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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2012.12355 | Fay\c{c}al Hammad | F. Hammad, P. Sadeghi, N. Fleury, A. Leblanc | What can we learn from the conformal noninvariance of the Klein-Gordon
equation? | Length reduced, typos corrected, references added, main results
emphasized. Accepted in IJMPA | Int. J. Mod. Phys. A 36, 2150224 (2021) | 10.1142/S0217751X21502249 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the Klein-Gordon equation in curved spacetime is
conformally noninvariant, both with and without a mass term. We show that such
a noninvariance provides nontrivial physical insights at different levels,
first within the fully relativistic regime, then in the nonrelativistic regime
leading to the Schr\"odinger equation, and then within the de Broglie-Bohm
causal interpretation of quantum mechanics. The conformal noninvariance of the
Klein-Gordon equation coupled to a vector potential is confronted with the
conformal invariance of Maxwell's equations in the presence of a charged
current. The conformal invariance of the non-minimally coupled Klein-Gordon
equation to gravity is then examined in light of the conformal invariance of
Maxwell's equations. Finally, the consequence of the noninvariance of the
equation on the Aharonov-Bohm effect in curved spacetime is discussed.
| [
{
"created": "Tue, 22 Dec 2020 21:09:20 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Nov 2021 12:09:59 GMT",
"version": "v2"
}
] | 2021-12-16 | [
[
"Hammad",
"F.",
""
],
[
"Sadeghi",
"P.",
""
],
[
"Fleury",
"N.",
""
],
[
"Leblanc",
"A.",
""
]
] | It is well known that the Klein-Gordon equation in curved spacetime is conformally noninvariant, both with and without a mass term. We show that such a noninvariance provides nontrivial physical insights at different levels, first within the fully relativistic regime, then in the nonrelativistic regime leading to the Schr\"odinger equation, and then within the de Broglie-Bohm causal interpretation of quantum mechanics. The conformal noninvariance of the Klein-Gordon equation coupled to a vector potential is confronted with the conformal invariance of Maxwell's equations in the presence of a charged current. The conformal invariance of the non-minimally coupled Klein-Gordon equation to gravity is then examined in light of the conformal invariance of Maxwell's equations. Finally, the consequence of the noninvariance of the equation on the Aharonov-Bohm effect in curved spacetime is discussed. |
gr-qc/9807062 | Mark E. Rupright | James W. York, Jr | Causal Propagation of Constraints and the Canonical Form of General
Relativity | 9 pages, no figures, Latex | null | null | IFP-UNC-525 | gr-qc | null | Studies of new hyperbolic systems for the Einstein evolution equations show
that the ``slicing density'' $\alpha(t,x)$ can be freely specified while the
lapse $N = \alpha g^{1/2}$ cannot. Implementation of this small change in the
Arnowitt-Deser-Misner action principle leads to canonical equations that agree
with the Einstein equations whether or not the constraints are satisfied. The
constraint functions, independently of their values, then propagate according
to a first order symmetric hyperbolic system whose characteristic cone is the
light cone. This result follows from the twice-contracted Bianchi identity and
constitutes the central content of the constraint ``algebra'' in the canonical
formalism.
| [
{
"created": "Wed, 22 Jul 1998 17:10:19 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"York,",
"James W.",
"Jr"
]
] | Studies of new hyperbolic systems for the Einstein evolution equations show that the ``slicing density'' $\alpha(t,x)$ can be freely specified while the lapse $N = \alpha g^{1/2}$ cannot. Implementation of this small change in the Arnowitt-Deser-Misner action principle leads to canonical equations that agree with the Einstein equations whether or not the constraints are satisfied. The constraint functions, independently of their values, then propagate according to a first order symmetric hyperbolic system whose characteristic cone is the light cone. This result follows from the twice-contracted Bianchi identity and constitutes the central content of the constraint ``algebra'' in the canonical formalism. |
gr-qc/0109011 | Fredrik Stahl | Fredrik St{\aa}hl | Fuchsian analysis of S^2xS^1 and S^3 Gowdy spacetimes | LaTeX 2e, AMSLaTeX, a4wide, 25 pages | Class.Quant.Grav.19:4483-4504,2002 | 10.1088/0264-9381/19/17/301 | AEI-2001-110 | gr-qc | null | The Gowdy spacetimes are vacuum solutions of Einstein's equations with two
commuting Killing vectors having compact spacelike orbits with T^3, S^2xS^1 or
S^3 topology. In the case of T^3 topology, Kichenassamy and Rendall have found
a family of singular solutions which are asymptotically velocity dominated by
construction. In the case when the velocity is between zero and one, the
solutions depend on the maximal number of free functions. We consider the
similar case with S^2xS^1 or S^3 topology, where the main complication is the
presence of symmetry axes. We use Fuchsian techniques to show the existence of
singular solutions similar to the T^3 case. We first solve the analytic case
and then generalise to the smooth case by approximating smooth data with a
sequence of analytic data. However, for the metric to be smooth at the axes,
the velocity must be 1 or 3 there, which is outside the range where the
constructed solutions depend on the full number of free functions. A plausible
explanation is that in general a spiky feature may develop at the axis, a
situation which is unsuitable for a direct treatment by Fuchsian methods.
| [
{
"created": "Tue, 4 Sep 2001 13:46:17 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Ståhl",
"Fredrik",
""
]
] | The Gowdy spacetimes are vacuum solutions of Einstein's equations with two commuting Killing vectors having compact spacelike orbits with T^3, S^2xS^1 or S^3 topology. In the case of T^3 topology, Kichenassamy and Rendall have found a family of singular solutions which are asymptotically velocity dominated by construction. In the case when the velocity is between zero and one, the solutions depend on the maximal number of free functions. We consider the similar case with S^2xS^1 or S^3 topology, where the main complication is the presence of symmetry axes. We use Fuchsian techniques to show the existence of singular solutions similar to the T^3 case. We first solve the analytic case and then generalise to the smooth case by approximating smooth data with a sequence of analytic data. However, for the metric to be smooth at the axes, the velocity must be 1 or 3 there, which is outside the range where the constructed solutions depend on the full number of free functions. A plausible explanation is that in general a spiky feature may develop at the axis, a situation which is unsuitable for a direct treatment by Fuchsian methods. |
1209.6148 | George Pappas | George Pappas and Theocharis A. Apostolatos | An all-purpose metric for the exterior of any kind of rotating neutron
star | Additional material can be found at
http://users.uoa.gr/~gpappas/MNRAS/neutron_stars_spacetime.html | Mon. Not. R. Astron. Soc. 429, 3007-3024 (2013) | 10.1093/mnras/sts556 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have tested the appropriateness of two-soliton analytic metric to describe
the exterior of all types of neutron stars, no matter what their equation of
state or rotation rate is. The particular analytic solution of the vaccuum
Einstein equations proved quite adjustable to mimic the metric functions of all
numerically constructed neutron-star models that we used as a testbed. The
neutron-star models covered a wide range of stiffness, with regard to the
equation of state of their interior, and all rotation rates up to the maximum
possible rotation rate allowed for each such star. Apart of the metric
functions themselves, we have compared the radius of the innermost stable
circular orbit $R_{\rm{ISCO}}$, the orbital frequency
$\Omega\equiv\frac{d\phi}{dt}$ of circular geodesics, and their epicyclic
frequencies $\Omega_{\rho}, \Omega_z$, as well as the change of the energy of
circular orbits per logarithmic change of orbital frequency $\Delta\tilde{E}$.
All these quantities, calculated by means of the two-soliton analytic metric,
fitted with good accuracy the corresponding numerical ones as in previous
analogous comparisons (although previous attempts were restricted to neutron
star models with either high or low rotation rates). We believe that this
particular analytic solution could be considered as an analytic faithful
representation of the gravitation field of any rotating neutron star with such
accuracy, that one could explore the interior structure of a neutron star by
using this space-time to interpret observations of astrophysical processes that
take place around it.
| [
{
"created": "Thu, 27 Sep 2012 07:39:10 GMT",
"version": "v1"
}
] | 2013-02-12 | [
[
"Pappas",
"George",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | We have tested the appropriateness of two-soliton analytic metric to describe the exterior of all types of neutron stars, no matter what their equation of state or rotation rate is. The particular analytic solution of the vaccuum Einstein equations proved quite adjustable to mimic the metric functions of all numerically constructed neutron-star models that we used as a testbed. The neutron-star models covered a wide range of stiffness, with regard to the equation of state of their interior, and all rotation rates up to the maximum possible rotation rate allowed for each such star. Apart of the metric functions themselves, we have compared the radius of the innermost stable circular orbit $R_{\rm{ISCO}}$, the orbital frequency $\Omega\equiv\frac{d\phi}{dt}$ of circular geodesics, and their epicyclic frequencies $\Omega_{\rho}, \Omega_z$, as well as the change of the energy of circular orbits per logarithmic change of orbital frequency $\Delta\tilde{E}$. All these quantities, calculated by means of the two-soliton analytic metric, fitted with good accuracy the corresponding numerical ones as in previous analogous comparisons (although previous attempts were restricted to neutron star models with either high or low rotation rates). We believe that this particular analytic solution could be considered as an analytic faithful representation of the gravitation field of any rotating neutron star with such accuracy, that one could explore the interior structure of a neutron star by using this space-time to interpret observations of astrophysical processes that take place around it. |
2407.21108 | Ian Newsome | Ian M. Newsome, Silvia Pla, and Paul R. Anderson | Quantum Effects in 3+1 Schwarzschild-de Sitter Spacetime: Properties of
the Hadamard Function | 22 pages, 7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a four-dimensional Schwarzschild-de Sitter background, the spherically
symmetric ($\ell=0$) contribution to the Hadamard two-point correlation
function is computed for a massless minimally-coupled scalar field in the Unruh
state. Consideration is given to spacetime points located exterior to the black
hole horizon, but within the cosmological horizon. Previously it was found in
two dimensions for spatially separated points that the Hadamard function
exhibits unbounded linear growth at late times, with a rate of growth
proportional to the sum of the black hole and cosmological surface gravities.
Here it is shown numerically that this behavior persists in four dimensions,
where scattering effects associated with the scalar field modes lead to a
modification of the two-dimensional result. An analytic approximation is
derived for the growth rate in four dimensions and, in the limit that the black
hole vanishes, the leading order contribution is equivalent to the rate of
growth for the Hadamard function found previously for de Sitter space in
cosmological coordinates.
| [
{
"created": "Tue, 30 Jul 2024 18:01:07 GMT",
"version": "v1"
}
] | 2024-08-01 | [
[
"Newsome",
"Ian M.",
""
],
[
"Pla",
"Silvia",
""
],
[
"Anderson",
"Paul R.",
""
]
] | In a four-dimensional Schwarzschild-de Sitter background, the spherically symmetric ($\ell=0$) contribution to the Hadamard two-point correlation function is computed for a massless minimally-coupled scalar field in the Unruh state. Consideration is given to spacetime points located exterior to the black hole horizon, but within the cosmological horizon. Previously it was found in two dimensions for spatially separated points that the Hadamard function exhibits unbounded linear growth at late times, with a rate of growth proportional to the sum of the black hole and cosmological surface gravities. Here it is shown numerically that this behavior persists in four dimensions, where scattering effects associated with the scalar field modes lead to a modification of the two-dimensional result. An analytic approximation is derived for the growth rate in four dimensions and, in the limit that the black hole vanishes, the leading order contribution is equivalent to the rate of growth for the Hadamard function found previously for de Sitter space in cosmological coordinates. |
gr-qc/9804057 | Jolien Creighton | Patrick R. Brady, Jolien D. E. Creighton, and Kip S. Thorne | Computing the merger of black-hole binaries: the IBBH problem | 6 pages RevTeX | Phys.Rev.D58:061501,1998 | 10.1103/PhysRevD.58.061501 | GRP-498 | gr-qc | null | Gravitational radiation arising from the inspiral and merger of binary black
holes (BBH's) is a promising candidate for detection by kilometer-scale
interferometric gravitational wave observatories. This paper discusses a
serious obstacle to searches for such radiation and to the interpretation of
any observed waves: the inability of current computational techniques to evolve
a BBH through its last ~10 orbits of inspiral (~100 radians of
gravitational-wave phase). A new set of numerical-relativity techniques is
proposed for solving this ``Intermediate Binary Black Hole'' (IBBH) problem:
(i) numerical evolutions performed in coordinates co-rotating with the BBH, in
which the metric coefficients evolve on the long timescale of inspiral, and
(ii) techniques for mathematically freezing out gravitational degrees of
freedom that are not excited by the waves.
| [
{
"created": "Wed, 22 Apr 1998 17:35:46 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Brady",
"Patrick R.",
""
],
[
"Creighton",
"Jolien D. E.",
""
],
[
"Thorne",
"Kip S.",
""
]
] | Gravitational radiation arising from the inspiral and merger of binary black holes (BBH's) is a promising candidate for detection by kilometer-scale interferometric gravitational wave observatories. This paper discusses a serious obstacle to searches for such radiation and to the interpretation of any observed waves: the inability of current computational techniques to evolve a BBH through its last ~10 orbits of inspiral (~100 radians of gravitational-wave phase). A new set of numerical-relativity techniques is proposed for solving this ``Intermediate Binary Black Hole'' (IBBH) problem: (i) numerical evolutions performed in coordinates co-rotating with the BBH, in which the metric coefficients evolve on the long timescale of inspiral, and (ii) techniques for mathematically freezing out gravitational degrees of freedom that are not excited by the waves. |
2107.08893 | Enrique Alvarez | Enrique \'Alvarez and Jes\'us Anero | Some comments on the Hamiltonian for Unimodular Gravity | 28 pages | null | 10.1103/PhysRevD.104.084096 | IFT-UAM/CSIC-21-84 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several alternative formulations of the first order approach to unimodular
gravity are presented. There is always a particular one such that it is {\em
classically} equivalent to the second order formulation; this we call {\em
educated}. It is often at variance with the {\em naive} approach, in which the
lagrangian is taken as given exactly by the same expression as in the second
order formulation; only the number and character of the independent variables
changes. Namely, typically some of the momenta are now considered as
coordinates. The ensuing Hamiltonians are thereby discussed and their physical
differences pointed out.
| [
{
"created": "Mon, 19 Jul 2021 14:07:27 GMT",
"version": "v1"
}
] | 2021-11-10 | [
[
"Álvarez",
"Enrique",
""
],
[
"Anero",
"Jesús",
""
]
] | Several alternative formulations of the first order approach to unimodular gravity are presented. There is always a particular one such that it is {\em classically} equivalent to the second order formulation; this we call {\em educated}. It is often at variance with the {\em naive} approach, in which the lagrangian is taken as given exactly by the same expression as in the second order formulation; only the number and character of the independent variables changes. Namely, typically some of the momenta are now considered as coordinates. The ensuing Hamiltonians are thereby discussed and their physical differences pointed out. |
1407.1698 | Yan-Gang Miao | Yan-Gang Miao, Fang-Fang Yuan, Zheng-Zheng Zhang | Thermodynamic approach to field equations in Lovelock gravity and f(R)
gravity revisited | 10 pages, no figures; v2: clarifications and references added, to
appear in Int. J. Mod. Phys. D | Int. J. Mod. Phys. D 23 (2014) 1450093 | 10.1142/S021827181450093X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first law of thermodynamics at black hole horizons is known to be
obtainable from the gravitational field equations. A recent study claims that
the contributions at inner horizons should be considered in order to give the
conventional first law of black hole thermodynamics. Following this method, we
revisit the thermodynamic aspects of field equations in the Lovelock gravity
and f(R) gravity by focusing on two typical classes of charged black holes in
the two theories.
| [
{
"created": "Mon, 7 Jul 2014 13:00:24 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Sep 2014 16:13:41 GMT",
"version": "v2"
}
] | 2014-10-20 | [
[
"Miao",
"Yan-Gang",
""
],
[
"Yuan",
"Fang-Fang",
""
],
[
"Zhang",
"Zheng-Zheng",
""
]
] | The first law of thermodynamics at black hole horizons is known to be obtainable from the gravitational field equations. A recent study claims that the contributions at inner horizons should be considered in order to give the conventional first law of black hole thermodynamics. Following this method, we revisit the thermodynamic aspects of field equations in the Lovelock gravity and f(R) gravity by focusing on two typical classes of charged black holes in the two theories. |
2001.00551 | Shahram Jalalzadeh | S. Jalalzadeh and A. J. S. Capistrano | Bohmian mechanics of Klein-Gordon equation via quantum metric and mass | 7 pages | Modern Physics Letters A, 34 (2019) 1950270 | 10.1142/S0217732319502705 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The causal stochastic interpretation of relativistic quantum mechanics has
the problems of superluminal velocities, motion backward in time and the
incorrect non-relativistic limit. In this paper, according to the original
ideas of de Broglie, Bohm and Takabayasi, we have introduced simultaneous
quantum mass and quantum metric of curved spacetime to obtain a correct
relativistic theory free of mentioned problems. \keywords{Bohmian mechanics;
Klein-Gordon equation; quantum conformal transformations.
| [
{
"created": "Thu, 2 Jan 2020 18:19:17 GMT",
"version": "v1"
}
] | 2020-01-03 | [
[
"Jalalzadeh",
"S.",
""
],
[
"Capistrano",
"A. J. S.",
""
]
] | The causal stochastic interpretation of relativistic quantum mechanics has the problems of superluminal velocities, motion backward in time and the incorrect non-relativistic limit. In this paper, according to the original ideas of de Broglie, Bohm and Takabayasi, we have introduced simultaneous quantum mass and quantum metric of curved spacetime to obtain a correct relativistic theory free of mentioned problems. \keywords{Bohmian mechanics; Klein-Gordon equation; quantum conformal transformations. |
gr-qc/9404021 | Todd Brun | Todd A. Brun (Department of Physics, Caltech) | The Decoherence of Phase Space Histories | 20 pages (RevTex 3.0 macros) | null | null | Caltech preprint CALT-68-1929 (Corrected the preprint code) | gr-qc hep-th | null | In choosing a family of histories for a system, it is often convenient to
choose a succession of locations in phase space, rather than configuration
space, for comparison to classical histories. Although there are no good
projections onto phase space, several approximate projections have been used in
the past; three of these are examined in this paper. Expressions are derived
for the probabilities of histories containing arbitrary numbers of projections
onto phase space, and the conditions for the decoherence of these histories are
studied.
| [
{
"created": "Tue, 12 Apr 1994 08:41:42 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Apr 1994 09:30:47 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Brun",
"Todd A.",
"",
"Department of Physics, Caltech"
]
] | In choosing a family of histories for a system, it is often convenient to choose a succession of locations in phase space, rather than configuration space, for comparison to classical histories. Although there are no good projections onto phase space, several approximate projections have been used in the past; three of these are examined in this paper. Expressions are derived for the probabilities of histories containing arbitrary numbers of projections onto phase space, and the conditions for the decoherence of these histories are studied. |
2207.05965 | Muhammad Zaeem-Ul-Haq Bhatti | M. Z. Bhatti, Z. Yousaf and M. Yousaf | Junction conditions in perfect fluid $f(\mathcal{G},~T)$ gravitational
theory | 27 pages, 1 figure, version submitted for publication | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This manuscript aims to establish the gravitational junction conditions(JCs)
for the $f(\mathcal{G},~T)$ gravity. In this gravitational theory, $f$ is an
arbitrary function of Gauss-Bonnet invariant $\mathcal{G}$ and the trace of the
energy-momentum tensor $T_{\mu\nu}$ i.e., $T$. We start by introducing this
gravity theory in its usual geometrical representation and posteriorly obtain a
dynamically equivalent scalar-tensor demonstration on which the arbitrary
dependence on the generic function $f$ in both $\mathcal G$ and $T$ is
exchanged by two scalar fields and scalar potential. We then derive the JCs for
matching between two different space-times across a separation hyper-surface
$\Sigma$, assuming the matter sector to be described by an isotropic perfect
fluid configuration. We take the general approach assuming the possibility of a
thin-shell arising at $\Sigma$ between the two space-times. However, our
results establish that, for the distribution formalism to be well-defined,
thin-shells are not allowed to emerge in the general version of this theory. We
thus obtain instead a complete set of JCs for a smooth matching at $\Sigma$
under the same conditions. The same results are then obtained in the
scalar-tensor representation of the theory, thus emphasizing the equivalence
between these two representations. Our results significantly constrain the
possibility of developing models for alternative compact structures supported
by thin-shells in $f(\mathcal{G},~T)$ gravity, e.g. gravastars and thin-shell
wormholes, but provide a suitable framework for the search of models presenting
a smooth matching at their surface, from which perfect fluid stars are possible
examples.
| [
{
"created": "Wed, 13 Jul 2022 05:08:24 GMT",
"version": "v1"
}
] | 2022-07-14 | [
[
"Bhatti",
"M. Z.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Yousaf",
"M.",
""
]
] | This manuscript aims to establish the gravitational junction conditions(JCs) for the $f(\mathcal{G},~T)$ gravity. In this gravitational theory, $f$ is an arbitrary function of Gauss-Bonnet invariant $\mathcal{G}$ and the trace of the energy-momentum tensor $T_{\mu\nu}$ i.e., $T$. We start by introducing this gravity theory in its usual geometrical representation and posteriorly obtain a dynamically equivalent scalar-tensor demonstration on which the arbitrary dependence on the generic function $f$ in both $\mathcal G$ and $T$ is exchanged by two scalar fields and scalar potential. We then derive the JCs for matching between two different space-times across a separation hyper-surface $\Sigma$, assuming the matter sector to be described by an isotropic perfect fluid configuration. We take the general approach assuming the possibility of a thin-shell arising at $\Sigma$ between the two space-times. However, our results establish that, for the distribution formalism to be well-defined, thin-shells are not allowed to emerge in the general version of this theory. We thus obtain instead a complete set of JCs for a smooth matching at $\Sigma$ under the same conditions. The same results are then obtained in the scalar-tensor representation of the theory, thus emphasizing the equivalence between these two representations. Our results significantly constrain the possibility of developing models for alternative compact structures supported by thin-shells in $f(\mathcal{G},~T)$ gravity, e.g. gravastars and thin-shell wormholes, but provide a suitable framework for the search of models presenting a smooth matching at their surface, from which perfect fluid stars are possible examples. |
gr-qc/0608115 | Evgeny Sorkin | Evgeny Sorkin | Nonuniform black strings in various dimensions | 32pp, 17 figs. v2: minor corrections to match the published version | Phys.Rev.D74:104027,2006 | 10.1103/PhysRevD.74.104027 | null | gr-qc hep-th | null | The nonuniform black strings branch, which emerges from the critical
Gregory-Laflamme string, is numerically constructed in dimensions 6 <= D <= 11
and extended into the strongly non-linear regime. All the solutions are more
massive and less entropic than the marginal string. We find the asymptotic
values of the mass, the entropy and other physical variables in the limit of
large horizon deformations. By explicit metric comparison we verify that the
local geometry around the ``waist'' of our most nonuniform solutions is
cone-like with less than 10% deviation. We find evidence that in this regime
the characteristic length scale has a power-law dependence on a parameter along
the branch of the solutions, and estimate the critical exponent.
| [
{
"created": "Sat, 26 Aug 2006 17:25:57 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2006 17:59:17 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Sorkin",
"Evgeny",
""
]
] | The nonuniform black strings branch, which emerges from the critical Gregory-Laflamme string, is numerically constructed in dimensions 6 <= D <= 11 and extended into the strongly non-linear regime. All the solutions are more massive and less entropic than the marginal string. We find the asymptotic values of the mass, the entropy and other physical variables in the limit of large horizon deformations. By explicit metric comparison we verify that the local geometry around the ``waist'' of our most nonuniform solutions is cone-like with less than 10% deviation. We find evidence that in this regime the characteristic length scale has a power-law dependence on a parameter along the branch of the solutions, and estimate the critical exponent. |
1810.07296 | Reinaldo Gleiser | Reinaldo J. Gleiser | Linear stability of the Linet - Tian solution with positive cosmological
constant | One reference added. Several typos corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to extend the analysis of gravitational
instability of the Linet - Tian solution to the case $\Lambda > 0$. A
fundamental difference brought about by $\Lambda >0$, as compared to
$\Lambda<0$ is in the structure of the resulting space time. Associated with
each of the two commuting Killing vectors $\partial_{\phi}$, and
$\partial_{z}$, there is a curvature singularity that has the same
characteristics as that associated to $\partial_{\phi}$ in the Levi - Civita
metric, and we show that there is an isometry relating these singularities that
reduces the effective parameter space of the metrics. In attempting to set up
and solve the linearized perturbation equations we are confronted with the
problem of a gauge ambiguity that leads to the introduction of a gauge
invariant function, $W_1$, that is shown to be also a {\em master function},
that satisfies a second order ODE, and in terms of which one can express all
the perturbation functions. Unfortunately, the equation satisfied by $W_1$
contains singular coefficients, and, although {\em all} its solutions are
regular, because of the presence of these singularities one cannot, as in the
case of negative $\Lambda$, set up an associated self adjoint problem that
provides a complete set of solutions for $W_1$. We are thus restricted to
solving numerically the perturbation equations, and using those solutions for
constructing $W_1$, for particular values of the parameters. In all the cases
analyzed we find unstable modes, which strongly suggests that all the Linet -
Tian space times with $\Lambda > 0$ are linearly unstable under gravitational
perturbations. The problem of determining the time evolution of arbitrary
initial data in terms of the $W_1$, or something equivalent, remains open.
| [
{
"created": "Tue, 16 Oct 2018 22:10:32 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Nov 2018 22:06:10 GMT",
"version": "v2"
}
] | 2018-11-07 | [
[
"Gleiser",
"Reinaldo J.",
""
]
] | The purpose of this paper is to extend the analysis of gravitational instability of the Linet - Tian solution to the case $\Lambda > 0$. A fundamental difference brought about by $\Lambda >0$, as compared to $\Lambda<0$ is in the structure of the resulting space time. Associated with each of the two commuting Killing vectors $\partial_{\phi}$, and $\partial_{z}$, there is a curvature singularity that has the same characteristics as that associated to $\partial_{\phi}$ in the Levi - Civita metric, and we show that there is an isometry relating these singularities that reduces the effective parameter space of the metrics. In attempting to set up and solve the linearized perturbation equations we are confronted with the problem of a gauge ambiguity that leads to the introduction of a gauge invariant function, $W_1$, that is shown to be also a {\em master function}, that satisfies a second order ODE, and in terms of which one can express all the perturbation functions. Unfortunately, the equation satisfied by $W_1$ contains singular coefficients, and, although {\em all} its solutions are regular, because of the presence of these singularities one cannot, as in the case of negative $\Lambda$, set up an associated self adjoint problem that provides a complete set of solutions for $W_1$. We are thus restricted to solving numerically the perturbation equations, and using those solutions for constructing $W_1$, for particular values of the parameters. In all the cases analyzed we find unstable modes, which strongly suggests that all the Linet - Tian space times with $\Lambda > 0$ are linearly unstable under gravitational perturbations. The problem of determining the time evolution of arbitrary initial data in terms of the $W_1$, or something equivalent, remains open. |
1210.4504 | Emanuele Alesci | Emanuele Alesci and Francesco Cianfrani | A new perspective on cosmology in Loop Quantum Gravity | 5 pages | null | 10.1209/0295-5075/104/10001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new cosmological model derived from Loop Quantum Gravity. The
formulation is based on a projection of the kinematical Hilbert space of the
full theory down to a subspace representing the proper arena for an
inhomogeneous Bianchi I model. This procedure gives a direct link between the
full theory and its cosmological sector. The emerging quantum cosmological
model represents a simplified arena on which the complete canonical
quantization program can be tested. The achievements of this analysis could
also shed light on Loop Quantum Cosmology and its relation with the full
theory.
| [
{
"created": "Tue, 16 Oct 2012 17:24:22 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Alesci",
"Emanuele",
""
],
[
"Cianfrani",
"Francesco",
""
]
] | We present a new cosmological model derived from Loop Quantum Gravity. The formulation is based on a projection of the kinematical Hilbert space of the full theory down to a subspace representing the proper arena for an inhomogeneous Bianchi I model. This procedure gives a direct link between the full theory and its cosmological sector. The emerging quantum cosmological model represents a simplified arena on which the complete canonical quantization program can be tested. The achievements of this analysis could also shed light on Loop Quantum Cosmology and its relation with the full theory. |
2007.04153 | Carlos A. R. Herdeiro | Dumitru Astefanesei, Carlos Herdeiro, Jo\~ao Oliveira and Eugen Radu | Higher dimensional black hole scalarization | 15 pages, 4 figures | null | 10.1007/JHEP09(2020)186 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the simplest scalar-tensor theories, wherein the scalar field is
non-minimally coupled to the Ricci scalar, spontaneous scalarization of
electrovacuum black holes (BHs) does not occur. This ceases to be true in
higher dimensional spacetimes, $d>4$. We consider the scalarization of the
higher dimensional Reissner-Nordstr\"om BHs in scalar-tensor models and provide
results on the zero modes for different $d$, together with an explicit
construction of the scalarized BHs in $d=5$, discussing some of their
properties. We also observe that a conformal transformation into the Einstein
frame maps this model into an Einstein-Maxwel-scalar model, wherein the
non-minimal coupling occurs between the scalar field and the Maxwell invariant
(rather than the Ricci scalar), thus relating the occurence of scalarization in
the two models. Next, we consider the spontaneous scalarization of the
Schwarzschild-Tangherlini BH in extended-scalar-tensor-Lovelock gravity in even
dimensions. In these models, the scalar field is non-minimally coupled to the
$(d/2)^{th}$ Euler density, in $d$ spacetime dimensions. We construct
explicitly examples in $d=6,8$, showing the properties of the four dimensional
case are qualitatively generic, but with quantitative differences. We compare
these higher $d$ scalarized BHs with the hairy BHs in shift-symmetric Horndeski
theory, for the same $d$, which we also construct.
| [
{
"created": "Wed, 8 Jul 2020 14:30:15 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Astefanesei",
"Dumitru",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Oliveira",
"João",
""
],
[
"Radu",
"Eugen",
""
]
] | In the simplest scalar-tensor theories, wherein the scalar field is non-minimally coupled to the Ricci scalar, spontaneous scalarization of electrovacuum black holes (BHs) does not occur. This ceases to be true in higher dimensional spacetimes, $d>4$. We consider the scalarization of the higher dimensional Reissner-Nordstr\"om BHs in scalar-tensor models and provide results on the zero modes for different $d$, together with an explicit construction of the scalarized BHs in $d=5$, discussing some of their properties. We also observe that a conformal transformation into the Einstein frame maps this model into an Einstein-Maxwel-scalar model, wherein the non-minimal coupling occurs between the scalar field and the Maxwell invariant (rather than the Ricci scalar), thus relating the occurence of scalarization in the two models. Next, we consider the spontaneous scalarization of the Schwarzschild-Tangherlini BH in extended-scalar-tensor-Lovelock gravity in even dimensions. In these models, the scalar field is non-minimally coupled to the $(d/2)^{th}$ Euler density, in $d$ spacetime dimensions. We construct explicitly examples in $d=6,8$, showing the properties of the four dimensional case are qualitatively generic, but with quantitative differences. We compare these higher $d$ scalarized BHs with the hairy BHs in shift-symmetric Horndeski theory, for the same $d$, which we also construct. |
gr-qc/0604103 | Brian Edgar | S. Brian Edgar and M.P. Machado Ramos | Obtaining a class of Type O pure radiation metrics with a cosmological
constant, using invariant operators | 29 pages | Gen.Rel.Grav.39:539-566,2007 | 10.1007/s10714-006-0392-0 | null | gr-qc | null | Using the generalised invariant formalism we derive a class of conformally
flat spacetimes whose Ricci tensor has a pure radiation and a Ricci scalar
component. The method used is a development of the methods used earlier for
pure radiation spacetimes of Petrov types O and N respectively. In this paper
we demonstrate how to handle, in the generalised invariant formalism,
spacetimes with isotropy freedom and rich Killing vector structure. Once the
spacetimes have been constructed, it is straightforward to deduce their
Karlhede classification: the Karlhede algorithm terminates at the fourth
derivative order, and the spacetimes all have one degree of null isotropy and
three, four or five Killing vectors.
| [
{
"created": "Mon, 24 Apr 2006 15:25:25 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Edgar",
"S. Brian",
""
],
[
"Ramos",
"M. P. Machado",
""
]
] | Using the generalised invariant formalism we derive a class of conformally flat spacetimes whose Ricci tensor has a pure radiation and a Ricci scalar component. The method used is a development of the methods used earlier for pure radiation spacetimes of Petrov types O and N respectively. In this paper we demonstrate how to handle, in the generalised invariant formalism, spacetimes with isotropy freedom and rich Killing vector structure. Once the spacetimes have been constructed, it is straightforward to deduce their Karlhede classification: the Karlhede algorithm terminates at the fourth derivative order, and the spacetimes all have one degree of null isotropy and three, four or five Killing vectors. |
1504.00295 | Lavinia Heisenberg | Jose Beltr\'an Jim\'enez, Lavinia Heisenberg and Gonzalo J. Olmo | Tensor perturbations in a general class of Palatini theories | 9 pages, Journal version | null | 10.1088/1475-7516/2015/06/026 | NORDITA-2015-36, IFIC/15-59 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a general class of gravitational theories formulated in the Palatini
approach and derive the equations governing the evolution of tensor
perturbations. In the absence of torsion, the connection can be solved as the
Christoffel symbols of an auxiliary metric which is non-trivially related to
the space-time metric. We then consider background solutions corresponding to a
perfect fluid and show that the tensor perturbations equations (including
anisotropic stresses) for the auxiliary metric around such a background take an
Einstein-like form. This facilitates the study in a homogeneous and isotropic
cosmological scenario where we explicitly establish the relation between the
auxiliary metric and the space-time metric tensor perturbations. As a general
result, we show that both tensor perturbations coincide in the absence of
anisotropic stresses.
| [
{
"created": "Wed, 1 Apr 2015 17:04:54 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Sep 2015 08:45:19 GMT",
"version": "v2"
}
] | 2015-09-30 | [
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Heisenberg",
"Lavinia",
""
],
[
"Olmo",
"Gonzalo J.",
""
]
] | We study a general class of gravitational theories formulated in the Palatini approach and derive the equations governing the evolution of tensor perturbations. In the absence of torsion, the connection can be solved as the Christoffel symbols of an auxiliary metric which is non-trivially related to the space-time metric. We then consider background solutions corresponding to a perfect fluid and show that the tensor perturbations equations (including anisotropic stresses) for the auxiliary metric around such a background take an Einstein-like form. This facilitates the study in a homogeneous and isotropic cosmological scenario where we explicitly establish the relation between the auxiliary metric and the space-time metric tensor perturbations. As a general result, we show that both tensor perturbations coincide in the absence of anisotropic stresses. |
gr-qc/0304060 | Farid Ya. Khalili | F.Ya.Khalili | Low pumping energy mode of the "optical bars''/"optical lever"
topologies of gravitational-wave antennae | 18 pages, 5 figures | Phys.Lett.A317:169-180,2003 | 10.1016/S0375-9601(03)01136-8 | null | gr-qc | null | The ``optical bars''/``optical lever'' topologies of gravitational-wave
antennae allow to obtain sensitivity better that the Standard Quantum Limit
while keeping the optical pumping energy in the antenna relatively low. Element
of the crucial importance in these schemes is the local meter which monitors
the local test mirror position. Using cross-correlation of this meter
back-action noise and its measurement noise it is possible to further decrease
the optical pumping energy. In this case the pumping energy minimal value will
be limited by the internal losses in the antenna only. Estimates show that for
values of parameters available for contemporary and planned gravitational-wave
antennae, sensitivity about one order of magnitude better than the Standard
Quantum Limit can be obtained using the pumping energy about one order of
magnitude smaller energy than is required in the traditional topology in order
to obtain the the Standard Quantum Limit level of sensitivity.
| [
{
"created": "Wed, 16 Apr 2003 07:57:18 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Khalili",
"F. Ya.",
""
]
] | The ``optical bars''/``optical lever'' topologies of gravitational-wave antennae allow to obtain sensitivity better that the Standard Quantum Limit while keeping the optical pumping energy in the antenna relatively low. Element of the crucial importance in these schemes is the local meter which monitors the local test mirror position. Using cross-correlation of this meter back-action noise and its measurement noise it is possible to further decrease the optical pumping energy. In this case the pumping energy minimal value will be limited by the internal losses in the antenna only. Estimates show that for values of parameters available for contemporary and planned gravitational-wave antennae, sensitivity about one order of magnitude better than the Standard Quantum Limit can be obtained using the pumping energy about one order of magnitude smaller energy than is required in the traditional topology in order to obtain the the Standard Quantum Limit level of sensitivity. |
gr-qc/0007059 | Hirotaka Ochiai | Hirotaka Ochiai and Katsuhiko Sato | Dynamical Properties of Euclidean Solutions in a Multidimensional
Cosmological Model | 13 pages and 5 figures | Prog.Theor.Phys. 103 (2000) 893-905 | 10.1143/PTP.103.893 | null | gr-qc astro-ph hep-th | null | In the framework of the Hartle-Hawking no-boundary proposal, we investigated
quantum creation of the multidimensional universe with a cosmological constant
($\Lambda$) but without matter fields. We have found that the classical
solutions of the Euclidean Einstein equations in this model have
``quasi-attractors'', i.e., most trajectories on the a-b plane, where a and b
are the scale factors of external and internal spaces, go around a point. It is
presumed that the wave function of the universe has a hump near this
quasi-attractor point. In the case that both the curvatures of external and
internal spaces are positive, and $\Lambda>0$, there exist Lorentzian solutions
which start near the quasi-attractor, the internal space remains microscopic,
and the external space evolves into our macroscopic universe.
| [
{
"created": "Sat, 22 Jul 2000 06:36:02 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ochiai",
"Hirotaka",
""
],
[
"Sato",
"Katsuhiko",
""
]
] | In the framework of the Hartle-Hawking no-boundary proposal, we investigated quantum creation of the multidimensional universe with a cosmological constant ($\Lambda$) but without matter fields. We have found that the classical solutions of the Euclidean Einstein equations in this model have ``quasi-attractors'', i.e., most trajectories on the a-b plane, where a and b are the scale factors of external and internal spaces, go around a point. It is presumed that the wave function of the universe has a hump near this quasi-attractor point. In the case that both the curvatures of external and internal spaces are positive, and $\Lambda>0$, there exist Lorentzian solutions which start near the quasi-attractor, the internal space remains microscopic, and the external space evolves into our macroscopic universe. |
1111.0395 | Muzaffer Adak | \"Ozcan Sert (Pamukkale U.) and Muzaffer Adak (Pamukkale U.) | Dirac field in topologically massive gravity | 12 pages. Title changed. Conclusion extended. Appendix added. To
appear in Gen. Rel. Grav | Gen Relativ Gravit 45 (2013) 69 | 10.1007/s10714-012-1460-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a Dirac field coupled minimally to the Mielke-Baekler model of
gravity and investigate cosmological solutions in three dimensions. We arrive
at a family of solutions which exists even in the limit of vanishing
cosmological constant.
| [
{
"created": "Wed, 2 Nov 2011 06:00:54 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Sep 2012 11:59:51 GMT",
"version": "v2"
}
] | 2013-09-24 | [
[
"Sert",
"Özcan",
"",
"Pamukkale U."
],
[
"Adak",
"Muzaffer",
"",
"Pamukkale U."
]
] | We consider a Dirac field coupled minimally to the Mielke-Baekler model of gravity and investigate cosmological solutions in three dimensions. We arrive at a family of solutions which exists even in the limit of vanishing cosmological constant. |
gr-qc/0503114 | Abel Camacho Mr. | Abel Camacho (Dept. of Physics, Universidad Autonoma
Metropolitana--Iztapalapa) | Continuous distribution of frequencies and deformed dispersion relations | Accepted in Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) 2101-2106 | 10.1088/0264-9381/22/11/012 | null | gr-qc quant-ph | null | The possibilities that, in the realm of the detection of the so--called
deformed dispersion relation, a light source with a continuous distribution of
frequencies offers is discussed. It will be proved that the presence of finite
coherence length entails the emergence of a new term in the interference
pattern. This is a novel trait, which renders a new possibility in the quest
for bounds associated with these deformed dispersion relations.
| [
{
"created": "Tue, 29 Mar 2005 16:51:29 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Camacho",
"Abel",
"",
"Dept. of Physics, Universidad Autonoma\n Metropolitana--Iztapalapa"
]
] | The possibilities that, in the realm of the detection of the so--called deformed dispersion relation, a light source with a continuous distribution of frequencies offers is discussed. It will be proved that the presence of finite coherence length entails the emergence of a new term in the interference pattern. This is a novel trait, which renders a new possibility in the quest for bounds associated with these deformed dispersion relations. |
gr-qc/0202092 | Anders Hoeglund | G. Bergqvist and A. Hoglund | Algebraic Rainich theory and antisymmetrisation in higher dimensions | 16 pages, LaTeX | Class.Quant.Grav. 19 (2002) 3341-3356 | 10.1088/0264-9381/19/12/316 | null | gr-qc | null | The classical Rainich(-Misner-Wheeler) theory gives necessary and sufficient
conditions on an energy-momentum tensor $T$ to be that of a Maxwell field (a
2-form) in four dimensions. Via Einstein's equations these conditions can be
expressed in terms of the Ricci tensor, thus providing conditions on a
spacetime geometry for it to be an Einstein-Maxwell spacetime. One of the
conditions is that $T^2$ is proportional to the metric, and it has previously
been shown in arbitrary dimension that any tensor satisfying this condition is
a superenergy tensor of a simple $p$-form. Here we examine algebraic Rainich
conditions for general $p$-forms in higher dimensions and their relations to
identities by antisymmetrisation. Using antisymmetrisation techniques we find
new identities for superenergy tensors of these general (non-simple) forms, and
we also prove in some cases the converse; that the identities are sufficient to
determine the form. As an example we obtain the complete generalisation of the
classical Rainich theory to five dimensions.
| [
{
"created": "Tue, 26 Feb 2002 14:49:20 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bergqvist",
"G.",
""
],
[
"Hoglund",
"A.",
""
]
] | The classical Rainich(-Misner-Wheeler) theory gives necessary and sufficient conditions on an energy-momentum tensor $T$ to be that of a Maxwell field (a 2-form) in four dimensions. Via Einstein's equations these conditions can be expressed in terms of the Ricci tensor, thus providing conditions on a spacetime geometry for it to be an Einstein-Maxwell spacetime. One of the conditions is that $T^2$ is proportional to the metric, and it has previously been shown in arbitrary dimension that any tensor satisfying this condition is a superenergy tensor of a simple $p$-form. Here we examine algebraic Rainich conditions for general $p$-forms in higher dimensions and their relations to identities by antisymmetrisation. Using antisymmetrisation techniques we find new identities for superenergy tensors of these general (non-simple) forms, and we also prove in some cases the converse; that the identities are sufficient to determine the form. As an example we obtain the complete generalisation of the classical Rainich theory to five dimensions. |
1908.00389 | Emmanuil Saridakis | Shin'ichi Nojiri, Sergei D. Odintsov, Emmanuel N. Saridakis | Holographic bounce | 7 pages, 1 figure, to appear in Nucl.Phys.B | null | 10.1016/j.nuclphysb.2019.114790 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the bounce realization arising from the application of the
holographic principle in the early universe, inspired by its well-studied
late-time application. We first consider as Infrared cutoffs the particle and
future event horizons, and we show that the decrease of the horizons at early
times naturally increases holographic energy density at bouncing scales, while
we additionally obtain the necessary null energy condition violation.
Furthermore, adding a simple correction to the horizons due to the Ultraviolet
cutoff we analytically obtain improved nonsingular bouncing solutions, in which
the value of the minimum scale factor is controlled by the UV correction.
Finally, we construct generalized scenarios, arisen from the use of extended
Infrared cutoffs, and as specific examples we consider cutoffs that can
reproduce $F(R)$ gravity, and the bounce realization within it.
| [
{
"created": "Thu, 1 Aug 2019 13:40:13 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Sep 2019 12:57:50 GMT",
"version": "v2"
}
] | 2019-10-28 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We investigate the bounce realization arising from the application of the holographic principle in the early universe, inspired by its well-studied late-time application. We first consider as Infrared cutoffs the particle and future event horizons, and we show that the decrease of the horizons at early times naturally increases holographic energy density at bouncing scales, while we additionally obtain the necessary null energy condition violation. Furthermore, adding a simple correction to the horizons due to the Ultraviolet cutoff we analytically obtain improved nonsingular bouncing solutions, in which the value of the minimum scale factor is controlled by the UV correction. Finally, we construct generalized scenarios, arisen from the use of extended Infrared cutoffs, and as specific examples we consider cutoffs that can reproduce $F(R)$ gravity, and the bounce realization within it. |
gr-qc/0103100 | Steven Carlip | S. Carlip | Liouville Lost, Liouville Regained: Central Charge in a Dynamical
Background | 8 pages, LaTeX, no figures; reference added | Phys.Lett.B508:168-172,2001 | 10.1016/S0370-2693(01)00484-1 | UCD-2001-1 | gr-qc hep-th | null | Several recent approaches to black hole entropy obtain the density of states
from the central charge of a Liouville theory. If Liouville theory is coupled
to a dynamical spacetime background, however, the classical central charge
vanishes. I show that the central charge can be restored by introducing
appropriate constraints, which may be interpreted as fall-off conditions at a
boundary such as a black hole horizon.
| [
{
"created": "Tue, 27 Mar 2001 23:00:17 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Mar 2001 00:13:10 GMT",
"version": "v2"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | Several recent approaches to black hole entropy obtain the density of states from the central charge of a Liouville theory. If Liouville theory is coupled to a dynamical spacetime background, however, the classical central charge vanishes. I show that the central charge can be restored by introducing appropriate constraints, which may be interpreted as fall-off conditions at a boundary such as a black hole horizon. |
1507.06664 | Abraao Capistrano | Abra\~ao J.S Capistrano, Antonio C. Guti\'errez-Pi\~neres, Sergio C.
Ulhoa, Ronni G.G. Amorim | On the thermal stability of a static spherically symmetric black holes
in Nash embedding framework | 10 pages,6 figures, 1 table, extended discussion on embeddings,
corrected typos and references | Annals of Physics (Print), v. 380, p. 106-120, 2017 | 10.1016/j.aop.2017.03.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the deformation caused by the influence of extrinsic curvature on a
vacuum spherically symmetric metric embedded in a five-dimensional bulk. In
this sense, we investigate the produced black-holes and derive general
characteristics such as their masses, horizons, singularities and thermal
properties. As a test, we also study the bending of light near such black-holes
analyzing the movement of a test particle and the modification caused by
extrinsic curvature on its movement. Accordingly, using the asymptotically
conformal flat condition for the extrinsic curvature, an analytical expansion
of a set of \emph{n}-scalar fields can be defined and we show that the
corresponding black holes must be large and constrained in the range of allowed
values $-1/2 \leq n \leq 1.8$. As a result, they are locally thermodynamically
stable, but not globally preferred.
| [
{
"created": "Mon, 20 Jul 2015 23:27:04 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2015 19:31:47 GMT",
"version": "v2"
},
{
"created": "Tue, 24 May 2016 15:45:06 GMT",
"version": "v3"
},
{
"created": "Fri, 29 Jul 2016 14:47:53 GMT",
"version": "v4"
}
] | 2017-04-06 | [
[
"Capistrano",
"Abraão J. S",
""
],
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Ulhoa",
"Sergio C.",
""
],
[
"Amorim",
"Ronni G. G.",
""
]
] | We study the deformation caused by the influence of extrinsic curvature on a vacuum spherically symmetric metric embedded in a five-dimensional bulk. In this sense, we investigate the produced black-holes and derive general characteristics such as their masses, horizons, singularities and thermal properties. As a test, we also study the bending of light near such black-holes analyzing the movement of a test particle and the modification caused by extrinsic curvature on its movement. Accordingly, using the asymptotically conformal flat condition for the extrinsic curvature, an analytical expansion of a set of \emph{n}-scalar fields can be defined and we show that the corresponding black holes must be large and constrained in the range of allowed values $-1/2 \leq n \leq 1.8$. As a result, they are locally thermodynamically stable, but not globally preferred. |
1904.00062 | Antonio Ferreiro | Antonio Ferreiro, Adrian del Rio, Jose Navarro-Salas, Silvia Pla,
Francisco Torrenti | Adiabatic regularization with a Yukawa interaction | 6 pages. Contribution to the Marcel Grossmann Meeting 2018 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the adiabatic regularization method for an expanding universe to
include the Yukawa interaction between a quantized Dirac field and a
homogeneous time-dependent scalar field. We present the renormalized
semiclassical equations that are needed in order to take into account the
backreaction of the produced Dirac fermions in both gravitational and scalar
background fields.
| [
{
"created": "Fri, 29 Mar 2019 19:29:12 GMT",
"version": "v1"
}
] | 2019-04-02 | [
[
"Ferreiro",
"Antonio",
""
],
[
"del Rio",
"Adrian",
""
],
[
"Navarro-Salas",
"Jose",
""
],
[
"Pla",
"Silvia",
""
],
[
"Torrenti",
"Francisco",
""
]
] | We extend the adiabatic regularization method for an expanding universe to include the Yukawa interaction between a quantized Dirac field and a homogeneous time-dependent scalar field. We present the renormalized semiclassical equations that are needed in order to take into account the backreaction of the produced Dirac fermions in both gravitational and scalar background fields. |
1404.5260 | Avirup Ghosh | Avirup Ghosh | Note on Kerr/CFT correspondence in a first order formalism | computation errors corrected, results changed and re-interpreted,
version accepted for publication in Phys. Rev. D | Phys. Rev. D 89, 124035(2014) | 10.1103/PhysRevD.89.124035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In symmetry based approaches to black hole entropy, we calculate the central
charge of the Virasoro algebra in the first order formulation of gravity for
both Palatini and Holst actions. In these calculations, we made use of the NHEK
metric and the Kerr-CFT correspondence. For the Palatini action the results
obtained in the second order formulation are reproduced. We also argue that the
Holst term does not contribute to the charge algebra no matter what
geometry/boundary conditions one is considering.
| [
{
"created": "Mon, 21 Apr 2014 18:10:43 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jun 2014 19:33:18 GMT",
"version": "v2"
}
] | 2014-07-01 | [
[
"Ghosh",
"Avirup",
""
]
] | In symmetry based approaches to black hole entropy, we calculate the central charge of the Virasoro algebra in the first order formulation of gravity for both Palatini and Holst actions. In these calculations, we made use of the NHEK metric and the Kerr-CFT correspondence. For the Palatini action the results obtained in the second order formulation are reproduced. We also argue that the Holst term does not contribute to the charge algebra no matter what geometry/boundary conditions one is considering. |
gr-qc/0103059 | Jeongwon Ho | Jeongwon Ho | A Proof of the Generalized Second Law for Two-Dimensional Black Holes | 15 pages, boundary condition of static black hole is added to clarify
the situation, abstract and section 4 (concluding remarks) is rewritten, and
minor corrections, references added | Phys.Rev. D64 (2001) 064019 | 10.1103/PhysRevD.64.064019 | null | gr-qc hep-th | null | We investigate the generalized second law for two-dimensional black holes in
equilibrium (Hartle-Hawking) and nonequilibrium (Unruh) with the heat bath
surrounding the black holes. We obtain a simple expression for the change of
total entropy in terms of covariant thermodynamic variables, which is valid not
only for the Hartle-Hawking state but also for the Unruh state up to leading
order, without assuming a quasi-stationary evolution of the black holes. Using
this expression, it is shown that the rate of local entropy production is
non-negative in the two-dimensional black hole systems.
| [
{
"created": "Fri, 16 Mar 2001 10:22:20 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Apr 2001 14:52:44 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Ho",
"Jeongwon",
""
]
] | We investigate the generalized second law for two-dimensional black holes in equilibrium (Hartle-Hawking) and nonequilibrium (Unruh) with the heat bath surrounding the black holes. We obtain a simple expression for the change of total entropy in terms of covariant thermodynamic variables, which is valid not only for the Hartle-Hawking state but also for the Unruh state up to leading order, without assuming a quasi-stationary evolution of the black holes. Using this expression, it is shown that the rate of local entropy production is non-negative in the two-dimensional black hole systems. |
2108.11423 | Jafar Khodagholizadeh | Jafar Khodagholizadeh | Neutrinos as a probe of curvature | 14 pages and 2 figures | Journal of High Energy Astrophysics, Volume 32, November 2021,
Pages 20-27 | 10.1016/j.jheap.2021.08.002 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutrinos, as the anisotropic stress tensor, have a damping effect on the
tensor mode perturbation from inflation to the $ \Lambda$ dominated era. First,
we study the squared amplitude reduction for the wavelength entering the
horizon during radiation and matter-dominated phases in the negatively curved
de Sitter spacetime. Then, by comparing with other spatial spacetimes, $ K=0 $
and $K=1$, the highest difference between closed and open cases is seen in the
matter-dominated era. Thus, neutrinos can be added as another candidate for
determining the nature of space-time.
| [
{
"created": "Wed, 25 Aug 2021 18:30:53 GMT",
"version": "v1"
}
] | 2021-08-27 | [
[
"Khodagholizadeh",
"Jafar",
""
]
] | Neutrinos, as the anisotropic stress tensor, have a damping effect on the tensor mode perturbation from inflation to the $ \Lambda$ dominated era. First, we study the squared amplitude reduction for the wavelength entering the horizon during radiation and matter-dominated phases in the negatively curved de Sitter spacetime. Then, by comparing with other spatial spacetimes, $ K=0 $ and $K=1$, the highest difference between closed and open cases is seen in the matter-dominated era. Thus, neutrinos can be added as another candidate for determining the nature of space-time. |
1210.8355 | Youngsub Yoon | Youngsub Yoon | Quantum corrections to the Hawking radiation spectrum | Section 9 "implications on the black hole information paradox" added.
arXiv admin note: text overlap with arXiv:0706.1979 by other authors | Journal of the Korean Physical Society, Vol. 68, No. 6, March
2016, pp. 730-734 | 10.3938/jkps.68.730 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1995, Bekenstein and Mukhanov suggested that the Hawking radiation
spectrum was discrete if the area spectrum was quantized in such a way that the
allowed areas were integer multiples of a single unit area. However, in 1996,
Barreira, Carfora, and Rovelli argued that the Hawking radiation spectrum was
continuous if the area spectrum was quantized with an infinite number of unit
areas, as predicted by loop quantum gravity, rather than quantized with the
single unit area considered by Bekenstein and Mukhanov. In this paper, contrary
to what Barreira, Carfora, and Rovelli argued, we show that the Hawking
radiation spectrum is still discrete when the area spectrum is quantized as
loop quantum gravity predicts. In particular, we show that, for a black hole of
a given temperature, the Hawking radiation spectrum is truncated at frequencies
below a certain frequency.
| [
{
"created": "Tue, 30 Oct 2012 18:45:01 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Feb 2013 08:59:56 GMT",
"version": "v2"
},
{
"created": "Wed, 6 May 2015 14:29:19 GMT",
"version": "v3"
},
{
"created": "Fri, 8 May 2015 08:35:33 GMT",
"version": "v4"
},
{
"created": "Wed, 7 Oct 2015 14:36:59 GMT",
"version": "v5"
},
{
"created": "Mon, 14 Mar 2016 12:53:48 GMT",
"version": "v6"
},
{
"created": "Wed, 11 May 2016 19:09:39 GMT",
"version": "v7"
}
] | 2016-05-12 | [
[
"Yoon",
"Youngsub",
""
]
] | In 1995, Bekenstein and Mukhanov suggested that the Hawking radiation spectrum was discrete if the area spectrum was quantized in such a way that the allowed areas were integer multiples of a single unit area. However, in 1996, Barreira, Carfora, and Rovelli argued that the Hawking radiation spectrum was continuous if the area spectrum was quantized with an infinite number of unit areas, as predicted by loop quantum gravity, rather than quantized with the single unit area considered by Bekenstein and Mukhanov. In this paper, contrary to what Barreira, Carfora, and Rovelli argued, we show that the Hawking radiation spectrum is still discrete when the area spectrum is quantized as loop quantum gravity predicts. In particular, we show that, for a black hole of a given temperature, the Hawking radiation spectrum is truncated at frequencies below a certain frequency. |
gr-qc/0304011 | Lorenzo Iorio | Lorenzo Iorio, Alberto Morea | The impact of the new Earth gravity models on the measurement of the
Lense-Thirring effect | LaTeX, 15 pages, no figures, 4 tables. To appear in General
Relativity and Gravitation | Gen.Rel.Grav. 36 (2004) 1321-1333 | 10.1023/B:GERG.0000022390.05674.99 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | null | In this paper we use, in a preliminary way, the recently released EIGEN2
Earth gravity model, which is based on six months of data of CHAMP only, in
order to reassess the systematic error due to the mismodelling in the even
zonal harmonics of geopotential in the LAGEOS-LAGEOS II Lense-Thirring
experiment involving the nodes of both the LAGEOS satellites and the perigee of
LAGEOS II. The first results from the GGM01C Earth gravity model including the
first GRACE data are very promising.
| [
{
"created": "Wed, 2 Apr 2003 07:30:42 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Apr 2003 21:11:50 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Aug 2003 09:47:12 GMT",
"version": "v3"
},
{
"created": "Sun, 7 Sep 2003 15:52:09 GMT",
"version": "v4"
},
{
"created": "Sun, 12 Oct 2003 12:42:28 GMT",
"version": "v5"
},
{
"created": "Tue, 11 Nov 2003 20:35:27 GMT",
"version": "v6"
},
{
"created": "Tue, 9 Dec 2003 18:51:08 GMT",
"version": "v7"
},
{
"created": "Fri, 12 Dec 2003 23:40:38 GMT",
"version": "v8"
},
{
"created": "Thu, 5 Feb 2004 07:09:00 GMT",
"version": "v9"
}
] | 2007-11-12 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Morea",
"Alberto",
""
]
] | In this paper we use, in a preliminary way, the recently released EIGEN2 Earth gravity model, which is based on six months of data of CHAMP only, in order to reassess the systematic error due to the mismodelling in the even zonal harmonics of geopotential in the LAGEOS-LAGEOS II Lense-Thirring experiment involving the nodes of both the LAGEOS satellites and the perigee of LAGEOS II. The first results from the GGM01C Earth gravity model including the first GRACE data are very promising. |
1803.01395 | Andr\'as L\'aszl\'o | Andras Laszlo, Zoltan Zimboras | Quantification of GR effects in muon g-2, EDM and other spin precession
experiments | Final, published version. Conclusions: no measurable GR effect for
g-2 experiments, but significant GR effect for EDM (frozen spin) experiments,
growing unboundedly with Lorentz factor | Classical and Quantum Gravity 35 (2018) 175003 | 10.1088/1361-6382/aacfee | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Morishima, Futamase and Shimizu published a series of manuscripts,
putting forward arguments, based on a post-Newtonian approximative calculation,
that there can be a sizable general relativistic (GR) correction in the
experimental determination of the muon magnetic moment based on spin
precession, i.e., in muon g-2 experiments. In response, other authors argued
that the effect must be much smaller than claimed. Further authors argued that
the effect exactly cancels. Also, the known formulae for de Sitter and
Lense-Thirring effect do not apply due to the non-geodesic motion. All this
indicates that it is difficult to estimate from first principles the influence
of GR corrections in the problem of spin propagation. Therefore, in this paper
we present a full general relativistic calculation in order to quantify this
effect. The main methodology is the purely differential geometrical tool of
Fermi-Walker transport over a Schwarzschild background. Also the Larmor
precession due to the propagation in the electromagnetic field of the
experimental apparatus is included. For the muon g-2 experiments the GR
correction turns out to be very small, well below the present sensitivity.
However, in other similar storage ring experimental settings, such as electric
dipole moment (EDM) search experiments, where the so-called frozen spin method
is used, GR gives a well detectable effect, and should be corrected for. All
frozen spin scenarios are affected which intend to reach a sensitivity of 0.1
microradians/second for the spin precession in the vertical plane.
| [
{
"created": "Sun, 4 Mar 2018 18:04:43 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Mar 2018 18:30:07 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Apr 2018 11:39:32 GMT",
"version": "v3"
},
{
"created": "Thu, 26 Jul 2018 07:16:23 GMT",
"version": "v4"
}
] | 2018-07-27 | [
[
"Laszlo",
"Andras",
""
],
[
"Zimboras",
"Zoltan",
""
]
] | Recently, Morishima, Futamase and Shimizu published a series of manuscripts, putting forward arguments, based on a post-Newtonian approximative calculation, that there can be a sizable general relativistic (GR) correction in the experimental determination of the muon magnetic moment based on spin precession, i.e., in muon g-2 experiments. In response, other authors argued that the effect must be much smaller than claimed. Further authors argued that the effect exactly cancels. Also, the known formulae for de Sitter and Lense-Thirring effect do not apply due to the non-geodesic motion. All this indicates that it is difficult to estimate from first principles the influence of GR corrections in the problem of spin propagation. Therefore, in this paper we present a full general relativistic calculation in order to quantify this effect. The main methodology is the purely differential geometrical tool of Fermi-Walker transport over a Schwarzschild background. Also the Larmor precession due to the propagation in the electromagnetic field of the experimental apparatus is included. For the muon g-2 experiments the GR correction turns out to be very small, well below the present sensitivity. However, in other similar storage ring experimental settings, such as electric dipole moment (EDM) search experiments, where the so-called frozen spin method is used, GR gives a well detectable effect, and should be corrected for. All frozen spin scenarios are affected which intend to reach a sensitivity of 0.1 microradians/second for the spin precession in the vertical plane. |
1803.08060 | Rodrigo Vicente | Rodrigo Vicente, Vitor Cardoso, Jorge C. Lopes | The Penrose process, superradiance and ergoregion instabilities | 20 pages, accepted for publication in PRD | null | 10.1103/PhysRevD.97.084032 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superradiant scattering is a radiation enhancement process that takes place
in many contexts, and which has recently found exciting applications in astro
and particle physics. In the framework of curved spacetime physics, it has been
associated with the classical Penrose process for particles. Superradiance is
usually also associated with bosonic fields around geometries with ergoregions
and horizons. These notions are in clear tension however: the Penrose process
occurs for horizonless geometries, and particles are composed of fermions.
Here, we resolve the tension in its different aspects, by showing that (i)
superradiance occurs for self-interacting fermions on flat spacetime; (ii)
superradiance occurs also for horizonless geometries, where it leads to an
ergoregion instability. Ultracompact, horizonless geometries will usually
respond with echoes of growing amplitude, until rotational (or electrostatic)
energy is extracted from the object; (iii) the Fourier-domain analysis leads to
absence of superradiance when horizons are not present. We elucidate why this
analysis fails to give meaningful results; (iv) finally, we show that
superradiant, ergoregion instabilities have a particle analog of similar growth
timescales and which can power the formation of a structure outside a compact,
rotating star.
| [
{
"created": "Wed, 21 Mar 2018 18:00:20 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Vicente",
"Rodrigo",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Lopes",
"Jorge C.",
""
]
] | Superradiant scattering is a radiation enhancement process that takes place in many contexts, and which has recently found exciting applications in astro and particle physics. In the framework of curved spacetime physics, it has been associated with the classical Penrose process for particles. Superradiance is usually also associated with bosonic fields around geometries with ergoregions and horizons. These notions are in clear tension however: the Penrose process occurs for horizonless geometries, and particles are composed of fermions. Here, we resolve the tension in its different aspects, by showing that (i) superradiance occurs for self-interacting fermions on flat spacetime; (ii) superradiance occurs also for horizonless geometries, where it leads to an ergoregion instability. Ultracompact, horizonless geometries will usually respond with echoes of growing amplitude, until rotational (or electrostatic) energy is extracted from the object; (iii) the Fourier-domain analysis leads to absence of superradiance when horizons are not present. We elucidate why this analysis fails to give meaningful results; (iv) finally, we show that superradiant, ergoregion instabilities have a particle analog of similar growth timescales and which can power the formation of a structure outside a compact, rotating star. |
1111.0967 | Frank C Eckert | Bianca Dittrich and Frank C Eckert | Towards computational insights into the large-scale structure of spin
foams | 10 pages, 9 figures, to be published in proceedings of the Loops'11
Madrid international conference on quantum gravity | null | 10.1088/1742-6596/360/1/012004 | null | gr-qc cond-mat.str-el hep-lat quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Understanding the large-scale physics is crucial for the spin foam approach
to quantum gravity. We tackle this challenge from a statistical physics
perspective using simplified, yet feature-rich models. In particular, this
allows us to explicitly answer whether broken symmetries will be restored by
renormalization: We observe a weak phase transition in both Migdal-Kadanoff and
tensor network renormalization. In this work we give a concise presentation of
the concepts, results and promises of this new direction of research.
| [
{
"created": "Thu, 3 Nov 2011 20:00:04 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Dittrich",
"Bianca",
""
],
[
"Eckert",
"Frank C",
""
]
] | Understanding the large-scale physics is crucial for the spin foam approach to quantum gravity. We tackle this challenge from a statistical physics perspective using simplified, yet feature-rich models. In particular, this allows us to explicitly answer whether broken symmetries will be restored by renormalization: We observe a weak phase transition in both Migdal-Kadanoff and tensor network renormalization. In this work we give a concise presentation of the concepts, results and promises of this new direction of research. |
1404.7210 | Peter Taylor | Peter Taylor | Propagation of Test Particles and Scalar Fields on a Class of Wormhole
Space-Times | Corrected a significant error in Sec. III. In a previous version, the
values of the coupling constant for which the scalar field is stable was
stated incorrectly | Phys. Rev. D 95, 109904 (2017) | 10.1103/PhysRevD.90.024057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider the problem of test particles and test scalar
fields propagating on the background of a class of wormhole space-times. For
test particles, we solve for arbitrary causal geodesics in terms of integrals
which are solved numerically. These integrals are parametrized by the radius
and shape of the wormhole throat as well as the initial conditions of the
geodesic trajectory. In terms of these parameters, we compute the conditions
for the geodesic to traverse the wormhole, to be reflected by the wormhole's
potential or to be captured on an unstable bound orbit at the wormhole's
throat. These causal geodesics are visualized by embedding plots in Euclidean
space in cylindrical coordinates. For massless test scalar fields, we compute
transmission coefficients and quasi-normal modes for arbitrary coupling of the
field to the background geometry in the WKB approximation. We show that
solutions of the scalar wave equation on this class of wormholes are stable
only for certain values of the coupling constant. This analysis is interesting
since recent computations of self-interactions of a static scalar field in
wormhole space-times reveal some anomalous dependence on the coupling constant
such as the existence of an infinite discrete set of poles. We show that this
pathological behavior of the self-field is an artifact of computing the
interaction for values of the coupling constant that do not lie in the domain
of stability.
| [
{
"created": "Tue, 29 Apr 2014 02:08:55 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2014 10:00:31 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Apr 2016 15:12:35 GMT",
"version": "v3"
}
] | 2017-05-31 | [
[
"Taylor",
"Peter",
""
]
] | In this paper, we consider the problem of test particles and test scalar fields propagating on the background of a class of wormhole space-times. For test particles, we solve for arbitrary causal geodesics in terms of integrals which are solved numerically. These integrals are parametrized by the radius and shape of the wormhole throat as well as the initial conditions of the geodesic trajectory. In terms of these parameters, we compute the conditions for the geodesic to traverse the wormhole, to be reflected by the wormhole's potential or to be captured on an unstable bound orbit at the wormhole's throat. These causal geodesics are visualized by embedding plots in Euclidean space in cylindrical coordinates. For massless test scalar fields, we compute transmission coefficients and quasi-normal modes for arbitrary coupling of the field to the background geometry in the WKB approximation. We show that solutions of the scalar wave equation on this class of wormholes are stable only for certain values of the coupling constant. This analysis is interesting since recent computations of self-interactions of a static scalar field in wormhole space-times reveal some anomalous dependence on the coupling constant such as the existence of an infinite discrete set of poles. We show that this pathological behavior of the self-field is an artifact of computing the interaction for values of the coupling constant that do not lie in the domain of stability. |
1910.05642 | Daniele Pranzetti | Laurent Freidel, Etera R. Livine, Daniele Pranzetti | Kinematical Gravitational Charge Algebra | version 2, 14 pages, some typos fixed; published version | Phys. Rev. D 101, 024012 (2020) | 10.1103/PhysRevD.101.024012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When formulated in terms of connection and coframes, and in the time gauge,
the phase space of general relativity consists of a pair of conjugate fields:
the flux 2-form and the Ashtekar connection. On this phase-space, one has to
impose the Gauss constraints, the vector, and scalar Hamiltonian constraints.
These are respectively generating local SU(2) gauge transformations, spatial
diffeomorphisms, and time diffeomorphisms. We write the Gauss and space
diffeomorphism constraints as conservation laws for a set of boundary charges,
representing spin and momenta, respectively. We prove that these kinematical
charges generate a local Poincar\'e ISU(2) symmetry algebra. This gives strong
support to the recent proposal of Poincar\'e charge networks as a new realm for
discretized general relativity [Classical Quantum Gravity 36, 195014 (2019)].
| [
{
"created": "Sat, 12 Oct 2019 20:17:09 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jan 2020 09:54:22 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Freidel",
"Laurent",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Pranzetti",
"Daniele",
""
]
] | When formulated in terms of connection and coframes, and in the time gauge, the phase space of general relativity consists of a pair of conjugate fields: the flux 2-form and the Ashtekar connection. On this phase-space, one has to impose the Gauss constraints, the vector, and scalar Hamiltonian constraints. These are respectively generating local SU(2) gauge transformations, spatial diffeomorphisms, and time diffeomorphisms. We write the Gauss and space diffeomorphism constraints as conservation laws for a set of boundary charges, representing spin and momenta, respectively. We prove that these kinematical charges generate a local Poincar\'e ISU(2) symmetry algebra. This gives strong support to the recent proposal of Poincar\'e charge networks as a new realm for discretized general relativity [Classical Quantum Gravity 36, 195014 (2019)]. |
gr-qc/9511041 | Renato Klippert Barcellos | Luciane R. de Freitas, M. Novello | What is the Velocity of Gravitational Waves? | 25 pages, LaTeX | null | null | LAFEX-95-MN1 | gr-qc | null | We present a new field theory of gravity. It incorporates a great part of
General Relativity (GR) and can be interpreted in the standard geometrical way
like GR as far as the interaction of matter to gravity is concerned. However,
it differs from GR when treating gravity to gravity interaction. The most
crucial distinction concerns the velocity of propagation of gravitational
waves. Since there is a large expectation that the detection of gravitational
waves will occur in the near future the question of which theory describes
Nature better will probably be settled soon.
| [
{
"created": "Tue, 14 Nov 1995 16:36:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Freitas",
"Luciane R.",
""
],
[
"Novello",
"M.",
""
]
] | We present a new field theory of gravity. It incorporates a great part of General Relativity (GR) and can be interpreted in the standard geometrical way like GR as far as the interaction of matter to gravity is concerned. However, it differs from GR when treating gravity to gravity interaction. The most crucial distinction concerns the velocity of propagation of gravitational waves. Since there is a large expectation that the detection of gravitational waves will occur in the near future the question of which theory describes Nature better will probably be settled soon. |
2011.13957 | Abolhassan Mohammadi | Abolhassan Mohammadi, Tayeb Golanbari, Jamil Enayati, Shahram
Jalalzadeh, Khaled Saaidi | Revisiting Scalar Tensor inflation by swampland criteria and Reheating | 28 pages, 14 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The scenario of the slow-roll inflation is studied in the frame of the
scalar-tensor theory of gravity where the scalar field has a non-minimal
coupling to the geometric part. After deriving the main dynamical and
perturbation equations, the model is investigated in detail for different
functions of the potential and the coupling function. Considering the
consistency of the model with observational model results into specific ranges
for the free constants of the model. Then, the obtained ranges are reconsidered
to realize whether they satisfy the swampland criteria. It is found that the
swampland criteria impose another limitation and reduce the ranges. Using the
final outcomes for the free constants of the model, we briefly consider the
reheating phase to find out about the number of e-fold for the phase and the
reheating temperature.
| [
{
"created": "Fri, 27 Nov 2020 19:02:55 GMT",
"version": "v1"
}
] | 2020-12-01 | [
[
"Mohammadi",
"Abolhassan",
""
],
[
"Golanbari",
"Tayeb",
""
],
[
"Enayati",
"Jamil",
""
],
[
"Jalalzadeh",
"Shahram",
""
],
[
"Saaidi",
"Khaled",
""
]
] | The scenario of the slow-roll inflation is studied in the frame of the scalar-tensor theory of gravity where the scalar field has a non-minimal coupling to the geometric part. After deriving the main dynamical and perturbation equations, the model is investigated in detail for different functions of the potential and the coupling function. Considering the consistency of the model with observational model results into specific ranges for the free constants of the model. Then, the obtained ranges are reconsidered to realize whether they satisfy the swampland criteria. It is found that the swampland criteria impose another limitation and reduce the ranges. Using the final outcomes for the free constants of the model, we briefly consider the reheating phase to find out about the number of e-fold for the phase and the reheating temperature. |
2212.02999 | Yergali Kurmanov Dr. | Kuantay Boshkayev, Talgar Konysbayev, Yergali Kurmanov, Orlando
Luongo, Marco Muccino, Hernando Quevedo, Gulnur Zhumakhanova | Numerical analyses of M31 dark matter profiles | 10 pages, 7 figures and 7 tables | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reproduce the rotation curve of the Andromeda galaxy (M31) by taking into
account its bulge, disk, and halo components, considering the last one to
contain the major part of dark matter mass. Hence, our prescription is to split
the galactic bulge into two components, namely, the inner and main bulges,
respectively. Both bulges are thus modeled by exponential density profiles
since we underline that the widely accepted de Vaucouleurs law fails to
reproduce the whole galactic bulge rotation curve. In addition, we adopt
various well-known phenomenological dark matter profiles to estimate the dark
matter mass in the halo region. Moreover, we apply the least-squares fitting
method to determine from the rotation curve the model free parameters, namely,
the characteristic (central) density, scale radius, and consequently the total
mass. To do so, we perform Markov chain Monte Carlo statistical analyses based
on the Metropolis algorithm, maximizing our likelihoods adopting velocity and
radii data points of the rotation curves. We do not fit separately the
components for bulges, disk and halo, but we perform an overall fit including
all the components and employing all the data points. Thus, we critically
analyze our corresponding findings and, in particular, we employ the Bayesian
Information Criterion to assess the most accredited model to describe M31 dark
matter dynamics.
| [
{
"created": "Tue, 6 Dec 2022 14:19:46 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Boshkayev",
"Kuantay",
""
],
[
"Konysbayev",
"Talgar",
""
],
[
"Kurmanov",
"Yergali",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Muccino",
"Marco",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Zhumakhanova",
"Gulnur",
""
]
] | We reproduce the rotation curve of the Andromeda galaxy (M31) by taking into account its bulge, disk, and halo components, considering the last one to contain the major part of dark matter mass. Hence, our prescription is to split the galactic bulge into two components, namely, the inner and main bulges, respectively. Both bulges are thus modeled by exponential density profiles since we underline that the widely accepted de Vaucouleurs law fails to reproduce the whole galactic bulge rotation curve. In addition, we adopt various well-known phenomenological dark matter profiles to estimate the dark matter mass in the halo region. Moreover, we apply the least-squares fitting method to determine from the rotation curve the model free parameters, namely, the characteristic (central) density, scale radius, and consequently the total mass. To do so, we perform Markov chain Monte Carlo statistical analyses based on the Metropolis algorithm, maximizing our likelihoods adopting velocity and radii data points of the rotation curves. We do not fit separately the components for bulges, disk and halo, but we perform an overall fit including all the components and employing all the data points. Thus, we critically analyze our corresponding findings and, in particular, we employ the Bayesian Information Criterion to assess the most accredited model to describe M31 dark matter dynamics. |
1701.08203 | Jos\'e Alberto Casto Nogales Vera | Renato Vieira dos Santos, Jos\'e A. C. Nogales | Cosmology from a Lagrangian formulation for Rastall's theory | 13 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a Lagrangian formulation for the theory of Rastall of gravitation.
After proposing a Lagrangian density that reproduces the equations of motion
postulated by Rastall, we study the cosmological consequences and fit the
parameters using recent data from Hubble function $H(z).$ According to two
model selection criteria, one based on corrected Akaike Information Criterion
(AICc) and another on Bayesian Information Criterion (BIC), known to penalize
models with a greater number of parameters, particularly BIC, we obtain some
competitive models relative do $\Lambda CDM.$ In one of these models the
cosmological constant is interpreted as having origin in the creation of matter
due to time dependent gravitational field, as opposed to the origin in the
vacuum energy.
| [
{
"created": "Fri, 27 Jan 2017 21:46:40 GMT",
"version": "v1"
}
] | 2017-01-31 | [
[
"Santos",
"Renato Vieira dos",
""
],
[
"Nogales",
"José A. C.",
""
]
] | We give a Lagrangian formulation for the theory of Rastall of gravitation. After proposing a Lagrangian density that reproduces the equations of motion postulated by Rastall, we study the cosmological consequences and fit the parameters using recent data from Hubble function $H(z).$ According to two model selection criteria, one based on corrected Akaike Information Criterion (AICc) and another on Bayesian Information Criterion (BIC), known to penalize models with a greater number of parameters, particularly BIC, we obtain some competitive models relative do $\Lambda CDM.$ In one of these models the cosmological constant is interpreted as having origin in the creation of matter due to time dependent gravitational field, as opposed to the origin in the vacuum energy. |
2201.07266 | Pablo Bueno | Pablo Bueno, Pablo A. Cano, Quim Llorens, Javier Moreno and Guido van
der Velde | Aspects of three-dimensional higher-curvature gravities | 41 pages; v2: typos fixed, references added | null | 10.1088/1361-6382/ac6cbf | CERN-TH-2022-006 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new results involving general higher-curvature gravities in three
dimensions. The most general Lagrangian can be written as a function of the
Ricci scalar $R$, $\mathcal{S}_2\equiv \tilde R_{a}^b \tilde R_b^a$ and
$\mathcal{S}_3\equiv \tilde R_a^b \tilde R_b^c \tilde R_c^a$ where $\tilde
R_{ab}$ is the traceless part of the Ricci tensor. First, we provide a formula
for the exact number of independent order-$n$ densities, $\#(n)$. This
satisfies the identity $\#(n-6)=\#(n)-n$. Then, we show that, linearized around
a general Einstein solution, a generic order-$n\geq 2$ density can be written
as a linear combination of $R^n$, which does not propagate the generic massive
graviton, plus a density which does not propagate the generic scalar mode,
$R^n-12n(n-1)R^{n-2}\mathcal{S}_2$, plus $\#(n)-2$ densities which contribute
trivially to the linearized equations. Next, we obtain an analytic formula for
the quasinormal frequencies of the BTZ black hole for a general theory. Then,
we provide a recursive formula as well as a general closed expression for
order-$n$ densities which non-trivially satisfy an holographic c-theorem,
clarify their relation with Born-Infeld gravities and prove that they never
propagate the scalar mode. We show that at each order there exist $\#(n-6)$
densities which satisfy the holographic c-theorem trivially and that all of
them are proportional to a single sextic density $\Omega_{(6)}\equiv 6
\mathcal{S}_3^2-\mathcal{S}_2^3$. We prove that there are also $\#(n-6)$
order-$n$ Generalized Quasi-topological densities in three dimensions, all of
which are "trivial" in the sense of making no contribution to the metric
function equation. The set of such densities turns out to coincide exactly with
the one of theories trivially satisfying the holographic c-theorem. We comment
on the relation of $\Omega_{(6)}$ to the Segre classification of
three-dimensional metrics.
| [
{
"created": "Tue, 18 Jan 2022 19:12:52 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jan 2022 14:55:26 GMT",
"version": "v2"
}
] | 2022-06-01 | [
[
"Bueno",
"Pablo",
""
],
[
"Cano",
"Pablo A.",
""
],
[
"Llorens",
"Quim",
""
],
[
"Moreno",
"Javier",
""
],
[
"van der Velde",
"Guido",
""
]
] | We present new results involving general higher-curvature gravities in three dimensions. The most general Lagrangian can be written as a function of the Ricci scalar $R$, $\mathcal{S}_2\equiv \tilde R_{a}^b \tilde R_b^a$ and $\mathcal{S}_3\equiv \tilde R_a^b \tilde R_b^c \tilde R_c^a$ where $\tilde R_{ab}$ is the traceless part of the Ricci tensor. First, we provide a formula for the exact number of independent order-$n$ densities, $\#(n)$. This satisfies the identity $\#(n-6)=\#(n)-n$. Then, we show that, linearized around a general Einstein solution, a generic order-$n\geq 2$ density can be written as a linear combination of $R^n$, which does not propagate the generic massive graviton, plus a density which does not propagate the generic scalar mode, $R^n-12n(n-1)R^{n-2}\mathcal{S}_2$, plus $\#(n)-2$ densities which contribute trivially to the linearized equations. Next, we obtain an analytic formula for the quasinormal frequencies of the BTZ black hole for a general theory. Then, we provide a recursive formula as well as a general closed expression for order-$n$ densities which non-trivially satisfy an holographic c-theorem, clarify their relation with Born-Infeld gravities and prove that they never propagate the scalar mode. We show that at each order there exist $\#(n-6)$ densities which satisfy the holographic c-theorem trivially and that all of them are proportional to a single sextic density $\Omega_{(6)}\equiv 6 \mathcal{S}_3^2-\mathcal{S}_2^3$. We prove that there are also $\#(n-6)$ order-$n$ Generalized Quasi-topological densities in three dimensions, all of which are "trivial" in the sense of making no contribution to the metric function equation. The set of such densities turns out to coincide exactly with the one of theories trivially satisfying the holographic c-theorem. We comment on the relation of $\Omega_{(6)}$ to the Segre classification of three-dimensional metrics. |
2104.12293 | Anna Ijjas | Anna Ijjas and Frans Pretorius and Paul J. Steinhardt and Andrew P.
Sullivan | The Effects of Multiple Modes and Reduced Symmetry on the Rapidity and
Robustness of Slow Contraction | 5 pages, 2 figures | Phys. Lett. B 820 (2021) 136490 | 10.1016/j.physletb.2021.136490 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that the rapidity and robustness of slow contraction in
homogenizing and flattening the universe found in simulations in which the
initial conditions were restricted to non-perturbative variations described by
a single fourier mode along only a single spatial direction are in general
enhanced if the initial variations are along two spatial directions, include
multiple modes, and thereby have reduced symmetry. Particularly significant are
shear effects that only become possible when variations are allowed along two
or more spatial dimensions. Based on the numerical results, we conjecture that
the counterintuitive enhancement occurs because more degrees of freedom are
activated which drive spacetime away from an unstable Kasner fixed point and
towards the stable Friedmann-Robertson-Walker fixed point.
| [
{
"created": "Mon, 26 Apr 2021 00:32:06 GMT",
"version": "v1"
}
] | 2021-07-13 | [
[
"Ijjas",
"Anna",
""
],
[
"Pretorius",
"Frans",
""
],
[
"Steinhardt",
"Paul J.",
""
],
[
"Sullivan",
"Andrew P.",
""
]
] | We demonstrate that the rapidity and robustness of slow contraction in homogenizing and flattening the universe found in simulations in which the initial conditions were restricted to non-perturbative variations described by a single fourier mode along only a single spatial direction are in general enhanced if the initial variations are along two spatial directions, include multiple modes, and thereby have reduced symmetry. Particularly significant are shear effects that only become possible when variations are allowed along two or more spatial dimensions. Based on the numerical results, we conjecture that the counterintuitive enhancement occurs because more degrees of freedom are activated which drive spacetime away from an unstable Kasner fixed point and towards the stable Friedmann-Robertson-Walker fixed point. |
2302.03418 | Tact Ikeda | Tact Ikeda, Kazufumi Takahashi and Tsutomu Kobayashi | Consistency of higher derivative couplings to matter fields in
scalar-tensor gravity | 11pages, no figure | null | 10.1103/PhysRevD.108.044006 | RUP-23-2, YITP-23-11 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Recently, a generalization of invertible disformal transformations containing
higher-order derivatives of a scalar field has been proposed in the context of
scalar-tensor theories of gravity. By applying this generalized disformal
transformation to the Horndeski theory, one can obtain the so-called
generalized disformal Horndeski theories which are more general healthy
scalar-tensor theories than ever. However, it is unclear whether or not the
generalized disformal Horndeski theories can be coupled consistently to matter
fields because introducing a matter field could break the degeneracy conditions
of higher-order scalar-tensor theories and hence yield the unwanted
Ostrogradsky ghost. We investigate this issue and explore the conditions under
which a minimal coupling to a matter field is consistent in the generalized
disformal Horndeski theories without relying on any particular gauge such as
the unitary gauge. We find that all the higher derivative terms in the
generalized disformal transformation are prohibited to avoid the appearance of
the Ostrogradsky ghost, leading to the conclusion that only the theories that
are related to the Horndeski theory through a conventional disformal
transformation remain ghost-free in the presence of minimally coupled matter
fields.
| [
{
"created": "Tue, 7 Feb 2023 12:05:30 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Aug 2023 06:24:13 GMT",
"version": "v2"
}
] | 2023-08-21 | [
[
"Ikeda",
"Tact",
""
],
[
"Takahashi",
"Kazufumi",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | Recently, a generalization of invertible disformal transformations containing higher-order derivatives of a scalar field has been proposed in the context of scalar-tensor theories of gravity. By applying this generalized disformal transformation to the Horndeski theory, one can obtain the so-called generalized disformal Horndeski theories which are more general healthy scalar-tensor theories than ever. However, it is unclear whether or not the generalized disformal Horndeski theories can be coupled consistently to matter fields because introducing a matter field could break the degeneracy conditions of higher-order scalar-tensor theories and hence yield the unwanted Ostrogradsky ghost. We investigate this issue and explore the conditions under which a minimal coupling to a matter field is consistent in the generalized disformal Horndeski theories without relying on any particular gauge such as the unitary gauge. We find that all the higher derivative terms in the generalized disformal transformation are prohibited to avoid the appearance of the Ostrogradsky ghost, leading to the conclusion that only the theories that are related to the Horndeski theory through a conventional disformal transformation remain ghost-free in the presence of minimally coupled matter fields. |
1906.08959 | Olivier Sarbach | Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos
Degollado, Alberto Diez-Tejedor, Miguel Megevand, Dar\'io N\'u\~nez, Olivier
Sarbach | Dynamical evolutions of $\ell$-boson stars in spherical symmetry | 17 pages, 8 figure. Updated version with more details on migrating
case, typos corrected and references added | null | 10.1088/1361-6382/ab4726 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous work, we have found new static, spherically symmetric boson star
solutions which generalize the standard boson stars by allowing a particular
superposition of scalar fields in which each of the fields is characterized by
a fixed value of its non-vanishing angular momentum number $\ell$. We call such
solutions "$\ell$-boson stars". Here, we perform a series of fully non-linear
dynamical simulations of perturbed $\ell$-boson stars in order to study their
stability, and the final fate of unstable configurations. We show that for each
value of $\ell$, the configuration of maximum mass separates the parameter
space into stable and unstable regions. Stable configurations, when perturbed,
oscillate around the unperturbed solution and very slowly return to a
stationary configuration. Unstable configurations, in contrast, can have three
different final states: collapse to a black hole, migration to the stable
branch, or explosion (dissipation) to infinity. Just as it happens with
$\ell=0$ boson stars, migration to the stable branch or dissipation to infinity
depends on the sign of the total binding energy of the star: bound unstable
stars collapse to black holes or migrate to the stable branch, whereas unbound
unstable stars either collapse to a black hole or explode to infinity. Thus,
the parameter $\ell$ allows us to construct a new set of stable configurations.
All our simulations are performed in spherical symmetry, leaving a more
detailed stability analysis including non-spherical perturbations for future
work.
| [
{
"created": "Fri, 21 Jun 2019 05:58:05 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Oct 2019 13:26:59 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Núñez",
"Darío",
""
],
[
"Sarbach",
"Olivier",
""
]
] | In previous work, we have found new static, spherically symmetric boson star solutions which generalize the standard boson stars by allowing a particular superposition of scalar fields in which each of the fields is characterized by a fixed value of its non-vanishing angular momentum number $\ell$. We call such solutions "$\ell$-boson stars". Here, we perform a series of fully non-linear dynamical simulations of perturbed $\ell$-boson stars in order to study their stability, and the final fate of unstable configurations. We show that for each value of $\ell$, the configuration of maximum mass separates the parameter space into stable and unstable regions. Stable configurations, when perturbed, oscillate around the unperturbed solution and very slowly return to a stationary configuration. Unstable configurations, in contrast, can have three different final states: collapse to a black hole, migration to the stable branch, or explosion (dissipation) to infinity. Just as it happens with $\ell=0$ boson stars, migration to the stable branch or dissipation to infinity depends on the sign of the total binding energy of the star: bound unstable stars collapse to black holes or migrate to the stable branch, whereas unbound unstable stars either collapse to a black hole or explode to infinity. Thus, the parameter $\ell$ allows us to construct a new set of stable configurations. All our simulations are performed in spherical symmetry, leaving a more detailed stability analysis including non-spherical perturbations for future work. |
1403.2849 | Roman Juarez | Rom\'an Ju\'arez and David Mart\'inez | Noncommutative Coherent States and Quantum Cosmology | 21 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The set of coherent states for a noncommutative quantum Bianchi I anisotropic
cosmology were built to circumvent the absence of a simultaneous set of
configuration observables. By extending known methods of path integrals with
coherent states to their noncommutative analogues allowed us to obtain the
formal expression of the propagator of the theory in terms of the covariant
Husimi Q-symbol of the quantum constraint. The analysis of the equations of
motion resulting from a steepest descent procedure showed the existence of
solutions displaying a minimum value of the volume scaling function which are,
in turn, compatible with a physically inspired definition for a bounce. More
importantly, a lower bound for the volume at the bounce which incorporates
quantum mechanical and noncommutativite contributions was established. The
asymptotic analysis of the solutions in the vicinity of the bounce was
performed by implementing techniques used in boundary-layer problems. The
numerical simulations that confirm our results are also presented.
| [
{
"created": "Wed, 12 Mar 2014 08:44:37 GMT",
"version": "v1"
}
] | 2014-03-13 | [
[
"Juárez",
"Román",
""
],
[
"Martínez",
"David",
""
]
] | The set of coherent states for a noncommutative quantum Bianchi I anisotropic cosmology were built to circumvent the absence of a simultaneous set of configuration observables. By extending known methods of path integrals with coherent states to their noncommutative analogues allowed us to obtain the formal expression of the propagator of the theory in terms of the covariant Husimi Q-symbol of the quantum constraint. The analysis of the equations of motion resulting from a steepest descent procedure showed the existence of solutions displaying a minimum value of the volume scaling function which are, in turn, compatible with a physically inspired definition for a bounce. More importantly, a lower bound for the volume at the bounce which incorporates quantum mechanical and noncommutativite contributions was established. The asymptotic analysis of the solutions in the vicinity of the bounce was performed by implementing techniques used in boundary-layer problems. The numerical simulations that confirm our results are also presented. |
1107.0466 | Luca Fabbri | Luca Fabbri | Conformal Standard Model | 9 pages | Gen.Rel.Grav.44:3127-3138,2012 | 10.1007/s10714-012-1440-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent papers we have constructed the conformal theory of metric-torsional
gravitation, and in this paper we shall include the gauge fields to study the
conformal U(1) X SU(2) Standard Model; we will show that the metric-torsional
degrees of freedom give rise to a potential of conformal-gauge dynamical
symmetry breaking: consequences are discussed.
| [
{
"created": "Sun, 3 Jul 2011 15:15:01 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2012 22:57:40 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Apr 2014 12:33:22 GMT",
"version": "v3"
}
] | 2014-04-11 | [
[
"Fabbri",
"Luca",
""
]
] | In recent papers we have constructed the conformal theory of metric-torsional gravitation, and in this paper we shall include the gauge fields to study the conformal U(1) X SU(2) Standard Model; we will show that the metric-torsional degrees of freedom give rise to a potential of conformal-gauge dynamical symmetry breaking: consequences are discussed. |
1108.4591 | Debraj Roy | Rabin Banerjee, Sunandan Gangopadhyay and Debraj Roy | Hamiltonian analysis of symmetries in a massive theory of gravity | 15 pages, LaTeX2e; References updated; 16 pages, Minor modifications,
version accepted for publication in JHEP | JHEP 1110 (2011) 121 | 10.1007/JHEP10(2011)121 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the generator of hamiltonian gauge symmetries in a 2+1
dimensional massive theory of gravity, proposed recently, through a systematic
off-shell algorithm. Using a field dependant map among gauge parameters we show
that the symmetries obtained from this generator are on-shell equivalent to the
Poincar\'{e} gauge symmetries. We also clarify certain subtle issues concerning
the implementation of this map.
| [
{
"created": "Tue, 23 Aug 2011 13:21:47 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2011 09:38:29 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Oct 2011 08:20:16 GMT",
"version": "v3"
}
] | 2011-11-30 | [
[
"Banerjee",
"Rabin",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Roy",
"Debraj",
""
]
] | We construct the generator of hamiltonian gauge symmetries in a 2+1 dimensional massive theory of gravity, proposed recently, through a systematic off-shell algorithm. Using a field dependant map among gauge parameters we show that the symmetries obtained from this generator are on-shell equivalent to the Poincar\'{e} gauge symmetries. We also clarify certain subtle issues concerning the implementation of this map. |
gr-qc/0212086 | Joan Ferrando | J.J. Ferrando (U. de Valencia), J.A. S\'aez (U. de Valencia) | On the classification of type D spacetimes | 29 pages, 0 figures | J.Math.Phys. 45 (2004) 652-667 | 10.1063/1.1640795 | null | gr-qc | null | We give a classification of the type D spacetimes based on the invariant
differential properties of the Weyl principal structure. Our classification is
established using tensorial invariants of the Weyl tensor and, consequently,
besides its intrinsic nature, it is valid for the whole set of the type D
metrics and it applies on both, vacuum and non-vacuum solutions. We consider
the Cotton-zero type D metrics and we study the classes that are compatible
with this condition. The subfamily of spacetimes with constant argument of the
Weyl eigenvalue is analyzed in more detail by offering a canonical expression
for the metric tensor and by giving a generalization of some results about the
non-existence of purely magnetic solutions. The usefulness of these results is
illustrated in characterizing and classifying a family of Einstein-Maxwell
solutions. Our approach permits us to give intrinsic and explicit conditions
that label every metric, obtaining in this way an operational algorithm to
detect them. In particular a characterization of the Reissner-Nordstr\"{o}m
metric is accomplished.
| [
{
"created": "Fri, 20 Dec 2002 14:56:55 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Ferrando",
"J. J.",
"",
"U. de Valencia"
],
[
"Sáez",
"J. A.",
"",
"U. de Valencia"
]
] | We give a classification of the type D spacetimes based on the invariant differential properties of the Weyl principal structure. Our classification is established using tensorial invariants of the Weyl tensor and, consequently, besides its intrinsic nature, it is valid for the whole set of the type D metrics and it applies on both, vacuum and non-vacuum solutions. We consider the Cotton-zero type D metrics and we study the classes that are compatible with this condition. The subfamily of spacetimes with constant argument of the Weyl eigenvalue is analyzed in more detail by offering a canonical expression for the metric tensor and by giving a generalization of some results about the non-existence of purely magnetic solutions. The usefulness of these results is illustrated in characterizing and classifying a family of Einstein-Maxwell solutions. Our approach permits us to give intrinsic and explicit conditions that label every metric, obtaining in this way an operational algorithm to detect them. In particular a characterization of the Reissner-Nordstr\"{o}m metric is accomplished. |
1105.0188 | Piero Nicolini | Piero Nicolini and Giorgio Torrieri | The Hawking-Page crossover in noncommutative anti-deSitter space | 24 pages, 6 figure, 1 table, version matching that published on JHEP | JHEP 1108:097,2011 | 10.1007/JHEP08(2011)097 | null | gr-qc hep-ph hep-th nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the problem of a Schwarzschild-anti-deSitter black hole in a
noncommutative geometry framework, thought to be an effective description of
quantum-gravitational spacetime. As a first step we derive the noncommutative
geometry inspired Schwarzschild-anti-deSitter solution. After studying the
horizon structure, we find that the curvature singularity is smeared out by the
noncommutative fluctuations. On the thermodynamics side, we show that the black
hole temperature, instead of a divergent behavior at small scales, admits a
maximum value. This fact implies an extension of the Hawking-Page transition
into a van der Waals-like phase diagram, with a critical point at a critical
cosmological constant size in Plank units and a smooth crossover thereafter. We
speculate that, in the gauge-string dictionary, this corresponds to the
confinement "critical point" in number of colors at finite number of flavors, a
highly non-trivial parameter that can be determined through lattice
simulations.
| [
{
"created": "Sun, 1 May 2011 17:56:20 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Sep 2011 08:24:22 GMT",
"version": "v2"
}
] | 2011-09-14 | [
[
"Nicolini",
"Piero",
""
],
[
"Torrieri",
"Giorgio",
""
]
] | We study the problem of a Schwarzschild-anti-deSitter black hole in a noncommutative geometry framework, thought to be an effective description of quantum-gravitational spacetime. As a first step we derive the noncommutative geometry inspired Schwarzschild-anti-deSitter solution. After studying the horizon structure, we find that the curvature singularity is smeared out by the noncommutative fluctuations. On the thermodynamics side, we show that the black hole temperature, instead of a divergent behavior at small scales, admits a maximum value. This fact implies an extension of the Hawking-Page transition into a van der Waals-like phase diagram, with a critical point at a critical cosmological constant size in Plank units and a smooth crossover thereafter. We speculate that, in the gauge-string dictionary, this corresponds to the confinement "critical point" in number of colors at finite number of flavors, a highly non-trivial parameter that can be determined through lattice simulations. |
0707.2519 | Jose Natario | Filipe C. Mena, Jose Natario and Paul Tod | Gravitational Collapse to Toroidal and Higher Genus asymptotically AdS
Black Holes | 15 pages, 2 figures; v2: typos corrected, references added | Adv.Theor.Math.Phys. 12 (2008) 1163-1181 | null | null | gr-qc astro-ph hep-th | null | We match collapsing inhomogeneous as well as spatially homogeneous but
anisotropic spacetimes to vacuum static exteriors with a negative cosmological
constant and planar or hyperbolic symmetry. The collapsing interiors include
the inhomogeneous solutions of Szekeres and of Barnes, which in turn include
the Lemaitre-Tolman and the McVittie solutions. The collapse can result in
toroidal or higher genus asymptotically AdS black holes.
| [
{
"created": "Tue, 17 Jul 2007 13:35:52 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Apr 2008 10:55:03 GMT",
"version": "v2"
}
] | 2008-07-15 | [
[
"Mena",
"Filipe C.",
""
],
[
"Natario",
"Jose",
""
],
[
"Tod",
"Paul",
""
]
] | We match collapsing inhomogeneous as well as spatially homogeneous but anisotropic spacetimes to vacuum static exteriors with a negative cosmological constant and planar or hyperbolic symmetry. The collapsing interiors include the inhomogeneous solutions of Szekeres and of Barnes, which in turn include the Lemaitre-Tolman and the McVittie solutions. The collapse can result in toroidal or higher genus asymptotically AdS black holes. |
1710.03783 | David Wallace | David Wallace | Why Black Hole Information Loss is Paradoxical | 26 pages. Corrected error in one diagram; other minor revisions | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I distinguish between two versions of the black hole information-loss
paradox. The first arises from apparent failure of unitarity on the spacetime
of a completely evaporating black hole, which appears to be
non-globally-hyperbolic; this is the most commonly discussed version of the
paradox in the foundational and semipopular literature, and the case for
calling it `paradoxical' is less than compelling. But the second arises from a
clash between a fully-statistical-mechanical interpretation of black hole
evaporation and the quantum-field-theoretic description used in derivations of
the Hawking effect. This version of the paradox arises long before a black hole
completely evaporates, seems to be the version that has played a central role
in quantum gravity, and is genuinely paradoxical. After explicating the
paradox, I discuss the implications of more recent work on AdS/CFT duality and
on the `Firewall paradox', and conclude that the paradox is if anything now
sharper. The article is written at a (relatively) introductory level and does
not assume advanced knowledge of quantum gravity.
| [
{
"created": "Tue, 10 Oct 2017 18:53:08 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 00:20:57 GMT",
"version": "v2"
}
] | 2018-06-18 | [
[
"Wallace",
"David",
""
]
] | I distinguish between two versions of the black hole information-loss paradox. The first arises from apparent failure of unitarity on the spacetime of a completely evaporating black hole, which appears to be non-globally-hyperbolic; this is the most commonly discussed version of the paradox in the foundational and semipopular literature, and the case for calling it `paradoxical' is less than compelling. But the second arises from a clash between a fully-statistical-mechanical interpretation of black hole evaporation and the quantum-field-theoretic description used in derivations of the Hawking effect. This version of the paradox arises long before a black hole completely evaporates, seems to be the version that has played a central role in quantum gravity, and is genuinely paradoxical. After explicating the paradox, I discuss the implications of more recent work on AdS/CFT duality and on the `Firewall paradox', and conclude that the paradox is if anything now sharper. The article is written at a (relatively) introductory level and does not assume advanced knowledge of quantum gravity. |
gr-qc/9912035 | Massimo Giovannini | D. Babusci (LNF, INFN) and M. Giovannini (Institute for Theoretical
Physics, Lausanne University) | Upgraded VIRGO detector(s) and stochastic gravitational waves
backgrounds | 19 pages in Revtex style, 9 figures | null | null | UNIL-IPT/99-7 | gr-qc astro-ph hep-ph hep-th | null | The sensitivity achievable by a pair of VIRGO detectors to stochastic and
isotropic gravitational wave backgrounds of cosmological origin is discussed in
view of the development of a second VIRGO interferometer. We describe a
semi-analytical technique allowing to compute the signal-to-noise ratio for
(monotonic or non-monotonic) logarithmic energy spectra of relic gravitons of
arbitrary slope. We apply our results to the case of two correlated and
coaligned VIRGO detectors and we compute their achievable sensitivities. The
maximization of the overlap reduction function is discussed. We focus our
attention on a class of models whose expected sensitivity is more promising,
namely the case of string cosmological gravitons. We perform our calculations
both for the case of minimal string cosmological scenario and in the case of a
non-minimal scenario where a long dilaton dominated phase is present prior to
the onset of the ordinary radiation dominated phase. In this framework, we
study possible improvements of the achievable sensitivities by selective
reduction of the thermal contributions (pendulum and pendulum's internal modes)
to the noise power spectra of the detectors. Since a reduction of the shot
noise does not increase significantly the expected sensitivity of a VIRGO pair
(in spite of the relative spatial location of the two detectors) our findings
support the experimental efforts directed towards a substantial reduction of
thermal noise.
| [
{
"created": "Thu, 9 Dec 1999 12:28:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Babusci",
"D.",
"",
"LNF, INFN"
],
[
"Giovannini",
"M.",
"",
"Institute for Theoretical\n Physics, Lausanne University"
]
] | The sensitivity achievable by a pair of VIRGO detectors to stochastic and isotropic gravitational wave backgrounds of cosmological origin is discussed in view of the development of a second VIRGO interferometer. We describe a semi-analytical technique allowing to compute the signal-to-noise ratio for (monotonic or non-monotonic) logarithmic energy spectra of relic gravitons of arbitrary slope. We apply our results to the case of two correlated and coaligned VIRGO detectors and we compute their achievable sensitivities. The maximization of the overlap reduction function is discussed. We focus our attention on a class of models whose expected sensitivity is more promising, namely the case of string cosmological gravitons. We perform our calculations both for the case of minimal string cosmological scenario and in the case of a non-minimal scenario where a long dilaton dominated phase is present prior to the onset of the ordinary radiation dominated phase. In this framework, we study possible improvements of the achievable sensitivities by selective reduction of the thermal contributions (pendulum and pendulum's internal modes) to the noise power spectra of the detectors. Since a reduction of the shot noise does not increase significantly the expected sensitivity of a VIRGO pair (in spite of the relative spatial location of the two detectors) our findings support the experimental efforts directed towards a substantial reduction of thermal noise. |
gr-qc/9404020 | Eric Woolgar | E. Woolgar | Positive Energy for Asymptotically Anti-de Sitter Schwarzschild
Spacetimes | talk given at Fifth Canadian Conference on General Relativity and
Relativistic Astrophysics, Waterloo, 1993. (Plain TeX) | null | null | null | gr-qc | null | Within the general class of Asymptotically Anti-de Sitter spacetimes that are
asymptotic to the A-de-S Schwarzschild metric, we give a simple positive mass
theorem based on arguments from causal structure. A general result for all
asymptotically A-de-S spacetimes will be given elsewhere.
| [
{
"created": "Mon, 11 Apr 1994 22:51:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Woolgar",
"E.",
""
]
] | Within the general class of Asymptotically Anti-de Sitter spacetimes that are asymptotic to the A-de-S Schwarzschild metric, we give a simple positive mass theorem based on arguments from causal structure. A general result for all asymptotically A-de-S spacetimes will be given elsewhere. |
0711.4558 | Enrico Barausse | E. Barausse (SISSA, Italy) and L. Rezzolla (AEI, Germany) | The influence of the hydrodynamic drag from an accretion torus on
extreme mass-ratio inspirals | 21 pages, 8 figures. Phys. Rev. D, in press. Typos fixed and minor
changes; added discussion on the gravitational pull exerted by the torus | Phys.Rev.D77:104027,2008 | 10.1103/PhysRevD.77.104027 | null | gr-qc astro-ph | null | We have studied extreme mass-ratio inspirals (EMRIs) in spacetimes containing
a rotating black hole and a non self-gravitating torus with constant specific
angular momentum. We have found that the effect of the hydrodynamic drag
exerted by the torus on the satellite is much smaller than the corresponding
one due to radiation reaction, for systems such as those generically expected
in AGNs and at distances from the SMBH which can be probed with LISA. However,
given the uncertainty on the parameters of these systems, there exist
configurations in which the effect of the hydrodynamic drag can be comparable
to the radiation-reaction one in phases of the inspiral which are detectable by
LISA. This is the case, for instance, for a 10^6 M_sun SMBH surrounded by a
corotating torus of comparable mass and with radius of 10^3-10^4 gravitational
radii, or for a 10^5 M_sun SMBH surrounded by a corotating 10^4 M_sun torus
with radius of 10^5 gravitational radii. Should these conditions be met in
astrophysical systems, EMRI-gravitational waves could provide a characteristic
signature of the presence of the torus. In fact, while radiation reaction
always increases the inclination of the orbit with respect to the equatorial
plane, the hydrodynamic drag from a torus corotating with the SMBH always
decreases it. However, even when initially dominating over radiation reaction,
the influence of the hydrodynamic drag decays very rapidly as the satellite
moves into the very strong-field region of the SMBH (i.e., p <~ 5M). Although
our results have been obtained for a specific class of tori, we argue that they
will be qualitatively valid also for more generic distributions of the specific
angular momentum.
| [
{
"created": "Wed, 28 Nov 2007 18:55:08 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2007 22:07:50 GMT",
"version": "v2"
},
{
"created": "Fri, 16 May 2008 12:21:39 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Barausse",
"E.",
"",
"SISSA, Italy"
],
[
"Rezzolla",
"L.",
"",
"AEI, Germany"
]
] | We have studied extreme mass-ratio inspirals (EMRIs) in spacetimes containing a rotating black hole and a non self-gravitating torus with constant specific angular momentum. We have found that the effect of the hydrodynamic drag exerted by the torus on the satellite is much smaller than the corresponding one due to radiation reaction, for systems such as those generically expected in AGNs and at distances from the SMBH which can be probed with LISA. However, given the uncertainty on the parameters of these systems, there exist configurations in which the effect of the hydrodynamic drag can be comparable to the radiation-reaction one in phases of the inspiral which are detectable by LISA. This is the case, for instance, for a 10^6 M_sun SMBH surrounded by a corotating torus of comparable mass and with radius of 10^3-10^4 gravitational radii, or for a 10^5 M_sun SMBH surrounded by a corotating 10^4 M_sun torus with radius of 10^5 gravitational radii. Should these conditions be met in astrophysical systems, EMRI-gravitational waves could provide a characteristic signature of the presence of the torus. In fact, while radiation reaction always increases the inclination of the orbit with respect to the equatorial plane, the hydrodynamic drag from a torus corotating with the SMBH always decreases it. However, even when initially dominating over radiation reaction, the influence of the hydrodynamic drag decays very rapidly as the satellite moves into the very strong-field region of the SMBH (i.e., p <~ 5M). Although our results have been obtained for a specific class of tori, we argue that they will be qualitatively valid also for more generic distributions of the specific angular momentum. |
1703.04840 | P. A. Gonzalez | P. A. Gonz\'alez, Marco Olivares, Eleftherios Papantonopoulos, Joel
Saavedra and Yerko V\'asquez | Motion of magnetically charged particles in a magnetically charged
stringy black hole spacetime | Version accepted for publication in PRD | Phys. Rev. D 95, 104052 (2017) | 10.1103/PhysRevD.95.104052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the motion of massive particles with electric and magnetic charges
in the background of a magnetically charged Garfinkle-Horowitz-Strominger
stringy black hole. We solve analytically the equations of motion of the test
particles and we describe the orbital motion in terms of the Weierstrass
elliptic functions. We find that there are critical values of the magnetic
charge of the black hole and the magnetic charge of the test particle which
characterize the bound and unbound orbits and we study two observables, the
perihelion shift and the Lense-Thirring effect. The trajectories depend on the
electric and magnetic charges of the test particle. While the angular-motion
depends on the electric charge of the test particle, the $r$ and $t$-motion
depends on the mass and the magnetic charge of the test particle.
| [
{
"created": "Tue, 14 Mar 2017 23:57:07 GMT",
"version": "v1"
},
{
"created": "Thu, 11 May 2017 13:11:59 GMT",
"version": "v2"
}
] | 2017-06-07 | [
[
"González",
"P. A.",
""
],
[
"Olivares",
"Marco",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Saavedra",
"Joel",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We study the motion of massive particles with electric and magnetic charges in the background of a magnetically charged Garfinkle-Horowitz-Strominger stringy black hole. We solve analytically the equations of motion of the test particles and we describe the orbital motion in terms of the Weierstrass elliptic functions. We find that there are critical values of the magnetic charge of the black hole and the magnetic charge of the test particle which characterize the bound and unbound orbits and we study two observables, the perihelion shift and the Lense-Thirring effect. The trajectories depend on the electric and magnetic charges of the test particle. While the angular-motion depends on the electric charge of the test particle, the $r$ and $t$-motion depends on the mass and the magnetic charge of the test particle. |
gr-qc/0011092 | Jose' P. S. Lemos | Jose' P. S. Lemos | Black holes with toroidal, cylindrical and planar horizons in anti-de
Sitter spacetimes in general relativity and their properties | LaTeX file (World Scientific macros), no figures, 16 pages, talk
given at the 10th Portuguese Meeting on Astronomy and Astrophysics, (Lisbon,
Portugal, 27-28 July 2000), in Astronomy and Astrophysics: Recent
Developments, Proceedings of the 10th A & A meeting, edited by J. P. S.
Lemos, A. Mourao, L. Teodoro, R. Ugoccioni, (World Scientific, 2001),
improved version, change of title, references added | null | 10.1142/9789812811110_0011 | null | gr-qc astro-ph hep-th | null | We review the toroidal, cylindrical and planar black hole solutions in
anti-de Sitter spacetimes and present their properties.
| [
{
"created": "Mon, 27 Nov 2000 15:51:38 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2001 20:43:32 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Lemos",
"Jose' P. S.",
""
]
] | We review the toroidal, cylindrical and planar black hole solutions in anti-de Sitter spacetimes and present their properties. |
1206.3675 | Sergio Ulhoa | S. C. Ulhoa and P. M. M. Rocha | Neutron Stars in Teleparallel Gravity | 19 pages, 14 figures. arXiv admin note: text overlap with
arXiv:1206.3317 | Brazilian Journal of Physics, June 2013, Volume 43, Issue 3, pp
162-171 | 10.1007/s13538-013-0121-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we deal with neutron stars, which are described by a perfect
fluid model, in the context of the teleparallel equivalent of general
relativity. We use numerical simulations to find the relationship between the
angular momentum of the field and the angular momentum of the source. Such a
relation was established for each stable star reached by the numerical
simulation once the code is fed with an equation of state, the central energy
density and the ratio between polar and equatorial radii. We also find a regime
where linear relation between gravitational angular momentum and moment of
inertia (as well as angular velocity of the fluid) is valid. We give the
spatial distribution of the gravitational energy and show that it has a linear
dependence with the squared angular velocity of the source.
| [
{
"created": "Sat, 16 Jun 2012 16:39:47 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Mar 2013 14:43:06 GMT",
"version": "v2"
}
] | 2013-12-06 | [
[
"Ulhoa",
"S. C.",
""
],
[
"Rocha",
"P. M. M.",
""
]
] | In this paper we deal with neutron stars, which are described by a perfect fluid model, in the context of the teleparallel equivalent of general relativity. We use numerical simulations to find the relationship between the angular momentum of the field and the angular momentum of the source. Such a relation was established for each stable star reached by the numerical simulation once the code is fed with an equation of state, the central energy density and the ratio between polar and equatorial radii. We also find a regime where linear relation between gravitational angular momentum and moment of inertia (as well as angular velocity of the fluid) is valid. We give the spatial distribution of the gravitational energy and show that it has a linear dependence with the squared angular velocity of the source. |
gr-qc/9706003 | Hongsu Kim | Hongsu Kim (Ewha Women's Univ., Korea) | Toward a Complete Analysis of the Global Structure of Kerr-Newman
Spacetime | 18 pages, Revtex | null | null | null | gr-qc hep-th | null | An attempt is made to supplement Carter's partial investigation of the global
structure of Kerr-Newman spacetime on the symmetry axis. Namely, the global
structure of \theta = const. timelike submanifolds of Kerr-Newman metric
starting from the symmetry axis all the way down to the equatorial plane are
studied by introducing a new time coordinate slightly different from the usual
Boyer-Lindquist time coordinate. It turns out that the maximal anaytic
extension of \theta = \theta_0 (0 \leq \theta_0 < \pi/2) submanifolds is the
same as that of the symmetry axis first studied by Carter whereas \theta =
\pi/2 equatorial plane has the topology identical to that of the
Reissner-Nordstrom spacetime. General applicability of this method to
Kerr-Newman-type black hole solutions in other gravity theories is discussed as
well.
| [
{
"created": "Mon, 2 Jun 1997 04:46:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kim",
"Hongsu",
"",
"Ewha Women's Univ., Korea"
]
] | An attempt is made to supplement Carter's partial investigation of the global structure of Kerr-Newman spacetime on the symmetry axis. Namely, the global structure of \theta = const. timelike submanifolds of Kerr-Newman metric starting from the symmetry axis all the way down to the equatorial plane are studied by introducing a new time coordinate slightly different from the usual Boyer-Lindquist time coordinate. It turns out that the maximal anaytic extension of \theta = \theta_0 (0 \leq \theta_0 < \pi/2) submanifolds is the same as that of the symmetry axis first studied by Carter whereas \theta = \pi/2 equatorial plane has the topology identical to that of the Reissner-Nordstrom spacetime. General applicability of this method to Kerr-Newman-type black hole solutions in other gravity theories is discussed as well. |
gr-qc/0501086 | Masato Minamitsuji | Masato Minamitsuji, Misao Sasaki and David Langlois | Kaluza-Klein gravitons are negative energy dust in brane cosmology | 17 pages | Phys.Rev.D71:084019,2005 | 10.1103/PhysRevD.71.084019 | YITP-05-03 | gr-qc astro-ph hep-th | null | We discuss the effect of Kaluza-Klein (KK) modes of bulk metric perturbations
on the second Randall-Sundrum (RS II) type brane cosmology, taking the possible
backreaction in the bulk and on the brane into account. KK gravitons may be
produced via quantum fluctuations during a de Sitter (dS) inflating phase of
our brane universe. In an effective 4-dimensional theory in which one
integrates out the extra-dimensional dependence in the action, KK gravitons are
equivalent to massive gravitons on the brane with masses $m>3H/2$, where $H$
represents the expansion rate of a dS brane. Thus production of even a tiny
amount of KK gravitons may eventually have a significant impact on the
late-time brane cosmology. As a first step to quantify the effect of KK
gravitons on the brane, we calculate the effective energy density and pressure
for a single KK mode. Surprisingly, we find that a KK mode behaves as cosmic
dust with a negative energy density on the brane. We note that the bulk energy
density of a KK mode is positive definite and there occurs no singular
phenomenon in the bulk.
| [
{
"created": "Thu, 27 Jan 2005 11:49:12 GMT",
"version": "v1"
}
] | 2009-10-09 | [
[
"Minamitsuji",
"Masato",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Langlois",
"David",
""
]
] | We discuss the effect of Kaluza-Klein (KK) modes of bulk metric perturbations on the second Randall-Sundrum (RS II) type brane cosmology, taking the possible backreaction in the bulk and on the brane into account. KK gravitons may be produced via quantum fluctuations during a de Sitter (dS) inflating phase of our brane universe. In an effective 4-dimensional theory in which one integrates out the extra-dimensional dependence in the action, KK gravitons are equivalent to massive gravitons on the brane with masses $m>3H/2$, where $H$ represents the expansion rate of a dS brane. Thus production of even a tiny amount of KK gravitons may eventually have a significant impact on the late-time brane cosmology. As a first step to quantify the effect of KK gravitons on the brane, we calculate the effective energy density and pressure for a single KK mode. Surprisingly, we find that a KK mode behaves as cosmic dust with a negative energy density on the brane. We note that the bulk energy density of a KK mode is positive definite and there occurs no singular phenomenon in the bulk. |
gr-qc/0606102 | Preston Jones | Preston Jones | Temporal variations in space-time and progenitors of gamma ray burst and
millisecond pulsars | Accept by International Journal of Modern Physics D | Int.J.Mod.Phys.D16:1871-1877,2007 | 10.1142/S0218271807011164 | null | gr-qc | null | A time varying space-time metric is shown to be a source of electromagnetic
radiation. The post-Newtonian approximation is used as a realistic model of the
connection between the space-time metric and a time varying gravitational
potential. Large temporal variations in the metric from the coalescence of
colliding black holes and neutron stars are shown to be possible progenitors of
gamma ray burst and millisecond pulsars.
| [
{
"created": "Fri, 23 Jun 2006 19:44:36 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2006 22:46:02 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Apr 2007 17:28:31 GMT",
"version": "v3"
},
{
"created": "Fri, 31 Aug 2007 16:08:43 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Jones",
"Preston",
""
]
] | A time varying space-time metric is shown to be a source of electromagnetic radiation. The post-Newtonian approximation is used as a realistic model of the connection between the space-time metric and a time varying gravitational potential. Large temporal variations in the metric from the coalescence of colliding black holes and neutron stars are shown to be possible progenitors of gamma ray burst and millisecond pulsars. |
0711.0697 | Kirill Krasnov | Kirill Krasnov | Non-metric gravity: A status report | 13 pages, no figures, invited brief review for MPLA | Mod.Phys.Lett.A22:3013-3026,2007 | 10.1142/S021773230702590X | null | gr-qc astro-ph hep-th | null | We review the status of a certain (infinite) class of four-dimensional
generally covariant theories propagating two degrees of freedom that are
formulated without any direct mention of the metric. General relativity itself
(in its Plebanski formulation) belongs to the class, so these theories are
examples of modified gravity. We summarize the current understanding of the
nature of the modification, of the renormalizability properties of these
theories, of their coupling to matter fields, and describe some of their
physical properties.
| [
{
"created": "Mon, 5 Nov 2007 17:12:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Krasnov",
"Kirill",
""
]
] | We review the status of a certain (infinite) class of four-dimensional generally covariant theories propagating two degrees of freedom that are formulated without any direct mention of the metric. General relativity itself (in its Plebanski formulation) belongs to the class, so these theories are examples of modified gravity. We summarize the current understanding of the nature of the modification, of the renormalizability properties of these theories, of their coupling to matter fields, and describe some of their physical properties. |
2312.07765 | Yerko V\'asquez | Alberto Fritis, Daniel Villalobos-Silva, Yerko V\'asquez, Carlos H.
L\'opez-Caraballo and Juan Carlos Helo | Dynamical system analysis and observational constraints of cosmological
models in mimetic gravity | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of homogeneous and isotropic
Friedmann-Lema\^itre-Robertson-Walker cosmological models with positive spatial
curvature in mimetic gravity theory, employing dynamical system techniques. Our
analysis yields phase space trajectories that describe physically relevant
solutions, capturing various stages of the cosmic evolution. Additionally, we
employ Bayesian statistical analysis to constraint the cosmological parameters
of the models, utilizing data from Supernovae Type Ia and the Hubble parameter
datasets. The observational datasets provide support for the viability of
mimetic gravity models, which effectively can describe the late-time
accelerated expansion of the universe.
| [
{
"created": "Tue, 12 Dec 2023 22:19:08 GMT",
"version": "v1"
}
] | 2023-12-14 | [
[
"Fritis",
"Alberto",
""
],
[
"Villalobos-Silva",
"Daniel",
""
],
[
"Vásquez",
"Yerko",
""
],
[
"López-Caraballo",
"Carlos H.",
""
],
[
"Helo",
"Juan Carlos",
""
]
] | We study the dynamics of homogeneous and isotropic Friedmann-Lema\^itre-Robertson-Walker cosmological models with positive spatial curvature in mimetic gravity theory, employing dynamical system techniques. Our analysis yields phase space trajectories that describe physically relevant solutions, capturing various stages of the cosmic evolution. Additionally, we employ Bayesian statistical analysis to constraint the cosmological parameters of the models, utilizing data from Supernovae Type Ia and the Hubble parameter datasets. The observational datasets provide support for the viability of mimetic gravity models, which effectively can describe the late-time accelerated expansion of the universe. |
1505.06572 | Avisa Behboodi | A. Behboodi, S. Akhshabi, K. Nozari | Braneworld Cosmological Perturbations in Teleparallel Gravity | null | Physics Letters B 750C (2015) pp. 601-608 | 10.1016/j.physletb.2015.09.031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the fully gauge invariant cosmological perturbation equations in
braneworld teleparallel gravity. In this theory, perturbations are the result
of small fluctuations in the pentad field. We derive the gauge invariant
'potentials' for both geometric and matter variables. Unlike the metric
fluctuations in general relativity, pentad perturbations can only contain
scalar and vector modes. As a result, in teleparallel gravity, tensor modes
including gravitational waves, come from the contortion tensor.
| [
{
"created": "Mon, 25 May 2015 09:19:06 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Aug 2015 05:30:38 GMT",
"version": "v2"
}
] | 2015-10-20 | [
[
"Behboodi",
"A.",
""
],
[
"Akhshabi",
"S.",
""
],
[
"Nozari",
"K.",
""
]
] | We describe the fully gauge invariant cosmological perturbation equations in braneworld teleparallel gravity. In this theory, perturbations are the result of small fluctuations in the pentad field. We derive the gauge invariant 'potentials' for both geometric and matter variables. Unlike the metric fluctuations in general relativity, pentad perturbations can only contain scalar and vector modes. As a result, in teleparallel gravity, tensor modes including gravitational waves, come from the contortion tensor. |
1908.01036 | Giovanni Tricella | Stefano Liberati (SISSA, INFN, IFPU), Giovanni Tricella (SISSA, INFN,
IFPU), Andrea Trombettoni (SISSA, INFN) | The information loss problem: an analogue gravity perspective | 35 pages | null | 10.3390/e21100940 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analogue gravity can be used to reproduce the phenomenology of quantum field
theory in curved spacetime and in particular phenomena such as cosmological
particle creation and Hawking radiation. In black hole physics, taking into
account the backreaction of such effects on the metric requires an extension to
semiclassical gravity and leads to an apparent inconsistency in the theory: the
black hole evaporation induces a breakdown of the unitary quantum evolution
leading to the so called information loss problem. Here we show that analogue
gravity can provide an interesting perspective on the resolution of this
problem, albeit the backreaction in analogue systems is not described by
semiclassical Einstein equations. In particular, by looking at the simpler
problem of cosmological particle creation, we show, in the context of
Bose--Einstein condensates analogue gravity, that the emerging analogue
geometry and quasi-particles have correlations due to the quantum nature of the
atomic degrees of freedom underlying the emergent spacetime. The quantum
evolution is, of course, always unitary, but on the whole Hilbert space, which
cannot be exactly factorised a posteriori in geometry and quasi-particle
components. In analogy, in a black hole evaporation one should expect a
continuous process creating correlations between the Hawking quanta and the
microscopic quantum degrees of freedom of spacetime, implying so that only a
full quantum gravity treatment would be able to resolve the information loss
problem by proving the unitary evolution on the full Hilbert space.
| [
{
"created": "Fri, 2 Aug 2019 20:12:18 GMT",
"version": "v1"
}
] | 2019-10-23 | [
[
"Liberati",
"Stefano",
"",
"SISSA, INFN, IFPU"
],
[
"Tricella",
"Giovanni",
"",
"SISSA, INFN,\n IFPU"
],
[
"Trombettoni",
"Andrea",
"",
"SISSA, INFN"
]
] | Analogue gravity can be used to reproduce the phenomenology of quantum field theory in curved spacetime and in particular phenomena such as cosmological particle creation and Hawking radiation. In black hole physics, taking into account the backreaction of such effects on the metric requires an extension to semiclassical gravity and leads to an apparent inconsistency in the theory: the black hole evaporation induces a breakdown of the unitary quantum evolution leading to the so called information loss problem. Here we show that analogue gravity can provide an interesting perspective on the resolution of this problem, albeit the backreaction in analogue systems is not described by semiclassical Einstein equations. In particular, by looking at the simpler problem of cosmological particle creation, we show, in the context of Bose--Einstein condensates analogue gravity, that the emerging analogue geometry and quasi-particles have correlations due to the quantum nature of the atomic degrees of freedom underlying the emergent spacetime. The quantum evolution is, of course, always unitary, but on the whole Hilbert space, which cannot be exactly factorised a posteriori in geometry and quasi-particle components. In analogy, in a black hole evaporation one should expect a continuous process creating correlations between the Hawking quanta and the microscopic quantum degrees of freedom of spacetime, implying so that only a full quantum gravity treatment would be able to resolve the information loss problem by proving the unitary evolution on the full Hilbert space. |
2209.00374 | Quentin Henry | Quentin Henry, Sylvain Marsat, Mohammed Khalil | Spin contributions to the gravitational-waveform modes for spin-aligned
binaries at the 3.5PN order | 36 pages | null | 10.1103/PhysRevD.106.124018 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We complete the post-Newtonian (PN) prediction at the 3.5PN order for the
spin contributions to the gravitational waveforms emitted by inspiraling
compact binaries, in the case of quasi-circular, equatorial orbits, where both
spins are aligned with the orbital angular momentum. Using results from the
multipolar post-Minkowskian wave generation formalism, we extend previous works
that derived the dynamics and gravitational-wave energy flux and phasing, by
computing the full waveform decomposed in spin-weighted spherical harmonics.
This new calculation requires the computation of multipolar moments of higher
multipolar order, new quadratic-in-spin contributions to the hereditary tail
terms entering at the 3.5PN order, as well as other non-linear interactions
between moments. When specialized to the test-mass limit, our results are
equivalent to those obtained in the literature for the waveform emitted by a
test-mass in equatorial, circular orbits around a Kerr black hole. We also
compute the factorized modes for use in effective-one-body waveform models,
correcting the 2.5PN nonspinning and 3PN quadratic-in-spin terms in the (2,1)
mode used in current models.
| [
{
"created": "Thu, 1 Sep 2022 11:36:35 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Oct 2022 16:05:34 GMT",
"version": "v2"
}
] | 2022-12-21 | [
[
"Henry",
"Quentin",
""
],
[
"Marsat",
"Sylvain",
""
],
[
"Khalil",
"Mohammed",
""
]
] | We complete the post-Newtonian (PN) prediction at the 3.5PN order for the spin contributions to the gravitational waveforms emitted by inspiraling compact binaries, in the case of quasi-circular, equatorial orbits, where both spins are aligned with the orbital angular momentum. Using results from the multipolar post-Minkowskian wave generation formalism, we extend previous works that derived the dynamics and gravitational-wave energy flux and phasing, by computing the full waveform decomposed in spin-weighted spherical harmonics. This new calculation requires the computation of multipolar moments of higher multipolar order, new quadratic-in-spin contributions to the hereditary tail terms entering at the 3.5PN order, as well as other non-linear interactions between moments. When specialized to the test-mass limit, our results are equivalent to those obtained in the literature for the waveform emitted by a test-mass in equatorial, circular orbits around a Kerr black hole. We also compute the factorized modes for use in effective-one-body waveform models, correcting the 2.5PN nonspinning and 3PN quadratic-in-spin terms in the (2,1) mode used in current models. |
0905.3673 | Santiago Esteban Perez Bergliaffa | Erico Goulart de Oliveira Costa, Santiago Esteban Perez Bergliaffa | A classification of the effective metric in nonlinear electrodynamics | Accepted for publication in Classical & Quantum Gravity | Class.Quant.Grav.26:135015,2009 | 10.1088/0264-9381/26/13/135015 | null | gr-qc hep-th physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that only two types of effective metrics are possible in certain
nonlinear electromagnetic theories. This is achieved by using the dependence of
the effective metric on the energy-momentum tensor of the background along with
the Segr\`e classification of the latter. Each of these forms is completely
determined by single scalar function, which characterizes the light cone of the
nonlinear theory. We compare this light cone with that of Minkowski in two
examples.
| [
{
"created": "Fri, 22 May 2009 12:49:40 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Costa",
"Erico Goulart de Oliveira",
""
],
[
"Bergliaffa",
"Santiago Esteban Perez",
""
]
] | We show that only two types of effective metrics are possible in certain nonlinear electromagnetic theories. This is achieved by using the dependence of the effective metric on the energy-momentum tensor of the background along with the Segr\`e classification of the latter. Each of these forms is completely determined by single scalar function, which characterizes the light cone of the nonlinear theory. We compare this light cone with that of Minkowski in two examples. |
gr-qc/0111066 | Max Karlovini | Max Karlovini | Axial perturbations of general spherically symmetric spacetimes | 16 pages, no figures, minor corrections | Class.Quant.Grav.19:2125-2140,2002 | 10.1088/0264-9381/19/8/305 | USITP 2001-9 | gr-qc | null | The aim of this paper is to present a governing equation for first order
axial metric perturbations of general, not necessarily static, spherically
symmetric spacetimes. Under the non-restrictive assumption of axisymmetric
perturbations, the governing equation is shown to be a two-dimensional wave
equation where the wave function serves as a twist potential for the
axisymmetry generating Killing vector. This wave equation can be written in a
form which is formally a very simple generalization of the Regge-Wheeler
equation governing the axial perturbations of a Schwarzschild black hole, but
in general the equation is accompanied by a source term related to matter
perturbations. The case of a viscous fluid is studied in particular detail.
| [
{
"created": "Tue, 20 Nov 2001 19:14:54 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Mar 2002 18:38:21 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Karlovini",
"Max",
""
]
] | The aim of this paper is to present a governing equation for first order axial metric perturbations of general, not necessarily static, spherically symmetric spacetimes. Under the non-restrictive assumption of axisymmetric perturbations, the governing equation is shown to be a two-dimensional wave equation where the wave function serves as a twist potential for the axisymmetry generating Killing vector. This wave equation can be written in a form which is formally a very simple generalization of the Regge-Wheeler equation governing the axial perturbations of a Schwarzschild black hole, but in general the equation is accompanied by a source term related to matter perturbations. The case of a viscous fluid is studied in particular detail. |
2405.03471 | Junji Jia | Xinguang Ying and Junji Jia | Off-equatorial deflections and gravitational lensing. II. In general
stationary and axisymmetric spacetimes | 17 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we develop a general perturbative procedure to find the
off-equatorial plane deflections in the weak deflection limit in general
stationary and axisymmetric spacetimes satisfying some common variable
separation conditions. Deflections of both null and timelike rays with the
finite distance effect of the source and detector taken into account are
obtained as dual series of $M/r_0$ and $r_0/r_{s,d}$. These deflections allow a
set of exact gravitational lensing equations from which the images' apparent
angular positions are solved. The method and general results are then applied
to the Kerr-Newmann, Kerr-Sen, and rotating Simpson-Visser spacetimes to study
the effect of the spin and characteristic (effective) charge of the spacetimes
and the source altitude on the deflection angles and image apparent angles. It
is found that in general, both the spacetime spin and charge only affect the
deflections from the second non-trivial order, while the source altitude
influences the deflection from the leading order. Because of these, it is found
that in gravitational lensing in realistic situations, it is hard to measure
the effects of the spacetime spin and charge from the images' apparent
locations. We also presented the off-equatorial deflections in the rotating
Bardeen, Hayward, Ghosh, and Tinchev black hole spacetimes.
| [
{
"created": "Mon, 6 May 2024 13:46:09 GMT",
"version": "v1"
}
] | 2024-05-07 | [
[
"Ying",
"Xinguang",
""
],
[
"Jia",
"Junji",
""
]
] | In this work, we develop a general perturbative procedure to find the off-equatorial plane deflections in the weak deflection limit in general stationary and axisymmetric spacetimes satisfying some common variable separation conditions. Deflections of both null and timelike rays with the finite distance effect of the source and detector taken into account are obtained as dual series of $M/r_0$ and $r_0/r_{s,d}$. These deflections allow a set of exact gravitational lensing equations from which the images' apparent angular positions are solved. The method and general results are then applied to the Kerr-Newmann, Kerr-Sen, and rotating Simpson-Visser spacetimes to study the effect of the spin and characteristic (effective) charge of the spacetimes and the source altitude on the deflection angles and image apparent angles. It is found that in general, both the spacetime spin and charge only affect the deflections from the second non-trivial order, while the source altitude influences the deflection from the leading order. Because of these, it is found that in gravitational lensing in realistic situations, it is hard to measure the effects of the spacetime spin and charge from the images' apparent locations. We also presented the off-equatorial deflections in the rotating Bardeen, Hayward, Ghosh, and Tinchev black hole spacetimes. |
1911.02900 | K\'aroly Zolt\'an Csuk\'as | K\'aroly Csuk\'as and Istv\'an R\'acz | Numerical investigations of the asymptotics of solutions to the
evolutionary form of the constraints | 42 page, 12 figures | K\'aroly Csuk\'as and Istv\'an R\'acz 2020 Class. Quantum Grav. 37
155006 | 10.1088/1361-6382/ab8fce | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Systematic numerical investigations of the asymptotics of near Schwarzschild
vacuum initial data sets is carried out by inspecting solutions to the
parabolic-hyperbolic and to the algebraic-hyperbolic forms of the constraints,
respectively. One of our most important findings is that the concept of near
Schwarzschild configurations, applied previously in [4, 5], is far too
restrictive. It is demonstrated that by relaxing the conditions on the freely
specifiable part of the data a more appropriate notion of near Schwarzschild
initial data configurations can be defined which allows us to generate
asymptotically flat initial data configurations.
| [
{
"created": "Thu, 7 Nov 2019 13:43:19 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2020 23:36:49 GMT",
"version": "v2"
}
] | 2020-07-21 | [
[
"Csukás",
"Károly",
""
],
[
"Rácz",
"István",
""
]
] | Systematic numerical investigations of the asymptotics of near Schwarzschild vacuum initial data sets is carried out by inspecting solutions to the parabolic-hyperbolic and to the algebraic-hyperbolic forms of the constraints, respectively. One of our most important findings is that the concept of near Schwarzschild configurations, applied previously in [4, 5], is far too restrictive. It is demonstrated that by relaxing the conditions on the freely specifiable part of the data a more appropriate notion of near Schwarzschild initial data configurations can be defined which allows us to generate asymptotically flat initial data configurations. |
1012.4246 | Ahmet Baykal | Ahmet Baykal and \"Ozgur Delice | A Unified Approach to Variational Derivatives of Modified Gravitational
Actions | null | Class. Quantum Grav. 28 (2011) 015014 | 10.1088/0264-9381/28/1/015014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our main aim in this paper is to promote the coframe variational method as a
unified approach to derive field equations for any given gravitational action
containing the algebraic functions of the scalars constructed from the Riemann
curvature tensor and its contractions. We are able to derive a master equation
which expresses the variational derivatives of the generalized gravitational
actions in terms of the variational derivatives of its constituent curvature
scalars. Using the Lagrange multiplier method relative to an orthonormal
coframe, we investigate the variational procedures for modified gravitational
Lagrangian densities in spacetime dimensions $n\geqslant 3$. We study
well-known gravitational actions such as those involving the Gauss-Bonnet and
Ricci-squared, Kretchmann scalar, Weyl-squared terms and their algebraic
generalizations similar to generic $f(R)$ theories and the algebraic
generalization of sixth order gravitational Lagrangians. We put forth a new
model involving the gravitational Chern-Simons term and also give three
dimensional New massive gravity equations in a new form in terms of the Cotton
2-form.
| [
{
"created": "Mon, 20 Dec 2010 07:06:16 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Baykal",
"Ahmet",
""
],
[
"Delice",
"Özgur",
""
]
] | Our main aim in this paper is to promote the coframe variational method as a unified approach to derive field equations for any given gravitational action containing the algebraic functions of the scalars constructed from the Riemann curvature tensor and its contractions. We are able to derive a master equation which expresses the variational derivatives of the generalized gravitational actions in terms of the variational derivatives of its constituent curvature scalars. Using the Lagrange multiplier method relative to an orthonormal coframe, we investigate the variational procedures for modified gravitational Lagrangian densities in spacetime dimensions $n\geqslant 3$. We study well-known gravitational actions such as those involving the Gauss-Bonnet and Ricci-squared, Kretchmann scalar, Weyl-squared terms and their algebraic generalizations similar to generic $f(R)$ theories and the algebraic generalization of sixth order gravitational Lagrangians. We put forth a new model involving the gravitational Chern-Simons term and also give three dimensional New massive gravity equations in a new form in terms of the Cotton 2-form. |
2210.03670 | Alexey Toporensky | A. Toporensky and O.Zaslavskii | General radially moving references frames in the black hole background | 20 pages with 1 jpg figure | Eur. Phys. J. C (2023) 83:225 | 10.1140/epjc/s10052-023-11370-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider general radially moving frames realized in the background of
nonextremal black holes having causal structure similar to that of the
Schwarzschild metric. In doing so, we generalize the Lema\^{\i}tre approach,
constructing free-falling frames which are built from the reference particles
with an arbitrary specific energy $e_{0}$ including $e_{0}<0$ and a special
case $e_{0}=0$. The general formula of 3-velocity of a freely falling particle
with the specific energy $e$ with respect to a frame with $% e_{0}$ is
presented. We point out the relation between the properties of considered
frames near a horizon and the Banados-Silk-West effect of an indefinite growth
of energy of particle collisions. Using our radially moving frames, we consider
also nonradial motion of test particles including the regions near the horizon
and singularity. We also point out the properties of the Lema\^{\i}tre time at
horizons depending on the frame and sign of particle energy.
| [
{
"created": "Fri, 7 Oct 2022 16:25:11 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Toporensky",
"A.",
""
],
[
"Zaslavskii",
"O.",
""
]
] | We consider general radially moving frames realized in the background of nonextremal black holes having causal structure similar to that of the Schwarzschild metric. In doing so, we generalize the Lema\^{\i}tre approach, constructing free-falling frames which are built from the reference particles with an arbitrary specific energy $e_{0}$ including $e_{0}<0$ and a special case $e_{0}=0$. The general formula of 3-velocity of a freely falling particle with the specific energy $e$ with respect to a frame with $% e_{0}$ is presented. We point out the relation between the properties of considered frames near a horizon and the Banados-Silk-West effect of an indefinite growth of energy of particle collisions. Using our radially moving frames, we consider also nonradial motion of test particles including the regions near the horizon and singularity. We also point out the properties of the Lema\^{\i}tre time at horizons depending on the frame and sign of particle energy. |
0902.0368 | Neil J. Cornish | Tyson B. Littenberg and Neil J. Cornish | A Bayesian Approach to the Detection Problem in Gravitational Wave
Astronomy | 19 pages, 12 figures, revised to address referee's comments | Phys.Rev.D80:063007,2009 | 10.1103/PhysRevD.80.063007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis of data from gravitational wave detectors can be divided into
three phases: search, characterization, and evaluation. The evaluation of the
detection - determining whether a candidate event is astrophysical in origin or
some artifact created by instrument noise - is a crucial step in the analysis.
The on-going analyses of data from ground based detectors employ a frequentist
approach to the detection problem. A detection statistic is chosen, for which
background levels and detection efficiencies are estimated from Monte Carlo
studies. This approach frames the detection problem in terms of an infinite
collection of trials, with the actual measurement corresponding to some
realization of this hypothetical set. Here we explore an alternative, Bayesian
approach to the detection problem, that considers prior information and the
actual data in hand. Our particular focus is on the computational techniques
used to implement the Bayesian analysis. We find that the Parallel Tempered
Markov Chain Monte Carlo (PTMCMC) algorithm is able to address all three phases
of the anaylsis in a coherent framework. The signals are found by locating the
posterior modes, the model parameters are characterized by mapping out the
joint posterior distribution, and finally, the model evidence is computed by
thermodynamic integration. As a demonstration, we consider the detection
problem of selecting between models describing the data as instrument noise, or
instrument noise plus the signal from a single compact galactic binary. The
evidence ratios, or Bayes factors, computed by the PTMCMC algorithm are found
to be in close agreement with those computed using a Reversible Jump Markov
Chain Monte Carlo algorithm.
| [
{
"created": "Mon, 2 Feb 2009 21:00:28 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jul 2009 17:54:14 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"Littenberg",
"Tyson B.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | The analysis of data from gravitational wave detectors can be divided into three phases: search, characterization, and evaluation. The evaluation of the detection - determining whether a candidate event is astrophysical in origin or some artifact created by instrument noise - is a crucial step in the analysis. The on-going analyses of data from ground based detectors employ a frequentist approach to the detection problem. A detection statistic is chosen, for which background levels and detection efficiencies are estimated from Monte Carlo studies. This approach frames the detection problem in terms of an infinite collection of trials, with the actual measurement corresponding to some realization of this hypothetical set. Here we explore an alternative, Bayesian approach to the detection problem, that considers prior information and the actual data in hand. Our particular focus is on the computational techniques used to implement the Bayesian analysis. We find that the Parallel Tempered Markov Chain Monte Carlo (PTMCMC) algorithm is able to address all three phases of the anaylsis in a coherent framework. The signals are found by locating the posterior modes, the model parameters are characterized by mapping out the joint posterior distribution, and finally, the model evidence is computed by thermodynamic integration. As a demonstration, we consider the detection problem of selecting between models describing the data as instrument noise, or instrument noise plus the signal from a single compact galactic binary. The evidence ratios, or Bayes factors, computed by the PTMCMC algorithm are found to be in close agreement with those computed using a Reversible Jump Markov Chain Monte Carlo algorithm. |
gr-qc/0206025 | Fabio Scardigli | Fabio Scardigli | Some Heuristic Semiclassical Derivations of the Planck Length, the
Hawking Effect and the Unruh Effect | LaTex file, 6 pages, no figures | NuovoCim.B110:1029-1034,1995 | 10.1007/BF02726152 | null | gr-qc | null | The formulae for Planck length, Hawking temperature and Unruh-Davies
temperature are derived by using only laws of classical physics together with
the Heisenberg principle. Besides, it is shown how the Hawking relation can be
deduced from the Unruh relation by means of the principle of equivalence; the
deep link between Hawking effect and Unruh effect is in this way clarified.
| [
{
"created": "Sun, 9 Jun 2002 15:00:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Scardigli",
"Fabio",
""
]
] | The formulae for Planck length, Hawking temperature and Unruh-Davies temperature are derived by using only laws of classical physics together with the Heisenberg principle. Besides, it is shown how the Hawking relation can be deduced from the Unruh relation by means of the principle of equivalence; the deep link between Hawking effect and Unruh effect is in this way clarified. |
gr-qc/0001079 | Jonathan Wilson | J. P. Wilson | Generalised hyperbolicity in space-times with conical singularities | 8 pages AmSTeX, 1 figure | Class.Quant.Grav. 17 (2000) 3199-3210 | 10.1088/0264-9381/17/16/308 | null | gr-qc | null | It is shown that the space-time with a conical singularity, which describes a
thin cosmic string, is hyperbolic in the sense that a unique H^1 solution
exists to the initial value problem for the wave equation with a certain class
of initial data.
| [
{
"created": "Tue, 25 Jan 2000 15:48:21 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Wilson",
"J. P.",
""
]
] | It is shown that the space-time with a conical singularity, which describes a thin cosmic string, is hyperbolic in the sense that a unique H^1 solution exists to the initial value problem for the wave equation with a certain class of initial data. |
1612.09511 | Ghanashyam Date | Ghanashyam Date and Sk Jahanur Hoque | Cosmological Horizon and the Quadrupole Formula in de Sitter Background | Version accepted for publication in phys. rev. D. This version is
slightly shortened, presentation is improved and 3 new references are added.
Results and conclusions are unchanged. 34 pages, 2 figures | Phys. Rev. D 96, 044026 (2017) | 10.1103/PhysRevD.96.044026 | IMSc/2016/12/07 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important class of observables for gravitational waves consists of the
fluxes of energy, momentum and angular momentum carried away by them and are
well understood for weak gravitational waves in Minkowski background. In de
Sitter background, the future null infinity, $\mathcal{J}^+$, is space-like
which makes the meaning of these observables subtle. A spatially compact source
in de Sitter background also provides a distinguished null hypersurface, its
{\em cosmological horizon}, $\mathcal{H}^+$. For sources supporting the short
wavelength approximation, we adopt the Isaacson prescription to define an
effective gravitational stress tensor. We show that the fluxes computed using
this effective stress tensor can be evaluated at $\mathcal{H}^+$, match with
those computed at $\mathcal{J}^+$ and also match with those given by Ashtekar
et al at $\mathcal{J}^+$ {{\em at a coarse grained level}}.
| [
{
"created": "Fri, 30 Dec 2016 15:43:36 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2017 06:49:56 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Aug 2017 07:33:10 GMT",
"version": "v3"
}
] | 2017-08-24 | [
[
"Date",
"Ghanashyam",
""
],
[
"Hoque",
"Sk Jahanur",
""
]
] | An important class of observables for gravitational waves consists of the fluxes of energy, momentum and angular momentum carried away by them and are well understood for weak gravitational waves in Minkowski background. In de Sitter background, the future null infinity, $\mathcal{J}^+$, is space-like which makes the meaning of these observables subtle. A spatially compact source in de Sitter background also provides a distinguished null hypersurface, its {\em cosmological horizon}, $\mathcal{H}^+$. For sources supporting the short wavelength approximation, we adopt the Isaacson prescription to define an effective gravitational stress tensor. We show that the fluxes computed using this effective stress tensor can be evaluated at $\mathcal{H}^+$, match with those computed at $\mathcal{J}^+$ and also match with those given by Ashtekar et al at $\mathcal{J}^+$ {{\em at a coarse grained level}}. |
gr-qc/0010029 | Dzhunushaliev Vladimir | V.Dzhunushaliev | An effective model of the spacetime foam | 12 pg, talk given at the NATO ARW, 24-27 September, Kiev, Ukraina | null | null | null | gr-qc hep-th | null | An approximate model of the spacetime foam is offered in which each quantum
handle (wormhole) is a 5D wormhole-like solution. A spinor field is introduced
for an effective description of this foam. The topological handles of the
spacetime foam can be attached either to one space or connect two different
spaces. In the first case we have a wormhole with the quantum throat and such
object can demonstrate a model of preventing the formation the naked
singularity with relation $e > m$. In the second case the spacetime foam looks
as a dielectric with quantum handles as dipoles. It is supposed that
supergravity theories with a nonminimal interaction between spinor and
electromagnetic fields can be considered as an effective model approximately
describing the spacetime foam.
| [
{
"created": "Mon, 9 Oct 2000 02:57:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dzhunushaliev",
"V.",
""
]
] | An approximate model of the spacetime foam is offered in which each quantum handle (wormhole) is a 5D wormhole-like solution. A spinor field is introduced for an effective description of this foam. The topological handles of the spacetime foam can be attached either to one space or connect two different spaces. In the first case we have a wormhole with the quantum throat and such object can demonstrate a model of preventing the formation the naked singularity with relation $e > m$. In the second case the spacetime foam looks as a dielectric with quantum handles as dipoles. It is supposed that supergravity theories with a nonminimal interaction between spinor and electromagnetic fields can be considered as an effective model approximately describing the spacetime foam. |
1204.4220 | J\"org Hennig | J\"org Hennig | Fully pseudospectral time evolution and its application to 1+1
dimensional physical problems | 18 pages, 8 figures | J. Comput. Phys. 235, 322 (2013) | 10.1016/j.jcp.2012.10.040 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently demonstrated that time-dependent PDE problems can numerically
be solved with a fully pseudospectral scheme, i.e. using spectral expansions
with respect to both spatial and time directions (Hennig and Ansorg, 2009
[15]). This was done with the example of simple scalar wave equations in
Minkowski spacetime. Here we show that the method can be used to study
interesting physical problems that are described by systems of nonlinear PDEs.
To this end we consider two 1+1 dimensional problems: radial oscillations of
spherically symmetric Newtonian stars and time evolution of Gowdy spacetimes as
particular cosmological models in general relativity.
| [
{
"created": "Wed, 18 Apr 2012 22:25:33 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Dec 2012 20:10:08 GMT",
"version": "v2"
}
] | 2012-12-18 | [
[
"Hennig",
"Jörg",
""
]
] | It was recently demonstrated that time-dependent PDE problems can numerically be solved with a fully pseudospectral scheme, i.e. using spectral expansions with respect to both spatial and time directions (Hennig and Ansorg, 2009 [15]). This was done with the example of simple scalar wave equations in Minkowski spacetime. Here we show that the method can be used to study interesting physical problems that are described by systems of nonlinear PDEs. To this end we consider two 1+1 dimensional problems: radial oscillations of spherically symmetric Newtonian stars and time evolution of Gowdy spacetimes as particular cosmological models in general relativity. |
1507.04266 | Christos Tsagas | Christos G. Tsagas and Miltiadis I. Kadiltzoglou | The deceleration parameter in `tilted' Friedmann universes | Typos corrected, published version | Phys.Rev.D92:043515,2015 | 10.1103/PhysRevD.92.043515 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Large-scale peculiar motions are believed to reflect the local inhomogeneity
and anisotropy of the universe, triggered by the ongoing process of structure
formation. As a result, realistic observers do not follow the smooth Hubble
flow but have a peculiar, `tilt', velocity relative to it. Our Local Group of
galaxies, in particular, moves with respect to the universal expansion at a
speed of roughly 600~km/sec. Relative motion effects are known to interfere
with the observations and their interpretation. The strong dipolar anisotropy
seen in the Cosmic Microwave Background, for example, is not treated as a sign
of real universal anisotropy, but as a mere artifact of our peculiar motion
relative to the Hubble flow. With these in mind, we look into the implications
of large-scale bulk motions for the kinematics of their associated observers,
by adopting a `tilted' Friedmann model. Our aim is to examine whether the
deceleration parameter measured in the rest-frame of the bulk flow can differ
from that of the actual universe due to relative-motion effects alone. We find
that there is a difference, which depends on the speed as well as the scale of
the bulk motion. The faster and the smaller the drifting domain, the larger the
difference. In principle, this allows relatively slow peculiar velocities to
have a disproportionately strong effect on the value of the deceleration
parameter measured by observers within bulk flows of, say, few hundred
megaparsecs. In fact, under certain circumstances, it is even possible to
change the sign of the deceleration parameter. It goes without saying that all
these effects vanish identically in the Hubble frame, which makes then an
illusion and mere artifact of the observers' relative motion.
| [
{
"created": "Wed, 15 Jul 2015 15:46:15 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jul 2015 15:08:01 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Jul 2015 15:48:17 GMT",
"version": "v3"
},
{
"created": "Thu, 27 Aug 2015 19:57:55 GMT",
"version": "v4"
}
] | 2015-09-23 | [
[
"Tsagas",
"Christos G.",
""
],
[
"Kadiltzoglou",
"Miltiadis I.",
""
]
] | Large-scale peculiar motions are believed to reflect the local inhomogeneity and anisotropy of the universe, triggered by the ongoing process of structure formation. As a result, realistic observers do not follow the smooth Hubble flow but have a peculiar, `tilt', velocity relative to it. Our Local Group of galaxies, in particular, moves with respect to the universal expansion at a speed of roughly 600~km/sec. Relative motion effects are known to interfere with the observations and their interpretation. The strong dipolar anisotropy seen in the Cosmic Microwave Background, for example, is not treated as a sign of real universal anisotropy, but as a mere artifact of our peculiar motion relative to the Hubble flow. With these in mind, we look into the implications of large-scale bulk motions for the kinematics of their associated observers, by adopting a `tilted' Friedmann model. Our aim is to examine whether the deceleration parameter measured in the rest-frame of the bulk flow can differ from that of the actual universe due to relative-motion effects alone. We find that there is a difference, which depends on the speed as well as the scale of the bulk motion. The faster and the smaller the drifting domain, the larger the difference. In principle, this allows relatively slow peculiar velocities to have a disproportionately strong effect on the value of the deceleration parameter measured by observers within bulk flows of, say, few hundred megaparsecs. In fact, under certain circumstances, it is even possible to change the sign of the deceleration parameter. It goes without saying that all these effects vanish identically in the Hubble frame, which makes then an illusion and mere artifact of the observers' relative motion. |
1907.00781 | Ricardo Gallego Torrom\'e | Ricardo Gallego Torrom\'e | Maximal acceleration geometries and spacetime curvature bounds | Minor corrections; some references added. 28 pages, no figures.
Accepted in International Journal of Geometric Methods in Modern Physics | null | 10.1142/S0219887820500607 | null | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A geometric framework for metrics of maximal acceleration which is applicable
to large proper accelerations is discussed, including a theory of connections
associated with the geometry of maximal acceleration. In such a framework it is
shown that the uniform bound on the proper maximal acceleration implies an
uniform bound for certain bilinear combinations of the Riemannian curvature
components in the domain of the spacetime where curvature is finite.
| [
{
"created": "Fri, 28 Jun 2019 09:59:28 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Dec 2019 12:58:58 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Dec 2019 08:06:23 GMT",
"version": "v3"
},
{
"created": "Sun, 2 Feb 2020 13:25:38 GMT",
"version": "v4"
},
{
"created": "Mon, 9 Mar 2020 16:12:16 GMT",
"version": "v5"
}
] | 2020-07-17 | [
[
"Torromé",
"Ricardo Gallego",
""
]
] | A geometric framework for metrics of maximal acceleration which is applicable to large proper accelerations is discussed, including a theory of connections associated with the geometry of maximal acceleration. In such a framework it is shown that the uniform bound on the proper maximal acceleration implies an uniform bound for certain bilinear combinations of the Riemannian curvature components in the domain of the spacetime where curvature is finite. |
2107.12141 | Hamid Shabani | Hooman Moradpour, Hamid Shabani, Amir Hadi Ziaie and Umesh Kumar
Sharma | Non-minimal coupling inspires the Dirac cosmological model | 8 pages, 3 figures | Eur. Phys. J. Plus 136, 731 (2021) | 10.1140/epjp/s13360-021-01713-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the framework of the generalized Rastall theory (GRT), we study the
ability of a non-minimal coupling between geometry and matter fields in order
to provide a setting which allows for a variable G during the cosmic evolution.
In this regard, the compatibility of this theory with Dirac hypothesis on the
variations of G is investigated, and additionally, the possibility of obtaining
the current accelerated universe is also addressed. In summary, our study
indicates that, in GRT, having in hand the G profile, one may find the
corresponding non-minimal coupling between the energy source and geometry and
vise versa, in a compatible way with the current accelerated universe.
| [
{
"created": "Sun, 11 Jul 2021 06:15:11 GMT",
"version": "v1"
}
] | 2021-07-27 | [
[
"Moradpour",
"Hooman",
""
],
[
"Shabani",
"Hamid",
""
],
[
"Ziaie",
"Amir Hadi",
""
],
[
"Sharma",
"Umesh Kumar",
""
]
] | In the framework of the generalized Rastall theory (GRT), we study the ability of a non-minimal coupling between geometry and matter fields in order to provide a setting which allows for a variable G during the cosmic evolution. In this regard, the compatibility of this theory with Dirac hypothesis on the variations of G is investigated, and additionally, the possibility of obtaining the current accelerated universe is also addressed. In summary, our study indicates that, in GRT, having in hand the G profile, one may find the corresponding non-minimal coupling between the energy source and geometry and vise versa, in a compatible way with the current accelerated universe. |
1707.08663 | Fabi\'an Chaverri-Miranda | Fabian Chaverri-Miranda, Francisco Frutos-Alfaro, Pedro Gomez-Ovarez,
Andree Oliva-Mercado | Innermost stable circular orbits of a Kerr-like Metric with Quadrupole | null | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The innermost stable circular orbit equation of a test particle is obtained
for an approximate Kerr-like spacetime with quadrupole moment. We derived the
effective potential for the radial coordinate by the Euler-Lagrange method.
This equation can be employed to measure the mass quadrupole by observational
means, because from this equation a quadratic polynomial for the quadrupole
moment can be found. As expected, the limiting cases of this equation are found
to be the known cases of Kerr and Schwarzschild.
| [
{
"created": "Wed, 26 Jul 2017 23:24:10 GMT",
"version": "v1"
}
] | 2017-07-28 | [
[
"Chaverri-Miranda",
"Fabian",
""
],
[
"Frutos-Alfaro",
"Francisco",
""
],
[
"Gomez-Ovarez",
"Pedro",
""
],
[
"Oliva-Mercado",
"Andree",
""
]
] | The innermost stable circular orbit equation of a test particle is obtained for an approximate Kerr-like spacetime with quadrupole moment. We derived the effective potential for the radial coordinate by the Euler-Lagrange method. This equation can be employed to measure the mass quadrupole by observational means, because from this equation a quadratic polynomial for the quadrupole moment can be found. As expected, the limiting cases of this equation are found to be the known cases of Kerr and Schwarzschild. |
2303.07385 | Edgar Gasperin | Justin Feng and Edgar Gasperin | Linearised conformal Einstein field equations | 31 pages, 2 figures. Matches published version | null | 10.1088/1361-6382/ace606 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The linearisation of a second-order formulation of the conformal Einstein
field equations (CEFEs) in Generalised Harmonic Gauge (GHG), with trace-free
matter is derived. The linearised equations are obtained for a general
background and then particularised for the study linear perturbations around a
flat background -- the inversion (conformal) representation of the Minkowski
spacetime -- and the solutions discussed. We show that the generalised Lorenz
gauge (defined as the linear analogue of the GHG-gauge) propagates. Moreover,
the equation for the conformal factor can be trivialised with an appropriate
choice for the gauge source functions; this permits a scri-fixing strategy
using gauge source functions for the linearised wave-like CEFE-GHG, which can
in principle be generalised to the nonlinear case. As a particular application
of the linearised equations, the far-field and compact source approximation is
employed to derive quadrupole-like formulae for various conformal fields such
as the perturbation of the rescaled Weyl tensor.
| [
{
"created": "Mon, 13 Mar 2023 18:02:21 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Aug 2023 17:27:55 GMT",
"version": "v2"
}
] | 2023-08-09 | [
[
"Feng",
"Justin",
""
],
[
"Gasperin",
"Edgar",
""
]
] | The linearisation of a second-order formulation of the conformal Einstein field equations (CEFEs) in Generalised Harmonic Gauge (GHG), with trace-free matter is derived. The linearised equations are obtained for a general background and then particularised for the study linear perturbations around a flat background -- the inversion (conformal) representation of the Minkowski spacetime -- and the solutions discussed. We show that the generalised Lorenz gauge (defined as the linear analogue of the GHG-gauge) propagates. Moreover, the equation for the conformal factor can be trivialised with an appropriate choice for the gauge source functions; this permits a scri-fixing strategy using gauge source functions for the linearised wave-like CEFE-GHG, which can in principle be generalised to the nonlinear case. As a particular application of the linearised equations, the far-field and compact source approximation is employed to derive quadrupole-like formulae for various conformal fields such as the perturbation of the rescaled Weyl tensor. |
2005.08071 | Saurya Das | Saurya Das (University of Lethbridge) | There is no coincidence after all! | This essay received an Honorable Mention in the 2020 Gravity Research
Foundation Essay Competition | null | 10.1142/S0218271820430130 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that if Dark Matter is made up of light bosons, they form a
Bose-Einstein condensate in the early Universe. This in turn naturally induces
a Dark Energy of approximately equal density and exerting negative
pressure.This explains the so-called coincidence problem.
| [
{
"created": "Sat, 16 May 2020 19:28:32 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Das",
"Saurya",
"",
"University of Lethbridge"
]
] | We show that if Dark Matter is made up of light bosons, they form a Bose-Einstein condensate in the early Universe. This in turn naturally induces a Dark Energy of approximately equal density and exerting negative pressure.This explains the so-called coincidence problem. |
1110.2094 | Steven Hergt | Steven Hergt, Jan Steinhoff, and Gerhard Schaefer | Elimination of the spin supplementary condition in the effective field
theory approach to the post-Newtonian approximation | 42 pages, document changed to match published version, in press; Ann.
Phys. (N. Y.) (2012) | Annals of Physics 327:1494-1537,2012 | 10.1016/j.aop.2012.02.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper addresses open questions regarding the handling of the spin
supplementary condition within the effective field theory approach to the
post-Newtonian approximation. In particular it is shown how the covariant spin
supplementary condition can be eliminated at the level of the potential (which
is subtle in various respects) and how the dynamics can be cast into a fully
reduced Hamiltonian form. Two different methods are used and compared, one
based on the well-known Dirac bracket and the other based on an action
principle. It is discussed how the latter approach can be used to improve the
Feynman rules by formulating them in terms of reduced canonical spin variables.
| [
{
"created": "Mon, 10 Oct 2011 16:16:17 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Nov 2011 12:00:24 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Mar 2012 13:58:26 GMT",
"version": "v3"
}
] | 2012-05-21 | [
[
"Hergt",
"Steven",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Schaefer",
"Gerhard",
""
]
] | The present paper addresses open questions regarding the handling of the spin supplementary condition within the effective field theory approach to the post-Newtonian approximation. In particular it is shown how the covariant spin supplementary condition can be eliminated at the level of the potential (which is subtle in various respects) and how the dynamics can be cast into a fully reduced Hamiltonian form. Two different methods are used and compared, one based on the well-known Dirac bracket and the other based on an action principle. It is discussed how the latter approach can be used to improve the Feynman rules by formulating them in terms of reduced canonical spin variables. |
gr-qc/0504109 | Piergiorgio Antonini | P. Antonini, M. Okhapkin, E. G\"okl\"u, S. Schiller | Test of constancy of speed of light with rotating cryogenic optical
resonators | 4 pages, 2 figures, accepted for publication Phys. Rev. A (2005) | Phys.Rev. A71 (2005) 050101 | 10.1103/PhysRevA.71.050101 | null | gr-qc | null | A test of Lorentz invariance for electromagnetic waves was performed by
comparing the resonance frequencies of two optical resonators as a function of
orientation in space. In terms of the Robertson-Mansouri-Sexl theory, we obtain
$\beta-\delta-1/2=(+0.5\pm 3\pm 0.7) E-10$, a ten-fold improvement compared to
the previous best results. We also set a first upper limit for a so far unknown
parameter of the Standard Model Extension test theory,
$|(\tilde{\kappa}_{e-})^{ZZ}| < 2\cdot E-14$.
| [
{
"created": "Fri, 22 Apr 2005 11:38:23 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Antonini",
"P.",
""
],
[
"Okhapkin",
"M.",
""
],
[
"Göklü",
"E.",
""
],
[
"Schiller",
"S.",
""
]
] | A test of Lorentz invariance for electromagnetic waves was performed by comparing the resonance frequencies of two optical resonators as a function of orientation in space. In terms of the Robertson-Mansouri-Sexl theory, we obtain $\beta-\delta-1/2=(+0.5\pm 3\pm 0.7) E-10$, a ten-fold improvement compared to the previous best results. We also set a first upper limit for a so far unknown parameter of the Standard Model Extension test theory, $|(\tilde{\kappa}_{e-})^{ZZ}| < 2\cdot E-14$. |
2404.01837 | Muhammad Lawrence Pattersons | M. Lawrence Pattersons, Freddy Permana Zen, Hadyan Luthfan Prihadi,
Getbogi Hikmawan, Agus Suroso | Anisotropic Hartle-Thorne formalism in Rastall gravity | 5 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we extend the Hartle-Thorne formalism for anisotropic pressure
condition in Rastall gravity. As an implication, Tolman-Oppeneimer-Volkoff
equation in anisotropic form is modified. The equations in anisotropic
Hartle-Thorne formalism are also modified due to the appearance of $\lambda$,
i.e. a constant that quantifies the deviation of Rastall gravity from general
relativity. However, our results do not cover $\kappa\lambda=1/4$ and
$\lambda=1/6$, since both would mathematically give singularity in the
calculation.
| [
{
"created": "Tue, 2 Apr 2024 10:49:01 GMT",
"version": "v1"
}
] | 2024-04-03 | [
[
"Pattersons",
"M. Lawrence",
""
],
[
"Zen",
"Freddy Permana",
""
],
[
"Prihadi",
"Hadyan Luthfan",
""
],
[
"Hikmawan",
"Getbogi",
""
],
[
"Suroso",
"Agus",
""
]
] | In this work, we extend the Hartle-Thorne formalism for anisotropic pressure condition in Rastall gravity. As an implication, Tolman-Oppeneimer-Volkoff equation in anisotropic form is modified. The equations in anisotropic Hartle-Thorne formalism are also modified due to the appearance of $\lambda$, i.e. a constant that quantifies the deviation of Rastall gravity from general relativity. However, our results do not cover $\kappa\lambda=1/4$ and $\lambda=1/6$, since both would mathematically give singularity in the calculation. |
2406.03196 | Eric Poisson | Tom Cadogan and Eric Poisson | Self-gravitating anisotropic fluid. III: Relativistic theory | 21 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the third and final entry in a sequence of papers devoted to the
formulation of a theory of self-gravitating anisotropic fluids in Newtonian
gravity and general relativity. In this third paper we elevate the Newtonian
theory of the second paper to general relativity, and apply it to the
construction of relativistic stellar models. The relativistic theory is crafted
by promoting the fluid variables to a curved spacetime, and promoting the
gravitational potential to the spacetime metric. The Newtonian action is then
generalized in a direct and natural way, and dynamical equations for all the
relevant variables are once more obtained through a variational principle. We
specialize our relativistic theory of a self-gravitating anisotropic fluid to
static and spherically symmetric configurations, and thus obtain models of
anisotropic stars in general relativity. As in the Newtonian setting, the
models feature a transition from an anisotropic phase at high density to an
isotropic phase at low density. Our survey of stellar models reveals that for
the same equations of state and the same central density, anisotropic stars are
always less compact than isotropic stars.
| [
{
"created": "Wed, 5 Jun 2024 12:25:50 GMT",
"version": "v1"
}
] | 2024-06-06 | [
[
"Cadogan",
"Tom",
""
],
[
"Poisson",
"Eric",
""
]
] | This is the third and final entry in a sequence of papers devoted to the formulation of a theory of self-gravitating anisotropic fluids in Newtonian gravity and general relativity. In this third paper we elevate the Newtonian theory of the second paper to general relativity, and apply it to the construction of relativistic stellar models. The relativistic theory is crafted by promoting the fluid variables to a curved spacetime, and promoting the gravitational potential to the spacetime metric. The Newtonian action is then generalized in a direct and natural way, and dynamical equations for all the relevant variables are once more obtained through a variational principle. We specialize our relativistic theory of a self-gravitating anisotropic fluid to static and spherically symmetric configurations, and thus obtain models of anisotropic stars in general relativity. As in the Newtonian setting, the models feature a transition from an anisotropic phase at high density to an isotropic phase at low density. Our survey of stellar models reveals that for the same equations of state and the same central density, anisotropic stars are always less compact than isotropic stars. |
2208.09739 | Saeed Rastgoo | Angel Garcia-Chung, Matthew F. Carney, James B. Mertens, Aliasghar
Parvizi, Saeed Rastgoo, Yaser Tavakoli | What do gravitational wave detectors say about polymer quantum effects? | 25 pages, 5 figures, v2: a few new comments added, matches the JCAP
published version | JCAP 11 (2022) 054 | 10.1088/1475-7516/2022/11/054 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the expected response of detector arms of gravitational wave
observatories to polymerized gravitational waves. The mathematical and
theoretical features of these waves were discussed in our previous work. In the
present manuscript, we find both perturbative analytical, and full
nonperturbative numerical solutions to the equations of motion of the detector
arms using the method of geodesic deviations. These results show the
modifications to both frequency and amplitude of the signal measured by the
detector. Furthermore, we study the detectability of these signals in LISA by
analyzing the modes in the frequency space.
| [
{
"created": "Sat, 20 Aug 2022 19:55:07 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2022 18:56:55 GMT",
"version": "v2"
}
] | 2022-11-29 | [
[
"Garcia-Chung",
"Angel",
""
],
[
"Carney",
"Matthew F.",
""
],
[
"Mertens",
"James B.",
""
],
[
"Parvizi",
"Aliasghar",
""
],
[
"Rastgoo",
"Saeed",
""
],
[
"Tavakoli",
"Yaser",
""
]
] | We compute the expected response of detector arms of gravitational wave observatories to polymerized gravitational waves. The mathematical and theoretical features of these waves were discussed in our previous work. In the present manuscript, we find both perturbative analytical, and full nonperturbative numerical solutions to the equations of motion of the detector arms using the method of geodesic deviations. These results show the modifications to both frequency and amplitude of the signal measured by the detector. Furthermore, we study the detectability of these signals in LISA by analyzing the modes in the frequency space. |
gr-qc/9706056 | Peter Leifer | Peter Leifer | Inertia as the ``Threshold of Elasticity'' of Quantum States | 14 pages, LaTeX, submitted for publication | Found.Phys.Lett. 11 (1998) 233-249 | null | null | gr-qc | null | A quantum mechanism of the inertia generation has been proposed. The
threshold of the parametric instability of ``goemetric'' Goldstone modes is
treated as a rest mass.
| [
{
"created": "Wed, 18 Jun 1997 07:26:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Leifer",
"Peter",
""
]
] | A quantum mechanism of the inertia generation has been proposed. The threshold of the parametric instability of ``goemetric'' Goldstone modes is treated as a rest mass. |
2105.11041 | Sebasti\'an N\'ajera Valencia | Sebasti\'an N\'ajera, Aldo Gamboa, Alejandro Aguilar-Nieto, Celia
Escamilla-Rivera | On Negative Mass Cosmology in General Relativity | 4 pages, Version accepted in Astronomy & Astrophysics as letter | A&A 651, L13 (2021) | 10.1051/0004-6361/202141394 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this Letter we present strong arguments in favour of thoroughly revising
the negative mass cosmology (NMC), which has been proposed as a simple
alternative explanation of dark energy and dark matter effects, within the
framework of General Relativity. We show that there are various physical
predictions in this model which require fine-tuning in order to make them
compatible with current cosmological surveys. In this way, the original
motivation of the NMC model becomes obscured due to the imposition of
fine-tuned unknown variables. We conclude that a more rigorous theoretical
treatment is needed in order to make the NMC a viable cosmological model.
| [
{
"created": "Sun, 23 May 2021 23:20:31 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Jul 2021 00:54:20 GMT",
"version": "v2"
}
] | 2021-08-04 | [
[
"Nájera",
"Sebastián",
""
],
[
"Gamboa",
"Aldo",
""
],
[
"Aguilar-Nieto",
"Alejandro",
""
],
[
"Escamilla-Rivera",
"Celia",
""
]
] | In this Letter we present strong arguments in favour of thoroughly revising the negative mass cosmology (NMC), which has been proposed as a simple alternative explanation of dark energy and dark matter effects, within the framework of General Relativity. We show that there are various physical predictions in this model which require fine-tuning in order to make them compatible with current cosmological surveys. In this way, the original motivation of the NMC model becomes obscured due to the imposition of fine-tuned unknown variables. We conclude that a more rigorous theoretical treatment is needed in order to make the NMC a viable cosmological model. |
2301.06976 | Sergey Bondarenko | Sergey Bondarenko, Victor De La Hoz-Coronell | Spinor fields, CPTM symmetry and smallness of cosmological constant in
framework of extended manifold | 31 pages | null | null | null | gr-qc cond-mat.other hep-th | http://creativecommons.org/licenses/by/4.0/ | A model of an extended manifold for the Dirac spinor field is considered. Two
Lagrangians related by CPTM (charge-parity-time-mass) symmetry are constructed
for a pair of the Dirac spinor fields with each spinor field defined in a
separate manifold. An interaction between the matter fields in the manifolds is
introduced through gravity. A fermionic effective action of the general system
is constructed and a tadpole one-loop spinor diagram and part of the one-loop
vacuum diagrams with two external gravitational off-shell fields which
contribute to the effective action are calculated. It is demonstrated that
among different versions of the second spinor Lagrangian there is a special one
for which a cancellation of the mentioned diagrams in the total effective
action takes place. As a result, the diagrams do not contribute to the
cosmological constant, as well there is a zero contribution of the zero point
energies of the spinor fields to the action. The non-zero leading order value
of the cosmological constant for each manifold in the framework is proportional
to the matter density of each separated manifold or difference of the
densities, depending on the chosen model of interaction of gravitational fields
with fermions. An appearance of the dark matter in the model is shortly
discussed as well as further applications of the approach.
| [
{
"created": "Tue, 17 Jan 2023 15:59:40 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jan 2023 10:39:05 GMT",
"version": "v2"
}
] | 2023-01-20 | [
[
"Bondarenko",
"Sergey",
""
],
[
"De La Hoz-Coronell",
"Victor",
""
]
] | A model of an extended manifold for the Dirac spinor field is considered. Two Lagrangians related by CPTM (charge-parity-time-mass) symmetry are constructed for a pair of the Dirac spinor fields with each spinor field defined in a separate manifold. An interaction between the matter fields in the manifolds is introduced through gravity. A fermionic effective action of the general system is constructed and a tadpole one-loop spinor diagram and part of the one-loop vacuum diagrams with two external gravitational off-shell fields which contribute to the effective action are calculated. It is demonstrated that among different versions of the second spinor Lagrangian there is a special one for which a cancellation of the mentioned diagrams in the total effective action takes place. As a result, the diagrams do not contribute to the cosmological constant, as well there is a zero contribution of the zero point energies of the spinor fields to the action. The non-zero leading order value of the cosmological constant for each manifold in the framework is proportional to the matter density of each separated manifold or difference of the densities, depending on the chosen model of interaction of gravitational fields with fermions. An appearance of the dark matter in the model is shortly discussed as well as further applications of the approach. |
gr-qc/0302071 | Simonetta Frittelli | Simonetta Frittelli (Duquesne University) and Roberto Gomez
(Pittsburgh Supercomputing Center) | Einstein boundary conditions for the 3+1 Einstein equations | Revtex 4, 6 pages, text and references added, typos corrected, to
appear in Phys. Rev. D | Phys.Rev. D68 (2003) 044014 | 10.1103/PhysRevD.68.044014 | null | gr-qc | null | In the 3+1 framework of the Einstein equations for the case of vanishing
shift vector and arbitrary lapse, we calculate explicitly the four boundary
equations arising from the vanishing of the projection of the Einstein tensor
along the normal to the boundary surface of the initial-boundary value problem.
Such conditions take the form of evolution equations along (as opposed to
across) the boundary for certain components of the extrinsic curvature and for
certain space-derivatives of the intrinsic metric. We argue that, in general,
such boundary conditions do not follow necessarily from the evolution equations
and the initial data, but need to be imposed on the boundary values of the
fundamental variables. Using the Einstein-Christoffel formulation, which is
strongly hyperbolic, we show how three of the boundary equations should be used
to prescribe the values of some incoming characteristic fields. Additionally,
we show that the fourth one imposes conditions on some outgoing fields.
| [
{
"created": "Mon, 17 Feb 2003 21:01:39 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Aug 2003 15:38:00 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Frittelli",
"Simonetta",
"",
"Duquesne University"
],
[
"Gomez",
"Roberto",
"",
"Pittsburgh Supercomputing Center"
]
] | In the 3+1 framework of the Einstein equations for the case of vanishing shift vector and arbitrary lapse, we calculate explicitly the four boundary equations arising from the vanishing of the projection of the Einstein tensor along the normal to the boundary surface of the initial-boundary value problem. Such conditions take the form of evolution equations along (as opposed to across) the boundary for certain components of the extrinsic curvature and for certain space-derivatives of the intrinsic metric. We argue that, in general, such boundary conditions do not follow necessarily from the evolution equations and the initial data, but need to be imposed on the boundary values of the fundamental variables. Using the Einstein-Christoffel formulation, which is strongly hyperbolic, we show how three of the boundary equations should be used to prescribe the values of some incoming characteristic fields. Additionally, we show that the fourth one imposes conditions on some outgoing fields. |
2206.03512 | Luis Alex Huahuachampi Mamani | Luis A. H. Mamani, Angel D. D. Masa, Lucas Timotheo Sanches and Vilson
T. Zanchin | Revisiting the quasinormal modes of the Schwarzschild black hole:
Numerical analysis | 15 pages, 4 figures | null | 10.1140/epjc/s10052-022-10865-1 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We revisit the problem of calculating the quasinormal modes of spin $0$,
$1/2$, $1$, $3/2$, $2$, and spin $5/2$ fields in the asymptotically flat
Schwarzschild black hole spacetime. Our aim is to investigate the problem from
the numerical point of view, by comparing some numerical methods available in
the literature and still not applied for solving the eigenvalue problems
arising from the perturbation equations in the Schwarzschild black hole
spacetime. We focus on the pseudo-spectral and the asymptotic iteration
methods. These numerical methods are tested against the available results in
the literature, and confronting the precision between each other. Besides
testing the different numerical methods, we calculate higher overtones
quasinormal frequencies for all the investigated perturbation fields in
comparison with the known results. In particular, we obtain purely imaginary
frequencies for spin $1/2$ and $3/2$ fields that are in agreement with analytic
results reported previously in the literature. The purely imaginary frequencies
for the spin $1/2$ field are exactly the same as the frequencies obtained for
the spin $3/2$ field. In turn, the quasinormal frequencies for the spin $5/2$
perturbation field are calculated for the very first time, and purely imaginary
frequencies are found also in this case. We conclude that both methods provide
accurate results and they complement each other.
| [
{
"created": "Tue, 7 Jun 2022 18:00:10 GMT",
"version": "v1"
}
] | 2022-10-26 | [
[
"Mamani",
"Luis A. H.",
""
],
[
"Masa",
"Angel D. D.",
""
],
[
"Sanches",
"Lucas Timotheo",
""
],
[
"Zanchin",
"Vilson T.",
""
]
] | We revisit the problem of calculating the quasinormal modes of spin $0$, $1/2$, $1$, $3/2$, $2$, and spin $5/2$ fields in the asymptotically flat Schwarzschild black hole spacetime. Our aim is to investigate the problem from the numerical point of view, by comparing some numerical methods available in the literature and still not applied for solving the eigenvalue problems arising from the perturbation equations in the Schwarzschild black hole spacetime. We focus on the pseudo-spectral and the asymptotic iteration methods. These numerical methods are tested against the available results in the literature, and confronting the precision between each other. Besides testing the different numerical methods, we calculate higher overtones quasinormal frequencies for all the investigated perturbation fields in comparison with the known results. In particular, we obtain purely imaginary frequencies for spin $1/2$ and $3/2$ fields that are in agreement with analytic results reported previously in the literature. The purely imaginary frequencies for the spin $1/2$ field are exactly the same as the frequencies obtained for the spin $3/2$ field. In turn, the quasinormal frequencies for the spin $5/2$ perturbation field are calculated for the very first time, and purely imaginary frequencies are found also in this case. We conclude that both methods provide accurate results and they complement each other. |
2406.01692 | Kyriakos Destounis Dr. | Romeo Felice Rosato, Kyriakos Destounis and Paolo Pani | Ringdown stability: greybody factors as stable gravitational-wave
observables | 12 pages, 11 figures, references updated, submitted version | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The quasinormal mode spectrum of black holes plays a crucial role in the
modelling of post-merger ringdown signals. However, the spectrum is extremely
sensitive to small deformations of the system and describes the linear response
only in a certain (not precisely defined) timeframe after the merger. We argue
here that the greybody factors, recently shown to describe the ringdown
spectral amplitude at relatively high frequencies, are instead stable under
small perturbations of the system and free of certain ambiguities that plague
the quasinormal mode spectrum. Our analysis also unveils a nontrivial
interplay: while certain ringdown quantities are dominated by the contribution
of spectrally unstable quasinormal modes, these modes conspire to produce
stable observables. Thus, we propose a complementary approach to ringdown
studies, which circumvents some limitations of the standard quasinormal mode
description.
| [
{
"created": "Mon, 3 Jun 2024 18:00:06 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jun 2024 10:33:44 GMT",
"version": "v2"
}
] | 2024-06-14 | [
[
"Rosato",
"Romeo Felice",
""
],
[
"Destounis",
"Kyriakos",
""
],
[
"Pani",
"Paolo",
""
]
] | The quasinormal mode spectrum of black holes plays a crucial role in the modelling of post-merger ringdown signals. However, the spectrum is extremely sensitive to small deformations of the system and describes the linear response only in a certain (not precisely defined) timeframe after the merger. We argue here that the greybody factors, recently shown to describe the ringdown spectral amplitude at relatively high frequencies, are instead stable under small perturbations of the system and free of certain ambiguities that plague the quasinormal mode spectrum. Our analysis also unveils a nontrivial interplay: while certain ringdown quantities are dominated by the contribution of spectrally unstable quasinormal modes, these modes conspire to produce stable observables. Thus, we propose a complementary approach to ringdown studies, which circumvents some limitations of the standard quasinormal mode description. |
1811.00047 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu, Robert B. Mann | Intrinsic curvature and topology of shadows in Kerr spacetime | 6 pages, 6 figures. Accepted for publication as a Rapid Communication
in Physical Review D | Phys. Rev. D 99, 041303 (2019) | 10.1103/PhysRevD.99.041303 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the viewpoint of differential geometry and topology, we investigate the
characterization of the shadows in a Kerr spacetime. Two new quantities, the
length of the shadow boundary and the local curvature radius are introduced.
Each shadow can be uniquely determined by these two quantities. For the black
hole case, the result shows that we can constrain the black hole spin and the
angular coordinate of the observer only by measuring the maximum and minimum of
the curvature radius. While for the naked singularity case, we adopt the length
parameter and the maximum of the curvature radius. This technique is completely
independent of the coordinate system and the location of the shadow, and is
expected to uniquely determine the parameters of the spacetime. Moreover, we
propose a topological covariant quantity to measure and distinguish different
topological structures of the shadows.
| [
{
"created": "Wed, 31 Oct 2018 18:19:59 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jan 2019 21:19:19 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Feb 2019 19:57:00 GMT",
"version": "v3"
}
] | 2019-02-13 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Mann",
"Robert B.",
""
]
] | From the viewpoint of differential geometry and topology, we investigate the characterization of the shadows in a Kerr spacetime. Two new quantities, the length of the shadow boundary and the local curvature radius are introduced. Each shadow can be uniquely determined by these two quantities. For the black hole case, the result shows that we can constrain the black hole spin and the angular coordinate of the observer only by measuring the maximum and minimum of the curvature radius. While for the naked singularity case, we adopt the length parameter and the maximum of the curvature radius. This technique is completely independent of the coordinate system and the location of the shadow, and is expected to uniquely determine the parameters of the spacetime. Moreover, we propose a topological covariant quantity to measure and distinguish different topological structures of the shadows. |
gr-qc/0210051 | Aleksandar Mikovic | A. Mikovic | Spin Foam Models of Yang-Mills Theory Coupled to Gravity | 10 pages | Class.Quant.Grav.20:239-246,2003 | 10.1088/0264-9381/20/1/317 | null | gr-qc hep-th | null | We construct a spin foam model of Yang-Mills theory coupled to gravity by
using a discretized path integral of the BF theory with polynomial interactions
and the Barret-Crane ansatz. In the Euclidian gravity case we obtain a vertex
amplitude which is determined by a vertex operator acting on a simple spin
network function. The Euclidian gravity results can be straightforwardly
extended to the Lorentzian case, so that we propose a Lorentzian spin foam
model of Yang-Mills theory coupled to gravity.
| [
{
"created": "Wed, 16 Oct 2002 14:41:24 GMT",
"version": "v1"
}
] | 2009-01-16 | [
[
"Mikovic",
"A.",
""
]
] | We construct a spin foam model of Yang-Mills theory coupled to gravity by using a discretized path integral of the BF theory with polynomial interactions and the Barret-Crane ansatz. In the Euclidian gravity case we obtain a vertex amplitude which is determined by a vertex operator acting on a simple spin network function. The Euclidian gravity results can be straightforwardly extended to the Lorentzian case, so that we propose a Lorentzian spin foam model of Yang-Mills theory coupled to gravity. |
1902.03106 | Joan Josep Ferrando | Bartolom\'e Coll, Joan Josep Ferrando and Juan Antonio S\'aez | A hydrodynamic approach to the classical ideal gas | 12 pages, no figures, submitted to Physical Review D | Phys. Rev. D 99, 084035 (2019) | 10.1103/PhysRevD.99.084035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The necessary and sufficient condition for a conservative perfect fluid
energy tensor to be the energetic evolution of a classical ideal gas is
obtained. This condition forces the square of the speed of sound to have the
form $c_s^2 = \frac{\gamma p}{\rho+p}$ in terms of the hydrodynamic quantities,
energy density $\rho$ and pressure $p$, $\gamma$ being the (constant) adiabatic
index. The {\em inverse problem} for this case is also solved, that is, the
determination of all the fluids whose evolutions are represented by a
conservative energy tensor endowed with the above expression of $c^2_s$, and it
shows that these fluids are, and only are, those fulfilling a Poisson law. The
relativistic compressibility conditions for the classical ideal gases and the
Poisson gases are analyzed in depth and the values for the adiabatic index
$\gamma$ for which the compressibility conditions hold in physically relevant
ranges of the hydrodynamic quantities $\rho, p$ are obtained. Some scenarios
that model isothermal or isentropic evolutions of a classical ideal gas are
revisited, and preliminary results are presented in applying our hydrodynamic
approach to looking for perfect fluid solutions that model the evolution of a
classical ideal gas or of a Poisson gas.
| [
{
"created": "Fri, 8 Feb 2019 14:38:15 GMT",
"version": "v1"
}
] | 2019-04-24 | [
[
"Coll",
"Bartolomé",
""
],
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | The necessary and sufficient condition for a conservative perfect fluid energy tensor to be the energetic evolution of a classical ideal gas is obtained. This condition forces the square of the speed of sound to have the form $c_s^2 = \frac{\gamma p}{\rho+p}$ in terms of the hydrodynamic quantities, energy density $\rho$ and pressure $p$, $\gamma$ being the (constant) adiabatic index. The {\em inverse problem} for this case is also solved, that is, the determination of all the fluids whose evolutions are represented by a conservative energy tensor endowed with the above expression of $c^2_s$, and it shows that these fluids are, and only are, those fulfilling a Poisson law. The relativistic compressibility conditions for the classical ideal gases and the Poisson gases are analyzed in depth and the values for the adiabatic index $\gamma$ for which the compressibility conditions hold in physically relevant ranges of the hydrodynamic quantities $\rho, p$ are obtained. Some scenarios that model isothermal or isentropic evolutions of a classical ideal gas are revisited, and preliminary results are presented in applying our hydrodynamic approach to looking for perfect fluid solutions that model the evolution of a classical ideal gas or of a Poisson gas. |
2004.01593 | Abdulla Al Mamon | Abdulla Al Mamon, Amir Hadi Ziaie and Kazuharu Bamba | A Generalized Interacting Tsallis Holographic Dark Energy Model and its
thermodynamic implications | v3: minor corrections, published in EPJC | Eur. Phys. J. C 80, 974 (2020) | 10.1140/epjc/s10052-020-08546-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with a theoretical model for interacting Tsallis holographic
dark energy (THDE) whose infrared (IR) cut-off scale is set by the Hubble
length. The interaction $Q$ between the dark sectors (dark energy and
pressureless dark matter) of the universe has been assumed to be
non-gravitational in nature. The functional form of $Q$ is chosen in such a way
that it reproduces well known and most used interactions as special cases. We
then study the nature of the THDE density parameter, the equation of state
parameter, the deceleration parameter and the jerk parameter for this
interacting THDE model. Our study shows that the universe exhibits the usual
thermal history, namely the successive sequence of radiation, dark matter and
dark energy epochs, before resulting in a complete dark energy domination in
the far future. It is shown the evolution of the Hubble parameter for our model
and compared that with the latest Hubble parameter data. Finally, we also
investigate both the stability and thermodynamic nature of this model in the
present context.
| [
{
"created": "Fri, 3 Apr 2020 14:35:07 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jul 2020 09:54:50 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Oct 2020 13:14:57 GMT",
"version": "v3"
}
] | 2020-10-27 | [
[
"Mamon",
"Abdulla Al",
""
],
[
"Ziaie",
"Amir Hadi",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | The paper deals with a theoretical model for interacting Tsallis holographic dark energy (THDE) whose infrared (IR) cut-off scale is set by the Hubble length. The interaction $Q$ between the dark sectors (dark energy and pressureless dark matter) of the universe has been assumed to be non-gravitational in nature. The functional form of $Q$ is chosen in such a way that it reproduces well known and most used interactions as special cases. We then study the nature of the THDE density parameter, the equation of state parameter, the deceleration parameter and the jerk parameter for this interacting THDE model. Our study shows that the universe exhibits the usual thermal history, namely the successive sequence of radiation, dark matter and dark energy epochs, before resulting in a complete dark energy domination in the far future. It is shown the evolution of the Hubble parameter for our model and compared that with the latest Hubble parameter data. Finally, we also investigate both the stability and thermodynamic nature of this model in the present context. |
gr-qc/0307107 | Claudio Benedito Silva Furtado | J. G. de Assis, V. B. Bezerra and C. Furtado | Loop variables and gravitational Berry's quantum phase in the space-time
of a rotating massive body | 8 pages, iopart style | null | null | null | gr-qc | null | In this paper we compute the holonomies along curves in the gravitational
field of a slowly rotating massive body. We use our results to study the
gravitational analogue of Aharanov-Bohm effect in this space-time. We also
investigate the behaviour of a scalar quantum particle in this space-time and
determine Berry's quantum phase acquired by this particle when transported
along a closed curve surrounding the body.
| [
{
"created": "Thu, 24 Jul 2003 19:09:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Assis",
"J. G.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Furtado",
"C.",
""
]
] | In this paper we compute the holonomies along curves in the gravitational field of a slowly rotating massive body. We use our results to study the gravitational analogue of Aharanov-Bohm effect in this space-time. We also investigate the behaviour of a scalar quantum particle in this space-time and determine Berry's quantum phase acquired by this particle when transported along a closed curve surrounding the body. |
2201.02622 | Narges Rashidi | Narges Rashidi | A Tachyon Field around the Black Hole | 20 Pages, 12 Figures, Accepted for publication in International
Journal of Modern Physics D | null | 10.1142/S0218271821501261 | null | gr-qc hep-ph hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We study the effects of the presence of the tachyon field around the black
hole. We show that in presence of the tachyon field, unlike the ordinary
canonical scalar field, the time evolution of the black hole mass depends on
the potential of this field. By considering several types of potential, we
study the behavior of the black hole mass and its time evolution and find some
interesting results. We find that the presence of the tachyon field causes the
accretion of the mass into the black hole. We also show that with linear and
hilltop potentials, in some ranges of the parameters space, the mass of the
black hole can decrease even without any Hawking radiation.
| [
{
"created": "Fri, 7 Jan 2022 08:40:09 GMT",
"version": "v1"
}
] | 2022-01-11 | [
[
"Rashidi",
"Narges",
""
]
] | We study the effects of the presence of the tachyon field around the black hole. We show that in presence of the tachyon field, unlike the ordinary canonical scalar field, the time evolution of the black hole mass depends on the potential of this field. By considering several types of potential, we study the behavior of the black hole mass and its time evolution and find some interesting results. We find that the presence of the tachyon field causes the accretion of the mass into the black hole. We also show that with linear and hilltop potentials, in some ranges of the parameters space, the mass of the black hole can decrease even without any Hawking radiation. |
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