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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1404.2747 | Donato Bini | Donato Bini and Thibault Damour | Two-body gravitational spin-orbit interaction at linear order in the
mass ratio | 22 pages, 3 figures, revtex macros | Phys. Rev. D 90, 024039 (2014) | 10.1103/PhysRevD.90.024039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically compute, to linear order in the mass-ratio, the "geodetic"
spin precession frequency of a small spinning body orbiting a large
(non-spinning) body to the eight-and-a-half post-Newtonian order, thereby
extending previous analytical knowledge which was limited to the third
post-Newtonian level. These results are obtained applying analytical
gravitational self-force theory to the first-derivative level generalization of
Detweiler's gauge-invariant redshift variable. We compare our analytic results
with strong-field numerical data recently obtained by S.~R.~Dolan et al.
[Phys.\ Rev.\ D {\bf 89}, 064011 (2014)]. Our new, high-post-Newtonian-order
results capture the strong-field features exhibited by the numerical data. We
argue that the spin-precession will diverge as $\approx -0.14/(1-3y)$ as the
light-ring is approached. We transcribe our kinematical spin-precession results
into a corresponding improved analytic knowledge of one of the two
(gauge-invariant) effective gyro-gravitomagnetic ratios characterizing
spin-orbit couplings within the effective-one-body formalism. We provide
simple, accurate analytic fits both for spin-precession and the effective
gyro-gravitomagnetic ratio. The latter fit predicts that the
linear-in-mass-ratio correction to the gyro-gravitomagnetic ratio changes sign
before reaching the light-ring. This strong-field prediction might be important
for improving the analytic modeling of coalescing spinning binaries.
| [
{
"created": "Thu, 10 Apr 2014 09:23:53 GMT",
"version": "v1"
}
] | 2014-07-23 | [
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
]
] | We analytically compute, to linear order in the mass-ratio, the "geodetic" spin precession frequency of a small spinning body orbiting a large (non-spinning) body to the eight-and-a-half post-Newtonian order, thereby extending previous analytical knowledge which was limited to the third post-Newtonian level. These results are obtained applying analytical gravitational self-force theory to the first-derivative level generalization of Detweiler's gauge-invariant redshift variable. We compare our analytic results with strong-field numerical data recently obtained by S.~R.~Dolan et al. [Phys.\ Rev.\ D {\bf 89}, 064011 (2014)]. Our new, high-post-Newtonian-order results capture the strong-field features exhibited by the numerical data. We argue that the spin-precession will diverge as $\approx -0.14/(1-3y)$ as the light-ring is approached. We transcribe our kinematical spin-precession results into a corresponding improved analytic knowledge of one of the two (gauge-invariant) effective gyro-gravitomagnetic ratios characterizing spin-orbit couplings within the effective-one-body formalism. We provide simple, accurate analytic fits both for spin-precession and the effective gyro-gravitomagnetic ratio. The latter fit predicts that the linear-in-mass-ratio correction to the gyro-gravitomagnetic ratio changes sign before reaching the light-ring. This strong-field prediction might be important for improving the analytic modeling of coalescing spinning binaries. |
2109.03700 | Christopher Kohler | Christopher Kohler | Gravity with a Dynamical Spinning Aether | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein-aether theory is extended by allowing for spinning degrees of
freedom of the aether. In addition to the acceleration, shear, expansion, and
vorticity of the aether velocity field, a spin rotation describing the dynamics
of a classical intrinsic angular momentum of the aether is introduced as a
kinematic quantity. The action of Einstein-aether theory is augmented by a term
quadratic in the spin rotation and by coupling terms with the vorticity and the
acceleration. Besides breaking the Lorentz boost invariance, the theory breaks
the invariance under spatial rotations in the direction of the aether velocity.
In the weak field limit, there is a linear relationship between the spin
rotation, the vorticity, and the acceleration. Linearized wave solutions
correspond to the ones of Einstein-aether theory where the speeds of the spin 0
and spin 1 mode are modified. The extension of Einstein-aether theory has a
natural formulation in the framework of a teleparallel geometry where the
kinematic quantities become torsion fields.
| [
{
"created": "Wed, 8 Sep 2021 15:05:28 GMT",
"version": "v1"
}
] | 2021-09-09 | [
[
"Kohler",
"Christopher",
""
]
] | Einstein-aether theory is extended by allowing for spinning degrees of freedom of the aether. In addition to the acceleration, shear, expansion, and vorticity of the aether velocity field, a spin rotation describing the dynamics of a classical intrinsic angular momentum of the aether is introduced as a kinematic quantity. The action of Einstein-aether theory is augmented by a term quadratic in the spin rotation and by coupling terms with the vorticity and the acceleration. Besides breaking the Lorentz boost invariance, the theory breaks the invariance under spatial rotations in the direction of the aether velocity. In the weak field limit, there is a linear relationship between the spin rotation, the vorticity, and the acceleration. Linearized wave solutions correspond to the ones of Einstein-aether theory where the speeds of the spin 0 and spin 1 mode are modified. The extension of Einstein-aether theory has a natural formulation in the framework of a teleparallel geometry where the kinematic quantities become torsion fields. |
2404.14756 | Jin Young Kim | Jin Young Kim | Deflection of light by a compact object with electric charge and
magnetic dipole in Einstein-Born-Infeld gravity | 11 pages, 1 figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the bending of light around a compact astrophysical object with
both the electric field and the magnetic field in Einstein-Born-Infeld theory.
From the null geodesic of a light ray passing a massive object with electric
charge and magnetic dipole, the effective metric was obtained from the light
cone condition reflecting the nonlinear electromagnetic effects. We found the
asymptotic form of the effective metric up to the first order in gravitational
constant $G$ and Born-Infeld parameter $1/\beta^2$ on the equatorial plane.
Then we compute the bending angle of light from the geodesic equation. The
result includes particular cases where only one type of field is present taking
the appropriate limits.
| [
{
"created": "Tue, 23 Apr 2024 05:43:28 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Kim",
"Jin Young",
""
]
] | We consider the bending of light around a compact astrophysical object with both the electric field and the magnetic field in Einstein-Born-Infeld theory. From the null geodesic of a light ray passing a massive object with electric charge and magnetic dipole, the effective metric was obtained from the light cone condition reflecting the nonlinear electromagnetic effects. We found the asymptotic form of the effective metric up to the first order in gravitational constant $G$ and Born-Infeld parameter $1/\beta^2$ on the equatorial plane. Then we compute the bending angle of light from the geodesic equation. The result includes particular cases where only one type of field is present taking the appropriate limits. |
1703.09738 | Tolga Birkandan | Tolga Birkandan, Ceren G\"uzelg\"un, Elif \c{S}irin, Mustafa Can Uslu | Symbolic and Numerical Analysis in General Relativity with Open Source
Computer Algebra Systems | 21 pages, 4 figures. Updated to match the published version | Gen Relativ Gravit (2019) 51: 4 | 10.1007/s10714-018-2486-x | null | gr-qc hep-th physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study three computer algebra systems, namely SageMath (with SageManifolds
package), Maxima (with ctensor package) and Python language (with GraviPy
module), which allow tensor manipulation for general relativity calculations
along with general algebraic calculations. We present a benchmark of these
systems using simple examples. After the general analysis, we focus on the
SageMath and SageManifolds system to derive, analyze and visualize the
solutions of the massless Klein-Gordon equation and geodesic motion with
Hamilton-Jacobi formalism. We compare our numerical result of the Klein-Gordon
equation with the asymptotic form of the analytical solution to see that they
agree.
| [
{
"created": "Tue, 28 Mar 2017 18:33:53 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Oct 2018 10:20:56 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Dec 2018 08:44:05 GMT",
"version": "v3"
}
] | 2018-12-19 | [
[
"Birkandan",
"Tolga",
""
],
[
"Güzelgün",
"Ceren",
""
],
[
"Şirin",
"Elif",
""
],
[
"Uslu",
"Mustafa Can",
""
]
] | We study three computer algebra systems, namely SageMath (with SageManifolds package), Maxima (with ctensor package) and Python language (with GraviPy module), which allow tensor manipulation for general relativity calculations along with general algebraic calculations. We present a benchmark of these systems using simple examples. After the general analysis, we focus on the SageMath and SageManifolds system to derive, analyze and visualize the solutions of the massless Klein-Gordon equation and geodesic motion with Hamilton-Jacobi formalism. We compare our numerical result of the Klein-Gordon equation with the asymptotic form of the analytical solution to see that they agree. |
0808.0713 | Yosef Zlochower | Manuela Campanelli, Carlos O. Lousto, Hiroyuki Nakano, Yosef Zlochower | Comparison of Numerical and Post-Newtonian Waveforms for Generic
Precessing Black-Hole Binaries | New figures, enhanced analysis, revisions throughout the paper | Phys.Rev.D79:084010,2009 | 10.1103/PhysRevD.79.084010 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare waveforms and orbital dynamics from the first long-term, fully
non-linear, numerical simulations of a generic black-hole binary configuration
with post-Newtonian predictions. The binary has mass ratio q~0.8 with
arbitrarily oriented spins of magnitude S_1/m_1^2~0.6 and S_2/m_2^2~0.4 and
orbits 9 times prior to merger. The numerical simulation starts with an initial
separation of r~11M, with orbital parameters determined by initial 2.5PN and
3.5PN post-Newtonian evolutions of a quasi-circular binary with an initial
separation of r=50M. The resulting binaries have very little eccentricity
according to the 2.5PN and 3.5PN systems, but show significant eccentricities
of e~0.01-0.02 and e~0.002-0.005 in the respective numerical simulations, thus
demonstrating that 3.5PN significantly reduces the eccentricity of the binary
compared to 2.5PN. We perform three numerical evolutions from r~11M with
maximum resolutions of h=M/48,M/53.3,M/59.3, to verify numerical convergence.
We observe a reasonably good agreement between the PN and numerical waveforms,
with an overlap of nearly 99% for the first six cycles of the (l=2,m=+-2)
modes, 91% for the (l=2,m=+-1) modes, and nearly 91% for the (l=3,m=+-3) modes.
The phase differences between numerical and post-Newtonian approximations
appear to be independent of the (l,m) modes considered and relatively small for
the first 3-4 orbits. An advantage of the 3.5 PN model over the 2.5 PN one
seems to be observed, which indicates that still higher PN order (perhaps even
4.0PN) may yield significantly better waveforms. In addition, we identify
features in the waveforms likely related to precession and precession-induced
eccentricity.
| [
{
"created": "Tue, 5 Aug 2008 20:01:05 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Aug 2008 01:34:18 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Jan 2009 19:59:14 GMT",
"version": "v3"
}
] | 2009-11-13 | [
[
"Campanelli",
"Manuela",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Zlochower",
"Yosef",
""
]
] | We compare waveforms and orbital dynamics from the first long-term, fully non-linear, numerical simulations of a generic black-hole binary configuration with post-Newtonian predictions. The binary has mass ratio q~0.8 with arbitrarily oriented spins of magnitude S_1/m_1^2~0.6 and S_2/m_2^2~0.4 and orbits 9 times prior to merger. The numerical simulation starts with an initial separation of r~11M, with orbital parameters determined by initial 2.5PN and 3.5PN post-Newtonian evolutions of a quasi-circular binary with an initial separation of r=50M. The resulting binaries have very little eccentricity according to the 2.5PN and 3.5PN systems, but show significant eccentricities of e~0.01-0.02 and e~0.002-0.005 in the respective numerical simulations, thus demonstrating that 3.5PN significantly reduces the eccentricity of the binary compared to 2.5PN. We perform three numerical evolutions from r~11M with maximum resolutions of h=M/48,M/53.3,M/59.3, to verify numerical convergence. We observe a reasonably good agreement between the PN and numerical waveforms, with an overlap of nearly 99% for the first six cycles of the (l=2,m=+-2) modes, 91% for the (l=2,m=+-1) modes, and nearly 91% for the (l=3,m=+-3) modes. The phase differences between numerical and post-Newtonian approximations appear to be independent of the (l,m) modes considered and relatively small for the first 3-4 orbits. An advantage of the 3.5 PN model over the 2.5 PN one seems to be observed, which indicates that still higher PN order (perhaps even 4.0PN) may yield significantly better waveforms. In addition, we identify features in the waveforms likely related to precession and precession-induced eccentricity. |
0909.0066 | Peter Zimmerman | Duncan A. Brown and Peter J. Zimmerman | The Effect of Eccentricity on Searches for Gravitational-Waves from
Coalescing Compact Binaries in Ground-based Detectors | 10 pages, 9 figures, as published in Phys. Rev. D | Phys.Rev.D81:024007,2010 | 10.1103/PhysRevD.81.024007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspiralling compact binaries are expected to circularize before their
gravitational-wave signals reach the sensitive frequency band of ground-based
detectors. Current searches for gravitational waves from compact binaries using
the LIGO and Virgo detectors therefore use circular templates to construct
matched filters. Binary formation models have been proposed which suggest that
some systems detectable by the LIGO--Virgo network may have non-negligible
eccentricity. We investigate the ability of the restricted 3.5 post-Newtonian
order TaylorF2 template bank, used by LIGO and Virgo to search for
gravitational waves from compact binaries with masses $M \le 35 M_\odot$, to
detect binaries with non-zero eccentricity. We model the gravitational waves
from eccentric binaries using the $x$-model post-Newtonian formalism proposed
by Hinder \emph{et. al.} [I. Hinder, F. Hermann, P. Laguna, and D. Shoemaker,
arXiv:0806.1037v1]. We find that small residual eccentricities ($e_0 \lesssim
0.05$ at 40 Hz) do not significantly affect the ability of current LIGO
searches to detect gravitational waves from coalescing compact binaries with
total mass $2 M_\odot < M < 15 M_\odot$. For eccentricities $e_0 \gtrsim 0.1$,
the loss in matched filter signal-to-noise ratio due to eccentricity can be
significant and so templates which include eccentric effects will be required
to perform optimal searches for such systems.
| [
{
"created": "Tue, 1 Sep 2009 02:01:34 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Feb 2010 15:14:29 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Brown",
"Duncan A.",
""
],
[
"Zimmerman",
"Peter J.",
""
]
] | Inspiralling compact binaries are expected to circularize before their gravitational-wave signals reach the sensitive frequency band of ground-based detectors. Current searches for gravitational waves from compact binaries using the LIGO and Virgo detectors therefore use circular templates to construct matched filters. Binary formation models have been proposed which suggest that some systems detectable by the LIGO--Virgo network may have non-negligible eccentricity. We investigate the ability of the restricted 3.5 post-Newtonian order TaylorF2 template bank, used by LIGO and Virgo to search for gravitational waves from compact binaries with masses $M \le 35 M_\odot$, to detect binaries with non-zero eccentricity. We model the gravitational waves from eccentric binaries using the $x$-model post-Newtonian formalism proposed by Hinder \emph{et. al.} [I. Hinder, F. Hermann, P. Laguna, and D. Shoemaker, arXiv:0806.1037v1]. We find that small residual eccentricities ($e_0 \lesssim 0.05$ at 40 Hz) do not significantly affect the ability of current LIGO searches to detect gravitational waves from coalescing compact binaries with total mass $2 M_\odot < M < 15 M_\odot$. For eccentricities $e_0 \gtrsim 0.1$, the loss in matched filter signal-to-noise ratio due to eccentricity can be significant and so templates which include eccentric effects will be required to perform optimal searches for such systems. |
2010.09481 | Martin Kolo\v{s} | Martin Kolo\v{s}, Arman Tursunov, Zden\v{e}k Stuchl\'ik | Radiative Penrose process: Energy Gain by a Single Radiating Charged
Particle in the Ergosphere of Rotating Black Hole | 5 pages, 1 figure, submitted | Phys. Rev. D 103, 024021 (2021) | 10.1103/PhysRevD.103.024021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate an extraordinary effect of energy gain by a single radiating
charged particle inside the ergosphere of a Kerr black hole in presence of
magnetic field. We solve numerically the covariant form of the Lorentz-Dirac
equation reduced from the DeWitt-Brehme equation and analyze energy evolution
of the radiating charged particle inside the ergosphere, where the energy of
emitted radiation can be negative with respect to a distant observer in
dependence on the relative orientation of the magnetic field, black hole spin
and the direction of the charged particle motion. Consequently, the charged
particle can leave the ergosphere with energy greater than initial in expense
of black hole's rotational energy. In contrast to the original Penrose process
and its various modification, the new process does not require the interactions
(collisions or decay) with other particles and consequent restrictions on the
relative velocities between fragments. We show that such a Radiative Penrose
effect is potentially observable and discuss its possible relevance in
formation of relativistic jets and in similar high-energy astrophysical
settings.
| [
{
"created": "Mon, 19 Oct 2020 13:22:55 GMT",
"version": "v1"
}
] | 2021-01-20 | [
[
"Kološ",
"Martin",
""
],
[
"Tursunov",
"Arman",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | We demonstrate an extraordinary effect of energy gain by a single radiating charged particle inside the ergosphere of a Kerr black hole in presence of magnetic field. We solve numerically the covariant form of the Lorentz-Dirac equation reduced from the DeWitt-Brehme equation and analyze energy evolution of the radiating charged particle inside the ergosphere, where the energy of emitted radiation can be negative with respect to a distant observer in dependence on the relative orientation of the magnetic field, black hole spin and the direction of the charged particle motion. Consequently, the charged particle can leave the ergosphere with energy greater than initial in expense of black hole's rotational energy. In contrast to the original Penrose process and its various modification, the new process does not require the interactions (collisions or decay) with other particles and consequent restrictions on the relative velocities between fragments. We show that such a Radiative Penrose effect is potentially observable and discuss its possible relevance in formation of relativistic jets and in similar high-energy astrophysical settings. |
1412.4267 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Macroscopic traversable wormholes with zero tidal forces inspired by
noncommutative geometry | 8 pages, no figures | Int. J. Mod. Phys. D, vol. 24, 1550023 (8 pages), 2015 | 10.1142/S0218271815500236 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper addresses the following issues: (1) the possible existence of
macroscopic traversable wormholes, given a noncommutative-geometry background,
and (2) the possibility of allowing zero tidal forces, given a known density.
It is shown that whenever the energy density describes a classical wormhole,
the resulting solution is incompatible with quantum field theory. If the energy
density originates from noncommutative geometry, then zero tidal forces are
allowed. Also attributable to the noncommutative geometry is the violation of
the null energy condition. The wormhole geometry satisfies the usual
requirements, including asymptotic flatness.
| [
{
"created": "Sat, 13 Dec 2014 18:27:01 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jan 2015 22:04:23 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Aug 2016 13:35:20 GMT",
"version": "v3"
},
{
"created": "Tue, 8 Jan 2019 17:02:09 GMT",
"version": "v4"
}
] | 2019-01-09 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | This paper addresses the following issues: (1) the possible existence of macroscopic traversable wormholes, given a noncommutative-geometry background, and (2) the possibility of allowing zero tidal forces, given a known density. It is shown that whenever the energy density describes a classical wormhole, the resulting solution is incompatible with quantum field theory. If the energy density originates from noncommutative geometry, then zero tidal forces are allowed. Also attributable to the noncommutative geometry is the violation of the null energy condition. The wormhole geometry satisfies the usual requirements, including asymptotic flatness. |
2006.11626 | Maria De F\'atima Alves da Silva PhD | L. S. M. Veneroni, A. Braz and M. F. A. da Silva | Compact Object with a Local Dark Energy Shell | 32 pages, 15 figures | null | 10.1142/S0218271821500395 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate some models of compact objects in the general relativity
theory with cosmological constant $\Lambda$, based on two density profiles, one
of them attributed to Stewart and the other one to Durgapal and Bannerji,
proposed in the literature to model "neutron stars". For them, a nonlocal
equation of state with cosmological constant is obtained as a consequence of
the chosen metric. In another direction, we obtain a solution for
configurations with null radial pressure. The first model (based on the
Stewart's density profile) turned out to be the most interesting, since
surprisingly it admits the presence of dark energy in the interior of the star,
in the outermost layers, for a certain range of mass-radius ratio $\gamma$.
This dark energy is independent of the cosmological constant, since it is a
consequence of the tangential pressure of the fluid be sufficiently negative.
Still in this case, for other values of $\gamma$, all the energy conditions are
satisfied. Another advantage of this model, as well as that based on the
density profile of Durgapal and Bannnerji is the existence of intervals of
$\gamma$ compatible with physically acceptable models for $\Lambda < 0$,
$\Lambda = 0$ and $\Lambda > 0$, which also allowed us to analyze the influence
of $\Lambda$ on the behavior of the fluid with respect to the energy
conditions. The other configuration studied here, $P_r=0$, only allow solutions
for $\Lambda<0$, in order to ensure a positive mass for the object and to
satisfy all the energy conditions in a specific range of $\gamma$.
| [
{
"created": "Sat, 20 Jun 2020 17:57:30 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2021 19:48:31 GMT",
"version": "v2"
}
] | 2021-05-12 | [
[
"Veneroni",
"L. S. M.",
""
],
[
"Braz",
"A.",
""
],
[
"da Silva",
"M. F. A.",
""
]
] | We investigate some models of compact objects in the general relativity theory with cosmological constant $\Lambda$, based on two density profiles, one of them attributed to Stewart and the other one to Durgapal and Bannerji, proposed in the literature to model "neutron stars". For them, a nonlocal equation of state with cosmological constant is obtained as a consequence of the chosen metric. In another direction, we obtain a solution for configurations with null radial pressure. The first model (based on the Stewart's density profile) turned out to be the most interesting, since surprisingly it admits the presence of dark energy in the interior of the star, in the outermost layers, for a certain range of mass-radius ratio $\gamma$. This dark energy is independent of the cosmological constant, since it is a consequence of the tangential pressure of the fluid be sufficiently negative. Still in this case, for other values of $\gamma$, all the energy conditions are satisfied. Another advantage of this model, as well as that based on the density profile of Durgapal and Bannnerji is the existence of intervals of $\gamma$ compatible with physically acceptable models for $\Lambda < 0$, $\Lambda = 0$ and $\Lambda > 0$, which also allowed us to analyze the influence of $\Lambda$ on the behavior of the fluid with respect to the energy conditions. The other configuration studied here, $P_r=0$, only allow solutions for $\Lambda<0$, in order to ensure a positive mass for the object and to satisfy all the energy conditions in a specific range of $\gamma$. |
gr-qc/9301017 | null | S.W. Hawking, R. Laflamme and G.W. Lyons | The Origin of Time Asymmetry | 41 pages, DAMTP R92/20 | Phys.Rev. D47 (1993) 5342-5356 | 10.1103/PhysRevD.47.5342 | null | gr-qc astro-ph | null | It is argued that the observed Thermodynamic Arrow of Time must arise from
the boundary conditions of the universe. We analyse the consequences of the no
boundary proposal, the only reasonably complete set of boundary conditions that
has been put forward. We study perturbations of a Friedmann model containing a
massive scalar field but our results should be independent of the details of
the matter content. We find that gravitational wave perturbations have an
amplitude that remains in the linear regime at all times and is roughly time
symmetric about the time of maximum expansion. Thus gravitational wave
perturbations do not give rise to an Arrow of Time. However density
perturbations behave very differently. They are small at one end of the
universe's history, but grow larger and become non linear as the universe gets
larger. Contrary to an earlier claim, the density perturbations do not get
small again at the other end of the universe's history. They therefore give
rise to a Thermodynamic Arrow of Time that points in a constant direction while
the universe expands and contracts again. The Arrow of Time does not reverse at
the point of maximum expansion. One has to appeal to the Weak Anthropic
Principle to explain why we observe the Thermodynamic Arrow to agree with the
Cosmological Arrow, the direction of time in which the universe is expanding.
| [
{
"created": "Mon, 18 Jan 1993 16:00:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Hawking",
"S. W.",
""
],
[
"Laflamme",
"R.",
""
],
[
"Lyons",
"G. W.",
""
]
] | It is argued that the observed Thermodynamic Arrow of Time must arise from the boundary conditions of the universe. We analyse the consequences of the no boundary proposal, the only reasonably complete set of boundary conditions that has been put forward. We study perturbations of a Friedmann model containing a massive scalar field but our results should be independent of the details of the matter content. We find that gravitational wave perturbations have an amplitude that remains in the linear regime at all times and is roughly time symmetric about the time of maximum expansion. Thus gravitational wave perturbations do not give rise to an Arrow of Time. However density perturbations behave very differently. They are small at one end of the universe's history, but grow larger and become non linear as the universe gets larger. Contrary to an earlier claim, the density perturbations do not get small again at the other end of the universe's history. They therefore give rise to a Thermodynamic Arrow of Time that points in a constant direction while the universe expands and contracts again. The Arrow of Time does not reverse at the point of maximum expansion. One has to appeal to the Weak Anthropic Principle to explain why we observe the Thermodynamic Arrow to agree with the Cosmological Arrow, the direction of time in which the universe is expanding. |
1503.05469 | Susana Valdez | Carlos A. Soto-Campos, Susana Valdez-Alvarado | Noncommutative Reissner-Nordstr{\o}m Black hole | 7 page | null | 10.1139/cjp-2017-0599 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A deformed embedding of the Reissner-Nordstr{\o}m spacetime is constructed
within the framework of a noncommutative Riemannian geometry. We find
noncommutative corrections to the usual Riemannian expressions for the metric
and curvature tensors, which, in the case of the metric, are valid to all
orders in the deformation parameter. We calculate the area of the event horizon
of the corresponding noncommutative R-N black-hole, obtaining corrections up to
fourth order in the deformation parameter for the area of the black-hole.
Finally we include some comments on the noncommutative version on one of the
second order scalar invariants of the Riemann tensor, the so called Kretschmann
invariant, a quantity regularly used in order to extend gravity to quantum
level.
| [
{
"created": "Wed, 18 Mar 2015 16:22:30 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2015 17:06:45 GMT",
"version": "v2"
}
] | 2018-05-18 | [
[
"Soto-Campos",
"Carlos A.",
""
],
[
"Valdez-Alvarado",
"Susana",
""
]
] | A deformed embedding of the Reissner-Nordstr{\o}m spacetime is constructed within the framework of a noncommutative Riemannian geometry. We find noncommutative corrections to the usual Riemannian expressions for the metric and curvature tensors, which, in the case of the metric, are valid to all orders in the deformation parameter. We calculate the area of the event horizon of the corresponding noncommutative R-N black-hole, obtaining corrections up to fourth order in the deformation parameter for the area of the black-hole. Finally we include some comments on the noncommutative version on one of the second order scalar invariants of the Riemann tensor, the so called Kretschmann invariant, a quantity regularly used in order to extend gravity to quantum level. |
1006.4809 | Sunil Maharaj | A. M. Msomi, K. S. Govinder, S. D. Maharaj | Gravitating fluids with Lie symmetries | 13 pages, To appear in J. Phys. A: Math. Theor | J. Phys. A 43: 285203, 2010 | 10.1088/1751-8113/43/28/285203 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the underlying nonlinear partial differential equation which
arises in the study of gravitating flat fluid plates of embedding class one.
Our interest in this equation lies in discussing new solutions that can be
found by means of Lie point symmetries. The method utilised reduces the partial
differential equation to an ordinary differential equation according to the Lie
symmetry admitted. We show that a class of solutions found previously can be
characterised by a particular Lie generator. Several new families of solutions
are found explicitly. In particular we find the relevant ordinary differential
equation for all one-dimensional optimal subgroups; in several cases the
ordinary differential equation can be solved in general. We are in a position
to characterise particular solutions with a linear barotropic equation of
state.
| [
{
"created": "Thu, 24 Jun 2010 15:06:41 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Msomi",
"A. M.",
""
],
[
"Govinder",
"K. S.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We analyse the underlying nonlinear partial differential equation which arises in the study of gravitating flat fluid plates of embedding class one. Our interest in this equation lies in discussing new solutions that can be found by means of Lie point symmetries. The method utilised reduces the partial differential equation to an ordinary differential equation according to the Lie symmetry admitted. We show that a class of solutions found previously can be characterised by a particular Lie generator. Several new families of solutions are found explicitly. In particular we find the relevant ordinary differential equation for all one-dimensional optimal subgroups; in several cases the ordinary differential equation can be solved in general. We are in a position to characterise particular solutions with a linear barotropic equation of state. |
gr-qc/9810075 | Gerard Clement | G\'erard Cl\'ement | Spinning ring wormholes: a classical model for elementary particles? | 15 pages, Latex | null | null | GCR-98/11/02 | gr-qc astro-ph hep-th | null | Static horizonless solutions to the Einstein--Maxwell field equations, with
only a circular cosmic string singularity, are extended to exact rotating
asymptotically flat solutions. The possible interpretation of these field
configurations as spinning elementary particles or as macroscopic rotating
cosmic rings is discussed.
| [
{
"created": "Thu, 22 Oct 1998 15:45:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Clément",
"Gérard",
""
]
] | Static horizonless solutions to the Einstein--Maxwell field equations, with only a circular cosmic string singularity, are extended to exact rotating asymptotically flat solutions. The possible interpretation of these field configurations as spinning elementary particles or as macroscopic rotating cosmic rings is discussed. |
2007.13956 | Luis Granda | L. N. Granda | Modified gravity with disappearing cosmological constant | 42 pages, 7 figures, version published in JHEP | J. High Energ. Phys. 2021, 205 (2021) | 10.1007/JHEP12(2021)205 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New corrections to General Relativity are considered in the context of
modified $f(R)$ gravity, that satisfy cosmological and local gravity
constraints. The proposed models behave asymptotically as $R-2\Lambda$ at large
curvature and show the vanishing of the cosmological constant at the flat
spacetime limit. The chameleon mechanism and thin shell restrictions for local
systems were analyzed, and bounds on the models were found. The steepness of
the deviation parameter $m$ at late times leads to measurable signal of
scalar-tensor regime in matter perturbations, that allows to detect departures
form the $\Lambda$CDM model. The theoretical results for the evolution of the
weighted growth rate $f\sigma_8(z)$, from the proposed models, were analyzed.
| [
{
"created": "Tue, 28 Jul 2020 02:39:43 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Aug 2020 21:10:59 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Jul 2021 02:39:33 GMT",
"version": "v3"
},
{
"created": "Wed, 12 Jan 2022 04:35:26 GMT",
"version": "v4"
}
] | 2022-01-13 | [
[
"Granda",
"L. N.",
""
]
] | New corrections to General Relativity are considered in the context of modified $f(R)$ gravity, that satisfy cosmological and local gravity constraints. The proposed models behave asymptotically as $R-2\Lambda$ at large curvature and show the vanishing of the cosmological constant at the flat spacetime limit. The chameleon mechanism and thin shell restrictions for local systems were analyzed, and bounds on the models were found. The steepness of the deviation parameter $m$ at late times leads to measurable signal of scalar-tensor regime in matter perturbations, that allows to detect departures form the $\Lambda$CDM model. The theoretical results for the evolution of the weighted growth rate $f\sigma_8(z)$, from the proposed models, were analyzed. |
0801.3683 | Robert R. Caldwell | P. P. Yu and R. R. Caldwell | Observer dependence of the quasi-local energy and momentum in
Schwarzschild space-time | 7 pages, 3 figures; accepted for publication in Gen. Rel. Grav | null | 10.1007/s10714-008-0686-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observer dependence of the quasi-local energy (QLE) and momentum in the
Schwarzschild geometry is illustrated. Using the Brown-York prescription, the
QLE for families of non-geodesic and geodesic observers penetrating the event
horizon is obtained. An explicit shell-building process is presented and the
binding energy is computed in terms of the QLE measured by a static observer
field at a radius outside the horizon radius. The QLE for a radially geodesic
observer field freely-falling from infinity is shown to vanish. Finally, a
simple relation for the dynamics of the quasi-local momentum density for a
geodesic observer field is noted.
| [
{
"created": "Wed, 23 Jan 2008 23:02:17 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 2008 19:54:54 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Yu",
"P. P.",
""
],
[
"Caldwell",
"R. R.",
""
]
] | The observer dependence of the quasi-local energy (QLE) and momentum in the Schwarzschild geometry is illustrated. Using the Brown-York prescription, the QLE for families of non-geodesic and geodesic observers penetrating the event horizon is obtained. An explicit shell-building process is presented and the binding energy is computed in terms of the QLE measured by a static observer field at a radius outside the horizon radius. The QLE for a radially geodesic observer field freely-falling from infinity is shown to vanish. Finally, a simple relation for the dynamics of the quasi-local momentum density for a geodesic observer field is noted. |
1010.3420 | Sabine Hossenfelder | Sabine Hossenfelder | Experimental Search for Quantum Gravity | This article is partly based on the talks at the workshop on
Experimental Search for Quantum Gravity, Stockholm, July 12-16 2010 | "Classical and Quantum Gravity: Theory, Analysis and
Applications," Chapter 5, Edited by V. R. Frignanni, Nova Publishers (2011) | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We offer a brief survey of existent and planned experimental tests for
quantum gravity. First, we outline the questions we wish to address, and then
introduce some of the phenomenological models that are currently used in
quantum gravity, both with and without a lowered Planck scale. After that, we
summarize experimental areas where these models can be tested or constrained
and discuss the status of the field.
| [
{
"created": "Sun, 17 Oct 2010 15:21:06 GMT",
"version": "v1"
}
] | 2011-12-16 | [
[
"Hossenfelder",
"Sabine",
""
]
] | We offer a brief survey of existent and planned experimental tests for quantum gravity. First, we outline the questions we wish to address, and then introduce some of the phenomenological models that are currently used in quantum gravity, both with and without a lowered Planck scale. After that, we summarize experimental areas where these models can be tested or constrained and discuss the status of the field. |
2204.00698 | Carolyn Raithel | Carolyn A. Raithel, Vasileios Paschalidis | Improving the convergence order of binary neutron star merger
simulations in the Baumgarte-Shapiro-Shibata-Nakamura formulation | 17 pages, 9 figures | null | 10.1103/PhysRevD.106.023015 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | High-accuracy numerical relativity simulations of binary neutron star mergers
are a necessary ingredient for constructing gravitational waveform templates to
analyze and interpret observations of compact object mergers. Numerical
convergence in the post-merger phase of such simulations is challenging to
achieve with many modern codes. In this paper, we study two ways of improving
the convergence properties of binary neutron star merger simulations within the
Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's equations. We show
that discontinuities in a particular constraint damping scheme in this
formulation can destroy the post-merger convergence of the simulation. A
continuous prescription, in contrast, ensures convergence until late times. We
additionally study the impact of the equation of state parametrization on the
pre- and post-merger convergence properties of the simulations. In particular,
we compare results for a piecewise polytropic parametrization, which is
commonly used in merger simulations but suffers unphysical discontinuities in
the sound speed, with results using a "generalized" piecewise polytropic
parametrization, which was designed to ensure both continuity and
differentiability of the equation of state. We report on the differences in the
gravitational waves and any spurious pre-merger heating, depending on which
equation of state parametrization is used.
| [
{
"created": "Fri, 1 Apr 2022 21:11:37 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2022 20:04:26 GMT",
"version": "v2"
}
] | 2022-07-27 | [
[
"Raithel",
"Carolyn A.",
""
],
[
"Paschalidis",
"Vasileios",
""
]
] | High-accuracy numerical relativity simulations of binary neutron star mergers are a necessary ingredient for constructing gravitational waveform templates to analyze and interpret observations of compact object mergers. Numerical convergence in the post-merger phase of such simulations is challenging to achieve with many modern codes. In this paper, we study two ways of improving the convergence properties of binary neutron star merger simulations within the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's equations. We show that discontinuities in a particular constraint damping scheme in this formulation can destroy the post-merger convergence of the simulation. A continuous prescription, in contrast, ensures convergence until late times. We additionally study the impact of the equation of state parametrization on the pre- and post-merger convergence properties of the simulations. In particular, we compare results for a piecewise polytropic parametrization, which is commonly used in merger simulations but suffers unphysical discontinuities in the sound speed, with results using a "generalized" piecewise polytropic parametrization, which was designed to ensure both continuity and differentiability of the equation of state. We report on the differences in the gravitational waves and any spurious pre-merger heating, depending on which equation of state parametrization is used. |
1712.04520 | Patrick Valageas | Philippe Brax, Patrick Valageas | Self-acceleration in scalar-bimetric theories | 35 pages | Phys. Rev. D 97, 103516 (2018) | 10.1103/PhysRevD.97.103516 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe scalar-bimetric theories where the dynamics of the Universe are
governed by two separate metrics, each with an Einstein-Hilbert term. In this
setting, the baryonic and dark matter components of the Universe couple to
metrics which are constructed as functions of these two gravitational metrics.
The scalar field, contrary to dark energy models, does not have a potential
whose role is to mimic a late-time cosmological constant. The late-time
acceleration of the expansion of the Universe can be easily obtained at the
background level in these models by appropriately choosing the coupling
functions appearing in the decomposition of the vierbeins for the baryonic and
dark matter metrics. We explicitly show how the concordance model can be
retrieved with negligible scalar kinetic energy. This requires the scalar
coupling functions to show variations of order unity during the accelerated
expansion era. This leads in turn to deviations of order unity for the
effective Newton constants and a fifth force that is of the same order as
Newtonian gravity, with peculiar features. The baryonic and dark matter
self-gravities are amplified although the gravitational force between baryons
and dark matter is reduced and even becomes repulsive at low redshift. This
slows down the growth of baryonic density perturbations on cosmological scales,
while dark matter perturbations are enhanced. In our local environment, the
upper bound on the time evolution of Newton's constant requires an efficient
screening mechanism that both damps the fifth force on small scales and
decouples the local value of Newton constant from its cosmological value. This
cannot be achieved by a quasi-static chameleon mechanism, and requires going
beyond the quasi-static regime and probably using derivative screenings, such
as Kmouflage or Vainshtein screening, on small scales.
| [
{
"created": "Mon, 11 Dec 2017 18:18:10 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Oct 2018 09:07:32 GMT",
"version": "v2"
}
] | 2018-10-09 | [
[
"Brax",
"Philippe",
""
],
[
"Valageas",
"Patrick",
""
]
] | We describe scalar-bimetric theories where the dynamics of the Universe are governed by two separate metrics, each with an Einstein-Hilbert term. In this setting, the baryonic and dark matter components of the Universe couple to metrics which are constructed as functions of these two gravitational metrics. The scalar field, contrary to dark energy models, does not have a potential whose role is to mimic a late-time cosmological constant. The late-time acceleration of the expansion of the Universe can be easily obtained at the background level in these models by appropriately choosing the coupling functions appearing in the decomposition of the vierbeins for the baryonic and dark matter metrics. We explicitly show how the concordance model can be retrieved with negligible scalar kinetic energy. This requires the scalar coupling functions to show variations of order unity during the accelerated expansion era. This leads in turn to deviations of order unity for the effective Newton constants and a fifth force that is of the same order as Newtonian gravity, with peculiar features. The baryonic and dark matter self-gravities are amplified although the gravitational force between baryons and dark matter is reduced and even becomes repulsive at low redshift. This slows down the growth of baryonic density perturbations on cosmological scales, while dark matter perturbations are enhanced. In our local environment, the upper bound on the time evolution of Newton's constant requires an efficient screening mechanism that both damps the fifth force on small scales and decouples the local value of Newton constant from its cosmological value. This cannot be achieved by a quasi-static chameleon mechanism, and requires going beyond the quasi-static regime and probably using derivative screenings, such as Kmouflage or Vainshtein screening, on small scales. |
1905.05516 | Mieszko Rutkowski | Mieszko Rutkowski | Nonlinear perturbations of Reissner-Nordstr\"om black holes | 9 pages | Phys. Rev. D 100, 044017 (2019) | 10.1103/PhysRevD.100.044017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a nonlinear perturbation theory of Reissner-Nordstr\"om black
holes. We show that, at each perturbation level, Einstein-Maxwell equations can
be reduced to four inhomogeneous wave equations, two for polar and two for
axial sector. Gravitational part of these equations is similar to Regge-Wheeler
and Zerilli equations with source and additional coupling to the
electromagnetic sector. We construct solutions to the inhomogeneous part of
wave equations in terms of sources for Einstein-Maxwell equations. We discuss
$\ell=0$ and $ \ell=1$ cases separately.
| [
{
"created": "Tue, 14 May 2019 11:00:44 GMT",
"version": "v1"
}
] | 2019-08-14 | [
[
"Rutkowski",
"Mieszko",
""
]
] | We develop a nonlinear perturbation theory of Reissner-Nordstr\"om black holes. We show that, at each perturbation level, Einstein-Maxwell equations can be reduced to four inhomogeneous wave equations, two for polar and two for axial sector. Gravitational part of these equations is similar to Regge-Wheeler and Zerilli equations with source and additional coupling to the electromagnetic sector. We construct solutions to the inhomogeneous part of wave equations in terms of sources for Einstein-Maxwell equations. We discuss $\ell=0$ and $ \ell=1$ cases separately. |
gr-qc/0411036 | Robert Milson | Robert Milson | Alignment and the classification of Lorentz-signature tensors | 8 pages. To be published in the proceedings of SPT2004 | null | 10.1142/9789812702142_0026 | null | gr-qc | null | We define the notion of an aligned null direction, a Lorentz-signature
analogue of the eigenvector concept that is valid for arbitrary tensor types.
The set of aligned null directions is described by a a system of alignment
polynomials whose coefficients are derived from the components of the tensor.
The algebraic properties of the alignment polynomials can be used to classify
the corresponding tensors and to put them into normal form. The alignment
classification paradigm is illustrated with a discussion of bivectors and of
Weyl-type tensors. Note: an earlier version of this manuscript was published in
the proceedings of SPT 2004. The present version has been expanded to include a
discussion of complexified alignment. Section 4 also corrects errors contained
in the earlier manuscript.
| [
{
"created": "Mon, 8 Nov 2004 11:29:11 GMT",
"version": "v1"
}
] | 2016-11-23 | [
[
"Milson",
"Robert",
""
]
] | We define the notion of an aligned null direction, a Lorentz-signature analogue of the eigenvector concept that is valid for arbitrary tensor types. The set of aligned null directions is described by a a system of alignment polynomials whose coefficients are derived from the components of the tensor. The algebraic properties of the alignment polynomials can be used to classify the corresponding tensors and to put them into normal form. The alignment classification paradigm is illustrated with a discussion of bivectors and of Weyl-type tensors. Note: an earlier version of this manuscript was published in the proceedings of SPT 2004. The present version has been expanded to include a discussion of complexified alignment. Section 4 also corrects errors contained in the earlier manuscript. |
2304.08574 | Maciej Dunajski | Maciej Dunajski | Equivalence principle, de-Sitter space, and cosmological twistors | First award winning essay of the 2023 Gravity Research Foundation
competition | Internat. J. Modern Phys. D32(2023), no.14, Paper No. 2341001 | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | I discuss the impact of the positive cosmological constant on the interplay
between the equivalence principle in general relativity, and the rules of
quantum mechanics. At the non--relativistic level there is an ambiguity in the
definition of a phase of a wave function measured by inertial and accelerating
observes. This is the cosmological analogue of the Penrose effect, which can
also be seen as a non--relativistic limit of the Unruh effect. The symmetries
of the associated Schr\"odinger equation are generated by the Newton--Hooke
algebra, which arises from a non--relativistic limit of a cosmological twistor
space.
| [
{
"created": "Mon, 17 Apr 2023 19:33:54 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Dec 2023 19:07:09 GMT",
"version": "v2"
}
] | 2023-12-19 | [
[
"Dunajski",
"Maciej",
""
]
] | I discuss the impact of the positive cosmological constant on the interplay between the equivalence principle in general relativity, and the rules of quantum mechanics. At the non--relativistic level there is an ambiguity in the definition of a phase of a wave function measured by inertial and accelerating observes. This is the cosmological analogue of the Penrose effect, which can also be seen as a non--relativistic limit of the Unruh effect. The symmetries of the associated Schr\"odinger equation are generated by the Newton--Hooke algebra, which arises from a non--relativistic limit of a cosmological twistor space. |
1508.00276 | Genly Le\'on | Alan A. Coley (Dalhousie U., Math. Dept.), Genly Leon (Valparaiso U.,
Catolica), Patrik Sandin (Potsdam, Max Planck Inst.), Joey Latta (Dalhousie
U., Math. Dept.) | Spherically symmetric Einstein-aether perfect fluid models | 52 pages, 7 figures. Matches the published version. arXiv admin note:
text overlap with arXiv:gr-qc/0603058 by other authors | JCAP12(2015)010 | 10.1088/1475-7516/2015/12/010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate spherically symmetric cosmological models in Einstein-aether
theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame
formalism and adopt the comoving aether gauge to derive the evolution
equations, which form a well-posed system of first order partial differential
equations in two variables. We then introduce normalized variables. The
formalism is particularly well-suited for numerical computations and the study
of the qualitative properties of the models, which are also solutions of Horava
gravity. We study the local stability of the equilibrium points of the
resulting dynamical system corresponding to physically realistic inhomogeneous
cosmological models and astrophysical objects with values for the parameters
which are consistent with current constraints. In particular, we consider dust
models in ($\beta-$) normalized variables and derive a reduced (closed)
evolution system and we obtain the general evolution equations for the
spatially homogeneous Kantowski-Sachs models using appropriate bounded
normalized variables. We then analyse these models, with special emphasis on
the future asymptotic behaviour for different values of the parameters.
Finally, we investigate static models for a mixture of a (necessarily
non-tilted) perfect fluid with a barotropic equations of state and a scalar
field.
| [
{
"created": "Sun, 2 Aug 2015 19:26:38 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Dec 2015 13:28:47 GMT",
"version": "v2"
}
] | 2015-12-08 | [
[
"Coley",
"Alan A.",
"",
"Dalhousie U., Math. Dept."
],
[
"Leon",
"Genly",
"",
"Valparaiso U.,\n Catolica"
],
[
"Sandin",
"Patrik",
"",
"Potsdam, Max Planck Inst."
],
[
"Latta",
"Joey",
"",
"Dalhousie\n U., Math. Dept."
]
] | We investigate spherically symmetric cosmological models in Einstein-aether theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic inhomogeneous cosmological models and astrophysical objects with values for the parameters which are consistent with current constraints. In particular, we consider dust models in ($\beta-$) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field. |
2210.02706 | Lalit Pathak | Lalit Pathak, Amit Reza, Anand S. Sengupta | Fast likelihood evaluation using meshfree approximations for
reconstructing compact binary sources | 9 Pages, 5 Figures | volume = 108, issue = 6, pages = 064055, year = 2023 | 10.1103/PhysRevD.108.064055 | LIGO DCC number: LIGO-P2200253 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several rapid parameter estimation methods have recently been advanced to
deal with the computational challenges of the problem of Bayesian inference of
the properties of compact binary sources detected in the upcoming science runs
of the terrestrial network of gravitational wave detectors. Some of these
methods are well-optimized to reconstruct gravitational wave signals in nearly
real-time necessary for multi-messenger astronomy. In this context, this work
presents a new, computationally efficient algorithm for fast evaluation of the
likelihood function using a combination of numerical linear algebra and
mesh-free interpolation methods. The proposed method can rapidly evaluate the
likelihood function at any arbitrary point of the sample space at a negligible
loss of accuracy and is an alternative to the grid-based parameter estimation
schemes. We obtain posterior samples over model parameters for a canonical
binary neutron star system by interfacing our fast likelihood evaluation method
with the nested sampling algorithm. The marginalized posterior distributions
obtained from these samples are statistically identical to those obtained by
brute force calculations. We find that such Bayesian posteriors can be
determined within a few minutes of detecting such transient compact binary
sources, thereby improving the chances of their prompt follow-up observations
with telescopes at different wavelengths. It may be possible to apply the
blueprint of the meshfree technique presented in this study to Bayesian
inference problems in other domains.
| [
{
"created": "Thu, 6 Oct 2022 06:41:17 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Dec 2023 19:10:08 GMT",
"version": "v2"
}
] | 2023-12-05 | [
[
"Pathak",
"Lalit",
""
],
[
"Reza",
"Amit",
""
],
[
"Sengupta",
"Anand S.",
""
]
] | Several rapid parameter estimation methods have recently been advanced to deal with the computational challenges of the problem of Bayesian inference of the properties of compact binary sources detected in the upcoming science runs of the terrestrial network of gravitational wave detectors. Some of these methods are well-optimized to reconstruct gravitational wave signals in nearly real-time necessary for multi-messenger astronomy. In this context, this work presents a new, computationally efficient algorithm for fast evaluation of the likelihood function using a combination of numerical linear algebra and mesh-free interpolation methods. The proposed method can rapidly evaluate the likelihood function at any arbitrary point of the sample space at a negligible loss of accuracy and is an alternative to the grid-based parameter estimation schemes. We obtain posterior samples over model parameters for a canonical binary neutron star system by interfacing our fast likelihood evaluation method with the nested sampling algorithm. The marginalized posterior distributions obtained from these samples are statistically identical to those obtained by brute force calculations. We find that such Bayesian posteriors can be determined within a few minutes of detecting such transient compact binary sources, thereby improving the chances of their prompt follow-up observations with telescopes at different wavelengths. It may be possible to apply the blueprint of the meshfree technique presented in this study to Bayesian inference problems in other domains. |
1506.08775 | Steven Carlip | S. Carlip | Dimensional reduction in causal set gravity | 6+1 pages; v2: added references, cite of new result on spectral
dimension; v3: minor corrections to match published version | Class. Quantum Grav. 32 (2015) 232001 | 10.1088/0264-9381/32/23/232001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Results from a number of different approaches to quantum gravity suggest that
the effective dimension of spacetime may drop to $d=2$ at small scales. I show
that two different dimensional estimators in causal set theory display the same
behavior, and argue that a third, the spectral dimension, may exhibit a related
phenomenon of "asymptotic silence."
| [
{
"created": "Mon, 29 Jun 2015 18:48:28 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Sep 2015 17:33:28 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Nov 2015 23:01:21 GMT",
"version": "v3"
}
] | 2015-11-18 | [
[
"Carlip",
"S.",
""
]
] | Results from a number of different approaches to quantum gravity suggest that the effective dimension of spacetime may drop to $d=2$ at small scales. I show that two different dimensional estimators in causal set theory display the same behavior, and argue that a third, the spectral dimension, may exhibit a related phenomenon of "asymptotic silence." |
1203.0675 | Lorenzo Iorio | Lorenzo Iorio | Lower bounds of characteristic scale of topological modification of the
Newtonian gravitation | Latex, 6 pages, no tables, 1 figure, 3 references. Accepted for
publication in International Journal of Modern Physics D (IJMPD) | Int. J. Mod. Phys.D 21:1250048,2012 | 10.1142/S0218271812500484 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically work out the long-term orbital perturbations induced by the
first term of the expansion of the perturbing potential arising from the local
modification of the Newton's inverse square law due to a topology R^2 x S^1
with a compactified dimension of radius R recently proposed by Floratos and
Leontaris. We neither restrict to any specific spatial direction for the
asymmetry axis nor to particular orbital configurations of the test particle.
Thus, our results are quite general. Non-vanishing long-term variations occur
for all the usual osculating Keplerian orbital elements, apart from the
semimajor axis which is left unaffected. By using recent improvements in the
determination of the orbital motion of Saturn from Cassini data, we
preliminarily inferred R >= 4-6 kau. As a complementary approach, the putative
topological effects should be explicitly modeled and solved-for with a modified
version of the ephemerides dynamical models with which the same data sets
should be reprocessed.
| [
{
"created": "Sat, 3 Mar 2012 18:30:07 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Apr 2012 07:54:03 GMT",
"version": "v2"
}
] | 2012-04-27 | [
[
"Iorio",
"Lorenzo",
""
]
] | We analytically work out the long-term orbital perturbations induced by the first term of the expansion of the perturbing potential arising from the local modification of the Newton's inverse square law due to a topology R^2 x S^1 with a compactified dimension of radius R recently proposed by Floratos and Leontaris. We neither restrict to any specific spatial direction for the asymmetry axis nor to particular orbital configurations of the test particle. Thus, our results are quite general. Non-vanishing long-term variations occur for all the usual osculating Keplerian orbital elements, apart from the semimajor axis which is left unaffected. By using recent improvements in the determination of the orbital motion of Saturn from Cassini data, we preliminarily inferred R >= 4-6 kau. As a complementary approach, the putative topological effects should be explicitly modeled and solved-for with a modified version of the ephemerides dynamical models with which the same data sets should be reprocessed. |
gr-qc/0502022 | Mohammad Vahid Takook | S. Moradi, S. Rouhani and M.V. Takook | Discrete Symmetries for Spinor Field in de Sitter Space | 13 pages, LaTeX; appendices added | Phys.Lett.B613:74-82,2005; Erratum-ibid.B658:284,2008 | 10.1016/j.physletb.2005.03.030 10.1016/j.physletb.2007.10.029 | null | gr-qc | null | Discrete symmetries, parity, time reversal, antipodal, and charge conjugation
transformations for spinor field in de Sitter space, are presented in the
ambient space notation, i.e. in a coordinate independent way. The PT and PCT
transformations are also discussed in this notation. The five-current density
is studied and their transformation under the discrete symmetries is discussed.
| [
{
"created": "Sat, 5 Feb 2005 17:28:40 GMT",
"version": "v1"
},
{
"created": "Mon, 9 May 2005 10:37:15 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Moradi",
"S.",
""
],
[
"Rouhani",
"S.",
""
],
[
"Takook",
"M. V.",
""
]
] | Discrete symmetries, parity, time reversal, antipodal, and charge conjugation transformations for spinor field in de Sitter space, are presented in the ambient space notation, i.e. in a coordinate independent way. The PT and PCT transformations are also discussed in this notation. The five-current density is studied and their transformation under the discrete symmetries is discussed. |
gr-qc/0101125 | Wade Naylor | Ian G Moss and Wade Naylor | Diagrams for heat kernel expansions | 17 pages, 4 figures, ReVTeX | Class.Quant.Grav. 16 (1999) 2611-2624 | 10.1088/0264-9381/16/8/304 | null | gr-qc | null | A diagramatic heat kernel expansion technique is presented. The method is
especially well suited to the small-derivative expansion of the heat kernel,
but it can also be used to reproduce the results obtained by the approach known
as covariant perturbation theory. The new technique gives an expansion for the
heat kernel at coincident points. It can also be used to obtain the derivative
of the heat kernel and this is useful for evaluating the expectation values of
the stress-energy tensor.
| [
{
"created": "Wed, 31 Jan 2001 10:39:45 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Moss",
"Ian G",
""
],
[
"Naylor",
"Wade",
""
]
] | A diagramatic heat kernel expansion technique is presented. The method is especially well suited to the small-derivative expansion of the heat kernel, but it can also be used to reproduce the results obtained by the approach known as covariant perturbation theory. The new technique gives an expansion for the heat kernel at coincident points. It can also be used to obtain the derivative of the heat kernel and this is useful for evaluating the expectation values of the stress-energy tensor. |
2401.10025 | Jeferson de Oliveira | Jeferson de Oliveira, R. D. B. Fontana and A. B. Pavan | Aspects of regular and singular
electromagnetic-generalized-quasitopological-gravities black holes in (2+1)
dimensions | 26 pages, 5 figures. References added | Phys.Rev.D 109 (2024) 2, 024027 | 10.1103/PhysRevD.109.024027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate quasitopological black holes in $(2+1)$ dimensions in the
context of electromagnetic-generalized-quasitopological-gravities (EM-GQT). For
three different families of geometries of quasitopological nature, we study the
causal structure and their response to a probe scalar field. To linear order,
we verify that the scalar field evolves stably, decaying in different towers of
quasinormal modes. The studied black holes are either charged geometries
(regular and singular) or a regular Ba\~nados-Teitelboim-Zanelli (BTZ)-like
black hole, both coming from the EM-GQT theory characterized by nonminimal
coupling parameters between gravity and a background scalar field. We calculate
the quasinormal modes applying different numerical methods with convergent
results between them. The oscillations demonstrate a very peculiar structure
for charged black holes: in the intermediate and near extremal cases, a
particular scaling arises, similar to that of the rotating BTZ geometry, with
the modes being proportional to the distance between horizons. For the single
horizon black hole solution, we identify the presence of different quasinormal
families by analyzing the features of that spectrum. In all three considered
geometries, no instabilities were found.
| [
{
"created": "Thu, 18 Jan 2024 14:50:36 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2024 14:01:20 GMT",
"version": "v2"
}
] | 2024-01-30 | [
[
"de Oliveira",
"Jeferson",
""
],
[
"Fontana",
"R. D. B.",
""
],
[
"Pavan",
"A. B.",
""
]
] | We investigate quasitopological black holes in $(2+1)$ dimensions in the context of electromagnetic-generalized-quasitopological-gravities (EM-GQT). For three different families of geometries of quasitopological nature, we study the causal structure and their response to a probe scalar field. To linear order, we verify that the scalar field evolves stably, decaying in different towers of quasinormal modes. The studied black holes are either charged geometries (regular and singular) or a regular Ba\~nados-Teitelboim-Zanelli (BTZ)-like black hole, both coming from the EM-GQT theory characterized by nonminimal coupling parameters between gravity and a background scalar field. We calculate the quasinormal modes applying different numerical methods with convergent results between them. The oscillations demonstrate a very peculiar structure for charged black holes: in the intermediate and near extremal cases, a particular scaling arises, similar to that of the rotating BTZ geometry, with the modes being proportional to the distance between horizons. For the single horizon black hole solution, we identify the presence of different quasinormal families by analyzing the features of that spectrum. In all three considered geometries, no instabilities were found. |
1006.4150 | Bahram Mashhoon | Bahram Mashhoon | Necessity of Acceleration-Induced Nonlocality | 12 pages; v2: improved version accepted for publication in Ann. Phys.
(Berlin) | Annalen Phys.523:226-234,2011 | 10.1002/andp.201010464 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to explain clearly why nonlocality must be an
essential part of the theory of relativity. In the standard local version of
this theory, Lorentz invariance is extended to accelerated observers by
assuming that they are pointwise inertial. This locality postulate is exact
when dealing with phenomena involving classical point particles and rays of
radiation, but breaks down for electromagnetic fields, as field properties in
general cannot be measured instantaneously. The problem is corrected in
nonlocal relativity by supplementing the locality postulate with a certain
average over the past world line of the observer.
| [
{
"created": "Mon, 21 Jun 2010 19:51:02 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Nov 2010 21:34:27 GMT",
"version": "v2"
}
] | 2011-04-07 | [
[
"Mashhoon",
"Bahram",
""
]
] | The purpose of this paper is to explain clearly why nonlocality must be an essential part of the theory of relativity. In the standard local version of this theory, Lorentz invariance is extended to accelerated observers by assuming that they are pointwise inertial. This locality postulate is exact when dealing with phenomena involving classical point particles and rays of radiation, but breaks down for electromagnetic fields, as field properties in general cannot be measured instantaneously. The problem is corrected in nonlocal relativity by supplementing the locality postulate with a certain average over the past world line of the observer. |
gr-qc/9809016 | Alejandro Perez | Ezra T. Newman and Alejandro Perez | Characteristic Surface Data for the Eikonal Equation | 16 pages, no figures, Scientific Work-Place 2.5, tex, Corrected typos | J.Math.Phys. 40 (1999) 1093-1102 | 10.1063/1.532708 | null | gr-qc | null | A method of solving the eikonal equation, in either flat or curved
space-times, with arbitrary Cauchy data, is extended to the case of data given
on a characteristic surface. We find a beautiful relationship between the
Cauchy and characteristic data for the same solution, namely they are related
by a Legendre transformation. From the resulting solutions, we study and
describe their associated wave-front singularities.
| [
{
"created": "Thu, 3 Sep 1998 17:54:21 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Sep 1998 21:46:30 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Newman",
"Ezra T.",
""
],
[
"Perez",
"Alejandro",
""
]
] | A method of solving the eikonal equation, in either flat or curved space-times, with arbitrary Cauchy data, is extended to the case of data given on a characteristic surface. We find a beautiful relationship between the Cauchy and characteristic data for the same solution, namely they are related by a Legendre transformation. From the resulting solutions, we study and describe their associated wave-front singularities. |
1509.05131 | Rashmi Uniyal | Ravi Shankar Kuniyal, Rashmi Uniyal, Hemwati Nandan and K. D. Purohit | Null Geodesics in a Magnetically Charged Stringy Black Hole Spacetime | 21 pages, 13 captioned figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesic motion of massless test particles in the background of
a magnetic charged black hole spacetime in four dimensions in dilaton-Maxwell
gravity. The behaviour of effective potential in view of the different values
of black hole parameters is analysed in the equatorial plane. The possible
orbits for null geodesics are also discussed in detail in view of the different
values of the impact parameter. We have also calculated the frequency shift of
photons in this spacetime. The results obtained are then compared with those
for the electrically charged stringy black hole spacetime and the Schwarzschild
black hole spacetime. It is observed that there exists no stable circular orbit
outside the event horizon for massless test particles.
| [
{
"created": "Thu, 17 Sep 2015 05:45:03 GMT",
"version": "v1"
}
] | 2015-09-18 | [
[
"Kuniyal",
"Ravi Shankar",
""
],
[
"Uniyal",
"Rashmi",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Purohit",
"K. D.",
""
]
] | We study the geodesic motion of massless test particles in the background of a magnetic charged black hole spacetime in four dimensions in dilaton-Maxwell gravity. The behaviour of effective potential in view of the different values of black hole parameters is analysed in the equatorial plane. The possible orbits for null geodesics are also discussed in detail in view of the different values of the impact parameter. We have also calculated the frequency shift of photons in this spacetime. The results obtained are then compared with those for the electrically charged stringy black hole spacetime and the Schwarzschild black hole spacetime. It is observed that there exists no stable circular orbit outside the event horizon for massless test particles. |
1106.1785 | Muhammad Jamil Amir | M. Jamil Amir, Sarfraz Ali and Tariq Ismaeel | Energy-Momentum Distribution of Non-Static Plane Symmetric Spacetimes in
GR and TPT | 18 pages | Chinese J of Physics, 50(01), 2012, p-14 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to explore the energy-momentum of non-static plane
symmetric spacetimes in the context of General Relativity and teleparallel
theory of gravity. For this purpose, we use four prescriptions, namely,
Einstein, Landau-Lifshitz, Bergmann-Thomson and M{\o}ller in both theories. It
is shown that the results for the first three prescriptions turn out to be same
in both the theories but different for last prescription. It is mentioning here
that our results coincide with the results obtained by Sharif and kanwal [1]
for Bell-Szekeres metric under certain choice of the metric functions.
| [
{
"created": "Thu, 9 Jun 2011 12:13:28 GMT",
"version": "v1"
}
] | 2013-12-06 | [
[
"Amir",
"M. Jamil",
""
],
[
"Ali",
"Sarfraz",
""
],
[
"Ismaeel",
"Tariq",
""
]
] | This paper is devoted to explore the energy-momentum of non-static plane symmetric spacetimes in the context of General Relativity and teleparallel theory of gravity. For this purpose, we use four prescriptions, namely, Einstein, Landau-Lifshitz, Bergmann-Thomson and M{\o}ller in both theories. It is shown that the results for the first three prescriptions turn out to be same in both the theories but different for last prescription. It is mentioning here that our results coincide with the results obtained by Sharif and kanwal [1] for Bell-Szekeres metric under certain choice of the metric functions. |
2101.00271 | Swagat Saurav Mishra | Swagat S. Mishra, Varun Sahni and Alexei A. Starobinsky | Curing inflationary degeneracies using reheating predictions and relic
gravitational waves | 41 pages, 13 figures, some clarifications and additional references.
Matches published version in JCAP | null | 10.1088/1475-7516/2021/05/075 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that the inflationary scenario often displays different sets
of degeneracies in its predictions for CMB observables. These degeneracies
usually arise either because multiple inflationary models predict similar
values for the scalar spectral index $n_{_S}$ and the tensor-to-scalar ratio
$r$, or because within the same model, the values of $\lbrace n_{_S}, r
\rbrace$ are insensitive to some of the model parameters, making it difficult
for CMB observations alone to constitute a unique probe of inflationary
cosmology. We demonstrate that by taking into account constraints on the
post-inflationary reheating parameters such as the duration of reheating
$N_{_{\rm re}}$, its temperature $T_{_{\rm re}}$ and especially its equation of
state (EOS), $w_{_{\rm re}}$, it is possible to break this degeneracy in
certain classes of inflationary models where identical values of $\lbrace
n_{_S}, r \rbrace$ can correspond to different reheating $w_{_{\rm re}}$. In
particular, we show how reheating constraints can break inflationary
degeneracies in the T-model and the E-model $\alpha$-attractors. Non-canonical
inflation is also studied. The relic gravitational wave (GW) spectrum provides
us with another tool to break inflationary degeneracies. This is because the GW
spectrum is sensitive to the post-inflationary EOS of the universe. Indeed a
stiff EOS during reheating $(w_{_{\rm re}} > 1/3)$ gives rise to a small scale
blue tilt in the spectral index $n_{_{\rm GW}} = \frac{d\log{\Omega_{_{\rm
GW}}}}{d\log{k}} > 0$, while a soft EOS $(w_{_{\rm re}} < 1/3)$ results in a
red tilt. Relic GWs therefore provide us with valuable information about the
post-inflationary epoch, and their spectrum can be used to cure inflationary
degeneracies in $\lbrace n_{_S}, r\rbrace$.
| [
{
"created": "Fri, 1 Jan 2021 17:17:40 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Mar 2021 14:36:07 GMT",
"version": "v2"
},
{
"created": "Mon, 31 May 2021 12:09:33 GMT",
"version": "v3"
}
] | 2021-06-01 | [
[
"Mishra",
"Swagat S.",
""
],
[
"Sahni",
"Varun",
""
],
[
"Starobinsky",
"Alexei A.",
""
]
] | It is well known that the inflationary scenario often displays different sets of degeneracies in its predictions for CMB observables. These degeneracies usually arise either because multiple inflationary models predict similar values for the scalar spectral index $n_{_S}$ and the tensor-to-scalar ratio $r$, or because within the same model, the values of $\lbrace n_{_S}, r \rbrace$ are insensitive to some of the model parameters, making it difficult for CMB observations alone to constitute a unique probe of inflationary cosmology. We demonstrate that by taking into account constraints on the post-inflationary reheating parameters such as the duration of reheating $N_{_{\rm re}}$, its temperature $T_{_{\rm re}}$ and especially its equation of state (EOS), $w_{_{\rm re}}$, it is possible to break this degeneracy in certain classes of inflationary models where identical values of $\lbrace n_{_S}, r \rbrace$ can correspond to different reheating $w_{_{\rm re}}$. In particular, we show how reheating constraints can break inflationary degeneracies in the T-model and the E-model $\alpha$-attractors. Non-canonical inflation is also studied. The relic gravitational wave (GW) spectrum provides us with another tool to break inflationary degeneracies. This is because the GW spectrum is sensitive to the post-inflationary EOS of the universe. Indeed a stiff EOS during reheating $(w_{_{\rm re}} > 1/3)$ gives rise to a small scale blue tilt in the spectral index $n_{_{\rm GW}} = \frac{d\log{\Omega_{_{\rm GW}}}}{d\log{k}} > 0$, while a soft EOS $(w_{_{\rm re}} < 1/3)$ results in a red tilt. Relic GWs therefore provide us with valuable information about the post-inflationary epoch, and their spectrum can be used to cure inflationary degeneracies in $\lbrace n_{_S}, r\rbrace$. |
1104.0449 | Mark Fisher | Mark Fisher, Todd A. Oliynyk | There are no magnetically charged particle-like solutions of the
Einstein Yang-Mills equations for Abelian models | 48 pages, 1 figure | Commun. Math. Phys. 312, 137-177 (2012) | 10.1007/s00220-011-1388-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that there are no magnetically charged particle-like solutions for
Abelian models in Einstein Yang-Mills, but for non-Abelian models the
possibility remains open. An analysis of the Lie algebraic structure of the
Yang-Mills fields is essential to our results. In one key step of our analysis
we use invariant polynomials to determine which orbits of the gauge group
contain the possible asymptotic Yang-Mills field configurations. Together with
a new horizontal/vertical space decomposition of the Yang-Mills fields this
enables us to overcome some obstacles and complete a dynamical system existence
theorem for asymptotic solutions with nonzero total magnetic charge. We then
prove that these solutions cannot be extended globally for Abelian models and
begin an investigation of the details for non-Abelian models.
| [
{
"created": "Mon, 4 Apr 2011 01:36:14 GMT",
"version": "v1"
}
] | 2012-06-28 | [
[
"Fisher",
"Mark",
""
],
[
"Oliynyk",
"Todd A.",
""
]
] | We prove that there are no magnetically charged particle-like solutions for Abelian models in Einstein Yang-Mills, but for non-Abelian models the possibility remains open. An analysis of the Lie algebraic structure of the Yang-Mills fields is essential to our results. In one key step of our analysis we use invariant polynomials to determine which orbits of the gauge group contain the possible asymptotic Yang-Mills field configurations. Together with a new horizontal/vertical space decomposition of the Yang-Mills fields this enables us to overcome some obstacles and complete a dynamical system existence theorem for asymptotic solutions with nonzero total magnetic charge. We then prove that these solutions cannot be extended globally for Abelian models and begin an investigation of the details for non-Abelian models. |
1808.10225 | Killian Martineau | Emanuele Alesci, Aur\'elien Barrau, Gioele Botta, Killian Martineau
and Gabriele Stagno | Phenomenology of Quantum Reduced Loop Gravity in the isotropic
cosmological sector | 18 pages, 12 figures | Phys. Rev. D 98, 106022 (2018) | 10.1103/PhysRevD.98.106022 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum reduced loop gravity is designed to consistently study symmetry
reduced systems within the loop quantum gravity framework. In particular, it
bridges the gap between the effective cosmological models of loop quantum
cosmology and the full theory, addressing the dynamics before the
minisuperspace reduction. This mostly preserves the graph structure and SU(2)
quantum numbers. In this article, we study the phenomenological consequences of
the isotropic sector of the theory, the so-called emergent bouncing universe
model. In particular, the parameter space is scanned and we show that the
number of inflationary e-folds is almost always higher than the observational
lower-bound. We also compute the primordial tensor power spectrum and study its
sensitivity upon the fundamental parameters used in the model.
| [
{
"created": "Thu, 30 Aug 2018 11:22:14 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Nov 2018 13:55:52 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Alesci",
"Emanuele",
""
],
[
"Barrau",
"Aurélien",
""
],
[
"Botta",
"Gioele",
""
],
[
"Martineau",
"Killian",
""
],
[
"Stagno",
"Gabriele",
""
]
] | Quantum reduced loop gravity is designed to consistently study symmetry reduced systems within the loop quantum gravity framework. In particular, it bridges the gap between the effective cosmological models of loop quantum cosmology and the full theory, addressing the dynamics before the minisuperspace reduction. This mostly preserves the graph structure and SU(2) quantum numbers. In this article, we study the phenomenological consequences of the isotropic sector of the theory, the so-called emergent bouncing universe model. In particular, the parameter space is scanned and we show that the number of inflationary e-folds is almost always higher than the observational lower-bound. We also compute the primordial tensor power spectrum and study its sensitivity upon the fundamental parameters used in the model. |
gr-qc/0504049 | Lucio Baggio | L. Baggio, G. A. Prodi | False discovery rate: setting the probability of false claim of
detection | 7 pages, 3 table, 3 figures. Prepared for the Proceedings of GWDAW 9
(http://lappc-in39.in2p3.fr/GWDAW9) A new section was added with a numerical
example, along with two tables and a figure related to the new section. Many
smaller revisions to improve readibility | Class.Quant.Grav. 22 (2005) S1373-S1380 | 10.1088/0264-9381/22/18/S50 | null | gr-qc | null | When testing multiple hypothesis in a survey --e.g. many different source
locations, template waveforms, and so on-- the final result consists in a set
of confidence intervals, each one at a desired confidence level. But the
probability that at least one of these intervals does not cover the true value
increases with the number of trials. With a sufficiently large array of
confidence intervals, one can be sure that at least one is missing the true
value. In particular, the probability of false claim of detection becomes not
negligible. In order to compensate for this, one should increase the confidence
level, at the price of a reduced detection power. False discovery rate control
is a relatively new statistical procedure that bounds the number of mistakes
made when performing multiple hypothesis tests. We shall review this method,
discussing exercise applications to the field of gravitational wave surveys.
| [
{
"created": "Tue, 12 Apr 2005 13:23:29 GMT",
"version": "v1"
},
{
"created": "Thu, 26 May 2005 13:03:02 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jul 2005 18:26:13 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Baggio",
"L.",
""
],
[
"Prodi",
"G. A.",
""
]
] | When testing multiple hypothesis in a survey --e.g. many different source locations, template waveforms, and so on-- the final result consists in a set of confidence intervals, each one at a desired confidence level. But the probability that at least one of these intervals does not cover the true value increases with the number of trials. With a sufficiently large array of confidence intervals, one can be sure that at least one is missing the true value. In particular, the probability of false claim of detection becomes not negligible. In order to compensate for this, one should increase the confidence level, at the price of a reduced detection power. False discovery rate control is a relatively new statistical procedure that bounds the number of mistakes made when performing multiple hypothesis tests. We shall review this method, discussing exercise applications to the field of gravitational wave surveys. |
0906.5588 | Jonathan Luk | Jonathan Luk | Improved decay for solutions to the linear wave equation on a
Schwarzschild black hole | Remarks and References Added | Annales Henri Poincare 11:805-880,2010 | 10.1007/s00023-010-0043-6 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that sufficiently regular solutions to the wave equation
$\Box_g\phi=0$ on the exterior of the Schwarzschild black hole obey the
estimates $|\phi|\leq C_\delta v_+^{-{3/2}+\delta}$ and $|\partial_t\phi|\leq
C_{\delta} v_+^{-2+\delta}$ on a compact region of $r$ and along the event
horizon. This is proved with the help of a new vector field commutator that is
analogous to the scaling vector field on Minkowski spacetime. This result
improves the known decay rates in the region of finite $r$ and along the event
horizon.
| [
{
"created": "Tue, 30 Jun 2009 16:56:28 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Oct 2009 19:48:23 GMT",
"version": "v2"
}
] | 2010-11-09 | [
[
"Luk",
"Jonathan",
""
]
] | We prove that sufficiently regular solutions to the wave equation $\Box_g\phi=0$ on the exterior of the Schwarzschild black hole obey the estimates $|\phi|\leq C_\delta v_+^{-{3/2}+\delta}$ and $|\partial_t\phi|\leq C_{\delta} v_+^{-2+\delta}$ on a compact region of $r$ and along the event horizon. This is proved with the help of a new vector field commutator that is analogous to the scaling vector field on Minkowski spacetime. This result improves the known decay rates in the region of finite $r$ and along the event horizon. |
2304.10193 | Takanao Tsuyuki | Yuichiro Sato, Takanao Tsuyuki | Spatially homogeneous solutions of vacuum Einstein equations in general
dimensions | 18 pages, 2 figures | null | null | null | gr-qc hep-th math.DG | http://creativecommons.org/licenses/by/4.0/ | We study time-dependent compactification of extra dimensions. We assume that
the spacetime is spatially homogeneous, and solve the vacuum Einstein equations
without cosmological constant in more than three dimensions. We consider
globally hyperbolic spacetimes in which almost abelian Lie groups act on the
spaces isometrically and simply transitively. We give left-invariant metrics on
the spaces and solve Ricci-flat conditions of the spacetimes. In the
four-dimensional case, our solutions correspond to the Bianchi type II
solution. By our results and previous studies, all spatially homogeneous
solutions whose spaces have zero-dimensional moduli spaces of left-invariant
metrics are found. For the simplest solution, we show that each of the spatial
dimensions cannot expand or contract simultaneously in the late-time limit.
| [
{
"created": "Thu, 20 Apr 2023 10:09:12 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Nov 2023 06:16:39 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Jan 2024 07:24:26 GMT",
"version": "v3"
}
] | 2024-02-01 | [
[
"Sato",
"Yuichiro",
""
],
[
"Tsuyuki",
"Takanao",
""
]
] | We study time-dependent compactification of extra dimensions. We assume that the spacetime is spatially homogeneous, and solve the vacuum Einstein equations without cosmological constant in more than three dimensions. We consider globally hyperbolic spacetimes in which almost abelian Lie groups act on the spaces isometrically and simply transitively. We give left-invariant metrics on the spaces and solve Ricci-flat conditions of the spacetimes. In the four-dimensional case, our solutions correspond to the Bianchi type II solution. By our results and previous studies, all spatially homogeneous solutions whose spaces have zero-dimensional moduli spaces of left-invariant metrics are found. For the simplest solution, we show that each of the spatial dimensions cannot expand or contract simultaneously in the late-time limit. |
2312.13935 | Johanna N. Borissova | Johanna N. Borissova, Bianca Dittrich, Kirill Krasnov | Area-metric gravity revisited | v1: 22 pages; v2: minor modifications, content matches version
published in PRD | null | 10.1103/PhysRevD.109.124035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Area metrics are an intriguing generalization of length metrics which appears
in several quantum-gravity approaches. We describe the space of
diffeomorphism-invariant area-metric actions quadratic in fluctuations and
derivatives. A general theory is found to be specified by four parameters, two
of which are mass parameters for the non-length degrees of freedom. We find
that a two-parameter subclass of theories exhibits an additional shift symmetry
of the kinetic term, and leads to a ghost-free graviton propagator for the
effective theory obtained after integrating out the non-length degrees of
freedom. One of the two parameters determines the strength of parity
violations, the other defines a mass parameter for the non-length degrees of
freedom. The same type of action has been found to appear from modified
Plebanski theory and in the continuum limit of (effective) spin foams.
We moreover find that area-metric actions in Lorentzian (but not in
Euclidean) signature feature wrong-sign kinetic and mass terms for the
non-length degrees of freedom. Nevertheless, despite a coupling of these
degrees of freedom to the length metric, the linearized dynamics turns out to
be stable for the above subclass of actions.
| [
{
"created": "Thu, 21 Dec 2023 15:29:11 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jun 2024 18:00:00 GMT",
"version": "v2"
}
] | 2024-06-18 | [
[
"Borissova",
"Johanna N.",
""
],
[
"Dittrich",
"Bianca",
""
],
[
"Krasnov",
"Kirill",
""
]
] | Area metrics are an intriguing generalization of length metrics which appears in several quantum-gravity approaches. We describe the space of diffeomorphism-invariant area-metric actions quadratic in fluctuations and derivatives. A general theory is found to be specified by four parameters, two of which are mass parameters for the non-length degrees of freedom. We find that a two-parameter subclass of theories exhibits an additional shift symmetry of the kinetic term, and leads to a ghost-free graviton propagator for the effective theory obtained after integrating out the non-length degrees of freedom. One of the two parameters determines the strength of parity violations, the other defines a mass parameter for the non-length degrees of freedom. The same type of action has been found to appear from modified Plebanski theory and in the continuum limit of (effective) spin foams. We moreover find that area-metric actions in Lorentzian (but not in Euclidean) signature feature wrong-sign kinetic and mass terms for the non-length degrees of freedom. Nevertheless, despite a coupling of these degrees of freedom to the length metric, the linearized dynamics turns out to be stable for the above subclass of actions. |
1310.1880 | Lars Andersson | Lars Andersson | Cosmological models and stability | Based on a talk at the conference "Relativity and Gravitation, 100
Years after Einstein in Prague", at Charles University, Prague, June 25-29,
2012 | null | 10.1007/978-3-319-06349-2_14 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Principles in the form of heuristic guidelines or generally accepted dogma
play an important role in the development of physical theories. In particular,
philosophical considerations and principles figure prominently in the work of
Albert Einstein. As mentioned in the talk by Jiri Bicak at this conference
Einstein formulated the equivalence principle, an essential step on the road to
general relativity, during his time in Prague 1911-1912. In this talk, I would
like to discuss some aspects of cosmological models. As cosmology is an area of
physics where "principles" such as the "cosmological principle" or the
"Copernican principle" play a prominent role in motivating the class of models
which form part of the current standard model, I will start by comparing the
role of the equivalence principle to that of the principles used in cosmology.
I will then briefly describe the standard model of cosmology to give a
perspective on some mathematical problems and conjectures on cosmological
models, which are discussed in the later part of this paper.
| [
{
"created": "Mon, 7 Oct 2013 18:29:32 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Andersson",
"Lars",
""
]
] | Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiri Bicak at this conference Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed in the later part of this paper. |
2109.05828 | Chen-Kai Qiao | Chen-Kai Qiao and Mi Zhou | The Gravitational Bending of Acoustic Schwarzschild Black Hole | 21 pages, 5 figures, 2 appendices, 2 tables; V2 is minor revision; V3
is major revision; V4: minor revision (astrophysical motivation is included
and small errors are corrected) V5: accepted version | The European Physical Journal C 83 (2023) 4, 271 | 10.1140/epjc/s10052-023-11376-3 | null | gr-qc cond-mat.other | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Acoustic black hole is becoming an attractive topic in recent years, for it
open-up new direction for experimental / observational explorations of black
holes. In this work, the gravitational bending of acoustic Schwarzschild black
hole is investigated. The gravitational deflection angle of particles traveling
along null geodesics, weak gravitational lensing and Einstein ring for acoustic
Schwarzschild black hole are carefully studied and analyzed. Particularly, in
the calculation of gravitational deflection angle, we resort to two approaches
-- the Gauss-Bonnet theorem and the geodesic method. The results show that the
gravitational bending effect in acoustic Schwarzschild black hole is enhanced,
compared with conventional Schwarzschild black hole. This result indicates that
the acoustic black holes may be more easily detectable in gravitational bending
effects and weak gravitational lensing observations.
| [
{
"created": "Mon, 13 Sep 2021 09:57:27 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Oct 2021 09:46:57 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Dec 2021 15:55:26 GMT",
"version": "v3"
},
{
"created": "Thu, 24 Mar 2022 14:44:00 GMT",
"version": "v4"
},
{
"created": "Sun, 9 Apr 2023 05:34:51 GMT",
"version": "v5"
}
] | 2023-04-11 | [
[
"Qiao",
"Chen-Kai",
""
],
[
"Zhou",
"Mi",
""
]
] | Acoustic black hole is becoming an attractive topic in recent years, for it open-up new direction for experimental / observational explorations of black holes. In this work, the gravitational bending of acoustic Schwarzschild black hole is investigated. The gravitational deflection angle of particles traveling along null geodesics, weak gravitational lensing and Einstein ring for acoustic Schwarzschild black hole are carefully studied and analyzed. Particularly, in the calculation of gravitational deflection angle, we resort to two approaches -- the Gauss-Bonnet theorem and the geodesic method. The results show that the gravitational bending effect in acoustic Schwarzschild black hole is enhanced, compared with conventional Schwarzschild black hole. This result indicates that the acoustic black holes may be more easily detectable in gravitational bending effects and weak gravitational lensing observations. |
1508.05810 | James Douglass | James W. Douglass | A nonmetric theory of gravitation that is nonsingular at the
Schwarzschild radius | 8 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A gravitational theory is formulated by considering the physical processes
underlying relativistic dilation of time and contraction of space. It is shown
that the point mass solution of general relativity's field equation - the
Schwarzschild metric - is a weak-field approximation to the more general
Lagrangian resulting here. Unlike general relativity the resulting theory does
not exhibit a singularity at the Schwarzschild radius and furthermore shows
that photons escape from that radius with a red shift of e^0.5 - 1.
Consequently black holes are not black. Experimental confirmations of general
relativity that have been conducted in the weak field domain may also be
considered as confirmations of the theory presented here since the two theories
provide nearly identical predictions there. Testable differentiation of these
two theories will require observations in the near vicinity of the
Scnwarzschild radius of a black hole. Issues related to experimental
confirmation are discussed.
| [
{
"created": "Mon, 24 Aug 2015 14:07:01 GMT",
"version": "v1"
}
] | 2015-08-25 | [
[
"Douglass",
"James W.",
""
]
] | A gravitational theory is formulated by considering the physical processes underlying relativistic dilation of time and contraction of space. It is shown that the point mass solution of general relativity's field equation - the Schwarzschild metric - is a weak-field approximation to the more general Lagrangian resulting here. Unlike general relativity the resulting theory does not exhibit a singularity at the Schwarzschild radius and furthermore shows that photons escape from that radius with a red shift of e^0.5 - 1. Consequently black holes are not black. Experimental confirmations of general relativity that have been conducted in the weak field domain may also be considered as confirmations of the theory presented here since the two theories provide nearly identical predictions there. Testable differentiation of these two theories will require observations in the near vicinity of the Scnwarzschild radius of a black hole. Issues related to experimental confirmation are discussed. |
gr-qc/0608084 | Maria Alice Gasparini | Maria Alice Gasparini and Florian Dubath | Matched filter for multi-transducers resonant GW antennas | 15 pages and 4 figures, version accepted for publication in PRD | Phys.Rev.D74:122003,2006 | 10.1103/PhysRevD.74.122003 | null | gr-qc astro-ph | null | We analyze two kinds of matched filters for data output of a spherical
resonant GW detector. In order to filter the data of a real sphere, a strategy
is proposed, firstly using an omnidirectional in-line filter, which is supposed
to select periodograms with excitations, secondly by performing a directional
filter on such selected periodograms, finding the wave arrival time, direction
and polarization. We point out that, as the analytical simplifications
occurring in the ideal 6 transducers TIGA sphere do not hold for a real sphere,
using a 5 transducers configuration could be a more convenient choice.
| [
{
"created": "Thu, 17 Aug 2006 12:58:07 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Nov 2006 22:34:29 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gasparini",
"Maria Alice",
""
],
[
"Dubath",
"Florian",
""
]
] | We analyze two kinds of matched filters for data output of a spherical resonant GW detector. In order to filter the data of a real sphere, a strategy is proposed, firstly using an omnidirectional in-line filter, which is supposed to select periodograms with excitations, secondly by performing a directional filter on such selected periodograms, finding the wave arrival time, direction and polarization. We point out that, as the analytical simplifications occurring in the ideal 6 transducers TIGA sphere do not hold for a real sphere, using a 5 transducers configuration could be a more convenient choice. |
2309.14765 | Asuka Ito | Asuka Ito, Kazunori Kohri, Kazunori Nakayama | Gravitational wave search through electromagnetic telescopes | 11 pages, 4 figures | Prog. Theor. Exp. Phys. 2024 023E03 | 10.1093/ptep/ptae004 | KEK-QUP-2023-0018, KEK-TH-2558, KEK-Cosmo-0327, TU-1205 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the graviton-photon conversion in the magnetic fields of the Earth,
the Milky Way Galaxy, and intergalactic regions. Requiring that the photon flux
converted from gravitons does not exceed the observed photon flux with
telescopes, we derive upper limits on the stochastic gravitational waves in
frequency ranges from $10^{7}$Hz to $10^{35}$Hz. Remarkably, the upper limits
on $h^2 \Omega_{{\rm GW}}$ could be less than unity in the frequency range of
$10^{18}$-$10^{23}$ Hz in a specific case. The detection of gravitational waves
using telescopes would open up a new avenue for high frequency gravitational
wave observations.
| [
{
"created": "Tue, 26 Sep 2023 08:54:58 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 03:03:11 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Ito",
"Asuka",
""
],
[
"Kohri",
"Kazunori",
""
],
[
"Nakayama",
"Kazunori",
""
]
] | We study the graviton-photon conversion in the magnetic fields of the Earth, the Milky Way Galaxy, and intergalactic regions. Requiring that the photon flux converted from gravitons does not exceed the observed photon flux with telescopes, we derive upper limits on the stochastic gravitational waves in frequency ranges from $10^{7}$Hz to $10^{35}$Hz. Remarkably, the upper limits on $h^2 \Omega_{{\rm GW}}$ could be less than unity in the frequency range of $10^{18}$-$10^{23}$ Hz in a specific case. The detection of gravitational waves using telescopes would open up a new avenue for high frequency gravitational wave observations. |
2208.00409 | Fabian L\'aszl\'o Konstantin Wagner | Eduardo Guendelman and Fabian Wagner | Momentum gauge fields from curved momentum space through Kaluza-Klein
reduction | 6 pages, no figures, v2: minor clarifications added references,
removed typos - published version | Class.Quant.Grav. 40 (2023) 13, 135007 | 10.1088/1361-6382/acd979 | null | gr-qc hep-ph hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate the relation between curved momentum space and
momentum-dependent gauge fields. While the former is a classic idea that has
been shown to be tied to minimal-length models, the latter constitutes a
relatively recent development in quantum gravity phenomenology. In particular,
the gauge principle in momentum space amounts to a modification of the position
operator of the form $\hat{X}^\mu\rightarrow\hat{X}^\mu-g A^\mu (\hat{P})$ akin
to a gauge-covariant derivative in momentum space according to the minimal
coupling prescription. Here, we derive both effects from a Kaluza-Klein
reduction of a higher-dimensional geometry exhibiting curvature in momentum
space. The interplay of the emerging gauge fields as well as the remaining
curved momentum space lead to modifications of the Heisenberg algebra. While
the gauge fields imply Moyal-type noncommutativity dependent on the analogue
field strength tensor, the dimensionally reduced curved momentum space geometry
translates to a Snyder-type noncommutative geometry.
| [
{
"created": "Sun, 31 Jul 2022 10:03:47 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Sep 2023 06:59:46 GMT",
"version": "v2"
}
] | 2023-09-25 | [
[
"Guendelman",
"Eduardo",
""
],
[
"Wagner",
"Fabian",
""
]
] | In this work we investigate the relation between curved momentum space and momentum-dependent gauge fields. While the former is a classic idea that has been shown to be tied to minimal-length models, the latter constitutes a relatively recent development in quantum gravity phenomenology. In particular, the gauge principle in momentum space amounts to a modification of the position operator of the form $\hat{X}^\mu\rightarrow\hat{X}^\mu-g A^\mu (\hat{P})$ akin to a gauge-covariant derivative in momentum space according to the minimal coupling prescription. Here, we derive both effects from a Kaluza-Klein reduction of a higher-dimensional geometry exhibiting curvature in momentum space. The interplay of the emerging gauge fields as well as the remaining curved momentum space lead to modifications of the Heisenberg algebra. While the gauge fields imply Moyal-type noncommutativity dependent on the analogue field strength tensor, the dimensionally reduced curved momentum space geometry translates to a Snyder-type noncommutative geometry. |
2211.04681 | Chongoh Lee | Seoktae Koh, Chong Oh Lee | Configuration entropy and instability of accelerating black hole in AdS | 7 pages, 7 figures, typos corrected, added comments, version to
appear in EPJ Plus | null | 10.1140/epjp/s13360-023-04033-x | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider an accelerating black hole with a negative cosmological constant
in four-dimensional spacetime. There are two configurations such as a black
string (BS) phase when a mass parameter is zero and a black hole (BH) phase
when a mass parameter is non-zero. We investigate their stability via the
configuration entropy (CE). It is found that the BS is not always stable but
the BH has a thermally stable range below the critical mass of the BH, which is
consistent with thermodynamic instability.
| [
{
"created": "Wed, 9 Nov 2022 04:45:54 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2023 01:28:50 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Koh",
"Seoktae",
""
],
[
"Lee",
"Chong Oh",
""
]
] | We consider an accelerating black hole with a negative cosmological constant in four-dimensional spacetime. There are two configurations such as a black string (BS) phase when a mass parameter is zero and a black hole (BH) phase when a mass parameter is non-zero. We investigate their stability via the configuration entropy (CE). It is found that the BS is not always stable but the BH has a thermally stable range below the critical mass of the BH, which is consistent with thermodynamic instability. |
0912.4922 | Don N. Page | Don N. Page | Some Gravitational Instantons | This is a paper I presented at a conference in Moscow in December
1978, but it was never published | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All known gravitational instantons with $\Lambda > 0$ ($S^4, CP^2, S^2 \times
S^2$ and $CP # \overline{CP}^2$) are described. They are all special cases of
the Taub-NUT-$\Lambda$ local solution. Hence they are Type D and are locally
conformably K\"ahler. They all may be expressed in Bianchi IX form and have
four or more Killing vectors.
| [
{
"created": "Sun, 27 Dec 2009 00:26:00 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Page",
"Don N.",
""
]
] | All known gravitational instantons with $\Lambda > 0$ ($S^4, CP^2, S^2 \times S^2$ and $CP # \overline{CP}^2$) are described. They are all special cases of the Taub-NUT-$\Lambda$ local solution. Hence they are Type D and are locally conformably K\"ahler. They all may be expressed in Bianchi IX form and have four or more Killing vectors. |
2007.09925 | Jackson Levi Said | Maria Caruana, Gabriel Farrugia, Jackson Levi Said | Cosmological bouncing solutions in f(T,B) gravity | null | Eur. Phys. J. C 80, 640 (2020) | 10.1140/epjc/s10052-020-8204-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Teleparallel Gravity offers the possibility of reformulating gravity in terms
of torsion by exchanging the Levi-Civita connection with the Weitzenb\"ock
connection which describes torsion rather than curvature. Surprisingly,
Teleparallel Gravity can be formulated to be equivalent to general relativity
for a appropriate setup. Our interest lies in exploring an extension of this
theory in which the Lagrangian takes the form of $f(T,B)$ where T and B are two
scalars that characterize the equivalency with general relativity. In this
work, we explore the possible of reproducing well-known cosmological bouncing
scenarios in the flat Friedmann-Lema\^itre-Robertson-Walker geometry using this
approach to gravity. We study the types of gravitational Lagrangians which are
capable of reconstructing analytical solutions for symmetric, oscillatory,
superbounce, matter bounce, and singular bounce settings. These new
cosmologically inspired models may have an effect on gravitational phenomena at
other cosmological scales.
| [
{
"created": "Mon, 20 Jul 2020 08:16:51 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jul 2020 06:35:36 GMT",
"version": "v2"
}
] | 2020-07-23 | [
[
"Caruana",
"Maria",
""
],
[
"Farrugia",
"Gabriel",
""
],
[
"Said",
"Jackson Levi",
""
]
] | Teleparallel Gravity offers the possibility of reformulating gravity in terms of torsion by exchanging the Levi-Civita connection with the Weitzenb\"ock connection which describes torsion rather than curvature. Surprisingly, Teleparallel Gravity can be formulated to be equivalent to general relativity for a appropriate setup. Our interest lies in exploring an extension of this theory in which the Lagrangian takes the form of $f(T,B)$ where T and B are two scalars that characterize the equivalency with general relativity. In this work, we explore the possible of reproducing well-known cosmological bouncing scenarios in the flat Friedmann-Lema\^itre-Robertson-Walker geometry using this approach to gravity. We study the types of gravitational Lagrangians which are capable of reconstructing analytical solutions for symmetric, oscillatory, superbounce, matter bounce, and singular bounce settings. These new cosmologically inspired models may have an effect on gravitational phenomena at other cosmological scales. |
1709.04365 | Muhammad Zaeem-Ul-Haq Bhatti | Z. Yousaf, M. Zaeem-ul-Haq Bhatti, Ume Farwa | Stability Analysis of Stellar Radiating Filaments | 28 pages, no figure | Class. Quantum Grav. 34, 145002 (2017) | 10.1088/1361-6382/aa73b9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this paper is to perform stability analysis of anisotropic
dissipative cylindrical collapsing model in $f(R,T,R_{\mu\nu} T^{\mu\nu})$
gravity. In this context, the modified version of hydrodynamical equation is
explored by means of dynamical equations and radial perturbation scheme. We
examined the role of adiabatic index, dissipation as well as the particular
cosmological model on the onset of dynamical instability of the evolving
cylindrical system that was initially in hydrostatic equilibrium with Newtonian
and post Newtonian approximations. It is pointed out that extra curvature terms
of $f(R,T,R_{\mu\nu}T^{\mu\mu\nu})$ gravity tends to increase the stability,
while that heat radiations push the system to enter into unstable window.
Further, our results reveal the significance of adiabatic index in the
stability analysis of cylindrical celestial model.
| [
{
"created": "Tue, 12 Sep 2017 04:11:41 GMT",
"version": "v1"
}
] | 2017-09-14 | [
[
"Yousaf",
"Z.",
""
],
[
"Bhatti",
"M. Zaeem-ul-Haq",
""
],
[
"Farwa",
"Ume",
""
]
] | The aim of this paper is to perform stability analysis of anisotropic dissipative cylindrical collapsing model in $f(R,T,R_{\mu\nu} T^{\mu\nu})$ gravity. In this context, the modified version of hydrodynamical equation is explored by means of dynamical equations and radial perturbation scheme. We examined the role of adiabatic index, dissipation as well as the particular cosmological model on the onset of dynamical instability of the evolving cylindrical system that was initially in hydrostatic equilibrium with Newtonian and post Newtonian approximations. It is pointed out that extra curvature terms of $f(R,T,R_{\mu\nu}T^{\mu\mu\nu})$ gravity tends to increase the stability, while that heat radiations push the system to enter into unstable window. Further, our results reveal the significance of adiabatic index in the stability analysis of cylindrical celestial model. |
1801.06528 | Manuel Hohmann | Manuel Hohmann | Scalar-torsion theories of gravity I: general formalism and conformal
transformations | 11 pages, no figures | Phys. Rev. D 98, 064002 (2018) | 10.1103/PhysRevD.98.064002 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the most general class of teleparallel scalar-torsion theories of
gravity in their covariant formulation. The only restrictions we impose are the
invariance of the action under diffeomorphisms and local Lorentz
transformations, as well as vanishing direct coupling of the matter fields to
the teleparallel spin connection. In this general setting we discuss the
implications of local Lorentz invariance and diffeomorphism invariance and
derive the general structure of the field equations. Further, we show how
different theories of this class are related to each other by conformal
transformations of the tetrad and redefinitions of the scalar field. We finally
show how the formalism can be generalized to an arbitrary number of scalar
fields, and provide a few examples.
| [
{
"created": "Fri, 19 Jan 2018 18:46:13 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Feb 2018 18:19:08 GMT",
"version": "v2"
}
] | 2018-09-12 | [
[
"Hohmann",
"Manuel",
""
]
] | We discuss the most general class of teleparallel scalar-torsion theories of gravity in their covariant formulation. The only restrictions we impose are the invariance of the action under diffeomorphisms and local Lorentz transformations, as well as vanishing direct coupling of the matter fields to the teleparallel spin connection. In this general setting we discuss the implications of local Lorentz invariance and diffeomorphism invariance and derive the general structure of the field equations. Further, we show how different theories of this class are related to each other by conformal transformations of the tetrad and redefinitions of the scalar field. We finally show how the formalism can be generalized to an arbitrary number of scalar fields, and provide a few examples. |
gr-qc/0702146 | Geoffrey Lovelace | Chao Li and Geoffrey Lovelace | A generalization of Ryan's theorem: probing tidal coupling with
gravitational waves from nearly circular, nearly equatorial,
extreme-mass-ratio inspirals | 10 pages, 1 figure, submitted to Phys. Rev. D | Phys.Rev.D77:064022,2008 | 10.1103/PhysRevD.77.064022 | null | gr-qc | null | Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals
(IMRIs)--binaries in which a stellar-mass object spirals into a massive black
hole or other massive, compact body--are important sources of gravitational
waves for LISA and LIGO, respectively. Thorne has speculated that the waves
from EMRIs and IMRIs encode, in principle, all the details of (i) the central
body's spacetime geometry (metric), (ii) the tidal coupling (energy and angular
momentum exchange) between the central body and orbiting object, and (iii) the
evolving orbital elements. Fintan Ryan has given a first partial proof that
this speculation is correct: Restricting himself to nearly circular, nearly
equatorial orbits and ignoring tidal coupling, Ryan proved that the central
body's metric is encoded in the waves. In this paper we generalize Ryan's
theorem. Retaining Ryan's restriction to nearly circular and nearly equatorial
orbits, and dropping the assumption of no tidal coupling, we prove that
Thorne's conjecture is nearly fully correct: the waves encode not only the
central body's metric but also the evolving orbital elements and (in a sense
slightly different from Thorne's conjecture) the evolving tidal coupling.
| [
{
"created": "Wed, 28 Feb 2007 08:24:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Li",
"Chao",
""
],
[
"Lovelace",
"Geoffrey",
""
]
] | Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs)--binaries in which a stellar-mass object spirals into a massive black hole or other massive, compact body--are important sources of gravitational waves for LISA and LIGO, respectively. Thorne has speculated that the waves from EMRIs and IMRIs encode, in principle, all the details of (i) the central body's spacetime geometry (metric), (ii) the tidal coupling (energy and angular momentum exchange) between the central body and orbiting object, and (iii) the evolving orbital elements. Fintan Ryan has given a first partial proof that this speculation is correct: Restricting himself to nearly circular, nearly equatorial orbits and ignoring tidal coupling, Ryan proved that the central body's metric is encoded in the waves. In this paper we generalize Ryan's theorem. Retaining Ryan's restriction to nearly circular and nearly equatorial orbits, and dropping the assumption of no tidal coupling, we prove that Thorne's conjecture is nearly fully correct: the waves encode not only the central body's metric but also the evolving orbital elements and (in a sense slightly different from Thorne's conjecture) the evolving tidal coupling. |
gr-qc/9807045 | Parthasarathi Majumdar | Parthasarathi Majumdar | Black Hole Entropy and Quantum Gravity | 13 pages, Revtex, 5 eps figures. Invited talk at National Symposium
on Trends and Perspectives in Theoretical Physics, IACS, Calcutta, India,
April, 1998. One reference added | null | null | IMSc/98/07/38 | gr-qc hep-th | null | An elementary introduction is given to the problem of black hole entropy as
formulated by Bekenstein and Hawking. The information theoretic basis of
Bekenstein's formulation is briefly reviewed and compared with Hawking's
approach. The issue of calculating the entropy by actual counting of
microstates is taken up next within two currently popular approaches to quantum
gravity, viz., string theory and canonical quantum gravity. The treatment of
the former assay is confined to a few remarks, mainly of a critical nature,
while some of the computational techniques of the latter approach are
elaborated. We conclude by trying to find commonalities between these two
rather disparate directions of work.
| [
{
"created": "Fri, 17 Jul 1998 12:07:30 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jul 1998 07:21:57 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jul 1998 11:01:44 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Majumdar",
"Parthasarathi",
""
]
] | An elementary introduction is given to the problem of black hole entropy as formulated by Bekenstein and Hawking. The information theoretic basis of Bekenstein's formulation is briefly reviewed and compared with Hawking's approach. The issue of calculating the entropy by actual counting of microstates is taken up next within two currently popular approaches to quantum gravity, viz., string theory and canonical quantum gravity. The treatment of the former assay is confined to a few remarks, mainly of a critical nature, while some of the computational techniques of the latter approach are elaborated. We conclude by trying to find commonalities between these two rather disparate directions of work. |
2204.00109 | Nosratollah Jafari Sonbolabadi | Nosrtollah Jafari | Rigidity and Parallelism in the spacetime | 11 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The effect of the linear-fractional transformations on the parallel lines in
the spacetime has been studied. Fock-Lorentz transformations maps a line to a
line, from which one can obtain the combinations rule for the velocities in the
Fock-Lorentz transformations. Rigidity is defined as a consequences of holding
parallelism under the transformations. The Fock-Lorentz transformations do not
preserve rigidity, which leads to some novel results such as growing distances
alongside with advancing time. Also, it is shown that the time coordinates of
events will come closer to each other in the transformed coordinates by going
back in time
| [
{
"created": "Thu, 31 Mar 2022 21:41:56 GMT",
"version": "v1"
}
] | 2022-04-04 | [
[
"Jafari",
"Nosrtollah",
""
]
] | The effect of the linear-fractional transformations on the parallel lines in the spacetime has been studied. Fock-Lorentz transformations maps a line to a line, from which one can obtain the combinations rule for the velocities in the Fock-Lorentz transformations. Rigidity is defined as a consequences of holding parallelism under the transformations. The Fock-Lorentz transformations do not preserve rigidity, which leads to some novel results such as growing distances alongside with advancing time. Also, it is shown that the time coordinates of events will come closer to each other in the transformed coordinates by going back in time |
gr-qc/0205127 | Reinhard Meinel | R. Meinel | Black holes: A physical route to the Kerr metric | 14 pages, 1 table, 4 figures, accepted for publication in Annalen der
Physik (Leipzig) | Annalen Phys.11:509-521,2002 | 10.1002/andp.20025140704 | null | gr-qc astro-ph hep-th | null | As a consequence of Birkhoff's theorem, the exterior gravitational field of a
spherically symmetric star or black hole is always given by the Schwarzschild
metric. In contrast, the exterior gravitational field of a rotating
(axisymmetric) star differs, in general, from the Kerr metric, which describes
a stationary, rotating black hole.
In this paper, I discuss the possibility of a quasi-stationary transition
from rotating equilibrium configurations of normal matter to rotating black
holes.
| [
{
"created": "Thu, 30 May 2002 11:30:16 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jun 2002 07:26:39 GMT",
"version": "v2"
}
] | 2022-09-22 | [
[
"Meinel",
"R.",
""
]
] | As a consequence of Birkhoff's theorem, the exterior gravitational field of a spherically symmetric star or black hole is always given by the Schwarzschild metric. In contrast, the exterior gravitational field of a rotating (axisymmetric) star differs, in general, from the Kerr metric, which describes a stationary, rotating black hole. In this paper, I discuss the possibility of a quasi-stationary transition from rotating equilibrium configurations of normal matter to rotating black holes. |
0712.4157 | Valeri Frolov | Valeri P. Frolov | Hidden Symmetries of Higher-Dimensional Black Hole Spacetimes | 10 pages, Prepared for the Proceedings of the ICGA8 conference | Prog.Theor.Phys.Suppl.172:210-219,2008 | 10.1143/PTPS.172.210 | null | gr-qc | null | The paper contains a brief review of recent results on hidden symmetries in
higher dimensional black hole spacetimes. We show how the existence of a
principal CKY tensor (that is a closed non-degenerate conformal Killing-Yano
2-form) allows one to generate a `tower' of Killing-Yano and Killing tensors
responcible for hidden symmetries. These symmetries imply complete
integrability of geodesic equations and the complete separation of variables in
the Hamilton-Jacobi, Klein-Gordon and Dirac equations in the general
Kerr-NUT-(A)dS metrics.
| [
{
"created": "Wed, 26 Dec 2007 23:33:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Frolov",
"Valeri P.",
""
]
] | The paper contains a brief review of recent results on hidden symmetries in higher dimensional black hole spacetimes. We show how the existence of a principal CKY tensor (that is a closed non-degenerate conformal Killing-Yano 2-form) allows one to generate a `tower' of Killing-Yano and Killing tensors responcible for hidden symmetries. These symmetries imply complete integrability of geodesic equations and the complete separation of variables in the Hamilton-Jacobi, Klein-Gordon and Dirac equations in the general Kerr-NUT-(A)dS metrics. |
2306.13871 | Chao Zhang | Chao Zhang, Ning Dai and Dicong Liang | Importance of including higher signal harmonics in the modeling of
extreme mass-ratio inspirals | 23 pages, 6 figures; PRD accepted | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme mass-ratio inspirals (EMRIs) are the most potential sources
detectable by the Laser Interferometer Space Antenna (LISA). To analyze the
influence of higher harmonics on parameter estimation for EMRIs efficiently, we
use the waveform model that the phase trajectories are relativistic flux-based
adiabatic trajectories and the waveforms are constructed by the augmented
analytic kludge method. We perform a Fisher-matrix error analysis of the EMRI
parameters using signals taking into account the motion of the LISA
constellation and higher harmonics of gravitational waves. Our results
demonstrate that including higher harmonics greatly reduces the errors on the
exterior parameters such as inclination angle $\iota$, the luminosity distance
$d_L$, the polarization angle $\psi$, and the initial phase $\Phi_0$, except
for source localization $\Delta \Omega$ when EMRIs face us. However, the
influence of higher harmonics on parameters $(\iota,d_L,\psi,\Phi_0)$ can be
negligible when the inclination angle is above $1.0$. For intrinsic parameters
such as the spin of central black and the masses of binaries, the influence of
higher harmonics can be negligible for any inclination angle. Our findings are
independent of the mass or spin of the EMRI system.
| [
{
"created": "Sat, 24 Jun 2023 05:41:08 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Aug 2023 01:57:57 GMT",
"version": "v2"
}
] | 2023-08-31 | [
[
"Zhang",
"Chao",
""
],
[
"Dai",
"Ning",
""
],
[
"Liang",
"Dicong",
""
]
] | Extreme mass-ratio inspirals (EMRIs) are the most potential sources detectable by the Laser Interferometer Space Antenna (LISA). To analyze the influence of higher harmonics on parameter estimation for EMRIs efficiently, we use the waveform model that the phase trajectories are relativistic flux-based adiabatic trajectories and the waveforms are constructed by the augmented analytic kludge method. We perform a Fisher-matrix error analysis of the EMRI parameters using signals taking into account the motion of the LISA constellation and higher harmonics of gravitational waves. Our results demonstrate that including higher harmonics greatly reduces the errors on the exterior parameters such as inclination angle $\iota$, the luminosity distance $d_L$, the polarization angle $\psi$, and the initial phase $\Phi_0$, except for source localization $\Delta \Omega$ when EMRIs face us. However, the influence of higher harmonics on parameters $(\iota,d_L,\psi,\Phi_0)$ can be negligible when the inclination angle is above $1.0$. For intrinsic parameters such as the spin of central black and the masses of binaries, the influence of higher harmonics can be negligible for any inclination angle. Our findings are independent of the mass or spin of the EMRI system. |
2304.08030 | Zhan-Feng Mai | Zhan-Feng Mai, Rui Xu, Dicong Liang, Lijing Shao | Extended thermodynamics of the bumblebee black holes | 10 pages, 3 figures; accepted for publication in PRD | Phys. Rev. D 108 (2023) 024004 | 10.1103/PhysRevD.108.024004 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | As a vector-tensor theory including nonminimal coupling between the Ricci
tensor and a vector field, the bumblebee gravity is a potential theory to test
Lorentz symmetry violation. Recently, a new class of numerical spherical black
holes in the bumblebee theory was constructed. In this paper, we investigate
the associated local thermodynamic properties. By introducing a pair of
conjugated thermodynamic quantities $X$ and $Y$, which can be interpreted as an
extension of electric potential and charge of the Reissner Nordstr\"om black
holes, we numerically construct a new first law of thermodynamics for bumblebee
black holes. We then study the constant-$Y$ processes in the entropy-charge
parameter space. For the constant-$Y$ processes, we also calculate the heat
capacity to study the local thermodynamic stability of the bumblebee black
holes. For a negative nonminimal coupling coefficient $\xi$, we find both
divergent and smooth phase transitions. For a positive but small $\xi$, only a
divergent phase transition is found. It turns out that there is a critical
value $0.4\kappa <\xi_c < 0.5\kappa$ such that when $\xi_c < \xi<2\kappa$, even
the divergent phase transition disappears and the bumblebee black holes thus
become locally thermodynamically unstable regardless of the bumblebee charge.
As for $\xi>2\kappa$, the smooth phase transition arises again but there no
longer exists any discontinuous phase transition for the bumblebee black holes.
| [
{
"created": "Mon, 17 Apr 2023 07:25:56 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Jul 2023 13:28:17 GMT",
"version": "v2"
}
] | 2023-07-14 | [
[
"Mai",
"Zhan-Feng",
""
],
[
"Xu",
"Rui",
""
],
[
"Liang",
"Dicong",
""
],
[
"Shao",
"Lijing",
""
]
] | As a vector-tensor theory including nonminimal coupling between the Ricci tensor and a vector field, the bumblebee gravity is a potential theory to test Lorentz symmetry violation. Recently, a new class of numerical spherical black holes in the bumblebee theory was constructed. In this paper, we investigate the associated local thermodynamic properties. By introducing a pair of conjugated thermodynamic quantities $X$ and $Y$, which can be interpreted as an extension of electric potential and charge of the Reissner Nordstr\"om black holes, we numerically construct a new first law of thermodynamics for bumblebee black holes. We then study the constant-$Y$ processes in the entropy-charge parameter space. For the constant-$Y$ processes, we also calculate the heat capacity to study the local thermodynamic stability of the bumblebee black holes. For a negative nonminimal coupling coefficient $\xi$, we find both divergent and smooth phase transitions. For a positive but small $\xi$, only a divergent phase transition is found. It turns out that there is a critical value $0.4\kappa <\xi_c < 0.5\kappa$ such that when $\xi_c < \xi<2\kappa$, even the divergent phase transition disappears and the bumblebee black holes thus become locally thermodynamically unstable regardless of the bumblebee charge. As for $\xi>2\kappa$, the smooth phase transition arises again but there no longer exists any discontinuous phase transition for the bumblebee black holes. |
2210.04769 | Qian Hu | Qian Hu and John Veitch | Accumulating errors in tests of general relativity with gravitational
waves: overlapping signals and inaccurate waveforms | 13 pages, 6 figures | The Astrophysical Journal, 945, 103 (2023) | 10.3847/1538-4357/acbc18 | ET-0211A-22 | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observations of gravitational waves (GWs) from compact binary coalescences
provide powerful tests of general relativity (GR), but systematic errors in
data analysis could lead to incorrect scientific conclusions. This issue is
especially serious in the third-generation GW detectors in which the
signal-to-noise ratio (SNR) is high and the number of detections is large. In
this work, we investigate the impacts of overlapping signals and inaccurate
waveform models on tests of GR. We simulate mock catalogs for Einstein
Telescope and Cosmic Explorer and perform parametric tests of GR using waveform
models with different levels of inaccuracy. We find the systematic error in
non-GR parameter estimates could accumulate toward a false deviation from GR
when combining results from multiple events, although a bayesian model
selection analysis may not favour a deviation. Waveform inaccuracies contribute
most to the systematic errors, but multiple overlapping signals could magnify
the effects of systematics due to the incorrect removal of signals. We also
point out that testing GR using selected ''golden binaries'' with high SNR is
even more vulnerable to false deviations from GR. The problem of error
accumulation is universal; we emphasize that it must be addressed to fully
exploit the data from third-generation GW detectors, and that further
investigations, particularly in waveform accuracy, will be essential.
| [
{
"created": "Mon, 10 Oct 2022 15:27:38 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Feb 2023 17:04:06 GMT",
"version": "v2"
}
] | 2023-03-16 | [
[
"Hu",
"Qian",
""
],
[
"Veitch",
"John",
""
]
] | Observations of gravitational waves (GWs) from compact binary coalescences provide powerful tests of general relativity (GR), but systematic errors in data analysis could lead to incorrect scientific conclusions. This issue is especially serious in the third-generation GW detectors in which the signal-to-noise ratio (SNR) is high and the number of detections is large. In this work, we investigate the impacts of overlapping signals and inaccurate waveform models on tests of GR. We simulate mock catalogs for Einstein Telescope and Cosmic Explorer and perform parametric tests of GR using waveform models with different levels of inaccuracy. We find the systematic error in non-GR parameter estimates could accumulate toward a false deviation from GR when combining results from multiple events, although a bayesian model selection analysis may not favour a deviation. Waveform inaccuracies contribute most to the systematic errors, but multiple overlapping signals could magnify the effects of systematics due to the incorrect removal of signals. We also point out that testing GR using selected ''golden binaries'' with high SNR is even more vulnerable to false deviations from GR. The problem of error accumulation is universal; we emphasize that it must be addressed to fully exploit the data from third-generation GW detectors, and that further investigations, particularly in waveform accuracy, will be essential. |
1607.04329 | Saibal Ray | Farook Rahaman, Nupur Paul, Ayan Banerjee, S.S. De, Saibal Ray and
A.A. Usmani | The Finslerian wormhole models | 9 pages and 7 figues | Eur. Phys. J. C (2016) 76:246 | 10.1140/epjc/s10052-016-4066-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present models of wormhole under the Finslerian structure of spacetime.
This is a sequel of our previous work (Eur Phys J 75:564, 2015) where we
constructed a toy model for compact stars based on the Finslerian spacetime
geometry. In the present investigation, a wide variety of solutions are
obtained that explore wormhole geometry by considering different choices for
the form function and energy density. The solutions, like the previous work,
are revealed to be physically interesting and viable models for the explanation
of wormholes as far as the background theory and literature are concerned.
| [
{
"created": "Sat, 9 Jul 2016 07:36:03 GMT",
"version": "v1"
}
] | 2016-07-18 | [
[
"Rahaman",
"Farook",
""
],
[
"Paul",
"Nupur",
""
],
[
"Banerjee",
"Ayan",
""
],
[
"De",
"S. S.",
""
],
[
"Ray",
"Saibal",
""
],
[
"Usmani",
"A. A.",
""
]
] | We present models of wormhole under the Finslerian structure of spacetime. This is a sequel of our previous work (Eur Phys J 75:564, 2015) where we constructed a toy model for compact stars based on the Finslerian spacetime geometry. In the present investigation, a wide variety of solutions are obtained that explore wormhole geometry by considering different choices for the form function and energy density. The solutions, like the previous work, are revealed to be physically interesting and viable models for the explanation of wormholes as far as the background theory and literature are concerned. |
1403.2961 | Alessandro Tronconi | Alexander Y. Kamenshchik, Alessandro Tronconi, Giovanni Venturi | Signatures of Quantum Gravity in a Born-Oppenheimer Context | 19 pages, 2 figures; final version accepted for publication in PLB | null | 10.1016/j.physletb.2014.05.028 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve a general equation describing the lowest order corrections arising
from quantum gravitational effects to the spectrum of cosmological
fluctuations. The spectra of scalar and tensor perturbations are calculated to
first order in the slow roll approximation and the results are compared with
the most recent observations. The slow roll approximation gives qualitatively
new quantum gravitational effects with respect to the pure de Sitter case.
| [
{
"created": "Wed, 12 Mar 2014 15:03:55 GMT",
"version": "v1"
},
{
"created": "Tue, 20 May 2014 16:10:02 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Kamenshchik",
"Alexander Y.",
""
],
[
"Tronconi",
"Alessandro",
""
],
[
"Venturi",
"Giovanni",
""
]
] | We solve a general equation describing the lowest order corrections arising from quantum gravitational effects to the spectrum of cosmological fluctuations. The spectra of scalar and tensor perturbations are calculated to first order in the slow roll approximation and the results are compared with the most recent observations. The slow roll approximation gives qualitatively new quantum gravitational effects with respect to the pure de Sitter case. |
0910.5931 | Manuel Tessmer | Manuel Tessmer | Gravitational waveforms from unequal-mass binaries with arbitrary spins
under leading order spin-orbit coupling | 13 pages, 2 figures, submitted to PRD on 11 Sep. 2009 | null | 10.1103/PhysRevD.80.124034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper generalizes the structure of gravitational waves from orbiting
spinning binaries under leading order spin-orbit coupling, as given in the work
by K\"onigsd\"orffer and Gopakumar [PRD 71, 024039 (2005)] for single-spin and
equal-mass binaries, to unequal-mass binaries and arbitrary spin
configurations. The orbital motion is taken to be quasi-circular and the
fractional mass difference is assumed to be small against one. The emitted
gravitational waveforms are given in analytic form.
| [
{
"created": "Fri, 30 Oct 2009 18:03:09 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2009 13:30:11 GMT",
"version": "v2"
}
] | 2015-05-14 | [
[
"Tessmer",
"Manuel",
""
]
] | The paper generalizes the structure of gravitational waves from orbiting spinning binaries under leading order spin-orbit coupling, as given in the work by K\"onigsd\"orffer and Gopakumar [PRD 71, 024039 (2005)] for single-spin and equal-mass binaries, to unequal-mass binaries and arbitrary spin configurations. The orbital motion is taken to be quasi-circular and the fractional mass difference is assumed to be small against one. The emitted gravitational waveforms are given in analytic form. |
gr-qc/9604003 | T. Jacobson | Ted Jacobson | 1+1 Sector of 3+1 Gravity | 9 pages, plain Latex, no figures | Class.Quant.Grav.13:L111-L116,1996; Erratum-ibid.13:3269,1996 | 10.1088/0264-9381/13/8/003 | THU-96/18 | gr-qc hep-th | null | The rank--1 sector of classical Ashtekar gravity is considered, motivated by
the degeneracy of the metric along the Wilson lines in quantum loop states. It
is found that the lines behave like 1+1 dimensional spacetimes with a pair of
massless complex fields propagating along them. The inclusion of matter and
extension to supergravity are also considered.
| [
{
"created": "Mon, 1 Apr 1996 15:57:45 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Jacobson",
"Ted",
""
]
] | The rank--1 sector of classical Ashtekar gravity is considered, motivated by the degeneracy of the metric along the Wilson lines in quantum loop states. It is found that the lines behave like 1+1 dimensional spacetimes with a pair of massless complex fields propagating along them. The inclusion of matter and extension to supergravity are also considered. |
gr-qc/0401092 | Richard Price | Elspeth W. Allen, Elizabeth Buckmiller, Lior M. Burko, Richard H.Price | Radiation tails and boundary conditions for black hole evolutions | submitted to Phys. Rev. D | Phys.Rev. D70 (2004) 044038 | 10.1103/PhysRevD.70.044038 | null | gr-qc | null | In numerical computations of Einstein's equations for black hole spacetimes,
it will be necessary to use approximate boundary conditions at a finite
distance from the holes. We point out here that ``tails,'' the inverse
power-law decrease of late-time fields, cannot be expected for such
computations. We present computational demonstrations and discussions of
features of late-time behavior in an evolution with a boundary condition.
| [
{
"created": "Wed, 21 Jan 2004 22:32:25 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Allen",
"Elspeth W.",
""
],
[
"Buckmiller",
"Elizabeth",
""
],
[
"Burko",
"Lior M.",
""
],
[
"Price",
"Richard H.",
""
]
] | In numerical computations of Einstein's equations for black hole spacetimes, it will be necessary to use approximate boundary conditions at a finite distance from the holes. We point out here that ``tails,'' the inverse power-law decrease of late-time fields, cannot be expected for such computations. We present computational demonstrations and discussions of features of late-time behavior in an evolution with a boundary condition. |
1306.1024 | Muhammad Sharif | M. Sharif and Z. Yousaf | Shearfree Spherically Symmetric Fluid Models | 9 pages, no figure | Chin. Phys. Lett. 29(2012)050403 (China) | 10.1088/0256-307X/29/5/050403 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We try to find some exact analytical models of spherically symmetric
spacetime of collapsing fluid under shearfree condition. We consider two types
of solutions: one is to impose a condition on the mass function while the other
is to restrict the pressure. We obtain totally of five exact models, and some
of them satisfy the Darmois conditions.
| [
{
"created": "Wed, 5 Jun 2013 09:12:49 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Sharif",
"M.",
""
],
[
"Yousaf",
"Z.",
""
]
] | We try to find some exact analytical models of spherically symmetric spacetime of collapsing fluid under shearfree condition. We consider two types of solutions: one is to impose a condition on the mass function while the other is to restrict the pressure. We obtain totally of five exact models, and some of them satisfy the Darmois conditions. |
gr-qc/9906108 | Kip S. Thorne | Vladimir B. Braginsky (1), Mikhail L. Gorodetsky (1), Farid Ya.
Khalili (1) and Kip S. Thorne (2) ((1) Physics Faculty, Moscow State
University, (2) Theoretical Astrophysics, California Institute of Technology) | Dual-Resonator Speed Meter for a Free Test Mass | RevTex: 13 pages with 4 embedded figures (two .eps format and two
drawn in TeX); Submitted to Physical Review D | Phys.Rev. D61 (2000) 044002 | 10.1103/PhysRevD.61.044002 | GRP-516 | gr-qc quant-ph | null | A description and analysis are given of a ``speed meter'' for monitoring a
classical force that acts on a test mass. This speed meter is based on two
microwave resonators (``dual resonators''), one of which couples evanescently
to the position of the test mass. The sloshing of the resulting signal between
the resonators, and a wise choice of where to place the resonators' output
waveguide, produce a signal in the waveguide that (for sufficiently low
frequencies) is proportional to the test-mass velocity (speed) rather than its
position. This permits the speed meter to achieve force-measurement
sensitivities better than the standard quantum limit (SQL), both when operating
in a narrow-band mode and a wide-band mode. A scrutiny of experimental issues
shows that it is feasible, with current technology, to construct a
demonstration speed meter that beats the wide-band SQL by a factor 2. A concept
is sketched for an adaptation of this speed meter to optical frequencies; this
adaptation forms the basis for a possible LIGO-III interferometer that could
beat the gravitational-wave standard quantum limit h_SQL, but perhaps only by a
factor 1/xi = h_SQL/h ~ 3 (constrained by losses in the optics) and at the
price of a very high circulating optical power --- larger by 1/xi^2 than that
required to reach the SQL.
| [
{
"created": "Sat, 26 Jun 1999 02:18:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Braginsky",
"Vladimir B.",
""
],
[
"Gorodetsky",
"Mikhail L.",
""
],
[
"Khalili",
"Farid Ya.",
""
],
[
"Thorne",
"Kip S.",
""
]
] | A description and analysis are given of a ``speed meter'' for monitoring a classical force that acts on a test mass. This speed meter is based on two microwave resonators (``dual resonators''), one of which couples evanescently to the position of the test mass. The sloshing of the resulting signal between the resonators, and a wise choice of where to place the resonators' output waveguide, produce a signal in the waveguide that (for sufficiently low frequencies) is proportional to the test-mass velocity (speed) rather than its position. This permits the speed meter to achieve force-measurement sensitivities better than the standard quantum limit (SQL), both when operating in a narrow-band mode and a wide-band mode. A scrutiny of experimental issues shows that it is feasible, with current technology, to construct a demonstration speed meter that beats the wide-band SQL by a factor 2. A concept is sketched for an adaptation of this speed meter to optical frequencies; this adaptation forms the basis for a possible LIGO-III interferometer that could beat the gravitational-wave standard quantum limit h_SQL, but perhaps only by a factor 1/xi = h_SQL/h ~ 3 (constrained by losses in the optics) and at the price of a very high circulating optical power --- larger by 1/xi^2 than that required to reach the SQL. |
gr-qc/9709071 | Hans-Juergen Schmidt | H.-J. Schmidt | A new proof of Birkhoff's theorem | 17 pages, LaTeX, no figures, Grav. and Cosm. in print | Grav.Cosmol. 3 (1997) 185-190 | null | Preprint UNIPO-MATH-97-September-25 | gr-qc | null | Assuming SO(3)-spherical symmetry, the 4-dimensional Einstein equation
reduces to an equation conformally related to the field equation for
2-dimensional gravity following from the Lagrangian L = R^(1/3).
Solutions for 2-dimensional gravity always possess a local isometry because
the traceless part of its Ricci tensor identically vanishes. Combining both
facts, we get a new proof of Birkhoff's theorem; contrary to other proofs, no
coordinates must be introduced.
The SO(m)-spherically symmetric solutions of the (m+1)-dimensional Einstein
equation can be found by considering L = R^(1/m) in two dimensions. This yields
several generalizations of Birkhoff's theorem in an arbitrary number of
dimensions, and to an arbitrary signature of the metric.
| [
{
"created": "Fri, 26 Sep 1997 15:54:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schmidt",
"H. -J.",
""
]
] | Assuming SO(3)-spherical symmetry, the 4-dimensional Einstein equation reduces to an equation conformally related to the field equation for 2-dimensional gravity following from the Lagrangian L = R^(1/3). Solutions for 2-dimensional gravity always possess a local isometry because the traceless part of its Ricci tensor identically vanishes. Combining both facts, we get a new proof of Birkhoff's theorem; contrary to other proofs, no coordinates must be introduced. The SO(m)-spherically symmetric solutions of the (m+1)-dimensional Einstein equation can be found by considering L = R^(1/m) in two dimensions. This yields several generalizations of Birkhoff's theorem in an arbitrary number of dimensions, and to an arbitrary signature of the metric. |
2312.11419 | Orlando Luongo | Alessio Belfiglio, Orlando Luongo, Stefano Mancini | Superhorizon entanglement from inflationary particle production | 11 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate entanglement generation between the sub- and super-Hubble
modes of inflaton fluctuations, in the context of particle production from
perturbations during inflation. We consider a large-field inflationary scenario
where inflation is driven by a vacuum energy symmetry breaking potential and
the scalar inflaton field is nonminimally coupled to spacetime curvature. In
particular, we focus on the slow-roll phase, adopting a quasi-de Sitter scale
factor to properly account for the presence of perturbations and computing the
pair production probability associated to the coupling between the inflaton and
spacetime inhomogeneities. The interaction Lagrangian at first order is
constructed from inhomogeneities induced by the inflaton dynamics, and the
initial Bunch-Davies vacuum state of the field evolves under the action of such
Lagrangian. In this framework, we quantify the total amount of entanglement via
the von Neumann entropy of the reduced density operator for superhorizon modes,
tracing out sub-Hubble degrees of freedom. We then compare these outcomes with
entanglement production for quadratic chaotic inflation and for a small-field
quadratic hilltop scenario, preserving field-curvature coupling in both cases
and pointing out the main differences between large and small-field approaches.
We show that the amount of entanglement entropy arising from such geometric
production grows rapidly in slow-roll regime and that it is typically higher in
large-field scenarios. We also discuss our outcomes in light of recent findings
for the squeezing entropy of cosmological perturbations and cubic
nonlinearities in de Sitter space.
| [
{
"created": "Mon, 18 Dec 2023 18:21:06 GMT",
"version": "v1"
}
] | 2023-12-19 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | We investigate entanglement generation between the sub- and super-Hubble modes of inflaton fluctuations, in the context of particle production from perturbations during inflation. We consider a large-field inflationary scenario where inflation is driven by a vacuum energy symmetry breaking potential and the scalar inflaton field is nonminimally coupled to spacetime curvature. In particular, we focus on the slow-roll phase, adopting a quasi-de Sitter scale factor to properly account for the presence of perturbations and computing the pair production probability associated to the coupling between the inflaton and spacetime inhomogeneities. The interaction Lagrangian at first order is constructed from inhomogeneities induced by the inflaton dynamics, and the initial Bunch-Davies vacuum state of the field evolves under the action of such Lagrangian. In this framework, we quantify the total amount of entanglement via the von Neumann entropy of the reduced density operator for superhorizon modes, tracing out sub-Hubble degrees of freedom. We then compare these outcomes with entanglement production for quadratic chaotic inflation and for a small-field quadratic hilltop scenario, preserving field-curvature coupling in both cases and pointing out the main differences between large and small-field approaches. We show that the amount of entanglement entropy arising from such geometric production grows rapidly in slow-roll regime and that it is typically higher in large-field scenarios. We also discuss our outcomes in light of recent findings for the squeezing entropy of cosmological perturbations and cubic nonlinearities in de Sitter space. |
gr-qc/0305033 | Wojciech Czaja | Marek Szydlowski, Wojciech Czaja | Particle-Like Description in Quintessential Cosmology | 35 pages, 26 figures, RevTeX4, some applications of our treatment to
investigation of quintessence models were added | Phys.Rev. D69 (2004) 083518 | 10.1103/PhysRevD.69.083518 | null | gr-qc | null | Assuming equation of state for quintessential matter: $p=w(z)\rho$, we
analyse dynamical behaviour of the scale factor in FRW cosmologies. It is shown
that its dynamics is formally equivalent to that of a classical particle under
the action of 1D potential $V(a)$. It is shown that Hamiltonian method can be
easily implemented to obtain a classification of all cosmological solutions in
the phase space as well as in the configurational space. Examples taken from
modern cosmology illustrate the effectiveness of the presented approach.
Advantages of representing dynamics as a 1D Hamiltonian flow, in the analysis
of acceleration and horizon problems, are presented. The inverse problem of
reconstructing the Hamiltonian dynamics (i.e. potential function) from the
luminosity distance function $d_{L}(z)$ for supernovae is also considered.
| [
{
"created": "Thu, 8 May 2003 23:14:05 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jul 2003 10:00:39 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Oct 2003 12:04:17 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Szydlowski",
"Marek",
""
],
[
"Czaja",
"Wojciech",
""
]
] | Assuming equation of state for quintessential matter: $p=w(z)\rho$, we analyse dynamical behaviour of the scale factor in FRW cosmologies. It is shown that its dynamics is formally equivalent to that of a classical particle under the action of 1D potential $V(a)$. It is shown that Hamiltonian method can be easily implemented to obtain a classification of all cosmological solutions in the phase space as well as in the configurational space. Examples taken from modern cosmology illustrate the effectiveness of the presented approach. Advantages of representing dynamics as a 1D Hamiltonian flow, in the analysis of acceleration and horizon problems, are presented. The inverse problem of reconstructing the Hamiltonian dynamics (i.e. potential function) from the luminosity distance function $d_{L}(z)$ for supernovae is also considered. |
1312.4532 | Leo Stein | Leo C. Stein, Kent Yagi, and Nicolas Yunes | Three-Hair Relations for Rotating Stars: Nonrelativistic Limit | 5 pages, 3 figures. Updated to match version published in ApJ | 2014 ApJ 788 15 | 10.1088/0004-637X/788/1/15 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational field outside of astrophysical black holes is completely
described by their mass and spin frequency, as expressed by the no-hair
theorems. These theorems assume vacuum spacetimes, and thus they apply only to
black holes and not to stars. Despite this, we analytically find that the
gravitational potential of arbitrarily rapid rigidly rotating stars can still
be described completely by only their mass, spin angular momentum, and
quadrupole moment. Although these results are obtained in the nonrelativistic
limit (to leading order in a weak-field expansion of general relativity, GR),
they are also consistent with fully relativistic numerical calculations of
rotating neutron stars. This description of the gravitational potential outside
the source in terms of just three quantities is approximately universal
(independent of equation of state). Such universality may be used to break
degeneracies in pulsar and future gravitational wave observations to extract
more physics and test GR in the strong-field regime.
| [
{
"created": "Mon, 16 Dec 2013 21:00:00 GMT",
"version": "v1"
},
{
"created": "Sat, 17 May 2014 15:55:02 GMT",
"version": "v2"
}
] | 2014-05-20 | [
[
"Stein",
"Leo C.",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The gravitational field outside of astrophysical black holes is completely described by their mass and spin frequency, as expressed by the no-hair theorems. These theorems assume vacuum spacetimes, and thus they apply only to black holes and not to stars. Despite this, we analytically find that the gravitational potential of arbitrarily rapid rigidly rotating stars can still be described completely by only their mass, spin angular momentum, and quadrupole moment. Although these results are obtained in the nonrelativistic limit (to leading order in a weak-field expansion of general relativity, GR), they are also consistent with fully relativistic numerical calculations of rotating neutron stars. This description of the gravitational potential outside the source in terms of just three quantities is approximately universal (independent of equation of state). Such universality may be used to break degeneracies in pulsar and future gravitational wave observations to extract more physics and test GR in the strong-field regime. |
1808.00847 | Markus Rummel | C.P. Burgess, Ryan Plestid and Markus Rummel | Effective Field Theory of Black Hole Echoes | v3: clarified role of IR Black Hole fixed point w.r.t. parameter \xi.
v2: now published in JHEP; references added, changed definition of time delay
and phase in echo spacing | 10.1007/JHEP09(2018)113 | 10.1007/JHEP09(2018)113 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave `echoes' during black-hole merging events have been
advocated as possible signals of modifications to gravity in the strong-field
(but semiclassical) regime. In these proposals the observable effect comes
entirely from the appearance of nonzero reflection probability at the horizon,
which vanishes for a standard black hole. We show how to apply EFT reasoning to
these arguments, using and extending earlier work for localized systems that
relates choices of boundary condition to the action for the physics responsible
for these boundary conditions. EFT reasoning applied to this action argues that
linear `Robin' boundary conditions dominate at low energies, and we determine
the relationship between the corresponding effective coupling (whose value is
the one relevant low-energy prediction of particular modifications to General
Relativity for these systems) and the phenomenologically measurable
near-horizon reflection coefficient. Because this connection involves only
near-horizon physics it is comparatively simple to establish, and we do so for
perturbations in both the Schwarzschild geometry (which is the one most often
studied theoretically) and the Kerr geometry (which is the one of observational
interest for post-merger ring down). In passing we identify the
renormalization-group evolution of the effective couplings as a function of a
regularization distance from the horizon, that enforces how physics does not
depend on the precise position where the boundary conditions are imposed. We
show that the perfect-absorber/perfect-emitter boundary conditions of General
Relativity correspond to the only fixed points of this evolution. Nontrivial
running of all other RG evolution reflects how modifications to gravity
necessarily introduce new physics near the horizon.
| [
{
"created": "Thu, 2 Aug 2018 15:04:20 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Sep 2018 11:02:19 GMT",
"version": "v2"
},
{
"created": "Sun, 31 May 2020 00:13:47 GMT",
"version": "v3"
}
] | 2020-06-02 | [
[
"Burgess",
"C. P.",
""
],
[
"Plestid",
"Ryan",
""
],
[
"Rummel",
"Markus",
""
]
] | Gravitational wave `echoes' during black-hole merging events have been advocated as possible signals of modifications to gravity in the strong-field (but semiclassical) regime. In these proposals the observable effect comes entirely from the appearance of nonzero reflection probability at the horizon, which vanishes for a standard black hole. We show how to apply EFT reasoning to these arguments, using and extending earlier work for localized systems that relates choices of boundary condition to the action for the physics responsible for these boundary conditions. EFT reasoning applied to this action argues that linear `Robin' boundary conditions dominate at low energies, and we determine the relationship between the corresponding effective coupling (whose value is the one relevant low-energy prediction of particular modifications to General Relativity for these systems) and the phenomenologically measurable near-horizon reflection coefficient. Because this connection involves only near-horizon physics it is comparatively simple to establish, and we do so for perturbations in both the Schwarzschild geometry (which is the one most often studied theoretically) and the Kerr geometry (which is the one of observational interest for post-merger ring down). In passing we identify the renormalization-group evolution of the effective couplings as a function of a regularization distance from the horizon, that enforces how physics does not depend on the precise position where the boundary conditions are imposed. We show that the perfect-absorber/perfect-emitter boundary conditions of General Relativity correspond to the only fixed points of this evolution. Nontrivial running of all other RG evolution reflects how modifications to gravity necessarily introduce new physics near the horizon. |
gr-qc/0305009 | Alberto Saa | L.R. Abramo, L. Brenig, E. Gunzig, and A. Saa | A note on dualities in Einstein's gravity in the presence of a
non-minimally coupled scalar field | 12 pages | Mod.Phys.Lett. A18 (2003) 1043 | 10.1142/S0217732303010958 | null | gr-qc | null | We show that the action of Einstein's gravity with a scalar field coupled in
a generic way to spacetime curvature is invariant under a particular set of
conformal transformations. These transformations relate dual theories for which
the effective couplings of the theory are scaled uniformly. In the simplest
case, this class of dualities reduce to the S-duality of low-energy effective
action of string theory.
| [
{
"created": "Fri, 2 May 2003 17:05:24 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Abramo",
"L. R.",
""
],
[
"Brenig",
"L.",
""
],
[
"Gunzig",
"E.",
""
],
[
"Saa",
"A.",
""
]
] | We show that the action of Einstein's gravity with a scalar field coupled in a generic way to spacetime curvature is invariant under a particular set of conformal transformations. These transformations relate dual theories for which the effective couplings of the theory are scaled uniformly. In the simplest case, this class of dualities reduce to the S-duality of low-energy effective action of string theory. |
1903.08251 | Foad Parsaei | Foad Parsaei and Sara Rastgoo | Asymptotically flat wormhole solutions with variable equation-of-state
parameter | 11 pages, 10 figures, two new solutions, NEC violation discussion and
references added | Phys. Rev. D 99, 104037 (2019) | 10.1103/PhysRevD.99.104037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study exact wormhole solutions in the framework of general
relativity with a general equation of state that reduced to a linear equation
of state asymptotically. By considering a special shape function, we find
classes of solutions which are asymptotically flat. We study the violation of
NEC as the main ingredient in the wormhole physics. We investigate the
possibility of finding wormhole solutions with asymptotically different state
parameter. We show that in principle, wormhole with vanishing redshift function
and the selected shape function, cannot satisfy NEC at large infinity. We
present solutions which have the positive total amount of mater in the "volume
integral quantifier" method. For this class of solutions, fluid near the
wormhole throat is in the phantom regime and at some $r=r_{2}$, the phantom
regime is connected to a dark energy regime. Thus, we need small amount of
exotic matter to construct wormhole solutions.
| [
{
"created": "Tue, 19 Mar 2019 20:39:09 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Apr 2019 10:02:54 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Parsaei",
"Foad",
""
],
[
"Rastgoo",
"Sara",
""
]
] | In this paper, we study exact wormhole solutions in the framework of general relativity with a general equation of state that reduced to a linear equation of state asymptotically. By considering a special shape function, we find classes of solutions which are asymptotically flat. We study the violation of NEC as the main ingredient in the wormhole physics. We investigate the possibility of finding wormhole solutions with asymptotically different state parameter. We show that in principle, wormhole with vanishing redshift function and the selected shape function, cannot satisfy NEC at large infinity. We present solutions which have the positive total amount of mater in the "volume integral quantifier" method. For this class of solutions, fluid near the wormhole throat is in the phantom regime and at some $r=r_{2}$, the phantom regime is connected to a dark energy regime. Thus, we need small amount of exotic matter to construct wormhole solutions. |
1206.2658 | Antonin Coutant | Antonin Coutant, Alessandro Fabbri, Renaud Parentani, Roberto Balbinot
and Paul Anderson | Hawking radiation of massive modes and undulations | 37 pages, 8 figures, published version | Phys. Rev. D 86, 064022 (2012) | 10.1103/PhysRevD.86.064022 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the analogue Hawking radiation for modes which posses a small wave
vector perpendicular to the horizon. For low frequencies, the resulting mass
term induces a total reflection. This generates an extra mode mixing that
occurs in the supersonic region, which cancels out the infrared divergence of
the near horizon spectrum. As a result, the amplitude of the undulation
(0-frequency wave with macroscopic amplitude) emitted in white hole flows now
saturates at the linear level, unlike what was recently found in the massless
case. In addition, we point out that the mass introduces a new type of
undulation which is produced in black hole flows, and which is well described
in the hydrodynamical regime.
| [
{
"created": "Tue, 12 Jun 2012 20:15:22 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Oct 2012 16:40:56 GMT",
"version": "v2"
}
] | 2012-10-05 | [
[
"Coutant",
"Antonin",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Parentani",
"Renaud",
""
],
[
"Balbinot",
"Roberto",
""
],
[
"Anderson",
"Paul",
""
]
] | We compute the analogue Hawking radiation for modes which posses a small wave vector perpendicular to the horizon. For low frequencies, the resulting mass term induces a total reflection. This generates an extra mode mixing that occurs in the supersonic region, which cancels out the infrared divergence of the near horizon spectrum. As a result, the amplitude of the undulation (0-frequency wave with macroscopic amplitude) emitted in white hole flows now saturates at the linear level, unlike what was recently found in the massless case. In addition, we point out that the mass introduces a new type of undulation which is produced in black hole flows, and which is well described in the hydrodynamical regime. |
1406.2181 | Cosimo Bambi | Cosimo Bambi, Daniele Malafarina, Naoki Tsukamoto | Note on the effect of a massive accretion disk in the measurements of
black hole spins | 5 pages, 2 figures. v2: corrected a few typos | Phys. Rev. D 89, 127302 (2014) | 10.1103/PhysRevD.89.127302 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spin measurement of black holes has important implications in physics and
astrophysics. Regardless of the specific technique to estimate the black hole
spin, all the current approaches assume that the space-time geometry around the
compact object is exactly described by the Kerr solution. This is clearly an
approximation, because the Kerr metric is a stationary solution of the vacuum
Einstein equations. In this paper, we estimate the effect of a massive
accretion disk in the measurement of the black hole spin with a simple
analytical model. For typical accretion disks, the mass of the disk is
completely negligible, even for future more accurate measurements. However, for
systems with very massive disks the effect may not be ignored.
| [
{
"created": "Mon, 9 Jun 2014 13:46:17 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jun 2014 21:20:57 GMT",
"version": "v2"
}
] | 2014-07-02 | [
[
"Bambi",
"Cosimo",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Tsukamoto",
"Naoki",
""
]
] | The spin measurement of black holes has important implications in physics and astrophysics. Regardless of the specific technique to estimate the black hole spin, all the current approaches assume that the space-time geometry around the compact object is exactly described by the Kerr solution. This is clearly an approximation, because the Kerr metric is a stationary solution of the vacuum Einstein equations. In this paper, we estimate the effect of a massive accretion disk in the measurement of the black hole spin with a simple analytical model. For typical accretion disks, the mass of the disk is completely negligible, even for future more accurate measurements. However, for systems with very massive disks the effect may not be ignored. |
0806.3735 | Atsushi Higuchi | Mir Faizal and Atsushi Higuchi | On the FP-ghost propagators for Yang-Mills theories and perturbative
quantum gravity in the covariant gauge in de Sitter spacetime | 8 pages, to appear in Phys Rev D | Phys.Rev.D78:067502,2008 | 10.1103/PhysRevD.78.067502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagators of the Faddeev-Popov (FP) ghosts for Yang-Mills theories and
perturbative quantum gravity in the covariant gauge are infrared (IR) divergent
in de Sitter spacetime. We point out, however, that the modes responsible for
these divergences will not contribute to loop diagrams in computations of
time-ordered products in either Yang-Mills theories or perturbative quantum
gravity. Therefore we propose that the IR divergent FP-ghost propagator should
be regularized by a small mass term that is sent to zero in the end of any
perturbative calculations. This proposal is equivalent to using the effective
FP-ghost propagators, which we present in an explicit form, obtained by
removing the modes responsible for the IR divergences. We also make some
comments on the corresponding propagators in anti-de Sitter spacetime.
| [
{
"created": "Mon, 23 Jun 2008 18:59:08 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jul 2008 22:37:13 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Sep 2008 21:03:36 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Faizal",
"Mir",
""
],
[
"Higuchi",
"Atsushi",
""
]
] | The propagators of the Faddeev-Popov (FP) ghosts for Yang-Mills theories and perturbative quantum gravity in the covariant gauge are infrared (IR) divergent in de Sitter spacetime. We point out, however, that the modes responsible for these divergences will not contribute to loop diagrams in computations of time-ordered products in either Yang-Mills theories or perturbative quantum gravity. Therefore we propose that the IR divergent FP-ghost propagator should be regularized by a small mass term that is sent to zero in the end of any perturbative calculations. This proposal is equivalent to using the effective FP-ghost propagators, which we present in an explicit form, obtained by removing the modes responsible for the IR divergences. We also make some comments on the corresponding propagators in anti-de Sitter spacetime. |
2406.09139 | Boris Daszuta | Boris Daszuta, William Cook, Peter Hammond, Jacob Fields, Eduardo M.
Guti\'errez, Sebastiano Bernuzzi, David Radice | Numerical relativity simulations of compact binaries: comparison of
cell- and vertex-centered adaptive meshes | null | null | null | null | gr-qc physics.comp-ph | http://creativecommons.org/licenses/by/4.0/ | Given the compact binary evolution problem of numerical relativity, in the
finite-difference, block-based, adaptive mesh refinement context, choices must
be made on how evolved fields are to be discretized. In GR-Athena++, the
space-time solver was previously fixed to be vertex-centered. Here, our recent
extensions to a cell-centered treatment, are described. Simplifications in the
handling of variables during the treatment of general relativistic
magneto-hydrodynamical (GRMHD) evolution are found. A novelty is that
performance comparison for the two choices of grid sampling is made within a
single code-base. In the case of a binary black hole inspiral-merger problem,
by evolving geometric fields on vertex-centers, an average $\sim 20\%$ speed
increase is observed, when compared against cell-centered sampling. The
opposite occurs in the GRMHD setting. A binary neutron star
inspiral-merger-collapse problem, representative of typical production
simulations is considered. We find that cell-centered sampling for the
space-time solver improves performance, by a similar factor.
| [
{
"created": "Thu, 13 Jun 2024 14:08:46 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Daszuta",
"Boris",
""
],
[
"Cook",
"William",
""
],
[
"Hammond",
"Peter",
""
],
[
"Fields",
"Jacob",
""
],
[
"Gutiérrez",
"Eduardo M.",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Radice",
"David",
""
]
] | Given the compact binary evolution problem of numerical relativity, in the finite-difference, block-based, adaptive mesh refinement context, choices must be made on how evolved fields are to be discretized. In GR-Athena++, the space-time solver was previously fixed to be vertex-centered. Here, our recent extensions to a cell-centered treatment, are described. Simplifications in the handling of variables during the treatment of general relativistic magneto-hydrodynamical (GRMHD) evolution are found. A novelty is that performance comparison for the two choices of grid sampling is made within a single code-base. In the case of a binary black hole inspiral-merger problem, by evolving geometric fields on vertex-centers, an average $\sim 20\%$ speed increase is observed, when compared against cell-centered sampling. The opposite occurs in the GRMHD setting. A binary neutron star inspiral-merger-collapse problem, representative of typical production simulations is considered. We find that cell-centered sampling for the space-time solver improves performance, by a similar factor. |
gr-qc/0010051 | Alena Pravdova | V. Pravda, A. Pravdova | Co-accelerated particles in the C-metric | 10 pages, 12 EPS figures, changes mainly in abstract & introduction | Class.Quant.Grav.18:1205-1216,2001 | 10.1088/0264-9381/18/7/305 | null | gr-qc | null | With appropriately chosen parameters, the C-metric represents two uniformly
accelerated black holes moving in the opposite directions on the axis of the
axial symmetry (the z-axis). The acceleration is caused by nodal singularities
located on the z-axis.
In the~present paper, geodesics in the~C-metric are examined. In general
there exist three types of timelike or null geodesics in the C-metric:
geodesics describing particles 1) falling under the black hole horizon;
2)crossing the acceleration horizon; and 3) orbiting around the z-axis and
co-accelerating with the black holes.
Using an effective potential, it can be shown that there exist stable
timelike geodesics of the third type if the product of the parameters of the
C-metric, mA, is smaller than a certain critical value. Null geodesics of the
third type are always unstable. Special timelike and null geodesics of the
third type are also found in an analytical form.
| [
{
"created": "Fri, 13 Oct 2000 12:11:30 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Oct 2000 15:09:52 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pravda",
"V.",
""
],
[
"Pravdova",
"A.",
""
]
] | With appropriately chosen parameters, the C-metric represents two uniformly accelerated black holes moving in the opposite directions on the axis of the axial symmetry (the z-axis). The acceleration is caused by nodal singularities located on the z-axis. In the~present paper, geodesics in the~C-metric are examined. In general there exist three types of timelike or null geodesics in the C-metric: geodesics describing particles 1) falling under the black hole horizon; 2)crossing the acceleration horizon; and 3) orbiting around the z-axis and co-accelerating with the black holes. Using an effective potential, it can be shown that there exist stable timelike geodesics of the third type if the product of the parameters of the C-metric, mA, is smaller than a certain critical value. Null geodesics of the third type are always unstable. Special timelike and null geodesics of the third type are also found in an analytical form. |
gr-qc/9601001 | Masaru Siino | Masaru Siino | Quantum Stability of (2+1)-Spacetimes with Non-Trivial Topology | 17 pages, revtex, 3 uuencoded figures contained | Class.Quant.Grav. 14 (1997) 687-697 | 10.1088/0264-9381/14/3/012 | null | gr-qc | null | Quantum fields are investigated in the (2+1)-open-universes with non-trivial
topologies by the method of images. The universes are locally de Sitter
spacetime and anti-de Sitter spacetime. In the present article we study
spacetimes whose spatial topologies are a torus with a cusp and a sphere with
three cusps as a step toward the more general case. A quantum energy momentum
tensor is obtained by the point stripping method. Though the cusps are no
singularities, the latter cusps cause the divergence of the quantum field. This
suggests that only the latter cusps are quantum mechanically unstable. Of
course at the singularity of the background spacetime the quantum field
diverges. Also the possibility of the divergence of topological effect by a
negative spatial curvature is discussed. Since the volume of the negatively
curved space is larger than that of the flat space, one see so many images of a
single source by the non-trivial topology. It is confirmed that this divergence
does not appear in our models of topologies. The results will be applicable to
the case of three dimensional multi black hole\cite{BR}.
| [
{
"created": "Mon, 1 Jan 1996 13:31:15 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Siino",
"Masaru",
""
]
] | Quantum fields are investigated in the (2+1)-open-universes with non-trivial topologies by the method of images. The universes are locally de Sitter spacetime and anti-de Sitter spacetime. In the present article we study spacetimes whose spatial topologies are a torus with a cusp and a sphere with three cusps as a step toward the more general case. A quantum energy momentum tensor is obtained by the point stripping method. Though the cusps are no singularities, the latter cusps cause the divergence of the quantum field. This suggests that only the latter cusps are quantum mechanically unstable. Of course at the singularity of the background spacetime the quantum field diverges. Also the possibility of the divergence of topological effect by a negative spatial curvature is discussed. Since the volume of the negatively curved space is larger than that of the flat space, one see so many images of a single source by the non-trivial topology. It is confirmed that this divergence does not appear in our models of topologies. The results will be applicable to the case of three dimensional multi black hole\cite{BR}. |
0707.2824 | Mikolaj Korzynski | Mikolaj Korzynski | Quasi--local angular momentum of non--symmetric isolated and dynamical
horizons from the conformal decomposition of the metric | Final version to appear in Classical and Quantum Gravity. One
reference added | Class.Quant.Grav.24:5935-5944,2007 | 10.1088/0264-9381/24/23/015 | null | gr-qc | null | A new definition of quasi--local angular momentum of non--axisymmetric
marginally outer trapped surfaces is proposed. It is based on conformal
decomposition of the two--dimensional metric and the action of the group of
conformal symmetries. The definition is completely general and agrees with the
standard one in axi--symmetric surfaces.
| [
{
"created": "Thu, 19 Jul 2007 00:37:40 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jul 2007 22:55:15 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Oct 2007 22:01:10 GMT",
"version": "v3"
},
{
"created": "Wed, 24 Oct 2007 10:20:20 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Korzynski",
"Mikolaj",
""
]
] | A new definition of quasi--local angular momentum of non--axisymmetric marginally outer trapped surfaces is proposed. It is based on conformal decomposition of the two--dimensional metric and the action of the group of conformal symmetries. The definition is completely general and agrees with the standard one in axi--symmetric surfaces. |
gr-qc/9709010 | Herbert Liebl | M.O. Katanaev, W. Kummer, H. Liebl, D.V. Vassilevich | Generalized 2d-dilaton models, the true black hole and quantum
integrability | 26 pages, latex, no figures | null | null | TUW-97-10 | gr-qc | null | All 1+1 dimensional dipheomorphism-invariant models can be viewed in a
unified manner. This includes also general dilaton theories and especially
spherically symmetric gravity (SSG) and Witten's dilatonic black hole (DBH). A
common feature --- also in the presence of matter fields of any type --- is the
appearance of an absolutely conserved quantity C which is determined by the
influx of matter. Only for a subclass of generalized dilaton theories the
singularity structure vanishes together with C. Such `physical' theories
include, of course, SSG and DBH. It seems to have been overlooked until
recently that the (classical) 'black hole' singularity of the DBH deviates from
SSG in a physically nontrivial manner. At the quantum level for all generalized
dilaton theories --- in the absence of matter --- the local quantum effects are
shown to disappear. This enables us to compute e.g. the second loop order
correction to the Polyakov term. For non-minimal scalar coupling we also
believe to have settled the controversial issue of Hawking radiation to
infinity with a somewhat puzzling result for the case of SSG.
| [
{
"created": "Thu, 4 Sep 1997 11:12:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Katanaev",
"M. O.",
""
],
[
"Kummer",
"W.",
""
],
[
"Liebl",
"H.",
""
],
[
"Vassilevich",
"D. V.",
""
]
] | All 1+1 dimensional dipheomorphism-invariant models can be viewed in a unified manner. This includes also general dilaton theories and especially spherically symmetric gravity (SSG) and Witten's dilatonic black hole (DBH). A common feature --- also in the presence of matter fields of any type --- is the appearance of an absolutely conserved quantity C which is determined by the influx of matter. Only for a subclass of generalized dilaton theories the singularity structure vanishes together with C. Such `physical' theories include, of course, SSG and DBH. It seems to have been overlooked until recently that the (classical) 'black hole' singularity of the DBH deviates from SSG in a physically nontrivial manner. At the quantum level for all generalized dilaton theories --- in the absence of matter --- the local quantum effects are shown to disappear. This enables us to compute e.g. the second loop order correction to the Polyakov term. For non-minimal scalar coupling we also believe to have settled the controversial issue of Hawking radiation to infinity with a somewhat puzzling result for the case of SSG. |
1104.4414 | Mark Durkee | Mark Durkee | New approaches to higher-dimensional general relativity | PhD thesis (University of Cambridge, submitted Jan 2011), 226 pages,
7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This PhD thesis contains a collection of work related to the algebraic
classification of spacetimes in higher dimensions, including an up-to-date
review of various aspects of the field. The work discussed includes the
higher-dimensional Geroch-Held-Penrose formalism, a partial generalization of
the Goldberg-Sachs theorem to higher-dimensions, and applications of these
results to studying the stability of extremal black holes.
| [
{
"created": "Fri, 22 Apr 2011 09:09:16 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Durkee",
"Mark",
""
]
] | This PhD thesis contains a collection of work related to the algebraic classification of spacetimes in higher dimensions, including an up-to-date review of various aspects of the field. The work discussed includes the higher-dimensional Geroch-Held-Penrose formalism, a partial generalization of the Goldberg-Sachs theorem to higher-dimensions, and applications of these results to studying the stability of extremal black holes. |
1508.01114 | Kirill Bronnikov | K.A. Bronnikov, A.M. Galiakhmetov | Wormholes without exotic matter in Einstein-Cartan theory | 7 pages, 3 figures | Grav. Cosmol, 21 (4) 283-288 (2015) | 10.1134/S0202289315040027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the possible existence of static traversable wormholes without
invoking exotic matter in the framework of the Einstein--Cartan theory. A
family of exact static, spherically symmetric wormhole solutions with an
arbitrary throat radius, with flat or AdS asymptotic behavior, has been
obtained with sources in the form of two noninteracting scalar fields with
nonzero potentials. Both scalar fields are canonical (that is, satisfy the weak
energy condition), one is minimally and the other nonminimally coupled to
gravity, and the latter is a source of torsion.
| [
{
"created": "Wed, 5 Aug 2015 16:05:08 GMT",
"version": "v1"
}
] | 2016-03-30 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Galiakhmetov",
"A. M.",
""
]
] | We study the possible existence of static traversable wormholes without invoking exotic matter in the framework of the Einstein--Cartan theory. A family of exact static, spherically symmetric wormhole solutions with an arbitrary throat radius, with flat or AdS asymptotic behavior, has been obtained with sources in the form of two noninteracting scalar fields with nonzero potentials. Both scalar fields are canonical (that is, satisfy the weak energy condition), one is minimally and the other nonminimally coupled to gravity, and the latter is a source of torsion. |
1410.7527 | Seyed Hossein Hendi Dr. | S. H. Hendi | (2+1)-dimensional solutions in $F(R)$ gravity | 10 pages, no figure, accepted in IJTP | Int. J. Theor. Phys. 53 (2014) 4170-4181 | 10.1007/s10773-014-2168-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the well-known charged BTZ black holes, we look for
$(2+1)$-dimensional solutions of $F(R)$ gravity. At first we investigate some
near horizon solutions and after that we obtain asymptotically Lifshitz black
hole solutions. Finally, we discuss about rotating black holes with exponential
form of $F(R)$ theory.
| [
{
"created": "Tue, 28 Oct 2014 06:06:34 GMT",
"version": "v1"
}
] | 2015-07-13 | [
[
"Hendi",
"S. H.",
""
]
] | Motivated by the well-known charged BTZ black holes, we look for $(2+1)$-dimensional solutions of $F(R)$ gravity. At first we investigate some near horizon solutions and after that we obtain asymptotically Lifshitz black hole solutions. Finally, we discuss about rotating black holes with exponential form of $F(R)$ theory. |
1808.09244 | Ulf Leonhardt | Jonathan Drori, Yuval Rosenberg, David Bermudez, Yaron Silberberg, Ulf
Leonhardt | Observation of Stimulated Hawking Radiation in Optics | null | Phys. Rev. Lett. 122, 010404 (2019) | 10.1103/PhysRevLett.122.010404 | null | gr-qc physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of Hawking radiation can be tested in laboratory analogues of
black holes. We use light pulses in nonlinear fiber optics to establish
artificial event horizons. Each pulse generates a moving perturbation of the
refractive index via the Kerr effect. Probe light perceives this as an event
horizon when its group velocity, slowed down by the perturbation, matches the
speed of the pulse. We have observed in our experiment that the probe
stimulates Hawking radiation, which occurs in a regime of extreme nonlinear
fiber optics where positive and negative frequencies mix.
| [
{
"created": "Tue, 28 Aug 2018 12:06:36 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2018 05:45:38 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Nov 2018 12:13:22 GMT",
"version": "v3"
},
{
"created": "Sun, 13 Jan 2019 11:11:05 GMT",
"version": "v4"
}
] | 2019-01-16 | [
[
"Drori",
"Jonathan",
""
],
[
"Rosenberg",
"Yuval",
""
],
[
"Bermudez",
"David",
""
],
[
"Silberberg",
"Yaron",
""
],
[
"Leonhardt",
"Ulf",
""
]
] | The theory of Hawking radiation can be tested in laboratory analogues of black holes. We use light pulses in nonlinear fiber optics to establish artificial event horizons. Each pulse generates a moving perturbation of the refractive index via the Kerr effect. Probe light perceives this as an event horizon when its group velocity, slowed down by the perturbation, matches the speed of the pulse. We have observed in our experiment that the probe stimulates Hawking radiation, which occurs in a regime of extreme nonlinear fiber optics where positive and negative frequencies mix. |
2204.01748 | Shahar Hod | Shahar Hod | Non-equatorial scalar rings supported by magnetized Schwarzschild-Melvin
black holes | 7 pages | Physical Review D 105, 084056 (2022) | 10.1103/PhysRevD.105.084056 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | It has recently been demonstrated that magnetized black holes in composed
Einstein-Maxwell-scalar-Gauss-Bonnet field theories with a non-minimal negative
coupling of the scalar field to the Gauss-Bonnet curvature invariant may
support spatially regular scalar hairy configurations. In particular, it has
been revealed that, for Schwarzschild-Melvin black-hole spacetimes, the onset
of the near-horizon spontaneous scalarization phenomenon is marked by the
numerically computed dimensionless critical relation
$(BM)_{\text{crit}}\simeq0.971$, where $\{M,B\}$ are respectively the mass and
the magnetic field of the spacetime. In the present paper we prove, using
analytical techniques, that the boundary between bald Schwarzschild-Melvin
black-hole spacetimes and hairy (scalarized) black-hole solutions of the
composed Einstein-Maxwell-scalar-Gauss-Bonnet theory is characterized by the
exact dimensionless relation
$(BM)_{\text{crit}}=\sqrt{{{\sqrt{6}-2}\over{2\sqrt{6}}}+\sqrt{{{\sqrt{6}-1}\over{2}}}}$
for the critical magnetic strength. Intriguingly, we prove that the critical
dimensionless magnetic parameter $(BM)_{\text{crit}}$ corresponds to magnetized
black holes that support a pair of linearized non-minimally coupled thin scalar
rings that are characterized by the non-equatorial polar angular relation
$(\sin^2\theta)_{\text{scalar-ring}}={{690-72\sqrt{6}+4\sqrt{3258\sqrt{6}-7158}}\over{789}}<1$.
It is also proved that the classically allowed angular region for the
negative-coupling near-horizon spontaneous scalarization phenomenon of
magnetized Schwarzschild-Melvin spacetimes is restricted to the black-hole
poles, $\sin^2\theta_{\text{scalar}}\to0$, in the asymptotic large-strength
magnetic regime $BM\gg1$.
| [
{
"created": "Mon, 4 Apr 2022 18:00:01 GMT",
"version": "v1"
}
] | 2022-05-11 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been demonstrated that magnetized black holes in composed Einstein-Maxwell-scalar-Gauss-Bonnet field theories with a non-minimal negative coupling of the scalar field to the Gauss-Bonnet curvature invariant may support spatially regular scalar hairy configurations. In particular, it has been revealed that, for Schwarzschild-Melvin black-hole spacetimes, the onset of the near-horizon spontaneous scalarization phenomenon is marked by the numerically computed dimensionless critical relation $(BM)_{\text{crit}}\simeq0.971$, where $\{M,B\}$ are respectively the mass and the magnetic field of the spacetime. In the present paper we prove, using analytical techniques, that the boundary between bald Schwarzschild-Melvin black-hole spacetimes and hairy (scalarized) black-hole solutions of the composed Einstein-Maxwell-scalar-Gauss-Bonnet theory is characterized by the exact dimensionless relation $(BM)_{\text{crit}}=\sqrt{{{\sqrt{6}-2}\over{2\sqrt{6}}}+\sqrt{{{\sqrt{6}-1}\over{2}}}}$ for the critical magnetic strength. Intriguingly, we prove that the critical dimensionless magnetic parameter $(BM)_{\text{crit}}$ corresponds to magnetized black holes that support a pair of linearized non-minimally coupled thin scalar rings that are characterized by the non-equatorial polar angular relation $(\sin^2\theta)_{\text{scalar-ring}}={{690-72\sqrt{6}+4\sqrt{3258\sqrt{6}-7158}}\over{789}}<1$. It is also proved that the classically allowed angular region for the negative-coupling near-horizon spontaneous scalarization phenomenon of magnetized Schwarzschild-Melvin spacetimes is restricted to the black-hole poles, $\sin^2\theta_{\text{scalar}}\to0$, in the asymptotic large-strength magnetic regime $BM\gg1$. |
gr-qc/0411081 | Sergio Dain | Sergio Dain | Elliptic systems | 23 pages, latex, uses svmult.cls style file (included). To appear in
the Proceeding of the March-2004 Heraeus Seminar in Bad Honnef | Lect.Notes Phys. 692 (2006) 117-139 | 10.1007/11550259_6 | null | gr-qc | null | In this article I will review some basic results on elliptic boundary value
problems with applications to General Relativity.
| [
{
"created": "Tue, 16 Nov 2004 13:51:43 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Dain",
"Sergio",
""
]
] | In this article I will review some basic results on elliptic boundary value problems with applications to General Relativity. |
1107.5036 | Dan Solomon | Dan Solomon | Comparing two methods of regularization of the kinetic energy density | Added an extra section. 15 pages | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will compare two different methods of regularizing the
kinetic energy density for a massless scalar field in the presence of a static
scalar potential. One method of regularization is to subtract the cosmological
constant from the "naive" expression for the kinetic energy density. The other
method is to use point split regularization. It is found that the two methods
yield different results. The result obtained using point split regularization
includes an extra ambiguous term.
| [
{
"created": "Sun, 24 Jul 2011 12:58:41 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Aug 2011 00:52:02 GMT",
"version": "v2"
}
] | 2011-08-11 | [
[
"Solomon",
"Dan",
""
]
] | In this paper we will compare two different methods of regularizing the kinetic energy density for a massless scalar field in the presence of a static scalar potential. One method of regularization is to subtract the cosmological constant from the "naive" expression for the kinetic energy density. The other method is to use point split regularization. It is found that the two methods yield different results. The result obtained using point split regularization includes an extra ambiguous term. |
1901.08988 | Adria Delhom | Jose Beltr\'an Jim\'enez and Adria Delhom | Ghosts in metric-affine higher order curvature gravity | 7 pages | Eur.Phys.J. C79 (2019) no.8, 656 | 10.1140/epjc/s10052-019-7149-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We disprove the widespread belief that higher order curvature theories of
gravity in the metric-affine formalism are generally ghost-free. This is
clarified by considering a sub-class of theories constructed only with the
Ricci tensor and showing that the non-projectively invariant sector propagates
ghost-like degrees of freedom. We also explain how these pathologies can be
avoided either by imposing a projective symmetry or additional constraints in
the gravity sector. Our results put forward that higher order curvature gravity
theories generally remain pathological in the metric-affine (and hybrid)
formalisms and highlight the key importance of the projective symmetry and/or
additional constraints for their physical viability and, by extension, of
general metric-affine theories.
| [
{
"created": "Fri, 25 Jan 2019 17:06:11 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Aug 2019 12:46:46 GMT",
"version": "v2"
}
] | 2019-08-21 | [
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Delhom",
"Adria",
""
]
] | We disprove the widespread belief that higher order curvature theories of gravity in the metric-affine formalism are generally ghost-free. This is clarified by considering a sub-class of theories constructed only with the Ricci tensor and showing that the non-projectively invariant sector propagates ghost-like degrees of freedom. We also explain how these pathologies can be avoided either by imposing a projective symmetry or additional constraints in the gravity sector. Our results put forward that higher order curvature gravity theories generally remain pathological in the metric-affine (and hybrid) formalisms and highlight the key importance of the projective symmetry and/or additional constraints for their physical viability and, by extension, of general metric-affine theories. |
2311.07456 | Adrian Abac | Adrian Abac, Tim Dietrich, Alessandra Buonanno, Jan Steinhoff and
Maximiliano Ujevic | New and Robust Gravitational-Waveform Model for High-Mass-Ratio Binary
Neutron Star Systems with Dynamical Tidal Effects | null | Phys. Rev. D 109, 024062 (2024) | 10.1103/PhysRevD.109.024062 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | For the analysis of gravitational-wave signals, fast and accurate
gravitational-waveform models are required. These enable us to obtain
information on the system properties from compact binary mergers. In this
article, we introduce the NRTidalv3 model, which contains a closed-form
expression that describes tidal effects, focusing on the description of binary
neutron star systems. The model improves upon previous versions by employing a
larger set of numerical-relativity data for its calibration, by including
high-mass ratio systems covering also a wider range of equations of state. It
also takes into account dynamical tidal effects and the known post-Newtonian
mass-ratio dependence of individual calibration parameters. We implemented the
model in the publicly available LALSuite software library by augmenting
different binary black hole waveform models (IMRPhenomD, IMRPhenomX, and
SEOBNRv5_ROM). We test the validity of NRTidalv3 by comparing it with
numerical-relativity waveforms, as well as other tidal models. Finally, we
perform parameter estimation for GW170817 and GW190425 with the new tidal
approximant and find overall consistent results with respect to previous
studies.
| [
{
"created": "Mon, 13 Nov 2023 16:41:19 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jul 2024 08:23:55 GMT",
"version": "v2"
}
] | 2024-07-17 | [
[
"Abac",
"Adrian",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Ujevic",
"Maximiliano",
""
]
] | For the analysis of gravitational-wave signals, fast and accurate gravitational-waveform models are required. These enable us to obtain information on the system properties from compact binary mergers. In this article, we introduce the NRTidalv3 model, which contains a closed-form expression that describes tidal effects, focusing on the description of binary neutron star systems. The model improves upon previous versions by employing a larger set of numerical-relativity data for its calibration, by including high-mass ratio systems covering also a wider range of equations of state. It also takes into account dynamical tidal effects and the known post-Newtonian mass-ratio dependence of individual calibration parameters. We implemented the model in the publicly available LALSuite software library by augmenting different binary black hole waveform models (IMRPhenomD, IMRPhenomX, and SEOBNRv5_ROM). We test the validity of NRTidalv3 by comparing it with numerical-relativity waveforms, as well as other tidal models. Finally, we perform parameter estimation for GW170817 and GW190425 with the new tidal approximant and find overall consistent results with respect to previous studies. |
2206.14714 | Alexander Zhidenko | R. A. Konoplya, A. F. Zinhailo, J. Kunz, Z. Stuchlik, A. Zhidenko | Quasinormal ringing of regular black holes in asymptotically safe
gravity: the importance of overtones | 20 pages, 7 figures | JCAP 10 (2022) 091 | 10.1088/1475-7516/2022/10/091 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Asymptotically safe gravity is based on the idea that the main contribution
to the Schwarzschild-like black hole spacetime is due to the value of the
gravitational coupling which depends on the distance from the origin and
approaches its classical value in the far zone. However, at some stage this
approach has an arbitrariness of choice of some identification parameter. The
two cases of identification are considered here: first, by the modified proper
length (the Bonanno-Reuter metric), and second, by the Kretschmann scalar (the
metric for this case coincides, up to the redefinition of constants, with the
Hayward metric). Even though the quasinormal modes of these metrics have been
extensively studied, a number of interesting points were missed. We have found
that quasinormal modes are qualitatively similar for both types of
identification. The deviation of the fundamental mode from its Schwarzschild
limit may be a few times larger than it was claimed in the previous studies.
The striking deviation from the Schwarzschild limit occurs for overtones, being
as large as hundreds of percent even when the fundamental mode is almost
coinciding with the Schwarzschild one. This happens because the above metrics
are very close to the Schwarzschild one everywhere, except a small region near
the event horizon, which is crucial for overtones. The spectrum of both metrics
contains purely imaginary (non-oscillatory) modes, which, for some values of
parameters, can appear already at the second overtone.
| [
{
"created": "Wed, 29 Jun 2022 15:22:05 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 2022 02:35:34 GMT",
"version": "v2"
}
] | 2022-11-01 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zinhailo",
"A. F.",
""
],
[
"Kunz",
"J.",
""
],
[
"Stuchlik",
"Z.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Asymptotically safe gravity is based on the idea that the main contribution to the Schwarzschild-like black hole spacetime is due to the value of the gravitational coupling which depends on the distance from the origin and approaches its classical value in the far zone. However, at some stage this approach has an arbitrariness of choice of some identification parameter. The two cases of identification are considered here: first, by the modified proper length (the Bonanno-Reuter metric), and second, by the Kretschmann scalar (the metric for this case coincides, up to the redefinition of constants, with the Hayward metric). Even though the quasinormal modes of these metrics have been extensively studied, a number of interesting points were missed. We have found that quasinormal modes are qualitatively similar for both types of identification. The deviation of the fundamental mode from its Schwarzschild limit may be a few times larger than it was claimed in the previous studies. The striking deviation from the Schwarzschild limit occurs for overtones, being as large as hundreds of percent even when the fundamental mode is almost coinciding with the Schwarzschild one. This happens because the above metrics are very close to the Schwarzschild one everywhere, except a small region near the event horizon, which is crucial for overtones. The spectrum of both metrics contains purely imaginary (non-oscillatory) modes, which, for some values of parameters, can appear already at the second overtone. |
1102.2090 | Yuta Yamada | Yuta Yamada, Hisa-aki Shinkai | Formation of naked singularities in five-dimensional space-time | 5 pages, 5 figures, To be published in Phys. Rev. D | Phys.Rev.D83:064006,2011 | 10.1103/PhysRevD.83.064006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigate the gravitational collapse of collisionless
particles in spheroidal configurations both in four and five-dimensional (5D)
space-time. We repeat the simulation performed by Shapiro and Teukolsky (1991)
that announced an appearance of a naked singularity, and also find that the
similar results in 5D version. That is, in a collapse of a highly prolate
spindle, the Kretschmann invariant blows up outside the matter and no apparent
horizon forms. We also find that the collapses in 5D proceed rapidly than in
4D, and the critical prolateness for appearance of apparent horizon in 5D is
loosened compared to 4D cases. We also show how collapses differ with spatial
symmetries comparing 5D evolutions in single-axisymmetry, SO(3), and those in
double-axisymmetry, U(1)$\times$U(1).
| [
{
"created": "Thu, 10 Feb 2011 12:02:19 GMT",
"version": "v1"
}
] | 2011-03-21 | [
[
"Yamada",
"Yuta",
""
],
[
"Shinkai",
"Hisa-aki",
""
]
] | We numerically investigate the gravitational collapse of collisionless particles in spheroidal configurations both in four and five-dimensional (5D) space-time. We repeat the simulation performed by Shapiro and Teukolsky (1991) that announced an appearance of a naked singularity, and also find that the similar results in 5D version. That is, in a collapse of a highly prolate spindle, the Kretschmann invariant blows up outside the matter and no apparent horizon forms. We also find that the collapses in 5D proceed rapidly than in 4D, and the critical prolateness for appearance of apparent horizon in 5D is loosened compared to 4D cases. We also show how collapses differ with spatial symmetries comparing 5D evolutions in single-axisymmetry, SO(3), and those in double-axisymmetry, U(1)$\times$U(1). |
1007.2780 | Lorenzo Iorio | Lorenzo Iorio | Classical and relativistic long-term time variations of some observables
for transiting exoplanets | LaTex2e, 19 pages, 5 figures, 2 tables. Some references updated. To
appear in Monthly Notices of the Royal Astronomical Society (MNRAS) | Mon.Not.Roy.Astron.Soc.411:167-183,2011 | 10.1111/j.1365-2966.2010.17669.x | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically work out the long-term, i.e. averaged over one orbital
revolution, time variations of some direct observable quantities Y induced by
classical and general relativistic dynamical perturbations of the two-body
pointlike Newtonian acceleration in the case of transiting exoplanets moving
along elliptic orbits. More specifically, the observables $Y$ with which we
deal are the transit duration, the radial velocity and the time interval
between primary and secondary eclipses. The dynamical effects considered are
the centrifugal oblateness of both the star and the planet, their tidal bulges
mutually raised on each other, a distant third body X, and general relativity
(both Schwarzschild and Lense-Thirring). We take into account the effects due
to the perturbations of all the Keplerian orbital elements involved in a
consistent and uniform way. First, we explicitly compute their instantaneous
time variations due to the dynamical effects considered and plug them in the
general expression for the instantaneous change of Y; then, we take the overall
average over one orbital revolution of the so-obtained instantaneous rate $\dot
Y(t)$ specialized to the perturbations considered. Instead, somewhat hybrid
expressions can be often found in literature: in them, the secular precession
of, typically, the periastron only is straightforwardly inserted into
instantaneous formulas. Numerical evaluations of the obtained results are given
for a typical star-planet scenario and compared with the expected observational
accuracies over a time span 10 yr long. Our results are, in principle, valid
also for other astronomical scenarios. They may allow, e.g., for designing
various tests of gravitational theories with natural and artificial bodies in
our solar system. (Abridged)
| [
{
"created": "Fri, 16 Jul 2010 14:23:41 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jul 2010 14:08:27 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Sep 2010 15:58:32 GMT",
"version": "v3"
},
{
"created": "Thu, 7 Oct 2010 18:07:59 GMT",
"version": "v4"
}
] | 2011-01-24 | [
[
"Iorio",
"Lorenzo",
""
]
] | We analytically work out the long-term, i.e. averaged over one orbital revolution, time variations of some direct observable quantities Y induced by classical and general relativistic dynamical perturbations of the two-body pointlike Newtonian acceleration in the case of transiting exoplanets moving along elliptic orbits. More specifically, the observables $Y$ with which we deal are the transit duration, the radial velocity and the time interval between primary and secondary eclipses. The dynamical effects considered are the centrifugal oblateness of both the star and the planet, their tidal bulges mutually raised on each other, a distant third body X, and general relativity (both Schwarzschild and Lense-Thirring). We take into account the effects due to the perturbations of all the Keplerian orbital elements involved in a consistent and uniform way. First, we explicitly compute their instantaneous time variations due to the dynamical effects considered and plug them in the general expression for the instantaneous change of Y; then, we take the overall average over one orbital revolution of the so-obtained instantaneous rate $\dot Y(t)$ specialized to the perturbations considered. Instead, somewhat hybrid expressions can be often found in literature: in them, the secular precession of, typically, the periastron only is straightforwardly inserted into instantaneous formulas. Numerical evaluations of the obtained results are given for a typical star-planet scenario and compared with the expected observational accuracies over a time span 10 yr long. Our results are, in principle, valid also for other astronomical scenarios. They may allow, e.g., for designing various tests of gravitational theories with natural and artificial bodies in our solar system. (Abridged) |
0904.0110 | Ali Reza Amani | J. Sadeghi, F. Milani and A. R. Amani | Bouncing universe with the non-minimally coupled scaler field and its
reconstructing | 16 pages, 9 figures. Accepted in MPLA | Mod.Phys.Lett.A24:2363-2376,2009 | 10.1142/S0217732309030783 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider a non-minimally coupled scaler field, and show its
equation of state parameter can crossing over -1, $\omega\to -1$, and bouncing
condition. Also we obtain the stability conditions and consider reconstructing
for our model.
| [
{
"created": "Wed, 1 Apr 2009 09:29:53 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Sadeghi",
"J.",
""
],
[
"Milani",
"F.",
""
],
[
"Amani",
"A. R.",
""
]
] | In this paper we consider a non-minimally coupled scaler field, and show its equation of state parameter can crossing over -1, $\omega\to -1$, and bouncing condition. Also we obtain the stability conditions and consider reconstructing for our model. |
gr-qc/9809090 | Herbert Hamber | H.W. Hamber | AENEAS - A Custom-built Parallel Supercomputer for Quantum Gravity | LaTeX, 11 pages, 3 figures | null | null | UCI-98-13 | gr-qc hep-lat hep-th | null | Accurate Quantum Gravity calculations, based on the simplicial lattice
formulation, are computationally very demanding and require vast amounts of
computer resources. A custom-made 64-node parallel supercomputer capable of
performing up to $2 \times 10^{10}$ floating point operations per second has
been assembled entirely out of commodity components, and has been operational
for the last ten months. It will allow the numerical computation of a variety
of quantities of physical interest in quantum gravity and related field
theories, including the estimate of the critical exponents in the vicinity of
the ultraviolet fixed point to an accuracy of a few percent.
| [
{
"created": "Wed, 30 Sep 1998 22:45:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hamber",
"H. W.",
""
]
] | Accurate Quantum Gravity calculations, based on the simplicial lattice formulation, are computationally very demanding and require vast amounts of computer resources. A custom-made 64-node parallel supercomputer capable of performing up to $2 \times 10^{10}$ floating point operations per second has been assembled entirely out of commodity components, and has been operational for the last ten months. It will allow the numerical computation of a variety of quantities of physical interest in quantum gravity and related field theories, including the estimate of the critical exponents in the vicinity of the ultraviolet fixed point to an accuracy of a few percent. |
2303.13105 | Xiangdong Zhang | Yongbin Du and Xiangdong Zhang | Topological classes of black holes in de-Sitter spacetime | 18 pages, 14 figures | Eur. Phys. J. C 83, 927 (2023) | 10.1140/epjc/s10052-023-12114-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the topological number of de-Sitter black hole
solutions with different charges $(q)$ and rotational $(a)$ parameters. By
using generalized free energy and Duan's $\phi$-mapping topological current
theory, we find that the topological numbers of black holes can still be
classified as three types. In addition, we interestingly found the topological
classes for de-Sitter $($dS$)$ spacetime with distinct horizon, i.e, black hole
event horizon and cosmological horizon, will be different. Moreover, we also
investigate topological classifications of dS black hole solutions in higher
dimensions with or without Gauss-Bonnet term.
| [
{
"created": "Thu, 23 Mar 2023 08:44:19 GMT",
"version": "v1"
}
] | 2023-10-17 | [
[
"Du",
"Yongbin",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | In this paper, we investigate the topological number of de-Sitter black hole solutions with different charges $(q)$ and rotational $(a)$ parameters. By using generalized free energy and Duan's $\phi$-mapping topological current theory, we find that the topological numbers of black holes can still be classified as three types. In addition, we interestingly found the topological classes for de-Sitter $($dS$)$ spacetime with distinct horizon, i.e, black hole event horizon and cosmological horizon, will be different. Moreover, we also investigate topological classifications of dS black hole solutions in higher dimensions with or without Gauss-Bonnet term. |
0903.5420 | Chen Songbai | Songbai Chen, Xiangyun Fu, Jiliang Jing | Density pertubation of unparticle dark matter in the flat Universe | 6pages, 4 figures, accepted for publication in Eur. Phys. J. C | Eur.Phys.J.C64:107-112,2009 | 10.1140/epjc/s10052-009-1141-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The unparticle has been suggested as a candidate of dark matter. We
investigated the growth rate of the density perturbation for the unparticle
dark matter in the flat Universe. First, we consider the model in which
unparticle is the sole dark matter and find that the growth factor can be
approximated well by $f=(1+3\omega_u)\Omega^{\gamma}_u$, where $\omega_u$ is
the equation of state of unparticle. Our results show that the presence of
$\omega_u$ modifies the behavior of the growth factor $f$. For the second model
where unparticle co-exists with cold dark matter, the growth factor has a new
approximation $f=(1+3\omega_u)\Omega^{\gamma}_u+\alpha \Omega_m$ and $\alpha $
is a function of $\omega_u$. Thus the growth factor of unparticle is quite
different from that of usual dark matter. These information can help us know
more about unparticle and the early evolution of the Universe.
| [
{
"created": "Tue, 31 Mar 2009 09:44:33 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Aug 2009 07:12:42 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Oct 2009 07:52:55 GMT",
"version": "v3"
}
] | 2009-11-05 | [
[
"Chen",
"Songbai",
""
],
[
"Fu",
"Xiangyun",
""
],
[
"Jing",
"Jiliang",
""
]
] | The unparticle has been suggested as a candidate of dark matter. We investigated the growth rate of the density perturbation for the unparticle dark matter in the flat Universe. First, we consider the model in which unparticle is the sole dark matter and find that the growth factor can be approximated well by $f=(1+3\omega_u)\Omega^{\gamma}_u$, where $\omega_u$ is the equation of state of unparticle. Our results show that the presence of $\omega_u$ modifies the behavior of the growth factor $f$. For the second model where unparticle co-exists with cold dark matter, the growth factor has a new approximation $f=(1+3\omega_u)\Omega^{\gamma}_u+\alpha \Omega_m$ and $\alpha $ is a function of $\omega_u$. Thus the growth factor of unparticle is quite different from that of usual dark matter. These information can help us know more about unparticle and the early evolution of the Universe. |
gr-qc/0604081 | Giovanni Venturi | F. Finelli, G. Marozzi, G.P. Vacca, G. Venturi | Second Order Gauge-Invariant Perturbations during Inflation | 17 pages, 6 figures. Final version to appear in Phys. Rev. D | Phys.Rev.D74:083522,2006 | 10.1103/PhysRevD.74.083522 | null | gr-qc astro-ph hep-th | null | The evolution of gauge invariant second-order scalar perturbations in a
general single field inflationary scenario are presented. Different second
order gauge invariant expressions for the curvature are considered. We evaluate
perturbatively one of these second order curvature fluctuations and a second
order gauge invariant scalar field fluctuation during the slow-roll stage of a
massive chaotic inflationary scenario, taking into account the deviation from a
pure de Sitter evolution and considering only the contribution of super-Hubble
perturbations in mode-mode coupling. The spectra resulting from their
contribution to the second order quantum correlation function are nearly
scale-invariant, with additional logarithmic corrections to the first order
spectrum. For all scales of interest the amplitude of these spectra depend on
the total number of e-folds. We find, on comparing first and second order
perturbation results, an upper limit to the total number of e-folds beyond
which the two orders are comparable.
| [
{
"created": "Wed, 19 Apr 2006 15:36:37 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2006 15:54:56 GMT",
"version": "v2"
},
{
"created": "Tue, 31 Oct 2006 15:46:18 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Finelli",
"F.",
""
],
[
"Marozzi",
"G.",
""
],
[
"Vacca",
"G. P.",
""
],
[
"Venturi",
"G.",
""
]
] | The evolution of gauge invariant second-order scalar perturbations in a general single field inflationary scenario are presented. Different second order gauge invariant expressions for the curvature are considered. We evaluate perturbatively one of these second order curvature fluctuations and a second order gauge invariant scalar field fluctuation during the slow-roll stage of a massive chaotic inflationary scenario, taking into account the deviation from a pure de Sitter evolution and considering only the contribution of super-Hubble perturbations in mode-mode coupling. The spectra resulting from their contribution to the second order quantum correlation function are nearly scale-invariant, with additional logarithmic corrections to the first order spectrum. For all scales of interest the amplitude of these spectra depend on the total number of e-folds. We find, on comparing first and second order perturbation results, an upper limit to the total number of e-folds beyond which the two orders are comparable. |
0910.1634 | Cosimo Bambi | Cosimo Bambi, Katherine Freese, Tomohiro Harada, Rohta Takahashi,
Naoki Yoshida | Accretion process onto super-spinning objects | 11 pages, 5 figures. v2: with explanation of the origin of the
critical value |a|/M = 1.4 | Phys.Rev.D80:104023,2009 | 10.1103/PhysRevD.80.104023 | IPMU09-0113 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accretion process onto spinning objects in Kerr spacetimes is studied
with numerical simulations. Our results show that accretion onto compact
objects with Kerr parameter (characterizing the spin) $|a| < M$ and $|a| > M$
is very different. In the super-spinning case, for $|a|$ moderately larger than
$M$, the accretion onto the central object is extremely suppressed due to a
repulsive force at short distance. The accreting matter cannot reach the
central object, but instead is accumulated around it, forming a high density
cloud that continues to grow. The radiation emitted in the accretion process
will be harder and more intense than the one coming from standard black holes;
e.g. $\gamma$-rays could be produced as seen in some observations.
Gravitational collapse of this cloud might even give rise to violent bursts. As
$|a|$ increases, a larger amount of accreting matter reaches the central object
and the growth of the cloud becomes less efficient. Our simulations find that a
quasi-steady state of the accretion process exists for $|a|/M \gtrsim 1.4$,
independently of the mass accretion rate at large radii. For such high values
of the Kerr parameter, the accreting matter forms a thin disk at very small
radii. We provide some analytical arguments to strengthen the numerical
results; in particular, we estimate the radius where the gravitational force
changes from attractive to repulsive and the critical value $|a|/M \approx 1.4$
separating the two qualitatively different regimes of accretion. We briefly
discuss the observational signatures which could be used to look for such
exotic objects in the Galaxy and/or in the Universe.
| [
{
"created": "Thu, 8 Oct 2009 23:58:48 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Oct 2009 01:37:22 GMT",
"version": "v2"
}
] | 2009-11-18 | [
[
"Bambi",
"Cosimo",
""
],
[
"Freese",
"Katherine",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Takahashi",
"Rohta",
""
],
[
"Yoshida",
"Naoki",
""
]
] | The accretion process onto spinning objects in Kerr spacetimes is studied with numerical simulations. Our results show that accretion onto compact objects with Kerr parameter (characterizing the spin) $|a| < M$ and $|a| > M$ is very different. In the super-spinning case, for $|a|$ moderately larger than $M$, the accretion onto the central object is extremely suppressed due to a repulsive force at short distance. The accreting matter cannot reach the central object, but instead is accumulated around it, forming a high density cloud that continues to grow. The radiation emitted in the accretion process will be harder and more intense than the one coming from standard black holes; e.g. $\gamma$-rays could be produced as seen in some observations. Gravitational collapse of this cloud might even give rise to violent bursts. As $|a|$ increases, a larger amount of accreting matter reaches the central object and the growth of the cloud becomes less efficient. Our simulations find that a quasi-steady state of the accretion process exists for $|a|/M \gtrsim 1.4$, independently of the mass accretion rate at large radii. For such high values of the Kerr parameter, the accreting matter forms a thin disk at very small radii. We provide some analytical arguments to strengthen the numerical results; in particular, we estimate the radius where the gravitational force changes from attractive to repulsive and the critical value $|a|/M \approx 1.4$ separating the two qualitatively different regimes of accretion. We briefly discuss the observational signatures which could be used to look for such exotic objects in the Galaxy and/or in the Universe. |
1502.00204 | Peng Wang | Peng Wang, Haitang Yang, Shuxuan Ying | Minimal Length Effects on Entanglement Entropy of Spherically Symmetric
Black Holes in Brick Wall Model | 15 pages. arXiv admin note: substantial text overlap with
arXiv:1501.06025 | null | 10.1088/0264-9381/33/2/025007 | CTP-SCU/2015004 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the black hole horizon entanglement entropy for a massless scalar
field in the brick wall model by incorporating the minimal length. Taking the
minimal length effects on the occupation number $n(\omega,l)$ and the Hawking
temperature into consideration, we obtain the leading UV divergent term and the
subleading logarithmic term in the entropy. The leading divergent term scales
with the horizon area. The subleading logarithmic term is the same as that in
the usual brick wall model without the minimal length.
| [
{
"created": "Sun, 1 Feb 2015 06:24:04 GMT",
"version": "v1"
}
] | 2016-01-13 | [
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
],
[
"Ying",
"Shuxuan",
""
]
] | We compute the black hole horizon entanglement entropy for a massless scalar field in the brick wall model by incorporating the minimal length. Taking the minimal length effects on the occupation number $n(\omega,l)$ and the Hawking temperature into consideration, we obtain the leading UV divergent term and the subleading logarithmic term in the entropy. The leading divergent term scales with the horizon area. The subleading logarithmic term is the same as that in the usual brick wall model without the minimal length. |
2104.12610 | Victor Shchigolev Konstantinovich | V. K. Shchigolev | Fractional-order derivatives in cosmological models of accelerated
expansion | 20 pages, no figures | Modern Physics Letters A , Vol. 36, No. 14 (2021) 2130014 (21
pages) | 10.1142/S0217732321300147 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this brief review, we present the results of the fractional differential
approach in cosmology in the context of the exact models of cosmological
accelerated expansion obtained by several authors to date. Most of these
studies are devoted to the problem of introducing fractional derivatives or
fractional integrals into the classical General Relativity (GR). There are
several observational and theoretical motivations to investigate the modified
or alternative theories of GR. Among other things, we cover General Relativity
modified by a phenomenological approach dealing with fractional calculus. At
the same time, a sufficiently large number of exact solutions of the
cosmological equations modified by this approach were obtained. Some of these
models may be especially relevant in the light of solving the problem of late
accelerated expansion of the universe. These studies are largely motivated by
rapid progress in the field of observational cosmology that now allows, for the
first time, precision tests of fundamental physics on the scale of the
observable Universe. The purpose of this review is to provide a reference tool
for researchers and students in cosmology and gravitational physics, as well as
a self-contained, comprehensive, and up-to-date introduction to the subject as
a whole.
| [
{
"created": "Mon, 26 Apr 2021 14:23:25 GMT",
"version": "v1"
}
] | 2021-05-18 | [
[
"Shchigolev",
"V. K.",
""
]
] | In this brief review, we present the results of the fractional differential approach in cosmology in the context of the exact models of cosmological accelerated expansion obtained by several authors to date. Most of these studies are devoted to the problem of introducing fractional derivatives or fractional integrals into the classical General Relativity (GR). There are several observational and theoretical motivations to investigate the modified or alternative theories of GR. Among other things, we cover General Relativity modified by a phenomenological approach dealing with fractional calculus. At the same time, a sufficiently large number of exact solutions of the cosmological equations modified by this approach were obtained. Some of these models may be especially relevant in the light of solving the problem of late accelerated expansion of the universe. These studies are largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive, and up-to-date introduction to the subject as a whole. |
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