",
"G. W.",
""
]
] | Conjectures play a central role in theoretical physics, especially those that assert an upper bound to some dimensionless ratio of physical quantities. In this paper we introduce a new such conjecture bounding the ratio of the magnetic moment to angular momentum in nature. We also discuss the current status of some old bounds on dimensionless and dimensional quantities in arbitrary spatial dimension. Our new conjecture is that the dimensionless Schuster-Wilson-Blackett number, c{\mu}/JG^{(1/2)}, where {\mu} is the magnetic moment and J is the angular momentum, is bounded above by a number of order unity. We verify that such a bound holds for charged rotating black holes in those theories for which exact solutions are available, including the Einstein-Maxwell theory, Kaluza-Klein theory, the Kerr-Sen black hole, and the so-called STU family of charged rotating supergravity black holes. We also discuss the current status of the Maximum Tension Conjecture, the Dyson Luminosity Bound, and Thorne's Hoop Conjecture. |
gr-qc/0205012 | Jacques L. Rubin | Jacques L. Rubin | Navigation of Spacetime Ships in Unified Gravitational and
Electromagnetic Waves | 28 pages. Relative to the second version some changes in the
mathematical results have been corrected without consequences in the physical
model. The conformally flatness of the substratum spacetime which is an
assumption used throughout in the mathematical developements from chapter 2,
has been well precised in the first chapter. Clearer explanations at the very
end of chapter 3 about accelerating frames are given. New references are
indicated and some of them corrected | null | null | Preprint INLN #2002/13 | gr-qc | null | On the basis of a "local" principle of equivalence of general relativity, we
consider a navigation in a kind of "4D-ocean" involving measurements of
conformally invariant physical properties only. Then, applying the Pfaff theory
for PDE to a particular conformally equivariant system of differential
equations, we show the dependency of any kind of function describing "spacetime
waves", with respect to 20 parametrizing functions. These latter, appearing in
a linear differential Spencer sequence and determining gauge fields of
deformations relatively to "ship-metrics" or to "flat spacetime ocean metrics",
may be ascribed to unified electromagnetic and gravitational waves. The present
model is based neither on a classical gauge theory of gravitation or a
gravitation theory with torsion, nor on any Kaluza-Klein or Weyl type
unifications, but rather on a post-Newtonian approach of gravitation in a four
dimensional conformal Cosserat spacetime.
| [
{
"created": "Thu, 2 May 2002 22:39:00 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jun 2002 10:54:52 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Oct 2004 13:22:47 GMT",
"version": "v3"
},
{
"created": "Thu, 7 Oct 2004 23:04:57 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Rubin",
"Jacques L.",
""
]
] | On the basis of a "local" principle of equivalence of general relativity, we consider a navigation in a kind of "4D-ocean" involving measurements of conformally invariant physical properties only. Then, applying the Pfaff theory for PDE to a particular conformally equivariant system of differential equations, we show the dependency of any kind of function describing "spacetime waves", with respect to 20 parametrizing functions. These latter, appearing in a linear differential Spencer sequence and determining gauge fields of deformations relatively to "ship-metrics" or to "flat spacetime ocean metrics", may be ascribed to unified electromagnetic and gravitational waves. The present model is based neither on a classical gauge theory of gravitation or a gravitation theory with torsion, nor on any Kaluza-Klein or Weyl type unifications, but rather on a post-Newtonian approach of gravitation in a four dimensional conformal Cosserat spacetime. |
1207.5496 | Kayll Lake | Majd Abdelqader and Kayll Lake | Visualizing Spacetime Curvature via Gradient Flows II: An Example of the
Construction of a Newtonian analogue | 12 pages twocolumn revtex 4-1 9 figures. Expanded and corrected | Phys. Rev. D 86, 124037 (2012) | 10.1103/PhysRevD.86.124037 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the first in a series of papers in which the gradient flows of
fundamental curvature invariants are used to formulate a visualization of
curvature. We start with the construction of strict Newtonian analogues (not
limits) of solutions to Einstein's equations based on the topology of the
associated gradient flows. We do not start with any easy case. Rather, we start
with the Curzon - Chazy solution, which, as history shows, is one of the most
difficult exact solutions to Einstein's equations to interpret physically. We
show that the entire field of the Curzon - Chazy solution, up to a region very
"close" to the the intrinsic singularity, strictly represents that of a
Newtonian ring, as has long been suspected. In this regard, we consider our
approach very successful. As regrades the local structure of the singularity of
the Curzon - Chazy solution within a fully general relativistic analysis,
however, whereas we make some advances, the full structure of this singularity
remains incompletely resolved.
| [
{
"created": "Mon, 23 Jul 2012 19:38:46 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Nov 2012 21:11:08 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Abdelqader",
"Majd",
""
],
[
"Lake",
"Kayll",
""
]
] | This is the first in a series of papers in which the gradient flows of fundamental curvature invariants are used to formulate a visualization of curvature. We start with the construction of strict Newtonian analogues (not limits) of solutions to Einstein's equations based on the topology of the associated gradient flows. We do not start with any easy case. Rather, we start with the Curzon - Chazy solution, which, as history shows, is one of the most difficult exact solutions to Einstein's equations to interpret physically. We show that the entire field of the Curzon - Chazy solution, up to a region very "close" to the the intrinsic singularity, strictly represents that of a Newtonian ring, as has long been suspected. In this regard, we consider our approach very successful. As regrades the local structure of the singularity of the Curzon - Chazy solution within a fully general relativistic analysis, however, whereas we make some advances, the full structure of this singularity remains incompletely resolved. |
1904.11600 | Ehsan Sadri | Ehsan Sadri, Martiros Khurshudyan, Ding-fang Zeng | Scrutinizing Various Phenomenological Interactions In The Context Of
Holographic Ricci Dark Energy Models | 27 pages, 60 figures | null | 10.1140/epjc/s10052-020-7983-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine two types of interacting holographic dark energy
model using Pantheon supernova data, BAO BOSS DR12, CMB Planck 2015, fgas (gas
mass fraction) and SZ/Xray (Sunyaev-Zeldovich effect and X-ray emission) data
from galaxy clusters (GC). In particular, we considered the Holographic Ricci
dark energy and Extended holographic Ricci dark energy models. During this
analysis we considered seven type of phenomenological interaction terms (three
linear and four non-linear) $Q_1=3Hb\rho_{D}$, $Q_2=3Hb\rho_{m}$,
$Q_3=3Hb\left(\rho_{D}+\rho_m\right)$,
$Q_4=3Hb\left(\rho_{D}+\frac{\rho_{D}^2}{\rho_{D}+\rho_m}\right)$,
$Q_5=3Hb\left(\rho_{m}+\frac{\rho_{m}^2}{\rho_{D}+\rho_m}\right)$,
$Q_6=3Hb\left(\rho_{D}+\rho_{m}+\frac{\rho_{D}^2}{\rho_{D}+\rho_m}\right)$,
$Q_7=3Hb\left(\rho_{D}+\rho_{m}+\frac{\rho_{m}^2}{\rho_{D}+\rho_m}\right)$
respectively. To find the best model we apply Akaike Information Criterion
(AIC) and Bayesian Information Criterion (BIC) and use the $\Lambda$CDM as the
referring model for comparison. Using AIC and BIC models selection method we
note that the $Q_1$ and $Q_4$ interaction terms are favored by observational
data within the context of the holographic Ricci dark energy models. The
obtained results also demonstrated that the considered types of holographic
Ricci dark energy model are not favored by observational data since the
$\Lambda$CDM is considered as the reference model. We also observed that the
values of the deceleration parameter and the transition redshift for all models
are compatible with the latest observational data and Planck 2015. In addition,
we studied the jerk parameter for all models. Using our modified CAMB code, we
observed that the interacting models suppress the CMB spectrum at low
multi-poles and enhances the acoustic peaks.
| [
{
"created": "Thu, 25 Apr 2019 21:44:25 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2019 22:39:58 GMT",
"version": "v2"
},
{
"created": "Sat, 11 Jul 2020 11:38:33 GMT",
"version": "v3"
}
] | 2020-07-14 | [
[
"Sadri",
"Ehsan",
""
],
[
"Khurshudyan",
"Martiros",
""
],
[
"Zeng",
"Ding-fang",
""
]
] | In this paper, we examine two types of interacting holographic dark energy model using Pantheon supernova data, BAO BOSS DR12, CMB Planck 2015, fgas (gas mass fraction) and SZ/Xray (Sunyaev-Zeldovich effect and X-ray emission) data from galaxy clusters (GC). In particular, we considered the Holographic Ricci dark energy and Extended holographic Ricci dark energy models. During this analysis we considered seven type of phenomenological interaction terms (three linear and four non-linear) $Q_1=3Hb\rho_{D}$, $Q_2=3Hb\rho_{m}$, $Q_3=3Hb\left(\rho_{D}+\rho_m\right)$, $Q_4=3Hb\left(\rho_{D}+\frac{\rho_{D}^2}{\rho_{D}+\rho_m}\right)$, $Q_5=3Hb\left(\rho_{m}+\frac{\rho_{m}^2}{\rho_{D}+\rho_m}\right)$, $Q_6=3Hb\left(\rho_{D}+\rho_{m}+\frac{\rho_{D}^2}{\rho_{D}+\rho_m}\right)$, $Q_7=3Hb\left(\rho_{D}+\rho_{m}+\frac{\rho_{m}^2}{\rho_{D}+\rho_m}\right)$ respectively. To find the best model we apply Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) and use the $\Lambda$CDM as the referring model for comparison. Using AIC and BIC models selection method we note that the $Q_1$ and $Q_4$ interaction terms are favored by observational data within the context of the holographic Ricci dark energy models. The obtained results also demonstrated that the considered types of holographic Ricci dark energy model are not favored by observational data since the $\Lambda$CDM is considered as the reference model. We also observed that the values of the deceleration parameter and the transition redshift for all models are compatible with the latest observational data and Planck 2015. In addition, we studied the jerk parameter for all models. Using our modified CAMB code, we observed that the interacting models suppress the CMB spectrum at low multi-poles and enhances the acoustic peaks. |
1308.1315 | Anuradha Gupta | Anuradha Gupta and Achamveedu Gopakumar | Time-domain inspiral templates for spinning compact binaries in
quasi-circular orbits described by their orbital angular momenta | 23 pages, 6 figures, Several improvements in the text, one new figure
and new references added, version accepted for publication in CQG | Class. Quantum Grav. 31 (2014) 065014 | 10.1088/0264-9381/31/6/065014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a prescription to compute the time-domain gravitational wave (GW)
polarization states associated with spinning compact binaries inspiraling along
quasi-circular orbits. We invoke the orbital angular momentum $\vek L$ rather
than its Newtonian counterpart $\vek L_{\rm N}$ to describe the binary orbits
while the two spin vectors are freely specified in an inertial frame associated
with the initial direction of the total angular momentum. We show that the use
of $\vek L$ to describe the orbits leads to additional 1.5PN order amplitude
contributions to the two GW polarization states compared to the $\vek L_{\rm
N}$-based approach and discuss few implications of our approach. Further, we
provide a plausible prescription for GW phasing based on few theoretical
considerations and which may be treated as the natural circular limit to GW
phasing for spinning compact binaries in inspiraling eccentric orbits
[Gopakumar A and Sch{\"a}fer G 2011 {\em Phys. Rev. D} {\bf 84} 124007].
| [
{
"created": "Tue, 6 Aug 2013 15:39:42 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2014 16:45:41 GMT",
"version": "v2"
}
] | 2014-03-03 | [
[
"Gupta",
"Anuradha",
""
],
[
"Gopakumar",
"Achamveedu",
""
]
] | We present a prescription to compute the time-domain gravitational wave (GW) polarization states associated with spinning compact binaries inspiraling along quasi-circular orbits. We invoke the orbital angular momentum $\vek L$ rather than its Newtonian counterpart $\vek L_{\rm N}$ to describe the binary orbits while the two spin vectors are freely specified in an inertial frame associated with the initial direction of the total angular momentum. We show that the use of $\vek L$ to describe the orbits leads to additional 1.5PN order amplitude contributions to the two GW polarization states compared to the $\vek L_{\rm N}$-based approach and discuss few implications of our approach. Further, we provide a plausible prescription for GW phasing based on few theoretical considerations and which may be treated as the natural circular limit to GW phasing for spinning compact binaries in inspiraling eccentric orbits [Gopakumar A and Sch{\"a}fer G 2011 {\em Phys. Rev. D} {\bf 84} 124007]. |
0911.3697 | Ali Mozaffari | Joao Magueijo, Ali Mozaffari | Simple generalizations of Anti-de Sitter space-time | 6 Pages, 5 Figures, Corrections and additions made for publication in
Journal of Classical and Quantum Gravity | Class.Quant.Grav.27:135004,2010 | 10.1088/0264-9381/27/13/135004 | Imperial/TP/2009/JM&AM/0911.3697 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider new cosmological solutions which generalize the cosmological
patch of the Anti-de Sitter (AdS) space-time, allowing for fluids with
equations of state such that $w\neq -1$. We use them to derive the associated
full manifolds. We find that these solutions can all be embedded in flat
five-dimensional space-time with $--+++$ signature, revealing deformed
hyperboloids. The topology and causal-structure of these spaces is therefore
unchanged, and closed time-like curves are identified, before a covering space
is considered. However the structure of Killing vector fields is entirely
different and so we may expect a different structure of Killing horizons in
these solutions.
| [
{
"created": "Thu, 19 Nov 2009 13:18:05 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jan 2010 22:02:29 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Mar 2010 18:43:48 GMT",
"version": "v3"
}
] | 2010-05-25 | [
[
"Magueijo",
"Joao",
""
],
[
"Mozaffari",
"Ali",
""
]
] | We consider new cosmological solutions which generalize the cosmological patch of the Anti-de Sitter (AdS) space-time, allowing for fluids with equations of state such that $w\neq -1$. We use them to derive the associated full manifolds. We find that these solutions can all be embedded in flat five-dimensional space-time with $--+++$ signature, revealing deformed hyperboloids. The topology and causal-structure of these spaces is therefore unchanged, and closed time-like curves are identified, before a covering space is considered. However the structure of Killing vector fields is entirely different and so we may expect a different structure of Killing horizons in these solutions. |
1407.5021 | Lorenzo Iorio | Lorenzo Iorio | Post-Keplerian corrections to the orbital periods of a two-body system
and their measurability | LaTex2e, 8 pages, no figures, no tables. Version matching the one at
press in Monthly Notices of the Royal Astronomical Society (MNRAS). Typos
corrected in equations (65)-(67) | Mon.Not.Roy.Astron.Soc. 460 : 2445-2452, 2016 | 10.1093/mnras/stw1155 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The orbital motion of a binary system is characterized by various
characteristic temporal intervals which, by definition, are different from each
other: the draconitic, anomalistic and sidereal periods. They all coincide in
the Keplerian case. Such a degeneracy is removed, in general, when a
post-Keplerian acceleration is present. We analytically work out the
corrections to such otherwise Keplerian periods which are induced by general
relativity (Schwarzschild and Lense-Thirring) and, at the Newtonian level, by
the quadrupole of the primary. In many astronomical and astrophysical systems,
like exoplanets, one of the most accurately determined quantities is just the
time span characterizing the orbital revolution, which is often measured
independently with different techniques like the transit photometry and the
radial velocities. Thus, our results could be useful, in principle, to either
constrain the physical properties of the central body and/or perform new tests
of general relativity, especially when no other standard observables like,
e.g., the orbital precessions are accessible to observations. The difference of
two independently measured periods would cancel out the common Keplerian term
leaving just a post-Keplerian correction. Furthermore, by comparing the
theoretically predicted post-Keplerian expressions $T^{(\textrm{pK})}$ with the
experimental accuracy $\sigma_{T_\textrm{exp}}$ in measuring the orbital
period(s) it is possible to identify those systems whose observations should be
re-processed with genuine post-Keplerian models if
$T^{(\textrm{pK})}>\sigma_{T_\textrm{exp}}$. It seems just the case for WASP-33
b since $\sigma_{T_\textrm{exp}}=0.04$ s, while $3$ s$\leq
T_\textrm{dra}^{(J_2)}\leq 9.5$ s, $T_\textrm{dra}^{(\textrm{GE)}}=0.36$ s.
| [
{
"created": "Thu, 17 Jul 2014 15:04:46 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2016 18:10:53 GMT",
"version": "v2"
},
{
"created": "Mon, 9 May 2016 14:31:43 GMT",
"version": "v3"
},
{
"created": "Wed, 25 May 2016 19:31:20 GMT",
"version": "v4"
}
] | 2016-06-15 | [
[
"Iorio",
"Lorenzo",
""
]
] | The orbital motion of a binary system is characterized by various characteristic temporal intervals which, by definition, are different from each other: the draconitic, anomalistic and sidereal periods. They all coincide in the Keplerian case. Such a degeneracy is removed, in general, when a post-Keplerian acceleration is present. We analytically work out the corrections to such otherwise Keplerian periods which are induced by general relativity (Schwarzschild and Lense-Thirring) and, at the Newtonian level, by the quadrupole of the primary. In many astronomical and astrophysical systems, like exoplanets, one of the most accurately determined quantities is just the time span characterizing the orbital revolution, which is often measured independently with different techniques like the transit photometry and the radial velocities. Thus, our results could be useful, in principle, to either constrain the physical properties of the central body and/or perform new tests of general relativity, especially when no other standard observables like, e.g., the orbital precessions are accessible to observations. The difference of two independently measured periods would cancel out the common Keplerian term leaving just a post-Keplerian correction. Furthermore, by comparing the theoretically predicted post-Keplerian expressions $T^{(\textrm{pK})}$ with the experimental accuracy $\sigma_{T_\textrm{exp}}$ in measuring the orbital period(s) it is possible to identify those systems whose observations should be re-processed with genuine post-Keplerian models if $T^{(\textrm{pK})}>\sigma_{T_\textrm{exp}}$. It seems just the case for WASP-33 b since $\sigma_{T_\textrm{exp}}=0.04$ s, while $3$ s$\leq T_\textrm{dra}^{(J_2)}\leq 9.5$ s, $T_\textrm{dra}^{(\textrm{GE)}}=0.36$ s. |
2202.03114 | Takahisa Igata | Takahisa Igata, Yohsuke Takamori | Periapsis shifts in dark matter distribution with a dense core | 14 pages, 3 figures; v2: published version | Phys. Rev. D 105, 124029 (2022) | 10.1103/PhysRevD.105.124029 | KEK-TH-2395, KEK-Cosmo-0285 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the periapsis shifts in dark matter distribution with a dense
core. We model the dark matter distribution as an isotropic gas sphere, the
Emden polytropic sphere of index 5 in general relativity. This model has a
parameter range where all the energy conditions are satisfied in the entire
region. Within the parameter range, the asymptotic analysis for stellar motion
allows us to identify two competing effects on the bounded motion: the
general-relativistic effect and a local-density effect of matter. Furthermore,
using nearly circular bound orbits, we demonstrate that retrograde periapsis
shifts occur near the center, where the local-density effect dominates over the
general-relativistic effect, whereas prograde periapsis shifts occur in the far
region, where the general-relativistic effect dominates over the local-density
effect. This result means that a natural explanation for the retrograde
periapsis shifts is not the existence of exotic objects (e.g., naked
singularities or wormholes) but the local distribution of physically reasonable
matter on the stellar orbit. Furthermore, it also implies that the periapsis
shift plays a crucial role in distinguishing black hole alternatives, such as
dark matter cores, from a pure black hole.
| [
{
"created": "Mon, 7 Feb 2022 12:47:48 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jul 2022 04:23:18 GMT",
"version": "v2"
}
] | 2022-07-18 | [
[
"Igata",
"Takahisa",
""
],
[
"Takamori",
"Yohsuke",
""
]
] | We consider the periapsis shifts in dark matter distribution with a dense core. We model the dark matter distribution as an isotropic gas sphere, the Emden polytropic sphere of index 5 in general relativity. This model has a parameter range where all the energy conditions are satisfied in the entire region. Within the parameter range, the asymptotic analysis for stellar motion allows us to identify two competing effects on the bounded motion: the general-relativistic effect and a local-density effect of matter. Furthermore, using nearly circular bound orbits, we demonstrate that retrograde periapsis shifts occur near the center, where the local-density effect dominates over the general-relativistic effect, whereas prograde periapsis shifts occur in the far region, where the general-relativistic effect dominates over the local-density effect. This result means that a natural explanation for the retrograde periapsis shifts is not the existence of exotic objects (e.g., naked singularities or wormholes) but the local distribution of physically reasonable matter on the stellar orbit. Furthermore, it also implies that the periapsis shift plays a crucial role in distinguishing black hole alternatives, such as dark matter cores, from a pure black hole. |
gr-qc/9504018 | Donald Marolf | Abhay Ashtekar, Jerzy Lewandowski, Donald Marolf, Jose Mourao, Thomas
Thiemann | Quantization of diffeomorphism invariant theories of connections with
local degrees of freedom | 30 pages Revtex, Section 6 corrected, references added, format
changed | J.Math.Phys.36:6456-6493,1995 | 10.1063/1.531252 | UCSBTH-95-7 | gr-qc | null | Quantization of diffeomorphism invariant theories of connections is studied.
A solutions of the diffeomorphism constraints is found. The space of solutions
is equipped with an inner product that is shown to satisfy the physical reality
conditions. This provides, in particular, a quantization of the
Husain-Kucha\v{r} model. The main results also pave way to quantization of
other diffeomorphism invariant theories such as general relativity. In the
Riemannian case (i.e., signature ++++), the approach appears to contain all the
necessary ingredients already. In the Lorentzian case, it will have to combined
in an appropriate fashion with a coherent state transform to incorporate
complex connections.
| [
{
"created": "Wed, 12 Apr 1995 21:06:50 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Jun 1995 16:35:53 GMT",
"version": "v2"
}
] | 2010-11-01 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Marolf",
"Donald",
""
],
[
"Mourao",
"Jose",
""
],
[
"Thiemann",
"Thomas",
""
]
] | Quantization of diffeomorphism invariant theories of connections is studied. A solutions of the diffeomorphism constraints is found. The space of solutions is equipped with an inner product that is shown to satisfy the physical reality conditions. This provides, in particular, a quantization of the Husain-Kucha\v{r} model. The main results also pave way to quantization of other diffeomorphism invariant theories such as general relativity. In the Riemannian case (i.e., signature ++++), the approach appears to contain all the necessary ingredients already. In the Lorentzian case, it will have to combined in an appropriate fashion with a coherent state transform to incorporate complex connections. |
1111.1766 | Chun-Yen Lin | Chun-Yen Lin | Emergence of Loop Quantum Cosmology from Loop Quantum Gravity: Lowest
Order in h | 31 pages MikteX file with 1 pdf figure | Chin. J. Phys. 53 (2015) 110104 | 10.6122/CJP.20150911 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To derive loop quantum cosmology from loop quantum gravity, I apply the model
given in \cite{lin1} to a system with coupled gravitational and matter fields.
The matter sector consists of a scalar field $phi$ serving as a cosmological
clock, and other fields ${psi}$ providing physical spatial coordinates and
frames. The physical Hilbert space of the model is constructed from the
kinematical Hilbert space of loop quantum gravity, and the local observables in
the physical Hilbert space are constructed using the matter coordinates and
frames. A specific coherent physical state is then chosen, whose expectation
values of the local observables give rise to homogeneous, isotropic and
spatially flat gravitational and $phi$ fields at a late clock time. The
equations governing these fields may be derived using the symmetry of the
physical Hilbert space. When the matter back reactions from ${psi}$ are
negligible, the result gives a specific loop quantum cosmological model in the
$O(hbar^0)$ approximation, with calculable higher order corrections.
| [
{
"created": "Mon, 7 Nov 2011 23:34:47 GMT",
"version": "v1"
}
] | 2018-07-23 | [
[
"Lin",
"Chun-Yen",
""
]
] | To derive loop quantum cosmology from loop quantum gravity, I apply the model given in \cite{lin1} to a system with coupled gravitational and matter fields. The matter sector consists of a scalar field $phi$ serving as a cosmological clock, and other fields ${psi}$ providing physical spatial coordinates and frames. The physical Hilbert space of the model is constructed from the kinematical Hilbert space of loop quantum gravity, and the local observables in the physical Hilbert space are constructed using the matter coordinates and frames. A specific coherent physical state is then chosen, whose expectation values of the local observables give rise to homogeneous, isotropic and spatially flat gravitational and $phi$ fields at a late clock time. The equations governing these fields may be derived using the symmetry of the physical Hilbert space. When the matter back reactions from ${psi}$ are negligible, the result gives a specific loop quantum cosmological model in the $O(hbar^0)$ approximation, with calculable higher order corrections. |
gr-qc/0310056 | Tomislav Prokopec | Tomislav Prokopec (U. Heidelberg) and Richard P. Woodard (U. Florida) | Dynamics of super-horizon photons during inflation with vacuum
polarization | 16 pages, 2 figures | Annals Phys. 312 (2004) 1-16 | 10.1016/j.aop.2004.01.012 | CERN-TH/2003-172, HD-THEP-03-38, UFIFT-HEP-03-20 | gr-qc astro-ph hep-ph | null | We study asymptotic dynamics of photons propagating in the polarized vacuum
of a locally de Sitter Universe. The origin of the vacuum polarization is
fluctuations of a massless, minimally coupled, scalar, which we model by the
one-loop vacuum polarization tensor of scalar electrodynamics. We show that
late time dynamics of the electric field on superhorizon scales approaches that
of an Airy oscillator. The magentic field amplitude, on the other hand,
asymptotically approaches a nonvanishing constant (plus an exponentially small
oscillatory component), which is suppressed with respect to the initial
(vacuum) amplitude. This implies that the asymptotic photon dynamics is more
intricate than that of a massive photon obeying the local Proca equation.
| [
{
"created": "Fri, 10 Oct 2003 16:52:27 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Oct 2003 23:57:55 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Prokopec",
"Tomislav",
"",
"U. Heidelberg"
],
[
"Woodard",
"Richard P.",
"",
"U. Florida"
]
] | We study asymptotic dynamics of photons propagating in the polarized vacuum of a locally de Sitter Universe. The origin of the vacuum polarization is fluctuations of a massless, minimally coupled, scalar, which we model by the one-loop vacuum polarization tensor of scalar electrodynamics. We show that late time dynamics of the electric field on superhorizon scales approaches that of an Airy oscillator. The magentic field amplitude, on the other hand, asymptotically approaches a nonvanishing constant (plus an exponentially small oscillatory component), which is suppressed with respect to the initial (vacuum) amplitude. This implies that the asymptotic photon dynamics is more intricate than that of a massive photon obeying the local Proca equation. |
1104.2765 | Maite Dupuis | Mait\'e Dupuis | Spin Foam Models for Quantum Gravity and semi-classical limit | PhD Thesis; Ecole Normale Sup\'erieure de Lyon. (192pages, many
figures) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spinfoam framework is a proposal for a regularized path integral for
quantum gravity. Spinfoams define quantum space-time structures describing the
evolution in time of the spin network states for quantum geometry derived from
Loop Quantum Gravity (LQG). The construction of this covariant approach is
based on the formulation of General Relativity as a topological theory plus the
so-called simplicity constraints which introduce local degrees of freedom. The
simplicity constraints are essential in turning the non-physical topological
theory into 4d gravity. In this PhD manuscript, an original way to impose the
simplicity constraints in 4d Euclidean gravity using harmonic oscillators is
proposed and new coherent states, solutions of the constraints, are given.
Moreover, a consistent spinfoam model for quantum gravity has to be connected
to LQG and must have the right semi-classical limit. An explicit map between
the spin network states of LQG and the boundary states of spinfoam models is
given connecting the canonical and the covariant approaches. Finally, new
techniques to compute semiclassical asymptotic expressions for the transition
amplitudes of 3d quantum gravity and to extract semi-classical information from
a spinfoam model are introduced. Explicit computations based on approximation
methods and on the use of recurrence relations on spinfoam amplitudes have been
performed. The results are relevant to derive quantum corrections to the
dynamics of the gravitational field.
| [
{
"created": "Thu, 14 Apr 2011 13:56:31 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Dupuis",
"Maité",
""
]
] | The spinfoam framework is a proposal for a regularized path integral for quantum gravity. Spinfoams define quantum space-time structures describing the evolution in time of the spin network states for quantum geometry derived from Loop Quantum Gravity (LQG). The construction of this covariant approach is based on the formulation of General Relativity as a topological theory plus the so-called simplicity constraints which introduce local degrees of freedom. The simplicity constraints are essential in turning the non-physical topological theory into 4d gravity. In this PhD manuscript, an original way to impose the simplicity constraints in 4d Euclidean gravity using harmonic oscillators is proposed and new coherent states, solutions of the constraints, are given. Moreover, a consistent spinfoam model for quantum gravity has to be connected to LQG and must have the right semi-classical limit. An explicit map between the spin network states of LQG and the boundary states of spinfoam models is given connecting the canonical and the covariant approaches. Finally, new techniques to compute semiclassical asymptotic expressions for the transition amplitudes of 3d quantum gravity and to extract semi-classical information from a spinfoam model are introduced. Explicit computations based on approximation methods and on the use of recurrence relations on spinfoam amplitudes have been performed. The results are relevant to derive quantum corrections to the dynamics of the gravitational field. |
gr-qc/0606093 | Eric Poisson | Brent Preston and Eric Poisson | Light-cone coordinates based at a geodesic world line | 11 pages, 1 figure | Phys.Rev. D74 (2006) 064009 | 10.1103/PhysRevD.74.064009 | null | gr-qc | null | Continuing work initiated in an earlier publication [Phys. Rev. D 69, 084007
(2004)], we construct a system of light-cone coordinates based at a geodesic
world line of an arbitrary curved spacetime. The construction involves (i) an
advanced-time or a retarded-time coordinate that labels past or future light
cones centered on the world line, (ii) a radial coordinate that is an affine
parameter on the null generators of these light cones, and (iii) angular
coordinates that are constant on each generator. The spacetime metric is
calculated in the light-cone coordinates, and it is expressed as an expansion
in powers of the radial coordinate in terms of the irreducible components of
the Riemann tensor evaluated on the world line. The formalism is illustrated in
two simple applications, the first involving a comoving world line of a
spatially-flat cosmology, the other featuring an observer placed on the axis of
symmetry of Melvin's magnetic universe.
| [
{
"created": "Wed, 21 Jun 2006 20:34:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Preston",
"Brent",
""
],
[
"Poisson",
"Eric",
""
]
] | Continuing work initiated in an earlier publication [Phys. Rev. D 69, 084007 (2004)], we construct a system of light-cone coordinates based at a geodesic world line of an arbitrary curved spacetime. The construction involves (i) an advanced-time or a retarded-time coordinate that labels past or future light cones centered on the world line, (ii) a radial coordinate that is an affine parameter on the null generators of these light cones, and (iii) angular coordinates that are constant on each generator. The spacetime metric is calculated in the light-cone coordinates, and it is expressed as an expansion in powers of the radial coordinate in terms of the irreducible components of the Riemann tensor evaluated on the world line. The formalism is illustrated in two simple applications, the first involving a comoving world line of a spatially-flat cosmology, the other featuring an observer placed on the axis of symmetry of Melvin's magnetic universe. |
1407.3027 | Leonid Perlov | Leonid Perlov | Convergent $\tilde{Y}$-Map for a new covariant Loop Quantum Gravity
formulation | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The most important part of the new spin-foam loop quantum gravity formulation
is the map $Y$: $H^{SU(2)} \rightarrow H^{SL(2,C)}$. It was only recently shown
that the Y-Map is convergent in spite of the fact that the classical Peter-Weyl
theorem is not applicable to it, as Lorentz group is not compact. In this paper
we provide an alternative map $\tilde{Y}$. The $\tilde{Y}$ map has an advantage
of preserving the Lorentz covariance, which gets broken in the case of Y-Map.
The image of a new map $\tilde{Y}$ contains the weighted infinite sum of
$SL(2,C)$ matrix coefficients. The sum is convergent and its limit is the
square integrable functions of $SL(2,C)$ with the measure $L^2(g,
e^{-|Y|^2/\hbar}\eta(g) du \,dY )$ according to the Holomorphic
Huebschmann-Peter-Weyl theorem, which is applicable to the rational
representations of the non-unitary groups, particularly non-unitary finite
Lorenz representations. Since in LQG the unitary evolution is not mandatory as
it does not follow from the Wheeler-DeWitt dynamics equation, the choice of the
non-unitary representation is valid. As it was stated in the original LQG
formulation: "there is no sense in which conventional unitarity is necessary in
the theory".
| [
{
"created": "Fri, 11 Jul 2014 05:04:31 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Feb 2015 06:27:57 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Oct 2015 02:49:07 GMT",
"version": "v3"
}
] | 2015-10-08 | [
[
"Perlov",
"Leonid",
""
]
] | The most important part of the new spin-foam loop quantum gravity formulation is the map $Y$: $H^{SU(2)} \rightarrow H^{SL(2,C)}$. It was only recently shown that the Y-Map is convergent in spite of the fact that the classical Peter-Weyl theorem is not applicable to it, as Lorentz group is not compact. In this paper we provide an alternative map $\tilde{Y}$. The $\tilde{Y}$ map has an advantage of preserving the Lorentz covariance, which gets broken in the case of Y-Map. The image of a new map $\tilde{Y}$ contains the weighted infinite sum of $SL(2,C)$ matrix coefficients. The sum is convergent and its limit is the square integrable functions of $SL(2,C)$ with the measure $L^2(g, e^{-|Y|^2/\hbar}\eta(g) du \,dY )$ according to the Holomorphic Huebschmann-Peter-Weyl theorem, which is applicable to the rational representations of the non-unitary groups, particularly non-unitary finite Lorenz representations. Since in LQG the unitary evolution is not mandatory as it does not follow from the Wheeler-DeWitt dynamics equation, the choice of the non-unitary representation is valid. As it was stated in the original LQG formulation: "there is no sense in which conventional unitarity is necessary in the theory". |
2307.12190 | Nikodem Poplawski | Nikodem Pop{\l}awski | Gravitational Collapse with Torsion and Universe in a Black Hole | 10 pages. In: Regular Black Holes: Towards a New Paradigm of
Gravitational Collapse, C. Bambi (ed.), p. 485 (Springer, 2023). arXiv admin
note: substantial text overlap with arXiv:2008.02136 | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider gravitational collapse of a sphere of a fluid with torsion
generated by spin, which forms a black hole. We use the Tolman metric and the
Einstein$-$Cartan field equations with a relativistic spin fluid as a source.
We show that gravitational repulsion of torsion prevents a singularity,
replacing it with a nonsingular bounce. Quantum particle creation during
contraction prevents shear from overcoming torsion. Particle creation during
expansion can generate a finite period of inflation and produce large amounts
of matter. The resulting closed universe on the other side of the event horizon
may have several bounces. Such a universe is oscillatory, with each cycle
larger than the preceding cycle, until it reaches a size at which dark energy
dominates and expands indefinitely. Our universe might have therefore
originated from a black hole existing in another universe.
| [
{
"created": "Sun, 23 Jul 2023 00:31:33 GMT",
"version": "v1"
}
] | 2023-09-22 | [
[
"Popławski",
"Nikodem",
""
]
] | We consider gravitational collapse of a sphere of a fluid with torsion generated by spin, which forms a black hole. We use the Tolman metric and the Einstein$-$Cartan field equations with a relativistic spin fluid as a source. We show that gravitational repulsion of torsion prevents a singularity, replacing it with a nonsingular bounce. Quantum particle creation during contraction prevents shear from overcoming torsion. Particle creation during expansion can generate a finite period of inflation and produce large amounts of matter. The resulting closed universe on the other side of the event horizon may have several bounces. Such a universe is oscillatory, with each cycle larger than the preceding cycle, until it reaches a size at which dark energy dominates and expands indefinitely. Our universe might have therefore originated from a black hole existing in another universe. |
1009.3667 | Anastasia Golubtsova | A. A. Golubtsova and V. D. Ivashchuk | On multidimensional analogs of Melvin's solution for classical series of
Lie algebras | 6 pages, based on a report at RUSGRAV-13 (23-28 June, 2008, PFUR,
Moscow) | Grav.Cosmol.15:144-147,2009 | 10.1134/S0202289309020078 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A multidimensional generalization of Melvin's solution for an arbitrary
simple Lie algebra $\cal G$ is presented. The gravitational model contains n
2-forms and $l \geq n$ scalar fields, wheren is the rank of $\cal G$. The
solution is governed by a set of n functions obeying n ordinary differential
equations with certain boundary conditions. It was conjectured earlier that
these functions should be polynomials (the so-called fluxbrane polynomials). A
program (in Maple) for calculating of these polynomials for classical series of
Lie algebras is suggested (see Appendix). The polynomials corresponding to the
Lie algebra D_4 are obtained. It is conjectured that the polynomials for A_n-,
B_n- and C_n-series may be obtained from polynomials for D_{n+1}-series by
using certain reduction formulas.
| [
{
"created": "Sun, 19 Sep 2010 23:06:27 GMT",
"version": "v1"
}
] | 2010-11-26 | [
[
"Golubtsova",
"A. A.",
""
],
[
"Ivashchuk",
"V. D.",
""
]
] | A multidimensional generalization of Melvin's solution for an arbitrary simple Lie algebra $\cal G$ is presented. The gravitational model contains n 2-forms and $l \geq n$ scalar fields, wheren is the rank of $\cal G$. The solution is governed by a set of n functions obeying n ordinary differential equations with certain boundary conditions. It was conjectured earlier that these functions should be polynomials (the so-called fluxbrane polynomials). A program (in Maple) for calculating of these polynomials for classical series of Lie algebras is suggested (see Appendix). The polynomials corresponding to the Lie algebra D_4 are obtained. It is conjectured that the polynomials for A_n-, B_n- and C_n-series may be obtained from polynomials for D_{n+1}-series by using certain reduction formulas. |
gr-qc/9311020 | Guillermo Mena | Guillermo A. Mena Marugan | Reality Conditions for Lorentzian and Euclidean Gravity in the Ashtekar
Formulation | 24 pages (Latex), Preprint CGPG-93/11-2 | Int. J. Mod. Phys. D3 (1994) 513-528 | 10.1142/S0218271894000678 | null | gr-qc | null | Using Ashtekar variables, we analyze Lorentzian and Euclidean gravity in
vacuum up to a constant conformal transformation. We prove that the reality
conditions are invariant under a Wick rotation of the time, and show that the
compatibility of the algebra of commutators and constraints with the involution
defined by the reality conditions restricts the possible values of the
conformal factor to be either real or purely imaginary. In the first case, one
recovers real Lorentzian general relativity. For purely imaginary conformal
factors, the classical theory can be interpreted as real Euclidean gravity. The
reality conditions associated with this Euclidean theory demand the hermiticity
of the Ashtekar connection, but the densitized triad is represented by an
anti-Hermitian operator. We also demonstrate that the Euclidean and Lorentzian
sets of reality conditions lead to inequivalent quantizations of full general
relativity. As a consequence, it seems impossible to obtain Lorentzian physical
predictions from the quantum theory constructed with the Euclidean reality
conditions.
| [
{
"created": "Thu, 11 Nov 1993 20:16:11 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Marugan",
"Guillermo A. Mena",
""
]
] | Using Ashtekar variables, we analyze Lorentzian and Euclidean gravity in vacuum up to a constant conformal transformation. We prove that the reality conditions are invariant under a Wick rotation of the time, and show that the compatibility of the algebra of commutators and constraints with the involution defined by the reality conditions restricts the possible values of the conformal factor to be either real or purely imaginary. In the first case, one recovers real Lorentzian general relativity. For purely imaginary conformal factors, the classical theory can be interpreted as real Euclidean gravity. The reality conditions associated with this Euclidean theory demand the hermiticity of the Ashtekar connection, but the densitized triad is represented by an anti-Hermitian operator. We also demonstrate that the Euclidean and Lorentzian sets of reality conditions lead to inequivalent quantizations of full general relativity. As a consequence, it seems impossible to obtain Lorentzian physical predictions from the quantum theory constructed with the Euclidean reality conditions. |
2205.11260 | Soham Sen | Soham Sen, Rituparna Mandal and Sunandan Gangopadhyay | Near horizon aspects (and beyond) of acceleration radiation of an atom
falling into a large class of static spherically symmetric black hole
geometries | This revised version of the manuscript has been accepted for
publication in Physical Review D | Phys. Rev. D 106 (2022) 025004 | 10.1103/PhysRevD.106.025004 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | The near horizon aspects (and beyond) of a black hole metric, which belongs
to a large class of static spherically symmetric black holes, are considered
here. It has been realized recently that an atom falling into a black hole
leads to the generation of acceleration radiation through virtual transitions.
In recent studies, it has been argued that this acceleration radiation can be
understood from the near horizon physics of the black hole. The near horizon
approximation leads to conformal symmetry in the problem. We go beyond the near
horizon approximation in our analysis. This breaks the conformal symmetry
associated with the near horizon physics of the black hole geometry. We observe
that even without the consideration of the conformal symmetry, the modified
equivalence relation holds. Further, our analysis reveals that the probability
of virtual transition retains its Planck like form with the amplitude getting
modified due to the beyond near horizon approximation. For the next part of our
analysis, we have observed the horizon brightened acceleration radiation
entropy (HBAR) for a Garfinkle-Horowitz-Strominger (GHS) black hole. We observe
that the HBAR entropy misses out on quantum gravity like corrections while
considering the conformal case. However, such corrections emerge when the
conformal symmetry gets broken in the beyond near horizon analysis.
| [
{
"created": "Fri, 20 May 2022 11:41:04 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jul 2022 02:51:40 GMT",
"version": "v2"
}
] | 2022-07-11 | [
[
"Sen",
"Soham",
""
],
[
"Mandal",
"Rituparna",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | The near horizon aspects (and beyond) of a black hole metric, which belongs to a large class of static spherically symmetric black holes, are considered here. It has been realized recently that an atom falling into a black hole leads to the generation of acceleration radiation through virtual transitions. In recent studies, it has been argued that this acceleration radiation can be understood from the near horizon physics of the black hole. The near horizon approximation leads to conformal symmetry in the problem. We go beyond the near horizon approximation in our analysis. This breaks the conformal symmetry associated with the near horizon physics of the black hole geometry. We observe that even without the consideration of the conformal symmetry, the modified equivalence relation holds. Further, our analysis reveals that the probability of virtual transition retains its Planck like form with the amplitude getting modified due to the beyond near horizon approximation. For the next part of our analysis, we have observed the horizon brightened acceleration radiation entropy (HBAR) for a Garfinkle-Horowitz-Strominger (GHS) black hole. We observe that the HBAR entropy misses out on quantum gravity like corrections while considering the conformal case. However, such corrections emerge when the conformal symmetry gets broken in the beyond near horizon analysis. |
1012.2431 | Balakin Alexander | Alexander B. Balakin and Vladimir V. Bochkarev | Archimedean-type force in a cosmic dark fluid: I. Exact solutions for
the late-time accelerated expansion | 13 pages, 1 figure, Part I, typos corrected, references corrected | Phys.Rev.D83:024035,2011 | 10.1103/PhysRevD.83.024035 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish a new self-consistent model in order to explain from a unified
viewpoint two key features of the cosmological evolution: the inflation in the
early Universe and the late-time accelerated expansion. The key element of this
new model is the Archimedean-type coupling of the dark matter with dark energy,
which form the so-called cosmic dark fluid. We suppose that dark matter
particles immersed into the dark energy reservoir are affected by the force
proportional to the four-gradient of the dark energy pressure. The
Archimedean-type coupling is shown to play a role of effective energy-momentum
redistributor between the dark matter and the dark energy components of the
dark fluid, thus providing the Universe's evolution to be a quasiperiodic
and/or multistage process. In the first part of the work we discuss a
theoretical base and new exact solutions of the model master equations. Special
attention is focused on the exact solutions for which the scale factor is
presented by the anti-Gaussian function: these solutions describe the late-time
acceleration and are characterized by a nonsingular behavior in the early
Universe. The second part contains qualitative and numerical analysis of the
master equations; we focus there on the solutions describing a
multi-inflationary Universe.
| [
{
"created": "Sat, 11 Dec 2010 07:36:15 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Feb 2011 17:56:33 GMT",
"version": "v2"
}
] | 2011-02-28 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Bochkarev",
"Vladimir V.",
""
]
] | We establish a new self-consistent model in order to explain from a unified viewpoint two key features of the cosmological evolution: the inflation in the early Universe and the late-time accelerated expansion. The key element of this new model is the Archimedean-type coupling of the dark matter with dark energy, which form the so-called cosmic dark fluid. We suppose that dark matter particles immersed into the dark energy reservoir are affected by the force proportional to the four-gradient of the dark energy pressure. The Archimedean-type coupling is shown to play a role of effective energy-momentum redistributor between the dark matter and the dark energy components of the dark fluid, thus providing the Universe's evolution to be a quasiperiodic and/or multistage process. In the first part of the work we discuss a theoretical base and new exact solutions of the model master equations. Special attention is focused on the exact solutions for which the scale factor is presented by the anti-Gaussian function: these solutions describe the late-time acceleration and are characterized by a nonsingular behavior in the early Universe. The second part contains qualitative and numerical analysis of the master equations; we focus there on the solutions describing a multi-inflationary Universe. |
1001.3074 | Luciano Rezzolla | Luciano Rezzolla, Luca Baiotti, Bruno Giacomazzo, David Link, Jose A.
Font | Accurate evolutions of unequal-mass neutron-star binaries: properties of
the torus and short GRB engines | 35 pages; small changes to match the published version | Class. Quantum Grav. 27 114105 (2010) | 10.1088/0264-9381/27/11/114105 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new results from accurate and fully general-relativistic
simulations of the coalescence of unmagnetized binary neutron stars with
various mass ratios. The evolution of the stars is followed through the
inspiral phase, the merger and prompt collapse to a black hole, up until the
appearance of a thick accretion disk, which is studied as it enters and remains
in a regime of quasi-steady accretion. Although a simple ideal-fluid equation
of state with \Gamma=2 is used, this work presents a systematic study within a
fully general relativistic framework of the properties of the resulting
black-hole--torus system produced by the merger of unequal-mass binaries. More
specifically, we show that: (1) The mass of the torus increases considerably
with the mass asymmetry and equal-mass binaries do not produce significant tori
if they have a total baryonic mass M_tot >~ 3.7 M_sun; (2) Tori with masses
M_tor ~ 0.2 M_sun are measured for binaries with M_tot ~ 3.4 M_sun and mass
ratios q ~ 0.75-0.85; (3) The mass of the torus can be estimated by the simple
expression M_tor(q, M_tot) = [c_1 (1-q) + c_2](M_max-M_tot), involving the
maximum mass for the binaries and coefficients constrained from the
simulations, and suggesting that the tori can have masses as large as M_tor ~
0.35 M_sun for M_tot ~ 2.8 M_sun and q ~ 0.75-0.85; (4) Using a novel technique
to analyze the evolution of the tori we find no evidence for the onset of
non-axisymmetric instabilities and that very little, if any, of their mass is
unbound; (5) Finally, for all the binaries considered we compute the complete
gravitational waveforms and the recoils imparted to the black holes, discussing
the prospects of detection of these sources for a number of present and future
detectors.
| [
{
"created": "Fri, 15 Jan 2010 19:12:28 GMT",
"version": "v1"
},
{
"created": "Thu, 13 May 2010 21:03:09 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Rezzolla",
"Luciano",
""
],
[
"Baiotti",
"Luca",
""
],
[
"Giacomazzo",
"Bruno",
""
],
[
"Link",
"David",
""
],
[
"Font",
"Jose A.",
""
]
] | We present new results from accurate and fully general-relativistic simulations of the coalescence of unmagnetized binary neutron stars with various mass ratios. The evolution of the stars is followed through the inspiral phase, the merger and prompt collapse to a black hole, up until the appearance of a thick accretion disk, which is studied as it enters and remains in a regime of quasi-steady accretion. Although a simple ideal-fluid equation of state with \Gamma=2 is used, this work presents a systematic study within a fully general relativistic framework of the properties of the resulting black-hole--torus system produced by the merger of unequal-mass binaries. More specifically, we show that: (1) The mass of the torus increases considerably with the mass asymmetry and equal-mass binaries do not produce significant tori if they have a total baryonic mass M_tot >~ 3.7 M_sun; (2) Tori with masses M_tor ~ 0.2 M_sun are measured for binaries with M_tot ~ 3.4 M_sun and mass ratios q ~ 0.75-0.85; (3) The mass of the torus can be estimated by the simple expression M_tor(q, M_tot) = [c_1 (1-q) + c_2](M_max-M_tot), involving the maximum mass for the binaries and coefficients constrained from the simulations, and suggesting that the tori can have masses as large as M_tor ~ 0.35 M_sun for M_tot ~ 2.8 M_sun and q ~ 0.75-0.85; (4) Using a novel technique to analyze the evolution of the tori we find no evidence for the onset of non-axisymmetric instabilities and that very little, if any, of their mass is unbound; (5) Finally, for all the binaries considered we compute the complete gravitational waveforms and the recoils imparted to the black holes, discussing the prospects of detection of these sources for a number of present and future detectors. |
2404.17849 | Mohammad Ali S. Afshar | Jafar Sadeghi, Mohammad Ali S. Afshar, Saeed Noori Gashti, Mohammad
Reza Alipour | Kramer's Escape Rate and Phase Transition Dynamics in AdS Black Holes
with Dark Structures | 32 pages, 11 figures. The updated version of manuscript includes new
calculations, discussions, and optimization of the results | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Traditional static methods in phase transition studies, such as the
swallowtail bifurcation diagram, provide good insights into the thermodynamics
of black holes. However, they practically lose sight of the dynamic aspects and
temporal sequence of events. The Kramers escape rate, central to our research,
offers a somewhat dynamic approach to phase transition. We examine the free
energy landscapes for black holes under the influence of âdarkâ and
âstringy+darkâ structures, assessing how additional parameters affect the
escape rates and dynamics of the transition during the first-order phase
transition from small to large black holes. In our analysis, we consider the
escape rate as a function of the black hole radius and study its variations. We
will observe that, on one hand, the escape rate well represents our assumption
based on the movement from zero, increasing to a maximum point, and then
decreasing back to zero as reactive structures become active during the phase
transition interval. However, the critical point in this method is the
encounter with a specific and distinct point. This is where the diagram of the
direct process (escape rate from small to large black holes) intersects with
the reverse process (large to small black holes), becoming equally probable
(contact point). The point, which seems improbable at the onset of the phase
transition or very negligible, gains more significance as the process
progresses. This increase indicates the dominance of a region where the escape
rate from larger black holes to smaller ones prevails. The predominance of the
reverse process, which increases as we approach the end of the process and is
necessarily accompanied by a variation in radius, may be considered as a
natural reaction of the black hole against the âphase changeâ action. A
reaction which attempting to prevent any uncontrolled radial growth that could
jeopardize the stability of the black hole.
| [
{
"created": "Sat, 27 Apr 2024 09:56:41 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jul 2024 11:44:25 GMT",
"version": "v2"
}
] | 2024-07-30 | [
[
"Sadeghi",
"Jafar",
""
],
[
"Afshar",
"Mohammad Ali S.",
""
],
[
"Gashti",
"Saeed Noori",
""
],
[
"Alipour",
"Mohammad Reza",
""
]
] | Traditional static methods in phase transition studies, such as the swallowtail bifurcation diagram, provide good insights into the thermodynamics of black holes. However, they practically lose sight of the dynamic aspects and temporal sequence of events. The Kramers escape rate, central to our research, offers a somewhat dynamic approach to phase transition. We examine the free energy landscapes for black holes under the influence of âdarkâ and âstringy+darkâ structures, assessing how additional parameters affect the escape rates and dynamics of the transition during the first-order phase transition from small to large black holes. In our analysis, we consider the escape rate as a function of the black hole radius and study its variations. We will observe that, on one hand, the escape rate well represents our assumption based on the movement from zero, increasing to a maximum point, and then decreasing back to zero as reactive structures become active during the phase transition interval. However, the critical point in this method is the encounter with a specific and distinct point. This is where the diagram of the direct process (escape rate from small to large black holes) intersects with the reverse process (large to small black holes), becoming equally probable (contact point). The point, which seems improbable at the onset of the phase transition or very negligible, gains more significance as the process progresses. This increase indicates the dominance of a region where the escape rate from larger black holes to smaller ones prevails. The predominance of the reverse process, which increases as we approach the end of the process and is necessarily accompanied by a variation in radius, may be considered as a natural reaction of the black hole against the âphase changeâ action. A reaction which attempting to prevent any uncontrolled radial growth that could jeopardize the stability of the black hole. |
gr-qc/0003062 | Kazuyasu Shigemoto | M. Kenmoku, M. Ohto, K. Shigemoto and K. Uehara | The Scenario for the Astrophysics with Scalar Field and the Cosmological
Constant | 16 pages, Latex | Nuovo Cim.B115:1203-1216,2000 | null | NWU-11/00 | gr-qc | null | In order to give the standard scenario of the astrophysics, we study the
Einstein theory with minimally coupled scalar field and the cosmological term
by considering the scalar field as a candidate of the dark matter. We obtained
the exact solution in the cosmological scale and the approximate gravitational
potential in the galactic or solar scale. We find that the scalar field plays
the role of the dark matter in some sense in the cosmological scale but it does
not play the role of the dark matter in the galactic or solar scale within our
approximation.
| [
{
"created": "Wed, 15 Mar 2000 14:47:48 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Kenmoku",
"M.",
""
],
[
"Ohto",
"M.",
""
],
[
"Shigemoto",
"K.",
""
],
[
"Uehara",
"K.",
""
]
] | In order to give the standard scenario of the astrophysics, we study the Einstein theory with minimally coupled scalar field and the cosmological term by considering the scalar field as a candidate of the dark matter. We obtained the exact solution in the cosmological scale and the approximate gravitational potential in the galactic or solar scale. We find that the scalar field plays the role of the dark matter in some sense in the cosmological scale but it does not play the role of the dark matter in the galactic or solar scale within our approximation. |
0806.3350 | Wladimir Belayev | W. B. Belayev | Variation of the light-like particle energy and its critical curve
equations | 5 pages, Eq. (1.2) is corrected. arXiv admin note: substantial text
overlap with arXiv:0911.0614 | null | null | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider variation of energy of the light-like particle in Riemann
space-time, find lagrangian, canonical momenta and forces. Equations of the
critical curve are obtained by the nonzero energy integral variation in
accordance with principles of the calculus of variations in mechanics. This
method is shown to not lead to violation of conformity of varied curve to the
null path in contradistinction of the interval variation. Though found
equations are differ from standard form of geodesics equations, for the
Schwarzschild space-time their solutions coincide with each other to within
parameter of differentiation.
| [
{
"created": "Fri, 20 Jun 2008 12:32:13 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Sep 2011 13:16:13 GMT",
"version": "v10"
},
{
"created": "Fri, 6 Jan 2012 12:26:35 GMT",
"version": "v11"
},
{
"created": "Sun, 22 Jun 2008 07:37:00 GMT",
"version": "v2"
},
{
"... | 2012-01-09 | [
[
"Belayev",
"W. B.",
""
]
] | We consider variation of energy of the light-like particle in Riemann space-time, find lagrangian, canonical momenta and forces. Equations of the critical curve are obtained by the nonzero energy integral variation in accordance with principles of the calculus of variations in mechanics. This method is shown to not lead to violation of conformity of varied curve to the null path in contradistinction of the interval variation. Though found equations are differ from standard form of geodesics equations, for the Schwarzschild space-time their solutions coincide with each other to within parameter of differentiation. |
gr-qc/0202049 | Amir H. Abbassi | Amir H. Abbassi & Amir M. Abbassi | Relational Relativity | 12 pages, no figure,published version | Apeiron,Vol.9,No.2,(April 2002)44-61 pp | null | null | gr-qc | null | According to a simple model of inertia a Machianized theory of special and
general relativity named as relational relativity is presented.
| [
{
"created": "Thu, 14 Feb 2002 14:12:27 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2002 09:34:26 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Abbassi",
"Amir H.",
""
],
[
"Abbassi",
"Amir M.",
""
]
] | According to a simple model of inertia a Machianized theory of special and general relativity named as relational relativity is presented. |
2105.10779 | Mert Mangut | Mert Mangut, Huriye G\"ursel and \.Izzet Sakall{\i} | Gravitational Lensing in Kerr-Newman Anti de Sitter Spacetime | null | Astroparticle Physics 30 July 2022 | 10.1016/j.astropartphys.2022.102763 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The method of Rindler and Ishak enables one to study how light is bent in the
vicinity of a non-rotating and spherically symmetric gravitational lens. This
method mainly aims to investigate the role of cosmological constant in the
consequent path. In this paper, we use the extension of Rindler-Ishak method
(RIM) in order to evaluate the deflection angle of null geodesics in the
equatorial plane of Kerr-Newman anti de Sitter (KNAdS) spacetime. We then use
astrophysical data to see the effect of rotation and charge on the bending
angle of light for seven distinct stars and two black holes under the
assumption of having a KNAdS background with a negative cosmological constant
$\Lambda$.
| [
{
"created": "Sat, 22 May 2021 18:00:59 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Aug 2022 09:12:42 GMT",
"version": "v2"
}
] | 2022-08-08 | [
[
"Mangut",
"Mert",
""
],
[
"Gürsel",
"Huriye",
""
],
[
"Sakallı",
"İzzet",
""
]
] | The method of Rindler and Ishak enables one to study how light is bent in the vicinity of a non-rotating and spherically symmetric gravitational lens. This method mainly aims to investigate the role of cosmological constant in the consequent path. In this paper, we use the extension of Rindler-Ishak method (RIM) in order to evaluate the deflection angle of null geodesics in the equatorial plane of Kerr-Newman anti de Sitter (KNAdS) spacetime. We then use astrophysical data to see the effect of rotation and charge on the bending angle of light for seven distinct stars and two black holes under the assumption of having a KNAdS background with a negative cosmological constant $\Lambda$. |
2009.03992 | J\"org Hennig | J\"org Hennig | Axis potentials for stationary $n$-black-hole configurations | 9 pages, 1 figure, accepted for publication in Class. Quantum Grav | Class. Quantum Grav. 37, 19LT01 (2020) | 10.1088/1361-6382/abb116 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend earlier discussions of the balance problem for two black holes and
study stationary spacetimes containing an arbitrary number of $n$ aligned
rotating and (possibly) charged black holes. For these hypothetical equilibrium
configurations, we obtain the most general form of the boundary data on the
symmetry axis in terms of a finite number of parameters. Hence future
investigations of $n$-black-hole configurations can be restricted to studying
properties of these finite families of solutions.
| [
{
"created": "Tue, 8 Sep 2020 20:53:43 GMT",
"version": "v1"
}
] | 2020-09-21 | [
[
"Hennig",
"Jörg",
""
]
] | We extend earlier discussions of the balance problem for two black holes and study stationary spacetimes containing an arbitrary number of $n$ aligned rotating and (possibly) charged black holes. For these hypothetical equilibrium configurations, we obtain the most general form of the boundary data on the symmetry axis in terms of a finite number of parameters. Hence future investigations of $n$-black-hole configurations can be restricted to studying properties of these finite families of solutions. |
2102.05039 | Claudio Nassif Cruz | Cl\'audio Nassif (retired professor) and A. C. Amaro de Faria Jr | Variation of the fundamental constants over the cosmological time:
veracity of Dirac's intriguing hypothesis | 6 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1211.1936, arXiv:2009.05397, arXiv:1205.2298 | Canadian Journal of Physics, Vol.94, n.1 (2016) | 10.1139/cjp-2015-0515 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate how the universal constants, including the fine structure
constant, have varied since the early universe close to the Planck energy scale
($E_P\sim 10^{19}$GeV) and, thus, how they have evoluted over the cosmological
time related to the temperature of the expanding universe. We have already
shown that the speed of light was much higher close to the Planck scale. In the
present work, we will go further, first by showing that both the Planck
constant and the electron charge were also too large in the early universe.
However, we conclude that the fine structure constant ($\alpha\cong 1/137$) has
remained invariant with the age and temperature of the universe, which is in
agreement with laboratory tests and some observational data. Furthermore, we
will obtain the divergence of the electron (or proton) mass and also the
gravitational constant ($G$) at the Planck scale. Thus, we will be able to
verify the veracity of Dirac's belief about the existence of "coincidences"
between dimensionless ratios of sub-atomic and cosmological quantities, leading
to a variation of $G$ with time, i.e., the ratio of the electrostatic to
gravitational force between an electron and a proton ($\sim 10^{41}$) is
roughly equal to the age of the universe divided by an elementary time
constant, so that the strength of gravity, as determined by $G$, must vary
inversely with time just in the approximation of lower temperature or for times
very far from the early period, in order to compensate for the time-variation
of the Hubble parameter ($H\sim t^{-1}$). In short, we will show the validity
of Dirac's hypothesis only for times very far from the early period or $T\sim
T_P\sim 10^{32}$K.
| [
{
"created": "Tue, 9 Feb 2021 01:30:36 GMT",
"version": "v1"
}
] | 2021-02-11 | [
[
"Nassif",
"Cláudio",
"",
"retired professor"
],
[
"Faria",
"A. C. Amaro de",
"Jr"
]
] | We investigate how the universal constants, including the fine structure constant, have varied since the early universe close to the Planck energy scale ($E_P\sim 10^{19}$GeV) and, thus, how they have evoluted over the cosmological time related to the temperature of the expanding universe. We have already shown that the speed of light was much higher close to the Planck scale. In the present work, we will go further, first by showing that both the Planck constant and the electron charge were also too large in the early universe. However, we conclude that the fine structure constant ($\alpha\cong 1/137$) has remained invariant with the age and temperature of the universe, which is in agreement with laboratory tests and some observational data. Furthermore, we will obtain the divergence of the electron (or proton) mass and also the gravitational constant ($G$) at the Planck scale. Thus, we will be able to verify the veracity of Dirac's belief about the existence of "coincidences" between dimensionless ratios of sub-atomic and cosmological quantities, leading to a variation of $G$ with time, i.e., the ratio of the electrostatic to gravitational force between an electron and a proton ($\sim 10^{41}$) is roughly equal to the age of the universe divided by an elementary time constant, so that the strength of gravity, as determined by $G$, must vary inversely with time just in the approximation of lower temperature or for times very far from the early period, in order to compensate for the time-variation of the Hubble parameter ($H\sim t^{-1}$). In short, we will show the validity of Dirac's hypothesis only for times very far from the early period or $T\sim T_P\sim 10^{32}$K. |
1211.0380 | Naoki Tsukamoto | Naoki Tsukamoto and Tomohiro Harada | Signed magnification sums for general spherical lenses | 14 pages, 4 figures, minor changes from v1 | Phys. Rev. D 87:024024, 2013 | 10.1103/PhysRevD.87.024024 | RUP-12-11 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the sum of signed magnifications is invariant for mass
lens systems. In this paper, we discuss the signed magnification sums of
general spherical lens models including the singular isothermal sphere, the
Schwarzschild lens and the Ellis wormhole, the last of which is an example of
the traversable wormholes of the Morris-Thorne class. We show that the signed
magnication sums are a very useful tool to distinguish exotic lens objects. For
example, we show that one can distinguish the Ellis wormholes from the
Schwarzschild lens with the signed magnification sums.
| [
{
"created": "Fri, 2 Nov 2012 07:06:22 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Dec 2012 07:04:59 GMT",
"version": "v2"
}
] | 2013-01-15 | [
[
"Tsukamoto",
"Naoki",
""
],
[
"Harada",
"Tomohiro",
""
]
] | It is well known that the sum of signed magnifications is invariant for mass lens systems. In this paper, we discuss the signed magnification sums of general spherical lens models including the singular isothermal sphere, the Schwarzschild lens and the Ellis wormhole, the last of which is an example of the traversable wormholes of the Morris-Thorne class. We show that the signed magnication sums are a very useful tool to distinguish exotic lens objects. For example, we show that one can distinguish the Ellis wormholes from the Schwarzschild lens with the signed magnification sums. |
gr-qc/0209012 | Scott A. Hughes | Scott A. Hughes | Tuning gravitational-wave detector networks to measure compact binary
mergers | 15 pages, 6 figures, submitted to PRD | Phys.Rev. D66 (2002) 102001 | 10.1103/PhysRevD.66.102001 | null | gr-qc astro-ph | null | Gravitational waves generated by the final merger of compact binary systems
depend on the structure of the binary's members. If the binary contains neutron
stars, measuring such waves can teach us about the properties of matter at
extreme densities. Unfortunately, these waves are typically at high frequency
where the sensitivity of broad-band detectors is not good. Learning about dense
matter from these waves will require networks of broad-band detectors combined
with narrow-band detectors that have good sensitivity at high frequencies. This
paper presents an algorithm by which a network can be ``tuned'', in accordance
with the best available information, in order to most effectively measure
merger waves. The algorithm is presented in the context of a toy model that
captures the qualitative features of narrow-band detectors and of certain
binary neutron star merger wave models. By using what is learned from a
sequence of merger measurements, the network can be gradually tuned in order to
accurately measure the waves. The number of measurements needed to reach this
stage depends upon the waves' signal strength, the number of narrow-band
detectors available for the measurement, and the detailed characteristics of
the waves that carry the merger information. Future studies will go beyond this
toy model, encompassing a more realistic description of both the detectors and
the gravitational waves.
| [
{
"created": "Wed, 4 Sep 2002 01:24:56 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hughes",
"Scott A.",
""
]
] | Gravitational waves generated by the final merger of compact binary systems depend on the structure of the binary's members. If the binary contains neutron stars, measuring such waves can teach us about the properties of matter at extreme densities. Unfortunately, these waves are typically at high frequency where the sensitivity of broad-band detectors is not good. Learning about dense matter from these waves will require networks of broad-band detectors combined with narrow-band detectors that have good sensitivity at high frequencies. This paper presents an algorithm by which a network can be ``tuned'', in accordance with the best available information, in order to most effectively measure merger waves. The algorithm is presented in the context of a toy model that captures the qualitative features of narrow-band detectors and of certain binary neutron star merger wave models. By using what is learned from a sequence of merger measurements, the network can be gradually tuned in order to accurately measure the waves. The number of measurements needed to reach this stage depends upon the waves' signal strength, the number of narrow-band detectors available for the measurement, and the detailed characteristics of the waves that carry the merger information. Future studies will go beyond this toy model, encompassing a more realistic description of both the detectors and the gravitational waves. |
gr-qc/0702119 | Nivaldo Agostinho Lemos | N. A. Lemos, G. A. Monerat, E. V. Corr\^ea Silva, G. Oliveira-Neto and
L. G. Ferreira Filho | Reply to "Comment on 'Quantization of FRW spacetimes in the presence of
a cosmological constant and radiation'" | 4 pages, accepted by Physical Review D | Phys.Rev.D75:068504,2007 | 10.1103/PhysRevD.75.068504 | null | gr-qc astro-ph hep-th | null | The Comment by Amore {\it et al.} [gr-qc/0611029] contains a valid criticism
of the numerical precision of the results reported in a recent paper of ours
[Phys. Rev. D {\bf 73}, 044022 (2006)], as well as fresh ideas on how to
characterize a quantum cosmological singularity. However, we argue that,
contrary to what is suggested in the Comment, the quantum cosmological models
we studied show hardly any sign of singular behavior.
| [
{
"created": "Thu, 22 Feb 2007 11:29:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lemos",
"N. A.",
""
],
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
],
[
"Oliveira-Neto",
"G.",
""
],
[
"Filho",
"L. G. Ferreira",
""
]
] | The Comment by Amore {\it et al.} [gr-qc/0611029] contains a valid criticism of the numerical precision of the results reported in a recent paper of ours [Phys. Rev. D {\bf 73}, 044022 (2006)], as well as fresh ideas on how to characterize a quantum cosmological singularity. However, we argue that, contrary to what is suggested in the Comment, the quantum cosmological models we studied show hardly any sign of singular behavior. |
1101.1012 | Gamal G.L. Nashed | G.G.L. Nashed | Gravitational radiation fields in teleparallel equivalent of general
relativity and their energies | Latex 12 pages | Chin.Phys.B19:110402,2010 | 10.1088/1674-1056/19/11/110402 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive two new retarded solutions in the teleparallel theory equivalent to
general relativity (TEGR). One of these solutions gives a divergent energy.
Therefore, we used the regularized expression of the gravitational
energy-momentum tensor, which is a coordinate dependent. A detailed analysis of
the loss of the mass of Bondi space-time is carried out using the flux of the
gravitational energy-momentum.
| [
{
"created": "Wed, 5 Jan 2011 15:51:01 GMT",
"version": "v1"
}
] | 2011-04-21 | [
[
"Nashed",
"G. G. L.",
""
]
] | We derive two new retarded solutions in the teleparallel theory equivalent to general relativity (TEGR). One of these solutions gives a divergent energy. Therefore, we used the regularized expression of the gravitational energy-momentum tensor, which is a coordinate dependent. A detailed analysis of the loss of the mass of Bondi space-time is carried out using the flux of the gravitational energy-momentum. |
1307.1520 | Narayan Banerjee | Narayan Banerjee and Somasri Sen | Towards a characterization of fields leading to black hole hair | 7 pages, no figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, it is shown that an asymptotically flat spherical black
hole can have a nontrivial signature of any field for an exterior observer if
the energy momentum tensor of the corresponding field is either tracefree or if
the trace falls off at least as rapidly as inverse cube of the radial distance.
In the absence of a general No Hair Theorem, this result can provide a
characterization of the fields leading to black hole hair.
| [
{
"created": "Fri, 5 Jul 2013 04:54:45 GMT",
"version": "v1"
}
] | 2013-07-08 | [
[
"Banerjee",
"Narayan",
""
],
[
"Sen",
"Somasri",
""
]
] | In the present work, it is shown that an asymptotically flat spherical black hole can have a nontrivial signature of any field for an exterior observer if the energy momentum tensor of the corresponding field is either tracefree or if the trace falls off at least as rapidly as inverse cube of the radial distance. In the absence of a general No Hair Theorem, this result can provide a characterization of the fields leading to black hole hair. |
1812.02278 | Elena Giorgi | Elena Giorgi | Boundedness and decay for the Teukolsky equation of spin $\pm1$ on
Reissner-Nordstr\"om spacetime: the $\ell=1$ spherical mode | Version accepted for publication in Classical and Quantum Gravity | Class. Quantum Grav. 36 (2019) 205001 | 10.1088/1361-6382/ab3c03 | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove boundedness and polynomial decay statements for solutions to the
spin $\pm1$ Teukolsky-type equation projected to the $\ell=1$ spherical
harmonic on Reissner-Nordstr\"om spacetime. The equation is verified by a
gauge-invariant quantity which we identify and which involves the
electromagnetic and curvature tensor. This gives a first description in
physical space of gauge-invariant quantities transporting the electromagnetic
radiation in perturbations of a charged black hole.
The proof is based on the use of derived quantities, introduced in previous
works on linear stability of Schwarzschild by Dafermos-Holzegel-Rodnianski. The
derived quantity verifies a Fackerell-Ipser-type equation, with right hand side
vanishing at the $\ell=1$ spherical harmonics. The boundedness and decay for
the projection to the $\ell\geq 2$ spherical harmonics are implied by the
boundedness and decay for the Teukolsky system of spin $\pm2$ obtained in our
previous work.
The spin $\pm1$ Teukolsky-type equation is verified by the curvature and
electromagnetic components of a gravitational and electromagnetic perturbation
of the Reissner-Nordstr\"om spacetime. Consequently, together with the
estimates obtained in our previous work, these bounds allow to prove the full
linear stability of Reissner-Nordstr\"om metric for small charge to coupled
gravitational and electromagnetic perturbations.
| [
{
"created": "Thu, 6 Dec 2018 00:36:51 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Sep 2019 15:34:39 GMT",
"version": "v2"
}
] | 2019-09-19 | [
[
"Giorgi",
"Elena",
""
]
] | We prove boundedness and polynomial decay statements for solutions to the spin $\pm1$ Teukolsky-type equation projected to the $\ell=1$ spherical harmonic on Reissner-Nordstr\"om spacetime. The equation is verified by a gauge-invariant quantity which we identify and which involves the electromagnetic and curvature tensor. This gives a first description in physical space of gauge-invariant quantities transporting the electromagnetic radiation in perturbations of a charged black hole. The proof is based on the use of derived quantities, introduced in previous works on linear stability of Schwarzschild by Dafermos-Holzegel-Rodnianski. The derived quantity verifies a Fackerell-Ipser-type equation, with right hand side vanishing at the $\ell=1$ spherical harmonics. The boundedness and decay for the projection to the $\ell\geq 2$ spherical harmonics are implied by the boundedness and decay for the Teukolsky system of spin $\pm2$ obtained in our previous work. The spin $\pm1$ Teukolsky-type equation is verified by the curvature and electromagnetic components of a gravitational and electromagnetic perturbation of the Reissner-Nordstr\"om spacetime. Consequently, together with the estimates obtained in our previous work, these bounds allow to prove the full linear stability of Reissner-Nordstr\"om metric for small charge to coupled gravitational and electromagnetic perturbations. |
1605.09586 | Hai-Guang Li | Hai-Guang Li, Yong Cai, and Yun-Song Piao | Towards the bounce inflationary gravitational wave | 19 pages, 12 figures | null | 10.1140/epjc/s10052-016-4554-2 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In bounce inflation scenario, the inflation is singularity-free, while the
advantages of inflation are reserved. We analytically calculate the power
spectrum of its primordial gravitational waves (GWs), and show a universal
result including the physics of the bounce phase. The spectrum acquires a
cutoff at large scale, while the oscillation around the cutoff scale is quite
drastic, which is determined by the details of bounce. Our work highlights that
the primordial GWs at large scale may encode the physics of the bounce ever
happened at about $\sim 60$ efolds before inflation.
| [
{
"created": "Tue, 31 May 2016 11:44:36 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Li",
"Hai-Guang",
""
],
[
"Cai",
"Yong",
""
],
[
"Piao",
"Yun-Song",
""
]
] | In bounce inflation scenario, the inflation is singularity-free, while the advantages of inflation are reserved. We analytically calculate the power spectrum of its primordial gravitational waves (GWs), and show a universal result including the physics of the bounce phase. The spectrum acquires a cutoff at large scale, while the oscillation around the cutoff scale is quite drastic, which is determined by the details of bounce. Our work highlights that the primordial GWs at large scale may encode the physics of the bounce ever happened at about $\sim 60$ efolds before inflation. |
gr-qc/0006100 | Luc Blanchet | Luc Blanchet and Guillaume Faye | Lorentzian regularization and the problem of point-like particles in
general relativity | 34 pages, to appear in J. Math. Phys | J.Math.Phys. 42 (2001) 4391-4418 | 10.1063/1.1384864 | null | gr-qc math-ph math.MP | null | The two purposes of the paper are (1) to present a regularization of the
self-field of point-like particles, based on Hadamard's concept of ``partie
finie'', that permits in principle to maintain the Lorentz covariance of a
relativistic field theory, (2) to use this regularization for defining a model
of stress-energy tensor that describes point-particles in post-Newtonian
expansions (e.g. 3PN) of general relativity. We consider specifically the case
of a system of two point-particles. We first perform a Lorentz transformation
of the system's variables which carries one of the particles to its rest frame,
next implement the Hadamard regularization within that frame, and finally come
back to the original variables with the help of the inverse Lorentz
transformation. The Lorentzian regularization is defined in this way up to any
order in the relativistic parameter 1/c^2. Following a previous work of ours,
we then construct the delta-pseudo-functions associated with this
regularization. Using an action principle, we derive the stress-energy tensor,
made of delta-pseudo-functions, of point-like particles. The equations of
motion take the same form as the geodesic equations of test particles on a
fixed background, but the role of the background is now played by the
regularized metric.
| [
{
"created": "Wed, 28 Jun 2000 17:26:44 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Apr 2001 15:50:10 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Blanchet",
"Luc",
""
],
[
"Faye",
"Guillaume",
""
]
] | The two purposes of the paper are (1) to present a regularization of the self-field of point-like particles, based on Hadamard's concept of ``partie finie'', that permits in principle to maintain the Lorentz covariance of a relativistic field theory, (2) to use this regularization for defining a model of stress-energy tensor that describes point-particles in post-Newtonian expansions (e.g. 3PN) of general relativity. We consider specifically the case of a system of two point-particles. We first perform a Lorentz transformation of the system's variables which carries one of the particles to its rest frame, next implement the Hadamard regularization within that frame, and finally come back to the original variables with the help of the inverse Lorentz transformation. The Lorentzian regularization is defined in this way up to any order in the relativistic parameter 1/c^2. Following a previous work of ours, we then construct the delta-pseudo-functions associated with this regularization. Using an action principle, we derive the stress-energy tensor, made of delta-pseudo-functions, of point-like particles. The equations of motion take the same form as the geodesic equations of test particles on a fixed background, but the role of the background is now played by the regularized metric. |
gr-qc/0207031 | Hanno Sahlmann | Hanno Sahlmann, Thomas Thiemann | Towards the QFT on Curved Spacetime Limit of QGR. II: A Concrete
Implementation | LaTeX, 49 p., one figure | Class.Quant.Grav.23:909-954,2006 | 10.1088/0264-9381/23/3/020 | AEI-2002-050 | gr-qc hep-th math-ph math.MP quant-ph | null | The present paper is the companion of [1] in which we proposed a scheme that
tries to derive the Quantum Field Theory (QFT) on Curved Spacetimes (CST) limit
from background independent Quantum General Relativity (QGR). The constructions
of [1] make heavy use of the notion of semiclassical states for QGR. In the
present paper, we employ the complexifier coherent states for QGR recently
proposed by Thiemann and Winkler as semiclassical states, and thus fill the
general formulas obtained in [1] with life. We demonstrate how one can, under
some simplifying assumptions, explicitely compute expectation values of the
operators relevant for the gravity-matter Hamiltonians of [1] in the
complexifier coherent states. These expectation values give rise to effective
matter Hamiltonians on the background on which the gravitational coherent state
is peaked and thus induce approximate notions of n-particle states and matter
propagation on fluctuating spacetimes. We display the details for the scalar
and the electromagnetic field. The effective theories exhibit two types of
corrections as compared to the the ordinary QFT on CST. The first is due to the
quantum fluctuations of the gravitational field, the second arises from the
fact that background independence forces both geometry and matter to propagate
on a spacetime that is the product of the real line and a (random) graph.
Finally we obtain explicit numerical predictions for non-standard dispersion
relations for the scalar and the electromagnetic field. They should, however,
not be taken too seriously, due to the many ambiguities in our scheme, the
analysis of the physical significance of which has only begun. We show however,
that one can classify these ambiguities at least in broad terms.
| [
{
"created": "Fri, 5 Jul 2002 13:59:50 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Sahlmann",
"Hanno",
""
],
[
"Thiemann",
"Thomas",
""
]
] | The present paper is the companion of [1] in which we proposed a scheme that tries to derive the Quantum Field Theory (QFT) on Curved Spacetimes (CST) limit from background independent Quantum General Relativity (QGR). The constructions of [1] make heavy use of the notion of semiclassical states for QGR. In the present paper, we employ the complexifier coherent states for QGR recently proposed by Thiemann and Winkler as semiclassical states, and thus fill the general formulas obtained in [1] with life. We demonstrate how one can, under some simplifying assumptions, explicitely compute expectation values of the operators relevant for the gravity-matter Hamiltonians of [1] in the complexifier coherent states. These expectation values give rise to effective matter Hamiltonians on the background on which the gravitational coherent state is peaked and thus induce approximate notions of n-particle states and matter propagation on fluctuating spacetimes. We display the details for the scalar and the electromagnetic field. The effective theories exhibit two types of corrections as compared to the the ordinary QFT on CST. The first is due to the quantum fluctuations of the gravitational field, the second arises from the fact that background independence forces both geometry and matter to propagate on a spacetime that is the product of the real line and a (random) graph. Finally we obtain explicit numerical predictions for non-standard dispersion relations for the scalar and the electromagnetic field. They should, however, not be taken too seriously, due to the many ambiguities in our scheme, the analysis of the physical significance of which has only begun. We show however, that one can classify these ambiguities at least in broad terms. |
gr-qc/9806001 | Dmitri Vassilevich | S.Yu. Alexandrov, D.V. Vassilevich | Path integral for the Hilbert-Palatini and Ashtekar gravity | Revtex, 16 pages | Phys.Rev. D58 (1998) 124029 | 10.1103/PhysRevD.58.124029 | SPb-IP-98 | gr-qc | null | To write down a path integral for the Ashtekar gravity one must solve three
fundamental problems. First, one must understand rules of complex contour
functional integration with holomorphic action. Second, one should find which
gauges are compatible with reality conditions. Third, one should evaluate the
Faddeev-Popov determinant produced by these conditions. In the present paper we
derive the BRST path integral for the Hilbert-Palatini gravity. We show, that
for certain class of gauge conditions this path integral can be re-written in
terms of the Ashtekar variables. Reality conditions define contours of
integration. For our class of gauges all ghost terms coincide with what one
could write naively just ignoring any Jacobian factors arising from the reality
conditions.
| [
{
"created": "Sat, 30 May 1998 11:28:56 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Alexandrov",
"S. Yu.",
""
],
[
"Vassilevich",
"D. V.",
""
]
] | To write down a path integral for the Ashtekar gravity one must solve three fundamental problems. First, one must understand rules of complex contour functional integration with holomorphic action. Second, one should find which gauges are compatible with reality conditions. Third, one should evaluate the Faddeev-Popov determinant produced by these conditions. In the present paper we derive the BRST path integral for the Hilbert-Palatini gravity. We show, that for certain class of gauge conditions this path integral can be re-written in terms of the Ashtekar variables. Reality conditions define contours of integration. For our class of gauges all ghost terms coincide with what one could write naively just ignoring any Jacobian factors arising from the reality conditions. |
2304.04444 | Moritz Reintjes | Moritz Reintjes | Strong Cosmic Censorship with Bounded Curvature | null | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we propose a weaker version of Penrose's much heeded Strong
Cosmic Censorship (SCC) conjecture, asserting inextentability of maximal Cauchy
developments by manifolds with Lipschitz continuous Lorentzian metrics and
Riemann curvature bounded in $L^p$. Lipschitz continuity is the threshold
regularity for causal structures, and curvature bounds rule out infinite tidal
accelerations, arguing for physical significance of this weaker SCC conjecture.
The main result of this paper, under the assumption that no extensions exist
with higher connection regularity $W^{1,p}_\text{loc}$, proves in the
affirmative this SCC conjecture with bounded curvature for $p$ sufficiently
large, ($p>4$ with uniform bounds, $p>2$ without uniform bounds).
| [
{
"created": "Mon, 10 Apr 2023 08:12:46 GMT",
"version": "v1"
}
] | 2023-04-11 | [
[
"Reintjes",
"Moritz",
""
]
] | In this paper we propose a weaker version of Penrose's much heeded Strong Cosmic Censorship (SCC) conjecture, asserting inextentability of maximal Cauchy developments by manifolds with Lipschitz continuous Lorentzian metrics and Riemann curvature bounded in $L^p$. Lipschitz continuity is the threshold regularity for causal structures, and curvature bounds rule out infinite tidal accelerations, arguing for physical significance of this weaker SCC conjecture. The main result of this paper, under the assumption that no extensions exist with higher connection regularity $W^{1,p}_\text{loc}$, proves in the affirmative this SCC conjecture with bounded curvature for $p$ sufficiently large, ($p>4$ with uniform bounds, $p>2$ without uniform bounds). |
gr-qc/0410038 | Jian-Yang Zhu | Jian-Yang Zhu | A dynamical evolution model on the black hole horizon | Accepted for publication in Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) 2671-2678 | 10.1088/0264-9381/22/13/010 | null | gr-qc | null | This paper demonstrates a dynamical evolution model of the black hole (BH)
horizon. The result indicates that a kinetic area-cells model of the BH's
horizon can model the evolution of BH due to the Hawking radiation, and this
area-cell system can be considered as an interacting geometrical particle
system. Thus the evolution turns into a problem of statistical physics. In the
present work, this problem is treated in the framework of non-equilibrium
statistics. It is proposed that each area-cell possesses the energy like a
microscopic black hole, and has the gravitational interaction with the other
area-cells. We consider both a non-interaction ideal system, and a system with
small nearest-neighbor interactions, and obtain an analytic expression of the
expected value of the horizon area of a dynamical BH. We find that, after a
long enough evolution, a dynamical BH with the Hawking radiation can be in
equilibrium with a finite temperature radiation field. However, we also find
that, the system has a critical point, and when the temperature of the
radiation field surrounding the BH approaches the critical temperature of the
BH, a critical slowing down phenomenon occurs.
| [
{
"created": "Fri, 8 Oct 2004 11:54:59 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2005 09:36:44 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Zhu",
"Jian-Yang",
""
]
] | This paper demonstrates a dynamical evolution model of the black hole (BH) horizon. The result indicates that a kinetic area-cells model of the BH's horizon can model the evolution of BH due to the Hawking radiation, and this area-cell system can be considered as an interacting geometrical particle system. Thus the evolution turns into a problem of statistical physics. In the present work, this problem is treated in the framework of non-equilibrium statistics. It is proposed that each area-cell possesses the energy like a microscopic black hole, and has the gravitational interaction with the other area-cells. We consider both a non-interaction ideal system, and a system with small nearest-neighbor interactions, and obtain an analytic expression of the expected value of the horizon area of a dynamical BH. We find that, after a long enough evolution, a dynamical BH with the Hawking radiation can be in equilibrium with a finite temperature radiation field. However, we also find that, the system has a critical point, and when the temperature of the radiation field surrounding the BH approaches the critical temperature of the BH, a critical slowing down phenomenon occurs. |
gr-qc/0108078 | Claudio Simeone | Claudio Simeone | Global phase time and path integral for the Kantowski--Sachs anisotropic
univers | 11 pages | Gen.Rel.Grav. 32 (2000) 1835-1844 | 10.1023/A:1001936815092 | null | gr-qc | null | The action functional of the anisotropic Kantowski--Sachs cosmological model
is turned into that of an ordinary gauge system. Then a global phase time is
identified for the model by imposing canonical gauge conditions, and the
quantum transition amplitude is obtained by means of the usual path integral
procedure of Fadeev and Popov.
| [
{
"created": "Thu, 30 Aug 2001 20:56:35 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Simeone",
"Claudio",
""
]
] | The action functional of the anisotropic Kantowski--Sachs cosmological model is turned into that of an ordinary gauge system. Then a global phase time is identified for the model by imposing canonical gauge conditions, and the quantum transition amplitude is obtained by means of the usual path integral procedure of Fadeev and Popov. |
1507.00028 | Mariam Bouhmadi-Lopez | Che-Yu Chen, Mariam Bouhmadi-Lopez, Pisin Chen | Modified Eddington-inspired-Born-Infeld Gravity with a Trace Term | 10 pages, 6 figures, RevTex4-1. References added and discussion
extended. Version accepted in EPJC | null | 10.1140/epjc/s10052-016-3879-1 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a modified Eddington-inspired-Born-Infeld (EiBI) theory with a
pure trace term $g_{\mu\nu}R$ being added to the determinantal action is
analysed from a cosmological point of view. It corresponds to the most general
action constructed from a rank two tensor that contains up to first order terms
in curvature. This term can equally be seen as a conformal factor multiplying
the metric $g_{\mu\nu}$. This very interesting type of amendment has not been
considered within the Palatini formalism despite the large amount of works on
the Born-Infeld-inspired theory of gravity. This model can provide smooth
bouncing solutions which were not allowed in the EiBI model for the same EiBI
coupling. Most interestingly, for a radiation filled universe there are some
regions of the parameter space that can naturally lead to a de Sitter
inflationary stage without the need of any exotic matter field. Finally, in
this model we discover a new type of cosmic "quasi-sudden" singularity, where
the cosmic time derivative of the Hubble rate becomes very large but finite at
a finite cosmic time.
| [
{
"created": "Tue, 30 Jun 2015 20:29:06 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jul 2015 19:28:17 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Dec 2015 13:02:47 GMT",
"version": "v3"
}
] | 2016-02-17 | [
[
"Chen",
"Che-Yu",
""
],
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Chen",
"Pisin",
""
]
] | In this paper, a modified Eddington-inspired-Born-Infeld (EiBI) theory with a pure trace term $g_{\mu\nu}R$ being added to the determinantal action is analysed from a cosmological point of view. It corresponds to the most general action constructed from a rank two tensor that contains up to first order terms in curvature. This term can equally be seen as a conformal factor multiplying the metric $g_{\mu\nu}$. This very interesting type of amendment has not been considered within the Palatini formalism despite the large amount of works on the Born-Infeld-inspired theory of gravity. This model can provide smooth bouncing solutions which were not allowed in the EiBI model for the same EiBI coupling. Most interestingly, for a radiation filled universe there are some regions of the parameter space that can naturally lead to a de Sitter inflationary stage without the need of any exotic matter field. Finally, in this model we discover a new type of cosmic "quasi-sudden" singularity, where the cosmic time derivative of the Hubble rate becomes very large but finite at a finite cosmic time. |
1808.08228 | Vijay Varma | Vijay Varma, Mark A. Scheel, and Harald P. Pfeiffer | Comparison of binary black hole initial data sets | Matches PRD version. 17 pages, 10 figures | Phys. Rev. D 98, 104011 (2018) | 10.1103/PhysRevD.98.104011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present improvements to construction of binary black hole initial data
used in SpEC (the Spectral Einstein Code). We introduce new boundary conditions
for the extended conformal thin sandwich elliptic equations that enforce the
excision surfaces to be slightly inside rather than on the apparent horizons,
thus avoiding extrapolation into the black holes at the last stage of initial
data construction. We find that this improves initial data constraint
violations near and inside the apparent horizons by about 3 orders of
magnitude. We construct several initial data sets that are intended to be
astrophysically equivalent but use different free data, boundary conditions,
and initial gauge conditions. These include free data chosen as a superposition
of two black holes in time-independent horizon-penetrating harmonic and damped
harmonic coordinates. We also implement initial data for which the initial
gauge satisfies the harmonic and damped harmonic gauge conditions; this can be
done independently of the free data, since this amounts to a choice of the time
derivatives of the lapse and shift. We compare these initial data sets by
evolving them. We show that the gravitational waveforms extracted during the
evolution of these different initial data sets agree very well after excluding
initial transients. However, we do find small differences between these
waveforms, which we attribute to small differences in initial orbital
eccentricity, and in initial BH masses and spins, resulting from the different
choices of free data. Among the cases considered, we find that superposed
harmonic initial data leads to significantly smaller transients, smaller
variation in BH spins and masses during these transients, smaller constraint
violations, and more computationally efficient evolutions. Finally, we study
the impact of initial data choices on the construction of zero-eccentricity
initial data.
| [
{
"created": "Fri, 24 Aug 2018 17:59:49 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 22:54:10 GMT",
"version": "v2"
}
] | 2018-11-15 | [
[
"Varma",
"Vijay",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | We present improvements to construction of binary black hole initial data used in SpEC (the Spectral Einstein Code). We introduce new boundary conditions for the extended conformal thin sandwich elliptic equations that enforce the excision surfaces to be slightly inside rather than on the apparent horizons, thus avoiding extrapolation into the black holes at the last stage of initial data construction. We find that this improves initial data constraint violations near and inside the apparent horizons by about 3 orders of magnitude. We construct several initial data sets that are intended to be astrophysically equivalent but use different free data, boundary conditions, and initial gauge conditions. These include free data chosen as a superposition of two black holes in time-independent horizon-penetrating harmonic and damped harmonic coordinates. We also implement initial data for which the initial gauge satisfies the harmonic and damped harmonic gauge conditions; this can be done independently of the free data, since this amounts to a choice of the time derivatives of the lapse and shift. We compare these initial data sets by evolving them. We show that the gravitational waveforms extracted during the evolution of these different initial data sets agree very well after excluding initial transients. However, we do find small differences between these waveforms, which we attribute to small differences in initial orbital eccentricity, and in initial BH masses and spins, resulting from the different choices of free data. Among the cases considered, we find that superposed harmonic initial data leads to significantly smaller transients, smaller variation in BH spins and masses during these transients, smaller constraint violations, and more computationally efficient evolutions. Finally, we study the impact of initial data choices on the construction of zero-eccentricity initial data. |
1302.3298 | Michael Devin | Michael Devin | Thermodynamics of Time Machines | null | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, a brief review of the consistent state approach to systems
containing closed timelike curves or similar devices is given, and applied to
the well known thermodynamic problem of Maxwell's demon. The 'third party
paradox' for acausal systems is defined and applied to CTC censorship and black
hole evaporation. Some traditional arguments for chronology protection are
re-examined.
| [
{
"created": "Fri, 8 Feb 2013 16:58:12 GMT",
"version": "v1"
}
] | 2013-02-15 | [
[
"Devin",
"Michael",
""
]
] | In this note, a brief review of the consistent state approach to systems containing closed timelike curves or similar devices is given, and applied to the well known thermodynamic problem of Maxwell's demon. The 'third party paradox' for acausal systems is defined and applied to CTC censorship and black hole evaporation. Some traditional arguments for chronology protection are re-examined. |
1101.1051 | Giovanni Marozzi Dr. | F. Finelli, G. Marozzi, G. P. Vacca, G. Venturi | Backreaction during inflation: a physical gauge invariant formulation | 4 pages. Typos corrected, comment added, version accepted for
publication in Phys. Rev. Lett | Phys.Rev.Lett.106:121304,2011 | 10.1103/PhysRevLett.106.121304 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within a genuinely gauge invariant approach recently developed for the
computation of the cosmological backreaction, we study, in a cosmological
inflationary context and with respect to various observers, the impact of
scalar fluctuations on the space-time dynamics in the long wavelength limit. We
stress that such a quantum backreaction effect is evaluated in a truly gauge
independent way using a set of effective equations which describe the dynamics
of the averaged geometry. In particular we show under what conditions the free
falling (geodetic) observers do not experience any scalar-induced backreaction
in the effective Hubble rate and fluid equation of state.
| [
{
"created": "Wed, 5 Jan 2011 19:17:22 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2011 19:03:35 GMT",
"version": "v2"
}
] | 2011-04-05 | [
[
"Finelli",
"F.",
""
],
[
"Marozzi",
"G.",
""
],
[
"Vacca",
"G. P.",
""
],
[
"Venturi",
"G.",
""
]
] | Within a genuinely gauge invariant approach recently developed for the computation of the cosmological backreaction, we study, in a cosmological inflationary context and with respect to various observers, the impact of scalar fluctuations on the space-time dynamics in the long wavelength limit. We stress that such a quantum backreaction effect is evaluated in a truly gauge independent way using a set of effective equations which describe the dynamics of the averaged geometry. In particular we show under what conditions the free falling (geodetic) observers do not experience any scalar-induced backreaction in the effective Hubble rate and fluid equation of state. |
gr-qc/0011044 | Hongsu Kim | Hongsu Kim, Chul Hoon Lee, Hyun Kyu Lee (Hanyang Univ., KOREA) | Non-vanishing Magnetic Flux through the Slightly-charged Kerr Black Hole | 33pages, 1 figure, Revtex, some comments added, typos corrected | Phys.Rev. D63 (2001) 064037 | 10.1103/PhysRevD.63.064037 | null | gr-qc astro-ph hep-th | null | In association with the Blanford-Znajek mechanism for rotational energy
extraction from Kerr black holes, it is of some interest to explore how much of
magnetic flux can actually penetrate the horizon at least in idealized
situations. For completely uncharged Kerr hole case, it has been known for some
time that the magnetic flux gets entirely expelled when the hole is
maximally-rotating. In the mean time, it is known that when the rotating hole
is immersed in an originally uniform magnetic field surrounded by an ionized
interstellar medium (plasma), which is a more realistic situation, the hole
accretes certain amount of electric charge. In the present work, it is
demonstrated that as a result of this accretion charge small enough not to
disturb the geometry, the magnetic flux through this slightly charged Kerr hole
depends not only on the hole's angular momentum but on the hole's charge as
well such that it never vanishes for any value of the hole's angular momentum.
| [
{
"created": "Mon, 13 Nov 2000 07:30:18 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Nov 2000 07:29:47 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kim",
"Hongsu",
"",
"Hanyang Univ., KOREA"
],
[
"Lee",
"Chul Hoon",
"",
"Hanyang Univ., KOREA"
],
[
"Lee",
"Hyun Kyu",
"",
"Hanyang Univ., KOREA"
]
] | In association with the Blanford-Znajek mechanism for rotational energy extraction from Kerr black holes, it is of some interest to explore how much of magnetic flux can actually penetrate the horizon at least in idealized situations. For completely uncharged Kerr hole case, it has been known for some time that the magnetic flux gets entirely expelled when the hole is maximally-rotating. In the mean time, it is known that when the rotating hole is immersed in an originally uniform magnetic field surrounded by an ionized interstellar medium (plasma), which is a more realistic situation, the hole accretes certain amount of electric charge. In the present work, it is demonstrated that as a result of this accretion charge small enough not to disturb the geometry, the magnetic flux through this slightly charged Kerr hole depends not only on the hole's angular momentum but on the hole's charge as well such that it never vanishes for any value of the hole's angular momentum. |
gr-qc/0507007 | Bernd Reimann | Miguel Alcubierre, Alejandro Corichi, Jos\'e A. Gonz\'alez, Dar\'io
N\'u\~nez, Bernd Reimann, Marcelo Salgado | Generalized harmonic spatial coordinates and hyperbolic shift conditions | 18 pages and 12 figures, extensively revised version explaining in
the new Section IV how the shift condition can be made 3-covariant | Phys.Rev.D72:124018,2005 | 10.1103/PhysRevD.72.124018 | AEI-2005-108 | gr-qc | null | We propose a generalization of the condition for harmonic spatial coordinates
analogous to the generalization of the harmonic time slices introduced by Bona
et al., and closely related to dynamic shift conditions recently proposed by
Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic
spatial coordinates imply a condition for the shift vector that has the form of
an evolution equation for the shift components. We find that in order to
decouple the slicing condition from the evolution equation for the shift it is
necessary to use a rescaled shift vector. The initial form of the generalized
harmonic shift condition is not spatially covariant, but we propose a simple
way to make it fully covariant so that it can be used in coordinate systems
other than Cartesian. We also analyze the effect of the shift condition
proposed here on the hyperbolicity of the evolution equations of general
relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible
development of blow-ups. Finally, we perform a series of numerical experiments
to illustrate the behavior of this shift condition.
| [
{
"created": "Fri, 1 Jul 2005 21:12:34 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Oct 2005 17:53:02 GMT",
"version": "v2"
}
] | 2011-04-21 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Corichi",
"Alejandro",
""
],
[
"González",
"José A.",
""
],
[
"Núñez",
"Darío",
""
],
[
"Reimann",
"Bernd",
""
],
[
"Salgado",
"Marcelo",
""
]
] | We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blow-ups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition. |
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