id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0403043 | George Japaridze | W. D. Flanders and G. S. Japaridze | Photon deflection and precession of the periastron in terms of spatial
gravitational fields | null | Class.Quant.Grav. 21 (2004) 1825-1831 | 10.1088/0264-9381/21/7/007 | null | gr-qc hep-th | null | We show that a Maxwell-like system of equations for spatial gravitational
fields $\bf g$ and $\bf B$ (latter being the analogy of a magnetic field),
modified to include an extra term for the $\bf B$ field in the expression for
force, leads to the correct values for the photon deflection angle and for the
precession of the periastron.
| [
{
"created": "Thu, 11 Mar 2004 01:04:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Flanders",
"W. D.",
""
],
[
"Japaridze",
"G. S.",
""
]
] | We show that a Maxwell-like system of equations for spatial gravitational fields $\bf g$ and $\bf B$ (latter being the analogy of a magnetic field), modified to include an extra term for the $\bf B$ field in the expression for force, leads to the correct values for the photon deflection angle and for the precession of the periastron. |
gr-qc/0308001 | Gregory M. Harry | Michael J. Mortonson, Christophoros C. Vassiliou, David J. Ottaway,
David H. Shoemaker, Gregory M. Harry | Effects of electrical charging on the mechanical Q of a fused silica
disk | submitted to Review of Scientific Instruments | Rev.Sci.Instrum.74:4840-4845,2003 | 10.1063/1.1619544 | null | gr-qc | null | We report on the effects of an electrical charge on mechanical loss of a
fused silica disk. A degradation of Q was seen that correlated with charge on
the surface of the sample. We examine a number of models for charge damping,
including eddy current damping and loss due to polarization. We conclude that
rubbing friction between the sample and a piece of dust attracted by the
charged sample is the most likely explanation for the observed loss.
| [
{
"created": "Thu, 31 Jul 2003 21:40:18 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Mortonson",
"Michael J.",
""
],
[
"Vassiliou",
"Christophoros C.",
""
],
[
"Ottaway",
"David J.",
""
],
[
"Shoemaker",
"David H.",
""
],
[
"Harry",
"Gregory M.",
""
]
] | We report on the effects of an electrical charge on mechanical loss of a fused silica disk. A degradation of Q was seen that correlated with charge on the surface of the sample. We examine a number of models for charge damping, including eddy current damping and loss due to polarization. We conclude that rubbing friction between the sample and a piece of dust attracted by the charged sample is the most likely explanation for the observed loss. |
0910.0839 | T. Padmanabhan | T. Padmanabhan | A Dialogue on the Nature of Gravity | Based on lectures given in several conferences (including VR lecture
of IAGRG); results have been updated and format has been changed to one
involving a dialogue; version 2: discussion significantly extended;
references added; 3 figures; 37 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I describe the conceptual and mathematical basis of an approach which
describes gravity as an emergent phenomenon. Combining principle of equivalence
and principle of general covariance with known properties of local Rindler
horizons, perceived by observers accelerated with respect to local inertial
frames, one can prove that the field equations describing gravity in any
diffeomorphism invariant theory can be given a thermodynamic re-interpretation.
This fact, in turn, leads us to the possibility of deriving the field equations
of gravity by maximising a suitably defined entropy functional, without using
the metric tensor as a dynamical variable. The approach synthesises concepts
from quantum theory, thermodynamics and gravity leading to a fresh perspective
on the nature of gravity. The description is presented here in the form of a
dialogue, thereby addressing several frequently-asked-questions.
| [
{
"created": "Mon, 5 Oct 2009 20:00:16 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Nov 2009 10:28:12 GMT",
"version": "v2"
}
] | 2009-11-22 | [
[
"Padmanabhan",
"T.",
""
]
] | I describe the conceptual and mathematical basis of an approach which describes gravity as an emergent phenomenon. Combining principle of equivalence and principle of general covariance with known properties of local Rindler horizons, perceived by observers accelerated with respect to local inertial frames, one can prove that the field equations describing gravity in any diffeomorphism invariant theory can be given a thermodynamic re-interpretation. This fact, in turn, leads us to the possibility of deriving the field equations of gravity by maximising a suitably defined entropy functional, without using the metric tensor as a dynamical variable. The approach synthesises concepts from quantum theory, thermodynamics and gravity leading to a fresh perspective on the nature of gravity. The description is presented here in the form of a dialogue, thereby addressing several frequently-asked-questions. |
1003.0614 | Mohammad Nouri-Zonoz | B. Nazari and M. Nouri-Zonoz | Casimir effect in a weak gravitational field and the spacetime index of
refraction | 11 pages, RevTex, typos corrected (combined with arXiv:0904.2904
published in PRD) | Phys.Rev.D82:044047,2010 | 10.1103/PhysRevD.85.044060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper [arXiv:0904.2904] using a conjecture it is shown how one
can calculate the effect of a weak stationary gravitational field on vacuum
energy in the context of Casimir effect in an external gravitational field
treated in 1+3 formulation of spacetime decomposition.. In this article,
employing quntum field theory in curved spacetime, we explicitly calculate the
effect of a weak static gravitational field on virtual massless scalar
particles in a Casimir apparatus. It is shown that, as expected from the
proposed conjecture, both the frequency and renormalized energy of the virtual
scalar field are affected by the gravitational field through its index of
refraction. This could be taken as a strong evidence in favour of the proposed
conjecture. Generalizations to weak {\it stationary} spacetimes and virtual
photons are also discussed.
| [
{
"created": "Tue, 2 Mar 2010 15:19:28 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Oct 2010 09:01:14 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Nazari",
"B.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | In a recent paper [arXiv:0904.2904] using a conjecture it is shown how one can calculate the effect of a weak stationary gravitational field on vacuum energy in the context of Casimir effect in an external gravitational field treated in 1+3 formulation of spacetime decomposition.. In this article, employing quntum field theory in curved spacetime, we explicitly calculate the effect of a weak static gravitational field on virtual massless scalar particles in a Casimir apparatus. It is shown that, as expected from the proposed conjecture, both the frequency and renormalized energy of the virtual scalar field are affected by the gravitational field through its index of refraction. This could be taken as a strong evidence in favour of the proposed conjecture. Generalizations to weak {\it stationary} spacetimes and virtual photons are also discussed. |
1702.05915 | Matt Visser | Prado Martin-Moruno (Universidad Complutense de Madrid) and Matt
Visser (Victoria University of Wellington) | Classical and semi-classical energy conditions | V1: 25 pages. Draft chapter, on which the related chapter of the book
"Wormholes, Warp Drives and Energy Conditions" (to be published by Springer),
will be based. V2: typos fixed. V3: small typo fixed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard energy conditions of classical general relativity are (mostly)
linear in the stress-energy tensor, and have clear physical interpretations in
terms of geodesic focussing, but suffer the significant drawback that they are
often violated by semi-classical quantum effects. In contrast, it is possible
to develop non-standard energy conditions that are intrinsically non-linear in
the stress-energy tensor, and which exhibit much better well-controlled
behaviour when semi-classical quantum effects are introduced, at the cost of a
less direct applicability to geodesic focussing. In this article we will first
review the standard energy conditions and their various limitations. (Including
the connection to the Hawking--Ellis type I, II, III, and IV classification of
stress-energy tensors). We shall then turn to the averaged, nonlinear, and
semi-classical energy conditions, and see how much can be done once
semi-classical quantum effects are included.
| [
{
"created": "Mon, 20 Feb 2017 10:13:45 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Mar 2017 09:11:51 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Mar 2017 08:52:01 GMT",
"version": "v3"
}
] | 2017-03-30 | [
[
"Martin-Moruno",
"Prado",
"",
"Universidad Complutense de Madrid"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The standard energy conditions of classical general relativity are (mostly) linear in the stress-energy tensor, and have clear physical interpretations in terms of geodesic focussing, but suffer the significant drawback that they are often violated by semi-classical quantum effects. In contrast, it is possible to develop non-standard energy conditions that are intrinsically non-linear in the stress-energy tensor, and which exhibit much better well-controlled behaviour when semi-classical quantum effects are introduced, at the cost of a less direct applicability to geodesic focussing. In this article we will first review the standard energy conditions and their various limitations. (Including the connection to the Hawking--Ellis type I, II, III, and IV classification of stress-energy tensors). We shall then turn to the averaged, nonlinear, and semi-classical energy conditions, and see how much can be done once semi-classical quantum effects are included. |
gr-qc/0108018 | Edward N. Glass | E.N. Glass (Department of Physics, University of Michigan, Ann Arbor,
Michgan) | A Conserved Bach Current | to appear in Class. Quantum Grav | Class.Quant.Grav. 18 (2001) 3935-3942 | 10.1088/0264-9381/18/18/312 | MCTP-01-35 | gr-qc | null | The Bach tensor and a vector which generates conformal symmetries allow a
conserved four-current to be defined. The Bach four-current gives rise to a
quasilocal two-surface expression for power per luminosity distance in the
Vaidya exterior of collapsing fluid interiors. This is interpreted in terms of
entropy generation.
| [
{
"created": "Mon, 6 Aug 2001 01:40:19 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Glass",
"E. N.",
"",
"Department of Physics, University of Michigan, Ann Arbor,\n Michgan"
]
] | The Bach tensor and a vector which generates conformal symmetries allow a conserved four-current to be defined. The Bach four-current gives rise to a quasilocal two-surface expression for power per luminosity distance in the Vaidya exterior of collapsing fluid interiors. This is interpreted in terms of entropy generation. |
gr-qc/0206074 | Lorenzo Iorio | Lorenzo Iorio | On a new observable for measuring the Lense-Thirring effect with
Satellite Laser Ranging | LaTex2e, 14 pages, 1 table, no figures. Some changes and additions to
the abstract, Introduction and Conclusions. References updated, typos
corrected. Equation corrected. To appear in General Relativity and
Gravitation | Gen.Rel.Grav. 35 (2003) 1583-1595 | 10.1023/A:1025727001141 | null | gr-qc astro-ph physics.space-ph | null | In this paper we present a rather extensive error budget for the difference
of the perigees of a pair of supplementary SLR satellites aimed to the
detection of the Lense-Thirring effect.
| [
{
"created": "Tue, 25 Jun 2002 07:47:56 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Sep 2002 14:42:33 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Apr 2003 07:36:53 GMT",
"version": "v3"
},
{
"created": "Wed, 16 Apr 2003 13:07:28 GMT",
"version": "v4"
},
{
"cr... | 2007-11-12 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we present a rather extensive error budget for the difference of the perigees of a pair of supplementary SLR satellites aimed to the detection of the Lense-Thirring effect. |
1108.4740 | Cosimo Bambi | Cosimo Bambi, Enrico Barausse | The final stages of accretion onto non-Kerr compact objects | 13 pages, 4 figures. v2: some typos corrected | Phys.Rev.D84:084034,2011 | 10.1103/PhysRevD.84.084034 | IPMU11-0132; LMU-ASC-24-12 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The $5 - 20 M_\odot$ dark objects in X-ray binary systems and the $10^5 -
10^9 M_\odot$ dark objects in galactic nuclei are currently thought to be the
Kerr black holes predicted by General Relativity. However, direct observational
evidence for this identification is still elusive, and the only viable approach
to confirm the Kerr black hole hypothesis is to explore and rule out any other
possibility. Here we investigate the final stages of the accretion process onto
generic compact objects. While for Kerr black holes and for more oblate bodies
the accreting gas reaches the innermost stable circular orbit (ISCO) and
plunges into the compact object, we find that for more prolate bodies several
scenarios are possible, depending on the spacetime geometry. In particular, we
find examples in which the gas reaches the ISCO, but then gets trapped between
the ISCO and the compact object. In this situation, accretion onto the compact
object is possible only if the gas loses additional angular momentum, forming
torus-like structures inside the ISCO.
| [
{
"created": "Wed, 24 Aug 2011 02:37:49 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2011 14:55:21 GMT",
"version": "v2"
}
] | 2012-04-09 | [
[
"Bambi",
"Cosimo",
""
],
[
"Barausse",
"Enrico",
""
]
] | The $5 - 20 M_\odot$ dark objects in X-ray binary systems and the $10^5 - 10^9 M_\odot$ dark objects in galactic nuclei are currently thought to be the Kerr black holes predicted by General Relativity. However, direct observational evidence for this identification is still elusive, and the only viable approach to confirm the Kerr black hole hypothesis is to explore and rule out any other possibility. Here we investigate the final stages of the accretion process onto generic compact objects. While for Kerr black holes and for more oblate bodies the accreting gas reaches the innermost stable circular orbit (ISCO) and plunges into the compact object, we find that for more prolate bodies several scenarios are possible, depending on the spacetime geometry. In particular, we find examples in which the gas reaches the ISCO, but then gets trapped between the ISCO and the compact object. In this situation, accretion onto the compact object is possible only if the gas loses additional angular momentum, forming torus-like structures inside the ISCO. |
gr-qc/0310020 | Mikhail Vysotsky | S.I. Blinnikov, L.B. Okun, M.I. Vysotsky (ITEP, Moscow, Russia) | Critical velocities $c/\sqrt 3$ and $c/\sqrt 2$ in general theory of
relativity | 13 pages | Phys.Usp.46:1099-1103,2003; Usp.Fiz.Nauk 46:1131-1136,2003 | 10.1070/PU2003v046n10ABEH001661 | null | gr-qc hep-ex hep-ph | null | We consider a few thought experiments of radial motion of massive particles
in the gravitational fields outside and inside various celestial bodies: Earth,
Sun, black hole. All other interactions except gravity are disregarded. For the
outside motion there exists a critical value of coordinate velocity ${\rm v}_c
= c/\sqrt 3$: particles with ${\rm v} < {\rm v}_c$ are accelerated by the
field, like Newtonian apples, particles with ${\rm v} > {\rm v}_c$ are
decelerated like photons. Particles moving inside a body with constant density
have no critical velocity; they are always accelerated. We consider also the
motion of a ball inside a tower, when it is thrown from the top (bottom) of the
tower and after classically bouncing at the bottom (top) comes back to the
original point. The total time of flight is the same in these two cases if the
initial proper velocity $v_0$ is equal to $c/\sqrt 2$.
| [
{
"created": "Fri, 3 Oct 2003 13:23:26 GMT",
"version": "v1"
}
] | 2010-12-17 | [
[
"Blinnikov",
"S. I.",
"",
"ITEP, Moscow, Russia"
],
[
"Okun",
"L. B.",
"",
"ITEP, Moscow, Russia"
],
[
"Vysotsky",
"M. I.",
"",
"ITEP, Moscow, Russia"
]
] | We consider a few thought experiments of radial motion of massive particles in the gravitational fields outside and inside various celestial bodies: Earth, Sun, black hole. All other interactions except gravity are disregarded. For the outside motion there exists a critical value of coordinate velocity ${\rm v}_c = c/\sqrt 3$: particles with ${\rm v} < {\rm v}_c$ are accelerated by the field, like Newtonian apples, particles with ${\rm v} > {\rm v}_c$ are decelerated like photons. Particles moving inside a body with constant density have no critical velocity; they are always accelerated. We consider also the motion of a ball inside a tower, when it is thrown from the top (bottom) of the tower and after classically bouncing at the bottom (top) comes back to the original point. The total time of flight is the same in these two cases if the initial proper velocity $v_0$ is equal to $c/\sqrt 2$. |
gr-qc/9809012 | Kayll Lake | Kevin Santosuosso, Denis Pollney, Nicos Pelavas, Peter Musgrave, Kayll
Lake | Invariants of the Riemann tensor for Class B Warped Product Spacetimes | 19 pages. To appear in Computer Physics Communications Thematic Issue
on "Computer Algebra in Physics Research". Uses Maple2e.sty | Comput.Phys.Commun. 115 (1998) 381-394 | 10.1016/S0010-4655(98)00134-9 | null | gr-qc hep-th | null | We use the computer algebra system \textit{GRTensorII} to examine invariants
polynomial in the Riemann tensor for class $B$ warped product spacetimes -
those which can be decomposed into the coupled product of two 2-dimensional
spaces, one Lorentzian and one Riemannian, subject to the separability of the
coupling: $ds^2 = ds_{\Sigma_1}^2 (u,v) + C(x^\gamma)^2 ds_{\Sigma_2}^2
(\theta,\phi)$ with $C(x^\gamma)^2=r(u,v)^2 w(\theta,\phi)^2$ and
$sig(\Sigma_1)=0, sig(\Sigma_2)=2\epsilon (\epsilon=\pm 1)$ for class $B_{1}$
spacetimes and $sig(\Sigma_1)=2\epsilon, sig(\Sigma_2)=0$ for class $B_{2}$.
Although very special, these spaces include many of interest, for example, all
spherical, plane, and hyperbolic spacetimes. The first two Ricci invariants
along with the Ricci scalar and the real component of the second Weyl invariant
$J$ alone are shown to constitute the largest independent set of invariants to
degree five for this class. Explicit syzygies are given for other invariants up
to this degree. It is argued that this set constitutes the largest functionally
independent set to any degree for this class, and some physical consequences of
the syzygies are explored.
| [
{
"created": "Wed, 2 Sep 1998 18:05:07 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Santosuosso",
"Kevin",
""
],
[
"Pollney",
"Denis",
""
],
[
"Pelavas",
"Nicos",
""
],
[
"Musgrave",
"Peter",
""
],
[
"Lake",
"Kayll",
""
]
] | We use the computer algebra system \textit{GRTensorII} to examine invariants polynomial in the Riemann tensor for class $B$ warped product spacetimes - those which can be decomposed into the coupled product of two 2-dimensional spaces, one Lorentzian and one Riemannian, subject to the separability of the coupling: $ds^2 = ds_{\Sigma_1}^2 (u,v) + C(x^\gamma)^2 ds_{\Sigma_2}^2 (\theta,\phi)$ with $C(x^\gamma)^2=r(u,v)^2 w(\theta,\phi)^2$ and $sig(\Sigma_1)=0, sig(\Sigma_2)=2\epsilon (\epsilon=\pm 1)$ for class $B_{1}$ spacetimes and $sig(\Sigma_1)=2\epsilon, sig(\Sigma_2)=0$ for class $B_{2}$. Although very special, these spaces include many of interest, for example, all spherical, plane, and hyperbolic spacetimes. The first two Ricci invariants along with the Ricci scalar and the real component of the second Weyl invariant $J$ alone are shown to constitute the largest independent set of invariants to degree five for this class. Explicit syzygies are given for other invariants up to this degree. It is argued that this set constitutes the largest functionally independent set to any degree for this class, and some physical consequences of the syzygies are explored. |
gr-qc/0506102 | J. Brian Pitts | J. Brian Pitts | Absolute Objects and Counterexamples: Jones-Geroch Dust, Torretti
Constant Curvature, Tetrad-Spinor, and Scalar Density | Minor editing, small content additions, added references. Forthcoming
in_Studies in History and Philosophy of Modern Physics_, June 2006 | Studies in History and Philosophy of Modern Physics 37 (2006)
347-371 | 10.1016/j.shpsb.2005.11.004 | null | gr-qc hep-th physics.hist-ph | null | James L. Anderson analyzed the novelty of Einstein's theory of gravity as its
lack of "absolute objects." Michael Friedman's related work has been criticized
by Roger Jones and Robert Geroch for implausibly admitting as absolute the
timelike 4-velocity field of dust in cosmological models in Einstein's theory.
Using the Rosen-Sorkin Lagrange multiplier trick, I complete Anna Maidens's
argument that the problem is not solved by prohibiting variation of absolute
objects in an action principle. Recalling Anderson's proscription of
"irrelevant" variables, I generalize that proscription to locally irrelevant
variables that do no work in some places in some models. This move vindicates
Friedman's intuitions and removes the Jones-Geroch counterexample: some regions
of some models of gravity with dust are dust-free and so naturally lack a
timelike 4-velocity, so diffeomorphic equivalence to (1,0,0,0) is spoiled.
Torretti's example involving constant curvature spaces is shown to have an
absolute object on Anderson's analysis, viz., the conformal spatial metric
density. The previously neglected threat of an absolute object from an
orthonormal tetrad used for coupling spinors to gravity appears resolvable by
eliminating irrelevant fields. However, given Anderson's definition, GTR itself
has an absolute object (as Robert Geroch has observed recently): a change of
variables to a conformal metric density and a scalar density shows that the
latter is absolute.
| [
{
"created": "Mon, 20 Jun 2005 15:30:14 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Sep 2005 13:24:20 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Jan 2006 16:59:07 GMT",
"version": "v3"
},
{
"created": "Tue, 28 Feb 2006 02:49:40 GMT",
"version": "v4"
}
] | 2016-03-21 | [
[
"Pitts",
"J. Brian",
""
]
] | James L. Anderson analyzed the novelty of Einstein's theory of gravity as its lack of "absolute objects." Michael Friedman's related work has been criticized by Roger Jones and Robert Geroch for implausibly admitting as absolute the timelike 4-velocity field of dust in cosmological models in Einstein's theory. Using the Rosen-Sorkin Lagrange multiplier trick, I complete Anna Maidens's argument that the problem is not solved by prohibiting variation of absolute objects in an action principle. Recalling Anderson's proscription of "irrelevant" variables, I generalize that proscription to locally irrelevant variables that do no work in some places in some models. This move vindicates Friedman's intuitions and removes the Jones-Geroch counterexample: some regions of some models of gravity with dust are dust-free and so naturally lack a timelike 4-velocity, so diffeomorphic equivalence to (1,0,0,0) is spoiled. Torretti's example involving constant curvature spaces is shown to have an absolute object on Anderson's analysis, viz., the conformal spatial metric density. The previously neglected threat of an absolute object from an orthonormal tetrad used for coupling spinors to gravity appears resolvable by eliminating irrelevant fields. However, given Anderson's definition, GTR itself has an absolute object (as Robert Geroch has observed recently): a change of variables to a conformal metric density and a scalar density shows that the latter is absolute. |
gr-qc/9310011 | P. Suntharothok-Priesmeyer | L. P. Grishchuk | Cosmological Rotation of Quantum-Mechanical Origin and Anisotropy of the
Microwave Background | WUGRAV 93-6, Phys. Rev. D (in press), 33 pages | Phys.Rev.D48:5581-5593,1993 | 10.1103/PhysRevD.48.5581 | null | gr-qc | null | It is shown that rotational cosmological perturbations can be generated in
the early Universe, similarly to gravitational waves. The generating mechanism
is quantum-mechanical in its nature, and the created perturbations should now
be placed in squeezed vacuum quantum states. The physical conditions under
which the phenomenon can occur are formulated. The generated perturbations can
contribute to the large-angular-scale anisotropy of the cosmic microwave
background radiation. An exact formula is derived for the angular correlation
function of the temperature variations caused by the quantum-mechanically
generated rotational perturbations. The multipole expansion begins from the
dipole component. The comparison with the case of gravitational waves is made.
| [
{
"created": "Wed, 6 Oct 1993 20:26:34 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Grishchuk",
"L. P.",
""
]
] | It is shown that rotational cosmological perturbations can be generated in the early Universe, similarly to gravitational waves. The generating mechanism is quantum-mechanical in its nature, and the created perturbations should now be placed in squeezed vacuum quantum states. The physical conditions under which the phenomenon can occur are formulated. The generated perturbations can contribute to the large-angular-scale anisotropy of the cosmic microwave background radiation. An exact formula is derived for the angular correlation function of the temperature variations caused by the quantum-mechanically generated rotational perturbations. The multipole expansion begins from the dipole component. The comparison with the case of gravitational waves is made. |
1111.6247 | Christian Boehmer | Christian G. Boehmer, Nyein Chan, Ruth Lazkoz | Dynamics of dark energy models and centre manifolds | 11 pages, 1 figure | Phys.Lett. B714 (2012) 11-17 | 10.1016/j.physletb.2012.06.064 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse dark energy models where self-interacting three-forms or phantom
fields drive the accelerated expansion of the Universe. The dynamics of such
models is often studied by rewriting the cosmological field equations in the
form of a system of autonomous differential equations, or simply a dynamical
system. Properties of these systems are usually studied via linear stability
theory. In situations where this method fails, for instance due to the presence
of zero eigenvalues in the Jacobian, centre manifold theory can be applied. We
present a concise introduction and show explicitly how to use this theory in
two concrete examples.
| [
{
"created": "Sun, 27 Nov 2011 11:25:14 GMT",
"version": "v1"
}
] | 2012-12-11 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Chan",
"Nyein",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | We analyse dark energy models where self-interacting three-forms or phantom fields drive the accelerated expansion of the Universe. The dynamics of such models is often studied by rewriting the cosmological field equations in the form of a system of autonomous differential equations, or simply a dynamical system. Properties of these systems are usually studied via linear stability theory. In situations where this method fails, for instance due to the presence of zero eigenvalues in the Jacobian, centre manifold theory can be applied. We present a concise introduction and show explicitly how to use this theory in two concrete examples. |
gr-qc/0308005 | S. Antoci | S. Antoci and D.-E. Liebscher | The topology of Schwarzschild's solution and the Kruskal metric | 12 pages, 2 figures, misprints corrected | null | null | null | gr-qc | null | Kruskal's extension solves the problem of the arrow of time of the
``Schwarzschild solution'' through combining two Hilbert manifolds by a
singular coordinate transformation. We discuss the implications for the
singularity problem and the definition of the mass point.
The analogy set by Rindler between the Kruskal metric and the Minkowski
spacetime is investigated anew. The question is answered, whether this analogy
is limited to a similarity of the chosen "Bildr\"aume'', or can be given a
deeper, intrinsic meaning. The conclusion is reached by observing a usually
neglected difference: the left and right quadrants of Kruskal's metric are
endowed with worldlines of absolute rest, uniquely defined through each event
by the manifold itself, while such worldlines obviously do not exist in the
Minkowski spacetime.
| [
{
"created": "Fri, 1 Aug 2003 15:07:33 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Aug 2003 09:20:24 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Sep 2005 09:09:11 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Antoci",
"S.",
""
],
[
"Liebscher",
"D. -E.",
""
]
] | Kruskal's extension solves the problem of the arrow of time of the ``Schwarzschild solution'' through combining two Hilbert manifolds by a singular coordinate transformation. We discuss the implications for the singularity problem and the definition of the mass point. The analogy set by Rindler between the Kruskal metric and the Minkowski spacetime is investigated anew. The question is answered, whether this analogy is limited to a similarity of the chosen "Bildr\"aume'', or can be given a deeper, intrinsic meaning. The conclusion is reached by observing a usually neglected difference: the left and right quadrants of Kruskal's metric are endowed with worldlines of absolute rest, uniquely defined through each event by the manifold itself, while such worldlines obviously do not exist in the Minkowski spacetime. |
2208.02280 | Leonardo Chataignier | Leonardo Chataignier, Alexander Yu. Kamenshchik, Alessandro Tronconi,
Giovanni Venturi | Regular black holes, universes without singularities, and phantom-scalar
field transitions | slightly expanded, with updated references and conceptual
clarifications. Matches the published version | null | 10.1103/PhysRevD.107.023508 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a procedure of elimination of cosmological singularities similar
to that suggested in the recent paper by Simpson and Visser for the
construction of regular black holes. It is shown that by imposing a
non-singular cosmological evolution with a bounce in a flat Friedmann universe
filled with a minimally coupled scalar field, we obtain a transition between
the standard scalar field and its phantom counterpart. In this case, the
potential of the scalar field has a non-analyticity of the cusp type. This
result is also readily reproduced in the case of an anisotropic Bianchi I
universe. We have also found a spherically symmetric static solution of the
Einstein equations, free of singularities and sustained by a scalar field.
| [
{
"created": "Wed, 3 Aug 2022 18:03:56 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jan 2023 20:25:15 GMT",
"version": "v2"
}
] | 2023-01-10 | [
[
"Chataignier",
"Leonardo",
""
],
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Tronconi",
"Alessandro",
""
],
[
"Venturi",
"Giovanni",
""
]
] | We consider a procedure of elimination of cosmological singularities similar to that suggested in the recent paper by Simpson and Visser for the construction of regular black holes. It is shown that by imposing a non-singular cosmological evolution with a bounce in a flat Friedmann universe filled with a minimally coupled scalar field, we obtain a transition between the standard scalar field and its phantom counterpart. In this case, the potential of the scalar field has a non-analyticity of the cusp type. This result is also readily reproduced in the case of an anisotropic Bianchi I universe. We have also found a spherically symmetric static solution of the Einstein equations, free of singularities and sustained by a scalar field. |
1001.4857 | Shan Gao | Shan Gao | On Di\'osi-Penrose criterion of gravity-induced quantum collapse | 5 pages, no figures | Int. J. Theor.Phys., 49, 849-853, 2010 | 10.1007/s10773-010-0266-9 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the Di\'osi-Penrose criterion of gravity-induced quantum
collapse may be inconsistent with the discreteness of space-time, which is
generally considered as an indispensable element in a complete theory of
quantum gravity. Moreover, the analysis also suggests that the discreteness of
space-time may result in rapider collapse of the superposition of energy
eigenstates than required by the Di\'osi-Penrose criterion.
| [
{
"created": "Wed, 27 Jan 2010 05:42:29 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Jul 2011 11:41:29 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Gao",
"Shan",
""
]
] | It is shown that the Di\'osi-Penrose criterion of gravity-induced quantum collapse may be inconsistent with the discreteness of space-time, which is generally considered as an indispensable element in a complete theory of quantum gravity. Moreover, the analysis also suggests that the discreteness of space-time may result in rapider collapse of the superposition of energy eigenstates than required by the Di\'osi-Penrose criterion. |
1301.3234 | Chen Songbai | Songbai Chen, Xiaofang Liu, Changqing Liu | $P-V$ criticality of AdS black hole in $f(R)$ gravity | 9 pages, 3 figures | Chin. Phys. Lett. 30(6), 060401 (2013) | 10.1088/0256-307X/30/6/060401 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study thermodynamics of a charged AdS black hole in the special $f(R)$
correction with the constant Ricci scalar curvature. Our results show that the
the $f(R)$ correction influences the Gibbs free energy and the phase transition
of system. The ratio $\rho_c$ occurred at the critical point increases
monotonically with the derivative term $f'(R_0)$. We also disclose that the
critical exponents are the same as those of the liquid-gas phase transition in
the Van der Waals model, which does not depend on the $f(R)$ correction
considered here.
| [
{
"created": "Tue, 15 Jan 2013 06:33:02 GMT",
"version": "v1"
},
{
"created": "Fri, 31 May 2013 03:01:35 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Chen",
"Songbai",
""
],
[
"Liu",
"Xiaofang",
""
],
[
"Liu",
"Changqing",
""
]
] | We study thermodynamics of a charged AdS black hole in the special $f(R)$ correction with the constant Ricci scalar curvature. Our results show that the the $f(R)$ correction influences the Gibbs free energy and the phase transition of system. The ratio $\rho_c$ occurred at the critical point increases monotonically with the derivative term $f'(R_0)$. We also disclose that the critical exponents are the same as those of the liquid-gas phase transition in the Van der Waals model, which does not depend on the $f(R)$ correction considered here. |
0708.2069 | Friedrich W. Hehl | Friedrich W. Hehl, Yuri N. Obukhov, Jean-Pierre Rivera, Hans Schmid | Relativistic analysis of magnetoelectric crystals: extracting a new
4-dimensional P odd and T odd pseudoscalar from Cr_2 O_3 data | 6 pages latex, 3 figures, accepted by Physics Letters A | null | 10.1016/j.physleta.2007.08.069 | null | gr-qc hep-th physics.class-ph | null | Earlier, the linear magnetoelectric effect of chromium sesquioxide Cr_2 O_3
has been determined experimentally as a function of temperature. One measures
the electric field-induced magnetization on Cr_2 O_3 crystals or the magnetic
field-induced polarization. From the magnetoelectric moduli of Cr_2 O_3 we
extract a 4-dimensional relativistic invariant pseudoscalar \tilde\alpha. It is
temperature dependent and of the order of ~ 10^{-4} Y_0, with Y_0 as vacuum
admittance. We show that the new pseudoscalar \tilde\alpha is odd under parity
transformation and odd under time inversion. Moreover, \tilde\alpha is for Cr_2
O_3 what Tellegen's gyrator is for two port theory, the axion field for axion
electrodynamics, and the PEMC (perfect electromagnetic conductor) for
electrical engineering.
| [
{
"created": "Wed, 15 Aug 2007 16:45:52 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Hehl",
"Friedrich W.",
""
],
[
"Obukhov",
"Yuri N.",
""
],
[
"Rivera",
"Jean-Pierre",
""
],
[
"Schmid",
"Hans",
""
]
] | Earlier, the linear magnetoelectric effect of chromium sesquioxide Cr_2 O_3 has been determined experimentally as a function of temperature. One measures the electric field-induced magnetization on Cr_2 O_3 crystals or the magnetic field-induced polarization. From the magnetoelectric moduli of Cr_2 O_3 we extract a 4-dimensional relativistic invariant pseudoscalar \tilde\alpha. It is temperature dependent and of the order of ~ 10^{-4} Y_0, with Y_0 as vacuum admittance. We show that the new pseudoscalar \tilde\alpha is odd under parity transformation and odd under time inversion. Moreover, \tilde\alpha is for Cr_2 O_3 what Tellegen's gyrator is for two port theory, the axion field for axion electrodynamics, and the PEMC (perfect electromagnetic conductor) for electrical engineering. |
1807.03068 | Sasa Ilijic | Sasa Ilijic and Marko Sossich | Compact stars in $f(T)$ extended theory of gravity | LaTeX, 12 pages, 3 figures, v2: references added | Phys. Rev. D 98, 064047 (2018) | 10.1103/PhysRevD.98.064047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider static spherically symmetric self-gravitating configurations of
the perfect fluid within the framework of the torsion-based extended theory of
gravity. In particular, we use the covariant formulation of $f(T)$ gravity with
$f(T) = T + \frac{\alpha}{2} T^2$, and for the fluid we assume the polytropic
equation of state with the adiabatic exponent $\Gamma = 2$. The constructed
solutions have a sharply defined radius [as in General Relativity (GR)] and can
be considered as models of nonrotating compact stars. The particle
number--to--stellar radius curves reveal that with positive (negative) values
of $\alpha$ smaller (greater) number of particles can be supported against
gravity then in GR. For the interpretation of the energy density and the
pressure within the star we adopt the GR picture where the effects due to
nonlinearity of $f(T)$ are seen as a $f(T)$ fluid, which together with the
polytropic fluid contributes to the effective energy momentum. We find that
sufficiently large positive $\alpha$ gives rise to an abrupt sign change (phase
transition) in the energy density and in the principal pressures of the $f(T)$
fluid, taking place within the interior of the star. The corresponding radial
profile of the effective energy density is approximately constant over the
central region of the star, mimicking an incompressible core. This interesting
phenomenon is not found in configurations with negative $\alpha$.
| [
{
"created": "Mon, 9 Jul 2018 12:18:14 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Oct 2018 08:49:16 GMT",
"version": "v2"
}
] | 2018-10-03 | [
[
"Ilijic",
"Sasa",
""
],
[
"Sossich",
"Marko",
""
]
] | We consider static spherically symmetric self-gravitating configurations of the perfect fluid within the framework of the torsion-based extended theory of gravity. In particular, we use the covariant formulation of $f(T)$ gravity with $f(T) = T + \frac{\alpha}{2} T^2$, and for the fluid we assume the polytropic equation of state with the adiabatic exponent $\Gamma = 2$. The constructed solutions have a sharply defined radius [as in General Relativity (GR)] and can be considered as models of nonrotating compact stars. The particle number--to--stellar radius curves reveal that with positive (negative) values of $\alpha$ smaller (greater) number of particles can be supported against gravity then in GR. For the interpretation of the energy density and the pressure within the star we adopt the GR picture where the effects due to nonlinearity of $f(T)$ are seen as a $f(T)$ fluid, which together with the polytropic fluid contributes to the effective energy momentum. We find that sufficiently large positive $\alpha$ gives rise to an abrupt sign change (phase transition) in the energy density and in the principal pressures of the $f(T)$ fluid, taking place within the interior of the star. The corresponding radial profile of the effective energy density is approximately constant over the central region of the star, mimicking an incompressible core. This interesting phenomenon is not found in configurations with negative $\alpha$. |
1310.2171 | Mariano Hermida de La Rica | Mariano Hermida de La Rica | Teleparallel Darkness | This article draws heavily on arXiv:0905.4026; This is a major
revision of the paper. Some clarifications and discussions have been added,
specially on the "qualitative" prediction of the amount of dark matter to be
expected according to the theory | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First a review of Teleparallel theory is done with special emphasis in the
derivation of conservation equations within this theory and in particular of
energy-momentum conservation. Given that we are allowed to speak about the
existence of negative energy, the question is that in its interaction with
matter, we need not have matter conservation: It is only the sum of both which
should remain constant. This does not only leads to an accelerated expansion
without the need of a cosmological constant, but it may also contribute to
explain the origin of dark matter, and poses questions about the origin of
inflation at earlier times. The prediction of the proposed model can be
qualitatively compared to recent results of Cosmic Microwave Background (CMB)
analysis.
| [
{
"created": "Tue, 8 Oct 2013 15:17:21 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Feb 2014 00:36:42 GMT",
"version": "v2"
}
] | 2014-02-18 | [
[
"de La Rica",
"Mariano Hermida",
""
]
] | First a review of Teleparallel theory is done with special emphasis in the derivation of conservation equations within this theory and in particular of energy-momentum conservation. Given that we are allowed to speak about the existence of negative energy, the question is that in its interaction with matter, we need not have matter conservation: It is only the sum of both which should remain constant. This does not only leads to an accelerated expansion without the need of a cosmological constant, but it may also contribute to explain the origin of dark matter, and poses questions about the origin of inflation at earlier times. The prediction of the proposed model can be qualitatively compared to recent results of Cosmic Microwave Background (CMB) analysis. |
gr-qc/0505125 | Eugen Radu | J.J. van der Bij and Eugen Radu | Inflationary solutions with a five dimensional complex scalar field | 11 pages, 2 figures; v2: section 2 expanded; discussion on multiple
modes added; some typos corrected | Mod.Phys.Lett. A21 (2006) 409-420 | 10.1142/S0217732306019700 | Freiburg-THEP-05/04 | gr-qc | null | We discuss inflationary solutions of the coupled Einstein-Klein-Gordon
equations for a complex field in a five dimensional spacetime with a compact
$x^5$-dimension. As a new feature, the scalar field contains a dependence on
the extra dimension of the form $\exp(i m x^5) $, corresponding to Kaluza-Klein
excited modes. In a four dimensional picture, a nonzero $m$ implies the
presence of a new term in the scalar field potential. An interesting feature of
these solutions is the possible existence of several periods of oscillation of
the scalar field around the equilibrium value at the minimum of the potential.
These oscillations lead to cosmological periods of accelerated expansion of the
universe.
| [
{
"created": "Wed, 25 May 2005 15:31:20 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jan 2006 13:43:08 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"van der Bij",
"J. J.",
""
],
[
"Radu",
"Eugen",
""
]
] | We discuss inflationary solutions of the coupled Einstein-Klein-Gordon equations for a complex field in a five dimensional spacetime with a compact $x^5$-dimension. As a new feature, the scalar field contains a dependence on the extra dimension of the form $\exp(i m x^5) $, corresponding to Kaluza-Klein excited modes. In a four dimensional picture, a nonzero $m$ implies the presence of a new term in the scalar field potential. An interesting feature of these solutions is the possible existence of several periods of oscillation of the scalar field around the equilibrium value at the minimum of the potential. These oscillations lead to cosmological periods of accelerated expansion of the universe. |
0901.3074 | Yuri Shtanov | Yuri Shtanov, Varun Sahni, Arman Shafieloo, Alexey Toporensky | Induced cosmological constant and other features of asymmetric brane
embedding | 17 pages, 4 figures. New results and two figures discussing transient
acceleration are included. Version accepted for publication in JCAP | JCAP 04 (2009) 023 | 10.1088/1475-7516/2009/04/023 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological properties of an "induced gravity" brane
scenario in the absence of mirror symmetry with respect to the brane. We find
that brane evolution can proceed along one of four distinct branches. By
contrast, when mirror symmetry is imposed, only two branches exist, one of
which represents the self-accelerating brane, while the other is the so-called
normal branch. This model incorporates many of the well-known possibilities of
brane cosmology including phantom acceleration (w < -1), self-acceleration,
transient acceleration, quiescent singularities, and cosmic mimicry.
Significantly, the absence of mirror symmetry also provides an interesting way
of inducing a sufficiently small cosmological constant on the brane. A small
(positive) Lambda-term in this case is induced by a small asymmetry in the
values of bulk fundamental constants on the two sides of the brane.
| [
{
"created": "Tue, 20 Jan 2009 15:16:27 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Apr 2009 21:54:20 GMT",
"version": "v2"
}
] | 2009-04-24 | [
[
"Shtanov",
"Yuri",
""
],
[
"Sahni",
"Varun",
""
],
[
"Shafieloo",
"Arman",
""
],
[
"Toporensky",
"Alexey",
""
]
] | We investigate the cosmological properties of an "induced gravity" brane scenario in the absence of mirror symmetry with respect to the brane. We find that brane evolution can proceed along one of four distinct branches. By contrast, when mirror symmetry is imposed, only two branches exist, one of which represents the self-accelerating brane, while the other is the so-called normal branch. This model incorporates many of the well-known possibilities of brane cosmology including phantom acceleration (w < -1), self-acceleration, transient acceleration, quiescent singularities, and cosmic mimicry. Significantly, the absence of mirror symmetry also provides an interesting way of inducing a sufficiently small cosmological constant on the brane. A small (positive) Lambda-term in this case is induced by a small asymmetry in the values of bulk fundamental constants on the two sides of the brane. |
1406.1016 | Istvan Racz | Istv\'an R\'acz | Is the Bianchi identity always hyperbolic? | 14 pages, no figures, the published version | Class. Quantum Grav. 31 (2014) 155004 | 10.1088/0264-9381/31/15/155004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $n+1$ dimensional smooth Riemannian and Lorentzian spaces
satisfying Einstein's equations. The base manifold is assumed to be smoothly
foliated by a one-parameter family of hypersurfaces. In both cases---likewise
it is usually done in the Lorentzian case---Einstein's equations may be split
into `Hamiltonian' and `momentum' constraints and a `reduced' set of field
equations. It is shown that regardless whether the primary space is Riemannian
or Lorentzian whenever the foliating hypersurfaces are Riemannian the
`Hamiltonian' and `momentum' type expressions are subject to a subsidiary first
order symmetric hyperbolic system. Since this subsidiary system is linear and
homogeneous in the `Hamiltonian' and `momentum' type expressions the
hyperbolicity of the system implies that in both cases the solutions to the
`reduced' set of field equations are also solutions to the full set of
equations provided that the constraints hold on one of the hypersurfaces
foliating the base manifold.
| [
{
"created": "Wed, 4 Jun 2014 12:00:57 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2014 18:44:14 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Rácz",
"István",
""
]
] | We consider $n+1$ dimensional smooth Riemannian and Lorentzian spaces satisfying Einstein's equations. The base manifold is assumed to be smoothly foliated by a one-parameter family of hypersurfaces. In both cases---likewise it is usually done in the Lorentzian case---Einstein's equations may be split into `Hamiltonian' and `momentum' constraints and a `reduced' set of field equations. It is shown that regardless whether the primary space is Riemannian or Lorentzian whenever the foliating hypersurfaces are Riemannian the `Hamiltonian' and `momentum' type expressions are subject to a subsidiary first order symmetric hyperbolic system. Since this subsidiary system is linear and homogeneous in the `Hamiltonian' and `momentum' type expressions the hyperbolicity of the system implies that in both cases the solutions to the `reduced' set of field equations are also solutions to the full set of equations provided that the constraints hold on one of the hypersurfaces foliating the base manifold. |
1408.5179 | Henry Stoltenberg | Henry Stoltenberg and Andreas Albrecht | No Firewalls or Information Problem for Black Holes Entangled with Large
Systems | 8 pages. V2: We have revised our discussion of the applicability of
our results in realistic cosmologies in Section 5. Also, typos fixed and
citations added. Our technical results are unchanged. V3: Final version
accepted for publication in PRD. Additional references added. No other
changes | null | 10.1103/PhysRevD.91.024004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss how under certain conditions the black hole information puzzle and
the (related) arguments that firewalls are a typical feature of black holes can
break down. We first review the arguments of AMPS favoring firewalls, focusing
on entanglements in a simple toy model for a black hole and the Hawking
radiation. By introducing a large and inaccessible system entangled with the
black hole (representing perhaps a de Sitter stretched horizon or inaccessible
part of a landscape) we show complementarity can be restored and firewalls can
be avoided throughout the black hole's evolution. Under these conditions black
holes do not have an "information problem". We point out flaws in some of our
earlier arguments that such entanglement might be generically present in some
cosmological scenarios, and call out certain ways our picture may still be
realized.
| [
{
"created": "Fri, 22 Aug 2014 00:45:46 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Oct 2014 19:09:28 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Jan 2015 03:51:11 GMT",
"version": "v3"
}
] | 2015-06-22 | [
[
"Stoltenberg",
"Henry",
""
],
[
"Albrecht",
"Andreas",
""
]
] | We discuss how under certain conditions the black hole information puzzle and the (related) arguments that firewalls are a typical feature of black holes can break down. We first review the arguments of AMPS favoring firewalls, focusing on entanglements in a simple toy model for a black hole and the Hawking radiation. By introducing a large and inaccessible system entangled with the black hole (representing perhaps a de Sitter stretched horizon or inaccessible part of a landscape) we show complementarity can be restored and firewalls can be avoided throughout the black hole's evolution. Under these conditions black holes do not have an "information problem". We point out flaws in some of our earlier arguments that such entanglement might be generically present in some cosmological scenarios, and call out certain ways our picture may still be realized. |
gr-qc/0310108 | Gyorgy Szondy | Gy. Szondy | Mathematical Equivalency of the Ether Based Gavitation Theory of Janossy
and General Relativity | 4 pages, reference to Smolin was added | null | null | null | gr-qc | null | "There are several interpretations and approaches to relativity. All of them
are characterized by the fact that none of them is accepted by physicists
without doubts, even the Einsteinian General Relativity! Only those theories
can get into the spotlight that predicts something that is different from
predictions of other concurrent theories. From this point of view the theory of
Janossy [1] is not an excellent idea, as he tried to show that his
materialistic approach also corresponds to the general principles and equations
of relativity. As his program was basically successful there was not any
additional result, except the philosophical part."
Since the death of Janossy, his work has almost been forgotten. Both what he
achieved and what he was not succeeded in. He was one of the founders of KFKI
(Central Physics Research Institute of the Hungarian Scientific Academy) but
his effort has not been carried over even there, however his collegues are
still remember his name and his work. Luckily his books are still available in
the Hungarian libraries. Additionally the most informed etherists in the world
who are lucky enough to know his work are consider his work as a No1 reference.
This paper is designated to refresh the idea of the ether based gravitation
theory of Janossy and introduce a well founded way to adjust it to be
equivalent with the experiences and General Relativity.
| [
{
"created": "Thu, 23 Oct 2003 18:23:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Szondy",
"Gy.",
""
]
] | "There are several interpretations and approaches to relativity. All of them are characterized by the fact that none of them is accepted by physicists without doubts, even the Einsteinian General Relativity! Only those theories can get into the spotlight that predicts something that is different from predictions of other concurrent theories. From this point of view the theory of Janossy [1] is not an excellent idea, as he tried to show that his materialistic approach also corresponds to the general principles and equations of relativity. As his program was basically successful there was not any additional result, except the philosophical part." Since the death of Janossy, his work has almost been forgotten. Both what he achieved and what he was not succeeded in. He was one of the founders of KFKI (Central Physics Research Institute of the Hungarian Scientific Academy) but his effort has not been carried over even there, however his collegues are still remember his name and his work. Luckily his books are still available in the Hungarian libraries. Additionally the most informed etherists in the world who are lucky enough to know his work are consider his work as a No1 reference. This paper is designated to refresh the idea of the ether based gravitation theory of Janossy and introduce a well founded way to adjust it to be equivalent with the experiences and General Relativity. |
2009.09999 | Elias Okon | Javier Berjon, Elias Okon and Daniel Sudarsky | Critical review of prevailing explanations for the emergence of
classicality in cosmology | 32 pages. Published version with additional section containing our
reply to a note added in arXiv:2004.10684 in response to an earlier version
of this paper | Phys. Rev. D 103, 043521 (2021) | 10.1103/PhysRevD.103.043521 | null | gr-qc physics.hist-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There have been recent attempts at justifying, from first principles, and
within the standard framework, the emergence of classical behavior in the
post-inflationary cosmological context. Accounting for this emergence is an
important issue, as it underlies the extraordinary empirical success of our
current understanding of cosmology. In this work, we offer a critique of
different efforts at explaining the emergence of classical behavior in
cosmology within the standard framework. We argue that such endeavors are
generically found lacking in conceptual clarity, as they invariably rely,
either upon unjustified, implicit assumptions, or on circular logic. We
conclude that, within the standard approach, the emergence of classical
behavior in cosmology constitutes an unexplained phenomenon.
| [
{
"created": "Mon, 21 Sep 2020 16:27:19 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Nov 2020 01:45:13 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Feb 2021 16:25:48 GMT",
"version": "v3"
}
] | 2021-02-24 | [
[
"Berjon",
"Javier",
""
],
[
"Okon",
"Elias",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | There have been recent attempts at justifying, from first principles, and within the standard framework, the emergence of classical behavior in the post-inflationary cosmological context. Accounting for this emergence is an important issue, as it underlies the extraordinary empirical success of our current understanding of cosmology. In this work, we offer a critique of different efforts at explaining the emergence of classical behavior in cosmology within the standard framework. We argue that such endeavors are generically found lacking in conceptual clarity, as they invariably rely, either upon unjustified, implicit assumptions, or on circular logic. We conclude that, within the standard approach, the emergence of classical behavior in cosmology constitutes an unexplained phenomenon. |
1906.08674 | Sunandan Gangopadhyay | Rituparna Mandal, Sunandan Gangopadhyay, Amitabha Lahiri | Cosmology of Bianchi type-I metric using renormalization group approach
for quantum gravity | 20 pages Latex, manuscript revised and comments added | Class. Quantum Grav. 37 (2020) 065012 | 10.1088/1361-6382/ab7287 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the anisotropic Bianchi type-I cosmological model at late times,
taking into account quantum gravitational corrections in the formalism of the
exact renormalization group flow of the effective average action for gravity.
The cosmological evolution equations are derived by including the scale
dependence of Newton's constant $G$ and cosmological constant $\Lambda$. We
have considered the solutions of the flow equations for $G$ and $\Lambda$ at
next to leading order in the infrared cutoff scale. Using these scale dependent
$G$ and $\Lambda$ in Einstein equations for the Bianchi-I model, we obtain the
scale factors in different directions. It is shown that the scale factors
eventually evolve into FLRW universe for known matter like radiation. However,
for dust and stiff matter we find that the universe need not evolve to the FLRW
cosmology in general, but can also show Kasner type behaviour.
| [
{
"created": "Wed, 19 Jun 2019 11:31:06 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Feb 2020 04:16:00 GMT",
"version": "v2"
}
] | 2020-02-24 | [
[
"Mandal",
"Rituparna",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Lahiri",
"Amitabha",
""
]
] | We study the anisotropic Bianchi type-I cosmological model at late times, taking into account quantum gravitational corrections in the formalism of the exact renormalization group flow of the effective average action for gravity. The cosmological evolution equations are derived by including the scale dependence of Newton's constant $G$ and cosmological constant $\Lambda$. We have considered the solutions of the flow equations for $G$ and $\Lambda$ at next to leading order in the infrared cutoff scale. Using these scale dependent $G$ and $\Lambda$ in Einstein equations for the Bianchi-I model, we obtain the scale factors in different directions. It is shown that the scale factors eventually evolve into FLRW universe for known matter like radiation. However, for dust and stiff matter we find that the universe need not evolve to the FLRW cosmology in general, but can also show Kasner type behaviour. |
1408.3566 | William Kelly | William R. Kelly and Aron C. Wall | A holographic proof of the averaged null energy condition | 13 pages, 1 figure. v4: corrected an error in the proof, results
remain unchanged, v3: added additional references along with minor editorial
changes, v2: added additional references and acknowledgments | Phys. Rev. D 90, 106003 (2014) | 10.1103/PhysRevD.90.106003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The averaged null energy conditions (ANEC) states that, along a complete null
curve, the negative energy fluctuations of a quantum field must be balanced by
positive energy fluctuations. We use the AdS/CFT correspondence to prove the
ANEC for a class of strongly coupled conformal field theories in flat
spacetime. A violation of the ANEC in the field theory would lead to acausal
propagation of signals in the bulk.
| [
{
"created": "Fri, 15 Aug 2014 15:34:53 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Sep 2014 21:41:54 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Nov 2014 18:41:46 GMT",
"version": "v3"
},
{
"created": "Sun, 22 Feb 2015 17:49:31 GMT",
"version": "v4"
}
] | 2015-02-24 | [
[
"Kelly",
"William R.",
""
],
[
"Wall",
"Aron C.",
""
]
] | The averaged null energy conditions (ANEC) states that, along a complete null curve, the negative energy fluctuations of a quantum field must be balanced by positive energy fluctuations. We use the AdS/CFT correspondence to prove the ANEC for a class of strongly coupled conformal field theories in flat spacetime. A violation of the ANEC in the field theory would lead to acausal propagation of signals in the bulk. |
gr-qc/0703056 | Eyo Ita III | Eyo Eyo Ita III | Finite states in four dimensional quantum gravity. The isotropic
minisuperspace Asktekar--Klein--Gordon model | 26 pages. Accepted for publication by Class. Quantum Grav. journal | Class. Quantum Grav. 25 (2008) 125002 (19pp) | 10.1088/0264-9381/25/12/125002 | null | gr-qc | null | In this paper we construct the generalized Kodama state for the case of a
Klein--Gordon scalar field coupled to Ashtekar variables in isotropic
minisuperspace by a new method. The criterion for finiteness of the state stems
from a minisuperspace reduction of the quantized full theory, rather than the
conventional techniques of reduction prior to quantization. We then provide a
possible route to the reproduction of a semiclassical limit via these states.
This is the result of a new principle of the semiclassical-quantum
correspondence (SQC), introduced in the first paper in this series. Lastly, we
examine the solution to the minisuperspace case at the semiclassical level for
an isotropic CDJ matrix neglecting any quantum corrections and examine some of
the implications in relation to results from previous authors on semiclassical
orbits of spacetime, including inflation. It is suggested that the application
of nonperturbative quantum gravity, by way of the SQC, might potentially lead
to some predictions testable below the Planck scale.
| [
{
"created": "Thu, 8 Mar 2007 12:07:32 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Oct 2007 23:51:16 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Nov 2007 08:11:13 GMT",
"version": "v3"
},
{
"created": "Mon, 11 Feb 2008 20:52:45 GMT",
"version": "v4"
},
{
"cre... | 2015-06-25 | [
[
"Ita",
"Eyo Eyo",
"III"
]
] | In this paper we construct the generalized Kodama state for the case of a Klein--Gordon scalar field coupled to Ashtekar variables in isotropic minisuperspace by a new method. The criterion for finiteness of the state stems from a minisuperspace reduction of the quantized full theory, rather than the conventional techniques of reduction prior to quantization. We then provide a possible route to the reproduction of a semiclassical limit via these states. This is the result of a new principle of the semiclassical-quantum correspondence (SQC), introduced in the first paper in this series. Lastly, we examine the solution to the minisuperspace case at the semiclassical level for an isotropic CDJ matrix neglecting any quantum corrections and examine some of the implications in relation to results from previous authors on semiclassical orbits of spacetime, including inflation. It is suggested that the application of nonperturbative quantum gravity, by way of the SQC, might potentially lead to some predictions testable below the Planck scale. |
2402.03184 | Israel Quiros | Israel Quiros | A theorem on local scale invariance | 9 pages, no figures | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a general proof that the only static and spherically symmetric,
vacuum solutions of the local scale invariant conformally coupled scalar theory
of gravity, are conformal to the Schwarzschild-de Sitter solution. In this
context the physical relevance of local scale symmetry is discussed.
| [
{
"created": "Mon, 5 Feb 2024 16:48:46 GMT",
"version": "v1"
}
] | 2024-02-06 | [
[
"Quiros",
"Israel",
""
]
] | We give a general proof that the only static and spherically symmetric, vacuum solutions of the local scale invariant conformally coupled scalar theory of gravity, are conformal to the Schwarzschild-de Sitter solution. In this context the physical relevance of local scale symmetry is discussed. |
1706.02323 | Michael Kalisch | Michael Kalisch, Sebastian Moeckel, Martin Ammon | Critical behavior of the black hole / black string transition | Version 4: matched with journal version but fixed a sign error in
equation (16) (accidentally, version 3 does not contain changes compared to
version 2) | null | 10.1007/JHEP08(2017)049 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically construct static localized black holes in five and six
spacetime dimensions which are solutions to Einstein's vacuum field equations
with one compact periodic dimension. In particular, we investigate the critical
regime in which the poles of the localized black hole are about to merge. A
well adapted multi-domain pseudo-spectral scheme provides us with accurate
results and enables us to investigate the phase diagram of those localized
solutions within the critical regime, which goes far beyond previous results.
We find that in this regime the phase diagram possesses a spiral structure
adapting to the one recently found for non-uniform black strings. When
approaching the common endpoint of both phases, the behavior of physical
quantities is described by complex critical exponents giving rise to a discrete
scaling symmetry. The numerically obtained values of the critical exponents
agree remarkably well with those derived from the double-cone metric.
| [
{
"created": "Wed, 7 Jun 2017 18:09:29 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Jun 2017 14:40:00 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Sep 2017 16:17:05 GMT",
"version": "v3"
},
{
"created": "Tue, 19 Sep 2017 15:33:28 GMT",
"version": "v4"
}
] | 2017-09-20 | [
[
"Kalisch",
"Michael",
""
],
[
"Moeckel",
"Sebastian",
""
],
[
"Ammon",
"Martin",
""
]
] | We numerically construct static localized black holes in five and six spacetime dimensions which are solutions to Einstein's vacuum field equations with one compact periodic dimension. In particular, we investigate the critical regime in which the poles of the localized black hole are about to merge. A well adapted multi-domain pseudo-spectral scheme provides us with accurate results and enables us to investigate the phase diagram of those localized solutions within the critical regime, which goes far beyond previous results. We find that in this regime the phase diagram possesses a spiral structure adapting to the one recently found for non-uniform black strings. When approaching the common endpoint of both phases, the behavior of physical quantities is described by complex critical exponents giving rise to a discrete scaling symmetry. The numerically obtained values of the critical exponents agree remarkably well with those derived from the double-cone metric. |
gr-qc/9210009 | Ralf Hecht | Ralf Hecht, Friedrich W. Hehl, J. Dermott McCrea, Eckehard W. Mielke
and Yuval Ne'eman | Improved Energy-Momentum Currents in Metric-Affine Spacetime | 14pp | Phys.Lett.A172:13-20,1992 | 10.1016/0375-9601(92)90182-L | null | gr-qc hep-th | null | In Minkowski spacetime it is well-known that the canonical energy-momentum
current is involved in the construction of the globally conserved currents of
energy-momentum and total angular momentum. For the construction of conserved
currents corresponding to (approximate) scale and proper conformal symmetries,
however, an improved energy-momentum current is needed. By extending the
Minkowskian framework to a genuine metric-affine spacetime, we find that the
affine Noether identities and the conformal Killing equations enforce this
improvement in a rather natural way. So far, no gravitational dynamics is
involved in our construction. The resulting dilation and proper conformal
currents are conserved provided the trace of the energy-momentum current
satisfies a (mild) scaling relation or even vanishes.
| [
{
"created": "Thu, 15 Oct 1992 17:35:59 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hecht",
"Ralf",
""
],
[
"Hehl",
"Friedrich W.",
""
],
[
"McCrea",
"J. Dermott",
""
],
[
"Mielke",
"Eckehard W.",
""
],
[
"Ne'eman",
"Yuval",
""
]
] | In Minkowski spacetime it is well-known that the canonical energy-momentum current is involved in the construction of the globally conserved currents of energy-momentum and total angular momentum. For the construction of conserved currents corresponding to (approximate) scale and proper conformal symmetries, however, an improved energy-momentum current is needed. By extending the Minkowskian framework to a genuine metric-affine spacetime, we find that the affine Noether identities and the conformal Killing equations enforce this improvement in a rather natural way. So far, no gravitational dynamics is involved in our construction. The resulting dilation and proper conformal currents are conserved provided the trace of the energy-momentum current satisfies a (mild) scaling relation or even vanishes. |
1403.7839 | Stanley P. Gudder | Stan Gudder | Labeled Causets in Discrete Quantum Gravity | 17 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1305.5184 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that labeled causets have a much simpler structure than
unlabeled causets. For example, labeled causets can be uniquely specified by a
sequence of integers. Moreover, each labeled causet processes a unique
predecessor and hence has a unique history. Our main result shows that an
arbitrary quantum sequential growth process (QSGP) on the set of labeled
causets "compresses" in a natural way onto a QSGP on the set of unlabeled
causets. The price we have to pay is that this procedure causes an "explosion"
of values due to multiplicities. We also observe that this procedure is not
reversible. This indicates that although many QSGPs on the set of unlabeled
causets can be constructed using this method, not all can, so it is not
completely general. We close by showing that a natural metric can be defined on
labeled and unlabeled causets and on their paths.
| [
{
"created": "Mon, 31 Mar 2014 00:17:54 GMT",
"version": "v1"
}
] | 2014-04-01 | [
[
"Gudder",
"Stan",
""
]
] | We point out that labeled causets have a much simpler structure than unlabeled causets. For example, labeled causets can be uniquely specified by a sequence of integers. Moreover, each labeled causet processes a unique predecessor and hence has a unique history. Our main result shows that an arbitrary quantum sequential growth process (QSGP) on the set of labeled causets "compresses" in a natural way onto a QSGP on the set of unlabeled causets. The price we have to pay is that this procedure causes an "explosion" of values due to multiplicities. We also observe that this procedure is not reversible. This indicates that although many QSGPs on the set of unlabeled causets can be constructed using this method, not all can, so it is not completely general. We close by showing that a natural metric can be defined on labeled and unlabeled causets and on their paths. |
2112.12110 | Ra\"ul Vera | Asier Alonso-Bardaji, David Brizuela, Ra\"ul Vera | An effective model for the quantum Schwarzschild black hole | 6 pages, one figure. Minor changes to match the published version,
and one reference updated | null | 10.1016/j.physletb.2022.137075 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an effective theory to describe the quantization of spherically
symmetric vacuum in loop quantum gravity. We include anomaly-free holonomy
corrections through a canonical transformation of the Hamiltonian of general
relativity, such that the modified constraint algebra closes. The system is
then provided with a fully covariant and unambigous geometric description,
independent of the gauge choice on the phase space. The resulting spacetime
corresponds to a singularity-free (black-hole/white-hole) interior and two
asymptotically flat exterior regions of equal mass. The interior region
contains a minimal smooth spacelike surface that replaces the Schwarzschild
singularity. We find the global causal structure and the maximal analytical
extension. Both Minkowski and Schwarzschild spacetimes are directly recovered
as particular limits of the model.
| [
{
"created": "Wed, 22 Dec 2021 18:20:11 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Apr 2023 12:55:11 GMT",
"version": "v2"
}
] | 2023-04-18 | [
[
"Alonso-Bardaji",
"Asier",
""
],
[
"Brizuela",
"David",
""
],
[
"Vera",
"Raül",
""
]
] | We present an effective theory to describe the quantization of spherically symmetric vacuum in loop quantum gravity. We include anomaly-free holonomy corrections through a canonical transformation of the Hamiltonian of general relativity, such that the modified constraint algebra closes. The system is then provided with a fully covariant and unambigous geometric description, independent of the gauge choice on the phase space. The resulting spacetime corresponds to a singularity-free (black-hole/white-hole) interior and two asymptotically flat exterior regions of equal mass. The interior region contains a minimal smooth spacelike surface that replaces the Schwarzschild singularity. We find the global causal structure and the maximal analytical extension. Both Minkowski and Schwarzschild spacetimes are directly recovered as particular limits of the model. |
1406.4367 | Taeyoon Moon | Yun Soo Myung and Taeyoon Moon | Primordial massive gravitational waves from Einstein-Chern-Simons-Weyl
gravity | 1+24 pages, no figure, version accepted for publication in JCAP | null | 10.1088/1475-7516/2014/08/061 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the evolution of cosmological perturbations during de Sitter
inflation in the Einstein-Chern-Simons-Weyl gravity. Primordial massive
gravitational waves are composed of one scalar, two vector and four tensor
circularly polarized modes. We show that the vector power spectrum decays
quickly like a transversely massive vector in the superhorizon limit $z\to 0$.
In this limit, the power spectrum coming from massive tensor modes decays
quickly, leading to the conventional tensor power spectrum. Also, we find that
in the limit of $m^2 \to 0$ (keeping the Weyl-squared term only), the vector
and tensor power spectra disappear. It implies that their power spectra are not
gravitationally produced because they (vector and tensor) are decoupled from
the expanding de Sitter background, as a result of conformal invariance.
| [
{
"created": "Tue, 17 Jun 2014 13:50:18 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Aug 2014 03:34:06 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We investigate the evolution of cosmological perturbations during de Sitter inflation in the Einstein-Chern-Simons-Weyl gravity. Primordial massive gravitational waves are composed of one scalar, two vector and four tensor circularly polarized modes. We show that the vector power spectrum decays quickly like a transversely massive vector in the superhorizon limit $z\to 0$. In this limit, the power spectrum coming from massive tensor modes decays quickly, leading to the conventional tensor power spectrum. Also, we find that in the limit of $m^2 \to 0$ (keeping the Weyl-squared term only), the vector and tensor power spectra disappear. It implies that their power spectra are not gravitationally produced because they (vector and tensor) are decoupled from the expanding de Sitter background, as a result of conformal invariance. |
gr-qc/0209064 | Sergey Vyatchanin | V. B. Braginsky, S. E. Strigin and S. P. Vyatchanin | Analysis of Parametric Oscillatory Instability in Power Recycled LIGO
Interferometer | 9 pages, 2 figures. submitted to Physics Letters A | Phys.Lett. A305 (2002) 111-124 | 10.1016/S0375-9601(02)01357-9 | null | gr-qc | null | We present the analysis of a nonlinear effect of parametric oscillatory
instability in power recycled LIGO interferometer with the Fabry-Perot (FP)
cavities in the arms. The basis for this effect is the excitation of the
additional (Stokes) optical mode and the mirror elastic mode, when the optical
energy stored in the main FP cavity main mode exceeds the certain threshold and
the frequencies are related so that sum of frequencies of Stokes and elastic
modes are approximately equal to frequencyof main mode. The presence of
anti-Stokes modes (with frequency approximately equal to sum of frequencies of
main and elastic modes) can depress parametric instability. However, it is very
likely that the anti-Stokes modes will not compensate the parametric
instability completely.
| [
{
"created": "Thu, 19 Sep 2002 05:19:35 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Braginsky",
"V. B.",
""
],
[
"Strigin",
"S. E.",
""
],
[
"Vyatchanin",
"S. P.",
""
]
] | We present the analysis of a nonlinear effect of parametric oscillatory instability in power recycled LIGO interferometer with the Fabry-Perot (FP) cavities in the arms. The basis for this effect is the excitation of the additional (Stokes) optical mode and the mirror elastic mode, when the optical energy stored in the main FP cavity main mode exceeds the certain threshold and the frequencies are related so that sum of frequencies of Stokes and elastic modes are approximately equal to frequencyof main mode. The presence of anti-Stokes modes (with frequency approximately equal to sum of frequencies of main and elastic modes) can depress parametric instability. However, it is very likely that the anti-Stokes modes will not compensate the parametric instability completely. |
0812.1117 | Yungui Gong | Xi-ming Chen, Yungui Gong and Emmanuel N. Saridakis | Phase-space analysis of interacting phantom cosmology | 6 figures, use revtex, v2: minor corrections, references added,
accepted for publication in JCAP | JCAP 0904:001,2009 | 10.1088/1475-7516/2009/04/001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed phase-space analysis of various phantom cosmological
models, where the dark energy sector interacts with the dark matter one. We
examine whether there exist late-time scaling attractors, corresponding to an
accelerating universe and possessing dark energy and dark matter densities of
the same order. We find that all the examined models, although accepting stable
late-time accelerated solutions, cannot alleviate the coincidence problem,
unless one imposes a form of fine-tuning in the model parameters. It seems that
interacting phantom cosmology cannot fulfill the basic requirement that led to
its construction.
| [
{
"created": "Fri, 5 Dec 2008 11:55:08 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Mar 2009 01:12:29 GMT",
"version": "v2"
}
] | 2009-12-04 | [
[
"Chen",
"Xi-ming",
""
],
[
"Gong",
"Yungui",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We perform a detailed phase-space analysis of various phantom cosmological models, where the dark energy sector interacts with the dark matter one. We examine whether there exist late-time scaling attractors, corresponding to an accelerating universe and possessing dark energy and dark matter densities of the same order. We find that all the examined models, although accepting stable late-time accelerated solutions, cannot alleviate the coincidence problem, unless one imposes a form of fine-tuning in the model parameters. It seems that interacting phantom cosmology cannot fulfill the basic requirement that led to its construction. |
1405.6281 | Nicholas Tsamis | N. C. Tsamis and R. P. Woodard | Classical Gravitational Back-Reaction | 14 pages | null | 10.1088/0264-9381/31/18/185014 | CCTP-2014-08, UFIFT-QG-14-03 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum gravitational back-reaction on inflation is based on the
self-gravitation of infrared gravitons which are ripped out of the vacuum
during inflation. The only quantum part of this process is the creation of
gravitons; after they have emerged from the vacuum their behaviour is
essentially classical. To test the thesis that a sufficiently dense ensemble of
classical gravitons can hold the universe together in pure gravity with a
positive cosmological constant, we compute the initial value and first time
derivative of an invariant measure of the expansion rate for arbitrary
classical initial value data. Our result is that the self-gravitation from the
kinetic energy of an initial ensemble of gravitons can indeed slow expansion
enough to hold the universe together.
| [
{
"created": "Sat, 24 May 2014 08:12:02 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Tsamis",
"N. C.",
""
],
[
"Woodard",
"R. P.",
""
]
] | The quantum gravitational back-reaction on inflation is based on the self-gravitation of infrared gravitons which are ripped out of the vacuum during inflation. The only quantum part of this process is the creation of gravitons; after they have emerged from the vacuum their behaviour is essentially classical. To test the thesis that a sufficiently dense ensemble of classical gravitons can hold the universe together in pure gravity with a positive cosmological constant, we compute the initial value and first time derivative of an invariant measure of the expansion rate for arbitrary classical initial value data. Our result is that the self-gravitation from the kinetic energy of an initial ensemble of gravitons can indeed slow expansion enough to hold the universe together. |
gr-qc/9908073 | Christopher J. Fewster | Christopher J. Fewster (University of York) and Edward Teo (University
of Cambridge and National University of Singapore) | Quantum inequalities and `quantum interest' as eigenvalue problems | 18 pages, RevTeX. One new result added; typos fixed. To appear in
Phys. Rev. D | Phys.Rev. D61 (2000) 084012 | 10.1103/PhysRevD.61.084012 | DAMTP-1999-109 | gr-qc hep-th math-ph math.MP | null | Quantum inequalities (QI's) provide lower bounds on the averaged energy
density of a quantum field. We show how the QI's for massless scalar fields in
even dimensional Minkowski space may be reformulated in terms of the positivity
of a certain self-adjoint operator - a generalised Schroedinger operator with
the energy density as the potential - and hence as an eigenvalue problem. We
use this idea to verify that the energy density produced by a moving mirror in
two dimensions is compatible with the QI's for a large class of mirror
trajectories. In addition, we apply this viewpoint to the `quantum interest
conjecture' of Ford and Roman, which asserts that the positive part of an
energy density always overcompensates for any negative components. For various
simple models in two and four dimensions we obtain the best possible bounds on
the `quantum interest rate' and on the maximum delay between a negative pulse
and a compensating positive pulse. Perhaps surprisingly, we find that - in four
dimensions - it is impossible for a positive delta-function pulse of any
magnitude to compensate for a negative delta-function pulse, no matter how
close together they occur.
| [
{
"created": "Mon, 30 Aug 1999 15:44:13 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jan 2000 15:33:09 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Fewster",
"Christopher J.",
"",
"University of York"
],
[
"Teo",
"Edward",
"",
"University\n of Cambridge and National University of Singapore"
]
] | Quantum inequalities (QI's) provide lower bounds on the averaged energy density of a quantum field. We show how the QI's for massless scalar fields in even dimensional Minkowski space may be reformulated in terms of the positivity of a certain self-adjoint operator - a generalised Schroedinger operator with the energy density as the potential - and hence as an eigenvalue problem. We use this idea to verify that the energy density produced by a moving mirror in two dimensions is compatible with the QI's for a large class of mirror trajectories. In addition, we apply this viewpoint to the `quantum interest conjecture' of Ford and Roman, which asserts that the positive part of an energy density always overcompensates for any negative components. For various simple models in two and four dimensions we obtain the best possible bounds on the `quantum interest rate' and on the maximum delay between a negative pulse and a compensating positive pulse. Perhaps surprisingly, we find that - in four dimensions - it is impossible for a positive delta-function pulse of any magnitude to compensate for a negative delta-function pulse, no matter how close together they occur. |
1405.6207 | Koutarou Kyutoku | Koutarou Kyutoku, Masaru Shibata, Keisuke Taniguchi | Reducing orbital eccentricity in initial data of binary neutron stars | 20 pages, 12 figures, matched to the published version | Phys. Rev. D 90, 064006 (2014) | 10.1103/PhysRevD.90.064006 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a method to compute low-eccentricity initial data of binary
neutron stars required to perform realistic simulations in numerical
relativity. The orbital eccentricity is controlled by adjusting the orbital
angular velocity of a binary and incorporating an approaching relative velocity
of the neutron stars. These modifications improve the solution primarily
through the hydrostatic equilibrium equation for the binary initial data. The
orbital angular velocity and approaching velocity of initial data are updated
iteratively by performing time evolutions over ~3 orbits. We find that the
eccentricity can be reduced by an order of magnitude compared to standard
quasicircular initial data, specifically from ~0.01 to <~0.001, by three
successive iterations for equal-mass binaries leaving ~10 orbits before the
merger.
| [
{
"created": "Fri, 23 May 2014 20:00:11 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 2014 19:35:37 GMT",
"version": "v2"
}
] | 2017-12-27 | [
[
"Kyutoku",
"Koutarou",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Taniguchi",
"Keisuke",
""
]
] | We develop a method to compute low-eccentricity initial data of binary neutron stars required to perform realistic simulations in numerical relativity. The orbital eccentricity is controlled by adjusting the orbital angular velocity of a binary and incorporating an approaching relative velocity of the neutron stars. These modifications improve the solution primarily through the hydrostatic equilibrium equation for the binary initial data. The orbital angular velocity and approaching velocity of initial data are updated iteratively by performing time evolutions over ~3 orbits. We find that the eccentricity can be reduced by an order of magnitude compared to standard quasicircular initial data, specifically from ~0.01 to <~0.001, by three successive iterations for equal-mass binaries leaving ~10 orbits before the merger. |
2105.03849 | Bobby Eka Gunara | Ahmad Khoirul Falah, Andy Octavian Latief, Husin Alatas, and Bobby Eka
Gunara | Higher-Dimensional Minimal Theory of Mass-Varying Massive Gravity And
Its Cosmological Consequences | 20 pages, 2 column, 4 figures, 2 tables. Minor corrections related to
vielbein and references. Match version with Phys Rev D | Phys. Rev. D 104, 084013 (2021) | 10.1103/PhysRevD.104.084013 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we construct higher-dimensional minimal theory of mass-varying
massive gravity (MTMVMG) where the masslike scalar potential is coupled to a
vielbein potential, unlike in the previous literature where it is coupled to
metric, such that the number of graviton degrees of freedom in the theory is
the same as in general relativity. We then study the cosmological aspects of
this theory and show that it has eight critical points: five in the massless
sector and three in the massive sector. In contrast to the standard theory of
mass-varying massive gravity where the graviton mass asymptotically approaches
zero at late times, hence making the contribution of massive gravity to the
late-time cosmic expansion minimum, the MTMVMG can provide good descriptions
both in the massless and massive sectors. Especially, there are at least two
interesting possible scenarios for the late-time cosmology in the theory: the
dark energy is either due to the constant graviton mass which comes from the
scalar field that becomes frozen after the reheating era, or due to the
quintessence paradigm where the scalar field is dynamic. Therefore, if the
accelerating expansion of the universe in the massless sector can be explained
by standard quintessence paradigm, in the massive sector it has to be explained
by the nontrivial interplay between quintessence and massive gravity.
| [
{
"created": "Sun, 9 May 2021 06:29:07 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 2021 09:44:25 GMT",
"version": "v2"
}
] | 2021-10-06 | [
[
"Falah",
"Ahmad Khoirul",
""
],
[
"Latief",
"Andy Octavian",
""
],
[
"Alatas",
"Husin",
""
],
[
"Gunara",
"Bobby Eka",
""
]
] | In this paper we construct higher-dimensional minimal theory of mass-varying massive gravity (MTMVMG) where the masslike scalar potential is coupled to a vielbein potential, unlike in the previous literature where it is coupled to metric, such that the number of graviton degrees of freedom in the theory is the same as in general relativity. We then study the cosmological aspects of this theory and show that it has eight critical points: five in the massless sector and three in the massive sector. In contrast to the standard theory of mass-varying massive gravity where the graviton mass asymptotically approaches zero at late times, hence making the contribution of massive gravity to the late-time cosmic expansion minimum, the MTMVMG can provide good descriptions both in the massless and massive sectors. Especially, there are at least two interesting possible scenarios for the late-time cosmology in the theory: the dark energy is either due to the constant graviton mass which comes from the scalar field that becomes frozen after the reheating era, or due to the quintessence paradigm where the scalar field is dynamic. Therefore, if the accelerating expansion of the universe in the massless sector can be explained by standard quintessence paradigm, in the massive sector it has to be explained by the nontrivial interplay between quintessence and massive gravity. |
gr-qc/0605153 | Dinesh Singh | Dinesh Singh, Nader Mobed, Giorgio Papini | Can Gravity Distinguish Between Dirac and Majorana Neutrinos? | 4 pages, 2 figures; minor changes of text; typo corrected; accepted
in Physical Review Letters | Phys.Rev.Lett. 97 (2006) 041101 | 10.1103/PhysRevLett.97.041101 | null | gr-qc hep-ph hep-th | null | We show that spin-gravity interaction can distinguish between Dirac and
Majorana neutrino wave packets propagating in a Lense-Thirring background.
Using time-independent perturbation theory and gravitational phase to generate
a perturbation Hamiltonian with spin-gravity coupling, we show that the
associated matrix element for the Majorana neutrino differs significantly from
its Dirac counterpart. This difference can be demonstrated through significant
gravitational corrections to the neutrino oscillation length for a two-flavour
system, as shown explicitly for SN1987A.
| [
{
"created": "Wed, 31 May 2006 18:47:16 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jun 2006 02:05:11 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Jul 2006 01:31:12 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Singh",
"Dinesh",
""
],
[
"Mobed",
"Nader",
""
],
[
"Papini",
"Giorgio",
""
]
] | We show that spin-gravity interaction can distinguish between Dirac and Majorana neutrino wave packets propagating in a Lense-Thirring background. Using time-independent perturbation theory and gravitational phase to generate a perturbation Hamiltonian with spin-gravity coupling, we show that the associated matrix element for the Majorana neutrino differs significantly from its Dirac counterpart. This difference can be demonstrated through significant gravitational corrections to the neutrino oscillation length for a two-flavour system, as shown explicitly for SN1987A. |
0807.0596 | Marko Vojinovic | Milovan Vasilic, Marko Vojinovic | Zero-size objects in Riemann-Cartan spacetime | 12 pages | JHEP 0808:104,2008 | 10.1088/1126-6708/2008/08/104 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the conservation law of the stress-energy and spin tensors to study
the motion of massive zero-size objects in Riemann-Cartan geometry. The
resultant world line equations turn out to exhibit a novel spin-curvature
coupling. In particular, the spin of the Dirac particle does not couple to the
background curvature. This is a consequence of its truly zero size which
consistently rules out the orbital degrees of freedom. As a test of
consistency, the wave packet solution of the free Dirac equation is considered.
It is shown that the wave packet spin and orbital angular momentum disappear
simultaneously in the zero-size limit.
| [
{
"created": "Thu, 3 Jul 2008 16:34:23 GMT",
"version": "v1"
}
] | 2010-10-12 | [
[
"Vasilic",
"Milovan",
""
],
[
"Vojinovic",
"Marko",
""
]
] | We use the conservation law of the stress-energy and spin tensors to study the motion of massive zero-size objects in Riemann-Cartan geometry. The resultant world line equations turn out to exhibit a novel spin-curvature coupling. In particular, the spin of the Dirac particle does not couple to the background curvature. This is a consequence of its truly zero size which consistently rules out the orbital degrees of freedom. As a test of consistency, the wave packet solution of the free Dirac equation is considered. It is shown that the wave packet spin and orbital angular momentum disappear simultaneously in the zero-size limit. |
1802.00650 | Tomi Koivisto | Tomi Koivisto | On an integrable geometrical foundation of gravity | 21 pages, 2 figures, proceedings submitted to IJGMMP | null | 10.1142/S0219887818400066 | NORDITA 2018-006 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a talk at the conference {\it Geometrical Foundations of Gravity at Tartu
2017}, it was suggested that the affine spacetime connection could be
associated with purely fictitious forces. This leads to gravitation in a flat
and smooth geometry. Fermions are found to nevertheless couple with the
metrical connection and a phase gauge field. The theory is reviewed in this
proceeding, in a Palatini and in a metric-affine gauge formulation.
| [
{
"created": "Fri, 2 Feb 2018 12:04:48 GMT",
"version": "v1"
}
] | 2018-09-13 | [
[
"Koivisto",
"Tomi",
""
]
] | In a talk at the conference {\it Geometrical Foundations of Gravity at Tartu 2017}, it was suggested that the affine spacetime connection could be associated with purely fictitious forces. This leads to gravitation in a flat and smooth geometry. Fermions are found to nevertheless couple with the metrical connection and a phase gauge field. The theory is reviewed in this proceeding, in a Palatini and in a metric-affine gauge formulation. |
gr-qc/0411045 | Christos G. Tsagas | John D. Barrow and Christos G. Tsagas (DAMTP) | New Isotropic and Anisotropic Sudden Singularities | Typos corrected. Published version | Class.Quant.Grav. 22 (2005) 1563-1571 | 10.1088/0264-9381/22/9/006 | null | gr-qc astro-ph hep-th | null | We show the existence of an infinite family of finite-time singularities in
isotropically expanding universes which obey the weak, strong, and dominant
energy conditions. We show what new type of energy condition is needed to
exclude them ab initio. We also determine the conditions under which
finite-time future singularities can arise in a wide class of anisotropic
cosmological models. New types of finite-time singularity are possible which
are characterised by divergences in the time-rate of change of the
anisotropic-pressure tensor. We investigate the conditions for the formation of
finite-time singularities in a Bianchi type $VII_{0}$ universe with anisotropic
pressures and construct specific examples of anisotropic sudden singularities
in these universes.
| [
{
"created": "Tue, 9 Nov 2004 12:47:47 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Mar 2005 22:42:54 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Mar 2005 19:43:51 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Barrow",
"John D.",
"",
"DAMTP"
],
[
"Tsagas",
"Christos G.",
"",
"DAMTP"
]
] | We show the existence of an infinite family of finite-time singularities in isotropically expanding universes which obey the weak, strong, and dominant energy conditions. We show what new type of energy condition is needed to exclude them ab initio. We also determine the conditions under which finite-time future singularities can arise in a wide class of anisotropic cosmological models. New types of finite-time singularity are possible which are characterised by divergences in the time-rate of change of the anisotropic-pressure tensor. We investigate the conditions for the formation of finite-time singularities in a Bianchi type $VII_{0}$ universe with anisotropic pressures and construct specific examples of anisotropic sudden singularities in these universes. |
2404.16081 | Gamal G.L. Nashed | G.G.L. Nashed | Extension of Hayward black hole in $f(R)$ gravity coupled with a scalar
field | 23 pages, four figures | Physics of the Dark Universe 44, 2024, 101462 | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This study looks into regular solutions in a theory of gravity called $f(R)$
gravity, which also involves a scalar field. The $f(R)$ theory changes
Einstein's ideas by adding a new function related to something called the Ricci
scalar. This lets us tweak the equations that describe how gravity works.
Adding a scalar field makes the theory more interesting, giving us more ways to
investigate and understand it. { The main goal of this research is to create
regular black holes using a combination of $f(R)$ gravitational theory and a
scalar field.} Regular solutions don't have any singularities, which are points
where certain physical quantities, like invariants, become really big or
undefined. { In this context, we find two regular black hole solutions by using
a spherical space with either an equal or unequal approach.} For the solutions
where we use the equal approach, we figure out the shape of $f(R)$ and how it
changes, along with its first and second derivatives. We demonstrate that
Hayward's solution in this theory stays steady because all the shapes of $f(R)$
and their first and second derivatives are positive. Next, we focus on the case
where the metric isn't equal and figure out the black hole solution. We also
find out what $f(R)$ and the scalar field look like in this situation. We
demonstrate that the solution in this case is a broader version of the Hayward
solution. When certain conditions are met, we end up back at the scenario where
the metrics are equal. We also prove that this model is stable because $f(R)$,
along with its first and second derivatives, are all positive. { We analyze the
trajectories of these black hole solutions and determine the forms of their
conserved quantities that remain same along those trajectories.
| [
{
"created": "Wed, 24 Apr 2024 13:40:12 GMT",
"version": "v1"
}
] | 2024-04-26 | [
[
"Nashed",
"G. G. L.",
""
]
] | This study looks into regular solutions in a theory of gravity called $f(R)$ gravity, which also involves a scalar field. The $f(R)$ theory changes Einstein's ideas by adding a new function related to something called the Ricci scalar. This lets us tweak the equations that describe how gravity works. Adding a scalar field makes the theory more interesting, giving us more ways to investigate and understand it. { The main goal of this research is to create regular black holes using a combination of $f(R)$ gravitational theory and a scalar field.} Regular solutions don't have any singularities, which are points where certain physical quantities, like invariants, become really big or undefined. { In this context, we find two regular black hole solutions by using a spherical space with either an equal or unequal approach.} For the solutions where we use the equal approach, we figure out the shape of $f(R)$ and how it changes, along with its first and second derivatives. We demonstrate that Hayward's solution in this theory stays steady because all the shapes of $f(R)$ and their first and second derivatives are positive. Next, we focus on the case where the metric isn't equal and figure out the black hole solution. We also find out what $f(R)$ and the scalar field look like in this situation. We demonstrate that the solution in this case is a broader version of the Hayward solution. When certain conditions are met, we end up back at the scenario where the metrics are equal. We also prove that this model is stable because $f(R)$, along with its first and second derivatives, are all positive. { We analyze the trajectories of these black hole solutions and determine the forms of their conserved quantities that remain same along those trajectories. |
1302.1066 | Joan Josep Ferrando | Joan Josep Ferrando and Juan Antonio S\'aez | A note on static metrics: the degenerate case | 5 pages | Class. Quantum Grav. {30} (2013) 057001 | 10.1088/0264-9381/30/5/057001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give the necessary and sufficient conditions for a 3-metric to be the
adapted spatial metric of a static vacuum solution. This work accomplishes for
the degenerate cases the already known study for the regular ones (Bartnik and
Tod 2006 {\it Class. Quantum Grav.} {\bf 23} 569-571).
| [
{
"created": "Tue, 5 Feb 2013 15:39:32 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | We give the necessary and sufficient conditions for a 3-metric to be the adapted spatial metric of a static vacuum solution. This work accomplishes for the degenerate cases the already known study for the regular ones (Bartnik and Tod 2006 {\it Class. Quantum Grav.} {\bf 23} 569-571). |
1807.00388 | Ali \"Ovg\"un Dr. | Ali \"Ovg\"un, \.Izzet Sakall{\i}, and Joel Saavedra | Shadow cast and Deflection angle of Kerr-Newman-Kasuya spacetime | 16 pages, 4 figures. Accepted for publication in Journal of Cosmology
and Astroparticle Physics (JCAP). arXiv admin note: text overlap with
arXiv:gr-qc/0301100 by other authors | JCAP 10 (2018), 041 | 10.1088/1475-7516/2018/10/041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the shadow cast or silhouette generated by a Kerr-Newman-Kasuya
(KNK) spacetime (rotating dyon black hole). It is shown that in addition to the
angular momentum of the black hole, the dyon charge also affects the shadow
image of the KNK black hole. Moreover, we analyze the weak gravitational
lensing by the KNK black hole by using the Gauss-Bonnet theorem. Finally, we
find that extra dyon charge decreases both the deflection angle and shadow of
the KNK black hole.
| [
{
"created": "Sun, 1 Jul 2018 20:23:58 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Oct 2018 08:46:03 GMT",
"version": "v2"
}
] | 2018-10-23 | [
[
"Övgün",
"Ali",
""
],
[
"Sakallı",
"İzzet",
""
],
[
"Saavedra",
"Joel",
""
]
] | We study the shadow cast or silhouette generated by a Kerr-Newman-Kasuya (KNK) spacetime (rotating dyon black hole). It is shown that in addition to the angular momentum of the black hole, the dyon charge also affects the shadow image of the KNK black hole. Moreover, we analyze the weak gravitational lensing by the KNK black hole by using the Gauss-Bonnet theorem. Finally, we find that extra dyon charge decreases both the deflection angle and shadow of the KNK black hole. |
0903.2565 | Jos\'e Wadih Maluf Dr. | J. W. Maluf, S. C.Ulhoa, F. F. Faria | Pound-Rebka experiment and torsion in the Schwarzschild spacetime | 16 pages, two figures, one typo fixed, one paragraph added in section
5 | Phys. Rev. D 80, 044036 (2009) | 10.1103/PhysRevD.80.044036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop some ideas discussed by E. Schucking [arXiv:0803.4128] concerning
the geometry of the gravitational field. First, we address the concept
according to which the gravitational acceleration is a manifestation of the
spacetime torsion, not of the curvature tensor. It is possible to show that
there are situations in which the geodesic acceleration of a particle may
acquire arbitrary values, whereas the curvature tensor approaches zero. We
conclude that the spacetime curvature does not affect the geodesic
acceleration. Then we consider the the Pound-Rebka experiment, which relates
the time interval $\Delta \tau_1$ of two light signals emitted at a position
$r_1$, to the time interval $\Delta \tau_2$ of the signals received at a
position $r_2$, in a Schwarzschild type gravitational field. The experiment is
determined by four spacetime events. The infinitesimal vectors formed by these
events do not form a parallelogram in the (t,r) plane. The failure in the
closure of the parallelogram implies that the spacetime has torsion. We find
the explicit form of the torsion tensor that explains the nonclosure of the
parallelogram.
| [
{
"created": "Sat, 14 Mar 2009 23:58:24 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Sep 2009 12:03:23 GMT",
"version": "v2"
}
] | 2009-09-02 | [
[
"Maluf",
"J. W.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Faria",
"F. F.",
""
]
] | We develop some ideas discussed by E. Schucking [arXiv:0803.4128] concerning the geometry of the gravitational field. First, we address the concept according to which the gravitational acceleration is a manifestation of the spacetime torsion, not of the curvature tensor. It is possible to show that there are situations in which the geodesic acceleration of a particle may acquire arbitrary values, whereas the curvature tensor approaches zero. We conclude that the spacetime curvature does not affect the geodesic acceleration. Then we consider the the Pound-Rebka experiment, which relates the time interval $\Delta \tau_1$ of two light signals emitted at a position $r_1$, to the time interval $\Delta \tau_2$ of the signals received at a position $r_2$, in a Schwarzschild type gravitational field. The experiment is determined by four spacetime events. The infinitesimal vectors formed by these events do not form a parallelogram in the (t,r) plane. The failure in the closure of the parallelogram implies that the spacetime has torsion. We find the explicit form of the torsion tensor that explains the nonclosure of the parallelogram. |
1104.4543 | Gerard Hooft 't | Gerard 't Hooft | A class of elementary particle models without any adjustable real
parameters | 28 pages (incl. title page), no figures | Foundations of Physics 41, no 12 (2011) pp 1829-1856 | 10.1007/s10701-011-9586-8 | ITP-UU-11/14; SPIN-11/08 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conventional particle theories such as the Standard Model have a number of
freely adjustable coupling constants and mass parameters, depending on the
symmetry algebra of the local gauge group and the representations chosen for
the spinor and scalar fields. There seems to be no physical principle to
determine these parameters as long as they stay within certain domains dictated
by the renormalization group. Here however, reasons are given to demand that,
when gravity is coupled to the system, local conformal invariance should be a
spontaneously broken exact symmetry. The argument has to do with the
requirement that black holes obey a complementarity principle relating ingoing
observers to outside observers, or equivalently, initial states to final
states. This condition fixes all parameters, including masses and the
cosmological constant. We suspect that only examples can be found where these
are all of order one in Planck units, but the values depend on the algebra
chosen. This paper combines findings reported in two previous preprints, and
puts these in a clearer perspective by shifting the emphasis towards the
implications for particle models.
| [
{
"created": "Sat, 23 Apr 2011 09:27:27 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Hooft",
"Gerard 't",
""
]
] | Conventional particle theories such as the Standard Model have a number of freely adjustable coupling constants and mass parameters, depending on the symmetry algebra of the local gauge group and the representations chosen for the spinor and scalar fields. There seems to be no physical principle to determine these parameters as long as they stay within certain domains dictated by the renormalization group. Here however, reasons are given to demand that, when gravity is coupled to the system, local conformal invariance should be a spontaneously broken exact symmetry. The argument has to do with the requirement that black holes obey a complementarity principle relating ingoing observers to outside observers, or equivalently, initial states to final states. This condition fixes all parameters, including masses and the cosmological constant. We suspect that only examples can be found where these are all of order one in Planck units, but the values depend on the algebra chosen. This paper combines findings reported in two previous preprints, and puts these in a clearer perspective by shifting the emphasis towards the implications for particle models. |
1010.2784 | Gary T. Horowitz | Gary T. Horowitz | Surprising Connections Between General Relativity and Condensed Matter | 14 pages; based on talk given at GR19 | Class.Quant.Grav.28:114008,2011 | 10.1088/0264-9381/28/11/114008 | null | gr-qc cond-mat.other cond-mat.supr-con | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This brief review is intended to introduce gravitational physicists to recent
developments in which general relativity is being used to describe certain
aspects of condensed matter systems, e.g., superconductivity.
| [
{
"created": "Wed, 13 Oct 2010 21:58:17 GMT",
"version": "v1"
}
] | 2011-05-25 | [
[
"Horowitz",
"Gary T.",
""
]
] | This brief review is intended to introduce gravitational physicists to recent developments in which general relativity is being used to describe certain aspects of condensed matter systems, e.g., superconductivity. |
1505.05105 | Farook Rahaman | Alireza Sepehri, Farook Rahaman, Mohammad Reza Setare, Anirudh
Pradhan, Salvatore Capozziello, Iftikar Hossain Sardar | Unifying inflation with late-time acceleration in BIonic system | 12 pages, 3 figures. Accepted in Phys.Lett.B. arXiv admin note:
substantial text overlap with arXiv:1502.05493 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this research, we propose a new model that allows to unify inflation,
deceleration and acceleration phases of expansion history in BIonic system. In
this model, in the beginning, there have been $k$ black fundamental strings
that transited to the BIon configuration at a corresponding point. At this
point, two universe brane and universe antibrane have been created, interacted
with each other via one wormhole and inflated. With decreasing temperature, the
energy of this wormhole flowed into universe branes and lead to inflation.
After a short time, wormhole died, inflation ended and deceleration epoch
started. With approaching two universe brane and antibrane together, tachyon
was born, grew and caused creation of one new wormhole. At this time, two
universe brane and antibrane connected again and late-time acceleration era of
the universe began. We compare our model with previous unified phantom model
and observational data and obtain some cosmological parameters like temperature
in terms of time. We also find that deceleration parameter is negative during
inflation and late-time acceleration epochs and positive during deceleration
era. This means that our model is consistent with previous prediction and
cosmological experiments.
| [
{
"created": "Mon, 18 May 2015 11:46:30 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Sepehri",
"Alireza",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Setare",
"Mohammad Reza",
""
],
[
"Pradhan",
"Anirudh",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Sardar",
"Iftikar Hossain",
""
]
] | In this research, we propose a new model that allows to unify inflation, deceleration and acceleration phases of expansion history in BIonic system. In this model, in the beginning, there have been $k$ black fundamental strings that transited to the BIon configuration at a corresponding point. At this point, two universe brane and universe antibrane have been created, interacted with each other via one wormhole and inflated. With decreasing temperature, the energy of this wormhole flowed into universe branes and lead to inflation. After a short time, wormhole died, inflation ended and deceleration epoch started. With approaching two universe brane and antibrane together, tachyon was born, grew and caused creation of one new wormhole. At this time, two universe brane and antibrane connected again and late-time acceleration era of the universe began. We compare our model with previous unified phantom model and observational data and obtain some cosmological parameters like temperature in terms of time. We also find that deceleration parameter is negative during inflation and late-time acceleration epochs and positive during deceleration era. This means that our model is consistent with previous prediction and cosmological experiments. |
gr-qc/9503062 | Gary Horowitz | Gary T. Horowitz and Robert Myers | The Value of Singularities | 5 pages, no figures; a few clarifying comments added | Gen.Rel.Grav.27:915-919,1995 | 10.1007/BF02113073 | UCSBTH-95-6, McGill/95-20 | gr-qc hep-th | null | We point out that spacetime singularities play a useful role in gravitational
theories by eliminating unphysical solutions. In particular, we argue that any
modification of general relativity which is completely nonsingular cannot have
a stable ground state. This argument applies both to classical extensions of
general relativity, and to candidate quantum theories of gravity.
| [
{
"created": "Thu, 30 Mar 1995 21:25:12 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 1995 22:31:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Horowitz",
"Gary T.",
""
],
[
"Myers",
"Robert",
""
]
] | We point out that spacetime singularities play a useful role in gravitational theories by eliminating unphysical solutions. In particular, we argue that any modification of general relativity which is completely nonsingular cannot have a stable ground state. This argument applies both to classical extensions of general relativity, and to candidate quantum theories of gravity. |
1107.0422 | Pedro Castelo Ferreira | P. Castelo Ferreira | Rotating Magnetic Solutions for 2+1D Einstein Maxwell Chern-Simons | 39 pages; 2 tables; revised version: mass and angular momentum
definitions consistent with embedded 2+1D systems (for example 3+1D systems
with cylindrical symmetry) | Scripta-Ingenia 9 (2018) 3-21 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article are computed magnetic solutions of Einstein Maxwell
Chern-Simons theory coupled to a dilaton-like scalar field. These solutions are
computed by applying a space-time duality suggested by the author to known
electric solutions of the same theory. As a redundancy check for the space-time
duality it is explicitly shown that the magnetic configurations obtained are,
as expected, solutions of the equations of motion. The magnetic configurations
have metric determinant $\sqrt{-g}\sim r^p$ for the range of the parameter
$p\in]-\infty,+\infty[/\{-1\}$ and are interpreted either as magnetic
string-like configurations, configurations driven by an externally applied
magnetic field or cosmological-like solutions with background magnetic fields.
| [
{
"created": "Sun, 3 Jul 2011 01:43:21 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2011 12:16:14 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Jul 2011 22:46:33 GMT",
"version": "v3"
},
{
"created": "Wed, 31 Jan 2018 15:49:35 GMT",
"version": "v4"
}
] | 2021-03-12 | [
[
"Ferreira",
"P. Castelo",
""
]
] | In this article are computed magnetic solutions of Einstein Maxwell Chern-Simons theory coupled to a dilaton-like scalar field. These solutions are computed by applying a space-time duality suggested by the author to known electric solutions of the same theory. As a redundancy check for the space-time duality it is explicitly shown that the magnetic configurations obtained are, as expected, solutions of the equations of motion. The magnetic configurations have metric determinant $\sqrt{-g}\sim r^p$ for the range of the parameter $p\in]-\infty,+\infty[/\{-1\}$ and are interpreted either as magnetic string-like configurations, configurations driven by an externally applied magnetic field or cosmological-like solutions with background magnetic fields. |
1406.3009 | Roger Tagne Wafo | Aurore Cabet, Piotr T. Chru\'sciel, Roger Tagne Wafo | On the characteristic initial value problem for nonlinear symmetric
hyperbolic systems, including Einstein equations | 85 pages, 11 figures | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a characteristic initial value problem for a class of symmetric
hyperbolic systems with initial data given on two smooth null intersecting
characteristic surfaces. We prove existence of solutions on a future
neighborhood of the initial surfaces. The general result is applied to general
semilinear wave equations, as well as the Einstein equations with or without
sources, and conformal variations thereof.
| [
{
"created": "Wed, 11 Jun 2014 19:36:21 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Mar 2016 09:15:41 GMT",
"version": "v2"
}
] | 2016-03-29 | [
[
"Cabet",
"Aurore",
""
],
[
"Chruściel",
"Piotr T.",
""
],
[
"Wafo",
"Roger Tagne",
""
]
] | We consider a characteristic initial value problem for a class of symmetric hyperbolic systems with initial data given on two smooth null intersecting characteristic surfaces. We prove existence of solutions on a future neighborhood of the initial surfaces. The general result is applied to general semilinear wave equations, as well as the Einstein equations with or without sources, and conformal variations thereof. |
gr-qc/9504035 | Jorma Louko | Domenico Giulini and Jorma Louko | Diffeomorphism invariant subspaces in Witten's 2+1 quantum gravity on
${\bf R} \times T^2$ | 14 pages, REVTeX v3.0 | Class.Quant.Grav. 12 (1995) 2735-2746 | 10.1088/0264-9381/12/11/006 | Freiburg THEP--95/7, WISC--MILW--95--TH--13 | gr-qc | null | We address the role of large diffeomorphisms in Witten's 2+1 gravity on the
manifold ${\bf R} \times T^2$. In a ``spacelike sector" quantum theory that
treats the large diffeomorphisms as a symmetry, rather than as gauge, the
Hilbert space is shown to contain no nontrivial finite dimensional subspaces
that are invariant under the large diffeomorphisms. Infinite dimensional closed
invariant subspaces are explicitly constructed, and the representation of the
large diffeomorphisms is thus shown to be reducible. Comparison is made to
Witten's theory on ${\bf R} \times \Sigma$, where $\Sigma$ is a higher genus
surface.
| [
{
"created": "Fri, 21 Apr 1995 20:27:52 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Giulini",
"Domenico",
""
],
[
"Louko",
"Jorma",
""
]
] | We address the role of large diffeomorphisms in Witten's 2+1 gravity on the manifold ${\bf R} \times T^2$. In a ``spacelike sector" quantum theory that treats the large diffeomorphisms as a symmetry, rather than as gauge, the Hilbert space is shown to contain no nontrivial finite dimensional subspaces that are invariant under the large diffeomorphisms. Infinite dimensional closed invariant subspaces are explicitly constructed, and the representation of the large diffeomorphisms is thus shown to be reducible. Comparison is made to Witten's theory on ${\bf R} \times \Sigma$, where $\Sigma$ is a higher genus surface. |
1708.09592 | Daiske Yoshida | Daiske Yoshida and Jiro Soda | Exploring the string axiverse and parity violation in gravity with
gravitational waves | 5 pages, 2 figures | International Journal of Modern Physics D, Vol. 27, No. 9 (2018)
1850096 | 10.1142/S0218271818500967 | KOBE-COSMO-17-10 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the parametric resonance of gravitational waves occurs due to
the axion coherent oscillation and the circular polarization of gravitational
waves is induced by the Chern-Simons coupling. However, we have never observed
these signatures in the data of gravitational waves. Using this fact, we give
stringent constraints on the Chern-Simons coupling constant $\ell$ and the
abundance of the light string axion. In particular, we improved the current
bound $\ell\leq10^{8}\,\,{\rm km}$ by many orders of magnitude.
| [
{
"created": "Thu, 31 Aug 2017 07:18:17 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Sep 2017 06:56:40 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Mar 2018 07:07:10 GMT",
"version": "v3"
}
] | 2018-07-06 | [
[
"Yoshida",
"Daiske",
""
],
[
"Soda",
"Jiro",
""
]
] | We show that the parametric resonance of gravitational waves occurs due to the axion coherent oscillation and the circular polarization of gravitational waves is induced by the Chern-Simons coupling. However, we have never observed these signatures in the data of gravitational waves. Using this fact, we give stringent constraints on the Chern-Simons coupling constant $\ell$ and the abundance of the light string axion. In particular, we improved the current bound $\ell\leq10^{8}\,\,{\rm km}$ by many orders of magnitude. |
2207.13202 | Atsushi Higuchi | Atsushi Higuchi, Lasse Schmieding and David Serrano Blanco | Automorphic scalar fields in two-dimensional de Sitter space | 33 pages, 2 figures, published version | Class.Quant.Grav. 40 (2023) 1, 015009 | 10.1088/1361-6382/aca73f | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study non-interacting automorphic quantum scalar fields with positive mass
in two-dimensional de Sitter space. We find that there are no Hadamard states
which are de Sitter invariant except in the periodic case, extending the result
of Epstein and Moschella for the anti-periodic case. We construct the two-point
Wightman functions for the non-Hadamard de Sitter-invariant states by
exploiting the fact that they are functions of the geodesic distance between
the two points satisfying an ordinary differential equation. We then examine a
certain Hadamard state, which is not de Sitter invariant, and show that it is
approximately a thermal state with the Gibbons-Hawking temperature when
restricted to a static region of the spacetime.
| [
{
"created": "Tue, 26 Jul 2022 22:32:03 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jan 2023 10:53:12 GMT",
"version": "v2"
}
] | 2023-01-12 | [
[
"Higuchi",
"Atsushi",
""
],
[
"Schmieding",
"Lasse",
""
],
[
"Blanco",
"David Serrano",
""
]
] | We study non-interacting automorphic quantum scalar fields with positive mass in two-dimensional de Sitter space. We find that there are no Hadamard states which are de Sitter invariant except in the periodic case, extending the result of Epstein and Moschella for the anti-periodic case. We construct the two-point Wightman functions for the non-Hadamard de Sitter-invariant states by exploiting the fact that they are functions of the geodesic distance between the two points satisfying an ordinary differential equation. We then examine a certain Hadamard state, which is not de Sitter invariant, and show that it is approximately a thermal state with the Gibbons-Hawking temperature when restricted to a static region of the spacetime. |
gr-qc/9806004 | Richard J. Epp | Richard J. Epp (1), R. B. Mann (1) ((1) University of Waterloo) | A New Approach to Black Hole Microstates | 6 pages, 0 figures, LaTeX; submitted to Mod. Phys. Lett. A.; this
essay received "honorable mention" from the Gravity Research Foundation, 1998 | Mod.Phys.Lett. A13 (1998) 1875-1880 | 10.1142/S0217732398001960 | WATPHYS TH-98/02 | gr-qc | null | If one encodes the gravitational degrees of freedom in an orthonormal frame
field there is a very natural first order action one can write down (which in
four dimensions is known as the Goldberg action). In this essay we will show
that this action contains a boundary action for certain microscopic degrees of
freedom living at the horizon of a black hole, and argue that these degrees of
freedom hold great promise for explaining the microstates responsible for black
hole entropy, in any number of spacetime dimensions. This approach faces many
interesting challenges, both technical and conceptual.
| [
{
"created": "Sat, 30 May 1998 21:28:33 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Epp",
"Richard J.",
"",
"University of Waterloo"
],
[
"Mann",
"R. B.",
"",
"University of Waterloo"
]
] | If one encodes the gravitational degrees of freedom in an orthonormal frame field there is a very natural first order action one can write down (which in four dimensions is known as the Goldberg action). In this essay we will show that this action contains a boundary action for certain microscopic degrees of freedom living at the horizon of a black hole, and argue that these degrees of freedom hold great promise for explaining the microstates responsible for black hole entropy, in any number of spacetime dimensions. This approach faces many interesting challenges, both technical and conceptual. |
1908.01254 | Wan Cong Ms | Wan Cong and Robert B. Mann | Thermodynamic Instabilities of Generalized Exotic BTZ Black Holes | 4 pages, 2 figures | null | 10.1007/JHEP11(2019)004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the conjecture that black holes violating the reverse
isoperimetric inequality have negative specific heat at constant volume $C_V$.
We test this conjecture on the family of generalized exotic Ba\~nados,
Teitelbiom and Zanelli (BTZ) black holes and find that $C_V$ can be positive
even when the reverse isoperimetric inequality is violated, providing a counter
example to the conjecture. However in all cases where $C_V$ is positive, the
specific heat at constant pressure $C_P$ is negative, indicating that
generalized exotic black holes are thermodynamically unstable, suggesting that
a broader version of the conjecture might hold.
| [
{
"created": "Sun, 4 Aug 2019 01:40:20 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Aug 2019 13:36:49 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Cong",
"Wan",
""
],
[
"Mann",
"Robert B.",
""
]
] | We examine the conjecture that black holes violating the reverse isoperimetric inequality have negative specific heat at constant volume $C_V$. We test this conjecture on the family of generalized exotic Ba\~nados, Teitelbiom and Zanelli (BTZ) black holes and find that $C_V$ can be positive even when the reverse isoperimetric inequality is violated, providing a counter example to the conjecture. However in all cases where $C_V$ is positive, the specific heat at constant pressure $C_P$ is negative, indicating that generalized exotic black holes are thermodynamically unstable, suggesting that a broader version of the conjecture might hold. |
2302.04962 | Georgios Fanaras | Georgios Fanaras, Alexander Vilenkin | Quantum cosmology, eternal inflation, and swampland conjectures | 28 pages, 9 figures | null | 10.1088/1475-7516/2023/04/034 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In light of the recent swampland conjectures, we explore quantum cosmology
and eternal inflation beyond the slow roll regime. We consider a model of a
closed universe with a scalar field $\phi$ in the framework of tunneling
approach to quantum cosmology. The scalar field potential is assumed to have a
maximum at $\phi=0$ and can be approximated in its vicinity as $V(\phi)\approx
3H^{2}-\frac{1}{2}m^{2}\phi^{2}$. Using the instanton method, we find that for
$m<2H$ the dominant nucleation channel for the universe is tunneling to a
homogeneous, spherical de Sitter space. For larger values of $m/H$, the most
probable tunneling is to an inhomogeneous closed universe with a domain wall
wrapped around its equator. We determine the quantum state of the field $\phi$
in the nucleated universe by solving the Wheeler-DeWitt equation with tunneling
boundary conditions. Our results agree with earlier work which assumed a
slow-roll regime $m\ll H$. We finally show that spherical universes nucleating
with $m<2H$ undergo stochastic eternal inflation with inflating regions forming
a fractal of dimension $d>2$. For larger values of $m$ the field $\phi$ is
unstable with respect to formation of domain walls and cannot be described by a
perturbative stochastic approach.
| [
{
"created": "Thu, 9 Feb 2023 22:36:24 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Feb 2023 16:49:40 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Fanaras",
"Georgios",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | In light of the recent swampland conjectures, we explore quantum cosmology and eternal inflation beyond the slow roll regime. We consider a model of a closed universe with a scalar field $\phi$ in the framework of tunneling approach to quantum cosmology. The scalar field potential is assumed to have a maximum at $\phi=0$ and can be approximated in its vicinity as $V(\phi)\approx 3H^{2}-\frac{1}{2}m^{2}\phi^{2}$. Using the instanton method, we find that for $m<2H$ the dominant nucleation channel for the universe is tunneling to a homogeneous, spherical de Sitter space. For larger values of $m/H$, the most probable tunneling is to an inhomogeneous closed universe with a domain wall wrapped around its equator. We determine the quantum state of the field $\phi$ in the nucleated universe by solving the Wheeler-DeWitt equation with tunneling boundary conditions. Our results agree with earlier work which assumed a slow-roll regime $m\ll H$. We finally show that spherical universes nucleating with $m<2H$ undergo stochastic eternal inflation with inflating regions forming a fractal of dimension $d>2$. For larger values of $m$ the field $\phi$ is unstable with respect to formation of domain walls and cannot be described by a perturbative stochastic approach. |
1410.0026 | Joshua Cooperman | Joshua H. Cooperman | Renormalization of lattice-regularized quantum gravity models I. General
considerations | 27 pages; revised and updated review of past literature. This is the
much delayed first paper in the two-part series | null | null | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lattice regularization is a standard technique for the nonperturbative
definition of a quantum theory of fields. Several approaches to the
construction of a quantum theory of gravity adopt this technique either
explicitly or implicitly. A crucial complement to lattice regularization is the
process of renormalization through which a continuous description of the
quantum theory arises. I provide a comprehensive conceptual discussion of the
renormalization of lattice-regularized quantum gravity models. I begin with a
presentation of the renormalization group from the Wilsonian perspective. I
then consider the application of the renormalization group in four contexts:
quantum field theory on a continuous nondynamical spacetime, quantum field
theory on a lattice-regularized nondynamical spacetime, quantum field theory of
continuous dynamical spacetime, and quantum field theory of lattice-regularized
dynamical spacetime. The first three contexts serve to identify successively
the particular issues that arise in the fourth context. These issues originate
in the inescability of establishing all scales solely on the basis of the
dynamics. While most of this discussion rehearses established knowledge, the
attention that I pay to these issues, especially the previously
underappreciated role of standard units of measure, is largely novel. I
conclude by briefly reviewing past studies of renormalization of
lattice-regularized quantum gravity models. In the second paper of this
two-part series, I illustrate the ideas presented here by proposing a
renormalization group scheme for causal dynamical triangulations.
| [
{
"created": "Tue, 30 Sep 2014 20:00:41 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Oct 2014 19:54:12 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Oct 2014 13:19:16 GMT",
"version": "v3"
}
] | 2014-10-22 | [
[
"Cooperman",
"Joshua H.",
""
]
] | Lattice regularization is a standard technique for the nonperturbative definition of a quantum theory of fields. Several approaches to the construction of a quantum theory of gravity adopt this technique either explicitly or implicitly. A crucial complement to lattice regularization is the process of renormalization through which a continuous description of the quantum theory arises. I provide a comprehensive conceptual discussion of the renormalization of lattice-regularized quantum gravity models. I begin with a presentation of the renormalization group from the Wilsonian perspective. I then consider the application of the renormalization group in four contexts: quantum field theory on a continuous nondynamical spacetime, quantum field theory on a lattice-regularized nondynamical spacetime, quantum field theory of continuous dynamical spacetime, and quantum field theory of lattice-regularized dynamical spacetime. The first three contexts serve to identify successively the particular issues that arise in the fourth context. These issues originate in the inescability of establishing all scales solely on the basis of the dynamics. While most of this discussion rehearses established knowledge, the attention that I pay to these issues, especially the previously underappreciated role of standard units of measure, is largely novel. I conclude by briefly reviewing past studies of renormalization of lattice-regularized quantum gravity models. In the second paper of this two-part series, I illustrate the ideas presented here by proposing a renormalization group scheme for causal dynamical triangulations. |
1403.2618 | Maurice Dupre | Maurice J. Dupre | An observer principle for general relativity | arXiv admin note: substantial text overlap with arXiv:0903.5225 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a mathematical uniqueness theorem which in particular shows that
symmetric tensors in general relativity are uniquely determined by their
monomial functions on the light cone. Thus, for an observer to observe a tensor
at an event in general relativity is to contract with the velocity vector of
the observer, repeatedly to the rank of the tensor. Thus two symmetric tensors
observed to be equal by all observers at a specific event are necessarily equal
at that event.
| [
{
"created": "Tue, 11 Mar 2014 15:45:05 GMT",
"version": "v1"
}
] | 2014-03-12 | [
[
"Dupre",
"Maurice J.",
""
]
] | We give a mathematical uniqueness theorem which in particular shows that symmetric tensors in general relativity are uniquely determined by their monomial functions on the light cone. Thus, for an observer to observe a tensor at an event in general relativity is to contract with the velocity vector of the observer, repeatedly to the rank of the tensor. Thus two symmetric tensors observed to be equal by all observers at a specific event are necessarily equal at that event. |
gr-qc/0506090 | Mauricio Cataldo MC | Mauricio Cataldo and Luis P. Chimento | Form invariant transformations between n-- and m-- dimensional flat
Friedmann--Robertson--Walker cosmologies | Accepted for publication in Iternational Journal of Modern Physics D | Int.J.Mod.Phys.D17:1981-1989,2008 | 10.1142/S0218271808013790 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We illustrate how the group of symmetry transformations, which preserve the
form of the n--dimensional flat Friedmann--Robertson--Walker cosmologies
satisfying Einstein equations, acts in any dimension. This group relates the
energy density and the isotropic pressure of the cosmic fluid to the expansion
rate. The freedom associated with the dimension of the space time yields
assisted inflation even when the energy density of the fluid is a dimensional
invariant and enriches the set of duality transformations leading to phantom
cosmologies.
| [
{
"created": "Thu, 16 Jun 2005 20:31:01 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jul 2008 14:50:09 GMT",
"version": "v2"
}
] | 2009-02-11 | [
[
"Cataldo",
"Mauricio",
""
],
[
"Chimento",
"Luis P.",
""
]
] | We illustrate how the group of symmetry transformations, which preserve the form of the n--dimensional flat Friedmann--Robertson--Walker cosmologies satisfying Einstein equations, acts in any dimension. This group relates the energy density and the isotropic pressure of the cosmic fluid to the expansion rate. The freedom associated with the dimension of the space time yields assisted inflation even when the energy density of the fluid is a dimensional invariant and enriches the set of duality transformations leading to phantom cosmologies. |
gr-qc/0005126 | Kirill Krasnov | A. Ashtekar, J. Baez and K. Krasnov | Quantum Geometry of Isolated Horizons and Black Hole Entropy | 66 pages, 4 figures | Adv.Theor.Math.Phys. 4 (2000) 1-94 | null | NSF-ITP-99-153 | gr-qc hep-th | null | Using the earlier developed classical Hamiltonian framework as the point of
departure, we carry out a non-perturbative quantization of the sector of
general relativity, coupled to matter, admitting non-rotating isolated horizons
as inner boundaries. The emphasis is on the quantum geometry of the horizon.
Polymer excitations of the bulk quantum geometry pierce the horizon endowing it
with area. The intrinsic geometry of the horizon is then described by the
quantum Chern-Simons theory of a U(1) connection on a punctured 2-sphere, the
horizon. Subtle mathematical features of the quantum Chern-Simons theory turn
out to be important for the existence of a coherent quantum theory of the
horizon geometry. Heuristically, the intrinsic geometry is flat everywhere
except at the punctures. The distributional curvature of the U(1) connection at
the punctures gives rise to quantized deficit angles which account for the
overall curvature. For macroscopic black holes, the logarithm of the number of
these horizon microstates is proportional to the area, irrespective of the
values of (non-gravitational) charges. Thus, the black hole entropy can be
accounted for entirely by the quantum states of the horizon geometry. Our
analysis is applicable to all non-rotating black holes, including the
astrophysically interesting ones which are very far from extremality.
Furthermore, cosmological horizons (to which statistical mechanical
considerations are known to apply) are naturally incorporated. An effort has
been made to make the paper self-contained by including short reviews of the
background material.
| [
{
"created": "Mon, 29 May 2000 19:03:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ashtekar",
"A.",
""
],
[
"Baez",
"J.",
""
],
[
"Krasnov",
"K.",
""
]
] | Using the earlier developed classical Hamiltonian framework as the point of departure, we carry out a non-perturbative quantization of the sector of general relativity, coupled to matter, admitting non-rotating isolated horizons as inner boundaries. The emphasis is on the quantum geometry of the horizon. Polymer excitations of the bulk quantum geometry pierce the horizon endowing it with area. The intrinsic geometry of the horizon is then described by the quantum Chern-Simons theory of a U(1) connection on a punctured 2-sphere, the horizon. Subtle mathematical features of the quantum Chern-Simons theory turn out to be important for the existence of a coherent quantum theory of the horizon geometry. Heuristically, the intrinsic geometry is flat everywhere except at the punctures. The distributional curvature of the U(1) connection at the punctures gives rise to quantized deficit angles which account for the overall curvature. For macroscopic black holes, the logarithm of the number of these horizon microstates is proportional to the area, irrespective of the values of (non-gravitational) charges. Thus, the black hole entropy can be accounted for entirely by the quantum states of the horizon geometry. Our analysis is applicable to all non-rotating black holes, including the astrophysically interesting ones which are very far from extremality. Furthermore, cosmological horizons (to which statistical mechanical considerations are known to apply) are naturally incorporated. An effort has been made to make the paper self-contained by including short reviews of the background material. |
2112.06503 | Ingemar Bengtsson | Ingemar Bengtsson, Tobias Eklund | Energy in Newtonian gravity | Version 2 has 18 pages, and was much improved by referees | Found. Phys. 53 (2023) 15 | 10.1007/s10701-022-00660-z | null | gr-qc physics.hist-ph | http://creativecommons.org/licenses/by/4.0/ | In Newtonian gravity it is a moot question whether energy should be localized
in the field or inside matter. An argument from relativity suggests a
compromise in which the contribution from the field in vacuum is positive
definite. We show that the same compromise is implied by Noether's theorem
applied to a variational principle for perfect fluids, if we assume Dirichlet
boundary conditions on the potential. We then analyse a thought experiment due
to Bondi and McCrea that gives a clean example of inductive energy transfer by
gravity. Some history of the problem is included
| [
{
"created": "Mon, 13 Dec 2021 09:25:37 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Dec 2022 13:16:54 GMT",
"version": "v2"
}
] | 2023-07-26 | [
[
"Bengtsson",
"Ingemar",
""
],
[
"Eklund",
"Tobias",
""
]
] | In Newtonian gravity it is a moot question whether energy should be localized in the field or inside matter. An argument from relativity suggests a compromise in which the contribution from the field in vacuum is positive definite. We show that the same compromise is implied by Noether's theorem applied to a variational principle for perfect fluids, if we assume Dirichlet boundary conditions on the potential. We then analyse a thought experiment due to Bondi and McCrea that gives a clean example of inductive energy transfer by gravity. Some history of the problem is included |
1711.10278 | Valentin Kuzmichev | V. E. Kuzmichev, V. V. Kuzmichev (Bogolyubov Institute for Theoretical
Physics) | Generalized uncertainty principle in quantum cosmology for the maximally
symmetric space | 13 pages, v.2: new section and title, abstract is revised | Ukr. J. Phys. 2019. Vol. 64, No. 2, pp. 100-108 | 10.15407/ujpe64.2.100 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The new uncertainty relation is derived in the context of the canonical
quantum theory with gravity for the case of the maximally symmetric space. This
relation establishes a connection between fluctuations of the quantities which
determine the intrinsic and extrinsic curvatures of the spacelike hypersurface
in spacetime and introduces the uncertainty principle for quantum gravitational
systems. The generalized time-energy uncertainty relation, which takes into
account gravity, is proposed. It is shown that known Unruh's uncertainty
relation follows, as a particular case, from the new uncertainty relation. As
an example, the sizes of fluctuations of the scale factor and its conjugate
momentum are calculated within an exactly solvable model. All known
modifications of the uncertainty principle deduced previously from different
approaches in the theory of gravity and string theory are obtained as
particular cases of the proposed general expression.
| [
{
"created": "Tue, 28 Nov 2017 13:23:49 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Nov 2018 13:16:44 GMT",
"version": "v2"
}
] | 2019-11-05 | [
[
"Kuzmichev",
"V. E.",
"",
"Bogolyubov Institute for Theoretical\n Physics"
],
[
"Kuzmichev",
"V. V.",
"",
"Bogolyubov Institute for Theoretical\n Physics"
]
] | The new uncertainty relation is derived in the context of the canonical quantum theory with gravity for the case of the maximally symmetric space. This relation establishes a connection between fluctuations of the quantities which determine the intrinsic and extrinsic curvatures of the spacelike hypersurface in spacetime and introduces the uncertainty principle for quantum gravitational systems. The generalized time-energy uncertainty relation, which takes into account gravity, is proposed. It is shown that known Unruh's uncertainty relation follows, as a particular case, from the new uncertainty relation. As an example, the sizes of fluctuations of the scale factor and its conjugate momentum are calculated within an exactly solvable model. All known modifications of the uncertainty principle deduced previously from different approaches in the theory of gravity and string theory are obtained as particular cases of the proposed general expression. |
2101.02687 | N. P. Landsman | Klaas Landsman | Singularities, black holes, and cosmic censorship: A tribute to Roger
Penrose | 28 pages. Section 3.2 expanded by a page and some references added | null | 10.1007/s10701-021-00432-1 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the light of his recent (and fully deserved) Nobel Prize, this pedagogical
paper draws attention to a fundamental tension that drove Penrose's work on
general relativity. His 1965 singularity theorem (for which he got the prize)
does not in fact imply the existence of black holes (even if its assumptions
are met). Similarly, his versatile definition of a singular space-time does not
match the generally accepted definition of a black hole (derived from his
concept of null infinity). To overcome this, Penrose launched his cosmic
censorship conjecture(s), whose evolution we discuss. In particular, we review
both his own (mature) formulation and its later, inequivalent reformulation in
the PDE literature. As a compromise, one might say that in "generic" or
"physically reasonable" space-times, weak cosmic censorship postulates the
appearance and stability of event horizons, whereas strong cosmic censorship
asks for the instability and ensuing disappearance of Cauchy horizons. As an
encore, an appendix by Erik Curiel reviews the early history of the definition
of a black hole.
| [
{
"created": "Thu, 7 Jan 2021 18:48:49 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Jan 2021 16:39:25 GMT",
"version": "v2"
}
] | 2021-04-14 | [
[
"Landsman",
"Klaas",
""
]
] | In the light of his recent (and fully deserved) Nobel Prize, this pedagogical paper draws attention to a fundamental tension that drove Penrose's work on general relativity. His 1965 singularity theorem (for which he got the prize) does not in fact imply the existence of black holes (even if its assumptions are met). Similarly, his versatile definition of a singular space-time does not match the generally accepted definition of a black hole (derived from his concept of null infinity). To overcome this, Penrose launched his cosmic censorship conjecture(s), whose evolution we discuss. In particular, we review both his own (mature) formulation and its later, inequivalent reformulation in the PDE literature. As a compromise, one might say that in "generic" or "physically reasonable" space-times, weak cosmic censorship postulates the appearance and stability of event horizons, whereas strong cosmic censorship asks for the instability and ensuing disappearance of Cauchy horizons. As an encore, an appendix by Erik Curiel reviews the early history of the definition of a black hole. |
1212.3764 | Khedmat Atazadeh | K. Atazadeh, Misha Mousavi | Vacuum spherically symmetric solutions in $f(T)$ gravity | 8 pages,typos corrected, Refs. added | Eur. Phys. J. C 73 (2013) 2272 | 10.1140/epjc/s10052-012-2272-y | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Spherically symmetric static vacuum solutions have been built in $f(T)$
models of gravity theory. We apply some conditions on the metric components;
then the new vacuum spherically symmetric solutions are obtained. Also, by
extracting metric coefficients we determine the analytical form of $f(T)$.
| [
{
"created": "Sun, 16 Dec 2012 08:45:52 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jan 2013 17:13:42 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Jan 2013 05:53:38 GMT",
"version": "v3"
}
] | 2013-11-19 | [
[
"Atazadeh",
"K.",
""
],
[
"Mousavi",
"Misha",
""
]
] | Spherically symmetric static vacuum solutions have been built in $f(T)$ models of gravity theory. We apply some conditions on the metric components; then the new vacuum spherically symmetric solutions are obtained. Also, by extracting metric coefficients we determine the analytical form of $f(T)$. |
1306.5739 | Farook Rahaman | Ahmad T Ali and F Rahaman | New Class of Magnetized Inhomogeneous Bianchi Type-I Cosmological Model
with Variable Magnetic Permeability in Lyra Geometry | Int. J. Theor. Phys. 52, 4055 (2013) | null | 10.1007/s10773-013-1719-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inhomogeneous Bianchi type-I cosmological model with electro-magnetic field
based on Lyra geometry is investigated. Using separated method, the Einstein
field equations have been solved analytically with the aid of Mathematica
programm. A new class of exact solutions have been obtained by considering the
potentials of metric and displacement field are functions of coordinates t and
x. We have assumed that F(12) is the only non-vanishing component of
electro-magnetic field tensor F(ij). The Maxwells equations show that F(12) is
the function of x alone whereas the magnetic permeability is the function of x
and t both. To get the deterministic solution, it has been assumed that the
expansion scaler Theta in the model is proportional to the value sigma(11) of
the shear tensor sigma(ij). Some physical and geometric properties of the model
are also discussed and graphed.
| [
{
"created": "Sat, 22 Jun 2013 07:32:16 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Dec 2013 09:22:53 GMT",
"version": "v2"
}
] | 2013-12-12 | [
[
"Ali",
"Ahmad T",
""
],
[
"Rahaman",
"F",
""
]
] | Inhomogeneous Bianchi type-I cosmological model with electro-magnetic field based on Lyra geometry is investigated. Using separated method, the Einstein field equations have been solved analytically with the aid of Mathematica programm. A new class of exact solutions have been obtained by considering the potentials of metric and displacement field are functions of coordinates t and x. We have assumed that F(12) is the only non-vanishing component of electro-magnetic field tensor F(ij). The Maxwells equations show that F(12) is the function of x alone whereas the magnetic permeability is the function of x and t both. To get the deterministic solution, it has been assumed that the expansion scaler Theta in the model is proportional to the value sigma(11) of the shear tensor sigma(ij). Some physical and geometric properties of the model are also discussed and graphed. |
2109.09769 | Konstantinos Kritos | Konstantinos Kritos and Joseph Silk | Mergers of Maximally Charged Primordial Black Holes | 13 pages, 3 figures | Phys.Rev.D 105 (2022) 6, 063011 | 10.1103/PhysRevD.105.063011 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Near-extremal primordial black holes stable over cosmological timescales may
constitute a significant fraction of the dark matter. Due to their charge the
coalescence rate of such black holes is enhanced inside clusters and the
non-extremal merger remnants are prone to Hawking evaporation. We demonstrate
that if these clusters of near-extremal holes contain a sufficient number of
members to survive up to low redshift, the hard photons from continued
evaporation begin to dominate the high energy diffuse background. We find that
the diffuse photon flux can be observed for a monochromatic mass spectrum of
holes lighter than about $10^{12}\rm g$. We place upper bounds on their
abundance respecting the current bounds set by gamma ray telescopes.
Furthermore, the gravitational wave background induced at the epoch of
primordial black hole formation may be detectable by future planned and
proposed ground-based and space-borne gravitational wave observatories
operating in the mHz to kHz frequency range and can be an important tool for
studying light charged primordial black holes over masses in the range $\rm
10^{12}g - 10^{19}g$.
| [
{
"created": "Mon, 20 Sep 2021 18:02:55 GMT",
"version": "v1"
},
{
"created": "Mon, 30 May 2022 21:18:49 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Jun 2022 15:35:40 GMT",
"version": "v3"
}
] | 2022-06-24 | [
[
"Kritos",
"Konstantinos",
""
],
[
"Silk",
"Joseph",
""
]
] | Near-extremal primordial black holes stable over cosmological timescales may constitute a significant fraction of the dark matter. Due to their charge the coalescence rate of such black holes is enhanced inside clusters and the non-extremal merger remnants are prone to Hawking evaporation. We demonstrate that if these clusters of near-extremal holes contain a sufficient number of members to survive up to low redshift, the hard photons from continued evaporation begin to dominate the high energy diffuse background. We find that the diffuse photon flux can be observed for a monochromatic mass spectrum of holes lighter than about $10^{12}\rm g$. We place upper bounds on their abundance respecting the current bounds set by gamma ray telescopes. Furthermore, the gravitational wave background induced at the epoch of primordial black hole formation may be detectable by future planned and proposed ground-based and space-borne gravitational wave observatories operating in the mHz to kHz frequency range and can be an important tool for studying light charged primordial black holes over masses in the range $\rm 10^{12}g - 10^{19}g$. |
1210.3804 | Deborah A. Konkowski | Deborah A. Konkowski and Thomas M. Helliwell | Quantum singularities in conformally static spacetimes | 7 pages, no figures, submitted to Proceedings of Relativity and
Gravitation: 100 years after Einstein in Prague, 25-29 June 2012, Prague,
Czech Republic | null | null | null | gr-qc | http://creativecommons.org/licenses/publicdomain/ | After a brief review of the standard definition and analysis of classical
singularities in general relativistic spacetimes, and of quantum singularities
in static spacetimes with timelike classical singularities, an extension of
quantum singularities to conformally static spacetimes is summarized and
applied to two test cases. The timelike classical singularities in a
Friedmann-Robertson-Walker (FRW) universe with a cosmic string, and in Roberts
spacetime, are shown to be quantum mechanically singular when tested by either
minimally coupled or conformally coupled scalar waves. In the Roberts case,
however, non-minimally coupled scalar waves with a coupling constant $\xi \ge
2$ do not detect the classical singularity.
| [
{
"created": "Sun, 14 Oct 2012 15:34:19 GMT",
"version": "v1"
}
] | 2012-10-16 | [
[
"Konkowski",
"Deborah A.",
""
],
[
"Helliwell",
"Thomas M.",
""
]
] | After a brief review of the standard definition and analysis of classical singularities in general relativistic spacetimes, and of quantum singularities in static spacetimes with timelike classical singularities, an extension of quantum singularities to conformally static spacetimes is summarized and applied to two test cases. The timelike classical singularities in a Friedmann-Robertson-Walker (FRW) universe with a cosmic string, and in Roberts spacetime, are shown to be quantum mechanically singular when tested by either minimally coupled or conformally coupled scalar waves. In the Roberts case, however, non-minimally coupled scalar waves with a coupling constant $\xi \ge 2$ do not detect the classical singularity. |
1207.3959 | Radouane Gannouji | Amna Ali, Radouane Gannouji, Md. Wali Hossain, M. Sami | Light mass galileons: Cosmological dynamics, mass screening and
observational constraints | 9 pages, 8 figures, minor clarifications added, final version to
appear in PLB | Phys.Lett. B718 (2012) 5-14 | 10.1016/j.physletb.2012.10.009 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine the cosmological viability of a light mass galileon
field consistent with local gravity constraints. The minimal,
L_3=\Box\phi(\partial_\mu \phi)^2, massless galileon field requires an
additional term in order to give rise to a viable ghost free late time
acceleration of Universe. The desired cosmological dynamics can either be
achieved by incorporating an additional terms in the action such as (L_4,L_5) -
the higher order galileon Lagrangians or by considering a light mass field a la
galileon field potential. We analyse the second possibility and find that: (1)
The model produces a viable cosmology in the regime where the non-linear
galileon field is subdominant, (2) The Vainshtein mechanism operates at small
scales where the non-linear effects become important and contribution of the
field potential ceases to be significant. Also the small mass of the field
under consideration is protected against strong quantum corrections thereby
providing quantum stability to the system.
| [
{
"created": "Tue, 17 Jul 2012 11:50:08 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Oct 2012 01:42:58 GMT",
"version": "v2"
}
] | 2014-06-11 | [
[
"Ali",
"Amna",
""
],
[
"Gannouji",
"Radouane",
""
],
[
"Hossain",
"Md. Wali",
""
],
[
"Sami",
"M.",
""
]
] | In this paper, we examine the cosmological viability of a light mass galileon field consistent with local gravity constraints. The minimal, L_3=\Box\phi(\partial_\mu \phi)^2, massless galileon field requires an additional term in order to give rise to a viable ghost free late time acceleration of Universe. The desired cosmological dynamics can either be achieved by incorporating an additional terms in the action such as (L_4,L_5) - the higher order galileon Lagrangians or by considering a light mass field a la galileon field potential. We analyse the second possibility and find that: (1) The model produces a viable cosmology in the regime where the non-linear galileon field is subdominant, (2) The Vainshtein mechanism operates at small scales where the non-linear effects become important and contribution of the field potential ceases to be significant. Also the small mass of the field under consideration is protected against strong quantum corrections thereby providing quantum stability to the system. |
2405.13079 | Malihe Heydari-Fard | Mitra Darvishi, Malihe Heydari-Fard and Morteza Mohseni | On optical appearance of Einstein-Maxwell-{\AE}ther black holes
surrounded by various accretions | 21 pages, 13 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | In this paper, we investigate the effects of the {\ae}ther field and the
electric charge on the observed shadow of two types of charged black holes in
the Einstein-Maxwell-{\AE}ther theory. By considering that the
Einstein-Maxwell-{\AE}ther black holes surrounded by the static/infalling
spherical accretion flows, as well as an optically and geometrically thin disk
accretion flow, we study the shadow luminosities and the observed specific
intensity of the image for these various profiles of accretion flows. We find
that in the thin disk accretion model the location and the emitted model of the
accretion gas affect on the optical appearance of charged Einstein-{\AE}ther
black holes in contrast to the spherical accretion flows. For a thin disk
profile, we show that the observer will receive more intensity for an emitted
model as Gaussian function when the innermost radiation radius lies in the
innermost stable circular orbit. Finally, comparing the results of the charged
Einstein-{\AE}ther black holes with neutral Einstein-{\AE}ther black holes, we
show that the charged Einstein-{\AE}ther black holes have smaller dark area,
whereas wider lensed ring and photon ring. Comparing the charged
Einstein-{\AE}ther black holes with Reissner-Nordstrom black hole gives a
reverse effect.
| [
{
"created": "Tue, 21 May 2024 05:23:06 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Darvishi",
"Mitra",
""
],
[
"Heydari-Fard",
"Malihe",
""
],
[
"Mohseni",
"Morteza",
""
]
] | In this paper, we investigate the effects of the {\ae}ther field and the electric charge on the observed shadow of two types of charged black holes in the Einstein-Maxwell-{\AE}ther theory. By considering that the Einstein-Maxwell-{\AE}ther black holes surrounded by the static/infalling spherical accretion flows, as well as an optically and geometrically thin disk accretion flow, we study the shadow luminosities and the observed specific intensity of the image for these various profiles of accretion flows. We find that in the thin disk accretion model the location and the emitted model of the accretion gas affect on the optical appearance of charged Einstein-{\AE}ther black holes in contrast to the spherical accretion flows. For a thin disk profile, we show that the observer will receive more intensity for an emitted model as Gaussian function when the innermost radiation radius lies in the innermost stable circular orbit. Finally, comparing the results of the charged Einstein-{\AE}ther black holes with neutral Einstein-{\AE}ther black holes, we show that the charged Einstein-{\AE}ther black holes have smaller dark area, whereas wider lensed ring and photon ring. Comparing the charged Einstein-{\AE}ther black holes with Reissner-Nordstrom black hole gives a reverse effect. |
0808.4080 | Cecilia Chirenti | Cecilia B. M. H. Chirenti and Luciano Rezzolla | On the ergoregion instability in rotating gravastars | 10 pages, 7 figures | Phys.Rev.D78:084011,2008 | 10.1103/PhysRevD.78.084011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ergoregion instability is known to affect very compact objects that
rotate very rapidly and do not possess a horizon. We present here a detailed
analysis on the relevance of the ergoregion instability for the viability of
gravastars. Expanding on some recent results, we show that not all rotating
gravastars are unstable. Rather, stable models can be constructed also with
J/M^2 ~ 1, where J and M are the angular momentum and mass of the gravastar,
respectively. The genesis of gravastars is still highly speculative and
fundamentally unclear if not dubious. Yet, their existence cannot be ruled out
by invoking the ergoregion instability. For the same reason, not all
ultra-compact astrophysical objects rotating with J/M^2 <~ 1 are to be
considered necessarily black holes.
| [
{
"created": "Fri, 29 Aug 2008 13:20:21 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chirenti",
"Cecilia B. M. H.",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | The ergoregion instability is known to affect very compact objects that rotate very rapidly and do not possess a horizon. We present here a detailed analysis on the relevance of the ergoregion instability for the viability of gravastars. Expanding on some recent results, we show that not all rotating gravastars are unstable. Rather, stable models can be constructed also with J/M^2 ~ 1, where J and M are the angular momentum and mass of the gravastar, respectively. The genesis of gravastars is still highly speculative and fundamentally unclear if not dubious. Yet, their existence cannot be ruled out by invoking the ergoregion instability. For the same reason, not all ultra-compact astrophysical objects rotating with J/M^2 <~ 1 are to be considered necessarily black holes. |
gr-qc/9710061 | Jai-chan Hwang | J. Hwang | Gravitational Wave Spectrums from Pole-like Inflations based on
Generalized Gravity Theories | 11 pages, revtex, no figures | Class.Quant.Grav. 15 (1998) 1401-1413 | 10.1088/0264-9381/15/5/021 | null | gr-qc | null | We present a general and unified formulation which can handle the classical
evolution and quantum generation processes of the cosmological gravitational
wave in a broad class of generalized gravity theories. Applications are made in
several inflation models based on the scalar-tensor theory, the induced
gravity, and the low energy effective action of string theory. The
gravitational wave power spectrums based on the vacuum expectation value of the
quantized fluctuating metric during the pole-like inflation stages are derived
in analytic forms. Assuming that the gravity theory transits to Einstein one
while the relevant scales remain in the superhorizon scale, we derive the
consequent power spectrums and the directional fluctuations of the relic
radiation produced by the gravitational wave. The spectrums seeded by the
vacuum fluctuations in the pole-like inflation models based on the generalized
gravity show a distinguished common feature which differs from the scale
invariant spectrum generated in an exponential inflation in Einstein gravity
which is supported by observations.
| [
{
"created": "Fri, 10 Oct 1997 16:50:15 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Hwang",
"J.",
""
]
] | We present a general and unified formulation which can handle the classical evolution and quantum generation processes of the cosmological gravitational wave in a broad class of generalized gravity theories. Applications are made in several inflation models based on the scalar-tensor theory, the induced gravity, and the low energy effective action of string theory. The gravitational wave power spectrums based on the vacuum expectation value of the quantized fluctuating metric during the pole-like inflation stages are derived in analytic forms. Assuming that the gravity theory transits to Einstein one while the relevant scales remain in the superhorizon scale, we derive the consequent power spectrums and the directional fluctuations of the relic radiation produced by the gravitational wave. The spectrums seeded by the vacuum fluctuations in the pole-like inflation models based on the generalized gravity show a distinguished common feature which differs from the scale invariant spectrum generated in an exponential inflation in Einstein gravity which is supported by observations. |
gr-qc/0605085 | Neil J. Cornish | Neil J. Cornish and Edward K. Porter | MCMC Exploration of Supermassive Black Hole Binary Inspirals | Submitted to CQG as a GWDAW-10 Conference Proceedings, 9 pages, 5
figures, Published Version | Class.Quant.Grav. 23 (2006) S761-S768 | 10.1088/0264-9381/23/19/S15 | null | gr-qc | null | The Laser Interferometer Space Antenna will be able to detect the inspiral
and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the
Universe. Standard matched filtering techniques can be used to detect and
characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally
suited to this and other LISA data analysis problems as they are able to
efficiently handle models with large dimensions. Here we compare the posterior
parameter distributions derived by an MCMC algorithm with the distributions
predicted by the Fisher information matrix. We find excellent agreement for the
extrinsic parameters, while the Fisher matrix slightly overestimates errors in
the intrinsic parameters.
| [
{
"created": "Mon, 15 May 2006 03:22:28 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Aug 2006 18:10:03 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Cornish",
"Neil J.",
""
],
[
"Porter",
"Edward K.",
""
]
] | The Laser Interferometer Space Antenna will be able to detect the inspiral and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the Universe. Standard matched filtering techniques can be used to detect and characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally suited to this and other LISA data analysis problems as they are able to efficiently handle models with large dimensions. Here we compare the posterior parameter distributions derived by an MCMC algorithm with the distributions predicted by the Fisher information matrix. We find excellent agreement for the extrinsic parameters, while the Fisher matrix slightly overestimates errors in the intrinsic parameters. |
1210.0981 | Narayan Banerjee | Koyel Ganguly, Narayan Banerjee | Spherically symmetric scalar field collapse | 10 pages, 4 figures; Accepted for publication in Pramana- Journal of
Physics, 2012 | null | 10.1007/s12043-012-0498-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that a scalar field, minimally coupled to gravity may have
collapsing modes even when the energy condition is violated, that is, for
$(\rho+3p)<0$. This result may be useful in the investigation of the possible
clustering of dark energy. All the examples dealt with have apparent horizons
which form before the formation of the singularity. The singularities formed
are shell focusing in nature. The density of the scalar field distribution is
seen to diverge at singularity. The Ricci scalar also diverges at the
singularity. The interior spherically symmetric metric is matched with exterior
Vaidya metric at the hypersurface and the appropriate junction conditions are
obtained.
| [
{
"created": "Wed, 3 Oct 2012 05:09:54 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Ganguly",
"Koyel",
""
],
[
"Banerjee",
"Narayan",
""
]
] | It is shown that a scalar field, minimally coupled to gravity may have collapsing modes even when the energy condition is violated, that is, for $(\rho+3p)<0$. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons which form before the formation of the singularity. The singularities formed are shell focusing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained. |
1709.08978 | Moonju Hong | Moonju Hong | Motion of a Test Particle in the Reissner-Nordstrom Spacetime | 7 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper focuses on the motion of a test particle moving around the
Reissner-Nordstrom black hole. It deals with circular motion and radial motion
of the neutral massive test particles, and shortly handles circular motion of
the charged massive test particles. Both neutral and charged particles are
affected by black hole's charge, but it is due to the fact that charge of the
black hole bends the spacetime more strongly. This procedure has nothing to do
with electromagnetic interactions, and these are only considered for charged
test particles. However, it only treats mathematically easy, approximated
situations and general motions and complex motions will not be discussed. This
paper has tried to get some physical information only with the easiest
mathematical tools and without difficult concepts that general relativity
contains. Contents of this paper would be suitable for those who want to know
something about the Reissner-Nordstrom black hole, but does not have much
knowledge in this field. They can begin their intellectual journey with this
paper.
| [
{
"created": "Tue, 26 Sep 2017 12:39:24 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Oct 2017 14:04:42 GMT",
"version": "v2"
}
] | 2017-10-06 | [
[
"Hong",
"Moonju",
""
]
] | This paper focuses on the motion of a test particle moving around the Reissner-Nordstrom black hole. It deals with circular motion and radial motion of the neutral massive test particles, and shortly handles circular motion of the charged massive test particles. Both neutral and charged particles are affected by black hole's charge, but it is due to the fact that charge of the black hole bends the spacetime more strongly. This procedure has nothing to do with electromagnetic interactions, and these are only considered for charged test particles. However, it only treats mathematically easy, approximated situations and general motions and complex motions will not be discussed. This paper has tried to get some physical information only with the easiest mathematical tools and without difficult concepts that general relativity contains. Contents of this paper would be suitable for those who want to know something about the Reissner-Nordstrom black hole, but does not have much knowledge in this field. They can begin their intellectual journey with this paper. |
gr-qc/9503015 | I\qigo Luis Egusquiza Egusquiza | I.L. Egusquiza (University of the Basque Country) | Self-adjoint extensions and Signature Change | 7 pages, REVTEX | Class.Quant.Grav. 12 (1995) L89-L92 | 10.1088/0264-9381/12/9/001 | null | gr-qc | null | We study the selfadjoint extensions of the spatial part of the D'Alembert
operator in a spacetime with two changes of signature. We identify a set of
boundary conditions, parametrised by U(2) matrices, which correspond to
Dirichlet boundary conditions for the fields, and from which we argue against
the suggestion that regions of signature change can isolate singularities.
| [
{
"created": "Wed, 8 Mar 1995 19:23:00 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Egusquiza",
"I. L.",
"",
"University of the Basque Country"
]
] | We study the selfadjoint extensions of the spatial part of the D'Alembert operator in a spacetime with two changes of signature. We identify a set of boundary conditions, parametrised by U(2) matrices, which correspond to Dirichlet boundary conditions for the fields, and from which we argue against the suggestion that regions of signature change can isolate singularities. |
1909.11044 | Andrzej Krasi\'nski | Andrzej Krasi\'nski | Gamma radiation from areal radius minima in a quasi-spherical Szekeres
metric | 35 pages, 9 figures. Literature on GRBs updated, conclusions section
extended, small editorial corrections. This text matches the published one.
Length spuriously increased because of APPB page display | Acta Phys. Polon. B51, 483 (2020) | 10.5506/APhysPolB.51.483 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous papers it was shown that in a quasi-spherical Szekeres (QSS)
metric, impulses of gamma radiation can arise that have several properties in
common with the observed gamma-ray bursts. This happens when the bang-time
function $t_B(r)$ has a gate-shaped hump around the origin of the QSS region.
The gamma rays arise along two preferred directions of the QSS geometry
(coincident with dipole extrema when axially symmetric, otherwise unrelated).
In these directions, the rays of the relic radiation are blueshifted rather
than redshifted. The blueshift is generated in a thin region between the Big
Bang (BB) and the extremum-redshift hypersurface (ERH). But the Szekeres models
can describe the real Universe only forward in time from the last-scattering
hypersurface (LSH) because the matter in them has zero pressure. The ERH is
tangent to the BB at the origin, so in a neighbourhood thereof the ERH lies
earlier than the LSH and no blueshift is generated in the physical region. The
question thus arose whether the BB and ERH can be ``unglued'' if the QSS region
has no origin, but the areal radius function $\Phi$ has a local maximum or
minimum somewhere. In the present paper it is demonstrated that this is indeed
the case. If the hump in $t_B(r)$ is centered around the minimum of $\Phi$,
then the BB and ERH in general do not coincide there and a stronger blueshift
is generated on rays passing nearby. It follows that a lower and narrower hump
on the BB set can generate sufficient blueshift to move the initial frequencies
of the relic radiation to the gamma range. These facts are demonstrated by
numerical calculations in an explicit example of a QSS region.
| [
{
"created": "Tue, 24 Sep 2019 16:53:24 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Feb 2020 13:04:26 GMT",
"version": "v2"
}
] | 2020-04-22 | [
[
"Krasiński",
"Andrzej",
""
]
] | In previous papers it was shown that in a quasi-spherical Szekeres (QSS) metric, impulses of gamma radiation can arise that have several properties in common with the observed gamma-ray bursts. This happens when the bang-time function $t_B(r)$ has a gate-shaped hump around the origin of the QSS region. The gamma rays arise along two preferred directions of the QSS geometry (coincident with dipole extrema when axially symmetric, otherwise unrelated). In these directions, the rays of the relic radiation are blueshifted rather than redshifted. The blueshift is generated in a thin region between the Big Bang (BB) and the extremum-redshift hypersurface (ERH). But the Szekeres models can describe the real Universe only forward in time from the last-scattering hypersurface (LSH) because the matter in them has zero pressure. The ERH is tangent to the BB at the origin, so in a neighbourhood thereof the ERH lies earlier than the LSH and no blueshift is generated in the physical region. The question thus arose whether the BB and ERH can be ``unglued'' if the QSS region has no origin, but the areal radius function $\Phi$ has a local maximum or minimum somewhere. In the present paper it is demonstrated that this is indeed the case. If the hump in $t_B(r)$ is centered around the minimum of $\Phi$, then the BB and ERH in general do not coincide there and a stronger blueshift is generated on rays passing nearby. It follows that a lower and narrower hump on the BB set can generate sufficient blueshift to move the initial frequencies of the relic radiation to the gamma range. These facts are demonstrated by numerical calculations in an explicit example of a QSS region. |
gr-qc/0504040 | Yu Tian | Yu Tian | De Sitter Thermodynamics from Diamonds's Temperature | 10 pages, 3 figures, LaTeX; v2: reorganized with a new section added
concerning a generalization of the GEMS picture from our result; v3: version
with minor corrections, to appear in JHEP | JHEP0506:045,2005 | 10.1088/1126-6708/2005/06/045 | null | gr-qc hep-th | null | The thermal time hypothesis proposed by Rovelli [1] regards the physical
basis for the flow of time as thermodynamical and provides a definition of the
temperature for some special cases. We verify this hypothesis in the case of de
Sitter spacetime by relating the uniformly accelerated observer in de Sitter
spacetime to the diamond in Minkowski spacetime. Then, as an application of it,
we investigate the thermal effect for the uniformly accelerated observer with a
finite lifetime in dS spacetime, which generalizes the corresponding result for
the case of Minkowski spacetime [2].
Furthermore, noticing that a uniformly accelerated dS observer with a finite
lifetime corresponds to a Rindler observer with a finite lifetime in the
embedding Minkowski spacetime, we show that the
global-embedding-Minkowski-spacetime (GEMS) picture of spacetime thermodynamics
is valid in this case. This is a rather nontrivial and unexpected
generalization of the GEMS picture, as well as a further verification of both
the thermal time hypothesis and the GEMS picture.
| [
{
"created": "Mon, 11 Apr 2005 11:53:02 GMT",
"version": "v1"
},
{
"created": "Wed, 11 May 2005 07:11:51 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Jun 2005 13:40:15 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Tian",
"Yu",
""
]
] | The thermal time hypothesis proposed by Rovelli [1] regards the physical basis for the flow of time as thermodynamical and provides a definition of the temperature for some special cases. We verify this hypothesis in the case of de Sitter spacetime by relating the uniformly accelerated observer in de Sitter spacetime to the diamond in Minkowski spacetime. Then, as an application of it, we investigate the thermal effect for the uniformly accelerated observer with a finite lifetime in dS spacetime, which generalizes the corresponding result for the case of Minkowski spacetime [2]. Furthermore, noticing that a uniformly accelerated dS observer with a finite lifetime corresponds to a Rindler observer with a finite lifetime in the embedding Minkowski spacetime, we show that the global-embedding-Minkowski-spacetime (GEMS) picture of spacetime thermodynamics is valid in this case. This is a rather nontrivial and unexpected generalization of the GEMS picture, as well as a further verification of both the thermal time hypothesis and the GEMS picture. |
gr-qc/9707043 | Takeshi Chiba | Takeshi Chiba, Shinji Mukohyama, and Takashi Nakamura | Anisotropy of the Cosmic Background Radiation implies the Violation of
the Strong Energy Condition in Bianchi type I Universe | 9 pages, to appear in Physics Letters B | Phys.Lett. B408 (1997) 47-51 | 10.1016/S0370-2693(97)00782-X | YITP-97-3 | gr-qc astro-ph | null | We consider the horizon problem in a homogeneous but anisotropic universe
(Bianchi type I). We show that the problem cannot be solved if (1) the matter
obeys the strong energy condition with the positive energy density and (2) the
Einstein equations hold. The strong energy condition is violated during
cosmological inflation.
| [
{
"created": "Fri, 18 Jul 1997 12:35:05 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Chiba",
"Takeshi",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Nakamura",
"Takashi",
""
]
] | We consider the horizon problem in a homogeneous but anisotropic universe (Bianchi type I). We show that the problem cannot be solved if (1) the matter obeys the strong energy condition with the positive energy density and (2) the Einstein equations hold. The strong energy condition is violated during cosmological inflation. |
2204.03566 | Nicolas Arnaud | Nicolas Arnaud | LIGO-Virgo detector characterization and data quality (DetChar): from
the O3 performance to the O4 preparation | Contribution to the 2021 Gravitation session of the 55th Rencontres
de Moriond. On behalf of the LIGO and Virgo DetChar groups | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Detector characterization and data quality -- in short "DetChar" --
activities are key to optimize the performance of data-taking periods ("runs")
and to turn gravitational-wave (GW) candidates into confirmed events. The LIGO
and Virgo DetChar groups are active from the detector to the final analysis and
cover various latencies: online first, to tag the data that search pipelines
can analyze in real-time; then, the quick vetting (few tens of minutes at most)
of the open public alerts targeting the broad astronomer community for
follow-up observations; finally, offline work to define the final datasets and
the final lists of GW events to be published and released publicly.
These proceedings summarize the LIGO-Virgo DetChar performance during the O3
run (April 2019 - March 2020) and describe the main improvements and upgrades
that are foreseen for the O4 run that should start during Summer 2022 and
include a fourth detector: KAGRA.
| [
{
"created": "Thu, 7 Apr 2022 16:42:17 GMT",
"version": "v1"
}
] | 2022-04-08 | [
[
"Arnaud",
"Nicolas",
""
]
] | Detector characterization and data quality -- in short "DetChar" -- activities are key to optimize the performance of data-taking periods ("runs") and to turn gravitational-wave (GW) candidates into confirmed events. The LIGO and Virgo DetChar groups are active from the detector to the final analysis and cover various latencies: online first, to tag the data that search pipelines can analyze in real-time; then, the quick vetting (few tens of minutes at most) of the open public alerts targeting the broad astronomer community for follow-up observations; finally, offline work to define the final datasets and the final lists of GW events to be published and released publicly. These proceedings summarize the LIGO-Virgo DetChar performance during the O3 run (April 2019 - March 2020) and describe the main improvements and upgrades that are foreseen for the O4 run that should start during Summer 2022 and include a fourth detector: KAGRA. |
1404.3224 | Alessandro Fabbri | Paul R. Anderson, Roberto Balbinot, Alessandro Fabbri and Renaud
Parentani | Gray-body factor and infrared divergences in 1D BEC acoustic black holes | 6 pages, 2 figures. Final version. A double misprint in Eq. (21) of
the published version has been corrected here | Phys. Rev. D 90, 104044 (2014) | 10.1103/PhysRevD.90.104044 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the gray-body factor for a one-dimensional elongated
Bose-Einstein condensate (BEC) acoustic black hole with one horizon does not
vanish in the low-frequency ($\omega\to 0$) limit. This implies that the analog
Hawking radiation is dominated by the emission of an infinite number
($\frac{1}{\omega}$) of soft phonons in contrast with the case of a
Schwarzschild black hole where the gray-body factor vanishes as $\omega\to 0$
and the spectrum is not dominated by low-energy particles. The infrared
behaviors of certain correlation functions are also discussed.
| [
{
"created": "Fri, 11 Apr 2014 21:13:18 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Sep 2014 20:03:37 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Jan 2015 21:05:03 GMT",
"version": "v3"
}
] | 2015-01-12 | [
[
"Anderson",
"Paul R.",
""
],
[
"Balbinot",
"Roberto",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Parentani",
"Renaud",
""
]
] | It is shown that the gray-body factor for a one-dimensional elongated Bose-Einstein condensate (BEC) acoustic black hole with one horizon does not vanish in the low-frequency ($\omega\to 0$) limit. This implies that the analog Hawking radiation is dominated by the emission of an infinite number ($\frac{1}{\omega}$) of soft phonons in contrast with the case of a Schwarzschild black hole where the gray-body factor vanishes as $\omega\to 0$ and the spectrum is not dominated by low-energy particles. The infrared behaviors of certain correlation functions are also discussed. |
1309.7464 | Shabbir Ghulam | Ghulam Shabbir, K S Mahomed, R J Moitsheki | A note on proper affine vector fields in special non static axially
symmetric Lorentzian manifolds | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A study of proper affine vector fields in non static axially symmetric
space-times is given by using holonomy and decomposability, the rank of the 6X6
Riemann matrix and direct integration techniques. It is shown that the special
class of the above space-times admits proper affine vector fields.
| [
{
"created": "Sat, 28 Sep 2013 14:10:34 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jan 2017 07:09:40 GMT",
"version": "v2"
}
] | 2017-01-11 | [
[
"Shabbir",
"Ghulam",
""
],
[
"Mahomed",
"K S",
""
],
[
"Moitsheki",
"R J",
""
]
] | A study of proper affine vector fields in non static axially symmetric space-times is given by using holonomy and decomposability, the rank of the 6X6 Riemann matrix and direct integration techniques. It is shown that the special class of the above space-times admits proper affine vector fields. |
1603.07742 | Parthapratim Pradhan | Parthapratim Pradhan | Area Functional Relation for 5D-Gauss-Bonnet-AdS Black Hole | Version accepted for publication in General Relativity and
Gravitation | General Relativity and Gravitation, August 2016, 48:116 | 10.1007/s10714-016-2109-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present \emph{area (or entropy) functional relation} for multi-horizons
five dimensional (5D) Einstein-Maxwell-Gauss-Bonnet-AdS Black Hole. It has been
observed by exact and explicit calculation that some complicated function of
two or three horizons area is \emph{mass-independent} whereas the entropy
product relation is \emph{not} mass-independent. We also study the local
thermodynamic stability of this black hole. The phase transition occurs at
certain condition. \emph{Smarr mass formula} and \emph{first law} of
thermodynamics have been derived. This \emph{mass-independent} relation
suggests they could turn out to be an \emph{universal} quantity and further
helps us to understanding the nature of black hole entropy (both interior and
exterior) at the microscopic level. In the \emph{Appendix}, we have derived the
thermodynamic products for 5D Einstein-Maxwell-Gauss-Bonnet black hole with
\emph{vanishing} cosmological constant.
| [
{
"created": "Thu, 24 Mar 2016 20:25:27 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2016 20:53:38 GMT",
"version": "v2"
}
] | 2016-08-03 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We present \emph{area (or entropy) functional relation} for multi-horizons five dimensional (5D) Einstein-Maxwell-Gauss-Bonnet-AdS Black Hole. It has been observed by exact and explicit calculation that some complicated function of two or three horizons area is \emph{mass-independent} whereas the entropy product relation is \emph{not} mass-independent. We also study the local thermodynamic stability of this black hole. The phase transition occurs at certain condition. \emph{Smarr mass formula} and \emph{first law} of thermodynamics have been derived. This \emph{mass-independent} relation suggests they could turn out to be an \emph{universal} quantity and further helps us to understanding the nature of black hole entropy (both interior and exterior) at the microscopic level. In the \emph{Appendix}, we have derived the thermodynamic products for 5D Einstein-Maxwell-Gauss-Bonnet black hole with \emph{vanishing} cosmological constant. |
1905.04133 | Metin Gurses | Metin Gurses and Yaghoub Heydarzade | New Classes of Spherically Symmetric, Inhomogeneous Cosmological Models | 35 pages one figure and two tables | Phys. Rev. D 100, 064048 (2019) | 10.1103/PhysRevD.100.064048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present two classes of inhomogeneous, spherically symmetric solutions of
the Einstein-Maxwell-Perfect Fluid field equations with cosmological constant
generalizing the Vaidya-Shah solution. Some special limits of our solution
reduce to the known inhomogeneous charged perfect fluid solutions of the
Einstein field equations and under some other limits we obtain new charged and
uncharged solutions with cosmological constant. Uncharged solutions in
particular represent cosmological models where the universe may undergo a
topology change and in between is a mixture of two different
Friedmann-Robertson-Walker universes with different spatial curvatures. We show
that there exist some spacelike surfaces where the Ricci scalar and pressure of
the fluid diverge but the mass density of the fluid distribution remains
finite. Such spacelike surfaces are known as (sudden) cosmological
singularities. We study the behavior of our new solutions in their general form
as the radial distance goes to zero and infinity. Finally, we briefly address
the null geodesics and apparent horizons associated to the obtained solutions.
| [
{
"created": "Fri, 10 May 2019 12:50:33 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Oct 2019 14:29:17 GMT",
"version": "v2"
}
] | 2019-10-09 | [
[
"Gurses",
"Metin",
""
],
[
"Heydarzade",
"Yaghoub",
""
]
] | We present two classes of inhomogeneous, spherically symmetric solutions of the Einstein-Maxwell-Perfect Fluid field equations with cosmological constant generalizing the Vaidya-Shah solution. Some special limits of our solution reduce to the known inhomogeneous charged perfect fluid solutions of the Einstein field equations and under some other limits we obtain new charged and uncharged solutions with cosmological constant. Uncharged solutions in particular represent cosmological models where the universe may undergo a topology change and in between is a mixture of two different Friedmann-Robertson-Walker universes with different spatial curvatures. We show that there exist some spacelike surfaces where the Ricci scalar and pressure of the fluid diverge but the mass density of the fluid distribution remains finite. Such spacelike surfaces are known as (sudden) cosmological singularities. We study the behavior of our new solutions in their general form as the radial distance goes to zero and infinity. Finally, we briefly address the null geodesics and apparent horizons associated to the obtained solutions. |
1806.05407 | Tomislav Prokopec | Lei-Hua Liu, Tomislav Prokopec and Alexei A. Starobinsky | Inflation in an effective gravitational model & asymptotic safety | 29 pages, 6 figures | Phys. Rev. D 98, 043505 (2018) | 10.1103/PhysRevD.98.043505 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an inflationary model motivated by quantum effects of
gravitational and matter fields near the Planck scale. Our Lagrangian is a
re-summed version of the effective Lagrangian recently obtained by Demmel,
Saueressig and Zanusso~\cite{Demmel:2015oqa} in the context of gravity as an
asymptotically safe theory. It represents a refined Starobinsky model, ${\cal
L}_{\rm eff}=M_{\rm P}^2 R/2 + (a/2)R^2/[1+b\ln(R/\mu^2)]$, where $R$ is the
Ricci scalar, $a$ and $b$ are constants and $\mu$ is an energy scale. By
implementing the COBE normalisation and the Planck constraint on the scalar
spectrum, we show that increasing $b$ leads to an increased value of both the
scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$. Requiring $n_s$
to be consistent with the Planck collaboration upper limit, we find that $r$
can be as large as $r\simeq 0.01$, the value possibly measurable by Stage IV
CMB ground experiments and certainly from future dedicated space missions. The
predicted running of the scalar spectral index $\alpha=d n_s/d\ln(k)$ is still
of the order $-5\times 10^{-4}$ (as in the Starobinsky model), about one order
of magnitude smaller than the current observational bound.
| [
{
"created": "Thu, 14 Jun 2018 08:09:29 GMT",
"version": "v1"
}
] | 2018-08-15 | [
[
"Liu",
"Lei-Hua",
""
],
[
"Prokopec",
"Tomislav",
""
],
[
"Starobinsky",
"Alexei A.",
""
]
] | We consider an inflationary model motivated by quantum effects of gravitational and matter fields near the Planck scale. Our Lagrangian is a re-summed version of the effective Lagrangian recently obtained by Demmel, Saueressig and Zanusso~\cite{Demmel:2015oqa} in the context of gravity as an asymptotically safe theory. It represents a refined Starobinsky model, ${\cal L}_{\rm eff}=M_{\rm P}^2 R/2 + (a/2)R^2/[1+b\ln(R/\mu^2)]$, where $R$ is the Ricci scalar, $a$ and $b$ are constants and $\mu$ is an energy scale. By implementing the COBE normalisation and the Planck constraint on the scalar spectrum, we show that increasing $b$ leads to an increased value of both the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$. Requiring $n_s$ to be consistent with the Planck collaboration upper limit, we find that $r$ can be as large as $r\simeq 0.01$, the value possibly measurable by Stage IV CMB ground experiments and certainly from future dedicated space missions. The predicted running of the scalar spectral index $\alpha=d n_s/d\ln(k)$ is still of the order $-5\times 10^{-4}$ (as in the Starobinsky model), about one order of magnitude smaller than the current observational bound. |
1412.7899 | Sijie Gao | Sijie Gao and Xiaobao Wang | Thin shell model revisited | 12 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconsider some fundamental problems of the thin shell model. First, we
point out that the "cut and paste" construction does not guarantee a
well-defined manifold because there is no overlap of coordinates across the
shell. When one requires that the spacetime metric across the thin shell is
continuous, it also provides a way to specify the tangent space and the
manifold. Other authors have shown that this specification leads to the
conservation laws when shells collide. On the other hand, the well-known areal
radius $r$ seems to be a perfect coordinate covering all regions of a
spherically symmetric spacetime. However, we show by simple but rigorous
arguments that $r$ fails to be a coordinate covering a neighborhood of the thin
shell if the metric across the shell is continuous. When two spherical shells
collide and merge into one, we show that it is possible that $r$ remains to be
a good coordinate and the conservation laws hold. To make this happen,
different spacetime regions divided by the shells must be glued in a specific
way such that some constraints are satisfied. We compare our new construction
with the old one by solving constraints numerically.
| [
{
"created": "Fri, 26 Dec 2014 07:00:44 GMT",
"version": "v1"
}
] | 2014-12-30 | [
[
"Gao",
"Sijie",
""
],
[
"Wang",
"Xiaobao",
""
]
] | We reconsider some fundamental problems of the thin shell model. First, we point out that the "cut and paste" construction does not guarantee a well-defined manifold because there is no overlap of coordinates across the shell. When one requires that the spacetime metric across the thin shell is continuous, it also provides a way to specify the tangent space and the manifold. Other authors have shown that this specification leads to the conservation laws when shells collide. On the other hand, the well-known areal radius $r$ seems to be a perfect coordinate covering all regions of a spherically symmetric spacetime. However, we show by simple but rigorous arguments that $r$ fails to be a coordinate covering a neighborhood of the thin shell if the metric across the shell is continuous. When two spherical shells collide and merge into one, we show that it is possible that $r$ remains to be a good coordinate and the conservation laws hold. To make this happen, different spacetime regions divided by the shells must be glued in a specific way such that some constraints are satisfied. We compare our new construction with the old one by solving constraints numerically. |
2305.04496 | Yongqiang Wang | Yuan Yue, Peng-Bo Ding, Yong-Qiang Wang | Boson star with parity-odd symmetry in wormhole spacetime | 9 pages, 5 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we revisit the model of bosonic matter in the form of a free
complex scalar field with a nontrivial wormhole spacetime topology supported by
a free phantom field. We obtain a new type of boson star with wormhole
solutions, in which the complex scalar field possess full parity-odd symmetry
with respect to the two asymptotically flat spacetime regions. When the size of
the throat is small, The behavior of boson stars with wormhole approaches that
of boson stars. When the size of the throat is intermediate, the typical
spiraling dependence of the mass and the particle number on the frequency of
the boson stars is replaced by a loop structure. However, as the size becomes
relatively large, the loop structure will also disappear. In particular, The
complex scalar field could form two boson stars with opposite phase differences
with respect to the two spacetime regions in the limit of vanishing throat
size. We analyze the properties of this new type of boson stars with wormhole
and further show that the wormhole spacetime geometry.
| [
{
"created": "Mon, 8 May 2023 06:46:26 GMT",
"version": "v1"
}
] | 2023-05-09 | [
[
"Yue",
"Yuan",
""
],
[
"Ding",
"Peng-Bo",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we revisit the model of bosonic matter in the form of a free complex scalar field with a nontrivial wormhole spacetime topology supported by a free phantom field. We obtain a new type of boson star with wormhole solutions, in which the complex scalar field possess full parity-odd symmetry with respect to the two asymptotically flat spacetime regions. When the size of the throat is small, The behavior of boson stars with wormhole approaches that of boson stars. When the size of the throat is intermediate, the typical spiraling dependence of the mass and the particle number on the frequency of the boson stars is replaced by a loop structure. However, as the size becomes relatively large, the loop structure will also disappear. In particular, The complex scalar field could form two boson stars with opposite phase differences with respect to the two spacetime regions in the limit of vanishing throat size. We analyze the properties of this new type of boson stars with wormhole and further show that the wormhole spacetime geometry. |
1610.02498 | Adam Chudecki Dr | Adam Chudecki | On geometry of congruences of null strings in 4-dimensional complex and
real pseudo-Riemannian spaces | null | Journal of Mathematical Physics 58, 112502 (2017) | 10.1063/1.4994166 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | 4-dimensional spaces equipped with 2-dimensional (complex holomorphic or real
smooth) completely integrable distributions are considered. The integral
manifolds of such distributions are totally null and totally geodesics
2-dimensional surfaces which are called the null strings. Properties of
congruences (foliations) of such 2-surfaces are studied. Some relations between
properties of congruences of null strings, Petrov-Penrose type of SD Weyl
spinor and algebraic types of the traceless Ricci tensor are analyzed.
| [
{
"created": "Sat, 8 Oct 2016 08:33:02 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2017 15:03:43 GMT",
"version": "v2"
}
] | 2017-11-21 | [
[
"Chudecki",
"Adam",
""
]
] | 4-dimensional spaces equipped with 2-dimensional (complex holomorphic or real smooth) completely integrable distributions are considered. The integral manifolds of such distributions are totally null and totally geodesics 2-dimensional surfaces which are called the null strings. Properties of congruences (foliations) of such 2-surfaces are studied. Some relations between properties of congruences of null strings, Petrov-Penrose type of SD Weyl spinor and algebraic types of the traceless Ricci tensor are analyzed. |
gr-qc/0110097 | Mauricio Cataldo | P. Salgado, M. Cataldo and S.del Campo | Supergravity and the Poincare group | 6 pages, Latex | Phys.Rev.D65:084032,2002 | 10.1103/PhysRevD.65.084032 | null | gr-qc | null | An action for 3+1-dimensional supergravity genuinely invariant under the
Poincare supergroup is proposed. The construction of the action is carried out
considering a bosonic lagrangian invariant under both local Lorentz rotations
and local Poincare translations as well as under diffeomorphism, and therefore
the Poincare algebra closes off-shell. Since the lagrangian is invariant under
the Poincare supergroup, the supersymmetry algebra closes off shell without the
need of auxiliary fields.
| [
{
"created": "Tue, 23 Oct 2001 13:35:08 GMT",
"version": "v1"
}
] | 2009-02-11 | [
[
"Salgado",
"P.",
""
],
[
"Cataldo",
"M.",
""
],
[
"del Campo",
"S.",
""
]
] | An action for 3+1-dimensional supergravity genuinely invariant under the Poincare supergroup is proposed. The construction of the action is carried out considering a bosonic lagrangian invariant under both local Lorentz rotations and local Poincare translations as well as under diffeomorphism, and therefore the Poincare algebra closes off-shell. Since the lagrangian is invariant under the Poincare supergroup, the supersymmetry algebra closes off shell without the need of auxiliary fields. |
1911.10560 | Pin Yu | Li Lai, Jiong-Yue Li and Pin Yu | On the rigidity of stationary charged black holes: small perturbations
of the non-extremal Kerr-Newman family | 36 pages, 4 figures | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a perturbative result concerning the uniqueness of Kerr-Newman
family of black holes: given an asymptotically flat space-time with bifurcate
horizons, if it agrees with a non-extremal Kerr-Newman space-time
asymptotically flat at infinity and it is sufficiently close to the Kerr-Newman
family, then the space-time must be one of the Kerr-Newman solutions. The
closeness to the Kerr-Newman family is measured by the smallness of a pair of
Mars-Simon type tensors, which were introduced by Wong in \cite{Wong_09} to
detect the Kerr-Newmann family.
| [
{
"created": "Sun, 24 Nov 2019 16:03:42 GMT",
"version": "v1"
}
] | 2019-11-26 | [
[
"Lai",
"Li",
""
],
[
"Li",
"Jiong-Yue",
""
],
[
"Yu",
"Pin",
""
]
] | We prove a perturbative result concerning the uniqueness of Kerr-Newman family of black holes: given an asymptotically flat space-time with bifurcate horizons, if it agrees with a non-extremal Kerr-Newman space-time asymptotically flat at infinity and it is sufficiently close to the Kerr-Newman family, then the space-time must be one of the Kerr-Newman solutions. The closeness to the Kerr-Newman family is measured by the smallness of a pair of Mars-Simon type tensors, which were introduced by Wong in \cite{Wong_09} to detect the Kerr-Newmann family. |
gr-qc/0003075 | Santiago Esteban Perez Bergliaffa | F. Baldovin, M. Novello, S. E. Perez Bergliaffa, and J.M. Salim | A nongravitational wormhole | LaTex, 9 pages with 5 figures, minor changes, accepted for
publication in Class. Quantum Grav | Class.Quant.Grav. 17 (2000) 3265-3276 | 10.1088/0264-9381/17/16/311 | null | gr-qc physics.optics | null | Using the effective metric formalism for photons in a nonlinear
electromagnetic theory, we show that a certain field configuration in
Born-Infeld electromagnetism in flat spacetime can be interpreted as an
ultrastatic spherically symmetric wormhole. We also discuss some properties of
the effective metric that are valid for any field configuration.
| [
{
"created": "Fri, 17 Mar 2000 20:58:36 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2000 12:24:37 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Baldovin",
"F.",
""
],
[
"Novello",
"M.",
""
],
[
"Bergliaffa",
"S. E. Perez",
""
],
[
"Salim",
"J. M.",
""
]
] | Using the effective metric formalism for photons in a nonlinear electromagnetic theory, we show that a certain field configuration in Born-Infeld electromagnetism in flat spacetime can be interpreted as an ultrastatic spherically symmetric wormhole. We also discuss some properties of the effective metric that are valid for any field configuration. |
1906.01991 | Andrea Geralico | Donato Bini, Andrea Geralico, Gabriele Gionti, Wolfango Plastino,
Nelson Velandia | Scattering of uncharged particles in the field of two extremely charged
black holes | 15 pages, 4 figures | null | 10.1007/s10714-019-2642-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the motion of uncharged particles scattered by a binary system
consisting of extremely charged black holes in equilibrium as described by the
Majumdar-Papapetrou solution. We focus on unbound orbits confined to the plane
containing both black holes. We consider the two complementary situations of
particles approaching the system along a direction parallel to the axis where
the black holes are displaced and orthogonal to it. We numerically compute the
scattering angle as a function of the particle's conserved energy parameter,
which provides a gauge-invariant information of the scattering process. We also
study the precession of a test gyroscope along such orbits and evaluate the
accumulated precession angle after a full scattering, which is another
gauge-invariant quantity.
| [
{
"created": "Wed, 5 Jun 2019 12:42:25 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Gionti",
"Gabriele",
""
],
[
"Plastino",
"Wolfango",
""
],
[
"Velandia",
"Nelson",
""
]
] | We investigate the motion of uncharged particles scattered by a binary system consisting of extremely charged black holes in equilibrium as described by the Majumdar-Papapetrou solution. We focus on unbound orbits confined to the plane containing both black holes. We consider the two complementary situations of particles approaching the system along a direction parallel to the axis where the black holes are displaced and orthogonal to it. We numerically compute the scattering angle as a function of the particle's conserved energy parameter, which provides a gauge-invariant information of the scattering process. We also study the precession of a test gyroscope along such orbits and evaluate the accumulated precession angle after a full scattering, which is another gauge-invariant quantity. |
gr-qc/0010103 | Gabriel Claude | Gabriel Cl | Spontaneous loss of charge of the Reissner-Nordstrom black hole | 10 pages, no figure, accepted for publication in Physical review D | Phys.Rev. D63 (2001) 024010 | null | null | gr-qc | null | In this paper, we study by a functional method the vacuum instability of a
charged scalar field, when it is quantized in the background of the
Reissner-Nordtrom black hole; we also show that the first stage of the
evaporation process of the black hole can be driven by a Schwinger-like effect.
| [
{
"created": "Fri, 27 Oct 2000 11:22:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cl",
"Gabriel",
""
]
] | In this paper, we study by a functional method the vacuum instability of a charged scalar field, when it is quantized in the background of the Reissner-Nordtrom black hole; we also show that the first stage of the evaporation process of the black hole can be driven by a Schwinger-like effect. |
2111.01149 | Sousuke Noda | Sousuke Noda, Yasusada Nambu, Masaaki Takahashi, Takuma Tsukamoto | Alfv\'enic superradiance for a monopole magnetosphere around a Kerr
black hole | 9 pages, 7 figures; matches published version in PRD | Phys. Rev. D 105, 064018 (2022) | 10.1103/PhysRevD.105.064018 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore superradiance for Alfv\'en waves (Alfv\'enic superradiance) in an
axisymmetric rotating magnetosphere of a Kerr black hole within the force-free
approximation. On the equatorial plane of the Kerr spacetime, the Alfv\'en wave
equation is reduced to a one-dimensional Schr\"{o}dinger-type equation by
separating variables of the wave function and introducing a tortoise coordinate
mapping the inner and outer light surfaces to $-\infty$ and $+\infty$,
respectively, and we investigate a wave scattering problem for Alfv\'en waves.
An analysis of the asymptotic solutions of the wave equation and the
conservation of the Wronskian give the superradiant condition for Alfv\'en
waves, and it will be shown that the condition coincides with that for the
Blandford-Znajek process. This means that when Alfv\'enic superradiance occurs,
the Blandford-Znajek process also occurs in the force-free magnetosphere. Then,
we evaluate the reflection rate of Alfv\'en waves numerically and confirm that
Alfv\'enic superradiance is indeed possible in the Kerr spacetime. Moreover, we
will discuss a resonant scattering of Alfv\'en waves, which is related to a
"quasinormal mode" of the magnetosphere.
| [
{
"created": "Mon, 1 Nov 2021 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Mar 2022 00:23:22 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Noda",
"Sousuke",
""
],
[
"Nambu",
"Yasusada",
""
],
[
"Takahashi",
"Masaaki",
""
],
[
"Tsukamoto",
"Takuma",
""
]
] | We explore superradiance for Alfv\'en waves (Alfv\'enic superradiance) in an axisymmetric rotating magnetosphere of a Kerr black hole within the force-free approximation. On the equatorial plane of the Kerr spacetime, the Alfv\'en wave equation is reduced to a one-dimensional Schr\"{o}dinger-type equation by separating variables of the wave function and introducing a tortoise coordinate mapping the inner and outer light surfaces to $-\infty$ and $+\infty$, respectively, and we investigate a wave scattering problem for Alfv\'en waves. An analysis of the asymptotic solutions of the wave equation and the conservation of the Wronskian give the superradiant condition for Alfv\'en waves, and it will be shown that the condition coincides with that for the Blandford-Znajek process. This means that when Alfv\'enic superradiance occurs, the Blandford-Znajek process also occurs in the force-free magnetosphere. Then, we evaluate the reflection rate of Alfv\'en waves numerically and confirm that Alfv\'enic superradiance is indeed possible in the Kerr spacetime. Moreover, we will discuss a resonant scattering of Alfv\'en waves, which is related to a "quasinormal mode" of the magnetosphere. |
1108.4342 | Larry Ford | Jen-Tsung Hsiang, Chun-Hsien Wu, L.H. Ford and Kin-Wang Ng | Quantum Stress Tensor Fluctuation Effects in Inflationary Cosmology | 8 pages, proceedings of IARD 2010, Conference on Classical and
Quantum Relativistic Dynamics of Particles and Fields, Hualien, Taiwan May
2010 | J. Phys. Conf. Series 330, 012006 (2011) | 10.1088/1742-6596/330/1/012006 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review several related investigations of the effects of the quantum stress
tensor of a conformal field in inflationary cosmology. Particular attention
will be paid to the effects of quantum stress tensor fluctuations as a source
of density and tensor perturbations in inflationary models. These effects can
possibly depend upon the total expansion factor during inflation, and hence be
much larger than one might otherwise expect. They have the potential to
contribute a non-scale invariant and non-Gaussian component to the primordial
spectrum of perturbations, and might be observable.
| [
{
"created": "Mon, 22 Aug 2011 15:18:54 GMT",
"version": "v1"
}
] | 2011-12-15 | [
[
"Hsiang",
"Jen-Tsung",
""
],
[
"Wu",
"Chun-Hsien",
""
],
[
"Ford",
"L. H.",
""
],
[
"Ng",
"Kin-Wang",
""
]
] | We review several related investigations of the effects of the quantum stress tensor of a conformal field in inflationary cosmology. Particular attention will be paid to the effects of quantum stress tensor fluctuations as a source of density and tensor perturbations in inflationary models. These effects can possibly depend upon the total expansion factor during inflation, and hence be much larger than one might otherwise expect. They have the potential to contribute a non-scale invariant and non-Gaussian component to the primordial spectrum of perturbations, and might be observable. |
2003.11831 | Rampei Kimura | A. Emir Gumrukcuoglu, Rampei Kimura, Kazuya Koyama | Massive gravity with non-minimal coupling | v2 : accepted for publication in PRD | Phys. Rev. D 101, 124021 (2020) | 10.1103/PhysRevD.101.124021 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose new massive gravity theories with 5 dynamical degrees of freedom.
We evade uniqueness theorems regarding the form of the kinetic and potential
terms by adopting the "generalized massive gravity" framework, where a global
translation invariance is broken. By exploiting the rotation symmetry in the
field space, we determine two novel classes of theories. The first one is an
extension of generalized massive gravity with a non-minimal coupling. On the
other hand, the second theory produces a mass term that is different from de
Rham, Gabadadze, Tolley construction and trivially has 5 degrees of freedom.
Both theories allows for stable cosmological solutions without infinite strong
coupling, which are free of ghost and gradient instabilities.
| [
{
"created": "Thu, 26 Mar 2020 11:00:27 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jun 2020 08:36:34 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Gumrukcuoglu",
"A. Emir",
""
],
[
"Kimura",
"Rampei",
""
],
[
"Koyama",
"Kazuya",
""
]
] | We propose new massive gravity theories with 5 dynamical degrees of freedom. We evade uniqueness theorems regarding the form of the kinetic and potential terms by adopting the "generalized massive gravity" framework, where a global translation invariance is broken. By exploiting the rotation symmetry in the field space, we determine two novel classes of theories. The first one is an extension of generalized massive gravity with a non-minimal coupling. On the other hand, the second theory produces a mass term that is different from de Rham, Gabadadze, Tolley construction and trivially has 5 degrees of freedom. Both theories allows for stable cosmological solutions without infinite strong coupling, which are free of ghost and gradient instabilities. |
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