id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9903066 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia, Jerzy Lukierski, Anatol Nowicki | Distance Measurement and $\kappa$-Deformed Propagation of Light and
Heavy Probes | 13 pages, Latex, to appear in Int. J. Mod. Phys. A | Int.J.Mod.Phys. A14 (1999) 4575-4588 | 10.1142/S0217751X99002141 | NEIP-99-004 | gr-qc | null | We investigate the implications for the measurability of distances of a
covariant dimensionful ``$\kappa$'' deformation of D=4 relativistic symmetries,
with quantum time coordinate and modified Heisenberg algebra. We show that the
structure of the deformed mass-shell condition has significant implications for
measurement procedures relying on light probes, whereas in the case of heavy
probes the most sizeable effect is due to the nontrivial commutation relation
between three-momenta and quantum time coordinate. We argue that these findings
might indicate that $\kappa$-Poincar\'e symmetries capture some aspects of the
physics of the Quantum-Gravity vacuum.
| [
{
"created": "Wed, 17 Mar 1999 17:32:06 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Lukierski",
"Jerzy",
""
],
[
"Nowicki",
"Anatol",
""
]
] | We investigate the implications for the measurability of distances of a covariant dimensionful ``$\kappa$'' deformation of D=4 relativistic symmetries, with quantum time coordinate and modified Heisenberg algebra. We show that the structure of the deformed mass-shell condition has significant implications for measurement procedures relying on light probes, whereas in the case of heavy probes the most sizeable effect is due to the nontrivial commutation relation between three-momenta and quantum time coordinate. We argue that these findings might indicate that $\kappa$-Poincar\'e symmetries capture some aspects of the physics of the Quantum-Gravity vacuum. |
gr-qc/0209067 | Jaime Villas da Rocha | R. Chan, M. F. A. da Silva, Jaime F. Villas da Rocha | Gravitational Collapse of Self-Similar and Shear-free Fluid with Heat
Flow | 34 pages, 9 figures, latex | Int.J.Mod.Phys. D12 (2003) 347-368 | 10.1142/S021827180300327X | null | gr-qc | null | A class of solutions to Einstein field equations is studied, which represents
gravitational collapse of thick spherical shells made of self-similar and
shear-free fluid with heat flow. It is shown that such shells satisfy all the
energy conditions, and the corresponding collapse always forms naked
singularities.
| [
{
"created": "Thu, 19 Sep 2002 20:22:14 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"da Rocha",
"Jaime F. Villas",
""
]
] | A class of solutions to Einstein field equations is studied, which represents gravitational collapse of thick spherical shells made of self-similar and shear-free fluid with heat flow. It is shown that such shells satisfy all the energy conditions, and the corresponding collapse always forms naked singularities. |
1509.08867 | Yann Bouffanais | Yann Bouffanais and Edward K. Porter | Detecting compact galactic binaries using a hybrid swarm-based algorithm | 19 pages, 5 figures | Phys. Rev. D 93, 064020 (2016) | 10.1103/PhysRevD.93.064020 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compact binaries in our galaxy are expected to be one of the main sources of
gravitational waves for the future eLISA mission. During the mission lifetime,
many thousands of galactic binaries should be individually resolved. However,
the identification of the sources, and the extraction of the signal parameters
in a noisy environment are real challenges for data analysis. So far,
stochastic searches have proven to be the most successful for this problem. In
this work we present the first application of a swarm-based algorithm combining
Particle Swarm Optimization and Differential Evolution. These algorithms have
been shown to converge faster to global solutions on complicated likelihood
surfaces than other stochastic methods. We first demonstrate the effectiveness
of the algorithm for the case of a single binary in a 1 mHz search bandwidth.
This interesting problem gave the algorithm plenty of opportunity to fail, as
it can be easier to find a strong noise peak rather than the signal itself.
After a successful detection of a fictitious low-frequency source, as well as
the verification binary RXJ0806.3+1527, we then applied the algorithm to the
detection of multiple binaries, over different search bandwidths, in the cases
of low and mild source confusion. In all cases, we show that we can
successfully identify the sources, and recover the true parameters within a
99\% credible interval.
| [
{
"created": "Tue, 29 Sep 2015 17:50:20 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Mar 2016 23:17:42 GMT",
"version": "v2"
}
] | 2016-03-23 | [
[
"Bouffanais",
"Yann",
""
],
[
"Porter",
"Edward K.",
""
]
] | Compact binaries in our galaxy are expected to be one of the main sources of gravitational waves for the future eLISA mission. During the mission lifetime, many thousands of galactic binaries should be individually resolved. However, the identification of the sources, and the extraction of the signal parameters in a noisy environment are real challenges for data analysis. So far, stochastic searches have proven to be the most successful for this problem. In this work we present the first application of a swarm-based algorithm combining Particle Swarm Optimization and Differential Evolution. These algorithms have been shown to converge faster to global solutions on complicated likelihood surfaces than other stochastic methods. We first demonstrate the effectiveness of the algorithm for the case of a single binary in a 1 mHz search bandwidth. This interesting problem gave the algorithm plenty of opportunity to fail, as it can be easier to find a strong noise peak rather than the signal itself. After a successful detection of a fictitious low-frequency source, as well as the verification binary RXJ0806.3+1527, we then applied the algorithm to the detection of multiple binaries, over different search bandwidths, in the cases of low and mild source confusion. In all cases, we show that we can successfully identify the sources, and recover the true parameters within a 99\% credible interval. |
2007.11066 | Alireza Talebian Ashkezari | Alireza Talebian, Amin Nassiri-Rad, Hassan Firouzjahi | Revisiting Magnetogenesis during Inflation | null | Phys. Rev. D 102, 103508 (2020) | 10.1103/PhysRevD.102.103508 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the mechanism of primordial magnetogenesis during inflation by
taking into account the dynamics of the stochastic noises of the
electromagnetic perturbations. We obtain the associated Langevin and
Fokker-Planck equations for the electromagnetic fields and solve them
analytically. It is shown that while the backreactions of the electric field
energy density may spoil inflation too early, but there are regions of
parameter space where the usual decaying behavior of the magnetic fields are
replaced by a mean-reverting process of stochastic dynamics. As a result, the
magnetic fields settle down into an equilibrium state with the amplitude
significantly larger than what is obtained in the absence of the stochastic
noises. We show that magnetic fields with present time amplitude $\sim
10^{-13}$ Gauss and coherent length ${\rm Mpc}$ can be generated while the
backreactions of the electric field perturbations are under control.
| [
{
"created": "Tue, 21 Jul 2020 19:49:41 GMT",
"version": "v1"
}
] | 2020-11-18 | [
[
"Talebian",
"Alireza",
""
],
[
"Nassiri-Rad",
"Amin",
""
],
[
"Firouzjahi",
"Hassan",
""
]
] | We revisit the mechanism of primordial magnetogenesis during inflation by taking into account the dynamics of the stochastic noises of the electromagnetic perturbations. We obtain the associated Langevin and Fokker-Planck equations for the electromagnetic fields and solve them analytically. It is shown that while the backreactions of the electric field energy density may spoil inflation too early, but there are regions of parameter space where the usual decaying behavior of the magnetic fields are replaced by a mean-reverting process of stochastic dynamics. As a result, the magnetic fields settle down into an equilibrium state with the amplitude significantly larger than what is obtained in the absence of the stochastic noises. We show that magnetic fields with present time amplitude $\sim 10^{-13}$ Gauss and coherent length ${\rm Mpc}$ can be generated while the backreactions of the electric field perturbations are under control. |
1509.00234 | Mustapha Azreg-A\"inou | Mustapha Azreg-A\"inou | Wormhole solutions sourced by fluids, II: Three-fluid two-charged
sources | 14 pages, no figures. New title. To appear in the European Physical
Journal C | Eur. Phys. J. C (2016) 76:7 | 10.1140/epjc/s10052-015-3836-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lack of a consistent metric for generating rotating wormholes motivates us to
present a new one endowed with interesting physical and geometrical properties.
When combined with the generalized method of superposition of fields, which
consists in attaching a form of matter to each moving frame, it generates
massive and charged (charge without charge) two-fluid-sourced, massive and
two-charged three-fluid-sourced, rotating as well as new static wormholes
which, otherwise, can hardly be derived by integration. If the lapse function
of the static wormhole is bounded from above, no closed timelike curves occur
in the rotating counterpart. For positive energy densities dying out faster
than $1/r$, the angular velocity includes in its expansion a correction term,
to the leading one that corresponds to ordinary stars, proportional to $\ln
r/r^4$. Such a term is not present in the corresponding expansion for the
Kerr-Newman black hole. Based on this observation and our previous work, the
dragging effects of falling neutral objects may constitute a substitute for
other known techniques used for testing the nature of the rotating black hole
candidates that are harbored in the center of galaxies. We discuss the
possibility of generating ($n+1$)-fluid-sourced, $n$-charged, rotating as well
as static wormholes.
| [
{
"created": "Tue, 1 Sep 2015 11:28:55 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Dec 2015 08:46:05 GMT",
"version": "v2"
}
] | 2016-01-07 | [
[
"Azreg-Aïnou",
"Mustapha",
""
]
] | Lack of a consistent metric for generating rotating wormholes motivates us to present a new one endowed with interesting physical and geometrical properties. When combined with the generalized method of superposition of fields, which consists in attaching a form of matter to each moving frame, it generates massive and charged (charge without charge) two-fluid-sourced, massive and two-charged three-fluid-sourced, rotating as well as new static wormholes which, otherwise, can hardly be derived by integration. If the lapse function of the static wormhole is bounded from above, no closed timelike curves occur in the rotating counterpart. For positive energy densities dying out faster than $1/r$, the angular velocity includes in its expansion a correction term, to the leading one that corresponds to ordinary stars, proportional to $\ln r/r^4$. Such a term is not present in the corresponding expansion for the Kerr-Newman black hole. Based on this observation and our previous work, the dragging effects of falling neutral objects may constitute a substitute for other known techniques used for testing the nature of the rotating black hole candidates that are harbored in the center of galaxies. We discuss the possibility of generating ($n+1$)-fluid-sourced, $n$-charged, rotating as well as static wormholes. |
1001.0084 | Nandinii Barbosa-Cendejas | N. Barbosa-Cendejas and M.A. Reyes | The Schrodinger picture of standard cosmology | 9 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a time independent Schrodinger type equation derived from the
equations of motion that drives a single scalar field in a standard cosmology
model for inflation in a flat space-time with a Friedman-Robertson-Walker (FRW)
metric with a cosmological constant. We find that all the 1-dimensional bound
state solutions of quantum mechanics lead to at least one exact solution for
the dynamical equations of standard cosmology, and that these solutions
resemble the most recurrent inflationary solutions found in the literature. The
analogies derived from this approach may be used to realize a deeper
understanding of the dynamics of the model.
| [
{
"created": "Thu, 31 Dec 2009 04:18:23 GMT",
"version": "v1"
}
] | 2010-01-05 | [
[
"Barbosa-Cendejas",
"N.",
""
],
[
"Reyes",
"M. A.",
""
]
] | We consider a time independent Schrodinger type equation derived from the equations of motion that drives a single scalar field in a standard cosmology model for inflation in a flat space-time with a Friedman-Robertson-Walker (FRW) metric with a cosmological constant. We find that all the 1-dimensional bound state solutions of quantum mechanics lead to at least one exact solution for the dynamical equations of standard cosmology, and that these solutions resemble the most recurrent inflationary solutions found in the literature. The analogies derived from this approach may be used to realize a deeper understanding of the dynamics of the model. |
1409.0474 | Furkan Semih D\"undar | Furkan Semih D\"undar | The Firewall Paradox | MSc. thesis submitted to ODTU. Table of contents entries referring to
subsections of the index are added (The only addition to the library
version). v2: more comprehensive, visually attractive v3: Published as a book
by LAP LAMBERT Academic Publishing (December 20, 2016) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this MSc. thesis, we have attempted to give an overview of the firewall
paradox and various approaches towards its resolution. After an introductory
chapter on some basic concepts in quantum field theory in curved spacetimes
such as Hawking radiation, we introduce the paradox. It arises out of
application of principles each of which is thought or assumed to be correct: 1)
unitary black hole evaporation, 2) validity of quantum field theory in curved
spacetime, 3) a measure of the number of black hole quantum states, 4)
Einstein's equivalence principle. Then, we present various approaches that
exist in the literature towards the resolution of the paradox.
| [
{
"created": "Wed, 27 Aug 2014 12:07:00 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2014 20:52:42 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Feb 2017 22:54:55 GMT",
"version": "v3"
}
] | 2017-02-06 | [
[
"Dündar",
"Furkan Semih",
""
]
] | In this MSc. thesis, we have attempted to give an overview of the firewall paradox and various approaches towards its resolution. After an introductory chapter on some basic concepts in quantum field theory in curved spacetimes such as Hawking radiation, we introduce the paradox. It arises out of application of principles each of which is thought or assumed to be correct: 1) unitary black hole evaporation, 2) validity of quantum field theory in curved spacetime, 3) a measure of the number of black hole quantum states, 4) Einstein's equivalence principle. Then, we present various approaches that exist in the literature towards the resolution of the paradox. |
1407.2528 | Gergely Sz\'ekely | H. Andr\'eka and J. X. Madar\'asz and I. N\'emeti and M. Stannett and
G. Sz\'ekely | Faster than light motion does not imply time travel | 11 pages, 5 figures | 2014 Class. Quantum Grav. 31 095005 | 10.1088/0264-9381/31/9/095005 | null | gr-qc math-ph math.LO math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Seeing the many examples in the literature of causality violations based on
faster-than- light (FTL) signals one naturally thinks that FTL motion leads
inevitably to the possibility of time travel. We show that this logical
inference is invalid by demonstrating a model, based on (3+1)-dimensional
Minkowski spacetime, in which FTL motion is permitted (in every direction
without any limitation on speed) yet which does not admit time travel.
Moreover, the Principle of Relativity is true in this model in the sense that
all observers are equivalent. In short, FTL motion does not imply time travel
after all.
| [
{
"created": "Wed, 9 Jul 2014 15:41:47 GMT",
"version": "v1"
}
] | 2014-07-10 | [
[
"Andréka",
"H.",
""
],
[
"Madarász",
"J. X.",
""
],
[
"Németi",
"I.",
""
],
[
"Stannett",
"M.",
""
],
[
"Székely",
"G.",
""
]
] | Seeing the many examples in the literature of causality violations based on faster-than- light (FTL) signals one naturally thinks that FTL motion leads inevitably to the possibility of time travel. We show that this logical inference is invalid by demonstrating a model, based on (3+1)-dimensional Minkowski spacetime, in which FTL motion is permitted (in every direction without any limitation on speed) yet which does not admit time travel. Moreover, the Principle of Relativity is true in this model in the sense that all observers are equivalent. In short, FTL motion does not imply time travel after all. |
0804.4144 | Emma Robinson | E. L. Robinson, J. D. Romano, A. Vecchio | Search for a stochastic gravitational-wave signal in the second round of
the Mock LISA Data Challenges | 10 pages, 3 figures, GWDAW12 conference proceedings | Class.Quant.Grav.25:184019,2008 | 10.1088/0264-9381/25/18/184019 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis method currently proposed to search for isotropic stochastic
radiation of primordial or astrophysical origin with the Laser Interferometer
Space Antenna (LISA) relies on the combined use of two LISA channels, one of
which is insensitive to gravitational waves, such as the symmetrised Sagnac.
For this method to work, it is essential to know how the instrumental noise
power in the two channels are related to one another; however, no quantitative
estimates of this key information are available to date. The purpose of our
study is to assess the performance of the symmetrised Sagnac method for
different levels of prior information regarding the instrumental noise. We
develop a general approach in the framework of Bayesian inference and an
end-to-end analysis algorithm based on Markov Chain Monte Carlo methods to
compute the posterior probability density functions of the relevant model
parameters. We apply this method to data released as part of the second round
of the Mock LISA Data Challenges. For the selected (and somewhat idealised)
cases considered here, we find that a prior uncertainty of a factor ~2 in the
ratio between the power of the instrumental noise contributions in the two
channels allows for the detection of isotropic stochastic radiation. More
importantly, we provide a framework for more realistic studies of LISA's
performance and development of analysis techniques in the context of searches
for stochastic signals.
| [
{
"created": "Fri, 25 Apr 2008 16:41:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Robinson",
"E. L.",
""
],
[
"Romano",
"J. D.",
""
],
[
"Vecchio",
"A.",
""
]
] | The analysis method currently proposed to search for isotropic stochastic radiation of primordial or astrophysical origin with the Laser Interferometer Space Antenna (LISA) relies on the combined use of two LISA channels, one of which is insensitive to gravitational waves, such as the symmetrised Sagnac. For this method to work, it is essential to know how the instrumental noise power in the two channels are related to one another; however, no quantitative estimates of this key information are available to date. The purpose of our study is to assess the performance of the symmetrised Sagnac method for different levels of prior information regarding the instrumental noise. We develop a general approach in the framework of Bayesian inference and an end-to-end analysis algorithm based on Markov Chain Monte Carlo methods to compute the posterior probability density functions of the relevant model parameters. We apply this method to data released as part of the second round of the Mock LISA Data Challenges. For the selected (and somewhat idealised) cases considered here, we find that a prior uncertainty of a factor ~2 in the ratio between the power of the instrumental noise contributions in the two channels allows for the detection of isotropic stochastic radiation. More importantly, we provide a framework for more realistic studies of LISA's performance and development of analysis techniques in the context of searches for stochastic signals. |
1604.01132 | Elizabeth Winstanley | Supakchai Ponglertsakul, Elizabeth Winstanley and Sam R. Dolan | Stability of gravitating charged-scalar solitons in a cavity | 17 pages, 13 figures, minor changes, accepted for publication in
Physical Review D | Phys. Rev. D 94, 024031 (2016) | 10.1103/PhysRevD.94.024031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new regular solutions of Einstein-charged scalar field theory in a
cavity. The system is enclosed inside a reflecting mirror-like boundary, on
which the scalar field vanishes. The mirror is placed at the zero of the scalar
field closest to the origin, and inside this boundary our solutions are
regular. We study the stability of these solitons under linear, spherically
symmetric perturbations of the metric, scalar and electromagnetic fields. If
the radius of the mirror is sufficiently large, we present numerical evidence
for the stability of the solitons. For small mirror radius, some of the
solitons are unstable. We discuss the physical interpretation of this
instability.
| [
{
"created": "Tue, 5 Apr 2016 04:29:08 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jul 2016 12:47:14 GMT",
"version": "v2"
}
] | 2016-07-18 | [
[
"Ponglertsakul",
"Supakchai",
""
],
[
"Winstanley",
"Elizabeth",
""
],
[
"Dolan",
"Sam R.",
""
]
] | We present new regular solutions of Einstein-charged scalar field theory in a cavity. The system is enclosed inside a reflecting mirror-like boundary, on which the scalar field vanishes. The mirror is placed at the zero of the scalar field closest to the origin, and inside this boundary our solutions are regular. We study the stability of these solitons under linear, spherically symmetric perturbations of the metric, scalar and electromagnetic fields. If the radius of the mirror is sufficiently large, we present numerical evidence for the stability of the solitons. For small mirror radius, some of the solitons are unstable. We discuss the physical interpretation of this instability. |
1106.0414 | Luca Fabbri | Stefano Vignolo, Luca Fabbri and Roberto Cianci | Dirac spinors in Bianchi-I f(R)-cosmology with torsion | 25 pages, 1 figure | J. Math. Phys. 52, 112502 (2011) | 10.1063/1.3658865 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Dirac spinors in Bianchi type-I cosmological models, within the
framework of torsional $f(R)$-gravity. We find four types of results: the
resulting dynamic behavior of the universe depends on the particular choice of
function $f(R)$; some $f(R)$ models do not isotropize and have no Einstein
limit, so that they have no physical significance, whereas for other $f(R)$
models isotropization and Einsteinization occur, and so they are physically
acceptable, suggesting that phenomenological arguments may select $f(R)$ models
that are physically meaningful; the singularity problem can be avoided, due to
the presence of torsion; the general conservation laws holding for
$f(R)$-gravity with torsion ensure the preservation of the Hamiltonian
constraint, so proving that the initial value problem is well-formulated for
these models.
| [
{
"created": "Thu, 2 Jun 2011 12:31:05 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Sep 2011 14:06:58 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Nov 2011 19:05:58 GMT",
"version": "v3"
}
] | 2011-11-14 | [
[
"Vignolo",
"Stefano",
""
],
[
"Fabbri",
"Luca",
""
],
[
"Cianci",
"Roberto",
""
]
] | We study Dirac spinors in Bianchi type-I cosmological models, within the framework of torsional $f(R)$-gravity. We find four types of results: the resulting dynamic behavior of the universe depends on the particular choice of function $f(R)$; some $f(R)$ models do not isotropize and have no Einstein limit, so that they have no physical significance, whereas for other $f(R)$ models isotropization and Einsteinization occur, and so they are physically acceptable, suggesting that phenomenological arguments may select $f(R)$ models that are physically meaningful; the singularity problem can be avoided, due to the presence of torsion; the general conservation laws holding for $f(R)$-gravity with torsion ensure the preservation of the Hamiltonian constraint, so proving that the initial value problem is well-formulated for these models. |
gr-qc/0606031 | J\"org Hennig | J\"org Hennig, Gernot Neugebauer | Collisions of rigidly rotating disks of dust in General Relativity | 30 pages, 9 figures | Phys.Rev. D74 (2006) 064025 | 10.1103/PhysRevD.74.064025 | null | gr-qc | null | We discuss inelastic collisions of two rotating disks by using the
conservation laws for baryonic mass and angular momentum. In particular, we
formulate conditions for the formation of a new disk after the collision and
calculate the total energy loss to obtain upper limits for the emitted
gravitational energy.
| [
{
"created": "Wed, 7 Jun 2006 14:44:07 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2006 11:09:21 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Sep 2006 08:57:30 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Hennig",
"Jörg",
""
],
[
"Neugebauer",
"Gernot",
""
]
] | We discuss inelastic collisions of two rotating disks by using the conservation laws for baryonic mass and angular momentum. In particular, we formulate conditions for the formation of a new disk after the collision and calculate the total energy loss to obtain upper limits for the emitted gravitational energy. |
2312.06631 | Digvijay Wadekar | Digvijay Wadekar, Javier Roulet, Tejaswi Venumadhav, Ajit Kumar Mehta,
Barak Zackay, Jonathan Mushkin, Seth Olsen, Matias Zaldarriaga | New black hole mergers in the LIGO-Virgo O3 data from a gravitational
wave search including higher-order harmonics | 15+7 pages, 6+5 figures. Our event catalog (including sub-threshold
events) and the samples from our PE runs are available at
https://github.com/JayWadekar/GW_higher_harmonics_search | null | null | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nearly all of the previous gravitational wave (GW) searches in the LIGO-Virgo
data included GW waveforms with only the dominant quadrupole mode, i.e.,
omitting higher-order harmonics which are predicted by general relativity.
Based on the techniques developed in Wadekar et al. [1,2], we improve the IAS
pipeline by ($i$) introducing higher harmonics in the GW templates, ($ii$)
downweighting noise transients ('glitches') to improve the search sensitivity
to high-mass and high-redshift binary black hole (BBH) mergers. We find 14 new
BBH mergers with $0.53\leq p_{\rm astro}\leq 0.88$ on running our pipeline over
the public LIGO-Virgo data from the O3 run (we use the detection threshold as
$p_{\rm astro}>0.5$ following the approach of other pipelines). We also broadly
recover the high-significance events from earlier catalogs, except some which
were either vetoed or fell below our SNR threshold for trigger collection.
A few notable properties of our new candidate events are as follows. At
$>95$\% credibility, 4 candidates have total masses in the IMBH range (i.e.,
above 100 $M_\odot$), and 9 candidates have $z>0.5$. 9 candidates have median
mass of the primary BH falling roughly within the pair instability mass gap,
with the highest primary mass being $300_{+60}^{-120} M_\odot$. 5 candidates
have median mass ratio $q < 0.5$. Under a prior uniform in effective spin
$\chi_{\rm eff}$, 6 candidates have $\chi_{\rm eff} > 0$ at $>95\%$
credibility. We also find that including higher harmonics in our search raises
the significance of a few previously reported marginal events (e.g.,
GW190711_030756). While our new candidate events have modest false alarm rates
($\gtrsim 1.6 $/yr), a population inference study including these can better
inform the parameter space of BHs corresponding to the pair instability mass
gap, high redshifts, positive effective spins and asymmetric mass ratios.
| [
{
"created": "Mon, 11 Dec 2023 18:50:10 GMT",
"version": "v1"
}
] | 2023-12-12 | [
[
"Wadekar",
"Digvijay",
""
],
[
"Roulet",
"Javier",
""
],
[
"Venumadhav",
"Tejaswi",
""
],
[
"Mehta",
"Ajit Kumar",
""
],
[
"Zackay",
"Barak",
""
],
[
"Mushkin",
"Jonathan",
""
],
[
"Olsen",
"Seth",
""
],
... | Nearly all of the previous gravitational wave (GW) searches in the LIGO-Virgo data included GW waveforms with only the dominant quadrupole mode, i.e., omitting higher-order harmonics which are predicted by general relativity. Based on the techniques developed in Wadekar et al. [1,2], we improve the IAS pipeline by ($i$) introducing higher harmonics in the GW templates, ($ii$) downweighting noise transients ('glitches') to improve the search sensitivity to high-mass and high-redshift binary black hole (BBH) mergers. We find 14 new BBH mergers with $0.53\leq p_{\rm astro}\leq 0.88$ on running our pipeline over the public LIGO-Virgo data from the O3 run (we use the detection threshold as $p_{\rm astro}>0.5$ following the approach of other pipelines). We also broadly recover the high-significance events from earlier catalogs, except some which were either vetoed or fell below our SNR threshold for trigger collection. A few notable properties of our new candidate events are as follows. At $>95$\% credibility, 4 candidates have total masses in the IMBH range (i.e., above 100 $M_\odot$), and 9 candidates have $z>0.5$. 9 candidates have median mass of the primary BH falling roughly within the pair instability mass gap, with the highest primary mass being $300_{+60}^{-120} M_\odot$. 5 candidates have median mass ratio $q < 0.5$. Under a prior uniform in effective spin $\chi_{\rm eff}$, 6 candidates have $\chi_{\rm eff} > 0$ at $>95\%$ credibility. We also find that including higher harmonics in our search raises the significance of a few previously reported marginal events (e.g., GW190711_030756). While our new candidate events have modest false alarm rates ($\gtrsim 1.6 $/yr), a population inference study including these can better inform the parameter space of BHs corresponding to the pair instability mass gap, high redshifts, positive effective spins and asymmetric mass ratios. |
2403.03399 | Christopher Reyes | Christopher Reyes, Jeremy Sakstein | Parameterized Post-Tolman-Oppenheimer-Volkoff Framework for Screened
Modified Gravity with an Application to the Secondary Component of GW190814 | 5 pages, 2 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The secondary component of GW190814 has mass in the range $2.5$--$2.67{\rm
M}_\odot$, placing it within the lower mass gap separating neutron stars from
black holes. According to the predictions of general relativity and
state-of-the-art nuclear equations of state, this object is too heavy to be a
neutron star.~In this work, we explore the possibility that this object is a
neutron star under the hypothesis that general relativity is modified to
include screening mechanisms, and that the neutron star formed in an unscreened
environment. We introduce a set of
parameterized-post-Tolman-Oppenheimer-Volkoff (post-TOV) equations appropriate
for screened modified gravity whose free parameters are environment-dependent.
We find that it is possible that the GW190814 secondary could be a neutron star
that formed in an unscreened environment for a range of reasonable post-TOV
parameters.
| [
{
"created": "Wed, 6 Mar 2024 01:46:25 GMT",
"version": "v1"
}
] | 2024-03-07 | [
[
"Reyes",
"Christopher",
""
],
[
"Sakstein",
"Jeremy",
""
]
] | The secondary component of GW190814 has mass in the range $2.5$--$2.67{\rm M}_\odot$, placing it within the lower mass gap separating neutron stars from black holes. According to the predictions of general relativity and state-of-the-art nuclear equations of state, this object is too heavy to be a neutron star.~In this work, we explore the possibility that this object is a neutron star under the hypothesis that general relativity is modified to include screening mechanisms, and that the neutron star formed in an unscreened environment. We introduce a set of parameterized-post-Tolman-Oppenheimer-Volkoff (post-TOV) equations appropriate for screened modified gravity whose free parameters are environment-dependent. We find that it is possible that the GW190814 secondary could be a neutron star that formed in an unscreened environment for a range of reasonable post-TOV parameters. |
1905.10066 | Jose Luis Hernandez-Pastora | Jos\'e Luis Hern\'andez-Pastora | A quadrupolar generalization of the Erez-Rosen coordinates | Accepted to be published in Classical and Quantum Gravity, May 2019 | null | 10.1088/1361-6382/ab2410 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The MSA system of coordinates [1] for the M Q-solution [2] is proved to be
the unique solution of certain partial differential equation with boundary and
asymptotic conditions. Such a differential equation is derived from the
orthogonality condition between two surfaces which hold a functional
relationship. The obtained expressions for the MSA system recover the
asymptotic expansions previously calculated [1] for those coordinates, as well
as the Erez-Rosen coordinates in the spherical case. It is also shown that the
event horizon of the M Q-solution can be easily obtained from those coordinates
leading to already known results. But in addition, it allows us to correct a
mistaken conclusion related to some bound imposed to the value of the
quadrupole moment [3]. Finally, it is explored the possibility of extending
this method of generalizing the Erez-Rosen coordinates to the general case of
solutions with any finite number of Relativistic Multipole Moments (RMM). It is
discussed as well, the possibility of determining the Weyl moments of those
solutions from their corresponding MSA coordinates, aiming to establish a
relation between the uniqueness of the MSA coordinates and the solutions
itself.
| [
{
"created": "Fri, 24 May 2019 07:21:56 GMT",
"version": "v1"
}
] | 2019-05-27 | [
[
"Hernández-Pastora",
"José Luis",
""
]
] | The MSA system of coordinates [1] for the M Q-solution [2] is proved to be the unique solution of certain partial differential equation with boundary and asymptotic conditions. Such a differential equation is derived from the orthogonality condition between two surfaces which hold a functional relationship. The obtained expressions for the MSA system recover the asymptotic expansions previously calculated [1] for those coordinates, as well as the Erez-Rosen coordinates in the spherical case. It is also shown that the event horizon of the M Q-solution can be easily obtained from those coordinates leading to already known results. But in addition, it allows us to correct a mistaken conclusion related to some bound imposed to the value of the quadrupole moment [3]. Finally, it is explored the possibility of extending this method of generalizing the Erez-Rosen coordinates to the general case of solutions with any finite number of Relativistic Multipole Moments (RMM). It is discussed as well, the possibility of determining the Weyl moments of those solutions from their corresponding MSA coordinates, aiming to establish a relation between the uniqueness of the MSA coordinates and the solutions itself. |
gr-qc/0001030 | Pia Astone | P.Astone, S.D'Antonio and G. Pizzella | Time Dispersion and Efficiency of Detection for Signals in Gravitational
Wave Experiments | 12 pages, 6 figures, Latex files using cernlik.cls (included). This
paper and related work are also available at
http://grwav3.roma1.infn.it/pia/papersweb.html Version 2: text unchanged.
Only a correction in the URL address | Phys.Rev.D62:042001,2000 | 10.1103/PhysRevD.62.042001 | null | gr-qc | null | Using simulated signals and measured noise with the EXPLORER and NAUTILUS
detectors we find the efficiency of signal detection and the signal arrival
time dispersion versus the signal-to-noise ratio.
| [
{
"created": "Tue, 11 Jan 2000 13:08:42 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jan 2000 14:40:29 GMT",
"version": "v2"
}
] | 2011-08-17 | [
[
"Astone",
"P.",
""
],
[
"D'Antonio",
"S.",
""
],
[
"Pizzella",
"G.",
""
]
] | Using simulated signals and measured noise with the EXPLORER and NAUTILUS detectors we find the efficiency of signal detection and the signal arrival time dispersion versus the signal-to-noise ratio. |
0912.4709 | J. -F. Pascual-Sanchez | A. San Miguel, F. Vicente and J.-F. Pascual-Sanchez | Numerical treatment of the light propagation problem in the
post-Newtonian formalism | 7 pages, 1 fig., Talk given by JFPS in Sept, 10, 2009, to be
published in JPCS as Proceedings of Spanish Relativity Meeting-ERE 2009 | J.Phys.Conf.Ser.229:012059,2010 | 10.1088/1742-6596/229/1/012059 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geometry of a light wavefront, evolving from a initial flat wavefront in
the 3-space associated with a post-Newtonian relativistic spacetime, is studied
numerically by means of the ray tracing method. For a discretization of the
bidimensional light wavefront, a surface fitting technique is used to determine
the curvature of this surface. The relationship between the intrinsic curvature
of the wavefront and the change of the arrival time at different points on the
Earth is also numerically discussed.
| [
{
"created": "Wed, 23 Dec 2009 18:52:39 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Miguel",
"A. San",
""
],
[
"Vicente",
"F.",
""
],
[
"Pascual-Sanchez",
"J. -F.",
""
]
] | The geometry of a light wavefront, evolving from a initial flat wavefront in the 3-space associated with a post-Newtonian relativistic spacetime, is studied numerically by means of the ray tracing method. For a discretization of the bidimensional light wavefront, a surface fitting technique is used to determine the curvature of this surface. The relationship between the intrinsic curvature of the wavefront and the change of the arrival time at different points on the Earth is also numerically discussed. |
gr-qc/0506114 | Pantelis Apostolopoulos | Pantelis S. Apostolopoulos | A geometric description of the intermediate behaviour for spatially
homogeneous models | Latex, 15 pages, no figures (uses iopart style/class files); added
one reference and minor corrections; (v3) improved and extended discussion;
minor corrections and several new references are added; to appear in Class.
Quantum Grav | Class.Quant.Grav. 22 (2005) 4425-4442 | 10.1088/0264-9381/22/21/002 | null | gr-qc | null | A new approach is suggested for the study of geometric symmetries in general
relativity, leading to an invariant characterization of the evolutionary
behaviour for a class of Spatially Homogeneous (SH) vacuum and orthogonal
$\gamma -$law perfect fluid models. Exploiting the 1+3 orthonormal frame
formalism, we express the kinematical quantities of a generic symmetry using
expansion-normalized variables. In this way, a specific symmetry assumption
lead to geometric constraints that are combined with the associated
integrability conditions, coming from the existence of the symmetry and the
induced expansion-normalized form of the Einstein's Field Equations (EFE), to
give a close set of compatibility equations. By specializing to the case of a
\emph{Kinematic Conformal Symmetry} (KCS), which is regarded as the direct
generalization of the concept of self-similarity, we give the complete set of
consistency equations for the whole SH dynamical state space. An interesting
aspect of the analysis of the consistency equations is that, \emph{at least}
for class A models which are Locally Rotationally Symmetric or lying within the
invariant subset satisfying $N_{\alpha}^{\alpha}=0 $, a proper KCS \emph{always
exists} and reduces to a self-similarity of the first or second kind at the
asymptotic regimes, providing a way for the ``geometrization'' of the
intermediate epoch of SH models.
| [
{
"created": "Thu, 23 Jun 2005 17:32:54 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jun 2005 15:18:39 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Sep 2005 08:04:44 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Apostolopoulos",
"Pantelis S.",
""
]
] | A new approach is suggested for the study of geometric symmetries in general relativity, leading to an invariant characterization of the evolutionary behaviour for a class of Spatially Homogeneous (SH) vacuum and orthogonal $\gamma -$law perfect fluid models. Exploiting the 1+3 orthonormal frame formalism, we express the kinematical quantities of a generic symmetry using expansion-normalized variables. In this way, a specific symmetry assumption lead to geometric constraints that are combined with the associated integrability conditions, coming from the existence of the symmetry and the induced expansion-normalized form of the Einstein's Field Equations (EFE), to give a close set of compatibility equations. By specializing to the case of a \emph{Kinematic Conformal Symmetry} (KCS), which is regarded as the direct generalization of the concept of self-similarity, we give the complete set of consistency equations for the whole SH dynamical state space. An interesting aspect of the analysis of the consistency equations is that, \emph{at least} for class A models which are Locally Rotationally Symmetric or lying within the invariant subset satisfying $N_{\alpha}^{\alpha}=0 $, a proper KCS \emph{always exists} and reduces to a self-similarity of the first or second kind at the asymptotic regimes, providing a way for the ``geometrization'' of the intermediate epoch of SH models. |
1410.2464 | John W. Moffat | J. W. Moffat | Scalar and Vector Field Constraints, Deflection of Light and Lensing in
Modified Gravity (MOG) | 8 pages, 1 figure | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A conformal coupling of the metric in the Jordan frame to the energy-momentum
tensor, screens the scalar field gravitational coupling strength $G$ in
modified gravity (MOG). The scalar field acquires a mass which depends on the
local matter density: the scalar field particle is massive for the Sun and
earth, where the density is high compared to low density environments in
cosmology and astrophysics. Together with the screening of the vector field
$\phi_\mu$, this guarantees that solar system tests of gravity are satisfied.
The conformal metric is coupled to the electromagnetic matter field and
energy-momentum tensor, screening $G$ for the Sun and the deflection of light
by the Sun and the Shapiro time delay in MOG are in agreement with general
relativity. For galaxies and galactic clusters the enhanced gravitational
coupling constant $G$ leads to agreement with gravitational lensing without
dark matter. For compact binary pulsars the screening of $G$ removes the
monopole and dipole gravitational radiation modes in agreement with the binary
pulsar timing data.
| [
{
"created": "Mon, 6 Oct 2014 20:12:59 GMT",
"version": "v1"
}
] | 2014-10-14 | [
[
"Moffat",
"J. W.",
""
]
] | A conformal coupling of the metric in the Jordan frame to the energy-momentum tensor, screens the scalar field gravitational coupling strength $G$ in modified gravity (MOG). The scalar field acquires a mass which depends on the local matter density: the scalar field particle is massive for the Sun and earth, where the density is high compared to low density environments in cosmology and astrophysics. Together with the screening of the vector field $\phi_\mu$, this guarantees that solar system tests of gravity are satisfied. The conformal metric is coupled to the electromagnetic matter field and energy-momentum tensor, screening $G$ for the Sun and the deflection of light by the Sun and the Shapiro time delay in MOG are in agreement with general relativity. For galaxies and galactic clusters the enhanced gravitational coupling constant $G$ leads to agreement with gravitational lensing without dark matter. For compact binary pulsars the screening of $G$ removes the monopole and dipole gravitational radiation modes in agreement with the binary pulsar timing data. |
gr-qc/0210080 | Sigbjorn Hervik | Sigbjorn Hervik | Vacuum Plane Waves in 4+1 D and Exact solutions to Einstein's Equations
in 3+1 D | 16 pages, no figures | Class.Quant.Grav.20:4315-4327,2003 | 10.1088/0264-9381/20/19/312 | null | gr-qc astro-ph hep-th | null | In this paper we derive homogeneous vacuum plane-wave solutions to Einstein's
field equations in 4+1 dimensions. The solutions come in five different types
of which three generalise the vacuum plane-wave solutions in 3+1 dimensions to
the 4+1 dimensional case. By doing a Kaluza-Klein reduction we obtain solutions
to the Einstein-Maxwell equations in 3+1 dimensions. The solutions generalise
the vacuum plane-wave spacetimes of Bianchi class B to the non-vacuum case and
describe spatially homogeneous spacetimes containing an extremely tilted fluid.
Also, using a similar reduction we obtain 3+1 dimensional solutions to the
Einstein equations with a scalar field.
| [
{
"created": "Wed, 23 Oct 2002 17:59:33 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jun 2003 13:24:45 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Hervik",
"Sigbjorn",
""
]
] | In this paper we derive homogeneous vacuum plane-wave solutions to Einstein's field equations in 4+1 dimensions. The solutions come in five different types of which three generalise the vacuum plane-wave solutions in 3+1 dimensions to the 4+1 dimensional case. By doing a Kaluza-Klein reduction we obtain solutions to the Einstein-Maxwell equations in 3+1 dimensions. The solutions generalise the vacuum plane-wave spacetimes of Bianchi class B to the non-vacuum case and describe spatially homogeneous spacetimes containing an extremely tilted fluid. Also, using a similar reduction we obtain 3+1 dimensional solutions to the Einstein equations with a scalar field. |
1312.3466 | Carles Bona | Milton Ruiz, Carlos Palenzuela and Carles Bona | Almost-Killing conserved currents: a general mass function | 21 pages, 3 figures | Phys. Rev. D 89 025011, 2014 | 10.1103/PhysRevD.89.025011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new class of conserved currents, describing non-gravitational
energy-momentum density, is presented. The proposed currents do not require the
existence of a (timelike) Killing vector, and are not restricted to spherically
symmetric spacetimes (or similar ones, in which the Kodama vector can be
defined). They are based instead on almost-Killing vectors, which could in
principle be defined on generic spacetimes. We provide local arguments, based
on energy density profiles in highly simplified (stationary, rigidly-rotating)
star models, which confirm the physical interest of these 'almost-Killing
currents'. A mass function is defined in this way for the spherical case,
qualitatively different from the Hern\'andez-Misner mass function. An elliptic
equation determining the new mass function is derived for the Tolman-Bondi
spherically symmetric dust metrics, including a simple solution for the
Oppenheimer-Schneider collapse. The equations for the non-symmetric case are
shown to be of a mixed elliptic-hyperbolic nature.
| [
{
"created": "Thu, 12 Dec 2013 12:38:23 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Ruiz",
"Milton",
""
],
[
"Palenzuela",
"Carlos",
""
],
[
"Bona",
"Carles",
""
]
] | A new class of conserved currents, describing non-gravitational energy-momentum density, is presented. The proposed currents do not require the existence of a (timelike) Killing vector, and are not restricted to spherically symmetric spacetimes (or similar ones, in which the Kodama vector can be defined). They are based instead on almost-Killing vectors, which could in principle be defined on generic spacetimes. We provide local arguments, based on energy density profiles in highly simplified (stationary, rigidly-rotating) star models, which confirm the physical interest of these 'almost-Killing currents'. A mass function is defined in this way for the spherical case, qualitatively different from the Hern\'andez-Misner mass function. An elliptic equation determining the new mass function is derived for the Tolman-Bondi spherically symmetric dust metrics, including a simple solution for the Oppenheimer-Schneider collapse. The equations for the non-symmetric case are shown to be of a mixed elliptic-hyperbolic nature. |
gr-qc/0509101 | Steve Drasco | Steve Drasco and Scott A. Hughes | Gravitational wave snapshots of generic extreme mass ratio inspirals | Minor changes in response to comments from readers, referees, and
editors. Final version, as it will appear in Physical Review D. Raw data and
a small program which will convert the data into waveforms lasting for
arbitrary lengths of time can be found at
http://gmunu.mit.edu/sdrasco/snapshots | Phys.Rev. D73 (2006) 024027 | 10.1103/PhysRevD.73.024027 | null | gr-qc astro-ph | null | Using black hole perturbation theory, we calculate the gravitational waves
produced by test particles moving on bound geodesic orbits about rotating black
holes. The orbits we consider are generic - simultaneously eccentric and
inclined. The waves can be described as having radial, polar, and azimuthal
"voices", each of which can be made to dominate by varying eccentricity and
inclination. Although each voice is generally apparent in the waveform, the
radial voice is prone to overpowering the others. We also compute the radiative
fluxes of energy and axial angular momentum at infinity and through the event
horizon. These fluxes, coupled to a prescription for the radiative evolution of
the Carter constant, will be used in future work to adiabatically evolve
through a sequence of generic orbits. This will enable the calculation of
inspiral waveforms that, while lacking certain important features, will
approximate those expected from astrophysical extreme mass ratio captures
sufficiently well to aid development of measurement algorithms on a relatively
short timescale.
| [
{
"created": "Mon, 26 Sep 2005 21:53:09 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jan 2006 23:19:18 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Drasco",
"Steve",
""
],
[
"Hughes",
"Scott A.",
""
]
] | Using black hole perturbation theory, we calculate the gravitational waves produced by test particles moving on bound geodesic orbits about rotating black holes. The orbits we consider are generic - simultaneously eccentric and inclined. The waves can be described as having radial, polar, and azimuthal "voices", each of which can be made to dominate by varying eccentricity and inclination. Although each voice is generally apparent in the waveform, the radial voice is prone to overpowering the others. We also compute the radiative fluxes of energy and axial angular momentum at infinity and through the event horizon. These fluxes, coupled to a prescription for the radiative evolution of the Carter constant, will be used in future work to adiabatically evolve through a sequence of generic orbits. This will enable the calculation of inspiral waveforms that, while lacking certain important features, will approximate those expected from astrophysical extreme mass ratio captures sufficiently well to aid development of measurement algorithms on a relatively short timescale. |
1001.1330 | Simone Mercuri | Simone Mercuri | Introduction to Loop Quantum Gravity | 91 pages, based on two invited lectures given at the 5th
International School on Field Theory and Gravitation, April 20-24, 2009
Cuiaba city, Brazil | PoS ISFTG:016, 2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The questions I have been asked during the 5th International School on Field
Theory and Gravitation, have compelled me to give an account of the premises
that I consider important for a beginner's approach to Loop Quantum Gravity.
After a description of some general arguments and an introduction to the
canonical theory of gravity, I review the background independent approach to
quantum gravity, giving only a brief survey of Loop Quantum Gravity.
| [
{
"created": "Fri, 8 Jan 2010 18:27:26 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Mercuri",
"Simone",
""
]
] | The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity. |
gr-qc/0209111 | Hisaaki Shinkai | Hisa-aki Shinkai and Gen Yoneda | Re-formulating the Einstein equations for stable numerical simulations:
Formulation Problem in Numerical Relativity | 50 pages, 18 figs, LaTeX. This is a review for a part of the book
"Progress in Astronomy and Astrophysics" (Nova Science Publ., 2003?). (Fig.2
is missing due to the file-size limitation). ver 2: added subtitle, revised
several comments, replaced Fig.8(b), and updated references | null | null | null | gr-qc astro-ph math-ph math.MP | null | We review recent efforts to re-formulate the Einstein equations for fully
relativistic numerical simulations. The so-called numerical relativity
(computational simulations in general relativity) is a promising research field
matching with ongoing astrophysical observations such as gravitational wave
astronomy. Many trials for longterm stable and accurate simulations of binary
compact objects have revealed that mathematically equivalent sets of evolution
equations show different numerical stability in free evolution schemes. In this
article, we first review the efforts of the community, categorizing them into
the following three directions: (1) modifications of the standard
Arnowitt-Deser-Misner equations initiated by the Kyoto group, (2) rewriting of
the evolution equations in hyperbolic form, and (3) construction of an
"asymptotically constrained" system. We next introduce our idea for explaining
these evolution behaviors in a unified way using eigenvalue analysis of the
constraint propagation equations. The modifications of (or adjustments to) the
evolution equations change the character of constraint propagation, and several
particular adjustments using constraints are expected to diminish the
constraint-violating modes. We propose several new adjusted evolution
equations, and include some numerical demonstrations. We conclude by discussing
some directions for future research.
| [
{
"created": "Mon, 30 Sep 2002 00:42:45 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Dec 2002 08:27:42 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Shinkai",
"Hisa-aki",
""
],
[
"Yoneda",
"Gen",
""
]
] | We review recent efforts to re-formulate the Einstein equations for fully relativistic numerical simulations. The so-called numerical relativity (computational simulations in general relativity) is a promising research field matching with ongoing astrophysical observations such as gravitational wave astronomy. Many trials for longterm stable and accurate simulations of binary compact objects have revealed that mathematically equivalent sets of evolution equations show different numerical stability in free evolution schemes. In this article, we first review the efforts of the community, categorizing them into the following three directions: (1) modifications of the standard Arnowitt-Deser-Misner equations initiated by the Kyoto group, (2) rewriting of the evolution equations in hyperbolic form, and (3) construction of an "asymptotically constrained" system. We next introduce our idea for explaining these evolution behaviors in a unified way using eigenvalue analysis of the constraint propagation equations. The modifications of (or adjustments to) the evolution equations change the character of constraint propagation, and several particular adjustments using constraints are expected to diminish the constraint-violating modes. We propose several new adjusted evolution equations, and include some numerical demonstrations. We conclude by discussing some directions for future research. |
2209.10564 | Sebastian V\"olkel | Sebastian H. V\"olkel, Nicola Franchini, Enrico Barausse, Emanuele
Berti | Constraining modifications of black hole perturbation potentials near
the light ring with quasinormal modes | 12 pages, 7 figures | Phys.Rev.D 106 (2022) 12, 124036 | 10.1103/PhysRevD.106.124036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In modified theories of gravity, the potentials appearing in the
Schr\"odinger-like equations that describe perturbations of non-rotating black
holes are also modified. In this paper we ask: can these modifications be
constrained with high-precision gravitational-wave measurements of the black
hole's quasinormal mode frequencies? We expand the modifications in a small
perturbative parameter regulating the deviation from the general-relativistic
potential, and in powers of $M/r$. We compute the quasinormal modes of the
modified potential up to quadratic order in the perturbative parameter. Then we
use Markov-chain-Monte-Carlo (MCMC) methods to recover the coefficients in the
$M/r$ expansion in an ``optimistic'' scenario where we vary them one at a time,
and in a ``pessimistic'' scenario where we vary them all simultaneously. In
both cases, we find that the bounds on the individual parameters are not
robust. Because quasinormal mode frequencies are related to the behavior of the
perturbation potential near the light ring, we propose a different strategy.
Inspired by Wentzel-Kramers-Brillouin (WKB) theory, we demonstrate that the
value of the potential and of its second derivative at the light ring can be
robustly constrained. These constraints allow for a more direct comparison
between tests based on black hole spectroscopy and observations of black hole
`shadows'' by the Event Horizon Telescope and future instruments.
| [
{
"created": "Wed, 21 Sep 2022 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 12 May 2023 15:36:40 GMT",
"version": "v2"
}
] | 2023-05-15 | [
[
"Völkel",
"Sebastian H.",
""
],
[
"Franchini",
"Nicola",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Berti",
"Emanuele",
""
]
] | In modified theories of gravity, the potentials appearing in the Schr\"odinger-like equations that describe perturbations of non-rotating black holes are also modified. In this paper we ask: can these modifications be constrained with high-precision gravitational-wave measurements of the black hole's quasinormal mode frequencies? We expand the modifications in a small perturbative parameter regulating the deviation from the general-relativistic potential, and in powers of $M/r$. We compute the quasinormal modes of the modified potential up to quadratic order in the perturbative parameter. Then we use Markov-chain-Monte-Carlo (MCMC) methods to recover the coefficients in the $M/r$ expansion in an ``optimistic'' scenario where we vary them one at a time, and in a ``pessimistic'' scenario where we vary them all simultaneously. In both cases, we find that the bounds on the individual parameters are not robust. Because quasinormal mode frequencies are related to the behavior of the perturbation potential near the light ring, we propose a different strategy. Inspired by Wentzel-Kramers-Brillouin (WKB) theory, we demonstrate that the value of the potential and of its second derivative at the light ring can be robustly constrained. These constraints allow for a more direct comparison between tests based on black hole spectroscopy and observations of black hole `shadows'' by the Event Horizon Telescope and future instruments. |
gr-qc/9604058 | Esko Keski-Vakkuri | Esko Keski-Vakkuri (Caltech) and Samir D. Mathur (MIT) | Quantum Gravity and Turning Points in the Semiclassical Approximation | 32 pages, 3 Postscript figures, uses epsf.tex and fps.sty, some
discussion, references and Acknowledgements added, version to appear in Phys.
Rev. D | Phys.Rev.D54:7391-7406,1996 | 10.1103/PhysRevD.54.7391 | MIT-CTP-2529, CALT-68-2056 | gr-qc hep-th | null | The wavefunctional in quantum gravity gives an amplitude for 3-geometries and
matter fields. The four-space is usually recovered in a semiclassical
approximation where the gravity variables are taken to oscillate rapidly
compared to matter variables; this recovers the Schrodinger evolution for the
matter. We examine turning points in the gravity variables where this
approximation appears to be troublesome. We investigate the effect of such a
turning point on the matter wavefunction, in simple quantum mechanical models
and in a closed minisuperspace cosmology. We find that after evolving
sufficiently far from the turning point the matter wavefunction recovers to a
form close to that predicted by the semiclassical approximation, and we compute
the leading correction (from `backreaction') in a simple model. We also show
how turning points can appear in the gravitational sector in dilaton gravity.
We give some remarks on the behavior of the wavefunctional in the vicinity of
turning points in the context of dilaton gravity black holes.
| [
{
"created": "Wed, 1 May 1996 00:19:02 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Aug 1996 05:35:18 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Aug 1996 04:37:40 GMT",
"version": "v3"
}
] | 2011-09-09 | [
[
"Keski-Vakkuri",
"Esko",
"",
"Caltech"
],
[
"Mathur",
"Samir D.",
"",
"MIT"
]
] | The wavefunctional in quantum gravity gives an amplitude for 3-geometries and matter fields. The four-space is usually recovered in a semiclassical approximation where the gravity variables are taken to oscillate rapidly compared to matter variables; this recovers the Schrodinger evolution for the matter. We examine turning points in the gravity variables where this approximation appears to be troublesome. We investigate the effect of such a turning point on the matter wavefunction, in simple quantum mechanical models and in a closed minisuperspace cosmology. We find that after evolving sufficiently far from the turning point the matter wavefunction recovers to a form close to that predicted by the semiclassical approximation, and we compute the leading correction (from `backreaction') in a simple model. We also show how turning points can appear in the gravitational sector in dilaton gravity. We give some remarks on the behavior of the wavefunctional in the vicinity of turning points in the context of dilaton gravity black holes. |
gr-qc/9705027 | Keisuke Taniguchi | Keisuke Taniguchi and Masaru Shibata | Solving the Darwin problem in the first post-Newtonian approximation of
general relativity | 33 pages, revtex, 4 figures(eps), accepted for publication in Phys.
Rev. D | Phys.Rev. D56 (1997) 798-810 | 10.1103/PhysRevD.56.798 | KUNS 1425, OU-TAP 55 | gr-qc | null | We analytically calculate the equilibrium sequence of the corotating binary
stars of incompressible fluid in the first post-Newtonian(PN) approximation of
general relativity. By calculating the total energy and total angular momentum
of the system as a function of the orbital separation, we investigate the
innermost stable circular orbit for corotating binary(we call it ISCCO). It is
found that by the first PN effect, the orbital separation of the binary at the
ISCCO becomes small with increase of the compactness of each star, and as a
result, the orbital angular velocity at the ISCCO increases. These behaviors
agree with previous numerical works.
| [
{
"created": "Tue, 13 May 1997 10:12:40 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Taniguchi",
"Keisuke",
""
],
[
"Shibata",
"Masaru",
""
]
] | We analytically calculate the equilibrium sequence of the corotating binary stars of incompressible fluid in the first post-Newtonian(PN) approximation of general relativity. By calculating the total energy and total angular momentum of the system as a function of the orbital separation, we investigate the innermost stable circular orbit for corotating binary(we call it ISCCO). It is found that by the first PN effect, the orbital separation of the binary at the ISCCO becomes small with increase of the compactness of each star, and as a result, the orbital angular velocity at the ISCCO increases. These behaviors agree with previous numerical works. |
2012.15331 | Luciano Petruzziello | Victor A. S. V. Bittencourt, Massimo Blasone, Fabrizio Illuminati,
Gaetano Lambiase, Giuseppe Gaetano Luciano, Luciano Petruzziello | Quantum nonlocality in extended theories of gravity | null | Phys. Rev. D 103, 044051 (2021) | 10.1103/PhysRevD.103.044051 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate how pure-state Einstein-Podolsky-Rosen correlations in the
internal degrees of freedom of massive particles are affected by a curved
spacetime background described by extended theories of gravity. We consider
models for which the corrections to the Einstein-Hilbert action are quadratic
in the curvature invariants and we focus on the weak-field limit. We quantify
nonlocal quantum correlations by means of the violation of the
Clauser-Horne-Shimony-Holt inequality, and show how a curved background
suppresses the violation by a leading term due to general relativity and a
further contribution due to the corrections to Einstein gravity. Our results
can be generalized to massless particles such as photon pairs and can thus be
suitably exploited to devise precise experimental tests of extended models of
gravity.
| [
{
"created": "Wed, 30 Dec 2020 21:35:51 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Bittencourt",
"Victor A. S. V.",
""
],
[
"Blasone",
"Massimo",
""
],
[
"Illuminati",
"Fabrizio",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Petruzziello",
"Luciano",
""
]
] | We investigate how pure-state Einstein-Podolsky-Rosen correlations in the internal degrees of freedom of massive particles are affected by a curved spacetime background described by extended theories of gravity. We consider models for which the corrections to the Einstein-Hilbert action are quadratic in the curvature invariants and we focus on the weak-field limit. We quantify nonlocal quantum correlations by means of the violation of the Clauser-Horne-Shimony-Holt inequality, and show how a curved background suppresses the violation by a leading term due to general relativity and a further contribution due to the corrections to Einstein gravity. Our results can be generalized to massless particles such as photon pairs and can thus be suitably exploited to devise precise experimental tests of extended models of gravity. |
1108.0942 | Gideon Livshits | Joseph Katz and Gideon I. Livshits | Affine Gravity, Palatini Formalism and Charges | The work is dedicated to Joshua Goldberg from whom I learned and got
interested in conservation laws in General Relativity (J.K) | null | 10.1007/s10714-011-1265-8 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Affine gravity and the Palatini formalism contribute both to produce a simple
and unique formula for calculating charges at spatial and null infinity for
Lovelock type Lagrangians whose variational derivatives do not depend on
second-order derivatives of the field components. The method is based on the
covariant generalization due to Julia and Silva of the Regge-Teitelboim
procedure that was used to define properly the mass in the classical
formulation of Einstein's theory of gravity. Numerous applications reproduce
standard results obtained by other secure but mostly specialized methods. As a
novel application we calculate the Bondi energy loss in five dimensional
gravity, based on the asymptotic solution given by Tanabe, Tanahashi and
Shiromizu, and obtain, as expected, the same result. We also give the
superpotential for Einstein-Gauss-Bonnet gravity and find the superpotential
for Lovelock theories of gravity when the number of dimensions tends to
infinity with maximally symmetrical boundaries. The paper is written in
standard component formalism.
| [
{
"created": "Wed, 3 Aug 2011 20:12:19 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Katz",
"Joseph",
""
],
[
"Livshits",
"Gideon I.",
""
]
] | Affine gravity and the Palatini formalism contribute both to produce a simple and unique formula for calculating charges at spatial and null infinity for Lovelock type Lagrangians whose variational derivatives do not depend on second-order derivatives of the field components. The method is based on the covariant generalization due to Julia and Silva of the Regge-Teitelboim procedure that was used to define properly the mass in the classical formulation of Einstein's theory of gravity. Numerous applications reproduce standard results obtained by other secure but mostly specialized methods. As a novel application we calculate the Bondi energy loss in five dimensional gravity, based on the asymptotic solution given by Tanabe, Tanahashi and Shiromizu, and obtain, as expected, the same result. We also give the superpotential for Einstein-Gauss-Bonnet gravity and find the superpotential for Lovelock theories of gravity when the number of dimensions tends to infinity with maximally symmetrical boundaries. The paper is written in standard component formalism. |
2402.03606 | Yun Soo Myung | Yun Soo Myung | Shadow bound of black holes with dark matter halo | 10 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the shadow cast of black holes immersed in a dark matter halo.
We use the M87* shadow data obtained by the EHT collaboration to constrain two
parameters ($M,a$) of dark matter halo surrounding a black hole with mass
$M_{\rm bh}$. For $a\ge10.8M$, we find the favored region (shadow bound), while
the disfavored region is found for $a<10.8M$ when imposing the EHT results.
This shadow bound is much less than the observation bound of galaxies ($a\ge
10^4 M$).
| [
{
"created": "Tue, 6 Feb 2024 00:46:54 GMT",
"version": "v1"
}
] | 2024-02-07 | [
[
"Myung",
"Yun Soo",
""
]
] | We investigate the shadow cast of black holes immersed in a dark matter halo. We use the M87* shadow data obtained by the EHT collaboration to constrain two parameters ($M,a$) of dark matter halo surrounding a black hole with mass $M_{\rm bh}$. For $a\ge10.8M$, we find the favored region (shadow bound), while the disfavored region is found for $a<10.8M$ when imposing the EHT results. This shadow bound is much less than the observation bound of galaxies ($a\ge 10^4 M$). |
1905.09465 | T.G Zlosnik | Constantinos Skordis, Tom Zlosnik | A general class of gravitational theories as alternatives to dark matter
where the speed of gravity always equals the speed of light | null | null | 10.1103/PhysRevD.100.104013 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A number of theories of gravity have been proposed as proxies for dark matter
in the regime of galaxies and cosmology. The recent observations of
gravitational waves (GW170817) from the merger of two neutron stars, followed
by an electromagnetic counterpart (GW170817a) have placed stringent constraints
on the difference of the speed of gravity to the speed of light, severely
restricting the phenomenological viability of such theories. We revisit the
impact of these observations on the Tensor-Vector-Scalar (TeVeS) paradigm of
relativistic Modified Newtonian Dynamics (MOND) and demonstrate the existence
of a previously unknown class of this paradigm where the speed of gravity
always equals the speed of light. We show that this holds without altering the
usual (bimetric) MOND phenomenology in galaxies.
| [
{
"created": "Thu, 23 May 2019 11:02:50 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Skordis",
"Constantinos",
""
],
[
"Zlosnik",
"Tom",
""
]
] | A number of theories of gravity have been proposed as proxies for dark matter in the regime of galaxies and cosmology. The recent observations of gravitational waves (GW170817) from the merger of two neutron stars, followed by an electromagnetic counterpart (GW170817a) have placed stringent constraints on the difference of the speed of gravity to the speed of light, severely restricting the phenomenological viability of such theories. We revisit the impact of these observations on the Tensor-Vector-Scalar (TeVeS) paradigm of relativistic Modified Newtonian Dynamics (MOND) and demonstrate the existence of a previously unknown class of this paradigm where the speed of gravity always equals the speed of light. We show that this holds without altering the usual (bimetric) MOND phenomenology in galaxies. |
0803.0125 | Ioannis Kouletsis | Ioannis Kouletsis | Covariance and Time Regained in Canonical General Relativity | 41 pages, no figures | Phys.Rev.D78:064014,2008 | 10.1103/PhysRevD.78.064014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Canonical vacuum gravity is expressed in generally-covariant form in order
that spacetime diffeomorphisms be represented within its equal-time phase
space. In accordance with the principle of general covariance, the time mapping
${\T}: {\yman} \to {\rman}$ and the space mapping ${\X}: {\yman} \to {\xman}$
that define the Dirac-ADM foliation are incorporated into the framework of the
Hilbert variational principle. The resulting canonical action encompasses all
individual Dirac-ADM actions, corresponding to different choices of foliating
vacuum spacetimes by spacelike hypersurfaces. In this framework, spacetime
observables, namely, dynamical variables that are invariant under spacetime
diffeomorphisms, are not necessarily invariant under the deformations of the
mappings $\T$ and $\X$, nor are they constants of the motion. Dirac observables
form only a subset of spacetime observables that are invariant under the
transformations of $\T$ and $\X$ and do not evolve in time. The conventional
interpretation of the canonical theory, due to Bergmann and Dirac, can be
recovered only by postulating that the transformations of the reference system
$({\T},{\X})$ have no measurable consequences. If this postulate is not deemed
necessary, covariant canonical gravity admits no classical problem of time.
| [
{
"created": "Sun, 2 Mar 2008 14:09:39 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Mar 2008 15:46:17 GMT",
"version": "v2"
}
] | 2009-02-20 | [
[
"Kouletsis",
"Ioannis",
""
]
] | Canonical vacuum gravity is expressed in generally-covariant form in order that spacetime diffeomorphisms be represented within its equal-time phase space. In accordance with the principle of general covariance, the time mapping ${\T}: {\yman} \to {\rman}$ and the space mapping ${\X}: {\yman} \to {\xman}$ that define the Dirac-ADM foliation are incorporated into the framework of the Hilbert variational principle. The resulting canonical action encompasses all individual Dirac-ADM actions, corresponding to different choices of foliating vacuum spacetimes by spacelike hypersurfaces. In this framework, spacetime observables, namely, dynamical variables that are invariant under spacetime diffeomorphisms, are not necessarily invariant under the deformations of the mappings $\T$ and $\X$, nor are they constants of the motion. Dirac observables form only a subset of spacetime observables that are invariant under the transformations of $\T$ and $\X$ and do not evolve in time. The conventional interpretation of the canonical theory, due to Bergmann and Dirac, can be recovered only by postulating that the transformations of the reference system $({\T},{\X})$ have no measurable consequences. If this postulate is not deemed necessary, covariant canonical gravity admits no classical problem of time. |
1107.5002 | Wolfgang Wieland | Wolfgang M. Wieland | Twistorial phase space for complex Ashtekar variables | 18 pages, to appear in: Class. Quantum Grav | Class. Quantum Grav. 29 (2012) 045007 | 10.1088/0264-9381/29/4/045007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalise the SU(2) spinor framework of twisted geometries developed by
Dupuis, Freidel, Livine, Speziale and Tambornino to the Lorentzian case, that
is the group SL(2,C). We show that the phase space for complex valued Ashtekar
variables on a spinnetwork graph can be decomposed in terms of twistorial
variables. To every link there are two twistors---one to each boundary
point---attached. The formalism provides a new derivation of the solution space
of the simplicity constraints of loop quantum gravity. Key properties of the
EPRL spinfoam model are perfectly recovered.
| [
{
"created": "Mon, 25 Jul 2011 17:20:13 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2012 10:58:27 GMT",
"version": "v2"
}
] | 2012-02-09 | [
[
"Wieland",
"Wolfgang M.",
""
]
] | We generalise the SU(2) spinor framework of twisted geometries developed by Dupuis, Freidel, Livine, Speziale and Tambornino to the Lorentzian case, that is the group SL(2,C). We show that the phase space for complex valued Ashtekar variables on a spinnetwork graph can be decomposed in terms of twistorial variables. To every link there are two twistors---one to each boundary point---attached. The formalism provides a new derivation of the solution space of the simplicity constraints of loop quantum gravity. Key properties of the EPRL spinfoam model are perfectly recovered. |
1912.00685 | Shuang-Yong Zhou | Xue Sun and Shuang-Yong Zhou | Relativistic stars in mass-varying massive gravity | 9 pages, 9 figures; published in PRD | Phys. Rev. D 101, 044060 (2020) | 10.1103/PhysRevD.101.044060 | USTC-ICTS-19-29 | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mass-varying massive gravity allows the graviton mass to vary according to
different environments. We investigate neutron star and white dwarf solutions
in this theory and find that the graviton mass can become very large near the
compact stars and settle down quickly to small cosmological values away the
stars, similar to that of black holes in the theory. It is found that there
exists a tower of compact star solutions where the graviton mass decreases
radially to zero non-trivially. We compute the massive graviton effects on the
mass-radius relations of the compact stars, and also compare the relative
strengths between neutron stars and white dwarfs in constraining the parameter
space of mass-varying massive gravity.
| [
{
"created": "Mon, 2 Dec 2019 11:09:49 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Mar 2020 08:35:22 GMT",
"version": "v2"
}
] | 2020-03-31 | [
[
"Sun",
"Xue",
""
],
[
"Zhou",
"Shuang-Yong",
""
]
] | Mass-varying massive gravity allows the graviton mass to vary according to different environments. We investigate neutron star and white dwarf solutions in this theory and find that the graviton mass can become very large near the compact stars and settle down quickly to small cosmological values away the stars, similar to that of black holes in the theory. It is found that there exists a tower of compact star solutions where the graviton mass decreases radially to zero non-trivially. We compute the massive graviton effects on the mass-radius relations of the compact stars, and also compare the relative strengths between neutron stars and white dwarfs in constraining the parameter space of mass-varying massive gravity. |
2402.03733 | Haximjan Abdusattar | Haximjan Abdusattar, Shi-Bei Kong | Cooling-Heating Properties of the FRW Universe in Gravity with a
Generalized Conformal Scalar Field | 9 pages, 4 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, within the framework of modified gravity involving a conformal
scalar field, we investigate the Joule-Thomson expansion of the FRW universe to
identify cooling and heating regions. Notably, we observe that the
Joule-Thomson coefficient, denoted as $\mu$, diverges at $R_A=\sqrt{-2\alpha}$
when $\alpha<0$, aligning with the thermodynamic singularity of the FRW
universe. Additionally, we determine the inversion temperature and inversion
pressure for the FRW universe, and illustrate the characteristics of inversion
curves and isenthalpic curves in the $T$-$P$ plane. We compare these findings
with results obtained under Einstein gravity, discussing the influence of the
modification term on the cooling and heating properties of the FRW universe.
This work contributes significantly to a deeper understanding of the formation
of cooling and heating regions within the FRW universe, thereby advancing our
comprehension of the physical mechanisms that govern the expansion of our
universe.
| [
{
"created": "Tue, 6 Feb 2024 05:59:40 GMT",
"version": "v1"
}
] | 2024-02-07 | [
[
"Abdusattar",
"Haximjan",
""
],
[
"Kong",
"Shi-Bei",
""
]
] | In this paper, within the framework of modified gravity involving a conformal scalar field, we investigate the Joule-Thomson expansion of the FRW universe to identify cooling and heating regions. Notably, we observe that the Joule-Thomson coefficient, denoted as $\mu$, diverges at $R_A=\sqrt{-2\alpha}$ when $\alpha<0$, aligning with the thermodynamic singularity of the FRW universe. Additionally, we determine the inversion temperature and inversion pressure for the FRW universe, and illustrate the characteristics of inversion curves and isenthalpic curves in the $T$-$P$ plane. We compare these findings with results obtained under Einstein gravity, discussing the influence of the modification term on the cooling and heating properties of the FRW universe. This work contributes significantly to a deeper understanding of the formation of cooling and heating regions within the FRW universe, thereby advancing our comprehension of the physical mechanisms that govern the expansion of our universe. |
0708.3038 | Salvatore Capozziello | S. Capozziello, R. Cianci, C. Stornaiolo, S. Vignolo | f(R) Gravity with Torsion: The Metric-Affine Approach | 12 pages | Class.Quant.Grav.24:6417-6430,2007 | 10.1088/0264-9381/24/24/015 | null | gr-qc | null | The role of torsion in f(R) gravity is considered in the framework of
metric-affine formalism. We discuss the field equations in empty space and in
presence of perfect fluid matter taking into account the analogy with the
Palatini formalism. As a result, the extra curvature and torsion degrees of
freedom can be dealt as an effective scalar field of fully geometric origin.
From a cosmological point of view, such a geometric description could account
for the whole Dark Side of the Universe.
| [
{
"created": "Wed, 22 Aug 2007 15:39:38 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Aug 2007 10:09:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Capozziello",
"S.",
""
],
[
"Cianci",
"R.",
""
],
[
"Stornaiolo",
"C.",
""
],
[
"Vignolo",
"S.",
""
]
] | The role of torsion in f(R) gravity is considered in the framework of metric-affine formalism. We discuss the field equations in empty space and in presence of perfect fluid matter taking into account the analogy with the Palatini formalism. As a result, the extra curvature and torsion degrees of freedom can be dealt as an effective scalar field of fully geometric origin. From a cosmological point of view, such a geometric description could account for the whole Dark Side of the Universe. |
gr-qc/0001049 | Jiri Podolsky | J. Podolsky, J. B. Griffiths | The collision and snapping of cosmic strings generating spherical
impulsive gravitational waves | 10 pages, 6 figures, To appear in Class. Quantum Grav | Class.Quant.Grav.17:1401-1413,2000 | 10.1088/0264-9381/17/6/306 | null | gr-qc | null | The Penrose method for constructing spherical impulsive gravitational waves
is investigated in detail, including alternative spatial sections and an
arbitrary cosmological constant. The resulting waves include those that are
generated by a snapping cosmic string. The method is used to construct an
explicit exact solution of Einstein's equations describing the collision of two
nonaligned cosmic strings in a Minkowski background which snap at their point
of collision.
| [
{
"created": "Mon, 17 Jan 2000 17:59:44 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Podolsky",
"J.",
""
],
[
"Griffiths",
"J. B.",
""
]
] | The Penrose method for constructing spherical impulsive gravitational waves is investigated in detail, including alternative spatial sections and an arbitrary cosmological constant. The resulting waves include those that are generated by a snapping cosmic string. The method is used to construct an explicit exact solution of Einstein's equations describing the collision of two nonaligned cosmic strings in a Minkowski background which snap at their point of collision. |
2405.05038 | Sreejith Nair | Sreejith Nair, Aditya Vijaykumar, Sudipta Sarkar | Bounds on the charge of the graviton using gravitational wave
observations | 9 pages, 3 figures | null | null | LIGO DCC P2400160 | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the graviton possesses a non-zero charge $q_g$, gravitational waves (GW)
originating from astrophysical sources would experience an additional time
delay due to intergalactic magnetic fields. This would result in a modification
of the phase evolution of the observed GW signal similar to the effect induced
by a massive graviton. As a result, we can reinterpret the most recent upper
limits on the graviton's mass as constraints on the joint mass-charge parameter
space, finding $|q_g|/{e} < 3\times 10^{-34}$ where $e$ represents the charge
of an electron. Additionally, we illustrate that a charged graviton would
introduce a constant phase difference in the gravitational waves detected by
two spatially separated GW detectors due to the Aharonov-Bohm effect. Using the
non-observation of such a phase difference for the GW event GW190814, we
establish a mass-independent constraint $|q_g|/e < 2\times 10^{-26}$. To the
best of our knowledge, our results constitute the first-ever bounds on the
charge of the graviton. We also discuss various caveats involved in our
measurements and prospects for strengthening these bounds with future GW
observations.
| [
{
"created": "Wed, 8 May 2024 13:11:02 GMT",
"version": "v1"
}
] | 2024-05-09 | [
[
"Nair",
"Sreejith",
""
],
[
"Vijaykumar",
"Aditya",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | If the graviton possesses a non-zero charge $q_g$, gravitational waves (GW) originating from astrophysical sources would experience an additional time delay due to intergalactic magnetic fields. This would result in a modification of the phase evolution of the observed GW signal similar to the effect induced by a massive graviton. As a result, we can reinterpret the most recent upper limits on the graviton's mass as constraints on the joint mass-charge parameter space, finding $|q_g|/{e} < 3\times 10^{-34}$ where $e$ represents the charge of an electron. Additionally, we illustrate that a charged graviton would introduce a constant phase difference in the gravitational waves detected by two spatially separated GW detectors due to the Aharonov-Bohm effect. Using the non-observation of such a phase difference for the GW event GW190814, we establish a mass-independent constraint $|q_g|/e < 2\times 10^{-26}$. To the best of our knowledge, our results constitute the first-ever bounds on the charge of the graviton. We also discuss various caveats involved in our measurements and prospects for strengthening these bounds with future GW observations. |
2210.14062 | Zhen Li | Zhen Li | Scalar Perturbation Around Rotating Regular Black Hole: Superradiance
Instability and Quasinormal Modes | 10 pages, 3 tables, 4 figures, Accepted for publication in Physical
Review D | null | 10.1103/PhysRevD.107.044013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes provide a natural laboratory to study particle physics and
astrophysics. When black holes are surrounded by matter fields, there will be
plenty of phenomena which can have observational consequences, from which we
can learn about the matter fields as well as black hole spacetime. In this
work, we investigate the massive scalar field in the vicinity of a newly
proposed rotating regular black hole inspired by quantum gravity. We will
especially investigate how this non-singular spactime will affect the
superradiance instability and quasinormal modes of the scalar filed. We derive
the superradiant conditions and the amplification factor by using the
Matching-asymptotic Method, and the quasinormal modes are computed through
Continued Fraction Method. In the Kerr limit, the results are in excellent
agreements with previous research. We also demonstrate how the quasinormal
modes will change as a function of black hole spin, regularity described by a
parameter $k$ and scalar field mass respectively, with other parameters taking
specific values.
| [
{
"created": "Tue, 25 Oct 2022 14:44:12 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jan 2023 19:33:41 GMT",
"version": "v2"
}
] | 2023-02-22 | [
[
"Li",
"Zhen",
""
]
] | Black holes provide a natural laboratory to study particle physics and astrophysics. When black holes are surrounded by matter fields, there will be plenty of phenomena which can have observational consequences, from which we can learn about the matter fields as well as black hole spacetime. In this work, we investigate the massive scalar field in the vicinity of a newly proposed rotating regular black hole inspired by quantum gravity. We will especially investigate how this non-singular spactime will affect the superradiance instability and quasinormal modes of the scalar filed. We derive the superradiant conditions and the amplification factor by using the Matching-asymptotic Method, and the quasinormal modes are computed through Continued Fraction Method. In the Kerr limit, the results are in excellent agreements with previous research. We also demonstrate how the quasinormal modes will change as a function of black hole spin, regularity described by a parameter $k$ and scalar field mass respectively, with other parameters taking specific values. |
0903.4230 | Hiromi Saida | Miho Urano, Akira Tomimatsu and Hiromi Saida | Mechanical First Law of Black Hole Spacetimes with Cosmological Constant
and Its Application to Schwarzschild-de Sitter Spacetime | Accepted for publication in Classical and Quantum Gravity, 16 pages,
no figure | Class.Quant.Grav.26:105010,2009 | 10.1088/0264-9381/26/10/105010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mechanical first law (MFL) of black hole spacetimes is a geometrical
relation which relates variations of mass parameter and horizon area. While it
is well known that the MFL of asymptotic flat black hole is equivalent to its
thermodynamical first law, however we do not know the detail of MFL of black
hole spacetimes with cosmological constant which possess black hole and
cosmological event horizons. Then this paper aims to formulate an MFL of the
two-horizon spacetimes. For this purpose, we try to include the effects of two
horizons in the MFL. To do so, we make use of the Iyer-Wald formalism and
extend it to regard the mass parameter and the cosmological constant as two
independent variables which make it possible to treat the two horizons on the
same footing. Our extended Iyer-Wald formalism preserves the existence of
conserved Noether current and its associated Noether charge, and gives the
abstract form of MFL of black hole spacetimes with cosmological constant. Then,
as a representative application of that formalism, we derive the MFL of
Schwarzschild-de Sitter (SdS) spacetime. Our MFL of SdS spacetime relates the
variations of three quantities; the mass parameter, the total area of two
horizons and the volume enclosed by two horizons. If our MFL is regarded as a
thermodynamical first law of SdS spacetime, it offers a thermodynamically
consistent description of SdS black hole evaporation process: The mass
decreases while the volume and the entropy increase. In our suggestion, the
generalized second law is not needed to ensure the second law of SdS
thermodynamics for its evaporation process.
| [
{
"created": "Wed, 25 Mar 2009 03:33:36 GMT",
"version": "v1"
}
] | 2009-05-20 | [
[
"Urano",
"Miho",
""
],
[
"Tomimatsu",
"Akira",
""
],
[
"Saida",
"Hiromi",
""
]
] | The mechanical first law (MFL) of black hole spacetimes is a geometrical relation which relates variations of mass parameter and horizon area. While it is well known that the MFL of asymptotic flat black hole is equivalent to its thermodynamical first law, however we do not know the detail of MFL of black hole spacetimes with cosmological constant which possess black hole and cosmological event horizons. Then this paper aims to formulate an MFL of the two-horizon spacetimes. For this purpose, we try to include the effects of two horizons in the MFL. To do so, we make use of the Iyer-Wald formalism and extend it to regard the mass parameter and the cosmological constant as two independent variables which make it possible to treat the two horizons on the same footing. Our extended Iyer-Wald formalism preserves the existence of conserved Noether current and its associated Noether charge, and gives the abstract form of MFL of black hole spacetimes with cosmological constant. Then, as a representative application of that formalism, we derive the MFL of Schwarzschild-de Sitter (SdS) spacetime. Our MFL of SdS spacetime relates the variations of three quantities; the mass parameter, the total area of two horizons and the volume enclosed by two horizons. If our MFL is regarded as a thermodynamical first law of SdS spacetime, it offers a thermodynamically consistent description of SdS black hole evaporation process: The mass decreases while the volume and the entropy increase. In our suggestion, the generalized second law is not needed to ensure the second law of SdS thermodynamics for its evaporation process. |
1703.06763 | Muhammad Sharif | M. Sharif and Iqra Nawazish | Cosmological Analysis of Scalar Field Models in f(R,T) Gravity | 25 pages, 8 figures, to appear in EPJC | Eur. Phys. J. C 77(2017)198 | 10.1140/epjc/s10052-017-4773-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper determines the existence of Noether symmetry in non-minimally
coupled $f(R,T)$ gravity admitting minimal coupling with scalar field models.
We consider a generalized spacetime which corresponds to different anisotropic
and homogeneous universe models. We formulate symmetry generators along with
conserved quantities through Noether symmetry technique for direct and indirect
curvature-matter coupling. For dust and perfect fluids, we evaluate exact
solutions and construct their cosmological analysis through some cosmological
parameters. We conclude that decelerated expansion is obtained for quintessence
model with dust distribution while perfect fluid with dominating potential
energy over kinetic energy leads to current cosmic expansion for both phantom
as well as quintessence models.
| [
{
"created": "Thu, 16 Mar 2017 07:31:53 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Sharif",
"M.",
""
],
[
"Nawazish",
"Iqra",
""
]
] | This paper determines the existence of Noether symmetry in non-minimally coupled $f(R,T)$ gravity admitting minimal coupling with scalar field models. We consider a generalized spacetime which corresponds to different anisotropic and homogeneous universe models. We formulate symmetry generators along with conserved quantities through Noether symmetry technique for direct and indirect curvature-matter coupling. For dust and perfect fluids, we evaluate exact solutions and construct their cosmological analysis through some cosmological parameters. We conclude that decelerated expansion is obtained for quintessence model with dust distribution while perfect fluid with dominating potential energy over kinetic energy leads to current cosmic expansion for both phantom as well as quintessence models. |
2209.01595 | Emmanuil Saridakis | Petros Asimakis, Emmanuel N. Saridakis, Spyros Basilakos, Kuralay
Yesmakhanova | Big Bang Nucleosynthesis constraints on $f(T,T_G)$ gravity | 9 pages, 3 figures, invited paper to appear in Universe Special Issue
"Torsion-Gravity and Spinors in Fundamental Theoretical Physics", Special
Issue Editor: Luca Fabbri | null | 10.3390/universe8090486 | Universe 8 (2022) 9, 486 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We confront $f(T,T_G)$ gravity, with Big Bang Nucleosynthesis (BBN)
requirements. The former is obtained using both the torsion scalar, as well as
the teleparallel equivalent of the Gauss-Bonnet term, in the Lagrangian,
resulting to modified Friedmann equations in which the extra torsional terms
constitute an effective dark energy sector. We calculate the deviations of the
freeze-out temperature $T_f$, caused by the extra torsion terms in comparison
to $\Lambda$CDM paradigm. Then we impose five specific $f(T,T_G)$ models and we
extract the constraints on the model parameters in order for the ratio $|\Delta
T_f/ T_f|$ to satisfy the observational BBN bound. As we find, in most of the
models the involved parameters are bounded in a narrow window around their
General Relativity values as expected, as in the power-law model where the
exponent $n$ needs to be $n\lesssim 0.5$. Nevertheless the logarithmic model
can easily satisfy the BBN constraints for large regions of the model
parameters. This feature should be taken into account in future model building.
| [
{
"created": "Sun, 4 Sep 2022 11:14:17 GMT",
"version": "v1"
}
] | 2022-09-20 | [
[
"Asimakis",
"Petros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Yesmakhanova",
"Kuralay",
""
]
] | We confront $f(T,T_G)$ gravity, with Big Bang Nucleosynthesis (BBN) requirements. The former is obtained using both the torsion scalar, as well as the teleparallel equivalent of the Gauss-Bonnet term, in the Lagrangian, resulting to modified Friedmann equations in which the extra torsional terms constitute an effective dark energy sector. We calculate the deviations of the freeze-out temperature $T_f$, caused by the extra torsion terms in comparison to $\Lambda$CDM paradigm. Then we impose five specific $f(T,T_G)$ models and we extract the constraints on the model parameters in order for the ratio $|\Delta T_f/ T_f|$ to satisfy the observational BBN bound. As we find, in most of the models the involved parameters are bounded in a narrow window around their General Relativity values as expected, as in the power-law model where the exponent $n$ needs to be $n\lesssim 0.5$. Nevertheless the logarithmic model can easily satisfy the BBN constraints for large regions of the model parameters. This feature should be taken into account in future model building. |
2107.02208 | Shammi Tahura | Shammi Tahura, David A. Nichols, Kent Yagi | Gravitational-wave memory effects in Brans-Dicke theory: Waveforms and
effects in the post-Newtonian approximation | 24 pages; v2: matches published version | null | 10.1103/PhysRevD.104.104010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave (GW) memory effects produce permanent shifts in the GW
strain and its time integrals after the passage of a burst of GWs. Their
presence is closely tied to symmetries of asymptotically flat spacetimes and
fluxes of conserved charges conjugate to these symmetries. While the
phenomenology of GW memory effects is well understood in general relativity
(GR), it is less well understood in the many modifications to GR. We recently
computed asymptotically flat solutions, symmetries, conserved quantities, and
GW memory effects in one such modified theory: Brans-Dicke theory. In this
paper, we apply our results from this earlier work to compute the GW memories
from compact binaries in the post-Newtonian (PN) approximation. In addition to
taking the PN limit of these effects, we work in the approximation that the
energy and angular momentum losses through scalar radiation are small compared
to the energy and angular momentum losses through (tensor) GWs. We focus on the
tensor (as opposed to scalar) GW memory effect, which we compute through
Newtonian order, and the small differences induced by scalar radiation at this
order. Specifically, we compute the nonlinear parts of the tensor displacement
and spin GW memory effects produced during the inspiral of quasicircular,
nonprecessing binaries in Brans-Dicke theory. Because the energy radiated
through the scalar dipole moment appears as a -1 PN order-effect, then in this
approximation, the displacement memory has a logarithmic dependence on the PN
parameter and the spin memory has a relative -1 PN-order correction; these
corrections are ultimately small because they are related to the total energy
and angular momentum radiated in the scalar field, respectively. At Newtonian
order, the scalar radiation also gives rise to a sky pattern of the memory
effect around an isolated source that differs from that of the memory effect in
GR.
| [
{
"created": "Mon, 5 Jul 2021 18:19:22 GMT",
"version": "v1"
},
{
"created": "Fri, 20 May 2022 19:20:36 GMT",
"version": "v2"
}
] | 2022-05-24 | [
[
"Tahura",
"Shammi",
""
],
[
"Nichols",
"David A.",
""
],
[
"Yagi",
"Kent",
""
]
] | Gravitational-wave (GW) memory effects produce permanent shifts in the GW strain and its time integrals after the passage of a burst of GWs. Their presence is closely tied to symmetries of asymptotically flat spacetimes and fluxes of conserved charges conjugate to these symmetries. While the phenomenology of GW memory effects is well understood in general relativity (GR), it is less well understood in the many modifications to GR. We recently computed asymptotically flat solutions, symmetries, conserved quantities, and GW memory effects in one such modified theory: Brans-Dicke theory. In this paper, we apply our results from this earlier work to compute the GW memories from compact binaries in the post-Newtonian (PN) approximation. In addition to taking the PN limit of these effects, we work in the approximation that the energy and angular momentum losses through scalar radiation are small compared to the energy and angular momentum losses through (tensor) GWs. We focus on the tensor (as opposed to scalar) GW memory effect, which we compute through Newtonian order, and the small differences induced by scalar radiation at this order. Specifically, we compute the nonlinear parts of the tensor displacement and spin GW memory effects produced during the inspiral of quasicircular, nonprecessing binaries in Brans-Dicke theory. Because the energy radiated through the scalar dipole moment appears as a -1 PN order-effect, then in this approximation, the displacement memory has a logarithmic dependence on the PN parameter and the spin memory has a relative -1 PN-order correction; these corrections are ultimately small because they are related to the total energy and angular momentum radiated in the scalar field, respectively. At Newtonian order, the scalar radiation also gives rise to a sky pattern of the memory effect around an isolated source that differs from that of the memory effect in GR. |
1711.06357 | Jens Boos | Jens Boos, Valeri P. Frolov | Stationary black holes with stringy hair | 10 pages, 3 figures, matches the published version | Phys. Rev. D 97, 024024 (2018) | 10.1103/PhysRevD.97.024024 | Alberta-Thy-13-17 | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss properties of black holes which are pierced by special
configurations of cosmic strings. For static black holes we consider radial
strings in the limit when the number of strings grows to infinity while the
tension of each single string tends to zero. In a properly taken limit the
stress-energy tensor of the string distribution is finite. We call such matter
stringy matter. We present a solution of the Einstein equations for an
electrically charged static black hole with the stringy matter, with and
without cosmological constant. This solution is a warped product of two
metrics. One of them is a deformed two-sphere whose Gaussian curvature is
determined by the energy-density of the stringy matter. We discuss the
embedding of a corresponding distorted sphere into a three-dimensional
Euclidean space and formulate consistency conditions. We also found a relation
between the square of the Weyl tensor invariant of the four dimensional
spacetime of the stringy black holes and the energy density of the stringy
matter. In the second part of the paper, we discuss test stationary strings in
the Kerr geometry and in its Kerr-NUT-(A)dS generalizations. Explicit solutions
for strings that are regular at the event horizon are obtained. Using these
solutions the stress-energy tensor of the stringy matter in these geometries is
calculated. Extraction of the angular momentum from rotating black holes by
such strings is also discussed.
| [
{
"created": "Thu, 16 Nov 2017 23:49:15 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2018 19:28:24 GMT",
"version": "v2"
}
] | 2018-01-31 | [
[
"Boos",
"Jens",
""
],
[
"Frolov",
"Valeri P.",
""
]
] | We discuss properties of black holes which are pierced by special configurations of cosmic strings. For static black holes we consider radial strings in the limit when the number of strings grows to infinity while the tension of each single string tends to zero. In a properly taken limit the stress-energy tensor of the string distribution is finite. We call such matter stringy matter. We present a solution of the Einstein equations for an electrically charged static black hole with the stringy matter, with and without cosmological constant. This solution is a warped product of two metrics. One of them is a deformed two-sphere whose Gaussian curvature is determined by the energy-density of the stringy matter. We discuss the embedding of a corresponding distorted sphere into a three-dimensional Euclidean space and formulate consistency conditions. We also found a relation between the square of the Weyl tensor invariant of the four dimensional spacetime of the stringy black holes and the energy density of the stringy matter. In the second part of the paper, we discuss test stationary strings in the Kerr geometry and in its Kerr-NUT-(A)dS generalizations. Explicit solutions for strings that are regular at the event horizon are obtained. Using these solutions the stress-energy tensor of the stringy matter in these geometries is calculated. Extraction of the angular momentum from rotating black holes by such strings is also discussed. |
2109.08150 | Kimet Jusufi | Farruh Atamurotov, Kimet Jusufi, Mubasher Jamil, Ahmadjon
Abdujabbarov, Mustapha Azreg-A\"inou | Axion-plasmon or magnetized plasma effect on an observable shadow and
gravitational lensing of a Schwarzschild black hole | 14 pages, 9 figures. Accepted for publication in Physical Review D | Physical Review D 104, 064053 (2021) | 10.1103/PhysRevD.104.064053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the influence of the axion-plasmon, as proposed in
(Phys. Rev. Lett. 120, 181803 (2018)) on the optical properties of the
Schwarzschild black hole. Our aim is to provide a test to detect the effects of
a fixed axion background using black holes. To accomplish our goal, we explore
the effect of the axion-plasmon coupling on the motion of photons around the
Schwarzschild black hole and check the possibility of observing those effects
upon the black hole shadow, the gravitational deflection angle, Einstein rings
and shadow images obtained by radially infalling gas on a black hole within a
plasma medium. We find that these quantities are indeed affected by the
axion-plasmon coupling parameters which consequently generalize some of the
well-known results in the literature. It is shown that the size of the black
hole shadow decreases with increasing axion-plasmon if observed from
sufficiently large distance.
| [
{
"created": "Thu, 16 Sep 2021 07:36:32 GMT",
"version": "v1"
}
] | 2021-09-22 | [
[
"Atamurotov",
"Farruh",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
]
] | In this paper, we study the influence of the axion-plasmon, as proposed in (Phys. Rev. Lett. 120, 181803 (2018)) on the optical properties of the Schwarzschild black hole. Our aim is to provide a test to detect the effects of a fixed axion background using black holes. To accomplish our goal, we explore the effect of the axion-plasmon coupling on the motion of photons around the Schwarzschild black hole and check the possibility of observing those effects upon the black hole shadow, the gravitational deflection angle, Einstein rings and shadow images obtained by radially infalling gas on a black hole within a plasma medium. We find that these quantities are indeed affected by the axion-plasmon coupling parameters which consequently generalize some of the well-known results in the literature. It is shown that the size of the black hole shadow decreases with increasing axion-plasmon if observed from sufficiently large distance. |
1011.0895 | Fernando Porcelli Dr. | Fernando Porcelli and Giancarlo Scibona | On the Black Hole's Thermodynamics and the Entropic Origin of Gravity | 10 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Schwarzschild's black hole dynamics in presence of gravity is described
on using the thermodynamic equations of state for contractile materials. Its
entropy and temperature, obtained by using classical principles, reproduce the
results derived from quantum field theories and statistical mechanics. The
given results show that, by using the gravitational dynamics to reproduce the
thermodynamic equation TdS/dx = Fgravity, there is no way to establish the
entropic origin of gravity, because the results can be seen the other way
around.
| [
{
"created": "Wed, 3 Nov 2010 14:27:11 GMT",
"version": "v1"
}
] | 2010-11-04 | [
[
"Porcelli",
"Fernando",
""
],
[
"Scibona",
"Giancarlo",
""
]
] | The Schwarzschild's black hole dynamics in presence of gravity is described on using the thermodynamic equations of state for contractile materials. Its entropy and temperature, obtained by using classical principles, reproduce the results derived from quantum field theories and statistical mechanics. The given results show that, by using the gravitational dynamics to reproduce the thermodynamic equation TdS/dx = Fgravity, there is no way to establish the entropic origin of gravity, because the results can be seen the other way around. |
2104.04970 | Mengjie Wang | Mengjie Wang, Zhou Chen, Xin Tong, Qiyuan Pan, Jiliang Jing | Bifurcation of the Maxwell quasinormal spectrum on asymptotically
anti-de Sitter black holes | 7 pages, published in Phys. Rev. D | Phys.Rev.D 103 (2021) 6, 064079 | 10.1103/PhysRevD.103.064079 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Maxwell quasinormal spectrum on asymptotically anti-de Sitter
black holes with a set of two Robin type boundary conditions, by requiring the
energy flux to vanish at asymptotic infinity. Focusing, for illustrative
purposes, on Schwarzschild-anti-de Sitter black holes both without and with a
global monopole, we unveil that, on the one hand, the Maxwell quasinormal
spectrum bifurcates as the black hole radius increases for both boundary
conditions, which is termed the mode split effect; while on the other hand,
with an appropriate fixed black hole radius but increasing the monopole
parameter, the first (second) boundary condition may trigger (terminate) the
mode split effect.
| [
{
"created": "Sun, 11 Apr 2021 09:26:34 GMT",
"version": "v1"
}
] | 2021-04-13 | [
[
"Wang",
"Mengjie",
""
],
[
"Chen",
"Zhou",
""
],
[
"Tong",
"Xin",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
]
] | We study the Maxwell quasinormal spectrum on asymptotically anti-de Sitter black holes with a set of two Robin type boundary conditions, by requiring the energy flux to vanish at asymptotic infinity. Focusing, for illustrative purposes, on Schwarzschild-anti-de Sitter black holes both without and with a global monopole, we unveil that, on the one hand, the Maxwell quasinormal spectrum bifurcates as the black hole radius increases for both boundary conditions, which is termed the mode split effect; while on the other hand, with an appropriate fixed black hole radius but increasing the monopole parameter, the first (second) boundary condition may trigger (terminate) the mode split effect. |
1203.5774 | Salvador Robles-Perez | Salvador Robles-Perez | Entanglement arrow of time in the multiverse | 6 pages, 1 figure. Some changes have been made in Sec. III and one
figure has been removed | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper it is presented the model of a multiverse made up of entangled
pairs of universes. The arrow of time obtained from the principles of
thermodynamics and the arrow of time given by the thermodynamics of
entanglement for single universes are analyzed. The latter requires that the
single universes expand once they have crossed the quantum barrier at the
Euclidean regime. The possible relationship with respect to the grow of local
structures in a single universe is also discussed.
| [
{
"created": "Mon, 26 Mar 2012 19:48:21 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Apr 2012 10:15:06 GMT",
"version": "v2"
}
] | 2012-04-10 | [
[
"Robles-Perez",
"Salvador",
""
]
] | In this paper it is presented the model of a multiverse made up of entangled pairs of universes. The arrow of time obtained from the principles of thermodynamics and the arrow of time given by the thermodynamics of entanglement for single universes are analyzed. The latter requires that the single universes expand once they have crossed the quantum barrier at the Euclidean regime. The possible relationship with respect to the grow of local structures in a single universe is also discussed. |
2110.14730 | Kamiel Janssens | Kamiel Janssens and Katarina Martinovic and Nelson Christensen and
Patrick M. Meyers and Mairi Sakellariadou | Impact of Schumann resonances on the Einstein Telescope and projections
for the magnetic coupling function | May 30th 2022 - New version contains updated figures in agreement
with erratum: https://doi.org/10.1103/PhysRevD.105.109904 | Phys. Rev. D 104, 122006 (2021) | 10.1103/PhysRevD.104.122006 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Correlated magnetic noise in the form of Schumann resonances could introduce
limitations to the gravitational-wave background searches of future Earth-based
gravitational-wave detectors. We consider recorded magnetic activity at a
candidate site for the Einstein Telescope, and forecast the necessary measures
to ensure that magnetic contamination will not pose a threat to the science
goals of this third-generation detector. In addition to global magnetic
effects, we study local magnetic noise and the impact it might have on
co-located interferometers. We express our results as upper limits on the
coupling function of magnetic fields to the interferometer arms, implying that
any larger values of magnetic coupling into the strain channel would lead to a
reduction in the detectors' sensitivity. For gravitational-wave background
searches below $\sim 30$ Hz it will be necessary for the Einstein Telescope
magnetic isolation coupling to be two to four orders of magnitude better than
that measured in the current Advanced LIGO and Virgo detectors.
| [
{
"created": "Wed, 27 Oct 2021 19:31:50 GMT",
"version": "v1"
},
{
"created": "Mon, 30 May 2022 11:23:10 GMT",
"version": "v2"
}
] | 2022-05-31 | [
[
"Janssens",
"Kamiel",
""
],
[
"Martinovic",
"Katarina",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Meyers",
"Patrick M.",
""
],
[
"Sakellariadou",
"Mairi",
""
]
] | Correlated magnetic noise in the form of Schumann resonances could introduce limitations to the gravitational-wave background searches of future Earth-based gravitational-wave detectors. We consider recorded magnetic activity at a candidate site for the Einstein Telescope, and forecast the necessary measures to ensure that magnetic contamination will not pose a threat to the science goals of this third-generation detector. In addition to global magnetic effects, we study local magnetic noise and the impact it might have on co-located interferometers. We express our results as upper limits on the coupling function of magnetic fields to the interferometer arms, implying that any larger values of magnetic coupling into the strain channel would lead to a reduction in the detectors' sensitivity. For gravitational-wave background searches below $\sim 30$ Hz it will be necessary for the Einstein Telescope magnetic isolation coupling to be two to four orders of magnitude better than that measured in the current Advanced LIGO and Virgo detectors. |
1501.03687 | Rui Chen | Ge-Rui Chen and Yong-Chang Huang | Revisiting the tunneling spectrum and information recovery of a general
charged and rotating black hole | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we revisit the tunneling spectrum of a charged and rotating
black hole--Kerr-Newman black hole by using Parikh and Wilczek's tunneling
method and get the most general result compared with the works [9, 10]. We find
an ambiguity in Parikh and Wilczek's tunneling method, and give a reasonable
description. We use this general spectrum to discuss the information recovery
based on the Refs. [11-13]. For the tunneling spectrum we obtained, there exit
correlations between sequential Hawking radiations, information can be carried
out by such correlations, and the entropy is conserved during the radiation
process. So we resolve the information loss paradox based on the methods
[11-13] in the most general case.
| [
{
"created": "Thu, 15 Jan 2015 14:13:55 GMT",
"version": "v1"
}
] | 2015-01-16 | [
[
"Chen",
"Ge-Rui",
""
],
[
"Huang",
"Yong-Chang",
""
]
] | In this paper we revisit the tunneling spectrum of a charged and rotating black hole--Kerr-Newman black hole by using Parikh and Wilczek's tunneling method and get the most general result compared with the works [9, 10]. We find an ambiguity in Parikh and Wilczek's tunneling method, and give a reasonable description. We use this general spectrum to discuss the information recovery based on the Refs. [11-13]. For the tunneling spectrum we obtained, there exit correlations between sequential Hawking radiations, information can be carried out by such correlations, and the entropy is conserved during the radiation process. So we resolve the information loss paradox based on the methods [11-13] in the most general case. |
gr-qc/0612014 | Ettore Minguzzi | E. Minguzzi | Eisenhart's theorem and the causal simplicity of Eisenhart's spacetime | Latex2e, 29 pages, 2 figures, uses psfrag package. v2: a problem with
theorem 5.5, which was erroneously stated twice, and some misprints have been
fixed, v3: change of definition of function I in theorem 5.5 | Class.Quant.Grav.24:2781-2808,2007 | 10.1088/0264-9381/24/11/002 | null | gr-qc | null | We give a causal version of Eisenhart's geodesic characterization of
classical mechanics. We emphasize the geometric, coordinate independent
properties needed to express Eisenhart's theorem in light of modern studies on
the Bargmann structures (lightlike dimensional reduction, pp-waves). The
construction of the space metric, Coriolis 1-form and scalar potential through
which the theorem is formulated is shown in detail, and in particular it is
proved a one-to-one correspondence between Newtonian frames and Abelian
connections on suitable lightlike principal bundles. The relation of
Eisenhart's theorem in the lightlike case with a Fermat type principle is
pointed out. The operation of lightlike lift is introduced and the existence of
minimizers for the classical action is related to the causal simplicity of
Eisenhart's spacetime.
| [
{
"created": "Sun, 3 Dec 2006 16:34:02 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Dec 2006 16:04:32 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Apr 2007 10:08:55 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Minguzzi",
"E.",
""
]
] | We give a causal version of Eisenhart's geodesic characterization of classical mechanics. We emphasize the geometric, coordinate independent properties needed to express Eisenhart's theorem in light of modern studies on the Bargmann structures (lightlike dimensional reduction, pp-waves). The construction of the space metric, Coriolis 1-form and scalar potential through which the theorem is formulated is shown in detail, and in particular it is proved a one-to-one correspondence between Newtonian frames and Abelian connections on suitable lightlike principal bundles. The relation of Eisenhart's theorem in the lightlike case with a Fermat type principle is pointed out. The operation of lightlike lift is introduced and the existence of minimizers for the classical action is related to the causal simplicity of Eisenhart's spacetime. |
gr-qc/0012100 | Alejandro Perez | Alejandro Perez and Osvaldo M. Moreschi | Characterizing exact solutions from asymptotic physical concepts | null | null | null | null | gr-qc | null | We contribute to the subject of the physical interpretation of exact
solutions by characterizing them through a systematic study in terms of
unambiguous physical concepts coming from systems in linearized gravity. We use
the physical meaning of the leading order behavior of the Weyl spinor
components $\Psi_0^0$, $\Psi_1^0$ and $\Psi_2^0$ and of the Maxwell spinor
components $\phi_0^0$ and $\phi_1^0$ and integrate from future null infinity
inwards the exact field equations. In this way it is assigned an unambiguous
physical meaning to exact solutions. We indicate a method to generalize the
procedure to radiating spacetimes.
| [
{
"created": "Wed, 27 Dec 2000 18:12:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Perez",
"Alejandro",
""
],
[
"Moreschi",
"Osvaldo M.",
""
]
] | We contribute to the subject of the physical interpretation of exact solutions by characterizing them through a systematic study in terms of unambiguous physical concepts coming from systems in linearized gravity. We use the physical meaning of the leading order behavior of the Weyl spinor components $\Psi_0^0$, $\Psi_1^0$ and $\Psi_2^0$ and of the Maxwell spinor components $\phi_0^0$ and $\phi_1^0$ and integrate from future null infinity inwards the exact field equations. In this way it is assigned an unambiguous physical meaning to exact solutions. We indicate a method to generalize the procedure to radiating spacetimes. |
1501.00007 | Veronika E. Hubeny | Veronika E. Hubeny | The AdS/CFT Correspondence | 51 pages, 1 figure. Written for a broad GR audience; submitted to
Classical and Quantum Gravity for its "Milestones of General Relativity"
focus issue to be published during the Centenary Year of GR; v2: minor edits
and added references; matches the published CQG version | null | 10.1088/0264-9381/32/12/124010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a brief review of the AdS/CFT correspondence, which posits the
equivalence between a certain gravitational theory and a lower-dimensional
non-gravitational one. This remarkable duality, formulated in 1997, has sparked
a vigorous research program which has gained in breadth over the years, with
applications to many aspects of theoretical (and even experimental) physics,
not least to general relativity and quantum gravity. To put the AdS/CFT
correspondence in historical context, we start by reviewing the relevant
aspects of string theory (of which no prior knowledge is assumed). We then
develop the statement of the correspondence, and explain how the two sides of
the duality map into each other. Finally, we discuss the implications and
applications of the correspondence, and indicate some of the current trends in
this subject. The presentation attempts to convey the main concepts in a simple
and self-contained manner, relegating supplementary remarks to footnotes.
| [
{
"created": "Tue, 30 Dec 2014 21:00:11 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Feb 2015 21:04:48 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Hubeny",
"Veronika E.",
""
]
] | We give a brief review of the AdS/CFT correspondence, which posits the equivalence between a certain gravitational theory and a lower-dimensional non-gravitational one. This remarkable duality, formulated in 1997, has sparked a vigorous research program which has gained in breadth over the years, with applications to many aspects of theoretical (and even experimental) physics, not least to general relativity and quantum gravity. To put the AdS/CFT correspondence in historical context, we start by reviewing the relevant aspects of string theory (of which no prior knowledge is assumed). We then develop the statement of the correspondence, and explain how the two sides of the duality map into each other. Finally, we discuss the implications and applications of the correspondence, and indicate some of the current trends in this subject. The presentation attempts to convey the main concepts in a simple and self-contained manner, relegating supplementary remarks to footnotes. |
2204.00767 | Pablo Guilleminot M. Sc. | Pablo Guilleminot, Nelson Merino and Rodrigo Olea | Thin shell dynamics in Lovelock gravity | null | null | 10.1140/epjc/s10052-022-10965-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study matching conditions for a spherically symmetric thin shell in
Lovelock gravity which can be read off from the variation of the corresponding
first-order action. In point of fact, the addition of Myers' boundary terms to
the gravitational action eliminates the dependence on the acceleration in this
functional and such that the canonical momentum appears in the surface term in
the variation of the total action. This procedure leads to junction conditions
given by the discontinuity of the canonical momentum defined for an evolution
normal to the boundary. In particular, we correct existing results in the
literature for the thin shell collapse in generic Lovelock theories, which were
mistakenly drawn from an inaccurate analysis of the total derivative terms in
the system.
| [
{
"created": "Sat, 2 Apr 2022 05:27:51 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Guilleminot",
"Pablo",
""
],
[
"Merino",
"Nelson",
""
],
[
"Olea",
"Rodrigo",
""
]
] | We study matching conditions for a spherically symmetric thin shell in Lovelock gravity which can be read off from the variation of the corresponding first-order action. In point of fact, the addition of Myers' boundary terms to the gravitational action eliminates the dependence on the acceleration in this functional and such that the canonical momentum appears in the surface term in the variation of the total action. This procedure leads to junction conditions given by the discontinuity of the canonical momentum defined for an evolution normal to the boundary. In particular, we correct existing results in the literature for the thin shell collapse in generic Lovelock theories, which were mistakenly drawn from an inaccurate analysis of the total derivative terms in the system. |
2206.11149 | Georgios Lukes-Gerakopoulos | Iason Timogiannis, Georgios Lukes-Gerakopoulos, Theocharis A.
Apostolatos | Spinning test body orbiting around a Kerr black hole: Comparing Spin
Supplementary Conditions for Circular Equatorial Orbits | 15 pages, 4 figures, 5 tables, 2 Mathematica notebooks | null | 10.1103/PhysRevD.106.044039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The worldline of a spinning test body moving in curved spacetime can be
provided by the Mathisson-Papapetrou-Dixon (MPD) equations when its centroid,
i.e. its center of mass, is fixed by a Spin Supplementary Condition (SSC). In
the present study, we continue the exploration of shifts between different
centroids started in a recently published work [ Phys. Rev. D 104, 024042
(2021)], henceforth Paper I, for the Schwarzschild spacetime, by examining the
frequencies of circular equatorial orbits under a change of the SSC in the Kerr
spacetime. In particular, we examine the convergence in the terms of the
prograde and retrograde orbital frequencies, when these frequencies are
expanded in power series of the spin measure and the centroid of the body is
shifted from the Mathisson-Pirani or the Ohashi-Kyrian-Semerak frame to the
Tulczyjew-Dixon one. Since in Paper I, we have seen that the innermost stable
circular orbits (ISCOs) hold a special place in this comparison process, we
focus on them rigorously in this work. We introduce a novel method of finding
ISCOs for any SSC and employ it for the Tulczyjew-Dixon and the
Mathisson-Pirani formalisms. We resort to numerical investigation of the
convergence between the SSCs for the ISCO case, due to technical difficulties
not allowing Paper's I analytical treatment. Our conclusion, as in Paper I, is
that there appears to be a convergence in the power series of the frequencies
between the SSCs, which is improved when the proper shifts are taken into
account, but there exists a limit in this convergence due to the fact that in
the spinning body approximation we consider only the first two lower multipoles
of the extended body and ignore all the higher ones.
| [
{
"created": "Wed, 22 Jun 2022 14:55:18 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Aug 2022 09:28:16 GMT",
"version": "v2"
}
] | 2022-08-31 | [
[
"Timogiannis",
"Iason",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | The worldline of a spinning test body moving in curved spacetime can be provided by the Mathisson-Papapetrou-Dixon (MPD) equations when its centroid, i.e. its center of mass, is fixed by a Spin Supplementary Condition (SSC). In the present study, we continue the exploration of shifts between different centroids started in a recently published work [ Phys. Rev. D 104, 024042 (2021)], henceforth Paper I, for the Schwarzschild spacetime, by examining the frequencies of circular equatorial orbits under a change of the SSC in the Kerr spacetime. In particular, we examine the convergence in the terms of the prograde and retrograde orbital frequencies, when these frequencies are expanded in power series of the spin measure and the centroid of the body is shifted from the Mathisson-Pirani or the Ohashi-Kyrian-Semerak frame to the Tulczyjew-Dixon one. Since in Paper I, we have seen that the innermost stable circular orbits (ISCOs) hold a special place in this comparison process, we focus on them rigorously in this work. We introduce a novel method of finding ISCOs for any SSC and employ it for the Tulczyjew-Dixon and the Mathisson-Pirani formalisms. We resort to numerical investigation of the convergence between the SSCs for the ISCO case, due to technical difficulties not allowing Paper's I analytical treatment. Our conclusion, as in Paper I, is that there appears to be a convergence in the power series of the frequencies between the SSCs, which is improved when the proper shifts are taken into account, but there exists a limit in this convergence due to the fact that in the spinning body approximation we consider only the first two lower multipoles of the extended body and ignore all the higher ones. |
1106.3817 | Shahar Hod | Shahar Hod | Higher-dimensional violations of the holographic entropy bound | 5 pages | Phys.Lett.B695:294-297,2011 | 10.1016/j.physletb.2010.10.045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The holographic bound, $S<=A/4{\ell^2_P}$, asserts that the entropy $S$ of a
system is bounded from above by a quarter of the area $A$ of a circumscribing
surface measured in Planck areas. This bound is widely regarded as part of the
elusive fundamental theory of nature. In fact, the bound is known to be valid
for generic weakly gravitating isolated systems in {\it three} spatial
dimensions. Nevertheless, the entropy content of a physical system is expected
to be an increasing function of the number of spatial dimensions (the more the
dimensions, the more ways there are to split up a given amount of energy).
Thus, one may expect the challenge to the holographic entropy bound to become
more and more serious as the number of spatial dimensions increases. In this
paper we explicitly show that thermal radiation in $D$ flat spatial dimensions
with $D\gtrsim 10^2$ may indeed violate the holographic entropy bound.
| [
{
"created": "Mon, 20 Jun 2011 06:15:25 GMT",
"version": "v1"
}
] | 2012-10-11 | [
[
"Hod",
"Shahar",
""
]
] | The holographic bound, $S<=A/4{\ell^2_P}$, asserts that the entropy $S$ of a system is bounded from above by a quarter of the area $A$ of a circumscribing surface measured in Planck areas. This bound is widely regarded as part of the elusive fundamental theory of nature. In fact, the bound is known to be valid for generic weakly gravitating isolated systems in {\it three} spatial dimensions. Nevertheless, the entropy content of a physical system is expected to be an increasing function of the number of spatial dimensions (the more the dimensions, the more ways there are to split up a given amount of energy). Thus, one may expect the challenge to the holographic entropy bound to become more and more serious as the number of spatial dimensions increases. In this paper we explicitly show that thermal radiation in $D$ flat spatial dimensions with $D\gtrsim 10^2$ may indeed violate the holographic entropy bound. |
gr-qc/9605033 | Andrzey Krolak | Pankaj S. Joshi, Andrzej Krolak | Naked strong curvature singularities in Szekeres space-times | latex, 9 pages | Class.Quant.Grav. 13 (1996) 3069-3074 | 10.1088/0264-9381/13/11/020 | null | gr-qc | null | We investigate the occurrence and nature of naked singularities in the
Szekeres space-times. These space-times represent irrotational dust. They do
not have any Killing vectors and they are generalisations of the
Tolman-Bondi-Lemaitre space-times. It is shown that in these space-times there
exist naked singularities that satisfy both the limiting focusing condition and
the strong limiting focusing condition. The implications of this result for the
cosmic censorship hypothesis are discussed.
| [
{
"created": "Fri, 17 May 1996 08:50:08 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Joshi",
"Pankaj S.",
""
],
[
"Krolak",
"Andrzej",
""
]
] | We investigate the occurrence and nature of naked singularities in the Szekeres space-times. These space-times represent irrotational dust. They do not have any Killing vectors and they are generalisations of the Tolman-Bondi-Lemaitre space-times. It is shown that in these space-times there exist naked singularities that satisfy both the limiting focusing condition and the strong limiting focusing condition. The implications of this result for the cosmic censorship hypothesis are discussed. |
1607.02510 | Shahar Hod | Shahar Hod | Hawking radiation and the Stefan-Boltzmann law: The effective radius of
the black-hole quantum atmosphere | 6 pages | Physics Letters B 757, 121 (2016) | 10.1016/j.physletb.2016.03.071 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been suggested [S. B. Giddings, Phys. Lett. B {\bf 754}, 39
(2016)] that the Hawking black-hole radiation spectrum originates from an
effective quantum "atmosphere" which extends well outside the black-hole
horizon. In particular, comparing the Hawking radiation power of a
$(3+1)$-dimensional Schwarzschild black hole of horizon radius $r_{\text{H}}$
with the familiar Stefan-Boltzmann radiation power of a $(3+1)$-dimensional
flat space perfect blackbody emitter, Giddings concluded that the source of the
Hawking semi-classical black-hole radiation is a quantum region outside the
Schwarzschild black-hole horizon whose effective radius $r_{\text{A}}$ is
characterized by the relation $\Delta r\equiv r_{\text{A}}-r_{\text{H}}\sim
r_{\text{H}}$. It is of considerable physical interest to test the general
validity of Giddings's intriguing conclusion. To this end, we study the Hawking
radiation of $(D+1)$-dimensional Schwarzschild black holes. We find that the
dimensionless radii $r_{\text{A}}/r_{\text{H}}$ which characterize the
black-hole quantum atmospheres, as determined from the Hawking black-hole
radiation power and the $(D+1)$-dimensional Stefan-Boltzmann radiation law, are
a decreasing function of the number $D+1$ of spacetime dimensions. In
particular, it is shown that radiating $(D+1)$-dimensional Schwarzschild black
holes are characterized by the relation
$(r_{\text{A}}-r_{\text{H}})/r_{\text{H}}\ll1$ in the large $D\gg1$ regime. Our
results therefore suggest that, at least in some physical cases, the Hawking
emission spectrum originates from quantum excitations very near the black-hole
horizon.
| [
{
"created": "Fri, 8 Jul 2016 20:00:02 GMT",
"version": "v1"
}
] | 2016-07-20 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been suggested [S. B. Giddings, Phys. Lett. B {\bf 754}, 39 (2016)] that the Hawking black-hole radiation spectrum originates from an effective quantum "atmosphere" which extends well outside the black-hole horizon. In particular, comparing the Hawking radiation power of a $(3+1)$-dimensional Schwarzschild black hole of horizon radius $r_{\text{H}}$ with the familiar Stefan-Boltzmann radiation power of a $(3+1)$-dimensional flat space perfect blackbody emitter, Giddings concluded that the source of the Hawking semi-classical black-hole radiation is a quantum region outside the Schwarzschild black-hole horizon whose effective radius $r_{\text{A}}$ is characterized by the relation $\Delta r\equiv r_{\text{A}}-r_{\text{H}}\sim r_{\text{H}}$. It is of considerable physical interest to test the general validity of Giddings's intriguing conclusion. To this end, we study the Hawking radiation of $(D+1)$-dimensional Schwarzschild black holes. We find that the dimensionless radii $r_{\text{A}}/r_{\text{H}}$ which characterize the black-hole quantum atmospheres, as determined from the Hawking black-hole radiation power and the $(D+1)$-dimensional Stefan-Boltzmann radiation law, are a decreasing function of the number $D+1$ of spacetime dimensions. In particular, it is shown that radiating $(D+1)$-dimensional Schwarzschild black holes are characterized by the relation $(r_{\text{A}}-r_{\text{H}})/r_{\text{H}}\ll1$ in the large $D\gg1$ regime. Our results therefore suggest that, at least in some physical cases, the Hawking emission spectrum originates from quantum excitations very near the black-hole horizon. |
gr-qc/0605009 | Mohammad Nouri-Zonoz | N. Ahmadi and M. Nouri-Zonoz | Quantum gravitational optics: Effective Raychaudhuri equation | 17 pages, 1 figure, RevTex format, Replaced with the published
version | Phys.Rev. D74 (2006) 044034 | 10.1103/PhysRevD.74.044034 | null | gr-qc | null | Vacuum polarization in QED in a background gravitational field induces
interactions which {\it effectively} modify the classical picture of light
rays, as the null geodesics of spacetime. These interactions violate the strong
equivalence principle and affect the propagation of light leading to
superluminal photon velocities. Taking into account the QED vacuum
polarization, we study the propagation of a bundle of rays in a background
gravitational field. To do so we consider the perturbative deformation of
Raychaudhuri equation through the influence of vacuum polarization on photon
propagation. We analyze the contribution of the above interactions to the
optical scalars namely, shear, vorticity and expansion using the Newman-Penrose
formalism.
| [
{
"created": "Mon, 1 May 2006 07:23:18 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Dec 2006 13:54:11 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Ahmadi",
"N.",
""
],
[
"Nouri-Zonoz",
"M.",
""
]
] | Vacuum polarization in QED in a background gravitational field induces interactions which {\it effectively} modify the classical picture of light rays, as the null geodesics of spacetime. These interactions violate the strong equivalence principle and affect the propagation of light leading to superluminal photon velocities. Taking into account the QED vacuum polarization, we study the propagation of a bundle of rays in a background gravitational field. To do so we consider the perturbative deformation of Raychaudhuri equation through the influence of vacuum polarization on photon propagation. We analyze the contribution of the above interactions to the optical scalars namely, shear, vorticity and expansion using the Newman-Penrose formalism. |
1907.07486 | Shaoqi Hou | Shaoqi Hou, Xi-Long Fan, Zong-Hong Zhu | Gravitational Lensing of Gravitational Waves: Rotation of Polarization
Plane | 6 pages, 1 figure. Match the published version | Phys. Rev. D 100, 064028 (2019) | 10.1103/PhysRevD.100.064028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Similar to the light, gravitational waves traveling in multiple paths may
arrive at the same location if there is a gravitational lens on their way.
Apart from the magnification of the amplitudes and the time delay between the
gravitational wave rays, gravitational lensing also rotates their polarization
planes. This results in the changes in the antenna pattern function, which
describes the response of the detector to its relative orientation to the
gravitational wave. These effects are all reflected in the strain, the signal
registered by the interferometers. The gravitational wave rays in various
directions stimulate different strains. Their strains differ from each other
due to different magnification factors, the phases and the rotation of the
polarization plane. The phase difference mainly comes from the time delay.
Moreover, the rotation of the polarization plane seemingly introduces the
\textit{apparent} vector polarizations, when these strains are compared with
each other. Because of the smallness of the deflection angles, the effect of
the rotation is negligible.
| [
{
"created": "Wed, 17 Jul 2019 12:54:39 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Sep 2019 00:22:41 GMT",
"version": "v2"
}
] | 2019-09-19 | [
[
"Hou",
"Shaoqi",
""
],
[
"Fan",
"Xi-Long",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | Similar to the light, gravitational waves traveling in multiple paths may arrive at the same location if there is a gravitational lens on their way. Apart from the magnification of the amplitudes and the time delay between the gravitational wave rays, gravitational lensing also rotates their polarization planes. This results in the changes in the antenna pattern function, which describes the response of the detector to its relative orientation to the gravitational wave. These effects are all reflected in the strain, the signal registered by the interferometers. The gravitational wave rays in various directions stimulate different strains. Their strains differ from each other due to different magnification factors, the phases and the rotation of the polarization plane. The phase difference mainly comes from the time delay. Moreover, the rotation of the polarization plane seemingly introduces the \textit{apparent} vector polarizations, when these strains are compared with each other. Because of the smallness of the deflection angles, the effect of the rotation is negligible. |
gr-qc/9802066 | Neil John Cornish | Neil J. Cornish and Neil G. Turok (DAMTP, Cambridge University) | Ringing the eigenmodes from compact manifolds | 11 pages, 8 figures, IOP format. To be published in the proceedings
of the Cleveland Cosmology and Topology Workshop 17-19 Oct 1997. Submitted to
Class. Quant. Grav | Class.Quant.Grav.15:2699-2710,1998 | 10.1088/0264-9381/15/9/016 | DAMTP-R-98/09 | gr-qc astro-ph | null | We present a method for finding the eigenmodes of the Laplace operator acting
on any compact manifold. The procedure can be used to simulate cosmic microwave
background fluctuations in multi-connected cosmological models. Other
applications include studies of chaotic mixing and quantum chaos.
| [
{
"created": "Thu, 26 Feb 1998 19:28:47 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Cornish",
"Neil J.",
"",
"DAMTP, Cambridge University"
],
[
"Turok",
"Neil G.",
"",
"DAMTP, Cambridge University"
]
] | We present a method for finding the eigenmodes of the Laplace operator acting on any compact manifold. The procedure can be used to simulate cosmic microwave background fluctuations in multi-connected cosmological models. Other applications include studies of chaotic mixing and quantum chaos. |
gr-qc/9403061 | null | B. L. Hu | Quantum Statistical Field Theory in Gravitation and Cosmology | Latex 38 pages, umdpp 94-45 Three Lectures given at the Canadian
Summer School for Theoretical Physics and the Third International Workshop on
Thermal Field Theories and Applications, Banff, Canada, Alberta, August
15-28, 1993. Proceedings edited by R. Kobes and G. Kunstatter (World
Scientific, Singapore, 1994) | null | null | null | gr-qc hep-th | null | We describe how the concepts of quantum open systems and the methods of
closed-time-path (CTP) effective action and influence functional (IF) can be
usefully applied to the analysis of statistical mechanical problems involving
quantum fields in gravitation and cosmology. In the first lecture we discuss in
general terms the relevance of open system concepts in the description of a
variety of physical processes, and outline the basics of the CTP and IF
formalisms. In the second lecture we illustrate the IF method with a model of
two interacting quantum fields, deriving the influence action via a
perturbative expansion involving the closed-time-path Green functions. We show
how noise of quantum fields can be defined and derive a general fluctuation-
dissipation relation for quantum fields. In the third lecture we discuss the
problem of backreaction in semiclassical gravity with the example of a scalar
field in a Bianchi Type-I universe. We show that the CTP effective action not
only yields a real and causal equation of motion with a dissipative term
depicting the effect of particle creation, as was found earlier, it also
contains a noise term measuring the fluctuations in particle number and
governing the metric fluctuations. The particle creation-backreaction problem
can be understood as a manifestation of a fluctuation-dissipation relation for
quantum fields in dynamic spacetimes, generalizing Sciama's observation for
black hole Hawking radiation. A more complete description of semiclassical
gravity is given by way of an Einstein-Langevin equation, the conventional
theory based on the expectation value of the energy momentum tensor being its
| [
{
"created": "Wed, 30 Mar 1994 12:59:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hu",
"B. L.",
""
]
] | We describe how the concepts of quantum open systems and the methods of closed-time-path (CTP) effective action and influence functional (IF) can be usefully applied to the analysis of statistical mechanical problems involving quantum fields in gravitation and cosmology. In the first lecture we discuss in general terms the relevance of open system concepts in the description of a variety of physical processes, and outline the basics of the CTP and IF formalisms. In the second lecture we illustrate the IF method with a model of two interacting quantum fields, deriving the influence action via a perturbative expansion involving the closed-time-path Green functions. We show how noise of quantum fields can be defined and derive a general fluctuation- dissipation relation for quantum fields. In the third lecture we discuss the problem of backreaction in semiclassical gravity with the example of a scalar field in a Bianchi Type-I universe. We show that the CTP effective action not only yields a real and causal equation of motion with a dissipative term depicting the effect of particle creation, as was found earlier, it also contains a noise term measuring the fluctuations in particle number and governing the metric fluctuations. The particle creation-backreaction problem can be understood as a manifestation of a fluctuation-dissipation relation for quantum fields in dynamic spacetimes, generalizing Sciama's observation for black hole Hawking radiation. A more complete description of semiclassical gravity is given by way of an Einstein-Langevin equation, the conventional theory based on the expectation value of the energy momentum tensor being its |
1511.02169 | Federico Piazza | Federico Piazza and Thomas Schucker | Minimal cosmography | 13 pages. v2: improved version to appear on Gen. Rel. and Grav | null | 10.1007/s10714-016-2039-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The minimal requirement for cosmography - a nondynamical description of the
universe - is a prescription for calculating null geodesics, and timelike
geodesics as a function of their proper time. In this paper, we consider the
most general linear connection compatible with homogeneity and isotropy, but
not necessarily with a metric. A light-cone structure is assigned by choosing a
set of geodesics representing light rays. This defines a "scale factor" and a
local notion of distance, as that travelled by light in a given proper time
interval. We find that the velocities and relativistic energies of free-falling
bodies decrease in time as a consequence of cosmic expansion, but at a rate
that can be different than that dictated by the usual metric framework. By
extrapolating this behavior to photons redshift, we find that the latter is in
principle independent of the "scale factor". Interestingly, redshift-distance
relations and other standard geometric observables are modified in this
extended framework, in a way that could be experimentally tested. An extremely
tight constraint on the model, however, is represented by the blackbody-ness of
the Cosmic Microwave Background. Finally, as a check, we also consider the
effects of a non-metric connection in a different set-up, namely, that of a
static, spherically symmetric spacetime.
| [
{
"created": "Thu, 5 Nov 2015 14:23:36 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Mar 2016 11:15:30 GMT",
"version": "v2"
}
] | 2016-04-13 | [
[
"Piazza",
"Federico",
""
],
[
"Schucker",
"Thomas",
""
]
] | The minimal requirement for cosmography - a nondynamical description of the universe - is a prescription for calculating null geodesics, and timelike geodesics as a function of their proper time. In this paper, we consider the most general linear connection compatible with homogeneity and isotropy, but not necessarily with a metric. A light-cone structure is assigned by choosing a set of geodesics representing light rays. This defines a "scale factor" and a local notion of distance, as that travelled by light in a given proper time interval. We find that the velocities and relativistic energies of free-falling bodies decrease in time as a consequence of cosmic expansion, but at a rate that can be different than that dictated by the usual metric framework. By extrapolating this behavior to photons redshift, we find that the latter is in principle independent of the "scale factor". Interestingly, redshift-distance relations and other standard geometric observables are modified in this extended framework, in a way that could be experimentally tested. An extremely tight constraint on the model, however, is represented by the blackbody-ness of the Cosmic Microwave Background. Finally, as a check, we also consider the effects of a non-metric connection in a different set-up, namely, that of a static, spherically symmetric spacetime. |
gr-qc/9701017 | Victor Berezin | Victor Berezin | Square-root quantization: application to quantum black holes | LaTeX file Talk given on the Second Conference on Constrained
Dynamics and Quantum Gravity, Santa Margherita, Ligure, Italy, 17-21
September 1996 | Nucl.Phys.Proc.Suppl. 57 (1997) 181-183 | 10.1016/S0920-5632(97)00370-8 | null | gr-qc | null | Two different ways of quantizing the relativistic Hamiltonian for radial
motion in the field of Coulomb-like potential are compared. The results depend
slightly on choice of time. In the case of Lorentzian time a Sommerfeld
spectrum is recovered. Application to quantum black holes gives a sqrt{n} mass
spectrum with about the same numerical factors.
| [
{
"created": "Fri, 10 Jan 1997 15:17:00 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Berezin",
"Victor",
""
]
] | Two different ways of quantizing the relativistic Hamiltonian for radial motion in the field of Coulomb-like potential are compared. The results depend slightly on choice of time. In the case of Lorentzian time a Sommerfeld spectrum is recovered. Application to quantum black holes gives a sqrt{n} mass spectrum with about the same numerical factors. |
1007.5175 | Sven Zschocke | Sven Zschocke and Sergei A. Klioner | Further simplification of the light deflection formula for solar system
objects | 9 pages, no figures, report for astrometric mission Gaia | null | null | GAIA-CA-TN-LO-SZ-005-1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The transformation n to k in post-post-Newtonian order is simplified. All
post-post-Newtonian terms of the order m^2/d^2 are neglected and we show that
the total sum of these terms is smaller than 15/4 pi m^2/d^2. This simpler
transformation will improve the efficiency of Gaia data reduction.
| [
{
"created": "Thu, 29 Jul 2010 10:13:31 GMT",
"version": "v1"
}
] | 2010-08-03 | [
[
"Zschocke",
"Sven",
""
],
[
"Klioner",
"Sergei A.",
""
]
] | The transformation n to k in post-post-Newtonian order is simplified. All post-post-Newtonian terms of the order m^2/d^2 are neglected and we show that the total sum of these terms is smaller than 15/4 pi m^2/d^2. This simpler transformation will improve the efficiency of Gaia data reduction. |
1012.4719 | Muxin Han | Eugenio Bianchi, Muxin Han, Elena Magliaro, Claudio Perini, Carlo
Rovelli, Wolfgang Wieland | Spinfoam fermions | 8 pages, no figure | Class. Quantum Grav. 30 (2013) 235023 | 10.1088/0264-9381/30/23/235023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a minimal coupling of fermions and Yang Mills fields to the loop
quantum gravity dynamics. The coupling takes a very simple form.
| [
{
"created": "Tue, 21 Dec 2010 16:25:46 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Oct 2013 09:40:16 GMT",
"version": "v2"
}
] | 2013-11-01 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Han",
"Muxin",
""
],
[
"Magliaro",
"Elena",
""
],
[
"Perini",
"Claudio",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Wieland",
"Wolfgang",
""
]
] | We describe a minimal coupling of fermions and Yang Mills fields to the loop quantum gravity dynamics. The coupling takes a very simple form. |
1311.0488 | Orchidea Maria Lecian | Orchidea Maria Lecian | Periodic orbits in cosmological billiards: the Selberg trace formula for
asymptotic Bianchi IX universes, evidence for scars in the wavefunction of
the quantum universe and large-scale structure anisotropies of the present
universe | 33 pages, 13 tables, 3 figures | null | null | null | gr-qc astro-ph.GA hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Selberg trace formula is specified for cosmological billiards in $4=3+1$
spacetime dimensions. The spectral formula is rewritten as an exact sum over
the initial conditions for the Einstein field equations for which periodic
orbits are implied. For this, a suitable density of measure invariant under the
billiard maps has been defined, within the statistics implied by the BKL
paradigm. The trace formula has also been specified for the stochastic limit of
the dynamics, where the sum over initial conditions has been demonstrated to be
equivalent to a sum over suitable symmetry operations on the generators of the
groups that define the billiard dynamics, and acquires different features for
the different statistical maps.
Evidence for scars at the quantum regime is provided. The validity of the
Selberg trace formula at the classical level and in the quantum regime enforces
the validity of the semiclassical descriptions of these systems, thus offering
further elements for the comparison of quantum-gravity effects and the present
observed structure of the universe. This procedure also constitutes a new
approach in hyperbolic geometry for the application of the Selberg trace
formula for a chaotic system whose orbits are associated to precise statistical
distributions, for both billiard tables corresponding to the desymmetrized
fundamental domain and to that a a congruence subgroup of it.
| [
{
"created": "Sun, 3 Nov 2013 16:20:01 GMT",
"version": "v1"
}
] | 2013-11-05 | [
[
"Lecian",
"Orchidea Maria",
""
]
] | The Selberg trace formula is specified for cosmological billiards in $4=3+1$ spacetime dimensions. The spectral formula is rewritten as an exact sum over the initial conditions for the Einstein field equations for which periodic orbits are implied. For this, a suitable density of measure invariant under the billiard maps has been defined, within the statistics implied by the BKL paradigm. The trace formula has also been specified for the stochastic limit of the dynamics, where the sum over initial conditions has been demonstrated to be equivalent to a sum over suitable symmetry operations on the generators of the groups that define the billiard dynamics, and acquires different features for the different statistical maps. Evidence for scars at the quantum regime is provided. The validity of the Selberg trace formula at the classical level and in the quantum regime enforces the validity of the semiclassical descriptions of these systems, thus offering further elements for the comparison of quantum-gravity effects and the present observed structure of the universe. This procedure also constitutes a new approach in hyperbolic geometry for the application of the Selberg trace formula for a chaotic system whose orbits are associated to precise statistical distributions, for both billiard tables corresponding to the desymmetrized fundamental domain and to that a a congruence subgroup of it. |
1303.7391 | Abdul Jawad | M. Sharif and Abdul Jawad | Thermodynamics in Closed Universe with Entropy Corrections | 25 pages, No figure | Int. J. Mod. Phys. D 22(2013)1350014 | 10.1142/S0218271813500144 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the generalized second law of thermodynamics in three different
systems by taking quantum corrections (logarithmic and power law) to
cosmological horizon entropy as well as black hole entropy. Firstly, we
consider phantom energy accretion onto the Schwarzschild black hole in the
closed FRW universe and investigate validity of the generalized second law of
thermodynamics on the apparent and event horizons. In another scenario, we
evaluate the critical mass of the Schwarzschild black hole with upper and lower
bounds under accretion process due to phantom-like modified generalized
chaplygin gas. It is found that the generalized second law of thermodynamics is
respected within these bounds and black hole cannot accrete outside them.
Finally, we explore this law for a closed universe filled with interacting
$n$-components of fluid (in thermal equilibrium case) and with non-interacting
dark matter and dark energy components (in thermal non-equilibrium case) on the
apparent and event horizons and find conditions for its validity.
| [
{
"created": "Tue, 26 Mar 2013 05:17:27 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Sharif",
"M.",
""
],
[
"Jawad",
"Abdul",
""
]
] | We discuss the generalized second law of thermodynamics in three different systems by taking quantum corrections (logarithmic and power law) to cosmological horizon entropy as well as black hole entropy. Firstly, we consider phantom energy accretion onto the Schwarzschild black hole in the closed FRW universe and investigate validity of the generalized second law of thermodynamics on the apparent and event horizons. In another scenario, we evaluate the critical mass of the Schwarzschild black hole with upper and lower bounds under accretion process due to phantom-like modified generalized chaplygin gas. It is found that the generalized second law of thermodynamics is respected within these bounds and black hole cannot accrete outside them. Finally, we explore this law for a closed universe filled with interacting $n$-components of fluid (in thermal equilibrium case) and with non-interacting dark matter and dark energy components (in thermal non-equilibrium case) on the apparent and event horizons and find conditions for its validity. |
gr-qc/0207032 | Stephen A. Fulling | S. A. Fulling, B.-G. Englert, and M. D. Pilloff | Interacting Bosons at Finite Temperature: How Bogolubov Visited a Black
Hole and Came Home Again | 25 pages, LaTeX. To appear in a special issue of Foundations of
Physics in honor of Jacob Bekenstein | Found.Phys. 33 (2003) 87-110 | 10.1023/A:1022819825765 | null | gr-qc cond-mat quant-ph | null | The structure of the thermal equilibrium state of a weakly interacting Bose
gas is of current interest. We calculate the density matrix of that state in
two ways. The most effective method, in terms of yielding a simple, explicit
answer, is to construct a generating function within the traditional framework
of quantum statistical mechanics. The alternative method, arguably more
interesting, is to construct the thermal state as a vector state in an
artificial system with twice as many degrees of freedom. It is well known that
this construction has an actual physical realization in the quantum
thermodynamics of black holes, where the added degrees of freedom correspond to
the second sheet of the Kruskal manifold and the thermal vector state is a
state of the Unruh or the Hartle-Hawking type. What is unusual about the
present work is that the Bogolubov transformation used to construct the thermal
state combines in a rather symmetrical way with Bogolubov's original
transformation of the same form, used to implement the interaction of the
nonideal gas in linear approximation. In addition to providing a density
matrix, the method makes it possible to calculate efficiently certain
expectation values directly in terms of the thermal vector state of the doubled
system.
| [
{
"created": "Fri, 5 Jul 2002 19:19:28 GMT",
"version": "v1"
}
] | 2022-10-12 | [
[
"Fulling",
"S. A.",
""
],
[
"Englert",
"B. -G.",
""
],
[
"Pilloff",
"M. D.",
""
]
] | The structure of the thermal equilibrium state of a weakly interacting Bose gas is of current interest. We calculate the density matrix of that state in two ways. The most effective method, in terms of yielding a simple, explicit answer, is to construct a generating function within the traditional framework of quantum statistical mechanics. The alternative method, arguably more interesting, is to construct the thermal state as a vector state in an artificial system with twice as many degrees of freedom. It is well known that this construction has an actual physical realization in the quantum thermodynamics of black holes, where the added degrees of freedom correspond to the second sheet of the Kruskal manifold and the thermal vector state is a state of the Unruh or the Hartle-Hawking type. What is unusual about the present work is that the Bogolubov transformation used to construct the thermal state combines in a rather symmetrical way with Bogolubov's original transformation of the same form, used to implement the interaction of the nonideal gas in linear approximation. In addition to providing a density matrix, the method makes it possible to calculate efficiently certain expectation values directly in terms of the thermal vector state of the doubled system. |
2212.13095 | M.V.S. Saketh | M. V. S. Saketh, Jan Steinhoff, Justin Vines, Alessandra Buonanno | Modeling horizon absorption in spinning binary black holes using
effective worldline theory | 29 Pages, 1 figure, 2 tables | null | 10.1103/PhysRevD.107.084006 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The mass and spin of black holes (BHs) in binary systems may change due to
the infall of gravitational-wave (GW) energy down the horizons. For spinning
BHs, this effect enters at 2.5 post-Newtonian (PN) order relative to the
leading-order energy flux at infinity. There is currently a discrepancy in the
literature in the expressions of these horizon fluxes in the test-body limit at
4PN order (relative 1.5PN order). Here, we model the horizon absorption as
tidal heating in an effective worldline theory of a spinning particle equipped
with tidally-induced quadrupole and octupole moments. We match the tidal
response to analytic solutions of the Teukolsky equation in a scattering
scenario, and obtain general formulae for the evolution of mass and spin. We
then specialize to the case of aligned-spin--quasi-circular binaries, obtaining
the corresponding contributions to the GW phasing through 4PN order.
Importantly, we find that the number of GW cycles due to horizon fluxes with
masses observed by LIGO-Virgo-KAGRA detectors is about 2-3 orders of magnitude
smaller than the other contributions to the phasing at the same PN order.
Furthermore, in the test-body limit, we find full agreement with results
obtained earlier from BH perturbation theory, with a small mass in an
equatorial circular orbit treated as a source perturbing the Kerr metric. Thus,
we weigh in on one side of the previous discrepancy.
| [
{
"created": "Mon, 26 Dec 2022 11:42:01 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jan 2023 14:02:51 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Saketh",
"M. V. S.",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Vines",
"Justin",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | The mass and spin of black holes (BHs) in binary systems may change due to the infall of gravitational-wave (GW) energy down the horizons. For spinning BHs, this effect enters at 2.5 post-Newtonian (PN) order relative to the leading-order energy flux at infinity. There is currently a discrepancy in the literature in the expressions of these horizon fluxes in the test-body limit at 4PN order (relative 1.5PN order). Here, we model the horizon absorption as tidal heating in an effective worldline theory of a spinning particle equipped with tidally-induced quadrupole and octupole moments. We match the tidal response to analytic solutions of the Teukolsky equation in a scattering scenario, and obtain general formulae for the evolution of mass and spin. We then specialize to the case of aligned-spin--quasi-circular binaries, obtaining the corresponding contributions to the GW phasing through 4PN order. Importantly, we find that the number of GW cycles due to horizon fluxes with masses observed by LIGO-Virgo-KAGRA detectors is about 2-3 orders of magnitude smaller than the other contributions to the phasing at the same PN order. Furthermore, in the test-body limit, we find full agreement with results obtained earlier from BH perturbation theory, with a small mass in an equatorial circular orbit treated as a source perturbing the Kerr metric. Thus, we weigh in on one side of the previous discrepancy. |
1301.2737 | Martin Richarte MR | Luis P. Chimento, M\'onica I. Forte, and Mart\'in G. Richarte | Modified holographic Ricci dark energy coupled to interacting dark
matter and a non interacting baryonic component | 11 pages, 6 figures, two columns. Accepted for publication in The
European Physical Journal C (2013) | The European Physical Journal C, Volume 73, article id. #2285
(2013) | 10.1140/epjc/s10052-013-2285-1 | null | gr-qc astro-ph.CO physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine a Friedmann-Robertson-Walker universe filled with interacting dark
matter, modified holographic Ricci dark energy (MHRDE), and a decoupled
baryonic component.The estimations of the cosmic parameters with Hubble data
lead to an age of the universe of $13.17 {\rm Gyr}$ and show that the MHRDE is
free from the cosmic-age problem at low redshift ($0 \leq z \leq 2$) in
contrast to holographic Ricci dark energy (HRDE) case. We constrain the
parameters with the Union2 data set and contrast with the Hubble data. We also
study the behavior of dark energy at early times by taking into account the
severe bounds found at recombination era and/or at big bang nucleosynthesis.
The inclusion of a non interacting baryonic matter forces that the amount of
dark energy at $z_{t} \sim {\cal O}(1)$ changes abruptly implying that
$\Omega_x (z\simeq 1100) =0.03$, so the bounds reported by the forecast of
Planck and CMBPol experiments are more favored for the MHRDE model than in the
case of HRDE cutoff. For the former model, we also obtain that at high redshift
the fraction of dark energy varies from 0.006 to 0.002, then the amount of
$\Omega_x $ at the big bang nucleosynthesis era does not disturb the observed
Helium abundance in the universe provided that the bound $\Omega_{x}(z\simeq
10^{10})<0.21$ is hold.
| [
{
"created": "Sun, 13 Jan 2013 00:36:23 GMT",
"version": "v1"
}
] | 2013-04-02 | [
[
"Chimento",
"Luis P.",
""
],
[
"Forte",
"Mónica I.",
""
],
[
"Richarte",
"Martín G.",
""
]
] | We examine a Friedmann-Robertson-Walker universe filled with interacting dark matter, modified holographic Ricci dark energy (MHRDE), and a decoupled baryonic component.The estimations of the cosmic parameters with Hubble data lead to an age of the universe of $13.17 {\rm Gyr}$ and show that the MHRDE is free from the cosmic-age problem at low redshift ($0 \leq z \leq 2$) in contrast to holographic Ricci dark energy (HRDE) case. We constrain the parameters with the Union2 data set and contrast with the Hubble data. We also study the behavior of dark energy at early times by taking into account the severe bounds found at recombination era and/or at big bang nucleosynthesis. The inclusion of a non interacting baryonic matter forces that the amount of dark energy at $z_{t} \sim {\cal O}(1)$ changes abruptly implying that $\Omega_x (z\simeq 1100) =0.03$, so the bounds reported by the forecast of Planck and CMBPol experiments are more favored for the MHRDE model than in the case of HRDE cutoff. For the former model, we also obtain that at high redshift the fraction of dark energy varies from 0.006 to 0.002, then the amount of $\Omega_x $ at the big bang nucleosynthesis era does not disturb the observed Helium abundance in the universe provided that the bound $\Omega_{x}(z\simeq 10^{10})<0.21$ is hold. |
1610.04443 | Yurii Ignat'ev | Yu.G. Ignat'ev and A.A. Agathonov | The Qualitative and Numerical Analysis of the Cosmological Model Based
on Phantom Scalar Field with Self | 12 pages, 12 figures, 12 references | null | 10.1007/s11182-017-1016-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the asymptotic behavior of the cosmological
model based on phantom scalar field on the ground of qualitative analysis of
the system of the cosmological model's differential equations and show that as
opposed to models with classical scalar field, such models have stable
asymptotic solutions with constant value of the potential both in infinite past
and infinite future. We also develop numerical models of the cosmological
evolution models with phantom scalar field in this paper.
{\bf keywords}: cosmological model, phantom scalar field, quality analysis,
asymptotic behavior, numerical simulation, numerical gravitation.\\ {\bf PACS}:
04.20.Cv, 98.80.Cq, 96.50.S 52.27.Ny
| [
{
"created": "Fri, 14 Oct 2016 13:10:48 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Ignat'ev",
"Yu. G.",
""
],
[
"Agathonov",
"A. A.",
""
]
] | In this paper we investigate the asymptotic behavior of the cosmological model based on phantom scalar field on the ground of qualitative analysis of the system of the cosmological model's differential equations and show that as opposed to models with classical scalar field, such models have stable asymptotic solutions with constant value of the potential both in infinite past and infinite future. We also develop numerical models of the cosmological evolution models with phantom scalar field in this paper. {\bf keywords}: cosmological model, phantom scalar field, quality analysis, asymptotic behavior, numerical simulation, numerical gravitation.\\ {\bf PACS}: 04.20.Cv, 98.80.Cq, 96.50.S 52.27.Ny |
gr-qc/0011108 | Simonetta Frittelli | Simonetta Frittelli, Thomas P. Kling and Ezra T. Newman | Image distortion from optical scalars in non perturbative gravitational
lensing | 17 pages, 3 figures, to appear in Phys. Rev. D (January 2001) | Phys.Rev. D63 (2001) 023007 | 10.1103/PhysRevD.63.023007 | null | gr-qc | null | In a previous article concerning image distortion in non-perturbative
gravitational lensing theory we described how to introduce shape and distortion
parameters for small sources. We also showed how they could be expressed in
terms of the scalar products of the geodesic deviation vectors of the source's
pencil of rays in the past lightcone of an observer. In the present work we
give an alternative approach to the description of the shape and distortion
parameters and their evolution along the null geodesic from the source to the
observer, but now in terms of the optical scalars (the convergence and shear of
null vector field of the observer's lightcone) and the associated optical
equations, which relate the optical scalars to the curvature of the spacetime.
| [
{
"created": "Wed, 29 Nov 2000 16:10:52 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Frittelli",
"Simonetta",
""
],
[
"Kling",
"Thomas P.",
""
],
[
"Newman",
"Ezra T.",
""
]
] | In a previous article concerning image distortion in non-perturbative gravitational lensing theory we described how to introduce shape and distortion parameters for small sources. We also showed how they could be expressed in terms of the scalar products of the geodesic deviation vectors of the source's pencil of rays in the past lightcone of an observer. In the present work we give an alternative approach to the description of the shape and distortion parameters and their evolution along the null geodesic from the source to the observer, but now in terms of the optical scalars (the convergence and shear of null vector field of the observer's lightcone) and the associated optical equations, which relate the optical scalars to the curvature of the spacetime. |
1807.02041 | Elena De Paoli | Tommaso De Lorenzo, Elena De Paoli, Simone Speziale | Spacetime Thermodynamics with Contorsion | 21 pages, 2 figures | Phys. Rev. D 98, 064053 (2018) | 10.1103/PhysRevD.98.064053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that a conserved effective energy-momentum tensor for
Einstein-Cartan theory can be identified from the Noether identities of the
matter Lagrangian, using the torsion field equations relating them. More
precisely, a one-parameter family labelled by the Immirzi parameter. We use
this result and the contorsion description to show that Jacobson's
thermodynamical derivation of the Einstein equations follows as in the metric
theory, namely from the equilibrium Clausius relation and the fact that a
Killing horizon is metric-geodetic. Our derivation works for an arbitrary
torsion field. In the course of our discussion we review the laws of black hole
mechanics and their dependence on torsion.
| [
{
"created": "Thu, 5 Jul 2018 15:00:34 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Sep 2018 15:54:11 GMT",
"version": "v2"
}
] | 2018-10-03 | [
[
"De Lorenzo",
"Tommaso",
""
],
[
"De Paoli",
"Elena",
""
],
[
"Speziale",
"Simone",
""
]
] | We prove that a conserved effective energy-momentum tensor for Einstein-Cartan theory can be identified from the Noether identities of the matter Lagrangian, using the torsion field equations relating them. More precisely, a one-parameter family labelled by the Immirzi parameter. We use this result and the contorsion description to show that Jacobson's thermodynamical derivation of the Einstein equations follows as in the metric theory, namely from the equilibrium Clausius relation and the fact that a Killing horizon is metric-geodetic. Our derivation works for an arbitrary torsion field. In the course of our discussion we review the laws of black hole mechanics and their dependence on torsion. |
gr-qc/0511121 | Guihua Tian | Guihua Tian | Does the Schwarzschild black hole really exist? | 4 pages, no figures | null | null | null | gr-qc | null | We use the Kruskal time coordinate T to define the initial time. By this way,
it naturally divides the stable study into one connected with the two regions:
the white-hole-connected region and the black-hole-connected region. The union
of the two regions covers the Schwarzschild space-time (r>2m). We also obtain
the very reasonable conclusion: the white-hole-connected region is instable;
whereas the black-hole-connected region is stable. If we take the instability
with caution and seriousness, it might be not unreasonable to regard that the
Schwarzschild black hole might be instable too.
| [
{
"created": "Tue, 22 Nov 2005 11:00:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tian",
"Guihua",
""
]
] | We use the Kruskal time coordinate T to define the initial time. By this way, it naturally divides the stable study into one connected with the two regions: the white-hole-connected region and the black-hole-connected region. The union of the two regions covers the Schwarzschild space-time (r>2m). We also obtain the very reasonable conclusion: the white-hole-connected region is instable; whereas the black-hole-connected region is stable. If we take the instability with caution and seriousness, it might be not unreasonable to regard that the Schwarzschild black hole might be instable too. |
1707.05280 | Jose Luis Bl\'azquez-Salcedo | Zahra Altaha Motahar, Jose Luis Bl\'azquez-Salcedo, Burkhard Kleihaus,
Jutta Kunz | Scalarization of neutron stars with realistic equations of state | 17 pages, 9 figures, matches version published in PRD | Phys. Rev. D 96, 064046 (2017) | 10.1103/PhysRevD.96.064046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the effect of scalarization on static and slowly rotating neutron
stars for a wide variety of realistic equations of state, including pure
nuclear matter, nuclear matter with hyperons, hybrid nuclear and quark matter,
and pure quark matter. We analyze the onset of scalarization, presenting a
universal relation for the critical coupling parameter versus compactness. We
find that the onset and the magnitude of the scalarization are strongly
correlated with the value of the gravitational potential (the metric component
$g_{tt}$) at the center of the star. We also consider the
moment-of-inertia--compactness relations and confirm universality for the
nuclear matter, hyperon and hybrid equations of state.
| [
{
"created": "Mon, 17 Jul 2017 16:54:19 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Sep 2017 12:05:08 GMT",
"version": "v2"
}
] | 2017-09-28 | [
[
"Motahar",
"Zahra Altaha",
""
],
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We consider the effect of scalarization on static and slowly rotating neutron stars for a wide variety of realistic equations of state, including pure nuclear matter, nuclear matter with hyperons, hybrid nuclear and quark matter, and pure quark matter. We analyze the onset of scalarization, presenting a universal relation for the critical coupling parameter versus compactness. We find that the onset and the magnitude of the scalarization are strongly correlated with the value of the gravitational potential (the metric component $g_{tt}$) at the center of the star. We also consider the moment-of-inertia--compactness relations and confirm universality for the nuclear matter, hyperon and hybrid equations of state. |
1310.8571 | Dennis Bessada | Dennis Bessada and Oswaldo D. Miranda | Probing a cosmological model with a $\Lambda = \Lambda_0 + 3\beta H^2$
decaying-vacuum | Published in Physical Review D | Phys. Rev. D 88, 083530 (2013) | 10.1103/PhysRevD.88.083530 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the evolution of matter-density perturbations for an
arbitrary $\Lambda(t)$ model, and specialize our analysis to the particular
phenomenological law $\Lambda = \Lambda_0 + 3\beta H^2$. We study the evolution
of the cosmic star formation rate in this particular dark energy scenario and,
by constraining the $\beta$ parameter using both the age of the universe and
the cosmic star formation rate curve, we show that it leads to a reasonable
physical model for $\beta\lesssim 0.1$.
| [
{
"created": "Thu, 31 Oct 2013 16:14:18 GMT",
"version": "v1"
}
] | 2013-11-01 | [
[
"Bessada",
"Dennis",
""
],
[
"Miranda",
"Oswaldo D.",
""
]
] | In this work we study the evolution of matter-density perturbations for an arbitrary $\Lambda(t)$ model, and specialize our analysis to the particular phenomenological law $\Lambda = \Lambda_0 + 3\beta H^2$. We study the evolution of the cosmic star formation rate in this particular dark energy scenario and, by constraining the $\beta$ parameter using both the age of the universe and the cosmic star formation rate curve, we show that it leads to a reasonable physical model for $\beta\lesssim 0.1$. |
gr-qc/9912049 | Carlo Ungarelli | M. Cavaglia` and C. Ungarelli | Recent developments in quantum string cosmology | 4 pages, one eps figures, uses espcrc2.sty. Talk given at the Third
Conference on Constrained Dynamics and Quantum Gravity | Nucl.Phys.Proc.Suppl. 88 (2000) 355-358 | 10.1016/S0920-5632(00)00801-X | null | gr-qc | null | In this talk we discuss the quantisation of a class of string cosmology
models characterised by scale factor duality invariance. The amplitudes for the
full set of classically allowed and forbidden transitions are computed by
applying the reduced phase space and path integral methods. In particular, the
path integral calculation clarifies the meaning of the instanton-like behaviour
of the transition amplitudes that has been first pointed out in previous
investigations.
| [
{
"created": "Mon, 13 Dec 1999 17:49:37 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Cavaglia`",
"M.",
""
],
[
"Ungarelli",
"C.",
""
]
] | In this talk we discuss the quantisation of a class of string cosmology models characterised by scale factor duality invariance. The amplitudes for the full set of classically allowed and forbidden transitions are computed by applying the reduced phase space and path integral methods. In particular, the path integral calculation clarifies the meaning of the instanton-like behaviour of the transition amplitudes that has been first pointed out in previous investigations. |
gr-qc/0501056 | Sergey Kozyrev | S.N. Andrianov, V.V. Bochkarev | Dynamic quantum theory of large additional dimensions for non-massive
particles | null | null | null | null | gr-qc | null | Brane model of universe is considered for zero-mass particle. Equation of
Wheeler - de Witt type is obtained using variation principle from the
well-known conservation laws inside the brane. This equation includes term
accounting the variation of brane topology. Solutions are obtained analytically
at some simplifications and the dispersion relations are derived for frequency
of wave associated with the particle.
| [
{
"created": "Wed, 19 Jan 2005 06:13:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Andrianov",
"S. N.",
""
],
[
"Bochkarev",
"V. V.",
""
]
] | Brane model of universe is considered for zero-mass particle. Equation of Wheeler - de Witt type is obtained using variation principle from the well-known conservation laws inside the brane. This equation includes term accounting the variation of brane topology. Solutions are obtained analytically at some simplifications and the dispersion relations are derived for frequency of wave associated with the particle. |
1305.0695 | Marit Sandstad | Marit Sandstad, Tomi S. Koivisto and David F. Mota | Non-locality of the C- and D-theories | 9 pages, no figures | Class. Quantum Grav. 30, 155005 (2013) | 10.1088/0264-9381/30/15/155005 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Apparent similarities between non-local theories of gravity and the so-called
C-theories are pointed out. It is shown that some simple C-theories can be
mapped exactly into a previously considered type of ghost-free nonlocal
gravity. This may introduce a useful tool to tackle some infinite-order
derivative theories and raises the possibility of describing renormalisable
gravity in a new context of D-theories.
| [
{
"created": "Fri, 3 May 2013 13:17:23 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2013 13:47:02 GMT",
"version": "v2"
}
] | 2013-06-26 | [
[
"Sandstad",
"Marit",
""
],
[
"Koivisto",
"Tomi S.",
""
],
[
"Mota",
"David F.",
""
]
] | Apparent similarities between non-local theories of gravity and the so-called C-theories are pointed out. It is shown that some simple C-theories can be mapped exactly into a previously considered type of ghost-free nonlocal gravity. This may introduce a useful tool to tackle some infinite-order derivative theories and raises the possibility of describing renormalisable gravity in a new context of D-theories. |
1703.07556 | Stav Zalel | Fay Dowker, Stav Zalel | Evolution of Universes in Causal Set Cosmology | null | null | 10.1016/j.crhy.2017.03.002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The causal set approach to the problem of quantum gravity is based on the
hypothesis that spacetime is fundamentally discrete. Spacetime discreteness
opens the door to novel types of dynamical law for cosmology and the Classical
Sequential Growth (CSG) models of Rideout and Sorkin form an interesting class
of such laws. It has been shown that a renormalisation of the dynamical
parameters of a CSG model occurs whenever the universe undergoes a Big
Crunch-Big Bang bounce. In this paper we propose a way to model the creation of
a new universe after the singularity of a black hole. We show that
renormalisation of dynamical parameters occurs in a CSG model after such a
creation event. We speculate that this could realise aspects of Smolin's
Cosmological Natural Selection proposal.
| [
{
"created": "Wed, 22 Mar 2017 08:11:40 GMT",
"version": "v1"
}
] | 2017-03-23 | [
[
"Dowker",
"Fay",
""
],
[
"Zalel",
"Stav",
""
]
] | The causal set approach to the problem of quantum gravity is based on the hypothesis that spacetime is fundamentally discrete. Spacetime discreteness opens the door to novel types of dynamical law for cosmology and the Classical Sequential Growth (CSG) models of Rideout and Sorkin form an interesting class of such laws. It has been shown that a renormalisation of the dynamical parameters of a CSG model occurs whenever the universe undergoes a Big Crunch-Big Bang bounce. In this paper we propose a way to model the creation of a new universe after the singularity of a black hole. We show that renormalisation of dynamical parameters occurs in a CSG model after such a creation event. We speculate that this could realise aspects of Smolin's Cosmological Natural Selection proposal. |
1002.0669 | Kinjal Banerjee | Kinjal Banerjee | Some Aspects of Holst and Nieh-Yan Terms in General Relativity with
Torsion | Minor changes, References added. | Class. Quant. Grav. 27:135012,2010 | 10.1088/0264-9381/27/13/135012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the relation of the Holst term with the Nieh-Yan term in terms of
metric variables. We show that the Holst term indeed affects the classical
equations of motion in the presence of matter with spin. Therefore the correct
term to add to the Einstein-Hilbert action such that the equations of motion
are not affected is the Nieh-Yan term. We then calculate the torsion charge due
to this term in the context of a perfect fluid sphere with torsion and show
that it vanishes once a horizon is formed but not otherwise. We also show that
adding on torsion to General Relativity the Einstein's equations are no longer
holographic in torsion although they continue to be so for the metric.
| [
{
"created": "Wed, 3 Feb 2010 08:56:02 GMT",
"version": "v1"
},
{
"created": "Tue, 18 May 2010 08:04:47 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Banerjee",
"Kinjal",
""
]
] | We explore the relation of the Holst term with the Nieh-Yan term in terms of metric variables. We show that the Holst term indeed affects the classical equations of motion in the presence of matter with spin. Therefore the correct term to add to the Einstein-Hilbert action such that the equations of motion are not affected is the Nieh-Yan term. We then calculate the torsion charge due to this term in the context of a perfect fluid sphere with torsion and show that it vanishes once a horizon is formed but not otherwise. We also show that adding on torsion to General Relativity the Einstein's equations are no longer holographic in torsion although they continue to be so for the metric. |
0902.0093 | Christian Corda cordac | C. Corda, S. A. Ali and C. Cafaro | Interferometer Response to Scalar Gravitational Waves | Accepted for publication by Int. Journ. Mod. Phys. D. Final version | Int.J.Mod.Phys.D19:2095-2109,2010 | 10.1142/S0218271810018219 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently suggested that the magnetic component of Gravitational Waves
(GWs) is relevant in the evaluation of frequency response functions of
gravitational interferometers. In this paper we extend the analysis to the
magnetic component of the scalar mode of GWs which arise from scalar-tensor
gravity theory. In the low-frequency approximation, the response function of
ground-based interferometers is calculated. The angular dependence of the
electric and magnetic contributions to the response function is discussed.
Finally, for an arbitrary frequency range, the proper distance between two test
masses is calculated and its usefulness in the high-frequency limit for
space-based interferometers is briefly considered.
| [
{
"created": "Sat, 31 Jan 2009 23:40:17 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2010 14:41:16 GMT",
"version": "v2"
}
] | 2010-11-15 | [
[
"Corda",
"C.",
""
],
[
"Ali",
"S. A.",
""
],
[
"Cafaro",
"C.",
""
]
] | It was recently suggested that the magnetic component of Gravitational Waves (GWs) is relevant in the evaluation of frequency response functions of gravitational interferometers. In this paper we extend the analysis to the magnetic component of the scalar mode of GWs which arise from scalar-tensor gravity theory. In the low-frequency approximation, the response function of ground-based interferometers is calculated. The angular dependence of the electric and magnetic contributions to the response function is discussed. Finally, for an arbitrary frequency range, the proper distance between two test masses is calculated and its usefulness in the high-frequency limit for space-based interferometers is briefly considered. |
1810.06507 | Ivano Dami\~ao Soares | Ivano Dami\~ao Soares | Boosted Kerr black holes in general relativity | 7 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1608.01174; typing mistakes in eq.(16), eq.(19) and eq.(27) of previous
version were corrected; new version with extended manuscript and new title;
typing corrections; accepted for publication in Phys. Rev. D, April 8, 2019 | Phys. Rev. D 99, 084054 (2019) | 10.1103/PhysRevD.99.084054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A solution of Einstein's vacuum field equation is derived that describes a
general boosted Kerr black hole relative to a Lorentz frame at future null
infinity. The metric contains five independent parameters -- mass $m$, rotation
$\omega$, boost parameter $v/c$ and the boost direction defined by
$(n_1,n_2,n_3)$ satisfying $(n_1)^2+(n_2)^2+(n_3)^2=1$ -- and reduces to the
Kerr black hole when the boost parameter is zero and $n_1=1$. The solution
describes the most general configuration that an astrophysical black hole must
have. The black hole rotates about the $z$-axis with angular momentum
proportional to $m \omega$ and the geometry has just one Killing vector
$\partial/\partial{u}$, where $u$ is the retarded time coordinate. The boost
turns the ergosphere asymmetric, with dominant lobes in the direction opposite
to the boost. The event and Cauchy horizons, defined for the case $\omega < m$,
are specified respectively by the radii $r_{\pm}=m \pm \sqrt{m^2-\omega^2}$.
The horizons are topologically spherical and the singularity has the topology
of a circle on planes that are orthogonal to the boost direction. We argue that
this black hole geometry is the natural set to describe the remnants of the
recently observed gravitational wave events $GW150914$, $GW151226$, $GW170814$
and $GW170817$\cite{gw1,gw2,gw3,gw4}. In the conclusions we discuss possible
astrophysical processes in the asymmetric ergosphere and the electromagnetic
dynamical effects that may result from the rotating black hole moving at
relativistic speeds together with the precession of the boost axis about the
rotation axis of the black hole.
| [
{
"created": "Mon, 15 Oct 2018 16:40:25 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Oct 2018 14:57:30 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Jan 2019 16:31:27 GMT",
"version": "v3"
},
{
"created": "Tue, 5 Feb 2019 14:25:53 GMT",
"version": "v4"
},
{
"cr... | 2019-05-08 | [
[
"Soares",
"Ivano Damião",
""
]
] | A solution of Einstein's vacuum field equation is derived that describes a general boosted Kerr black hole relative to a Lorentz frame at future null infinity. The metric contains five independent parameters -- mass $m$, rotation $\omega$, boost parameter $v/c$ and the boost direction defined by $(n_1,n_2,n_3)$ satisfying $(n_1)^2+(n_2)^2+(n_3)^2=1$ -- and reduces to the Kerr black hole when the boost parameter is zero and $n_1=1$. The solution describes the most general configuration that an astrophysical black hole must have. The black hole rotates about the $z$-axis with angular momentum proportional to $m \omega$ and the geometry has just one Killing vector $\partial/\partial{u}$, where $u$ is the retarded time coordinate. The boost turns the ergosphere asymmetric, with dominant lobes in the direction opposite to the boost. The event and Cauchy horizons, defined for the case $\omega < m$, are specified respectively by the radii $r_{\pm}=m \pm \sqrt{m^2-\omega^2}$. The horizons are topologically spherical and the singularity has the topology of a circle on planes that are orthogonal to the boost direction. We argue that this black hole geometry is the natural set to describe the remnants of the recently observed gravitational wave events $GW150914$, $GW151226$, $GW170814$ and $GW170817$\cite{gw1,gw2,gw3,gw4}. In the conclusions we discuss possible astrophysical processes in the asymmetric ergosphere and the electromagnetic dynamical effects that may result from the rotating black hole moving at relativistic speeds together with the precession of the boost axis about the rotation axis of the black hole. |
2201.00648 | Hajime Sotani | Hajime Sotani and Akira Dohi | Gravitational wave asteroseismology on cooling neutron stars | accepted for publication in PRD | null | 10.1103/PhysRevD.105.023007 | RIKEN-iTHEMS-Report-22 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We examine the gravitational wave frequencies from neutron stars during
thermal evolution, adopting the relativistic Cowling approximation. We
particularly focus on the neutron star models, in which the direct Urca (rapid
cooling process) does not work, without the superfluidity and
superconductivity. For such models, the cooling curve hardly depends on the
equation of state (EOS) as well as the mass of neutron star, while we show that
the gravitational wave frequencies strongly depend on the both properties.
Then, we find that the frequencies of the fundamental and the 1st pressure mode
multiplied with the stellar mass are well expressed as a function of the
stellar compactness almost independently of the EOS. We also find that the
frequency of the 1st gravity mode in later phase of the thermal evolution is
strongly correlated with the stellar compactness. In addition, we derive the
empirical formula estimating the threshold mass for the onset of the direct
Urca inside the neutron star as a function of the nuclear saturation parameter.
This formula will give us a constraint on the neutron star properties, if it
would be observationally found that the direct Urca occurs (or does not work)
inside the neutron star.
| [
{
"created": "Thu, 30 Dec 2021 08:15:36 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Sotani",
"Hajime",
""
],
[
"Dohi",
"Akira",
""
]
] | We examine the gravitational wave frequencies from neutron stars during thermal evolution, adopting the relativistic Cowling approximation. We particularly focus on the neutron star models, in which the direct Urca (rapid cooling process) does not work, without the superfluidity and superconductivity. For such models, the cooling curve hardly depends on the equation of state (EOS) as well as the mass of neutron star, while we show that the gravitational wave frequencies strongly depend on the both properties. Then, we find that the frequencies of the fundamental and the 1st pressure mode multiplied with the stellar mass are well expressed as a function of the stellar compactness almost independently of the EOS. We also find that the frequency of the 1st gravity mode in later phase of the thermal evolution is strongly correlated with the stellar compactness. In addition, we derive the empirical formula estimating the threshold mass for the onset of the direct Urca inside the neutron star as a function of the nuclear saturation parameter. This formula will give us a constraint on the neutron star properties, if it would be observationally found that the direct Urca occurs (or does not work) inside the neutron star. |
1304.4089 | Vasilis Oikonomou | V. K. Oikonomou | An Exponential F(R) Dark Energy Model | similar to journal version, new important references added | null | 10.1007/s10714-013-1597-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an exponential $F(R)$ modified gravity model in the Jordan and the
Einstein frame. We use a general approach in order to investigate and
demonstrate the viability of the model. Apart from the general features that
this models has, which actually render it viable at a first step, we address
the issues of finite time singularities, Newton's law corrections and the
scalaron mass. As we will evince, the model passes these latter two tests
successfully and also has no finite time singularities, a feature inherent to
other well studied exponential models.
| [
{
"created": "Mon, 15 Apr 2013 13:21:04 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2013 12:24:44 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Oikonomou",
"V. K.",
""
]
] | We present an exponential $F(R)$ modified gravity model in the Jordan and the Einstein frame. We use a general approach in order to investigate and demonstrate the viability of the model. Apart from the general features that this models has, which actually render it viable at a first step, we address the issues of finite time singularities, Newton's law corrections and the scalaron mass. As we will evince, the model passes these latter two tests successfully and also has no finite time singularities, a feature inherent to other well studied exponential models. |
1812.06112 | Carlos Villalpando | Carlos Villalpando, Sujoy K. Modak | Minimal length effect on the broadening of free wave-packets and its
physical implications | v4, 34 pages, 7 figures - matches published version in PRD | Phys. Rev. D 100, 024054 (2019) | 10.1103/PhysRevD.100.024054 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Generalized Uncertainty Principle (GUP) modified time evolution
for the width of wave-packets for a scalar potential. Free particle case is
solved exactly where the wave-packet broadening is modified by a coupling
between the GUP parameter and higher order moments in the probability
distribution in momentum space. We consider two popular forms of deformations
widely used in the literature - one of which modifies the commutator with a
quadratic term in momentum, while the other modifies it with terms both linear
and quadratic in momentum. Unlike the standard case, satisfying Heisenberg
uncertainty, here the GUP modified broadening rates, for both deformations, not
only depend on the initial size (both in position and momentum space) of the
wave-packet, but also on the initial probability distribution and momentum of
the particle. The new rates of wave-packet broadening, for both situations, are
modified by a handful of new terms - such as the skewness and kurtosis
coefficients, as well as the (constant) momentum of the particle. Comparisons
with the standard Heisenberg Uncertainty Principle (HUP)-based results show
potentially measurable differences in the rates of free wave-packet broadening
for physical systems such as the $C_{60}$ and $C_{176}$ molecules, and more so
for large organic molecular wave-packets. In doing so, we open a path to scan
the GUP parameter space by several orders of magnitude inside the best existing
upper bounds for both forms of GUP.
| [
{
"created": "Fri, 14 Dec 2018 19:07:54 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jan 2019 04:22:35 GMT",
"version": "v2"
},
{
"created": "Sat, 11 May 2019 22:12:36 GMT",
"version": "v3"
},
{
"created": "Tue, 6 Aug 2019 15:23:43 GMT",
"version": "v4"
}
] | 2019-08-07 | [
[
"Villalpando",
"Carlos",
""
],
[
"Modak",
"Sujoy K.",
""
]
] | We study the Generalized Uncertainty Principle (GUP) modified time evolution for the width of wave-packets for a scalar potential. Free particle case is solved exactly where the wave-packet broadening is modified by a coupling between the GUP parameter and higher order moments in the probability distribution in momentum space. We consider two popular forms of deformations widely used in the literature - one of which modifies the commutator with a quadratic term in momentum, while the other modifies it with terms both linear and quadratic in momentum. Unlike the standard case, satisfying Heisenberg uncertainty, here the GUP modified broadening rates, for both deformations, not only depend on the initial size (both in position and momentum space) of the wave-packet, but also on the initial probability distribution and momentum of the particle. The new rates of wave-packet broadening, for both situations, are modified by a handful of new terms - such as the skewness and kurtosis coefficients, as well as the (constant) momentum of the particle. Comparisons with the standard Heisenberg Uncertainty Principle (HUP)-based results show potentially measurable differences in the rates of free wave-packet broadening for physical systems such as the $C_{60}$ and $C_{176}$ molecules, and more so for large organic molecular wave-packets. In doing so, we open a path to scan the GUP parameter space by several orders of magnitude inside the best existing upper bounds for both forms of GUP. |
2202.11252 | Gerardo Vel\'azquez-Rodr\'iguez | Abigail \'Alvarez, Mois\'es Bravo-Gaete, Mar\'ia Montserrat
Ju\'arez-Aubry and Gerardo Vel\'azquez Rodr\'iguez | Thermodynamics of non-linearly charged Anti-de Sitter black holes in
four-dimensional Critical Gravity | null | null | 10.1103/PhysRevD.105.084032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we provide new examples of Anti-de Sitter black holes with a
planar base manifold in four-dimensional Critical Gravity by considering
nonlinear electrodynamics as a matter source. We find a general solution
characterized by the presence of only one integration constant where, for a
suitable election of coupling constants, we can show the existence of one or
more horizons. Additionally, we compute its non-null thermodynamical quantities
through a variety of techniques, testing the validity of the first law of
thermodynamics as well as a Smarr formula. Finally, we analyze the local
thermodynamical stability of the solutions. To our knowledge, these charged
configurations are the first example with Critical Gravity where their
thermodynamical quantities are not zero.
| [
{
"created": "Wed, 23 Feb 2022 00:51:09 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Apr 2022 00:09:38 GMT",
"version": "v2"
}
] | 2022-05-04 | [
[
"Álvarez",
"Abigail",
""
],
[
"Bravo-Gaete",
"Moisés",
""
],
[
"Juárez-Aubry",
"María Montserrat",
""
],
[
"Rodríguez",
"Gerardo Velázquez",
""
]
] | In this work, we provide new examples of Anti-de Sitter black holes with a planar base manifold in four-dimensional Critical Gravity by considering nonlinear electrodynamics as a matter source. We find a general solution characterized by the presence of only one integration constant where, for a suitable election of coupling constants, we can show the existence of one or more horizons. Additionally, we compute its non-null thermodynamical quantities through a variety of techniques, testing the validity of the first law of thermodynamics as well as a Smarr formula. Finally, we analyze the local thermodynamical stability of the solutions. To our knowledge, these charged configurations are the first example with Critical Gravity where their thermodynamical quantities are not zero. |
1309.0693 | Sumanta Chakraborty | Sumanta Chakraborty | Constraining Alternative Gravity Theories Using The Solar Neutrino
Problem | 21 pages, 6 figures, 3 tables; Mathches Published Version | Class. Quantum. Grav 31 (2014) 055005 | 10.1088/0264-9381/31/5/055005 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The neutrino flavor oscillation is studied in some classes of alternative
gravity theories in a plane specified by $\theta =\pi /2$, exploiting the
spherical symmetry and general equations for oscillation phases are given. We
first calculate the phase in a general static spherically symmetric model and
then we discuss some spherically symmetric solutions in alternative gravity
theories. Among them we discuss the effect of cosmological term in
Schwarzschild-(anti)de Sitter solution, which is the vacuum solution in $F(R)$
theory, the effect of charge and Gauss-Bonnet coupling parameter on the
oscillation phase is presented. Finally we discuss a charged solution with
spherical symmetry in $F(R)$ theory and also its implication to the oscillation
phase. We calculate the oscillation length and transition probability in these
spherically symmetric spacetime and have presented a graphical representation
for transition probability with various choice for parameters in our theory.
From this we could constrain parameters appearing in these alternative theories
using standard solar neutrino results.
| [
{
"created": "Mon, 2 Sep 2013 03:39:13 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Mar 2014 05:11:03 GMT",
"version": "v2"
}
] | 2014-03-14 | [
[
"Chakraborty",
"Sumanta",
""
]
] | The neutrino flavor oscillation is studied in some classes of alternative gravity theories in a plane specified by $\theta =\pi /2$, exploiting the spherical symmetry and general equations for oscillation phases are given. We first calculate the phase in a general static spherically symmetric model and then we discuss some spherically symmetric solutions in alternative gravity theories. Among them we discuss the effect of cosmological term in Schwarzschild-(anti)de Sitter solution, which is the vacuum solution in $F(R)$ theory, the effect of charge and Gauss-Bonnet coupling parameter on the oscillation phase is presented. Finally we discuss a charged solution with spherical symmetry in $F(R)$ theory and also its implication to the oscillation phase. We calculate the oscillation length and transition probability in these spherically symmetric spacetime and have presented a graphical representation for transition probability with various choice for parameters in our theory. From this we could constrain parameters appearing in these alternative theories using standard solar neutrino results. |
1810.09188 | Thomas Buchert | Thomas Buchert | Is Dark Energy Simulated by Structure Formation in the Universe ? | 7 pages + cover page. Talk presented at 2nd World Summit on Exploring
the Dark Side of the Universe, 25-29 June 2018, University of Antilles,
Guadeloupe; matches accepted version | PoS(EDSU2018)038 | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard model of cosmology assumes that the Universe can be described to
hover around a homogeneous-isotropic solution of Einstein's general theory of
relativity. This description needs (sometimes hidden) hypotheses that restrict
the generality, and relaxing these restrictions is the headline of a new
physical approach to cosmology that refurnishes the cosmological framework.
Considering a homogeneous geometry as a template geometry for the in reality
highly inhomogeneous Universe must be considered a strong idealization.
Unveiling the limitations of the standard model opens the door to rich
consequences of general relativity, giving rise to effective (i.e. spatially
averaged) cosmological models that may even explain the longstanding problems
of dark energy and dark matter. We explore in this talk the influence of
structure formation on average properties of the Universe by discussing: (i)
general thoughts on why considering average properties, on the key-issue of
non-conserved curvature, and on the global gravitational instability of the
standard model of cosmology; (ii) the general set of cosmological equations
arising from averaging the scalar parts of Einstein's equations, the generic
property of structure formation interacting with the average properties of the
Universe in a scale-dependent way, and the description of cosmological
backreaction in terms of an effective scalar field.
| [
{
"created": "Mon, 22 Oct 2018 11:39:28 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2018 12:02:25 GMT",
"version": "v2"
}
] | 2018-12-21 | [
[
"Buchert",
"Thomas",
""
]
] | The standard model of cosmology assumes that the Universe can be described to hover around a homogeneous-isotropic solution of Einstein's general theory of relativity. This description needs (sometimes hidden) hypotheses that restrict the generality, and relaxing these restrictions is the headline of a new physical approach to cosmology that refurnishes the cosmological framework. Considering a homogeneous geometry as a template geometry for the in reality highly inhomogeneous Universe must be considered a strong idealization. Unveiling the limitations of the standard model opens the door to rich consequences of general relativity, giving rise to effective (i.e. spatially averaged) cosmological models that may even explain the longstanding problems of dark energy and dark matter. We explore in this talk the influence of structure formation on average properties of the Universe by discussing: (i) general thoughts on why considering average properties, on the key-issue of non-conserved curvature, and on the global gravitational instability of the standard model of cosmology; (ii) the general set of cosmological equations arising from averaging the scalar parts of Einstein's equations, the generic property of structure formation interacting with the average properties of the Universe in a scale-dependent way, and the description of cosmological backreaction in terms of an effective scalar field. |
1403.0449 | Meng-Sen Ma | Meng-Sen Ma, Fang Liu, Ren Zhao | Continuous phase transition and critical behaviors of 3D black hole with
torsion | 15 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1310.1491 | Class. Quantum Grav. 31(2014) 095001 | 10.1088/0264-9381/31/9/095001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the phase transition and the critical behavior of the BTZ black hole
with torsion obtained in $(1+2)$-dimensional Poincar\'{e} gauge theory.
According to Ehrenfest's classification, when the parameters in the theory are
arranged properly the BTZ black hole with torsion may posses the second order
phase transition which is also a smaller mass/larger mass black hole phase
transition. Nevertheless, the critical behavior is different from the one in
the van der Waals liquid/gas system. We also calculated the critical exponents
of the relevant thermodynamic quantities, which are the same as the ones
obtained in the Ho\v{r}ava-Lifshitz black hole and the Born-Infeld black hole.
| [
{
"created": "Mon, 3 Mar 2014 14:46:29 GMT",
"version": "v1"
}
] | 2014-04-10 | [
[
"Ma",
"Meng-Sen",
""
],
[
"Liu",
"Fang",
""
],
[
"Zhao",
"Ren",
""
]
] | We study the phase transition and the critical behavior of the BTZ black hole with torsion obtained in $(1+2)$-dimensional Poincar\'{e} gauge theory. According to Ehrenfest's classification, when the parameters in the theory are arranged properly the BTZ black hole with torsion may posses the second order phase transition which is also a smaller mass/larger mass black hole phase transition. Nevertheless, the critical behavior is different from the one in the van der Waals liquid/gas system. We also calculated the critical exponents of the relevant thermodynamic quantities, which are the same as the ones obtained in the Ho\v{r}ava-Lifshitz black hole and the Born-Infeld black hole. |
2312.09549 | \"Ozcan Sert | \"Ozcan Sert | Wormholes in the Non-minimally Coupled Gravity with Electromagnetism | 23 pages | Nucl. Phys. B 1006 (2024) 116651 | 10.1016/j.nuclphysb.2024.116651 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Since the general relativistic approach requires exotic matter with negative
energy density, constructing wormholes containing realistic matter is a crucial
challenge. Therefore, extending General Relativity to non-minimal cases may be
an alternative option. In this paper, we investigate wormholes which are
supported by the non-minimally coupled electromagnetic fields to gravity in
$Y(R)F^2$ form where $F^2$ is the Maxwell invariant and $Y(R)$ is a function of
the Ricci scalar $R$. We consider both electrically and magnetically charged
cases. Then we give some exact asymptotically AdS/dS and flat solutions for
traversable wormhole geometries. By discussing whether these obtained
geometries satisfy the energy conditions and vanishing sound speed condition,
we determine stable solutions containing realistic matter for some parameter
values.
| [
{
"created": "Fri, 15 Dec 2023 06:02:02 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2024 19:06:40 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Aug 2024 20:22:53 GMT",
"version": "v3"
}
] | 2024-08-15 | [
[
"Sert",
"Özcan",
""
]
] | Since the general relativistic approach requires exotic matter with negative energy density, constructing wormholes containing realistic matter is a crucial challenge. Therefore, extending General Relativity to non-minimal cases may be an alternative option. In this paper, we investigate wormholes which are supported by the non-minimally coupled electromagnetic fields to gravity in $Y(R)F^2$ form where $F^2$ is the Maxwell invariant and $Y(R)$ is a function of the Ricci scalar $R$. We consider both electrically and magnetically charged cases. Then we give some exact asymptotically AdS/dS and flat solutions for traversable wormhole geometries. By discussing whether these obtained geometries satisfy the energy conditions and vanishing sound speed condition, we determine stable solutions containing realistic matter for some parameter values. |
2109.04450 | Shafqat Ul Islam | Jitendra Kumar, Shafqat Ul Islam, Sushant G. Ghosh | Investigating strong gravitational lensing effects by suppermassive
black holes with Horndeski gravity | 12 pages, 8 figures, 7 tables, title of the paper changed and some
typos in the text corrected | null | 10.1140/epjc/s10052-022-10357-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study gravitational lensing in strong-field limit by a static spherically
symmetric black hole in quartic scalar field Horndeski gravity having
additional hair parameter $q$, evading the no-hair theorem. We find an increase
in the deflection angle $\alpha_D$, photon sphere radius $x_{ps}$, and angular
position $\theta_{\infty}$ that increases more quickly while angular separation
$s$ more slowly, but the ratio of the flux of the first image to all other
images $r_{mag}$ decreases rapidly with increasing magnitude of the hair $q$.
We also discuss the astrophysical consequences in the supermassive black holes
at the centre of several galaxies and note that the black holes in Horndeski
gravity can be quantitatively distinguished from the Schwarzschild black hole.
Notably, we find that the deviation $\Delta\theta_{\infty}$ of black holes in
Horndeski gravity from their general relativity (GR) counterpart, for
supermassive black holes Sgr A* and M87, for $q=-1$ respectively, can reach as
much as $25.192~\mu$as and $18.92~\mu$as while $\Delta s$ is about
$1.121~\mu$as for Sgr A* and $0.8424~\mu$as for M87*. The ratio of the flux of
the first image to all other images suggest that the Schwarzschild images are
brighter than those of the black holes in Horndeski gravity, wherein the
deviation $|\Delta r_{mag}|$ is as much as 3.082. The results suggest that
observational tests of hairy black holes in Horndeski gravity are indeed
feasible.
| [
{
"created": "Thu, 9 Sep 2021 17:49:26 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Oct 2021 13:52:28 GMT",
"version": "v2"
}
] | 2022-06-01 | [
[
"Kumar",
"Jitendra",
""
],
[
"Islam",
"Shafqat Ul",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | We study gravitational lensing in strong-field limit by a static spherically symmetric black hole in quartic scalar field Horndeski gravity having additional hair parameter $q$, evading the no-hair theorem. We find an increase in the deflection angle $\alpha_D$, photon sphere radius $x_{ps}$, and angular position $\theta_{\infty}$ that increases more quickly while angular separation $s$ more slowly, but the ratio of the flux of the first image to all other images $r_{mag}$ decreases rapidly with increasing magnitude of the hair $q$. We also discuss the astrophysical consequences in the supermassive black holes at the centre of several galaxies and note that the black holes in Horndeski gravity can be quantitatively distinguished from the Schwarzschild black hole. Notably, we find that the deviation $\Delta\theta_{\infty}$ of black holes in Horndeski gravity from their general relativity (GR) counterpart, for supermassive black holes Sgr A* and M87, for $q=-1$ respectively, can reach as much as $25.192~\mu$as and $18.92~\mu$as while $\Delta s$ is about $1.121~\mu$as for Sgr A* and $0.8424~\mu$as for M87*. The ratio of the flux of the first image to all other images suggest that the Schwarzschild images are brighter than those of the black holes in Horndeski gravity, wherein the deviation $|\Delta r_{mag}|$ is as much as 3.082. The results suggest that observational tests of hairy black holes in Horndeski gravity are indeed feasible. |
2404.11910 | Chao Zhang | Chao Zhang and Ryotaro Kase | Even-parity stability of hairy black holes in $U(1)$ gauge-invariant
scalar-vector-tensor theories | 30 pages, 4 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The $U(1)$ gauge-invariant scalar-vector-tensor theories, which catches five
degrees of freedom, are valuable for its implications to inflation problems,
generation of primordial magnetic fields, new black hole (BH) and neutron star
solutions, etc. In this paper, we derive conditions for the absence of ghosts
and Laplacian instabilities of nontrivial BH solutions dressed with scalar hair
against both odd- and even-parity perturbations on top of the static and
spherically symmetric background in the most general $U(1)$ gauge-invariant
scalar-vector-tensor theories with second-order equations of motion. In
addition to some general discussions, several typical concrete models are
investigated. Specially, we show that the stability against even-parity
perturbations is ensured outside the event horizon under certain constraints to
these models. This is a crucial step to check the self-consistency of the
theories and to shed light on the physically accessible models of such theories
for future studies.
| [
{
"created": "Thu, 18 Apr 2024 05:22:40 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2024 14:00:10 GMT",
"version": "v2"
}
] | 2024-04-29 | [
[
"Zhang",
"Chao",
""
],
[
"Kase",
"Ryotaro",
""
]
] | The $U(1)$ gauge-invariant scalar-vector-tensor theories, which catches five degrees of freedom, are valuable for its implications to inflation problems, generation of primordial magnetic fields, new black hole (BH) and neutron star solutions, etc. In this paper, we derive conditions for the absence of ghosts and Laplacian instabilities of nontrivial BH solutions dressed with scalar hair against both odd- and even-parity perturbations on top of the static and spherically symmetric background in the most general $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order equations of motion. In addition to some general discussions, several typical concrete models are investigated. Specially, we show that the stability against even-parity perturbations is ensured outside the event horizon under certain constraints to these models. This is a crucial step to check the self-consistency of the theories and to shed light on the physically accessible models of such theories for future studies. |
gr-qc/0311001 | Merced Montesinos | Merced Montesinos | The double role of Einstein's equations: as equations of motion and as
vanishing energy-momentum tensor | 7 pages, no figures, latex file. Contribution to the meeting in honor
of Plebanski. Any comments on this issue are welcome | null | null | null | gr-qc hep-th physics.class-ph | null | Diffeomorphism covariant theories with dynamical background metric, like
gravity coupled to matter fields in the way expressed by Einstein-Hilbert's
action or relativistic strings described by Polyakov's action, have `on-shell'
vanishing energy-momentum tensor $t_{\mu\nu}$ because $t_{\mu\nu}$ is,
essentially, the Eulerian derivative associated with the dynamical background
metric and thus $t_{\mu\nu}$ vanishes `on-shell.' Therefore, the equations of
motion for the dynamical background metric play a double role: as equations of
motion themselves and as a reflection of the fact that $t_{\mu\nu}=0$.
Alternatively, the vanishing property of $t_{\mu\nu}$ can be seen as a
reflection of the so-called `problem of time' present in diffeomorphism
covariant theories in the sense that $t_{\mu\nu}$ are written as linear
combinations of first class constraints only.
| [
{
"created": "Fri, 31 Oct 2003 22:22:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Montesinos",
"Merced",
""
]
] | Diffeomorphism covariant theories with dynamical background metric, like gravity coupled to matter fields in the way expressed by Einstein-Hilbert's action or relativistic strings described by Polyakov's action, have `on-shell' vanishing energy-momentum tensor $t_{\mu\nu}$ because $t_{\mu\nu}$ is, essentially, the Eulerian derivative associated with the dynamical background metric and thus $t_{\mu\nu}$ vanishes `on-shell.' Therefore, the equations of motion for the dynamical background metric play a double role: as equations of motion themselves and as a reflection of the fact that $t_{\mu\nu}=0$. Alternatively, the vanishing property of $t_{\mu\nu}$ can be seen as a reflection of the so-called `problem of time' present in diffeomorphism covariant theories in the sense that $t_{\mu\nu}$ are written as linear combinations of first class constraints only. |
2310.18022 | Sudipta Sarkar | Kabir Chakravarti, Rajes Ghosh, and Sudipta Sarkar | Formation and Stability of Area Quantized Black Holes | 8 pages, 6 figures, numerical codes will be made available upon
request | Phys.Rev.D 109 (2024) 4, 046001 | 10.1103/PhysRevD.109.046001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the ergoregion instability of area-quantized rotating quantum
black holes (QBH) under gravitational perturbation. We show that the
instability can be avoided in binary systems that include QBHs if the
separation between the inspiralling components at the onset of black hole
formation is less than a critical value. We also analyze the formation history
of such systems from stellar progenitors and demonstrate that a significant
fraction of progenitor masses cannot lead to QBH formation, making it unlikely
for LIGO-Virgo black hole binaries to comprise rotating QBHs.
| [
{
"created": "Fri, 27 Oct 2023 09:58:40 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Chakravarti",
"Kabir",
""
],
[
"Ghosh",
"Rajes",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | We investigate the ergoregion instability of area-quantized rotating quantum black holes (QBH) under gravitational perturbation. We show that the instability can be avoided in binary systems that include QBHs if the separation between the inspiralling components at the onset of black hole formation is less than a critical value. We also analyze the formation history of such systems from stellar progenitors and demonstrate that a significant fraction of progenitor masses cannot lead to QBH formation, making it unlikely for LIGO-Virgo black hole binaries to comprise rotating QBHs. |
gr-qc/9807019 | H. M. Antia | H. M. Antia (Tata Institute of Fundamental Research, Mumbai) | Can Naked Singularities Yield Gamma Ray Bursts? | 4 pages, TeX, no figures | Gen.Rel.Grav. 31 (1999) 1675-1680 | 10.1023/A:1026758015746 | null | gr-qc astro-ph | null | Gamma-ray bursts are believed to be the most luminous objects in the
Universe. There has been some suggestion that these arise from quantum
processes around naked singularities. The main problem with this suggestion is
that all known examples of naked singularities are massless and hence there is
effectively no source of energy. It is argued that a globally naked singularity
coupled with quantum processes operating within a distance of the order of
Planck length of the singularity will probably yield energy burst of the order
of M_pc^2\approx2\times 10^{16} ergs, where M_p is the Planck mass.
| [
{
"created": "Thu, 9 Jul 1998 10:12:08 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Antia",
"H. M.",
"",
"Tata Institute of Fundamental Research, Mumbai"
]
] | Gamma-ray bursts are believed to be the most luminous objects in the Universe. There has been some suggestion that these arise from quantum processes around naked singularities. The main problem with this suggestion is that all known examples of naked singularities are massless and hence there is effectively no source of energy. It is argued that a globally naked singularity coupled with quantum processes operating within a distance of the order of Planck length of the singularity will probably yield energy burst of the order of M_pc^2\approx2\times 10^{16} ergs, where M_p is the Planck mass. |
2204.13837 | Shinji Tsujikawa | Masato Minamitsuji, Kazufumi Takahashi, Shinji Tsujikawa | Linear stability of black holes with static scalar hair in full
Horndeski theories: generic instabilities and surviving models | 29 pages, no figures | Phys. Rev. D 106, 044003 (2022) | 10.1103/PhysRevD.106.044003 | YITP-22-41, WUAP-22-03 | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In full Horndeski theories, we show that the static and spherically symmetric
black hole (BH) solutions with a static scalar field~$\phi$ whose kinetic
term~$X$ is nonvanishing on the BH horizon are generically prone to
ghost/Laplacian instabilities. We then search for asymptotically Minkowski
hairy BH solutions with a vanishing $X$ on the horizon free from
ghost/Laplacian instabilities. We show that models with regular coupling
functions of $\phi$ and $X$ result in no-hair Schwarzschild BHs in general. On
the other hand, the presence of a coupling between the scalar field and the
Gauss-Bonnet (GB) term $R_{\rm GB}^2$, even with the coexistence of other
regular coupling functions, leads to the realization of asymptotically
Minkowski hairy BH solutions without ghost/Laplacian instabilities. Finally, we
find that hairy BH solutions in power-law $F(R_{\rm GB}^2)$ gravity are plagued
by ghost instabilities. These results imply that the GB coupling of the form
$\xi(\phi)R_{\rm GB}^2$ plays a prominent role for the existence of
asymptotically Minkowski hairy BH solutions free from ghost/Laplacian
instabilities.
| [
{
"created": "Fri, 29 Apr 2022 00:45:41 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2022 12:46:30 GMT",
"version": "v2"
}
] | 2022-08-03 | [
[
"Minamitsuji",
"Masato",
""
],
[
"Takahashi",
"Kazufumi",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | In full Horndeski theories, we show that the static and spherically symmetric black hole (BH) solutions with a static scalar field~$\phi$ whose kinetic term~$X$ is nonvanishing on the BH horizon are generically prone to ghost/Laplacian instabilities. We then search for asymptotically Minkowski hairy BH solutions with a vanishing $X$ on the horizon free from ghost/Laplacian instabilities. We show that models with regular coupling functions of $\phi$ and $X$ result in no-hair Schwarzschild BHs in general. On the other hand, the presence of a coupling between the scalar field and the Gauss-Bonnet (GB) term $R_{\rm GB}^2$, even with the coexistence of other regular coupling functions, leads to the realization of asymptotically Minkowski hairy BH solutions without ghost/Laplacian instabilities. Finally, we find that hairy BH solutions in power-law $F(R_{\rm GB}^2)$ gravity are plagued by ghost instabilities. These results imply that the GB coupling of the form $\xi(\phi)R_{\rm GB}^2$ plays a prominent role for the existence of asymptotically Minkowski hairy BH solutions free from ghost/Laplacian instabilities. |
gr-qc/0701056 | Mariusz Dabrowski P. | Mariusz P. Dabrowski and Adam Balcerzak | Big-Rip, Sudden Future, and other exotic singularities in the universe | 3 pages, MG11 proceedings contribution | null | 10.1142/9789812834300_0321 | null | gr-qc astro-ph hep-th | null | We discuss exotic singularities in the evolution of the universe motivated by
the progress of observations in cosmology. Among them there are: Big-Rip (BR),
Sudden Future Singularities (SFS), Generalized Sudden Future Singularities
(GSFS), Finite Density Singularities (FD), type III, and type IV singularities.
We relate some of these singularities with higher-order characteristics of
expansion such as jerk and snap. We also discuss the behaviour of pointlike
objects and classical strings on the approach to these singularities.
| [
{
"created": "Wed, 10 Jan 2007 09:54:44 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Balcerzak",
"Adam",
""
]
] | We discuss exotic singularities in the evolution of the universe motivated by the progress of observations in cosmology. Among them there are: Big-Rip (BR), Sudden Future Singularities (SFS), Generalized Sudden Future Singularities (GSFS), Finite Density Singularities (FD), type III, and type IV singularities. We relate some of these singularities with higher-order characteristics of expansion such as jerk and snap. We also discuss the behaviour of pointlike objects and classical strings on the approach to these singularities. |
gr-qc/9911100 | Mauricio Bellini | Mauricio Bellini (UNMdP), Pablo D. Sisterna (UNMdP) and Roberto R.
Deza (UNMdP) | Quantally fed steady-state domain distributions in Stochastic Inflation | 10 pages, 1 figure, accepted for publication to Il Nuovo Cimento B | Nuovo Cim. B115 (2000) 239-244 | null | null | gr-qc | null | Within the framework of stochastic inflationary cosmology we derive
steady-state distributions P_c(V) of domains in comoving coordinates, under the
assumption of slow-rolling and for two specific choices of the coarse-grained
inflaton potential $V(\Phi)$. We model the process as a Starobinsky-like
equation in V-space plus a time-independent source term P_w(V) which carries
(phenomenologically) quantum-mechanical information drawn from either of two
known solutions of the Wheeler-De Witt equation: Hartle-Hawking's and
Vilenkin's wave functions. The presence of the source term leads to the
existence of nontrivial steady-state distributions P^w_c(V). The relative
efficiencies of both mechanisms at different scales are compared for the
proposed potentials.
| [
{
"created": "Thu, 25 Nov 1999 16:16:46 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Bellini",
"Mauricio",
"",
"UNMdP"
],
[
"Sisterna",
"Pablo D.",
"",
"UNMdP"
],
[
"Deza",
"Roberto R.",
"",
"UNMdP"
]
] | Within the framework of stochastic inflationary cosmology we derive steady-state distributions P_c(V) of domains in comoving coordinates, under the assumption of slow-rolling and for two specific choices of the coarse-grained inflaton potential $V(\Phi)$. We model the process as a Starobinsky-like equation in V-space plus a time-independent source term P_w(V) which carries (phenomenologically) quantum-mechanical information drawn from either of two known solutions of the Wheeler-De Witt equation: Hartle-Hawking's and Vilenkin's wave functions. The presence of the source term leads to the existence of nontrivial steady-state distributions P^w_c(V). The relative efficiencies of both mechanisms at different scales are compared for the proposed potentials. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.