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/0302075 | Yasushi Mino | Yasushi Mino | Perturbative Approach to an orbital evolution around a Supermassive
black hole | accepted for publication in the Physical Review | Phys.Rev. D67 (2003) 084027 | 10.1103/PhysRevD.67.084027 | null | gr-qc | null | A charge-free, point particle of infinitesimal mass orbiting a Kerr black
hole is known to move along a geodesic. When the particle has a finite mass or
charge, it emits radiation which carries away orbital energy and angular
momentum, and the orbit deviates from a geodesic.
In this paper we assume that the deviation is small and show that the
half-advanced minus half-retarded field surprisingly provides the correct
radiation reaction force, in a time-averaged sense, and determines the orbit of
the particle.
| [
{
"created": "Tue, 18 Feb 2003 17:34:03 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Mino",
"Yasushi",
""
]
] | A charge-free, point particle of infinitesimal mass orbiting a Kerr black hole is known to move along a geodesic. When the particle has a finite mass or charge, it emits radiation which carries away orbital energy and angular momentum, and the orbit deviates from a geodesic. In this paper we assume that the deviation is small and show that the half-advanced minus half-retarded field surprisingly provides the correct radiation reaction force, in a time-averaged sense, and determines the orbit of the particle. |
1303.0194 | Mohd. Shahalam | R. Myrzakulov, M. Shahalam | Statefinder hierarchy of bimetric and galileon models for concordance
cosmology | 15 pages, 8 figures, LaTeX, some texts, Refs. added, to appear in
JCAP | JCAP 10 (2013) 047 | 10.1088/1475-7516/2013/10/047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we use Statefinder hierarchy method to distinguish between
bimetric theory of massive gravity, galileon modified gravity and DGP models
applied to late time expansion of the universe. We also carry out comparison
between bimetric and DGP models using Statefinder pairs {r, s} and {r, q}. We
show that statefinder diagnostic can differentiate between {\Lambda}CDM and
above mentioned cosmological models of dark energy, and finally show that
Statefinder S2 is an excellent discriminant of {\Lambda}CDM and modified
gravity models.
| [
{
"created": "Thu, 28 Feb 2013 06:10:43 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jun 2013 07:40:27 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Oct 2013 10:35:59 GMT",
"version": "v3"
}
] | 2013-10-28 | [
[
"Myrzakulov",
"R.",
""
],
[
"Shahalam",
"M.",
""
]
] | In this paper, we use Statefinder hierarchy method to distinguish between bimetric theory of massive gravity, galileon modified gravity and DGP models applied to late time expansion of the universe. We also carry out comparison between bimetric and DGP models using Statefinder pairs {r, s} and {r, q}. We show that statefinder diagnostic can differentiate between {\Lambda}CDM and above mentioned cosmological models of dark energy, and finally show that Statefinder S2 is an excellent discriminant of {\Lambda}CDM and modified gravity models. |
2307.04572 | Federico Schianchi | Federico Schianchi, Henrique Gieg, Vsevolod Nedora, Anna Neuweiler,
Maximiliano Ujevic, Mattia Bulla, Tim Dietrich | M1 neutrino transport within the numerical-relativistic code BAM with
application to low mass binary neutron star mergers | 29 pages, 27 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutrino interactions are essential for an accurate understanding of the
binary neutron star merger process. In this article, we extend the code
infrastructure of the well-established numerical-relativity code BAM that until
recently neglected neutrino-driven interactions. In fact, while previous work
allowed already the usage of nuclear-tabulated equations of state and employing
a neutrino leakage scheme, we are moving forward by implementing a first-order
multipolar radiation transport scheme (M1) for the advection of neutrinos.
After testing our implementation on a set of standard scenarios, we apply it to
the evolution of four low-mass binary systems, and we perform an analysis of
ejecta properties. We also show that our new ejecta analysis infrastructure is
able to provide numerical relativity-informed inputs for the codes
$\texttt{POSSIS}$ and $\texttt{Skynet}$, for the computation of kilonova
lightcurves and nucleosynthesis yields, respectively.
| [
{
"created": "Mon, 10 Jul 2023 14:06:59 GMT",
"version": "v1"
}
] | 2023-07-11 | [
[
"Schianchi",
"Federico",
""
],
[
"Gieg",
"Henrique",
""
],
[
"Nedora",
"Vsevolod",
""
],
[
"Neuweiler",
"Anna",
""
],
[
"Ujevic",
"Maximiliano",
""
],
[
"Bulla",
"Mattia",
""
],
[
"Dietrich",
"Tim",
""
]
] | Neutrino interactions are essential for an accurate understanding of the binary neutron star merger process. In this article, we extend the code infrastructure of the well-established numerical-relativity code BAM that until recently neglected neutrino-driven interactions. In fact, while previous work allowed already the usage of nuclear-tabulated equations of state and employing a neutrino leakage scheme, we are moving forward by implementing a first-order multipolar radiation transport scheme (M1) for the advection of neutrinos. After testing our implementation on a set of standard scenarios, we apply it to the evolution of four low-mass binary systems, and we perform an analysis of ejecta properties. We also show that our new ejecta analysis infrastructure is able to provide numerical relativity-informed inputs for the codes $\texttt{POSSIS}$ and $\texttt{Skynet}$, for the computation of kilonova lightcurves and nucleosynthesis yields, respectively. |
2311.06881 | David Garfinkle | George F R Ellis and David Garfinkle | The Synge G-Method: cosmology, wormholes, firewalls, geometry | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unphysical equations of state result from the unrestricted use of the Synge
G-trick of running the Einstein field equations backwards; in particular often
this results in $\rho + p < 0$ which implies negative inertial mass density,
which does not occur in reality. This is the basis of some unphysical spacetime
models including phantom energy in cosmology and traversable wormholes.
The slogan ``ER = EPR'' appears to have no basis in physics and is merely the
result of vague and unbridled speculation. Wormholes (the ``ER'' of the slogan)
are a mathematical curiosity of general relativity that have little to no
application to a description of our universe. In contrast quantum correlations
(the ``EPR'' of the slogan) are a fundamental property of quantum mechanics
that follows from the principle of superposition and is true regardless of the
properties of gravity.
The speculative line of thought that led to ``ER = EPR'' is part of a current
vogue for anti-geometrical thinking that runs counter to (and threatens to
erase) the great geometrical insights of the global structure program of
general relativity.
| [
{
"created": "Sun, 12 Nov 2023 16:05:38 GMT",
"version": "v1"
}
] | 2023-11-17 | [
[
"Ellis",
"George F R",
""
],
[
"Garfinkle",
"David",
""
]
] | Unphysical equations of state result from the unrestricted use of the Synge G-trick of running the Einstein field equations backwards; in particular often this results in $\rho + p < 0$ which implies negative inertial mass density, which does not occur in reality. This is the basis of some unphysical spacetime models including phantom energy in cosmology and traversable wormholes. The slogan ``ER = EPR'' appears to have no basis in physics and is merely the result of vague and unbridled speculation. Wormholes (the ``ER'' of the slogan) are a mathematical curiosity of general relativity that have little to no application to a description of our universe. In contrast quantum correlations (the ``EPR'' of the slogan) are a fundamental property of quantum mechanics that follows from the principle of superposition and is true regardless of the properties of gravity. The speculative line of thought that led to ``ER = EPR'' is part of a current vogue for anti-geometrical thinking that runs counter to (and threatens to erase) the great geometrical insights of the global structure program of general relativity. |
1606.00758 | Muhammad Sharif | M. Sharif and Rubab Manzoor | Dynamics of Axial Symmetric System in Self-Interacting Brans-Dicke
Gravity | 24 pages, no figure, accepted for publication in publication in Eur.
Phys. J. C | Eur. Phys. J. C 76(2016)330 | 10.1140/epjc/s10052-016-4161-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates dynamics of axial reflection symmetric model in
self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate
hydrodynamical equations and discuss oscillations using time-dependent
perturbation for both spin as well as spin-independent cases. The expressions
of frequency, total energy density and equation of motion of oscillating model
are obtained. We study instability of oscillating models in weak
approximations. It is found that the oscillations and stability of the model
depend upon the dark energy source along with anisotropy and reflection
effects. We conclude that the axial reflection system remains stable for
stiffness parameter $\Gamma=1$, collapses for $\Gamma>1$ and becomes unstable
for $0<\Gamma<1$.
| [
{
"created": "Wed, 1 Jun 2016 01:55:39 GMT",
"version": "v1"
}
] | 2016-07-22 | [
[
"Sharif",
"M.",
""
],
[
"Manzoor",
"Rubab",
""
]
] | This paper investigates dynamics of axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using time-dependent perturbation for both spin as well as spin-independent cases. The expressions of frequency, total energy density and equation of motion of oscillating model are obtained. We study instability of oscillating models in weak approximations. It is found that the oscillations and stability of the model depend upon the dark energy source along with anisotropy and reflection effects. We conclude that the axial reflection system remains stable for stiffness parameter $\Gamma=1$, collapses for $\Gamma>1$ and becomes unstable for $0<\Gamma<1$. |
1901.04586 | Marc Casals | Marc Casals and Lu\'is F. Longo Micchi | Spectroscopy of Extremal (and Near-Extremal) Kerr Black Holes | 32 pages, 13 figures. In version 2, we included QNMs in extremal Kerr
for spin=-2, l=m=2 and 3 | Phys. Rev. D 99, 084047 (2019) | 10.1103/PhysRevD.99.084047 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate linear, spin-field perturbations of Kerr black holes in the
extremal limit throughout the complex-frequency domain. We calculate
quasi-normal modes of extremal Kerr, as well as of near-extremal Kerr, via a
novel approach: using the method of Mano, Suzuki and Takasugi (MST). We also
show how, in the extremal limit, a branch cut is formed at the
superradiant-bound frequency, $\omega_{SR}$, via a simultaneous accumulation of
quasi-normal modes and totally-reflected modes. For real frequencies, we
calculate the superradiant amplification factor, which yields the amount of
rotational energy that can be extracted from a black hole. In the extremal
limit, this factor is the largest and it displays a discontinuity at
$\omega_{SR}$ for some modes. Finally, we find no exponentially-growing modes
nor branch points on the upper-frequency plane in extremal Kerr after a
numerical investigation, thus providing evidence of the mode-stability of this
space-time away from the horizon.
| [
{
"created": "Mon, 14 Jan 2019 22:16:36 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Feb 2019 03:36:41 GMT",
"version": "v2"
}
] | 2019-05-08 | [
[
"Casals",
"Marc",
""
],
[
"Micchi",
"Luís F. Longo",
""
]
] | We investigate linear, spin-field perturbations of Kerr black holes in the extremal limit throughout the complex-frequency domain. We calculate quasi-normal modes of extremal Kerr, as well as of near-extremal Kerr, via a novel approach: using the method of Mano, Suzuki and Takasugi (MST). We also show how, in the extremal limit, a branch cut is formed at the superradiant-bound frequency, $\omega_{SR}$, via a simultaneous accumulation of quasi-normal modes and totally-reflected modes. For real frequencies, we calculate the superradiant amplification factor, which yields the amount of rotational energy that can be extracted from a black hole. In the extremal limit, this factor is the largest and it displays a discontinuity at $\omega_{SR}$ for some modes. Finally, we find no exponentially-growing modes nor branch points on the upper-frequency plane in extremal Kerr after a numerical investigation, thus providing evidence of the mode-stability of this space-time away from the horizon. |
0811.2468 | Peter Collas | Peter Collas and David Klein | Causality violating geodesics in Bonnor's rotating dust metric | null | Gen.Rel.Grav.36:2549,2004 | 10.1023/B:GERG.0000046853.99745.e4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11]
and considered also by Steadman [13], and show that coordinate time runs
backward along a portion of these geodesics.
| [
{
"created": "Sat, 15 Nov 2008 09:34:15 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Collas",
"Peter",
""
],
[
"Klein",
"David",
""
]
] | We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11] and considered also by Steadman [13], and show that coordinate time runs backward along a portion of these geodesics. |
2310.19148 | Sabir Ramazanov Dr. | Sabir Ramazanov | Spectrum of gravitational waves from long-lasting primordial sources | 15 pages; clarifications added; matches published version | JCAP02(2024)027 | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss long-lasting gravitational wave sources arising and operating
during radiation-dominated stage. Under a set of assumptions, we establish the
correspondence between cosmological evolution of a source and the resulting
gravitational wave spectrum. Namely, for the source energy density $\rho_s$
falling as a power law characterized by the exponent $\beta$, i.e., $\rho_s
\propto 1/a^{\beta}$, where $a$ is the Universe scale factor, the spectrum
takes the form $\Omega_{gw} \propto f^{2\beta-8}$ in certain ranges of values
of constant $\beta$ and frequencies $f$. In particular, matching to the best
fit power law shape of stochastic gravitational wave background discovered
recently by Pulsar Timing Array collaborations, one identifies $\beta \approx
5$. We demonstrate the correspondence with concrete examples of long-lasting
sources: domain walls and cosmic strings.
| [
{
"created": "Sun, 29 Oct 2023 20:48:22 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Nov 2023 18:42:21 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Feb 2024 05:57:36 GMT",
"version": "v3"
}
] | 2024-02-23 | [
[
"Ramazanov",
"Sabir",
""
]
] | We discuss long-lasting gravitational wave sources arising and operating during radiation-dominated stage. Under a set of assumptions, we establish the correspondence between cosmological evolution of a source and the resulting gravitational wave spectrum. Namely, for the source energy density $\rho_s$ falling as a power law characterized by the exponent $\beta$, i.e., $\rho_s \propto 1/a^{\beta}$, where $a$ is the Universe scale factor, the spectrum takes the form $\Omega_{gw} \propto f^{2\beta-8}$ in certain ranges of values of constant $\beta$ and frequencies $f$. In particular, matching to the best fit power law shape of stochastic gravitational wave background discovered recently by Pulsar Timing Array collaborations, one identifies $\beta \approx 5$. We demonstrate the correspondence with concrete examples of long-lasting sources: domain walls and cosmic strings. |
1307.1757 | Alexander Nitz | Alexander H. Nitz, Andrew Lundgren, Duncan A. Brown, Evan Ochsner,
Drew Keppel, Ian W. Harry | Accuracy of gravitational waveform models for observing
neutron-star--black-hole binaries in Advanced LIGO | 17 pages, 15 figures, abstract shortened to the 1920 character limit | Phys. Rev. D 88, 124039 (2013) | 10.1103/PhysRevD.88.124039 | LIGO Document P1300063 | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves radiated by the coalescence of compact-object binaries
containing a neutron star and a black hole are one of the most interesting
sources for the ground-based gravitational-wave observatories Advanced LIGO and
Advanced Virgo. Advanced LIGO will be sensitive to the inspiral of a $1.4\,
M_\odot$ neutron star into a $10\,M_\odot$ black hole to a maximum distance of
$\sim 900$ Mpc. Achieving this sensitivity and extracting the physics imprinted
in observed signals requires accurate modeling of the binary to construct
template waveforms. In a NSBH binary, the black hole may have significant
angular momentum (spin), which affects the phase evolution of the emitted
gravitational waves. We investigate the ability of post-Newtonian (PN)
templates to model the gravitational waves emitted during the inspiral phase of
NSBH binaries. We restrict the black hole's spin to be aligned with the orbital
angular momentum and compare several approximants. We examine restricted
amplitude waveforms that are accurate to 3.5PN order in the orbital dynamics
and complete to 2.5PN order in the spin dynamics. We also consider PN waveforms
with the recently derived 3.5PN spin-orbit and 3PN spin-orbit tail corrections.
We compare these approximants to the effective-one-body model. For all these
models, large disagreements start at low to moderate black hole spins,
particularly for binaries where the spin is anti-aligned with the orbital
angular momentum. We show that this divergence begins in the early inspiral at
$v \sim 0.2$ for $\chi_{BH} \sim 0.4$. PN spin corrections beyond those
currently known will be required for optimal detection searches and to measure
the parameters of neutron star--black hole binaries. While this complicates
searches, the strong dependence of the gravitational-wave signal on the spin
dynamics will make it possible to extract significant astrophysical
information.
| [
{
"created": "Sat, 6 Jul 2013 06:50:21 GMT",
"version": "v1"
},
{
"created": "Tue, 20 May 2014 18:18:07 GMT",
"version": "v2"
}
] | 2014-05-21 | [
[
"Nitz",
"Alexander H.",
""
],
[
"Lundgren",
"Andrew",
""
],
[
"Brown",
"Duncan A.",
""
],
[
"Ochsner",
"Evan",
""
],
[
"Keppel",
"Drew",
""
],
[
"Harry",
"Ian W.",
""
]
] | Gravitational waves radiated by the coalescence of compact-object binaries containing a neutron star and a black hole are one of the most interesting sources for the ground-based gravitational-wave observatories Advanced LIGO and Advanced Virgo. Advanced LIGO will be sensitive to the inspiral of a $1.4\, M_\odot$ neutron star into a $10\,M_\odot$ black hole to a maximum distance of $\sim 900$ Mpc. Achieving this sensitivity and extracting the physics imprinted in observed signals requires accurate modeling of the binary to construct template waveforms. In a NSBH binary, the black hole may have significant angular momentum (spin), which affects the phase evolution of the emitted gravitational waves. We investigate the ability of post-Newtonian (PN) templates to model the gravitational waves emitted during the inspiral phase of NSBH binaries. We restrict the black hole's spin to be aligned with the orbital angular momentum and compare several approximants. We examine restricted amplitude waveforms that are accurate to 3.5PN order in the orbital dynamics and complete to 2.5PN order in the spin dynamics. We also consider PN waveforms with the recently derived 3.5PN spin-orbit and 3PN spin-orbit tail corrections. We compare these approximants to the effective-one-body model. For all these models, large disagreements start at low to moderate black hole spins, particularly for binaries where the spin is anti-aligned with the orbital angular momentum. We show that this divergence begins in the early inspiral at $v \sim 0.2$ for $\chi_{BH} \sim 0.4$. PN spin corrections beyond those currently known will be required for optimal detection searches and to measure the parameters of neutron star--black hole binaries. While this complicates searches, the strong dependence of the gravitational-wave signal on the spin dynamics will make it possible to extract significant astrophysical information. |
1802.07137 | David Vasak | D. Vasak, J. Kirsch, J. Struckmeier, H. Stoecker | On the cosmological constant in the deformed Einstein-Cartan gauge
gravity in De Donder-Weyl Hamiltonian formulation | This is superseded by the newest version of arXiv:2209.00501 which
was created accidentally during the first update attempt of arXiv:1802.07131
and kept up-to-date since | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modification of the Einstein-Hilbert theory, the Covariant Canonical Gauge
Gravity (CCGG), leads to a cosmological constant that represents the energy of
the space-time continuum when deformed from its (A)dS ground state to a flat
geometry. CCGG is based on the canonical transformation theory in the De
Donder-Weyl (DW) Hamiltonian formulation. That framework modifies the
Einstein-Hilbert Lagrangian of the free gravitational field by a quadratic
Riemann-Cartan concomitant. The theory predicts a total energy-momentum of the
system of space-time and matter to vanish, in line with the conjecture of a
"Zero-Energy-Universe" going back to Lorentz (1916) and Levi-Civita (1917).
Consequently a flat geometry can only exist in presence of matter where the
bulk vacuum energy of matter, regardless of its value, is eliminated by the
vacuum energy of space-time.% $\lambda_0$. The observed cosmological constant
$\Lambda_{\mathrm{obs}}$ is found to be merely a small correction %of the order
$10^{-120} \,\lambda_0$ attributable to deviations from a flat geometry and
effects of complex dynamical geometry of space-time, namely torsion and
possibly also vacuum fluctuations. That quadratic extension of General
Relativity, anticipated already in 1918 by Einstein \cite{einstein18}, thus
provides a significant and natural contribution to resolving the "cosmological
constant problem".
| [
{
"created": "Tue, 20 Feb 2018 14:49:05 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Apr 2018 09:09:07 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Aug 2018 11:03:57 GMT",
"version": "v3"
},
{
"created": "Thu, 24 Jun 2021 14:44:59 GMT",
"version": "v4"
},
{
"created": "Wed, 7 Sep 2022 16:05:57 GMT",
"version": "v5"
},
{
"created": "Thu, 6 Oct 2022 12:59:24 GMT",
"version": "v6"
},
{
"created": "Wed, 20 Sep 2023 09:31:08 GMT",
"version": "v7"
}
] | 2023-09-21 | [
[
"Vasak",
"D.",
""
],
[
"Kirsch",
"J.",
""
],
[
"Struckmeier",
"J.",
""
],
[
"Stoecker",
"H.",
""
]
] | A modification of the Einstein-Hilbert theory, the Covariant Canonical Gauge Gravity (CCGG), leads to a cosmological constant that represents the energy of the space-time continuum when deformed from its (A)dS ground state to a flat geometry. CCGG is based on the canonical transformation theory in the De Donder-Weyl (DW) Hamiltonian formulation. That framework modifies the Einstein-Hilbert Lagrangian of the free gravitational field by a quadratic Riemann-Cartan concomitant. The theory predicts a total energy-momentum of the system of space-time and matter to vanish, in line with the conjecture of a "Zero-Energy-Universe" going back to Lorentz (1916) and Levi-Civita (1917). Consequently a flat geometry can only exist in presence of matter where the bulk vacuum energy of matter, regardless of its value, is eliminated by the vacuum energy of space-time.% $\lambda_0$. The observed cosmological constant $\Lambda_{\mathrm{obs}}$ is found to be merely a small correction %of the order $10^{-120} \,\lambda_0$ attributable to deviations from a flat geometry and effects of complex dynamical geometry of space-time, namely torsion and possibly also vacuum fluctuations. That quadratic extension of General Relativity, anticipated already in 1918 by Einstein \cite{einstein18}, thus provides a significant and natural contribution to resolving the "cosmological constant problem". |
gr-qc/9505010 | Jean-Alain Marck | J.A. Marck | SHORTCUT METHOD OF SOLUTION OF GEODESIC EQUATIONS FOR SCHWARZSCHILD
BLACK HOLE | 11 pages, 2 PostScript figures (available as uuencoded compressed tar
file), uses epsfig.tex). Accepted on February 1995 for publication in
Classical and Quantum Gravity | Class.Quant.Grav. 13 (1996) 393-402 | 10.1088/0264-9381/13/3/007 | Preprint Observatoire de Paris | gr-qc | null | It is shown how the use of the Kerr-Schild coordinate system can greatly
simplify the formulation of the geodesic equation of the Schwarzschild
solution. An application of this formulation to the numerical computation of
the aspect of a non-rotating black hole is presented. The generalization to the
case of the Kerr solution is presented too.
| [
{
"created": "Wed, 10 May 1995 22:07:08 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Marck",
"J. A.",
""
]
] | It is shown how the use of the Kerr-Schild coordinate system can greatly simplify the formulation of the geodesic equation of the Schwarzschild solution. An application of this formulation to the numerical computation of the aspect of a non-rotating black hole is presented. The generalization to the case of the Kerr solution is presented too. |
2301.07449 | Chen Wu | Mao-Yuan Wan and Chen Wu | Absorption and scattering of a high dimensional noncommutative black
hole | 10 pages and 4 figures | Eur. Phys. J. C (2023) 83:28 | 10.1140/epjc/s10052-022-11167-2 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | In this work, we investigate the scattering of massless plane scalar waves by
the high dimensional noncommutative Schwarzschild-Tangherlini black hole. We
use the partial wave approach to determine the scattering and absorption cross
sections in the incident wavelength range. Our numerical results demonstrate
that the bigger the noncommutative parameter, the smaller the maximum value of
the related partial absorption cross section, however the tendency is slightly.
We also discovered that when the noncommutative parameter is weak, the
absorption cross section of the high dimensional black hole oscillates in the
low frequency zone. The total absorption cross section oscillates around the
geometrical optical limit in the high frequency range, and the scattering
characteristics of black holes with various parameters are visibly different.
The influence on the differential scattering cross section is particularly
pronounced at large angles.
| [
{
"created": "Wed, 18 Jan 2023 11:45:04 GMT",
"version": "v1"
}
] | 2023-01-23 | [
[
"Wan",
"Mao-Yuan",
""
],
[
"Wu",
"Chen",
""
]
] | In this work, we investigate the scattering of massless plane scalar waves by the high dimensional noncommutative Schwarzschild-Tangherlini black hole. We use the partial wave approach to determine the scattering and absorption cross sections in the incident wavelength range. Our numerical results demonstrate that the bigger the noncommutative parameter, the smaller the maximum value of the related partial absorption cross section, however the tendency is slightly. We also discovered that when the noncommutative parameter is weak, the absorption cross section of the high dimensional black hole oscillates in the low frequency zone. The total absorption cross section oscillates around the geometrical optical limit in the high frequency range, and the scattering characteristics of black holes with various parameters are visibly different. The influence on the differential scattering cross section is particularly pronounced at large angles. |
2212.03098 | David Benisty | David Benisty, Philippe Brax, Anne-Christine Davis | Stringent Pulsar Timing Bounds on Light Scalar Couplings to Matter | 17 pages, 9 figures, Accepted in Phys. Rev. D | null | 10.1103/PhysRevD.107.064049 | null | gr-qc astro-ph.HE astro-ph.SR hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Pulsar Timing constraints on scalar-tensor theories with conformal and
disformal couplings to matter are discussed. Reducing the dynamics to the
motion in the centre of mass frame and using the mean anomaly parametrisation,
we find the first post-Newtonian corrections induced by the conformal and
disformal interactions in the form of a generalized quasi-Keplerian solution.
We also derive the radiation reaction force due to scalar radiation and the
corresponding Post-Keplerian Parameters (PKP). We use different pulsar time of
arrival (TOA) data sets to probe the scalar corrections to the PKP. In
particular, we focus on systems with large orbital frequencies as the
contributions to the PKP terms induced by the disformal coupling are sensitive
to higher frequencies. We find that the most constraining { {pulsar timings}}
are PSR B1913+16 and the double pulsar PSR J0737-3039A/B, being {{of the order
of}} the Cassini bound on the conformal coupling obtained from the Shapiro
effect in the solar system. { {The combined constraints using other pulsar
timings give an upper bound on the conformal coupling $\beta^2 < 2.33 \cdot
10^{-5}$ and a lower bound on the disformal coupling scale of $\Lambda \geq
1.12 \ {\rm MeV}$ which is comparable to the Cassini bound and to the GW-170817
constraints respectively}}. Future measurements for pulsar timing with black
hole companions are also discussed.
| [
{
"created": "Tue, 6 Dec 2022 16:06:55 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Mar 2023 13:49:53 GMT",
"version": "v2"
}
] | 2023-03-24 | [
[
"Benisty",
"David",
""
],
[
"Brax",
"Philippe",
""
],
[
"Davis",
"Anne-Christine",
""
]
] | Pulsar Timing constraints on scalar-tensor theories with conformal and disformal couplings to matter are discussed. Reducing the dynamics to the motion in the centre of mass frame and using the mean anomaly parametrisation, we find the first post-Newtonian corrections induced by the conformal and disformal interactions in the form of a generalized quasi-Keplerian solution. We also derive the radiation reaction force due to scalar radiation and the corresponding Post-Keplerian Parameters (PKP). We use different pulsar time of arrival (TOA) data sets to probe the scalar corrections to the PKP. In particular, we focus on systems with large orbital frequencies as the contributions to the PKP terms induced by the disformal coupling are sensitive to higher frequencies. We find that the most constraining { {pulsar timings}} are PSR B1913+16 and the double pulsar PSR J0737-3039A/B, being {{of the order of}} the Cassini bound on the conformal coupling obtained from the Shapiro effect in the solar system. { {The combined constraints using other pulsar timings give an upper bound on the conformal coupling $\beta^2 < 2.33 \cdot 10^{-5}$ and a lower bound on the disformal coupling scale of $\Lambda \geq 1.12 \ {\rm MeV}$ which is comparable to the Cassini bound and to the GW-170817 constraints respectively}}. Future measurements for pulsar timing with black hole companions are also discussed. |
1905.07105 | Siamak Akhshabi | S. Gharibi Nodijeh, S. Akhshabi, and F. Khajenabi | Orbits of particles and black hole thermodynamics in a spacetime with
torsion | 10 paes, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the static spherically symmetric vacuum solution for a spacetime
with non-vanishing torsion by solving the field equations analytically. The
effects of torsion appear as a single parameter in the line element. For the
positive values of this parameter, the resulting line element is found to be of
the Reissner-Nordstrom type. This parameter is related to the spin of matter
and acts as a torsion 'charge' much like the electric charge in conventional
Reissner-Nordstrom geometry. We also analyze the existence and stability of the
orbits for both massless and massive particles in this setup and compare the
results to the corresponding case in general relativity. We also derive the
first law of black hole thermodynamics for a black hole with torsion and define
the black hole temperature and entropy in terms of its mass and torsion charge.
| [
{
"created": "Fri, 17 May 2019 03:50:04 GMT",
"version": "v1"
}
] | 2019-05-20 | [
[
"Nodijeh",
"S. Gharibi",
""
],
[
"Akhshabi",
"S.",
""
],
[
"Khajenabi",
"F.",
""
]
] | We derive the static spherically symmetric vacuum solution for a spacetime with non-vanishing torsion by solving the field equations analytically. The effects of torsion appear as a single parameter in the line element. For the positive values of this parameter, the resulting line element is found to be of the Reissner-Nordstrom type. This parameter is related to the spin of matter and acts as a torsion 'charge' much like the electric charge in conventional Reissner-Nordstrom geometry. We also analyze the existence and stability of the orbits for both massless and massive particles in this setup and compare the results to the corresponding case in general relativity. We also derive the first law of black hole thermodynamics for a black hole with torsion and define the black hole temperature and entropy in terms of its mass and torsion charge. |
gr-qc/9309022 | Jasjeet Bagla | J.S.Bagla and T.Padmanabhan | Nonlinear Evolution of Density Perturbations | (Paper presented at the 6th Asia Pacific regional meeting of the IAU)
, 7 pages, 8 figures ( 4 figures not included, available on request),
uuencoded postscript file | J.Astrophys.Astron. 16 (1995) 77 | null | null | gr-qc astro-ph | null | : From the epoch of recombination $(z\approx 10^3)$ till today, the typical
density contrasts have grown by a factor of about $10^6$ in a Friedmann
universe with $\Omega=1$. However, during the same epoch the typical
gravitational potential has grown only by a factor of order unity. We present
theoretical arguments explaining the origin of this approximate constancy of
gravitational potential. This fact can be exploited to provide a new, powerful,
approximation scheme to study the formation of nonlinear structures in the
universe. The essential idea of this method is to evolve the initial
distribution of particles using a gravitational potential frozen in time
(Frozen Potential Approximation). This approximation provides valuable insight
into understanding various features of nonlinear evolution; for example, it
provides a simple explanation as to why pancakes remain thin during the
evolution even in the absence of any artificial, adhesion-like, damping terms.
We compare the trajectories of particles in various approximations. We also
discuss a few applications of the frozen potential approximation.
| [
{
"created": "Thu, 23 Sep 1993 19:31:32 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Bagla",
"J. S.",
""
],
[
"Padmanabhan",
"T.",
""
]
] | : From the epoch of recombination $(z\approx 10^3)$ till today, the typical density contrasts have grown by a factor of about $10^6$ in a Friedmann universe with $\Omega=1$. However, during the same epoch the typical gravitational potential has grown only by a factor of order unity. We present theoretical arguments explaining the origin of this approximate constancy of gravitational potential. This fact can be exploited to provide a new, powerful, approximation scheme to study the formation of nonlinear structures in the universe. The essential idea of this method is to evolve the initial distribution of particles using a gravitational potential frozen in time (Frozen Potential Approximation). This approximation provides valuable insight into understanding various features of nonlinear evolution; for example, it provides a simple explanation as to why pancakes remain thin during the evolution even in the absence of any artificial, adhesion-like, damping terms. We compare the trajectories of particles in various approximations. We also discuss a few applications of the frozen potential approximation. |
1112.4613 | Alfio Bonanno | Alfio Bonanno and Sante Carloni | Dynamical System Analysis of Cosmologies with Running Cosmological
Constant from Quantum Einstein Gravity | 26 pages, 4 figures. To appear in New Journal of Physics | null | 10.1088/1367-2630/14/2/025008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a mechanism that induces a time-dependent vacuum energy on
cosmological scales. It is based on the instability induced renormalization
triggered by the low energy quantum fluctuations in a Universe with a positive
cosmological constant. We employ the dynamical systems approach to study the
qualitative behavior of Friedmann-Robertson-Walker cosmologies where the
cosmological constant is dynamically evolving according with this
nonperturbative scaling at low energies. It will be shown that it is possible
to realize a "two regimes" dark energy phases, where an unstable early phase of
power-law evolution of the scale factor is followed by an accelerated expansion
era at late times.
| [
{
"created": "Tue, 20 Dec 2011 09:17:45 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Bonanno",
"Alfio",
""
],
[
"Carloni",
"Sante",
""
]
] | We discuss a mechanism that induces a time-dependent vacuum energy on cosmological scales. It is based on the instability induced renormalization triggered by the low energy quantum fluctuations in a Universe with a positive cosmological constant. We employ the dynamical systems approach to study the qualitative behavior of Friedmann-Robertson-Walker cosmologies where the cosmological constant is dynamically evolving according with this nonperturbative scaling at low energies. It will be shown that it is possible to realize a "two regimes" dark energy phases, where an unstable early phase of power-law evolution of the scale factor is followed by an accelerated expansion era at late times. |
1702.04724 | Liang Dai | Liang Dai, Tejaswi Venumadhav | On the waveforms of gravitationally lensed gravitational waves | 5 pages, 4 figures, comments welcome | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Strong lensing by intervening galaxies can produce multiple images of
gravitational waves from sources at cosmological distances. These images
acquire additional phase-shifts as the over-focused wavefront passes through
itself along the line of sight. Time domain waveforms of Type-II images
(associated with saddle points of the time delay) exhibit a non-trivial
distortion from the unlensed waveforms. This phenomenon is in addition to the
usual frequency-independent magnification, and happens even in the geometric
limit where the wavelength is much shorter than the deflector's gravitational
length scale. Similarly, Type-III images preserve the original waveform's shape
but exhibit a sign flip. We show that for non-precessing binaries undergoing
circular inspiral and merger, these distortions are equivalent to rotating the
line of sight about the normal to the orbital plane by $45^\circ$ (Type II) and
$90^\circ$ (Type III). This effect will enable us to distinguish between the
different topological types among a set of multiple images, and give us
valuable insight into the lens model. Furthermore, we show that for eccentric
binaries, the waveform of a Type-II image is distorted in a manner that is
inequivalent to a change of the source's orbital parameters.
| [
{
"created": "Wed, 15 Feb 2017 19:00:01 GMT",
"version": "v1"
}
] | 2017-02-17 | [
[
"Dai",
"Liang",
""
],
[
"Venumadhav",
"Tejaswi",
""
]
] | Strong lensing by intervening galaxies can produce multiple images of gravitational waves from sources at cosmological distances. These images acquire additional phase-shifts as the over-focused wavefront passes through itself along the line of sight. Time domain waveforms of Type-II images (associated with saddle points of the time delay) exhibit a non-trivial distortion from the unlensed waveforms. This phenomenon is in addition to the usual frequency-independent magnification, and happens even in the geometric limit where the wavelength is much shorter than the deflector's gravitational length scale. Similarly, Type-III images preserve the original waveform's shape but exhibit a sign flip. We show that for non-precessing binaries undergoing circular inspiral and merger, these distortions are equivalent to rotating the line of sight about the normal to the orbital plane by $45^\circ$ (Type II) and $90^\circ$ (Type III). This effect will enable us to distinguish between the different topological types among a set of multiple images, and give us valuable insight into the lens model. Furthermore, we show that for eccentric binaries, the waveform of a Type-II image is distorted in a manner that is inequivalent to a change of the source's orbital parameters. |
2010.07549 | Neda Ebrahimi | Fatemeh Koohestani, Neda Ebrahimi, Mehdi Vatandoost, Yousef Bahrampour | The cosmological time functions and lightlike rays | 12 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is proved that all discontinuity points of a finite cosmological time
function, $\tau$, are on past lightlike rays. As a result, it is proved that if
$(M,g)$ is a chronological space-time without past lightlike rays then there is
a representation of $g$ such that its cosmological time function is regular. In
addition, by reducing conditions of regularity sufficient conditions for causal
simplicity and causal pseudoconvexity of space-time is given. It is also proved
that the second condition of regularity can be reduced to satisfies only on
inextendible past-directed causal rays if $(M,g)$ be a space-time, conformal
with an open subspace of Minkowski space-time or $\tau$ be continuous.
| [
{
"created": "Thu, 15 Oct 2020 06:54:54 GMT",
"version": "v1"
}
] | 2020-10-16 | [
[
"Koohestani",
"Fatemeh",
""
],
[
"Ebrahimi",
"Neda",
""
],
[
"Vatandoost",
"Mehdi",
""
],
[
"Bahrampour",
"Yousef",
""
]
] | It is proved that all discontinuity points of a finite cosmological time function, $\tau$, are on past lightlike rays. As a result, it is proved that if $(M,g)$ is a chronological space-time without past lightlike rays then there is a representation of $g$ such that its cosmological time function is regular. In addition, by reducing conditions of regularity sufficient conditions for causal simplicity and causal pseudoconvexity of space-time is given. It is also proved that the second condition of regularity can be reduced to satisfies only on inextendible past-directed causal rays if $(M,g)$ be a space-time, conformal with an open subspace of Minkowski space-time or $\tau$ be continuous. |
1807.09745 | Andrew DeBenedictis | Andrew DeBenedictis, Sasa Ilijic | Energy condition respecting warp drives: The role of spin in
Einstein-Cartan theory | 18 pages, 6 figures. v3: minor clarifications included to match
version accepted for publication in Classical and Quantum Gravity | Class. Quantum Grav. 35 215001 (2018) | 10.1088/1361-6382/aae326 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the so called "warp drive" spacetimes within the
$U_{4}$ Riemann-Cartan manifolds of Einstein-Cartan theory. Specifically, the
role that spin may play with respect to energy condition violation is
considered. It turns out that with the addition of spin, the torsion terms in
Einstein-Cartan gravity do allow for energy condition respecting warp drives.
Limits are derived which minimize the amount of spin required in order to have
a weak/null-energy condition respecting system. This is done both for the
traditional Alcubierre warp drive as well as for the modified warp drive of Van
Den Broeck which minimizes the amount of matter required for the drive. The
ship itself is in a region of effectively vacuum and hence the torsion, which
in Einstein-Cartan theory is localized in matter, does not affect the geodesic
nature of the ship's trajectory. We also comment on the amount of spin and
matter required in order for these conditions to hold.
| [
{
"created": "Wed, 25 Jul 2018 17:49:28 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Jul 2018 01:13:59 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Sep 2018 20:08:00 GMT",
"version": "v3"
}
] | 2018-10-09 | [
[
"DeBenedictis",
"Andrew",
""
],
[
"Ilijic",
"Sasa",
""
]
] | In this paper we study the so called "warp drive" spacetimes within the $U_{4}$ Riemann-Cartan manifolds of Einstein-Cartan theory. Specifically, the role that spin may play with respect to energy condition violation is considered. It turns out that with the addition of spin, the torsion terms in Einstein-Cartan gravity do allow for energy condition respecting warp drives. Limits are derived which minimize the amount of spin required in order to have a weak/null-energy condition respecting system. This is done both for the traditional Alcubierre warp drive as well as for the modified warp drive of Van Den Broeck which minimizes the amount of matter required for the drive. The ship itself is in a region of effectively vacuum and hence the torsion, which in Einstein-Cartan theory is localized in matter, does not affect the geodesic nature of the ship's trajectory. We also comment on the amount of spin and matter required in order for these conditions to hold. |
gr-qc/0212006 | Israel Quiros Rodriguez | Olga Arias, Israel Quiros (Physics Department, Las Villas Central
University, Santa Clara) | New exact cosmological solutions to Brans-Dicke gravity with a
self-interacting scalar-field | 10 pages, latex, 3 ps figures | null | null | null | gr-qc | null | We derive a new parametric class of exact cosmological solutions to
Brans-Dicke theory of gravity with a self-interacting scalar field and a
barotropic perfect fluid of ordinary matter, by assuming a linear relationship
between the Hubble expansion parameter and the time derivative of the scalar
field. As a consequence only a class of exponential potentials and their
combinations can be treated. The relevance of the solutions found for the
description of the cosmic evolution are discussed in detail. We focus our
discussion mainly on the possibility to have superquintessence behavior.
| [
{
"created": "Sun, 1 Dec 2002 19:17:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Arias",
"Olga",
"",
"Physics Department, Las Villas Central\n University, Santa Clara"
],
[
"Quiros",
"Israel",
"",
"Physics Department, Las Villas Central\n University, Santa Clara"
]
] | We derive a new parametric class of exact cosmological solutions to Brans-Dicke theory of gravity with a self-interacting scalar field and a barotropic perfect fluid of ordinary matter, by assuming a linear relationship between the Hubble expansion parameter and the time derivative of the scalar field. As a consequence only a class of exponential potentials and their combinations can be treated. The relevance of the solutions found for the description of the cosmic evolution are discussed in detail. We focus our discussion mainly on the possibility to have superquintessence behavior. |
1509.06963 | Mariam Bouhmadi-Lopez | Mariam Bouhmadi-L\'opez, Maxim Brilenkov, Ruslan Brilenkov, Jo\~ao
Morais, Alexander Zhuk | Scalar perturbations in the late Universe: viability of the Chaplygin
gas models | 18 pages, no figures. Discussion improved. Version accepted in JCAP | JCAP 12 (2015) 037 | 10.1088/1475-7516/2015/12/037 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the late-time evolution of the Universe where dark energy (DE) is
parametrized by a modified generalized Chaplygin gas (mGCG) on top of cold dark
matter (CDM). We also take into account the radiation content of the Universe.
In this context, the late stage of the evolution of the universe refers to the
epoch where CDM is already clustered into inhomogeneously distributed discrete
structures (galaxies, groups and clusters of galaxies). Under these conditions,
the mechanical approach is an adequate tool to study the Universe deep inside
the cell of uniformity. To be more accurate, we study scalar perturbations of
the Friedmann-Lema\^itre-Robertson-Walker metric due to inhomogeneities of CDM
as well as fluctuations of radiation and mGCG, the later driving the late-time
acceleration of the universe. Our analysis applies as well to the case where
mGCG plays the role of DM and DE. We select the sets of parameters of the mGCG
that are compatible with the mechanical approach. These sets define prospective
mGCG models. By comparing the selected sets of models with some of the latest
observational data results, we conclude that the mGCG is in tight agreement
with those observations particularly for a mGCG playing the role of DE and DM.
| [
{
"created": "Sat, 12 Sep 2015 10:59:07 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2015 15:07:11 GMT",
"version": "v2"
}
] | 2015-12-22 | [
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Brilenkov",
"Maxim",
""
],
[
"Brilenkov",
"Ruslan",
""
],
[
"Morais",
"João",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study the late-time evolution of the Universe where dark energy (DE) is parametrized by a modified generalized Chaplygin gas (mGCG) on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. In this context, the late stage of the evolution of the universe refers to the epoch where CDM is already clustered into inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies). Under these conditions, the mechanical approach is an adequate tool to study the Universe deep inside the cell of uniformity. To be more accurate, we study scalar perturbations of the Friedmann-Lema\^itre-Robertson-Walker metric due to inhomogeneities of CDM as well as fluctuations of radiation and mGCG, the later driving the late-time acceleration of the universe. Our analysis applies as well to the case where mGCG plays the role of DM and DE. We select the sets of parameters of the mGCG that are compatible with the mechanical approach. These sets define prospective mGCG models. By comparing the selected sets of models with some of the latest observational data results, we conclude that the mGCG is in tight agreement with those observations particularly for a mGCG playing the role of DE and DM. |
2105.00491 | Yu-Xiao Liu | Si-Jiang Yang, Run Zhou, Shao-Wen Wei, Yu-Xiao Liu | Kinetics of a phase transition for a Kerr-AdS black hole on the
free-energy landscape | 16 pages, 10 figures, published version | Phys.Rev.D 105 (2022) 8, 084030 | 10.1103/PhysRevD.105.084030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By treating the order parameter as a stochastic thermal fluctuating variable
for small-large black hole phase transition, we investigate the kinetic process
of phase transition for the Kerr-AdS (anti-de Sitter) black holes on free
energy landscape. We find that the extremal points of the off shell Gibbs free
energy correspond to physical black holes. For small-large black hole phase
transition, the off shell Gibbs free energy exhibits a double well behavior
with the same depth. Contrary to previous research for the kinetics of phase
transition for the Kerr-Newman-AdS family black holes on a free energy
landscape, we find that there is a lower bound for the order parameter and the
lower bound corresponds to extremal black holes. In particular, the off shell
Gibbs free energy is zero instead of divergent as previous work suggested for
vanishing black hole horizon radius, which corresponds to the Gibbs free energy
of a thermal AdS space. The investigation for the evolution of the probability
distribution for the phase transition indicates that the initial stable small
(large) black hole tends to switch to stable large (small) black hole.
Increasing the temperature along the coexistence curve, the switching process
becomes faster and the probability distribution reaches the final stationary
Boltzmann distribution at a shorter time. The distribution of the first passage
time indicates the time scale of the small-large black hole phase transition,
and the peak of the distribution becomes sharper and shifts to the left with
the increase of temperature along the coexistence curve. This suggests that a
considerable first passage process occurs at a shorter time for higher
temperature. The investigation of the kinetics of phase transition might
provide us new insight into the underlying microscopic interactions.
| [
{
"created": "Sun, 2 May 2021 14:57:42 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2022 12:21:02 GMT",
"version": "v2"
}
] | 2022-04-21 | [
[
"Yang",
"Si-Jiang",
""
],
[
"Zhou",
"Run",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | By treating the order parameter as a stochastic thermal fluctuating variable for small-large black hole phase transition, we investigate the kinetic process of phase transition for the Kerr-AdS (anti-de Sitter) black holes on free energy landscape. We find that the extremal points of the off shell Gibbs free energy correspond to physical black holes. For small-large black hole phase transition, the off shell Gibbs free energy exhibits a double well behavior with the same depth. Contrary to previous research for the kinetics of phase transition for the Kerr-Newman-AdS family black holes on a free energy landscape, we find that there is a lower bound for the order parameter and the lower bound corresponds to extremal black holes. In particular, the off shell Gibbs free energy is zero instead of divergent as previous work suggested for vanishing black hole horizon radius, which corresponds to the Gibbs free energy of a thermal AdS space. The investigation for the evolution of the probability distribution for the phase transition indicates that the initial stable small (large) black hole tends to switch to stable large (small) black hole. Increasing the temperature along the coexistence curve, the switching process becomes faster and the probability distribution reaches the final stationary Boltzmann distribution at a shorter time. The distribution of the first passage time indicates the time scale of the small-large black hole phase transition, and the peak of the distribution becomes sharper and shifts to the left with the increase of temperature along the coexistence curve. This suggests that a considerable first passage process occurs at a shorter time for higher temperature. The investigation of the kinetics of phase transition might provide us new insight into the underlying microscopic interactions. |
gr-qc/9611011 | Martin Rainer | A. Zhuk | On Relation between String Theory and Multidimensional Cosmology | latex, to appear in Gravitation and Cosmology | Grav.Cosmol. 2 (1996) 319-320 | null | OU-DTP/96-01 | gr-qc | null | It is shown that a transition from a multidimensional cosmological model with
one internal space of the dimension d_1 to the effective tree-level bosonic
string corresponds to an infinite number of the internal dimensions: d_1 ->
infinity.
| [
{
"created": "Tue, 5 Nov 1996 16:17:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zhuk",
"A.",
""
]
] | It is shown that a transition from a multidimensional cosmological model with one internal space of the dimension d_1 to the effective tree-level bosonic string corresponds to an infinite number of the internal dimensions: d_1 -> infinity. |
gr-qc/9907032 | Sang Pyo Kim | Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh, and Jae Hyung
Yee | Wave Functions for Quantum Black Hole Formation in Scalar Field Collapse | RevTex, 14 pages, no figures; Eq. (36) and references added; revised
version for PRD | Phys.Rev. D61 (2000) 044005 | 10.1103/PhysRevD.61.044005 | null | gr-qc | null | We study quantum mechanically the self-similar black hole formation by
collapsing scalar field and find the wave functions that give the correct
semiclassical limit. In contrast to classical theory, the wave functions for
the black hole formation even in the supercritical case have not only incoming
flux but also outgoing flux. From this result we compute the rate for the black
hole formation. In the subcritical case our result agrees with the
semiclassical tunneling rate. Furthermore, we show how to recover the classical
evolution of black hole formation from the wave function by defining the
Hamilton-Jacobi characteristic function as $W = \hbar {\rm Im} \ln \psi$. We
find that the quantum corrected apparent horizon deviates from the classical
value only slightly without any qualitative change even in the critical case.
| [
{
"created": "Thu, 8 Jul 1999 03:17:44 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 1999 06:28:10 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Oct 1999 07:40:53 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Bak",
"Dongsu",
""
],
[
"Kim",
"Sang Pyo",
""
],
[
"Kim",
"Sung Ku",
""
],
[
"Soh",
"Kwang-Sup",
""
],
[
"Yee",
"Jae Hyung",
""
]
] | We study quantum mechanically the self-similar black hole formation by collapsing scalar field and find the wave functions that give the correct semiclassical limit. In contrast to classical theory, the wave functions for the black hole formation even in the supercritical case have not only incoming flux but also outgoing flux. From this result we compute the rate for the black hole formation. In the subcritical case our result agrees with the semiclassical tunneling rate. Furthermore, we show how to recover the classical evolution of black hole formation from the wave function by defining the Hamilton-Jacobi characteristic function as $W = \hbar {\rm Im} \ln \psi$. We find that the quantum corrected apparent horizon deviates from the classical value only slightly without any qualitative change even in the critical case. |
gr-qc/0505146 | Alberto Saa | Ricardo A. Mosna and Alberto Saa | Volume elements and torsion | Revtex, 8 pages, 1 figure. v2 includes a discussion on
$\lambda$-symmetry | J.Math.Phys. 46 (2005) 112502 | 10.1063/1.2121207 | null | gr-qc math-ph math.MP | null | We reexamine here the issue of consistency of minimal action formulation with
the minimal coupling procedure (MCP) in spaces with torsion. In Riemann-Cartan
spaces, it is known that a proper use of the MCP requires that the trace of the
torsion tensor be a gradient, $T_\mu=\partial_\mu\theta$, and that the modified
volume element $\tau_\theta = e^\theta \sqrt{g} dx^1\wedge...\wedge dx^n $ be
used in the action formulation of a physical model. We rederive this result
here under considerably weaker assumptions, reinforcing some recent results
about the inadequacy of propagating torsion theories of gravity to explain the
available observational data. The results presented here also open the door to
possible applications of the modified volume element in the geometric theory of
crystalline defects.
| [
{
"created": "Sun, 29 May 2005 19:44:51 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2005 14:04:07 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Mosna",
"Ricardo A.",
""
],
[
"Saa",
"Alberto",
""
]
] | We reexamine here the issue of consistency of minimal action formulation with the minimal coupling procedure (MCP) in spaces with torsion. In Riemann-Cartan spaces, it is known that a proper use of the MCP requires that the trace of the torsion tensor be a gradient, $T_\mu=\partial_\mu\theta$, and that the modified volume element $\tau_\theta = e^\theta \sqrt{g} dx^1\wedge...\wedge dx^n $ be used in the action formulation of a physical model. We rederive this result here under considerably weaker assumptions, reinforcing some recent results about the inadequacy of propagating torsion theories of gravity to explain the available observational data. The results presented here also open the door to possible applications of the modified volume element in the geometric theory of crystalline defects. |
gr-qc/0409121 | Michael B. Mensky | Michael B. Mensky (P.N.Lebedev Physical Institute, Moscow) | Energy conservation and equivalence principle in General Relativity | 9 pages, Latex, one figure | Phys.Lett. A328 (2004) 261-269 | 10.1016/j.physleta.2004.06.040 | null | gr-qc | null | The generalized Stokes theorem (connecting integrals of dimensions 3 and 4)
is formulated in a curved space-time in terms of paths in Minkowski space
(forming Path Group). A covariant integral form of the conservation law for the
energy-momentum of matter is then derived in General Relativity. It extends
Einstein's equivalence principle on the energy conservation, since it
formulates the conservation law for the energy-momentum of matter without
explicit including the gravitational field in the formulation.
| [
{
"created": "Thu, 30 Sep 2004 13:32:34 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Mensky",
"Michael B.",
"",
"P.N.Lebedev Physical Institute, Moscow"
]
] | The generalized Stokes theorem (connecting integrals of dimensions 3 and 4) is formulated in a curved space-time in terms of paths in Minkowski space (forming Path Group). A covariant integral form of the conservation law for the energy-momentum of matter is then derived in General Relativity. It extends Einstein's equivalence principle on the energy conservation, since it formulates the conservation law for the energy-momentum of matter without explicit including the gravitational field in the formulation. |
2401.17495 | Sudhagar Suyamprakasam | Bernard Hall, Sudhagar Suyamprakasam, Nairwita Mazumder, Anupreeta
More, Sukanta Bose | Identifying noise transients in gravitational-wave data arising from
nonlinear couplings | 25 Pages, 10 figures. Reviewed by LIGO Scientific Collaboration (LSC)
with LIGO Document Number P2200344 | null | null | null | gr-qc astro-ph.IM physics.data-an | http://creativecommons.org/licenses/by/4.0/ | Noise in various interferometer systems can sometimes couple non-linearly to
create excess noise in the gravitational wave (GW) strain data. Third-order
statistics, such as bicoherence and biphase, can identify these couplings and
help discriminate those occurrences from astrophysical GW signals. However, the
conventional analysis can yield large bicoherence values even when no
phase-coupling is present, thereby, resulting in false identifications.
Introducing artificial phase randomization in computing the bicoherence reduces
such occurrences with negligible impact on its effectiveness for detecting true
phase-coupled disturbances. We demonstrate this property with simulated
disturbances in this work. Statistical hypothesis testing is used for
distinguishing phase-coupled disturbances from non-phase coupled ones when
employing the phase-randomized bicoherence. We also obtain an expression for
the bicoherence value that minimizes the sum of the probabilities of false
positives and false negatives. This can be chosen as a threshold for
shortlisting bicoherence triggers for further scrutiny for the presence of
non-linear coupling. Finally, the utility of the phase-randomized bicoherence
analysis in GW time-series data is demonstrated for the following three
scenarios: (1) Finding third-order statistical similarities within categories
of noise transients, such as blips and koi fish. If these non-Gaussian noise
transients, or glitches, have a common source, their bicoherence maps can have
similarities arising from common bifrequencies related to that source. (2)
Differentiating linear or non-linear phase-coupled glitches from compact binary
coalescence signals through their bicoherence maps. This is explained with a
simulated signal. (3) Identifying repeated bifrequencies in the second and
third observation runs (i.e., O2 and O3) of LIGO and Virgo.
| [
{
"created": "Tue, 30 Jan 2024 23:00:40 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2024 18:16:04 GMT",
"version": "v2"
}
] | 2024-07-29 | [
[
"Hall",
"Bernard",
""
],
[
"Suyamprakasam",
"Sudhagar",
""
],
[
"Mazumder",
"Nairwita",
""
],
[
"More",
"Anupreeta",
""
],
[
"Bose",
"Sukanta",
""
]
] | Noise in various interferometer systems can sometimes couple non-linearly to create excess noise in the gravitational wave (GW) strain data. Third-order statistics, such as bicoherence and biphase, can identify these couplings and help discriminate those occurrences from astrophysical GW signals. However, the conventional analysis can yield large bicoherence values even when no phase-coupling is present, thereby, resulting in false identifications. Introducing artificial phase randomization in computing the bicoherence reduces such occurrences with negligible impact on its effectiveness for detecting true phase-coupled disturbances. We demonstrate this property with simulated disturbances in this work. Statistical hypothesis testing is used for distinguishing phase-coupled disturbances from non-phase coupled ones when employing the phase-randomized bicoherence. We also obtain an expression for the bicoherence value that minimizes the sum of the probabilities of false positives and false negatives. This can be chosen as a threshold for shortlisting bicoherence triggers for further scrutiny for the presence of non-linear coupling. Finally, the utility of the phase-randomized bicoherence analysis in GW time-series data is demonstrated for the following three scenarios: (1) Finding third-order statistical similarities within categories of noise transients, such as blips and koi fish. If these non-Gaussian noise transients, or glitches, have a common source, their bicoherence maps can have similarities arising from common bifrequencies related to that source. (2) Differentiating linear or non-linear phase-coupled glitches from compact binary coalescence signals through their bicoherence maps. This is explained with a simulated signal. (3) Identifying repeated bifrequencies in the second and third observation runs (i.e., O2 and O3) of LIGO and Virgo. |
2008.05899 | Oem Trivedi | Oem Trivedi | The exact solution approach to warm inflation | v2, matches the published version in Astroparticle Physics, 10 pages
with no figures | Astropart.Phys. 158 (2024) 102951 | 10.1016/j.astropartphys.2024.102951 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The theory of cosmic inflation has received a great amount of deserved
attention in recent years due to it's stunning predictions about the early
universe. Alongside the usual cold inflation paradigm, warm inflation has
garnered a huge amount of interest in modern inflationary studies. It's
peculiar features and specifically different predictions from cold inflation
have led to a substantial amount of literature about it. Various modified
cosmological scenarios have also been studied in the warm inflationary regime.
In this work, we introduce the exact solution approach for warm inflation. This
approach allows one to directly study warm inflationary regime in a variety of
modified cosmological scenarios. We begin by outlining our method and show that
it generalizes the modified Friedmann approach of Del Campo , and reduces to
the well known Hamilton-Jacobi formalism for inflation in particular limits. We
also find the perturbation spectra for cosmological and tensor perturbations in
the early universe, and then apply our method to study warm inflation in a
Tsallis entropy modified Friedmann universe. We end our paper with some
concluding remarks on the domain of applicability of our work.
| [
{
"created": "Wed, 12 Aug 2020 16:57:09 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2024 14:08:27 GMT",
"version": "v2"
}
] | 2024-08-02 | [
[
"Trivedi",
"Oem",
""
]
] | The theory of cosmic inflation has received a great amount of deserved attention in recent years due to it's stunning predictions about the early universe. Alongside the usual cold inflation paradigm, warm inflation has garnered a huge amount of interest in modern inflationary studies. It's peculiar features and specifically different predictions from cold inflation have led to a substantial amount of literature about it. Various modified cosmological scenarios have also been studied in the warm inflationary regime. In this work, we introduce the exact solution approach for warm inflation. This approach allows one to directly study warm inflationary regime in a variety of modified cosmological scenarios. We begin by outlining our method and show that it generalizes the modified Friedmann approach of Del Campo , and reduces to the well known Hamilton-Jacobi formalism for inflation in particular limits. We also find the perturbation spectra for cosmological and tensor perturbations in the early universe, and then apply our method to study warm inflation in a Tsallis entropy modified Friedmann universe. We end our paper with some concluding remarks on the domain of applicability of our work. |
2108.00957 | Lucrezia Ravera | N. Myrzakulov, R. Myrzakulov, L. Ravera | Metric-Affine Myrzakulov Gravity Theories | 45 pages | Symmetry 13 (2021) no.10, 1855 | 10.3390/sym13101855 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we review the Myrzakulov Gravity models (MG-N, with $\mathrm{N
= I, II, \ldots, VIII}$) and derive their respective metric-affine
generalizations (MAMG-N), discussing also their particular sub-cases. The field
equations of the theories are obtained by regarding the metric tensor and the
general affine connection as independent variables. We then focus on the case
in which the function characterizing the aforementioned metric-affine models is
linear and consider a Friedmann-Lema\^{i}tre-Robertson-Walker background to
study cosmological aspects and applications.
| [
{
"created": "Fri, 30 Jul 2021 07:32:50 GMT",
"version": "v1"
}
] | 2021-11-03 | [
[
"Myrzakulov",
"N.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Ravera",
"L.",
""
]
] | In this paper we review the Myrzakulov Gravity models (MG-N, with $\mathrm{N = I, II, \ldots, VIII}$) and derive their respective metric-affine generalizations (MAMG-N), discussing also their particular sub-cases. The field equations of the theories are obtained by regarding the metric tensor and the general affine connection as independent variables. We then focus on the case in which the function characterizing the aforementioned metric-affine models is linear and consider a Friedmann-Lema\^{i}tre-Robertson-Walker background to study cosmological aspects and applications. |
2203.02282 | Christian Corda Prof. | Christian Corda | On the equivalence between rotation and gravity: "Gravitational" and
"cosmological" redshifts in the laboratory | 18 pages, 1 figure, final version matching the one published in
Foundations of Physics. Comments are welcome | Found Phys 52, 42 (2022) | 10.1007/s10701-022-00558-w | null | gr-qc astro-ph.CO hep-ex hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The M\"ossbauer rotor effect recently gained a renewed interest due to the
discovery and explanation of an additional effect of clock synchronization
which has been missed for about 50 years, i.e. starting from a famous book of
Pauli, till some recent experimental analyses. The theoretical explanation of
such an additional effect is due to some recent papers in both the general
relativistic and the special relativistic frameworks. In the first case
(general relativistic framework) the key point of the approach is the
Einstein's equivalence principle (EEP), which, in the words of the same
Einstein, enables "the point of view to interpret the rotating system K' as at
rest, and the centrifugal field as a gravitational field". In this paper, we
analyse both the history of the M\"ossbauer rotor effect and its interpretation
from the point of view of Einstein's general theory of relativity (GTR) by
adding some new insight. In particular, it will be shown that, if on one hand
the "traditional" effect of redshift has a strong analogy with the
gravitational redshift, on the other hand the additional effect of clock
synchronization has an intriguing analogy with the cosmological redshift.
Finally, we show that a recent claim in the literature that the second effect
of clock synchronization does not exist is not correct.
| [
{
"created": "Wed, 2 Mar 2022 15:06:52 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Mar 2022 16:38:36 GMT",
"version": "v2"
}
] | 2022-03-30 | [
[
"Corda",
"Christian",
""
]
] | The M\"ossbauer rotor effect recently gained a renewed interest due to the discovery and explanation of an additional effect of clock synchronization which has been missed for about 50 years, i.e. starting from a famous book of Pauli, till some recent experimental analyses. The theoretical explanation of such an additional effect is due to some recent papers in both the general relativistic and the special relativistic frameworks. In the first case (general relativistic framework) the key point of the approach is the Einstein's equivalence principle (EEP), which, in the words of the same Einstein, enables "the point of view to interpret the rotating system K' as at rest, and the centrifugal field as a gravitational field". In this paper, we analyse both the history of the M\"ossbauer rotor effect and its interpretation from the point of view of Einstein's general theory of relativity (GTR) by adding some new insight. In particular, it will be shown that, if on one hand the "traditional" effect of redshift has a strong analogy with the gravitational redshift, on the other hand the additional effect of clock synchronization has an intriguing analogy with the cosmological redshift. Finally, we show that a recent claim in the literature that the second effect of clock synchronization does not exist is not correct. |
0704.3550 | Alessandro Nagar | Thibault Damour, Alessandro Nagar | Final spin of a coalescing black-hole binary: an Effective-One-Body
approach | 8 pages, two figures. To appear in Phys. Rev. D | Phys.Rev.D76:044003,2007 | 10.1103/PhysRevD.76.044003 | null | gr-qc | null | We update the analytical estimate of the final spin of a coalescing
black-hole binary derived within the Effective-One-Body (EOB) approach. We
consider unequal-mass non-spinning black-hole binaries. It is found that a more
complete account of relevant physical effects (higher post-Newtonian accuracy,
ringdown losses) allows the {\it analytical} EOB estimate to `converge towards'
the recently obtained {\it numerical} results within 2%. This agreement
illustrates the ability of the EOB approach to capture the essential physics of
coalescing black-hole binaries. Our analytical approach allows one to estimate
the final spin of the black hole formed by coalescing binaries in a mass range
($\nu=m_1m_2/(m_1+m_2)^2 < 0.16 $) which is not presently covered by numerical
simulations.
| [
{
"created": "Thu, 26 Apr 2007 14:22:01 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jul 2007 15:30:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Damour",
"Thibault",
""
],
[
"Nagar",
"Alessandro",
""
]
] | We update the analytical estimate of the final spin of a coalescing black-hole binary derived within the Effective-One-Body (EOB) approach. We consider unequal-mass non-spinning black-hole binaries. It is found that a more complete account of relevant physical effects (higher post-Newtonian accuracy, ringdown losses) allows the {\it analytical} EOB estimate to `converge towards' the recently obtained {\it numerical} results within 2%. This agreement illustrates the ability of the EOB approach to capture the essential physics of coalescing black-hole binaries. Our analytical approach allows one to estimate the final spin of the black hole formed by coalescing binaries in a mass range ($\nu=m_1m_2/(m_1+m_2)^2 < 0.16 $) which is not presently covered by numerical simulations. |
gr-qc/9901003 | Aharon Davidson | Aharon Davidson, David Karasik, and Yoav Lederer | Wave Function of a Brane-like Universe | Revtex, 4 twocolumn pages, 3 eps figures (accepted for publication in
Class. Quan. Grav.) | Class.Quant.Grav. 16 (1999) 1349-1356 | 10.1088/0264-9381/16/4/023 | null | gr-qc hep-th | null | Within the mini-superspace model, brane-like cosmology means performing the
variation with respect to the embedding (Minkowski) time $\tau$ before fixing
the cosmic (Einstein) time $t$. The departure from Einstein limit is
parameterized by the 'energy' conjugate to $\tau$, and characterized by a
classically disconnected Embryonic epoch. In contrast with canonical quantum
gravity, the wave-function of the brane-like Universe is (i) $\tau$-dependent,
and (ii) vanishes at the Big Bang. Hartle-Hawking and Linde proposals dictate
discrete 'energy' levels, whereas Vilenkin proposal resembles $\alpha$-particle
disintegration.
| [
{
"created": "Sat, 2 Jan 1999 10:57:26 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Davidson",
"Aharon",
""
],
[
"Karasik",
"David",
""
],
[
"Lederer",
"Yoav",
""
]
] | Within the mini-superspace model, brane-like cosmology means performing the variation with respect to the embedding (Minkowski) time $\tau$ before fixing the cosmic (Einstein) time $t$. The departure from Einstein limit is parameterized by the 'energy' conjugate to $\tau$, and characterized by a classically disconnected Embryonic epoch. In contrast with canonical quantum gravity, the wave-function of the brane-like Universe is (i) $\tau$-dependent, and (ii) vanishes at the Big Bang. Hartle-Hawking and Linde proposals dictate discrete 'energy' levels, whereas Vilenkin proposal resembles $\alpha$-particle disintegration. |
1805.03314 | Gregory Ashton | Gregory Ashton, and Reinhard Prix, and Ian Jones | A semicoherent glitch-robust continuous gravitational wave search | 9 pages, 6 figures, 2 tables | Phys. Rev. D 98, 063011 (2018) | 10.1103/PhysRevD.98.063011 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Continuous gravitational-wave signals from isolated non-axisymmetric rotating
neutron stars may undergo episodic spin-up events known as glitches. If
unmodelled by a search, these can result in missed or misidentified detections.
We outline a semicoherent glitch-robust search method that allows
identification of glitching signal candidates and inference about the model
parameters.
| [
{
"created": "Tue, 8 May 2018 22:59:26 GMT",
"version": "v1"
}
] | 2018-09-26 | [
[
"Ashton",
"Gregory",
""
],
[
"Prix",
"Reinhard",
""
],
[
"Jones",
"Ian",
""
]
] | Continuous gravitational-wave signals from isolated non-axisymmetric rotating neutron stars may undergo episodic spin-up events known as glitches. If unmodelled by a search, these can result in missed or misidentified detections. We outline a semicoherent glitch-robust search method that allows identification of glitching signal candidates and inference about the model parameters. |
1501.01482 | Sunandan Gangopadhyay | Sunandan Gangopadhyay, Abhijit Dutta, Mir Faizal | Constraints on the Generalized Uncertainty Principle from Black Hole
Thermodynamics | To appear in Euro.Phys.Lett | Euro.Phys.Lett.112 (2015) 20006 | 10.1209/0295-5075/112/20006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we calculate the modification to the thermodynamics of a
Schwarzschild black hole in higher dimensions because of Generalized
Uncertainty Principle (GUP). We use the fact that the leading order corrections
to the entropy of a black hole has to be logarithmic in nature to restrict the
form of GUP. We observe that in six dimensions, the usual GUP produces the
correct form for the leading order corrections to the entropy of a black hole.
However, in five and seven dimensions a linear GUP, which is obtained by a
combination of DSR with the usual GUP, is needed to produce the correct form of
the corrections to the entropy of a black hole. Finally, we demonstrate that in
five dimensions, a new form of GUP containing quadratic and cubic powers of the
momentum also produces the correct form for the leading order corrections to
the entropy of a black hole.
| [
{
"created": "Wed, 7 Jan 2015 13:16:45 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Oct 2015 05:15:59 GMT",
"version": "v2"
}
] | 2015-12-09 | [
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Dutta",
"Abhijit",
""
],
[
"Faizal",
"Mir",
""
]
] | In this paper, we calculate the modification to the thermodynamics of a Schwarzschild black hole in higher dimensions because of Generalized Uncertainty Principle (GUP). We use the fact that the leading order corrections to the entropy of a black hole has to be logarithmic in nature to restrict the form of GUP. We observe that in six dimensions, the usual GUP produces the correct form for the leading order corrections to the entropy of a black hole. However, in five and seven dimensions a linear GUP, which is obtained by a combination of DSR with the usual GUP, is needed to produce the correct form of the corrections to the entropy of a black hole. Finally, we demonstrate that in five dimensions, a new form of GUP containing quadratic and cubic powers of the momentum also produces the correct form for the leading order corrections to the entropy of a black hole. |
1004.0339 | Harald Lueck | Harald L\"uck, Christopf Affeldt, Jerome Degallaix, Andreas Freise,
Hartmut Grote, Martin Hewitson, Stefan Hild, Jonathan Leong, Mirko Prijatelj,
Kenneth A. Strain, Benno Willke, Holger Wittel, Karsten Danzmann | The upgrade of GEO600 | 9 pages, Amaldi 8 conference contribution | J.Phys.Conf.Ser.228:012012,2010 | 10.1088/1742-6596/228/1/012012 | Amaldi2009GEO | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The German / British gravitational wave detector GEO 600 is in the process of
being upgraded. The upgrading process of GEO 600, called GEO-HF, will
concentrate on the improvement of the sensitivity for high frequency signals
and the demonstration of advanced technologies. In the years 2009 to 2011 the
detector will undergo a series of upgrade steps, which are described in this
paper.
| [
{
"created": "Fri, 2 Apr 2010 14:14:42 GMT",
"version": "v1"
}
] | 2015-03-13 | [
[
"Lück",
"Harald",
""
],
[
"Affeldt",
"Christopf",
""
],
[
"Degallaix",
"Jerome",
""
],
[
"Freise",
"Andreas",
""
],
[
"Grote",
"Hartmut",
""
],
[
"Hewitson",
"Martin",
""
],
[
"Hild",
"Stefan",
""
],
[
"Leong",
"Jonathan",
""
],
[
"Prijatelj",
"Mirko",
""
],
[
"Strain",
"Kenneth A.",
""
],
[
"Willke",
"Benno",
""
],
[
"Wittel",
"Holger",
""
],
[
"Danzmann",
"Karsten",
""
]
] | The German / British gravitational wave detector GEO 600 is in the process of being upgraded. The upgrading process of GEO 600, called GEO-HF, will concentrate on the improvement of the sensitivity for high frequency signals and the demonstration of advanced technologies. In the years 2009 to 2011 the detector will undergo a series of upgrade steps, which are described in this paper. |
1211.2848 | Carlos Molina Mendes | J. C. S. Neves and C. Molina | Rotating black holes in a Randall-Sundrum brane with a cosmological
constant | 10 pages, 3 figures. Version published on Physical Review D | Phys.Rev.D86, 124047 (2012) | 10.1103/PhysRevD.86.124047 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have constructed axially symmetric vacuum solutions of the
gravitational field equations in a Randall-Sundrum brane. A non-null effective
cosmological constant is considered, and asymptotically de Sitter and anti-de
Sitter spacetimes are obtained. The solutions describe rotating black holes in
a four-dimensional brane. Optical features of the solutions are treated,
emphasizing the rotation of the polarization vector along null congruences.
| [
{
"created": "Mon, 12 Nov 2012 22:32:06 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2013 17:19:57 GMT",
"version": "v2"
}
] | 2013-01-14 | [
[
"Neves",
"J. C. S.",
""
],
[
"Molina",
"C.",
""
]
] | In this work we have constructed axially symmetric vacuum solutions of the gravitational field equations in a Randall-Sundrum brane. A non-null effective cosmological constant is considered, and asymptotically de Sitter and anti-de Sitter spacetimes are obtained. The solutions describe rotating black holes in a four-dimensional brane. Optical features of the solutions are treated, emphasizing the rotation of the polarization vector along null congruences. |
1909.12664 | Antonina Zinhailo | A. F. Zinhailo | Quasinormal modes of Dirac field in the Einstein-dilaton-Gauss-Bonnet
and Einstein-Weyl gravities | 10 pages, 5 figures | null | 10.1140/epjc/s10052-019-7425-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasinormal modes of Dirac field in the background of a non-Schwarzschild
black holes in theories with higher curvature corrections are investigated in
this paper. With the help of the semi-analytic WKB approximation and further
using of Pad\'e approximants as prescribed in [1] we consider quasinormal modes
of a test massless Dirac field in the Einstein-dilaton-Gauss-Bonnet (EdGB) and
Einstein-Weyl (EW) theories. Even though the effective potential for one of the
chiralities has a negative gap we show that the Dirac field is stable in both
theories. We find the dependence of the modes on the new dimensionless
parameter $p$ (related to the coupling constant in each theory) for different
values of the angular parameter $\ell$ and show that the frequencies tend to
linear dependence on $p$. The allowed deviations of qausinormal modes from
their Schwarzschild limit are one order larger for the Einstein-Weyl theory
than for the Einstein-dilaton-Gauss-Bonnet one, achieving the order of tens of
percents. In addition, we test the Hod conjecture which suggests the upper
bound for the imaginary part of the frequency of the longest lived quasinormal
modes by the Hawking temperature multiplied by a factor. We show that in both
non-Schwarzschild metrics the Dirac field obeys the above conjecture for the
whole range of black-hole parameters.
| [
{
"created": "Fri, 27 Sep 2019 13:03:36 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Zinhailo",
"A. F.",
""
]
] | Quasinormal modes of Dirac field in the background of a non-Schwarzschild black holes in theories with higher curvature corrections are investigated in this paper. With the help of the semi-analytic WKB approximation and further using of Pad\'e approximants as prescribed in [1] we consider quasinormal modes of a test massless Dirac field in the Einstein-dilaton-Gauss-Bonnet (EdGB) and Einstein-Weyl (EW) theories. Even though the effective potential for one of the chiralities has a negative gap we show that the Dirac field is stable in both theories. We find the dependence of the modes on the new dimensionless parameter $p$ (related to the coupling constant in each theory) for different values of the angular parameter $\ell$ and show that the frequencies tend to linear dependence on $p$. The allowed deviations of qausinormal modes from their Schwarzschild limit are one order larger for the Einstein-Weyl theory than for the Einstein-dilaton-Gauss-Bonnet one, achieving the order of tens of percents. In addition, we test the Hod conjecture which suggests the upper bound for the imaginary part of the frequency of the longest lived quasinormal modes by the Hawking temperature multiplied by a factor. We show that in both non-Schwarzschild metrics the Dirac field obeys the above conjecture for the whole range of black-hole parameters. |
1803.04268 | Rashmi Uniyal | Rashmi Uniyal, Hemwati Nandan and Philippe Jetzer | Bending angle of light in equatorial plane of Kerr-Sen Black Hole | arXiv admin note: text overlap with arXiv:0907.5352 by other authors | Phys.Lett. B782 (2018) 185-192 | 10.1016/j.physletb.2018.05.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravitational lensing by a Kerr-Sen Black Hole arising in
heterotic string theory. A closed form expression for the bending angle of
light in equatorial plane of Kerr-Sen Black Hole is derived as a function of
impact parameter, spin and charge of the Black Hole. Results obtained are also
compared with the corresponding cases of Kerr Black Hole in general relativity.
It is observed that charge parameter behaves qualitatively similar as the spin
parameter for photons travelling in direct orbits while behaves differently for
photons in retrograde orbits around Black Hole. As the numerical value of the
Black Hole charge increases, bending angle becomes larger in strong field
limit. Further it is observed that this effect is more pronounced in case of
direct orbits in comparison to the retro orbits. For both the direct and retro
motion, the bending angle exceeds 2\pi, which in turn results in multiple loops
and formation of relativistic images.
| [
{
"created": "Fri, 9 Mar 2018 12:57:35 GMT",
"version": "v1"
},
{
"created": "Wed, 23 May 2018 05:16:39 GMT",
"version": "v2"
}
] | 2018-05-24 | [
[
"Uniyal",
"Rashmi",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Jetzer",
"Philippe",
""
]
] | We study the gravitational lensing by a Kerr-Sen Black Hole arising in heterotic string theory. A closed form expression for the bending angle of light in equatorial plane of Kerr-Sen Black Hole is derived as a function of impact parameter, spin and charge of the Black Hole. Results obtained are also compared with the corresponding cases of Kerr Black Hole in general relativity. It is observed that charge parameter behaves qualitatively similar as the spin parameter for photons travelling in direct orbits while behaves differently for photons in retrograde orbits around Black Hole. As the numerical value of the Black Hole charge increases, bending angle becomes larger in strong field limit. Further it is observed that this effect is more pronounced in case of direct orbits in comparison to the retro orbits. For both the direct and retro motion, the bending angle exceeds 2\pi, which in turn results in multiple loops and formation of relativistic images. |
1704.08640 | Konstantinos Ntrekis | George Koutsoumbas, Konstantinos Ntrekis, Eleftherios Papantonopoulos,
Emmanuel N. Saridakis | Unification of Dark Matter - Dark Energy in Generalized Galileon
Theories | 15 pages, 6 figures, version published in JCAP | JCAP 1802 (2018) no.02, 003 | 10.1088/1475-7516/2018/02/003 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a unified description of the dark matter and the dark energy
sectors, in the framework of shift-symmetric generalized Galileon theories.
Considering a particular combination of terms in the Horndeski Lagrangian in
which we have not introduced a cosmological constant or a matter sector, we
obtain an effective unified cosmic fluid whose equation of state $w_U$ is zero
during the whole matter era, namely from redshifts $z\sim3000$ up to
$z\sim2-3$. Then at smaller redshifts it starts decreasing, passing the bound
$w_U=-1/3$, which marks the onset of acceleration, at around $z\sim0.5$. At
present times it acquires the value $w_U=-0.7$. Finally, it tends toward a
de-Sitter phase in the far future. This behaviour is in excellent agreement
with observations. Additionally, confrontation with Supernovae type Ia data
leads to a very efficient fit. Examining the model at the perturbative level,
we show that it is free from pathologies such as ghosts and Laplacian
instabilities, at both scalar and tensor sectors, at all times.
| [
{
"created": "Thu, 27 Apr 2017 16:17:45 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2018 12:36:09 GMT",
"version": "v2"
}
] | 2018-02-07 | [
[
"Koutsoumbas",
"George",
""
],
[
"Ntrekis",
"Konstantinos",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We present a unified description of the dark matter and the dark energy sectors, in the framework of shift-symmetric generalized Galileon theories. Considering a particular combination of terms in the Horndeski Lagrangian in which we have not introduced a cosmological constant or a matter sector, we obtain an effective unified cosmic fluid whose equation of state $w_U$ is zero during the whole matter era, namely from redshifts $z\sim3000$ up to $z\sim2-3$. Then at smaller redshifts it starts decreasing, passing the bound $w_U=-1/3$, which marks the onset of acceleration, at around $z\sim0.5$. At present times it acquires the value $w_U=-0.7$. Finally, it tends toward a de-Sitter phase in the far future. This behaviour is in excellent agreement with observations. Additionally, confrontation with Supernovae type Ia data leads to a very efficient fit. Examining the model at the perturbative level, we show that it is free from pathologies such as ghosts and Laplacian instabilities, at both scalar and tensor sectors, at all times. |
gr-qc/0410114 | Deborah A. Konkowski | D.A. Konkowski, C. Reese, T.M. Helliwell, C. Wieland | Classical and Quantum Singularities of Levi-Civita Spacetimes with and
without a Positive Cosmological Constant | 14 pages, no figures, submitted to Proceedings of the Workshop on
Dynamics and Thermodynamics of Blackholes and Naked Singularities (Milan, May
2004) | null | null | null | gr-qc | null | Levi-Civita spacetimes have classical naked singularities. They also have
quantum singularities. Quantum singularities in general relativistic spacetimes
are determined by the behavior of quantum test particles. A static spacetime is
said to be quantum mechanically singular if the spatial portion of the wave
operator is not essentially self-adjoint on a $C_{0}^{\infty}$ domain in
$L^{2}$, a Hilbert space of square integrable functions. Here we summarize how
Weyl's limit point-limit circle criterion can be used to determine whether a
wave operator is essentially self-adjoint and how this test can then be applied
to scalar wave packets in Levi-Civita spacetimes with and without a
cosmological constant to help elucidate the physical properties of these
spacetimes.
| [
{
"created": "Thu, 21 Oct 2004 20:52:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Konkowski",
"D. A.",
""
],
[
"Reese",
"C.",
""
],
[
"Helliwell",
"T. M.",
""
],
[
"Wieland",
"C.",
""
]
] | Levi-Civita spacetimes have classical naked singularities. They also have quantum singularities. Quantum singularities in general relativistic spacetimes are determined by the behavior of quantum test particles. A static spacetime is said to be quantum mechanically singular if the spatial portion of the wave operator is not essentially self-adjoint on a $C_{0}^{\infty}$ domain in $L^{2}$, a Hilbert space of square integrable functions. Here we summarize how Weyl's limit point-limit circle criterion can be used to determine whether a wave operator is essentially self-adjoint and how this test can then be applied to scalar wave packets in Levi-Civita spacetimes with and without a cosmological constant to help elucidate the physical properties of these spacetimes. |
2401.11482 | Liping Meng | Liping Meng, Zhaoyi Xu, Meirong Tang | Destroying the Event Horizon of Cold Dark Matter-Black Hole System | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the Weak Cosmic Censorship Conjecture was proposed, research on this
conjecture has been ongoing. This paper explores the conjecture in black holes
that are closer to those existing in the real universe (i.e., rotating black
holes enveloped by dark matter). In this paper, we obtained a first-order
corrected analytical solution for the black hole event horizon through an
approximate solution. The validity of the first-order corrected analytical
solution will be provided in the appendix. We conduct our study by introducing
a test particle and a scalar field into the black hole. Our conclusions show
that, in extremal case, both a test particle and a scalar field can disrupt the
event horizon of the Kerr-like black hole; in near-extremal case, both a test
particle and a scalar field can disrupt the event horizon of the Kerr-like
black hole. When cold dark matter is not considered, the conclusion is
consistent with previous research.
| [
{
"created": "Sun, 21 Jan 2024 13:08:29 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 09:23:39 GMT",
"version": "v2"
},
{
"created": "Tue, 25 Jun 2024 14:34:09 GMT",
"version": "v3"
},
{
"created": "Mon, 29 Jul 2024 08:58:28 GMT",
"version": "v4"
}
] | 2024-07-30 | [
[
"Meng",
"Liping",
""
],
[
"Xu",
"Zhaoyi",
""
],
[
"Tang",
"Meirong",
""
]
] | Since the Weak Cosmic Censorship Conjecture was proposed, research on this conjecture has been ongoing. This paper explores the conjecture in black holes that are closer to those existing in the real universe (i.e., rotating black holes enveloped by dark matter). In this paper, we obtained a first-order corrected analytical solution for the black hole event horizon through an approximate solution. The validity of the first-order corrected analytical solution will be provided in the appendix. We conduct our study by introducing a test particle and a scalar field into the black hole. Our conclusions show that, in extremal case, both a test particle and a scalar field can disrupt the event horizon of the Kerr-like black hole; in near-extremal case, both a test particle and a scalar field can disrupt the event horizon of the Kerr-like black hole. When cold dark matter is not considered, the conclusion is consistent with previous research. |
1112.0880 | Claes Uggla | Claes Uggla and John Wainwright | Scalar Cosmological Perturbations | null | null | 10.1088/0264-9381/29/10/105002 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar perturbations of Friedmann-Lemaitre cosmologies can be analyzed in a
variety of ways using Einstein's field equations, the Ricci and Bianchi
identities, or the conservation equations for the stress-energy tensor, and
possibly introducing a timelike reference congruence. The common ground is the
use of gauge invariants derived from the metric tensor, the stress-energy
tensor, or from vectors associated with a reference congruence, as basic
variables. Although there is a complication in that there is no unique choice
of gauge invariants, we will show that this can be used to advantage.
With this in mind our first goal is to present an efficient way of
constructing dimensionless gauge invariants associated with the tensors that
are involved, and of determining their inter-relationships. Our second goal is
to give a unified treatment of the various ways of writing the governing
equations in dimensionless form using gauge-invariant variables, showing how
simplicity can be achieved by a suitable choice of variables and normalization
factors. Our third goal is to elucidate the connection between the metric-based
approach and the so-called 1+3 gauge-invariant approach to cosmological
perturbations. We restrict our considerations to linear perturbations, but our
intent is to set the stage for the extension to second order perturbations.
| [
{
"created": "Mon, 5 Dec 2011 10:34:13 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Uggla",
"Claes",
""
],
[
"Wainwright",
"John",
""
]
] | Scalar perturbations of Friedmann-Lemaitre cosmologies can be analyzed in a variety of ways using Einstein's field equations, the Ricci and Bianchi identities, or the conservation equations for the stress-energy tensor, and possibly introducing a timelike reference congruence. The common ground is the use of gauge invariants derived from the metric tensor, the stress-energy tensor, or from vectors associated with a reference congruence, as basic variables. Although there is a complication in that there is no unique choice of gauge invariants, we will show that this can be used to advantage. With this in mind our first goal is to present an efficient way of constructing dimensionless gauge invariants associated with the tensors that are involved, and of determining their inter-relationships. Our second goal is to give a unified treatment of the various ways of writing the governing equations in dimensionless form using gauge-invariant variables, showing how simplicity can be achieved by a suitable choice of variables and normalization factors. Our third goal is to elucidate the connection between the metric-based approach and the so-called 1+3 gauge-invariant approach to cosmological perturbations. We restrict our considerations to linear perturbations, but our intent is to set the stage for the extension to second order perturbations. |
2102.10650 | Kouji Nakamura | Kouji Nakamura | Formal solutions of any-order mass, angular-momentum, dipole
perturbations on the Schwarzschild background spacetime | 10 pages, no figure. arXiv admin note: text overlap with
arXiv:2102.00830 (v1), arXiv:1403.1004; 11 pages no figure. The whole
presentations are changed and references are re-organized and added, although
the main assertion of this paper is unchanged. (v2); introduction is changed,
references are added. (v3) | Letters in High Energy Physics vol.2021 (2021), 215 | 10.31526/lhep.2021.215 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Formal solutions of any-order mass, angular-momentum, dipole perturbations on
the Schwarzschild background spacetime are derived in a gauge-invariant manner.
Once we accept the proposal in [K. Nakamura, Class. Quantum Grav. {\bf 38}
(2021), 145010.], we can extend the gauge-invariant linear perturbation theory
on the Schwarzschild background spacetime including the monopole ($l=0$) and
dipole ($l=1$) modes to any-order perturbations of the same background
spacetime through the arguments in [K. Nakamura, Class. Quantum Grav. {\bf 31}
(2014), 135013.]. As a result of this resolution, we reached to a simple
derivation of the above formal solutions of any order.
| [
{
"created": "Sun, 21 Feb 2021 17:22:26 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jun 2021 09:29:50 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Jun 2021 08:14:51 GMT",
"version": "v3"
}
] | 2021-11-02 | [
[
"Nakamura",
"Kouji",
""
]
] | Formal solutions of any-order mass, angular-momentum, dipole perturbations on the Schwarzschild background spacetime are derived in a gauge-invariant manner. Once we accept the proposal in [K. Nakamura, Class. Quantum Grav. {\bf 38} (2021), 145010.], we can extend the gauge-invariant linear perturbation theory on the Schwarzschild background spacetime including the monopole ($l=0$) and dipole ($l=1$) modes to any-order perturbations of the same background spacetime through the arguments in [K. Nakamura, Class. Quantum Grav. {\bf 31} (2014), 135013.]. As a result of this resolution, we reached to a simple derivation of the above formal solutions of any order. |
1809.07345 | Zhan-Feng Mai | Jia-Hui Huang, Mu-Zi Zhang, Tian-Tian Cao, Yi-Feng Zou and Zhan-Feng
Mai | Superradiant instability of dyonic black holes in string theory | 14 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When a scalar wave perturbation is properly scattering off a charged or
rotating black hole, the energy of the reflected scalar wave may be amplified.
This is a superradiant process. If this amplification process can occur back
and forth through certain confining mechanism, it will lead to strong
instability of the black hole. In this paper, the superradiant stability is
investigated for a special kind of dyonic black holes in string theory.
Although the dynoic black hole has a similar spacetime metric with a
electrically charged RN black hole, it is found that the dyonic black hole is
more unstable than a RN black hole due to the coupling between magnetic charge
of the dyonic black hole and the imping electrically charged scalar wave. We
find two superradiantly stable regions in the parameter space for the dyonic
black holes and charged massive scalar perturbation.
| [
{
"created": "Wed, 19 Sep 2018 18:00:15 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Oct 2018 02:49:36 GMT",
"version": "v2"
},
{
"created": "Sat, 16 May 2020 03:49:22 GMT",
"version": "v3"
},
{
"created": "Sat, 5 Sep 2020 04:21:28 GMT",
"version": "v4"
}
] | 2020-09-08 | [
[
"Huang",
"Jia-Hui",
""
],
[
"Zhang",
"Mu-Zi",
""
],
[
"Cao",
"Tian-Tian",
""
],
[
"Zou",
"Yi-Feng",
""
],
[
"Mai",
"Zhan-Feng",
""
]
] | When a scalar wave perturbation is properly scattering off a charged or rotating black hole, the energy of the reflected scalar wave may be amplified. This is a superradiant process. If this amplification process can occur back and forth through certain confining mechanism, it will lead to strong instability of the black hole. In this paper, the superradiant stability is investigated for a special kind of dyonic black holes in string theory. Although the dynoic black hole has a similar spacetime metric with a electrically charged RN black hole, it is found that the dyonic black hole is more unstable than a RN black hole due to the coupling between magnetic charge of the dyonic black hole and the imping electrically charged scalar wave. We find two superradiantly stable regions in the parameter space for the dyonic black holes and charged massive scalar perturbation. |
1102.4572 | Lorenzo Iorio | Lorenzo Iorio | An Empirical Explanation of the Anomalous Increases in the Astronomical
Unit and the Lunar Eccentricity | Latex2e, no figures, no tables, 9 pages, 51 references. Published in
The Astronomical Journal (AJ) | Astron.J.142: 68, 2011 | 10.1088/0004-6256/142/3/68 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Both the recently reported anomalous secular increase of the astronomical
unit, of the order of a few cm yr^-1, and of the eccentricity of the lunar
orbit e_ = (9+/-3) 10^-12 yr^-1 can be phenomenologically explained by
postulating that the acceleration of a test particle orbiting a central body,
in addition to usual Newtonian component, contains a small additional radial
term proportional to the radial projection vr of the velocity of the particle's
orbital motion. Indeed, it induces secular variations of both the semi-major
axis a and the eccentricity e of the test particle's orbit. In the case of the
Earth and the Moon, they numerically agree rather well with the measured
anomalies if one takes the numerical value of the coefficient of
proportionality of the extra-acceleration approximately equal to that of the
Hubble parameter H0 = 7.3 10^-11 yr^-1.
| [
{
"created": "Tue, 22 Feb 2011 18:23:15 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2011 07:04:45 GMT",
"version": "v2"
},
{
"created": "Tue, 3 May 2011 15:51:58 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Jun 2011 20:39:27 GMT",
"version": "v4"
},
{
"created": "Sun, 3 Jul 2011 08:08:49 GMT",
"version": "v5"
},
{
"created": "Fri, 15 Jul 2011 15:34:54 GMT",
"version": "v6"
},
{
"created": "Mon, 18 Jul 2011 16:09:04 GMT",
"version": "v7"
},
{
"created": "Mon, 25 Jul 2011 14:56:02 GMT",
"version": "v8"
}
] | 2011-07-26 | [
[
"Iorio",
"Lorenzo",
""
]
] | Both the recently reported anomalous secular increase of the astronomical unit, of the order of a few cm yr^-1, and of the eccentricity of the lunar orbit e_ = (9+/-3) 10^-12 yr^-1 can be phenomenologically explained by postulating that the acceleration of a test particle orbiting a central body, in addition to usual Newtonian component, contains a small additional radial term proportional to the radial projection vr of the velocity of the particle's orbital motion. Indeed, it induces secular variations of both the semi-major axis a and the eccentricity e of the test particle's orbit. In the case of the Earth and the Moon, they numerically agree rather well with the measured anomalies if one takes the numerical value of the coefficient of proportionality of the extra-acceleration approximately equal to that of the Hubble parameter H0 = 7.3 10^-11 yr^-1. |
2302.11998 | Tsvetan Vetsov Assoc. Prof. Dr. | V. Avramov, H. Dimov, M. Radomirov, R. C. Rashkov, and T. Vetsov | On Thermodynamic Stability of Black Holes. Part I: Classical Stability | Minor update: 1. Conclusion revision, 2. Added missing references | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the classical thermodynamic stability of the standard black hole
solutions by implementing the intrinsic necessary and sufficient conditions for
stable global and local thermodynamic equilibrium. The criteria for such
equilibria are quite generic and well-established in classical thermodynamics,
but they have not been fully utilized in black hole physics. We show how weaker
or incomplete conditions could lead to misleading or incorrect results for the
thermodynamic stability of the system. We also stress the importance of finding
all possible local heat capacities in order to fully describe the classical
equilibrium picture of black holes. Finally, we thoroughly investigate the
critical and phase transition curves and the limits of the classical analysis.
This paper is the first in the line of intended works on thermodynamic
stability of black holes in modified theories of gravity and holography.
| [
{
"created": "Thu, 23 Feb 2023 13:20:07 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2023 13:32:00 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Apr 2024 15:39:14 GMT",
"version": "v3"
}
] | 2024-04-02 | [
[
"Avramov",
"V.",
""
],
[
"Dimov",
"H.",
""
],
[
"Radomirov",
"M.",
""
],
[
"Rashkov",
"R. C.",
""
],
[
"Vetsov",
"T.",
""
]
] | We revisit the classical thermodynamic stability of the standard black hole solutions by implementing the intrinsic necessary and sufficient conditions for stable global and local thermodynamic equilibrium. The criteria for such equilibria are quite generic and well-established in classical thermodynamics, but they have not been fully utilized in black hole physics. We show how weaker or incomplete conditions could lead to misleading or incorrect results for the thermodynamic stability of the system. We also stress the importance of finding all possible local heat capacities in order to fully describe the classical equilibrium picture of black holes. Finally, we thoroughly investigate the critical and phase transition curves and the limits of the classical analysis. This paper is the first in the line of intended works on thermodynamic stability of black holes in modified theories of gravity and holography. |
2403.08467 | David Katona | David Katona | Uniqueness of extremal charged black holes in de Sitter | 18 pages, 2 figures | null | null | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a uniqueness theorem for the charged Nariai black holes and
ultracold black holes in four dimensions. In particular, we show that an
analytic solution to four-dimensional Einstein-Maxwell theory with a positive
cosmological constant containing a static extremal Killing horizon with
spherical cross-sections of large radius (compared to the cosmological scale),
must be locally isometric to the extremal Reissner-Nordstr\"om-de Sitter black
hole or its near-horizon geometry. The theorem generalises to extremal static
horizons with small radius, establishing uniqueness of cold black holes for
generic values of the radius.
| [
{
"created": "Wed, 13 Mar 2024 12:29:00 GMT",
"version": "v1"
}
] | 2024-03-14 | [
[
"Katona",
"David",
""
]
] | We prove a uniqueness theorem for the charged Nariai black holes and ultracold black holes in four dimensions. In particular, we show that an analytic solution to four-dimensional Einstein-Maxwell theory with a positive cosmological constant containing a static extremal Killing horizon with spherical cross-sections of large radius (compared to the cosmological scale), must be locally isometric to the extremal Reissner-Nordstr\"om-de Sitter black hole or its near-horizon geometry. The theorem generalises to extremal static horizons with small radius, establishing uniqueness of cold black holes for generic values of the radius. |
1512.08755 | Hernando Quevedo | Sasha A. Zaldivar and Hernando Quevedo | Ideal quantum gases: A geometrothermodynamic approach | Final version published in Journal of Geometry and Physics 189
(2023): 104837 | Journal of Geometry and Physics 189 (2023): 104837 | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the fundamental thermodynamic equation for Fermi-Dirac and
Bose-Einstein quantum gases, which contains the first order contribution due to
the quantum nature of the gas particles. Then, we analyze the fundamental
equation in the context of geometrothermodynamics. Although the corresponding
Hamiltonian does not contain a potential, indicating the lack of classical
thermodynamic interaction, we show that the curvature of the equilibrium space
is non-zero and can be interpreted as a measure of the effective quantum
interaction between the gas particles. In the limiting case of a classical
Boltzmann gas, we show that the equilibrium space becomes flat, as expected
from the physical viewpoint. In addition, we derive a thermodynamic fundamental
equation for the Bose-Einstein condensation and, using the Ehrenfest scheme, we
show that it can be considered as a first order phase transition which in the
equilibrium space corresponds to a curvature singularity. This result indicates
that the curvature of the equilibrium space can be used to measure in an
invariant way the thermodynamic interaction in classical and quantum ideal
gases.
| [
{
"created": "Tue, 29 Dec 2015 19:01:24 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2016 20:51:57 GMT",
"version": "v2"
},
{
"created": "Tue, 24 May 2016 02:06:27 GMT",
"version": "v3"
},
{
"created": "Thu, 21 Mar 2024 16:32:00 GMT",
"version": "v4"
}
] | 2024-03-22 | [
[
"Zaldivar",
"Sasha A.",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We derive the fundamental thermodynamic equation for Fermi-Dirac and Bose-Einstein quantum gases, which contains the first order contribution due to the quantum nature of the gas particles. Then, we analyze the fundamental equation in the context of geometrothermodynamics. Although the corresponding Hamiltonian does not contain a potential, indicating the lack of classical thermodynamic interaction, we show that the curvature of the equilibrium space is non-zero and can be interpreted as a measure of the effective quantum interaction between the gas particles. In the limiting case of a classical Boltzmann gas, we show that the equilibrium space becomes flat, as expected from the physical viewpoint. In addition, we derive a thermodynamic fundamental equation for the Bose-Einstein condensation and, using the Ehrenfest scheme, we show that it can be considered as a first order phase transition which in the equilibrium space corresponds to a curvature singularity. This result indicates that the curvature of the equilibrium space can be used to measure in an invariant way the thermodynamic interaction in classical and quantum ideal gases. |
1710.02607 | Miguel Cruz | Miguel Cruz, Norman Cruz and Samuel Lepe | Accelerated and decelerated expansion in a causal dissipative cosmology | 13 pages, 5 figures. Improved version accepted for publication in PRD | Phys. Rev. D 96, 124020 (2017) | 10.1103/PhysRevD.96.124020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore a new cosmological solution for an universe filled
with one dissipative fluid, described by a barotropic EoS $p = \omega \rho$, in
the framework of the full Israel-Stewart theory. The form of the bulk viscosity
has been assumed of the form $\xi = \xi_{0}\rho^{1/2}$. The relaxation time is
taken to be a function of the EoS, the bulk viscosity and the speed of bulk
viscous perturbations, $c_{b}$. The solution presents an initial singularity,
where the curvature scalar diverges as the scale factor goes to zero. Depending
on the values for $\omega$, $\xi_{0}$, $c_{b}$ accelerated and decelerated
cosmic expansion can be obtained. In the case of accelerated expansion, the
viscosity drives the effective EoS to be of quintessence type, for the single
fluid with positive pressure. Nevertheless, we show that only the solution with
decelerated expansion satisfies the thermodynamics conditions $dS/dt > 0$
(growth of the entropy) and $d^{2}S/dt^{2} < 0$ (convexity condition). We show
that an exact stiff matter EoS is not allowed in the framework of the full
causal thermodynamic approach; and in the case of a EoS very close to the stiff
matter regime, we found that dissipative effects becomes negligible so the
entropy remains constant. Finally, we show numerically that the solution is
stable under small perturbations.
| [
{
"created": "Fri, 6 Oct 2017 23:32:02 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Dec 2017 18:25:59 GMT",
"version": "v2"
}
] | 2017-12-20 | [
[
"Cruz",
"Miguel",
""
],
[
"Cruz",
"Norman",
""
],
[
"Lepe",
"Samuel",
""
]
] | In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic EoS $p = \omega \rho$, in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form $\xi = \xi_{0}\rho^{1/2}$. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, $c_{b}$. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for $\omega$, $\xi_{0}$, $c_{b}$ accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions $dS/dt > 0$ (growth of the entropy) and $d^{2}S/dt^{2} < 0$ (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations. |
2304.07209 | Aisha Rashid | M. Farasat Shamir, Mushtaq Ahmad, G. Mustafa, Aisha Rashid | Ricci Inverse Anisotropic Stellar Structures | 14 pages, 19 figures | Chin. J. Phys. 81 (2023) 51 | 10.1016/j.cjph.2022.11.011 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper offers novel quintessence compact relativistic spherically
symmetrical anisotropic solutions under the recently developed Ricci inverse
gravity Amendola et al., 2020), by employing Krori and Barua gravitational
potentials, $Ar^2=\nu(r), ~\&~Br^2+C=\mu(r)$ (with A, B, and C being real
constants). For this objective, a specific explicit equation of state,
connecting energy density and radial pressure, i.e., $p_r=\omega\rho$, such
that $0<\omega<1$, has been utilized with an anisotripic fluid source. Ricci
inverse field equations are used to find the exclusive expressions of the
energy density, radial and tangential stresses, and the quintessence energy
density, the critical physical attributes reflecting the exceptional conduct of
extremely dense matter configuration. For the observatory source stars $Her
X-1$, $SAX J 1808.4-3658$ and $4U 1820-30$, all the important physical
quantities like energy densities, tangential and radial pressures, energy
conditions, gradients, anisotropy, redshift and mass-radius functions, and
stellar compactness have been worked out and analyzed graphically. It has been
concluded that all of the stellar formations under consideration remain free
from any undesirable central singularity and are stable.
| [
{
"created": "Fri, 14 Apr 2023 15:48:32 GMT",
"version": "v1"
}
] | 2023-04-17 | [
[
"Shamir",
"M. Farasat",
""
],
[
"Ahmad",
"Mushtaq",
""
],
[
"Mustafa",
"G.",
""
],
[
"Rashid",
"Aisha",
""
]
] | This paper offers novel quintessence compact relativistic spherically symmetrical anisotropic solutions under the recently developed Ricci inverse gravity Amendola et al., 2020), by employing Krori and Barua gravitational potentials, $Ar^2=\nu(r), ~\&~Br^2+C=\mu(r)$ (with A, B, and C being real constants). For this objective, a specific explicit equation of state, connecting energy density and radial pressure, i.e., $p_r=\omega\rho$, such that $0<\omega<1$, has been utilized with an anisotripic fluid source. Ricci inverse field equations are used to find the exclusive expressions of the energy density, radial and tangential stresses, and the quintessence energy density, the critical physical attributes reflecting the exceptional conduct of extremely dense matter configuration. For the observatory source stars $Her X-1$, $SAX J 1808.4-3658$ and $4U 1820-30$, all the important physical quantities like energy densities, tangential and radial pressures, energy conditions, gradients, anisotropy, redshift and mass-radius functions, and stellar compactness have been worked out and analyzed graphically. It has been concluded that all of the stellar formations under consideration remain free from any undesirable central singularity and are stable. |
1411.6513 | Alessio Belenchia | Alessio Belenchia, Dionigi M. T. Benincasa and Stefano Liberati | Nonlocal Scalar Quantum Field Theory from Causal Sets | 24 pages, 7 figures. Published in JHEP 1503 (2015) 036 | JHEP 1503 (2015) 036 | 10.1007/JHEP03(2015)036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a non-local scalar quantum field theory in flat spacetime derived
from the dynamics of a scalar field on a causal set. We show that this
non-local QFT contains a continuum of massive modes in any dimension. In 2
dimensions the Hamiltonian is positive definite and therefore the quantum
theory is well-defined. In 4-dimensions, we show that the unstable modes of the
non-local d'Alembertian are propagated via the so called Wheeler propagator and
hence do not appear in the asymptotic states. In the free case studied here the
continuum of massive mode are shown to not propagate in the asymptotic states.
However the Hamiltonian is not positive definite, therefore potential issues
with the quantum theory remain. Finally, we conclude with hints toward what
kind of phenomenology one might expect from such non-local QFTs.
| [
{
"created": "Mon, 24 Nov 2014 16:28:59 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Mar 2015 19:48:30 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Belenchia",
"Alessio",
""
],
[
"Benincasa",
"Dionigi M. T.",
""
],
[
"Liberati",
"Stefano",
""
]
] | We study a non-local scalar quantum field theory in flat spacetime derived from the dynamics of a scalar field on a causal set. We show that this non-local QFT contains a continuum of massive modes in any dimension. In 2 dimensions the Hamiltonian is positive definite and therefore the quantum theory is well-defined. In 4-dimensions, we show that the unstable modes of the non-local d'Alembertian are propagated via the so called Wheeler propagator and hence do not appear in the asymptotic states. In the free case studied here the continuum of massive mode are shown to not propagate in the asymptotic states. However the Hamiltonian is not positive definite, therefore potential issues with the quantum theory remain. Finally, we conclude with hints toward what kind of phenomenology one might expect from such non-local QFTs. |
1105.6034 | Parthasarathi Mitra | A. Ghosh and P. Mitra | Black hole state counting in loop quantum gravity | 5 pages | Mod. Phys. Lett. A26 (2011) 1817 | 10.1142/S0217732311036073 | SINP/TNP/2011/05 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The two ways of counting microscopic states of black holes in the U(1)
formulation of loop quantum gravity, one counting all allowed spin network
labels j,m and the other only m labels, are discussed in some detail. The
constraints on m are clarified and the map between the flux quantum numbers and
m discussed. Configurations with |m|=j, which are sometimes sought after, are
shown to be important only when large areas are involved. The discussion is
extended to the SU(2) formulation.
| [
{
"created": "Thu, 26 May 2011 08:29:09 GMT",
"version": "v1"
}
] | 2014-05-22 | [
[
"Ghosh",
"A.",
""
],
[
"Mitra",
"P.",
""
]
] | The two ways of counting microscopic states of black holes in the U(1) formulation of loop quantum gravity, one counting all allowed spin network labels j,m and the other only m labels, are discussed in some detail. The constraints on m are clarified and the map between the flux quantum numbers and m discussed. Configurations with |m|=j, which are sometimes sought after, are shown to be important only when large areas are involved. The discussion is extended to the SU(2) formulation. |
0705.3363 | G P Procopio | Alessandro Fabbri, Giovanni Paolo Procopio | The Holographic Interpretation of Hawking Radiation | 10 pages, 1 figure, Honorable Mention in the Gravity Research
Foundation Essay Competition 2007 | Int.J.Mod.Phys.D17:2433-2438,2009 | 10.1142/S0218271808014102 | DAMTP-2007-45 | gr-qc hep-th | null | Holography gives us a tool to view the Hawking effect from a new, classical
perspective. In the context of Randall-Sundrum braneworld models, we show that
the basic features of four-dimensional evaporating solutions are nicely
translated into classical five-dimensional language. This includes the dual
bulk description of particles tunneling through the horizon.
| [
{
"created": "Wed, 23 May 2007 12:48:04 GMT",
"version": "v1"
}
] | 2009-03-20 | [
[
"Fabbri",
"Alessandro",
""
],
[
"Procopio",
"Giovanni Paolo",
""
]
] | Holography gives us a tool to view the Hawking effect from a new, classical perspective. In the context of Randall-Sundrum braneworld models, we show that the basic features of four-dimensional evaporating solutions are nicely translated into classical five-dimensional language. This includes the dual bulk description of particles tunneling through the horizon. |
2207.01150 | Emilio Rub\'in de Celis | E. Rub\'in de Celis and C. Simeone | Further considerations about the traversability of thin-shell wormholes | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Traversability in relation with tides in thin-shell wormholes is revisited to
investigate the possibility of improving recently noted restrictive conditions
for a safe travel across a wormhole throat. We consider wormholes
mathematically constructed starting from background geometries which are
solutions of scalar-tensor theories as dilaton gravity and Brans--Dicke
gravity. The advantages of working within such frameworks are studied by
examining the dependence of the extrinsic curvature and tides at the throat
with the parameters determining the departure from pure relativity; the
associated behaviour of tides in the smooth regions of the geometries is also
analyzed. Other related but different approaches are briefly discussed in the
appendices.
| [
{
"created": "Mon, 4 Jul 2022 00:35:38 GMT",
"version": "v1"
}
] | 2022-07-05 | [
[
"de Celis",
"E. Rubín",
""
],
[
"Simeone",
"C.",
""
]
] | Traversability in relation with tides in thin-shell wormholes is revisited to investigate the possibility of improving recently noted restrictive conditions for a safe travel across a wormhole throat. We consider wormholes mathematically constructed starting from background geometries which are solutions of scalar-tensor theories as dilaton gravity and Brans--Dicke gravity. The advantages of working within such frameworks are studied by examining the dependence of the extrinsic curvature and tides at the throat with the parameters determining the departure from pure relativity; the associated behaviour of tides in the smooth regions of the geometries is also analyzed. Other related but different approaches are briefly discussed in the appendices. |
gr-qc/9512031 | Alexander Vilenkin | Alexander Vilenkin | Quantum Cosmology and the Constants of Nature | 12 pages; talk given at the RESCEU Symposium, Tokyo, Nov. 1995 | null | null | null | gr-qc astro-ph | null | In models where the constants of Nature can take more than one set of values,
the cosmological wave function $\psi$ describes an ensemble of universes with
different values of the constants. The probability distribution for the
constants can be determined with the aid of the `principle of mediocrity' which
asserts that we are a `typical' civilization in this ensemble. I discuss the
implications of this approach for inflationary scenarios, the origin of density
fluctuations, and the cosmological constant.
| [
{
"created": "Fri, 15 Dec 1995 12:34:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vilenkin",
"Alexander",
""
]
] | In models where the constants of Nature can take more than one set of values, the cosmological wave function $\psi$ describes an ensemble of universes with different values of the constants. The probability distribution for the constants can be determined with the aid of the `principle of mediocrity' which asserts that we are a `typical' civilization in this ensemble. I discuss the implications of this approach for inflationary scenarios, the origin of density fluctuations, and the cosmological constant. |
1808.09826 | Jun-Qi Guo | Jun-Qi Guo and Hongsheng Zhang | Dynamics of critical collapse | Title changed. 11 pages, 8 figures, 1 table | Eur. Phys. J. C 79, 625 (2019) | 10.1140/epjc/s10052-019-7144-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Critical collapse of a massless scalar field in spherical symmetry is
systematically studied. We combine numerical simulations and asymptotic
analysis, and synthesize critical collapse, spacetime singularities, and
complex science. First set of approximate analytic expressions near the center
are obtained. We observe that, near the center, the spacetime is nearly
conformally flat, the dynamics is not described by the Kasner solution, and the
Kreschmann scalar is proportional to r^(-5.30), where r is the areal radius.
These features are significantly different from those in black hole
singularities. It is speculated that the scalar field in critical collapse may
be a special standing wave.
| [
{
"created": "Wed, 29 Aug 2018 13:49:45 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Oct 2018 10:37:38 GMT",
"version": "v2"
},
{
"created": "Sun, 28 Jul 2019 00:46:29 GMT",
"version": "v3"
}
] | 2019-07-30 | [
[
"Guo",
"Jun-Qi",
""
],
[
"Zhang",
"Hongsheng",
""
]
] | Critical collapse of a massless scalar field in spherical symmetry is systematically studied. We combine numerical simulations and asymptotic analysis, and synthesize critical collapse, spacetime singularities, and complex science. First set of approximate analytic expressions near the center are obtained. We observe that, near the center, the spacetime is nearly conformally flat, the dynamics is not described by the Kasner solution, and the Kreschmann scalar is proportional to r^(-5.30), where r is the areal radius. These features are significantly different from those in black hole singularities. It is speculated that the scalar field in critical collapse may be a special standing wave. |
1710.04485 | Farhad Darabi | Y. Heydarzade, F. Darabi | Surrounded Vaidya Solution by Cosmological Fields | 37 pages, 31 figures | Eur. Phys. J. C, (2018), 78:582 | 10.1140/epjc/s10052-018-6041-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study the general surrounded Vaidya solution by the
various cosmological fields and its nature describing the possibility of the
formation of naked singularities or black holes. Motivated by the fact that
real astrophysical black holes as non-stationary and non-isolated objects are
living in non-empty backgrounds, we focus on the black hole subclasses of this
general solution describing a dynamical evaporating-accreting black holes in
the dynamical cosmological backgrounds of dust, radiation, quintessence,
cosmological constant-like and phantom fields, the so called surrounded Vaidya
black hole. Then, we analyze the timelike geodesics associated with the
obtained surrounded black holes and we find that some new correction terms
arise relative to the case of Schwarzschild black hole. Also, we address some
of the subclasses of the obtained surrounded black hole solution for both
dynamical and stationary limits. Moreover, we classify the obtained solutions
according to their behaviors under imposing the positive energy condition and
discuss how this condition imposes some severe and important restrictions on
the black hole and its background field dynamics.
| [
{
"created": "Thu, 12 Oct 2017 12:58:45 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Dec 2018 11:15:08 GMT",
"version": "v2"
}
] | 2018-12-11 | [
[
"Heydarzade",
"Y.",
""
],
[
"Darabi",
"F.",
""
]
] | In the present work, we study the general surrounded Vaidya solution by the various cosmological fields and its nature describing the possibility of the formation of naked singularities or black holes. Motivated by the fact that real astrophysical black holes as non-stationary and non-isolated objects are living in non-empty backgrounds, we focus on the black hole subclasses of this general solution describing a dynamical evaporating-accreting black holes in the dynamical cosmological backgrounds of dust, radiation, quintessence, cosmological constant-like and phantom fields, the so called surrounded Vaidya black hole. Then, we analyze the timelike geodesics associated with the obtained surrounded black holes and we find that some new correction terms arise relative to the case of Schwarzschild black hole. Also, we address some of the subclasses of the obtained surrounded black hole solution for both dynamical and stationary limits. Moreover, we classify the obtained solutions according to their behaviors under imposing the positive energy condition and discuss how this condition imposes some severe and important restrictions on the black hole and its background field dynamics. |
1509.05297 | Alexandre Feller | Alexandre Feller, Etera R. Livine | Ising Spin Network States for Loop Quantum Gravity: a Toy Model for
Phase Transitions | 17 pages | Class.Quant.Grav. 33 (2016) 6, 065005 | 10.1088/0264-9381/33/6/065005 | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-perturbative approaches to quantum gravity call for a deep understanding
of the emergence of geometry and locality from the quantum state of the
gravitational field. Without background geometry, the notion of distance should
entirely emerge from the correlations between the gravity fluctuations. In the
context of loop quantum gravity, quantum states of geometry are defined as spin
networks. These are graphs decorated with spin and intertwiners, which
represent quantized excitations of areas and volumes of the space geometry.
Here, we develop the condensed matter point of view on extracting the physical
and geometrical information out of spin network states: we introduce new Ising
spin network states, both in 2d on a square lattice and in 3d on a hexagonal
lattice, whose correlations map onto the usual Ising model in statistical
physics. We construct these states from the basic holonomy operators of loop
gravity and derive a set of local Hamiltonian constraints which entirely
characterize our states. We discuss their phase diagram and show how the
distance can be reconstructed from the correlations in the various phases.
Finally, we propose generalizations of these Ising states, which open the
perspective to study the coarse graining and dynamics of spin network states
using well-known condensed matter techniques and results.
| [
{
"created": "Thu, 17 Sep 2015 15:38:56 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Feller",
"Alexandre",
""
],
[
"Livine",
"Etera R.",
""
]
] | Non-perturbative approaches to quantum gravity call for a deep understanding of the emergence of geometry and locality from the quantum state of the gravitational field. Without background geometry, the notion of distance should entirely emerge from the correlations between the gravity fluctuations. In the context of loop quantum gravity, quantum states of geometry are defined as spin networks. These are graphs decorated with spin and intertwiners, which represent quantized excitations of areas and volumes of the space geometry. Here, we develop the condensed matter point of view on extracting the physical and geometrical information out of spin network states: we introduce new Ising spin network states, both in 2d on a square lattice and in 3d on a hexagonal lattice, whose correlations map onto the usual Ising model in statistical physics. We construct these states from the basic holonomy operators of loop gravity and derive a set of local Hamiltonian constraints which entirely characterize our states. We discuss their phase diagram and show how the distance can be reconstructed from the correlations in the various phases. Finally, we propose generalizations of these Ising states, which open the perspective to study the coarse graining and dynamics of spin network states using well-known condensed matter techniques and results. |
gr-qc/0410123 | Christodoulakis Theodosios | T. Christodoulakis and Petros A. Terzis | Automorphisms and a Cartography of the Solution Space for Vacuum Bianchi
Cosmologies: The Type III Case | 19 pages, LatTex source file, no figures, accepted in JMP | J.Math.Phys. 47 (2006) 102502 | 10.1063/1.2359141 | null | gr-qc | null | The theory of symmetries of systems of coupled, ordinary differential
equations (ODE's) is used to develop a concise algorithm for cartographing the
space of solutions to vacuum Bianchi Einstein's Field Equations (EFE). The
symmetries used are the well known automorphisms of the Lie algebra for the
corresponding isometry group of each Bianchi Type, as well as the scaling and
the time eparameterization symmetry. Application of the method to Type III
results in: a) the recovery of all known solutions without prior assumption of
any extra symmetry, b) the enclosure of the entire unknown part of the solution
space into a single, second order ODE in terms of one dependent variable and c)
a partial solution to this ODE. It is also worth-mentioning the fact that the
solution space is seen to be naturally partitioned into three distinct,
disconnected pieces: one consisting of the known Siklos (pp-wave) solution,
another occupied by the Type III member of the known Ellis-MacCallum family and
the third described by the aforementioned ODE in which an one parameter
subfamily of the known Kinnersley geometries resides. Lastly, preliminary
results reported show that the unknown part of the solution space for other
Bianchi Types is described by a strikingly similar ODE, pointing to a natural
operational unification as far as the problem of solving the cosmological EFE's
is concerned.
| [
{
"created": "Tue, 26 Oct 2004 10:22:55 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jul 2006 11:05:46 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Oct 2006 13:10:01 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Christodoulakis",
"T.",
""
],
[
"Terzis",
"Petros A.",
""
]
] | The theory of symmetries of systems of coupled, ordinary differential equations (ODE's) is used to develop a concise algorithm for cartographing the space of solutions to vacuum Bianchi Einstein's Field Equations (EFE). The symmetries used are the well known automorphisms of the Lie algebra for the corresponding isometry group of each Bianchi Type, as well as the scaling and the time eparameterization symmetry. Application of the method to Type III results in: a) the recovery of all known solutions without prior assumption of any extra symmetry, b) the enclosure of the entire unknown part of the solution space into a single, second order ODE in terms of one dependent variable and c) a partial solution to this ODE. It is also worth-mentioning the fact that the solution space is seen to be naturally partitioned into three distinct, disconnected pieces: one consisting of the known Siklos (pp-wave) solution, another occupied by the Type III member of the known Ellis-MacCallum family and the third described by the aforementioned ODE in which an one parameter subfamily of the known Kinnersley geometries resides. Lastly, preliminary results reported show that the unknown part of the solution space for other Bianchi Types is described by a strikingly similar ODE, pointing to a natural operational unification as far as the problem of solving the cosmological EFE's is concerned. |
1512.08953 | Dejan Gajic | Dejan Gajic | Linear waves in the interior of extremal black holes II | 68 pages, 3 figures | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider solutions to the linear wave equation in the interior region of
extremal Kerr black holes. We show that axisymmetric solutions can be extended
continuously beyond the Cauchy horizon and moreover that, if we assume suitably
fast polynomial decay in time along the event horizon, their local energy is
finite. We also extend these results to non-axisymmetric solutions on slowly
rotating extremal Kerr-Newman black holes. These results are the analogues of
results obtained in [D. Gajic, Linear waves in the interior of extremal black
holes I, arXiv:1509.06568] for extremal Reissner-Nordstr\"om and stand in stark
contrast to previously established results for the subextremal case, where the
local energy was shown to generically blow up at the Cauchy horizon.
| [
{
"created": "Wed, 30 Dec 2015 14:37:18 GMT",
"version": "v1"
}
] | 2015-12-31 | [
[
"Gajic",
"Dejan",
""
]
] | We consider solutions to the linear wave equation in the interior region of extremal Kerr black holes. We show that axisymmetric solutions can be extended continuously beyond the Cauchy horizon and moreover that, if we assume suitably fast polynomial decay in time along the event horizon, their local energy is finite. We also extend these results to non-axisymmetric solutions on slowly rotating extremal Kerr-Newman black holes. These results are the analogues of results obtained in [D. Gajic, Linear waves in the interior of extremal black holes I, arXiv:1509.06568] for extremal Reissner-Nordstr\"om and stand in stark contrast to previously established results for the subextremal case, where the local energy was shown to generically blow up at the Cauchy horizon. |
gr-qc/9708005 | Inyong Cho | Inyong Cho and Alexander Vilenkin | Spacetime structure of an inflating global monopole | 18 pages, REVTeX, 8 PostScript figures, submitted to the Physical
Review D | Phys.Rev. D56 (1997) 7621-7626 | 10.1103/PhysRevD.56.7621 | null | gr-qc astro-ph | null | The evolution of a global monopole with an inflating core is investigated. An
analytic expression for the exterior metric at large distances from the core is
obtained. The overall spacetime structure is studied numerically, both in
vacuum and in a radiation background.
| [
{
"created": "Mon, 4 Aug 1997 17:20:59 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Cho",
"Inyong",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | The evolution of a global monopole with an inflating core is investigated. An analytic expression for the exterior metric at large distances from the core is obtained. The overall spacetime structure is studied numerically, both in vacuum and in a radiation background. |
gr-qc/0403098 | Ngangbam Ibohal | Ng Ibohal | Rotating metrics admitting non-perfect fluids in General Relativity | LaTex, 39 pages | Gen.Rel.Grav. 37 (2005) 19-51 | 10.1007/s10714-005-0002-6 | null | gr-qc | null | In this paper, by applying Newman-Janis algorithm in spherical symmetric
metrics, a class of embedded rotating solutions of field equations is
presented. These solutions admit non-perfect fluids
| [
{
"created": "Wed, 24 Mar 2004 07:24:50 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ibohal",
"Ng",
""
]
] | In this paper, by applying Newman-Janis algorithm in spherical symmetric metrics, a class of embedded rotating solutions of field equations is presented. These solutions admit non-perfect fluids |
1411.2329 | Cosimo Bambi | Dan Liu, Zilong Li, Cosimo Bambi | Testing a class of non-Kerr metrics with hot spots orbiting SgrA$^*$ | 1+14 pages, 3 figures. v2: refereed version | JCAP 1501:020,2015 | 10.1088/1475-7516/2015/01/020 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | SgrA$^*$, the supermassive black hole candidate at the Galactic Center,
exhibits flares in the X-ray, NIR, and sub-mm bands that may be interpreted
within a hot spot model. Light curves and images of hot spots orbiting a black
hole are affected by a number of special and general relativistic effects, and
they can be potentially used to check whether the object is a Kerr black hole
of general relativity. However, in a previous study we have shown that the
relativistic features are usually subdominant with respect to the background
noise and the model-dependent properties of the hot spot, and eventually it is
at most possible to estimate the frequency of the innermost stable circular
orbit. In this case, tests of the Kerr metric are only possible in combination
with other measurements. In the present work, we consider a class of non-Kerr
spacetimes in which the hot spot orbit may be outside the equatorial plane.
These metrics are difficult to constrain from the study of accretion disks and
indeed current X-ray observations of stellar-mass and supermassive black hole
candidates cannot put interesting bounds. Here we show that near future
observations of SgrA$^*$ may do it. If the hot spot is sufficiently close to
the massive object, the image affected by Doppler blueshift is brighter than
the other one and this provides a specific observational signature in the hot
spot's centroid track. We conclude that accurate astrometric observations of
SgrA$^*$ with an instrument like GRAVITY should be able to test this class of
metrics, except in the more unlikely case of a small viewing angle.
| [
{
"created": "Mon, 10 Nov 2014 05:26:02 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Dec 2014 19:02:34 GMT",
"version": "v2"
}
] | 2015-01-15 | [
[
"Liu",
"Dan",
""
],
[
"Li",
"Zilong",
""
],
[
"Bambi",
"Cosimo",
""
]
] | SgrA$^*$, the supermassive black hole candidate at the Galactic Center, exhibits flares in the X-ray, NIR, and sub-mm bands that may be interpreted within a hot spot model. Light curves and images of hot spots orbiting a black hole are affected by a number of special and general relativistic effects, and they can be potentially used to check whether the object is a Kerr black hole of general relativity. However, in a previous study we have shown that the relativistic features are usually subdominant with respect to the background noise and the model-dependent properties of the hot spot, and eventually it is at most possible to estimate the frequency of the innermost stable circular orbit. In this case, tests of the Kerr metric are only possible in combination with other measurements. In the present work, we consider a class of non-Kerr spacetimes in which the hot spot orbit may be outside the equatorial plane. These metrics are difficult to constrain from the study of accretion disks and indeed current X-ray observations of stellar-mass and supermassive black hole candidates cannot put interesting bounds. Here we show that near future observations of SgrA$^*$ may do it. If the hot spot is sufficiently close to the massive object, the image affected by Doppler blueshift is brighter than the other one and this provides a specific observational signature in the hot spot's centroid track. We conclude that accurate astrometric observations of SgrA$^*$ with an instrument like GRAVITY should be able to test this class of metrics, except in the more unlikely case of a small viewing angle. |
1903.07123 | Tevian Dray | Tevian Dray and Carlo Rovelli | Reflections on the Energy of Black Holes | Essay written for the Gravity Research Foundation 2019 Awards for
Essays on Gravitation | null | 10.1142/S0218271819440048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inside a black hole, there is no local way to say which side of a sphere is
the inside, and which is the outside. One can easily be gulled by this fact
into mixing up the sign of the energy. We lead the reader astray with a na\"ive
treatment of the energy of a null shell in black hole spacetimes. We then
resolve the confusion, showing that global, rather than local, considerations
offer good guidance.
| [
{
"created": "Sun, 17 Mar 2019 16:26:19 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Dray",
"Tevian",
""
],
[
"Rovelli",
"Carlo",
""
]
] | Inside a black hole, there is no local way to say which side of a sphere is the inside, and which is the outside. One can easily be gulled by this fact into mixing up the sign of the energy. We lead the reader astray with a na\"ive treatment of the energy of a null shell in black hole spacetimes. We then resolve the confusion, showing that global, rather than local, considerations offer good guidance. |
2303.14251 | John Bayron Orjuela Quintana | J. Bayron Orjuela-Quintana, Savvas Nesseris | Tracking the validity of the quasi-static and sub-horizon approximations
in modified gravity | 28 pages, 18 figures. Changes match published version | null | 10.1088/1475-7516/2023/08/019 | IFT-UAM/CSIC-23-27 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of modified gravity (MG), the quasi-static (QS) and
sub-horizon (SH) approximations are widely used in analyses aiming to identify
departures from the concordance model at late-times. In general, it is assumed
that time derivatives are subdominant with respect to spatial derivatives given
that the relevant physical modes are those well inside the Hubble radius. In
practice, the perturbation equations under these approximations are reduced to
a tractable algebraic system in terms of the gravitational potentials and the
perturbations of involved matter fields. Here, in the framework of $f(R)$
theories, we revisit standard results when these approximations are invoked
using a new parameterization scheme that allows us to track the relevance of
each time-derivative term in the perturbation equations. This new approach
unveils terms which are neglected in the standard procedure. We assess the
relevance of these differences by comparing results from both approaches
against full numerical solutions for two well-known toy-models: the designer
$f(R)$ model and the Hu-Sawicki model. We find that: i) the SH approximation
can be safely applied to linear perturbation equations for scales $0.06 h/$Mpc
$\lesssim k \lesssim 0.2 h/$Mpc, ii) in this "safety region", the QS
approximation provides a very accurate description of the late-time
cosmological dynamics even when dark energy significantly contribute to the
cosmic budget, and iii) our new methodology performs better than the standard
procedure, even for several orders of magnitude in some cases. Although, the
impact of this major improvement on the linear observables is minimal for the
studied cases, this does not represent an invalidation for our approach.
Instead, our findings indicate that the perturbation expressions derived under
these approximations in more general MG theories, such as Horndeski, should be
also revisited.
| [
{
"created": "Fri, 24 Mar 2023 19:31:38 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Aug 2023 12:26:15 GMT",
"version": "v2"
}
] | 2023-08-15 | [
[
"Orjuela-Quintana",
"J. Bayron",
""
],
[
"Nesseris",
"Savvas",
""
]
] | Within the framework of modified gravity (MG), the quasi-static (QS) and sub-horizon (SH) approximations are widely used in analyses aiming to identify departures from the concordance model at late-times. In general, it is assumed that time derivatives are subdominant with respect to spatial derivatives given that the relevant physical modes are those well inside the Hubble radius. In practice, the perturbation equations under these approximations are reduced to a tractable algebraic system in terms of the gravitational potentials and the perturbations of involved matter fields. Here, in the framework of $f(R)$ theories, we revisit standard results when these approximations are invoked using a new parameterization scheme that allows us to track the relevance of each time-derivative term in the perturbation equations. This new approach unveils terms which are neglected in the standard procedure. We assess the relevance of these differences by comparing results from both approaches against full numerical solutions for two well-known toy-models: the designer $f(R)$ model and the Hu-Sawicki model. We find that: i) the SH approximation can be safely applied to linear perturbation equations for scales $0.06 h/$Mpc $\lesssim k \lesssim 0.2 h/$Mpc, ii) in this "safety region", the QS approximation provides a very accurate description of the late-time cosmological dynamics even when dark energy significantly contribute to the cosmic budget, and iii) our new methodology performs better than the standard procedure, even for several orders of magnitude in some cases. Although, the impact of this major improvement on the linear observables is minimal for the studied cases, this does not represent an invalidation for our approach. Instead, our findings indicate that the perturbation expressions derived under these approximations in more general MG theories, such as Horndeski, should be also revisited. |
1909.03887 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu, Robert B. Mann | Ruppeiner Geometry, Phase Transitions, and the Microstructure of Charged
AdS Black Holes | 31 pages and 17 figures. Seciton VII is added to discuss the
microstructures of Van der Waals fluids and black holes | Phys. Rev. D 100, 124033 (2019) | 10.1103/PhysRevD.100.124033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Originally considered for van der Waals fluids and charged black holes [Phys.
Rev. Lett. 123, 071103 (2019)], we extend and generalize our approach to
higher-dimensional charged AdS black holes. Beginning with thermodynamic
fluctuations, we construct the line element of the Ruppeiner geometry and
obtain a universal formula for the scalar curvature $R$. We first review the
thermodynamics of a van der Waals fluid and calculate the coexistence and
spinodal curves. From this we are able to clearly display the phase diagram.
Notwithstanding the invalidity of the equation of state in the coexistence
phase regions, we find that the scalar curvature is always negative for the van
der Waals fluid, indicating that attractive interactions dominate amongst the
fluid microstructures. Along the coexistence curve, the scalar curvature $R$
decreases with temperature, and goes to negative infinity at a critical
temperature. We then numerically study the critical phenomena associated with
the scalar curvature. We next consider four-dimensional charged AdS black
holes. Vanishing of the heat capacity at constant volume yields a divergent
scalar curvature. In order to extract the corresponding information, we define
a new scalar curvature that has behaviour similar to that of a van der Waals
fluid. We analytically confirm that at the critical point of the small/large
black hole phase transition, the scalar curvature has a critical exponent 2,
and $R(1-\tilde{T})^{2}C_{v}=1/8$, the same as that of a van der Waals fluid.
However we also find that the scalar curvature can be positive for the small
charged AdS black hole, implying that repulsive interactions dominate among the
black hole microstructures. We then generalize our study to higher-dimensional
charged AdS black holes.
| [
{
"created": "Mon, 9 Sep 2019 14:29:34 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2019 02:34:50 GMT",
"version": "v2"
}
] | 2019-12-24 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Mann",
"Robert B.",
""
]
] | Originally considered for van der Waals fluids and charged black holes [Phys. Rev. Lett. 123, 071103 (2019)], we extend and generalize our approach to higher-dimensional charged AdS black holes. Beginning with thermodynamic fluctuations, we construct the line element of the Ruppeiner geometry and obtain a universal formula for the scalar curvature $R$. We first review the thermodynamics of a van der Waals fluid and calculate the coexistence and spinodal curves. From this we are able to clearly display the phase diagram. Notwithstanding the invalidity of the equation of state in the coexistence phase regions, we find that the scalar curvature is always negative for the van der Waals fluid, indicating that attractive interactions dominate amongst the fluid microstructures. Along the coexistence curve, the scalar curvature $R$ decreases with temperature, and goes to negative infinity at a critical temperature. We then numerically study the critical phenomena associated with the scalar curvature. We next consider four-dimensional charged AdS black holes. Vanishing of the heat capacity at constant volume yields a divergent scalar curvature. In order to extract the corresponding information, we define a new scalar curvature that has behaviour similar to that of a van der Waals fluid. We analytically confirm that at the critical point of the small/large black hole phase transition, the scalar curvature has a critical exponent 2, and $R(1-\tilde{T})^{2}C_{v}=1/8$, the same as that of a van der Waals fluid. However we also find that the scalar curvature can be positive for the small charged AdS black hole, implying that repulsive interactions dominate among the black hole microstructures. We then generalize our study to higher-dimensional charged AdS black holes. |
2109.01193 | P. Vaishak | Vaishak Prasad | Generalized source multipole moments of dynamical horizons in binary
black hole mergers | 9 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we uncover new features in the evolution of the deformations of
the dynamical horizon geometry in a binary black hole merger scenario using
numerical relativity. First, in the inspiral phase, owing to the deformations,
the dynamical horizons of the two black holes are found to steadily acquire
multipole moments that vanish when the horizons are isolated. Out of these, the
dominant moment is found to be the quadrupole moment. Second, we show that they
encode detailed information about the dynamics of the binary black hole system.
The dominant quadrupole multipole moment is particularly shown to be strongly
correlated with the gravitational field of the system at future null infinity.
Therefore, the gravitational waves carried away from the system contain
information about the geometrical structure of the black holes in the
strong-field regime. Third, we also find that, in the post-merger phase, the
multipolar structure of the outer common dynamical horizon of the system is
strongly correlated with that of the individual horizons just before the
merger. The outer common horizon then settles down to equilibrium as suggested
by the decay of the multipole moments gained by the system through the inspiral
phase.
| [
{
"created": "Thu, 2 Sep 2021 19:49:11 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Sep 2021 17:12:43 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Jan 2022 18:40:43 GMT",
"version": "v3"
}
] | 2022-01-21 | [
[
"Prasad",
"Vaishak",
""
]
] | In this work, we uncover new features in the evolution of the deformations of the dynamical horizon geometry in a binary black hole merger scenario using numerical relativity. First, in the inspiral phase, owing to the deformations, the dynamical horizons of the two black holes are found to steadily acquire multipole moments that vanish when the horizons are isolated. Out of these, the dominant moment is found to be the quadrupole moment. Second, we show that they encode detailed information about the dynamics of the binary black hole system. The dominant quadrupole multipole moment is particularly shown to be strongly correlated with the gravitational field of the system at future null infinity. Therefore, the gravitational waves carried away from the system contain information about the geometrical structure of the black holes in the strong-field regime. Third, we also find that, in the post-merger phase, the multipolar structure of the outer common dynamical horizon of the system is strongly correlated with that of the individual horizons just before the merger. The outer common horizon then settles down to equilibrium as suggested by the decay of the multipole moments gained by the system through the inspiral phase. |
gr-qc/0111004 | J. Brian Pitts | J. Brian Pitts, W.C. Schieve | Null Cones in Lorentz-Covariant General Relativity | groupoid nature of gauge transformations explained; shortened, new
references, 102 pages | null | null | null | gr-qc hep-th | null | The oft-neglected issue of the causal structure in the flat spacetime
approach to Einstein's theory of gravity is considered. Consistency requires
that the flat metric's null cone be respected, but this does not happen
automatically. After reviewing the history of this problem, we introduce a
generalized eigenvector formalism to give a kinematic description of the
relation between the two null cones, based on the Segre' classification of
symmetric rank 2 tensors with respect to a Lorentzian metric. Then we propose a
method to enforce special relativistic causality by using the naive gauge
freedom to restrict the configuration space suitably. A set of new variables
just covers this smaller configuration space and respects the flat metric's
null cone automatically. In this smaller space, gauge transformations do not
form a group, but only a groupoid. Respecting the flat metric's null cone
ensures that the spacetime is globally hyperbolic, indicating that the Hawking
black hole information loss paradox does not arise.
| [
{
"created": "Fri, 2 Nov 2001 06:40:04 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2002 17:12:06 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Pitts",
"J. Brian",
""
],
[
"Schieve",
"W. C.",
""
]
] | The oft-neglected issue of the causal structure in the flat spacetime approach to Einstein's theory of gravity is considered. Consistency requires that the flat metric's null cone be respected, but this does not happen automatically. After reviewing the history of this problem, we introduce a generalized eigenvector formalism to give a kinematic description of the relation between the two null cones, based on the Segre' classification of symmetric rank 2 tensors with respect to a Lorentzian metric. Then we propose a method to enforce special relativistic causality by using the naive gauge freedom to restrict the configuration space suitably. A set of new variables just covers this smaller configuration space and respects the flat metric's null cone automatically. In this smaller space, gauge transformations do not form a group, but only a groupoid. Respecting the flat metric's null cone ensures that the spacetime is globally hyperbolic, indicating that the Hawking black hole information loss paradox does not arise. |
1108.1158 | Michele Vallisneri | Michele Vallisneri | Beyond Fisher: exact sampling distributions of the maximum-likelihood
estimator in gravitational-wave parameter estimation | 4 pages, 3 figures, RevTeX 4.1. Fixed typos, revised for clarity | Phys. Rev. Lett. 107, 191104 (2011) | 10.1103/PhysRevLett.107.191104 | null | gr-qc physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave astronomers often wish to characterize the expected
parameter-estimation accuracy of future observations. The Fisher matrix
provides a lower bound on the spread of the maximum-likelihood estimator across
noise realizations, as well as the leading-order width of the posterior
probability, but it is limited to high signal strengths often not realized in
practice. By contrast, Monte Carlo Bayesian inference provides the full
posterior for any signal strength, but it is too expensive to repeat for a
representative set of noises. Here I describe an efficient semianalytical
technique to map the exact sampling distribution of the maximum-likelihood
estimator across noise realizations, for any signal strength. This technique
can be applied to any estimation problem for signals in additive Gaussian
noise.
| [
{
"created": "Thu, 4 Aug 2011 18:24:50 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2011 23:37:08 GMT",
"version": "v2"
}
] | 2011-11-08 | [
[
"Vallisneri",
"Michele",
""
]
] | Gravitational-wave astronomers often wish to characterize the expected parameter-estimation accuracy of future observations. The Fisher matrix provides a lower bound on the spread of the maximum-likelihood estimator across noise realizations, as well as the leading-order width of the posterior probability, but it is limited to high signal strengths often not realized in practice. By contrast, Monte Carlo Bayesian inference provides the full posterior for any signal strength, but it is too expensive to repeat for a representative set of noises. Here I describe an efficient semianalytical technique to map the exact sampling distribution of the maximum-likelihood estimator across noise realizations, for any signal strength. This technique can be applied to any estimation problem for signals in additive Gaussian noise. |
2206.15246 | Lionel London | L. London and S. A. Hughes | Bi-orthogonal harmonics for the decomposition of gravitational radiation
II: applications for extreme and comparable mass-ratio black hole binaries | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The estimation of a physical system's normal modes is a fundamental problem
in physics. The quasi-normal modes of perturbed Kerr black holes, with their
related spheroidal harmonics, are key examples, and have diverse applications
in gravitational wave theory and data analysis. Recently, it has been shown
that \textit{adjoint}-spheroidal harmonics and the related spheroidal multipole
moments may be used to estimate the radiative modes of arbitrary sources. In
this paper, we investigate whether spheroidal multipole moments, relative to
their spherical harmonic counterparts, better approximate the underlying modes
of binary black hole spacetimes. We begin with a brief introduction to
adjoint-spheroidal harmonics. We then detail a rudimentary kind of spheroidal
harmonic decomposition, as well as its generalization which simultaneously
estimates pro- and retrograde moments. Example applications to numerical
waveforms from comparable and extreme mass-ratio binary black hole coalescences
are provided. We discuss the morphology of related spheroidal moments during
inspiral, merger, and ringdown. We conclude by discussing potential
applications in gravitational wave theory and signal modeling.
| [
{
"created": "Thu, 30 Jun 2022 12:44:57 GMT",
"version": "v1"
}
] | 2022-07-01 | [
[
"London",
"L.",
""
],
[
"Hughes",
"S. A.",
""
]
] | The estimation of a physical system's normal modes is a fundamental problem in physics. The quasi-normal modes of perturbed Kerr black holes, with their related spheroidal harmonics, are key examples, and have diverse applications in gravitational wave theory and data analysis. Recently, it has been shown that \textit{adjoint}-spheroidal harmonics and the related spheroidal multipole moments may be used to estimate the radiative modes of arbitrary sources. In this paper, we investigate whether spheroidal multipole moments, relative to their spherical harmonic counterparts, better approximate the underlying modes of binary black hole spacetimes. We begin with a brief introduction to adjoint-spheroidal harmonics. We then detail a rudimentary kind of spheroidal harmonic decomposition, as well as its generalization which simultaneously estimates pro- and retrograde moments. Example applications to numerical waveforms from comparable and extreme mass-ratio binary black hole coalescences are provided. We discuss the morphology of related spheroidal moments during inspiral, merger, and ringdown. We conclude by discussing potential applications in gravitational wave theory and signal modeling. |
gr-qc/0310119 | Mauro Hueller | L. Carbone, A. Cavalleri, R. Dolesi, C. D. Hoyle, M. Hueller, S.
Vitale, W. J. Weber | Upper limits on stray force noise for LISA | To be published in Classical and Quantum Gravity, special issue on
Amaldi5 2003 conference proceedings (10 pages, 6 figures) | Class.Quant.Grav. 21 (2004) S611-S620 | 10.1088/0264-9381/21/5/033 | null | gr-qc | null | We have developed a torsion pendulum facility for LISA gravitational
reference sensor ground testing that allows us to put significant upper limits
on residual stray forces exerted by LISA-like position sensors on a
representative test mass and to characterize specific sources of disturbances
for LISA. We present here the details of the facility, the experimental
procedures used to maximize its sensitivity, and the techniques used to
characterize the pendulum itself that allowed us to reach a torque sensitivity
below 20 fNm /sqrt{Hz} from 0.3 to 10 mHz. We also discuss the implications of
the obtained results for LISA.
| [
{
"created": "Tue, 28 Oct 2003 08:45:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Carbone",
"L.",
""
],
[
"Cavalleri",
"A.",
""
],
[
"Dolesi",
"R.",
""
],
[
"Hoyle",
"C. D.",
""
],
[
"Hueller",
"M.",
""
],
[
"Vitale",
"S.",
""
],
[
"Weber",
"W. J.",
""
]
] | We have developed a torsion pendulum facility for LISA gravitational reference sensor ground testing that allows us to put significant upper limits on residual stray forces exerted by LISA-like position sensors on a representative test mass and to characterize specific sources of disturbances for LISA. We present here the details of the facility, the experimental procedures used to maximize its sensitivity, and the techniques used to characterize the pendulum itself that allowed us to reach a torque sensitivity below 20 fNm /sqrt{Hz} from 0.3 to 10 mHz. We also discuss the implications of the obtained results for LISA. |
0711.2033 | David Delphenich | David Delphenich | Transverse geometry and physical observers | 23 pages, no figures | null | null | null | gr-qc | null | It is proposed that the mathematical formalism that is most appropriate for
the study of spatially non-integrable cosmological models is the transverse
geometry of a one-dimensional foliation (congruence) defined by a physical
observer. By that means, one can discuss the geometry of space, as viewed by
that observer, without the necessity of introducing a complementary sub-bundle
to the line bundle of the observer or a codimension-one foliation transverse to
the foliation of the observer. The concept of groups of transverse isometries
acting on such a spacetime and the relationship of transverse geometry to
spacetime threadings (1+3 decompositions) is also discussed.
| [
{
"created": "Tue, 13 Nov 2007 17:16:11 GMT",
"version": "v1"
}
] | 2007-11-14 | [
[
"Delphenich",
"David",
""
]
] | It is proposed that the mathematical formalism that is most appropriate for the study of spatially non-integrable cosmological models is the transverse geometry of a one-dimensional foliation (congruence) defined by a physical observer. By that means, one can discuss the geometry of space, as viewed by that observer, without the necessity of introducing a complementary sub-bundle to the line bundle of the observer or a codimension-one foliation transverse to the foliation of the observer. The concept of groups of transverse isometries acting on such a spacetime and the relationship of transverse geometry to spacetime threadings (1+3 decompositions) is also discussed. |
2102.10797 | Kirill Bronnikov | Kirill A. Bronnikov, Vin\'icius A.G. Barcellos, Laura P. de Carvalh,
J\'ulio C. Fabris | The simplest wormhole in Rastall and k-essence theories | 15 pages, no figures | null | 10.1140/epjc/s10052-021-09164-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geometry of the Ellis-Bronnikov wormhole is implemented in the Rastall
and k-essence theories of gravity with a self-interacting scalar field. The
form of the scalar field potential is determined in both cases. A stability
analysis with respect to spherically symmetric time-dependent perturbations is
carried out, and it shows that in k-essence theory the wormhole is unstable,
like the original version of this geometry supported by a massless phantom
scalar field in general relativity. In Rastall's theory, it turns out that a
perturbative approach reveals the same inconsistency that was found previously
for black hole solutions: time-dependent perturbations of the static
configuration prove to be excluded by the equations of motion, and the wormhole
is, in this sense, stable under spherical perturbations.
| [
{
"created": "Mon, 22 Feb 2021 06:30:57 GMT",
"version": "v1"
}
] | 2021-05-26 | [
[
"Bronnikov",
"Kirill A.",
""
],
[
"Barcellos",
"Vinícius A. G.",
""
],
[
"de Carvalh",
"Laura P.",
""
],
[
"Fabris",
"Júlio C.",
""
]
] | The geometry of the Ellis-Bronnikov wormhole is implemented in the Rastall and k-essence theories of gravity with a self-interacting scalar field. The form of the scalar field potential is determined in both cases. A stability analysis with respect to spherically symmetric time-dependent perturbations is carried out, and it shows that in k-essence theory the wormhole is unstable, like the original version of this geometry supported by a massless phantom scalar field in general relativity. In Rastall's theory, it turns out that a perturbative approach reveals the same inconsistency that was found previously for black hole solutions: time-dependent perturbations of the static configuration prove to be excluded by the equations of motion, and the wormhole is, in this sense, stable under spherical perturbations. |
1503.09054 | Ahmadjon Abdujabbarov | A. A. Abdujabbarov, L. Rezzolla and B. J. Ahmedov | A coordinate-independent characterization of a black hole shadow | 12 pages, 8 figures, accepted for publication on MNRAS | MNRAS 454, 2423 (2015) | 10.1093/mnras/stv2079 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A large international effort is under way to assess the presence of a shadow
in the radio emission from the compact source at the centre of our Galaxy,
Sagittarius A$^*$ (Sgr A$^*$). If detected, this shadow would provide the first
direct evidence of the existence of black holes and that Sgr A$^*$ is a
supermassive black hole. In addition, the shape of the shadow could be used to
learn about extreme gravity near the event horizon and to determine which
theory of gravity better describes the observations. The mathematical
description of the shadow has so far used a number of simplifying assumptions
that are unlikely to be met by the real observational data. We here provide a
general formalism to describe the shadow as an arbitrary polar curve expressed
in terms of a Legendre expansion. Our formalism does not presume any knowledge
of the properties of the shadow, e.g. the location of its centre, and offers a
number of routes to characterize the distortions of the curve with respect to
reference circles. These distortions can be implemented in a coordinate
independent manner by different teams analysing the same data. We show that the
new formalism provides an accurate and robust description of noisy
observational data, with smaller error variances when compared to previous
approaches for the measurement of the distortion.
| [
{
"created": "Mon, 30 Mar 2015 10:21:41 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Sep 2015 08:54:19 GMT",
"version": "v2"
}
] | 2016-06-03 | [
[
"Abdujabbarov",
"A. A.",
""
],
[
"Rezzolla",
"L.",
""
],
[
"Ahmedov",
"B. J.",
""
]
] | A large international effort is under way to assess the presence of a shadow in the radio emission from the compact source at the centre of our Galaxy, Sagittarius A$^*$ (Sgr A$^*$). If detected, this shadow would provide the first direct evidence of the existence of black holes and that Sgr A$^*$ is a supermassive black hole. In addition, the shape of the shadow could be used to learn about extreme gravity near the event horizon and to determine which theory of gravity better describes the observations. The mathematical description of the shadow has so far used a number of simplifying assumptions that are unlikely to be met by the real observational data. We here provide a general formalism to describe the shadow as an arbitrary polar curve expressed in terms of a Legendre expansion. Our formalism does not presume any knowledge of the properties of the shadow, e.g. the location of its centre, and offers a number of routes to characterize the distortions of the curve with respect to reference circles. These distortions can be implemented in a coordinate independent manner by different teams analysing the same data. We show that the new formalism provides an accurate and robust description of noisy observational data, with smaller error variances when compared to previous approaches for the measurement of the distortion. |
2112.13573 | Francisco A. Brito | M.A. Anacleto, F.A. Brito, G.C. Luna, E. Passos | The generalized uncertainty principle effect in acoustic black holes | 12 pages, no figures, version published in Annals of Physics | Annals Phys. 440 (2022) 168837 | 10.1016/j.aop.2022.168837 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We obtain an effective acoustic metric with quantum corrections that are
provided by a minimum length implemented by the generalized Heisenberg
uncertainty principle (GUP) in the Abelian Higgs model. The effective acoustic
metric now depends on the contribution of scalar and vector potentials. We also
explore the Hawking radiation and entropy by considering the effective
canonical acoustic black hole and find that the modified Hawking temperature
leads to logarithm corrections to the entropy. Finally, we investigate the
dispersion relations of the model to establish the relationships among the
deviations of the group velocity, frequency and temperature due to the GUP.
| [
{
"created": "Mon, 27 Dec 2021 08:50:45 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Mar 2022 09:16:35 GMT",
"version": "v2"
}
] | 2022-03-22 | [
[
"Anacleto",
"M. A.",
""
],
[
"Brito",
"F. A.",
""
],
[
"Luna",
"G. C.",
""
],
[
"Passos",
"E.",
""
]
] | We obtain an effective acoustic metric with quantum corrections that are provided by a minimum length implemented by the generalized Heisenberg uncertainty principle (GUP) in the Abelian Higgs model. The effective acoustic metric now depends on the contribution of scalar and vector potentials. We also explore the Hawking radiation and entropy by considering the effective canonical acoustic black hole and find that the modified Hawking temperature leads to logarithm corrections to the entropy. Finally, we investigate the dispersion relations of the model to establish the relationships among the deviations of the group velocity, frequency and temperature due to the GUP. |
1010.4211 | Alexandros P. Kouretsis | Alexandros P. Kouretsis and Christos G. Tsagas | Raychaudhuri's equation and aspects of relativistic charged collapse | Revised version, to appear in PRD | Phys.Rev.D82:124053,2010 | 10.1103/PhysRevD.82.124053 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the Raychaudhuri equation to probe certain aspects related to the
gravitational collapse of a charged medium. The aim is to identify the stresses
the Maxwell field exerts on the fluid and discuss their potential implications.
Particular attention is given to those stresses that resist contraction. After
looking at the general case, we consider the two opposite limits of poor and
high electrical conductivity. In the former there are electric fields but no
currents, while in the latter the situation is reversed. When the conductivity
is low, we find that the main agents acting against the collapse are the
Coulomb forces triggered by the presence of an excess charge. At the ideal
Magnetohydrodynamic (MHD) limit, on the other hand, the strongest resistance
seems to come from the tension of the magnetic forcelines. In either case, we
discuss whether and how the aforementioned resisting stresses may halt the
contraction and provide a set of conditions making this likely to happen.
| [
{
"created": "Wed, 20 Oct 2010 14:22:31 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Nov 2010 12:54:29 GMT",
"version": "v2"
}
] | 2011-01-17 | [
[
"Kouretsis",
"Alexandros P.",
""
],
[
"Tsagas",
"Christos G.",
""
]
] | We use the Raychaudhuri equation to probe certain aspects related to the gravitational collapse of a charged medium. The aim is to identify the stresses the Maxwell field exerts on the fluid and discuss their potential implications. Particular attention is given to those stresses that resist contraction. After looking at the general case, we consider the two opposite limits of poor and high electrical conductivity. In the former there are electric fields but no currents, while in the latter the situation is reversed. When the conductivity is low, we find that the main agents acting against the collapse are the Coulomb forces triggered by the presence of an excess charge. At the ideal Magnetohydrodynamic (MHD) limit, on the other hand, the strongest resistance seems to come from the tension of the magnetic forcelines. In either case, we discuss whether and how the aforementioned resisting stresses may halt the contraction and provide a set of conditions making this likely to happen. |
2212.03755 | Alexander Petrov Nikolaevich | E.D. Emtsova, A.N. Petrov, A.V. Toporensky | Conserved quantities in STEGR and applications | Published Version | Eur. Phys. J. C (2023) 83:366 | 10.1140/epjc/s10052-023-11460-8 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We derive conservation laws in Symmetric Teleparallel Equivalent of General
Relativity (STEGR) with direct application of Noether's theorem. This approach
allows us to construct covariant conserved currents, corresponding
superpotentials and invariant charges. A necessary component of our
constructions is the concept of "turning off" gravity, introduced in the
framework of STEGR to define the flat and torsionless connection. By
calculating currents, one can obtain local characteristics of gravitational
field like energy density. Surface integration of superpotentials gives charges
which correspond to global quantities of the system like mass, momentum, etc.
To test our results for the obtained currents and superpotentials, we calculate
the energy density measured by freely falling observer in the simple solutions
(Friedman universe, Schwartzchild black hole) and total mass of the
Schwartzchild black hole. We find ambiguities in obtaining the connection,
which explicitly affect the values of conserved quantities, and discuss
possible solutions to this problem.
| [
{
"created": "Wed, 7 Dec 2022 16:27:42 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jan 2023 12:42:47 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Mar 2023 18:27:15 GMT",
"version": "v3"
},
{
"created": "Tue, 31 Oct 2023 17:59:59 GMT",
"version": "v4"
}
] | 2023-11-01 | [
[
"Emtsova",
"E. D.",
""
],
[
"Petrov",
"A. N.",
""
],
[
"Toporensky",
"A. V.",
""
]
] | We derive conservation laws in Symmetric Teleparallel Equivalent of General Relativity (STEGR) with direct application of Noether's theorem. This approach allows us to construct covariant conserved currents, corresponding superpotentials and invariant charges. A necessary component of our constructions is the concept of "turning off" gravity, introduced in the framework of STEGR to define the flat and torsionless connection. By calculating currents, one can obtain local characteristics of gravitational field like energy density. Surface integration of superpotentials gives charges which correspond to global quantities of the system like mass, momentum, etc. To test our results for the obtained currents and superpotentials, we calculate the energy density measured by freely falling observer in the simple solutions (Friedman universe, Schwartzchild black hole) and total mass of the Schwartzchild black hole. We find ambiguities in obtaining the connection, which explicitly affect the values of conserved quantities, and discuss possible solutions to this problem. |
1903.09311 | Faizuddin Ahmed | Faizuddin Ahmed and Hassan Hassanabadi | Spin-zero system of DKP equation in the background of a flat class of
G\"{o}del-type space-time | 16 pages, introduction section shorten and number of references
reduced, section 2 & 3 merged, overall presentation improved, Accepted for
publication in Mod. Phys. Lett. A | Mod. Phys. Lett. A 35, No. 07, 2050031 (2020) | 10.1142/S0217732320500315 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the Duffin-Kemmer-Petiau (DKP) equation for
spin-zero system of charge-free particles in the background of a flat class of
G\"{o}del-type space-times, and evaluate the individual energy levels and
corresponding wave-functions, in details.
| [
{
"created": "Thu, 21 Mar 2019 13:21:44 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Sep 2019 05:18:50 GMT",
"version": "v2"
}
] | 2020-03-12 | [
[
"Ahmed",
"Faizuddin",
""
],
[
"Hassanabadi",
"Hassan",
""
]
] | In this paper, we investigate the Duffin-Kemmer-Petiau (DKP) equation for spin-zero system of charge-free particles in the background of a flat class of G\"{o}del-type space-times, and evaluate the individual energy levels and corresponding wave-functions, in details. |
0712.1462 | Raul Vera | Marc Mars, Jos\'e M. M. Senovilla and Ra\"ul Vera | Accelerating expansion and change of signature | LaTeX, 4 pages. Uses the eas.cls class. To appear in the proceedings
of the Spanish Relativity Meeting ERE'07 | null | 10.1051/eas:0830050 | null | gr-qc | null | We show that some types of sudden singularities admit a natural explanation
in terms of regular changes of signature on brane-worlds in AdS$_{5}$. The
present accelerated expansion of the Universe and its possible ending at a
sudden singularity may therefore simply be an indication that our braneworld is
about to change its Lorentzian signature to an Euclidean one, while remaining
fully regular. An explicit example of this behaviour satisfying the weak and
strong energy conditions is presented.
| [
{
"created": "Mon, 10 Dec 2007 16:31:47 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Mars",
"Marc",
""
],
[
"Senovilla",
"José M. M.",
""
],
[
"Vera",
"Raül",
""
]
] | We show that some types of sudden singularities admit a natural explanation in terms of regular changes of signature on brane-worlds in AdS$_{5}$. The present accelerated expansion of the Universe and its possible ending at a sudden singularity may therefore simply be an indication that our braneworld is about to change its Lorentzian signature to an Euclidean one, while remaining fully regular. An explicit example of this behaviour satisfying the weak and strong energy conditions is presented. |
1511.00600 | Surajit Chattopadhyay | Antonio Pasqua, Surajit Chattopadhyay, Ratbay Myrzakulov | Consequences of three modified forms of holographic dark energy models
in bulk-brane interaction | 34 pages, 20 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the effects which are produced by the interaction
between a brane Universe and the bulk in which the Universe is embedded. Taking
into account the effects produced by the interaction between a brane Universe
and the bulk, we derived the Equation of State (EoS) parameter $\omega_D$ for
three different models of Dark Energy (DE), \emph{i.e.} the Holographic DE
(HDE) model with infrared (IR) cut-off given by the Granda-Oliveros cut-off,
the Modified Holographic Ricci DE (MHRDE) model and a DE model which is
function of the Hubble parameter $H$ squared and to higher derivatives of $H$.
Moreover, we have considered two different cases of scale factor (namely, the
power law and the emergent ones). A nontrivial contribution of the DE is
observed to be different from the standard matter fields confined to the brane.
Such contribution has a monotonically decreasing behavior upon the evolution of
the Universe for the emergent scenario of the scale factor, while monotonically
increasing for the power-law form of the scale factor $a(t)$.
| [
{
"created": "Thu, 22 Oct 2015 10:02:12 GMT",
"version": "v1"
}
] | 2015-11-03 | [
[
"Pasqua",
"Antonio",
""
],
[
"Chattopadhyay",
"Surajit",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this paper, we study the effects which are produced by the interaction between a brane Universe and the bulk in which the Universe is embedded. Taking into account the effects produced by the interaction between a brane Universe and the bulk, we derived the Equation of State (EoS) parameter $\omega_D$ for three different models of Dark Energy (DE), \emph{i.e.} the Holographic DE (HDE) model with infrared (IR) cut-off given by the Granda-Oliveros cut-off, the Modified Holographic Ricci DE (MHRDE) model and a DE model which is function of the Hubble parameter $H$ squared and to higher derivatives of $H$. Moreover, we have considered two different cases of scale factor (namely, the power law and the emergent ones). A nontrivial contribution of the DE is observed to be different from the standard matter fields confined to the brane. Such contribution has a monotonically decreasing behavior upon the evolution of the Universe for the emergent scenario of the scale factor, while monotonically increasing for the power-law form of the scale factor $a(t)$. |
gr-qc/0410068 | Peter Ostermann | Peter Ostermann | A Strange Detail Concerning the Variational Principle of General
Relativity Theory | This final arXiv-version v4 extended to 8 (+ 25) pages, 51 (+ 106
groups of) relations for article (+ appendix of detailed verification);
thanks to 1 particular hint after a public arXiv-request via v3 | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A mathematical complication due to an unnecessary formal assumption
concerning the variational principle of general relativity theory, which
apparently bothered Einstein and Hilbert, is shown and cleared up. Some
historical confusion seems caused by the impossibility to use the conventional
Euler-Lagrange formalism directly there, which even otherwise is nothing but
one of various possible procedures to apply the superior principle of least
action. Correspondingly to the absence of any direct calculation in the
literature so far, only a numerical modification in parts - explicitly taken
into account now after once mentioned by Hilbert without implementation - would
allow to compute the fundamental Einstein tensor density from these authors'
initial formulae, which must not be taken literally. Nevertheless adhering to a
merely symbolic Euler-Lagrange formalism, this needs a clear distinction
between 'component differentiation' and 'tensor differentiation' defined here.
Various corresponding solutions are shown including the probably most natural
one. Two of them are additionally verified in the detailed supplementary
material appended to the electronic edition of the note.
| [
{
"created": "Fri, 15 Oct 2004 11:02:46 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2005 12:53:44 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Dec 2013 19:04:38 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Feb 2014 18:16:31 GMT",
"version": "v4"
}
] | 2014-02-12 | [
[
"Ostermann",
"Peter",
""
]
] | A mathematical complication due to an unnecessary formal assumption concerning the variational principle of general relativity theory, which apparently bothered Einstein and Hilbert, is shown and cleared up. Some historical confusion seems caused by the impossibility to use the conventional Euler-Lagrange formalism directly there, which even otherwise is nothing but one of various possible procedures to apply the superior principle of least action. Correspondingly to the absence of any direct calculation in the literature so far, only a numerical modification in parts - explicitly taken into account now after once mentioned by Hilbert without implementation - would allow to compute the fundamental Einstein tensor density from these authors' initial formulae, which must not be taken literally. Nevertheless adhering to a merely symbolic Euler-Lagrange formalism, this needs a clear distinction between 'component differentiation' and 'tensor differentiation' defined here. Various corresponding solutions are shown including the probably most natural one. Two of them are additionally verified in the detailed supplementary material appended to the electronic edition of the note. |
1109.6577 | Benjamin C. Harms | Paul H. Cox, Benjamin C. Harms, Shaoqi Hou | Statistical Mechanics of Wormholes | 8 pages, 1 figure Corrected typo | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The statistical mechanics of a gas of Einstein-Kalb-Ramond wormholes is
studied in this paper. The wormholes studied are the result of sewing together
two Reissner-Nordstrom-type black hole metrics at their horizons. By requiring
the stress-energy tensor associated with this geometry to be that of a
Kalb-Ramond field, we obtain the mass and Kalb-Ramond `charge` of the wormholes
in terms of the parameters describing the mass density, tension and pressure.
We investigate the statistical mechanics of this system of wormholes within the
context of the statistical bootstrap model. A gas of such wormholes is found to
obey the bootstrap condition only for an extreme, non-thermodynamic, energy and
`charge` distribution among the particles. We comment briefly on the scattering
of quantum wormholes.
| [
{
"created": "Thu, 29 Sep 2011 16:15:22 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Oct 2011 16:30:13 GMT",
"version": "v2"
}
] | 2011-10-10 | [
[
"Cox",
"Paul H.",
""
],
[
"Harms",
"Benjamin C.",
""
],
[
"Hou",
"Shaoqi",
""
]
] | The statistical mechanics of a gas of Einstein-Kalb-Ramond wormholes is studied in this paper. The wormholes studied are the result of sewing together two Reissner-Nordstrom-type black hole metrics at their horizons. By requiring the stress-energy tensor associated with this geometry to be that of a Kalb-Ramond field, we obtain the mass and Kalb-Ramond `charge` of the wormholes in terms of the parameters describing the mass density, tension and pressure. We investigate the statistical mechanics of this system of wormholes within the context of the statistical bootstrap model. A gas of such wormholes is found to obey the bootstrap condition only for an extreme, non-thermodynamic, energy and `charge` distribution among the particles. We comment briefly on the scattering of quantum wormholes. |
1307.1679 | Frank Hellmann | Frank Hellmann and Wojciech Kaminski | Holonomy spin foam models: Asymptotic geometry of the partition function | 63 pages, 5 figures v2: Reference corrected | null | 10.1007/JHEP10(2013)165 | null | gr-qc hep-lat | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the asymptotic geometry of the spin foam partition function for a
large class of models, including the models of Barrett and Crane, Engle,
Pereira, Rovelli and Livine, and, Freidel and Krasnov.
The asymptotics is taken with respect to the boundary spins only, no
assumption of large spins is made in the interior. We give a sufficient
criterion for the existence of the partition function. We find that geometric
boundary data is suppressed unless its interior continuation satisfies certain
accidental curvature constraints. This means in particular that most Regge
manifolds are suppressed in the asymptotic regime. We discuss this explicitly
for the case of the configurations arising in the 3-3 Pachner move. We identify
the origin of these accidental curvature constraints as an incorrect twisting
of the face amplitude upon introduction of the Immirzi parameter and propose a
way to resolve this problem, albeit at the price of losing the connection to
the SU(2) boundary Hilbert space.
The key methodological innovation that enables these results is the
introduction of the notion of wave front sets, and the adaptation of tools for
their study from micro local analysis to the case of spin foam partition
functions.
| [
{
"created": "Fri, 5 Jul 2013 17:56:18 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jul 2013 14:55:01 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Hellmann",
"Frank",
""
],
[
"Kaminski",
"Wojciech",
""
]
] | We study the asymptotic geometry of the spin foam partition function for a large class of models, including the models of Barrett and Crane, Engle, Pereira, Rovelli and Livine, and, Freidel and Krasnov. The asymptotics is taken with respect to the boundary spins only, no assumption of large spins is made in the interior. We give a sufficient criterion for the existence of the partition function. We find that geometric boundary data is suppressed unless its interior continuation satisfies certain accidental curvature constraints. This means in particular that most Regge manifolds are suppressed in the asymptotic regime. We discuss this explicitly for the case of the configurations arising in the 3-3 Pachner move. We identify the origin of these accidental curvature constraints as an incorrect twisting of the face amplitude upon introduction of the Immirzi parameter and propose a way to resolve this problem, albeit at the price of losing the connection to the SU(2) boundary Hilbert space. The key methodological innovation that enables these results is the introduction of the notion of wave front sets, and the adaptation of tools for their study from micro local analysis to the case of spin foam partition functions. |
2311.01863 | Dmitri Fursaev | D.V. Fursaev, E.A. Davydov, I.G. Pirozhenko, V.A. Tainov | Gravitational Waves Generated by Null Cosmic Strings | 30 paqes, 2 figures, v2, where a new section, comments and references
are added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Null cosmic strings are shown to disturb gravitational fields of massive
bodies and create outgoing gravitational waves (GW). Perturbations of the
metric caused by a straight null string and a point-like massive source are
found as solutions to linearized Einstein equations on a flat space-time. An
analytic approximation for their asymptotic at future null infinity is derived.
A space-time created by the source and the string is shown to have
asymptotically polyhomogeneous form. We calculate GW flux in such space-times
and demonstrate that the averaged intensity of the radiation is maximal in the
direction of the string motion. Opportunities to detect null string generated
gravity waves are briefly discussed.
| [
{
"created": "Fri, 3 Nov 2023 12:12:36 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2024 12:17:06 GMT",
"version": "v2"
}
] | 2024-04-11 | [
[
"Fursaev",
"D. V.",
""
],
[
"Davydov",
"E. A.",
""
],
[
"Pirozhenko",
"I. G.",
""
],
[
"Tainov",
"V. A.",
""
]
] | Null cosmic strings are shown to disturb gravitational fields of massive bodies and create outgoing gravitational waves (GW). Perturbations of the metric caused by a straight null string and a point-like massive source are found as solutions to linearized Einstein equations on a flat space-time. An analytic approximation for their asymptotic at future null infinity is derived. A space-time created by the source and the string is shown to have asymptotically polyhomogeneous form. We calculate GW flux in such space-times and demonstrate that the averaged intensity of the radiation is maximal in the direction of the string motion. Opportunities to detect null string generated gravity waves are briefly discussed. |
gr-qc/0607035 | Richard O'Shaughenssy | Richard O'Shaughnessy | Coating thermal noise for arbitrary shaped beams | 3 pages. Originally performed in August 2004. Submitted to CQG. (v2)
: Corrections from referee and others | Class.Quant.Grav.23:7627-7630,2006 | 10.1088/0264-9381/23/24/N01 | null | gr-qc | null | Advanced LIGO's sensitivity will be limited by coating noise. Though this
noise depends on beam shape, and though nongaussian beams are being seriously
considered for advanced LIGO, no published analysis exists to compare the
quantitative thermal noise improvement alternate beams offer. In this paper, we
derive and discuss a simple integral which completely characterizes the
dependence of coating thermal noise on shape. The derivation used applies
equally well, with minor modifications, to all other forms of thermal noise in
the low-frequency limit.
| [
{
"created": "Mon, 10 Jul 2006 01:48:10 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Oct 2006 15:44:39 GMT",
"version": "v2"
}
] | 2009-04-03 | [
[
"O'Shaughnessy",
"Richard",
""
]
] | Advanced LIGO's sensitivity will be limited by coating noise. Though this noise depends on beam shape, and though nongaussian beams are being seriously considered for advanced LIGO, no published analysis exists to compare the quantitative thermal noise improvement alternate beams offer. In this paper, we derive and discuss a simple integral which completely characterizes the dependence of coating thermal noise on shape. The derivation used applies equally well, with minor modifications, to all other forms of thermal noise in the low-frequency limit. |
2305.03337 | Hamid R. Bakhtiarizadeh | Hamid R. Bakhtiarizadeh and Hanif Golchin | Rotating black strings beyond Maxwell's electrodynamics | LaTex file, 21 pages, 4 figures, v2: version to appear in JCAP | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the asymptotically Anti de Sitter solutions of
rotating black strings coupled to Born-Infeld and Modified Maxwell non-linear
electrodynamics in the context of Einsteinian, Einsteinian cubic and
Einsteinian quartic gravity. By studying the near-horizon behavior of
solutions, we find the mass parameter, surface gravity and accordingly the
Hawking temperature. We also compute the entropy, mass, angular momentum,
electric charge, and the electrostatic potential of solutions to show that, in
the context of above theories and in the presence of two mentioned non-linear
electrodynamics, the first law of thermodynamics for rotating black strings is
also exactly hold. We also investigate extremality, thermal stability and phase
transition of solutions.
| [
{
"created": "Fri, 5 May 2023 07:41:31 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Dec 2023 17:30:51 GMT",
"version": "v2"
}
] | 2023-12-22 | [
[
"Bakhtiarizadeh",
"Hamid R.",
""
],
[
"Golchin",
"Hanif",
""
]
] | In this paper, we investigate the asymptotically Anti de Sitter solutions of rotating black strings coupled to Born-Infeld and Modified Maxwell non-linear electrodynamics in the context of Einsteinian, Einsteinian cubic and Einsteinian quartic gravity. By studying the near-horizon behavior of solutions, we find the mass parameter, surface gravity and accordingly the Hawking temperature. We also compute the entropy, mass, angular momentum, electric charge, and the electrostatic potential of solutions to show that, in the context of above theories and in the presence of two mentioned non-linear electrodynamics, the first law of thermodynamics for rotating black strings is also exactly hold. We also investigate extremality, thermal stability and phase transition of solutions. |
0801.1073 | Marek Szydlowski | Jakub Mielczarek, Marek Szydlowski | Emerging singularities in the bouncing loop cosmology | RevTeX4, 8 pages, 4 figures; v2 change of title, more discussion on
co-existence of singularity and bounce | Phys.Rev.D77:124008,2008 | 10.1103/PhysRevD.77.124008 | null | gr-qc hep-th | null | In this paper we calculate $\mathcal{O}(\mu^4)$ corrections from holonomies
in the Loop Quantum Gravity, usually not taken into account. Allowance of the
corrections of this kind is equivalent with the choice of the new quatization
scheme. Quantization ambiguities in the Loop Quantum Cosmology allow for this
additional freedom and presented corrections are consistent with the standard
approach. We apply these corrections to the flat FRW cosmological model and
calculate the modified Friedmann equation. We show that the bounce appears in
the models with the standard $\mathcal{O}(\mu^2)$ quantization scheme is
shifted to the higher energies $\rho_{\text{bounce}} = 3 \rho_{\text{c}}$. Also
a pole in the Hubble parameter appears for $\rho_{\text{pole}} = {3/2}
\rho_{\text{c}}$ corresponding to \emph{hyper-inflation/deflation} phases. This
pole represents a curvature singularity at which the scale factor is finite. In
this scenario the singularity and bounce co-exist. Moreover we find that an
ordinary bouncing solution appears only when quantum corrections in the lowest
order are considered. Higher order corrections can lead to the nonperturbative
effects.
| [
{
"created": "Mon, 7 Jan 2008 17:24:11 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Feb 2008 13:39:04 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mielczarek",
"Jakub",
""
],
[
"Szydlowski",
"Marek",
""
]
] | In this paper we calculate $\mathcal{O}(\mu^4)$ corrections from holonomies in the Loop Quantum Gravity, usually not taken into account. Allowance of the corrections of this kind is equivalent with the choice of the new quatization scheme. Quantization ambiguities in the Loop Quantum Cosmology allow for this additional freedom and presented corrections are consistent with the standard approach. We apply these corrections to the flat FRW cosmological model and calculate the modified Friedmann equation. We show that the bounce appears in the models with the standard $\mathcal{O}(\mu^2)$ quantization scheme is shifted to the higher energies $\rho_{\text{bounce}} = 3 \rho_{\text{c}}$. Also a pole in the Hubble parameter appears for $\rho_{\text{pole}} = {3/2} \rho_{\text{c}}$ corresponding to \emph{hyper-inflation/deflation} phases. This pole represents a curvature singularity at which the scale factor is finite. In this scenario the singularity and bounce co-exist. Moreover we find that an ordinary bouncing solution appears only when quantum corrections in the lowest order are considered. Higher order corrections can lead to the nonperturbative effects. |
gr-qc/0506009 | A. Latif Choudhury | A. Latif Choudhury | Influence Of Collapsing Matter On The Enveloping Expanding Universe | 7 pages | null | null | null | gr-qc | null | Using a collapsing matter model at the center of an expanding universe as
described by Weinberg we assume a special type of generated pressure. This
pressure transmits into the surrounding expanding universe. Under certain
restriction the ensuing hubble parameter is positive. The deacceleration
parameter fluctuates with time, indicating that the universe accelerates for
certain time and decelerates for other time intervals.
| [
{
"created": "Wed, 1 Jun 2005 16:57:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Choudhury",
"A. Latif",
""
]
] | Using a collapsing matter model at the center of an expanding universe as described by Weinberg we assume a special type of generated pressure. This pressure transmits into the surrounding expanding universe. Under certain restriction the ensuing hubble parameter is positive. The deacceleration parameter fluctuates with time, indicating that the universe accelerates for certain time and decelerates for other time intervals. |
1404.3518 | Stephane Fay | St\'ephane Fay | From inflation to late time acceleration with a decaying vacuum coupled
to radiation or matter | 9 pages, 7 figures | Phys. Rev. D 89, 063514 (2014) | 10.1103/PhysRevD.89.063514 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider General Relativity with matter and radiation, one of these fluids
being coupled to vacuum. We find that Universe dynamics starts by an inflation
phase if the coupled fluid has a negative energy density at early time. Then,
there is always a finite scale factor singularity but when vacuum and matter
are coupled and matter density behaves like a negative radiation density.
Moreover, the convergence to the LCDM model is clearly easier to reach when
vacuum is coupled to matter rather than to radiation. Two classes of theories
are studied to illustrate these results.
| [
{
"created": "Mon, 14 Apr 2014 09:56:08 GMT",
"version": "v1"
}
] | 2014-04-15 | [
[
"Fay",
"Stéphane",
""
]
] | We consider General Relativity with matter and radiation, one of these fluids being coupled to vacuum. We find that Universe dynamics starts by an inflation phase if the coupled fluid has a negative energy density at early time. Then, there is always a finite scale factor singularity but when vacuum and matter are coupled and matter density behaves like a negative radiation density. Moreover, the convergence to the LCDM model is clearly easier to reach when vacuum is coupled to matter rather than to radiation. Two classes of theories are studied to illustrate these results. |
1510.01352 | Irina Dymnikova | Irina Dymnikova | Electromagnetic source for the Kerr-Newman geometry | 8 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1510.01126 | International Journal of Modern Physics D Vol. 24, No. 14 (2015)
1550094 (8 pages) | 10.1142/S0218271815500947 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Source-free equations of nonlinear electrodynamics minimally coupled to
gravity (NED-GR) admit regular axially symmetric asymptotically Kerr-Newman
solutions, which describe electrically charged rotating black holes and
spinning solitons. Asymptotic analysis of solutions shows the existence of de
Sitter vacuum interior which has the properties of a perfect conductor and an
ideal diamagnetic. The Kerr ring singularity (a naked singularity in the case
without horizons) is replaced with a superconducting current, which serves as a
nondissipative source of the Kerr-Newman fields and can be responsible for an
unlimited life time of a spinning object.
| [
{
"created": "Fri, 2 Oct 2015 13:28:21 GMT",
"version": "v1"
}
] | 2015-10-07 | [
[
"Dymnikova",
"Irina",
""
]
] | Source-free equations of nonlinear electrodynamics minimally coupled to gravity (NED-GR) admit regular axially symmetric asymptotically Kerr-Newman solutions, which describe electrically charged rotating black holes and spinning solitons. Asymptotic analysis of solutions shows the existence of de Sitter vacuum interior which has the properties of a perfect conductor and an ideal diamagnetic. The Kerr ring singularity (a naked singularity in the case without horizons) is replaced with a superconducting current, which serves as a nondissipative source of the Kerr-Newman fields and can be responsible for an unlimited life time of a spinning object. |
2304.13647 | Francois Larrouturou | L. Blanchet, G. Faye, Q. Henry, F. Larrouturou and D. Trestini | Gravitational waves from compact binaries to the fourth post-Newtonian
order | Contribution to the 2023 Gravitation session of the 57th Rencontres
de Moriond. 5 pages, 1 figure; v2 : references added and minor changes in the
text | null | 10.58027/bsnq-2422 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The precise knowledge of the gravitational phase evolution of compact
binaries is crucial to the data analysis for gravitational waves. Until
recently, it was known analytically (for non-spinning systems) up to the 3.5
post-Newtonian (PN) order, i.e. up to the $(v/c)^7$ correction beyond the
leading order quadrupole formula. Using a PN-multipolar-post-Minkowskian
algorithm, we have pushed the accuracy to the next 4PN level. This derivation
involved challenging technical issues, due to the appearance of non-physical
divergences, which have to be properly regularized, as well as effects of
non-linear multipole interactions.
| [
{
"created": "Wed, 26 Apr 2023 16:10:31 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2023 20:22:18 GMT",
"version": "v2"
}
] | 2024-01-23 | [
[
"Blanchet",
"L.",
""
],
[
"Faye",
"G.",
""
],
[
"Henry",
"Q.",
""
],
[
"Larrouturou",
"F.",
""
],
[
"Trestini",
"D.",
""
]
] | The precise knowledge of the gravitational phase evolution of compact binaries is crucial to the data analysis for gravitational waves. Until recently, it was known analytically (for non-spinning systems) up to the 3.5 post-Newtonian (PN) order, i.e. up to the $(v/c)^7$ correction beyond the leading order quadrupole formula. Using a PN-multipolar-post-Minkowskian algorithm, we have pushed the accuracy to the next 4PN level. This derivation involved challenging technical issues, due to the appearance of non-physical divergences, which have to be properly regularized, as well as effects of non-linear multipole interactions. |
1511.08543 | Kiyoshi Shiraishi | Kiyoshi Shiraishi | Spinning a charged dilaton black hole | 6 pages, 2 figures | Physics Letters A166, Nos. 5&6, pp. 298-302 (1992) | 10.1016/0375-9601(92)90712-U | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A charged dilaton black hole which possesses infinitesimal angular momentum
is studied. We find that the gyromagnetic ratio of the dilaton black hole
depends not only on the parameter which appears in the interaction between the
dilaton and the electric field but also nonlinearly on the ratio of the charge
to the mass of the black hole. The moment of inertia for the charged dilaton
hole in the limit of infinitesimal angular momentum is also calculated.
| [
{
"created": "Fri, 27 Nov 2015 02:45:38 GMT",
"version": "v1"
}
] | 2015-11-30 | [
[
"Shiraishi",
"Kiyoshi",
""
]
] | A charged dilaton black hole which possesses infinitesimal angular momentum is studied. We find that the gyromagnetic ratio of the dilaton black hole depends not only on the parameter which appears in the interaction between the dilaton and the electric field but also nonlinearly on the ratio of the charge to the mass of the black hole. The moment of inertia for the charged dilaton hole in the limit of infinitesimal angular momentum is also calculated. |
1607.07883 | Nematollah Riazi | S. N. Sajadi, N. Riazi | Thermodynamic Stability of Wormholes | 9 pages. arXiv admin note: text overlap with arXiv:1511.03508,
arXiv:1202.1706 by other authors The authors withdraw the manuscript
temporarily to remove the text overlaps | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the context of GR, we study the thermodynamic stability of evolving
Lorentzian wormholes at the apparent horizon. The average pressure of the
anisotrropic components is considered as the pressure of the wormhole.
According to the requirements of stable equilibrium in conventional
thermodynamics, we calculate the heat capacity at constant pressure and Gibbs
free energy and analyze the local and global thermodynamic stability of the
wormhole.
| [
{
"created": "Tue, 26 Jul 2016 20:05:08 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2016 10:56:28 GMT",
"version": "v2"
}
] | 2016-07-29 | [
[
"Sajadi",
"S. N.",
""
],
[
"Riazi",
"N.",
""
]
] | In the context of GR, we study the thermodynamic stability of evolving Lorentzian wormholes at the apparent horizon. The average pressure of the anisotrropic components is considered as the pressure of the wormhole. According to the requirements of stable equilibrium in conventional thermodynamics, we calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of the wormhole. |
2004.05879 | Roman Konoplya | R. A. Konoplya and M. S. Churilova | Non-evident stability of a Dirac field in Schwarzschild-de Sitter
spacetime | The problem was solved in an earlier publication by other authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbations of the Dirac field in the Schwarzschild spacetime are
characterized by two wave equations (for two chiralities) with effective
potentials which are iso-spectral and one of which is positive definite.
Therefore, the stability of a Dirac field in the Schwarzschild background is
straightforward. This is not so for the Schwarzschild-de Sitter case, because
potentials for both chiralities have negative gaps and the fact that the
stability is not automatically guaranteed in the asymptotically de Sitter case
was apparently omitted in the literature. Performing the time-domain
integration of the wave equations and, thereby, taking into consideration all
the quasinormal modes of the spectrum, we demonstrate stability of the Dirac
field in the Schwarzschild-de Sitter spacetime. The analysis of stability is
extended also to the Reissner-Nordstrom-de Sitter solution.
| [
{
"created": "Mon, 13 Apr 2020 12:00:29 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2021 14:40:42 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Konoplya",
"R. A.",
""
],
[
"Churilova",
"M. S.",
""
]
] | Perturbations of the Dirac field in the Schwarzschild spacetime are characterized by two wave equations (for two chiralities) with effective potentials which are iso-spectral and one of which is positive definite. Therefore, the stability of a Dirac field in the Schwarzschild background is straightforward. This is not so for the Schwarzschild-de Sitter case, because potentials for both chiralities have negative gaps and the fact that the stability is not automatically guaranteed in the asymptotically de Sitter case was apparently omitted in the literature. Performing the time-domain integration of the wave equations and, thereby, taking into consideration all the quasinormal modes of the spectrum, we demonstrate stability of the Dirac field in the Schwarzschild-de Sitter spacetime. The analysis of stability is extended also to the Reissner-Nordstrom-de Sitter solution. |
1511.03191 | Giulia Gubitosi | Giulia Gubitosi, Michele Arzano, Joao Magueijo | Quantization of fluctuations in DSR: the two-point function and beyond | 5 pages, 1 figure | Phys. Rev. D 93, 065027 (2016) | 10.1103/PhysRevD.93.065027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the two-point function of a quantum field theory with de Sitter
momentum space (herein called DSR) can be expressed as the product of a
standard delta function and an energy-dependent factor. This is a highly
non-trivial technical result in any theory without a preferred frame. Applied
to models exhibiting running of the dimensionality of space, this result is
essential in proving that vacuum fluctuations are generally scale-invariant at
high energies whenever there is running to two dimensions. This is equally true
for theories with and without a preferred frame, with differences arising only
as we consider higher order correlators. Specifically, the three-point function
of DSR has a unique structure of "open triangles", as shown here.
| [
{
"created": "Tue, 10 Nov 2015 17:19:59 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Gubitosi",
"Giulia",
""
],
[
"Arzano",
"Michele",
""
],
[
"Magueijo",
"Joao",
""
]
] | We show that the two-point function of a quantum field theory with de Sitter momentum space (herein called DSR) can be expressed as the product of a standard delta function and an energy-dependent factor. This is a highly non-trivial technical result in any theory without a preferred frame. Applied to models exhibiting running of the dimensionality of space, this result is essential in proving that vacuum fluctuations are generally scale-invariant at high energies whenever there is running to two dimensions. This is equally true for theories with and without a preferred frame, with differences arising only as we consider higher order correlators. Specifically, the three-point function of DSR has a unique structure of "open triangles", as shown here. |
2111.15477 | Dr. Sudhaker Upadhyay | J. Sadeghi, B. Pourhassan, S. Noori Gashti and S. Upadhyay | Swampland Conjecture and Inflation Model from Brane Perspective | 21 pages, 15 captioned figures, Published in Physica Scripta | Phys. Scr. 96, 125317 (2021) | 10.1088/1402-4896/ac39bc | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Over the past few decades, inflation models have been studied by researchers
from different perspectives and conditions in order to introduce a model for
the expanding universe. In this paper, we introduce a modified $f(R)$
gravitational model as ($R+\gamma R^{p}$) in order to examine a new condition
for inflation models. Given that our studies are related to a modified $f(R)$
gravitational model on the brane, therefore we will encounter modified
cosmological parameters. So, we first introduce these modified cosmological
parameters such as spectral index, a number of e-folds and etc. Then, we apply
these conditions to our modified $f(R)$ gravitational model in order to adapt
to the swampland criteria. Finally, we determine the range of each of these
parameters by plotting some figures and with respect to observable data such as
Planck 2018.
| [
{
"created": "Sun, 28 Nov 2021 13:06:47 GMT",
"version": "v1"
}
] | 2021-12-01 | [
[
"Sadeghi",
"J.",
""
],
[
"Pourhassan",
"B.",
""
],
[
"Gashti",
"S. Noori",
""
],
[
"Upadhyay",
"S.",
""
]
] | Over the past few decades, inflation models have been studied by researchers from different perspectives and conditions in order to introduce a model for the expanding universe. In this paper, we introduce a modified $f(R)$ gravitational model as ($R+\gamma R^{p}$) in order to examine a new condition for inflation models. Given that our studies are related to a modified $f(R)$ gravitational model on the brane, therefore we will encounter modified cosmological parameters. So, we first introduce these modified cosmological parameters such as spectral index, a number of e-folds and etc. Then, we apply these conditions to our modified $f(R)$ gravitational model in order to adapt to the swampland criteria. Finally, we determine the range of each of these parameters by plotting some figures and with respect to observable data such as Planck 2018. |
1701.00550 | Jonathan Blackman | Jonathan Blackman, Scott E. Field, Mark A. Scheel, Chad R. Galley,
Daniel A. Hemberger, Patricia Schmidt, Rory Smith | A Surrogate Model of Gravitational Waveforms from Numerical Relativity
Simulations of Precessing Binary Black Hole Mergers | 34 pages, 26 figures | Phys. Rev. D 95, 104023 (2017) | 10.1103/PhysRevD.95.104023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first surrogate model for gravitational waveforms from the
coalescence of precessing binary black holes. We call this surrogate model
NRSur4d2s. Our methodology significantly extends recently introduced
reduced-order and surrogate modeling techniques, and is capable of directly
modeling numerical relativity waveforms without introducing phenomenological
assumptions or approximations to general relativity. Motivated by GW150914,
LIGO's first detection of gravitational waves from merging black holes, the
model is built from a set of $276$ numerical relativity (NR) simulations with
mass ratios $q \leq 2$, dimensionless spin magnitudes up to $0.8$, and the
restriction that the initial spin of the smaller black hole lies along the axis
of orbital angular momentum. It produces waveforms which begin $\sim 30$
gravitational wave cycles before merger and continue through ringdown, and
which contain the effects of precession as well as all $\ell \in \{2, 3\}$
spin-weighted spherical-harmonic modes. We perform cross-validation studies to
compare the model to NR waveforms \emph{not} used to build the model, and find
a better agreement within the parameter range of the model than other,
state-of-the-art precessing waveform models, with typical mismatches of
$10^{-3}$. We also construct a frequency domain surrogate model (called
NRSur4d2s_FDROM) which can be evaluated in $50\, \mathrm{ms}$ and is suitable
for performing parameter estimation studies on gravitational wave detections
similar to GW150914.
| [
{
"created": "Mon, 2 Jan 2017 23:06:19 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2017 06:23:34 GMT",
"version": "v2"
}
] | 2017-05-24 | [
[
"Blackman",
"Jonathan",
""
],
[
"Field",
"Scott E.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Galley",
"Chad R.",
""
],
[
"Hemberger",
"Daniel A.",
""
],
[
"Schmidt",
"Patricia",
""
],
[
"Smith",
"Rory",
""
]
] | We present the first surrogate model for gravitational waveforms from the coalescence of precessing binary black holes. We call this surrogate model NRSur4d2s. Our methodology significantly extends recently introduced reduced-order and surrogate modeling techniques, and is capable of directly modeling numerical relativity waveforms without introducing phenomenological assumptions or approximations to general relativity. Motivated by GW150914, LIGO's first detection of gravitational waves from merging black holes, the model is built from a set of $276$ numerical relativity (NR) simulations with mass ratios $q \leq 2$, dimensionless spin magnitudes up to $0.8$, and the restriction that the initial spin of the smaller black hole lies along the axis of orbital angular momentum. It produces waveforms which begin $\sim 30$ gravitational wave cycles before merger and continue through ringdown, and which contain the effects of precession as well as all $\ell \in \{2, 3\}$ spin-weighted spherical-harmonic modes. We perform cross-validation studies to compare the model to NR waveforms \emph{not} used to build the model, and find a better agreement within the parameter range of the model than other, state-of-the-art precessing waveform models, with typical mismatches of $10^{-3}$. We also construct a frequency domain surrogate model (called NRSur4d2s_FDROM) which can be evaluated in $50\, \mathrm{ms}$ and is suitable for performing parameter estimation studies on gravitational wave detections similar to GW150914. |
1109.6801 | Gianluca Calcagni | Kinjal Banerjee, Gianluca Calcagni, Mercedes Mart\'in-Benito | Introduction to Loop Quantum Cosmology | null | SIGMA 8 (2012), 016, 73 pages | 10.3842/SIGMA.2012.016 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | This is an introduction to loop quantum cosmology (LQC) reviewing mini- and
midisuperspace models as well as homogeneous and inhomogeneous effective
dynamics.
| [
{
"created": "Fri, 30 Sep 2011 11:51:27 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Mar 2012 07:32:27 GMT",
"version": "v2"
}
] | 2012-03-27 | [
[
"Banerjee",
"Kinjal",
""
],
[
"Calcagni",
"Gianluca",
""
],
[
"Martín-Benito",
"Mercedes",
""
]
] | This is an introduction to loop quantum cosmology (LQC) reviewing mini- and midisuperspace models as well as homogeneous and inhomogeneous effective dynamics. |
gr-qc/9804076 | null | R. Durrer, M. Gasperini, M. Sakellariadou and G. Veneziano | Seeds of large-scale anisotropy in string cosmology | 27 pages, LATEX, one figure included using epsf | Phys.Rev.D59:043511,1999 | 10.1103/PhysRevD.59.043511 | CERN-TH/98-69 | gr-qc astro-ph | null | Pre-big bang cosmology predicts tiny first-order dilaton and metric
perturbations at very large scales. Here we discuss the possibility that other
-- more copiously generated -- perturbations may act, at second order, as
scalar seeds of large-scale structure and CMB anisotropies. We study, in
particular, the cases of electromagnetic and axionic seeds. We compute the
stochastic fluctuations of their energy-momentum tensor and determine the
resulting contributions to the multipole expansion of the temperature
anisotropy. In the axion case it is possible to obtain a flat or slightly
tilted blue spectrum that fits present data consistently, both for massless and
for massive (but very light) axions.
| [
{
"created": "Tue, 28 Apr 1998 13:21:02 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Durrer",
"R.",
""
],
[
"Gasperini",
"M.",
""
],
[
"Sakellariadou",
"M.",
""
],
[
"Veneziano",
"G.",
""
]
] | Pre-big bang cosmology predicts tiny first-order dilaton and metric perturbations at very large scales. Here we discuss the possibility that other -- more copiously generated -- perturbations may act, at second order, as scalar seeds of large-scale structure and CMB anisotropies. We study, in particular, the cases of electromagnetic and axionic seeds. We compute the stochastic fluctuations of their energy-momentum tensor and determine the resulting contributions to the multipole expansion of the temperature anisotropy. In the axion case it is possible to obtain a flat or slightly tilted blue spectrum that fits present data consistently, both for massless and for massive (but very light) axions. |
gr-qc/0402117 | Julio Cesar Fabris | F.G. Alvarenga, A.B. Batista, J.C. Fabris, S.V.B. Goncalves | Troubles with quantum anisotropic cosmological models: loss of unitarity | Latex file, 4 pages. To appear in the proceedings of the Tenth Marcel
Grossman Meeting | null | null | null | gr-qc | null | The anisotropic Bianchi I cosmological model coupled with perfect fluid is
quantized in the minisuperspace. The perfect fluid is described by using the
Schutz formalism which allows to attribute dynamical degrees of freedom to
matter. It is shown that the resulting model is non-unitary. This breaks the
equivalence between the many-worlds and dBB interpretations of quantum
mechanics.
| [
{
"created": "Wed, 25 Feb 2004 18:08:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Alvarenga",
"F. G.",
""
],
[
"Batista",
"A. B.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Goncalves",
"S. V. B.",
""
]
] | The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. It is shown that the resulting model is non-unitary. This breaks the equivalence between the many-worlds and dBB interpretations of quantum mechanics. |
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