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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2401.01705 | Tanmoy Paul | Hitender Kumar, Tanmoy Paul, Soumitra SenGupta | f(R) gravity with spacetime torsion | EPL Accepted | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The duality between a higher curvature $f(R)$ gravity model and a
scalar-tensor theory helps to bring out the role of the additional degree of
freedom originating from the higher derivative terms in the gravity action.
Such a degree of freedom which appears as a scalar field has been shown to have
multiple implications in Cosmological/Astrophysical scenario. The present work
proposes a novel generalization to this correspondence between $f(R)$ gravity
and a dual scalar-tensor theory when the affine connection is considered to
have an antisymmetric part. It turns out that the $f(R)$ action in presence of
spacetime torsion can be recast to a $non-minimally$ coupled scalar-tensor
theory with a 2-rank massless antisymmetric tensor field in the Einstein frame,
where the scalar field gets coupled with the antisymmetric field through
derivative coupling(s).
| [
{
"created": "Wed, 3 Jan 2024 12:15:35 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Jun 2024 06:39:01 GMT",
"version": "v2"
}
] | 2024-06-21 | [
[
"Kumar",
"Hitender",
""
],
[
"Paul",
"Tanmoy",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | The duality between a higher curvature $f(R)$ gravity model and a scalar-tensor theory helps to bring out the role of the additional degree of freedom originating from the higher derivative terms in the gravity action. Such a degree of freedom which appears as a scalar field has been shown to have multiple implications in Cosmological/Astrophysical scenario. The present work proposes a novel generalization to this correspondence between $f(R)$ gravity and a dual scalar-tensor theory when the affine connection is considered to have an antisymmetric part. It turns out that the $f(R)$ action in presence of spacetime torsion can be recast to a $non-minimally$ coupled scalar-tensor theory with a 2-rank massless antisymmetric tensor field in the Einstein frame, where the scalar field gets coupled with the antisymmetric field through derivative coupling(s). |
gr-qc/0407071 | Gaetano Lambiase | G. Lambiase, A.R. Prasanna | Gauge Invariant Wave Equations in Curved Space-Times and Primordial
Magnetic Fields | 5 pages, no figures, 1 table | Phys.Rev. D70 (2004) 063502 | 10.1103/PhysRevD.70.063502 | null | gr-qc | null | The inflationary production of magnetic field seeds for galaxies is
discussed. The analysis is carried out by writing the wave equation of the
electromagnetic field in curved spacetimes. The conformal invariance is broken
by taking into account of the interaction of the electromagnetic field with the
curvature tensor of the form $\lambda R_{\alpha\beta\gamma\delta}
F^{\alpha\beta} F^{\gamma\delta}$. Such a term induces an amplification of the
magnetic field during the reheating phase of the universe, but no growth of the
magnetic field occurs in the de Sitter epoch. The resulting primordial magnetic
field turns out to have strengths of astrophysical interest.
| [
{
"created": "Mon, 19 Jul 2004 11:16:55 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Lambiase",
"G.",
""
],
[
"Prasanna",
"A. R.",
""
]
] | The inflationary production of magnetic field seeds for galaxies is discussed. The analysis is carried out by writing the wave equation of the electromagnetic field in curved spacetimes. The conformal invariance is broken by taking into account of the interaction of the electromagnetic field with the curvature tensor of the form $\lambda R_{\alpha\beta\gamma\delta} F^{\alpha\beta} F^{\gamma\delta}$. Such a term induces an amplification of the magnetic field during the reheating phase of the universe, but no growth of the magnetic field occurs in the de Sitter epoch. The resulting primordial magnetic field turns out to have strengths of astrophysical interest. |
0712.3838 | Peter Collas | David Klein and Peter Collas | General Transformation Formulas for Fermi-Walker Coordinates | 23 pages. Corrected typos in the last two equations. Accepted for
publication in Classical and Quantum Gravity | Class.Quant.Grav.25:145019,2008 | 10.1088/0264-9381/25/14/145019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the transformation and inverse transformation, in the form of
Taylor expansions, from arbitrary coordinates to Fermi-Walker coordinates in
tubular neighborhoods of arbitrary timelike paths for general spacetimes.
Explicit formulas for coefficients and the Jacobian matrix are given.
| [
{
"created": "Sat, 22 Dec 2007 08:18:36 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Mar 2008 05:10:23 GMT",
"version": "v2"
},
{
"created": "Sat, 31 May 2008 23:35:56 GMT",
"version": "v3"
},
{
"created": "Fri, 27 Jun 2008 07:40:55 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Klein",
"David",
""
],
[
"Collas",
"Peter",
""
]
] | We calculate the transformation and inverse transformation, in the form of Taylor expansions, from arbitrary coordinates to Fermi-Walker coordinates in tubular neighborhoods of arbitrary timelike paths for general spacetimes. Explicit formulas for coefficients and the Jacobian matrix are given. |
2007.12552 | Ra\"ul Vera | Marc Mars, Borja Reina, Ra\"ul Vera | Existence and uniqueness of compact rotating configurations in GR in
second order perturbation theory | 81 pages, no figures | null | 10.4310/ATMP.2022.v26.n8.a9 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Existence and uniqueness of rotating fluid bodies in equilibrium is still
poorly understood in General Relativity (GR). Apart from the limiting case of
infinitely thin disks, the only known global results in the stationary rotating
case (Heilig [14] and Makino [21] [arXiv:1705.07392]) show existence in GR
nearby a Newtonian configuration (under suitable additional restrictions). In
this work we prove existence and uniqueness of rigidly (slowly) rotating fluid
bodies in equilibrium to second order in perturbation theory in GR. The most
widely used perturbation framework to describe slowly rigidly rotating stars in
the strong field regime is the Hartle-Thorne model. The model involves a number
of hypotheses, some explicit, like equatorial symmetry or that the perturbation
parameter is proportional to the rotation, but some implicit, particularly on
the structure and regularity of the perturbation tensors and the conditions of
their matching at the surface. In this work, with basis on the gauge results
obtained in [25], the Hartle-Thorne model is fully derived from first
principles and only assuming that the perturbations describe a rigidly rotating
finite perfect fluid ball (with no layer at the surface) with the same
barotropic equation of state as the static ball. Rigidly rotating fluid balls
are analyzed consistently in second order perturbation theory by imposing only
basic differentiability requirements and boundedness. Our results prove in
particular that, at this level of approximation, the spacetime must be indeed
equatorially symmetric and is fully determined by two parameters, namely the
central pressure and the uniform angular velocity of the fluid.
| [
{
"created": "Fri, 24 Jul 2020 15:00:52 GMT",
"version": "v1"
}
] | 2024-01-26 | [
[
"Mars",
"Marc",
""
],
[
"Reina",
"Borja",
""
],
[
"Vera",
"Raül",
""
]
] | Existence and uniqueness of rotating fluid bodies in equilibrium is still poorly understood in General Relativity (GR). Apart from the limiting case of infinitely thin disks, the only known global results in the stationary rotating case (Heilig [14] and Makino [21] [arXiv:1705.07392]) show existence in GR nearby a Newtonian configuration (under suitable additional restrictions). In this work we prove existence and uniqueness of rigidly (slowly) rotating fluid bodies in equilibrium to second order in perturbation theory in GR. The most widely used perturbation framework to describe slowly rigidly rotating stars in the strong field regime is the Hartle-Thorne model. The model involves a number of hypotheses, some explicit, like equatorial symmetry or that the perturbation parameter is proportional to the rotation, but some implicit, particularly on the structure and regularity of the perturbation tensors and the conditions of their matching at the surface. In this work, with basis on the gauge results obtained in [25], the Hartle-Thorne model is fully derived from first principles and only assuming that the perturbations describe a rigidly rotating finite perfect fluid ball (with no layer at the surface) with the same barotropic equation of state as the static ball. Rigidly rotating fluid balls are analyzed consistently in second order perturbation theory by imposing only basic differentiability requirements and boundedness. Our results prove in particular that, at this level of approximation, the spacetime must be indeed equatorially symmetric and is fully determined by two parameters, namely the central pressure and the uniform angular velocity of the fluid. |
1806.11110 | Papantonopoulos Eleftherios | Theodoros Kolyvaris, Marina Koukouvaou, Antri Machattou, Eleftherios
Papantonopoulos | Superradiant Instabilities in a Class of Scalar-Tensor Horndeski Theory | 8 Figures, 21 Pages, accepted for publication to Physical Review D.
arXiv admin note: substantial text overlap with arXiv:1702.04618; text
overlap with arXiv:1304.6474 by other authors | null | 10.1103/PhysRevD.98.024045 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We study the superradiance effect in a class of scalar-tensor Horndeski
theory. We first study the dynamics of a massive charged scalar wave scattered
off the horizon of a Reissner-Nordstr\"om black hole which except its canonical
coupling to gravity it is also coupled kinetically to curvature. We find that a
trapping potential is formed outside the horizon of a Reissner-Nordstr\"om
black hole, due to this coupling, and as the strength of the new coupling is
increased, the scattered wave is superradiantly amplified, resulting to the
instability of the Reissner-Nordstr\"om spacetime. We then considered the
backreacting effect of the scalar field coupled to curvature interacting with
the background metric and we study the superradiant effect and find the
superradiance conditions of a massive charged wave scattered off the horizon of
a Horndeski black hole.
| [
{
"created": "Thu, 28 Jun 2018 15:25:40 GMT",
"version": "v1"
}
] | 2018-08-15 | [
[
"Kolyvaris",
"Theodoros",
""
],
[
"Koukouvaou",
"Marina",
""
],
[
"Machattou",
"Antri",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We study the superradiance effect in a class of scalar-tensor Horndeski theory. We first study the dynamics of a massive charged scalar wave scattered off the horizon of a Reissner-Nordstr\"om black hole which except its canonical coupling to gravity it is also coupled kinetically to curvature. We find that a trapping potential is formed outside the horizon of a Reissner-Nordstr\"om black hole, due to this coupling, and as the strength of the new coupling is increased, the scattered wave is superradiantly amplified, resulting to the instability of the Reissner-Nordstr\"om spacetime. We then considered the backreacting effect of the scalar field coupled to curvature interacting with the background metric and we study the superradiant effect and find the superradiance conditions of a massive charged wave scattered off the horizon of a Horndeski black hole. |
1506.03278 | Olivier Minazzoli | Hendrik Ludwig, Olivier Minazzoli, Salvatore Capozziello | Merging matter and geometry in the same Lagrangian | null | Physics Letters B, Volume 751, 17 December 2015, Pages 576-578 | 10.1016/j.physletb.2015.11.023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a Lagrangian density proportional to $\sqrt{-g} \L_m^2/R$
reduces to a pressuron theory of gravity that is indistinguishable from General
Relativity in the dust limit. The combination of matter and geometry in the
same Lagrangian density intrinsically satisfies Mach's Principle --- since
matter cannot exist without curvature and vice versa --- while it may have the
correct phenomenology in order to describe actual gravity.
| [
{
"created": "Wed, 10 Jun 2015 12:36:11 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Oct 2015 15:27:27 GMT",
"version": "v2"
}
] | 2015-11-24 | [
[
"Ludwig",
"Hendrik",
""
],
[
"Minazzoli",
"Olivier",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | We show that a Lagrangian density proportional to $\sqrt{-g} \L_m^2/R$ reduces to a pressuron theory of gravity that is indistinguishable from General Relativity in the dust limit. The combination of matter and geometry in the same Lagrangian density intrinsically satisfies Mach's Principle --- since matter cannot exist without curvature and vice versa --- while it may have the correct phenomenology in order to describe actual gravity. |
2204.11293 | Francois Larrouturou | Luc Blanchet and Guillaume Faye and Fran\c{c}ois Larrouturou | The Quadrupole Moment of Compact Binaries to the Fourth post-Newtonian
Order: From Source to Canonical Moment | 25 pages, no figure | CQG 39(2022)195003 | 10.1088/1361-6382/ac840c | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | As a crucial step towards the completion of the fourth post-Newtonian (4PN)
gravitational-wave generation from compact binary systems, we obtain the
expressions of the so-called "canonical" multipole moments of the source in
terms of the "source" and "gauge" moments. The canonical moments describe the
propagation of gravitational waves outside the source's near zone, while the
source and gauge moments encode explicit information about the matter source.
Those two descriptions, in terms of two sets of canonical moments or in terms
of six sets of source and gauge moments, are isometric. We thus construct the
non-linear diffeomorphism between them up to the third post-Minkowskian order,
and we exhibit the concrete expression of the canonical mass-type quadrupole
moment at the 4PN order. This computation is one of the last missing pieces for
the determination of the gravitational-wave phasing of compact binary systems
at 4PN order.
| [
{
"created": "Sun, 24 Apr 2022 14:51:20 GMT",
"version": "v1"
},
{
"created": "Tue, 3 May 2022 20:26:53 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Aug 2022 08:22:03 GMT",
"version": "v3"
},
{
"created": "Fri, 2 Sep 2022 17:40:06 GMT",
"version": "v4"
}
] | 2022-09-14 | [
[
"Blanchet",
"Luc",
""
],
[
"Faye",
"Guillaume",
""
],
[
"Larrouturou",
"François",
""
]
] | As a crucial step towards the completion of the fourth post-Newtonian (4PN) gravitational-wave generation from compact binary systems, we obtain the expressions of the so-called "canonical" multipole moments of the source in terms of the "source" and "gauge" moments. The canonical moments describe the propagation of gravitational waves outside the source's near zone, while the source and gauge moments encode explicit information about the matter source. Those two descriptions, in terms of two sets of canonical moments or in terms of six sets of source and gauge moments, are isometric. We thus construct the non-linear diffeomorphism between them up to the third post-Minkowskian order, and we exhibit the concrete expression of the canonical mass-type quadrupole moment at the 4PN order. This computation is one of the last missing pieces for the determination of the gravitational-wave phasing of compact binary systems at 4PN order. |
1211.3725 | Cristian Stelea | Cristian Stelea, Marian C. Ghilea | A black ring on the Taub-bolt instanton in five dimensions | 14 pages, 1 figure, added references. arXiv admin note: text overlap
with arXiv:1211.3154 | null | 10.1016/j.physletb.2013.01.009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a solution generating technique, we derive a new exact solution
describing a charged static black ring on the Taub-bolt gravitational instanton
in five dimensions. Unlike the black ring constructed on the self-dual Taub-NUT
instanton, it turns out that it is possible to find values of the parameters
for which the static black ring is in equilibrium and the conical singularities
disappear. We compute its conserved charges and discuss some of its
thermodynamic properties.
| [
{
"created": "Thu, 15 Nov 2012 20:37:55 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Nov 2012 20:00:30 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Stelea",
"Cristian",
""
],
[
"Ghilea",
"Marian C.",
""
]
] | Using a solution generating technique, we derive a new exact solution describing a charged static black ring on the Taub-bolt gravitational instanton in five dimensions. Unlike the black ring constructed on the self-dual Taub-NUT instanton, it turns out that it is possible to find values of the parameters for which the static black ring is in equilibrium and the conical singularities disappear. We compute its conserved charges and discuss some of its thermodynamic properties. |
gr-qc/9511031 | Luis Anchordoqui | G. E. Romero, J. A. Combi, S. E. Perez Bergliaffa, L. A. Anchordoqui | Centaurus A as a source of extragalactic cosmic rays with arrival
energies well beyond the GZK cutoff | Some remarks by the referee added, to appear in Astroparticle Physics | Astropart.Phys.5:279-283,1996 | 10.1016/0927-6505(96)00029-1 | null | gr-qc | null | The ultra--high energy cosmic rays recently detected by several air shower
experiments could have an extragalactic origin. In this case, the nearest
active galaxy Centaurus A might be the source of the most energetic particles
ever detected on Earth. We have used recent radio observations in order to
estimate the arrival energy of the protons accelerated by strong shock fronts
in the outer parts of this southern radio source. We expect detections
corresponding to particles with energies up to $\sim 2.2 \times 10^{21}$ eV and
an arrival direction of ($l \approx 310^{\circ}$, $b \approx 20^{\circ}$) in
galactic coordinates. The future Southern Hemisphere Pierre Auger Observatory
might provide a decisive test for extragalactic models of the origin of the
ultra--high energy cosmic rays.
| [
{
"created": "Fri, 10 Nov 1995 00:24:07 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 1996 22:09:03 GMT",
"version": "v2"
}
] | 2011-05-23 | [
[
"Romero",
"G. E.",
""
],
[
"Combi",
"J. A.",
""
],
[
"Bergliaffa",
"S. E. Perez",
""
],
[
"Anchordoqui",
"L. A.",
""
]
] | The ultra--high energy cosmic rays recently detected by several air shower experiments could have an extragalactic origin. In this case, the nearest active galaxy Centaurus A might be the source of the most energetic particles ever detected on Earth. We have used recent radio observations in order to estimate the arrival energy of the protons accelerated by strong shock fronts in the outer parts of this southern radio source. We expect detections corresponding to particles with energies up to $\sim 2.2 \times 10^{21}$ eV and an arrival direction of ($l \approx 310^{\circ}$, $b \approx 20^{\circ}$) in galactic coordinates. The future Southern Hemisphere Pierre Auger Observatory might provide a decisive test for extragalactic models of the origin of the ultra--high energy cosmic rays. |
gr-qc/0204051 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Quantum-Gravity Phenomenology: Status and Prospects | 28 pages, LaTex, invited Brief Review to appear in a a special issue
of Modern Physics Letters A devoted to the First IUCAA Meeting on the
Interface of Gravitational and Quantum Realms | Mod.Phys.Lett. A17 (2002) 899-922 | 10.1142/S0217732302007612 | null | gr-qc | null | Over the last few years part of the quantum-gravity community has adopted a
more optimistic attitude toward the possibility of finding experimental
contexts providing insight on non-classical properties of spacetime. I review
those quantum-gravity phenomenology proposals which were instrumental in
bringing about this change of attitude, and I discuss the prospects for the
short-term future of quantum-gravity phenomenology.
| [
{
"created": "Mon, 15 Apr 2002 21:20:27 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | Over the last few years part of the quantum-gravity community has adopted a more optimistic attitude toward the possibility of finding experimental contexts providing insight on non-classical properties of spacetime. I review those quantum-gravity phenomenology proposals which were instrumental in bringing about this change of attitude, and I discuss the prospects for the short-term future of quantum-gravity phenomenology. |
1209.4892 | James Ryan | Bianca Dittrich and James P. Ryan | On the role of the Barbero-Immirzi parameter in discrete quantum gravity | 16 + 12 pages | null | 10.1088/0264-9381/30/9/095015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 1-parameter family of transformations identified by Barbero and Immirzi
plays a significant role in non-perturbative approaches to quantum gravity,
among them Loop Quantum Gravity and Spin Foams. It facilitates the loop
quantization programme and subsequently the Barbero-Immirzi parameter (gamma)
arises in both the spectra of geometrical operators and in the dynamics
provided by Spin Foams. However, the debate continues as to whether quantum
physics should be Barbero-Immirzi parameter dependent. Starting from a discrete
SO(4)-BF theory phase space, we find two possible reductions with respect to a
discrete form of the simplicity constraints. The first reduces to a phase space
with gamma-dependent symplectic structure and more generally in agreement with
the phase space underlying Loop Quantum Gravity restricted to a single graph -
a.k.a. Twisted Geometries. The second, fuller reduction leads to a
gamma-independent symplectic structure on the phase space of
piecewise-flat-linear geometries - a.k.a. Regge geometries. Thus, the
gamma-dependence of physical predictions is related to the choice of phase
space underlying the quantization.
| [
{
"created": "Fri, 21 Sep 2012 19:50:31 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Dittrich",
"Bianca",
""
],
[
"Ryan",
"James P.",
""
]
] | The 1-parameter family of transformations identified by Barbero and Immirzi plays a significant role in non-perturbative approaches to quantum gravity, among them Loop Quantum Gravity and Spin Foams. It facilitates the loop quantization programme and subsequently the Barbero-Immirzi parameter (gamma) arises in both the spectra of geometrical operators and in the dynamics provided by Spin Foams. However, the debate continues as to whether quantum physics should be Barbero-Immirzi parameter dependent. Starting from a discrete SO(4)-BF theory phase space, we find two possible reductions with respect to a discrete form of the simplicity constraints. The first reduces to a phase space with gamma-dependent symplectic structure and more generally in agreement with the phase space underlying Loop Quantum Gravity restricted to a single graph - a.k.a. Twisted Geometries. The second, fuller reduction leads to a gamma-independent symplectic structure on the phase space of piecewise-flat-linear geometries - a.k.a. Regge geometries. Thus, the gamma-dependence of physical predictions is related to the choice of phase space underlying the quantization. |
1707.09205 | Georgios Papadopoulos O | Georgios O. Papadopoulos | Finding integrals and identities in the Newman Penrose formalism: a
comment on Class. Quantum Grav. 26 (2009) 105022 and on Gen. Relativ. Gravit.
(2014)46:1703 | 7 pages, no figures, submitted to a journal | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1969 Kinnersley, using the NP formalism, found all the Petrov type D,
Ricci flat, solutions to the Einstein's Field Equations. Yet, in doing so -as
it seems- he neglected two fundamental identities (or constraints) on four NP
variables and Cartan invariants as well, namely $\tau\bar{\tau}-\pi\bar{\pi}=0$
and $\rho\bar{\mu}-\mu\bar{\rho}=0$. Since then, these identities have been
constantly either overlooked or proven under special circumstances (e.g.
electrovac solutions). It was only until 2009 when Edgar et al. by making an
extended use of the GHP formalism, and of a computer algebra system, succeeded
in proving those identities in the general case. In that reference, it was
-rather indirectly- implied that the results under consideration were provable
only within the GHP formalism and thus the latter is the optimal tool towards
the invariant classification and study of classes of solutions to the EFEs. In
2014 there was a kind of response to that paper by J.J. Ferrando & J.A. Saez.
Using the tensorial algebra (of 2-forms), and without the aid of a CAS, the
authors proved the desired result and they offer a much more refined and
extended classification of the Petrov type D, Ricci flat, solutions. Never the
less when someone reads that third work, although beautiful and conceptually
simple, one has the feeling that the authors know in advance what they want to
prove; something which is not always the case. The goal of the present short
work is to prove, through the specific example (i.e., the class of Ricci flat,
Petrov type D geometries), that the original NP formalism, seen as an exterior
differential system suffices to provide the desired results -thus commenting on
the second cited paper- not only without (in principle) the aid of a CAS, but
also to obtain a new further (unknown until now) integral of the EDS -thus
commenting on the third cited paper.
| [
{
"created": "Fri, 28 Jul 2017 12:25:42 GMT",
"version": "v1"
}
] | 2017-07-31 | [
[
"Papadopoulos",
"Georgios O.",
""
]
] | In 1969 Kinnersley, using the NP formalism, found all the Petrov type D, Ricci flat, solutions to the Einstein's Field Equations. Yet, in doing so -as it seems- he neglected two fundamental identities (or constraints) on four NP variables and Cartan invariants as well, namely $\tau\bar{\tau}-\pi\bar{\pi}=0$ and $\rho\bar{\mu}-\mu\bar{\rho}=0$. Since then, these identities have been constantly either overlooked or proven under special circumstances (e.g. electrovac solutions). It was only until 2009 when Edgar et al. by making an extended use of the GHP formalism, and of a computer algebra system, succeeded in proving those identities in the general case. In that reference, it was -rather indirectly- implied that the results under consideration were provable only within the GHP formalism and thus the latter is the optimal tool towards the invariant classification and study of classes of solutions to the EFEs. In 2014 there was a kind of response to that paper by J.J. Ferrando & J.A. Saez. Using the tensorial algebra (of 2-forms), and without the aid of a CAS, the authors proved the desired result and they offer a much more refined and extended classification of the Petrov type D, Ricci flat, solutions. Never the less when someone reads that third work, although beautiful and conceptually simple, one has the feeling that the authors know in advance what they want to prove; something which is not always the case. The goal of the present short work is to prove, through the specific example (i.e., the class of Ricci flat, Petrov type D geometries), that the original NP formalism, seen as an exterior differential system suffices to provide the desired results -thus commenting on the second cited paper- not only without (in principle) the aid of a CAS, but also to obtain a new further (unknown until now) integral of the EDS -thus commenting on the third cited paper. |
2211.01243 | Uwe R. Fischer | Caio C. Holanda Ribeiro, Uwe R. Fischer | Impact of trans-Planckian excitations on black-hole radiation in dipolar
condensates | 6+4 pages, 2 figures | Phys. Rev. D 107, L121502 (2023) | 10.1103/PhysRevD.107.L121502 | null | gr-qc cond-mat.quant-gas quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a quasi-one-dimensional dipolar condensate in an analogue black
hole setup. It is shown that the existence of a roton minimum in the condensate
dispersion relation leaves deep imprints onto the Hawking radiation spectrum.
In particular, the emitted radiation can be either more intense or suppressed,
depending on the depth of the roton minimum in the excitation spectrum. In
addition, we find that spontaneous particle creation occurs even when the
horizon is removed. Our results establish that dipolar condensates offer a
richer and more versatile environment for the simulation of particle production
from the quantum vacuum in the presence of horizon-interfaces than their
contact-interaction counterparts.
| [
{
"created": "Wed, 2 Nov 2022 16:25:22 GMT",
"version": "v1"
}
] | 2024-01-29 | [
[
"Ribeiro",
"Caio C. Holanda",
""
],
[
"Fischer",
"Uwe R.",
""
]
] | We consider a quasi-one-dimensional dipolar condensate in an analogue black hole setup. It is shown that the existence of a roton minimum in the condensate dispersion relation leaves deep imprints onto the Hawking radiation spectrum. In particular, the emitted radiation can be either more intense or suppressed, depending on the depth of the roton minimum in the excitation spectrum. In addition, we find that spontaneous particle creation occurs even when the horizon is removed. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon-interfaces than their contact-interaction counterparts. |
1901.07541 | Jose Rafael Arce-Gamboa | J. R. Arce-Gamboa and F. Frutos-Alfaro | Classical General Relativity Effects to Second Order in Mass, Spin, and
Quadrupole Moment | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this contribution, we calculate the light deflection, perihelium shift,
time delay and gravitational redshift using an approximate metric that contains
the Kerr metric and an approximaction of the Erez-Rosen spacetime. The results
were obtained directly using Mathematica. The results agree with the ones
presented in the literature, but they are extended until second order terms of
mass, angular momentum and mass quadrupole.
| [
{
"created": "Mon, 21 Jan 2019 22:11:30 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Feb 2019 17:15:58 GMT",
"version": "v2"
},
{
"created": "Sun, 7 Apr 2019 23:39:18 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Aug 2019 03:04:20 GMT",
"version": "v4"
}
] | 2019-08-09 | [
[
"Arce-Gamboa",
"J. R.",
""
],
[
"Frutos-Alfaro",
"F.",
""
]
] | In this contribution, we calculate the light deflection, perihelium shift, time delay and gravitational redshift using an approximate metric that contains the Kerr metric and an approximaction of the Erez-Rosen spacetime. The results were obtained directly using Mathematica. The results agree with the ones presented in the literature, but they are extended until second order terms of mass, angular momentum and mass quadrupole. |
2303.00190 | Xjao-Jun Gao | Xiao-Jun Gao, Xiao-kun Yan, Yihao Yin and Ya-Peng Hu | Gravitational lensing by a charged spherically symmetric black hole
immersed in thin dark matter | 14 pages, 3 figures; v2: adding some references | Eur. Phys. J. C (2023) 83:281 | 10.1140/epjc/s10052-023-11414-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gravitational lensing effect around a spherically
symmetric black hole, whose metric is obtained from the Einstein field equation
with electric charge and perfect-fluid dark matter contributing to its
energy-momentum tensor. We do the calculation analytically in the weak field
limit and we assume that both the charge and the dark matter are much less
abundant (only give rise to the next-leading-order contribution) in comparison
to the black hole mass. In particular, we derive the light deflection angle and
the size of the Einstein ring, where approximations up to the next-leading
order are done with extra care, especially for the logarithmic term from
perfect-fluid dark matter. We expect our results will be useful in the future
to relate the theoretical model of perfect fluid dark matter with observations
of celestial bodies immersed in thin dark matter.
| [
{
"created": "Wed, 1 Mar 2023 02:39:50 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2023 06:27:41 GMT",
"version": "v2"
}
] | 2023-04-13 | [
[
"Gao",
"Xiao-Jun",
""
],
[
"Yan",
"Xiao-kun",
""
],
[
"Yin",
"Yihao",
""
],
[
"Hu",
"Ya-Peng",
""
]
] | We investigate the gravitational lensing effect around a spherically symmetric black hole, whose metric is obtained from the Einstein field equation with electric charge and perfect-fluid dark matter contributing to its energy-momentum tensor. We do the calculation analytically in the weak field limit and we assume that both the charge and the dark matter are much less abundant (only give rise to the next-leading-order contribution) in comparison to the black hole mass. In particular, we derive the light deflection angle and the size of the Einstein ring, where approximations up to the next-leading order are done with extra care, especially for the logarithmic term from perfect-fluid dark matter. We expect our results will be useful in the future to relate the theoretical model of perfect fluid dark matter with observations of celestial bodies immersed in thin dark matter. |
gr-qc/0306101 | Gagab Gad | Ragab M. Gad (Minia University) | Energy Distribution of a Stringy Charged Black Hole | Latex, no figures | Astrophys.Space Sci. 295 (2005) 459-462 | 10.1007/s10509-005-1195-6 | null | gr-qc | null | The energy distribution associated with a stringy charged black hole is
studied using M{\o}ller's energy-momentum complex. Our result is reasonable and
it differs from that known in literature using Einstein's energy-momentum
complex.
| [
{
"created": "Sun, 22 Jun 2003 15:26:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Gad",
"Ragab M.",
"",
"Minia University"
]
] | The energy distribution associated with a stringy charged black hole is studied using M{\o}ller's energy-momentum complex. Our result is reasonable and it differs from that known in literature using Einstein's energy-momentum complex. |
2004.11542 | Cosimo Bambi | Honghui Liu, Haiyang Wang, Askar B. Abdikamalov, Dimitry Ayzenberg,
Cosimo Bambi | Reflection features in the X-ray spectrum of Fairall 9 and implications
for tests of general relativity | 10 pages, 7 figures | Astrophys.J. 896: 160 (2020) | 10.3847/1538-4357/ab917a | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | X-ray reflection spectroscopy is potentially a powerful tool to probe the
spacetime geometry around astrophysical black holes and test general relativity
in the strong field regime. However, precision tests of general relativity are
only possible if we employ the correct astrophysical model and we can limit the
systematic uncertainties. It is thus crucial to select the sources and the
observations most suitable for these tests. In this work, we analyze
simultaneous observations of XMM-Newton and NuSTAR of the supermassive black
hole in Fairall 9. This source has a number of properties that make it a
promising candidate for tests of general relativity using X-ray reflection
spectroscopy. Nevertheless, we find that with the available data there is not a
unique interpretation of the spectrum of Fairall 9, which prevents, for the
moment, to use this source for robust tests of general relativity. This issue
may be solved by future X-ray missions with a higher energy resolution near the
iron line.
| [
{
"created": "Fri, 24 Apr 2020 05:50:43 GMT",
"version": "v1"
}
] | 2020-06-25 | [
[
"Liu",
"Honghui",
""
],
[
"Wang",
"Haiyang",
""
],
[
"Abdikamalov",
"Askar B.",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Bambi",
"Cosimo",
""
]
] | X-ray reflection spectroscopy is potentially a powerful tool to probe the spacetime geometry around astrophysical black holes and test general relativity in the strong field regime. However, precision tests of general relativity are only possible if we employ the correct astrophysical model and we can limit the systematic uncertainties. It is thus crucial to select the sources and the observations most suitable for these tests. In this work, we analyze simultaneous observations of XMM-Newton and NuSTAR of the supermassive black hole in Fairall 9. This source has a number of properties that make it a promising candidate for tests of general relativity using X-ray reflection spectroscopy. Nevertheless, we find that with the available data there is not a unique interpretation of the spectrum of Fairall 9, which prevents, for the moment, to use this source for robust tests of general relativity. This issue may be solved by future X-ray missions with a higher energy resolution near the iron line. |
1912.06222 | Reinoud Slagter | Reinoud J. Slagter and Jebin Larosh | On the BTZ Black Hole and the Spinning Cosmic String | version--V3: the 3D exact solution is added-- comments welcome-- 8
pages-- 6 figures | null | 10.1007/s12036-020-09645-8 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reviewed the Ba\u nados-Teitelboim-Zanelli (BTZ) black hole solution in
connection with the spinning string solution. We find a new exact solution,
which can be related to the $(2+1)$-dimensional spinning point particle
solution. There is no need for a cosmological constant, so the solution can be
up-lifted to $(3+1)$ dimensions. The exact solution in a conformal invariant
gravity model, where the spacetime is written as $g_{\mu\nu}=\omega^2 \tilde
g_{\mu\nu}$, is horizon free and has an ergo-circle, while $\tilde g_{\mu\nu}$
is the BTZ solution. The dilaton $\omega$ determines the scale of the model. In
accordance with the spinning cosmic string solution, it is conjectured that the
new solution can be linked to the mass of the interior of the spinning cosmic
string.
| [
{
"created": "Thu, 12 Dec 2019 21:25:46 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Dec 2019 11:01:00 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Dec 2019 12:07:11 GMT",
"version": "v3"
}
] | 2020-11-18 | [
[
"Slagter",
"Reinoud J.",
""
],
[
"Larosh",
"Jebin",
""
]
] | We reviewed the Ba\u nados-Teitelboim-Zanelli (BTZ) black hole solution in connection with the spinning string solution. We find a new exact solution, which can be related to the $(2+1)$-dimensional spinning point particle solution. There is no need for a cosmological constant, so the solution can be up-lifted to $(3+1)$ dimensions. The exact solution in a conformal invariant gravity model, where the spacetime is written as $g_{\mu\nu}=\omega^2 \tilde g_{\mu\nu}$, is horizon free and has an ergo-circle, while $\tilde g_{\mu\nu}$ is the BTZ solution. The dilaton $\omega$ determines the scale of the model. In accordance with the spinning cosmic string solution, it is conjectured that the new solution can be linked to the mass of the interior of the spinning cosmic string. |
1910.05631 | Rocco D'Agostino | Alexander Bonilla, Rocco D'Agostino, Rafael C. Nunes, Jos\'e C. N. de
Araujo | Forecasts on the speed of gravitational waves at high $z$ | 22 pages, 15 figures | JCAP 03 (2020) 015 | 10.1088/1475-7516/2020/03/015 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of GW170817 binary neutron star (BNS) merger event has
imposed strong bounds on the speed of gravitational waves (GWs) locally,
inferring that the speed of GWs propagation is equal to the speed of light.
Current GW detectors in operation will not be able to observe BNS merger to
long cosmological distance, where possible cosmological corrections on the
cosmic expansion history are expected to play an important role, specially for
investigating possible deviations from general relativity. Future GW detectors
designer projects will be able to detect many coalescences of BNS at high $z$,
such as the third generation of the ground GW detector called Einstein
Telescope (ET) and the space-based detector deci-hertz interferometer
gravitational wave observatory (DECIGO). In this paper, we relax the condition
$c_T/c = 1$ to investigate modified GW propagation where the speed of GWs
propagation is not necessarily equal to the speed of light. Also, we consider
the possibility for the running of the Planck mass corrections on modified GW
propagation. We parametrize both corrections in terms of an effective GW
luminosity distance and we perform a forecast analysis using standard siren
events from BNS mergers, within the sensitivity predicted for the ET and
DECIGO. We find at high $z$ very strong forecast bounds on the running of the
Planck mass, namely $\mathcal{O}(10^{-1})$ and $\mathcal{O}(10^{-2})$ from ET
and DECIGO, respectively. Possible anomalies on GW propagation are bound to
$|c_T/c - 1| \leq 10^{-2} \,\,\, (10^{-2})$ from ET (DECIGO), respectively. We
finally discuss the consequences of our results on modified gravity
phenomenology.
| [
{
"created": "Sat, 12 Oct 2019 19:10:59 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Mar 2020 19:21:20 GMT",
"version": "v2"
}
] | 2020-03-10 | [
[
"Bonilla",
"Alexander",
""
],
[
"D'Agostino",
"Rocco",
""
],
[
"Nunes",
"Rafael C.",
""
],
[
"de Araujo",
"José C. N.",
""
]
] | The observation of GW170817 binary neutron star (BNS) merger event has imposed strong bounds on the speed of gravitational waves (GWs) locally, inferring that the speed of GWs propagation is equal to the speed of light. Current GW detectors in operation will not be able to observe BNS merger to long cosmological distance, where possible cosmological corrections on the cosmic expansion history are expected to play an important role, specially for investigating possible deviations from general relativity. Future GW detectors designer projects will be able to detect many coalescences of BNS at high $z$, such as the third generation of the ground GW detector called Einstein Telescope (ET) and the space-based detector deci-hertz interferometer gravitational wave observatory (DECIGO). In this paper, we relax the condition $c_T/c = 1$ to investigate modified GW propagation where the speed of GWs propagation is not necessarily equal to the speed of light. Also, we consider the possibility for the running of the Planck mass corrections on modified GW propagation. We parametrize both corrections in terms of an effective GW luminosity distance and we perform a forecast analysis using standard siren events from BNS mergers, within the sensitivity predicted for the ET and DECIGO. We find at high $z$ very strong forecast bounds on the running of the Planck mass, namely $\mathcal{O}(10^{-1})$ and $\mathcal{O}(10^{-2})$ from ET and DECIGO, respectively. Possible anomalies on GW propagation are bound to $|c_T/c - 1| \leq 10^{-2} \,\,\, (10^{-2})$ from ET (DECIGO), respectively. We finally discuss the consequences of our results on modified gravity phenomenology. |
1506.01184 | Peter Hess O | Gunther Caspar and Isaac Rodriguez and Peter O. Hess and Walter
Greiner | Vacuum fluctuation inside a star and their consequences for neutron
stars, a simple model | 19 pages, 5 figures | null | 10.1142/S0218301316500270 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Applying semi-classical Quantum Mechanics, the vacuum fluctuations within a
star are determined, assuming a constant mass density and applying a monopole
approximation. It is found that the density for the vacuum fluctuations does
not only depend linearly on the mass density, as assumed in a former
publication, where neutron stars up to 6 solar masses were obtained. This is
used to propose a simple model on the dependence of the dark energy to the mass
density, as a function of the radial distance r. It is shown that stars with up
to 200 solar masses can, in principle, be obtained. Though, we use a simple
model, it shows that in the presence of vacuum fluctuations stars with large
masses can be stabilized and probably stars up to any mass can exist, which
usually are identified as black holes.
| [
{
"created": "Wed, 3 Jun 2015 09:51:07 GMT",
"version": "v1"
}
] | 2016-05-25 | [
[
"Caspar",
"Gunther",
""
],
[
"Rodriguez",
"Isaac",
""
],
[
"Hess",
"Peter O.",
""
],
[
"Greiner",
"Walter",
""
]
] | Applying semi-classical Quantum Mechanics, the vacuum fluctuations within a star are determined, assuming a constant mass density and applying a monopole approximation. It is found that the density for the vacuum fluctuations does not only depend linearly on the mass density, as assumed in a former publication, where neutron stars up to 6 solar masses were obtained. This is used to propose a simple model on the dependence of the dark energy to the mass density, as a function of the radial distance r. It is shown that stars with up to 200 solar masses can, in principle, be obtained. Though, we use a simple model, it shows that in the presence of vacuum fluctuations stars with large masses can be stabilized and probably stars up to any mass can exist, which usually are identified as black holes. |
2402.17422 | Dar\'io Jaramillo Garrido | Dar\'io Jaramillo-Garrido, Antonio L. Maroto, and Prado
Mart\'in-Moruno | Symmetry restoration for TDiff scalar fields | V2: 24 pages, new section V, new appendix, new applications,
conclusions unchanged, version accepted for publication in PRD. V1: 9 pages,
1 Appendix | null | null | IPARCOS-UCM-24-013 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the idea of restoring the full diffeomorphism (Diff) invariance in
theories with only transverse diffeomorphisms (TDiff) by the introduction of
additional fields. In particular, we consider in detail the case of a TDiff
invariant scalar field and how Diff symmetry can be restored preserving
locality by introducing an additional vector field. We reobtain the
corresponding dynamics and energy-momentum tensor from the covariantized action
and analyze the potential and kinetic domination regimes. For the former, the
theory describes a cosmological constant-type behaviour, while for the latter
we show that the theory can describe an adiabatic perfect fluid whose equation
of state and speed of sound is obtained in a straightforward way. Furthermore,
the reformulation with the full symmetry allows us to analyze the gravitational
properties of the theory beyond those particular regimes. In particular, we
find the general expression for the effective speed of sound of the
non-adiabatic perfect fluid, which provides us with physically reasonable
conditions that should be satisfied by the coupling functions. Finally, we
investigate the particular models leading to an adiabatic fluid.
| [
{
"created": "Tue, 27 Feb 2024 11:31:40 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jun 2024 14:08:37 GMT",
"version": "v2"
}
] | 2024-06-28 | [
[
"Jaramillo-Garrido",
"Darío",
""
],
[
"Maroto",
"Antonio L.",
""
],
[
"Martín-Moruno",
"Prado",
""
]
] | We explore the idea of restoring the full diffeomorphism (Diff) invariance in theories with only transverse diffeomorphisms (TDiff) by the introduction of additional fields. In particular, we consider in detail the case of a TDiff invariant scalar field and how Diff symmetry can be restored preserving locality by introducing an additional vector field. We reobtain the corresponding dynamics and energy-momentum tensor from the covariantized action and analyze the potential and kinetic domination regimes. For the former, the theory describes a cosmological constant-type behaviour, while for the latter we show that the theory can describe an adiabatic perfect fluid whose equation of state and speed of sound is obtained in a straightforward way. Furthermore, the reformulation with the full symmetry allows us to analyze the gravitational properties of the theory beyond those particular regimes. In particular, we find the general expression for the effective speed of sound of the non-adiabatic perfect fluid, which provides us with physically reasonable conditions that should be satisfied by the coupling functions. Finally, we investigate the particular models leading to an adiabatic fluid. |
1102.4067 | Mikhail Gorbatenko | M. V. Gorbatenko, V. P. Neznamov | Uniqueness and Self-Conjugacy of Dirac Hamiltonians in arbitrary
Gravitational Fields | 23 pages | Phys.Rev.D83:105002,2011 | 10.1103/PhysRevD.83.105002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Proofs of two statements are provided in this paper. First, the authors prove
that the formalism of the pseudo-Hermitian quantum mechanics allows describing
the Dirac particles motion in arbitrary stationary gravitational fields.
Second, it is proved that using the Parker weight operator and the subsequent
transition to the \eta -representation gives the transformation of the
Schroedinger equation for nonstationary metric, when the evolution operator
becomes self-conjugate. The scalar products in the \eta -representation are
flat, which makes possible the use of a standard apparatus for the Hermitian
quantum mechanics. Based on the results of this paper the authors draw a
conclusion about solution of the problem of uniqueness and self-conjugacy of
Dirac Hamiltonians in arbitrary gravitational fields including those dependent
on time. The general approach is illustrated by the example of Dirac
Hamiltonians for several stationary metrics, as well as for the cosmologically
flat and the open Friedmann models.
| [
{
"created": "Sun, 20 Feb 2011 13:30:27 GMT",
"version": "v1"
}
] | 2011-05-12 | [
[
"Gorbatenko",
"M. V.",
""
],
[
"Neznamov",
"V. P.",
""
]
] | Proofs of two statements are provided in this paper. First, the authors prove that the formalism of the pseudo-Hermitian quantum mechanics allows describing the Dirac particles motion in arbitrary stationary gravitational fields. Second, it is proved that using the Parker weight operator and the subsequent transition to the \eta -representation gives the transformation of the Schroedinger equation for nonstationary metric, when the evolution operator becomes self-conjugate. The scalar products in the \eta -representation are flat, which makes possible the use of a standard apparatus for the Hermitian quantum mechanics. Based on the results of this paper the authors draw a conclusion about solution of the problem of uniqueness and self-conjugacy of Dirac Hamiltonians in arbitrary gravitational fields including those dependent on time. The general approach is illustrated by the example of Dirac Hamiltonians for several stationary metrics, as well as for the cosmologically flat and the open Friedmann models. |
gr-qc/9511082 | null | Nivaldo A. Lemos (Center for Theoretical Physics, MIT) | Radiation-Dominated Quantum Friedmann Models | 18 pages, LaTex, to appear in J. Math. Phys | J.Math.Phys. 37 (1996) 1449-1460 | 10.1063/1.531443 | MIT-CTP-2493 | gr-qc | null | Radiation-filled Friedmann-Robertson-Walker universes are quantized according
to the Arnowitt-Deser-Misner formalism in the conformal-time gauge. Unlike
previous treatments of this problem, here both closed and open models are
studied, only square-integrable wave functions are allowed, and the boundary
conditions to ensure self-adjointness of the Hamiltonian operator are
consistent with the space of admissible wave functions. It turns out that the
tunneling boundary condition on the universal wave function is in conflict with
self-adjointness of the Hamiltonian. The evolution of wave packets obeying
different boundary conditions is studied and it is generally proven that all
models are nonsingular. Given an initial condition on the probability density
under which the classical regime prevails, it is found that a closed universe
is certain to have an infinite radius, a density parameter $\Omega = 1$
becoming a prediction of the theory. Quantum stationary geometries are shown to
exist for the closed universe model, but oscillating coherent states are
forbidden by the boundary conditions that enforce self-adjointness of the
Hamiltonian operator.
| [
{
"created": "Thu, 30 Nov 1995 18:10:35 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Lemos",
"Nivaldo A.",
"",
"Center for Theoretical Physics, MIT"
]
] | Radiation-filled Friedmann-Robertson-Walker universes are quantized according to the Arnowitt-Deser-Misner formalism in the conformal-time gauge. Unlike previous treatments of this problem, here both closed and open models are studied, only square-integrable wave functions are allowed, and the boundary conditions to ensure self-adjointness of the Hamiltonian operator are consistent with the space of admissible wave functions. It turns out that the tunneling boundary condition on the universal wave function is in conflict with self-adjointness of the Hamiltonian. The evolution of wave packets obeying different boundary conditions is studied and it is generally proven that all models are nonsingular. Given an initial condition on the probability density under which the classical regime prevails, it is found that a closed universe is certain to have an infinite radius, a density parameter $\Omega = 1$ becoming a prediction of the theory. Quantum stationary geometries are shown to exist for the closed universe model, but oscillating coherent states are forbidden by the boundary conditions that enforce self-adjointness of the Hamiltonian operator. |
2408.02538 | Masroor C. Pookkillath | Masroor C. Pookkillath, Nandan Roy | $G_{3}$ -- interacting scalar tensor dark energy | 22 pages, 6 figures, revtex | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the effect of adding an interaction in the $G_3$ term of Horndeski
theory, where the propagation of gravitational waves are not modified. We
derive the background and perturbation equations of motion from the action. We
also derive the no-ghost and Laplacian instability conditions for tensor modes
and scalar mode propagation. Then we study the evolution of the matter
perturbation in the quasi-static approximation. We find that the gravitational
couplings to the baryonic and cold dark matter over density are modified in
this theory. We introduce a concrete model of the free function in the theory
and study the background and linear perturbation dynamics. We then use the
genetic algorithm to test the model. We compare the $H(z)$ function of the
model and the $H(z)$ curve predicted by the genetic algorithm, using the $H(z)$
data. For the perturbation sector we compute the $f\sigma_{8}$ observable for
the model and compare it with the predicted function from the genetic algorithm
from the $f\sigma_{8}$ data.
| [
{
"created": "Mon, 5 Aug 2024 15:11:09 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Pookkillath",
"Masroor C.",
""
],
[
"Roy",
"Nandan",
""
]
] | We study the effect of adding an interaction in the $G_3$ term of Horndeski theory, where the propagation of gravitational waves are not modified. We derive the background and perturbation equations of motion from the action. We also derive the no-ghost and Laplacian instability conditions for tensor modes and scalar mode propagation. Then we study the evolution of the matter perturbation in the quasi-static approximation. We find that the gravitational couplings to the baryonic and cold dark matter over density are modified in this theory. We introduce a concrete model of the free function in the theory and study the background and linear perturbation dynamics. We then use the genetic algorithm to test the model. We compare the $H(z)$ function of the model and the $H(z)$ curve predicted by the genetic algorithm, using the $H(z)$ data. For the perturbation sector we compute the $f\sigma_{8}$ observable for the model and compare it with the predicted function from the genetic algorithm from the $f\sigma_{8}$ data. |
1902.02585 | Iber\^e Kuntz | Iber\^e Kuntz | Non-smooth gravity and parity violation | null | null | 10.1007/s10701-019-00240-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A conservative extension of general relativity is proposed by alleviating the
differentiability of the metric and allowing for non-smooth solutions. We show
that these metrics break some symmetries of the Riemann tensor, yielding a new
scalar curvature invariant besides the usual Ricci scalar. To first order in
the curvature, this adds a new piece of information to the action, containing
interesting and unexplored physics. The spectrum of the theory reveals the
presence of an additional massless spin-1 field apart from the massless spin-2
graviton. We argue that this new contribution violates P and CP symmetries at
leading order in the curvature and we discuss the possibility of observing
these effects in existing experiments.
| [
{
"created": "Thu, 7 Feb 2019 12:31:01 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Kuntz",
"Iberê",
""
]
] | A conservative extension of general relativity is proposed by alleviating the differentiability of the metric and allowing for non-smooth solutions. We show that these metrics break some symmetries of the Riemann tensor, yielding a new scalar curvature invariant besides the usual Ricci scalar. To first order in the curvature, this adds a new piece of information to the action, containing interesting and unexplored physics. The spectrum of the theory reveals the presence of an additional massless spin-1 field apart from the massless spin-2 graviton. We argue that this new contribution violates P and CP symmetries at leading order in the curvature and we discuss the possibility of observing these effects in existing experiments. |
gr-qc/9212006 | Sean Hayward | Sean A. Hayward | On Cosmological Isotropy, Quantum Cosmology and the Weyl Curvature
Hypothesis | 5 pages | Class.Quant.Grav.10:L7-L11,1993 | 10.1088/0264-9381/10/1/002 | null | gr-qc | null | The increasing entropy, large-scale isotropy and approximate flatness of the
universe are considered in the context of signature change, which is a
classical model of quantum tunnelling in quantum cosmology. The signature
change hypothesis implies an initial inflationary epoch, the magnetic half of
the Weyl curvature hypothesis, and a close analogue of the conformal
singularity hypothesis. Adding the electric half of the Weyl curvature
hypothesis yields, for a perfect fluid, only homogeneous and isotropic
cosmologies. In the cosmological-constant case, the unique solution is the
Vilenkin tunnelling solution, which gives a de Sitter cosmology.
| [
{
"created": "Thu, 10 Dec 1992 10:21:52 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Hayward",
"Sean A.",
""
]
] | The increasing entropy, large-scale isotropy and approximate flatness of the universe are considered in the context of signature change, which is a classical model of quantum tunnelling in quantum cosmology. The signature change hypothesis implies an initial inflationary epoch, the magnetic half of the Weyl curvature hypothesis, and a close analogue of the conformal singularity hypothesis. Adding the electric half of the Weyl curvature hypothesis yields, for a perfect fluid, only homogeneous and isotropic cosmologies. In the cosmological-constant case, the unique solution is the Vilenkin tunnelling solution, which gives a de Sitter cosmology. |
gr-qc/0410028 | Eric Black | Eric D. Black, Akira Villar, and Kenneth G. Libbrecht | Thermoelastic-damping noise from sapphire mirrors in a
fundamental-noise-limited interferometer | 4 pages, 2 figures | Phys.Rev.Lett. 93 (2004) 241101 | 10.1103/PhysRevLett.93.241101 | null | gr-qc | null | We report the first high-precision interferometer using large sapphire
mirrors, and we present the first direct, broadband measurements of the
fundamental thermal noise in these mirrors. Our results agree well with the
thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A
264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have
been used to predict the astrophysical reach of advanced interferometric
gravitational wave detectors.
| [
{
"created": "Wed, 6 Oct 2004 22:09:57 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Black",
"Eric D.",
""
],
[
"Villar",
"Akira",
""
],
[
"Libbrecht",
"Kenneth G.",
""
]
] | We report the first high-precision interferometer using large sapphire mirrors, and we present the first direct, broadband measurements of the fundamental thermal noise in these mirrors. Our results agree well with the thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A 264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have been used to predict the astrophysical reach of advanced interferometric gravitational wave detectors. |
gr-qc/9409062 | T. P. Singh | T. P. Singh and P. S. Joshi | The Final Fate of Spherical Inhomogeneous Dust Collapse | 23 pages; Plain Tex; TIFR-TAP preprint | Class.Quant.Grav. 13 (1996) 559-572 | 10.1088/0264-9381/13/3/019 | null | gr-qc astro-ph hep-th | null | We examine the role of the initial density and velocity distribution in the
gravitational collapse of a spherical inhomogeneous dust cloud. Such a collapse
is described by the Tolman-Bondi metric which has two free functions: the
`mass-function' and the `energy function', which are determined by the initial
density and velocity profile of the cloud. The collapse can end in a black-hole
or a naked singularity, depending on the initial parameters characterizing
these profiles. In the marginally bound case, we find that the collapse ends in
a naked singularity if the leading non-vanishing derivative of the density at
the center is either the first one or the second one. If the first two
derivatives are zero, and the third derivative non-zero, the singularity could
either be naked or covered, depending on a quantity determined by the third
derivative and the central density. If the first three derivatives are zero,
the collapse ends in a black hole. In particular, the classic result of
Oppenheimer and Snyder, that homogeneous dust collapse leads to a black hole,
is recovered as a special case. Analogous results are found when the cloud is
not marginally bound, and also for the case of a cloud starting from rest. We
also show how the strength of the naked singularity depends on the density and
velocity distribution. Our analysis generalizes and simplifies the earlier work
of Christodoulou and Newman [4,5] by dropping the assumption of evenness of
density functions. It turns out that relaxing this assumption allows for a
smooth transition from the naked singularity phase to the black-hole phase, and
also allows for the occurrence of strong curvature naked singularities.
| [
{
"created": "Fri, 30 Sep 1994 10:00:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Singh",
"T. P.",
""
],
[
"Joshi",
"P. S.",
""
]
] | We examine the role of the initial density and velocity distribution in the gravitational collapse of a spherical inhomogeneous dust cloud. Such a collapse is described by the Tolman-Bondi metric which has two free functions: the `mass-function' and the `energy function', which are determined by the initial density and velocity profile of the cloud. The collapse can end in a black-hole or a naked singularity, depending on the initial parameters characterizing these profiles. In the marginally bound case, we find that the collapse ends in a naked singularity if the leading non-vanishing derivative of the density at the center is either the first one or the second one. If the first two derivatives are zero, and the third derivative non-zero, the singularity could either be naked or covered, depending on a quantity determined by the third derivative and the central density. If the first three derivatives are zero, the collapse ends in a black hole. In particular, the classic result of Oppenheimer and Snyder, that homogeneous dust collapse leads to a black hole, is recovered as a special case. Analogous results are found when the cloud is not marginally bound, and also for the case of a cloud starting from rest. We also show how the strength of the naked singularity depends on the density and velocity distribution. Our analysis generalizes and simplifies the earlier work of Christodoulou and Newman [4,5] by dropping the assumption of evenness of density functions. It turns out that relaxing this assumption allows for a smooth transition from the naked singularity phase to the black-hole phase, and also allows for the occurrence of strong curvature naked singularities. |
1201.5999 | Chris Pankow | the LIGO Scientific Collaboration, the Virgo Collaboration: J. Abadie,
B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese,
C. Adams, R. Adhikari, C. Affeldt, M. Agathos, K. Agatsuma, P. Ajith, B.
Allen, E. Amador Ceron, D. Amariutei, S. B. Anderson, W. G. Anderson, K.
Arai, M. A. Arain, M. C. Araya, S. M. Aston, P. Astone, D. Atkinson, P.
Aufmuth, C. Aulbert, B. E. Aylott, S. Babak, P. Baker, G. Ballardin, S.
Ballmer, J. C. B. Barayoga, D. Barker, F. Barone, B. Barr, L. Barsotti, M.
Barsuglia, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, A. Basti, J.
Batch, J. Bauchrowitz, Th. S. Bauer, M. Bebronne, D. Beck, B. Behnke, M.
Bejger, M.G. Beker, A. S. Bell, A. Belletoile, I. Belopolski, M. Benacquista,
J. M. Berliner, A. Bertolini, J. Betzwieser, N. Beveridge, P. T. Beyersdorf,
I. A. Bilenko, G. Billingsley, J. Birch, R. Biswas, M. Bitossi, M. A.
Bizouard, E. Black, J. K. Blackburn, L. Blackburn, D. Blair, B. Bland, M.
Blom, O. Bock, T. P. Bodiya, C. Bogan, R. Bondarescu, F. Bondu, L. Bonelli,
R. Bonnand, R. Bork, M. Born, V. Boschi, S. Bose, L. Bosi, B. Bouhou, S.
Braccini, C. Bradaschia, P. R. Brady, V. B. Braginsky, M. Branchesi, J. E.
Brau, J. Breyer, T. Briant, D. O. Bridges, A. Brillet, M. Brinkmann, V.
Brisson, M. Britzger, A. F. Brooks, D. A. Brown, T. Bulik, H. J. Bulten, A.
Buonanno, J. Burguet-Castell, D. Buskulic, C. Buy, R. L. Byer, L. Cadonati,
G. Cagnoli, E. Calloni, J. B. Camp, P. Campsie, J. Cannizzo, K. Cannon, B.
Canuel, J. Cao, C. D. Capano, F. Carbognani, L. Carbone, S. Caride, S.
Caudill, M. Cavaglia, F. Cavalier, R. Cavalieri, G. Cella, C. Cepeda, E.
Cesarini, O. Chaibi, T. Chalermsongsak, P. Charlton, E. Chassande-Mottin, S.
Chelkowski, W. Chen, X. Chen, Y. Chen, A. Chincarini, A. Chiummo, H. Cho, J.
Chow, N. Christensen, S. S. Y. Chua, C. T. Y. Chung, S. Chung, G. Ciani, F.
Clara, D. E. Clark, J. Clark, J. H. Clayton, F. Cleva, E. Coccia, P.-F.
Cohadon, C. N. Colacino, J. Colas, A. Colla, M. Colombini, A. Conte, R.
Conte, D. Cook, T. R. Corbitt, M. Cordier, N. Cornish, A. Corsi, C. A. Costa,
M. Coughlin, J.-P. Coulon, P. Couvares, D. M. Coward, M. Cowart, D. C. Coyne,
J. D. E. Creighton, T. D. Creighton, A. M. Cruise, A. Cumming, L. Cunningham,
E. Cuoco, R. M. Cutler, K. Dahl, S. L. Danilishin, R. Dannenberg, S.
D'Antonio, K. Danzmann, V. Dattilo, B. Daudert, H. Daveloza, M. Davier, E. J.
Daw, R. Day, T. Dayanga, R. De Rosa, D. DeBra, G. Debreczeni, W. Del Pozzo,
M. del Prete, T. Dent, V. Dergachev, R. DeRosa, R. DeSalvo, S. Dhurandhar, L.
Di Fiore, A. Di Lieto, I. Di Palma, M. Di Paolo Emilio, A. Di Virgilio, M.
Diaz, A. Dietz, F. Donovan, K. L. Dooley, M. Drago, R. W. P. Drever, J. C.
Driggers, Z. Du, J.-C. Dumas, S. Dwyer, T. Eberle, M. Edgar, M. Edwards, A.
Effler, P. Ehrens, G. Endroczi, R. Engel, T. Etzel, K. Evans, M. Evans, T.
Evans, M. Factourovich, V. Fafone, S. Fairhurst, Y. Fan, B. F. Farr, D. Fazi,
H. Fehrmann, D. Feldbaum, F. Feroz, I. Ferrante, F. Fidecaro, L. S. Finn, I.
Fiori, R. P. Fisher, R. Flaminio, M. Flanigan, S. Foley, E. Forsi, L. A.
Forte, N. Fotopoulos, J.-D. Fournier, J. Franc, S. Frasca, F. Frasconi, M.
Frede, M. Frei, Z. Frei, A. Freise, R. Frey, T. T. Fricke, D. Friedrich, P.
Fritschel, V. V. Frolov, M.-K. Fujimoto, P. J. Fulda, M. Fyffe, J. Gair, M.
Galimberti, L. Gammaitoni, J. Garcia, F. Garufi, M. E. Gaspar, G. Gemme, R.
Geng, E. Genin, A. Gennai, L. A. Gergely, S. Ghosh, J. A. Giaime, S.
Giampanis, K. D. Giardina, A. Giazotto, S. Gil, C. Gill, J. Gleason, E.
Goetz, L. M. Goggin, G. Gonzalez, M. L. Gorodetsky, S. Gossler, R. Gouaty, C.
Graef, P. B. Graff, M. Granata, A. Grant, S. Gras, C. Gray, N. Gray, R. J. S.
Greenhalgh, A. M. Gretarsson, C. Greverie, R. Grosso, H. Grote, S. Grunewald,
G. M. Guidi, C. Guido, R. Gupta, E. K. Gustafson, R. Gustafson, T. Ha, J. M.
Hallam, D. Hammer, G. Hammond, J. Hanks, C. Hanna, J. Hanson, J. Harms, G. M.
Harry, I. W. Harry, E. D. Harstad, M. T. Hartman, K. Haughian, K. Hayama,
J.-F. Hayau, J. Heefner, A. Heidmann, M. C. Heintze, H. Heitmann, P. Hello,
M. A. Hendry, I. S. Heng, A. W. Heptonstall, V. Herrera, M. Hewitson, S.
Hild, D. Hoak, K. A. Hodge, K. Holt, M. Holtrop, T. Hong, S. Hooper, D. J.
Hosken, J. Hough, E. J. Howell, B. Hughey, S. Husa, S. H. Huttner, T.
Huynh-Dinh, D. R. Ingram, R. Inta, T. Isogai, A. Ivanov, K. Izumi, M.
Jacobson, E. James, Y. J. Jang, P. Jaranowski, E. Jesse, W. W. Johnson, D. I.
Jones, G. Jones, R. Jones, L. Ju, P. Kalmus, V. Kalogera, S. Kandhasamy, G.
Kang, J. B. Kanner, R. Kasturi, E. Katsavounidis, W. Katzman, H. Kaufer, K.
Kawabe, S. Kawamura, F. Kawazoe, D. Kelley, W. Kells, D. G. Keppel, Z.
Keresztes, A. Khalaidovski, F. Y. Khalili, E. A. Khazanov, B. Kim, C. Kim, H.
Kim, K. Kim, N. Kim, Y. -M. Kim, P. J. King, D. L. Kinzel, J. S. Kissel, S.
Klimenko, K. Kokeyama, V. Kondrashov, S. Koranda, W. Z. Korth, I. Kowalska,
D. Kozak, O. Kranz, V. Kringel, S. Krishnamurthy, B. Krishnan, A. Krolak, G.
Kuehn, R. Kumar, P. Kwee, P. K. Lam, M. Landry, B. Lantz, N. Lastzka, C.
Lawrie, A. Lazzarini, P. Leaci, C. H. Lee, H. K. Lee, H. M. Lee, J. R. Leong,
I. Leonor, N. Leroy, N. Letendre, J. Li, T. G. F. Li, N. Liguori, P. E.
Lindquist, Y. Liu, Z. Liu, N. A. Lockerbie, D. Lodhia, M. Lorenzini, V.
Loriette, M. Lormand, G. Losurdo, J. Lough, J. Luan, M. Lubinski, H. Luck, A.
P. Lundgren, E. Macdonald, B. Machenschalk, M. MacInnis, D. M. Macleod, M.
Mageswaran, K. Mailand, E. Majorana, I. Maksimovic, N. Man, I. Mandel, V.
Mandic, M. Mantovani, A. Marandi, F. Marchesoni, F. Marion, S. Marka, Z.
Marka, A. Markosyan, E. Maros, J. Marque, F. Martelli, I. W. Martin, R. M.
Martin, J. N. Marx, K. Mason, A. Masserot, F. Matichard, L. Matone, R. A.
Matzner, N. Mavalvala, G. Mazzolo, R. McCarthy, D. E. McClelland, S. C.
McGuire, G. McIntyre, J. McIver, D. J. A. McKechan, S. McWilliams, G. D.
Meadors, M. Mehmet, T. Meier, A. Melatos, A. C. Melissinos, G. Mendell, R. A.
Mercer, S. Meshkov, C. Messenger, M. S. Meyer, C. Michel, L. Milano, J.
Miller, Y. Minenkov, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, O.
Miyakawa, B. Moe, M. Mohan, S. D. Mohanty, S. R. P. Mohapatra, D. Moraru, G.
Moreno, N. Morgado, A. Morgia, T. Mori, S. R. Morriss, S. Mosca, K. Mossavi,
B. Mours, C. M. Mow-Lowry, C. L. Mueller, G. Mueller, S. Mukherjee, A.
Mullavey, H. Muller-Ebhardt, J. Munch, D. Murphy, P. G. Murray, A. Mytidis,
T. Nash, L. Naticchioni, V. Necula, J. Nelson, G. Newton, T. Nguyen, A.
Nishizawa, A. Nitz, F. Nocera, D. Nolting, M. E. Normandin, L. Nuttall, E.
Ochsner, J. O'Dell, E. Oelker, G. H. Ogin, J. J. Oh, S. H. Oh, B. O'Reilly,
R. O'Shaughnessy, C. Osthelder, C. D. Ott, D. J. Ottaway, R. S. Ottens, H.
Overmier, B. J. Owen, A. Page, G. Pagliaroli, L. Palladino, C. Palomba, Y.
Pan, C. Pankow, F. Paoletti, M. A. Papa, M. Parisi, A. Pasqualetti, R.
Passaquieti, D. Passuello, P. Patel, M. Pedraza, P. Peiris, L. Pekowsky, S.
Penn, A. Perreca, G. Persichetti, M. Phelps, M. Pickenpack, F. Piergiovanni,
M. Pietka, L. Pinard, I. M. Pinto, M. Pitkin, H. J. Pletsch, M. V. Plissi, R.
Poggiani, J. Pold, F. Postiglione, M. Prato, V. Predoi, T. Prestegard, L. R.
Price, M. Prijatelj, M. Principe, S. Privitera, R. Prix, G. A. Prodi, L. G.
Prokhorov, O. Puncken, M. Punturo, P. Puppo, V. Quetschke, R. Quitzow-James,
F. J. Raab, D. S. Rabeling, I. Racz, H. Radkins, P. Raffai, M. Rakhmanov, B.
Rankins, P. Rapagnani, V. Raymond, V. Re, K. Redwine, C. M. Reed, T. Reed, T.
Regimbau, S. Reid, D. H. Reitze, F. Ricci, R. Riesen, K. Riles, N. A.
Robertson, F. Robinet, C. Robinson, E. L. Robinson, A. Rocchi, S. Roddy, C.
Rodriguez, M. Rodruck, L. Rolland, J. G. Rollins, J. D. Romano, R. Romano, J.
H. Romie, D. Rosinska, C. Rover, S. Rowan, A. Rudiger, P. Ruggi, K. Ryan, P.
Sainathan, F. Salemi, L. Sammut, V. Sandberg, V. Sannibale, L. Santamaria, I.
Santiago-Prieto, G. Santostasi, B. Sassolas, B. S. Sathyaprakash, S. Sato, P.
R. Saulson, R. L. Savage, R. Schilling, R. Schnabel, R. M. S. Schofield, E.
Schreiber, B. Schulz, B. F. Schutz, P. Schwinberg, J. Scott, S. M. Scott, F.
Seifert, D. Sellers, D. Sentenac, A. Sergeev, D. A. Shaddock, M. Shaltev, B.
Shapiro, P. Shawhan, D. H. Shoemaker, A. Sibley, X. Siemens, D. Sigg, A.
Singer, L. Singer, A. M. Sintes, G. R. Skelton, B. J. J. Slagmolen, J.
Slutsky, J. R. Smith, M. R. Smith, R. J. E. Smith, N. D. Smith-Lefebvre, K.
Somiya, B. Sorazu, J. Soto, F. C. Speirits, L. Sperandio, M. Stefszky, A. J.
Stein, L. C. Stein, E. Steinert, J. Steinlechner, S. Steinlechner, S.
Steplewski, A. Stochino, R. Stone, K. A. Strain, S. E. Strigin, A. S.
Stroeer, R. Sturani, A. L. Stuver, T. Z. Summerscales, M. Sung, S. Susmithan,
P. J. Sutton, B. Swinkels, M. Tacca, L. Taffarello, D. Talukder, D. B.
Tanner, S. P. Tarabrin, J. R. Taylor, R. Taylor, P. Thomas, K. A. Thorne, K.
S. Thorne, E. Thrane, A. Thuring, K. V. Tokmakov, C. Tomlinson, A. Toncelli,
M. Tonelli, O. Torre, C. Torres, C. I. Torrie, E. Tournefier, F. Travasso, G.
Traylor, K. Tseng, D. Ugolini, H. Vahlbruch, G. Vajente, J. F. J. van den
Brand, C. Van Den Broeck, S. van der Putten, A. A. van Veggel, S. Vass, M.
Vasuth, R. Vaulin, M. Vavoulidis, A. Vecchio, G. Vedovato, J. Veitch, P. J.
Veitch, C. Veltkamp, D. Verkindt, F. Vetrano, A. Vicere, A. E. Villar, J.-Y.
Vinet, S. Vitale, S. Vitale, H. Vocca, C. Vorvick, S. P. Vyatchanin, A. Wade,
L. Wade, M. Wade, S. J. Waldman, L. Wallace, Y. Wan, M. Wang, X. Wang, Z.
Wang, A. Wanner, R. L. Ward, M. Was, M. Weinert, A. J. Weinstein, R. Weiss,
L. Wen, P. Wessels, M. West, T. Westphal, K. Wette, J. T. Whelan, S. E.
Whitcomb, D. J. White, B. F. Whiting, C. Wilkinson, P. A. Willems, L.
Williams, R. Williams, B. Willke, L. Winkelmann, W. Winkler, C. C. Wipf, A.
G. Wiseman, H. Wittel, G. Woan, R. Wooley, J. Worden, I. Yakushin, H.
Yamamoto, K. Yamamoto, K. Yamamoto, C. C. Yancey, H. Yang, D. Yeaton-Massey,
S. Yoshida, P. Yu, M. Yvert, A. Zadrozny, M. Zanolin, J.-P. Zendri, F. Zhang,
L. Zhang, W. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig | Search for Gravitational Waves from Intermediate Mass Binary Black Holes | 13 pages, 4 figures: data for plots and archived public version at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=62326, see also the
public announcement at http://www.ligo.org/science/Publication-S5IMBH/ | null | 10.1103/PhysRevD.85.102004 | P1100068 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the results of a weakly modeled burst search for gravitational
waves from mergers of non-spinning intermediate mass black holes (IMBH) in the
total mass range 100--450 solar masses and with the component mass ratios
between 1:1 and 4:1. The search was conducted on data collected by the LIGO and
Virgo detectors between November of 2005 and October of 2007. No plausible
signals were observed by the search which constrains the astrophysical rates of
the IMBH mergers as a function of the component masses. In the most efficiently
detected bin centered on 88+88 solar masses, for non-spinning sources, the rate
density upper limit is 0.13 per Mpc^3 per Myr at the 90% confidence level.
| [
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{
"created": "Thu, 2 Feb 2012 00:43:18 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Apr 2012 20:08:50 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"the LIGO Scientific Collaboration",
"",
""
],
[
"the Virgo Collaboration",
"",
""
],
[
"Abadie",
"J.",
""
],
[
"Abbott",
"B. P.",
""
],
[
"Abbott",
"R.",
""
],
[
"Abbott",
"T. D.",
""
],
[
"Abernathy",
"M.",
""
],
[
"Accadia",
"T.",
""
],
[
"Acernese",
"F.",
""
],
[
"Adams",
"C.",
""
],
[
"Adhikari",
"R.",
""
],
[
"Affeldt",
"C.",
""
],
[
"Agathos",
"M.",
""
],
[
"Agatsuma",
"K.",
""
],
[
"Ajith",
"P.",
""
],
[
"Allen",
"B.",
""
],
[
"Ceron",
"E. Amador",
""
],
[
"Amariutei",
"D.",
""
],
[
"Anderson",
"S. B.",
""
],
[
"Anderson",
"W. G.",
""
],
[
"Arai",
"K.",
""
],
[
"Arain",
"M. A.",
""
],
[
"Araya",
"M. C.",
""
],
[
"Aston",
"S. M.",
""
],
[
"Astone",
"P.",
""
],
[
"Atkinson",
"D.",
""
],
[
"Aufmuth",
"P.",
""
],
[
"Aulbert",
"C.",
""
],
[
"Aylott",
"B. E.",
""
],
[
"Babak",
"S.",
""
],
[
"Baker",
"P.",
""
],
[
"Ballardin",
"G.",
""
],
[
"Ballmer",
"S.",
""
],
[
"Barayoga",
"J. C. B.",
""
],
[
"Barker",
"D.",
""
],
[
"Barone",
"F.",
""
],
[
"Barr",
"B.",
""
],
[
"Barsotti",
"L.",
""
],
[
"Barsuglia",
"M.",
""
],
[
"Barton",
"M. A.",
""
],
[
"Bartos",
"I.",
""
],
[
"Bassiri",
"R.",
""
],
[
"Bastarrika",
"M.",
""
],
[
"Basti",
"A.",
""
],
[
"Batch",
"J.",
""
],
[
"Bauchrowitz",
"J.",
""
],
[
"Bauer",
"Th. S.",
""
],
[
"Bebronne",
"M.",
""
],
[
"Beck",
"D.",
""
],
[
"Behnke",
"B.",
""
],
[
"Bejger",
"M.",
""
],
[
"Beker",
"M. G.",
""
],
[
"Bell",
"A. S.",
""
],
[
"Belletoile",
"A.",
""
],
[
"Belopolski",
"I.",
""
],
[
"Benacquista",
"M.",
""
],
[
"Berliner",
"J. M.",
""
],
[
"Bertolini",
"A.",
""
],
[
"Betzwieser",
"J.",
""
],
[
"Beveridge",
"N.",
""
],
[
"Beyersdorf",
"P. T.",
""
],
[
"Bilenko",
"I. A.",
""
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] | We present the results of a weakly modeled burst search for gravitational waves from mergers of non-spinning intermediate mass black holes (IMBH) in the total mass range 100--450 solar masses and with the component mass ratios between 1:1 and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the IMBH mergers as a function of the component masses. In the most efficiently detected bin centered on 88+88 solar masses, for non-spinning sources, the rate density upper limit is 0.13 per Mpc^3 per Myr at the 90% confidence level. |
1502.01003 | Daniel Guariento | Alan M. da Silva, Daniel C. Guariento, C. Molina | Cosmological black holes and white holes with time-dependent mass | 12 pages, 5 figures | Phys. Rev. D 91, 084043 (2015) | 10.1103/PhysRevD.91.084043 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the causal structure of generalized uncharged McVittie spacetimes
with increasing central mass $m (t)$ and positive Hubble factor $H (t)$. Under
physically reasonable conditions, namely, a big bang singularity in the past, a
positive cosmological constant and an upper limit to the central mass, we prove
that the patch of the spacetime described by the cosmological time and areal
radius coordinates is always geodesically incomplete, which implies the
presence of event horizons in the spacetime. We also show that, depending on
the asymptotic behavior of the $m$ and $H$ functions, the generalized McVittie
spacetime can have a single black hole, a black-hole/white-hole pair or,
differently from classic fixed-mass McVittie, a single white hole. A simple
criterion is given to distinguish the different causal structures.
| [
{
"created": "Tue, 3 Feb 2015 20:39:53 GMT",
"version": "v1"
}
] | 2015-04-29 | [
[
"da Silva",
"Alan M.",
""
],
[
"Guariento",
"Daniel C.",
""
],
[
"Molina",
"C.",
""
]
] | We consider the causal structure of generalized uncharged McVittie spacetimes with increasing central mass $m (t)$ and positive Hubble factor $H (t)$. Under physically reasonable conditions, namely, a big bang singularity in the past, a positive cosmological constant and an upper limit to the central mass, we prove that the patch of the spacetime described by the cosmological time and areal radius coordinates is always geodesically incomplete, which implies the presence of event horizons in the spacetime. We also show that, depending on the asymptotic behavior of the $m$ and $H$ functions, the generalized McVittie spacetime can have a single black hole, a black-hole/white-hole pair or, differently from classic fixed-mass McVittie, a single white hole. A simple criterion is given to distinguish the different causal structures. |
gr-qc/9303022 | Jason Twamley | J. Twamley | Inconsistency between alternative approaches to Quantum Decoherence in
special systems | 10 pages | null | null | null | gr-qc | null | We study the decoherence properties of a certain class of Markovian quantum
open systems from both the Decohering Histories and Environment Induced
Superselection paradigms. The class studied includes many familiar quantum
optical cases. For this class, we show that there always exists a basis which
leads to {\em exactly} consistent histories for any coarse graining {\em
irrespective} of the initial conditions. The magnitude of the off--diagonal
elements of the reduced density matrix $\rho$ in this basis however, depends on
the initial conditions. Necessary requirements for classicality as advanced by
the two paradigms are thus in direct conflict in these systems.
| [
{
"created": "Fri, 19 Mar 1993 19:54:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Twamley",
"J.",
""
]
] | We study the decoherence properties of a certain class of Markovian quantum open systems from both the Decohering Histories and Environment Induced Superselection paradigms. The class studied includes many familiar quantum optical cases. For this class, we show that there always exists a basis which leads to {\em exactly} consistent histories for any coarse graining {\em irrespective} of the initial conditions. The magnitude of the off--diagonal elements of the reduced density matrix $\rho$ in this basis however, depends on the initial conditions. Necessary requirements for classicality as advanced by the two paradigms are thus in direct conflict in these systems. |
2312.10792 | Giorgio Mentasti | Giorgio Mentasti and Carlo R. Contaldi and Marco Peloso | Probing the galactic and extragalactic gravitational wave backgrounds
with space-based interferometers | null | null | null | null | gr-qc astro-ph.CO astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | We employ the formalism developed in \cite{Mentasti:2023gmg} and
\cite{Bartolo_2022} to study the prospect of detecting an anisotropic
Stochastic Gravitational Wave Background (SGWB) with the Laser Interferometer
Space Antenna (LISA) alone, and combined with the proposed space-based
interferometer Taiji. Previous analyses have been performed in the frequency
domain only. Here, we study the detectability of the individual coefficients of
the expansion of the SGWB in spherical harmonics, by taking into account the
specific motion of the satellites. This requires the use of time-dependent
response functions, which we include in our analysis to obtain an optimal
estimate of the anisotropic signal. We focus on two applications. Firstly, the
reconstruction of the anisotropic galactic signal without assuming any prior
knowledge of its spatial distribution. We find that both LISA and LISA with
Taiji cannot put tight constraints on the harmonic coefficients for realistic
models of the galactic SGWB. We then focus on the discrimination between a
galactic signal of known morphology but unknown overall amplitude and an
isotropic extragalactic SGWB component of astrophysical origin. In this case,
we find that the two surveys can confirm, at a confidence level $\gtrsim
3\sigma$, the existence of both the galactic and extragalactic background if
both have amplitudes as predicted in standard models. We also find that, in the
LISA-only case, the analysis in the frequency domain (under the assumption of a
time average of data taken homogeneously across the year) provides a nearly
identical determination of the two amplitudes as compared to the optimal
analysis.
| [
{
"created": "Sun, 17 Dec 2023 18:40:48 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Feb 2024 23:58:42 GMT",
"version": "v2"
}
] | 2024-02-13 | [
[
"Mentasti",
"Giorgio",
""
],
[
"Contaldi",
"Carlo R.",
""
],
[
"Peloso",
"Marco",
""
]
] | We employ the formalism developed in \cite{Mentasti:2023gmg} and \cite{Bartolo_2022} to study the prospect of detecting an anisotropic Stochastic Gravitational Wave Background (SGWB) with the Laser Interferometer Space Antenna (LISA) alone, and combined with the proposed space-based interferometer Taiji. Previous analyses have been performed in the frequency domain only. Here, we study the detectability of the individual coefficients of the expansion of the SGWB in spherical harmonics, by taking into account the specific motion of the satellites. This requires the use of time-dependent response functions, which we include in our analysis to obtain an optimal estimate of the anisotropic signal. We focus on two applications. Firstly, the reconstruction of the anisotropic galactic signal without assuming any prior knowledge of its spatial distribution. We find that both LISA and LISA with Taiji cannot put tight constraints on the harmonic coefficients for realistic models of the galactic SGWB. We then focus on the discrimination between a galactic signal of known morphology but unknown overall amplitude and an isotropic extragalactic SGWB component of astrophysical origin. In this case, we find that the two surveys can confirm, at a confidence level $\gtrsim 3\sigma$, the existence of both the galactic and extragalactic background if both have amplitudes as predicted in standard models. We also find that, in the LISA-only case, the analysis in the frequency domain (under the assumption of a time average of data taken homogeneously across the year) provides a nearly identical determination of the two amplitudes as compared to the optimal analysis. |
0802.4374 | Sini R | Sini R, Nijo Varghese and V C Kuriakose | Absorption cross section of RN and SdS extremal black hole | 11 pages, Preprint to IJMPA | Int.J.Mod.Phys.A23:4011-4021,2008 | 10.1142/S0217751X0804158X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nature of scalar wave functions near the horizon of Reissner Nordstrom
(RN) extremal and Schwarzschild-de Sitter (SdS) extremal black holes are found
using WKB approximation and the effect of reflection of waves from the horizon.
The absorption cross section $\sigma_{abs}$ when RN extremal and SdS extremal
black holes placed in a Klein-Gordon field is calculated.
| [
{
"created": "Fri, 29 Feb 2008 12:17:39 GMT",
"version": "v1"
}
] | 2009-02-16 | [
[
"R",
"Sini",
""
],
[
"Varghese",
"Nijo",
""
],
[
"Kuriakose",
"V C",
""
]
] | The nature of scalar wave functions near the horizon of Reissner Nordstrom (RN) extremal and Schwarzschild-de Sitter (SdS) extremal black holes are found using WKB approximation and the effect of reflection of waves from the horizon. The absorption cross section $\sigma_{abs}$ when RN extremal and SdS extremal black holes placed in a Klein-Gordon field is calculated. |
1602.03329 | Jibitesh Dutta | Jibitesh Dutta, Wompherdeiki Khyllep and Erickson Syiemlieh | Late time accelerated scaling attractors in DGP
(Dvali-Gabadadze-Porrati) braneworld | 18 pages, 28 figs. Comments wellcome | Eur. Phys. J. Plus (2016) 131: 33 | 10.1140/epjp/i2016-16033-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the evolution of late universe, the main source of matter are Dark energy
and Dark matter. They are indirectly detected only through their gravitational
manifestations. So the possibility of interaction with each other without
violating observational restrictions is not ruled out. With this motivation, we
investigate the dynamics of DGP braneworld where source of dark energy is a
scalar field and it interacts with matter source. Since observation favours
phantom case more, we have also studied the dynamics of interacting phantom
scalar field. In non interacting DGP braneworld there are no late time
accelerated scaling attractors and hence cannot alleviate Coincidence problem.
In this paper, we shall show that it is possible to get late time accelerated
scaling solutions. The phase space is studied by taking two categories of
potentials (Exponential and Non exponential functions). The stability of
critical points are examined by taking two specific interactions. The first
interaction gives late time accelerated scaling solution for phantom field only
under exponential potential, while for second interaction we do not get any
scaling solution. Furthermore, we have shown that this scaling solution is also
classically stable.
| [
{
"created": "Wed, 10 Feb 2016 11:07:22 GMT",
"version": "v1"
}
] | 2016-02-23 | [
[
"Dutta",
"Jibitesh",
""
],
[
"Khyllep",
"Wompherdeiki",
""
],
[
"Syiemlieh",
"Erickson",
""
]
] | In the evolution of late universe, the main source of matter are Dark energy and Dark matter. They are indirectly detected only through their gravitational manifestations. So the possibility of interaction with each other without violating observational restrictions is not ruled out. With this motivation, we investigate the dynamics of DGP braneworld where source of dark energy is a scalar field and it interacts with matter source. Since observation favours phantom case more, we have also studied the dynamics of interacting phantom scalar field. In non interacting DGP braneworld there are no late time accelerated scaling attractors and hence cannot alleviate Coincidence problem. In this paper, we shall show that it is possible to get late time accelerated scaling solutions. The phase space is studied by taking two categories of potentials (Exponential and Non exponential functions). The stability of critical points are examined by taking two specific interactions. The first interaction gives late time accelerated scaling solution for phantom field only under exponential potential, while for second interaction we do not get any scaling solution. Furthermore, we have shown that this scaling solution is also classically stable. |
0810.1978 | Simone Speziale | Simone Speziale | Background-free propagation in loop quantum gravity | Invited contribution to a special issue of Advanced Science Letters
edited by Martin Bojowald. 14 pages. v2 minor corrections | null | null | pi-qg-98 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review the definition of n-point functions in loop quantum gravity,
discussing what has been done and what are the main open issues. Particular
attention is dedicated to gauge aspects and renormalization.
| [
{
"created": "Fri, 10 Oct 2008 22:41:43 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2008 13:42:32 GMT",
"version": "v2"
}
] | 2008-11-20 | [
[
"Speziale",
"Simone",
""
]
] | I review the definition of n-point functions in loop quantum gravity, discussing what has been done and what are the main open issues. Particular attention is dedicated to gauge aspects and renormalization. |
2006.11575 | S. N Sajadi | S. H. Hendi, S. N. Sajadi, Maryam. Khademi | Physical Properties of a Regular Rotating Black Hole: Thermodynamics,
Stability, Quasinormal Modes | 19 pages, 14 figures | Phys. Rev. D 103, 064016 (2021) | 10.1103/PhysRevD.103.064016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Respecting the angular momentum conservation of torque-free systems, it is
natural to consider rotating solutions of massive objects. Besides that,
motivated by the realistic astrophysical black holes that rotate, we use the
Newman-Janis formalism to construct a regular rotating black hole. We start
with a nonlinearly charged regular static black hole in the framework of the
standard general relativity and then obtain the associated rotating solution
through such a formalism. We investigate the geometrical properties of the
metric by studying the boundary of ergosphere. We also analyze thermodynamic
properties of the solution in AdS spacetime and examine thermal stability and
possible phase transition. In addition, we perturb the black hole by using of a
real massless scalar field as a probe to investigate its dynamic stability. We
obtain an analytic expression for the real and imaginary parts of the
quasinormal frequencies. Finally, we look for a connection between the
quasinormal frequencies and the properties of the photon sphere in the eikonal
limit.
| [
{
"created": "Sat, 20 Jun 2020 13:50:37 GMT",
"version": "v1"
}
] | 2021-03-17 | [
[
"Hendi",
"S. H.",
""
],
[
"Sajadi",
"S. N.",
""
],
[
"Khademi",
"Maryam.",
""
]
] | Respecting the angular momentum conservation of torque-free systems, it is natural to consider rotating solutions of massive objects. Besides that, motivated by the realistic astrophysical black holes that rotate, we use the Newman-Janis formalism to construct a regular rotating black hole. We start with a nonlinearly charged regular static black hole in the framework of the standard general relativity and then obtain the associated rotating solution through such a formalism. We investigate the geometrical properties of the metric by studying the boundary of ergosphere. We also analyze thermodynamic properties of the solution in AdS spacetime and examine thermal stability and possible phase transition. In addition, we perturb the black hole by using of a real massless scalar field as a probe to investigate its dynamic stability. We obtain an analytic expression for the real and imaginary parts of the quasinormal frequencies. Finally, we look for a connection between the quasinormal frequencies and the properties of the photon sphere in the eikonal limit. |
1004.5052 | Alvaro De La Cruz-Dombriz | A. de la Cruz-Dombriz | Some cosmological and astrophysical aspects of modified gravity theories | PhD. thesis, April 2010, Complutense University of Madrid. 129 pages.
Preface, five chapters and conclusions. Two appendices | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis will try to contribute to the understanding of open issues in
cosmology by considering f(R) and brane-world theories. In Chapter 1, we shall
summarize the main features of f(R) gravities in the metric formalism and we
shall introduce both the notion of brane excitations, the branons, and the
brane-skyrmions. We shall finish the chapter by providing some insight about
the possibility of mini black holes detection in the LHC as a signature for the
validity of these modified gravity theories.
The Chapter 2 will deal with f(R) theories able to mimic Einstein-Hilbert
plus cosmological constant solutions and f(R) theories will be shown to be able
to mimic the cosmological evolution generated by any perfect fluid with
constant equation of state.
The Chapter 3 will be devoted to the computation of cosmological
perturbations for f(R) theories. Special attention will be paid here to obtain
a completely general differential equation for the evolution of perturbations
and its particularization for the so-called sub-Hubble scales will be
explicitly shown.
In the Chapter 4 we shall focus on the study of black holes in f(R) gravities
in an arbitrary number of dimensions. With this purpose we shall study constant
curvature solutions for f(R) theories as well as perturbative solutions around
the standard SAdS geometry. An important part of this chapter will be then
devoted to the thermodynamics of SAdS black holes in f(R) theories.
In the Chapter 5 we will thoroughly study brane-skyrmions. In this context,
the recent claim of detection of an unexpected feature in the CMB, referred to
as the cold spot, will be explained as a topological defect on the brane in
complete agreement with those calculations in the literature that tried to
explain that cold spot as a texture of a NLSM.
Main conclusions are summarized all together in Chapter 6 .
| [
{
"created": "Wed, 28 Apr 2010 14:59:46 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Apr 2010 15:41:12 GMT",
"version": "v2"
},
{
"created": "Wed, 5 May 2010 09:32:06 GMT",
"version": "v3"
}
] | 2010-05-06 | [
[
"de la Cruz-Dombriz",
"A.",
""
]
] | This thesis will try to contribute to the understanding of open issues in cosmology by considering f(R) and brane-world theories. In Chapter 1, we shall summarize the main features of f(R) gravities in the metric formalism and we shall introduce both the notion of brane excitations, the branons, and the brane-skyrmions. We shall finish the chapter by providing some insight about the possibility of mini black holes detection in the LHC as a signature for the validity of these modified gravity theories. The Chapter 2 will deal with f(R) theories able to mimic Einstein-Hilbert plus cosmological constant solutions and f(R) theories will be shown to be able to mimic the cosmological evolution generated by any perfect fluid with constant equation of state. The Chapter 3 will be devoted to the computation of cosmological perturbations for f(R) theories. Special attention will be paid here to obtain a completely general differential equation for the evolution of perturbations and its particularization for the so-called sub-Hubble scales will be explicitly shown. In the Chapter 4 we shall focus on the study of black holes in f(R) gravities in an arbitrary number of dimensions. With this purpose we shall study constant curvature solutions for f(R) theories as well as perturbative solutions around the standard SAdS geometry. An important part of this chapter will be then devoted to the thermodynamics of SAdS black holes in f(R) theories. In the Chapter 5 we will thoroughly study brane-skyrmions. In this context, the recent claim of detection of an unexpected feature in the CMB, referred to as the cold spot, will be explained as a topological defect on the brane in complete agreement with those calculations in the literature that tried to explain that cold spot as a texture of a NLSM. Main conclusions are summarized all together in Chapter 6 . |
gr-qc/9903092 | Diego A. R. Dalvit | Diego A. R. Dalvit and Francisco D. Mazzitelli | Quantum corrections to the geodesic equation | Revtex file, 6 pages, no figures. Talk presented at the meeting
"Trends in Theoretical Physics II", Buenos Aires, Argentina, December 1998 | null | 10.1063/1.59666 | null | gr-qc | null | In this talk we will argue that, when gravitons are taken into account, the
solution to the semiclassical Einstein equations (SEE) is not physical. The
reason is simple: any classical device used to measure the spacetime geometry
will also feel the graviton fluctuations. As the coupling between the classical
device and the metric is non linear, the device will not measure the
`background geometry' (i.e. the geometry that solves the SEE). As a particular
example we will show that a classical particle does not follow a geodesic of
the background metric. Instead its motion is determined by a quantum corrected
geodesic equation that takes into account its coupling to the gravitons. This
analysis will also lead us to find a solution to the so-called gauge fixing
problem: the quantum corrected geodesic equation is explicitly independent of
any gauge fixing parameter.
| [
{
"created": "Thu, 25 Mar 1999 18:52:46 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dalvit",
"Diego A. R.",
""
],
[
"Mazzitelli",
"Francisco D.",
""
]
] | In this talk we will argue that, when gravitons are taken into account, the solution to the semiclassical Einstein equations (SEE) is not physical. The reason is simple: any classical device used to measure the spacetime geometry will also feel the graviton fluctuations. As the coupling between the classical device and the metric is non linear, the device will not measure the `background geometry' (i.e. the geometry that solves the SEE). As a particular example we will show that a classical particle does not follow a geodesic of the background metric. Instead its motion is determined by a quantum corrected geodesic equation that takes into account its coupling to the gravitons. This analysis will also lead us to find a solution to the so-called gauge fixing problem: the quantum corrected geodesic equation is explicitly independent of any gauge fixing parameter. |
1711.08845 | Mehdi Saravani | A. Emir Gumrukcuoglu, Mehdi Saravani and Thomas P. Sotiriou | Ho\v{r}ava Gravity after GW170817 | null | Phys. Rev. D 97, 024032 (2018) | 10.1103/PhysRevD.97.024032 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detection of gravitational wave GW170817 has placed a severe bound
on the deviation of the speed of gravitational waves from the speed of light.
We explore the consequences of this detection for Horava gravity.
| [
{
"created": "Fri, 24 Nov 2017 00:35:41 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2018 11:15:23 GMT",
"version": "v2"
}
] | 2018-02-12 | [
[
"Gumrukcuoglu",
"A. Emir",
""
],
[
"Saravani",
"Mehdi",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | The recent detection of gravitational wave GW170817 has placed a severe bound on the deviation of the speed of gravitational waves from the speed of light. We explore the consequences of this detection for Horava gravity. |
gr-qc/0411057 | Raoul-Martin Memmesheimer | Raoul-Martin Memmesheimer, Gerhard Sch\"afer | Third post-Newtonian constrained canonical dynamics for binary point
masses in harmonic coordinates | 42 pages, submitted to Phys. Rev. D | Phys.Rev.D71:044021,2005 | 10.1103/PhysRevD.71.044021 | null | gr-qc | null | The conservative dynamics of two point masses given in harmonic coordinates
up to the third post-Newtonian (3pN) order is treated within the framework of
constrained canonical dynamics. A representation of the approximate Poincar\'e
algebra is constructed with the aid of Dirac brackets. Uniqueness of the
generators of the Poincar\'e group resp. the integrals of motion is achieved by
imposing their action on the point mass coordinates to be identical with that
of the usual infinitesimal Poincar\'e transformations. The second
post-Coulombian approximation to the dynamics of two point charges as predicted
by Feynman-Wheeler electrodynamics in Lorentz gauge is treated similarly.
| [
{
"created": "Thu, 11 Nov 2004 16:50:05 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Memmesheimer",
"Raoul-Martin",
""
],
[
"Schäfer",
"Gerhard",
""
]
] | The conservative dynamics of two point masses given in harmonic coordinates up to the third post-Newtonian (3pN) order is treated within the framework of constrained canonical dynamics. A representation of the approximate Poincar\'e algebra is constructed with the aid of Dirac brackets. Uniqueness of the generators of the Poincar\'e group resp. the integrals of motion is achieved by imposing their action on the point mass coordinates to be identical with that of the usual infinitesimal Poincar\'e transformations. The second post-Coulombian approximation to the dynamics of two point charges as predicted by Feynman-Wheeler electrodynamics in Lorentz gauge is treated similarly. |
gr-qc/0008033 | Claus Laemmerzahl | Christian J. Bord\'e, Jean-Claude Houard, and Alain Karasiewicz | Relativistic phase shifts for Dirac particles interacting with weak
gravitational fields in matter-wave interferometers | 32 pages, LaTex, needs rotating and lscape usepackages, to appear in
C. L\"ammerzahl, C.W.F. Everitt, F.W. Hehl (eds.): ``Gyros, Clocks, and
Interferometers: Testing Relativistic Gravity in Space'', Springer-Verlag,
Berlin 2000 | Lect.Notes Phys. 562 (2001) 403-438 | 10.1007/3-540-40988-2_21 | null | gr-qc quant-ph | null | We present a second-quantized field theory of massive spin one-half particles
or antiparticles in the presence of a weak gravitational field treated as a
spin two external field in a flat Minkowski background. We solve the
difficulties which arise from the derivative coupling and we are able to
introduce an interaction picture. We derive expressions for the scattering
amplitude and for the outgoing spinor to first-order. In several appendices,
the link with the canonical approach in General Relativity is established and a
generalized stationary phase method is used to calculate the outgoing spinor.
We show how our expressions can be used to calculate and discuss phase shifts
in the context of matter-wave interferometry (especially atom or antiatom
interferometry). In this way, many effects are introduced in a unified
relativistic framework, including spin-gravitation terms: gravitational red
shift, Thomas precession, Sagnac effect, spin-rotation effect, orbital and spin
Lense-Thirring effects, de Sitter geodetic precession and finally the effect of
gravitational waves. A new analogy with the electromagnetic interaction is
pointed out.
| [
{
"created": "Tue, 15 Aug 2000 09:50:11 GMT",
"version": "v1"
}
] | 2016-12-07 | [
[
"Bordé",
"Christian J.",
""
],
[
"Houard",
"Jean-Claude",
""
],
[
"Karasiewicz",
"Alain",
""
]
] | We present a second-quantized field theory of massive spin one-half particles or antiparticles in the presence of a weak gravitational field treated as a spin two external field in a flat Minkowski background. We solve the difficulties which arise from the derivative coupling and we are able to introduce an interaction picture. We derive expressions for the scattering amplitude and for the outgoing spinor to first-order. In several appendices, the link with the canonical approach in General Relativity is established and a generalized stationary phase method is used to calculate the outgoing spinor. We show how our expressions can be used to calculate and discuss phase shifts in the context of matter-wave interferometry (especially atom or antiatom interferometry). In this way, many effects are introduced in a unified relativistic framework, including spin-gravitation terms: gravitational red shift, Thomas precession, Sagnac effect, spin-rotation effect, orbital and spin Lense-Thirring effects, de Sitter geodetic precession and finally the effect of gravitational waves. A new analogy with the electromagnetic interaction is pointed out. |
1309.7428 | S. Davood Sadatian | S. Davood Sadatian | Rip Singularity Scenario and Bouncing Universe in a Chaplygin Gas Dark
Energy Model | 13 pages, 7 figures, Accepted for Publication in IJTP | Int J Theor Phys, 53: pp 675-684 (2014) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We choose a modified Chaplygin Gas Dark energy model for considering some its
cosmological behaviors. In this regards, we study different Rip singularity
scenarios and bouncing model of the universe in context of this model. We show
that by using suitable parameters can explain some cosmological aspects of the
model.
| [
{
"created": "Sat, 28 Sep 2013 05:29:28 GMT",
"version": "v1"
}
] | 2014-01-21 | [
[
"Sadatian",
"S. Davood",
""
]
] | We choose a modified Chaplygin Gas Dark energy model for considering some its cosmological behaviors. In this regards, we study different Rip singularity scenarios and bouncing model of the universe in context of this model. We show that by using suitable parameters can explain some cosmological aspects of the model. |
gr-qc/9407012 | Tevian Dray | Stuart Boersma and Tevian Dray | Parametric Manifolds II: Intrinsic Approach | Plain TeX, 13 pages, no figures | J.Math.Phys. 36 (1995) 1394-1403 | 10.1063/1.531128 | null | gr-qc dg-ga math.DG | null | A parametric manifold is a manifold on which all tensor fields depend on an
additional parameter, such as time, together with a parametric structure,
namely a given (parametric) 1-form field. Such a manifold admits natural
generalizations of Lie differentiation, exterior differentiation, and covariant
differentiation, all based on a nonstandard action of vector fields on
functions. There is a new geometric object, called the deficiency, which
behaves much like torsion, and which measures whether a parametric manifold can
be viewed as a 1-parameter family of orthogonal hypersurfaces.
| [
{
"created": "Tue, 12 Jul 1994 21:38:12 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Boersma",
"Stuart",
""
],
[
"Dray",
"Tevian",
""
]
] | A parametric manifold is a manifold on which all tensor fields depend on an additional parameter, such as time, together with a parametric structure, namely a given (parametric) 1-form field. Such a manifold admits natural generalizations of Lie differentiation, exterior differentiation, and covariant differentiation, all based on a nonstandard action of vector fields on functions. There is a new geometric object, called the deficiency, which behaves much like torsion, and which measures whether a parametric manifold can be viewed as a 1-parameter family of orthogonal hypersurfaces. |
0905.2001 | L. C. Garcia de Andrade | Garcia de Andrade | Cosmic dynamo analogue and decay of magnetic fields in 3D Ricci flows | Departamento de fisica Teorica-IF-Universidade do Estado do Rio de
Janeiro-Brasil | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Magnetic curvature effects, investigated by Barrow and Tsagas (BT) [Phys Rev
D \textbf{77},(2008)],as a mechanism for magnetic field decay in open Friedmann
universes (${\Lambda}<0$), are applied to dynamo geometric Ricci flows in 3D
curved substrate in laboratory. By simple derivation, a covariant
three-dimensional magnetic self-induced equation, presence of these curvature
effects, indicates that de Sitter cosmological constant (${\Lambda}\ge{0}$),
leads to enhancement in the fast kinematic dynamo action which adds to
stretching of plasma flows. From the magnetic growth rate, the strong shear
case, anti-de Sitter case (${\Lambda}<0$) BT magnetic decaying fields are
possible while for weak shear, fast dynamos are possible. The self-induced
equation in Ricci flows is similar to the equation derived by BT in
$(3+1)$-spacetime continuum. Lyapunov-de Sitter metric is obtained from Ricci
flow eigenvalue problem. In de Sitter analogue there is a decay rate of
${\gamma}\approx{-{\Lambda}}\approx{-10^{-35}s^{-2}}$ from corresponding
cosmological constant ${\Lambda}$, showing that, even in the dynamo case,
magnetic field growth is slower than de Sitter inflation, which strongly
supports to BT result.
| [
{
"created": "Wed, 13 May 2009 02:15:37 GMT",
"version": "v1"
}
] | 2009-05-14 | [
[
"de Andrade",
"Garcia",
""
]
] | Magnetic curvature effects, investigated by Barrow and Tsagas (BT) [Phys Rev D \textbf{77},(2008)],as a mechanism for magnetic field decay in open Friedmann universes (${\Lambda}<0$), are applied to dynamo geometric Ricci flows in 3D curved substrate in laboratory. By simple derivation, a covariant three-dimensional magnetic self-induced equation, presence of these curvature effects, indicates that de Sitter cosmological constant (${\Lambda}\ge{0}$), leads to enhancement in the fast kinematic dynamo action which adds to stretching of plasma flows. From the magnetic growth rate, the strong shear case, anti-de Sitter case (${\Lambda}<0$) BT magnetic decaying fields are possible while for weak shear, fast dynamos are possible. The self-induced equation in Ricci flows is similar to the equation derived by BT in $(3+1)$-spacetime continuum. Lyapunov-de Sitter metric is obtained from Ricci flow eigenvalue problem. In de Sitter analogue there is a decay rate of ${\gamma}\approx{-{\Lambda}}\approx{-10^{-35}s^{-2}}$ from corresponding cosmological constant ${\Lambda}$, showing that, even in the dynamo case, magnetic field growth is slower than de Sitter inflation, which strongly supports to BT result. |
gr-qc/0206056 | Pierre Teyssandier | Bernard Linet and Pierre Teyssandier | Quantum phase shift and neutrino oscillations in a stationary, weak
gravitational field | 14 pages, no figure. Enlarged version; added references. In the
Schwarzschild case, our results on the non-radial propagation are compared
with the previous works | Mod.Phys.Lett.A26:1737-1751,2011 | 10.1142/S0217732311036115 | null | gr-qc astro-ph hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new method based on Synge's world function is developed for determining
within the WKB approximation the gravitationally induced quantum phase shift of
a particle propagating in a stationary spacetime. This method avoids any
calculation of geodesics. A detailed treatment is given for relativistic
particles within the weak field, linear approximation of any metric theory. The
method is applied to the calculation of the oscillation terms governing the
interference of neutrinos considered as a superposition of two eigenstates
having different masses. It is shown that the neutrino oscillations are not
sensitive to the gravitomagnetic components of the metric as long as the spin
contributions can be ignored. Explicit calculations are performed when the
source of the field is a spherical, homogeneous body. A comparison is made with
previous results obtained in Schwarzschild spacetime.
| [
{
"created": "Wed, 19 Jun 2002 14:38:03 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2011 14:41:29 GMT",
"version": "v2"
}
] | 2011-08-10 | [
[
"Linet",
"Bernard",
""
],
[
"Teyssandier",
"Pierre",
""
]
] | A new method based on Synge's world function is developed for determining within the WKB approximation the gravitationally induced quantum phase shift of a particle propagating in a stationary spacetime. This method avoids any calculation of geodesics. A detailed treatment is given for relativistic particles within the weak field, linear approximation of any metric theory. The method is applied to the calculation of the oscillation terms governing the interference of neutrinos considered as a superposition of two eigenstates having different masses. It is shown that the neutrino oscillations are not sensitive to the gravitomagnetic components of the metric as long as the spin contributions can be ignored. Explicit calculations are performed when the source of the field is a spherical, homogeneous body. A comparison is made with previous results obtained in Schwarzschild spacetime. |
1404.2139 | Haidar Sheikhahmadi | K. Saaidi, H. Sheikhahmadi, T. Golanbari and S.W. Rabiei | On the holographic dark energy in chameleon scalar-tensor cosmology | 10 pages | Astrophys. Space Sci. 348 (2013) 233 | 10.1007/s10509-013-1491-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the holographic dark energy (HDE) model in generalized Brans-Dicke
scenario with a non-minimal coupling between the scalar field and matter
lagrangian namely Chameleon Brans Dicke (CBD) mechanism. In this study we
consider the interacting and non-interacting cases for two different cutoffs.
The physical quantities of the model such as, equation of state (EoS)
parameter, deceleration parameter and the evolution equation of dimensionless
parameter of dark energy are obtained. We shall show that this model can
describe the dynamical evolution of fraction parameter of dark energy in all
epochs. Also we find the EoS parameter can cross the phantom divide line by
suitable choices of parameters without any mines kinetic energy term.
| [
{
"created": "Tue, 8 Apr 2014 14:10:38 GMT",
"version": "v1"
}
] | 2014-07-02 | [
[
"Saaidi",
"K.",
""
],
[
"Sheikhahmadi",
"H.",
""
],
[
"Golanbari",
"T.",
""
],
[
"Rabiei",
"S. W.",
""
]
] | We study the holographic dark energy (HDE) model in generalized Brans-Dicke scenario with a non-minimal coupling between the scalar field and matter lagrangian namely Chameleon Brans Dicke (CBD) mechanism. In this study we consider the interacting and non-interacting cases for two different cutoffs. The physical quantities of the model such as, equation of state (EoS) parameter, deceleration parameter and the evolution equation of dimensionless parameter of dark energy are obtained. We shall show that this model can describe the dynamical evolution of fraction parameter of dark energy in all epochs. Also we find the EoS parameter can cross the phantom divide line by suitable choices of parameters without any mines kinetic energy term. |
1009.4816 | Lorenzo Sebastiani | Emilio Bellini, Roberto Di Criscienzo, Lorenzo Sebastiani, Sergio
Zerbini | Black Hole entropy for two higher derivative theories of gravity | 10 pages, 1 figure | Entropy.12:2186,2010 | 10.3390/e12102186 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dark energy issue is focusing the attention of an incresing number of
physicists all over the world. Among the possible alternatives in order to
explain what as been named the "Mystery of the Millennium" are the so-called
Modified Theories of Gravity. A crucial test for such models is represented by
the existence and (if this is the case) the properties of their black hole
solutions. Nowadays, to our knowledge, only two non-trivial, spherically
symmetric, solutions with vanishing cosmological constant are known by Barrow &
Clifton (2005) and Deser, Sarioglu & Tekin (2008). Aim of the paper is to
discuss some features of such solutions, with emphasis on their thermodynamic
properties such as entropy and temperature, little progress being possible
along the way which leads to a consistent definition of mass.
| [
{
"created": "Fri, 24 Sep 2010 12:07:59 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Nov 2010 16:10:57 GMT",
"version": "v2"
}
] | 2015-05-20 | [
[
"Bellini",
"Emilio",
""
],
[
"Di Criscienzo",
"Roberto",
""
],
[
"Sebastiani",
"Lorenzo",
""
],
[
"Zerbini",
"Sergio",
""
]
] | The dark energy issue is focusing the attention of an incresing number of physicists all over the world. Among the possible alternatives in order to explain what as been named the "Mystery of the Millennium" are the so-called Modified Theories of Gravity. A crucial test for such models is represented by the existence and (if this is the case) the properties of their black hole solutions. Nowadays, to our knowledge, only two non-trivial, spherically symmetric, solutions with vanishing cosmological constant are known by Barrow & Clifton (2005) and Deser, Sarioglu & Tekin (2008). Aim of the paper is to discuss some features of such solutions, with emphasis on their thermodynamic properties such as entropy and temperature, little progress being possible along the way which leads to a consistent definition of mass. |
2003.11128 | Alexander Saffer | Alexander Saffer and Kent Yagi | Parameter Estimation for Tests of General Relativity with the
Astrophysical Stochastic Gravitational Wave Background | 10 pages, 6 figures, submitted to Phys. Rev. D | Phys. Rev. D 102, 024001 (2020) | 10.1103/PhysRevD.102.024001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observations of gravitational waves from binary black holes and
neutron stars allow us to probe the strong and dynamical field regime of
gravity. On the other hand, a collective signal from many individual,
unresolved sources results in what is known as a stochastic background. We here
consider probing gravity with such a background from stellar-mass binary black
hole mergers. We adopt a simple power-law spectrum and carry out a parameter
estimation study with a network of current and future ground-based detectors by
including both general relativistic and beyond general relativistic variables.
For a network of second-generation detectors, we find that one can place
meaningful bounds on the deviation parameter in the gravitational-wave
amplitude if it enters at a sufficiently negative post-Newtonian order.
However, such future bounds from a stochastic background are weaker than
existing bounds from individual sources, such as GW150914 and GW151226. We also
find that systematic errors due to mismodeling of the spectrum is much smaller
than statistical errors, which justifies our use of the power-law model.
Regarding a network of third-generation detectors, we find that the bounds on
the deviation parameter from statistical errors improve upon the
second-generation case, though systematic errors now dominate the error budget
and thus one needs to use a more realistic spectrum model. We conclude that
individual sources seem to be more powerful in probing general relativity than
the astrophysical stochastic background.
| [
{
"created": "Tue, 24 Mar 2020 22:00:39 GMT",
"version": "v1"
}
] | 2021-10-08 | [
[
"Saffer",
"Alexander",
""
],
[
"Yagi",
"Kent",
""
]
] | Recent observations of gravitational waves from binary black holes and neutron stars allow us to probe the strong and dynamical field regime of gravity. On the other hand, a collective signal from many individual, unresolved sources results in what is known as a stochastic background. We here consider probing gravity with such a background from stellar-mass binary black hole mergers. We adopt a simple power-law spectrum and carry out a parameter estimation study with a network of current and future ground-based detectors by including both general relativistic and beyond general relativistic variables. For a network of second-generation detectors, we find that one can place meaningful bounds on the deviation parameter in the gravitational-wave amplitude if it enters at a sufficiently negative post-Newtonian order. However, such future bounds from a stochastic background are weaker than existing bounds from individual sources, such as GW150914 and GW151226. We also find that systematic errors due to mismodeling of the spectrum is much smaller than statistical errors, which justifies our use of the power-law model. Regarding a network of third-generation detectors, we find that the bounds on the deviation parameter from statistical errors improve upon the second-generation case, though systematic errors now dominate the error budget and thus one needs to use a more realistic spectrum model. We conclude that individual sources seem to be more powerful in probing general relativity than the astrophysical stochastic background. |
gr-qc/9609003 | Werner Martins Vieira | Werner M. Vieira and Patricio S. Letelier | Curvature and Chaos in General Relativity | 8 pages, REVTEX, two postscript figures included, to appear in Class.
Quantum Grav | Class.Quant.Grav. 13 (1996) 3115-3120 | 10.1088/0264-9381/13/11/025 | null | gr-qc | null | We clarify some points about the systems considered by Sota, Suzuki and Maeda
in Class. Quantum Grav. 13, 1241 (1996). Contrary to the authors' claim for a
non-homoclinic kind of chaos, we show the chaotic cases they considered are
homoclinic in origin. The power of local criteria to predict chaos is once more
questioned. We find that their local, curvature--based criterion is neither
necessary nor sufficient for the occurrence of chaos. In fact, we argue that a
merit of their search for local criteria applied to General Relativity is just
to stress the weakness of locality itself, free of any pathologies related to
the motion in effective Riemannian geometries.
| [
{
"created": "Fri, 30 Aug 1996 12:58:32 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Vieira",
"Werner M.",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | We clarify some points about the systems considered by Sota, Suzuki and Maeda in Class. Quantum Grav. 13, 1241 (1996). Contrary to the authors' claim for a non-homoclinic kind of chaos, we show the chaotic cases they considered are homoclinic in origin. The power of local criteria to predict chaos is once more questioned. We find that their local, curvature--based criterion is neither necessary nor sufficient for the occurrence of chaos. In fact, we argue that a merit of their search for local criteria applied to General Relativity is just to stress the weakness of locality itself, free of any pathologies related to the motion in effective Riemannian geometries. |
2105.01295 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | Testing the microstructure of $d$-dimensional charged Gauss-Bonnet
anti-de Sitter black holes | 18 pages, 15 figures, and 3 tables | Phys. Rev. D 104, 024062 (2021) | 10.1103/PhysRevD.104.024062 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Understanding black hole microstructure via the thermodynamic geometry can
provide us with more deeper insight into black hole thermodynamics in modified
gravities. In this paper, we study the black hole phase transition and
Ruppeiner geometry for the $d$-dimensional charged Gauss-Bonnet anti-de Sitter
black holes. The results show that the small-large black hole phase transition
is universal in this gravity. By reducing the thermodynamic quantities with the
black hole charge, we clearly exhibit the phase diagrams in different parameter
spaces. Of particular interest is that the radius of the black hole horizon can
act as the order parameter to characterize the black hole phase transition. We
also disclose that different from the five-dimensional neutral black holes, the
charged ones allow the repulsive interaction among its microstructure for small
black hole of higher temperature. Another significant difference between them
is that the microscopic interaction changes during the small-large black hole
phase transition for the charged case, where the black hole microstructure
undergoes a sudden change. These results are helpful for peeking into the
microstructure of charged black holes in the Gauss-Bonnet gravity.
| [
{
"created": "Tue, 4 May 2021 05:21:12 GMT",
"version": "v1"
}
] | 2021-08-04 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Understanding black hole microstructure via the thermodynamic geometry can provide us with more deeper insight into black hole thermodynamics in modified gravities. In this paper, we study the black hole phase transition and Ruppeiner geometry for the $d$-dimensional charged Gauss-Bonnet anti-de Sitter black holes. The results show that the small-large black hole phase transition is universal in this gravity. By reducing the thermodynamic quantities with the black hole charge, we clearly exhibit the phase diagrams in different parameter spaces. Of particular interest is that the radius of the black hole horizon can act as the order parameter to characterize the black hole phase transition. We also disclose that different from the five-dimensional neutral black holes, the charged ones allow the repulsive interaction among its microstructure for small black hole of higher temperature. Another significant difference between them is that the microscopic interaction changes during the small-large black hole phase transition for the charged case, where the black hole microstructure undergoes a sudden change. These results are helpful for peeking into the microstructure of charged black holes in the Gauss-Bonnet gravity. |
gr-qc/0310025 | Hongya Liu | Hongya Liu | Bounce Models in Brane Cosmology and a Gravitational Stability Condition | 18 pages, 3 figures, title changed and references added | null | null | null | gr-qc astro-ph hep-th | null | Five-dimensional cosmological models with two 3-branes and with a buck
cosmological constant are studied. It is found that for all the three cases
($\Lambda =0$, $\Lambda >0$, and $\Lambda <0$), the conventional space-time
singularity ``big bang'' could be replaced by a matter singularity ``big
bounce'', at which the ``size'' of the universe and the energy density are
finite while the pressure diverges, and across which the universe evolves from
a pre-existing contracting phase to the present expanding phase. It is also
found that for the $\Lambda >0$ case the brane solutions could give an
oscillating universe model in which the universe oscillates with each cosmic
cycle begins from a ``big bounce'' and ends to a ``big crunch'', with a
distinctive characteristic that in each subsequent cycle the universe expands
to a larger size and then contracts to a smaller (but non-zero) size. By
studying the gravitational force acted on a test particle in the bulk, a
gravitational stability condition is derived and then is used to analyze those
brane models. It predicts that if dark energy takes over ordinary matter,
particles on the brane may become unstable in the sense that they may escape
from our 4D-world and dissolve in the bulk due to the repulsive force of dark
energy.
| [
{
"created": "Sun, 5 Oct 2003 03:38:39 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jan 2004 03:18:47 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Liu",
"Hongya",
""
]
] | Five-dimensional cosmological models with two 3-branes and with a buck cosmological constant are studied. It is found that for all the three cases ($\Lambda =0$, $\Lambda >0$, and $\Lambda <0$), the conventional space-time singularity ``big bang'' could be replaced by a matter singularity ``big bounce'', at which the ``size'' of the universe and the energy density are finite while the pressure diverges, and across which the universe evolves from a pre-existing contracting phase to the present expanding phase. It is also found that for the $\Lambda >0$ case the brane solutions could give an oscillating universe model in which the universe oscillates with each cosmic cycle begins from a ``big bounce'' and ends to a ``big crunch'', with a distinctive characteristic that in each subsequent cycle the universe expands to a larger size and then contracts to a smaller (but non-zero) size. By studying the gravitational force acted on a test particle in the bulk, a gravitational stability condition is derived and then is used to analyze those brane models. It predicts that if dark energy takes over ordinary matter, particles on the brane may become unstable in the sense that they may escape from our 4D-world and dissolve in the bulk due to the repulsive force of dark energy. |
0705.3070 | Martin Reiris | Martin Reiris | The Constant Mean Curvature Einstein flow and the Bel-Robinson energy | 71 pages. This is an improved version of part of arXiv:0705.3070 that
we now replace. An improved version of the second part of arXiv:0705.3070
will come out as a new submission | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give an extensive treatment of the Constant Mean Curvature (CMC) Einstein
flow from the point of view of the Bel-Robinson energies. The article, in
particular, stresses on estimates showing how the Bel-Robinson energies and the
volume of the evolving states control intrinsically the flow along evolution.
The treatment is for flows over compact three-manifolds of arbitrary
topological type, although the form of the estimates may vary depending on the
Yamabe invariant of the manifold. We end up showing well posedness of the CMC
Einstein flow with H^{3} x H^{2} regularity, and proving a criteria for a flow
to be a long-time flow on manifolds with non-positive Yamabe invariant in terms
only of the first order Bel-Robinson energy.
| [
{
"created": "Mon, 21 May 2007 23:11:32 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2008 19:07:04 GMT",
"version": "v2"
}
] | 2008-09-19 | [
[
"Reiris",
"Martin",
""
]
] | We give an extensive treatment of the Constant Mean Curvature (CMC) Einstein flow from the point of view of the Bel-Robinson energies. The article, in particular, stresses on estimates showing how the Bel-Robinson energies and the volume of the evolving states control intrinsically the flow along evolution. The treatment is for flows over compact three-manifolds of arbitrary topological type, although the form of the estimates may vary depending on the Yamabe invariant of the manifold. We end up showing well posedness of the CMC Einstein flow with H^{3} x H^{2} regularity, and proving a criteria for a flow to be a long-time flow on manifolds with non-positive Yamabe invariant in terms only of the first order Bel-Robinson energy. |
1604.08285 | Hiroyuki Nakano | Hiroyuki Nakano, Norichika Sago, Takahiro Tanaka, Takashi Nakamura | Estimate of the radius responsible for quasinormal modes in the extreme
Kerr limit and asymptotic behavior of the Sasaki-Nakamura transformation | 12 pages, 2 figures, added some references, modifications to match
the published version in PTEP | Prog. Theor. Exp. Phys. (2016) 083E01 | 10.1093/ptep/ptw098 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Sasaki-Nakamura transformation gives a short-ranged potential and a
convergent source term for the master equation of perturbations in the Kerr
space-time. In this paper, we study the asymptotic behavior of the
transformation, and present a new relaxed necessary and sufficient condition of
the transformation to obtain the short-ranged potential in the assumption that
the transformation converges in the far distance. Also, we discuss quasinormal
mode frequencies which are determined by the information around the peak of the
potential in the WKB analysis. Finally, in the extreme Kerr limit, $a/M \to 1$,
where $M$ and $a$ denote the mass and spin parameter of a Kerr black hole,
respectively, we find the peak location of the potential, $r_p/M \lesssim 1 +
1.8 \,(1-a/M)^{1/2}$ by using the new transformation. The uncertainty of the
location is as large as that expected from the equivalence principle.
| [
{
"created": "Thu, 28 Apr 2016 01:59:02 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2016 00:06:10 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Apr 2017 08:18:42 GMT",
"version": "v3"
}
] | 2017-04-27 | [
[
"Nakano",
"Hiroyuki",
""
],
[
"Sago",
"Norichika",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Nakamura",
"Takashi",
""
]
] | The Sasaki-Nakamura transformation gives a short-ranged potential and a convergent source term for the master equation of perturbations in the Kerr space-time. In this paper, we study the asymptotic behavior of the transformation, and present a new relaxed necessary and sufficient condition of the transformation to obtain the short-ranged potential in the assumption that the transformation converges in the far distance. Also, we discuss quasinormal mode frequencies which are determined by the information around the peak of the potential in the WKB analysis. Finally, in the extreme Kerr limit, $a/M \to 1$, where $M$ and $a$ denote the mass and spin parameter of a Kerr black hole, respectively, we find the peak location of the potential, $r_p/M \lesssim 1 + 1.8 \,(1-a/M)^{1/2}$ by using the new transformation. The uncertainty of the location is as large as that expected from the equivalence principle. |
1707.01416 | Kimet Jusufi | Kimet Jusufi, Ali \"Ovg\"un, Ayan Banerjee | Light deflection by charged wormholes in Einstein-Maxwell-dilaton theory | 7 pages, 1 figure, accepted for publication in PRD | Phys. Rev. D 96, 084036 (2017) | 10.1103/PhysRevD.96.084036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the deflection of light by a class of charged
wormholes within the context of the Einstein-Maxwell-dilaton theory. The
primordial wormholes are predicted to exist in the early universe, where
inflation driven by the dilaton field. We perform our analysis through optical
geometry using the Gibbons-Werner method (GW), by adopting the Gauss-Bonnet
theorem and the standard geodesics approach. We report an interesting result
for the deflection angle in leading-order terms--namely, the deflection angle
increases due to the electric charge $Q$ and the magnetic charge $P$, whereas
it decreases due to the dilaton charge $\Sigma$. Finally, we confirm our
findings by means of geodesics equations. Our computations show that the GW
method gives an exact result in leading order terms.
| [
{
"created": "Wed, 5 Jul 2017 14:25:04 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2017 09:05:16 GMT",
"version": "v2"
}
] | 2017-10-25 | [
[
"Jusufi",
"Kimet",
""
],
[
"Övgün",
"Ali",
""
],
[
"Banerjee",
"Ayan",
""
]
] | In this paper, we study the deflection of light by a class of charged wormholes within the context of the Einstein-Maxwell-dilaton theory. The primordial wormholes are predicted to exist in the early universe, where inflation driven by the dilaton field. We perform our analysis through optical geometry using the Gibbons-Werner method (GW), by adopting the Gauss-Bonnet theorem and the standard geodesics approach. We report an interesting result for the deflection angle in leading-order terms--namely, the deflection angle increases due to the electric charge $Q$ and the magnetic charge $P$, whereas it decreases due to the dilaton charge $\Sigma$. Finally, we confirm our findings by means of geodesics equations. Our computations show that the GW method gives an exact result in leading order terms. |
1308.2074 | Jan Harms | Jan Harms, Bram J. J. Slagmolen, Rana X. Adhikari, M. Coleman Miller,
Matthew Evans, Yanbei Chen, Holger M\"uller, Masaki Ando | Low-Frequency Terrestrial Gravitational-Wave Detectors | 19 pages, 12 figures | Phys. Rev. D 88, 122003 (2013) | 10.1103/PhysRevD.88.122003 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Direct detection of gravitational radiation in the audio band is being
pursued with a network of kilometer-scale interferometers (LIGO, Virgo, KAGRA).
Several space missions (LISA, DECIGO, BBO) have been proposed to search for
sub-Hz radiation from massive astrophysical sources. Here we examine the
potential sensitivity of three ground-based detector concepts aimed at
radiation in the 0.1 -- 10\,Hz band. We describe the plethora of potential
astrophysical sources in this band and make estimates for their event rates and
thereby, the sensitivity requirements for these detectors. The scientific
payoff from measuring astrophysical gravitational waves in this frequency band
is great. Although we find no fundamental limits to the detector sensitivity in
this band, the remaining technical limits will be extremely challenging to
overcome.
| [
{
"created": "Fri, 9 Aug 2013 10:04:28 GMT",
"version": "v1"
}
] | 2013-12-16 | [
[
"Harms",
"Jan",
""
],
[
"Slagmolen",
"Bram J. J.",
""
],
[
"Adhikari",
"Rana X.",
""
],
[
"Miller",
"M. Coleman",
""
],
[
"Evans",
"Matthew",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Müller",
"Holger",
""
],
[
"Ando",
"Masaki",
""
]
] | Direct detection of gravitational radiation in the audio band is being pursued with a network of kilometer-scale interferometers (LIGO, Virgo, KAGRA). Several space missions (LISA, DECIGO, BBO) have been proposed to search for sub-Hz radiation from massive astrophysical sources. Here we examine the potential sensitivity of three ground-based detector concepts aimed at radiation in the 0.1 -- 10\,Hz band. We describe the plethora of potential astrophysical sources in this band and make estimates for their event rates and thereby, the sensitivity requirements for these detectors. The scientific payoff from measuring astrophysical gravitational waves in this frequency band is great. Although we find no fundamental limits to the detector sensitivity in this band, the remaining technical limits will be extremely challenging to overcome. |
gr-qc/0005072 | Mauricio Bellini | Mauricio Bellini (Universidad Nac. de Mar del Plata) | Primordial fluctuations of the metric in the warm inflation scenario | Accepted for publication in Il Nuovo Cimento B, 5 pages, no figures | Nuovo Cim. B115 (2000) 369-374 | null | null | gr-qc | null | I consider a semiclassical expansion of the scalar field in the warm
inflation scenario. I study the evolution for the fluctuations of the metric
around the Friedmann-Robertson-Walker one. The formalism predicts that, in the
power-law expansion universe, the fluctuations of the metric decreases with
time.
| [
{
"created": "Tue, 16 May 2000 17:03:04 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bellini",
"Mauricio",
"",
"Universidad Nac. de Mar del Plata"
]
] | I consider a semiclassical expansion of the scalar field in the warm inflation scenario. I study the evolution for the fluctuations of the metric around the Friedmann-Robertson-Walker one. The formalism predicts that, in the power-law expansion universe, the fluctuations of the metric decreases with time. |
2008.13753 | Maciej Kolanowski | Maciej Kolanowski and Jerzy Lewandowski | Energy of gravitational radiation in the de Sitter universe at the scri
and at a horizon | 30 pages | Phys. Rev. D 102, 124052 (2020) | 10.1103/PhysRevD.102.124052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we investigate outcomes of a symplectic formula for the
gravitational waves charges in the general relativity linearized around the de
Sitter spacetime. We derive their explicit form at {\it scri} in the Bondi
frame, compare with the connected Noether expression and analyze their gauge
dependence which allows us to fix unambiguously boundary terms. We also discuss
minimal requirements needed to impose on initial data to have finite values of
charges. Furthermore, we analyze transformation laws of the energy upon the
action of the de Sitter group and discuss its physical interpretation. Finally,
we calculate its flux through a cosmological horizon instead of {\it scri}. We
show that in the limit $\Lambda \to 0$, one recovers Trautman--Bondi formula
strengthening recent proposal that one should choose a~null surface as a more
natural boundary for the astrophysical systems in the presence of the
cosmological constant.
| [
{
"created": "Mon, 31 Aug 2020 17:22:28 GMT",
"version": "v1"
}
] | 2021-01-04 | [
[
"Kolanowski",
"Maciej",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | In this note we investigate outcomes of a symplectic formula for the gravitational waves charges in the general relativity linearized around the de Sitter spacetime. We derive their explicit form at {\it scri} in the Bondi frame, compare with the connected Noether expression and analyze their gauge dependence which allows us to fix unambiguously boundary terms. We also discuss minimal requirements needed to impose on initial data to have finite values of charges. Furthermore, we analyze transformation laws of the energy upon the action of the de Sitter group and discuss its physical interpretation. Finally, we calculate its flux through a cosmological horizon instead of {\it scri}. We show that in the limit $\Lambda \to 0$, one recovers Trautman--Bondi formula strengthening recent proposal that one should choose a~null surface as a more natural boundary for the astrophysical systems in the presence of the cosmological constant. |
1007.4250 | Francisco Navarro-Lerida | Masoud Allahverdizadeh, Jutta Kunz and Francisco Navarro-Lerida | Extremal Charged Rotating Dilaton Black Holes in Odd Dimensions | 20 pages, 3 figures | Phys.Rev.D82:064034,2010 | 10.1103/PhysRevD.82.064034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Employing higher order perturbation theory, we find a new class of charged
rotating black hole solutions of Einstein-Maxwell-dilaton theory with general
dilaton coupling constant. Starting from the Myers-Perry solutions, we use the
electric charge as the perturbative parameter, and focus on extremal black
holes with equal-magnitude angular momenta in odd dimensions. We perform the
perturbations up to 4th order for black holes in 5 dimensions and up to 3rd
order in higher odd dimensions. We calculate the physical properties of these
black holes and study their dependence on the charge and the dilaton coupling
constant.
| [
{
"created": "Sat, 24 Jul 2010 06:51:39 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Allahverdizadeh",
"Masoud",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lerida",
"Francisco",
""
]
] | Employing higher order perturbation theory, we find a new class of charged rotating black hole solutions of Einstein-Maxwell-dilaton theory with general dilaton coupling constant. Starting from the Myers-Perry solutions, we use the electric charge as the perturbative parameter, and focus on extremal black holes with equal-magnitude angular momenta in odd dimensions. We perform the perturbations up to 4th order for black holes in 5 dimensions and up to 3rd order in higher odd dimensions. We calculate the physical properties of these black holes and study their dependence on the charge and the dilaton coupling constant. |
1410.8527 | Edward Malec | Piotr Jaranowski, Patryk Mach, Edward Malec, Michal Pirog | General-relativistic versus Newtonian: geometric dragging and dynamic
anti-dragging in stationary disks in the first post-Newtonian approximation | Minor changes in the introduction and the summary. Accepted by the
Physical Review D. 12 pages, 5 figures | null | 10.1103/PhysRevD.91.024039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We evaluate general-relativistic effects in motion of stationary accretion
disks around a Schwarzschild black hole, assuming the first post-Newtonian
(1PN) approximation. There arises an integrability condition, that leads to the
emergence of two types of general-relativistic corrections to a Newtonian
rotation curve. The well known geometric dragging of frames accelerates
rotation but the hitherto unknown dynamic term, that reflects the disk
structure, deccelerates rotation. The net result can diminish the Newtonian
angular velocity of rotation in a central disk zone but the geometric dragging
of frames dominates in the disk boundary zone. Both effects are nonlinear in
nature and they disappear in the limit of test fluids. Dust disks can be only
geometrically dragged while uniformly rotating gaseous disk are untouched at
the 1PN order. General-relativistic contributions can strongly affect rotation
periods in Keplerian motion for compact systems.
| [
{
"created": "Thu, 30 Oct 2014 17:03:37 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Dec 2014 17:20:03 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Jaranowski",
"Piotr",
""
],
[
"Mach",
"Patryk",
""
],
[
"Malec",
"Edward",
""
],
[
"Pirog",
"Michal",
""
]
] | We evaluate general-relativistic effects in motion of stationary accretion disks around a Schwarzschild black hole, assuming the first post-Newtonian (1PN) approximation. There arises an integrability condition, that leads to the emergence of two types of general-relativistic corrections to a Newtonian rotation curve. The well known geometric dragging of frames accelerates rotation but the hitherto unknown dynamic term, that reflects the disk structure, deccelerates rotation. The net result can diminish the Newtonian angular velocity of rotation in a central disk zone but the geometric dragging of frames dominates in the disk boundary zone. Both effects are nonlinear in nature and they disappear in the limit of test fluids. Dust disks can be only geometrically dragged while uniformly rotating gaseous disk are untouched at the 1PN order. General-relativistic contributions can strongly affect rotation periods in Keplerian motion for compact systems. |
1305.0217 | Markus B. Fr\"ob | Markus B. Fr\"ob | Fully renormalized stress tensor correlator in flat space | 23 pages, 2 figures | null | 10.1103/PhysRevD.88.045011 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general procedure to renormalize the stress tensor two-point
correlation function on a Minkowski background in position space. The method is
shown in detail for the case of a free massive scalar field in the standard
Minkowski vacuum state, and explicit expressions are given for the counterterms
and finite parts, which are in full accordance with earlier results for the
massless case. For the general case in position space, only regularized --- but
not renormalized --- results have been obtained previously. After a Fourier
transformation to momentum space, we also check agreement with a previous
calculation there. We generalize our results to general Hadamard states.
Furthermore, the proposed procedure can presumably be generalized to the
important case of an inflationary spacetime background, where the transition to
momentum space is in general not possible.
| [
{
"created": "Wed, 1 May 2013 16:22:11 GMT",
"version": "v1"
}
] | 2013-08-14 | [
[
"Fröb",
"Markus B.",
""
]
] | We present a general procedure to renormalize the stress tensor two-point correlation function on a Minkowski background in position space. The method is shown in detail for the case of a free massive scalar field in the standard Minkowski vacuum state, and explicit expressions are given for the counterterms and finite parts, which are in full accordance with earlier results for the massless case. For the general case in position space, only regularized --- but not renormalized --- results have been obtained previously. After a Fourier transformation to momentum space, we also check agreement with a previous calculation there. We generalize our results to general Hadamard states. Furthermore, the proposed procedure can presumably be generalized to the important case of an inflationary spacetime background, where the transition to momentum space is in general not possible. |
gr-qc/0505049 | Ivan S. N. Booth | Ivan Booth, Stephen Fairhurst | Horizon energy and angular momentum from a Hamiltonian perspective | 39 pages, 3 figures, Final Version : content essentially unchanged
but many small improvements made in response to referees, a few references
added | Class.Quant.Grav. 22 (2005) 4515-4550 | 10.1088/0264-9381/22/21/006 | null | gr-qc | null | Classical black holes and event horizons are highly non-local objects,
defined in terms of the causal past of future null infinity. Alternative,
(quasi)local definitions are often used in mathematical, quantum, and numerical
relativity. These include apparent, trapping, isolated, and dynamical horizons,
all of which are closely associated to two-surfaces of zero outward null
expansion. In this paper we show that three-surfaces which can be foliated with
such two-surfaces are suitable boundaries in both a quasilocal action and a
phase space formulation of general relativity. The resulting formalism provides
expressions for the quasilocal energy and angular momentum associated with the
horizon. The values of the energy and angular momentum are in agreement with
those derived from the isolated and dynamical horizon frameworks.
| [
{
"created": "Wed, 11 May 2005 12:22:18 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Oct 2005 15:27:43 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Booth",
"Ivan",
""
],
[
"Fairhurst",
"Stephen",
""
]
] | Classical black holes and event horizons are highly non-local objects, defined in terms of the causal past of future null infinity. Alternative, (quasi)local definitions are often used in mathematical, quantum, and numerical relativity. These include apparent, trapping, isolated, and dynamical horizons, all of which are closely associated to two-surfaces of zero outward null expansion. In this paper we show that three-surfaces which can be foliated with such two-surfaces are suitable boundaries in both a quasilocal action and a phase space formulation of general relativity. The resulting formalism provides expressions for the quasilocal energy and angular momentum associated with the horizon. The values of the energy and angular momentum are in agreement with those derived from the isolated and dynamical horizon frameworks. |
gr-qc/0701081 | D. Petroff | David Petroff | Slowly Rotating Homogeneous Stars and the Heun Equation | 16 pages, uses document class iopart, v2: minor corrections | Class.Quant.Grav.24:1055-1068,2007 | 10.1088/0264-9381/24/5/003 | null | gr-qc math-ph math.MP | null | The scheme developed by Hartle for describing slowly rotating bodies in 1967
was applied to the simple model of constant density by Chandrasekhar and Miller
in 1974. The pivotal equation one has to solve turns out to be one of Heun's
equations. After a brief discussion of this equation and the chances of finding
a closed form solution, a quickly converging series solution of it is
presented. A comparison with numerical solutions of the full Einstein equations
allows one to truncate the series at an order appropriate to the slow rotation
approximation. The truncated solution is then used to provide explicit
expressions for the metric.
| [
{
"created": "Mon, 15 Jan 2007 14:49:05 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2007 14:23:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Petroff",
"David",
""
]
] | The scheme developed by Hartle for describing slowly rotating bodies in 1967 was applied to the simple model of constant density by Chandrasekhar and Miller in 1974. The pivotal equation one has to solve turns out to be one of Heun's equations. After a brief discussion of this equation and the chances of finding a closed form solution, a quickly converging series solution of it is presented. A comparison with numerical solutions of the full Einstein equations allows one to truncate the series at an order appropriate to the slow rotation approximation. The truncated solution is then used to provide explicit expressions for the metric. |
0802.2447 | Ugo Moschella | Ugo Moschella, Richard Schaeffer | A note on canonical quantization of fields on a manifold | null | JCAP 0902:033,2009 | 10.1088/1475-7516/2009/02/033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a general construction of quantum states for linear canonical
quantum fields on a manifold, which encompasses and generalizes the "standard"
procedures existing in textbooks. Our method provides pure and mixed states on
the same footing. A large class of examples finds a simple and unified
treatment in our approach. Applications discussed here include thermodynamical
equilibrium states for Minkowski fields and quantum field theory in the
Rindler's and in the open de Sitter universes. Our approach puts the above
examples into perspective and unravels new possibilities for quantization. We
call our generalization "extended canonical quantization" as it is suited to
attack cases not directly covered by the standard canonical approach.
| [
{
"created": "Mon, 18 Feb 2008 13:32:42 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2009 14:17:15 GMT",
"version": "v2"
}
] | 2009-04-01 | [
[
"Moschella",
"Ugo",
""
],
[
"Schaeffer",
"Richard",
""
]
] | We propose a general construction of quantum states for linear canonical quantum fields on a manifold, which encompasses and generalizes the "standard" procedures existing in textbooks. Our method provides pure and mixed states on the same footing. A large class of examples finds a simple and unified treatment in our approach. Applications discussed here include thermodynamical equilibrium states for Minkowski fields and quantum field theory in the Rindler's and in the open de Sitter universes. Our approach puts the above examples into perspective and unravels new possibilities for quantization. We call our generalization "extended canonical quantization" as it is suited to attack cases not directly covered by the standard canonical approach. |
gr-qc/0209002 | Wolfgang Graf | Wolfgang Graf | Geometric Dilaton Coupling and Smooth Charged Wormholes | 23 pages, 1 table, 1 TeX-figure. Minor changes, to agree with with
paper accepted for publication by Phys. Rev. D | Phys.Rev.D67:024002,2003 | 10.1103/PhysRevD.67.024002 | UWThPh-2002-24 | gr-qc hep-th | null | A particular type of coupling of the dilaton field to the metric is shown to
admit a simple geometric interpretation in terms of a volume element density
independent from the metric. For dimension n = 4 two families of either
magnetically or electrically charged static spherically symmetric solutions to
the Maxwell-Einstein-Dilaton field equations are derived. Whereas the metrics
of the "magnetic" spacetimes are smooth, geodesically complete and have the
topology of a wormhole, the "electric" metrics behave similarly as the singular
and geodesically incomplete classical Reissner-Nordstroem metrics. At the price
of losing the simple geometric interpretation, a closely related "alternative"
dilaton coupling can nevertheless be defined, admitting as solutions smooth
"electric" metrics.
| [
{
"created": "Mon, 2 Sep 2002 18:19:56 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Nov 2002 21:11:14 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Graf",
"Wolfgang",
""
]
] | A particular type of coupling of the dilaton field to the metric is shown to admit a simple geometric interpretation in terms of a volume element density independent from the metric. For dimension n = 4 two families of either magnetically or electrically charged static spherically symmetric solutions to the Maxwell-Einstein-Dilaton field equations are derived. Whereas the metrics of the "magnetic" spacetimes are smooth, geodesically complete and have the topology of a wormhole, the "electric" metrics behave similarly as the singular and geodesically incomplete classical Reissner-Nordstroem metrics. At the price of losing the simple geometric interpretation, a closely related "alternative" dilaton coupling can nevertheless be defined, admitting as solutions smooth "electric" metrics. |
gr-qc/0105061 | Diego Jose Navarro Sanz | A. Fabbri (Bologna U. and INFN), D. J. Navarro and J. Navarro-Salas
(Valencia U. and IFIC) | A Planck-like problem for quantum charged black holes | 6 pages, LaTeX file, Awarded Fifth Prize in the Gravity Research
Foundation Essay Competition for 2001 | Gen.Rel.Grav. 33 (2001) 2119-2124 | 10.1023/A:1015289603115 | null | gr-qc hep-th | null | Motivated by the parallelism existing between the puzzles of classical
physics at the beginning of the XXth century and the current paradoxes in the
search of a quantum theory of gravity, we give, in analogy with Planck's black
body radiation problem, a solution for the exact Hawking flux of evaporating
Reissner-Nordstrom black holes. Our results show that when back-reaction
effects are fully taken into account the standard picture of black hole
evaporation is significantly altered, thus implying a possible resolution of
the information loss problem.
| [
{
"created": "Thu, 17 May 2001 16:37:53 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Fabbri",
"A.",
"",
"Bologna U. and INFN"
],
[
"Navarro",
"D. J.",
"",
"Valencia U. and IFIC"
],
[
"Navarro-Salas",
"J.",
"",
"Valencia U. and IFIC"
]
] | Motivated by the parallelism existing between the puzzles of classical physics at the beginning of the XXth century and the current paradoxes in the search of a quantum theory of gravity, we give, in analogy with Planck's black body radiation problem, a solution for the exact Hawking flux of evaporating Reissner-Nordstrom black holes. Our results show that when back-reaction effects are fully taken into account the standard picture of black hole evaporation is significantly altered, thus implying a possible resolution of the information loss problem. |
2407.09970 | Aaqid Bhat | Raja Solanki, Aaqid Bhat, P.K. Sahoo | Bulk viscous cosmological model in $f(T,\mathcal{T})$ modified gravity | Astroparticle Physics accepted version | Astroparticle Physics, 163 (2024) 103013 | 10.1016/j.astropartphys.2024.103013 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | This article explores the impact of bulk viscosity on understanding the
universe's accelerated expansion within the context of modified
$f(T,\mathcal{T})$ gravity, which is an extension of the $f(T)$ gravitational
theory, allowing a broad coupling between the energy-momentum scalar
$\mathcal{T}$ and the torsion scalar $T$. We consider two $f(T,\mathcal{T})$
functions, specifically $f(T,\mathcal{T})=\alpha T + \beta \mathcal{T}$ and
$f(T,\mathcal{T})=\alpha \sqrt{-T} + \beta \mathcal{T}$, where $\alpha$ and
$\beta$ are arbitrary constants, along with the fluid part incorporating the
coefficient of bulk viscosity $\zeta=\zeta_0 > 0$. We calculate the analytical
solutions of the corresponding field equations for a flat FLRW environment, and
then we constrain the free parameters of the obtained solution using CC,
Pantheon+, and the CC+Pantheon+ samples. We perform the Bayesian statistical
analysis to estimate the posterior probability utilizing the likelihood
function and the MCMC random sampling technique. Further, to assess the
effectiveness of our MCMC analysis, we estimate the corresponding AIC and BIC
values, and we find that there is strong evidence supporting the assumed
viscous modified gravity models for all three data sets. Also, we find that the
linear model precisely mimics the $\Lambda$CDM model. We also investigate the
evolutionary behavior of some prominent cosmological parameters. We observe
that the effective equation of state parameter for both models predict the
accelerating behavior of the cosmic expansion phase. In addition, from the
statefinder test, we find that the parameters of the considered MOG models
favor the quintessence-type behavior.
| [
{
"created": "Sat, 13 Jul 2024 18:19:59 GMT",
"version": "v1"
}
] | 2024-07-29 | [
[
"Solanki",
"Raja",
""
],
[
"Bhat",
"Aaqid",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This article explores the impact of bulk viscosity on understanding the universe's accelerated expansion within the context of modified $f(T,\mathcal{T})$ gravity, which is an extension of the $f(T)$ gravitational theory, allowing a broad coupling between the energy-momentum scalar $\mathcal{T}$ and the torsion scalar $T$. We consider two $f(T,\mathcal{T})$ functions, specifically $f(T,\mathcal{T})=\alpha T + \beta \mathcal{T}$ and $f(T,\mathcal{T})=\alpha \sqrt{-T} + \beta \mathcal{T}$, where $\alpha$ and $\beta$ are arbitrary constants, along with the fluid part incorporating the coefficient of bulk viscosity $\zeta=\zeta_0 > 0$. We calculate the analytical solutions of the corresponding field equations for a flat FLRW environment, and then we constrain the free parameters of the obtained solution using CC, Pantheon+, and the CC+Pantheon+ samples. We perform the Bayesian statistical analysis to estimate the posterior probability utilizing the likelihood function and the MCMC random sampling technique. Further, to assess the effectiveness of our MCMC analysis, we estimate the corresponding AIC and BIC values, and we find that there is strong evidence supporting the assumed viscous modified gravity models for all three data sets. Also, we find that the linear model precisely mimics the $\Lambda$CDM model. We also investigate the evolutionary behavior of some prominent cosmological parameters. We observe that the effective equation of state parameter for both models predict the accelerating behavior of the cosmic expansion phase. In addition, from the statefinder test, we find that the parameters of the considered MOG models favor the quintessence-type behavior. |
1812.08686 | Marvin L\"uben | Marvin L\"uben, Edvard M\"ortsell and Angnis Schmidt-May | Bimetric cosmology is compatible with local tests of gravity | 6 pages, 2 figures | null | null | MPP-2018-303 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Kenna-Allison et.al. claimed that bimetric gravity cannot give rise
to a viable cosmological expansion history while at the same time being
compatible with local gravity tests. In this note we review that claim and
combine various results from the literature to provide several simple counter
examples. We conclude that the results of Kenna-Allison et.al. cannot hold in
general.
| [
{
"created": "Thu, 20 Dec 2018 16:38:47 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Oct 2019 19:02:15 GMT",
"version": "v2"
}
] | 2019-10-16 | [
[
"Lüben",
"Marvin",
""
],
[
"Mörtsell",
"Edvard",
""
],
[
"Schmidt-May",
"Angnis",
""
]
] | Recently, Kenna-Allison et.al. claimed that bimetric gravity cannot give rise to a viable cosmological expansion history while at the same time being compatible with local gravity tests. In this note we review that claim and combine various results from the literature to provide several simple counter examples. We conclude that the results of Kenna-Allison et.al. cannot hold in general. |
2407.01478 | Orhan Donmez | Orhan Donmez and Fatih Dogan | Estimating the possible QPOs of M87* from the parameters of a hairy Kerr
black hole | 39 pages, 11 figures, updated | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the dynamics of the shock cone formed around the
hairy Kerr black hole due to BHL accretion and investigate the QPO behaviors
resulting from the black hole-cone interaction, aiming to predict the QPO
frequencies that may occur around the M87* black hole. To achieve this, we use
the hairy Kerr black hole parameters consistent with the observed shadow
parameters of M87* as initial conditions in numerical simulations, revealing
the structure of the resulting shock cone and QPOs in a strong gravitational
field. Numerical calculations show that the deviation of the hairy Kerr black
hole from the Kerr metric and the hair parameters significantly influence the
complex behavior of the resulting QPOs. It is found that the Lense-Thirring
effect and the pressure modes trapped within the cone lead to the excitation of
QPOs. The hair parameter has been observed to suppress the resulting QPO
frequencies. The Lense-Thirring effect, in a strong gravitational field with a
black hole spin parameter of a/M > 0.7, also suppresses other modes and
generates high-frequency QPOs. It is predicted that the QPO frequencies
observed around the M87* black hole could span a wide range from nHz to mHz.
Using both Kerr and hairy Kerr gravities, the QPO frequencies formed around the
M87* black hole can be explained. Especially in cases where the black hole is
spinning rapidly, PSD analyses have shown very distinct low-frequency QPOs and
resonance conditions in both gravities. By comparing the results obtained from
numerical calculations with observational and analytical results, we discuss
the observability of the QPO frequencies that may occur around the M87* black
hole.
| [
{
"created": "Mon, 1 Jul 2024 17:09:35 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Aug 2024 21:33:36 GMT",
"version": "v2"
}
] | 2024-08-16 | [
[
"Donmez",
"Orhan",
""
],
[
"Dogan",
"Fatih",
""
]
] | In this paper, we study the dynamics of the shock cone formed around the hairy Kerr black hole due to BHL accretion and investigate the QPO behaviors resulting from the black hole-cone interaction, aiming to predict the QPO frequencies that may occur around the M87* black hole. To achieve this, we use the hairy Kerr black hole parameters consistent with the observed shadow parameters of M87* as initial conditions in numerical simulations, revealing the structure of the resulting shock cone and QPOs in a strong gravitational field. Numerical calculations show that the deviation of the hairy Kerr black hole from the Kerr metric and the hair parameters significantly influence the complex behavior of the resulting QPOs. It is found that the Lense-Thirring effect and the pressure modes trapped within the cone lead to the excitation of QPOs. The hair parameter has been observed to suppress the resulting QPO frequencies. The Lense-Thirring effect, in a strong gravitational field with a black hole spin parameter of a/M > 0.7, also suppresses other modes and generates high-frequency QPOs. It is predicted that the QPO frequencies observed around the M87* black hole could span a wide range from nHz to mHz. Using both Kerr and hairy Kerr gravities, the QPO frequencies formed around the M87* black hole can be explained. Especially in cases where the black hole is spinning rapidly, PSD analyses have shown very distinct low-frequency QPOs and resonance conditions in both gravities. By comparing the results obtained from numerical calculations with observational and analytical results, we discuss the observability of the QPO frequencies that may occur around the M87* black hole. |
0705.3024 | Steven Carlip | S. Carlip | Symmetries, Horizons, and Black Hole Entropy | 6 pages; first prize essay, 2007 Gravity Research Foundation essay
contest | Gen.Rel.Grav.39:1519-1523,2007; Int.J.Mod.Phys.D17:659-664,2008 | 10.1007/s10714-007-0467-6 10.1142/S0218271808012401 | null | gr-qc hep-th | null | Black holes behave as thermodynamic systems, and a central task of any
quantum theory of gravity is to explain these thermal properties. A statistical
mechanical description of black hole entropy once seemed remote, but today we
suffer an embarrassment of riches: despite counting very different states, many
inequivalent approaches to quantum gravity obtain identical results. Such
``universality'' may reflect an underlying two-dimensional conformal symmetry
near the horizon, which can be powerful enough to control the thermal
characteristics independent of other details of the theory. This picture
suggests an elegant description of the relevant degrees of freedom as
Goldstone-boson-like excitations arising from symmetry breaking by the
conformal anomaly.
| [
{
"created": "Mon, 21 May 2007 17:45:39 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | Black holes behave as thermodynamic systems, and a central task of any quantum theory of gravity is to explain these thermal properties. A statistical mechanical description of black hole entropy once seemed remote, but today we suffer an embarrassment of riches: despite counting very different states, many inequivalent approaches to quantum gravity obtain identical results. Such ``universality'' may reflect an underlying two-dimensional conformal symmetry near the horizon, which can be powerful enough to control the thermal characteristics independent of other details of the theory. This picture suggests an elegant description of the relevant degrees of freedom as Goldstone-boson-like excitations arising from symmetry breaking by the conformal anomaly. |
0805.2955 | Andrew Randono | Andrew Randono | A Mesoscopic Quantum Gravity Effect | 10 pages, 2 figures | Gen.Rel.Grav.42:1909-1917,2010 | 10.1007/s10714-010-0982-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the symmetry reduced form of a non-perturbative solution to the
constraints of quantum gravity corresponding to quantum de Sitter space. The
system has a remarkably precise analogy with the non-relativistic formulation
of a particle falling in a constant gravitational field that we exploit in our
anaylsis. We find that the solution reduces to de Sitter space in the
semi-classical limit, but the uniquely quantum features of the solution have
peculiar property. Namely, the unambiguous quantum structures are neither of
Planck scale nor of cosmological scale. Instead, we find a periodicity in the
volume of the universe whose period, using the observed value of the
cosmological constant, is on the order of the volume of the proton.
| [
{
"created": "Mon, 19 May 2008 21:02:05 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Randono",
"Andrew",
""
]
] | We explore the symmetry reduced form of a non-perturbative solution to the constraints of quantum gravity corresponding to quantum de Sitter space. The system has a remarkably precise analogy with the non-relativistic formulation of a particle falling in a constant gravitational field that we exploit in our anaylsis. We find that the solution reduces to de Sitter space in the semi-classical limit, but the uniquely quantum features of the solution have peculiar property. Namely, the unambiguous quantum structures are neither of Planck scale nor of cosmological scale. Instead, we find a periodicity in the volume of the universe whose period, using the observed value of the cosmological constant, is on the order of the volume of the proton. |
1811.03446 | Marco Cariglia Dr | Marco Cariglia | General theory of Galilean gravity | 6 pages, no figures. V2: references added | null | 10.1103/PhysRevD.98.084057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the complete theory of Newton-Cartan gravity in a curved spacetime
by considering the large $c$ limit of the vielbein formulation of General
Relativity. Milne boosts originate from local Lorentzian transformations, and
the special cases of torsionless and twistless torsional geometries are
explained in the context of the larger locally Lorentzian theory. We write the
action for Newton-Cartan fields in the first order Palatini formalism, and the
large $c$ limit of the Einstein equations. Finally, we obtain the generalised
Eisenhart-Duval lift of the metric that plays an important role in
non-relativistic holography.
| [
{
"created": "Tue, 6 Nov 2018 22:26:46 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2018 14:42:36 GMT",
"version": "v2"
}
] | 2018-11-13 | [
[
"Cariglia",
"Marco",
""
]
] | We obtain the complete theory of Newton-Cartan gravity in a curved spacetime by considering the large $c$ limit of the vielbein formulation of General Relativity. Milne boosts originate from local Lorentzian transformations, and the special cases of torsionless and twistless torsional geometries are explained in the context of the larger locally Lorentzian theory. We write the action for Newton-Cartan fields in the first order Palatini formalism, and the large $c$ limit of the Einstein equations. Finally, we obtain the generalised Eisenhart-Duval lift of the metric that plays an important role in non-relativistic holography. |
gr-qc/9910063 | null | G. K\"albermann (Soil and Water department, Faculty of Agriculure,
Hebrew University, Israel) | Communication through an extra dimension | Latex format, 12 pages. References modified | Int.J.Mod.Phys. A15 (2000) 3197-3206 | 10.1142/S0217751X00001920 | null | gr-qc hep-ph hep-th | null | If our visible universe is considered a trapped shell in a five-dimensional
hyper-universe, all matter in it may be connected by superluminal signals
traveling through the fifth dimension. Events in the shell are still causal,
however, the propagation of signals proceeds at different velocities depending
on the fifth coordinate.
| [
{
"created": "Tue, 19 Oct 1999 07:59:36 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 1999 07:34:43 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Kälbermann",
"G.",
"",
"Soil and Water department, Faculty of Agriculure,\n Hebrew University, Israel"
]
] | If our visible universe is considered a trapped shell in a five-dimensional hyper-universe, all matter in it may be connected by superluminal signals traveling through the fifth dimension. Events in the shell are still causal, however, the propagation of signals proceeds at different velocities depending on the fifth coordinate. |
1410.1894 | Carlos Molina Mendes | M. C. Baldiotti, Walace S. Elias, C. Molina, Thiago S. Pereira | Thermodynamics of quantum photon spheres | Published version | Phys. Rev. D 90, 104025 (2014) | 10.1103/PhysRevD.90.104025 | null | gr-qc astro-ph.HE hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Photon spheres, surfaces where massless particles are confined in closed
orbits, are expected to be common astrophysical structures surrounding
ultracompact objects. In this paper a semiclassical treatment of a photon
sphere is proposed. We consider the quantum Maxwell field and derive its energy
spectra. A thermodynamic approach for the quantum photon sphere is developed
and explored. Within this treatment, an expression for the spectral energy
density of the emitted radiation is presented. Our results suggest that photon
spheres, when thermalized with their environment, have nonusual thermodynamic
properties, which could lead to distinct observational signatures.
| [
{
"created": "Tue, 7 Oct 2014 20:15:50 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Nov 2014 17:51:48 GMT",
"version": "v2"
}
] | 2014-11-24 | [
[
"Baldiotti",
"M. C.",
""
],
[
"Elias",
"Walace S.",
""
],
[
"Molina",
"C.",
""
],
[
"Pereira",
"Thiago S.",
""
]
] | Photon spheres, surfaces where massless particles are confined in closed orbits, are expected to be common astrophysical structures surrounding ultracompact objects. In this paper a semiclassical treatment of a photon sphere is proposed. We consider the quantum Maxwell field and derive its energy spectra. A thermodynamic approach for the quantum photon sphere is developed and explored. Within this treatment, an expression for the spectral energy density of the emitted radiation is presented. Our results suggest that photon spheres, when thermalized with their environment, have nonusual thermodynamic properties, which could lead to distinct observational signatures. |
1604.06369 | Sanjeev S. Seahra | Jack Gegenberg, Shohreh Rahmati, Sanjeev S. Seahra | A big bounce, slow-roll inflation and dark energy from conformal gravity | 8 pages, 3 figures, references added, version matches the one
published in PRD | Phys. Rev. D 95, 043509 (2017) | 10.1103/PhysRevD.95.043509 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the cosmological sector of a gauge theory of gravity based on the
SO(4,2) conformal group of Minkowski space. We allow for conventional matter
coupled to the spacetime metric as well as matter coupled to the field that
gauges special conformal transformations. An effective cosmological constant is
generated dynamically via solution of the equations of motion, and this allows
us to recover the late time acceleration of the universe. Furthermore,
gravitational fields sourced by ordinary cosmological matter (i.e. dust and
radiation) are significantly weakened in the very early universe, which has the
effect of replacing the big bang with a big bounce. Finally, we find that this
bounce is followed by a period of nearly-exponential slow roll inflation that
can last long enough to explain the large scale homogeneity of the cosmic
microwave background.
| [
{
"created": "Thu, 21 Apr 2016 16:06:07 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Apr 2016 13:51:06 GMT",
"version": "v2"
},
{
"created": "Mon, 1 May 2017 13:32:34 GMT",
"version": "v3"
}
] | 2017-05-02 | [
[
"Gegenberg",
"Jack",
""
],
[
"Rahmati",
"Shohreh",
""
],
[
"Seahra",
"Sanjeev S.",
""
]
] | We examine the cosmological sector of a gauge theory of gravity based on the SO(4,2) conformal group of Minkowski space. We allow for conventional matter coupled to the spacetime metric as well as matter coupled to the field that gauges special conformal transformations. An effective cosmological constant is generated dynamically via solution of the equations of motion, and this allows us to recover the late time acceleration of the universe. Furthermore, gravitational fields sourced by ordinary cosmological matter (i.e. dust and radiation) are significantly weakened in the very early universe, which has the effect of replacing the big bang with a big bounce. Finally, we find that this bounce is followed by a period of nearly-exponential slow roll inflation that can last long enough to explain the large scale homogeneity of the cosmic microwave background. |
gr-qc/0112050 | Julio Cesar Fabris | Julio C. Fabris | In the Search of Singularity-Free Cosmological Models in Effective
Actions | Latex file, 14 pages, to appear in the "Mario Novello Festschrift" | null | null | null | gr-qc | null | Fundamental theories, like strings, supergravity, Kaluza-Klein, lead after
dimensional reduction and a suitable choice of field configurations, to an
effective action in four dimensions where gravity is coupled non-mininally to
one scalar field, and minimally to another scalar field. These scalar fields
couple non-trivially between themselves. A radiation field is also considered
in this effective action. All the possibilities connected to those fundamental
theories are labeled by two parameters $n$ (related to the non-trivial coupling
of the scalar fields) and $\omega$, connected to the coupling of the
Brans-Dicke like field to gravity. Exact solutions are found, exhibiting a
singulariy-free behaviour, from the four dimensional point of view, for some
values of those parameter. The flatness and horizon problems for these
solutions are also analyzed. It is discussed to which extent the solutions
found are non-singular from the point of view of the original frames. This
reveals to be a much complex problem.
| [
{
"created": "Wed, 19 Dec 2001 19:16:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fabris",
"Julio C.",
""
]
] | Fundamental theories, like strings, supergravity, Kaluza-Klein, lead after dimensional reduction and a suitable choice of field configurations, to an effective action in four dimensions where gravity is coupled non-mininally to one scalar field, and minimally to another scalar field. These scalar fields couple non-trivially between themselves. A radiation field is also considered in this effective action. All the possibilities connected to those fundamental theories are labeled by two parameters $n$ (related to the non-trivial coupling of the scalar fields) and $\omega$, connected to the coupling of the Brans-Dicke like field to gravity. Exact solutions are found, exhibiting a singulariy-free behaviour, from the four dimensional point of view, for some values of those parameter. The flatness and horizon problems for these solutions are also analyzed. It is discussed to which extent the solutions found are non-singular from the point of view of the original frames. This reveals to be a much complex problem. |
1301.0200 | Remo Garattini | Remo Garattini and Gianluca Mandanici | Finite Zero Point Gravitational Energy in the context of Modified
Dispersion Relations | 3 pages; contribution to the proceedings of the Thirteenth Marcel
Grossmann Meeting, Stockholm University, Sweden, 1-7 July, 2012; based on a
talk in the ST1"Planckian and Transplanckian Physics" parallel session | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the Zero Point Energy in a spherically symmetric background
distorted at high energy as predicted by Gravity's Rainbow. In this context we
setup a Sturm-Liouville problem with the cosmological constant considered as
the associated eigenvalue. The eigenvalue equation is a reformulation of the
Wheeler-DeWitt equation. We find that the ordinary divergences can here be
handled by an appropriate choice of the rainbow's functions, in contrast to
what happens in other conventional approaches.
| [
{
"created": "Wed, 2 Jan 2013 10:15:32 GMT",
"version": "v1"
}
] | 2013-01-03 | [
[
"Garattini",
"Remo",
""
],
[
"Mandanici",
"Gianluca",
""
]
] | We compute the Zero Point Energy in a spherically symmetric background distorted at high energy as predicted by Gravity's Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. We find that the ordinary divergences can here be handled by an appropriate choice of the rainbow's functions, in contrast to what happens in other conventional approaches. |
gr-qc/0109029 | Krasnikov | S. Krasnikov | The time travel paradox | Minor changes + an explanatory note concerning the lions with the
same world lines | Phys.Rev. D65 (2002) 064013 | 10.1103/PhysRevD.65.064013 | null | gr-qc | null | We define the time travel paradox in physical terms and prove its existence
by constructing an explicit example. We argue further that in theories -- such
as general relativity -- where the spacetime geometry is subject to nothing but
differential equations and initial data no paradoxes arise.
| [
{
"created": "Mon, 10 Sep 2001 00:08:32 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2002 22:25:06 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Krasnikov",
"S.",
""
]
] | We define the time travel paradox in physical terms and prove its existence by constructing an explicit example. We argue further that in theories -- such as general relativity -- where the spacetime geometry is subject to nothing but differential equations and initial data no paradoxes arise. |
gr-qc/9704006 | Diego Torres | Diego F. Torres | Boson Stars in General Scalar-Tensor Gravitation: Equilibrium
Configurations | 19 pages in latex, 3 figures -postscript- may be sent via e-mail upon
request | Phys.Rev.D56:3478-3484,1997 | 10.1103/PhysRevD.56.3478 | null | gr-qc | null | We study equilibrium configurations of boson stars in the framework of
general scalar-tensor theories of gravitation. We analyse several possible
couplings, with acceptable weak field limit and, when known, nucleosynthesis
bounds, in order to work in the cosmologically more realistic cases of this
kind of theories. We found that for general scalar-tensor gravitation, the
range of masses boson stars might have is comparable with the general
relativistic case. We also analyse the possible formation of boson stars along
different eras of cosmic evolution, allowing for the effective gravitational
constant far out form the star to deviate from its current value. In these
cases, we found that the boson stars masses are sensitive to this kind of
variations, within a typical few percent. We also study cases in which the
coupling is implicitly defined, through the dependence on the radial
coordinate, allowing it to have significant variations in the radius of the
structure.
| [
{
"created": "Wed, 2 Apr 1997 16:15:02 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Torres",
"Diego F.",
""
]
] | We study equilibrium configurations of boson stars in the framework of general scalar-tensor theories of gravitation. We analyse several possible couplings, with acceptable weak field limit and, when known, nucleosynthesis bounds, in order to work in the cosmologically more realistic cases of this kind of theories. We found that for general scalar-tensor gravitation, the range of masses boson stars might have is comparable with the general relativistic case. We also analyse the possible formation of boson stars along different eras of cosmic evolution, allowing for the effective gravitational constant far out form the star to deviate from its current value. In these cases, we found that the boson stars masses are sensitive to this kind of variations, within a typical few percent. We also study cases in which the coupling is implicitly defined, through the dependence on the radial coordinate, allowing it to have significant variations in the radius of the structure. |
2402.05461 | B. S. Ratanpal | R. Sharma, B. S. Ratanpal and Rinkal Patel | Anisotropic star with a linear equation of state (EOS) | nil | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of solutions defining the interior of a static, spherically
symmetric, compact anisotropic star is described by considering a new form of
the equation of state (EOS). The analytic solution is derived by using the
Finch and Skea ansatz for the metric potential g_rr, which has a clear
geometric interpretation for the related background spacetime. The model
parameters are fixed by smooth matching of the interior solution to the
Schwarzschild exterior metric over the bounding surface of the compact star,
together with the requirement that the radial pressure vanishes at the
boundary. Data available for the pulsar 4U1802030 has been utilized to analyze
the physical viability of the developed model. The model is shown to be stable.
| [
{
"created": "Thu, 8 Feb 2024 07:42:44 GMT",
"version": "v1"
}
] | 2024-02-09 | [
[
"Sharma",
"R.",
""
],
[
"Ratanpal",
"B. S.",
""
],
[
"Patel",
"Rinkal",
""
]
] | A family of solutions defining the interior of a static, spherically symmetric, compact anisotropic star is described by considering a new form of the equation of state (EOS). The analytic solution is derived by using the Finch and Skea ansatz for the metric potential g_rr, which has a clear geometric interpretation for the related background spacetime. The model parameters are fixed by smooth matching of the interior solution to the Schwarzschild exterior metric over the bounding surface of the compact star, together with the requirement that the radial pressure vanishes at the boundary. Data available for the pulsar 4U1802030 has been utilized to analyze the physical viability of the developed model. The model is shown to be stable. |
1912.05583 | Guillem Dom\`enech | Guillem Dom\`enech | Induced gravitational waves in a general cosmological background | revised version | null | 10.1142/S0218271820500285 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves are inevitably produced by second order terms in
cosmological perturbation theory. Most notably, the so-called induced
gravitational waves are a window to the small scales part of the primordial
spectrum of fluctuations and a key counterpart to the primordial black hole
scenario. However, semi-analytical solutions are only known for matter and
radiation domination eras. In this paper, we present new analytic integral
formulas for the induced gravitational waves on subhorizon scales in a general
cosmological background with a constant equation of state. We also discuss
applications to a peaked primordial scalar power spectrum and the primordial
black hole scenario.
| [
{
"created": "Wed, 11 Dec 2019 19:15:23 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Dec 2019 21:36:52 GMT",
"version": "v2"
},
{
"created": "Sun, 23 Feb 2020 16:28:32 GMT",
"version": "v3"
}
] | 2020-04-22 | [
[
"Domènech",
"Guillem",
""
]
] | Gravitational waves are inevitably produced by second order terms in cosmological perturbation theory. Most notably, the so-called induced gravitational waves are a window to the small scales part of the primordial spectrum of fluctuations and a key counterpart to the primordial black hole scenario. However, semi-analytical solutions are only known for matter and radiation domination eras. In this paper, we present new analytic integral formulas for the induced gravitational waves on subhorizon scales in a general cosmological background with a constant equation of state. We also discuss applications to a peaked primordial scalar power spectrum and the primordial black hole scenario. |
0804.3693 | Alan D. Rendall | Nikolaus Berndt and Alan D. Rendall | Isotropization in the approach to big rip singularities for Cardassian
models | 17 pages, 2 figures | Class.Quant.Grav.25:145007,2008 | 10.1088/0264-9381/25/14/145007 | AEI-2008-026 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cardassian models are an alternative to general relativity which have been
proposed as an approach to explaining accelerated cosmic expansion while
avoiding directly introducing dark energy. They are generally formulated only
in the homogeneous and isotropic case. In this paper an extension of the usual
formulation to general spatially homogeneous geometries is given. A
characteristic feature of many classes of Cardassian models is the occurrence
of big rip singularities where the scale factor tends to infinity after a
finite time. It is shown that big rip singularities are also widespread in more
general homogeneous cases. It is also shown that there is isotropization in the
approach to a big rip singularity which bears a strong resemblance to the
late-time isotropization observed in cosmological spacetimes which accelerate
forever in the future.
| [
{
"created": "Wed, 23 Apr 2008 11:38:45 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Berndt",
"Nikolaus",
""
],
[
"Rendall",
"Alan D.",
""
]
] | Cardassian models are an alternative to general relativity which have been proposed as an approach to explaining accelerated cosmic expansion while avoiding directly introducing dark energy. They are generally formulated only in the homogeneous and isotropic case. In this paper an extension of the usual formulation to general spatially homogeneous geometries is given. A characteristic feature of many classes of Cardassian models is the occurrence of big rip singularities where the scale factor tends to infinity after a finite time. It is shown that big rip singularities are also widespread in more general homogeneous cases. It is also shown that there is isotropization in the approach to a big rip singularity which bears a strong resemblance to the late-time isotropization observed in cosmological spacetimes which accelerate forever in the future. |
1905.02056 | Abbas Sherif | Abbas Sherif, Rituparno Goswami and Sunil Maharaj | Some Result on Cosmological and Astrophysical Horizons and Trapped
Surfaces | 26 pages, | Class. Quantum Grav. 36 (2019) 215001 | 10.1088/1361-6382/ab45bc | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of horizons of black holes in the $1+1+2$ covariant
setting and investigate various properties intrinsic to the geometry of the
foliation surfaces of these horizons. This is done by interpreting formulations
of various quantities in terms of the geometric and thermodynamic quantities.
We establish a causal classification for horizons in different classes of
spacetimes. We have also recovered results by Ben-Dov and Senovilla which put
cut-offs on the equation of state parameter $\sigma$, determining the
spacelike, timelike and non-expanding horizons in the the Robertson-Walker
class of spacetimes. We show that stability of marginally trapped surfaces
(MTS) in the Robertson-Walker spacetimes is only achievable under the
conditions of negative pressure, and also classify the spacelike future outer
trapping horizons (SFOTH) in the Robertson-Walker spacetimes via bounds on the
equation of state parameter $\sigma$. For the Lemaitre-Tolman-Bondi (LTB)
model, it is shown that a relationship between the energy density and the
electric part of the Weyl curvature, $\mathcal{E}$, gives the causal
classification of the MTTs. It is further shown that only spacelike MTTs are
foliated by stable MTS, and that this stability guarantees no shell crossing.
We also provide an explicit proof of the third law of black hole thermodynamics
for the LRS II class of spacetimes, and by extension, any spacetime whose
outgoing and ingoing null geodesics are normal to the MTS.
| [
{
"created": "Mon, 6 May 2019 14:12:22 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Oct 2019 18:48:49 GMT",
"version": "v2"
}
] | 2019-10-16 | [
[
"Sherif",
"Abbas",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Maharaj",
"Sunil",
""
]
] | We study the evolution of horizons of black holes in the $1+1+2$ covariant setting and investigate various properties intrinsic to the geometry of the foliation surfaces of these horizons. This is done by interpreting formulations of various quantities in terms of the geometric and thermodynamic quantities. We establish a causal classification for horizons in different classes of spacetimes. We have also recovered results by Ben-Dov and Senovilla which put cut-offs on the equation of state parameter $\sigma$, determining the spacelike, timelike and non-expanding horizons in the the Robertson-Walker class of spacetimes. We show that stability of marginally trapped surfaces (MTS) in the Robertson-Walker spacetimes is only achievable under the conditions of negative pressure, and also classify the spacelike future outer trapping horizons (SFOTH) in the Robertson-Walker spacetimes via bounds on the equation of state parameter $\sigma$. For the Lemaitre-Tolman-Bondi (LTB) model, it is shown that a relationship between the energy density and the electric part of the Weyl curvature, $\mathcal{E}$, gives the causal classification of the MTTs. It is further shown that only spacelike MTTs are foliated by stable MTS, and that this stability guarantees no shell crossing. We also provide an explicit proof of the third law of black hole thermodynamics for the LRS II class of spacetimes, and by extension, any spacetime whose outgoing and ingoing null geodesics are normal to the MTS. |
2301.10867 | Ewa Czuchry | Ewa Czuchry | Resolution of cosmological singularity in Ho\v{r}ava-Lifshitz cosmology | Submitted to Universe. Rewritten in order to remove repetitions from
the previous papers | Universe 9, 160 (2023) | 10.3390/universe9040160 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The standard $\Lambda$CDM model despite its agreement with observational data
still has some issues unaddressed, lie the problem of initial singularity.
Solving that problem usually requires modifications of general relativity.
However, there appeared the Ho\v{r}ava-Lifshitz (HL) theory of gravity, in
which equations governing cosmological evolution include a new term scaling
similarly as dark radiation term in the Friedmann equations, enabling a bounce
of the universe instead of initial singularity. This review describes past
works on a stability of such a bounce in different formulations of HL theory,
initial detailed balance scenario and further projectable versions containing
higher than quadratic term to the original action.
| [
{
"created": "Wed, 25 Jan 2023 23:29:22 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2023 21:26:37 GMT",
"version": "v2"
}
] | 2023-03-29 | [
[
"Czuchry",
"Ewa",
""
]
] | The standard $\Lambda$CDM model despite its agreement with observational data still has some issues unaddressed, lie the problem of initial singularity. Solving that problem usually requires modifications of general relativity. However, there appeared the Ho\v{r}ava-Lifshitz (HL) theory of gravity, in which equations governing cosmological evolution include a new term scaling similarly as dark radiation term in the Friedmann equations, enabling a bounce of the universe instead of initial singularity. This review describes past works on a stability of such a bounce in different formulations of HL theory, initial detailed balance scenario and further projectable versions containing higher than quadratic term to the original action. |
gr-qc/9712059 | Jose-Luis Rosales | Jose-Luis Rosales | Thermodynamics, topology and dimension of initial real tunneling
manifolds | null | null | null | FR-THEP-NR 97/34 | gr-qc | null | We develop the argument that initial real tunneling in quantum gravity be
contemplated as a thermodynamical analogous to a black hole condensate in
equilibrium with Hawking's radiation in a box. The total entropy is always
maximized in the Lorentzian sector of the manifold, and, in this sense,
tunneling is predicted.
| [
{
"created": "Fri, 12 Dec 1997 14:19:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rosales",
"Jose-Luis",
""
]
] | We develop the argument that initial real tunneling in quantum gravity be contemplated as a thermodynamical analogous to a black hole condensate in equilibrium with Hawking's radiation in a box. The total entropy is always maximized in the Lorentzian sector of the manifold, and, in this sense, tunneling is predicted. |
2011.06303 | Andrea Orizzonte | Alice Bonino, Stefano Camera, Lorenzo Fatibene and Andrea Orizzonte | Solar System Tests in Brans-Dicke and Palatini f(R)-theories | 22 pages, 2 figures | null | 10.1140/epjp/s13360-020-00982-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare Mercury's precession test in standard General Relativity (GR),
Brans-Dicke theories (BD), and Palatini f(R)-theories. We avoid post Newtonian
(PN) approximation and compute exact precession in these theories. We show that
the well-known mathematical equivalence between Palatini f(R)-theories and a
specific subset of BD theories does not extend to a really physical equivalence
among theories since equivalent models still allow different incompatible
precession for Mercury depending on the solution one chooses. As a result one
cannot use BD equivalence to rule out Palatini f(R)-theories. On the contrary,
we directly discuss that Palatini f(R)-theories can (and specific models do)
easily pass Solar System tests as Mercury's precession.
| [
{
"created": "Thu, 12 Nov 2020 10:35:04 GMT",
"version": "v1"
}
] | 2022-01-11 | [
[
"Bonino",
"Alice",
""
],
[
"Camera",
"Stefano",
""
],
[
"Fatibene",
"Lorenzo",
""
],
[
"Orizzonte",
"Andrea",
""
]
] | We compare Mercury's precession test in standard General Relativity (GR), Brans-Dicke theories (BD), and Palatini f(R)-theories. We avoid post Newtonian (PN) approximation and compute exact precession in these theories. We show that the well-known mathematical equivalence between Palatini f(R)-theories and a specific subset of BD theories does not extend to a really physical equivalence among theories since equivalent models still allow different incompatible precession for Mercury depending on the solution one chooses. As a result one cannot use BD equivalence to rule out Palatini f(R)-theories. On the contrary, we directly discuss that Palatini f(R)-theories can (and specific models do) easily pass Solar System tests as Mercury's precession. |
0803.1704 | Hideki Maeda | Hideki Maeda and Masato Nozawa | Static and symmetric wormholes respecting energy conditions in
Einstein-Gauss-Bonnet gravity | 10 pages, 2 tables; v2, typos corrected, references added; v3,
interpretation of the solution for n=5 in section IV corrected; v4, a very
final version to appear in Physical Review D | Phys.Rev.D78:024005,2008 | 10.1103/PhysRevD.78.024005 | CECS-PHY-08/03 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Properties of $n(\ge 5)$-dimensional static wormhole solutions are
investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological
constant $\Lambda$. We assume that the spacetime has symmetries corresponding
to the isometries of an $(n-2)$-dimensional maximally symmetric space with the
sectional curvature $k=\pm 1, 0$. It is also assumed that the metric is at
least $C^{2}$ and the $(n-2)$-dimensional maximally symmetric subspace is
compact. Depending on the existence or absence of the general relativistic
limit $\alpha \to 0$, solutions are classified into general relativistic (GR)
and non-GR branches, respectively, where $\alpha$ is the Gauss-Bonnet coupling
constant. We show that a wormhole throat respecting the dominant energy
condition coincides with a branch surface in the GR branch, otherwise the null
energy condition is violated there. In the non-GR branch, it is shown that
there is no wormhole solution for $k\alpha \ge 0$. For the matter field with
zero tangential pressure, it is also shown in the non-GR branch with
$k\alpha<0$ and $\Lambda \le 0$ that the dominant energy condition holds at the
wormhole throat if the radius of the throat satisfies some inequality. In the
vacuum case, a fine-tuning of the coupling constants is shown to be necessary
and the radius of a wormhole throat is fixed. Explicit wormhole solutions
respecting the energy conditions in the whole spacetime are obtained in the
vacuum and dust cases with $k=-1$ and $\alpha>0$.
| [
{
"created": "Wed, 12 Mar 2008 05:06:39 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Mar 2008 18:11:41 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Jun 2008 23:24:29 GMT",
"version": "v3"
},
{
"created": "Thu, 3 Jul 2008 22:00:31 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Maeda",
"Hideki",
""
],
[
"Nozawa",
"Masato",
""
]
] | Properties of $n(\ge 5)$-dimensional static wormhole solutions are investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological constant $\Lambda$. We assume that the spacetime has symmetries corresponding to the isometries of an $(n-2)$-dimensional maximally symmetric space with the sectional curvature $k=\pm 1, 0$. It is also assumed that the metric is at least $C^{2}$ and the $(n-2)$-dimensional maximally symmetric subspace is compact. Depending on the existence or absence of the general relativistic limit $\alpha \to 0$, solutions are classified into general relativistic (GR) and non-GR branches, respectively, where $\alpha$ is the Gauss-Bonnet coupling constant. We show that a wormhole throat respecting the dominant energy condition coincides with a branch surface in the GR branch, otherwise the null energy condition is violated there. In the non-GR branch, it is shown that there is no wormhole solution for $k\alpha \ge 0$. For the matter field with zero tangential pressure, it is also shown in the non-GR branch with $k\alpha<0$ and $\Lambda \le 0$ that the dominant energy condition holds at the wormhole throat if the radius of the throat satisfies some inequality. In the vacuum case, a fine-tuning of the coupling constants is shown to be necessary and the radius of a wormhole throat is fixed. Explicit wormhole solutions respecting the energy conditions in the whole spacetime are obtained in the vacuum and dust cases with $k=-1$ and $\alpha>0$. |
gr-qc/9804018 | Uwe Gunther | U. Guenther, A. Zhuk | Multidimensional perfect fluid cosmology with stable compactified
internal dimensions | 11 pages, Latex2e, uses IOP packages, submitted to Class.Quant.Grav | Class.Quant.Grav. 15 (1998) 2025-2035 | 10.1088/0264-9381/15/7/017 | null | gr-qc astro-ph hep-th | null | Multidimensional cosmological models in the presence of a bare cosmological
constant and a perfect fluid are investigated under dimensional reduction to
4-dimensional effective models. Stable compactification of the internal spaces
is achieved for a special class of perfect fluids. The external space behaves
in accordance with the standard Friedmann model. Necessary restrictions on the
parameters of the models are found to ensure dynamical behavior of the external
(our) universe in agreement with observations.
| [
{
"created": "Mon, 6 Apr 1998 10:55:38 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Guenther",
"U.",
""
],
[
"Zhuk",
"A.",
""
]
] | Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the parameters of the models are found to ensure dynamical behavior of the external (our) universe in agreement with observations. |
gr-qc/0111072 | Roberto Casadio | Roberto Casadio, Alessandro Fabbri, Lorenzo Mazzacurati | New black holes in the brane-world? | 4 pages, RevTeX, 3 eps figures, final version to appear in Phys. Rev.
D | Phys.Rev.D65:084040,2002 | 10.1103/PhysRevD.65.084040 | null | gr-qc astro-ph hep-th | null | It is known that the Einstein field equations in five dimensions admit more
general spherically symmetric black holes on the brane than four-dimensional
general relativity. We propose two families of analytic solutions (with
g_tt\not=-1/g_rr), parameterized by the ADM mass and the PPN parameter beta,
which reduce to Schwarzschild for beta=1. Agreement with observations requires
|\beta-1| |\eta|<<1. The sign of eta plays a key role in the global causal
structure, separating metrics which behave like Schwarzschild (eta<0) from
those similar to Reissner-Nordstroem (eta>0). In the latter case, we find a
family of black hole space-times completely regular.
| [
{
"created": "Wed, 21 Nov 2001 16:13:17 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2002 09:53:29 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Casadio",
"Roberto",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Mazzacurati",
"Lorenzo",
""
]
] | It is known that the Einstein field equations in five dimensions admit more general spherically symmetric black holes on the brane than four-dimensional general relativity. We propose two families of analytic solutions (with g_tt\not=-1/g_rr), parameterized by the ADM mass and the PPN parameter beta, which reduce to Schwarzschild for beta=1. Agreement with observations requires |\beta-1| |\eta|<<1. The sign of eta plays a key role in the global causal structure, separating metrics which behave like Schwarzschild (eta<0) from those similar to Reissner-Nordstroem (eta>0). In the latter case, we find a family of black hole space-times completely regular. |
1806.07782 | Muhammed Amir | Muhammed Amir, Kimet Jusufi, Ayan Banerjee, Sudan Hansraj | Shadow images of Kerr-like wormholes | 21 pages, 5 figures, accepted version for publication in CQG | Class. Quantum Grav. 36, 215007 (2019) | 10.1088/1361-6382/ab42be | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Investigations of shadows of astrophysical entities constitute a major source
of insight into the evolution of compact objects. Such effects depend on the
nature of the compact object and arise on account of the strong gravitational
lensing that casts a shadow on the bright background. We consider the Kerr-like
wormhole spacetime (Phys.\ Rev.\ D 97:024040, 2018), which is a modification of
the Kerr black hole that degenerates into wormholes for nonzero values of the
deviation parameter $\lambda^2$. The results suggest that the Kerr spacetime
can reproduce far away from the throat of the wormhole. We obtain the shapes of
the shadow for the Kerr-like wormholes and discuss the effect of the spin $a$,
the inclination angle $\theta_0$, and the deviation parameter $\lambda^2$ on
the size and nature of the shadow. As a consequence, it is discovered that the
shadow is distorted due to the spin as well as the deviation parameter and the
radius of the shadow decreases with $\lambda^2$ if the ADM mass of the
Kerr-like wormholes is considered.
| [
{
"created": "Wed, 20 Jun 2018 15:10:29 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Sep 2019 09:42:29 GMT",
"version": "v2"
}
] | 2019-10-21 | [
[
"Amir",
"Muhammed",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Banerjee",
"Ayan",
""
],
[
"Hansraj",
"Sudan",
""
]
] | Investigations of shadows of astrophysical entities constitute a major source of insight into the evolution of compact objects. Such effects depend on the nature of the compact object and arise on account of the strong gravitational lensing that casts a shadow on the bright background. We consider the Kerr-like wormhole spacetime (Phys.\ Rev.\ D 97:024040, 2018), which is a modification of the Kerr black hole that degenerates into wormholes for nonzero values of the deviation parameter $\lambda^2$. The results suggest that the Kerr spacetime can reproduce far away from the throat of the wormhole. We obtain the shapes of the shadow for the Kerr-like wormholes and discuss the effect of the spin $a$, the inclination angle $\theta_0$, and the deviation parameter $\lambda^2$ on the size and nature of the shadow. As a consequence, it is discovered that the shadow is distorted due to the spin as well as the deviation parameter and the radius of the shadow decreases with $\lambda^2$ if the ADM mass of the Kerr-like wormholes is considered. |
0803.1714 | Nima Khosravi | N. Khosravi, H. R. Sepangi | The cosmological implications of a fundamental length: a DSR inspired
de-Sitter spacetime | 10 pages, 3 figures, to appear in JCAP | JCAP 0804:011,2008 | 10.1088/1475-7516/2008/04/011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a de-Sitter model in the framework of a Deformed Special Relativity
(DSR) inspired structure. The effects of this framework appear as the existence
of a fundamental length which influences the behavior of the scale factor. We
show that such a deformation can either be used to control the unbounded growth
of the scale factor in the present accelerating phase or account for the
inflationary era in the early evolution of the universe.
| [
{
"created": "Wed, 12 Mar 2008 08:08:04 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Apr 2008 05:36:02 GMT",
"version": "v2"
}
] | 2009-12-15 | [
[
"Khosravi",
"N.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | We study a de-Sitter model in the framework of a Deformed Special Relativity (DSR) inspired structure. The effects of this framework appear as the existence of a fundamental length which influences the behavior of the scale factor. We show that such a deformation can either be used to control the unbounded growth of the scale factor in the present accelerating phase or account for the inflationary era in the early evolution of the universe. |
0911.0437 | Claudio Perini | Elena Magliaro, Claudio Perini, Leonardo Modesto | Fractal Space-Time from Spin-Foams | 5 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we perform the calculation of the spectral dimension of
spacetime in 4d quantum gravity using the Barrett-Crane (BC) spinfoam model. We
realize this considering a very simple decomposition of the 4d spacetime
already used in the graviton propagator calculation and we introduce a boundary
state which selects a classical geometry on the boundary. We obtain that the
spectral dimension of the spacetime runs from $\approx 2$ to 4, across a
$\approx 1.5$ phase, when the energy of a probe scalar field decreases from
high $E \lesssim E_P/25$ to low energy. The spectral dimension at the Planck
scale $E \approx E_P$ depends on the areas spectrum used in the calculation.
For three different spectra $l_P^2 \sqrt{j(j+1)}$, $l_P^2 (2 j+1)$ and $l_P^2
j$ we find respectively dimension $\approx 2.31$, 2.45 and 2.08.
| [
{
"created": "Mon, 2 Nov 2009 21:21:12 GMT",
"version": "v1"
}
] | 2009-11-04 | [
[
"Magliaro",
"Elena",
""
],
[
"Perini",
"Claudio",
""
],
[
"Modesto",
"Leonardo",
""
]
] | In this paper we perform the calculation of the spectral dimension of spacetime in 4d quantum gravity using the Barrett-Crane (BC) spinfoam model. We realize this considering a very simple decomposition of the 4d spacetime already used in the graviton propagator calculation and we introduce a boundary state which selects a classical geometry on the boundary. We obtain that the spectral dimension of the spacetime runs from $\approx 2$ to 4, across a $\approx 1.5$ phase, when the energy of a probe scalar field decreases from high $E \lesssim E_P/25$ to low energy. The spectral dimension at the Planck scale $E \approx E_P$ depends on the areas spectrum used in the calculation. For three different spectra $l_P^2 \sqrt{j(j+1)}$, $l_P^2 (2 j+1)$ and $l_P^2 j$ we find respectively dimension $\approx 2.31$, 2.45 and 2.08. |
2207.00968 | Vinod Bhardwaj Dr. | Vinod Kumar Bhardwaj, Priyanka Garg, Anirudh Pradhan, Syamala
Krishnannair | Corrected holographic dark energy with power-law entropy and Hubble
Horizon cut-off in FRW Universe | 18 pages, 12 figures | Chinese Journal of Physics (2022) | 10.1016/j.cjph.2022.06.028 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In the present work, we investigate the power-law entropy corrected
holographic dark energy (PLECHDE) model with Hubble horizon cutoff. We use 46
observational Hubble data points in the redshift range $0 \leq z \leq 2.36$ to
determine the present Hubble constant $H_0$ and the model parameter $n$. It
represents a phase transition of the universe from deceleration to acceleration
and has the transition point at $z_t = 0.71165$.
We investigate the observational constraints on the model and calculate some
relevant cosmological parameters. We examine the model's validity by drawing
state-finder parameters that yield the result compatible with the modern
observational data. The model's physical and geometrical characteristics are
also explored, and they are shown to match well with current observations of
observational Hubble data (OHD) and the latest joint light curves(JLA)
datasets.
| [
{
"created": "Sun, 3 Jul 2022 06:56:42 GMT",
"version": "v1"
}
] | 2022-07-05 | [
[
"Bhardwaj",
"Vinod Kumar",
""
],
[
"Garg",
"Priyanka",
""
],
[
"Pradhan",
"Anirudh",
""
],
[
"Krishnannair",
"Syamala",
""
]
] | In the present work, we investigate the power-law entropy corrected holographic dark energy (PLECHDE) model with Hubble horizon cutoff. We use 46 observational Hubble data points in the redshift range $0 \leq z \leq 2.36$ to determine the present Hubble constant $H_0$ and the model parameter $n$. It represents a phase transition of the universe from deceleration to acceleration and has the transition point at $z_t = 0.71165$. We investigate the observational constraints on the model and calculate some relevant cosmological parameters. We examine the model's validity by drawing state-finder parameters that yield the result compatible with the modern observational data. The model's physical and geometrical characteristics are also explored, and they are shown to match well with current observations of observational Hubble data (OHD) and the latest joint light curves(JLA) datasets. |
1805.05665 | Elias C. Vagenas | Saurya Das, Mir Faizal, Elias C. Vagenas | Renormalizing gravity: a new insight into an old problem | This essay received an honorable mention in the 2018 Gravity Research
Foundation Essay Competition on Gravitation; v2: change of counting of d.o.f.
from (3+1) to (d+1) spacetime dimensions, references updated | Int.J.Mod.Phys. D27 (2018) 1847002 | 10.1142/S0218271818470028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that perturbative quantum gravity is non-renormalizable. The
metric or vierbein has generally been used as the variable to quantize in
perturbative quantum gravity. In this essay, we show that one can use the spin
connection instead, in which case it is possible to obtain a ghost-free
renormalizable theory of quantum gravity. Furthermore in this approach,
gravitational analogs of particle physics phenomena can be studied. In
particular, we study the gravitational Higgs mechanism using spin connection as
a gauge field, and show that this provides a mechanism for the effective
reduction in the dimensionality of spacetime.
| [
{
"created": "Tue, 15 May 2018 09:37:27 GMT",
"version": "v1"
},
{
"created": "Sun, 27 May 2018 19:13:44 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Jul 2018 14:31:46 GMT",
"version": "v3"
}
] | 2018-07-20 | [
[
"Das",
"Saurya",
""
],
[
"Faizal",
"Mir",
""
],
[
"Vagenas",
"Elias C.",
""
]
] | It is well-known that perturbative quantum gravity is non-renormalizable. The metric or vierbein has generally been used as the variable to quantize in perturbative quantum gravity. In this essay, we show that one can use the spin connection instead, in which case it is possible to obtain a ghost-free renormalizable theory of quantum gravity. Furthermore in this approach, gravitational analogs of particle physics phenomena can be studied. In particular, we study the gravitational Higgs mechanism using spin connection as a gauge field, and show that this provides a mechanism for the effective reduction in the dimensionality of spacetime. |
gr-qc/9302033 | Charles Torre | C. G. Torre and I. M. Anderson | Symmetries of the Einstein Equations | 15 pages, FTG-114-USU, Plain TeX | Phys.Rev.Lett. 70 (1993) 3525-3529 | 10.1103/PhysRevLett.70.3525 | null | gr-qc | null | Generalized symmetries of the Einstein equations are infinitesimal
transformations of the spacetime metric that formally map solutions of the
Einstein equations to other solutions. The infinitesimal generators of these
symmetries are assumed to be local, \ie at a given spacetime point they are
functions of the metric and an arbitrary but finite number of derivatives of
the metric at the point. We classify all generalized symmetries of the vacuum
Einstein equations in four spacetime dimensions and find that the only
generalized symmetry transformations consist of: (i) constant scalings of the
metric (ii) the infinitesimal action of generalized spacetime diffeomorphisms.
Our results rule out a large class of possible ``observables'' for the
gravitational field, and suggest that the vacuum Einstein equations are not
integrable.
| [
{
"created": "Tue, 23 Feb 1993 22:53:10 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Torre",
"C. G.",
""
],
[
"Anderson",
"I. M.",
""
]
] | Generalized symmetries of the Einstein equations are infinitesimal transformations of the spacetime metric that formally map solutions of the Einstein equations to other solutions. The infinitesimal generators of these symmetries are assumed to be local, \ie at a given spacetime point they are functions of the metric and an arbitrary but finite number of derivatives of the metric at the point. We classify all generalized symmetries of the vacuum Einstein equations in four spacetime dimensions and find that the only generalized symmetry transformations consist of: (i) constant scalings of the metric (ii) the infinitesimal action of generalized spacetime diffeomorphisms. Our results rule out a large class of possible ``observables'' for the gravitational field, and suggest that the vacuum Einstein equations are not integrable. |
0705.3973 | Jordi Sod-Hoffs | Jordi Sod-Hoffs, Egor D Rodchenko | On the properties of the Ernst-Manko-Ruiz equatorially antisymmetric
solutions | 15 pages, 5 figures, submitted to Classical and Quantum Gravity | Class.Quant.Grav.24:4617-4630,2007 | 10.1088/0264-9381/24/18/004 | null | gr-qc | null | Two new equatorially antisymmetric solutions recently published by Ernst et
al are studied. For both solutions the full set of metric functions is derived
in explicit analytic form and the behavior of the solutions on the symmetry
axis is analyzed. It is shown in particular that two counter-rotating equal
Kerr-Newman-NUT objects will be in equilibrium when the condition
m^2+\nu^2=q^2+b^2 is verified, whereas two counter-rotating equal masses
endowed with arbitrary magnetic and electric dipole moments cannot reach
equilibrium under any choice of the parameters, so that a massless strut
between them will always be present.
| [
{
"created": "Sun, 27 May 2007 19:06:04 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sod-Hoffs",
"Jordi",
""
],
[
"Rodchenko",
"Egor D",
""
]
] | Two new equatorially antisymmetric solutions recently published by Ernst et al are studied. For both solutions the full set of metric functions is derived in explicit analytic form and the behavior of the solutions on the symmetry axis is analyzed. It is shown in particular that two counter-rotating equal Kerr-Newman-NUT objects will be in equilibrium when the condition m^2+\nu^2=q^2+b^2 is verified, whereas two counter-rotating equal masses endowed with arbitrary magnetic and electric dipole moments cannot reach equilibrium under any choice of the parameters, so that a massless strut between them will always be present. |
1111.0825 | Juhua Chen | Juhua Chen, Hao Liao and Yongjiu Wang | Scattering of Scalar Waves by Schwarzschild Black Hole Immersed in
Magnetic Field | 7 pages, 10 figures. arXiv admin note: substantial text overlap with
arXiv:0707.1156 by other authors | Eur. Phys. J. C 73, 2395(2013) | 10.1140/epjc/s10052-013-2395-9 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | The magnetic field is one of the most important constituents of the cosmic
space and one of the main sources of the dynamics of interacting matter in the
universe. The astronomical observations imply the existence of a strong
magnetic fields of up to $10^4-10^8G$ near supermassive black holes in the
active galactic nuclei and even around stellar mass black holes. In this paper,
with the quantum scattering theory, we analysis the Schr\"{o}edinger-type
scalar wave equation of black hole immersed in magnetic field and numerically
investigate its absorption cross section and scattering cross section. We find
that the absorption cross sections oscillate about the geometric optical value
in the high frequency regime. Furthermore in low frequency regime, the magnetic
field makes the absorption cross section weaker and this effect is more
obviously on lower frequency brand. On the other hand, for the effects of
scattering cross sections for the black hole immersed in magnetic field, we
find that the magnetic field makes the scattering flux weaker and its width
narrower in the forward direction. We find that there also exists the glory
phenomenon along the backforward direction. At fixed frequency, the glory peak
is higher and the glory width becomes narrower due to the black hole immersed
in magnetic field.
| [
{
"created": "Thu, 3 Nov 2011 12:57:21 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Chen",
"Juhua",
""
],
[
"Liao",
"Hao",
""
],
[
"Wang",
"Yongjiu",
""
]
] | The magnetic field is one of the most important constituents of the cosmic space and one of the main sources of the dynamics of interacting matter in the universe. The astronomical observations imply the existence of a strong magnetic fields of up to $10^4-10^8G$ near supermassive black holes in the active galactic nuclei and even around stellar mass black holes. In this paper, with the quantum scattering theory, we analysis the Schr\"{o}edinger-type scalar wave equation of black hole immersed in magnetic field and numerically investigate its absorption cross section and scattering cross section. We find that the absorption cross sections oscillate about the geometric optical value in the high frequency regime. Furthermore in low frequency regime, the magnetic field makes the absorption cross section weaker and this effect is more obviously on lower frequency brand. On the other hand, for the effects of scattering cross sections for the black hole immersed in magnetic field, we find that the magnetic field makes the scattering flux weaker and its width narrower in the forward direction. We find that there also exists the glory phenomenon along the backforward direction. At fixed frequency, the glory peak is higher and the glory width becomes narrower due to the black hole immersed in magnetic field. |
0807.0315 | Th. M. Nieuwenhuizen | Theo M. Nieuwenhuizen | Supermassive Black Holes as Giant Bose-Einstein Condensates | 6 pages, no figures | Europhys.Lett.83:10008,2008 | 10.1209/0295-5075/83/10008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Schwarzschild metric has a divergent energy density at the horizon, which
motivates a new approach to black holes. If matter is spread uniformly
throughout the interior of a supermassive black hole, with mass $M\sim M_\star=
2.34 10^8M_\odot$, it may arise from a Bose-Einstein condensate of densely
packed H-atoms. Within the Relativistic Theory of Gravitation with a positive
cosmological constant, a bosonic quantum field is coupled to the curvature
scalar. In the Bose-Einstein condensed groundstate an exact, selfconsistent
solution for the metric is presented. It is regular with a specific shape at
the origin. The redshift at the horizon is finite but large, $z\sim
10^{14}$$M_\star/M$. The binding energy remains as an additional parameter to
characterize the BH; alternatively, the mass observed at infinity can be any
fraction of the rest mass of its constituents.
| [
{
"created": "Wed, 2 Jul 2008 10:01:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nieuwenhuizen",
"Theo M.",
""
]
] | The Schwarzschild metric has a divergent energy density at the horizon, which motivates a new approach to black holes. If matter is spread uniformly throughout the interior of a supermassive black hole, with mass $M\sim M_\star= 2.34 10^8M_\odot$, it may arise from a Bose-Einstein condensate of densely packed H-atoms. Within the Relativistic Theory of Gravitation with a positive cosmological constant, a bosonic quantum field is coupled to the curvature scalar. In the Bose-Einstein condensed groundstate an exact, selfconsistent solution for the metric is presented. It is regular with a specific shape at the origin. The redshift at the horizon is finite but large, $z\sim 10^{14}$$M_\star/M$. The binding energy remains as an additional parameter to characterize the BH; alternatively, the mass observed at infinity can be any fraction of the rest mass of its constituents. |
gr-qc/9301001 | Barnich Glenn | Olivier Coussaert and Marc Henneaux | Bianchi Cosmological Models and Gauge Symmetries | 16 pages, Latex file, ULB-PMIF-92/10 | Class.Quant.Grav.10:1607-1618,1993 | 10.1088/0264-9381/10/8/018 | null | gr-qc | null | We analyze carefully the problem of gauge symmetries for Bianchi models, from
both the geometrical and dynamical points of view. Some of the geometrical
definitions of gauge symmetries (=``homogeneity preserving diffeomorphisms'')
given in the literature do not incorporate the crucial feature that local gauge
transformations should be independent at each point of the manifold of the
independent variables ( = time for Bianchi models), i.e, should be arbitrarily
localizable ( in time). We give a geometrical definition of homogeneity
preserving diffeomorphisms that does not possess this shortcoming. The proposed
definition has the futher advantage of coinciding with the dynamical definition
based on the invariance of the action ( in Lagrangian or Hamiltonian form). We
explicitly verify the equivalence of the Lagrangian covariant phase space with
the Hamiltonian reduced phase space. Remarks on the use of the Ashtekar
variables in Bianchi models are also given.
| [
{
"created": "Tue, 5 Jan 1993 14:51:07 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Coussaert",
"Olivier",
""
],
[
"Henneaux",
"Marc",
""
]
] | We analyze carefully the problem of gauge symmetries for Bianchi models, from both the geometrical and dynamical points of view. Some of the geometrical definitions of gauge symmetries (=``homogeneity preserving diffeomorphisms'') given in the literature do not incorporate the crucial feature that local gauge transformations should be independent at each point of the manifold of the independent variables ( = time for Bianchi models), i.e, should be arbitrarily localizable ( in time). We give a geometrical definition of homogeneity preserving diffeomorphisms that does not possess this shortcoming. The proposed definition has the futher advantage of coinciding with the dynamical definition based on the invariance of the action ( in Lagrangian or Hamiltonian form). We explicitly verify the equivalence of the Lagrangian covariant phase space with the Hamiltonian reduced phase space. Remarks on the use of the Ashtekar variables in Bianchi models are also given. |
1110.1913 | Xue-Mei Deng | Xue-Mei Deng | A Modified Generalized Chaplygin Gas as the Unified Dark Matter-Dark
Energy Revisited | 23 pages,15 figures; Accepted by Brazilian Journal of Physics | Brazilian Journal of Physics, Volume 41, Issue 4-6, pp.
333-348,2011 | 10.1007/s13538-011-0044-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modified generalized Chaplygin gas (MGCG) is considered as the unified dark
matter-dark energy revisited. The character of MGCG is endued with the dual
role, which behaves as matter at early times and as an quiessence dark energy
at late times. The equation of state for MGCG is
$p=-\alpha\rho/(1+\alpha)-\vartheta(z)\rho^{-\alpha}/(1+\alpha) $, where
$\vartheta(z)=-[\rho_{0c}(1+z)^{3}]^{(1+\alpha)}(1-\Omega_{0B})^{\alpha}\{\alpha\Omega_{0DM}+
\Omega_{0DE}[\omega_{DE}+\alpha(1+\omega_{DE})](1+z)^{3\omega_{DE}(1+\alpha)}\}$.
Some cosmological quantities, such as the densities of different components of
the universe $\Omega_{i}$ ($i$ respectively denotes baryons, dark matter and
dark energy) and the deceleration parameter $q$, are obtained. The present
deceleration parameter $q_{0}$, the transition redshift $z_{T}$ and the
redshift $z_{eq}$, which describes the epoch when the densities in dark matter
and dark energy are equal, are also calculated. To distinguish MGCG from
others, we then apply the Statefinder diagnostic. Later on, the parameters
($\alpha$ and $\omega_{DE}$) of MGCG are constrained by combination of the
sound speed $c^{2}_{s}$, the age of the universe $t_{0}$, the growth factor $m$
and the bias parameter $b$. It yields
$\alpha=-3.07^{+5.66}_{-4.98}\times10^{-2}$ and
$\omega_{DE}=-1.05^{+0.06}_{-0.11}$. Through the analysis of the growth of
density perturbations for MGCG, it is found that the energy will transfer from
dark matter to dark energy which reach equal at $z_{eq}\sim 0.48$ and the
density fluctuations start deviating from the linear behavior at $z\sim 0.25$
caused by the dominance of dark energy.
| [
{
"created": "Mon, 10 Oct 2011 03:02:07 GMT",
"version": "v1"
}
] | 2013-07-05 | [
[
"Deng",
"Xue-Mei",
""
]
] | A modified generalized Chaplygin gas (MGCG) is considered as the unified dark matter-dark energy revisited. The character of MGCG is endued with the dual role, which behaves as matter at early times and as an quiessence dark energy at late times. The equation of state for MGCG is $p=-\alpha\rho/(1+\alpha)-\vartheta(z)\rho^{-\alpha}/(1+\alpha) $, where $\vartheta(z)=-[\rho_{0c}(1+z)^{3}]^{(1+\alpha)}(1-\Omega_{0B})^{\alpha}\{\alpha\Omega_{0DM}+ \Omega_{0DE}[\omega_{DE}+\alpha(1+\omega_{DE})](1+z)^{3\omega_{DE}(1+\alpha)}\}$. Some cosmological quantities, such as the densities of different components of the universe $\Omega_{i}$ ($i$ respectively denotes baryons, dark matter and dark energy) and the deceleration parameter $q$, are obtained. The present deceleration parameter $q_{0}$, the transition redshift $z_{T}$ and the redshift $z_{eq}$, which describes the epoch when the densities in dark matter and dark energy are equal, are also calculated. To distinguish MGCG from others, we then apply the Statefinder diagnostic. Later on, the parameters ($\alpha$ and $\omega_{DE}$) of MGCG are constrained by combination of the sound speed $c^{2}_{s}$, the age of the universe $t_{0}$, the growth factor $m$ and the bias parameter $b$. It yields $\alpha=-3.07^{+5.66}_{-4.98}\times10^{-2}$ and $\omega_{DE}=-1.05^{+0.06}_{-0.11}$. Through the analysis of the growth of density perturbations for MGCG, it is found that the energy will transfer from dark matter to dark energy which reach equal at $z_{eq}\sim 0.48$ and the density fluctuations start deviating from the linear behavior at $z\sim 0.25$ caused by the dominance of dark energy. |
1710.10011 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Bl\'azquez-Salcedo | Radially Excited AdS$_5$ Black Holes in Einstein--Maxwell--Chern--Simons
Theory | 18 pages, 9 figures, invited paper for the "Entropy" special issue
"Geometry in Thermodynamics II", editor George Ruppeiner | Entropy 2017, 19(10), 567 | 10.3390/e19100567 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the large coupling regime of the 5-dimensional
Einstein--Maxwell--Chern--Simons theory, charged and rotating cohomogeneity-1
black holes form sequences of extremal and non-extremal radially excited
configurations. These asymptotically global Anti-de Sitter (AdS$_5$) black
holes form a discrete set of solutions, characterised by the vanishing of the
total angular momenta, or the horizon angular velocity. However, the solutions
are not static. In this paper, we study the branch structure that contains
these excited states, and its relation with the static Reissner-Nordstr\"om-AdS
black hole. Thermodynamic properties of these solutions are considered,
revealing that the branches with lower excitation number can become
thermodynamically unstable beyond certain critical solutions that depend on the
free parameters of the configuration.
| [
{
"created": "Fri, 27 Oct 2017 07:32:51 GMT",
"version": "v1"
}
] | 2017-10-30 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
]
] | In the large coupling regime of the 5-dimensional Einstein--Maxwell--Chern--Simons theory, charged and rotating cohomogeneity-1 black holes form sequences of extremal and non-extremal radially excited configurations. These asymptotically global Anti-de Sitter (AdS$_5$) black holes form a discrete set of solutions, characterised by the vanishing of the total angular momenta, or the horizon angular velocity. However, the solutions are not static. In this paper, we study the branch structure that contains these excited states, and its relation with the static Reissner-Nordstr\"om-AdS black hole. Thermodynamic properties of these solutions are considered, revealing that the branches with lower excitation number can become thermodynamically unstable beyond certain critical solutions that depend on the free parameters of the configuration. |
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