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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2206.05132 | Khadijeh Jafarzade | S. H. Hendi, Kh. Jafarzade, B. Eslam Panah | Black holes in dRGT massive gravity with the signature of EHT
observations of M87* | 23 pages, 6 figures | JCAP 02 (2023) 022 | 10.1088/1475-7516/2023/02/022 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent Event Horizon Telescope (EHT) observations of the M87* have led to
a surge of interest in studying the shadow of black holes. Besides,
investigation of time evolution and lifetime of black holes helps us to
veto/restrict some theoretical models in gravitating systems. Motivated by such
exciting properties, we study optical features of black holes, such as the
shadow geometrical shape and the energy emission rate in modified gravity. We
consider a charged AdS black hole in dRGT massive gravity and look for criteria
to restrict the free parameters of the theory. The main goal of this paper is
to compare the shadow of the mentioned black hole in a rotating case with the
EHT data to obtain the allowed regions of the model parameters. Therefore, we
employ the Newman-Janis algorithm to build the rotating counterpart of static
solution in dRGT massive gravity. We also calculate the energy emission rate
for the rotating case and discuss how the rotation factor and other parameters
affect the emission of particles around the black holes.
| [
{
"created": "Fri, 10 Jun 2022 14:14:00 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Sep 2022 04:10:25 GMT",
"version": "v2"
},
{
"created": "Sun, 12 Feb 2023 05:54:16 GMT",
"version": "v3"
}
] | 2023-02-14 | [
[
"Hendi",
"S. H.",
""
],
[
"Jafarzade",
"Kh.",
""
],
[
"Panah",
"B. Eslam",
""
]
] | The recent Event Horizon Telescope (EHT) observations of the M87* have led to a surge of interest in studying the shadow of black holes. Besides, investigation of time evolution and lifetime of black holes helps us to veto/restrict some theoretical models in gravitating systems. Motivated by such exciting properties, we study optical features of black holes, such as the shadow geometrical shape and the energy emission rate in modified gravity. We consider a charged AdS black hole in dRGT massive gravity and look for criteria to restrict the free parameters of the theory. The main goal of this paper is to compare the shadow of the mentioned black hole in a rotating case with the EHT data to obtain the allowed regions of the model parameters. Therefore, we employ the Newman-Janis algorithm to build the rotating counterpart of static solution in dRGT massive gravity. We also calculate the energy emission rate for the rotating case and discuss how the rotation factor and other parameters affect the emission of particles around the black holes. |
0802.0880 | William Donnelly | William Donnelly | Entanglement Entropy in Loop Quantum Gravity | 4 pages, no figures | Phys.Rev.D77:104006,2008 | 10.1103/PhysRevD.77.104006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entanglement entropy between quantum fields inside and outside a black
hole horizon is a promising candidate for the microscopic origin of black hole
entropy. We show that the entanglement entropy may be defined in loop quantum
gravity, and compute its value for spin network states. The entanglement
entropy for an arbitrary region of space is expressed as a sum over punctures
where the spin network intersects the region's boundary. Our result agrees
asymptotically with results previously obtained from the isolated horizon
framework, and we give a justification for this agreement. We conclude by
proposing a new method for studying corrections to the area law and its
implications for quantum corrections to the gravitational action.
| [
{
"created": "Wed, 6 Feb 2008 21:44:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Donnelly",
"William",
""
]
] | The entanglement entropy between quantum fields inside and outside a black hole horizon is a promising candidate for the microscopic origin of black hole entropy. We show that the entanglement entropy may be defined in loop quantum gravity, and compute its value for spin network states. The entanglement entropy for an arbitrary region of space is expressed as a sum over punctures where the spin network intersects the region's boundary. Our result agrees asymptotically with results previously obtained from the isolated horizon framework, and we give a justification for this agreement. We conclude by proposing a new method for studying corrections to the area law and its implications for quantum corrections to the gravitational action. |
1908.02697 | Robert Buckley | Robert G. Buckley and Eric M. Schlegel | Physical geometry of the quasispherical Szekeres models | 26 pages, 15 figures. Submitted to Phys. Rev. D | Phys. Rev. D 101, 023511 (2020) | 10.1103/PhysRevD.101.023511 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quasispherical Szekeres metric is an exact solution to Einstein's
equations describing an inhomogeneous and anisotropic cosmology. Though its
governing equations are well-known, there are subtle, often-overlooked details
in how the model's functions relate to its physical layout, including the
shapes and relative positions of structures. We present an illustrated overview
of the quasispherical Szekeres models and show exactly how the model functions
relate to the physical shape and distribution of matter. In particular, we
describe a shell rotation effect that has not previously been fully understood.
We show how this effect relates to other known properties, and lay out some
mathematical tools useful for constructing models and picturing them
accurately.
| [
{
"created": "Wed, 7 Aug 2019 16:08:54 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Dec 2019 14:57:44 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Feb 2020 20:55:13 GMT",
"version": "v3"
}
] | 2020-02-19 | [
[
"Buckley",
"Robert G.",
""
],
[
"Schlegel",
"Eric M.",
""
]
] | The quasispherical Szekeres metric is an exact solution to Einstein's equations describing an inhomogeneous and anisotropic cosmology. Though its governing equations are well-known, there are subtle, often-overlooked details in how the model's functions relate to its physical layout, including the shapes and relative positions of structures. We present an illustrated overview of the quasispherical Szekeres models and show exactly how the model functions relate to the physical shape and distribution of matter. In particular, we describe a shell rotation effect that has not previously been fully understood. We show how this effect relates to other known properties, and lay out some mathematical tools useful for constructing models and picturing them accurately. |
2406.09251 | Valerio Faraoni | Numa Karolinski and Valerio Faraoni | The Tolman-Ehrenfest criterion of thermal equilibrium in scalar-tensor
gravity | 9 pages, latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Tolman-Ehrenfest criterion for the thermal equilibrium of a fluid at rest
in a static general-relativistic geometry is generalized to scalar-tensor
gravity. The gravitational scalar field, which fixes the strength of the
effective gravitational coupling, plays a role in determining thermal
equilibrium. As a result, heat sinks more in a gravitational field where the
geometry is more curved, but also where gravity is stronger.
| [
{
"created": "Thu, 13 Jun 2024 15:55:43 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Karolinski",
"Numa",
""
],
[
"Faraoni",
"Valerio",
""
]
] | The Tolman-Ehrenfest criterion for the thermal equilibrium of a fluid at rest in a static general-relativistic geometry is generalized to scalar-tensor gravity. The gravitational scalar field, which fixes the strength of the effective gravitational coupling, plays a role in determining thermal equilibrium. As a result, heat sinks more in a gravitational field where the geometry is more curved, but also where gravity is stronger. |
0904.3224 | Steven Willison | Steven Willison | Lovelock gravity and Weyl's tube formula | 16 pages, 1 figure, RevTex. Version 2: references and a few
additional comments added | Phys.Rev.D80:064018,2009 | 10.1103/PhysRevD.80.064018 | CECS-PHY-09/04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In four space-time dimensions, there are good theoretical reasons for
believing that General Relativity is the correct geometrical theory of gravity,
at least at the classical level. If one admits the possibility of extra
space-time dimensions, what would we expect classical gravity to be like? It is
often stated that the most natural generalisation is Lovelock's theory, which
shares many physical properties with GR. But there are also key differences and
problems. A potentially serious problem is the breakdown of determinism, which
can occur when the matrix of coefficients of second time derivatives of the
metric degenerates. This can be avoided by imposing inequalities on the
curvature. Here it is argued that such inequalities occur naturally if the
Lovelock action is obtained from Weyl's formulae for the volume and surface
area of a tube. Part of the purpose of this article is to give a treatment of
the Weyl tube formula in terminology familiar to relativists and to give an
appropriate (straightforward) generalisation to a tube embedded in Minkowski
space.
| [
{
"created": "Tue, 21 Apr 2009 16:43:22 GMT",
"version": "v1"
},
{
"created": "Wed, 20 May 2009 16:49:33 GMT",
"version": "v2"
}
] | 2009-10-20 | [
[
"Willison",
"Steven",
""
]
] | In four space-time dimensions, there are good theoretical reasons for believing that General Relativity is the correct geometrical theory of gravity, at least at the classical level. If one admits the possibility of extra space-time dimensions, what would we expect classical gravity to be like? It is often stated that the most natural generalisation is Lovelock's theory, which shares many physical properties with GR. But there are also key differences and problems. A potentially serious problem is the breakdown of determinism, which can occur when the matrix of coefficients of second time derivatives of the metric degenerates. This can be avoided by imposing inequalities on the curvature. Here it is argued that such inequalities occur naturally if the Lovelock action is obtained from Weyl's formulae for the volume and surface area of a tube. Part of the purpose of this article is to give a treatment of the Weyl tube formula in terminology familiar to relativists and to give an appropriate (straightforward) generalisation to a tube embedded in Minkowski space. |
1307.5499 | Marcus Khuri | Marcus A. Khuri, Gilbert Weinstein | Rigidity in the Positive Mass Theorem with Charge | 12 pages; final version | J. Math. Phys., 54 (2013), 092501 | 10.1063/1.4820469 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we show how a natural coupling of the Dirac equation with the
generalized Jang equation, leads to a proof of the rigidity statement in the
positive mass theorem with charge, without the maximal slicing condition,
provided a solution to the coupled system exists.
| [
{
"created": "Sun, 21 Jul 2013 06:48:50 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2013 02:21:41 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Aug 2013 13:27:56 GMT",
"version": "v3"
},
{
"created": "Sat, 14 Sep 2013 22:57:40 GMT",
"version": "v4"
}
] | 2013-09-18 | [
[
"Khuri",
"Marcus A.",
""
],
[
"Weinstein",
"Gilbert",
""
]
] | In this paper we show how a natural coupling of the Dirac equation with the generalized Jang equation, leads to a proof of the rigidity statement in the positive mass theorem with charge, without the maximal slicing condition, provided a solution to the coupled system exists. |
1408.5581 | Eugen Radu | Yves Brihaye, Carlos Herdeiro and Eugen Radu | Myers-Perry black holes with scalar hair and a mass gap | 11 pages, 6 figures | null | 10.1016/j.physletb.2014.10.019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a family of asymptotically flat, rotating black holes with
scalar hair and a regular horizon, within five dimensional Einstein's gravity
minimally coupled to a complex, massive scalar field doublet. These solutions
are supported by rotation and have no static limit. They are described by their
mass $M$, two equal angular momenta $J_1=J_2\equiv J$ and a conserved Noether
charge $Q$, measuring the scalar hair. For vanishing horizon size the solutions
reduce to five dimensional boson stars. In the limit of vanishing Noether
charge density, the scalar field becomes point-wise arbitrarily small and the
geometry becomes, locally, arbitrarily close to that of a specific set of
Myers-Perry black holes (MPBHs); but there remains a global difference with
respect to the latter, manifest in a finite mass gap. Thus, the scalar hair
never becomes a linear perturbation of MPBHs. This is a qualitative difference
when compared to Kerr black holes with scalar hair~\cite{Herdeiro:2014goa}.
Whereas the existence of the latter can be anticipated in linear theory, from
the existence of scalar bound states on the Kerr geometry (i.e. scalar clouds),
the hair of these MPBHs is intrinsically non-linear.
| [
{
"created": "Sun, 24 Aug 2014 08:52:10 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Brihaye",
"Yves",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
]
] | We construct a family of asymptotically flat, rotating black holes with scalar hair and a regular horizon, within five dimensional Einstein's gravity minimally coupled to a complex, massive scalar field doublet. These solutions are supported by rotation and have no static limit. They are described by their mass $M$, two equal angular momenta $J_1=J_2\equiv J$ and a conserved Noether charge $Q$, measuring the scalar hair. For vanishing horizon size the solutions reduce to five dimensional boson stars. In the limit of vanishing Noether charge density, the scalar field becomes point-wise arbitrarily small and the geometry becomes, locally, arbitrarily close to that of a specific set of Myers-Perry black holes (MPBHs); but there remains a global difference with respect to the latter, manifest in a finite mass gap. Thus, the scalar hair never becomes a linear perturbation of MPBHs. This is a qualitative difference when compared to Kerr black holes with scalar hair~\cite{Herdeiro:2014goa}. Whereas the existence of the latter can be anticipated in linear theory, from the existence of scalar bound states on the Kerr geometry (i.e. scalar clouds), the hair of these MPBHs is intrinsically non-linear. |
2008.13318 | Zi-Yu Tang | Zi-Yu Tang, Bin Wang, Thanasis Karakasis and Eleftherios
Papantonopoulos | Curvature Scalarization of Black Holes in f(R) Gravity | 18 pages, 12 figures | Phys. Rev. D 104, 064017 (2021) | 10.1103/PhysRevD.104.064017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider f(R) gravity theories in the presence of a scalar field minimally
coupled to gravity with a self-interacting potential. When the scalar field
backreacts to the metric we find at large distances scalarized
Schwarzschild-AdS and Schwarzschild-AdS-like black hole solutions. At small
distances due to strong curvature effects and the scalar dynamis we find a rich
structure of scalarized black hole solutions. When the scalar field is
conformally coupled to gravity we also find scalarized black hole solutions at
small distances.
| [
{
"created": "Mon, 31 Aug 2020 02:18:08 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Sep 2020 10:24:35 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Oct 2020 10:57:31 GMT",
"version": "v3"
}
] | 2021-09-15 | [
[
"Tang",
"Zi-Yu",
""
],
[
"Wang",
"Bin",
""
],
[
"Karakasis",
"Thanasis",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We consider f(R) gravity theories in the presence of a scalar field minimally coupled to gravity with a self-interacting potential. When the scalar field backreacts to the metric we find at large distances scalarized Schwarzschild-AdS and Schwarzschild-AdS-like black hole solutions. At small distances due to strong curvature effects and the scalar dynamis we find a rich structure of scalarized black hole solutions. When the scalar field is conformally coupled to gravity we also find scalarized black hole solutions at small distances. |
2110.13565 | Wenyi Wang | Wenyi Wang, Hua Chen, Taishi Katsuragawa | Static and spherically symmetric solutions in f(Q) gravity | 7 pages,version to appear in Physical Review D | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | f(Q) gravity is the extension of symmetric teleparallel general relativity
(STGR), in which both curvature and torsion vanish, and gravity is attributed
to nonmetricity. This work performs theoretical analyses of static and
spherically symmetric solutions with an anisotropic fluid for general f(Q)
gravity. We find that the off-diagonal component of the field equation due to a
coincident gauge leads to stringent restrictions on the functional form of f(Q)
gravity. In addition, although the exact Schwarzschild solution only exists in
STGR, we obtain Schwarzschild-like solutions in nontrivial f(Q) gravity and
study its asymptotic behavior and deviation from the exact one.
| [
{
"created": "Tue, 26 Oct 2021 10:50:15 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 10:52:25 GMT",
"version": "v2"
}
] | 2022-02-10 | [
[
"Wang",
"Wenyi",
""
],
[
"Chen",
"Hua",
""
],
[
"Katsuragawa",
"Taishi",
""
]
] | f(Q) gravity is the extension of symmetric teleparallel general relativity (STGR), in which both curvature and torsion vanish, and gravity is attributed to nonmetricity. This work performs theoretical analyses of static and spherically symmetric solutions with an anisotropic fluid for general f(Q) gravity. We find that the off-diagonal component of the field equation due to a coincident gauge leads to stringent restrictions on the functional form of f(Q) gravity. In addition, although the exact Schwarzschild solution only exists in STGR, we obtain Schwarzschild-like solutions in nontrivial f(Q) gravity and study its asymptotic behavior and deviation from the exact one. |
1505.00743 | Supriya Pan | Supriya Pan and Subenoy Chakraborty | A Cosmological Study in Massive Gravity theory | 21 Pages, 5 figures, Published version | Annals of Phys, 360 (2015) 180-193 | 10.1016/j.aop.2015.04.003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A detailed study of the various cosmological aspects in massive gravity
theory has been presented in the present work. For the homogeneous and
isotropic FLRW model, the deceleration parameter has been evaluated, and, it
has been examined whether there is any transition from deceleration to
acceleration in recent past, or not. With the proper choice of the free
parameters, it has been shown that the massive gravity theory is equivalent to
Einstein gravity with a modified Newtonian gravitational constant together with
a negative cosmological constant. Also, in this context, it has been examined
whether the emergent scenario is possible, or not, in massive gravity theory.
Finally, we have done a cosmographic analysis in massive gravity theory.
| [
{
"created": "Thu, 30 Apr 2015 12:28:19 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2015 13:55:05 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Pan",
"Supriya",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | A detailed study of the various cosmological aspects in massive gravity theory has been presented in the present work. For the homogeneous and isotropic FLRW model, the deceleration parameter has been evaluated, and, it has been examined whether there is any transition from deceleration to acceleration in recent past, or not. With the proper choice of the free parameters, it has been shown that the massive gravity theory is equivalent to Einstein gravity with a modified Newtonian gravitational constant together with a negative cosmological constant. Also, in this context, it has been examined whether the emergent scenario is possible, or not, in massive gravity theory. Finally, we have done a cosmographic analysis in massive gravity theory. |
gr-qc/9809077 | K. S. Virbhadra | K. S. Virbhadra (University of Cape Town) | Naked singularities and Seifert's conjecture | RevTex, no figures, new results included, published in Physical
Review D 60, 104041 (1999) | Phys.Rev. D60 (1999) 104041 | 10.1103/PhysRevD.60.104041 | null | gr-qc astro-ph hep-th | null | It is shown that for a general nonstatic spherically symmetric metric of the
Kerr-Schild class several energy-momentum complexes give the same energy
distribution as in the Penrose prescription, obtained by Tod. This result is
useful for investigating the Seifert conjecture for naked singularities. The
naked singularity forming in the Vaidya null dust collapse supports the Seifert
conjecture. Further, an example and a counterexample to this conjecture are
presented in the Einstein massless scalar theory.
| [
{
"created": "Mon, 28 Sep 1998 15:21:05 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jan 2000 14:03:07 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Virbhadra",
"K. S.",
"",
"University of Cape Town"
]
] | It is shown that for a general nonstatic spherically symmetric metric of the Kerr-Schild class several energy-momentum complexes give the same energy distribution as in the Penrose prescription, obtained by Tod. This result is useful for investigating the Seifert conjecture for naked singularities. The naked singularity forming in the Vaidya null dust collapse supports the Seifert conjecture. Further, an example and a counterexample to this conjecture are presented in the Einstein massless scalar theory. |
1604.05547 | Chiang-Mei Chen | James M. Nester, Chiang-Mei Chen | Gravity: a gauge theory perspective | 10 pages, contribution to the Proceedings of the Second LeCosPA
Symposium "Everything about Gravity", Taipei, 14-18 Dec., 2015 | null | 10.1142/S0218271816450024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of a generally covariant theory is under-determined. One
hundred years ago such dynamics had never before been considered; its
ramifications were perplexing, its future important role for all the
fundamental interactions under the name gauge principle could not be foreseen.
We recount some history regarding Einstein, Hilbert, Klein and Noether and the
novel features of gravitational energy that led to Noether's two theorems.
Under-determined evolution is best revealed in the Hamiltonian formulation. We
developed a covariant Hamiltonian formulation. The Hamiltonian boundary term
gives covariant expressions for the quasi-local energy, momentum and angular
momentum. Gravity can be considered as a gauge theory of the local Poincar\'e
group. The dynamical potentials of the Poincar\'e gauge theory of gravity are
the frame and the connection. The spacetime geometry has in general both
curvature and torsion. Torsion naturally couples to spin; it could have a
significant magnitude and yet not be noticed, except on a cosmological scale
where it could have significant effects.
| [
{
"created": "Tue, 19 Apr 2016 12:52:49 GMT",
"version": "v1"
}
] | 2016-11-23 | [
[
"Nester",
"James M.",
""
],
[
"Chen",
"Chiang-Mei",
""
]
] | The evolution of a generally covariant theory is under-determined. One hundred years ago such dynamics had never before been considered; its ramifications were perplexing, its future important role for all the fundamental interactions under the name gauge principle could not be foreseen. We recount some history regarding Einstein, Hilbert, Klein and Noether and the novel features of gravitational energy that led to Noether's two theorems. Under-determined evolution is best revealed in the Hamiltonian formulation. We developed a covariant Hamiltonian formulation. The Hamiltonian boundary term gives covariant expressions for the quasi-local energy, momentum and angular momentum. Gravity can be considered as a gauge theory of the local Poincar\'e group. The dynamical potentials of the Poincar\'e gauge theory of gravity are the frame and the connection. The spacetime geometry has in general both curvature and torsion. Torsion naturally couples to spin; it could have a significant magnitude and yet not be noticed, except on a cosmological scale where it could have significant effects. |
1408.4358 | Jose Luis Flores | I.P. Costa e Silva, J.L. Flores | Lightlike sets with applications to the rigidity of null geodesic
incompleteness | 23 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important, if relatively less well known aspect of the singularity
theorems in Lorentzian Geometry is to understand how their conclusions fare
upon weakening or suppression of one or more of their hypotheses. Then,
theorems with modified concusions may arise, showing that those conclusions
will fail only in special cases, at least some of which may be described. These
are the so-called rigidity theorems, and have many important examples in the
especialized literature. In this paper, we prove rigidity results for
generalized plane waves and certain globally hyperbolic spacetimes in the
presence of maximal compact surfaces. Motivated by some general properties
appearing in these proofs, we develop the theory of lightlike sets, entities
similar to achronal sets, but more appropriate to deal with low-regularity null
submanifolds.
| [
{
"created": "Tue, 19 Aug 2014 15:04:45 GMT",
"version": "v1"
}
] | 2014-08-20 | [
[
"Silva",
"I. P. Costa e",
""
],
[
"Flores",
"J. L.",
""
]
] | An important, if relatively less well known aspect of the singularity theorems in Lorentzian Geometry is to understand how their conclusions fare upon weakening or suppression of one or more of their hypotheses. Then, theorems with modified concusions may arise, showing that those conclusions will fail only in special cases, at least some of which may be described. These are the so-called rigidity theorems, and have many important examples in the especialized literature. In this paper, we prove rigidity results for generalized plane waves and certain globally hyperbolic spacetimes in the presence of maximal compact surfaces. Motivated by some general properties appearing in these proofs, we develop the theory of lightlike sets, entities similar to achronal sets, but more appropriate to deal with low-regularity null submanifolds. |
2404.11468 | Luca Guido Molinari | Carlo Alberto Mantica and Luca Guido Molinari | Conformal Killing cosmology -- Geometry, dark sector, growth of
structures, and big rip | 20 pages, 6 figures. Introduction reviewed, with references. Section
on H(z) and datasets reviewed with improved figures, evolution of dark energy
density and pressure, future singularities | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce Sinyukov-like tensors, a special kind of conformal Killing
tensors. In Robertson-Walker space-times they have the perfect-fluid form and
only depend on two constants and the scale factor. They are the candidate for
the dark term of the newly proposed Conformal Killing Gravity, by Harada. In
addition to ordinary matter, the Friedmann equations contain a dark term and a
Lambda term that parametrize the Sinyukov-like tensor. The expression of H(z)
is tested on cosmological data based on cosmic chronometers CC or including
baryon acoustic oscillations BAO. There is a large incertitude in Omega_Lambda
and Omega_dark that may become negative, but their sum is close to Omega_Lambda
of Lambda-CDM. In any case, there is a future singularity, that is a big rip
for all Omegas positive. We solve the equation for the evolution, in linear
approximation, of the density contrast in matter-dominated universe. The dark
sector and the Lambda term give no significative deviation from Lambda-CDM and
GR results.
| [
{
"created": "Wed, 17 Apr 2024 15:16:50 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Apr 2024 14:28:37 GMT",
"version": "v2"
},
{
"created": "Thu, 9 May 2024 13:04:54 GMT",
"version": "v3"
},
{
"created": "Sat, 25 May 2024 07:09:47 GMT",
"version": "v4"
}
] | 2024-05-28 | [
[
"Mantica",
"Carlo Alberto",
""
],
[
"Molinari",
"Luca Guido",
""
]
] | We introduce Sinyukov-like tensors, a special kind of conformal Killing tensors. In Robertson-Walker space-times they have the perfect-fluid form and only depend on two constants and the scale factor. They are the candidate for the dark term of the newly proposed Conformal Killing Gravity, by Harada. In addition to ordinary matter, the Friedmann equations contain a dark term and a Lambda term that parametrize the Sinyukov-like tensor. The expression of H(z) is tested on cosmological data based on cosmic chronometers CC or including baryon acoustic oscillations BAO. There is a large incertitude in Omega_Lambda and Omega_dark that may become negative, but their sum is close to Omega_Lambda of Lambda-CDM. In any case, there is a future singularity, that is a big rip for all Omegas positive. We solve the equation for the evolution, in linear approximation, of the density contrast in matter-dominated universe. The dark sector and the Lambda term give no significative deviation from Lambda-CDM and GR results. |
2210.16339 | Andrew Svesko | Damien A. Easson, Tucker Manton and Andrew Svesko | Einstein-Maxwell theory and the Weyl double copy | 25 pages + an appendix | null | 10.1103/PhysRevD.107.044063 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Weyl double copy relates vacuum solutions in general relativity to
Abelian gauge fields in Minkowski spacetime. In a previous work, we showed how
the Weyl double copy can be extended to provide a treatment of external
gravitational sources consistent with the classical Kerr-Schild double copy.
Using this generalization, here we provide a complete double copy analysis of
electrovacuum Petrov type D spacetimes. This includes the first analysis of the
charged C-metric, whose single copy interpretation invokes the two-potential
formalism of electrodynamics. We also present the first double copy
prescription for the Ricci spinor, which for non-accelerating spacetimes, takes
a form similar to the original double copy relation for the Weyl spinor.
| [
{
"created": "Fri, 28 Oct 2022 18:01:04 GMT",
"version": "v1"
}
] | 2023-03-08 | [
[
"Easson",
"Damien A.",
""
],
[
"Manton",
"Tucker",
""
],
[
"Svesko",
"Andrew",
""
]
] | The Weyl double copy relates vacuum solutions in general relativity to Abelian gauge fields in Minkowski spacetime. In a previous work, we showed how the Weyl double copy can be extended to provide a treatment of external gravitational sources consistent with the classical Kerr-Schild double copy. Using this generalization, here we provide a complete double copy analysis of electrovacuum Petrov type D spacetimes. This includes the first analysis of the charged C-metric, whose single copy interpretation invokes the two-potential formalism of electrodynamics. We also present the first double copy prescription for the Ricci spinor, which for non-accelerating spacetimes, takes a form similar to the original double copy relation for the Weyl spinor. |
1904.06558 | Valentin Boyanov | Carlos Barcel\'o, Valentin Boyanov, Ra\'ul Carballo-Rubio, Luis J.
Garay | Semiclassical gravity effects near horizon formation | 41 pages, 19 figures, v2: added one new figure and minor changes in
text to match published version | Class. Quantum Grav., vol. 36, no. 16, 2019 | 10.1088/1361-6382/ab2e43 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the magnitude of semiclassical gravity effects near the formation of
a black-hole horizon in spherically-symmetric spacetimes. As a probe for these
effects we use a quantised massless scalar field. Specifically, we calculate
two quantities derived from it: the renormalised stress-energy tensor (a
measure of how the field vacuum state affects the spacetime) and the effective
temperature function (a generalisation of Hawking temperature related to the
energy flux of the field vacuum). The subject of our study are spacetimes which
contain a spherical distribution of matter and an empty exterior Schwarzschild
region, separated by a surface which is moving in proximity to the
Schwarzschild radius $r_{\rm s}=2M$, with $M$ the total mass. In particular, we
analyse the consequences of three types of surface movement: an oscillation
just above $r_{\rm s}$, a monotonous approach towards $r_{\rm s}$ in infinite
time and a crossing of $r_{\rm s}$ at different velocities. For a collapsing
matter distribution which follows the expected dynamical evolution in general
relativity, we recover the standard picture of black-hole formation and its
tenuous semiclassical effects. In more general dynamical regimes, allowing
deviations from the standard classical evolution, we obtain a variety of
different effects: from the emission of Hawking-like radiation without the
formation of a horizon, to large values of the renormalised stress-energy
tensor, related to the Boulware vacuum divergence in static spacetimes.
| [
{
"created": "Sat, 13 Apr 2019 14:46:30 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Nov 2019 10:58:24 GMT",
"version": "v2"
}
] | 2019-11-07 | [
[
"Barceló",
"Carlos",
""
],
[
"Boyanov",
"Valentin",
""
],
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Garay",
"Luis J.",
""
]
] | We study the magnitude of semiclassical gravity effects near the formation of a black-hole horizon in spherically-symmetric spacetimes. As a probe for these effects we use a quantised massless scalar field. Specifically, we calculate two quantities derived from it: the renormalised stress-energy tensor (a measure of how the field vacuum state affects the spacetime) and the effective temperature function (a generalisation of Hawking temperature related to the energy flux of the field vacuum). The subject of our study are spacetimes which contain a spherical distribution of matter and an empty exterior Schwarzschild region, separated by a surface which is moving in proximity to the Schwarzschild radius $r_{\rm s}=2M$, with $M$ the total mass. In particular, we analyse the consequences of three types of surface movement: an oscillation just above $r_{\rm s}$, a monotonous approach towards $r_{\rm s}$ in infinite time and a crossing of $r_{\rm s}$ at different velocities. For a collapsing matter distribution which follows the expected dynamical evolution in general relativity, we recover the standard picture of black-hole formation and its tenuous semiclassical effects. In more general dynamical regimes, allowing deviations from the standard classical evolution, we obtain a variety of different effects: from the emission of Hawking-like radiation without the formation of a horizon, to large values of the renormalised stress-energy tensor, related to the Boulware vacuum divergence in static spacetimes. |
gr-qc/0202047 | Henrique P. de Oliveira | H. P. de Oliveira, A. M. Ozorio de Almeida, I. Dami\~ao Soares and E.
V. Tonini | Homoclinic chaos in the dynamics of a general Bianchi IX model | 11 pages, 6 ps figures. Accepted for publication in Phys. Rev. D | Phys.Rev. D65 (2002) 083511 | 10.1103/PhysRevD.65.083511 | null | gr-qc | null | The dynamics of a general Bianchi IX model with three scale factors is
examined. The matter content of the model is assumed to be comoving dust plus a
positive cosmological constant. The model presents a critical point of
saddle-center-center type in the finite region of phase space. This critical
point engenders in the phase space dynamics the topology of stable and unstable
four dimensional tubes $R \times S^3$, where $R$ is a saddle direction and
$S^3$ is the manifold of unstable periodic orbits in the center-center sector.
A general characteristic of the dynamical flow is an oscillatory mode about
orbits of an invariant plane of the dynamics which contains the critical point
and a Friedmann-Robertson-Walker (FRW) singularity. We show that a pair of
tubes (one stable, one unstable) emerging from the neighborhood of the critical
point towards the FRW singularity have homoclinic transversal crossings. The
homoclinic intersection manifold has topology $R \times S^2$ and is constituted
of homoclinic orbits which are bi-asymptotic to the $S^3$ center-center
manifold. This is an invariant signature of chaos in the model, and produces
chaotic sets in phase space. The model also presents an asymptotic DeSitter
attractor at infinity and initial conditions sets are shown to have fractal
basin boundaries connected to the escape into the DeSitter configuration
(escape into inflation), characterizing the critical point as a chaotic
scatterer.
| [
{
"created": "Thu, 14 Feb 2002 10:12:34 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"de Oliveira",
"H. P.",
""
],
[
"de Almeida",
"A. M. Ozorio",
""
],
[
"Soares",
"I. Damião",
""
],
[
"Tonini",
"E. V.",
""
]
] | The dynamics of a general Bianchi IX model with three scale factors is examined. The matter content of the model is assumed to be comoving dust plus a positive cosmological constant. The model presents a critical point of saddle-center-center type in the finite region of phase space. This critical point engenders in the phase space dynamics the topology of stable and unstable four dimensional tubes $R \times S^3$, where $R$ is a saddle direction and $S^3$ is the manifold of unstable periodic orbits in the center-center sector. A general characteristic of the dynamical flow is an oscillatory mode about orbits of an invariant plane of the dynamics which contains the critical point and a Friedmann-Robertson-Walker (FRW) singularity. We show that a pair of tubes (one stable, one unstable) emerging from the neighborhood of the critical point towards the FRW singularity have homoclinic transversal crossings. The homoclinic intersection manifold has topology $R \times S^2$ and is constituted of homoclinic orbits which are bi-asymptotic to the $S^3$ center-center manifold. This is an invariant signature of chaos in the model, and produces chaotic sets in phase space. The model also presents an asymptotic DeSitter attractor at infinity and initial conditions sets are shown to have fractal basin boundaries connected to the escape into the DeSitter configuration (escape into inflation), characterizing the critical point as a chaotic scatterer. |
2403.05642 | Nishad Muhammed | Nishad Muhammed, Matthew D. Duez, Pavan Chawhan, Noora Ghadiri, Luisa
T. Buchman, Francois Foucart, Patrick Chi-Kit Cheong, Lawrence E. Kidder,
Harald P. Pfeiffer and Mark A. Scheel | Stability of hypermassive neutron stars with realistic rotation and
entropy profiles | 12 pages, 9 figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Binary neutron star mergers produce massive, hot, rapidly differentially
rotating neutron star remnants; electromagnetic and gravitational wave signals
associated with the subsequent evolution depend on the stability of these
remnants. Stability of relativistic stars has previously been studied for
uniform rotation and for a class of differential rotation with monotonic
angular velocity profiles. Stability of those equilibria to axisymmetric
perturbations was found to respect a turning point criterion: along a constant
angular momentum sequence, the onset of unstable stars is found at maximum
density less than but close to the density of maximum mass. In this paper, we
test this turning point criterion for non-monotonic angular velocity profiles
and non-isentropic entropy profiles, both chosen to more realistically model
post-merger equilibria. Stability is assessed by evolving perturbed equilibria
in 2D using the Spectral Einstein Code. We present tests of the code's new
capability for axisymmetric metric evolution. We confirm the turning point
theorem and determine the region of our rotation law parameter space that
provides highest maximum mass for a given angular momentum.
| [
{
"created": "Fri, 8 Mar 2024 19:29:09 GMT",
"version": "v1"
}
] | 2024-03-12 | [
[
"Muhammed",
"Nishad",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Chawhan",
"Pavan",
""
],
[
"Ghadiri",
"Noora",
""
],
[
"Buchman",
"Luisa T.",
""
],
[
"Foucart",
"Francois",
""
],
[
"Cheong",
"Patrick Chi-Kit",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
]
] | Binary neutron star mergers produce massive, hot, rapidly differentially rotating neutron star remnants; electromagnetic and gravitational wave signals associated with the subsequent evolution depend on the stability of these remnants. Stability of relativistic stars has previously been studied for uniform rotation and for a class of differential rotation with monotonic angular velocity profiles. Stability of those equilibria to axisymmetric perturbations was found to respect a turning point criterion: along a constant angular momentum sequence, the onset of unstable stars is found at maximum density less than but close to the density of maximum mass. In this paper, we test this turning point criterion for non-monotonic angular velocity profiles and non-isentropic entropy profiles, both chosen to more realistically model post-merger equilibria. Stability is assessed by evolving perturbed equilibria in 2D using the Spectral Einstein Code. We present tests of the code's new capability for axisymmetric metric evolution. We confirm the turning point theorem and determine the region of our rotation law parameter space that provides highest maximum mass for a given angular momentum. |
1801.00768 | Mehdi Assanioussi | Mehdi Assanioussi, Andrea Dapor, Klaus Liegener, Tomasz Paw{\l}owski | Emergent de Sitter epoch of the quantum Cosmos | 6 pages, 2 figures, revised version accepted for publication in
Phys.Rev.Lett., with the addition of fig.2 and subsequent comments | Phys. Rev. Lett. 121, 081303 (2018) | 10.1103/PhysRevLett.121.081303 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum nature of the Big Bang is reexamined in the framework of Loop
Quantum Cosmology. The strict application of a regularization procedure to the
Hamiltonian, originally developed for the Hamiltonian in loop quantum gravity,
leads to a qualitative modification of the bounce paradigm. Quantum gravity
effects still lead to a quantum bounce connecting deterministically large
classical Universes. However, the evolution features a large epoch of de Sitter
Universe, with emergent cosmological constant of Planckian order, smoothly
transiting into a flat expanding Universe.
| [
{
"created": "Tue, 2 Jan 2018 18:46:57 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Aug 2018 17:10:24 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Assanioussi",
"Mehdi",
""
],
[
"Dapor",
"Andrea",
""
],
[
"Liegener",
"Klaus",
""
],
[
"Pawłowski",
"Tomasz",
""
]
] | The quantum nature of the Big Bang is reexamined in the framework of Loop Quantum Cosmology. The strict application of a regularization procedure to the Hamiltonian, originally developed for the Hamiltonian in loop quantum gravity, leads to a qualitative modification of the bounce paradigm. Quantum gravity effects still lead to a quantum bounce connecting deterministically large classical Universes. However, the evolution features a large epoch of de Sitter Universe, with emergent cosmological constant of Planckian order, smoothly transiting into a flat expanding Universe. |
2402.13951 | J\'unior Diniz Toniato | J\'unior D. Toniato and Mart\'in G. Richarte | A Post-Newtonian Analysis of Regularized 4D-EGB Theory: Complete Set of
PPN Parameters and Observational Constraints | 14 pages, 2 tables, 1 appendix. References added. Submitted to PRD | Phys. Rev. D 109, 104068 (2024) | 10.1103/PhysRevD.109.104068 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We performed a post-Newtonian analysis of the regularized four-dimensional
Einstein-Gauss-Bonnet gravitational theory (4D-EGB). The resulting metric
differs from the classical parametrized post-Newtonian (PPN) formalism in that
a new gravitational potential arises from the integration of the approximate
field equations. We also investigated the conserved quantities and equations of
motion for massive bodies and light rays to a certain degree. By computing the
predicted periastron advance rate in a binary system, we obtained an
observational constraint that is stronger than those of previous analyses.
Although the usual 10 PPN parameters can still be derived within the PPN
framework, an extra parameter is needed to account for the full post-Newtonian
tests.
| [
{
"created": "Wed, 21 Feb 2024 17:29:05 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 19:05:41 GMT",
"version": "v2"
}
] | 2024-06-25 | [
[
"Toniato",
"Júnior D.",
""
],
[
"Richarte",
"Martín G.",
""
]
] | We performed a post-Newtonian analysis of the regularized four-dimensional Einstein-Gauss-Bonnet gravitational theory (4D-EGB). The resulting metric differs from the classical parametrized post-Newtonian (PPN) formalism in that a new gravitational potential arises from the integration of the approximate field equations. We also investigated the conserved quantities and equations of motion for massive bodies and light rays to a certain degree. By computing the predicted periastron advance rate in a binary system, we obtained an observational constraint that is stronger than those of previous analyses. Although the usual 10 PPN parameters can still be derived within the PPN framework, an extra parameter is needed to account for the full post-Newtonian tests. |
0908.3227 | Kazuhiro Agatsuma | Kazuhiro Agatsuma, Takashi Uchiyama, Kazuhiro Yamamoto, Masatake
Ohashi, Seiji Kawamura, Shinji Miyoki, Osamu Miyakawa, Souichi Telada and
Kazuaki Kuroda | Direct Measurement of Thermal Fluctuation of High-Q Pendulum | 10 pages, 4 figures | PRL 104, 040602 (2010) | 10.1103/PhysRevLett.104.040602 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We achieved for the first time a direct measurement of the thermal
fluctuation of a pendulum in an off-resonant region using a laser
interferometric gravitational wave detector. These measurements have been well
identified for over one decade by an agreement with a theoretical prediction,
which was derived by a fluctuation-dissipation theorem. Thermal fluctuation is
dominated by the contribution of resistances in coil-magnet actuator circuits.
When we tuned these resistances, the noise spectrum also changed according to a
theoretical prediction. The measured thermal noise level corresponds to a high
quality factor on the order of 10^5 of the pendulum.
| [
{
"created": "Sun, 23 Aug 2009 06:17:39 GMT",
"version": "v1"
}
] | 2014-01-28 | [
[
"Agatsuma",
"Kazuhiro",
""
],
[
"Uchiyama",
"Takashi",
""
],
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Ohashi",
"Masatake",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Miyoki",
"Shinji",
""
],
[
"Miyakawa",
"Osamu",
""
],
[
"Telada",
"Souichi",
""
],
[
"Kuroda",
"Kazuaki",
""
]
] | We achieved for the first time a direct measurement of the thermal fluctuation of a pendulum in an off-resonant region using a laser interferometric gravitational wave detector. These measurements have been well identified for over one decade by an agreement with a theoretical prediction, which was derived by a fluctuation-dissipation theorem. Thermal fluctuation is dominated by the contribution of resistances in coil-magnet actuator circuits. When we tuned these resistances, the noise spectrum also changed according to a theoretical prediction. The measured thermal noise level corresponds to a high quality factor on the order of 10^5 of the pendulum. |
1206.5797 | Hossein Farajollahi | H. Farajollahi, A. Salehi | Chameleon gravity on cosmological scales | 7 pages, 11 figures | Phys. Rev. D 85, 083514 (2012) | 10.1103/PhysRevD.85.083514 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In conventional approach to the chameleon mechanism, by assuming a static and
spherically symmetric solutions in which matter density and chameleon field are
given by $\rho=\rho(r)$ and $\phi=\phi(r)$, it has been shown that mass of
chameleon field is matter density-dependent. In regions of high matter density
such as earth, chameleon field is massive, in solar system it is low and in
cosmological scales it is very low. In this article we revisit the mechanism in
cosmological scales by assuming a redshift dependence of the matter density and
chameleon field, i.e. $\rho=\rho(z)$, $\phi=\phi(z)$. To support our analysis,
we best fit the model parameters with the observational data. The result shows
that in cosmological scales, the mass of chameleon field increases with the
redshift, i.e. more massive in higher redshifts. We also find that in both
cases of power-law and exponential potential function, the current universe
acceleration can be explained by the low mass chameleon field. In comparison
with the high redshift observational data, we also find that the model with
power-law potential function is in better agreement with the observational
data.
| [
{
"created": "Mon, 25 Jun 2012 14:22:49 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Farajollahi",
"H.",
""
],
[
"Salehi",
"A.",
""
]
] | In conventional approach to the chameleon mechanism, by assuming a static and spherically symmetric solutions in which matter density and chameleon field are given by $\rho=\rho(r)$ and $\phi=\phi(r)$, it has been shown that mass of chameleon field is matter density-dependent. In regions of high matter density such as earth, chameleon field is massive, in solar system it is low and in cosmological scales it is very low. In this article we revisit the mechanism in cosmological scales by assuming a redshift dependence of the matter density and chameleon field, i.e. $\rho=\rho(z)$, $\phi=\phi(z)$. To support our analysis, we best fit the model parameters with the observational data. The result shows that in cosmological scales, the mass of chameleon field increases with the redshift, i.e. more massive in higher redshifts. We also find that in both cases of power-law and exponential potential function, the current universe acceleration can be explained by the low mass chameleon field. In comparison with the high redshift observational data, we also find that the model with power-law potential function is in better agreement with the observational data. |
2106.01412 | Ramin G. Daghigh | Ramin G. Daghigh and Michael D. Green | Gravitational and electromagnetic radiation from an electrically charged
black hole in general nonlinear electrodynamics | 25 pages. Minor corrections are made and one figure is added. The
paper is going to be published in Phys. Rev. D soon | null | 10.1103/PhysRevD.105.024055 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We derive the equations for the odd and even parity perturbations of coupled
electromagnetic and gravitational fields of a black hole with an electric
charge within the context of general nonlinear electrodynamics. The Lagrangian
density is a generic function of the Lorentz invariant scalar quantities of the
electromagnetic fields. We include the Hodge dual of the electromagnetic field
tensor and the cosmological constant in our calculations. For each type of
parity, we reduce the system of Einstein field equations coupled to nonlinear
electrodynamics to two coupled Schr\"odinger-type wave equations, one for the
gravitational field and one for the electromagnetic field. The stability
conditions in the presence of the Hodge dual of the electromagnetic field are
derived.
| [
{
"created": "Wed, 2 Jun 2021 18:30:01 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Aug 2021 22:01:50 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Nov 2021 19:20:07 GMT",
"version": "v3"
},
{
"created": "Tue, 4 Jan 2022 21:39:10 GMT",
"version": "v4"
}
] | 2022-02-02 | [
[
"Daghigh",
"Ramin G.",
""
],
[
"Green",
"Michael D.",
""
]
] | We derive the equations for the odd and even parity perturbations of coupled electromagnetic and gravitational fields of a black hole with an electric charge within the context of general nonlinear electrodynamics. The Lagrangian density is a generic function of the Lorentz invariant scalar quantities of the electromagnetic fields. We include the Hodge dual of the electromagnetic field tensor and the cosmological constant in our calculations. For each type of parity, we reduce the system of Einstein field equations coupled to nonlinear electrodynamics to two coupled Schr\"odinger-type wave equations, one for the gravitational field and one for the electromagnetic field. The stability conditions in the presence of the Hodge dual of the electromagnetic field are derived. |
gr-qc/9911083 | Julia Kopeikina | Sergei M. Kopeikin (Dept. of Phys. and Astron., Univ.
Missouri-Columbia) | Lorentz Covariant Theory of Precise Doppler Measurements | 4 pages, the afternoon talk at Journees Relativistes 1999, Weimar,
Germany, September 1999 | null | null | null | gr-qc astro-ph physics.space-ph | null | The Lorentz covariant theory of precise Doppler measurements (PDM) based on
the retarded Li\'{e}nard-Wiechert solution of the Einstein equations is
described. An exact solution of equations of light propagation in the field of
arbitrary moving bodies, which drastically extends the range of applicability
of the new theory of PDM, is obtained. An explicit formula for the
gravitational shift of frequency is given in analytic form. The limiting cases
of the Doppler observations in gravitational lensing and of the spacecraft's
Doppler tracking are described in more detail. We also present the
post-Newtonian theory of the PDM developed for searching relativistic effects
in close optical binaries and massive planetary systems.
| [
{
"created": "Mon, 22 Nov 1999 13:54:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kopeikin",
"Sergei M.",
"",
"Dept. of Phys. and Astron., Univ.\n Missouri-Columbia"
]
] | The Lorentz covariant theory of precise Doppler measurements (PDM) based on the retarded Li\'{e}nard-Wiechert solution of the Einstein equations is described. An exact solution of equations of light propagation in the field of arbitrary moving bodies, which drastically extends the range of applicability of the new theory of PDM, is obtained. An explicit formula for the gravitational shift of frequency is given in analytic form. The limiting cases of the Doppler observations in gravitational lensing and of the spacecraft's Doppler tracking are described in more detail. We also present the post-Newtonian theory of the PDM developed for searching relativistic effects in close optical binaries and massive planetary systems. |
1203.3703 | Gabriel Pascu | Gabriel Pascu | New Spherical Scalar Modes on the de Sitter Expanding Universe | postprint that reflects the changes made after the revision process,
and subsequent publishing | Mod. Phys. Lett. A, vol. 27, No. 23 (2012) 1250124 | 10.1142/S0217732312501246 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New spherical scalar modes on the expanding part of Sitter spacetime,
eigenfunctions of a conserved Hamiltonian-like operator are found by solving
the Klein-Gordon equation in the appropriate coordinate chart, with the help of
a time evolution picture technique specially developed for spatially flat FLRW
charts. Transition coefficients are computed between these modes and the rest
of the scalar spherical and plane wave modes, either momentum or energy
eigenfunctions on the spatially flat FLRW chart.
| [
{
"created": "Fri, 16 Mar 2012 13:42:12 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Sep 2012 19:23:13 GMT",
"version": "v2"
}
] | 2012-09-24 | [
[
"Pascu",
"Gabriel",
""
]
] | New spherical scalar modes on the expanding part of Sitter spacetime, eigenfunctions of a conserved Hamiltonian-like operator are found by solving the Klein-Gordon equation in the appropriate coordinate chart, with the help of a time evolution picture technique specially developed for spatially flat FLRW charts. Transition coefficients are computed between these modes and the rest of the scalar spherical and plane wave modes, either momentum or energy eigenfunctions on the spatially flat FLRW chart. |
1201.1298 | Andrew Lundgren | Andrew P. Lundgren, Mihai Bondarescu, Ruxandra Bondarescu | Depressing de Sitter in the Frozen Future | 5 pages, no figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we focus on the gravitational thermodynamics of the far future.
Cosmological observations suggest that most matter will be diluted away by the
cosmological expansion, with the rest collapsing into supermassive black holes.
The likely future state of our local universe is a supermassive black hole
slowly evaporating in an empty universe dominated by a positive cosmological
constant. We describe some overlooked features of how the cosmological horizon
responds to the black hole evaporation. The presence of a black hole depresses
the entropy of the cosmological horizon by an amount proportional to the
geometric mean of the entropies of the black hole and cosmological horizons. As
the black hole evaporates and loses its mass in the process, the total entropy
increases obeying the second law of thermodynamics. The entropy is produced by
the heat from the black hole flowing across the extremely cold cosmological
horizon. Once the evaporation is complete, the universe becomes empty de Sitter
space that (in the presence of a true cosmological constant) is the maximum
entropy thermodynamic equilibrium state. We propose that flat Minkowski space
is an improper limit of this process which obscures the thermodynamics. The
cosmological constant should be regarded not only as an energy scale, but also
as a scale for the maximum entropy of a universe. In this context, flat
Minkowski space is indistinguishable from de Sitter with extremely small
cosmological constant, yielding a divergent entropy. This introduces an
unregulated infinity in black hole thermodynamics calculations, giving possibly
misleading results.
| [
{
"created": "Thu, 5 Jan 2012 21:01:58 GMT",
"version": "v1"
}
] | 2012-01-09 | [
[
"Lundgren",
"Andrew P.",
""
],
[
"Bondarescu",
"Mihai",
""
],
[
"Bondarescu",
"Ruxandra",
""
]
] | In this paper we focus on the gravitational thermodynamics of the far future. Cosmological observations suggest that most matter will be diluted away by the cosmological expansion, with the rest collapsing into supermassive black holes. The likely future state of our local universe is a supermassive black hole slowly evaporating in an empty universe dominated by a positive cosmological constant. We describe some overlooked features of how the cosmological horizon responds to the black hole evaporation. The presence of a black hole depresses the entropy of the cosmological horizon by an amount proportional to the geometric mean of the entropies of the black hole and cosmological horizons. As the black hole evaporates and loses its mass in the process, the total entropy increases obeying the second law of thermodynamics. The entropy is produced by the heat from the black hole flowing across the extremely cold cosmological horizon. Once the evaporation is complete, the universe becomes empty de Sitter space that (in the presence of a true cosmological constant) is the maximum entropy thermodynamic equilibrium state. We propose that flat Minkowski space is an improper limit of this process which obscures the thermodynamics. The cosmological constant should be regarded not only as an energy scale, but also as a scale for the maximum entropy of a universe. In this context, flat Minkowski space is indistinguishable from de Sitter with extremely small cosmological constant, yielding a divergent entropy. This introduces an unregulated infinity in black hole thermodynamics calculations, giving possibly misleading results. |
1405.0249 | Petr Horava | Petr Horava, Arif Mohd, Charles M. Melby-Thompson, Peter Shawhan | GR 20 Parallel Session A3: Modified Gravity | 12 pages, 2 figures | Gen. Rel. Grav. 46 (2014) 1720 | 10.1007/s10714-014-1720-4 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the contribution representing Parallel Session A3, on Modified
Gravity, in the Proceedings of the GR 20 Conference (July 2013, Warszawa,
Poland). It consists of three invited chapters, selected by the Session Chair
(P.H.) to represent the broad spectrum of topics discussed in the Session,
which ranged from theoretical and phenomenological, to experimental,
observational and numerical aspects of gravity. The three chapters are
"Einstein-Aether Theory: Thermodynamics of Universal Horizons" by Arif Mohd,
"The Curious Case of Conformal Anomalies in Horava-Lifshitz Gravity" by Charles
M. Melby-Thompson, and "Detectability of Scalar Gravitational-Wave Bursts with
LIGO and Virgo" by Peter Shawhan.
| [
{
"created": "Thu, 1 May 2014 18:47:54 GMT",
"version": "v1"
}
] | 2014-05-02 | [
[
"Horava",
"Petr",
""
],
[
"Mohd",
"Arif",
""
],
[
"Melby-Thompson",
"Charles M.",
""
],
[
"Shawhan",
"Peter",
""
]
] | This is the contribution representing Parallel Session A3, on Modified Gravity, in the Proceedings of the GR 20 Conference (July 2013, Warszawa, Poland). It consists of three invited chapters, selected by the Session Chair (P.H.) to represent the broad spectrum of topics discussed in the Session, which ranged from theoretical and phenomenological, to experimental, observational and numerical aspects of gravity. The three chapters are "Einstein-Aether Theory: Thermodynamics of Universal Horizons" by Arif Mohd, "The Curious Case of Conformal Anomalies in Horava-Lifshitz Gravity" by Charles M. Melby-Thompson, and "Detectability of Scalar Gravitational-Wave Bursts with LIGO and Virgo" by Peter Shawhan. |
1401.1189 | Vincenzo Vitagliano | Valerio Faraoni, Vincenzo Vitagliano | Horizon thermodynamics and spacetime mappings | 12 pages | null | 10.1103/PhysRevD.89.064015 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When black holes are dynamical, event horizons are replaced by apparent and
trapping horizons. Conformal and Kerr-Schild transformations are widely used in
relation with dynamical black holes and we study the behaviour under such
transformations of quantities related to the thermodynamics of these horizons,
such as the Misner-Sharp-Hernandez mass (internal energy), the Kodama vector,
surface gravity, and temperature. The transformation properties are not those
expected on the basis of naive arguments.
| [
{
"created": "Mon, 6 Jan 2014 20:24:36 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Faraoni",
"Valerio",
""
],
[
"Vitagliano",
"Vincenzo",
""
]
] | When black holes are dynamical, event horizons are replaced by apparent and trapping horizons. Conformal and Kerr-Schild transformations are widely used in relation with dynamical black holes and we study the behaviour under such transformations of quantities related to the thermodynamics of these horizons, such as the Misner-Sharp-Hernandez mass (internal energy), the Kodama vector, surface gravity, and temperature. The transformation properties are not those expected on the basis of naive arguments. |
gr-qc/9705070 | Matt Visser | Matt Visser (Washington University) | General Relativistic Energy Conditions: The Hubble expansion in the
epoch of galaxy formation | 25 pages; plain LaTeX; uses epsf.sty; three encapsulated postscript
figures. A brief summary of these ideas was published in Science 276 (4 April
1997) 88--90 | Phys.Rev. D56 (1997) 7578-7587 | 10.1103/PhysRevD.56.7578 | null | gr-qc | null | The energy conditions of Einstein gravity (classical general relativity) are
designed to extract as much information as possible from classical general
relativity without enforcing a particular equation of state for the
stress-energy. This systematic avoidance of the need to specify a particular
equation of state is particularly useful in a cosmological setting --- since
the equation of state for the cosmological fluid in a
Friedmann-Robertson-Walker type universe is extremely uncertain. I shall show
that the energy conditions provide simple and robust bounds on the behaviour of
both the density and look-back time as a function of red-shift. I shall show
that current observations suggest that the so-called strong energy condition
(SEC) is violated sometime between the epoch of galaxy formation and the
present. This implies that no possible combination of ``normal'' matter is
capable of fitting the observational data.
| [
{
"created": "Mon, 26 May 1997 21:03:15 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Visser",
"Matt",
"",
"Washington University"
]
] | The energy conditions of Einstein gravity (classical general relativity) are designed to extract as much information as possible from classical general relativity without enforcing a particular equation of state for the stress-energy. This systematic avoidance of the need to specify a particular equation of state is particularly useful in a cosmological setting --- since the equation of state for the cosmological fluid in a Friedmann-Robertson-Walker type universe is extremely uncertain. I shall show that the energy conditions provide simple and robust bounds on the behaviour of both the density and look-back time as a function of red-shift. I shall show that current observations suggest that the so-called strong energy condition (SEC) is violated sometime between the epoch of galaxy formation and the present. This implies that no possible combination of ``normal'' matter is capable of fitting the observational data. |
gr-qc/0010012 | Fatimah Shojai | Fatimah Shojai, Ali Shojai | Nonminimal Scalar-Tensor Theories and Quantum Gravity | 15 pages | Int.J.Mod.Phys. A15 (2000) 1859-1868 | 10.1142/S0217751X0000080X | null | gr-qc | null | Recentely, it is shown that the quantum effects of matter determine the
conformal degree of freedom of the space-time metric. This was done in the
framework of a scalar-tensor theory with one scalar field. A point with that
theory is that the form of quantum potential is preassumed. Here we present a
scalar-tensor theory with two scalar fields, and no assumption on the form of
quantum potential. It is shown that using the equations of motion one gets the
correct form of quantum potential plus some corrections.
| [
{
"created": "Wed, 4 Oct 2000 10:44:51 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Shojai",
"Fatimah",
""
],
[
"Shojai",
"Ali",
""
]
] | Recentely, it is shown that the quantum effects of matter determine the conformal degree of freedom of the space-time metric. This was done in the framework of a scalar-tensor theory with one scalar field. A point with that theory is that the form of quantum potential is preassumed. Here we present a scalar-tensor theory with two scalar fields, and no assumption on the form of quantum potential. It is shown that using the equations of motion one gets the correct form of quantum potential plus some corrections. |
gr-qc/9407031 | Friedrich Wilhelm Hehl | E.W. Mielke, Y.N. Obukhov, and F.W. Hehl | Yang--Mills Configurations from 3D Riemann--Cartan Geometry | 14 pages, preprint Cologne-thp-1994-h10 | Phys.Lett. A192 (1994) 153-162 | 10.1016/0375-9601(94)90237-2 | null | gr-qc hep-th | null | Recently, the {\it spacelike} part of the $SU(2)$ Yang--Mills equations has
been identified with geometrical objects of a three--dimensional space of
constant Riemann--Cartan curvature. We give a concise derivation of this
Ashtekar type (``inverse Kaluza--Klein") {\it mapping} by employing a
$(3+1)$--decomposition of {\it Clifford algebra}--valued torsion and curvature
two--forms. In the subcase of a mapping to purely axial 3D torsion, the
corresponding Lagrangian consists of the translational and Lorentz {\it
Chern--Simons term} plus cosmological term and is therefore of purely
topological origin.
| [
{
"created": "Thu, 21 Jul 1994 20:32:04 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Mielke",
"E. W.",
""
],
[
"Obukhov",
"Y. N.",
""
],
[
"Hehl",
"F. W.",
""
]
] | Recently, the {\it spacelike} part of the $SU(2)$ Yang--Mills equations has been identified with geometrical objects of a three--dimensional space of constant Riemann--Cartan curvature. We give a concise derivation of this Ashtekar type (``inverse Kaluza--Klein") {\it mapping} by employing a $(3+1)$--decomposition of {\it Clifford algebra}--valued torsion and curvature two--forms. In the subcase of a mapping to purely axial 3D torsion, the corresponding Lagrangian consists of the translational and Lorentz {\it Chern--Simons term} plus cosmological term and is therefore of purely topological origin. |
gr-qc/0111111 | Matt Visser | Matt Visser (Washington University in Saint Louis) Carlos Barcelo
(Washington University in Saint Louis) Stefano Liberati (U of Maryland) | Analogue models of and for gravity | Plain LaTeX2E; 20 page mini-survey; one eps figure. Plenary talk at
the Australasian Relativity Conference (Perth, July 2001). Proceedings to
appear in ``General Relativity and Gravitation'' | Gen.Rel.Grav. 34 (2002) 1719-1734 | null | null | gr-qc | null | Condensed matter systems, such as acoustics in flowing fluids, light in
moving dielectrics, or quasiparticles in a moving superfluid, can be used to
mimic aspects of general relativity. More precisely these systems (and others)
provide experimentally accessible models of curved-space quantum field theory.
As such they mimic kinematic aspects of general relativity, though typically
they do not mimic the *dynamics*. Although these analogue models are thereby
limited in their ability to duplicate all the effects of Einstein gravity they
nevertheless are extremely important -- they provide black hole analogues (some
of which have already been seen experimentally) and lead to tests of basic
principles of curved-space quantum field theory. Currently these tests are
still in the realm of *gedanken-experiments*, but there are plausible candidate
models that should lead to laboratory experiments in the not too distant
future.
| [
{
"created": "Fri, 30 Nov 2001 03:06:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Visser",
"Matt",
"",
"Washington University in Saint Louis"
],
[
"Barcelo",
"Carlos",
"",
"Washington University in Saint Louis"
],
[
"Liberati",
"Stefano",
"",
"U of Maryland"
]
] | Condensed matter systems, such as acoustics in flowing fluids, light in moving dielectrics, or quasiparticles in a moving superfluid, can be used to mimic aspects of general relativity. More precisely these systems (and others) provide experimentally accessible models of curved-space quantum field theory. As such they mimic kinematic aspects of general relativity, though typically they do not mimic the *dynamics*. Although these analogue models are thereby limited in their ability to duplicate all the effects of Einstein gravity they nevertheless are extremely important -- they provide black hole analogues (some of which have already been seen experimentally) and lead to tests of basic principles of curved-space quantum field theory. Currently these tests are still in the realm of *gedanken-experiments*, but there are plausible candidate models that should lead to laboratory experiments in the not too distant future. |
1506.06358 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Lemaitre model and cosmic mass | 10 pages, no figures, to appear in Gen. Rel. Gravit | null | 10.1007/s10714-015-1926-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mass of a sphere of simmetry in the Lemaitre universe is discussed using
the Hawking-Hayward quasi-local energy and clarifying existing ambiguities. A
covariantly conserved current introduced by Cahill and McVittie is shown to be
a multiple of the Kodama energy current.
| [
{
"created": "Sun, 21 Jun 2015 12:43:20 GMT",
"version": "v1"
}
] | 2015-07-15 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | The mass of a sphere of simmetry in the Lemaitre universe is discussed using the Hawking-Hayward quasi-local energy and clarifying existing ambiguities. A covariantly conserved current introduced by Cahill and McVittie is shown to be a multiple of the Kodama energy current. |
2109.06425 | Hao Tian Sun | Rong-Gen Cai, Li Li, Hao-Tian Sun | Instability in charged Gauss-Bonnet-de Sitter black holes | 13 pages + appendix, 13 figures; title changed, matches published
version in PRD | Phys. Rev. D 105, 064032 (2022) | 10.1103/PhysRevD.105.064032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the instability of the charged Gauss-Bonnet de Sitter black holes
under gravito-electromagnetic perturbations. We adopt two criteria to search
for an instability of the scalar type perturbations, including the local
instability criterion based on the $AdS_2$ Breitenl\"{o}hner-Freedman (BF)
bound at extremality and the dynamical instability via quasinormal modes by
full numerical analysis. We uncover the gravitational instability in five
spacetime dimensions and above, and construct the complete parameter space in
terms of the ratio of event and cosmological horizons and the Gauss-Bonnet
coupling. We show that the BF bound violation is a sufficient but not necessary
condition for the presence of dynamical instability. While the physical origin
of the instability without the Gauss-Bonnet term has been argued to be from the
$AdS_2$ BF bound violation, our analysis suggests that the BF bound violation
can not account for all physical origin of the instability for the charged
Gauss-Bonnet black holes.
| [
{
"created": "Tue, 14 Sep 2021 04:22:45 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Mar 2022 08:42:34 GMT",
"version": "v2"
}
] | 2022-03-22 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Li",
"Li",
""
],
[
"Sun",
"Hao-Tian",
""
]
] | We study the instability of the charged Gauss-Bonnet de Sitter black holes under gravito-electromagnetic perturbations. We adopt two criteria to search for an instability of the scalar type perturbations, including the local instability criterion based on the $AdS_2$ Breitenl\"{o}hner-Freedman (BF) bound at extremality and the dynamical instability via quasinormal modes by full numerical analysis. We uncover the gravitational instability in five spacetime dimensions and above, and construct the complete parameter space in terms of the ratio of event and cosmological horizons and the Gauss-Bonnet coupling. We show that the BF bound violation is a sufficient but not necessary condition for the presence of dynamical instability. While the physical origin of the instability without the Gauss-Bonnet term has been argued to be from the $AdS_2$ BF bound violation, our analysis suggests that the BF bound violation can not account for all physical origin of the instability for the charged Gauss-Bonnet black holes. |
gr-qc/9405019 | U. Bleyer | U. Bleyer, A. Zhuk | Classical and Quantum Behaviour of Multidimensional Integrable
Cosmologies | 33 pages, 13 figures available on request from ubleyer@aip.de, LaTeX,
Potsdam University, preprint Free University Berlin FUB-HEP/94-1 | null | null | null | gr-qc | null | Multidimensional cosmological models with $n~(n > 1)$ Einstein spaces are
discussed classically and with respect to canonical quantization. These models
are integrable in the case of Ricci flat internal spaces. For negative
curvature of the external space we find exact classical solutions modelling
dynamical as well as spontaneous compactification of the internal spaces.
Spontaneous compactification turns out to be an attractor solution. Solutions
of the quantum Wheeler-DeWitt equation are also obtained. Some of them describe
the tunneling process to be interpreted as the birth of the universe from
''nothing''.
| [
{
"created": "Fri, 6 May 1994 13:41:59 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Bleyer",
"U.",
""
],
[
"Zhuk",
"A.",
""
]
] | Multidimensional cosmological models with $n~(n > 1)$ Einstein spaces are discussed classically and with respect to canonical quantization. These models are integrable in the case of Ricci flat internal spaces. For negative curvature of the external space we find exact classical solutions modelling dynamical as well as spontaneous compactification of the internal spaces. Spontaneous compactification turns out to be an attractor solution. Solutions of the quantum Wheeler-DeWitt equation are also obtained. Some of them describe the tunneling process to be interpreted as the birth of the universe from ''nothing''. |
0802.1508 | Michele Levi | Michele Levi | Next-to-leading order gravitational spin1-spin2 coupling with
Kaluza-Klein reduction | 12 pages, revtex4-1, 3 figures; v2: reference added; v3: edited,
section 3 elaborated; v4: published | Phys.Rev.D82:064029,2010 | 10.1103/PhysRevD.82.064029 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the recently proposed Kaluza-Klein (KK) reduction over the time
dimension, within an effective field theory (EFT) approach, to calculate the
next to leading order (NLO) gravitational spin1-spin2 interaction between two
spinning compact objects. It is shown here that to NLO in the spin1-spin2
interaction, the reduced KK action within the stationary approximation is
sufficient to describe the gravitational interaction, and that it simplifies
calculation substantially. We also find here that the gravito-magnetic vector
field defined within the KK decomposition of the metric mostly dominates the
mediation of the interaction. Our results coincide with those calculated in the
ADM Hamiltonian formalism, and we provide another explanation for the
discrepancy with the result previously derived within the EFT approach, thus
demonstrating clearly the equivalence of the ADM Hamiltonian formalism and the
EFT action approach.
| [
{
"created": "Mon, 11 Feb 2008 19:32:19 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Feb 2008 12:49:48 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Jul 2010 13:10:00 GMT",
"version": "v3"
},
{
"created": "Fri, 24 Sep 2010 22:36:38 GMT",
"version": "v4"
}
] | 2010-12-02 | [
[
"Levi",
"Michele",
""
]
] | We use the recently proposed Kaluza-Klein (KK) reduction over the time dimension, within an effective field theory (EFT) approach, to calculate the next to leading order (NLO) gravitational spin1-spin2 interaction between two spinning compact objects. It is shown here that to NLO in the spin1-spin2 interaction, the reduced KK action within the stationary approximation is sufficient to describe the gravitational interaction, and that it simplifies calculation substantially. We also find here that the gravito-magnetic vector field defined within the KK decomposition of the metric mostly dominates the mediation of the interaction. Our results coincide with those calculated in the ADM Hamiltonian formalism, and we provide another explanation for the discrepancy with the result previously derived within the EFT approach, thus demonstrating clearly the equivalence of the ADM Hamiltonian formalism and the EFT action approach. |
2010.13579 | Pablo Arrighi | Pablo Arrighi and Marios Christodoulou and Am\'elia Durbec | On quantum superpositions of graphs, no-signalling and covariance | null | 2021 Talk https://youtu.be/r5-aWIiWHDk | null | null | gr-qc cs.DM math.DS quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a mathematically and conceptually robust notion of quantum
superpositions of graphs. We argue that, crucially, quantum superpositions of
graphs require node names for their correct alignment, which we demonstrate
through a no-signalling argument. Nevertheless, node names are a fiducial
construct, serving a similar purpose to the labelling of points through a
choice of coordinates in continuous space. Graph renamings, aka isomorphisms,
are understood as a change of coordinates on the graph and correspond to a
natively discrete analogue of continuous diffeomorphisms. We postulate renaming
invariance as a symmetry principle in discrete topology of similar weight to
diffeomorphism invariance in the continuous. We explain how to impose renaming
invariance at the level of quantum superpositions of graphs, in a way that
still allows us to talk about an observable centred at a specific node.
| [
{
"created": "Mon, 26 Oct 2020 13:32:16 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Nov 2021 15:05:13 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Mar 2023 23:14:35 GMT",
"version": "v3"
}
] | 2023-03-09 | [
[
"Arrighi",
"Pablo",
""
],
[
"Christodoulou",
"Marios",
""
],
[
"Durbec",
"Amélia",
""
]
] | We provide a mathematically and conceptually robust notion of quantum superpositions of graphs. We argue that, crucially, quantum superpositions of graphs require node names for their correct alignment, which we demonstrate through a no-signalling argument. Nevertheless, node names are a fiducial construct, serving a similar purpose to the labelling of points through a choice of coordinates in continuous space. Graph renamings, aka isomorphisms, are understood as a change of coordinates on the graph and correspond to a natively discrete analogue of continuous diffeomorphisms. We postulate renaming invariance as a symmetry principle in discrete topology of similar weight to diffeomorphism invariance in the continuous. We explain how to impose renaming invariance at the level of quantum superpositions of graphs, in a way that still allows us to talk about an observable centred at a specific node. |
2310.20378 | Juan Calderon Bustillo | Ver\'onica Villa-Ortega, Ana Lorenzo-Medina, Juan Calder\'on Bustillo,
Milton Ruiz, Davide Guerra, Pablo Cerd\'a-Duran, Jos\'e A. Font | Self-consistent treatment of thermal effects in neutron-star
post-mergers: observational implications for third-generation
gravitational-wave detectors | 9 pages, 3 Figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We assess the impact of accurate, self-consistent modelling of thermal
effects in neutron-star merger remnants in the context of third-generation
gravitational-wave detectors. This is done through the usage, in Bayesian model
selection experiments, of numerical-relativity simulations of binary neutron
star (BNS) mergers modelled through: a) nuclear, finite-temperature (or
``tabulated'') equations of state (EoSs), and b) their simplifed piecewise (or
``hybrid'') representation. These cover four different EoSs, namely SLy4, DD2,
HShen and LS220. Our analyses make direct use of the Newman-Penrose scalar
$\psi_4$ outputted by numerical simulations. Considering a detector network
formed by three Cosmic Explorers, we show that differences in the
gravitational-wave emission predicted by the two models are detectable with a
natural logarithmic Bayes Factor $\log{\cal{B}}\geq 5$ at average distances of
$d_L \simeq 50$Mpc, reaching $d_L \simeq 100$Mpc for source inclinations $\iota
\leq 0.8$, regardless of the EoS. This impact is most pronounced for the HShen
EoS. For low inclinations, only the DD2 EoS prevents the detectability of such
modelling differences at $d_L \simeq 150$Mpc. Our results suggest that the
usage a self-consistent treatment of thermal effects is crucial for
third-generation gravitational wave detectors.
| [
{
"created": "Tue, 31 Oct 2023 11:37:23 GMT",
"version": "v1"
}
] | 2023-11-01 | [
[
"Villa-Ortega",
"Verónica",
""
],
[
"Lorenzo-Medina",
"Ana",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Ruiz",
"Milton",
""
],
[
"Guerra",
"Davide",
""
],
[
"Cerdá-Duran",
"Pablo",
""
],
[
"Font",
"José A.",
""
]
] | We assess the impact of accurate, self-consistent modelling of thermal effects in neutron-star merger remnants in the context of third-generation gravitational-wave detectors. This is done through the usage, in Bayesian model selection experiments, of numerical-relativity simulations of binary neutron star (BNS) mergers modelled through: a) nuclear, finite-temperature (or ``tabulated'') equations of state (EoSs), and b) their simplifed piecewise (or ``hybrid'') representation. These cover four different EoSs, namely SLy4, DD2, HShen and LS220. Our analyses make direct use of the Newman-Penrose scalar $\psi_4$ outputted by numerical simulations. Considering a detector network formed by three Cosmic Explorers, we show that differences in the gravitational-wave emission predicted by the two models are detectable with a natural logarithmic Bayes Factor $\log{\cal{B}}\geq 5$ at average distances of $d_L \simeq 50$Mpc, reaching $d_L \simeq 100$Mpc for source inclinations $\iota \leq 0.8$, regardless of the EoS. This impact is most pronounced for the HShen EoS. For low inclinations, only the DD2 EoS prevents the detectability of such modelling differences at $d_L \simeq 150$Mpc. Our results suggest that the usage a self-consistent treatment of thermal effects is crucial for third-generation gravitational wave detectors. |
1706.01416 | Chris Stevens | Florian Beyer, J\"org Frauendiener, Chris Stevens and Ben Whale | The numerical initial boundary value problem for the generalized
conformal field equations | 27 pages, 7 figures | Phys. Rev. D 96, 084020 (2017) | 10.1103/PhysRevD.96.084020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study a numerical implementation for the initial boundary
value formulation for the generalized conformal field equations. We propose a
formulation which is well suited for the study of the long-time behaviour of
perturbed exact solutions such as a Schwarzschild or even a Kerr black hole. We
describe the derivation of the implemented equations which we give in terms of
the space-spinor formalism. We discuss the conformal Gauss gauge, and a slight
generalization thereof which seems to be particularly useful in the presence of
boundaries. We discuss the structure of the equations at the boundary and
propose a method for imposing boundary conditions which allow the correct
number of degrees of freedom to be freely specified while still preserving the
constraints. We show that this implementation yields a numerically well-posed
system by testing it on a simple case of gravitational perturbations of
Minkowski space-time and subsequently with gravitational perturbations of
Schwarzschild space-time.
| [
{
"created": "Mon, 5 Jun 2017 16:47:42 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Jun 2017 06:39:55 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Aug 2017 06:58:18 GMT",
"version": "v3"
},
{
"created": "Mon, 28 Aug 2017 08:38:43 GMT",
"version": "v4"
}
] | 2017-10-18 | [
[
"Beyer",
"Florian",
""
],
[
"Frauendiener",
"Jörg",
""
],
[
"Stevens",
"Chris",
""
],
[
"Whale",
"Ben",
""
]
] | In this paper we study a numerical implementation for the initial boundary value formulation for the generalized conformal field equations. We propose a formulation which is well suited for the study of the long-time behaviour of perturbed exact solutions such as a Schwarzschild or even a Kerr black hole. We describe the derivation of the implemented equations which we give in terms of the space-spinor formalism. We discuss the conformal Gauss gauge, and a slight generalization thereof which seems to be particularly useful in the presence of boundaries. We discuss the structure of the equations at the boundary and propose a method for imposing boundary conditions which allow the correct number of degrees of freedom to be freely specified while still preserving the constraints. We show that this implementation yields a numerically well-posed system by testing it on a simple case of gravitational perturbations of Minkowski space-time and subsequently with gravitational perturbations of Schwarzschild space-time. |
2110.02745 | Muhammad Sharif | M. Sharif and Faisal Javed | Stability of $d$-dimensional Gravastars with Variable Equation of State | 21 pages, 12 figures, to appear in Chinese J. Physics | Chinese J. Phys. 77(2022)804-815 | 10.1016/j.cjph.2021.08.024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we are interested to explore stable configurations of
$d$-dimensional gravastars constructed from the interior $d$-dimensional de
Sitter and exterior $d$-dimensional Schwarzschild/Reissner-Nordstr\"om (de
Sitter) black holes through cut and paste approach. We consider the linearized
radial perturbation preserving the original symmetries to explore their
stability by using three different types of matter distributions. The resulting
frameworks represent unstable structures for barotropic, Chaplygin, and
phantomlike models for every considered choice of exterior geometries. However,
matter contents with variable equations of state have a remarkable role to
maintain the stability of gravastars. We conclude that stable structures of
gravastars are obtained only for generalized variable models with exterior
$d$-dimensional Schwarzschild/Reissner-Nordstr\"om-de Sitter black holes.
| [
{
"created": "Tue, 5 Oct 2021 09:34:53 GMT",
"version": "v1"
}
] | 2022-05-10 | [
[
"Sharif",
"M.",
""
],
[
"Javed",
"Faisal",
""
]
] | In this paper, we are interested to explore stable configurations of $d$-dimensional gravastars constructed from the interior $d$-dimensional de Sitter and exterior $d$-dimensional Schwarzschild/Reissner-Nordstr\"om (de Sitter) black holes through cut and paste approach. We consider the linearized radial perturbation preserving the original symmetries to explore their stability by using three different types of matter distributions. The resulting frameworks represent unstable structures for barotropic, Chaplygin, and phantomlike models for every considered choice of exterior geometries. However, matter contents with variable equations of state have a remarkable role to maintain the stability of gravastars. We conclude that stable structures of gravastars are obtained only for generalized variable models with exterior $d$-dimensional Schwarzschild/Reissner-Nordstr\"om-de Sitter black holes. |
2003.13847 | Jens Boos | Jens Boos | Angle deficit & non-local gravitoelectromagnetism around a slowly
spinning cosmic string | v2: Matches published version, 10 pages, 1 figure. v1: 9 pages, 1
figure. Essay written for the Gravity Research Foundation 2020 Awards for
Essays on Gravitation, awarded an Honorable Mention | Int. J Mod. Phys. D 29 (2020) no. 14, 2043027 | 10.1142/S0218271820430270 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmic strings, as remnants of the symmetry breaking phase in the Early
Universe, may be susceptible to non-local physics. Here we show that the
presence of a Poincar\'e-invariant non-locality -- parametrized by a factor
$\exp(-\Box\ell^2)$ -- regularizes the gravitational field and thereby changes
the properties of spacetime: it is now simply connected and the angle deficit
around the cosmic string becomes a function of the radial distance. Similar
changes occur for the non-local gravitomagnetic field of a rotating cosmic
string, and we translate these mathematical facts into the language of
non-local gravitoelectromagnetism and thereby provide a physical
interpretation. We hope that these insights might prove helpful in the search
for traces of non-local physics in our Universe.
| [
{
"created": "Mon, 30 Mar 2020 22:26:20 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Feb 2021 01:02:35 GMT",
"version": "v2"
}
] | 2021-02-16 | [
[
"Boos",
"Jens",
""
]
] | Cosmic strings, as remnants of the symmetry breaking phase in the Early Universe, may be susceptible to non-local physics. Here we show that the presence of a Poincar\'e-invariant non-locality -- parametrized by a factor $\exp(-\Box\ell^2)$ -- regularizes the gravitational field and thereby changes the properties of spacetime: it is now simply connected and the angle deficit around the cosmic string becomes a function of the radial distance. Similar changes occur for the non-local gravitomagnetic field of a rotating cosmic string, and we translate these mathematical facts into the language of non-local gravitoelectromagnetism and thereby provide a physical interpretation. We hope that these insights might prove helpful in the search for traces of non-local physics in our Universe. |
1711.00584 | Miko{\l}aj Korzy\'nski | Miko{\l}aj Korzy\'nski and Jaros{\l}aw Kopi\'nski | Optical drift effects in general relativity | Matches the version published in JCAP | JCAP03(2018)012 | 10.1088/1475-7516/2018/03/012 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the question of determining the optical drift effects in general
relativity, i.e. the rate of change of the apparent position, redshift, Jacobi
matrix, angular distance and luminosity distance of a distant object as
registered by an observer in an arbitrary spacetime. We present a fully
relativistic and covariant approach, in which the problem is reduced to a
hierarchy of ODE's solved along the line of sight. The 4-velocities and
4-accelerations of the observer and the emitter and the geometry of the
spacetime along the line of sight constitute the input data. We build on the
standard relativistic geometric optics formalism and extend it to include the
time derivatives of the observables. In the process we obtain two general,
non-perturbative relations: the first one between the gravitational lensing,
represented by the Jacobi matrix, and the apparent position drift, also called
the cosmic parallax, and the second one between the apparent position drift and
the redshift drift. The applications of the results include the theoretical
study of the drift effects of cosmological origin (so-called real-time
cosmology) in numerical or exact Universe models.
| [
{
"created": "Thu, 2 Nov 2017 01:19:57 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 2017 14:33:50 GMT",
"version": "v2"
},
{
"created": "Sat, 9 Dec 2017 01:21:18 GMT",
"version": "v3"
},
{
"created": "Fri, 9 Mar 2018 11:32:16 GMT",
"version": "v4"
}
] | 2018-03-12 | [
[
"Korzyński",
"Mikołaj",
""
],
[
"Kopiński",
"Jarosław",
""
]
] | We consider the question of determining the optical drift effects in general relativity, i.e. the rate of change of the apparent position, redshift, Jacobi matrix, angular distance and luminosity distance of a distant object as registered by an observer in an arbitrary spacetime. We present a fully relativistic and covariant approach, in which the problem is reduced to a hierarchy of ODE's solved along the line of sight. The 4-velocities and 4-accelerations of the observer and the emitter and the geometry of the spacetime along the line of sight constitute the input data. We build on the standard relativistic geometric optics formalism and extend it to include the time derivatives of the observables. In the process we obtain two general, non-perturbative relations: the first one between the gravitational lensing, represented by the Jacobi matrix, and the apparent position drift, also called the cosmic parallax, and the second one between the apparent position drift and the redshift drift. The applications of the results include the theoretical study of the drift effects of cosmological origin (so-called real-time cosmology) in numerical or exact Universe models. |
1412.4828 | Diego Blas | Diego Blas and Eugene Lim | Phenomenology of theories of gravity without Lorentz invariance: the
preferred frame case | 38 pages, 3 figures; v2 references added | null | 10.1142/S0218271814430093 | CERN-PH-TH-2014-193 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories of gravitation without Lorentz invariance are candidates of
low-energy descriptions of quantum gravity. In this review we will describe the
phenomenological consequences of the candidates associated to the existence of
a preferred time direction
| [
{
"created": "Mon, 15 Dec 2014 22:43:08 GMT",
"version": "v1"
},
{
"created": "Tue, 12 May 2015 08:57:10 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Blas",
"Diego",
""
],
[
"Lim",
"Eugene",
""
]
] | Theories of gravitation without Lorentz invariance are candidates of low-energy descriptions of quantum gravity. In this review we will describe the phenomenological consequences of the candidates associated to the existence of a preferred time direction |
2406.01758 | Ahmed Sheta | Ahmed Sheta, Yuri Levin | Gravitational Wave Driven Inspirals of Binaries Connected by Cosmic
Strings | 12 pages, 8 figures. v2: minor changes and removed word from title,
as published in PRD | Phys. Rev. D 110, 024074 (2024) | 10.1103/PhysRevD.110.024074 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider gravitational waves from a pair of monopoles or black holes that
are moving non-relativistically and are connected by a cosmic string. Shortly
after the binary's formation, the connecting string straightens due the direct
coupling of its motion to gravitational radiation. Afterwards, the motion of
the binary can be well-approximated by a non-relativistic motion of its
components that have an additional constant mutual attraction force due to the
tension of the straight string that connects them. The orbit shrinks due to the
gravitational radiation backreacting on the binary's components. We find that
if the binary's semimajor axis $a\gg \sqrt{R_1 R_2/{\mu}}$, its eccentricity
grows on the inspiral's timescale; here $R_1$ and $R_2$ are the gravitational
radii of the binary components, and $\mu$ is the dimensionless tension of the
string. When the eccentricity is high, it approaches unity super-exponentially.
If the binary's components are monopole-antimonopole pair, this leads to the
physical collision that would likely destroy the string and annihilate the
monopoles when the semimajor axis is still many orders of magnitude greater
than the string thickness. If the binary's components are black holes, then the
eccentricity reaches its peak when $a\sim \sqrt{R_1 R_2/\mu}$, and then decays
according to the standard Peter's formula. The black-hole spins initially
become locked to the orbital motion, but then lag behind as the inspiral
proceeds. We estimate the string-tension-induced dimensionless spins just prior
to the merger and find them to be $\sim\mu^{3/8}\ll 1$.
| [
{
"created": "Mon, 3 Jun 2024 19:53:42 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jul 2024 15:58:11 GMT",
"version": "v2"
}
] | 2024-07-30 | [
[
"Sheta",
"Ahmed",
""
],
[
"Levin",
"Yuri",
""
]
] | We consider gravitational waves from a pair of monopoles or black holes that are moving non-relativistically and are connected by a cosmic string. Shortly after the binary's formation, the connecting string straightens due the direct coupling of its motion to gravitational radiation. Afterwards, the motion of the binary can be well-approximated by a non-relativistic motion of its components that have an additional constant mutual attraction force due to the tension of the straight string that connects them. The orbit shrinks due to the gravitational radiation backreacting on the binary's components. We find that if the binary's semimajor axis $a\gg \sqrt{R_1 R_2/{\mu}}$, its eccentricity grows on the inspiral's timescale; here $R_1$ and $R_2$ are the gravitational radii of the binary components, and $\mu$ is the dimensionless tension of the string. When the eccentricity is high, it approaches unity super-exponentially. If the binary's components are monopole-antimonopole pair, this leads to the physical collision that would likely destroy the string and annihilate the monopoles when the semimajor axis is still many orders of magnitude greater than the string thickness. If the binary's components are black holes, then the eccentricity reaches its peak when $a\sim \sqrt{R_1 R_2/\mu}$, and then decays according to the standard Peter's formula. The black-hole spins initially become locked to the orbital motion, but then lag behind as the inspiral proceeds. We estimate the string-tension-induced dimensionless spins just prior to the merger and find them to be $\sim\mu^{3/8}\ll 1$. |
gr-qc/0006002 | Patricio S. Letelier | Guillermo A. Gonz\'alez and Patricio S. Letelier | Rotating Relativistic Thin Disks | 18 eps figures, to be published PRD | Phys.Rev. D62 (2000) 064025 | 10.1103/PhysRevD.62.064025 | null | gr-qc | null | Two families of models of rotating relativistic disks based on Taub-NUT and
Kerr metrics are constructed using the well-known "displace, cut and reflect"
method. We find that for disks built from a generic stationary axially
symmetric metric the "sound velocity", $(pressure/density)^{1/2}$, is equal to
the geometric mean of the prograde and retrograde geodesic circular velocities
of test particles moving on the disk. We also found that for generic disks we
can have zones with heat flow. For the two families of models studied the
boundaries that separate the zones with and without heat flow are not stable
against radial perturbations (ring formation).
| [
{
"created": "Thu, 1 Jun 2000 16:43:13 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"González",
"Guillermo A.",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | Two families of models of rotating relativistic disks based on Taub-NUT and Kerr metrics are constructed using the well-known "displace, cut and reflect" method. We find that for disks built from a generic stationary axially symmetric metric the "sound velocity", $(pressure/density)^{1/2}$, is equal to the geometric mean of the prograde and retrograde geodesic circular velocities of test particles moving on the disk. We also found that for generic disks we can have zones with heat flow. For the two families of models studied the boundaries that separate the zones with and without heat flow are not stable against radial perturbations (ring formation). |
2203.11041 | Phongpichit Channuie | Apirak Payaka (Walailak U.), Waluka Amaek (Walailak U.), Phongpichit
Channuie (Walailak U.) | Warm deformed $R^{2}$ inflation | v3: 20 pages, 5 figures,, version accepted for publication in Nuclear
Physics B | Nuclear Physics B 986 (2023) 116052 | 10.1016/j.nuclphysb.2022.116052 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we study warm inflationary scenario based on a deformation of
$R^{2}$ gravity. We start considering $R^{p}$ and assume $p=2(1+\delta)$ with
$\delta\ll 1$ so that we simply obtain warm $R^{2}$ inflation when setting
$\delta=0$. We then derive the potential in the Einstein frame and consider a
dissipation parameter of the form $\Gamma = C_{1}T$ with $C_1$ being a coupling
parameter. We focus only on the strong regime of which the interaction between
inflaton and radiation fluid has been taken into account. We compute
inflationary observables and constrain the parameters of our model using latest
observational data reported by Planck. From our analysis, we discover that with
proper choices of parameters the derived $n_s$ and $r$ are in good agreement
with the Planck 2018 observational constraints. Particularly, we constrain the
potential scale $U_{0}$ of the models.
| [
{
"created": "Mon, 21 Mar 2022 15:03:28 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Apr 2022 08:06:54 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Dec 2022 13:10:39 GMT",
"version": "v3"
}
] | 2022-12-20 | [
[
"Payaka",
"Apirak",
"",
"Walailak U."
],
[
"Amaek",
"Waluka",
"",
"Walailak U."
],
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
]
] | In this work, we study warm inflationary scenario based on a deformation of $R^{2}$ gravity. We start considering $R^{p}$ and assume $p=2(1+\delta)$ with $\delta\ll 1$ so that we simply obtain warm $R^{2}$ inflation when setting $\delta=0$. We then derive the potential in the Einstein frame and consider a dissipation parameter of the form $\Gamma = C_{1}T$ with $C_1$ being a coupling parameter. We focus only on the strong regime of which the interaction between inflaton and radiation fluid has been taken into account. We compute inflationary observables and constrain the parameters of our model using latest observational data reported by Planck. From our analysis, we discover that with proper choices of parameters the derived $n_s$ and $r$ are in good agreement with the Planck 2018 observational constraints. Particularly, we constrain the potential scale $U_{0}$ of the models. |
1310.6399 | David Sloan | Alejandro Corichi and David Sloan | Inflationary Attractors and their Measures | 8 pages, 1 figure | Class. Quant. Grav. 31 (2014) 062001 | 10.1088/0264-9381/31/6/062001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several recent misconceptions about the measure problem in inflation and the
nature of inflationary attractors are addressed. We show that within the
Hamiltonian system of flat Friedmann-Lema\^itre-Robertson-Walker cosmology
coupled to a massive scalar field, the focussing of the Liouville measure on
attractor solutions is brought about by a spread in a gauge degree of freedom -
the spatial volume. Using this we show how the Liouville measure formulated on
a surface of constant Hubble rate induces a probability distribution function
on surfaces of other Hubble rates, and the attractor behaviour is seen through
the focussing of this function on a narrow range of physical observables. One
can conclude then that standard techniques from Hamiltonian dynamics suffice to
provide a satisfactory description of attractor solutions and the measure
problem.
Updated to match published version.
| [
{
"created": "Wed, 23 Oct 2013 21:34:54 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Feb 2014 16:13:14 GMT",
"version": "v2"
}
] | 2015-07-28 | [
[
"Corichi",
"Alejandro",
""
],
[
"Sloan",
"David",
""
]
] | Several recent misconceptions about the measure problem in inflation and the nature of inflationary attractors are addressed. We show that within the Hamiltonian system of flat Friedmann-Lema\^itre-Robertson-Walker cosmology coupled to a massive scalar field, the focussing of the Liouville measure on attractor solutions is brought about by a spread in a gauge degree of freedom - the spatial volume. Using this we show how the Liouville measure formulated on a surface of constant Hubble rate induces a probability distribution function on surfaces of other Hubble rates, and the attractor behaviour is seen through the focussing of this function on a narrow range of physical observables. One can conclude then that standard techniques from Hamiltonian dynamics suffice to provide a satisfactory description of attractor solutions and the measure problem. Updated to match published version. |
1810.12111 | Pedro Cañate Casseres | Pedro Ca\~nate, Nora Breton | Black Hole-Wormhole transition in (2+1) Einstein -- anti-de Sitter
Gravity Coupled to Nonlinear Electrodynamics | Typos corrected. Published in Physical Review D. arXiv admin note:
text overlap with arXiv:1307.6655 by other authors | null | 10.1103/PhysRevD.98.104012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present two results in $(2+1)$ gravity coupled to nonlinear
electrodynamics. First it is determined the general form of the electromagnetic
field tensor in $(2+1)$ gravity coupled to nonlinear electrodynamics in
stationary cyclic spacetimes. Secondly, it is determined a family of exact
solutions in $(2+1)$ gravity sourced by a nonlinear electromagnetic field. The
solutions are characterized by five parameters: mass $M$, angular momentum $J$,
cosmological constant $\Lambda$ and two electromagnetic charges, $q_{\alpha}$
and $q_{\beta}$. Remarkably, the solution can be interpreted as a traversable
wormhole, provided the fulfillment of certain inequalities by the
characteristic parameters; fine tunning of the cosmological constant leads to
an extreme black hole, whereas by switching off one of the electromagnetic
charges, we obtain the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole.
| [
{
"created": "Fri, 26 Oct 2018 00:50:01 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jul 2019 12:04:00 GMT",
"version": "v2"
}
] | 2019-07-03 | [
[
"Cañate",
"Pedro",
""
],
[
"Breton",
"Nora",
""
]
] | In this paper we present two results in $(2+1)$ gravity coupled to nonlinear electrodynamics. First it is determined the general form of the electromagnetic field tensor in $(2+1)$ gravity coupled to nonlinear electrodynamics in stationary cyclic spacetimes. Secondly, it is determined a family of exact solutions in $(2+1)$ gravity sourced by a nonlinear electromagnetic field. The solutions are characterized by five parameters: mass $M$, angular momentum $J$, cosmological constant $\Lambda$ and two electromagnetic charges, $q_{\alpha}$ and $q_{\beta}$. Remarkably, the solution can be interpreted as a traversable wormhole, provided the fulfillment of certain inequalities by the characteristic parameters; fine tunning of the cosmological constant leads to an extreme black hole, whereas by switching off one of the electromagnetic charges, we obtain the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. |
0803.3936 | Narayan Banerjee | Sudipta Das, Narayan Banerjee | Brans-Dicke Scalar Field as a Chameleon | 10 pages, 8 figures; Contents added, References added; Revised
version accepted for publication in Physical Review D | Phys.Rev.D78:043512,2008 | 10.1103/PhysRevD.78.043512 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper it is shown that in Brans - Dicke theory, if one considers a
non-minimal coupling between the matter and the scalar field, it can give rise
to a late time accelerated expansion for the universe preceded by a decelerated
expansion for very high values of the Brans - Dicke parameter $\omega$.
| [
{
"created": "Thu, 27 Mar 2008 14:26:45 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jul 2008 11:35:26 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Das",
"Sudipta",
""
],
[
"Banerjee",
"Narayan",
""
]
] | In this paper it is shown that in Brans - Dicke theory, if one considers a non-minimal coupling between the matter and the scalar field, it can give rise to a late time accelerated expansion for the universe preceded by a decelerated expansion for very high values of the Brans - Dicke parameter $\omega$. |
1801.05826 | Sean Gryb | Sean Gryb and Karim P. Y. Th\'ebault | Bouncing Unitary Cosmology II: Mini-Superspace Phenomenology | Version published in Classical Quantum Gravity. 20 pages, 8 figures | null | 10.1088/1361-6382/aaf837 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A companion paper provides a proposal for cosmic singularity resolution based
upon general features of a bouncing unitary cosmological model in the
mini-superspace approximation. This paper analyses novel phenomenology that can
be identified within particular solutions of that model. First, we justify our
choice of particular solutions based upon a clearly articulated and
observationally-motivated principle. Second, we demonstrate that the chosen
solutions follow a classical mini-superspace cosmology before smoothly bouncing
off the classically singular region. Third, and most significantly, we identify
a `Rayleigh-scattering' limit for physically reasonable choices of parameters
within which the solutions display effective behaviour that is insensitive to
the details of rapidly oscillating Planck-scale physics. This effective physics
is found to be compatible with an effective period of cosmic inflation well
below the Planck scale. The detailed effective physics of this
Rayleigh-scattering limit is provided via: i) an exact analytical treatment of
the model in the de~Sitter limit; and ii) numerical solutions of the full
model.
| [
{
"created": "Wed, 17 Jan 2018 19:08:24 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Dec 2018 11:40:35 GMT",
"version": "v2"
}
] | 2018-12-17 | [
[
"Gryb",
"Sean",
""
],
[
"Thébault",
"Karim P. Y.",
""
]
] | A companion paper provides a proposal for cosmic singularity resolution based upon general features of a bouncing unitary cosmological model in the mini-superspace approximation. This paper analyses novel phenomenology that can be identified within particular solutions of that model. First, we justify our choice of particular solutions based upon a clearly articulated and observationally-motivated principle. Second, we demonstrate that the chosen solutions follow a classical mini-superspace cosmology before smoothly bouncing off the classically singular region. Third, and most significantly, we identify a `Rayleigh-scattering' limit for physically reasonable choices of parameters within which the solutions display effective behaviour that is insensitive to the details of rapidly oscillating Planck-scale physics. This effective physics is found to be compatible with an effective period of cosmic inflation well below the Planck scale. The detailed effective physics of this Rayleigh-scattering limit is provided via: i) an exact analytical treatment of the model in the de~Sitter limit; and ii) numerical solutions of the full model. |
1903.05996 | Phongpichit Channuie | Phongpichit Channuie (Walailak U.) | Deformed Starobinsky model in gravity's rainbow | v1: 16 pages, 8 figures | Eur. Phys. J. C79 (2019) no.6, 508 | 10.1140/epjc/s10052-019-7031-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of gravity's rainbow, we study the deformed Starobinsky model
in which the deformations take the form $f(R)\sim R^{2(1-\alpha)}$, with $R$
the Ricci scalar and $\alpha$ a positive parameter. We show that the spectral
index of curvature perturbation and the tensor-to-scalar ratio can be written
in terms of $N,\,\lambda$ and $\alpha$, with $N$ being the number of {\it
e}-foldings, $\lambda$ a rainbow parameter. We compare the predictions of our
models with Planck data. With the sizeable number of {\it e}-foldings and
proper choices of parameters, we discover that the predictions of the model are
in excellent agreement with the Planck analysis. Interestingly, we obtain the
upper limit and the lower limit of a rainbow parameter $\lambda$ and a positive
constant $\alpha$, respectively.
| [
{
"created": "Sat, 9 Mar 2019 12:36:54 GMT",
"version": "v1"
}
] | 2019-06-18 | [
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
]
] | In the context of gravity's rainbow, we study the deformed Starobinsky model in which the deformations take the form $f(R)\sim R^{2(1-\alpha)}$, with $R$ the Ricci scalar and $\alpha$ a positive parameter. We show that the spectral index of curvature perturbation and the tensor-to-scalar ratio can be written in terms of $N,\,\lambda$ and $\alpha$, with $N$ being the number of {\it e}-foldings, $\lambda$ a rainbow parameter. We compare the predictions of our models with Planck data. With the sizeable number of {\it e}-foldings and proper choices of parameters, we discover that the predictions of the model are in excellent agreement with the Planck analysis. Interestingly, we obtain the upper limit and the lower limit of a rainbow parameter $\lambda$ and a positive constant $\alpha$, respectively. |
1005.5565 | Edward Wilson-Ewing | Edward Wilson-Ewing | Loop quantum cosmology of Bianchi type IX models | 20 pages | Phys.Rev.D82:043508,2010 | 10.1103/PhysRevD.82.043508 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The loop quantum cosmology "improved dynamics" of the Bianchi type IX model
are studied. The action of the Hamiltonian constraint operator is obtained via
techniques developed for the Bianchi type I and type II models, no new input is
required. It is shown that the big bang and big crunch singularities are
resolved by quantum gravity effects. We also present the effective equations
which provide modifications to the classical equations of motion due to quantum
geometry effects.
| [
{
"created": "Sun, 30 May 2010 23:23:38 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Wilson-Ewing",
"Edward",
""
]
] | The loop quantum cosmology "improved dynamics" of the Bianchi type IX model are studied. The action of the Hamiltonian constraint operator is obtained via techniques developed for the Bianchi type I and type II models, no new input is required. It is shown that the big bang and big crunch singularities are resolved by quantum gravity effects. We also present the effective equations which provide modifications to the classical equations of motion due to quantum geometry effects. |
1703.00373 | Sharmanthie Fernando | Sharmanthie Fernando | Spinning dilaton black hole in 2+1 dimensions as a particle accelerator | 13 pages, 4 figures, accepted to be published in Modern Physics
Letters A | Mod. Phys. Lett. A, Vol.32, No. 13, 1750074 (2017) | 10.1142/S0217732317500742 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have studied particle collision around a spinning dilaton
black hole in 2 +1 dimensions. This black hole is a solution to the low energy
string theory in 2+1 dimensions. Time-like geodesics are presented in detail
and the center of mass energy of two particles collision at the horizon of a
spinning black hole is considered. We noticed that there is a possibility of
the two masses to create infinite center of mass energy.
| [
{
"created": "Wed, 1 Mar 2017 16:37:12 GMT",
"version": "v1"
}
] | 2017-05-03 | [
[
"Fernando",
"Sharmanthie",
""
]
] | In this paper we have studied particle collision around a spinning dilaton black hole in 2 +1 dimensions. This black hole is a solution to the low energy string theory in 2+1 dimensions. Time-like geodesics are presented in detail and the center of mass energy of two particles collision at the horizon of a spinning black hole is considered. We noticed that there is a possibility of the two masses to create infinite center of mass energy. |
2206.12641 | Andronikos Paliathanasis | Andronikos Paliathanasis | New inflationary exact solution from Lie symmetries | 19 pages, 5 figures, to appear in MPLA | null | 10.1142/S021773232250119X | null | gr-qc astro-ph.CO math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | For the inflaton field we determine a new exact solution by using the Lie
symmetry analysis. Specifically, we construct a second-order differential
master equation for arbitrary scalar field potential by assuming that the
spectral index for the density perturbations $n_{s}$ and the scalar to tensor
ratio $r$ are related as $n_{s}-1=h\left( r\right) $. Function $h\left(
r\right) $ is classified according to the admitted Lie symmetries for the
master equation. The possible admitted Lie symmetries form the $A_{2}$,
$A_{3,2}$, $A_{3,3}$ and $sl\left( 3,R\right) $ Lie algebras. The new
inflationary solution is recovered by the Lie symmetries of the $A_{3,3}$
algebra. Scalar field potential is derived explicitly, while we compare the
resulting spectral indices with the observations.
| [
{
"created": "Sat, 25 Jun 2022 12:54:21 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | For the inflaton field we determine a new exact solution by using the Lie symmetry analysis. Specifically, we construct a second-order differential master equation for arbitrary scalar field potential by assuming that the spectral index for the density perturbations $n_{s}$ and the scalar to tensor ratio $r$ are related as $n_{s}-1=h\left( r\right) $. Function $h\left( r\right) $ is classified according to the admitted Lie symmetries for the master equation. The possible admitted Lie symmetries form the $A_{2}$, $A_{3,2}$, $A_{3,3}$ and $sl\left( 3,R\right) $ Lie algebras. The new inflationary solution is recovered by the Lie symmetries of the $A_{3,3}$ algebra. Scalar field potential is derived explicitly, while we compare the resulting spectral indices with the observations. |
2308.08759 | Nikolaos Dimakis | N. Dimakis, A. Paliathanasis and T. Christodoulakis | Exploring Quantum Cosmology within the Framework of Teleparallel
$f(T)$-gravity | 40 pages, 5 figures, Latex2e source file, version accepted by PRD | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate quantum cosmology in teleparallel $f(T)$-gravity. We delve
extensively into the minisuperspace description within the context of
teleparallelism. The $f(T)$-theory constitutes a second-order theory of
gravity, whose cosmological counterpart is delineated by a degenerate
point-like Lagrangian. To formulate the Hamiltonian function encompassing all
constraints and degrees of freedom inherent to $f(T)$ cosmology, we employ the
Dirac-Bergmann algorithm. Subsequently, we determine the wave function of the
universe and introduce a ``probabilistic'' interpretation. We perform
comparisons to some classical solutions to see to what extent the quantum
approach can cure classical singularities.
| [
{
"created": "Thu, 17 Aug 2023 03:14:57 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Dec 2023 13:19:22 GMT",
"version": "v2"
}
] | 2023-12-27 | [
[
"Dimakis",
"N.",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | We investigate quantum cosmology in teleparallel $f(T)$-gravity. We delve extensively into the minisuperspace description within the context of teleparallelism. The $f(T)$-theory constitutes a second-order theory of gravity, whose cosmological counterpart is delineated by a degenerate point-like Lagrangian. To formulate the Hamiltonian function encompassing all constraints and degrees of freedom inherent to $f(T)$ cosmology, we employ the Dirac-Bergmann algorithm. Subsequently, we determine the wave function of the universe and introduce a ``probabilistic'' interpretation. We perform comparisons to some classical solutions to see to what extent the quantum approach can cure classical singularities. |
1006.5214 | Herbert Hamber | Herbert W. Hamber and Reiko Toriumi | Cosmological Density Perturbations with a Scale-Dependent Newton's G | 54 pages, 4 figures | Phys.Rev.D82:043518,2010 | 10.1103/PhysRevD.82.043518 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore possible cosmological consequences of a running Newton's constant
$ G ( \Box ) $, as suggested by the non-trivial ultraviolet fixed point
scenario in the quantum field-theoretic treatment of Einstein gravity with a
cosmological constant term. In particular we focus here on what possible
effects the scale-dependent coupling might have on large scale cosmological
density perturbations. Starting from a set of manifestly covariant effective
field equations derived earlier, we systematically develop the linear theory of
density perturbations for a non-relativistic, pressure-less fluid. The result
is a modified equation for the matter density contrast, which can be solved and
thus provides an estimate for the growth index parameter $\gamma$ in the
presence of a running $G$. We complete our analysis by comparing the fully
relativistic treatment with the corresponding results for the non-relativistic
(Newtonian) case, the latter also with a weakly scale dependent $G$.
| [
{
"created": "Sun, 27 Jun 2010 14:18:30 GMT",
"version": "v1"
}
] | 2011-09-08 | [
[
"Hamber",
"Herbert W.",
""
],
[
"Toriumi",
"Reiko",
""
]
] | We explore possible cosmological consequences of a running Newton's constant $ G ( \Box ) $, as suggested by the non-trivial ultraviolet fixed point scenario in the quantum field-theoretic treatment of Einstein gravity with a cosmological constant term. In particular we focus here on what possible effects the scale-dependent coupling might have on large scale cosmological density perturbations. Starting from a set of manifestly covariant effective field equations derived earlier, we systematically develop the linear theory of density perturbations for a non-relativistic, pressure-less fluid. The result is a modified equation for the matter density contrast, which can be solved and thus provides an estimate for the growth index parameter $\gamma$ in the presence of a running $G$. We complete our analysis by comparing the fully relativistic treatment with the corresponding results for the non-relativistic (Newtonian) case, the latter also with a weakly scale dependent $G$. |
gr-qc/9511029 | null | Mathias Trucks (Technische Universit\"at Berlin, Germany) | Correlations of Quantum Fields on Robertson-Walker Spacetimes | 14 pages, Latex2e | Class.Quant.Grav. 13 (1996) 2941-2952 | 10.1088/0264-9381/13/11/010 | null | gr-qc | null | It is a well known fact that quantum fields on Minkowski spacetime are
correlated for each pair of spacetime regions. In Robertson-Walker spacetimes
there are spacelike separated regions with disjoint past horizons but the
absence of correlations in that case was never proved. We derive in this paper
formulae for correlations of quantum fields on Robertson-Walker spacetimes.
Such correlations could have reasonably influenced the formation of structure
in the early universe. We use methods of algebraic and constructive quantum
field theory.
| [
{
"created": "Thu, 9 Nov 1995 16:30:37 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Trucks",
"Mathias",
"",
"Technische Universität Berlin, Germany"
]
] | It is a well known fact that quantum fields on Minkowski spacetime are correlated for each pair of spacetime regions. In Robertson-Walker spacetimes there are spacelike separated regions with disjoint past horizons but the absence of correlations in that case was never proved. We derive in this paper formulae for correlations of quantum fields on Robertson-Walker spacetimes. Such correlations could have reasonably influenced the formation of structure in the early universe. We use methods of algebraic and constructive quantum field theory. |
gr-qc/9306013 | Todd Brun | Todd A. Brun | Quasiclassical Equations of Motion for Nonlinear Brownian Systems | 24 pages, CALT-68-1848 (RevTeX 2.0 macros) | Phys.Rev. D47 (1993) 3383-3393 | 10.1103/PhysRevD.47.3383 | null | gr-qc | null | Following the formalism of Gell-Mann and Hartle, phenomenological equations
of motion are derived from the decoherence functional formalism of quantum
mechanics, using a path-integral description. This is done explicitly for the
case of a system interacting with a ``bath'' of harmonic oscillators whose
individual motions are neglected. The results are compared to the equations
derived from the purely classical theory. The case of linear interactions is
treated exactly, and nonlinear interactions are compared using classical and
quantum perturbation theory.
| [
{
"created": "Tue, 8 Jun 1993 22:46:23 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Brun",
"Todd A.",
""
]
] | Following the formalism of Gell-Mann and Hartle, phenomenological equations of motion are derived from the decoherence functional formalism of quantum mechanics, using a path-integral description. This is done explicitly for the case of a system interacting with a ``bath'' of harmonic oscillators whose individual motions are neglected. The results are compared to the equations derived from the purely classical theory. The case of linear interactions is treated exactly, and nonlinear interactions are compared using classical and quantum perturbation theory. |
2303.14854 | Eugene Yew Siang Chua | Eugene Y. S. Chua, Craig Callender | No Time for Time from No-Time | Presented at Philosophy of Science Association 2021 meeting | Philosophy of Science 88 (5), 2021 | 10.1086/714870 | null | gr-qc physics.hist-ph | http://creativecommons.org/licenses/by/4.0/ | Programs in quantum gravity often claim that time emerges from fundamentally
timeless physics. In the semiclassical time program time arises only after
approximations are taken. Here we ask what justifies taking these
approximations and show that time seems to sneak in when answering this
question. This raises the worry that the approach is either unjustified or
circular in deriving time from no-time.
| [
{
"created": "Sun, 26 Mar 2023 23:36:12 GMT",
"version": "v1"
}
] | 2023-03-28 | [
[
"Chua",
"Eugene Y. S.",
""
],
[
"Callender",
"Craig",
""
]
] | Programs in quantum gravity often claim that time emerges from fundamentally timeless physics. In the semiclassical time program time arises only after approximations are taken. Here we ask what justifies taking these approximations and show that time seems to sneak in when answering this question. This raises the worry that the approach is either unjustified or circular in deriving time from no-time. |
0907.2481 | Hui Yao | Hui Yao (Cambridge U) | Towards Quantum Field Theory in Curved Spacetime for an Arbitrary
Observer | 22 pages, 2 figures; submitted to Found. Phys | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new framework of quantum field theory for an arbitrary observer
in curved spacetime, defined in the spacetime region in which each point can
both receive a signal from and send a signal to the observer. Multiple
motivations for this proposal are discussed. We argue that radar time should be
applied to slice the observer's spacetime region into his simultaneity
surfaces. In the case where each such surface is a Cauchy surface, we construct
a unitary dynamics which evolves a given quantum state at a time for the
observer to a quantum state at a later time. We speculate on possible loss of
information in the more general cases and point out future directions of our
work.
| [
{
"created": "Wed, 15 Jul 2009 17:21:49 GMT",
"version": "v1"
}
] | 2009-07-16 | [
[
"Yao",
"Hui",
"",
"Cambridge U"
]
] | We propose a new framework of quantum field theory for an arbitrary observer in curved spacetime, defined in the spacetime region in which each point can both receive a signal from and send a signal to the observer. Multiple motivations for this proposal are discussed. We argue that radar time should be applied to slice the observer's spacetime region into his simultaneity surfaces. In the case where each such surface is a Cauchy surface, we construct a unitary dynamics which evolves a given quantum state at a time for the observer to a quantum state at a later time. We speculate on possible loss of information in the more general cases and point out future directions of our work. |
gr-qc/0107068 | Vojtich Pravda | A. Pravdova, V. Pravda | Boost-rotation symmetric vacuum spacetimes with spinning sources | REVTeX 4, 9 pages | J.Math.Phys.43:1536-1546,2002 | 10.1063/1.1433941 | null | gr-qc | null | Boost-rotation symmetric vacuum spacetimes with spinning sources which
correspond to gravitational field of uniformly accelerated spinning "particles"
are studied. Regularity conditions and asymptotic properties are analyzed. News
functions are derived by transforming the general spinning boost-rotation
symmetric vacuum metric to Bondi-Sachs coordinates.
| [
{
"created": "Fri, 20 Jul 2001 13:23:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pravdova",
"A.",
""
],
[
"Pravda",
"V.",
""
]
] | Boost-rotation symmetric vacuum spacetimes with spinning sources which correspond to gravitational field of uniformly accelerated spinning "particles" are studied. Regularity conditions and asymptotic properties are analyzed. News functions are derived by transforming the general spinning boost-rotation symmetric vacuum metric to Bondi-Sachs coordinates. |
0908.4495 | Clovis Jacinto de Matos | Clovis Jacinto de Matos | Physical Vacuum in Superconductors | 22 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although experiments carried out by Jain et al. showed that the Cooper pairs
obey the strong equivalence principle, The measurement of the Cooper pairs
inertial mass by Tate et al. revealed an anomalous excess of mass. In the
present paper we interpret these experimental results in the framework of an
electromagnetic model of dark energy for the superconductors' vacuum. We argue
that this physical vacuum is associated with a preferred frame. Ultimately from
the conservation of energy for Cooper pairs we derive a model for a variable
vacuum speed of light in the superconductors physical vacuum in relation with a
possible breaking of the weak equivalence principle for Cooper pairs.
| [
{
"created": "Mon, 31 Aug 2009 10:25:37 GMT",
"version": "v1"
}
] | 2009-09-01 | [
[
"de Matos",
"Clovis Jacinto",
""
]
] | Although experiments carried out by Jain et al. showed that the Cooper pairs obey the strong equivalence principle, The measurement of the Cooper pairs inertial mass by Tate et al. revealed an anomalous excess of mass. In the present paper we interpret these experimental results in the framework of an electromagnetic model of dark energy for the superconductors' vacuum. We argue that this physical vacuum is associated with a preferred frame. Ultimately from the conservation of energy for Cooper pairs we derive a model for a variable vacuum speed of light in the superconductors physical vacuum in relation with a possible breaking of the weak equivalence principle for Cooper pairs. |
2104.01607 | Yaser Ahmadi | Y. Ahmadi, F. Jalilifard, M. V. Takook | Scalar spinor fields interaction in de Sitter ambient space formalism | 10 pages, 1 figure | Modern Physics Letters A, Vol. 34, No. 25, 1950205 (2019) | 10.1142/S0217732319502055 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In de Sitter ambient space formalism, the massless minimally coupled scalar
field can be constructed from a massless conformally coupled scalar field and a
constant five-vector $A^{\alpha}$. Also, a constant five-vector $B^{\alpha}$
appears in the interaction Lagrangian of massless minimally coupled scalar and
spinor fields in this formalism. These constant five-vector fields can be fixed
in the interaction case in the null curvature limit. Here we will calculate the
$\cal S$ matrix elements of scalar-spinor fields interaction in the tree level
approximation. Then the constant five-vectors $A^{\alpha}$ and $B^{\alpha}$,
will be fixed by comparing the $\cal S$ matrix elements in the null curvature
limits with the Minkowskian counterparts.
| [
{
"created": "Sun, 4 Apr 2021 12:59:48 GMT",
"version": "v1"
}
] | 2021-04-06 | [
[
"Ahmadi",
"Y.",
""
],
[
"Jalilifard",
"F.",
""
],
[
"Takook",
"M. V.",
""
]
] | In de Sitter ambient space formalism, the massless minimally coupled scalar field can be constructed from a massless conformally coupled scalar field and a constant five-vector $A^{\alpha}$. Also, a constant five-vector $B^{\alpha}$ appears in the interaction Lagrangian of massless minimally coupled scalar and spinor fields in this formalism. These constant five-vector fields can be fixed in the interaction case in the null curvature limit. Here we will calculate the $\cal S$ matrix elements of scalar-spinor fields interaction in the tree level approximation. Then the constant five-vectors $A^{\alpha}$ and $B^{\alpha}$, will be fixed by comparing the $\cal S$ matrix elements in the null curvature limits with the Minkowskian counterparts. |
2212.00550 | Kuan-Nan Lin | Kuan-Nan Lin, Pisin Chen | Reflections on reflections | 8 pages, 4 figures | null | null | null | gr-qc hep-ex hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Analog Hawking radiation emitted by a perfectly reflecting mirror in
(1+3)-dimensional flat spacetime is investigated. This is accomplished by
studying the reflected frequency and momentum based on Einstein mirror, instead
of the canonical way of solving, if possible, wave equations subjected to a
dynamical Dirichlet boundary condition. In the case of a finite-size mirror,
diffraction pattern appears in the radiation spectrum. Based on the relevant
parameters in the proposed AnaBHEL experiment, where the Hawking temperature TH
= 0.03 eV and the mirror area A = 0.1 mm2, the Hawking photon yield is
estimated to be N = 16 per laser shot (assuming a high reflectivity mirror can
be generated in the proposed AnaBHEL experiment).
| [
{
"created": "Thu, 1 Dec 2022 14:55:47 GMT",
"version": "v1"
}
] | 2022-12-02 | [
[
"Lin",
"Kuan-Nan",
""
],
[
"Chen",
"Pisin",
""
]
] | Analog Hawking radiation emitted by a perfectly reflecting mirror in (1+3)-dimensional flat spacetime is investigated. This is accomplished by studying the reflected frequency and momentum based on Einstein mirror, instead of the canonical way of solving, if possible, wave equations subjected to a dynamical Dirichlet boundary condition. In the case of a finite-size mirror, diffraction pattern appears in the radiation spectrum. Based on the relevant parameters in the proposed AnaBHEL experiment, where the Hawking temperature TH = 0.03 eV and the mirror area A = 0.1 mm2, the Hawking photon yield is estimated to be N = 16 per laser shot (assuming a high reflectivity mirror can be generated in the proposed AnaBHEL experiment). |
0812.3057 | Luca Lusanna | David Alba and Luca Lusanna | Charged Particles and the Electro-Magnetic Field in Non-Inertial Frames
of Minkowski Spacetime | 106 pAGES | null | null | null | gr-qc astro-ph hep-th physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the 3+1 point of view and parametrized Minkowski theories we develop
the theory of {\it non-inertial} frames in Minkowski space-time. The transition
from a non-inertial frame to another one is a gauge transformation connecting
the respective notions of instantaneous 3-space (clock synchronization
convention) and of the 3-coordinates inside them. As a particular case we get
the extension of the inertial rest-frame instant form of dynamics to the
non-inertial rest-frame one. We show that every isolated system can be
described as an external decoupled non-covariant canonical center of mass
(described by frozen Jacobi data) carrying a pole-dipole structure: the
invariant mass and an effective spin. Moreover we identify the constraints
eliminating the internal 3-center of mass inside the instantaneous 3-spaces.
In the case of the isolated system of positive-energy scalar particles with
Grassmann-valued electric charges plus the electro-magnetic field we obtain
both Maxwell equations and their Hamiltonian description in non-inertial
frames. Then by means of a non-covariant decomposition we define the
non-inertial radiation gauge and we find the form of the non-covariant Coulomb
potential. We identify the coordinate-dependent relativistic inertial
potentials and we show that they have the correct Newtonian limit.
Then we study properties of Maxwell equations in non-inertial frames like the
wrap-up effect and the Faraday rotation in astrophysics. Also the 3+1
description without coordinate-singularities of the rotating disk and the
Sagnac effect are given, with added comments on pulsar magnetosphere and on a
relativistic extension of the Earth-fixed coordinate system.
| [
{
"created": "Tue, 16 Dec 2008 13:46:47 GMT",
"version": "v1"
}
] | 2008-12-17 | [
[
"Alba",
"David",
""
],
[
"Lusanna",
"Luca",
""
]
] | By using the 3+1 point of view and parametrized Minkowski theories we develop the theory of {\it non-inertial} frames in Minkowski space-time. The transition from a non-inertial frame to another one is a gauge transformation connecting the respective notions of instantaneous 3-space (clock synchronization convention) and of the 3-coordinates inside them. As a particular case we get the extension of the inertial rest-frame instant form of dynamics to the non-inertial rest-frame one. We show that every isolated system can be described as an external decoupled non-covariant canonical center of mass (described by frozen Jacobi data) carrying a pole-dipole structure: the invariant mass and an effective spin. Moreover we identify the constraints eliminating the internal 3-center of mass inside the instantaneous 3-spaces. In the case of the isolated system of positive-energy scalar particles with Grassmann-valued electric charges plus the electro-magnetic field we obtain both Maxwell equations and their Hamiltonian description in non-inertial frames. Then by means of a non-covariant decomposition we define the non-inertial radiation gauge and we find the form of the non-covariant Coulomb potential. We identify the coordinate-dependent relativistic inertial potentials and we show that they have the correct Newtonian limit. Then we study properties of Maxwell equations in non-inertial frames like the wrap-up effect and the Faraday rotation in astrophysics. Also the 3+1 description without coordinate-singularities of the rotating disk and the Sagnac effect are given, with added comments on pulsar magnetosphere and on a relativistic extension of the Earth-fixed coordinate system. |
2302.07022 | Mario A. Acero | A. Oliveros, Mario A. Acero | Late-time cosmology in a model of modified gravity with an exponential
function of the curvature | 23 pages, 16 figures. References added. Minor modifications,
conclusions unchanged. Accepted for publication in Physics of the Dark
Universe. Matched accepted version | Phys.Dark Univ. 40 (2023) 101207 | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this work, we analyse the late-time evolution of the universe for a
particular $f(R)$ gravity model built from an exponential function of the
scalar curvature. Following the literature, we write the field equations in
terms of a suited statefinder function ($y_H(z)$) and considering well
motivated physical initial conditions, the resulting equations are solved
numerically. Also, the cosmological parameters $w_{\rm{DE}}$, $w_{\rm{eff}}$,
$\Omega_{\rm{DE}}$ and $H(z)$ and the statefinder quantities $q$, $j$, $s$ and
$Om(z)$ are explicitly expressed in terms of $y_H(z)$ and its derivatives.
Furthermore, setting an appropriate set of values for the model parameters, the
cosmological parameters as well as the statefinder quantities are plotted, and
their present values (at $z=0$), are shown to be compatible with Planck 2018
observations and the $\Lambda$CDM-model values. Considering updated
measurements from the dynamics of the expansion of the universe, $H(z)$, we
perform an statistical analysis to constrain the free parameters of the model,
finding a particular set of values that fit the data well and predict
acceptable values for the cosmological and statefinder parameters at present
time. Therefore, the $f(R)$ gravity model is found to be consistent with the
considered observational data, and a viable alternative to explain the
late-time acceleration of the universe.
| [
{
"created": "Tue, 14 Feb 2023 13:05:16 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Feb 2023 15:23:20 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Mar 2023 13:27:39 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Mar 2023 21:52:53 GMT",
"version": "v4"
}
] | 2023-10-18 | [
[
"Oliveros",
"A.",
""
],
[
"Acero",
"Mario A.",
""
]
] | In this work, we analyse the late-time evolution of the universe for a particular $f(R)$ gravity model built from an exponential function of the scalar curvature. Following the literature, we write the field equations in terms of a suited statefinder function ($y_H(z)$) and considering well motivated physical initial conditions, the resulting equations are solved numerically. Also, the cosmological parameters $w_{\rm{DE}}$, $w_{\rm{eff}}$, $\Omega_{\rm{DE}}$ and $H(z)$ and the statefinder quantities $q$, $j$, $s$ and $Om(z)$ are explicitly expressed in terms of $y_H(z)$ and its derivatives. Furthermore, setting an appropriate set of values for the model parameters, the cosmological parameters as well as the statefinder quantities are plotted, and their present values (at $z=0$), are shown to be compatible with Planck 2018 observations and the $\Lambda$CDM-model values. Considering updated measurements from the dynamics of the expansion of the universe, $H(z)$, we perform an statistical analysis to constrain the free parameters of the model, finding a particular set of values that fit the data well and predict acceptable values for the cosmological and statefinder parameters at present time. Therefore, the $f(R)$ gravity model is found to be consistent with the considered observational data, and a viable alternative to explain the late-time acceleration of the universe. |
gr-qc/0507037 | Kristina Giesel | Kristina Giesel, Thomas Thiemann | Consistency Check on Volume and Triad Operator Quantisation in Loop
Quantum Gravity II | 67 pages, 6 figures, 36 pages paper, 31 pages appendix | Class.Quant.Grav. 23 (2006) 5693-5772 | 10.1088/0264-9381/23/18/012 | AEI-2005-120 | gr-qc | null | In this paper we provide the techniques and proofs for the resuls presented
in our companion paper concerning the consistency check on volume and triad
operator quantisation in Loop Quantum Gravity.
| [
{
"created": "Fri, 8 Jul 2005 11:51:48 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jul 2005 15:21:28 GMT",
"version": "v2"
}
] | 2017-01-18 | [
[
"Giesel",
"Kristina",
""
],
[
"Thiemann",
"Thomas",
""
]
] | In this paper we provide the techniques and proofs for the resuls presented in our companion paper concerning the consistency check on volume and triad operator quantisation in Loop Quantum Gravity. |
gr-qc/0703146 | Brihaye Yves | Y. Brihaye and T. Delsate | Charged-rotating black holes and black strings in higher dimensional
Einstein-Maxwell theory with a positive cosmological constant | 21 pages, 9 figures | Class.Quant.Grav.24:4691-4710,2007 | 10.1088/0264-9381/24/18/010 | null | gr-qc | null | We present arguments for the existence of charged, rotating black holes in
$d=2N+1$ dimensions, with $d\geq 5$ with a positive cosmological constant.
These solutions posses both, a regular horizon and a cosmological horizon of
spherical topology and have $N$ equal-magnitude angular momenta. They approach
asymptotically the de Sitter spacetime background. The counterpart equations
for $d=2N+2$ are investigated, by assuming that the fields are independant of
the extra dimension $y$, leading to black strings solutions. These solutions
are regular at the event horizon. The asymptotic form of the metric is not the
de Sitter form and exhibit a naked singularity at finite proper distance.
| [
{
"created": "Thu, 29 Mar 2007 13:05:01 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Brihaye",
"Y.",
""
],
[
"Delsate",
"T.",
""
]
] | We present arguments for the existence of charged, rotating black holes in $d=2N+1$ dimensions, with $d\geq 5$ with a positive cosmological constant. These solutions posses both, a regular horizon and a cosmological horizon of spherical topology and have $N$ equal-magnitude angular momenta. They approach asymptotically the de Sitter spacetime background. The counterpart equations for $d=2N+2$ are investigated, by assuming that the fields are independant of the extra dimension $y$, leading to black strings solutions. These solutions are regular at the event horizon. The asymptotic form of the metric is not the de Sitter form and exhibit a naked singularity at finite proper distance. |
2012.04486 | Maximiliano Isi | Maximiliano Isi, Will M. Farr, Matthew Giesler, Mark A. Scheel, and
Saul A. Teukolsky | Testing the black-hole area law with GW150914 | 3 pages, 3 figures (journal version) | Phys. Rev. Lett. 127, 011103 (2021) | 10.1103/PhysRevLett.127.011103 | LIGO-P2000507 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We present observational confirmation of Hawking's black-hole area theorem
based on data from GW150914, finding agreement with the prediction with 97%
(95%) probability when we model the ringdown including (excluding) overtones of
the quadrupolar mode. We obtain this result from a new time-domain analysis of
the pre- and postmerger data. We also confirm that the inspiral and ringdown
portions of the signal are consistent with the same remnant mass and spin, in
agreement with general relativity.
| [
{
"created": "Tue, 8 Dec 2020 15:26:20 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2021 20:04:43 GMT",
"version": "v2"
}
] | 2021-07-07 | [
[
"Isi",
"Maximiliano",
""
],
[
"Farr",
"Will M.",
""
],
[
"Giesler",
"Matthew",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | We present observational confirmation of Hawking's black-hole area theorem based on data from GW150914, finding agreement with the prediction with 97% (95%) probability when we model the ringdown including (excluding) overtones of the quadrupolar mode. We obtain this result from a new time-domain analysis of the pre- and postmerger data. We also confirm that the inspiral and ringdown portions of the signal are consistent with the same remnant mass and spin, in agreement with general relativity. |
gr-qc/9307006 | null | J. Fernando Barbero and Madhavan Varadarajan | The Phase Space of 2+1 Dimensional Gravity in the Ashtekar Formulation | 19 pages, preprint# SU-GP-93/64 | Nucl.Phys.B415:515-532,1994 | 10.1016/0550-3213(94)90121-X | null | gr-qc | null | The Ashtekar formulation of 2+1 gravity differs from the geometrodynamical
and Witten descriptions when the 2-metric is degenerate. We study the phase
space of 2+1 gravity in the Ashtekar formulation to understand these degenerate
solutions to the field equations. In the process we find two new systems of
first class constraints which describe part of the degenerate sectors of the
Ashtekar formulation. One of them also generalizes the Witten constraints.
Finally we argue that the Ashtekar formulation has an arbitrarily large number
of degrees of freedom in contrast to the usual descriptions. TO GET THE FIGURES
CONTACT Barbero@suhep.phy.syr.edu or Madhavan@suhep.phy.syr.edu
| [
{
"created": "Thu, 8 Jul 1993 21:52:00 GMT",
"version": "v1"
}
] | 2017-03-24 | [
[
"Barbero",
"J. Fernando",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | The Ashtekar formulation of 2+1 gravity differs from the geometrodynamical and Witten descriptions when the 2-metric is degenerate. We study the phase space of 2+1 gravity in the Ashtekar formulation to understand these degenerate solutions to the field equations. In the process we find two new systems of first class constraints which describe part of the degenerate sectors of the Ashtekar formulation. One of them also generalizes the Witten constraints. Finally we argue that the Ashtekar formulation has an arbitrarily large number of degrees of freedom in contrast to the usual descriptions. TO GET THE FIGURES CONTACT Barbero@suhep.phy.syr.edu or Madhavan@suhep.phy.syr.edu |
0807.3325 | Victor Taveras | Victor Taveras | Corrections to the Friedmann Equations from LQG for a Universe with a
Free Scalar Field | Phys. Rev. D78, 064072 (2008) | Phys.Rev.D78:064072,2008 | 10.1103/PhysRevD.78.064072 | IGC-08/7-2 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In loop quantum cosmology the quantum dynamics is well understood. We
approximate the full quantum dynamics in the infinite dimensional Hilbert space
by projecting it on a finite dimensional submanifold thereof, spanned by
suitably chosen semiclassical states. This submanifold is isomorphic with the
classical phase space and the projected dynamical flow provides effective
equations incorporating the leading quantum corrections to the classical
equations of motion. Numerical work has been done using quantum states which
are semiclassical at late times. These states follow the classical trajectory
until the density is on the order of 1% of the Planck density then deviate
strongly from the classical trajectory. The effective equations we obtain
reproduce this behavior to surprising accuracy.
| [
{
"created": "Mon, 21 Jul 2008 19:16:47 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Nov 2008 20:38:34 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Taveras",
"Victor",
""
]
] | In loop quantum cosmology the quantum dynamics is well understood. We approximate the full quantum dynamics in the infinite dimensional Hilbert space by projecting it on a finite dimensional submanifold thereof, spanned by suitably chosen semiclassical states. This submanifold is isomorphic with the classical phase space and the projected dynamical flow provides effective equations incorporating the leading quantum corrections to the classical equations of motion. Numerical work has been done using quantum states which are semiclassical at late times. These states follow the classical trajectory until the density is on the order of 1% of the Planck density then deviate strongly from the classical trajectory. The effective equations we obtain reproduce this behavior to surprising accuracy. |
gr-qc/9702024 | Franciso Turrubiates | Jerzy F. Plebanski (Cinvestav-phys), G.R. Moreno (Cinvestav-math) and
F.J. Turrubiates (Cinvestav-phys) | Differential Forms, Hopf Algebra and General Relativity I | 36 pages, LaTeX file, no figures | Acta Phys.Polon. B28 (1997) 1515-1552 | null | CINVESTAV-FIS-05/97 | gr-qc | null | We review the language of differential forms and their applications to
Riemannian Geometry with an orientation to General Relativity. Working with the
principal algebraic and differential operations on forms, we obtain the
structure equations and their symmetries in terms of a new product (the
co-multiplication). It is showen how the Cartan - Grassmann algebra can be
endowed with the structure of a Hopf algebra.
| [
{
"created": "Thu, 13 Feb 1997 18:51:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Plebanski",
"Jerzy F.",
"",
"Cinvestav-phys"
],
[
"Moreno",
"G. R.",
"",
"Cinvestav-math"
],
[
"Turrubiates",
"F. J.",
"",
"Cinvestav-phys"
]
] | We review the language of differential forms and their applications to Riemannian Geometry with an orientation to General Relativity. Working with the principal algebraic and differential operations on forms, we obtain the structure equations and their symmetries in terms of a new product (the co-multiplication). It is showen how the Cartan - Grassmann algebra can be endowed with the structure of a Hopf algebra. |
1712.04237 | Seiga Sato | Seiga Sato and Kei-ichi Maeda | Hybrid Higgs Inflation: The Use of Disformal Transformation | 16 pages, 6 figures, 1 table | Phys. Rev. D 97, 083512 (2018) | 10.1103/PhysRevD.97.083512 | WU-AP/1706/17 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a hybrid type of the conventional Higgs inflation and new Higgs
inflation models. We perform a disformal transformation into the Einstein frame
and analyze the background dynamics and the cosmological perturbations in the
truncated model, in which we ignore the higher-derivative terms of the Higgs
field. From the observed power spectrum of the density perturbations, we obtain
the constraint on the non-minimal coupling constant $\xi$ and the mass
parameter $M$ in the derivative coupling. Although the primordial tilt $n_s$ in
the hybrid model barely changes, the tensor-to-scalar ratio $r$ moves from the
value in new Higgs inflationary model to that in the conventional Higgs
inflationary model as $|\xi|$ increases. We confirm our results by numerical
analysis by ADM formalism of the full theory in the Jordan frame.
| [
{
"created": "Tue, 12 Dec 2017 11:15:36 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Dec 2017 09:41:21 GMT",
"version": "v2"
}
] | 2018-04-25 | [
[
"Sato",
"Seiga",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We propose a hybrid type of the conventional Higgs inflation and new Higgs inflation models. We perform a disformal transformation into the Einstein frame and analyze the background dynamics and the cosmological perturbations in the truncated model, in which we ignore the higher-derivative terms of the Higgs field. From the observed power spectrum of the density perturbations, we obtain the constraint on the non-minimal coupling constant $\xi$ and the mass parameter $M$ in the derivative coupling. Although the primordial tilt $n_s$ in the hybrid model barely changes, the tensor-to-scalar ratio $r$ moves from the value in new Higgs inflationary model to that in the conventional Higgs inflationary model as $|\xi|$ increases. We confirm our results by numerical analysis by ADM formalism of the full theory in the Jordan frame. |
1405.1283 | Luke Butcher | Luke M. Butcher | Casimir Energy of a Long Wormhole Throat | 17 pages, 3 figures. Submitted to Phys. Rev. D | Phys. Rev. D 90, 024019 (2014) | 10.1103/PhysRevD.90.024019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the Casimir energy-momentum tensor induced in a scalar field by
a macroscopic ultrastatic spherically-symmetric long-throated traversable
wormhole, and examine whether this exotic matter is sufficient to stabilise the
wormhole itself. The Casimir energy-momentum tensor is obtained (within the
$\mathbb{R}\times S_2$ throat) by a mode sum approach, using a sharp energy
cut-off and the Abel-Plana formula; Lorentz invariance is then restored by use
of a Pauli-Villars regulator. The massless conformally-coupled case is found to
have a logarithmic divergence (which we renormalise) and a conformal anomaly,
the thermodynamic relevance of which is discussed. Provided the throat radius
is above some fixed length, the renormalised Casimir energy-density is seen to
be negative by all timelike observers, and almost all null rays; furthermore,
it has sufficient magnitude to stabilise a long-throated wormhole far larger
than the Planck scale, at least in principle. Unfortunately, the renormalised
Casimir energy-density is zero for null rays directed exactly parallel to the
throat, and this shortfall prevents us from stabilising the ultrastatic
spherically-symmetric wormhole considered here. Nonetheless, the negative
Casimir energy does allow the wormhole to collapse extremely slowly, its
lifetime growing without bound as the throat-length is increased. We find that
the throat closes slowly enough that its central region can be safely traversed
by a pulse of light.
| [
{
"created": "Tue, 6 May 2014 14:35:57 GMT",
"version": "v1"
}
] | 2014-07-09 | [
[
"Butcher",
"Luke M.",
""
]
] | We calculate the Casimir energy-momentum tensor induced in a scalar field by a macroscopic ultrastatic spherically-symmetric long-throated traversable wormhole, and examine whether this exotic matter is sufficient to stabilise the wormhole itself. The Casimir energy-momentum tensor is obtained (within the $\mathbb{R}\times S_2$ throat) by a mode sum approach, using a sharp energy cut-off and the Abel-Plana formula; Lorentz invariance is then restored by use of a Pauli-Villars regulator. The massless conformally-coupled case is found to have a logarithmic divergence (which we renormalise) and a conformal anomaly, the thermodynamic relevance of which is discussed. Provided the throat radius is above some fixed length, the renormalised Casimir energy-density is seen to be negative by all timelike observers, and almost all null rays; furthermore, it has sufficient magnitude to stabilise a long-throated wormhole far larger than the Planck scale, at least in principle. Unfortunately, the renormalised Casimir energy-density is zero for null rays directed exactly parallel to the throat, and this shortfall prevents us from stabilising the ultrastatic spherically-symmetric wormhole considered here. Nonetheless, the negative Casimir energy does allow the wormhole to collapse extremely slowly, its lifetime growing without bound as the throat-length is increased. We find that the throat closes slowly enough that its central region can be safely traversed by a pulse of light. |
2301.09395 | David Trestini | David Trestini, Luc Blanchet | Gravitational-wave tails of memory | 40 page, 1 figure, 1 table and 2 ancillary files | Phys. Rev. D 107, 104048 (2023) | 10.1103/PhysRevD.107.104048 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational-wave tails are linear waves that backscatter on the curvature
of space-time generated by the total mass-energy of the source. The non-linear
memory effect arises from gravitational waves sourced by the stress-energy
distribution of linear waves themselves. These two effects are due to quadratic
multipolar interactions (mass-quadrupole and quadrupole-quadrupole) and are
well known. Also known are the tails generated by tails themselves (cubic
"tails-of-tails") and the tails generated by tails-of-tails or vice versa
(quartic "tails-of-tails-of-tails"). In this work, we focus on the cubic
"tails-of-memory" corresponding to the mass-quadrupole-quadrupole interaction,
as well as the "spin-quadrupole tails", which are due to the cubic interaction
between the mass, the total angular momentum and the quadrupole. The
tails-of-memory and the spin-quadrupole tails contribute to the asymptotic
waveform at the fourth-post-Newtonian (4PN) order beyond quadrupolar radiation.
| [
{
"created": "Mon, 23 Jan 2023 12:32:10 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Feb 2024 16:50:18 GMT",
"version": "v2"
}
] | 2024-02-16 | [
[
"Trestini",
"David",
""
],
[
"Blanchet",
"Luc",
""
]
] | Gravitational-wave tails are linear waves that backscatter on the curvature of space-time generated by the total mass-energy of the source. The non-linear memory effect arises from gravitational waves sourced by the stress-energy distribution of linear waves themselves. These two effects are due to quadratic multipolar interactions (mass-quadrupole and quadrupole-quadrupole) and are well known. Also known are the tails generated by tails themselves (cubic "tails-of-tails") and the tails generated by tails-of-tails or vice versa (quartic "tails-of-tails-of-tails"). In this work, we focus on the cubic "tails-of-memory" corresponding to the mass-quadrupole-quadrupole interaction, as well as the "spin-quadrupole tails", which are due to the cubic interaction between the mass, the total angular momentum and the quadrupole. The tails-of-memory and the spin-quadrupole tails contribute to the asymptotic waveform at the fourth-post-Newtonian (4PN) order beyond quadrupolar radiation. |
gr-qc/0111042 | Patricia Purdue | Patricia Purdue | An analysis of a QND speed-meter interferometer | 12 pages, 5 figures; corrected formula and some values describing
power requirements | Phys.Rev. D66 (2002) 022001 | 10.1103/PhysRevD.66.022001 | null | gr-qc | null | In the quest to develop viable designs for third-generation optical
interferometric gravitational-wave detectors (e.g. LIGO-III and EURO), one
strategy is to monitor the relative momentum or speed of the test-mass mirrors,
rather than monitoring their relative position. This paper describes and
analyzes the most straightforward design for a {\it speed meter interferometer}
that accomplishes this -- a design (due to Braginsky, Gorodetsky, Khalili and
Thorne) that is analogous to a microwave-cavity speed meter conceived by
Braginsky and Khalili. A mathematical mapping between the microwave speed meter
and the optical interferometric speed meter is developed and is used to show
(in accord with the speed being a Quantum Nondemolition [QND] observable) that
{\it in principle} the interferometric speed meter can beat the
gravitational-wave standard quantum limit (SQL) by an arbitrarily large amount,
over an arbitrarily wide range of frequencies, and can do so without the use of
squeezed vacuum or any auxiliary filter cavities at the interferometer's input
or output. However, {\it in practice}, to reach or beat the SQL, this specific
speed meter requires exorbitantly high input light power. The physical reason
for this is explored, along with other issues such as constraints on
performance due to optical dissipation. This analysis forms a foundation for
ongoing attempts to develop a more practical variant of an interferometric
speed meter and to combine the speed meter concept with other ideas to yield a
promising LIGO-III/EURO interferometer design that entails low laser power.
| [
{
"created": "Tue, 13 Nov 2001 23:13:13 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Oct 2004 16:17:19 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Purdue",
"Patricia",
""
]
] | In the quest to develop viable designs for third-generation optical interferometric gravitational-wave detectors (e.g. LIGO-III and EURO), one strategy is to monitor the relative momentum or speed of the test-mass mirrors, rather than monitoring their relative position. This paper describes and analyzes the most straightforward design for a {\it speed meter interferometer} that accomplishes this -- a design (due to Braginsky, Gorodetsky, Khalili and Thorne) that is analogous to a microwave-cavity speed meter conceived by Braginsky and Khalili. A mathematical mapping between the microwave speed meter and the optical interferometric speed meter is developed and is used to show (in accord with the speed being a Quantum Nondemolition [QND] observable) that {\it in principle} the interferometric speed meter can beat the gravitational-wave standard quantum limit (SQL) by an arbitrarily large amount, over an arbitrarily wide range of frequencies, and can do so without the use of squeezed vacuum or any auxiliary filter cavities at the interferometer's input or output. However, {\it in practice}, to reach or beat the SQL, this specific speed meter requires exorbitantly high input light power. The physical reason for this is explored, along with other issues such as constraints on performance due to optical dissipation. This analysis forms a foundation for ongoing attempts to develop a more practical variant of an interferometric speed meter and to combine the speed meter concept with other ideas to yield a promising LIGO-III/EURO interferometer design that entails low laser power. |
1805.10673 | Dirk Puetzfeld | Dirk Puetzfeld, Yuri N. Obukhov, Claus L\"ammerzahl | Gravitational clock compass in General Relativity | 12 pages, 6 figures | Phys. Rev. D 98, 024032 (2018) | 10.1103/PhysRevD.98.024032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how a suitably prepared set of clocks can be used to determine all
components of the gravitational field in General Relativity. We call such an
experimental setup a clock compass, in analogy to the usual gravitational
compass. Particular attention is paid to the construction of the underlying
reference frame. Conceptual differences between the clock compass and the
standard gravitational compass, which is based on the measurement of the mutual
accelerations between the constituents of a swarm of test bodies, are
highlighted. Our results are of direct operational relevance for the setup of
networks of clocks, for example in the context of relativistic geodesy.
| [
{
"created": "Sun, 27 May 2018 18:27:36 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jul 2018 13:58:35 GMT",
"version": "v2"
}
] | 2018-07-26 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
],
[
"Lämmerzahl",
"Claus",
""
]
] | We show how a suitably prepared set of clocks can be used to determine all components of the gravitational field in General Relativity. We call such an experimental setup a clock compass, in analogy to the usual gravitational compass. Particular attention is paid to the construction of the underlying reference frame. Conceptual differences between the clock compass and the standard gravitational compass, which is based on the measurement of the mutual accelerations between the constituents of a swarm of test bodies, are highlighted. Our results are of direct operational relevance for the setup of networks of clocks, for example in the context of relativistic geodesy. |
1406.6096 | Eugeny Babichev | Eugeny Babichev and Alessandro Fabbri | Rotating black holes in massive gravity | 7 pages; v2: typos corrected, references added; v3: matches published
version | Phys. Rev. D 90, 084019 (2014) | 10.1103/PhysRevD.90.084019 | LPT-Orsay-14-80 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a solution for rotating black holes in massive gravity. We first
give a solution of massive gravity with one dynamical metric. Both metrics of
this solution are expressed in the advanced Eddington-Finkelstein-like
coordinates: the physical metric has the original Kerr line element, while the
fiducial metric is flat, but written in a rotating Eddington-Finkelstein form.
For the bi-gravity theory we give an analogue of this solution: the two metrics
have the original Kerr form, but, in general, different black hole masses. The
generalisation of the solution to include the electric charge is also given, it
is an analogue of the Kerr-Newman solution in General Relativity. We also
discuss further possible ways to generalise the solutions.
| [
{
"created": "Mon, 23 Jun 2014 21:11:50 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jul 2014 18:39:40 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Oct 2014 09:20:00 GMT",
"version": "v3"
}
] | 2014-11-07 | [
[
"Babichev",
"Eugeny",
""
],
[
"Fabbri",
"Alessandro",
""
]
] | We present a solution for rotating black holes in massive gravity. We first give a solution of massive gravity with one dynamical metric. Both metrics of this solution are expressed in the advanced Eddington-Finkelstein-like coordinates: the physical metric has the original Kerr line element, while the fiducial metric is flat, but written in a rotating Eddington-Finkelstein form. For the bi-gravity theory we give an analogue of this solution: the two metrics have the original Kerr form, but, in general, different black hole masses. The generalisation of the solution to include the electric charge is also given, it is an analogue of the Kerr-Newman solution in General Relativity. We also discuss further possible ways to generalise the solutions. |
gr-qc/9909067 | N. K. Dadhich | Naresh Dadhich | Electromagnetic duality in general relativity | 18 pages, LaTEX version | Gen.Rel.Grav. 32 (2000) 1009-1023 | 10.1023/A:1001913409254 | IUCAA-36/99 | gr-qc | null | By resolving the Riemann curvature relative to a unit timelike vector into
electric and magnetic parts, we consider duality relations analogous to the
electromagnetic theory. It turns out that the duality symmetry of the Einstein
action implies the Einstein vacuum equation without the cosmological term. The
vacuum equation is invariant under interchange of active and passive electric
parts giving rise to the same vacuum solutions but the gravitational constant
changes sign. Further by modifying the equation it is possible to construct
interesting dual solutions to vacuum as well as to flat spacetimes.
| [
{
"created": "Tue, 21 Sep 1999 12:15:01 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Dadhich",
"Naresh",
""
]
] | By resolving the Riemann curvature relative to a unit timelike vector into electric and magnetic parts, we consider duality relations analogous to the electromagnetic theory. It turns out that the duality symmetry of the Einstein action implies the Einstein vacuum equation without the cosmological term. The vacuum equation is invariant under interchange of active and passive electric parts giving rise to the same vacuum solutions but the gravitational constant changes sign. Further by modifying the equation it is possible to construct interesting dual solutions to vacuum as well as to flat spacetimes. |
2207.14683 | Mariaveronica De Angelis | Mariaveronica De Angelis, Giovanni Montani | On the emergence of a classical Isotropic Universe from a Quantum $f(R)$
Bianchi Cosmology in the Jordan Frame | 9 pages, 4 figures | null | 10.1140/epjc/s10052-023-11454-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate a spontaneous tendency of quantum wave packets to become
quasi-classical, providing a classical limit for the Universe dynamics.
However, this limit is not maintained in the future (after a critical value of
the relational time) and a spreading process is turned on. We show that the
onset of an inflationary scenario is not able to make this localization stable
of the wave packets for the Bianchi I model. Instead, when we implement a
perturbative inflationary scenario for the isotropic Universe a mechanism of
stable classicalization of the Universe emerges. This result outlines a sharp
difference between the standard relativistic cosmology and a modified $f(R)$
paradigm.
| [
{
"created": "Fri, 29 Jul 2022 13:57:20 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2023 17:03:12 GMT",
"version": "v2"
}
] | 2023-04-12 | [
[
"De Angelis",
"Mariaveronica",
""
],
[
"Montani",
"Giovanni",
""
]
] | We demonstrate a spontaneous tendency of quantum wave packets to become quasi-classical, providing a classical limit for the Universe dynamics. However, this limit is not maintained in the future (after a critical value of the relational time) and a spreading process is turned on. We show that the onset of an inflationary scenario is not able to make this localization stable of the wave packets for the Bianchi I model. Instead, when we implement a perturbative inflationary scenario for the isotropic Universe a mechanism of stable classicalization of the Universe emerges. This result outlines a sharp difference between the standard relativistic cosmology and a modified $f(R)$ paradigm. |
2011.05328 | Abdel Nasser Tawfik | Abdel Nasser Tawfik (ECTP, Cairo, WLCAPP, Cairo), Abdel Magied Diab
(Modern University for Technology and Information, Cairo, WLCAPP, Cairo),
Sameh Shenawy (Modern Acamdey for Engineering, Cairo, WLCAPP, Cairo), Eiman
Abou El Dahab (Modern University for Technology and Information, Cairo,
WLCAPP, Cairo) | Consequences of Minimal Length Discretization on Line Element, Metric
Tensor and Geodesic Equation | 4 pages, 0 figure, invited talk at 9th int. Workshop on Astronomy and
Relativistic Astrophysics (IWARA2020 Video Conference). accepted for
publication in Astronomical Note (AN) | Astronomische Nachrichten, 2021; 1-4 | 10.1002/asna.202113880 | ECTP-2020-15-15, WLCAPP-2020-15-15 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When minimal length uncertainty emerging from generalized uncertainty
principle (GUP) is thoughtfully implemented, it is of great interest to
consider its impacts on {\it "gravitational} Einstein field equations (gEFE)
and to try to find out whether consequential modifications in metric
manifesting properties of quantum geometry due to quantum gravity. GUP takes
into account the gravitational impacts on the noncommutation relations of
length (distance) and momentum operators or time and energy operators, etc. On
the other hand, gEFE relates {\it classical geometry or general relativity
gravity} to the energy-momentum tensors, i.e. proposing quantum equations of
state. Despite the technical difficulties, we confront GUP to the metric tensor
so that the line element and the geodesic equation in flat and curved space are
accordingly modified. The latter apparently encompasses acceleration, jerk, and
snap (jounce) of a particle in the {\it "quasi-quantized"} gravitational field.
Finite higher-orders of acceleration apparently manifest phenomena such as
accelerating expansion and transitions between different radii of curvature,
etc.
| [
{
"created": "Tue, 10 Nov 2020 08:37:20 GMT",
"version": "v1"
}
] | 2021-02-26 | [
[
"Tawfik",
"Abdel Nasser",
"",
"ECTP, Cairo, WLCAPP, Cairo"
],
[
"Diab",
"Abdel Magied",
"",
"Modern University for Technology and Information, Cairo, WLCAPP, Cairo"
],
[
"Shenawy",
"Sameh",
"",
"Modern Acamdey for Engineering, Cairo, WLCAPP, Cairo"
],
[
"Dahab",
"Eiman Abou El",
"",
"Modern University for Technology and Information, Cairo,\n WLCAPP, Cairo"
]
] | When minimal length uncertainty emerging from generalized uncertainty principle (GUP) is thoughtfully implemented, it is of great interest to consider its impacts on {\it "gravitational} Einstein field equations (gEFE) and to try to find out whether consequential modifications in metric manifesting properties of quantum geometry due to quantum gravity. GUP takes into account the gravitational impacts on the noncommutation relations of length (distance) and momentum operators or time and energy operators, etc. On the other hand, gEFE relates {\it classical geometry or general relativity gravity} to the energy-momentum tensors, i.e. proposing quantum equations of state. Despite the technical difficulties, we confront GUP to the metric tensor so that the line element and the geodesic equation in flat and curved space are accordingly modified. The latter apparently encompasses acceleration, jerk, and snap (jounce) of a particle in the {\it "quasi-quantized"} gravitational field. Finite higher-orders of acceleration apparently manifest phenomena such as accelerating expansion and transitions between different radii of curvature, etc. |
gr-qc/9908082 | Thomas P. Kling | Thomas P. Kling, Ezra T. Newman and Alejandro Perez (University of
Pittsburgh) | Iterative Approach to Gravitational Lensing Theory | 27 pages, 2 figures, submitted to Phys.Rev.D, minor revisions, new
references | Phys.Rev. D61 (2000) 104007 | 10.1103/PhysRevD.61.104007 | null | gr-qc astro-ph | null | We develop an iterative approach to gravitational lensing theory based on
approximate solutions of the null geodesic equations. The approach can be
employed in any space-time which is ``close'' to a space-time in which the null
geodesic equations can be completely integrated, such as Minkowski space-time,
Robertson-Walker cosmologies, or Schwarzschild-Kerr geometries. To illustrate
the method, we construct the iterative gravitational lens equations and time of
arrival equation for a single Schwarzschild lens. This example motivates a
discussion of the relationship between the iterative approach, the standard
thin lens formulation, and an exact formulation of gravitational lensing.
| [
{
"created": "Tue, 31 Aug 1999 18:34:36 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jan 2000 19:15:27 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kling",
"Thomas P.",
"",
"University of\n Pittsburgh"
],
[
"Newman",
"Ezra T.",
"",
"University of\n Pittsburgh"
],
[
"Perez",
"Alejandro",
"",
"University of\n Pittsburgh"
]
] | We develop an iterative approach to gravitational lensing theory based on approximate solutions of the null geodesic equations. The approach can be employed in any space-time which is ``close'' to a space-time in which the null geodesic equations can be completely integrated, such as Minkowski space-time, Robertson-Walker cosmologies, or Schwarzschild-Kerr geometries. To illustrate the method, we construct the iterative gravitational lens equations and time of arrival equation for a single Schwarzschild lens. This example motivates a discussion of the relationship between the iterative approach, the standard thin lens formulation, and an exact formulation of gravitational lensing. |
2105.07042 | Selman Ipek | Selman Ipek | The Entropic Dynamics of Relativistic Quantum Fields in Curved
Space-time | 172 pages; author's doctoral dissertation, Department of Physics,
University at Albany-SUNY, April 2021 | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | It has often been the case in history that the laws of physics have been used
as the framework for understanding and implementing information processing. The
tacit assumption is that the laws of physics are fundamental and that the
notion of information is derived from these laws. Here we take the opposite
view: the laws of physics are an application of the rules for processing
information. In this dissertation we apply the Entropic Dynamics (ED) framework
to construct a quantum dynamics for scalar fields in space-time. We begin by
considering a toy model consisting of many interacting particles, resulting in
the familiar Schrodinger equation for non-relativistic particles. Using a
similar methodology, we construct a theory of quantum scalar fields in flat
space-time that is relativistic, but not manifestly so. Here we also discuss a
novel way in which the ED of quantum scalar fields appears to evade the
so-called Wallstrom objection. To go further towards constructing a manifestly
covariant quantum ED of fields on a curved space-time, both fixed and
dynamical, we borrow from the "many-time" approaches of P. Weiss, P. Dirac, K.
Kuchar, and C. Teitelboim. For a fixed background the result is a manifestly
covariant ED of scalar fields that is in the spirit of the covariant quantum
theories proposed by S. Tomonaga and J. Schwinger. However, the formalism is
sufficiently flexible so as to allow for the possibility of modeling the back
reaction of the quantum matter fields on a fully dynamical classical
background. The simplest realization of this classical-quantum interaction
shares some formal similarity to semi-classical gravity models, and the
semi-classical Einstein equations, in particular. We consider such a theory and
discuss its plausibility as a candidate for a quantum gravity theory.
| [
{
"created": "Fri, 14 May 2021 19:24:21 GMT",
"version": "v1"
}
] | 2021-05-18 | [
[
"Ipek",
"Selman",
""
]
] | It has often been the case in history that the laws of physics have been used as the framework for understanding and implementing information processing. The tacit assumption is that the laws of physics are fundamental and that the notion of information is derived from these laws. Here we take the opposite view: the laws of physics are an application of the rules for processing information. In this dissertation we apply the Entropic Dynamics (ED) framework to construct a quantum dynamics for scalar fields in space-time. We begin by considering a toy model consisting of many interacting particles, resulting in the familiar Schrodinger equation for non-relativistic particles. Using a similar methodology, we construct a theory of quantum scalar fields in flat space-time that is relativistic, but not manifestly so. Here we also discuss a novel way in which the ED of quantum scalar fields appears to evade the so-called Wallstrom objection. To go further towards constructing a manifestly covariant quantum ED of fields on a curved space-time, both fixed and dynamical, we borrow from the "many-time" approaches of P. Weiss, P. Dirac, K. Kuchar, and C. Teitelboim. For a fixed background the result is a manifestly covariant ED of scalar fields that is in the spirit of the covariant quantum theories proposed by S. Tomonaga and J. Schwinger. However, the formalism is sufficiently flexible so as to allow for the possibility of modeling the back reaction of the quantum matter fields on a fully dynamical classical background. The simplest realization of this classical-quantum interaction shares some formal similarity to semi-classical gravity models, and the semi-classical Einstein equations, in particular. We consider such a theory and discuss its plausibility as a candidate for a quantum gravity theory. |
gr-qc/0209063 | Kayll Lake | Kayll Lake | Non conducting spherically symmetric fluids | 4 pages revtex4. Added references | Gen.Rel.Grav. 36 (2003) 193-197 | 10.1023/B:GERG.0000006965.74658.1c | null | gr-qc astro-ph | null | A class of spherically symmetric spacetimes invariantly defined by a zero
flux condition is examined first from a purely geometrical point of view and
then physically by way of Einstein's equations for a general fluid
decomposition of the energy-momentum tensor. The approach, which allows a
formal inversion of Einstein's equations, explains, for example, why
spherically symmetric perfect fluids with spatially homogeneous energy density
must be shearfree.
| [
{
"created": "Wed, 18 Sep 2002 22:43:50 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Nov 2002 01:28:24 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Feb 2003 14:02:16 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Lake",
"Kayll",
""
]
] | A class of spherically symmetric spacetimes invariantly defined by a zero flux condition is examined first from a purely geometrical point of view and then physically by way of Einstein's equations for a general fluid decomposition of the energy-momentum tensor. The approach, which allows a formal inversion of Einstein's equations, explains, for example, why spherically symmetric perfect fluids with spatially homogeneous energy density must be shearfree. |
2407.00989 | Simran Arora | Ayush Hazarika, Simran Arora, P.K. Sahoo, Tiberiu Harko | $f(Q,L_m)$ gravity, and its cosmological implications | 21 pages, 11 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In the present work, we extend the $f(Q)$ symmetric teleparallel gravity by
introducing an arbitrary coupling between the non-metricity $Q$ and matter
Lagrangian $L_m$ in the Lagrangian density $f$ of the theory, which thus leads
to the $f\left(Q,L_m\right)$ theory. This generalisation encompasses Coincident
General Relativity (CGR) and the Symmetric Teleparallel Equivalent to GR
(STEGR). Using the metric formalism, we derive the field equation of the
theory, which generalizes the field equations of $f(Q)$ gravity. From the study
of the covariant divergence of the field equations, it follows that the
presence of the geometry-matter coupling leads to the non-conservation of the
matter energy-momentum tensor. The cosmological implications of the theory are
investigated in the case of a flat, homogeneous, and isotropic
Friedmann-Lemaitre-Robertson-Walker geometry. As a first step in this
direction, we obtain the modified Friedmann equations for the $f(Q,L_m)$
gravity in a general form. Specific cosmological models are investigated for
several choices of $f(Q,L_m)$, including $f(Q,L_m)=-\alpha Q + 2L_m + \beta$,
and $f(Q,L_m)=- \alpha Q + (2L_m)^2 + \beta$, respectively. Comparative
analyses with the standard $\Lambda$ CDM paradigm are carried out, and the
observational implications of the models are investigated in detail.
| [
{
"created": "Mon, 1 Jul 2024 05:55:36 GMT",
"version": "v1"
}
] | 2024-07-02 | [
[
"Hazarika",
"Ayush",
""
],
[
"Arora",
"Simran",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Harko",
"Tiberiu",
""
]
] | In the present work, we extend the $f(Q)$ symmetric teleparallel gravity by introducing an arbitrary coupling between the non-metricity $Q$ and matter Lagrangian $L_m$ in the Lagrangian density $f$ of the theory, which thus leads to the $f\left(Q,L_m\right)$ theory. This generalisation encompasses Coincident General Relativity (CGR) and the Symmetric Teleparallel Equivalent to GR (STEGR). Using the metric formalism, we derive the field equation of the theory, which generalizes the field equations of $f(Q)$ gravity. From the study of the covariant divergence of the field equations, it follows that the presence of the geometry-matter coupling leads to the non-conservation of the matter energy-momentum tensor. The cosmological implications of the theory are investigated in the case of a flat, homogeneous, and isotropic Friedmann-Lemaitre-Robertson-Walker geometry. As a first step in this direction, we obtain the modified Friedmann equations for the $f(Q,L_m)$ gravity in a general form. Specific cosmological models are investigated for several choices of $f(Q,L_m)$, including $f(Q,L_m)=-\alpha Q + 2L_m + \beta$, and $f(Q,L_m)=- \alpha Q + (2L_m)^2 + \beta$, respectively. Comparative analyses with the standard $\Lambda$ CDM paradigm are carried out, and the observational implications of the models are investigated in detail. |
gr-qc/0108006 | Florian Siebel | Florian Siebel (MPA), Jose A. Font (MPA) and Philippos Papadopoulos
(Portsmouth) | Scalar field induced oscillations of neutron stars and gravitational
collapse | 12 pages, 13 figures, submitted to Phys. Rev. D | Phys.Rev. D65 (2002) 024021 | 10.1103/PhysRevD.65.024021 | null | gr-qc astro-ph | null | We study the interaction of massless scalar fields with self-gravitating
neutron stars by means of fully dynamic numerical simulations of the
Einstein-Klein-Gordon perfect fluid system. Our investigation is restricted to
spherical symmetry and the neutron stars are approximated by relativistic
polytropes. Studying the nonlinear dynamics of isolated neutron stars is very
effectively performed within the characteristic formulation of general
relativity, in which the spacetime is foliated by a family of outgoing light
cones. We are able to compactify the entire spacetime on a computational grid
and simultaneously impose natural radiative boundary conditions and extract
accurate radiative signals. We study the transfer of energy from the scalar
field to the fluid star. We find, in particular, that depending on the
compactness of the neutron star model, the scalar wave forces the neutron star
either to oscillate in its radial modes of pulsation or to undergo
gravitational collapse to a black hole on a dynamical timescale. The radiative
signal, read off at future null infinity, shows quasi-normal oscillations
before the setting of a late time power-law tail.
| [
{
"created": "Thu, 2 Aug 2001 14:37:59 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Siebel",
"Florian",
"",
"MPA"
],
[
"Font",
"Jose A.",
"",
"MPA"
],
[
"Papadopoulos",
"Philippos",
"",
"Portsmouth"
]
] | We study the interaction of massless scalar fields with self-gravitating neutron stars by means of fully dynamic numerical simulations of the Einstein-Klein-Gordon perfect fluid system. Our investigation is restricted to spherical symmetry and the neutron stars are approximated by relativistic polytropes. Studying the nonlinear dynamics of isolated neutron stars is very effectively performed within the characteristic formulation of general relativity, in which the spacetime is foliated by a family of outgoing light cones. We are able to compactify the entire spacetime on a computational grid and simultaneously impose natural radiative boundary conditions and extract accurate radiative signals. We study the transfer of energy from the scalar field to the fluid star. We find, in particular, that depending on the compactness of the neutron star model, the scalar wave forces the neutron star either to oscillate in its radial modes of pulsation or to undergo gravitational collapse to a black hole on a dynamical timescale. The radiative signal, read off at future null infinity, shows quasi-normal oscillations before the setting of a late time power-law tail. |
2407.17846 | Olivier Minazzoli | Olivier Minazzoli and Maxime Wavasseur | Schwarzschild black-hole immersed in uniform electric or magnetic
backgrounds in Entangled Relativity | 5 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we present the solution for a Schwarzschild black-hole
immersed in an electric or magnetic background field within the framework of
Entangled Relativity. Previous solutions in Entangled Relativity required
black-holes to be charged for the matter field to be defined everywhere. This
is because the theory precludes the existence of vacuum solutions, thereby
satisfying Einstein's definition of Mach's Principle. The current black-hole
solutions represent the first exact and neutral black-hole solutions of
Entangled Relativity discovered to date. The Schwarzschild black-hole of
General Relativity emerges as a limit of these solutions when the background
field approaches zero, whereas the Melvin solution of General Relativity does
not emerge as a limit when the black hole's size approaches zero. This finding
suggests that astrophysical black-holes in Entangled Relativity are
indistinguishable from those in General Relativity, given the generally weak
interstellar density of matter fields.
| [
{
"created": "Thu, 25 Jul 2024 07:59:30 GMT",
"version": "v1"
}
] | 2024-07-26 | [
[
"Minazzoli",
"Olivier",
""
],
[
"Wavasseur",
"Maxime",
""
]
] | In this paper, we present the solution for a Schwarzschild black-hole immersed in an electric or magnetic background field within the framework of Entangled Relativity. Previous solutions in Entangled Relativity required black-holes to be charged for the matter field to be defined everywhere. This is because the theory precludes the existence of vacuum solutions, thereby satisfying Einstein's definition of Mach's Principle. The current black-hole solutions represent the first exact and neutral black-hole solutions of Entangled Relativity discovered to date. The Schwarzschild black-hole of General Relativity emerges as a limit of these solutions when the background field approaches zero, whereas the Melvin solution of General Relativity does not emerge as a limit when the black hole's size approaches zero. This finding suggests that astrophysical black-holes in Entangled Relativity are indistinguishable from those in General Relativity, given the generally weak interstellar density of matter fields. |
1002.2035 | Dah-Wei Chiou | Dah-Wei Chiou and Kai Liu | Cosmological inflation driven by holonomy corrections of loop quantum
cosmology | 7 pages, 2 figures, 1 table; one reference added. | Phys.Rev.D81:063526,2010 | 10.1103/PhysRevD.81.063526 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | At the level of heuristic effective dynamics, we investigate the cosmological
inflation with holonomy corrections of loop quantum cosmology (LQC) in the
$k=0$ Friedmann-Robertson-Walker model with a single inflaton field subject to
a simple potential. In the symmetric bouncing scenario of LQC, the condition
for occurrence of the quantum bounce naturally and uniquely fixes the initial
conditions at the bouncing epoch. Around the quantum bounce, the universe
undergoes a short super-inflationary phase, which drives the inflaton field to
its potential hill and thus sets the proper initial conditions for the standard
slow-roll inflation. Between the super-inflation and the standard inflation,
there is a non-inflationary phase, which violates the slow-roll condition. The
violation of slow roll is expected to give some suppression on the low angular
power spectrum of the cosmic microwave background and different orders of
holonomy corrections shall yield different suppressions.
| [
{
"created": "Wed, 10 Feb 2010 07:49:58 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Mar 2010 06:50:02 GMT",
"version": "v2"
}
] | 2010-04-29 | [
[
"Chiou",
"Dah-Wei",
""
],
[
"Liu",
"Kai",
""
]
] | At the level of heuristic effective dynamics, we investigate the cosmological inflation with holonomy corrections of loop quantum cosmology (LQC) in the $k=0$ Friedmann-Robertson-Walker model with a single inflaton field subject to a simple potential. In the symmetric bouncing scenario of LQC, the condition for occurrence of the quantum bounce naturally and uniquely fixes the initial conditions at the bouncing epoch. Around the quantum bounce, the universe undergoes a short super-inflationary phase, which drives the inflaton field to its potential hill and thus sets the proper initial conditions for the standard slow-roll inflation. Between the super-inflation and the standard inflation, there is a non-inflationary phase, which violates the slow-roll condition. The violation of slow roll is expected to give some suppression on the low angular power spectrum of the cosmic microwave background and different orders of holonomy corrections shall yield different suppressions. |
1303.0752 | Daniel Mart\'in-de Blas | Daniel Mart\'in-de Blas, Mercedes Mart\'in-Benito, Guillermo A. Mena
Marug\'an | Inclusion of matter in inhomogeneous loop quantum cosmology | 4 pages. Contribution to the Proceedings of Spanish Relativity
Meeting ERE2011, Madrid 2011 | AIP Conf.Proc. 1458 (2011) 467-470 | 10.1063/1.4734461 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the hybrid quantization of the linearly polarized Gowdy $T^3$ model
with a massless scalar field with the same symmetries as the metric. For
simplicity, we quantize its restriction to the model with local rotational
symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the
geometry are quantized \`a la loop, leading to the resolution of the
cosmological singularity. A Fock quantization is employed both for the matter
and the gravitational inhomogeneities. Owing to the inclusion of the massless
scalar field this system allows us to modelize flat Friedmann-Robertson-Walker
cosmologies filled with inhomogeneities propagating in one direction, providing
a perfect scenario to study the quantum back-reaction of the inhomogeneities on
the polymeric homogeneous and isotropic background.
| [
{
"created": "Mon, 4 Mar 2013 16:53:13 GMT",
"version": "v1"
}
] | 2013-03-05 | [
[
"Blas",
"Daniel Martín-de",
""
],
[
"Martín-Benito",
"Mercedes",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | We study the hybrid quantization of the linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric. For simplicity, we quantize its restriction to the model with local rotational symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the geometry are quantized \`a la loop, leading to the resolution of the cosmological singularity. A Fock quantization is employed both for the matter and the gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction, providing a perfect scenario to study the quantum back-reaction of the inhomogeneities on the polymeric homogeneous and isotropic background. |
1710.10360 | William Barker Mr | William Barker, Tom\'a\v{s} Ledvinka, Donald Lynden-Bell, Ji\v{r}\'i
Bi\v{c}\'ak | Rotation of inertial frames by angular momentum of matter and waves | 16 pages, 3 figures | 2017 Class. Quantum Grav. 34 205006 | 10.1088/1361-6382/aa8a34 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We elucidate the dynamics of a thin spherical material shell with a
tangential pressure, using a new approach. This is both simpler than the
traditional method of extrinsic curvature junction conditions (which we also
employ), and suggests an expression for a `gravitational potential energy' of
the shell. Such a shell, if slowly spinning, can rotationally drag the inertial
frames within it through a finite angle as it collapses and rebounds from a
minimum radius. Rebounding `spherical' and cylindrical pulses of rotating
gravitational waves were studied previously. Here we calculate their angular
momentum and show that their rotational frame dragging is in agreement with
that of the rotating spherical shell and a rotating cylindrical dust shell.
This shows that Machian effects occur equally for material and analogous
`immaterial' sources.
| [
{
"created": "Sat, 28 Oct 2017 00:38:22 GMT",
"version": "v1"
}
] | 2017-10-31 | [
[
"Barker",
"William",
""
],
[
"Ledvinka",
"Tomáš",
""
],
[
"Lynden-Bell",
"Donald",
""
],
[
"Bičák",
"Jiří",
""
]
] | We elucidate the dynamics of a thin spherical material shell with a tangential pressure, using a new approach. This is both simpler than the traditional method of extrinsic curvature junction conditions (which we also employ), and suggests an expression for a `gravitational potential energy' of the shell. Such a shell, if slowly spinning, can rotationally drag the inertial frames within it through a finite angle as it collapses and rebounds from a minimum radius. Rebounding `spherical' and cylindrical pulses of rotating gravitational waves were studied previously. Here we calculate their angular momentum and show that their rotational frame dragging is in agreement with that of the rotating spherical shell and a rotating cylindrical dust shell. This shows that Machian effects occur equally for material and analogous `immaterial' sources. |
2403.05682 | Chen-Kai Qiao | Chen-Kai Qiao and Ping Su | Time Delay of Light in the Gravitational lensing of Supermassive Black
Holes in Dark Matter Halos | 22 pages, 7 figures, 2 Appendices V2: some errors are corrected; V3:
major revision, two appendices added | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dark matter halo has non-negligible effects on the gravitational lensing
of supermassive black hole in the galaxy center. Our work presents a study on
the time-delay of light in gravitational lensing of black holes enclosed by
dark matter halos. To provide a precise description on the distribution of dark
matter in galaxies, we choose several famous phenomenological dark matter halo
models in astrophysics, including the NFW, Beta, Burkert and Moore models, to
carry out the present study. Through numerically calculating the time-delay of
light in gravitational lensing, a comparative analysis of the dark matter
effects within different halo models has been performed. Assuming typical
length scales associated with the galactic gravitational lensing, numerical
results indicate that the NFW, Beta, Burkert and Moore dark matter halos can
significantly enhance the time delay of light in gravitational lenisng of
central supermassive black holes. The enhancing effect becomes more pronounced
with a small dark matter halo scale and an increasing dark matter halo mass.
Keywords: Black Hole; Gravitational Lensing; Time Delay; Dark Matter Halo
| [
{
"created": "Fri, 8 Mar 2024 21:26:24 GMT",
"version": "v1"
},
{
"created": "Sun, 12 May 2024 08:15:27 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Aug 2024 02:24:06 GMT",
"version": "v3"
}
] | 2024-08-13 | [
[
"Qiao",
"Chen-Kai",
""
],
[
"Su",
"Ping",
""
]
] | The dark matter halo has non-negligible effects on the gravitational lensing of supermassive black hole in the galaxy center. Our work presents a study on the time-delay of light in gravitational lensing of black holes enclosed by dark matter halos. To provide a precise description on the distribution of dark matter in galaxies, we choose several famous phenomenological dark matter halo models in astrophysics, including the NFW, Beta, Burkert and Moore models, to carry out the present study. Through numerically calculating the time-delay of light in gravitational lensing, a comparative analysis of the dark matter effects within different halo models has been performed. Assuming typical length scales associated with the galactic gravitational lensing, numerical results indicate that the NFW, Beta, Burkert and Moore dark matter halos can significantly enhance the time delay of light in gravitational lenisng of central supermassive black holes. The enhancing effect becomes more pronounced with a small dark matter halo scale and an increasing dark matter halo mass. Keywords: Black Hole; Gravitational Lensing; Time Delay; Dark Matter Halo |
1902.03378 | Arpit Das Indian Institute of Science Education and Research | Arpit Das and Narayan Banerjee | Unitarity in Reissner-Nordstr\"{o}m background: striding away from
information loss | 11 pages, no figure. Some clarifications. Main results unchanged | Eur. Phys. J. C (2019) 79: 475 | 10.1140/epjc/s10052-019-6991-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have shown analytically that radiation from a collapsing shell which leads
to a charged black hole, whose exterior is described by the RN
(Reissner-Nordstr\"om) metric (and hence the background spacetime is
non-globally hyperbolic), is processed with a unitary evolution. For the
analysis, we have used the Wheeler-deWitt formalism which in turn gave rise to
a Schr\"{o}dinger-like wave equation. We showed the existence of unitarity by
proving that the trace of the squared density matrix of the outgoing radiation,
from a quantized massless scalar field, is unity and that the conservation of
probability holds for the wave function of the system.
| [
{
"created": "Sat, 9 Feb 2019 06:16:37 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2019 09:36:18 GMT",
"version": "v2"
}
] | 2019-06-19 | [
[
"Das",
"Arpit",
""
],
[
"Banerjee",
"Narayan",
""
]
] | We have shown analytically that radiation from a collapsing shell which leads to a charged black hole, whose exterior is described by the RN (Reissner-Nordstr\"om) metric (and hence the background spacetime is non-globally hyperbolic), is processed with a unitary evolution. For the analysis, we have used the Wheeler-deWitt formalism which in turn gave rise to a Schr\"{o}dinger-like wave equation. We showed the existence of unitarity by proving that the trace of the squared density matrix of the outgoing radiation, from a quantized massless scalar field, is unity and that the conservation of probability holds for the wave function of the system. |
1012.1556 | Stefano Finazzi | Stefano Finazzi and Renaud Parentani | Spectral properties of acoustic black hole radiation: Broadening the
horizon | 12 pages, 12 figures, revtex4, minor corrections, version accepted on
prd | Phys.Rev.D83:084010,2011 | 10.1103/PhysRevD.83.084010 | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The sensitivity of the black hole spectrum when introducing short distance
dispersion is studied in the context of atomic Bose condensates. By considering
flows characterized by several length scales, we show that, while the spectrum
remains remarkably Planckian, the temperature is no longer fixed by the surface
gravity. Rather it is determined by the average of the flow gradient across the
horizon over an interval fixed by the healing length and the surface gravity,
as if the horizon were broadened. This remains valid as long as the flow does
not induce nonadiabatic effects that produce oscillations or some parametric
amplification of the flux.
| [
{
"created": "Tue, 7 Dec 2010 17:15:54 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Apr 2011 18:59:58 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Finazzi",
"Stefano",
""
],
[
"Parentani",
"Renaud",
""
]
] | The sensitivity of the black hole spectrum when introducing short distance dispersion is studied in the context of atomic Bose condensates. By considering flows characterized by several length scales, we show that, while the spectrum remains remarkably Planckian, the temperature is no longer fixed by the surface gravity. Rather it is determined by the average of the flow gradient across the horizon over an interval fixed by the healing length and the surface gravity, as if the horizon were broadened. This remains valid as long as the flow does not induce nonadiabatic effects that produce oscillations or some parametric amplification of the flux. |
1009.2161 | Edward Anderson | Edward Anderson | Shape Quantities for Relational Quadrilateralland | Seminar I on relational quadrilaterals (2-d 4-body problem as a
whole-universe model in the absense of all absolute connotations). The set of
shape quantities given here was found to be incomplete, as pointed out and
completed in arXiv:1202.4186 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I investigate useful shape quantities for the classical and quantum mechanics
of the relational quadrilateral in 2-d. This is relational in the sense that
only relative times, relative ratios of separations and relative angles are
significant. Relational particle mechanics models such as this paper's have
many analogies with the geometrodynamical formulation of general relativity.
This renders them suitable as toy models for 1) studying Problem of Time in
Quantum Gravity strategies, in particular timeless, semiclassical and histories
theory approaches and combinations of these. 2) For consideration of various
other quantum-cosmological issues, such as structure formation/inhomogeneity
and notions of uniform states and their significance. The relational
quadrilateral is more useful in these respects than previously investigated
simpler RPM's due to simultaneously possessing linear constraints, nontrivial
subsystems and nontrivial complex-projective mathematics. Such shape have been
found to be useful in simpler relational models such as the relational triangle
and in 1-d.
| [
{
"created": "Sat, 11 Sep 2010 12:16:47 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Oct 2010 14:15:58 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Jan 2011 01:28:28 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Aug 2013 00:25:57 GMT",
"version": "v4"
}
] | 2013-08-08 | [
[
"Anderson",
"Edward",
""
]
] | I investigate useful shape quantities for the classical and quantum mechanics of the relational quadrilateral in 2-d. This is relational in the sense that only relative times, relative ratios of separations and relative angles are significant. Relational particle mechanics models such as this paper's have many analogies with the geometrodynamical formulation of general relativity. This renders them suitable as toy models for 1) studying Problem of Time in Quantum Gravity strategies, in particular timeless, semiclassical and histories theory approaches and combinations of these. 2) For consideration of various other quantum-cosmological issues, such as structure formation/inhomogeneity and notions of uniform states and their significance. The relational quadrilateral is more useful in these respects than previously investigated simpler RPM's due to simultaneously possessing linear constraints, nontrivial subsystems and nontrivial complex-projective mathematics. Such shape have been found to be useful in simpler relational models such as the relational triangle and in 1-d. |
0911.1634 | Eva Hackmann | E. Hackmann, V. Kagramanova, J. Kunz, C. L\"ammerzahl | Analytic solutions of the geodesic equation in axially symmetric
space-times | 4 pages, 4 figures, accepted for publication in EPL | Europhys.Lett.88:30008,2009 | 10.1209/0295-5075/88/30008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The complete sets of analytic solutions of the geodesic equation in
Taub--NUT--(anti-)de Sitter, Kerr--(anti-)de Sitter and also in general
Plebanski--Demianski space--times without acceleration are presented. The
solutions are given in terms of the Kleinian sigma functions.
| [
{
"created": "Mon, 9 Nov 2009 12:28:08 GMT",
"version": "v1"
}
] | 2011-08-11 | [
[
"Hackmann",
"E.",
""
],
[
"Kagramanova",
"V.",
""
],
[
"Kunz",
"J.",
""
],
[
"Lämmerzahl",
"C.",
""
]
] | The complete sets of analytic solutions of the geodesic equation in Taub--NUT--(anti-)de Sitter, Kerr--(anti-)de Sitter and also in general Plebanski--Demianski space--times without acceleration are presented. The solutions are given in terms of the Kleinian sigma functions. |
2301.12103 | Li Tang | Hai-Nan Lin and Li Tang and Rui Zou | Revised constraints on the photon mass from well-localized fast radio
bursts | 9 pages, 4 figures | MNRAS 520, 1324-1331 (2023) | 10.1093/mnras/stad228 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We constrain the photon mass from well-localized fast radio bursts (FRBs)
using Bayes inference method. The probability distributions of dispersion
measures (DM) of host galaxy and intergalactic medium are properly taken into
account. The photon mass is tightly constrained from 17 well-localized FRBs in
the redshift range $0<z<0.66$. Assuming that there is no redshift evolution of
host DM, the $1\sigma$ and $2\sigma$ upper limits of photon mass are
constrained to be $m_\gamma<4.8\times 10^{-51}$ kg and $m_\gamma<7.1\times
10^{-51}$ kg, respectively. Monte Carlo simulations show that, even enlarging
the FRB sample to 200 and extending the redshift range to $0<z<3$ couldn't
significantly improve the constraining ability on photon mass. This is because
of the large uncertainty on the DM of intergalactic medium.
| [
{
"created": "Sat, 28 Jan 2023 06:09:31 GMT",
"version": "v1"
}
] | 2023-09-21 | [
[
"Lin",
"Hai-Nan",
""
],
[
"Tang",
"Li",
""
],
[
"Zou",
"Rui",
""
]
] | We constrain the photon mass from well-localized fast radio bursts (FRBs) using Bayes inference method. The probability distributions of dispersion measures (DM) of host galaxy and intergalactic medium are properly taken into account. The photon mass is tightly constrained from 17 well-localized FRBs in the redshift range $0<z<0.66$. Assuming that there is no redshift evolution of host DM, the $1\sigma$ and $2\sigma$ upper limits of photon mass are constrained to be $m_\gamma<4.8\times 10^{-51}$ kg and $m_\gamma<7.1\times 10^{-51}$ kg, respectively. Monte Carlo simulations show that, even enlarging the FRB sample to 200 and extending the redshift range to $0<z<3$ couldn't significantly improve the constraining ability on photon mass. This is because of the large uncertainty on the DM of intergalactic medium. |
1105.1008 | Zohre Azarmi | F. Adabi, K. Karami, F. Felegary, Z. Azarmi | Interacting viscous entropy-corrected holographic scalar field models of
dark energy with time-varying G in modified FRW cosmology | 14 pages, Accepted for publication in Research in Astronomy and
Astrophysics | Res. Astron. Astrophys. 12 (2012) 26 | 10.1088/1674-4527/12/1/002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the entropy-corrected version of the holographic dark energy (HDE)
model in the framework of modified FRW cosmology. We consider a non-flat
universe filled with an interacting viscous entropy-corrected HDE (ECHDE) with
dark matter. We also include the case of variable gravitational constant G in
our model. We obtain the equation of state and the deceleration parameters of
the interacting viscous ECHDE. Moreover, we reconstruct the potential and the
dynamics of the quintessence, tachyon, K-essence and dilaton scalar field
models according to the evolutionary behavior of the interacting viscous ECHDE
model with time-varying G.
| [
{
"created": "Thu, 5 May 2011 08:13:58 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 2011 16:45:11 GMT",
"version": "v2"
}
] | 2012-01-30 | [
[
"Adabi",
"F.",
""
],
[
"Karami",
"K.",
""
],
[
"Felegary",
"F.",
""
],
[
"Azarmi",
"Z.",
""
]
] | We study the entropy-corrected version of the holographic dark energy (HDE) model in the framework of modified FRW cosmology. We consider a non-flat universe filled with an interacting viscous entropy-corrected HDE (ECHDE) with dark matter. We also include the case of variable gravitational constant G in our model. We obtain the equation of state and the deceleration parameters of the interacting viscous ECHDE. Moreover, we reconstruct the potential and the dynamics of the quintessence, tachyon, K-essence and dilaton scalar field models according to the evolutionary behavior of the interacting viscous ECHDE model with time-varying G. |
gr-qc/9506094 | Dr. sayan Kar | Sayan Kar and Deshdeep Sahdev | Evolving Lorentzian Wormholes | 10 pages( RevTex, Twocolumn format), Two figures available on request
from the first author. transmission errors corrected. | Phys.Rev. D53 (1996) 722-730 | 10.1103/PhysRevD.53.722 | IP--BBSR--95/38 | gr-qc | null | Evolving Lorentzian wormholes with the required matter satisfying the Energy
conditions are discussed. Several different scale factors are used and the
corresponding consequences derived. The effect of extra, decaying (in time)
compact dimensions present in the wormhole metric is also explored and certain
interesting conclusions are derived for the cases of exponential and
Kaluza--Klein inflation.
| [
{
"created": "Thu, 29 Jun 1995 19:47:22 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 1995 21:48:24 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Jul 1995 18:57:22 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Kar",
"Sayan",
""
],
[
"Sahdev",
"Deshdeep",
""
]
] | Evolving Lorentzian wormholes with the required matter satisfying the Energy conditions are discussed. Several different scale factors are used and the corresponding consequences derived. The effect of extra, decaying (in time) compact dimensions present in the wormhole metric is also explored and certain interesting conclusions are derived for the cases of exponential and Kaluza--Klein inflation. |
gr-qc/9710065 | I. H. Dwivedi | I. H. Dwivedi | Field of a Radiation Distributuion | Latex file, 13 pages, no figures. Accepted for publication in Phys.
Rev. D | Phys.Rev. D58 (1998) 084029 | 10.1103/PhysRevD.58.084029 | null | gr-qc | null | General relativistic spherically symmetric matter field with a vanishing
stress energy scalar is analyzed. Procedure for generating exact solutions of
the field equations for such matter distributions is given. It is further
pointed out that all such type I spherically symmetric fields with distinct
eignvalues in the radial two space can be treated as a mixture of isotropic and
directed radiations. Various classes of exact solutions are given. Junction
conditions for such a matter field to the possible exterior solutions are also
discussed.
| [
{
"created": "Sun, 12 Oct 1997 11:00:24 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Jun 1998 09:08:33 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Dwivedi",
"I. H.",
""
]
] | General relativistic spherically symmetric matter field with a vanishing stress energy scalar is analyzed. Procedure for generating exact solutions of the field equations for such matter distributions is given. It is further pointed out that all such type I spherically symmetric fields with distinct eignvalues in the radial two space can be treated as a mixture of isotropic and directed radiations. Various classes of exact solutions are given. Junction conditions for such a matter field to the possible exterior solutions are also discussed. |
gr-qc/0610071 | Timothy Clifton | T. Clifton | Alternative Theories of Gravity | 205 pages. PhD thesis | null | null | null | gr-qc astro-ph hep-th | null | This work investigates alternative theories of gravity, the solutions to
their field equations and the constraints that can be imposed upon them from
observation and experiment. Specifically, we consider the cosmologies and
spherically symmetric solutions that can be expected to result from
scalar-tensor and fourth-order theories of gravity. We find exact cosmological
solutions of various different kinds; isotropic and anisotropic, homogeneous
and inhomogeneous. These solutions are used to investigate the behaviour of the
Universes at both late and early times, to investigate the effects of
corrections to general relativity on approach to an initial singularity and to
look for effects which may be observable in the present day Universe. We use
physical processes, such as the primordial nucleosynthesis of the light
elements, to impose constraints upon any deviations from the standard model.
Furthermore, we investigate the vacuum spherically symmetric solutions of these
theories. This environment is of particular interest for considerations of the
local effects of gravity, where the most accurate experiments and observations
of gravitational phenomena can be performed. Exact solutions are obtained for
this situation and their stability analysed. It is found that a variety of new
behaviour is obtainable in these theories that was not previously possible in
the standard model. This new behaviour allows us an extended framework in which
to consider gravitational physics, and its cosmological consequences.
| [
{
"created": "Fri, 13 Oct 2006 18:17:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Clifton",
"T.",
""
]
] | This work investigates alternative theories of gravity, the solutions to their field equations and the constraints that can be imposed upon them from observation and experiment. Specifically, we consider the cosmologies and spherically symmetric solutions that can be expected to result from scalar-tensor and fourth-order theories of gravity. We find exact cosmological solutions of various different kinds; isotropic and anisotropic, homogeneous and inhomogeneous. These solutions are used to investigate the behaviour of the Universes at both late and early times, to investigate the effects of corrections to general relativity on approach to an initial singularity and to look for effects which may be observable in the present day Universe. We use physical processes, such as the primordial nucleosynthesis of the light elements, to impose constraints upon any deviations from the standard model. Furthermore, we investigate the vacuum spherically symmetric solutions of these theories. This environment is of particular interest for considerations of the local effects of gravity, where the most accurate experiments and observations of gravitational phenomena can be performed. Exact solutions are obtained for this situation and their stability analysed. It is found that a variety of new behaviour is obtainable in these theories that was not previously possible in the standard model. This new behaviour allows us an extended framework in which to consider gravitational physics, and its cosmological consequences. |
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